Jet printing ink composition, method of forming printed images and articles printed thereby

Abstract: A jet printing ink composition includes aqueous resin dispersion and an aqueous colourant, and is substantially free of volatile organic compounds. Compositions are provided that form printed images that, without curing, are solvent washable with isopropanol, ethanol, water, and mixtures thereof, and are retortable, without curing. Ink jet compositions capable of forming coloured images capable of being washed with isopropanol, ethanol, water, and mixtures thereof, after curing, are also provided. Finally, jet printing inks capable of withstanding washing with strong organic solvents, such as methylethylketone and methanol, after curing, are also provided.

Description: The present invention relates to a jet printing ink composition, also to a method of forming a printed image and to articles bearing a printed image formed by such ink or by such method. The invention particularly, but not exclusively, relates to a jet printing ink composition that adheres to a non-porous substrate and has reduced levels of volatile organic compounds, and also to a method of forming a printed image on a non-porous substrate. Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the direction of the stream electronically so that the droplets are caused to form the desired printed image on that surface. This technique of non-contact printing is particularly well-suited for application of characters onto irregularly shaped surfaces, including, for example, the bottom of beverage containers. In general, an ink jet composition must meet certain rigid requirements to be useful in ink jet printing operations. These relate to viscosity, resistivity, solubility, compatibility of components and wetability of the substrate. Further, the ink must be quick-drying and smear resistant, must be capable of passing through the ink jet nozzle without clogging, and must permit rapid clean-up of the machine components with minimum effort. Many of the surfaces on which ink jet printing is utilized are non-porous, such as the above-mentioned beverage container. The ink used for these applications must adhere well to the non-porous substrate and normally must be water-resistant. Presently used ink for such applications conventionally contains a resin, a dye, a carrier, and other components. In order to obtain satisfactory adhesion of a water-resistant jet printing ink composition to a non-porous substrate, it has previously been necessary to use an organic solvent as the carrier to dissolve the resin and/or the dye. For example, U.S. Patent No. 4,260,531 discloses a jet printing ink composition comprising a styrene-acrylic copolymer resin, a dye, and a mixture of water and one or more water-miscible C1-C3 alcohols as the diluent. U.S. Patent 4,246,154 discloses an ink jet printing composition comprising an aqueous vinyl polymer suspension which is added to a solution of a hydrophobic dye previously dissolved in an organic solvent. Use of these organic solvents poses toxicity and flammability problems for the ink jet formulator. However, the use of organic solvents is undesirable for an additional reason - they pose an environmental hazard. After the ink has been applied to the substrate, the solvent evaporates, releasing organic compounds into the atmosphere. These volatile organic compounds adversely affect the environment in the atmosphere and are the subject of both federal and state governmental regulations in the USA. Volatile organic compounds are defined as any compound of carbon that evaporates from a paint or coating film under specific test conditions. The amount of volatile organic compounds, present in a given composition in grams per litre of coating, also known as volatile organic content (VOC), can be determined by using the following formula: where W s is the weight of volatile compounds in grams; W w is the weight of water in grams; W es is the weight of exempt compounds in grams; V m is the volume of material in litres; V w is the volume of water in litres; and V es is the volume of exempt compounds in litres. In the above formula, exempt compounds are volatile organic compounds whose use is specifically sanctioned by regulatory agencies. Trichloroethane is an example of an exempt compound. The maximum acceptable level of volatile organic compounds varies for different coating applications. For example, the maximum acceptable level of volatile organic compounds set for the aerospace coatings industry is 340 grams/litre. However, until the present invention, there was no jet printing ink composition that met any of the government standards and still had the qualities necessary for satisfactory use in ink jet printing operations on non-porous substrates. From the foregoing it is clear that a general need exists for a substantially organic solvent-free, jet printing ink composition that adheres to non-porous substrates and is water-resistant, as well as for a jet printing ink composition which poses minimal toxicity and flammability problems, while being easily disposable by the formulator and end user. A specific need also exists for a jet printing ink composition suitable for use in ink jet printing operations on non-porous substrates which has a volatile organic compound level less than 500 grams/litre, preferably less than 340 grams/litre. Although such needs in the art have existed for years, no practical solution has yet been found. Certain specialized application needs also exist which remain unfilled by present-day jet printing ink formulations. In many instances printed images formed from the ink jet printing operation are printed onto substrates which must be sterilized, as through steam sterilization. For such applications, the jet printing ink formulation must be capable of forming printed images that remain substantially unaffected after retorting. Such retortability is especially critical with respect to containers for use in the food industry. Generally, such containers are made of glass or are cans made of tin-free steel ("TFS") or aluminium. In other instances, the substrate with the printed image thereon must be exposed to aqueous and/or non-aqueous solvent washing procedures. For such applications the jet printing ink must be capable of forming printed images that withstand solvents, such as isopropanol, ethanol, water, and mixtures thereof, and in other instances, contact with methylethylketone ("MEK") or methanol. Jet printing ink formulations meeting the aforementioned and other needs have previously not been available, or have been available only in formulations that contain large quantities of volatile solvents. Such needs are now satisfied by the present invention. According to one aspect of the present invention a jet printing ink composition includes a resin and a dye, characterised in that, the resin is an aqueous resin dispersion selected from a group consisting of polyester, styrene-acrylic, aromatic urethane, aliphatic urethane, alkyd, epoxy, vinyl and phenolic resin dispersions, in that the dye is an aqueous colorant, and in that the volatile organic compound level of the composition is less than 500 grams per litre. By utilising an aqueous resin and an aqueous colorant instead of organic solvents, the toxicity, flammability and disposal problems inherent in the use of organic solvents are avoided. More importantly, the ink composition of the present invention complies with the present U.S. government standards for acceptable levels of volatile organic compounds. The aqueous colorant may be a pigment dispersion or a dye. The present invention provides black, ink jet compositions that, directly after application to a non-porous substrate, are retortable and resist solvents such as isopropanol, ethanol,. water and mixtures thereof. The printed images formed from such inks may be heat-cured to render the images also resistant to other organic solvents, such as methanol and MEK. Additionally, the present invention provides coloured ink jet compositions that may be printed onto non-porous substrates and, if additional solvent resistance is desired, the printed images formed from such jet ink compositions may be heat-cured to provide images that resist attack or degradation from contact with isopropanol, ethanol, water and mixture thereof. The jet printing ink compositions of the present invention, in addition to including an aqueous resin dispersion and an aqueous colorant, may also include water, and other optional components in carefully balanced proportions to achieve preferred operation of the ink in an ink jet printing apparatus. In the case where the jet printing ink composition is to be jet printed onto a non-porous surface of glass, or tin-free steel, or aluminium, the aqueous resin dispersion may be an aqueous vinyl resin dispersion or an aqueous phenolic resin dispersion, and the dye may be carbon black. In this case, jet printed images on tin-free steel or on aluminium can be retorted without prior heat curing, and such images on glass, or tin-free steel or aluminium after heat curing can be washed with water, or isopropanol, or ethanol, or mixtures thereof. Such retorting or washing does not cause substantial degradation of the printed images. In the case where the jet printing ink composition is to be jet printed onto a non-porous surface of glass, or tin-free steel, or aluminium, the resin dispersion is preferably an aqueous phenolic resin dispersion, and the dye may be carbon black. In this case, jet printed images can be retorted without prior heat curing, or after heat curing can be washed with methylethylketone or methanol, in either case without causing substantial degradation. In the case where the jet printing ink composition is to be jet printed onto a non-porous surface of glass, or tin-free steel, or aluminium, the aqueous resin dispersion is preferably an aqueous vinyl resin dispersion or an aqueous phenolic resin dispersion, and the dye preferably has a functional group capable of reacting with said vinyl or phenolic resin under elevated temperature conditions to form a covalent bond. In this case coloured printed images can, after prior heat curing, be washed with water, or ethanol, or isopropanol without substantial degradation. In such jet printing ink compositions, the aqueous resin dispersion is preferably present in an amount from about 20% to 60% of the total weight of the composition. Such jet printing ink compositions preferably have a viscosity from about 1.6 to about 7.0 centipoises at 25°C. Such jet printing ink compositions preferably have an electrical resistivity from about 50 to about 2000 ohm-cm. Such jet printing ink compositions preferably have less than 340 grams/litre of volatile organic compounds and desirably there are less than 300 grams/litre of volatile organic compounds. Preferably such jet printing ink compositions are bar code readable. According to another aspect of the present invention an article has a surface on which an image is jet printed using one of the aforesaid jet printing ink compositions. Such article may be formed of tin-free steel or aluminium to have a non-porous surface bearing an image formed by non-contact jet printing with such jet printing ink composition, such image not being heat cured, and the article is capable of being retorted without substantial degradation of the image. Such article may alternatively be formed of glass to have a non-porous surface bearing an image formed by non-contact jet printing with such jet printing ink composition, the image having been heat cured whereby the article is capable of being washed with water, or isopropanol, or ethanol, or mixtures thereof, without substantial degradation of said image. Such article may alternatively be formed of glass, or tin-free steel, or aluminium to have a non-porous surface bearing an image formed by non-contact jet printing with such jet printing ink composition, the image not being heat cured, but the article being capable of being retorted without substantial degradation of the image. Alternatively such article may be formed of glass, or tin-free steel, or aluminium to have a non-porous surface bearing an image formed by non-contact jet printing with such jet printing ink composition, the image having been heat cured, and the article being capable of being washed with methylethylketone or methanol without substantial degradation of the image. Alternatively such article may be formed of glass, or tin-free steel, or aluminium to have a non-porous surface bearing an image formed by non-contact jet printing with such jet printing ink composition, the image having been heat cured, and the article being capable of being washed with water, or ethanol, or isopropanol without substantial degradation of the image. According to a further aspect of the present invention a method of forming a sterilized printed image on a non-porous substrate of tin-free steel, or of aluminium, includes jet printing a jet printing ink composition onto said substrate to form said printed image, said composition including carbon black and an aqueous vinyl resin dispersion or an aqueous phenolic resin dispersion, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, retorting said substrate. Alternatively, a method of forming a sterilized printed image on a glass substrate includes jet printing a jet printing ink composition onto said substrate to form said printed image, said composition including an aqueous phenolic resin dispersion and carbon black, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, retorting said substrate. Alternatively, a method of forming a solvent-washed printed image on a non-porous substrate of glass, or tin-free steel or aluminium, includes jet printing a jet printing ink composition onto said substrate to form said printed image, said composition including carbon black and either an aqueous vinyl resin dispersion or an aqueous phenolic resin dispersion, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, washing the printed substrate with a solvent selected from the group consisting of ethanol, isopropanol, water and mixtures thereof. Alternatively, a method of forming a solvent-washed printed image on a non-porous substrate of glass, or tin-free steel, or aluminium, includes jet printing a jet printing ink composition onto said substrate, to form said printed image, said composition including an aqueous phenolic resin dispersion and carbon black, said composition having a volatile organic compound level of less than 500 grams per litre, heat curing said printed substrate and subsequently washing the printed substrate with a solvent selected from the group consisting of methylethylketone and methanol. Alternatively, a method of forming a solvent-washed printed image on a non-porous substrate of glass, or tin-free steel, or aluminium, includes jet printing a jet printing ink composition onto said substrate to form said printed image, said composition including an aqueous vinyl resin dispersion or an aqueous phenolic resin dispersion, and a dye having a functional group capable of reacting with said vinyl or phenolic resin under elevated temperature conditions to form a covalent bond, said composition having a volatile organic compound level of less than 500 grams per litre, heat curing said printed substrate and subsequently washing the printed substrate with a solvent selected from the group consisting of ethanol, isopropanol, water and mixtures thereof. In this manner a coloured image can be jet printed onto the substrate. In general, the jet printing ink compositions of the present invention exhibit the following characteristics: (1) a viscosity from about 1.6 to about 7.0 centipoises at 25°C; (2) an electrical resistivity from about 50 to about 2000 ohm-cm; and (3) a sonic velocity from about 1200 to about 1300 meters/second. Such jet printing inks dry within about 4-6 seconds, with good adhesion when printed on non-porous substrates, such as bare tinplate, aluminium, polymeric-coated tin or aluminium, or polymeric-coated tin cans, TFS, glass, or aluminium. The jet printing ink compositions of the present invention may also be used for graphic applications on porous substrates such as paper, glossy paper, Tyvek envelopes, corrugated cardboard and other graphic paper products. Additionally, where carbon black is used as the colorant, the ink composition of the present invention can be used to print bar codes that can be scanned visually or by infrared (IR) spectroscopy. The jet printing ink compositions of the present invention are substantially free of volatile organic compounds. To be substantially free of volatile organic compounds, the ink composition should be formulated so that it has a volatile organic compound level (VOC) of less than 500 grams/litre. Preferably, the ink compositions of the present invention have a volatile organic compound level of less than 340 grams/litre, with a volatile organic compound level of 300 grams/litre or less being most preferred. Suitable aqueous resin dispersions for use in the ink compositions of the present invention must meet certain requirements. The resin particles in the dispersion should be uniform in size, with a particle size from about 0.01 to about 1.0 microns. The dispersion should also be stable. Dispersion properties should remain constant at temperatures up to about 49°C, and the dispersion should not show any sedimentation for at least 18 months. There should additionally be no agglomeration of resin particles in the dispersion. The invention will now be further described, by way of example only, with reference to various examples:- The type of aqueous dispersion used depends on the specific needs of the end user. Examples of suitable aqueous resin dispersions are polyester resin dispersions (commercially available as 72-7230 from Cargill Inc.,), styrene-acrylic dispersions (commercially available as Acrysol WS-68 from Rohm & Haas), aromatic urethane dispersions (commercially available as Spensol L-44 from Reichold Chemicals, Inc.), aliphatic urethane dispersions (commercially available as Spensol L-52 from Reichold Chemicals, Inc.), alkyl dispersions (commercially available as Arolon 585 from NL Chemicals Co.), epoxy resin dispersions (available as CMD 35201 from Hi-Tek Polymers, Inc.), vinyl dispersions (commercially available as UCAR AW-875) or phenolic dispersions (commercially available as UCAR BRUA-2370). This list is not exhaustive; other aqueous resin dispersions not specifically mentioned above may also be used depending on the nature of the ink jet printing application. In general, these aqueous resin dispersions are present in the ink composition in an amount from about 20% to 60% by weight of the composition. Suitable aqueous colourants for use in the present invention include both pigment dispersions and dyes. These colourants, which are added directly to the aqueous resin dispersion, may or may not be water-resistant, depending upon the desired application. The aqueous colourants used in the present invention are used directly, without the need for incorporation into polymeric resin particles, as is necessary with the compositions of U.S. Patent No. 4,246,154. As already indicated, one of the water-resistant colourants useful in the present invention is carbon black, which is commercially available in a pigment dispersion as Black Acroverse Dispersion = 32B32D from Penn Color. When immediate solvent resistance is desired, the carbon black may be used in combination with a vinyl or phenolic water-dispersed resin. When printed onto non-porous substrates such as glass, aluminium, and TFS, such inks do not require curing to afford resistance to solvents such as isopropanol, ethanol, water, and mixtures thereof. Further, if carbon black is used as the colourant and a phenolic water-dispersed resin is employed as the resin, after curing, the printed images are resistant to strong organic solvents such as methanol and MEK. Curing of the carbon black/phenolic resin-type of ink composition may be accomplished under non-critical curing conditions. Typically, curing temperatures will be from about 100°C to about 150°C, preferably from about 125°C to about 150°C, and curing times will be from about 15 seconds to about 60 seconds, preferably from about 30 seconds to about 60 seconds. A general cure condition is about one minute at about 150°C. Examples of other water-resistant colourants useful in the present invention are those pigments listed in Table 1 below. If the jet printing ink composition need not be water resistant, virtually any acidic or basic aqueous dye can be utilized. Examples of dyes include those listed in Table 2 below. Further, when the ink compositions are to be used for applications that require coloured images that are resistant to solvents such as isopropanol, methanol, water and mixtures thereof, the dyes should contain functional groups that are capable of forming a covalent bond with the resin. For example, hydroxyl groups that are present in dyes containing a polyol moiety, are capable of reacting with resin that also contain functional groups, when subjected to heat-curing. Representative dyes for such applications include the following: Representative resins for use in forming a covalent bond or linkage with the functional group-containing dyes include vinyl resins and phenolic resins. Thus, when solvent resistance of the final printed image is desired, a combination of a dye having a reactive functional group and a resin containing a functional group capable of reacting, under elevated temperature conditions, with the functional group of the dye is required. There then is formed a covalent bond between the dye and the resin, after the ink is used to print an image on the desired substrate and the substrate is then subjected to heat curing. Suitable aqueous vinyl resin dispersions include those disclosed in U.S. Patent Nos. 4,415,698; 4,202,808, and 3,862,076, all of which are hereby incorporated by reference, and those aqueous vinyl resin dispersions marketed by Union Carbide Corporation under the trademark UCAR AW-875 and other members of that series. Suitable aqueous phenolic resin dispersions include those disclosed in U.S. Patent Nos. 4,788,236; 4,420,571; 4,366,303; 4,206,095; 4,124,554; 4,039,525; and 4,026,848, all of which are hereby incorporated by reference, and those aqueous vinyl resin dispersions marketed by Union Carbide Corporation under the trademark UCAR BKUA-2370 and other members of that series. The temperature at which the heat curing occurs is not critical, nor is the time of curing. Obviously, the length of the cure time will vary with the cure temperature. The only requirement is that the curing conditions be such that the covalent bond is formed between the dye and the resin, without substantially degrading the components of the ink jet composition. Typically, curing temperatures will be from about 100°C to about 150°C, preferably from about 145°C to about 160°C, and curing times will be from about 15 seconds to about 60 seconds, preferably from about 30 seconds to about 60 seconds. A general cure condition is about one minute at about 150°C. In general, if an aqueous pigment dispersion is used, the dispersion should be present in the ink composition in an amount from about 5% to about 20% by weight of the composition. If an aqueous dye is used, it should be present in an amount from about 2% to about 5% by weight of the ink composition. Water is used as the carrier for the aqueous resin dispersion and the aqueous colourant in the ink compositions of the present invention. Typically, water is present in an amount from about 40% to about 80% by weight of the ink composition. Other components may also be included in the ink compositions of the present invention to impart characteristics desirable for ink jet printing applications. These components include defoamers, which improve processing and printer performance. Suitable defoamers include acetylenic diols (commercially available as Surfynol 104 from Air Products and Chemicals, Inc.) and butanol. Small amounts of organic solvents may also be added to improve drying time and reduce surface tension. Suitable solvents include n-methyl-2-pyrrolidone and butanol. It also may be desirable to add humectants, such as ethylene glycol or propylene glycol methyl ether, to prevent the ink jet tip from drying. Electrolytes can be added to adjust the specific resistivity of the ink. Usable electrolytes include dimethylamine hydrochloride and hydroxylamine hydrochloride. Finally, crosslinking resins, such as melamine resins, may be added to cross link with other polymers to give improved adhesion and increased solvent resistance. The following examples are illustrative of ink compositions of the present invention. Example I The following composition was formulated: The resulting ink composition had a viscosity of 3.0 cps, a resistivity of 190 ohm-cm, and adhered well to non-porous substrates such as tin plate, glass and plastics. The level of volatile organic compounds present in the ink composition was 289 grams/litre. Example II The following composition was formulated: The resulting ink composition had a viscosity of 3.0 cps, a resistivity of 194 ohm-cm, and adhered well to metal. The level of volatile organic compounds present in the ink composition was 348 grams/litre. Example III The following composition was formulated: The resulting ink composition had a viscosity of 3.43 cps, a resistivity of 192 ohm-cm, and adhered well to metal. The level of volatile organic compounds present in the ink composition was 202.7 grams/litre. Example IV The following composition was formulated: The resulting ink composition had a viscosity of 5.0 cps, a resistivity of 204 ohm-cm, and adhered well to metal. The level of volatile organic compounds present in the ink composition was 323 grams/litre. Example V The following composition was formulated: The resulting jet ink had a viscosity of 3.56 cps, a resistivity of 348 ohm-cm, and adhered well to metal. The level of volatile organic compounds present in the ink composition was 223.6 grams/litre. Example VI The following ink jet composition capable of producing solvent-resistant images, without curing, was formulated: The ink of this composition is found to form ink jet printed images on TFS, aluminium and glass, that, without curing, resist solvent rubs with water, isopropanol, or ethanol. Further, it is found that the printed images made through the ink jet printing of the ink composition of this invention onto TFS and aluminium, without heat curing, are capable of resisting retorting. Example VII The following ink jet composition, capable of producing solvent-resistant images, with curing, was formulated: The ink of this composition is found to form printed images that, without curing, resist solvent rubs with water, isopropanol, or ethanol. It is also found that the printed images made through the ink jet printing of the ink composition of this invention onto glass, as well as onto TFS and aluminium, without heat curing, are capable of resisting retorting. Further, it is found that the printed images made the invention onto TFS, aluminium and glass, after curing at 150°C, for not more than one minute, are capable of resisting methanol and MEK. Examples VIII - XVI Ink jet formulations capable of producing solvent-resistant coloured images, after curing, having the compositions set forth in Table I, were formulated. It is found that the printed images made through the ink jet printing of the ink composition of this invention onto TFS, aluminium and glass, after curing at 150°C, for not more than one minute, are capable of resisting water, isopropanol and ethanol.

Claims: A jet printing ink composition including a resin and a dye, characterised in that, the resin is an aqueous resin dispersion selected from a group consisting of polyester, styrene-acrylic, aromatic urethan, aliphatic urethan, alkyd, epoxy, vinyl and phenolic resin dispersions, in that the dye is an aqueous colorant, and in that the volatile organic compound level of the composition is less than 500 grams per litre. A jet printing ink composition as in Claim 1, characterised in that, the aqueous colorant is from a group comprising pigment dispersions and dyes. A jet printing ink composition as in Claim 1 suitable for ink jet printing onto a non-porous surface selected from the group consisting of glass, tin-free steel and aluminium, characterised in that, said aqueous resin dispersion is selected from the group consisting of aqueous vinyl resin dispersions and aqueous phenolic resin dispersions, and said dye is carbon black. A jet printing ink composition as in Claim 1 suitable for ink jet printing onto a non-porous surface selected from the group consisting of glass, tin-free steel and aluminium, characterised in that, said aqueous resin dispersion is an aqueous phenolic resin dispersion, and said dye is carbon black. A jet printing ink composition as in Claim 1 suitable for ink jet printing onto a non-porous surface selected from the group consisting of glass, tin-free steel and aluminium, characterised in that, said aqueous resin dispersion is selected from the group consisting of aqueous vinyl resin dispersions and aqueous phenolic resin dispersions, and said dye has a functional group capable of reacting with said vinyl or phenolic resin under elevated temperature conditions to form a covalent bond. A jet printing ink composition as in any of Claims 1 to 5, characterised in that, the aqueous resin dispersion is present in an amount from 20 percent to 60 percent of the total weight of the composition. A jet printing ink composition as in any of Claims 1 to 6, characterised in that, it has a viscosity from 1.6 to 7.0 centipoises at 25°C and an electrical resistivity from 50 to 2000 ohm-cm. A jet printing ink composition as in any of Claims 1 to 7, characterised in that, there are less than 340 grams/litre of volatile organic compounds. A jet printing ink composition as in Claim 8, characterised in that, there are less than 300 grams/litre of volatile organic compounds. A jet printing ink composition as in any preceding claim, characterised in that, it is bar code readable. An article formed of tin-free steel or aluminium having a non-porous surface bearing an image formed by non-contact jet printing with a jet printing ink composition, characterised in that, said image is formed from a jet printing ink composition as in any of Claims 3 to 10 and has not been heat cured, and said article is capable of being retorted without substantial degradation of said image. An article formed of glass having a non-porous surface bearing an image formed by non-contact jet printing with a jet printing ink composition, characterised in that, said image is formed from a jet printing ink composition as in any of Claims 3 to 10 and has been heat cured, and said article is capable of being washed with at least one substance from the group comprising water, isopropanol, ethanol, and mixtures thereof, without substantial degradation of said image. An article formed of glass, tin-free steel or aluminium having a non-porous surface bearing an image formed by non-contact jet printing with a jet printing ink composition, characterised in that, said image is formed from a jet printing ink composition as in any of Claims 4 to 10 and has not been heat cured, and said article is capable of being retorted without substantial degradation of said image. An article formed of glass, tin-free steel or aluminium having a non-porous surface bearing an image formed by non-contact jet printing with a jet printing ink composition, characterised in that, said image is formed from a jet printing ink composition as in any of Claims 4 to 10 and has been heat cured, and said article is capable of being washed with at least one substance from the group comprising methylethylketon and methanol without substantial degradation of said image. An article formed of glass, tin-free steel or aluminium having a non-porous surface bearing an image formed by non-contact jet printing with a jet printing ink composition, characterised in that, said image is formed from a jet printing ink composition as in any of Claims 5 to 10 and has been heat cured, and said article is capable of being washed with at least one substance from the group comprising water, ethanol and isopropanol without substantial degradation of said image. A method of forming a sterilized printed image on a non-porous substrate selected from the group consisting of tin-free steel and aluminium including jet printing a jet printing ink composition onto said substrate to form said printed image, characterised in that, said composition includes carbon black and an aqueous resin dispersion selected from the group consisting of aqueous vinyl resin dispersions and aqueous phenolic resin dispersions, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, retorting said substrate. A method of forming a sterilized printed image on a glass substrate including jet printing a jet printing ink composition onto said substrate to form said printed image, characterised in that, said composition includes an aqueous phenolic resin dispersion and carbon black, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, retorting said substrate. A method of forming a solvent-washed printed image on a non-porous substrate selected from the group consisting of glass, tin-free steel and aluminium including jet printing a jet printing ink composition onto said substrate to form said printed image, characterised in that, said composition includes carbon black and an aqueous resin dispersion selected from the group consisting of aqueous vinyl resin dispersions and aqueous phenolic resin dispersions, said composition having a volatile organic compound level of less than 500 grams per litre and, without prior heat curing, washing the printed substrate with a solvent selected from the group consisting of ethanol, isopropanol, water and mixtures thereof. A method of forming a solvent-washed printed image on a non-porous substrate selected from the group consisting of glass, tin-free steel and aluminium including jet printing a jet printing ink composition onto said substrate to form said printed image, characterised in that, said composition includes an aqueous phenolic resin dispersion and carbon black, said composition having a volatile organic compound level of less than 500 grams per litre, heat curing said printed substrate and subsequently washing the printed substrate with a solvent selected from the group consisting of methylethylketone and methanol. A method of forming a solvent-washed printed image on a non-porous substrate selected from the group consisting of glass, tin-free steel and aluminium including jet printing a jet printing ink composition onto said substrate to form said printed image, characterised in that, said composition includes an aqueous resin dispersion selected from the group consisting of aqueous vinyl resin dispersions and aqueous phenolic resin dispersions, and a dye having a functional group capable of reacting with said vinyl or phenolic resin under elevated temperature conditions to form a covalent bond, said composition having a volatile organic compound level of less than 500 grams per litre, heat curing said printed substrate and subsequently washing the printed substrate with a solvent selected from the group consisting of ethanol, isopropanol, water and mixtures thereof. An article comprising a non-porous substrate having a printed image formed by the method of any of Claims 16 to 20.

Inventors: LENT BRUCE A, LORIA ADRIAN M, LENT, BRUCE A., LORIA, ADRIAN M.
Applicants: VIDEOJET SYSTEMS INT, VIDEOJET SYSTEMS INTERNATIONAL, INC.
Application year: 1991
Main classification: C09D11
IPC codes: C09D11