Recording method and recording device

Abstract

The present invention provides a recording method that reduces image unevenness caused by the non-white ink composition and improves the image quality of the image formed by the white ink composition when recording a non-white ink composition image on a white ink composition layer. [Solution] A recording method for recording on a recording medium using an aqueous white ink composition containing a white colorant and an aqueous non-white ink composition containing a non-white colorant, comprising: a white ink attachment step of ejecting the white ink composition from an inkjet head and adhering it to the recording medium; a drying step of drying the white ink composition adhering to the recording medium; and a non-white ink attachment step of ejecting the non-white ink composition from an inkjet head and adhering it to the recording medium, wherein the non-white ink composition is attached on top of the white ink composition dried in the drying step, the recording medium is a low-absorption recording medium or a non-absorption recording medium, the white ink attachment step is performed by a main scan while moving the relative position of the inkjet head and the recording medium, the non-white ink attachment step is performed by a main scan after the main scan of the white ink attachment step while moving the relative position of the inkjet head and the recording medium, and the white ink composition contains a silicone-based surfactant A having a surface tension of 28.0 mN / m or less for a 0.1% by mass aqueous solution of the surfactant, and a surface tension of 28.0 mN / m or less for a 0.1% by mass propylene glycol solution of the surfactant.

Description

[Technical Field]

[0001] This invention relates to a recording method and a recording apparatus. [Background technology]

[0002] Inkjet recording methods are rapidly developing in various fields because they enable the recording of high-resolution images with relatively simple equipment. In this context, in order to obtain good visibility of color images (non-white images) even when recording on recording media such as transparent film, a method of layering and coating a white ink composition (hereinafter also referred to as "white ink composition") and a non-white ink composition (hereinafter also referred to as "color ink") is being employed.

[0003] For example, Patent Document 1 describes an inkjet recording method in which a white ink composition and a non-white ink composition are layered and attached to a low-absorption recording medium or a non-absorption recording medium. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-167518 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when performing a main scan to deposit a white ink composition, followed by a main scan to deposit a non-white ink composition on top of the white ink composition, and recording a non-white ink composition image on top of the white ink composition layer, it was difficult to suppress the occurrence of image unevenness caused by the non-white ink composition while ensuring the image quality of the image formed by the white ink composition. [Means for solving the problem]

[0006] One aspect of the recording method according to the present invention is: A recording method for recording on a recording medium using an aqueous white ink composition containing a white colorant and an aqueous non-white ink composition containing a non-white colorant, A white ink application step in which the white ink composition is ejected from the inkjet head and adhered to the recording medium, A drying step for drying the white ink composition adhering to the recording medium, A non-white ink application step in which the non-white ink composition is ejected from the inkjet head and adhered to the recording medium, It has, The non-white ink composition is then applied to the white ink composition that has been dried by the drying process. The recording medium is a low-absorption recording medium or a non-absorption recording medium. The white ink application process is performed by a main scan while moving the relative position of the inkjet head and the recording medium. The non-white ink application process is performed after the main scan of the white ink application process, by moving the relative position of the inkjet head and the recording medium during the main scan. The aforementioned white ink composition contains a silicone-based surfactant A, the surface tension of which of the surfactant in a 0.1% by mass aqueous solution is 28.0 mN / m or less, and the surface tension of the surfactant in a 0.1% by mass propylene glycol solution is 28.0 mN / m or less.

[0007] One aspect of the recording device according to the present invention is: A recording device that performs the above recording method, The white ink composition, The non-white ink composition, The inkjet head that performs the white ink application process, A drying mechanism that performs the aforementioned drying process, The system includes the inkjet head that performs the non-white ink application step. [Brief explanation of the drawing]

[0008] [Figure 1]Schematic cross-sectional view schematically showing an inkjet recording apparatus. [Figure 2] Perspective view showing an example of a configuration around a carriage of an inkjet recording apparatus. [Figure 3] Table 1 showing compositions of a white ink composition and a non-white ink composition. [Figure 4] Table 2 showing compositions of treatment liquids. [Figure 5] Table 3 showing conditions and evaluation results of Examples. [Figure 6] Table 4 showing conditions and evaluation results of Examples. [Figure 7] Table 5 showing conditions and evaluation results of Examples, Comparative Examples and Reference Examples. MODE FOR CARRYING OUT THE INVENTION

[0009] Embodiments of the present invention are described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited in any way to the following embodiments, and also includes various modified embodiments that are carried out without changing the gist of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0010] In the present specification, a numerical range expressed using "~" means a range that includes the numerical values described before and after "~" as the lower limit and the upper limit. In the present specification, "(meth)acryl" represents acryl or methacryl, and "(meth)acrylate" represents acrylate or methacrylate.

[0011] 1. Recording Method The recording method according to the present embodiment is a recording method for performing recording on a recording medium by using an aqueous white ink composition containing a white colorant and an aqueous non-white ink composition containing a non-white colorant.

[0012] The recording method according to this embodiment includes a white ink attachment step of ejecting a white ink composition from an inkjet head and adhering it to a recording medium, a drying step of drying the white ink composition adhering to the recording medium, and a non-white ink attachment step of ejecting a non-white ink composition from an inkjet head and adhering it to a recording medium.

[0013] The recording method according to this embodiment involves applying a non-white ink composition on top of a white ink composition that has been dried in a drying step, the recording medium being a low-absorption recording medium or a non-absorption recording medium, the white ink application step being performed by a main scan while moving the relative position between the inkjet head and the recording medium, and the non-white ink application step being performed by a main scan after the main scan of the white ink application step, while moving the relative position between the inkjet head and the recording medium.

[0014] Furthermore, the white ink composition used in the recording method according to this embodiment contains a silicone-based surfactant A, the surface tension of which is 28.0 mN / m or less when it is a 0.1% by mass aqueous solution of the surfactant, and the surface tension of which is 28.0 mN / m or less when it is a 0.1% by mass propylene glycol solution of the surfactant.

[0015] 1.1. White ink application process In the white ink application process, the white ink composition is ejected from the inkjet head and applied to the recording medium.

[0016] 1.1.1. White Ink Composition The white ink composition is an aqueous composition containing a white colorant. The white ink composition also contains a silicone-based surfactant A, the surface tension of which is 28.0 mN / m or less when dissolved in a 0.1% by mass aqueous solution of the surfactant, and the surface tension of which is 28.0 mN / m or less when dissolved in a 0.1% by mass propylene glycol solution of the surfactant.

[0017] 1.1.1.(1) White coloring material The white ink composition contains a white pigment. Examples of white pigments include CI Pigment White 1, which is basic lead carbonate; CI Pigment White 4, which is zinc oxide; CI Pigment White 5, which is a mixture of zinc sulfide and barium sulfate; CI Pigment White 6, which is titanium dioxide; CI Pigment White 6:1, which is titanium dioxide containing other metal oxides; CI Pigment White 7, which is zinc sulfide; CI Pigment White 18, which is calcium carbonate; CI Pigment White 19, which is clay; CI Pigment White 20, which is titanium mica; CI Pigment White 21, which is barium sulfate; CI Pigment White 22, which is gypsum; CI Pigment White 26, which is magnesium oxide and silicon dioxide; CI Pigment White 27, which is silicon dioxide; and CI Pigment White 28, which is anhydrous calcium silicate. Among these, it is preferable to use CI Pigment White 6, which has excellent color development and opacity. In addition, particles having a hollow structure may be used as the white pigment, and known particles with a hollow structure can be used.

[0018] The volume-average particle size of the white colorant is preferably 30 nm to 500 nm, more preferably 50 nm to 450 nm, and even more preferably 200 nm to 400 nm. Setting the volume-average particle size of the white colorant within this range tends to ensure ejection stability from the inkjet head and also tends to improve opacity.

[0019] In this specification, unless otherwise specified, "volume-average particle diameter" refers to the volume-based particle size distribution, which is the particle diameter at a cumulative distribution of 50 vol%. The volume-average particle diameter is measured using the dynamic light scattering method or the laser diffraction method described in JIS Z8825. Specifically, a particle size analyzer that uses the dynamic light scattering method as its measurement principle (for example, "Microtrac UPA" manufactured by Nikkiso Co., Ltd.) can be used.

[0020] In the present specification, the term "white" when referring to a white ink composition, a white colorant, or the like does not refer only to pure white, and includes chromatic colors, achromatically colored colors, and glossy colors as long as they are visually recognizable as white. The term also includes those named and sold under names that suggest that the ink or colorant is a white ink or white colorant.

[0021] More quantitatively, in CIELAB, for example, "white" of a recorded matter refers to not only a color having an L * value of 100, but also includes colors where L * is 60 or more and 100 or less, and each of a * and b * is ±10 or less.

[0022] More specifically, for example, when a white ink composition is recorded in an amount that sufficiently covers the surface of a recording medium made of a transparent film, the lightness (L * ) and chromaticity (a * , b * ) of the recorded portion of the recorded matter, when measured using a spectrophotometer compliant with CIELAB , it is preferable that the values fall within the above ranges. A recorded matter recorded in an amount that provides sufficient coverage has, for example, an adhesion amount of 15 mg / inch 2 . More preferably, 80≦L * ≦100, -4.5≦a * ≦2, -10≦b * ≦2.5. Examples of the recording medium made of a transparent film include LAG Jet E-1000ZC (manufactured by Lintec Corporation). Examples of the spectrophotometer compliant with CIELAB include Spectrolino (trade name, manufactured by GretagMacbeth), and measurement is performed under the following settings: D50 light source, observation visual field of 2°, DIN NB density, Abs white reference, no filter, and measurement mode of Reflectance. Anything other than "white" is defined as "non-white".

[0023] The content of the white colorant is preferably 1% to 30% by mass, more preferably 5% to 25% by mass, even more preferably 10% to 20% by mass, particularly preferably 10% to 15% by mass, and most particularly preferably 10% to 12% by mass, relative to the total amount of the white ink composition. When the content of the white colorant is within the above range, friction fastness can be improved, the background opacity of the image by the white ink composition is further enhanced, and better color development (whiteness) tends to be obtained.

[0024] To improve the dispersibility of the white colorant in the ink composition, it is preferable to either surface-treat the colorant or incorporate a dispersant.

[0025] The surface treatment of the white colorant is preferably a physical or chemical treatment that directly or indirectly bonds functional groups such as carbonyl groups, carboxyl groups, aldehyde groups, hydroxyl groups, sulfone groups, ammonium groups, and salts thereof to the surface of the colorant. In particular, the surface treatment is more preferably a treatment that modifies the surface of the colorant by oxidizing or sulfonating the surface of the colorant with, for example, ozone, hypochlorous acid, or fuming sulfuric acid.

[0026] When a dispersant is added to a white ink composition, it is preferable to use a dispersant that has both a hydrophobic portion (hydrophobic group) and a hydrophilic portion (hydrophilic group) in its molecular structure. Such a dispersant has the effect of the hydrophobic portion adsorbing to the surface of the colorant particles and the hydrophilic portion orienting towards the aqueous medium side of the ink composition. This action tends to make it possible to include the colorant in the ink composition as a dispersion more stably.

[0027] Such dispersants are not particularly limited, but examples include acrylic resins, styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylate copolymers and other styrene-acrylic resins, styrene-maleic acid resins, and their salts, formalin condensates of aromatic sulfonates, and one or more selected from this group can be used. Commercially available dispersants may also be used.

[0028] When dispersing a white colorant with a dispersant, the ratio of the white colorant to the dispersant is preferably 10:1 to 1:10, and more preferably 4:1 to 1:3.

[0029] Alternatively, a method may be used in which the particles of the white colorant are coated with a resin or other material to impart dispersibility. Possible methods for coating the white colorant include acid precipitation, phase inversion emulsification, and miniemulsion polymerization.

[0030] 1.1.1.(2) Silicone-based surfactant A The white ink composition contains silicone-based surfactant A. Silicone-based surfactant A has a surface tension of 28.0 mN / m or less in a 0.1% by mass aqueous solution of the surfactant, and a surface tension of 28.0 mN / m or less in a 0.1% by mass propylene glycol solution of the surfactant.

[0031] In this specification, the condition that the surface tension of a 0.1% by mass aqueous solution of the surfactant is 28.0 mN / m or less, and the surface tension of a 0.1% by mass propylene glycol solution of the surfactant is 28.0 mN / m or less, is sometimes referred to as "condition (a)". The surface tension for condition (a) is the value at 25°C. The surface tension can be measured in the same way as the surface tension of the white ink composition described later.

[0032] To prepare a silicone-based surfactant A that satisfies condition (a), one can prepare a 0.1% by mass aqueous solution of a silicone-based surfactant and a 0.1% by mass propylene glycol solution, measure their surface tension, and confirm whether they satisfy condition (a). In this way, silicone-based surfactant A can be prepared.

[0033] Examples of silicone-based surfactant A, in which the surface tension of a 0.1% by mass aqueous solution of the surfactant is 28.0 mN / m or less, and the surface tension of a 0.1% by mass propylene glycol solution of the surfactant is 28.0 mN / m or less, include BYK-3420 and BYK-3480 (product names, manufactured by BYK Chemie Japan).

[0034] The surface tension of a 0.1% by mass aqueous solution of silicone surfactant A is preferably 20.0 to 28.0 mN / m, more preferably 21.0 to 27.0 mN / m, and even more preferably 22.0 to 26.0 mN / m.

[0035] The surface tension of a 0.1% by mass propylene glycol solution of silicone surfactant A is preferably 20.0 to 28.0 mN / m, more preferably 23.0 to 27.5 mN / m, and even more preferably 25.0 to 27.3 mN / m.

[0036] If the white ink composition has not yet dried after being deposited onto the recording medium during the white ink application process, the white ink composition will not be completely dry, and a large amount of water will remain. On the other hand, if the white ink composition has dried considerably after being deposited, the water in the white ink composition will have dried, and a large amount of organic solvent will remain. This is because organic solvents with a standard boiling point higher than that of water are used to impart moisture retention to the white ink composition.

[0037] Furthermore, it has been found that the surface tension of the white ink composition at the time of contact with the white ink composition affects how ink droplets of the non-white ink composition spread when the non-white ink composition comes into contact with the white ink composition.

[0038] The surface tension of a 0.1% by mass aqueous solution of surfactant is thought to be related to the surface tension of the white ink composition when it has not yet dried after impact, while the surface tension of a 0.1% by mass propylene glycol surfactant solution is thought to be related to the surface tension of the white ink composition when it has dried after impact.

[0039] Therefore, by including a silicone-based surfactant A that satisfies condition (a), the ink droplets of non-white ink that come into contact with the recording medium before the white ink composition has dried after landing, and the ink droplets of non-white ink that come into contact with the recording medium after the white ink composition has dried after landing, both exhibit similar wetting properties, thereby reducing unevenness in the resulting non-white ink image.

[0040] Furthermore, if the white ink composition does not use a surfactant that satisfies condition (a), the wetting properties of ink droplets of the non-white ink will not be similar between ink droplets that come into contact with the white ink composition before it has dried and ink droplets that come into contact with the white ink composition after it has dried. This will result in some ink droplets in the image spreading widely and others spreading only slightly, which will make the unevenness of the image of the non-white ink more noticeable. It is thought that they are connected.

[0041] Furthermore, if there are variations in the surface temperature of the recording medium or in the wind speed and temperature used for drying during the drying process of the white ink composition, it is presumed that differences in the degree of drying of the white ink composition will occur depending on the location on the recording medium, resulting in some areas of the white ink composition being under-dried and others being over-dried. Also, if the time from when the white ink composition adheres to the recording medium until the non-white ink composition overlaps and adheres differs depending on the location on the recording medium, it is presumed that differences in the degree of drying of the white ink composition when the non-white ink composition overlaps and adheres will result in some areas of the white ink composition being under-dried and others being over-dried.

[0042] It is presumed that silicone-based surfactant A, which satisfies condition (a), satisfies condition (a) because it has a good balance of hydrophilicity and hydrophobicity, resulting in excellent surfactant activity in both aqueous solutions and propylene glycol solutions.

[0043] The content of silicone-based surfactant A in the white ink composition is preferably 0.05% by mass or more and 2% by mass or less, more preferably 0.1% by mass or more and 1.5% by mass or less, and even more preferably 0.2% by mass or more and 1% by mass or less. A further preferable range is 0.5% by mass or more and 0.8% by mass or less. When the content of silicone-based surfactant A in the white ink composition is within this range, the granularity, pinhole filling, and abrasion resistance of the resulting image can be further improved.

[0044] The silicone surfactant A may be, and is preferred, a silicone surfactant represented by the following formula (1). When such a silicone surfactant is used, it is easier to obtain a silicone surfactant that satisfies condition a. Since the silicone surfactant represented by general formula (1) has a structure modified at both ends, the balance between hydrophilicity and hydrophobicity can be adjusted by adjusting the length of the main skeleton having siloxane bonds, excluding the polyether-modified group portion. This makes it easier to adjust it to satisfy condition a.

[0045] [ka]

[0046] (In the formula, a is an integer between 7 and 50, x and y are each independent integers between 1 and 4, m and n are each independent integers between 1 and 20, o and p are each independent integers between 0 and 20, m+n is between 2 and 40, o+p is between 0 and 40, R 1 and R 2 Each of these is independently selected from the group consisting of a hydrogen atom, a hydroxyl 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) and OP (PO) units is not significant.

[0047] In equation (1); a is an integer between 7 and 50, preferably between 8 and 48, more preferably between 9 and 45, more preferably between 10 and 40, even more preferably between 11 and 30, and particularly preferably between 11 and 20. x and y are each independent integers between 1 and 4, preferably between 1 and 3, and more preferably between 2 and 3. m and n are each independent integers from 1 to 20, but preferably from 2 to 15, and more preferably from 2 to 15. The value is between 4 and 10, and more preferably between 5 and 8. o and p are each independent integers between 0 and 20, but are preferably between 0 and 10, more preferably between 0 and 5, even more preferably between 0 and 3, particularly preferably between 0 and 1, and most particularly preferably 0. m+n is between 2 and 40, preferably between 4 and 30, more preferably between 8 and 20, and even more preferably between 10 and 15. o+p is between 0 and 40, preferably between 0 and 20, more preferably between 0 and 10, even more preferably between 0 and 3, particularly preferably between 0 and 1, and most particularly preferably 0. R 1 and R 2 Each of these is independently selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group, but a hydroxyl group is preferred. The order between the OE (EO) unit and the OP (PO) unit is not important; that is, if there is one or more OE (EO) units and one OP (PO) unit, the order of the units does not matter. P is a propylene group, and examples include a 1,2-propylene group and a 1,3-propylene group, with the 1,2-propylene group being preferred.

[0048] The silicone-based surfactant A may be, and is preferred, a silicone-based surfactant represented by the following formula (2).

[0049] [ka]

[0050] (In the formula, R 3 Each independently represents an alkyl group having 1 to 6 carbon atoms, and R 4 This represents an alkylene group with 1 to 4 carbon atoms, R 5 ∫ represents a group selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group. EO represents an ethylene oxide group, PO represents a propylene oxide group, the order between the EO and PO units is not significant, d and e are integers greater than or equal to 1, d+e represents an integer between 2 and 10, f is an integer between 1 and 20, and g is an integer between 0 and 20.

[0051] In equation (2); d+e is an integer between 2 and 10, preferably between 3 and 8, and more preferably between 3 and 6. It is preferable that d and e are each half of d+e. R 4 The group is an alkylene group having 1 to 4 carbon atoms, preferably 1 to 3, and more preferably 2 to 3. f is an integer between 1 and 20, but is preferably between 2 and 15, more preferably between 4 and 10, and even more preferably between 5 and 8. g is an integer between 0 and 20, but is preferably between 0 and 10, more preferably between 0 and 5, even more preferably between 0 and 3, particularly preferably between 0 and 1, and most particularly preferably 0. R 5 The group is selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, and a (meth)acrylic group, but a hydroxyl group is preferred.

[0052] The silicone surfactant A may also be obtained by synthesis. For example, it can be synthesized by an addition reaction between a silicone oil having a Si-H structure and a polyether having a carbon-carbon double bond at its terminus. Synthesis can be carried out by an addition reaction using a Pt-based catalyst or the like. The silicone oil having a Si-H structure can be a compound in which the Si atom to which the polyether-modified group is bonded in the compound of formula (1) or formula (2) is replaced with a hydrogen atom. The polyether having a carbon-carbon double bond at its terminus can be a compound in which the Si atom of the carbon atom bonded to the Si atom of the polyether-modified group in the polyether-modified group portion of formula (1) or formula (2) is replaced with a carbon-carbon double bond.

[0053] Furthermore, it is preferable that the silicone-based surfactant A has a maximum peak in the molecular weight range of 1000 to 4500 in the molecular weight distribution of gel permeation chromatography (GPC) in the range of molecular weight 300 or higher. When the molecular weight of the silicone-based surfactant A is within this range, the abrasion resistance of the resulting image can be further improved.

[0054] Furthermore, if the surfactant is a silicone-based surfactant having a molecular weight within the above range, it is preferable as it is easier to satisfy condition (a) above. For example, the size of the surfactant molecule is related to the ease with which surfactant molecules associate and arrange in solution, and it is presumed that if the surfactant is a silicone-based surfactant having a molecular weight within the above range, the ease with which surfactant molecules associate and arrange in aqueous solution and in propylene glycol solution will be similar, making it easier to satisfy condition (a). However, this is a presumption, and the reason is not limited to this.

[0055] In the molecular weight distribution of gel permeation chromatography, the maximum peak in the molecular weight range of 300 or more is more preferably in the molecular weight range of 1500 to 4000. Furthermore, it is more preferably in the molecular weight range of 1550 to 3000, and even more preferably in the molecular weight range of 1600 to 2500.

[0056] The maximum peak for silicone-based surfactants in the molecular weight range of 300 or higher can be identified from a molecular weight distribution chart obtained in GPC, where the horizontal axis is the logarithm of molecular weight M (LogM) and the vertical axis is the differential value of the concentration fraction (dw / d(LogM)). Here, "maximum peak" refers to the largest peak (mountain) in the molecular weight range of 300 or higher. Furthermore, "maximum peak in the molecular weight range of 300 or higher" means that peaks with molecular weights below 300 are ignored. In other words, there may be a maximum peak below 300 molecular weight, but this is the maximum peak when considering only the molecular weight range of 300 or higher.

[0057] While not particularly limited, for example, the measurement conditions in the GPC measurement in this embodiment can be those described in the examples, and the molecular weight can be determined using standard polystyrene.

[0058] The white ink composition may further contain silicone-based surfactants other than silicone-based surfactant A, i.e., silicone-based surfactants that do not satisfy condition (a). Examples of such silicone-based surfactants include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348, BYK-349 (all product names, manufactured by Bic Chemie Japan), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all product names, manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG002, 005, 503A, 008 (all product names, manufactured by Japan Examples include products manufactured by Shin Chemical Industry Co., Ltd.

[0059] Furthermore, if a silicone-based surfactant that does not satisfy condition (a) is included in the white ink composition, it is preferable that the amount is such that it does not inhibit the action of the silicone-based surfactant that satisfies the above condition (a).

[0060] 1.1.1.(3) Water The white ink composition is a water-based inkjet ink. "Water-based" means that it contains at least water as a solvent component, and may contain water as the main solvent component. "Inkjet ink" refers to an ink composition used for recording by ejecting it from an inkjet head using an inkjet method.

[0061] Examples of suitable water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water, which has reduced ionic impurities. Furthermore, using water sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can suppress the growth of bacteria and fungi when storing the white ink composition for a long period of time.

[0062] The water content is preferably 50% by mass or more, more preferably 50 to 100% by mass, in the liquid medium component. Furthermore, it is preferably 60 to 90% by mass, and more preferably 70 to 80% by mass. The liquid medium refers to a solvent component such as water or an organic solvent. Furthermore, the water content is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, relative to the total mass of the white ink composition. There is no particular upper limit to the water content, but for example, it is preferably 99% by mass or less, more preferably 90% by mass or less, 80% by mass or less, 70% by mass or less, and 60% by mass or less, relative to the total mass of the white ink composition.

[0063] 1.1.1.(4) Organic solvents The white ink composition may contain an organic solvent. The inclusion of an organic solvent tends to improve the wetting and spreading of the ink, resulting in better coverage of the white ink composition on the recording medium, and consequently, a reduction in the occurrence of unevenness in color images.

[0064] Examples of organic solvents include esters, alkylene glycol ethers, cyclic esters, amides, alcohols, and polyhydric alcohols.

[0065] Esters include glycol monoacetates such as 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, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, methoxybutyl acetate, ethylene glycol diacetate, and diethylene glycol. Examples of glycol diesters include propyl 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, and dipropylene glycol acetate propionate.

[0066] Alkylene glycol ethers include alkylene glycol monoethers or Any diether is acceptable, 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, and tripropylene glycol monobutyl ether. Examples include alkylene glycol monoalkyl ethers such as ethyl ether; 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, and 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, and ε-decanolactone, as well as compounds in which the hydrogen atoms of the methylene group adjacent to the carbonyl group are substituted with alkyl groups having 1 to 4 carbon atoms.

[0068] Examples of amides include cyclic amides and acyclic amides. Examples of acyclic amides include alkoxyalkyl amides.

[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, and 1-(2-hydroxyethyl)pyrrolidine-2-one.

[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, and 3-n-propoxy-N,N-methylethylpropionamide. Examples include ethylpropionamide, 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, and N,N-dimethylisobutyrate amide.

[0071] Examples of alcohols include compounds in which one hydrogen atom of an alkane is replaced by a hydroxyl group. The alkane preferably has 10 or fewer carbon atoms, more preferably 6 or fewer, and even more preferably 3 or fewer. The alkane has 1 or more carbon atoms, preferably 2 or more. 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, and phenoxypropanol.

[0072] Polyhydric alcohols are molecules that contain two or more hydroxyl groups. Examples of polyhydric alcohols include alkanediols and polyols.

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

[0074] Examples of 1,2-alkanediols 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, and 3,4-dimethyl-1,2-pentanediol. Examples include hexanediol, 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-hexanediol, and 3-ethyl-4-methyl-1,2-hexanediol.

[0075] Other examples of alkanediols include 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, and 2-methyl-2-propyl-1,3-propanediol.

[0076] Among alkanediols, diols of alkanes with 5 or more carbon atoms are preferred, and diols of alkanes with 5 to 10 carbon atoms are more preferred. Or diols of alkanes with 4 or fewer carbon atoms. Diols of alkanes having 2 to 3 carbon atoms are also preferred, and more preferably so.

[0077] Examples of polyols include condensates formed by the intermolecular condensation of two or more alkanediol molecules via hydroxyl groups, and compounds having three or more hydroxyl groups.

[0078] Examples of condensates formed by the intermolecular condensation of two or more alkanediol molecules at their hydroxyl groups include dialkylene glycols such as diethylene glycol and dipropylene glycol, and trialkylene glycols such as triethylene glycol and tripropylene glycol. A condensate formed by the intermolecular condensation of two or more diols of alkanes having 4 or fewer carbon atoms via hydroxyl groups is preferred, and a condensate formed by the intermolecular condensation of two or more diols of alkanes having 2 to 3 carbon atoms via hydroxyl groups is more preferred.

[0079] Compounds having three or more hydroxyl groups are compounds with an alkane or polyether structure as their backbone and containing three or more hydroxyl groups. Examples of compounds having three or more hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, and polyoxypropylenetriol.

[0080] Organic solvents may be used individually or in combination of two or more types.

[0081] The content of the organic solvent is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, even more preferably 10 to 30% by mass, and most preferably 15 to 25% by mass, based on the total amount of the white ink composition. It is also preferable that the content of polyhydric alcohols be within the above range, and that the content of alkanediols be within the above range.

[0082] The white ink composition preferably contains 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and most preferably 0% by mass (none), of an organic solvent with a standard boiling point exceeding 280°C, relative to the total amount of the white ink composition. This is preferable for excellent white print quality and scratch resistance.

[0083] On the other hand, it is also preferable to include it, preferably 0.5% by mass or more, and more preferably 1% by mass or more. In this case, nozzle reliability and other properties are superior, which is preferable.

[0084] Examples of organic solvents with a standard boiling point exceeding 280°C include triethylene glycol and glycerin.

[0085] Furthermore, the white ink composition contains an organic solvent, and more preferably contains 20% by mass or more, even more preferably 30% by mass or more, and more preferably 50% by mass or more, of the total amount of organic solvent with a standard boiling point of 200°C or lower. This improves the scratch resistance and reduction of image unevenness of the white ink composition. This effect is particularly pronounced when the amount of white ink composition applied is large. The upper limit is preferably 100% by mass or less, and more preferably 80% by mass or less, in terms of superior nozzle reliability and other factors.

[0086] Furthermore, the white ink composition contains an organic solvent, and of the contained organic solvents, the standard boiling point of the organic solvent with the highest standard boiling point is preferably 300°C or lower, more preferably 290°C or lower, and even more preferably 280°C or lower. It is even more preferable that it be 250°C or lower. Furthermore, it is preferable that it be 210°C or lower.

[0087] This method improves the abrasion resistance of the white ink composition. This effect is particularly noticeable when a large amount of the white ink composition is applied.

[0088] The lower limit is preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher. This is preferable in terms of nozzle reliability and other factors.

[0089] 1.1.1.(5) Other ingredients <Resin particles> The white ink composition may contain resin particles. The resin particles function as a so-called fixing resin, improving the adhesion and abrasion resistance of the ink components attached to the recording medium. The resin particles may be in powder form, but an emulsion form is preferred.

[0090] Examples of resins used for resin particles include urethane resins, acrylic resins, fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, ethylene vinyl acetate resins, vinyl acetate resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, benzoguanamine resins, phenolic resins, silicone resins, epoxy resins, paraffinic resins, and fluororesins.

[0091] Urethane resins are a general term for resins that contain urethane bonds. In addition to urethane bonds, urethane resins may also use polyether-type urethane resins containing ether bonds in the main chain, polyester-type urethane resins containing ester bonds in the main chain, polycarbonate-type urethane resins containing carbonate bonds in the main chain, etc. As the urethane resin, commercially available products may be used. For example, you may select and use from commercially available products such as Superflex 210, 460, 460s, 840, E-4000 (product name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Rezamin D-1060, D-2020, D-4080, D-4200, D-6300, D-6455 (product name, manufactured by Dainichi Seika Kogyo Co., Ltd.), Takelac WS-6020, WS-6021, W-512-A-6 (product name, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.), SanCure 2710 (product name, manufactured by LUBRIZOL), Permarin UA-150 (product name, manufactured by Sanyo Chemical Industries, Ltd.).

[0092] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer, such as (meth)acrylic acid or (meth)acrylic acid ester. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, are examples. Furthermore, copolymers with vinyl monomers such as styrene are examples. For example, styrene-acrylic resins are examples. Acrylamide and acrylonitrile can also be used as acrylic monomers.

[0093] As the acrylic resin, commercially available products may be used, for example, selected from FK-854 (product name, manufactured by Chuo Rika Kogyo Co., Ltd.), Movinyl 6969D, 952B, 718A (product name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852, LX874 (product name, manufactured by Nippon Zeon Co., Ltd.), Polysol AT860 (manufactured by Showa Denko K.K.), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001 (product name, manufactured by DIC Corporation, acrylic resin emulsion), etc.

[0094] In this specification, the acrylic resin may be a styrene-acrylic resin as described above.

[0095] Styrene-acrylic resins are copolymers obtained from styrene monomers and acrylic monomers, and examples include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, and styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers. As for styrene-acrylic resins, commercially available products may be used, such as Joncryl 62J, 7100, 390, 711, 511, 7001, 631, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (product names, manufactured by BASF), Movinyl 966A, 975N (product names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

[0096] The vinyl chloride resin may also be a vinyl chloride-vinyl acetate copolymer.

[0097] Polyolefin resins have olefins such as ethylene, propylene, and butylene as their structural framework, and known types can be appropriately selected and used. Commercially available polyolefin resins can be used, for example, Arrowbase CB-1200, CD-1200 (trade names, manufactured by Unitika Ltd.), Hi-Tec E-6500 (trade name, manufactured by Toho Chemical Co., Ltd., polyethylene wax emulsion), SN-2002 (trade name, manufactured by Toho Chemical Co., Ltd., polyester resin emulsion), etc.

[0098] Examples of commercially available resin emulsions include Microgel E-1002, E-5002 (product names from Nippon Paint Co., Ltd., styrene-acrylic resin emulsion), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001, 5454 (product names from DIC Corporation, styrene-acrylic resin emulsion), Polysol AM-710, AM-920, AM-2300, AP-4735, AT-860, PSASE-4210E (acrylic resin emulsion), and Polysol AP-7020 (styrene-acrylic resin emulsion). Polysol SH-502 (vinyl acetate resin emulsion), Polysol AD-13, AD-2, AD-10, AD-96, AD-17, AD-70 (ethylene vinyl acetate resin emulsion), Polysol PSASE-6010 (ethylene vinyl acetate resin emulsion) (product name of Showa Denko Co., Ltd.), Polysol SAE1014 (product name, styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Saibinol SK-200 (product name, acrylic resin emulsion, manufactured by Saiden Chemical Co., Ltd.), AE-120A (product name of JSR Corporation, acrylic resin emulsion) Lujon), AE373D (product name manufactured by E-Tech, carboxy-modified styrene-acrylic resin emulsion), Seikadine 1900W (product name manufactured by Dainichi Seika Kogyo, ethylene-vinyl acetate resin emulsion), Vinibran 2682 (acrylic resin emulsion), Vinibran 2886 (vinyl acetate-acrylic resin emulsion), Vinibran 5202 (acrylic acetate resin emulsion) (product name manufactured by Nisshin Chemical Industry Co., Ltd.), Vinibran 700, 2586 (manufactured by Nisshin Chemical Industry Co., Ltd.), Elitel KA-5071S, KT-8803, KT-9204, KT-8701 , KT-8904, KT-0507 (Unitika Corporation product name, polyester resin emulsion), Hi-Tec E-6500 (Toho Chemical Co., Ltd. product name, polyethylene wax emulsion), SN-2002 (Toho Chemical Co., Ltd. product name, polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (Mitsui Chemicals Polyurethane Co., Ltd. product name, urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 620, 700 (Daiichi Kogyo Seiyaku Co., Ltd. product name,Urethane resin emulsion), Permarin UA-150 (manufactured by Sanyo Chemical Industries, Ltd., urethane resin emulsion), SunCure 2710 (manufactured by Lubrizol Japan, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (manufactured by Kusumoto Chemicals Co., Ltd., urethane resin emulsion), Adekabon Titer HUX-380, 290K, You may also select and use from among the following: (Urethane resin emulsion manufactured by ADEKA Corporation), Movinyl 966A, Movinyl 7320 (manufactured by Nippon Synthetic Chemical Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 631, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (all manufactured by BASF), NK Binder R-5HN (manufactured by Shin Nakamura Chemical Industry Co., Ltd.), Hydran WLS-210 (non-crosslinked polyurethane: manufactured by DIC Corporation), etc.

[0099] Furthermore, the glass transition temperature (Tg) of the resin particles is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. On the other hand, it is preferably 120°C or lower, more preferably 100°C or lower, even more preferably 90°C or lower, and particularly preferably 80°C or lower. When the glass transition temperature (Tg) of the resin particles is within the above range, it may be possible to achieve superior clogging recovery properties. The glass transition temperature (Tg) of the resin particles can be confirmed by standard methods such as differential scanning calorimetry (DSC).

[0100] The content of resin particles (solids) is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and particularly preferably 10% by mass or more, based on the total amount of the white ink composition. Furthermore, the content of resin particles (solids) is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on the total amount of the white ink composition.

[0101] <wax> The white ink composition may contain wax. The wax is not particularly limited, but examples include hydrocarbon waxes and ester waxes, which are condensates of fatty acids with monohydric or polyhydric alcohols. The hydrocarbon wax is not particularly limited, but examples include paraffin wax and polyolefin waxes such as polyethylene wax and polypropylene wax. These waxes may be used individually or in combination of two or more.

[0102] Examples of commercially available paraffin waxes include AQUACER497 and AQUACER539 (product names, manufactured by BYK).

[0103] Examples of commercially available polyolefin waxes include Chemipearl S120, S650, S75N (product names, manufactured by Mitsui Chemicals, Inc.), AQUACER501, AQUACER506, AQUACER513, AQUACER515, AQUACER526, AQUACER593, and AQUACER582 (product names, manufactured by BYK).

[0104] The wax (solids) content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and particularly preferably 1.5% by mass or more, based on the total amount of the white ink composition. Furthermore, the wax (solids) content is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on the total amount of the white ink composition.

[0105] <Metal sealant> The white ink composition may contain a metal saturating agent (chelating agent). The metal saturating agent can remove specific ions from the reaction solution.

[0106] Examples of metal encapsulants include ethylenediaminetetraacetic acid and its salts, such as EDTA (ethylenediaminetetraacetic acid), EDTA-2Na (ethylenediaminetetraacetic acid disodium dihydrogen salt), EDTA-3Na (ethylenediaminetetraacetic acid trisodium monohydrogen salt), EDTA-4Na (ethylenediaminetetraacetic acid tetrasodium salt), and EDTA-3K (ethylenediaminetetraacetic acid tripotassium monohydrogen salt); DTPA, DTPA-2Na (diethylenetriaminepentaacetic acid disodium salt), and DTPA-5Na (diethylene Examples include diethylenetriaminepentaacetic acid and its salts, such as nitrilotriacetic acid pentasodium salt (nitrilopentaacetic acid pentasodium salt); nitrilotriacetic acid and its salts, such as NTA, NTA-2Na (nitrilotriacetate disodium salt), and NTA-3Na (nitrilotriacetate trisodium salt); ethylenediamine-N,N'-disuccinic acid and its salts; 3-hydroxy-2,2'-iminodisuccinic acid and its salts; L-aspartic acid-N,N'-diacetic acid and its salts; and N-(2-hydroxyethyl)iminodiacetic acid and its salts. Also, examples include ethylenediaminetetramethylenephosphonic acid and its salts; ethylenediaminetetrametaphosphate and its salts; ethylenediamine pyrophosphate and its salts; and ethylenediamine metaphosphate and its salts.

[0107] Metal sealants may be used individually or in combination of two or more types.

[0108] If a metal sealant is included, its content can be, for example, 0.005% by mass or more and 0.1% by mass or less, preferably 0.01% by mass or more and 0.05% by mass or less, relative to the total amount of the white ink composition.

[0109] <Other ingredients> The white ink composition may optionally contain additives such as pH adjusters, preservatives / fungal agents, rust inhibitors, viscosity modifiers, solubilizers, antioxidants, and alkaline agents. When such additives are included, the content is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.1 to 1% by mass, relative to the total amount of the white ink composition.

[0110] 1.1.1.(6) Physical properties The viscosity of the white ink composition is preferably 1.0 to 10 mPa·s at 20°C, more preferably 2.0 to 10 mPa·s, even more preferably 3.0 to 8.0 mPa·s, and particularly preferably 4.0 to 6.0 mPa·s. In particular, a viscosity of 4.0 mPa·s or higher tends to yield better color development. A viscosity of 6.0 mPa·s or lower tends to yield better discharge stability.

[0111] The surface tension of the white ink composition is preferably 10 to 40 mN / m at 20°C, more preferably 15 to 35 mN / m, even more preferably 20 to 30 mN / m, and particularly preferably 20 to 27 mN / m.

[0112] 1.1.2. Inkjet Method The white ink application process is performed during the main scan, which involves moving the relative position of the inkjet head and the recording medium.

[0113] The "inkjet method" is a method of ejecting droplets of inkjet ink from the nozzles of an inkjet head and adhering them to a recording medium.

[0114] The amount of white ink composition applied is preferably 4 to 30 mg / inch per unit area of ​​the region on the recording medium where the white ink composition is applied. 2 More preferably, 6-25 mg / inch 2 And more preferably 8-20 mg / inch 2 And, particularly preferably, 10-15 mg / inch 2 Furthermore, among the amounts of white ink composition that adhere, the maximum The amount of adhesion may also be within the above range, which is preferable.

[0115] Furthermore, the amount of white ink composition adhering to the recording medium is 15 mg / inch. 2 The above recording area may be formed. In this case, the background opacity of the image by the white ink composition is further improved, and the effects of this recording method, such as suppressing image unevenness caused by the non-white ink composition, become more pronounced.

[0116] In the recording method of this embodiment, after the white ink application step, a drying step described later is performed, followed by a non-white ink application step described later, in which the white ink composition and the non-white ink composition are layered and applied on the recording medium. That is, a white image formed by the white ink composition is first formed on the recording medium, and after the drying step, a color image formed by the non-white ink composition is layered on top of the white image on the recording medium. In this case, unevenness in the color image is likely to occur, so the recording method according to this embodiment is more effective.

[0117] The method of application for the white ink application process and the non-white ink application process described later is preferably carried out by scanning (hereinafter also referred to as "scanning"), in which the inkjet head ejects ink and adheres it to the recording medium while the relative positions of the inkjet head and the recording medium move.

[0118] In this scanning process, the inkjet head may move relative to the recording medium, or the recording medium may move relative to the inkjet head. In other words, the movement of the inkjet head relative to the recording medium can also be described as the movement of the recording medium relative to the inkjet head. That is, it is the movement of the relative positions of the inkjet head and the recording medium.

[0119] The inkjet head can be mounted on a carriage, for example. The inkjet head may be moved as the carriage moves; in this case as well, it is the movement of the inkjet head.

[0120] The number of scans performed on the same scanning area in the recording medium is not particularly limited and may be one or more scans, independently of the white ink application step and the non-white ink application step.

[0121] When the same scanning area on a recording medium is scanned multiple times, the inkjet head that ejects ink passes over the same area on the recording medium multiple times. The more times the scanning is performed, the more ink can be applied to the desired area in multiple passes, which tends to improve the image quality of the resulting recording. In this case, the number of scans is one or more, but from the viewpoint of better image quality, two or more is preferable, three or more is more preferable, four or more is even more preferable, and six or more is particularly preferable. There is no upper limit, but from the viewpoint of better productivity, 15 or less is preferable, 10 or less is more preferable, and 8 or less is even more preferable. The number of scans described above is set for each type of ink.

[0122] In cases where multiple passes are used, it is preferable to record by performing the scan (main scan) and sub-scan multiple times each. For example, the main scan and sub-scan can be performed alternately and repeatedly.

[0123] For example, when recording in 4 passes, if the length of one sub-scan in the sub-scanning direction is one-quarter the length of the nozzle row aligned in the sub-scanning direction of the inkjet head, then for a rectangular scanning area that is the length of one sub-scan in the sub-scanning direction and extends in the main scanning direction, This means that four main scans are performed on the same part (the same scanning area). The number of scans in this way is called the number of scans or passes.

[0124] "Sub-scanning" refers to the operation of moving the relative position of the inkjet head and the recording medium in the sub-scanning direction. The "sub-scanning direction" is the direction that intersects with the main scanning direction (i.e., the direction in which the inkjet head moves relative to the recording medium).

[0125] For example, by applying ink to a certain area of ​​the recording medium during a main scan, moving the recording medium slightly during a sub-scan, and then performing the next main scan, the process of applying ink adjacent to or partially overlapping the previously applied ink can be repeated to record data. Note that "sub-scan" also refers to the movement of the inkjet head relative to the recording medium; the inkjet head may move relative to the recording medium, or the recording medium may move relative to the inkjet head. The direction of such relative movement is called the sub-scan direction.

[0126] On the other hand, it is also preferable to perform the same scanning area on the recording medium once in the white ink application step and once in the non-white ink application step. In this case, the white ink composition tends to not adequately cover the recording medium, and unevenness in the color image is likely to occur. However, according to the recording method of this embodiment, even in this configuration, the white ink can adequately cover the recording medium, and the occurrence of unevenness in the color image can be reduced.

[0127] If the number of scans performed on the same scanning area in the recording medium is set to one in the white ink application process and one in the non-white ink application process, the scans may be performed using the same scan or different scans.

[0128] Furthermore, the direction of the first main scan in the non-white ink application process, described later, may be opposite to the direction of the last main scan in the white ink application process, which is performed on the same main scan area of ​​the recording medium. That is, after applying the white ink composition to the recording medium with one main scan, the non-white ink composition may be applied with the next return main scan without performing a sub-scan. In this case as well, the drying process can be carried out, for example, by a platen heater or by blowing air.

[0129] In this specification, when a white ink composition is applied to a recording medium with one main scan, and then a non-white ink composition is applied with the next main scan without performing a sub-scan, the case where the "next main scan" is scanned in the same direction as the "first main scan" is sometimes referred to as "Uni-d," and the case where the "next main scan" is scanned in the opposite direction to the "first main scan" is sometimes referred to as "Bi-d."

[0130] 1.1.3. Recording media The recording method of this embodiment uses a low-absorption recording medium or a non-absorption recording medium as the recording medium.

[0131] A low-absorption or non-absorption recording medium refers to a recording medium that does not absorb liquid at all or absorbs very little liquid. Quantitatively, a low-absorption or non-absorption recording medium is defined as "a recording medium that absorbs liquid at all or very little liquid from the start of contact in the Bristow method." 1 / 2 Up to 10 mL / m² of water absorption capacity 2This refers to the following recording media. The Bristow method is the most widely used method for measuring liquid absorption in a short time and is also adopted by the Japan Paper & Pulp Technology Association (JAPAN TAPPI). Details of the test method are described in standard No. 51 "Paper and cardboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper & Pulp Test Methods 2000 Edition". In contrast, absorbent recording media are, This refers to recording media that do not fall under the categories of low-absorption recording media or non-absorption recording media.

[0132] Examples of low-absorption recording media include recording media with a low-absorption coating layer on their surface, known as coated paper. Examples of paper-based recording media include art paper, coated paper, matte paper, and other printing papers. Examples of plastic-based recording media include those coated with polymers on the surface of polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc., or those coated with silica, titanium, or other particles together with a binder.

[0133] Examples of non-absorbent recording media include those in which a plastic coating is applied to a substrate such as paper, those in which a plastic film is adhered to a substrate such as paper, and plastic films that do not have an absorbent layer (receiving layer). Examples of such plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

[0134] 1.2.Drying process The recording method of this embodiment includes a drying step for drying the white ink composition attached to the recording medium. After the white ink attachment step, a non-white ink composition is attached to the white ink composition that has been dried by the drying step, in a non-white ink attachment step described later.

[0135] While the drying process further dries the white ink composition, improving the abrasion resistance of the resulting recording, it can also lead to insufficient coverage of the white ink composition on the recording medium, resulting in unevenness in the color image. However, according to the recording method of this embodiment, the image quality of the white ink composition can be improved, and the occurrence of unevenness in the color image can be reduced.

[0136] The drying process involves heating the recording medium before the white ink application process, or applying heat or airflow to the recording medium during the white ink application process or shortly after the white ink composition has adhered to the recording medium, in order to quickly dry the ink.

[0137] The drying process is a process for drying at least a portion of the solvent component of the ink that has adhered to the recording medium, to the extent that it reduces the flow of the ink. The drying process may be carried out by allowing the ink to adhere to a heated recording medium, or it may be carried out early after adhesion to accelerate drying.

[0138] In the drying process, it is preferable that the drying of ink droplets that have landed on the recording medium begins no later than 0.5 seconds after the droplets land. The drying unit (drying mechanism) for drying the ink on the recording medium is not particularly limited, but examples include platen heaters, hot air heaters, IR heaters, etc., which have a heating function, and blowers, etc., which do not have a heating function.

[0139] Examples of drying mechanisms include conduction type, which heats the recording medium by transferring heat from a component in contact with the recording medium to the recording medium; radiation type, which heats the recording medium by radiating radiation such as IR to the recording medium; and blown air type, which blows air towards the recording medium. Two or more drying mechanisms may be used in combination. In particular, blown air type may be used in combination with other methods.

[0140] The air-blowing method includes methods that use hot air to blow air onto the recording medium while simultaneously warming it, and methods that use room-temperature air to promote ink drying without heating. The method without heating is preferable because it suppresses the drying of ink in the inkjet head nozzles, which can reduce ejection stability. It is also preferable to use either the conduction method or the radiation method in combination with the air-blowing method. Furthermore, the blow-air method is preferable even if it does not involve heating. If the drying process is carried out by blow-air without heating, the effect of suppressing image unevenness caused by the non-white ink composition becomes more pronounced.

[0141] In the drying process, the surface temperature of the recording medium is preferably 60°C or lower, more preferably 55°C or lower. Furthermore, it is more preferably 30-50°C, even more preferably 30-45°C. On the other hand, it is more preferably 40°C or lower, even more preferably 35°C or lower, particularly preferably 30°C or lower, and even more preferably 25-28°C.

[0142] When the surface temperature of the recording medium is within the above range, drying properties are improved, and the abrasion resistance of the resulting recorded material tends to be improved. Furthermore, clogging recovery, ejection stability, and color development are also better, which is preferable.

[0143] When using a fan-type system, the wind speed near the recording medium is preferably 0.5 to 10 m / s, more preferably 1 to 5 m / s, and even more preferably 2 to 3 m / s. The wind temperature is preferably 45°C or lower, more preferably 40°C or lower, even more preferably 32°C or lower, and particularly preferably 20 to 27°C. This further suppresses image unevenness caused by the non-white ink composition.

[0144] The drying step may include a blowing step of blowing air onto the white ink composition adhering to the recording medium.

[0145] As mentioned above, during the drying process, differences in the degree of drying of the white ink composition occur depending on the location of the recording medium, resulting in some areas of the white ink composition being under-dried and others being fully dried. However, with the white ink used in this embodiment, even after the drying process, unevenness in the image quality of the non-white ink can be reduced.

[0146] 1.3. Non-white ink application process The non-white ink application process is performed during a main scan that takes place after the main scan of the white ink application process, while moving the relative position between the inkjet head and the recording medium. In the non-white ink application process, the non-white ink composition is applied on top of the white ink composition that has been dried in the drying process described above.

[0147] 1.3.1. Non-white ink compositions The non-white ink composition may have the same composition as the white ink composition, except that it contains a non-white material instead of a white colorant and does not necessarily contain the aforementioned silicone-based surfactant A.

[0148] The non-white ink composition is an ink having a color other than white, and the color is not limited to black ink, yellow ink, magenta ink, cyan ink, or orange ink, green ink, etc.

[0149] The components contained in the non-white ink composition are described below. Unless otherwise specified, components common to the white ink composition described above may have the same composition as those in the white ink composition.

[0150] 1.3.1.(1) Non-white coloring material The non-white ink composition contains a non-white colorant. The non-white colorant is a colorant other than the white colorant mentioned above, and examples include non-white pigments and dyes. As pigments, for example, inorganic pigments and organic pigments can be used.

[0151] While there are no particular limitations on the inorganic pigments, examples include carbon blacks such as CI Pigment Black 6 (Lamp Black, Vegetable Black), CI Pigment Black 7 (Furnace Black, Channel Black, Thermal Black, Acetylene Black), CI Pigment Black 8 (Charcoal Black), and CI Pigment Black 10 (Graphite).

[0152] Commercially available carbon black products include Mitsubishi Chemical Corporation's No. 2300, 900, MCF88, No. 20B, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc.; and Degussa's Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Pritex 35, U, V, 140U, etc. Examples include Shallblack 6, 5, 4A, 4, 250, etc.; Columbia Carbon's Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc.; and Cabot's Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc.

[0153] Examples of organic pigments include quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ancenthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimimidazolone pigments, isoindolinone pigments, azomethine pigments, or azo pigments.

[0154] Specific examples of organic pigments include the following:

[0155] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc.; CI Bat Blue 4, 60, etc. Preferably, one or more mixtures selected from the group consisting of CI Pigment Blue 15:3, 15:4, and 60 can be exemplified.

[0156] Examples of magenta pigments include CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 168, 184, 202, and CI Pigment Violet 19. Preferably, one or more mixtures selected from the group consisting of CI Pigment Red 122, 202, and 209, and CI Pigment Violet 19 can be exemplified.

[0157] Examples of yellow pigments include CI 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 CI Pigment Yellow 74, 109, 110, 128, 138, 150, and 180 can be exemplified.

[0158] Other colored pigments can also be used. For example, orange pigment and green pigment can be used.

[0159] Pigments may be used individually or in combination of two or more types.

[0160] Even with pigments used as non-white colorants, in order to improve their dispersibility in the ink composition, As with white colorants, it is preferable to apply a surface treatment or to incorporate a dispersant, as described above.

[0161] The dyes used are not particularly limited and include acid dyes, direct dyes, reactive dyes, and basic dyes. Dyes may be used individually or in combination of two or more.

[0162] There are no particular restrictions on the dyes used, but for example, CI Acid Yellow 17, 23, 42, 44, 79, 142; CI Acid Red 52, 80, 82, 249, 254, 289; CI Acid Blue 9, 45, 249; CI Acid Black 1, 2, 24, 94; CI Food Black 1, 2; CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 14 Examples include 2, 144, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, 35.

[0163] The content of the non-white colorant is preferably 0.1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 8% by mass or less, and even more preferably 2% by mass or more and 6% by mass or less, based on the total amount of the non-white ink composition.

[0164] 1.3.1.(2) Water The non-white ink composition is a water-based inkjet ink. The "water-based" composition can be the same as that of the white ink composition described above.

[0165] The water content is preferably 50% by mass or more, more preferably 50 to 100% by mass, in the liquid medium component. Furthermore, it is preferably 60 to 90% by mass, and more preferably 75 to 85% by mass. The liquid medium refers to a solvent component such as water or an organic solvent.

[0166] Furthermore, the water content is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, relative to the total mass of the non-white ink composition. There is no particular upper limit to the water content, but for example, it is preferably 99% by mass or less, more preferably 90% by mass or less, and 80% by mass or less, relative to the total mass of the non-white ink composition.

[0167] 1.3.1.(3) Surfactants The non-white ink composition may contain the silicone-based surfactant A described above, or other silicone-based surfactants other than A (hereinafter also referred to as "other silicone-based surfactants").

[0168] The weight-average molecular weight Mw of other silicone-based surfactants is not particularly limited, but is preferably 8000 or less, more preferably 7000 or less, and even more preferably 5000 or less. The lower limit of the weight-average molecular weight Mw is also not particularly limited, but is preferably greater than 2000, more preferably greater than 3000, and even more preferably greater than 4000.

[0169] Furthermore, the weight-average molecular weight Mw of other silicone-based surfactants is preferably measured by gel permeation chromatography (GPC), as described above.

[0170] The surface tension of a 0.1% by mass aqueous solution of other silicone-based surfactants is preferably 35 mN / m or less, more preferably 33 mN / m or less, and 30 mN / m or less. It is even more preferable that the surface tension is 28 mN / m or less. The lower limit of the surface tension is not particularly limited, but is preferably 15 mN / m or more, more preferably 17 mN / m or more, and even more preferably 20 mN / m or more.

[0171] Other silicone-based surfactants include, for example, SAG002 (Silface SAG002 (manufactured by Nisshin Chemical Industry Co., Ltd.), does not meet condition (a)), SAG503A (Silface SAG503A (manufactured by Nisshin Chemical Industry Co., Ltd.), does not meet condition (a)), SAG005 (Silface SAG005 (manufactured by Nisshin Chemical Industry Co., Ltd.), does not meet condition (a)), BYK-333 (silicone-based surfactant (manufactured by Bic Chemie Japan), does not meet condition (a)), BYK-348 (silicone-based surfactant (manufactured by Bic Chemie Japan), does not meet condition (a)), and BYK-349 (silicone-based surfactant (manufactured by Bic Chemie Japan), does not meet condition (a)).

[0172] Furthermore, the non-white ink composition may contain surfactants other than silicone-based surfactants. The surfactant has the function of adjusting the surface tension of the non-white ink composition and, for example, adjusting the wettability with the white ink composition on the recording medium. Among surfactants, for example, acetylene glycol-based surfactants and fluorine-based surfactants can be preferably used.

[0173] Acetylene glycol-based surfactants are not particularly limited, but examples include Surfinol 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 are brand names, manufactured by Air Products & Chemicals). Examples include Orphine 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 product names, manufactured by Nisshin Chemical Industry Co., Ltd.), and Acetyleneol E00, E00P, E40, E100 (all product names, manufactured by Kawaken Fine Chemical Co., Ltd.).

[0174] As fluorine-based surfactants, it is preferable to use fluorine-modified polymers. Specific examples include BYK-3440 (manufactured by Bic Chemie Japan), Surflon S-241, S-242, S-243 (all trade names, manufactured by AGC Seimi Chemical Co., Ltd.), and Futergent 215M (manufactured by Neos Co., Ltd.).

[0175] The surfactant content in a non-white ink composition can be similar to the content of a specific polyether-modified silicone surfactant in a white ink composition.

[0176] 1.3.1.(4) Other ingredients (Organic solvents) Non-white ink compositions may contain organic solvents. The inclusion of organic solvents tends to improve ink wetting and spreading, and to further reduce the occurrence of unevenness in color images.

[0177] The composition of organic solvents in the non-white ink composition can be the same as that of the white ink composition described above.

[0178] (Resin particles) The non-white ink composition may contain resin particles. The composition of resin particles in the non-white ink composition can be the same as that of the white ink composition described above.

[0179] The content of resin particles (solids) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and particularly preferably 2% by mass or more, based on the total amount of the non-white ink composition. Furthermore, the content of resin particles (solids) is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, based on the total amount of the non-white ink composition.

[0180] (wax) The non-white ink composition may contain wax. The composition of wax in the non-white ink composition can be the same as that of the white ink composition described above.

[0181] (Metal sealant) The non-white ink composition may contain a metal sealant. The composition of the metal sealant in the non-white ink composition can be the same as that of the white ink composition described above.

[0182] (Other ingredients) The non-white ink composition may optionally contain additives such as pH adjusters, preservatives / fungal agents, rust inhibitors, viscosity modifiers, solubilizers, and antioxidants. When such additives are included, the content is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.1 to 1% by mass, relative to the total amount of the non-white ink composition.

[0183] 1.3.1.(5) Physical properties The viscosity and surface tension of the non-white ink composition can be the same as those of the white ink composition described above.

[0184] 1.3.2. Inkjet Method and Recording Medium The non-white ink application process is performed during the main scan, which involves moving the relative position of the inkjet head and the recording medium.

[0185] The inkjet method is the same as the white ink application process described above. It is performed during a main scan that takes place after the main scan of the white ink application process, while moving the relative position of the inkjet head and the recording medium. The recording medium is also the same as in the white ink application process described above.

[0186] 1.4. Processing liquid application process The recording method of this embodiment may include a processing liquid attachment step. The processing liquid attachment step involves attaching a processing liquid containing a coagulant to the recording medium.

[0187] 1.4.1. Treatment solution The treatment solution is preferably an aqueous solution containing a coagulant. The treatment solution may also contain the silicone-based surfactant A mentioned above, and it is more preferable that it contains silicone-based surfactant A.

[0188] 1.4.1.(1) Coagulants The processing solution contains a coagulant that aggregates the components of the ink composition. The coagulant reacts with components such as colorants and resin particles contained in the ink, thereby agglomerating the colorants and resin particles. However, the degree of aggregation of colorants and resin particles by the coagulant varies depending on the type of coagulant, colorant, and resin particles, and can be adjusted. Furthermore, the coagulant reacts with the colorants and resin particles contained in the ink, thereby agglomerating the colorants and resin particles. This can be achieved. Such aggregation can, for example, enhance the color development of colorants, improve the fixation of resin particles, and / or increase the viscosity of ink.

[0189] While not particularly limited, examples of flocculants include metal salts, inorganic acids, organic acids, and cationic compounds. Cationic compounds include cationic resins (cationic polymers) and cationic surfactants. Among these, polyvalent metal salts are preferred as metal salts, and cationic resins are preferred as cationic compounds. Therefore, selecting a flocculant from cationic resins, organic acids, and polyvalent metal salts is preferable in terms of obtaining particularly excellent image quality, scratch resistance, gloss, etc.

[0190] While polyvalent metal salts are preferred as the metal salts, other metal salts can also be used. Among these flocculants, it is preferable to use at least one selected from metal salts and organic acids because of its excellent reactivity with the components contained in the ink. Furthermore, among cationic compounds, it is preferable to use cationic resins because they dissolve easily in the treatment solution. It is also possible to use multiple types of flocculants in combination.

[0191] A polyvalent metal salt is a compound composed of a metal ion with two or more valencies and an anion. Examples of metal ions with two or more valencies include calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, and iron. Among the metal ions that make up these polyvalent metal salts, it is preferable that at least one of calcium ions and magnesium ions is present, given their excellent ability to aggregate the components of the ink.

[0192] The anions constituting the polyvalent metal salt are inorganic ions or organic ions. In other words, the polyvalent metal salt in this invention consists of an inorganic ion or organic ion and a polyvalent metal. Examples of such inorganic ions include chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, hydroxide ions, etc. Examples of organic ions include organic acid ions, such as carboxylate ions.

[0193] Furthermore, the polyvalent metal compound is preferably an ionic polyvalent metal salt, and in particular, the stability of the treatment solution is better when the polyvalent metal salt is a magnesium salt or a calcium salt. In addition, either an inorganic acid ion or an organic acid ion may be used as the counterion for the polyvalent metal.

[0194] Specific examples of the polyvalent metal salts mentioned above include calcium carbonate such as heavy calcium carbonate and light calcium carbonate, calcium nitrate, calcium chloride, calcium sulfate, magnesium sulfate, calcium hydroxide, magnesium chloride, magnesium carbonate, barium sulfate, barium chloride, zinc carbonate, zinc sulfide, aluminum silicate, calcium silicate, magnesium silicate, copper nitrate, calcium formate, calcium acetate, magnesium acetate, and aluminum acetate. These polyvalent metal salts may be used individually or in combination of two or more. Among these, at least one of calcium formate, magnesium sulfate, calcium nitrate, and calcium chloride is preferred because it ensures sufficient solubility in water and reduces residue left by the treatment solution (making the residue less noticeable), with calcium formate and calcium nitrate being more preferred. These metal salts may also contain hydration water in their raw material form.

[0195] Examples of metal salts other than polyvalent metal salts include monovalent metal salts such as sodium salts and potassium salts, such as sodium sulfate and potassium sulfate.

[0196] Examples of organic acids include poly(meth)acrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, Tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyrrolic acid, pyrrole carboxylic acid, furanic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, or salts thereof are preferred examples. Organic acids may be used individually or in combination of two or more. Salts of organic acids that are metal salts are included in the above-mentioned metal salts.

[0197] Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Inorganic acids may be used individually or in combination of two or more.

[0198] Examples of cationic resins (cationic polymers) include cationic urethane resins, cationic olefin resins, and cationic amine resins. Cationic polymers are preferably water-soluble.

[0199] As cationic urethane resins, commercially available products can be used, such as Hydran CP-7010, CP-7020, CP-7030, CP-7040, CP-7050, CP-7060, CP-7610 (product names, manufactured by Dainippon Ink and Chemicals, Inc.), Superflex 600, 610, 620, 630, 640, 650 (product names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and Urethane Emulsion WBR-2120C, WBR-2122C (product names, manufactured by Taisei Fine Chemical Co., Ltd.).

[0200] Cationic olefin resins have olefins such as ethylene and propylene as their structural framework, and known ones can be appropriately selected and used. Cationic olefin resins may also be in an emulsion state dispersed in a solvent such as water or an organic solvent. Commercially available cationic olefin resins can be used, such as Arrowbase CB-1200 and CD-1200 (trade names, manufactured by Unitika Ltd.).

[0201] As cationic amine resins (cationic polymers), any resin having an amino group in its structure is acceptable, and known resins can be appropriately selected and used. Examples include polyamine resins, polyamide resins, and polyallylamine resins. Polyamine resins are resins having an amino group in the main skeleton of the resin. Polyamide resins are resins having an amide group in the main skeleton of the resin. Polyallylamine resins are resins having a structure derived from an allyl group in the main skeleton of the resin.

[0202] Furthermore, examples of cationic polyamine resins include Unisense KHE103L (hexamethylenediamine / epichlorohydrin resin, 1% aqueous solution with a pH of approximately 5.0, viscosity of 20-50 (mPa·s), and solid content of 50% by mass) and Unisense KHE104L (dimethylamine / epichlorohydrin resin, 1% aqueous solution with a pH of approximately 7.0, viscosity of 1-10 (mPa·s), and solid content of 20% by mass) manufactured by Senka Co., Ltd. Furthermore, specific examples of commercially available cationic polyamine resins include FL-14 (manufactured by SNF), Arafix 100, 251S, 255, 255LOX (manufactured by Arakawa Chemical Co., Ltd.), DK-6810, 6853, 6885; WS-4010, 4011, 4020, 4024, 4027, 4030 (manufactured by Seikou PMC Co., Ltd.), and Papiogen P-105 (manufactured by Senka Co., Ltd.). Examples include Sumirez Resin 650(30), 675A, 6615, SLX-1 (manufactured by Taoka Chemical Industry Co., Ltd.), Kachiomaster (registered trademark) PD-1, 7, 30, A, PDT-2, PE-10, PE-30, DT-EH, EPA-SK01, TMHMDA-E (manufactured by Yokkaichi Gosei Co., Ltd.), and Jetfix 36N, 38A, 5052 (manufactured by Satoda Chemical Co., Ltd.).

[0203] Polyamine resins also include polyallylamine resins. Examples of polyallylamine resins include polyallylamine hydrochloride, polyallylamine amide sulfate, and allylamine. Examples include hydrochloride-diallylamine hydrochloride copolymer, allylamine acetate-diallylamine acetate copolymer, allylamine acetate-diallylamine acetate copolymer, allylamine hydrochloride-dimethylallylamine hydrochloride copolymer, allylamine-dimethylallylamine copolymer, polydiallylamine hydrochloride, polymethyldiallylamine hydrochloride, polymethyldiallylamine amide sulfate, polymethyldiallylamine acetate, polydiallyldimethylammonium chloride, diallylamine acetate-sulfur dioxide copolymer, diallylmethylethylammonium ethyl sulfate-sulfur dioxide copolymer, methyldiallylamine hydrochloride-sulfur dioxide copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, and diallyldimethylammonium chloride-acrylamide copolymer.

[0204] Multiple types of these flocculants may be used. Furthermore, selecting at least one of these flocculants—a polyvalent metal salt, an organic acid, or a cationic resin—results in better flocculation, thus enabling the formation of higher-quality images (especially those with good color reproduction).

[0205] The total content of the flocculant in the processing solution is preferably 0.1% to 20% by mass, more preferably 1% to 20% by mass, and more preferably 2% to 15% by mass, relative to the total mass of the processing solution. Even when the flocculant is shared in a solution or dispersion, it is preferable that the solid content is within the above range. If the flocculant content is 1% by mass or more, the ability of the flocculant to flocculate the components contained in the ink is sufficiently obtained. Furthermore, if the flocculant content is 30% by mass or less, the solubility and dispersibility of the flocculant in the processing solution are improved, and the storage stability of the processing solution can be improved.

[0206] Even if the organic solvent contained in the treatment solution has high hydrophobicity, the solubility of the coagulant in the treatment solution will be good. Therefore, it is preferable to use a coagulant that has a solubility of 1 g or more in 100 g of water at 25°C, and more preferably one that is between 3 g and 80 g.

[0207] 1.4.1.(2) Water The processing solution is an aqueous solution. The composition of the "aqueous solution" can be the same as that of the white ink composition described above.

[0208] 1.4.1.(3) Silicone-based surfactant A The processing solution may contain silicone-based surfactant A. Since silicone-based surfactant A is the same as described in the description of the white ink application process, its description will be omitted.

[0209] 1.4.1.(4) Other ingredients The processing solution may contain surfactants, organic solvents, and other components. These components can be the same as those in the white ink composition described above.

[0210] 1.4.1.(5) Physical properties of the treatment solution From the viewpoint of ensuring appropriate wetting spread on the recording medium, the surface tension of the processing solution at 25°C is preferably 40 mN / m or less, more preferably 38 mN / m or less, more preferably 35 mN / m or less, and even more preferably 30 mN / m or less. The surface tension can be measured by using an automatic surface tensimeter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the composition in an environment of 25°C.

[0211] The processing solution is more preferably applied to the recording medium by an inkjet method. In that case, the viscosity at 20°C should be between 1.5 mPa·s and 15 mPa·s. A pressure of 1.5 mPa·s or more and 7 mPa·s or less is preferred, and a pressure of 1.5 mPa·s or more and 5.5 mPa·s or less is even more preferred. When the processing liquid is applied to the recording medium by an inkjet method, it is easy to efficiently form a predetermined processing liquid application area on the recording medium.

[0212] 1.5. Other processes <Post-heating process> The recording method according to this embodiment may include a post-heating step in which the recording medium is further heated after the non-white ink application step described above. The post-heating step can be carried out, for example, using an appropriate heating means. The post-heating step can be carried out, for example, by an after-heater (in the example of the inkjet recording device described later, this corresponds to heating heater 5). Furthermore, the heating means is not limited to the heating means provided in the inkjet recording device, but other drying means can also be used. This allows the resulting image to be dried and fixed more thoroughly, so that, for example, the recorded material can be made usable sooner.

[0213] The temperature of the recording medium in this case is not particularly limited, but can be set considering, for example, the Tg of the resin components constituting the resin particles contained in the recording material. When considering the Tg of the resin components constituting the resin particles or wax, it is preferable to set the temperature to 5.0°C or higher, preferably 10.0°C or higher, than the Tg of the resin components constituting the resin particles.

[0214] The surface temperature of the recording medium reached by the post-heating step is 30.0°C to 120.0°C, preferably 40.0°C to 100.0°C, more preferably 50.0°C to 95°C, and even more preferably 70°C to 90°C. The surface temperature of the recording medium reached by the post-heating step is particularly preferably 80°C or higher. When the temperature of the recording medium is within this range, the resin particles and wax contained in the recording material can be film-formed and planarized, and the resulting image can be dried and fixed more sufficiently.

[0215] 1.6. Other conditions, etc. In the recording method of this embodiment, the travel length of the main scan in the white ink application step and the non-white ink application step may be 50 cm or more, or 1 m or more, respectively. In this case, the time from the application of the white ink composition to the application of the non-white ink composition (impact time difference) becomes longer, creating conditions that make it easy for image unevenness due to the non-white ink composition to occur. However, since the white ink composition contains a silicone-based surfactant A, image unevenness due to the non-white ink composition can be suppressed. The above travel length is more preferably 1 to 3 m, and even more preferably 1.5 to 2 m.

[0216] Furthermore, in the recording method of this embodiment, if the direction of the first main scan in the non-white ink adhesion process is opposite to the direction of the last main scan in the white ink adhesion process performed on the same main scan area (Bi-d), the time from the adhesion of the white ink composition to the adhesion of the non-white ink composition (the difference in impact time) becomes uneven (the difference in impact time is large), creating conditions that make it easy for image unevenness due to the non-white ink composition to occur. However, as a result of the white ink composition containing a silicone-based surfactant A, image unevenness due to the non-white ink composition can be suppressed.

[0217] 1.7. Effects In the recording method of this embodiment, as a result of the white ink composition containing a silicone-based surfactant A, the wettability of the non-white ink composition droplets is similar whether they come into contact with the recording medium before the white ink composition has dried after landing, or whether they come into contact with the recording medium after the white ink composition has dried after landing. The difference in image quality between color images is reduced, and image unevenness can be suppressed.

[0218] In the recording method of this embodiment, since a drying process (heating in the platen, blowing air, etc.) is included, the image quality (unevenness) of the white ink composition is easily suppressed, but drying is accelerated, making it easy for unevenness in the color image to occur. Also, uneven drying is likely to occur in the drying process, which also makes it easy for unevenness in the color image to occur. However, the recording method of this embodiment can sufficiently obtain the above effects.

[0219] The above effects can be fully obtained even when the main scanning distance is long or when using Bi-d printing, which are prone to color image unevenness. In the case of line printers, the time difference between the adhesion of the white ink composition and the adhesion of the non-white ink composition is short, making it less likely for the drying degree of the white ink composition to be uneven and thus less likely for color image unevenness to occur. From this viewpoint, the recording method of this embodiment is particularly useful for serial type inkjet recording devices and so-called lateral type inkjet recording devices.

[0220] 2. Recording device An example of a recording device suitable for the recording method according to this embodiment will be described with reference to the drawings. The recording device according to this embodiment is a recording device that performs the above-described recording method and comprises a white ink composition, a non-white ink composition, an inkjet head that performs a white ink application step, a drying mechanism that performs a drying step, and an inkjet head that performs a non-white ink application step.

[0221] Figure 1 is a schematic cross-sectional view showing the inkjet recording device 1. Figure 2 is a perspective view showing an example of the configuration around the carriage of the inkjet recording device 1 shown in Figure 1.

[0222] As shown in Figures 1 and 2, the inkjet recording device 1 comprises 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 movement mechanism 13, a transport means 14, and a control unit CONT. The operation of the entire inkjet recording device 1 is controlled by the control unit CONT shown in Figure 2.

[0223] The inkjet head 2 has an inkjet head that ejects a white ink composition and an inkjet head that ejects a non-white ink composition, and can record onto the recording medium M by ejecting the white ink composition and the non-white ink composition from the nozzles of the respective inkjet heads and adhering them to the recording medium M.

[0224] In this embodiment, the inkjet head 2 is a serial inkjet head that scans the recording medium M one or more times in the main scanning direction relative to the recording medium M to deposit a white ink composition and a non-white ink composition onto the recording medium M. The inkjet head 2 is mounted on a carriage 9 shown in Figure 2. The inkjet head 2 is scanned one or more times in the main scanning direction relative to the recording medium M by the operation of a carriage movement mechanism 13 that moves the carriage 9 in the media width direction of the recording medium M. The media width direction is the main scanning direction of the inkjet head 2. Scanning in the main scanning direction is also called main scanning.

[0225] Here, the main scanning direction is the direction in which the carriage 9, on which the inkjet head 2 is mounted, moves. In Figure 1, this is the direction that intersects the sub-scanning direction, which is the transport direction of the recording medium M indicated by arrow SS. In Figure 2, the width direction of the recording medium M, i.e., 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, scanning is performed in the main scanning direction, i.e., in either the direction of arrow S1 or arrow S2.

[0226] The cartridge 12 that supplies each ink to the inkjet head 2 includes a plurality of independent cartridges. The cartridge 12 is detachably mounted on the carriage 9 on which the inkjet head 2 is mounted. Each of the plurality of cartridges may be filled with a different type of ink, and ink is supplied from the cartridge 12 to each nozzle. The recording method described above can be performed by filling at least one of the cartridges 12 with a white ink composition and at least one other of the cartridges 12 with a non-white ink composition.

[0227] In this embodiment, the example shown illustrates that the cartridge 12 is mounted on the carriage 9. However, the embodiment is not limited to this configuration, and the cartridge 12 may be provided in a location other than the carriage 9 and supplied to each nozzle by a supply pipe (not shown).

[0228] Conventional known methods can be used for ejection from the inkjet head 2. In this embodiment, a method is used that ejects droplets using the vibration of a piezoelectric element, that is, an ejection method that forms ink droplets by the mechanical deformation of an electrostrictive element.

[0229] The inkjet recording device 1 is equipped with a ventilation fan 8, an IR heater 3, and a platen heater 4 for drying the ink ejected from the inkjet head 2 and adhering to the recording medium M. The drying process can be performed by using these ventilation fan 8, IR heater 3, and platen heater 4 in appropriate combinations. In the drying process, it is not always necessary to heat the recording medium M; the ventilation fan 8 may be used alone to provide airflow at room temperature.

[0230] Furthermore, by using the IR heater 3, the recording medium M can be heated radiantly by infrared radiation from the inkjet head 2 side. This makes it easier for the inkjet head 2 to be heated at the same time, but the temperature can be raised without being affected by the thickness of the recording medium M, compared to when the recording medium M is heated from the back side by a platen heater 4 or the like. In addition, various fans (e.g., ventilation fan 8) may be provided to dry the ink on the recording medium M by blowing warm air or air at the same temperature as the environment onto the recording medium M.

[0231] The platen heater 4 can heat the recording medium M via the platen 11 at a position opposite the inkjet head 2 so that the ink ejected by the inkjet head 2 can dry quickly from the moment it adheres to the recording medium M. The platen heater 4 can heat the recording medium M by conduction, thereby allowing ink to adhere to the heated recording medium M.

[0232] Furthermore, it is preferable that the surface temperature of the recording medium M, due to heating by the IR heater 3 and the platen heater 4, be within the range described in the drying process above.

[0233] The heating element 5 is a heater for drying and solidifying the ink attached to the recording medium M, in other words, a heater for secondary drying. The heating element 5 can be used in the secondary drying process. When the heating element 5 heats the recording medium M on which the image is recorded, moisture and other substances contained in the ink evaporate more quickly and are scattered, and an ink film is formed by the resin particles that may be contained in the ink. In this way, the ink film is firmly fixed or adhered to the recording medium M, resulting in excellent film-forming properties, and a high-quality image can be obtained in a short time.

[0234] The surface temperature of the recording medium M due to heating by the heating element 5 is preferably within the range described in the secondary drying step above. When the temperature is within the aforementioned range, high-quality images tend to be obtained in a short time.

[0235] The inkjet recording device 1 may have a cooling fan 6. After the applied ink dries, the ink on the recording medium M is cooled by the cooling fan 6, thereby forming an ink coating on the recording medium M with good adhesion.

[0236] Furthermore, the inkjet recording device 1 may be equipped with a preheater 7 that preheats the recording medium M before ink is applied to it. In addition, the inkjet recording device 1 may be equipped with a ventilation fan 8 to allow the ink applied to the recording medium M to dry more efficiently.

[0237] Below the carriage 9 are a platen 11 that supports the recording medium M, a carriage movement mechanism 13 that moves the carriage 9 relative to the recording medium M, and a transport means 14 which is a roller that transports the recording medium M in the sub-scanning direction. The operation of the carriage movement mechanism 13 and the transport means 14 is controlled by the control unit CONT.

[0238] According to this recording device, the white ink composition contains a silicone-based surfactant A whose surface tension is 28 mN / m or less for both the 0.1% by mass aqueous solution of the surfactant and the 0.1% PG (propylene glycol) solution of the surfactant. As a result, non-white ink composition droplets that come into contact with the white ink composition before it has dried much after impact, and non-white ink composition droplets that come into contact with the white ink composition after it has dried more significantly after impact, both exhibit similar wetting properties. This minimizes differences in image quality of non-white images and allows for the formation of images with suppressed image unevenness.

[0239] 3. Examples and Comparative Examples The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" refer to mass unless otherwise specified. Evaluations are performed under conditions of 25°C and 40.0% relative humidity unless otherwise specified.

[0240] 3.1. Preparation of white ink composition, non-white ink composition, and processing solution The components were placed in a container and mixed to obtain the compositions shown in Tables 1 and 2. After stirring for 2 hours, the mixture was filtered using a 5.0 μm PTFE membrane filter to obtain white ink compositions (W1 to W9), non-white ink compositions (C1), second ink compositions (C2-1 to C2-2), and processing solutions (R1 to R6). The values ​​in the tables represent mass percent. Pure water was used, and it was added so that the mass of each composition was 100% by mass. The pigments and dispersant resins were prepared using the dispersion solutions described later.

[0241] Of the components shown in Tables 1 and 2, the components other than the compound names are as follows: PB15:3 : CI Pigment Blue 15:3 • Joncryl 631: Manufactured by BASF, styrene-acrylic resin particles • Hi-Tec E-6500: Product name manufactured by Toho Chemical Co., Ltd., polyethylene wax emulsion ·BYK-3420: silicone-based surfactant (manufactured by BYK-Chemie Japan), satisfies condition (a). ·BYK-3480: silicone-based surfactant (manufactured by BYK-Chemie Japan), satisfies condition (a). ·SAG503A: Silface SAG002 (manufactured by Nissin Chemical Industry Co., Ltd.), does not satisfy condition (a). ·PD002W: Olfine PD002W (acetylene-based surfactant), manufactured by Nissin Chemical Industry Co., Ltd. ·1,2-BD: 1,2-butanediol ·1,3-BD: 1,3-butanediol ·TEG: triethylene glycol ·Cationic polymer: "Catiomaster PD-7, polyamine resin (epichlorohydrin -amine derivative resin)" manufactured by Yokkaichi Gosei Co., Ltd. ·1,2-HD: 1,2-hexanediol ·PG: propylene glycol ·Preparation Example 1: as follows

[0242] <Preparation Example 1 of Silicone-Based Surfactant> Synthesis is performed as described below to obtain Preparation Example 1, which is a silicone-based surfactant. To a solution of 7.0 g of heptaethylene glycol monoallyl ether in 20 mL of tetrahydrofuran, 5.8 g of a compound having -H bonds on the Si atoms at both terminals of dimethylpolysiloxane having 19 Si atoms and 0.1 mL of chloroplatinic acid are added, and the mixture is allowed to react by holding at 65°C for 24 hours while stirring. After completion of the reaction, the solvent is distilled off by rotary evaporation to obtain Preparation Example 1 of silicone-based surfactant.

[0243] The structure of Preparation Example 1 of silicone-based surfactant is as follows in the above formula (1); a=17, x, y=3, n, m=7, o, p=0, R 1 , R 2 = hydroxy group, That is the case.

[0244] The measurement conditions for GPC measurement in each silicone-based surfactant are as follows: [Measurement conditions] • Solvent: Tetrahydrofuran • Column: TSKgelSuperHZM-N x 2 · +TSKgel guardcolumn SuperHZ-L Column temperature: 40°C ·Injection volume: 25μL • Detector: Differential refraction (RI) ·Flow rate: 0.35mL / min • Calibration curve: A calibration curve is used based on 13 samples of standard polystyrene (STKstandard polystyrene, manufactured by Tosoh Corporation) with Mw values ​​ranging from 1,000,000 to 500.

[0245] For each silicone-based surfactant, a 0.1% by mass aqueous solution of the surfactant and a 0.1% by mass propylene glycol solution of the surfactant were prepared, and the surface tension was measured as described above. The measured values ​​for each silicone-based surfactant are summarized in Table 6.

[0246] In each table, whether a silicone-based surfactant satisfies condition (a), which states that the surface tension of a 0.1% aqueous solution of the surfactant is 28.0 mN / m or less and the surface tension of a 0.1% propylene glycol solution of the surfactant is 28.0 mN / m or less, is indicated as "Y" if it is satisfied and "N" if it is not satisfied.

[0247] 3.2. Evaluation Method 3.2.1. Evaluation Criteria Printer: SC-R5050 (Seiko Epson) modified machine Resolution: 1200 x 1200 dpi Adhesion amount (percentage of material applied): As shown in Tables 3-5 (mg / inch) 2 ) Number of scans: 9 times (per ink) Surface temperature of recording medium: as described in Tables 3 to 5 (surface temperature of the recording medium on the platen). Note that the notation 25 (RT) indicates room temperature without heating by the platen. Drying fan wind speed: wind speed on the paper surface, as described in Tables 3 to 5 Post-drying temperature (secondary drying temperature): 80°C Recording medium: Orajet3165G-010 Printing width refers to the width of the recording medium. 64 inches = 162.56 cm 50 inches = 127 cm 74 inches = 187.96 cm

[0248] 3.2.2. Evaluation of aggregation (white) (white-only pattern) Visually check the solid pattern image of the recorded matter obtained as described above, and observe the presence or absence of bleed unevenness (aggregation unevenness caused by adjacent ink droplets gathering together). Evaluate aggregation unevenness according to the following evaluation criteria. A: No aggregation (shading unevenness) is observed in the pattern. B: Fine aggregation (shading unevenness) can be observed upon close inspection. C: Fine aggregation (shading unevenness) is slightly observed. D: Fine aggregation (shading unevenness) is clearly observed. E: Large aggregation (shading unevenness) is observed.

[0249] 3.2.3. Evaluation of whiteness (white-only pattern) Place the recorded matter obtained as described above on black paper, visually observe the ease of visual recognition of the image, and evaluate the visibility according to the following evaluation criteria. Note that when the adhesion amount of the white ink composition is small, the hiding property of the image is insufficient, so the black color of the underlying black paper can be seen through, making the image difficult to recognize. A: Easy to recognize visually. B: Appears slightly blackish, but easy to recognize visually. C: Appears blackish and slightly difficult to recognize visually. D: Appears blackish and difficult to recognize visually.

[0250] 3.2.4. Evaluation of image unevenness of color-on-white (white+color pattern) Using the recording method described above, a solid pattern of white ink and a solid pattern of cyan ink are recorded on top of each other. The presence or absence of areas with different degrees of uneven aggregation of cyan ink in the width direction of the recording medium within the printed material is then compared. A: In the printed material, the uneven aggregation of cyan ink is not visible when observed with a magnifying glass. B: Differences in cyan ink aggregation within the printed material are not visible to the naked eye, but are visible with a magnifying glass. C: In the printed material, slight differences in cyan ink aggregation are visible to the naked eye. D: Significant differences in cyan ink aggregation are visible to the naked eye within the printed material.

[0251] 3.2.5. Evaluation of abrasion resistance (white + color pattern) The solid ink area will be tested. The friction material will be Kanakin. A JSPS (Japan Society for the Promotion of Science) test (500g x 30 times) will be performed. A: No color transfer to the friction element or soiling of the printed surface was observed. B: Color transfer to the friction element is observed, but no soiling of the printed surface is found. C: There is some background staining on the printed surface, but it is not very noticeable. D: The printed surface is noticeably soiled.

[0252] 3.2.6. Evaluation of Dispensing Stability (White only) Recording will be performed for 2 hours according to the evaluation conditions. However, this will be a simulated recording in which no ink is ejected from the head after recording. After recording, suction cleaning will be performed to restore non-ejecting nozzles, and then a nozzle inspection will be conducted. Each cleaning cycle will involve ejecting 1 cc of ink from the nozzle row. The evaluation will be performed only on the white ink composition. A: All nozzles are restored after one cleaning. B: All nozzles recovered after 3 cleaning cycles. C: All nozzles recovered after 6 cleaning cycles. D: Some nozzles do not recover after 6 cleaning cycles.

[0253] 3.3. Evaluation Results Tables 3 to 5 show that when the white ink composition contains silicone-based surfactant A, and a drying step is performed to dry the white ink composition attached to the recording medium, image unevenness of the white overlay color is suppressed in all cases, and good results are obtained. In contrast, Comparative Examples 1 and 2, in which the white ink composition does not contain silicone-based surfactant A, both show insufficient image unevenness of the white overlay color. Furthermore, Comparative Example 3 and Reference Example 1, which do not have a drying step to dry the white ink composition attached to the recording medium, show insufficient whiteness of the image produced by the white ink composition.

[0254] The present invention includes configurations substantially identical to those described in the embodiments, for example, configurations with the same function, method, and results, or configurations with the same purpose and effect. Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0255] The following can be derived from the embodiments and modifications described above.

[0256] The recording method is: A recording method for recording on a recording medium using an aqueous white ink composition containing a white colorant and an aqueous non-white ink composition containing a non-white colorant, A white ink application step in which the white ink composition is ejected from the inkjet head and adhered to the recording medium, A drying step for drying the white ink composition adhering to the recording medium, A non-white ink application step in which the non-white ink composition is ejected from the inkjet head and adhered to the recording medium, It has, The non-white ink composition is then applied to the white ink composition that has been dried by the drying process. The recording medium is a low-absorption recording medium or a non-absorption recording medium. The white ink application process is performed by a main scan while moving the relative position of the inkjet head and the recording medium. The non-white ink application process is performed after the main scan of the white ink application process, by moving the relative position of the inkjet head and the recording medium during the main scan. The aforementioned white ink composition contains a silicone-based surfactant A, the surface tension of which of the surfactant in a 0.1% by mass aqueous solution is 28.0 mN / m or less, and the surface tension of the surfactant in a 0.1% by mass propylene glycol solution is 28.0 mN / m or less.

[0257] According to this recording method, the white ink composition contains a silicone-based surfactant A whose surface tension is 28 mN / m or less for both the 0.1% by mass aqueous solution of the surfactant and the 0.1% PG (propylene glycol) solution of the surfactant. As a result, the wettability of non-white ink composition droplets that come into contact with the white ink composition when it has not yet dried much after impact, and non-white ink composition droplets that come into contact with it after it has dried more significantly after impact, are similar. This reduces the difference in image quality of non-white images and allows for the formation of images with suppressed image unevenness. Furthermore, the drying process is By having this feature, the whiteness (image quality) of white images can also be improved.

[0258] White ink compositions generally use organic solvents with a higher standard boiling point than water to provide moisture retention. Therefore, when a white ink composition has not yet dried after impact, a large amount of water remains, while when the white ink composition has dried after impact, the water evaporates first, leaving a large amount of organic solvent.

[0259] The inventors have concluded that the surface tension of a 0.1% by mass aqueous solution of surfactant is related to the surface tension of a white ink composition that has not yet dried since impact, while the surface tension of a 0.1% by mass PG solution of surfactant is related to the surface tension of a white ink composition that has dried since impact.

[0260] Therefore, the wettability of droplets of the non-white ink composition when the non-white ink composition comes into contact with the white ink composition is related to the surface tension of the white ink composition at the time of contact with the non-white ink composition. It is estimated that by keeping both of these values ​​below 28 mN / m, image unevenness can be reduced. Furthermore, by using a silicone-based surfactant, the surfactant activity is easily exhibited in both aqueous solutions and PG solutions, making it easier to achieve such effects.

[0261] Furthermore, since the above recording method includes a drying step, it is less likely to cause image unevenness due to the white ink composition, but it is more likely to cause image unevenness due to the non-white ink composition. However, since the white ink composition contains the above-mentioned silicone-based surfactant A, it is possible to suppress such image unevenness due to the non-white ink composition.

[0262] In the above recording method, The surface temperature of the recording medium in the drying process may be 30°C or higher and 45°C or lower.

[0263] This recording method further suppresses image unevenness caused by non-white ink compositions.

[0264] In the above recording method, The drying step may include a blowing step of blowing air onto the white ink composition adhering to the recording medium.

[0265] This recording method makes the effect of suppressing image unevenness caused by non-white ink compositions more pronounced.

[0266] In the above recording method, The recording medium has a white ink composition adhesion amount of 15 mg / inch. 2 The recording area may have the above-mentioned features.

[0267] This recording method improves the background opacity of the image using the white ink composition, and also more significantly reduces image unevenness caused by the non-white ink composition.

[0268] In the above recording method, The content of the white colorant in the white ink composition may be 10% by mass or more and 20% by mass or less.

[0269] This recording method further improves the background opacity of the image using the white ink composition.

[0270] In the above recording method, The process may include a step of applying a processing solution containing a coagulant to the recording medium.

[0271] This recording method further improves the color reproduction of images produced by the white ink composition.

[0272] In the above recording method, The travel length of the main scan in the white ink application step and the non-white ink application step may each be 1 m or more.

[0273] This recording method can suppress image unevenness even under conditions where the time difference between projectiles is longer and image unevenness is more likely to occur due to non-white ink compositions.

[0274] In the above recording method, The white ink composition may contain an organic solvent, and may contain 50% by mass or more of an organic solvent having a standard boiling point of 200°C or lower, relative to the total amount of the organic solvent contained.

[0275] This recording method can improve the abrasion resistance of the white ink composition. This effect is particularly pronounced when a large amount of the white ink composition is applied.

[0276] In the above recording method, The white ink composition contains an organic solvent, and the standard boiling point of the organic solvent with the highest standard boiling point may be 250°C or lower.

[0277] This recording method can improve the abrasion resistance of the white ink composition. This effect is particularly pronounced when a large amount of the white ink composition is applied.

[0278] In the above recording method, The direction of the first main scan in the non-white ink application process may be opposite to the direction of the last main scan in the white ink application process, which is performed on the same main scan area.

[0279] This recording method tends to create conditions where differences in impact time are more likely to occur, potentially leading to image unevenness due to non-white ink compositions. However, even in such cases, image unevenness can be suppressed.

[0280] The recording device is A recording device that performs any of the recording methods described above, The white ink composition, The non-white ink composition, The inkjet head that performs the white ink application process, A drying mechanism that performs the aforementioned drying process, The system includes the inkjet head that performs the non-white ink application step.

[0281] According to this recording device, the white ink composition contains a silicone-based surfactant A whose surface tension is 28 mN / m or less for both the 0.1% by mass aqueous solution of the surfactant and the 0.1% PG (propylene glycol) solution of the surfactant. As a result, non-white ink composition droplets that come into contact with the white ink composition before it has dried much after impact, and non-white ink composition droplets that come into contact with the white ink composition after it has dried more significantly after impact, both exhibit similar wetting properties. This minimizes differences in image quality of non-white images and allows for the formation of images with suppressed image unevenness. [Explanation of Symbols]

[0282] 1... Inkjet recording device, 2... Inkjet head, 3... IR heater, 4... Platen heater, 5... Heating heater, 6... Cooling fan, 7... Preheater, 8... Ventilation fan, 9... Carriage, 11... Platen, 12... Cartridge, 13... Carriage movement mechanism, 14... Transport means, CONT... Control unit, MS... Main scanning direction, SS... Sub-scanning direction, M... Recording medium

Claims

1. A recording method for recording on a recording medium using an aqueous white ink composition containing a white colorant and an aqueous non-white ink composition containing a non-white colorant, A white ink application step in which the white ink composition is ejected from the inkjet head and adhered to the recording medium, A drying step for drying the white ink composition adhering to the recording medium, A non-white ink application step in which the non-white ink composition is ejected from the inkjet head and adhered to the recording medium, It has, The non-white ink composition is then applied to the white ink composition that has been dried by the drying process. The recording medium is a low-absorption recording medium or a non-absorption recording medium. The white ink application process is performed by a main scan while moving the relative position of the inkjet head and the recording medium. The non-white ink application process is performed after the main scan of the white ink application process, by moving the relative position of the inkjet head and the recording medium during the main scan. A recording method comprising the white ink composition containing a silicone-based surfactant A, wherein the surface tension of a 0.1% by mass aqueous solution of the surfactant is 28.0 mN / m or less, and the surface tension of a 0.1% by mass propylene glycol solution of the surfactant is 28.0 mN / m or less.

2. In claim 1, A recording method wherein the surface temperature of the recording medium in the drying step is 30°C or higher and 45°C or lower.

3. In claim 1, A recording method wherein the drying step includes a blowing step of blowing air onto the white ink composition adhering to the recording medium.

4. In claim 1, The recording medium has a white ink composition adhering to it of 15 mg / inch. ２ A recording method having the above-mentioned recording area.

5. In claim 1, A recording method wherein the content of the white colorant in the white ink composition is 10% by mass or more and 20% by mass or less.

6. In claim 1, A recording method comprising a process step of applying a processing liquid containing a coagulant to the recording medium.

7. In claim 1, A recording method wherein the travel length of the main scan in the white ink application step and the non-white ink application step is 1 m or more.

8. In claim 1, The white ink composition contains an organic solvent, and contains 50% by mass or more of the organic solvent having a standard boiling point of 200°C or lower, relative to the total amount of the organic solvent contained.

9. In claim 1, A recording method wherein the white ink composition contains an organic solvent, and the standard boiling point of the organic solvent with the highest standard boiling point is 250°C or lower.

10. In claim 1, A recording method wherein the direction of the first main scan in the non-white ink application process is opposite to the direction of the last main scan in the white ink application process, which is performed on the same main scan area.

11. A recording device that performs the recording method described in any one of claims 1 to 10, The white ink composition, The non-white ink composition, The inkjet head that performs the white ink application process, A drying mechanism that performs the aforementioned drying process, A recording apparatus having an inkjet head that performs the non-white ink application process.

Images