US3235395A - Transfers for metallic coatings - Google Patents

Description

Feb. 15, 1966 W. G. SCHARF TRANSFERS FOR METALLIC COATINGS Filed March 27, 1962 INVENTOR. Mare@ G Sul/4QF Afro/Ney Q/:Jgl (2 And.

United States Patent 3,235,395 TRANSFERS FOR METALLIC COATNGS Walter G. Scharf, 243 Palmer Court, Ridgewood, NJ. Filed Mar. 27, 1962, Ser. No. 182,756 4 Claims. (Cl. 117-33) This invention relates generally to transfer techniques for applying metallic coatings to desired substrates, and more particularly to a transfer sheet or web which includes a releasing layer interposed between the metal film to be transferred and a carrier, the layer functioning also to protect the transferred film.

The use of transfer techniques to apply metallic coatings to substrates, such as fabric, leather or plastic surfaces, is well known. Thus bookbinders employ gold foil transfer sheets to attach gold letters to leather bindings. These transfer sheets are constituted by a waxed carrier web for supporting the gold foil, the gold being coated with a heat-activated adhesive layer. In practice, the .transfer sheet is hot pressed with a heated die to adhere the metal foil to the leather, the carrier then being i stripped away. The waxy parting layer serves to maintain the gold leaf in position on the carrier prior to its transfer and to permit release of the carrier after the gold has been Iaffixed to the leather.

After the gold leaf is attached, its outer surface is exposed and unprotected, hence with continued use of the leather article, the gold surface is abraded and the lettering gradually wears away. Such erosion is also encountered with modern transfer sheets where metal films, rather than foil, are deposited on wax treated carriers by vapor deposition or sputtering, and coated with adhesives for transfer to leather or other surfaces to be decorated. Once the metal film is transferred, its outer surface is exposed to wear.

Many atempts in recent years have been made to apply metallic nishes to fabrics directly rather than by transfer techniques. Thus metal has been applied to cloth by sputter-ing molten metal thereon. But such surfaces usually present a dull, semi-metallic and unattractive appearance. Another approach in producing metallized cloth is by applying metallic lacquers in liquid form. However, the liquid binder penetrates the fibers and stiffens the fabric. In neither case does the cloth have a metallized finish of high luster. Also, the textile characteristics of the cloth are often degraded by direct metallizing finishes of this type.

In recent years the transfer technique has been used for fabric in connection with a transfer sheet in which a metal film is deposited directly on a carrier web and then J coated with a curable adhesive bonding composition. In transfer, the adhesive layer is pressed onto the fabric surface and cured to a solvent-resistant and heat resistant state, the carrier then being stripped from the metal film. While this technique affords a highly reflective metallic film on the surface of the cloth, this film, as in the case of all other prior metallizing techniques, is entirely unprotected. Hence with continued use and with repeated dry-cleaning, the metallized finish becomes eroded and the fabric ceases to be attractive.

In view of the foregoing, it is the main object of this invention to provide -a transfer sheet or a continuous web which obviates the drawbacks incident to the prior art and renders possible the formation of metallized finishes of superior quality.

More specifically, it is an object of this invention to provide .a metal transfer web, which when applied to natural or synthetic fabrics, paper or any other substrate, enhances the decorative qualities thereof without impairing its wearing or draping characteristics or its hand.

A significant advantage of the invention is that the metallized fabric may be washed or dry-cleaned without loss of luster, and the fabric may be repeatedly folded or crumpled without adversely affecting its metallic appearance. As applied to a paper substrate, the resultant metallized paper is brighter and more .attractive than aluminum foil and paper laminate.

Yet another object of the invention is to provide a transfer technique wherein the metal film applied to the substrate is protectively coated with a material which initially functions to release the film from the carrier. Thus the applied film resists abrasion and maintains its luster for a prolonged period.

A further object of the invention is to provide a transfer sheet of the above type which may be inexpensively manufactured and which may be applied to any suitable surface by conventional techniques, as by hot or cold presmg.

Briefly stated, these objects are accomplished by means of a transfer constituted by a carrier web coated with a resinous solution which when dried forms a transparent layer of a material normally incompatible with the material of the carrier web, whereby the layer may readily be stripped from the Web.

The outer surface of this release layer is metallized by vacuum deposition to form a film thereon which may then be coated with an adhesive layer of ya character suitable for the substrate to which transfer is to be effected. Alternatively, the adhesive layer may be applied to the substrate rather than the metal film. In any event, when the transfer is applied to the substrate, as by hot pressing, the metal film is bonded thereto, and when the carrier is stripped away, what is exposed is not the naked surface of the metal film but the protective layer thereon, the layer being transparent and hence effectively invisible. It is also possible to add coloring matter to the protective layer whereby the color presented to the observer is the resultant of the metal color in combination with the protective pigment.

For a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawings, wherein:

FIG. l is a section taken through a transfer sheet in accordance with the invention, the dimensions being greatly exaggerated for purposes o-f clar-ity.

FIG. 2 shows the applicaton of the transfer sheet to cloth.

FIG. 3 schematically illustrates a preferred method for fabricating the transfer sheet.

Referring now to the drawings, and more particularly to FIG. l, the transfer in accordance with the invention generally comprises a carrier web 10, a release layer 11 coated on said web and forming a protective surface for a metal film 12 deposited on said layer, and an adhesive coating 13, which may be heat or pressure sensitive, formed on the metal film.

The carrier web may be constituted by any suitable flexible material capable of being coated by a resinous solution of the type to be described, such as cellophane, acetate or triacetate, and is preferably formed of polymerized ethylene glycol terephthalate, one form of which is known commercially as Mylar. The web need not have a thickness greater than 2 mils, although Webs as thick as 4 or 5 mils may be used.

The release layer 11 is formed by coating the carrier web with a resinous solution consisting of solvents not greatly affecting the web and an organic solute not normally compatible therewith, such as polymethylmethacrylate. This coating is applied uniformly as by a roller coater, a reverse roller coater, or by the flexographic or rotogravure process. Whcn the coating is dried it constitutes a clear transparent layer which while not bonded to the carrier web in any chemical sense, superficially adheres thereto.

The surface of the protective layer 11 is then coated with a ne metal film 12 which may be of gold, silver, aluminum, magnesium, titanium nickel or any other metal, the thickness of the film preferably not exceeding 1/50,000th of an inch. The deposition may be carried out by known thermal evaporation or cathodic sputtering techniques.

The nature of the adhesive layer 13 applied to the metal film 12 will depend on the character of the substrate. For example, if the transfer is to be used for metallizing a rigid plastic surface, then it is not important that the adhesive have flexible as well as bonding properties, and the choice of adhesive will depend on the material of the plastic substrate. But with fabrics it is essential that the adhesives also be flexible. For this purpose, highly fiexible heat curing combinations of rubbery polymers and compatible heat-advancing adhesive resins will provide good bonding between fabric and metal. Plasticizers, tackifiers, other curing agent catalysts, etc. may be added as desired.

The invention is of particular value for metallizing paper. Paper, because of its inherent qualities, cannot as a practical matter be metallized directly, as by vacuum deposition. The present transfer technique makes metallization possible and produces a more brilliant result than is obtained with metal foil paper combinations.

Transfer may be effected as a continuous film or as an incomplete patterned transfer. As shown in FlG. 2, assuming a paper or fabric substrate 14, the transfer sheet is laid thereon with the adhesive layer 13 in Contact with the substrate. The combination is conveyed through hot or cold pressure rollers, depending on the nature of the adhesive layer, to effect bonding therebetween, after which the carrier is stripped away,

In the example given above, the transfer sheet was provided with a continuous and uniform adhesive layer over the metal film. To effect pattern transfer, the adhesive layer may be made discontinuous in the form of contoured or patterned areas whereby only corresponding `areas of the metal film will be removed from the transfer sheet when the carrier is stripped therefrom. In this manner many interesting decorative effects may be realized. It is, of course, also possible to provide Ia transfer sheet or web of the above-described type without an adhesive coating and instead to apply the necessary adhesive coating either in continuous or patterned form directly to the surface to be metallized before the transfer is pressed thereon.

When the carrier web is stripped away, the metal film 12 then becomes visible through the protective layer 11 which in practice should be extremely thin. To obtain different color effects, dyes or pigments may be added to the resinous solution coated on the carrier web, the color thereof combining with the color of the metal film to produce different hues. Thus an aluminum film, whose appearance with a clear layer is silvery, may be made golden or given still another metallic hue depending on the color added.

Referring now to FIG. 3, the process for forming a transfer sheet is illustrated, the carrier web 10 being drawn from a supply roll 15, one surface of the web being coated with the resinous solution contained in a bath 16. The liquid coating is applied by a direct three roll coater including a first roller 17 rotated in bath 16 and acting to apply the liquid to :a second roller 18 which engages the undersurface of the web, the web being pressed against the second roller by means of a third roller 19.

As noted previously, coloring may be added to the solution. Preferably dyestuff is used, such as Acetosol dyes manufactured by the Sandoz Company, or Orasol made by Ciba or Grasol made by Geigy. The advantage of dye over pigment is that the latter is composed of solid particles which form a suspension in the plastic solution and tend to make the layer thicker and less flexible.

The web is dried by passage through an oven 20 which is properly heated and vented to drive off all solvents. To this end, gas heat or infra-red radiation may be employed. The dried solution formed the release layer on the web, the layer then being metallized by passing it through vacuum chamber 21. If thermal evaporation is used, metal vapor is generated by dried heat as from an electric arc or a glowing filament. To effect maximum adherence of the film plate, the metal molecules should pass linearly from their source to the surface to be coated, this requiring maintenance of pressures of about 10F4 of mercury in a vacuum chamber.

In cathode sputtering, a high voltage is impressed between an anode and the plating metal. The cathode is vaporized by positive ion bombardment, some of the vapor diffusing `away from the cathode and depositing on the surface to be plated. The voltage requirements depend on the nature of the cathode metal. At pressures of 0.01 to 0.10 mm. of mercury necessary to maintain the glow discharge, the ordinary laws of diffusion prevail. After plating the web is re-rolled in preparation for the next step.

Finally, the metallized web passes through a coating bath 22 to apply an adhesive layer on the metallized film, this layer being dried to a non-tacky state and rolled for future use.

Among the useful carriers, Adhesives and Release Coatings which are useable in accordance with the invention are the following:

Carrier (film):

Polyethylene terephthalate Crystallized copolymers of polyethylene terephthalate `and isophthalate Oriented polystyrene Polyvinyl fluoride Acetate coated paper Polyolefins such as polyethylene and polypropylene Adhesives:

Rubber-Phenolic systems Polyester-Isocyanate systems Water dispersions of rubber, polyvinyl chloride and polyvinyl acetate Release coatings:

Polyurethanes Solutions of phenol formaldehyde Solvent systems of polyesters and combinations such as methyl methacrylate, ethylene terephthalate, ethylene lisophthalate Water and solvent systems of polyvinyl acetate and polyvinyl chloride.

While there has been shown what is considered to be a preferred embodiment of the invention, it is to be understood that many changes and modifications may be made t-herein without departing from the essential spirit of the Iinvention as set forth in the appended claims.

What is claimed is: 1. A transfer comprising: (a) a carrier web formed of synthetic plastic material, ('b) a release layer formed on said web and adhering supercially thereto, said layer being formed of a synthetic transparent plastic material whose characteristics render it incompatible with said web and readily strippable therefrom, and (c) a metal film one face of which is adhered directly to said release layer, the other face thereof being adherable to a substrate, the carrier web being removable to expose said one face of said metal film through said transparent release layer adhered thereto whereby the release layer then functions as a protective layer.

2. A transfer as set forth in claim 1, wherein said transparent release layer includes coloring matter to impart a hue thereto different from that of said metal ilrn, whereby when the carrier web is removed the colors of said metal lm and said release layer combine to produce a third color.

3. A transfer as set forth in claim 1, wherein said Web is formed of ethylene glycol terephthalate and said release layer is formed of polymethyl rnethacrylate.

4. A transfer as set forth in claim 1, further including a layer of adhesive coated on the other face of said met-al lm.

References Cited by the Examiner UNITED STATES PATENTS Humphner 1l7-3.4 Francis 117-34 Terry 117-3.4 Oughton 117-33 Matthes 117-3 .4 Persoon 1l7-3.4 Reese 1173.4

WILLIAM D. MARTIN, Primary Examiner.

MURRAY KATZ, RICHARD D. NEVIUS, Examiners.

Claims (1)

1. A TRANSFER COMPRISING: (A) A CARRIER WEB FORMED OF SYNTHETIC PLASTIC MATERIAL, (B) A RELEASE LAYER FORMED ON SAID WEB AND ADHERING SUPERFICIALLY THERETO, SAID LAYER BEING FORMED OF A SYNTHETIC TRANSPARENT PLASTIC MATERIAL WHOSE CHARACTERISTIC RENDER IT INCOMPATIBLE WITH SAID WEB AND READILY STRIPPABLE THEREFROM AND (C) A METAL FILM ONE FACE OF WHICH IS ADHERED DIRECTLY TO SAID RELEASE LAYER, THE OTHER FACE THEREOF BEING ADHERABLE TO A SUBSTRATE, THE CARRIER WEB BEING REMOVABLE TO EXPOSE SAID ONE FACE OF SAID METAL FILM THROUGH SAID TRANSPARENT RELEASE LAYER ADHERED THERETO WHEREBY THE RELEASE LAYER THEN FUNCTIONS AS A PROTECTIVE LAYER.

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