JPH0819359B2 - Inkjet recording liquid and inkjet recording method using the recording liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applicable to recording materials such as paper, film, cloth, etc., especially paper generally used in offices and schools, so-called plain paper, and recording head. A recording liquid (hereinafter referred to as an ink) suitable for recording by a so-called inkjet recording method, in which droplets ejected from an ejection port provided on the recording medium are ejected onto a recording surface, and the ink is used. The present invention relates to an inkjet recording method.

(Prior Art and Problems Thereof) Various compositions have been proposed as inks for recording on recording materials such as writing instruments, stamps, recorders, and inkjet recording. . Many of them are various dyes dissolved or dispersed in water or other organic solvents.

However, due to the peculiarity of the recording method, inkjet inks require more stringent conditions with many characteristics than inks for writing instruments, stamps, and recorders. The preferable conditions are listed below. (1) Droplets are always stably discharged from a fine discharge port and clogging does not occur.

(2) Stable ejection can be obtained immediately after resuming recording even if the recording medium is left uncapped during recording suspension. That is, the ink in the vicinity of the ejection port is hard to dry, and clogging does not occur.

(3) High-quality printing without irregular shape or irregular bleeding can be obtained. (4) Fixing property (printing drying property) is fast with respect to the recording material, and the printed matter is not stained even if it is rubbed. (5) (6) The printed matter is excellent in water resistance and light resistance. (7) Good in storage stability and ink performance is maintained for a long time. (8) Member in contact with ink. It does not violate.

It is considerably difficult to satisfy the above conditions at the same time.

This is because the above conditions are often in a reciprocal relationship with each other, and trying to satisfy one of them often adversely affects the other. For example, a slow-drying solvent with a high boiling point is used for the purpose of preventing drying of the tip of the ejection port of the recording head, but in this case, the fixing property (printing drying property) is deteriorated with respect to the recording material, If you rub the print with a damp finger, it will get dirty. In addition, penetrants such as surfactants are generally used for the purpose of improving fixability.
In this case, irregular or irregular bleeding occurs and the print becomes blurred.

Further, when printing is performed on plain paper, it is impossible to obtain a clear image with high contrast as when printing is performed on coated paper. When the print density is low, the quality of the printed matter will not be expressed because the entire printed matter will have a smooth and unclear appearance, regardless of how much bleeding is suppressed and high-quality printing is intended. For this reason, generally, when the content of the recording agent (dye) is increased in order to increase the print density, the ejection port tends to be clogged.

Further, in order to improve the water resistance and light resistance of the printed matter, a direct dye is generally used as a recording agent. The direct dye has a merit that it is less likely to bleed because it has a stronger dyeing property to the cellulose of the paper than an acid dye or a basic dye, and is therefore suitable as a recording agent. However, it generally has a low solubility in a solvent and is likely to be deposited due to environmental changes and the like, so that the nozzle is likely to be clogged.

For the above reasons, no proposal has been found in the prior art that satisfies all the above conditions.

Therefore, in the conventional ink jet recording method, the paper is treated so that the ink absorbency is good and the bleeding is uniform,
A combination of this special paper and ink for the purpose of preventing the drying of the tip of the discharge port of the recording head, using a paper for exclusive use of ink jet recording that gives clear printing with high contrast and also has water resistance and light resistance. To solve the problem as a system.

However, such a special paper is not preferable for the user because it is more expensive and difficult to obtain than general paper, and the selectivity of the paper is limited.

From the above, ordinary papers in offices and schools, such as notebooks, report papers, copy papers,
There has been a demand for ink that satisfies all the above conditions for plain paper such as letter paper and postcards.

Therefore, an object of the present invention is to provide an inkjet ink that satisfies all the above-mentioned required conditions. That is, it provides an inkjet ink having a high print density on plain paper, no irregular or irregular bleeding, good fixing property, excellent drying resistance of a recording head portion, and excellent storage stability. That is.

(Means for Solving Problems) The above object is achieved by the present invention described below.

That is, the present invention provides, as a recording agent, an ink used in a recording method in which a droplet ejected from an ejection port provided in a recording head is ejected onto a recording surface to perform recording.
A liquid medium containing CI Direct Black 168 and dissolving or dispersing this recording agent is at least the following (a), (b),
An ink jet ink comprising the components (c) and (d) and an ink jet recording method using the ink.

(A) Thiodiglycol (b) At least one volatile solvent selected from methanol, ethanol and butanol (c) At least one hygroscopic solvent selected from glycerin, trimethylolethane and trimethylolpropane (D) Water (Function) The ink of the present invention is used in a recording method in which droplets ejected from ejection ports provided in a recording head are ejected onto a recording surface to perform recording, and specific recording is performed. By combining an agent with a liquid medium of a specific composition, good printing can be performed not only on special paper but also on ordinary paper, that is, plain paper such as notebook, report paper, copy paper, letter paper, postcards, etc. It is possible. Also, it can be used without any problem in a special recording system, for example, a system in which thermal energy corresponding to a recording signal is applied to ink in the chamber of the recording head and a droplet is generated by the energy. In the case of this method, when general ink is used, solid content (dye and additive) in the ink is thermally acted upon continuous printing for a long period of time, and the impurities on the heater surface inside the discharge port. In many cases, they are deposited on the surface of the ink and the ejection direction is changed, or the ejection is not performed.
However, the ink of the present invention does not have such a problem, stable ejection can be obtained for a long period of time, and excellent printing is possible.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

CI Direct Black 168 used as a recording agent of the ink of the present invention is excellent in water resistance and light resistance,
Further, compared to other dyes, the dye does not have irregular or irregular bleeding when printed on plain paper, and the periphery of dots is sharp and high-quality printing can be obtained.

However, on the other hand, when a solid portion (a continuous dot portion obtained by simultaneously driving all the nozzles) is printed, a blank area is formed without filling the space between the dots, so that the optical density tends to decrease. Therefore, it is necessary to devise a method to uniformly and largely spread dots.

The content of the dye is determined depending on the type of liquid medium component, properties required for the ink, etc., but generally 0.1 to 15% by weight, preferably 0.5 to 10% by weight based on the total weight of the ink.
%, More preferably 1 to 5% by weight.
If the content is less than 1% by weight, the print density is insufficient, and if it exceeds 5% by weight, the degree of freedom of the liquid medium component for matching tends to be narrower.

Of course, the above dyes can be used alone or in combination with other dyes, that is, the dyes can be used as an essential component in combination with other dyes such as other direct dyes and acid dyes.

Next, the liquid medium component comprising at least the components (a) to (d) used in the present invention will be described.

First, thiodiglycol which is the component (a) has an effect of uniformly and greatly spreading ejected ink droplets on plain paper, and clear printing with high printing density can be obtained without degrading printing quality. Have an effect. Also, since the solubility of the dye is poor, it is difficult to use it alone, but when used in combination with another hygroscopic solvent, it has the action of promoting the solubility of the dye, so it is suitable for use in a mixed system. There is.

For this reason, the content of thiodiglycol is generally 1 to 30% by weight, more preferably 5 to 20% by weight, based on the total weight of the ink. Content is 5
If it is less than wt%, the effect of increasing the print density is weak, and
If it exceeds 20% by weight, irregular or irregular bleeding tends to occur.

Next, regarding the component (b), volatile solvents such as methanol, ethanol, and butanol among these components act as a fixing accelerator because they have the action of promoting the penetrating ability of droplets into paper and the vaporizing ability. effective.

Among these volatile solvents, methanol is dangerous when it gets into the eyes, butanol is a problem of odor,
Ethanol is preferred. The content of these volatile solvents is generally 0.1 to 15% by weight, more preferably 0.5 to 10% by weight, based on the total weight of the ink. If the content is less than 0.5% by weight, both the penetrating ability and the evaporating ability are insufficient, and in the range exceeding 10% by weight, the penetrating ability to paper is too remarkable and irregular or irregular bleeding is likely to occur. And the print density also decreases.

Next, regarding the component (c), the recording agent, the component (a) and the component (b) alone are insufficient in the clogging prevention effect, and are used to impart a sufficient clogging prevention effect. It is preferable that a small amount is effective. Among them, glycerin is most preferable in that it is unlikely to cause irregular or irregular bleeding, and trimethylolethane and trimethylolpropane are preferable in terms of the effect of preventing clogging. The content thereof is generally 1 to 20% by weight, more preferably 3 to 15% by weight, based on the total weight of the ink. If the content is less than 3% by weight, the effect of preventing clogging is insufficient, and if it exceeds 15% by weight, irregular or irregular bleeding tends to occur, and the fixing property is also insufficient.

Next, the component (d), water, is the basic component for forming the water-soluble ink, and its content is generally 20 to 95% by weight based on the total weight of the ink. It is preferably 50 to 80% by weight.

The ink of the present invention, which comprises the above-mentioned components as essential components, has a high printing density not only on the special paper but also on ordinary plain paper, can obtain clear and high-quality characters, and has a good fixability. Does not stain printed matter, has excellent water resistance and light resistance,
Further, although it has excellent properties such as good storage stability, a viscosity adjusting agent, a surface tension adjusting agent,
It is also possible to add additives such as a pH adjusting agent, an antifungal agent and an antirust agent.

Many inkjet recording methods using the ink of the present invention have been publicly known, and any of these known methods can be used in the ink of the present invention.

(Example) The present invention will be described in more detail by the following examples and comparative examples. In the following, all "parts" indicate "parts by weight".

Example 1 CI Direct Black 168 3 parts Thioglycol 16 parts Ethanol 5 parts Glycerin 6 parts Water 70 parts After sufficiently stirring with the above composition, the pore size was 0.45 μm.
Under pressure filtration using a Fluoropore filter (trade name of a filter manufactured by Sumitomo Electric Industries, Ltd.) to obtain the ink of the present invention. In the same manner, the inks of Examples 2 to 10 and the inks of Comparative Examples 1 to 5 were obtained as the inks of the present invention and the inks of the comparative examples.

Example 2 CI direct black 168 3 parts thiodiglycol 15 parts ethanol 5 parts trimethylolethane 5 parts water 72 parts Example 3 CI direct black 168 3 parts thiodiglycol 14 parts ethanol 5 parts trimethylolpropane 6 parts water 72 parts Example 4 CI direct black 168 2.5 parts thiodiglycol 10 parts methanol 4 parts trimethylolethane 4 parts water 79.5 parts Example 5 CI direct black 168 3 parts thiodiglycol 13 parts butanol 1 part glycerin 4 parts water 79 parts Example 6 CI Direct Black 168 3 parts Thiodiglycol 18 parts Ethanol 4 parts Trimethylolpropane 4 parts Water 71 parts Example 7 CI Direct Black 168 4 parts Thiodiglycol 14 parts Ethanol 5 parts Glycerin 6 parts Water 71 parts Example 8 CI Direct Black 168 3 parts thiodiglycol 4 parts Ethanol 5 parts Trimethylolpropane 10 parts Ethylene glycol 6 parts Water 72 parts Example 9 CI Direct Black 168 5 parts Thiodiglycol 22 parts Ethanol 6 parts Trimethylolpropane 10 parts Water 72 parts Example 10 CI Direct Black 168 3 Parts thiodiglycol 10 parts butanol 0.4 parts trimethylolethane 6 parts diethylene glycol 10 parts water 70.6 parts The following describes comparative examples.

Comparative Example 1 CI Direct Black 168 3 parts Ethanol 5 parts Trimethylolpropane 6 parts Ethylene glycol 14 parts Water 72 parts Comparative Example 2 CI Acid Black 2 3 parts Diethylene glycol 5 parts Polyethylene glycol (average molecular weight 300) 15 parts Water 77 parts Comparative Example 3 CI Direct Black 19 3 parts Glycerin 10 parts Ethylene glycol 5 parts Score Roll 700 (Nonionic surfactant, Kao Corporation)
0.02 parts Water 81.98 parts Comparative Example 4 CI Food Black 2 3 parts Glycerin 10 parts Diethylene glycol 20 parts Water 67 parts Comparative Example 5 CI Direct Black 154 3 parts Triethanolamine 10 parts Polyethylene glycol (average molecular weight 200) 15 parts Water 72 Part Example 11 An on-demand type multi-head (orifice size 50 × 40 μm) in which each ink of Examples 1 to 10 and Comparative Examples 1 to 5 is subjected to thermal energy to the ink in the recording head to generate droplets for recording. , Drive voltage 30V, frequency 4KHz)
Printing performance when mounted on a recording device with
The evaluation results of discharge performance and storage stability are shown in Table 1 below. The method and conditions of each evaluation item are as follows.

(1) Printing Density: Commercially available continuous slip paper was printed by simultaneously driving all nozzles, a patch was prepared and naturally dried in a room for 24 hours, and then the optical density of the patch was measured and evaluated according to the following criteria.

○: Optical density is 1.26 or more △: Optical density is 1.10 to 1.25 ×: Optical density is 1.09 or less (2) Occurrence rate of bleeding ... Commercial continuous slip paper is continuously printed so that 300 dots do not touch each other After air-drying for 24 hours, the number of dots with irregular or irregular bleeding was counted with a microscope, and the percentage was evaluated according to the following criteria.

○: 15% or less △: 16 to 40% ×: 41% or more (2) Fixing property (printing and drying property): 10, 20, 30, 40, 50 after printing alphanumeric characters on commercially available continuous slip paper After 60 seconds, the printed part was rubbed with a lens cleaning paper, and the number of seconds until the printed part was not stained was measured and evaluated according to the following criteria.

○: within 20 seconds △: 21 to 40 seconds ×: 41 seconds or more (4) Water resistance: Tap water is put in a petri dish and allowed to stand. The patch evaluated in the previous item (1) was gently dipped in it, allowed to stand for 5 minutes and dried, and the optical density was measured in the same manner as in the previous item (1). The optical density residual ratio (optical density after immersion / immersion) The previous optical density × 100; percentage) was calculated and evaluated according to the following criteria.

○: Remaining optical density is 80% or more △: Remaining optical density is 60 to 79% ×: Remaining optical density is 59% or less (5) Discharge stability: Printed on 100 sheets of continuous slips Evaluated.

○: No abnormality ×: No ejection or print disorder occurred (6) Clogging property (sticking recovery property)… Leave it in a constant temperature bath at 60 ° C for 1 month, and then leave it at room temperature for 24 hours to recover (suction by pumping). After performing the operation), printing was performed and evaluation was performed according to the following criteria.

◯: Return to normal printing state within 5 times of recovery operation Δ: Return to normal printing state after 6 to 10 times of recovery operation ×: No ejection or print disorder during recovery operations 6 to 10 (7) Storage stability ... Each 10 ink in a heat-resistant glass bottle
After inserting each 0 cc, sealing and storing for 3 months in a constant temperature bath of 60 ° C., 100 sheets of continuous slip paper were printed on the recording device and evaluated according to the following criteria.

○: No abnormality ×: No ejection, print disturbance or discoloration As described above, by using the ink of the present invention, (1) it is possible to obtain clear and high-quality printing with high printing density on plain paper.

(2) The fixing property (printing drying property) is fast, and the printed matter is not stained even if it is rubbed.

(3) Long-term storage stability of the ink is good, and stable ejection is always obtained.

(4) The printed matter has good water resistance and light resistance.

(5) The recording head is hard to dry, and stable ejection can be obtained from the start of recording even if the recording apparatus is left for a long time.

The ink of the present invention is suitable as an inkjet ink.

Claims (2)

[Claims] 1. A recording liquid used in a recording system for recording by ejecting droplets ejected from an ejection port provided in a recording head onto a recording surface, containing CI Direct Black 168 as a recording agent, An ink jet recording liquid, wherein a liquid medium for dissolving or dispersing this recording agent comprises at least the following components (a), (b), (c) and (d). (A) Thiodiglycol (b) At least one volatile solvent selected from methanol, ethanol and butanol (c) At least one hygroscopic solvent selected from glycerin, trimethylolethane and trimethylolpropane (D) water 2. An ink jet recording method, wherein thermal energy is applied to the recording liquid according to claim 1 to form droplets, and recording is performed using the droplets.