Digital ink-jet glass printer

ES 2 345 985 T3

DESCRIPTION

Ink for ceramic surfaces.

Field of the invention

The present invention relates to an ink for printing on ceramic surfaces, especially glass, after printing, the surface is subjected to calcination (firing) at temperatures above 600 ° C.

Background of the invention

Ceramic materials are hard, brittle, heat and corrosion resistant substrates by shaping and then heating a non-metallic mineral such as clay to an elevated temperature. Enamels, porcelain, and bricks are examples of materials that are produced by molding or shaping minerals and firing them at high temperatures.

Vitreous products are typically produced by melting silicates with boric oxide, aluminum oxide, or phosphorous pentoxide at elevated temperatures. They have highly variable mechanical and optical properties and solidify from the molten state without crystallization into a transparent or translucent form. As glass objects in general are hard and brittle, their lack of crystalline structure places them in the class of amorphous solids. Glass objects that may require printed graphics include windows, mirrors, kitchen utensils, bottles, containers, etc.

From a printing point of view, various methods are available for decorating glass and ceramics with high-quality images. The printing processes used to print glass and ceramics have a variety of ink systems. Contrary to sublimation inks, most inks fall into one of two families: organic and inorganic.

Organic inks are typically used in screen printing, inkjet printing and pad printing and consist of organic pigments and resins along with other chemicals that cure over time and depend on temperature or any other form of energy to create a bond with the substrate. The most effective organic inks are produced as two-component or two-part systems. These inks generally contain polymerizable resins that are mixed with catalysts to initiate polymerization. Heating products to a temperature of approximately 200 ° C after printing can speed up the curing process and improve adhesion. Furthermore, this exposure to heat will typically improve the mechanical and chemical resistance of the print. After printing, organic ink films will require at least 48 hours to polymerize, unless heat is applied.

Inorganic inks use mineral-based pigments and materials that, once printed, must be heated and melted at elevated temperatures to combine with the surface of the substrate and form a permanent bond.

Ceramic colors, as inorganic ceramic inks are called, are a mixture of pigments (metal oxides and salts) and finely ground glass particles, called frits. These materials are fused into the substrate by calcining ("firing") at temperatures between 600-1450 ° C. Firing temperatures will vary based on color structure, nature of substrate, and other application criteria, but in all cases, temperatures must be carefully controlled to achieve specific colors after firing.

These high firing temperatures are used because ceramic color components need to melt so that they can melt into the ceramic surface on which they are printed. While these inks are typically referred to as "inorganic," they can also contain small amounts of organic material. Organic components are the materials in which the pigment and frit are suspended to create a printing ink. These organic materials, which are oily in nature, are designed to burn quickly during cooking, without affecting print quality and final color.

Inorganic inks come in many forms. They include color formulations for screen and pad printing processes, thermoplastic varieties and total transfer inks. Both screen printing and full transfer are known as "cool color" inks, which means that they do not need to be heated to be printable, while thermoplastic inks must be heated before they can be applied to the substrate.

Thermoplastic ink systems are waxy at room temperature and must be heated to print. For pad printing, the inkwell, plate and occasionally pad are kept at a temperature of approximately (60 ° C). When the ink-bearing pad comes into contact with the cold object to be printed, the ink cools and sticks to the object.

When screen printing with thermoplastic inks, the mesh is made of stainless steel and an electric current is passed through. This heats the mesh and melts the ink, which then flows through the mesh and solidifies when it comes in contact with cold ceramic or glass. Control of current flow is critical because too much will overheat the color and burn the mesh.

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While printing on ceramic surfaces with organic inks can be obtained by mechanical screen printing, pad printing or digital printing, commercial ceramic inks are difficult to use in inkjet printing, because they typically have a higher viscosity than is required for printing of inkjet (about 20-40 cps) and the glass frit contained in them, which is in the micrometer size range, It tends to settle and also clogs the nozzles on the perforated plate from which ink is ejected during ink jet printing.

It would be highly desirable to use ink jet printing on ceramic surfaces with ceramic pigments, rather than the commonly used methods of mechanical screen printing or pad printing. Converting to digital printing can have the following advantages: reduced costs involved in storing silkscreen or transfer devices due to digital storage of desired patterns rather than physical storage; reduced costs for low-value printing that can be prohibitive in screen printing; greater ease and versatility of change from one design to another, ability to use edge-to-edge printing.

Until now, attempts at printing ceramic colors with the inkjet process and thus making the inkjet process available to decorate ceramic items such as glass, enamel and porcelain have failed, due to the pronounced trend specifically heavy and coarse colored powders to form sediments. The specific gravity of enamelling and glazing colors ranges from 3.5 to 6.0 kg / 1 and the average grain fineness of these products ranges from 3 to 5 pm. These products settle from aqueous or alcoholic suspensions that have the viscosity of conventional inkjet processing in the span of a few seconds to 50% in some cases. These suspensions would quickly lead to blockage of the print nozzles and the entire ink jet printer. Liquid color pastes that have a substantially higher viscosity, for example 5000 mPa-s, such as those used in screen printing to decorate glass, will not be suitable for inkjet printing because the viscosity is much higher for printers. inkjet machines present today.

US Patent No. 6,357,868, incorporated herein by reference, discloses a method for decorating ceramics by ink jet technology, using inorganic pigments and glass frit present in a thermoplastic medium having a melting point of at least 30 ° C (as wax). The medium, which is solid under storage conditions, eliminates the sedimentation of inorganic pigments. The ink melts just before being used by a heatable ink jet printer head.

According to this patent, sedimentation is removed using a thermoplastic medium that immediately solidifies.

EP 1,223,201, incorporated herein by reference, discloses an ink for printing on heat resistant substrates comprising pigment, glass fusible agents with particles less than 10 µ and a carrier. The carrier according to this patent is also thermoplastic with a high melting point for phase change of the ink. Such ink, which is solid at room temperature, needs to be heated before printing.

Ink that is solid at room temperature and needs to be heated in the ink jet head before printing is awkward to handle, load, and requires special equipment for actual printing. If the ink is liquid at room temperature, the performance and maintenance of the printer will be much better.

JP 2002 324966 A relates to a method for forming new circuit patterns in which a conductive paste containing metallic particles is applied to a substrate by ink jet printing. The ink contains a thermoset resinous compound that functions as an organic binder.

US 2003/026957 A1 relates to an image transfer element that is capable of forming a multi-color image on a variety of substrates by non-direct transfer printing.

EP-0 774 315 A relates to a W-Cu compound which is composed of individual particles having a tungsten phase and a copper phase, wherein the tungsten phase substantially encapsulates the copper phase.

FR-2 735 461 A describes a compound of the formula A (M, Tb) O₃, where A is one or more alkaline earth metals and M is Sn or Ti and where M and Tb are present in solid solution. The compound particles can be used as a color pigment especially in plastics, paints, lacquers, rubbers, paper, ink, cosmetics, mineral binders and layer coatings) and, when coated with a transparent oxide layer (esp. silica, alumina, zirconia, etc.), as a color pigment in ceramics or enamels.

JP 8134388 A refers to an electrically conductive ink containing at least one solvent, organic binder and a mixture comprising 80.0-95.0% by volume of Cu0, 1.0-7.0 µm in diameter particle average, 1.0-10.0% by volume of at least one type of metal powder selected from Ni, Mo, Zr and Mn, 1.06.0 μm average particle diameter and 4.0-10, 0% by volume of an inorganic binder, 1.0-5.0 μm average particle diameter, with the inorganic ingredient dispersed in the final ink.

Document JP 7 176210 A refers to a conductive ink where a mixture of 70.0% by weight of CuO and from 5.0 to 30.3% by weight of inorganic binder is obtained as an inorganic component and at least a

ES 2 345 985 T3 solvent and an organic binder, to disperse the inorganic component so as to compose a conductive ink. Because glass is the inorganic binder, it must be softened between 850 ° C and 950 ° C and the particle diameter of CuO, since it is the conductive substance, is obtained from 1.0 to 7.0 mm, while the particle diameter of the glass being the inorganic binder, it is obtained from 1.0 to 5.0 pm.

Document WO 94/22966 A refers to a light-modifying composition comprising a color pigment and a light-conditioning component, which is a gray pigment characterized by having the ability to absorb light and reflect at least part of the absorbed light.

Document US 5 407 474 relates to an ink composition comprising an inorganic pigment for use in an ink jet printer for printing on ceramics or glass to provide a decoration, after subsequent firing.

JP 3 062863 A relates to an aqueous ink comprising a colorant, a binder (for example, a water-soluble resin having a molecular weight of 1000-30000) and a release agent, wherein the release agent is ( thio) urea or one of its derivatives.

The purpose of the ink in JP 3 062863 A is to provide clear holographs to a white material made of ceramic or plastic, which can be easily and completely erased with dry cloth, paper, felt, etc. after drying.

JP 1 056776 A refers to a heat-resistant ink, obtained by using a solid substance hydrolyzed (from a metal alkoxide) in a glass-based component in an ink, consisting of the glass-based component, a solvent, binder and an agent that imparts electrical conductivity and is useful for ink jet printers.

Synthesis of the invention

The present invention refers to an ink composition for printing on a ceramic substrate, to melt with the substrate after firing, the ink is characterized by:

(a) have a viscosity of less than 20 cps at jet temperature;

(b) be an integral part of the substrate after exposure to temperatures above 500 ° C;

the ink composition comprises:

1) an organic solvent as a liquid vehicle at room temperature;

2) submicron particles of a glass frit as defined in appended claim 1 as a binder composition.

The above composition is pigment free and thus is not intended to provide a color printed pattern; rather, the "substrate that forms the binder composition" (see below) is printed to produce a "non-colored pattern", for example, to provide the glass with a rough pattern, a "matte" opaque pattern, desired to sometimes for aesthetic or functional purposes on glass (in order to avoid accidental collision of passengers with glass doors).

In a preferred embodiment, the ink of the invention also comprises pigments that maintain their optical properties (color, absorbance, etc.) even after firing, which produces a colored pattern after printing.

Thus, in a preferred embodiment, the present invention provides an ink composition for printing on a ceramic substrate, for melting on the substrate after firing as defined in appended claim 2, wherein the ink is characterized by :

(a) have a viscosity of less than 20 cps at jet temperature;

(b) maintain its optical properties after exposure to temperatures above 500 ° C;

(c) become an integral part of the substrate after exposure to temperatures above 500 ° C;

where the ink composition comprises:

1) heat resistant inorganic pigment particles having an average size of less than 1.2 microns;

2) a liquid vehicle at room temperature;

3) submicron particles of a binder composition.

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The phrase "ceramic substrate" refers to an inorganic non-metallic substrate processed or used at high temperatures. This includes surfaces such as glass for windows in buildings, cars, electrical appliances such as ovens, etc., ceramic surfaces such as those formed by clay minerals such as tiles, enamel, and other ceramic materials.

Preferably, the ceramic substrate is glass.

The ink of the invention is of the type to melt into the substrate after firing, so that it becomes an integral part of the substrate, especially glass. The integration can be for the purpose of creating a "non-colored pattern" (dull or rough pattern) or a "colored pattern".

Integrating the ink into the substrate (glass) to provide a colored pattern may be required, for example, in vehicle windshields and windows that have a thin painted frame around their tops that protects the glue that holds the window to the car. from UV irradiation and decorates the windshield. This ink must be heat resistant, scratch resistant, so that it has to become an integral part of the glass.

In architecture, many times, the window for internal and external use must have heat resistant properties for safety reasons and the decorative patterns present in it must be an integral part of the window, in order to be durable.

Various electrical appliances, such as microwave oven windows, ovens and refrigerators, often have designs, decorative or functional, that need to demonstrate durability at high temperatures, typically resistance to temperatures in excess of 600 ° C. Again, such windows need to have a design fused with the glass.

Integration of pigment-free ink into a surface to provide a non-colored pattern can be used especially in architecture to provide rough, opaque or "matte" designs or surfaces on glass windows or doors both for aesthetic reasons and to avoid collisions. accidental.

Finally, other glass designs need to show resistance to harsh conditions such as heat, resistance to imbibition in hot sulfuric acid, sodium hydroxide solutions, etc. and designs present there contain a pigment fused to the glass and are integrated with it.

The ink of the present invention is intended for these purposes.

Ink is characterized by various characteristics. It has a viscosity that allows it to be printed by means of ink jet printing, typically a viscosity (at room temperature) of less than 50 cps or a viscosity at jet temperature (the temperature present at the ink print head during printing ) printing less than 20 cps, more preferably less than 15 cps, most preferably between 10 and 13 cps.

The term "jet temperature" refers to the temperature of the ink in the print head and is typically 30-60 ° C, preferably 35-45 ° C.

The viscosity in the inks described in this invention is measured by means of a Brookfield DV-II + viscometer, with a small sample adapter, while using an S18 spindle, at 80 rpm.

When the ink also comprises pigment particles to provide a color pattern, the ink should retain its optical properties after exposure to temperatures above 500 °, preferably after exposures to temperatures above 580 °, most preferably after expose to a temperature higher than 600 °. The "optical properties" that should be maintained are selected from color, optical density, UV blocking, gloss, and so on. This means that the pigments used according to these embodiments do not lose their optical properties after firing.

The ink of the present invention becomes an integral part of the substrate when the substrate and ink are exposed to temperatures above 500 °, preferably above 550 °, most preferably above 600 °. Preferably, the ink of the present invention can be integrated with the substrate at a temperature below 700 °, as will be explained hereinafter.

The expression "becomes an integral part" means that the ink is sintered, melted or melted to become inseparable from the upper surface of the glass-ceramic substrate, so that it cannot be scratched after conventional physical or chemical abrasion tests. , do not separate from the surface after heating or exposure to substances such as strong acid solutions.

In the following, when particle sizes are mentioned, the number refers to the average size of the particles.

The ink composition according to the "pigment-containing" aspect (for producing a color pattern) of the present invention essentially comprises submicron particles of heat-resistant inorganic pigment.

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Preferably the average size of the inorganic pigments is less than 1.2 µ, preferably less than 0.9 µ, more preferably less than 0.7 µ, most preferably the average size of the inorganic pigment is less at 550 nanometers (0.55 μ). Preferably, when the color of the pigment is white, the mean pigment size is between 0.17 and 0.25 µ.

The term "inorganic pigment" refers to a pigment that is at least partially inorganic. In a preferred embodiment, the inorganic pigments are metal oxides that are present a priori in an appropriate form to provide the desired optical properties and do not need to be oxidized in situ on the substrate during firing to provide these properties. However, in other options, the pigments can be organometallic which, after their organic parts are fired, burn and the metallic constituents are oxidized to form metal oxides. Organic pigments can also be produced using other compounds comprising metallic elements which, after burning, oxidize to form colored metallic oxide.

Various metal oxides can be used such as chromium oxide, copper oxide, mixed oxides of CuCr oxide₂OR₃ (for black color), titanium dioxide (for white color), iron oxide red (pigment red 101), rutile nickel yellow, antimony and titanium (pigment yellow 53), cobalt aluminate blue spinel (pigment blue 28), etc.

The term "heat resistant" in the context of inorganic pigment refers to the fact that the pigment does not burn completely during the firing process of the substrate (although some of it can burn as in the organometallic composition) and some of its optical properties as previously described (color, optical density, UV absorbance, gloss, etc.) are maintained after firing.

The liquid vehicle at room temperature 15-28 ° C is composed of at least one organic solvent (it can be a combination of various organic solvents).

Finally, the ink also comprises submicron particles of a compound that is called a "binder composition", where this term refers to a composition (it can comprise a mixture of several different compounds) that, after firing, sinters and melts with the ceramic substrate (glass), becoming an integral part.

The binder composition comprises a glass frit as defined in the appended claims. Typically, in the final ink formulation, the concentration (w / w) of the solid components (inorganic pigments together with the binder composition {glass frit particles} to the liquid carrier (solvent-based) is 10 to 60% , preferably 25 to 50%, most preferably about 45%.

Typically, the concentration (w / w), in the solid content of the ink (without the vehicle), of the heat-resistant inorganic pigment to the binder composition (glass frit) is 1 to 3, preferably 1 to 2.5 most preferably 1 to 2. This ratio depends on the required properties of the fired substrate, such as optical density.

Preferably, the ink also comprises at least one dispersing agent and / or wetting agent, such as Bykumen (solution of a low molecular weight unsaturated acid polycarboxylic acid polyester and White spirit / isobutanol = 2/1), Disperbyk-166 ( solution of a high molecular weight block copolymer with pigment related groups and methoxypropyl acetate / butyl acetate = 1/4), Disperbyk-164 (solution of a high molecular weight block copolymer with related groups of pigment and butyl acetate), Disperbyk-130 (polyamine solution of unsaturated polycarboxylic acids and alkylbenzene / butylglycol = 5/1), Disperbyk-182 ( solution of a high molecular weight block copolymer with pigment related groups and methoxypropyl acetate / methoxy-propoxypropanol / butyl acetate = 4/4/4), Disperbyk-163 (solution of high molecular block copolymer with pigment related groups, in 3/1/1 xylene / butyl acetate / methoxypropyl acetate); Disperbyk-161 (solution of a high molecular block copolymer with pigment related groups and methoxypropyl acetate / butyl acetate = 6/1), Disperbyk-101 (solution of a long-chain polyamine salt, acid esters and mineral alcohol / butylglycol = 8/1), Disperbyk-160 (solution of a high molecular weight block copolymer with pigment related groups and xylene / butyl acetate = 6/1), BYK-P-104 (solution of a low molecular weight unsaturated polycarboxylic acid polymer and xylene / diisobutyl ketone = 9/1), BYK-P-104 S (solution of a low molecular weight unsaturated polycarboxylic acid polymer with a copolymer polysiloxane and xylene / diisobutyl ketone = 9/1), Disperbyk-180 (alkyl ammonium salt of a block copolymer with acid groups), Disperbyk-110 (solution of a copolymer with acid groups and methoxypropyl acetate / alkylbenzene = 1/1 ), BYK-348 (polyether-modified poly-dimethyl siloxane), BYK-346 (solution of a polyester-modified poly-dimethyl-siloxane in dipropylene glycol monomethyl ether), BYK-381 (solution of a polyacrylic copolymer and dipropylene glycol monomethyl ether) (ChemieBYK, Germany) , BYK-306 (solution of a polyether and xylene modified poly-dimethyl-siloxane / monophenylglycol + 7/2), BYK-358N (solution of polyacrylate and alkylbenzene copolymer), BYK-333 (poly-dimethyl-siloxane modified with polyether), Tego Dispers 650 (specially modified polyether with pigment related groups), Tego Dispers 652 (concentrate of a fatty acid derivative), Tego Dispers 710 (solution of a basic urethane copolymer) (TegoChemie Service, Germany), Solsperse 43000 (dispersant 50% polymeric in water), Solsperse 40000 (84% polymeric dispersant in water with diethanolamine) (Avecia, UK). Some of these dispersants are suitable for both solvent-based and water-based inkjet formulations and others for solvent-based or water-based inks, or both.

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The ink, according to the invention, may comprise additional components typically selected from crosslinking agents, dispersing agents, antifoaming agents, wetting agents, rheology control agents, organic polymers as binders and fixing agents that provide "green strength" (such as polyacrylates or polyvinylpyrrolidone, PVP), anticorrosive agents, coalescing agents, pH control agents and biocides.

The liquid carrier is an organic solvent such as PM (propylene glycol monomethyl ether), DPM (dipropylene glycol monomethyl ether), TPM (tripropylene glycol monomethyl ether), PnB (propylene glycol mono-n-butylether), DPnB (dipropylene glycol monobutyl ether), TPnB (tripropylene glycol monobutyl ether), TPnB (tripropylene glycol monobutyl ether) butyl ether), PnP (propylene glycol monopropylether), DPnP (dipropylene glycol monopropylether), TPnB-H (propylene glycol butylether), PMA (propylene glycol monomethyl ether acetate), Dowanol DB (diethylene glycol monobutyl ether) or other ethylene- or propylene glycol ethers (Dow Chemical Company, USA). The vehicle can also be a mixture of two or more different organic solvents.

According to this embodiment, the binder compositions are submicron particles of a glass frit or glass frit with a special additive, which reduces the sintering temperature. This ink is especially useful for printing a glass substrate. According to the "solvent soluble ink", typically, the particle size in the glass frit is less than 0.9 µ. Suitable inkjet glass frits have a particle size of less than 0.7 µ or even less than 0.6 µ.

The glass frit is a glass frit composed of a combination of SiO₂, Bi₂OR₃ and B₂OR₃, as will be explained in more detail below. Typically, the weight concentration of SiO₂ in the glass frit is 5070% (w / w) and the concentration by weight of Bi2O3 in the glass frit is 10-20% (w / w) and the concentration by weight of B2O3 in the glass frit is 3-20% (w / w).

Besides the main compounds such as SiO2, Bi2O3 and B2O3, the glass frit can contain Al2O3 (0.5-9%), K2O (1-2%), Na2O (2-14%), CaO (1-7 %), BaO (15%), PbO (25-60%), ZrO2 (1-2%), ZnO (2-9%), MgO (0.5-1%), TiO₂ (5-10%), F (1-2%). The exact composition of the glass frit is selected according to the required properties such as sintering temperature, resistance to acids and bases, etc.

The solvent-based ink can also comprise at least one UV curable agent. Many times, it is desired to fix the ink to the substrate, prior to firing, in order to improve the printing properties. The addition of UV curable agents allows rapid fixation of the printed design by exposing surface bearing ink droplets to UV radiation after printing. Since UV curable agents are organic molecules, they burn during the firing of the printed design on the glass.

The term "UV curable agent" refers to a composition that can be polymerized after application of UV irradiation. Typically, they are photopolymerizable monomers or oligomers, together with photoinitiators and / or photosensitizers.

Preferably the solvent based ink comprises the glass frit, at least one inorganic pigment and at least one solvent together with a dispersing agent, more preferably it also comprises a wetting agent and most preferably a polymeric binder. organic like PVP or polyacrylates.

It should be noted that the ink can be used without a pigment to provide a non-colored design (rough or opaque / matte design) or it can be used in conjunction with a pigment to provide a colored design.

Brief description of the drawings

In order to understand the invention and see how it is carried out in practice, a preferred embodiment will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 shows a photo microscopic of UV / solvent based ink with UV curable agents printed on Spectra Print Head (Spectra, USA) (a) and (b) before and after exposure to UV irradiation, of the sample 9, (c) and (d) before and after exposure to UV irradiation of sample 10.

Detailed description of the invention

Pigments

When the ink of this invention is designed to produce a colored pattern, it contains heat-resistant inorganic pigments having an average size of less than 1.2 microns. Although, in this invention, we describe a black ink, the invention can be easily applied to pigments having other colors. These inorganic pigments can be metal oxides such as chromium oxide, copper oxide or mixed oxides of CuCr2O3 (for the black color), titanium dioxide (for the white color), red iron oxide (for the red color), nickel, antimony and titanium yellow rutile (for the yellow color), cobalt blue and aluminum spinel (for the blue color), etc. An important characteristic of pigments, in order to be suitable for inkjet printing,

ES 2 345 985 T3 is the requirement for a very small pigment size. Conventional ceramic pigments, which are currently used for screen printing or pad printing, are in the micrometer size range (such as, for example, those mentioned in EP 1,223,201 which are 10 μ), which is unacceptable for printing. ink jet. Consequently, the required mean pigment size is less than about one micron (more precisely, less than about 1.2 microns), preferably less than 0.9 µ, more preferably less than 0.7 µ, most preferably , less than 0.55 μ, can be obtained by milling and grinding the micron-sized pigments (by means of appropriate instruments such as ball mill, pearl flour, jet mill, etc.) or synthesizing the pigment under conditions that give submicron particles (such as precipitation from solution, forced hydrolysis, from metal alkoxides, gas phase reaction, etc.). It should be emphasized that, in all types of inkjet ink for glass inks described in this invention, the pigment should provide, after printing and high temperature firing, appropriate optical properties such as optical density, UV blocking, gloss, etc. .

The pigment can also be an organometallic material, where after firing the organic constituent burns and the metallic constituent oxidizes to form metal oxides. Alternatively, colors can be produced using compounds containing metallic elements that, upon burning, oxidize to form colored metallic oxides. The resulting ink can be any color, preferably black, cyan, magenta, yellow, or white, or a variation of the above.

Proper selection of the relationship between the concentration of the pigment and the substrate that forms the binder composition of the pigment in the ink and the particle size distribution of the ink can achieve these optical properties.

1. Solvent Based Inkjet Ink

The binder composition in this exemplary ink is a glass frit, ground to a particle size of less than 0.7 microns. The glass frit composition is selected such that the glass has a sintering temperature of less than 600 ° C and low thermal expansion. The glass frit comprises: SiO₂, Bi₂OR₃, B₂OR₃, in order of decreasing molar concentration and the glass frit is dispersed in an organic solvent (dispersion of the glass frit particles in a solvent). The exact composition of the submicron particles in the frit can be measured according to the required melting temperature, degree of crystallinity, thermal expansion and chemical resistance. Typically, the molar concentration ranges for these components are: 50-70%, 10-20%, and 320%, respectively.

The submicron particles were obtained by wet grinding of a micron-sized frit powder, dispersed in Dowanol DB (diethylene glycol monobutyl ether - Dow Chemical Company, USA) in the presence of Disperbyk-180 as a dispersing agent. The addition of Dowanol DB and dispersant improves grinding and allows a particle size of less than 0.9 µ to be obtained without aggregation.

(In the solvent-based ink examples, the "frit" is the dispersion of the frit, which has a solids content of 65-75% by weight).

The pigments in these formulations were also prepared by wet grinding Cr-Cu oxide micron-size pigment dispersed in Dowanol DB in the presence of a dispersant (in the examples, the "pigment" is the black pigment dispersion having a solids content 65-75% by weight). Pigment particles were less than 0.7 microns, while 90% of the particles were less than 0.4 microns.

The resulting dispersions of the submicron glass frit and the pigments were mixed in such a ratio to obtain a 3: 1 or 2: 1 ratio by weight of the frit particles to the pigment particles. The dispersion was then diluted with Dowanol DB and additional solvents (TPM, PMA) and a dispersant was added to achieve a low viscosity ink with a solids content of 39-50%. In some cases, an organic polymer such as pVp or polyacrylate is added, which allows the fixation of the printed design, before sintering at high temperature, thus achieving a good green strength. This improves the handling of the printed glass.

1.2 Preparation procedure

Add pigment dispersion, cosolvent (TPM or PMA) and Disperbyk-163^TM (Byk-Chemie, Germany) to the frit and mix with Dispermat for 5 min after each addition of material. Then add Dowanol DB during mixing and remix with Dispermat (30 min, 9000 rpm).

The resulting inks were filtered through 1 micron filters (Cefar, Swiss), without clogging the filter and without any significant change in solids content.

For an initial test, the samples were applied to glass as a 5 µl drop and dried in an oven at 580650 ° C for 10 min.

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Other tests were performed by injecting the ink at 35 ° C, 45 ° C, or 55 ° C (ink viscosity is approximately 11 cps at 45 ° C). The exact composition and properties of inkjet inks are presented in the following tables.

Overall, the overall ink performance in the inkjet head (Spectra, USA) was found to be very good (nozzle, line definition, nozzle confidence, no print head clogging) and that the Printed designs have gloss and good optical density after firing at 580-650 ° C. In some cases, the printing was done on preheated glass, in order to allow a quick fixation of the ink drops on the glass. Heating continued during and / or throughout the printing process with an IR heater or hot air or a combination of both. The printing was made several times with the same design (several layers), in order to obtain designs with a sufficient thickness to meet the final requirements for the inks, such as appropriate optical density after high temperature firing.

Chemical resistance was tested by immersion in sulfuric acid solutions at 80 ° C, 4 hours and NaOH solution overnight, and found to be excellent.

Sample 1 was tested for several days, while on the print head, and it was found that even after prolonged non-use, a simple purge and cleaning of the perforated plate produced immediate printing and full head performance. of impression.

1.3 Specific formulations

<td rowspan="2">Sample name</td><td rowspan="2">Composition</td><td rowspan="2">% solids</td><td colspan="2">Viscosity a</td><td rowspan="2">Surface tension mN / m</td><td rowspan="2">Particle size in composition, nm, by volume (measured with HPPS instrument, Malvern Instruments Limited, England)</td>

<td> 45 ^QC</td><td> 55 ^QC</td>

<td> 1</td><td>Frit IJFRITID- 57.89 g Pigment IJBLAC2D -19.3 g</td><td> 46,5</td><td> 11,9</td><td> -</td><td> 26,1 ± 0,05</td><td>100% less than 530 mm</td>

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<td></td><td>ΤΡΜ - 8.57 g Disperbyk-163 - 0.87 g Dowanol DB - 34, 62 g</td><td></td><td></td><td></td><td></td><td></td>

<td> 2</td><td>Frit JRK617BF - 57.89 g Pigment 2003-12-15 - 19.3 g PMA-7.72g Bykumen-1.13 g Dowanol DB -25.48 g BYK-306 -1.13 g</td><td> 46,9</td><td> 12,0</td><td></td><td> 22,6 ± 0,07</td><td>100% less than 520 mm</td>

<td> 3</td><td>Frit TEST 1 -56.6 g Pigment 2004-04-08 - 26.55 g PMA-8.32g Bykumen - 2.97 g Dowanol DB -22.87 g BYK-358N -1.19 g</td><td> 48,9</td><td> 11,5</td><td></td><td> 27,3 ± 0,1</td><td>100% less than 520 mm</td>

<td> 4</td><td>Frit JRK617BF-53.32 g Pigment 2004-04-08 - 26.66 g TPM-16.00 g Disperbyk-180 - 0.11 g Dowanol DB - 7.12 g</td><td> 51,22</td><td> 12,2</td><td></td><td> 28,7 ± 0,05</td><td>100% less than 350 mm</td>

<td> 5</td><td>Frit TEST 1 -59.17 g Pigment 2004-04-08 - 27.77 g PMA-8.70g Tego 652-3.31 g Dowanol DB -33.47 g BYK-333 -1.34 g</td><td> 44,7</td><td> 11,0</td><td></td><td> 29,2 ± 0,07</td><td>100% less than 750 mm</td>

<td> 6</td><td>Frit JRK617BF-68.8 g Pigment 2004-04-08 - 34.40 g TPM-10.32 g Bykumen -1.56 g Dowanol DB-39.73 g PVP -1.56 g</td><td> 44,7</td><td> 12,1</td><td></td><td> 28,5 ± 0,09</td><td>100% less than 320 mm</td>

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1.4 Injection ink for white glass

The above procedure, used for the preparation of black ink, can be used, with slight modifications, for the preparation of inkjet inks for white glass. Various types of Kronos titanium dioxide were used as the white pigment (obtained from Kronos, USA).

Preparation procedure

Add cosolvent (TPM or PMA), Dowanol DB, and dispersant to the frit and mix with Dispermat for 5 min after each material addition. Then add powdered pigment during mixing and remix with Dispermat (30 min, 9000 rpm).

The resulting inks were filtered through a 1 micron filter, without clogging the filter and without significant changes in solids content.

For an initial test, samples were applied to glass as 5 µl drops and dried in an oven at 580650 ° C for 10 min.

Further tests were performed by injecting the ink at 45 ° C or 55 ° C, at which temperature the viscosities of the inks were approximately 11 cps. The exact composition and properties of the two inkjet inks are presented in the following table.

<td>Sample name</td><td>Composition</td><td>% solids</td><td>Viscosity a Four. Five ^QC</td><td>Particle size in composition, nm (HPPS, by volume)</td>

<td> 7</td><td>Frit TEST 1 -50.73 g Kronos 2300 Pigment - 17.1 g PMA-6.79 g Disperbyk-163 - 2.48 g Dowanol DB - 22.38 g</td><td> 51,6</td><td> 10,7</td><td>100% less than 750 mm</td>

<td> 8</td><td>Frit TEST 1 -55.50 g Kronos Pigment 2300 -18.71 g PMA-7.43 g Disperbyk-110-2.71 g Dowanol DB - 24.48 g</td><td> 51,6</td><td> 10,9</td><td>100% less than 550 mm</td>

The properties of the submicron frit used in the solvent-based ink examples are given in the following table:

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Technical data for glass frit IJFRIT1D

<td>features</td><td>Specification</td>

<td>Chemical composition</td><td>Bismuth borosilicate</td>

<td>Glass transition temperature Tg (measured by DSC as inflection point)</td><td>(479 ± 5) ° C</td>

<td>Particle size (in number)</td><td>D₅₀ = 0.06 pm Dg₀ = 0.11 pm</td>

<td>Particle size (by volume)</td><td>D₅₀ = 0.14 pm Dg₀ = 0.90 pm</td>

IJBLAC2D pigment black: The pigment dispersion obtained after wet grinding contains copper chromite (70-73%) and Dowanol DB (27-30%).

The difference between various glass frits and pigments, used in the examples of the invention, is obtained by milling and the solids contents and particle size vary from batch to batch. The numbers given are the lot numbers.

All batches of glass frit and pigment were received ground from Johnson Matthey BV Company. The numbers given are the lot numbers.

1.5 Solvent based ink with UV curable agents

Many times, it is desired to fix the ink to the substrate before firing, in order to improve the printing properties.

When the ink contains photocurable components, rapid fixation of the printed design can be achieved by exposing the ink droplets to UV radiation after printing. These components cause an increase in the viscosity of the individual droplets (in some cases, a solid droplet forms even though the ink as a whole is still liquid at room temperature, thus providing a fixation of the ink droplet on the substrate. of glass. As these additives are organic molecules, they burn during the firing of the printed design on the glass.

In the present invention, the UV curable composition (monomers, oligomers, photoinitiators, photosensitizers) is added to the solvent-based ink described above, thus imparting a partial UV curability to the ink that is sufficient to cause fixation. of the printed droplets, immediately after exposure to UV light.

These additives, which can polymerize after exposure to UV light, for example: acrylic or vinyl monomer (from Sartomer: SR-504 (NONYLPHENOL ACRYLATE ETHOXYLATE (4)), SR-355 (DITRIMETHYLOLPROPANE TETRAACRYLATE), SR-454 (TRIMETHYLOLPROPANE TRIACRYLATE ETHOXYLATE (3)), SR-9036 (DITRIMETHYLOLPROPANE TETRAACRYLATE (3)), SR-9036 (ETHRIMETHYLOLPROPANE 30 DIMETHACRYLATE) -399 (DIPENTAERITHRITOL PENTAACRYLATE), SR-9016 (METAL DIACRYLATE), SR-351 (TRIMETHYLOLPROPANE TRIAACRYLATE), SR423 (ISOBORNYL METHACRYLATE), CD-550 (METHYLOXYCYPOLYL MONOMETHACRYLATE), 25 METHYL CYPOLYL-3502 (METHYLOXYMACRYLATE MONOMETHACRYLATE) POLYETHYLENE GLYCOL (600)), SR-203 (TETRAHYDROFURFURYL METHACRYLATE) and photoinitiators, such as Darocur-4265 (50% 2-hydroxy-2-methyl-1-phenyl-1-propenone and diphenyl (2,4,6-trimethylbenzoyl) -phosphine (MAPO ) 50% phosphine oxide), Darocur-TPO (diphenyl (2,4,6-trimethylbenzoyl) phosphine (MAPO) phosphine oxide), Irgacure-907 (2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone), Irgacure-369 (Benzyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1 -butanone, Irgacure-184 (1-hydroxy -cyclohexyl-phenyl-ketone), Irgacure-819 (phosphine oxide, phenyl-bis-1- (2,4,6-trimethylbenzoyl) (Ciba, Basel), Speedcure ITX (isopropyl-9Hthioxanthen-9-one, 97%, mixture of isomers 2 and 4 ) (Aldrich, United States).

Preparation procedure

Add monomer and photoinitiators directly to the solvent-based glass ink as previously prepared and mix with a stirrer until the additives are completely dissolved. Slight heating can be used to accelerate dissolution.

A similar ink will be obtained by adding the monomer and photoinitiators to the ink solvent, Dowanol DB and mixing with a stirrer until the additives are completely dissolved. The pigment, frit, cosolvent (TPM or PMA) and dispersant are then added and mixed with Dispermat for 5 min after each material addition. Then add Dowanol DB, which contains the UV additives, and remix with Dispermat (30 min, 9000 rpm).

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The resulting inks were filtered through a 1 micron filter without clogging the filter and without significant change in solids content.

For an initial test, the samples were applied to glass as 5 µl drops and immediately exposed to UV light (Cure spot, Adas Technologies) for 30 seconds, thus causing rapid fixation of the drop on the glass substrate. Final cooking was carried out in an oven at 580-650 ° C for 10 min.

Further tests were performed by injecting the ink at 45 ° C or 55 ° C, a temperature at which the viscosities of the inks were approximately 11 cps. The exact composition and properties of inkjet inks are presented in the following table.

<td>Sample name</td><td>Composition</td><td>% solids</td><td>Viscosity at 45 ⁹C</td>

<td>Sample 9</td><td>Frit JRK617BF - 50.92 g Pigment 2004-12-11 -17.0 g TPM -13.6 g Dowanol DB - 8.16 g Disperbyk-180 - 0.91 g Byk-306 - 0.91 g Irgacure 819 - 1.5 g Irgacure 907 - 0.0375 g Speedcure ITX -1.0 g SR 355 - 6.0 g</td><td> 45,3</td><td> 10,6</td>

<td>Sample 10</td><td>Frit JRK617BF - 44.71 g Pigment 2004-12-11 -14.9 g PMA-5.96g Dowanol DB -19.67 g Bykumen -0.88 g Byk-306N - 0.88 g Irgacure 819-3.0 g Speedcure ITX-2.0g SR 355 - 6.0 g CN 381 - 2.0 g</td><td> 39,8</td><td> 11,1</td>

<td>Sample 11</td><td>Frit TEST 1 -37.61 g Pigment 2004-12-11 - 12.54 g PMA-5.01 g Dowanol DB-16.55g Bykumen - 0.73 g</td><td> 43,0</td><td> 10,6</td>

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<td></td><td>Byk-358N - 0.73 g Irgacure 819 -1.2 g Irgacure 907 - 0.03 g Speedcure ITX - 0.8 g SR 355 - 4.8 g</td><td></td><td></td>

Chemical resistance was tested by immersion in 80 ° C sulfuric acid solutions for 4 hours and NaOH solution overnight and found to be excellent.

The printed droplets were found to be much smaller and to have a higher optical density, while the ink contained the UV additives and UV curing was done immediately after printing.

Fig 1 (a) and Fig 1 (b) show the microscopic images of ink droplets of sample 9 without and with cure and Fig 1 (c) and Fig 1 (d) show microscopic images of ink droplets of the sample without and with cure. As can be seen, all droplet parameters such as smaller spherical spots, defined edges with higher optical density are obtained when the printed design is exposed to UV light just after printing indicative of good substrate fixation were better in UV curable sample, compared to control.