JPH03252470A - Ink for recording picture - Google Patents

Abstract

PURPOSE:To obtain the title ink clearly recording in high concentration, having thixotropic fluidity, not oozing on common paper, having excellent fixation, not clogging, having excellent shelf stability of ink and water resistance of printed matter. CONSTITUTION:The objective ink which consists of preferably a dispersion medium, a colorant and a fixing agent, is liquid ink of colloidal fluid wherein the fixing agent is dispersed into the dispersion medium and has thixotropic flow characteristics. The ink preferably contains synthetic trioctahedral smectites.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording ink for recording an image using liquid ink.

[Prior Art] Conventionally, when liquid ink such as inkjet ink adheres to recording paper, the quality of prints and images deteriorates because the ink flows along the cellulose fibers of the recording paper due to capillary action, as shown in Figure 2. Significantly decreased.

Furthermore, when the printing speed is increased, the drying properties of the ink are poor, resulting in show-through, smudged letters, trailing, etc. when sheets are stacked on top of each other. Furthermore, when a full-color image is created by overlapping process colors, the image blurs and blurs occur due to color mixture.

From this point of view, various inks for recording on plain paper have been proposed.

For example, JP-A No. 55-29546 proposes adding a specific surfactant to lower the surface tension and increase the absorption of ink into paper.
Publication No. 862 discloses a method and characteristics for controlling dot spread and absorbency by chemically dissolving sizing agents and pulp materials, which are water-resistant treatment agents for plain paper, by adding a strong basic substance to increase the pH (pH). Japanese Patent Publication No. 58-13675 proposes a method in which polyvinylpyrrolidone having a molecular weight of 40,000 or more is added to ink to control dot spread and absorption into paper.

[Problems to be Solved by the Invention] However, such conventional proposals have the following problems.

When printing at high speed on plain paper, each has a certain effect, but ink containing surfactants dries faster but has a lower surface tension, so the ink spreads along the paper fibers. Without improvement, bleeding occurs and print quality deteriorates.

Furthermore, since bubbles are generated by the surfactant, air bubbles tend to enter the nozzles of the recording head, making it impossible to obtain stable ejection.

In addition, ink containing strong basic substances has high ink absorption and fixing properties, but has poor drying properties, resulting in trailing and bleeding due to poor ink diffusion along paper fibers, resulting in unsatisfactory print quality. The problem was that it was not possible to obtain

Furthermore, ink containing polyvinylpyrrolidone with a molecular weight of 40,000 or more has a very low margin against nozzle clogging and has poor drying properties, resulting in trailing.

Therefore, the present invention aims to solve these problems.
The first object of the present invention is to use a printing device that records an image using liquid ink to print and print on any transfer material.
An object of the present invention is to provide an image recording ink that enables high-density, high-gloss printing without image bleeding.

A second object of the present invention is to provide an image recording ink that dries and fixes quickly, does not cause trailing, and allows full-color images to be produced by superimposing process colors at high speeds.

A third object of the present invention is to provide an image recording ink that has excellent ejection stability and reliability and does not cause clogging in nozzles, ink distribution channels, or slits.

[Means for Solving the Problems] The image recording ink of the present invention is characterized in that the image recording ink used in a printing device that records images using liquid ink has thixotropic flow characteristics.

Also, as a means of imparting thixotropic flow characteristics,
The image recording ink is characterized in that it consists of at least a dispersion medium, a colorant, and a fixing agent, and the fixing agent is a colloidal fluid dispersed in the dispersion medium.

Further, as a means for imparting other thixotropic flow characteristics, the image recording ink is characterized in that it contains synthetic trioctahedral smectite.

[Example] According to the above configuration of the present invention, the image recording ink is the first
As shown in the figure, there is a continuous type that uses thixotropic flow characteristics to generate ink droplets continuously and controls the charge of the droplets, an on-demand type that ejects ink droplets only when necessary for printing, and a super type. The viscosity is easily lowered when micro droplets are generated under high sliding speeds such as ink mist type using sound waves, etc., so when flying, uniform micro droplets with excellent ejection stability and no satellites are flown. On the contrary, after the ink flies, the flow characteristics suddenly change (increase in viscosity) on the transfer medium, so the ink does not flow, does not bleed, and quickly solidifies and fixes.

That is, the present invention satisfies the fact that the lower the viscosity, the better the image recording ink will fly, and the higher the viscosity, the better the print quality on the transfer target.

In addition, since the viscosity can be set relatively high during storage,
It is also possible to use a heterogeneous ink that uses pigments that have poor dispersion stability and poor storage stability.

As a means of imparting thixotropic flow characteristics to the image recording ink, the form of the ink is resin emulsion, wax emulsion, or colloidal dispersion type, but inorganic powder, clay (hydrous silicate of aluminum, magnesium, or iron) can be used. Alternatively, addition of fillers such as clay-like synthetic substances, addition of polymer particles, thickening agents such as water-soluble polymers such as protein N (casein, glue gelatin, gluten, soybean protein), alginates (ammonium alginate, potassium alginate), etc. , sodium alginate), other vegetable thickeners (gum arabic,
Gum tragacanth, gum karaya, guar gum, locust bean gum, iris moss, soybean lecithin, pectic acid, agar), mineral thickener (bentonite clay), acrylic acid thickener (ammonium polyacrylate, sodium polyacrylate, Polymethacrylammonium), polyvinyl alcohol, potassium salt of vinyl polymer, vinylpyrrolidone copolymer polyacrylamide, polyethylene oxide, cellulose derivatives (carboxylated methylcellulose, methylcellulose), oleic acid, ammonium oleate, sodium silicate, cation activator (cetyltrimethylammonium bromide, cetylpyridinium bromide) etc. on the surface of emulsion resin particles, pigment particles, aggregates of dye molecules (
ion micelles) to form a three-dimensional network structure,
Thixotropic properties can be imparted.

Further, a coagulant (formic acid, acetic acid, calcium nitrate, calcium chloride, cyclohexylamine acetate, etc.) can be used.

In addition, sodium silifluoride, potassium silifluoride, etc. can also be used as a gelling agent.

In particular, the larger the thixotropy index shown in formula (2), the easier it is to fly, and the less likely it is to bleed or flow. Things that increase the Chickentropy index include colloidal fluids such as resin emulsions and wax emulsions in which a fixing agent is dispersed in a dispersion medium, polymer fine particles,
It is effective to add synthetic trioctahedral smectite, which is a synthetic material similar to clay.

As a synthetic trioctahedral smectite, Laponite (manufactured by Nippon Silikani Industry) has a thixotropic index that increases easily when added to water, and has excellent dispersion stability and adsorption properties.
can improve flight characteristics and printing characteristics.

Viscosity at 12 rpm thixotropic index T = ■60
Viscosity at r pm As for the physical properties of the ink of the present invention, from the viewpoint of ejection stability, the viscosity value during storage is 50 cP (centivoids) under high shear force.
It is preferably below, and particularly preferably adjusted to below 30 cP.

The colorant used in the present invention may be any water-based dye or oil-based dye used in conventional inks, as long as it does not change color tone or form precipitates when added to other ink components.

Further, as the pigment, a finely divided ordinary organic/inorganic pigment is used, and it is preferable that the pigment is dispersed in a particle size of 1 μm or less.

As for the amount of dye/pigment added, if it is less than 1.0% by weight, sufficient color tone and density cannot be obtained, and if it exceeds 20.0% by weight, clogging tends to occur.
0.0% by weight is preferred.

The dispersion medium used in the present invention includes water, organic solvents (e.g., aliphatic hydrocarbons, naphthenic hydrocarbons, aromatic hydrocarbons, glycols, fatty acids, fatty acid esters, nitrogen-containing compounds), and water-soluble organic solvents. (Alkyl alcohols having 1 to 4 carbon atoms, ketones, ethers, polyalkylene glycols, alkylene glycols, glycerin, lower alkyl ethers of polyhydric alcohols, etc. can be used, but are not limited to these. do not have.

The basic structure of the present invention is as described above, but other conventionally known dispersants, surfactants, viscosity modifiers, surface tension modifiers, resistivity modifiers, pH modifiers, fungicides, penetrants, etc. can be added as necessary.

Hereinafter, the present invention will be specifically explained by giving Examples and Comparative Examples, but these Examples do not limit the present invention.

Example 1 All ink composition amounts (%) shown in the following examples are weight %.

Water-soluble dye 3% Commercially available acrylic emulsion 20% (solid content 40%) Ion-exchanged water 50% Diethylene glycol 10% The above ingredients were thoroughly mixed and stirred in a container, filtered through a membrane filter with a pore size of 1 μm, and recorded ink. was created.

Example 2 Carbon black 5% Polyethylene glycol dimethacrylate 3% Methyl methacrylate 5% n-butyl acrylate 6% Methacrylic acid 2% 2-ethylhexyl methacrylate 2% Potassium persulfate 0.02% Ion exchange water 70.98% Ethanol 2% Glycerin 4% Temperature control device, stirrer After deaerating and replacing the air with nitrogen gas in a flask equipped with a nitrogen gas inlet tube and a dropping funnel, put ion exchange water, warm it to 70°C, and add potassium persulfate for 3 hours. Polyethylene glycol dimethacrylate, methyl methacrylate, acrylic acid n-
A monomer mixture consisting of butyl, methacrylic acid, and 2-ethyl methacrylate was added dropwise over 2 hours.

After dropping potassium persulfate, the temperature was raised to 80°C and
The mixture was stirred for a period of time and filtered under reduced pressure using a membrane filter with a pore size of 0.8 μm to prepare an emulsion with an average particle size of 80 nm.

Carbon black was added to the prepared emulsion and heated to 30°C using an ultrasonic homogenizer with a temperature control mechanism.
Below, the pigment is made into primary particles by ultrasonic dispersion, and after vacuum filtration with a membrane filter with a pore size of 5 μm, ethanol and glycerin are added and stirred for 30 minutes.
A recording ink was produced.

Example 3 The emulsion prepared in Example 2 was spray-dried, and the obtained ultrafine particles were redispersed in aliphatic hydrocarbon (kerosene) to a solid content of 20%, and carbon black 5.
% was cross-linked, dispersed for 8 hours using an attritor, and filtered under reduced pressure using a Teflon membrane filter with a pore size of 5 μm to prepare a recording ink.

Example 4 Oil-soluble dye yellow cyan, magenta 83% Methyl methacrylate 10% n-butyl acrylate 5% Glycidyl methacrylate 3% Ion exchange water 75.95% Potassium persulfate 0.05% Surfactant 1% Diethylene glycol monobutyl ether 2% Using the same apparatus as in Example 1, ion-exchanged water and a surfactant were placed in a flask and dissolved by heating at 70°C. Next, while potassium persulfate was added dropwise over a period of 3 hours, a monomer mixture consisting of methyl methacrylate, n-butyl acrylate, and glycidyl acrylate was added dropwise over a period of 2 hours.

After dropping potassium persulfate, the temperature was raised to 80°C and
After stirring for an hour, the temperature was lowered to 70°C, and the oil-soluble dyes of each color were heated and stirred for 2 hours to be uniformly dispersed, filtered under reduced pressure through a membrane filter with a pore size of 0.8 μm, and resin-colored with an average particle size of 50 nm. A three-color emulsion ink was produced.

Example 5 Water-soluble dye 3% Laponite RD (manufactured by Nippon Silikani Co., Ltd.) 1% Glycerin 5% Sodium dioctyl sulfosuccinate 0. 5% diethylene glycol monobutyl ether 0.5% ion-exchanged water 90% The above components were thoroughly mixed and stirred in a container, and filtered through a membrane filter with a pore size of 0.8 μm to prepare a recording ink.

Comparative Example As Comparative Example 1, a commercially available ink for on-demand inkjet printers was used, and as Comparative Example 2, a commercially available ink for bubble jet printers was used.

Using the above ink, the recording method is ■ A commercially available on-demand inkjet printer ■ Ejection orifice diameter 50 μm, piezo vibrator drive voltage 50 V
, a prototype multi-head with a frequency of 5 kHz ■ Charged ink mist method using ultrasonic atomization (% formula %) Examples 1 to 5 and Comparative Examples 1 to 2
Table 1 shows the evaluation results and physical properties of the ink when high-speed recording was performed using the recording ink.

The evaluation method is shown below.

*1. Bleeding evaluation Observation with a microscope at 100x and 400x and visual observation ■ = Dots are retained on the fibers without any bleeding along the woven fibers O: There is some bleeding along the fibers, but it is not visible visually Δ: Slight smearing is visible with the naked eye ×: There is considerable smearing and the edges are jagged *2. Quick-drying evaluation After 3 seconds, 6 seconds, and 12 seconds of printing, rub the printed area with the edge of the paper. : No trailing after 3 seconds ○: No trailing after 6 seconds △: Trailing after 6 seconds and 1 wheat ×: Trailing after 12 seconds *3. Fixability evaluation After leaving for 24 hours, rub vigorously with your fingers 0: Cannot be removed ×: Can be removed*4. Clogging evaluation Nozzle left without cap at room temperature for 1 month O: Printable Δ: Printable by circulating ink and cleaning X: Printable *5. Ink preservability Put the ink into a sample bottle and store it in an open state at 40°C for 3 months, and check for the presence of foreign matter, odor, aggregation, and sediment O: None ×: Yes *6. Recording density Measurement of reflection 0-D value using a Macbeth densitometer *7. Water resistance evaluation After 1 hour of printing, the printed matter was immersed in water for 5 minutes and the ink flow was observed. O: None ×: Yes *8. Glossiness evaluation Measurement of 75 degree specular glossiness using a digital glossy needle (Murakami Color Technology Institute type) O: 80 or more Δ: 51-79 x: 50 or less $9. Recording on OHP paper O: Recordable ×: Record not possible *10. Lightfastness evaluation Xenon lamp irradiation for 10 hours Blue scale fading O: Less than 50% x: 50% or more The method for investigating ink physical properties is shown below.

*A, Viscosity Measured at 12 rpm using a B-type viscometer (Tokyo Keiki) Surface tension Measured at 60 rpm (Kyowa Kaimen Wagaku) *C1 average particle size Laser light scattering method zeta electrometer ELS800 (manufactured by Daikyu Denshi) Nyoru particle size distribution measurement *B.

As is clear from Table 1, the recording inks of Examples 1 to 5 having a large thixotropy index TI gave good results in common to each recording method.

Furthermore, by overlapping the three colors of yellow, magenta, and cyan in Example 4, a clear full-color image could be reproduced.

[Effects of the Invention] As explained above, the image recording ink of the present invention does not smear on plain paper, which has been a problem in the past, and can provide unprecedented quick-drying properties, making it possible to fix excellent in sex,
It also enables recording with excellent ink storage stability and water resistance of printed matter without causing clogging, and has the effect of enabling high-density, clear recording.

Furthermore, the image recording ink of the present invention has the effect that high-speed, high-quality printing is possible even on OHP paper, which cannot be used in ordinary jet recording.

Furthermore, by using three process color inks, the first and second colors have good drying and fixing properties, making it possible to record a high-resolution full-color image.

The image recording ink of the present invention also has the effect that it can be used as a wet developer for plain paper using an electrophotographic process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing how the ink of the present invention is attached to fibers. FIG. 2 is a schematic diagram showing how ink smears in a conventional example. 1...More than paper fiber ink

Claims (3)

[Claims] (1) An image recording ink used in a printing device that records images using liquid ink, wherein the ink has thixotropic flow characteristics. (2) The image recording ink according to claim 1, wherein the ink comprises at least a dispersion medium, a colorant, and a fixing agent, and the fixing agent is a colloidal fluid dispersed in the dispersion medium. (3) The image recording ink according to claim 1, wherein the ink contains synthetic trioctahedral smectite.