Ink set and ink jet recording method

Abstract

The ink set according to the present invention includes an ink containing at least a pigment and a processing liquid containing at least a coagulant, and is used for forming an image by applying the ink and the processing liquid to a recording medium and combining the ink and the processing liquid, the static surface tension of the processing liquid being in the range of 18-25 mN / m at 25 DEG C, the processing liquid has a surface life of 50 msec and a dynamic surface tension of 25-35 mN / min at 25 DEG C, the ink contains a polyolefin resin, and the recording medium is a non-absorbent substrate.

Description

Technical Field

[0001] The present invention relates to an ink set and an inkjet recording method, and in particular, provides an ink set having good ink storage stability, high image quality, and good adhesion to a non-absorbent substrate in a two-liquid inkjet recording method. Background Art

[0002] In the inkjet recording method, it is known that a liquid offset phenomenon occurs in which ink droplets land on a recording medium, and image quality is degraded due to bleeding, which is bleeding between different colors.

[0003] As a means of solving these problems, a treatment liquid for agglomerating the colorant in the ink is discharged, and the treatment liquid and the ink are combined on the recording medium before the treatment liquid dries. Thus, a two-liquid inkjet recording method is disclosed that allows the ink to be well fixed on the recording medium without reducing the image quality (for example, refer to Patent Document 1).

[0004] In addition, in recent years, the technology of printing by inkjet in packaging materials of food, beverages, daily necessities, etc. has been developed. Therefore, the development of ink corresponding to non-absorbent recording media such as plastic films is promoted. The polypropylene substrate used in packaging materials is non-polar and crystalline, and it is difficult to make the ink close. Therefore, an inkjet recording method is disclosed in which a polyolefin resin that is appropriately close to these substrate types is used in the resin types in the ink (for example, refer to patent document 2).

[0005] In addition, an inkjet recording method is disclosed in which a two-liquid inkjet recording method is used for an ink containing a polyolefin resin to achieve both high image quality and adhesion to a polypropylene substrate (for example, see Patent Document 3).

[0006] As described above, various plastic materials are used for packaging materials for food, beverages, daily necessities, etc. In order to perform inkjet recording on packaging materials, substrate versatility that can correspond to these multiple substrate types is required, which has become a problem.

[0007] In particular, for printing surfaces with poor ink wettability, such as polypropylene surfaces not subjected to corona discharge treatment and gravure printing ink surfaces, liquid offset occurs, where ink drops merge with each other. As a result, it is known that image formation is difficult.

[0008] In order to form a good image on such a printing surface having poor wettability, a surfactant or a wetting solvent is added to improve the wettability of the ink.

[0009] However, it is known that these additives are likely to impair the stability of the ink. In particular, in the case of polyolefin resins, the number of hydrophilic groups on the resin surface is designed to be small from the viewpoint of adhesion to the plastic substrate, and the amount of dispersing aid added is suppressed. Therefore, in the ink containing polyolefin resins, it is not preferred to add a large amount of surfactants and wetting solvents that improve wettability from the viewpoint of ink stability.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 8-52867

[0013] Patent Document 2: Japanese Patent Application Publication No. 2013-193324

[0014] Patent Document 3: Japanese Patent Application Publication No. 2014-024944 Summary of the invention

[0015] Problems to be solved by the invention

[0016] The present invention has been made in view of the above problems and circumstances, and the problems to be solved are as follows: To provide an ink set and an inkjet recording method having good ink storage stability, high image quality, and good adhesion to a non-absorbent substrate in a two-liquid inkjet recording method.

[0017] Means for solving problems

[0018] The present inventors have discovered the importance of keeping the static and dynamic surface tensions of the treatment liquid within a specific range in order to solve the above-mentioned problems during the process of studying the causes of the above-mentioned problems. As a result, even if the ink contains a polyolefin resin, the storage stability of the ink is improved in the inkjet recording method of the two-liquid method. In addition, an ink set and an inkjet recording method having excellent image quality and good adhesion to a non-absorbent substrate can be provided.

[0019] That is, the above-mentioned problems according to the present invention are solved by the following means.

[0020] 1. An ink set comprising an ink containing at least a pigment and a treatment liquid containing at least a coagulant, and for forming an image by combining the ink and the treatment liquid by applying them to a recording medium,

[0021] The static surface tension of the treatment liquid is in the range of 18 to 25 mN / m at 25°C.

[0022] The surface life of the treatment liquid is 50 msec, and the dynamic surface tension is in the range of 25 to 35 mN / min at 25°C.

[0023] The ink contains a polyolefin resin, and

[0024] The above-mentioned recording medium is a non-absorbing substrate.

[0025] 2. The ink set according to item 1, wherein the static surface tension of the ink is in the range of 25 to 35 mN / m at 25°C.

[0026] The ink has a surface life of 50 msec and a dynamic surface tension of 35 to 45 mN / min at 25°C.

[0027] 3. The ink set according to item 1, wherein the polyolefin resin is an acid-modified polyolefin resin.

[0028] 4. The ink set according to item 1, wherein the treatment liquid contains a trisiloxane-based surfactant.

[0029] 5. The ink set according to item 1, wherein the ink contains polyolefin resin particles having an average particle size within a range of 10 to 80 nm and resin particles having an average particle size within a range of 100 to 300 nm.

[0030] 6. The ink set according to item 1, wherein the ink contains polyolefin resin particles having an average particle size within a range of 10 to 80 nm and polyolefin resin particles having an average particle size within a range of 100 to 300 nm.

[0031] 7. The ink set according to item 1, wherein an average particle size of pigment particles contained in the pigment is within a range of 50 to 100 nm.

[0032] 8. The ink set according to item 1, wherein the ink contains wax.

[0033] 9. An inkjet recording method, comprising recording an image on a recording medium using the ink set described in any one of items 1 to 8.

[0034] 10. The inkjet recording method according to item 9, wherein the amount of the treatment liquid applied per unit area for forming the image is 5.0 g / m 2 the following.

[0035] Effects of the Invention

[0036] According to the above means of the present invention, it is possible to provide an ink set and an inkjet recording method having good ink storage stability and excellent image quality and adhesion to a non-absorbent substrate in a two-liquid inkjet recording method.

[0037] The manifestation mechanism and action mechanism of the effects of the present invention are not yet clear, but are presumed as follows.

[0038] In the present invention, the static surface tension and dynamic surface tension of the treatment liquid are set within the above-mentioned specific ranges. When the static surface tension and dynamic surface tension are lower than the above-mentioned specific ranges, the treatment liquid expands, excessive wetting and spreading, and thus the reproducibility of the text deteriorates. On the other hand, when the static surface tension and dynamic surface tension are higher than the above-mentioned specific ranges, the treatment liquid is repelled by the substrate, and the reproducibility of the text deteriorates.

[0039] Thus, in the present invention, by adjusting the static surface tension and dynamic surface tension of the treatment liquid to be within a specific range, the addition of a surfactant or a wetting solvent to improve wettability can be suppressed to a minimum in the ink. For example, even if a surfactant is used, a surfactant that does not damage the storage stability of the ink can be used, or the use can be suppressed to a degree that does not damage the above storage stability. In particular, when a polyolefin resin is used, the effect is very effective.

[0040] Therefore, even when using an ink containing a polyolefin resin, high wettability is ensured for a non-absorbent substrate, and the image quality (especially text reproducibility) formed is excellent. In addition, the adhesion to the non-absorbent substrate is also excellent.

[0041] In addition, in the past, when the ink containing the dispersed resin is dried to form a coating, it is known that the film-forming property and the substrate adhesion can be improved by reducing the dispersed particle size. On the other hand, it is known that the ink coating formed on the non-absorbent substrate by the two-liquid inkjet recording method cracks during the drying of the ink due to its coagulation reaction, and the full coating (ベタ) homogeneity decreases. In particular, it is known that if the particle size of the dispersed resin particles in the ink is small, its influence is significant. Therefore, in the present invention, it is preferred to mix two kinds of polyolefin resins with different particle size ranges in the ink. As a result, the film-forming property is good and the cracking of the coating can be prevented. As the above two kinds of particle size ranges, the average particle size range of 10 to 80nm and the range of 100 to 300nm are preferred. In addition, a small-diameter polyolefin resin and a large-diameter resin other than a polyolefin resin can be mixed and used. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1A It is a diagram for explaining a state in which the processing liquid and the ink in the present invention are combined.

[0043] Figure 1B It is a diagram for explaining a state in which the processing liquid and the ink in the present invention are combined.

[0044] Figure 1C It is a diagram for explaining a state in which the processing liquid and the ink in the present invention are combined.

[0045] Figure 2 This is a schematic diagram showing an example of a recording device preferred in the present invention.

[0046] Figure 3 This is a cross-sectional view of packaging material for canned food. DETAILED DESCRIPTION

[0047] The ink set of the present invention is an ink set that includes an ink containing at least a pigment and a treatment liquid containing at least a coagulant, and is used to form an image by applying the above-mentioned ink and the above-mentioned treatment liquid to a recording medium and combining them, the static surface tension of the above-mentioned treatment liquid is in the range of 18 to 25 mN / m at 25°C, the surface life of the above-mentioned treatment liquid is 50 msec, and the dynamic surface tension is in the range of 25 to 35 mN / min at 25°C, the above-mentioned ink contains a polyolefin resin, and the above-mentioned recording medium is a non-absorbent substrate.

[0048] This feature is a common or corresponding technical feature of the following embodiments.

[0049] As an embodiment of the present invention, the static surface tension of the ink is preferably in the range of 25 to 35 mN / m at 25° C. In addition, the surface life of the ink is preferably 50 msec and the dynamic surface tension is preferably in the range of 35 to 45 mN / min at 25° C. When the static surface tension and dynamic surface tension of the ink are in the above ranges, the ink has good storage stability and can be stably discharged from the inkjet head.

[0050] In addition, in order to obtain high character reproducibility in a two-liquid inkjet recording method, it is preferred that the polyolefin resin is an acid-modified polyolefin resin.

[0051] In addition, in order to obtain high character reproducibility in a two-liquid inkjet recording method, it is preferred that the treatment liquid contains a trisiloxane-based surfactant.

[0052] Furthermore, the ink preferably contains polyolefin resin particles with an average particle size (average particle size) of 10 to 80 nm and resin particles with an average particle size of 100 to 300 nm. By mixing two types of resins with different particle sizes, film forming properties are excellent and cracking of the coating film can be prevented.

[0053] The resin particles having an average particle size within the range of 100 to 300 nm may be resin particles other than polyolefin resin particles, but are preferably polyolefin resin particles.

[0054] In terms of making the average particle size of the resin particles within the above range, if it is 10 nm or more, the film-forming property of the resin when the ink is dried will not be excessively increased, and nozzle clogging can be prevented. In addition, if the average particle size of the resin particles is 300 nm or less, the particle size will not be excessively increased, so if an inkjet head is used, the discharge property becomes good. As a result, the film-forming property is good and the substrate adhesion is also good.

[0055] In addition, in terms of excellent ink adhesion to a non-absorptive substrate, it is preferred that the average particle size of the pigment particles contained in the pigment is within a range of 50 to 100 nm.

[0056] In addition, the ink preferably contains wax in terms of excellent ink adhesion to a non-absorptive substrate.

[0057] The inkjet recording method of the present invention uses the ink set to record an image on a recording medium. Thus, in a two-liquid inkjet recording method, the ink storage stability is good, and the image quality and adhesion to a non-absorbent substrate are excellent.

[0058] In order to obtain high text reproducibility in the two-liquid inkjet recording method, it is preferred that the amount of the processing liquid applied per unit area for forming the image is 5.0 g / m 2 the following.

[0059] Hereinafter, the present invention and its constituent elements and forms and modes for carrying out the present invention will be described. It should be noted that in the present application, "to" is used to mean that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0060] [Overview of the ink set of the present invention]

[0061] The ink set of the present invention is an ink set that includes an ink containing at least a pigment and a treatment liquid containing at least a coagulant, and is used to form an image by applying the above-mentioned ink and the above-mentioned treatment liquid to a recording medium and combining them, the static surface tension of the above-mentioned treatment liquid is in the range of 18 to 25 mN / m at 25°C, the surface life of the above-mentioned treatment liquid is 50 msec, and the dynamic surface tension is in the range of 25 to 35 mN / min at 25°C, the above-mentioned ink contains a polyolefin resin, and the above-mentioned recording medium is a non-absorbent substrate.

[0062] The "treatment liquid" and "ink" mentioned in the present invention refer to "treatment liquid (also referred to as "pretreatment liquid" or "primer") and "ink (also referred to as "water-based ink" or "aqueous ink")" using at least water or a water-soluble solvent as a solvent. It is preferred that 60% by mass or more of the solvent used is "water".

[0063] The term “merge” as used in the present invention means that droplets of the treatment liquid and ink are overlapped or contacted on the recording medium to form a liquid body in which the respective components are mixed with each other, and finally form a pixel constituting an image.

[0064] For example, Figure 1A As shown in FIG. 1 , before the ink is landed on the recording medium (impact), a droplet 12 of the treatment liquid is landed on the recording medium F via the inkjet head. After the treatment liquid is landed, as shown in FIG. Figure 1BAs shown in FIG. 1 , the ink droplets 22 are landed on the recording medium F on which the treatment liquid has landed. As a result, as shown in FIG. Figure 1C As shown in FIG. 1 , the droplets 12 of the treatment liquid are mixed with the droplets 22 of the ink, and the pigment P in the ink is aggregated and precipitated by the aggregating agent in the treatment liquid. Then, the image layer G is formed on the recording medium F.

[0065] In addition, the treatment liquid may be landed after the ink is landed on the recording medium.

[0066] <Static surface tension>

[0067] In the present invention, the "static surface tension" refers to the surface tension when the liquid surface approaches an equilibrium state due to diffusion of components in the ink or the treatment liquid over the life of the surface.

[0068] The static surface tension of the ink or the treatment liquid can be measured by using an automatic surface tension meter (e.g., Kyowa Interface Science Co., Ltd., model "CBVP-Z") using a platinum plate. Unless otherwise specified, the static surface tension in this specification is the static surface tension measured at 25°C.

[0069] The static surface tension of the treatment liquid of the ink set of the present invention is in the range of 18 to 25 mN / m at 25°C. However, in terms of making the static surface tension of the treatment liquid within the above range, if it is lower than 18 mN / m, the treatment liquid expands, excessive wetting and spreading, and the reproducibility of the text deteriorates. On the other hand, when the static surface tension of the treatment liquid is higher than 25 mN / m, the treatment liquid is repelled by the substrate, and the reproducibility of the text deteriorates.

[0070] The ink set of the present invention preferably has a static surface tension of 25 to 35 mN / m at 25° C. When the static surface tension of the ink is within the above range, the ink has good storage stability and can be stably discharged onto a recording medium.

[0071] <Dynamic surface tension>

[0072] The "dynamic surface tension" in the present invention refers to the surface tension when the liquid surface is in a non-equilibrium state immediately after the liquid surface (gas-liquid interface) is formed, and is a value measured at 25°C using the maximum bubble pressure method.

[0073] In addition, the so-called "surface life" is the time after the liquid surface is formed, that is, the life of the bubbles generated in the maximum bubble pressure method, also known as the bubble life. Specifically, it refers to the time from the moment a new interface is generated in the probe tip of the dynamic surface tension meter to the time when the maximum bubble pressure is reached.

[0074] The dynamic surface tension of the treatment liquid or ink can be measured by using a dynamic surface tensiometer. Examples of the dynamic surface tensiometer include a bubble pressure dynamic surface tensiometer (manufactured by KRUSS, model number "BP100").

[0075] Unless otherwise specified, the dynamic surface tension in this specification is a dynamic surface tension measured at 25° C. and 15 ms using a maximum bubble pressure method.

[0076] The surface life of the treatment liquid of the ink set of the present invention is 50 msec, and the dynamic surface tension is in the range of 25 to 35 mN / m at 25°C. Here, in terms of making the dynamic surface tension of the treatment liquid within the above range, if it is lower than 25 mN / m, the treatment liquid expands, excessively wets and spreads, and the reproducibility of the text deteriorates. On the other hand, when the dynamic surface tension of the treatment liquid is higher than 35 mN / m, the treatment liquid is repelled by the substrate, and the reproducibility of the text deteriorates.

[0077] The ink set of the present invention preferably has a surface life of 50 msec and a dynamic surface tension of 35 to 45 mN / min at 25° C. When the static surface tension of the ink is within the above range, the ink has good storage stability and can be stably discharged onto a recording medium.

[0078] In order to adjust the static surface tension and the dynamic surface tension of the treatment liquid to be within the above ranges, the type and content of the surfactant, the type and content of the water-soluble solvent, the type and content of the coagulant, etc. may be controlled.

[0079] Specifically, as the surfactant contained in the treatment liquid, various polyether-modified silicone and / or acetylene glycol surfactants are preferably used. In particular, trisiloxane surfactants are preferably used. In addition, it is preferred that the content of the surfactant is within the range of 0.1 to 2.0 mass % relative to the treatment liquid.

[0080] Furthermore, as a water-soluble solvent, it is preferred to use a water-soluble solvent having an SP value of 24 (J / cm 3 ) 1 / 2 The water-soluble solvent having a boiling point in the range of 150° C. to 250° C. is contained in an amount in the range of 5 to 40% by mass.

[0081] In addition, as the coagulant, for example, an organic acid, a multivalent metal salt, a soluble cationic polymer, etc. are preferably used, as described later, so that the content of the coagulant in the treatment liquid is within the range of 1 to 8 mass %. Furthermore, it is preferably contained within the range of 1 to 4 mass %. By reaching such a range, the anionic components in the ink can be effectively coagulated. As a result, the balance between image quality and hot water resistance becomes good.

[0082] In order to make the static surface tension and dynamic surface tension of the ink fall within the above ranges, the type and content of the surfactant, the type and content of the water-soluble solvent, the type and content of the pigment dispersant, the type and content of the resin particles, the type and content of the additives, etc. can be listed. In addition, as for the surfactant, a surfactant that does not impair the storage stability of the ink is used, or the amount of the surfactant that does not impair the storage stability is used.

[0083] Specifically, various polyether-modified silicones and / or acetylene glycol-based surfactants are preferably used as the surfactant contained in the ink. The content of the surfactant is preferably within a range of 0.1 to 2.0% by mass relative to the ink.

[0084] As a water-soluble solvent, it is preferred to use a solvent with an SP value of 24 (J / cm 3 ) 1 / 2 The water-soluble solvent having a boiling point in the range of 150° C. to 250° C. is contained in an amount in the range of 5 to 40% by mass.

[0085] As the pigment dispersant, it is preferable to use various low molecular weight dispersants, nonionic polymer dispersants, anionic polymer dispersants, or appropriately use a resin-coated pigment dispersion.

[0086] Furthermore, as the type of the resin fine particles, it is preferable to use resin fine particles of a polyolefin resin, and the content thereof is adjusted to be within a range of 1 to 15% by mass based on the ink.

[0087] The polyolefin resin preferably contains resin particles having an average particle diameter within a range of 10 to 80 nm and resin particles having an average particle diameter within a range of 100 to 300 nm.

[0088] In addition, it is preferable to use wax as an additive, and the content thereof is preferably within a range of 0.1 to 5% by mass based on the ink.

[0089] [Processing liquid]

[0090] The processing liquid according to the present invention can accelerate the formation of an ink image by aggregating or thickening the ink when an image is recorded on a substrate by an inkjet printing method.

[0091] The treatment liquid according to the present invention contains at least a coagulant. In addition, the treatment liquid preferably contains a water-soluble solvent, a surfactant, and water.

[0092] <Coagulant>

[0093] The treatment liquid according to the present invention contains a material that generates aggregates when in contact with ink, namely, a coagulant that is a multivalent metal salt. The coagulant increases the interaction with the ink, and the ink dots can be further fixed.

[0094] (polyvalent metal salt)

[0095] The polyvalent metal salt can aggregate anionic components (usually colorants or pigments, etc.) in the ink described later by salting out.

[0096] As the polyvalent metal salt, a salt of a metal having a valence of 2 or more can be used. The type of metal (cation) constituting the polyvalent metal salt is not particularly limited, and examples thereof include Ca 2+ , Cu 2+ 、Ni 2+ Mg 2+ 、Zn 2+ , Ba 2+ Divalent metal ions such as Al 3+ , Fe 3+ Cr 3+ , Y 3+ Trivalent metal ions, Zr 4+ And other quadrivalent metal ions, etc.

[0097] The type of salt constituting the polyvalent metal salt is not particularly limited, and for example, known salts such as carbonates, sulfates, nitrates, hydrochlorides, organic carboxylates, organic sulfonates, borates, phosphates, bromates, hydroiodates, and thiocyanates can be used.

[0098] Examples of the organic carboxylate salt include acetic acid, oxalic acid, lactic acid, fumaric acid, fumaric acid, citric acid, salicylic acid, and benzoic acid.

[0099] Specific examples of particularly preferred polyvalent metal salts include calcium salts or magnesium salts of carboxylic acids such as calcium chloride, magnesium chloride, calcium nitrate, magnesium nitrate, magnesium acetate, calcium acetate, magnesium lactate, and calcium pantothenate.

[0100] (Organic Acid)

[0101] The treatment liquid according to the present invention may further contain an organic acid as a coagulant in addition to the above-mentioned polyvalent metal salt.

[0102] As a coagulant, the organic acid contained in the treatment liquid can cause the colorant contained in the ink to coagulate, and the first dissociation constant is preferably 3.5 or less. In particular, the first dissociation constant is preferably in the range of 1.5 to 3.5. If it is within this range, the liquid deviation in the low concentration area is further prevented, and the ink mixing (bubbling) in the high concentration area is improved.

[0103] In addition, by using an organic acid, it is easy to maintain the storage stability of the treatment solution, and it is not easy to cause adhesion after the treatment solution is applied and dried. From the above viewpoints, it is preferred that the organic acid contained in the coagulant is a compound having a carboxyl group such as formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and its derivatives, methacrylic acid and its derivatives, acrylamide and its derivatives, sulfonic acid derivatives, or phosphoric acid and its derivatives.

[0104] It is preferred that the organic acid be one that is not completely neutralized by a base. Neutralized by a base means that the acidic groups of these acids are ionically bonded to other positively charged elements or compounds (e.g., inorganic compounds such as metals). In addition, the term "not completely neutralized" means that there are acidic groups in the acidic groups of the organic acid that have not yet formed the above-mentioned ionic bonds.

[0105] In addition, by using an organic acid, the storage stability of the treatment liquid is easily maintained, and sticking is less likely to occur after the treatment liquid is applied and dried. From the above viewpoints, preferred organic acids include formic acid, acetic acid, propionic acid, benzoic acid, and the like.

[0106] (Inorganic Acid)

[0107] In the treatment liquid according to the present invention, in addition to the polyvalent metal salt, an inorganic acid may be further added as a coagulant. The inorganic acid can coagulant anionic components in the ink due to pH fluctuation.

[0108] The inorganic acid can aggregate a pigment that may be contained in the ink described below. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, and aminosulfonic acid.

[0109] In addition, a soluble cationic polymer can be used as a coagulant.

[0110] Examples of the soluble cationic polymer contained in the treatment liquid include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride.

[0111] Examples of commercially available products of the soluble cationic polymer include KHE100L and FPA100L manufactured by Senka Corporation, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nike Air Media Corporation.

[0112] The content of the polyvalent metal salt is preferably in the range of 0.5 to 20 mass %, more preferably in the range of 1 to 10 mass %, relative to the total mass 100 mass % of the treatment liquid. This allows the anionic components in the ink to be effectively aggregated, which is preferred from the viewpoint of balancing image quality and hot water resistance.

[0113] When an organic acid is contained, the content of the organic acid is preferably in the range of 0.1 to 10 mass %, more preferably in the range of 1 to 3 mass %, relative to 100 mass % of the total mass of the treatment liquid.

[0114] When an inorganic acid is contained, the content of the inorganic acid is preferably in the range of 0.1 to 10 mass %, more preferably in the range of 1 to 3 mass %, relative to 100 mass % of the total mass of the treatment liquid.

[0115] The content of the polyvalent metal salt or organic acid in the aqueous solution can be measured by a known method, for example, in the case of a polyvalent metal salt, the content can be measured by ICP emission analysis, and in the case of an organic acid, the content can be measured by high-performance liquid chromatography (HPLC).

[0116] It should be noted that when an organic acid is used, the amount of the organic acid added is preferably such that the pH of the treatment liquid is adjusted to an amount equal to or less than the neutralization equivalent of the anion component contained in the ink. In addition, when the anion component is a compound having a carboxyl group, the first dissociation constant of the organic acid is preferably 3.5 or less from the viewpoint of making it more difficult for the image to bleed.

[0117] <Water-soluble solvent>

[0118] As the water-soluble solvent contained in the treatment liquid according to the present invention, a water-soluble solvent having a boiling point within a range of 150 to 250°C is preferred.

[0119] Examples of such a water-soluble solvent include alcohols, polyols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0120] In addition, it is preferred to use an SP value of 24 (J / cm 3 ) 1 / 2 The above water-soluble solvents.

[0121] By using an SP value of 24 (J / cm 3 ) 1 / 2 The above water-soluble solvents lower the turbidity point of the processing liquid. Therefore, in the ink drying process, the processing liquid can be heated to a temperature above the turbidity point, and an image having good adhesion to a non-absorbent substrate can be obtained.

[0122] It should be noted that in the present invention, the so-called SP value is called the solubility parameter. The SP value in the present invention is a value calculated by the Fedors method. It is calculated from the molar heat of evaporation of the water-soluble solvent and the molar volume of the water-soluble solvent at 25°C. It should be noted that the unit of the SP value is generally cal, and when converted to the SI unit system, it can be calculated using (cal / cm 3 ) 1 / 2 =2.046×10 3 (J / m 3 ) 1 / 2 In the following description, the unit of SP value is sometimes omitted, and SP value is expressed as (J / cm 3 ) 1 / 2 The value expressed in units of .

[0123] The above SP value is 24 (J / cm 3 ) 1 / 2 Examples of the water-soluble solvent having a boiling point of 150° C. to 250° C. include polyols having 2 to 8 carbon atoms and polyalkylene glycols.

[0124] Examples of the polyols having 2 to 8 carbon atoms include 1,2-ethylene glycol (SP value: 30.3, boiling point: 197°C), 1,2-propylene glycol (SP value: 28.0, boiling point 188°C), 1,3-propylene glycol (SP value: 32.9, boiling point 213°C), 1,2-butylene glycol (SP value: 26.1, boiling point 192°C), 1,3-butylene glycol (SP value: 30.3, boiling point: 207°C), 1,4-butylene glycol (SP value: 30.7, boiling point 230°C), 2,3-butylene glycol (SP value: 32.9, boiling point 213°C), : 29.9, boiling point: 177°C), 2-methyl-1,3-propanediol (SP value: 30.3, boiling point 214°C), 1,2-pentanediol (SP value: 25.0, boiling point: 210°C), 1,5-pentanediol (SP value: 29.0, boiling point: 242°C), 1,2-hexanediol (SP value: 24.1, boiling point: 223°C), 1,6-hexanediol (SP value: 27.7, boiling point: 249°C), 2-methylpentane-2,4-diol (SP value: 26.8, boiling point 197°C), etc.

[0125] Examples of the polyalkylene glycols include diethylene glycol (SP value: 30.6, boiling point 244° C.), dipropylene glycol (SP value: 27.2, boiling point 230° C.), and the like.

[0126] The treatment liquid may contain one or more selected from these water-soluble solvents in combination.

[0127] The water-soluble solvent having a boiling point of 150°C to 250°C may be contained in the ink at least one kind thereof, and may include alcohols other than those mentioned above, polyols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0128] Examples of solvents other than water-soluble solvents having a boiling point of 150°C to 250°C include glycerin (SP value: 33.5, boiling point 290°C), trimethylolpropane (SP value: 32.5, boiling point: 295°C), triethylene glycol (SP value: 27.8, boiling point 287°C), and tetraethylene glycol (SP value: 26.1, boiling point: 275°C).

[0129] The total content of the water-soluble solvent is preferably in the range of 5 to 40 mass %, more preferably in the range of 10 to 40 mass %, relative to 100 mass % of the total mass of the treatment liquid.

[0130] <Surfactant>

[0131] The surfactant contained in the treatment liquid according to the present invention can improve the injection stability of the treatment liquid from the nozzle and control the spread of the droplets landed on the recording medium (enlargement of the dot diameter).

[0132] The surfactant is not particularly limited. When an anionic compound is contained in other components of the ink, the ionicity of the surfactant is preferably anionic, nonionic or betaine.

[0133] In the present invention, it is preferred to use a fluorine-based or silicone-based surfactant with high static surface tension reduction ability, an anionic surfactant such as dioctyl sulfosuccinate with high dynamic surface tension reduction ability, a relatively low molecular weight polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, acetylene glycols, pullonik type surfactants (pullonik is a registered trademark), a nonionic surfactant such as sorbitan derivatives. It is also preferred to use a fluorine-based or silicone-based surfactant in combination with a surfactant with high dynamic surface tension reduction ability.

[0134] Examples of the polyoxyethylene alkyl ether include TRITON HW-1000 (TRITON is a registered trademark) manufactured by Dow Chemical Co., Ltd.

[0135] By adding a silicone or fluorine-based surfactant as the surfactant, ink mixing (bubbling) can be further suppressed for recording media with low ink absorption capacity such as vinyl chloride sheets and printing paper, etc. As a result, a high-quality printed image can be obtained.

[0136] As the above-mentioned silicone-based surfactant, polyether-modified silicone is preferred. For example, siloxanes having oxyalkylene groups on the side chains and / or both ends of the polydimethylsiloxane chain can be listed. Specifically, BYK-331, BYK-333, BYK-345, BYK-3450, BYK-3451, BYK-3455, BYK-346, BYK-347, BYK-348, BYK-349 manufactured by BYK Chemical Co., Ltd., TEGOWet KL245, TEGOWet 250, TEGOWet 260, TEGOWet 270, TEGO Wet280, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22-4515, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

[0137] As the polyether-modified silicone, trisiloxane having an oxyalkylene group in a side chain and / or at both ends of a polydimethylsiloxane chain is particularly preferred.

[0138] By using trisiloxane, the dynamic surface tension of the processing liquid can be effectively reduced, and an image having good adhesion to the substrate can be obtained.

[0139] As trisiloxane, a structure represented by the following general formula (1) is preferred.

[0140] [Chemistry 1]

[0141] General formula (1)

[0142]

[0143] In the above general formula (1), "EO" represents a repeating unit structure of polyethylene oxide, that is, a structure in which ethylene oxide is ring-opened as a three-membered ring cyclic ether.

[0144] In addition, "PO" represents a repeating unit structure of polypropylene oxide, that is, a structure in which propylene oxide is ring-opened as a three-membered ring cyclic ether.

[0145] Here, the phrase “[EO]m and [PO]n may be in any order” means that in the molecule of the compound represented by the general formula (1), the order of the bonding positions with respect to the siloxane skeleton serving as the parent body may be appropriately changed.

[0146] In the above general formula (1), X is preferably an alkylene group having 3 carbon atoms (ie, a propylene group).

[0147] In the above general formula (1), m is preferably an integer of 5 to 20, and n is preferably an integer of 0 to 6.

[0148] Specific examples of the silicone-based surfactant having a structure represented by the general formula (1) are shown below as S-1 to S-8, but are not limited to these.

[0149] (S-1): In the above general formula (1), R = methyl, X = alkylene with 3 carbon atoms, m = 9, n = 0

[0150] (S-2): In the above general formula (1), R = butyl, X = alkylene with 3 carbon atoms, m = 25, n = 6

[0151] (S-3): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 3, n = 0

[0152] (S-4): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 33, n = 0

[0153] (S-5): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 22, n = 16

[0154] (S-6): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 9, n = 0

[0155] (S-7): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 12, n = 3

[0156] (S-8): In the above general formula (1), R = hydrogen atom, X = alkylene group with 3 carbon atoms, m = 1, n = 0

[0157] Examples of the trisiloxane include BYK-3450 and BYK-3451 manufactured by BYK-Chemie Japan Ltd. and TEGOWET-KL245, TEGOWET-250 and TEGOWET-260 manufactured by Ebonic Corporation.

[0158] The content of the polyether-modified silicone is preferably in the range of 0.5 to 2 mass %, more preferably in the range of 0.5 to 1.5 mass %, relative to 100 mass % of the total mass of the treatment liquid.

[0159] The fluorine-based surfactant is a surfactant obtained by replacing a portion or all of the hydrogen bonded to carbon in the hydrophobic group of a common surfactant with fluorine. Among them, a surfactant having a perfluoroalkyl group in the molecule is preferred.

[0160] Among the above-mentioned fluorine-based surfactants, certain surfactants are commercially available under the following trade names.

[0161] Trade name: Megafac F (Dainippon Ink & Chemical Industry Co., Ltd.)

[0162] Product name: Surflon (Asahi Glass Co., Ltd.)

[0163] Product name: Fluorad (Fluorad) FC (ミネソタ・マ(イニング・アンド・マニファクチュアリング・カンパニー Company)

[0164] Product name: Monflor (Monflor) (Monflor Co., Ltd.)

[0165] Product name: Zonyl s (Zonyl s)

[0166] Product name: Licowet (Licowet) VPF (Florida Co., Ltd.)

[0167] In particular, the treatment liquid according to the present invention preferably contains a surfactant that is not contained in the ink described below, and the following two types are exemplified.

[0168] When the surfactant contained in the ink is defined as surfactant S1,

[0169] (i) It is preferable that the surfactant contained in the treatment liquid is a surfactant S2 different from the surfactant S1 contained in the ink.

[0170] It is preferable that the surfactant contained in the treatment liquid (ii) further contains the above-mentioned surfactant S2 in addition to the above-mentioned surfactant S1.

[0171] Specifically, as a preferred combination of surfactants, the surfactant contained in the treatment liquid is preferably polyether-modified silicone, trisiloxane-based surfactants, etc. In addition, as a surfactant contained in the ink, acetylene glycol-based surfactants, etc. and polyether-modified silicone, etc. are preferred.

[0172] As described above, by adding a surfactant not contained in the ink (that is, a surfactant that destabilizes the dispersion stability of the ink) to the treatment liquid, the cohesiveness can be further improved.

[0173] The content of the surfactant in the treatment liquid is not particularly limited, but is preferably in the range of 0.1 to 5.0% by mass, and more preferably in the range of 0.1 to 2.0% by mass, based on the total mass of the treatment liquid.

[0174] <Water>

[0175] The treatment liquid according to the present invention may contain water, and the water that can be used is not particularly limited. For example, ion exchange water, distilled water, or pure water can be used.

[0176] The treatment liquid may contain other components such as a cross-linking agent, a mildew preventer, and a bactericide as appropriate, within a range not impairing the effects of the present invention.

[0177] Furthermore, the ultraviolet absorbers described in, for example, Japanese Patent Laid-Open Nos. 57-74193, 57-87988, and 62-261476, and the ultraviolet absorbers described in Japanese Patent Laid-Open Nos. 57-74192, 57-87989, 60-72785, 61-146591, Japanese Patent Laid-Open Nos. 1-95091 and 3-13376 may also be contained. Various known additives such as anti-fading agents recorded in Japanese Patent Publication Nos. 59-42993, 59-52689, 62-280069, 61-242871 and 4-219266, defoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, etc.

[0178] The treatment liquid layer is preferably prepared by directly applying and drying the treatment liquid according to the present invention as a coating liquid on a substrate. Here, it is preferred that the additives used in the treatment liquid be sufficiently dissolved before use as a coating liquid.

[0179] As a method of applying the treatment liquid, an inkjet method is used.

[0180] [ink]

[0181] The ink according to the present invention contains at least a pigment and a resin. In addition, the ink according to the present invention preferably contains a water-soluble solvent, a surfactant, a wax, and water.

[0182] <Pigment>

[0183] As the pigment contained in the ink according to the present invention, it is preferred to use anionic dispersed pigments, for example, self-dispersible pigments having anionic groups on the surface, pigments dispersed by anionic polymer dispersants, and dispersed pigments whose surfaces are coated with anionic resins.

[0184] In particular, it is preferable to use a pigment dispersed with an anionic polymer dispersant because of its excellent dispersibility and the ability to react appropriately with the treatment liquid to perform pinning.

[0185] As the pigment, any conventionally known pigment can be used without particular limitation. For example, organic pigments such as insoluble pigments and lake pigments and inorganic pigments such as titanium oxide can be preferably used.

[0186] In addition, in titanium oxide, for which it is generally difficult to ensure ink discharge stability and adhesion, according to the present invention, bleeding is particularly unlikely to occur and adhesion can be improved.

[0187] Titanium oxide has three crystal forms: anatase, rutile and brookite. As a common crystal form, it can be roughly divided into anatase and rutile. It is not particularly limited, but the rutile type with a large refractive index and high concealment is preferred. Specifically, the TR series of Fuji Titanium Industry Co., Ltd., the JR series of Teika Co., Ltd., and the time of Ishihara Industry Co., Ltd. can be listed.

[0188] The insoluble pigment is not particularly limited, and preferred examples include azo, azomethine, methamine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindolinone, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0189] Specific examples of organic pigments that can be preferably used include the following.

[0190] Examples of pigments for magenta or red include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 202, CI Pigment Red 222, and CI Pigment Violet 19.

[0191] Examples of orange or yellow pigments include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 15:3, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 128, CI Pigment Yellow 94, CI Pigment Yellow 138, and CI Pigment Yellow 155. In terms of the balance between color tone and light resistance, CI Pigment Yellow 155 is preferred.

[0192] Examples of the green or cyan pigment include CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, CI Pigment Blue 60, and CI Pigment Green 7.

[0193] Moreover, as a pigment for black, CI Pigment Black 1, CI Pigment Black 6, CI Pigment Black 7 etc. are mentioned, for example.

[0194] <Pigment dispersant>

[0195] The ink according to the present invention preferably contains a pigment dispersant for dispersing the above-mentioned pigment.

[0196] The pigment dispersant is not particularly limited, but is preferably a polymer dispersant having an anionic group, and a polymer dispersant having a molecular weight within a range of 5,000 to 200,000 can be preferably used.

[0197] Examples of polymer dispersants include block copolymers, random copolymers, and salts thereof, polyoxyalkylenes, and polyoxyalkylene alkyl ethers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives.

[0198] The polymer dispersant preferably has an acryloyl group and is preferably added after being neutralized with a neutralizing base. Here, the neutralizing base is not particularly limited, and is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, morpholine, etc. In particular, when the pigment is titanium oxide, it is preferred to disperse the titanium oxide with a polymer dispersant having an acryloyl group.

[0199] The amount of the polymer dispersant added is preferably within a range of 10 to 100% by mass, more preferably within a range of 10 to 40% by mass, based on the pigment.

[0200] The pigment is particularly preferably in the form of a so-called capsule pigment coated with the above-mentioned polymer dispersant. As a method for coating the pigment with a polymer dispersant, various known methods can be used, for example, a phase inversion emulsification method, an acid precipitation method, or a method in which the pigment is dispersed by a polymerizable surfactant, a monomer is supplied thereto, and the pigment is coated while polymerizing.

[0201] As a particularly preferred method, the following method can be cited: a water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and then the acidic groups in the resin are partially or completely neutralized with an alkali, and then a pigment and ion exchange water are added to disperse the mixture, and then the organic solvent is removed and water is added as needed to prepare the mixture.

[0202] The average particle size of the pigment particles contained in the pigment in the ink in a dispersed state is preferably in the range of 40 to 200 nm, and particularly preferably in the range of 50 to 100 nm. This can improve the dispersion stability of the pigment and the storage stability of the ink.

[0203] The particle size of the pigment can be measured by using a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc. In particular, the measurement using the dynamic light scattering method is simple and can measure the particle size range with high accuracy.

[0204] The pigment can be used by being dispersed with a disperser together with a dispersant and other additives required for each desired purpose.

[0205] As a disperser, a conventionally known ball mill, sand mill, online mill, high-pressure homogenizer, etc. can be used. Among them, if the pigment is dispersed by a sand mill, the particle size distribution becomes narrower, so it is preferred. In addition, there is no particular limitation on the material of the beads dispersed by the sand mill, but from the viewpoint of preventing the formation of bead fragments and the contamination of ion components, zirconium oxide or zircon is preferred. Furthermore, the bead diameter is preferably in the range of 0.3 to 3 mm.

[0206] The content of the pigment in the ink is not particularly limited, but is preferably in the range of 7 to 18% by mass for titanium oxide and in the range of 0.5 to 7% by mass for organic pigments.

[0207] <Resin>

[0208] The resin contained in the ink according to the present invention contains at least a polyolefin resin.

[0209] As the polyolefin resin, for example, polyethylene, polypropylene, ethylene-propylene copolymer, random copolymer or block copolymer (for example, ethylene-propylene-butene copolymer etc.) of ethylene and / or propylene and other comonomers (for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, α-olefin comonomers having 2 to 6 carbon atoms) can be used. In addition, products obtained by copolymerizing two or more of the other comonomers and products obtained by mixing two or more of the above polymers can also be used.

[0210] In addition, the above-mentioned polyolefin resin can use commercially available products. Examples of commercially available polyolefin resins include Aurobe SB-1200 (manufactured by Unichika Co., Ltd., "Aurobe" is a registered trademark of the company), Aurobe 150A, Aurobe AE-301 (manufactured by Nippon Paper Industries, Ltd., "Aurobe" is a registered trademark of the company), Supercapron E-415 (manufactured by Nippon Paper Industries, Ltd., "Supercapron" is a registered trademark of the company), and Hardren Na-1001 (manufactured by Toyobo Co., Ltd., "Hardren" is a registered trademark of the company).

[0211] In the present invention, among the above-mentioned polyolefin resins, acid-modified polyolefin resins are preferred because they are excellent in character reproducibility in a two-liquid inkjet recording method.

[0212] The acid-modified polyolefin resin is preferably a resin obtained by modifying a polyolefin resin such as polyethylene or polypropylene with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, or itaconic acid. Among these acid-modified polyolefin resins, a polyolefin resin modified with maleic anhydride is preferably used.

[0213] In addition, the polyolefin resin preferably contains polyolefin resin particles with an average particle size of 10 to 80 nm and polyolefin resin particles with an average particle size of 100 to 300 nm. By mixing resin particles of two particle size ranges, film forming properties are improved, and cracking of the coating film can be prevented.

[0214] Hereinafter, the polyolefin resin particles having an average particle diameter of 10 to 80 nm are also referred to as small-diameter polyolefin resin particles, and the polyolefin resin particles having an average particle diameter of 100 to 300 nm are also referred to as large-diameter polyolefin resin particles.

[0215] The ratio of the content (mass %) of the above-mentioned small-diameter polyolefin resin particles to the above-mentioned large-diameter polyolefin resin particles in the polyolefin resin (content of large-diameter polyolefin resin particles: content of small-diameter polyolefin resin particles) is preferably in the range of 10:90 to 90:10, more preferably in the range of 30:70 to 70:30, and particularly preferably 50:50.

[0216] The average particle size of the polyolefin resin particles can be determined by using a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc. In particular, the measurement using the dynamic light scattering method is simple and can measure the particle size range with high accuracy.

[0217] The content of the polyolefin resin in the ink (the total content of the small-diameter and large-diameter polyolefin resin particles) is preferably within a range of 1 to 15% by mass.

[0218] It should be noted that the resin of the present invention preferably contains large-diameter polyolefin resin particles and small-diameter polyolefin resin particles, but is not limited thereto. The resin of the present invention may contain, for example, small-diameter polyolefin resin particles and other resin particles of large diameter (average particle size of 100 to 300 nm).

[0219] Examples of the other resin particles include acrylic resin particles, polyester resin particles, and polyurethane resin particles, and acrylic resin particles are preferred.

[0220] As the acrylic resin, commercially available products can be used, and examples of commercially available products include NeoCryl A-1127 manufactured by Kusumoto Chemicals Co., Ltd., Movinyl 6899D, 6969D, 6800, and 6810 manufactured by Japan Composites Co., Ltd., and TOCRYL W-7146, W-7150, and W-7152 manufactured by Toyokhem Co., Ltd.

[0221] <Water-soluble solvent>

[0222] As the water-soluble solvent contained in the ink according to the present invention, a water-soluble solvent having a boiling point within a range of 150 to 250°C is preferred.

[0223] Examples of such a water-soluble solvent include alcohols, polyols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms. Examples of the water-soluble solvents include those exemplified in the above-mentioned treatment liquid.

[0224] The ink may contain one or two or more selected from the above-mentioned water-soluble solvents in combination.

[0225] The content of the water-soluble solvent in the ink is not particularly limited, but is preferably within a range of 10 to 60% by mass.

[0226] <Surfactant>

[0227] By incorporating a surfactant into the ink according to the present invention, it is possible to improve the ink injection stability and control the spread (dot diameter) of the droplets landed on the recording medium.

[0228] The surfactant that can be used in the ink of the present invention is not limited, and the surfactants exemplified in the above-mentioned treatment liquid can be used as long as they are surfactants that do little to damage the storage stability of the ink. In particular, as described above, it is preferred that the treatment liquid does not contain the same surfactant as the surfactant contained in the ink.

[0229] The content of the surfactant in the ink is not particularly limited as long as it does not impair the storage stability of the ink, but is preferably in the range of 0.1 to 5.0% by mass, and more preferably in the range of 0.1 to 2.0% by mass.

[0230] <Water>

[0231] The water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.

[0232] <Wax>

[0233] As the wax contained in the ink according to the present invention, polyolefin wax is preferably used. When the ink contains polyolefin wax, the water resistance and abrasion resistance of the obtained recorded object are improved.

[0234] The polyolefin wax is not particularly limited, and for example, waxes made from olefins such as ethylene, propylene, butene, or derivatives thereof and copolymers thereof may be cited, and specifically, polyethylene waxes, polypropylene waxes, polybutene waxes, etc. may be cited. Among these, polyethylene waxes are preferred from the viewpoint of being able to more effectively reduce the generation of cracks in an image. The polyolefin waxes may be used alone or in combination of two or more.

[0235] The polyolefin wax is preferably used in the form of a polyolefin wax emulsion in which solid wax particles are dispersed in water by the above-mentioned surfactant.

[0236] As a polyolefin wax emulsion, for example, a method for producing a polyethylene wax emulsion is exemplified. The polyethylene wax is produced by polymerizing ethylene, synthesizing from hydrocarbon compounds, or reducing the molecular weight of polyethylene for general molding by thermal decomposition. Then, the polyethylene wax is oxidized to add carboxyl groups and hydroxyl groups. Furthermore, a surfactant is used to emulsify the polyethylene wax to obtain a polyethylene wax emulsion in the form of an aqueous wax emulsion with excellent stability.

[0237] Commercially available products of polyolefin waxes include "Chemipal W4005" (manufactured by Mitsui Chemicals, Ltd., polyethylene wax, particle size 200 to 800 nm, ring and ball softening point 110°C, penetration hardness 3, solid content 40%) and other Chemipal series products. In addition, AQUACER513 (polyethylene wax, particle size 100 to 200 nm, melting point 130°C, solid content 30%), AQUACER497, AQUACER513, AQUACER517 (all BYK Additives & Ins truments Co., Ltd.), etc. AQUACER series, ハイテックE-7025P, ハイテックE-2213, Haze E-9460, Haze E-9015, Haze E-4A, Hexafluoroethylene E-5403P, Tetrafluoroethylene E-8237 (the above products are manufactured by Toho Chemical Co., Ltd.), etc. Teco series, Nono PEM-17 (manufactured by Sanko Co., Ltd., polyethylene emulsion, particle size 40nm), etc.

[0238] These are commercially available in the form of aqueous emulsions obtained by dispersing polyolefin wax in water by a conventional method. Therefore, they can be directly added to ink in the form of aqueous emulsions.

[0239] In the ink used in the present invention, in addition to the above-mentioned ones, various known additives such as polysaccharides, viscosity modifiers, resistivity modifiers, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, mildew inhibitors, rust inhibitors, etc. can be appropriately selected and used as needed to improve injection stability, print head, ink cartridge compatibility, storage stability, image preservation, and other performances. For example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, oil droplet particles such as silicone oil, Japanese Patent Publication No. 57-74193, Japanese Patent Publication No. 57-87988, etc. can be cited. The ultraviolet absorbers described in Japanese Patent Publication No. 57-74192, No. 57-87989, No. 60-72785, No. 61-146591, Japanese Patent Publication No. 1-95091, No. 3-13376, etc., the fluorescent whitening agents described in Japanese Patent Publication No. 59-42993, No. 59-52689, No. 62-280069, No. 61-242871, Japanese Patent Publication No. 4-219266, etc.

[0240] The viscosity of the ink used in the present invention having the above-mentioned structure is preferably 1 to 40 mPa·s at 25° C., and more preferably 2 to 10 mPa·s.

[0241] [Inkjet recording method]

[0242] In the inkjet recording method of the present invention, an ink set including the above-mentioned treatment liquid and ink is used, and the two inks are respectively applied to the surface of the recording medium by droplet discharge means and merged to form an image. Thus, the inkjet recording method of the present invention is a so-called two-liquid recording method.

[0243] According to this recording method, for example, one inkjet printer can be used to continuously and efficiently apply the treatment liquid and print with the ink on the surface of a substrate (recording medium). Furthermore, the treatment liquid and the ink can be combined on the substrate, and the deviation of the dot diameter between substrates can be reduced. As a result, it is possible to print text, patterns, etc. with excellent image quality.

[0244] Specifically, first, after the treatment liquid is applied to the substrate, the ink is applied to the area where the treatment liquid is applied in a state wetted with the treatment liquid without undergoing a heating and drying step.

[0245] That is, the inkjet recording method includes a treatment liquid applying step and an ink applying step.

[0246] The processing liquid applying step is a step of applying the processing liquid to the recording area of ​​the substrate.

[0247] The ink applying step is a step of applying ink by an inkjet recording method to the region to which the processing liquid has been applied in the processing liquid applying step in a state where the region is wetted with the processing liquid.

[0248] Furthermore, the inkjet recording method of the present invention preferably includes an ink heating and drying step in addition to the above-mentioned steps.

[0249] The ink heating and drying step is a step of heating and drying the processing liquid and ink applied to the substrate after the ink applying step to form an image (image layer).

[0250] In addition, in the ink applying step, it is preferred that the ink is applied to the area to which the treatment liquid is applied when the drying rate of the treatment liquid is 30% or less. In addition, it is preferred that the ink applying step is performed within 10 seconds after the treatment liquid applying step. It is particularly preferred that the ink applying step is performed within 0.1 to 5 seconds after the treatment liquid applying step when the drying rate of the treatment liquid is in the range of 1 to 10%.

[0251] <Base material>

[0252] The substrate (recording medium) applicable to the inkjet recording method of the present invention is a non-absorbing substrate composed of a non-absorbing material.

[0253] In the present invention, the term "non-absorbent recording substrate (medium)" refers to a substrate having a water absorption amount of 10 mL / m2 from the start of contact to 30 msec in the Bristow method. 2The following recording substrates (mediums) are described in detail in, for example, "JAPAN TAPPI Pulp Testing Methods 2000 Edition" Standard No. 51 "Paper and Board - Liquid Absorption Test Method - Bristowe Method".

[0254] As the non-absorbing substrate, a known plastic film can be used.

[0255] Specific examples of the known plastic films include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, biodegradable films such as polylactic acid films, and the like.

[0256] In addition, in order to impart gas barrier properties, moisture resistance, fragrance retention, etc., polyvinylidene chloride is preferably applied to one or both sides of the film. In addition, a film deposited with a metal oxide can also be preferably used. As for non-absorbent films, an unstretched film can be preferably used, and a stretched film can also be preferably used.

[0257] The thickness of the substrate is preferably within a range of 10 to 120 μm, more preferably 12 to 60 μm, in the case of a plastic film.

[0258] In addition, as non-absorbent substrates, metal substrates such as tinplate for three-piece cans and tin-free steel sheets (TFS sheets, thickness 0.1 to 0.6 μm) are also preferably used. For example, it can be preferably used for packaging materials for canned foods provided with a thermosetting resin as a coating layer.

[0259] As packaging materials for canned food, for example, the following materials are generally used to block air, moisture, and light and seal the food inside: epoxy-phenolic coatings and polyester laminating agents are used on the food side, and polyester and acrylic thermosetting coatings are used on the outside.

[0260] Hereinafter, each step of the inkjet recording method will be described.

[0261] <Processing liquid application step>

[0262] In the treatment liquid applying step, the above-mentioned treatment liquid is applied onto the recording medium as a substrate.

[0263] The method of applying the treatment liquid to the recording medium is an inkjet method.

[0264] When the substrate used is a metal substrate, it is preferred to place the metal substrate on a conveyor belt and apply the treatment liquid layer while conveying the conveyor belt. In addition, it is also preferred to use a flat bed type printer with a fixed substrate for forming the treatment liquid layer.

[0265] In the process of applying the processing liquid, the additional amount of the processing liquid (also referred to as "the amount applied") is preferably 5.0 g / m2 per unit area where the image is formed. 2 In particular, 0.3 to 5.0 g / m 2 Thus, in the two-liquid inkjet recording method, high text reproducibility is obtained.

[0266] <Ink application process>

[0267] The ink applying step is a step of applying the ink of the above-mentioned ink set by inkjet method simultaneously with or immediately after applying the treatment liquid to the recording medium as the substrate. In particular, it is preferred that the ink is applied to the area to which the treatment liquid is applied after the treatment liquid applying step when the drying rate of the treatment liquid is 30% or less. In addition, it is preferred that the ink is applied to the area to which the treatment liquid is applied within 10 seconds after the treatment liquid is applied to the substrate.

[0268] In addition, the drying rate of the processing liquid is defined by the following formula.

[0269] (Drying rate of treatment liquid) = 1 - ((mass of treatment liquid after drying (g)) / (mass of treatment liquid before drying (g))

[0270] By applying the ink in a state where the drying rate of the processing liquid is 30% or less, the ink and the processing liquid are combined and mixed.

[0271] Furthermore, by applying the ink within 10 seconds after applying the processing liquid to the substrate, the penetration of the processing liquid into the absorptive substrate and the repulsion of the processing liquid in the non-absorptive substrate can be suppressed, thereby achieving higher image quality.

[0272] In order to make the drying rate of the treatment liquid 30% or less, the time from the application of the treatment liquid to the application of the ink may be adjusted as described above, and the temperature of the recording medium may be appropriately adjusted.

[0273] In addition, in the ink imparting process, the amount of ink droplets is adjusted in such a manner that the additional amount of ink (also referred to as "imparting amount") is within the range of 2 to 25 times the additional amount of the processing liquid per unit area. In terms of achieving high image quality, the more preferred range of the above-mentioned additional amount is preferably 2.5 to 3.5 times.

[0274] The inkjet method is not particularly limited, and a printer equipped with an inkjet head filled with ink can be used. Specifically, ink can be discharged as droplets from the nozzles of the inkjet head based on digital signals, and can be printed by making the droplets land on the treatment liquid layer of the substrate.

[0275] The inkjet head may be any of an on-demand type and a continuous type. Examples of on-demand type inkjet heads include electro-mechanical conversion types including single-chamber type, dual-chamber type, bend type, piston type, shared pattern type, and shared wall type, and electro-thermal conversion types including thermal inkjet type and Bubble Jet (“Bubble Jet” is a registered trademark of Canon Inc.).

[0276] Among the above-mentioned inkjet heads, an inkjet head using a piezoelectric element as an electro-mechanical conversion element for an electro-mechanical conversion method (also referred to as a piezoelectric type inkjet head) is preferable.

[0277] The inkjet printer may be a scanning type or a single-pass type inkjet head. In the case of the single-pass type, a line head type inkjet head is preferably used.

[0278] The so-called linear head type inkjet head refers to an inkjet head having a length greater than the width of the printing range. As a linear head type inkjet head, an inkjet head having a length greater than the width of the printing range can be used. Alternatively, a plurality of heads can be combined to form a structure greater than the width of the printing range.

[0279] In addition, a plurality of heads may be arranged in parallel so that the nozzles thereof are arranged in a zigzag pattern, thereby improving the overall resolution of the heads.

[0280] The conveying speed of the recording medium as a substrate can be set within a range of, for example, 1 to 120 m / min. The faster the conveying speed, the faster the image forming speed.

[0281] According to the present invention, even at a very high line speed of 50 to 120 m / min, which is applicable to a single-pass inkjet image forming method, a high-definition image with high ink fixability can be obtained.

[0282] <Ink heating and drying process>

[0283] In the ink heating and drying step, the ink applied on the recording medium as a substrate, that is, the area where the ink is applied is heated, thereby drying the ink and the processing liquid.

[0284] In the ink heating and drying step, the heating temperature of the region to which the ink is applied is preferably within a range of 60 to 200° C. The heating time of the ink is appropriately adjusted according to the type of recording medium and the amount of ink applied.

[0285] By heating the area to which the ink is applied, water, water-soluble solvents, etc., which are solvent components of the treatment liquid and the ink, are removed. In addition, at the same time as this removal, the polyvalent metal salt is dried at a temperature above the thermal decomposition temperature, particularly in the metal substrate, and thermally decomposed. In addition, the abrasion resistance of the image and the adhesion to the substrate become good.

[0286] In addition, the heat drying can be carried out using, for example, a non-contact heating type drying device such as a drying furnace or a hot air blower, or a contact heating type drying device such as a hot plate or a hot roller.

[0287] The drying temperature can be obtained by measuring any one of (a) the temperature inside the furnace or the hot air temperature when a non-contact heating type drying device such as a drying furnace or a hot air blower is used, (b) the temperature of the contact heating portion when a contact heating type drying device such as a hot plate or a hot roller is used, or (c) the surface temperature of the surface to be dried during the entire period of drying of the treatment liquid. As the measurement location, it is more preferable to measure (c) the surface temperature of the surface to be dried.

[0288] The thickness of the image layer obtained as described above is preferably in the range of 0.3 to 3.0 μm, and more preferably in the range of 0.3 to 2.0 μm. If the thickness of the image layer is 0.3 μm or more, the adhesion and abrasion resistance of the image are easily improved. If the thickness of the image layer is 3.0 μm or less, the deformation stress applied to the image layer can be reduced, so the adhesion of the image layer is not easily damaged.

[0289] [Recording device]

[0290] Figure 2 This is a schematic diagram of a preferred recording device of the present invention. However, the present invention is not limited thereto.

[0291] The recording apparatus 1 is mainly composed of a process liquid applying section 10 and an ink applying section 20. The process liquid applying section 10 applies the process liquid to the substrate F, and the ink applying section 20 applies the ink.

[0292] The processing liquid applying unit 10 is an inkjet head 11 that can discharge the processing liquid toward the substrate.

[0293] The ink applying section 20 is an inkjet head 21 that can discharge ink toward a substrate.

[0294] In such a recording apparatus 1 , the processing liquid droplets 12 are discharged from the inkjet head 11 onto the substrate F fed out from the feed roller 30 , thereby forming the processing liquid layer C.

[0295] Next, ink droplets 22 are discharged from the inkjet head 21 onto the treatment liquid layer C, so that the treatment liquid and the ink are combined.

[0296] Then, the region to which the ink is applied is heated and dried by the drying section 23 to form the image layer G. Next, the base material F on which the image layer G is formed is wound up by the winding roller 40 to obtain an image recorded material.

[0297] It should be noted that Figure 2 In the figure, the case where the substrate F is a film substrate is shown. In the case of a metal substrate, the metal substrate can be arranged on a conveyor belt, and the treatment liquid and ink can be applied at one time while the conveyor belt is being conveyed.

[0298] In addition, Figure 2 In the embodiment, the ink is applied after the treatment liquid is applied to the substrate, or the treatment liquid and the ink are applied simultaneously. Alternatively, the ink is preferably discharged from the inkjet head when the drying rate of the treatment liquid layer is 30% or less. Furthermore, the treatment liquid may be applied after the ink is applied and before the ink is dried.

[0299] As Figure 2 In addition to the recording device shown in , it is preferable to use a flat bed type printer for coating the treatment liquid and ink. The flat bed type printer can fix the substrate and move the inkjet head in the main scanning direction and the sub-scanning direction intersecting the main scanning direction. Therefore, printing can be performed without conveying the substrate.

[0300] Metal substrates such as tinplate cannot be conveyed from roll to roll like resin film substrates, so it is preferable to use a flat bed type printer that does not require conveying of the substrate.

[0301] As an example of such a flat bed type printer, the printer described in FIG. 1 of Japanese Patent Application Laid-Open No. 2015-74161 and FIG. 1 of Japanese Patent Application Laid-Open No. 2017-177578 can be cited.

[0302] [Visual Records]

[0303] The image recorded material according to the present invention comprises a substrate and an image layer formed by applying a processing liquid and an ink on the substrate using the above-mentioned ink set and combining them.

[0304] The above configuration is a minimum configuration, and other functional layers may be formed between the substrate and the image layer. In addition, a non-absorbent film substrate or the like may be bonded to the upper layer of the image layer via a laminated adhesive layer, for example.

[0305] As an example of the image recorded material of the present invention, a preferred structure is one in which a first layer containing a thermosetting resin, an image layer containing the above-mentioned treatment liquid and ink, and a second layer containing a thermosetting resin are sequentially laminated on a metal substrate.

[0306] Specific examples of the image recorded object preferably include packaging materials for packaging canned foods, canned foods, beverages, and the like.

[0307] exist Figure 3 , a cross-sectional view of a canned food packaging material as an example of the image recorded material of the present invention is shown.

[0308] A thermosetting resin (e.g., TW-1407 series manufactured by T&K TOKA) is roll-coated on a tinplate substrate 51 to form a thermosetting resin layer (undercoat layer) 52. On top of the tinplate substrate 51, a treatment liquid and ink are combined to form an image layer 53. Next, a thermosetting resin (e.g., AX-10 series manufactured by T&K TOKA) is roll-coated to form a thermosetting resin layer (topcoat layer) 54. After that, the canned food packaging material 50 is obtained by heat curing and drying.

[0309] Example

[0310] The present invention is specifically described below by way of examples, but the present invention is not limited thereto. It should be noted that, in the following examples, unless otherwise specified, the operation is performed at room temperature (25° C.). In addition, unless otherwise specified, “%” and “parts” mean “mass %” and “mass parts”, respectively.

[0311] [Preparation of treatment solution T1]

[0312] To 4.0% by mass of calcium acetate·hydrate as a coagulant, 28.0% by mass of propylene glycol and 5.0% by mass of 2-methyl-1,3-propanediol as solvents, 1.0% by mass of polyoxyethylene alkyl ether (TRITON HW-1000, manufactured by Dow Chemical Co., Ltd.) as a surfactant, 0.1% by mass of 1,2-benzisothiazolin-3-one (Procell GXL (S), manufactured by SC Jonson Co., Ltd.) as a mildew preventive, and ion exchange water (remainder: amount to make the total amount 100% by mass) were added while stirring. The obtained mixed solution was filtered through a 1 μm filter to obtain a treated solution T1.

[0313] [Preparation of treatment solutions T2 and T3]

[0314] In the preparation of the above-mentioned treatment liquid T1, the types and addition amounts of the coagulant and surfactant were changed as described in the following Tables I to VI. In addition, the addition amount (remainder) of ion exchange water was also changed, and the treatment liquids T2 and T3 were prepared in the same manner. In the following tables, the description of the solvent, mildewproof agent and ion exchange water is omitted.

[0315] The abbreviations in the following Tables I to VI are as follows.

[0316] <Surfactant>

[0317] "TRITON HW-1000" (made by Dow Chemical Co.): Polyoxyethylene alkyl ether

[0318] "BYK3450" BYK Chemicals Co., Ltd.): trisiloxane polyoxyalkylene

[0319] "Surfinol 440" (manufactured by Nissin Chemical Co., Ltd.): acetylene glycol

[0320] "Olfin E1010" (manufactured by Nissin Chemical Co., Ltd.): acetylene glycol

[0321] "KF-351A" (produced by Shin-Etsu Chemical Co., Ltd.): Polyether-modified silicone

[0322] "Serofluoron S242" (manufactured by AGC Semiconductor Co., Ltd.): Perfluoroalkyl compound

[0323] [Preparation of black ink]

[0324] <Preparation of dispersions of black pigments A and B>

[0325] A mixed solution of 8% by mass of anionic polymer dispersant ("Diocryle 819" manufactured by BASF), 20% by mass of propylene glycol, 0.1% by mass of antifungal agent Procell GXL (S) and ion exchange water was added to 20% by mass of black pigment (carbon black) and premixed.

[0326] Then, the pigment was dispersed using a bead mill filled with 0.3 mm zirconia beads at a volume ratio of 50%, thereby preparing a pigment dispersion having a pigment content of 20% by mass.

[0327] At this time, the dispersion conditions were changed so as to achieve the target average particle diameter (pigment particle diameter) shown in Tables I to VI below, respectively, to obtain a dispersion liquid of black pigment A and a dispersion liquid of black pigment B.

[0328] The average particle size of the pigment particles contained in these pigment dispersions was 110 nm for the dispersion of black pigment A and 80 nm for the dispersion of black pigment B. The average particle size was measured using "Zeta Sizer S-90" manufactured by Maruvalon Corporation.

[0329] <Preparation of dispersion of polyolefin resin A>

[0330] 100 g of a propylene-based random copolymer (96 mol% of propylene component, 4 mol% of ethylene component, weight average molecular weight of 100,000, Tm = 125° C.), 4 g of maleic anhydride, and 3 g of dicumyl peroxide were fully mixed. Then, a kneading reaction was performed using a twin-screw extruder set at 180° C. The extruder was degassed under reduced pressure to remove the remaining unreacted product, thereby obtaining a maleic anhydride-modified polyolefin resin.

[0331] 2 kg of the resin was placed in a 50 L reactor, 20 L of chloroform was added, and the mixture was stirred at 2 kg / cm 2 While irradiating with ultraviolet rays under a pressure of , gaseous chlorine was blown into the bottom of the reactor to chlorinate. Thus, a sample with a chlorine content of 18% by mass was obtained.

[0332] Next, the chloroform as the solvent was distilled off with an evaporator to adjust the solid content to 30% by mass. After adding 1.5% by mass of a stabilizer (tert-butylphenyl glycidyl ether) relative to the resin to the chloroform solution, solidification was performed using a twin-screw extruder set at a barrel temperature of 90°C.

[0333] The obtained chlorinated polyolefin resin had a weight average molecular weight of 92,000, a graft mass of maleic anhydride of 3.5% by mass, a chlorine content of 15.5% by mass, and a melting point of 85°C.

[0334] Next, a stirrer, a condenser, a thermometer and a funnel were installed in a four-necked flask. 100 g of the obtained chlorinated modified polyolefin resin, 20 g of a surfactant (N,N-polyoxyalkylene-alkylamine), 18 g of 25%-ammonia water (neutralizer) and 25 g of toluene were added to the four-necked flask and kneaded at 120° C. for 30 minutes.

[0335] Then, 290 g of deionized water at 90° C. was added over 60 minutes. Then, the solvent was removed by reducing the pressure, and the mixture was cooled to room temperature while stirring.

[0336] The average particle size of the obtained aqueous dispersion of chlorinated modified polyolefin resin was 73 nm. Hereinafter, the aqueous dispersion of chlorinated modified polyolefin resin obtained here is referred to as dispersion of polyolefin resin A.

[0337] <Dispersion of polyolefin resins B and C>

[0338] A stirrer, condenser, thermometer and dropping funnel were installed in a four-necked flask. 300 g of a propylene-based random copolymer (propylene component 96 mol%, ethylene component 4 mol%, weight average molecular weight 100,000, Tm = 125°C) was heated and dissolved in 700 g of toluene in the four-necked flask.

[0339] Then, while the temperature of the system was maintained at 115° C., 13 g of maleic anhydride and 12 g of di-tert-butyl peroxide as a radical generator were added dropwise over 2 hours, respectively, with stirring, and then aged for 3 hours.

[0340] After the reaction, the reaction product was cooled to room temperature and then added to 20 L of acetone and purified to obtain a maleic anhydride graft copolymer (average molecular weight 18,500) having a graft amount of 2.1% by mass.

[0341] 100 g of the obtained modified polyolefin resin was placed in a reactor equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, and heated at 120° C. to melt.

[0342] Then, 6 g of morpholine as a basic substance and 40 g of polyethylene oxide as a surfactant were added while stirring, and after stirring until the mixture became uniform, 600 g of water was added in small amounts to obtain an aqueous product by a phase inversion method.

[0343] At this time, the reaction conditions were changed so as to achieve the target average particle diameter (first or second resin average particle diameter) shown in Tables I to VI below, and dispersions of polyolefin resin B and polyolefin resin C were obtained, respectively.

[0344] The average particle size of the resin particles contained in these resin dispersions was 78 nm for the dispersion of polyolefin resin B and 108 nm for the dispersion of polyolefin resin C. The average particle size was measured using "Zeta Sizerano S-90" manufactured by Maruballon.

[0345] <Dispersion of acrylic resin D>

[0346] As the dispersion liquid of the acrylic resin D, NeoCryl A-1127 manufactured by Kusumoto Chemicals Co., Ltd., which is a commercially available product, was used.

[0347] <Preparation of black ink K1>

[0348] In a dispersion of 20.0% by mass of black pigment A (4.0% by mass in terms of solid content (the addition amount in terms of solid content is described in the table below), a dispersion of polyolefin resin A (the addition amount is adjusted so that the resin particles (solid content) in the ink become 4.0% by mass), 27.0% by mass of propylene glycol and 5.0% by mass of 2-methyl-1,3-propanediol as solvents, 1.0% by mass of trisiloxane polyoxyalkylene (BYK3450, manufactured by BYK Chemical Co., Ltd.), 0.1% by mass of 1,2-benzisothiazolin-3-one (Procell GXL (S), manufactured by SC Chemical Co., Ltd.) as a mildewproofing agent, and ion exchange water (remainder: the amount to make the total amount 100% by mass) were added while stirring. The obtained mixed solution was filtered through a 1 μm filter to obtain black ink K1. There was basically no change in composition before and after filtration.

[0349] <Preparation of black inks K2 to K12>

[0350] In the preparation of black ink K1, the types and blending amounts (mass %) of the pigment dispersion, resin dispersion (first resin and second resin), wax, and surfactant were changed as described in Tables I to VI below. In addition, the amount of ion exchange water added (remainder) was also changed accordingly, and each treatment liquid K2 to K12 was prepared in the same manner. It should be noted that in the following tables, the description of the solvent, mildewproofing agent, and ion exchange water is omitted.

[0351] In addition, "AQUACER 1547" (manufactured by BYK) was used as the wax shown in the following table.

[0352] [Physical property values]

[0353] The static surface tension and the dynamic surface tension of each of the obtained processing liquids and each of the black inks were measured by the following methods.

[0354] <Static surface tension>

[0355] The static surface tension of the treatment liquid and black ink prepared above at 25° C. was measured using a static surface tensiometer (CBVP-Z: manufactured by Kyowa Interface Science Co., Ltd.) using the Uilhelm method. The measured values ​​(unit: mN / m) are shown in Tables I to VI below.

[0356] <Dynamic surface tension>

[0357] The dynamic surface tension of the treatment liquid and ink prepared above at a surface life of 50 msec was measured using a dynamic surface tension meter (BP-100: manufactured by KRUSS) using the maximum bubble pressure method. The measurement temperature was adjusted to 25° C. The dynamic surface tension (in mN / m) at a surface life of 50 msec is shown in the following Tables I to VI.

[0358] [evaluate]

[0359] <Ink Storage Stability>

[0360] Each of the inks prepared above was heat stored at 60°C for 2 weeks, and then the average particle size was measured using a particle size analyzer (Zetascale Nano S-90). The ink storage properties were then evaluated according to the following criteria. The following "AA" and "A" were set to be practically problem-free.

[0361] (Benchmark)

[0362] AA: The difference between the average particle size after storage at 60°C for 2 weeks and the average particle size before storage at 60°C for 2 weeks was less than 10 nm.

[0363] A: The difference between the average particle size after storage at 60°C for 2 weeks and the average particle size before storage at 60°C for 2 weeks is 10 nm or more and less than 30 nm.

[0364] B: The difference between the average particle size after storage at 60°C for 2 weeks and the average particle size before storage at 60°C for 2 weeks is 30 nm or more.

[0365] [Printing test]

[0366] About the process liquid and ink prepared above, the printing test was carried out by the following method using the ink set which becomes the combination of following Table I - Table VI.

[0367] As a recording medium, a polypropylene substrate (#20FOR, manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) was prepared.

[0368] A scanning printer equipped with two independently driven inkjet heads (360 npi, discharge volume 6 pL, 1024 nozzles) manufactured by Konica Minolta Inc. was prepared. The head for recording first was filled with each processing liquid, and the head for recording later was filled with each ink.

[0369] Then, the image with a resolution of 720×720 dpi is divided into four images (180×180 dpi) in two in the scanning direction X and the conveying direction Y. In the four-pass mode in which one printing area is printed four times, printing is necessarily performed in one direction in the direction in which the processing liquid is first recorded.

[0370] The carriage transport speed was set to 300 mm / sec, and no drying process was provided between the processing liquid and the ink recording. The printing test was conducted in an environment of 25°C and 50% RH.

[0371] For recording with the treatment liquid, the application amount shown in Tables I to VI below was set to a maximum printing rate of 33%, and the application was performed according to the image area of ​​the ink. In addition, for recording with ink, the application amount of each ink was 18 g / m 2 Under the condition of setting, it is set to full coating to print.

[0372] The time from the application of the processing liquid to the application of the ink was measured and calculated to be 0.2 seconds.

[0373] [Drying of recorded materials]

[0374] In the above printing test, after the ink was applied, the polypropylene film was placed in a dryer set at 90° C. and heated and dried for 5 minutes to obtain an image recorded material.

[0375] In addition, printing of characters was performed under the same conditions as above to prepare various samples for evaluation (image records).

[0376] [evaluate]

[0377] <Image quality (text reproduction)>

[0378] The character reproducibility of each evaluation sample was evaluated according to the following criteria: "AA" and "A" were regarded as having no practical problems.

[0379] (Benchmark)

[0380] AA: 8pt characters are reproduced beautifully and can be recognized without any problems.

[0381] A: 10pt characters are reproduced beautifully and can be recognized without any problems.

[0382] B: Part of the 10pt text is missing and some of the text is difficult to recognize.

[0383] <Image quality (coating uniformity)>

[0384] The full coating pattern of each evaluation sample was visually evaluated, and the reflection density was measured and evaluated according to the following criteria. The reflection density was measured using a fluorescence spectrophotometer (FD-7 manufactured by Konica Minolta, Inc.) under a D50 light source. The following "AA" and "A" were set to be practically problem-free.

[0385] (Benchmark)

[0386] AA: Full coating with no streaks, etc., and reflection density of 1.5 or more

[0387] A: Full coating with no streaks, etc., and a reflection density of 1.3 or more and less than 1.5

[0388] B: The stripes can be recognized visually, and the reflection density is less than 1.3

[0389] <Adhesion>

[0390] The adhesion test (cross cut method) of JIS-K5600 was carried out on the fully coated part of each evaluation sample prepared using Nichivan Cellotryp (Cellotryp is a registered trademark) to evaluate the peeling state. The following "AA" and "A" were set as having no practical problem.

[0391] (Benchmark)

[0392] AA: No peeling

[0393] A: The peeled mesh is less than 20%

[0394] B: 20% or more of the mesh peeling off [Table 1]

[0395]

[0396] [Table 2]

[0397]

[0398] [Table 3]

[0399]

[0400] [Table 4]

[0401]

[0402] [Table 5]

[0403]

[0404] [Table 6]

[0405]

[0406] As shown in the above results, it is understood that the ink according to the present invention is superior in storage stability to the ink of the comparative example.

[0407] In addition, it is considered that the ink set of the present invention is superior in character reproducibility and full coating uniformity, and also has good adhesion, compared with the ink set of the comparative example.

[0408] Industrial Applicability

[0409] The present invention can be used in an ink set and an inkjet recording method that have good ink storage stability, high image quality, and good adhesion to a non-absorbent substrate in a two-liquid inkjet recording method.

[0410] Description of Reference Numerals

[0411] 1 Recording device

[0412] 10 Treatment liquid applying part

[0413] 11 Inkjet Head

[0414] 12 Treatment liquid droplets

[0415] 20 Ink giving department

[0416] 21 Inkjet Head

[0417] 22 Ink Drops

[0418] 23 Drying Section

[0419] 30 Delivery roller

[0420] 40 Winding roller

[0421] C Treatment liquid layer

[0422] G Image Layer

[0423] F substrate (recording medium)

[0424] 50 Packaging materials for canned food

[0425] 51 Tinplate substrate

[0426] 52 Thermosetting resin layer (primer layer)

[0427] 53 Image Layers

[0428] 54 Thermosetting resin layer (top coating)

Claims

1. An ink set comprising an ink containing at least a pigment and a treatment liquid containing at least a coagulant, for forming an image by applying the ink and the treatment liquid to a recording medium and combining them, wherein: The static surface tension of the treatment liquid is in the range of 18 to 25 mN / m at 25°C. The dynamic surface tension of the treatment liquid at a surface life of 50 msec is in the range of 25 to 35 mN / min at 25°C. The ink contains a polyolefin resin, and The recording medium is a non-absorbing substrate.

2. The ink set according to claim 1, wherein: The static surface tension of the ink is in the range of 25 to 35 mN / m at 25°C. The ink has a surface life of 50 msec and a dynamic surface tension of 35 to 45 mN / min at 25°C.

3. The ink set according to claim 1, wherein: The polyolefin resin is an acid-modified polyolefin resin.

4. The ink set according to claim 1, wherein: The treatment liquid contains a trisiloxane-based surfactant.

5. The ink set according to claim 1, wherein: The ink contains polyolefin resin particles having an average particle diameter within a range of 10 to 80 nm and resin particles having an average particle diameter within a range of 100 to 300 nm.

6. The ink set according to claim 1, wherein: The ink contains polyolefin resin particles having an average particle size within a range of 10 to 80 nm and polyolefin resin particles having an average particle size within a range of 100 to 300 nm.

7. The ink set according to claim 1, wherein: The average particle size of the pigment particles contained in the pigment is within a range of 50 to 100 nm.

8. The ink set according to claim 1, wherein: The ink contains wax.

9. An inkjet recording method, wherein: Using the ink set according to any one of claims 1 to 8, an image is recorded on a recording medium.

10. The inkjet recording method according to claim 9, wherein The amount of the treatment liquid applied per unit area for forming the image was 5.0 g / m 2 the following.

Images