JPH01182383A - Recording liquid and image-forming method using same - Google Patents

Abstract

PURPOSE:To obtain a recording liquid having excellent storage stability and giving a recorded image having high water resistance, etc., without causing the plugging of recording pen, etc., by dispersing a micro-encapsulated oil phase in a dye-containing aqueous medium in emulsified state and suppressing Ca<2+> concentration. CONSTITUTION:The objective recording liquid is produced by dispersing a micro- encapsulated oil phase in emulsified state in an aqueous medium (preferably a mixture of water and a water-soluble organic solvent such as diethylene glycol) containing a dye (preferably acid dye, etc.) and adjusting the Ca<2+> concentration to <=4ppm. The recording liquid can be produced e.g., by emulsifying an oil phase in a dye-containing aqueous medium subjected to Ca<2+> elimination treatment with an ion exchange column packed with a chelate resin, adding and reacting a wall-forming material such as ethylene glycol to the emulsion to form a microcapsule, separating the microcapsule e.g., by centrifugal separation and redispersing in the above de-containing aqueous medium.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a recording liquid (hereinafter referred to as ink) used in various recording instruments such as writing instruments and printers, and an image forming method using the same. The present invention relates to an ink suitable for an inkjet recording method in which recording is performed by ejecting droplets from an orifice of a head, and an image forming method using the ink.

More specifically, an ink that improves the water resistance and light resistance of recorded images, has excellent long-term storage stability, and does not cause clogging at the tip of a writing instrument or ejection orifice, and image formation using the same. Regarding the method.

(Prior Art) Conventionally, inkjet recording methods have the advantages of generating less noise during recording, being easily compatible with color printing, and being able to obtain high-resolution recorded images at high speed.

In the inkjet recording method, an ink in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent is used. In this case, the characteristics of the ink used are that physical properties such as viscosity and surface tension are within appropriate ranges, that the dissolved components have high dissolution stability, that they do not clog minute orifices, and that they have a sufficiently high concentration. It is required that it provides a recorded image and that no change in physical properties or precipitation of solids occurs during storage.

In addition to the above characteristics, recording can be performed without being restricted by the type of recording material, the fixing speed is high, and the recorded image has excellent light resistance, water resistance, and solvent resistance (especially alcohol resistance). In addition, properties such as providing recorded images with excellent resolution are also required.

(Problem to be solved by the invention) Conventionally, water-soluble dyes have been mainly used as coloring materials for ink in inkjet recording systems because the liquid medium is water-based. Many of the above basic requirements of the recording system are met.

However, when water-soluble dyes are used, the light resistance of recorded images often becomes a problem because these water-soluble dyes inherently have poor light resistance. In other words, if the recorded image is exposed to sunlight,
When exposed to light from a light source such as a fluorescent lamp or a projector, recorded images may disappear, become difficult to read, or fade during long-term storage.

Furthermore, since the dye is water-soluble, water resistance of recorded images often becomes a problem. That is, if a recorded image is exposed to rain, sweat, or water from drinking or drinking, the recorded image may blur or disappear.

Therefore, it is known to add existing ultraviolet absorbers and antioxidants to ink for the purpose of improving the light resistance of water-soluble dyes.

However, many of these UV absorbers are insoluble in the ink medium, and even those that are slightly soluble precipitate and aggregate in the ink, causing clogging at the tip of the orifice and pen tip. There is.

Therefore, the main object of the present invention is to provide an ink that solves the problems of conventional inks as described above, that is, it provides an image with good light fastness and water resistance, has excellent storage stability as an ink, and is suitable for use with pens. An object of the present invention is to provide an ink that does not cause clogging at the tip or the tip of an orifice, and an image forming method using the ink.

(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 ink in which a microencapsulated oil phase is emulsified and dispersed in an aqueous medium containing at least a pigment, and the concentration of calcium ions in the ink is 4 ppm or less, and the second invention is an ink in which a microencapsulated oil phase is emulsified and dispersed in an aqueous medium containing at least a pigment, the ink having a calcium ion content of 4 ppm or less. This is a recording method in which recording is performed using ink having a concentration of 4 ppm or less, and the image forming method is characterized in that microcapsules on a recording material are destroyed after recording.

(Function) By emulsifying and dispersing the microencapsulated oil phase in the ink containing the pigment and suppressing the concentration of calcium ions in the ink to 4 ppm or less, the quality and clogging of the ink storage chamber are improved. The water resistance of the image formed using the above-mentioned oil and the microcapsules destroyed is improved because the above-mentioned oil acts as a water repellent.

Further, in a preferred embodiment, an ultraviolet absorber and/or an antioxidant is contained in the oil phase, thereby making it possible to provide an image with excellent light resistance.

That is, commercially available dyes usually contain impurities such as inorganic salts such as sodium chloride and sodium sulfate, as well as metals (ions) such as calcium, iron, and silicon. Preparing ink with dyes containing such impurities causes clogging of the nib or orifice tip. In order to solve this problem, an ink in which the concentration of calcium ions in the ink is specified has been proposed (Japanese Patent Application Laid-Open No. 147064/1983).

However, the above proposal is applied to a water-soluble homogeneous ink, and the ink according to the present invention is one in which microcapsulated oil droplets are dispersed in an aqueous phase (hereinafter referred to as microcapsule-containing ink). Therefore, the above proposal cannot be applied as is.

In particular, in the case of ink containing microcapsules, the dispersion system of microcapsules is easily destroyed due to the influence of not only the storage temperature and the pH of the ink but also trace components in the ink.
Problems tend to occur in the long-term storage stability of the ink.

As a result of extensive research, the present inventor has found that in the case of microencapsulated ink, the long-term storage stability of the ink deteriorates significantly, especially when the concentration of calcium ions in the aqueous phase becomes crystalline.
In addition, it was discovered that clogging occurs significantly in the ejection orifice filled with ink and the capillary opening of the pen tip, leading to the present invention.

The mechanism of this phenomenon is unknown, but the presence of large amounts of calcium ions in the aqueous phase can lead to long-term effects.

During storage, calcium ions interact with emulsifiers to stabilize the microcapsular aqueous phase.
It is thought that the distributed system is destroyed. Furthermore, after the water evaporates at the tip of the orifice, calcium in the aqueous phase precipitates and promotes coagulation and solidification of the capsule, which is considered to be a cause of clogging.

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

As for the dyes used in the present invention, most of the dyes listed in the Color Index can be used, and even those not listed in the Color Index are often suitable. In particular, water-soluble acid dyes, direct dyes, basic dyes, reactive dyes, etc. are used numerically, and low-dispersion dyes (including reactive disperse dyes) can also be used. Particularly preferred are acid dyes and direct dyes.

These dyes are present at 5% by weight in the microencapsulated ink.
It is preferable to use the concentration below; if the concentration exceeds this, the storage stability of the ink may decrease due to agglomeration or precipitation of microencapsulated oil droplets, or the eyelids at the tip of the pen or orifice may occur. This is not preferable as it tends to cause clogging.

In the present invention, the calcium ion concentration can be controlled by salting out the dye and filtering it to separate it from the mother liquor containing calcium ions, or by passing an aqueous dye solution through an ion exchange column filled with a chelate resin to capture calcium ions. Any conventionally known method can be used.

In the present invention, it is necessary to use these methods to reduce the concentration of calcium ions in the dye to at least 4 ppm or less in the ink.

The ink of the present invention is characterized in that a microencapsulated oil phase is emulsified and dispersed in the ink containing the dye described above and having a calcium ion concentration of 4 ppm or less.

The oil phase used above is not particularly limited as long as it is substantially insoluble in water, but it is preferable that the vapor pressure is low, and a high vapor pressure may cause the odor of the oil and the stability of the ink. It can become an interlude. Also, the specific gravity is close to that of water, for example! For example, ink having a specific gravity of about 0.8 to 1.2 is preferable from the viewpoint of storage stability of the ink.

Preferred oil phases include 16, for example, vegetable oils (e.g.
(olive oil, soybean oil, castor oil, etc.), mineral oils (e.g., petroleum, Kesilon, paraffin, etc.), hydrocarbons (e.g., alkyl-substituted benzene, alkyl-substituted naphthalene,
(alkyl-substituted biphenyls, etc.), esters (e.g., phthalates, benzoates, fatty acid esters,
phosphoric acid esters, etc.), ethers (
For example, glycol ether, etc.), higher alcohols,
Examples include higher fatty acids, amides, chlorinated paraffins, and silicone oils.

These oil phases are used in a weight ratio of 1% to 50%, preferably 3% to 30%, relative to the aqueous phase which is the ink medium.

Examples of methods for emulsifying and dispersing the above-mentioned oil phase in an aqueous medium containing a dye include a method using ultrasonic waves and a method using various dispersers and stirrs. At this time, surfactants that serve as various emulsifiers and dispersants, such as fatty acid salts,
Anionic surfactants such as alkyl sulfate salts, alkylbenzene sulfonate salts, alkylnaphthalene sulfonate salts, dialkyl sulfophosphate salts, alkyl phosphate salts, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl sulfate salts, etc. , polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene oxybrobylene block copolymer These emulsifiers are used in an amount of 0.01 to 20% by weight, preferably 0.1 to 5% by weight, based on the aqueous phase.

Furthermore, in addition to or in place of the above-mentioned surfactants, polymeric substances such as PVA% PvP and gum arabic can also be used as protective colloids.

As a method for converting the emulsion into microcapsules, wall-forming materials are separately present in both the organic phase and the aqueous phase, and a polymerization reaction is caused at the interface between the organic phase and the aqueous phase to form microcapsules. Interfacial polymerization method, so-called in-5 in-itu polymerization method, in which microcapsules are formed by dissolving or allowing a wall-forming material to exist only in the organic phase, and polymer-concentrated phase polymerization is performed by changing the pH, temperature, concentration, etc. of an aqueous solution of the polymer. Examples include the coacervagedine method, in which microcapsules are formed by phase separation.

Examples of wall forming materials include terephthaloyl chloride, toluene diisocyanate, bisphenol A,
Examples include ethylene diamine, ethylene glycol, styrene, divinylbenzene, gelatin, gum arabic, and carboxymethyl cellulose.

In order to make the final ink using the microcapsules formed in this way, the capsules are once removed by centrifugation or filtration, and redispersed in the ink solvent, and if necessary, a water-soluble organic solvent is added and the pH is adjusted. It is also possible to add agents, surfactants, preservatives, etc. to make ink with desired physical properties, or to make ink by adding necessary additives such as those mentioned above without taking the microcapsules out of the water. The method of making ink is not particularly limited.

The particle size of the emulsified dispersion obtained as described above is preferably such that the mode of the particle size distribution is 10 μm or less, from the viewpoint of ink storage stability and orifice clogging. If it exceeds this range, the emulsified particles in the ink will tend to aggregate, causing storage stability problems, which is not preferable.

Furthermore, in a preferred embodiment of the present invention, the light resistance of the formed image can be further improved by incorporating an ultraviolet absorber and/or an antioxidant into the microencapsulated oil phase.

Preferred examples of the ultraviolet absorber to be dissolved or dispersed in the oil phase include 1, for example.

2-Hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-
Sulfobenzophenone Na salt, 2.2'-dihydroxy-4-methoxybenzophenone, 2-bitroxy-4-octoxybenzophenone, 2.4-dihydroxybenzophenone, 2(2'-hydroxy-5-methylphenyl)benzotriazole, Tinuvin 234 (Product name, manufactured by Ciba Geigy)
, 320, 326, 327, 328, Uvin
u1400 (product name, manufactured by BASF), M40, D
49, 490, D50, MS40, N35, N539, Cyasorb UV9 (product name, manufactured by American Cyanami VF), UV24, UV207, U
V284, same UV531. Same UV1O-84, same UV5
411 etc. are mentioned.

Further, preferable examples of the antioxidant include 2.6-tert-butyl-p-cresol, 2.
6-tert-butyl-4-ethylphenol, 2(3
)-butyl-4-oxy-anisole (BHA), 2.6-tert-butyl-oxytoluene (BI
T), 2,2'-methylenebis(4-methy7L/-6-te
rt-butylphenol), 4,4'-butylidenebis(3-methyl-6-Lert
-butylphenol), 4.4'-thiobis(3-methyl-6-tert-butylphenol), 2.2'-thiobis(4-methyl-6-tert-butylphenol), 2.4-dimethyl-6-tert- Butylphenol, 4-isooctylphenol, hydroquinone, Irganox 245 (trade name, manufactured by Ciba Geigy)
, 259, 565, 101O1 1035FF1
The same 1O flow, the same 1081, the same 1098, the same 1222, the same 1330, the same 1425WL.

Cyanox l 790 (product name, manufactured by American Cyanamid), Cyanox 425, Cyanox 2246, Cyanox 711,
Examples include 1212, LTDP, MTDP, and 5TDP.

The above-mentioned ultraviolet absorbers and/or antioxidants are contained in an amount of 1 to 50% by weight, preferably 10% by weight, based on the oil phase.
Dissolved or dispersed in an amount of 30% to 30% by weight.

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.

□ is a water-soluble organic solvent used by mixing with water.
For example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 5ec-butyl alcohol, tart-
Butyl alcohol, isobutyl alcohol, etc. with 1 carbon number
to 4 alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketone or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene gelicols such as polyethylene glycol and polypropylene glycol : Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol, etc. : 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. Examples include 3-dimethyl-2-imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

When the water-soluble organic solvent is contained in the ink, it is generally 0 to 95% by weight, preferably 10 to 80% by weight, more preferably 20 to 50% by weight based on the total weight of the ink.
% by weight.

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.

The pH adjuster used in the above ink is as follows:
Examples include various organic amines such as jetanolamine and triethanolamine, inorganic alkaline agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, organic acids, and mineral acids.

The ink of the present invention as described above has a viscosity of 1 at 25°C.
to 20 cps with a surface tension of 30 dyne/ct
It is preferable to have physical properties such that the pH is about 4 to 1o and the pH is about 4 to 1o.

Image forming methods using the ink of the present invention include not only general writing instruments such as general pens, fountain pens, felt pens, and brushes, but also mechanical image forming methods such as pen plotters and inkjet methods. Although not particularly limited, a particularly suitable method is an inkjet method,
The ink of the present invention can be suitably used in any of the various conventionally known inkjet systems.

In addition, the recording materials used include general paper, coated paper, synthetic paper,
Any of various plastic films can be used and is not particularly limited.

In particular, in the image forming method of the present invention, after forming an image using the ink on a suitable recording material, the microcapsules on the recording material are destroyed by conventionally known means such as pressure, heat, light, etc. to cover the inclusions. It can also be spread uniformly on the recording material, and in this way, the dye, oil phase, ultraviolet absorber and/or i-curing inhibitor are integrated, so the water resistance and light resistance of the image are significantly improved. Therefore, favorable results can be obtained.

(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.

Example 1 A 5% aqueous solution of Dye C,1 and Acid Red 8 was prepared,
After removing inorganic salts using a reverse osmosis device (manufactured by Toshi), calcium ions were removed through a column filled with chelate resin (R-1o (manufactured by Mitsubishi Kasei). This was evaporated and dried to form a dye powder. , 4 g of this powder was dissolved in 66 g of water, 10 g of ultraviolet absorber Uvinul 490 (trade name), and antioxidant Irganox 565 (
(Product name) 10g and toluene diisocyanate 20g were dissolved in 110g of 1-methylnaphthalene, emulsified and dispersed in 250g of water containing 20g of ethylene glycol using a Branson ultrasonic disperser, and kept at 60°C for 3 hours to form microcapsules. was formed. Microcapsules were separated using a centrifuge, washed with water and dried, and 4 g of the microcapsules were added to the above dye solution, followed by 1 g of glycerin.

g, 20 g of diethylene glycol, and 2 g of Niracol NP-7,5 (trade name) as a dispersant were added and stirred for 2 hours to prepare the ink of the present invention.

Comparative Example 1-1 An ink of a comparative example was obtained in exactly the same manner as in Example 1, except that the dye decalcification step was omitted.

Comparative Example 1-2 Dye C.1 and Acid Red 8 were decalcified in the same manner as in Example 1, and 4 g of this was taken and dissolved in 66 g of water.
Furthermore, 10 g of glycerin and 20 g of diethylene glycol were added, and the mixture was stirred for 3 hours to obtain an ink of a comparative example.

Example 2 A 20% aqueous solution of Dye C, 1 and Food Black 2 was prepared, and sodium chloride was added to salt out the dye. The precipitate was collected by filtration, washed with a 10% sodium chloride solution in water, and dried. The dye was extracted with nityl cellosolve and the solvent was evaporated to dryness to obtain a dye powder. Ultraviolet absorber Cyasorb u
V 9 (trade name) 15g to diethyl phthalate 85g
Using a homo mixer manufactured by Tokushu Kika Kogyo, mix the
The mixture was emulsified and dispersed in 200 g of lθ% gelatin aqueous solution under the conditions of , 000 rpm and 15 minutes. Add 200g of 10% gum arabic aqueous solution to this, and adjust the pH to 4 with 10% acetic acid aqueous solution.
, 3, cooled to 5° C., added 10 g of 30% formalin aqueous solution, and adjusted to pH 9 with 10% caustic soda. The temperature was slowly increased to 50°C to form microcapsules. After taking 100g of this and concentrating it to 70g, 3g of the above dye 1 polyethylene glycol #30010
g and 17 g of N-methyl-2-pyrrolidone were added and stirred for 2 hours to obtain an ink of the present invention.

Comparative Example 2-1 An ink of a comparative example was obtained in exactly the same manner as in Example 2, except that the dye decalcification step was omitted.

Comparative Example 2-2 Dye C61 and Food Black 2 were decalcified in the same manner as in Example 2, 3 g of this was taken and dissolved in 70 g of water, and further 10 g of polyethylene glycol #300 and 17 g of N-methyl-2-pyrrolidone were added. The mixture was stirred for 3 hours to obtain an ink of a comparative example.

Example 3 Dye C01 and Acid Blue 199 were dissolved in water, and after removing inorganic salts using an ultrafiltration device (manufactured by Nitto Denko), chelate resin Dowex A-1 (manufactured by Dow Chemical) was added.
Calcium ions were adsorbed and removed by passing through a column packed with This was evaporated to dryness to form a dye powder. ! - Dissolve 10 g of terephthal chloride in 90 g of methylnaphthalene, add this to 360 g of a 1% aqueous solution of nonionic surfactant NP-7,5 (manufactured by Nikko Chemicals), and use a homomixer manufactured by Tokushu Kikako 1 to perform 10. Emulsification and dispersion was carried out under the conditions of OOOrpm for 11 and 20 minutes. 40 g of ethylene glycol was added and reacted to form microcapsules. 2 g of the above dye powder was dissolved in this microcapsule-containing liquid sag, 18 g of glycerin was added, and the mixture was stirred to obtain the ink of the present invention.

Comparative Example 3-1 An ink of a comparative example was obtained in exactly the same manner as in Example 3, except that the dye decalcification step was omitted.

Comparative Example 3-2 Dye C,1, Direct Blue 199 was decalcified in the same manner as in Example 3, and 2 g and 18 g of glycerin were added.
was dissolved in 80 g of water to prepare an ink of a comparative example.

Example 4 and Comparative Example 4 An on-demand recording head that ejects ink using a piezoelectric vibrator using the inks of the above examples and comparative examples (discharge orifice diameter 50 μm, piezoelectric vibrator drive voltage 60V, frequency 4) An image was formed by printing on copy paper using an inkjet recording device having an inkjet recording device (lz), passed between pressure rollers, and the resulting image was irradiated with light for 30 hours using a xenon fade meter (manufactured by Suga Test Instruments). The light resistance was evaluated by determining the color difference between the actual color and the color difference after irradiation.

Further, water resistance was evaluated by dropping water droplets on the obtained image and visually judging the degree of blurring of the image.

Also, each ink was filled into the recording device and heated at 60°C for 2 hours.
The discharge after being left for a week was examined and the clogging property was evaluated.

Also, the used ink was sealed in a glass bottle and kept at -30℃.
After storage at 20°C and 60°C for 3 months, storage stability was evaluated by measuring the occurrence of precipitates and changes in liquid physical properties.

Further, the calcium ion concentration of each ink was measured using an atomic absorption spectrophotometer (manufactured by Shima Ritsu Seisakusho).

The evaluation results are shown in Table 1 below. ◎ in the table indicates excellent quality, O
indicates good quality, Δ indicates slightly poor quality, and × indicates poor quality.

γ 1 Example 1 0000 1.8 Comparative example rt OOΔx 7.8 Comparative example 1-2
X
2 Δ Δ 00 3.2 Example 300001.
6 Comparative Example 3-1 0 0 X Δ 4.9 Comparative Example 3-20 By emulsifying and dispersing the solidified oil phase and suppressing the concentration of calcium ions in the ink to 4 ppm or less, the storage stability and clogging resistance of the ink are improved. By destroying the oil, the oil acts as a water repellent, thereby improving the water resistance of the image.

Further, in a preferred embodiment, an ultraviolet absorber and/or an antioxidant is contained in the oil phase, thereby making it possible to provide an image with excellent light resistance.

Patent applicant: Canon Co., Ltd.

Claims (5)

[Claims] (1) A recording liquid in which a microencapsulated oil phase is emulsified and dispersed in an aqueous medium containing at least a dye, and the concentration of calcium ions in the recording liquid is 4 ppm or less. . (2) Recording is performed using a recording liquid in which a microencapsulated oil phase is emulsified and dispersed in an aqueous medium containing at least a dye, and the concentration of calcium ions in the recording liquid is 4 ppm or less. An image forming method comprising: destroying microcapsules on a recording material after recording. (3) The recording liquid and image forming method according to claims (1) and (2), wherein the dye is a water-soluble dye or a disperse dye. (4) The recording liquid and image forming method according to claims (1) and (2), wherein the oil phase contains an ultraviolet absorber and/or an antioxidant. (5) The recording liquid and image forming method according to claims (1) and (2), wherein the dye has a concentration of 5% by weight or less in the recording liquid.