JP6883748B2 - Inkjet printing ink - Google Patents

Description

The present disclosure relates to an ink jet printing ink having excellent ejection stability and safety for a living body.

Inkjet printers have become remarkably widespread due to their advantages such as low noise and low running cost, and color printers capable of printing on plain paper are also being actively offered on the market. However, in an inkjet printer, it is very difficult to satisfy all the required characteristics such as image color reproducibility, image dryness, character bleeding, color boundary bleeding, and ejection stability. Therefore, the type of ink to be applied is selected based on the application and the preferred characteristics.

For example, water-based ink containing water as a main component, which contains a colorant such as a dye or a pigment and a wetting agent such as glycerin, is generally known. However, such a water-based ink may have insufficient image fixability depending on the type of the object to be printed.

In recent years, inks containing an organic solvent and having high drying properties have also been provided. However, inks containing organic solvents may be inferior in terms of safety to living organisms and the environment. Therefore, such inks have not been practical for applications where biosafety is required.

On the other hand, in order to expand the types of printable objects to be printed, inks containing a UV curable resin that is cured by UV irradiation or the like are also provided. However, in an ink containing such a reactive compound, an unreacted compound may remain, and such an unreacted compound may also affect a living body or the like. Therefore, UV curable inks have also been impractical for applications that require biosafety.

Here, edible ink has been proposed as an ink having high biosafety. For example, edible screen printing inks containing water, alcohol, surfactants, edible insoluble inorganic fine powder having hiding power, thickeners, resins, edible polymer substances and the like have been proposed (for example, Patent Documents). 1). Further, a card-type cosmetic or the like in which a turbid liquid in which a powdery agent for cosmetics and an oil compound are dispersed in a water-soluble binder is poured by screen printing has also been proposed (for example, Patent Document 2). However, these inks and suspensions have compositions suitable for screen printing methods, and it has been difficult to immediately apply them to inks for inkjet printing. On the other hand, as an edible ink that can be printed by inkjet, an ink containing an edible dye has also been reported (Patent Document 3).

Japanese Unexamined Patent Publication No. 63-63363 Japanese Unexamined Patent Publication No. 3-157313 Japanese Unexamined Patent Publication No. 9-302294

However, with edible inks as described in Patent Document 3, there are problems such as deterioration of the coloring material due to light and oxygen is likely to occur, and the durability of the obtained image is low, so that biosafety and durability are present. In the actual situation, ink jet printing ink having both properties and ejection stability has not been obtained.

The present disclosure has been made in view of such issues. That is, the present disclosure provides an ink jet printing ink having high biosafety, stable ejection from an inkjet printer, and high durability of the obtained image.

As a result of diligent studies by the present inventors, in an inkjet printing ink containing pigments, acrylic particles, alcohol, and water, the alcohol content is set to a certain amount or less, and the alcohol contains at least trivalent alcohol. We have found that stable ejection is possible from an inkjet printer. At this time, it was also found that the fixability of the obtained image is improved by setting the amount of the acrylic particles with respect to the pigment within a certain range. It has also been found that an ink containing mainly pigments, acrylic particles, alcohol, and water can be used as an ink having both high durability and biosafety, and the present application has been made.

[1] An inkjet printing ink containing a pigment, acrylic particles, alcohol, and water. The alcohol contains a trivalent alcohol, and the content of the alcohol with respect to the total mass of the inkjet printing ink. Is 30% by mass or less, the content of the acrylic particles is 0.5 to 10 parts by mass with respect to 10 parts by mass of the pigment, and the skin irritation is negative.

[2] The ink for inkjet printing according to [1], wherein the trihydric alcohol is glycerin.
[3] The ink for inkjet printing according to [1] or [2], wherein the alcohol further contains a divalent alcohol.

The ink for inkjet printing of the present disclosure has high biosafety, can be stably ejected from an inkjet printer, and has high durability and fixability of the obtained image. Therefore, it is possible to form a high-definition image on various printed materials such as plain paper, special recording paper, plastic, and cloth.

FIG. 1A is a photograph showing an ink adhesion state after the tissue is pressed against the ink printing surface after the fixability test of Comparative Example 3-1. FIG. 1B is a photograph showing the ink adhesion state after the water resistance test of Comparative Example 3-1. It is a photograph which shows the state of sticking of ink after pressing a tissue against a printing surface. FIG. 2A is a photograph showing an ink adhesion state after the tissue is pressed against the ink printing surface after the fixability test of Comparative Example 3-2, and FIG. 2B is a photograph showing the ink adhesion state after the water resistance test of Comparative Example 3-2. It is a photograph which shows the state of sticking of ink after pressing a tissue against a printing surface. FIG. 3A is a photograph showing an ink adhesion state after the tissue is pressed against the ink printing surface after the fixability test of Comparative Example 3-3, and FIG. 3B is a photograph showing the ink adhesion state after the water resistance test of Comparative Example 3-3. It is a photograph which shows the state of sticking of ink after pressing a tissue against a printing surface. FIG. 4A is a photograph showing an ink adhesion state after the tissue is pressed against the ink printing surface after the fixability test of Example 3-1. FIG. 4B is a photograph showing the ink adhesion state after the water resistance test of Example 3-1. It is a photograph which shows the state of sticking of ink after pressing a tissue against a printing surface.

The inkjet printing inks of the present disclosure include at least pigments, acrylic particles, alcohol, and water. The ink for inkjet printing may contain other components, if necessary.

The inkjet printing inks of the present disclosure are negative for skin irritation. That is, since it has high biosafety, it can be applied to various uses, for example, it can be applied to a printed matter used in contact with skin or the like. Here, in the present disclosure, "negative skin irritation" means that the cell survival rate is more than 50% when the test is performed using a three-dimensional skin model which is an alternative method of the skin irritation test. Say something. In the alternative method of the skin irritation test, a 5% sodium dodecyl sulfate (SDS) solution is used as an irritant control, and phosphate buffered saline (PBS) is used as a negative control. In addition, after exposing the ink to a three-dimensional skin model for 18 hours, the cell viability is evaluated by the MTT test.

In the present disclosure, as an example of a method for making the skin irritation of an inkjet printing ink negative, all the components contained in the inkjet printing ink are designated as the components listed in the ingredient display name list of cosmetics based on the Pharmaceutical Affairs Law. The method can be mentioned.

Here, the ink jet printing ink of the present disclosure contains at least a trihydric alcohol. In general, if the dryness of the ink is excessively high, clogging or the like is likely to occur in the inkjet head of the inkjet printer. On the other hand, when a trihydric alcohol is contained like the inkjet printing ink of the present disclosure, the dryness of the inkjet printing ink is appropriately adjusted, and the ink is stable from the inkjet printer without causing clogging or the like. Can be discharged.

Further, in the ink for inkjet printing, the content of acrylic particles is within a certain range with respect to the content of pigment. Therefore, in the image obtained from the ink for inkjet printing, the acrylic particles function as a binder for binding the pigment and the object to be printed, the fixability of the image becomes very high, and the water resistance of the obtained image also increases. Further, in the inkjet printing ink of the present disclosure, since the component for coloring the ink is a pigment, the image is less likely to be deteriorated by light or oxygen, and the durability of the image is improved.

Hereinafter, each component contained in such an inkjet printing ink will be described.

(Pigment)
The pigment contained in the inkjet printing ink of the present disclosure is not particularly limited, but is selected from the ingredients listed in the ingredient display name list of cosmetics based on the Pharmaceutical Affairs Law as described above from the viewpoint of skin irritation. It is preferable to have. The pigment may be either a known inorganic pigment or an organic pigment. The pigment is appropriately selected according to the color and appearance required for the color of the printed matter. The pigments include, for example, not only colored pigments for coloring ink for inkjet printing, but also pearl pigments for imparting gloss to images. The ink for inkjet printing may contain only one type of pigment, or may contain two or more types of pigments.

The pigment can be a known pigment applicable to cosmetics and the like, and specific examples thereof include inorganic red pigments of iron oxide, iron hydroxide and iron titanate; and inorganic brown pigments such as γ-iron oxide. Inorganic yellow pigments such as yellow iron oxide and ocher; Inorganic black pigments such as black iron oxide and carbon black; Inorganic white pigments such as titanium oxide; Inorganic purple pigments such as manganese violet and cobalt violet; , Inorganic green pigments such as cobalt oxide and cobalt titanate; Inorganic blue pigments such as navy blue (ferrous ferrocyanide) and ultramarine; raked various tar pigments; raked various natural pigments; And synthetic resin powder obtained by combining these powders and the like are included.

Examples of pearl pigments include titanium oxide-coated mica, titanium oxide-coated mica, bismuth oxychloride, titanium oxide-coated bismuth oxychloride, titanium oxide-coated talc, fish scale foil, titanium oxide-coated colored mica, and the like.

The shape of these pigments is not particularly limited and may be any shape such as spherical or needle-shaped, but the median value of the integrated value of the particle size distribution measured by the laser diffraction method of the pigment (median diameter (D50)). Is preferably 0.001 to 0.6 μm, more preferably 0.01 to 0.3 μm. When the median diameter (D50) of the particle size distribution of the pigment is in the above range, stable ejection can be performed from the head of the inkjet printer.

The amount of the pigment contained in the inkjet printing ink is 40% by mass or less, more preferably 3 to 10% by mass, based on the total mass of the inkjet printing ink. When the amount of the pigment is 3% by mass or more, the printed matter is sufficiently colored and the printed matter is likely to be glossed. Further, if the amount of the pigment is excessive, the head of the inkjet printer is likely to be clogged, or the pigment may be aggregated when the ink for inkjet printing is stored. However, if the amount is 40% by mass or less, the pigment may aggregate. Aggregation of pigments is unlikely to occur, and stable ejection from an inkjet printer is possible.

(Acrylic particles)
The acrylic particles function as a binder that binds the pigment to the printed material. The acrylic particles are not particularly limited as long as they are made of an acrylic resin that is not irritating to the skin and can be stably and uniformly dispersed in water or alcohol. Such acrylic particles are preferably selected from the ingredients listed in the ingredient display name list of cosmetics based on the Pharmaceutical Affairs Law, and may be particles of known acrylic resins applied to cosmetics and the like. it can.

Examples of acrylic particles include homopolymers of acrylic monomers, copolymers of two or more kinds of acrylic monomers, copolymers of acrylic monomers and other monomers, and the like. The ink for inkjet printing may contain only one type of acrylic particles, or may contain two or more types of acrylic particles.

Examples of the acrylic monomer include acrylic acid, methyl acrylate, ethyl acrylate, acrylate amide, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and the like. N, N-dimethylaminoethyl acrylate, acrylonitrile, methacrylic acid, ethyl methacrylate, methacrylic acid amide, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, methacrylic acid Includes hydroxyethyl, N, N-dimethylaminoethyl methacrylate, and the like.

Examples of other monomers copolymerizable with the acrylic monomer include styrene, vinyl acetate, silicone macromer, fluorine-based monomer, alkoxysilane unsaturated monomer and the like.

With the acrylic particles, the fixability of the image tends to be good, and the durability of the image tends to be good.

Here, the amount of acrylic particles contained in the ink for inkjet printing is 0.5 to 10 parts by mass, more preferably 1 when the amount of the above-mentioned pigment is 10 parts by mass. It is .5-5.7 parts by mass. As described above, when the amount of the acrylic particles with respect to the pigment is in the above range, the fixability of the image obtained from the ink for inkjet printing is enhanced. However, if the amount of acrylic particles is excessive, the viscosity of the inkjet printing ink tends to increase excessively. Further, if the amount of acrylic particles is excessive, clogging of the inkjet head may occur during printing. On the other hand, when the amount of acrylic particles is in the above range, the viscosity of the inkjet printing ink can be in a desired range, and the inkjet printing ink can be stably ejected from the inkjet printer.

When preparing the ink for inkjet printing, the acrylic particles are usually mixed with pigments, water, alcohol, etc. in a state (emulsion) in which the acrylic particles are dispersed in a dispersion medium. The dispersion medium used at this time is also preferably a solvent that is not irritating to the skin, and is preferably alcohol or water, which will be described later.

(alcohol)
Alcohol functions as an ink drying inhibitor and as a solvent in ink jet printing inks. Alcohol is absorbed or volatilized by the object to be printed after the ink for inkjet printing is dropped onto the object to be printed.

Alcohols include trihydric alcohols, as described above. When the ink for inkjet printing contains trihydric alcohol, it is possible to suppress the volatilization of water and alcohol inside the inkjet printer. As a result, clogging of the inkjet head is less likely to occur, and an image can be stably formed. Further, since the viscosity of the ink for inkjet printing is kept constant, stable image formation becomes possible.

Here, the trihydric alcohol is not particularly limited as long as it is not irritating to the skin, but is preferably glycerin. Glycerin is highly biosafe. Further, when the ink for inkjet printing contains glycerin, aggregation of pigments is easily suppressed, and even if the ink for inkjet printing is stored for a long period of time, thickening of the ink is less likely to occur.

Here, the ink for inkjet printing may contain a divalent alcohol or a monohydric alcohol. Examples of divalent alcohols include diethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol, hexanediol and the like. Examples of monohydric alcohols include alcohols having 1 to 4 carbon atoms such as ethanol, propanol, isopropanol and butyl alcohol. Among these, a divalent alcohol is preferable, and propylene glycol is particularly preferable. Divalent alcohol has a lower viscosity than water and glycerin, and has a lower surface tension. Therefore, when the inkjet printing ink contains a dihydric alcohol, the wettability of the inkjet printing ink with respect to the object to be printed becomes good, and the obtained image is less likely to cause unevenness.

In the present disclosure, the ink for inkjet printing contains 30% by mass or less of alcohol. The amount of alcohol is preferably 10 to 30% by mass, more preferably 20 to 30% by mass. When the amount of alcohol in the ink for inkjet printing becomes excessive, pigments and the like tend to aggregate easily. On the other hand, when the amount of alcohol is 30% by mass or less, the agglomeration of pigments is unlikely to occur, and the ink for inkjet printing can be stably ejected from the inkjet printer.

The amount of trihydric alcohol with respect to the total amount of ink for inkjet printing is preferably 10 to 30% by mass, more preferably 10 to 20%. That is, it is particularly preferable that the ink for inkjet printing contains 10 to 30% by mass of glycerin. When the amount of trivalent alcohol is in the above range, the volatility of alcohol and water is appropriately adjusted in the inkjet printing ink, and the inkjet printing ink can be stably ejected from the inkjet printer.

Further, the amount of divalent alcohol with respect to the total amount of ink for inkjet printing is preferably 10 to 30% by mass, more preferably 10 to 20% by mass. When the amount of divalent alcohol is in the above range, the viscosity of the inkjet printing ink tends to fall within a desired range, and the inkjet printing ink can be stably ejected from the inkjet printer.

(water)
The water contained in the inkjet printing ink of the present disclosure is preferably purified. The amount of water contained in the inkjet printing ink is appropriately selected according to the viscosity of the inkjet printing ink and the like.

(Other)
The ink for inkjet printing may contain components other than the above components as long as the effects of the present disclosure are not impaired. However, other components are also preferably compounds that are negative for skin irritation. Examples of other ingredients include surfactants, acidity regulators, thickeners, UV absorbers, UV scatterers, antiseptic and antifungal agents, oxygen scavengers, antioxidants, preservatives, anti-fading agents, defoamers. Includes agents, fragrances, solvents and solvents other than water.

(Preparation method of ink for inkjet printing)
The above-mentioned ink for inkjet printing is obtained by sufficiently mixing pigments, emulsions containing acrylic particles, alcohol, water, other components, and the like with a disperser. Mixing of each component can be performed by a known ball mill, sand mill, roll mill, homomixer, disperser such as an attritor, or the like.

(Physical characteristics of ink for inkjet printing)
The viscosity of the ink for inkjet printing is 1 to 20 mPa · s at 25 ° C. when measured with a cone plate viscometer at a shear rate of 100 (1 / s) or 1000 (1 / s). Is preferable, and more preferably 3.5 to 8 mPa · s. When the viscosity of the ink for inkjet printing is in the above range, it becomes easy to stably eject the ink from the inkjet printer.

The pH of the inkjet printing ink is preferably 7.0 to 9.5. When the pH of the ink for inkjet printing is in the above range, it is stable inside the inkjet printer. Further, when the pH is in the above range, even if the ink for inkjet printing is stored for a long period of time, the pigments are less likely to aggregate and the ink is easily discharged from the inkjet printer.

The surface tension of the inkjet printing ink at 25 ° C. is preferably 32 mN / m to 46 mN / m. If the surface tension is lower than the above range, ink droplets are likely to bleed on the object to be printed when the ink for inkjet printing is ejected from the inkjet printer to various objects to be printed, and if the surface tension is higher than the above range, the ink is ink. Repelling of droplets is likely to occur. When the surface tension is within the above range, when the ink for inkjet printing is ejected from the inkjet printer to various printing objects, the wettability of the ink droplets becomes good, and an image having a uniform thickness can be formed. Although various measuring methods can be applied to the surface tension, the above values are values measured by the suspension method (pendant drop method) developed in general-purpose equipment.

Further, the median value (median diameter (D50)) of the integrated value of the particle size distribution measured by the laser diffraction method of the particles contained in the ink for inkjet printing is preferably 600 nm or less, more preferably 10 to 300 nm. Is. When the median diameter of the pigment is in the above range, stable ejection is possible from the inkjet printer. Further, the value (D90) of 90% of the integrated value of the particle size distribution is preferably 900 nm or less. When the values of D50 and D90 are in the above range, the ink for inkjet printing can be stably ejected from the inkjet printer.

(Printing using ink for inkjet printing)
Further, the inkjet printer that ejects the inkjet printing ink of the present disclosure is not particularly limited, and any known piezo type, thermal type, or electrostatic type apparatus may be used, but it is a piezo element type inkjet printer. Is particularly preferred. The piezo element type inkjet printer has an advantage that heating is not required as in the thermal inkjet method.

On the other hand, the object to be printed that ejects the ink for inkjet printing of the present disclosure is not particularly limited, and various known objects to be printed can be applied, and various objects to be printed such as plain paper, special recording paper, plastic, and cloth. Applicable to. The printed matter may consist of only one layer, or may have two or more layers laminated. The inkjet printing ink of the present disclosure is not irritating to the skin and has high biosafety even in the obtained printed matter. Therefore, it is possible to print on various sheets made of biocompatible materials, which are used, for example, directly or indirectly attached to or in close contact with the skin.

Examples of biocompatible materials include polyglycolic acid, polylactic acid, polycaprolactone, polyethylene succinate, polyethylene terephthalate, and polyesters typified by copolymers thereof; typified by polyethylene glycol and polypropylene glycol. Polyethers; Polyethylenes represented by nylon, polyglutamic acid, polyaspartic acid, or salts thereof; Polysaccharides represented by purulan, cellulose, starch, chitin, chitosan, alginic acid, hyaluronic acid, corn starch or salts thereof Acrylic silicones, silicones typified by trimethylsiloxysilicic acid; alkyl acrylates, silicone acrylates, acrylates amides, and acrylates represented by copolymers thereof; polyvinyl alcohols; polyurethanes; polycarbonates; polyacid anhydrides. Things; polyethylene; polypropylene; etc. are included.

Examples of sheets made of biocompatible materials include sheets for fixing medical members, sports taping sheets, skin decoration sheets, cosmetic sheets, and the like.

Here, the thickness of the object to be printed is not particularly limited, and is appropriately selected according to the type and application of the object to be printed. Since the inkjet printing ink of the present disclosure contains acrylic particles together with the pigment, the pigment is likely to be fixed to the surface of the object to be printed by the acrylic particles. Therefore, according to the inkjet printing ink of the present disclosure, it is possible to print on a thin film having a thickness of, for example, 10 nm or more and 3000 nm or less, more preferably 10 nm or more and 1000 nm or less.

When forming an image on such a thin film, printing may be performed on a laminate in which the thin film and a support supporting the thin film are laminated, and the thin film may be peeled off from the support after printing. Such a support can be made of, for example, a material having high water absorption. When the support has water absorbency, alcohol and water can be quickly absorbed by the support, and only pigments and acrylic particles can be fixed to the surface of the thin film. Therefore, it is possible to form a high-definition image without causing blurring or the like in the obtained image. Examples of the highly water-absorbent support include a base material made of paper, cloth, non-woven fabric, woven fabric, porous layer coating sheet, nanofiber sheet, water-absorbent polymer, water-soluble polymer and the like.

Hereinafter, the present invention will be described with reference to examples. By way of examples, the scope of the invention is not construed as limiting.

[material]
The materials used in each Example and Comparative Example are as follows.

(Pigment)
Yellow pigment: Iron oxide yellow (D50: 217 nm)
Red pigment: Iron oxide red (D50: 291 nm)
White pigment: titanium oxide (D50: 103 nm)
Blue pigment: Ferrocyanide ferric (D50: 159 nm)
Black pigment: carbon black (D50: 112 nm)

(Acrylic particles)
Acrylate Copolymer

(solvent)
Glycerin 1,3-propanediol (PD)
purified water

(Other)
pH regulator Nonionic surfactant (sucrose fatty acid ester)
Anionic surfactant (polyoxyethylene lauryl ether sodium acetate)
Polyvinyl alcohol Silicon-based particles (dimethicone)

[Example 1]
Each material was mixed with the component ratios shown in Table 1 below to prepare yellow ink, red ink, white ink, blue ink, and black ink (ink for inkjet printing). In some examples, the pH of the ink jet printing ink was adjusted by replacing a part of water with a pH adjuster so that the pH was within the range of 7.0 to 9.5. Therefore, Table 1 shows the total amount of water and the pH regulator.

[Evaluation]
The skin irritation, particle size distribution and viscosity of the obtained inkjet printing ink were measured as follows. In addition, the ink fixability of the ink for inkjet printing was also confirmed by the following method. The results are shown in Table 1.

(Skin irritation)
The skin irritation of the prepared ink was evaluated by an alternative method of the skin irritation test using a three-dimensional skin model. Specifically, a 5% sodium dodecyl sulfate (SDS) solution was used as an irritant control, and phosphate buffered saline (PBS) was used as a negative control. As the test sample, a printed matter obtained by printing the prepared ink on a polyester film by inkjet printing was used. For the test sample, the ink-printed surface was exposed to the skin model for 18 hours, and then the skin model was washed with PBS to completely remove the test sample, and 0.3 mg / mL 3- (4,5-dimethyl-2) was used. -Thiazolyl) -2,5-diphenyl-2H-Tetrazolium bromide (MTT) was transferred to a test medium and cultured for 3 hours. The skin model was then immersed in acidic isopropanol for 24 hours to extract blue formazan. The absorbance of the extract at 550 nm was measured with a microplate reader. Then, when the cell viability of each test sample is expressed as a percentage when the absorbance of the skin model exposed to the negative control is 100, the case where it is more than 50% is less than 50% without skin irritation. In some cases, it was evaluated as having skin irritation.

(Particle size distribution)
The particle size distribution of each of the prepared inks was measured. The particle size distribution was measured using a Microtrack particle size distribution meter UPA150 manufactured by Nikkiso Co., Ltd. under the conditions of a laser wavelength of 780 nm and a laser output of 3 mW. The particle size distribution was measured immediately after the ink was prepared, 2 weeks and 4 weeks later, and the change with time was evaluated. If there is no change in the particle size distribution, it can be evaluated that stable ejection is possible from the inkjet printer. Table 1 shows the median value of the particle size distribution (D50) and the value of 90% of the integrated value of the particle size distribution (D90) after 4 weeks from the ink preparation. At this time, if (D50) is 600 nm or less and (D90) is 900 nm or less, it can be evaluated that stable printing is possible from the inkjet printer.

(viscosity)
The viscosity of each of the prepared inks was measured using a thermoscientific viscosity / viscoelasticity measuring device HAAKE MARS. 0.3 cc of ink was collected with a syringe and sampled on a cone plate, and measurement was performed while changing the measurement temperature at 25 ° C. and the shear rate at 0.1 to 1000 (1 / s). If the viscosity at 25 ° C. is 20 mPa · s or less, stable printing is possible from an inkjet printer, and particularly if it is 8 mPa · s or less, it can be evaluated that printing is very stable.

(Ink fixability)
The obtained color inks were filled in the ink tank of an inkjet printer equipped with an LB3 inkjet head manufactured by Panasonic Precision Device Co., Ltd. Then, a rectangular fill pattern of 15 mm × 5 mm was formed on the filter paper (thickness 270 μm) to be printed by using each ink. The printed sheet (printed matter) was allowed to stand in an environment of room temperature or 50 ° C.

Further, a polylactic acid sheet having a thickness of 200 nm was attached to a support made of filter paper. As a method of sticking, first, each of the sticking surfaces of polylactic acid and the support was wet with water, and then the wet surfaces of the sheets were stuck and stuck, and dried for 12 hours or more. A rectangular fill pattern of 15 mm × 5 mm was formed on the laminated printing sheet thus produced by using an inkjet printer in the same manner as described above. The printed sheet (printed matter) was allowed to stand in an environment of room temperature or 50 ° C.

A tissue was pressed against each of the above print patterns every few minutes, and the ink fixability was evaluated based on the presence or absence of ink adhesion at this time.
The evaluation criteria were the following four stages.
⊚: No ink adhesion within 5 minutes 〇: Ink adhesion within 5 minutes, but no ink adhesion within 10 minutes Δ: Ink adhesion within 10 minutes, but 30 minutes No ink adhesion within x: Ink adhered even after 30 minutes.

(result)
As shown in Table 1 above, in an inkjet printing ink containing a pigment, acrylic particles, alcohol, and water, the alcohol contains a trivalent alcohol, and the alcohol contains the total mass of the ink. When the amount is 30% by mass or less and the amount of the acrylic particles with respect to 10 parts by mass of the pigment is 0.5 to 10 parts by mass, the particle size distribution and viscosity will be high regardless of the pigment used. It was within the desired range, and stable ejection was possible from the inkjet printer. Further, in the printed matter obtained from the ink for inkjet printing, the ink could be sufficiently fixed regardless of the type of the object to be printed.

[Example 2]
Each material was mixed with the component ratios shown in Table 2 below to prepare yellow ink (ink for inkjet printing). With respect to the obtained ink for inkjet printing, the stability of ejection from the inkjet printer was evaluated. Moreover, the skin irritation was confirmed in the same manner as in Example 1.

(Discharge stability)
The obtained color inks were filled in the ink tank of an inkjet printer equipped with an LB3 inkjet head manufactured by Panasonic Precision Device Co., Ltd. Then, on the inkjet recording paper (thickness 270 μm) to be printed, each ink is used to form a grid pattern in which adjacent vertical and horizontal lines are arranged at intervals of 350 to 370 μm from immediately after printing to the next printing. It was continuously formed while changing the stop interval of. The ejection stability was evaluated from the grid pattern recorded on the printed matter after the stop interval was 0 to 5 minutes. The evaluation criteria were the following four stages.
⊚: Lattice pattern is formed after 5 minutes 〇: Lattice pattern is formed after 3 minutes but not after 5 minutes Δ: Lattice pattern is formed after 0 minutes but not after 3 minutes X: Table 2 shows the results that the lattice pattern is not formed even after 0 minutes.

(result)
As shown in Table 2, when the amount of alcohol was 30% by mass or less with respect to the total amount of ink (Examples 2-1 to 2-3), the ejection stability was good. On the other hand, when the amount of alcohol exceeded 30% by mass (Comparative Example 2-1), the discharge stability decreased. The larger the amount of trihydric alcohol (glycerin), the more difficult it is for the ink to dry, so the ejection stability tends to increase. However, when the amount of alcohol becomes excessive, the viscosity of the ink tends to increase and the ejection stability decreases. It is inferred that.

Moreover, when the trihydric alcohol (glycerin) and the divalent alcohol were combined, the discharge stability was greatly improved. It is presumed that the ejection stability was improved because the balance between the ink viscosity and the ink drying property was good.

[Example 3]
Each component was mixed with the composition shown in Table 3 below to prepare a white ink (ink for inkjet printing). The skin irritation of the obtained ink jet printing ink was evaluated in the same manner as in Example 1. In addition, the fixability and water resistance were confirmed by the following methods. The results are shown in Table 3 and FIGS. FIG. 1A is a photograph showing an ink adhesion state after the tissue is pressed against the ink printing surface after the fixability test of Comparative Example 3-1. FIG. 1B is a photograph showing the ink adhesion state after the water resistance test of Comparative Example 3-1. Is a photograph showing the state of adhesion of ink after pressing the ink against the printing surface. Similarly, FIGS. 2 to 4 show the ink adhesion state of Comparative Examples 3-2, 3-3, and Example 3-1 after the tissue was pressed against the printing surface after the fixability test and the water resistance test, respectively. It is a photograph showing.

(Fixability evaluation)
The obtained white ink is applied onto a polyester film to be printed by a spin coating method (under the condition of a rotation speed of 2000 rpm) to form a white ink layer in order to make it easier to observe the state of the coating film after printing. did. The sheet (printed matter) after forming the white ink layer was allowed to stand at room temperature for 1 hour. Tissues were pressed against the white print layer after standing, and the fixability of the ink was evaluated based on the presence or absence of ink adhesion at this time.

The evaluation criteria were the following two stages.
〇: No discoloration ×: With discoloration

(Water resistance evaluation)
Similar to the above fixability evaluation, a printed matter obtained by spin-coating a white ink on a polyester film was allowed to stand at room temperature for 1 hour. Then, 1 cc of water was dropped onto the white print layer with a syringe, and then the tissue was pressed against the white print layer. The water resistance of the printed matter was evaluated based on the presence or absence of ink adhesion at this time.
The evaluation criteria were the following two stages.
〇: No discoloration ×: With discoloration

As shown in Table 3 and FIGS. 1 to 4, when acrylic particles were contained, the fixability and water resistance were improved (Example 3-1). On the other hand, when the ink does not contain resin or when the resin is silicon-based particles, the fixability is not sufficiently improved, and the streaky or striped ink discoloration caused by pressing the tissue is discolored. Of course, the water resistance was also evaluated low (Comparative Examples 3-1 and 3-3). When the ink contained polyvinyl alcohol, the fixability was good, but when water was dropped, the ink was discolored and the water resistance was insufficient (Comparative Example 3-2).

[Example 4]
Each component was mixed with the composition shown in Table 4 below to prepare a yellow ink (ink for inkjet printing). The skin irritation of the obtained inkjet printing ink was evaluated in the same manner as in Example 1. Further, the fixability and water resistance were confirmed by the same method as in Example 3. The results are shown in Table 4.

As shown in Table 4 above, when the acrylic particles were included as the binder, the fixability and water resistance were improved (Examples 4-1 to 4-4). On the other hand, when the ink did not contain acrylic particles, the fixability of the ink and the water resistance of the image were low (Comparative Example 4-1). On the other hand, when the amount of acrylic particles is excessive, the discharge stability tends to decrease (Comparative Example 4-2).

The inkjet printing ink of the present disclosure has biosafety, does not clog the head during printing, and has excellent ejection stability. Therefore, high-definition printing is possible not only on plain paper but also on printed materials other than paper such as special recording paper, plastic, and cloth. Therefore, it is useful as a printing ink for coloring, packaging container manufacturing, etc. in the fields of medicine, food, and cosmetics.

Claims (16)

An inkjet printing ink containing pigments, acrylic particles, alcohol, and water.
The alcohol contains 10 to 20% by mass of a trihydric alcohol based on the total mass of the inkjet printing ink and 10 to 20% by mass of a divalent alcohol based on the total mass of the inkjet printing ink. ,
The divalent alcohol is a compound selected from the group consisting of diethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol, and hexanediol.
The alcohol content is 30% by mass or less with respect to the total mass of the inkjet printing ink.
The amount of the acrylic particles with respect to 10 parts by mass of the pigment is 0.5 to 10 parts by mass.
The pigment contains a colored inorganic pigment and contains
The acrylic particles are composed of an acrylic resin containing at least one of a homopolymer of an acrylic monomer and a copolymer of two or more kinds of acrylic monomers.
Inkjet printing ink for printing on a film with a thickness of 10 nm or more and 3000 nm or less. The trihydric alcohol is glycerin,
The ink for inkjet printing according to claim 1. The amount of the acrylic particles with respect to 10 parts by mass of the pigment is 1.5 to 5.7 parts by mass.
The ink for inkjet printing according to claim 1. The alcohol content is 20 to 30% by mass with respect to the total mass of the inkjet printing ink.
The ink for inkjet printing according to claim 1. Surfactants, pH regulators, thickeners, UV absorbers, UV scatterers, antiseptic and fungicides, oxygen scavengers, antioxidants, fungicides, anti-fading agents, defoamers, fragrances, and solvents (but , Excluding the alcohol and the water), further comprising one or more components selected from the group.
The ink for inkjet printing according to claim 1. The pH is 7.0-9.5,
The ink for inkjet printing according to claim 1. The median diameter of the particle size distribution of the pigment is 0.01 to 0.3 μm.
The ink for inkjet printing according to claim 1. The surface tension at 25 ° C. is 32 mN / m to 46 mN / m.
The ink for inkjet printing according to claim 1. The pigment rakes an inorganic red pigment, an inorganic brown pigment, an inorganic yellow pigment, an inorganic black pigment, an inorganic white pigment, an inorganic purple pigment, an inorganic green pigment, an inorganic blue pigment, and a tar pigment. Contains one or more components selected from the group consisting of those made from natural pigments, those made from natural pigments, and synthetic resin powders that are composites of these powders.
The ink for inkjet printing according to claim 1. The acrylic particles are Acrylate copolymers.
The ink for inkjet printing according to claim 1. The divalent alcohol comprises 1,3-propanediol.
The ink for inkjet printing according to claim 1. The ink for inkjet printing according to claim 1, wherein the pigment further contains a pearl pigment. A film with a thickness of 10 nm to 1000 nm and
Including a water-absorbent support laminated on the back surface side of the film so as to be peelable.
The ink jet printing ink according to claim 1 is applied to the surface of the film opposite to the support.
A thin film sheet that adheres to the skin. At least one selected from the group consisting of polyesters, polyethers, polyamides, polysaccharides or salts thereof, silicones, acrylic acids, polyvinyl alcohol, polyurethane, polycarbonate, polyacid anhydride, polyethylene, and polypropylene. including,
The thin film sheet according to claim 13. The film is made of a biocompatible material.
The thin film sheet according to claim 13. The support comprises at least one material selected from the group consisting of paper, cloth, non-woven fabric, woven fabric, porous layer coating sheet, nanofiber sheet, water-absorbent polymer, and water-soluble polymer.
The thin film sheet according to claim 13.

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