Laminated Identification Card

Abstract

A permanent identification card is disclosed having a photographic print with identifying indicia thereon. Typically, the photographic print is a color diffusion transfer print having thereon a picture of the cardholder and certain other information. An adhesive composition is used to laminate an optically-transparent, plastic, protective sheet, such as polyvinyl chloride, to the surface of the photographic print. The adhesive composition contains a thermally-activatable polyester adhesive capable of bonding the plastic sheet to the treated photographic print and a peroxide bonding promoter.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to permanent identification cards formed by bonding optically-transparent plastic sheets to the emulsion surfaces of photographic prints having identifying indicia thereon.

2. Description of the Prior Art

Badges, driver's licenses, I.D. cards, credit cards, etc. often contain black and white or color photographic film with a picture of the holder together with other identifying information thereon. To protect the film, an optically-transparent plastic sheet is frequently applied over the photographic film. Customarily, a clear or pigmented, opaque, plastic sheet, such as pigmented, semi-rigid polyvinyl chloride, cellulose acetate butyrate or polymerized glycol esters, is applied on the opposite side.

Often, the front and rear plastic sheets are provided in the form of a plastic pouch having one or more open sides. The open edges are heat sealed after the film is slipped into the pouch. One serious drawback to such pouches is that the film is loosely held inside the pouch, and it can be easily removed if the pouch is opened. This presents a severe security problem since the photographic film can be removed and another piece inserted in its place.

Because of this, there is a great need for an adhesive composition which would uniformly bond the surface of photographic prints to an optically-transparent, plastic, protective sheet over the entire surface area of the print. With such an adhesive, a laminated structure could be prepared so that it would be impossible to separate the protective sheet from the print surface without destroying the picture and/or other information on the print. Such a system would provide much more security as can be easily appreciated.

While many adhesives are known, they have proven to be unsatisfactory for this particular application for one reason or another. An example of attempts to use a commercially available adhesive is illustrated in U.S. Pat. No. 3,614,839, to Thomas, which teaches that ethylene/vinyl acetate copolymer adhesives can be used in such laminates. Nevertheless, the use of standard adhesive compositions, such as these, has not proven to be adequate.

This is not surprising in view of the many stringent requirements for adhesive compositions in such laminates. Among these requirements are the following:

Since many photographic films have emulsions containing polyvinyl alcohol or polyvinyl alcohol and polyvinyl pyridine, the adhesive composition must bond to this emulsion. It has, however, been found extremely difficult to find adhesives that will form satisfactory bonds to this type of emulsion.

To be practical, the laminated structure must not delaminate under a wide variety of environmental conditions such as temperatures to 120.degree.F. and humidities to 100 %. Additionally, for security purposes, the bond must be strong enough to withstand attempts to separate the plastic film from the emulsion so that any such attempts result in destruction of the photographic emulsion.

Because the print must be easily viewable, the adhesive composition must be optically-transparent in its dry state. It might or might not be optically transparent in its wet state, and might even, in some cases, present an advantage if it is not clear in its wet state because any parts of the laminated structure not properly cured could be immediately noted.

It must bond to black and white or color prints, and to freshly-processed and wet or old and dry prints.

It must be heat-activatable under minimum time/temperature conditions, such as being activated by a heated plate at 250.degree.F. for a dwell time of less than 10 seconds.

Sheets coated with the adhesive compositions must be non-blocking, i.e., not adhere to themselves, and also must not adhere to other materials, under extreme environmental conditions such as temperatures up to 140.degree.F. and relative humidities up to 80%.

It must not degrade the information contained on the photographic print in any manner. This is a particularly stringent requirement with the sensitive but complex physical structure and chemical formulation of color diffusion transfer prints.

It must have good shelf life, often at least six months or more.

It must be precision coatable.

Frequently, a plastic sheet is also bonded to the non-emulsion side of the film. This film can be clear, or pigmented to make it embossable. It is desirable, therefore, that the adhesive composition used to bond the protective plastic sheet to the front surface of the print will also bond the desired plastic to the back of the print, which is customarily coated baryta paper, and will also bond the edges of the two plastic sheets at their outer periphery. The bond at the edges of the two plastic sheets must be an extremely good one because people often flex credit and identification cards thereby inducing great stresses at these points.

In addition to the above-recited requirements, it is very desirable to have an adhesive composition which can be used in a single coat method.

SUMMARY OF AN EMBODIMENT OF THE INVENTION

One embodiment of this invention comprises an identification card formed by bonding an optically-transparent, plastic sheet, such as polyvinyl chloride, to the surface of a black and white or color photographic print. The adhesive composition contains a thermally-activatable adhesive and a bonding promoter which converts normally non-bondable photographic emulsions to a bondable state.

Typically, the photographic print is a diffusion transfer print having an emulsion containing a combination of polyvinyl alcohol and polyvinyl pyridine at its surface. The polyvinyl alcohol/polyvinyl pyridine combination has been found to be non-bondable with traditional adhesives. A suitable adhesive composition for this combination of materials has been found to be certain polyester resin adhesives with certain peroxide bonding promoters.

Of course, additional ingredients can be added to improve the basic adhesive composition. Such ingredients might include, for example: compounds which swell polyvinyl alcohol emulsions such as glycols; wetting agents such as dimethylsulfoxide; and other ingredients typically used in adhesive compositions which are well known to those skilled in the art.

The above-described identification cards and adhesive compositions therefor have been found to have many advantages over any heretofore known. Simply stated, they have been found to meet all of the stringent requirements as set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a driver's license, prepared according to this invention;

FIG. 2 is a sectional view of a permanent identification card prepared according to this invention; and,

FIG. 3 is a diagrammatical view illustrating the production of permanent identification cards according to this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The permanent identification cards described herein are laminated structures formed from optically-transparent, plastic, protective sheets bonded to the emulsion surfaces of photographic prints.

In forming such laminated structures, it is customary to use a diffusion transfer photographic print because of the speed and ease with which they can be developed. Suitable systems for taking prints and making laminates therefrom include those marketed under the trademarks QUAD and DUOMATIC by Avant, Inc., Concord, Mass. Typical diffusion transfer films are described in the following U.S. Pat. Nos. 2,983,606; 3,113,866; 3,148,061; 3,222,171; 3,246,984; and, 3,255,002. The teachings of all of these patents are hereby incorporated by reference.

Diffusion transfer films often have an emulsion having a topcoat formed from polyvinyl alcohol, alone, or in combination with a polyvinyl pyridine such as poly-4-vinyl-pyridine. Often, such topcoats comprise about 3 parts polyvinyl alcohol and about 1 part polyvinyl pyridine. It is possible, of course, to use films other than diffusion transfer films, including conventional silver halide black and white or color films, those films utilizing reversibly-activatable photoconductors, print-out films, etc. Also, it is possible to use films which have emulsions formed from materials other than polyvinyl alcohol and polyvinyl pyridine, such as gelatin emulsions.

The optically-transparent, protective, plastic film laminated to the surface of the print is very often a vinyl film, and most often is a clear rigid or semi-rigid polyvinyl chloride. Other clear plastic films such as copolymers of polyvinyl chloride and polyvinyl acetate, polyethylene terephthalate and polycarbonate could, of course, be used.

Permanent identification cards and their production according to this invention can be further illustrated by referring to the Figures.

FIG. 1 illustrates a driver's license 2 having a picture of the licensed operator and certain other identifying indicia thereon. The operator's picture and other identifying indicia are customarily placed on licenses of this type photographically. As described above, it is typical to use color diffusion transfer films for this purpose.

FIG. 2 illustrates a cross-sectional view of a permanent identification card such as the license shown in FIG. 1. As can be seen, these identification cards are formed from several distinct layers laminated together. Backing 16 protects the rear surface of color film 14. This layer is optional, but when used, usually comprises a relatively stiff plastic film such as rigid polyvinyl chloride, cellulose acetate butyrate or polyglycol esters, often pigmented to make it embossable. A typical thickness for backing 16 in driver's licenses, credit cards, etc. is 10-25, and preferably 20 mils. Backing 16 is laminated to the rear of color film 14 by an adhesive which may be the ones described herein, or may be traditional adhesives since the back of color film 14 is usually coated baryta paper which easily bonds to plastic materials using standard adhesives.

As mentioned above, color film 14 is typically a color diffusion transfer film, such as those produced by Polaroid Corp., Waltham, Mass., but can additionally be other types of photographic film. Typically, color diffusion transfer film is about 9 mils thick, but this is not a limiting parameter.

Adhesive layer 12, as described herein, is applied between the emulsion side of color film 14 and protective PVC sheet 10. The adhesive is heat-activatable, and is typically applied as a heated solution in a layer 0.5-4 mils, and preferably 1.25-1.50 mils thick. Strong bonds are formed by the laminating procedure described infra. Customarily, PVC sheet 10 is about 1-10 mils, and preferably about 5 mils, thick.

FIG. 3 illustrates the production of laminated, permanent identification cards. A sheet of optically transparent polyvinyl chloride 20 passes through guide rollers 22 and 24, after which solvent-based liquid adhesive 26 is applied. Doctor blade 30 is adjusted to provide the desired adhesive layer thickness. Developed film 32, having identifying indicia thereon, passes around guide roller 34 and is brought into contact with cooled adhesive layer 28. A strong bond is formed between developed film 32 and polyvinyl chloride layer 20 by passing the composite material through heated, pressure rollers 36. Typical laminating conditions are temperatures of 245.degree.-350.degree.F., pressures of 20-75 psi, and dwell times of 2-5 seconds. The preferred laminating conditions are temperatures around 300.degree.F., pressures around 25 psi, and dwell times of about 3 seconds.

New adhesive compositions are used in the identification cards described supra.

An essential ingredient in the adhesive compositions is a thermally-activatable adhesive. This adhesive must be activatable under the conditions of bonding, i.e., typically a heated roller at 300.degree.F. is used with a dwell time of about 3 seconds, followed by the application of 25-75 psi to the laminate. It must also be optically-transparent when cured.

In view of the demanding criteria, it will be recognized that most commercially available adhesives are unsatisfactory. Certain polyester resins, but by no means all such resins, have been found suitable. Some of those which operate can be classified as medium molecular weight, linear, saturated polyesters. Two specific examples of commercially available satisfactory polyester adhesives are: Vitel 207 sold by Goodyear; and, USM 7140 sold by USM Corp. Some of the characterizing properties of Vitel 207 resins are: color, staw; odor, none; specific gravity, 1.215; intrinsic viscosity, 0.775 .+-. 0.03; Tg, 6.degree.C; R & B softening point, 252.degree.F.; tensile strength, 3,500; elongation, 700 %; MVTR, 50.0; O.sub.2 diffusion, 148; hydroxyl number, 2.5-3.0; and, heat seal temperature, 175.degree.-350.degree.F. Those skilled in the art will know or be able to ascertain many other suitable polyester adhesives which are suitable because their physical and chemical characteristics are close to those presented.

In addition, it has been found highly desirable, although not necessary, to include in the adhesive compositions a copolymer of vinyl pyrrolidone with a comonomer which makes the copolymer substantially compatible with polyester resins. By substantially compatible, it is not means that the copolymer is completely soluble. It might be slightly insoluble, i.e., so that a slight haze is formed. It is important, however, that the copolymer does not completely settle out of the adhesive as a homopolymer of vinyl pyrrolidone would. Two suitable copolymers are sold under the trade names Kollima 55 and 75 by GAF, and are copolymers of polyvinyl pyrrolidone and polyvinyl acetate. Other suitable comonomers besides vinyl acetate include certain acrylics such as ethyl acrylate and butyl acrylate. Although the function of the copolymer of vinyl pyrrolidone is not totally understood, it has been surprisingly found that this ingredient increases the capability of the adhesive compositions to bond to both new, wet prints and to old, dry prints. Also, it seems to enhance the non-blocking characteristics of films having the adhesive composition thereon.

Since most photographic emulsions are naturally non-bondable, and particularly those having topcoats containing polyvinyl alcohol alone or with polyvinyl pyridine, it has been found that an essential ingredient in the adhesive compositions described herein comprises a bonding promoter. This bonding promoter serves the function of converting the emulsion from a non-bondable to a bondable condition.

Where the emulsion contains a mixture of polyvinyl alcohol and polyvinyl pyridine, it has been found that suitable bonding promoters comprise one or more organic peroxide or hydroperoxide compounds. In choosing suitable peroxides, a balance must be struck between higher-activity peroxides which are desirable from the viewpoint of maximizing their promoter qualities, and lower-activity peroxides which are desirable from the viewpoint of improving shelf life. In general, it has been found that peroxide promoters should have a half-life above about 10 hours at 50.degree.C. but a half-life of under about 5 minutes at 100.degree.C. Those skilled in the art will know suitable peroxides, keeping these parameters in mind, or will be able to determine them by no more than routine experimentation. Nevertheless, the following specific peroxides, which have been found to be suitable, are pointed out: benzoyl peroxide; 2,5-dimethylhexane-2,5-di-per(2-ethylhexanoate), sold commercially under the trade name USP 245, and 2,4-dichlorobenzoyl peroxide, sold commercially in dibutyl phthalate under the trade name Luperco CDB. The most preferred bonding promoter comprises equal parts by weight of USP 245 and Luperco CDB.

While not intending to be bound by this theory, it is believed that the peroxide promoters oxidize the pyridine rings, and may also attack unreacted vinyl groups, which is responsible for causing the normally non-bondable emulsion to become bondable. Aside from the theory, it has been repeatedly empirically observed that the peroxide promoters are efficacious in converting normally non-bondable polyvinyl alcohol/polyvinyl pyridine emulsion surfaces of diffusion transfer prints to a bondable condition.

Swelling agents for the photographic emulsion are also used in the adhesive compositions. For polyvinyl alcohol/polyvinyl pyridine emulsions, glycols have been found satisfactory. Here again, a balance is required between lower molecular weight glycols which have better emulsion permeability and higher molecular weight glycols which have concomittantly higher vapor pressures insuring that they won't be rapidly volatilized during the lamination process. It has been found desirable to have the glycol or mixtures of glycols have equivalent molecular weights between 35 and 400. By way of specific examples, equal proportions by weight of tetraethylene glycol, Quadrol (substituted quartenary amine glycols having an equivalent molecular weight around 400 sold by Wyandotte), and dimethylsulfoxide have been found to provide an outstanding swelling agent. The dimethylsulfoxide is added for its wetting properties. With the above parameters in mind, those skilled in the art will be able to determine many other suitable combinations of glycols and wetting liquids to serve as a swelling agent.

The adhesive compositions described herein have definite limits on the amount of the possible constituents as would be expected. Broadly, the new compositions contain three types of ingredients, i.e., adhesive, bonding promoter, and swelling agent. It is believed that the adhesive (including a polyvinyl pyrrolidone copolymer, if present) should comprise about 69-94%, and preferably about 80-89.5%; the bonding promoter should comprise about 0.2-2%, and preferably about 0.5-1.5%; and the swelling agent should comprise about 5-29%, and preferably about 10-19.5%. Additionally, when a copolymer of polyvinyl pyrrolidone is used, it should comprise about 2-25%, and preferably about 10-15%, by weight, of the total of the adhesive component. Since some ingredients come in solvents, such as the polyester resins, the above weight percentages are based on a dry basis for consistency.

In most cases, the adhesive compositions described herein will bond the clear plastic sheet directly to the print, but in some cases it is necessary to use a second or tie coat.

Of course, many additionally ingredients commonly used in adhesive compositions can be added to the basic compositions described herein without departing from the scope of the invention. Such ingredients are well known to those skilled in the art and are included within the scope of the compositions claimed in the appended claims.

Unless otherwise specified, all percentages presented herein are by weight. The following Example further illustrates the invention.

EXAMPLE I

Equal parts (1 part) by weight of the peroxides USP 245 and Luperco CDB are added to 31 parts of dimethylsulfoxide. This mixture is combined with 33 parts of tetraethylene glycol 33 parts of Quadrol, and the resulting solution is mixed well in a ball mill. Twenty parts of the combined solution is transferred to a closed stainless steel reactor equipped with an agitator and a reflux condenser. One hundred parts of a resin adhesive formed from 80 parts of USM 7140 (polyester in 40% solution of iso-toluene) and 20 parts of Kollima 55 (copolymer of polyvinyl pyrrolidone/polyvinyl acetate in 50% solution of iso-propanol) is mixed in with constant agitation and under a nitrogen blanket.

To test the resulting adhesive composition, colored Polaroid diffusion transfer prints, both wet and dry, are laminated to a piece of clear polyvinyl chloride having a thickness of 5 mils. Lamination is accomplished by passing the composite through rollers which apply 25 psi and are heated to 300.degree.F. with a dwell time of 3 seconds. After cooling, the protective polyvinyl chloride sheets have peel strengths in excess of 10 pounds per linear inch. Attempts to manually separate the PVC sheet from the print with the aid of a knife edge result in destruction of the emulsion before the bond is broken.

Claims

What is claimed is:

1. A permanent identification card comprising a photographic print having identifying indicia thereon and an optically-transparent, plastic sheet bonded to said photographic print by a heat-activatable, medium molecular weight, linear, saturated polyester adhesive composition containing from about 0.2% to about 2% by weight of an organic peroxide bonding promoter, and about 2% to about 25% by weight of a copolymer formed from vinyl pyrrolidone and a comonomer substantially compatible with said polyester adhesive, said weight percent being based on the total of the polyester adhesive and vinyl pyrrolidone copolymer said polyester adhesive composition also being optically-transparent when cured.

2. A card of claim 1 wherein said organic peroxide bonding promoter comprises a material selected from the group consisting of benzoyl peroxide, 2,5-dimethylhexane-2,5-di-per (2-ethylhexanoate) and 2,4-dichlorobenzoyl peroxide.

3. A card of claim 1 wherein said organic peroxide bonding promoter comprises equal parts by weight of 2,5-dimethyl-hexane-2,5-di-per (2-ethylhexanoate) and 2,4-dichlorobenzoyl peroxide.

4. A card of claim 3 wherein said copolymer comprises a copolymer of vinyl pyrrolidone and vinyl acetate.

5. A card of claim 4 wherein said photographic print comprises a diffusion transfer print.

6. A card of claim 4 wherein said photographic print comprises a color diffusion transfer print.

7. A card of claim 6 wherein the photographic emulsion of said color diffusion transfer print has a topcoat containing polyvinyl alcohol and polyvinyl pyridine.

8. A card of claim 7 wherein said plastic sheet comprises polyvinyl chloride.

9. A card of claim 8 which additionally contains a protective plastic sheet bonded to the rear of said photographic print.