US3298850A - Dry transfer materials - Google Patents

Description

Jan. 17,'- K. J- REED ETAL 3,298,350

' DRY TRANSFER MATERIALS Filed March 18, 1963 FIGB 3,298,850 DRY TRANSFER MATERIALS Kenneth James Reed and Alan Lennox Lythgoe, London,

England, assignors to Letraset Limited, London, England, a British company v Filed Mar. 18, 1963, Ser. No. 265,996 Claims priority, application Great Britain, Mar. 21, 1962,

18 Claims. (Cl. 117-3.1)'

The invention relates to adhesive transfers (decalcomanias) and more particularly to a form of transfer material in which an image, design or printed matter (hereinafter generally referred to as indicia") may be transferred from a carrier sheet toa receiving surface. The invention includes transfer materials, their production and the processess of their use. i

It is an object of the present invention to provide a new form of dry transfer material in which the indicia can be transferred intact, without the necessity of applying any liquid to release the indicia from the carrier sheet.

Transfer may be effected in a suprisingly simple, quick and effective manner to all types of receiving surface and the adhesive strength may be designed in the range of low to very high adhesion values. The method of transfer consists in placing the transfer material on a receiving surface with the adhesive side down and applying pressure or pressure plus activating means to the back of the carrier sheet over the indicia to be transferred so that when the carrier sheet is lifted away the transferable indicia will be released and transferred intact and substantially without distortion and will be adhered by a continuous layer of adhesive beneath the indicia this layer being exactly contiguous therewith.

The transfers are prepared by applying to one side of a carrier sheet by aprinting operation the transferable indicia and over which there is then applied an adhesive which completely covers the indicia (contiguous adhesive) and also overlaps onto the surrounding carrier sheet. The overlapping adhesive avoids the alternative and virtually impossible requirement of perfect registration of adhesive and indicia but introduces the serious problems of transfer of the overlapping adhesive onto the receiving surface, as free contaminating adhesive, or if the overlapping adhesive is made non-transferable the cohesive strength of the adhesive, which usually increases as the adhesive strength increases, will inhibit transfer or tear off the edges of the indicia during transfer.

The transfers of the present invention are characterised in that the overlapping adhesive is non-transferable onto the receiving surface and free adhesive will not contarninate the receiving surface even when pressure has been applied to the carrier sheet over the overlapping adhesive. Non-transference of adhesive in the overlap area is achieved partly by natural adhesion of the adhesive to the carrier sheet and also by the additional feature of carrier sheet reaction which may either increase the natural adhesion of the adhesive to the carrier sheet or preferably reduce or eliminate the adhesion of the overlapping adhesive for the receiving surface.

According to the present invention therefore, there is provided a dry transfer material which comprises a carrier sheet which has a polymer surface susceptible to solvent attack, indicia in printing ink on said carrier sheet, said indicia being resistant to said solvent attack and adhesive covering said indicia, and overlapping onto said carrier sheet, the adhesive power of the adhesive for a receiving surface determined by its peel bond adhesion ited States Patent M thereto, being less in the said overlapping areas than in usually suitable.

3,298,850 Patented Jan. 17., 1967 the areas registering with the indicia, by reason of a modification of the adhesive solely in the overlapping areas resultant on solvent action on the surface of the carrier sheet in those areas. H

The solvent action referred to may result from the presence of a solvent in the adhesive itself or the modification of the surface of the carrier sheet may be achieved by applying a solvent to the assembly of the indicia on the carrier sheet before applying the adhesive, the indicia constituting in both cases a barrier to the action of the solvent on the carrier sheet in those areas covered by the indicia. The solvent action may cause an actual weakening or shear of the adhesive layer exactly at the margins of the indicia to take place during the production of the transfer (so-called pre-shear) or the result may be so to weaken the adhesive film in the overlapping areas referred to that shear takes place at the margins of the indicia at the moment of transfer.

As noted above, the transfer materials of the present invention may employ adhesives of considerable tensile strength since, due to the deactivation of the adhesive in the areas lying outside the indicia, the danger of transferring such overlapping adhesive is eliminated. This is a factor of great importance as permitting very strong .adhesion of the indicia to the receiving surface. However, it is necessary to ensure'that the indicia do not transfer prematurely, e.g., on storage or handling. One way of achieving this is to provide a removable protective sheet which lies over the adhesiveface of the transfer and can be removed when the transfer is required for use; in this case ofcourse the protective sheet must itself have very high release properties and a silicone-treated paper is In another method it may be arranged that the adhesion of theindicia to the carrier sheet may be of sufficient strength that risk of premature transfer is thus minimised, the release of the indicia from the carrier sheet being accomplished by effecting a local stretching of the carrier sheet relative to the ink indicia. Both the aforesaid methods may be employed together. i

It will thus be appreciated that Within the scope of this invention transfer materials of variously different charac ter may be produced, care being taken in all casesso to select the. characteristics of the elements of the transfer that the desired interfacial adhesi-ons are achieved to lead to the correct end result, i.e. to the'transfe-r of the indicia and to the transfer with the indicia only of adhesive exactly coextensive with the indicia.

The desirable characteristics of the individual elements of the transfer materials of this invention will now be described in further detail.

CARRIER SHEETS To obtain accurate positioning of the transfer on the receiving surface, it is desirable that the carrier sheet and adhesive should be light transmitting, i.e. transparent or translucent, so that the receiving surface is visible through the transfer sheet at'the moment of transfer. The carrier sheet may have either a high gloss,.semi-gloss, matt or embossed finish and the indicia will transfer with a replica of the carrier sheet surface from which it has been transferred. A matt surface provides a substantially easier dry release of the indicia and an embossed surface shows easier stretch-freeing.

The thickness of the carrier sheet may bevaried between quite widelirnits determined in the thinner gauges by the difliculty of handling very thin and flimsy sheets, particularly where colour to colour register is required; in the thicker gauges the stretch-free process requires increasing localised pressures. A practical caliper range is 3 .0005.008 inch and the most useful range is .0015-.003 inch.

The carrier sheet reaction involves softening or swelling the carrier sheet surface. Consequently the carrier sheet surface may intermix with the adhesive, or it may physically occlude the adhesive. A substantial disturbance of the carrier sheet surface is desirable in order to break up the adhesive film and occlude it.

Such disturbance is best achieved by using a molecularly orientated organic polymer either as a self supporting sheet or as a layer on another support. An orientated self supporting polymer sheet has a stressed surface and can be identified by heating at or above the softening point and measuring the heat retraction in sheet dimensions. Sheet orientated by monoaxial stretching will retract in one dimension; sheet orientated by biaxial stretching will retract equally in two dimensions and sheet which has triaxial orientation will contact unequally in two dimensions. If the polymer is orientated non uniformly or locally, or is supported on another support sheet, orientation may be measured by birefringence or by X-ray diffraction or infra-red dichroism.

Orientated i.e. stressed, carrier sheet reaction to the adhesive is visible as a stresscracked, etched or reticulated effect. It appears that in an extreme case the surface breaks up into a laminar or scale-like effect which may further curl over and effectively mask the adhesive. Such carrier sheet reaction therefore is most easily distinguished by a difference in surface finish, i.e. gloss value, of the carrier sheet in the reacted and non reacted regions. If the adhesive has caused the reaction, rather than a solvent applied before the adhesive, the difference in surface finish is usually still visible but if necessary, an adhesive unmodified chemically by the carrier sheet may be removed by extraction with a solvent inert towards the carrier sheet. Since the carrier sheet does not react (i.e. change in surface finish from its original condition) beneath the indicia, by removal of one element of indicia, and by comparing the carrier sheet surface finish beneath this element of indicia and in the adjacent overlapping region, the carrier sheet reaction may be visually observed.

INDICIA The indicia must be composed of a material which acts as a barrier and prevents reaction of the carrier sheet with the adhesive in the areas of indicia. Generally, the indicia itself, or the printing ink from which the indicia are derived, should not itself react with the carrier sheet, although a very mild etching of the carrier sheet may be permitted, this degree of reaction being very slight compared to the overlapping adhesive reaction. Strong reaction of the carrier sheet with the indicia would be shown as a marked change in surface finish beneath the indicia and almost always in disintegration of the indicia film which will no longer transfer intact. Such disintegration of the overlapping adhesive film is of course, highly desirable in order to provide the pre-shear characteristics. Barrier properties are generally obtained by selection of dry indicia films which are not dissolved by the liquid adhesive solvents. Continuous indicia, free from pinholes, and with sufficient film thickness are required. It is perhaps surprising that an indicia in the form of a dot or a line .002 inch Wide may still provide a fully satisfactory barrier and will transfer perfectly even when a very strong pressure sensitive adhesive is used and explains why the finest detail may be produced in the transfers of this invention. The adhesive contiguous with the indicia usually has a smooth, highly gloss appearance and contrasts sharply with the overlapping, reacted adhesive.

The indicia should have suflicient tensile strength and flexibility to transfer without breaking and without distortion even when transfer pressure is applied as lines or bands leaving small gaps. Generally the tensile strength is measured by the force necessary to break a one inch 4 wide strip of indicia and the lower limit must exceed the peel bond of the indicia to the carrier sheet and withstand the forces involved in stretching the carrier sheet. A tensile strength of at least 20 grams per inch is normally required (which equals about psi. for .0003 inch thick indicia) and tensile strength values of 200' grams may be achieved. The flexibility of the indicia, measured by elongation at yield and break points must be sufiicient to withstand handling stresses but must not be so high as to prevent the stretch-freeing mechanism if that is to be employed.

ADHESIVE Substantial shearing of the overlapping adhesive, during preparation of the transfer will usually occur. If shear is inadequate, then on transfer the edges of the indicia will be torn or transfer will be inhibited, or the adhesive itself will transfer. The greater the film or cohesive strength of the adhesive, the greater must be the pre-shear, which is believed to be caused by disintegration of the overlapping adhesive by the severe surface stresscracking of the carrier sheet. A smaller proportion of adhesive post-shear may occur at the moment of transfer. Pre-shear may be measured by comparing the force necessary to peel a long thin element of indicia off the transfer sheet compared. to the force when the long edges of such element have been cut.

It is highly desirable that there should be a considerable difference in tack between the adhesive in the area of the indicia and in the overlapping area, since otherwise a powerful adhesive will tear a receiving surface such as paper in the overlapping regions when the carrier sheet is pulled away. Using sufficiently large indicia, e.g. as strips one inch wide, the tack differential may be measured by applying the indicia to a receiving surface and then peeling off and comparing this (high) value with the force necessary to peel off a one inch wide strip of carrier sheet with overlapping adhesive when applied to the receiving surface with the same force as the indicia.

The overlapping adhesive may have high natural adhesion to the carrier sheet; the non-transfer properties are, however, further enhanced by the carrier sheet reaction which increases the adhesive bond to the carrier sheet. and also by the tack differential.

Initially the indicia will adhere to the carrier sheet with a measurable peel bond. Whereas this peel bond may only be about 4 grams per inch width, it has been found that there is also an edge effect on each of the indicia which increases the force required to remove the indicia to many times the peel bond value (which is measured with the edge of the indicia already separated from the carrier sheet). This edge adhesion is a useful feature in preventing premature transfer. There is a possibility that the perfect contact between indicia and carrier sheet owes its edge adhesion to atmosphere pressure. Irrespective of the theory of adhesion, a positive means of ensuring transfer instantly when required is achieved by the stretch-freeing mechanism. In practice, to test this feature, the indicia are applied to the carrier sheet which is then supported at its ends and then strokes with a stylus or serrated bar are applied through the carrier to the indicia which are not in contact with any surface. The same test may be applied after the adhesive has been applied. Freeing of the indicia is visible as small spots of different colour or tone occuring (due to air entering between indicia and carrier sheet) or a complete change of tone, showing the whole indicia has been released, may be observed. The freed indicia clings to the carrier sheet by static electricity forces. It only requires that a small amount of such freed points occur at the edge of the indicia to break the edge adhesion bond and permit easy and reliable transfer. Apart from visual changes, the stretch-freeing may be identified by determining the percentage transfer before and afterstretching by the pre-stretch process, Data, which refers to certain of the examples which follow later herein, are set out in the following Table 1:

TABLE 1 Transfer at- Example Stretched p.s.i. p.s.i. 50 p.s.i. 110

r Y 1 p.s.1. 1

High Tack Adhesive,. 0% Example 1, 10% 100% 100% 100% Low Tack Adhesive, 0% 0% 25% Example 3, 0% 100% 100% 100% The specification'of the physical and chemical prop I erties of a carrier sheet and indicia combination which will exhibit stretch-freeing involve a number of complicated measurements and calculations and suitable materials are best selected by the visual andtransfer characteristics described above. terials is assisted by a knowledge of the importance 'of the elongation characteristics of the materials used. The basic requirement for stretch-freeing is that when the carrier sheet is stretched, the indicia should resist stretching (and not fracture) to anextent sufli-cient to break some or all the bonds of adhesion. Obviously'the stronger the bonds of adhesion, the greater must be the resistance of the indicia. As an approximation, the percentage elongation of the carrier sheet at break point, usually a known or easily determined value, and the elongation of the indicia at break-point which is readily determined, are correlated whereby the carrier sheet elongation should exceed the elongation of the indicia with the limitation that the indicia should preferably not exceed 50% elongation otherwise an impractical amount of carrier stretching is required. Values for actual examples which show and do not show stretch-free relationships are given in Table 2. e

TABLE 2 Property Example 1 Example 2 Example 3 Example 4 Stretch-free Good Good Excellent Nil Carrier Sheet Elongation, percent 10 10 100 100 Indieia Elongation,

percent 5-6 5-6 15 55 Adhesion values and their inter-relationships are very important physical properties in the three element assembly and its ancillary protective cover and receiving surface. There are eight adhesion properties identified as follows:

Adhesion values are conveniently estimated by peel bond values which are determined by applying a long However selection of ma- 1 test strip, one inch wide to a standard surface, such as matt polyester drawing film under specified pressures and then measuring the force in grams required to peel off the strip again at right angles at a rate of peel of one foot per minute.

Adhesion 1 and 2.-Adhesion 1 is measured by a direct 90% pull and not as a peel bond, the test procedure serving to measure the force necessary to break the edge adhesion of the indicia. Very high forces are required to overcome edge adhesion but once an edge has yielded, the subsequent force (-peel bond) to completely remove the indicia may be a small fraction of the edge value. The edge value may be 2,500 grams per sq. inch of indicia with a corresponding peel bond of only 4 grams i per inch width. The stretch-free mechanism is perfectly able to overcome the high edge adhesion, which explains its importance. Adhesion No. 2 must be lower than Adhesion 5 since it is the latter value which pulls the indicia off the carrier sheet after it has been stretchfreed, unless 100% stretch-freeing is used.

Adhesion 3.This should exceed other values, so that the adhesive never parts from the indicia.

' Adhesion 4.-When accurate positioning is required this value should be lower than No. 1 unless pre-stretching is used when No. 4 should be lower than No. 2.

Adhesion 5 .This determines the final adhesion of the indicia to the receiving surface after transfer by the correct transfer process. A range of very high values to very low values may be designed. For example on paper surfaces 2. value below 100' grams e.g. 50 grams is de sirable if it is required to subsequently remove the indicia without tearing the surface.

Adhesion 6.-T his must exceed the forces tending to cause removal of the adhesive that is adhesion to the receiving surface, i.e. Adhesion 7.

Adhesion 7 must in turn be less than Adhesion 5 to give the required tack differential and in fact No. 7 is frequently zero.

Adhesion 8 should be as low as possible and less than Adhesion l and preferably less than Adhesion 2.

By way of example, some of the above adhesion values are given in Table 3:

TABLE 3 0. 100 at C.

Selected indicia may be permanently fixed to the receiving surface by the application of a fixing liquid after transfer. indicia are selected so that they may be softened by the application of a liquid which causes the indicia to become soft and tacky and makes direct contact with the receiving surface. The liquid should not however cause the indicia to soften to such an extent that it flows and loses its shape. The combination of an active solvent, which softens the indicia but causes it to flow, and an inert liquid which prevents the flow, provides a suitable composition. The correct proportions are determined by gradually adding the inert solvent to the active solvent until flow is controlled and the indicia still makes full contact with the receiving surface. The fixing liquid may contain a polymer to provide an additional protective film over the indicia (see Example 5).

The stretching process as noted above, may be used as an important additional feature to provide positive protection against premature transfer. The necessity for such protection is best understood by considering the confiicting requirements of the transfer assembly when using a pressure sensitive adhesive. It is necessary to store and transport very large quantities of the transfers even under adverse conditions, with the protective cover in situ but when the latter is removed prior to transfer, the indicia must be completely from transfer onto the protective cover. Furthermore, during transfer it is necessary to position the transfer accurately onto the receiving surface and several contacts may be made under light finger or hand pressure, in which no trans-fer must occur. Nevertheless when the final position is achieved, instant transfer must be possible. In a transfer constructed so that the adhesive pulls the indicia off the carrier sheet it is difficult to achieve positive protection from accidental transfer, particularly as the adhesion of a transfer varies according to the roughness and type of the receiving surface and according to the indicia area.

When the stretching process is to be employed it is preferred to provide a three element transfer assembly in which transfer will positively not occur under light finger pressure /2 p.s.i.) and preferably no transfer will occur up to a pressure of 15 or even 50 psi. However, if the carrier sheet under the indicia is stretched, reversibly or irreversibly, the indicia is partly or completely freed from adhesion to the carrier sheet and will completely and instantly transfer at a low pressure such as 50 or 15 p.s.i. Stretching may be carried out manually by applying a series of strokes of a small radiused rod, ball pen or pencil and a pressure of at least 50 p.s.i. must be applied to cause such stretch-freeing of the indicia. In practice a pressure of 500 or even 1500 psi. is used, the latter being achieved by applying light Writing load of 2 ounces to a ball pen having a .04 inch diameter ball.

Naturally such stretching pressure in addition to freeing the indicia, will simultaneously transfer the indicia. Stretching and transfer in two separate stages may also be practiced and is particularly valuable when either the heavy stretching pressure must not be applied to a delicate receiving surface, or in mechanised application of the transfer. For example the carrier sheet may be pulled over a serrated bar to cause local stretch release at 500 p.s.i. at the tips of the serrations and then applied by a 15 p.s.i. pressure of a rubber roller.

Bearing in mind the requirements in terms of'physical characteristics discussed in detail above, the materials employed may be selected from the following, which are by way of example.

CARRIER SHEET The carrier sheets may consist of individual sheets or reels of a polymer or co-polymer which may be a selfsupporting film or may be applied to a support such as paper, regenerated cellulose, foil or other polymer. Suitable polymers and copolymers are as followspo lystyrene and polystyrene homologues and substituted polystryrene polymers including high impact polystyrene, polystyrenes with rubbery additives such as butadiene as comonomer, polystyrene-butadiene-acrylontrile copolymers; acrylic polymers such as polymethylmethacrylate, and other alkymethacrylates, acrylic polymers with other polymers or co-monomers such as butadiene, and acrylonitrile; vinyl polymers including vinyl-halides, -esters, -acetals and -alcohols and copolymers and with other polymers and co-monomers, cellulose esters and ethers, polycarbonates, rubber hydrochloride, polyolefins such as polyethylene of normal and high density and polypropylene; polyesters; polyamides; gelatin.

Carrier sheets which are soluble or swell or are stress cracked in selective solvents or are reactive towards adhesive liquids are all useable.

The above carrier sheets are characterised in that they soften, swell or etch in selective reactive liquids such as organic solvents, water, acids, which may also be present in the adhesive composition, to provide a reactive adhesive and indicia may be selected from the following list to resist particular liquids and act as the barrier layer.

In the preferred form of the invention, the above polymers are additionally molecularly orientated. Orientation by biaxial stretching is particularly useful and polystyrene and polystyrene containing polymers, polyvinylhalides and copolymers, preferably unplasticised, and polypropylene and polyethylene are particularly useful.

INDICIA The dry indicia preferably consists of an organic polymer which may also contain plasticizers, dyes, pigments, stabilisers and fillers. Suitable polymers are cellulose nitrate; cellulose acetate; cellulose acetobutyrate; ethyl cellulose; ethylhydroxyethyl cellulose; dry oils and dry oil varnishes; alkyds and alkyds modified or copolymerized with a drying oil, styrene, urethane, vinyl, silicone or acrylic resin; polyvinyl-halides, -esters -acetals and alcohols; polyurethanes; epoxy polymers, epoxy-phenolic, epoxy-polyamide and catalysed epoxy resins and copolymers; urea-, melamine-, and benzoguanamine-formaldehyde polymers; chlorinated and isonerised rubber; polystyrene and polyvinyl toluene; polysiloxanes and silicone containing polymers; polyacrylates, polymethacrylates and thermosetting acrylic resins; gelatin; zein; casein, starch or modified starch.

The above polymersare applied to the carrier sheet preferably in the form of a layer of viscous liquid such as a lacquer, i.e. a solution in organic solvents, or an aqueous emulsion, hot melt, plastisol, organosol or as a liquid monomer or liquid polymer containing catalyst. Various printing processes may be used such as screen process, fiexographic or gravure printing. The liquid indicia are then dried or set. If the lacquer contains a solvent this must not react with the carrier sheet under the particular drying conditions and coating thickness, to damage it mechanically or to cause distintegration of the indicia film or increase the adhesion of the indicia past the acceptable limits.

The dry indicia is formulated to provide the necessary specifications of barrier properties, tensile strength, elongation and adhesion to the carrier sheet. Tensile strength is mainly determined by the polymer used and to a less extent on the plasticizer concentration; elongation is also determined mainly by the polymer and the amount of plasticizer; mutual adhesion between carrier sheet and indicia is determined by the polymers used for both the carrier sheet and indicia and also by the plasticizer concentration of the latter, a high plasticizer concentration giving more adhesion than a'low plasticizer concentration by reducing the stretch-free properties. The same chemical class of polymer is preferably not used for the carrier sheet and the indicia since strong specific adhesion forces may be produced.

The pigments, dyes, fillers and stabilisers which may be incorporated in the transferable layer have a moderate effect on tensile strength, elongation and adhesion which must be allowed for. The tensile strength of the indicia is dependent on its thickness and this is also controlled.

PRESSURE SENSITIVE ADHESIVES These consist of a tacky resin or polymer. Alternative- 1y an intrinsically tacky polymer or elastomer may be tackified by the addition of a tacky or non tacky resin or plasticiser. Suitable polymers and tackifying materials are as follows: natural unvulcanised rubber, vulcanised rubber, synthetic rubber such as polyisobutylene, polychloroprene, polybutadiene, polyacrylonitrile and copolymers of these and with styrene and styrene homologues and acrylic monomers; polyvinyl alkyl ethers such as methyl, ethyl and butyl ethers; acrylic and methacrylic polymers such as polybutylacrylate and copolymer with polybutylmethacrylate. Tacky and tackifying resins conv non blocking at room temperature.

. taken place.

sist ofrosin and rosin derivatives such as hydrogenated rosin, esters and alcohols; liquid polymeric styrenes and styrene homologues; polymerised terpenes such as pinene; ketone resins; low molecular weight polyisobutylenes and other olefins.

If required, a tack controlling agent may be added preferably in the form of a soft or easily deformable material to allow good flow and contact with the receiving surface. Particularly suitable materials are long chain "hydrocarbons containing 12 or more carbon atoms such as parafiin and microcrystalline wax, polyethylene waxes, fatty acids and their derivatives such as metal salts, esters,

glycols and fatty alcohol ethers of polyethylene glycols;

: polyethylene and polypropylene glycols.

The adhesives are preferably dissolved or dispersed in organic solvents or emulsified in water, the solvent or even the nonvolatile constituents of the adhesive being reactive towards the carrier sheet surface, at a given suitable temperature.

HEAT ACTIVATED ADHESIVES I These contain a polymer which may become tacky on heating or a tackifying resin or plasticiser is added, preferably to form a composition which is non tacky or even The incorporation of a solid plasticiser as a fine dispersion of crystals in the polymer is valuable as a delayed tack heat activated adhesive whereby the plasticiser melts and tackifies the poly- 1" mer at the activating temperature, but when the adhesive cools it remains tacky until the plasticiser crystallises again. Suitable polymers are ethyl and hydroxyethyl cellulose; polyvinyl acetate; polyamides. rials are included in the materials listed for pressure sensitive adhesives.

Many of the above heat seal adhesives may be used as solvent activated adhesives.

PRQTECTIV E SHEETS Suitable protective sheets may consist of a support sheet .to which is applied a release material to provide the required low adhesion values to the adhesive layer. Suitable support sheets are cellulosic materials such as kraft paper, glassine paper and vegetable parchment paper.

Suitable release materials are fatty acid chromium complexes or siloxanes such as polymethyl-siloxanes.

The siloxane is preferably obtained by applying a reactive material to the support which polymerises or copolymcrises with the support sheet to provide a siloxane which is insoluble, non-migratory and strongly adherent and therefore does not affect the adhesive properties of the and the materials may be applied as fluids, solution in organic solvents or aqueous emulsions.

The materials and method of the present invention, in

. a preferred form thereof, are illustrated in the accompanying drawings the details of which'are set out separately below. In each of these drawings the elements consist of a carrier film 1, indicia 2, adhesive 3 and a receiving sheet 4. The use is also shown of a ball point pen 5 as a means for effecting the transfer.

Referring to these drawings:

In FIGURE 1 there is shown in diagrammatic cross section a transfer material in which no reaction between the carrier film 1 and the adhesive 3 is shown to have When an attempt is made to transfer the indicia 2 onto a receiving surface the adhesive will either prevent transfer altogether if its cohesion is high enough, or will tear the indicia during transfer, or will tear the Tackifying matereceiving surface or will itself transfer and contaminate the receiving surface.

In FIGURE 2 there is similarly shown a transfer material according to the present invention wherein the initial orientation of the carrier film 1 has been broken up by the solvent in the adhesive 3 so that the film in the nonindicia areas is coarsely matted and at least partially occludes the adhesive 3, which shears at the margin of the indicia.

In FIGURE 3 there is diagrammatically represented a transfer material of this invention wherein the surface of the carrier film has been subjected to an advanced stage of stress cracking. The adhesive is occluded and sheared at the margins of the indicia.

FIGURE 4 illustrates an actual method of effecting transfer using a ball-point pen 5 to apply the pressure to the film 1. The pressure causes localised stretching of the film and thus establishes a mechanical break in the adhesion betwene indicia 2 and film 1. This in fact becomes visible as a change of colour, as viewed through the film, due to the entry of air between the film 1 and indicia 2.

FIGURE 5 illustrates the first step of removing the film 1 from the assembly, leaving the indicia 2 adherent via the adhesive 3 to the receiving sheet 4. No adhesive transfers outside the area of the indicia. The film 1 has a matt appearance except in the area from which the indicia have been transferred, which area is a clear, unmatted film, normally appearing darker than the rest because it is not scattering light as does the matted area.

In the transfer assembly and method of transfer of the present invention no pieces of overlapping adhesive will be attached to the edges of the transferred indicia after transfer nor will the edges of the transferred indicia be torn off or damaged. Moreover, adhesives ranging from low to very high adhesion values and adhesives normally having very high cohesive strength, including many conventional adhesives and pressure sensitive adhesives, may all be used in the operation of the invention because as another basic feature of the invention, shearing of the adhesive layer precisely around all the indicia edges, however complex and delicate, is provided.

Any type of transferable printed indicia may be provided including those with very fine detail, very high print quality, or multi-colours and either one or more of these may be printed on a single transfer sheet or reel, using adequate spacing between adjacent indicia to permit each transfer to be transferred without transference of adjacent indicia. The transferable indicia may comprise typographical characters such as letters, alphabets, numerals, punctuation and other printed matter such as designs, pictures, symbols, drawings, word instructions, nameplates, trademarks, half-tone dots and shading and mechanical tints, simulated wood grains and other finishes, and also discrete uniform areas of clear or coloured indicia. Designs with fine detail may be overprinted on a clear area of transferable indicia which ties together the whole design to give faster rate of transfer or ease of mechanical transfer.

The pressure required to transfer an indicia may be applied by manual or mechanical means, but pressure need not be applied necessarily to every part of indicia having high film strength for when pressure is applied as a series of close strokes of a stylus or ball point pen or radiused rod or threaded or serrated bar or blade, this may leave narrow gaps Where no pressure is applied. Of course if an indicia design consists of several pieces of disconnected detail each individual piece must be subjected sufiiciently to pressure unless the pieces are overprinted with a clear transferable indicia film as described above. Particular attention is given to applying pressure to the edges of the indicia from which peeling of the carrier sheet is commenced.

The following examples will serve to illustrate the invention (parts given are by weight).

1 1 Example I A carrier sheet is employed which consists of a light transmitting film of biaxially orientated polystyrene which retracts on heating above its softening point to one ninth of its original length and breadth and having a high gloss surface and a caliper of .0015 inch and an elongation of 10%.

To this carrier sheet an indicia is applied consisting of cellulose nitrate polymer and plasticiser, to provide a clear transparent indicia; the additional incorporation of a pigment or dye produces a coloured indicia, the clear and coloured indicia having compositions in the following range:

Parts Cellulose nitrate (nitrogen content 10.511%) 100 Plasticiser 20150 Pigment or dye 200 The very high pigment concentration is used when really opaque indicia are required to obliterate the underlying receiving surface after transfer.

Typically a black indicia ink consists of:

Parts Cellulose nitrate 100 Castor oil modified glyceryl sebacate 60 Dimethylcyclohexyladipate 14 Carbon black 20 A viscous solution of the above polymer and plasticiser in the following solvent is prepared:

Parts Isopropanol 43 Ethylene glycol monoethylether 350 and the pigment incorporated by triple roll milling and the ink is applied by screen process printing and dried by evaporation in a stream of warm air at 60 C. to give dry indicia with a thickness in the range of .0002 to .001 inch, depending on the printing conditions. The indicia may be substantially freed by stretching the carrier sheet.

Additional colours may be applied to the same sheet as a further printing operation to give multi-colour effects and indicia having numerous disconnected pieces may be tied together by printing clear indicia before or after the coloured indicia.

The solvents used in the above inks do not react with the carrier sheet even at the above elevated drying temperature, as shown by removing an indicia, e.g. with adhesive tape, and observing that there is no loss of gloss of the carrier film beneath the indicia compared to the unprinted adjacent film. A slight etching, i.e. seen as a semi-gloss finish on the carrier sheet, is acceptable particularly if it is desired to increase the mutual adhesion of indicia and carrier sheet, and this is achieved in the above ink compositions by replacing the ethylene glycol monoethylether by ethylene glycol monoethylether acetate.

To the carrier sheet and indicia, there is applied a tacky, cohesive and strong pressure sensitive adhesive having a composition in the following range:

Parts Elastomer 100 Tackifyin g resin 50-8 00 Antioxidant 110 The elastomer may be natural crepe rubber or reclaimed vulcanise-d rubber which are milled on a two roll mill or Banbury mixer to give suitable physical properties including solubility and viscosity in organic solvents. Solvents and tackifying resins are then introduced with vigorous agitation.

Typically an adhesive consists of:

Parts Crepe rubber 100 Po-lymerised B-pinene 170 Dihydroabietylphthalate 130 Diamylhydroquinone 4 This adhesive is dissolved into the following solvent mixture, which is reactive with the carrier sheet at C.:

Parts Aromatic hydrocarbon, boiling range 164-220 C.,

kauri-butanol value 500 Aliphatic hydrocarbon, boiling range l70198 C.,

kauri-butanol value 35 400 to give a viscous liquid which is roller-coated to give a uniform coating and then dried in a stream ofhot air at 90 C. to give a dry film of thickness, on the indicia, in the range of 0002-0005 inch. A-pronounced reaction between the overlapping adhesive and carrier sheet occurs during drying and is seen as a coarse matt finish on the dried sheet. If an element of indicia is now transferred, the contrast between the unreacted, glossy carrier film exactly beneath the indicia, and the surrounding reacted carrier film, is sharply visible.

To the above prepared transfer assembly, there is applied a I protective cover sheet consisting of vegetable parchment paper sheet coated with methylhydrogen polysiloxane polymer in toluene solution containing a metallic salt catalyst which is dried andpolyrnerised at 150 C. for one minute to provide a non migratory and strongly adherent high release coating to the vegetable parchment sheet.

Example 2 To a carrier sheet and black indicia prepared according to Example 1, there is applied a low tack pressure sensitive adhesive having a composition in the following range:

Parts Tacky elastomer or intrinsically tacky elastomer plus tackifying resins Tack controlling component 6-600 The tack controlling component reduces the tack of the otherwise very tacky adhesive to a designed level. Typical ly an adhesive consists of:

Parts Polyisobutylene M.Wt. 15,000 (very tacky elastomer) Paraffin wax, M.Pt. 150 F.

The elastomer solution is prepared as Example 1 and the wax is inconporated by heating the solution until the wax dissolves and then cooling with agitation to obtain a fine dispersion of the wax. The adhesive is dissolved in the same solvent mixture as Example 1 and applied by screen process printing to give a dry thickness over the indicia, after drying at 90 C. of .0005 inch.

This adhesive produces a highly reacted carrier sheet in which the overlapping adhesive is considerably occluded by the scale-like surface. By the application of the above relatively thick coating of adhesive, a small proportion of the overlapping adhesive remains unoccluded to leave a small residual tack in the overlapping adhesive which is most useful for holding the transfer sheet stationary on the receiving surface while pressure is being transmitted to the indicia to transfer it. Also the adhesive is substantially but not entirely p're-sheared and the residual cohesion of the adhesive holds the indicia onto the carrier sheet and has a useful but minor effect in preventing premature transfer.

Example 3 This is prepared exactly as Example 2 except that the low tack adhesive consists of an intrinsically tacky polymer plus tackifying resin and tack controlling agent as follows:

Paraffin wax, M.Pt. 145150 F 37 Parts Cellulose nitrate polymer 100 Epoxy soya bean oil 75 Rutile titanium dioxide pigment.a 135 There is then applied a heat activatable adhesive consisting of:

1 Parts Ethvlhydroxyethyl cellulose ,100 Dihydroabiethylphthalate s 400 The adhesive is dissolved in the same solvent mixture as Example 1 and applied by reverse roll coating and dried by heat at 90 C. to produce a highly-reacted carrier sheet which occludes the overlapping adhesive.

The transfer is carried out by applying the transfer to a surface at 50 C. or more. This activates theadhesive to a strong tack whereas the overlapping adhesive develops no tack. The carrier sheet may be prestretched, i.e. the indicia freed by mechanical or manual means before application to the receiving surface and before application of heat so that transfer can finally be carried out by a light pressure of 5 p.s.i.

Example 5 Fixing solvent for indicia of Example 1 may consist of the following:

t v I Parts Ethvl acetate (active solvent) 74 OP ethyl alcohol 90 This solvent is conveniently applied as an aerosol spray consisting of:

l Parts Above solvent mixture 34 Dichlorodifluoromethane propellant L...... 66

The following is an example of a.fixing solvent containing a polymer for permanent fixing of the indica of Example. 1 and which may be appliedby brushing and providing a protective coating over the indicia:

Parts Cellulose nitrate spirit. soluble gradefpolymer) a 13 Dimethylcyclohexylphthalate (plasticiser) 5.8 n-Butylacetatefactive solvent) 5.8

n-Butanol (inert solvent) 75.4

. Example 6 I An example of adhesive which is activated by solvent to a tacky condition. prior to transfer is provided by using the carrier sheet and indicia of Example 1 followed by the following adhesive i i preferably applied as aerosol spray. l

The transfer materials of the present indicia may consist of a varietyof adhesives and indicia, within the scope 'ofv the above "specifications, to provide new and valuable 'u'sesasfollowsr t t Direct 1mm plate-The indicia a Example 1 may be transferred to offset lithographic plates as direct images.

normal barrier properties Such plates may consist of paper or metal supports and direct images are commonly applied by typewriter or drawing with a greasy ink. The indicia of Example 1 provide precision images, equal to the highest quality printing, and in the form of lettering sheets provide a means for applying titles, text and designs directly to litho plates without the need for. photography. The indicia of Example 1 are sufficiently hydrophobic to accept ink and to print perfectly and the strength of the adhesive withstands printing stresses to provide long runs. Since no ov rla ping adhesive contaminates the litho plate and the adhesive is sheared perfectly at the edges of the indicia, clean images without scum of the surrounding plate are obtained. If very long runs are requiredfixing with a solvent which softens the adhesive or the indicia, such as carbon tetrachloride. for the adhesive and the fixing solvents of Example 5 for the indicia particularly in spray form are suitable. 1

Screen printing stencil.The indicia may be transferred to a screen printing mesh to provide a direct screen stencil, using printing inks which do not attack the indicia. A threaded curved or circular bar of one inch diameter is a convenient wav of stretch-freeing and transferring the indicia without distortion on the delicate printing mesh surface. If long runs are reouired, the permanent fixing process may be used. Additionally a liquid stencil :filler may be applied to all over the mesh after application of the transfer. and the original transfer removed, when the stencil filler has dried, the indicia acting purely as a mask. The indicia ofExample 2 having a lower adhesive power are suitable for this a plication.

Movie tricks.-Indicia of the present invention may also be a lied directly to positive motion picture film to give sufficient adhesion to withstand repeated projection and yet are sufiiciently thin to remain in focus and not interfere with rotection equipment or damage the film. Moreover, the indicia may be positioned and transferred to the film in an exact position. For example indicia may be printed in the form of a series of iris or other transitional effect to provide a fade-in and fade-out sequence extending over a considerable number of frames andthese effects may be exactly registered with the appropriate frames. If necessary the individual indicia may be tied together by a closely registering clear indicia to enable the whole strip to be transferred in one operation involving only the application of pressure. Naturally the pre-stretch process may be used so that onlv pressure of 15 p.s.i. is required to effect transfer and this will not damage the film.

1 Projection transfer.--Transfers for direct projection including the overhead projectors, may be prepared according to the present invention. The main requirements for projection of colour is that the transferred indicia has a glossy outer surface (i.e. non-light scattering), the adhesive is transparent, and the indicia is coloured by transparent pigments or dyes in solid solution in the indicia. t

Metallised indicia.Another novel application. is achieved by vacuum metallising the carrier film e.g. with aluminium, before applying the indicia. The overlapping metallising, if sufficiently thin, will be occluded or along with the overlapping adhesive, or may be chemically attached prior to the adhesive so that some transparency of the otherwise opaque carrier sheet is obtained to assistin positioning the transfer. When the indicia are transferred, the vacuum metallised coating is transferred along with the indicia and provides a brilliant mirror-likemetallic effect. Gold effects may be obtained by applying an extremely thin coated layer of orange or yellow transparent lacquer to the carrier sheet before metallising which has transfer properties obtained bythe formulating principles specified for the indicia, but is also attacked by the adhesive, and so is occluded along with the adhesive and" the indicia is formulated to have the Etch resisI.The indicia, due to their'powerful :ad-

hesion, may be applied to metals and used as an etch resist. Indicia of fully polymerized urea-formaldehyde and chlorinated rubber are particularly resistant to acids, ferric chloride, etc.

Stoving indicia-The indicia may be composed of partially polymerised thermosetting indicia such as epoxyphenolic, ureaor melamineformaldehyde, silicone and acrylic mixtures and thermosetting acrylics, which after application may be stoved on the receiving surface to a fully converted form which increases hardness and adhesion.

Ceramic indicia.-The indiciamay contain ceramic pigments so that after transfer to a glass or ceramic surface, the latter with or without glaze, the indicia may be fired into the surface. The indicia polymer may consist of polymers which burn away or depolymerise, such polymethylethacrylate, without discolouring or blistering.

Resistor indicz'a.-The indicia may contain conductive pigments, such as graphite or silver oxide, which provide indicia having electrical conductivity and after transfer to a receiving surface they provide conductive circuits or printed resistors of predetermined resistance values.

Book marking.The indicia of Example I have excellent adhesion and resistance to removal on book-binding materials and therefore find valuable application as a means of marking books, e.g. by libraries, particularly for the numerical and decimal classification systems.

Initials-Similarly the very high adhesion to leather and plastic goods provides a means of applying initials and monograms, e.g. even in pure metallised gold indicia.

General uses-Apart from the preceding novel applications, the transfers of the invention have advantages in known applications for dry transfers such as lettering sheets for artwork, drawings, and prototypes, signs and notices, nameplates for manufactured articles, and instructions for machinery.

We claim as our invention:

1.-A dry transfer material which comprises -(a) a carrier sheet which has a surface of highpolymeric material,

(b) transfer films on said surface,

(c) pressure-sensitive adhesive material covering said transfer films and overlapping onto said carrier sheet surface in overlap areas,

(d) the polymeric surface material in said overlap areas having greater adhesive-retaining properties as compared to those of the portions of said carrier sheet surface occupied by said transfer films,

(e) the adhesive power of the adhesive material for a receiving surface, determined by the peel bond adhesion thereto, being less in said overlap areas than in those areas occupied by said transfer films by reason of interaction between said adhesive material and said polymeric material in said overlap areas.

2. A dry transfer material as in claim 1 wherein the cohesiveness of said adhesive material is weakened by the interaction between said adhesive material and said polymeric material in said overlap areas and said adhesive material is thereby caused to be at least partially presheared around the outlines of said transfer films.

3. A dry transfer material as in claim 1 wherein said carrier sheet polymeric material is molecularly oriented in the areas in register with said transfer films and at least partially disoriented in said overlap areas.

4. A dry transfer material as in claim 1 wherein said carrier sheet is locally stretchable by application of pressure of at least 50 pounds per square inch and the adherence of said transfer films to said carrier sheet is reduced by such local stretching.

5. A dry transfer material as in claim 1 wherein said .carrier sheet polymeric material is softened and swelled in said overlap areas but not in areas occupied by said transfer films,

6. A dry transfer material as in claim 1 wherein said carrier sheet polymeric material is stress-cracked in said overlap areas but not in areas occupied by said transfer films.

7. A dry transfer material as in claim 1 wherein said adhesive material is at least partially disintegrated in said overlap areas but not in areas occupied by said transfer films.

8. A dry transfer material as in claim 1 wherein said adhesive is at least partially occluded in said polymeric material in said overlap areas and not in areas occupied by said transfer films.

9. A dry transfer as in claim 1 wherein the interfacial adhesions of the components of said dry transfer material prevent transfer of said transfer films to a receiving surface upon application of pressures up to 50 pounds per square inch.

10. A dry transfer material which comprises (a) a carrier sheet which has a surface of a synthetic polymeric material,

(b) a transparent film covering an area of said surface and leaving other areas of said surface uncovered by said clear film,

(0) one or more indicia films on said transparent film,

(d) pressure-sensitive adhesive material covering-said indicia films and said transparent film and overlapping onto said carrier sheet surface in said other areas uncovered by said transparent film;

(e) the release properties of said polymeric material being reduced in said overlapped areas as compared to areas occupied by said transparent film, and

(f) the adhesive power of the materials in said other areas for a receiving surface, determined by the peel bond adhesion thereto, being less than the adhesive power of said adhesive material in said certain areas occupied by said transparent film.

11. The process of producing a dry transfer material comprising (a) providing a carrier sheet which has a surface of a synthetic polymeric material,

(b) placing on said surface transfer films occupying only certain areas of said surface and leaving other areas of said surface uncovered by transfer films,

(c) placing a pressure-sensitive adhesive material on said transfer films and on at least some of said other surface areas uncovered by said films, and

(d) interacting said adhesive material with said polymeric material in said other adhesive-covered areas to cause the adhesive power of the interacted adhesive and polymeric materials for a receiving surface in said other areas, determined by the peel bond adhesion thereto, to be less than the adhesive power of said adhesive material in said certain areas occupied by said transfer films.

12. The process of producing a dry transfer materia comprising (a) providing a carrier sheet which has a surface of a synthetic polymeric material,

(b) placing on said surface transfer films occupying only certain areas of said surface and leaving other areas of said surface uncovered by transfer films,

(c) increasing the adhesive retaining characteristics of the polymeric material of said surface by modification of said surface by solvent action,

((1) placing a pressure-sensitive adhesive material on said transfer films and on at least some of said other areas of said surface adjoining said film, and

(e) interacting said adhesive material with said polymeric material in said other areas to cause the adhesive power of the resulting materials in said other areas for a receiving surface, determined by the peel bond adhesion thereto, to be less than the adhesive power of said adhesive material in said certain areas occupied by said transfer films.

13. The process of producing a dry transfer material having a carrier sheet bearing transfer films covered by a pressure-sensitive adhesive material overlapping onto areas of said carrier sheet not covered by said films, comprising the step of reducing the pressure-responsive adhesiveness of the adhesive material at said overlap areas relative to the adhesiveness of said adhesive material covering said films by modifying the adhesiveretaining surface characteristics of the surface of said carrier sheet in said overlap areas, said carrier sheet surface being composed of a synthetic polymeric material and said reducing step causing said adhesive material to interact with said polymeric material to inhibit separation of said adhesive material from said carrier sheet.

14. The process of producing a dry transfer material having a carrier sheet bearing transfer films covered by a-pressure-sensitive adhesive material overlapping onto areas of said carrier sheet not covered by said films, comprising the step of reducing the pressure-responsive adhesiveness of the adhesive material at said overlap areas relative to the adhesiveness of said adhesive material covering said films by modifying the adhesive-retaining surface characteristics of the surface of said carrier sheet in said overlap areas, said carrier being susceptible to solvent attack and said carrier-surface-characteristic modifying being accomplished by subjecting said carrier sheet surface and transfer films to a solvent essentially inert to said films but reactable with said carrier sheet material to modify said adhesive-retaining characteristics.

15. The process as in claim 14 wherein said solvent is applied together with said adhesive material.

16. The process as in claim 14 wherein said solvent is applied separately from said adhesive material.

17. A dry transfer material which comprises (a) a carrier sheet which has a surface of a synthetic polymeric material,

(b) transfer films on said polymeric material and occupying only certain areas of said surface and leaving uncovered at least some other areas of said surface adjoining said certain areas,

() pressure-sensitive adhesive material covering said transfer films and at least some of said other areas uncovered by transfer films,

(d) the adhesive material on said other areas having penetrated into said polymeric material, and

(e) the adhesive power of the materials in said other areas for a receiving surface, determined by the peel bond adhesion thereto, being less than the adhesive power of said adhesive material in said certain areas occupied by said transfer films.

18. The process for producing a dry transfer material I comprising (a) providing a carrier sheet which has a molecularly oriented surface composed of a synthetic polymeric material selected from the class of materials which have as a principal constituent polyethylene, polypropylene, polystyrene or a polyvinyl halide,

(b) placing on said surface transfer films occupying only certain areas of said surface and leaving other areas of said surface uncovered by said films,

(c) modifying the adhesive-retaining surface characteristics of said carrier sheet surface in said overlap areas by subjecting said carrier sheet surface to a solvent essentially inert to said films but reactable to said carrier sheet surface material to disorient said polymeric material in said overlap areas and (d) placing a pressure-sensitive adhesive material on said fihns and overlapping onto said areas of said surface uncovered by said films,

(e) the disoriented material in said overlap areas reducing the pressure-responsive adhesiveness of said adhesive material in said overlap areas relative to the adhesiveness of said adhesive material covering said References Cited by the Examiner UNITED STATES PATENTS 2,626,226 1/ 1953 Adair 156240 3,131,106 4/1964 Mackenzie 156230 3,212,913 10/1965 Mackenzie 117-3.1

FOREIGN PATENTS 589,276 12/1959 Canada.

EARL M. BERGERT, Primary Examiner.

M. L. KATZ, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 298, 850 January 17, 1967 Kenneth James Reed et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 22, .for "isonerized" read isomerized column 14, line 62, for "attached" read attacked Signed and sealed this 24th day of October 1967 (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

Claims (1)

1. DRY TRANSFER MATERIAL WHICH COMPRISES (A) A CARRIER SHEET WHICH HAS A SURFACE OF HIGHPOLYMERIC MATERIAL, (B) TRANSFER FILMS ON SAID SURFACE, (C) PRESSURE-SENSITIVE ADHESIVE MATEIRAL COVERING SAID TRANSFER FILMS AND OVERLAPPING ONTO SAID CARRIER SHEET SURFACE IN OVERLAP AREAS, (D) THE POLYMERIC SURFACE MATERIAL IN SAID OVERLAP AREAS HAVING ADHESIVE-RETAINING PROPERTIES AS COMPARED TO THOSE OF THE PORTION OF SAID CARRIER SHEET SURFACE OCCUPIED BY SAID FILMS, (E) THE ADHESIVE POWER OF THE ADHESIVE MATERIAL FOR A RECEIVING SURFACE, DETERMINED BY THE PEEL BOND ADHESION THERETO, BEING LESS IN SAID OVERLAP AREAS THAN IN THOSE AREAS OCCUPIED BY SAID TRANSFER FILMS BY REASON OF INTERACTION BETWEEN ADHESIVE MATERIAL AND SAID POLYMERIC MATERIAL IN SAID OVERLAP AREAS.

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