Ink set and recording device

Abstract

To provide an ink set and recording device that produce high-resolution images and have good adhesion, pinning properties, and scratch resistance, and that can prevent color bleeding. [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 resin fine particles, an organic solvent, water, and a surfactant. The ratio of pigment to binder in the first ink is 0 to 1.1. The ratio of pigment to binder in the second ink is 1.3 to 3.0. The density of the second ink is 0.05 g / cm³ lower than the density of the third ink. 3 That's all.

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] In inkjet printing on flexible packaging such as a resin film, the recording medium is often transparent. In order to increase the hiding power of an image formed on such a transparent recording medium, a white ink may be used to form a base, and then printing may be performed with a color ink on the base. Further, when droplets are ejected so as to overlap the inks, there is a problem that the droplet diameter of the ink ejected later expands more than the droplet diameter of the ink ejected earlier. In this case, problems such as occurrence of bleeding between the hiding power by the white ink and the image occur.

[0003] For example, in Patent Document 1, the pigment and binder ratios of a dark white ink and a light white ink are defined, and the dark white ink is printed first, and the light white ink is ejected onto the dark white ink to ensure scratch resistance and hiding power. Further, in Patent Document 2, the viscosities and surface tensions of the first ink and the second ink before ejection are limited to improve pinning properties. Further, in Patent Document 3, it is disclosed that in the droplet ejection process of the ink, droplets are ejected in order from the ink having a small solid content among a plurality of inks.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, the amount of binder in the white ink printed first is insufficient, resulting in poor adhesion to the substrate and inadequate abrasion resistance. Furthermore, in Patent Documents 2 and 3, the viscosity and surface tension of the ink when it adheres to the substrate surface after ink ejection do not necessarily match the specifications, making it insufficient to achieve pinning properties. Moreover, the bleeding suppression effect is even lower for the third ink and subsequent inks, resulting in insufficient pinning properties.

[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 and have good adhesion, pinning properties, and abrasion resistance, and that can prevent color bleeding. [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 resin fine particles, an organic solvent, water, and a surfactant. The ratio of pigment to binder contained in the first ink is between 0 and 1.1. The ratio of pigment to binder in the second ink is between 1.3 and 3.0. The density of the second ink is 0.05 g / cm³ lower than the density of the third ink. 3 That's all.

[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 present invention, it is possible to produce high-quality images with good adhesion, pinning properties, and abrasion resistance, while preventing color bleeding. [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. [Figure 3] This is a diagram illustrating the evaluation of abrasion resistance. [Figure 4] This figure shows the relationship between the ratio of pigment to binder and the opacity. [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 ink, the second ink, and the third ink contains resin fine particles, an organic solvent, water, and a surfactant.

[0013] In this embodiment, the ink set is an aqueous ink used for surface printing where an ink coating film exists on the outermost layer. Surface printing refers to printing on the front side of a recording medium (non-absorbent medium), that is, the side of the recording medium that is visible to the viewer. When the viewer views the surface-printed recording medium, the positional relationship of "viewer, image, recording medium" is formed, and the image is directly visible to the viewer. Also, in this embodiment, printing is performed by ejecting the first ink, the second ink, and the third ink in this order onto a transparent recording medium. Note that the ink set in the present invention may be used not only for surface printing and non-absorbent media but also for, for example, back printing or printing on an opaque recording medium.

[0014] The resin fine particles exist in a state of being dispersed in water (aqueous medium) and have a function as a binder for adhering the recording medium and the pigment. The resin fine particles (binder) optimize 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, propylene glycol and triethylene glycol monobutyl ether are preferable as the organic solvent.

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

[0017] The first ink is a white ink. For example, a white pigment such as titanium oxide is used in the first ink.

[0018] Furthermore, the binder contained in the first ink includes at least resin fine particles of acrylic resin or polyolefin resin. In this embodiment, the ratio of pigment (p) to binder (B) (p / B) of the first ink is low. Specifically, the ratio of the first ink is preferably 0 to 1.1.

[0019] This makes it possible to increase the opacity of the resulting image by forming a base layer on a transparent recording medium using white ink. Furthermore, by lowering the ratio of pigment to binder (p / B) of the first ink that directly contacts the transparent recording medium, i.e., by increasing the amount of binder, adhesion to the transparent recording medium can be ensured.

[0020] The proportion of binder contained in the first ink is not limited to this, as the p / B ratio is determined by the amounts of pigment and binder, but the binder resin is preferably 3% by mass or more and 20% by mass or less.

[0021] The solvent type or composition is not limited to what is shown in the examples, but the preferred content of the organic solvent in the first ink is 1.0% to 25% by mass for propylene glycol and 0.2% to 10.0% by mass for triethylene glycol monobutyl ether.

[0022] The surfactant species and composition are not limited to those described below or in the examples, but within the range of what can be dispensed, the surfactant content in the first ink is preferably 0.05% to 0.5% by mass.

[0023] The solvent composition is not limited to the following or the examples, but the water content in the first ink is preferably 50% by mass or more and 80% by mass or less.

[0024] Furthermore, the first ink does not have to contain a white pigment, meaning its ratio (p / B) is 0. In this case, the first ink functions as an adhesive layer that bonds the recording medium to the second ink, which is white ink, ensuring adhesion and opacity to the recording medium.

[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] Furthermore, the binder contained in the second ink is made of resin microparticles with an elongation at break of 50% or less. In this embodiment, the ratio of pigment (p) to binder (B) (p / B) of the second ink is higher than the ratio of pigment (p) to binder (B) (p / B) of the first ink. Specifically, the ratio of the second ink is preferably 1.3 to 3.0. Typically, the ratio of white ink is higher than that of the color ink because the density of titanium dioxide used in the white ink is high. Note that the second ink is not limited to resin microparticles with an elongation at break of 50% or less; for example, resin microparticles with an elongation at break of 300% may be used.

[0027] This ensures adhesion even with large-particle white inks, as the second ink, which contains more pigment, is ejected onto the recording medium after the first ink, which contains more binder. Furthermore, opacity and abrasion resistance can be ensured by setting the second ink to a specified ratio (p / B).

[0028] The binder content in the second ink is not limited to this, as the ratio (p / B) is determined by the amount of pigment to binder, but the binder resin is preferably 3% by mass or more and 20% by mass or less.

[0029] The solvent type or composition is not limited to what is shown in the examples, but the preferred content of the organic solvent in the second ink is 1.0% to 25% by mass for propylene glycol and 0.2% to 10.0% by mass for triethylene glycol monobutyl ether.

[0030] The surfactant species and composition are not limited to those described below or in the examples, but the surfactant content in the second ink is preferably 0.05% by mass or more and 0.5% by mass or less.

[0031] The solvent composition is not limited to the following or the examples, but the water content in the second ink is preferably 50% by mass or more and 80% by mass or less.

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

[0033] Furthermore, the third ink uses resin microparticles with a break elongation of 50% or less as a binder. However, the third ink is not limited to resin microparticles with a break elongation of 50% or less; for example, resin microparticles with a break elongation of 290% may be used.

[0034] The binder content in the third ink is not limited to this, but is preferably 3% by mass or more and 20% by mass or less.

[0035] The solvent type or composition is not limited to what is 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.

[0036] The surfactant species and composition are not limited to those described below or in the examples, but the surfactant content in the third ink is preferably 0.05% by mass or more and 0.5% by mass.

[0037] The water content in the third ink is preferably 50% by mass or more and 80% by mass or less.

[0038] In this embodiment, the density of the second ink is higher than the density of the third ink. Specifically, when the density of the second ink is ρ2 and the density of the third ink is ρ3, ρ2-ρ3>0.05(g / cm³). 3 The following relationship holds true. Note that density is the mass of pigment per unit volume of ink.

[0039] This increases the density of the second ink compared to the third ink, which in turn increases the aggregation of the second ink. As a result, the third ink, which is ejected after the second ink, is more likely to aggregate. Consequently, when the inks from the third ink onward are ejected, the diffusion of the ink is suppressed, and the pinning performance is significantly improved.

[0040] The above ink set has a pigment-to-binder ratio (p / B) of 0 to 1.1 for the first ink, a pigment-to-binder ratio (p / B) of 1.3 to 3.0 for the second ink, and the density of the second ink (ρ2) is higher than the density of the third ink (ρ3), with ρ2-ρ3 > 0.05 (g / cm³). 3 The relationship described above allows for the creation of an ink that exhibits excellent pinning, adhesion, and abrasion resistance on various non-absorbent media, and prevents color bleeding. Furthermore, its superior abrasion resistance makes it possible to use printed materials without surface printing or lamination.

[0041] 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.

[0042] 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. Moreover, 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. In other words, the base inks for the first and second inks do not necessarily have to be white ink.

[0043] <Recording device> This invention describes a recording device 10 that performs tasks such as ejecting an ink set and drying the ejected ink.

[0044] Figure 1 is a block diagram showing the configuration of the recording device 10.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The ejection unit 13 ejects the first ink, second ink, third ink, and fourth ink onto the recording medium. For example, the ejection unit 13 includes a head unit equipped with the first ink, second ink, third ink, and fourth 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, second ink, third ink, and fourth ink onto the recording medium in that order.

[0049] 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. At least the line heads for the first ink and the second ink are equipped with a circulation head that has a mechanism to prevent the ink from drying near the nozzle by circulating the ink to the vicinity of the nozzle.

[0050] 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.

[0051] 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, and fourth ink, etc.) have been ejected.

[0052] 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 as long as it can sufficiently dry the first ink, second ink, third ink, and fourth ink, and form an ink set on the recording medium that exhibits good pinning properties, adhesion, and abrasion resistance and prevents color bleeding, it does not need to have a first drying mechanism 18 or a preheating unit 19, a line head does not need to be used in the ejection unit 13, and the line heads for the first and second inks do not need to be circulation heads.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Furthermore, using a circulating head improves the stability of the ink discharge. In addition, in the case of white ink, it has the effect of suppressing pigment sedimentation.

[0057] 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.

[0058] <Examples> The following describes embodiments of the present invention. Note that the following embodiments are merely examples of the present invention, and the present invention is not limited to the configurations of the embodiments described below.

[0059] <Ink manufacturing method> In this invention, a first ink, a second ink, a third ink, and a fourth ink are manufactured as an ink set. Dispersion A is used in the first and second inks, dispersion B is used in the third ink, and dispersion C is used in the fourth ink.

[0060] <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.).

[0061] The following pigments are used: White pigment: "CR-50" manufactured by Ishihara Sangyo Co., Ltd.

[0062] The following pigment dispersants are used as pigment dispersants. SOLSPERSE (registered trademark) W100, manufactured by Lubrizol Japan Co., Ltd.

[0063] <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.

[0064] <Preparation of dispersion C> Dispersion C, contained in the fourth 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. Yellow pigment: BASF "Yellow D 1115J" (Pigment Yellow 155) "DISPERBYK-2010" manufactured by Big Chemie Japan Co., Ltd.

[0065] <Evaluation Method> The following methods were used to evaluate the pinning properties, adhesion, abrasion resistance, and opacity of the ink sets of Examples 1-10 and Comparative Examples 1-4.

[0066] Figure 2 is a diagram relating to the evaluation of pinning properties. Figure 2A shows the case where there is no density difference between the second and third inks. Figure 2B shows the case where there is a density difference between the second and third inks.

[0067] For the evaluation of pinning properties, a simple jig was created using a Kyocera "1200dpi circulation head," and as shown in Figure 2, the first ink, second and third inks, and fourth inks were ejected. The length of the bleeding at the crossing of the 5-dot lines was measured using a measuring microscope. The substrate onto which the ink was ejected was Futamura Chemical's "corona-treated PET." The substrate preheating temperature (the process of warming the transport plate that carries 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.

[0068] As shown in Figure 2, the front solid area is printed with white ink (first and second inks), and then color ink (third ink) is printed. Figure 2A shows that when there is no difference in ink density, the color ink does not pin and bleeds. Also, as shown in Figure 2B, when there is a difference in density, the length of the color bleeding is shorter compared to the case where there is no difference in density shown in Figure 2A. Therefore, in this embodiment, the density of the second ink is 0.06 g / cm³ lower than the density of the third ink. 3 The ink is adjusted to achieve the above result.

[0069] The criteria for evaluating pinning performance are as follows: a spread length of 20 μm or less is rated A (excellent), a spread length of 20 μm or more but shorter than 50 μm is rated B (good), and a spread length of 50 μm or more is rated C (poor).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Figure 3 shows the evaluation of abrasion resistance. Figure 3A shows the case when the binder ratio is low. Figure 3B shows the case when the binder ratio is appropriate.

[0074] For the evaluation of abrasion resistance, a solid image was printed on the substrate using the first and second inks. A 100% solid image of the third ink was then printed on top of this solid image, dried at 110°C for 20 minutes, and left for one day. 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 change in the image's ID and the FD value on the CC90.

[0075] 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.

[0076] As shown in Figure 3A, when the ratio of the binder (adhesive layer) between the first and second inks is low, that is, when the amount of binder is small and the p / B ratio is large, a portion of the substrate will be exposed due to friction. In contrast, when the amount of binder is appropriate, sufficient abrasion resistance can be obtained. The appropriate amount refers to a ratio of 0 to 1.1 for the first ink and a ratio of 1.3 to 3.0 for the second ink, satisfying both conditions.

[0077] Figure 4 shows the relationship between the ratio of pigment to binder and the opacity. In Figure 4, the horizontal axis represents the ratio of pigment to binder p / B (%), and the vertical axis represents the opacity (%). In other words, Figure 4 shows the plot of the change in opacity when the ratio p / B changes.

[0078] The opacity rate was evaluated using an image forming apparatus (inkjet recording device with line head, Kyocera Document Solutions test machine) under conditions of 25°C and 50% RH. PET film (Toray Industries' "Lumirror S10") was used as the recording medium. Five solid images of 150mm x 200mm, each with first and second inks, were formed on the recording medium from the recording head. After warming the image-formed recording medium for a certain period to confirm that the image was dry, the image density K value was measured using a portable reflectivity meter RD-19 (Gretag Macbeth Corporation) and judged according to the following criteria.

[0079] Furthermore, the K value, which is the black density of a black opacity test paper, is measured, and a white film print is placed on top of the opacity test paper. The K value of the opacity test paper with the film print placed on top is then measured. The degree to which the film print hides the underlying black is calculated as the BK opacity. The BK opacity was calculated using the following formula as the evaluation standard.

[0080] [BK Opacity %] = (1 - (K value of the image forming area) / (K value of the base material)) × 100 If [BK opacity %] > 90%, it is rated A (very good). If 90 ≥ [BK opacity %] > 85%, it is rated B (good). If 85 ≤ [BK opacity %], it is rated C (poor).

[0081] As shown in Figure 4, a higher ratio of pigment to binder (p / B) results in higher opacity. Furthermore, when the ratio of pigment to binder (p / B) exceeds 200%, the opacity leveles off. Therefore, the ratio of pigment to binder (p / B) for the second ink is preferably between 1.3 and 3.0.

[0082] <Ink adjustment> As shown in Tables 1 to 20 below, the first ink, second ink, third ink, and fourth ink were prepared as in Examples 1 to 10.

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

[0084] Here, Binder A is "Acryset EF-009" manufactured by Nippon Shokubai Co., Ltd. Binder D is "Superflex 820" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The surfactant used is "Sylface SAG503A," a silicone-based surfactant manufactured by Nisshin Chemical Industry Co., Ltd. The percentages of each component shown in the following table are in mass percent.

[0085] [Table 1]

[0086] [Table 2]

[0087] In all of the examples in Example 1, the pinning properties, adhesion, abrasion resistance, and opacity were good or particularly good.

[0088] The following explanation of common ink types will be omitted.

[0089] <Example 2> In Example 2, the first ink (ink 1-1), second ink (ink 2-2), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 3. The evaluation results for Example 2 are shown in Table 4.

[0090] [Table 3]

[0091] [Table 4]

[0092] In Example 2, the pinning properties, adhesion, abrasion resistance, and opacity were all particularly good. This is thought to be because the ratio (p / B) and density of ink 2-2 were higher than those of ink 2-1, resulting in improved pinning properties and opacity.

[0093] <Example 3> In Example 3, the first ink (ink 1-2), second ink (ink 2-1), third ink (ink 3-2), and fourth ink (ink 4-2) were prepared as shown in Table 5. The evaluation results for Example 3 are shown in Table 6.

[0094] [Table 5]

[0095] [Table 6]

[0096] In all three examples, the pinning properties, adhesion, abrasion resistance, and opacity were good or particularly good. This suggests that sufficient adhesion to the printing medium can be expected even when the ink 1-1 ratio is increased from 0.2 to 1.1.

[0097] <Example 4> In Example 4, the first ink (ink 1-2), second ink (ink 2-2), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 7. The evaluation results for Example 4 are shown in Table 8.

[0098] [Table 7]

[0099] [Table 8]

[0100] In all of the examples in Example 4, the pinning properties, adhesion, abrasion resistance, and opacity were particularly good. This suggests that sufficient adhesion to the printing medium can be expected even when the ratio of ink 1-1 is increased from 0.2 to 1.1. Furthermore, it is thought that the higher ratio (p / B) and density of ink 2-2 compared to ink 2-1 resulted in improved pinning properties and opacity.

[0101] <Example 5> In Example 5, the first ink (ink 1-3), second ink (ink 2-3), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 9. The evaluation results for Example 5 are shown in Table 10.

[0102] [Table 9]

[0103] [Table 10]

[0104] In all of the 5 examples, the pinning properties, adhesion, abrasion resistance, and opacity were particularly good. This suggests that even with inks 1-3, which function as an adhesive layer without pigment, sufficient pinning properties, adhesion, abrasion resistance, and opacity can be achieved by layering and dispensing inks 2-3, which contain a large amount of pigment (high ratio).

[0105] <Example 6> In Example 6, the first ink (ink 1-4), second ink (ink 2-2), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 11. The evaluation results for Example 6 are shown in Table 12.

[0106] In Example 6, a polyolefin resin is used for binder B in the first ink. In Example 6, "Arrowbase SB1010" manufactured by Unitika Corporation is used for binder B.

[0107] [Table 11]

[0108] [Table 12]

[0109] In all of the 6 examples, the pinning properties, adhesion, abrasion resistance, and opacity were particularly good. This suggests that sufficient pinning properties, adhesion, abrasion resistance, and opacity can be achieved even when the binder contained in the first ink is polyolefin.

[0110] <Example 7> In Example 7, the first ink (ink 1-5), second ink (ink 2-2), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 13. The evaluation results for Example 7 are shown in Table 14.

[0111] In Example 7, urethane resin is used as the binder for the first ink. Also in Example 7, "Superflex 150" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. is used as binder C.

[0112] [Table 13]

[0113] [Table 14]

[0114] In all of the 7 examples, the pinning properties, adhesion, abrasion resistance, and opacity were good or particularly good. This suggests that sufficient pinning properties, adhesion, abrasion resistance, and opacity can be achieved even when the binder contained in the first ink is urethane.

[0115] <Example 8> In Example 8, the first ink (ink 1-2), second ink (ink 2-4), third ink (ink 3-3), and fourth ink (ink 4-3) were prepared as shown in Table 15. The evaluation results for Example 8 are shown in Table 16.

[0116] Example 8 is characterized by having a break elongation of 50% for the binders used in the second, third, and fourth inks. In Example 8, "Superflex 170" manufactured by Daiichi Kogyo Seiyaku is used for binder E.

[0117] [Table 15]

[0118] [Table 16]

[0119] In all 8 examples, the pinning properties, adhesion, abrasion resistance, and opacity were particularly good. This is thought to be because using a binder with low elongation at break hardened the coating film, resulting in improved abrasion resistance.

[0120] <Example 9> In Example 9, the first ink (ink 1-2), second ink (ink 2-5), third ink (ink 3-4), and fourth ink (ink 4-1) were prepared as shown in Table 17. The evaluation results for Example 9 are shown in Table 18.

[0121] Example 9 is characterized by the fact that the binders used in the second, third, and fourth inks have a break elongation of 290%. In Example 9, "Superflex 420" manufactured by Daiichi Kogyo Seiyaku is used as binder F.

[0122] [Table 17]

[0123] [Table 18]

[0124] In all of the 9 examples, the pinning properties, adhesion, abrasion resistance, and opacity were good or particularly good. This suggests that even if the elongation at break of the binder used after the second ink exceeds 50%, sufficient pinning properties, adhesion, abrasion resistance, and opacity can be achieved.

[0125] <Example 10> In Example 10, the first ink (ink 1-2), second ink (ink 2-9), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 19. The evaluation results for Example 10 are shown in Table 20.

[0126] [Table 19]

[0127] [Table 20]

[0128] In all 10 examples, the pinning properties, adhesion, abrasion resistance, and opacity were good or particularly good. This suggests that even with a pigment-to-binder ratio (p / B) of 1.3 (lower limit) for the second ink, sufficient pinning properties, adhesion, abrasion resistance, and opacity can be achieved.

[0129] <Comparative Example> The following describes comparative examples of the present invention.

[0130] As shown in Tables 21-28 below, the first, second, third, and fourth inks were prepared as in Comparative Examples 1-4.

[0131] <Comparative Example 1> In Comparative Example 1, the first ink (ink 1-6), second ink (ink 2-3), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 21. The evaluation results for Comparative Example 1 are shown in Table 22.

[0132] [Table 21]

[0133] [Table 22]

[0134] In Comparative Example 1, the adhesion was poor. This is likely because the ratio of pigment to binder (p / B) of the first ink was 1.4, exceeding the upper limit of 1.1, indicating that the amount of binder was insufficient.

[0135] <Comparative Example 2> In Comparative Example 2, the first ink (ink 1-2), second ink (ink 2-6), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 23. The evaluation results for Comparative Example 2 are shown in Table 24.

[0136] [Table 23]

[0137] [Table 24]

[0138] Comparative Example 2 showed poor pinning properties. This was because the difference between the density of the second ink (ρ2) and the density of the third ink (ρ3) was 0.04 g / cm³. 3 Therefore, ρ2-ρ3>0.06(g / cm³) 3 This is likely due to the fact that the condition is not met.

[0139] <Comparative Example 3> In Comparative Example 3, the first ink (ink 1-2), second ink (ink 2-7), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 25. The evaluation results for Comparative Example 3 are shown in Table 26.

[0140] [Table 25]

[0141] [Table 26]

[0142] In Comparative Example 3, the opacity was poor. This is because the ratio of pigment to binder (p / B) of the second ink was 1.8. In other words, it is considered that the opacity is insufficient when the ratio of pigment to binder (p / B) of the second ink is lower than 1.3.

[0143] <Comparative Example 4> In Comparative Example 4, the first ink (ink 1-2), second ink (ink 2-8), third ink (ink 3-1), and fourth ink (ink 4-1) were prepared as shown in Table 27. The evaluation results for Comparative Example 4 are shown in Table 28.

[0144] [Table 27]

[0145] [Table 28]

[0146] Comparative Example 4 showed poor abrasion resistance. This is likely because the ratio of pigment to binder (p / B) of the second ink was 3.4, exceeding the upper limit of 3.0, resulting in insufficient abrasion resistance. [Explanation of Symbols]

[0147] 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 resin fine particles, an organic solvent, water, and a surfactant. The ratio of pigment to binder contained in the first ink is 0 or more and 1.1 or less. The ratio of pigment to binder contained in the second ink is 1.3 to 3.

0. 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.

2. The ink set according to claim 1, The first ink and the second ink are white inks. 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 first ink, the second ink, and the third ink are water-based inks used for surface printing, where the ink coating is on the outermost layer. Ink set.

5. An ink set according to claim 1 or 2, The first ink includes at least resin fine particles of an acrylic resin or a polyolefin resin. Ink set.

6. An ink set according to claim 1 or 2, The second ink uses resin fine particles with a break elongation of 50% or less. The third ink uses resin fine particles with a break elongation of 50% or less. Ink set.

7. 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 dispensing unit that dispenses 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 on which the first ink, the second ink, and the third ink have been dispensed. Recording device.

8. A recording device according to claim 7, 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.

9. A recording device according to claim 7, 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.

10. A recording device according to claim 8, The aforementioned discharge unit uses a line head. At least the line heads between the first discharge section and the second discharge section are circulation heads. Recording device.

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