TECHNICAL FIELD OF THE INVENTION
The invention relates to a transfer material in the form of a
sheet for the dye-sublimation transfer method of an inkjet
10 printed image, comprising a base and a dye-absorbing layer on
the front side. The invention therefore relates in particular
to a transfer paper which is provided for printing using
sublimable dyes by means of the inkjet printing method and
from 1•1hich, after the printing, the dyes can be transferred
15 onto a receiving material by sublimation under the influence
of heat. The invention also relates to the transfer method
using the transfer material.
20
TECHNICAL BACKGROUND OF THE INVENTION
Transfer printing methods in lvhich a flexible transfer
material in the form of sheet is first printed on and the
printed image is transferred therefrom onto the object to be
printed on 'l-end--themselves to printing on materials such as
25 textiles or stiff bodies on 1-1hich, for mechanical reasons, it
is hardly possible to print effectively. A specific embodiment
for a transfer printing method of this kind is the dyesublimation
method, lvhich is described in B. Thompson:
Printing Materials - Science and Technology (1998) on page
30 468, for example. In this method, the image to be printed is
applied to the transfer material using printing dyes 1vhich,
after the print has dried, are evaporated under the effect of
il
~
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2
heat and, on the basis of the image, are deposited again in
the gas phase on the material to be finally printed on. The
sublimation dyes may advantageously be applied to the transfer
material by means of digital printing, in particular by means
5 of the inkjet printing method, 1-1hich makes it possible to
produce individual and personalised prints on textiles, for
example. Inkjet printing methods using dyes that can be
transferred to the final printing carrier by sublimation are
disclosed in DE 102 46 209 Al, for example.
10
The transfer material on which the first printing step is
carried out by the inkjet printing technique, is preferably a
paper transfer material. EP 1 101 682 Al describes a coated
paper that has a low air permeability on the side to be
15 printed on. This is intended to prevent some of the sublimable
dyes from entering the porous interior of the paper during the
sublimation transfer step and thus from being lost for the
transfer to the material to be finally printed on. Hmvever,
papers of this kind having a lm1 porosity on the side to be
20 printed on only absorb the inkjet ink liquid very slowly and,
in particular at high printing speeds, lead to slow drying and
to the ink running on the surface and thus to an
unsatisfactory printing sharpness.
25 EP 2 743 091 A1 describes a transfer material and proposes
coating a substrate having low air permeability Hith a
hydrophilic polymer or a salt of a hydrophilic polymer. The
coating may also contain an inorganic oxide as a filler in
amounts of up to 10 wt.%. Coating solutions of this kind
30 all'lays form a polymer film, 1-1hich may have gaps 11hen lol-l
amounts are applied and coarse base materials are used. Quick
absorption and drying of the ink having sublimable dyes,
I _,
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3
applied by means of the inkjet printing method, is therefore
not achieved.
Therefore, US 2008/229962 Al proposed a coating for a transfer
5 paper containing silica and a comparably loH amount of binder
and thus having a considerable air permeability. Absorption of
the ink liquid is therefore achieved; hoHever, sublimable dye
is not prevented from being lost into the interior of the
paper during the transfer to the material to be finally
10 printed on.
SUMMARY OF THE INVENTION
The object of the invention is to provide a transfer paper for
5 the inkjet-printing of sublimable dyes that dries quickly and
has a high printing sharpness 1·1hen aqueous printing inks are
used and, at the same time, ensures that the sublimable dyes
are largely completely transferred to the material to be
finally printed on and is not, or only to a small extent,
10 subject to the sublimable dyes bleeding through to the rear
side of the transfer paper.
Transfer material for the dye-sublimation transfer method of
an inkjet printed image, comprising a base and a dye-absorbing
15 layer on the front side of the transfer material, whereby the
dye-absorbing layer is porous, the porous dye-absorbing layer
has an average pore diameter of from 10 hm to 5 ~m and an air
permeability, according to Bendtsen, of greater than 100
ml/min and the transfer material contains a barrier layer with
20 an air permeability, according to Bendt sen, of lower than 100
ml/min that is arranged either on the rear side of the
transfer material or bet1·1een the base and the porous dyeabsorbing
layer.
5
The barrier layer may be arranged either between the porous
dye-absorbing layer and t h e suppor t paper or on the surface of
the support paper opposing the dye-absorbing layer.
The invention also relates to a method for transferring an
image to a surface in 11hich an image is printed on a transfer
material according to the invention by means of the inkjet
printing method and the .. image is transferred to the surface by
sublimation.
10
DETAILED DESCRIPTION OF THE INVENTION
The transfer papers according to the invention comprise a
support paper having a porous dye-absorbing layer applied_on
15 the printing side and a barrier layer that is arranged bet\-;een
the dye-absorbing layer and the paper support and/or
preferably on the surface of the paper support opposing the
dye-absorbing layer.
20 The support paper is preferably an uncoated or surface-sized
paper. In addition to pulp fibres, the support paper may
contain sizing agents such as alkyl ketene dimers, fatty acids
and/or fatty acid salts, epoxidised fatty acid amides, alkenyl
or alkyl succi-nic anhydride, starch, resin, Het-strength
25 agents such as polyamine polyamide epichlorohydrin, drystrength
agents such as anionic, cationic or amphoteric
polyamides, visual brighteners, pigments, dyes, anti-foaming
agents and other chemical additives known in the paper
industry. The raH paper may be surface-sized. Sizing agents
30 suitable for this purpose are polyvinyl alcohol or oxidised
starch, for example. The raH paper may be produced on a
Fourdrinier paper machine or a Yankee paper machine (cylinder
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5
paper machine). The grammage of the raw paper may be from 30
to 200 g/m2
, in particular from 40 to 120 g/m2
• The raw paper
may be used in compressed or non-compressed form (smoothed).
RaH papers having a density of from 0. 6 to 1. 05 g/cm3
, in
5 particular from 0.70 to 0.9 g/cm3
, are particularly suitable.
The smoothing may take place in the usual manner by
calendering.
For the paper production, all pulps commonly used for this
10 purpose may be used. The pulp for the paper production is
preferably a eucalyptus pulp having an amount of fibres
smaller than 200 rm, after refining, of from 10 to 35 wt.% and
an average fibre length of from 0.5 to 0.75 mm. It has been
sh01m that the use of a pulp having a limited amount of fibres
15 smaller than 200 pm reduces the loss in stiffness that occurs
Hhen filler is used.
Hard1vood pulps (NBHK - northern bleached hardwood kraft pulp)
and softHood pulps may also be used. In addition to pulp
20 fibres, amounts of other natural or synthetic fibres may also
be used for the production of the paper support. Preferably,
the amount of the other fibres in the total fibre mass is
l01-1er than 40 wt.%; particularly preferably, amounts of other
fibres are .loH.er than 20 wt.%.
25
Kaolins, calcium carbonate in its natural form such as
limestone, marmor or dolomite, precipitated calcium carbonate,
calcium sulfate, barium sulfate, titanium dioxide, talcum,
silica, aluminium oxide and mixtures thereof, for example, may
30 be used in the raw base paper as fillers for the sheet
production. Calcium carbonate having a particle size
distribution in which at least 60% of the particles are
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6
smaller than 2 pm and at most 40% thereof are smaller than 1
pm is particularly preferred. In a particular embodiment of
the invention, calcite is used that has a numerical particle
size distribution in which approximately 25% of the particles
5 have a particle size of less than 1 pm and approximately 85%
of the particles have a particle size of less than 2 pm.
According to another embodiment of the invention, a calcium
carbonate may be used that has a numerical particle size
distribution in which at least 70%, preferably at least 80%,
10 of the particles are smaller than 2 pm and at most 70% of the
particles are smaller than 1 pm.
One or more additional layers may be arranged between the
paper supportand the dye-absorbing layer and/or the barrier
15 layer. Said layers are preferably layers containing a
hydrophilic binder.
The dye-receiving layer, Hhich is arranged on the side of the
base paper to be printed on, is porous according to the
20 invention. Said layer preferably contains inorganic pigment
and binder. Inorganic pigments having an anionic, neutral or
only weakly cationic surface, such as silica, calcium
carbonate, kaolin, talcum, bentonite or aluminium oxides or
aluminium oxide dihydrates are particularly preferred.
25 Hm~ever, finely particulate, polymeric compounds may also be
contained, high-melting-point thermoplastic or thermosetting
polymers being preferred. In another embodiment of the
invention, the dye-absorbing layer may also contain a mixture
of two or more pigments. The pigments preferably have an
30 average particle size of from 100 nm to 30 pm, particularly
preferably from 200 nm to 10 pm.
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7
The dye-receiving layer preferably additionally contains a
polymeric binder, preferably a hydrophilic polymeric binder.
The binder may be a binder that is water-soluble or dispersed
in 1·1ater. Preferred binders are styrene copolymers, polyvinyl
5 alcohol, starch, modified starch, polyvinyl acetate, acrylates
or polyurethane dispersions. The mass ratio of pigment to
binder is from 100:1 to 100:50, preferably from 100:40 to
100:2.
10 The dye-receiving layer is preferably applied by applying an
aqueous coating slip to the paper support, it being possible
to use any application method commonly used in the paper
industry. Application by means of a blade, doctor blade, film
press or curtain coater is particularly preferred.
15
The coating slip may contain other common additives such as a
\•letting agent, thickeners, rheological auxiliaries, dyes and
optical brighteners. The application weight of the dyereceiving
layer is preferably from 1 g/m2 to 50 g/m2 ,
20 particularly preferably from 3 g/m2 to 30 g/m2
• The air
permeability of the dye-receiving layer, measured according to
Bendtsen, is greater than 100 ml/min, preferably from 200
ml/min to 700 ml/min. The dye-receiving layer comprises pores
that may comprise~an average pore diameter of from 10 nm to 5
25 pro, preferably from 100 nm to 1.5 pm and particularly
preferably from 500 nm to 1 pm. The pore diameter of porous
dye-receiving layers may be determined by mercury porosimetry.
The mercury porosimetry method for determining pore diameters
is described, for example, in M.J. Mouraa, P.J. Ferreirab,
30 M.M. Figueiredob: Mercury intrusion porosimetry in pulp and
paper technology, Powder Technology, 160(2), p 61-66 (2005).
For the purposes of the invention, the mercury porosimetry was
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8
carried out by means of the porosimeter PASCAL 440 from
Porotec I Thermo Fisher Scientific in order to determine the
pore size of the dye-receiving layer.
5 According to the invention, a barrier layer is arranged
between the dye-absorbing layer and the paper support and/or
on the rear side of the paper support. The barrier layer is
distinguished by a low permeability to air and gases and to
~later vapour. The air permeability of the barrier layer,
10 measured according to Bendtsen, is l01ver than 100 ml/min,
preferably lo1ver than 10 ml/min. The barrier layer preferably
contains one or more polymeric compounds. In an embodiment of
the invention, the barrier layer contains one or more
thermoplastic polymers, thermoplastic polymers having a high
15 melting point, such as polyester or polymethylpentene, being
particularly preferred. In this embodiment, the barrier layer
may be applied by means of the melt-extrusion coating method.
In a particularly preferred embodiment of the invention, the
20 barrier layer is formed by applying an aqueous solution or an
aqueous dispersion of ·one or more polymers that are watersoluble
or dispersed in water. Preferred polymers are styrene
copolymers, polyvinyl alcohols or polyvinyl acetate. In
another preLerred 'embodiment of the invention, the barrier
25 layer contains polymers based on renewable raw materials, such
as starch, modified starch and/or cellulose derivatives, for
example carboxymethyl cellulose (CMC) .
The application \•Ieight of the barrier layer is preferably from
30 1 g/m2 to 40 g/m2
, particularly preferably from 2 g/m2 to 20
g/m2.
5
10
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9
The transfer material according to the invention is suitable
in particular for transferring a printed image to a surface
selected from polyester fabric, polyester non-woven fabric, a
surface coated with a polyester layer, or a polyester surface.
The foll01·1ing examples are used to further describe the
invention.
EXAMPLES
1. Production of a support paper
A eucalyptus pulp was used to produce the support paper. For
refining, the pulp, as an approximately 5% aqueous suspension
15 (thick stock), was refined to a degree of refining of 26 °SR
by means of a refiner. The concentration of the pulp fibres in
the thin stock \vas 1 wt.%, based on the mass of the pulp
suspension. Other additives 1-1ere added to the thin stock, such
as a neutral sizing agent, namely alkyl ketene dimer (AKD), in
20 an amount of 0.23 wt.%, a \-let-strength agent, namely polyamine
polyamide epichlorohydrin resin (Kymene®), in an amount of 0.60
wt.%, starch (C-Bond HR 35845) in an amount of 1.0 wt.%, and a
25
natural, refined CaC03 in an amount of 15 wt.%. The amounts
specified ar.e on the basis of the mass of the pulp.
The thin stock, the pH value of 1vhich was set to approximately
7.5, was brought onto the Hire of the paper machine by the
headbox; subsequently, while dewatering the web, the sheet
formation took place in the wire section of the paper machine.
30 In the press section, the paper 1veb \•las further dewatered to a
water content of 60 wt.%, based on the weight of the web. The
further drying took place by means of heated drying cylinders
MI/ms 150648\>/0
7. November 2017
10
in the dryer section of the paper machine. A raw paper having
a grammage of 90 g/m2
, a filler content of 10 wt.% and a
moisture content of approximately 5. 5% 1-1as formed.
5 The raw paper is surface-sized with starch solution,
containing 3 l•lt.% C-Film 05731 starch from Cargill, and 1-1ith
water, on both sides in a size press. The starch application
on the two sides together is approximately 1. 5 g/m2
• After the
starch has been applied, the support paper is dried and
10 smoothed again. The base paper thus obtained has an air
permeability, measured according to the Bendtsen method
according to DIN 53120-1, of 700 ml/min.
15
2. Production of a coating slip for the dye-receiving layer
13 g of a precipitated silica (CP510 from Grace) and 134 g of
an aqueous 10 wt.% solution of a fully saponified polyvinyl
alcohol (Mowiol"' 28-99 from Kuraray) are slo1-1ly added to 208 g
of a diluted dispersion of precipitated calcium carbonate
20 (Precarb" 724 from Schaefer Kalk) having a solids content of 45
wt.%, and the mixture is mixed by means of a dissolver
agitator. 1. 5 g of a 1-1etting agent, Surfynol" 440 from Air
Products, is then mixed in. The coating slip obtained has a
solids content of 34 wt.% and a pH of from 7 to 8. The average
25 pore diameter of a layer produced from this coating slip,
measured by means of mercury porosimetry, is 750 ± 50 nm.
3. Production of a coating slip for the barrier layer
30 4 g of a wetting agent, Surfynol"' 440 from Air Products, is
added to 1,000 g of an aqueous solution of 10 wt.% fully
saponified polyvinyl alcohol (M01-1iol0 28-99).
5
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7. November 2017
4. Comparative material Vl
11
A commercially available transfer material having a release
and blocking layer (Transjet Classic 831 100 g/m2
) is used as
a comparative material. This comparative material does not
have a porous coating on the printing side.
5. Production of a transfer paper not having a barrier layer
10 (comparison V2)
15
The coating slip from example 2 is applied, by means of a
doctor blade, to the support paper produced according to
example 1 and is dried. The dry application is 15 g/m2
•
6. Production of a transfer paper having a barrier layer
between the dye-absorbing layer and the supportpaper
(invention El)
20 The coating slip for the barrier layer from example 3 is
applied, by means of a doctor blade, to the support paper from
example 1 and is dried. The dry application ~1as 5 g/m2
•
Subsequently, the coating slip from example 2 is applied, by
means of a ·doe·toor "bl·ade i to the barrier layer thus obtained
25 and is dried. The dry application of this layer is 20 g/m2 •
30
7. Production of a transfer paper having a dye-absorbing
layer on the front side and a barrier layer 82 on the rear
side of the support paper (invention E2)
The coating slip from example 2 is applied, by means of a
doctor blade, to the support paper produced in example 1 and
MI/ms 150648WO
7. November 2017
12
is dried. The dry application is 15 g/m2 • The coating slip for
the barrier layer from example 3 is applied, by means of a
doctor blade, to the side of the support paper opposing the
barrier layer thus obtained and is dried. The dry application
5 was 5 g/m2
•
Testing method
A colour image was printed on the transfer materials obtained,
10 using the inkjet printer EPSON WP4015 together with
sublimation colour inks SubliJet IQ from Sawgrass.
15
The drying after the inkjet printing was assessed using two
testing methods:
a) Smearfastness test: after a defined time (fresh, 30 sec, 1
min, 3 min, 5 min) , a finger was run over four solid-dye
printed boxes in the colours cyan, magenta, yellow and black
and the smearing of the colours was assessed.
b) Imprint test: the printed solid-dye surfaces CMYK are
20 brought into direct contact with the rear side of a second
sheet of the transfer material immediately after the printing
and pressed by a 5 kg cylinder (Cobb cylinder).
25
Subsequently, a visual assessment is made as to how much dye
has passed through to the rear side of the second sheet.
Transfer of the printed image to a textile fabric by
sublimation:
In a transfer press, Rotex Autoswing X from Sefa, the image
30 side of the printed-on transfer material is brought into
contact with a polyester fabric, Berger-Backlight satin FR+w;
a sheet of office copying paper having a grammage of 80 g/m2 is
MIIms 1506481'10
7. November 2017
13
additionally placed-onto the rear side of the transfer
material in order to assess the dye bleed-through. At a
temperature of 200°C1 a contact pressure at level 30 according
to the level indicator scale of the press is exerted for 30
5 seconds. The fabric and the copying paper are then separated
from the transfer material.
The printing sharpness is assessed visually and by means of a
microscope, both on the transfer material before the image
10 transfer and on the fabric after the sublimation transfer.
The dye density for the solid-dye boxes CMYK is measured by
means of a spectrophotometer, SpectroEye from X-rite.
15 The dye bleed-through is visually assessed on the basis of the
dye that was transferred to the copying paper, placed onto the
rear side, during the sublimation transfer process.
Table - test results for Vl V2 E1 and E2 I I
V1 V2 E1 E2
~ir permeability
(Bendtsen, DIN
1 mllmin 225 mllmin < 1 mllmin 1 mllmin
53120-1 edition < <
1998-06) ' '•'
Drying (average of
smearfastness and --- +++ ++ +++
imprint)
Printing line
sharpness before
and after the
I + +++
sublimation
+ I +++ ++ I + +++ I +++
transfer onto the
fabric
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7. November 2017
Transferred dye
density
Dye bleed-through
+++
+++
14
++ +++ ++
-- ++ +++
The test results in the table show that the transfer materials
according to the invention have very good drying properties
after inkjet printing, demonstrate high line sharpness, even
5 in the image transferred to the fabric, transfer the
sublimation dye to the fabric to a large degree during the
sublimation transfer process, and release only very little dye
through the rear side.
10 The pore size was determined by means of a porosimeter PASCAL
440 from Porotec I Thermo Fisher Scientific. Mercury was used
as the pressure medium. The initial weight of the sample
material was 1. 0 g, the maximum pressure 1vas 400 MPa, and the
temperature was 22.7 °C.

Claims for national phase
1. Transfer material for the dye-sublimation transfer method
5 of an inkjet printed image, comprising a support and a dyeabsorbing
layer on the front side of the transfer material,
characterised in that the dye-absorbing layer is porous, the
porous dye-absorbing layer has an average pore diameter of
from 10 nm to 5 rm and an air permeability, according to
10 Bendtsen, of greater than 100 ml/min and the transfer material
contains a barrier layer with an air permeability, according
to Bendtsen, of lower than 100 ml/min that is arranged either
on the rear side of the transfer material or between the
15
support and the porous dye-absorbing layer.
2. Transfer material according to claim 1, characterised in
that the support is a paper support.
3. Transfer material according to claim 1 or 2, characterised
20 in that the barrier layer is arranged on the side of the paper
base facing away from the dye-absorbing layer.
4. Transfer material according to any of claims 1 to 3,
characterised in that the barrier layer has an air
25 permeability, according to Bendtsen, of lower than 50 or 20
ml/min.
5. Transfer material according to any of claims 1 to 4,
characterised in that the surface of the dye-absorbing layer
30 is anionically charged or neutral.
5
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7. November 2017
6. Transfer material according to any of claims 1 to 5,
characterised in that the dye-absorbing layer has a pH of at
least 7.0 on the surface.
7. Transfer material according to any of claims 1 to 6,
characterised in that the dye-absorbing layer contains a
pigment, selected from calcium carbonate, kaolin or silica.
8. Transfer material according to any of claims 1 to 7,
10 characterised in that the barrier layer contains a ~latersoluble
polymer.
9. Transfer material according to claim 8, characterised in
that the water-soluble polymer is a polyvinyl alcohol, starch,
15 modified starch or a cellulose derivative.
20
10. Transfer material according to any of claims 1 to 9,
characterised in that the barrier layer has a grammage of from
2 g/m2 to 20 g/m2
•
11. Transfer material according to any of claims 1 to 10,
characterised in that the grammage of the dye-absorbing layer
is from 3 g/m2 to 30 g/m2
•
25 12. Method for transferring an image to a surface,
characterised in that an image is printed on a transfer
material according to any of claims 1 to 11 by means of the
inkjet printing method and the image is transferred to the
surface by sublimation.
30
13. Method according to claim 12, characterised in that the
surface is selected from polyester fabric, polyester non-lvoven
MI/ms 150648\'10
fabric, a surface coated lvi th a polyester layer, or a
polyester surface.