Ink set and recording method

Abstract

To provide an ink set which comprises a process liquid and an inkjet ink composition, can excellently reduce banding unevenness, and has excellent ink storage stability.SOLUTION: An ink set according to the present invention comprises a process liquid containing a coagulant and an inkjet ink composition. The ink set is used for recording in a low absorbent or non-absorbent record medium. The inkjet ink composition is a water-based ink which contains a coloring material, a water-soluble organic compound having a solubility in 100 g of water at 20°C of over 10 g, and a hardly water-soluble organic compound having a solubility in 100 g of water at 20°C of 0.1-10 g. The hardly water-soluble organic compound contains 2.3 mass% or less of diol or glycol ether having a standard boiling point of 180-300°C based on the total mass of the ink composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an ink set and a recording method.

Background Art

[0002] An inkjet recording method is known in which minute ink droplets are ejected from nozzles of a recording head of an inkjet recording apparatus to record an image on a recording medium, and its use in the field of signature printing and high-speed label printing is also being studied. And even when recording an image on a recording medium with low ink absorption (for example, art paper or coated paper) or a recording medium with non-ink absorption (for example, plastic film), from the viewpoints of the global environment and safety to the human body, etc., the use of an aqueous inkjet ink composition (hereinafter also referred to as "aqueous ink" or "ink") having water as one of the main solvents is being studied.

[0003] In recording on a low-absorption or non-absorption recording medium using such an aqueous ink, for the purpose of improving the image quality, that is, fixing the ink adhering to the recording medium early and reducing the aggregation of ink dots (ink bleed), a technique of recording using a treatment liquid for aggregating the components of the ink is known (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of recording on a low-absorbing or non-absorbing recording medium using aqueous ink, since the ink hardly spreads (has poor filling) on the recording medium, even a slight deviation in the discharge amount of the ink droplets ejected from the nozzle or a slight deviation in the landing position causes banding unevenness where streak-like unevenness can be seen in the recorded image.

[0006] Furthermore, in the mode of performing recording using a treatment liquid for aggregating the components of the ink for the purpose of improving the image quality, since the ink droplets are even more difficult to spread on the recording medium, banding unevenness is more likely to occur. On the other hand, when the treatment liquid is not used, ink bleeding cannot be reduced, so excellent image quality cannot be obtained.

[0007] Furthermore, there are problems such as foreign substances being likely to occur when the ink dries and the storage stability being likely to deteriorate, and the recorded matter having poor rub resistance.

Means for Solving the Problems

[0008] One aspect of the ink set according to the present invention is an ink set including a treatment liquid containing a flocculant and an inkjet ink composition, which is used for recording on a low-absorbing or non-absorbing recording medium, wherein the inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, and a hardly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, and the hardly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3 mass% or less based on the total mass of the ink composition.

[0009] One aspect of the recording method according to the present invention is a recording method of performing recording using the ink set of the above aspect, An ink adhesion step of discharging the inkjet ink composition by an inkjet method and attaching it to a recording medium, and a treatment liquid adhesion step of attaching the treatment liquid to the recording medium. The recording medium is a low-absorbing or non-absorbing recording medium.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described. The embodiments described below are examples of the present invention. The present invention is not limited to the following embodiments at all, and also includes various modified forms implemented within the scope of not changing the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

[0012] 1. Ink Set An ink set according to an embodiment of the present invention is an ink set including a treatment liquid containing a flocculant and an inkjet ink composition, and is used for recording on a low-absorbing or non-absorbing recording medium. The inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, and a hardly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C. The hardly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition.

[0013] The ink set according to this embodiment includes an inkjet ink composition (hereinafter also referred to as "ink composition" or "ink") containing a specific sparingly water-soluble organic compound in a predetermined amount or less. Thereby, even when the ink set according to this embodiment is used together with a treatment liquid and used for recording on a low-absorbing or non-absorbing recording medium, it is possible to achieve both excellent reduction of banding unevenness and excellent storage stability of the ink.

[0014] In the present invention, the "ink set" refers to an inkjet ink composition and a treatment liquid used for recording as a set. The ink and the treatment liquid included in the ink set may be respectively accommodated in separate liquid containers, or may be accommodated in an integrated liquid container.

[0015] The ink set includes at least one (one type) of the inkjet ink composition and at least one (one type) of the treatment liquid. One or both of the inkjet ink composition and the treatment liquid may be provided in two or more. The inkjet ink composition is an ink used for recording by ejecting ink from an inkjet head by an inkjet method.

[0016] First, the recording medium used for recording with the ink set according to this embodiment will be described below, and then the inkjet ink composition and the treatment liquid that constitute the ink set will be described.

[0017] 1.1. Recording Medium The ink set according to this embodiment is used for recording on a low-absorbing or non-absorbing recording medium. In recording on a low-absorbing or non-absorbing recording medium, since the ink hardly spreads (has poor filling) on the recording medium, due to a slight deviation in the ejection amount of the ink droplets ejected from the nozzles or a slight deviation in the landing position, banding unevenness in which streak-like unevenness can be seen in the recorded image is likely to occur. However, according to the ink set according to this embodiment, even when used for recording on such a recording medium, it is possible to achieve both excellent reduction of banding unevenness and excellent storage stability of the ink.

[0018] The "low-absorbing recording medium" or "non-absorbing recording medium" refers to a recording medium that does not absorb or hardly absorbs liquid. Quantitatively, the "low-absorbing recording medium" or "non-absorbing recording medium" refers to "a recording medium with a water absorption of 10 mL / m or less from the start of contact to 30 msec in the Bristow method". 1 / 2 up to". 2 This Bristow method is the most popular method for measuring the liquid absorption amount in a short time and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). The details of the test method are described in Standard No. 51, "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of "JAPAN TAPPI Paper and Pulp Test Methods 2000 Edition".

[0019] (Low-absorbing recording medium) The low-absorbing recording medium is not particularly limited, and examples include coated paper provided with a coating layer for receiving ink on the surface. The coated paper is not particularly limited, and examples include printing papers such as art paper, coated paper, and matte paper. The coating layer is difficult to absorb ink, and examples include those coated with particles such as inorganic compounds together with a binder.

[0020] (Non-absorbing recording medium) The non-absorbing recording medium is not particularly limited, and examples include recording media such as plastic, glass, metal, and ceramics.

[0021] When the recording medium is plastic, examples include plastic films. Examples of such plastic films include polyester films, polyurethane films, polycarbonate films, polyphenylene sulfide films, polyimide films, polyamideimide films, etc. Other examples include polyolefins such as polyethylene and polypropylene, and polyvinyl chloride. Also included are biomass-derived plastic films, for example, PLA, PBS, PHA, bio-PE, bio-PP, bio-PET, etc. can be exemplified.

[0022] Also, it may be a film made of plastic, or one in which plastic is coated on a base material such as paper, or one in which a plastic film is adhered to a base material such as paper.

[0023] When the recording medium is metal, it may be a base material made of a metal such as iron, silver, copper, aluminum, etc., or one in which these various metals are vapor-deposited on the recording surface of a base material other than metal such as plastic. That is, as long as the recording surface is made of metal.

[0024] Note that the recording medium may be a recording medium having translucency such as colorless transparent, translucent, or colored transparent. Or, it may be one having no translucency such as colored opaque or achromatic opaque. Also, as the recording medium, an object having a three-dimensional shape such as a sheet shape, a spherical shape, or a rectangular parallelepiped shape, or a paper container, etc. may be used.

[0025] Among these low-absorbing or non-absorbing recording media, from the viewpoint of being able to more enjoy the effects exhibited by the present invention, it is preferably a non-absorbing recording medium, and more preferably the recording medium is plastic. That is, such a recording medium is particularly likely to cause banding unevenness because the ink is more difficult to wet and spread, but according to the ink set according to this embodiment, even with such a recording medium, it is possible to achieve both excellent reduction of banding unevenness and excellent storage stability of the ink.

[0026] 1.2. Inkjet Ink Composition The inkjet ink composition constituting the ink set according to this embodiment is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, and a sparingly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C. The sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition.

[0027] Hereinafter, each component contained in the inkjet ink composition constituting the ink set according to this embodiment will be described.

[0028] 1.2.1. Coloring Material The inkjet ink composition constituting the ink set according to this embodiment contains a coloring material. As the coloring material, at least one of a pigment and a dye can be used.

[0029] <Pigment> As the pigment, either an inorganic pigment or an organic pigment can be used. Using a pigment as the coloring material may improve the light resistance of the ink composition and is preferable.

[0030] As the inorganic pigment, carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide can be used.

[0031] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments; phthalocyanine pigments; perylene and perinone pigments; anthraquinone pigments; quinacridone pigments; dioxane pigments; thioindigo pigments; isoindolinone pigments; polycyclic pigments such as quinophthalone pigments; dye chelates (e.g., basic dye type chelates, acid dye type chelates, etc.); dyed lakes (basic dye type lakes, acid dye type lakes); nitro pigments; nitroso pigments; aniline black; and daylight fluorescent pigments.

[0032] More specifically, examples of carbon black used as black ink include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (manufactured by Mitsubishi Chemical Corporation); Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (manufactured by Carbon Columbia); Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (manufactured by CABOT JAPAN K.K.); Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printe x 140U, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, etc. (manufactured by Degussa) and the like.

[0033] Examples of pigments used in white ink include C.I. Pigment White 6, 18, and 21.

[0034] Examples of pigments used in yellow ink include C.I. Pigment Yellow 1, C.I. Pigment Yellow 2, C.I. Pigment Yellow 3, C.I. Pigment Yellow 4, C.I. Pigment Yellow 5, C.I. Pigment Yellow 6, C.I. Pigment Yellow 7, C.I. Pigment Yellow 10, C.I. Pigment Yellow 11, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 16, C.I. Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 34, C.I. Pigment Yellow 35, C.I. Pigment Yellow 37, C.I. Pigment Yellow 53, C.I. Pigment Yellow 55, C.I. Pigment Yellow 65, C.I. Pigment Yellow 73, C.I. Pigment Yellow 74, C.I. Pigment Yellow 75, C.I. Pigment Yellow 81, C.I. Pigment Yellow 83, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 97, C.I. Pigment Yellow 98, C.I. Pigment Yellow 99, C.I. Pigment Yellow 108, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 113, C.I. Pigment Yellow 114, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, C.I. Pigment Yellow 124, C.I. Pigment Yellow 128, C.I. Pigment Yellow 129, C.I. Pigment Yellow 133, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 151, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 167, C.I. Pigment Yellow 172, C.I. Pigment Yellow 180 are mentioned.

[0035] As pigments used in magenta ink, there are C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 4, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 8, C.I. Pigment Red 9, C.I. Pigment Red 10, C.I. Pigment Red 11, C.I. Pigment Red 12, C.I. Pigment Red 14, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 17, C.I. Pigment Red 18, C.I. Pigment Red 19, C.I. Pigment Red 21, C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 30, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 37, C.I. Pigment Red 38, C.I. Pigment Red 40, C.I. Pigment Red 41, C.I. Pigment Red 42, C.I. Pigment Red 48(Ca), C.I. Pigment Red 48(Mn), C.I. Pigment Red 57(Ca), C.I. Pigment Red 57:1, C.I. Pigment Red 88, C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 149, C.I. Pigment Red 150, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 184, C.I. Pigment Red 185, C.I. Pigment Red 187, C.I. Pigment Red 202, C.I. Pigment Red 209, C.I. Pigment Red 219, C.I. Pigment Red 224, C.I. Pigment Red 245, or C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 33, C.I. Pigment Violet 36, C.I. Pigment Violet 38, C.I. Pigment Violet 43, C.I. Pigment Violet 50.

[0036] Examples of pigments used in cyan ink include C.I. Pigment Blue 1, C.I. Pigment Blue 2, C.I. Pigment Blue 3, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:34, C.I. Pigment Blue 15:4, C.I. Pigment Blue 16, C.I. Pigment Blue 18, C.I. Pigment Blue 22, C.I. Pigment Blue 25, C.I. Pigment Blue 60, C.I. Pigment Blue 65, C.I. Pigment Blue 66, C.I. Vat Blue 4, C.I. Vat Blue 60.

[0037] In addition, examples of pigments other than magenta, cyan, and yellow include C.I. Pigment Green 7, C.I. Pigment Green 10, and C.I. Pigment Brown 3, C.I. Pigment Brown 5, C.I. Pigment Brown 25, C.I. Pigment Brown 26, C.I. Pigment Orange 1, C.I. Pigment Orange 2, C.I. Pigment Orange 5, C.I. Pigment Orange 7, C.I. Pigment Orange 13, C.I. Pigment Orange 14, C.I. Pigment Orange 15, C.I. Pigment Orange 16, C.I. Pigment Orange 24, C.I. Pigment Orange 34, C.I. Pigment Orange 36, C.I. Pigment Orange 38, C.I. Pigment Orange 40, C.I. Pigment Orange 43, and C.I. Pigment Orange 63.

[0038] The above pigments may be used alone or in combination of two or more.

[0039] When using the above pigments, the average particle size is preferably 300 nm or less, more preferably 50 to 200 nm. When the average particle size is within the above range, the reliability such as ejection stability and dispersion stability in the ink composition is further improved, and an image with excellent image quality tends to be formed. Here, the average particle size in this specification is measured by the dynamic light scattering method.

[0040] 〔Pigment Dispersion〕 The above pigments may exist in a dispersed state in the ink composition, that is, as a pigment dispersion. Here, the pigment dispersion in this specification means including a pigment dispersion liquid and a slurry of a pigment (low-viscosity aqueous dispersion).

[0041] Examples of the pigment dispersion include, but are not limited to, self-dispersible pigments, polymer-dispersed pigments, pigments coated with polymers, and the like.

[0042] (Self-dispersible Pigment) Self-dispersible pigments are pigments that can be dispersed or dissolved in an aqueous medium without a dispersant. Here, "dispersed or dissolved in an aqueous medium without a dispersant" means that even without using a dispersant for dispersing the pigment, due to the hydrophilic groups on its surface, it is in a state of being stably present in the aqueous medium. Therefore, there is almost no foaming due to the decrease in defoaming property caused by the dispersant, and it is easy to prepare an ink with excellent ejection stability. Also, since a significant increase in viscosity caused by the dispersant is suppressed, it becomes possible to contain more pigments and sufficiently increase the printing density, etc., and it is easy to handle.

[0043] The above hydrophilic groups are preferably one or more hydrophilic groups selected from the group consisting of -OM, -COOM, -CO-, -SO3M, -SO2M, -SO2NH2, -RSO2M, -PO3HM, -PO3M2, -SO2NHCOR, -NH3, and -NR3.

[0044] In these chemical formulas, M represents a hydrogen atom, an alkali metal, ammonium, a phenyl group which may have a substituent, or an organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms or a naphthyl group which may have a substituent. Also, the above M and R are each independently selected.

[0045] Self-dispersible pigments are produced, for example, by subjecting the pigment to a physical treatment or a chemical treatment to bond (graft) the above hydrophilic groups to the surface of the pigment. Examples of the physical treatment include vacuum plasma treatment and the like. Also, examples of the chemical treatment include a wet oxidation method of oxidizing with an oxidant in water, a method of bonding a carboxyl group via a phenyl group by bonding p-aminobenzoic acid to the pigment surface, and the like.

[0046] (Polymer-dispersed pigment) Polymer-dispersed pigments are pigments that can be dispersed by polymer dispersion. The polymers used in polymer-dispersed pigments include, but are not limited to, for example, the glass transition temperature (Tg) of the dispersion polymer used for pigment dispersion is preferably 55°C or lower, more preferably 50°C or lower. When the Tg is 55°C or lower, the fixing property of the ink may be improved.

[0047] Also, the weight-average molecular weight of the above polymer by gel permeation chromatography (GPC) is preferably 10,000 or more and 200,000 or less. This may further improve the storage stability of the ink. Here, the weight-average molecular weight (Mw) in this specification can be measured as the weight-average molecular weight in terms of polystyrene using gel permeation chromatography (GPC) of the L7100 system manufactured by Hitachi, Ltd.

[0048] As the above polymer, since it tends to be more excellent in the fixing property and glossiness of the ink, it is preferable that 70 mass% or more of its constituent components are polymers obtained by copolymerization of (meth)acrylate and (meth)acrylic acid. It is preferable that it is polymerized from a monomer component in which at least one of alkyl (meth)acrylates having 1 to 24 carbon atoms and cyclic alkyl (meth)acrylates having 3 to 24 carbon atoms is 70 mass% or more. Specific examples of the monomer component include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)ac Examples include relato, tetramethylpiperidyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyl oxy (meth) acrylate, and behenyl (meth) acrylate. As other monomer components for polymerization, hydroxy (meth) acrylates having a hydroxyl group such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and diethylene glycol (meth) acrylate, urethane (meth) acrylate, and epoxy (meth) acrylate can also be used.

[0049] In this specification, the notation "(meth)acryl" means at least one of acrylic and methacrylic. The notation "(meth)acrylate" means at least one of acrylate and methacrylate.

[0050] (Pigment coated with polymer) In addition, since it tends to have excellent ink fixing properties, glossiness, and color reproducibility, among the above polymer-dispersed pigments, pigments coated with a polymer, that is, microencapsulated pigments, are preferably used.

[0051] The pigment coated with the polymer is obtained by the phase inversion emulsification method. That is, the above polymer is dissolved in an organic solvent such as methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, and dibutyl ether. A pigment is added to the obtained solution, and then a neutralizing agent and water are added, followed by kneading and dispersion treatment to adjust an oil-in-water type dispersion. Then, by removing the organic solvent from the obtained dispersion, a pigment coated with a polymer can be obtained as an aqueous dispersion. For the kneading and dispersion treatment, for example, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, and a high-speed stirring type disperser can be used.

[0052] As neutralizing agents, tertiary amines such as ethylamine and trimethylamine, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc. are preferable. The pH of the obtained aqueous dispersion is preferably 6 to 10.

[0053] As the polymer for coating the pigment, those having a weight average molecular weight of about 10,000 to 150,000 by GPC are preferable in terms of stably dispersing the pigment.

[0054] <Dye> The dyes are not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. Examples of the dyes include C.I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. Acid Red 52, 80, 82, 249, 254, 289, C.I. Acid Blue 9, 45, 249, C.I. Acid Black 1, 2, 24, 94, C.I. Food Black 1, 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. Reactive Red 14, 32, 55, 79, 249, C.I. Reactive Black 3, 4, 35, etc.

[0055] The above dyes may be used alone or in combination of two or more.

[0056] The content of the coloring material (solid content) is preferably, for example, 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more with respect to the total mass of the ink composition. Further, the content of the coloring material (solid content) is preferably 10% by mass or less, more preferably 8% by mass or less, and still more preferably 6% by mass or less with respect to the total mass of the ink composition. When the content of the coloring material is within the above range, the storage stability may be more excellent.

[0057] 1.2.2. Water The inkjet ink composition constituting the ink set according to the present embodiment is an aqueous inkjet ink composition (aqueous ink) and contains water. The "aqueous" composition is a composition having water as one of the main solvents.

[0058] Examples of the water include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, and distilled water, and those with reduced ionic impurities such as ultrapure water. Also, when using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., the generation of bacteria and fungi can be suppressed when the inkjet ink composition is stored for a long time.

[0059] The content of water is preferably 40% by mass or more, more preferably 45% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more with respect to the total mass of the ink composition. Also, the upper limit of the water content is not particularly limited, but for example, it is preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less with respect to the total mass of the ink composition.

[0060] 1.2.3. Water-soluble organic compound The inkjet ink composition constituting the ink set according to the present embodiment is an aqueous ink containing a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C. Examples of the water-soluble organic compound include those that are liquid at normal temperature and those that are solid at normal temperature. By containing the water-soluble organic compound in the ink, the clogging recovery property, storage stability, image quality, etc. of the ink are excellent.

[0061] The method for determining the solubility of the water-soluble organic compound is as follows. First, in an environment of 20°C, a predetermined amount of the water-soluble organic compound is mixed with 100 g of water and stirred for 30 minutes. After stirring, for a compound that is liquid at normal temperature, if it is not phase-separated or in a sea-island structure, it is judged to be dissolved. Also, for a compound that is solid at normal temperature, if there is no undissolved residue, it is judged to be dissolved. In this way, when a predetermined amount of an organic compound is mixed with 100 g of water, the maximum value among the predetermined amounts when it is determined to be dissolved is defined as the solubility. An organic compound with a solubility exceeding 10 g is defined as a water-soluble organic compound.

[0062] Note that the water-soluble organic compound can be a compound that is completely miscible with water or a compound that is miscible with water. In this specification, "completely miscible with water" refers to the case where water and the organic compound dissolve in each other, that is, the case where the solubility of the organic compound with respect to 100 g of water at 20°C is infinite. Also, "miscible with water" refers to the case where water and the organic compound have a finite solubility, and specifically, the case where the solubility of the organic compound with respect to 100 g of water at least at 20°C exceeds 10 g.

[0063] The molecular weight of the water-soluble organic compound is preferably 500 or less as the weight average molecular weight. More preferably, it is 400 or less, and even more preferably, it is 300 or less. Further, the inkjet ink composition preferably contains, as the water-soluble organic compound, those having a standard boiling point of 150 to 350°C. More preferably, the standard boiling point is 150 to 300°C. Also, the water-soluble organic compound preferably contains a compound having a melting point of 90°C or lower. Further preferably, it contains a compound having a melting point of 80°C or lower. Also, the melting point is preferably -70°C or higher. The solubility of the water-soluble organic compound exceeds 10 g, but the upper limit is not limited and can be infinite. The solubility is preferably 11 g or more, and more preferably 50 g or more.

[0064] Examples of water-soluble organic compounds having a solubility exceeding 10 g with respect to 100 g of water at 20°C include resin solubilizing substances, polyols, glycol ethers, alkanolamines, etc. The resin solubilizing substance is any one of amides, sulfur-containing solvents, and cyclic ethers. Among them, resin solubilizing substances, polyols, and glycol ethers are preferred. More preferably, examples thereof include resin-dissolving substances which are any of amides, sulfur-containing solvents, and cyclic ethers having a standard boiling point of 150 to 300°C, and compounds which are any of polyols and glycol ethers having a standard boiling point of 150 to 250°C. Optionally, other water-soluble organic compounds may be included.

[0065] The water-soluble organic compound is preferably contained in an amount of 40% by mass or less based on the total mass of the ink composition. Further, it is preferably contained in an amount of 1% by mass or more based on the total mass of the ink composition. More preferably, it is 5 to 30% by mass, and even more preferably 10 to 25% by mass.

[0066] <Resin-dissolving substance> Examples of the water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C include resin-dissolving substances which are any of amides, sulfur-containing solvents, and cyclic ethers. Among them, it is preferable to contain a resin-dissolving substance which is any of amides, sulfur-containing solvents, and cyclic ethers having a standard boiling point of 150 to 300°C. The resin-dissolving substance is an organic compound having a function of dissolving the resin and improving the abrasion resistance, but is not limited to this function.

[0067] Examples of the amides include cyclic amides (lactams) such as 2-pyrrolidone (2P), 2-piperidone, ε-caprolactam (CPL), N-methyl-ε-caprolactam, N-cyclohexyl-2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-butylpyrrolidone, 5-methyl-2-pyrrolidone, β-propiolactam, ω-heptalactam, etc., and chain amides such as N,N-dimethylacetoacetamide, N,N-diethylacetoacetamide, N-methylacetoacetamide, N,N-dimethylisobutyramide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, 3-methoxy-N,N-dimethylpropanamide (DMPA), 3-n-butoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-diethylpropionamide, 3-n-butoxy-N,N-methylethylpropionamide, 3-n-propoxy-N,N-dimethylpropionamide, 3-n-propoxy-N,N-diethylpropionamide, 3-n-propoxy-N,N-methylethylpropionamide, 3-iso-propoxy-N,N-dimethylpropionamide, 3-iso-propoxy-N,N-diethylpropionamide, 3-iso-propoxy-N,N-methylethylpropionamide, 3-tert-butoxy-N,N-dimethylpropionamide, 3-tert-butoxy-N,N-diethylpropionamide, 3-tert-butoxy-N,N-methylethylpropionamide. Among these, any one of 2-pyrrolidone (2P), ε-caprolactam (CPL), and 3-methoxy-N,N-dimethylpropanamide (DMPA) is more preferable, and it tends to make the storage stability of the ink more excellent.

[0068] Examples of the sulfur-containing solvent include 3-methylsulfolane, sulfolane, ethyl isopropyl sulfone, ethyl methyl sulfone, dimethyl sulfone, dimethyl sulfoxide (DMSO) , diethyl sulfoxide, tetramethylene sulfoxide, methyl phenyl sulfoxide, and the like. Among these, dimethyl sulfoxide (DMSO) is more preferable, and it tends to make the storage stability of the ink more excellent.

[0069] Examples of the cyclic ethers include isosorbide dimethyl ether, 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol (DMHD), 2-hydroxymethyloxetane, tetrahydrofurfuryl alcohol, sorbitol ketal, glycerol formal, 1,4-dioxane-2,3-diol, dihydrolevoglucosenone, and the like. Among these, 3-ethyl-3-oxetanemethanol (DMHD) is more preferable, and it tends to make the storage stability of the ink more excellent.

[0070] Among these, resin-dissolving substances that are amides and have a standard boiling point of 150 to 300 °C are preferable because they tend to have better storage stability. Further, the resin-dissolving substance is preferably a compound having a melting point of 80 °C or lower. When the melting point is within the above range, the clogging recovery property tends to be excellent.

[0071] The inkjet ink composition constituting the ink set according to the present embodiment preferably contains, as a water-soluble organic compound, a resin-dissolving substance that is any one of amides, sulfur-containing solvents, and cyclic ethers, in an amount of 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total mass of the ink composition. Further, the lower limit is 0% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more. Also, the content of the resin-dissolving substance that is any one of amides, sulfur-containing solvents, and cyclic ethers and has a standard boiling point of 150 to 300 °C may be within the above range. When the contents of these resin-dissolving substances are within the above ranges, the compatibility between the water-soluble organic compound and the hardly water-soluble organic compound in the ink composition becomes good, and the storage stability and rubbing resistance tend to be excellent. On the other hand, when the contents of these resin-dissolving substances exceed the above ranges, the storage stability decreases or the reduction property of banding unevenness decreases. This is presumably because the relative decrease in the water content in the ink composition makes it difficult for the hardly water-soluble organic compound to dissolve.

[0072] <Polyols, glycol ethers> The inkjet ink composition constituting the ink set according to the present embodiment preferably contains any one of polyols and glycol ethers as the water-soluble organic compound other than the above resin-dissolving substances. In particular, it is preferable to contain any one of polyols and glycol ethers having a standard boiling point of 150 to 250 °C.

[0073] (Polyols) The polyols are preferably glycol or a compound in which glycol is intermolecularly condensed by hydroxyl groups. In this case, it is a compound having two hydroxyl groups. Alternatively, examples of the polyols include compounds in which the hydrogen atoms that glycol or a compound in which glycol is intermolecularly condensed by hydroxyl groups had are substituted with hydroxyl groups. In this case, it is a compound having three or more hydroxyl groups. The glycol unit in the glycol or the compound in which glycol is intermolecularly condensed by hydroxyl groups constituting the polyols preferably has 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. Also, the polyols preferably have 2 to 15 carbon atoms in the molecule, more preferably 3 to 10 carbon atoms. The polyols preferably have a standard boiling point of 150 to 250 °C.

[0074] Examples of the polyols having a standard boiling point of 150 to 250°C include ethylene glycol (standard boiling point 198°C, miscible with water), diethylene glycol (standard boiling point 244°C, completely miscible with water), 1,2-propanediol (propylene glycol) (standard boiling point 188°C, completely miscible with water), dipropylene glycol (standard boiling point 227°C, completely miscible with water), 1,2-butanediol (standard boiling point 193°C, miscible with water), 1,2-pentanediol (standard boiling point 210°C, miscible with water), 1,2-hexanediol (standard boiling point 224°C, completely miscible with water), 1,3-propanediol (standard boiling point 214°C, completely miscible with water), 1,4-butanediol (standard boiling point 228°C, completely miscible with water), 2,3-butanediol (standard boiling point 177°C, miscible with water), 1,3-butylene glycol (standard boiling point 207°C, completely miscible with water), 3-methyl-1,3-butanediol (standard boiling point 203°C, completely miscible with water), 2-methyl-1,3-propanediol (standard boiling point 214°C, completely miscible with water), 2,2-dimethyl-1,3-propanediol (standard boiling point 208°C, solubility 83 [g / 100 g of water]), 2-methylpentane-2,4-diol (standard boiling point 197°C, completely miscible with water), 2,5-dimethyl-2,5-hexanediol (standard boiling point 218°C, solubility 14 [g / 100 g of water]), 1,5-pentanediol (standard boiling point 242°C, miscible with water), 3-methyl-1,5-pentanediol (standard boiling point 250°C, completely miscible with water), 1,6-hexanediol (standard boiling point 250°C, miscible with water), and the like. As the polyols, polyols having 10 or less carbon atoms are more preferable.

[0075] Among the polyols, alkanediols having a standard boiling point of 150 to 250°C and 10 or less carbon atoms are more preferable, and alkanediols having a standard boiling point of 150 to 250°C and 6 or less carbon atoms are even more preferable. Examples of the alkanediols include ethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, etc., which are 1,2-alkanediols, and 1,3-propanediol, 1,3-butylene glycol, etc.

[0076] (Glycol Ethers) Glycol ethers are compounds in which one or more hydroxyl groups of glycol are etherified. As the above glycol ethers, monoethers or diethers of alkylene glycol are preferred. As the ether for the above etherification, alkyl ether is preferred. The alkylene of the alkylene glycol and the alkyl of the alkyl ether constituting the glycol ethers are each preferably independently having 1 to 5 carbon atoms, more preferably 2 to 4 carbon atoms. Glycol ethers having a standard boiling point of 150 to 250 ° C are preferred.

[0077] Examples of glycol ethers include ethylene glycol monomethyl ether (completely miscible with water), ethylene glycol monoethyl ether (miscible with water), ethylene glycol monoisopropyl ether (solubility 100 [g / 100 g of water]), ethylene glycol monopropyl ether (miscible with water), ethylene glycol monoisobutyl ether (solubility 75.5 [g / 100 g of water]), ethylene glycol mono-tert-butyl ether (miscible with water), ethylene glycol monobutyl ether (solubility 100 [g / 100 g of water]), diethylene glycol monomethyl ether (completely miscible with water), diethylene glycol monoethyl ether (completely miscible with water), diethylene glycol monoisopropyl ether (miscible with water), diethylene glycol monoisobutyl ether (completely miscible with water), diethylene glycol monobutyl ether (completely miscible with water), triethylene glycol monomethyl ether (completely miscible with water), triethylene glycol monoethyl ether (completely miscible with water), triethylene glycol monobutyl ether (miscible with water), tetraethylene glycol monomethyl ether (miscible with water), propylene glycol monomethyl ether (miscible with water), propylene glycol monoethyl ether (completely miscible with water), propylene glycol monopropyl ether (miscible with water), dipropylene glycol monomethyl ether ( (miscible with water), dipropylene glycol monopropyl ether (solubility 19 [g / 100 g of water]), tripropylene glycol monomethyl ether (miscible with water), 1,3-propanediol monomethyl ether (3-methoxy-1-propanol) (miscible with water), 1,3-butylene glycol-3-monomethyl ether (3-methoxy-1-butanol) (miscible with water), and other alkylene glycol monoalkyl ethers, and ethylene glycol dimethyl ether (miscible with water), diethylene glycol dimethyl ether (miscible with water), diethylene glycol methyl ethyl ether (miscible with water), diethylene glycol diethyl ether (miscible with water), triethylene glycol dimethyl ether (miscible with water), tetraethylene glycol dimethyl ether (miscible with water), dipropylene glycol dimethyl ether (solubility 52.6 [g / 100 g of water]), tripropylene glycol dimethyl ether (solubility 23.6 [g / 100 g of water]), and other alkylene glycol dialkyl ethers (glymes).

[0078] Also, among the above glycol ethers, the diether tends to be more likely to dissolve or swell the resin in the ink than the monoether, and is more preferable in terms of improving the rub resistance of the formed image. On the other hand, the monoether is preferable in terms of excellent wet spreading property of the ink.

[0079] The inkjet ink composition constituting the ink set according to the present embodiment preferably contains any one of polyols and glycol ethers as a water-soluble organic compound in an amount of 30% by mass or less, more preferably 25% by mass or less, based on the total mass of the ink composition. Further, as the lower limit value, it is 0% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, based on the total mass of the ink composition. Also, it is preferable that the content of any one of polyols and glycol ethers having a standard boiling point of 150 to 250 °C be in the above range. When these water-soluble organic compounds are contained within the above ranges, the compatibility between the water-soluble organic compound and the sparingly water-soluble organic compound becomes better, and the storage stability tends to be more excellent. Among polyols having a standard boiling point of 150 to 250 °C, it is more preferable that they are alkanediols having a standard boiling point of 150 to 250 °C and 10 or less carbon atoms as described above.

[0080] The inkjet ink composition constituting the ink set according to the present embodiment preferably contains alkanediols having a standard boiling point of 150 to 250 °C and 6 or less carbon atoms as a water-soluble organic compound in an amount of 10 to 25% by mass, more preferably 12 to 20% by mass, and even more preferably 15 to 18% by mass based on the total mass of the ink composition. When the water-soluble organic compound is contained within the above ranges, the compatibility between the water-soluble organic compound and the sparingly water-soluble organic compound becomes better, and the storage stability tends to be more excellent.

[0081] <Other Compounds> The inkjet ink composition constituting the ink set according to the present embodiment may contain other water-soluble organic compounds as necessary.

[0082] (Alkanolamines) The inkjet ink composition may contain alkanolamines as a water-soluble organic compound. Alkanolamines are compounds having a hydroxyl group and an amino group in an alkane skeleton. The number of hydroxyl groups in the alkanolamine molecule is 1 or more, preferably 1 to 5, and more preferably 2 to 3. The number of carbon atoms in the alkanolamine molecule is preferably 1 to 20, more preferably 2 to 10, and even more preferably 6 to 9. The alkane skeleton preferably has 1 to 6 carbon atoms per alkane skeleton, and more preferably 2 to 4. The number of amino groups in the alkanolamine molecule is 1 or more, preferably 1 to 5, and more preferably 1 to 2.

[0083] The alkanolamines are not particularly limited, and examples thereof include ethanolamine (miscible with water), N-methylethanolamine (solubility 100 [g / 100 g of water]), N,N-dimethylethanolamine (completely miscible with water), N-ethylethanolamine (miscible with water), N-butylethanolamine (miscible with water), N,N-diethylethanolamine (miscible with water), diethanolamine (solubility 100 [g / 100 g of water]), N-methyldiethanolamine (solubility 100 [g / 100 g of water]), N-ethyldiethanolamine (miscible with water), N-butyl diethanolamine (miscible with water), N-tert-butyldiethanolamine (completely miscible with water), triethanolamine (completely miscible with water), isopropanolamine (miscible with water), N,N-dimethylisopropanolamine (completely miscible with water), N,N-diethylisopropanolamine (miscible with water), diisopropanolamine (solubility 87 [g / 100 g of water]), triisopropanolamine (solubility 83 [g / 100 g of water]), N,N-dimethylpropanolamine (miscible with water), 2-amino-1-propanol (completely miscible with water), 2-amino-2-methyl-1-propanol (completely miscible with water), 5-amino-1-pentanol (miscible with water), 2-amino-2-methyl-1,3-propanediol (miscible with water), 2-amino-2-hydroxymethyl-1,3-propanediol (miscible with water), 3-amino-1,2-propanediol (miscible with water), 3-methylamino-1,2-propanediol (completely miscible with water), tripropanolamine, and tributanolamine. Among these, triethanolamine and triisopropanolamine are preferable, and triisopropanolamine is more preferable. The alkanolamines may be used alone or in combination of two or more.

[0084] The content of the alkanolamines relative to the total mass of the ink composition is preferably 1% by mass or less, and more preferably 0.05 to 0.5% by mass.

[0085] (Polyols with a standard boiling point exceeding 280 °C) The inkjet ink composition preferably contains polyols having a standard boiling point exceeding 280°C as a water-soluble organic compound in an amount not exceeding 3% by mass based on the total mass of the ink composition. More preferably, it does not exceed 1% by mass, and even more preferably, it does not exceed 0.5% by mass. In this case, polyols having a standard boiling point exceeding 280°C may or may not be contained in the ink. Even if contained, the content is below the above range. When the content of polyols having a standard boiling point exceeding 280°C is within the above range, it is possible to prevent a significant decrease in the drying property of the ink. As a result, even when recording on a low-absorbing or non-absorbing recording medium, the image fixing property can be prevented from decreasing. Also, when performing heat drying, the temperature of the recording medium can be relatively low and sufficient drying can tend to be performed. Examples of such polyols having a standard boiling point exceeding 280°C include glycerin (standard boiling point 290°C), and alkanolamines such as triisopropanolamine are not included.

[0086] 1.2.4. Sparingly water-soluble organic compounds The inkjet ink composition constituting the ink set according to the present embodiment is an aqueous ink containing a sparingly water-soluble organic compound having a solubility in 100 g of water at 20°C of 0.1 to 10 g. The sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition. Thereby, excellent banding unevenness suppression can be obtained in a low-absorbing or non-absorbing recording medium. Also, the storage stability and abrasion resistance of the ink are excellent. In particular, in recording on a non-absorbing recording medium such as a plastic film, banding unevenness is more likely to occur, but excellent banding unevenness suppression can be obtained. The reason is that sparingly water-soluble compounds tend to have low affinity with water. Therefore, in low-absorbing Alternatively, since it has a high affinity for a non-absorbent recording medium and tends to spread easily when wet, it is presumed that the ink has excellent wet spreading and excellent banding unevenness suppression. However, the reason is not limited to this.

[0087] As a method for determining the solubility of a sparingly water-soluble organic compound, it is as follows. The solubility is determined in the same manner as the solubility of the above-mentioned water-soluble organic compound. A compound having a solubility of 0.1 to 10 g is defined as a sparingly water-soluble organic compound.

[0088] Examples of the sparingly water-soluble organic compound include diols or glycol ethers having a solubility of 0.1 to 10 g in 100 g of water at 20°C and a standard boiling point of 180 to 300°C. If necessary, other sparingly water-soluble organic compounds may be used.

[0089] Note that as the sparingly water-soluble organic compound, it is preferably a weight average molecular weight of 500 or less. Further, 400 or less is more preferable, and 300 or less is even more preferable. Furthermore, the melting point of the sparingly water-soluble organic compound is preferably 130°C or lower. Also, the melting point is preferably -120°C or higher. Further, -50 to 60°C is preferable, and -30 to 50°C is more preferable. The standard boiling point of the sparingly water-soluble organic compound is preferably 200 to 280°C, and more preferably 230 to 270°C.

[0090] <Diols> Examples of diols having a solubility of 0.1 to 10 g in 100 g of water at 20°C and a standard boiling point of 180 to 300°C include 1,3-alkanediols, other aliphatic diols, alicyclic diols, and the like.

[0091] As the above-mentioned 1,3-alkanediols, 2,2-diethyl-1,3-propanediol (DEPOD, boiling point 240°C, solubility 10.0 [g / 100 g of water]), 2-methyl-2-propyl-1,3-propanediol (MPPD, boiling point 230°C, melting point 57°C, solubility 7.5 [g / 100 g of water]), 2-butyl-2-ethyl-1,3-propanediol (BEPD, boiling point 264°C, melting point 43°C, solubility 0.9 [g / 100 g of water]), 2,2-diisobutyl-1,3-propanediol (DIBPD, boiling point 253°C, melting point 77°C, solubility 0.5 [g / 100 g of water]), 2,2-dibutyl-1,3-propanediol (DBPD, boiling point 269°C, solubility 0.2 [g / 100 g of water]), 2,2,4-trimethyl-1,3-pentanediol (TMPD, boiling point 232°C, melting point 54°C, solubility 1.9 [g / 100 g of water]), 2-ethyl-1,3-hexanediol (EHD, boiling point 244°C, melting point -40°C, solubility 4.2 [g / 100 g of water]), etc. can be mentioned.

[0092] As the above-mentioned other aliphatic diols, 1,2-octanediol (1,2OD, boiling point 267°C, melting point 26°C, solubility 0.8 [g / 100 g of water]), 1,9-nonanediol (1,9ND, boiling point 289°C, melting point 46°C, solubility 0.6 [g / 100 g of water]), 2,4-diethyl-1,5-pentanediol (DEPD, boiling point 257°C, liquid (25°C), solubility 1.0 [g / 100 g of water]), etc. can be mentioned.

[0093] As the above-mentioned alicyclic diols, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD, boiling point 220°C, melting point 126°C, solubility 6.1 [g / 100 g of water]), 1,4-cyclohexanedimethanol (CHDM, boiling point 286°C, melting point 35°C, solubility 0.8 [g / 100 g of water]), etc. can be mentioned.

[0094] Among these diols with a standard boiling point of 180 to 300°C, it is preferable that they are 1,3-alkanediols and alicyclic diols represented by the following general formula (1).

Chemical formula

[0095] Furthermore, in the above formula, it is preferable that R1 and R2 are not hydrogen at the same time. When R1, R2, and R3 are alkyl groups, the alkyl groups are preferably independently 1 to 5 carbon atoms, more preferably 2 to 4 carbon atoms. The total number of carbon atoms of R1, R2, and R3 is preferably 4 to 5, more preferably 4 to 6. R3 is preferably an alkyl group.)

[0096] Examples of the 1,3 - alkanediols and alicyclic diols of the general formula (1) include 2 - methyl - 2 - propyl - 1,3 - propanediol (MPPD), 2 - butyl - 2 - ethyl - 1,3 - propanediol (BEPD), 2,2,4 - trimethyl - 1,3 - pentanediol (TMPD), 2 - ethyl - 1,3 - hexanediol (EHD), etc.)

[0097] When the diols having a standard boiling point of 180 to 300 °C are the 1,3 - alkanediols and alicyclic diols of the above general formula (1), they tend to be more excellent in reducing banding unevenness and abrasion resistance.)

[0098] <Glycol ethers> Examples of glycol ethers having a solubility of 0.1 to 10 g in 100 g of water at 20 °C and a standard boiling point of 180 to 300 °C include glycol monoethers and glycol diethers.)

[0099] Examples of the glycol monoethers include ethylene glycol monohexyl ether (EGHE, boiling point: 208°C, melting point: -45°C, solubility: 1.0 [g / 100 g of water]), ethylene glycol mono-2-ethylhexyl ether (EHG, boiling point: 229°C, melting point: -105°C, solubility: 0.1 [g / 100 g of water]), diethylene glycol monohexyl ether (HDG, boiling point: 259°C, liquid (25°C), solubility: 1.7 [g / 100 g of water]), diethylene glycol mono-2-ethylhexyl ether (EHDG, boiling point: 277°C, melting point: -82°C, solubility: 0.5 [g / 100 g of water]), dipropylene glycol monobutyl ether (BPDG, boiling point: 230°C, liquid (25°C), solubility: 4.0 [g / 100 g of water]), tripropylene glycol monobutyl ether (BPTG, boiling point: 276°C, solubility: 4.0 [g / 100 g of water]), and the like.

[0100] Examples of the glycol diethers include diethylene glycol butyl methyl ether (BMTG, boiling point: 212°C, liquid (25°C)), diethylene glycol dibutyl ether (DBDG, boiling point: 256°C, melting point: -60°C, solubility: 0.3 [g / 100 g of water]), and the like.

[0101] Among these glycol ethers with a standard boiling point of 180 to 300°C, glycol ethers having 6 or more carbon atoms are preferred. Examples of the glycol ethers having 6 or more carbon atoms include, for example, ethylene glycol monohexyl ether (EGHE), ethylene glycol mono-2-ethylhexyl ether (EHG), diethylene glycol monohexyl ether (HDG), diethylene glycol mono-2-ethylhexyl ether (EHDG), dipropylene glycol monobutyl ether (BPDG), tripropylene glycol monobutyl ether (BPTG), diethylene glycol butyl methyl ether (BMTG), diethylene glycol dibutyl ether (DBDG), and the like.

[0102] When the glycol ethers are glycol ethers having 6 or more carbon atoms in this way, they tend to be more excellent in reducing banding unevenness and storage stability.

[0103] Also, as the glycol ethers, it is preferably any one of ethylene glycol monohexyl ether (EGHE), ethylene glycol mono-2-ethylhexyl ether (EHG), diethylene glycol monohexyl ether (HDG), diethylene glycol mono-2-ethylhexyl ether (EHDG), and diethylene glycol dibutyl ether (DBDG). When using these glycol ethers, they tend to be particularly excellent in reducing banding unevenness and storage stability.

[0104] The inkjet ink composition constituting the ink set according to this embodiment contains, as a water-insoluble organic compound, diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less, preferably 0.1 to 2.0% by mass, more preferably 0.15 to 1.5% by mass, still more preferably 0.25 to 1.0% by mass, and particularly preferably 0.35 to 0.7% by mass based on the total mass of the ink composition. When the content of such a water-insoluble organic compound is within the above range, it ensures good reduction of banding unevenness and tends to have more excellent storage stability.

[0105] 1.2.5. Components other than the above The inkjet ink composition constituting the ink set according to this embodiment may also use resins, waxes, antifoaming agents, surfactants, and other additives in combination according to the purpose in addition to the above-described components.

[0106] (Resin) The inkjet ink composition constituting the ink set according to the present embodiment may contain a resin. The resin can be formulated as a water-soluble resin or an emulsion of resin particles. Such a resin may function as a so-called fixing resin that improves the adhesion and abrasion resistance of the components of the pigment ink adhered to the recording medium. An emulsion of resin particles is preferred.

[0107] Examples of the resin include urethane resins, acrylic resins, fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, ethylene vinyl acetate resins, vinyl acetate resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, benzoguanamine resins, phenol resins, silicone resins, epoxy resins, paraffin resins, fluorine resins, and the like. These resins are often handled in the form of an emulsion, but may also be in the form of powder. The resin can be used alone or in combination of two or more.

[0108] The urethane resin is a general term for resins having a urethane bond. In addition to the urethane bond, polyether-type urethane resins containing an ether bond in the main chain, polyester-type urethane resins containing an ester bond in the main chain, polycarbonate-type urethane resins containing a carbonate bond in the main chain, etc. may be used as the urethane resin. As the urethane resin, commercially available products may be used. For example, Superflex 210, 460, 460s, 840, E-400 0 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Resamin D-1060, D-2020, D-4080, D-4200, D-6300, D-6455 (trade name, manufactured by Dainichi Seiko Kogyo Co., Ltd.), Takelac WS-6020, WS-6021, W-512-A-6 (trade name, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.), Suncure 2710 (trade name, manufactured by Lubrizol Corporation), Permaline UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.), etc. may be selected and used from commercially available products.

[0109] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer such as (meth)acrylic acid and (meth)acrylic acid esters. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers and other monomers. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, can be mentioned. Further, for example, copolymers with vinyl monomers such as styrene can be mentioned. As acrylic monomers, acrylamide, acrylonitrile, etc. can also be used.

[0110] For the resin emulsion using an acrylic resin as a raw material, commercially available products may be used. For example, FK-854 (trade name, manufactured by Central Research Institute of Electric Industry Co., Ltd.), Mobinyl 952B, 718A (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852, LX874 (trade name, manufactured by Nippon Zeon Co., Ltd.), Polyzol AT860 (manufactured by Showa Denko KK), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001 (trade name, manufactured by DIC Corporation, acrylic resin emulsion), etc. may be selected and used.

[0111] In this specification, the acrylic resin may be a styrene-acrylic resin as described above. Also, in this specification, the notation "(meth)acrylic" means at least one of acrylic and methacrylic.

[0112] Styrene acrylic resin is a copolymer obtained from a styrene monomer and an acrylic monomer, and examples thereof include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, and the like. As the styrene acrylic resin, commercially available products may be used, for example, Joncryl 62J, 7100, 390, 711, 511, 7001, 631, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (trade name, manufactured by BASF), Mobinyl 966A, 975N (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and the like.

[0113] The vinyl chloride resin may be a vinyl chloride-vinyl acetate copolymer.

[0114] Polyolefin resins have olefins such as ethylene, propylene, and butylene in their structural skeletons, and known ones can be appropriately selected and used. As the polyolefin resin, commercially available products can be used, and for example, they can be selected and used from Arrow Base CB-1200, CD-1200 (trade name, manufactured by Unitika Ltd.), and the like.

[0115] Also, the resin may be supplied in the form of an emulsion. Examples of commercially available products of such resin emulsions include Microgel E-1002, E-5002 (trade name of Nippon Paint Co., Ltd., styrene-acrylic resin emulsion), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001, 5454 (trade name of DIC Corporation, styrene-acrylic resin emulsion), Polyzol AM-710, AM-920, AM -2300, AP-4735, AT-860, PSASE-4210E (acrylic resin emulsion), Polyzol AP-7020 (styrene-acrylic resin emulsion), Polyzol SH-502 (vinyl acetate resin emulsion), Polyzol AD-13, AD-2, AD-10, AD-96, AD-17, AD-70 (ethylene-vinyl acetate resin emulsion), Polyzol PSASE-6010 (ethylene-vinyl acetate resin emulsion) (product name of Showa Denko KK), Polyzol SAE1014 (product name, styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (product name, acrylic resin emulsion, manufactured by Cyden Chemical Co., Ltd.), AE-120A (product name of JSR Corporation, acrylic resin emulsion), AE373D (product name of E-Tech Co., Ltd., carboxy-modified styrene-acrylic resin emulsion), Seikadine 1900W (product name of Dainichi Seika Kogyo Co., Ltd., ethylene-vinyl acetate resin emulsion), Vinibran 2682 (acrylic resin emulsion), Vinibran 2886 (vinyl acetate-acrylic resin emulsion), Vinibran 5202 (acrylic acetate resin emulsion) (product name of Nisshin Chemical Industry Co., Ltd.), Vinibran 700, 2586 (manufactured by Nisshin Chemical Industry Co., Ltd.), Elitel KA-5071S, KT-8803, KT-9204, KT-8701, KT-8904, KT-0507 (product name of Unitika Ltd., polyester resin emulsion), Hi-Tech SN-2002 (product name of Toho Chemical Co., Ltd., polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (product name of Mitsui Chemicals Polyurethane Co., Ltd., urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 620, 700 (product name of Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), Permalin UA-150 (manufactured by Sanyo Chemical Industries, Ltd., urethane resin emulsion), Sun Cure 2710 (manufactured by Nippon Lubrizol Corporation, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (manufactured by Kusumoto Chemicals, Ltd., urethane resin emulsion), Adeka Bon Titer HUX-380,290K (manufactured by ADEKA CORPORATION, urethane-based resin emulsion), Mobinyl 966A, Mobinyl 7320 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 631, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (above, manufactured by BASF), NK Binder R-5HN (manufactured by Shin-Nakamura Chemical Co., Ltd.), Hydran WLS-210 (non-crosslinkable polyurethane: manufactured by DIC CORPORATION), Joncryl 7610 (manufactured by BASF), etc. may be selected and used from among them.,

[0116] Among these resins, acrylic resins are preferred, and styrene-acrylic resins are more preferred. With such resins, the abrasion resistance tends to be more excellent.,

[0117] Also, the glass transition temperature (Tg) of the resin is preferably 60°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, and particularly preferably 90°C or higher. On the other hand, it is preferably 120°C or lower, more preferably 115°C or lower, still more preferably 110°C or lower, and particularly preferably 105°C or lower. When the glass transition temperature (Tg) of the resin is within the above range, banding unevenness can be further reduced, and it may be possible to obtain a product with more excellent abrasion resistance.,

[0118] Note that the glass transition temperature (Tg) of the resin can be confirmed by a standard method using differential scanning calorimetry (DSC) or the like.,

[0119] The content of the resin is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1.0% by mass or more and 15.0% by mass or less, still more preferably 2.0% by mass or more and 10.0% by mass or less, and particularly preferably 3.0% by mass or more and 8.0% by mass or less, as a solid content based on the total mass of the ink composition.,

[0120] (Wax) The inkjet ink composition constituting the ink set according to the present embodiment may contain wax. Examples of the wax include those that dissolve in the ink composition or those that are dispersed in the form of fine particles such as an emulsion. By using such a wax, a recording material with particularly excellent abrasion resistance tends to be obtained. In particular, it tends to contribute to the improvement of abrasion resistance by being unevenly distributed on the surface of the ink coating film on the recording medium, that is, at the interface between air and the ink coating film.

[0121] Such waxes are not particularly limited, and examples thereof include ester waxes of higher fatty acids and higher monohydric alcohols or dihydric alcohols, paraffin waxes, microcrystalline waxes, polyolefin waxes, or mixtures thereof.

[0122] Examples of the polyolefin wax include waxes produced from olefins such as ethylene, propylene, and butylene or their derivatives and their copolymers. Specifically, polyethylene-based waxes, polypropylene-based waxes, polybutylene-based waxes, etc. can be mentioned. As the polyolefin wax, commercially available products can be used. Specifically, Nopcoat PEM17 (trade name, manufactured by San Nopco Ltd.), Chem Pearl W4005 (trade name, manufactured by Mitsui Chemicals, Inc.), AQUACER515, AQUACER593 (above trade names, manufactured by BYK-Chemie Japan Co., Ltd.), High Tech E-6500 (manufactured by Toho Chemical Industry Co., Ltd., polyethylene wax), etc. can be used.

[0123] When containing wax, the content is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 4% by mass or less, and even more preferably 0.3% by mass or more and 3% by mass or less with respect to the total mass of the ink composition. When the content of the wax is within the above range, it is preferable because it tends to improve abrasion resistance and keep the viscosity of the ink low, and has excellent discharge stability and clogging recovery properties.

[0124] (Antifoaming agent) The inkjet ink composition constituting the ink set according to the present embodiment may contain an antifoaming agent. The antifoaming agent is not particularly limited, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, fatty acid ester-based antifoaming agents, and acetylene glycol-based antifoaming agents. Commercially available products of antifoaming agents include BYK-011, BYK-012, BYK-017, BYK-018, BYK-019, BYK-020, BYK-021, BYK-022, BYK-023, BYK-024, BYK-025, BYK-028, BYK-038, BYK-044, BYK-080A, BYK-094, BYK-1610, BYK-1615, BYK-1650, BYK-1730, BYK-1770 (trade names above, manufactured by BYK-Chemie Japan Co., Ltd.), Surfynol DF37, DF110D, DF58, DF75, DF220, MD-20, EnviroGem AD01 (trade names above, manufactured by Nissin Chemical Industry Co., Ltd.). The antifoaming agent may be used alone or in combination of two or more.

[0125] When containing an antifoaming agent, the content is preferably 0.03% by mass or more and 0.7% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and even more preferably 0.08% by mass or more and 0.3% by mass or less with respect to the total mass of the ink composition.

[0126] (Surfactant) The inkjet ink composition constituting the ink set according to the present embodiment preferably contains a surfactant. The surfactant is not particularly limited, and examples thereof include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants. are mentioned.

[0127] The acetylene glycol-based surfactants are not particularly limited. For example, Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (all of the above are trade names, manufactured by Air Products Japan Co., Ltd.), Orfin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP.4001, EXP.4036, EXP.4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all of the above are trade names, manufactured by Nissin Chemical Industry Co., Ltd.), and Acetylenol E00, E00P, E40, E100 (all of the above are trade names, manufactured by Kawaken Fine Chemicals Co., Ltd.) can be mentioned.

[0128] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer. Specific examples include BYK-340 (trade name, manufactured by Big Chemie Japan Co., Ltd.).

[0129] The silicone-based surfactants are not particularly limited, but polysiloxane-based compounds are preferably mentioned. The polysiloxane-based compounds are not particularly limited, and for example, polyether-modified organosiloxanes can be mentioned. Commercially available products of the polyether-modified organosiloxanes include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348 (all of the above are trade names, manufactured by Big Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all of the above are trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG503A, Silface SAG014 (all of the above are trade names, manufactured by Nissin Chemical Industry Co., Ltd.), etc.

[0130] The above surfactant may be used alone or in combination of two or more kinds.

[0131] When containing a surfactant, its content is preferably 0.1% by mass or more and 1.5% by mass or less based on the total mass of the ink composition.

[0132] The inkjet ink composition constituting the ink set according to the present embodiment preferably contains the above surfactant in an amount of 0.1 to 1.5% by mass based on the total mass of the ink composition. Preferably it is 1.3% by mass or less, more preferably 1.1% by mass or less, still more preferably 0.9% by mass or less, particularly preferably 0.7% by mass or less. Also, preferably it is 0.15% by mass or more, more preferably 0.25% by mass or more, still more preferably 0.3% by mass or more, particularly preferably 0.35% by mass or more, and even more preferably 0.4% by mass or more. Moreover, it is also good and preferable that the content of the silicone-based surfactant or the fluorine-based surfactant among the above surfactants is within the above range. Further, it is also good and preferable that the content of the silicone-based surfactant among the above surfactants is within the above range.

[0133] Generally, by containing a silicone-based surfactant in an ink composition, the image quality tends to be more improved, but it is liable to be inferior in rubbing resistance and defoaming property. However, in the inkjet ink composition constituting the ink set according to the present embodiment, even with a small addition amount within the above range, it can have excellent image quality and also good rubbing resistance and defoaming property.

[0134] (Other Additives) The inkjet ink composition constituting the ink set according to the present embodiment may contain various additives such as a chelating agent, a rust preventive, a fungicide, an antioxidant, a reduction preventive, and an evaporation accelerator, if necessary.

[0135] 1.2.6. Method for Preparing Ink Composition The inkjet ink composition constituting the ink set according to this embodiment is obtained by mixing the above-described components in an arbitrary order and, if necessary, filtering etc. to remove impurities. As a method for mixing each component, a method of sequentially adding materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirring and mixing is preferably used. As a filtering method, centrifugal filtration, filter filtration etc. can be carried out as necessary.

[0136] From the viewpoint of the balance between image quality and reliability as an ink for inkjet recording, the surface tension (static surface tension) at 20°C of the inkjet ink composition constituting the ink set according to this embodiment is preferably 18 mN / m or more and 40 mN / m or less, more preferably 20 mN / m or more and 35 mN / m or less, and even more preferably 22 mN / m or more and 33 mN / m or less. Incidentally, the surface tension can be measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) and checking the surface tension when a platinum plate is wetted with the ink in an environment of 20°C.

[0137] From the same viewpoint, the viscosity of the ink at 20°C is preferably 3 mPa·s or more and 10 mPa·s or less, and more preferably 3 mPa·s or more and 8 mPa·s or less. Incidentally, the viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica) and measuring the viscosity in an environment of 20°C.

[0138] 1.3. Treatment liquid The treatment liquid constituting the ink set according to this embodiment contains a flocculant. Hereinafter, each component contained in the treatment liquid will be described.

[0139] 1.3.1. Flocculant The treatment liquid constituting the ink set according to this embodiment contains a flocculant that aggregates the components of the ink composition. Since the treatment liquid contains a flocculant, in the ink adhesion step described later, the flocculant reacts promptly with the coloring materials, resins, etc. contained in the ink composition. Then, the dispersion state of the coloring materials and resins in the ink composition is disrupted and they aggregate, and this aggregate inhibits the penetration of the coloring materials into the recording medium, so it is considered to be excellent in terms of improving the image quality of the recorded image.

[0140] Examples of the flocculant include polyvalent metal salts, cationic resins, cationic compounds such as cationic surfactants, and organic acids. These flocculants may be used alone or in combination of two or more. Among these flocculants, from the viewpoint of excellent reactivity with the components contained in the ink composition, it is preferable to use at least one flocculant selected from the group consisting of polyvalent metal salts, organic acids, and cationic resins.

[0141] The polyvalent metal salt is composed of a polyvalent metal ion of divalent or higher and an anion that binds to these polyvalent metal ions, and is a compound soluble in water. Specific examples of the polyvalent metal ion include divalent metal ions such as Ca 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Zn 2+ , Ba 2+ ; trivalent metal ions such as Al 3+ , Fe 3+ , Cr 3+ . Examples of the anion include Cl - , I - , Br - , SO4 2- , ClO 3- , NO 3- , and HCOO - , CH3COO - . Among these polyvalent metal salts, calcium salts and magnesium salts are preferable from the viewpoints of the stability of the treatment liquid and the reactivity as a flocculant.

[0142] Examples of the organic acid include poly(meth)acrylic acid, formic acid, acetic acid, propionic acid, glycolic acid, oxalic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, citric acid, tartaric acid, lactic acid, pyruvic acid, pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid, nicotinic acid, derivatives of these compounds, salts thereof, etc. The organic acid may be used alone or in combination of two or more. Those that are salts of organic acids and are also polyvalent metal salts shall be included in the polyvalent metal salts.

[0143] Examples of the cationic resin include cationic urethane resins, cationic olefin resins, cationic amine-based resins, etc. The cationic amine-based resin may be any resin having an amino group, and examples thereof include allylamine resins, polyamine resins, quaternary ammonium salt polymers, polyamide resins, etc. Examples of the polyamine resin include those having an amino group in the main skeleton of the resin. Examples of the allylamine resin include those having a structure derived from an allyl group in the main skeleton of the resin. Examples of the quaternary ammonium salt polymer include resins having a quaternary ammonium salt in the structure. Examples of the polyamide resin include those having an amide group in the main skeleton of the resin and an amino group in the side chain of the resin. Among the cationic resins, the cationic amine-based resin is preferred because it not only has excellent reactivity but also is easily available.

[0144] The concentration of the aggregating agent in the treatment liquid is preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 3% by mass or more with respect to the total mass of the treatment liquid. Also, the concentration of the aggregating agent in the treatment liquid is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less with respect to the total mass of the treatment liquid.

[0145] 1.3.2. Components other than the above In the treatment liquid constituting the ink set according to the present embodiment, as components other than the aggregating agent, water, water-soluble organic compounds, hardly water-soluble organic compounds, defoaming agents, surfactants, other additives, etc. may be contained. Regarding these components and the content thereof in the treatment liquid, etc., since they are the same as those of the above-described inkjet ink composition, the description thereof is omitted. Note that, except for containing the aggregating agent, the treatment liquid can be independent of the above-described ink composition in terms of the content of components other than the coloring material that the ink composition may contain, their content, characteristics, etc. Note that the content of the above-described coloring material in the treatment liquid is 0.2 mass% or less, preferably 0.1 mass% or less, more preferably 0.05 mass% or less, and the lower limit is 0 mass%.

[0146] Note that the treatment liquid constituting the ink set according to the present embodiment preferably contains either diols or glycol ethers, which are the above-described hardly water-soluble organic compounds and have a standard boiling point of 180 to 300°C, and more preferably contains diols having a standard boiling point of 180 to 300°C. When the treatment liquid contains such a hardly water-soluble organic compound, banding unevenness may be further reduced or the abrasion resistance may be more excellent, which is preferable.

[0147] 1.3.3. Method for preparing the treatment liquid The treatment liquid constituting the ink set according to the present embodiment can be produced by dispersing and mixing the above-described respective components by an appropriate method. After sufficiently stirring the above-described respective components, filtration is performed to remove coarse particles and foreign matters that cause clogging, thereby obtaining the target treatment liquid.

[0148] 1.3.4. Physical properties of the treatment liquid When the processing liquid constituting the ink set according to this embodiment is ejected by an inkjet head, it preferably has a surface tension at 25°C of 18 mN / m or more and 40 mN / m or less, more preferably 20 mN / m or more and 35 mN / m or less, and even more preferably 22 mN / m or more and 33 mN / m or less. The surface tension can be measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the processing liquid in an environment of 25°C.

[0149] Also, from the same viewpoint, the viscosity of the processing liquid at 25°C is preferably 3 mPa·s or more and 10 mPa·s or less, and more preferably 3 mPa·s or more and 8 mPa·s or less. The viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica) to measure the viscosity in an environment of 25°C.

[0150] 2. Recording method A recording method according to an embodiment of the present invention is a recording method for performing recording using the above-described ink set, including an ink adhesion step of ejecting the inkjet ink composition by an inkjet method and attaching it to a recording medium, and a processing liquid adhesion step of attaching the processing liquid to the recording medium, wherein the recording medium is a low-absorbing or non-absorbing recording medium.

[0151] The ink set used in the recording method according to this embodiment includes an inkjet ink composition containing a specific hardly water-soluble organic compound in a predetermined amount or less. Thereby, the recording method according to this embodiment can achieve both excellent reduction of banding unevenness and excellent storage stability of the ink even when recording is performed on a low-absorbing or non-absorbing recording medium using a processing liquid.

[0152] Hereinafter, each step in the recording method according to this embodiment will be described. An inkjet recording apparatus that can be suitably used for the implementation of each step will be described later.

[0153] 2.1. Ink Attachment Step In the ink attachment step in the recording method according to this embodiment, the inkjet ink composition constituting the above-described ink set is ejected by an inkjet method and attached to a low-absorbing or non-absorbing recording medium.

[0154] Note that the description of the low-absorbing or non-absorbing recording medium is omitted because it is as described above.

[0155] In the ink attachment step, the amount of the ink composition attached per unit area of the recording medium in the area where the ink is attached to the recording medium is preferably 3 mg / inch 2 or more, more preferably 5 mg / inch 2 or more, still more preferably 10 mg / inch 2 or more. The amount of the ink composition attached per unit area of the recording medium is preferably 20 mg / inch 2 or less, more preferably 18 mg / inch 2 or less, still more preferably 16 mg / inch 2 or less. When the amount of the ink composition attached is within the above range, banding unevenness tends to be further reduced. Also, it is preferable that the amount of the ink composition attached per unit area of the recording medium in the area where the amount of the ink attached to the recording medium is the largest in the area where the ink is attached to the recording medium, that is, the maximum amount of the ink attached, is within the above range.

[0156] 2.2. Treatment Liquid Attachment Step In the treatment liquid attachment step in the recording method according to this embodiment, the treatment liquid constituting the above-described ink set is attached to a low-absorbing or non-absorbing recording medium.

[0157] The treatment liquid attachment step can be performed simultaneously with the above-described ink attachment step, or before or after the above-described ink attachment step.

[0158] As methods for attaching the processing liquid, for example, dipping coating in which the recording medium is immersed in the processing liquid, roller coating in which the processing liquid is attached using a brush, roller, spatula, roll coater, etc., spray coating in which the processing liquid is sprayed with a spray device, inkjet coating in which the processing liquid is attached by an inkjet method, etc. can be mentioned. Among these, inkjet coating is preferably used.

[0159] In the processing liquid attachment step, the amount of the processing liquid attached to the area where the ink and the processing liquid of the recording medium are overlapped and attached is preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 9% by mass or more with respect to the amount of the ink composition attached in the above-described ink attachment step. On the other hand, the amount of the processing liquid attached is preferably 25% by mass or less, more preferably 21% by mass or less, further preferably 17% by mass or less, and particularly preferably 13% by mass or less with respect to the amount of the ink composition attached in the above-described ink attachment step. When the amount of the processing liquid attached is within the above range, there is a tendency that the image quality such as banding unevenness and aggregation unevenness and the rub resistance can be preferably compatible. Also, the amount of the processing liquid attached to the area where the ink and the processing liquid of the recording medium are overlapped and attached is preferably 0.1 to 5 mg / inch 2 is preferred. Also, it is also preferably good to set the amount of the processing liquid attached in the area where the amount of the ink attached is the largest in the area where the ink and the processing liquid of the recording medium are overlapped and attached within the above range.

[0160] 2.3. Serial type recording method The recording method according to the present embodiment performs recording by a plurality of main scans, and it is preferable to perform a plurality of main scans on the same scan area. That is, it is preferable to perform the above-described ink attachment step and processing liquid attachment step as a serial type recording method.

[0161] For example, the ink application step and the treatment liquid application step can be carried out as a serial recording method using an inkjet recording apparatus having a serial recording head (recording head 2) as shown in FIGS. 1 and 2 described later. In such a serial recording method, the ink application step and the treatment liquid application step are performed by a plurality of main scans in which the ink composition and the treatment liquid are attached to the same scanning area of the recording medium M while changing the relative position between the recording head 2 and the recording medium M in the main scanning direction MS, and a plurality of sub-scans in which the relative positions of the carriage 9 and the recording medium M are changed in the sub-scanning direction SS intersecting the main scanning direction MS. The number of main scans is preferably 2 to 20, more preferably 3 to 15, and even more preferably 4 to 10.

[0162] In this case, on the nozzle surface (not shown) of the recording head 2, there are a plurality of nozzle rows in which nozzles are arranged in the sub-scanning direction SS along the main scanning direction MS, and the plurality of nozzle rows are arranged so that at least a part thereof overlaps when projected along the main scanning direction MS. For each nozzle row, it is preferable to be able to discharge the treatment liquid and the ink composition. By doing so, the treatment liquid and the ink composition can be discharged and attached to the same position in the sub-scanning direction of the recording medium in the same main scan.

[0163] When the recording method according to the present embodiment performs recording by a plurality of main scans and performs a plurality of main scans in the same scanning area, the amount of ink droplets attached by one main scan is small. In such a case, since the ink droplets are discretely attached to the recording medium, the chance of contact with adjacent ink droplets is reduced. If so, the filling of the ink on the recording medium is poor, and banding unevenness in which streaky unevenness is visible in the recorded image is more likely to occur. That is, in the serial recording method, there is a problem that banding unevenness is more likely to occur. However, according to the recording method according to the present embodiment, since an ink set including an inkjet ink composition containing a specific hardly water-soluble organic compound below a predetermined amount is used, even in such a serial recording method, banding unevenness can be reduced well, and the storage stability of the ink tends to be excellent. For this reason, it is possible to preferably reduce banding unevenness and to have excellent storage stability of the ink.

[0164] Note that performing multiple main scans on the same scanning area means scanning again the area that has been scanned once. For example, when the distance of one sub-scan is shorter than the length of the nozzle row that discharges ink in the sub-scanning direction, the scanned area of one main scan will be scanned again. For example, if the distance of one sub-scan is one-fourth of the length of the nozzle row that discharges ink in the sub-scanning direction, four main scans will be performed on the same scanning area. In this case, the number of main scans is said to be 4. Note that the recording method according to this embodiment may also be a line type recording method that performs recording by one scan using a line head. Also in this case, streak-like unevenness may occur along the scanning direction, but according to this embodiment, the streak-like unevenness can be reduced.

[0165] 2.4. Primary heating step The recording method according to this embodiment preferably includes a primary heating step of heating the inkjet ink composition adhered to the recording medium.

[0166] In the recording method, by including the primary heating step, it is possible to particularly quickly dry the ink composition and the treatment liquid on the recording medium, which is preferable in terms of improving the image quality (aggregation unevenness). On the other hand, in the primary heating step, since the ink and the like are quickly dried, it becomes difficult for the ink to wet and spread on the recording medium. That is, the recording method including the primary heating step has a problem that banding unevenness is more likely to occur. However, according to the recording method according to this embodiment, even in such a case, there is a tendency to be able to satisfactorily reduce the banding unevenness.

[0167] The primary heating process is a process of heating and drying the ink adhered to the recording medium at an early stage. The primary heating process is a heating process for drying at least a part of the solvent component of the ink so as to reduce at least the flow of the ink adhered to the recording medium. In the primary heating process, the ink may be adhered to the heated recording medium, or may be heated at an early stage after adhesion. In the primary heating process, it is preferable that heating is started within 0.5 seconds at the latest from the landing of the ink droplet on the recording medium. Further, the primary heating process may be applied to the applied treatment liquid in the same manner as the ink.

[0168] The primary heating process is preferably by an IR heater, microwave radiation, a platen heater, or blowing warm air by a fan onto the recording medium.

[0169] The heating in the primary heating process may be performed at least one of before, simultaneously with, and at an early stage after the above-described ink adhesion process and treatment liquid adhesion process, and is preferably performed simultaneously. With such a heating order, the ink adhesion process and the treatment liquid adhesion process can be performed.

[0170] The heating temperature in the primary heating process is the surface temperature of the recording medium at the time of ink adhesion when the ink is adhered to the heated recording medium, and is the surface temperature of the recording medium at the time of heating when heating is performed at an early stage after ink adhesion. It is also the maximum temperature during the primary heating process. The heating temperature in the primary heating process is preferably 28°C or higher, more preferably 30°C or higher, still more preferably 32°C or higher, and particularly preferably 34°C or higher at the surface temperature of the recording surface of the heated recording medium. Also, the heating temperature in the primary heating process is 50°C or lower at the surface temperature of the recording surface of the heated recording medium. is preferably 45°C or lower, more preferably 40°C or lower, and even more preferably 40°C or lower. When the heating temperature in the primary heating step is within the above range, banding unevenness can be favorably reduced, and there is a tendency to obtain good image quality (aggregation unevenness) and good clogging recovery properties.

[0171] 2.5. Post-heating step The recording method according to the present embodiment preferably includes a post-heating step of heating the recording medium after the above-described ink adhesion step and treatment liquid adhesion step.

[0172] Since the inkjet ink composition constituting the ink set used in the recording method according to the present embodiment contains a poorly water-soluble organic compound, the drying property after the ink adhesion step is better than when no poorly water-soluble organic compound is contained. And since the recording method according to the present embodiment includes a post-heating step, there is a tendency to be able to obtain a recording with improved drying property and more excellent abrasion resistance, which is preferable.

[0173] The post-heating step is a heating step that completes the recording and sufficiently heats the recording to a degree where it can be used. The post-heating step is a heating step for sufficiently drying the solvent components of the ink and the treatment liquid, and heating the resin contained in the ink to flatten the ink coating film. The post-heating step is preferably started more than 0.5 seconds after the ink and the treatment liquid have adhered to the recording medium. For example, it is preferable to start heating the area more than 0.5 seconds after all the adhesion of the ink and the treatment liquid to a certain recording area of the recording medium has been completed. Also, it is preferable that the preferable temperature in the primary heating step is different from the preferable temperature in the post-heating step.

[0174] In the post-heating process, heating of the recording medium can be performed using appropriate heating means, for example, when using an inkjet recording apparatus. Further, it can be performed not only by the heating means provided in the inkjet recording apparatus but also by appropriate heating means. In this case, the surface temperature of the recording medium is preferably 60°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, and particularly preferably 85°C or higher. Further, the surface temperature of the recording medium heated in the post-heating process is preferably 120°C or lower, more preferably 110°C or lower, still more preferably 100°C or lower, and particularly preferably 95°C or lower. According to the recording method according to the present embodiment, even at the surface temperature of the recording medium within the above range, the ink can be sufficiently dried, and a recording having excellent rub resistance can be obtained.

[0175] 2.6. Inkjet recording apparatus An example of an inkjet recording apparatus that can be suitably used for carrying out each step in the recording method according to the present embodiment will be described with reference to the drawings.

[0176] <Schematic of device configuration> FIG. 1 is a schematic cross-sectional view schematically showing an inkjet recording apparatus. FIG. 2 is a perspective view showing an example of the configuration around the carriage of the inkjet recording apparatus 1 of FIG. 1. As shown in FIGS. 1 and 2, the inkjet recording apparatus 1 includes a recording head 2, an IR heater 3, a platen heater 4, a heating heater 5, a cooling fan 6, a preheater 7, a ventilation fan 8, a carriage 9, a platen 11, a carriage moving mechanism 13, a conveying means 14, and a control unit CONT. The operation of the entire inkjet recording apparatus 1 is controlled by the control unit CONT shown in FIG. 2.

[0177] <Configuration related to recording head> The recording head 2 is configured to perform recording on the recording medium M by discharging and adhering an inkjet ink composition from the nozzles of the recording head 2. The same applies to the treatment liquid. It is possible. The recording head 2 shown in FIGS. 1 and 2 is a serial recording head, which scans the recording medium M a plurality of times in the main scanning direction relative to the recording medium M to attach ink or a processing liquid to the recording medium M. The recording head 2 is mounted on the carriage 9 shown in FIG. 2. The recording head 2 is scanned a plurality of times in the main scanning direction relative to the recording medium M by the operation of the carriage moving mechanism 13 that moves the carriage 9 in the medium width direction of the recording medium M. The medium width direction is the main scanning direction of the recording head 2. The scanning in the main scanning direction is also referred to as the main scanning.

[0178] Also, here, the main scanning direction is the direction in which the carriage 9 on which the recording head 2 is mounted moves. In FIG. 1, it is a direction intersecting the sub-scanning direction, which is the conveyance direction of the recording medium M indicated by the arrow SS. In FIG. 2, the width direction of the recording medium M, that is, the direction represented by S1 - S2 is the main scanning direction MS, and the direction represented by T1 → T2 is the sub-scanning direction SS. Note that in one scan, the scanning is performed in the main scanning direction, that is, either in the direction of arrow S1 or arrow S2. Then, by repeatedly performing the main scanning of the recording head 2 and the sub-scanning, which is the conveyance of the recording medium M, a plurality of times, recording is performed on the recording medium M.

[0179] The cartridge 12 that supplies ink or a processing liquid to the recording head 2 includes a plurality of independent cartridges. The cartridge 12 is detachably attached to the carriage 9 on which the recording head 2 is mounted. Each of the plurality of cartridges can be filled with different types of inkjet ink compositions or processing liquids, and the inkjet ink compositions or processing liquids are supplied from the cartridge 12 to each nozzle. Note that in FIGS. 1 and 2, an example where the cartridge 12 is attached to the carriage 9 is shown, but it is not limited to this, and it may be provided at a location other than the carriage 9 and supplied to each nozzle by a supply pipe (not shown).

[0180] A conventionally known method can be used for the ejection of the recording head 2. Here, a method of ejecting droplets by utilizing the vibration of a piezoelectric element, that is, an ejection method of forming ink droplets or the like by the mechanical deformation of an electrostrictive element is used.

[0181] <Primary heating mechanism> The inkjet recording apparatus 1 can be provided with a primary heating mechanism that heats the recording medium M when discharging ink or a processing liquid from the recording head 2 and attaching it to the recording medium. As the primary heating mechanism, a conduction type, a blowing type, a radiation type, etc. can be used. The conduction type conducts heat from a member in contact with the recording medium to the recording medium. For example, a platen heater or the like can be mentioned. The blowing type blows normal-temperature air or warm air onto the recording medium to dry ink or the like. For example, a blowing fan can be mentioned. The radiation type radiates radiation that generates heat onto the recording medium to heat the recording medium. For example, IR radiation can be mentioned. Further, although not shown, a heater similar to the platen heater may be provided immediately downstream of the platen heater 4 in the SS direction. These primary heating mechanisms may be used alone or in combination. For example, as the primary heating mechanism, an IR heater 3 and a platen heater 4 are provided.

[0182] When the IR heater 3 is used, the recording medium M can be heated in a radiation manner by the radiation of infrared rays from the recording head 2 side. As a result, the recording head 2 is also likely to be heated at the same time, but it is possible to increase the temperature without being affected by the thickness of the recording medium M as compared with the case of heating from the back surface of the recording medium M such as the platen heater 4. In addition, various fans (for example, a ventilation fan 8) that blow warm air or air at the same temperature as the environment onto the recording medium M to dry ink or the like on the recording medium M may be provided.

[0183] The platen heater 4 can heat the recording medium M through the platen 11 at a position facing the recording head 2. The platen heater 4 is capable of heating the recording medium M in a conduction manner and is used as needed in the inkjet recording method.

[0184] Further, the inkjet recording apparatus 1 may be provided with a preheater 7 that preheats the recording medium M before ink or a processing liquid is attached to the recording medium M.

[0185] <Post-heating mechanism> After the ink adhesion step and the treatment liquid adhesion step, a post-heating mechanism for heating the recording medium to dry and fix the ink or the like may be provided.

[0186] The heating heater 5 used in the post-heating mechanism is for drying and solidifying the ink or the like adhered to the recording medium M. By heating the recording medium M on which the image is recorded with the heating heater 5, moisture and the like contained in the ink or the treatment liquid evaporate and disperse more quickly, and an ink film is formed by the resin contained in the ink. In this way, the ink film is firmly fixed or adhered on the recording medium M to have excellent film-forming properties, and an excellent high-quality image can be obtained in a short time.

[0187] <Other configurations> The inkjet recording apparatus 1 may have a cooling fan 6. After drying the ink or the like recorded on the recording medium M, by cooling the ink on the recording medium M with the cooling fan 6, an ink coating film with good adhesion can be formed on the recording medium M.

[0188] Below the carriage 9, a platen 11 for supporting the recording medium M, a carriage moving mechanism 13 for relatively moving the carriage 9 with respect to the recording medium M, and a conveying means 14 which is a roller for conveying the recording medium M in the sub-scanning direction are provided. The operations of the carriage moving mechanism 13 and the conveying means 14 are controlled by the control unit CONT.

[0189] <Electrical control> Figure 3 is a functional block diagram of the inkjet recording apparatus 1. The control unit CONT is a control unit for controlling the inkjet recording apparatus 1. The interface unit 101 (I / F) is for transmitting and receiving data between the computer 130 (COMP) and the inkjet recording apparatus 1. The CPU 102 is an arithmetic processing unit for controlling the entire inkjet recording apparatus 1. The memory 103 (MEM) is for securing an area for storing the program of the CPU 102, a work area, and the like. The CPU 102 controls each unit by the unit control circuit 104 (UCTRL). Note that the detector group 121 (DS) monitors the situation inside the inkjet recording apparatus 1, and based on the detection result, the control unit CONT controls each unit.

[0190] The conveyance unit 111 (CONVU) controls the sub-scanning (conveyance) of inkjet recording. Specifically, it controls the conveyance direction and conveyance speed of the recording medium M. More specifically, it controls the conveyance direction and conveyance speed of the recording medium M by controlling the rotation direction and rotation speed of the conveyance roller driven by a motor.

[0191] The carriage unit 112 (CARU) controls the main scanning (pass) of inkjet recording. Specifically, it reciprocates the recording head 2 in the main scanning direction. The carriage unit 112 includes a carriage 9 on which the recording head 2 is mounted, and a carriage moving mechanism 13 for reciprocating the carriage 9.

[0192] The head unit 113 (HU) controls the discharge amount of ink and processing liquid from the nozzles of the recording head 2. For example, when the nozzles of the recording head 2 are driven by piezoelectric elements, it controls the operation of the piezoelectric elements at each nozzle. The head unit 113 controls the timing of adhesion of each ink and processing liquid, the dot size of the ink and processing liquid, and the like. Also, by combining the control of the carriage unit 112 and the head unit 113, The adhesion amount of ink and processing liquid per scan is controlled.

[0193] The drying unit 114 (DU) controls the temperatures of various heaters such as the IR heater 3, the preheater 7, the platen heater 4, and the heating heater 5.

[0194] The inkjet recording apparatus 1 alternately repeats the operation of moving the carriage 9 mounting the recording head 2 in the main scanning direction and the conveyance operation (sub-scanning). At this time, when performing each pass, the control unit CONT controls the carriage unit 112 to move the recording head 2 in the main scanning direction, and controls the head unit 113 to discharge droplets of ink or processing liquid from a predetermined nozzle hole of the recording head 2, and attach the droplets of ink or processing liquid to the recording medium M. Further, the control unit CONT controls the conveyance unit 111 to convey the recording medium M in the conveyance direction at a predetermined conveyance amount (feed amount) during the conveyance operation.

[0195] In the inkjet recording apparatus 1, by repeating the main scanning (pass) and the sub-scanning (conveyance operation), the recording area to which a plurality of droplets are attached is gradually conveyed. Then, the heating heater 5 dries the droplets attached to the recording medium M, and the image is completed. Thereafter, the completed recording may be wound into a roll by a winding mechanism or conveyed by a flatbed mechanism.

[0196] 3. Examples Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. Hereinafter, “%” is based on mass unless otherwise specified.

[0197] 3.1. Preparation of Inkjet Ink Composition Each component was put into a container so as to have the compositions shown in Table 1 and Table 2 below, mixed and stirred with a magnetic stirrer for 2 hours, and then filtered through a membrane filter with a pore diameter of 5 μm to obtain inkjet ink compositions A to Y (inks A to Y) according to Examples and Comparative Examples. The numerical values in the table for the pigment, resin, and wax represent their solid contents. The following pigment dispersion was used as the pigment.

[0198] (Preparation of Pigment Dispersion Liquid) Also, the pigment dispersion liquid used was prepared in advance as follows. First, 50 g of methyl ethyl ketone (MEK) was added to a flask equipped with a dropping funnel, a nitrogen inlet tube, a reflux condenser, a thermometer, and a stirrer, and the mixture was heated to 75°C while bubbling nitrogen. Then, a mixture of 80 g of butyl methacrylate, 50 g of methyl methacrylate, 15 g of styrene, 20 g of methacrylic acid, 50 g of MEK, and 500 mg of a polymerization initiator (azobisisobutyronitrile / AIBN) was added dropwise from the dropping funnel over 3 hours. After the addition, the mixture was heated under reflux for 6 more hours, and after cooling, MEK corresponding to the evaporated amount was added to obtain a resin solution (resin solid content: 50% by mass, acid value: 79 mg / KOH, Tg: 65°C). A predetermined amount of a 20% by mass aqueous sodium hydroxide solution was added to 20 g of the solution as a neutralizing agent to neutralize the salt-forming groups by 100%. Then, while stirring, 50 g of a pigment (C.I. Pigment Blue 15:3) was added little by little, and the mixture was kneaded with a bead mill for 2 hours. 200 g of ion-exchanged water was added to the obtained kneaded product, and after stirring, the mixture was heated under reduced pressure to distill off MEK. Furthermore, the concentration was adjusted with ion-exchanged water to obtain a pigment dispersion (pigment solid content: 20% by mass, resin solid content: 5% by mass).

[0199] 3.2. Preparation of Treatment Liquid Each component was put into a container so as to have the composition shown in Table 3 below, and after mixing and stirring with a magnetic stirrer for 2 hours, the treatment liquids A to H according to the examples and comparative examples were obtained by filtering through a membrane filter with a pore size of 5 μm. Note that the numerical values in the table for the cationic resin represent the solid content.

[0200]

Table 1

[0201]

Table 2

[0202]

Table 3

[0203] For each component shown in Table 1 to Table 3 above, supplementary explanations are provided. <Water-soluble organic compound (resin-dissolving substance)> · CPL: ε-caprolactam, boiling point 267 °C, melting point 70 °C, solid (25 °C), cyclic amides · 2P: 2-pyrrolidone, boiling point 245 °C, melting point 25 °C, liquid (25 °C), cyclic amides · DMPA: 3-methoxy-N,N-dimethylpropanamide, boiling point 215 °C, melting point -49 °C, liquid (25 °C), chain amides · DMSO: Dimethyl sulfoxide, boiling point 189 °C, melting point 19 °C, liquid (25 °C), sulfur-containing solvents · EOXM: 3-ethyl-3-oxetanemethanol, boiling point 220 °C, melting point -31 °C, liquid (25 °C), cyclic ethers <Water-soluble organic compound (others)> · PG: Propylene glycol, boiling point 188 °C, melting point -59 °C, liquid (25 °C), aliphatic diols, completely miscible with water · DMHD: 2,5-dimethyl-2,5-hexanediol, boiling point 218 °C, melting point 89 °C, solid (25 °C), aliphatic diols, solubility 14 [g / 100 g of water] · 1,2HD: 1,2-hexanediol, boiling point 224 °C, melting point 2 °C, liquid (25 °C), aliphatic diols, completely miscible with water · TIPA: Triisopropanolamine, boiling point 301 °C, melting point 45 °C, solid (25 °C), amines, solubility 83 [g / 100 g of water]

[0204] <Poorly water-soluble organic compound (diols)> · BEPD: 2-butyl-2-ethyl-1,3-propanediol, boiling point 264 °C, melting point 43 °C, solid (25 °C), aliphatic diols, solubility 0.9 [g / 100 g of water] · CHDM: 1,4-cyclohexanedimethanol, boiling point 286 °C, melting point 35 °C, solid (25 °C), alicyclic diols, solubility 0.8 [g / 100 g of water] ·TMPD: 2,2,4-Trimethyl-1,3-pentanediol, boiling point 232 °C, melting point 54 °C, solid (25 °C), aliphatic diols, solubility 1.9 [g / 100 g of water] ·EHD: 2-Ethyl-1,3-hexanediol, boiling point 244 °C, melting point -40 °C, liquid (25 °C), aliphatic diols, solubility 4.2 [g / 100 g of water] ·TMCD: 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, boiling point 220 °C, melting point 126 °C, solid (25 °C), alicyclic diols, solubility 6.1 [g / 100 g of water] ·MPPD: 2-Methyl-2-propyl-1,3-propanediol, boiling point 230 °C, melting point 57 °C, solid (25 °C), aliphatic diols, solubility 7.5 [g / 100 g of water] ·EHGL: Ethylhexyl glycerin, boiling point 325 °C, melting point -76 °C, liquid (25 °C), aliphatic diols, solubility 0.2 [g / 100 g of water] <Poorly water-soluble organic compounds (glycol ethers)> ·EHDG: Diethylene glycol mono 2-ethylhexyl ether, boiling point 277 °C, melting point -82 °C, liquid (25 °C), glycol monoethers, solubility 0.5 [g / 100 g of water] ·DBDG: Diethylene glycol dibutyl ether, boiling point 256 °C, melting point -60 °C, liquid (25 °C), glycol diethers, solubility 0.3 [g / 100 g of water] ·EHG: Ethylene glycol mono 2-ethylhexyl ether, boiling point 229 °C, melting point -105 °C, liquid (25 °C), glycol monoethers, solubility 0.1 [g / 100 g of water] <Poorly water-soluble organic compounds (others)> ·NOP: N-Octyl-2-pyrrolidone, boiling point 306 °C, melting point -23 °C, liquid (25 °C), cyclic amides, solubility 0.1 [g / 100 g of water]

[0205] <Other components> (Resin) ·Joncryl 631: Trade name of BASF Japan, styrene acrylic resin, Tg 105 °C (Wax) · Hi-Tech E-6500: Product name of Toho Chemical Industry Co., Ltd., polyethylene wax (Defoaming agent) · Surfynol DF110D: Product name of Nissin Chemical Industry Co., Ltd., acetylene diol-based surfactant (Surfactant) · BYK333: Product name of BYK-Chemie Japan Co., Ltd., silicone-based surfactant (Cationic resin) · Cation Master PD-30: Product name of Yokkaichi Gosei Co., Ltd., amine-epichlorohydrin copolymer (Organic acid) · L-Tartaric acid: Boiling point 275 °C, melting point 168 °C

[0206]

Table 4

[0207] 3.3. Evaluation method 3.3.1. Storage stability (ink composition) 30 g of each inkjet ink composition obtained above was sealed in an aluminum pack so that no air bubbles were mixed in, and left at 60 °C for 6 days using a constant temperature bath. After leaving, it was taken out and allowed to cool naturally, and the viscosity at room temperature was measured with a rheometer (product name "MCR702", manufactured by Anton Paar) at a shear rate of 200 s -1 and the thickening rate was calculated by comparing with the viscosity at the initial stage (immediately after ink preparation). (Evaluation criteria) AA: Thickening rate less than 1% A: Thickening rate 1% or more and less than 3% B: Thickening rate 3% or more and less than 5% C: Thickening rate 5% or more

[0208] 3.3.2. Image quality (banding unevenness) The inkjet inksets of each example consisting of the inkjet ink composition and the treatment liquid obtained above were filled into a modified printer "SC-R5050" manufactured by Seiko Epson Corporation, and a recording medium (PVC film, trade name "Orajet 3165G-010", manufactured by Orafol Japan) was set, and solid patterns were printed under the printing conditions in Table 4 above.

[0209] More specifically, the inkjet ink composition (ink) and the treatment liquid in each example described in Table 4 above were filled into the ink cartridges of "SC-R5050". By the inkjet method, the ink adhesion amount was 12 mg / inch 2 , and the treatment liquid adhesion amount was as described in Table 4 above. The ink and the treatment liquid were ejected from the inkjet head onto the above recording medium, and a solid pattern was printed at a resolution of 1200×1200 dpi and with 9 scanning passes. During recording, the platen heater was controlled so that the surface temperature of the recording medium in the platen area facing the head became the heating temperature (adhesion temperature) in Table 4 above.

[0210] Finally, a printed matter was obtained by heating and drying for about 3 minutes with a secondary heater on the downstream side of the inkjet head so that the surface temperature of the recording medium became 90°C. The obtained printed matter was visually observed and judged according to the following evaluation criteria. (Evaluation Criteria) AA: No density unevenness extending in the main scanning direction (appearing linearly different in density in the main scanning direction) can be seen. A: There is slightly a linear unevenness with a light color, but the density difference is small and not noticeable. B: There is linear density unevenness and the density difference is large, but it is acceptable. C: There is linear density unevenness, the density difference is large, and it is noticeable.

[0211] 3.3.3. Image Quality (Aggregation Unevenness) A printed matter was obtained in the same manner as the evaluation test of "Image Quality (Bandining Unevenness)" except that the ink adhesion amount was 16 mg / inch. 2 The obtained printed matter was visually observed and judged according to the following evaluation criteria. (Evaluation Criteria) AA: No agglomeration unevenness A: There is agglomeration unevenness, but it is not a concern B: The agglomeration unevenness is noticeable, but acceptable C: The agglomeration unevenness is prominent

[0212] 3.3.4. Rub resistance A printed matter was obtained in the same manner as the evaluation test of "image quality (banding unevenness)", except that the ink adhesion amount was set to 16 mg / inch 2 After that, the obtained printed matter was left at room temperature for 30 minutes, and then the solid pattern printing part was cut into a 30×150 mm rectangle and rubbed 100 times with a Kagaku-shinbun type rub tester (load 500 g) using a plain woven fabric. The degree of ink peeling at this time was visually observed and judged according to the following evaluation criteria (Evaluation criteria) AA: No peeling A: There is peeling less than 20% of the evaluation area B: There is peeling of 20% or more and less than 40% of the evaluation area C: There is peeling of 40% or more and less than 60% of the evaluation area D: There is peeling of 60% or more of the evaluation area

[0213] 3.3.5. Clogging recovery (ink composition) The same printing conditions as the evaluation test of "image quality (banding unevenness)" were used. However, non-discharge was intentionally generated in the ink nozzles, and it was a simulated recording in which the ink was not discharged from the head and the head was run empty. The treatment liquid was also not discharged. The simulated recording was performed for 3 hours. After that, cleaning was performed 3 times, and after cleaning, the number of nozzles that were not discharging ink in the ink nozzles was judged according to the following evaluation criteria. In one cleaning, 1 g of ink was discharged from the nozzle row. Note that intentional non-discharge of the nozzles was generated by hitting the nozzle surface with a bent cot moistened with water. The nozzle row consists of 400 nozzles (Evaluation criteria) AA: No nozzle non-discharge A: Nozzle non-discharge is less than 3% B: Nozzle non-discharge is 3% or more and less than 5% C: Nozzle non-discharge is 5% or more

[0214] 3.3.6. Defoaming property (ink composition) 20 g of the inkjet ink composition obtained above was placed in a 110 mL screw tube and reciprocated up and down 10 times at a distance of 30 cm. The height of the generated bubbles was observed over time and judged according to the following evaluation criteria. (Evaluation criteria) AA: Within 15 minutes until the bubble height becomes 2 mm or less A: It takes 15 minutes or more and 30 minutes or less until the bubble height becomes 2 mm or less B: It takes 30 minutes or more and 1 hour or less until the bubble height becomes 2 mm or less C: It takes 1 hour or more until the bubble height becomes 2 mm or less

[0215] 3.3.7. Landing deviation (treatment liquid) The same apparatus configuration as in the evaluation test of "image quality (banding unevenness)" was used. Immediately after performing flushing with a head filled with the treatment liquid, a nozzle check pattern was recorded. Then, without discharging the inkjet ink composition and without discharging the treatment liquid, an idle run was performed for 1 minute. After the idle run, the same nozzle check pattern was recorded again with the treatment liquid and judged according to the following evaluation criteria. The deviation distance of the landing position was taken as the average value for all nozzles. However, non-discharging nozzles were excluded. (Evaluation criteria) A: No difference in the landing position before and after the idle run B: There is a deviation within the nozzle pitch C: There is a deviation exceeding the nozzle pitch

[0216] 3.4. Evaluation results The evaluation results are shown in Table 4 above.

[0217] From the above evaluation results, all of the examples were excellent in image quality (reduction of aggregation unevenness), excellent reduction of banding unevenness, excellent storage stability of the inkjet ink composition, and abrasion resistance.

[0218] On the other hand, all of the comparative examples were inferior in any of image quality, reduction of banding unevenness, storage stability, and abrasion resistance. In Comparative Example 1, the ink did not contain a hardly water-soluble organic compound and was inferior in reducing banding unevenness. In Comparative Example 2, the content of the specific hardly water-soluble organic compound contained in the ink was not within the predetermined range, and the storage stability of the ink was inferior. In Comparative Examples 3 and 4, the hardly water-soluble organic compound contained in the ink was not a specific hardly water-soluble organic compound, and the storage stability or rubbing resistance of the ink was inferior. In Comparative Examples 5 and 6, a treatment liquid was not used, and the image quality (aggregation unevenness) was inferior. Although not described in the table, in Ink A, an ink that does not contain PG, 1,2HD, or TIPA as a water-soluble organic compound was prepared, and evaluation was performed in the same manner as in Example 1 except that this ink was used. As a result, at least the clogging recovery property was inferior.

[0219] The following content is derived from the above-described embodiments.

[0220] One aspect of the ink set is an ink set including a treatment liquid containing a flocculant and an inkjet ink composition, which is used for recording on a low-absorbing or non-absorbing recording medium, wherein the inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, and a hardly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, and the hardly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition.

[0221] In the aspect of the above ink set, the diols or glycol ethers having a standard boiling point of 180 to 300°C may be any of 1,3-alkanediols, alicyclic diols, and glycol ethers having 6 or more carbon atoms of the general formula (1).

Chemical formula

[0222] In any aspect of the above ink set, the inkjet ink composition may contain, as the water-soluble organic compound, a resin-dissolving substance which is any one of amides, sulfur-containing solvents, and cyclic ethers having a standard boiling point of 150 to 300°C, in an amount of 20% by mass or less based on the total mass of the ink composition.

[0223] In any aspect of the above ink set, the inkjet ink composition may contain, as the water-soluble organic compound, any one of polyols and glycol ethers having a standard boiling point of 150 to 250°C, in an amount of 30% by mass or less based on the total mass of the ink composition.

[0224] In any aspect of the above ink set, the inkjet ink composition may contain, as the water-soluble organic compound, alkanediols having a standard boiling point of 150 to 250°C and 6 or less carbon atoms, in an amount of 10 to 25% by mass based on the total mass of the ink composition.

[0225] In any aspect of the above ink set, the treatment liquid may be the water-insoluble organic compound containing any one of diols or glycol ethers having a standard boiling point of 180 to 300°C.

[0226] In any aspect of the above ink set, the inkjet ink composition may contain a silicone-based surfactant in an amount of 0.1 to 1.5% by mass based on the total mass of the ink composition.

[0227] One aspect of the recording method is A recording method for performing recording using an ink set according to any of the above aspects, including an ink adhesion step of ejecting the inkjet ink composition by an inkjet method and attaching it to a recording medium, and a treatment liquid adhesion step of attaching the treatment liquid to the recording medium. The recording medium is a low-absorbing or non-absorbing recording medium.

[0228] In an aspect of the above recording method, recording may be performed by a plurality of main scans, and a plurality of main scans may be performed on the same scan area.

[0229] In any aspect of the above recording method, it may include a primary heating step of heating the inkjet ink composition attached to the recording medium.

[0230] In any aspect of the above recording method, it may include a post-heating step of heating the recording medium after the ink adhesion step and the treatment liquid adhesion step.

[0231] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiments, for example, a configuration having the same functions, methods, and results, or a configuration having the same purposes and effects. Further, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiments is replaced. Further, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiments or a configuration that can achieve the same purpose. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiments.

Description of Reference Numerals

[0232] 1... Inkjet recording apparatus, 2... Recording head, 3... IR heater, 4... Platen heater, 5... Heating heater, 6... Cooling fan, 7... Preheater, 8... Ventilation fan, 9... Carriage, 11... Platen, 12... Cartridge, 13... Carriage movement mechanism, 14... Conveying means, 101... Interface section, 102... CPU, 103... Memory, 104... Uni tt control circuit, 111... Conveying unit, 112... Carriage unit, 113... Head unit, 114... Drying unit, 121... Detector group, 130... Computer, CONT... Control section, MS... Main scanning direction, SS... Sub-scanning direction, M... Recording medium

Claims

1. An ink adhesion step of discharging an inkjet ink composition by an inkjet method and attaching it to a recording medium, A treatment liquid adhesion step of attaching a treatment liquid containing a flocculant to the recording medium, The inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, a sparingly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, a silicone-based surfactant, and a fixing resin. The sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition. The diols or glycol ethers having a standard boiling point of 180 to 300°C are any of 1,3-alkanediols, alicyclic diols, and glycol ethers having 6 or more carbon atoms of the general formula (1). 【Chemical 1】 (In formula (1), R1, R2, and R3 are independently hydrogen or an alkyl group. The total number of carbon atoms of R1, R2, and R3 is 3 to 9.) The coloring material is a pigment. The inkjet ink composition does not contain polyols having a standard boiling point of more than 280°C as the water-soluble organic compound in an amount exceeding 3% by mass based on the total mass of the ink composition. The recording medium is a low-absorbing recording medium or a non-absorbing recording medium. The low-absorbing recording medium is coated paper, and the non-absorbing recording medium is plastic. Recording method.

2. An ink adhesion step of discharging an inkjet ink composition by an inkjet method and attaching it to a recording medium, A treatment liquid adhesion step of attaching a treatment liquid containing a flocculant to the recording medium, The inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, a sparingly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, a silicone-based surfactant, and a fixing resin. The sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition. The coloring material is a pigment. The inkjet ink composition contains, as the water-soluble organic compound, a resin dissolution substance which is any one of amides, sulfur-containing solvents, and cyclic ethers having a standard boiling point of 150 to 300°C, in an amount of 20% by mass or less based on the total mass of the ink composition. The inkjet ink composition does not contain, as the water-soluble organic compound, polyols having a standard boiling point exceeding 280°C, in an amount exceeding 3% by mass based on the total mass of the ink composition. The recording medium is a low-absorbing recording medium or a non-absorbing recording medium. The low-absorbing recording medium is coated paper, and the non-absorbing recording medium is plastic. A recording method.

3. An ink adhesion step of discharging an inkjet ink composition by an inkjet method and attaching it to a recording medium, A treatment liquid adhesion step of attaching a treatment liquid containing a flocculant to the recording medium. The inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, a sparingly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, a silicone-based surfactant, and a fixing resin. The sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C, in a content of 2.3% by mass or less based on the total mass of the ink composition. The coloring material is a pigment. The inkjet ink composition does not contain, as the water-soluble organic compound, polyols having a standard boiling point exceeding 280°C, in an amount exceeding 3% by mass based on the total mass of the ink composition. The treatment liquid contains any one of diols or glycol ethers, which is the sparingly water-soluble organic compound and has a standard boiling point of 180 to 300°C. The recording medium is a low-absorbing recording medium or a non-absorbing recording medium. The low-absorbing recording medium is coated paper, and the non-absorbing recording medium is plastic. A recording method.

4. The recording method according to any one of claims 1 to 3, wherein the inkjet ink composition contains, as the water-soluble organic compound, any one of polyols and glycol ethers having a standard boiling point of 150 to 250°C, in an amount of 30% by mass or less based on the total mass of the ink composition.

5. The recording method according to any one of claims 1 to 4, wherein the inkjet ink composition contains, as the water-soluble organic compound, alkanediols having a standard boiling point of 150 to 250°C and 6 or less carbon atoms in an amount of 10 to 25% by mass based on the total mass of the ink composition.

6. The recording method according to any one of claims 1 to 5, wherein the inkjet ink composition contains the silicone-based surfactant in an amount of 0.1 to 1.5% by mass based on the total mass of the ink composition.

7. The recording method according to any one of claims 1 to 6, wherein recording is performed by a plurality of main scans, and a plurality of main scans are performed on the same scan area.

8. The recording method according to any one of claims 1 to 7, comprising a primary heating step of heating the inkjet ink composition adhered to the recording medium.

9. The recording method according to any one of claims 1 to 8, comprising a post-heating step of heating the recording medium after the ink adhesion step and the treatment liquid adhesion step.

10. An ink set comprising a treatment liquid containing a flocculant and an inkjet ink composition, which is used for recording on a low-absorbing or non-absorbing recording medium, wherein the inkjet ink composition is an aqueous ink containing a coloring material, a water-soluble organic compound having a solubility of more than 10 g in 100 g of water at 20°C, and a sparingly water-soluble organic compound having a solubility of 0.1 to 10 g in 100 g of water at 20°C, the sparingly water-soluble organic compound contains diols or glycol ethers having a standard boiling point of 180 to 300°C in a content of 2.3% by mass or less based on the total mass of the ink composition, the inkjet ink composition contains, as the water-soluble organic compound, a resin dissolution substance which is any one of amides, sulfur-containing solvents, and cyclic ethers having a standard boiling point of 150 to 300°C in a content of 20% by mass or less based on the total mass of the ink composition, the inkjet ink composition contains, as the water-soluble organic compound, alkanediols having a standard boiling point of 150 to 250°C and 6 or less carbon atoms in an amount of 10 to 25% by mass based on the total mass of the ink composition.

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