JP2562634B2 - Recording liquid and image forming method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses a recording liquid (hereinafter referred to as an ink) suitable for an inkjet recording system in which droplets are ejected from an orifice of a recording head to perform recording, and the ink is used. Image forming method.

(Prior Art) The inkjet recording system has advantages that noise during recording is small, color compatibility is easy, and a high-resolution recorded image can be obtained at high speed.

In the ink jet recording system, various types of water-soluble dyes dissolved in water or a mixed liquid of water and an organic solvent are used as ink. In this case, as the characteristics of the ink used, the physical properties such as viscosity and surface tension are in an appropriate range, the dissolution stability of the dissolved component is high, the fine orifice is not clogged, and the sufficiently high concentration It is required to give a recorded image and to prevent the change of physical properties or the precipitation of solid matter during storage.

Further, 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 is excellent in light resistance, water resistance, and solvent resistance (particularly alcohol resistance). In addition, properties such as providing a recorded image with excellent resolution are also required.

(Problems to be Solved by the Invention) Conventionally, a water-soluble dye is mainly used as a coloring material of an ink in an inkjet recording method because a liquid medium is aqueous. Many of the above basic requirements for recording systems are satisfied.

However, when a water-soluble dye is used, these water-soluble dyes are originally inferior in light resistance, so that the light resistance of a recorded image often becomes a problem. That is, when the recorded image is exposed to sunlight, a fluorescent lamp, or the light source of a projector, the recorded image may disappear, become difficult to read, or discolor during storage for a long time.

Further, since the dye is water-soluble, the water resistance of the recorded image often becomes a problem. That is, when the recorded image is exposed to rain, sweat, water for drinking, etc., the recorded image may bleed or disappear.

Therefore, in order to solve the above-mentioned problems of light resistance and water resistance, it is considered to use a pigment or an oil-soluble dye as a pigment. However, since the pigment has poor dispersion stability and easily sediments, the storage stability of the ink is poor. Further, since the re-dissolving property is poor, the nozzle is likely to be clogged, and the state becomes unrecoverable.

On the other hand, the oil-based ink using the oil-soluble dye has a low surface tension and the ejection state is unstable. Further, the blur of ink is large and the feathering is likely to occur, so that the image quality is remarkably poor.

Therefore, a main object of the present invention is to provide an ink that solves the problems of the conventional ink as described above, that is, an ink that gives an image having good light resistance and water resistance and is excellent in storage stability as an ink. Is to provide.

(Means for Solving Problems) The above object is achieved by the present invention described below.

That is, the present invention is a composition in which microcapsules containing at least a water-insoluble dye and an ultraviolet absorber or an antioxidant are dispersed in an aqueous medium, and the mode of the particle size of the microcapsules is Is 10 μm or less, and an image is formed through a step of applying the ink to a recording material by an inkjet method and a step of destroying the microcapsules in the recording material. And an image forming method.

(Function) By adopting a microencapsulated dye having a mode value of 10 μm or less as a recording agent component of ink,
An oil-soluble dye or pigment can be used without causing problems such as dispersion stability, storage stability, and bleeding, and an image having excellent water resistance and light resistance can be provided.

In a preferred embodiment, the light resistance can be further improved by using an ultraviolet absorber and / or an antioxidant together with the dye.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The microencapsulated dye used in the present invention and mainly characterizing the present invention is a dye which is dissolved or dispersed in a solvent which is substantially insoluble in water, and which is emulsified and dispersed in water. It is obtained by microencapsulation by an appropriate means.

The solvent used for the microencapsulation is not particularly limited as long as it is substantially insoluble in water,
It is preferable that the vapor pressure is low, and if the vapor pressure is high, the odor of the solvent and the stability of the ink become problems. Further, it is preferable that the specific gravity is close to that of water from the viewpoint of storage stability of the ink.

Preferred solvents include, for example, vegetable oils (for example,
Olive oil, soybean oil, castor oil, etc.), mineral oils (eg petroleum, kesilon, paraffin etc.), hydrocarbons (eg alkyl substituted benzene, alkyl substituted naphthalene, alkyl substituted biphenyl etc.), esters (eg phthalic acid) Ester, benzoic acid ester, fatty acid ester, citric acid ester, phosphoric acid ester, etc.), ethers (eg glycol ethers), higher alcohols, higher fatty acids, amides, chlorinated paraffin, silicone oil, etc. .

These solvents are used in a weight ratio of 1% to 50%, preferably 3% to 30% with respect to the aqueous phase.

Water-insoluble dyes such as pigments and oil-soluble dyes are preferably used as the dye dissolved or dispersed in the solvent. Specifically, all commercially available pigments can be used as the pigment, and examples thereof include carbon black, phthalocyanine blue (CI74160), phthalocyanine green (CI74260), and Hansa Yellow 3G.
(CI11670), Disazo Yellow GR (CI21200), Permanent Red 4R (CI12335), Brilliant Carmine 6
B (CI15850), quinacridone red (CI46500), etc. can be used.

As the oil-soluble dye, for example, the following dyes are preferably used.

CI Solvent Yellow 1, 2, 3, 13, 19, 22, 29,
36, 37, 38, 39, 40, 43, 44, 45, 47, 62, 63, 71, 7
6, 81, 85, 86; CI Solvent Red 8, 27, 35, 36, 37, 38, 39, 4
0, 58, 60, 65, 67, 69, 81, 86, 89, 91, 92, 97, 9
9, 100, 109, 118, 119, 122; CI Solvend Blue 14, 24, 26, 34, 37, 38, 39, 4
2, 43, 45, 48, 52, 53, 55, 59, 67; CI Solvent Black 3, 5, 7, 8, 14, 17, 19,
Examples include, but are not limited to, 20, 22, 24, 26, 27, 28, 29, 43, 45 and the like.

In addition, even among various conventionally known water-soluble dyes, dyes which are water-insoluble and solvent-soluble by exchanging counter ions (usually sodium, potassium, ammonium ions) with an organic amine or the like can also be used. it can.

Further, various additives such as an ultraviolet absorber, an antioxidant or a color improving agent may be added to the solvent together with the dye, depending on the purpose.

In a preferred embodiment of the present invention, a preferable example of the ultraviolet absorber in which the dye and / or pigment is used in combination with the ultraviolet absorber and / or the antioxidant is, for example, 2-hydroxy-4-methoxy-5-sulfo. Benzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone Na salt, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,4-dihydroxy Benzophenone, 2 (2'-hydroxy-5-methylphenyl) benzotriazole, Tinuvin234 (trade name, manufactured by Ciba-Geigy), the same 320, the same 3
26, 327, 328, Uvinul400 (trade name, made by BASF), M40, D49, 49
0, same D50, same MS40, same N35, same N539, Cyasorb UV9 (trade name, made by American Cyanamid), same UV24, same UV207, same UV284, same UV531, same UV108
4, same UV5411 and the like.

Further, preferable examples of the antioxidant include, for example, 2,6-di-tert-butyl-p-cresol, 2,6-tert-butyl-4-ethylphenol, 2 (3) -butyl-4-oxy. -Anisole (BH
A), 2,6-di-tert-butyl-oxytoluene (BHT), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6- tert-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, Irganox245 (trade name, manufactured by Ciba-Geigy), 259, 5
65, 1010, 1035FF, 1076, 1081, 1098, 12
22, 1330, 1425WL, Cyanox1790 (trade name, manufactured by American Cyanamid), 425, 2246, 711, 1212, LTDP, MTD.
P, the same STDP, etc.

The above dyes (and UV absorbers and / or antioxidants)
Examples of the method for emulsifying and dispersing the water-insoluble solvent in which is dissolved or dispersed in water include a method using an ultrasonic wave, a method using various dispersers and a stirrer, and the like. At this time, various emulsifiers and dispersants, as well as emulsifying or dispersing aids such as protective colloids can be used as required. Examples thereof include polymeric substances such as PVA, PVP and gum arabic, anionic surfactants and nonionic surfactants.

As a method of microencapsulating the emulsified body, the wall forming material is separately present in both the organic phase and the aqueous phase,
An interfacial polymerization method in which a polymerization reaction is caused at the interface between an organic phase and an aqueous phase to form microcapsules, a so-called In-Situ polymerization method in which a material forming a wall only in the organic phase is dissolved or present to form microcapsules , A coacervation method in which the concentrated phase of the polymer is phase-separated by changing the pH, temperature, concentration and the like of the aqueous solution of the polymer to form microcapsules.

Examples of the wall forming material include terephthaloyl chloride, toluene diisocyanate, bisphenol A, ethylenediamine, ethylene glycol, styrene, divinylbenzene, gelatin, gum arabic, carboxymethyl cellulose and the like.

The particle size of the microcapsules obtained as described above is
From the viewpoint of ink storage stability and nozzle clogging, the mode of particle size distribution is preferably 10 μm or less.

Using the microcapsules formed in this way, to obtain the final ink, the capsules are once taken out by centrifugation or filtration, redispersed in the ink solvent, and a water-soluble organic solvent and pH adjustment if necessary. It is also possible to add an agent, a surfactant, an antiseptic, etc. to make an ink having desired physical properties, or to make an ink by adding the necessary additives as described above without removing the microcapsules from water. The method of forming an ink is not particularly limited.

The microencapsulated dye as described above is generally used in a proportion of about 0.1 to 20% by weight in the total amount of the ink including the ink medium, as in the case of the conventional ink. The same as

A suitable solvent for use in the ink of the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and a particularly preferable solvent is a mixed solvent of water and a water-soluble organic solvent, which is water-soluble. As the organic solvent, a polyhydric alcohol having an effect of preventing ink drying is contained. As the water, it is preferable to use deionized water instead of general water containing various ions.

Examples of the water-soluble organic solvent used by mixing with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and the like. Alkyl alcohols having 1 to 4 carbon atoms; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylenes such as polyethylene glycol and polypropylene glycol Glycols; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol,
Alkylene glycols in which the alkylene group such as hexylene glycol and diethylene glycol contains 2 to 6 carbon atoms; glycerin; ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) Lower alkyl ethers of polyhydric alcohols such as ethers; N-methyl-2-pyrrolidone, 1,3-
Dimethyl-2-imidazolidinone and the like can be mentioned. 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.

The content of the above water-soluble organic solvent in the ink 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. .

Examples of the pH adjuster used in the above ink formation include various organic amines such as diethanolamine and triethanolamine, inorganic alkalis such as sodium hydroxide, lithium hydroxide, and alkali metal hydroxides such as potassium hydroxide. Agents, organic acids and mineral acids.

In addition to the above components, the ink of the present invention may contain a surfactant, a clay modifier, a surface tension modifier, etc., if necessary.

The image forming method of the present invention is performed by an inkjet method using the ink of the present invention. All conventionally known various inkjet methods are suitable in the present invention.

The recording material used may be any of ordinary paper, coated paper, synthetic paper, various plastic films, etc., and is not particularly limited.

Particularly, in the image forming method of the present invention, after the image is formed on a suitable recording material by using the ink, the microcapsules on the recording material are destroyed by a conventionally known means such as pressure, heat or light to cover the inclusions. It can be spread evenly on the recording material. By doing so, the continuous gradation of the image is remarkably improved, and a preferable result can be obtained.

(Examples) Next, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Usage Examples. In the text,% is based on weight unless otherwise specified.

Example 1 90 g of 1-methyl-naphthalene with CI Solvent Black 3 (Orient Oil Black HB, manufactured by Orient Chemical Co., Ltd.)
B) 10 g and terephthaloyl chloride 1 g were dissolved. On the other hand, 4g of non-ionic surfactant BL-9EX (manufactured by Nikko Chemicals) and 5g of sodium carbonate were dissolved in 300g of water, and the above 1-methylnaphthalene solution was added to this, and output using an ultrasonic disperser manufactured by Branson. It was emulsified and dispersed under the conditions of 200 W and 10 minutes. To this, 100 g of 20% ethylene glycol aqueous solution was added and stirred for 3 hours to form microcapsules. 80 g of this microcapsule-containing liquid was added, 20 g of diethylene glycol was added, and the mixture was further stirred for 3 hours to obtain an ink of the present invention.

Example 2 8 g of CI sorbene track 7 (manufactured by BASF, Nigrosine base LK) and 80 g of styrene in 80 g of di-n-butyl phthalate.
g, divinylbenzene 2 g and benzoyl peroxide 35 mg were dissolved. The above solution was added to 500 g of 20% aqueous solution of gum arabic and the output was 200 W using an ultrasonic disperser manufactured by Branson.
And emulsified and dispersed for 10 minutes. This was kept at 80 ° C. for 5 hours to form microcapsules. The microcapsule-containing material was centrifuged to separate the microcapsules. 10 g of the microcapsules were added to 60 g of distilled water, 10 g of ethylene glycol and 20 g of glycerin were added, and the mixture was stirred for 2 hours to give an ink of the present invention.

Example 3 CI Solvent Red 2 in 10 g of tri-n-butyl phosphate
4 (Orient Chemical Red, Orient Oil Red RR) 2g
Was dissolved. Add this to 30 g of 10% gelatin aqueous solution,
Using a special mixer Homo mixer, 12,000 rpm and 15
After emulsification and dispersion under the condition of 1 minute, 30 g of a 10% aqueous solution of gum arabic was added and mixed. Add 40g of water at 40 ℃ and add 10%
The pH was adjusted to 4.0-4.4 with acetic acid. Cool it to 5 ° C,
1 g of 30% formalin was added and the pH was adjusted to 9 with 10% NaOH. Five
The temperature was gradually increased to 0 ° C. to form microcapsules. Take 70g of this and 15g of polyethylene glycol
And 15 g of N-methyl-2-pyrrolidone were added and the mixture was stirred for 2 hours to give an ink of the present invention.

Example 4 100 g of carbon black (MA-100 manufactured by Mitsubishi Kasei) was added to 400 g of oleic acid, and a dispersion treatment was carried out for 100 hours with a ball mill. 80 g of this dispersion was taken, added to 100 g of a 10% aqueous solution of polyvinyl alcohol, and emulsified and dispersed for 15 minutes at 12,000 rpm with a homomixer manufactured by Tokushu Kika Kogyo. Further, 100 g of a 10% aqueous solution of polyvinyl alcohol and 5 g of 1% hydrochloric acid were added, and after stirring for 15 minutes, 5 g of formalin was added and stirred at 40 ° C. for 1 hour to form microcapsules. 60 g of this was taken, 15 g of propylene glycol and 25 g of 1,3-dimethyl-2-imidazolidinone were added and stirred for 3 hours to obtain an ink of the present invention.

Example 5 An ink of the present invention was obtained in the same manner as in Example 1 except that 10 g of the ultraviolet absorber 2,4-dihydroxybenzophenone was used in combination with the dye.

Example 6 An ink of the present invention was obtained in the same manner as in Example 2, except that 10 g of the antioxidant Irganox 565 was used in combination with the dye.

Comparative Example 1 CI Direct Black 154 (manufactured by Daiwa Kasei) 2 g of water 7
Dissolve in 8 g, add 20 g of diethylene glycol,
The ink was agitated for 2 hours to obtain a comparative ink.

Comparative Example 2 Water-soluble acrylic resin 5 g, nonionic surfactant MYS-2
(Nikko Chemicals) 1 g, carbon black (Mitsubishi Kasei, MA-100) 10 g, ethylene glycol 10 g and distilled water 7
4 g was mixed and stirred, and dispersed by a ball mill for 100 minutes.
80 g of this was taken, 20 g of diethylene glycol was added, and the mixture was stirred for 5 hours to obtain a comparative ink.

Comparative Example 3 An ink of Comparative Example was prepared in exactly the same manner as in Example 1, except that the emulsification and dispersion conditions were three-one motor (trade name) at 601 rpm for 30 minutes.

Example of use An on-demand type recording head (ejection orifice system 50 μm, piezo oscillator drive voltage) in which ink is ejected by a piezo oscillator using each of the inks of the above-mentioned implementation and comparative examples.
With an inkjet recording device with 60V, frequency 4KHz), print on copy paper to form an image, pass it between pressure rollers, and use a xenon fade meter (made by Gas Tester) for 30 hours for the obtained image. Irradiate,
The light resistance was evaluated by obtaining the color difference before and after irradiation.

Further, water was applied to the obtained image to visually judge the degree of stain of the image, and the water resistance was evaluated. Further, the storage stability of the used ink was −30 ° C. and 20 ° C., respectively.
After storing at 60 ° C. for 1 month, generation of precipitates and changes in liquid physical properties were measured and evaluated.

The evaluation results are shown in Table 1 below. ◎ in the table is excellent
◯ means good, Δ means slightly bad, and x means bad.

Further, the particle size of the microcapsules in each of the inks of Examples and Comparative Examples was measured using a Coulter Counter (manufactured by Coulter Electronics) and is shown in Table 1.

Table 1 Ink Lightfastness Waterfastness Storage Mode Mode value of particle size Example 1 ○ ◎ ○ 7.5 μm Example 2 ○ ◎ ○ 4.2 μm Example 3 ○ ◎ ○ 6.3 μm Example 4 ◎ ◎ ○ 8.5 μm Example 5 ◎ ◎ ○ ○ 7.2 μm Example 6 ◎ ◎ ○ 4.6 μm Comparative Example 1 △ × ◎ 2 μm or less Comparative Example 2 ◎ ◎ × 2 μm or less Comparative Example 3 ◎ ◎ × 12 μm (Effect) As apparent from the above description, this The ink of the invention has a specific gravity of the microcapsules close to that of the continuous phase and a small particle size, so that aggregation and precipitation hardly occur and the storage stability is excellent. Further, since an ultraviolet absorber and / or an antioxidant is contained in the microcapsules, the image recorded using the microcapsules has excellent light resistance. Further, the oil in the microcapsules acts as a water repellent, and thus the water resistance is improved. It is also very suitable as an ink.

In addition, since the mode of the particle size of the microcapsules is 10 μm or less, the microcapsules do not aggregate or precipitate, and the storage stability is excellent.

Claims (4)

(57) [Claims] 1. A microcapsule containing at least a water-insoluble dye and an ultraviolet absorber or an antioxidant,
An ink jet recording liquid, which is a composition dispersed in an aqueous medium, wherein the mode of particle size of the microcapsules is 10 μm or less. 2. The recording liquid according to claim 1, wherein the dye is a pigment or an oil-soluble dye. 3. A microcapsule containing at least a water-insoluble dye and an ultraviolet absorber or an antioxidant,
A process of applying a recording paper for inkjet, which is a composition dispersed in an aqueous medium, wherein the mode of the particle size of the microcapsules is 10 μm or less to a recording material by an inkjet method, and the recording material. An image forming method, characterized in that an image is formed through a process of destroying the microcapsules. 4. The image forming method according to claim 3, wherein the dye is a pigment or an oil-soluble dye.