JPS61157566A - Recording liquid - Google Patents

Abstract

PURPOSE:To provide a recording liquid composed of specific amounts of a recording agent, water, and a water-soluble organic solvent, having a specific water activity, free from the precipitation of solid components, the change in physical properties and the clogging of the nozzle during storage, harmless to human body, and suitable for ink-jet recording. CONSTITUTION:The objective recording liquid having a water activity of 0.70-0.90 can be produced by mixing 0.5-20(wt)%, preferably 1-6% recording material (e.g. dye), water, a water-soluble organic solvent (e.g. methyl alcohol), and if necessary, a viscosity modifier, a surfactant, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording liquid suitable for use in an inkjet system or a writing instrument in which recording is performed by ejecting droplets from an orifice of a recording head.

[Prior art] Inkjet recording methods are used in these inkjet recording methods because they generate less noise and can perform high-speed recording without requiring special fixing compared to paper passing. The recording liquid used must have physical properties such as viscosity and surface tension within appropriate ranges, and must not clog the fine ejection openings (orifices).1g It must provide a recorded image with a bright color tone and sufficiently high density. In addition, properties such as no change in physical properties or precipitation of solid content during storage are required. In addition to these properties, recording can be performed without any restrictions on the type of recording material such as paper, high fixing speed to the recording material, water resistance, solvent resistance (especially alcohol resistance). It is also required to have properties such as being excellent in light resistance and abrasion resistance, providing images with excellent resolution, and being non-toxic to the human body.

On the other hand, even in conventional writing instruments such as fountain pens and felt pens, replenishment of recording liquid to the pen tip is done using capillary phenomenon, so the dissolution stability of the recording agent is excellent. The properties required for the above-mentioned inkjet recording liquid are also required. Therefore, in general, any recording liquid that satisfies the required characteristics as a recording liquid for inkjet recording can be used as a recording liquid for conventional writing instruments.

Now, the recording liquid used in the inkjet recording method is basically composed of a dye as a recording agent and its solvent, and the various properties of the recording liquid mentioned above depend on the inherent properties of the dye and the solvent composition. There are many places where it is done. Therefore, selecting the dye and solvent composition so that the recording liquid has the above characteristics is an extremely important technique in this technical field.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and provides a recording liquid that is less likely to cause precipitation of solid content or change in physical properties during storage, and whose ejection ports are less likely to be clogged. It was done in order to

Another object of the present invention is to provide a recording liquid that is non-toxic to the human body.

[Means and effects for solving the problems] According to the present invention, there is provided a recording liquid containing as essential components a recording agent of 0.5 to 2o 1%, water, and a water-soluble organic solvent, which has a water activity. (A%
There is provided a recording liquid characterized in that I) is 0.70 to 0.80.

In the recording liquid as an essential component, the water activity of the recording liquid (
Ay) is 0.70 to 0.90.

Water activity as referred to in the present invention
:Ay) is defined as follows.

Ａ　w　＝　P　/　P　.

PO: Maximum water vapor pressure P at the measurement temperature: Water vapor pressure of the recording liquid at the measurement temperature A Conway water activity meter is used to measure the water activity.

Conway water activity meter (see Figure 1, where L =
A standard solution with a known water activity value (88m layer) and a sample were placed in a container that kept the relative humidity constant and kept at a constant temperature (25°C).
) for about 2 hours and measure the increase or decrease in water in the sample.
This is usually done using four standard solutions, and the water activity value (Ay) of the sample is determined from the increase or decrease.

The recording agent contained in the recording liquid of the present invention serves as a color component of the recording liquid, and is a substance generally classified as a dye or a pigment.

The content of the recording agent in the recording liquid is determined depending on the component composition of water and wetting agent as well as the properties required of the recording liquid, but is at least in the range of 0.5 to 20% by weight. It is desirable that the content is preferably in the range of 1 to 10% by weight, more preferably 1 to 6% by weight.

The recording liquid of the present invention contains water and a water-soluble organic solvent as essential components as a liquid medium of the recording material.

Examples of water-soluble organic solvents include methyl alcohol,
Alkyl alcohols having 1 to 4 carbon atoms such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 5ec-butyl alcohol, tart-butyl alcohol, and isobutyl alcohol Amides such as dimethylformamide and dimethylacetamide Acetone, diacetone alcohol Keto alcohols; Ethers such as tetrahydrofuran and dioxane; Polyalxylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycols, butylene gelicol, triethylene glycol, 1. 2.2-6 fullkylene groups such as 6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol, etc.
alkylene glycols containing 5 carbon atoms; glycerin; lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-
Examples include nitrogen-containing double (cyclic ketones) such as 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone.

The recording liquid of the present invention prepared from such components has excellent recording properties (signal response, droplet formation stability, ejection stability) as a recording liquid for writing instruments or a recording liquid for so-called inkjet recording. storage stability, dissolution stability of the recording agent, fixation to the recording material, or light resistance, weather resistance, and water resistance of the recorded image. , #alcoholicity, etc. are both well-balanced and excellent. In order to further improve such characteristics, various conventionally known additives may be further added and contained.

Such additives include, for example, polyvinyl alcohol, celluloses, viscosity modifiers for water-based resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as jetanolamine and triethanolamine. Adjustment agent; PH adjustment agent using a buffering agent, etc. can be mentioned.

In order to prepare a recording liquid used in a type of recording method in which the recording liquid is charged, a resistivity adjusting agent such as inorganic salts such as lithium chloride, ammonium chloride, and sodium chloride is used. Further, urea and thiourea are preferably used as water retention improvers at the tip of the discharge orifice. Note that in the case of a type in which recording liquid is ejected by the action of thermal energy, thermal physical property values (eg, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted.

The recording liquid of the present invention has particularly excellent properties as a recording liquid for inkjet recording, but it can also be used for recording with conventional writing instruments such as fountain pens and felt-tip pens that record on recording materials such as paper. It can also be used as a liquid.

〔Example〕

The present invention will be explained in more detail with reference to the following synthesis examples and examples.

Synthesis Example 1 (Reaction-1) 0.25 mol of 2-naphthylamine-8-sulfonic acid was added to a 30 flask, and the temperature was kept at 0.25 mol so that the temperature did not exceed 40°C until the pH reached 7. 1 Gradually drop NNaOH aqueous solution 6 Next, add 500 g of ice, and after the temperature has fallen to 10°C, add 100 cc of 37% concentrated hydrochloric acid and 3
85 cc of 0% NaNO2 solution is added, and the reaction mixture is kept at 18°C and reacted for 2 hours with stirring. On the other hand, there are 5 standing 3
0.34 mole of m-)luidine was added in the flask;
500 cc of distilled water and 50 cc of 37% concentrated hydrochloric acid were added to this, dissolved at 50°C, cooled to 30°C in an ice water bath, and then the reaction solution in the 30 flasks in the above 2 sentences was added and reacted at 20°C for 30 minutes. Next, 500 cc of a 20% aqueous sodium acetate solution was added, and the mixture was stirred at room temperature for about 20 hours, and 125 cc of 37% a salt was added to make it acidic. Let it dry inside.

(Reaction-2) Add the entire amount of the product obtained in Reaction-1 to two beakers, add one cup of distilled water and 60 cc of 40% NaOH aqueous solution, dissolve at a temperature of 40 to 50°C, and then add 30% NaN
Add O2 aqueous solution. Meanwhile, 200 cc of 37% concentrated hydrochloric acid and 800 g of ice were added to a 30-ml flask, and while stirring vigorously, the contents of the beaker prepared earlier were gradually added and stirring was continued for 1 hour. Next, the reaction product is filtered using qualitative paper, and the filtered paste is added to a 2 fL beaker, and 400 g of ice and 500 cc of distilled water are added and stirred to mix and dissolve. In addition, 0.35 mole of 1-amino-2ethoxynaphthalene-6-sulfonic acid was added to 4 flasks of 30, and 0.35 mole of 1-amino-2ethoxynaphthalene-6-sulfonic acid was added to 1 mole of distilled water and 0.35 mole of 1-amino-2ethoxynaphthalene-6-sulfonic acid. IN NaO
Add H aqueous solution dropwise until the pH becomes 7.0 and completely dissolve at 40°C. Transfer the contents of 30 flasks to 2 in an ice water bath.
The mixture is cooled to 0 to 25°C, and the above paste solution is added dropwise thereto, followed by 450 cc of 20% sodium acetate solution. After that, stirring was continued for 7 hours, and then Na200
335, Og was added and heated until the temperature reached 60°C over 1 to 2 hours, and then about 1 hour of 110% NaC aqueous solution was added to salt out. - Dry inside.

(Reaction-3) Add the entire amount of the product obtained in Reaction-2 to a 30-meter flask, add 800 cc of distilled water and 400 cc of 50% acetic acid, and stir for 2 hours without letting the temperature exceed 30°C. After cooling to below 20°C, 30% Ha) JO2 aqueous solution 1
00cc was added and stirred for 7 hours to obtain Solution A.

Meanwhile, add 0.28 mol of H acid into 2 30 flasks,
Add 500 cc of distilled water to this, dissolve it, and then add 40 cc of distilled water.
After adding 32 cc of % NaOH aqueous solution and 315 g of Na2 CO, and raising the temperature to 70° C., 50 g of acetic anhydride was added, and stirring was continued until the temperature reached room temperature while allowing the mixture to cool. The resulting reaction solution was added to an In 30 flask containing 1.5 g of pyridine and 2 kg of ice, and mixed thoroughly. Next, Solution A was further added, and after stirring at 80°C for 1 hour,
Add about 2 portions of 10% aqueous solution and after salting out, filter using qualitative paper to obtain a filter cake.

(Purification) 250cc of methyl cellosolve for 10g of filter cake
Stir both in a beaker for about 3 hours at a ratio of 7. After mixing and dissolving the two, filter using No. 2 qualitative filter paper (manufactured by Toyo Roshi ■), and concentrate and dry the furnace liquid with an evaporator to obtain the dye. I got an A.

Synthesis Example 2 In (Reaction-1) of Synthesis Example 1, the same molar amount of naphthionic acid was used instead of 2-naphthylamine-8-sulfonic acid, and in (Reaction-3), the same molar amount of PR was used instead of H acid.
Dye B was obtained by repeating the same operation as in Synthesis Example 1 except that an acid was used.

Synthesis Example 3 Same operation as Synthesis Example 1 except that in (Reaction-1) of Synthesis Example 1, the same molar amount of 1-naphthylamine-5-sulfonic acid was used instead of 2-naphthylamine-8-sulfonic acid. Dye C was obtained by repeating the steps.

Synthesis Example 4 In (Reaction-1) of Synthesis Example 1, instead of 2-naphthylamine-8-sulfonic acid, the same molar amount of crepe acid-7,
A dye was obtained by repeating the same operations as in Synthesis Example 1, except that in (Reaction-3), the same molar amount of H acid was used instead of H acid.

Examples 1 to 8 and Comparative Examples 1 to 3 Recording liquids were prepared using the dyes obtained in Synthesis Examples 1 to 4 and commercially available dyes based on the following four types of formulations.

Blend composition Nidiethylene glycol 30 parts by weight N-methyl-2-pyrrolidone 15 // Distilled water
551/dye 1.5~
3 tt composition ■ Glycerin IO // Polyethylene glycol 300 5 tt Distilled water
85〃 Dye 1~4 tt Combination example ■ Polyethylene glycol 300 2 Offi parts diethylene glycol lOl/distilled water
70〃 Dye 1.5-3 //Formulation example■ Polyethylene glycol 300 10 Parts by weight Distilled water 90〃 Dye 1-4 ttFormulation example V Glycerin 10 Parts by weight Diethylene glycol 15 ttN-Methyl-2-
Pyrrolidone: 15 Distilled water: 60 Dye: 1 to 4 tt After storage, this was filtered under pressure using a Teflon filter with a pore size of 1 #Lm, and the presence or absence of a precipitate and the amount of the precipitate were examined.

The evaluation criteria were as follows.

-No second precipitate +: A slight amount of precipitate was observed on the filter.

++: Precipitate was observed on the filter.

[Safety] After being stored in a sealed glass container at 135° C. for one day, a general bacterial count test was conducted.

The evaluation criteria were as follows.

1: 100 or less/g +2102 to 1037 g ++: 103 to 105/g The above ingredients are thoroughly mixed and dissolved in a container with a pore size of 1 g.
After pressure filtration with a Teflon filter, the solution was degassed using a vacuum pump to obtain a recording liquid.

The composition of each recording liquid is summarized in Table 1.

Water activity value (Aw), storage stability, and safety tests were conducted on these recording liquids. The results are also shown in Table 1. In addition, each evaluation test of the recording liquid was carried out by the following method.

[Water Activity Value] Using a Conway water activator, a standard solution with a known water activity value and a recording liquid were kept at a constant relative humidity and left at 25°C for 2 hours, and then the increase or decrease in water in the recording liquid was measured. The water activity value of the recording liquid was determined from this increase/decrease.

[Storage Stability] The recording solution was left sealed in a glass container at 35° C. for one day, and evaluated according to Haki evaluation criteria.

Table 1

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing the Conway water activity measuring device.

Claims (1)

[Claims] (1) A recording liquid containing 0.5 to 20% by weight of a recording agent, water, and a water-soluble organic solvent as essential components, the water activity (A
A recording liquid characterized in that w) is 0.70 to 0.90.