ES2751729B2 - DIGITAL CERAMIC INJECTION INKS FOR GLASS AND PROCEDURE TO OBTAIN THE SAME - Google Patents

Description

DESCRIPTION

DIGITAL CERAMIC INJECTION INKS FOR GLASS AND

PROCEDURE TO OBTAIN THE SAME

OBJECT OF THE INVENTION

The object of the present invention is the development of novel ceramic ink jet inks for non-porous substrates (such as glasses and metals), by which the viscosity of the inks at the jet application temperature of 33-50 ° C is 8-20 mPa.s and increases substantially by a factor of more than 5 (to more than 100 mPa.s) after discharging onto the substrate. The invention also relates to processing / formulation steps and the adjustment of volumetric and dynamic properties suitable for (i) ink jet printing in the print head channel and (ii) the desirable high viscosity after discharge onto the glass substrate. These inks can be reliably jetted onto a ceramic surface such as glass using commercial drop-on-demand inkjet devices, and mitigate ink spatter, diffusion during and after discharge, and eliminate / reduce image defects due to to dust contamination by the environment on wet inks after printing. After jet application, these inks can be dried at room temperature without the use of any external heating source such as IR lamp or oven with no side effects on image definition and dust contamination problems.

BACKGROUND OF THE INVENTION

Digital ceramic glass surface inks contain glass frit and inorganic pigment as the main functional components. Standard commercial inkjet systems have very stringent requirements in terms of both physical and chemical properties to satisfy printhead and jet application criteria. Most industrial inkjet print heads require a fluid viscosity of less than 50 mPa.s to eject the droplet at a speed greater than 5 m / s. The high solids content and particle size in the ink is a problem for the ink jet print head in terms of nozzle blockage and reliable jet application. Typically, drop-on-demand inkjet ink should have

• 8-20 mPa.s volumetric viscosity at jet application temperature,

• 20-40 mN / m surface tension,

• Highly stable pigment / particle size <1 for printing reliability and to prevent nozzle blockage.

Today's commercial ceramic glass inks have more than 40% by weight solids consisting of frits and pigments. The viscosity of such inks is generally viscoelastic, whereby the viscosity decreases with increasing shear rates. Often times the viscosity at a lower shear rate (at shear rate 1) could be a factor of almost two or more to the viscosity at a shear rate of 100-1000.

Temperature has a considerable influence on the viscosity of the ink. The viscosity of most inkjet inks drops by almost 50% when the temperature is doubled. Quite often these inks are printed above room temperature to bring the viscosity of the ink within the specifications of the print head.

Unlike ceramic tiles, since glass is not an absorbent substrate, there are several difficulties in printing inkjet ink on glass. Dust from the environment is often discharged onto the wet ink substrate while the ink is drying. Consequently, the powder penetrates the ink and results in post-print defects such as fish eyes and craters that are clearly visible in the final image when the ink dries and is tempered. For printing, when a high deposition volume is required, the ink often migrates due to its greater thickness and results in the loss of fine line definitions. Therefore, it is highly recommended to print in a clean room environment (dust free) to prevent problems related to dust discharged onto the printed substrate.

It is therefore the objective of the present invention to overcome the drawbacks of the state of the art, namely:

- increase ink stability and significantly reduce sedimentation of highly charged ceramic inks of particles containing glass frit and inorganic pigments;

- lowering the print head drive voltage required for jetting due to a significant drop in viscosity at the jetting temperature;

- eliminate ink splatter and retard ink diffusion along the edges; - retard / eliminate defects caused by the discharge of any airborne contamination such as dust in wet paint.

DESCRIPTION OF THE INVENTION

As mentioned above, the object of the invention is the development of novel ceramic ink jet inks for non-porous substrates (such as glass and metals), by which the viscosity of the inks at the jet application temperature of 33-50 ° C is 8-20 mPa.s and increases substantially by a factor of more than 5 (greater than 100 mPa.s) after discharging onto the substrate. The invention also relates to processing / formulation steps and the adjustment of volumetric and dynamic properties suitable for (i) ink jet printing in the print head channel and (ii) the desirable high viscosity after discharge onto the glass substrate. These inks can be reliably jetted onto a ceramic surface such as glass using commercial drop-on-demand inkjet devices, and mitigate ink spatter, diffusion during and after discharge, and eliminate / reduce image defects due to to dust contamination by the environment on wet inks after printing. After jet application, these inks can be dried at room temperature without the use of any external heating source such as IR lamp or oven with no side effects on image definition and dust contamination problems.

The inventions relate to a formulation of novel ceramic inkjet ink compositions resulting in (i) hybrid thermoplastic ink and (ii) hybrid photosensitive ink . The key features are that both families of inks are liquid at room temperature and within print head specifications at jet application temperatures, but change to high viscosity liquid (> 100 mPa.s) on the substrate after download.

Hybrid thermoplastic ink jet ink is designed such that the viscosity is around 6-20 mPa.s at a jet application temperature of 33 ° C and above and increases significantly to more than 100 mPa.s when the Ink temperature drops by less than 10 ° C at ambient conditions. Compared to this, the viscosity of standard inkjet ink increases by a maximum factor of 2 or less for a 10 ° C drop in temperatures. The wet inks on the substrate can be subsequently air dried or any form of conventional drying technique used, followed by tempering or high temperature firing.

The hybrid photosensitive inkjet ink is designed such that the viscosity is around 6-20 mPa.s at a jet application temperature of 33 ° C and above. After discharge onto the substrate, the viscosity of the ink increases significantly by more than 100 mPa.s by partial curing of the ink using a UV, IR or LED lamp. The highly viscous wet inks on the substrate can then be air dried or use any form of conventional drying technique, followed by tempering or high temperature firing (500-750 ° C) to melt the frit onto the substrates for color and final properties.

Such novel inkjet ink with such a drastic change in ink viscosity has key benefits:

• In bottle:

◦ High ink stability and negligible sedimentation of highly charged ceramic inks of particles containing glass frit and inorganic pigments in the bottle, due to the high viscosity of the ink at room temperature.

• During printing:

- Lowers printhead drive voltage required for jetting due to a significant drop in viscosity at jetting temperature (33 ° C and above).

• On non-porous substrate:

◦ After jetting, once the droplet is discharged onto the substrate, the viscosity of the ink increases rapidly resulting in many benefits.

■ Image definition: The high viscosity also eliminates ink splatter and slows the diffusion of ink along the edges, especially when multiple drops are deposited. This helps retain line / image definitions.

■ Dust Problems: Delays / eliminates defects caused by the discharge of any airborne contamination such as dust on wet paint.

• Due to the high viscosity ink under ambient conditions, the incoming migration of dust on the wet ink surface is retarded, resulting in "low dirt pick-up" and thereby significantly reduces defects such as fish eyes and craters. on the final printed surface.

The key ink components of glass inks are:

The final composition of the ink has 30-60% solids consisting of glass frits and inorganic pigments with a volumetric particle size: D ^90_vol <1.5 ^ m.

Frit (15-50% by weight)

The frit is the key component of ceramic inkjet inks that are designed to meet both the chemical and mechanical properties of the final fired / tempered glass. Detailed compositions are varied depending on the required frit glass transition temperature, tempering requirements and final substrate, acid and base resistance. The frit is prepared by fusing a variety of minerals in a furnace and then rapidly cooling the molten materials. The glass frit used for the ceramic recipe is mainly composed of SiO ² , B ² O ³ and Bi ² O ³ or ZnO. Various families of glass frits are used, namely bismuth and / or zinc based frits.

Common components of frit family compositions are:

- 20-49% by weight of SiO ² ,

- 3-20% by weight of B ² O ³ ,

- 1-9% by weight of Na ² O,

- 0.1-5% by weight of K ² O,

- 1-7% by weight of TIO ² ,

- ⁰ , ^{0 1 - 1} % by weight of AI ² O ³ ,

And the rest of the composition can be a combination of B ² O ³ , LÍ ² O and ZnO, or B ² O ³ and ZnO, or B ² O ³ and Li ² O, or ZnO and U ² O.

Examples of Bismuth / Zinc Glass Frit Composition ( Frit F1 )

- 20-49% by weight of SiO ² ,

- 3-20% by weight of B ² O ³ ,

- 1-9% by weight of Na ² O,

- 0.1-5% by weight of K ² O,

- 1-7% by weight of TiO ² ,

- 0.01-1% by weight of AhO3,

- 40-55% by weight of Bi2O3,

- 0.5-3% by weight of ZnO,

-0.1-4% by weight of U ² O,

- mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight;

Composition Examples of Lithium Free Bismuth / Zinc Glass Frit ( Frit F2 )

- 20-49% by weight of SiO ² ,

- 3-20% by weight of B ² O ³ ,

- 1-9% by weight of Na ² O,

- 0.1-5% by weight of K ² O,

- 1-7% by weight of TiO ² ,

- 0.01-1% by weight of AhO3,

- 50-60% by weight of Bi2O3,

- 7-12% by weight of ZnO,

- mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight;

Examples of bismuth frit composition ( Frit F3 )

- 20-49% by weight of SiO ² ,

- 3-20% by weight of B ² O ³ ,

- 1-9% by weight of Na ² O,

- 0.1-5% by weight of K ² O,

- 1-7% by weight of TIO ² ,

- ⁰ , ^{0 1 - 1} % by weight of AI ² O ³ ,

- 45-55% by weight of BÍ ² O ³ ,

- 0.1-4% by weight of LÍ ² O,

- mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight.

Examples of Zn Frit Composition ( Frit F4 )

- 20-49% by weight of SiO ² ,

- 3-20% by weight of B ² O ³ ,

- 1-9% by weight of Na ² O,

- 0.1-5% by weight of K ² O,

- 1-7% by weight of TiO ² ,

- 0.01-1% by weight of A ^ O ³ ,

- 7-15% by weight of ZnO,

- 1-5% by weight of U ² O.

The glass frit composition is in the form of particles having a volumetric particle size distribution DV ⁹⁰ of less than 1.5 µm, as measured by laser diffraction. By "% by weight" is meant the percentage by weight of the total weight of the glass frit composition.

Pigments (1-25% by weight)

Inorganic pigments can be metal oxides such as chromium oxide, titanium dioxide (for white) or mixed oxides and iron oxide for different colors. Pigments are heat resistant inorganic pigments having an average size of 2-3 microns, chemically inert and stable to UV light. They have high durability and coverage power.

Examples of suitable inorganic pigments are bluish green cobalt chromite spinel, cobalt aluminate spinel blue, iron oxide red, manganese ferrite, rutile nickel yellow, antimony titanium, copper chromite spinel black, manganese ferrite , rutile white and titanium dioxide anatase, green cobalt titanate spinel and teal cobalt chromite spinel. The bright vivid colors yellow, orange and red that are able to withstand tempering conditions are inorganic pigments in the cadmium range, such as yellow 37 (cadmium sulfide), orange 20, red 108 (cadmium sulfoselenide) and yellow 35 ( zinc cadmium sulfide).

Carriers:

30-50% solvents that contain a mixture of solvents to meet specific requirements.

• Slow drying solvents to prevent ink drying at the nozzle and prevent nozzle blockage.

• Fast drying solvent to prevent ink transfer / diffusion after discharging onto substrate.

Non-polar inks

• One or more straight chain hydrocarbons such as kerosene, naphtha; aliphatics such as cyclohexane, light petroleum, mineral turpentine, white spirit, or a mixture thereof. Carriers may be a mixture of linear C ¹⁰ -C ²⁴ alkanes, preferably linear C ¹⁰ -C ²² alkanes, more preferably linear C ¹² -C ¹⁸ alkanes.

Polar inks

• One or more alcohols, such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methylglycol (MG), ethylglycol, propylglycol, butylglycol (BG); glycol ethers, such as methoxypropanol (PM), ethoxypropanol (EP), diacetonepropanol (DAA), methoxybutanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol monomethyl ether (PM) di- or tripropylene glycol (BDPyldPyglycolmonoether (DP) Polypropylene glycol monoether (PM) di- or tripropylene glycol) esters, such as methyl acetate, ethyl acetate (ETAC), propyl acetate (IPAC), butyl acetate (BUAC), methoxypropyl acetate (PMA), ethyl-3-ethoxypropanol (EEP); ketones, such as acetone, methyl ethyl ketone (MEK), methyl butyl ketone, and cyclohexanone.

Aqueous inks

• Contain water and a mixture of one or more alcohols, such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methylglycol (MG), ethylglycol, propylglycol, butylglycol (BG); Glycol ethers, such as methoxypropanol (PM), ethoxypropanol (EP), diketonepropanol (DAA), methoxybutanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol monoether (DPG propylene glycol), DP ); esters, such as methyl acetate, ethyl acetate (ETAC), propyl acetate (IPAC), butyl acetate (BUAC), methoxypropyl acetate (PMA), ethyl-3-ethoxypropanol (EEP), or a mixture thereof .

Thermoplastics

• Suitable carriers can be mixtures of alkane waxes with a low melting point of 40-100 ° C, being solid at room temperature. Examples of such carriers are low melting point paraffin wax.

Photosensitive solvent

• One or more solvents can be mixtures of acrylate monomers, dimers and / or oligomers and photoinitiators. Examples of such solvents could be mixtures of N-vinylcaprolactam (C ⁸ H ¹³ NO) (1-vinyl-2-pyrrolidone), multifunctional acrylate, acrylic acid, monoalkylaryl or alkylaryl, polyethylene glycol diacrylate, and photoinitiators such as 2-benzyl- 2-dimethylamino-4-morpholinobutyrophenone.

Additives

• Additives: 0-10% to meet specific substrate and blast application requirements.

◦ Viscosity control agent (if required),

◦ Surfactant (reduces surface tension to 20-30 mN / m if required),

◦ Binders: Resins (acrylic, alkyd, amino-based),

◦ Anti-settling / anti-static agents: such as Aerosil and Disparlon, rheology additives, etc.

◦ Dispersing / wetting agent,

◦ Defoaming / deaerating agent,

◦ Tack agents: hydroxypropylcellulose, methacrylics and alkyd resins.

Physical properties of ink

Printhead and jetting requirements:

• Despite the larger particle size and higher solids content, ink properties are tightly controlled and optimized to meet print head and in-flight conditions to generate reliable droplets.

◦ Viscosity: 6-20 mPa.s at blasting temperature and blasting conditions

■ The high volumetric shear viscosity at room temperature is between 8-50 mPa.s

◦ Surface tension: 20-40 mN / m (dependent on process and substrate)

◦ Particle size: <= 1.5 microns (system dependent)

■ High particle stability for reliable blasting.

Substrate requirements:

• After download:

◦ Ink properties are specially adjusted for

■ prevent droplet splashing, transfer and diffusion after discharge onto hard surfaces such as glass;

■ retain edge definition of printed image during drying and tempering.

• Drying

◦ The ink formulation is adjusted with appropriate resins / additives to give a good grip after the ink has dried on the substrate at a temperature> 200 ° C, for manual handling.

• Final temper properties:

◦ The composition of the frit (one of the main components of ceramic inkjet ink) is refined during frit preparation to meet the final substrate requirements after tempering such as

■ glass transition temperature to melt and fuse with ceramic surfaces

■ acid resistance

■ scratch resistance.

◦ Pigment type size and particle interaction are adjusted during formulation to meet

■ the final temper color

■ the power of coverage and opacity.

The present invention also relates to a process for producing the ceramic ink jet ink as a process comprising the following steps:

A) prepare a glass frit paste ( FP ) by grinding and grinding the frit powder in the presence of a dispersing agent and a solvent, to achieve a volumetric particle size distribution of pigment D ^v90 of less than 1.5 ^ m; B) preparing a pigment paste ( PP ) by milling and grinding inorganic pigment particles in the presence of a dispersing agent and a solvent, to achieve a volumetric particle size distribution of Dv90 pigment of less than 1 µm;

C) mixing the frit paste from step (A) and the pigment paste from step (B) in a high shear mixer or bead mixer;

D) add a diluent made up of a mixture of solvents and additives to the concentrated ink of step (C), to achieve specific final formulations in the deposition medium, which has a final solids content of 30-60% by weight of the total weight of the mixture and the desired ink properties; and

E) filter the mixture from step (D) through a micrometer pore size filter, thus obtaining a ceramic ink jet ink having a viscosity of 6-20 mPa.s at the jet application temperature and conditions jet application.

Fried paste:

Frits are supplied in powder form with a particle size of less than 10 microns. The stability and particle size of the frit are maintained through multiple steps that involve

The grinding of the jet-milled frit powder (average particle size 8-12 microns) is carried out in a high-shear mixer of mixing frit powder with specific dispersant, resins (such as polyacrylate, polyalkyd and Polyamide) with a selected choice of solvents (non-polar aliphatic hydrocarbon, polar glycolether family, aqueous water, thermoplastic paraffin wax, or mixture of one or many solvents).

This is then followed by wet milling in a special chamber component such as zirconia, silicon nitrite, and / or silicon carbide. wet milling can be carried out in batches in multi-pass operations until the desired particle size is obtained.

The final composition is a well dispersed frit paste with a final particle size <1.5. ^ M. Examples of ground frit paste (FP) with different types of solvent are shown below.

All components are initially mixed in a high shear mixer and are then ground in a basket mill or horizontal wet mill with zirconia grinding chamber for more than 24 hours. This resulted in a highly stable frit with no or minimal sedimentation and a particle size <= 1.5 | was obtained.

B: Inorganic pigment paste

Inorganic color pigments are provided externally and supplied as powders. Standard inorganic pigments have sizes greater than 2-3 microns and are unsuitable for inkjet applications.

Preferably, the pigment paste of step B comprises 45-85% by weight of pigment, 2-20% by weight of dispersing agent and 10-55% by weight of solvent.

The pigment is ground and ground in the presence of a dispersing agent and a solvent, thus resulting in a pigment paste having a volumetric distribution of Dv90 pigment particle size of less than 1 µm, preferably less than 1 µm. . The combination of the dispersing agent and the grinding step is crucial to obtain a highly stable pigment paste with negligible / no sedimentation for a long time.

Grinding of pigment powder (7-20 micron average particle size) is carried out by premixing pigment powder with specific dispersant, resins, selected choice of solvent (non-polar aliphatic hydrocarbon, polar glycol ethers family, water aqueous, thermoplastic paraffin wax).

This is then followed by wet milling using a basket mill or a special chamber component such as zirconia, silicon nitrite and / or silicon carbide. wet milling can be carried out in batches in multi-pass operations until the desired particle size is obtained.

The choice of dispersant and grinding steps is crucial to obtain a highly stable pigment paste with little / no sedimentation for a long time.

Preferably the dispersing agent is an acid group copolymer (Disperbyk 110, Disperbyk 111), alkyl ammonium salt of acid group copolymer (Disperbyk-180), solution of high molecular weight copolymers with pigment-like groups (Disperbyk 182, Disperbyk 184, Disperbyk 190), copolymer with pigment-like groups (Disperbyk 191, Disperbyk 192, Disperbyk 194, Tego Dispers 7502, Tego Dispers 752W, Tego Dispers 656), block copolymer with pigment-like groups (Disperbyk 2155), alkyllamino salt solution of a higher molecular weight acidic polymer (Anti-terra-250), structured acrylate copolymer with pigment-like groups pigment (Disperbyk 2010, Disperbyk 2015), polyvinylpyrrolidone (PVP K-15, PVP K-30, PVP K-60), polymeric hyperdispersant (Solsperse J930, Solsperse J945, Solsperse J955, Solsperse J980, Solsperse J981, Solsperse J981, Solsperse J981, Solsperse Jolsperse J981, Solsperse J981, Solsperse J989 , Solsperse J955), high molecular weight polyurethane (Efka PU 4009, EFKA PU 4010), high molecular weight carboxylic acid salts (Efka Fa4564) or a mixture thereof.

Examples of pigment paste used in final ink formulations are given below.

PP1: Black pigment paste 1- non-polar

• Inorganic pigment: Spinel Black = 60%

• Binder: Polyamide resins = 3%

• Carrier: C14-C18 n-alkane hydrocarbons = 37%

PP2: White pigment paste 1- non-polar

• Inorganic pigment: Spinel black = 60%

• Dispersant: Disperbyk 194 N = 5%

• Carrier: C14-C18 n-alkane hydrocarbons = 35%

PP3: 2- polar black pigment paste

• Inorganic pigment: Spinel Black = 65%

• Dispersant Disperbyk 194N = 7%

• Carrier: DPM = 23%

PP4: Aqueous 3- black pigment paste

• Inorganic pigment: Spinel Black = 55%

• Dispersant Disperbyk 194N: 10%

• Additives: PVP 30 = 3%

• Carrier: Water = 22%

• DPM: 10%

PP5: Blue pigment paste 4: Thermoplastics

• Inorganic pigment: Spinel blue = 50%

• Paraffin wax: 30%

• Aliphatic hydrocarbon solvent: 20%

• Grinding temperature: 60 ° C

Inkjet ink formulations

The final ceramic inkjet ink may also comprise additives, such as carriers, rheology agents, surfactants, anti-settling / anti-static agents, flow and leveling agents, anti-foaming / deaerating agents, and resins. Appropriate additives can improve surface grip after drying at a temperature greater than or equal to 150 ° C, for manual handling.

Additives can be up to 10% by weight to improve blasting and substrate adhesion performances. By "weight%" is meant weight percent of the total weight of the ceramic inkjet ink.

Suitable surfactants can be a solution of polyether modified polydimethylsiloxane (commercially available as BYK-301, BYK-302, BYK 306, BYK 337, BYK 341), polyether modified polydimethylsiloxane (commercially available as BYK-307), solution of a Polyester modified polydimethylsiloxane (commercially available as BYK-310, BYK-313), polyester modified polymethylalkylsiloxane solution (commercially available as BYK-315), polyether modified dimethylpolysiloxane (commercially available as BYK378), or a mixture thereof.

Suitable flow and leveling agents can be a non-silicone polymeric solution of polyester modified acrylic polymer, specialty dimethylpolysiloxanes (commercially available as Tego Flow ATF 2), polyethersiloxane copolymer (commercially available as Tego Glide 100, Tego Wet 240), or a mixture of them.

Suitable deaerating / defoaming agents may be silicone-free (commercially available as BYK 051, BYK 052, BYK 053, BYK 054, BYK 055, BYK 057, BYK 1752, BYK-A 535), hydrophobic solids emulsion, foam-busting emulsifiers and polysiloxanes (commercially available as BYK-610), fluoromodified silicone defoamer (commercially available as Dynoadd F-470), silicone-free anionic ( commercially available as Dynoadd F-603), organomodified polysiloxane (commercially available as Tego Airex 900), deaerating organic polymers with silicone tip (commercially available as Tego Airex 990, Tego Airex 991), non-silicone deaerator (commercially available as Tego Airex 920 ), polyacrylate solution (commercially available as Tego Flow ZFS 460), or a mixture thereof.

Suitable rheology and anti-settling agents can be modified urea solution (commercially available as BYK 410, BYK 420), urea modified polyurethane solution (commercially available as BYK-425), polyurethane solution with a highly branched structure (commercially available as BYK-428), high molecular weight urea-modified polar polyamide solution (commercially available as BYK-430, BYK-431) hybridized amide (commercially available as Disparlon AQH 800), non-ionic polyurethane-based thickener (commercially available as Tego ViscoPlus 3000, Tego ViscoPlus 3030, Tego ViscoPlus 3060), fumed silica (Aerosil grades) or a mixture thereof.

Suitable resins may be hydroxypropylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, nitrocellulose, polyacrylic (including thermoplastic acrylic, thermosetting, water-dilutable, and non-aqueous dispersion), polyester, amino, polyurethane, polyisocyanates, polyalkid, polyamide, polyalbic acid, or hydrocarbon mixture of them. Examples of such resins could be Klucel grades, Degalan series, Neocryls 73, Nebores BS 35-60, Paraloid B67, Paroloid B82, Eurola AL1905Q, Rapsolato 7470, Laropal A81, Nytex 846, Wingtack 86, Wingtack 95.

EXPLANATION OF THE FIGURES

As a complement to the present description, and in order to help make the characteristics of the invention more easily understood, in accordance with a preferred practical exemplary embodiment thereof, said description is accompanied by a set of drawings that constitute an integral part hereof, which by way of illustration and not limitation represents the following.

Figure 1a shows the stationary shear profile at 25 and 33 ° C for standard ink.

Figure 1b shows the stationary shear profile at 25 and 33 ° C for hybrid ink A.

Figure 2: shows the effect of dust contamination on wet printed samples with (a) standard blue inks and (b) A hybrid blue ink.

Figure 3: shows the effect of dust contamination on wet printed samples with (a) standard yellow inks and (b) with hybrid yellow ink.

PREFERRED EMBODIMENT OF THE INVENTION

Hybrid thermoplastic inks

It is quite preferable to have a high viscosity ink once the ink is discharged onto the glass substrate. This has many advantages:

• High viscosity ink slows the migration of contaminated dust that is discharged over the top penetrating the paint and causing fish eyes and craters.

• High viscosity also eliminates ink splatter and slows ink diffusion along edges, especially when multiple drops are deposited. This helps retain line / image definitions.

However, most print heads are limited in viscosity in terms of blasting ability. To meet viscosity requirements, these ceramic inkjet inks are often jet applied at 30-50 ° C, at a viscosity at jetting temperature of 8-20 mPa.s. After discharging onto the substrate, the temperature of the ink can quickly reach the substrate temperature of 20-25 ° C, which would often lead to an increase in the viscosity of such ink to about 16-40 mPa.s.

In the novel formulation, hybrid thermoplastic inks, a small amount of concentrated solution of low melting thermoplastic material is introduced into the formulation in the deposition step, after preparing the concentrated frit and the pigment paste. The main carrier in the frit and the pigment paste and therefore the final ink could be made up of any type of solvent (non-polar, polar, or aqueous).

Suitable thermoplastic materials can be mixtures of alkane paraffin waxes with a low melting point of 35-60 ° C, which are solid at room temperature.

The key to the benefit of having a small amount of paraffin in the inks is significantly altering the viscosity versus temperature behavior. With the correct choice of paraffin, at the jet application temperature (in this case 33 ° C), the presence of such a component has a low or negligible influence on viscosity and is similar to standard inks (around 12- 13 mPa.s) within the specification of the print head requirements. However, when the temperature drops to 25 ° C, the viscosity increased by a significant factor due to the phase transition of the wax. In the example illustrated below, the hybrid inks with wax, the viscosity is almost 10 times or more up to around 140 mPa.s when the temperature drops to 25 ° C. In the case of the standard ink without paraffin wax, the viscosity only increased from 12 to 14 mPa.s. Detailed changes of ink viscosity are shown at 25 and 33 ° C in

the example of standard and hybrid inks rheology change recipe comparisons illustrated in the table below.

Hybrid A Hybrid B Standard Thermoplastic Thermoplastic Inks

Figures 1 (a) and 1 (b) clearly demonstrate that, at jetting temperature, both the standard and hybrid A ink had a similar viscosity profile of about 12 mPa.s. However, the hybrid ink A showed a significant increase in viscosity when the temperature dropped to 25 ° C compared to the modest increase for the standard ink (without thermoplastic wax).

Formulating such hybrid inks with such drastic viscosity variation offers significant advantages:

(i) At jetting temperatures, the viscosity of the inks in the channel is within the specification of the print head, thus requiring less drive voltage to eject the ink.

(ii) After being discharged onto hard ceramic surfaces, such as glass, unwanted effects such as droplet splashing, transfer and diffusion of inks are eliminated. In addition, defects caused by dust discharge on wet inks are minimized. Due to the high viscosity of the ink and the presence of wax on the top layer, the dust floats on the surface of the substrate, instead of penetrating the glass, and thus defects such as fish eyes and craters on the glass are eliminated. final tempered glass.

(iii) Due to the rapid viscosity gain once the ink is jetted onto the substrate at room temperature, the dot structure is protected for accurate color reproduction and thus the edge definition of the image is retained. printed during drying and tempering.

Jetting tests of such inks showed very reliable jetting and removal of visible defects on printed samples as a result of dust contaminations. The photographs illustrate a scenario whereby, for thermoplastic hybrid inks, dust is seen floating on top of the inks, while in the case of standard ink, dust enters the paint and sticks to the glass. Drying and tempering clearly show visible crater and image defects in the case of standard inks and none of such defects are seen on hybrid inks. The example of photographs is shown in Figures 2 (a) and 2 (b) and 3 (a) and 3 (b) for blue and yellow ceramic inks.

In Figure 2 (a), the effect of dust contamination on wet printed samples with standard blue inks can be seen, the effects of which are that the surrounding dust leads to a considerable number of defects such as craters. as highlighted, while in Figure 2 (b), of hybrid blue ink A with little or negligible influence of dust on the final image, there are no appreciable craters visible.

Figure 1 shows the effect of dust contamination on wet printed samples with (a) standard yellow inks, in which dust from the environment leads to a considerable number of defects such as craters as highlighted, and (b) with ink hybrid yellow, with little or negligible dust influence on the final image, no appreciable craters visible.

Hybrid photosensitive inks

In this novel formulation, the viscosity of the ink increases dramatically after it is discharged onto the substrate (directly after jetting) by introducing a small amount of photosensitive solvents such as UV-sensitive multifunctional acrylates (e.g., Sartomer 506, Sartomer 399, Ebercryl 965), LED-sensitive solvents or infrared-sensitive resins in the inks in the deposition during stage D after preparing the concentrated frit and pigment paste. The carrier in the frit and the pigment paste and therefore the final ink could be constituted by any type of solvent (non-polar, polar or aqueous).

Once the ink is discharged onto the substrate, a partial cure of these solvents is initiated in the presence of their light source, thereby significantly increasing the ink viscosity while it is retained in liquid form.

The key benefit of increasing ink viscosity on the substrate is the same as described above for hybrid thermoplastic ink, mainly retaining image definition, eliminating splashing and droplet diffusion, and mitigating defects caused by discharging dust. about coating ink.

The example of the recipe in the rheology of standard and hybrid photosensitive inks is illustrated in the table below.

d

Claims (13)

1. Digital ceramic inkjet inks for glass comprising: - glass frit composition, 25-60% by weight, which is in the form of particles having a volumetric particle size distribution Dv90 of less than 1.5 µm, measured by laser diffraction; - inorganic pigments, 1-25% by weight, comprising metal oxides and are heat-resistant inorganic pigments having an average size of 2-3 microns, chemically inert and stable to ultraviolet light; - carriers, 30-40% by weight, comprising mainly polar, non-polar or aqueous solvents; - additives, 0-1 ⁰ % by weight; characterized in that the solvents are also mixtures of less than 15% by weight of acrylate monomers, dimers and / or oligomers and photoinitiators. 2. Digital ceramic inkjet inks for glass according to claim 1, characterized in that the photoinitiators are a mixture of N-vinylcaprolactam (C ⁸ H ¹³ NO) ( ^1- vinyl- ² -pyrrolidone), multifunctional acrylate, acrylic acid, monoalkylaryl or alkylaryl, polyethylene glycol diacrylate and photoinitiator such as ^2- benzyl- ^2- dimethylamino-4-morpholinobutyrophenone. 3. Digital ceramic inkjet inks for glass according to claim ¹ or ² , characterized by: - the glass frit composition has in% by weight of the total weight of the glass frit composition: ◦ 20-49% by weight of SiO ² , ◦ 3-20% by weight of B ² O ³ , ◦ 1-9% by weight of Na ² O, ◦ 01-5% by weight of K ² O, ◦ 1-7% by weight of TiO ² , ◦% by weight of A ^ O ³ , and the rest of the composition up to 100% by weight is a combination of, LÍ ² O and ZnO, or ZnO or B ² O ³ and U ² O, or ZnO and U ² O, - the metal oxides of inorganic pigments, 1-25% by weight, are such as chromium oxide, titanium dioxide, for white, or mixed oxides, iron oxide for different colors, they are heat-resistant inorganic pigments that have a medium size 2-3 microns, chemically inert and stable to ultraviolet light; - the carriers, 30-40% by weight, are additionally of one of the following types: ◦ non-polar inks ◦ polar inks ◦ aqueous ink - the additives, 0-1 ⁰ % by weight, are one or a combination of: carriers, rheology agents, surfactants, anti-settling / anti-static agents, flow and leveling agents, anti-foaming / deaerating agents, and resins; the additives can be in an amount of up to ¹⁰ % by weight. 4. Digital ceramic inkjet inks for glass according to claim ² , wherein the glass frit composition is one of the following: - bismuth / zinc glass frit composition, F1 frit - 20-49% by weight of SiO ² , - 3-20% by weight of B ² O ³ , - 1-9% by weight of Na ² O, - 0.1-5% by weight of K ² O, - 1-7% by weight of TiO ² , - 0.01-1% by weight of AhO3, - 40-55% by weight of Bi2O3, - 0.5-3% by weight of ZnO, -0.1-4% by weight of U ² O, - mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight; - lithium-free bismuth / zinc frit composition, frit F2 - 20-49% by weight of SiO ² , - 3-20% by weight of B ² O ³ , - 1-9% by weight of Na ² O, - 0.1-5% by weight of K ² O, - 1-7% by weight of TiO ² , - ⁰ , ^{0 1 - 1} % by weight of AhO ³ , - 50-60% by weight of Bi ² O ³ , - 7-12% by weight of ZnO, - mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight; - composition of bismuth frit , frit F3 - 20-49% by weight of SiO ² , - 3-20% by weight of B ² O ³ , - 1-9% by weight of Na ² O, - 0.1-5% by weight of K ² O, - 1-7% by weight of TiO ² , - 0.01-1% by weight of AhO3, - 45-55% by weight of Bi2O3, - 0.1-4% by weight of U ² O, - mixture of other oxides such as CaO, BaO, MgO, P ² O ⁵ , Fe ² O ³ and SrO in an amount less than 10% by weight. - Zn frit composition, F4 frit - 20-49% by weight of SiO ² , - 3-20% by weight of B ² O ³ , - 1-9% by weight of Na ² O, - 0.1-5% by weight of K ² O, - 1-7% by weight of TiO ² , - 0.01-1% by weight of A ^ O ³ , - 7-15% by weight of ZnO, - 1-5% by weight of U ² O. 5. Digital ceramic inkjet inks for glass according to claim 2 or 3 or 4, characterized in that the inorganic pigments are cobalt chromite spinel bluish green, cobalt aluminate spinel blue, iron oxide red, manganese ferrite, yellow Nickel Antimony Titanium Rutile, Copper Chromite Spinel Black, Manganese Ferrite, Titanium Dioxide Rutile White and Anatase, Cobalt Titanate Spinel Green, and Cobalt Chromite Blue Green Spinel; The bright vivid colors yellow, orange and red that are able to withstand tempering conditions are inorganic pigments in the cadmium range, such as yellow 37 (cadmium sulfide), orange 20, red 108 (cadmium sulfoselenide) and yellow 35 ( zinc cadmium sulfide). 6. Digital ceramic inkjet inks for glass according to any preceding claim from 2 to 5, characterized in that the carriers are a mixture of linear C ¹⁰ -C ²⁴ alkanes, preferably linear C ¹⁰ -C ²² alkanes, more preferably C ¹² alkanes - C ¹⁸ linear. 7. Digital ceramic injection inks for glass according to any preceding claim from 2 to 6, characterized in that the carriers are one or more alcohols such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methylglycol (MG), ethylglycol, propylglycol, butylglycol (BG); glycol ethers, such as methoxypropanol (PM), ethoxypropanol (EP), diacetonepropanol (DAA), methoxybutanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol monol (BD) Polypropylene (DP) polypropylene (DP) polypropylene (DP) propylene glycol mon ether (DP) ; esters such as methyl acetate, ethyl acetate (ETAC), propyl acetate (IPAC), butyl acetate (BUAC), methoxypropyl acetate (PMA), ethyl-3-ethoxypropanol (EEP); ketones, such as acetone, methyl ethyl ketone (MEK), methyl butyl ketone, and cyclohexanone. 8. Digital ceramic injection inks for glass according to any preceding claim from 2 to 7, characterized in that the carriers are water and a mixture of one or more alcohols such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methylglycol (MG), ethylglycol, propylglycol, butylglycol (BG); Glycol ethers, such as methoxypropanol (PM), ethoxypropanol (EP), diacetonepropanol (DAA), methoxybutanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol monol (BD) Polypropylene TP (DP) propylene glycol monomethyl ether (DP) ; esters such as methyl acetate, ethyl acetate (ETAC), propyl acetate (IPAC), butyl acetate (BUAC), methoxypropyl acetate (PMA), ethyl-3-ethoxypropanol (EEP), or a mixture thereof. 9. Process for manufacturing digital ceramic inks for glass according to any preceding claim, characterized in that it comprises the following steps: A) Prepare a glass frit paste ( FP ) by grinding and grinding the frit powder in the presence of a dispersing agent and a solvent, to achieve a volumetric particle size distribution of Dv ⁹⁰ pigment of less than 1.5 ^ m; B) preparing a pigment paste ( PP ) by milling and grinding inorganic pigment particles in the presence of a dispersing agent and a solvent, to achieve a volumetric particle size distribution of Dv90 pigment of less than 1 µm; C) mixing the frit paste from step (A) and the pigment paste from step (B) in a high shear mixer or bead mixer; D) add a diluent made up of a mixture of solvents and additives to the concentrated ink of step (C), to achieve specific final formulations in the deposition medium, which has a final solids content of 30-60% by weight of the total weight of the mixture and the desired ink properties; and E) filter the mixture from step (D) through a micrometer pore size filter, thus obtaining a ceramic ink jet ink having a viscosity of 6-20 mPa.s at the jet application temperature and conditions jet application. 10. Process for the manufacture of digital ceramic inks according to claim 7, characterized in that the grinding for the preparation of the frit paste is carried out by means of a shear mixing mixer of frit powder with dispersant, resins, such as resins polyacrylate, polyalkyd and polyamide, a selection of solvents, from non-polar aliphatic hydrocarbon, polar glycol ethers family, aqueous water, thermoplastics, paraffin wax or a mixture of one or many solvents; followed by wet milling in a chamber component such as zirconia, silicon nitrite and / or silicon carbide, and the final composition is dispersed frit paste with a final particle size <1.5 µm. 11 Process for the manufacture of digital ceramic inks according to claim 10, characterized in that the wet ground frit paste is one of the following table:

12. Process for the manufacture of digital ceramic inks according to claim 9, characterized in that the inorganic pigment paste comprises 85% by weight of pigment, 2-20% by weight of dispersing agent and 10-55% by weight of solvent , in which the pigment is ground and ground in the presence of a dispersing agent and a solvent, in which the milling of the pigment powder (average particle size of 7-20 microns) is carried out by premixing the pigment powder with specific dispersant, resins and the selected choice of solvents (non-polar aliphatic hydrocarbon, polar glycol ethers family, aqueous water, thermoplastic and paraffin wax), this is then followed by wet milling using basket milling or chamber components such as zirconia, silicon nitrite and / or silicon carbide; wet milling can be carried out in batches in multi-pass operations until the desired particle size is obtained. 13. Process for the manufacture of digital ceramic inks according to claim 12, characterized in that the dispersing agent is a copolymer with acid group, Disperbyk 110, Disperbyk 111; alkyl ammonium salt of acid group copolymer, Disperbyk-180; solution of high molecular block copolymers with pigment-like groups, Disperbyk 182, Disperbyk 184, Disperbyk 190; copolymer with pigment-like groups, Disperbyk 191, Disperbyk 192, Disperbyk 194, Bykjet 9142 Tego Dispers 7502, Tego Dispers 752W; pigment-like group block copolymer, Disperbyk 2155; Alkylammonium salt solution of a higher molecular weight acidic polymer, Anti-terra-250; structured acrylate copolymer with pigment-like groups, Disperbyk 2010, Disperbyk 2015; polyvinylpyrrolidone, PVP K-15, PVP K-30, PVP K-60; polymeric hyperdispersant, Solsperse J930, Solsperse J945, Solsperse J955, Solsperse J980, Solsperse J981, Solsperse J944, Solsperse J950, Solsperse J955; high molecular weight polyurethane, Efka PU 4009, EFKA PU 4010; high molecular weight carboxylic acid salts, Efka Fa4564 or a mixture thereof.