JPH01308468A - Ink - Google Patents

Abstract

PURPOSE:To obtain an ink which is excellent in anticlogging property and storage stability and can give an image of excellent light fastness and water resistance, by dispersing colored particles formed by dissolving or dispersing a dye in a low-melting water-insoluble compound in an aqueous medium. CONSTITUTION:A dye which is preferably water-insoluble is dissolved or dispersed in a low-melting water-insoluble compound which preferably melts at 50-150 deg.C (e.g., p-toluenesulfonamide), and this solution or dispersion is emulsified in, for example, an aqueous solution in which a surfactant is dissolved. The formed emulsion is cooled to obtain colored particles of a mode of a particle diameter distribution of, desirably, <=10mum. The colored particles are dispersed in an aqueous medium which is desirably a mixed solvent comprising water and a water-soluble organic solvent (e.g., diethylene glycol).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to inks used in various recording instruments such as writing instruments and printers. This invention relates to a water-based ink that provides images with excellent light fastness, abrasion resistance, etc.

(Prior Art) The inkjet recording method has the advantage that it generates little noise during recording, is easily compatible with color printing, and can 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 the fine 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 a water-soluble dye is used, the water resistance and light resistance of the recorded image often become a problem because the dye is water-soluble and generally has poor light resistance. In other words, if a recorded image is exposed to rain, sweat, or water from drinking or drinking, the recorded image may blur or disappear, and may also fade or change color due to sunlight or various types of illumination light. There are many cases.

Therefore, in order to solve the above-mentioned problems of light resistance and water resistance, it is possible to use pigments or oil-soluble dyes as dyes. However, since pigments have poor dispersion stability and tend to settle, the storage stability of inks is poor. Furthermore, since the redispersibility is poor, the nozzle is likely to become clogged, resulting in an irreversible state.

On the other hand, oil-based ink using oil-soluble dye has a surface tension of 1?
The discharge condition is unstable. Furthermore, the ink bleeds significantly and feathering is likely to occur, resulting in extremely poor image quality.

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, and has anti-clogging properties and storage stability. The objective is to provide ink with excellent properties.

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

That is, the present invention is an ink characterized by dispersing a water-insoluble low melting point compound in which a dye is dissolved or dispersed in an aqueous medium.

(Function) By using colored particles in which a dye is dissolved or dispersed in a water-insoluble compound with a relatively low melting point as the recording agent component of the ink, it is free from bleeding and has excellent optical density, and has water resistance, light resistance, Images with excellent abrasion resistance etc. can be provided.

Further, even if such an ink becomes clogged in an inkjet nozzle, its ejection properties can be easily restored by heating.

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

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

The colored particles used in the present invention and which mainly characterize the present invention are particles of a relatively low melting point compound colored with a dye, and examples of the dye include direct dyes, acid dyes, basic dyes, reactive dyes, etc. Water-soluble dyes can also be used, but
Water-insoluble dyes such as oil-soluble dyes and disperse dyes are preferably used. By using these water-insoluble dyes, the problem of ink bleeding during printing can be solved.

Furthermore, among the various water-soluble dyes mentioned above, dyes made water-insoluble and solvent-soluble by exchanging their counter ions (usually sodium, potassium, or ammonium ions) with organic amines, etc. are also preferably used. can.

The relatively low melting point compound used in the present invention is a water-insoluble compound that is solid at least at room temperature, preferably melts and liquefies at a temperature of about 50 to 150°C, such as alkylbenzene, alkylnaphthalene, which is solid at room temperature, Examples include stiff sulfonamide, carbonamide, low molecular weight polyethylene, low molecular weight polypropylene, paraffin wax, microcrystalline wax, carnauba wax, higher fatty acid amide, wax, and solid plasticizer.

Particularly preferred are sulfonamides or carbonamides, which have excellent dye solubility. Among these, materials with low film-forming performance are particularly preferred; if a resin with high film-forming performance is used, the ejection recovery property will be lowered when the nozzle becomes clogged.

The amount of the dye added to the above-mentioned relatively low melting point compound is not particularly limited, but is approximately 1 part by weight per 100 parts by weight of the low melting point compound.
The preferred range is from 100 parts by weight. In particular, by sufficiently dissolving the dye by using a material with high dye solubility as a low melting point material, it is possible to create an ink with a high optical density (forming an image with excellent translucency when used in OHP). .

In addition to the dye, various additives such as an ultraviolet absorber, an antioxidant, or a color development improver can be added to the low melting point compound depending on the purpose.

A method for dissolving or dispersing a dye in a low melting point compound is to liquefy these low melting point compounds by heating, and then add the dye therein and dissolve or disperse the dye.

In addition, as a method for emulsifying and dispersing the above-mentioned colored low-melting compound in water, it is possible to solidify the colored material once, pulverize it to an appropriate particle size, and then disperse it, or to Particle formation and dispersion may be performed simultaneously in cold water or hot water as well as in water. Examples of emulsifying and dispersing methods include methods using ultrasonic waves and methods using various dispersers and stirrers. At this time, various emulsifiers, dispersants, and emulsifying or dispersing aids such as protective colloids may be used as necessary. Examples include polymeric substances such as PVA, PVP, and gum arabic, anionic surfactants, and nonionic surfactants.

The particle size of the colored particles 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 nozzle clogging.

In order to make the final ink using the colored particles formed in this way, the colored particles are once removed by centrifugation or filtration, redispersed in an ink solvent, and if necessary, a water-soluble organic solvent, pH It is also possible to create an ink with the desired physical properties by adding modifiers, surfactants, preservatives, etc., or to create an ink by adding necessary additives such as those mentioned above without removing the colored particles from the water. The method of making ink is not particularly limited.

The above-mentioned colored particles are generally about 0.1 to 2 in the total amount of ink including the ink medium, as in the case of conventional inks.
The solvent used in the ink of the present invention is water or a mixed solvent of water and a water-soluble organic solvent. Particularly preferred is a mixed solvent of water and a water-soluble organic solvent, which contains a polyhydric alcohol having an effect of preventing ink from drying as the water-soluble 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, 5eC-butyl alcohol, tert-butyl alcohol, and isobutyl alcohol. Alkyl alcohols having 1 to 4 carbon atoms; amides such as dimethylformamide and dimethylacetamide; ketone or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylenes such as polyethylene glycol and polypropylene glycol Gelicols: ethylene glycol, propylene glycol, butylene gellicol, triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol, etc., in which the alkylene group has 2 to 6 carbon atoms. Alkylene glycols containing; 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- Examples include pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like. 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 water-soluble organic solvent in the ink is generally 0 to 95% by weight, preferably 10 to 80% by weight, more preferably 20 to 5% by weight based on the total weight of the ink.
It is in the range of 0% by weight.

Examples of pH adjusters used in the above ink production include various organic amines such as jetanolamine and triethanolamine, alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide. Examples include inorganic alkaline agents, organic acids and mineral acids.

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

The recording method using the ink of the present invention is not particularly limited, and can be used not only with so-called general writing instruments such as a general pen, fountain pen, felt pen, and brush, but also with mechanical recording methods such as a pen plotter and an inkjet method. However, a particularly preferred method is an inkjet method, and any of the various conventionally known inkjet methods are suitable for the present invention.

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 using the ink of the present invention, after forming an image using the ink on a suitable recording material, the colored particles on the recording material are treated with conventionally known means such as pressure or heat to remove the colored particles. By fixing it on the recording material, the wear resistance of the image can be further improved.

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

Example I 90 g of P-1-luenesulfonamide was melted and liquefied at 140°C, and C,1, Solvent Black 3 (Orient Chemical Source, Orient Oil Black HBB) 1O
g was mixed and dissolved.

On the other hand, nonionic surfactant B was added to 300 g of water at a temperature of 80°C.
Dissolve 4 g of L-9EX (manufactured by Nikko Chemicals) and 5 g of sodium carbonate, gradually add the above coloring liquid to this at 140°C, and use an ultrasonic dispersion machine manufactured by Branson to obtain an output of 20
The mixture was emulsified and dispersed at 0 W for 10 minutes and cooled to 20°C.

To this was added 100 g of a 20% ethylene glycol aqueous solution, and the mixture was stirred for 3 hours. Take 80g of this colored particle-containing liquid,
20 g of diethylene glycol was added and stirred for an additional 3 hours to obtain the ink of the present invention.

Example 2 p- and O-toluenesulfonamide mixture (melting point ca.
20℃) 80g of C, R, Solvent Black 7 (B
Nigrosine Base L (manufactured by ASF) 8g at about 130℃
was added and uniformly dissolved. The above colored solution was added to 500 g (80° C.) of a 0.5% aqueous solution of a surfactant, and emulsified and dispersed using a Branson ultrasonic dispersion machine at an output of 200 W and for 10 minutes. After cooling this to 25° C., it was centrifuged to separate colored particles. This colored particle L
og to 60g of distilled water, and then add ethylene glycol L.
og and glycerin zog were added and stirred for 2 hours to prepare the ink of the present invention.

Example 3 100 g of carnauba wax was melted at 100° C., and 20 g of C,1, Solvent Red 24 (Orient Chemical Source, Orient Oillet RR) was dissolved therein. The ink of the present invention was prepared in the same manner as in Example 1.

Example 4 Ethylene bis stearylamide long and c, r.

The ink of the present invention was prepared in the same manner as in Example 1 except that 10 g of Solvent Blue 14 was used.

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 In Example 2, the antioxidant 1rganox 565
An ink of the present invention was obtained in the same manner as in Example 2 except that 10 g of the dye was used in combination with the dye.

Comparative Example I C, 1, Direct Black 154 (manufactured by Daiwa Kasei) 2
g in 7 Bg of water, and then diethylene glycol 2
0 g was added and stirred for 2 hours to prepare an ink of a comparative example.

Comparative Example 2 Water-soluble acrylic resin 5g, nonionic surfactant MYS-
2 (manufactured by Nikko Chemicals), 10 g of carbon black (MA-100, manufactured by Mitsubishi Kasei), 10 g of ethylene glycol, and 74 g of distilled water were mixed and stirred, and dispersed in a ball mill for 100 hours. 80 g of this was taken, 20 g of diethylene glycol was added thereto, and the mixture was stirred for 5 hours to obtain an ink of a comparative example.

Usage example: An ink jet having an on-demand recording head (discharge orifice system 50 μm, piezo vibrator drive voltage 60 V, frequency 4) that discharges ink using a piezo vibrator using the inks of the above examples and comparative examples, respectively. An image is printed on copy paper using a recording device, passed between heating rollers, and a xenon fade meter (manufactured by Suga Test Instruments) is used to examine the resulting image.
Light resistance was evaluated by irradiating for a time and determining the color difference before and after irradiation.

Further, water resistance was evaluated by pouring water onto the obtained image and visually determining the degree of staining of the image.

In addition, the storage stability of the ink used was evaluated at -30°C and 20°C, respectively.
After being stored at 60°C and 60°C for one month, the formation of precipitates and changes in liquid physical properties were measured and evaluated.

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

Furthermore, using a Coulter Counter (manufactured by Coulter Electronics), the particle diameters of the colored particles in the inks of the Examples and Comparative Examples were measured and are shown in Table 1.

(Space below) ′″U n ゛
'S Example 10 ◎ Q 7.5μ
m Example 20 ◎ Q 4.2 μm Example 30 ◎ Q 6.3 μm Example 4 0
@ 0 8.5am Example 50 ◎
Q 7.2 μm Example 60 ◎ 0
4.6gm Comparative Example 1 Δ × ◎ 2μ
m or less Comparative Example 2 ◎ ◎ × 2 μm or less (
Effects) As is clear from the above explanation, the colored particles of the ink of the present invention are unlikely to cause aggregation or precipitation because the dye is coated with another material, and have excellent storage stability. In addition, since the colored particles contain ultraviolet absorbers and/or antioxidants, images recorded using them have excellent light resistance, and if a water-insoluble dye is used, there is no bleeding during printing. It also has improved water resistance and is extremely suitable as an ink.

Patent applicant: Canon Co., Ltd. Agent: Patent Attorney Yoshi 1) Hiroshi Katsuki

Claims (2)

[Claims] (1) An ink characterized by dispersing a water-insoluble low melting point compound in which a dye is dissolved or dispersed in an aqueous medium. (2) The ink according to claim 1, which is for inkjet use.