Ink set and recording method

Abstract

To provide an ink set having excellent dry rub resistance and wet rub resistance.SOLUTION: An ink set according to an embodiment of the present invention has a color ink composition and a clear ink composition, which is used for a recording method in which the color ink composition and the clear ink composition are adhered in an overlapped manner on a recording medium by an inkjet method, where the color ink composition is an aqueous composition containing coloring material, and the clear ink composition is an aqueous composition containing resin and silicone-based surfactant having a dissolving amount of 1.0 to 3.0 pts.mass to 100 pts.mass of 1,2-hexanediol 3 mass% aqueous solution.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] The inkjet recording method uses a relatively simple device and can record high-definition images, and has been rapidly developed in various fields. Among them, in order to improve the abrasion resistance of the recording material, the use of a clear ink containing a resin has been studied.

[0003] For example, Patent Document 1 describes an inkjet recording method in which a recording area for discharging a colored ink composition from an inkjet head in a main scan and a recording area for discharging a clear ink composition containing a resin and a silicone-based surfactant from the inkjet head in the main scan overlap.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When using clear ink, as abrasion resistance, there are dry rubbing resistance when the recording material is rubbed in a dry state and wet rubbing resistance when the recording material is rubbed in an environment where it is wet or moist. There are cases where the dry rubbing resistance is poor or the wet rubbing resistance is poor. Therefore, it is required to be excellent in both dry rubbing resistance and wet rubbing resistance.

Means for Solving the Problems

[0006] One aspect of the ink set according to the present invention is an ink set having a colored ink composition and a clear ink composition, It is used in a recording method in which the colored ink composition and the clear ink composition are superposed and adhered to a recording medium by an inkjet method, The colored ink composition is an aqueous composition containing a coloring material, The clear ink composition is an aqueous composition containing a resin and a silicone surfactant whose dissolution amount in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol is 1.0 to 3.0 parts by mass.

[0007] One aspect of the recording method according to the present invention is, A recording method performed using the ink set of the above aspect, A step of adhering the colored ink composition to a recording medium by an inkjet method, A step of adhering the clear ink composition to the recording medium by an inkjet method, and has, The colored ink composition and the clear ink composition are superposed and adhered on the recording medium.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Embodiments of the present invention will be described below. The embodiments described below are examples of the present invention. The present invention is not limited to the following embodiments, and 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.

[0010] In this specification, a numerical range represented using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, "(meth)acryl" represents acrylic or methacrylic, and "(meth)acrylate" represents acrylate or methacrylate.

[0011] 1. Ink set An ink set according to an embodiment of the present invention is an ink set having a colored ink composition and a clear ink composition, and is used for a recording method in which the colored ink composition and the clear ink composition are overlapped and adhered to a recording medium by an inkjet method. The colored ink composition is an aqueous composition containing a coloring material, and the clear ink composition is an aqueous composition containing a resin and a silicone-based surfactant having a dissolution amount of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2-hexanediol.

[0012] Conventionally, studies have been made to improve the abrasion resistance of a recorded material using a clear ink containing a resin. In the inkjet recording method, the clear ink is also applied by the inkjet method, so that a necessary amount can be applied to a necessary part, and since it is a non-contact application, there is an advantage that a color image (an image recorded with a colored ink composition) is not easily soiled. Furthermore, since the color ink and the clear ink can be adhered simultaneously or continuously, it is also advantageous in terms of the recording speed (productivity).

[0013] However, even when using clear ink, there were cases where the dry rubbing fastness was poor or the wet rubbing fastness was poor. Moreover, it has been found that the dry rubbing fastness and wet rubbing fastness may deteriorate due to the presence of the clear ink film.

[0014] As a result of investigations, when the silicone surfactant contained in the clear ink is a silicone surfactant with a solubility of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, it has been possible to obtain excellent dry rubbing fastness and wet rubbing fastness.

[0015] In the present invention, an "ink set" is a set of inks that combines at least a colored ink composition and a clear ink composition. The ink set is a set of inks used for recording. The colored ink composition included in the ink set may be only one or two or more. The same applies to the clear ink composition included in the ink set.

[0016] 1.1 Clear ink composition The ink set according to this embodiment has a clear ink composition, and the clear ink composition is an aqueous composition containing a resin and a silicone surfactant with a solubility of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol.

[0017] The clear ink composition is not a colored ink composition and is not an ink used for coloring purposes. It may contain a coloring material contained in the ink composition described later, but the coloring material is more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even further preferably 0.01% by mass or less with respect to the total amount of the clear ink composition. These also include the mode of not containing (0% by mass).

[0018] Hereinafter, each component contained in the clear ink composition will be described.

[0019] 1.1.1 Resin The clear ink composition contains a resin. The resin has a function as a so-called fixing resin that improves, for example, the adhesion and abrasion resistance of the ink components.

[0020] Examples of the resin include urethane resins, acrylic resins (including styrene-acrylic resins), fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate resins, and the like. Among them, urethane resins, acrylic resins, polyolefin resins, and polyester resins are preferred. These resins may be water-soluble resins or resin particles, but preferably in the form of resin particles. Resin particles are often handled in emulsion form, but may also be in powder form. Further, the resin can be used alone or in combination of two or more.

[0021] 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 for the urethane resin. Also, commercially available products may be used as the urethane resin. For example, commercially available products such as Superflex 460, 460s, 840, E-4000 (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Resamin D-1060, D-2020, D-4080, D-4200, D-6300, D-6455 (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.), Takelac WS-6021, W-512-A-6 (trade name, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.), Sun Cure 2710 (trade name, manufactured by Lubrizol Corporation), Permalin UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.) may be used.

[0022] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or (meth)acrylic acid ester as one component, and examples thereof include resins obtained from acrylic monomers and copolymers of acrylic monomers and other monomers. Examples thereof include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers. Examples of vinyl monomers include styrene.

[0023] As the acrylic monomer, acrylamide, acrylonitrile, etc. can also be used. For the resin emulsion using an acrylic resin as a raw material, a commercially available product may be used, and may be selected from, for example, FK-854 (trade name, manufactured by Chuo Rika Kogyo Co., Ltd.), Mowinyl 6969D, 6899D, 952B, 718A (trade names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852, LX874 (trade names, manufactured by Nippon Zeon Co., Ltd.), and the like.

[0024] In this specification, the acrylic resin may be a styrene-acrylic resin, which will be described later.

[0025] Styrene-acrylic resins are made from styrene monomers and (meth)acrylic monomers. Examples of copolymers that can be used include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, and styrene-α-methylstyrene-acrylic acid-acrylate copolymer. As the styrene-acrylic resin, commercially available products may be used, such as JONCRYL 62J, 7100, 390, 711, 511, 7001, 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, and 7610 (trade names, manufactured by BASF), Mowinyl 966A and 975N (trade names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and Vinyblan 2586 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0026] 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 olefin resin, commercially available products can be used, and for example, Arrowbase CB-1200, CD-1200 (trade names, manufactured by Unitika Ltd.) etc. may be used.

[0027] 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 names of products manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin emulsions), Boncoat 4001 (trade name of a product manufactured by DIC Corporation, acrylic resin emulsion), Boncoat 5454 (trade name of a product manufactured by 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) (trade name of a product manufactured by Showa Denko K.K.), Polyzol SAE1014 (trade name, styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (trade name, acrylic resin emulsion, manufactured by Siden Chemical Co., Ltd.), AE-120A (trade name of a product manufactured by JSR Corporation, acrylic resin emulsion), AE373D (trade name of a product manufactured by E-Tech Co., Ltd., carboxy-modified styrene-acrylic resin emulsion), Seikadine 1900W (trade name of a product manufactured by 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) (trade names of products manufactured by Nisshin Chemical Industry Co., Ltd.), Elitel KA-5071S, KT-8803, KT-9204, KT-8701, KT-8904, KT-0507 (trade names of products manufactured by Unitika Ltd., polyester resin emulsion), Hi-Tech SN-2002 (trade name of a product manufactured by Toho Chemical Co., Ltd., polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (trade names of products manufactured by Mitsui Chemicals Polyurethane Co., Ltd., urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 700 (trade names of products manufactured by Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), Permalin UA-150 (manufactured by Sanyo Chemical Industries, Ltd.,Urethane resin emulsion), Sanki Cure 2710 (manufactured by Nippon Lubrizol Corporation, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (manufactured by Kusumoto Chemical Co., Ltd., urethane resin emulsion), Adeka Bon Titer HUX-380, 290K (manufactured by ADEKA Corporation, urethane resin emulsion), Mobinyl 966A, Mobinyl 7320 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 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.

[0028] The glass transition temperature Tg of the resin contained in the clear ink composition is preferably 0 °C or higher, more preferably 30 °C or higher, still more preferably 50 °C or higher, particularly preferably 60 °C or higher, and even more particularly preferably 70 °C or higher. When the glass transition temperature Tg of the resin is particularly 60 °C or higher, it tends to be more excellent in dry rubbing resistance. Also, it tends to be more excellent in clogging recovery property. The upper limit value of the glass transition temperature Tg of the resin is not particularly limited, but is preferably 150 °C or lower, more preferably 100 °C or lower, and still more preferably 80 °C or lower. The measurement of the glass transition temperature is performed, for example, in accordance with JIS K7121 (Method for Measuring Transition Temperature of Plastics) using a differential scanning calorimeter "DSC7000" manufactured by Hitachi High-Tech Science Corporation.

[0029] The content of the resin in the clear ink composition is 1% by mass or more and 30% by mass or less, preferably 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and even more preferably 11 to 15% by mass, in terms of solid content, based on the total mass of the clear ink composition.

[0030] 1.1.2 Specific silicone surfactant The clear ink composition contains a silicone surfactant (hereinafter also referred to as "specific silicone surfactant") with a solubility of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol.

[0031] When the above solubility in the silicone surfactant is high, it has been found that the wet rub resistance deteriorates. This is presumably because when the above solubility is high, the hydrophilicity is strong and the surfactant easily absorbs moisture (humidity), causing the clear ink coating film to swell and dissolve, and the colorant in the colored ink layer to redisperse. On the other hand, when the above solubility in the silicone surfactant is low, it has been found that the dry rub resistance deteriorates. This is presumably because when the above solubility is low, the hydrophobicity is strong and it easily affinity with organic components such as resins in the clear ink, reducing the drying property of the ink containing organic components and resulting in insufficient drying of the ink coating film. Since the silicone surfactant has a high boiling point and is difficult to evaporate, when it coexists with organic components, the drying property of the ink tends to decrease. In contrast, in the case of a specific silicone surfactant, it has an excellent balance between hydrophilicity and hydrophobicity, and can achieve excellent wet rub resistance and dry rub resistance. Also, by confirming the solubility in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, it has been found that it can be used as an index for the balance between hydrophilicity and hydrophobicity, and it is possible to determine whether it is a silicone surfactant that can achieve excellent wet rub resistance and dry rub resistance.

[0032] When applying clear ink by an inkjet method, from the viewpoint of inkjet ejection stability, it is preferable to contain a silicone-based surfactant that can easily lower the surface tension of the ink. In particular, when applying to a low-absorbency or non-absorbency recording medium, a silicone-based surfactant is also preferable in terms of wet spreading on the recording medium, and the required amount can be uniformly applied. On the other hand, in the case of an acetylene glycol-based surfactant, it is difficult to lower the surface tension, and it is inferior in terms of wet spreading property and ejection stability on the recording medium.

[0033] The dissolution amount of the surfactant in 100 parts by mass of a 3% by mass aqueous solution of 1,2-hexanediol was measured by preparing 100 g of a 3% by mass aqueous solution of 1,2-hexanediol in a 100 mL beaker and adding a predetermined amount of the surfactant thereto. After the addition, it was gently stirred with a stirrer, and when it settled, the turbidity of the liquid was visually observed using black paper as the background. If it was cloudy or there was no visible undissolved residue, it was judged to be dissolved. For example, when considering addition amounts of the surfactant of 0.1 part by mass, 0.5 part by mass, and 1 part by mass with respect to 100 parts by mass of the aqueous solution, after adding 0.1 g of the surfactant to 100 g of a 3% by mass aqueous solution of 1,2-hexanediol and determining the presence or absence of dissolution, subsequently 0.4 g of the surfactant was additionally added to determine the presence or absence of dissolution. Further, subsequently, 0.5 g of the surfactant was additionally added to determine the presence or absence of dissolution. In this way, the maximum mass of the surfactant that can be judged to be dissolved is confirmed. In this way, it is confirmed several times (for example, 3 times or 5 times), and the average value of the mass of the confirmed surfactant is taken as the dissolution amount. The measurement is to be carried out under normal temperature (25°C) environment.

[0034] The dissolution amount of a specific silicone-based surfactant in 100 parts by mass of a 3% by mass aqueous solution of 1,2-hexanediol is 1.0 to 3.0 parts by mass, preferably 1.5 to 2.8 parts by mass, more preferably 1.8 to 2.7 parts by mass, and particularly preferably 2.0 to 2.5 parts by mass.

[0035] A specific silicone surfactant is preferably a silicone surfactant represented by the following formula (1). When it is such a silicone surfactant, it is easy to adjust the above dissolution amount within the above range. Further, since it has a structure with modified both ends, by adjusting the length of the main skeleton having a siloxane bond other than the polyether-modified group portion, it is easy to adjust the molecular weight and the above dissolution amount to a preferable range. As a result, it tends to have an excellent balance between hydrophilicity and hydrophobicity and to have excellent wet rubbing resistance and dry rubbing resistance. [Chemical formula] (In the formula, a is an integer from 1 to 30, x and y are each independently an integer from 1 to 4, m and n are each independently an integer from 1 to 20, o and p are each independently an integer from 0 to 20, m + n is from 2 to 40, o + p is from 0 to 40, R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group. E is an ethylene group and P is a propylene group. The order between the OE(EO) unit and the OP(PO) unit is arbitrary.

[0036] In formula (1); a is an integer from 1 to 30, preferably 25 or less, more preferably 20 or less, still more preferably from 2 to 17, even more preferably from 5 to 15, and particularly preferably from 7 to 13. x and y are each independently an integer from 1 to 4, preferably 1 to 3, and more preferably 2 to 3. m and n are each independently an integer from 1 to 20, preferably 2 to 15, more preferably 4 to 10, and still more preferably 5 to 8. o and p are each independently an integer from 0 to 20, preferably 0 to 10, more preferably 0 to 5, even more preferably 0 to 3, particularly preferably 0 to 1, and even more particularly preferably 0. m + n is from 2 to 40, preferably from 4 to 30, more preferably from 8 to 20, and even more preferably from 10 to 15. o + p is from 0 to 40, preferably from 0 to 20, more preferably from 0 to 10 and even more preferably from 0 to 3, particularly preferably from 0 to 1, and even more particularly preferably 0. R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group, and are preferably a hydroxy group. The order between the OE(EO) unit and the OP(PO) unit is arbitrary. That is, when there is at least one OE(EO) unit and at least one OP(PO) unit, the order of one OE(EO) unit and one P(PO) unit does not matter. P is a propylene group, and examples include a 1,2 - propylene group and a 1,3 - propylene group, with a 1,2 - propylene group being preferred.

[0037] It is also preferable that a specific silicone - based surfactant is a silicone - based surfactant represented by the following formula (2).

Chemical formula

[0038] In formula (2); d + e is an integer from 1 to 50, preferably from 1 to 25, more preferably from 1 to 20, still more preferably from 1 to 17, even more preferably from 1 to 15, particularly preferably from 1 to 13, and even more particularly preferably from 1 to 7. d and e are each preferably half of d + e. R 4 is an alkylene group having 1 to 4 carbon atoms, preferably 1 to 3, and more preferably 2 to 3. f is an integer from 1 to 20, preferably from 2 to 15, more preferably from 4 to 10, and still more preferably from 5 to 8. g is an integer from 0 to 20, preferably from 0 to 10, more preferably from 0 to 5, even more preferably from 0 to 3, particularly preferably from 0 to 1, and even more particularly preferably 0. R 5 is selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group, and is preferably a hydroxy group.

[0039] A specific silicone surfactant may be obtained by synthesis. For example, it can be synthesized by an addition reaction of a silicone oil having an Si-H structure and a polyether having a carbon-carbon double bond at the end.

[0040] In the case of the silicone surfactant of formula (1), more specifically, it is represented by the following formula (A) It is preferable to synthesize by subjecting a silicone oil and a polyether represented by the following formula (B) to an addition reaction using a Pt-based catalyst or the like. Thereby, the silicone surfactant represented by the above formula (1) can be preferably synthesized.

[0041]

Chemical formula

[0042] In formula (A), b is an integer from 1 to 30, preferably 25 or less, more preferably 20 or less, still more preferably 2 to 17, even more preferably 5 to 15, and particularly preferably 7 to 13. In the case of the silicone surfactant of formula (2), more specifically, the polyether-modified group part including R of formula (2) 4 is preferably synthesized by subjecting a silicone oil in which the polyether-modified group part including R is replaced with a hydrogen atom and a polyether represented by the following formula (B) to an addition reaction using a Pt-based catalyst or the like. Also in this case, the silicone oil has an Si-H structure.

[0043] [Chemical formula] (In the formula, c is an integer from 1 to 40, R 6 represents an ethylene group or a propylene group, and R 7 is selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group.)

[0044] In formula (B); The allyl group part of formula (B) reacts with the -H of Si-H of the silicone oil to become the polyether-modified group part of formula (1) or formula (2). When obtaining the silicone surfactant of formula (1), a polyether of formula (B) corresponding to the polyether-modified group of formula (1) may be used. When obtaining the silicone surfactant of formula (2), a polyether of formula (B) corresponding to the polyether-modified group of formula (2) may be used. Also, c is preferably an integer from 1 to 20. When R 6 is an ethylene group, c is preferably 2 to 15, more preferably 4 to 10, and still more preferably 5 to 8. c is an integer from 1 to 20, but when R 6 is a propylene group, it is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. R 6 is an ethylene group or a propylene group, with the ethylene group being preferred. R 7 is selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group, and is preferably a hydroxy group.

[0045] A specific silicone surfactant preferably has a maximum peak in the range of a molecular weight of 1000 to 3000 in the molecular weight distribution in gel permeation chromatography (GPC). In the case of such a silicone surfactant, it is easy to adjust the above dissolution amount within the above range, and thus it tends to have an excellent balance between hydrophilicity and hydrophobicity and excellent wet rubbing resistance and dry rubbing resistance.

[0046] The maximum peak in the range of a molecular weight of 300 or more in the molecular weight distribution in gel permeation chromatography is preferably in the range of a molecular weight of 1000 to 3000, more preferably in the range of a molecular weight of 1200 to 2500, and even more preferably in the range of a molecular weight of 1300 to 2000. Further, the range of a molecular weight of 1400 to 1800 is preferred, and the range of a molecular weight of 1500 to 1700 is more preferred.

[0047] The maximum peak in the range of a molecular weight of 300 or more of the silicone surfactant can be specified from the chart of the molecular weight distribution in GPC obtained with the horizontal axis being "logarithmic value of molecular weight M (LogM)" and the vertical axis being "differential value of concentration fraction (dw / d(LogM))". Here, the "maximum peak" means the largest one among the peaks (mountains) in the range of a molecular weight of 300 or more. Also, the "maximum peak in the range of a molecular weight of 300 or more" means that peaks with a molecular weight of less than 300 are ignored. That is, there may be a maximum peak with a molecular weight of less than 300, but it is the maximum peak when viewed only in the range of a molecular weight of 300 or more.

[0048] Although not particularly limited, for example, the measurement conditions in the GPC measurement in the present embodiment can be the conditions described in the examples, and the molecular weight can be specified using standard polystyrene.

[0049] The content of the specific silicone surfactant is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.5% by mass or less, further more preferably 0.4% by mass or less, and particularly preferably 0.3% by mass or less, based on the total mass of the clear ink composition. Also, the lower limit of the content of the specific silicone surfactant is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.10% by mass or more, further more preferably 0.15% by mass or more, and particularly preferably 0.2% by mass or more, and preferably 0.25% by mass or more, based on the total mass of the clear ink composition. When such a content is particularly 0.3% by mass or less, the wet rub resistance tends to be better. Also, the separation of the surfactant in the ink is less likely to occur.

[0050] The clear ink composition may contain other surfactants other than the above specific silicone surfactant. Examples of other surfactants include silicone surfactants other than the above specific silicone surfactant, acetylene glycol-based surfactants, and fluorine-based surfactants.

[0051] Examples of silicone surfactants other than the above specific silicone surfactant include BYK-333 (trade name, manufactured by BYK-Chemie Japan, solubility in 100 parts by mass of 3% by mass aqueous solution of 1,2-hexanediol is 0.7 parts by mass, in the molecular weight distribution measured by GPC, the maximum peak in the range of molecular weight of 300 or more is 4000 - 7000), BYK-348 (trade name, manufactured by BYK-Chemie Japan, the above solubility is 5 parts by mass, the above maximum peak is 1540), BYK-3480 (trade name, manufactured by BYK-Chemie Japan, the above solubility is 0.1 parts by mass, the above maximum peak is 4000 - 4500), BYK-349 (trade name, manufactured by BYK-Chemie Japan, the above solubility is 0.1 parts by mass, the above maximum peak is 1400 - 1500), Silface SAG503A (trade name, manufactured by Nissin Chemical Industry Co., Ltd., the above maximum peak is 1500 - 1900), PD5 08 (trade name, manufactured by Nissin Chemical Industry Co., Ltd., the above maximum peak is 6230), and the like.

[0052] The acetylene glycol-based surfactants are not particularly limited. Examples include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol. Examples of commercially available acetylene glycol - based surfactants include 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 & Chemicals, Inc.), 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.), Acetylenol E00, E00P, E40, E100 (all of the above are trade names, manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0053] The fluorine - based surfactants are not particularly limited. For example, they include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds. Examples of commercially available fluorine - based surfactants include BYK - 3440 (manufactured by BYK - Chemie Japan), Surfron S - 241, S - 242, S - 243 (the above are trade names, manufactured by AGC Seimi Chemical Co., Ltd.), Fartergent 215M (manufactured by Neos Co., Ltd.), and the like.

[0054] The content of other surfactants is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably not contained (0% by mass) based on the total mass of the clear ink composition.

[0055] 1.1.3 Water The clear ink composition is an aqueous composition. "Aqueous" means containing at least water as a solvent component, and may contain water as the main solvent component.

[0056] Examples of water include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, and distilled water, as well as water with reduced ionic impurities such as ultrapure water. In addition, when using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., the generation of bacteria and fungi can be suppressed when the clear ink composition is stored for a long time.

[0057] The water content is preferably 50% by mass or more, more preferably 50 to 100% by mass in the liquid medium component. Further, it is preferably 70 to 100% by mass, more preferably 90 to 100% by mass, and still more preferably 95 to 99% by mass. Note that the liquid medium is a solvent component such as water or an organic solvent. Also, the water content is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more with respect to the total mass of the clear ink composition. The upper limit of the water content is not particularly limited, but for example, it is preferably 99% by mass or less, and further 90% by mass or less with respect to the total mass of the clear ink composition.

[0058] 1.1.4 Amine The clear ink composition preferably contains an amine having a standard boiling point of 250°C or higher. When containing an amine having a standard boiling point of 250°C or higher, the moisture retention of the ink is excellent and the clogging recovery property can be improved. On the other hand, since the drying property of the ink is reduced, the wet rubbing resistance may be inferior. In contrast, according to the ink set according to this embodiment, even when containing an amine having a standard boiling point of 250°C or higher, there is a tendency that the clogging recovery property can be improved and the wet rubbing resistance can also be good.

[0059] Examples of the amine include aliphatic amines, aromatic amines, and heterocyclic amines. Among these, aliphatic amines are preferred, and alkanolamines, which are compounds having a hydroxy group and an amine group in an alkane skeleton, are more preferred.

[0060] Examples of alkanolamines with a standard boiling point of 250 °C or higher include diethanolamine (standard boiling point: 268 °C, property at 25 °C: solid [melting point 28 °C]), N-ethyldiethanolamine (standard boiling point: 251 °C, property at 25 °C: liquid), N-butyldiethanolamine (standard boiling point: 275 °C, property at 25 °C: liquid), N-tert-butyldiethanolamine (abbreviation: tBDEA, standard boiling point: 271 °C, property at 25 °C: solid [melting point 49 °C]), triethanolamine (abbreviation: TEA, standard boiling point: 335 °C, property at 25 °C: liquid), triisopropanolamine (abbreviation: TPA, standard boiling point: 305 °C, property at 25 °C: solid [melting point 45 °C]), 2-amino-1,3-propanediol (standard boiling point: 274 °C, property at 25 °C: solid [melting point 52 °C]), 2-amino-2-hydroxymethyl-1,3-propanediol (standard boiling point: 288 °C, property at 25 °C: solid [melting point 170 °C]), 2-amino-2-methyl-1,3-propanediol (standard boiling point: 260 °C, property at 25 °C: solid [melting point 108 °C]), 2-amino-2-ethyl-1,3-propanediol (standard boiling point: 259 °C, property at 25 °C: solid [melting point 34 °C]), and the like.

[0061] Among the alkanolamines with a standard boiling point of 250 °C or higher, it is preferably at least one selected from triethanolamine and triisopropanolamine.

[0062] The standard boiling point of the amine is preferably 250 °C or higher, more preferably 270 °C or higher, still more preferably 290 °C or higher, and particularly preferably 300 °C or higher. In such a standard boiling point range, the clogging recovery property tends to be more excellent. The upper limit range of the standard boiling point of the amine is not particularly limited, but is preferably 350 °C or lower, and more preferably 340 °C or lower.

[0063] The content of amines with a standard boiling point of 250 °C or higher is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.4% by mass or less, even more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less, based on the total mass of the clear ink composition. When such content is particularly 0.4% by mass or less, it tends to have an excellent balance between moisture retention and dryness, and can achieve good clogging recovery properties, dry rubbing resistance, and wet rubbing resistance at the same time. The lower limit range of the content of amines with a standard boiling point of 250 °C or higher is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.15% by mass or more.

[0064] 1.1.5 Organic solvents The clear ink composition may contain an organic solvent. Examples of the organic solvent include esters, alkylene glycol ethers, cyclic esters, amides, alcohols, polyhydric alcohols, etc. A water-soluble organic solvent is preferred.

[0065] Examples of the esters include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, Glycol monoacetates such as propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, methoxybutyl acetate, etc., ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, diethylene glycol acetate butyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, dipropylene glycol acetate butyrate, dipropylene glycol acetate propionate, etc. are included.

[0066] As the alkylene glycol ethers, monoesters or diesters of alkylene glycol may be used, and alkyl ethers are preferred. Specific examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether and other alkylene glycol monoalkyl ethers; and alkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol dimethyl ether.

[0067] Examples of cyclic esters include cyclic esters (lactones) such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, β-butyrolactone, β-valerolactone, γ-valerolactone, β-hexanolactone, γ-hexanolactone, δ-hexanolactone, β-heptanolactone, γ-heptanolactone, δ-heptanolactone, ε-heptanolactone, γ-octanolactone, δ-octanolactone, ε-octanolactone, δ-nonalactone, ε-nonalactone, ε-decanolactone, etc., and compounds in which the hydrogen of the methylene group adjacent to the carbonyl group is substituted with an alkyl group having 1 to 4 carbon atoms.

[0068] Examples of amides include cyclic amides, acyclic amides, etc. Acyclic Examples of acyclic amides include alkoxyalkylamides, etc.

[0069] Examples of cyclic amides include lactams. Examples of lactams include pyrrolidones such as 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, etc.

[0070] Examples of alkoxyalkylamides include 3-methoxy-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-dimethylpropionamide, 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, N,N-dimethylisobutyramide, and the like.

[0071] Examples of alcohols include compounds in which one hydrogen atom of an alkane is substituted by a hydroxyl group. The alkane preferably has 10 or fewer carbon atoms, more preferably 6 or fewer carbon atoms, and even more preferably 3 or fewer carbon atoms. The alkane has 1 or more carbon atoms, preferably 2 or more carbon atoms. The alkane may be linear or branched. Examples of alcohols include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol, 2-phenoxyethanol, benzyl alcohol, phenoxypropanol, and the like.

[0072] Polyhydric alcohols have two or more hydroxyl groups in the molecule. Examples of polyhydric alcohols include alkanediols and polyols.

[0073] Alkanediols are, for example, compounds in which an alkane is substituted with two hydroxyl groups. Examples of alkanediols include 1,2-alkanediol, which is a general term for compounds in which a hydroxyl group is substituted at the 1- and 2-positions of an alkane, and other alkanediols other than 1,2-alkanediol.

[0074] Examples of 1,2-alkanediol include ethylene glycol, 1,2-propanediol (propylene glycol), 1,2-butanediol (1,2BD), 1,2-pentanediol (1,2PD), 1,2-hexanediol (1,2HD), 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-methyl-1,2-butanediol, 3-methyl-1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,4-dimethyl-1,2-pentanediol, 3-ethyl-1,2-pentanediol, 4-ethyl-1,2-pentanediol, 3-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, 5-methyl-1,2-hexanediol, 3,4-dimethyl-1,2-hexanediol, 3,5-dimethyl-1,2-hexanediol, 4,5-dimethyl-1,2-hexanediol, 3-ethyl-1,2-hexanediol, 4-ethyl-1,2-hexanedi ol, 3-ethyl-4-methyl-1,2-hexanediol, and the like.

[0075] Examples of other alkane diols include, for example, 1,3-propanediol, 1,3-butylene glycol (also known as: 1,3-butanediol), 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, 2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and the like. Among the alkane diols, those having 5 or more carbon atoms are preferred, and those having 5 to 10 carbon atoms are more preferred.

[0076] Examples of polyols include, for example, condensates in which two or more molecules of alkane diols are intermolecularly condensed through hydroxyl groups, compounds having three or more hydroxyl groups, and the like.

[0077] Examples of condensates in which two or more molecules of alkane diols are intermolecularly condensed through hydroxyl groups include, for example, dialkylene glycols such as diethylene glycol and dipropylene glycol, and trialkylene glycols such as triethylene glycol and tripropylene glycol.

[0078] Compounds having three or more hydroxyl groups are compounds having three or more hydroxyl groups with an alkane or polyether structure as the backbone. Examples of compounds having three or more hydroxyl groups include, for example, glycerin, trimethylolethane, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, polyoxypropylene triol, and the like.

[0079] The organic solvent may be used alone or in combination of two or more.

[0080] The content of the organic solvent is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and particularly preferably not contained (0% by mass) with respect to the total mass of the clear ink composition.

[0081] On the other hand, it may contain an organic solvent. With respect to the total mass of the clear ink composition, the organic solvent is preferably 1% by mass or more, more preferably 1 to 40% by mass, still more preferably 3 to 30% by mass, even more preferably 5 to 25% by mass, and particularly preferably 7 to 20% by mass.

[0082] Also, it is preferable that the content of polyhydric alcohols is within the above range. Also, it is preferable that the content of alkanediols is within the above range. Furthermore, the content of alkanediols having 5 or more carbon atoms is preferably 0.5% by mass or more, more preferably 1 to 20% by mass, still more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass with respect to the total mass of the clear ink composition. The organic solvent of polyhydric alcohols having a standard boiling point exceeding 280°C is preferably not contained in excess of 1% by mass, more preferably not contained in excess of 0.5% by mass, and still more preferably not contained in excess of 0.1% by mass with respect to the total mass of the clear ink composition. Also, all organic solvents not limited to polyhydric alcohols having a standard boiling point exceeding 280°C are preferably not contained in excess of 1% by mass, more preferably not contained in excess of 0.5% by mass, and still more preferably not contained in excess of 0.1% by mass with respect to the total mass of the clear ink composition. In this case, the abrasion resistance of the recording material and the like are more excellent and preferable.

[0083] 1.1.6 Other Components The clear ink composition may contain components such as additives, resin dispersants, antiseptic and antifungal agents, rust preventives, chelating agents, viscosity modifiers, antioxidants, etc. in addition to the above components as long as the functions are not impaired.

[0084] Examples of the additives include ureas, saccharides, etc. Examples of ureas include urea, ethylene urea, tetramethyl urea, thiourea, 1,3-dimethyl-2-imidazolidinone, etc., and betaines (trimethylglycine, triethylglycine, tripropylglycine, triisopropylglycine, N,N,N-trimethylalanine, N,N,N-triethylalanine, N,N,N-triisopropylalanine, N,N,N-trimethylmethylalanine, carnitine, acetylcarnitine, etc.). Examples of saccharides include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose, etc.

[0085] 1.2 Colored ink composition The ink set according to this embodiment has a colored ink composition, and the colored ink composition is an aqueous composition containing a colorant. Hereinafter, each component contained in the colored ink composition will be described.

[0086] 1.2.1 Colorant The colored ink composition contains a colorant. Examples of colorants include pigments and dyes.

[0087] (Pigment) As the pigment, for example, carbon black, inorganic pigments including titanium white, organic pigments, etc. can be used.

[0088] As inorganic pigments, carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, channel black, iron oxide, titanium oxide, zinc oxide, silica, etc. can be used.

[0089] Examples of carbon black include No. 2300, 900, MCF88, No. 20B, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No2200B, etc. manufactured by Mitsubishi Chemical Corporation. Examples of carbon black manufactured by Degussa include Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, Special Black 6, 5, 4A, 4, 250, etc. Examples of carbon black manufactured by Columbian Carbon include Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc. Examples of carbon black manufactured by Cabot include Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc.

[0090] Examples of organic pigments include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, or azo pigments, etc.

[0091] The colorant in the colored ink composition is preferably a quinacridone pigment. Quinacridone pigments are excellent in color development and weather resistance, while having a tendency to be redispersed by moisture. Therefore, when using a colored ink composition containing a quinacridone pigment, the wet rubbing resistance may be poor. On the other hand, according to the ink set according to this embodiment, even when using a colored ink composition containing a quinacridone pigment, a good wet rubbing resistance tends to be obtained.

[0092] Examples of quinacridone pigments include, for example, C.I. Pigment Red 122, 209, 202, C.I. Pigment Violet 19, C.I. Pigment Orange 48, 49, etc.

[0093] Specific examples of the organic pigments used in the colored ink composition include the following.

[0094] Examples of cyan pigments include C.I. Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc.; C.I. Vat Blue 4, 60, etc. Preferably, one or more mixtures selected from the group consisting of C.I. Pigment Blue 15:3, 15:4, and 60 can be exemplified.

[0095] Examples of magenta pigments include C.I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 112, 122, 123, 168, 184, 202, C.I. Pigment Violet 19, etc. Preferably, one or more mixtures selected from the group consisting of C.I. Pigment Red 122, 202, and 209, C.I. Pigment Violet 19 can be exemplified. A solid solution of the above pigments may also be used.

[0096] Examples of yellow pigments include C.I. Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 119, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, 185, etc. Preferably, one or more mixtures selected from the group consisting of C.I. Pigment Yellow 74, 109, 110, 128, 138, 155, and 180 can be exemplified.

[0097] Examples of orange pigments include C.I. Pigment Orange 36 or 43 or a mixture thereof. Examples of green pigments include C.I. Pigment Green 7 or 36 or a mixture thereof.

[0098] In addition, a fluorescent pigment may be used. There is no particular limitation as long as it can exhibit fluorescence when attached to a medium. For example, metal particles of one or more alloys (also referred to as metal pigments) selected from the group consisting of aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, and copper, and pearl pigments having a pearl luster can be mentioned. Representative examples of pearl pigments include pigments having a true pearl luster or an interference luster such as titanium dioxide-coated mica, fish scale foil, and bismuth oxychloride. Further, the fluorescent pigment may be subjected to a surface treatment for suppressing the reaction with water.

[0099] In addition, a white pigment may be used. For example, metal compounds such as metal oxides, barium sulfate, and calcium carbonate can be mentioned. Examples of metal oxides include titanium dioxide, zinc oxide, silica, alumina, magnesium oxide, and the like. Further, particles having a hollow structure may be used as the white pigment.

[0100] The above pigments may be used alone or in combination of two or more. The pigment is preferably an organic pigment from the viewpoint of storage stability such as light resistance, weather resistance, and gas resistance.

[0101] The volume average particle diameter (D50) of the pigment is such that the volume average particle (D50) measured by the dynamic light scattering method is 20 nm or more and 300 nm or less, more preferably the volume average particle diameter (D50) is 30 nm or more and 200 nm or less, and still more preferably the volume average particle diameter (D50) is 40 nm or more and 100 nm or less.

[0102] The measurement of the volume average particle diameter may be performed, for example, by using a NanoTrack series particle size distribution measuring device manufactured by MicrotracBEL Corporation. Further, as a method for adjusting the volume average particle diameter, for example, a method for adjusting the degree of pulverization of the pigment before dispersion, a method for adjustment by stirring conditions (for example, stirring speed, stirring temperature, etc.) during dispersion, a method for adjustment by filtration using a filter after dispersion, and the like can be mentioned.

[0103] ​The pigment may be dispersed and used with a pigment dispersant. Also, the pigment may be dispersed and used as a self-dispersing pigment by oxidizing or sulfonating the pigment surface with ozone, hypochlorous acid, fuming sulfuric acid, etc.

[0104] The pigment dispersant has a function of dispersing the pigment in the coloring ink composition. The pigment dispersant may be water-soluble, but those without complete water-solubility are preferred. It is considered that part or all of it binds or adsorbs to the pigment, enhancing the hydrophilicity of the pigment surface and thus dispersing the pigment. The pigment dispersant is preferably a high molecular compound, and more preferably a resin. In addition, the pigment dispersed by the pigment dispersant that is a resin is also particularly referred to as a resin-dispersed pigment.

[0105] Examples of the resin of the pigment dispersant include acrylic resins such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylate copolymer, vinyl acetate-(meth)acrylate copolymer, vinyl acetate-(meth)acrylic acid copolymer, vinyl naphthalene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, styrene-α-methylstyrene-(meth)acrylic acid-(meth)acrylate copolymer, etc., and their salts. In this specification, a polymer having a skeleton derived from (meth)acrylic acid and not having a skeleton derived from maleic acid or its similar compounds is referred to as an acrylic resin.

[0106] Also, examples of the resin of the pigment dispersant include maleic acid resins such as styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, etc., and their salts; urethane resins and their salts regardless of the presence or absence of a crosslinked structure; polyvinyl alcohols; resins such as vinyl acetate-crotonic acid copolymer and their salts.

[0107] In addition to the polymers of the acrylic monomers (acrylic monomers) as described above, the acrylic resin may also be a copolymer of an acrylic monomer and another monomer. For example, an acrylic vinyl resin that is a copolymer with a vinyl monomer as another monomer is also referred to as an acrylic resin. Also, for example, among the above styrene resins, those that are copolymers of a styrene monomer and an acrylic monomer are also included in the acrylic resins. Furthermore, when referring to an acrylic resin, its salts and esterified products are also included.

[0108] Examples of commercially available pigment dispersants include X-200, X-1, X-205, X-220, X-228 (manufactured by Starlight PMC Co., Ltd.), Nopcosperse (registered trademark) 6100, 6110 (manufactured by Sanshin Nopco Co., Ltd.), Joncryl 67, 586, 611, 678, 680, 682, 819 (manufactured by BASF), DISPERBYK-190 (manufactured by BYK Chemie Japan Co., Ltd.), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, E-EN10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), etc. Examples of commercially available acrylic pigment dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, BYK-199 (manufactured by BYK Chemie GmbH), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, CL-2 (manufactured by Toagosei Co., Ltd.), etc.

[0109] Examples of commercially available urethane pigment dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by BYK Chemie GmbH), TEGO Disperse 710 (manufactured by Evonic Tego Chemi), Borchi (registered trademark) Gen1350 (manufactured by OMG Borschers), etc.

[0110] Examples of commercially available urethane pigment dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by BYK Chemie GmbH), TEGO Disperse 710 (manufactured by Evonic Tego Chemi), Borchi (registered trademark) Gen1350 (manufactured by OMG Borschers), etc.

[0111] The pigment dispersant may be used alone or in combination of two or more. The total content of the pigment dispersant is 0.1% by mass or more and 30% by mass or less, preferably 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, based on 100% by mass of the colored ink composition. When the content of the pigment dispersant is 0.1% by mass or more, the dispersion stability of the pigment can be ensured. Also, when the content of the pigment dispersant is 30% by mass or less, the viscosity of the colored ink composition can be suppressed to be low.

[0112] Furthermore, the weight average molecular weight of the pigment dispersant is more preferably 500 or more. By using such a pigment dispersant, there is less odor and the dispersion stability of the pigment can be further improved.

[0113] When dispersing the pigment with a pigment dispersant, the ratio of the pigment to the pigment dispersant is preferably 10:1 to 1:10, more preferably 4:1 to 1:3.

[0114] A self-dispersing pigment refers to a pigment whose surface is surface-modified by the direct or indirect bonding of one or more functional groups selected from the group consisting of, for example, a carbonyl group, a carboxyl group, an aldehyde group, a hydroxyl group, a sulfone group, an ammonium group, and salts thereof.

[0115] Examples of self-dispersing pigments include organic pigments such as carbon black, azo lake, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dioxazine pigments, anthraquinone pigments, nitro pigments, nitroso pigments, and aniline black, and inorganic pigments such as titanium white, zinc white, lead white, carbon black-based, red iron oxide, vermilion, cadmium red, lead yellow, ultramarine blue, cobalt blue, cobalt violet, and zinc chromate.

[0116] Among these, the self-dispersing pigment is preferably carbon black from the viewpoint that it can print black at a high concentration and has further excellent ejection reliability.

[0117] As the self-dispersing pigment, a prepared product or a commercially available product prepared by a known method is used. Examples of commercially available products include "Micro Jet CW1" and "Micro Jet CW2" manufactured by Orient Chemical Industries, Ltd., and "CAB-O-JET 200" and "CAB-O-JET 300" manufactured by Cabot Corporation.

[0118] (Dye) In the colored ink composition, a dye may be used as a coloring material. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, basic dyes, and disperse dyes can be used.

[0119] The content of the coloring material is not particularly limited, but is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, still more preferably 1 to 8% by mass, still more preferably 1.5 to 6% by mass, and particularly preferably 2 to 5% by mass with respect to the total amount of the colored ink composition.

[0120] 1.2.2 Water The colored ink composition is an aqueous composition. The description of "aqueous" is the same as that in the above-described clear ink composition, and is described by reading "clear ink composition" as "colored ink composition".

[0121] The content of water may be the same as that of the above-described clear ink composition with respect to the total mass of the colored ink composition. Furthermore, 65% by mass or more is preferable, 80% by mass or more is more preferable, 90% by mass or more is still more preferable, and 95% by mass or more is particularly preferable. The upper limit of the water content is not particularly limited, but is preferably 99% by mass or less, and more preferably 98% by mass or less with respect to the total mass of the clear ink composition.

[0122] 1.2.3 Surfactant The colored ink composition may contain a surfactant. Examples of the surfactant include a silicone-based surfactant (a specific silicone-based surfactant) having a solubility of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2-hexanediol described above, and other surfactants other than the specific silicone-based surfactant. These surfactants are the same as those described in the above clear ink composition, and are described by replacing "clear ink composition" with "colored ink composition". In this embodiment, the clear ink composition is superposed and adhered to the region where the colored ink composition of the recording medium is adhered. Therefore, the colored ink composition layer is protected by the clear ink composition. For this reason, even when the surfactant contained in the colored ink composition is other than the specific silicone-based surfactant described above, the abrasion resistance of the recorded matter is less likely to be inferior. On the other hand, by containing other than the specific silicone-based surfactant in the clear ink composition for protecting the colored ink composition layer, excellent abrasion resistance of the recorded matter can be obtained. In addition, the degree of freedom in designing the composition of the colored ink composition is increased, which is preferable.

[0123] The content of the surfactant is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, further preferably 0.4% by mass or less, and particularly preferably 0.3% by mass or less with respect to the total mass of the colored ink composition. The lower limit of the content of the surfactant is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.10% by mass or more, and particularly preferably 0.15% by mass or more with respect to the total mass of the colored ink composition.

[0124] 1.2.4 Organic Solvent The colored ink composition may contain an organic solvent. The organic solvent is the same as that described in the above clear ink composition, and is described by replacing "clear ink composition" with "colored ink composition".

[0125] 1.2.5 Amine The colored ink composition may contain an amine. The description of the amine is the same as that in the clear ink composition described above, and is described by replacing "clear ink composition" with "colored ink composition".

[0126] 1.2.6 Other Components The colored ink composition used in the recording method according to this embodiment may contain other components. The other components are the same as those in the clear ink composition described above, and are described by replacing "clear ink composition" with "colored ink composition".

[0127] 1.3 Uses The ink set according to this embodiment is used for a recording method in which the above-described colored ink composition and clear ink composition are superposed and adhered to a recording medium by an inkjet method. As such a recording method, the recording method described later is preferable.

[0128] As a mode of superposing and adhering the colored ink composition and the clear ink composition to the recording medium by an inkjet method, for example, a mode of sequentially adhering the colored ink composition and the clear ink composition to the recording medium and laminating the colored ink composition and the clear ink composition (first adhesion mode), and a mode of simultaneously adhering the colored ink composition and the clear ink composition to the recording medium (second adhesion mode) can be mentioned. Details will be described later.

[0129] The recording medium is not particularly limited, and examples thereof include an absorbent recording medium, a low-absorbent recording medium, or a non-absorbent recording medium. From the viewpoint of more surely achieving the effects of the present invention, the material of the recording medium is preferably a non-absorbent or low-absorbent one, and more preferably a non-absorbent one.

[0130] The low-absorbent or non-absorbent recording medium refers to a recording medium having a property of not absorbing liquid at all or hardly absorbing it. Quantitatively, the low-absorbent or non-absorbent recording medium is one in which "the water absorption amount from the start of contact to 30 msec in the Bristow method is 10 mL / m" 1 / 2 up to 10 mL / m2 Refers to a "recording medium" as follows. This Bristow method is the most widespread method for measuring the liquid absorption amount in a short time and is also adopted by the Japan Paper Pulp Technology 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 Pulp Test Methods 2000 Edition". Note that, in contrast, an absorbent recording medium refers to a recording medium that does not correspond to a low-absorbency or non-absorbent recording medium.

[0131] Examples of low-absorbency recording media include recording media provided with a low-absorbency coating layer on the surface, which are called coated papers. For example, as those with a paper substrate, there are offset papers, coated papers, matte papers, etc. used for printing, and when the substrate is a plastic film, those with a polymer or the like coated on the surface of polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc., and those with particles such as silica and titanium coated together with a binder can be mentioned.

[0132] Examples of non-absorbent recording media include those with plastic coated on a substrate such as paper, those with a plastic film adhered to a substrate such as paper, and plastic films without an absorption layer (reception layer). Examples of the plastic include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc.

[0133] As the recording medium, a recording medium with a polyolefin-based film substrate having a surface roughness Sa of 0.3 μm or more on the surface to which ink is adhered may be used, and this is preferable. Such a recording medium is likely to generate fine powder when the surface is rubbed. Since the fine powder scratches the ink coating film in the image area, the dry rubbing resistance is likely to be poor. In contrast, according to the ink set according to this embodiment, even with such a recording medium, the dry rubbing resistance and wet rubbing resistance tend to be good. tend to be made good.

[0134] "Polyolefin-based" is a general term for polymers with alkenes (olefins) as monomers. For example, polyethylene, polypropylene, etc. can be mentioned.

[0135] "Surface roughness Sa" represents the average value of the absolute value of the height difference (z(x,y)) from the average plane of each measurement point in the reference area A, and is expressed by the following formula. The details of "surface roughness Sa" are defined in ISO25178. "Surface roughness Sa" is also referred to as "arithmetic mean height Sa". Sa = (1 / A) ∬ A |z(x,y)| dxdy

[0136] The surface roughness Sa can be measured, for example, using a laser microscope (VK-X1000 manufactured by Keyence) by a method compliant with ISO25178.

[0137] The surface roughness Sa of the surface to which the ink of the recording medium adheres is preferably 0.3 μm or more, more preferably 0.4 μm or more, still more preferably 0.5 μm or more, and particularly preferably 0.6 μm or more. The upper limit of the surface roughness Sa is not particularly limited, but is preferably 1.0 μm or less, and more preferably 0.8 μm or less.

[0138] The recording medium may contain inorganic particles on the surface of the base material. As the inorganic particles, for example, silica such as colloidal silica, titanium dioxide, aluminum oxide (alumina), zinc oxide, antimony oxide, magnesium oxide, zirconium oxide and other inorganic oxides, calcium carbonate and other inorganic carbonates, or calcium sulfate and other inorganic sulfates are preferably used, and mixtures thereof may also be used.

[0139] The shape of the inorganic particles may be, for example, spherical, rod-shaped, bead-shaped in which spherical particles are connected and combined, needle-shaped, or the like. Among these, spherical or rod-shaped is preferable, and spherical is particularly preferable.

[0140] The shape of the inorganic particles can be confirmed by observing with a scanning electron microscope. In the present invention, the term "spherical" means that when observed with a scanning electron microscope, it excludes the cases where bead-like, rod-like, needle-like shapes formed by continuous connection of primary particles are observed, and is not limited to a perfect sphere or an ellipsoidal sphere.

[0141] 2. Recording method The recording method according to an embodiment of the present invention is a recording method using the above-described ink set, and includes a step of attaching a colored ink composition to a recording medium by an inkjet method and a step of attaching a clear ink composition to the recording medium by an inkjet method, and the colored ink composition and the clear ink composition are attached to the recording medium in an overlapping manner.

[0142] Since the recording method according to the present embodiment uses the above-described ink set, it can be excellent in both dry rubbing resistance and wet rubbing resistance.

[0143] As a mode of attaching the colored ink composition and the clear ink composition included in the above-described ink set to the recording medium in an overlapping manner in the recording method according to the present embodiment, for example, the following two modes can be mentioned.

[0144] Here, the meaning of the terms in the recording method according to the present embodiment will be described. In this specification, when the colored ink composition and the clear ink composition are not particularly distinguished, they are simply referred to as "ink composition".

[0145] The "inkjet method" is a method of discharging droplets of ink or the like from the nozzles of an inkjet head and attaching them to a recording medium.

[0146] "Main scanning" refers to the operation of discharging an ink composition from an inkjet head while moving the relative position of the inkjet head with respect to a recording medium, and attaching the ink composition to the recording medium. The inkjet head can be mounted on a carriage, for example. The inkjet head may be moved by moving the carriage. In this case as well, it is the movement of the inkjet head.

[0147] "Main scanning direction" refers to the direction of movement of the relative position of the inkjet head with respect to the recording medium, and refers to the width direction of the recording medium. Note that "main scanning" is the movement of the relative position of the inkjet head with respect to the recording medium. The inkjet head may move with respect to the recording medium, or the recording medium may move with respect to the inkjet head. The direction of such relative movement is the main scanning direction. The movement of the relative position of the inkjet head with respect to the recording medium can also be referred to as the movement of the relative position of the recording medium with respect to the inkjet head. That is, it is the relative movement of the inkjet head and the recording medium.

[0148] "Sub-scanning" refers to the operation of moving the relative position of the inkjet head and the recording medium in the sub-scanning direction. "Sub-scanning direction" is a direction intersecting the main scanning direction. For example, by attaching an ink composition to a certain area of the recording medium during main scanning, moving the recording medium slightly during sub-scanning, and then performing the next main scanning, the operation of attaching the ink composition adjacent to or partially overlapping the previously attached ink composition is repeated to perform recording. Note that "sub-scanning" is also the movement of the relative position of the inkjet head with respect to the recording medium. The inkjet head may move with respect to the recording medium, or the recording medium may move with respect to the inkjet head. The direction of such relative movement is the sub-scanning direction.

[0149] It is preferable to perform recording by performing main scanning and sub-scanning a plurality of times respectively. For example, main scanning and sub-scanning may be alternately repeated.

[0150] 2.1 First Attachment Mode The first attachment mode is a mode in which a colored ink composition and a clear ink composition are sequentially attached to a recording medium and the colored ink composition and the clear ink composition are laminated. It is also referred to as laminated printing or laminated printing. In this mode, in the colored ink attachment step and the clear ink attachment step described later, a colored ink image formed by the colored ink composition and a clear ink image formed by the clear ink composition are formed by overlapping them on the recording medium.

[0151] When implementing the first attachment mode, for example, the colored ink composition and the clear ink composition are attached to the same scanning area of the recording medium by different main scans, so that a layer containing the colored ink composition and a layer containing the clear ink composition are laminated and formed.

[0152] Note that in the first attachment mode, it is preferable to first attach the colored ink composition to the recording medium and then attach the clear ink composition from above the layer of the colored ink composition.

[0153] In the first attachment mode, different main scans for attaching the colored ink composition and the clear ink composition to the same scanning area may be performed a plurality of times respectively. For example, it is conceivable to record the colored ink composition in 4 passes and then record the clear ink composition in 4 passes.

[0154] 2.2 Second Attachment Mode The second attachment mode is a mode in which a colored ink composition and a clear ink composition are simultaneously attached to a recording medium. It is also referred to as simultaneous printing or simultaneous printing. In this mode, in the colored ink attachment step and the clear ink attachment step described later, a main scan is performed in which the ink composition is ejected while moving the relative position of the inkjet head with respect to the recording medium to attach it to the recording medium. The main scan attaches the colored ink composition and the clear ink composition to the same scanning area of the recording medium by the same main scan.

[0155] In the second attachment mode, since it is not necessary to laminate layers of ink compositions such as a layer of a colored ink composition and a layer of a clear ink composition, the recording speed can be improved.

[0156] When implementing the second attachment mode, for example, by attaching the colored ink composition and the clear ink composition to the same scanning area of the recording medium by the same main scanning, a layer including the colored ink composition and the clear ink composition is formed. That is, the colored ink attachment step and the clear ink attachment step are performed by the same main scanning.

[0157] In the second attachment mode, the main scanning for attaching the colored ink composition and the clear ink composition to the scanning area may be performed a plurality of times on the same area. That is, after a layer including the colored ink composition and the clear ink composition is attached to a certain area on the recording medium by a certain main scanning, it is preferable to further attach a layer including the colored ink composition and the clear ink composition on it by another main scanning. In this case, the main scanning for attaching the colored ink composition and the clear ink composition passes a plurality of times over the same area. The more the number of scans, the more the ink can be attached to the desired area in multiple times (multiple passes), and the image quality of the obtained recording tends to be more improved.

[0158] When recording an arbitrary area, the number of times the inkjet head passes over that area is referred to as the "number of passes". For example, when performing four main scans to attach a colored ink composition and a clear ink composition over the same area, the number of passes is referred to as four passes. For example, if the length of one sub-scan in the sub-scanning direction is one-fourth of the length of the nozzle array arranged in the sub-scanning direction of the inkjet head in the sub-scanning direction, for a rectangular scanning area that extends in the main scanning direction with a length of one sub-scan in the sub-scanning direction, four main scans are performed on the same portion (the same scanning area). The number of scans when viewed in this way is referred to as the number of scans, or the number of passes, etc. The number of scans is 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and particularly preferably 8 or more. It is preferable that the above range or more is satisfied in terms of excellent image quality. The upper limit is not limited, but preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, and still more preferably 4 or less. It is preferable that the above range or less is satisfied in terms of high recording speed. Note that the above number of scans is provided for each ink type.

[0159] 2.3 Colored Ink Attachment Step The recording method according to this embodiment includes a step of attaching a colored ink composition to a recording medium by an inkjet method (colored ink attachment step).

[0160] The amount of the colored ink composition attached is preferably 2.0 to 20 mg / inch per unit area of the area on the recording medium where the colored ink composition is attached (hereinafter, also referred to as the "attachment area of the colored ink composition"). 2 More preferably, it is 3.0 to 10 mg / inch 2 More preferably still, it is 6.0 to 8.0 mg / inch 2 It is. Also, among the amounts of the colored ink composition attached, it is also preferably good that the maximum amount of attachment is within the above range.

[0161] The maximum weight range per drop of the droplets of the colored ink composition is preferably 0.5 to 20 ng, preferably 0.5 to 15 ng, and more preferably 1 to 10 ng More preferably, it is 3 to 9 ng, and particularly preferably 5 to 8 ng.

[0162] 2.4 Clear Ink Adhesion Step The recording method according to the present embodiment includes a step of adhering a clear ink composition to a recording medium by an inkjet method (clear ink adhesion step).

[0163] The adhesion amount of the clear ink composition is preferably 2.0 to 20 mg / inch per unit area of the region where the colored ink composition and the clear ink composition are overlapped and adhered on the recording medium (hereinafter, also referred to as "image adhesion region of the clear ink composition"). 2 More preferably, it is 3.0 to 10 mg / inch 2 Even more preferably, it is 6.0 to 8.0 mg / inch 2 Moreover, among the adhesion amounts of the clear ink composition, it is very preferable that the maximum adhesion amount is within the above range.

[0164] In the image adhesion region of the clear ink composition, the ratio of the adhesion amount of the clear ink composition to the adhesion amount of the colored ink composition (adhesion amount of the clear ink composition / adhesion amount of the colored ink composition) is preferably 0.1 to 2, more preferably 0.5 to 1.8, even more preferably 0.7 to 1.6, particularly preferably 1.0 to 1.4, and very particularly preferably 1.1 to 1.2. When the ratio of the adhesion amounts is within the above range, the dry rubbing resistance and wet rubbing resistance tend to be excellently balanced.

[0165] The maximum weight range per drop of the droplets of the clear ink composition is preferably 0.5 to 20 ng, preferably 0.5 to 15 ng, more preferably 1 to 10 ng, even more preferably 3 to 9 ng, and particularly preferably 5 to 8 ng.

[0166] The recording method according to the present embodiment may include a step of adhering a clear ink composition to a region (non-image portion) of the recording medium where the colored ink composition is not adhered.

[0167] In particular, in the case of a recording medium that is a polyolefin-based film substrate with a surface roughness Sa of the surface to which the ink adheres being 0.3 μm or more, fine powder is likely to be generated when the surface of the non-image area is rubbed. Since this fine powder scratches the ink coating film in the image area, the dry rub resistance is likely to be poor. Therefore, by applying a clear ink composition to the non-image area, it is possible to reduce the fine powder generated from the surface of the non-image area and improve the dry rub resistance. On the other hand, when a clear ink composition is applied to the non-image area, it peels off due to moisture such as humidity, and promotes the redispersion of the ink coating film in the image area, so the wet rub resistance tends to deteriorate. In contrast, according to the recording method according to the present embodiment, while enjoying the effect of improving the dry rub resistance by applying a clear ink composition to the non-image area, there is a tendency to maintain good wet rub resistance.

[0168] The adhesion amount of the clear ink composition in the area where the colored ink composition of the recording medium is not adhered is preferably 2.0 to 20 mg / inch per unit area. 2 More preferably, it is 4.0 to 12 mg / inch. 2 Even more preferably, it is 7.0 to 9.0 mg / inch. 2 That is.

[0169] It is preferable that the adhesion amount of the clear ink composition in the area (non-image area) where the colored ink composition of the recording medium is not adhered and the clear ink composition is adhered is not more than the adhesion amount of the clear ink composition in the area (image area) where the colored ink composition and the clear ink composition of the recording medium are overlapped and adhered. Specifically, the ratio (non-image area clear ink composition adhesion amount / image area clear ink composition adhesion amount) of the adhesion amount of the clear ink composition in the area where the colored ink composition and the clear ink composition of the recording medium are overlapped and adhered (clear ink composition adhesion amount in the image area) to the adhesion amount of the clear ink composition in the area where the colored ink composition of the recording medium is not adhered and the clear ink composition is adhered (clear ink composition adhesion amount in the non-image area) is preferably 0.1 to 1.0, more preferably 0.3 to 1.0, still more preferably 0.5 to 1.0, particularly preferably 0.7 to 1.0, and even more particularly preferably 0.9 to 1.0. In the case of such an adhesion amount relationship, a decrease in wet rubbing resistance can be reduced, and there is a tendency to balance and improve wet rubbing resistance and dry rubbing resistance well.

[0170] 2.5 Primary drying process The recording method according to the present embodiment may include a primary drying process of drying the ink composition adhered to the recording medium by a drying mechanism. The primary drying process is a process of heating the recording medium before the ink adhesion process, or performing heating, blowing, etc. on the recording medium during the ink adhesion process or at an early stage after the ink adheres to the recording medium to dry the ink early. The primary drying process is a 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. The primary drying process may be such that the ink is adhered to the heated recording medium, or may be performed at an early stage after adhesion to promote drying. In the primary drying process, it is preferable that drying of the ink droplets landing on the recording medium starts within 0.5 seconds at the latest from the landing of the ink droplets. The drying unit (drying mechanism) for drying the ink on the recording medium is not particularly limited, and examples include a platen heater, a hot air heater, an IR heater, etc. having a heating function, and a blower, etc. not having a heating function.

[0171] As types of drying mechanisms, there are a conduction type that conducts heat from a member in contact with the recording medium to the recording medium to heat the recording medium, a radiation type that radiates radiation such as IR to the recording medium to heat the recording medium, a blowing type that blows air toward the recording medium, and the like.

[0172] The blowing type includes a method of heating the recording medium while blowing warm air, and a method of promoting the drying of ink with normal-temperature air without heating. In the case of the method without heating, it is preferable because it can suppress the drying of the ink in the nozzles of the inkjet head and the deterioration of the ejection stability. It is also preferable to use either the conduction type or the radiation type in combination with the blowing type. When used in combination, the blowing type may be a method without heating, which is preferable.

[0173] In the primary drying process, the surface temperature of the recording medium is preferably 60°C or lower, more preferably 55°C or lower. Further, it is more preferably 30 to 50°C, and still more preferably 40 to 45°C. On the other hand, it is more preferably 40°C or lower, still more preferably 35°C or lower, particularly preferably 30°C or lower, and even more preferably 25 to 28°C. When the surface temperature of the recording medium is within the above range, the drying property is further improved, and the abrasion resistance of the obtained recording tends to be further improved. Also, the clogging recovery property, ejection stability, and color development property are more excellent and preferable. It is also possible not to perform the primary drying process or not to perform a process involving heating as the primary drying process. In this case as well, the surface temperature of the recording medium on the platen may be below the above range.

[0174] When using the blowing type, the wind speed near the recording medium is preferably 0.5 to 10 m / s, more preferably 1 to 5 m / s, and still more preferably 2 to 3 m / s. The wind temperature is preferably 45°C or lower, more preferably 40°C or lower, still more preferably 32°C or lower, and particularly preferably 20 to 27°C.

[0175] 2.6 Secondary heating process The recording method according to this embodiment may have a heating step (secondary heating step) of heating a recording medium to which a coloring ink composition and a clear ink composition are attached. The secondary heating step is a step of sufficiently heating to complete the recording and make the recorded matter usable. Further, the secondary heating step is a step for sufficiently drying the solvent component of the ink and heating a resin or the like contained in the ink to flatten the ink coating film.

[0176] The secondary heating step is preferably started more than 0.5 seconds after the ink is attached to the recording medium. For example, it is preferable to start heating the recording area after more than 0.5 seconds from the completion of the attachment of the ink to a certain recording area of the recording medium.

[0177] The surface temperature of the recording medium in the secondary heating step is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. In the secondary heating step, especially when the surface temperature of the recording medium is heated at 60°C or higher, the drying property is excellent and the wet rubbing resistance tends to be better. As the secondary heating mechanism, a conduction type, a radiation type, a blowing type, or the like can be used.

[0178] 2.7 Recording apparatus An example of a recording apparatus suitable for the recording method according to this embodiment will be described with reference to the drawings.

[0179] FIG. 1 is a schematic cross-sectional view schematically showing an inkjet recording apparatus 1. FIG. 2 is a perspective view showing an example of the configuration around the carriage of the inkjet recording apparatus 1 in FIG. 1. As shown in FIGS. 1 and 2, the inkjet recording apparatus 1 includes an inkjet 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.

[0180] The inkjet head 2 has an inkjet head 2a that discharges a colored ink composition and an inkjet head 2b that discharges a clear ink composition, and recording can be performed on the recording medium M by discharging and attaching the colored ink composition and the clear ink composition from the nozzles of the respective inkjet heads.

[0181] In this embodiment, the inkjet head 2 is a serial type inkjet head, and scans the recording medium M a plurality of times in the main scanning direction relative to the recording medium M to attach the colored ink composition and the clear ink composition to the recording medium M. The inkjet head 2 is mounted on the carriage 9 shown in FIG. 2. The inkjet 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 inkjet head 2. Scanning in the main scanning direction is also referred to as main scanning.

[0182] FIG. 3 shows an arrangement in which the inkjet head 2a that discharges the colored ink composition and the inkjet head 2b that discharges the clear ink composition are arranged side by side horizontally at the same position with respect to the conveyance direction (T2 direction) of the recording medium M. For example, with such an arrangement, the colored ink composition and the clear ink composition can be superposed and attached in a mode (second attachment mode) in which they are simultaneously attached to the recording medium. Note that the nozzle rows shown in FIG. 3 are the nozzle rows for discharging ink in each inkjet head.

[0183] FIG. 4 shows an arrangement in which the inkjet head 2b that discharges the clear ink composition is arranged downstream of the inkjet head 2a that discharges the colored ink composition with respect to the conveyance direction (T2 direction) of the recording medium M. For example, with such an arrangement, the colored ink composition and the clear ink composition can be attached to the recording medium in order, and superposed and attached in a mode (first attachment mode) in which the colored ink composition and the clear ink composition are laminated. Note that the nozzle rows shown in FIG. 4 are the nozzle rows for discharging ink in each inkjet head.

[0184] Here, the main scanning direction is the direction in which the carriage 9 equipped with the inkjet head 2 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 inkjet 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. That is, the coloring ink adhesion step and the clear ink adhesion step are performed by a plurality of main scans in which the inkjet head 2 moves in the main scanning direction and a plurality of sub-scans in which the recording medium M moves in the sub-scanning direction intersecting the main scanning direction.

[0185] The cartridge 12 that supplies each ink to the inkjet head 2 includes a plurality of independent cartridges. The cartridge 12 is detachably attached to the carriage 9 equipped with the inkjet head 2. Each of the plurality of cartridges can be filled with a different type of ink, and the ink is supplied from the cartridge 12 to each nozzle. Note that in this embodiment, an example where the cartridge 12 is attached to the carriage 9 is shown, but it is not limited thereto, and it may be provided at a location other than the carriage 9 and supplied to each nozzle by a supply pipe (not shown).

[0186] A conventionally known method can be used for the ejection of the inkjet head 2. In this embodiment, a method of ejecting droplets by utilizing the vibration of a piezoelectric element, that is, an ejection method of forming ink droplets by the mechanical deformation of an electrostrictive element is used.

[0187] The inkjet recording apparatus 1 includes a ventilation fan 8, an IR heater 3, and a platen heater 4 for drying the ink discharged from the inkjet head 2 and adhering to the recording medium M. By appropriately combining and using these, the ventilation fan 8, the IR heater 3, and the platen heater 4, a primary drying process can be performed. In the primary drying process, it is not necessarily required to heat the recording medium M, and the ventilation fan 8 may be used alone for performing blowing at room temperature.

[0188] Note that when the IR heater 3 is used, the recording medium M can be heated in a radiative manner by infrared radiation from the side of the inkjet head 2. As a result, the inkjet head 2 is also likely to be heated simultaneously, but it can be heated without being affected by the thickness of the recording medium M as compared with the case where it is heated from the back surface of the recording medium M such as the platen heater 4. Also, various fans (for example, the ventilation fan 8) that blow warm air or air at the same temperature as the environment onto the recording medium M to dry the ink on the recording medium M may be provided.

[0189] The platen heater 4 can heat the recording medium M via the platen 11 at a position facing the inkjet head 2 so that the ink discharged by the inkjet head 2 can be dried early when it adheres to the recording medium M. The platen heater 4 can heat the recording medium M in a conductive manner, and the ink can be adhered to the heated recording medium M.

[0190] Note that the surface temperature of the recording medium M due to the heating of the IR heater 3 and the platen heater 4 is preferably within the range described in the above primary drying process.

[0191] The heating heater 5 is a heater for secondary heating that dries and solidifies the ink adhered to the recording medium M. The heating heater 5 can be used in the secondary heating process. By heating the recording medium M on which an image is recorded with the heating heater 5, moisture and the like contained in the ink evaporate and disperse more quickly, and an ink film is formed by the resin contained in the clear ink composition. In this way, the ink film firmly adheres or adheres on the recording medium M to have excellent film-forming properties, and an excellent high-quality image can be obtained in a short time.

[0192] The surface temperature of the recording medium M due to the heating of the heating heater 5 is preferably in the range described in the above-mentioned secondary heating process. When the temperature is in the above-mentioned range, a high-quality image tends to be obtained in a short time.

[0193] The inkjet recording apparatus 1 may have a cooling fan 6. After drying the ink recorded on the recording medium M, by cooling the ink on the recording medium M with the cooling fan 6, an ink coating film can be formed with good adhesion on the recording medium M.

[0194] Further, the inkjet recording apparatus 1 may include a preheater 7 that preheats the recording medium M before the ink is adhered to the recording medium M. Furthermore, the inkjet recording apparatus 1 may include a ventilation fan 8 so that the ink adhered to the recording medium M dries more efficiently.

[0195] Below the carriage 9, there are provided a platen 11 that supports the recording medium M, a carriage moving mechanism 13 that relatively moves the carriage 9 with respect to the recording medium M, and a conveying means 14 that is a roller for conveying the recording medium M in the sub-scanning direction. The operations of the carriage moving mechanism 13 and the conveying means 14 are controlled by the control unit CONT.

[0196] In another embodiment, the inkjet recording apparatus may be a line type inkjet recording apparatus in which the inkjet head 2 is a line head. For example, in FIG. 1, the inkjet head 2 is a line head having a length equal to or greater than the recording width in the width direction of the recording medium, and its position is fixed. Ink is ejected from the inkjet head 2 onto the conveyed recording medium M and adheres to the recording medium. In this case, recording is performed by one main scan. When the inkjet head 2 is a line head, other configurations may be the same as those in the above-described serial type case.

[0197] 3. Examples Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Hereinafter, “%” is based on mass unless otherwise specified.

[0198] 3.1 Preparation of Colored Ink Composition and Clear Ink Composition For the colored ink composition and the clear ink composition used in each example or each comparative example, for the clear ink composition, each component is put into a container so as to have the composition shown in Table 1 (FIG. 5), and for the colored ink composition, so as to have the composition shown in Table 2 (FIG. 6). Pure water is added so that the total amount of each composition is 100% by mass, and after mixing and stirring with a magnetic stirrer for 2 hours, further, dispersion treatment is performed with a bead mill filled with zirconia beads having a diameter of 0.3 mm to mix sufficiently, and after stirring for 1 hour, it is obtained by filtering using a 5 μm PTFE membrane filter. The units of the numerical values in Tables 1 and 2 are% by mass.

[0199] Note that the colorant used in the preparation of the colored ink composition was previously mixed with water at a mass ratio of 2:1 (pigment: pigment dispersant), which is a water-soluble styrene-acrylic resin (not shown in the table), and stirred well to prepare a pigment dispersion liquid, which was used in the preparation of the ink. In addition, the colorant column shows the mass% of the pigment converted from the solid content concentration of the pigment dispersion liquid. Table 1 shows the net added amount of the solid content of the resin emulsion.

[0200] The surfactant of "Example 1" described in Table 1 was synthesized as follows.

[0201] Using the compound of the aforementioned formula (A) and the compound of formula (B), the surfactant of formula (1) was synthesized. Hexaethylene glycol monoallyl ether (in formula (B), c is 6, R 6 is an ethylene group, and R 7 is a hydroxy group) 7.0 g of a 20 mL solution of tetrahydrofuran was added with 5.8 g of the compound of b = 7 of formula (A) and 0.1 mL of chloroplatinic acid, and the mixture was maintained at 65 °C for 24 hours with stirring to cause a reaction. After completion of the reaction, the solvent was distilled off by rotary evaporation to obtain a silicone-based surfactant (Example 1). Similarly, by changing b of formula (A), a silicone-based surfactant (Example 2) was obtained.

[0202] The structure of the silicone-based surfactant (Example 1) is, in formula (1); a = 7, x, y = 3, n, m = 7, o, p = 0, R 1 and R 2 = hydroxy group, is.

[0203] The structure of the silicone-based surfactant (Example 2) is, in formula (1); a = 17, x, y = 3, n, m = 7, o, p = 0, R 1 and R 2 = hydroxy group, is.

[0204] The descriptions of the matters in Table 1 and Table 2 are supplemented as follows.

[0205] <Surfactant> · BYK3420 (a silicone surfactant with a solubility of 2.5 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, having a maximum peak at a molecular weight of 1610 in the molecular weight distribution in GPC, trade name manufactured by BYK - Chemie Japan) · The silicone surfactant of (Example 1) (a silicone surfactant with a solubility of 2.9 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, having a maximum peak at a molecular weight of 1300 in the molecular weight distribution in GPC) · The silicone surfactant of (Example 2) (a silicone surfactant with a solubility of 1.7 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, having a maximum peak at a molecular weight of 2000 in the molecular weight distribution in GPC) · BYK333 (a silicone surfactant with a solubility of 0.7 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, having a maximum peak at a molecular weight of 4000 - 7000 in the molecular weight distribution in GPC, trade name manufactured by BYK - Chemie Japan) · BYK348 (a silicone surfactant with a solubility of 5 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol, having a maximum peak at a molecular weight of 1540 in the molecular weight distribution in GPC, trade name manufactured by BYK - Chemie Japan)

[0206] The measurement conditions for GPC measurement of the surfactant were as follows. 〔Measurement conditions〕 · Solvent: Tetrahydrofuran · Column: TSKgel SuperHZM - N × 2 · + TSKgel guardcolumn SuperHZ - L · Column temperature: 40 °C · Injection volume: 25 μL · Detector: Differential refractive index (RI) · Flow rate: 0.35 mL / min · Calibration curve: A calibration curve was used with 13 samples of standard polystyrene STK (manufactured by Tosoh Corporation) with Mw ranging from 1,000,000 to 500.

[0207] <Neutralizing agent (amine)> · TEA (triethanolamine, standard boiling point: 335 °C) · TPA (triisopropanolamine, standard boiling point: 305 °C)

[0208] <Resin> · Mobinyl 6969D (acrylic resin emulsion, glass transition temperature 71 °C, trade name of Nippon Synthetic Chemical Industry Co., Ltd.) · Mobinyl 6899D (acrylic resin emulsion, glass transition temperature 49 °C, trade name of Nippon Synthetic Chemical Industry Co., Ltd.)

[0209] 3.2 Printing conditions The records in the evaluation test were made under the following conditions. Printer: Modified SurePress L-4533AW (manufactured by Seiko Epson Corporation) Resolution: 1440 × 1440 dpi Printing pattern: Solid pattern in the image area, and the entire recordable area in the non-image area Color condition: 7 mg / inch 2 , Iw = 6 ng / dot Clear condition: Adhesion amount described in Tables 3 and 4, Iw = 6 ng / dot Scanning times: Described in Tables 3 and 4 Surface temperature of the recording medium on the platen (primary drying process): 45 °C as the surface temperature of the recording medium Secondary heating temperature (drying oven temperature): Described in Tables 3 and 4 Recording medium: Described in Tables 3 and 4

[0210] Note that the "solid pattern" means a pattern in which dots are recorded for all pixels of the pixels, which are the minimum recording unit areas defined by the recording resolution. The "secondary heating temperature" is the surface temperature on the recording medium where the secondary heating process is performed after passing through the platen.

[0211] In Table 3 (Fig. 7), Table 4 (Fig. 8); "Substrate 1" is "YUPO#80" (product name made by Yupo Corporation). The recording medium is a polypropylene film substrate having a surface roughness Sa of 0.6 μm on the surface to which the ink is applied. "Substrate 2" represents a recording medium called "PET50A" (product name manufactured by Lintec Corporation), which is a PET-based film substrate having a surface roughness Sa of 0.02 μm on the surface to which ink is applied. The surface roughness Sa was measured using a laser microscope (VK-X1000 / manufactured by Keyence) according to a method conforming to ISO 25178. The objective lens magnification was 20x, and the average value of n=3 measurements was used. "Op" represents a clear ink composition. "Ma" represents a colored ink composition. The "image area" refers to an area on a recording medium where the color ink composition and the clear ink composition are applied in an overlapping manner. The "non-image area" refers to an area of ​​the recording medium to which the color ink composition is not applied, and refers to the entire recorded area of ​​the recording medium other than the image area that is adjacent to the periphery of the color ink image. "Separate passes" refers to an embodiment in which the colored ink composition and the clear ink composition are applied in sequence to a recording medium, and the colored ink composition and the clear ink composition are layered, and the colored ink composition and the clear ink composition are applied to the same scanned area of ​​the recording medium by different main scans. "Same pass" refers to an embodiment in which the color ink composition and the clear ink composition are applied to a recording medium at the same time, and the color ink composition and the clear ink composition are applied to the same scanning area of ​​the recording medium by the same main scan.

[0212] 3.3 Evaluation Test 3.3.1 Dry rub resistance The obtained colored ink composition and clear ink composition were filled into a printing machine. After printing a solid pattern on a recording medium under the above printing conditions, it was left at room temperature overnight. Then, the solid pattern printed area was cut into a 30×200 mm rectangle, and the degree of ink peeling when rubbed 50 times with a Kagaku Shimbun type rubbing tester (load 500 g) using a plain woven fabric was visually evaluated. (Judgment criteria) A: No peeling B: Peeling exists in less than 10% of the evaluation area C: Peeling exists in 10% or more and less than 50% of the evaluation area D: Peeling exists in 50% or more of the evaluation area (NG)

[0213] 3.3.2 Wet rub resistance The obtained colored ink composition and clear ink composition were filled into a printing machine. After printing a solid pattern on a recording medium under the above printing conditions, it was left at room temperature overnight. Then, the solid pattern printed area was cut into a 30×200 mm rectangle, 5 drops of water were dropped onto a plain woven fabric, and the degree of ink peeling when rubbed 50 times with a Kagaku Shimbun type rubbing tester (load 500 g) was visually evaluated. (Judgment criteria) A: No peeling B: Peeling exists in less than 10% of the evaluation area C: Peeling exists in 10% or more and less than 50% of the evaluation area D: Peeling exists in 50% or more of the evaluation area (NG)

[0214] 3.3.3 Clogging recovery The obtained colored ink composition and clear ink composition were filled into a printing machine, and non-discharge was intentionally caused in the nozzles. In this state, it was run idle for 90 minutes under the above printing conditions. After recording, cleaning was performed 3 times, and finally, the degree of nozzle non-discharge was judged according to the following criteria. One cleaning discharged 1 g of ink from the nozzle row. Note that nozzle non-discharge was caused by tapping the nozzle surface with a bent cot moistened with water. (Judgment criteria) A: No nozzle non-discharge B: Nozzle non-discharge is less than 3% of all nozzles C: The non-discharge of nozzles is more than 3% and less than 5% of all nozzles D: The non-discharge of nozzles is 5% or more of all nozzles

[0215] 3.3.4 Discharge stability The obtained colored ink composition and clear ink composition were filled into a printing machine, and image recording was continuously performed for 1 hour under the above printing conditions. After the recording, the nozzles of the discharged nozzle group were inspected. The total number of non-discharged nozzles was divided by the total number of nozzles and evaluated according to the following criteria. (Judgment criteria) A: 1% or less of non-discharged nozzles B: More than 1% and 2% or less of non-discharged nozzles C: More than 2% and less than 5% of non-discharged nozzles D: 5% or more of non-discharged nozzles

[0216] 3.3.5 Ink activator separation 30 g of each ink composition obtained above was sealed in a sample tube and left in a 70°C constant temperature bath for 6 days. Immediately after taking it out and after natural cooling, it was observed whether the activator was separated from the ink to form two layers, and evaluated according to the following criteria. (Judgment criteria) A: Not separated even immediately after taking out B: Separated immediately after taking out, but redissolved after cooling for a few minutes C: Separated immediately after taking out, but redissolved after cooling for several tens of minutes D: Separated immediately after taking out and does not redissolve even after some time

[0217] 3.3.6 Color development property The obtained colored ink composition and clear ink composition were filled into a printing machine, and a solid pattern was printed under the above printing conditions. The c * value (c * =(a *2 +b *2 ) 1 / 2 ) of the printed matter was measured and evaluated according to the following criteria. The measuring device used was "i1Pro2" (manufactured by X-reite), and the measuring conditions were a D50 light source, Status T, and a standard observer of 2°. (Judgment Criteria) A: c * The value is large. Taking the pattern of Example 1 as 100%. B: c * The value is that of c in Judgment A * 90% or more and less than 100% C: c * The value is that of c in Judgment A * 80% or more and less than 90% D: c * The value is that of c in Judgment A * Less than 80%

[0218] 3.4 Evaluation Results The evaluation results are shown in Tables 3 and 4.

[0219] From the results described in Tables 3 and 4, an ink set having a colored ink composition and a clear ink composition, which is used in a recording method in which the colored ink composition and the clear ink composition are superposed and adhered to a recording medium by an inkjet method. The colored ink composition is an aqueous composition containing a coloring material, and the clear ink composition is an aqueous composition containing a resin and a silicone surfactant in which the dissolution amount in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol is 1.0 to 3.0 parts by mass, was excellent in both dry rub resistance and wet rub resistance.

[0220] On the other hand, in each comparative example that does not satisfy the above configuration, it was inferior in at least either dry rub resistance or wet rub resistance.

[0221] The evaluation results are supplemented and explained as follows. In Example 4, although the clear ink composition was not adhered to the non - image area, since Substrate 2 was used, there was no generation of fine powder in the non - image area of the recording medium, and there was no influence on the deterioration of dry rub resistance. On the other hand, in Example 10, since Substrate 1 was used, when the clear ink composition was not adhered to the non - image area, fine powder was generated in the non - image area of the recording medium, and the dry rub resistance deteriorated.

[0222] ​In Reference Example 1, since the clear ink composition did not contain a surfactant, the ejection stability was poor and it was difficult to apply the inkjet method. However, problems regarding dry rub resistance and wet rub resistance did not occur. Although not described in the table, when evaluated in the same manner as the examples in the table except that the surface temperature of the recording medium in the primary drying step was set to 30°C in each example, the rub resistance in each example was the same as the results of the examples in the table, and the clogging recovery and ejection stability were improved. Excellent rub resistance was obtained even when the surface temperature of the recording medium in the primary drying step was made lower.

[0223] The following content is derived from the above-described embodiments.

[0224] One aspect of an ink set is an ink set having a colored ink composition and a clear ink composition, which is used in a recording method of overlapping and attaching the colored ink composition and the clear ink composition to a recording medium by an inkjet method, wherein the colored ink composition is an aqueous composition containing a coloring material, and the clear ink composition is an aqueous composition containing a resin and a silicone-based surfactant having a dissolution amount of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2-hexanediol.

[0225] In one aspect of the above ink set, the content of the silicone-based surfactant may be 0.3% by mass or less based on the total mass of the clear ink composition.

[0226] In any aspect of the above ink set, the recording medium may be a polyolefin-based film substrate having a surface roughness Sa of 0.3 μm or more on the surface to which the ink is attached.

[0227] In any aspect of the above ink set, the clear ink composition may contain an amine having a standard boiling point of 250°C or higher.

[0228] In any aspect of the above ink set, the content of the amine may be 0.4% by mass or less based on the total mass of the clear ink composition.

[0229] In any aspect of the above ink set, the glass transition temperature Tg of the resin contained in the clear ink composition may be 60°C or higher.

[0230] In any aspect of the above ink set, the colorant contained in the colored ink composition may be a quinacridone-based pigment.

[0231] In any aspect of the above ink set, the silicone-based surfactant may be a silicone-based surfactant having a maximum peak in the range of a molecular weight of 1000 to 3000 in the molecular weight distribution in gel permeation chromatography.

[0232] One aspect of the recording method is a recording method performed using the ink set of any of the above aspects, a step of attaching the colored ink composition to a recording medium by an inkjet method, a step of attaching the clear ink composition to the recording medium by an inkjet method, and the colored ink composition and the clear ink composition are overlapped and attached on the recording medium.

[0233] In one aspect of the above recording method, it may have a step of attaching the clear ink composition to a region of the recording medium where the colored ink composition is not attached.

[0234] In one aspect of the above recording method, The amount of the clear ink composition adhered to the region where the clear ink composition is adhered without adhering the colored ink composition of the recording medium may be equal to or less than the amount of the clear ink composition adhered to the region where the colored ink composition and the clear ink composition of the recording medium are superposed and adhered.

[0235] In any aspect of the above recording method, The recording medium to which the colored ink composition and the clear ink composition are adhered may have a heating step of heating the recording medium at a surface temperature of 60 ° C or higher.

[0236] 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 embodiment, for example, a configuration having the same functions, methods, and results, or a configuration having the same purpose and effects. Further, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment 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 embodiment.

Explanation of reference numerals

[0237] 1... Inkjet recording apparatus, 2... Inkjet head (2a... Inkjet head for discharging colored ink composition, 2b... Inkjet head for discharging clear ink composition), 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, CONT... Control unit, MS... Main scanning direction, SS... Sub-scanning direction, M... Recording medium.

Claims

1. An ink set comprising a colored ink composition and a clear ink composition, which is used in a recording method of laminating and adhering the colored ink composition and the clear ink composition to a recording medium by an inkjet method, wherein the colored ink composition is an aqueous composition containing a coloring material, and the clear ink composition is an aqueous composition containing a resin and a silicone surfactant having a solubility of 1.0 to 3.0 parts by mass in 100 parts by mass of a 3% by mass aqueous solution of 1,2 - hexanediol.

2. The ink set according to claim 1, wherein the content of the silicone surfactant is 0.3% by mass or less based on the total mass of the clear ink composition.

3. The ink set according to claim 1, wherein the recording medium is a polyolefin - based film substrate having a surface roughness Sa of 0.3 μm or more on the surface to which the ink is adhered.

4. The ink set according to claim 1, wherein the clear ink composition contains an amine having a standard boiling point of 250°C or higher.

5. The ink set according to claim 4, wherein the content of the amine is 0.4% by mass or less based on the total mass of the clear ink composition.

6. The ink set according to claim 1, wherein the glass transition temperature Tg of the resin contained in the clear ink composition is 60°C or higher.

7. The ink set according to claim 1, wherein the coloring material contained in the colored ink composition is a quinacridone - based pigment.

8. The ink set according to claim 1, wherein the silicone surfactant has a maximum peak in the molecular weight range of 1000 - 3000 in the molecular weight distribution in gel permeation chromatography.

9. A recording method using the ink set according to claim 1, comprising: adhering the colored ink composition to a recording medium by an inkjet method; and adhering the clear ink composition to the recording medium by an inkjet method, wherein the colored ink composition and the clear ink composition are laminated and adhered on the recording medium.

10. The recording method according to claim 9, further comprising a step of adhering the clear ink composition to a region of the recording medium where the colored ink composition is not adhered.

11. ​ The recording method according to claim 10, wherein the amount of the clear ink composition adhered to the region where the clear ink composition is adhered without adhering the colored ink composition of the recording medium is not more than the amount of the clear ink composition adhered to the region where the colored ink composition and the clear ink composition of the recording medium are adhered in an overlapping manner.

12. The recording method according to claim 9, further comprising a heating step of heating the recording medium to which the colored ink composition and the clear ink composition are adhered at a surface temperature of 60°C or higher of the recording medium.

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