JPH0676570B2 - Recording liquid and image forming method using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a recording liquid (hereinafter referred to as ink) used for various recording instruments such as writing instruments and printers, and an image forming method using the ink, particularly recording. The present invention relates to an ink and an image forming method suitable for an inkjet recording system in which droplets are ejected from an orifice of a head to perform recording.

(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, the properties of the ink used are that the physical properties such as viscosity and surface tension are in appropriate ranges, that the dissolution stability of the dissolved components is high, that fine orifices are not clogged, and that the concentration is sufficiently high. It is required that the recorded image of No. 1 is given, and that changes in physical properties or precipitation of solid matter do not occur 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, as a coloring material for ink in an inkjet recording system, a water-soluble dye is mainly used because the liquid medium is aqueous, and by using the water-soluble dye,
Many of the above basic requirements of ink jet 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, the recorded image is sunlight,
When exposed to the light of a fluorescent lamp or a light source of a projector, a recorded image may disappear, be difficult to read, or discolor during storage for a long time.

Therefore, it is known to add an existing ultraviolet absorber or antioxidant to the ink for the purpose of improving the light resistance of the water-soluble dye.

However, many of these UV absorbers and the like are insoluble in the ink medium, and even if they are slightly soluble, they precipitate and agglomerate in the ink and cause hanging of the orifice tip or pen tip. There is.

Therefore, in order to solve these problems, it is also proposed to dissolve an ultraviolet absorber or the like in a water-insoluble organic solvent and to emulsify and disperse it in the ink, but in this case also during storage of the ink. There is a problem with stability over time, especially during storage at low temperatures.

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 of an oily substance containing at least an ultraviolet absorber or an antioxidant are dispersed in an aqueous medium containing a dye, and the mode of the particle size of the microcapsules is 10 μm. The present invention is an ink characterized by the following, and an image forming method using the ink.

(Function) By incorporating an ultraviolet absorber and an antioxidant into a microcapsule in addition to a dye which is a recording agent in the ink, there are no problems such as dispersion stability and storage stability, and water resistance and It is possible to provide an image having excellent light resistance.

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

As the dye used in the present invention, most dyes described in the color index can be used, and many dyes not described in the color index are suitable. Particularly commonly used ones are water-soluble acid dyes, direct dyes, basic dyes and reactive dyes, and other disperse dyes and reactive disperse dyes can also be used.

These dyes are used in an ink medium of 0.5 to 2 in an aqueous medium.
It is used in an amount of 0% by weight, preferably 1 to 10% by weight.

The microencapsulated oil used in the present invention, which is a feature of the present invention, includes a UV absorber and / or an antioxidant dissolved or dispersed in a solvent substantially insoluble in water, which is emulsified in water. It is obtained by dispersing and further microencapsulating by a conventionally known appropriate means.

The solvent used for the microencapsulation is not particularly limited as long as it is substantially insoluble in water, but 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 are high. It becomes a problem. 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 (eg 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,
Examples thereof include citric acid esters, phosphoric acid esters, etc.), ethers (eg glycol ethers), higher alcohols, higher fatty acids, amides, chlorinated paraffin, silicone oil and the like.

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

The solvent may contain various additives.

In the present invention, an ultraviolet absorber and / or an antioxidant is used as at least the above additive. Preferred examples of the ultraviolet absorber include, for example, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone Na salt, 2,2'- Dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2 (2'-hydroxy-5-methylphenyl) benzotriazole, Tinuvin 234 (trade name, manufactured by Ciba-Geigy), the same. 320, 32
6, the same 327, the same 328, Uvinul400 (trade name, made by BASF), the same M40, the same D49, the same 490,
Same D50, same MS40, same N35, same 539, Cyasorb uv9 (trade name, American, made by 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-di-tert-butyl-4-ethylphenol, 2 (3) -butyl-4. -Oxy-anisole (BHA), 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, Irgnaox 245 (trade name, manufactured by Ciba Geiger), 259, 56
5, 1010, 1035FF, 1076, 1081, 1098, 122
2, 1330, 1425WL, Cyanox1790 (trade name, made by American Cyanamid), 425, 2246, 711, 1212, LTDP, MTD
P, the same STDP, etc.

Examples of the method for emulsifying and dispersing the water-insoluble solvent in which the above-mentioned ultraviolet absorber and / or antioxidant are dissolved or dispersed in water include a method using ultrasonic waves, a method using various dispersers and stirrers, 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, a wall-forming material is separately present in both the organic phase and the aqueous phase, and an interface for forming a microcapsule by causing a polymerization reaction at the interface between the organic phase and the aqueous phase. Polymerization method, so-called In-Situ polymerization method in which a material that forms a wall only in the organic phase is dissolved or present to form microcapsules, concentrated phase of polymer by changing pH, temperature, concentration, etc. of aqueous solution of polymer Examples include a coacervation method in which microcapsules are formed by phase separation of

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

Regarding the particle size of the microcapsules obtained as described above, it is preferable that the mode of particle size distribution is 10 μm or less from the viewpoint of storage stability of ink and clogging of nozzles.

Using the microcapsules formed in this way, to obtain the final ink, the capsules are once taken out by centrifugation or filtration, and then added to the ink already prepared or redispersed in the ink solvent to form the dye. In addition, if necessary, a water-soluble organic solvent, a pH adjuster, a surfactant, an antiseptic agent, etc. are added to prepare an ink having a desired physical property value, or the microcapsules are not removed from the water and the above dye and A method in which necessary additives are added to form an ink is also possible, and the method for forming an ink is not particularly limited.

The above-mentioned microencapsulated oily substance is preferably used in a proportion of about 5 to 25% by weight in the total amount of the ink.

The solvent suitable for use in the ink of the present invention is water or a mixed solvent of water and a water-soluble solvent, and particularly preferable is a mixed solvent of water and a water-soluble organic solvent. The agent contains a polyhydric alcohol having an effect of preventing ink drying. 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; polyalkyl such as polyethylene glycol and polypropylene glycol Lene 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 preferable.

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. .

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

In addition to the above components, the ink of the present invention may optionally contain
Surfactants, viscosity modifiers, surface tension modifiers and the like may be included.

The image forming method of the present invention is characterized by using the above-mentioned ink of the present invention, and as a recording method, in addition to a so-called general writing instrument such as a general pen, a fountain pen, a felt pen, a writing brush, a pen plotter or an inkjet printer. A mechanical recording method such as a method can also be used and is not particularly limited, but an inkjet method is particularly suitable, and various conventionally known inkjet methods are all suitable in the present invention.

The recording material used is ordinary paper, coated paper, synthetic paper,
Any of various plastic films can be used without any particular limitation.

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, and in this case, the dye and the oil containing the ultraviolet absorber and / or the antioxidant are brought into contact with each other, and the water resistance and light resistance of the image are remarkably improved. 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 12.5 g of CI Acid Red 35, 4 g of nonionic surfactant BO-10TX (manufactured by Nikko Chemicals) and 5 g of sodium carbonate were dissolved in 300 g of water. 90 g of 1-methylnaphthalene solution, 5 g of terephthaloyl chloride, UV absorber (Tinuvin32
8. Add 2.5g of trade name) and 2.5g of antioxidant (Irganox1098, trade name) to the above dye aqueous solution, and emulsify with Branson ultrasonic disperser under conditions of output 200W and 10 minutes. did. To this, 100 g of a 20% aqueous solution of ethylene glycol was added and reacted to form microcapsules. 20 g of diethylene glycol was added to 80 g of this microcapsule-containing liquid to prepare an ink of the present invention.

Example 2 5 g of terephthaloyl chloride and an ultraviolet absorber (Tinuvin3
28, trade name) 2.5 g was dissolved in 92.5 g of 1-methylnaphthalene to obtain an ink of the present invention in the same manner as in Example 1.

Comparative Example 1 CI Acid Red 352 g and diethyl glycol 20 g were added to 78 g of water and dissolved by stirring to obtain a comparative ink.

Example 3 25 g of CI Food Black 2 and 5 g of a nonionic surfactant NP-7.5 (manufactured by Nikko Chemicals) were dissolved in 370 g of water. To this aqueous solution, add 80 g of dimethyl phthalate to an ultraviolet absorber (Cyaso
rb UV284, trade name) 10 g, styrene 20 g, divinylbenzene 2 g, and benzoyl peroxide 35 mg were added to the solution, and the mixture was emulsified and dispersed under the conditions of 12,000 rpm and 15 minutes using a homomixer manufactured by Tokushu Kika Kogyo. . This was kept at 80 ° C. for 5 hours to form microcapsules. To 60g of this microcapsule liquid, 30g of ethylene glycol and 10g of glycerin
g was added and stirred to obtain the ink of the present invention.

Comparative Example 2 Ink for Comparative Example was prepared by dissolving 23 g of CI Food Black in a mixed solution of 57 g of water, 30 g of ethylene glycol and 10 g of glycerin.

Comparative Example 3 Three-one motor (trade name) was used for the emulsification and dispersion conditions.
An ink of Comparative Example was prepared in exactly the same manner as in Example 1 except that the ink was used under the conditions of 600 rpm and 30 minutes.

Example of use An on-demand type recording head (ejection orifice system 50 μm, piezo-vibrator drive voltage) in which ink is ejected by a piezo-vibrator using the inks of the above-mentioned examples and comparative examples, respectively
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 Suga Test Instruments) for 30 hours. Irradiate,
The light resistance was evaluated by obtaining the color difference before and after irradiation.

Further, water resistance was evaluated by applying water to the obtained image and visually observing the degree of stain of the image.

The storage stability of the used ink was evaluated by measuring the generation of precipitates and changes in liquid physical properties after storage at -30 ° C, 20 ° C and 60 ° C for 1 month, respectively.

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

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 the results are shown in Table 1.

(Effects) As is clear from the above description, the ink of the present invention has a specific gravity of the microcapsules close to that of the continuous phase and a small particle size, and therefore does not easily agglomerate and precipitate and is excellent in storage stability. . 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 and precipitate, and the storage stability is excellent.

Claims (5)

[Claims] 1. A composition in which microcapsules of an oily substance containing at least an ultraviolet absorber or an antioxidant are dispersed in an aqueous medium containing a dye, and the mode of the particle size of the microcapsules is 10 μm. A recording liquid comprising: 2. The recording liquid according to claim 1, wherein the dye is a water-soluble dye. 3. The recording liquid according to claim 1, which is for ink jet. 4. A composition in which microcapsules of an oily substance containing at least an ultraviolet absorber or an antioxidant are dispersed in an aqueous medium containing a dye, and the mode of the particle size of the microcapsules is 10 μm or less. An image forming method, characterized in that an image is formed through a step of applying the recording liquid to a recording material by an inkjet method and a step of destroying the microcapsules in the recording material. 5. The image forming method according to claim 4, wherein the dye is a water-soluble dye.