DIGITAL CERAMIC INJECT INKS FOR GLASS AND PROCEDURE TO OBTAIN THE SAME

Abstract

Ceramic inkjet inks for non-porous substrates (such as glass, metals) whereby the viscosity of the inks at the jetting temperature of 33-50° C. is 8-20 mPa.s and increase substantially to more than a factor of 5 (greater than 100 mPa.s) after landing on the substrate. The invention also relates to processing/formulating steps and tuning of the bulk and dynamic properties suitable for (i) inkjet printing in the printhead channel and (ii) desirable high viscosity after landing on the glass substrate. The ink comprises: Glass Frit composition which is in the form of particles having a volume particle size distribution Dv90 of less than 1.5 μm, carriers (30-50 wt %) and additives (0-10%). The ceramic ink mitigate ink splattering, spreading during and after landing, eliminate/reduce image defects because of dust contaminations from the environment on wet inks after printing

Claims

1. Digital ceramic inject inks for glass comprising: Glass Frit composition being present between 25 wt. % and 60 wt. % which is in the form of particles having a volume particle size distribution Dv90 of less than 1.5 μm, as measured by laser diffraction; Inorganic pigments being present between 1 wt. % and 25 wt. % comprising oxides of metals and are heat resistant inorganic pigments having an average size of 2-3 microns, chemically inert and stable to ultraviolet light; Carriers being present between 30 wt. % and 40 wt %, comprising mainly of polar, non-polar or Aqueous solvents; Additives being present between 0 wt. % and 10 wt %; wherein the solvents are also less than 10 wt. % mixtures of alkane waxes with a low melting point of 40-100° C., being solid at room temperature.

2. The digital ceramic inject inks for glass according to claim 1, wherein characterized in that: the glass Frit composition has in wt % weight percent of the total weight of the glass frit composition: 20-49 wt. % SiO.sub.2, 3-20 wt. % B.sub.2O.sub.3, 1-9 wt. % Na.sub.2O, 0.1-5 wt. % K.sub.20, 1-7 wt. % TiO.sub.2, 0.01-1 wt. % Al.sub.2O.sub.3, And the rest of the composition up to 100 wt % is either a combination of B.sub.2O.sub.3, Li.sub.2O and ZnO, or B.sub.2O.sub.3 and ZnO or B.sub.2O.sub.3 and Li.sub.2O, or ZnO and Li.sub.2O the oxides metals of the Inorganic pigments (1-25 Wt %) are such as chromium oxide, titanium dioxide (for white), or mixed oxides, iron oxide for different colours, are heat resistant inorganic pigments having an average size of 2-3 microns, chemically inert and stable to ultraviolet light. the carriers (30-40 wt %), are additionally one of the following types: Non polar inks; Polar inks; or Aqueous ink the Additives, 0-10 wt % are one or a combination of: Carriers, rheology agents, surfactants, anti-settling/static agents, flow and levelling agents, de-foaming/de-aeration agents, and resins. The additives can be in an amount up to 10 wt. %.

3. The digital ceramic inject inks for glass according to claim 3, wherein the glass frit composition is one of the following: glass Bismuth/Zinc frit composition Frit F1 including: 20-49 wt. % SiO.sub.2, 3-20 wt. % B.sub.2O.sub.3, 1-9 wt. % Na.sub.2O, 0.1-5 wt. % K.sub.2O, 1-7 wt. % TiO.sub.2, 0.01-1 wt. % Al.sub.2O.sub.3, 40-55 wt. % Bi.sub.2O.sub.3, 0.5-3 wt. % ZnO, 0.1-4 wt % Li.sub.2O, mixture of other oxides such as CaO, BaO, MgO, P.sub.2O.sub.5, Fe.sub.2O.sub.3, SrO in an amount less than 10 wt %; or Lithium free Bismuth/Zinc frit composition Frit F2 including: 20-49 wt. % SiO.sub.2, 3-20 wt. % B.sub.2O.sub.3, 1-9 wt. % Na.sub.2O, 0.1-5 wt. % K.sub.2O, 1-7 wt. % TiO.sub.2, 0.01-1 wt. % Al.sub.2O.sub.3, 50-60 wt. % Bi.sub.2O.sub.3, 7-12 wt. % mixture of other oxides such as CaO, BaO, MgO, P.sub.2O.sub.5, Fe.sub.2O.sub.3, SrO in an amount less than 10 wt %; or Bismuth frit composition Frit F3 including: 20-49 wt. % SiO.sub.2, 3-20 wt. % B.sub.2O.sub.3, 1-9 wt. % Na.sub.2O, 0.1-5 wt. % K.sub.2O, 1-7 wt. % TiO.sub.2, 0.01-1 wt. % Al.sub.2O.sub.3, 45-55 wt. % Bi.sub.2O.sub.3, 0.1-4 wt. % Li.sub.2O mixture of other oxides such as CaO, BaO, MgO, P.sub.2O.sub.5, Fe.sub.2O.sub.3, SrO in an amount less than 10 wt. %; or Zn frit composition Frit F4 including: 20-49 wt. % SiO.sub.2, 3-20 wt. % B.sub.2O.sub.3, 1-9 wt. % Na.sub.2O, 0.1-5 wt. % K.sub.2O, 1-7 wt. % TiO.sub.2, 0.01-1 wt. % Al.sub.2O.sub.3, 7-15 wt. % 1-5 wt % Li.sub.2O.

4. The digital ceramic inject inks for glass according to claim 2, wherein the inorganic pigments are Cobalt chromite Blue green Spinel, Cobalt Aluminate Blue Spinel, Iron oxide red, Manganese Ferrite, Nickel Antimony Titanium Yellow Rutile, Copper Chromite Black Spinel, manganese ferrite, White titanium dioxide rutile and Anatase, Cobalt Titanate Green Spinel, Cobalt Chromite Blue Green Spinel. Brilliant bright colours yellow, oranges and red, which are capable of withstanding tempering conditions are cadmium range inorganic pigments such as Yellow 37 (Cadmium sulphide), Orange 20, Red 108 (Cadmium sulfoslenide) and Yellow 35 (Zinc cadmium Sulphide).

5. The digital ceramic inject inks for glass according to claim 2, wherein the carriers are a mixture of linear C.sub.10-C.sub.24 alkanes, preferably linear C.sub.10-C.sub.22 alkanes, more preferably linear C.sub.12-C.sub.18 alkanes.

6. The digital ceramic inject inks for glass according to claim 2, wherein the carriers are one or more alcohols, such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methyl glycol (MG), ethyl glycol, propyl glycol, butyl glycol (BG); glycol ethers, such as methoxy propanol (PM), ethoxy propanol (EP), diacetone propanol (DAA), methoxy butanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol mono methyl ether (PM), di or tri propylene glycol mono propyl ether (DPnP, TPnP), butyl diglycol (BDG); esters, such as methyl acetate, ethyl acetate (ETAC), propyl acetate(IPAC), butyl acetate (BUAC), methoxy propyl acetate (PMA), ethyl-3-ethoxy-propanol (EEP); ketones, such as acetone, methyl ethyl ketone (MEK), methyl butyl ketone, cyclohexanone.

7. The digital ceramic inject inks for glass according to claim 2, wherein the carriers are water and mixture of one or more alcohols, such as methyl alcohol, ethyl alcohol, propyl alcohols, butyl alcohols; glycols, such as methyl glycol (MG), ethyl glycol, propyl glycol, butyl glycol (BG); glycol ethers, such as methoxy propanol (PM), ethoxy propanol (EP), diacetone propanol (DAA), methoxy butanol, dipropylene glycol monomethyl ether (DPM), tripropylene glycol methyl ether (TPM), propylene glycol mono methyl ether (PM), di or tri propylene glycol mono propyl ether (DPnP, TPnP), butyl diglycol (BDG); esters, such as methyl acetate, ethyl acetate (ETAC), propyl acetate(IPAC), butyl acetate (BUAC), methoxy propyl acetate (PMA), ethyl-3-ethoxy-propanol (EEP), or a mixture thereof.

8. A process for manufacturing the digital ceramik inks for glass according to claim 1, wherein the process it comprises the following steps: A. Preparing a glass frit paste (FP) by milling and grinding frit powder in the presence of a dispersant agent and a solvent to achieve a pigment volume particle size distribution Dv90 of less than 1.5 μm; B. Preparing an inorganic pigment paste (PP) by milling and grinding pigment particles in the presence of a dispersant agent and a solvent to achieve a pigment volume particle size distribution Dv90 of less than 1 μm; C. Mixing the frit paste of step (A) and pigment paste of step (B) in a high shear mixer or bead mixer; D. Add a thinner constituting of mixture of solvents and additives to the concentrated ink of step (C) to achieve specific final formulations in the let-down medium, having a final solid content 30-60 wt. % on the total weight of the mixture and desired ink properties; and E. Filtering the mixture of step (D) through a micrometer pore size filter, thereby obtaining a ceramic inkjet ink having a viscosity of 6-20 mPa.s at jetting temperature and jetting conditions.

9. The process for manufacturing the digital ceramik inks according to claim 7 wherein in the milling for preparation of the frit paste is carried out by a mixing shear mixer of frit powder with dispersant, resins (such as polyacrylate, polyalkyd and polyamide resins) an a selection of solvents (non-polar aliphatic hydrocarbon, Polar glycol ether family, Aqueous water, thermoplastic paraffin wax, or mixture of one or many solvents), being 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 final particle size <1.5 μm.

10. The process for manufacturing the digital ceramik inks according to claim 9, wherein the wet milled frit paste is one of the following table: TABLE-US-00004 Bismuth- Bismuth- Zinc Zinc Zinc Zinc FP1-Non FP2- FP3-Non FP4- Components polar Polar Polar Polar Bismuth/Zinc based 60-65% 60-65% Frit F1 Zinc based Frit F4 60-65% 60-65% C14-C18, n-alkanes 30-40% 30-40% hydrocarbon Dipropylene glycol 30-40% 30-40% monomethyl ether (DPM) Polyamide resins  2-5% Disperbyk 180  5-10% Tego Dispers 656  5-10%

11. The process for manufacturing the digital ceramik inks according to claim 8, wherein the inorganic pigment paste comprises 45-85 wt. % pigment, 2-20 wt. % dispersant agent and 10-55 wt. % solvent wherein the pigment is milled and grinded in the presence of a dispersant agent and a solvent, wherein the milling of the pigment powder (average particle size of 7-20 micron) is carried out by pre-mixing of pigment powder with specific dispersant, resins the selected choice of solvents (non-polar aliphatic hydrocarbon, Polar glycol ether family, Aqueous water, thermoplastic paraffin wax), this is then followed by wet milling using basket mill or a chamber components such as zirconia, silicon nitrite and/or silicon carbide.

12. The process for manufacturing the digital ceramik inks according to claim 11, wherein the dispersant agent is a copolymer with acidic group Disperbyk 110, Disperbyk 111; alkylol ammonium salt of copolymer with acidic groups Disperbyk-180), solution of high molecular weight block copolymers with pigment affinic groups Disperbyk 182, Disperbyk 184, Disperbyk 190; copolymer with pigment affinic groups Disperbyk 191, Disperbyk 192, Disperbyk 194, Bykjet 9142Tego Dispers 7502, Tego Dispers 752W; block-copolymer with pigment affinic groups Disperbyk 2155; solution of alkylol ammonium salt of a higher molecular weight acidic polymer Anti-terra-250; structured acrylate copolymer with pigment affinic 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.

Description

EXPLANATION OF THE FIGURES

[0179] As a complement to the present description, and for the purpose of helping to make the characteristics of the invention more readily understandable, in accordance with a preferred practical exemplary embodiment thereof, said description is accompanied by a set of drawings constituting an integral part of the same, which by way of illustration and not limitation represent the following.

[0180] FIG. 1a shows the steady shear profile at 25 and 33° C. for standard ink

[0181] FIG. 1b shows the steady shear profile at 25 and 33° C. for hybrid ink A.

[0182] FIG. 21: shows the effect of dust contamination on the wet printed samples with (a) standard Blue inks, and (b) hybrid Blue ink A.

[0183] FIG. 2: shows the effect of dust contamination on the wet printed samples with (a) standard Yellow inks, and (b)with hybrid Yellow ink.

PREFERRED EMBODIMENT OF THE INVENTION

[0184] Hybrid Thermoplastic Inks

[0185] It is quite preferable to have a high viscosity ink once the inks lands on the glass substrate. This has many advantage [0186] High viscosity ink slows migration of the contaminated dust that lands on the top from penetrating into the paint and causing fish eyes, craters. [0187] High viscosity also eliminates ink splattering and slows down ink spreading along the edges, especially when multiple drops are laid down. This helps to retain the line/image definitions.

[0188] However, most printhead have viscosity limitation in terms of jetting capability. To meet the viscosity requirements, often these ceramics inkjet inks are jetted at 30-50 C at the jetting temperature viscosity of 8-20 mPa.s. Upon landing on substrate, the ink temperature may quickly reach substrate temperature of 20-25 C, which would often lead to increase in the viscosity of such ink to about 16-40 mPa.s.

[0189] In our novel formulation, hybrid thermoplastic inks, a small amount concentrated solution of low meting point thermoplastic material are introduced in the formulation in the let-down stage, after preparing the concentrated frit and pigment paste. The main carrier in the frit and pigment paste and hence the final ink could constitute any of the solvent type (Non-polar, polar or aqueous).

[0190] Suitable thermoplastic materials can be mixtures of alkane paraffin waxes with a low melting point of 35-60 C, being solid at room temperature.

[0191] The key of benefit of having small quantity of paraffin in the inks is to significantly alter the temperature-viscosity behaviour. With the right choice of paraffin, at the jetting temperature (in our case 33° C.), the presence of such component has little or negligible influence on the viscosity and is similar to the standard inks (around 12-13 mPa.s) within the specification of printhead requirement. However, when the temperature is dropped to 25° C., the viscosity increased by a significant factor due to the phase transition of wax. In the example illustrated below, the hybrid inks with wax, the viscosity is almost 10 times or more to around 140 mPa.s when the temperature drops to 25 C. In the case of our standard ink without the paraffin wax, the viscosity only increased from 12 to 14 mPa.s. Detailed changes in the ink viscosity at 25 and 33 C is shown in

[0192] The example of the recipe comparisons of change in the rheology of standard and hybrid inks is illustrated in table below.

TABLE-US-00002 Hybrid Hybrid Thermo- Thermo- Std inks plastic plastic Weight ink A ink B Formulations % Weight % Weight % STEP 1. Mix Step A Bismuth frit paste- FP1- Non-polar .sup. 58% 58% 58%  (60 wt % Concentrated milled Frit paste in C10-C13, n-alkanes hydrocarbon) Inorganic pigment paste Black 1 .sup. 18% 18% 18%  (60 wt % Concentrated milled pigment paste in C10-C13, n-alkanes hydrocarbon) Hydrocarbon resin   2%  2% 2% Acrylic resin (85 wt % in Octanol) .sup. 10% 10% 8% Surfactant (BYK 307) 0.20% 0.20%.sup.  0.20%   Rheology additive (BYK 431) 0.80% 0.80%.sup.  0.80%   STEP 2. Dissolve Paraffin wax in solvents and mix to Step 1 Paraffin wax —  5% 8% C14-C18, n-alkanes hydrocarbon  8.6% 4.5%  4% C11-C14, n-alkanes hydrocarbon  2.9% 1.5%  1% Total Weight %  100% 100%  100%  Viscosity change from 35 to 25° C. change in temperature Viscosity at 33° C. (jetting conditions) 12   11.7   13.5 at 100 shear rate (mPa .Math. s) Viscosity at 25° C. (at substrate 14 130 190 condition) at 100 shear rate (mPa .Math. s) % Viscosity increase for 8° C. 16.7% 977%  1307%   drop in temperature

[0193] FIGS. 1(a) and 1(b) clearly demonstrate that at the jetting temperature both standard and hybrid ink A had similar viscosity profile around 12 mPa.s. However, hybrid ink A showed significant increase in viscosity when the temperature is dropped to 25° C. compared to modest increase for standard ink (without the thermoplastic wax).

[0194] The formulation of such hybrid inks with such drastic viscosity variation offer significant advantages: [0195] (i) At the jetting temperature, the inks viscosity in the channel is within the print head specification, thus requiring lower drive voltage to eject the ink, [0196] (ii) After landing on hard ceramic surfaces, such as glass, undesired effects such as drop splattering, bleed and spread of ink s are eliminated. Furthermore, defects caused by dust landing on the wet inks are minimised. Due to high viscosity of the ink and presence of wax on top coat, dust floats on the ink surface, rather than penetrating the glass thus eliminates defects such as fish eyes, crater on the final tempered glass. [0197] (iii) Due to rapid gain in viscosity once the ink is jetted on the substrate at room temperature, protect the structure of the dots for accurate colour reproduction and hence edge definition of the printed image during drying and tempering is retained.

[0198] The jetting trials of such inks showed very reliable jetting and elimination of visible defect on the printed samples as a result of dust contaminations. The photographs illustrate a scenario whereby for thermoplastic hybrid inks, the dust is seen floating on the top of the inks, where as in the case of standard ink, the dust enters into the paint and stick on the glass. The dried and tempered clearly shows a visible crater and image defect in the case of standard inks and no such defects are seen on the hybrid inks. Example of photographs is shown in Figures FIG. 21 and FIG. 2 for ceramic blue and yellow inks.

[0199] In FIG. 2(a) can be observed the Effect of dust contamination on the wet printed samples with standard Blue inks, whose effects are that dust from the environmental leads to considerable number of defects such as cratering as highlighted, while in FIG. 2(b) hybrid Blue ink A in which little or negligible influence of the dust on final image there are not noticeable crater visible.

[0200] FIG. 3 shows the effect of dust contamination on the wet printed samples with (a) standard Yellow inks wherein dust from the environmental leads to considerable number of defects such as cratering as highlighted, and (b) with hybrid Yellow ink wherein little or negligible influence of the dust on final image there are Not noticeable crater visible.

[0201] Hybrid Photo-Sensitive Inks

[0202] In this novel formulation, the viscosity of the ink is drastically increased after landing on the substrate (straight after jetting) by introducing small quantity of photo-sensitive solvents such as UV sensitive multi-functional acrylates (eg, Sartomer 506, Sartomer 399, Ebercryl 965), LED sensitive solvents, or Infrared sensitive resins in the inks in the let-down during Stage D after preparing the concentrated fit and pigment paste. The carrier in the frit and pigment paste and hence the final ink could constitute any of the solvent type (Non-polar, polar or aqueous).

[0203] Once the ink is landed on the substrate, partial curing of these solvents is initiated in presence of their light source, thus significantly increasing the ink viscosity whilst still retaining as liquid.

[0204] The key of benefit of increasing ink viscosity on substrate is same as described earlier for hybrid thermoplastic ink, mainly retaining image definition, elimination of drop splattering and spread and mitigate defects caused by dust landing on the coating ink.

[0205] The example of the recipe in the rheology of standard and hybrid photo-sensitive inks is illustrated in table below.

TABLE-US-00003 Hybrid Hybrid photo- photo- sensitive sensitive Std inks ink C ink D Formulations Weight % Weight % Weight % STEP 1. Mix Step A Bismuth frit paste- FP1- Non-polar 60% 60% 60% (60 wt % Concentrated milled Frit paste in C10-C13, n-alkanes hydrocarbon) Inorganic pigment paste White1 PP2 16% 16% 16% (60 wt % Concentrated milled pigment paste in C10-C13, n-alkanes hydrocarbon) Hydrocarbon resin  2%  2%  2% Acrylic resin (85 wt % in Octanol) 10% 10%  8% Surfactant (BYK 307) 0.20%.sup.  0.20%.sup.  0.20%.sup.  Rheology additive (BYK 431) 0.80%.sup.  STEP 2. Mix photosensitive material and thinners and mix to Step 1 Multifunctional Acrylate —  5% 10% Photo initiator 0.2%  0.4%  C14-C18, n-alkanes hydrocarbon 8.6%  13.6%.sup.  9.4%  C11-C14, n-alkanes hydrocarbon 2.9%   5%  4% Total Weight % 100%  100%  100%