JPH0214262A - 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 trimethylolethane 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.% trimethylolethane 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 to an inkjet recording liquid that uses thermal energy to fly ink as droplets to perform recording. The present invention relates to inks suitable for recording methods and inkjet recording methods.

(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 (]), the common method is to provide sufficient density by increasing the density of the dye. If you are trying to do this, you will inevitably need 7. 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, the higher the concentration of the dye, the more easily this phenomenon occurs.

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 moisturizing agents are usually liquids, evaporation and drying cannot be avoided, resulting in the formation of hard precipitates of dye, and therefore, the recovery properties are also very poor.

A solution to this problem was seen by using a large amount of such a water-retaining wetting agent, but as a result, the viscosity of the ink increased, and when printing with such ink, it became difficult to print on the recording material. Because the amount of wetting agent per unit 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 of the conventional ink as mentioned above, but the most required performance is when recording with the ink. , the nozzle of the printer device is clogged when recording is interrupted and 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 trimethylolethane 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, wherein the ink contains dye and water. In addition, at least 0.5 to 25% by weight of trimethylolethane and 1.0% of lower alcohol.
This is an inkjet recording method characterized in that the content is from 10.0% by weight.

(Function) The present inventor improved the inkjet ink in order to simultaneously satisfy the various required performances as described above, and as a result, the ink contains trimethyole ethane, which is a highly hygroscopic solid component. This improves the prevention of ink evaporation, and even if the liquid component in the ink at the nozzle tip completely evaporates, trimethylolethane 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 droplets ejected from the nozzle onto the recording material is promoted, so that trimethylolethane 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.

Furthermore, since such ink has excellent storage stability, it exhibits excellent ejection stability without depositing foreign matter on the surface of the heat generating head, especially in inkjet printers that utilize thermal energy.

(Preferred Embodiment) The inkjet ink of the present invention contains at least a dye and water and a specific organic substance, that is, trimethylolethane. The ink is characterized by containing 5 to 25% by weight and 1.0 to 10.0% by weight of lower alcohol, and the amount of trimethylolethane added to the ink is preferably 0.5 to 25% by weight of the ink. is in the range of 1 to 20% by weight. If the content of trimethylolethane is less than 0.5% by weight, the effect of preventing ink evaporation will not only be insufficient, but also the function as a solid content, which is an important point of the present invention, that is, the ink at the tip of the nozzle. Even if the liquid component inside 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 25% by weight, the effect of preventing ink evaporation will become too large, and vice versa. This impedes the quick drying of the ink on the recording material, which causes a problem on the recording material that irregular bleeding cannot be instantaneously suppressed.

Further, as the lower alcohol used in the present invention, methanol, ethanol, isopropanol, butyl alcohol, etc. are preferable, and the usage range is 1.0 to 10.0% by weight.

If the amount of lower alcohol is less than 1.0% by weight, the evaporation and penetration of ink droplets on the recording material will be insufficient, resulting in slow fixation and drying, and if the amount exceeds 10.0% by weight, If it is contained, irregular bleeding will occur more frequently, making it impossible to obtain dots with a good shape that is close to a perfect circle.
Furthermore, the evaporation of the ink at the tip of the nozzle is accelerated, resulting in clogging after printing is stopped, which is undesirable.

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 - numerically, it is 0.1 to 1 to the total amount of ink.
A range of 5% by weight is preferred.

In addition to the above-mentioned components, the ink of the present invention may optionally contain a water-soluble organic solvent, a surfactant, a pH adjuster, a rust preventive agent, an antiseptic agent, an antioxidant, an evaporation promoter, a 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 gelicols such as polyethylene glycol and polypropylene glycol; ethylene glycol; Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms, such as propylene glycol, butylene gelcol, triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin: Lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether: N-methyl-2-pyrrolidone, 1,3-dimethyl -2-imidazolidinone, 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 more detail by giving examples and comparative examples. Incidentally, the term "part part" or "%" is based on weight.

Examples 1 to 8 The following components were mixed, sufficiently stirred to dissolve, and filtered under pressure using a Fluorobor filter (manufactured by Sumitomo Electric Industries, Ltd.) with a pore size of 0° and 45 μm to prepare the following inks.

1. Ink C, 1, Food Black 2 Trimethylolethane Ethyl Alcohol Bruronic - 62 people) Methanol Water - 2. Ink C, T, Direct Black 154 Trimethylolethane Triethylene Glycol Isopropanol Water - 3. Ink C, 1. Direct Blue 86 Trimethylolethane Ethyl alcohol 6 parts 10 parts 20 parts (Trademark manufactured by Asahi Denka Kogyo ■ 0.2 parts 4 parts 60 parts 8 types of invention 7 parts 15 parts 5 parts 3 parts 70 parts 5 parts 15 Part 5 parts Water Dye A Dye B Trimethylolethane n-Butyl alcohol water 2'-5 parts Dye A Dye B Trimethylolethane Ethyl alcohol water 75 parts 3 parts 3 parts 15 parts 2 parts 77 parts 3 parts 3 parts 15 parts 5 parts 74 parts 6 Ink C11, foot black 2 Trimethylolethanesulfolane glycerin methanol water -7 ink C,l acid yellow 23 Trimethylolethane diethylene glycol isopropyl alcohol water - da8 ink C,1, Acid Red 35 Trimethylolethanethiodiglycol n-butyl alcohol water 5 parts 1 part 10 parts 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 Process A Four types of comparative inks were prepared in the same manner as in Example 1.

Ink in row 1 Dye A 3 parts Dye 8
3 parts trimethylolethane 30 parts water
64 parts Ink 2 Comparative ink composition obtained by removing trimethylolethane from the ink composition of Example 6 Ink 3 Dye A 3 parts Dye B
3 parts trimethylolethane 15 parts ethyl alcohol
0.5 part water
78.5 parts 4 parts Dye A 3 parts Dye 8
3 parts trimethylolethane 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 (20°C ± 5°C, 50 parts 10% R) I
).

O: within 20 seconds Δ: within 20 to 40 seconds After leaving for more than an hour, the number of bleeding dots was counted using a microscope and expressed as a percentage (20 parts, 5°C, 50±10%R).
1 (printed at).

O: 10% or less △: 11 to 30% ×: 31% or more (3) Printing - Clogged when reprinting after stopping Printing - For clogging when reprinting after stopping, check the printer according to the specified After filling the ink and printing alphanumeric characters continuously for 10 minutes, stop the print, leave it for a while 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±1O%R)I).

There are no defects from the O knee letter onwards.

△A part of the knee letters 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, I would like to perform the operation to recover from the nozzle clogging, and determine how many times it takes to print normally without blurring or missing characters, etc. at 60℃, lO ± 5%RH.
(Leave it there).

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

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

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

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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 trimethylolethane 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 trimethylolethane and 1.0 to 10.0% by weight of lower alcohol. An inkjet recording method characterized by containing %.