JP7016244B2 - Inkjet ink - Google Patents

Description

The present invention relates to an inkjet ink suitable for directly printing, for example, characters or symbols for identification on the surface of a solid pharmaceutical product such as a tablet, which is taken as a pharmaceutical product or the like.

Techniques for printing directly on the surface of tablets, capsules, and other solid formulations taken as pharmaceuticals using inkjet ink are becoming widespread.
As the inkjet ink for printing on the surface of a solid preparation, a water-based inkjet ink containing a colorant such as an edible dye and water is usually used. It is also considered to add a fatty acid ester that can be used for foods, such as sorbitan fatty acid ester, as a surfactant to adjust the surface tension, wettability, etc. of the water-based inkjet ink. (Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-169301

However, according to the study of the inventor, the inkjet ink described in Patent Document 1 has a problem that the nozzle of the inkjet printer is clogged at the printing decap time and the ink is easily blurred when printing is restarted.
The decap time is the inkjet ink in the nozzles provided in the on-demand inkjet printer, which is in a standby state in which ink droplets are not ejected according to the print pattern during intermittent printing. Refers to the time being printed.

Inkjet printers usually have a function to close (cap) the nozzles so that the inkjet ink in the nozzles will not dry out due to exposure to the outside air and cause clogging when the operation is stopped. It is generally given.
However, since the cap is released at the time of printing, the nozzle that is in the standby state at the time of intermittent printing remains in a state in which the nozzle is not closed (decap state) until the next ink droplet is ejected. .. During that time, the inkjet ink in the nozzle is continuously exposed to the outside air, so that the longer the time, that is, the decap time, the more likely the nozzle is to be clogged.

In the following, the characteristic that the nozzle is less likely to be clogged during the decap time will be evaluated as the quality of "intermittent printability". The longer the decap time that does not cause clogging or the like, the better the intermittent printability of the inkjet ink can be evaluated.
Further, the inkjet ink described in Patent Document 1 has a problem that paddling is likely to occur.

Paddling is ink jet ink that separates from the ink droplets and remains on the nozzle side when the ink droplets are ejected through the nozzles, and spreads around the nozzle outlet of the nozzle plate on which the nozzles are formed. It is a phenomenon that forms a pool (paddle).
When paddling occurs around the outlet of the nozzle, the ejection of ink droplets from the nozzle is hindered, the trajectory of the ejected ink droplets changes, or the ink droplets of a predetermined volume to be ejected are not ejected. , Ink droplets are not ejected at all, and ejection defects are likely to occur. Then, as a result of these ejection defects, good printing may not be possible.

In the following, the characteristic that ink droplet ejection failure due to paddling is unlikely to occur when printing is repeated will be evaluated as the quality of "continuous printability". It can be evaluated that the inkjet ink has better continuous printability as the number of prints that can be continuously printed without causing ejection failure due to paddling increases.
An object of the present invention is to provide an inkjet ink that can be used for printing on the surface of a solid pharmaceutical product and has excellent intermittent printability and continuous printability as compared with conventional ones. ..

The present invention includes food dyes as colorants , surfactants, and water, wherein the surfactants are:
(A) Polyoxyethylene polyoxypropylene glycol and
(B) Two types of polyoxyethylene sorbitan fatty acid ester, which are inkjet inks used for printing directly on the surface of a solid pharmaceutical product .

According to the present invention, it is possible to provide an inkjet ink that can be used for printing on the surface of a solid pharmaceutical product and that is superior in intermittent printability and continuous printability as compared with conventional ones.

As described above, the present invention contains an edible dye as a colorant , a surfactant, and water, and the surfactant is a substance.
(A) Polyoxyethylene polyoxypropylene glycol (hereinafter sometimes abbreviated as "surfactant A"), and.
(B) Polyoxyethylene sorbitan fatty acid ester (hereinafter, may be abbreviated as "surfactant B")
These are two types of inkjet inks, which are used for printing directly on the surface of a solid pharmaceutical product .

Both of the above two types of surfactants (A) and (B) are known as surfactants that can be used for foods and the like.
According to the study of the inventor, the surfactant B is excellent in the function of improving the intermittent printability of the inkjet ink.
During the standby period when the ink droplets are not ejected, a meniscus is formed at the gas-liquid interface between the inkjet ink and the outside air in the nozzle of the inkjet printer, and the inkjet ink is in a stationary state.

However, when the decap time becomes long, the concentration of the inkjet ink increases due to drying, the surface tension changes, and the wettability of the inkjet ink with respect to the inner surface of the nozzle and the contact angle of the meniscus associated therewith change. As a result, it may not be possible to maintain a stable meniscus in the nozzle. In addition, as the density increases, the viscosity of the inkjet ink may increase or precipitates may easily form.

Then, these causes clogging of the nozzle or the like during the decap time, and causes faintness or the like when printing is restarted.
In addition, the drying of the inkjet ink progresses during the decap time, the position where the meniscus is formed gradually recedes in the nozzle, and the ejection of the inkjet ink is delayed when printing is restarted, which is also a cause of fading. Become.

On the other hand, since the surfactant B has a low surface tension and a high wettability, it is oriented at the gas-liquid interface forming the meniscus to suppress the drying of the inkjet ink and stabilize the wettability of the inkjet ink. It works to do. Therefore, a stable meniscus can be maintained at a predetermined position in the nozzle.
Moreover, the surfactant B forms micelles by surrounding the solid content contained in the inkjet ink, such as a colorant such as an edible dye and a head residue generated when the inkjet ink is repeatedly ejected. It also functions to suppress the precipitation of these solids in the inkjet ink.

Therefore, by using the surfactant B as the surfactant, the intermittent printability of the inkjet ink can be improved.
However, since the surfactant B has high wettability as described above, when it is used alone, the inkjet ink wets and spreads around the nozzle outlet of the nozzle plate, and paddling is likely to occur. .. Then, the continuous printability of the inkjet ink may be deteriorated.

On the other hand, since the surfactant A has a high surface tension and a low wettability, it does not have the above-mentioned function of improving the intermittent printability. However, since the surfactant A has a high surface tension and a low wettability, it has a function of suppressing the ink jet ink separated from the ink droplets and remaining on the nozzle side from spreading on the surface of the nozzle plate and causing paddling. Are better.
Moreover, the surfactant A is also excellent in compatibility with the surfactant B.

If the compatibility of the two types of surfactants used in combination is low, the concentration of the inkjet ink tends to increase, and the above-mentioned solid content tends to precipitate, so that the intermittent printability of the inkjet ink deteriorates and storage stability is achieved. The sex may decrease.
However, as described above, the surfactant A is excellent in compatibility with the surfactant B. Therefore, by using both of them as a surfactant in combination, the wettability is adjusted to an appropriate range while maintaining good intermittent printability without deteriorating storage stability, and paddling is expanded by surface tension. Can be adjusted to improve continuous printability.

Therefore, according to the present invention, it is possible to provide an inkjet ink that can be used for printing on the surface of a solid pharmaceutical product and that is superior in intermittent printability and continuous printability as compared with conventional ones. ..
Further, the surfactant B has a high foaming property and is easily foamed. Therefore, in particular, when used in a so-called thermal inkjet printer, which heats inkjet ink to generate bubbles and ejects the increased volume of inkjet ink as ink droplets from the nozzle, ejection failure due to bubble biting Is likely to occur. On the other hand, since the surfactant A has a defoaming property, by using the surfactant A together with the surfactant B, it is possible to suppress the occurrence of ejection failure due to foam biting.

<Surfactant A>
As the surfactant A, for example, the formula (1):
HO (C ₂ H ₄ O) _a- (C ₃ H ₆ O) _b- (C ₂ H ₄ O) _c H (1)
Examples thereof include polyoxyethylene polyoxypropylene glycol, which is a condensate of polyoxyethylene and polyoxypropylene represented by the above-mentioned function and has the above-mentioned functions.

Of these, polyoxyethylene polyoxypropylene glycol, which is liquid at 15 to 25 ° C., is preferable in terms of the effect of improving the continuous printability of the inkjet ink.
Examples of polyoxyethylene polyoxypropylene glycol that are liquid in the above temperature range include, for example.
E. represented by a + c in equation (1). O. The number of repeating units of (ethylene oxide) is 3 or more, 200 or less, particularly 170 or less, and P.I. O. The number of repeating units of (propylene oxide) is 15 or more, 70 or less, especially 40 or less,
Examples include compounds that are.

Specific examples of the polyoxyethylene polyoxypropylene glycol include, but are not limited to, one or more of the following various compounds.
Among the New Pole (registered trademark) PE series manufactured by Sanyo Kasei Kogyo Co., Ltd., PE-61 [a + c = 5, b = 30, a + b + c = 35, cloud point (1 mass% water diluted solution): 24 ° C.], PE -62 [a + c = 10, b = 30, a + b + c = 40, cloud point (1 mass% aqueous diluted solution): 30 ° C.], PE-71 [a + c = 5, b = 35, a + b + c = 40, cloud point (1) Mass% water diluted solution): 20 ° C.], PE-74 [a + c = 30, b = 35, a + b + c = 65, cloud point (1 mass% water diluted solution): 56 ° C.], PE-75 [a + c = 48, b = 35, a + b + c = 83, cloud point (1 mass% aqueous diluted solution): 69 ° C.].

ADEKA (registered trademark) Pluronic L series manufactured by ADEKA Corporation L-31 [a + c = 3, b = 17, a + b + c = 20, cloud point: 39 ° C.], F-68 [a + c = of the Pluronic F series 160, b = 30, a + b + c = 190, cloud point: over 100 ° C], F-87 [a + c = 120, b = 40, a + b + c = 160, cloud point: over 100 ° C], F-127 [a + c = 196, b = 67, a + b + c = 263, cloud point: over 100 ° C.], P-85 [a + c = 54, b = 39, a + b + c = 93, cloud point: 75 ° C.], P-123 [a + c = 42, b = 67, a + b + c = 109].

P188 [a + c = 160, b = 30, a + b + c = 190], P407 [a + c = 196, b = 67, a + b + c = 263] of the BASF Japan Co., Ltd. = 160, b = 30, a + b + c = 190, cloud point: over 100 ° C.], F127 [a + c = 196, b = 67, a + b + c = 263].

Among them, a compound having a + b + c in the formula (1) of 40 or less, particularly 35 or less is preferable in terms of the effect of improving continuous printability .
<Surfactant B>
As the surfactant B, various polyoxyethylene sorbitan fatty acid esters having a sorbitan ester / ethylene oxide addition type structure and having the above-mentioned functions can be used. Among them, polyoxyethylene sorbitan fatty acid ester having an HLB of 10 or more and 20 or less is preferable in terms of the effect of improving the intermittent printability of the inkjet ink.
Specific examples of the polyoxyethylene sorbitan fatty acid ester include, but are not limited to, one or more of the following various compounds.

Of the Emazole® series manufactured by Kao Corporation, L-120V [polyoxyethylene sorbitan monolaurate, HLB: 16.7], O-120V [polyoxyethylene sorbitan monooleate, HLB: 15], S-120V [Polyoxyethylene sorbitan monostearate, HLB: 14.9].
Among the nonion (trade name) series manufactured by Nichiyu Co., Ltd., LT-221 [polyoxyethylene sorbitan monolaurate, HLB: 16.7], LT-280 [polyoxyethylene sorbitan monolaurate, HLB: 19. 0], ST-221 [Polyoxyethylene sorbitan monostearate, HLB: 15.7], OT-221 [Polyoxyethylene sorbitan monooleate, HLB : 15.7], OT-521 [Polyoxyethylene sorbitan triole] Ate, HLB: 10.8].

Of the Wilsurf (registered trademark) series manufactured by NOF CORPORATION, TF-20 [polyoxyethylene sorbitan monolaurate, HLB: 16.7], TF-60 [polyoxyethylene sorbitan monostearate, HLB: 15] .7], TF-80 [Polyoxyethylene sorbitan monooleate, HLB: 15.7].
Among them, a compound having an HLB of 14 or more, particularly 15 or more, is preferable in terms of the effect of improving the intermittent printability.

As the surfactant, only two types of the above-mentioned surfactant A and the surfactant B (including the case where two or more kinds are used in combination for each surfactant) are used.
<Content, content ratio>
The content of the surfactant A is preferably 0.01% by mass or more, particularly 0.08% by mass or more, and more preferably 2% by mass or less, particularly 1.6% by mass or less , based on the total amount of the inkjet ink. Is preferable.

If the content of the surfactant A is less than this range, the wettability of the inkjet ink can be adjusted to an appropriate range by using it in combination with the above-mentioned surfactant B, and the effect of improving the continuous printability and bubbles can be obtained. In some cases, the effect of suppressing the occurrence of ejection defects due to biting may not be sufficiently obtained.
On the other hand, when the content of the surfactant A exceeds the above range, the surface tension of the inkjet ink is high and the wettability is too low, so that the inkjet ink cannot be smoothly supplied to the nozzle of the inkjet printer. Poor ejection may occur.

On the other hand, by setting the content of the surfactant A in the above range, the wettability of the inkjet ink is adjusted to an appropriate range, and continuous printing is performed without causing supply failure or ejection failure due to bubble biting. It is possible to improve the sex.
The content of the surfactant B is preferably 0.01% by mass or more, particularly 0.08% by mass or more, and more preferably 2% by mass or less, particularly 1.6% by mass or less , based on the total amount of the inkjet ink. Is preferable.

If the content of the surfactant B is less than this range, the above-mentioned effect of improving the intermittent printability may not be sufficiently obtained.
On the other hand, when the content of the surfactant B exceeds the above range, the surface tension of the inkjet ink is low, the wettability becomes too high, and the continuous printability may deteriorate as described above. In addition, the inkjet ink may leak from the tip of the nozzle without forming a meniscus in the nozzle. Furthermore, there are cases where ejection defects due to foam biting are likely to occur.

On the other hand, by setting the content of the surfactant B in the above range, the wettability of the inkjet ink can be adjusted in an appropriate range, without causing ejection failure or leakage due to bubble biting, and continuous printability. Intermittent printability can be improved without causing a decrease in printing.
The content ratio of the surfactant A and the surfactant B is preferably 0.05 or more, particularly preferably 0.25 or more, and particularly preferably 20.0 or less, particularly 4.00 or less in terms of the mass ratio A / B. Is preferable. Further, considering that the intermittent printability is further improved when the inkjet ink contains a water-soluble organic solvent and a binder as described later, the mass ratio A / B is further 1 even in the above range. It is preferably .30 or less.

When the amount of surfactant A is less than this range, by using it in combination with surfactant B, the wettability of the inkjet ink can be adjusted to an appropriate range to improve continuous printability and ejection by bubble biting. The effect of suppressing the occurrence of defects may not be sufficiently obtained.
Further, since the amount of the surfactant B is relatively large, the surface tension of the inkjet ink is low, the wettability is too high, the continuous printability is deteriorated, and the meniscus is not formed in the nozzle, and the inkjet ink is not formed. May leak from the tip of the nozzle. In addition, ejection defects due to foam biting may be likely to occur.

Further, when the amount of the surfactant A is larger than the above range, the surface tension of the inkjet ink is high and the wettability is too low, so that the inkjet ink cannot be smoothly supplied to the nozzle of the inkjet printer, resulting in ejection failure. May occur.
In addition, the amount of the surfactant B may be relatively small, and the effect of improving the intermittent printability may not be sufficiently obtained.

On the other hand, by setting the mass ratio A / B of the surfactant A and the surfactant B to the above range, the wettability of the inkjet ink is adjusted to an appropriate range, and the supply failure or the ejection failure due to bubble biting is poor. It is possible to improve continuous printability and intermittent printability without causing leakage or the like.
The total content A + B of the surfactant A and the surfactant B is preferably 0.02% by mass or more, particularly 0.16% by mass or more, and particularly preferably 4% by mass or less, particularly 3. It is preferably 2% by mass or less .

When the total content is less than this range, the wettability of the inkjet ink due to the combined use of the surfactant A and the surfactant B is adjusted to an appropriate range without causing ejection defects or leakage. The effect of improving continuous printability and intermittent printability may not be sufficiently obtained.
Further, when the total content exceeds the above range, the compatibility between the two surfactants is lowered, the concentration of the inkjet ink is increased, and the solid content is likely to be precipitated. The continuous printability and intermittent printability of the inkjet ink may decrease, and the storage stability may decrease.

On the other hand, by setting the total content of the surfactant A and the surfactant B in the above range, the wettability of the inkjet ink can be adjusted to an appropriate range, resulting in poor supply or ejection failure due to bubble biting. Continuous printability and intermittent printability can be improved without causing leakage or the like.
<Colorant>
As the colorant, various colorants approved for use as food additives or pharmaceutical additives can be used. Examples of the colorant include one or more of synthetic or natural food dyes and the like.

Among these, as the synthetic food coloring, for example, edible red No. 2, edible red No. 3, edible red No. 102, edible red 104, edible red 105, edible red 106, edible yellow No. 4, and edible yellow No. 5 , Edible Green No. 1, Edible Blue No. 1, Edible Blue No. 2, Edible Red No. 40, Edible Red No. 40 Aluminum Lake, Edible Red No. 3 Aluminum Lake, Edible Yellow No. 4 Aluminum Lake, Edible Blue No. 1 Aluminum Lake, Edible Blue No. 2 aluminum lake and the like can be mentioned.

Examples of natural food coloring include caramel pigment, tomato pigment, turmeric pigment, chlorophyll pigment, β-carotene pigment, palm oil carotene, marigold pigment, monascus pigment, capsicum pigment, monascus pigment, anato pigment, and rack pigment. Cochinil pigment, Monascus pigment, Beet red pigment, Red cabbage pigment, Purple potato pigment, Red daikon pigment, Grape bark pigment, Anthocyanin pigment, Perilla pigment, Elderberry pigment, Purple corn pigment, Cutinashi pigment, Cacao pigment, Kaki pigment, Kouryan Pigments, spirulina pigments, paprika pigments, squid pigments, riboflavin, riboflavin butyrate, riboflavin phosphate sodium, chlorophyll, copper chlorophyll and its metal salts (sodium salt, etc.), iron chlorophyll and its metal salts (sodium salt, etc.), etc. Can be mentioned.

The type and content of the colorant can be appropriately set according to the color taste, color density and the like.
<Water-soluble organic solvent>
Inkjet ink using only water as a solvent can be dried in a short time by heating or the like after printing. Therefore, the inkjet ink of the present invention may be composed using only water as a solvent.

However, when a water-soluble organic solvent is used in combination with water as the solvent, it is possible to impart quick-drying property to the inkjet ink and omit heating after printing.
Examples of the water-soluble organic solvent include alcohols having 3 to 4 carbon atoms such as ethanol, butanol, isopropyl alcohol and normal propyl alcohol, 2-ethoxyethanol (ethylene glycol monoethyl ether) and 2-methoxyethanol (ethylene glycol monomethyl). One kind or two or more kinds such as ethylene glycol ether such as ether) can be mentioned. In particular, ethanol is preferable.

The content of the water-soluble organic solvent is preferably 10% by mass or more, and preferably 20% by mass or less of the total amount of the inkjet ink.
<Binder>
Inkjet ink containing a water-soluble organic solvent has improved quick-drying property, so that it is easy to dry even during standby when ink droplets are not ejected, and intermittent printability may be deteriorated.

According to the study of the inventor, in order to improve the intermittent printability of the inkjet ink containing a water-soluble organic solvent, it is preferable to add a binder that can be used for foods and the like. Examples of such a binder include polysaccharides, disaccharides, monosaccharides and the like, and polysaccharides are particularly preferable.
Polysaccharides have moderate solubility in both water and water-soluble organic solvents, which are not too strong, and are dissolved in inkjet ink from the beginning without any margin of solubility. ing.

In this state, when the ink jet ink in the nozzle stands still and the meniscus is formed in the standby state, the polysaccharides are rapidly deposited on the liquid surface of the formed meniscus to form a very thin film. As a result, the drying of the inkjet ink is suppressed, and the inkjet ink inside the film is maintained in a low viscosity state in which it can be ejected during the standby state.
Moreover, since the polysaccharide is a hard and brittle component having almost no film-forming property, the thin film made of the polysaccharide is easily broken by the ejection pressure applied to the inkjet ink in the nozzle at the next ejection. Therefore, a predetermined volume of ink droplets can be ejected immediately after the end of the standby state, and as a result, intermittent printability can be improved.

Examples of the polysaccharide include one or more of dextrin, starch, cellulose, pectin, carrageenan and the like, and dextrin is particularly preferable . As dextrins, among the broadly defined dextrins produced by hydrolyzing starch, narrowly defined dextrins (DE≤10), maltodextrins (10 <DE <20), and maltodextrins classified by dextrose equivalent (DE), and One kind or two or more kinds such as starch candy (DE ≧ 20) can be used.

Examples of other binders include disaccharides such as maltose, sucrose, and trehalose, monosaccharides such as mannitol, glucose, fructose, and galactose, or oligotooth, which is a linear oligosaccharide containing maltotriose as a main component. And so on.
The content of the binder such as polysaccharide is preferably 0.1% by mass or more and preferably 1% by mass or less of the total amount of the inkjet ink.

The inkjet ink of the present invention is prepared by further adding water (for example, ultrapure water) to each of the above components to make the total amount 100% by mass.
The inkjet ink of the present invention containing each of the above components can be suitably used for the above-mentioned on-demand type inkjet printer. In particular, it can be used in an on-demand thermal inkjet printer to print directly on the surface of tablets, capsules and other solid formulations.

Hereinafter, the present invention will be described based on Examples and Comparative Examples, but the configuration of the present invention is not necessarily limited to these Examples and Comparative Examples.
<Example 1>
After blending each of the following components, an inkjet ink was prepared by filtering using a 5 μm membrane filter.

Each component in the table is as follows.
Colorant: Edible Red No. 102 Surfactant A: Polyoxyethylene polyoxypropylene glycol having a + c = 5, b = 30, a + b + c = 35 in the formula (1) [The above, manufactured by Sanyo Chemical Industries, Ltd. New Pole PE-61, cloud point (1% by mass water diluted solution): 24 ° C]
Surfactant B: Polyoxyethylene sorbitan monolaurate [above, Emazole L-120V manufactured by Kao Corporation, HLB: 16.7]
The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Example 2>
The inkjet ink was prepared in the same manner as in Example 1 except that the content of the surfactant B in the total amount of the inkjet ink was 1.0% by mass and the content of the ultrapure water was 96.9% by mass. .. The mass ratio of the surfactant A and the surfactant B was A / B = 0.1, and the total content was A + B = 1.1% by mass.

<Example 3>
Except for the fact that the content of surfactant A in the total amount of inkjet ink was 1.5% by mass, the content of surfactant B was 1.5% by mass, and the content of ultrapure water was 95.0% by mass. Prepared an inkjet ink in the same manner as in Example 1. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 3.0% by mass.

<Example 4>
As the surfactant A, polyoxyethylene polyoxypropylene glycol having a + c = 5, b = 35, a + b + c = 40 in the formula (1) [the above-mentioned New Pole PE-71 manufactured by Sanyo Chemical Industries, Ltd. , Cloud point (1 mass% aqueous diluted solution): 20 ° C.] was blended, and an inkjet ink was prepared in the same manner as in Example 1. The content of the surfactant A was 0.1% by mass in the total amount of the inkjet ink. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Example 5>
Inkjet in the same manner as in Example 1 except that polyoxyethylene sorbitan monostearate [emazole S-120V manufactured by Kao Corporation, HLB: 14.9] described above was blended as the surfactant B. Ink was prepared. The content of the surfactant B was 0.1% by mass in the total amount of the inkjet ink. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Comparative Example 1>
An inkjet ink was prepared in the same manner as in Example 1 except that the content of the surfactant A in the total amount of the inkjet ink was 0.2% by mass and the surfactant B was not blended.
<Comparative Example 2>
An inkjet ink was prepared in the same manner as in Example 1 except that the surfactant A was not blended and the content of the surfactant B in the total amount of the inkjet ink was 0.2% by mass.

<Comparative Example 3>
Instead of the surfactant B, a sorbitan fatty acid ester, sorbitan monolaurate [Emazole L-10V manufactured by Kao Corporation, HLB: 8.6] (hereinafter referred to as "surfactant C") was blended. An inkjet ink was prepared in the same manner as in Example 1 except for the above. The content of the surfactant C was 0.1% by mass in the total amount of the inkjet ink.

<Comparative Example 4>
An inkjet ink was prepared in the same manner as in Example 1 except that only the same surfactant C as used in Comparative Example 3 was blended in place of the surfactant A and the surfactant B. The content of the surfactant C was set to 0.2% by mass in the total amount of the inkjet ink. This corresponds to a reproduction of the conventional inkjet ink described in Patent Document 1.

<Continuous printability test>
Using an on-demand thermal inkjet printer [Print Mail Wide Array manufactured by Videojet Co., Ltd.], the inkjet inks prepared in Examples and Comparative Examples were used to create a two-point handakuon on the surface of the tablet.゜ ”was printed continuously.

Then, the printing was visually observed, and the number of printing times in which printing was not chipped, crushed, scattered, etc. due to poor ejection of the inkjet ink was recorded, and the continuous printability was evaluated according to the following criteria.
◯: 1 million times or more △: 400,000 times or more, less than 1 million times ×: less than 400,000 times <Intermittent printability test>
Using the same inkjet printer used in the continuous printability evaluation, a 2-point handakuon "°" was printed on the surface of the tablet with the inkjet inks prepared in Examples and Comparative Examples for a predetermined time. After standing still in the decapped state, printing was performed again. Then, the standing time during which clear printing without blurring was possible was recorded, and the intermittent printability was evaluated according to the following criteria.

⊚: 100 minutes or more ◯: 65 minutes or more, less than 100 minutes Δ: 30 minutes or more, less than 65 minutes ×: less than 30 minutes The results of the above are shown in Tables 2 and 3.

From the results of Examples 1 to 5 and Comparative Examples 1 to 4 in Tables 2 and 3, as a surfactant, polyoxyethylene polyoxypropylene glycol (surfactant A) was used instead of the conventional sorbitan fatty acid ester. It was found that the combined use with the polyoxyethylene sorbitan fatty acid ester (surfactant B) can provide an inkjet ink having excellent intermittent printability and continuous printability.

From the results of Examples 1 to 3, in order to improve the above-mentioned characteristics, the contents of the surfactant A and the surfactant B are both 0.01% by mass or more of the total amount of the inkjet ink, particularly 0. It was found that it is preferably 8.08% by mass or more, preferably 2% by mass or less, and particularly preferably 1.6% by mass or less. The total content of the surfactant A and the surfactant B is preferably 0.02% by mass or more, particularly 0.16% by mass or more, and particularly 4% by mass or less, particularly 3) of the total amount of the inkjet ink. It was found that it is preferably 2% by mass or less.

From the results of Examples 1 and 4, as the polyoxyethylene polyoxypropylene glycol (surfactant A), a + b + c in the formula (1) is 40 or less, particularly 35 or less, in terms of the effect of improving the intermittent printability. It was found that the compound is preferable.
From the results of Examples 1 and 5, the polyoxyethylene sorbitan fatty acid ester (surfactant B) is preferably a compound having an HLB of 14 or more, particularly 15 or more, in terms of the effect of improving intermittent printability. understood.

<Examples 6 to 9>
The inkjet ink was prepared in the same manner as in Example 1 except that the contents of the surfactant A and the surfactant B and the mass ratio A / B in the total amount of the inkjet ink were set to the values shown in Table 4, respectively. did. The total content A + B of the surfactant A and the surfactant B was 0.2% by mass in each case.

The inkjet inks prepared in each example were subjected to the above-mentioned continuous printability test and intermittent printability test to evaluate their characteristics. The results are shown in Table 4 together with the results of Example 1.

From the results of Examples 1 and 6 to 9 in Table 4, the mass ratio A / B of the surfactant A and the surfactant B is 0.05 in consideration of improving both continuous printability and intermittent printability. As described above, it was found that the content is particularly preferably 0.25 or more, preferably 20.0 or less, and particularly preferably 4.00 or less.
<Example 10>
After blending each of the following components, an inkjet ink was prepared by filtering using a 5 μm membrane filter.

Each component in the table is as follows.
Colorant: Edible Red No. 102 Surfactant A: Polyoxyethylene polyoxypropylene glycol having a + c = 5, b = 30, a + b + c = 35 in the formula (1) [The above, manufactured by Sanyo Chemical Industries, Ltd. New Pole PE-61, cloud point (1% by mass water diluted solution): 24 ° C]
Surfactant B: Polyoxyethylene sorbitan monolaurate [above, Emazole L-120V manufactured by Kao Corporation, HLB: 16.7]
Polysaccharide: Powdered candy [K-SPD (registered trademark) manufactured by Showa Sangyo Co., Ltd., DE value: 25-29]
The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Example 11>
Inkjet inks were prepared in the same manner as in Example 10 except that the content of polysaccharides in the total amount of inkjet ink was 0.5% by mass and the content of ultrapure water was 79.3% by mass. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Example 12>
Inkjet inks were prepared in the same manner as in Example 10 except that the content of polysaccharides in the total amount of inkjet ink was 1.0% by mass and the content of ultrapure water was 78.8% by mass. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.2% by mass.

<Example 13>
Except for the fact that the content of surfactant A in the total amount of inkjet ink was 0.01% by mass, the content of surfactant B was 0.01% by mass, and the content of ultrapure water was 79.48% by mass. Prepared an inkjet ink in the same manner as in Example 11. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 0.02 mass%.

<Example 14>
Except for the fact that the content of surfactant A in the total amount of inkjet ink was 1.0% by mass, the content of surfactant B was 1.0% by mass, and the content of ultrapure water was 77.5% by mass. Prepared an inkjet ink in the same manner as in Example 11. The mass ratio of the surfactant A and the surfactant B was A / B = 1.0, and the total content was A + B = 2.0 mass%.

<Example 15>
Except for the fact that the content of surfactant A in the total amount of inkjet ink was 2.0% by mass, the content of surfactant B was 1.0% by mass, and the content of ultrapure water was 76.5% by mass. Prepared an inkjet ink in the same manner as in Example 11. The mass ratio of the surfactant A and the surfactant B was A / B = 2.0, and the total content was A + B = 3.0% by mass.

The inkjet inks prepared in each example were subjected to the above-mentioned continuous printability test and intermittent printability test to evaluate their characteristics. The results are shown in Table 6.

From the results of Examples 10 to 12 in Table 6, it was found that the intermittent printability can be improved by blending a polysaccharide in a system containing ethanol, which is a water-soluble organic solvent, together with water. Further, it was found that the content of the polysaccharide is preferably 0.1% by mass or more and preferably 1% by mass or less of the total amount of the inkjet ink.

From the results of Examples 11 and 13 to 15, the contents of the surfactant A and the surfactant B are both 0.01% by mass or more of the total amount of the inkjet ink, particularly 0. It was found that it is preferably 08% by mass or more, preferably 2% by mass or less, and particularly preferably 1.6% by mass or less. The total content of the surfactant A and the surfactant B is preferably 0.02% by mass or more, particularly 0.16% by mass or more, and particularly 4% by mass or less, particularly 3) of the total amount of the inkjet ink. It was found that it is preferably 2% by mass or less. Further, the mass ratio A / B of the surfactant A and the surfactant B is preferably 0.05 or more, particularly preferably 0.25 or more, 20.0 or less, particularly 4.00 or less, particularly 1.30 or less. It turned out that it is preferable.

Claims (4)

The surfactant comprises an edible pigment as a colorant , a surfactant, and water.
(A) Polyoxyethylene polyoxypropylene glycol and
(B) Two types of polyoxyethylene sorbitan fatty acid ester, an inkjet ink used for printing directly on the surface of a solid pharmaceutical product . The inkjet ink according to claim 1, further comprising a water-soluble organic solvent and a polysaccharide as a binder. The inkjet ink according to claim 2, wherein the polysaccharide is dextrin. The polyoxyethylene polyoxypropylene glycol of the above (A) has the formula (1):
HO (C ₂ H ₄ O) _a -(C ₃ H ₆ O) _b -(C ₂ H ₄ O) _c H (1)
The inkjet ink according to any one of claims 1 to 3, wherein a + b + c in the formula is 35 or less, which is polyoxyethylene polyoxypropylene glycol.