JPH03162466A - Ink for recording image - Google Patents

Abstract

PURPOSE:To provide the subject ink employed for ink jets, etc., having excellent bleeding resistance, fixing property, etc., to plain paper and giving lustrous clear-cut recordings by incorporating water, a coloring agent, a sticking agent and a heat-sensitive coagulating agent, resin particles as the fixing agent being dispersed into a dispersion medium. CONSTITUTION:For example, preferably, water such as distilled water, a water- soluble organic solvent employed after mixed with the water, 0.5-10wt.% of a coloring agent such as an aqueous dye, 3-20wt.% of a fixing agent comprising a resin such as vinyl chloride homopolymer, a heat-sensitive coagulating agent such as aluminum nitrate (in an amount of approximately 1wt.% based of the resin content), a dispersing agent, a surfactant, etc., are compounded with each other to provide the objective ink in which the fixing agent is dispersed in a dispersion medium and which is a fluid having a viscosity of 1.2-10cP (at 20 deg.C).

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an image recording ink used in an ink jet recording method or ink mist recording method in which fine droplets or atomized ink are ejected from a recording head to perform recording. Regarding.

[Prior Art] Conventionally, when image recording ink adheres to recording paper, as shown in FIG.
，! Because the ink flows along the edges, the quality of print and images deteriorates significantly. Furthermore, the density deteriorates significantly when it soaks into the paper. In addition, drying and fixing properties are poor, so increasing the printing speed may cause bleed-through due to the overlapping paper, and when creating a full-color image by overlapping process colors, the image may be blurred or blurred due to color mixing.

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 reduce the surface strength and increase the absorption of ink into paper.
Publication No. 862 describes 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 Publication No. 5S-1SA75 proposes a method in which polyvinylpyrrolidone with 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 foaming occurs due to the surfactant, air bubbles tend to enter the nozzles of the recording head, resulting in problems such as the inability to obtain stable ejection.

In addition, with ink containing strong basic substances, the absorbency of the ink
Although the fixing properties are high, the drying properties are poor, and there are problems in that trailing and ink diffusion along the paper fibers are not sufficiently improved, smearing occurs, and satisfactory print quality cannot be obtained.

Further, ink containing polyvinylpyrrolidone having a molecular weight of 40,000 or more has a problem that the margin against nozzle clogging is very low and that trailing occurs due to poor drying properties.

Therefore, the present invention aims to solve these problems.
The purpose of this is to create prints and images on plain paper in the inkjet or ink mist recording method, in which fine droplets or mist ink are ejected from the recording head and the ink is deposited on plain paper. An object of the present invention is to provide an image recording ink that does not cause bleeding, dries quickly, does not cause trailing, and has excellent ejection stability without causing clogging.

[Means for Solving the Problems] An image recording ink used in an inkjet or ink mist recording method comprises at least water, a colorant, a fixing agent, and a heat-sensitive coagulant, and resin particles as a fixing agent are included in a separation medium. It is characterized by being a fluid in which are dispersed.

[Function] According to the above configuration of the present invention, the chemical affinity between the fixing agent particles and the colorant and the film forming power of the fixing agent (fusion of resin particles due to interfacial tension caused by evaporation of solvent and decrease in surface solid content concentration) As shown in Figure 1, the particles of the fixing agent, which are uniformly dispersed and adsorbing and supporting the dye or pigment as the coloring agent, form a dot shape on the lm fibers of the paper. Forms a film that retains its properties, solving bleeding, drying, and fixing problems.

Furthermore, based on the knowledge that heat-sensitive coagulants used as auxiliary materials in emulsions, latex solutions, etc. are stable at low temperatures, they rapidly uniformly gel the entire latex when heated above a certain temperature. Applying
By adding a heat-sensitive coagulant to the image recording ink and thermally fixing it, an ink that can impart quick drying and quick fixing properties can be obtained.

[Example] The heat-sensitive coagulant used in the present invention is ammonium nitrate.
Inorganic ammonium salts such as ammonium sulfate and organic ammonium salts such as ammonium acetate are used, and these are used in an amount of about 1% of the resin content. In the unlikely event that storage stability is unstable, increase the ammonia concentration of the image recording ink or add an activator. Stability can be improved.

In addition, toaacetin, which is a triacetic acid ester of glycerin, and trypsin can also be used.

Further, water-soluble polymer substances such as polyvinyl methyl ether, polyalkylene glycol, polyether polyformal, and functional polysiloxane can be used.

These heat-sensitive coagulants are added to the image recording ink, the image recording ink is adjusted to a gelling temperature of about 60°C to 100°C, and then heated with hot air or a heat roll from the surface or back of the transfer target. The recording ink is completely dried and fixed by being heated to the gelling temperature.

As for the amount of resin added as a fixing agent, if it is less than 3% by weight, it will not be possible to solve the problems of bleeding, drying and fixing properties, and if it is more than 20% by weight, the viscosity will increase and problems with ejection stability will occur. 3% to 20% by weight is preferred, and is usually produced as an emulsion, a latex solution, in which the resin is homogeneously dispersed in water.

The resins used include vinyl acetate, acrylic,
Homopolymer or copolymer resins such as styrene and olefin resins can be used.

As the colorant used in the present invention, any water-soluble dye used in conventional inks can be used as long as it does not change the color tone or form a precipitate when added with other ink components.

in particular, Direct black #19 (C.I.35255) Direct black #22 Direct black #154 Hood black #2 (C.I.27755) Acid Yellow #23 (C. I. 19140) Acid Red #87 (C.I.45380) Acid Red #106 (C.I.45100) Acid Red #254 Acid Blue #9 (C.I.42090) Direct Blue #86 (C.I.74180) etc.

Further, as the pigment, a fine particle dispersion of ordinary organic/inorganic pigment is used, and the pigment particle size is 0. Preferably, the particles are finely divided into particles of 1 μm or less.

The amount of dye/pigment to be added is preferably from 0.5 to 10% by weight because if it is less than 0.5% by weight, the color tone and density cannot be obtained, and if it exceeds 10% by weight, clogging tends to occur.

The solvent used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent.

As water, it is preferable to use distilled pure water or ion-exchanged water.

Examples of water-soluble organic solvents used in combination with water include alkyl alcohols with 1 to 4 carbon atoms, ketones, ethers, polyalkylene glycols, alkylene glycols, glycerin, and lower alkyl ethers of polyhydric alcohols. Used deep inside.

These water-soluble organic solvents can be used alone, or two or more kinds of solvents can be used in combination in order to impart appropriate physical properties to the ink.

As for the physical properties of the ink of the present invention, the viscosity at 20°C is 1.
If it is lower than 2 cp, problems will occur in high-speed printing such as bleeding and drying properties, and if it is larger than 10 cp, clogging will occur and problems will occur in ejection stability, so 1.2 to 10 cp is preferable.

The basic structure of the present invention is as described above, but in addition, conventionally known dispersants, surfactants, viscosity modifiers, surface tension modifiers, resistivity modifiers, pH modifiers, antifungal agents, etc. are required. Can be added as required.

Furthermore, when used in an inkjet system in which ink is ejected by the action of thermal energy, the thermal properties (eg, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) are adjusted using various additives.

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 %.

Direct Black #19 3% Micro Genore (manufactured by Nippon Paint) 67% (solid content concentration 20%) Ammonium nitrate 0.5% distilled pure water
19.5% glycerin
10% Each of the above components was thoroughly mixed and stirred in a container and filtered through a membrane filter with a bore size of 0.5 μm to prepare a recording ink.

Example 2 Carbon plaque (pigment) 5% Microgel (manufactured by Nippon Paint) 60% (solid content concentration 20%) Triacetin 5% Distilled pure water
20% triethanolamine
After mixing and stirring 10% of the above components, they were dispersed in a ball mill until the pigment particle size became 0.1 μm or less to prepare a recording ink.

Example 3 Acid Yellow #23 3% Micro Genore (manufactured by Nippon Paint) (solid content concentration 20%) 50% polyvinyl ether 7% distilled pure water
30% glycerin
10% Acid Red #87 Microgel (manufactured by Nippon Paint) (solid content concentration 20%) Polyvinyl ether distilled pure water glycerin 3% 50% 7% 30% 10% Acid Blue #9 Microgel (manufactured by Nippon Paint) 3% (solid content concentration 20%) 50% polyvinyl ether 7% distilled pure water
30% glycerin
10% Each of the above components was thoroughly mixed and stirred in a container, and the bore size was 0. The mixture was filtered through a 1 μm membrane filter to prepare a recording ink.

Comparative Example 1 Direct Black #19 3% diethylene glycol 10% distilled pure water
87% As a comparative example, each of the above components was thoroughly mixed and stirred in a container and filtered through a membrane filter with a bore size of 0.5 μm to prepare a recording ink.

Using the above ink, the recording method is: ■ Using a commercially available on-demand inkjet printer, drying with hot air at 80°C after printing ■ Ejection orifice diameter 50 μm, Viezo vibrator drive voltage 5
After printing with a prototype multi-head at 0V and a frequency of 5KHz, drying and fixing using a 100°C heat roll ■Charged ink mist recording method using ultrasonic atomization (ultrasonic vibrator drive frequency 1.5MHz, drive voltage 50V)
After printing, drying and fixing with a heat roll at 100'C, using A4 size paper according to method number 2 of the above three types, high speed recording and full color by superimposing three colors of yellow, magenta and cyan in Example 3. The evaluation method when recording was performed is shown below, and the evaluation results and ink physical property measurement results are shown in Table 1.

*1. Bleeding evaluation Ma Observation at 100x and 400x with a mirror and visual observation O: Dots are retained on the fibers without any bleeding along the fibers O: There is some bleeding along the fibers, but it is not visible by visual inspection. Not sure △: Slight bleeding is visible with the naked eye ×: Significant smearing and jagged edges *2, Evaluation of drying and fixing properties Rub the printed area with the edge of the paper after 3 seconds, 6 seconds, and 12 seconds after printing. @: No trailing after 3 seconds of printing O: No trailing after 6 seconds of printing Δ: Trailing after 6 seconds of printing ×: Trailing after 12 seconds of printing *3. Clogging evaluation Nozzle left without cap at room temperature for 1 month 0: Printable ×: Printable *4. Ink storage properties Put the ink into a sample bottle and store it in an open state at 40°C for 3 months. Observe the presence or absence of foreign matter, odor, aggregation, and sediment. 0: None ×: Yes *5. Measurement of reflection 0-D value using recording density Macbeth densitometer *6. Water Resistance Evaluation After 1 hour of printing, soak the printed matter in water for 5 minutes and observe ink flow O; None ×: Yes *7. Glossiness evaluation Measurement of 75 degree specular gloss using a digital gloss meter (manufactured by Murakami Color Technology Institute) ○: 80 or more Δ: 51 to 79 ×: 50 or less * Recording on 8.0 HP paper ○: Recordable ×: Record As is clear from Table 1, the recording inks of Examples 1 to 3 gave good results in common to each recording method.

Further, by overlapping each color of yellow, cyan, and magenta of the recording ink of Example 3, a clear full-color image could be reproduced.

On the other hand, it can be seen that in the case of the recording ink of the comparative example, bleeding occurs depending on the recording paper, and the drying and fixing properties are also poor.

[Effects of the Invention] As explained above, the image recording ink of the present invention eliminates bleeding on plain paper, which has been a problem in the past.
Excellent drying and fixing properties, and prevents clogging and ink storage.
It has the effect of enabling high-speed recording, high density, glossy and clear recording with excellent water resistance of printed matter.

Furthermore, by using three process color inks (black is also used if necessary), a high-resolution full-color image can be recorded.

Furthermore, the 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 with ordinary inkjet inks.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing how the ink of the present invention adheres to paper fibers. FIG. 2 is a schematic diagram showing how ink bleeds into paper fibers in a conventional example. 1...paper fibers 2...more than ink

Claims (1)

[Claims] (1) Image recording ink used in inkjet or ink mist recording methods is a fluid consisting of at least water, a colorant, a fixing agent, and a heat-sensitive coagulant, with resin particles as the fixing agent dispersed in a dispersion medium. An image recording ink characterized by the following.