Patent Application
20130075296
This invention relates to containers, and more particularly to marking components of metal cans.
Two piece metal cans include a can body on which a can end is attached by a seam. Commercial two piece beverage cans are formed by a drawing and ironing process that forms the body sidewall integral with the base. Three piece metal cans include a cylindrical body, each end of which has a can end attached by a seam.
Two piece beverage cans are produced in vast quantities for beverages and foods use; three piece beverage cans are produced in vast quantities for food uses. Accordingly, the components of the cans must be produced at high speeds.
Conventional beverage cans and many easy open food cans have pull tabs. Pull tabs are formed from metal sheet in a tab press. Because of the quantities required, conventional tab presses form many tabs at once in several lanes.
Typically, pre-lacquered coil of aluminum is fed into a shell press to form the can end shells. A pre-lacquered coil of aluminum is fed into a tab press to form the pull tabs. The shells and pull tabs are combined in a conversion press to form the unseamed can end.
Decoration of can ends, especially pull tabs, is known. For example, U.S. Pat. No. 6,105,806 discloses laser etching or removal of portions of a coating on a pull tab. U.S. Pat. No. 6,498,318 acknowledges difficulties in marking metal cans and discloses ablating metal pull tab stock.
The inventors are aware of a commercial, conventional system for laser etching pull tabs that includes a CO2 laser that often operates at about 100 W. Each lane of a tab press has its own laser such that the tab press can operate at about 700 tabs per minute with a laser having a resolution or dimension of approximately 100 microns. Typically, a dark coloured lacquer is removed by the laser to expose bare aluminum in the form of a simple logo or a few characters. The limitation on the process speed is also a limitation on the amount of decoration.
Laser marking of coatings is employed for flexible and card packaging for various marking applications. Typically, a thermally active pigment is loaded into a transparent or light colored lacquer, and a CO2 laser induces a color change. For example, a laser may be applied to a white lacquer label to display black text. Laser marking systems of this type are available from Sun Chemical, under the trade name Sunlase and employ a 100 micron YAG laser.
A process for high speed, high resolution decoration by laser marking for can ends, especially can end center panels, can end chuck walls, and can pull tabs, is provided. The can ends and pull tabs resulting from the process are also provided.
The method of decorating can ends comprises the steps of: providing a can end substrate, such as a can end center panel, chuck wall, and/or pull tab, of a metal material, such as aluminum, or in some cases steel; coating at least a portion of the can end substrate with a lacquer that includes a photonically active component; and applying a laser to the coated substrate to change an appearance of at least a portion of the photonically active component substantially without burning, etching, or ablating the lacquer, thereby forming an image.
Preferably the photonically active component includes a thermally active pigment. Preferably the change in appearance is a change in color, such as from transparent or light color to an opaque or darker color.
Preferably, a CO2 laser is employed that has a beam width that is less than approximately 50 microns, more preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and preferably approximately 5 microns. Accordingly the image may be formed by dots that have a dimension of less than approximately 50 microns, preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and preferably approximately 5 microns. Accordingly the image may be formed by dots that have a dimension of less than approximately 50 microns.
The inventors contemplate that the laser marking process may be applied to end stock or tab stock coil, applied to the tabs after the tab press before the conversion press, applied to the end shells after the shell press before the conversion press, or after the conversion press to the unseamed can end.
The inventors surmise that the decorated ends may be suitable for withstanding pasteurization at up to 75 C for 20 minutes, such as may be encountered by beverage can ends after seaming. Also, the inventors surmise that the decorated ends may be suitable for withstanding retort temperatures of up to 131 C for 90 minutes, such as may be encountered by food can ends after seaming. Accordingly, the inventive method includes the pasteurization or retort steps.
A decorated can end comprises: an end shell and a pull tab, each one of the end shell and the pull tab comprising preferably aluminium, but also possibly steel, and a coating, the coating comprising a lacquer and a photonically active component; and an image applied to at least one of a center panel of the end shell, a topside of a pull tab, and an underside of the pull tab, the image formed by application of a laser that changes an appearance of at least a portion of the photonically active component substantially without burning, etching, or ablating the lacquer.
Preferably, the image is a color that is darker than the lacquer. Also preferably, the image may be formed by dots, and the dots have a dimension of less than approximately 50 microns, preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and preferably approximately 5 microns.
Also, a decorated can end is provided that has machine readable codes, such a matrix barcode, which encompasses two dimensional codes, such as QR codes, Data Matrix codes, the inverses of QR codes and Data Matrix codes, and the like. The description employs a QR code for illustration purposes only.
The end has (i) an unopened configuration in which the end is sealed and (ii) an opened configuration in which the beverage contents of the can are accessible. The can end comprises an end shell and a pull tab. The pull tab has an orientation that is approximately parallel to a center panel of the end shell in the unopened configuration, and is capable of being actuated to a part vertical position by lifting an end of the pull tab to rupture a score on the center panel and thereby achieve the opened configuration. Preferably the can end is an aluminum beverage can end. Ends of other materials or uses may also be employed, such as aluminum or steel ends for food cans. The term “part vertical” is used to describe the position of the pull tab at which rupture and opening of the pour opening panel of a beverage end occurs. When used with food can ends, it is the position of the pull tab at which opening of the relevant portion of the panel occurs.
The plural images, such as QR codes distributed about a rivet that couples the tab to the center panel, are located on a center panel of the end shell, each one of the images being machine-readable. The plural images are located on the center panel such that the pull tab obscures a portion of each one of the images regardless of the rotational position of the pull tab. Thus, none of the plural images are readable when the beverage can is in its unopened configuration. Then, at least one of the images is fully exposed, intact, and capable of being read by a machine upon the tab being actuated to its part vertical position, even if the tear panel of the end is displaced.
The images may be formed from ink jet printing, and the end may be aluminum or steel. The images also may be formed by application of a laser that changes an appearance of at least a portion of a photonically active component substantially without burning, etching, or ablating the lacquer.
A method of providing information on a can end described above is also provided. The method comprises the steps of: providing a metal beverage can end including: an end shell, a pull tab, and plural images located on a center panel of the end shell, each one of the images being machine-readable, the plural images being located on the center panel such that the pull tab obscures a portion of each one of the images regardless of the rotational position of the pull tab such that none of the plural images are readable; and lifting an end of the pull tab until the pull tab is part vertical to rupture a score on the center panel, whereby in the part vertical position at least one of the images is fully exposed, intact, and capable of being read by a machine. The step of reading the image is performed with a machine while the tab is in a part vertical position.
Preferably, the machine that reads the information formed by the photonically sensitive ink is a handheld wireless communication device, which is intended to mean a smart phone of the type operated by a ubiquitous, common users (in other words, a “smartphone,” such as an iphone or android phone, equipped with a camera and the ability to download applications), as distinguished from the type of industrial readers of one dimensional or two dimensional bar code readers that are employed for manufacturing or inventory purposes in an industrial or retail environment.
The preferred marking system employs a conventional lacquer to which a photonically active component, such as a pigment, colorant, dye, or ink or like compound commercially available from Datalase, is added. A laser causes local change in the appearance—that is, visual perceptible attributes—of the photonically active component and/or lacquer. The inventors contemplate several possible arrangements or embodiments in which the laser may be applied to the photonically active components to create a color change, and thereby to form an image.
The inventors surmise that images may be formed by laser markings applied to food or beverage ends or food or beverage can pull tabs. The images broadly encompass decorations, such as logos, pictures, or aesthetically pleasing marks, or information, such as text or QR codes.
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A description of the location of the application of the laser marking process in the end or pull tab manufacturing process is provided below, followed by a description of the preferred type of laser and a description of the photonically sensitive components that the inventors surmise may be employed.
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Preferably, a CO2 laser having a characteristic dimension or beam width of less than 50 microns, more preferably less than 30 microns, more preferably less than 10 microns, and preferably approximately 5 microns. A CO2 laser of this type may be employed with the photonically sensitive components commercially supplied by Datalase.
The inventors contemplate using photonically active component in the lacquer of the can end and/or pull tab that changes appearance when irradiated by a laser, preferably a CO2 infra-red laser or a near infra-red laser, to create monochrome black or colored laser images. As used herein, the phrase “photonically active component” encompasses pigments or like compositions that are capable of changing appearance upon application of a laser. In other words, when a laser strikes the material that includes the photonically active component, the photonically active component causes a change in appearance in the component or the lacquer in a way that is visually perceptible. Below are examples of photonically active component technology that the inventors surmise may be employed in the present marking systems, methods, and products.
Various pigments have been proposed to enable marking upon application of a laser. For example, a plastics moulding composition comprising a polyoxymethylene and animal charcoal is disclosed in patent applications WO-A-00/43456, JP-A-11001065, EP-A0522370, EP-A-0797511, and U.S. Pat. Nos. 5,053,440 and 5,350,792. A copper hydroxy phosphate for laser marking is disclosed in U.S. Pat. Nos. 5,928,780, 6,017,972 and 6,019,831. U.S. Pat. Nos. 5,489,639 and 5,884,079 disclose additional useful compounds.
U.S. Pat. No. 7,485,403 discloses oxyanions of a multivalent metal, especially Ammonium octamolybdate, having the formula (NH4)4Mo8O26 (“AOM”), in combination with polymer binders, such as those having a labile group, absorb at the wavelength of CO2 laser light (10,600 nm) and undergo a color change due to a change in oxidation state. The combination is not the temperatures typically encountered in pasteurization.
Also, several compositions have been disclosed that change color or otherwise produce a change in visual appearance upon application of a NIR laser. For example, WO05/068207 discloses the use of NIR laser radiation (i.e. at 800 to 2000 nm) to initiate a color change reaction when a NIR-absorbing metal salt is used in combination with a substance that normally undergoes a color change reaction at much longer wavelength (˜10,600 nm), for example AOM. Several metal salts are described; including salts are of copper, such as copper hydroxy phosphate.
JP8127670 discloses the use of reduced titanium oxide compounds for incorporation into thermoplastics, for the laser marking
U.S. Pat. No. 5,578,120 describes the use of a laser beam-absorbing inorganic substance and a colorant. Examples of the colorants that can be used include those mentioned in JP-A-49-82340, including zinc oxide semiconductors and titanium dioxide semiconductors.
U.S. Pat. No. 5,911,921 discloses the use of non-stoichiometric ytterbium phosphate to produce NIR absorbing inks, such as for printing stealth bar codes.
United States Patent Application Number US20100015558A1 discloses a non-stoichiometric compound such as r-ITO, e.g. in the form of a nanopowder, as an absorber of near infra-red radiation in the region 900 to 2500 nm to create a contrasting image when incorporated in, for example, an AOM-based ink formulation and subjected to laser radiation in the near infrared region of the electromagnetic spectrum (780 to 2500 nm). A metal salt as a functional IR-absorber/color developer material which, on absorption of radiation from a laser source, can directly produce a color-forming reaction when in combination with a component that will otherwise undergo the desired reaction on irradiation at a higher wavelength. For example, it can be used in combination with an oxymetal anion component in an applied coating, to generate a distinct colored image. Alternatively, a color-forming component is used, to generate a distinct image. A fibre, diode, diode array or CO2 laser for imaging applications may be used.
U.S. Pat. No. 6,602,595 discloses the use of non-stoichiometric nano-materials for use in inks, such as r-ITO (reduced indium tin oxide), which acts as an NIR absorber.
WO2009093028A2 discloses a compound that will undergo a color change upon irradiation. The compound has the general structure: X—C≡C—C≡C—Y—(CO)n—QZ wherein X is H, alkyl or —Y—(CO) n—QW; each Y is the same or a different divalent alkylene group; Q is O, S or NR; R is H or alkyl; W is H, alkyl or Z; each Z is the same or a different unsaturated alkyl group; and each n is 0 or 1.
EP1365923B2 discloses laser marking an object that includes a material including a functional group and a metal compound or acid that causes an elimination reaction on irradiation with a laser, to form a reaction product of contrasting color The process comprises directing a laser beam on to the areas of the object to be marked. For example, by using a carbohydrate and a metal salt, effective marking can be achieved on the coating of a pill or other edible material. The inventors surmise that these compositions may be used on a can end.
United States Patent Application Number US20090117353A1 discloses a method for marking a substrate by coating the substrate with a white or colorless solution of a soluble alkali or alkaline earth metal salt of a weak acid, and then irradiating areas of the substrate to be marked such that those areas change color. The substrate typically comprises a polysaccharide material, preferably a cellulosic material such as cellulose, and the inventors surmise that this process can be employed on a metal substrate such as a can end and/or pull tab. As used herein, the claimed step of applying a laser to the coated substrate encompasses the change in color described in this paragraph.
Preferably, the image produced by the above process produces a dot having a diameter or other characteristic dimension (such as width if the laser marking is producing a line) of no more than approximately 50 microns, preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and most preferably approximately 5 microns. It is understood a dot formed as described herein may merge with an adjacent dot. Accordingly, the dot diameter or characteristic dimension may be measured upon initial formation or at other convenient time.
The phrase “substantially without burning, etching, or ablating the lacquer” does not require no loss of matter. The inventors surmise that a light mist coming from the laser beam application when applied in flexible patent applications, in fact, indicates outgassing, loss of volatile matter, or other loss of matter. The present invention encompasses some loss of matter during the application of the laser so long as it does not constitute burning, etching, or ablating, as those terms are commonly understood.
This claims the benefit of U.S. patent application Ser. No. 61/539,784 filed Sep. 27, 2011, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.
| Number | Date | Country | |
|---|---|---|---|
| 61539784 | Sep 2011 | US |
