KR101752681B1 - Aqueous ceramic blue ink for ink-jet printing - Google Patents

Abstract

The present invention relates to an aqueous blue ink for use in inkjet printing, which comprises 30 to 40% by weight of a blue ceramic inorganic pigment having a spinel structure, 0.1 to 2.0 mg / m 2 of an anionic polyelectrolyte relative to the specific surface area of the ceramic inorganic pigment, 0.01 to 2.0 parts by weight of a surface tension modifier for adjusting the surface tension of the ink with respect to 100 parts by weight of the blue ceramic inorganic pigment, 1 part by weight of a polyethylene glycol and polyethylene oxide per 100 parts by weight of the blue ceramic inorganic pigment, Wherein the ink has a surface tension in the range of 20 to 45 mN · m ^-1 and a viscosity in the range of 2 to 20 mPa · s and the pH of the ink is in the range of 5 to pH ≪ 10. ≪ / RTI > The present invention relates to an aqueous blue ceramic ink for inkjet printing. According to the present invention, there are no problems such as restriction of volatile organic compounds (VOCs) and shortening of the lifetime of the inkjet head due to organic solvents, and the dispersion stability can be improved by using blue ceramic inorganic pigments used for raw materials of pottery No nozzle clogging occurs during inkjet printing, and it is eco-friendly based on water system.

Description

[0001] The present invention relates to a water-based blue ceramic ink for ink-jet printing,

The present invention relates to a water-based blue ceramic ink for ink-jet printing, and more particularly, to a water-based blue ceramic ink composition having a dispersion stability and free of nozzle clogging during ink-jet printing using blue ceramic inorganic pigment .

Ceramic materials, which are superior in heat resistance, abrasion resistance and corrosion resistance compared to metals and organic materials, are used in products such as living porcelain, sanitary ware, and tile in the field of traditional ceramics. In recent years, And color ceramic products are required to be developed. In the design of such ceramic products, although the ink-jet printing technique has many advantages, it has not been applied for a long time due to the demand for the development of ceramic pigments and inks suitable for ink-jet printing.

Ink-jet printing technology is a technology developed for the purpose of PC (personal computer) printing output printer. It is a printing technology that has revolutionized the existing dot-matrix printer with a high-impact impact contact printing method. By jetting ink-like fluids in a micro-liquid form through nozzles in a printer head, . Since a very small amount of fluid is injected on a desired point and space by a digital signal, it has the advantage of being able to freely direct-write various shapes designed in a virtual space of a computer. Since the fluid is deposited from the substrate in a non-contact manner, the shape can be freely printed on various substrates such as paper, fabric, metal, ceramics, and polymers, and printing can be performed from several tens of micrometers to a large area of several square meters or more .

Ink-jet printing technology does not require processes such as development, etching, and the like required in conventional patterning techniques such as photolithography, so that the characteristics of the substrate or material are not changed due to chemical effects, It is an environmentally friendly patterning technology. In addition, pattern on demand process that can pattern as much material as required is possible, and it is possible to fabricate fine pattern with extremely simple process, and the utilization efficiency of material is close to 100%, and expensive vacuum equipment It is very cost effective and competitive price. Due to the superiority of such ink-jet printing technology, application studies are actively carried out in the fields of displays, electronic circuits, MEMS (Micro Electro Mechanical Systems), and bio-chips, which are required not only for document printing technology but also pattern processing of several tens of microns have.

The inkjet printing system can realize all colors through 4 primary colors (CMYK; Cyan, Magenta, Yellow, blacK) and it can produce various product groups under mass production system by patterning through digital files. When compared, the process time is very short. In addition, the inkjet printing system discharges ink only at a desired position by a digital signal, and has a high ink efficiency, thereby reducing the production cost.

Currently commercialized nanoceramic inks use organic solvents that are relatively favorable for ensuring dispersion stability. However, interest in aqueous systems has been increasing due to problems such as the regulation of volatile organic compounds (VOCs) and the shortening of the lifetime of the ink jet head due to organic solvents.

Korean Patent Publication No. 10-2009-0053793

A problem to be solved by the present invention is that there are no problems such as restriction of volatile organic compounds (VOCs) and shortening of the life of the inkjet head due to organic solvents, and the use of blue ceramic inorganic pigments for dispersion stability, The present invention provides an environmentally friendly blue ceramic ink based on a water-free environment.

The present invention relates to an aqueous blue ink for use in inkjet printing, which comprises 30 to 40% by weight of a blue ceramic inorganic pigment having a spinel structure, 0.1 to 2.0 mg / m 2 of an anionic polyelectrolyte relative to the specific surface area of the ceramic inorganic pigment, 0.01 to 2.0 parts by weight of a surface tension modifier for adjusting the surface tension of the ink with respect to 100 parts by weight of the blue ceramic inorganic pigment, 1 part by weight of a polyethylene glycol and polyethylene oxide per 100 parts by weight of the blue ceramic inorganic pigment, Wherein the ink has a surface tension in the range of 20 to 45 mN · m ^-1 and a viscosity in the range of 2 to 20 mPa · s and the pH of the ink is in the range of 5 to pH ≪ 10. ≪ / RTI >

The anionic polyelectrolyte may include polyacrylic acid.

The polyacrylic acid may comprise polyacrylic acid with Na ⁺ salt.

It is preferable that the polyacrylic acid having Na ⁺ salt has a molecular weight of 1200 to 15000 g / mol.

The anionic polyelectrolyte may include polymethacrylic acid having Na ⁺ salt.

It is preferable that the ceramic inorganic pigment contains 0.01 to 0.2 mg / m 2 of polymethacrylic acid having the Na ⁺ salt as the specific surface area of the ceramic inorganic pigment.

The polymethacrylic acid having Na ⁺ salt preferably has a molecular weight of 8000-400 K g / mol.

The surface tension modifier may include at least one material selected from hydrophobic silica, polydimethyloxane, and polysiloxane.

The polyethylene glycol preferably has a molecular weight of 10K to 35K g / mol.

The polyethylene oxide preferably has a molecular weight of 80 to 300 K g / mol.

The blue ceramic inorganic pigments include _{Co 2 SiO 4, (Co,} Zn) 2 SiO 4, CoAl 2 O 4, Co 2 SnO 4, (Co, Zn) Al 2 O 4, Co (Al, Cr) 3 O 4, (Co, Mg) Al ₂ O ₄ and (Co, Zn) TiO ₃ .

The blue ceramic inorganic pigment preferably has an average particle diameter of 50 to 500 nm.

The water-based blue ceramic ink for ink-jet printing has an inverse number (Oh ^-1 = Z) of Onespoke number in the range of 3 < Z <

According to the present invention, blue ceramic inorganic pigments used for raw materials of pottery are used to provide dispersion stability, nozzle clogging does not occur during ink jet printing, and environmentally friendly, based on water.

According to the present invention, there are no problems such as restrictions on volatile organic compounds (VOCs) and shortening of the life of the inkjet head due to organic solvents.

Figure 1 is a graph showing the fluid confinement range for inkjet printing.
2 is an optical photograph and a scanning electron microscope (SEM) photograph of the CoAl ₂ O ₄ pigment used in Experimental Example.
3 is a view showing an X-ray diffraction (XRD) pattern of the CoAl ₂ O ₄ pigment used in Experimental Example.
4A to 4D are graphs showing steady state flow according to shear rate while increasing the amount of anionic polyelectrolyte added to a 35 wt% CoAl ₂ O ₄ slurry in a solid content of 35 wt% .
FIG. 5 is a graph showing the change in viscosity with respect to the addition amount of an anionic polyelectrolyte using the apparent viscosity according to Experimental Example.
6 is a graph showing a change in pH according to an anionic polyelectrolyte.
7 is a graph showing a decrease in surface tension according to an addition amount of a surface tension modifier according to an experimental example.
8 is a diagram showing the results of ejection test of an ink to which no surface tension modifier is added according to Experimental Example.
FIG. 9 is a view showing a result of ejection test of an ink whose surface tension is adjusted according to an experimental example.
FIGS. 10A to 10D are diagrams showing ejection test results of an ink containing 10K g / mol of polyethylene glycol (PEG) Mw according to Experimental Example.
11 is a view showing a discharge test result of an ink to which polyethylene glycol (PEG) Mw of 100 K g / mol was added according to Experimental Example.
12 is a graph showing a general limit range of the ink fluid.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

The present invention discloses an environmentally friendly ceramic ink based on a water-based ceramic ink having nano-sized ceramic inorganic pigments such as CoAl ₂ O ₄ , which has dispersion stability and does not cause nozzle clogging during inkjet printing.

Inkjet technology requires three technologies, inkjet printhead, ink and system / firmware, and integrated technology that can synthesize these technologies. In particular, ink technology, which is a core technology, requires a technique to control the rheological behavior of the final compounded ink as a complex interlocking mechanism of the fluid system. This is because the size and distribution of ink droplets are often a function of ink rheology at the time of ink ejection. For example, in the case of high viscosity ink, the pressure at the end of a nozzle becomes large and forms a fine pattern . Rheology may be used as an indicator of the stability of the ink. Therefore, it is necessary to carry out research that enables wide application and application of ink jet technology.

Ceramic tile inkjet printing technology can realize all colors through digital four primary colors (CMYK; Cyan, Magenta, Yellow, blacK) and it is possible to produce various product groups under mass production system by patterning through digital files. Compared with other processes, the process time is very short. Inkjet printing system for ceramic tiles can print digital images quickly and precisely, and then sintered at a high temperature of 1000 ° C or higher to avoid erasure, discoloration, It has a semi-permanent lifetime.

The pigment for inkjet printing used for the production of ceramic products is a very important factor in the thermal stability and chemical resistance at high temperature according to the firing process. In consideration of this, an inorganic pigment having a spinel structure which exhibits stable color development at a high temperature of 1000 占 폚 or higher is used.

Inorganic pigments having a spinel structure not only realize a wide range of colors but also have thermal and chemical stability, and the formula is AB ₂ O ₄ . The inorganic pigments of the spinel structure have the advantage of obtaining various colors by substituting A ²⁺ ions at the tetrahedral positions and B ³⁺ ions at the octahedral positions and substituting the coloring elements at the A and B positions. In the proportion of the inorganic pigment to color blue is _{Co 2 SiO 4 (Olivine),} (Co, Zn) 2 SiO 4 (Willemite), CoAl 2 O 4 (Spinel), Co 2 SnO 4, (Co, Zn) Al 2 O _4, there are _{Co (Al, Cr) 3 O} 4, (Co, Mg) , such as _{Al 2 O 4, (Co,} Zn) TiO 3, and mixtures thereof.

In general, the viscosity and surface tension of ink are known to be the main factors determining droplet formation behavior such as satellite generation. Particularly, viscosity tends to adversely affect droplet ejection in terms of inducing flow resistance, and acts as a high load on the driving portion of the ink jet head. Therefore, it is necessary to maintain the viscosity in an appropriate range. Various studies have been carried out to understand the phenomenon of droplet discharge by this viscosity.

In order to prevent nozzle clogging due to sedimentation of particles in the ink during the inkjet printing process, the viscosity is preferably maintained at 2 to 20 mPa · s.

The surface tension along with the viscosity of the ink is one of the main properties determining the discharge characteristics of the droplet. The capillarity force due to the surface tension acts on the nozzle to eject the droplet, and then the ink is replenished in the pressure chamber. As the surface tension of the ink increases, the tendency to lower the surface energy of the ink in contact with the air reduces the separation time and separation distance due to the tendency to lower the surface energy. Proper values should be maintained to maintain stable droplet ejection during printing. Surface tension can be regarded as one of the major differences between an ink system and an organic solvent system. Due to the high surface tension of water, surface tension control through a surface tension modifier is essential in an aqueous system. It is preferable that the surface tension is in a suitable range of 20 to 45 mNm &lt; ^-1 &gt; for stable droplet ejection.

In recent years, there is a need to understand the droplet discharge characteristics according to physical properties of fluids by necessity of patterning technology of various materials using inkjet printing technology in industry.

Fluids are largely classified as Newtonian fluids and Non-Newtonian fluids. Newtonian fluids are fluids whose viscosity is always constant regardless of shear rate at a given temperature and pressure. Typical Newtonian fluids are water and oil, and pure fluids except dispersants are mostly Newtonian fluids. Non-Newtonian fluids vary in shear stresses with varying shear rates. This viscosity is called the apparent viscosity. Shear thinning fluids show a decrease in apparent viscosity as the shear rate increases and are sometimes referred to as pseudoplastic fluids because they behave like Bingham fluids when shear rates increase. Shear thickening fluids exhibit an apparent viscosity increase with increasing shear rate.

It is generally known that fluid viscosity and surface tension are the main factors in determining satellite generation. Particularly, when the viscosity is increased, a high load is applied to the driving part of the ink jet head and the tail is made longer at the moment of falling from the nozzle surface, thereby increasing the possibility of generating the setter. The high viscosity of the fluid can be a cause of meniscus instability during high speed printing. Therefore, it is necessary to maintain the viscosity within a proper range.

Recently, in many applications using inkjet printing technology, physical phenomena related to droplet generation and ejection have been complicated and diversified by using inks having various compositions. When the polymer is added, the ink will exhibit the behavior of non-Newtonian fluids. In addition, depending on the additive, the fluidity of the ink is affected, and other behaviors are exhibited when droplets are generated.

The viscosity is adjusted through the thickener to adjust the viscosity. The increase of the viscosity affects the stabilization of the dispersed particles, and has effects such as prevention of settling of the pigment during storage, improvement of redispersibility, prevention of flow, and necessary adjustment for application to inkjet printing.

The surface tension is the force that minimizes the surface area that acts only on the downward perpendicular direction from the liquid surface due to unbalanced pulling force on the molecules on the liquid surface. In the case of a water system having a relatively high surface tension, The surface tension is controlled by adding a material having a lower surface tension than water but soluble in water including water.

The surface tension in ejecting the ink is one of important physical properties. The capillary force due to the surface tension acts on the nozzle to repel the ink in the pressure chamber after the droplet is ejected. As the surface tension increases, the ink exposed to the air at the moment when the droplet is separated from the nozzle reduces the surface area, Due to the tendency to lower the separation time and separation distance by making the shape of droplets in a short time, the tail of the droplet is shortened. This tendency is advantageous for the stabilization of the meniscus, but it is important to maintain the same value as the viscosity because the volume and velocity of the droplet decrease.

(Yang) indicates that the high surface tension due to strong capillary force causes the liquid droplet to have a spherical shape sooner, and the viscosity of the high viscosity liquid has relatively slow separation time and droplet velocity, Respectively.

Reynolds number is the fluid mechanist of the United Kingdom. It was discovered by O. Reynolds. The Reynolds number depends on the diameter of the liquid, the viscosity of the liquid, the density, and the average flow rate. The critical velocity at which the flow changes from one form to another as the fluid flows is defined by the following equation It is called the Reynolds number.

[Equation 1]

The surface tension of the fluid is defined as γ, the density as ρ, the flow velocity as v, and the diameter of the nozzle as α. It is important to study the fluid flow. When this value is small, a regular laminar flow is formed, but when it is more than a certain value, it becomes turbulent. In general, the value of R, which is the boundary between turbulence and laminar flow, is called the critical Reynolds number. Below 2,100 is a laminar section, more than 4,000 is a turbulent section, and between 2,100 and 4,000 is a transition region, which is laminar or turbulent depending on the state of the inlet and the distance from the inlet.

The Weber number is very useful for analyzing the flow of fluids having an interface between two fluids, and is defined by the following equation (2).

&Quot; (2) &quot;

The Weber number represents an indicator of the inertial force on the surface tension acting on each fluid element. It can be very useful for analyzing the flow of thin film liquids and the formation of droplets and bubbles.

The Ohnesorge number solves these two properties by solving the Navier-Stokes equation of the fluid to establish a fluid dynamics model for the ink jet process. The fluid properties As a non-dimensional number. The Ohnesorge number (Z) is defined as the ratio between the Reynolds number and the square root of the Weber number, as shown in Equation 3 below.

&Quot; (3) &quot;

The viscosity of the fluid is defined as η, the density as ρ, the flow velocity as ν, the diameter of the nozzle as α, and the surface tension as γ. The Ohnesorge number is compared by taking the reciprocal (Z) thereof. Generally, the commercial DOD printing ink exhibits a value between 1 and 10.

The printability of the fluid can be predicted through the Ohnesorge number as shown in FIG. When the Z value is less than 1, the viscosity becomes the dominant factor, requiring a large pressure for discharging the droplet, decreasing the velocity of the droplet and increasing the tail of the droplet. In this region, And the influence of the surface tension relatively decreases. This causes the formation of satellite droplets that degrade resolution after ejection. On the other hand, if the value is greater than 10, the surface tension is increased, and the tail of the droplet is shortened and the droplet is formed within a short time.

Aqueous blue ink for inkjet printing according to a preferred embodiment of the present invention is an aqueous blue ink for use in inkjet printing comprising 30 to 40% by weight of a blue ceramic inorganic pigment having a spinel structure and a specific surface area of the ceramic inorganic pigment 0.01 to 2.0 parts by weight of a surface tension modifier for adjusting the surface tension of the ink to 100 parts by weight of the blue ceramic inorganic pigment and 0.1 to 2.0 parts by weight of the blue ceramic inorganic pigment 0.01 to 6.0 parts by weight of at least one material selected from the group consisting of polyethylene glycol and polyethylene oxide per 100 parts by weight of the ink, wherein the surface tension of the ink is in the range of 20 to 45 mNm ^-1 and the viscosity of the ink is in the range of 2 to 20 mPa · S, and the pH of the ink is in the range of 5 <pH <10.

The aqueous blue ceramic ink for inkjet printing according to a preferred embodiment of the present invention is an aqueous ink based on water (H ₂ O), wherein the blue ceramic inorganic pigment, the anionic polyelectrolyte, the surface tension modifier, the polyethylene glycol And polyethylene oxide are composed of water (H ₂ O) as a solvent.

The anionic polyelectrolyte may include polyacrylic acid.

The polyacrylic acid may comprise polyacrylic acid with Na ⁺ salt.

It is preferable that the polyacrylic acid having Na ⁺ salt has a molecular weight of 1200 to 15000 g / mol.

The anionic polyelectrolyte may include polymethacrylic acid having Na ⁺ salt.

It is preferable that the ceramic inorganic pigment contains 0.01 to 0.2 mg / m 2 of polymethacrylic acid having the Na ⁺ salt as the specific surface area of the ceramic inorganic pigment.

The polymethacrylic acid having Na ⁺ salt preferably has a molecular weight of 8000-400 K g / mol.

The surface tension modifier may include at least one material selected from hydrophobic silica, polydimethyloxane, and polysiloxane.

The polyethylene glycol preferably has a molecular weight of 10K to 35K g / mol.

The polyethylene oxide preferably has a molecular weight of 80 to 300 K g / mol.

The blue ceramic inorganic pigments include _{Co 2 SiO 4, (Co,} Zn) 2 SiO 4, CoAl 2 O 4, Co 2 SnO 4, (Co, Zn) Al 2 O 4, Co (Al, Cr) 3 O 4, (Co, Mg) Al ₂ O ₄ and (Co, Zn) TiO ₃ .

The blue ceramic inorganic pigment preferably has an average particle diameter of 50 to 500 nm.

The water-based blue ceramic ink for ink-jet printing has an inverse number (Oh ^-1 = Z) of Onespoke number in the range of 3 < Z <

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited by the following experimental examples.

A blue ceramic ink based on a water - based inkless printing inkjet printing method was prepared using nano - sized CoAl ₂ O ₄ inorganic pigments.

For this purpose, the optimum amount of anionic polyelectrolyte added was defined through the dispersion stability test of an ink using anionic polyelectrolyte. The surface tension of the dispersed ink was controlled by using a polysiloxane surfactant as a surface tension modifier. Finally, the viscosity was controlled by using polyethylene glycol (PEG) and polyethylene oxide (PEO). The droplet formation behavior of the ink was confirmed by controlling the physical properties of the ink and measuring a drop watcher. The relationship between the physical properties of the ink and the droplet formation behavior was investigated by calculating the Reynolds number, Weber number, and Ohnesorge number of all the inks used in the experiment.

The blue ceramic inorganic pigment CoAl ₂ O ₄ used in the experimental examples of the present invention was obtained by using commercialized products of Korean-Japanese ceramics. The crystal structure of blue ceramic inorganic pigments was analyzed using an X-ray diffraction analyzer (XRD, Rigaku, D / MAX2500, Japan) and the particle size and shape were observed using FE-SEM (Jeol, JSM-6390, Japan) Respectively. BET surface area values were also obtained using a specific surface area meter (BET, TRISTA II 3020, Micromeritics, USA). The blue ceramic inorganic pigment has a spinel crystal structure, and has an average particle diameter of 200 nm, a density of 4.4430 g / cm 3, and a specific surface area value of 5.5483 m 2 / g. The microstructure and properties of the pigment are shown in FIG. 2, and the X-ray diffraction pattern is shown in FIG.

In order to disperse blue ceramic inorganic pigments, anionic polyelectrolytes were used to determine the dispersion characteristics. The anionic polyelectrolyte is polyacrylic acid (Poly (acrylic acid) (Na -PAA) ( molecular weight 1200, 8100, 15000 g / mol ), and polymethylmethacrylate having a Na ⁺ salt (salt) having a Na ⁺ salt (salt) The chemical structure of the poly (methacrylic acid) (Na-PMAA) (molecular weight 9500 g / mol) (Aldrich, Korea) (1) and (2).

[Structural Formula 1] Polyacrylic acid (Na-PAA) having Na ⁺ salt [

[Structural Formula 2] Polymethacrylic acid (Na-PMAA) having Na ⁺ salt [

Surface tension modifiers include hydrophobic silica-based additives (BYK-12, BYK), polydimethyloxane-based additives (BYK-19, BYK), and polysiloxane-based additives -28, BYK) was used to observe the surface tension change.

Thickeners such as polyethylene glycol (PEG) Mw 10K g / mol, 35K g / mol, polyethylene oxide (PEO) Mw 100K g / mol, 200K g / mol and 400K g / mol (Aldrich, Korea) Were used to define the viscosity control range for each additive.

The anionic polymer electrolytes Na-PAA (molecular weight 1200, 8100, 15000 g / mol) and Na-PMAA (molecular weight 9500 g / mol), which are the most suitable anionic polyelectrolytes for the aqueous dispersion of ceramic inorganic pigments, A total of 7 samples were used.

Each anionic polyelectrolyte was added to the third distilled water in a range of 0 to 2.0 mg / m ² (0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0 mg / m ² ) relative to the specific surface area of the ceramic inorganic pigment , And the mixture was stirred for 2 hours to form a chemical equilibrium state between the water and the anionic polyelectrolyte. Then, a ceramic inorganic pigment CoAl ₂ O ₄ (HANIL, P-521, Korea) was added. The slurry having a solid content of 35 wt% was milled using zirconia balls for 72 hours to allow the particles to sufficiently mix and wet to prepare an ink. The prepared ink was rolled after removing the zirconia balls to prevent aggregation, and the measurement was performed after 24 hours to achieve equilibrium. The rheology and the pH test of the ink thus prepared were used to define the composition of the anionic polyelectrolyte and the amount of addition which exhibited the most effective dispersion. The measurement of rheology was carried out using a steady-state shear and an oscillation shear measurement using a rotary rheometer (HAAKE MARS III, Thermo Fisher Scientific Inc., Germany) Rheological properties and viscosity were confirmed. The geometry of all rheological measurements can be used to obtain accurate results in the low viscosity and low shear rates areas and the CC10DIN of Cup & Bob (Coaxial Cylinders) type which can prevent evaporation. Ti under the same conditions at 25 캜. The steady-state shear was performed in a controlled rate (CR) mode in shear rates ranging from 10 ^-4 to 10 ² s ^{-1 in} the rotation step.

The pH was measured with a pH meter (HI-4521, HANNA Inc., USA) and the sedimentation test was carried out using a measuring cylinder to observe the sedimentation volume visually for two months.

Specific properties are required for use as a ceramic ink for inkjet printing. The two most important physical properties are surface tension and viscosity. These two properties have a great influence on the formation of droplets. The control of the surface tension is the most important part in the water system in particular.

Hydrophobic silica, polydimethyloxane and polysiloxane type surface tension modifier were used to control the surface tension of ink dispersed using anionic polyelectrolyte. The ink was prepared by adding 0.1, 0.5 and 1.0 wt% to the solid content of the ink, and then the surface tension was confirmed.

In order to confirm the droplet formation behavior according to the control of the surface tension of the ink, a basic ink containing Na-PAA (Mw of 15000 g / mol) 0.8 mg / m ² and 0.1 wt% of polysiloxane relative to the solids content of the ink was prepared and then polyethylene oxide ) (Weight average molecular weight: 100K, 200K, 400K g / mol) was added to each ink in an amount of 2 wt% based on the solid content of the ink, and the droplet formation behavior before and after the addition of the polysiloxane of 0.1% was compared.

In order to confirm the droplet formation behavior according to the viscosity change of the ink, a basic ink containing Na-PAA (Mw of 15000 g / mol) 0.8 mg / m ² and 0.1 wt% of polysiloxane based on the solids content of the ink was prepared and then polyethylene glycol (PEG) 10, and 35 Kg / mol were added to the solid content of the ink in an amount of 3, 5 wt%, and polyethylene oxide (PEO) molecular weight of 100 K and 400 Kg / mol, respectively, relative to the solid content of the ink.

A drop watcher (STI Co., Korea) was used to evaluate the droplet formation behavior during inkjet printing according to the physical properties of the ink. The inkjet system used in this experiment consists of a DOD piezo head, a pressure pulse generating system, a CCD (charge coupled device) camera and a system computer.

As a printing condition, the temperature was increased to 25 ° C. and the driving voltage was set to 70 to 75 V for all the samples. The rising time and the falling time were 1.5 μs, (dwell time) was measured in the range of 13 ~ 15 ㎲. Rolling was continued to maintain dispersion of all dispersed inks. The droplet images were measured at intervals of 20 μs, and the ejection pattern and separation distance of the droplets flying from the nozzle were confirmed.

Anionic polyelectrolytes were used to disperse CoAl ₂ O ₄ ceramic inorganic pigments. The rheological behavior of the CoAl ₂ O ₄ slurry was investigated with increasing the amount of anionic polyelectrolyte. The anionic polyelectrolyte adsorbed on the surface of the particles has a great influence on the rheological behavior and dispersion stability.

The steady state flow according to the shear rate was analyzed while increasing the amount of the anionic polyelectrolyte added to the solid content 35 wt% CoAl ₂ O ₄ slurry and is shown in FIGS. 4A to 4D. FIG. 4A shows the case where Na-PAA Mw of 1200 g / mol is added to the anionic polymer electrolyte, FIG. 4B shows the case where Na-PAA Mw of 8100 g / mol is added to the anionic polymer electrolyte, FIG. 4D shows a case where Na-PMAA Mw of 9500 g / mol is added as an anionic polymer electrolyte. 4A to 4D, 'PAA1200-0' represents the case where 0 mg / m ² of Na-PAA Mw of 1200 g / mol is added to the specific surface area of the pigment, 'PAA 1200-0.1' represents Na-PAA Mw of 1200 g / and if it is the mol was added to 0.1 mg / m ² over a specific surface area of the pigment, "PAA1200-0.2 'is Na-PAA Mw 1200 g / mol case where the addition of 0.2 mg / m ² over a specific surface area of the pigment," PAA1200-0.4 'was obtained by adding 0.4 mg / m ² of Na-PAA Mw of 1200 g / mol to the specific surface area of the pigment, and' PAA1200-0.6 'was obtained by adding Na-PAA Mw of 1200 g / mol to the specific surface area and when the addition of ^{0.6 mg / m 2, 'PAA1200-0.8} ' is Na-PAA Mw 1200 g / mol, and the case of adding 0.8 mg / m ² over a specific surface area of the pigment, 'PAA1200-1.0' is Na- PAA Mw of 1200 g / mol was added to 1.0 mg / m ² of the specific surface area of the pigment, and 'PAA1200-1.5' was added to the pigment of 1.5 mg / m ² of the specific surface area of the PAA Mw of 1200 g / and if it is, 'PAA1200-2.0' is Na-PAA Mw 1200 g / mol by the addition of a specific surface area compared to 2.0 mg / m ² of the pigment Right, and this anionic polyelectrolyte according to the example, such as the addition amount is applied, similar to the graph shown in Figure 4b to Figure 4d.

Low shear rates (<100s ^{- 1)} samples of the difference in viscosity between means a difference of dispersibility. The non-Newtonian flow, which does not show a constant viscosity value according to the shear rate, was observed in all samples and the shear thinning behavior was observed. The dispersibility can be confirmed by the degree of shear thinning behavior. Na-PAA is showed a similar all without the tendency of the difference in molecular weight and addition amount, Na-PMAA did dispersibility than Na-PAA good, 0.6 mg / m ² the anionic polyelectrolyte added amount in the anionic polymer the following And showed similar viscosity to the sample without the electrolyte added.

Using a graph of steady-state flow, the viscosity at shear rate 1 / s was defined as the apparent viscosity. A graph of the viscosity change with respect to the addition amount of the anionic polyelectrolyte using the apparent viscosity is shown in FIG. In FIG. 5, 'PAA1200' is an anionic polyelectrolyte with Na-PAA Mw of 1200 g / mol added, 'PAA8100' is an anionic polyelectrolyte with Na-PAA Mw of 8100 g / PAA15000 'is an anionic polyelectrolyte with Na-PAA Mw of 15000 g / mol and' PMAA9500 'is an anionic polyelectrolyte with Na-PMAA Mw of 9500 g / mol. Referring to FIG. 5, in the dispersed ink through the anionic polyelectrolyte, the lowest viscosity was observed at the addition amount of Na-PAA (Mw 15000 g / mol) of 0.8 mg / m ² . The conditions of the addition of the lowest viscosity were determined as the conditions that exhibited the most effective dispersion characteristics.

In order to apply ceramic ink to inkjet printing, it is necessary to adjust the pH. The ink is preferably in the range of 5 < pH < 10, because it may affect the life due to corrosion of the head during inkjet printing.

The Na-PMAA dispersed ink in the dispersion using anionic polyelectrolytes exceeded the allowable maximum value of 10 from 0.2 mg / m ² , and the Na-PAA dispersed ink has the pH in the range of 9.2 to 10, It was confirmed that the values correspond to the pH range at all conditions after the addition of the electrolyte. This is shown in Fig. In FIG. 6, 'PAA1200' is an anionic polyelectrolyte added with Na-PAA Mw of 1200 g / mol, 'PAA8100' is an anionic polyelectrolyte containing Na-PAA Mw of 8100 g / PAA15000 'is an anionic polyelectrolyte with Na-PAA Mw of 15000 g / mol and' PMAA9500 'is an anionic polyelectrolyte with Na-PMAA Mw of 9500 g / mol.

Due to the nature of the water-based system, the capillary force acts on the nozzle during ink ejection due to its high surface tension. As soon as the droplet is separated from the nozzle, the surface area is shortened within a short period of time. However, it is important to maintain 20 to 45 mN · m ^-1 as an appropriate range of surface tension generally required for inkjet printing.

The surface tension test was carried out by adding a surface tension modifier after dispersing the pigment with 0.8 mg / m ² of Na-PAA (Mw = 15000 g / mlo) selected through dispersion experiment using an anionic polyelectrolyte . Surface tension modifiers serve to lower surface energy and remove bubbles. Hydrophobic silica, polydimethyloxane and polysiloxane additive were added to the ink in an amount of 0.1, 0.5 and 1.0 wt% based on the solid content of the ink.

As shown in FIG. 7, surface tension was decreased according to the addition amount of the surface tension modifier. Hydrophobic silica showed the lowest surface tension reduction with a surface tension of 32mN / m at 1wt% addition, and 23mN / m at 1wt% addition of polydimethyloxane. But there was a compatibility problem with the ink in which the layer was separated. The polysiloxane was 25 mN / m when added at 1 wt%, and its surface tension lowering ability was lower than that of polydimethyloxane. However, the surface tension modifier was selected as an optimal surface tension modifier because there is no problem in compatibility with the ink. In the case of polysiloxane, the surface tension value corresponding to the appropriate range was obtained by adding 0.1 wt%.

During inkjet printing, droplet formation behavior is associated with systems that respond to pressure applied to the fluid. The transfer and recoil of the pressure pulse delivered during inkjet printing varies greatly depending on the physical and rheological characteristics of the fluid and the characteristics of the printing head, which has a large influence on the droplet formation mechanism. After fixing the driving voltage condition at 70 ~ 75V during inkjet printing, we investigated the droplet formation behavior according to the physical properties of the fluid and observed the relation with printability.

In order to compare the droplet formation behavior with the addition of surface tension modifier, the addition of 0.8 mg / m ² of Na-PAA (Mw = 15,000 g / mol) and the addition of polysiloxane . In both cases, the viscosity of the ink itself was too low to control by adding 2% of polyethylene oxide (PEO) (Mw = 100K, 200K, 400K g / mol). The composition and physical properties of the ink thus prepared are shown in Table 1.

[Table 1]

As a result of the ejection test of the ink without adding the surface tension modifier, a meniscus of a convex shape was formed at 0 to 20 mu s as shown in Fig. 8, and a pressure oscillation And the droplet was separated at 80 μs, but the small setter was separated from the droplet.

The length of the tail was short due to the high surface tension, and the inverse Z of Onegi number was 12.72, 10.18, 4.24, respectively, which was slightly higher than 1 <Z <10 of the general DOD printing ink. Also, it was confirmed that the distance between the setterite approaches to that of polyethylene oxide (PEO) as the viscosity increases to 4.35, 5.43, and 12.9.

The surface tension was adjusted from 62 mN / m to 32.5 mN / m by adding 0.1% polysiloxane. The composition and physical properties of the ink thus prepared are shown in Table 2 below.

[Table 2]

As shown in Fig. 9, a meniscus was formed at 0 to 20 占 결과, and the droplet was stretched to 40 to 60 占 퐏 and separated into a single droplet at 80 占 퐏. Z values were 8.6, 6.75 and 3.06, respectively, which corresponded to the general Z value range, and exhibited the most stable type of discharge characteristics at polyethylene oxide (PEO) Mw 400K.

The basic ink was prepared by adding 0.8 wt / m ^{2 of} Na-PAA (Mw 15000 g / mol) and 0.1 wt% of polysiloxane to the solid content of the ink to confirm the droplet formation behavior according to the viscosity change of the ink, and then polyethylene glycol (PEG ) 3, 5 wt%, and polyethylene oxide (PEO) molecular weight of 100K and 400K g / mol, respectively, were added to the solids of the inks by 2, 4, and 6 wt%, respectively, relative to the solids content of the inks. The composition and physical properties of the ink added with polyethylene oxide (PEO) are shown in Table 3, and the composition and physical properties of the ink containing polyethylene glycol (PEG) are shown in Tables 4 and 5.

[Table 3]

[Table 4]

[Table 5]

Polyethylene glycol (PEG) The viscosity of the inks prepared by using 10K of molecular weight was 2.85 and 3.13 mPa · s at the addition amount of polyethylene glycol (PEG) 10K, respectively. The polyethylene glycol (PEG) 35K was 3.82 and 5.31 mPa The viscosity of s was expressed. The viscosity range of 2.8 and 5.2 mPa · s could be formed in all of the polyethylene glycol (PEG) added inks.

FIGS. 10A to 10D are diagrams showing results of ejection tests of an ink containing 10K g / mol of polyethylene glycol (PEG) Mw. 10A shows a case where 10 wt% of polyethylene glycol (PEG) Mw is added in an amount of 3 wt% based on the solid content of the ink, and FIG. 10B shows a case where 10 wt% of polyethylene glycol (PEG) Fig. 10C shows a case where 35 wt% of polyethylene glycol (PEG) Mw is added in an amount of 3 wt% based on the solid content of the ink, and Fig. 10D shows a case where 35 wt% of polyethylene glycol (PEG) Mw is added in an amount of 5 wt% based on the solid content of the ink.

As a result of the discharge test, a single droplet was formed at 3 and 5 wt% as shown in Figs. 10A to 10D. At 5wt%, the setter was formed, and after 140μs, the liquid droplets were rejoined to form a single droplet. However, in the case of such a droplet, it may be an element that hinders the resolution due to air inflow into the droplet during the formation process. In the case of polyethylene glycol (PEG) 35K, the addition of 3wt% formed the setterite and the formation of 5wt% single droplet. In the case of polyethylene glycol (PEG) 10K, Z value was 14.73, 13.52, which was slightly higher than the general range.

The polyethylene oxide (PEO) molecular weight of 100K exhibited a viscosity of 4.63, 7.27 and 11.41 mPa · s, respectively, depending on the amount added. The polyethylene oxide (PEO) molecular weight of 400K exhibited a large viscosity change of 13.57 ~ 329.14 mPa · s . 11 is a view showing a discharge test result of an ink containing 100 kg / mol of polyethylene glycol (PEG) Mw. 11 (a) shows a case in which 2 wt% of polyethylene glycol (PEG) Mw is added in an amount of 2 wt% based on the solid content of the ink, and FIG. 11 (b) shows a case in which 100 kg / mol of polyethylene glycol (PEG) . As a result of the discharge test, as shown in FIG. 11, the polyethylene oxide (PEO) molecular weight of 400 K did not cause ink ejection due to an excessively high viscosity, and the polyethylene oxide (PEO) , Formation of a single droplet was confirmed.

The inverse number (Z) of One Soil water was not ejected in the case of polyethylene oxide (PEO) 400K, and the number and density of droplets were calculated by arbitrarily applying the average value of the ink droplet diameter and velocity. However, the viscosity was 3.14, 0.7 and 0.13 The droplet could not be formed while exhibiting a too low Z value. However, the Z values of polyethylene oxide (PEO) 100K were 9.02, 5.65, and 3.68, respectively, and the values agreed with the general Z value range were observed, but the droplet was formed only at 2 wt%. The viscosity control through polyethylene oxide (PEO) and polyethylene glycol (PEG) was successful, but the Z value was too low due to the high viscosity range, making it difficult to form droplets.

As a result of checking the droplet formation behavior by controlling the viscosity through polyethylene oxide (PEO) and polyethylene glycol (PEG), the polyethylene oxide (PEO) has a high molecular weight and an excessively high viscosity when it is added in a large amount, It was confirmed that glycol (PEG) can be adjusted to a suitable viscosity range.

Preferably, the range of the number of printable fluids in the DOD inkjet printing is 1 < Z < 10. It is necessary to enter the numerical value corresponding to the green area of FIG. 12 to perform printing. When Z value is low, printing is difficult due to low energy, and when Z value is high, splashing occurs.

12 is a graph obtained by substituting the inverse number (Z) of the number of Oneso of a general DOD according to the droplet ejection form of the ink prepared in this Experimental Example. As a result, it was found that the printable range of the ink prepared in this experiment was 3 < Z < 14. It is possible to evaluate the printable range of the fluid by simulation of the fluid through the onyse water, but it can not be used as an index of the absolute ink printable range as a theoretical range, and the range may vary depending on the characteristics of the inkjet printing head or fluid .

Thus, it is believed that a settler is formed, although a general Z range is met, and a single droplet may be formed, even though it is out of range.

As described above, in the experimental example of the present invention, an aqueous CoAl ₂ O ₄ nanoceramic ink for environmentally friendly inkjet printing was prepared by using an aqueous system. As a result, the experiment was divided into ink jet printing, dispersion property, physical property control, and droplet formation behavior.

In order to define the optimal condition of addition of anionic polyelectrolyte in the water system, the rheological properties and pH, sedimentation rate of the ink prepared by using the anionic polyelectrolyte, Were measured.

The rheological properties were evaluated by the difference of shear thinning behavior in the steady state flow and the dispersed ink through the anionic polymer electrolyte was evaluated by shear thinning (Mw 15,000 g / mol) was added at a dose of 0.8 mg / m ² as measured by a shear rate 1 / s viscosity regression equation using regression equation And showed an optimal viscosity lowering effect.

pH range that does not affect the life of the ink jet printing head in the measurement of the ink pH 5 <pH <showed a pH value in line with most of the ink 10, from Na-PMAA 0.2mg / m ² outside the pH range of ink It is confirmed that the effect is not suitable due to the influence on the life of the head.

Water-based inks are required to adjust the surface tension within a proper range by shortening the tail, and the surface tension required for ceramic ink-jet printing (20 to 45 mN · M ^-1 ) was used as a surface tension modifier to control the surface tension of the dispersed ink.

The surface tension was adjusted by adding 0.1wt% polysiloxane to the solids content of the ink after dispersing through 35wt% of ceramic inorganic pigment and 0.8mg / m ² of anionic polyelectrolyte Na-PAA (Mw 15,000g / mol) One ink was defined as the optimum basic ink composition. The viscosity of the ink was adjusted to meet the required viscosity (4 ~ 40 mPa · s) requirement by using polyethylene glycol (PEG) and polyethylene oxide (PEO) as thickeners for viscosity control.

The droplet formation behavior was confirmed by changing the physical properties of the ink through the drop watcher measurement. The Reynolds number, Weber number, Ohnesorge number, through the calculation and the physical properties of the droplet formation behavior and the results compared to the inverse range of typical DOD inkjet printing, the number of possible carry over of the ink arose 1 the inverse of the number of the manufactured ink arose possession Unlike <Z <10 (Oh ^-1 = Z) was in the range of 3 < Z < 14 in which a single droplet was formed. Thus, by adjusting the physical properties of the ink, the reciprocal number of the Onegi paper is matched to the range of 3 < Z < 14, thereby greatly increasing the possibility of forming a single droplet.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

Claims (12)

As an aqueous blue ink used for inkjet printing,
30 to 40 wt% of a blue ceramic inorganic pigment having a spinel structure;
0.1 to 2.0 mg / m 2 of an anionic polyelectrolyte relative to the specific surface area of the ceramic inorganic pigment;
0.01 to 2.0 parts by weight of a surface tension modifier for adjusting the surface tension of the ink to 100 parts by weight of the blue ceramic inorganic pigment;
0.01 to 6.0 parts by weight of at least one material selected from polyethylene glycol and polyethylene oxide based on 100 parts by weight of the blue ceramic inorganic pigment,
The surface tension of the ink is in the range of 20 to 45 mNm ^-1 ,
The viscosity of the ink is in the range of 2 to 20 mPa 占 퐏,
Wherein the pH of the ink is in the range of 5 < pH < 10.
The aqueous blue ceramic ink for inkjet printing according to claim 1, wherein the anionic polyelectrolyte comprises polyacrylic acid.
The aqueous blue ceramic ink for ink jet printing according to claim 2, wherein the polyacrylic acid comprises polyacrylic acid having Na ⁺ salt.
4. The aqueous blue ceramic ink for inkjet printing according to claim 3, wherein the polyacrylic acid having Na ⁺ salt has a molecular weight of 1200 to 15000 g / mol.
The aqueous blue ceramic ink for inkjet printing according to claim 1, wherein the anionic polyelectrolyte comprises polymethacrylic acid having Na ⁺ salt.
The aqueous blue ceramic ink for ink-jet printing according to claim 5, which comprises 0.01 to 0.2 mg / m 2 of polymethacrylic acid having the Na ⁺ salt as the specific surface area of the ceramic inorganic pigment.
The aqueous blue ceramic ink for ink-jet printing according to claim 5, wherein the polymethacrylic acid having Na ⁺ salt has a molecular weight of 8000-400 K g / mol.
The aqueous blue ceramic ink for inkjet printing according to claim 1, wherein the surface tension modifier comprises at least one material selected from the group consisting of hydrophobic silica, polydimethyloxane and polysiloxane.
2. The composition according to claim 1, wherein the polyethylene glycol has a molecular weight of from 10K to 35K g / mol,
Wherein the polyethylene oxide has a molecular weight of 80K to 300K g / mol.
The method of claim 1, wherein the blue ceramic inorganic pigments include _{Co 2 SiO 4, (Co,} Zn) 2 SiO 4, CoAl 2 O 4, Co 2 SnO 4, (Co, Zn) Al 2 O 4, Co (Al, _{Cr) 3 O 4, (Co} , Mg) Al 2 O 4 , and (Co, Zn) TiO _3, a blue water-based ceramic ink for ink-jet printing comprising the one or more materials that are selected from.
The aqueous blue ceramic ink for ink-jet printing according to claim 1, wherein the blue ceramic inorganic pigment has an average particle diameter of 50 to 500 nm.
The aqueous blue ceramic ink for ink-jet printing according to claim 1, wherein the water-based blue ceramic ink for ink-jet printing has an inverse number (Oh ^-1 = Z) of the number of Onesuka ranges from 3 <

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