Ink set and recording device

Abstract

To provide an ink set and recording device that can produce high-resolution images, have good adhesion and abrasion resistance, and are suitable for lamination. [Solution] To achieve the above objective, an ink set according to one embodiment of the present invention includes a first ink, a second ink, and a third ink. Each of the first ink, the second ink, and the third ink contains a binder, an organic solvent, water, and a surfactant, and the binder contained in the first ink contains at least one of an acrylic resin or a polyolefin resin. The binders contained in the second ink and the third ink contain a urethane resin. The absolute difference between the surface tension of the first ink and the surface tension of the second ink is 2.0 mN / m or less. The absolute difference between the surface tension of the first ink and the surface tension of the third ink is 2.0 mN / m or less.

Description

Technical Field

[0001] The present invention relates to an ink set applicable to printing of a recording medium and the like, and a recording apparatus.

Background Art

[0002] Since water-based ink ejected onto a non-absorbent medium does not exhibit a penetration phenomenon, bleeding between colors becomes a major issue. In order to suppress bleeding, measures such as imparting quick-drying properties to the ink or increasing the drying heat quantity are taken, but this may cause clogging of the head nozzles, leading to ejection failure and a decrease in productivity. In addition, for white ink with a large particle size, adhesion and abrasion resistance are issues. Also, resistance to lamination is required for both front printing and back printing.

[0003] For example, in Patent Document 1, an ink containing a polyolefin copolymer having a structural unit derived from an unsaturated carboxylic acid, a structural unit derived from an olefin, and a structural unit derived from an acrylate ester in a pretreatment liquid and containing a polyester polyurethane resin in the ink is disclosed. In Patent Document 2, an ink containing an acrylic resin and urethane-based resin fine particles is disclosed. In Patent Documents 3 and 4, inks containing two types of resins are disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not mention surface tension, and if the difference in surface tension between the inks is too large, pinning properties cannot be ensured and bleeding occurs. Furthermore, Patent Documents 2, 3, and 4 contain two types of resins, such as acrylic resin and urethane resin fine particles, in the ink, but there are difficulties in satisfactory performance and stability during storage.

[0006] In view of the above circumstances, the object of the present invention is to provide an ink set and a recording device that produce high-resolution images, have good adhesion and scratch resistance, and are suitable for lamination. [Means for solving the problem]

[0007] To achieve the above objective, an ink set according to one embodiment of the present invention includes a first ink, a second ink, and a third ink. Each of the first ink, the second ink, and the third ink comprises a binder, an organic solvent, water, and a surfactant. The binder contained in the first ink comprises at least one of an acrylic resin or a polyolefin resin. The binder contained in the second ink and the third ink contains a urethane-based resin. The absolute value of the difference between the surface tension of the first ink and the surface tension of the second ink is 2.0 mN / m or less. The absolute value of the difference between the surface tension of the first ink and the surface tension of the third ink is 2.0 mN / m or less.

[0008] A recording device using an ink set according to one embodiment of the present invention comprises an ejection unit, a drying unit, and a control unit. The ejection unit ejects the first ink, the second ink, and the third ink onto the recording medium. The drying unit dries the first ink, the second ink, and the third ink applied to the recording medium. The control unit controls the ejection unit to eject the first ink, the second ink, and the third ink onto the recording medium in that order, and the drying unit to dry the recording medium on which the first ink, the second ink, and the third ink have been ejected. [Effects of the Invention]

[0009] According to the invention, it is possible to provide an ink that produces high-resolution images, has good adhesion and abrasion resistance, and is suitable for lamination. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing the configuration of the recording device. [Figure 2] This is a diagram illustrating the evaluation of pinning properties. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] <Ink Set> An ink set according to an embodiment of the present invention includes a first ink, a second ink, and a third ink. Each of the first, second, and third inks contains a binder, an organic solvent, water, and a surfactant. In this embodiment, printing is performed by ejecting the first, second, and third inks onto a transparent recording medium in that order.

[0013] For example, the ink set is used for front printing and back printing. Front printing refers to printing on the front side of a recording medium (non-absorbent medium) in printing on a transparent recording medium (the side that the viewer can visually recognize). When a viewer visually recognizes the front-printed recording medium, the positional relationship of "viewer, image, recording medium" is formed, and the image is directly visually recognized by the viewer. Back printing refers to printing on the back side of a recording medium (the side opposite to the side that is visually recognized by the viewer) in printing on a transparent recording medium. When a viewer visually recognizes the back-printed recording medium, the positional relationship of "viewer, recording medium, image" is formed, and the image is visually recognized by the viewer through the recording medium.

[0014] The binder exists in a state of being dispersed in water (aqueous medium) and has a function as a binder that adheres the recording medium and the pigment. The binder optimizes the fixing property of pigments such as titanium oxide particles to the recording medium.

[0015] The organic solvent is used to improve the hiding property and visibility of the recording medium by the white ink. For example, the organic solvent is preferably propylene glycol and triethylene glycol monobutyl ether, but the solvent type and composition are not limited as long as they are shown in the examples.

[0016] The surfactant optimizes the compatibility and dispersion stability of each component contained in the ink. The surfactant used in the first ink, the second ink, and the third ink preferably contains a silicone-based surfactant. Note that the surfactant is not limited to the silicone-based surfactant, and each surfactant of anionic, cationic, amphoteric, and fluorine-based may be included.

[0017] The first ink is white ink. For example, titanium oxide or other white pigments are used in the first ink. By forming a base layer using white ink on a transparent recording medium, it becomes possible to increase the hiding power of the formed image. Also, the first ink may be clear ink, that is, it may not contain a white pigment. In this case, the first ink functions as an adhesive layer that adheres the recording medium and the second ink which is white ink, and can ensure the adhesion and hiding power with the recording medium.

[0018] In this embodiment, the binder contained in the first ink contains an acrylic resin or a polyolefin resin. For example, the binder contained in the first ink is preferably prepared as an acrylic emulsion or a polyolefin emulsion.

[0019] By including an acrylic resin or a polyolefin resin excellent in adhesion to the recording medium (base material), the adhesion between the first ink and the recording medium is improved.

[0020] The content ratio of the binder contained in the first ink is preferably 5% by mass or more and 20% by mass or less.

[0021] Note that the binder contained in the first ink is not limited. For example, an appropriate binder may be included according to the material and properties of the recording medium.

[0022] Although the solvent type and composition are not limited as long as shown in the examples, as the content ratio of the organic solvent contained in the first ink, propylene glycol is preferably 1.0% by mass or more and 20% by mass or less, and triethylene glycol monobutyl ether is preferably 2.0 to 10.0% by mass.

[0023] Although the addition amount of the surfactant is not limited as long as shown in the examples, as the content ratio of the surfactant contained in the first ink, 0.05% by mass or more and 0.5% by mass or less is preferable.

[0024] The water content in the first ink is preferably 55% by mass or more and 75% by mass or less.

[0025] The second ink is a white ink. For example, the second ink contains a white pigment such as titanium dioxide, a binder to bond the recording medium and the pigment, etc.

[0026] In this embodiment, the binder contained in the second ink contains a urethane-based resin with excellent abrasion resistance and lamination suitability. For example, it is preferable that the binder contained in the second ink be prepared as a urethane-based emulsion. This results in an ink with good adhesion, abrasion resistance, and lamination suitability.

[0027] The binder content in the second ink is preferably 10 to 15% by mass.

[0028] Furthermore, the binder included in the second ink is not limited. For example, an appropriate binder may be used depending on the components contained in the first ink.

[0029] The solvent type and composition are not limited to those shown in the examples, but the preferred content of the organic solvent in the second ink is 1.0% to 20% by mass for propylene glycol and 2.0 to 10.0% by mass for triethylene glycol monobutyl ether.

[0030] The surfactant content in the second ink is preferably 0.05% by mass or more and 0.5% by mass or less.

[0031] The water content in the second ink is preferably 55% by mass or more and 75% by mass or less.

[0032] The third ink is a colored ink. For example, the third ink may use cyan, yellow, or magenta pigments.

[0033] In this embodiment, the binder contained in the third ink includes a urethane-based resin with excellent abrasion resistance and lamination suitability. For example, it is preferable that the binder contained in the third ink be prepared as a urethane-based emulsion. This results in an ink with good adhesion, abrasion resistance, and lamination suitability.

[0034] The binder content in the third ink is preferably 7.0 to 10.0% by mass.

[0035] Furthermore, the binder included in the third ink is not limited. For example, an appropriate binder may be used depending on the components included in the first ink or the second ink.

[0036] The solvent type and composition are not limited to those shown in the examples, but the preferred content of the organic solvent in the third ink is 1.0% to 25% by mass for propylene glycol and 0.2% to 10.0% by mass for triethylene glycol monobutyl ether.

[0037] The surfactant content in the third ink is preferably 0.05% by mass or more and 0.5% by mass or less.

[0038] The water content in the third ink is preferably 50% by mass or more and 80% by mass or less.

[0039] In this embodiment, the absolute value of the difference between the surface tension of the first ink and the surface tension of the second ink is 2.0 mN / m or less. Furthermore, in this embodiment, it is preferable that the ratio (p / B) of pigment (p) to binder (B) contained in the first ink is 1.1 or less.

[0040] This reduces the difference in surface tension between the first and second inks, and between the first and third inks, thereby suppressing ink bleeding and achieving excellent pinning performance. Furthermore, by setting the ratio of pigment to binder to 1.1 or less, a better adhesion effect is obtained when the second and third inks are dispensed on top of the first ink that is dispensed first.

[0041] The above ink set is characterized in that the binder in the first ink contains an acrylic resin or a polyolefin resin, the binders in the second and third inks contain a urethane resin, the absolute difference between the surface tension of the first ink and the surface tension of the second ink is 2.0 mN / m or less, and the absolute difference between the surface tension of the first ink and the surface tension of the third ink is 2.0 mN / m or less. As a result, an ink was obtained that provides high-quality images on non-absorbent media, as well as good adhesion, abrasion resistance, pinning properties, and lamination suitability.

[0042] Furthermore, although the difference in surface tension between the second and third inks is not specified, since the second ink is a white ink using a pigment with a high specific gravity, a density difference occurs between the second and third inks. In this embodiment, it is preferable that the density of the second ink (ρ2) is higher than the density of the third ink (ρ3), and that the relationship ρ2-ρ3>0.05 holds. This suppresses the diffusion of the dot diameter of the ink droplets dropped later compared to the dot diameter of the ink droplets dropped earlier, thereby achieving a pinning effect.

[0043] In addition to the above, the ink set may also contain known additives such as dissolving stabilizers, drying inhibitors, antioxidants, viscosity modifiers, pH adjusters, and antifungal agents, as needed.

[0044] Furthermore, the colors of the first, second, and third inks are not limited, and various colors (pigments) other than white ink may be used. Also, white ink may include not only pure white, but also other white-based colors such as ivory, pale eggshell, oyster orange, snow white, moon white, and grayish white. Additionally, the recording medium on which the ink set is ejected is not limited to transparent recording media used for front-side or back-side printing, but may also be opaque recording media.

[0045] <Recording device> This invention describes a recording device 10 that performs tasks such as ejecting an ink set and drying the ejected ink.

[0046] Figure 1 is a block diagram showing the configuration of the recording device 10.

[0047] As shown in Figure 1, the recording device 10 includes a recording medium storage unit 11, a transport unit 12, a discharge unit 13, a drying unit 14, and a control unit 20.

[0048] The recording medium storage unit 11 stores recording media from which ink is ejected. For example, a transparent recording medium used for surface printing is stored there, and one sheet at a time is supplied to the transport unit 12 when printing is performed.

[0049] The transport unit 12 transports the recording medium to the discharge unit 13 and the drying unit 14. For example, the transport unit 12 is equipped with a transport belt, transport rollers, and registration rollers for transporting the recording medium from the recording medium storage unit 11 to the discharge unit 13 and from the discharge unit 13 to the drying unit 14, as well as a support plate for supporting the recording medium and ventilation holes for adsorbing the recording medium onto the transport belt.

[0050] The ejection unit 13 ejects the first ink, the second ink, and the third ink onto the recording medium. For example, the ejection unit 13 includes a head unit equipped with the first ink, the second ink, and the third ink, a plurality of nozzles for ejecting each ink (for example, a first ejection unit 14 for ejecting the first ink, a second ejection unit 15 for ejecting the second ink, and a third ejection unit 16 for ejecting the third ink), a drive circuit for controlling the amount of ink ejected, and a pressurizing element for pressurizing the nozzles. In this embodiment, the ejection unit 13 ejects the first ink, the second ink, and the third ink onto the recording medium in that order.

[0051] In this embodiment, the ejection unit 13 uses a line head that fixes a liquid ejection head having a width greater than or equal to the recording width of the recording medium to the inkjet device.

[0052] The drying unit 17 dries the ink ejected onto the recording medium. In this embodiment, the drying unit 17 has a first drying mechanism 18 for drying the first ink when the first ink is ejected. For example, the first drying mechanism 18 is provided between the first ejection unit 14 that ejects the first ink and the second ejection unit 15 that ejects the second ink. That is, the first drying mechanism 18 dries the first ink before the second ink is ejected onto the recording medium.

[0053] The drying unit 17 also includes a preheating unit 19 that heats the transport unit 12 that transports the recording medium. For example, the preheating unit 19 preheats the transport belt that transports the recording medium. In this embodiment, the transport unit 12 is heated at the timing when each ink is ejected, and drying is performed quickly after all the inks (first ink, second ink, third ink, etc.) have been ejected.

[0054] The method of drying the ink by the drying unit 17 is not limited, and an infrared heater or a fan that blows warm air may be used. Furthermore, the recording device 10 is not limited to the above configuration, and does not need to have a first drying mechanism 18 or a preheating unit 19, as long as it can sufficiently dry the first ink, second ink, and third ink and form an ink set on the recording medium that exhibits good adhesion, abrasion resistance, and lamination suitability.

[0055] The control unit 20 controls the recording device 10. In this embodiment, the control unit 20 controls the ejection unit 13 to eject the first ink, second ink, and third ink to the recording medium in that order, and the drying unit 17 to dry the first ink, second ink, and third ink after they have been ejected to the recording medium. For example, the control unit 20 has an arithmetic unit and a storage unit (not shown). The arithmetic unit is, for example, a CPU (Central Processing Unit). The storage unit includes a storage medium such as ROM (Read Only Memory), RAM (Random Access Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing a control program stored in the storage unit.

[0056] For example, the control unit 20 may perform image formation by supplying a discharge signal corresponding to the pixel to the pressure element of the discharge unit 13 based on the input image data, and controlling the drying process by the drying unit 17 at an appropriate timing. In addition to controlling the discharge unit 13 and the drying unit 17, the control unit 20 may also control various components mounted on the storage device 10, such as an operation unit where user operations are input, or a display unit having a display that shows operation menus, status, etc.

[0057] As a result, the first drying mechanism 18 dries the first ink before the second ink is ejected, which reduces the amount of liquid on the substrate or increases the viscosity of the ink on the substrate, thereby improving pinning performance. Whether the response is a reduction in the amount of liquid on the substrate or an increase in the viscosity of the ink on the substrate depends on the degree of ink drying.

[0058] Furthermore, the preheating unit 19 preheats the transport belt that carries the recording medium, thereby improving initial pinning performance. In addition, rapid drying after all ink colors have been ejected allows for image quality with sustained pinning effect.

[0059] <Examples> The following describes embodiments of the present invention.

[0060] <Ink manufacturing method> In this invention, a first ink, a second ink, and a third ink are manufactured as an ink set. Dispersion A is used in the first and second inks, and dispersion B is used in the third ink.

[0061] <Preparation of Dispersion A> Dispersion A, contained in the first and second inks, is prepared by mixing 50g of pigment, 14.5g of pigment dispersant, and 41.3g of water in a ball mill, and then dispersing zirconia beads (diameter: 1.0mm) at a packing rate of 70% and a speed of 8m / s for 60 minutes using a bead mill (device name: Research Lab, manufactured by Shinmaru Enterprises, Inc.).

[0062] The following pigments are used: White pigment: "CR-50" manufactured by Ishihara Sangyo Co., Ltd.

[0063] The following pigment dispersants are used as pigment dispersants. SOLSPERSE (registered trademark) W100, manufactured by Lubrizol Japan Co., Ltd.

[0064] <Preparation of Dispersion B> Dispersion B, contained in the third ink, is prepared in the same manner as dispersion A. The difference from dispersion A lies in the pigment and pigment dispersant used; the following pigment and pigment dispersant are used. Cyan pigment: Heubach "PV FAST BLUE BG" (Pigment Blue 15:3) "DISPERBYK-2010" manufactured by Big Chemie Japan Co., Ltd.

[0065] <Evaluation Method> The pinning properties, adhesion, abrasion resistance, and lamination of the ink sets of Examples 1-7 and Comparative Examples 1-3 were evaluated using the following method.

[0066] Figure 2 is a diagram related to the evaluation of pinning properties.

[0067] For the evaluation of pinning properties, a simple jig was created using the KJ4B-1200 (manufactured by Kyocera Corporation), and as shown in Figure 2, the first ink, second ink, and third ink were ejected, and the width of the formed lines was measured. The substrate onto which the ink was ejected was "corona-treated PET" manufactured by Futamura Chemical Co., Ltd. The substrate preheating temperature (the process of warming the transport plate that transports the substrate before drying the ejected ink) was set to 50°C, and after ejecting the substrate onto the ink, drying was performed at 110°C for 5 minutes after 2 seconds. In Figure 2, the line width results for printing with the first ink and the second ink, and printing with the first ink and the third ink, were judged to be the same, so they are shown together.

[0068] The criteria for evaluating pinning performance are as follows: a line width of 45 μm or more and 55 μm or less is rated A (exceptionally good), a line width of 56 μm or more and 65 μm or less is rated B (good), and a line width of 66 μm or more is rated C (poor). Furthermore, the overall evaluation criteria for the pinning performance of each ink are as follows: if the pinning of the first and second inks is B or higher (first condition), AND the pinning of the first and third inks is B or higher (second condition), then pinning is considered OK. Also, if the pinning of the first and second inks is B or higher, AND the pinning of the first, second, and third inks is B or higher (third condition), then pinning is considered OK. If the pinning of any of the first, second, or third conditions is less than B (C), then pinning is considered NG.

[0069] For the evaluation of adhesion, the substrates used were Futamura Chemical's "Corona-treated PET" and Futamura Chemical's "Corona-treated OPP film." The first and second inks were printed as solid images on these substrates, and then the third ink was printed as a solid image on top of these solid images. After drying at 110°C for 20 minutes, the substrates were left to stand for one day.

[0070] Furthermore, 25 squares were created in the solid-colored area as described in JIS K5600 General Test Methods for Paints, and Nichiban Co., Ltd.'s "Sellotape (registered trademark)" (18mm width, CT-18S) was applied using the cross-cut method. The surface condition of the image after peeling was observed, and the adhesion was evaluated based on the evaluation criteria below.

[0071] Regarding the criteria for evaluating adhesion, A (exceptionally good) indicates no peeling of the tape, B (good) indicates peeling of 1 to 3 grid-like cuts but at a level that is practically acceptable, and C (poor) indicates peeling of 4 or more grid-like cuts that is not practically acceptable.

[0072] For the evaluation of abrasion resistance, the first and second inks were printed as solid images on the substrate, and then a 100% solid image of the third ink was printed on top of these solid images. After drying at 110°C for 20 minutes, the substrate was left for one day (hereinafter, this substrate will be referred to as the recording material). In the evaluation method, A4 size copy paper (Mondi's "Copy Paper CC90") was used as the recording medium, and a dry friction test was performed on the solid image. Abrasion resistance was evaluated by measuring the amount of change in the image's ID and the FD value on the CC90.

[0073] The criteria for evaluating abrasion resistance are as follows: A (exceptionally good) if the base material is not exposed after 1000 friction cycles, B (good) if the base material is not exposed after 100 friction cycles, and C (poor) if the base material is exposed.

[0074] For the evaluation of lamination suitability, a laminating adhesive was prepared by mixing Mitsui Chemicals' "Takelac® A-525S" as the main component and Mitsui Chemicals' "Takenate® A-50" as the curing agent in a mass ratio of 9:1. This adhesive was applied to a wire bar to achieve a dry film thickness of 3 μm. It was also applied to the recording material used for the above-mentioned abrasion resistance evaluation, and the diluted solvent was evaporated and dried using a dryer. The adhesive surface of the recording material coated with the adhesive composition was laminated to a PET film. After lamination, the materials were stored at 40°C for 3 days, and a peel test was performed. The peel test was evaluated by holding one end of the non-adhesive portion of the laminate film with a jig and pulling the other end by hand.

[0075] The criteria for evaluating lamination suitability are as follows: B (good) indicates no peeling at all, and C (poor) indicates some peeling or easy peeling.

[0076] <Ink adjustment> As shown in Tables 1 to 16 below, the first ink, second ink, and third ink were prepared as in Examples 1 to 8.

[0077] <Example 1> In Example 1, the first ink (ink 1-1), the second ink (ink 2-1), and the third ink (ink 3-1) were prepared as shown in Table 1. The evaluation results for Example 1 are shown in Table 2. Here, the evaluation results are described as follows: the pinning of the first and second inks is pinning 1-2, the pinning of the first and third inks is pinning 1-3, and the pinning of the first, second, and third inks is pinning 1-2-3.

[0078] Here, Binder A is "Acryset EF-009" manufactured by Nippon Shokubai Co., Ltd. Binder C is "Superflex 210" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In addition, the surfactant used is "Sylface SAG503A," a silicone-based surfactant manufactured by Nisshin Chemical Industry Co., Ltd. Note that the percentages (excluding p / B (ratio)) of each component shown in the following table are in mass percent.

[0079] [Table 1]

[0080] [Table 2]

[0081] In all of the examples in Example 1, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good.

[0082] The following explanation of common ink types will be omitted.

[0083] <Example 2> In Example 2, the first ink (ink 1-2), the second ink (ink 2-1), and the third ink (ink 3-1) were prepared as shown in Table 3. The evaluation results for Example 2 are shown in Table 4.

[0084] In Example 2, the binder B used in the first ink is "Arrowbase SB1010" manufactured by Unitika, which is a polyolefin resin.

[0085] [Table 3]

[0086] [Table 4]

[0087] In all of the examples in Example 2, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good. This suggests that the same effects as in Example 1 can be obtained even if the binder contained in ink 1-2, which functions as a pigment-free adhesive layer, is changed to a polyolefin resin.

[0088] <Example 3> In Example 3, the first ink (ink 1-3), the second ink (ink 2-1), and the third ink (ink 3-1) were prepared as shown in Table 5. The evaluation results for Example 3 are shown in Table 6.

[0089] [Table 5]

[0090] [Table 6]

[0091] In all of the three examples, the pinning properties were OK, the adhesion, the abrasion resistance, and the lamination suitability were good or particularly good. This suggests that a better pinning effect can be obtained by applying inks 1-3, which are white inks using pigments with a high specific gravity, to the recording medium.

[0092] <Example 4> In Example 4, the first ink (ink 1-4), the second ink (ink 2-2), and the third ink (ink 3-1) were prepared as shown in Table 7. The evaluation results for Example 4 are shown in Table 8.

[0093] [Table 7]

[0094] [Table 8]

[0095] In all of the examples in Example 4, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good. This suggests that even when the difference in surface tension between the first and second inks is 2.0 mN / m (upper limit), sufficient pinning properties, adhesion, abrasion resistance, and lamination suitability can be achieved.

[0096] <Example 5> In Example 5, the first ink (ink 1-4), the second ink (ink 2-1), and the third ink (ink 3-2) were prepared as shown in Table 9. The evaluation results for Example 5 are shown in Table 10.

[0097] [Table 9]

[0098] [Table 10]

[0099] In all of the 5 examples, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good. This suggests that even when the difference in surface tension between the first and third inks is 2.0 mN / m (upper limit), sufficient pinning properties, adhesion, abrasion resistance, and lamination suitability can be achieved.

[0100] <Example 6> In Example 6, the first ink (ink 1-5), the second ink (ink 2-1), and the third ink (ink 3-1) were prepared as shown in Table 11. The evaluation results for Example 6 are shown in Table 12.

[0101] [Table 11]

[0102] [Table 12]

[0103] In all of the six examples, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good. This suggests that even when the difference in surface tension between the first and second inks is 0 mN / m (the same value), sufficient pinning properties, adhesion, abrasion resistance, and lamination suitability can be achieved.

[0104] <Example 7> In Example 7, the first ink (ink 1-6), the second ink (ink 2-1), and the third ink (ink 3-2) were prepared as shown in Table 13. The evaluation results for Example 7 are shown in Table 14.

[0105] [Table 13]

[0106] [Table 14]

[0107] In all of the 7 examples, the pinning properties were OK, the adhesion, abrasion resistance, and lamination suitability were good or particularly good. Furthermore, since the p / B ratio was not 1.1 or lower, the adhesion was deemed good.

[0108] <Example 8> In Example 8, the first ink (ink 1-2), the second ink (ink 2-4), and the third ink (ink 3-1) were prepared as shown in Table 15. The evaluation results for Example 8 are shown in Table 16.

[0109] [Table 15]

[0110] [Table 16]

[0111] In all 8 examples, the pinning properties, adhesion, abrasion resistance, and lamination suitability were good or particularly good. This is because the density ρ2 of the second ink was 0.07 g / cm³ higher than the density ρ3 of the third ink. 3 This is likely because the value is large, meaning the relationship ρ2-ρ3>0.05 holds true.

[0112] <Comparative Example> The following describes comparative examples of the present invention.

[0113] As shown in Tables 17-22 below, the first ink, second ink, and third ink were prepared as in Comparative Examples 1-3.

[0114] <Comparative Example 1> In Comparative Example 1, the first ink (ink 1-7), the second ink (ink 2-1), and the third ink (ink 3-1) were prepared as shown in Table 17. The evaluation results for Comparative Example 1 are shown in Table 18.

[0115] [Table 17]

[0116] [Table 18]

[0117] In Comparative Example 1, the adhesion was poor. This is thought to be because the binder contained in the first ink was urethane resin.

[0118] <Comparative Example 2> In Comparative Example 2, the first ink (ink 1-8), the second ink (ink 2-3), and the third ink (ink 3-3) were prepared as shown in Table 19. The evaluation results for Comparative Example 2 are shown in Table 20.

[0119] [Table 19]

[0120] [Table 20]

[0121] Comparative Example 2 showed poor abrasion resistance. This is thought to be because the binders contained in the second and third inks were acrylic resins instead of urethane resins.

[0122] <Comparative Example 3> In Comparative Example 3, the first ink (ink 1-9), the second ink (ink 2-2), and the third ink (ink 3-2) were prepared as shown in Table 21. The evaluation results for Comparative Example 3 are shown in Table 22.

[0123] [Table 21]

[0124] [Table 22]

[0125] Comparative Example 3 failed in terms of pinning properties. This is likely because the difference between the surface tension of the first ink and the second ink, and the difference between the surface tension of the first ink and the third ink, was 2.5 mN / m, which exceeds 2.0 mN / m (the upper limit). [Explanation of Symbols]

[0126] 10…Recording device 13...Discharge part 14...First discharge part 15...Second discharge part 16…Third discharge part 17...Drying section 18...First drying mechanism 19… Preheating section 20... Control Unit

Claims

1. An ink set comprising a first ink, a second ink, and a third ink, Each of the first ink, the second ink, and the third ink comprises a binder, an organic solvent, water, and a surfactant. The binder contained in the first ink comprises at least one of an acrylic resin or a polyolefin resin. The binder contained in the second ink and the third ink contains a urethane-based resin. The absolute value of the difference between the surface tension of the first ink and the surface tension of the second ink is 2.0 mN / m or less. The absolute value of the difference between the surface tension of the first ink and the surface tension of the third ink is 2.0 mN / m or less. Ink set.

2. The ink set according to claim 1, The first ink is white ink or clear ink. The second ink is white ink. Ink set.

3. An ink set according to claim 1 or 2, The surfactant includes a silicone-based surfactant. Ink set.

4. An ink set according to claim 1 or 2, The ratio of pigment to binder contained in the first ink is 1.1 or less. Ink set.

5. An ink set according to claim 1 or 2, The density of the second ink is 0.05 g / cm³ lower than the density of the third ink. ３ That's all. Ink set.

6. A recording device using the ink set described in claim 1 or 2, A dispensing unit that dispenses the first ink, the second ink, and the third ink onto a recording medium, A drying unit for drying the first ink, the second ink, and the third ink applied to the recording medium, The system comprises a discharge unit that discharges the first ink, the second ink, and the third ink onto the recording medium in that order, and a control unit that controls the drying unit to dry the recording medium from which the first ink, the second ink, and the third ink have been discharged. Recording device.

7. A recording device according to claim 6, The discharge unit comprises a first discharge unit for discharging the first ink, a second discharge unit for discharging the second ink, and a third discharge unit for discharging the third ink. The drying unit has a first drying mechanism for drying the first ink discharged by the first discharge unit. Recording device.

8. A recording device according to claim 6, further, The transport unit includes a transport plate for transporting the recording medium, The drying unit further includes a preheating unit that preheats the transport plate before the ink is dispensed by the dispensing unit. Recording device.

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