JPH0214260A - Ink jet recording solution and ink jet recording - Google Patents

Abstract

PURPOSE:To obtain the title recording solution having excellent shelf stability and discharge stability free from clogging of nozzle even in long-term interruption of recording containing dye, water, specific amount of trimethylolpropane and specific amount of lower alcohol. CONSTITUTION:The aimed recording solution containing dye (e.g. C.I. food black), water, 0.5-25wt.%, preferably 1-20wt.% trimethylolpropane and 1.0-10.0wt.% lower alcohol (preferably methanol, ethanol, isopropanol or butyl alcohol). Droplets of the recording solution are flied by using heat energy and attached to materials to be recorded to carry out recording.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an inkjet recording liquid (hereinafter referred to as ink) and an inkjet recording method, and in particular, it uses thermal energy to fly ink as droplets, and performs 3J. The present invention relates to an ink suitable for an inkjet recording method and an inkjet recording method.

(Prior art) Ink for inkjet recording must (1) provide sufficient density necessary for recording, (2) not clog the nozzles of the printer head, and (3) ensure that the ink does not flow on the recording material. (4) There is little irregular bleeding on the recording material; (5) There is no change in physical properties or precipitation of solid content during storage; (6) There is no need to use thermal energy. In an inkjet recording method in which small droplets of ink are ejected, performance is required such as preventing the deposition of foreign matter on the heat generating head that heats the ink.

In order to satisfy these required performances, the following measures have conventionally been taken.

First, regarding (1), the common method is to provide sufficient density by increasing the density of the dye. If you are going to do that, you will inevitably need it. However, when the diameter of the ink ejection nozzle is small, such as in an inkjet printer, the ink evaporates quickly from the nozzle tip when the printer is stopped, causing the solid dye to precipitate, causing problem (2). leading to. Moreover, there was a problem in that the higher the concentration of the dye, the more easily this phenomenon occurred.

Therefore, for (2), measures have been taken to prevent evaporation drying by adding a polyhydric alcohol-based wetting agent with high water retention, but if the printer is stopped for a long time or left in a high temperature environment, In such cases, since these wetting agents are usually liquids, evaporation and drying is inevitable, resulting in the formation of hard precipitates of dye, and therefore, the recovery properties are also very poor.

This may be improved by using a large amount of such water-retaining wetting agents, but as a result, the viscosity of the ink increases, and when printing with such ink, the unit on the recording material Because the amount of wetting agent per area increases (3)
A new problem will arise.

To solve this problem, surfactants are added to lower the surface tension of the ink and improve its permeability and drying properties, but if they are used to the extent that the effect of the addition is fully exerted, it may cause damage. A problem was observed in which the performance (4) could not be satisfied, that is, irregular bleeding of the ink on the recording material occurred frequently.

Regarding performance (6), a method has been proposed to minimize impurities such as inorganic salts in the ink, but dyes as recording agents and organic liquids as wetting agents can also be degraded by heat-generating elements due to thermal decomposition. This causes surface deposits, and the problem has not been solved satisfactorily.

As mentioned above, although it is possible to find a means to satisfy each performance individually in the conventional technology, it is difficult to satisfy these performances simultaneously.
At present, no ink or inkjet recording method that solves this series of problems is known.

(Problem to be solved by the invention) It is natural that various performances are required for conventional inks such as those mentioned above, but in particular, performances that require acid are recorded using ink. In this case, the nozzle of the printer device becomes clogged when recording is interrupted or when no recording is performed for a long period of time.

In particular, in the inkjet method that uses thermal energy, the ejection power is the acting force generated by the rapid volume change of the ink, so the ejection force is smaller than other inkjet methods that apply pressure to the ink and eject it from a nozzle. For this reason, it is disadvantageous in terms of compensating for clogging due to increase in ink viscosity due to ink evaporation at the tip of the nozzle or solid content precipitation with ejection force, so prevention of clogging and its recovery are particularly important issues. be.

Furthermore, suppression of irregular bleeding on the recording material and quick drying properties are also becoming important performances that are indispensable for the popularization of versatile inkjet printers that can be used with any recording material.

Therefore, the purpose of the present invention is to solve the above-mentioned drawbacks of the prior art. That is, despite the high concentration of dye, clogging of the printer head can be prevented even when the printer is temporarily stopped or stopped for a long time. Even if clogging occurs, it is easy to recover from, and it also dries quickly on the recording material, producing high-quality images made of round dots with less irregular bleeding. At the same time, we provide an ink that has excellent storage stability and does not cause foreign matter to be deposited on the surface of the heating head of an inkjet printer that uses thermal energy. be.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention consists of two inventions, and the first invention is an inkjet ink containing dye and water containing at least 0.5 to 25% by weight of trimethylolpropane and 1.0 to 10.0% by weight of lower alcohol. The second invention is an inkjet recording method in which recording is performed by ejecting small droplets of ink using thermal energy and adhering them to a recording material, in which the Hokki ink is characterized by a dye and a dye. In addition to water, at least 0.5 to 25% by weight of trimethylolpropane and 1% of lower alcohol
．． 0 to 1. This is an inkjet recording method characterized by containing 0% by weight of O.

(Function) The present inventor has developed an inkjet ink that simultaneously satisfies the various performance requirements described above.As a result of improving the ink, the ink contains trimethylolpropane, a solid component with high hygroscopicity. This improves the prevention of ink evaporation, and even if the liquid component in the ink at the nozzle tip completely evaporates, trimethylolpropane remains as a solid content along with the dye, which alleviates the strong agglomeration and precipitation of the dye. It has been found that recovery from nozzle clogging is extremely easy due to its high hygroscopicity.

Furthermore, by containing a highly volatile lower alcohol, the evaporation and penetration of the droplets discharged from the nozzle onto the recording material is promoted, so that the trimethylolpropane is quickly recorded as a solid content along with the dye. Because it stays on the material, it dries quickly, and we found that the printed dots maintain a nearly perfect circle shape.

In addition, such ink has excellent storage stability, so even in inkjet printers that use thermal energy, it exhibits excellent ejection stability without depositing foreign matter on the surface of the heat generating head. .

(Preferred Embodiment) The inkjet ink of the present invention is an inkjet ink containing at least a dye and water, and a specific organic substance, that is, 0.5 to 25% by weight of trimethylolpropane and 1.0 to 10.0% by weight of a lower alcohol. It is characterized by containing %.

The amount of trimethylolpropane added to the ink is from 0.5 to 25% of the ink, more preferably 1%.
The range is from 20% to 20%.

If the content of trimethylolpropane is less than 0.5% by weight, the effect of preventing ink evaporation will not only be insufficient, but also the function as solid content, which is an important point of the present invention, will be insufficient.
In other words, even if the liquid component in the ink at the tip of the nozzle evaporates, it will not be able to satisfy the function of alleviating the strong agglomeration and precipitation of the dye, and if the content exceeds 1% by weight, the effect of preventing ink evaporation will be reduced. If it becomes too large, it will actually hinder the quick drying of the ink on the recording material, which will cause problems on the recording material, such as the inability to instantly suppress the occurrence of irregular bleeding. Become.

Further, as the lower alcohol used in the present invention, methanol, ethanol, isopropanol, butyl alcohol, etc. are preferable, and the range of use thereof is 1.0 to 10.0 f.
flfffi% range.

If the amount of lower alcohol is less than 1.0% by weight, the evaporation and penetration of the ink droplets on the recording material will be insufficient, resulting in slow cleaning and drying. If the content exceeds the amount, irregular bleeding will occur more frequently, making it impossible to obtain dots with a good shape that is close to a perfect circle.
Furthermore, this is undesirable because the accelerated evaporation of ink at the nozzle tip causes clogging after printing is stopped.

The dye used in the present invention is a color index (Col
Almost all of the water-soluble acidic dyes, direct dyes, basic dyes, and reactive dyes listed in the following can be used.

Also, even if it is not listed in the color index,
Any water-soluble dye can be used.

The amount of these dyes to be used is not particularly limited, but it is preferably in the range of 0.1 to 15% by weight based on the total weight of the ink.

In addition to the above-mentioned components, the ink of the present invention may optionally contain a water-soluble organic solvent, a surfactant, and pH! ii Conditioner, rust preventive agent, preservative and fungicide, antioxidant, evaporation accelerator, chelating agent,
Various additives such as water-soluble polymers may be added.

Specific water-soluble organic solvents include amides such as dimethylformamide and dimethylacetamide; ketones such as acetone; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol;
coal, propylene glycol, butylene glycol,
Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol; Glycerin: ethylene glycol methyl (or ethyl) Lower alkyl ethers of polyhydric alcohols such as ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, Examples include triethanolamine, sulfolane, dimethyl sulfoxide, and the like.

The inkjet recording method of the present invention is a method using the above-mentioned ink of the present invention, and the inkjet recording method includes:
For example, in the method described in Japanese Unexamined Patent Publication No. 54-59936, ink subjected to the action of thermal energy undergoes a rapid volume change, and the acting force due to this state change causes
This is a method in which ink is ejected from a nozzle. By using the ink of the present invention in such a system, even if recording is performed continuously for a long time, no foreign matter will be deposited on the heat generating head, and stable recording can be performed.

(Example) Next, the present invention will be explained in detail with reference to Examples and Comparative Examples. Incidentally, the term "conidia" or "%" is based on weight b1.

Examples 1 to 8 The following components were mixed, sufficiently stirred to dissolve, and then filtered under pressure using a Fluorobor filter (manufactured by Sumitomo Electric Industries, Ltd.) with a pore size of 0.45 μm to prepare eight types of inks of the present invention.

-1 Ink C, 1, Food Black 2 6 parts Trimethylolpropane 10 parts Ethylene glycol 20 parts Pluronic L-62
(Trade name of Asahi Denka Kogyo@)
0.2 part methanol
4 parts water
60 parts' - Row 2 ink c, r, Direct Black 154 7 parts trimethylolpropane 15 parts triethylene glycol 5 parts isopropanol
3 parts water
70 parts - 1 agency 3 ink (:, 1. Direct Blue 86 5 parts trimethylolpropane 15 parts ethyl alcohol water Dye A Dye B Trimethylolpropane n-butyl alcohol water 2 parts 5 inks ゛Dye A Dye B Tri Methylolpropane ethyl alcohol 5 parts 75 parts 3 parts 15 parts 2 parts 77 parts 3 parts 15 parts 5 parts Water'' 6 Ink C, R, Food Black 2 Trimethylol Propane Sulfolane Glycerin Methanol Water 7.17 Ink C , 1, Acid Yellow 23 Trimethylolpropane diethylene glycol isopropyl alcohol water Me 8 ink (:, 1. Acid Red 35 Trimethylolpropane diglycol n-butyl alcohol water 74 parts 5 parts 1 part 10 parts 8 parts 66 parts 4 parts, 10 parts, 10 parts, 6 parts, 70 parts, 5 parts, 10 parts, 5 parts, 1 part, 79 parts.

Ink in row 1: Dye A 3 parts Dye 8
3 parts trimethylolpropane 30 parts water
64 parts “Ifi2 ink” Comparative ink composition obtained by removing trimethylolpropane from the ink composition of Example 6” 3 parts Dye A 3 parts Dye 8
3 parts trimethylolpropane 15 parts ethyl alcohol
05 part water
78.5 parts obscuring silicone dye A 3 parts dye 8
3 parts trimethylolpropane 15 parts ethyl alcohol
15 parts water
Example of use of 64 copies Inks of Examples 1 to 8 and Comparative Examples 1 to 4 were installed in an inkjet printer BJ-80A (manufactured by Canon, nozzle size 50 x 40 μm, number of nozzles 24) that uses a heating element as an ink ejection energy source. Table 1 shows the evaluation results of the dryness of the print, the incidence of bleeding, clogging during reprinting after a print stop, and clogging recovery when reprinting after a long print stop. show.

(Evaluation method and evaluation criteria) (1) Printing dryness Regarding the printing dryness, after printing alphanumeric characters with a printer on commercially available continuous slip paper, 10.20.30.40.
After 50 and 60 seconds, it was rubbed with a filter paper (Toyo Roshi Co., Ltd. No. 2 (trade name)) and judged based on the number of seconds until the printed area was no longer stained (at 20°C ± 5°C, 50 ± 10% RH). measurement).

O: Within 20 seconds △: Within 20 to 40 seconds The number of dots that developed ooze was counted using a microscope and expressed as a percentage (20 parts at 5°C, 50 parts at 10%, 1
111).

O: 10% or less △: 11 to 30% After filling the ink and printing alphanumeric characters continuously for 10 minutes, stop printing, leave it for 10 minutes without capping, etc., then print alphanumeric characters again, and the characters will be blurred, missing, etc. Judgment was made based on the presence or absence of defective parts (left at 20±5° C., 50±10% R11).

There are no defects starting from the O knee letter.

△Part of the knee letter is faded or missing.

×The knee character cannot be printed at all.

(4) Recovery from clogging when reprinting after a long-term printing stop After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, stop printing and leave it without a cap for 7 days. After leaving it for a while, we performed an operation to recover from the nozzle clogging, and determined how many times it took to print normally without blurring or missing characters (60℃, IO ± 5%RH).
(Leave it there).

O: Normal printing is possible after 1 to 5 recovery operations.

△: Normal printing is possible after 6 to 10 recovery operations.

×: Normal printing is possible after 11 or more recovery operations.

77 1 Mi( (Evaluation result) ”-L 〔11-21壬-3Otsu2-1n all 22 major ~ Li1OO○
F --2-) Knee 22 = Shiichi ΣL1-1 no
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Claims (2)

[Claims] (1) An inkjet recording liquid containing a dye and water, which contains at least 0.5 to 25% by weight of trimethylolpropane and 1.0 to 10.0% by weight of a lower alcohol. (2) Flying small droplets of recording liquid using thermal energy,
In an inkjet recording method in which recording is performed by adhering to a recording material, the recording liquid contains, in addition to the dye and water, at least 0.5 to 25% by weight of trimethylolpropane and 1.0 to 10.0% by weight of lower alcohol. An inkjet recording method characterized by containing %.