Ink-jet ink and ink-jet printing method

Abstract

The invention belongs to the field of ink-jet printing, and relates to ink-jet ink and an ink-jet printing method. The inkjet ink includes a nano binder, an adhesion promoter, a colorant, water, a solvent, and an auxiliary agent. According to the technical scheme provided by the invention, an ink-jet printing product with good definition and resistance can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of inkjet printing and relates to an inkjet ink and an inkjet printing method. Background Art

[0002] Inkjet printing, especially inkjet printing on absorbent substrates such as paper, is easy to diffuse and penetrate on the substrate before drying because the main carrier of the ink is water, which is difficult to evaporate. This greatly reduces the clarity and color depth of the pattern. Heating after printing can accelerate the evaporation of water, but the increase in temperature reduces the viscosity of the ink, which further aggravates the diffusion and penetration of the ink on the substrate. It is usually necessary to coat the absorbent substrate to fix the printed ink.

[0003] In order to reduce ink bleeding and improve the clarity of inkjet printing, the industry has conducted research on ink formulations. Usually, increasing ink tension can reduce ink bleeding, but excessive tension will make it difficult to spray the ink and reduce the bonding force between the ink and the substrate. Konica's phase-changeable ink uses heated ink to spray on a cold substrate, and the ink is then fixed on the surface of the substrate. Because the nozzle and pipeline need to be heated at a constant temperature, the inkjet system is complex, and it is difficult to start and stop maintenance, making it difficult to promote. The textile dispersed direct-jet ink of the Suzhou University team uses thermosensitive gel to inhibit ink diffusion and improve printing clarity, but the material used has a low gel temperature, a narrow temperature range, and is a reversible gel. It only presents a gel state between 40 and 60°C. After the temperature continues to rise and the heating is stopped, it returns to a liquid state, loses its fixing effect, and is easily soluble in water; its disperse dye must react with polyester fibers at a high temperature of nearly 200°C before it can be combined with the substrate to achieve water resistance and abrasion resistance. Therefore, this ink and method are not suitable for other types of dyes and substrates. Summary of the invention

[0004] The present application provides an inkjet ink and an inkjet printing method, which can obtain inkjet printed products with good clarity and resistance.

[0005] In order to achieve the above technical purpose, the technical solution adopted by the present application is an inkjet ink, comprising the following substances in percentage by weight:

[0006]

[0007] The nano adhesive is an adhesive that can undergo a thermally irreversible gel reaction, including nano starch and / or nano coagulated polysaccharide.

[0008] Furthermore, the nano adhesive is dispersed and suspended in the ink in the form of nano particles, and the particle size of the nano particles is less than 0.5 microns.

[0009] Furthermore, the particle size of the nano adhesive is less than 0.1 micrometer.

[0010] Furthermore, the weight percentage of the nano adhesive in the ink is 2-10%.

[0011] Furthermore, the thermally irreversible gelling temperature of the nano adhesive is 50-130°C.

[0012] Furthermore, the thermal irreversible gel temperature of the nano adhesive is 80-120°C.

[0013] Another object of the present application is to provide an inkjet printing method, wherein after the aforementioned inkjet ink is printed on a substrate, the substrate is heated to promote gelation and drying of the inkjet ink, and the substrate heating temperature is 50 to 130°C.

[0014] Furthermore, the heating temperature of the substrate is 80-120°C.

[0015] Beneficial Effects

[0016] The inkjet ink of the present application adopts a binder with thermally irreversible gel properties, as well as components such as colorants, water, adhesion promoters, cosolvents, and additives. After inkjet printing onto a substrate, the viscosity of the ink increases significantly at 50-80°C, the fluidity decreases, and the diffusion to the edge and downward penetration are controlled, resulting in a printed image with higher clarity and saturation; when the printed product reaches above 80°C, the binder undergoes an irreversible gel reaction, and the gel is difficult to swell in water after drying, and the dye pigment in the ink adheres to the substrate, resulting in better water and abrasion resistance.

[0017] The technical solution of the present application is particularly suitable for inkjet printing of absorbent paper, and no additional treatment of the substrate surface is required. DETAILED DESCRIPTION

[0018] The inkjet ink of the present application adopts nano adhesive with thermal irreversible gel properties, as well as components such as colorants, water, adhesion promoters, solvents, and additives. The aforementioned adhesive with thermal irreversible gel properties includes nano starch and nano coagulated polysaccharides, which are dispersed and suspended in the ink in the form of nano particles, and the particle size is less than 0.5 microns, and the best is less than 0.1 microns. The mass content of the nano adhesive in the ink is 1-20%, and the best is 2-20%. The thermal irreversible gel temperature of the adhesive is 50-130°C, and the best is 80-120°C. After inkjet printing on the substrate, the substrate is heated at 80-120°C, and the viscosity of the ink at 50-80°C increases significantly, the fluidity decreases, and the diffusion to the edge and downward penetration are controlled, so as to obtain a printed image with higher clarity and saturation; when the printed product reaches above 80°C, the adhesive undergoes an irreversible gel reaction, and the gel is difficult to swell in water after drying. The dye in the ink adheres to the substrate, and better water and abrasion resistance is obtained. It is particularly suitable for inkjet printing on absorbent paper without the need for additional surface treatment of the substrate.

[0019] Specifically, an inkjet ink comprises the following substances in percentage by weight:

[0020]

[0021] The nano adhesive is an adhesive that can undergo thermal irreversible gel reaction, including nano starch and / or nano coagulated polysaccharide. The mass percentage of the nano adhesive is 1-20%, and the optimal mass percentage is 2-10%.

[0022] Nano starch can generally be purchased commercially, or you can choose to prepare it yourself.

[0023] Preparation example of nano starch particles:

[0024] Corn starch was added to water to prepare a starch solution with a mass fraction of 12%, and then added to a high-pressure homogenizer (Shanghai Shenlu Homogenizer Co., Ltd.) at a pressure of 30 MPa and a temperature of less than 50°C for 1 hour. The supernatant was removed by high-speed centrifugation, and then treated with a 250W ultrasonic cleaner (Kunshan Ultrasonic Instrument Co., Ltd.) for 0.5 hour. After standing for 12 hours, the bottom precipitate was discarded and filtered with a 100nm filter membrane to obtain a nano starch suspension (nano starch mass fraction of about 15%). The nano starch yield was about 60%, and the average particle size of the particles was 80nm.

[0025] The source of the nano-sized coagulant polysaccharide is commercial coagulant polysaccharide (the trade name is curdlan, and the manufacturer is Jiangsu Yiming Biological Co., Ltd.), and the nano-size method is similar to the preparation of the above-mentioned nano starch.

[0026] Due to the requirements of inkjet print heads on the viscosity range of ink (such as the ink viscosity of Kyocera inkjet print heads is 4-7mPa·s, and the recommended viscosity is 5-6mPa·s), an adhesion promoter can be used to adjust the viscosity of the inkjet ink to be suitable for ejection by the inkjet head. The adhesion promoter can be a water-soluble or water-dispersible resin, such as polyvinyl alcohol, carboxymethyl cellulose, and acrylic emulsion.

[0027] Among them, the role of colorant is to provide the color of ink and form a printed image after printing, including pigments and dyes, such as carbon black, titanium white, phthalocyanine blue, pigment yellow or acid fuchsin, etc. For inkjet ink, the pigment is usually pre-dispersed in water to become a nano-color paste, such as carbon black dispersion to prepare a black color paste.

[0028] The solvent is usually an alcohol solvent or an ether solvent containing hydrophilic groups such as hydroxyl groups, which assists in dissolving, improves the compatibility of ink formulations, and adjusts the drying speed of inks. Alcohol solvents include ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, glycerol, etc.; ether solvents include ethylene glycol butyl ether, propylene glycol ethyl ether, diethylene glycol ethyl ether acetate, etc.

[0029] Among them, additives include wetting agents, leveling agents, defoaming agents, antibacterial agents, etc., which are added according to ink performance and application requirements.

[0030] For the stability and inkjet performance of the ink, the nano adhesive is dispersed and suspended in the ink in the form of nanoparticles, the particle size of the nanoparticles is less than 0.5 microns, and the best particle size is less than 0.1 microns. If the particle size is large, it is easy to settle and easily clog the inkjet head.

[0031] The weight percentage of the nano adhesive in the ink is 1-20%, preferably 3-10%. If the content is insufficient, the effect of the present invention cannot be achieved, and if the content is too high, the ink viscosity is too high and printing is impossible.

[0032] The thermal irreversible gel temperature of the nano adhesive is 50-130° C., preferably 80-120° C. At low temperatures, the stability of the ink deteriorates, making it difficult to store and use. At too high a temperature, the energy consumption is too large, and the heating conditions are difficult to reach the ink reaction temperature, resulting in poor application effects and possible damage to the inkjet system and printing materials.

[0033] Another object of the present application is to provide an inkjet printing method, wherein after the aforementioned inkjet ink is printed on a substrate, the substrate is heated to promote gelation and drying of the inkjet ink, and the substrate heating temperature is 50 to 130° C. Further, the substrate heating temperature is 80 to 120° C.

[0034] The following is a black inkjet ink and its inkjet printing as an example of the present invention.

[0035] Example:

[0036] Prepare inkjet ink according to the following proportions:

[0037] Table 1 Inkjet ink ratio

[0038] Mass percentage % Nano adhesive Adhesion promoter Colorants Solvents Additives water Example 1 1 4 4 10 0.5 margin Example 2 3 3 4 10 0.5 margin Example 3 6 1.5 4 10 0.5 margin Example 4 10 0 4 10 0.5 margin Example 5 20 0 4 10 0.5 margin Example 6 7 1 4 10 0.5 margin Comparative Example 1 0 4.5 4 10 0.5 margin

[0039] In the table, the nano adhesive in Examples 1 to 5 is nano starch (nano starch is mixed with water during use to form a nano starch suspension, and the solid content in the nano starch suspension is 15%), the nano adhesive in Example 6 is 2% nano starch + 5% nano coagulated polysaccharide, and the nano adhesive in Comparative Example 2 is a reversible gel PEG-PCLA copolymer. The adhesion promoter is polyvinyl alcohol 1788, the colorant is a black color paste (such as: carbon black paste with a carbon black weight content of 20%), the solvent is propylene glycol, and the auxiliary agent is a leveling agent (Di Gao 450).

[0040] Table 2 Viscosity and nozzle ejection performance of the inks of the embodiments and comparative examples at different temperatures

[0041] Viscosity mPa·s Viscosity@25℃ Viscosity@55℃ Viscosity@85℃ Nozzle spray performance Example 1 5.2 12 50 normal Example 2 5.3 20 110 normal Example 3 5.5 70 450 normal Example 4 5.9 190 >1000 normal Example 5 8.5 620 >1000 Sprayable* Example 6 5.6 78 550 normal Comparative Example 1 5.1 3.4 2.3 normal Comparative Example 2 5.6 75 9.5 normal

[0042] * The ink of Example 5 can be sprayed at room temperature 25℃, but it is easy to break. The ink can be sprayed normally when the nozzle system is heated to 40℃. The subsequent application data is for reference only.

[0043] As the content of nano starch in the ink increases, the viscosity of the ink increases with temperature and it may lose fluidity at high temperatures. The viscosity of the ink without nano starch decreases as the temperature increases. The viscosity of the ink containing reversible gel increases when heated, but the viscosity decreases again as the temperature continues to rise. The viscosity of the ink in Example 5 is not within the optimal range of the test nozzle, and the ejection performance is reduced. Increasing the temperature of the nozzle system or using a high viscosity nozzle (such as the Ricoh G5 nozzle ink viscosity of 10 to 12 mPa·s) can also adapt to high-content inks.

[0044] Inkjet printing method:

[0045] The ink was printed on the paper using a Kyocera KJ4B inkjet print head, and then the printed product was heated with 95°C hot air for 3 minutes. After the ink dried, it was naturally cooled at room temperature.

[0046] The ink printed on the paper heats up rapidly under the hot air, and the viscosity increases rapidly, and then the adhesive undergoes an irreversible gel reaction and is fixed on the surface of the paper substrate, obtaining a high-definition, high-color concentration printed image with good water resistance.

[0047] The test method for ink printed images is:

[0048] Color density: The color density of the graphic color block is measured using an X-Rite 508 reflection densitometer.

[0049] Resolution, print 200 micron lines, and measure the actual width of the printed lines under a microscope after drying.

[0050] Wet friction resistance: The printed surfaces of two printed samples were stacked together and a wet friction resistance test was performed using an ink friction resistance tester (Jinan Languang Electromechanical Technology Co., Ltd.) to observe the discoloration of the printed products (level 5 is the best).

[0051] Table 3 Ink printing image performance test

[0052]

[0053]

[0054] It can be seen from the examples and comparative examples that due to the thermal irreversible gel reaction, the color density, resolution and wet friction resistance of the ink containing nano starch are greatly improved. The ink of comparative example 2 contains reversible gel, and the color density and resolution are also improved, but the wet friction resistance is insufficient.

[0055] The above ink and inkjet printing method are merely embodiments of the present invention, and the content of the present invention is not limited to the embodiments.

Claims

1. An inkjet ink comprising the following substances in percentage by weight: The nano adhesive is an adhesive that can undergo a thermally irreversible gel reaction, and includes one of nano starch and nano coagulated polysaccharide or two of them in any mass ratio.

2. An inkjet ink according to claim 1, characterized in that: The nano adhesive is dispersed and suspended in the ink in the form of nano particles, and the particle size of the nano particles is less than 0.5 microns.

3. An inkjet ink according to claim 2, characterized in that: The particle size of the nano adhesive is less than 0.1 micron.

4. An inkjet ink according to claim 1, characterized in that: The weight percentage of the nano adhesive in the ink is 2-10%.

5. An inkjet ink according to claim 1, characterized in that: The thermal irreversible gel temperature of the nano adhesive is 50-130°C.

6. An inkjet ink according to claim 5, characterized in that: The thermal irreversible gel temperature of the nano adhesive is 80-120°C.

7. An inkjet printing method, characterized in that: After the inkjet ink described in any one of claims 1 to 6 is printed on a substrate, the substrate is heated to promote gelation and drying of the inkjet ink, and the heating temperature of the substrate is 50 to 130°C.

8. An inkjet printing method according to claim 7, characterized in that: The heating temperature of the substrate is 80-120°C.

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