Inkjet printing method

Abstract

The present invention provides an inkjet printing method for forming a printed image on a printing medium, the printed image including a rich image forming section and a light image forming section, the printing duty ratio of an ink containing a colorant being greater than the printing duty ratio of the ink containing the colorant being greater than the printing duty ratio of the ink containing the colorant being greater than the printing duty ratio of the light image forming section. The inkjet printing method includes: a step 1 of applying a pretreatment liquid to an outer edge portion of a portion where a dense image forming portion is formed to obtain a printing medium having a pretreatment liquid applying portion; and a step 2 of applying an ink containing a colorant to a region on the surface of the printing medium obtained in the step 1, said region becoming a dense image forming section, said surface having the pretreatment liquid applying section.

Description

Technical Field

[0001] This invention relates to inkjet printing methods. Background Technology

[0002] Inkjet printing has many advantages, such as eliminating the need for plate making, easily adapting to variable information, and not coming into contact with the printing medium during printing. Therefore, in addition to its applications in office and home use, it has gradually expanded into commercial printing applications with very large print runs in recent years.

[0003] In commercial printing applications, there is a demand for improved image quality not only for low-absorbency printing media such as printing paper, but also for non-absorbent printing media such as resin films. Various solutions have been proposed to address this need.

[0004] For example, Japanese Patent Application Publication No. 2018-126972 (Patent Document 1) discloses an image forming apparatus. Its purpose is to provide an image forming apparatus capable of suppressing the seepage between the image portion and the non-image portion and obtaining an image with high image density. This image forming apparatus includes: a recording medium; an ink containing a coloring material, an organic solvent, and water; a liquid containing an organic solvent and water but without a coloring material; a unit for applying the ink to the recording medium to form an image portion; and a unit for applying the liquid to the non-image portion of the recording medium other than the image portion. The ink has a static surface tension γ at 25°C. A The static surface tension γ of the above liquid at 25°C B To satisfy a specific relationship, the liquid is not applied to the aforementioned image section.

[0005] Furthermore, Japanese Patent Application Publication No. 2009-196274 (Patent Document 2) discloses an inkjet recording method, the purpose of which is to prevent colored ink from bleeding when using any recording medium, whether it is a recording medium with good ink absorption capacity or a recording medium with poor ink absorption capacity. In this inkjet recording method, colored ink containing coloring material is used to record on the recording medium, and transparent ink without coloring material is used to record at the edge of the recording area recorded by the colored ink. The static surface tension and dynamic surface tension of the transparent ink at a lifetime of 100 milliseconds are both lower than those of the colored ink. Summary of the Invention

[0006] This invention relates to an inkjet printing method, wherein the inkjet printing method forms a printed image on a printing medium, the printed image including a dark image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dark image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region.

[0007] The inkjet printing method includes:

[0008] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0009] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has the pretreatment liquid application part, which becomes the concentrated image forming part, using a line-head type inkjet method. Detailed Implementation

[0010] High productivity is required in commercial printing applications, necessitating high-speed printing. To accommodate this high-speed printing, linear array printheads have been developed. While conventional serial printheads involve multiple printhead movements, linear array printheads possess printheads capable of inkjet printing across a width equal to or greater than the length of the printing medium in a direction perpendicular to the transport direction. Therefore, high-speed printing can be achieved simply by scanning the printing medium while the printhead is stationary. However, unlike serial printhead printing, linear array printheads do not repeatedly move back and forth within the printing area. Consequently, they cannot compensate for ink misalignment caused by ejection deviation, leading to the problem of streaks (lines). Furthermore, in printing on low-absorbency printing media, where an image including a dense image forming section and a light image forming section is formed, bleed-through occurs at the boundary between the dense and light image forming sections, resulting in an unclear printed image. However, the technology in Patent Documents 1 and 2 cannot adequately solve this problem. It is hoped that a technology can be developed that can suppress the appearance of streaks even in inkjet printing using a linear array printhead with a low absorbency printing medium (specifically, a resin film), and achieve clarity of the printed image, including both dark and light image forming areas, especially with excellent sharpness for printed images of hollow text.

[0011] This invention relates to an inkjet printing method that, even in inkjet printing using a linear printhead with a low absorbency printing medium, can suppress the appearance of streaks on the resulting printed material and produce a print image with excellent clarity, including both dark and light image forming sections.

[0012] The inventors of this invention have discovered that the above-mentioned technical problems can be solved by the following inkjet printing method, which is an inkjet printing method for forming a printed image including a dark image forming portion and a light image forming portion on a printing medium, wherein the method includes: applying a pretreatment liquid to the outer edge portion of the portion that becomes the dark image forming portion to obtain a printing medium having a pretreatment liquid application portion; and applying ink containing a colorant to the portion of the printing medium obtained in the step that becomes the dark image forming portion on the side having the pretreatment liquid application portion using a linear printhead inkjet method.

[0013] That is, the present invention provides an inkjet printing method, wherein the inkjet printing method forms a printed image on a printing medium, the printed image including a dark image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dark image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region.

[0014] The inkjet printing method includes:

[0015] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0016] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0017] The present invention provides an inkjet printing method that, even in inkjet printing using a linear printhead with a low absorbency printing medium, can suppress the appearance of streaks on the resulting printed material and produce a print image with excellent clarity, including both dark and light image forming sections. Attached Figure Description

[0018] Figure 1 This is an example of a schematic diagram showing a printed image including a dark image forming area and a light image forming area. In the diagram, the solid lines are the boundary lines between the dark image forming area and the light image forming area, the area enclosed by the solid lines represents the light image forming area, and the area enclosed by the solid lines and dotted lines represents the outer edge of the part that becomes the dark image forming area.

[0019] Figure 2This is an example of a schematic diagram showing a printed image including a dark image forming area and a light image forming area. In the diagram, the solid lines are the boundary lines between the dark image forming area and the light image forming area. The area enclosed by the solid lines represents the light image forming area. The area enclosed by the solid lines and the dotted lines represents the outer edge of the part that becomes the dark image forming area. The area enclosed by the solid lines and the dashed lines represents the inner edge of the part that becomes the dark image forming area.

[0020] Figure 3 This is a schematic diagram of a printed image of hollow text formed by a light image forming section (i) (0% printing duty cycle of ink containing colorant) and a dark image forming section (ii) (100% printing duty cycle of ink containing colorant) formed in Examples 1-8, 10-12 and Comparative Examples 1-2.

[0021] Figure 4-a This is an explanatory diagram showing the area where the pretreatment liquid is applied in step 1 of Examples 1 to 10 and 12.

[0022] Figure 4-b This is a diagram illustrating the area where the pretreatment solution is applied in step 1 of Example 11.

[0023] Figure 5 This is an explanatory diagram showing the areas to which the ink containing the colorant is applied in step 2 of Examples 1-12 and Comparative Examples 1-2.

[0024] Figure 6 It is a photograph of the printed image of the hollow text obtained in Example 1.

[0025] Figure 7 It is a photograph of the printed image of the hollow text obtained in Comparative Example 2.

[0026] Figure 8 This is a schematic diagram of a barcode printing image formed in Example 13, consisting of a light image forming section (i) (0% printing duty cycle of ink containing colorant) and a dark image forming section (ii) (100% printing duty cycle of ink containing colorant).

[0027] Figure 9 This is an explanatory diagram showing the area where the pretreatment liquid is applied in step 1 of Example 13.

[0028] Figure 10 It is a photograph of the printed image of the barcode obtained in Example 13.

[0029] [Inkjet printing method]

[0030] The inkjet printing method of the present invention (hereinafter also referred to as "the printing method of the present invention") is an inkjet printing method for forming a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the colorant-containing ink (hereinafter also referred to as "colorant-containing ink") in the dense image forming region is greater than the printing duty cycle of the colorant-containing ink in the light image forming region, and the inkjet printing method includes:

[0031] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0032] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0033] In this invention, "printing" includes the concepts of printing and engraving of text or images.

[0034] According to the printing method of the present invention, even in inkjet printing using a linear array printhead with a low absorbency printing medium, it is possible to suppress streaks on the resulting printed matter, and the clarity of the printed image, including both the dark and light image forming sections, is excellent. The reasons for this are not yet certain, but are believed to be as follows.

[0035] In the printing method of the present invention, a printed image is formed on a printing medium. The printed image includes a dense image forming section and a light image forming section, wherein the printing duty cycle of the colorant-containing ink in the dense image forming section is greater than that in the light image forming section. Furthermore, by including steps 1 and 2, the pretreatment liquid comes into contact with the colorant-containing ink at the boundary between the outer edge of the dense image forming section to which the pretreatment liquid is applied and the boundary of the dense image forming section to which the colorant-containing ink is applied. Therefore, ink wetting and spreading are suppressed, and ink penetration at the boundary between the light and dense image forming sections is suppressed, thereby improving the clarity of the printed image including both the dense and light image forming sections. Specifically: Step 1 involves applying pretreatment liquid to the outer edge of the portion forming the dense image forming section to obtain a printing medium having a pretreatment liquid application portion; Step 2 involves applying colorant-containing ink to the portion of the printing medium obtained in Step 1 that has the pretreatment liquid application portion, which forms the dense image forming section, using a linear printhead inkjet method.

[0036] On the other hand, in this invention, the pretreatment liquid is not applied to the entire surface of the printing medium. When the pretreatment liquid is applied to the entire surface of the printing medium, the dense image forming area or the light image forming area is printed using a linear printhead with colorant-containing ink. This suppresses the wetting and spreading of the pretreatment liquid applied to the dense and light image forming areas, making the aforementioned stripes more noticeable. However, in this invention, most of the dense and light image forming areas are not treated with pretreatment liquid, thus reducing the likelihood of stripes appearing. Furthermore, the effect of the pretreatment liquid is better displayed at the boundary between the dense and light image forming areas. As a result, both the suppression of stripe appearance and the improvement of the clarity of the printed image, including both the dense and light image forming areas, can be achieved simultaneously.

[0037] The inkjet printing method of the present invention is a method for forming a printed image on a printing medium, the printed image including a dark image forming section and a light image forming section, wherein the printing duty cycle of the colorant-containing ink in the dark image forming section is greater than the printing duty cycle of the colorant-containing ink in the light image forming section.

[0038] In this invention, "printing duty cycle of colorant-containing ink" refers to the proportion of area occupied by colorant-containing ink within a specified area on the printing medium, that is, the ratio of the cumulative area to which colorant-containing ink is applied. For example, "printing duty cycle of colorant-containing ink 100%" in this invention means that when ink droplets are applied to the area to which colorant-containing ink is applied in a square grid pattern without intervals, the ink droplets are applied in such a way that the ends of adjacent ink dots that expand circularly on the printing medium are in contact with each other at the circumferential position, forming the distance between the dots. For example, a dense image forming section with a "printing duty cycle of colorant-containing ink" of 100% refers to a fully coated printing section. On the other hand, "printing duty cycle of colorant-containing ink 0%" in this invention means that no ink is applied to a specified area on the printing medium. For example, a light image forming section with a "printing duty cycle of colorant-containing ink" of 0% refers to a non-printing section.

[0039] From the viewpoint of achieving a clear outline of the dense image forming portion and forming a high-quality printed image, the printing duty cycle of the colorant-containing ink in the dense image forming portion is preferably greater than 50%, more preferably 70% or more, further preferably 90% or more, and even more preferably 100%. From the viewpoint of obtaining a printed image with hollow text, the printing duty cycle of the colorant-containing ink in the dense image forming portion is preferably 100%.

[0040] From the viewpoint of achieving clear outlines in the dark image forming area and forming a high-quality printed image, the printing duty cycle of the colorant-containing ink in the light image forming area is 0% or more, and preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less. From the viewpoint of obtaining a printed image with hollow text, the printing duty cycle of the colorant-containing ink in the light image forming area is preferably 0%.

[0041] Regarding the difference between the printing duty cycle of the colorant-containing ink in the dense image forming section and the printing duty cycle of the colorant-containing ink in the light image forming section, from the viewpoint of ensuring clear outlines of the dense image forming section and forming a high-quality printed image, it is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. From the viewpoint of obtaining a printed image with hollow text, the difference between the printing duty cycle of the colorant-containing ink in the dense image forming section and the printing duty cycle of the colorant-containing ink in the light image forming section is preferably 100%.

[0042] In this invention, the printed images formed can include images such as hollow text, barcodes and other one-dimensional codes, matrix or stacked two-dimensional codes, and extremely small text.

[0043] In this invention, "image of hollow text" refers to an image in which text can be recognized using a light image forming part of a color other than the first color, against a background of a dark image forming part formed by inkjet printing of a first color.

[0044] At this point, the first color and other colors besides the first color can be primary colors such as yellow, magenta, cyan, and black, or they can be mixtures of these primary colors, i.e., secondary colors.

[0045] From the viewpoint of suppressing stripes on the resulting printed material and improving the clarity of the printed image, hollow text images are preferred as the formed printed image.

[0046] <Process 1>

[0047] Step 1 is a process of applying a pretreatment liquid to the outer edge of the area that becomes the concentrated image forming section, thereby obtaining a printing medium having a pretreatment liquid application section.

[0048] In this invention, such as Figure 1 As shown, the outer edge of the region that forms the dark image region belongs to the light image region in the formed printed image.

[0049] From the perspective of practicality in preventing ejection deviation or misalignment of the printing medium, and from the perspective of suppressing streaks on the resulting printed material and improving the clarity of the printed image, the outer edge of the region that forms the dense image region is preferably the following area: a region located at a distance of 0.01 mm or more, more preferably 0.1 mm or more, further preferably 0.2 mm or more, and preferably 1 mm or less, more preferably 0.7 mm or less, and further preferably 0.4 mm or less, measured from the boundary line between the dense image region and the light image region.

[0050] Regarding the application of the pretreatment liquid in step 1, it is sufficient to apply it only to the outer edge of the portion of the printed image that forms a dense image, but it is also permissible to apply it to the entire light image forming portion, including the outer edge of the portion forming a dense image. In the printing method of the present invention, regarding the application of the pretreatment liquid in step 1, it is preferable to apply it only to the outer edge of the portion forming a dense image. When the printing duty cycle of the colorant-containing ink in the light image forming portion is 0%, it is more preferable to apply the pretreatment liquid in step 1 only to the outer edge of the portion forming a dense image.

[0051] Regarding the application of the pretreatment liquid in step 1, if the printing duty cycle of the colorant-containing ink in the light image forming section exceeds 0%, it is possible to apply the ink not only to the outer edge of the section that becomes the dark image forming section, but also to the portion of the section that becomes the light image forming section where the colorant-containing ink has not been applied. Furthermore, in this case, in step 2 described later, the portion of the printing medium obtained in step 1 that has the side with the pretreatment liquid application section and becomes the light image forming section where the colorant-containing ink has been applied is treated with the colorant-containing ink using a linear printhead inkjet method.

[0052] Furthermore, when the printing duty cycle of the colorant-containing ink in the light image forming section exceeds 0%, the "partial not assigned to colorant-containing ink" refers to the non-output portion of the raster image data used to output the colorant-containing ink. For example, when the printing duty cycle of the colorant-containing ink in the light image forming section is 40%, the "partial not assigned to colorant-containing ink" refers to the non-output portion of the colorant-containing ink that accounts for 60% of the raster image used to output the colorant-containing ink in that light image forming section.

[0053] In step 1, from the viewpoint of suppressing stripes on the obtained printed material and improving the clarity of the printed image, it is preferable to: (1) not apply the pretreatment liquid to the area that forms a dense image; or, (2) if the pretreatment liquid is applied to the area that forms a dense image, further apply the pretreatment liquid to the inner edge portion of the area that forms a dense image, but not apply the pretreatment liquid to the dense image forming portion other than the inner edge portion of the area that forms a dense image. In the case of (2) above, the positional shift between the pretreatment liquid application portion formed in step 1 and the ink-attached portion containing colorant ink formed in step 2 can be suppressed, and the clarity of the printed image can be improved even for fine printed images.

[0054] In this invention, such as Figure 2 As shown, in the formed printed image, the inner edge of the part that becomes the dense image forming part belongs to the dense image forming part.

[0055] From the perspective of practicality in preventing ejection deviation or misalignment of the printing medium, as well as the viewpoint of suppressing positional shift of the inked portion of the ink containing colorant and further improving the clarity of the printed image, the inner edge portion of the part that forms the dense image is preferably the following region: a region that, measured from the boundary line between the dense image and the light image, is located away from the light image on the side preferably 0.01 mm or more, more preferably 0.1 mm or more, even more preferably 0.2 mm or more, and preferably 1 mm or less, more preferably 0.7 mm or less, and even more preferably 0.4 mm or less.

[0056] (Printing media)

[0057] As the printing medium used in this invention, either a low-absorbency printing medium or a high-absorbency printing medium can be used. From the viewpoint of suppressing the appearance of stripes on the obtained print and the clarity of the printed image, a low-absorbency printing medium is preferred.

[0058] In this invention, the water absorption of the printing medium when the contact time between the printing medium and pure water is 100 milliseconds can be used to determine whether the printing medium has low or high water absorption. The method for measuring the water absorption is as follows: using an automatic scanning absorbent meter (for example, "KM500win" manufactured by Kumagai Riki Kogyo Co., Ltd.), under conditions of 23°C and 50% relative humidity, the amount of water transferred when the contact time with pure water is 100 milliseconds is measured, and this amount is taken as the water absorption.

[0059] In this invention, "low absorbency" is a concept that includes both low absorbency and non-absorbency, meaning that the water absorption is 0 g / m³. 2 Above 7g / m 2Hereafter, "high absorbency" means that the water absorption capacity exceeds 7g / m³. 2 .

[0060] Examples of low-absorbency printing media include low-absorbency coated paper and non-absorbent resin film. Examples of coated paper include general-purpose glossy paper and multi-color foam glossy paper. As for the resin film, at least one selected from polyester film, polyvinyl chloride film, polypropylene film, and polyethylene film is preferred, and polyester film is more preferred. Films that have undergone surface treatment such as corona treatment can be used as these resin films.

[0061] As a highly absorbent printing medium, highly absorbent ordinary paper can be cited as an example.

[0062] When using a resin film as a low-absorbency printing medium, during step 1, the printing image can be set as follows: based on a mirror image obtained by inverting the desired printing image, the areas for forming a dense image and the areas for forming a light image are set, so that the target image can be seen when viewed from the opposite side of the printing image forming surface of the non-absorbent film.

[0063] (Pretreatment solution)

[0064] <Component A that inhibits wetting and spreading>

[0065] The pretreatment liquid involved in this invention preferably contains component (A) that inhibits the wetting and spreading of the colorant-containing ink used in step 2 on the printing medium (hereinafter sometimes simply referred to as "component (A) that inhibits wetting and spreading").

[0066] It can be considered that since the pretreatment liquid involved in the present invention contains a component (A) that inhibits wetting and spreading, at the boundary between the outer edge of the concentrated image forming part to which the pretreatment liquid is applied and the boundary of the concentrated image forming part to which the colorant ink is applied, the component (A) that inhibits wetting and spreading can inhibit the entry of the colorant ink into the light image forming part, can inhibit the penetration of ink at the boundary between the light image forming part and the concentrated image forming part, and can improve the clarity of the printed image including the concentrated image forming part and the light image forming part.

[0067] In this invention, the component (A) for inhibiting wetting and spreading is preferably selected from one or more of an agglutinating compound (A1) and a hydrophobic compound (A2). That is, the pretreatment solution according to this invention preferably contains one or more of an agglutinating compound (A1) and a hydrophobic compound (A2). These will be described below.

[0068] [Agglutinating compound (A1)]

[0069] In this invention, "agglomerating compound (A1)" refers to a component that, when applied to a printing medium, causes the dispersed matter present in the colorant-containing ink to agglomerate due to reduced dispersibility, or causes a decrease in the solubility of the solute, thereby leading to thickening or precipitation in the ink and inhibiting the ink from entering the light image forming section. In this invention, the dispersed matter present in the colorant-containing ink refers to ink components such as pigments that are actually dispersed in the ink in a solid state. Furthermore, the solute present in the colorant-containing ink refers to a component that is dissolved in the ink, but whose solubility is impaired upon contact with a printing medium treated with a pretreatment solution, resulting in thickening or precipitation. Specific examples of components (solutes) that are dissolved in the colorant-containing ink but whose solubility is impaired upon contact with a printing medium treated with a pretreatment solution, resulting in thickening or precipitation, include dyes and water-soluble resins.

[0070] Examples of agglutinating compounds (A1) include metal salts, acids or their salts, and cationic compounds. Agglutinating compounds (A1) can be used alone or in combination of two or more.

[0071] Examples of metal salts include monovalent metal salts and divalent or higher metal salts. Examples of acids include organic acids and inorganic acids. Examples of cationic compounds include cationic resins and cationic surfactants. Among these, the agglomerating compound (A1) is more preferably selected from one or more of metal salts, acids or their salts, and cationic resins.

[0072] (metal salt)

[0073] From the viewpoint of suppressing streaks on the resulting printed material and improving the clarity of the printed image, the metal salt used as the agglomerative compound (A1) is preferably a multivalent metal salt.

[0074] For polyvalent metal salts, any salt can be used as long as it consists of a divalent or higher polyvalent metal ion and an anion (the balance ion of the polyvalent metal ion). Examples of divalent or higher polyvalent metal ions include ions of calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, and iron. Among these, from the viewpoint of suppressing streaks on the obtained printed material and improving the clarity of the printed image, divalent or trivalent metal ions are preferred, and divalent metal ions are more preferred. Examples of divalent metal ions include ions of elements belonging to Group 2 of the periodic table, specifically magnesium ions, calcium ions, and ferrous (II) ions. Examples of trivalent metal ions include aluminum ions and iron (III) ions. Among these, from the viewpoint of suppressing streaks on the obtained printed material and improving the clarity of the printed image, it is further preferred to select one or more of magnesium ions, calcium ions, and aluminum ions, even more preferably one or more of magnesium ions and calcium ions, and even more preferably calcium ions.

[0075] Anions that are polyvalent metal salts can be either inorganic or organic ions.

[0076] As inorganic ions, examples include monovalent anions such as nitrate ions and halide ions, and divalent anions such as sulfate ions.

[0077] As organic ions, examples include carboxylate ions and other organic acid ions.

[0078] Among these, the anion is preferably an inorganic ion, more preferably one or more selected from nitrate ions and sulfate ions, and even more preferably nitrate ions.

[0079] From the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, the polyvalent metal salt is preferably selected from one or more of magnesium nitrate, magnesium sulfate, calcium nitrate and aluminum nitrate, more preferably selected from one or more of magnesium nitrate, calcium nitrate and aluminum nitrate, even more preferably selected from one or more of magnesium nitrate and calcium nitrate, and even more preferably calcium nitrate.

[0080] Polyvalent metal salts can also contain hydrated water in their raw material form.

[0081] Regarding polyvalent metal salts, one type can be used alone, or two or more types can be used in combination.

[0082] (acid)

[0083] As an acid used as a condensing compound (A1), one or more can be selected from organic acids and inorganic acids.

[0084] Examples of organic acids include aliphatic carboxylic acids, aliphatic dicarboxylic acids, hydroxycarboxylic acids, heterocyclic carboxylic acids, derivatives of these compounds, and their salts.

[0085] Examples of aliphatic carboxylic acids include formic acid and acetic acid.

[0086] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, and fumaric acid.

[0087] Examples of hydroxycarboxylic acids include glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid.

[0088] Examples of heterocyclic carboxylic acids include ascorbic acid, pyrrolidone carboxylic acid, pyranocarboxylic acid, pyrrolic carboxylic acid, furanocarboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, and nicotinic acid.

[0089] Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

[0090] Among these, from the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, the acid is preferably an organic acid or its salt, more preferably an aliphatic dicarboxylic acid or its salt, further preferably one or more selected from oxalic acid, malonic acid and succinic acid, and even more preferably malonic acid.

[0091] Regarding acids, one type can be used alone, or two or more can be used in combination.

[0092] These acids can also form salts, but if the acid forms a metal salt, it is included in the metal salts mentioned above.

[0093] (Catonic resin)

[0094] Examples of cationic compounds used as agglutinating compounds (A1) include cationic resins and cationic surfactants.

[0095] Cationic resins preferably have cationic groups.

[0096] In this invention, "cationic group" refers to a cationic group or a group that can be ionized to become a cationic group. Examples of cationic groups include primary amino (-NH2), secondary amino (-NHR, =NH (imino)), tertiary amino (-NRR'), quaternary ammonium, and hydrazine groups. From the viewpoint of suppressing streaks on the obtained printed material and improving the clarity of the printed image, the cationic resin preferably has one or more selected from primary amino, secondary amino, tertiary amino, and quaternary ammonium groups, and more preferably has a quaternary ammonium group.

[0097] In addition, basic groups include those that are neutralized by acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, and lactic acid.

[0098] Regarding cationic resins, one type can be used alone, or two or more types can be used in combination.

[0099] Regarding the cationicity of the cationic resin, from the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, it is preferably 0.5 meq / g or more, more preferably 3.0 meq / g or more, and more preferably 10 meq / g or less. The cationicity of the cationic resin can be determined by colloidal titration using potassium polyvinyl sulfate reagent.

[0100] Examples of cationic resins include cationic vinyl resins, cationic olefin resins, cationic polyurethane resins, and cationic amine resins.

[0101] Examples of cationic vinyl resins include vinyl resins containing structural units derived from vinyl monomers having cationic groups.

[0102] Preferred examples of vinyl monomers having cationic groups include: quaternary ammonium salts of alkyl (meth)acrylates, quaternary ammonium salts of alkyl (meth)acrylamides, (meth)acrylates having dialkylamino groups, (meth)acrylamides having dialkylamino groups, styrene monomers having dialkylamino groups, amino heterocyclic vinyl monomers, and allylamine compounds.

[0103] Examples of alkyl (meth)acrylate quaternary ammonium salts include: (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyltriethylammonium chloride, (meth)acryloyloxyethyldimethylbenzylammonium chloride, (meth)acryloyloxyethylmethylmorpholinoammonium chloride, and 2-hydroxy-3-(meth)acryloyloxypropyltrimethylammonium chloride.

[0104] Examples of alkyl (meth)acrylamide quaternary ammonium salts include: (meth)acryloylaminoethyl triethylammonium chloride, (meth)acryloylaminoethyl dimethyl benzylammonium chloride, etc.

[0105] Examples of (meth)acrylates containing dialkylamino groups include: trimethyl[(vinylphenyl)methyl]ammonium chloride, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, diisopropylaminoethyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, diisobutylaminoethyl (meth)acrylate, ditert-butylaminoethyl (meth)acrylate, and so on.

[0106] Examples of (meth)acrylamides containing dialkylamino groups include: dimethylaminopropyl (meth)acrylamides, diethylaminopropyl (meth)acrylamides, dipropylaminopropyl (meth)acrylamides, diisopropylaminopropyl (meth)acrylamides, dibutylaminopropyl (meth)acrylamides, diisobutylaminopropyl (meth)acrylamides, di-tert-butylaminopropyl (meth)acrylamides, etc.

[0107] Examples of styrene containing dialkylamino groups include dimethylaminostyrene and dimethylaminomethylstyrene.

[0108] Examples of amino-containing heterocyclic vinyl monomers include N-vinylpyrrolidone, N-vinylpyrrolidone, and N-vinylcarbazole.

[0109] Examples of allylamine compounds include allylamine, dimethylallylamine, diallylamine, and methyldiallylamine.

[0110] Cationic vinyl resins can also be resins containing structural units derived from other monomers (i.e., monomers other than vinyl monomers having cationic groups).

[0111] Other monomers that can be listed include, for example, alkyl (meth)acrylic acid monomers, oxidized olefin (meth)acrylic acid monomers, oxidized olefin (meth)acrylic acid monomers, and aromatic ring (meth)acrylic acid monomers.

[0112] Examples of styrene monomers include styrene and α-methylstyrene.

[0113] Examples of alkyl (meth)acrylic acid monomers include: methyl methacrylate, butyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, etc.

[0114] Examples of monomers containing oxidized olefin chains (meth)acrylic acids include: (poly)ethylene glycol mono(meth)acrylate, (poly)propylene glycol mono(meth)acrylate, (poly)(ethylene glycol-propylene glycol) mono(meth)acrylate, etc.

[0115] Examples of monomers containing aromatic rings (meth)acrylic acids include phenyl methacrylate, benzyl methacrylate, and ethyl methacrylate phenoxyethyl ester.

[0116] Among these, from the viewpoint of suppressing streaks on the resulting printed matter and improving the clarity of the printed image, cationic vinyl resins are preferably polyallylamine resins with a structure derived from allylamine compounds in the main skeleton.

[0117] Examples of polyallylamine resins include homopolymers or copolymers of the aforementioned allylamine compounds.

[0118] Specific examples of polyallylamine resins include: polyallylamine hydrochloride, polyallylamine amide sulfate, allylamine hydrochloride / diallylamine hydrochloride copolymer, allylamine acetate / diallylamine acetate copolymer, allylamine acetate / diallylamine acetate copolymer, allylamine hydrochloride / dimethylallylamine hydrochloride copolymer, allylamine / dimethylallylamine copolymer, polydiallylamine hydrochloride, polymethyldiallylamine hydrochloride, polymethyldiallylamine amide sulfate, polymethyldiallylamine acetate, polydiallyldimethylammonium chloride, diallylamine acetate / sulfur dioxide copolymer, diallyl methyl ethyl ammonium ethyl sulfate / sulfur dioxide copolymer, methyldiallylamine hydrochloride / sulfur dioxide copolymer, diallyl dimethyl ammonium chloride / sulfur dioxide copolymer, diallyl dimethyl ammonium chloride / acrylamide copolymer, etc.

[0119] Regarding cationic vinyl resins, resins synthesized by known methods or commercially available products can be used. Examples of commercially available cationic vinyl resins include diallyl dimethyl ammonium chloride polymers such as PAS-H-1L (manufactured and traded by NITTOBO MEDICAL CO.,LTD.).

[0120] Cationic olefin resins are resins with structural units derived from olefins such as ethylene and propylene as their basic framework, and well-known products can be appropriately selected and used. Furthermore, cationic olefin resins can be used in emulsion form dispersed in a medium containing water or organic solvents. Commercially available cationic olefin resins can be used. Examples of commercially available cationic olefin resins include Arrow Base CB-1200 and the related CD-1200 (both manufactured and traded by Unitika Ltd.).

[0121] Examples of cationic polyurethane resins include: a polyurethane prepolymer obtained by reacting the isocyanate group of an organic compound (polyol) having two or more alcoholic hydroxyl groups in one molecule with a polyisocyanate through an addition polymerization reaction, and then reacting the isocyanate group with an active hydrogen compound used to introduce a cationic hydrophilic group. In the above addition polymerization reaction, a chain extender or a reaction terminator can be used as needed. By using a chain extender, the molecular weight can be further increased. Examples of chain extenders include polyols or polyamines; examples of reaction terminators include monohydric alcohols or monoamines.

[0122] Cationic polyurethane resins are preferably used in the form of emulsions, which may contain dispersants such as surfactants as needed.

[0123] The preferred cationic polyurethane resins are cationic polycarbonate polyol polyurethane resins, cationic polyester polyol polyurethane resins, and cationic polyether polyol polyurethane resins.

[0124] Commercially available cationic polyurethane resins can be used. These include HYDRAN CP-7010, CP-7020, CP-7030, CP-7040, CP-7050, CP-7060, and CP-7610 (all manufactured and traded by DIC Corporation); SUPERFLEX 600, 610, 620, 630, 640, and 650 (all manufactured and traded by Daiichi Kogyo Pharmaceutical Co., Ltd.); and Urethane emulsion WBR-2120C and WBR-2122C (all manufactured and traded by TAISEI FINE CHEMICAL CO., LTD.).

[0125] Examples of cationic amine resins include polyamine resins and polyamide resins.

[0126] Polyamine resin is a resin whose main skeleton contains amino groups.

[0127] Examples of polyamine resins include: polyalkylene imine, polyethylene polyamine, condensates of alkylamines and epoxy halides, and condensates of alkylamines / ammonia / epoxy halides.

[0128] Polyamide resin is a resin whose main skeleton contains amide groups.

[0129] As a cationic amine resin, commercially available products can be used.

[0130] Commercially available cationic amine resins include: UNISENCE KHE103L (hexamethylenediamine / epoxychloropropane condensate), and KHE104L (dimethylamine / epoxychloropropane condensate, 20% by mass aqueous solution) (all manufactured by SENKA Corporation, trade names); FL-14 (manufactured by SNF Corporation, trade name); ARAFIX 100, 251S, 255, and 255LOX (all manufactured by Arakawa Chemical Industries, Ltd.). Modified polyamine resins such as DK6810, DK6853, and DK6885; polyamide epichlorohydrin resins or polyamine epichlorohydrin resins such as WS4010, WS4011, WS4020, WS4024, WS4027, and WS4030 (all of which are manufactured and traded by Chemipaz Corporation); dimethylamine / ammonia / epoxychlorohydrin condensates such as PAPYOGEN P-105 (manufactured and traded by SENKA Corporation); polyamide epoxy resins such as Sumirez Resin 650 (30), 675A, 6615, and SLX-1 (all of which are manufactured and traded by Taoka Chemical Co., Ltd.); Catiomaster PD-1, PD-7 (dimethylamine / epoxychloropropane condensate), Catiomaster PD-30, A (a related series), PDT-2 (a related series), PE-10 (a related series), PE-30 (dimethylamine / ethylenediamine / epoxychloropropane condensate), DT-EH, EPA-SK01 (polyamide / polyamine / epoxychloropropane condensate), TMHMDA-E (all of the above are manufactured and traded by Yokkaichi Chemical Company Limited); Jetfix 36N, 38A (a related series), 5052 (all of the above are manufactured and traded by Satoda Chemical Industrial Co., Ltd.).

[0131] (Catonic surfactants)

[0132] Cationic surfactants can be listed as examples of cationic compounds used as agglutinating compounds (A1). In this invention, a "cationic surfactant" refers to a compound having both a hydrophobic group and a cationic group that is a hydrophilic group, and which does not have a repeating structure derived from a monomer.

[0133] Preferred examples of hydrophobic groups in cationic surfactants include alkyl groups with 10 to 22 carbon atoms.

[0134] Examples of cationic surfactants include alkylamine salts and alkyl quaternary ammonium salts.

[0135] Examples of alkylamine salts include laurylamine acetate and stearamine acetate.

[0136] Examples of alkyl quaternary ammonium salts include alkyl trimethyl ammonium salts, dialkyl dialkyl ammonium salts, and alkyl benzyl dimethyl ammonium salts.

[0137] Among these, the cationic surfactant is preferably an alkyl quaternary ammonium salt, more preferably an alkyltrimethylammonium chloride having an alkyl group having 10 or more but less than 22 carbon atoms.

[0138] [Hydrophobic compound (A2)]

[0139] In this invention, "hydrophobic compound (A2)" refers to a compound containing a hydrophobic structure. Although this compound does not cause thickening or precipitation of the colorant-containing ink, at the boundary between the outer edge of the concentrated image forming section to which the pretreatment liquid is applied and the boundary of the concentrated image forming section to which the colorant-containing ink is applied, the hydrophobic structure has low affinity for the ink, thereby inhibiting the penetration of the ink into the light image forming section.

[0140] The hydrophobic compound (A2) is preferably selected from one or more of anionic resins and hydrophobic surfactants.

[0141] (Anionic resin)

[0142] The term "anionic resin" used as the hydrophobic compound (A2) refers to a resin whose solubility is less than 10g when an anionic resin that has been dried at 105°C for 2 hours to reach constant weight is dissolved in 100g of water at 25°C to reach saturation. Furthermore, when the anionic resin has anionic groups and these anionic groups are neutralized by a neutralizing agent, the solubility is determined based on the presence of the neutralizing agent, provided that the mass ratio of the anionic resin to the neutralizing agent is the same as the mass ratio in the pretreatment solution.

[0143] From the viewpoint of compatibility and dispersion stability in the pretreatment solution, anionic resins are preferably resins having anionic groups.

[0144] In this invention, "anionic group" refers to an anionic group or a group that can be ionized to become an anionic group. Examples of anionic groups include carboxyl groups (-COOM), sulfonic acid groups (-SO3M), and phosphate groups (-OPO3M2). In the above chemical formulas, M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium. Among these, the anionic resin preferably has a carboxyl group as the anionic group, and M is preferably ammonium.

[0145] Examples of anionic resins include anionic vinyl resins, anionic polyurethane resins, and anionic silicone resins.

[0146] Regarding anionic resins, one type can be used alone, or two or more types can be used in combination.

[0147] Anionic vinyl resins are preferably vinyl resins containing structural units derived from vinyl monomers having anionic groups.

[0148] As a vinyl monomer having an anionic group, it is preferably selected from one or more of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and citraconic acid, more preferably selected from one or more of acrylic acid and methacrylic acid, and even more preferably acrylic acid.

[0149] The anionic vinyl resin can be either a homopolymer or a copolymer, preferably a vinyl resin that contains structural units derived from hydrophobic vinyl monomers in addition to structural units derived from vinyl monomers having anionic groups.

[0150] As hydrophobic vinyl monomers, preferably one or more are selected from alkyl (meth)acrylates having a straight-chain, branched, or cyclic alkyl group having 1 to 22 carbon atoms, aryl (meth)acrylates having an aryl group having 6 to 22 carbon atoms, and styrene monomers.

[0151] As an alkyl ester of (meth)acrylate having 1 to 22 carbon atoms, preferred examples include: alkyl esters of (meth)acrylate having straight-chain or branched alkyl groups selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, and stearyl methacrylate; and cycloalkyl esters of (meth)acrylate selected from cyclopentyl methacrylate, cyclohexyl methacrylate, and cycloheptyl methacrylate.

[0152] As an aryl (meth)acrylate having an aryl group having 6 to 22 carbon atoms, examples preferably include, for example, one or more selected from phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate.

[0153] As a styrene monomer, preferably one or more selected from styrene, α-methylstyrene, vinyltoluene, and vinylnaphthalene are listed.

[0154] Among these, the hydrophobic vinyl monomer is more preferably selected from one or more of straight-chain or branched alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and styrene monomers having 1 to 8 carbon atoms, and is even more preferably selected from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, styrene, and α-methylstyrene.

[0155] The content of vinyl monomers having anionic groups in the raw material monomers constituting the anionic vinyl resin, or the content of structural units derived from vinyl monomers having anionic groups in the anionic vinyl resin, is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 36% by mass or less, further preferably 32% by mass or less.

[0156] The content of hydrophobic vinyl monomers in the raw material monomers constituting the anionic vinyl resin, or the content of structural units derived from hydrophobic vinyl monomers in the anionic vinyl resin, is preferably 60% by mass or more, more preferably 64% by mass or more, and even more preferably 68% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0157] From the viewpoint of suppressing streaks on the obtained printed material and improving the clarity of the printed image, anionic vinyl resins preferably have a cross-linked structure. As an anionic vinyl resin with a cross-linked structure, from the same viewpoint as above, it is preferable to obtain a resin by reacting an anionic vinyl resin (which comprises structural units derived from vinyl monomers having anionic groups and structural units derived from hydrophobic vinyl monomers) with a cross-linking agent. In this case, the anionic vinyl resin with a cross-linked structure includes, in addition to the structural units derived from vinyl monomers having anionic groups and structural units derived from hydrophobic vinyl monomers, a structure derived from the cross-linking agent.

[0158] From the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, a polyglycidyl ether compound of a polyol having a hydrocarbon group having 3 to 8 carbon atoms is preferred as a crosslinking agent. More preferably, it is selected from one or more of pentaerythritol polyglycidyl ether and trimethylolpropane polyglycidyl ether. Trimethylolpropane polyglycidyl ether is even more preferred.

[0159] The crosslinking rate of the anionic vinyl resin having a crosslinked structure is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less. Regarding the crosslinking rate of the anionic vinyl resin having a crosslinked structure, when the anionic vinyl resin (which comprises structural units derived from vinyl monomers having anionic groups and structural units derived from hydrophobic vinyl monomers) is reacted with a crosslinking agent, the crosslinking rate is calculated based on the equivalent amount of anionic groups in the anionic vinyl resin before crosslinking and the equivalent amount of crosslinking functional groups in the crosslinking agent, and is expressed as "the molar equivalent number of crosslinking functional groups in the crosslinking agent / the molar equivalent number of anionic groups in the anionic vinyl resin before crosslinking".

[0160] Anionic vinyl resins can be either appropriately synthesized products or commercially available products. Anionic vinyl resins can be manufactured by copolymerizing the raw material monomers using known polymerization methods.

[0161] Anionic vinyl resins are preferably used in the form of dispersions.

[0162] The acid value of the anionic vinyl resin is preferably 40 mg KOH / g or more, more preferably 80 mg KOH / g or more, even more preferably 100 mg KOH / g or more, and even more preferably 120 mg KOH / g or more. It is also preferably 320 mg KOH / g or less, more preferably 280 mg KOH / g or less, even more preferably 240 mg KOH / g or less, and even more preferably 200 mg KOH / g or less.

[0163] The weight-average molecular weight of the anionic vinyl resin is preferably 5,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and preferably 3,000,000 or less, more preferably 1,000,000 or less, even more preferably 200,000 or less.

[0164] The acid value and weight-average molecular weight of the anionic vinyl resin can be determined according to the methods described in the examples. Furthermore, the acid value of the anionic vinyl resin can also be calculated based on the mass ratio of the constituent monomers. In the case where the anionic vinyl resin has a crosslinked structure, the acid value of the anionic vinyl resin can also be calculated based on the mass ratio of the constituent monomers to the crosslinking agent.

[0165] Anionic polyurethane resins possess structural units derived from organic compounds (polyols) having two or more alcoholic hydroxyl groups in a single molecule, structural units derived from polyisocyanates, and structural units derived from dialkyl carboxylic acids. Anionic polyurethane resins are obtained by addition polymerization of polyols, polyisocyanates, and dialkyl carboxylic acids.

[0166] As the polyol constituting the anionic polyurethane resin, there are no particular restrictions on any compound having two or more alcoholic hydroxyl groups in one molecule. Polycarbonate polyols, polyester polyols, and polyether polyols are preferred, and polycarbonate polyols and polyester polyols are more preferred. That is, the anionic polyurethane resin is preferably a polycarbonate-based polyurethane or a polyester-based polyurethane.

[0167] Polycarbonate polyols are compounds obtained by reacting carbonate compounds with diols, i.e., diols with carbonate structures.

[0168] Examples of carbonate compounds include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, and diethylene carbonate.

[0169] Examples of diols include: aliphatic diols that can be substituted by lower alcohols; alicyclic diols such as cyclohexanediol and hydrogenated xylenediol; and aromatic diols such as xylenediol. Among these, aliphatic diols are preferred, and aliphatic diols with a carbon chain length of 4 to 9 are more preferred, such as 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, heptanediol, octanediol, and nonanediol.

[0170] Polyester polyols are compounds obtained by condensing low-molecular-weight diols with dicarboxylic acids, i.e., diols with ester structures.

[0171] Examples of low-molecular-weight diols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and 1,4-butanediol, which have 2 to 6 carbon atoms. Among these, ethylene glycol, propylene glycol, and 1,4-butanediol are preferred.

[0172] Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, and brassylic acid; and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. Among these, aliphatic dicarboxylic acids are preferred, and dicarboxylic acids such as adipic acid, pimelic acid, octanoic acid, azelaic acid, and sebacic acid with a methylene chain length of 4 to 8 are more preferred.

[0173] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0174] Examples of polyisocyanates that constitute anionic polyurethane resins include: chain-like aliphatic diisocyanates, aliphatic diisocyanates with cyclic structures, aliphatic diisocyanates with aromatic rings, aromatic diisocyanates, and modified forms of these diisocyanates (such as those containing carbodiimide, ureadione, urea-ketoneimide, etc.).

[0175] Examples of chain-like aliphatic diisocyanates include: tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0176] Examples of aliphatic diisocyanates with cyclic structures include isophorone diisocyanate, hydrogenated xylene diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

[0177] Examples of aliphatic diisocyanates with aromatic rings include xylene diisocyanate and tetramethylxylene diisocyanate.

[0178] Examples of aromatic diisocyanates include toluene diisocyanate and diphenylmethane diisocyanate.

[0179] Among these, preferably one or more are selected from aliphatic diisocyanates and aromatic diisocyanates.

[0180] Examples of dialkyl carboxylic acids that constitute anionic polyurethane resins include dimethylolbutyric acid, dimethylolpropionic acid, and their salts.

[0181] Anionic polyurethane resins can be obtained by using chain extenders or reaction terminators as needed. By using chain extenders, the molecular weight can be further increased. Examples of chain extenders include polyols or polyamines; examples of reaction terminators include monohydric alcohols or monoamines.

[0182] Anionic polyurethane resins are preferably used in the form of emulsions, which may contain dispersants such as surfactants as needed.

[0183] The acid value of the anionic polyurethane resin is preferably 3 mg KOH / g or more, more preferably 5 mg KOH / g or more, and even more preferably 7 mg KOH / g or more. It is also preferably 50 mg KOH / g or less, more preferably 40 mg KOH / g or less, and even more preferably 35 mg KOH / g or less.

[0184] Anionic silicone resins are resins that possess both silicone structures and anionic groups in their structure. The silicone structure can exist within the main chain of the resin or as a side chain.

[0185] In this invention, when an anionic resin has not only a silicone structure but also a polyurethane structure or a vinyl structure, if the resin structure has a silicone structure, it is classified as an anionic silicone resin.

[0186] Examples of commercially available anionic silicone resins include CHALINE FE-230N (silicone / acrylic graft polymerization type, aqueous emulsion, acid value: 7.7 mg KOH / g), CHALINE FE-502 (silicone / acrylic graft polymerization type, aqueous emulsion, acid value: 17.3 mg KOH / g), and CHALINE RU-911 (blended type (formulated polyurethane), acid value: 2.2 mg KOH / g), all manufactured by Nissin Chemical Industries, Ltd.

[0187] The acid value of the anionic silicone resin is preferably 2 mg KOH / g or more, more preferably 4 mg KOH / g or more, and even more preferably 6 mg KOH / g or more. It is also preferably 20 mg KOH / g or less, more preferably 10 mg KOH / g or less, and even more preferably 5 mg KOH / g or less.

[0188] (Hydrophobic surfactant)

[0189] The term "hydrophobic surfactant" as used in the context of hydrophobic compound (A2) refers to a surfactant that does not form a single phase when mixed with ion-exchanged water at a mass ratio of 1:1 at 25°C. However, cationic surfactants that meet this condition are not included in the category of hydrophobic surfactants.

[0190] As the hydrophobic surfactant used as the hydrophobic compound (A2), a nonionic surfactant is preferred. Among the nonionic hydrophobic surfactants, one or more selected from acetylenic diol surfactants and silicone surfactants are preferred.

[0191] Alkyne diol surfactants are diols or oxyethylidene (hereinafter also referred to as "EO") adducts of diols whose central carbon-carbon triple bond is present, and whose adjacent carbon atoms have hydroxyl groups. Alkyne diol surfactants can be synthesized by reacting an alkyne with a ketone or aldehyde corresponding to the target alkyne diol. For example, they can be obtained by the methods described in "New Introduction to Surfactants" by Takehiko Fujimoto, fully revised edition (Sanyo Chemical Industry Co., Ltd., 1992), pp. 94-107.

[0192] The HLB value of acetylenic diol surfactants is preferably 8 or less. Here, HLB (Hydrophile-Lipophile Balance) value is a value that represents the affinity of the surfactant for water and oil. The HLB value of acetylenic diol surfactants can be calculated using the Griffin method from the following formula.

[0193] HLB value = 20 × [(total formula weight of hydrophilic groups in the surfactant) / (molecular weight of the surfactant)]

[0194] Examples of hydrophilic groups contained in surfactants include hydroxyl groups and oxyethylidenes.

[0195] As an alkynyldiol surfactant, preferably one or more selected from 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,5-dimethyl-3-hexyn-2,5-diol, and their EO adducts. More preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its EO adducts; even more preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its EO adducts with an average molar number of 6 or less; even more preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol with an average EO molar number of 1.3, and 2,4,7,9-tetramethyl-5-decyn-4,7-diol with an average EO molar number of 3.

[0196] Commercially available surfactants of the acetylenic diol class include: SURFYNOL 104PG-50 (2,4,7,9-tetramethyl-5-decyn-4,7-diol, average molar addition of EO is 0, 50% propylene glycol solution, HLB value: 3.0 (calculation formula: 20 × (34 / 226))) and SURFYNOL 420 (2,4,7,9-tetramethyl-5-decyn-4,7-diol with an average EO molar addition of 1.3, HLB value: 6.4 (calculation formula: 20 × ((34 + 44 × 1.3) / (226 + 44 × 1.3))))) by Nissin Chemical Industry Co., Ltd. and Air Products & Chemicals Co., Ltd.

[0197] Silicone surfactants have both silicone and hydrophilic structures; examples of hydrophilic structures include polyether groups.

[0198] The HLB value of silicone surfactants is preferably 7 or less. Here, the HLB values ​​of silicone surfactants can be those listed in the product catalog.

[0199] Commercially available silicone surfactants include, but are not limited to: KF-6015 (polyether-modified silicone (linear type), HLB value: 4.5 (catalog value)), KF-6017 (polyether-modified silicone (linear type), HLB value: 4.5 (catalog value)), KF-6028 (polyether-modified silicone (branched type), HLB value: 4.0 (catalog value)), KF-6038 (polyether-modified silicone (branched type, alkyl co-modified type), HLB value: 3.0 (catalog value)), and KF-6048 (polyether-modified silicone (linear type, alkyl modified type), HLB value: 3.5 (catalog value)).

[0200] From the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, the pretreatment liquid according to the present invention preferably contains one or more of the following as the component (A) for suppressing wetting spread: metal salt, organic acid or salt thereof, cationic resin, anionic resin and hydrophobic surfactant; more preferably, it contains one or more of the following: metal salt, organic acid or salt thereof, cationic resin and anionic resin; and even more preferably, it contains one or more of the following: metal salt, organic acid or salt thereof, cationic resin and anionic resin having a crosslinking structure.

[0201] <Organic Solvent (B)>

[0202] From the viewpoint of suppressing streaks on the obtained printed matter and improving the clarity of the printed image, the pretreatment liquid involved in the present invention preferably also contains an organic solvent (B).

[0203] Regarding organic solvent (B), one can be used alone, or two or more can be used in combination.

[0204] Regarding the static surface tension of the organic solvent (B) measured at 25°C, from the viewpoint of suppressing the appearance of streaks on the obtained printed matter and improving the clarity of the printed image, it is preferably 40 mN / m or less, more preferably 38 mN / m or less, and preferably 18 mN / m or more, more preferably 20 mN / m or more, further preferably 22 mN / m or more, and even more preferably 24 mN / m or more.

[0205] The static surface tension of the organic solvent (B) at 25°C was determined according to the method described in the examples.

[0206] When two or more organic solvents are used as organic solvent (B), the static surface tension of organic solvent (B) is a weighted average calculated by weighting the content (mass%) of each organic solvent.

[0207] Regarding the boiling point of the organic solvent (B) at atmospheric pressure, from the viewpoint of promoting evaporation from the printing medium, suppressing the appearance of streaks on the obtained printed matter, and improving the clarity of the printed image, it is preferably 280°C or below, more preferably 260°C or below, and even more preferably 240°C or below. From the viewpoint of preventing the evaporation rate from being excessively promoted, preventing the local aggregation of components that inhibit wetting and spreading, suppressing the appearance of streaks on the obtained printed matter, and improving the clarity of the printed image, it is preferably 140°C or above, more preferably 160°C or above, and even more preferably 180°C or above.

[0208] When two or more organic solvents are used as organic solvent (B), the boiling point of organic solvent (B) is a weighted average calculated by weighting the content (mass%) of each organic solvent.

[0209] Examples of organic solvents (B) include: polyols; ethers such as polyol alkyl ethers, polyol aryl ethers, and polyol aralkyl ethers; nitrogen-containing heterocyclic compounds; amides; amines; and sulfur-containing compounds. Among these, one or more of polyols and polyol alkyl ethers are preferred.

[0210] Examples of polyols include, for example, ethylene glycol, diethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, dipropylene glycol (a mixture of isomers), 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, and other diols.

[0211] Examples of polyol alkyl ethers include, for instance, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dimethyl ether, etc., which are (poly)alkylene glycol monoalkyl ethers.

[0212] Examples of polyol aryl ethers include, for example, ethylene glycol monophenyl ether. Examples of polyol aralkyl ethers include, for example, ethylene glycol monobenzyl ether.

[0213] Examples of nitrogen-containing heterocyclic compounds include: 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolium ketone, and ε-caprolactam.

[0214] Examples of amides include formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

[0215] Examples of amines include monoethanolamine, diethanolamine, triethanolamine, and triethylamine.

[0216] Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, and thiodiethanol.

[0217] In addition to the above, other organic solvents include, for example, propylene carbonate and ethylene carbonate.

[0218] 〔water〕

[0219] The pretreatment solution involved in this invention preferably further contains water. The pretreatment solution involved in this invention is preferably aqueous. "Aqueous" in the context of this invention means that water constitutes the largest proportion of the liquid components contained in the pretreatment solution, based on a mass basis.

[0220] The preferred type of water is pure water or ultrapure water, such as ion-exchange water, ultrafiltration water, reverse osmosis water, or distilled water, which has removed ionic impurities to the greatest extent.

[0221] The pretreatment solution involved in this invention may further contain, as needed, other components such as surfactants other than the above-mentioned cationic and hydrophobic surfactants, pH adjusters, color-fixing agents, colorants, defoamers, preservatives and mildew inhibitors, and rust inhibitors.

[0222] The pretreatment solution involved in this invention preferably further contains surfactants other than the cationic surfactants and hydrophobic surfactants mentioned above.

[0223] In addition to the aforementioned cationic and hydrophobic surfactants, hydrophilic nonionic surfactants are preferred.

[0224] In this invention, "hydrophilic nonionic surfactant" refers to a surfactant that becomes a single phase when mixed with ion-exchanged water at a mass ratio of 1:1 at 25°C.

[0225] Examples of hydrophilic nonionic surfactants include, for example, hydrophilic polyoxyalkylene alkyl ether surfactants, hydrophilic alkyne surfactants, hydrophilic polyol surfactants, hydrophilic fatty acid alkanolamides, hydrophilic silicone surfactants, and hydrophilic fluorinated surfactants. Among these, one or more selected from hydrophilic alkyne surfactants and hydrophilic silicone surfactants are preferred.

[0226] The HLB value of hydrophilic alkyne surfactants is preferably greater than 8. Here, the HLB value of hydrophilic alkyne surfactants can be determined using the Griffin method from the above formula.

[0227] As hydrophilic alkyne surfactants, examples include one or more oxyethylidene (EO) adducts selected from 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, and 2,4-dimethyl-5-hexyn-3-ol. The average molar number (n) of the EO adduct is preferably greater than 8, and more preferably 20 or less, and more preferably 10 or less.

[0228] As a hydrophilic silicone surfactant, a polyether-modified silicone surfactant is preferred. The polyether group of the polyether-modified silicone surfactant is preferably, for example, polyethoxy, polypropoxy, or polyalkoxy formed by the block or random addition of ethoxy and propoxy (trimethoxy or propane-1,2-dioxy). Compounds in which the polyether group is grafted onto the silicone backbone or compounds in which the polyether group is block-jointed to both ends of the silicone backbone can be used.

[0229] The HLB value of hydrophilic silicone surfactants is preferably greater than 8. Here, the HLB values ​​of hydrophilic silicone surfactants can be those listed in the product catalog.

[0230] Examples of commercially available hydrophilic nonionic surfactants include the "SURFYNOL" series produced by Nissin Chemical Industries, Ltd. and Air Products & Chemicals, and the "KF" series produced by Shin-Etsu Chemical Industries, Ltd.

[0231] Regarding hydrophilic nonionic surfactants, one type can be used alone, or two or more can be used in combination. Among these, from the viewpoint of suppressing streaks on the resulting printed material and improving the clarity of the printed image, it is preferable to use a combination of a hydrophilic acetylenic diol surfactant and a hydrophilic silicone surfactant.

[0232] The pretreatment solution involved in this invention may contain a pH adjuster.

[0233] A pH adjuster is a formulation that can suppress pH fluctuations caused by environmental changes and maintain a constant pH in the pretreatment solution. Regarding the pH adjuster, any known formulation can be selected according to the pH of the pretreatment solution involved in this invention.

[0234] The pretreatment solution involved in this invention may contain a colorant, without impairing the effects of this invention. Examples of such colorants include those used in colorant-containing inks, which will be described later. When the pretreatment solution involved in this invention contains a colorant, pigments and hydrophobic dyes are preferred from the viewpoint of water resistance; pigments are preferred from the viewpoint of exhibiting high weather resistance.

[0235] From the viewpoint of improving the clarity of printed images, the content of colorant in the pretreatment solution is preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.1% by mass or less, even more preferably 0.01% by mass or less, and even more preferably free of colorant.

[0236] [Composition of the pretreatment solution]

[0237] Regarding the content of the component (A) that inhibits wetting spread in the pretreatment liquid involved in the present invention, from the viewpoint of suppressing the appearance of stripes on the obtained printed matter and improving the clarity of the printed image, it is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. Furthermore, from the same viewpoint as above, it is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

[0238] Regarding the content of organic solvent (B) in the pretreatment liquid involved in this invention, from the viewpoint of suppressing the appearance of streaks on the obtained printed matter and improving the clarity of the printed image, it is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, and even more preferably 25% by mass or more. Furthermore, from the same viewpoint as above, it is preferably 50% by mass or less, more preferably 45% by mass or less, further preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0239] Regarding the mass ratio of the content of the component (A) that inhibits wetting spread to the content of the organic solvent (B) in the pretreatment liquid involved in the present invention [component (A) that inhibits wetting spread / organic solvent (B)], from the viewpoint of suppressing the appearance of streaks on the obtained printed matter and improving the clarity of the printed image, it is preferably 0.01 or more, more preferably 0.03 or more, further preferably 0.05 or more, and even more preferably 0.07 or more. Furthermore, from the same viewpoint as above, it is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less.

[0240] The water content in the pretreatment liquid involved in this invention is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0241] In the case where a hydrated form containing hydrated water is used as a raw material for a polyvalent metal salt, the water content in the pretreatment liquid involved in this invention refers to the amount including the water content from the hydrated form of the polyvalent metal salt.

[0242] When the pretreatment solution involved in this invention contains a hydrophilic nonionic surfactant, the content of the hydrophilic nonionic surfactant in the pretreatment solution is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0243] The colorant content in the pretreatment solution involved in this invention is preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0244] The pretreatment solution involved in this invention is preferably prepared by appropriately mixing a component (A) that inhibits wetting and spreading, an organic solvent (B), and water or other components mentioned above, as needed. The pH of the pretreatment solution can be appropriately adjusted using the pH adjuster mentioned above.

[0245] From the viewpoint of improving the clarity of printed images, when applying the pretreatment liquid involved in this invention to the printing medium, it is preferable to apply it in a full-coat manner, that is, preferably in a manner in which the printing duty cycle of the pretreatment liquid is 100%.

[0246] Here, "printing duty cycle of pretreatment liquid" refers to the proportion of the area occupied by pretreatment liquid within a specified area on the printing medium, that is, the ratio of the cumulative area given to pretreatment liquid.

[0247] As a method for applying the pretreatment liquid to the printing medium, preferred methods include spraying, brushing, or inkjet printing. Among these, from the viewpoints of ease of adjusting the application position of the pretreatment liquid, suppressing streaks on the resulting printed material, and improving the clarity of the printed image, applying the pretreatment liquid is more preferably done by inkjet printing.

[0248] From the viewpoint of being able to continuously perform steps 1 and 2, it is preferable to use an apparatus that integrates the means of applying the pretreatment liquid used in step 1 and the means of applying the colorant-containing ink used in step 2. More preferably, it is an apparatus that uses a linear printhead inkjet method as the means of applying the pretreatment liquid used in step 1 and the means of applying the colorant-containing ink used in step 2.

[0249] Regarding the amount of the pretreatment liquid applied to the printing medium, from the viewpoint of suppressing streaks on the printed material and improving the clarity of the printed image, 0.003 g / m³ is preferred. 2 The above, and more preferably, is 0.01 g / m 2 The above, and more preferably 0.1 g / m 2 Furthermore, considering the same viewpoint as above, 10 g / m² is preferred. 2 The following, or more preferably, is 5g / m 2 The following, and more preferably 1g / m 2 The following, and more preferably, is 0.5 g / m 2 the following.

[0250] Regarding the amount of the component (A) that inhibits wetting spread contained in the pretreatment solution of the printing medium, from the viewpoint of suppressing streaks on the printed material and improving the clarity of the printed image, it is preferably 0.0001 g / m 2 The above, and more preferably, is 0.0005 g / m2 The above, and more preferably, is 0.001 g / m 2 Furthermore, considering the same viewpoint as above, 0.1 g / m is preferred. 2 The following, or more preferably, is 0.01 g / m 2 The following, and more preferably, is 0.001 g / m 2 the following.

[0251] In the printing method of the present invention, step 1 preferably includes a step of maintaining the printing medium with the pretreatment liquid at a temperature of 25°C or higher after the pretreatment liquid has been applied to the printing medium. This step has the function of removing volatile components from the pretreatment liquid from the printing medium with the pretreatment liquid applied, and is able to dry the printing medium (hereinafter, the step of maintaining the printing medium with the pretreatment liquid applied to it at a temperature of 25°C or higher in step 1 is also referred to as the "drying step of step 1").

[0252] Furthermore, in the printing method of the present invention, step 1 preferably includes a step of drying the printing medium to which the pretreatment liquid has been applied. Also, in the printing method of the present invention, step 1 preferably includes a step of immobilizing the pretreatment liquid application portion.

[0253] That is, the drying step in step 1 described above is preferably a step in which the printing medium to which the pretreatment liquid has been applied is kept at a temperature of 25°C or higher, thereby drying the printing medium to which the pretreatment liquid has been applied; more preferably, it is a step in which the printing medium to which the pretreatment liquid has been applied is kept at a temperature of 25°C or higher, thereby drying the printing medium to which the pretreatment liquid has been applied, and fixing the pretreatment liquid application part. As a result, the clarity of the printed image can be further improved.

[0254] In step 1, preferred methods for maintaining the printing medium, to which the pretreatment solution has been applied, at a temperature of 25°C or higher include standing, air supply, heating, and depressurization. In the printing method of the present invention, the drying step of step 1 does not include the application of active energy rays such as ultraviolet light or radiation.

[0255] Regarding the holding temperature of the printing medium in the drying process of step 1, from the viewpoint of suppressing deformation of the printing medium, it is preferably 120°C or below, more preferably 110°C or below, and even more preferably 100°C or below; and from the viewpoint of completing drying in a short time and further improving the clarity of the printed image, it is preferably 25°C or above, more preferably 30°C or above, and even more preferably 40°C or above.

[0256] The holding time (holding time) of the temperature in the drying process of step 1 is preferably 0.5 seconds or more, more preferably 1 second or more, and even more preferably 1.5 seconds or more. It is also preferably 30 minutes or less, more preferably 20 minutes or less, even more preferably 10 minutes or less, and even more preferably 1 minute or less.

[0257] Regarding the drying rate of the pretreatment liquid in the drying process of step 1 (i.e., the removal rate of volatile components in the pretreatment liquid), from the viewpoint of improving the clarity, especially the sharpness, of the printed image, it is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0258] In this invention, "drying rate of the pretreatment liquid" refers to the percentage of the total mass of the components actually removed by the drying process relative to the total mass of the components contained in the pretreatment liquid that can be removed by the drying process of step 1. When the mass of the printing medium (M0), the mass of the printing medium immediately after the pretreatment liquid is applied in step 1 (M1), and the mass of the printing medium after the process of maintaining the printing medium at 25°C or above (M2) are set, and the proportion of the total mass of the components in the pretreatment liquid that can be removed by the drying process of step 1 is set to X mass% is calculated by the following formula.

[0259]

[0260] In this invention, the proportion X (mass%) of the total mass of components in the pretreatment liquid that can be removed by the drying step of step 1 is preferably the water content (mass%) in the pretreatment liquid.

[0261] <Process 2>

[0262] Step 2 is a process of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, using a linear printhead inkjet method.

[0263] When the printing duty cycle of the colorant-containing ink in the light image forming section is 0%, it is preferable not to apply the colorant-containing ink to the light image forming section in step 2. That is, in this case, step 2 is preferably step 2-1 as described below.

[0264] Step 2-1: A step in which ink containing colorant is applied to the part of the printing medium obtained in Step 1 that has the pretreatment liquid application part, which becomes the concentrated image forming part, using a linear printhead inkjet method.

[0265] Furthermore, when the printing duty cycle of the colorant-containing ink in the light image forming section is greater than 0%, in step 2, in addition to applying the colorant-containing ink to the portion of the printing medium obtained in step 1 that has the pretreatment liquid application portion and becomes the dark image forming section, the colorant-containing ink is also applied to the portion of the light image forming section where the colorant-containing ink has been applied. That is, in this case, step 2 is preferably step 2-2 as described below.

[0266] Step 2-2: Applying colorant-containing ink to the portion of the printing medium obtained in Step 1 that has a pretreatment liquid application portion, which becomes a dark image forming portion and a light image forming portion, by applying colorant-containing ink using a linear printhead inkjet method.

[0267] (Inks containing colorants)

[0268] The present invention will describe the colorant-containing inks (colorant-containing inks) involved in this invention.

[0269] The colorant-containing inks involved in this invention are preferably selected from one or more of black inks and colored inks.

[0270] [Coloring agent]

[0271] As the colorant used in the colorant-containing ink according to the present invention, any one of dyes and pigments can be used. Among these, from the viewpoint of having water resistance, light resistance, weather resistance, gas resistance, etc., pigments are preferred as the colorant.

[0272] As a pigment, any of the known organic and inorganic pigments can be used. Regarding pigments, one type can be used alone or in combination of two or more, and mixed crystals can also be used.

[0273] Examples of inorganic pigments include: titanium dioxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.

[0274] Examples of organic pigments include: azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Examples of polycyclic pigments include: phthalocyanine pigments, perylene pigments, violet ketone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindolinone pigments, and quinophthalone pigments. Examples of dye chelates include: basic dye chelates and acidic dye chelates.

[0275] Specific examples of pigments used in black inks include carbon-based, metallic, and organic pigments. Examples of carbon-based pigments include lampblack (CI Pigment Black 6), furnace black, acetylene black, and carbon black from the channel black process (CI Pigment Black 7). Examples of metallic pigments include copper-chromium oxide (CI Pigment Black 28), iron oxide (CI Pigment Black 11), and titanium oxide (CI Pigment Black 35). Examples of organic pigments include aniline black (CI Pigment Black 1).

[0276] Specific examples of pigments used in colored inks include various types of products selected from one or more of CI pigments: yellow, orange, red, purple, blue, and green.

[0277] There are no specific limitations on dyes; examples include acid dyes, basic dyes, direct dyes, and reactive dyes. Dyes can be used alone or in combination of two or more.

[0278] Examples of dyes selected from CI Acid Yellow, CI Acid Red, CI Acid Blue, CI Acid Black, CI Food Black, CI Direct Yellow, CI Direct Red, CI Direct Blue, CI Direct Black, CI Reactive Red, and CI Reactive Black can be cited.

[0279] In the case of a colorant-containing ink containing pigments, the pigments are dispersed in the medium within the ink. Examples of pigment forms in colorant-containing inks include: forms dispersed using a resin (hereinafter also referred to as "pigment dispersion resin") or a surfactant as a dispersant, or self-dispersible pigments that can be dispersed without the use of a dispersant. Among these, forms dispersed using a pigment dispersion resin are preferred as pigment forms in colorant-containing inks.

[0280] As a pigment dispersion resin, it can be any type of water-soluble resin or water-insoluble resin.

[0281] Here, the "water solubility" and "water insolubility" of resin are determined as follows: Resin dried at 105°C for 2 hours to constant weight is dissolved in 100g of water at 25°C until saturation. If the amount dissolved exceeds 10g, it is considered "water solubility"; if the amount dissolved is less than 10g, it is considered "water insolubility". Furthermore, as described later, when the resin has anionic groups, its solubility refers to the amount dissolved in the presence of a neutralizing agent, under the same mass ratio of resin to neutralizing agent and the same mass ratio in the colorant-containing ink.

[0282] Specifically, from the viewpoint of improving the dispersion stability of pigments, the preferred forms of pigments in colorant inks include: (a) forms in which water-soluble resins are adsorbed on the pigment surface; (b) forms in which water-soluble surfactants or water-dispersible surfactants are adsorbed on the pigment surface; (c) forms in which self-dispersible pigments are dispersed without the use of pigment dispersing resins and surfactants by introducing hydrophilic functional groups to the pigment surface in a chemical or physical manner; and (d) forms in which pigments are covered with water-insoluble resins, etc.

[0283] Pigments having the above-described forms (a) to (d) preferably have anionic properties. In form (a), the water-soluble resin preferably has anionic groups; in form (b), the water-soluble surfactant or water-dispersible surfactant preferably has anionic groups; in form (c), the hydrophilic functional groups introduced onto the pigment surface preferably have anionic groups; and in form (d), the water-insoluble resin preferably has anionic groups.

[0284] As an anionic group, it is defined the same as that in anionic resins containing hydrophobic compounds (A2). Examples of anionic groups include carboxyl groups (-COOM), sulfonic acid groups (-SO3M), and phosphate groups (-OPO3M2). In the above chemical formula, M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium. Among these, anionic resins preferably have a carboxyl group as an anionic group, and M is preferably an alkali metal.

[0285] Regarding the pigment morphology in colorant-containing inks, when the wetting-spreading inhibitor (A) in the pretreatment solution is an agglomerating compound (A1), the dispersibility of the dispersed particles present in the ink can be reduced, and an agglomerating effect can be efficiently exhibited. When the wetting-spreading inhibitor (A) in the pretreatment solution is a hydrophobic compound (A2), excessive wetting-spreading of the ink can be prevented. Therefore, the efficiency of preventing wetting-spreading can be improved, streaks on the resulting printed matter can be suppressed, and the clarity of the printed image can be improved. From this viewpoint, it is preferable to select one or more morphologies (c) and (d), and more preferably morphology (d).

[0286] When the pigment in the colorant ink is in the form of form (d), the forms in which the pigment is covered by water-insoluble resin include: the form in which the pigment is encapsulated in the water-insoluble resin (encapsulation), the form in which the pigment is uniformly dispersed in the water-insoluble resin, the form in which the pigment is exposed from the surface of the water-insoluble resin particles, and the form in which the water-insoluble resin is adsorbed onto the pigment.

[0287] When the pigment in the colorant-containing ink is in form (d), it is preferable to cover the pigment form with a water-insoluble resin having a cross-linked structure. As the form in which the pigment is covered with a water-insoluble resin having a cross-linked structure, the water-insoluble resin preferably has a structure comprising a polymer (which has a linear two-dimensional structure, which may have branches) and a component derived from a cross-linking agent. Such a cross-linked structure is considered to be a polymer with a linear (which may have branches) two-dimensional structure forming a three-dimensional structure through a component derived from the cross-linking agent.

[0288] [Pigment Dispersion Resin]

[0289] In the case of colorant-containing ink in form (d), there is no particular limitation on the type of water-insoluble resin used to disperse pigments as pigment dispersion resin for colorant-containing ink.

[0290] Specific examples of water-insoluble resins include: (meth)acrylic resins, styrene / (meth)acrylic resins, maleic acid resins, styrene / maleic acid resins, polyurethane resins, and polyester resins. Furthermore, when the pigment in the colorant ink is in form (d), and the pigment form is covered by a water-insoluble resin with a cross-linked structure, from the viewpoint of forming a high-quality printed image, it is preferable, from the viewpoint of forming a component of the aforementioned polymer having a linear (which may have branched) two-dimensional structure, to be selected from one or more of (meth)acrylic resins, styrene / (meth)acrylic resins, polyurethane resins, and polyester resins, and more preferably from one or more of (meth)acrylic resins and styrene / (meth)acrylic resins.

[0291] Regarding water-insoluble resins, products synthesized using known methods or commercially available products can be used. Water-insoluble resins can be used alone or in combination of two or more.

[0292] The number average molecular weight of the pigment dispersion resin is preferably 5,000 or more, more preferably 7,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less.

[0293] The number-average molecular weight of the pigment dispersion resin was determined using the method described in the examples.

[0294] When the pigment-containing ink is in form (d), and the pigment is covered by a water-insoluble resin with a cross-linked structure, the number average molecular weight of the constituent components of the above-mentioned polymer with a straight chain (which may have branches) in the water-insoluble resin used for pigment dispersion is preferably 5,000 or more, more preferably 7,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less.

[0295] The acid value of the pigment dispersion resin is preferably 5 mg KOH / g or more, more preferably 50 mg KOH / g or more, further preferably 70 mg KOH / g or more, even more preferably 90 mg KOH / g or more, and preferably 800 mg KOH / g or less, more preferably 500 mg KOH / g or less, and even more preferably 300 mg KOH / g or less.

[0296] The acid value of the pigment dispersion resin can be determined using the method described in the examples, or it can be calculated based on the mass ratio of the constituent monomers. When the pigment dispersion resin has a cross-linked structure, the acid value of the pigment dispersion resin can also be calculated based on the mass ratio of the constituent monomers and the cross-linking agent.

[0297] [Fixing resin]

[0298] From the viewpoint of forming high-quality printed images, colorant-containing inks may also contain resin (hereinafter also referred to as "fixing resin") that functions as a fixing aid. The fixing resin in colorant-containing inks is preferably in the form of resin uncovered by pigment, and more preferably in the form of pigment-free resin particles.

[0299] There are no particular restrictions on the type of fixing resin; it can be appropriately selected according to the purpose. Specific examples of fixing resins include: polyurethane resins, polyester resins, acrylic resins, vinyl acetate resins, styrene resins, butadiene resins, styrene / butadiene resins, vinyl chloride resins, styrene / acrylic resins, and silicone acrylic resins.

[0300] Ink can be obtained by mixing particulate resin (as a fixing resin) with colorant, water, organic solvent, etc. Both synthetic and commercially available products can be used as fixing resins.

[0301] Regarding fixing resin, one type can be used alone, or two or more types can be used in combination.

[0302] 〔wax〕

[0303] From the perspective of creating high-quality printed images, inks containing colorants may contain wax.

[0304] In this specification, "wax" refers to an organic substance that is solid or semi-solid at room temperature (25°C) and becomes liquid upon heating. Here, "semi-solid wax" means that the wax will deform and flow if force is applied, but can maintain a certain shape when no force is applied. Furthermore, the temperature at which wax becomes liquid upon heating (the so-called melting point of wax) exists in the temperature range above 45°C.

[0305] The wax can be any type of natural or synthetic wax.

[0306] Natural waxes include: petroleum waxes such as paraffin wax and microcrystalline wax; plant waxes such as carnauba wax, candelilla wax, and rice bran wax; and animal waxes such as lanolin and beeswax.

[0307] Synthetic waxes include: polyolefin waxes, Fischer-Tropsch waxes, and other synthetic hydrocarbon waxes; silicone waxes; and modified waxes such as paraffin wax derivatives, lignite wax derivatives, and microcrystalline wax derivatives. Among these, polyolefin waxes with olefin monomers as the main component are preferred.

[0308] Regarding waxes, one type can be used alone, or two or more types can be used in combination.

[0309] Colorant-containing inks preferably contain wax as a dispersion (hereinafter also referred to as "wax dispersion").

[0310] There are no particular limitations on wax dispersions. For example, wax dispersions formed by emulsifying wax using known surfactants can be listed. Nonionic surfactants, anionic surfactants, etc., can be used as surfactants.

[0311] Examples of nonionic surfactants include oxyethylidene adducts of higher alcohols and oxyethylidene adducts of alkylated phenols.

[0312] Examples of anionic surfactants include: sulfate or phosphate salts based on oxyalkylene adducts of higher alcohols; alkylated benzenesulfonates, etc.

[0313] Among these, from the viewpoint of improving the ejection stability of ink and the image durability of printed materials, the wax dispersion is preferably a nonionic wax dispersion formed by emulsifying wax with a nonionic surfactant, and more preferably a nonionic polyolefin wax dispersion.

[0314] Examples of commercially available wax dispersions include: the "Hytec E" series produced by Toho Chemical Industry Co., Ltd., the "AQUACER" series produced by BYK Corporation, the "Selosol" series produced by Chukyo Oils & Fats Co., Ltd., and the "Chemipearl" series produced by Mitsui Chemicals Co., Ltd.

[0315] 〔water〕

[0316] The medium for colorant-containing inks is preferably an aqueous medium. That is, colorant-containing inks are preferably aqueous inks containing water.

[0317] Here, "water-based" means that, by mass, water constitutes the largest proportion of the medium containing colorant inks.

[0318] For the water contained in colorant-containing inks, ion-exchanged water, ultrafiltration water, reverse osmosis water, or distilled water are preferred.

[0319] [Water-soluble organic solvents]

[0320] Colorant-containing inks may also contain water-soluble organic solvents as an aqueous medium. Examples of water-soluble organic solvents in such inks include: polyols; ethers of polyol alkyl ethers, polyol aryl ethers, polyol aralkyl ethers, etc.; nitrogen-containing heterocyclic compounds; amides; amines; sulfur-containing compounds, etc.

[0321] Regarding the water content in the water-based medium containing the colorant ink, from an environmental point of view, it is preferably 51% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. It is also preferably 95% by mass or less, more preferably 90% by mass or less, further preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0322] Depending on the requirements, inks containing colorants may also contain surfactants, defoamers, preservatives, mildew inhibitors, rust inhibitors, pH adjusters, etc.

[0323] [Composition of inks containing colorants]

[0324] Regarding the content of colorant in the colorant-containing ink, from the viewpoint of increasing the image density of the printed matter, it is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0325] When the ink containing colorant contains pigment as a colorant, from the viewpoint of increasing the image density of the printed matter, the pigment content in the ink is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0326] When the colorant ink contains pigment dispersion resin, from the viewpoint of pigment dispersion stability and forming a high-quality printed image, the content of pigment dispersion resin in the ink is preferably 2% by mass or more, more preferably 4% by mass or more; and from the viewpoint of improving the image density of the printed matter, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0327] When the colorant ink contains pigment dispersion resin, the mass ratio of pigment content to pigment dispersion resin content in the ink [pigment / pigment dispersion resin] is preferably 0.30 or more, more preferably 0.50 or more, and even more preferably 0.70 or more, from the viewpoint of improving the image density of the printed matter; and from the viewpoint of pigment dispersion stability and forming a high-quality printed image, it is preferably 1.00 or less, more preferably 0.90 or less, and even more preferably 0.80 or less.

[0328] When the colorant-containing ink contains fixing resin, the content of fixing resin in the ink is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of forming a high-quality printed image; and from the viewpoint of improving the image density of the printed matter, it is preferably 10% by mass or less, more preferably 7% by mass or less.

[0329] When the ink containing colorant contains wax, from the viewpoint of forming a high-quality printed image, the wax content in the ink is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, and preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0330] When the colorant ink contains a water-soluble organic solvent, from the viewpoint of forming a high-quality printed image, the content of the water-soluble organic solvent in the ink is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0331] Regarding the water content in the colorant-containing ink, from an environmental point of view, it is preferably 40% by mass or more, more preferably 45% by mass or more, further preferably 50% by mass or more, even more preferably 60% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0332] (Linear array printhead inkjet method)

[0333] The inkjet printing method of the present invention uses a linear array printhead.

[0334] In an online printhead, there is a printhead capable of inkjet printing on the printing medium with a length equal to or wider than that in the direction perpendicular to the transport direction. Therefore, high-speed printing can be achieved by simply scanning the printing medium while the printhead is fixed.

[0335] A linear printhead can be a structure consisting of multiple individual printheads arranged in a line. It is preferable to equip each color of ink containing colorant with a linear printhead.

[0336] From the viewpoint of forming high-quality printed images, the nozzle spacing of the linear array printhead is preferably 120 npi or more, more preferably 180 npi or more, further preferably 300 npi or more, and even more preferably 600 npi or more. Furthermore, from the same viewpoint as above, it is preferably 6000 npi or less, more preferably 3600 npi or less, further preferably 2400 npi or less, and even more preferably 1600 npi or less.

[0337] In this invention, the unit “npi” representing the nozzle spacing of a linear printhead refers to the number of nozzles per inch along the length of the printhead’s nozzle array.

[0338] There are various ways to eject the printhead. In the printing method of the present invention, either a piezoelectric method using a piezoelectric element or a thermal method using a heating element can be used. Among these, from the viewpoint of forming a high-quality printed image, the printhead ejection method is preferably a piezoelectric method.

[0339] In this invention, regarding the conveying speed of the printing medium, from the viewpoint of efficiently obtaining printed matter, it is preferably 10 m / min or more, more preferably 15 m / min or more, and even more preferably 20 m / min or more; and from the viewpoint of forming high-quality printed images, it is preferably 100 m / min or less, more preferably 80 m / min or less, and even more preferably 60 m / min or less.

[0340] In this invention, regarding the amount of ink droplets containing colorant discharged, from the viewpoint of forming a high-quality printed image, it is preferably 1 pL or more, more preferably 1.5 pL or more, even more preferably 2 pL or more, and preferably 15 pL or less, more preferably 10 pL or less, even more preferably 7.5 pL or less, and even more preferably 5 pL or less.

[0341] Here, "pL (picoliter)" means 10 times the volume of "L (liter)". -12 times.

[0342] The amount of ink droplets ejected containing colorants can be set using the inkjet head control device.

[0343] In this invention, the resolution of the printing medium in the direction parallel to the transport direction, i.e., the density of ink dots on the printing medium, is preferably 600 dpi or more, more preferably 800 dpi or more, and even more preferably 1000 dpi or more; and, from the same viewpoint as above, it is preferably 3600 dpi or less, more preferably 2400 dpi or less, even more preferably 1800 dpi or less, and even more preferably 1200 dpi or less.

[0344] In this invention, the resolution of the printing medium in the direction perpendicular to the transport direction, i.e., the density of ink dots on the printing medium, is preferably 600 dpi or more, more preferably 800 dpi or more, and even more preferably 1000 dpi or more; and, from the same viewpoint as above, it is preferably 3600 dpi or less, more preferably 2400 dpi or less, even more preferably 1800 dpi or less, and even more preferably 1200 dpi or less.

[0345] In this invention, the unit “dpi” representing resolution refers to the number of ink dots per inch in a direction parallel or perpendicular to the transport direction of the printing medium.

[0346] In cases where the resolution varies due to different ink colors, the highest resolution is considered as the resolution of this invention.

[0347] In this invention, regarding the diameter of the ink dots that are applied to the printing medium (hereinafter also simply referred to as "the diameter of the ink dots"), from the viewpoint of forming a high-quality printed image, it is preferably 20 μm or more, more preferably 23 μm or more, and even more preferably 25 μm or more; and from the same viewpoint as above, it is preferably 60 μm or less, more preferably 55 μm or less, and even more preferably 50 μm or less.

[0348] Regarding the diameter of the ink dots on the printing medium, as described in the embodiments, it can be: after ink is applied using inkjet printing, the printing medium is observed using a microscope. At this time, 10 ink dots are observed, and their average value is taken as the diameter of the ink dots.

[0349] Regarding the amount of colorant-containing ink applied to the areas forming the concentrated image in step 2, from the viewpoint of suppressing streaks on the obtained print and improving the clarity of the printed image, 1 g / m² is preferred. 2 The above, and more preferably 3g / m 2 The above, and more preferably 4.5 g / m 2 The above; and, considering the same viewpoint as above, 10 g / m² is preferred. 2 The following, or more preferably, is 7g / m 2 The following, and more preferably 5g / m 2 the following.

[0350] <Process 3>

[0351] In this invention, from the viewpoint of forming a high-quality printed image by making the outline of the thick image forming part clear, it is preferable to further include a step 3, before step 1 or after step 2, in which a white ink containing white pigment (hereinafter also simply referred to as "white ink") is applied to the printing medium or the side of the printing medium that has been given ink containing colorant.

[0352] If step 3 is also included, it is preferable to apply white ink to the side of the printing medium opposite to the side to which the colorant ink was applied (i.e., the printing medium) or the side of the printing medium to which the colorant ink was applied after step 2.

[0353] When using a resin film as a low-absorbency printing medium, and when forming a mirror image on the printing medium that is a reversed image of the desired printed image in such a way that it becomes the target image when viewed from the opposite side of the printing image forming surface of the non-absorbent film, step 3 is preferably applied to the entire surface of the printing medium on which the colorant ink has been applied.

[0354] As pigments for white inks, examples of white inorganic pigments include titanium dioxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. From the viewpoint of improving whiteness and thus improving the sharpness of hollow text, it is preferable to select one or more of titanium dioxide and zinc oxide, and more preferably titanium dioxide (CI Pigment White 6).

[0355] While untreated titanium oxide can be used, surface-treated titanium oxide is preferred from the viewpoint of obtaining good dispersibility. Surface treatments for titanium oxide can include those using inorganic materials or those using organic materials such as titanium coupling agents, silane coupling agents, and silicone oils; surface treatment using inorganic materials is preferred.

[0356] In this invention, a white pigment is dispersed in a medium in the white ink. Examples of the form of white pigment in the white ink include: a form dispersed using the aforementioned pigment dispersion resin or surfactant as a dispersant, or a self-dispersible pigment that can be dispersed without a dispersant. Among these, a form dispersed using a pigment dispersion resin is preferred. The pigment dispersion resin is preferably the same resin exemplified in the aforementioned colorant-containing ink. Furthermore, the white ink may further contain the aforementioned fixing resin.

[0357] The medium for white ink is preferably an aqueous medium. That is, white ink is preferably an aqueous ink containing water.

[0358] Here, "water-based" means that, by weight, water constitutes the largest proportion of the medium in white ink.

[0359] For the water contained in white ink, ion-exchanged water, ultrafiltration water, reverse osmosis water, or distilled water are preferred.

[0360] Furthermore, depending on the requirements, white ink may also contain wax, water-soluble organic solvents, surfactants, defoamers, preservatives and mildew inhibitors, rust inhibitors, pH adjusters, etc.

[0361] The preferred range of the content of each component, such as white pigment, in white ink is the same as the preferred range of the content of each component, such as colorant, in ink containing colorant.

[0362] Methods for applying white ink in step 3 include, for example, coating using a roller, coating using a sprayer, coating using a brush, and coating using an inkjet method. Among these, from the viewpoint of being able to apply white ink conveniently and evenly, coating using a roller or coating using an inkjet method is preferred.

[0363] Specific examples of rollers used in roller coating include: offset gravure coating machines, gravure coating machines, doctor blade coating machines, bar coating machines, scraper coating machines, flexographic coating machines, and roller coating machines. Among these, it is preferable to select one or more of doctor blade coating machines, bar coating machines, and roller coating machines.

[0364] As a specific example of coating using inkjet technology, coating using linear inkjet technology is preferred.

[0365] Furthermore, from the viewpoint of being able to continuously perform processes 1, 2, and 3, it is preferable to use an apparatus that integrates the means for applying the pretreatment liquid used in process 1 and the means for applying the colorant-containing ink used in process 2 as the apparatus for applying white ink to the printing medium or the surface of the printed image in process 3. In this case, for example, it could be an apparatus that assembles a white ink applying means such as a roller coater within an inkjet printing apparatus, or an apparatus that assembles an inkjet head for coating white ink within an inkjet printing apparatus.

[0366] Regarding the amount of white ink applied to the printing medium in step 3, from the viewpoint of forming a high-quality printed image, 1 g / m² is preferred. 2 The above, and more preferably 5g / m 2 The above, and more preferably, is 10g / m 2 The above; and, considering the same viewpoint as above, 50 g / m² is preferred. 2 The following, or more preferably, is 30g / m 2 The following, and more preferably, is 15g / m 2 the following.

[0367] In the case where the printing method of the present invention includes step 3, from the viewpoint of forming a high-quality printed image, step 3 preferably includes a step of maintaining the printing medium to which the white ink has been applied after applying white ink to the printing medium or the side of the printing medium to which the colorant ink has been applied, at a temperature of 25°C or higher. This step has the effect of removing volatile components from the white ink applied to the printing medium or printed matter, and is able to dry the printing medium or printed matter (hereinafter, the step of maintaining the printing medium to which the white ink has been applied at a temperature of 25°C or higher in step 3 is also referred to as the "drying step of step 3").

[0368] In step 3, methods for maintaining the printing medium coated with white ink at a temperature above 25°C include standing, air supply, heating, and pressure reduction. In the printing method of the present invention, the drying step in step 3 does not include the application of active energy rays such as ultraviolet light or radiation.

[0369] Regarding the holding temperature of the printing medium in the drying process of step 3, from the viewpoint of suppressing deformation of the printing medium, it is preferably 120°C or below, more preferably 100°C or below, further preferably 90°C or below, and even more preferably 80°C or below; and from the viewpoint of completing drying in a short time, it is preferably 25°C or above, more preferably 30°C or above.

[0370] The holding time (holding time) of the temperature in the drying process of step 3 is preferably 0.5 seconds or more, more preferably 1 second or more, further preferably 3 seconds or more, even more preferably 5 seconds or more, and preferably 30 minutes or less, more preferably 20 minutes or less, further preferably 10 minutes or less, and even more preferably 1 minute or less.

[0371] The inkjet printing apparatus of the present invention is the inkjet printing apparatus used in the inkjet printing method of the present invention, comprising: an inkjet head filled with a pretreatment liquid and an inkjet head filled with an ink containing a colorant.

[0372] In the inkjet printing apparatus of the present invention, the meanings of pretreatment liquid and ink containing colorant are the same as those used in the printing method of the present invention described above.

[0373] In the inkjet printing apparatus of the present invention, the inkjet head filled with ink containing colorant can be a single inkjet head or multiple inkjet heads. From the viewpoint of using a variety of inks containing colorant, multiple inkjet heads are preferred.

[0374] Furthermore, the inkjet printing apparatus of the present invention is preferably equipped with an inkjet head filled with a pretreatment solution and an inkjet head filled with ink containing a colorant, as well as an inkjet head filled with white ink containing a white pigment. That is, the inkjet printing apparatus of the present invention is preferably equipped with an inkjet head filled with a pretreatment solution, an inkjet head filled with ink containing a colorant, and an inkjet head filled with white ink containing a white pigment. More preferably, the inkjet printing apparatus of the present invention is equipped with an inkjet head filled with a pretreatment solution, a plurality of inkjet heads filled with ink containing a colorant, and an inkjet head filled with white ink containing a white pigment.

[0375] The inkjet printing apparatus of the present invention is preferably used in the printing method of the present invention described above, or in the method for manufacturing printed matter of the present invention described later.

[0376] The ink assembly for inkjet printing of the present invention is the ink assembly for inkjet printing used in the inkjet printing method of the present invention, and includes a pretreatment liquid and an ink containing a colorant.

[0377] In the ink assembly for inkjet printing of the present invention, the meanings of pretreatment liquid and ink containing colorant are the same as those used in the printing method of the present invention described above.

[0378] In the inkjet printing ink assembly of the present invention, the ink containing the colorant can be one type or multiple types, preferably multiple types. Furthermore, the inkjet printing ink assembly of the present invention is preferably a white ink containing a white pigment, in addition to a pretreatment liquid and an ink containing a colorant. That is, the inkjet printing ink assembly of the present invention is preferably a white ink containing a pretreatment liquid, an ink containing a colorant, and a white ink containing a white pigment, more preferably a white ink containing a pretreatment liquid, multiple inks containing colorants, and a white ink containing a white pigment.

[0379] The ink assembly for inkjet printing of the present invention is preferably used in the printing method of the present invention described above, or in the method for manufacturing printed matter of the present invention described later.

[0380] [Methods for manufacturing printed materials]

[0381] The printed matter involved in this invention can be obtained by the printing method of this invention described above.

[0382] That is, the method for manufacturing printed matter of the present invention forms a printed image on a printing medium, the printed image including a dark image forming section and a light image forming section, wherein the printing duty cycle of the ink containing colorant in the dark image forming section is greater than the printing duty cycle of the ink containing colorant in the light image forming section, wherein,

[0383] The method for manufacturing this printed material includes:

[0384] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0385] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0386] In the method for manufacturing printed matter of the present invention, the meanings of steps 1 and 2 are the same as those of steps 1 and 2 in the printing method of the present invention.

[0387] Furthermore, the method for manufacturing printed matter according to the present invention preferably includes, before step 1 or after step 2, a step 3 in which white ink is applied to the printing medium or the side of the printing medium to which the colorant-containing ink has been applied. In the method for manufacturing printed matter according to the present invention, the meaning of step 3 is the same as that of step 3 in the printing method of the present invention described above.

[0388] The method for manufacturing printed matter according to the present invention has the above-described features, and therefore, it is possible to suppress the appearance of stripes on the obtained printed matter, and the clarity of the printed image including the dark image forming portion and the light image forming portion is excellent.

[0389] The present invention also includes the following methods.

[0390] <1> An inkjet printing method for forming a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dense image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region, wherein,

[0391] The inkjet printing method includes:

[0392] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0393] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0394] <2> An inkjet printing method for forming a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dense image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region, wherein,

[0395] The inkjet printing method includes:

[0396] Step 1: Applying a pretreatment solution to the outer edge of the portion forming the concentrated image, and maintaining the printing medium with the pretreatment solution applied at a temperature of 25°C or higher to obtain a printing medium having a pretreatment solution applied portion; and

[0397] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0398] <3> An inkjet printing method for forming a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dense image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region, wherein,

[0399] The inkjet printing method includes:

[0400] Step 1: Applying a pretreatment solution to the outer edge of the portion forming the concentrated image, and drying the printing medium to which the pretreatment solution has been applied, to obtain a printing medium having a pretreatment solution application portion; and

[0401] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0402] <4> An inkjet printing method for forming a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dense image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region, wherein,

[0403] The inkjet printing method includes:

[0404] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section, and fixing the pretreatment solution application section to obtain a printing medium having the pretreatment solution application section; and

[0405] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0406] <5> The inkjet printing method as described in any one of <1> to <4> above, wherein the printing medium is a low-absorption printing medium.

[0407] <6> The inkjet printing method described in <5> above, wherein the non-absorbent printing medium is a resin film.

[0408] <7> The inkjet printing method described in <6> above, wherein the resin film is a polyester film.

[0409] <8> The inkjet printing method as described in any one of <1> and <3> to <7> above, wherein step 1 includes a step of maintaining the printing medium to which the pretreatment liquid has been applied at a temperature of 25°C or higher.

[0410] <9> The inkjet printing method as described in any one of <1>, <2> and <4> to <7> above, wherein step 1 includes a step of drying the printing medium to which a pretreatment solution has been applied.

[0411] <10> The inkjet printing method as described in any one of <1> to <3> and <5> to <7> above, wherein step 1 includes a step of immobilizing the pretreatment liquid.

[0412] <11> The inkjet printing method as described in any one of <1> to <10> above, wherein,

[0413] Step 1 includes: holding the printing medium to which the pretreatment liquid has been applied at a temperature of 40°C to 100°C for 1.5 seconds to 1 minute to dry the pretreatment liquid and to fix the pretreatment liquid.

[0414] <12> The inkjet printing method as described in any one of <1> to <11> above, wherein the pretreatment liquid contains one or more selected from agglomerating compound (A1) and hydrophobic compound (A2).

[0415] <13> In the inkjet printing method described in <12> above, the agglomerating compound (A1) is selected from one or more of metal salts, organic acids or their salts, and cationic resins.

[0416] <14> In the inkjet printing method described in <13> above, the agglomerating compound (A1) is calcium nitrate.

[0417] <15> In the inkjet printing method described in <13> above, the agglomerating compound (A1) is malonic acid.

[0418] <16> The inkjet printing method described in <13> above, wherein the agglomerating compound (A1) is a diallyl dimethyl ammonium chloride polymer.

[0419] <17> The inkjet printing method described in <12> above, wherein the hydrophobic compound (A2) is selected from one or more of anionic resins and hydrophobic surfactants.

[0420] <18> The inkjet printing method described in <13> above, wherein the anionic resin is selected from one or more of anionic vinyl resin, anionic polyurethane resin, and anionic silicone resin.

[0421] <19> The inkjet printing method described in <12> above, wherein the hydrophobic compound (A2) is a cross-linked acrylic / styrene resin.

[0422] <20> The inkjet printing method as described in any one of <1> to <19> above, wherein the outer edge portion of the portion that becomes the dense image forming portion is a region that is 0.01 mm to 1 mm away from the boundary line between the dense image forming portion and the light image forming portion.

[0423] <21> In the inkjet printing method described in <20> above, the outer edge portion is a region that is 0.1 mm to 0.4 mm away from the boundary line between the dark image forming portion and the light image forming portion, measured from the boundary line between the dark image forming portion and the light image forming portion.

[0424] <22> The inkjet printing method as described in any one of <1> to <21> above, wherein, in step 1, the aforementioned pretreatment liquid is further applied to the inner edge portion of the portion that becomes the concentrated image forming portion.

[0425] <23> The inkjet printing method as described in any one of <1> to <22> above, wherein the inner edge portion of the portion that becomes the dense image forming portion is a region that is 0.01 mm to 1 mm away from the boundary line between the dense image forming portion and the light image forming portion.

[0426] <24> In the inkjet printing method described in <23> above, the inner edge portion is a region that is 0.2 mm to 0.4 mm away from the boundary line between the dark image forming portion and the light image forming portion, measured from the boundary line between the dark image forming portion and the light image forming portion.

[0427] <25> The inkjet printing method as described in any one of <1> to <24> above, wherein the difference between the printing duty cycle of the ink containing colorant in the dark image forming section and the printing duty cycle of the ink containing colorant in the light image forming section is 50% or more.

[0428] <26> In the inkjet printing method described in <25> above, the difference between the printing duty cycle of the ink containing colorant in the dark image forming section and the printing duty cycle of the ink containing colorant in the light image forming section is 90% or more.

[0429] <27> In the inkjet printing method described in <25> above, the difference between the printing duty cycle of the ink containing colorant in the dark image forming section and the printing duty cycle of the ink containing colorant in the light image forming section is 100%.

[0430] <28> The inkjet printing method as described in any one of <1> to <27> above, wherein the printing duty cycle of the ink containing colorant in the light image forming section is 0%.

[0431] <29> The inkjet printing method as described in any one of <1> to <28> above, wherein the printed image is an image of hollow text.

[0432] <30> The inkjet printing method as described in any one of <1> to <29> above, wherein, before step 1 or after step 2, it further includes step 3: applying white ink containing white pigment to the printing medium or the side of the printing medium to which the ink containing colorant has been applied.

[0433] <31> In the inkjet printing method described in any one of <1> to <30> above, the printing duty cycle of the ink containing colorant in the light image forming section is greater than 0%. In step 1, in addition to applying a pretreatment liquid to the outer edge of the section that becomes the dark image forming section, a pretreatment liquid is also applied to the portion of the section that becomes the light image forming section where no ink containing colorant has been applied.

[0434] <32> An inkjet printing apparatus for use in any one of <1> to <31> of the above, wherein,

[0435] It has: an inkjet head filled with the above-mentioned pretreatment liquid, and an inkjet head filled with the above-mentioned ink containing colorant.

[0436] <33> An ink assembly for inkjet printing, used in any one of <1> to <32> above, wherein,

[0437] It includes: the above-mentioned pretreatment solution and the above-mentioned ink containing colorant.

[0438] <34> A method for manufacturing a printed matter, wherein a printed image is formed on a printing medium, the printed image including a dark image forming section and a light image forming section, wherein the printing duty cycle of the ink containing colorant in the dark image forming section is greater than the printing duty cycle of the ink containing colorant in the light image forming section, wherein,

[0439] The method for manufacturing this printed material includes:

[0440] Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and

[0441] Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

[0442] Example

[0443] In the following preparation examples, manufacturing examples, embodiments, and comparative examples, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass". Furthermore, the methods for determining various physical properties are as follows.

[0444] The physical properties of resins, etc., are determined according to the following methods.

[0445] [Determination of number-average and weight-average molecular weight of resins]

[0446] The determination was performed using gel permeation chromatography. The determination conditions are shown below.

[0447] GPC device: "HLC-8320GPC" manufactured by Tosoh Corporation.

[0448] Column: "TSKgel SuperAWM-H", "TSKgel SuperAW3000", "TSKgelguardcolum Super AW-H" manufactured by Tosoh Corporation.

[0449] Eluent: A solution obtained by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively.

[0450] Flow rate: 0.5 mL / min.

[0451] Standard materials: Monodisperse polystyrene kits with known molecular weights [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)] (all manufactured by Tosoh Corporation).

[0452] Sample determination: Mix 0.1g of resin with 10mL of the above eluent in a glass bottle, stir at 25°C for 10 hours using a magnetic stirrer, filter the obtained substance using a syringe filter "DISMIC-13HP" (PTFE, 0.2μm, Advantec Co., Ltd.), and calculate the number-average molecular weight or weight-average molecular weight of the resin.

[0453] [Determination of the acid value of the resin]

[0454] In the case of a resin without a cross-linking structure, the resin is dissolved in a titration solvent composed of toluene and acetone (2:1). In the case of a resin with a cross-linking structure, the resin is dispersed in the titration solvent. Titration is performed using a potentiometric titration apparatus (Kyoto Electronics Industry Co., Ltd., electric burette, model: APB-610) with a 0.1N potassium hydroxide / ethanol solution, and the inflection point on the titration curve is taken as the endpoint. The acid value (mgKOH / g) is calculated based on the titration volume of the potassium hydroxide solution at the endpoint.

[0455] [Determination of solid component concentration]

[0456] Weigh 10.0 g of sodium sulfate, which has reached constant weight in a desiccator, into a 30 mL polypropylene container (φ = 40 mm, height = 30 mm). Add approximately 1.0 g of sample to the container, mix well, and weigh accurately. Maintain the mixture at 105 °C for 2 hours to remove volatile components. Then, place the container in a desiccator for 15 minutes and determine the mass. Divide the mass of the sample after removing volatile components as the solid content by the mass of the added sample to obtain the solid content concentration (%).

[0457] [Determination of the average particle size of resin particles without pigment and resin particles containing pigment]

[0458] Accumulation analysis was performed using an ELS-8000 laser particle analyzer system (manufactured by Otsuka Electronics Co., Ltd.). The obtained average particle size of the accumulated amount was used as the average particle size of resin particles without pigment or resin particles containing pigment. The concentration of the particles to be measured was obtained by dilution with water to a value of 5 × 10⁻⁶. -3 A dispersion of mass % (converted from solid component concentration) was used as the test sample. The test conditions were as follows: temperature 25℃, angle between incident light and detector 90°, cumulative number of tests 100, and the refractive index of the dispersion medium was input as the refractive index of water (1.333).

[0459] [Determination of static surface tension of organic solvent (B) at 25°C]

[0460] A platinum sheet was immersed in a cylindrical polyethylene container (3.6 cm in diameter × 1.2 cm in depth) containing 5 g of sample, which was set to 25 °C. The static surface tension at 25 °C was measured using a surface tension meter (manufactured by Kyowa Interface Chemicals Co., Ltd., “CBVP-Z”) and the Wilhelmy method.

[0461] Manufacturing Example 1 (Manufacturing of Acrylic / Styrene Resin)

[0462] A monomer mixture was prepared by mixing 31 parts of acrylic acid with 69 parts of styrene.

[0463] Add 10 parts of methyl ethyl ketone (hereinafter referred to as "MEK"), 0.2 parts of 2-mercaptoethanol as a polymerization chain transfer agent, and 10% of the above monomer mixture to the reaction vessel, mix them, and fully replace with nitrogen.

[0464] On the other hand, the remaining portion (90% of the monomer mixture), 0.13 parts of the polymerization chain transfer agent, 30 parts of MEK, and 1.1 parts of 2,2'-azobis(2,4-dimethylpentanonitrile) (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd., "V-65") as an azo radical polymerization initiator were added to a dropping funnel. Under a nitrogen atmosphere, the monomer mixture in the reaction vessel was heated to 65°C while stirring, and the mixture in the dropping funnel was added dropwise over 3 hours. After the addition was completed, the mixture was heated to 65°C for 2 hours, and then added to a solution in which 0.1 parts of the polymerization initiator were dissolved in 2 parts of MEK. The mixture was then cured at 65°C for 2 hours and at 70°C for 2 hours. After that, it was dried under reduced pressure to obtain acrylic / styrene resin (number average molecular weight: 19000, acid value: 240 mg KOH / g).

[0465] Manufacturing Example 2 (Manufacturing of cross-linked acrylic / styrene resin aqueous dispersion)

[0466] 15.3 parts of the acrylic / styrene resin obtained in Manufacturing Example 1 were mixed with 63.5 parts of deionized water, and then 1.8 parts of 25% ammonia were added to neutralize the mixture so that the molar ratio of ammonia to the molar ratio of carboxyl groups in the acrylic / styrene resin reached 40% (degree of neutralization: 40 mol%). The neutralized mixture was heated to 90°C in a warm water bath and stirred for 1 hour to disperse the acrylic / styrene resin in water. The mixture was then cooled to room temperature (25°C) to obtain a dispersion of acrylic / styrene resin.

[0467] Add 4.6 parts of trimethylolpropane polyglycidyl ether (Denacol EX-321LT, manufactured by Nagase ChemteX Co., Ltd., epoxy equivalent: 140) as a crosslinking agent to the obtained acrylic / styrene resin dispersion and seal the container. Stir the mixture while heating at 90°C for 1.5 hours. Then, perform crosslinking treatment using a crosslinking dose that reacts with 50% of the total carboxyl groups contained in the acrylic / styrene resin (crosslinking rate: 50%). Afterward, cool the dispersion to room temperature (25°C) and filter it using a 25 mL needle-free syringe (Terumo Corporation) fitted with a 5 μm pore size membrane filter (Minisart, manufactured by Sartorius, material: cellulose acetate). Add deionized water to adjust the solids concentration to 20%, obtaining an aqueous dispersion of crosslinked acrylic / styrene resin (acid value: 120 mg KOH / g).

[0468] Preparation Examples 1-8

[0469] The components of the pretreatment solution were added to a container equipped with a mixer according to the preparation composition shown in Table 1. After mixing at 25°C for 1 hour, the mixture was filtered using the 5μm pore size membrane filter and needleless syringe described above to obtain various pretreatment solutions.

[0470] The components shown in Table 1 are as follows.

[0471] <Component A that inhibits wetting and spreading>

[0472] [Agglutinating compound (A1)]

[0473] (Catonic resin)

[0474] Cationic vinyl resin A1-1: NITTOBO MEDICAL CO., LTD. produces "PAS-H-1L" (diallyl dimethyl ammonium chloride polymer).

[0475] (metal salt)

[0476] Calcium nitrate: Calcium nitrate tetrahydrate (a reagent manufactured by Tokyo Chemical Industry Co., Ltd.)

[0477] The amounts of calcium nitrate shown in Table 1 are based on anhydrous calcium.

[0478] (Organic acids)

[0479] Malonic acid: (a reagent manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd.)

[0480] [Hydrophobic compound (A2)]

[0481] (Anionic resin)

[0482] Anionic vinyl resin A2-1: An aqueous dispersion (solids concentration: 20%) of crosslinked acrylic / styrene resin (acid value: 120 mg KOH / g) obtained in Manufacturing Example 2.

[0483] Anionic vinyl resin A2-2: BASF's "Joncryl 7100" (styrene / acrylic resin emulsion, acid value: 51 mg KOH / g, active ingredient: 48%)

[0484] Anionic polyurethane resin A2-3: Covestro's "NeoRez R-600" (aliphatic polyurethane resin aqueous dispersion, acid value: 7 mg KOH / g, active ingredient: 38%)

[0485] Anionic silicone resin A2-4: "Chaline Ru-911" manufactured by Nissin Chemical Industry Co., Ltd. (blended type (formulated polyurethane), form: aqueous emulsion, acid value: 2.2 mg KOH / g, active ingredient: 36%)

[0486] The amount of anionic resin (A2-1 to A2-4) is the amount of active ingredient.

[0487] (Hydrophobic surfactant)

[0488] Surfynol 420: "Surfynol 420" manufactured by Nissin Chemical Industries, Ltd. (1.3 mol EO average of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, HLB value: 6.4 (calculation formula: 20 × ((34 + 44 × 1.3) / (226 + 44 × 1.3))))

[0489] <Organic Solvent (B)>

[0490] Diethylene glycol monobutyl ether: (a reagent manufactured by Fujifilm and Kojun Chemical Co., Ltd., with a static surface tension of 26.2 mN / m at 25°C)

[0491] Propylene glycol: (a reagent manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., static surface tension at 25°C: 36.0 mN / m)

[0492] (Hydrophilic nonionic surfactant)

[0493] Surfynol 465: "Surfynol 465" manufactured by Nissin Chemical Industries, Ltd. (the average 10 mol EO adduct of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, HLB value: 14.2 (calculated as: 20 × ((34 + 44 × 10) / (226 + 44 × 10))))

[0494] KF-6011: "KF-6011" (PEG-11 methyl ether polydimethylsiloxane (side-chain polyether modified linear silicone), HLB value: 14.5 (product catalog value) manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0495] [Table 1]

[0496]

[0497] Manufacturing Example 3 (Manufacturing of an aqueous dispersion of cross-linked resin particles containing black pigment)

[0498] 100 parts of the acrylic / styrene resin obtained in Manufacturing Example 1 were mixed with 78.6 parts of MEK, and then 41.2 parts of a 5N sodium hydroxide aqueous solution (sodium hydroxide content: 16.9%) as a neutralizing agent were added for neutralization (degree of neutralization: 40 mol%). 800 parts of deionized water were further added, along with 100 parts of black pigment (CB, CI Pigment Black 7, "Monarch 717" manufactured by Cabot Corporation). The mixture was stirred for 60 minutes at 20°C and 7000 rpm using a disperser ("Ultra Despa" manufactured by Asada Iron Works Co., Ltd.). The resulting mixture was then dispersed 10 times at a pressure of 200 MPa using a Microfluidizer (manufactured by Microfluidics Co., Ltd., trade name).

[0499] Next, 250 parts of deionized water were added to the obtained dispersion and stirred. MEK was removed under reduced pressure at 60°C, and then some water was removed to adjust the pigment concentration to 10%. 35.7 parts of trimethylolpropane polyglycidyl ether (Denacol EX-321 manufactured by Nagase ChemteX Co., Ltd., epoxy equivalent: 140) as a crosslinking agent were added and sealed. The mixture was stirred with a stirrer and heated at 70°C for 5 hours. After that, it was cooled to room temperature (25°C) to obtain an aqueous dispersion of crosslinked resin particles containing black pigment (crosslinking rate: 60 mol%) (solid component concentration: 23.4%, pigment content: 9.7%, acid value: 96 mg KOH / g (calculated value)).

[0500] Manufacturing Example 4 (Manufacturing of an aqueous dispersion of resin particles without pigments)

[0501] In a reaction vessel equipped with a dropping funnel, the monomers shown in the "Initial Feed Monomer Solution" in Table 2, sodium polyoxyethylene alkyl ether sulfate (Kao Corporation's "Latemul E-118B" as a surfactant) (hereinafter referred to as "Latemul E-118B"), potassium persulfate (Fujifilm and Kojun Chemical Co., Ltd. as a polymerization initiator), and deionized water were added, mixed, and purged with nitrogen to obtain the initial feed monomer solution. Separately, the monomers, surfactants, polymerization initiators, and deionized water shown in the "Droplet Addition Monomer Solution" in Table 2 were mixed to obtain the droplet addition monomer solution, which was then added to the dropping funnel and purged with nitrogen.

[0502] Under a nitrogen atmosphere, the initial monomer solution in the reaction vessel was stirred while being heated from room temperature (25°C) to 80°C over 30 minutes and maintained at 80°C. At this temperature, the monomer was slowly added dropwise from the dropping funnel into the reaction vessel over 3 hours. After the addition was complete, the mixture was stirred for 1 hour while maintaining the temperature inside the reaction vessel. Then, it was filtered through a 200-mesh sieve to obtain an aqueous dispersion of pigment-free resin particles (solids concentration: 44.1%, average particle size: 94 nm).

[0503] The resin that constitutes the pigment-free resin particles has a weight-average molecular weight of 750,000 and an acid value of 16 mg KOH / g.

[0504] [Table 2]

[0505]

[0506] Manufacturing Example 5 (Manufacturing of Black Ink Bk1)

[0507] The following were added: 33.0 parts of an aqueous dispersion of cross-linked resin particles containing black pigment obtained in Manufacturing Example 3 (solid content concentration: 23.4%, pigment content: 9.7%), 11.3 parts of an aqueous dispersion of resin particles without pigment obtained in Manufacturing Example 4 (solid content concentration: 44.1%), 11.5 parts of propylene glycol (manufactured by Fujifilm and Kohden Chemical Co., Ltd.), 3.5 parts of diethylene glycol monoisobutyl ether (manufactured by Fujifilm and Kohden Chemical Co., Ltd.), and a polyether-modified silicone surfactant ("Silface SAG005" manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 7 (catalog value), kinematic viscosity: 170 mmHg. 2 A mixture was prepared by mixing 0.2 parts of acetylenol surfactant (Surfynol 104PG-50 manufactured by Nissin Chemical Industry Co., Ltd.), a propylene glycol solution of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, active ingredient: 50%, HLB value: 3.0 (calculation formula: 20×(34 / 226))) and 1.0 parts of ion-exchanged water to achieve a total volume of 100 parts. The mixture was then filtered using the membrane filter and needleless syringe described above to obtain black ink Bk1.

[0508] Manufacturing Example 6 (Manufacturing of an aqueous dispersion of resin particles containing white pigment)

[0509] Add 2500g of polyacrylic acid ("Aron A-10SL", manufactured by Toa Synthetic Co., Ltd., weight average molecular weight: 6000, acid value: 735mgKOH / g, solid content concentration: 40%) and 3.57g of deionized water to a 5L plastic container. Cool the container in an ice bath, and while stirring at 100rpm, slowly add 1666.43g of 5N sodium hydroxide aqueous solution to neutralize the solution. Add deionized water to the neutralized aqueous solution to adjust the solid content concentration to 20%, obtaining a neutralized aqueous solution of polyacrylic acid (neutralization degree: 53 mol%, acid value: 735mgKOH / g).

[0510] Next, in a 2L plastic container (Nikko Hansen & Co., Ltd., J-type bottle, round wide mouth, natural color), 33.0g of a neutralized aqueous solution of polyacrylic acid (solid content concentration: 20%), 300g of titanium dioxide (Ishihara Sangyo Co., Ltd. "Tipaque CR-80", CI Pigment White 6, rutile type, Al-Si treated, average particle size: 250nm (catalog value)) and 300g of water were added, along with 1000g of zirconia beads. The mixture was dispersed for 8 hours using a benchtop mill stand (AS ONE Co., Ltd.). The zirconia beads were removed using a metal mesh, and the solid content concentration was adjusted using deionized water to obtain an aqueous dispersion of resin particles containing white pigment (solid content concentration: 51%, pigment content: 50%, polyacrylic acid content: 1%, average particle size: 280nm, pH: 7.6).

[0511] Manufacturing Example 7 (Manufacturing of White Ink W2)

[0512] Add 20.0 g of the aqueous dispersion of resin particles containing white pigment obtained in Manufacturing Example 6 (solid content concentration: 51%), 10.4 g of styrene / acrylic resin emulsion (BASF's "Joncryl 7100", acid value: 51 mg KOH / g, solid content 48%), 3.0 g of diethylene glycol monoisobutyl ether (Japan Emulsifier Co., Ltd.), 30.0 g of propylene glycol, and 1 g of acetylenol surfactant (Nikshin Chemical Industry Co., Ltd.'s "Surfynol"). A mixture was prepared by adding 104PG-50”, a propylene glycol solution of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (active ingredient: 50%, HLB value: 3.0 (calculated value)), 3.0g of silicone surfactant (Shin-Etsu Chemical Industry Co., Ltd. "KF-6011", HLB value: 14.5 (catalog value)), 2.4g of 1N sodium hydroxide aqueous solution, and ion-exchanged water to a total volume of 100g. The mixture was then filtered using the membrane filter and needleless syringe described above to obtain white ink W2.

[0513] Examples 1-12, Comparative Examples 1-2

[0514] Using the combination of printing media, pretreatment solution, pretreatment solution application area, and drying process with or without pretreatment solution on the printing media shown in Table 3, inkjet printing was performed in the following manner, and the following evaluation was conducted.

[0515] (Process 1)

[0516] In an environment of 25±1℃ and 30±5% relative humidity, a printing evaluation apparatus (manufactured by TRITEC Co., Ltd.) equipped with multiple inkjet heads (KYOCERACorporation "KJ4B-HD06MHG-STDV", piezoelectric type) was filled with various pretreatment solutions shown in Table 3 and black ink Bk1 obtained as a colorant-containing ink in manufacturing example 5.

[0517] The printhead voltage is set to 26V, frequency to 26kHz, printhead temperature to 32℃, resolution to 1200dpi, pre-discharge rinsing times to 200, and negative pressure to -4.0kPa. The printing medium is fixed on the conveyor table with its long side aligned with the conveying direction using pressure reduction. At this time, the printing medium uses a non-absorbent PET film FE 2001 (manufactured by FUTAMURACHEMICAL CO.,LTD., water absorption: 0g / m³). 2 Or OK top coated paper (manufactured by Oji Paper Co., Ltd., water absorption: 4.9g / m²) as a coated paper. 2 ).

[0518] In Examples 1 to 8 and 10, step 1 is performed using a mirror image of the hollow text reversed as shown in FIG4-a, so that when viewed from the side of the non-absorbent film opposite to the side where the printed image is formed, a pattern is formed. Figure 3 The image shown is a printed image of hollow text with a text size of 12, consisting of a light image forming section (i) (0% printing duty cycle containing colorant ink) and a dark image forming section (ii) (100% printing duty cycle containing colorant ink).

[0519] Similarly, in Example 9, since the mirror image of the hollow text being reversed as shown in FIG4-a is used, the printed image formed in Example 9 becomes an image that is the reverse of the printed images formed in Examples 1 to 8 and 10.

[0520] In step 1 of Examples 1-10, a pretreatment solution is applied to the printing medium in a full-coat manner (100% printing duty cycle) to the outer edge (iii) of the region (ii') in Figure 4-a that forms a dense image region. The outer edge (iii) of the region (ii') in Figure 4-a is... Figure 3 The portion corresponding to the outer edge of the dense image forming part (ii) is equivalent to Figure 3 The light image forming section (i). The outer edge (iii) of the part that becomes the dark image forming section (ii') in Figure 4-a is the area within 0.3 mm away from the boundary line between the dark image forming section and the light image forming section. The part that becomes the light image forming section (i') in Figure 4-a corresponds to Figure 3 The light image forming part (i).

[0521] Furthermore, in Example 11, for the printed image, the images formed in Examples 1 to 8 and 10 are used. Figure 3 The text size of the hollow text printed image shown is adjusted to level 8. Pretreatment liquid is applied to the printing medium in a full-coverage manner (100% printing duty cycle) to both the outer edge (iii) and inner edge (iv) of the region (ii') in Figure 4-b, which forms the dense image region. The outer edge (iii) of the region (ii') in Figure 4-b is... Figure 3 The portion corresponding to the outer edge of the dense image forming part (ii) belongs to Figure 3 The light image forming section (i). The outer edge (iii) of the section that becomes the dark image forming section in Figure 4-b is the area within 0.3 mm away from the boundary line between the dark image forming section and the light image forming section. The section (i') that becomes the light image forming section in Figure 4-b corresponds to Figure 3 The light image forming part (i).

[0522] Furthermore, the inner edge (iv) of the region (ii') that forms the dense image in Figure 4-b is related to... Figure 3 The portion corresponding to the inner edge of the concentrated image forming part (ii) belongs to Figure 3 The dense image forming section (ii). The inner edge portion (iv) of the part (ii') that becomes the dense image forming section in Figure 4-b is the area within 0.3 mm away from the boundary line between the dense image forming section and the light image forming section.

[0523] Furthermore, in Example 12, for the printed image, the images formed in Examples 1 to 8 and 10 are used. Figure 3The text size of the hollow text printed image is adjusted to level 8. The amount of pretreatment liquid applied and the amount of liquid droplets discharged are the same as in Examples 1 to 10. The pretreatment liquid is applied to the printing medium in a full coating state (the printing duty cycle of the pretreatment liquid is 100%).

[0524] In Comparative Example 1, the pretreatment liquid was applied to the entire surface of the printing medium in a full-coverage manner with a droplet volume of 1.5 pL and a printing duty cycle of 100%; in Comparative Example 2, no pretreatment liquid was applied to the printing medium.

[0525] After applying the pretreatment solution, as a drying step, the temperature of the surface of the printing medium to which the pretreatment solution was applied is maintained at 100°C for 1.5 seconds using warm air to dry the pretreatment solution. During this time, the temperature of the printing medium is determined using a non-contact thermometer. Alternatively, in Example 10, after applying the pretreatment solution, the above drying step is not performed; the medium is placed in an environment with a temperature of 25±1°C and a relative humidity of 30±5% for 3 seconds.

[0526] (Process 2)

[0527] On the side of the printing medium obtained in step 1 that has the pretreatment liquid supply section, an inkjet head filled with the black ink Bk1 obtained in manufacturing example 5 is used with the apparatus used in step 1. Figure 5 The part (i) that becomes the light image forming part is applied to the part (ii) that becomes the dark image forming part in step 1 in the manner of the part (i') that becomes the light image forming part in Figure 4-a or Figure 4-b, with a droplet volume of 2 pL and a printing duty cycle of 100%.

[0528] In addition, in Comparative Example 2, for the printing medium, to Figure 5 The part (ii) that becomes the concentrated image forming part is given black ink with a droplet volume of 2 pL and a printing duty cycle of 100%.

[0529] exist Figure 5 The portion (ii) in which the colorant-containing ink is applied to form a concentrated image area corresponds to... Figure 3 The dense image forming part (ii).

[0530] (Process 3)

[0531] In the same printing apparatus as in step 1, the white ink W2 obtained in manufacturing example 7 is filled. The entire surface of the printing medium obtained in step 2, on which the black ink was applied, is then coated with white ink, with a droplet volume of 5 pL and a printing duty cycle of 100%. In example 9, step 3 is omitted, and white ink is not applied.

[0532] Photographs of the printed images of the hollow characters obtained in Example 1 and Comparative Example 2 are shown respectively. Figure 6 and Figure 7 .in, Figure 6 and Figure 7 It is a photograph taken from the side of the non-absorbent film opposite to the side where the printed image is formed.

[0533] Example 13

[0534] The printed image is changed to a barcode, otherwise the printing is carried out in the same manner as in Example 1.

[0535] In Example 13, using Figure 9 The process 1 involves inverting a barcode image and performing step 1, so that when viewed from the side of the non-absorbent film opposite to the side where the printed image was formed, a pattern is formed. Figure 8 The image shown is a printed image of a barcode consisting of a light image forming section (i) (0% printing duty cycle containing colorant ink) and a dark image forming section (ii) (100% printing duty cycle containing colorant ink).

[0536] In process 1, to Figure 9 The pretreatment solution is applied to the printing medium at the outer edge of the portion (ii') that forms the concentrated image section (iii) with a droplet volume of 1.5 pL and in a full-coverage manner (100% printing duty cycle of the pretreatment solution). As a drying step, the temperature of the surface of the printing medium to which the pretreatment solution has been applied is maintained at 100°C for 1.5 seconds using warm air to dry the pretreatment solution. At this time, the temperature of the printing medium is determined using a non-contact thermometer.

[0537] Next, in step 2, the side of the printing medium obtained in step 1 that has the pretreatment liquid application section is filled with the black ink Bk1 obtained in manufacturing example 5 using the inkjet head of the device used in step 1, so that the part (i”) (not shown) that becomes the light image forming section is utilized in step 1. Figure 9 In a manner that the portion forming the light image (i') is treated, black ink is applied to the portion forming the dark image (ii") (not shown) with a droplet volume of 2 pL and a printing duty cycle of 100%. Furthermore, as step 3, white ink W2 obtained in manufacturing example 7 is filled into the same printing apparatus as in step 1. White ink is applied to the entire surface of the printing medium in step 2 that has been coated with black ink, with a droplet volume of 5 pL and a printing duty cycle of 100%.

[0538] exist Figure 9 The outer edge (iii) of the part that forms the concentrated image (ii') is with Figure 8 The portion corresponding to the outer edge of the dense image forming part (ii) belongs to Figure 8 The light image forming part (i).

[0539] A photograph of the printed image of the barcode obtained in Example 13 is shown below. Figure 10 .in, Figure 10 It is a photograph taken from the side of the non-absorbent film opposite to the side where the printed image is formed.

[0540] <Evaluation of the appearance of stripes>

[0541] Observe the black ink portion of the printed material and visually evaluate the stripes.

[0542] (Evaluation Criteria)

[0543] 4: No stripes, uniform and in good condition.

[0544] 3: Some stripes are visible.

[0545] 2: The stripes are visible, but the level is not problematic in practical use.

[0546] 1. The stripes are clearly visible, which presents a problem in practical use.

[0547] In practical use, a score of 2 or higher based on the above evaluation criteria is sufficient.

[0548] <Evaluation of the sharpness of printed images (sharpness of hollow text and sharpness of barcode edges)>

[0549] Observe the hollow text or barcode portion of the printed material and visually evaluate the clarity of the printed image (sharpness of the hollow text and sharpness of the edges of the barcode).

[0550] (Evaluation Criteria)

[0551] 4. It can clearly identify hollow text or barcodes.

[0552] 3: Hollow text or barcodes are blunted, but can still be recognized.

[0553] 2: Hollow text or barcodes are blunted and difficult to read, but this is not a problem in practical use.

[0554] 1: Hollow text or barcodes are covered by black ink and cannot be recognized.

[0555] In practical use, a score of 2 or higher based on the above evaluation criteria is sufficient.

[0556] [Table 3]

[0557]

[0558] As shown in Table 3, compared with the comparative example, the printed material obtained in the example can suppress the appearance of stripes and the clarity of the printed image (sharpness of hollow text or barcode) is excellent.

[0559] [Industry availability]

[0560] According to the present invention, even in inkjet printing using a linear array printhead with a low absorbency printing medium, it is possible to obtain printed materials with excellent clarity, including both dark and light image formation areas, where the appearance of streaks is suppressed.

[0561] [Explanation of reference numerals in the attached figures]

[0562] (i) Faded image forming part;

[0563] (ii) Concentrated image forming section;

[0564] (i') is the part that forms the light image;

[0565] (ii') The part that becomes the concentrated image forming part;

[0566] (iii) The outer edge of the region (ii') that forms the dense image;

[0567] (iv) The inner edge portion of the part that forms the dense image (ii');

[0568] (i) The part that becomes the light image forming part;

[0569] (ii) becomes the part of the dense image forming part.

Claims

1. An inkjet printing method, wherein, This inkjet printing method forms a printed image on a printing medium, the printed image including a dense image forming region and a light image forming region, wherein the printing duty cycle of the ink containing colorant in the dense image forming region is greater than the printing duty cycle of the ink containing colorant in the light image forming region, and... The inkjet printing method includes: Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

2. The inkjet printing method as described in claim 1, wherein, The printing medium is a low-absorption printing medium.

3. The inkjet printing method as described in claim 1 or 2, wherein, Step 1 includes the step of maintaining the printing medium, to which the pretreatment liquid has been applied, at a temperature above 25°C.

4. The inkjet printing method according to any one of claims 1 to 3, wherein, Step 1 includes the step of drying the printing medium that has been given the pretreatment solution.

5. The inkjet printing method according to any one of claims 1 to 4, wherein, Step 1 includes the step of immobilizing the pretreatment liquid in the treatment unit.

6. The inkjet printing method according to any one of claims 1 to 5, wherein, The pretreatment solution contains one or more compounds selected from agglutinating compounds (A1) and hydrophobic compounds (A2).

7. The inkjet printing method as described in claim 6, wherein, The agglutinating compound (A1) is selected from one or more of metal salts, organic acids or their salts, and cationic resins.

8. The inkjet printing method as described in claim 6, wherein, The hydrophobic compound (A2) is selected from one or more of anionic resins and hydrophobic surfactants.

9. The inkjet printing method according to any one of claims 1 to 8, wherein, The outer edge of the region that forms the dense image forming section is the area 0.01 mm to 1 mm away from the boundary line between the dense image forming section and the light image forming section.

10. The inkjet printing method according to any one of claims 1 to 9, wherein, In step 1, the pretreatment liquid is further applied to the inner edge portion of the area that becomes the concentrated image forming section.

11. The inkjet printing method as described in claim 10, wherein, The inner edge portion of the dense image forming section is the area 0.01 mm to 1 mm away from the boundary line between the dense image forming section and the light image forming section.

12. The inkjet printing method according to any one of claims 1 to 11, wherein, The difference between the printing duty cycle of the ink containing colorant in the dark image forming section and the printing duty cycle of the ink containing colorant in the light image forming section is 50% or more.

13. The inkjet printing method according to any one of claims 1 to 12, wherein, The printing duty cycle of the ink containing colorant in the light image forming section is 0%.

14. The inkjet printing method according to any one of claims 1 to 13, wherein, The printed image is an image of hollow text.

15. The inkjet printing method according to any one of claims 1 to 14, wherein, Before step 1 or after step 2, the process also includes step 3, which involves applying white ink containing white pigment to one side of the printing medium or the side of the printing medium that has been coated with ink containing colorant.

16. The inkjet printing method according to any one of claims 1 to 15, wherein, The printing duty cycle of the colorant-containing ink in the light image forming section is greater than 0%. In step 1, pretreatment liquid is applied not only to the outer edge of the part that forms a dark image, but also to the part of the part that forms a light image where no ink containing colorant is applied.

17. An inkjet printing apparatus for use in the inkjet printing method according to any one of claims 1 to 16, wherein, It comprises: an inkjet head filled with the pretreatment liquid and an inkjet head filled with ink containing the colorant.

18. An ink assembly for inkjet printing, used in the inkjet printing method according to any one of claims 1 to 16, wherein, The ink comprises the pretreatment solution and the colorant.

19. A method for manufacturing printed matter, wherein, The method for manufacturing this printed material forms a printed image on a printing medium. The printed image includes a dense image forming section and a light image forming section. The printing duty cycle of the ink containing colorant in the dense image forming section is greater than the printing duty cycle of the ink containing colorant in the light image forming section. The method for manufacturing this printed material includes: Step 1: Applying a pretreatment solution to the outer edge of the area that forms the concentrated image forming section to obtain a printing medium having a pretreatment solution application section; and Step 2: A step of applying ink containing colorant to the part of the printing medium obtained in Step 1 that has a pretreatment liquid application section, which becomes the concentrated image forming section, by using a linear printhead inkjet method.

Images