ES2751729A1 - DIGITAL CERAMIC INJECTION INKS FOR GLASS AND PROCEDURE FOR OBTAINING THE SAME (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Digital ceramic inkjet inks for glass and the procedure to obtain them. Ceramic inkjet inks for non-porous substrates (such as glass and metals), whereby the viscosity of the inks at the jetting temperature of 33-50ºC is 8-20 mPa.s and increases substantially by a factor more than 5 (at more than 100 mPa.s) after discharging onto the substrate. The invention also relates to processing/formulation steps and adjusting the volumetric and dynamic properties suitable for (i) inkjet printing in the print head channel and (ii) the desirable high viscosity after discharge onto the glass substrate. The ink comprises: Glass frit composition which is in the form of particles having a Dv90 particle size volumetric distribution of less than 1.5 μm, carriers (30-50% by weight) and additives (0-10 %). Ceramic ink mitigates ink spatter, diffusion during and after discharge, and eliminates/reduces image defects due to environmental dust contamination on wet inks after printing. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

DIGITAL CERAMIC INJECTION INKS FOR GLASS AND

PROCEDURE TO OBTAIN THEM

OBJECT OF THE INVENTION

It is the object of the present invention to develop novel ceramic inkjet inks for non-porous substrates (such as glass and metals), whereby the viscosity of the inks at the jetting temperature of 33-50 ° C it 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 adjusting the volumetric and dynamic properties suitable for (i) inkjet 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 on-demand drop inkjet devices, and mitigate ink spatter, diffusion during and after discharge, and eliminate / reduce image defects due to environmental dust contamination on wet inks after printing. After jetting, these inks can be dried at room temperature without the use of any external heating source such as IR lamp or stove 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 meet the criteria for print head and jet application. Most industrial inkjet print heads require a fluid viscosity of less than 50 mPa.s to eject the droplet at a rate greater than 5 m / s. The high solids content and particle size in the ink is a problem for the inkjet print head in terms of nozzle blocking and reliable jetting. Typically, on-demand drop inkjet ink should have

• 8-20 mPa.s of volumetric viscosity at the jetting temperature,

• 20-40 mN / m of surface tension,

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

Today's commercial ceramic inks for glass have more than 40% by weight of solids consisting of frits and pigments. The viscosity of such inks is generally viscoelastic, whereby the viscosity decreases with increasing shear rates. Often, the viscosity at the 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. Often, the surrounding dust is discharged onto the wet ink substrate while the ink is drying. Consequently, the powder penetrates the ink and results in postpress defects such as fish eyes and craters that are clearly visible in the final image when the ink is dried and tempered. For printing, when a high deposition volume is required, the ink often migrates due to its increased thickness and results in loss of fine line definitions. Therefore, it is highly recommended to print in a clean room environment (dust-free) to prevent problems related to discharged dust on the printed substrate.

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

- increase ink stability and significantly reduce the sedimentation of highly particle-loaded ceramic inks 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 the defects caused by the discharge of any air pollution such as dust in the wet paint.

DESCRIPTION OF THE INVENTION

As mentioned above, the object of the invention is the development of novel ceramic inkjet inks for non-porous substrates (such as glass and metals), whereby the viscosity of the inks at the jetting 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 discharge onto the substrate. The invention also relates to processing / formulation steps and adjusting the volumetric and dynamic properties suitable for (i) inkjet 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 on-demand drop inkjet devices, and mitigate ink spatter, diffusion during and after discharge, and eliminate / reduce image defects due to environmental dust contamination on wet inks after printing. After jetting, these inks can be dried at room temperature without the use of any external heating source such as IR lamp or stove 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 the specifications of the print head at jetting temperatures, but change to high viscosity liquid (> 100 mPa.s) on the substrate after the download.

The hybrid thermoplastic inkjet ink is designed such that the viscosity is around 6-20 mPa.s at a jetting temperature of 33 ° C and above and increases significantly to more than 100 mPa.s when the Ink temperature drops below 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. Wet inks on the substrate can be air-dried later or use any form of conventional drying technique, 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 ink viscosity 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 on the substrates for color and final properties.

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

• In bottle:

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

• During printing:

- Lowers the print head drive voltage required for jetting due to a significant drop in viscosity at the jetting temperature (33 ° C and higher).

• On non-porous substrate:

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

Image Definition: High viscosity also eliminates ink splatter and slows ink diffusion along the edges, especially when multiple droplets are deposited. This helps retain the line / image definitions.

■ Dust Problems: Delays / eliminates defects caused by the discharge of any airborne contamination such as dust in 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 pickup" and thus significantly reduces defects such as fish eyes and craters on the final printed surface.

The key ink components of glass inks are:

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

Fried (15-50% by weight)

The frit is the key component of ceramic inkjet inks that are designed to satisfy both the chemical and mechanical properties of the final fired / tempered glass. Detailed compositions are varied depending on the required frit glass transition temperature, quenching and final substrate requirements, acid and base resistance. The frit is prepared by melting a variety of minerals in an oven 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 UNCLE 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;

Lithium-free zinc bismuth / glass frit composition examples ( 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;

Composition examples 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 UNCLE 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.

Zn frit composition examples ( 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 ^ m, measured by laser diffraction. By "weight%" is meant the weight percent 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 that are 2-3 microns in size on average, chemically inert and UV stable. They have high durability and coverage power.

Examples of suitable inorganic pigments are teal cobalt chromite spinel, cobalt aluminate spinel blue, iron oxide red, manganese ferrite, rutile nickel, antimony and titanium yellow, copper chromite spinel black, manganese ferrite , rutile white and anatase titanium dioxide, green cobalt titanate spinel and teal cobalt chromite spinel. the bright vivid colors yellow, orange and red that are capable of withstanding 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 sulfide and cadmium).

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.

• Quick drying solvent to prevent the transfer / diffusion of ink after discharging onto the substrate.

Non-polar inks

• One or more straight chain hydrocarbons such as kerosene, naphtha; aliphatics such as cyclohexane, petroleum ether, mineral turpentine, turpentine, or a mixture thereof. Carriers can 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 methyl (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol monopropyl glycol monopropyl glycol monopropol 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

• They 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 methyl (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol (PM) ); 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 spray and substrate 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 / antistatic agents: such as Aerosil and Disparlon, rheology additives, etc.

◦ dispersing / wetting agent,

◦ Defoaming / deaerating agent,

◦ Gripping agents: hydroxypropyl cellulose, methacrylics and alkyd resins.

Physical properties of ink

Print head and jet application requirements:

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

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

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

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

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

■ high particle stability for reliable jet application.

Substrate requirements:

• After download:

◦ The ink properties are specially adjusted for

■ prevent dripping, dripping and spreading after discharge on hard surfaces such as glass;

■ Retain the edge definition of the printed image during drying and tempering.

• drying

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

• Properties of the final temper:

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

■ glass transition temperature to melt and blend with ceramic surfaces

■ acid resistance

■ scratch resistance.

◦ The pigment type size and its 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 ceramic inkjet ink as a process comprising the following steps:

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

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

D) adding a diluent consisting 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 mix weight and desired ink properties; and

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

Fried pasta:

The 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 stages involving

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

This is then followed by wet grinding into a special chamber component such as zirconia, silicon nitrite and / or silicon carbide. wet milling can be carried out in batches in multi-step 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 they are then ground in a basket mill or horizontal wet mill with a 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 | is obtained.

B: Inorganic pigment paste

Inorganic color pigments are provided externally and supplied as powders. Standard inorganic pigments are larger than 2-3 microns in size 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, thereby resulting in a pigment paste having a volume distribution of Dv90 pigment particle size of less than 1 ^ m, preferably less than 1 ^ m . 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 the pigment powder (average particle size 7-20 microns) is carried out by premixing pigment powder with specific dispersant, resins, the selected choice of solvent (non-polar aliphatic hydrocarbon, family of polar glycol ethers, water aqueous, thermoplastic paraffin wax).

This is then followed by wet grinding 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-step operations until the desired particle size is obtained.

The choice of dispersant and grinding stages is crucial to obtain a highly stable pigment paste with little / no settling 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), high molecular weight copolymer solution with pigment related groups (Disperbyk 182, Disperbyk 184, Disperbyk 190), copolymer with pigment related groups (Disperbyk 191, Disperbyk 192, Disperbyk 194, Tego Dispers 7502, Tego Dispers 752W, Tego Dispers 656), block copolymer with pigment related groups (Disperbyk 2155), alkylamino salt solution of a higher molecular weight acidic polymer (Anti-terra-250), structured acrylate copolymer with groups related to 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 J98pe, Solsperse J501 , 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 the final ink formulations are given below.

PP1: 1- non-polar black pigment paste

• Inorganic pigment: Black spinel = 60%

• Binder: Polyamide resins = 3%

• Carrier: Hydrocarbons n-alkanes C14-C18 = 37%

PP2: 1- non polar white pigment paste

• Inorganic Pigment: Spinel Black = 60%

• Dispersant: Disperbyk 194 N = 5%

• Carrier: Hydrocarbons n-alkanes C14-C18 = 35%

PP3: 2- polar black pigment paste

• Inorganic pigment: Black spinel = 65%

• Dispersant Disperbyk 194N = 7%

• Carrier: DPM = 23%

PP4: 3- aqueous black pigment paste

• Inorganic pigment: Black spinel = 55%

• Dispersant Disperbyk 194N: 10%

• Additives: RRP 30 = 3%

• Carrier: Water = 22%

• DPM: 10%

PP5: Blue Pigment Paste 4: Thermoplastics

• Inorganic pigment: Blue spinel = 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 / antistatic agents, flow and leveling agents, antifoaming / 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.

The additives can be in an amount of up to 10% by weight to improve jetting and substrate adhesion performance. By "% by weight" is meant percentage by weight of the total weight of the ceramic inkjet ink.

Suitable surfactants may be a polyether modified polydimethylsiloxane solution (commercially available as BYK-301, BYK-302, BYK 306, BYK 337, BYK 341), polyether modified polydimethylsiloxane (commercially available as BYK-307), a solution of a polyester modified polydimethylsiloxane (commercially available as BYK-310, BYK-313), polyester modified polymethylalkyl siloxane 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 silicone-free polymeric solution of polyester-modified acrylic polymer, special dimethylpolysiloxanes (commercially available as Tego Flow ATF 2), polyethersiloxane copolymer (commercially available as Tego Glide 100, Tego Wet 240) or a mixture of the same.

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), emulsion of hydrophobic solids, emulsifiers and foam-destroying polysiloxanes (commercially available as BYK-610), fluoromodified silicone antifoam (commercially available as Dynoadd F-470), silicone-free anionic ( commercially available as Dynoadd F-603), organomodified polysiloxane (commercially available as Tego Airex 900), silicone-tip deaerating organic polymers (commercially available as Tego Airex 990, Tego Airex 991), silicone-free deaerating (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), highly branched structure polyurethane solution (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), thickener based on nonionic polyurethane (commercially available as Tego ViscoPlus 3000, Tego ViscoPlus 3030, Tego ViscoPlus 3060), pyrolysis silica (Aerosil grades) or a mixture thereof.

Suitable resins can be hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, nitrocellulose, polyacrylics (including thermoplastic, thermosetting, water-dilutable, and non-aqueous dispersible acrylics), polyester, amino, polyurethane, polyisocyanates, polyalkyd, polyamide, hydrocarbonate mixture of the same. Examples of such resins could be Klucel grades, Degalan series, Neocryls 73, Nebores BS 35-60, Paraloid B67, Paroloid B82, Eurola AL1905Q, Rapsolate 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, according to a preferred practical exemplary embodiment thereof, said description is accompanied by a set of drawings that constitute an integral part thereof, which by way of illustration and not of 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 the wet printed samples with (a) standard blue inks and (b) hybrid blue ink A.

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 powder that discharges onto 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 droplets are deposited. This helps retain the line / image definitions.

However, most print heads have a viscosity limitation in terms of jetting ability. To meet viscosity requirements, these ceramic inkjet inks are often jetted at 30-50 ° C, at a jetting temperature viscosity 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 approximately 16-40 mPa.s.

In the novel formulation, hybrid thermoplastic inks, a small amount of concentrated solution of low melting point thermoplastic material is introduced into the formulation at the deposition stage, after preparing the concentrated frit and 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 (nonpolar, 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 to significantly alter the behavior of viscosity versus temperature. 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 the 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 increases by a significant factor due to the phase transition of the wax. In the example illustrated below, hybrid wax inks, 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 standard ink without paraffin wax, the viscosity only increased from 12 to 14 mPa.s. Detailed changes in ink viscosity are shown at 25 and 33 ° C in

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

Standard thermoplastic thermoplastic inks hybrid A hybrid B

Figures 1 (a) and 1 (b) clearly demonstrate that, at the jetting temperature, both standard and hybrid A ink had a similar viscosity profile of about 12 mPa.s. However, hybrid ink A showed a significant increase in viscosity when the temperature dropped to 25 ° C compared to the modest increase for 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 discharging onto hard ceramic surfaces, such as glass, unwanted effects such as drop spatter, transfer and diffusion of the inks are eliminated. In addition, defects caused by powder discharge on wet inks are minimized. Due to the high viscosity of the ink and the presence of wax on the top layer, the powder floats on the surface of the substrate, instead of penetrating the glass, and therefore defects such as fish eyes and craters are eliminated on the final tempered glass.

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

Jet application tests of such inks showed very reliable jet application and elimination of visible defects on printed samples as a result of dust contamination. The photographs illustrate a scenario where, for thermoplastic hybrid inks, the powder is seen floating on top of the inks, while in the case of standard ink, the powder 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 ceramic blue and yellow 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 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 low 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 the surrounding dust leads to a considerable number of defects such as craters as highlighted, and (b) with ink Hybrid yellow, with little or negligible influence of dust on the final image, no appreciable craters are visible.

Hybrid photosensitive inks

In this novel formulation, the viscosity of the ink increases dramatically after being discharged onto the substrate (directly after jetting) by introducing a small amount of photosensitive solvents such as multifunctional UV-sensitive acrylates (eg, 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 made up of any type of solvent (non-polar, polar or aqueous).

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

The key to the benefit of increasing the ink viscosity on the substrate is the same as described above for hybrid thermoplastic ink, mainly to retain image definition, eliminate spatter and droplet diffusion, and mitigate defects caused by dust being discharged. on the coating ink.

The recipe example is illustrated in the rheology of hybrid standard and photosensitive inks 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 Dv90 particle size volumetric distribution of less than 1.5 ^ m, 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 glass injection inks 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 in that: - the glass frit composition has in% by weight of the total weight of the glass frit composition: ◦ 20-49% by weight 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 remainder 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 metallic oxides of the 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 UV stable; - 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-sedimentation / antistatic agents, flow and leveling agents, antifoaming / deaerating agents and resins; the additives may be in an amount of up to ¹⁰ % by weight. 4. Digital ceramic inkjet inks for glass according to claim ² , in which the composition of the glass frit is one of the following: - composition of bismuth / zinc glass frit, 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; - composition of lithium-free bismuth / zinc frit, F2 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 , ^{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. - composition of Zn frit, 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 teal cobalt chromite spinel, cobalt aluminate spinel blue, iron oxide red, manganese ferrite, yellow nickel rutile, antimony and titanium, black copper chromite spinel, manganese ferrite, rutile white and anatase titanium dioxide, cobalt titanate spinel green and teal cobalt chromite spinel; the bright vivid colors yellow, orange and red that are capable of withstanding 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 sulfide and cadmium). 6. Digital ceramic glass injection inks according to any preceding claim 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 inkjet inks for glass according to any preceding claim 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 methyl (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol (PM), di- or tripropylene glycol (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 inkjet 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 methyl (TPM), propylene glycol monomethyl ether (PM), di- or tripropylene glycol (PM), di- or tripropylene 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. 9. Procedure for manufacturing the digital ceramic inks for glass according to any preceding claim, characterized in that it comprises the following steps: A) preparing 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 volume distribution of Dv ⁹⁰ pigment particle size of less than 1.5 ^ m; B) preparing a pigment paste ( PP ) by grinding and grinding inorganic pigment particles in the presence of a dispersing agent and a solvent, to achieve a Dv90 pigment volumetric particle size distribution of less than 1 ^ m; C) mixing the frit paste from step (A) and the pigment paste from step (B) in a high shear mixer or bead mixer; D) adding a diluent consisting 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 mix weight and desired ink properties; and E) filtering the mixture from step (D) through a micron pore size filter, thus obtaining a ceramic inkjet ink having a viscosity of 6-20 mPa.s at the jetting 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 mixer for mixing frit powder with dispersant, resins, such as resins from polyacrylate, polyalkyd and polyamide, a choice of solvents, from non-polar aliphatic hydrocarbon, family of polar glycol ethers, aqueous water, thermoplastics, paraffin wax or a mixture of one or many solvents; followed by wet grinding 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 ^ m. Method for manufacturing digital ceramic inks according to claim 10, characterized in that the wet ground frit paste is one of the following table:

12. Method for manufacturing the digital ceramic inks according to claim 9, characterized in that the inorganic pigment paste comprises 45 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 crushed in the presence of a dispersing agent and a solvent, in which the grinding of the pigment powder (average particle size of 7-20 microns) is carried out by premixing of the pigment powder with specific dispersant, resins and the selected choice of solvents (non-polar aliphatic hydrocarbon, family of polar glycol ethers, aqueous water, thermoplastic and paraffin wax), this is then followed by wet milling using basket mill or chamber components such as zirconia, silicon nitrite and / or silicon carbide; wet milling can be carried out in batches in multi-step operations until the desired particle size is obtained. 13. Process for manufacturing the digital ceramic inks according to claim 12, characterized in that the dispersing agent is an acid group copolymer, Disperbyk 110, Disperbyk 111; Alkyllammonium salt of copolymer with acid groups, Disperbyk-180; high molecular weight block copolymer solution with pigment related groups, Disperbyk 182, Disperbyk 184, Disperbyk 190; copolymer with pigment-related groups, Disperbyk 191, Disperbyk 192, Disperbyk 194, Bykjet 9142 Tego Dispers 7502, Tego Dispers 752W; block copolymer with pigment related groups, Disperbyk 2155; Alkylammonium salt solution of a higher molecular weight acidic polymer, Anti-terra-250; structured acrylate copolymer with pigment related 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.