MXPA99010579A - Archival imaging and method therefor - Google Patents

Abstract

An archival medium, such as a compact disc, is made of a metal such as aluminum which is mechanically roughened and visibly imageable by selective exposure to infrared laser radiation. A mechanically roughened aluminum medium can also be anodically oxidized under conditions that do not impair the ability of the substrate to be laser imaged. The archival medium can be coated with opaque and transparent polymer coatings before or after imaging for security and/or protection. The coating can be a laser ablatable coating to provide a tamper-proof medium.

Description

FORMATION OF IMAGES FOR ARCHIVING AND METHOD FOR THE SAME DESCRIPTION OF THE INVENTION This is a continuation in part of the co-pending application with Serial No. 09 / 038,672 filed on March 11, 1998, which is a continuation in part of the 09 / 019,830 filed on February 6, 1998 which is a continuation in part of the co-pending provisional application with Serial No. 60 / 047,446 filed on May 22, 1997, all of which are incorporated herein by reference. This invention relates to the formation of images for archiving on metal substrates such as aluminum and method for producing the same. The invention can be used for security or for credit cards that incorporate such a substrate. For a long time there has been a need for permanent storage of both analog and digital data. The storage of electronic data on tapes and discs is subject to deterioration over time and can not be reliable for long-term archival storage. The present invention provides a laser imaging storage medium that is completely inorganic, does not corrode, is resistant to abrasion, can not be easily disturbed once the image has been formed and is not affected by heat until 500 ° F or ultraviolet light. According to the present invention, the metal substrate is treated in such a way that visible images on the surface can be formed by selective writing with an infrared laser. A preferred treatment for this purpose is rotary brush granulation. The phrase "rotating brush granulation" is intended to refer to any process that utilizes axially rotating brushes that tangentially contact one. surface that will be granulated in the presence of a suspension containing particulate material such as alumina, silica and the like. The phrase also includes equivalent processes that produce the same result. The rotating brush granulation allows the substrate to absorb the incident infrared laser radiation and thus create an image on the substrate. The preferred metal substrate is aluminum. In an alternative embodiment, the aluminum can be anodized after the rotary brush granulation. To provide a counterfeit-proof product, the image is first formed on the substrate with the desired data with an infrared laser and then coated with a wear coating. Any attempt to re-form the image on the substrate or alter the image will wear away the coating and the region where the image was re-formed will be obvious. This image is indelible in the sense that the reformation of images is not possible. BRIEF DESCRIPTION OF THE DRAWINGS. Figures 1A-C are SEMS of the 1P surfaces, 2P and 3P at a magnification of 100,000X. It has been found that sufficient treatment of a metal substrate by rotary brush granulation produces a surface on which visible images can be formed by selective exposure to infrared laser radiation. The amount of rotating brush granulation required to impart the ability to image by the infrared laser can be determined empirically. For example, three samples were prepared representing different degrees of granulation by rotating brush. The same granulation unit brush and brushes were used for each sample. The brush granulation station contained 8 brushes, each 14 inches in diameter. The brush filaments will be 2-inch long nylon. The brushes were rotated axially at 750 rpm.The suspension contained 33% unmelted laminar alumina. " An aluminum net was passed through the brush granulation unit at a speed of 80 feet per minute. A sample was removed and identified as 1P (one pass). The already grained web was passed through the brush granulation unit at the same speed of 80 feet per minute a second time. The sample was removed and identified as 2P (two passes). The granulated aluminum net 2 times was stopped once more through the brush granulation unit at the same speed with a third time. The final sample was removed and identified as 3P (three passes). FIGURES 6A-C are SEMs of the 1P surfaces, 2P and 3P to a 100,000X application. The three plate samples were subjected to laser imaging in a Gerber Crescent 42T Plate Image Setter manufactured by Gerber Scientific of South Winson, Connecticut. The conditions for forming images were the same for each sample. Sample 1P had an image that was barely visible. In the sample 2P had a slightly more visible image, but the contrast was still somewhat weak. The 3P sample had a strong lived image. Although the three samples were found to have similar topographies as characterized by stylus profiling and roughness measurement techniques, the ability to image by the laser is significantly different for the samples. Since it is not limited by any particular theory, it seems that the extensive embedding of particles during the granulation process provides a unique character of the surface on which images are formed. Rotary brush granulation results in a surface where multiple particles (eg calcined alumina) are embedded within the surface of the sheet, with most being covered by a metal film as a result of extensive erosion. The particles have a low thermal conductivity in relation to the metal. In this way, hard particles (relative to the metal substrate) low thermal conductivity, especially hard metal oxide particles, are preferred for use in the present invention. These particles embedded within the metal matrix perform a very sinuous path and thus less efficient for heat dissipation. The energy captured on the surface can not be transferred efficiently to the substrate by means of the thin transversal cuts • by which the thermal continuity to the volume of the metal sheet of the substrate is maintained. This results in a temperature increase on the surface of the granulated metal sheet which is efficient to cause a certain amount of localized melting of the aluminum on the surface. Since it has been demonstrated that rotary brush granulation is an efficient method to produce these surfaces, other equivalent methods such as high pressure lamination, blasting blasting, pelletizing, or the like, which produce a surface of Metal with a relatively high degree of embedded particulate material can also be used. Not all granulation methods are suitable to produce a surface on which images can be formed with an infrared laser. For example, granulation techniques that do not imbibe particles such as chemical or electrochemical granulation, known to produce adequate lithographic surfaces, do not produce a surface on which images can be formed by an infrared laser. However, these techniques can be used for special purposes while the substrate is subsequently granulated by rotating brush. Rotary brush granulation typically increases the roughness of the surface. However, the present invention does not require that the roughness of the substrate be increased to be able to image by laser. For example, it is possible to etch or electrochemically granulate a substrate to produce a coarse rough surface, in which laser images can not be formed. Rotary brush granulation as described herein will provide a substrate in which laser images can be formed and can also reduce the roughness of the surface as measured, for example, by a stylet-like profiling instrument. Likewise, the jet with very fine particles can reduce the roughness of the surface of a substrate having a coarser initial topography. The present invention requires a treatment which provides a substrate, in which images can be formed with an infrared laser, but that the roughness of the surface may be increased or decreased as a result of rotating brush granulation or an equivalent treatment as described herein. - Subsequent to the brush granulation process, treatment with hard chemicals can cause the surface to lose its ability to form laser images. For example, recording with sodium hydroxide, as described in US Pat. No. 4,731,317, alters the surface in such a way that no images can be formed. Additionally, excessive anodization in electrolytes such as sulfuric acid or phosphoric acid can alter the surface in such a way that images can not be formed. It is believed that these types of treatment remove the embedded particles and thus alter the efficiency with which thermal energy is conducted from the substrate into the substrate sheet. It is possible to anodize the granulated surface by brush and retain the ability to form images on the surface with infrared lasers at 1064 nm. Anodization in sulfuric acid at low temperatures with relatively low oxide coating weights is effective to produce a surface on which laser images can be formed. Although aluminum is the preferred substrate, other metals can be granulated with a rotating brush according to the present invention, can be coated with a wear-resistant coating, and can be imaged selectively with an infrared laser in such a way that the coating wears away at the areas written by laser. Suitable metals include zinc, tin, iron, steel and alloys thereof. Metal laminates can also be used as tin, zinc, lead and alloys of these coated or steel plated. In a preferred embodiment, the substrate is prepared in a continuous roll anodizing line. The aluminum netting is first subjected to a cleaning or degreasing process to remove the oil residue from the surface lamination. These processes are well known in the art of preparing aluminum surfaces for subsequent anodization. The aluminum net is rinsed in water after the cleaning step. It is then subjected to a granulation process by rotating brushes using a series of axially rotating brushes which tangentially contact the network in the presence of a suspension comprising unmelted laminar alumina having a particle size of between 2 to 5 microns up to approximately 10 microns. As previously described, three passes through an 8-brush granulation unit at 80 feet per minute results in a surface on which laser images can be formed or can cause a wear coating to wear on the surface. An equivalent result can be obtained either by a single pass through an 8-brush granulator at a total throughput speed of approximately 27 feet per minute, or by a single pass through a brush granulator 24 at 80 feet per minute. Although subsequent anodization is preferred, on the aluminum surface thus granulated by itself images can also be formed and can also cause a coating on the same to wear out when images are formed by means of an infrared laser. A useful method for granulating is taught in the North American Patent 4,183,788 of Fromson. After the granulation the aluminum network is rinsed in water and anodized by methods well known in the art. The electrolyte can be, for example, sulfuric acid or phosphoric acid. Sulfuric acid is preferred since it allows the formation of oxide at lower dissolution levels. Further anodization is preferably carried out at relatively lower temperatures to further minimize the redissolution of the anodic oxide coating with the additional benefit of producing a harder oxide layer than the anodization processes at higher electrolyte temperatures. Preferred oxide coating weights are in the range of 0.1 to 3.0 mg per square inch. The most preferred oxide coating weights are in the range of 0.2 to 0.8 milligrams per square inch. The American Patent Re29, 754 issued to Fromson describes a preferred method for anodizing. Preferred laser imaging systems use YAG infrared lasers that operate at capacities up to 15 watts. Gerber Scientific of South Indsor, Connecticut and Sean Graphics of edel, Germany supplies commercial systems which can be used to form images in archiving media prepared in accordance with the present invention. An example of a means for archiving prepared in accordance with the present invention is an optical disc, very similar to a compact disc (CD) that can be granulated and anodized on both sides to form images on both sides. By using a YAG laser point of one or two microns, up to one trillion bytes of information can be stored on each side of a 5-inch disk.

In a further embodiment, the archiving means of the invention can be used for illustration or signaling purposes. It can also be used as a security or credit card that has no visible code or account information. This is achieved by placing a coating on a substrate in which images can be imaged with a polymer or a similar coating that is opaque to visible light to obscure code or counting information placed within the substrate as described herein. The coating is transparent to either IR or UV radiation allowing the card to be "read" by an appropriate scanning device. A combination of coatings that are opaque to visible light in a transparent area in other areas can also be used. The polymer coatings can be thermoplastic or thermoset and include epoxy and phenolic resins, acrylic polymers, polycarbonates, PVC polymers and the like. The coatings may contain dyes or pigments to darken the surface on which images of the underlying substrate were formed and can be printed on top with information to identify the card holder and the like. By using non-wearing polymers that are transparent to the infrared laser radiation, the archival substrates of the invention can be coated for security and / or protection prior to laser image forming. Images can be formed on security, credit and ATM cards with analogue or digital information before or after applying the darkening coating. Such a coating can also carry holograms, magnetic strips and the like. In a further embodiment, a wear-resistant coating can be applied to a file medium in which laser images have been formed to provide a counterfeit-proof product such as a security or credit card. Such coating may be transparent, translucent or opaque. Any attempt to form the image again on the substrate or alter the image with a laser will also wear out the overlay which is "easily detected." A credit card, for example, with portions of the coating removed by wear will not be accepted. by sellers Coatings comprising certain phenolic polymers or silicone resins can be used as wearing coatings according to the present invention.Other wear coatings can be determined empirically.The wear coat may not be sensitive to light, such as phenylmethylsiloxanes or light sensitive, such as positive action coatings based on phenolic resins Such positive action coatings are well known in the art and have been found to wear easily with an infrared laser when applied to a medium for archiving the present invention Examples of the phenolic resins useful in the practice of this invention, such as Novolac or resole resins, are described in Chapter XV of "Synthetic Resins in Coatings" H.P. Press, Noyes Development Corporation (1965), Pearl River, New York. The wear coating should be as thin as possible but should still adequately cover the substrate to provide a safety coating. Coating weights in the range of about 50 to about 500 milligrams per square foot can be used, "-but it is preferable to work in the range of approximately 100 to 200 milligrams per square foot." It has been found that in a substrate in which images have been formed by laser can not be imaged again due to the alteration of the surface resulting from the infrared imaging.The initial image in this way is indelible in the sense that any - Attempt to alter the information of images on the substrate will be easily apparent upon examination visually or by the inability to read the card electronically or optically.

This feature of the invention can be used to advantage by exposing in a blanket a substrate in which images have been formed or imaged in a network pattern on or around the image on the substrate. Blanket exposure or imaging in a network pattern with an infrared laser will permanently alter areas where substrate information does not exist. It is preferred to leave an edge belt around the image to provide sufficient contrast to view or read the desired image. The formation of images in a network pattern around the desired image is similar to the printing of a watermark on bond paper. This feature of invention can be used in different ways. The writing of a means for archiving can be done in such a way that all the areas where there is no information of the medium are exposed to the writing laser beam. The surface in this way is altered in these areas and new information can not be added in these regions. Alternatively, areas where medium information does not exist can be written to have a recognizable pattern. For example: xxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxx XXXJohn DoeXXXXXXXXX XXXPresidentXXXXXXXXX XXXAny CorporationXXXXX XXXID No. 123456789XXXX XXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXX New information can not be added in the region where the "X" pattern appears in areas where there is no information. The formation of images in pattern or blanket of the areas where there is preferably no information "will be done during the process of writing information, but optionally it can be done after the writing process .. The following examples are illustrative without being limiting. Example 1 Several samples and two comparative samples were prepared from an aluminum roll of Alcoa 3103-H26 alloy, the roll was granulated and anodized under the variable conditions set out in the following table.All samples "except T-30 are anodized at 25 ° C. % sulfuric acid. The T-30 was anodized in a 2% tartaric acid solution.

TABLE 1 All the samples were placed in a Gerber 42T Píate Image Setter and were exposed in the sense of the image with a YAG laser at 9, 7 and 5 wats. After the exhibition, a permanent visible image was created in samples EX 140, 147, 148 and T-30 at all energy levels. The samples EX-113 and Delta are comparative samples which have been etched in a sodium hydroxide solution and have been demolished in a nitric acid solution before anodization. The recording destroys the ability of these samples to form images.

Example 2 To demonstrate the archival nature of the image, the samples in which EX-140 and EX-147 images were formed were subjected to three different conditions: 1. Heat: Samples were placed in an oven at 260 ° C during 4 hours. 2. Water: the samples were immersed in water at room temperature for 100 hours. 3. Actinic exposure: The samples were exposed for 1 hour in a Theimer Copymat 64-CP exposure unit that has a MuHi spectrum bulb of 2500 wats. The total exposure exceeded 16,000 mj / cm2 TABLE 2 The color value properties of the imaging and non-imaging areas of each plate were measured in a Hunter Labs spectrophotometer Colorquest. The data, in the form of L, values a and b for each section, are reported in Table 2. The data in Table 2 show that the three test conditions - did not significantly alter the surface contrast for EX-140 or EX -147. In all cases, the differential of image formation / non-image formation was maintained. EXAMPLE 3 Two substrates of anodized aluminum and granulate by brushes (EX-140 and EX-147 of Table 1) were placed in a Gerber 42T Píate Image Setter and exposed in the image direction with a YAG laser to 9, 7 and 5 wats. After the exposure, a permanent visible image was obtained on the surface of the granulated anodized aluminum with brushes. The change caused by the YAG laser produced enough contrast for the visible image to be detected up to 5 watts. Example 4 Mechanically eroded samples were prepared for each of the types of flat sheet metal: Stainless steel coated with Terme (Pb / Sn alloy) Galvanized steel Tin plated steel Zinc For each sample, granulation was performed by a single pass by a series of eight cylindrical nylon brushes that rotated at 750 rpm. The speed through the granulation was 12 feet / minute. The granulation medium was unmelted aluminum oxide (calcined alumina). Images were formed on the eroded leaves in a Gerber Crescent 42 Thermal Píate Imager. All the samples showed evidence of a visible image at low contrast as a result of the selective structure by the laser. Example 5 The following positive action light-sensitive safety coating formula was prepared: Arcosolve PM 42.86% Ethanol 21.34% P-cresol resin of 1,1-naphthoquinone diazide [2] -5-sulphonyloxy 9.26% cresol resin 20.70% T-butyl phenol formaldehyde 0.36% resin Phenol formaldehyde resin 4.76% Blue coloring 0.76% BYK 344 0.08% Medium for archiving EX-147, (Table 1) with credit card data in a Gerber Crescent 42T Setter with the laser at a capacity of 6.5 wats. The above coating was then applied to the archiving medium with formed images at a dry coating weight of 140 mg / square foot. The coating wears away when trying to re-form the images and this was easily detected. Example 6 An example of a sheet for archiving in which images have previously been formed. The substrate EX-147 of Table 1 was used. Shade images were formed in the middle of the substrate in a Gerber Crescent 42T Imager. The side where laser images were visually appeared much clearer than the other side. Subsequently the sheet was coated with a light sensitive safety coating of the Example to a dry coating weight of 140 mg / square foot. Then images were selectively imaged on the coated sheet with a Gerber Crescent 42T Imager at 200 Hz 7.9 wats such that the selective pattern overlapped on both the lighter and darker sides of the substrate. On the darker side the coating was worn in the areas where laser images were formed, the analyzed substrate had a clearly distinguishable visible image. On the clear side of the substrate which had undergone blanket imaging before coating, the coating did not wear out, and the visible image on the aluminum substrate had an extremely weak contrast indicating that on the substrate on which images were formed in blanket can not form images.

Claims (21)

1. CLAIMS 1. A method for preparing an archiving means characterized in that it comprises: a) granulating the surface of an aluminum substrate with particulate material under conditions that imbibe particulate material on the surface; and b) without an intermediate treatment which can remove the embedded particulate material, form images directly on the granulated substrate of step (a) with an infrared laser to form areas without visible formation on the substrate by localized melting of aluminum into the surface .
2. 2. The method according to claim 1, characterized in that the granulated substrate is granulated by a rotating brush. -
3. 3. The method according to claim 1, characterized in that the granulated substrate is anodized before forming the images by laser.
4. 4. A method for preparing a filing medium comprising: a) granulating the surface on a metal substrate with particulate material under conditions that imbibe the particulate material within the surface; and b) without any intermediate treatment which can remove the embedded particulate material, directly form images on the granulated substrate of step (a) with an infrared laser to form areas without visible formation on the substrate by localized melting of the metal on the surface.
5. 5. The method of compliance with the claim 4, characterized in that the metal substrate is selected from the group consisting of tin, zinc, lead or steel-coated with zinc, tin or lead, and alloys thereof.
6. 6. The method of compliance with the claim 4, characterized in that ^ the substrate is granulated by a rotating brush.
7. 7. The method for preparing a tamper-proof archiving medium characterized in that it comprises the coating of the substrate with imaging made by the method according to claims 1, 3 or 4 with a transparent coating so that infrared laser radiation can wear away the surface where the substrate collides with infrared radiation.
8. 8. The method according to 7, characterized in that the coating wears selectively in areas different from the information areas.
9. 9. The method _ in accore with the claim 7, characterized in that the coating wears selectively in the information areas.
10. 10. The method according to claim 7, characterized in that the coating is transparent, translucent or opaque to visible radiation. The method for preparing a tamper-proof archiving means characterized in that it comprises coating the granulated substrate of step (a) of the method according to claims 1, 3 or 4 before forming the images with a radiation-transparent coating of the infrared laser that can wear out where the substrate collides with infrared radiation. The method according to claim 11, characterized in that the coating wears selectively after imaging in areas other than the information areas. 13. The method according to the claim 11, characterized in that the coating is transparent, translucent or opaque to visible radiation. 14. A filing means characterized in that it comprises a granular aluminum substrate having particulate material embedded in the surface thereof, which, without an intermediate treatment which can remove embedded particulate material, has information areas formed on the surface by the Localized melting of aluminum within the information areas by direct imaging with an infrared laser. The archiving means according to claim 14, characterized in that the granulated substrate is anodized before the information areas are formed without removing the embedded particulate material. 16. The means for filing in accore with claim 14, characterized in that it has a coating that is opaque to visible light but transparent to ultraviolet or infrared radiation. 17. archiving means according to claim 14, characterized in that it has a coating which is transparent to visible light. 18. archiving medium according to claim 14, characterized in that it has a combination of opaque and transparent coating to visible light. 19. archiving means according to claim 14, characterized in that it has a coating transparent to laser radiation that can be abraded from substrate when it hits laser radiation. 20. A filing means characterized in that it comprises a granulated metal substrate having granulated metal embedded in surface eof, which, without any intermediate treatment which can remove embedded particulate material, has forming areas formed on surface by Localized melting of metal within information areas by direct imaging with an infrared laser. 21. archiving medium according to claim 20, characterized in that metal substrate is selected from group consisting of tin, zinc, lead or steel coated with zinc, tin or lead and alloys eof.