US 2647849 A
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3 D. J- DOUGLAS ET AL 7 2,647,849
LETTERING-FILMS Filed April 10, 1950' TM /5 1*! la j /Za lJ g 45 [NVENTO/QS DONALD J. DOUGLAS PH/L/P V. PALMQu/sT b JEROME!) GROVE W IWMXP/Qz/q ATTORNEYS metal.
Patented Aug. 4, 1953 PATENT OFFICE LETTERING FILM Donald J. Douglas, Mendota Township, Dakota County, Philip V. Palmquist, New Canada Township, Ramsey County, and Jerome D. Grove, St. Paul, Minn., assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware Application April 10, 1950, Serial No. 155,102
8 Claims. (Cl. 154-468) This invention relates to lettering-films and to the application of such films, in the form of letters, designs and the like,-to bare metal and. other surfaces. The products of the invention have found particular utility in providing lettering and insignia for the bare metal exterior surfaces of airplanes and for the beaded surfaces of reflex-reflective roadside signs.
Of the previously available means for providing letters and insignia on metal and other surfaces, hand painting and stenciling are perhaps the best known. On metal, the process ordinarily involves extensive preliminary preparation of the surface, including cleaning and priming, followed by application and drying of the paint. The process is time-consuming, particularly since it must be frequently repeated. On glass-beaded reflex-reflective signs, hand lettering has been the general rule. The time required for drying of the paint, added to the time required by the artist, makes this procedure slow and costly, particularly since the available paints do not hold up as long as the beaded surface, but must be replaced at least once during the useful outdoor life of the sign.
One way which has previously been suggested for the rapid application of letters and insignia to various surfaces is by means of printed transfers or decalcomanias. One advantage of such procedure is that the printed material may be i) produced economically and with exact uniformity from sample to sample. These decals are ordinarily in the form of extremely thin printed films bonded to an overlapping carrier web, from which they are removable on moistening with water or other appropriate solvent. The thin film is then either floated on to the work-surface, where it adheres by virtue of a soluble adhesive component, or is directly transferred to the work-piece after either the work-piece or the printed film is first coated with a thin layer of adhesive. Varnish is commonly employed in the latter case as the adhesive material. It forms a fully acceptable bond to many painted surfaces; however it does not adhere well to glass or bare Water-soluble adhesives are undesirable for outdoor application where prolonged weatherresistance is a requirement. Where a liquid adhesive is applied to the work-surface, such as a beaded sign, it invariably extends past the boundaries of the subsequently applied decal film, and thus interferes with reflex-reflection of underlying beaded surfaces. Large areas, long stripes and the like are not conveniently applied by these Prior art methods.
For these and other reasons, prior art preformed lettering films and decals have not been found satisfactory for such applications as the lettering of reflex-reflective beaded signs, striping of automobile bodies, and the marking of bare aluminum airplane panels. In spite of the disadvantages attendant therewith, beaded signs, for example, have consequently been lettered for the most part by hand painting.
It is therefore a principal object of the present invention to provide a lettering-film which overcomes the several defects and disadvantages of prior art decalcomania-type products and the like, and permits the application of accurately and uniformly shaped segments or sections of the film to bare metal, beaded signs, and other Work-surfaces to provide weather-resistant, longwearing, firmly bonded letters and other insignia. A related object is to provide a flexible and conformable lettering-film consisting of a weather-resistant decorative layer and a strong and highly adherent adhesive layer, supported on a temporary carrier web in position for direct application to the work-surface. A further object is the provision of such composite letteringfilms in roll or stack form, the film and carrier web being of such nature that the stack may be stamped, sawed, or otherwise formed to provide a large number of letters or insignia, and such that the individual letters or insignia, together with their individual lightly adherent carrier webs, may then be separated from the stack. The film is of a kind that can be directly applied to the work-surface to become firmly bonded thereto, and the carrier web can be removed without moistening or other treatment.
The present invention accomplishes these and other objects by providing a product which will be more fully described later by means of a number of specific examples, and which is illustrated in the accompanying drawing, in which Figure 1 is a view in perspective of a pre-cut stack of letters,
Figure 2 is a section taken at 2-2 of Figure 1 showing adjacent portions of two layers of the stack of letters of Figure 1 but on an enlarged scale, and
Figure 3 is a sectional representation of a portion of the lettering film applied to a reflexreflective beaded surface.
The construction of the lettering-film is represented in Figure 2, which shows in cross-section two consecutive layers of the film with attendant temporary carrier web as taken from the stack .20 of Figure 1. The lettering-film I0 consists of a decorative weather-resistant protective film layer 12 and a non-tacky, heat or solvent activatible, waterproof, adhesive layer II. The weather-resistant layer is lightly adhered to one surface I 1-of the carrier web 13, the opposite surface l5 of which contacts the adhesive layer Ila of the of the next adjacent lettering-film Ilia in the stack.
The application of the film to a reflex-reflective beaded surface 16 is shown in Figure 3. In removing a single letter fromthe stackill; separation occurs between the surface 15 of carrier web l3 and the adhesive surface Ha of. lettering film Na. At the same time the fil'mi lil= remains. attached to its carrier I3, and film lOa to its carrier 13a. The detached section, consisting of the film l and carrier 13, is-thenplaced: on the beaded surface with the adhesive layer ll contacting such surface, and is heated and pressed into full adhesive contact therewith.
The'film if! isnecessarily flexible and'easily deformable in order tooonform to the beaded surface; l6, and if handled separately in the form of cut-out letters WOllldf be easily pulled out of shape and would be'dimcult if not impossible to position accurately on the work-surface. The weather-resistant layer is, in some cases, somewhat tacky'wh'en heated, and has a tendencyto adhere to many surfaces; such adhesion is avoidedby the presence of the treated carrier 7 web. Hence it is desirable; particularly where heat-activation is to be-employed, that the lettering-film remain attached to the carrier until after it isbondedto'thework-surface. Thereafter, the carrier isdry-stripped away; as shown in Figure 3, leaving the film permanently bonded to the-beaded surface. The'heat-activated adhesive'layer H, under the heat and pressure applied; is caused to conform to the irregular surfaceof. the. work-piece, while leaving the weather=resistant decorative layer l2 unchanged.
The same relationships are generally true where the adhesive is solvent-activated. In some cases, however, as where the film is to-be applied as-a long stripe along a curved line or. in a larger area over a work-surface having compound curves, the activating solvent is applied to the film. while inplace on the carrier, and the film is-then at least partially stripped from the. carrier before application. to the work-piece.
Where the lettering-film, with its attendant carrier web, is wound'up in roll. form, it will be apparent that the same general relationships between adjacent layers stillapply. In such case, however, since the film. and carrierv remain as continuouswebs in the roll and during unwindin there. isless. likelihood. of the. temporary bond between film surface. i2 and carrierv surface l4 being broken,v and hence theadhesionbetween adhesive surface Ha. and carrier surface [-5 may safely be somewhat higher than. in the case of stacks of. pre-cut letters as in Figure 1..
The adhesive relationship between the various surfaces within the stack 20 of Figure l is critical to the successful removal of individual units from the stack and the subsequent successful removal of the carrier web from the individual letter or other segment before or after bonding to the work-surface. Over-all adhesion must be suflicient to keep the individual units together in the stack both before, during and after stamping or cutting into a specific desired shape. The
bond between adjacent units of the structure must'be, andlremain, low-enoughso that the'individual units may be separated from the stack and two parts of Xylol.
without disturbing the relationship between the film and carrier web components of such units, and without delaminating or otherwise interfering with either component. The bond between the two component portions ofeach unit must, on the other hand, be sufiiciently high to overcome the pull applied in separating the adjacent units, but must be readily broken when it becomes necessary to strip the carrier web from the decorative film, again without delamination or. disruption of the film or carrier.
These-several qualifications are attained, and theseveral objects of the invention accomplished, by means whichwill now be described in terms ofspecific but non-limitative examples.
Example 1 The carrier web consists of heavy fiat paper, for: example having a ream weight of '70 lbs. The paper is coated or sized on one side (the face sideof the finished web, corresponding to the surface M- of. Figure 2) with a plasticized heatadvancing amino-aldehyde resin face-size, and on the back side (surface I5 of Figure 2) with a polyethylene resin back-size. Heating of the coated web cures the amino-aldehyde resin and fuses the polyethylene resin into a continuous layer.
The face-size comprises an amino-aldehyde resin solution which is prepared as follows, all parts being by weight unless otherwise specified. To IOOOparts of 37% formaldehyde solution, add concentrated ammonium hydroxide to a pH of 7-8. Add 240 parts of urea, and heat the mix- 7 ture in a suitable kettle at C..for 50-55 minutesor until the ureais all dissolved. Apply a vacuum and drop the temperature to 55-60 C., and then add 592 parts of n-butyl alcohol, 60 parts petroleum Xylol (or Xylol) and 6 parts of orthophosphoric acid. Continue heating and distilling under vacuum, removing the water but returning. the organic solvent to the batch. When no more water comes over, cautiously distill out a portion of the solvent, to produce a viscous, clear solution containing, about 58% by weight of. residual solids as determined b heating a weighed 2-3 gram sample in an open dish at an oven temperature of. C. for two hours and weighing the residue. This solution is dil'utedwith n-butylalcohol to 50% solids-content for. use. Beetle Resin 227-8 is a commercially available example of such a resin solution, containing. 50% of a urea-formaldehyde-butyl alcohol resin in. amixture of three parts of butanol For best results these resins. should. have a turbidity value of about 93-98, where turbidity value is the percentage of xylol in. a solution brought just to turbidity at 25 C. by adding'further xylol to a solution of 10 gramsof the 50% resin solution in 75 ml. of xylol.
One part of. castor oil is added to two parts of the resin solution described above, and, shortly before coating, 60 ml. of a 50% solution in butyl alcohol of an acid alkyl'ester of phosphoric acid is added to each 5 gallons of solution as a catalyst.
The solution is applied to the paper at a wet weight of about 10-13 grains per 24 sq. in., and dried for 10-15 minutes in an oven heated to about 275 F.
The castor oil serves as an effective plasticizer for the thermoset amino-aldehyderesin coating. Oil-modified alkyd: resins. have also been found suitable as plasticizers.
The backsize is next applied, and consists of about 6-15 grains per 24 sq. in. of a solution of one part polyethylene resin in two parts of xylol. The coated web is then heated for about 5 minutes in an oven at 300 E, which completes the cure of the face coat and fuses the back coat into a continuous structure.
In each case, some of the solution penetrates and impregnates the paper, but suflicient solution remains on the surface to provide a smooth glossy finish.
The lettering-film is coated from solutiondirectly on to the face side of the carrier web, and in two layers.
The first layer, which forms the weather-resistant decorative layer of the lettering-film product, is composed of pigmented nitrocellulose lacquer. Application may be by spray-coating or brush-coating, or by means of spreader bars or knives, coating rolls, intaglio printing, or screen process, or in any other conventional manner. The volatile vehicle is then removed by evaporation. In general, the thickness of this decorative layer should be at least about one mil; and preferably at least about 1 mils, in order that the lettering-film will not be perforated and torn when pressed on to glass beaded or other irregular surface.
The final layer consists of the heat or solvent activatible adhesive. The solution employed consists of 100 parts of rubbery butadiene-acrylonitrile copolymer, 10 parts of zinc oxide, 50 parts Vinsol" Ester Gum (glycerol ester of gasolineinsoluble resinous extract of pine wood), 50 parts heat-advancing 100% phenol-formaldehyde resin compatible with the copolymer, and 7.8 parts of dibutyl phthalate, in 400 parts methyl ethyl ketone. About 34 grains per 24 sq. in. of this solution is applied over the dried n-butyl methacrylate film, and dried at moderate temperatures. The resulting surface is temporarily activated at 180 F. to a condition in which it aggressively adheres under pressure to metal, glass, and other surfaces. The total thickness of the two layers is about 3-4 mils.
The composite product may then be wound into rolls or cut into sheets and arranged in stacks, and is ready for use. The stacked sheets may simultaneously be cut into units representing letters or other insignia by punching, sawing, or in other ways. The individual units remain together in the stack under ordinary handling, but may be easily removed when required. During removal, the film remains attached to the treated face side of the carrier Web, with the adhesive surface exposed and ready for activation and application to a work-surface. The film may be firmly and permanently bonded to bare metal surfaces, reflex-reflective beaded surfaces, painted or lacquered surfaces, etc. by pressing thereagainst at a pressure of not more than about 10-15 lbs. per sq. in. and at a temperature of about 200 F. The carrier web is then readily stripped from the film, preferably by a sharp jerking motion, leaving the glossy colored decorative letter in firmly bonded position on the work-surface.
As an alternative means of bonding the film, the adhesive surface may be activated by lightly moistening with a slow-drying solvent such as cyclohexanone, and by then pressing the activated film in place and removing the carrier Web. The solvent gradually escapes, and the film remains firmly bonded. For this method, the presence of the carrier web during brush or swab application of the solvent is particularly desirable.
Bonded to the clean but unprimed bare metal exterior surface of an airplane, such films show remarkable weather-resistance and abrasion resistance, remaining well bonded and attractive in appearance long after conventional painted areas have deteriorated.
While the specific adhesive described in ,Example 1 is found to give superior results over a wide range of conditions and is much preferred, nevertheless other adhesive compositions have given good results in a number of applications. Adhesives based on rubbery butadiene-acrylonitrile polymers and on polychloroprene rubber, in combination with compatible reactive phenol-aldehyde resin, and on butadiene-styrene rubbery polymers as well as crude rubber in combination with oil-soluble heat-advancing phenol-aldehyde resins, have been so used. One specific example consists essentially of a blend of 100 parts of polychloroprene, parts of heat-advancing phenol-formaldehyde resin, and 25 parts of hard coumarone-indene resin, applied from solution in 350 parts of toluol.
Polyethylene has been used on the carrier web as both face size and back size, in place of the carrier-web structure of Example 1. Films of polyethylene have also been used as the carrier web. In such cases, it is believed that the required differential in adherency within the stack of sheets is obtained because of the fact that the decorative film layer I2 is applied to the carrier web from solution, while the adhesive layer I I is pre-dried before it contacts the carrier web.
Example 2 In this example, ethyl methacrylate polymer, or alternatively a copolymer of four parts of ethyl methacrylate and one part of n-butyl methacrylate, is employed as the face size of the carrier web, with polyethylene as the back size. An air-drying alkyd resin enamel is then coated on the methacrylate-treated surface and allowed to dry and harden. The adhesive composition of Example 1 is coated on the polyethylene-treated surface of the carrier and dried to a tacky, partly cured, firm state, after which the sheet is wound up on itself in roll form. The still tacky adhesive then adheres preferentially to the alkyd resin coating, and separates from the polyethylene surface when the roll is unwound. Instead of using the reverse side of the same carrier web, a separate carrier may be employed for spreading, partially drying, and applying the adhesive layer.
A solution-of the condensation product of glycerine, phthalic anhydride, and linseed. oil free .fatty acids, suitably pigmented and with driers Example 3 A paper carrier web coated on both face side and back side with polyethylene was coated. on the face side with a layer of air-drying enamel comprising a drying oil varnish containing a decorative pigment. The coating may be applied in decorative, weather-resistant,
firmly bonded to such work-surface.
any convenient manner. The coating 'was airdried until hard. Acoating of the adhesive compositionof'Example l wasthen'applied as'there described. The resulting sheets 'could'be stacked, cut, removed as individual units, the film adhered to various surfaces, and the carrier web removed, in providing decorative letters and other insignia.
Example 4 eral colors were individually applied by means of screen-process technique.
The final color could also 'be applied as a continuous layer, serving as a background as well as a part of the design. After the enamel had dried, the entire surface was covered with the adhesive composition of Example'l, applied as a pre-formed and partially dried coating from a removable carrier web. The completed sheetwas cut into individual segments corresponding to the individual printed designs, the unprinted areas being discarded. The designs could be applied to bare metal and other surfaces, andthe'carrier web removed, to form firmly bonded coatings.
It will be seen that our invention provides a number of advantages in the application of decorative coatings, letters, stripes, designs and the like to bare metal, painted surfaces, beaded reflex-reflective surfaces, etc. As previously noted, 7 these pre-formed and pre-dried'coatings or films are thicker, and much more resistant to physical damage and weathering, than films of the same paintable lacquers, varnishes or enamels which have been applied directly to the sign or other work-surface by painting, and are also more The films are easily prepared by a variety of coating methods, and may readily be produced either as singlecolor protective or lettering-films or in multi-colored patterns. Designs may be pre-out in multiple units, the individual units thus being necessarilyidentical. Such units may be kept in stack form for convenience in handling, the individual sheets being adequately held together in the stack but being readily removable when desired. The letters or other insignia may be adhered directly to bare metal and other surfaces without priming of the surface and without the application of liquid adhesives, and when once appliedarefound -to be firmly and permanently bonded, anditobe immediately weather-resistant andnon-tacky without the necessity of preliminary drying or curing. The film asapplied to the work-piece is flexible and conformable so that it is suitable for highly complex curved surfaces as well as flat surfaces, yet is considerably thicker and hence much more weather-resistant than films formed in situ by spraying or brushing.
Having described various embodiments of our invention for purposes of illustration, but without intent to be limited thereto, what we claim is as follows:
1. A composite supported lettering-film structure as herein described, adapted for storing and for. forming into desired shapes while in stack ;form-, with subsequent ready removal of individual units therefrom, said structure comprising a thin, flexible'and conformable lettering-film temporarily mounted on a unitary carrier sheet,
the lettering film comprising: (1) a decorative weather-resistant film, at least one mil thick, of paintable organic film-forming material selected from the class consisting of drying-oil varnishes, cellulosic lacquers, and air-drying alkyd resins; and, permanently bonded to one surface of said film, (2) a layer of normally non-tacky waterproof adhesive selected'from the class consisting of heat-activatible and solvent-activatible adhesives and comprising a rubbery polymeric base and a compatible heat-advancing phenol aldehyde resin; the carrier sheet being temporarily adhered to the other surface of said decorative film and dry-strippable therefrom; said carrier sheet comprising a flexible sheet material each surface of which constitutes a smooth continuous film of a flexible waterproof film-forming polymer selected from the class consisting of thermoset plasticized amino-aldehyde resin, polyethylene, cellulosic polymer, and methaerylate polymer; the elements of the structure being selected such that the adhesion at normal temperatures -of the decorative film to the adjacent surface of thecarrier-sheet is greater than the adhesion of the adhesive layer to the opposite surface of the carrier sheet.
2. A unitary package of lettering-film having a plurality of juxtaposed composite layers lightly and removably adherently bonded together, each of said composite layers consisting of a thin, fiexible and conformable continuous lettering-film temporarily mounted on, and substantially cotei ininous with, a flexible unitary carrier sheet; said lettering-film comprising: (1) a decorative weather-resistant film, at least one mil thick, of p-aintable organic film-forming material selected from the class consisting of drying-oil varnishes, cellulosic lacquers, and air-drying alkyd resins; and, permanently bonded to one surface of said film, (2) a layer of normally non-tacky waterproof adhesive selected from the class consisting of heat-activatible and solvent-activatible adhesives and comprising a rubbery polymeric base and a compatible heat-advancing phenolaldehyde resin; the carrier sheet being temporarily adhered to the other surface of said decorative film and dry-strippable therefrom; said carrier sheet comprising a flexible sheet material each surface of which constitutes a smooth continuous film of a flexible waterproof film-forming polymer selected from the class consisting of thermoset plasticized amino-aldehyde resin, polyethylene, cellulosic polymer, and methacrylate polymer; and said unitary package being further characterized in that the adhesive bond at normal temperatures between the decorative film and the adjacent surface of the carrier sheet within one said composite layer of said package is greater'than the bond between the adhesive layer and the opposing'surface of the carrier sheet of the next adjacent composite layer of said package, to a degree permitting removal of the outermost of said composite layers from said package without disruption of the temporary bond be tween the carrier sheet and the weather-resistant film of said outermost composite layer.
3. The article of claim 1 in which the surface of the carrier sheet temporarily adhered to the decorative film is constituted of a methacrylate polymer, and the decorative film comprises an air-drying alkyd resin.
4. The article of claim 1 in which the surface of the carrier sheet temporarily adhered to the decorative film is constituted of a thermoset plasticized amino-aldehyde resin, and the decorative film comprises a dry-oil varnish.
5. The article of claim 1 in which the surface of the carrier sheet temporarily adhered to the decorative film is constituted of a thermoset plasticized amino-aldehyde resin, and the decorative film comprises a cellulosic lacquer.
6. An article having a surface and, firmly adherently bonded thereto, a thin decorative lettering-film as defined in claim 1 in which the decorative layer comprises an air-drying alkyd resin.
7. An article having a surface and, firmly adherently bonded thereto, a thin decorative lettering-film as defined in claim 1 in which the decorative layer comprises a drying-oil varnish.
8. An article having a surface and, firmly adherently bonded thereto, a thin decorative lettering-film as defined in claim 1 in which the decorative layer comprises a cellulosic lacquer.
DONALD J. DOUGLAS. PHILIP V. PALMQUIST. JEROME D. GROVE.
References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Laws Nov. 11, 1941 Groff Mar. 10, 1942 Humphner Oct. 27, 1942 Francis et al. July 18, 1944 Palmquist Aug. 28, 1945 Burdick Jan. 2, 1951 Wittgren July 3, 1951 Buck July 10, 1951 Buck Ant. 8. 1952