JP2002114929A - Ink composition for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new ink composition for ink jet recording, which can realize the printing of an image excellent in water resistance. SOLUTION: The ink composition is obtained by dissolving a dye, which is insoluble in water and soluble in N-methyl-2-pyrrolidone, in N-methyl-2- pyrrolidone or a nonaqueous solvent mixture containing at least 60 wt.% N- methyl-2-pyrrolidone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used for an on-demand type ink jet printer, particularly for a thermal ink jet system and a bubble jet (registered trademark) system which perform printing by discharging ink droplets by heating. The present invention relates to an inkjet ink composition to be used.

[0002]

2. Description of the Related Art In recent years, with the spread of small computers such as personal computers and workstations, various inexpensive and high-performance printers to be connected to and used have been provided. Among them, what is currently the mainstream is a so-called on-demand type ink-jet printer which performs printing by intermittently ejecting fine droplets of ink from nozzles according to print data. As, depending on the ink ejection method,
(a) Thermal ink jet method or bubble jet method in which a fixed amount of ink is ejected from the tip of a nozzle by generating fine bubbles by heating ink with a heater provided in the printer head, (b) Deformation of piezo element There is known a Mach jet method in which a fixed amount of ink is ejected from the tip of a nozzle by using a nozzle.

[0003]

Heretofore, as an ink composition used in this type of on-demand type ink jet printer, a composition in which a water-soluble dye is dissolved in an aqueous solvent mainly composed of water is generally used. However, there is a problem that an image printed with such an aqueous ink composition has poor water resistance. An object of the present invention is to provide a novel ink jet ink composition that can print an image having excellent water resistance.

[0004]

Means for Solving the Problems and Effects of the Invention In order to solve the above-mentioned problems, the present inventors have used a dye which is insoluble in water and soluble in an organic solvent to provide an image having excellent water resistance. We considered making up the ink composition. In order to obtain an organic solvent-based ink composition that can be used without modification of a conventional ink jet printer for aqueous ink compositions, various organic solvents were studied.

[0005]

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[0006] N-methyl-2-pyrrolidone represented by the following formulas:-It has a low volatility in an organic solvent, so that a stable ink composition can be formed. It is difficult to produce. ・ Since the viscosity is low, it can be ejected as droplets having a good shape when ejected from the tip of the nozzle.It can constitute an ink composition having an appropriate viscosity for inkjet, Since the power is large, a large amount of the dye can be dissolved without increasing the viscosity or destabilizing the ink due to the precipitation of the dye, thereby increasing the image density. And found that it was suitable as a solvent for the ink composition.

Therefore, as a result of further study on the composition of the ink composition using N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone alone or N-methyl-2-pyrrolidone was used as a solvent at 60% by weight. While using a non-aqueous mixed solvent containing the above ratio,
When a dye which is insoluble in water and soluble in N-methyl-2-pyrrolidone is used as the dye, the on-demand type ink jet printer, among them, especially the thermal ink jet system, without remodeling the bubble jet system ink jet printer The present inventors have found that an ink composition which can be used as it is and can print a good image having excellent water resistance can be obtained, and the present invention has been completed.

That is, the ink-jet ink composition of the present invention comprises (A) a non-aqueous mixed solvent containing N-methyl-2-pyrrolidone or N-methyl-2-pyrrolidone in a proportion of 60% by weight or more as a solvent. And (B) a dye that is insoluble in water and soluble in N-methyl-2-pyrrolidone;
It is characterized by including.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ink composition for inkjet according to the present invention will be described below. In the ink-jet ink composition of the present invention, (A-1) N-methyl-2-pyrrolidone (boiling point: 202
C) or (A-2) a non-aqueous mixed solvent containing N-methyl-2-pyrrolidone in a proportion of 60% by weight or more.

Of the above-mentioned mixed solvents (A-2), N-
The reason why the proportion of methyl-2-pyrrolidone is limited to 60% by weight or more is that if the ratio is less than this range, the solvent of the mixed solvent with respect to the dye is reduced and the dye is unstable due to precipitation of the dye. In addition, N-methyl-
The proportion of 2-pyrrolidone is determined by the effect of adding another organic solvent to form a mixed solvent, particularly when the boiling point is 200
Considering the effect of adjusting the boiling point of the ink composition by adding an organic solvent at a temperature of not more than 95 ° C., it is preferably at most 95% by weight.

Along with N-methyl-2-pyrrolidone (A-
Other organic solvents constituting the mixed solvent of 2) include a solvent having a boiling point of 200 which is compatible with N-methyl-2-pyrrolidone.
An organic solvent having a temperature of not more than ° C is preferably used. N-methyl-2
-An organic solvent having no compatibility with pyrrolidone is not preferable because it cannot form a uniform ink composition. Also,
The reason for using an organic solvent having a boiling point of 200 ° C. or lower is to adjust the boiling point of the ink composition as described above, particularly in a thermal inkjet system or a bubble jet system.
This is to promote the generation of bubbles by heating.

That is, since N-methyl-2-pyrrolidone alone has a slightly higher boiling point, if printing is carried out under the same conditions as when an aqueous ink composition is used, the size of bubbles generated by heating is not sufficient. However, the amount of ink ejected from the tip of the nozzle slightly decreases, and the density of the image tends to decrease. However, when the boiling point of the ink composition is adjusted by adding an organic solvent having a boiling point of 200 ° C. or lower, these Can be solved.

Considering such effects, the boiling point of the organic solvent is more preferably 50 to 100 ° C. even within the above range. As the above-mentioned organic solvent, any of various organic solvents having a boiling point of 200 ° C. or lower and having compatibility with N-methyl-2-pyrrolidone can be used, and a preferable example is methanol (boiling point: 64.67). ° C), ethanol (boiling point 78.3 ° C), 1-propanol (boiling point 9
7.20 ° C.), isopropyl alcohol (boiling point 82.2)
Alcohols such as s-butanol (boiling point 99.5 ° C) and t-butanol (boiling point 82.5 ° C).

The organic solvent can be used alone or in combination of two or more. That is, N-methyl-2
-A mixed solvent may be composed of pyrrolidone and two or more kinds of organic solvents. As the dye of (B) constituting the ink composition together with the solvent of (A), various dyes that are insoluble in water and soluble in N-methyl-2-pyrrolidone, as described above, may be used. Can also be used.

For example, dyes used for black ink include C.I. I. Solvent Black 28, C.I. I. Solvent Black 29, C.I. I. Solvent Black 45
And so on. Examples of the colorant used for each color ink for full-color printing include C.I. I. Solvent Blue 35, C.I. I. Solvent blue 44,
C. I. Solvent Blue 45, C.I. I. Solvent Blue 67, C.I. I. Solvent Blue 70, C.I. I. Cyan dyes such as Solvent Blue 136; I. Solvent Red 27, C.I. I. Solvent Red 90:
1, C.I. I. Solvent Red 91, C.I. I. Solvent Red 92, C.I. I. Solvent Red 122, C.I.
I. Solvent Red 124, C.I. I. Solvent Red 125, C.I. I. Solvent Red 127, C.I. I.
Solvent Red 130, C.I. I. Solvent Red 2
Magenta dyes such as C.33; I. Solvent Yellow 16, C.I. I. Solvent Yellow 25, C.I. I. Solvent Yellow 62, C.I. I. Solvent Yellow 7
9, C.I. I. Solvent Yellow 88, C.I. I. Solvent Yellow 89, C.I. I. Solvent Yellow 146
And other yellow dyes.

The amount of the dye added is 1 to the total amount of the ink.
About 30% by weight, especially about 3 to 12% by weight is preferable.
The ink composition containing the solvent of the above (A) and the dye of the (B), in particular, using the above-described thermal inkjet or bubble jet inkjet printer, under the same conditions as when using an aqueous ink composition. Considering that the liquid is ejected as a droplet having a good shape when ejected from the tip of the nozzle, the viscosity at 25 ° C. is preferably 1 to 10 cP, more preferably 1 to 5 cP.

In order to adjust the viscosity to this range, for example, the amount of the dye added is adjusted within the above range, or in the case of a mixed solvent, the ratio of N-methyl-2-pyrrolidone is adjusted within the above range. Or the type of other organic solvent to be mixed with N-methyl-2-pyrrolidone may be changed.
As described above, the above-mentioned ink composition is particularly preferably used for a thermal inkjet type or a bubble jet type inkjet printer, but can also be used for a Mach jet type inkjet printer.

[0018]

The present invention will be described below based on examples and comparative examples. Example 1 96.0 parts by weight of N-methyl-2-pyrrolidone as a solvent and C.I. I. Solvent Yellow 146 [ORASOL manufactured by Ciba Specialty Chemicals, Inc.
Yellow 4GN] was mixed with 4.0 parts by weight, and the yellow dye was dissolved to prepare an ink composition of Example 1. The viscosity at 25 ° C. of the ink composition was 1.41 cP.

The viscosity is measured using a viscometer [TOKI SANGYO CO. LTD.
VISCOMETER MODEL RL] was used at an ambient temperature of 25 ° C. and a rotation speed of 60 rpm at the time of measurement (the same applies hereinafter). Example 2 As a solvent, a mixed solvent 9 in which N-methyl-2-pyrrolidone and ethanol were mixed at a weight ratio of 90:10.
An ink composition of Example 2 was produced in the same manner as in Example 1 except that 6.0 parts by weight was used. The viscosity at 25 ° C. of the ink composition was 1.55 cP.

Examples 3 to 5 N-methyl-2-pyrrolidone and ethanol were used as solvents in a weight ratio of 80:20 (Example 3), 70:30.
(Example 4) and the ink compositions of Examples 3 to 5 in the same manner as in Example 1 except that 96.0 parts by weight of a mixed solvent mixed at a ratio of 60:40 (Example 5) was used. Was manufactured. The viscosity at 25 ° C. of each ink composition was 1.69 cP (Example 3), 1.85 cP (Example 4), and 2.01 cP (Example 5).

Comparative Example 1 As a solvent, a mixed solvent 9 in which N-methyl-2-pyrrolidone and ethanol were mixed at a weight ratio of 50:50.
An ink composition was prepared in the same manner as in Example 1 except that 6.0 parts by weight were used. However, since the dye was not completely dissolved in the mixed solvent, the subsequent test was abandoned. . The viscosity at 25 ° C. of the ink composition was 2.15 cP.

Comparative Example 2 The following components were mixed and dissolved to prepare an aqueous ink composition of Comparative Example 2. (Component) (parts by weight) Dye C.I. I. Direct Yellow 86 2.5 [Pro-Jet Yellow 1G manufactured by Zeneca]-Wetting agent 1,5-pentanediol 8.0-Surfactant Olfin E-1010 2.5 [Air Products]-Solvent Ultra pure Water 87.0 The viscosity at 25 ° C. of the ink composition was 1.42 cP.

The ink compositions of the above Examples and Comparative Examples were subjected to the following tests to evaluate the characteristics. Initial Image Density Test Each of the ink compositions of Examples and Comparative Examples was filled into an empty black ink cartridge (Part No. 51645A) for a thermal inkjet type inkjet printer [DeskJet 895Cxi manufactured by Hewlett-Packard Japan].
After printing on the surface of plain paper (recycled PPC paper R manufactured by Fuji Xerox Co., Ltd.), the density of the solid portion of the image was measured using a spectral colorimeter (Nippon Denshoku). The measurement was performed four times for one sample, and the density of each time was recorded, and an average value of the four times was obtained.

Water resistance test Immediately after printing, the plain paper on which the above image was printed was immersed in water, left for 1 minute, pulled up, and dried at room temperature.
Then, the density of the solid portion of the image was measured using the same spectral colorimeter as above. The measurement was carried out four times for one sample in the same manner as described above, and the density of each time was recorded, and the average value of the four times was obtained. Table 1 shows the results.

[0025]

[Table 1]

From the table, it was found that the ordinary aqueous ink composition of Comparative Example 2 had a high initial image density, but flowed out by being immersed in water, resulting in a significant decrease in image density. On the other hand, since the image density after immersion in water was not significantly reduced as compared with the initial density, the ink compositions of Examples were confirmed to be excellent in water resistance.

Further, comparing the examples, it was found that N
Examples 2 to 5 using a mixed solvent of N-methyl-2-pyrrolidone and ethanol had higher initial image densities than Example 1 using -methyl-2-pyrrolidone alone, and It has also proven favorable.

Claims (3)

[Claims] (A) N-methyl-2-pyrrolidone or N-methyl-2-pyrrolidone as a solvent is 60% by weight.
An ink-jet ink composition comprising: a non-aqueous mixed solvent contained in the above ratio; and (B) a dye insoluble in water and soluble in N-methyl-2-pyrrolidone. 2. A solvent constituting a mixed solvent of N-methyl-2-pyrrolidone and a non-aqueous solvent is an organic solvent having a boiling point of 200 ° C. or less and having compatibility with N-methyl-2-pyrrolidone. The ink composition for inkjet according to claim 1, wherein 3. The ink composition according to claim 1, wherein the viscosity at 25 ° C. is 1 to 10 cP.