JPH02202965A - Ink and method of recording therewith - Google Patents

Abstract

PURPOSE:To improve the discoloration resistance of an image by recording with an ink contg. a specific dye and a specific liq. medium by an ink jet system on a recording material having a surface layer capable of accepting an ink contg. a pigment and a binder. CONSTITUTION:A liq. medium contg. 0.1-15wt.% dye of formula I (wherein R1 and R2 are each H, OH, etc.; R3 and R4 is alkoxy, etc.; X is acetyl, formula II, etc.; R5 and R6 are each H or -C2H4OH; M is an alkali metal, ammonium, etc.) (e.g. formula III), 35wt.% or more water and 2-80wt.% water-sol. org. solvent (e.g. glycerin) is, if necessary, mixed a pH controlling agent, a viscosity controlling agent, a surface tension controlling agent, etc., and filtered under pressure to give an ink having a viscosity at 25 deg.C of 1-20cp, a surface tension of 30dyne/cm or higher and a pH of 1-10. The resulting ink is put into an ink jet printer, and used to print on a recording material such as a coated paper having a surface layer capable of accepting an ink contg. a pigment such as silica and a binder, thus giving a highly discoloration-resistant image.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ink and a recording method using the same, and more particularly to an aqueous ink that provides a black image with improved indoor discoloration and a recording method using the ink. , particularly related to inkjet recording methods.

(Prior Art) Conventionally, water-based inks in which water-soluble dyes are dissolved in an aqueous medium have been used as inks for fountain pens, feltbens, etc., and inks for inkjet recording. A water-soluble organic solvent is generally added to prevent ink from clogging in ink discharge nozzles.

These conventional inks must provide an image with sufficient density, do not clog the pen tip or nozzle, dry well on the recording material, have little bleeding, and have storage stability. In particular, in the case of an inkjet method that uses thermal energy, it is required to have excellent heat resistance, and it is also required that the image formed has sufficient light resistance, water resistance, etc.

Also, inks of various hues are prepared from dyes of various hues, among which black ink is the most important ink used for both monochrome and full color images. Conventionally, C,1, and Food Black 2 have been mainly used as dyes for stiff black ink, considering various performances (Japanese Patent Application Laid-open Nos. 59-93766 and 59-9).
(See Publication No. 3768).

(Problems to be Solved by the Invention) Among the various required performances mentioned above, durability of the formed image is particularly important.

Conventionally, problems with image durability have been mainly due to fading due to direct sunlight and various types of illumination light, and attempts have been made to solve these fading problems by selecting dyes with excellent light resistance.

However, recently, in addition to these fading problems, the problem of image discoloration has been attracting attention. In other words, images made with conventional ink suffer from not only fading but also discoloration, and this discoloration is a change in hue although the density does not change much. Especially in black ink, which is used in the largest amount, black The problem of medicinal oats turning brown is an important problem, and especially in the case of full-color images, this oat causes a sharp drop in image quality.

This problem progresses even indoors where there is no direct sunlight, and discoloration is also accelerated depending on the type of recording material used to form the image.C, 1. In Food Black 2, this problem with Yakumu was unavoidable.

In particular, in the case of so-called coated paper, in which an ink-receiving layer containing a pigment and a binder is formed on a base material such as paper, in order to improve image quality such as color development, clarity, and resolution of ink,
In the case of plain paper, even if an ink with little problem of discoloration is used, it will cause a noticeable stain, and this problem cannot be solved simply by selecting a dye with good light fastness.

Therefore, it is an object of the present invention to provide an ink and a recording method that can satisfy the general performance requirements as described above, and also be capable of producing images that do not cause problems even on coated paper.

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

That is, the present invention provides an ink containing at least a dye and a liquid medium, characterized in that the dye is a dye represented by the following general formula (I), and a recording method using the ink.

(In the above general formula, R1 and R2 are a hydrogen atom, a hydroxyl group, or -5o, M, R3 and R4 are an alkoxy group or an acetylamino group, and X is an acetyl group, a benzoyl group, -5O*C5Hs, -5O*CaH4- C) Is or -C2H,OH; M represents an alkali metal, an ammonium group or an organic ammonium group; ) (Function) By using the dye of the general formula (I) as an ink dye, a black ink that gives an image with little indoor discoloration, ie, brown discoloration, can be provided even on coated paper.

Further, in the second aspect of the present invention, a black image with little browning can be provided on coated paper using the above ink.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The black dyes used in the present invention are generally soda salts of water-soluble groups such as sulfonic acid groups, but the present invention is not limited to these soda salts, and their counter ions are potassium, lithium, Ammonia, organic amines, etc. have the same effect, and the present invention also includes dyes containing counterions other than these.

Specific examples of the dye represented by the above general formula (I) include the following dyes, but are not limited to these dyes.

No. 1 NO12 (MIINHsCH*) No. 3 NO04 (M-Nil (C, ++40) 1), ) No. 5 The above dyes can be produced according to the synthesis of known azo dyes. As an example, the synthesis example of dye No. 1 will be given.

0.1 mol of l-naphthylamine-2-sulfonic acid in 3 mol of water
00nnj! Dissolve in alkaline solution, add 0.3 mol of hydrochloric acid, cool on ice, and add 0.1 mol of sodium nitrite to 50 mf of water.
A solution dissolved in f1 is added at 0 to 5°C to diazotize. The above diazotization solution was poured into a mixture of 0.1 mol of 5-acetylamino-〇-anisidine dissolved in 200 rnfi of water and 0.2 mol of hydrochloric acid, and the pH was adjusted to 5 with caustic soda.
Adjust the temperature to 5 to 6°C and stir for 1 hour at 5 to 10°C. Add 0.3 mol of hydrochloric acid to this, add 0.1 mol of sodium nitrite to 5 mol of water.
At 0°C, the dissolved solution is further added to diazotize. 300 mft of an aqueous solution of 0.1 mol of N-acetyl H acid prepared by the method described in Yutaka Hosoda, Dye Kagaku (Gihodo), page 580
Add the above diazotization solution to the solution and adjust the pH to 8 to 9 with caustic soda.
and stir at 5 to 10°C for 2 hours. The mixture is heated to 60°C, salt is added, and the precipitated dye is collected by filtration. After repeating this salting-out operation several times to remove impurities, hydrochloric acid is added for acid precipitation, and the dye is neutralized with ammonia to convert the sulfonic acid group of the dye into an anthonium salt. After salt purification using an ultrafiltration device (manufactured by Sartorius), the solution was evaporated to dryness to obtain a powder of dye No. 1.

According to the above method, 1-naphthylamine-4,7-disulfonic acid was coupled with 2,5-jethoxyaniline, and further diazotized, and this was prepared as N-benzoyl H acid according to the description on page 536 of the above publication. Coupling with. The process of adding lithium chloride and salting out is repeated to remove impurities and at the same time change the counter ions of the dye to lithium ions. Thereafter, desalting was carried out in the same manner as in the above example to obtain powder of dye No. 4.

The amount of the dye used in the ink of the present invention is not particularly limited, but - numerically, it is 0.1 to 15% by weight, preferably 0.3 to 10% by weight, more preferably 0.3 to 10% by weight, based on the total weight of the ink. An amount of 0.5 to 6% by weight is preferred.

The aqueous medium suitable for use in the ink of the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferred is a mixed solvent of water and a water-soluble organic solvent, which is water-soluble. The ink contains polyhydric alcohol, which has the effect of preventing ink from drying, as an organic solvent. Further, as water, it is preferable to use deionized water rather than ordinary water containing various ions.

Examples of water-soluble organic solvents used in combination with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 56C-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-butyl alcohol. - Alkyl alcohols having 1 to 5 carbon atoms such as pentanol; amides such as dimethylformamide and dimethylacetamide; ketone or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol and polypropylene Polyalkylene gelylcols such as glycol: alkylene groups such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethyl nonglycol, etc. Alkylene glycols containing 2 to 6 carbon atoms; glycerin;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; triethylene glycol dimethyl (or ethyl) ether, tetraethylene Lower dialkyl ethers of polyhydric alcohols such as glycol dimethyl (or ethyl) ether; sulfolane, N-methyl-2-pyrrolidone, 1
．． Examples include 3-dimethyl-2-imidazolidinone.

An appropriate organic solvent is selected and used from the above organic solvents, but glycerin or polyethylene oxide with a degree of polymerization of 3 to 6 is particularly good for preventing ink clogging, and nitrogen-containing cyclic A compound or an ether compound of polyalkylene oxide is preferable, and lower alcohols and surfactants are preferably used for frequency response. Therefore, a preferable solvent composition in the present invention is a composition containing the various components described above in addition to water.

The content of the water-soluble organic solvent in the ink is generally 2 to 80% by weight, preferably 3 to 70% by weight of the total weight of the ink.
% by weight, more preferably from 4 to 60!1% by weight.

In addition, the water used accounts for 35% or more, preferably 45% or more by weight of the entire ink. If the amount of water is small, a large amount of low-volatile organic solvent will remain in the formed image, and the dye will not be absorbed. This is not preferable because problems such as migration and image blurring occur.

In addition to the above-mentioned components, the ink of the present invention may optionally contain:
It may include pH adjusters, viscosity adjusters, surface tension adjusters, and the like. Examples of pH adjusting agents used in the above ink include various organic amines such as jetanolamine and triethanolamine, and inorganic inorganic hydroxides such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide. Examples include alkaline agents, organic acid salts such as lithium acetate, organic acids, and mineral acids.

The ink of the present invention as described above has a viscosity of 1 at 25°C.
20 cP to 20 cP, preferably 1 to 15 cP, and a surface tension of 30 dyne/cm or more, preferably 40 dyne/cm.
It is preferable to have physical properties of e/cm or more and a pH of about 4 to 10.

The recording method of the present invention is a recording method characterized by using the above-mentioned ink, and the recording method and recording material are not particularly limited, but in particular, the recording method is an inkjet method, and the recording material is coated paper. A method using the following is particularly effective.

The inkjet method may be any conventionally known method and is not particularly limited, but in the present invention, for example, the method described in Japanese Patent Application Laid-Open No. 54-59936 is used, in which the ink is rapidly heated by the action of thermal energy. Particularly useful is a method in which a volume change is caused, and ink is ejected from a nozzle by the force exerted by this state change.

That is, with this method, in the case of conventional ink, there was a risk that foreign matter would settle on the heat-generating head in the device, causing problems such as ink failure to eject, but the ink of the present invention is free from such foreign matter. Stable recording is possible because no deposits occur.

The recording material used in the present invention can be any recording material such as general plain paper, high-quality paper, coated paper, plastic film for OHP, etc., but it is especially noticeable when coated paper is used. A great effect is produced.

These coated papers are made of paper such as plain paper or high-quality paper, and have an ink-receiving layer that serves as a pigment and binder on the surface to improve color development, clarity, dot shape, etc. with ink. That is.

In the case of these coated papers, those using fine pigments such as synthetic silica with a BET specific surface area of 35 to 650 rn"7g provide images with excellent color development and clarity, but conventional inks cannot be used. Although the theoretical reason for this is unknown, the problem of brown discoloration is particularly noticeable over time in images using black ink, and this is a serious problem not only in black monochrome images but also in full color images.

In addition, similar to these coated papers, recording materials that have a thin layer of pigment and binder on a paper base material, and in which fibers of the base paper are mixed, also cause similar problems. There is.

It has been found that even when a black monochrome image or a full color image is formed using the ink of the present invention on the coated paper as described above, the problem of brown discoloration as described above does not occur. Therefore, according to the method of the present invention, the BET specific surface area is 35 to 6.
Recorded images that do not cause discoloration indoors for a long period of time using not only coated paper using a pigment of 50♂/g, coated paper using a pigment with a BET specific surface area of less than that, but also plain paper and other arbitrary recording materials. can be provided.

Incidentally, the recording method using the inkjet method and the various recording materials described above are publicly known, and various proposals have been made by the applicant and others, but these recording methods and recording materials may be used as they are in the present invention. Can be used.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. Note that % in the text is based on weight unless otherwise specified.

(1) Ink formulation example The following components were mixed and 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 the ink of the present invention.

Doctor 1 Exemplary dye No.l 3% diethylene glycol 17% water
80% Exemplary dye No. 2 4% Glycerin 14% Diethylene glycol 1,000 methyl ether 12% Water 70%
Medical example dye No. 4 4% ethyl alcohol 5% diethylene glycol 15% N-methyl-2-
Pyrrolidone 10% water
66% Flood Exemplary Dye No. 5 3% Glycerin 20% Emulgen 98
5 (Product name, manufactured by Kao) 0.05% water
76.95% (2) Usage Example The inks of Examples 1 to 4 were installed in an inkjet printer BJ-8OA (Canon family, nozzle size 50 x 40 μm, number of nozzles 24) that uses a heating element as an ink ejection energy source. When printing on recording materials A to C, clogging during reprinting after a print stop, clogging recovery during reprinting after a long print stop, and color fastness were evaluated.

Recording material A: Inkjet coated paper NM (product name,
(manufactured by Mitsubishi Paper Industries) Recording material B: Coco-8 paper C-3 for inkjet (product name, manufactured by Jujo Paper Industries) Recording material Carbee paper Canon PAPER DRY
(Product name, manufactured by Canon Inc.) (3) Evaluation method and evaluation results (1) Printing - Clogged when reprinting after stopping Printer was filled with the specified ink and the recording material was continuously used for 10 minutes. After printing alphanumeric characters on C, printing was stopped, and after leaving it for 10 minutes without a cap, etc., alphanumeric characters were printed again, and judgment was made based on the presence or absence of defects such as faded or missing characters ( (Left at 20±5℃, 50flO%RH)
However, no defective parts were found.

(2) Recovery from clogging when reprinting after a long printing stop After filling the printer with the specified ink and printing alphanumeric characters on the recording material C continuously for 10 minutes, stop printing and replace the cap, etc. Leave it for 7 days (60℃, lO±5
%R)l), the nozzle was recovered from clogging, and the number of recovery operations until normal printing without blurred or missing characters was possible was determined. 5
Normal printing was possible after several recovery operations.

(3) After printing a solid black pattern of 10 mm x 30 + o + a on the color-fast recording materials A, B, and C, the ozone concentration is always kept in the range of 0.1 ± 0.05 volume % by light shielding as a method of promoting discoloration. The printed matter was left in the bath for 30 minutes and the color difference ΔE"ab of the printed matter before and after the test was measured (according to JIS Z8730), and ΔE"ab was 5 or less in all cases.

(4) Comparative Example Instead of the dyes used in Ink Formulation Examples 1 to 4 of the above Examples, c, i, Food Black 2, C, E, Direct Black 62, C, 1, Direct Black 11B and c
, R, and Acid Black 24 were prepared in the same manner as in the examples, and solid black printing was performed on recording materials A and B using a recording device in the same manner as in the above usage example. A similar test was conducted using this printed matter as a test piece in the ozone test tank described above, and ΔE''ab was all 15 or more.

(Effects) As described above, according to the present invention, it is possible to form images that not only have excellent performance such as ink clogging resistance, which is numerically required, but also have excellent color fastness. Ta.

Claims (5)

[Claims] (1) An ink containing at least a dye and a liquid medium, wherein the dye is a dye represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the above general formula, R_1 and R_2 are hydrogen atoms, hydroxyl groups, or -SO_3M, R_3 and R_4 are alkoxy groups or acetylamino groups, and X is acetyl group, benzoyl group. , -SO_2C_6H_5, -SO_2C_6H_4-C
H_3 or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, R_
5 and R_6 represent a hydrogen atom or -C_2H_4OH, and M represents an alkali metal, an ammonium group, or an organic ammonium group. ) (2) A recording method performed by applying ink to a recording material, characterized in that the ink contains at least a dye and a liquid medium, and the dye is a dye represented by the following general formula (I). . ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the above general formula, R_1 and R_2 are hydrogen atoms, hydroxyl groups, or -SO_3M, R_3 and R_4 are alkoxy groups or acetylamino groups, and X is acetyl group, benzoyl group. , -SO_2C_5H_5, -SO_2C_6H_4-C
H_3 or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, R_
5 and R_6 represent a hydrogen atom or -C_2H_4OH, and M represents an alkali metal, an ammonium group, or an organic ammonium group. ) (3) The recording method according to claim 2, wherein recording is performed using an inkjet method. (4) The recording method according to claim 3, wherein the inkjet method is a method in which thermal energy is applied to the ink and the ink is ejected as droplets from micropores. (5) The recording method according to claim 2, wherein the recording material has an ink-receiving layer made of a pigment and a binder on its surface.