JP6028301B2 - Non-aqueous inkjet ink - Google Patents

Description

  The present invention particularly relates to a non-aqueous inkjet ink used for printing on a food packaging film or the like.

  For example, when printing a shelf life, production lot number, barcode, etc. directly on a non-absorbable surface such as a food packaging film by the inkjet printing method, in order to improve the drying and fixing properties of printing, A so-called non-aqueous ink-jet ink that uses a non-aqueous solvent that is superior in volatility, penetrability to the surface, and the like than a water-based ink-jet ink is preferably used.

  In addition, the non-aqueous inkjet ink has not only the above-mentioned good drying and fixing properties, but also has excellent characteristics (ejection stability) that makes it difficult to cause clogging and the like at the nozzles of an inkjet printer, and that can be stably ejected from the nozzles. Is also required. This is because, in the food industry in particular, strict safety management is required for products, and printing cannot be read due to clogging or the like.

Furthermore, since it is for food, the non-aqueous inkjet ink is required to have high safety.
Patent Document 1 includes a dye, a binder resin, and an organic solvent as a non-aqueous inkjet ink suitable for printing on the surface of the food packaging film and the like, and the organic solvent is a lower carbon number of 4 or less. A non-aqueous inkjet ink that contains an alcohol and an ester solvent and does not contain a ketone solvent has been proposed.

  Patent Document 2 similarly includes a non-aqueous inkjet ink suitable for printing on the surface of a food packaging film or the like, a coloring material such as a dye or pigment, a binder resin, and an organic solvent. A non-aqueous ink-jet ink containing methyl acetate has been proposed.

Japanese Patent Laid-Open No. 2002-60661 JP 2002-201393 A

  However, according to the inventor's study, the conventional non-aqueous inkjet inks described in Patent Documents 1 and 2 are too dry, so that the nozzles are clogged particularly when used in an on-demand inkjet printer. Or the like, resulting in a decrease in ejection stability, or a solid content such as a coloring material or a binder resin is likely to be precipitated, resulting in a decrease in the stability of itself.

This is because the compositions of the conventional non-aqueous ink-jet inks are designed mainly for the purpose of improving the drying properties of printing for continuous ink-jet printers.
If it is a continuous type ink jet printer that always prints while continuously discharging the non-aqueous ink jet ink, the non-aqueous ink jet ink is used to fix the printing on a non-absorbent surface such as a food packaging film as quickly as possible. The ink is more preferable as the drying property is higher.

However, non-aqueous inkjet inks for on-demand inkjet printers that have time to stop ejection during printing or when printing are too dry to dry while remaining in the nozzles when stopped As a result, the colorant and the binder resin are deposited, and the nozzle is easily clogged, and the discharge stability is lowered.
In addition, as a dye or a binder resin as a coloring material, a water-insoluble one is often used in order to improve solubility in an organic solvent or improve water resistance of printing.

  However, if the drying property of the non-aqueous inkjet ink is too high, a large amount of moisture is easily embraced by the latent heat of vaporization at the time of drying, thereby lowering the solubility of the dye and binder resin and precipitating in the non-aqueous inkjet ink. , The stability of the non-aqueous inkjet ink is reduced. In addition, the deposition tends to cause clogging of the nozzle and the discharge stability is also lowered. That is, the decrease in stability also causes a decrease in ejection stability.

  An object of the present invention is to provide a non-aqueous inkjet ink which is highly safe and suitable for printing on a non-absorbing surface, is excellent in ejection stability without clogging of nozzles, etc., and also has excellent stability. It is to provide.

The present invention is a non-aqueous inkjet ink containing a dye, a binder resin, and an organic solvent, wherein the organic solvent is
(1) Formula (a):
CH ₃ CH (OH) COOR (a)
And at least one lactic acid ester in which R is an alkyl group having 1 or 2 carbon atoms, and
(2) R in the formula (a) is a mixed solvent of at least one lactate ester having an alkyl group having 3 to 5 carbon atoms.

In the present invention, the colorant is limited to the dye for the following reason.
That is, when the colorant is a pigment, when the non-aqueous inkjet ink remaining in the nozzle starts to dry, the pigment starts to aggregate and precipitate, and the next new non-aqueous inkjet ink is sent to the nozzle. However, it does not re-disperse well, and it becomes difficult to eject the non-aqueous inkjet ink from the nozzle in a normal state, and the ejection stability is lowered.

On the other hand, even when the non-aqueous inkjet ink starts to dry and starts to precipitate while remaining in the nozzle, the dye is quickly and well improved when the next new non-aqueous inkjet ink is sent to the nozzle. Since it is redissolved, the non-aqueous inkjet ink can be ejected from the nozzle in a normal state, and the ejection stability is excellent.
The organic solvent is limited to the lactic acid ester of the two types (1) and (2) for the following reasons.

That is, in the formula (a), any lactic acid ester in which the alkyl group represented by R has 1 to 5 carbon atoms is excellent in safety.
However, the lactic acid ester of the above (1) in which the alkyl group has 1 or 2 carbon atoms (hereinafter may be abbreviated as “lactic acid ester (1)”) has a strong solubility in dyes and binder resins but is volatilized. It tends to be easy. On the other hand, the lactic acid ester (2) (hereinafter sometimes abbreviated as “lactic acid ester (2)”) in which the alkyl group has 3 to 5 carbon atoms has a solubility higher than that of the lactic acid ester (1). Although it is weak, it tends to be difficult to volatilize.

Therefore, when the two types of lactic acid esters are used in combination, while maintaining good solubility with the lactic acid ester (1), the combined use of the lactic acid ester (2) suppresses volatility and is good for non-aqueous inkjet inks. Discharge stability and stability can be imparted.
In general, the ejection stability of ink used in an on-demand type ink jet printer is greatly related to the size of a margin (allowable range) of the ink pressure in the nozzle, that is, the water head pressure.

That is, in an on-demand type ink jet printer, as the response frequency of a recording head equipped with nozzles increases, the reciprocating speed of a carriage that reciprocates between printing widths with the recording head mounted also tends to increase. Along with this, an increase in pressure fluctuation during the movement of the carriage and a decrease in ejection stability due to this increase have become a problem.
Specifically, if the water head pressure increases due to pressure fluctuations due to the movement of the carriage and becomes positive (positive pressure in the ink ejection direction), unnecessary ink splatters from the nozzles even during the ejection operation, and the print becomes dirty. If the negative pressure (negative pressure in the ink ejection direction) becomes larger than the allowable value, there is a risk of ejection failure due to air drawing from the nozzle.

For this reason, it is required to improve the ejection stability by stabilizing the ink ejection during the acceleration / deceleration when the acceleration of the carriage becomes the largest, and stabilizing the ink ejection.
The water head pressure also changes depending on the amount of ink in the ink supply container. That is, the water head pressure tends to decrease as the ink is consumed. As the water head pressure decreases, the influence of the pressure fluctuation on the negative pressure side on the ink ejection increases.

The ink has poor wettability with respect to the inner surface of the ink supply container, the nozzle, and the tube (the surface directly contacting the ink) constituting the ink jet printer, and the ink does not flow smoothly through the parts. This is considered as one of the causes of the problem.
On the other hand, among the two types of lactic acid esters, the lactic acid ester (2) functions as a lactic acid residue in the formula (a) as a hydrophilic group and an alkyl group having 3 to 5 carbon atoms as a hydrophobic group. It plays a role as a surfactant by the balance between hydrophilicity and hydrophobicity by the group.

And it functions in order to improve the wettability of the non-aqueous inkjet ink with respect to the surface where the non-aqueous inkjet ink is in direct contact with the inner surface of the ink supply container of the inkjet printer, the nozzle, and the pipe connecting the two.
Therefore, the non-aqueous inkjet ink of the present invention using the lactic acid ester (2) in combination with the lactic acid ester (1) having excellent solubility in dyes and binder resins as described above is based on the function of the lactic acid ester (2). The inside of each part flows smoothly without chewing bubbles, the head pressure margin is increased, various problems due to the pressure fluctuation are less likely to occur, and the discharge stability is improved.

The organic solvent is preferably a mixed solvent of ethyl lactate in the lactate ester (1) and butyl lactate in the lactate ester (2).
Ethyl lactate is preferred as the lactate ester (1), and it is difficult to hydrolyze, and even if it is hydrolyzed, the resulting alcohol is ethanol, which is particularly excellent in safety among the lactate ester (1). Because.

  The lactic acid ester (2) is preferably butyl lactate when used in combination with the ethyl lactate so that the solubility of the ethyl lactate and the butyl lactate function as a surfactant so that the water head of the non-aqueous inkjet ink can be used. This is because there is a good balance with the effect of increasing the pressure margin and the effect of improving the discharge stability of the non-aqueous inkjet ink is excellent.

In the combined system, the blending ratio of ethyl lactate E and butyl lactate B is preferably 75/25 to 95/5 expressed by mass ratio E / B.
When the amount of butyl lactate is less than the above range, the effect of preventing clogging by suppressing volatility and the effect of increasing the margin of water head pressure due to the butyl lactate becomes insufficient. There is a possibility that the discharge stability is lowered.

On the other hand, when the amount of ethyl lactate is less than the above range, the solubility of the dye or binder resin due to the ethyl lactate is insufficient, and the stability of the non-aqueous inkjet ink may be lowered.
On the other hand, when ethyl lactate and butyl lactate are blended in the above proportions, the respective functions are expressed more effectively, and the discharge stability and stability of the non-aqueous inkjet ink are further improved. Can do.

The binder resin is preferably a styrene acrylic resin.
The lactic acid ester (1) is a pyrrolidone or lactone used in ordinary non-aqueous inkjet inks, although the solubility of dyes and binder resins is good among the lactic acid esters having 1 to 5 carbon atoms in R. Compared to organic solvents such as those, the solubility in the binder resin is not very strong.

However, the styrene acrylic resin is particularly excellent in solubility in the mixed solvent of the lactic acid ester (1) and the lactic acid ester (2) mainly due to the action of the styrene component. Therefore, the styrene acrylic resin is used as the binder resin. Thus, the precipitation can be suppressed, and the stability of the non-aqueous inkjet ink can be improved.
The styrene acrylic resin also functions to improve the fixability of printing on the surface of a film for food packaging made of, for example, polyethylene or polypropylene, mainly by the action of acrylic.

  According to the present invention, there is provided a non-aqueous inkjet ink that is highly safe and suitable for printing on a non-absorbing surface, has no nozzle clogging, has excellent ejection stability, and also has excellent stability. Can be provided.

The non-aqueous inkjet ink of the present invention contains a dye, a binder resin, and an organic solvent,
(1) Formula (a):
CH ₃ CH (OH) COOR (a)
And at least one lactic acid ester (1) wherein R is an alkyl group having 1 or 2 carbon atoms, and
(2) R in the formula (a) is at least one mixed solvent of lactic acid ester (2), which is an alkyl group having 3 to 5 carbon atoms.

<Organic solvent>
Among them, the lactic acid ester (1) includes at least one of methyl lactate and ethyl lactate, and ethyl lactate is preferably used particularly for the reason explained above.
Examples of the lactic acid ester (2) include at least one selected from the group consisting of propyl lactate, butyl lactate, and amyl lactate (pentyl lactate), and particularly as the lactate ester (2) used in combination with the ethyl lactate. Butyl lactate is preferred. The reason for this is as described above.

In the combined system of the two kinds of lactic acid esters, the blending ratio of ethyl lactate E and butyl lactate B is preferably 75/25 to 95/5 expressed by mass ratio E / B.
When the amount of butyl lactate is less than the above range, the effect of preventing clogging by suppressing volatility and the effect of increasing the margin of water head pressure due to the butyl lactate becomes insufficient. There is a possibility that the discharge stability is lowered.

On the other hand, when the amount of ethyl lactate is less than the above range, the solubility of the dye or binder resin due to the ethyl lactate is insufficient, and the stability of the non-aqueous inkjet ink may be lowered. Further, the drying property of the non-aqueous inkjet ink may be lowered.
On the other hand, when ethyl lactate and butyl lactate are blended in the above proportions, the respective functions are expressed more effectively, and the discharge stability and stability of the non-aqueous inkjet ink are further improved. Can do.

The blending ratio of the mixed solvent composed of the two types of lactic acid esters (1) and (2) in the total amount of the non-aqueous inkjet ink is the remaining amount of binder resin, dye, and the like described below. That is, a mixed solvent in which two kinds of lactic acid esters are blended in the above ratio may be added to the binder resin, the dye, and the like so that the total amount becomes 100 mass%.
<Binder resin>
As the binder resin, any of various binder resins having solubility in the mixed solvent of the lactic acid esters (1) and (2) can be used.

Examples of such binder resins include one or more of styrene maleic resins such as semi-esterified styrene maleic resin and styrene maleic anhydride resin, styrene acrylic resin, and acrylic resin.
Among these, styrene acrylic resin is preferable as the binder resin. The reason for this is as described above.

Examples of the styrene acrylic resin include various styrene acrylic resins containing, as a repeating unit, an acrylic component such as acrylic acid, its ester or salt, and a styrene component.
The styrene acrylic resin has a weighted average molecular weight Mw of 2000 or more, particularly 2500 or more, preferably 4000 or less, particularly 3500 or less.

When the weight average molecular weight Mw is less than the above range, there is a possibility that the effect of improving the fixability of printing on the surface of a film for food packaging made of, for example, polyethylene, polypropylene, or the like by a styrene acrylic resin may not be obtained.
On the other hand, when it exceeds the above range, the solubility in the mixed solvent becomes insufficient, and the stability of the non-aqueous inkjet ink may be lowered.

The styrene acrylic resin preferably has an acid value of 70 mgKOH / g or more, and preferably 400 mgKOH / g or less.
If the acid value is less than the above range, the effect of improving the fixability of printing on the surface of a film for food packaging made of, for example, polyethylene, polypropylene, or the like by styrene acrylic resin may not be obtained.

On the other hand, when the above range is exceeded, it is likely to cause hydrolysis of the lactic acid ester. When the lactic acid ester is hydrolyzed, the viscosity of the non-aqueous inkjet ink fluctuates, and in particular, a dye or binder resin due to the lactic acid ester (1). There is a concern that the solubility of the non-aqueous inkjet ink may be insufficient and the stability of the non-aqueous inkjet ink may be insufficient.
The blending ratio of the styrene acrylic resin is preferably 2% by mass or more of the total amount of the non-aqueous inkjet ink, and is preferably 8% by mass or less.

When the blending ratio is less than the above range, there is a possibility that the effect of improving the fixability of printing on the surface of a film for food packaging made of, for example, polyethylene, polypropylene, or the like by styrene acrylic resin may not be obtained.
On the other hand, when the above range is exceeded, the viscosity of the non-aqueous inkjet ink may increase or an excessive amount of styrene acrylic resin may precipitate, which may reduce the stability and ejection stability of the non-aqueous inkjet ink.

<dye>
As the dye, any of various dyes having solubility in the mixed solvent of lactic acid esters (1) and (2) can be used. Of these, oil-soluble metal complex dyes (metal-containing dyes) are preferable in terms of solubility, light resistance, coloring power, and the like.
Among the metal complex dyes, yellow metal complex dyes include, for example, Balifast Yellow 3104 [trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I. I. Solvent Yellow 19], Philamid Yellow R [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Yellow 21], Bali Fast Yellow 3105 [trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I. I. Solvent Yellow 21], C.I. I. Solvent Yellow 32, Eisenspiron Yellow GRH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Yellow 61], C.I. I. Solvent Yellow 65, C.I. I. Solvent Yellow 76, C.I. I. Solvent Yellow 79, Eisenmetallon Yellow NRRS [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Yellow 80], C.I. I. Solvent Yellow 81, Bali Fast Yellow 4120 [trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I. I. Solvent Yellow 82], C.I. I. Solvent Yellow 83, Orazole Yellow 2GLN [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Yellow 88], Orazole Yellow 2RLN [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Yellow 89], C.I. I. Solvent Yellow 90, C.I. I. One type or two or more types such as Solvent Yellow 91 and Eisenspiron Yellow GRH Special (trade name, manufactured by Hodogaya Chemical Co., Ltd.) may be mentioned.

  Examples of orange-based metal complex dyes include Balifast Orange 3206 [trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I. I. Solvent Orange 5], Zapon Fast Orange RR [trade name, manufactured by BASF Corp., C.I. I. Solvent Orange 6], C.I. I. Solvent Orange 11, C.I. I. Solvent Orange 20, C.I. I. Solvent Orange 36, Eisen Spiron Orange GRH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Orange 37], Eisenspiron Orange 2RH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Orange 40], Zapon Fast Orange RE [trade name, manufactured by BASF Corp., C.I. I. Solvent Orange 44], Zapon Fast Yellow 3RE [trade name, manufactured by BASF Corp., C.I. I. Solvent Orange 45], C.I. I. Solvent Orange 54, C.I. I. Solvent Orange 56, C.I. I. Solvent Orange 57, C.I. I. Solvent Orange 58, C.I. I. Solvent Orange 59, C.I. I. 1 type, or 2 or more types, such as Solvent Orange 62, are mentioned.

  Examples of red metal complex dyes include Balifast Red 3304 [trade name, manufactured by Orient Chemical Industry Co., Ltd., C.I. I. Solvent Red 8], C.I. I. Solvent Red 35, C.I. I. Solvent Red 78, Eisen Spiron Red BEH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Red 83], Eisenspiron Red GEH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Red 84], C.I. I. Solvent Red 96, C.I. I. Solvent Red 99, Bali Fast Red 3305 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Solvent Red 100], C.I. I. Solvent Red 102, Zapon Fast Ferry Red B [trade name, manufactured by BASF, C.I. I. Solvent Red 109], C.I. I. Solvent Red 118, C.I. I. Solvent Red 119, Eisenmetallon Red HGRS [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Red 121], Oreosol Fast Red RL [trade name, manufactured by Taoka Chemical Co., Ltd., C.I. I. Solvent Red 122], C.I. I. Solvent Red 123, C.I. I. Solvent Red 124, Orazol Pink 5BLG [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Red 127], C.I. I. Solvent Red 128, C.I. I. Solvent Red 129, Orazol Red 3GL [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Red 130], C.I. I. Solvent Red 131, Bali Fast Red 3320 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Solvent Red 132], C.I. I. Solvent Red 133, C.I. I. Solvent Red 134, C.I. I. Solvent Red 142, C.I. I. 1 type, or 2 or more types, such as Solvent Red 160, are mentioned.

Examples of purple metal complex dyes include C.I. I. Solvent Violet 1, C.I. I. Solvent Violet 2, C.I. I. Solvent Violet 19, Eisenspiron Violet RH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. 1 type or 2 types or more, such as Solvent Violet 21].
Examples of blue metal complex dyes include C.I. I. Solvent Blue 24, Eisenzot Blue 1 [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Blue 25], C.I. I. Solvent Blue 46, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 64, Orazole Blue GN [trade name, manufactured by Ciba Geigy, C.I. I. Solvent Blue 67], Bali Fast Blue 2606 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Solvent Blue 70], C.I. I. 1 type, or 2 or more types, such as Solvent Blue 75, are mentioned.

Examples of green metal complex dyes include C.I. I. Solvent Green 16, C.I. I. Solvent Green 21, C.I. I. 1 type, or 2 or more types, such as Solvent Green 22, etc. are mentioned.
Examples of brown metal complex dyes include C.I. I. Solvent Brown 23, C.I. I. Solvent Brown 24, C.I. I. Solvent Brown 25, C.I. I. Solvent Brown 37, C.I. I. Solvent Brown 42, C.I. I. Solvent Brown 43, C.I. I. Solvent Brown 44, C.I. I. 1 type or 2 or more types, such as Solvent Brown 58, are mentioned.

  Further, examples of black metal complex dyes include Eisenspiron Black BH [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Black 22], Eisenspiron Black GSH Special [trade name, manufactured by Hodogaya Chemical Co., Ltd., C.I. I. Solvent Black 23], C.I. I. Solvent Black 25, Bali Fast Black 3820 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Solvent Black 27], Orazole Black CN [trade name, manufactured by Ciba Geigy Corporation, C.I. I. Solvent Black 28], C.I. I. Solvent Black 29, C.I. I. Solvent Black 30, Bali Fast Black 3804 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Solvent Black 34], C.I. I. Solvent Black 35, Bali Fast Black 3804 [trade name, manufactured by Orient Chemical Co., Ltd., C.I. I. Acid Black 123], Bonjet BC261 [trade name, manufactured by Orient Chemical Co., Ltd.], Eisenspiron Black RLH [trade name, manufactured by Hodogaya Chemical Co., Ltd.], and the like. It is done.

The metal complex dye can be used alone or in combination of two or more colors according to the color of the non-aqueous inkjet ink.
The metal complex dye can be used in combination with water-insoluble oil-soluble dyes, disperse dyes, and the like.
The blending ratio of the dye is preferably 0.5% by mass or more, and preferably 20% by mass or less, based on the total amount of the non-aqueous inkjet ink.

If the blending ratio is less than the above range, there is a possibility that printing having a sufficient optical density cannot be obtained.
On the other hand, when the above range is exceeded, the viscosity of the non-aqueous inkjet ink may increase or excessive dye may be deposited, which may reduce the stability and ejection stability of the non-aqueous inkjet ink.

<Others>
The non-aqueous inkjet ink of the present invention may further contain, for example, a silicone-based, fluorine-based, acrylic-based surfactant or the like for adjusting the surface tension at a predetermined ratio, if necessary. .

<Example 1>
C. as a dye I. Solvent black 29, styrene acrylic resin as a binder resin [weight average molecular weight Mw: 3000, acid value: 250 mg KOH / g], ethyl lactate as lactate ester (1), and butyl lactate as lactate ester (2) A non-aqueous inkjet ink was prepared by blending in the proportions shown in Table 1 and mixing in a uniform phase. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 2>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of methyl lactate was added as the lactate ester (1) instead of ethyl lactate.
<Example 3>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of propyl lactate was added as the lactate ester (2) instead of butyl lactate.

<Example 4>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of amyl lactate was used as the lactate ester (2) instead of butyl lactate.
<Example 5>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the blending ratio of ethyl lactate was 76 parts by mass and the blending ratio of butyl lactate was 4 parts by mass. The mass ratio E / B of ethyl lactate E to butyl lactate B was 95/5.

<Example 6>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the blending ratio of ethyl lactate was 60 parts by mass and the blending ratio of butyl lactate was 20 parts by mass. The mass ratio E / B of ethyl lactate E to butyl lactate B was 75/25.
<Example 7>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the blending ratio of ethyl lactate was 55 parts by mass and the blending ratio of butyl lactate was 25 parts by mass. The mass ratio E / B of ethyl lactate E to butyl lactate B was 69/31.

<Example 8>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the blending ratio of ethyl lactate was 78 parts by mass and the blending ratio of butyl lactate was 2 parts by mass. The mass ratio E / B of ethyl lactate E to butyl lactate B was 97.5 / 2.5.
<Example 9>
Non-aqueous as in Example 1 except that the same amount of half-esterified styrene maleic acid resin [weight average molecular weight Mw: 1700, acid value: 270 mgKOH / g] was used instead of the styrene acrylic resin as the binder resin. An inkjet ink was produced. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 10>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of acrylic resin [weight average molecular weight Mw: 2000, acid value: 70 mgKOH / g] was used instead of styrene acrylic resin as the binder resin. . The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 11>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of a styrene acrylic resin having a weight average molecular weight Mw of 1700 and an acid value of 238 mgKOH / g was blended as the binder resin. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 12>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of styrene acrylic resin having a weight average molecular weight Mw of 4600 and an acid value of 108 mgKOH / g was blended as the binder resin. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 13>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the same amount of styrene acrylic resin having a weight average molecular weight Mw of 8100 and an acid value of 53 mgKOH / g was blended as the binder resin. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Example 14>
Nonaqueous inkjet ink as in Example 1 except that the same amount of styrene maleic anhydride resin [weight average molecular weight Mw: 5500, acid value: 480 mgKOH / g] was blended as the binder resin in place of the styrene acrylic resin. Manufactured. The mass ratio E / B of ethyl lactate E to butyl lactate B was 87.5 / 12.5.

<Comparative example 1>
A non-aqueous inkjet ink was produced in the same manner as in Example 1 except that the blending ratio of ethyl lactate was 80 parts by mass and butyl lactate was not blended.
<Comparative example 2>
In order to reproduce Patent Document 1, a non-aqueous inkjet ink was produced in the same manner as in Example 1 except that 75 parts by mass of ethanol and 5 parts by mass of propylene glycol monomethyl ether acetate were blended as the organic solvent.

<Comparative Example 3>
In order to reproduce Patent Document 2, a non-aqueous inkjet ink was produced in the same manner as in Example 1 except that 13 parts by mass of ethanol, 54 parts by mass of acetone, and 13 parts by mass of methyl acetate were blended as the organic solvent.
<Discharge stability evaluation I (clogging)>
Using a piezo-type on-demand type ink jet printer, a ruled line having a width of 1 point was printed on the surface of the polypropylene film at regular time intervals using the non-aqueous ink jet inks of the above Examples and Comparative Examples. Specifically, after the first printing, the printer was stopped, and after 20 seconds had elapsed, printing was performed 6 times at 5 second intervals, a total of 7 times including the first time. And the quality of the discharge stability by the presence or absence of the clogging by drying of a non-aqueous inkjet ink was evaluated on the following reference | standard.

○: The ruled lines were printed neatly until the end of the seventh time. No clogging. Good ejection stability Δ: The ruled line could not be printed cleanly between the 6th and 7th times. Although there is a slight clogging, the discharge stability is at a practical level.
X: The ruled line could not be printed cleanly from the first time to the fifth time. There is clogging. Discharge stability is poor.

<Discharge stability evaluation II (water head pressure margin)>
In order to reproduce the fluctuation of the nozzle head pressure due to the consumption of the non-aqueous inkjet ink in the inkjet printer, the following test was performed. That is, in a state where the water head pressure is set to 0 mmH ₂ O (= 0 kPa), 10,000 droplets are ejected to measure the total ink mass (W1), and the water head pressure is set to −180 mmH ₂ O ( = -1.77 kPa), 10,000 droplets were ejected and the total ink mass (W2) was weighed. Based on the following criteria, the quality of ejection stability depending on the size of the water head pressure margin was evaluated.

○: The reduction rate of W2 with respect to W1 was less than 15%. Large margin of water head pressure. Good discharge stability.
(Triangle | delta): The said reduction rate was 15% or more and less than 20%. The head pressure margin is moderate. Discharge stability is at a practical level.
X: The reduction rate was 20% or more. Small margin of water head pressure. Discharge stability is poor.

<Stability evaluation I>
After adding 1 part by weight of water to 100 parts by weight of the non-aqueous inkjet ink of each of the above Examples and Comparative Examples and allowing to stand at 45 ° C. for 1 month, 250 ml is taken and filtered with an 8 μm mesh filter. The time required for the measurement was measured, and the presence or absence of a decrease in stability due to hydrolysis accompanying water inclusion was evaluated according to the following criteria. The greater the amount of precipitate due to the decrease in stability, the longer the time required for filtration.

○: Filtration was completed within 25 minutes. Good stability.
Δ: Over 25 minutes and filtration was completed within 35 minutes. Practical level.
X: Filtration was not completed even if it exceeded 35 minutes . Stability failure.
<Stability evaluation II>
After leaving the non-aqueous inkjet ink of each of the above Examples and Comparative Examples at 45 ° C. for 1 month, 250 ml was collected and the time required for filtration with an 8 μm mesh filter was measured. Then, the presence or absence of stability decrease during storage was evaluated. Also in this case, the longer the amount of precipitation due to the decrease in stability, the longer the time required for filtration.

○: Filtration was completed within 25 minutes. Good stability.
Δ: Over 25 minutes and filtration was completed within 35 minutes. Practical level.
X: Filtration was not completed even if it exceeded 35 minutes . Stability failure.
<Fixability evaluation>
A ruled line having a width of 1 point was printed on the surface of the polypropylene film using the non-aqueous inkjet ink of each of the examples and comparative examples using the piezo-type on-demand inkjet printer. Then, after naturally drying for 1 day, a scratch test with a nail was performed, and the fixing property was evaluated according to the following criteria.

○: The ruled line was not removed even after scratching 10 times or more. Good fixability.
Δ: A ruled line was drawn with scratches of 6 round trips or more and 9 round trips or less, but it was evaluated as a practical level.
X: The ruled line was removed with scratches of 5 round trips or less. Fixing failure.
The above results are shown in Tables 2-4. The symbols in the table are as follows.
(Other solvents)
PGMMA: Propylene glycol monomethyl ether acetate (binder resin)
SAc: Styrene acrylic resin eSMa: Half-esterified styrene maleic acid resin SdMa: Styrene maleic anhydride resin Ac: Acrylic resin

  From the results of Comparative Examples 2 and 3 in Table 4, the combination of organic solvents described in Patent Documents 1 and 2 is too dry to be used for an on-demand type ink jet printer, and water is included. It was found that the non-aqueous ink-jet ink is not sufficiently stable, and is clogged easily and the ejection stability is not sufficient.

From the results of Comparative Example 1, when only the lactic acid ester (1) is used alone as the organic solvent, the drying property is too high, so that clogging is likely to occur and the head pressure margin is small. It was found that the stability was insufficient.
On the other hand, from the results of Examples 1 to 14 in Tables 2 to 4, the stability, ejection stability, and fixability are improved by using two kinds of lactic acid esters (1) and (2) as an organic solvent. It was also found that a good non-aqueous inkjet ink having a practical level (Δ) or more can be obtained.

Further, particularly from the results of Examples 1 to 8, it is preferable to combine ethyl lactate E and butyl lactate B as the two kinds of lactic acid esters, and the ethyl lactate E and butyl lactate B are combined in a mass ratio E / B. It was found that it is preferable to blend at a ratio of 75/25 to 95/5.
Furthermore, from the results of Examples 1 and 9 to 14, the binder resin is preferably a styrene acrylic resin, and the styrene acrylic resin preferably has a weighted average molecular weight Mw of 2000 or more, particularly 2500 or more, preferably 4000 or less, In particular, it was found that 3500 or less is preferable, and that the styrene acrylic resin has an acid value of preferably 70 mgKOH / g or more, and preferably 400 mgKOH / g or less.

Claims (4)

A non-aqueous inkjet ink comprising a dye, a binder resin, and an organic solvent, wherein the organic solvent is
(1) Formula (a):
CH ₃ CH (OH) COOR (a)
And at least one lactic acid ester in which R is an alkyl group having 1 or 2 carbon atoms, and
(2) A non-aqueous inkjet ink, wherein R in the formula (a) is a mixed solvent of at least one lactic acid ester having an alkyl group having 3 to 5 carbon atoms.   The non-aqueous inkjet ink according to claim 1, wherein the organic solvent is a mixed solvent of ethyl lactate and butyl lactate.   The non-aqueous inkjet ink according to claim 2, wherein the ethyl lactate E and the butyl lactate B are blended in a mass ratio E / B = 75/25 to 95/5.   The non-aqueous inkjet ink according to any one of claims 1 to 3, wherein the binder resin is a styrene acrylic resin.