Transfer sheet

The present invention provides a transfer sheet comprising a releasable base and, as disposed successively thereon, at least one picture printing layer, a UV-curing adhesive layer and a release layer and a transfer process employing a transfer sheet which comprises peeling off the releasable base from the sheet, transferring the printing layer and UV-curing adhesive layer as a unit to a substrate and curing the adhesive layer by UV irradiation.

TECHNICAL FIELD 
The present invention relates to a transfer sheet. The transfer sheet of 
the invention is particularly useful in design transfer or decalcomania 
for decorating ceramics (mugs, tea cups, etc.), glassware (cups, bowls, 
etc.), metal ware (key holders, containers, etc.), plastic articles (cups, 
toys, etc.) and so on with patterns. 
Throughout the specification, "%" and "parts" are "weight %" and "parts by 
weight", respectively. 
BACKGROUND ART 
In the transfer of a design or picture to the surface of a ceramic article 
or like base product, it is common practice to use a water slide 
technique. According to the technique, a water-soluble size or paste layer 
is first formed on a release paper, a multicolor picture layer is formed 
thereon and, where necessary, a picture-supporting layer is further 
disposed on the picture layer to provide a transfer sheet. In transfer 
printing, the thus-obtained transfer sheet is wetted with water to 
dissolve out the water-soluble size and, hence, let the picture layer 
leave from the release sheet, whereupon the picture layer is 
slide-transferred to the surface of a ceramic or other substrate. Then, 
using a squeegee and like tools, water between the picture layer and the 
substrate ware is squeezed out. The substrate ware is allowed to stand for 
drying the picture layer. After completion of drying, the ware is calcined 
at as high as about 1000.degree. C. to permanently fix the design or 
picture thereto. 
However, this technique has the disadvantage that since a step for 
high-temperature calcining at about 1000.degree. C. is essential, the use 
of heat-labile coloring materials, which are rich in colors, color tones, 
etc., is limited. Further, because the squeegee and like tools are 
essentially used in the technique, the manual labor of skillful operator 
is required, thereby increasing the production costs. 
Japanese Unexamined Patent Publication 252,600/1990 discloses "a transfer 
sheet comprising a release paper or film base carrying thereon a 
water-soluble size or releaser, a supporting layer disposed on said base 
and capable of maintaining the shape of a picture layer to be transferred 
and, as formed thereon, a picture layer comprising a printing layer 
selected having a B stage so as to insure a greater bond strength with 
respect to a substrate ware than the bond strength to said supporting 
layer" and a transfer process employing said transfer sheet. 
In the process, calcining or curing the printing layer is performed at a 
temperature of 80.degree.-300.degree. C. and, therefore, the 
above-mentioned problem associated with high-temperature calcination is 
overcome. However, when the process is applied to multicolor decalcomania, 
it takes a long time for the printing layer to establish the B stage, with 
the result that the efficiency of production of the transfer sheet is 
inevitably low. 
Furthermore, when the printing layer is calcined at a relatively low 
temperature of 80.degree.-170.degree. C., a sufficient degree of cure can 
be achieved only after prolonged heating leading to an inadequate adhesion 
of the printing layer to the substrate ware. There also is the 
disadvantage that the water resistance of the picture to water, in 
particular, to warm water is low. 
It is a primary object of the invention to provide a novel transfer sheet 
which permits the use of heat-labile coloring materials and enables 
multicolor decalcomania at a comparatively low temperature without 
procedural complexity. 
It is a further object of the invention to provide a novel transfer process 
which affords multicolor decalcomania at a comparatively low temperature 
without procedural complexity. 
Other objects and advantages of the invention will become apparent in view 
of the following description. 
SUMMARY OF THE INVENTION 
The inventors have conducted research in view of the foregoing state of the 
prior art and found that when a ultraviolet (UV)-curing adhesive is used 
as a bonding material for bonding a printing layer and a substrate, the 
problems of the prior art are substantially eliminated or drastically 
alleviated. 
Thus, the invention provides the following transfer sheets and transfer 
processes. 
1. A transfer sheet comprising a releasable base and, as disposed 
successively thereon, at least one picture printing layer, a UV-curing 
adhesive layer and a release layer. 
2. A transfer sheet of item 1 wherein the film-forming component of said 
picture printing layer comprises an UV-curing resin. 
3. A transfer sheet of item 1 or 2 wherein said picture printing layer 
comprises a non-variable color layer. 
4. A transfer sheet of item 1 or 2 wherein said picture printing layer 
comprises a reversible thermochromic layer. 
5. A transfer sheet of item 1 or 2 wherein said picture printing layer 
comprises a non-variable color layer and a reversible thermochromic layer. 
6. A transfer sheet of any of items 1 to 5 wherein said picture printing 
layer contains a silane coupling agent. 
7. A process of transfer printing using said transfer sheet as defined in 
any one of items 1 to 6, the process comprising peeling off the releasable 
base from said sheet, transferring said picture printing layer and 
UV-curing adhesive layer as a unit to a substrate ware, and curing said 
adhesive layer by UV irradiation. 
8. A process of item 7 wherein the substrate is pretreated with a silane 
coupling agent. 
9. A process of item 7 wherein said picture printing layer contains a 
silane coupling agent.

DETAILED DESCRIPTION OF THE INVENTION 
A. Releasable base 
The releasable base (hereinafter referred to briefly as the base) of the 
invention can be a paper or a film made of polyethylene, polypropylene, 
polyethylene terephthalate, polyvinyl chloride, polybutene, polybutadiene, 
polyurethane, polymethylpentene, ethylenevinyl acetate copolymer and other 
films, on which a known release material such as acrylic, silicone, vinyl, 
polyester, urethane, polyolefin and other release materials are coated. 
Among the release materials mentioned above, acrylic release materials 
with Tg values of not below 100.degree. C. are more preferable. A 
thickness of the base, is not limited to but, generally ranges from about 
25 to about 125 .mu.m. 
B. Printing Layer 
The printing layer on the base is formed by printing the base with a known 
UV-curing ink, oil based ink, cold setting ink, reversible thermochromic 
ink or the like according to screen printing, offset printing or other 
technique, followed by subjecting the printing layer to ultraviolet 
irradiation, drying or the like according to the properties of the ink. 
A resin component of the UV-curing ink is not particularly limited but 
includes the following. 
Photopolymerizable prepolymers and polymers such as polyether 
(meth)acrylate, urethane (meth)acrylate, epoxy (meth)acrylate, polyester 
(meth)acrylate, oligo (meth)acrylate, alkyd (meth)acrylate, polyol 
(meth)acrylate, etc. These photopolymerizable prepolymers and polymers 
have a molecular weight of about 500 to about 50,000. They are usable 
alone or in combination. 
Mono/polyfunctional reactive monomers such as 
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 
2-hydroxyethyl acryloyl phosphate, tetrahydrofurfuryl acrylate, acrylate 
of tetrahydrofurfuryl derivative, dicyclopentenyl acrylate, 
dicyclopentenyloxyethyl, 1,3-butanediol diacrylate, 1,4-butanediol 
diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, 
neopentyl glycol diacrylate, polyethylene glycol 400 diacrylate, 
hydroxypivalic acid ester neopentyl glycol diacrylate, tripropylene glycol 
diacrylate, 
1,3-bis(3"-acryloxyethoxy-2'-hydroxypropyl)-5,5-dimethylhydantoin, 
diacrylate of hydroxypivalic acid ester neopentyl glycol derivative, 
trimethylolpropane triacrylate, pentaerythritol triacrylate, 
pentaerythritol hexacrylate, etc. 
Photopolymerization initiators such as biacetyl, acetophenone, 
benzophenone, Michler's ketone, benzyl, benzoin, benzoin isobutyl ether, 
benzyl methyl ketal, tetramethylthiuram sulfide, azobisisobutyronitrile, 
benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl 
ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 
1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 
2-chlorothioxanthone, methylbenzoyl formate, etc. 
The coloring material may be any of the known inorganic pigments, organic 
pigments and thermochromic pigments, for instance. 
The UV-curing ink is preferably a composition comprising (a) 20-90 parts by 
weight of at least one member selected from the group consisting of 
urethane (meth)acrylates in the molecular weight range of about 500-50000 
and polyester (meth)acrylates in the molecular weight range of about 
500-50000, (b) 80-10 parts by weight of at least one mono/polyfunctional 
reactive monomer, and based on the above total of 100 parts by weight, (c) 
1-15 parts by weight of at least one photopolymerization initiator 
selected from the group consisting of acetophenone, benzophenone and 
thioxanthone type initiators. Said composition preferably contains 60-95 
weight % of (a), (b) and (c) combined and 40-5 weight % of a pigment 
component. 
The UV-curing ink may further contain, in addition to the above resin 
component and coloring material (inorganic pigment, organic pigment, 
thermochromic or other pigment), such other additives as a sensitizer, 
filler, inert organic polymer, leveling agent, thixotropic agent, 
thermopolymerization inhibitor, solvent and so on. 
The oil based ink essentially comprises an evaporation-drying type resin 
component showing a good bonding affinity for the substrate, such as an 
acrylic, epoxy, urethane or other resins, a solvent component such as an 
aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, glycols, ketones, 
esters or ethers, and a coloring material such as an inorganic pigment, 
organic pigment, thermochromic pigment, etc. 
The cold setting ink essentially comprises a resin system containing a base 
resin and a curing agent, and a coloring material (an inorganic pigment, 
organic pigment, thermochromic pigment, etc.). In addition, the ink may 
contain a cure accelerator, curing catalyst, reactive diluent and 
stabilizer, etc., where necessary. The combination of the base resin and 
the curing agent in cold setting ink is not particularly limited to but 
includes the following, for instance. 
* Base resin--epoxy resins and modified epoxy resins 
Curing agent--aliphatic amines, alicyclic amines, aromatic amines, 
polyamides, amine adducts, polysulfides, acid anhydrides, etc. 
* Base resin--acrylic resins and modified acrylic resins 
Curing agent--divalent and multivalent metals, metal oxides, etc. 
* Base resin--urethane resins and modified urethane resins 
Curing agent--polyamines, polycarboxylic acids, hydroxy-terminated 
polyesters 
In the invention, known reversible thermochromic ink compositions can be 
used to print on the substrate or in superposition on the printing layer 
formed with the above-mentioned ink. The reversible thermochromic ink 
composition comprises an electron-donating chromogenic organic compound 
(color producing agent), an electron-accepting compound (developer) and a 
desensitizer, and such compositions are described in a variety of 
publications. The species of such a color producing agent, developer and 
desensitizer constituting reversible thermochromic compositions are not 
limited to, but those mentioned in Japanese Unexamined Patent Publication 
174,591/1989 are useful. Such compositions may have been 
microencapsulated. 
If necessary, a silane coupling agent may be incorporated in any of the 
above inks so as to enhance bond strength between the picture layer and 
the substrate. The same object can also be accomplished by dipping the 
substrate in an aqueous solution of the silane coupling agent. The silane 
coupling agent includes epoxysilanes, aminosilanes, vinylsilanes, 
acrylsilanes, .gamma.-chloropropyltrimethoxysilanes etc. Epoxysilane and 
aminosilane type coupling agents are preferred. The silane coupling agent 
is formulated preferably about 0.05-10%, more preferably about 1-5% 
relative to a weight of the ink. 
C. UV-Curing Adhesive Layer 
The UV-curing adhesive layer according to the invention is provided using a 
UV-curing adhesive composition essentially comprising about 0.1-15 parts 
of a crosslinking or curing agent (hereinafter referred to as the 
crosslinking agent) and about 10-70 parts of a UV-curing resin per 100 
parts of an alkyl (meth)acrylate polymer. 
The number of carbon atoms in the alkyl ester moiety of said alkyl 
(meth)acrylate polymer may range from 1 to 14. If the carbon number 
exceeds 14, no sufficient adhesion can be obtained due to glass transition 
temperature (Tg). The carbon number of the alkyl ester moiety is 
preferably 4-12. From the standpoint of adhesion and heat resistance, the 
molecular weight of said alkyl (meth)acrylate polymer is generally about 
3.times.10.sup.5 to 1.times.10.sup.6, preferably about 4.times.10.sup.5 to 
1.times.10.sup.6. Examples of the alkyl (meth)acrylate polymer are butyl 
(meth)acrylate polymer and 2-ethylhexyl (meth)acrylate polymer. 
The crosslinking agent present in the UV-curing adhesive composition of the 
invention undergoes crosslinking reaction with the hydroxyl and carboxyl 
groups of said polymer and .alpha.,.beta.-unsaturated carboxylic acid to 
enhance and stabilize adhesion and cohesive force of the composition. The 
crosslinking agent includes isocyanate, epoxy, metal and N-methylol type 
crosslinking agents. Particularly preferred are isocyanate type 
crosslinking agents such as tolylene diisocyanate, xylylene diisocyanate, 
hexamethylene diisocyanate, isopropylene diisocyanate, 
trimethylhexamethylene diisocyanate, isophorone diisocyanate and so on. 
Said crosslinking agent is formulated in an amount of about 0.1-0.5%, 
preferably about 0.5-3%, based on the weight of the polymer or the total 
weight of the polymer and .alpha.,.beta.-unsaturated carboxylic acid as 
nonvolatile matter. If the amount of the crosslinking agent is too small, 
no sufficient cohesive force will be attained. On the other hand, with an 
excessive amount of the crosslinking agent, the adhesion thereof is 
decreased. 
The adhesive composition may contain, if necessary, an 
.alpha.,.beta.-unsaturated carboxylic acid in lieu of part of said polymer 
(up to about 15%), in which case adhesion and tackiness of the composition 
are improved. The .alpha.,.beta.-unsaturated carboxylic acid includes 
(meth)acrylic acid, itaconic acid, maleic acid and fumaric acid, etc. 
The UV-curing resin incorporated in the UV-curing adhesive composition of 
the invention undergoes crosslinking reaction, on exposure to UV 
irradiation, with the hydroxyl and carboxyl groups of the alkyl 
(meth)acrylate polymer, .alpha.,.beta.-unsaturated carboxylic acid and 
resin component of said ink to provide a firm bond with the substrate 
ware. 
The UV-curing resin is prepared using about 0.3 to about 20 parts, 
preferably about 0.5 to about 10 parts, of a photopolymerization initiator 
(hereinafter simply referred to as "initiator") per 100 parts of the 
photopolymerizable prepolymer (and/or photopolymerizable polymer, 
hereinafter simply referred to as "photopolymerizable prepolymer" unless 
specifically indicated) or 100 parts of the total of the 
photopolymerizable prepolymer and photopolymerizable monomer. 
Examples of the photopolymerizable prepolymer are polyether (meth)acrylate, 
urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, 
alkyd (meth)acrylate, etc. At least one of these polymers can be used. 
Among them, polyester (meth)acrylate, epoxy (meth)acrylate, urethane 
(meth)acrylate and the like are preferred. The photopolymerizable 
prepolymers have a molecular weight which is not specifically limited but 
is in the range of about 500 to about 150,000. They are usable alone or in 
combination. 
A photopolymerizable monomer is employable, for example, to impart the 
properties such as flexibility, heat resistance, etc. or to adjust the 
viscosity. Examples of such photopolymerizable monomers are 2-ethylhexyl 
(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy (meth)acryloyl 
phosphate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylate of 
tetrafurfuryl derivative, dicyclopentenyl (meth)acrylate, 
dicyclopentenyloxyethyl (meth)acrylate, 1,3-butanediol (meth)acrylate, 
1,4-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene 
glycol (meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene 
glycol 400 di(meth)acrylate, hydroxypivalic acid ester neopentyl glycol 
di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane 
tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol 
hexane(meth)acrylate, etc. At least one of them is used in this invention. 
The photopolymerizable monomer to be mixed with the photopolymerizable 
prepolymer is used in an amount not exceeding 80% based on the weight of 
the mixture. 
Useful polymerization initiators include, for example, radical 
polymerization initiators such as acetophenones, benzoimines, 
benzophenones, thioxanthones, amines and the like and cationic 
polymerization initiators such as iron-allen complex, diphenylsulfide 
derivatives, etc. Among them, preferred are acetophenones and 
thioxanthones. The amount of the initiator used is about 0.3 to about 20 
parts, preferably about 0.5 to about 10 parts, per 100 parts of the 
photopolymerizable prepolymer or 100 parts of the combined amount of the 
photopolymerizable prepolymer and the photopolymerizable monomer. When an 
excess amount of the initiator is used, only the surface of the adhesive 
layer is cured due to self absorption. On the other hand, a lesser amount 
of initiator used results in the reduction of curability. 
When required, the UV-curing resin may contain known additives such as 
sensitizers, oxidation inhibitors, polymerization inhibitors, fillers, 
etc. 
Useful sensitizers include, for example, amines such as aliphatic amines, 
aromatic group-containing amines, etc.; urea compounds such as allylurea, 
o-tolylthiourea, etc.; sulfur-containing compounds such as sodium diethyl 
dithiophosphate, soluble salt of aromatic sulfinic acid, etc.; 
N,N-di-substituted (R1, R2)-p-aminobenzonitrile compounds (wherein R1 and 
R2 are the same or different and each is a methyl group, an ethyl group, a 
.beta.-cyanoethyl group, a .beta.-chloroethyl group or the like); 
phosphorus compounds such as tri-n-butylphosphine, sodium diethyl 
dithiophosphate, etc.; nitrogen-containing compounds such as oxazoline 
compounds, N-nitrosohydroxylamine derivatives, Michler's ketone, etc.; 
chlorine-containing compounds such as carbon tetrachloride, 
hexachloroethane, etc. 
Useful polymerization inhibitors include, for example, hydroquinone, 
hydroquinone monomethyl ether, etc. 
Useful oxidation inhibitors include, for example, phenols, aromatic amines, 
organic sulfur compounds, etc. 
Useful fillers include, for example, calcium carbonate, magnesium 
carbonate, silicate, etc. 
The amount of the UV-curing resin used is about 10 to about 70%, preferably 
about 30 to about 60%, based on the weight of alkyl (meth)acrylate polymer 
or the combined weight of alkyl (meth)acrylate polymer and 
.alpha.,.beta.-unsaturated carboxylic acid. A lesser amount of the 
UV-curing resin fails to achieve satisfactory improvement of the adhesion. 
The UV-curing adhesive composition used in the invention may contain, when 
required, vinyl monomers for further increasing the adhesion and cohesive 
force of the composition. Examples of useful vinyl monomers are alkyl 
(meth)acrylate of 1 to 14 carbon atoms such as methyl (meth)acrylate, 
ethyl (meth)acrylate, isopropyl (meth)acrylate, 2-ethylhexyl 
(meth)acrylate, etc.; hydroxyl-containing unsaturated monomers such as 
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, diethylene 
glycol monoacrylate, etc.; styrene monomers such as styrene, vinyltoluene, 
chlorostyrene, etc.; carboxyl-containing unsaturated acids such as acrylic 
acid, methacrylic acid, itaconic acid, maleic acid, etc.; other 
ethylenically unsaturated monomers such as vinyl acetate, etc.; and 
unsaturated monomers containing a functional group such as an amino group, 
a glycidyl group or the like, etc. The amount of the vinyl monomer used is 
up to 60%, preferably about 10 to about 60%, based on the weight of alkyl 
(meth)acrylate polymer or the combined weight of alkyl (meth)acrylate 
polymer and .alpha.,.beta.-unsaturated carboxylic acid. 
To enhance the adhesion, cohesive force and heat resistance of the 
composition, the UV-curing adhesive composition used in the invention may 
contain rosin-type resin, terpene resin, aliphatic petroleum resin, 
aromatic petroleum resin, alicyclic petroleum resin, cumarone resin, 
styrene resin, alkylphenol resin, xylene resin, etc. which have Tg values 
of not lower than 80.degree. C. The amount of the resin used is up to 
150%, preferably about 10 to about 150% based on the weight of alkyl 
(meth)acrylate polymer or the combined weight of alkyl (meth)acrylate 
polymer and .alpha.,.beta.-unsaturated carboxylic acid. 
The UV-curing adhesive composition to be used in the invention is applied 
usually as a solution in an organic solvent to the surface of the picture 
printing layer. Useful solvents are, for example, ketones such as acetone, 
diethyl ketone, cyclohexane, etc.; esters such as methyl acetate, ethyl 
acetate, butyl acetate, etc.; ethers such as ethylene glycol monomethyl 
ether, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; 
and aliphatic hydrocarbons such as hexene, heptane, etc. At least one of 
them is used in the invention. The concentration of the UV-curing adhesive 
composition in the solution is properly adjusted according to the intended 
use but are not specifically limited. 
The construction of the transfer sheet of the invention and the process for 
its manufacture are now described in detail with reference to the 
drawings. 
As shown in sectional view in FIG. 1, a base 1 is coated with a release 
composition in the conventional manner (screen printing, coating, etc.) 
and the solvent is evaporated to form a release layer 3. The evaporation 
of the solvent can be carried out, but is not limited to, by air-drying 
(about 10-30 minutes at room temperature), forced drying (e.g. about 1-5 
minutes at 60.degree. C.), etc. 
Then, a plurality of picture patterns are reverse-printed on the release 
layer 3 by the conventional technique (screen printing, offset printing, 
etc.) and subjected to ultraviolet irradiation or thermal drying according 
to the type of resin component in the ink used, whereby the resin 
component is cured to give picture printing layers 5, 7. The number of 
picture printing layers can be selected according to the desired design. 
Thereafter, said UV-curing adhesive composition is coated on the picture 
printing layer 7 in the conventional manner (e.g. screen printing, offset 
printing, etc.), by evaporating off the solvent, followed by applying a 
release sheet 11 on the picture printing layer 7 to form a UV-curing 
adhesive layer 9. The release sheet is not limited to in type but the 
conventional sheet-releaser assemblies can be utilized. The conditions for 
evaporation of the solvent can also be freely selected according to the 
type of solvent but may, for example, be about 1-5 minutes at 80.degree. 
C. 
In use, the thus-obtained transfer sheet is punched and half-cut to provide 
a necessary picture. As shown in FIG. 2, the release sheet 11 is then 
peeled off and the UV-curing adhesive layer 9 is applied to a substrate 
ware 13. Thereafter, the base 1 is peeled off and the ware 13 is subjected 
to UV irradiation to cure the UV-curing adhesive layer 9, whereby the 
picture is firmly fixed to the ware. The curing procedure can be carried 
out in the conventional manner using a known UV irradiation device and the 
curing conditions are not specifically limited. The curing is complete in 
about 2 to about 10 seconds. 
In the invention, ultrafine titanium oxide, an ultraviolet absorber or the 
like may be incorporated in the picture printing layer and/or releaser 
layer in the per se known manner, whereby photoresistance of the transfer 
sheet and of the picture layer can be enhanced. 
The following significant effects can be realized according to the 
invention. 
(1) Since immersion in water of the transfer sheet and the subsequent 
application to the substrate with a squeegee are not needed, a remarkable 
improvement in workability is realized so that the picture formation of 
the substrate ware can be mechanized. 
(2) Since the picture layer in B to C stage is formed in a short time, 
multicolor decalcomania can be easily accomplished and the workability is 
also improved. 
(3) Unlike the conventional technology using known adhesives, the UV-curing 
adhesive layer according to the invention is not temperature-dependent so 
that there occurs no such a trouble as displacement or detachment of the 
picture layer in use of the ware. 
(4) Since the UV-curing adhesive layer is cured at room temperature in a 
short time (usually up to 10 seconds), a high work efficiency can be 
obtained. 
(5) Since the picture layer formed shows good adhesion to the substrate 
ware, it is remarkably durable even in the presence of water or warm 
water. 
(6) The picture formed on the ware has a satisfactory gloss adding much to 
the marketability of the product ware. 
(7) Since there is no blocking, the transfer sheet has a long shelf-life. 
(8) When a silane coupling agent is incorporated in the UV-curing adhesive 
layer, or a substrate ware is pretreated with a silane coupling agent, a 
further improvement is insured in the adhesion to the substrate ware. 
(9) Known water transfer processes were compared with the process of the 
present invention in respect of the process starting from the preparation 
of a transfer sheet until the formation of a picture printing layer on the 
substrate ware. The results of comparison are shown below in Table 1. It 
is apparent that a significant improvement in production efficiency is 
insured in the present invention. 
______________________________________ 
Water Transfer Process 
Present Invention 
______________________________________ 
1. Printing 
Manually printed one by 
A roll of sheets is 
one. continuously printable. 
A cold setting, water- 
A UV-curing adhesive 
soluble size or paste composition 
composition is applied 
is applied to a release 
to continuous sheet 
sheet and dried for 
and dried for a few seconds. 
1 hour or more. 
2. Transfer 
After immersion in water, 
The design is auto- 
the design is transferred by 
matically transferable. 
a squeegee. Manual operation 
E.g. one autolabeller 
is limited to one capable of 
can transfer designs 
operating on about 700 
on 24,000 articles a day. 
articles a day. 
3. Fixation 
The article is heated at 
Fixation is complete 
140.degree. C. for 30 minutes for drying. 
in a few seconds, namely 
one dryer can achieve fixation 
is feasible with 
about 4,000 articles a day. 
efficiency comparable 
to or higher than that 
of transfer operation. 
______________________________________ 
EXAMPLES AND COMATIVE EXAMPLES 
The following examples and comparative examples are intended to further 
illustrate the outstanding features of the invention in detail. 
The releasable base and UV-curing adhesive compositions used in the 
examples and comparative examples were as follows. 
I. Releasable base 
An acrylic release composition was deposited on a 100 .mu.m-thick clear PET 
film by screen printing and dried at room temperature to provide a 
releasable base. 
II. Components of the UV-curing adhesive compositions (the materials other 
than those shown below are specifically described in the respective 
examples). 
Acrylic ester copolymer (hereinafter "polyacrylate") 
Polyacrylate 1 . . . "SK Dyne 1313" (trade mark), product of Soken Kagaku 
K.K., nonvolatile matter=30%; 
Polyacrylate 2 . . . "Nissetsu" (trade mark), product of Nippon Carbide 
Industries Co., Inc., nonvolatile matter=40%; 
Polyacrylate 3 . . . "SK Dyne 100" (trade mark), product of Soken Kagaku 
K.K., self-curing type, nonvolatile matter=40%; 
Polyacrylate 4 . . . "Haipon 9940" (trade mark), product of Hitachi Kasei 
Polymer Co., Inc., EVA hot melt type. 
Photopolymerizable prepolymer (hereinafter "prepolymer") 
Prepolymer 1 . . . "M-1100" (trade mark), product of Toa Gosei Kagaku K.K., 
polyurethane acrylate, molecular weight=about 2,000; 
Prepolymer 2 . . . "M-7100" (trade mark), product of Toa Gosei Kagaku K.K., 
polyester acrylate, molecular weight=about 1,000; 
Prepolymer 3 . . . "AR-G" (trade mark), product of San Pou Kagaku Kenkyu 
Sho, polyepoxy acrylate, molecular weight=about 120,000. 
Photopolymerizable monomer (hereinafter "monomer") 
Monomer 1 . . . "KS-HDDA" (trade mark), product of Nippon Kayaku Co., Ltd., 
difunctional monomer; 
Monomer 2 . . . "R564" (trade mark), product of Nippon Kayaku Co., Ltd., 
monofunctional monomer 
Photopolymerizaton initiator 
"Darocur 1173" (trade mark), product of Merck & Co., Inc., acetophenone 
type, photosensitizer 
Photosensitizer 
"KAKURE DMBI" (trade mark), product of Nippon Kayaku Co., Ltd., 
4-dimethylaminoisoamyl benzoate. 
Crosslinking agent 
Crosslinking agent . . . "L-45" (trade mark), product of Soken Kagaku K.K., 
TDI-TMP adduct (nonvolatile matter=45%). 
Silane coupling agent 
Silane coupling agent . . . "KBM 703" (trade mark), product of Shin-etsu 
Kagaku K.K., chloropropyl methoxysilane. 
Coloring pigment 
Coloring pigment 1 . . . "820 Series Green" (trade mark), product of 
Sterling Industrial Colors Ltd., organic pigment; 
Coloring pigment 2 . . . "820 Series Pink" (trade mark), product of 
Sterling Industrial Colors Ltd., organic pigment; 
Coloring pigment 3 . . . "TC Powder Black 45" (trade mark), product of 
Sakura Color Products Co., thermochromic pigment; 
Coloring pigment 4 . . . "TC Powder Blue 15" (trade mark), product of 
Sakura Color Products Co., thermochromic pigment. 
EXAMPLE 1 
Using an ink composition of the following formulation, a polka dot pattern 
was formed on a releasable base by screen reverse printing, followed by 
ultraviolet irradiation to form a design. 
______________________________________ 
Polyester acrylate 70.2 parts 
(product of Toa Gosei Kagaku K.K., "Aronix 
M-700" (trade mark), molecular weight = about 
1000) 
1,6-hexanediol diacrylate 17.1 parts 
Acetophenone photopolymerization initiator 
1.8 parts 
(product of Ciba-Geigy, "Irgacure 651" (trade 
mark)) 
Thioxanthone photopolymerization initiator 
0.9 parts 
(product of Nippon Kayaku Co., Ltd., "Kayacure 
DETX" (trade mark)) 
Coloring pigment 1 10.0 parts 
______________________________________ 
Using an applicator, a UV-curing adhesive composition was coated in a 
thickness of 20 .mu.m on the above design and dried at 80.degree. C. for 5 
minutes. A release sheet was superimposed thereon to provide a transfer 
sheet. 
______________________________________ 
Polyacrylate 1 90 parts 
Prepolymer 1 8 parts 
Monomer 1 2 parts 
Photopolymerization initiator 
0.1 part 
Photosensitizer 0.1 part 
Crosslinking agent 1.6 parts 
______________________________________ 
The release sheet was peeled off from the transfer sheet thus obtained and 
the design was transferred to a ceramic substrate mug in a manner to bring 
the UV-curing adhesive layer into contact with the surface of the 
substrate mug. After the releasable base was peeled off, the mug was 
irradiated with ultraviolet rays using a metal halide lamp (80 
W/cm.sup.2). 
The thus-obtained mug carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design as evidenced in Test 
Example 1 which appears hereinafter. 
In the process as described above, the time taken from the production of 
transfer sheet until the formation of picture pattern on the substrate mug 
was made markedly shorter than the time from the production of 
conventional thermosetting transfer sheets to the formation of picture 
pattern by the water transfer process. 
Moreover, when the transfer sheet according to the example was stored for a 
long term, it posed no problem. 
COMATIVE EXAMPLE 1 
A transfer sheet was manufactured in the same manner as Example 1 except 
that polyacrylate 4 was used as the adhesive, and using a silicone rubber, 
the transfer sheet was stuck to a substrate mug by a thermal transfer 
process. 
The transferred polka dot pattern showed a good bond strength with respect 
to the mug but was poor in resistance to warm water. 
COMATIVE EXAMPLE 2 
A transfer sheet was manufactured in the same manner as Example 1 except 
that the following composition was used as the UV-curing adhesive 
composition and the design was transferred to a substrate mug by UV 
irradiation. 
______________________________________ 
Polyacrylate 3 90 parts 
Prepolymer 1 8 parts 
Monomer 2 2 parts 
Photopolymerization initiator 
0.1 part 
Photosensitizer 0.1 part 
Crosslinking agent 1.6 parts 
______________________________________ 
The transferred polka dot pattern showed a good bond strength with respect 
to the mug but was poor in resistance to warm water. 
COMATIVE EXAMPLE 3 
A transfer sheet was manufactured in the same manner as Example 1 except 
that the following adhesive composition was used and the design was 
transferred to a substrate mug by a thermal transfer process. 
______________________________________ 
Polyacrylate 1 100 parts 
Crosslinking agent 1.6 parts 
______________________________________ 
The transferred polka dot pattern showed a good bond strength with respect 
to the mug but was poor in resistance to warm water. 
COMATIVE EXAMPLE 4 
A transfer sheet was manufactured in the same manner as Example 1 except 
that the following UV-curing adhesive composition was used and the design 
was transferred to a substrate mug. 
______________________________________ 
Polyacrylate 1 80 parts 
Prepolymer 1 16 parts 
Photopolymerization initiator 
0.2 part 
Photosensitizer 0.2 part 
Crosslinking agent 1.6 parts 
______________________________________ 
The transferred polka dot pattern was unsatisfactory in bond strength and 
resistance to warm water. 
EXAMPLE 2 
An ink composition was prepared by mixing together with stirring 100 parts 
of a UV-curing medium (trade mark "RIG Medium", product of Seiko Advance 
Co., Ltd., urethane acrylate type), 10 parts of a coloring pigment 1 and 
20 parts of coloring pigment 3. A polka dot pattern was printed on a 
releasable base by screen reverse printing, followed by ultraviolet 
irradiation to form a design. 
Then, using an applicator, a UV-curing adhesive composition of the 
following formulation was coated in a thickness of 20 .mu.m on the above 
design, and dried at 80.degree. C. for 5 minutes. A release sheet was 
superimposed thereon to provide a transfer sheet. 
______________________________________ 
Polyacrylate 1 90 parts 
Prepolymer 2 7 parts 
Monomer 1 3 parts 
Photopolymerization initiator 
0.15 parts 
Photosensitizer 0.15 parts 
Crosslinking agent 1.7 parts 
Silane coupling agent 2.0 parts 
______________________________________ 
The release sheet was peeled off from the transfer sheet and the design was 
transferred to a ceramic substrate mug in a manner to bring the UV-curing 
adhesive layer into contact with the surface of the substrate mug. After 
the releasable base was peeled off, the mug was irradiated with 
ultraviolet rays using a metal halide lamp (80 W/cm.sup.2). 
The resultant mug carrying a polka dot pattern was excellent in bond 
strength of the pattern to the substrate mug as well as the resistance 
thereof to warm water as clear from the results of Test Example 1 to be 
described later. 
The thus-obtained mug carrying a polka dot pattern was black at room 
temperature but when it was filled with warm water, the pattern turned 
brilliant fluorescent green. 
The transfer sheet obtained in the example showed no problem, even after 
prolonged storage. 
EXAMPLE 3 
One-hundred parts of an epoxy resin ("Epikote 828" (trade mark), product of 
Yuka Shell Epoxy K.K.), 5 parts of a reactive diluent ("Cardura" (trade 
mark), product of Yuka Shell Epoxy K.K.), 0.5 part of a defoaming agent 
("BYK-077" (trade mark), product of BYK Chemie Japan) and 40 parts of 
coloring pigment 1 were mixed under stirring, followed by adding 25 parts 
of a curing agent ("Epicure U" (trade mark), product of Yuka Shell Epoxy 
K.K.) and mixing to provide an ink composition. 
Using the ink composition, a polka dot pattern was formed on a releasable 
base by screen reverse printing. The design cured at room temperature for 
fixation. 
Then, the UV-curing adhesive composition of the following formulation was 
coated and dried. A release sheet was superimposed thereon to provide a 
transfer sheet. 
______________________________________ 
Polyacrylate 1 85 parts 
Prepolymer 1 8 parts 
Monomer 1 2 parts 
Photopolymerization initiator 
0.15 parts 
Photosensitizer 0.15 parts 
______________________________________ 
The release sheet was peeled off from the transfer sheet thus obtained and 
the design was transferred to a ceramic substrate mug so as to bring the 
UV-curing adhesive layer into contact with the surface of the substrate 
mug. After the releasable base was peeled off, the mug was irradiated with 
ultraviolet rays in the same manner as in Example 1. 
The thus-obtained mug carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design. 
The transfer sheet obtained in the example showed no problem, even after 
prolonged storage. 
EXAMPLE 4 
One-hundred parts of an epoxy resin ("Epikote 828" (trade mark), product of 
Yuka Shell Epoxy-K.K.), 5 parts of a reactive diluent ("Cardura" (trade 
mark), product of Yuka Shell Epoxy K.K.), 0.5 part of a defoaming agent 
("BYK-077" (trade mark), product of BYK Chemie Japan), 40 parts of 
coloring pigment 2 and 30 parts of coloring pigment 4 were mixed under 
stirring, followed by adding 25 parts of a curing agent ("Epicure U" 
(trade mark), product of Yuka Shell Epoxy K.K.) and mixing to provide an 
ink composition. 
Using the ink composition, a polka dot pattern was formed on a releasable 
base by screen reverse printing. The design cured at room temperature for 
fixation. 
Then, the UV-curing adhesive composition used in Example 3 was coated and 
dried. A release sheet was superimposed thereon to provide a transfer 
sheet. 
The release sheet was peeled off from the transfer sheet thus obtained and 
the design was transferred to a glass substrate mug in a manner to bring 
the UV-curing adhesive layer into contact with the surface of the glass 
substrate. After the releasable base was peeled off, the mug was 
irradiated with ultraviolet rays in the same manner as in Example 1. 
The thus-obtained glass carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design. 
The glass carrying a polka dot pattern was pink-colored at room temperature 
but when filled with cold water, turned blue. 
The transfer sheet obtained in the example showed no problem, even after 
prolonged storage. 
EXAMPLE 5 
Using a blue oil based ink (trade mark "Sericol PS391", product of Teikoku 
Ink Seizo K.K.), a polka dot pattern was formed on the releasable base by 
screen reverse printing and the design cured at room temperature for 
fixation. 
Then, the UV-curing adhesive composition of the following formulation was 
coated and dried. A release sheet was superimposed thereon to provide a 
transfer sheet. 
______________________________________ 
Polyacrylate 2 90 parts 
Prepolymer 1 8 parts 
Monomer 1 2 parts 
Photopolymerization initiator 
0.15 parts 
Photosensitizer 0.15 parts 
______________________________________ 
The release sheet was peeled off from the transfer sheet thus obtained and 
the design was transferred to a substrate glass in a manner to bring the 
UV-curing adhesive layer into contact with the surface of the substrate 
glass. After the releasable base was peeled off, the glass was irradiated 
with ultraviolet rays in the same manner as in Example 1. 
The thus-obtained glass carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design. 
The transfer sheet obtained in the example showed no problem, even after 
prolonged storage. 
EXAMPLE 6 
A transfer sheet was manufactured in the same manner as Example 1 except 
that the following composition was used as the UV-curing adhesive 
composition and the design was transferred to a substrate mug. 
______________________________________ 
Polyacrylate 2 85 parts 
Prepolymer 2 10 parts 
Monomer 2 2.5 parts 
Photopolymerization initiator 
0.1 part.sup. 
Photosensitizer 0.1 part.sup. 
Adhesion imparting agent 
2.5 parts 
______________________________________ 
The thus-obtained mug carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design. 
The transfer sheet obtained in the example showed no problem, even after a 
long term storage. 
EXAMPLE 7 
A transfer sheet was manufactured in the same manner as Example 1 except 
that the following composition was used as the UV-curing adhesive 
composition and the design was transferred to a substrate glass. 
______________________________________ 
Polyacrylate 2 85 parts 
Prepolymer 3 7.5 parts 
Monomer 2 7.5 parts 
Photopolymerization initiator 
0.2 part.sup. 
Photosensitizer 0.2 part.sup. 
Silane coupling agent 2 parts 
______________________________________ 
The thus-obtained glass carrying a polka dot pattern was excellent in bond 
strength and warm water resistance of the design. 
The transfer sheet obtained in the example showed no problem, even after a 
long term storage. 
EXAMPLES 8 to 12 
Mugs carrying a polka dot pattern were manufactured in the same manner as 
Example 1 except that UV-curing adhesive compositions different in the 
formulation as set forth below were used. 
Example 8 
One part of a silane coupling agent was added to the UV-curing adhesive 
composition of Example 1. 
Example 9 
One part of a silane coupling agent was added to the UV-curing adhesive 
composition of Example 2. 
Example 10 
One part of a silane coupling agent was added to the UV-curing adhesive 
composition of Example 3. 
Example 11 
One part of a silane coupling agent was added to the UV-curing adhesive 
composition of Example 3. 
Example 12 
One part of a silane coupling agent was added to the UV-curing adhesive 
composition of Example 4. 
Any of the thus-obtained mugs was excellent in bond strength and warm water 
resistance of the design. The transfer sheets obtained in these examples 
showed outstanding storage stability. 
EXAMPLE 13 
A picture pattern was formed on a substrate mug in the same manner as 
Example 1 except that the mug was pretreated with a 1% aqueous solution of 
a silane coupling agent. 
The thus-obtained mug carrying a picture pattern was higher in bond 
strength and warm water resistance of the design than the mug obtained in 
Example 1. 
TEST EXAMPLE 1 
The mugs and glasses manufactured in the above examples and comparative 
examples were evaluated by the following methods in bond strength, warm 
water resistance, water resistance and adhesion of the designs formed 
thereon. 
(a) Bond strength 
Using a cutting knife, the design (10 mm.times.10 mm) on the mug was cut in 
longitudinal and lateral directions (cross-cut, 11 parallel lines) at 1 mm 
pitches to form 100 squares. An adhesive tape was applied to the cross-cut 
design and, then, pulled and the number of residual squares was counted. 
(b) Warm water resistance 
The mug carrying a transferred design was immersed in warm water at 
80.degree. C. for 30 minutes. Then, in the same manner as the bond 
strength test, the design was cross-cut and the number of residual squares 
was counted. 
(c) Water resistance 
The mug carrying a transferred design was immersed in water at room 
temperature for 24 hours. Then, in the same manner as the bond strength 
test, the design was cross-cut and the number of residual squares was 
counted. 
(d) Adhesion 
The mug carrying a transferred design was immersed in warm water at 
80.degree. C. for 2 hours. Then, in the same manner as the bond strength 
test, the picture was cross-cut and the number of residual squares was 
counted. 
The results are shown in Table 2. 
The results of Table 2 show that the picture printing layers formed on the 
transfer sheets manufactured according to the present invention are 
outstanding in bond strength, warm water resistance, water resistance and 
adhesion. 
TABLE 2 
______________________________________ 
Resistance 
Bond to warm Water 
strength 
water resistance 
Adhesion 
______________________________________ 
Example 1 
100/100 100/100 100/100 99/100 
Comparative 
100/100 0/100 20/100 0/100 
Example 1 
Comparative 
100/100 15/100 30/100 0/100 
Example 2 
Comparative 
100/100 25/100 60/100 0/100 
Example 3 
Comparative 
0/100 0/100 0/100 0/100 
Example 4 
Example 2 
100/100 100/100 100/100 100/100 
Example 3 
100/100 100/100 100/100 97/100 
Example 4 
100/100 100/100 100/100 98/100 
Example 5 
100/100 100/100 100/100 95/100 
Example 6 
100/100 100/100 100/100 99/100 
Example 7 
100/100 100/100 100/100 100/100 
Example 8 
100/100 100/100 100/100 100/100 
Example 9 
100/100 100/100 100/100 100/100 
Example 10 
100/100 100/100 100/100 100/100 
Example 11 
100/100 100/100 100/100 100/100 
Example 12 
100/100 100/100 100/100 100/100 
Example 13 
100/100 100/100 100/100 100/100 
______________________________________ 
It is apparent from the results of Table 2 that the designs formed using 
the transfer sheets of the invention are excellent in bond strength, warm 
water resistance, water resistance and adhesion.