JPH0729477B2 - Inkjet recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable not only to designated papers specially prepared for ink jet, but also to other offices such as copy papers, report papers, bond papers and continuous slip papers. The present invention relates to an ink jet recording method capable of obtaining a recorded material having excellent fastness to paper and various cloths generally used at home.

[Conventional technology]

As the ink jet recording method, various ink ejection methods (for example, an electrostatic suction method, a method of applying mechanical vibration or displacement to ink by using a piezoelectric element, a method of heating ink and utilizing pressure at that time, etc. are known. Is used to form ink droplets, and a part or all of them are attached to a recording material such as paper for recording.

As the ink to be used, a method in which recording is performed by using a recording liquid (also referred to as ink) in which water and a water-soluble organic solvent as a main component and a dye is dissolved is the mainstream.

In the recording method using this type of ink, although the required items are slightly different depending on the method, the items commonly required are: (1) No bleeding and a good-quality printed image can be obtained. .

(2) The fixing speed of the ink is high.

(3) The durability of the printed matter such as water resistance and light resistance is excellent.

(4) The ink should not be clogged in the nozzle and ink circulation path.

(5) Stable discharge can be obtained for a long time.

(6) The ink should not change even after being stored for a long time.

Etc. are especially important.

In order to satisfy some or all of the above purposes, vigorous studies have been made from both sides of the ink and the device.
A considerable effect has been recognized depending on the required performance.

[Problems to be solved by the invention]

However, most of the conventional water-based inks described above use a direct dye or an acid dye as a dye, and therefore, when recording is performed by various ink jet methods, fibers are particularly exposed on a recording surface as a recording material. When such paper or cloth is used, various types of toughness, particularly water resistance, occur.

In order to deal with this problem, it has been proposed to use a pigment-dispersed water-based ink (for example, JP-A-56-1478).
59 publication). According to this method, although the robustness of the recorded matter can be satisfied to some extent, the problem of clogging in the nozzle when used as an ink for ink jet, the problem of ink storage stability, It is much more serious than ink.

Therefore, the main object of the present invention is not only designated paper specially prepared for ink jet but also recording material having fibers exposed on other recording surfaces, particularly copy paper, report paper, bond paper, continuous slip paper. Another object of the present invention is to provide an ink jet recording method capable of obtaining various types of fastness, particularly excellent water resistance recording, even on sized general plain paper represented by.

Another object of the present invention is to provide an ink jet recording method using an ink which has excellent storage stability and does not cause clogging.

[Means for solving problems]

 The above object is achieved by the present invention described below.

That is, the present invention provides an ink jet recording method for recording by recording an aqueous ink containing a water-soluble dye on a recording material, wherein the water-soluble group of the dye is converted into a water-insoluble group by oxidation to be recorded on the recording material. The ink jet recording method is characterized in that the ink is fixed on the ink jet recording medium.

[Action]

The present invention will be described in more detail. The main feature of the present invention is that a pigment is not used as a coloring material for having high fastness,
That is, an ink using a water-soluble dye is used.

That is, since such an ink is a dissolution type, its color material concentration, viscosity, surface tension, etc. can be changed relatively freely,
In addition, since it does not have insolubles or precipitable components, it does not cause clogging of the ink supply path or nozzles, etc., and unlike ink for ink jetting that contains conventional pigments, its stability and ink jet suitability are extremely good. , No problem on the device occurs.

The second feature of the present invention is that after the ink is attached to the recording surface, the water-soluble group of the water-soluble dye contained in the ink is changed to a water-insoluble group by oxidation and fixed. . By doing so, the dye itself becomes insoluble in water, and a recorded matter having extremely excellent water resistance can be obtained as in the case of using a pigment type ink.

The aqueous, dye-dissolving ink used in the present invention and which is the first feature of the present invention basically has the following components.

First, as the dye characterizing the ink used in the present invention, any dye can be used as long as it is a water-soluble dye and changes its structure to water-insoluble by oxidation. Among them, a soluble vat dye, a soluble sulfur dye, a dye Water-soluble dyes such as leuco salts of dyes and dyes, leuco salts of sulfur dyes, and oxidation dyes are particularly preferable from the viewpoint of ink performance.

To obtain such dyes, those developed for dyeing fibers, which are generally commercially available, are used as they are. For example, in the case of leuco salt type dyes, conventionally known vat dyes and sulfur dyes according to a conventional method. Can be easily obtained by those skilled in the art by reducing and alkalizing.

Of course, these dyes can be used alone, but in order to adjust the color tone and the concentration, they may be further combined with other water-soluble dyes such as direct dyes and acid dyes.

The content of the above dyes is determined depending on the type of liquid medium component, the characteristics required for the ink, etc., but generally 0.2 to 20% by weight, preferably 0.5 to 10% by weight based on the total weight of the ink. , And more preferably in the range of 1 to 5% by weight.

As the liquid medium for dissolving the water-soluble dye as described above in the ink used in the present invention, any medium used as a medium of a conventional general ink jet recording ink can be used. It is preferable to have a solvent together, and as the organic solvent, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol, etc. C1-C5 alkyl alcohols; amides such as dimethylformamide, dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol, polypropylene glycol Polyalkylene glycols such as coal; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene groups having 2 to 6 carbon atoms Alkylene glycols containing atoms; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl)
Lower monoalkyl ethers of polyhydric alcohols such as ether and triethylene glycol monomethyl (or ethyl) ether; lower dialkyl of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether Ethers: sulfolane, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned.

The above-mentioned solvent is used together with water, but preferably contains at least one water-soluble high-boiling point organic solvent such as diethylene glycol, propylene glycol or glycerin as the solvent. .

The essential components of the ink used in the present invention are as described above, but various other surfactants, viscosity modifiers, surface tension modifiers, optical brighteners, pH modifiers, antifungal agents, chelating agents, etc. Can be added as required.

For example, viscosity adjusting agents such as polyvinyl alcohol, celluloses and water-soluble resins; surface tension adjusting agents such as various cationic, anionic or nonionic surfactants, diethanolamine and triethanolamine; pH by buffer solution
A regulator etc. can be mentioned.

Further, in order to prepare the ink used in the ink jet recording method of the type that charges the ink, lithium chloride,
Resistivity adjusting agents such as ammonium chloride and inorganic salts of sodium chloride are added. When applied to an ink jet method in which ink is ejected by the action of thermal energy, thermal physical property values (for example, specific heat, thermal expansion coefficient, thermal conductivity, etc.) may be adjusted.

As described above, the ink for ink jet used in the present invention is required to have a property of less bleeding and good fixability in addition to the fastness on plain paper or cloth on which fibers are exposed. It is desirable that the surface tension at 25 ° C. is adjusted to 35 to 68 dyne / cm and the viscosity is adjusted to 10 cp or less, preferably 5 cp or less, and more preferably 3 cp or less.

The above is the outline of the ink used in the present invention. The second characteristic of the present invention is that the water-soluble group of the water-soluble dye contained in the ink after the ink adheres to the recording surface is described. It is the point that is converted into a water-insoluble group by oxidation and fixed.

As a specific oxidation method, in addition to exposing to an oxidizing atmosphere such as air oxidation by leaving it for a long time, preferably the recording material itself is used, such as using acidic paper or adding an oxidizing substance to the recording material. There is a method of adjusting. Further, as a more preferable method, a thermal oxidation means using a heating roller or warm air,
Providing a photo-oxidizing means by irradiating infrared light to ultraviolet rays can be mentioned.

The present invention obtained as described above does not cause clogging as in the case of using a conventional water-based ink using a direct dye or an acid dye, and has the advantage of excellent long-term storage stability of the ink and pigment dispersion. It is an ink jet recording method which simultaneously achieves the advantages of extremely excellent fastness of recorded matter, especially high water resistance when using a mold ink.

Next, the present invention will be further described with reference to Examples and Comparative Examples.
In the text, parts or% are based on weight.

Reference Example 1 (Production example of vat dye leuco salt) After stirring the following components at a bath temperature of 50 ° C. for 3 hours, a pore size 1
Dye I used in the present invention was obtained by filtering under pressure with a μm membrane filter (trade name: Fluoropore Filter manufactured by Sumitomo Electric Co., Ltd.) and further spray-drying the filtrate.

Ingredient for adjusting Dye I Reference Example 2 (Production Example of Sulfide Dye Leuco Salt) After mixing the following components and boiling for 1 hour, hot water at 60 ° C. was added to 100 parts, and the mixture was further boiled for 1 hour and cooled, and a membrane filter with a pore size of 1 μmm was used. (Commercial name: Fluoropore Filter, manufactured by Sumitomo Electric Co., Ltd.) under pressure filtration, and the filtrate was atomized and dried to obtain Dye II used in the present invention.

Ingredients for adjusting Dye II Reference Examples 3 to 8 (Preparation of Inks A to E and F) After stirring the following components for 5 hours, pressure filtration was performed with a membrane filter (trade name: Fluoropore Filter, manufactured by Sumitomo Electric Industries) having a pore size of 0.45 micron. Inks A to E used in Examples of the present invention and Ink F used in Comparative Examples were obtained.

Ink A Ink B Ink C Ink D Ink E Ink F Reference Example 9 (Preparation of Pigment Ink Used for Comparison) Among the following components, a ceramic is added to a mixed solution of water and sodium hydroxide, and stirred and dissolved at room temperature.

Next, Emulgen 931, ethylene glycol, and the rest of the ingredients were added sequentially, premixed with a stirrer for 2 hours, and further ground with a ball mill for 20 hours, and then a membrane filter with a pore size of 1 μm (trade name: Fluoropore Filter, manufactured by Sumitomo Electric Industries, Ltd. ) To obtain an ink G used in a comparative example of the present invention.

Ink G Reference Example 10 (Preparation of ink containing vat dye not for leuco salt type used for comparison) 50 parts of Mikeslen Yellow 4GF (trade name: manufactured by Mitsui Toatsu) is dispersed in a liquid composed of 180 parts of water and 30 parts of 10% caustic soda solution. Then, 4 parts of hydrosulfite is added to obtain a reddish brown transparent solution. SMA Resin 144 as a dispersant in this solution
After adding 60 parts of 0 (styrene-ammonium maleate copolymer; molecular weight about 1500: Alcochemical) and mixing, gradually add 30 parts of 35% hydrogen peroxide solution and oxidize to obtain a yellow dispersion liquid. . After neutralizing by adding 30 parts of 10% phosphoric acid aqueous solution, 100 parts of diethylene glycol is added. This solution was added to a polyolefin ultrafiltration membrane (NTU-2006:
After adding the same amount of water as the amount of the filtrate (containing excess inorganic salt) discharged using a Nitto Denko Corporation) and ultrafiltration device (UW-1: Nitto Denko Corporation), a membrane filter with a pore size of 1 μm (Industrial name: Fluoropore Filter, manufactured by Sumitomo Electric Co., Ltd.) was subjected to pressure filtration to obtain an ink H used in a comparative example of the present invention.

Examples 1 to 5 and Comparative Examples 1 to 3 Ink jet printers (orifice size 40 × 50 μm, heater) using inks A to H obtained in Reference Examples and using a heating element as an ink ejection energy source in an ink jet recording device. Size 50 × 150μm,
Use 24 nozzles, drive voltage 24.5V, frequency 2KHz) to print on commercially available copy paper and bond paper.
The water resistance of the print obtained by passing through a hot roller at 0 ° C was evaluated.

Also, perform the capping operation on the print head at 40 ° C.
After left for a month, the printing operation was performed again, and after printing three lines, the printer was turned off and the clogging of 24 nozzles was examined.

The above evaluation results and the physical properties of the ink at 25 ° C are
Shown in the table.

* 1 Viscosity measurement Using a VISCONIC ELD manufactured by Tokyo Keiki.

* 2 Surface tension measurement Kyowa CBVP Surf Tensiometer A-1 manufactured by Kyowa Chemical Co., Ltd. is used.

* 3 Water resistance evaluation Commercially available copy and bond papers are printed with alphabet letters A to Z, passed through a heat roller at 120 ° C for 1 hour, and then the printed matter is immersed in water for 5 minutes to flow out of the printed area. And the white background was examined for contamination and water resistance was evaluated.

○: No outflow of printed area or contamination of white background is observed.

△: A part of the printed part spilled out, and there was some contamination of the white background.

×: The printed part leaked, making it difficult to read the characters.
White background pollution is also seen.

* 4 Evaluation of clogging The evaluation was made based on the number of clogged nozzles out of 24 nozzles.

○ …… 0 pieces △ …… 1 to 3 pieces × …… 4 pieces or more Examples 6 to 10 UV lamps with a wavelength of 366 nm (trade name: Topcon PAN UV LAMP, instead of the treatment with the heating roller in Examples 1 to 5).
A recorded matter was obtained in exactly the same manner as in Examples 1 to 5, except that irradiation with PUV-1, manufactured by Tokyo Optical Machine Co., Ltd., was performed for 10 minutes. After 1 hour of recording, the water resistance was evaluated under the same conditions, and as in Examples 1 to 5, no outflow of the printed part and contamination of the white background were observed, and the water resistance was good.

Examples 11 to 15 Recorded matter was obtained in exactly the same manner as in Examples 1 to 5 except that the treatment with the heating roller in Examples 1 to 5 was not performed. After 10 days of recording, the water resistance was evaluated under the same conditions. As a result, no outflow of the printed part and contamination of the white background were observed, and the water resistance was good.

〔effect〕

According to the ink jet recording method of the present invention, not only specified paper specially prepared for ink jet but also recording material having fibers exposed on the other recording surface, particularly copy paper, report paper, bond paper, continuous slip Even on sized ordinary plain paper represented by paper, various fastnesses, particularly excellent water resistance, can be obtained.

Furthermore, since the ink used in the present invention is excellent in storage stability, it is possible to perform ink jet recording excellent in practicability without causing clogging of nozzles and the like.

Claims (7)

[Claims] 1. An ink jet recording method for recording by recording a water-based ink containing a water-soluble dye on a recording material, wherein the water-soluble group of the dye is converted to a water-insoluble group by oxidation. An ink jet recording method, characterized in that the ink is fixed on the ink. 2. The ink jet recording method according to claim 1, wherein the water-soluble dye is any one of a soluble vat dye, a soluble sulfur dye, a leuco salt of a vat dye, and a leuco salt of a sulfur dye. . 3. The ink jet recording method according to claim 1, wherein the recording material has fibers exposed on its recording surface. 4. The ink jet recording method according to claim 1, wherein the recording material is sized paper. 5. The ink jet recording method according to claim 1, wherein the recording material is acid paper. 6. The ink jet recording method according to claim 1, wherein a heating means is used as the oxidizing means. 7. The ink jet recording method according to claim 1, wherein a light irradiation means is used as the oxidizing means.