Ink set

Abstract

To provide an ink set and the like excellent in discharge stability, and capable of obtaining a high quality decorative image having no granular feeling, and having natural visual effects, in printing which is easy to adjust coloring on every part to be applied with decoration, and discharges ink as droplets.SOLUTION: The ink set and the like is an ink set used for printing which discharges ink droplets by 100 pL or more and 5,000 pL or less, including at least two kinds of ink A and B, where all of the following conditions 1-3 are satisfied in a coordinate value (L*A, a*A, b*A) of the ink A in a CIE L*a*b* color space, and a coordinate value (L*B, a*B, b*B) of the ink B. Condition 1: the coordinate value a*A and a*B both are 5 or more and 35 or less, the coordinate value b*A and b*B both are 10 or more and 40 or less. Condition 2: the hue angles hA and hB expressed by formulae (II-1) and (II-2) both are 40 degrees or more and 70 degrees or less. Condition 3: the saturation difference ΔC expressed by formula (III) is 2 or more and 20 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink set, a printing method using the ink set, and a handy cosmetic inkjet printer using the ink set.

[0002] Inkjet printing is a printing method in which ink droplets are ejected from extremely fine nozzles directly onto a substrate to produce characters or images. This method has become extremely popular due to its many advantages, including the ease of full-color printing, low cost, the ability to use regular paper as the substrate, and no contact with the substrate. Recently, in order to impart weather resistance and water resistance to printed matter, inkjet printing inks using pigments as colorants have been widely used in inkjet printing methods.

[0003] For example, Patent Document 1 describes, for the purpose of providing an ink composition containing a white pigment having a good hue, an ink jet recording method using the ink composition, and the like, an ink composition that contains a white pigment, a dye for adjusting hue, a polymerizable compound, and a polymerization initiator, in which the ratio of the weight of the dye for adjusting hue to the weight of the white pigment is within a predetermined range, and an ink jet recording method using the ink composition. Patent Document 2 aims to provide a cartridge for use in an apparatus and method for applying a composition to a keratinous surface such as the skin, and describes in the examples a composition containing yellow iron oxide, red iron oxide, and titanium dioxide as colorants.

[0004] Also, a handy printer that uses an inkjet printing method for makeup has been proposed. Patent document 3 shows a schematic diagram of a handy printer equipped with multiple print heads with different shades of flesh-colored ink, with the aim of providing a handy printer that can easily align the handy printer with the area to be treated, such as a stain, birthmark, or scratch, and that can make the area to be treated, such as a stain, birthmark, or scratch, look the same as its surrounding areas, making the area to be treated less noticeable. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-209289 A [Patent Document 2] Special Publication No. 2018-529395 [Patent Document 3] JP 2018-118427 A Summary of the Invention [Problem to be solved by the invention]

[0006] The reason why full color printing is easy with inkjet printing is that the size of the ink droplets ejected by inkjet is very small, and the diameter of the ink dots applied to the printed material by inkjet is less than 50 μm, which is the limit of human visibility. Therefore, printed images formed by inkjet printing are drawn as pointillism with dots smaller than the limit of visibility, and full color printing is possible with the three primary colors of yellow, magenta, and cyan. In other words, full color printing is possible if the three ink colors of yellow, magenta, and cyan are prepared as the basic colors, and at least three inkjet heads are required. On the other hand, to make the diameter of an ink dot 50 μm or less, which is the limit of visibility, the amount of ink droplet ejected must be 32.5 pL or less, based on calculations. This is because when a 32.5 pL ink droplet lands on a substrate and its shape changes from a sphere to a hemisphere, the size of the hemisphere is the same as half of a 65 pL sphere. To reduce the size of ink droplets, it is necessary to design the ink flow path and nozzle size to be fine and the distance between nozzles to be short. However, when the ink flow path and nozzle size are fine, problems arise such as nozzle clogging due to drying of ink and reduced ejection stability due to accumulation or sedimentation of ink in the ink flow path. In addition, when the distance between nozzles is short, unintended ejection from nozzles or drying of nozzles occurs due to vibration reverberation, sympathetic vibration, and thermal conduction from adjacent nozzles, resulting in impaired ejection stability.

[0007] Patent Document 1 describes that an inkjet head is driven so as to be able to eject multi-size dots of 8 to 30 pL. Patent Document 2 describes applying a treatment composition using titanium oxide and iron oxide, which are inorganic pigments that tend to settle, as colorants by combining a thermal inkjet printer head and cartridge. However, Patent Document 2 does not provide any detailed description of the dimensions of the inkjet head used, and only describes that the composition is applied in the form of droplets having an average diameter of about 0.1 to 50 μm. When this range of average droplet diameter is converted into the diameter of a dot having a hemispherical shape, it is in the range of 0.12 to 63 μm. Therefore, it is believed that good print image quality is obtained by setting the dot size to 8 to 30 pL in the technology of Patent Document 1 and the dot diameter to 0.12 to 63 μm in the technology of Patent Document 2, but the ink droplet size is small and the ejection stability is poor. Furthermore, the technology in Patent Document 3 only describes the installation of ink tanks of yellow or a skin color lighter than light skin color, magenta or a skin color, cyan or a dark skin color, and black or a skin color darker than dark skin color, but does not consider the size of the droplets ejected from the inkjet head. Therefore, when the size of the ink droplets is increased in the techniques of Patent Documents 1 to 3, the graininess becomes noticeable, resulting in a decrease in print image quality. Furthermore, since the technology of Patent Document 2 uses a single color ink for printing, when an inkjet head with a large dot diameter is used, the boundary between the printed and non-printed areas becomes conspicuous, and the dots themselves become visible, resulting in a print quality with a noticeable graininess. Such uneven print quality with a noticeable graininess makes the human face, which is the most visible part of the appearance, look unnatural and is recognized as a low quality makeup image.

[0008] Furthermore, one of the major challenges with makeup cosmetics such as face powders, face powders, makeup bases, foundations, concealers, and foundations is the difficulty in selecting a makeup cosmetic that matches the skin color of the user, and it is particularly difficult to select a foundation that matches well with both the face and neck. Generally, depending on factors such as the thickness of the skin and how easily it burns in the sun, the face tends to be reddish and the neck yellowish, and even the same person's face and neck may have different colors. Therefore, the criterion for selecting a foundation is to apply the foundation from the cheeks to the chin in natural light, and to select one whose color matches every part of the face. However, when there is a large color difference between the face and the neck, a procedure is taken in which a foundation is first selected or adjusted to match the color of the neck, and the same foundation is then applied to the face, and the color that appears slightly dull is then added to the face using highlighter and blush. In addition, it is common to consider such a procedure to be cumbersome and to choose a foundation whose color is between the neck and the face. However, in either case, the result is a low satisfaction in terms of natural, well-matched makeup. In addition, many Asians have yellowish skin, which also tends to become yellowish with age. In the case of such yellowish skin, adding a little redness with foundation creates the illusion that the color of hemoglobin in the blood vessels in the deeper layers of the skin is visible through the skin, emphasizing the transparency of the skin. However, when applying makeup by hand, it is difficult to add just the right amount of redness, and adding too much redness can give the impression of being unsophisticated. For this reason, there is a demand for makeup images that allow easy adjustment of the color tone for each part of the body to which makeup is applied, that are free of graininess overall regardless of the part of the body to which makeup is applied, and that have a good natural appearance.

[0009] The present invention aims to provide an ink set that allows easy adjustment of color for each part to be applied to makeup, has excellent ejection stability in printing in which ink is ejected as droplets, and is free of graininess, making it possible to obtain a high-quality cosmetic image that looks natural; a printing method that uses the ink set; and a handy inkjet printer for makeup that uses the ink set. [Means for solving the problem]

[0010] The inventors of the present invention have focused on the size of the ejected ink droplets and the color development of the ink dots applied to the printed material in the printing process in which ink droplets are ejected, and have set the amount of ink droplets ejected per droplet within a predetermined range and further set the CIE L * a * b * Color space coordinates (L * , a * , b * ) chromaticity coordinates (a * , b * The present inventors have found that the above problems can be solved by using an ink set containing two types of inks each of which satisfies certain conditions.

[0011] That is, the present invention provides the following [1] to [3]. [1] An ink set for use in printing in which ink droplets are ejected at 100 pL or more and 5,000 pL or less, At least two inks, ink A and ink B, The CIE L of the printed surface when Ink A and Ink B are printed solidly on polyester film at a printing duty of 100%. * a * b * Coordinate value of ink A in color space (L * A , a * A , b *A ) and the coordinate value of ink B (L * B , a * B , b * B ) an ink set that satisfies all of the following conditions 1 to 3. Condition 1: Coordinate value a * A and coordinate value a * B are all between 5 and 35, and the coordinate value b * A and coordinate value b * B are all between 10 and 40. Condition 2: Hue angle h given by the following formula (II-1) A and the hue angle h given by the following formula (II-2) B All of these are between 40 and 70 degrees. h A =tan -1 (b * A / a * A ) (II-1) h B =tan -1 (b * B / a * B ) (II-2) Condition 3: The saturation difference ΔC represented by the following formula (III) is 2 or more and 20 or less. ΔC=((a * A -a * B ) 2 +(b * A -b * B ) 2 ) 0.5 (III) [2] A printing method comprising a step of ejecting at least ink A and ink B contained in the ink set described in [1] above as ink droplets from a plurality of ejection holes. [3] An inkjet head that ejects at least ink A and ink B contained in the ink set described in [1] above, and a main body static elimination device that eliminates static electricity, The main body static elimination device of the cosmetic handheld inkjet printer is a capacitor or an earth circuit. Effect of the Invention

[0012] According to the present invention, it is possible to provide an ink set, a printing method using said ink set, and a handy inkjet printer for makeup using said ink set, which enable easy adjustment of color for each area to be applied to makeup, and which is capable of obtaining high-quality makeup images that are excellent in ejection stability and free of graininess and have a natural appearance in printing in which ink is ejected as droplets. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram showing an example of a square lattice printing pattern in which application areas a of ink A and application areas b of ink B alternate, as used in the printing method of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of a triangular lattice-shaped printing pattern in which application areas a of ink A and application areas b of ink B alternate, as used in the printing method of the present invention. [Diagram 3] 1 is a diagram showing a handheld unit mounted vertically on a dock unit in a cosmetic handy inkjet printer according to a first embodiment of the present invention. FIG. [Figure 4] 1 is a block diagram showing a configuration of a cosmetic handy inkjet printer according to a first embodiment of the present invention. [Diagram 5] FIG. 2 is a block diagram showing a configuration of a cosmetic handy inkjet printer according to a second or third embodiment of the present invention. [Figure 6] FIG. 11 is a diagram illustrating a mist collection device of a cosmetic handy inkjet printer according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a diagram illustrating a mist collection device of a cosmetic handy inkjet printer according to a third embodiment of the present invention. [Figure 8] FIG. 13 is a diagram for explaining a static elimination device for a printed object of a cosmetic handy inkjet printer according to a fourth embodiment of the present invention. [Figure 9] FIG. 13 is a diagram for explaining a static elimination device for a printed material of a cosmetic handy inkjet printer according to a fifth embodiment of the present invention. [Figure 10] FIG. 13 is a block diagram showing the configuration of a cosmetic handy inkjet printer according to a sixth embodiment of the present invention. [Figure 11] FIG. 13 is a diagram illustrating the configuration of a mist detection device of a cosmetic handy inkjet printer according to a sixth embodiment of the present invention. [Figure 12] 13A to 13C are diagrams illustrating a mist detection method using a mist detection device of a cosmetic handheld inkjet printer according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Ink set] The ink set of the present invention is an ink set used for printing in which ink droplets are ejected at 100 pL or more and 5,000 pL or less, At least two inks, ink A and ink B, The CIE L of the printed surface when Ink A and Ink B are printed solidly on polyester film at a printing duty of 100%. * a * b * Coordinate value of ink A in color space (L * A , a * A , b * A ) and the coordinate value of ink B (L * B , a * B , b * B ) is an ink set that satisfies all of the following conditions 1 to 3. Condition 1: Coordinate value a * A and coordinate value a* B are all between 5 and 35, and the coordinate value b * A and coordinate value b * B are all between 10 and 40. Condition 2: Hue angle h given by the following formula (II-1) A and the hue angle h given by the following formula (II-2) B All of these are between 40 and 70 degrees. h A =tan -1 (b * A / a * A ) (II-1) h B =tan -1 (b * B / a * B ) (II-2) Condition 3: The saturation difference ΔC represented by the following formula (III) is 2 or more and 20 or less. ΔC=((a * A -a * B ) 2 +(b * A -b * B ) 2 ) 0.5 (III)

[0015] According to the present invention, it is easy to adjust the color for each part to be applied with makeup, and in printing in which ink is ejected as droplets, it is possible to obtain a high-quality makeup image that is excellent in ejection stability, has no graininess, and looks natural. The reason for this is unclear, but it is thought to be as follows. In the present invention, by using an ink set for printing in which the volume of ink droplets ejected is 100 pL or more, a droplet ejection head with low pressure loss can be used, a system with excellent ink fluidity can be designed, and ejection stability can be improved. On the other hand, when the amount of ink droplet ejected is typically 100 pL or more, the ink dots applied when the ink droplets are ejected onto the substrate become visible in size, resulting in a noticeable graininess and an unnatural-looking printed image. Here, there are three types of cones in humans that have different spectral sensitivities, and the three types of complexes are called blue cones (S cones), green cones (M cones), and red cones (L cones) from the short wavelength side according to the absorption wavelength at which they show the highest sensitivity. The ratio of the number of these cones is not equal. Humans have the highest ability to detect light quanta via red cones, and from the spectral reflectance curves for each wavelength of applied color, they are highly sensitive to yellow, whose spectral reflectance increases sharply around 500 nm, and red, whose spectral reflectance increases sharply around 600 nm. For this reason, an important factor in the visibility of colored ink dots is how conspicuous the ink dots are to be observed against the color of the background or surrounding colors. In the present invention, CIE L * a * b * It was found that by using at least two different inks that satisfy the above conditions 2 and 3 within the range of hue angles from -60 degrees (300 degrees) to 90 degrees related to the color development from red to yellow defined in the color space and that have a hue angle and chroma difference ΔC within a predetermined range, it is possible to suppress graininess and make ink dots less noticeable even in large ink droplets of 100 pL or more. * a * b * It has been found that if the conditions 2 and 3 in the color space definition are satisfied, and the amount of ink droplets ejected is in the range of 5,000 pL or less, the ink dots are not noticeable and there is no practical problem.

[0016] Furthermore, healthy and youthful-looking skin is macroscopically even in color, and for example, the color changes of each facial part are continuous, and there are no sudden color changes such as visible blemishes or redness, but on the other hand, on the microscopic level, there are slight color changes due to capillaries and light scattering due to downy hair, and microscopic non-uniformity is inherent in the macroscopic uniformity. This state is recognized as a natural appearance, and in order for a human face drawn by computer graphics to overcome the uncanny valley and have a natural appearance, it is an important factor to provide similar microscopic non-uniformity. Given this human ability to perceive appearance, when one monochrome ink is used to print on the skin, the printed area appears uniform and flat. In the present invention, the chromaticity coordinate value (a * ,b * ) satisfies condition 1 and condition 2, and at least two types of ink having similar hue and saturation are used in combination, so that even in printing that ejects ink droplets with a dot diameter large enough to exceed the limit of visibility, it is possible to impart a visually pleasing level of uniformity and non-uniformity in a well-balanced manner, thereby making it possible to achieve a good natural appearance. By satisfying condition 3 and setting the chroma difference ΔC between the two inks within a predetermined range, the inks are made to have similar hues and chroma, and when printed, it is possible to conceal macroscopically steep color changes while still allowing for slight color changes. This makes it possible to achieve a high-quality makeup image that looks natural, which is difficult to achieve by printing with a single color ink, and it is also believed to be easy to adjust the color for each part of the body where makeup is applied.

[0017] The ink set of the present invention comprises at least two types of ink, ink A and ink B. As an index of color development, each ink was printed solidly on a polyester film (hereinafter also referred to as "PET film") at a printing duty of 100%, and the CIE L * a * b * Using the color space, the coordinate value of ink A (L *A , a * A , b * A ) and the coordinate value of ink B (L * B , a * B , b * B ) has a relationship in which all of the above conditions 1 to 3 are satisfied. Coordinate value of ink A (L * A , a * A , b * A ) and the coordinate value of ink B (L * B , a * B , b * B ) is determined by printing ink A and ink B separately on a PET film in a solid state at a printing duty of 100%, and measuring the printed surface of the obtained print using a spectrophotometer / densitometer, as described in the examples. In this invention, "printing duty 100%" refers to applying ink droplets in a square lattice pattern without thinning out the ink application area, so that the ink droplets are applied at a dot-to-dot distance such that the ends of adjacent ink dots spread in a circle on the polyester film substrate come into contact at the circumferential position.

[0018] Unlike absorbent media such as paper, skin does not have a void layer or swelling layer on its surface to absorb ink. Therefore, the behavior of the ink dots on the skin surface after application of the ink droplets and the phenomenon of the colorant being unevenly distributed on the periphery of the ink dots (coffee ring phenomenon) caused by Marangoni flow during the drying process of the ink dots are similar to those of PET film, a non-absorbent medium. For example, the surface free energy of the cheek is 40 to 50 mN / m, which is close to the surface free energy of a PET film, and the ink wetting properties of the skin and the PET film are also similar. Therefore, in the present invention, a PET film is used as a model printing medium of a pseudo-skin (facial skin) to measure the coordinate values. The PET film is preferably an untreated PET film whose surface has not been modified and into which no resin or additive has been kneaded, but only in cases where the film has such excessive wetness that the average diameter of the ink droplets applied to the printed material (hereinafter also referred to as "dot diameter") cannot be determined, or where the film has no liquid repellency, a PET film whose surface has been treated to match the wettability of the target ink on the skin can be used. An example of a case where a surface-treated PET film is used is when it is practical for the practitioner to apply a milky lotion or skin lotion to the skin in advance and measure the coordinate value according to the surface energy of the skin that has changed as a result of the application.

[0019] The ink set of the present invention is used for printing in which ink droplets are ejected in an amount of 100 pL or more and 5,000 pL or less per droplet. Examples of printing methods using the ink set of the present invention include on-demand printing such as inkjet printing and nanodispenser printing, and the method can be selected depending on the viscosity of the inks in the ink set. On-demand printing is a plateless method that does not require a printing plate, and is a method of printing in a non-contact state with respect to a substrate. On-demand printing can eject ink droplets to deposit a desired amount of ink droplets in a desired area, and can control the amount of ink droplets per droplet, the amount of ink droplets deposited per area of ​​the ink droplets, the area to which the ink droplets are deposited, and the like, to achieve a good natural appearance. From this viewpoint, the printing method is preferably a printing method that ejects ink droplets by one or more methods selected from an inkjet method and a nanodispenser method.

[0020] <Amount of ink per droplet> Inkjet heads are manufactured using microfabrication techniques such as semiconductor manufacturing processes, and it is required that ink flows smoothly through the tiny tubes (nozzles) of the head. Ink that is prone to ink accumulation in the ink flow path is prone to resistance in the ink flow path and nozzle, which makes the meniscus shape of the ink droplets in the ejection nozzle unstable, leading to unstable ejection and even failure to eject. Since the flow path resistance in the ink flow path and nozzle increases fourfold when the flow path diameter is halved, it is preferable to enlarge the ink flow path, i.e., increase the amount of ejected ink droplets, within a range that does not affect ejection stability or cosmetic image quality. Furthermore, in inkjet printers where the ink droplets ejected are small, a portion of the ink ejected once floats as a mist and adheres to the head orifice, causing different types of ink to mix on the head orifice. In addition, ink droplets floating as a mist near the nozzle of the other color head enter the nozzle of the other color head due to the vibration of the meniscus accompanying the ejection of the head, causing contamination (so-called contamination) inside the head chamber. This can cause hetero-aggregation on the head orifice or in the head chamber, leading to unstable ejection and even the inability to eject. In addition, mist that does not adhere to the head orifice can cause unintended contamination of surrounding areas or the user's clothing, or the user can inhale the mist. If the amount of ink droplet per ejected droplet is 100 pL or more, the ejection stability can be improved without causing the above-mentioned ejection instability or ejection failure, and if the amount of ink droplet is 5,000 pL or less, graininess can be suppressed and a natural appearance can be achieved. From this viewpoint, the amount of ink droplet per ejected droplet is preferably 200 pL or more, more preferably 300 pL or more, and even more preferably 400 pL or more, and is preferably 4,000 pL or less, more preferably 3,000 pL or less, and even more preferably 2,000 pL or less. The amount of ink droplet per droplet can be calculated from the average diameter of the ejected ink droplets when the printing method is a method in which ink droplets are ejected by an inkjet method, a nanodispenser method, or the like, or can be calculated from the change in mass of ink when a certain number of ink droplets are ejected.

[0021] <Condition 1> Condition 1 is the coordinate value a * A and a * B are all between 5 and 35, and the coordinate value b * A and b * B are all between 10 and 40. Condition 1 indicates that the hues of ink A and ink B are both in the range from red to yellow. By making the chromaticity coordinate values ​​of ink A and ink B satisfy condition 1, graininess can be suppressed and a natural appearance can be achieved. a * A In order to suppress graininess and improve the naturalness of the appearance, is 5 or more, preferably more than 5, more preferably 10 or more, even more preferably 15 or more, still more preferably 17 or more, and is 35 or less, preferably less than 35, more preferably 30 or less, even more preferably 25 or less, still more preferably 23 or less. a * B is not particularly limited as long as it is 5 or more and 35 or less, preferably more than 5 and less than 35. * A and a * B The absolute value of the difference between * A -a * B) is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more from the viewpoint of achieving a good natural appearance, and is preferably 20 or less, more preferably 16 or less, even more preferably 14 or less, still more preferably 12 or less, still more preferably 10 or less, and even more preferably 8 or less, from the viewpoint of suppressing graininess. b * A In order to suppress graininess and improve the naturalness of the appearance, the value is 10 or more, preferably more than 10, more preferably 13 or more, even more preferably 15 or more, still more preferably 20 or more, and is 40 or less, preferably less than 40, more preferably 35 or less, even more preferably 30 or less, and still more preferably 27 or less. b * B is not particularly limited as long as it is 10 or more and 40 or less, preferably more than 10 and less than 40. * A and b * B The absolute value of the difference between * A -b * B ) is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more from the viewpoint of improving the naturalness of the appearance, and is preferably 20 or more, more preferably 16 or less, even more preferably 14 or less, and even more preferably 12 or less, from the viewpoint of suppressing graininess.

[0022] <Condition 2> Condition 2 is the hue angle h given by the following formula (II-1): A and the hue angle h given by the following formula (II-2) B All of these are between 40 and 70 degrees. h A =tan -1 (b * A / a * A ) (II-1) h B =tan -1 (b *B / a * B ) (II-2) The hue angle indicates the degree of red to yellow in terms of angular distribution. Condition 2 indicates that the hue angles of ink A and ink B are in the above range from red to yellow. A and the hue angle h of ink B B By satisfying the above condition 2, graininess can be suppressed and the image can be made to look natural. h A From the above viewpoint, is 40 degrees or more, preferably 43 degrees or more, more preferably 45 degrees or more, even more preferably 47 degrees or more, and is 70 degrees or less, preferably less than 70 degrees, more preferably 65 degrees or less, even more preferably 60 degrees or less, still more preferably 55 degrees or less, and even more preferably 53 degrees or less. h B is not particularly limited as long as it is 40 degrees or more and 70 degrees or less, preferably 40 degrees or more and less than 70 degrees, A and B The absolute value of the difference between A -h B ) is preferably 0 or more, more preferably 2 or more, and even more preferably 3 or more from the viewpoint of improving the naturalness of the appearance, and is preferably 20 or more, more preferably 18 or less, and even more preferably 16 or less, from the viewpoint of suppressing graininess.

[0023] <Condition 3> Condition 3 is that the saturation difference ΔC represented by the following formula (III) is 2 or more and 20 or less. ΔC=((a * A -a * B ) 2 +(b * A -b * B ) 2 ) 0.5 (III) The saturation difference ΔC indicates the difference in the degree of color vividness between ink A and ink B. When the saturation difference ΔC satisfies the above condition 3, it indicates that ink A and ink B are inks with similar hues, and when printed, it is possible to conceal abrupt color changes macroscopically while still allowing for slight color changes microscopically. This makes it possible to achieve a good natural appearance, which is difficult to achieve with printing using single-color ink. From the viewpoint of adjusting the color development between ink A and ink B and achieving a good natural appearance, the saturation difference ΔC is 2 or more, preferably 4 or more, more preferably 6 or more, even more preferably 8 or more, and is 20 or less, preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, and still more preferably 12 or less.

[0024] <Condition 4> It is preferable that the ink set of the present invention further satisfies the following condition 4. Condition 4: The color difference ΔE represented by the following formula (IV) is 2 or more and 40 or less. ΔE=((L * A -L * B ) 2 +(a * A -a * B ) 2 +(b * A -b * B ) 2 ) 0.5 (IV) The color difference ΔE indicates the overall total color difference between ink A and ink B, and by the color difference ΔE satisfying the above condition 4, it is possible to suppress graininess and achieve a more natural appearance. From this viewpoint, the color difference ΔE is preferably 3 or more, more preferably 5 or more, even more preferably 7 or more, and is preferably less than 40, more preferably 35 or less, even more preferably 30 or less, still more preferably 25 or less, still more preferably 20 or less, still more preferably 15 or less, still more preferably 13 or less, and still more preferably 11 or less.

[0025] (Coloring agent) In the present invention, there are no limitations on the composition of ink A and ink B as long as they satisfy the above-mentioned conditions 1 to 3, and preferably conditions 1 to 4, but it is preferable that both ink A and ink B contain at least a colorant. Examples of the colorant include inorganic pigments; and colorants other than inorganic pigments, such as organic pigments, hydrophobic dyes (oil-soluble dyes, disperse dyes), and water-soluble dyes (acid dyes, reactive dyes, direct dyes, etc.). The hydrophobic dye preferably has a solubility of less than 6% by mass in 100 g of water (at 20° C.). Examples of inorganic pigments include carbon black, metal oxides, etc. Both white inorganic pigments and non-white inorganic pigments other than white can be used. Examples of the white inorganic pigment include titanium oxide and zinc oxide. Examples of non-white inorganic pigments include yellow iron oxide, red iron oxide, black iron oxide, carbon black, ultramarine, Prussian blue, Prussian blue titanium oxide, black titanium oxide, chromium oxide, chromium hydroxide, titanium / titanium oxide sintered product, and the like. Colorants other than inorganic pigments include organic pigments such as Red No. 201, Red No. 202, Yellow No. 401, Blue No. 404, etc.; lake pigments such as Red No. 104, Red No. 230, Yellow No. 4, Yellow No. 5, Blue No. 1, etc.; dyes such as Red No. 226, Acid Yellow 1, Acid Orange 7, Food Blue 2, Acid Red 52, etc.; and these pigments and dyes coated with resins such as polymethacrylate esters. The colorants used in ink A and ink B preferably contain an inorganic pigment, from the standpoint of suppressing graininess and improving the natural appearance. When both ink A and ink B contain an inorganic pigment as the colorant, the density of the inorganic pigment is preferably 1 g / cm 3 More preferably, 2 g / cm 3 More preferably, 3 g / cm 3 and preferably 6 g / cm 3 The following is the result. The colorants can be used alone or in combination of two or more kinds. From the viewpoint of suppressing graininess and improving the natural appearance, it is preferable to use two or more kinds in combination.

[0026] The hues of the colorants include achromatic colors such as white, black, and gray; and chromatic colors such as yellow, magenta, cyan, blue, red, orange, and green. The achromatic colorants and chromatic colorants may each be used alone or in combination of two or more. From the viewpoint of suppressing graininess and improving the natural appearance, the achromatic colorant is preferably an achromatic pigment, more preferably one or more selected from a white pigment and a black pigment, even more preferably one or more selected from titanium oxide and black iron oxide, and still more preferably a combination of titanium oxide and black iron oxide. From the viewpoints of suppressing graininess and improving the naturalness of the appearance, the chromatic colorant is preferably a chromatic pigment, more preferably one or more selected from a yellow pigment and a red pigment, even more preferably one or more selected from yellow iron oxide and red iron oxide, and still more preferably a combination of yellow iron oxide and red iron oxide. In the present invention, from the viewpoint of suppressing graininess and improving the natural appearance, it is more preferable that both ink A and ink B contain an achromatic pigment and a chromatic pigment.

[0027] The mass ratio of the achromatic pigment to the chromatic pigment contained in each of Ink A and Ink B [achromatic pigment / chromatic pigment] is, from the viewpoints of suppressing graininess and improving the natural appearance, and of improving the ability to hide stains, bruises, and the like, preferably 2 or more, more preferably 2.3 or more, even more preferably 2.5 or more, and is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, still more preferably 4 or less, and even more preferably 3.5 or less.

[0028] From the viewpoint of improving dispersibility in the ink and water resistance of the cosmetic image, the colorant is preferably one whose surface has been hydrophobized. The hydrophobization treatment is preferably a hydrophobization treatment that is performed on ordinary cosmetic powders using various hydrophobization agents, and examples of the hydrophobization treatment include silicone treatment, fatty acid treatment, lauroyl lysine treatment, surfactant treatment, metal soap treatment, fluorine compound treatment, lecithin treatment, nylon treatment, and polymer treatment.

[0029] From the viewpoint of coloring uniformity, water resistance of cosmetic images, improving ejection stability, and suppressing graininess to improve the naturalness of appearance, the colorant is preferably dispersed in a dispersing polymer, and is more preferably used as dispersing polymer particles containing a colorant (hereinafter also referred to as "colorant-containing polymer particles"). The colorant-containing polymer particles may be particles formed by a colorant and a dispersing polymer, and the particle form includes, for example, a particle form in which the colorant is coated with a dispersing polymer, a particle form in which the colorant is encapsulated in a dispersing polymer, a particle form in which the colorant is uniformly dispersed in a dispersing polymer, a particle form in which the colorant is exposed on the surface of a polymer particle, and mixtures thereof are also included. From the viewpoint of improving the ejection stability, each of inks A and B used in the present invention is preferably a water-based ink containing colorant-containing polymer particles. Usually, when water-based ink dries at the nozzle opening, clogging and deflection of the discharged ink are likely to occur due to the thickening of the ink at the nozzle opening. The phenomenon of clogging and deflection of the discharged ink is believed to be caused by the fact that the distance between the pigment particles narrows as the water contained in the water-based ink dries at the nozzle opening, and the relative dielectric constant of the vehicle around the pigment particles decreases, and the dissociation degree of the dispersing polymer that stabilizes the pigment particles decreases, which reduces the charge repulsion between the pigment particles and causes the pigment particles to aggregate. In addition, when the dispersing polymer is neutralized, salts such as sodium used for neutralization are released and the osmotic pressure around the pigment particles increases, so that the pigment concentration near the nozzle decreases to relieve the osmotic pressure, and the pigment particles move into the ink flow path. When the pigment particles move in this way, the viscosity increased by drying affects the ink fluidity. Specifically, if the viscosity increases by two times, the pressure loss is thought to increase by two times. On the other hand, since the ink set of the present invention is used for printing in which the amount of ink droplets ejected per droplet is within the aforementioned range, it can be applied to printers equipped with wide ink flow paths, which is thought to facilitate the movement of pigment particles within the ink flow path, suppress clogging and deflection of the ejection direction, and improve ejection stability.

[0030] (Dispersible polymer) The dispersible polymer constituting the colorant-containing polymer particles is preferably a polymer having an ionic group from the viewpoint of improving the dispersibility of the colorant, and a cationic polymer having a cationic group or an anionic polymer having an anionic group can be used.

[0031] [Cationic polymer] The cationic polymer is preferably a polymer having cationic groups such as proton acid salts of primary, secondary, or tertiary amino groups, and quaternary ammonium groups. The cationic polymer includes natural cationic polymers and synthetic cationic polymers. Natural cationic polymers include polymers obtained by extraction, purification, etc. from natural products, and chemically modified polymers, and include those having glucose residues in the polymer backbone. Specific examples include cationic guar gum, cationic tara gum, cationic locust bean gum, cationic cellulose, cationic hydroxyalkyl cellulose, cationic starch, etc.

[0032] Examples of synthetic cationic polymers include polyethyleneimine, polyallylamine or acid neutralized products thereof, polyglycol-polyamine condensates, cationic polyvinyl alcohol, cationic polyvinylpyrrolidone, cationic silicone polymers, 2-(dimethylamino)ethyl methacrylate polymers or acid neutralized products thereof, poly(trimethyl-2-methacryloyloxyethyl ammonium chloride), amine / epichlorohydrin copolymers, N,N-dimethylaminoethyl diethyl methacrylate sulfate / vinylpyrrolidone copolymers, N,N-dimethylaminoethyl diethyl methacrylate sulfate / N,N-dimethylacrylamide / polyethylene glycol dimethacrylate copolymers, polydiallyldimethylammonium chloride, Examples of the copolymer include diallyldimethylammonium chloride / acrylamide copolymer, diallyldimethylammonium chloride / sulfur dioxide copolymer, diallyldimethylammonium chloride / hydroxyethylcellulose copolymer, 1-allyl-3-methylimidazolium chloride / vinylpyrrolidone copolymer, alkylamino(meth)acrylate / vinylpyrrolidone copolymer, alkylamino(meth)acrylate / vinylpyrrolidone / vinylcaprolactam copolymer, (3-(meth)acrylamidopropyl)trimethylammonium chloride / vinylpyrrolidone copolymer, alkylaminoalkylacrylamide / alkylacrylamide / (meth)acrylate / polyethylene glycol(meth)acrylate copolymer, etc. These may be used alone or in combination of two or more. As commercially available cationic polymers, cationic polymers used in cosmetic applications are preferred, and examples thereof include HC Polymer 3M, HC-Polymer 5 (both manufactured by Osaka Organic Chemical Industry Co., Ltd.), Pluscise L-514 (manufactured by GOO Chemical Industry Co., Ltd.), etc. Among these, cationic silicone polymers are preferred from the viewpoints of improving ejection stability and suppressing graininess to improve the natural appearance.

[0033] The cationic silicone polymer is preferably a poly(N-acylalkyleneimine) / organopolysiloxane copolymer comprising an organopolysiloxane segment (x), and a poly(N-acylalkyleneimine) segment (y) consisting of an alkylene group containing a cationic nitrogen atom bonded to at least one silicon atom of the segment (x), and a repeating unit of N-acylalkyleneimine represented by the following general formula (1-1):

[0034] [ka] (In the formula, R 1 represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, or an arylalkyl group or alkylaryl group having 7 to 22 carbon atoms, and a is 2 or 3.

[0035] The organopolysiloxane that forms the segment (x) is, for example, a compound represented by the following general formula (1-2). [ka] (In the formula, R 2 represents an alkyl group having 1 to 22 carbon atoms, a phenyl group, or an alkyl group containing a nitrogen atom, and a plurality of R 2 may be the same or different, but at least one of them is an alkyl group containing a cationic nitrogen atom. b is 100 or more and 5,000 or less.

[0036] As the poly(N-acylalkyleneimine) / organopolysiloxane copolymer, one in which segment (y) is bonded to at least one silicon atom at the end or in the side chain of segment (x) via an alkylene group containing a cationic nitrogen atom is preferred. The mass ratio of the content of segment (x) to the total content of segment (x) and segment (y) in the poly(N-acylalkyleneimine) / organopolysiloxane copolymer [content of segment (x) / [total content of segment (x) and segment (y)]] is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.4 or more, and is preferably 0.99 or less, more preferably 0.95 or less, even more preferably 0.9 or less. In this specification, the mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]] is the ratio of the mass (Mx) of segment (x) to the total mass (Mx) of segment (x) and the mass (My) of segment (y) in the poly(N-acylalkyleneimine) / organopolysiloxane copolymer. The mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]] was determined by dissolving 5% by mass of poly(N-acylalkyleneimine) / organopolysiloxane copolymer in deuterated chloroform and measuring the mass ratio by nuclear magnetic resonance ( 1 It can be calculated from the integral ratio of the alkyl group or phenyl group in the segment (x) to the methylene group in the segment (y) by H-NMR analysis.

[0037] The weight average molecular weight of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 70,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 200,000 or less. The weight average molecular weight of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer can be calculated from the weight average molecular weight of the organopolysiloxane forming the segment (x) and the above-mentioned mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]].

[0038] Suitable examples of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer include poly(N-formylethyleneimine) / organopolysiloxane copolymer, poly(N-acetylethyleneimine) / organopolysiloxane copolymer, poly(N-propionylethyleneimine) / organopolysiloxane copolymer, and the like. The poly(N-acylalkyleneimine) / organopolysiloxane copolymer can be obtained, for example, by reacting poly(N-acylalkyleneimine), which is a ring-opening polymer of cyclic iminoether, with an organopolysiloxane forming the segment (x). More specifically, it can be obtained, for example, by the method described in JP 2011-126978 A. The poly(N-acylalkyleneimine) / organopolysiloxane copolymer used as the cationic silicone polymer can be used alone or in combination of two or more kinds.

[0039] [Anionic polymer] The anionic polymer preferably contains a group that exhibits acidity by dissociating and releasing a hydrogen ion, such as a carboxyl group (-COOM), a sulfonic acid group (-SO3M), or a phosphoric acid group (-OPO3M2), or a dissociated ionic form thereof (-COO - , -SO3 - , -OPO3 2- , -OPO3 -In the above chemical formula, M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium. Specific examples of the basic skeleton of the anionic polymer include acrylic polymers, polyesters, polyurethanes, etc. Among these, acrylic polymers are preferred. That is, the anionic polymer is preferably an anionic acrylic polymer containing a constituent unit derived from a monomer having an acidic group. The monomer having an acidic group is preferably a monomer having a carboxy group, more preferably at least one selected from (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid and 2-methacryloyloxymethylsuccinic acid, and even more preferably (meth)acrylic acid. Here, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid.

[0040] The anionic polymer preferably contains a constituent unit derived from a monomer having an acidic group and a constituent unit derived from a (meth)acrylic acid alkyl ester, more preferably contains a constituent unit derived from a monomer having an acidic group, a constituent unit derived from a (meth)acrylic acid alkyl ester, and a constituent unit derived from an (N-alkyl)(meth)acrylamide, still more preferably is a (meth)acrylic acid / (meth)acrylic acid alkyl ester / (N-alkyl)(meth)acrylamide copolymer, and even more preferably is an acrylic acid / acrylic acid alkyl ester / (N-alkyl)acrylamide copolymer. Examples of commercially available anionic acrylic polymers include ((meth)acrylic acid / (meth)acrylic acid alkyl ester / (N-alkyl)alkylacrylamide) copolymers AMP, such as Pluscise L-9909B (manufactured by GOO Chemical Industry Co., Ltd.). Other commercially available polymers having structural units derived from acrylic acid or methacrylic acid as monomers having acidic groups, which are used in cosmetics, include Aniset KB-100H and Aniset NF-1000 (both manufactured by Osaka Organic Chemical Industry Co., Ltd.); Ultrahold 8, Ultrahold Strong, Ultrahold Power (all manufactured by BASF); Plussize L-9900, Plussize L-9909U, Plussize L-9540B, Plussize L-9600U, Plussize L-9715, Plussize L-53, Plussize L-6330, Plussize L-6466, Plussize L-6740B, Plussize L-53D for Color A, and Plussize L-75CB (all manufactured by GOO Chemical Industry Co., Ltd.).

[0041] When colorant-containing polymer particles are used as the colorant, the volume average particle size of the colorant-containing polymer particles is preferably 10 nm or more, more preferably 50 nm or more, and is preferably 1,000 nm or less, more preferably 900 nm or less. The volume average particle size of the colorant-containing polymer particles is measured, for example, using a zeta potential / particle size measurement system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.) when the particle concentration to be measured is about 5×10 -3 The dispersion liquid diluted with water to a mass % is placed in a measurement cell, and measurements can be made by cumulant analysis at a temperature of 25°C, with 100 cumulative measurements, and by inputting the refractive index of water (1.333) as the refractive index of the dispersion solvent. Furthermore, when the colorant is titanium oxide particles, for example, a laser diffraction / scattering particle size distribution analyzer "LA950" (manufactured by HORIBA, Ltd.) is used to measure the refractive index of titanium oxide as 2.75, the refractive index of water as 1.333, the circulation speed of the apparatus is set to 5, and the ultrasonic waves are set to 3. After irradiating with ultrasonic waves for 1 minute, the measurement is performed, and the value of the volume median particle diameter (D50) at this time can be regarded as the volume average particle diameter of the titanium oxide particles.

[0042] (Ink manufacturing) When ink A and ink B each contain an inorganic pigment as a colorant, the inorganic pigment contained in ink A and ink B is preferably contained as inorganic pigment particles dispersed in a water-dispersible polymer. In this case, ink A and ink B preferably contain a colorant aqueous dispersion containing inorganic pigment particles dispersed in a water-dispersible polymer, and, as necessary, an organic solvent, water, and various additives. In addition, when ink A and ink B contain a colorant other than an inorganic pigment, these inks may further contain a colorant water dispersion in which the other colorant is dispersed in a water-dispersible polymer.

[0043] The colorant water dispersion using an inorganic pigment and other colorant can be obtained by dispersing the colorant, the water-dispersible polymer, and, if necessary, the neutralizing agent, the surfactant, etc., by a known method. Specifically, it is preferable to obtain it by a production method including the following steps I and II, but is not necessarily limited to this method. Step I: A step of dispersing a colorant mixture containing water, a colorant, a water-dispersible polymer, and an organic solvent to obtain a colorant dispersion. Step II: A step of removing the organic solvent from the colorant dispersion obtained in step I to obtain a colorant aqueous dispersion.

[0044] It is desirable that the organic solvent used in step I has high affinity with the water-dispersible polymer and good wettability with the colorant. The organic solvent is preferably ethanol or isopropanol from the viewpoints of improving wettability with the colorant and adsorption of the water-dispersible polymer during coloring, and from the viewpoint of safety due to the organic solvent remaining after printing on the skin.

[0045] When a hydrophobic pigment such as titanium oxide, zinc oxide, or iron oxide that has been hydrophobically treated is used as the inorganic pigment, step I preferably includes steps I-1 and I-2 using the above-mentioned cationic silicone polymer and anionic polymer in combination as the water-dispersible polymer. Step I-1: A step of suspending the hydrophobic pigment that has been subjected to the hydrophobic treatment using a cationic silicone polymer to obtain a suspension of the hydrophobic pigment. Step I-2: A step of adding an anionic polymer to the suspension of the hydrophobic pigment obtained in step I-1 to obtain a colorant mixture, and then dispersing the colorant mixture to obtain a colorant dispersion.

[0046] In step I-1, the hydrophobic silicone portion of the cationic silicone polymer is adsorbed on the surface of the hydrophobic pigment, while the hydrophilic cationic portion of the cationic silicone polymer is oriented toward the medium, so that the pigment particles can be stably suspended in a state of having a positive zeta potential. Next, in step I-2, an anionic polymer is added, so that the anionic polymer is adsorbed to the cationic group of the cationic silicone polymer adsorbed on the hydrophobic pigment, and the pigment particles are dispersed in a state of having a negative zeta potential, so that a stable dispersion can be obtained even when a hydrophobic pigment is used.

[0047] In the dispersion treatment of step I, a means for applying shear stress can be used, for example, a kneading machine such as a roll mill, a kneader, or an extruder, a high-pressure homogenizer such as Microfluidizer (trade name, Microfluidics Corp.), or a media-type dispersing machine such as a paint shaker or a bead mill. Of these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the colorant. When the dispersion treatment is carried out using a high-pressure homogenizer, the colorant can be controlled to have a desired particle size by controlling the treatment pressure and the number of passes of the dispersion treatment.

[0048] The method for removing the organic solvent in step II is not particularly limited, and may be a known method. Note that a part of the water contained in the colorant dispersion may be removed simultaneously with the organic solvent. The temperature and time for removing the organic solvent can be appropriately selected depending on the type of the organic solvent used.

[0049] In order to adjust the physical properties, Ink A and Ink B may contain various additives that are commonly used in inks, such as a wetting agent, a penetrating agent, a dispersing agent such as a surfactant, a viscosity modifier such as hydroxypropyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, an antifoaming agent such as silicone oil, an antifungal agent, and an antirust agent. Examples of wetting agents and penetrating agents include polyhydric alcohols such as ethylene glycol, propylene glycol (1,2-propanediol), 1,2-hexanediol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyoxyethylene glycerin, trimethylolpropane, and diethylene glycol diethyl ether, as well as ethers and acetates of such polyhydric alcohols, with propylene glycol (1,2-propanediol), 1,2-hexanediol, polyethylene glycol, glycerin, polyoxyethylene glycerin, triethylene glycol, and trimethylolpropane being preferred. Examples of the surfactant include non-ionic surfactants such as ethylene oxide adducts of acetylene diol and polyoxyethylene alkyl ethers.

[0050] (Composition and properties of Ink A and Ink B) The content of the colorant in Ink A and Ink B is, from the viewpoint of improving ejection stability and from the viewpoint of enhancing the concealing ability of the cosmetic image against blemishes, bruises, and the like, preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less, still more preferably 13% by mass or less, and even more preferably 10% by mass or less. The content of the inorganic pigment in the total amount of colorant contained in Ink A and Ink B is, from the viewpoint of improving the ejection properties and from the viewpoint of increasing the concealing ability of the cosmetic image against blemishes, bruises, and the like, preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less, and even more preferably 100% by mass.

[0051] The content of the water-dispersible polymer in Ink A and Ink B is, from the viewpoint of improving the ejection stability and from the viewpoint of increasing the concealing ability of the cosmetic image against blemishes, bruises, and the like, preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, and is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less. From the viewpoint of improving ejection stability, the water content in Ink A and Ink B is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, still more preferably 65% ​​by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0052] From the viewpoint of improving ejection stability, the static surface tension of Ink A and Ink B at 20°C is preferably 25 mN / m or more, more preferably 27 mN / m or more, even more preferably 29 mN / m or more, and is preferably 45 mN / m or less, more preferably 40 mN / m or less, even more preferably 35 mN / m or less. From the viewpoint of improving the ejection stability, the viscosity of Ink A and Ink B at 20°C is preferably 3 mPa·s or more, more preferably 4 mPa·s or more, even more preferably 6 mPa·s or more, still more preferably 8 mPa·s or more, and is preferably 20 mPa·s or less, more preferably 15 mPa·s or less, and even more preferably 12 mPa·s or less. The static surface tension at 20° C. and the viscosity at 20° C. can be measured by the method described in the Examples.

[0053] From the viewpoint of being able to form a high-quality cosmetic image in which graininess is suppressed and which has a good natural appearance, the ink set of the present invention is preferably used as a cosmetic ink set, more preferably used as a skin cosmetic, and even more preferably used as a make-up cosmetic such as face powder, face powder, makeup base, foundation, concealer, blusher, etc.

[0054] [Printing method] The ink set of the present invention is used for printing in which ink droplets are ejected at 100 pL or more and 5,000 pL or less. The printing method using the ink set is not particularly limited as long as it is a method capable of ejecting ink droplets with an amount of ink droplets of 100 pL or more and 5,000 pL or less per droplet. Among them, a printing method including a step of ejecting at least ink A and ink B contained in the ink set as ink droplets from a plurality of ejection holes is preferred. The amount of ink droplet per ejected droplet is as described above.

[0055] The average diameter (dot diameter) of the ink droplets applied to the substrate is preferably 50 μm or more, more preferably 70 μm or more, even more preferably 90 μm or more, still more preferably 100 μm or more, and preferably 500 μm or less, more preferably 450 μm or less, even more preferably 400 μm or less, still more preferably 350 μm or less, and still more preferably 300 μm or less.

[0056] When the printing method is a method using an inkjet system, either a thermal system or a piezoelectric system can be used as the inkjet ejection system. From the viewpoint of suppressing graininess and improving the natural appearance, the voltage applied to the inkjet ejection head is preferably 5 V or more, more preferably 10 V or more, even more preferably 15 V or more, and is preferably 50 V or less, more preferably 45 V or less, even more preferably 40 V or less. From the viewpoint of suppressing graininess and improving the natural appearance, the driving frequency of the inkjet ejection head is preferably 1 kHz or more, more preferably 3 kHz or more, and is preferably 300 kHz or less, more preferably 150 kHz or less, even more preferably 90 kHz or less, and even more preferably 50 kHz or less.

[0057] When the printing method is a method using a nanodispenser system, the ejection system of the nanodispenser is preferably a jet system capable of ejecting ink without contacting the substrate, and more preferably a jet system using a piezoelectric element. The voltage applied to the ejection head of the nanodispenser is preferably 5 V or more, more preferably 10 V or more, even more preferably 15 V or more, from the viewpoint of suppressing graininess and improving the natural appearance, and is preferably 100 V or less, more preferably 80 V or less, even more preferably 60 V or less. From the viewpoint of suppressing graininess and improving the natural appearance, the drive frequency of the nanodispenser ejection head is preferably 1 Hz or more, more preferably 5 Hz or more, and is preferably 30 kHz or less, more preferably 10 kHz or less, even more preferably 5 kHz or less, and even more preferably 1 kHz or less.

[0058] The printing method may be a method in which the application ratio and application area of ​​ink A and ink B are adjusted for each part to be printed, and printing is performed so as to include at least a printed area to which ink A and ink B are applied, respectively. For example, ink A and ink B may be applied uniformly to a desired application area alone. In this case, the entire printed area to which decorative printing is performed includes an area to which ink A is applied alone and an area to which ink B is applied alone, and since ink A and ink B satisfy the above-mentioned conditions 1 to 3, and preferably conditions 1 to 4, a high-quality decorative image that is free of graininess and looks natural can be obtained.

[0059] In order to further improve the effect of suppressing graininess and improving the natural appearance of the printing method, it is preferable to adjust the printing pattern, the number of prints, the application area to which ink A and ink B are applied, or the application order, etc. In the present invention, the printing pattern used may be, for example, a triangular lattice pattern, a square lattice pattern, a rectangular lattice pattern, or a honeycomb lattice pattern. The printing pattern may be one type alone or two or more types in combination. Among them, one or more types selected from the triangular lattice pattern and the square lattice pattern are preferred. In the present invention, the application of ink A and ink B may be a printing in which desired amounts of ink A and ink B are applied to all desired areas in a single printing run, or may be a printing in which desired areas are selected and desired amounts of ink A and ink B are applied in multiple printing runs.

[0060] Furthermore, in the present invention, from the viewpoint of improving the naturalness of the appearance, it is preferable to adjust the regions to which ink A and ink B are applied and the order in which they are applied. From the same viewpoint as above, the printing pattern used is preferably a printing pattern in which the region to which ink droplets of ink A are applied and the region to which ink droplets of ink B are applied are adjacent to each other, and more preferably a printing pattern in which the region to which ink droplets of ink A are applied and the region to which ink droplets of ink B are applied are adjacent to each other and alternate. By using such a printing pattern and selectively adjusting the regions to which ink A is applied and the regions to which ink B is applied, it is possible to impart a microscopically slight color change, impart a visually pleasing degree of uniformity and non-uniformity in a well-balanced manner, and achieve a more natural appearance. Furthermore, a printed region that has been decoratively printed using such a printing pattern will have microscopic non-uniformity inherent within its macroscopic uniformity, and the difference between the printed region and a non-printed region that has microscopic non-uniformity can be made smaller. As an example of the printing method, when the printing pattern is a square lattice pattern, as shown in FIG. 1, droplets of ink A are applied to each lattice shown as region a of the square lattice printing pattern, and droplets of ink B are applied to each lattice shown as region b, so that the application regions a of ink A and the application regions b of ink B are adjacent to each other and alternate. In addition, when the printing pattern is a triangular lattice pattern, a method can be used in which droplets of ink A are applied to each lattice shown as region a of the triangular lattice printing pattern as shown in Figure 2, and droplets of ink B are applied to each lattice shown as region b, so that the application regions a of ink A and the application regions b of ink B are adjacent and alternate.

[0061] The printing method of the present invention includes a method (i) in which ink A and ink B are applied in advance to a substrate such as a tape or sheet as a printing substrate to form a cosmetic image, and then the substrate on which the cosmetic image is formed is attached to the skin to transfer the cosmetic image to the skin, and a method (ii) in which ink A and ink B are applied onto the skin to form a cosmetic image. In the case of method (i), a printing device that ejects ink droplets used in normal printing can be used. In the case of method (ii), a more natural appearance can be achieved. From this viewpoint, method (ii) in which ink droplets of ink A and ink B are applied onto the skin is preferred.

[0062] [Handy Cosmetic Inkjet Printer] When the printing method using the ink set of the present invention is the above-mentioned method (ii), it is preferable to use a cosmetic handy inkjet printer from the viewpoint of improving the natural appearance. In this invention, "handy" means having a shape or size that allows a user to hold it in his / her hand, and although in English it is called "hand-held," in this specification the term "handy" will be used.

[0063] Inkjet printers using inkjet technology are designed in an environment where the relative positions of the inkjet head and the printed material are strictly controlled, and can obtain high-quality images. However, for handheld inkjet printers that can be used by hand, it is difficult to strictly control the relative positions of the inkjet head and the printed material, and even for those that print on flat paper, there have been few proposals for a practical level, and the current situation is that the maturity of the technology is not high. The cosmetic handy inkjet printer used in the present invention includes an inkjet head that ejects at least ink A and ink B contained in the ink set, and a main body static eliminator that eliminates static electricity, and the main body static eliminator is preferably a capacitor or an earth circuit, which makes it possible to easily obtain high-quality cosmetic images that have a good natural appearance.

[0064] (First embodiment) <Configuration of a handy cosmetic inkjet printer> In the present invention, a cosmetic handy inkjet printer 1 according to a first embodiment includes inkjet heads 4 and 5 for ejecting at least ink A and ink B, and ink tanks 6 and 7 for ink A and ink B. In the present invention, the inkjet heads and tanks for Ink A and Ink B are preferably arranged as independent heads and ink tanks, and when a nozzle blockage or the like occurs in a head to which Ink A or Ink B is applied, it is preferable that only the head in which the nozzle blockage or the like has occurred can be replaced. Similarly, with regard to ink tanks, it is preferable to be able to replace only the tanks that are no longer suitable for ejecting ink due to a shortage of ink therein. In addition, when the ink set includes other inks in addition to ink A and ink B, the cosmetic handy inkjet printer 1 can further include an inkjet head that ejects the other inks and an ink tank for the other inks. From the viewpoint of printer size reduction and ease of use, the cosmetic handy inkjet printer 1 according to the first embodiment preferably comprises a dock unit 2 and a handheld unit 3 that is separated from the dock unit 2 and performs cosmetic printing.

[0065] FIG. 3 shows a cosmetic handheld inkjet printer 1 that includes a dock unit 2 and a handheld unit 3 that is mounted vertically on the dock unit 2. The hand-held portion 3 is connected to the dock-side conductive terminal 26 via the hand-held-side conductive terminal 33, and is connected to the ground 27 via the ground circuit 25. These are only representative conductors, and other conductors are omitted. The cosmetic handy inkjet printer 1 according to the first embodiment can employ, as the main body static eliminator, a configuration in which a capacitor 505 is provided in the handheld portion, or a configuration in which an earth circuit 25 is provided in the dock portion. Furthermore, if the handle has grip 35 made of conductive material, by holding grip 35 in the hand during use, the user's static electricity is grounded and static electricity to the device is prevented from building up. Furthermore, when the hand-held portion 3 has a pair of rollers 8, 9, good decorative printing can be performed on skin, which is a non-flat printing target. Furthermore, when the hand-held portion 3 has the light source portions 10 and 11 as optical sensors, good cosmetic printing can be performed on skin, which is a non-flat printing target.

[0066] 4 is a block diagram showing the components of the dock unit 2 and the hand-held unit 3. The upper block shows the components of the dock unit 2, and the lower block shows the components of the hand-held unit 3. A CPU 20 is installed on the control board of the dock unit 2, and is connected to a charging device unit 21 for supplying power and a maintenance device unit 22 for inputting and displaying information required for decorative printing. The CPU 20 receives image data from an information processing and input device such as a smartphone and an image capture device from a camera via a transmission / reception unit 23 wirelessly or via a wire, creates print pattern data in an image processing circuit 24 that performs image input, return, transfer, etc., and transfers the data to the inkjet heads 4 and 5 via the head control unit 30 of the handheld unit 3. At this time, it is also possible to complete image processing and data sorting processing required for ink ejection from the inkjet heads 4 and 5 using an app on the smartphone. The CPU 20 built into the dock unit 2 transfers the print pattern data received from the smartphone to the head control unit 30 of the handheld unit 3. As an example of generating and transferring print pattern data by a smartphone or the like as described above, it is also preferable to develop image data into bitmap data and transfer it to this device.

[0067] When the head control unit 30 receives dot-shaped print pattern data equivalent to one line of the inkjet head, it synchronizes the print pattern data with the movement amount data of the hand-held unit 3 and sends ejection signals to the inkjet heads 4 and 5 at a predetermined timing. The head drive unit includes a drive waveform generation circuit that reads drive waveforms and voltage values ​​written in advance in a ROM near the inkjet heads 4 and 5. A roller encoder 32 and an optical position sensor 31 are used as a circuit for detecting how far the inkjet heads 4 and 5 have moved relative to the skin during printing. The roller encoder 32 is installed on a pair of rollers 8, 9 that come into contact with the treatment area where cosmetic printing is performed using ink and apply tension to the treatment area to make it virtually flat. The rollers come into contact with the treatment area and rotate as the handheld part moves, measuring the amount of movement of the handheld part 3 from the amount of rotation of the rollers. The optical position sensor 31 is a technology used in optical mice for personal computers, and can detect the amount of movement of the handheld part 3 by irradiating light onto an object, capturing the surface shape of the object, and detecting the amount of movement of the surface shape. Based on the drive command sent to the inkjet heads 4 and 5 and the optical position sensor 31 that reads the movement distance of the inkjet heads 4 and 5, the actuators of the inkjet heads 4 and 5 are driven to eject ink at predetermined positions to form a cosmetic image. When the handy inkjet printer 1 is scanned over the skin, two types of light with different maximum absorption wavelengths are emitted from the light sources 10 and 11 simultaneously or alternately, and the reflected light is detected by a light receiving unit (not shown), thereby obtaining optical information of the skin. The obtained optical information is input to the head control unit 30, which transmits image data to the CPU 20 and image processing circuit 24 via the transceiver unit 23, where image processing is performed, and the data is sent again via the transceiver unit 23 to the head control unit 30, which ejects ink A and ink B from the inkjet heads 4 and 5 based on the data. Moreover, ejection control is possible without using the CPU 20 or the image processing circuit 24. Two types of light with different maximum absorption wavelengths are exposed simultaneously or alternately from the light source units 10 and 11, and the reflected light is detected by a light receiving unit (not shown), to obtain optical information of the skin. The obtained optical information of the skin can also be sent directly to the head control unit 30, and ink A and ink B can be ejected from the inkjet heads 4 and 5 based on the data.

[0068] A camera for photographing the appearance of skin preferably comprises at least two light source units (light source unit 10, light source unit 11) and at least two light receiving units (light receiving unit 10', light receiving unit 11') (not shown) as optical sensors. Each light source unit and light receiving unit are paired, and simple detectors and detection circuits can be used. For example, an LED or semiconductor laser can be used as the light emitting member of the light source unit. The light receiving unit can be any device that receives light reflected by the skin and detects the amount of light, and for example, a photodiode or phototransistor can be used. As the light source unit 10, a blue light emitting diode having a maximum light absorption wavelength of 440 to 460 nm can be preferably used, and as the light source unit 11, a green light emitting diode having a maximum light absorption wavelength of 500 to 600 nm can be preferably used. The light source unit 10 and the light source unit 11 can be turned on independently, and skin information can be taken into the light receiving unit 10' and the light receiving unit 11'. The light source unit 10 and the light source unit 11 can be turned on alternately or simultaneously, but when turned on alternately, it is not necessary to consider the wavelength as a system of the light receiving unit, and therefore the device can be simplified.

[0069] In the present invention, the chromaticity coordinate value (a * ,b * By using at least two types of ink A and ink B having similar hues and saturations that satisfy the above conditions 1 and 2, a high-quality cosmetic image that is free of graininess and looks natural can be formed. By further providing an optical sensor, the printing process speed can be improved compared to the case where color information is typically scanned and analyzed over the entire wavelength range when detecting abnormal areas of the skin and issuing ejection commands for each ink. The optical sensor exposes the skin to two specific lights alternately or simultaneously, and measures the reflection intensity of each specific wavelength with a detector paired with an exposure source, thereby making it possible to efficiently control the ink ejection state with a small amount of information. Specifically, for example, the light source unit 10 exposes to blue light with a maximum absorption wavelength of 440 to 460 nm, and the light source unit 11 exposes to green light with a maximum absorption wavelength of 500 to 600 nm, detecting the presence of melanin with the blue light and hemoglobin with the green light. The skin surface is scanned or photographed using these exposure sources and detectors, and, for example, the a of ink A is measured. * A is ink B a * B When the a of ink B is higher than that of ink B and strong absorption is confirmed with blue light, ink A is discharged and the melanin stains can be erased by the concealing effect of ink A. * B b of ink A * AWhen the blue light exposure is higher than 1000 nm and strong absorption is obtained by the green light exposed to the skin surface following the blue light exposure, ink B is discharged to adjust local redness while exerting the concealing effect of the yellowish ink B. Such switching of light irradiation is performed according to the processing speed of the camera, and ink is instantly discharged while acquiring data of 10 to 1000 sheets per second, thereby quickly and easily improving the appearance of the skin.

[0070] The inkjet heads 4 and 5 are not particularly limited, and for example, a thermal inkjet type, a piezoelectric type, or any other type can be used. In the inkjet heads 4 and 5, a situation in which the ink ejection performance is impaired is a defective ejection due to drying of the ink in the nozzle. When the ink dries in the nozzle, the ink viscosity increases, and the responsiveness of the meniscus in the nozzle to the external force applied from the inkjet heads 4 and 5 deviates from the design value. This causes a change in the ejection condition of the ink droplets, resulting in non-ejection, ejection deflection, ink mist, etc. In particular, when the ink droplets are small, the ink droplets lose kinetic energy due to air resistance, etc. between the ejection of the ink droplets and the impact on the printed material, and become ink mist that floats in the air, and the colorant may adhere to unintended locations. In addition, since there is a risk that the user may inhale the ink mist generated during printing, it is also necessary to suppress the generation of ink mist. From this viewpoint, in the present invention, maintenance may be performed by periodically discharging a large amount of ink from the nozzles, thereby renewing the ink in the nozzles and restoring the responsiveness of the meniscus, thereby enabling stable ejection of ink and suppressing the generation of ink mist. However, in the present invention, since the amount of ink droplet per droplet ejected from the inkjet heads 4 and 5 is within the aforementioned range, an increase in pressure loss can be suppressed and non-ejection, deflected ejection, and ink mist can be suppressed. As a result, the number of times the maintenance is performed can be reduced and the amount of ink used in ejecting the maintenance can also be reduced, resulting in comfortable use without stress and reduced running costs.

[0071] <Main body static elimination device> The cosmetic handheld inkjet printer 1 according to the first embodiment includes a main body static eliminator in order to control the electric charge of the printer itself. Due to its ease of use, the cosmetic handy inkjet printer 1 is difficult to use in a wired, earthed environment, and a configuration can be adopted in which a capacitor 505 as a main body static eliminator is provided in the handheld part 3 near the inkjet heads 4 and 5 as shown in FIG. 3. An example of the capacitor 505 is a multilayer ceramic chip capacitor. By providing the capacitor 505 as a main body static eliminator in the handheld part 3, the charge generated during decorative printing can be stored in the capacitor 505, and the capacitor 505 can be used as a pseudo earth. By providing the capacitor 505 as a main body static eliminator, the charge of the cosmetic handy inkjet printer 1 can be earthed, and therefore damage to the device circuitry and generation of mist due to static electricity can be suppressed.

[0072] Furthermore, since it is difficult to use the cosmetic handheld inkjet printer 1 in an environment where it is wired and earthed, a configuration can be adopted in which an earth circuit 25 is provided as a main body electricity elimination device in the dock unit 2 separate from the handheld unit 3, as shown in Fig. 3. By providing the earth circuit 25 as a main body electricity elimination device in the dock unit 2, the charge on the handheld unit 3 can be eliminated by connecting the handheld unit 3 to the dock unit 2. By providing the earth circuit 25 as a main body electricity elimination device, the charge on the cosmetic handheld inkjet printer 1 can be earthed, thereby preventing damage to the device circuitry and generation of mist due to static electricity.

[0073] In addition, in order to improve the static elimination effect of the main static eliminator, it is preferable to further provide a static eliminator for eliminating static electricity in the handheld portion, separate from the main static eliminator. In such a static eliminator, it is preferable that a part of the handle portion (grip portion 35) of the handheld portion 3 is made of a conductive material. When a part of the grip portion 35 of the handheld portion 3 is made of a conductive material, it is preferable that the conductive material is electrically connected to the dock portion 2 and the handheld portion 3 from the viewpoint of improving the static elimination effect. Specifically, when removing the hand-held part 3 from the dock part 2 or when replacing the ink tanks 6 and 7, if the user's hands are charged with static electricity, the static electricity may cause unintended charging of the hand-held part 3 or may cause discharge and destroy the circuit boards mounted on the inkjet heads 4 and 5. Therefore, it is preferable to use a conductive material for the grip of the hand-held part 3. An example of the conductive material is a conductive resin. The surface resistance of the conductive material is 10 5 Ω / □ or more 10 11 It is preferable that the resistance is Ω / □ or less. By using a conductive material for the grip portion 35 of the handle portion 3, even if the user is charged with static electricity, the user's static electricity can be quickly grounded before use, thereby preventing damage to the device circuitry and the generation of ink mist due to static electricity. In the cosmetic handheld inkjet printer 1, the handheld unit 3 is detached from the dock unit 2, and the rollers 8 and 9 provided in front of the inkjet heads 4 and 5 are pressed against the skin to perform cosmetic printing. The rollers 8 and 9 press against the skin to keep the surface of the skin in a pseudo-flat state, thereby enabling cosmetic printing to be performed while preventing the nozzles of the inkjet heads 4 and 5 from coming into contact with the skin.

[0074] Second embodiment The second embodiment differs from the first embodiment in that it further includes a mist collection device 12, as shown in Fig. 5. The second embodiment will be described below in terms of the differences from the first embodiment. In the following description of different embodiments, the same reference numerals will be used to designate members having the same configuration.

[0075] <Mist collection device> The mist collection device 12 of the cosmetic handheld inkjet printer 1 according to the second embodiment collects ink mist that is by-produced with the ink ejection operation from the inkjet heads 4 and 5 using a tool such as a roller. Even if an inkjet head exhibits high printing performance when first used, ink mist may be generated due to poor maintenance of the device or deterioration of the actuator sensitivity over long-term use, etc. For this reason, a mist collection device 12 can be provided as a mechanism for removing ink mist. Ink mist, which is a by-product of inkjet ejection, tends to be positively charged due to the Lenard effect caused by evaporation and fragmentation of the surface layer during flight, while positive charges accumulate in the center and the surface layer, respectively. Therefore, it is preferable that the mist collection device 12 is provided with a negatively charged roller or other jig near the inkjet head. A specific example of the mist collecting device 12 is one in which at least the surface of the roller that contacts the skin and is the trailing roller in the printer scanning direction (hereinafter also referred to as the "rear roller") is made of a material that is easily negatively charged in the electrification series. Examples of materials that are easily negatively charged include polyester, silicone rubber, and polytetrafluoroethylene (PTFE). Among these, PTFE is preferable. When a roller made of these materials is prepared and rubbed against the skin that is easily positively charged, the trailing side becomes negatively charged, and the ink mist is collected and the collected mist can be transferred to the skin by the roller. In addition, in order to stably negatively charge the trailing roller and maintain the cleanliness of its surface, it is also preferable to use nylon or leather that is easily positively charged as an auxiliary roller for the trailing roller and as a cleaning roller.

[0076] In addition, it is preferable that at least one of the pair of rollers that contact the skin has a shape with multiple protrusions on the outer circumferential surface of the roller. A star wheel shape is preferable as such a shape. By making the roller have a star wheel shape, the contact area between the roller and the skin can be reduced, and the peeling of the cosmetic image caused by the ink applied to the skin adhering to the roller can be suppressed, and a predetermined cosmetic image can be formed with high quality. Furthermore, by making the roller into a star wheel shape, the tips of the convex parts on the outer circumferential surface of the roller become easily charged, and by selecting a material for the outer circumferential surface of the roller that is easily negatively charged in the triboelectric series, the mist is collected at the apexes of the convex parts on the outer circumferential surface of the roller, making it easy to collect the mist. Also, by making the roller into a star wheel shape, it becomes easy to transfer the mist collected at the apexes of the convex parts to the skin.

[0077] As a specific example, the mist collecting device 12a will be described with reference to FIG. For the sake of convenience, FIG. 6 shows a configuration having only the inkjet head 4, but in reality, an inkjet head is provided for at least ink A and ink B, and if the ink set includes inks other than ink A and ink B, inkjet heads for the other inks are further provided. First, in order to collect the generated ink mist 506 well, it is preferable to negatively charge the roller 503 as the mist collecting device 12a. The material of the roller 503 is as described above. The roller 503 is negatively charged by contacting the skin 507, which is the printing object, and rotating. In order to charge the roller 503 more reliably, it is preferable to make contact with the roller 504 wrapped with a nylon nonwoven fabric and rotate the roller 503. The negatively charged roller 503 can adsorb the generated ink mist 506 and press the adsorbed ink mist 506 against the skin 507 to fix it. In addition, since the roller 504 accumulates a positive charge, the positive charge can be transferred to the multilayer ceramic chip capacitor 505, so that the roller 503 and the roller 504 can contact and separate again to promote the generation of a negative charge in the roller 503.

[0078] In the present invention, the cosmetic handy inkjet printer according to the second embodiment is equipped with a main body static elimination device and further equipped with a mist collection device, so that even if ink mist is by-produced in association with the ink ejection operation, the ink mist can be collected by the mist collection device.

[0079] (Third embodiment) The third embodiment differs from the first embodiment in that, like the second embodiment, the third embodiment further includes a mist collection device 12. The differences between the first embodiment and the third embodiment will be described below. In the following description of different embodiments, the same reference numerals will be used to designate components having the same configuration.

[0080] <Mist collection device> A mist collection device 12 of a cosmetic handheld inkjet printer 1 according to the third embodiment collects ink mist that is by-produced with the ejection of ink from an inkjet head using a jig such as a conductive mesh. As a specific example, the mist collecting device 12b will be described with reference to FIG. The mist collection device 12b is a negatively charged conductive mesh 903 that uses a capacitor 901, such as a multilayer ceramic chip capacitor, a battery 902, etc.

[0081] When the mist collection device 12b ejects ink from the inkjet heads 4 and 5, ink droplets 905, which are main droplets at the time of ejection, pass through the gaps in the conductive mesh 903 and reach the skin 907, which is held in a pseudo-flat shape by the rollers 908 and 909. On the other hand, the positively charged ink mist 906 is attracted to the negative charges 904 of the conductive mesh 903 and is captured by the conductive mesh 903.

[0082] In the present invention, the cosmetic handy inkjet printer according to the third embodiment is equipped with a main body static elimination device and further equipped with a mist collection device, so that even if ink mist is by-produced in association with the ink ejection operation, the ink mist can be collected by the mist collection device.

[0083] (Fourth embodiment) The fourth embodiment differs from the first embodiment in that it further includes a print substrate static elimination device 5a that eliminates static electricity from the print substrate before printing, as shown in Fig. 8. The differences between the first embodiment and the fourth embodiment will be described below. In addition, in the following description of different embodiments, members having the same configuration will be given the same reference numerals.

[0084] <Printed material static eliminator> The printed object static electricity removal device 5a in the cosmetic handheld inkjet printer 1 according to the fourth embodiment includes a conductive roller 501 having electrical conductivity and a static electricity removal section 502 connected to the conductive roller 501, as shown in FIG. 8. For the sake of convenience, FIG. 8 shows a configuration having only inkjet head 4, but in reality, an inkjet head is provided for at least ink A and ink B, and if the ink set includes inks other than ink A and ink B, inkjet heads for the other inks are further provided.

[0085] Even when the cosmetic handy inkjet printer 1 according to the first embodiment is designed to minimize the amount of ink mist generated during ejection and droplets are formed normally, the ink droplets 120 are likely to be positively charged due to the above-mentioned Lenard effect, just like the ink mist. On the other hand, the skin 507 is also likely to be positively charged due to the triboelectric series, and the positive charges of the ink droplets 120 and the skin 507 repel each other, soiling the nozzle 118 and other devices, impairing the ejection properties of the ink, and may result in the by-product of ink mist. Therefore, the print substrate static elimination device 5a is provided as a device for removing the charge of the skin 507 before printing, and the conductive roller 501 having conductivity is slid on the skin 507 before printing, and the positive charge can be eliminated through the conductive roller 501. Specifically, when the conductive roller 501 comes into contact with the skin 507, the charge of the skin 507 is transferred to the conductive roller 501, and most of the charge transferred to the conductive roller 501 is quickly transferred to the static elimination unit 502 to be eliminated. In other words, the skin 507 immediately before printing can be made electrically neutral by sliding the conductive roller 501 having conductivity. Therefore, by providing the print substrate static elimination device 5a, the skin 507 is quickly eliminated, and even if the ink mist 506 is generated, it is unlikely to be repelled by the skin 507, and the ink mist 506 can land on the skin 507 like the ink droplets 120.

[0086] The material of the conductive roller 501 is not particularly limited as long as it has conductivity, and examples thereof include copper, stainless steel, and conductive resin. The static elimination unit 502 is not particularly limited as long as it has a static elimination function, and examples thereof include a capacitor and an earth circuit. Among capacitors, a multilayer ceramic chip capacitor capable of storing static electricity and dispersing the charge is preferable.

[0087] In the present invention, the cosmetic handy inkjet printer according to the fourth embodiment is equipped with a main body static elimination device and further equipped with a printed object static elimination device 5a, so that the static electricity on the skin before printing can be efficiently removed and the ink mist can be significantly reduced.

[0088] Fifth embodiment The fifth embodiment differs from the first embodiment in that it further includes a print substrate static elimination device 5b that eliminates static electricity from the print substrate before printing, as shown in Fig. 9. The fifth embodiment will be described below in terms of the differences from the first embodiment. In addition, in the following description of different embodiments, members having the same configuration will be given the same reference numerals.

[0089] <Printed material static eliminator> The print substrate static elimination device 5b in the cosmetic handheld inkjet printer 1 according to the fifth embodiment applies negatively charged water particles 606 to the print substrate, i.e., skin 607, before printing, as shown in FIG. For the sake of convenience, FIG. 9 shows a configuration having only inkjet head 4, but in reality, an inkjet head is provided for at least ink A and ink B, and if the ink set includes inks other than ink A and ink B, inkjet heads for the other inks are further provided. There are no particular limitations on the printed material de-electrification device 5b as long as it is capable of spraying negatively charged aqueous microparticles, and examples include devices that can generate negatively charged water microparticles 606 by performing corona discharge or the like on water microparticles generated by an ultrasonic atomizer or the like.

[0090] The print substrate static electricity removal device 5b first applies a voltage of -5 kV from a power source 603 to a terminal electrode 602 cooled by a Peltier element 601. Water vapor or droplets 604 in the air condense on the cooled terminal electrode 602, and are negatively charged by the terminal electrode 602 to form a cone-shaped structure called a Taylor cone, and charged water particles 606 fly from the end of the Taylor cone toward an earth electrode 605. The charged water particles 606 then pass through the gaps in the earth electrode 605 and are applied onto the skin 607, giving the skin 607 a negative charge. The applied negative charge is stored as a potential on the surface of a conductive roller 608, which attracts positively charged ink mist 609 generated from the inkjet heads 4 and 5, and causes the ink mist 609 to adhere to the conductive roller 608. The attached ink mist 609 is transferred via the conductive roller 608 to the skin 607, which is held in a quasi-flat shape by rollers 608 and 614, and the ink mist 609 is collected on the skin 607. In addition, the Peltier element 601 is in contact with a heat sink 610, as the side opposite to the cooling surface heats up, thereby cooling the Peltier element 601. When the charged water particles 606 are sprayed, the hand-held part 3 of the cosmetic handheld inkjet printer 1 is not connected to earth, so the terminal electrode 602 and the earth electrode 605 are connected to a capacitor 611 such as a multilayer ceramic chip capacitor as an alternative to earth. The charge stored in the capacitor 611 when no charged water particles are being generated is discharged by a discharge circuit including a resistor 612 and a switch 613 .

[0091] In the present invention, the cosmetic handy inkjet printer according to the fifth embodiment is equipped with a main body static elimination device and further equipped with a printed object static elimination device 5b, so that the static electricity on the skin before printing can be efficiently removed and the mist can be significantly reduced.

[0092] Sixth embodiment The sixth embodiment differs from the first embodiment in that it further includes a mist detection device 13, as shown in Fig. 10. The sixth embodiment will be described below in terms of the differences from the first embodiment. In the following description of different embodiments, the same reference numerals will be used to designate components having the same configuration.

[0093] <Mist detection device> The mist detection device 13 of the cosmetic handheld inkjet printer 1 according to the sixth embodiment detects mist that is by-produced in association with the ejection operation of the ink A and the ink B from the inkjet heads 4 and 5.

[0094] Even if an inkjet head exhibits high printing performance when first used, ink mist may be generated due to the maintenance status of the device or deterioration of the actuator sensitivity over a long period of use. By providing the mist detector 13, if the generation of ink mist cannot be sufficiently suppressed, the user is prompted to stop using the cosmetic handy inkjet printer 1 and perform appropriate maintenance, thereby preventing the user from the risk of inhaling the mist. In addition, if the ejection is stable and the generation of ink mist is sufficiently suppressed, the mist detector 13 stops unnecessary functions such as the mist collection device of the cosmetic handy inkjet printer 1, thereby reducing battery consumption and wear and tear on the device.

[0095] 11, the mist detection device 13 includes a transparent member 700, a light source unit 704, and a light receiving unit 705. The mist detection device 13 does not need to measure the particle size distribution of the generated ink mist, but only needs to detect that a laser light or the like emitted from the light source unit 704 hits a mist-adhered object and scatters the light, so that a simple detector and detection circuit can be used.

[0096] The transparent member 700 is a right-angled prism having a mist adhesion surface 701, a first inclined surface 702, and a second inclined surface 703. The side surface of the transparent member 700 is defined by the mist adhesion surface 701, the first inclined surface 702, and the second inclined surface 703, and has the shape of a right-angled isosceles triangle. The first inclined surface 702 has an inclination of 45 degrees with respect to the mist attachment surface 701. The first inclined surface 702 is a light-transmitting surface through which incident light 706 emitted from the light source unit 704 toward the transparent member 700 enters the transparent member 700. The second inclined surface 703 has an inclination of 45 degrees with respect to the mist adhering surface 701. The angle between the first inclined surface 702 and the second inclined surface 703 is 90 degrees. The second inclined surface 703 is a surface having optical transparency through which reflected light 707 that enters the transparent member 700 from the first inclined surface 702 and is totally reflected by the mist adhering surface 701 exits from the transparent member 700. The light source section 704 can use, as a light emitting member, for example, an LED or a semiconductor laser. The light receiving section 705 is a device that receives reflected light 707 that is totally reflected by the mist adhering surface 701 of the transparent member 700 and detects the amount of light, and for example, a photodiode or a phototransistor can be used.

[0097] From the viewpoint that ink mist is easily positively charged, the transparent member 700 is preferably made of a material that is easily positively charged in the triboelectric series. This is because, if a resin that is easily negatively charged is used, the mist collection device will take away ink mist that it would have been able to collect, resulting in excessive detection of ink mist. On the other hand, if a material that is easily positively charged is used, it is possible to suppress the adsorption of positively charged ink mist, and the ink mist can be detected appropriately. Examples of transparent materials that are easily positively charged include glass and quartz. When glass or quartz is used as the transparent member 700, even if the glass or quartz is dirty, automatic calibration is performed in the dirty state, and the tendency for the dirty state to become even dirtier is detected, and the generation of ink mist can be detected. This is achieved by detecting and comparing the amount of light at the start of use and the amount of light during use. This makes it possible to deal with the deterioration of the performance of the light source and battery due to the deterioration of the device over time, and effectively extend the lifespan.

[0098] A case where ink mist 810 adheres to the mist detection device 13 will be described with reference to Fig. 12. The transparent member 800 is a right-angled prism having a mist adhering surface 801, a first inclined surface 802, and a second inclined surface 803. First, in the mist detection device 13, a transparent member 800 is placed in the atmosphere near the nozzle of an inkjet head where ink mist may float. Light is irradiated from a light source unit 804 to a mist-adhering surface 801 from a first inclined surface 802 of the transparent member 800. When ink mist 810 is not attached to the mist-adhering surface 801, incident light 806 is reflected at the interface between the transparent member 800 and air, and becomes reflected light 807, which enters a light receiving unit 805. On the other hand, when mist is attached to the mist-adhering surface 801, the incident light 806 is scattered by the attached ink mist 810, and the amount of light detected by the light receiving unit 805 changes from before the ink mist was attached. This change in the measured value makes it possible to detect the ink mist. Specifically, when the transparent member of the mist detection device 13 is quartz, and mist 810 containing an inorganic pigment such as titanium oxide adheres to the mist adhesion surface 801, the quartz and titanium oxide form an optically continuous layer, and the interface with the air is not quartz but titanium oxide particles contained in the ink mist 810. In this case, not all of the incident light 806 is totally reflected at the interface between the quartz and the air, but is refracted, scattered, and reflected at the interface between the titanium oxide and the air, but since titanium oxide is not a uniform crystal, most of the light becomes scattered light 808, 809. As a result, the intensity of the reflected light 807 incident on the light receiving unit 805 decreases. This allows the adhesion of the ink mist 810 to be detected.

[0099] It is preferable that the mist detection device 13 further includes a light scattering type particle detector (not shown) that uses laser light as a light source. By including a particle detector, it is possible to detect particles such as inorganic pigments contained in the ink mist that adheres to the mist adhesion surface, and it is possible to accurately manage the generation status of the ink mist. Moreover, it is preferable that the mist detection device 13 further includes an optical filter (not shown) that blocks directly reflected light and transmits only scattered light. By including an optical filter, the light receiving sensitivity of the light receiving section can be increased, making it easier to manage the generation of mist.

[0100] (Other embodiments) In the above description, the first to sixth embodiments have been shown as the cosmetic handheld inkjet printer 1, but the first embodiment may be appropriately combined with the second to sixth embodiments. In other words, the embodiments shown in the above description may be appropriately combined, or all of them may be combined. EXAMPLES

[0101] The physical properties of the polymer used in the ink, the ink, etc. were measured by the following methods.

[0102] [Number average molecular weight of poly(N-propionylethyleneimine)] Measurements were performed using 1 mmol / L Farmin DM20 (trade name, manufactured by Kao Corporation) / chloroform as an eluent, gel permeation chromatography (measurement column: two Showa Denko K-804L columns connected in series, flow rate: 1 mL / min, column temperature: 40°C, detector: differential refractometer) and polystyrene of known molecular weight as a standard substance. 100 μL of the measurement sample was used at a concentration of 5 mg / mL.

[0103] [Solid content concentration] Using an infrared moisture meter "FD-230" (Kett Electric Laboratory Co., Ltd.), 5 g of the measurement sample was dried under conditions of a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 minutes / fluctuation range 0.05%), and the moisture content (mass%) of the measurement sample was measured and the solid content concentration was calculated using the following formula. Solid content (mass%) = 100 - moisture content of measurement sample (mass%)

[0104] [Static surface tension of ink] A platinum plate was immersed in a cylindrical polyethylene container (diameter 3.6 cm × depth 1.2 cm) containing 5 g of sample adjusted to 20°C, and the static surface tension at 20°C was measured by the Wilhelmy method using a surface tensiometer (manufactured by Kyowa Interface Science Co., Ltd., "CBVP-Z").

[0105] [Ink viscosity] The viscosity was measured at 20° C. using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34'×R24, rotation speed 50 rpm).

[0106] [Ink coordinate value (L * , a * , b * )] In an environment of 25±1°C temperature and 50±5% relative humidity, an inkjet printer (FUJIFILM Corporation, model number: DMP-2850) was equipped with a head cartridge for discharging 10 pL droplets, the dot distance was set to 35 μm, and solid printing was performed on a PET film (Toray Industries, Inc., product number: Lumirror T60, film thickness 50 μm) with a print duty of 100% in a printing area of ​​4 cm length x 4 cm width. The printed surface was then dried with hot air using a dryer to obtain a printout. The measurement device used was a spectrophotometer / densitometer (manufactured by X-Rite Inc., product name: Spectro Eye). The measurement conditions were: light source D65, observation field of view 2 degrees, density standard DIN, white base "Abs", built-in filter "No", and CIE L was measured at 10 random points on the printed surface of the obtained print. * a * b * Color space coordinates (L * , a * , b * ) was measured and the average value was calculated.

[0107] Synthesis Example 1 (Synthesis of Cationic Silicone Polymer 1) 73.7 g (0.74 mol) of 2-ethyl-2-oxazoline was mixed with 156.0 g of ethyl acetate, and the resulting mixture was dehydrated with 12.0 g of molecular sieve "Zeorum A-4" (manufactured by Tosoh Corporation) at 28°C for 15 hours. 2.16 g (0.014 mol) of diethyl sulfate was added to the resulting ethyl acetate solution of dehydrated 2-ethyl-2-oxazoline, and the mixture was heated under reflux at 80°C for 8 hours under a nitrogen atmosphere to obtain a terminal-reactive poly(N-propionylethyleneimine) (number average molecular weight is 6,000) solution. Separately, 70.0 g of side-chain primary aminopropyl-modified polydimethylsiloxane "KF-864" (Shin-Etsu Chemical Co., Ltd., weight average molecular weight 50,000 (catalog value), amine equivalent 3,800) was mixed with 140.0 g of ethyl acetate, and the mixture was dehydrated with 15.0 g of molecular sieves at 28°C for 15 hours. Next, the above-obtained reactive terminal poly(N-propionylethyleneimine) solution was added to the above-obtained dehydrated side chain primary aminopropyl modified polydimethylsiloxane solution all at once, and heated to reflux at 80° C. for 10 hours. The reaction mixture was concentrated under reduced pressure to obtain a poly(N-propionylethyleneimine) / dimethylpolysiloxane copolymer (hereinafter referred to as "cationic silicone polymer 1") as a white rubber-like solid (135 g). The mass ratio [content of organopolysiloxane segment (x) / [total content of organopolysiloxane segment (x) and poly(N-acylalkyleneimine) segment (y)]] was 0.50, and the weight average molecular weight of cationic silicone polymer 1 was 100,000 (calculated value). Primary ethanol was added to the obtained cationic silicone polymer 1 to obtain a solution of cationic silicone polymer 1 (solid concentration 40% by mass).

[0108] Production Example 1 (Production of Ink I-1) [Step I: Preparation of colorant dispersion] In a sealed and temperature-controllable glass jacket, 46.6 g of the solution of cationic silicone polymer 1 obtained in Synthesis Example 1 (solid concentration 40% by mass) was added, and the colorant shown in Table 1 was added while stirring at 1,400 rpm at a jacket temperature of 15 ° C. using a high-speed disperser "TK Robomix" (manufactured by Primix Corporation) (stirring part: Homo Disper 2.5 type (blade diameter 40 mm)) at a jacket temperature of 15 ° C., and further stirred at 2,000 rpm at a jacket temperature of 15 ° C. for 1 hour to blend the colorant into the solution of cationic silicone polymer 1. Next, 139.7 g of anionic acrylic polymer solution "Plussize L-9909U" (manufactured by GOO Chemical Industry Co., Ltd., acid value 50 mg KOH / g, 100% neutralization, neutralizing agent 2-amino-2-methyl-1-propanol, ethanol solution with a solid concentration of 40% by mass) was added, and stirred at a jacket temperature of 15 ° C. for 1 hour at 2,000 rpm. Next, while maintaining the jacket temperature at 15°C, the rotation speed was changed to 8,000 rpm, and 409.8 g of primary isopropanol and 260.8 g of ion-exchanged water were added and stirred for 3 hours to obtain a colorant mixture (ethanol concentration in the medium: 66.7% by mass, solids concentration: 25% by mass). The obtained colorant mixture was subjected to 20-pass dispersion treatment at a pressure of 180 MPa using a Microfluidizer (Microfluidics, model: M-140K), and then 695.3 g of ion-exchanged water was added to obtain each colorant dispersion with a solid content concentration of 15% by mass. [Step II: Removal of organic solvent] Each of the obtained colorant dispersions was kept at a pressure of 10 kPa for 2 hours in a warm bath adjusted to 40°C using a vacuum distillation apparatus (rotary evaporator, N-1000S type, manufactured by Tokyo Rikakikai Co., Ltd.) to remove the organic solvent. Furthermore, the warm bath was adjusted to 62°C, the pressure was reduced to 7 kPa, and the mixture was kept for 4 hours to remove the organic solvent and a part of the water so that the total concentration (solid content concentration) of the colorant and polymer was 20 to 22%. Next, the total concentration (solid content concentration) of the colorant and polymer was measured, and the total concentration of the colorant and polymer was adjusted to 20 mass% with ion-exchanged water. The mixture was then filtered successively using 5 μm and 1.2 μm membrane filters "Minisart" (manufactured by Sartorius) to obtain a colorant water dispersion D-1.

[0109] [Ink production] Colorant water dispersion D-1, 1,2-hexanediol, 1,2-propanediol, modified glycerin "Liponic EG-1" (manufactured by Vantage Specialty Ingredients, 26 moles of ethylene oxide adduct of glycerin) (hereinafter referred to as "Liponic EG-1"), and ion-exchanged water were added and mixed in the formulation shown in Table 1, and the resulting mixture was filtered through a 0.45 μm membrane filter "Minisart" (manufactured by Sartorius) to obtain water-based ink I-1. The static surface tension and viscosity at 20° C. of the resulting water-based ink are shown in Table 1.

[0110] Production Examples 2 to 27 and C-1 to C-2 (Production of Inks I-2 to I-27 and IC-1 to IC-2) Water-based inks I-2 to I-27 and IC-1 to IC-2 were obtained in the same manner as in Production Example 1, except that the types and blending compositions were changed to those shown in Tables 1 and 2. The static surface tension and viscosity at 20°C of each of the obtained water-based inks are shown in Tables 1 and 2.

[0111] Details of the colorants used are given below. *1: Silicone-coated titanium oxide white pigment "SI-Titanium CR-50 LHC" (manufactured by Miyoshi Kasei Co., Ltd.) *2: Silicone-coated yellow iron oxide pigment "SI-Yellow LL-100P LHC" (manufactured by Miyoshi Kasei Co., Ltd.) *3: Silicone-coated red iron oxide pigment "SI-Red R-516PS LHC" (manufactured by Miyoshi Kasei Co., Ltd.) *4: Silicone-coated black iron oxide pigment "SI-Black BL-100P LHC" (Miyoshi Kasei Co., Ltd.)

[0112] [Table 1]

[0113] [Table 2]

[0114] Examples 1 to 26 and Comparative Examples 1 to 3 (Printing using ink sets) Using the ink set (Ink A and Ink B) described in Table 3 and a cosmetic handy inkjet printer equipped with an inkjet head that ejects 1,000 pL of droplets, printing was performed by ejecting ink droplets of Ink A and Ink B onto an area of ​​4 cm x 4 cm on the skin of the cheek of the face. The printing conditions were as follows: ink dots were arranged in application area a of ink A and in application area b of ink B to form a square grid-shaped printing pattern as shown in Figure 1; printing was performed so that the application ratio (volume basis) of ink A and ink B onto the skin was ink A:ink B = 50%:50%, forming a cosmetic image. The cosmetic handheld inkjet printer used was equipped with a dock section and a handheld section that was separated from the dock section for applying the cosmetic printing, and was equipped with a multilayer ceramic chip capacitor (main static elimination device) in the handheld section that can release static electricity, and was further equipped with a mist collection device and a static elimination device for the printed material, as described below. The multilayer ceramic chip capacitor used was a multilayer ceramic chip capacitor manufactured by TDK Corporation (catalog number: CGA3EAC0G2A103J080AC). The multilayer ceramic chip capacitors used in the mist collecting device and printed material static electricity removing device described below were similarly manufactured by TDK Corporation.

[0115] (Mist collection device) [Rear roller] A PTFE star wheel, which is easily negatively charged, was used as the roller 503 on the rear side in the printer scanning direction of the mist collecting device 12a shown in FIG. 6, and the roller 503 was negatively charged. The PTFE star wheel was made by covering a metal star wheel with a diameter of 1.2 mm and a length of 25.4 mm with a PTFE heat shrink tube (product number: TKF-100-2) manufactured by Chukoh Chemical Industries, Ltd. and heating and shrinking it in an electric furnace heated to 330°C, using the metal star wheel as a core. A nylon brush roller manufactured by Kyoshin Giken Co., Ltd. was used as roller 504 of mist collection device 12a shown in Fig. 6. After rubbing with charged roller 503, roller 504 removes the positive charge on the surface with a metal wire, and the removed positive charge is stored in capacitor 505 through a copper wire. Although not shown, the charge stored in capacitor 505 is grounded via a ground circuit when the handheld part is connected to the dock part.

[0116] [Conductive mesh] A metal mesh serving as the conductive mesh 903 of the mist recovery device 12b shown in FIG. 7 was given a negative charge to adsorb the positively charged ink mist. The metal mesh was a stainless steel metal mesh No. 100 (wire diameter 0.1 mm, mesh size 0.154 mm, void ratio 36.5%). The metal mesh was placed in front of the inkjet head nozzle so that the ink, which is the main droplet, ejected from the inkjet head nozzle passed through the mesh openings.

[0117] (Static charge eliminator for printed matter) The printed object static elimination device 5a shown in FIG. 8 is equipped with a conductive roller 501 made of a conductive material and a static elimination unit 502 which is a multilayer ceramic chip capacitor, and incorporates a mechanism for transferring the charge on the surface of the skin 507, which is the printed object, to the static elimination unit 502 via the conductive roller 501. As shown in FIG. 9, a printed object static elimination device 5b consisting of a Peltier element 601, a terminal electrode 602, an earth electrode 605, and a heat sink 610 was formed by using a charged water microparticle generating unit that was a nanoe unit taken out of a humidified air purifier "F-UXS90" manufactured by Panasonic Corporation, and charged water microparticles were generated.

[0118] <Evaluation> (Discharge stability) During the five-minute usage time of the cosmetic handheld inkjet printer, a nozzle check pattern was printed every minute, and the number of nozzles that were able to eject ink normally out of a total of 120 nozzles in the head was counted, and the ratio of the number of nozzles that were able to eject ink normally to the total number of nozzles was measured. Since a high-quality cosmetic image can be obtained if the percentage of nozzles that can eject ink normally is 90% or more, if the percentage of nozzles that can eject ink normally for either ink A or ink B is less than 90%, a maintenance operation was performed. Table 3 shows the number of maintenances performed during a 5-minute usage period. In Table 3, "5 times" indicates that maintenance was required every minute, and "0 times" indicates that no maintenance was required during the 5-minute usage period. If maintenance is required 5 times, it is highly likely that ejection cannot be stabilized for 1 minute continuously, and even if the nozzle defect can be repaired through maintenance, a good cosmetic image cannot be guaranteed.

[0119] (Graininess and natural appearance) The graininess and natural appearance of the cosmetic images applied in the Examples and Comparative Examples were visually observed from the distances listed in Table 3, and five evaluators evaluated the results using a maximum of 5 points according to the following evaluation criteria. The combined scores obtained are shown in Table 3. The higher this combined score is, the less noticeable the graininess of the ink dots in the cosmetic image is, and the more natural the appearance is. The visual observation by the evaluators was performed by observing the makeup images from a specific distance away from the practitioner. Specifically, the spatial distance between close friends such as family members or partners facing each other is about 50 cm, although this varies to some extent depending on culture and social status, and the spatial distance between strangers conversing with each other is about 100 cm. Therefore, the evaluators performed visual observation and evaluation from a position 50 cm away from the practitioner and a position 100 cm away from the practitioner.

[0120] [Evaluation criteria for graininess] 5: No graininess is noticeable even when looking closely. 4: There is almost no graininess even when you look closely. 3: Although a slight graininess can be seen when looking closely, it is barely noticeable and the graininess is barely noticeable at first glance. 2: When one stares at the image, one immediately senses graininess, and the graininess becomes bothersome thereafter, causing problems in terms of practical use. 1: At first glance, the texture is grainy and resembles a skin disorder or rough skin, which is problematic for practical use.

[0121] [Evaluation criteria for natural appearance] 5: It looks so natural that even when you stare at it, you won't notice that it has been printed. 4: It looks so natural that at first glance you would not guess it was printed. 3: If you look closely, you can see that cosmetic printing has been done, but the areas that have been done are hardly noticeable, and it gives the impression of very light makeup, so there are no problems with the appearance. 2: Upon close inspection, it is clear that cosmetic printing has been applied, giving the impression of being a little too heavily made up, and the appearance is somewhat questionable. 1: It is immediately obvious that cosmetic printing has been done, and it does not look natural.

[0122] [Table 3]

[0123] From Table 3, it can be seen that the ink sets of Examples 1 to 26 have good ejection stability, and compared to Comparative Examples 1 to 3, the graininess is suppressed, and cosmetic images with a good natural appearance can be formed.

[0124] Examples 27 to 31, Comparative Example 4 Using the ink set (Ink A and Ink B) listed in Table 4, a cosmetic handy inkjet printer having the same configuration as that used in Example 1, except that the inkjet head was changed to a thermal inkjet head in which the ink flow path was designed so that the amount of ink droplets ejected by the Micro Electro Mechanical System (MEMS) process was 40 pL to 5,000 pL, was used to eject ink droplets of Ink A and Ink B onto an area of ​​4 cm x 4 cm on the skin on the cheek of the face. The printing conditions were as follows: ink dots were arranged in application area a of ink A and in application area b of ink B to form a triangular lattice-shaped printing pattern as shown in Figure 2; printing was performed so that the application ratio (volume basis) of ink A and ink B onto the skin was ink A:ink B = 50%:50%, forming a cosmetic image. The ejection stability and the absence of graininess were evaluated in the same manner as above, and the results are shown in Table 4. Visual observations by the evaluators were also performed at positions 80cm and 150cm away from the therapist, in addition to the positions 50cm and 100cm away from the therapist mentioned above. This is because the spatial distance at which a business-like conversation can take place is about 80cm, while the spatial distance at which people simply pass each other without conversation is about 150cm.

[0125] [Table 4]

[0126] From Table 4, it can be seen that the ink sets of Examples 27 to 31 are capable of forming decorative images with suppressed graininess, and are superior to Comparative Example 4 in ejection stability.

[0127] Examples 32 to 33 Using the ink set (ink A and ink B) listed in Table 5, a cosmetic handy inkjet printer having the same configuration as that used in Example 1 was used, except that the inkjet head was changed to a thermal inkjet head in which the ink flow path was designed so that the amount of ink droplets ejected by the MEMS process was 1,000 pL. The printing conditions were such that ink dots were arranged in application area a of ink A and application area b of ink B so as to form a triangular lattice printing pattern as shown in Figure 2, and the application ratio (volume basis) of ink A and ink B on the skin for each part of the face was changed as shown in Table 5, and printing was performed over the entire face so that the printing for each part of the face did not overlap with each other, thereby forming a cosmetic image. The absence of graininess and the naturalness of the appearance were evaluated in the same manner as above, and the results are shown in Table 5. Visual observations by the evaluators were also performed at positions 80 cm and 150 cm away from the therapist, in addition to the positions 50 cm and 100 cm away from the therapist mentioned above.

[0128] [Table 5]

[0129] From Table 5, it can be seen that the ink sets of Examples 32 and 33 make it easy to adjust the color for each area to which makeup is applied, and can form a cosmetic image that is free of graininess overall, regardless of the area to which makeup is applied. [Industrial Applicability]

[0130] According to the ink set of the present invention, it is easy to adjust the color for each area to which makeup is applied, and in printing in which the ink is ejected as droplets, it is possible to obtain a high-quality cosmetic image that is free of graininess and has a natural appearance, and therefore the ink set can be suitably used as a cosmetic ink set. [Explanation of symbols]

[0131] 1: Handy Cosmetic Inkjet Printer 2: Dock section 3:Handheld part 4,5: Inkjet head 6,7: Ink tank 8,9: Roller 10,11:Light source part 12: Mist collection device 13: Mist detector 20: CPU 21: Charging device section 22: Maintenance Equipment Department 23: Transmitter / receiver 24: Image processing circuit 25: Earth circuit (main body static elimination device) 26: Dock side electric terminal 27: Earth 30: Head control unit 31: Optical sensor 32: Roller encoder 33: Handheld electric terminal 35: Grip 505: Capacitor (main body static elimination device)

Claims

1. A cosmetic ink set for use in printing in which ink droplets are ejected at 100 pL or more and 5,000 pL or less, At least two inks, ink A and ink B, Both the ink A and the ink B contain an achromatic pigment and a chromatic pigment, a content mass ratio of the achromatic pigment to the chromatic pigment contained in each of the inks A and B [achromatic pigment / chromatic pigment] is 2 or more and 10 or less, The CIE L of the printed surface when the ink A and the ink B are solid-printed on a polyester film at a printing duty of 100% * a * b * Coordinate value of ink A in color space (L * A , a * A , b * A ) and the coordinate value of ink B (L * B , a * B , b * B ) A cosmetic ink set that satisfies all of the following conditions 1 to 3. Condition 1: Coordinate value a * A and coordinate value a * B are all greater than or equal to 5 and less than or equal to 35, and the coordinate value b * A and coordinate value b * B are all between 10 and 40. Condition 2: hue angle h represented by the following formula (II-1) A and the hue angle h represented by the following formula (II-2): B In all cases, the angle is between 40 degrees and 70 degrees. h A =tan -1 (b) * A / / ] * A ) (II-1) h B =tan -1 (b) * B / / ] * B ) (II-2) Condition 3: The saturation difference ΔC represented by the following formula (III) is 2 or more and 20 or less. ΔS((E). * A 10 * B ) 2 D(N * A 10 * B ) 2 ) 0.5 (III)

2. The cosmetic ink set according to claim 1 , further satisfying the following condition 4: Condition 4: The color difference ΔE represented by the following formula (IV) is 2 or more and 40 or less. ΔE=((: * A -, * B ) ) 2 +(a * A -a * B ) ) 2 +(b * A b * B ) ) 2 ) ) 0.5 (IV)

3. Both ink A and ink B contain an inorganic pigment, and the density of the inorganic pigment is 3 g / cm 3 The cosmetic ink set according to claim 1 or 2.

4. The cosmetic ink set according to any one of claims 1 to 3, wherein the printing is printing onto skin.

5. A printing method comprising a step of ejecting at least the ink A and the ink B contained in the cosmetic ink set according to any one of claims 1 to 4 as ink droplets from a plurality of ejection holes.

6. The printing method according to claim 5 , further comprising applying ink droplets of the ink A and the ink B onto the skin.

7. The cosmetic ink set according to any one of claims 1 to 4 includes an inkjet head that ejects at least the ink A and the ink B, and a main body static elimination device that eliminates static electricity, The main body static elimination device of the cosmetic handheld inkjet printer is a capacitor or an earth circuit.

8. 8. The cosmetic handheld inkjet printer according to claim 7, further comprising a mist recovery device that recovers ink mist generated as a by-product in association with the ejection of the ink A and the ink B from the inkjet head.

9. The cosmetic handheld inkjet printer according to claim 8, wherein the mist collecting device is a negatively charged roller.

10. The cosmetic handheld inkjet printer according to claim 9, wherein the roller has a star wheel shape.

11. The cosmetic handheld inkjet printer according to claim 8, wherein the mist collecting device is a negatively charged conductive mesh.

12. The cosmetic handheld inkjet printer according to any one of claims 7 to 11, further comprising a print substrate static eliminator for eliminating static electricity from the print substrate before printing.

13. The cosmetic handheld inkjet printer according to claim 12, wherein the print substrate static elimination device comprises a conductive roller having electrical conductivity, and a static elimination unit connected to the conductive roller.

14. The cosmetic handheld inkjet printer according to claim 12, wherein the print substrate static elimination device applies negatively charged water particles to the print substrate before printing.

15. 15. The cosmetic handy inkjet printer according to claim 7, further comprising a mist detection device that detects ink mist generated as a by-product in association with the ejection of the ink A and the ink B from the inkjet head.

16. The cosmetic handy inkjet printer according to any one of claims 7 to 15, comprising a dock section and a handheld section that is separated from the dock section and that applies cosmetic printing.

17. The cosmetic handheld inkjet printer according to claim 16, further comprising a static eliminator in the handheld portion for eliminating static electricity, separate from the static eliminator in the main body.

Images