Manufacture of signs

A method of making a sign is described which comprises taking a transfer material and a temporary support sheet, the transfer material comprising a transparent or translucent carrier sheet bearing on one side a plurality of transferable indicia, which are either sufficiently adhesive as such to enable their transfer to the support sheet or which bear a layer of adhesive on their face remote from the carrier sheet, or which are non adhesive but transferable by virtue of a coating of adhesive on the temporary support sheet, the adhesive if present being adapted to adhere the indicia to the temporary support sheet more strongly than they adhere to the carrier sheet, and wherein the material of the indicia is adhesive under the application of heat and pressure, transferring indicia from the transfer material to the temporary support sheet in the desired order to build up the desired legend for the sign, and applying the transferred indicia under heat and pressure to the surface of a transparent or translucent sheet, e.g. of acrylic plastics, to form the sign. After such transfer the indicia may be overcoated, e.g. with a contrasting color background. The legend is read through the transparent or translucent sheet which protects it against abrasion or other damage.

This invention relates to sign manufacture and particularly to sign 
manufacturing using transfer materials. 
Dry transfer lettering materials have been known for many years and are 
described for example in British Patent Specification Nos. 959,670 and 
954,459. Such dry transfer materials conventionally consist of a flexible, 
transparent or translucent plastics film on which are arranged a plurality 
of transferable indicia, usually alphabetic letters, numbers and 
punctuation marks. On top of each indicium is a coating of adhesive which 
enables the indicium to be transferred from the carrier sheet and adhered 
to a receptor surface. In order to facilitate such transfer, the relative 
mechanical characteristics of the indicium and the carrier sheet may be so 
chosen that the bond between the carrier sheet and the indicium may be 
weakened or broken by local stretching of the carrier sheet effected by 
rubbing over the back of the carrier sheet is the region of an indicium 
with a suitable stylus. This system is described in Specification No. 
959,670. 
Such dry transfer materials have been used widely for some years in various 
applications. Because of the relatively fragile nature of the ink film of 
which the indicia composed, such materials are generally unsuited for the 
production of signs which may be exposed to the weather, cleaning by 
detergent solutions or the like and accordingly in the manufacture of 
signs, where it is desired to use preformed lettering rather than 
hand-printed lettering, there has been a tendency to use die-cut vinyl 
lettering rather than dry transfer lettering. Dry transfer lettering may 
be used in constructing a composite sign where the lettering is overlaid 
by a protective sheet e.g. the lettering on a suitable carrier such as 
paper may be inserted in a frame and protected by a glass or plastics 
cover through which the lettering is visible. Such systems are generally 
unsatisfactory and tend sometimes to be unsightly. 
We have now found that visually much more pleasing signs which have the 
advantage of high durability may be produced using a special dual-purpose 
transfer material. 
According to the present invention there is provided a method of making a 
sign which comprises taking a transfer material and a temporary support 
sheet, the transfer material comprising a transparent or translucent 
carrier sheet bearing on one side a plurality of transferable indicia, 
which are either sufficiently adhesive as such to enable their transfer to 
the support sheet or which bear a layer of adhesive on their face remote 
from the carrier sheet or which are non adhesive but transferable by 
virtue of a coating of adhesive on the temporary support sheet, the 
adhesive if present being adapted to adhere the indicia to the temporary 
support sheet more strongly than they adhere to the carrier sheet, and 
wherein the material of the indicia is adhesive under the application of 
heat and pressure, transferring indicia from the transfer material to the 
temporary support sheet in the desired order to build up the desired 
legend for the sign, and applying the transferred indicia under heat and 
pressure to the surface of a transparent or translucent sheet to form a 
sign. 
The heat and pressure should be sufficient to cause the indicia to adhere 
to the transparent or translucent sheet more strongly than they are 
adhered to the temporary support sheet by the sign. The temporary support 
sheet can then be stripped away and if desired the indicia covered by a 
layer of suitable material, e.g. paint, which accordingly constitutes a 
background to the indicia in the sign as viewed. The background may also 
be provided by a coloured paper or foil adhered over the indicia or held 
against them. Alternatively, the layer may be provided by transferring a 
coloured layer from a blocking foil under pressure and, if necessary, 
heating. 
Because, under the action of the heat and pressure, the indicia come into 
intimate contact with the surface of the transparent or translucent sheet, 
that surface is totally "wetted" and the indicia appear optically dense 
and perfectly flat. The indicia in the sign are protected by the 
transparent or translucent sheet through which they are viewed, which may 
accordingly be chosen for that purpose. The transparent or translucent 
sheet may be of glass but is preferably of a plastics material; most 
preferred are polyvinylchloride, cellulose triacetate and 
polymethylmethacrylate e.g. those sold under the Registered Trade Marks 
PERSPEX and PLEXIGLAS. 
The property of the indicia that they should be adhesive under the action 
of heat and pressure may be imparted to the indicia e.g. by constructing 
them on a basis of a thermoplastic polymeric material which softens to 
tacky adhesive condition on the application of heat. Alternatively a 
thermosettable material which likewise softens initially on heating may be 
used as a base material. In such a case, the finished sign may be rendered 
exceptionally heat-stable by heating after its manufacture so as to cure 
the thermosettable base to a hard thermoset film adherent to the 
transparent or translucent sheet. The indicia may thus be regarded as 
being formed of a hot melt or heat seal adhesive together with a suitable 
pigment or dyestuff to render the area of the indicium visible. 
Preferably the transfer material used in the method of the present 
invention is constructed generally as a dry transfer material of the 
stretch release type i.e. as described in British Patent Specification No. 
959,670. The indicia are preferably formed by screen printing using an 
appropriate printing ink and subsequently the whole printed area of the 
sheet including the spaces between the indicia is supercoated with a 
substantially non-tacky pressure sensitive adhesive. The indicia may also 
be formed, in known fashion, by printing an indicium area in a colourless 
carrier film and a visible image in coloured ink. The film may be printed 
by screen printing and the visible image by e.g. gravure, letterpress or 
lithographic printing, either before or after the film is printed. 
Substantially non-tacky pressure-sensitive adhesives are generally not 
particularly strong, and indeed use may have to be made of the stretch 
release technique mentioned above in order to ensure that a relatively 
weak adhesive has sufficient pulling power to remove the indicia from the 
carrier sheet when the dry transfer material is used. The fact that the 
bond produced by heat and pressure between the indicia and the transparent 
or translucent sheet through which they are to be viewed is generally very 
much stronger than the adhesive bond produced by the adhesive of the 
transfer material or on the temporary support sheet enables the temporary 
support sheet on to which the indicia were originally transferred when the 
message or the like was being composed to be peeled away, either hot or 
cold, to leave the indicia firmly adherent to the transparent or 
translucent sheet. 
The individual components of the preferred dry transfer materials for use 
in the method of the invention will now be described in detail. 
SUPPORT FILM 
The support film of the transfer material of the present invention may be 
any of those conventionally used in the manufacture of dry transfer 
lettering sheets. Transparent or translucent plastics films are preferred, 
most preferably polyethylene, styrene/butadiene copolymers, polypropylene 
and polyethylene terephthalate films. Coated papers may also be used. The 
thickness of the film is preferably 0.1 to 0.15 mm. 
The support film may have a release coating on the surface carrying the 
indicia. 
INDICIA 
The indicia may be formed of a printing ink based on a film forming 
polymeric thermoplastic material. Both plastisol and organosol inks may be 
used and inks may be used which while based on the thermosetting polymeric 
materials have an adequate content of modifying agents to give the overall 
indicia thermoplastic heat seal or hot melt adhesive properties. For 
example, inks based on nitrocellulose may be given thermoplastic heat seal 
properties by a suitable choice of plasticiser; polymeric plasticisers, 
used at a sufficiently high level, impart the desired properties while 
still enabling the indicia to be printed without difficulty, and enabling 
the production of dry transfer materials working by so-called "stretch 
release", as described in British Patent Specification No. 959,670. The 
indicia may be simply applied by a single printing process or they may be 
built up in a number of layers, which may vary, and which are applied by 
successive printing processes. Alternatively, it is possible to produce 
appropriate indicia photographically by modifying one of the known 
photographic methods of producing dry transfer materials. Such methods are 
described inter alia in British Patent Specification Nos. 1,079,661, 
1,291,960 and 1,364,627. The melting or softening point of the indicia 
should be chosen with care and particularly having regard to the types of 
transparent or translucent sheet on to which the indicia are to be 
adhered. 
ADHESIVE 
As noted in the above, the adhesive is preferably of a substantially 
non-tacky pressure sensitive type. Preferred adhesives consist of a highly 
tacky polymeric component such as polyisobutylene, polyvinyl ethyl ether, 
polyvinyl isobutyl ether, or a mixture containing one or more of these 
together with a tack-modifying or tack-reducing component. Typical 
tack-reducing components are finely divided mineral materials, 
particularly finely divided silica and waxy materials such as natural or 
synthetic waxes. 
The formulation of the inks constituting the indicia may be chosen relative 
to the intended use of the material. For example, if it is desired to use 
the material in the manufacture of signs which are to consist of a sheet 
of acrylic plastic through which the indicia are to be viewed, the indicia 
may be formulated so as to be compatible chemically with the material of 
the transparent or translucent sheet. Likewise, if the transparent or 
translucent sheet is of polyvinylchloride, the ink may be chosen to give 
an ink which is compatible therewith and can be easily heat sealed on to 
such a surface with visually satisfactory results. Types of plastics 
sheets which may be used in the manufacture of signs include 
polymethylmethacrylate sheets of the types noted above, polyvinylchloride 
sheets, polystyrene sheets, polyethylene and polypropylene sheets, 
polycarbonate sheets and cellulose triacetate sheets. Suitable materials 
for the temporary support sheet are plastics films such as polyethylene 
terephthalate sheet, various treated papers and, for example, aluminium 
foil. Such temporary support material should of course be able to 
withstand the heat applied during the step of adhering the indicia to the 
transparent or translucent sheet under heat and pressure. Likewise, the 
adhesive forming part of the transfer material of the present invention 
should not be adversely affected by the heat and pressure used to adhere 
the indicia to the surface of the transparent or translucent sheet. In 
particular, the adhesive should not melt at too low a temperature, which 
would give rise to slippage between indicia and temporary support sheet 
during the heat transfer step. Particularly preferred adhesives comprise a 
highly tacky thermoplastic polymeric component together with an 
appropriate quantity of a finely divided silica to reduce the overall tack 
of the adhesive. 
The adhesive is preferably solvent soluble in a non-solvent for the 
transparent or translucent sheet. This enables any residues of adhesive to 
be easily cleaned off the sign, so producing a clean finish. It is 
particularly important to remove such residues if the indicia are to be 
overcoated with a sprayed paint coating. In the Examples given below, the 
adhesives can be dissolved in hexane or heptane. 
If an error is made, it is preferable to enable the transferred indicia to 
be removable either from the temporary support sheet or from the 
transparent or translucent base sheet by solvent action also. The indicia 
in the examples below may be removed by dissolving in industrial 
methylated spirits. 
If the transparent or translucent sheet on to which the indicia are to be 
transferred is very thin, e.g. is a thin plastics foil, that sheet may be 
backed up during the heat transfer step by a suitable rigid backing. 
The following examples will serve to illustrate the invention. In these 
examples all parts and percentages are by weight unless otherwise stated.

EXAMPLE 1 
A printing ink was formulated as follows: A mixture was made up of: 
methylmethacrylate copolymer: 20 parts 
ethylene glycol ethylether acetate: 68 parts and 
polyvinylchloride, polyvinylacetate copolymer (Vinylite VYHH ex. Bakelite): 
11 parts 
43 parts by weight of this mixture were then triple roll milled together 
with 9 parts by weight of aniline black pigment, 0.2 parts by weight of 
fumed silica (Aerosil 300 ex. Degussa) and 3.8 parts by weight ethylene 
glycol mono ethyl ether acetate. Milling was continued to Hegman Gauge 7. 
Thereafter, 24 further parts by weight of the mixture, 10 parts by weight 
of a 40% by weight solution of methyl methacrylate/butyl methacrylate 
copolymer (Paraloid B66 ex. Rohm and Hass) in ethylene glycol mono ethyl 
ether acetate and 10 parts by weight of a methyl methacrylate copolymer 
solution (40% by weight Paraloid B82 ex. Rohm and Haas in ethylene glycol 
mono ethyl ether acetate) were added and the mixture stirred to 
homogeneity. 
The black ink so made was used to print letters onto 150 micron thick 
sheets of high density polyethylene. Silk screen process printing was 
used, printing being through a 240 mesh screen. The printed images were 
dried on a belt drier for 30 seconds dwell time at 60.degree. C. 
An adhesive was made up as follows: 
The following ingredients were stirred together in the proportions by 
weight given: 
Fumed silica (Aerosil R972 ex. Degussa): 8.0 parts 
Aliphatic hydrocarbon solvent (Exsol 145/160, ex. Esso): 48.0 parts 
Polyisobutylene solution (Low molecular weight Oppanol B10 ex. BASF 30% by 
weight solids solution in Exsol 145/160): 7.7 parts 
Polyisobutylene solution (High molecular weight Oppanol B50 ex. BASF 20% by 
weight solution in Exsol 145/160): 20.0 parts 
Polybutene (Low molecular weight Hyvis 10. Ex. B.P. Chemicals Ltd): 13.8 
parts 
The last ingredient was added to the others while hot stirring at 
50.degree. to 60.degree. C. 
99.0 parts by weight of a 10% by weight solution of polyethylene wax was 
then added. The polyethylene wax was type ACP6 ex. Allied Chemicals 
Limited and the solvent was Exsol 145/160. 
Finally, a molten 50% by weight solution of a fatty amide (Oleamide, 
Crodamide 0 ex. Croda Chemicals) in Exsol 145/160 was added and stirring 
continued to produce a homogeneous adhesive. 
This adhesive was applied by screen printing an overall layer through a 240 
mesh screen onto the previously printed polyethylene sheets. The adhesive 
coating was dried by passing the sheets through a belt dryer at a 30 
second dwell time at 65.degree. C. The transfer sheets so produced were 
protected by interleaving with siliconised vegetable parchment paper 
sheets. 
Using the transfer materials so produced in the usual way, a word was built 
up from individual letters on a 50 micron thick sheet of polyethylene 
terephthalate film (Melinex ex. I.C.I.). The film bearing the letters was 
then passed with the letters in contact with a 2 mm sheet of polymethyl 
methacrylate (Perspex ex. ICI Limited) through a heated nip. The 
temperature of the nip rolls was 170.degree. C. and the assembly was 
passed between them at a rate of 4 m/minute. 
The polyethylene terephthalate sheet was then peeled away from the 
polymethyl methacrylate sheet to leave the letters firmly adherent to the 
surface of th polymethyl methacrylate sheet and the right way round when 
viewed through that sheet. The side of the sheet bearing the letters was 
then oversprayed with spray paint to give a sign in which the black 
letters stood out clearly against the coloured paint background and which 
had a generally pleasing appearance. 
EXAMPLE 2 
The following ingredients were mixed together in the following proportions 
by weight: 
Rutile titanium dioxide (grade R-HD3 ex. British Titan Products): 29 parts 
Copolymer mixture (as in Example 1): 43 parts 
Fumed silica (Aerosil 300 ex. Degussa): 0.2 parts 
Ethylene glycol mono ethyl ether acetate: 7.8 parts 
This mixture was dispersed on a triple roll mill until a fineness of 7 on a 
Hegman Gauge was achieved and there was then added 10 parts by weight of a 
methyl methacrylate/butyl methacrylate copolymer solution (as in Example 
1) and 10 parts by weight of a methyl methacrylate copolymer solution (as 
in Example 1). 
Dry transfer sheets were prepared by printing this ink as in Example 1 onto 
150 micron thick high density polyethylene sheets and subsequently drying 
and adhesing those sheets exactly as in Example 1. 
Words were made up using these sheets in the usual way by transferring 
individual letters onto 50 micron polyethylene terephthalate sheets. The 
sheet bearing the words was then passed together with a 1 mm thick 
transparent polyvinyl chloride sheet through a heated nip. The nip 
temperature was 120.degree. C. and the polyethylene terephthalate and PVC 
sheet were passed through at a speed of 4 m/minute. After passing through 
the nip, the polethylene terephthalate sheet could be peeled away to leave 
the white letters adhered to the PVC sheet. The side of the PVC sheet 
bearing the letters was then sprayed over with black cellulose lacquer and 
air dried. The resulting sign was of pleasing appearance. 
It was found that higher operating speeds could be used in conjunction with 
higher nip temperatures, for example a nip temperature of 160.degree. C. 
and a pass speed of 9 m/minute. If high temperatures are used with low 
speeds, there is a tendency to distortion of the PVC sheet. 
EXAMPLE 3 
The black ink of Example 1 was used to print indicia on 100 micron high 
density polyethylene sheets by screen printing using a 61T mesh. 
The indicia so printed were overprinted in register using colourless 
carrier film of the following formulation: 
Fumed silica (Acrosil 130V ex Degussa): 2.8 parts 
Polymeric plasticiser (Uralac 923/68 ex Synthetic Resins Ltd): 30.0 parts 
Monomeric plasticiser (Howflex SP ex Laporte): 3.7 parts 
Ethylene glycol monoethyl ether acetate: 99.5 parts 
Cellulose nitrate (33% DHX 3/5 in butanol): 63.9 parts 
After each printing, the sheets were belt dried with a 40 second dwell time 
at 85.degree. C. 
The sheets were then overprinted overall with an adhesive of the following 
formulation: 
Fumed silica (Aerosil 300 ex Degussa): 8.8 parts 
Aliphatic hydrocarbon solvent (ECS 2033 ex Esso): 76.9 parts 
Ethylene glycol monoethyl ether: 26.0 parts 
Xylene: 10.3 parts 
Polyvinyl ethyl ether (low viscosity ex Union Carbide): 16.0 parts 
Polyvinyl ethyl ether (high viscosity ex Union Carbide): 2.0 parts 
Polyterpene resin (A125 ex R. H. Cole Co.) 3.2 parts 
The adhesive was printed through a 100T mesh and subsequently dried by 
passing the transfer materials through a belt dryer with a 40 second dwell 
time at 85.degree. C. 
The transfer material so made was used to build up words on 50 micron thick 
polyethylene terephthalate sheets (Melinex Grade S ex. I.C.I.) and the 
legend so formed placed in contact with polymethyl methacrylate sheets 2 
mm thick. The assembly of polymethyl methacrylate sheet and letter bearing 
polyethylene terephthalate sheet was then passed through a heated nip. The 
nip was heated to 180.degree. C. and speed was 8 m/min. The polyethylene 
terephthalate sheet could then be peeled away to leave the letters firmly 
adhering to the polymethyl methacrylate sheet. 
In order to show up those letters, the polymethyl methacrylate sheet was 
then backed with a backing of retroreflective material (e.g. Scotchlite ex 
3M Company or a microbead-containing paint) to form, when framed, a 
vehicle identification plate or so-called "numberplate", which was of 
pleasing appearance and very legible. 
EXAMPLE 4 
Example 1 was repeated but using white and black inks made up as follows: 
First a base medium was made up by mixing together 
Poly methyl methacrylate (Plexigum P 24. ex-Cornelius Chemical Co.): 90 
parts 
Ethylene glycol monoethyl ether acetate: 110 parts 
Di ethylene glycol monobutyl ether acetate: 5 parts 
Aromatic hydrocarbon fraction boiling between 168.degree.-200.degree. C. 
(Aromasol H. ex-I.C.I.): 10 parts 
This base medium was then used to make up ink(s) of the following 
formulation: 
Base medium: 215 parts 
Butyl phthallyl butyl glycollate (Reomol 4PG. ex-CIBA-GEIGY): 9 parts 
Amide Wax (Dehysol wax): 2.6 parts 
Titanium dioxide (Rutile grade RH472 ex-Laporte): 68 parts 
or Carbon black (Elftex 150 ex-Cabot carbon): 14 parts 
The ingredients were premixed using a palette knife and then ground on a 
triple roller mill to Hegman gauge 7 degree of fineness. 
The ink(s) thus produced were used as in Examples 1 and 4 for making signs 
and numberplates; similar satisfactory results were obtained. 
If it is desired to use very fine detail indicia, the indicia may be 
printed in two stages: first a general area is printed using an ink as 
noted above but not containing pigment to deposit a colourless carrier 
film. Thereafter, the fine detail indicia are printed on the area with the 
coloured ink. Alternatively the indicia may be printed first and then 
overprinted with clear film area. Because the colourless carrier film is 
based on an acrylic polymer it does not adversely affect the appearance of 
the finished sign. 
EXAMPLE 5 
Example 1 was repeated using black and white inks of the following 
composition, and using an adhesive as set out below: 
______________________________________ 
White Ink % 
______________________________________ 
Cellulose nitrate (33% n-butanol damped in 
48.3 
ethylene glycol monoethyl ether acetate) 
Polymeric Plasticiser (Paraplex G25 ex 
14.0 
Rohm & Haas) 
Titanium Dioxide 30.0 
Ethylene glycol monoethyl ether (oxitol) 
7.7 
______________________________________ 
The ink was triple roll milled to Hegman 7 and the final viscosity was 
adjusted for printing with oxitol acetate. 
______________________________________ 
Black Ink % 
______________________________________ 
Cellulose nitrate (33% n-butanol damped in 
62.5 
ethylene glycol monoethyl ether acetate) 
Polymeric Plasticiser (Pararplex G25 ex 
16.5 
Rohm & Haas). 
Carbon Black 7.5 
Ethylene glycol monoethyl ether 9.5 
Dehysol wax (ex Henkel & Cie GmbH) 
flow 2.0 
agents 
Modaflow (ex Monsanto Chemicals Ltd) 2.0 
______________________________________ 
The ink was triple roll milled to Hegman 7 and the final viscosity adjusted 
for printing with oxitol acetate. 
______________________________________ 
Adhesive % 
______________________________________ 
Fumed silica (Aerosil R972 ex Degussa) 
4.0 
Aliphatic hydrocarbon solvent (Exsol 145/160, 
17.2 
ex Esso) 
Oleamide (Crodamide `O` ex Croda Chemicals 
10.12 
Limited) 
Polyisobutylene solution (low molecular weight 
2.33 
Oppanol B10 ex BASF 50% by weight in Exsol 
145/160) 
Polyisobutylene solution (High molecular weight 
10.00 
Oppanol B50 ex BASF 20% by weight in Exsol 
145/160) 
Polybutene (Medium molecular weight Hyvis 30 
6.89 
ex B.P. Chemicals Ltd.) 
Polyethylene wax solution (Type ACP6 ex Allied 
49.46 
Chemicals Ltd. 10% by weight dispersed in 
Exsol 145/160). 
______________________________________ 
Similar very satisfactory results were obtained.