Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H1/0252—Laminate comprising a hologram layer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H1/024—Hologram nature or properties
  • G03H1/0244—Surface relief holograms
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2250/00—Laminate comprising a hologram layer
  • G03H2250/36—Conform enhancement layer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2250/00—Laminate comprising a hologram layer
  • G03H2250/39—Protective layer

Definitions

• holograms comprising a relief-patterned metal surface electrolessly deposited to conform to a relief-patterned polymeric substrate. Also disclosed are methods for producing electrolessly deposited metal holograms. BACKGROUND OF THE INVENTION Holograms and other types of diffraction gratings comprising reflective metal surface on a relief-patterned substrate are commonly used for decorative packaging, artistic images and security devices, e.g. on credit cards, currency and other official documents. Such holograms can be prepared by a variety of methods such as embossing deformable metal foil laminates with a holographic image stamp. Due to the resilience of laminate components, such embossed holograms tend to be of poor quality especially when subjected to elevated temperatures.
• a holographic polymeric substrate is formed by casting and curing a polymer precursor in contact with a holographic relief-patterned mold to form a polymeric substrate with a holographic relief- patterned surface; a metal reflective surface is then deposited on the relief-patterned surface, e.g. by vapor deposition techniques.
• the resulting relief- patterned metal surface serves to reflect incident light into a reconstructed image of the hologram.
• a disadvantage of such metal deposition is the requirement to conduct such metal deposition in a vacuum environment and to mask areas where metal deposition is not desired especially if the hologram is mounted on a document.
• An object of this invention is to provide such reflective metal holograms which can be prepared by metal deposition techniques that do not require vacuum environments or masking.
• One method for depositing metal onto polymeric substrates is electroless deposition.
• electroless deposition of metal has some disadvantages which do not commend it to such hologram preparation. For instance, many techniques for electroless deposition of metal onto plastics require etching to achieve a effective level of adhesion; such etching, e.g. with strong acids or solvents, can destroy the holographic relief pattern of the polymeric substrate surface.
• electroless deposition techniques often utilize catalytic materials of a size on the order of magnitude of the holographic relief pattern; deposition of dispersed particulate catalytic materials can distort the reproduction of the holographic relief pattern in the metal coating.
• this invention provides a hologram comprising a relief-patterned metal surface electrolessly-deposited to conform to a relief-patterned polymeric substrate, whereby light incident to the surface of said metal opposite to said polymeric substrate is reflected to provide a holographic reproduction of a holographic image inherent in said relief-patterned polymeric substrate.
• metal surface is provided in a thin, conforming layer that reproduces the holographic relief- patterned surface of the polymeric substrate by electroless deposition techniques.
• This invention also provides methods of preparing electrolessly deposited metal holograms, e.g. preparing a polymeric substrate having a holographic relief-patterned surface and electrolessly depositing a conforming holographic metal reflective layer on said relief-patterned surface.
• a polymeric substrate having a holographic relief-patterned surface is prepared by casting and curing polymeric precursor in a holographic relief-patterned mold.
• the conforming holographic metal reflective surface is prepared by electrolessly depositing metal onto the holographic relief-patterned surface in a method comprising: (a) coating a holographic relief-patterned polymeric substrate surface with a film-forming solution of a polymer and a Group 8 metal;
• a polymeric substrate 1 which can be prepared by molding a molten thermoplastic, e.g. a high glass temperature thermoplastic such as a polyimide or polyetherketone , in a mold having a holographic relief pattern on its surface.
• a molten thermoplastic e.g. a high glass temperature thermoplastic such as a polyimide or polyetherketone
• such polymeric substrate can be prepared by casting and curing thermoset polymer precursor, e.g. crosslinkable material such as an acrylate, urethane or epoxy polymer precursor, in a mold having a holographic relief pattern.
• Methods for preparing such substrates are known in the art and are disclosed by D'Amato et al. in European Patent Publication 0 338 378, the specification of which is incorporated herein by reference.
• Conforming to the holographic relief pattern of the polymeric substrate is an electrolessly deposited metal layer 2 which provides reflective surfaces from which incident light can be reflected into a reconstructed image of the hologram inherent in the holographic relief pattern.
• electroless deposition techniques are inherently incompatible for use in preparing holographic metal surfaces. It has been discovered that electroless deposition techniques such as those disclosed by
• the improved electroless deposition methods of this invention comprise: (a) coating a holographic relief-patterned polymeric substrate 1 with a film- forming solution, preferably substantially aqueous, comprising a polymer, e.g. polyvinyl alcohol, and a
• Group 8 metal e.g. a palladium salt
• drying said film-forming solution to form a polymeric film essentially conforming to and reproducing said holographic relief pattern
• heating said polymeric film by exposure to a temperature of at least about 200° C to provide a catalytic surface thereon;
• applying to said catalytic surface an electroless depositing metal solution for a contact time of less than 20 seconds to electrolessly deposit thereon a metal surface 2 which essentially conforms to and reproduces said holographic relief pattern.
• the drying and heating can be simultaneously effected.
• the contact time for applying said electroless deposition solution should be sufficient to electrolessly deposit a metal layer 2 in sufficient thickness, e.g. at least about 5 nanometers thick, to provide a mirror like surface and sufficiently thin, e.g. not more than about 300 nanometers thick so as to not obscure the underlying holographic image.
• a balance of good reproduction of the holographic image and durability of a mirror like finish is achieved when the metal layer is between about 10 and 100 nanometers thick. Most preferred metal layers are about 20 to 60 nanometers thick.
• Preferred contacts times are less than 10 seconds, more preferably less than 5 seconds.
• the contact time can be effectively reduced by adjusting the electroless deposition environment, e.g. by elevating temperatures of the substrate and the electroless deposition solution for instance up to about 80 - 90" C.
• Useful metals for the electrolessly deposited layer include nickel, cobalt, copper, palladium, silver, platinum and gold which can be applied as a single metal layer or a laminate of metal layers.
• the metal layer can be optionally overcoated with a protective wear layer, e.g of a clear acrylate or urethane topcoat which does not interfere with the transmission of light to and from the metal layer.
• An advantage of the electrolessly deposited holograms of this invention is the application of methods of preparation thereof to continuous processing of web material containing such holograms including web material comprising holograms of extended length as on artistic or decorative sheets and web material comprising holograms on selected areas of the web as on security documents.
• Such continuous processes are disclosed in European Patent Publication 0 338 378 referred to hereinabove.
• the electroless deposition methods can be effected by applying the film forming solution and electrolessly depositing metal solutions from solution saturated surfaces in register with a moving web so as to contact the holographic relief surface of the polymeric substrate and catalyzed relief surface, respectively.
• EXAMPLE This example illustrates the electroless deposition of a nickel onto a relief-patterned polymeric substrate.
• a catalytic metal solution was prepared from
• a water soluble polymer solution was prepared from 0.12 g polyvinylalcohol (125,000 M.W. , 88 mole % hydrolyzed) and 0.013 g Triton X-100 polyoxyethylene surfactant (Rohm & Haas) and about 6 ml water.
• a polymeric substrate having a hologram generating relief-patterned surface was coated by wiping the surface with a sponge saturated with the film forming solution.
• the film forming solution was dried by holding the dry side of the polymeric substrate in a 220" C air stream for about 10 seconds to provide a catalytic surface on the hologram generating relief- patterned surface.
• the polymeric substrate was placed on a 95° C surface while the catalytic surface was covered for about 5 seconds with a solution of electroless depositing nickel solution (obtained from MacDer id, Inc. identified as XD7054EN) comprising 6 g/l nickel and 30 g/l sodium hypophosphite monohydrate adjusted to pH 5.5 with ammonium hydroxide solution and maintained at about 80° C. After the 5 second exposure, the nickel solution was rinsed off with water providing a reflective holographic nickel surface.
• electroless depositing nickel solution obtained from MacDer id, Inc. identified as XD7054EN

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Holo Graphy (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (1)

Family

ID=27052660

Family Applications (1)

Country Status (7)

Cited By (2)

Families Citing this family (1)

Citations (5)

• 1991
  • 1991-02-26 CA CA002077536A patent/CA2077536A1/en not_active Abandoned
  • 1991-02-26 AU AU74780/91A patent/AU641231B2/en not_active Withdrawn - After Issue
  • 1991-02-26 JP JP91506040A patent/JPH05505887A/ja active Pending
  • 1991-02-26 EP EP19910906231 patent/EP0521042A1/en not_active Withdrawn
  • 1991-02-26 WO PCT/US1991/001262 patent/WO1991014975A1/en not_active Application Discontinuation
  • 1991-03-21 CN CN91101847A patent/CN1055247A/zh active Pending
  • 1991-03-21 IL IL97630A patent/IL97630A0/xx not_active IP Right Cessation

Patent Citations (5)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events