JPH028905B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of forming a color image by an inkjet method using a plurality of color inks including black ink. Recently, research and development of color graphic printers, color digital copy machines, etc. using a pen recorder method or an inkjet method has become active. The equipment described above mainly uses cyan ink, magenta ink, and yellow ink (with black ink added as appropriate), and if necessary, two or more types of ink may be overlapped or mixed to produce color ( It is designed to form a multicolored image. In this way, when obtaining a color image using a plurality of color inks, first, the dyes forming the colorants of the cyan, magenta, and yellow inks must each have as accurate an absorption spectrum as possible, and must be compatible with paper, etc. It must have excellent color reproducibility when attached to recording materials such as . Furthermore, when obtaining a color image by overlapping two or more color inks, it is necessary to prepare each color ink so that the overlapping/combined image on the recording material can reproduce the tone faithful to the original. There is. Conventionally, various inks have been prepared from the above perspective, and attempts have been made to theoretically combine these inks to obtain a color image with the desired tone. It was extremely difficult to obtain color reproducibility of . Therefore, an object of the present invention is to solve problems that have hitherto not been solved in this technical field. That is, an object of the present invention is to provide a method for reliably obtaining a high-quality color image that is faithfully reproduced in color to the original using two or more types of color inks. In order to achieve the above object, the present invention provides a method for forming a color image on a recording material by an inkjet recording method using two or more types of ink selected from a plurality of aqueous color inks including black ink. Therefore, two or more color inks are used in combination so that the difference in transfer rate (Rf) defined in the text, which is defined in the text of the dye contained in each color ink, is 0.30 or less, and The method is characterized in that it includes a step of forming a color mixing section. Hereinafter, the present invention will be explained in detail with reference to specific examples and examples. In the present invention, each color ink (here,
The basic idea is to select dyes (including black ink) by paying attention to their chromatographic characteristics.
By preparing the ink so that the chromatographic characteristics of each dye are similar to each other, the above object is achieved without causing separation of dyes of different colors in the recording material. In the present invention, the value of the transfer rate (obtained by paper chromatography) defined below is used as a guideline for the chromatographic properties of the dye used. How to determine the transfer rate of dye A test solution is prepared by dissolving 5% by weight of the desired dye in a mixed solvent of water/diethylene glycol (volume ratio: 55/45). Apply this test liquid to a Toyo filter.
After applying a 2μ charge to the lower end of Paper No. 50 (trade name; manufactured by Toyo Paper Co., Ltd.), development is carried out for a predetermined period of time according to a conventional method using the above mixed solvent as a developing solvent. At this time, the developing distance (A) of the developing solvent from the charging point and the moving distance (B) of the dye from the charging point are measured, and the ratio of the two is; B/A=Rf
Find the value of and use this Rf value as the transfer rate of the target dye. According to the knowledge obtained by the present inventors as a result of intensive studies, the transfer rates of the dyes in each color ink used in combination on the same recording material are determined, and the difference between them is determined. It has been found that when the maximum value is approximately 0.30 or less, it is possible to reproduce colors with virtually no problems in practical terms. Furthermore, we compared the migration rates of multiple dyes contained in each color ink and determined the maximum difference between them.
It has also been found that when the value is 0.20 or less, it is possible to obtain a high-quality color image in which color reproduction is close to the theoretical value. It was also found that under the above conditions, the permeation speed and degree of diffusion of each color ink into the same recording material were approximately similar, and minute differences were not visually discernible. Therefore, when color inks used in combination on the same recording material overlap at the same point, defects such as color unevenness and color shift do not occur at all. When composing and preparing the color ink used in the present invention, various water-soluble dyes (particularly direct dyes and acid dyes) that exhibit colors such as cyan, magenta, yellow, and black are used. Among these, the dyes listed below are particularly suitable in the present invention. In addition, all the numerical values in parentheses appended to the dye names exemplified below indicate the migration rates determined by the method described above. Cyan Dyes CI Acid Blue 254 (0.94) CI Acid Blue 1 (0.99) CI Acid Blue 9 (0.99) CI Acid Blue 290 (0.82) CI Acid Blue 103 (0.92) CI Acid Blue 40 (0.97) CI Acid Blue 127 (0.97) CI Direct Blue 86 (0.86) CI Acid Blue 113 (0.96) CI Acid Blue 120 (0.91) Magenta Dye CI Acid Red 276 (0.74) CI Acid Red 274 (0.95) CI Assisted Lead 289 (0.99) CI Assisted Lead 122 (0.98) CI Assisted Lead 155 (0.96) CI Assisted Lead 161 (0.86) CI Assisted Lead 131 (0.96) CI Assisted Lead 249 (0.94) CI Assisted Lead・Rezzed 35 (0.95) CI assisted red 106 (0.99) CI assisted red 264 (0.97) CI assisted red 254 (0.99) CI assisted red 52 (0.91) CI assisted red 27 (0.91) CI assisted red 265 (0.91) CI Acid Red 257 (0.79) CI Acid Red 42 (0.93) CI Acid Red 111 (0.68) CI Acid Red 145 (0.92) Yellow Dye CI Acid Yellow 23 (0.90) CI Acid Yellow 29 (0.82) CI Acid Yellow 38 (0.85) CI Acid Yellow 65 (0.85) CI Direct Yellow 12 (0.87) Black Dye CI Acid Black 24 (0.93) CI Acid Black 26 (0.90) CI Acid Black 107 (0.85) CI Acid Black 110 (0.86) CI Acid Black 52:1 (0.97) CI Acid Black 139 (0.90) The dyes exemplified above are generally contained in an amount of 0.5 to 30% by weight in each color ink. , more preferably 1 to 10
Contains about % by weight. In addition, the composition and composition of each color ink used in the present invention are
In addition to the dye, liquid medium components are used in the preparation. As such a component, water or a mixture of water and various water-soluble organic solvents is used. Examples of water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol.
alcohol, sec-butyl alcohol, tert-
Alkyl alcohols with 1 to 4 carbon atoms such as butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane Nitrogen-containing heterocyclic ketones such as N-methyl-2-pyrrolidone and 1,3 dimethyl-2-imidazolidinone; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol , triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene glycols containing 2 to 6 carbon atoms; glycerin; ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether, and the like. Among these many water-soluble organic solvents, diethylene glycol, a polyhydric alcohol, and triethylene glycol monomethyl (or ethyl) ether, a lower alkyl ether of a polyhydric alcohol, are particularly preferred as humectants for ink. Each ink used in the present invention is basically prepared using the above-mentioned components, but may further contain various conventionally known additives, if necessary. Examples of additives include viscosity modifiers such as polyvinyl alcohol, cellulose, and water-soluble resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as diethanolamine and triethanolamine; PH adjustment by buffering agents. Adjustment agents and the like can be mentioned. Further, in order to prepare ink used in the type of inkjet recording method in which ink droplets are charged, a resistivity adjusting agent such as inorganic salts such as lithium chloride, ammonium chloride, and sodium chloride is used. In addition, urea and thiourea are also suitably used as water retention improvers at the tip of the discharge orifice.
Note that when a recording method in which ink is ejected by the action of thermal energy is employed, the thermal physical properties of the ink (eg, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted. By the way, in the present invention, as a member for receiving a color image using ink, that is, as a recording material, a sheet or film of paper, cloth, wood, resin, etc. is generally used, and in special cases, a sheet or film of paper, cloth, wood, resin, etc. is used. etc. are also used. In addition, especially when using paper, the so-called
In addition to plain paper, so-called coated paper, which is a base paper coated with a water-soluble resin paint (which may or may not contain a white pigment), is suitable. Incidentally, if the recording material used here originally has poor ink absorbency, it is desirable to improve the ink absorbency in advance by, for example, making it porous. . Examples will be described below to illustrate the effects of the present invention. Example 1 Yellow ink, magenta ink, and cyan ink were prepared by individually stirring each composition shown below and passing it through a filter. Yellow ink (composition) CI Direct Yellow 12 2 parts by weight Ion-exchanged water 68 〃 Diethylene glycol 30 〃 Magenta ink (composition) CI Acid Red 276 2 parts by weight Ion-exchanged water 68 〃 Diethylene glycol 30 〃 Diane ink (composition) CI Direct Blue 86 2 parts by weight Ion-exchanged water 68 Diethylene glycol 30 These three types of ink were each injected into an on-demand ink jet head equipped with a piezoelectric vibrator (discharge orifice diameter, 50μ; piezoelectric vibrator drive voltage, 60V; The same frequency (4KHz) is emitted onto the recording materials listed below according to a predetermined image signal.
In each case, a color image consisting of seven colors was formed. All of the images obtained had clear color tones, and no color unevenness was observed, especially in the mixed color area.

[Table] Example 2 A paint obtained by grinding and mixing 100 parts by weight of finely divided silicic acid and 10 parts by weight of polyacrylamide binder in water was applied to one side of base paper with a basis weight of 60 g/m ² at 3 g/m2. After coating at a ratio of ^2:2 and drying, coated paper was prepared. Next, each composition shown below was individually stirred and passed through a filter to prepare a total of four color inks: yellow ink, magenta ink, cyan ink, and black ink. Yellow ink (composition) CI acid yellow 65 4 parts by weight Ion exchange water 60 N-methyl-2-pyrrolidone 16 Diethylene glycol 20 Magenta ink (composition) CI acid red 161 4 parts by weight Ion exchange water 60 N- Methyl-2-pyrrolidone 16 〃 Diethylene glycol 20 〃 Diane ink (composition) CI acid blue 290 4 parts by weight Ion exchange water 60 〃 N-methyl-2-pyrrolidone 16 〃 diethylene glycol 20 〃 Black ink (composition) CI acid black 107 4 parts by weight Ion-exchanged water 60 〃 N-Methyl-2-pyrrolidone 16 〃 Diethylene glycol 20 〃 These four types of ink were respectively injected into an on-demand ink jet head equipped with a piezo vibrator (discharge orifice diameter: 50μ; Vibrator drive voltage: 60 V; frequency: 4 KHz) was ejected onto the coated paper according to an image signal based on a predetermined full-color original. At this time, ink was ejected while the four parallel heads were moved back and forth (relatively) for each line on the coated paper surface. As a result, each color is clear on the coated paper, and
Full-color photographs with extremely good color reproducibility were reproduced. Examples 3 to 12 Full-color inkjet recording was performed in exactly the same manner as in Example 2, except that only the dyes in each ink (composition) in Example 2 were replaced with those exemplified in the table below. In both cases, high-quality full-color photographs could be reproduced as in Example 2.

【table】

【table】

[Table] Comparative Examples 1 to 3 Full-color inkjet recording was performed in the same manner as in Example 2, except that only the dyes in each ink (composition) in Example 2 were replaced with those exemplified in the table below. .

[Table] As a result, the images obtained in Comparative Example 1 and Comparative Example 2 had a bluish tone overall, and the images obtained in Comparative Example 3
The resulting image had a reddish tone throughout, and in both cases it was not possible to reproduce colors faithful to the original. In both cases, color unevenness was observed in the mixed color area. Example 13 10 parts by weight of a 50% toluene solution of acrylic resin (SKY-1 manufactured by Toagosei Kagaku Co., Ltd.), 60 parts by weight of methyl ethyl ketone, and 1μ particles of 13X type synthetic zeolite (Molecular Sieve 13X manufactured by UCC Corporation)
30 parts by weight were mixed and pulverized and mixed in a ball mill for 3 days. The resulting mixture was applied to a thickness of 1 mm on a mirror-finished stainless steel plate using a coating rod and dried. The dried film was peeled off from the stainless steel plate, immersed in an aqueous citric acid solution adjusted to pH 3 for 2 minutes, washed with water, and dried to obtain an opaque porous film sheet. Example 1 was applied on one side of this porous film sheet.
Inkjet recording was performed using the same ink and equipment as in the above, and a color image consisting of seven colors was formed. Then, while pressing a commercially available iron heated to a surface temperature of about 150°C on the surface of the sheet,
After the sheet was melted and cooled, the sheet became transparent. The color images obtained on the sheet thus made transparent had clear colors and good color reproducibility. Furthermore, when the obtained sheet was projected using an overhead projector, a color image with clear tones could be displayed.

Claims (1)

[Claims] 1 In a method of forming a color image on a recording material by an inkjet recording method using two or more types of ink selected from a plurality of aqueous color inks including black ink, dyes contained in each color ink are used. This includes the process of forming a mixed color portion on the recording material by using a combination of two or more color inks whose transfer rates (Rf) as defined in the text are 0.30 or less. Characteristic color image formation method.