WO2022070932A1

WO2022070932A1 - Edible ink jet printer and printing method

Info

Publication number: WO2022070932A1
Application number: PCT/JP2021/034024
Authority: WO
Inventors: 篤生小林; 洋平菅沼; 和美大井
Original assignee: Dic株式会社
Priority date: 2020-09-29
Filing date: 2021-09-16
Publication date: 2022-04-07
Also published as: JPWO2022070932A1

Abstract

The present invention provides: a printing method using an edible ink jet printer having excellent ejectability; and an edible ink jet printer using the printing method. More specifically, this edible ink jet printer has a path for an ink extending from an ink tank to a head, and this printing method uses the same. The ink jet printer is characterized in that the ink path is provided with a hollow-fiber degassing module that can perform degassing, and that the ink is an edible inkjet ink having a zirconium concentration in the ink of less than 0.01 ppm.

Description

Edible inkjet printer and printing method

The present invention relates to an inkjet printer using an inkjet ink containing an edible material and a printing method using the same.

Conventionally, inkjet ink using edible materials has been used to print characters and patterns on foods such as eggs and confectionery using inkjet. Dyes are generally used as the coloring material for inkjet inks using edible materials, but pigments may also be used when water resistance and light resistance are required.

For example, an inkjet ink in which titanium oxide or an aluminum lake pigment is dispersed as a coloring material is known (see, for example, Patent Document 1). Ink for eggshell printing using red iron oxide pigment, which is recognized as a food additive (see, for example, Patent Document 2), charcoal, which is recognized as a food additive, and inkjet ink using charcoal. Etc. are also known (see, for example, Patent Document 3 and Patent Document 4).

These edible inkjet inks contain a liquid component, a pigment and a dispersant for satisfactorily dispersing the pigment in the liquid component. The pigment is generally pulverized to a size that can be ejected by inkjet, and is dispersed so as not to aggregate, and is adjusted so that the stability of dispersion is not impaired over time.

And, in the dispersion processing in the case of producing the inkjet ink containing the pigment as the coloring material in this way, a disperser generally called a bead mill is used. A bead mill is a spherical medium called beads (also called "dispersion media") that is flipped off using a disc with a special shape to give strong kinetic energy to the beads, collide with the powder, and crush the powder into small pieces. It is a device that disperses. In order to make the powder finer and more stably dispersed, zirconia (zirconium oxide) beads having a large specific gravity and a high surface hardness are often used. Also, the disc that flicks the zirconia beads is often made of zirconia for the same reason as the beads.

When a bead mill is used as a disperser, the disc and the beads collide with each other and wear each other. Therefore, it is inevitable that zirconia, which is a material for the disc and the beads, is mixed in the powder in a small amount. Similarly, when zirconia beads are used as the dispersion medium and a zirconia disc is used for the dispersion treatment of the inkjet ink, zirconia is mixed in the inkjet ink, although the amount is small. Zirconia and zirconium are considered to have no safety problems when taken orally into the human body, but since there are no specified values that regulate safety in particular, they are mixed into inkjet inks. It is considered preferable to avoid.

Therefore, in the production of inkjet ink, we provide an inkjet ink that is dispersed by a disperser using a dispersion medium and suppresses the mixing of zirconia and zirconium, and a method for producing the same. Further, the inkjet ink is used for a long period of time. A printing method capable of continuous printing is provided (see Reference 5).

Japanese Unexamined Patent Publication No. 2000-507820 JP-A-2007-106913 JP-A-2007-106915 Japanese Unexamined Patent Publication No. 2010-248313 Japanese Unexamined Patent Publication No. 2015-224270

However, in an edible inkjet printer equipped with a hollow fiber degassing module, it is clear that the presence of zirconium even in a very small amount affects the degassing performance, which in turn tends to reduce the ejection property of the inkjet printer. became.

Therefore, an object to be solved by the present invention is to provide a printing method using an edible inkjet printer having excellent ejection properties, and an edible inkjet printer used in the printing method.

The present inventors have found that the above problem can be solved by printing with an edible inkjet ink in the substantially absence of zirconium in an edible inkjet printer equipped with a hollow thread degassing module.

That is, the present invention is a printing method using an edible inkjet printer having an ink path from an ink tank to a head, wherein the inkjet printer includes a hollow thread degassing module capable of degassing in the ink path. The ink relates to a printing method, characterized in that the ink is an edible inkjet ink having a zirconium concentration of less than 0.01 ppm in the ink.

Further, the present invention relates to an edible inkjet printer having an ink path from an ink tank to a head.
The inkjet printer is provided with a hollow thread degassing module capable of degassing in the ink path. The ink is an edible inkjet ink having a zirconium concentration of less than 0.01 ppm in the ink. Regarding inkjet printers.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a printing method using an edible inkjet printer having excellent ejection properties, and an edible inkjet printer used for the printing method.

Schematic diagram of the configuration of the degassing module. Layout of the degassing module during degassing. It is a figure which shows the structural example from the ink tank to the head of this invention. It is a schematic diagram which shows an example of the ink circulation path of this invention.

The printing method of the present invention is a printing method using an edible inkjet printer having an ink path from an ink tank to a head.
The inkjet printer is provided with a hollow thread degassing module capable of degassing in the ink path. The ink is an edible inkjet ink having a zirconium concentration of less than 0.01 ppm in the ink. do.

The edible inkjet printer used in the present invention is not particularly limited as long as it has a conventionally known structure. For example, the inkjet printer of the present invention is an inkjet printer having an ink path from an ink tank to a head. Therefore, a hollow thread degassing module capable of degassing the ink is provided in the middle of the ink path, and the pressure of the ink at the ink inlet of the external or internal recirculation type hollow thread degassing module at the time of degassing is applied. It is preferable to provide an adjustable liquid feed pump and an image recording means for ejecting ink using a head and recording an image.

The hollow fiber degassing module used in the present invention may be either an external reflux type or an internal reflux type, but the degassing treatment may be performed under the condition that the pressure loss of the hollow fiber degassing module at the time of degassing is low. The external reflux type is preferable because it can be used.

Hereinafter, the external reflux type hollow fiber degassing module will be described based on the schematic diagram shown in FIG. As shown in FIG. 1, the external reflux type hollow fiber degassing module performs degassing by flowing ink 5 from the ink inlet 2 to the outside of the hollow fiber and depressurizing and evacuating the inside of the hollow fiber 1. Is. Even if the ink has a high viscosity, it can be degassed without reducing the pressure loss at the time of degassing and without reducing the efficiency by flowing a thick flow path and depressurizing and vacuuming the inside of the thin hollow fiber. It is possible, and it is possible to efficiently degas without impairing the dispersion stability of the pigment ink. Here, 3 is an ink outlet and 4 is a vacuum pump. As such an external reflux type hollow fiber degassing module, a commercially available one can be used, and examples thereof include DIC Corporation SEPAREL EF-002A-P and SEPAREL EF-004P. FIG. 1B schematically shows how the dissolved air and the like in the ink 5 pass through the hollow fiber 6 and move into the hollow fiber 1 under reduced pressure. Further, FIG. 1 (c) schematically shows a cross section of the three hollow fibers in the direction perpendicular to the length direction.

In FIG. 1 (c), it is preferable that the outer diameter 61 of the hollow fiber is 150 μm or more and 250 μm or less, and the inner diameter 62 is 50 μm or more and 180 μm or less. If the outer diameter 61 of the hollow fiber is less than 150 μm, it becomes difficult to manufacture the hollow fiber in terms of strength. On the other hand, when the outer diameter 61 of the hollow fiber exceeds 250 μm, the specific surface area of the hollow fiber tends to be small, and the degassing efficiency tends to decrease. Further, if the inner diameter 62 is less than 50 μm, the degassing efficiency tends to decrease. On the other hand, when the inner diameter 62 exceeds 180 μm, it tends to be difficult to manufacture in terms of strength. The wall thickness of the hollow fiber is preferably 30 μm or more from the viewpoint of strength.
Here, the diameter refers to the diameter when the cross section is circular, and when the cross-sectional shape is not circular, it is the diameter when the cross-sectional area is replaced with a circle having the same area. It can be measured by observing the cross section with an electron microscope.

In FIG. 1 (c), for convenience, only the configuration for three hollow fibers is shown, but the external reflux type hollow fiber degassing module of the present embodiment is shown in FIG. 1 (a). The structure is such that a large number of hollow fibers are arranged. Here, in the present invention, the number of hollow fibers in the hollow fiber degassing module may be any number, and is not limited to the present embodiment. When a plurality of hollow fibers are provided, it is preferable that the inner and outer diameters of all the hollow fibers are within the above-mentioned ranges.

On the other hand, although not shown, the internal reflux type hollow fiber degassing module can perform degassing by flowing ink inside the hollow fiber having an inner diameter of 100 μm to 200 μm and depressurizing and vacuuming the outside of the hollow fiber. can. As such an internal reflux type hollow fiber degassing module, a commercially available one can be used, and examples thereof include DIC Corporation SEPAREL PF-001D and SEPAREL PF-004D.

In both the internal reflux type and the external reflux type, various resins are used as the material of the hollow yarn, and in particular, a polyolefin resin such as polypropylene and poly-4-methylpentene 1 resin, or a fluororesin such as polytetrafluoroethylene resin. And so on. These are preferable because the degassing performance does not deteriorate even when a large amount of ink is processed, and the surfactants and dispersants contained in the ink do not easily adhere to the outer surface of the hollow fiber and the ink components do not change easily. Is mentioned as.

When the hollow fiber membrane module used in the present invention is an internal recirculation type, the pressure outside the hollow fiber membrane (gas phase side) of the internal recirculation type hollow fiber membrane module is maintained under reduced pressure, and the pressure inside the hollow fiber membrane (liquid phase side) is maintained. Degas by passing liquid from. On the other hand, when the hollow fiber membrane module used in the present invention is an external recirculation type, the pressure inside the hollow fiber membrane (gas phase side) of the external recirculation type hollow fiber membrane module is kept under reduced pressure, and the outside of the hollow fiber membrane (liquid phase) is maintained. Degas by passing liquid from the side). In either case, it is preferable that the liquid phase side is a skin layer (dense layer) and the gas phase side is a layer having pores (porous layer). When it comes into contact with an ink containing zirconium on the porous layer side, it tends to have a particularly large effect on the deterioration of degassing performance, and thus also has a large tendency to reduce the ejection property of the inkjet printer.

The inkjet printer used in the present invention preferably includes a liquid feed pump capable of adjusting the ink pressure at the ink inlet of the hollow thread degassing module at the time of degassing.

In the external reflux type, the pressure loss of the hollow fiber degassing module at the time of degassing is preferably 0.2 MPa or less, more preferably 0.1 MPa or less, and further preferably 0.05 MPa or less. On the other hand, in the internal reflux type, the pressure loss of the hollow fiber degassing module at the time of degassing is preferably 1.0 MPa or less, more preferably 0.5 MPa or less, and further preferably 0.025 MPa or less. preferable. The pressure loss of the hollow thread degassing module at the time of degassing in the present invention means the pressure applied to the inlet of the hollow thread degassing module, and can be measured by a pressure gauge inserted upstream of the hollow thread degassing module. ..

The degree of degassing in the present invention can be measured by the dissolved oxygen concentration. As a method for measuring the dissolved oxygen concentration, for example, the Ostwald method (see Experimental Chemistry Course 1 Basic Operation [I], page 241, 1975, Maruzen), the mass spectrum method, the galvanic cell type, and the polarograph type. It can be measured using a simple oxygen concentration meter or colorimetric analysis method. Further, the dissolved oxygen concentration can be easily measured by using a commercially available dissolved oxygen concentration meter (DO-30A type manufactured by Toa Denpa Kogyo Co., Ltd.).

The degree of degassing of the ink in the present invention is preferably 8.0 ppm (or “mg / L”; the same applies hereinafter) or less, preferably 6 It is more preferably 9.0 ppm or less, further preferably 4.0 ppm or less, particularly preferably 2.0 ppm or less, and the lower limit is not particularly limited, but is preferably 0 ppm or more, more preferably 1 ppb or more.

In the present invention, the degassing rate (%) is not particularly limited as long as the degassing degree of the ink is within the above dissolved oxygen concentration range, but is preferably 20% or more, more preferably 50% or more, and more preferably 80%. That is all.
The degassing rate (%) represents the percentage of the dissolved oxygen concentration in the ink removed by degassing.

The hollow fiber degassing module may be placed anywhere between the ink tank and the head, but since there are many air supply points such as thin resin pipes and joints in the ink flow path, it is as close to the head as possible. Is preferable. An example of the configuration from the ink tank to the head is shown in FIG. 3, but the configuration of the present invention is not limited thereto.

In FIG. 3, the ink 5 filled in the ink tank 8 is sent to the head 12 by the liquid feed pump 9, and in the meantime, the hollow shown in FIG. 1 is connected to the vacuum pump 4 via the filter 100. It is sent to the thread degassing module 10, where it is degassed, and then the pressure is adjusted by the back pressure regulator 11 to reach the head 12 through the filter 100.

Further, the ink tank in the present invention is a storage place for ink, and is a reserve tank when ink is circulated by a bottle and only liquid is poured into a printer, and ink is circulated in an ink cartridge or a bottle and is a cartridge. Or, if the bottle itself doubles as an ink tank, this is the case.

Subsequently, in an inkjet printer having an ink circulation path for returning the ink jet ink discharged from the head to the head again, an inkjet printer having an degassing step by the above-mentioned degassing method for ink jet ink in the middle of the ink circulation path will be described. do.

FIG. 4 shows an example of the configuration of the ink circulation path, but it goes without saying that the present invention is not limited to this. When the ink 5 is introduced, the solenoid valve A is opened, the solenoid valve B is closed, the ink tank 8 is passed through the filter 100 by the liquid feed pump 9, the intermediate tank 30, the back pressure regulator 11 and the filter 100 are passed, and the ink is sent to the head 12. Meet. At this time, the dissolved air in the ink 5 is degassed by the degassing module 10 shown in FIG. 1, which is arranged in the middle and connected to the vacuum pump 4. At the time of head maintenance, the head cap 7 is brought into close contact with the head 12, and then the inside of the cap is depressurized by the liquid feed pump 9, and ink is sucked out from the head 12 or ink is ejected from the head 12 to the head cap 7. At this time, by closing the solenoid valve A and opening the solenoid valve B at the same time, the ink in the head cap is again degassed by the degassing module 10 and then sent to the head 12, and is used again for ejection.

Here, FIG. 4 shows an example in which ink is circulated from the head cap, but the ink is not limited to the head cap, and may be circulated from a common ink chamber of the head or a gutter for ejection, for example.

The degassing module may be placed anywhere between the ink tank and the head, but since there are many air supply points such as thin resin pipes and joints in the ink flow path, it is as close to the head as possible. Is preferable.

In an inkjet printer having an ink circulation path for returning the ink jet ink discharged from the head of the present invention to the head again, the inkjet printer having an degassing step by the above-mentioned degassing method for ink jet ink in the middle of the ink circulation path. For example, inkjet recording is possible, which has excellent ejection stability, high reliability, and eliminates unnecessary ink other than that used for recording as much as possible. The present invention is particularly suitable for printing for industrial printing applications.

The form of the head 12 in the above embodiment is not particularly limited, but may be any recording head used in an on-demand method such as a piezo method using a piezo element or a thermal inkjet method using heat energy.

The amount of ink ejected droplets is preferably 0.5 pL or more, more preferably 1.0 pL or more, still more preferably 1.0 pL or more per drop, from the viewpoint of avoiding the influence of air flow and maintaining the accuracy of the landing position of the ink droplets. It is 1.5 pL or more, more preferably 3.0 pL or more. Further, when small characters are printed, it is preferably 30 pL or less, more preferably 10 pL or less, still more preferably 5.0 pL or less, from the viewpoint of avoiding the possibility that the characters are crushed due to the thickening of the characters and improving the obtained image quality. ..

The average ejection speed of the ink droplets is preferably 6 m / s or more, more preferably 8 m / s or more, still more preferably 10 m / s or more, and preferably 20 m / s or less, more preferably 18 m / s or less. It is more preferably 15 m / s or less.

Next, the inkjet ink used in the present invention will be described. The edible inkjet ink used in the present invention is not particularly limited as long as it is an inkjet ink used in an on-demand inkjet method using an edible material, but for example, at least water, ethanol, and an edible polymer dispersant. , Contains edible resins and edible pigments.

Here, as the ethanol used in the present invention, known ethanol can be used, and examples thereof include fermented ethanol for beverages and foods. In addition, although it is an optional component, a water-soluble organic solvent such as propylene glycol and glycerin, which has a boiling point higher than that of water and can be taken orally into the human body, is added to ethanol as a wetting agent to add 0 to 0 to the entire inkjet ink. It can be used in the range of 10% by weight.

Here, as the edible polymer dispersant used in the present invention, known ones can be used, but for example, a cellulosic resin is preferably used. Further, examples of the cellulosic resin include methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose and the like. The content in the inkjet ink is not particularly limited, but when the total amount of the inkjet ink is 100 parts by mass, it is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and preferably 20 parts by mass. It is in the range of 10 parts or less, more preferably 15 parts by mass or less.

Here, as the edible resin used in the present invention, known ones can be used, and examples thereof include edible resins obtained by purifying a resinous substance derived from an animal or a plant, which are naturally derived. Therefore, it may be a mixture of many kinds of resin acids and their esterified products, waxes, dyes and the like, and alcohol-soluble types are particularly preferably used. Examples of such an edible resin include shellac resin (edible resin obtained by purifying a resinous substance derived from scale insects).

Here, as the edible pigment used in the present invention, known ones can be used, but for example, those approved as food additives or pigments compliant with the Pharmaceutical Affairs Law are used. Examples of such pigments include titanium oxide, aluminum lake of food coloring, iron oxide, charcoal powder pigment, squid ink and the like. In particular, as the charcoal powder pigment, crushed Bincho charcoal, bamboo charcoal, activated carbon and the like can be used. The particle size of these pigments is not particularly limited, but the average particle size is preferably in the range of 0.01 μm or more, and preferably 10 μm or less, from the viewpoint of improving efficiency during dispersion treatment and improving ejectability during printing. be.

The content of the edible pigment in the inkjet ink is related to the content by weight of other components, but when the total amount of the inkjet ink is 100 parts by mass, it is preferably 0.1 part by mass or more, more preferably 0.5 part by mass. It is in the range of 7 parts by mass or more, more preferably 1 part by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less.

As described above, the edible inkjet ink of the present invention containing water, ethanol, an edible resin, an edible pigment and an edible polymer dispersant is produced, for example, by the method for producing an inkjet ink of the present invention described in detail below. Is preferable.

The method for producing an edible inkjet ink of the present invention includes a step (1) for producing an edible polymer dispersant solution. In the step (1), the edible polymer dispersant solution can be prepared by dissolving the edible polymer dispersant in water. In particular, when a cellulosic resin is used as an edible polymer dispersant, the cellulosic resin is dissolved in water alone or in a mixed solution of water and alcohol (preferably ethanol).

As the solution for dissolving the cellulosic resin, it is preferable that the water content is 50 parts by mass or more and the ethanol content is less than 50 parts by mass when the total amount of the inkjet ink is 100 parts by mass. Dispersion in a solution containing 50 parts by mass or more of ethanol may make the dispersion of the edible pigment unstable in the step (2).

The method for producing an edible inkjet ink of the present invention next includes a step (2) of mixing an edible pigment with the edible polymer dispersant solution and using a disperser to produce a pigment dispersion.

In the step (2), it is preferable to use a medialess disperser as a disperser for mixing and dispersing the edible pigment in the edible polymer dispersant solution. Examples of the medialess disperser include a microfluidizer (trade name), a nanomizer (trade name), and a starburst (registered trademark).

In the method for producing an edible inkjet ink of the present invention, a step (3) of stirring and mixing the edible resin solution in which the edible resin is dissolved in a solvent containing 50% by mass or more of ethanol and the pigment dispersion is subsequently performed. Have.

In the above steps (1) to (3), a pH adjuster can be added in order to adjust the solubility and stability of the edible resin and the edible polymer dispersant contained in the inkjet ink. Acetic acid, citric acid and the like can be exemplified for the adjustment to acidity, and ammonium carbonate and the like can be exemplified for the adjustment to alkalinity.

The edible inkjet ink produced by the above method can be filled in the edible inkjet printer of the present invention and printed on pharmaceuticals, foods, packaging materials thereof, and tableware.

In the following production examples, preparation examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. Each measurement method is as follows.

(Manufacturing of dispersion 1)
Hydroxypropyl cellulose (hereinafter referred to as "HPC") was dissolved in purified water to prepare 30 parts by mass of a polymer dispersant solution having a solid content concentration of 20%. Next, 20 parts by mass of Bincho charcoal made from Ubamekashi was mixed in the polymer dispersant solution, and the jacket temperature was 60 ° C. using a beadless dispersion (Aikosha mixer "ACM-0.8LLVT"). Kneading was performed for 3 hours at a stirring blade rotation speed of 25 rpm (revolution number of 80 rpm). Next, 50 parts by mass of purified water was added little by little and stirred to obtain a dispersion 1.

(Manufacturing of dispersion 2)
HPC was dissolved in purified water to prepare 35 parts by mass of a polymer dispersant solution having a solid content concentration of 20%. Next, 20 parts by mass of titanium oxide was mixed in the polymer dispersant solution, and the jacket temperature was 60 ° C. and the stirring blade rotation speed was 25 rpm (Aikosha mixer "ACM-0.8LLVT") by beadless dispersion (Aikosha mixer "ACM-0.8LLVT"). Kneading was carried out for 3 hours at a revolution number of 80 rpm). Next, 45 parts by mass of purified water was added little by little and stirred to obtain a dispersion 2.

(Manufacturing of dispersion 3)
HPC was dissolved in purified water to prepare 40 parts by mass of a polymer dispersant solution having a solid content concentration of 20%. Next, 20 parts by mass of iron sesquioxide was mixed in the polymer dispersant solution, and the jacket temperature was 60 ° C. and the stirring blade rotation speed was 25 rpm by beadless dispersion (Aikosha mixer "ACM-0.8LLVT"). Kneading was carried out at (revolution number 80 rpm) for 3 hours. Next, a mixed solution of 20 parts by mass of purified water and 20 parts by mass of ethanol was added little by little and stirred to obtain a dispersion 3.

(Manufacturing of dispersion 4)
HPC was dissolved in purified water to prepare 45 parts by mass of a polymer dispersant solution having a solid content concentration of 20%. Next, 15 parts by mass of food coloring No. 1 lake was mixed in the polymer dispersant solution, and the jacket temperature was 60 ° C. and the stirring blade was rotated by beadless dispersion (Aikosha mixer "ACM-0.8LLVT"). Kneading was carried out at several 25 rpm (revolution number 80 rpm) for 3 hours. Next, 40 parts by mass of purified water was added little by little and stirred to obtain a dispersion 4.

(Manufacturing of dispersion 5)
HPC was dissolved in purified water to prepare 45 parts by mass of a polymer dispersant solution having a solid content concentration of 20%. Next, 15 parts by mass of food coloring No. 5 rake was mixed in the polymer dispersant solution, and the jacket temperature was 60 ° C. and the stirring blade was rotated by beadless dispersion (Aikosha mixer "ACM-0.8LLVT"). Kneading was carried out at several 25 rpm (revolution number 80 rpm) for 3 hours. Next, 40 parts by mass of purified water was added little by little and stirred to obtain a dispersion 5.

(Manufacturing of dispersion for comparative example)
Hydroxypropyl cellulose (hereinafter referred to as "HPC") was dissolved in water with the blending composition and blending amount shown in Table 2 to prepare a polymer dispersant solution. Next, Bicho charcoal made from Ubamekashi is mixed in the polymer dispersant solution, and zirconia beads (bead composition: ZrO ₂ is contained in an amount of 95% by weight, and HfO ₂ and Y ₂ O ₃ are contained in a trace amount. , Bead particle size: φ0.3 mm) with a horizontal sand mill (Dynomill Multilab manufactured by Willy et Bacoffen, equipped with a bead stirring disk made of urethane resin and zirconia reinforced alumina lining). Dispersion treatment was performed at 12 m / sec for 2 hours to prepare a dispersion for comparative examples (referred to as “comparative dispersion” in the table).

(Manufacturing of inkjet ink)
Using the above dispersions 1 to 5 and comparative dispersions 1 to 5, put them into a household mixer (healthy mix manufactured by Zojirushi Co., Ltd.) so as to have the composition and amount shown in the table below, seal them tightly, and stir and dissolve for 15 minutes. , Manufactured inkjet ink.

"Ethanol solution (1)" represents a 25% white shellac (acid value 83) ethanol solution.
"Ethanol solution (2)" represents a 50% white shellac (acid value 85) ethanol solution.

Each evaluation in the table was performed by the following method.

(Zirconium content)
The zirconium concentration was measured by an ICP emission spectrometer (HORIBA, Ltd. model ULTIMA2).

(Average particle size)
The median diameter (d50) of the pigment in the inkjet ink was measured using a particle size distribution meter (UPA type) manufactured by Nikkiso Co., Ltd.

(viscosity)
The measurement was performed using a viscometer (EH cone type) manufactured by TOKI Sangyo Co., Ltd.

(PH)
It was measured using a pH meter.

(Redispersity)
The inkjet ink left for 24 hours or more after production was vigorously shaken 20 times and then filtered, and evaluated by whether or not the pigment remained on the filter paper.

(Water resistance (elution))
The printed surface of the object to be printed printed with the inkjet ink produced in each example was confirmed by the presence or absence of ink leaching when moistened with water and the coloring of the ink.

(Adhesion (peeling))
The object to be printed was a pseudo-tablet, and printing was performed on the tablet using the inkjet ink prepared in each example, and the presence or absence of peeling when the printed portion was rubbed with a cotton swab was confirmed.

(Printing performance)
Using an in-house manufactured inkjet ejection observation device having an electronic balance capable of adjusting the applied voltage, pulse width, and drive frequency as an evaluation device, the equipment is arranged as an inkjet printer as shown in FIG. 3, and a hollow thread degassing module (DIC) is used. "SEPAREL EF-AG5-B" manufactured by Co., Ltd. (film area 0.5 m ² ), vacuum pump 4 is operated at a vacuum degree of 6.7 kPa (absolute pressure), and the pressure of the hollow thread degassing module when degassing is "Yes". The loss is 0.02 MPa when the degassing rate is 80 (%), 0.06 MPa when the degassing rate is 60 (%), and 0.10 MPa when the degassing rate is 40 (%). The degassing treatment device was installed using the pressure loss of the module (with 0.02 MPa), and two circulation type (drop-on-demand) DOD inkjet heads were installed. While the inkjet device is operating and one of the above two inkjet heads is printing on the object to be printed, the other inkjet head is made to stand by at the maintenance station, and the precursor, flushing, and wiping are constant during the standby. It was carried out at intervals. Then, among the two inkjet heads, the inkjet head used for printing and the inkjet head made to stand by at the maintenance station were changed at predetermined time intervals to continue printing.

(Measurement of dissolved oxygen concentration and degassing rate)
The dissolved oxygen concentration was measured using an organic solvent compatible DO meter B-506S manufactured by Iijima Denshi Kogyo Co., Ltd. The dissolved oxygen concentration of the ink before degassing was the dissolved oxygen concentration of the ink in the ink tank 8. For the dissolved oxygen after degassing, the inkjet printer was operated for a certain period of time, and the dissolved oxygen concentration was measured when the flow rate became stable. Since it is difficult to attach the dissolved oxygen meter directly to the inkjet printer, the ink degassed in the container is collected from the outlet of the filter 100 from the back pressure regulator at the time of measurement, and the dissolved oxygen meter is used. The dissolved oxygen concentration was measured.

(Printing performance in high temperature environment)
The printing performance was evaluated on a 5-point scale according to the following criteria based on the presence or absence of printing defects, font abnormalities, etc. when a printing test was performed with an inkjet printer in an environment room where the room temperature was maintained at 45 ° C.
5: Very good 4: Good 3: Slightly inferior to good product 2: Obvious defect 1: No evaluation

(Printing performance in a low room temperature environment)
When a printing test was performed with an inkjet printer in an environment room where the room temperature was maintained at 5 ° C., the printing performance was evaluated on a 5-point scale according to the above criteria based on the presence or absence of printing defects, font abnormalities, and the like.

(Continuous ejection)
When a printing test was performed with an inkjet printer for 1 hour in an environment room where the room temperature was maintained at 25 ° C., the nozzle was clogged and evaluated on a 5-point scale.
5: Very good 4: Good 3: Slightly inferior to good product 2: Obvious defect 1: No evaluation

1 Hollow fiber 2 Ink inlet 3 Ink outlet 4 Vacuum pump 5 Ink 6 Hollow fiber membrane 61 (Hollow fiber) Outer diameter 62 (Hollow fiber) Inner diameter V Decompression / Vacuum S Dissolved oxygen 7 Head cap 8 Ink tank 9 Pressurized pump (feed) Liquid pump)
P Pressure gauge F Flow meter D Dissolved oxygen meter 10 Degassing module 11 Back pressure regulator 12 Head 30 Intermediate tank 41 Nozzle 100 Filter A, B Solenoid valve 51 Heater section 52 Ink supply port

Claims

In a printing method using an edible inkjet printer having an ink path from an ink tank to a head.
The inkjet printer is provided with a hollow thread degassing module capable of degassing in the ink path. The ink is an edible inkjet ink having a zirconium concentration of less than 0.01 ppm in the ink. How to print.
The printing method according to claim 1, wherein printing is performed while degassing the dissolved oxygen concentration of the ink to a range of 8.0 ppm or less by the hollow fiber degassing module.
The printing method according to claim 1 or 2, wherein the degassing is performed in the absence of zirconium in the ink.
In an edible inkjet printer that has an ink path from the ink tank to the head
The inkjet printer is provided with a hollow thread degassing module capable of degassing in the ink path. The ink is an edible inkjet ink having a zirconium concentration of less than 0.01 ppm in the ink. Inkjet printer.