JP6106703B2 - Ink jet ink and printing method thereof - Google Patents

Description

  The present invention is used for printing and recording on the surface of foods (foods include medicinal tablets; the same applies hereinafter), packaging materials that wrap foods, materials that have an opportunity to come into contact with foods, and the like. More particularly, the present invention relates to a drop-on-demand inkjet ink with improved continuous stable ejection and drying properties, and a printing method thereof. Furthermore, it is related with the inkjet ink printed on the surface of the tablet which disintegrates easily in an oral cavity, and its printing method.

  In recent years, food and food packaging materials are required to display the production location, producer, production history, and the like, and the quality is required to display the expiration date, the date of manufacture, and the like. Displaying these pieces of information can confirm safety and provide a sense of security and reliability for the product. In addition, the quality can be improved from such a viewpoint.

  On the other hand, processing characters, figures, designs, and the like on foods and related packaging materials is also an important factor for making a product that incentivizes purchase. When recording directly on food, naturally it is necessary to use ink made of edible materials, but even when recording on food-related materials such as packaging, using edible ink materials, A sense of security can be obtained. From such a viewpoint, an ink composed of a material composed of a food material or a food additive is desired.

  However, preparing inks made of foods or food additives has limitations on ink materials. In addition, since there are few types of such ink materials, it is difficult to prepare them in the same manner as general inkjet inks.

As one of the fields mainly used for foods or food additives, there are tablets with oral administration. Here, so-called OD tablets, which are easily disintegrated in the oral cavity, are increasing as the properties of drugs to cope with aging.
In this tablet, there is a need for printing on the surface of the tablet in order to facilitate the discrimination of the tablet, but since the surface has become a material that tends to collapse, it is difficult to cope with conventional engraving and printing.
Therefore, it has been considered to use an ink jet printer that cannot perform conventional normal printing but can perform printing without contact.
In printing on such a tablet, quick drying after printing and adhesion on the tablet surface are required.
However, there are limitations on materials for foods or drugs (tablets), and general ink materials cannot be used.

As an edible ink for printing on foods such as eggs, Patent Document 1 discloses an ink composed of charcoal and a non-aqueous solvent such as liquid paraffin. Although various activators are shown, there is no description of ingredients that will fix charcoal.
Patent Document 2 discloses a method of treating charcoal with hypochlorous acid. Although there is no disclosure of a specific formulation for this ink, it is recognized that it is intended for water-based inks mainly composed of water. There is no description about suitability for drying and fixability in films and the like.
Patent Document 3 discloses an ink composed of charcoal and a non-polar non-aqueous solvent. There is no description about the component which fixes charcoal in this.

By the way, Patent Document 4 describes that polyvinyl pyrrolidone (hereinafter sometimes abbreviated as “PVP”) is used for inkjet ink. However, the ink in a so-called continuous type printer only describes the composition of the dye, PVP and water. It is not intended for orally available ink, but for applications such as printing on paper.
Similarly, Patent Document 5 and Patent Document 6 also describe the use of PVP, but use carbon black or a direct dye as a color material, and are limited to ink mainly for paper.

JP 2007-106915 A JP 2007-126583 A JP 2007-126592 A JP 55-48266 A JP-A-4-46970 Japanese Patent Laid-Open No. 4-132773

An object of the present invention is to provide an ink-jet ink having sufficient fixability even when recorded on various foods, materials in contact with foods, food packaging materials, and the like.
In particular, the subject of the present invention is a food or drug (tablet) that can be eaten in the mouth as a food or drug (tablet). Treat it as a similar recording object. In addition, tablets that are difficult to perform general printing such as OD tablets and plain tablets are mainly used as objects.

As a result of intensive research in order to solve the above-mentioned conventional problems, the present inventors, as a resin that has been approved for use in foods, have been subjected to various researches, such as drying, adhesion, and printers. We examined discharge stability.
In June 2014, the revision of the Food Sanitation Law Enforcement Regulations allowed the use of PVP in foods. We examined the use of PVP and further used caprylic acid esters. The present inventors have found that an ink having a predetermined composition is an ink that is excellent in continuous stable ejection with a printer, drying property with a tablet, and fixing, and has completed the present invention.

That is, the inkjet ink according to the present invention includes an edible pigment, polyvinylpyrrolidone, water, and caprylic acid ester having a structure in which caprylic acid is added to glycerin or a glycerin polymer, and the content ratio of the caprylic acid ester Is 1 to 15% by weight.
In the printing method according to the present invention, the ink-jet ink is ejected from the drop-on-demand ink-jet apparatus, and the ink-jet ink is attached to the object to be printed for printing. The inkjet ink is circulated between an inkjet head and an ink tank housing of the drop-on-demand inkjet apparatus.

According to the present invention, there is provided an ink-jet ink that is composed only of materials that are allowed to be added to foods and medicines, an edible pigment is stably dispersed in water by PVP, and has excellent performance such as fixability. be able to.
As described above, the ink composed of the food material and the food additive or the material approved by the Pharmaceutical Affairs Law can be used for food, medicine, food packaging material and the like with peace of mind. Even if food is not printed directly, product packaging materials related to foods are materials that are safe for oral intake even if they are mixed or contacted by ink during the recording process. There is a sense of security above.

Hereinafter, embodiments of the present invention will be described. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, it should be noted that the present invention is not construed as being limited to the description of the embodiments.
Examples of objects that can be printed using the inkjet ink of the present invention include foods, drugs (tablets), packaging materials for packaging foods, and materials that come into contact with foods.
In particular, it is suitably used in tablets and capsules such as OD tablets, plain tablets, film-coated tablets (FC tablets).

[Inkjet ink]
The inkjet ink according to the present invention includes an edible pigment, PVP, water, and caprylic acid ester.

<Dye>
In the present invention, the dye may be a dye or a pigment, but is an edible or edible dye that is edible or approved for use in tablets.
As such pigments, colorants that are normally certified as food additives and “Act on the Assurance of Quality, Effectiveness, and Safety of Pharmaceuticals, Medical Devices, etc. (abbreviation: Law on Medical Products, Medical Devices, etc.)” Use the dyes recognized in.
As the coloring matter, since the dye is unlikely to cause problems such as sedimentation, it is preferable to handle it with an ink jet printer because it is relatively easy to handle such as maintenance. However, depending on the light resistance and the surface condition of the tablet or the like, it may be blurred, and in some cases, there is a risk of discoloration or fading. It can be said.

Preferable examples of such pigments include titanium oxide, iron oxide, charcoal dye, tar-based aluminum lake, and squid dye.
Further, as iron oxide, ferric oxide, yellow ferric oxide, black iron oxide and the like are used, and as the coal powder pigment, vegetable charcoal powder and the like are preferably used. As plant charcoal powder, powders such as Bincho charcoal and bamboo charcoal are preferable.
For example, these pigments can be used in a proportion of 0.1 to 5% by weight in the ink to provide a preferable color and display with visibility.

<PVP>
In the present invention, PVP is used as a resin for dispersing or fixing the dye.
The PVP used in the present invention preferably has a weight average molecular weight of 5,000 to 100,000.
The weight average molecular weight of PVP is measured by a GPC-light dispersion method in which a light scattering detector is combined with GPC (gel permeation chromatography). DMF (dimethylformamide) is used as an eluent, and polyethylene glycol is used as a standard substance.

Since PVP exhibits good solubility in water and ethanol, it can be used as an ink having good drying properties, and can be quickly dried on the tablet surface.
By using PVP having a weight average molecular weight of 5,000 to 100,000, it becomes an inkjet ink suitable for fixing property and viscosity adjustment, and stable ejection as an inkjet can also be realized. In particular, even in a tablet having a tablet surface formed of a disintegrating material, it is possible to impart good fixability and coating strength that hardly causes transfer or peeling to other tablets.
Further, PVP having a weight average molecular weight of 5,000 to 100,000 has a very small amount of foaming in the production of the ink and the stirring of the ink as compared with the cellulose derivative and is easy to handle. Therefore, even if compared with other water-based resins, it also exhibits stable discharge suitability from the nozzle.
From the above viewpoint, the weight average molecular weight of PVP is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.

From the viewpoint of the effect of adding PVP as described above, the blending amount of the PVP is preferably 0.01 to 5% by weight with respect to the total amount of ink. The ratio is more preferably 0.03 to 1.5% by weight, and particularly preferably 0.05 to 1.2% by weight.
Further, on the surface intended for disintegration of tablets and the like, even if the amount used is 1% by weight or less in the ink, it can have good fixability and coating strength that does not peel off even when rubbed.
Therefore, especially in a drop-on-demand (hereinafter referred to as “DOD”) type printer, it is possible to cope with a very small amount as compared with the content intended to be firmly fixed on paper or film. Since it is possible, more stable discharge property is shown.
This prescription of the ink in a small amount eliminates the blockage of the PVP nozzle, which has a relatively poor characteristic with respect to the clogging at the nozzle, and the problem of initial dot non-ejection in re-ejection after printing is stopped Could also be solved.

  In addition, since the ink of the present invention is assumed to be a raw material for printing on foods or tablets, the characteristics of lead 2 ppm or less, aldehyde 500 ppm or less, 1-vinyl-2-pyrrolidone 10 ppm or less, and hydrazine 1 ppm or less. It is preferable that both of these are satisfied.

Regarding PVP, use in inks such as carbon black is described in Patent Documents 4 to 6, but there is no known literature that suggests the use of PVP for edible dyes, and tablets There was no suggestion of suitability for the surface.
In addition, edible dyes are not treated to facilitate dispersion, such as surface treatment, and therefore are relatively difficult to disperse compared to general dyes, and can only be dispersed with limited materials. Therefore, it was a new discovery that PVP having the predetermined weight average molecular weight has the dispersion, fixing and strength suitable for the edible dye.
In addition, as a water-based ink, a printing method using a DOD printer for improving the drying property can be supported by using this PVP and a caprylic acid ester described later.

<Solvent>
In the present invention, the solvent component of the ink contains water. It is preferable to use water as a main component.
As the solvent component, volatile ethanol may be included.
As a proportion of ethanol, stabilization can be achieved even in a proportion of 0 to 80 parts by weight of ethanol with respect to 100 parts by weight of water. It is more preferable that the ratio is 1 to 50 parts by weight of ethanol with respect to 100 parts by weight of water.
In order to suppress drying of the nozzle, it is also preferable to use propylene glycol in combination. As a ratio of propylene glycol, a ratio of 0 to 150 parts by weight is preferable with respect to 100 parts by weight of water, and a ratio of 10 to 120 parts by weight is more preferable.

<Caprylic acid ester>
In the present invention, various additives have been studied in order to further satisfy the contradictory requirements of rapid penetration, drying and fixing into tablets and prevention of nozzle drying in printers.
However, such characteristics were not easily exhibited.
As a result of intensive studies on such characteristics, when caprylic acid ester is used in an ink of 1 to 15% by weight, preferably 4 to 10% by weight, drying prevention at the nozzle and shortening of the drying speed on the tablet surface are achieved. Becomes an area where
Note that caprylic acid esters are not expected to be used in excess of 0.5% by weight, since a general reduction in aqueous solution is 0.5% by weight and a sufficient reduction in surface tension is obtained. However, when used excessively, drying control at the nozzle and shortening of the drying speed on the tablet surface were obtained.
In the present invention, caprylic acid ester is preferably monocaprylic acid decaglycerin, that is, monoester obtained by adding caprylic acid to glycerin decamer.
The caprylic acid ester is preferably one having an HLB of 15-17.
As the amount used, 1 to 15% by weight sufficiently improves the characteristics before addition, and the effects of preventing drying of the nozzle, fixing on the tablet surface, and drying are remarkable.

<Ink formulation>
In the above, the suitable range of the blending ratio of each raw material was individually mentioned, but the blending of the entire ink is as described above, assuming that the caprylic acid ester is in a ratio of 1 to 15% by weight. The pigment is 0.1 to 5% by weight, the polyvinyl pyrrolidone is 0.01 to 5% by weight, the ethanol is 0 to 40% by weight, the water is 10 to 80% by weight, and the propylene glycol is 0 to 55% by weight. It is preferable that the ratio is sufficient in order to sufficiently exhibit the effects of the present invention. The pigment is 0.02 to 3% by weight, the polyvinyl pyrrolidone is 0.05 to 1.2% by weight, and the ethanol is 0 to 30%. More preferably, the proportion is 20% by weight, 20 to 70% by weight of the water, and 10 to 50% by weight of the propylene glycol.

[Production of inkjet ink]
A method for producing the inkjet ink according to the present invention is not particularly limited. For example, first, PVP is dissolved in a first solvent mainly composed of water to form a resin solution, and a pigment is mixed into the resin solution. It is preferable to use a mill base and to disperse this into a dispersion by using a medialess disperser with less contamination or a media disperser with coating (lining).
By this dispersion, the ink can be produced by finely dispersing the pigment, adjusting the viscosity, and filtering coarse particles.
The addition timing of caprylic acid ester is not particularly limited, but it is preferable to add it when preparing ink from the dispersion.
In dispersion, since PVP also serves as a dispersant, it can be dispersed without the addition of other dispersants. Furthermore, various dispersions for food such as sorbitan fatty acid ester, glycerin fatty acid ester, sucrose fatty acid ester, etc. Dispersion can also be carried out in combination with an agent.

[Printing method]
The printing method using the inkjet ink of the present invention is not particularly limited, but when the inkjet ink is ejected from a DOD inkjet apparatus and the inkjet ink is attached to a printing target, printing is performed. A printing method is preferred in which the inkjet ink discharged from the inkjet device is circulated between the inkjet head of the DOD inkjet device and the ink tank housing.

As a conventional DOD type ink, an ink containing a large amount of alcohol such as ethanol is generally too fast to be dried at a nozzle and cannot stably discharge.
Therefore, even when ethanol is contained, the limit is about 5% by weight.
In the above-described printing method of the present invention, the ink is circulated between the nozzle portion and the ink supply portion, and by providing a method such as a slight vibration at the nozzle portion when ejection is not performed, By using in combination, it is possible to ensure stable continuous ejection even with ink imparted with drying properties.
In this way, an ink containing a large amount of a volatile ethanol component can be used to cope with improving the drying property on the tablet surface.
Therefore, in the ink-jet ink of the present invention, printing can be performed without any problems even when the solvent composition is 0 to 80 parts by weight of ethanol and 0 to 150 parts by weight of propylene glycol with respect to 100 parts by weight of water. By using a predetermined amount of caprylic acid ester, it becomes a printing method corresponding to a high transport speed even on easily disintegrating tablet surfaces and the like.
Also in this high-speed printing method, it is possible to prevent ink transfer and contamination to the transport system, and ink transfer and peeling from rubbing between tablets.

In order to prevent a change in ejection amount due to a change in viscosity due to a temperature change in the environment, in order to achieve a stable printing method, when circulating the inkjet ink between the inkjet head and the ink tank housing, the circulating ink It is preferable to adjust the temperature.
In order to ensure stable ejection at high speed, it is preferable to defoam the circulating ink when the ink-jet ink is circulated between the ink-jet head and the ink tank housing.
Further, for stable ejection at high speed, it is preferable to provide a deaeration device in order to prevent and stabilize dot non-ejection. When the ink-jet ink is circulated between the ink-jet head and the ink tank housing, the circulating ink is preferably degassed.
In addition, in order to handle edible materials, when using ink with a high proportion of water, the ink-jet ink can be sterilized by a sterilization mechanism when circulating between the ink-jet head and the ink tank housing. preferable.
As such a sterilization mechanism, a deep ultraviolet LED, a sterilization filter, or a sterilization mechanism that is an instantaneous heating heater is used.

Furthermore, in the printing method of the present invention, a plurality of inkjet heads are provided for continuous long-term operation, and at least one inkjet head is operating for printing (provided for ink ejection). It is preferable that at least one other inkjet head is kept in a standby state in a state suitable for ejection of inkjet ink.
For this purpose, for example, while at least one inkjet head is operating for printing, at least one other inkjet head is moved to a predetermined area (hereinafter referred to as “maintenance area” or “maintenance station”). It is sufficient to make it stand by. Then, the ink jet head that is driven for printing and the ink jet head that is waiting in the maintenance area are exchanged at predetermined intervals.
The inkjet head that has been waiting in the maintenance area (maintenance station) can be kept in a state suitable for ejection of inkjet ink by performing flushing, wiping, precursor, and the like.
Here, flushing is to remove deposits in the vicinity of the nozzles of the inkjet head and eliminate the bending of the flight. Forcibly ejecting ink from all nozzles of the head. Wiping is the nozzle This refers to wiping off dust and splashed ink adhering to the ink. Further, the term “precursor” means that the ink meniscus is vibrated by generating a slight vibration that does not eject ink from the nozzles of the inkjet head.
The process at such a maintenance station is particularly effective in an ink composition that exhibits ink drying properties. The intervals between the flushing, wiping, precursor, and the like at the maintenance station must also correspond to the allowable value of the ink drying property.

  The printing method of the present invention can be suitably used with a tablet as an object to be printed.

  Examples of the present invention will be described below. The present invention is not construed as being limited to the description of the following examples.

In the following examples, a PVP solution was prepared, then a dispersion was prepared using the PVP solution, and then an inkjet ink was prepared using the dispersion.
Therefore, first, the preparation of the PVP solution and the dispersion used in the examples are described, and then the preparation of each inkjet ink of the examples is described.
Further, a comparative example will be described following the description of the examples. In this comparative example, a dispersion was produced, and then an inkjet ink was produced using the dispersion.
Therefore, in the description of the comparative example, first, the preparation of the dispersion used in the comparative example is described, and then the preparation of each inkjet ink of the comparative example is described.
Then, evaluation and consideration about the physical property of each ink and printing performance are shown.

[Preparation of PVP solution used in Examples]
<Preparation of PVP solution (1)>
In 29.4 parts by weight of purified water, 0.6 part by weight of PVP (weight average molecular weight 25800, lead 2 ppm or less, aldehyde 500 ppm or less, 1-vinyl-2-pyrrolidone 10 ppm or less, hydrazine 1 ppm or less) is dissolved, and the PVP solution (1) was produced.

<Preparation of PVP solutions (2) to (7)>
Except for using the PVP with different weight average molecular weights (all satisfying the conditions of lead 2 ppm or less, aldehyde 500 ppm or less, 1-vinyl-2-pyrrolidone 10 ppm or less, hydrazine 1 ppm or less) and the formulation shown in Table 1 below. PVP solutions (2) to (7) were prepared in the same manner as in the preparation of the PVP solution (1).
In Table 1 below, the formulation of the PVP solution (1) is also shown. Moreover, the numerical value which shows prescription in a table | surface represents the weight part.

[Preparation of dispersion used in Examples]
<Preparation of Dispersion (1)>
A mill base was prepared by mixing 30 parts by weight of the PVP solution (1) with 2 parts by weight of Bincho charcoal made from swallow.
This mill base is made of glass beads (bead composition: SiO ₂ is 70 to 73 wt%, Al ₂ O ₃ is 1 to 3 wt%, Na ₂ O is 12 to 15 wt%, and K ₂ O is 0 to 1.5 wt%. %, CaO 7 to 12 wt%, MgO 1 to 4.5 wt%, bead particle size: φ0.3 to 0.5 mm (with distribution)) A dispersion (1) was prepared by carrying out dispersion treatment for 2 hours using a star mill LMZ06 manufactured by Ashizawa Finetech Co., Ltd., which was equipped with urethane lining.
In dispersion (1), the average particle diameter of Bincho charcoal, which is a pigment, was 0.37 μm.
Further, when the zirconium concentration of the dispersion (1) was measured with a high frequency inductively coupled plasma (ICP) emission spectrometer (Model ULTIMA2 manufactured by HORIBA, Ltd.), the zirconium content was 5 mg / kg or less for detection limit, millions of minutes When expressed in terms of percentage, it was 5 ppm or less.

<Preparation of dispersions (2) to (7)>
Dispersions (2) to (7) were prepared in the same manner as the dispersion (1) except that the additive components and addition amount were changed according to the formulation in Table 2 below.
The average particle diameters of the pigments in the dispersions (2) to (7) are as shown in Table 2 below.
Further, when the zirconium concentration of the dispersions (2) to (7) was measured in the same manner as the dispersion (1), the zirconium content was expressed in parts per million in a detection limit of 5 mg / kg or less. And 5 ppm or less.
In Table 2 below, the formulation of the dispersion (1) is also shown. Moreover, the numerical value which shows prescription in a table | surface represents the weight part.

[Example 1]
Dispersion (1) 32 parts by weight, propylene glycol 35 parts by weight, purified water 28 parts by weight, monocaprylic acid decaglycerin (HLB 16.1) 5 parts by weight were put into a glass beaker, using a stainless steel propeller. After stirring and mixing, the mixture was filtered through a filter having a filtration accuracy of 1 μm to produce an inkjet ink.
When the zirconium concentration of the ink-jet ink produced in Example 1 was measured with an ICP emission analyzer (Model ULTIMA2 manufactured by HORIBA, Ltd.), the zirconium content was the detection limit of 5 mg / kg or less, like the dispersion (1). It was 5 ppm or less in parts per million.

[Examples 2 to 17]
Ink jet inks of Examples 2 to 17 were produced in the same manner as in Example 1 except that the additive components and the addition amount were changed according to the formulation in Table 3 below.
Regarding the inkjet inks of Examples 2 to 17, when the concentration of zirconium was measured in the same manner as in Example 1, the zirconium content was 5 ppm or less of the detection limit.
In Table 3 below, the ink formulation of Example 1 is also shown. Moreover, the numerical value which shows prescription in a table | surface represents the weight part.

[Preparation of dispersion used in comparative example]
<Preparation of dispersions (1A) to (7A)>
Dispersions (1A) to (7A) were prepared in the same manner as the dispersion (1) except that the additive components and addition amount were changed according to the formulation in Table 4 below.
In addition, the numerical value which shows prescription in the table | surface represents the weight part.
Further, HPC (* 1) is one in which the viscosity of a 2% by weight HPC (hydroxypropylcellulose) aqueous solution is 2.5 mPa · s. HPC (* 2) is such that the viscosity of a 2 wt% HPC aqueous solution is 3.85 mPa · s. CMC is carboxymethylcellulose.

[Comparative Examples 1-7]
Ink jet inks of Comparative Examples 1 to 7 were produced in the same manner as in Example 1 except that the additive components and the addition amount were changed according to the formulation in Table 5 below.
In addition, the numerical value which shows prescription in the table | surface represents the weight part.
Further, HPC (* 1) is one in which the viscosity of a 2 wt% HPC aqueous solution is 2.5 mPa · s. HPC (* 2) is such that the viscosity of a 2 wt% HPC aqueous solution is 3.85 mPa · s. CMC is carboxymethylcellulose.

[Evaluation of physical properties of inks of Examples 1 to 17 and Comparative Examples 1 to 7]
The inkjet ink of each Example and Comparative Example was filled in a DOD type inkjet printer (HQ-MSI manufactured by Kishu Giken Kogyo Co., Ltd.), a printing test was continuously performed, and the performance was evaluated based on the printing test. The uncoated tablet is used for the printing target object at this time.
The results for Examples 1 to 17 are shown in Table 6 below, and the results for Comparative Examples 1 to 7 are shown in Table 7 below.

Here, the physical properties of the inks shown in Tables 6 and 7 are measured and evaluated as follows.
“Average particle diameter” was measured by using a particle size distribution meter (UPA type) manufactured by Nikkiso Co., Ltd. to measure the median diameter (d50) of the pigment in the inkjet ink.
“Viscosity” (20 ° C., mPa · s) was measured using a viscometer (EH cone type) manufactured by TOKI Sangyo Co., Ltd.
The “redispersibility” was evaluated by whether or not the ink-jet ink left for 24 hours or more after production was shaken by human hands 20 times and filtered, and the pigment remained on the filter paper.
For “smudge”, the printed tablet surface was visually evaluated.
“Fixability (peeling)” means that when the object to be printed is a pseudo tablet (plain tablet), printing is performed on the tablet using the inkjet ink prepared in each example, and the printed part is rubbed with a cotton swab. It confirmed by the presence or absence of peeling.
“Visibility” was evaluated by visually observing the printed matter and distinguishing characters.
For “rubbing”, the presence or absence of peeling by rubbing tablets was evaluated.
In “transfer”, the tablet was brought into contact with the printing surface immediately after printing to confirm whether or not to transfer. Further, immediately after printing, the ink was contacted with a bristle brush to confirm ink adhesion.
“45 ° C. environmental printing performance” was evaluated for continuous discharge performance and printing performance when a printing test was performed with an ink jet printer in an environmental chamber maintained at a room temperature of 45 ° C.
“5 ° C. environmental printing performance” was evaluated for continuous discharge performance and printing performance when a printing test was performed with an ink jet printer in an environmental chamber maintained at a room temperature of 5 ° C.
“Continuous ejection properties” were determined by the presence or absence of nozzle clogging, printing failure, font abnormality, and the like.
“Initial dots without a circulation mechanism” was confirmed by the presence or absence of non-ejection in the printing state in the first printing after being left for 1 hour.
The “drying property” was evaluated based on the presence or absence of transfer by bringing a hair brush into contact with the printing surface immediately after printing at the timing set to the number of seconds immediately after printing.
The criteria for determination are as follows.
◎ is very good ○ is good △ is slightly inferior to good products.
X is clearly defective.
― Is not evaluated.

[Consideration of the above evaluation results]
In the above test, it can be said that all the examples showed good printing performance in general. In addition, although the printing test was similarly performed on OD tablet and FC tablet, both showed good printing.
None of the inks of the examples detected zirconium contamination in the dispersion. Further, the ink had good resolvability without ink re-dispersibility and bleeding.
A printed product with good visibility without rubbing or transferring in printing with tablets could be produced.
It should be noted that the viscosity can be adjusted in a wide range from the weight average molecular weight of PVP, and there was no problem of fixing property or transfer even when the amount used exceeded 1% by weight. Affinity with the tablet surface was observed. Moreover, since it was the usage-amount of PVP in such a small amount, the environmental test of the temperature change and the continuous test also showed favorable discharge property.
By using 1-15 parts by weight of caprylic acid ester, continuous ejection is stable for a long time, and it exhibits good drying properties on the tablet surface, which also causes transfer of undried ink in the transport system. There wasn't. Also, even in the first printing after being left for 1 hour, the initial dots were not ejected, and printing blurring did not occur.

The ink-jet ink of Comparative Example 1 had good redispersibility in ink when the solvent was not ethanol but water alone. However, it has a composition with a large amount of purified water and is weakly fixed on the tablet surface. In the DOD printer, the nozzles were dried too quickly, resulting in ejection failure.
In the inkjet ink of Comparative Example 2, since CMC and ethanol were also dissolved in the dispersion (2A), the state of dispersion of iron sesquioxide in the ink was not good (redispersibility). Measurement was not possible. It could not be put into the printer.
Since the inkjet inks of Comparative Examples 3 and 4 do not use caprylic acid ester and use decagrin monomyristic acid, the continuous ejection from the nozzle is not stable, and the initial printing after leaving for 1 hour is initial. Dots caused ejection failure and print fading. Also, the printing state with tablets was not good, and the stains due to transfer and rubbing were conspicuous. Not suitable for DOD printer.
The inkjet ink of Comparative Example 5 is a dispersion (5A) and does not use purified water at all, and edible red No. 40 aluminum lake is dispersed, so the redispersibility with the ink is poor and the average particle size cannot be measured. It was.
In the inkjet ink of Comparative Example 6, although dispersion of the dispersion (6A) proceeded, stable ejection was still not possible.
In the inkjet ink of Comparative Example 7, dispersion of the dispersion (7A) proceeded, but when left for 24 hours, it agglomerated and almost all the pigment remained on the filter paper. This is because the dispersion treatment was performed only with caprylic acid ester. Therefore, print evaluation and discharge evaluation were not performed.

Example 18
The inkjet ink produced in the said Examples 1-17 was filled in the DOD type inkjet apparatus, and the continuous printing was implemented.
The used DOD type ink jet apparatus has an ink circulation path between the ink jet head and the ink tank housing and in the ink jet head (circulation type DOD).
By using an ink jet apparatus having such a circulation mechanism, ink retention and pigment settling were eliminated in the ink jet head, and stable ejection for a long time and high-definition printing were obtained. The ink circulation path is provided with a heating means and a heat dissipation means, and by using such a temperature adjustment mechanism, it is possible to eliminate changes in the environmental temperature, and changes in the ink temperature in the operating state. Stable ejection and high-definition printing could be continued.

Example 19
The inkjet ink produced in Examples 1 to 17 was filled into a circulation type DOD, and continuous printing was performed.
In Example 19, when the ink-jet ink was circulated between the ink-jet head and the ink tank housing, the circulating ink was degassed and degassed.
Specifically, a degassing mechanism using a cartridge-like hollow fiber and a defoaming mechanism using a porous member were attached to the circulation path.
As a result, even when bubbles are generated due to a change in ink pressure, vibrations due to ink flow, and bubbles due to external vibrations, the degassing mechanism and the defoaming mechanism cause gas or bubbles in the inkjet ink. Can be removed, and high-speed printing can be continued stably.

Example 20
In order to print on a printing object with an inkjet apparatus using the inkjet ink produced in the said Examples 1-17, two circulation type DOD inkjet heads were installed.
While the inkjet device is in operation and one of the above two units is printing on an object to be printed, the other inkjet head is placed on standby at the maintenance station, and the precursor, flushing, and wiping are kept constant during standby. Performed at intervals.
And, by changing the ink jet head used for printing and the ink jet head waiting for the maintenance station among the two ink jet heads every predetermined time, further stable ejection and printing can be continued for a long time. I was able to.
Also, both printing accuracy and printing quality were good.

Example 21
The inkjet ink produced in the said Examples 1-17 was filled in the DOD type inkjet apparatus, and the continuous printing was implemented.
The used DOD type ink jet apparatus has an ink circulation path between the ink jet head and the ink tank housing and in the ink jet head (circulation type DOD).
A sterilization mechanism using deep ultraviolet LEDs was provided in the ink flow path portion of such a circulation mechanism to sterilize general live fungi in the ink circulation.
By providing a sterilization mechanism in this ink circulation path, it is possible to prevent the growth of bacteria without using a sterilizing agent, and the hygiene of the oral ink is ensured.

Claims (19)

An edible pigment, polyvinylpyrrolidone, water, and caprylic acid ester having a structure in which caprylic acid is added to glycerin or a glycerin polymer ,
The content ratio of the caprylic acid ester is 1 to 15% by weight,
Inkjet ink.   The inkjet ink according to claim 1, wherein the polyvinyl pyrrolidone has a weight average molecular weight of 5,000 to 100,000.   The inkjet ink according to claim 1 or 2, wherein the pigment is at least one selected from the group consisting of titanium oxide, iron oxide, carbon powder pigment, tar-based pigment aluminum lake, and squid pigment.   The inkjet ink according to any one of claims 1 to 3, further comprising propylene glycol.   The pigment is contained in a proportion of 0.1 to 5% by weight, the polyvinyl pyrrolidone is 0.01 to 5% by weight, the water is 10 to 80% by weight, and propylene glycol is 0 to 40% by weight. The inkjet ink in any one of 1-4.   The inkjet ink according to any one of claims 1 to 5, wherein the caprylic acid ester is monocaprylic acid decaglycerin.   The inkjet ink according to any one of claims 1 to 6, which is used for display on a capsule or tablet surface.   The inkjet ink according to any one of claims 1 to 7, wherein the polyvinyl pyrrolidone satisfies the following characteristics: lead 2 ppm or less, aldehyde 500 ppm or less, 1-vinyl-2-pyrrolidone 10 ppm or less, and hydrazine 1 ppm or less. .   When the inkjet ink according to any one of claims 1 to 8 is ejected from a drop-on-demand inkjet apparatus and the inkjet ink is attached to a printing target and printed, the inkjet ink is ejected from the drop-on-demand inkjet apparatus. A printing method, wherein the ink-jet ink is circulated between an ink-jet head of the drop-on-demand ink-jet apparatus and an ink tank housing.   The printing method according to claim 9, wherein the object to be printed is a tablet.   The printing method according to claim 9 or 10, wherein the circulating ink is degassed when the inkjet ink is circulated between the inkjet head and an ink tank casing.   The printing method according to claim 9, wherein the circulating ink is defoamed when the inkjet ink is circulated between the inkjet head and an ink tank housing.   The printing method according to claim 9, wherein the temperature of the circulating ink is adjusted when the inkjet ink is circulated between the inkjet head and the ink tank housing.   As the drop-on-demand ink jet apparatus, one having at least two ink jet heads is used, and at least one of the ink jet heads is suitable for ejecting ink jet ink while at least one of the ink jet heads is suitable for ejecting ink jet ink. The printing method according to claim 9, wherein the printing method is kept in a standby state.   The printing method according to any one of claims 9 to 14, wherein a fine vibration is applied to a nozzle that does not eject ink within a predetermined time to prevent the nozzle from being blocked at a constant interval.   The printing method according to claim 9, wherein flushing is performed to maintain at least one of the inkjet heads in a state suitable for ejection of inkjet ink.   The printing method according to claim 9, wherein wiping is performed to maintain at least one of the inkjet heads in a state suitable for ejection of inkjet ink.   18. When the ink-jet ink is circulated between the ink-jet head and the ink tank housing, the ink-jet ink is sterilized by a sterilization mechanism that is a deep ultraviolet LED, a sterilization filter, or an instantaneous heating heater. Printing method.   The printing method according to claim 9, wherein the inkjet ink has a zirconium concentration of 50 ppm or less.