A PRINTABLE SHEET THAT IS ULTRA-SMOOTH AND RECYCLABLE,
AND ITS METHOD OF FABRICATION
The present invention relates to a printable sheet
that is smooth or ultra-smooth and recyclable, and also
5 to its method of fabrication. The sheet may be used in
distinct fields such as packaging, electronics, optics,
or graphic arts, e.g. as a print medium, in particular
for printing a photographic image.
In the prior art, an ultra-smooth sheet can be
10 fabricated by laminating a plastics film on one face of a
paper, the plastics film defining an ultra-smooth face on
the paper. The base paper is made of a fibrous material
and its faces present relatively large roughness, of the
order of about 20 micrometers (pm), i.e. each of its
15 faces has projections and indentations with the height
between them being of the order of 20 pm. Laminating a
plastics film on one of the faces of such a paper serves
to impart very small roughness to that face, roughness of
the order of 1 pm when using a polyethylene terephthalate
20 (PET) film.
Since paper is a material that is relatively
expensive and that is produced on a large scale, it is
important for it to be recyclable. Nevertheless, a
paper-based sheet that is ultra-smooth because it
25 includes a plastics film is not recyclable or is
difficult to recycle, which is therefore neither
ecological nor inexpensive. When recycling paper-based
sheets, the sheets are chopped up and mixed with water in
a pulper in order to form a paper pulp. When such sheets
30 include plastics films, those films are torn up in the
pulper and their plastics material pollutes the pulp.
With the present state of the art, it is therefore
not possible to fabricate an ultra-smooth sheet that is
recyclable, and preferably entirely recyclable.
35 Furthermore, such an ultra-smooth sheet is not
printable and a printable resin needs to be deposited on
the plastics film of the sheet in order to make it
printable. That technique is used in particular for
fabricating paper-based sheets for printing photographic
images (known as "resin-coated photographic papers"),
where such sheets have a polyethylene (PE) film with Bekk
5 smoothness of about 6000 seconds (s).
A smooth sheet may also be fabricated by depositing
a coating layer on one face of a paper, with that
composition, once dry, defining a smooth face on the
paper. That technique makes it possible to fabricate a
10 smooth sheet without a plastics film. The composition is
deposited on the paper by a curtain coating technique,
with a scraper or trailing blade, with an air knife, by
photogravure, or by rollers (size press, film press,
etc.). The face of the base paper onto which the coating
15 composition is deposited has alternating depressions and
projections, the depressions being filled by the coating
composition and the projections being made even during
coating, thereby enabling the roughness of the paper to
be reduced. Nevertheless, that technique does not enable
20 a sheet to be obtained that is as smooth as a sheet
covered in a plastics film, even if the sheet is
subsequently smoothed, e.g. by calendering.
The method presently used for fabricating a smooth
and glossy sheet consists in depositing a coating
25 composition on a base paper by means of a mechanical
roller having a cylindrical surface that is very smooth
and that is covered in a layer of chromium. The Bekk
smoothness of a sheet obtained by that method is of the
order of 50 s and is therefore nevertheless smaller than
30 that of a sheet having a plastics film (which is about
6000 s when a PE film is applied).
Furthermore, it is difficult to obtain a smooth
sheet by coating a composition onto a paper that is
relatively rough. When the above-mentioned depressions
35 in the face of the paper are too large or too numerous,
the coating composition does not fill the depressions
completely, or else too great a quantity of composition
is required to do that.
This applies for example to a paper having
relatively large bulk, e.g. greater than 1.10 cubic
5 centimeters per gram (cm3/g), which therefore has faces
that are relatively rough and poor printability. Coating
a composition on a face of such paper, even using large
quantities of composition, does not enable a smooth sheet
to be fabricated, and also considerably reduces its bulk.
10 Furthermore, even though calendering the sheet makes it
possible to increase its smoothness, that is achieved to
the detriment of its bulk.
In the prior art, it is therefore not possible to
fabricate, under satisfactory conditions, a smooth sheet
15 starting from a rough paper and/or having relatively
large bulk.
A particular object of the invention is to provide a
solution to the problems of the prior art that is simple,
effective, and inexpensive.
20 The invention proposes a method of fabricating a
sheet that is smooth, also known as ultra-smooth in the
meaning of the invention, with the smoothness of the
sheet being independent of the roughness of the paper or
more generally of the base substrate used, and the sheet
25 not including a plastics film and therefore being
recyclable, at least in part, or indeed biodegradable.
To this end, the invention provides a method of
fabricating a printable sheet presenting at least one
face that is smooth, and advantageously ultra-smooth, the
30 sheet comprising a substrate, in particular made of
paper, having at least one face covered at least in part
in a layer or a plurality of superposed layers, the
method comprising the steps consisting in:
a) preparing or providing a multilayer structure
35 comprising at least, or constituted by, a preferably
smooth plastics film, an anti-adhesive layer, and a
printable layer, the anti-adhesive layer being interposed
between the plastics film and the printable layer;
b) pasting adhesive on a face of the substrate
and/or the face of the multilayer structure situated
5 opposite from the plastics film, and applying said face
of the substrate against said face of the multilayer
structure so as to laminate the multilayer structure and
the substrate; and
c) withdrawing the plastics film from the printable
10 layer, the printable layer defining said smooth or ultrasmooth
face of the sheet.
In a particular implementation of the invention, the
multilayer structure is prepared prior to implementing
the method of fabricating the printable sheet. Under
15 such circumstances, the multilayer structure is provided
for performing the method of fabricating the printable
sheet.
In the invention, the smooth or ultra-smooth face of
the sheet is defined by a printable layer that is
20 prepared on a so-called "donor" plastics film, said
printable layer at this stage being contained within a
multilayer structure and then being transferred onto the
so-called "receiver" base substrate. The smoothness of
the printable layer and thus of the sheet is determined
25 by the smoothness of the plastics film of the multilayer
structure, and therefore does not depend on the
smoothness of the base substrate used. The invention
thus enables the surface state of a plastics film to be
transferred onto any substrate. In other words, the
30 invention makes it possible to fabricate a smooth or
ultra-smooth sheet from any substrate, advantageously
such as a rough paper and/or a paper having relatively
large bulk, e.g. greater than or equal to 1.10 cm3/g, and
without including a plastics film in the sheet as made in
35 this way.
The sheet prepared by the method of the invention is
thus both printable and recyclable.
In the present application, a printable sheet or a
substrate for use in preparing a printable sheet means a
thin element (thickness not exceeding 500 pm) that is
preferably non-rigid and/or flexible.
5 The term printable layer or sheet is used to mean a
layer or sheet suitable for being printed by any printing
technique, and in particular by offset printing, ink jet
printing, laser printing, heliogravure, flexography, dry
toner printing, liquid toner printing,
10 electrophotography, lithography, etc. A printable layer
typically comprises a mixture of pigments and at least
one binder, or is formed by a printable varnish based on
one or more polymers of the following types: acrylic,
vinyl, polyurethane, styrene, starch, polyvinyl alcohol,
15 ethylene, or a mixture thereof. The ink is for
depositing on the smooth or the ultra-smooth free surface
of the printable sheet or of the printable layer. A
recyclable sheet is a sheet that does not include a
plastics film, e.g. a film made of a thermoplastic
20 material or a thermosetting material.
According to a characteristic of the invention,
printing on the printable layer does not lead to
structural modification thereof, and in particular does
not lead to a change in the state or the phase thereof
25 (such as for example passing from a solid state to a
liquid state and then returning to the solid state).
A multilayer structure of the invention as prepared
or provided in the context of the method of the invention
includes in particular, or is constituted by: a bottom
30 plastics film, an intermediate anti-adhesive layer, and a
printable top layer. The anti-adhesive layer covers at
least a portion of the top face of the plastics film, and
the printable layer covers at least a portion of the top
face of the anti-adhesive layer.
35 The plastics film serves as a support for
fabricating the printable layer. This film does not
remain in the final product, i.e. the sheet, so the sheet
is therefore recyclable. The top face of the film
(situated beside the printable layer) is advantageously
as smooth as possible, since the surface quality of the
top face of the sheet, as defined by the printable layer,
5 is a function of the surface quality of said top face of
the plastics film. In other words, the smoother the
plastics film of the multilayer structure, the smoother
the resulting sheet.
The plastics film is selected from films made of the
10 following plastics: polyethylene terephthalate (PET);
polyethylene (PE); polypropylene (PP); a polymer based on
polylactic acid (PLA); any polymer based on cellulose,
etc. By way of example, the film has thickness of about
12 pm.
15 Advantageously, the plastics film does not include
and/or is not covered in polyvinylidene fluoride (PVDF),
polypropylene (PP), Teflon, silica, boron nitride,
chromic chloride stearate, or any other substance having
anti-adhesive properties.
20 The face of the film situated beside the printable
layer is preferably smooth and may have smoothness
greater than 10,000 s on the Bekk scale.
The thickness, the hardness, and the gloss
transition temperature of the plastics film have little
25 or no influence on the characteristics of the printable
layer. Only the smoothness, or on the contrary the
roughness, of the plastics film has an influence on the
smoothness or the roughness of the printable layer. The
smoother the plastics film, the smoother the printable
30 layer. The person skilled in the art is nevertheless
capable of determining which characteristics of the
plastics film are likely to influence the surface state
of the printable layer, and of optimizing those
characteristics as a function of the final smoothness
35 that is to be obtained for the printable layer.
The anti-adhesive layer of the multilayer structure
is deposited on the plastics film by any technique, e.g.
by photogravure. The function of the anti-adhesive layer
is to limit adhesion between the printable layer and the
plastics film and to facilitate separation and withdrawal
of the plastics film from the printable layer in step c)
5 of the above-defined method. The anti-adhesive layer has
little or no modifying effect on the smoothness and the
surface quality of the face of the plastics film on which
said layer is deposited.
The anti-adhesive layer may adhere more strongly to
10 the plastics film than to the printable layer, so that
most or even all of the anti-adhesive layer remains stuck
to the plastics film when it is withdrawn from the
printable layer. Nevertheless, it may happen that
portions or traces of the anti-adhesive layer persist on
15 the printable layer after the plastics film has been
withdrawn.
In a variant, the anti-adhesive layer may adhere
more strongly to the printable layer than to the plastics
film, in which case it is intended to remain at least in
20 part on the printable layer when the plastics film is
withdrawn.
In yet another variant, the anti-adhesive layer is
intended to split substantially into two portions while
the plastics film is being withdrawn, a first portion
25 remaining on the plastics film and a second portion
remaining on the printable layer.
The multilayer structure may have two superposed
anti-adhesive layers between the plastics film and the
printable layer, these two layers being designed to
30 separate from each other while the plastics film is being
withdrawn (one of the anti-adhesive layers remaining on
the plastics film and the other anti-adhesive layer
remaining on the printable layer).
Leaving some or all of the anti-adhesive layer on
35 the printable layer is particularly advantageous when the
sheet is for use as a support in a casting application.
A casting application consists in extruding or casting at
least one polymer (such as polyurethane (PU), polyvinyl
chloride (PVC), etc.) on a support coated in an antiadhesive
layer. The polymer may have a surface that is
textured in order to impart a particular appearance on
5 the sheet (e.g. similar to leather). Leaving an antiadhesive
layer on the sheet of the invention avoids the
need for depositing another such layer on said sheet for
a casting application, and is therefore advantageous in
particular in terms of cost and in terms of the time
10 required for preparing the support for the casting
application.
The anti-adhesive layer has thickness less than or
equal to 5 pm and preferably less than or equal to 1 pm.
The anti-adhesive layer may be made up of silicone(s),
15 siloxane(s), polysiloxane(s) or derivatives thereof,
Werner complex(es), such as chromic chloride stearates,
or waxes of polyethylene, propylene, polyurethane,
polyamide, polytetrafluoroethylene, etc.
Advantageously, the anti-adhesive layer does not
20 include PVDF.
The printable layer of the multilayer structure may
be selected from a printable varnish, from a paper
coating, etc.
In the present application, the term printable
25 varnish is used to mean a substance based on: acrylic
polymer, polyurethane, polymethyl methacrylate, styrenebutadiene,
vinyl acetate, polyamide, nitrocellulose or
any other cellulose, polyvinyl alcohol, starch, etc.
This substance is generally deposited in liquid form and
30 solidified by drying/heating or by ultraviolet (UV)
radiation or electronic radiation.
The term "paper coating" is used to mean applying a
composition comprising a binder and pigments. The binder
may be based on: acrylic, polyurethane, polymethyl
35 methacrylate, styrene-butadiene, vinyl acetate,
polyamide, nitrocellulose or any other cellulose,
polyvinyl alcohol, starch, or a mixture thereof. The
pigments may be selected from calcium carbonates,
kaolins, titanium dioxide, talc, silicas, mica,
pearlescent particles, plastics pigments (polystyrene
(PS), polyurethane (PU), etc.), and mixtures thereof.
5 The quantity of binder relative to the pigments lies in
the range 5% to 50% approximately, and preferably in the
range 8% to 25%, by dry weight. The pigments generally
comprise a majority relative to the binder in a paper
coating so as to create pores to improve ink absorption.
10 In contrast, in a thermal transfer layer the binders are
in the majority over the pigments since the purpose is to
avoid having surface pores.
The plastics material used in the printable layer
(as binder and/or pigments) is easily fragmented and does
15 not pollute the paper pulp on being recycled. In
contrast, plastics films retain cohesion and clog filters
when the paper pulp is put into suspension. Water
soluble binders (such as starch, polyvinyl alcohol (PVA),
etc.) are particularly advantageous in this respect,
20 since they disperse in water during recycling.
The paper coating may also include a dispersant
and/or a rheology modifier and/or a dye and/or a
spreading or surface agent and/or a conductive additive.
The conductive additive may be used to reduce the surface
25 resistivity of the sheet.
Preferably, the printable layer is free of antiadhesion
agents and/or of substances that could reduce
the surface energy of the layer, such as a silicone
material or the like, PVDF, PP, Teflon, silica, boron
30 nitride, etc. That type of agent or substance may be
necessary for printing on a layer by thermal transfer, in
particular in order to avoid the paper adhering to the
printer ribbon. The printable layer of the invention may
therefore be unsuitable for thermal transfer printing.
35 The printable layer may be made up of a plurality of
sublayers superposed one on another, each sublayer being
printable and being selected from the above-specified
types (printable varnish, paper coating, etc.) .
The printable layer may have thickness that is less
than or equal to 30 pm, preferably less than or equal to
15 pm, and more preferably less than or equal to 10 pm.
Its grammage (i-e. its weight in grams per square meter
(g/m2)), is advantageously less than or equal to 30 g/m2,
preferably less than or equal to 15 g/m2, and more
preferably less than or equal to 10 g/m2. By way of
example, the printable layer may have thickness and
grammage that are less than or equal to the following
combined values: 10 pm and 10 g/m2; 3 pm and 10 g/m2; 2 pm
and 10 g/m2; 5 pm and 5 g/m2; 3 pm and 5 g/m2; 2 pm and
5 g/m2; 5 pm and 2 g/m2; 3 pm and 2 g/m2; or 2 pm and
2 g/m2.
The printable layer may be deposited on the antiadhesive
layer by any technique, e.g. by photogravure.
The printable layer may be deposited on the antiadhesive
layer in the liquid or semi-liquid state and
then solidified by drying, heating, or by electronic or
UV radiation. After solidification and/or drying, the
printable layer, which is in contact with the smooth face
of the plastics film via the anti-adhesive layer,
presents a face situated beside the plastics film that is
smooth.
The printable layer is thus dried and/or solidified
prior to being transferred onto the substrate, in
particular so as to avoid modifying the surface state of
said layer as imparted by the plastics film. In other
words, the multilayer structure is prepared prior to
transferring the printable layer onto the substrate, and
the printable layer is in the solid and/or dry state
while it is being transferred onto the substrate, i.e.
during steps b) and c) of the method of the invention.
The surface state of the printable layer is thus created
while preparing the structure.
In the method of the invention, the printable layer
is thus fabricated independently of the base substrate.
This makes it possible in particular to implement the
method with standard industrial tools, thus making
5 optimized production rates possible.
The smooth face of the sheet may have Bekk
smoothness greater than 900 s or 1000 s approximately,
preferably greater than 2000 s, and more preferably
greater than 5000 s. In the present application, a face
10 is said to be smooth or ultra-smooth when it presents
Bekk smoothness greater than 900 s or 1000 s
approximately, advantageously greater than 2000 sf and
more preferably greater than 5000 s.
The smooth face may present gloss greater than 70%,
15 and preferably greater than 80%, the gloss being measured
for example at 75" using the TAPPI@ T480 om-92 method.
The gloss may be similar to or greater than the gloss of
a resin-coated photographic paper that includes a
plastics film.
20 The multilayer structure may include at least one
additional layer that is deposited on the printable layer
on its side opposite from the plastics film, the free
face of the additional layer or of the additional layer
farthest from the plastics film serving, in step b), to
25 be pasted and applied against the above-specified face of
the substrate.
The additional layer(s) may be functional or nonfunctional.
By way of example, it may be insulating
(dielectric) or it may form a barrier (against gas, e.g.
30 oxygen, liquids, e.g. water, fats, etc. ) .
When the multilayer structure includes a single
additional layer, it is deposited on the top face of the
printable layer, i.e. on the face of the printable layer
that is situated on its side opposite from the plastics
35 film of the multilayer structure. This additional layer
may be of any kind, and therefore need not necessarily be
printable. When the multilayer structure has two or more
additional layers, these additional layers are superposed
one on another and deposited on the above-mentioned top
face of the printable layer. The technique(s) used for
depositing the additional layer(s) on the printable layer
5 may be of the above-mentioned types, or of any other
type.
The multilayer structure may thus include, in
addition to the above-mentioned three elements (plastics
film, anti-adhesive layer, and printable layer), one or
10 more optionally-printable additional layers on the
printable layer (on the side opposite from the plastics
film). The multilayer structure may also include a layer
or film of adhesive covering the layer that is farthest
from the plastics film (i.e. the printable layer or the
15 or one of the additional layer(s)).
Step b) of the method of the invention then consists
in pasting the face of the substrate that is to receive
the printable layer or the face of the multilayer
structure that is situated on its side opposite from the
20 plastics film, and in applying those faces against each
other so as to fasten them together.
The substrate may be selected from: paper, tracing
paper, card stock, and coated or precoated paper. The
paper may present relatively large bulk, greater than or
25 equal to 1.10 cm3/g, preferably greater than or equal to
1.2 cm3/g, more preferably greater than or equal to
1.3 cm3/g, more particularly greater than or equal to
1.4 cm3/g, and even more particularly greater than or
equal to 1.5 cm3/g.
30 The method of the invention makes it possible to
make a sheet having bulk and smoothness that are
considerable, which is not possible in the prior art. In
the prior art it is not possible to make a sheet having
both large bulk and good surface quality. A substrate
35 having large bulk may be made of a material that is
inexpensive. With a paper, the paper pulp used may
comprise cellulose fibers, a binder, and a small amount
of fillers and/or additives, such as starch.
In a particular implementation of the invention, the
method of the invention leads to a small reduction in the
bulk of the paper substrate, by about 2% to 5%.
A smooth or ultra-smooth sheet presenting large bulk
and fabricated by the method of the invention presents
good printability and low gramrnage, thereby enabling
packaging to be made that is light in weight but that
presents relatively great rigidity.
During step b) of the method, the face for lining
the substrate or the free face of the printable layer or
of an additional layer of the multilayer structure is
pasted using an appropriate adhesive.
In a variant, the two above-mentioned faces of the
substrate and of the multilayer structure are pasted
simultaneously, or else one after the other.
Pasting consists in depositing a layer of adhesive
on the above-mentioned face(s) using any technique, e.g.
such as photogravure. The adhesive may be of the thermal
type, of the non-thermal type, of the UV-cured type, or
of the type involving a chemical reaction. The adhesive
may be deposited on the or each of the above-mentioned
faces in liquid or non-liquid form (e-g. it may be a
thermoadhesive film). By way of example, the adhesive is
selected from the following polymers: acrylic,
polyurethane, polymethyl methacrylate, styrene-butadiene,
vinyl acetate, polyamide, nitrocellulose or any other
cellulose, polyvinyl alcohol, or starch. The or each
layer of deposited adhesive may present thickness that is
less than or equal to 10 pm, preferably less than or
equal to 3 pm.
In a particular implementation of the invention, the
adhesive is deposited on the above-specified face of the
multilayer structure while the structure is being
prepared. The adhesive then forms an integral portion of
the multilayer structure. The adhesive may be formed by
a thermally activatable adhesive layer, which layer is
activated by heating while the multilayer structure is
being applied against the (receiver) substrate.
The nature of the adhesive and the adhesion process
(on the film and/or on the paper) may have a considerable
influence on the final surface state of the paper. For
example, it is important for the adhesive to be deposited
uniformly while avoiding any cavities being formed
between the paper and the printable layer.
Concerning the uniformity of the deposited adhesive,
adhesive deposition is preferably uniform so as to avoid
there being too much or too little adhesive in various
locations, since that would give rise to a final sheet
presenting surface roughnesses. Advantageously, the
adhesive spreads well over the support (film or paper)
because it has appropriate surface tension and rheology.
The way in which the adhesive is coated may also be
important. Coating methods that give rise to a deposit
that is as uniform as possible, such as photogravure
(reverse roll or kiss coating) are preferred. Deposition
is preferably selected to that it fills the pores or
surface irregularities of the paper as much as possible.
For example, when paper has mean surface roughness (e.g.
Sa) of about 20 pm, then it is preferable to deposit the
adhesive with a thickness of not less than 10 pm in order
to fill in the pores. Adhesive deposition is preferably
performed on the paper when the paper is not too rough.
If deposition on the paper is not sufficient, then
cavities form between the surface of the paper and the
printable layer. During printing, these cavities become
points of weakness in the paper that may either cave in
if pressure is exerted, or else flake off if traction is
exerted.
Advantageously, the thickness of the adhesive
deposited on the paper and/or the printable layer is
equal to not less than half the mean surface roughness
(e.g. Ra or Sa) of the paper. In an implementation of
the invention, the adhesive is deposited on at least one
face of the substrate in step b), and the thickness of
the deposited adhesive layer is not less than half the
mean roughness of the face of the substrate, and is
5 preferably equal to said mean roughness.
The adhesive may have a water base, a solvent base,
or be without solvent, and comprise two components or
only one component.
The adhesive enables the printable layer (or an
10 additional layer) to be fastened onto the substrate and,
where appropriate, enables surface irregularities of the
substrate to be compensated. In particular, the adhesive
fills in depressions in the face for lining of the
substrate and thus enables said face to be made plane,
15 but without modifying the characteristics of the
substrate such as its bulk.
Step b) of the method then consists in applying the
above-mentioned face of the substrate against the abovementioned
face of the multilayer structure so as to
20 laminate them together. The printable layer is then
sandwiched between firstly the substrate with the
adhesive on one side (possibly together with one or more
additional layers), and secondly the plastics film with
the anti-adhesive layer on the other side.
25 When the adhesive used for sticking the substrate
onto the multilayer structure is of the thermally
adhesive type, the substrate is applied to the multilayer
structure while hot, at some given temperature, which may
for example lie in the range about 50°C to 200°C. In a
30 variant, the substrate may be applied and bonded to the
multilayer structure at ambient temperature.
A small amount of pressure may be necessary for
ensuring good adhesion of the printable layer on the
substrate, via the adhesive.
35 The temperature and/or the pressure used during
application and bonding should nevertheless not modify
the characteristics of the printable layer, and in
particular the surface state of its face situated beside
the plastics film. For example, the printable layer must
not be softened by high temperature application, since
that could lead to a modification of and a decrease in
5 the surface quality of its face situated beside the
plastics film.
Thereafter, step c) of the method consists in
withdrawing the plastics film from the printable layer
and the substrate in such a manner that the printable
10 layer (and where appropriate the above-mentioned
additional layer(s) of the multilayer structure)
remain(s) on the substrate. The printable layer, and
where appropriate the additional layer(s), is/are thus
transferred from the "donor" plastics film of the
15 multilayer structure onto the "receiver" substrate.
As explained above, at least some and advantageously
most or all of the anti-adhesive layer may remain on the
plastics film so that it is withdrawn from the printable
layer while the plastics film is being withdrawn. The
20 face of the printable layer that was situated beside the
plastics film in the multilayer structure is therefore
exposed, said face defining the smooth face of the sheet.
The printable layer of the multilayer structure may
be transferred onto the substrate during steps b) and c)
25 of the method in the manner described below when the
substrate and the multilayer structure are in the form of
continuous strips.
The multilayer structure and the substrate may be
laminated together by passing them between two parallel
30 and adjacent mechanical rollers rotating in opposite
directions. The thickness of the resulting product is a
function in particular of the distance between the
rollers. Once the adhesive has dried or solidified, the
plastics film is withdrawn from the sheet while it is
35 being driven by another mechanical roller.
In a variant, it is possible to paste either the
multilayer structure or the substrate, to allow the
adhesive to dry, and then to put those two elements into
contact one against the other while applying a determined
temperature and pressure.
Prior to step b), the method may also consist in the
above-mentioned face of the substrate being precoated
with at least one smoothing coat having one or more
thermoplastic polymers (such as at least a polystyrene, a
polyurethane, an acrylic, etc.) or a mixture of pigments
(such as kaolins, calcium carbonates, talc, titanium
dioxide, etc., and mixtures thereof) and at least one
binder (such as a binder based on: acrylic, polyurethane,
polymethyl methacrylate, styrene-butadiene, vinyl
acetate, polyamide, nitrocellulose or any other
cellulose, starch, or PVA) .
This precoated face of the substrate may also be
calendered prior to step b) in order to increase its
smoothness.
The method of the invention may include an
additional step consisting in printing the sheet with an
ink having electrical and/or optical properties.
The present invention also provides a method of
preparing a multilayer structure comprising at least or
constituted by: a plastics film, an anti-adhesive layer,
and a printable layer, the anti-adhesive layer being
interposed between the plastics film and the printable
layer.
The present invention also provides a method of
printing a sheet prepared by the above-described method,
the printing method comprising a step of printing the
sheet without modifying the state of its printable layer,
i.e. without softening or melting said layer during
printing. By way of example, the sheet may be printed by
offset printing, ink jet printing, laser printing,
photogravure, flexographic printing, dry toner, liquid
toner, electrophotography, lithography, etc.
The present invention also provides a method of
fabricating a sheet for casting application presenting at
least one smooth face, the sheet having a substrate, in
particular a paper substrate, with at least one face
covered at least in part by a layer or a plurality of
superposed layers, the method comprising the steps
5 consisting in:
a) preparing or providing a multilayer structure
comprising at least, or constituted by, a plastics film,
an anti-adhesive layer, and a layer for casting
application, the anti-adhesive layer being interposed
10 between the plastics film and the layer for casting
application;
b) pasting adhesive on a face of the substrate
and/or the face of the multilayer structure situated
opposite from the plastics film, and applying said face
15 of the substrate against said face of the multilayer
structure so as to laminate the multilayer structure and
the substrate; and
c) withdrawing the plastics film from the layer for
casting application, the printable layer defining said
20 smooth face of the sheet.
By way of example, the layer for casting application
is a layer of PVA. The layer for casting application may
have anti-adhesive properties.
The present invention also provides a printable
25 sheet presenting at least one face that is smooth and
advantageously ultra-smooth, the sheet comprising a
substrate, in particular a paper substrate, having at
least one face covered at least in part in one or more
layers including a printable layer defining said smooth
30 or ultra-smooth face, the sheet being characterized in
that said smooth or ultra-smooth face has Bekk smoothness
greater than 900 sf or greater than 1000 sf
approximately, preferably greater than 2000 sf and more
preferably greater than 5000 s.
35 The smooth or ultra-smooth face of the sheet may
have gloss greater than 70% and preferably greater than
80%, the gloss being measured for example at 75' using
the TAPPIQ T480 om-92 method.
The printable layer of the sheet may have thickness
less than or equal to 30 pm, preferably less than or
5 equal to 15 pm, and more preferably less than or equal to
10 pm. The gramrnage of the printable layer may be less
than or equal to 30 g/m2, preferably less than or equal to
15 g/m2, and more preferably less than or equal to
10 g/m2. By way of example, the printable layer may have
10 thickness and gramrnage that are less than or equal to the
following combined values: 10 pm and 10 g/m2; 3 pm and
10 g/m2; 2 pm and 10 g/m2; 5 pm and 5 g/m2; 3 pm and
3 g/m2; 2 pm and 5 g/m2; 5 pm and 2 g/m2; 3 pm and 2 g/m2;
or 2 pm and 2 g/m2.
15 The present invention also provides the use of a
printable sheet as described above for making an
electronic or optical component, the sheet being printed
by means of an ink having electrical and/or optical
properties.
20 The sheet of the invention may be compatible with
electronic organic inks for electronic applications, such
as for example making radio frequency identification
(RFID) chips, display or detection systems, etc.,
directly on the sheet.
25 In the prior art, an RFID chip can be made on a
sheet constituted by a plastics film of polyethylene
terephthalate (PET). Nevertheless, such a plastics film
is of mechanical strength and temperature behavior that
are relatively poor, thereby limiting potential
30 applications for the chip and preventing the film being
printed with inks at relatively high temperatures.
Furthermore, a film made of PET is not simple to recycle.
In contrast, when the substrate of the sheet of the
invention is made of paper, the sheet presents better
35 mechanical strength and better high temperature behavior.
A sheet printed with an ink having electrical
properties advantageously comprises a flexible substrate
and a printable layer that presents little or no
electrical conductivity. A sheet of this type can be
used for making organic thin-film transistors using
conductive or semiconductive organic inks.
The sheet of the invention may also be used for
making optical components, such as waveguides,
holographic patterns, etc.
By way of example, the above-defined method may
include, prior to step a), a preliminary step consisting
in making, e.g. by etching, recessed or projecting
patterns on the face of the plastics film that is to
receive the anti-adhesive layer and the printable layer,
the printable layer being intended to fit closely to the
shape of the patterns so as to include an imprint of the
above-mentioned face of the plastics film.
Under such circumstances, transferring the surface
state of the film to the printable layer comprises both
transferring the smooth surface and also the patterns of
the plastics film. The patterns transferred to the
printable layer themselves present surfaces and/or walls
that are smooth in appearance and that are accurately
defined. The method is thus particularly advantageous
for making optical components of the above-specified
type-
Finally, the present invention provides the use of a
printable sheet as described above for printing a
photographic image, for making packaging, and/or for a
casting application.
The invention can be better understood and other
details, characteristics, and advantages of the present
invention appear more clearly on reading the following
description made by way of non-limiting example and with
reference to the accompanying drawings, in which:
Figure 1 is a highly diagrammatic view of the
steps in the method of the invention for fabricating a
smooth or ultra-smooth printable sheet;
Figure 2 is a highly diagrammatic view showing a
variant implementation of the method of the invention;
Figures 3 and 4 are highly diagrammatic views of
means for performing the transfer step of the method of
5 the invention; and
Figures 5 and 6 are images obtained by a scanning
electron microscope (SEB) respectively showing a face of
base paper and a face of a smooth or ultra-smooth sheet
obtained by the method of the invention.
10 Reference is made to Figure 1 which shows in highly
diagrammatic manner the steps a), b), and c) of the
method of the invention for fabricating a smooth or
ultra-smooth printable sheet 10 that is entirely
recyclable.
15 Step a) of the method consists in preparing a
multilayer structure 12 comprising a bottom.plastics film
14, an anti-adhesive intermediate layer 16, and a
printable top layer 18. This structure 12 may be
prepared in a single step or in a plurality of successive
20 steps.
The anti-adhesive layer 16 and the printable layer
18 may be deposited simultaneously on the plastics film
14, e.g. using a curtain coating technique.
In a variant, the anti-adhesive layer 16 is
25 deposited on the plastics film 14, and then the printable
layer 18 is deposited on the anti-adhesive layer.
The quality of the top face 20 of the plastics film
14 is transmitted to the bottom face 22 of the printable
layer 18 (via the anti-adhesive layer 16). The surface
30 characteristics of the face 22 of the printable layer are
thus defined by the surface characteristics of the face
20 of the plastics film 14.
By way of example, the roughnesses of the films and
papers have been tested using an Altisurf 500 type
35 topography-measuring appliance from the supplier Altimet.
The first tested film had roughness (e.g. Sa) of 1 pm.
That film was used for transferring a printable layer
onto Bristola paper from the supplier Arjowiggins. The
roughness measured on said printable layer was 1.1 pm.
The second film had roughness of 0.5 pm. That film was
used for transferring a printable layer onto another
5 Bristola paper. The roughness measured on said printable
layer was 0.7 pm. The roughness (or surface state) of
the film was thus indeed transferred from the films to
the printable layers. After drying and/or solidification
of the printable layer, the surface characteristics of
10 the face 22 are "frozen" and are not intended to be
modified during other steps of the method, and in
particular while transferring the printable layer 18 onto
a substrate 24, such as a paper, to be lined.
The printable layer 18 may be made of a printable
15 varnish or a resin or a paper coating including a binder
and pigments. In a variant, the printable layer may
comprise two or more sublayers that are selected from a
printable varnish and a paper coating. When the
printable layer comprises two sublayers, i.e. a printable
20 varnish and a paper coating, the printable varnish is
situated over or under the paper layer, such that the
above-mentioned bottom face 22 of the printable layer is
defined by the printable varnish or by the paper coating.
Step b) of the method consists in depositing a layer
25 or film of adhesive 26 on the top face 28 of the
printable layer 18 or on the bottom face 30 for lining of
the substrate 24, or indeed on both of the faces 28 and
30, and then in applying these faces 28 and 30 against
each other in order to laminate the multilayer structure
30 12 and the substrate 24, and thus form a laminated
product 32.
Step c) of the method consists in withdrawing the
plastics film 14 and the anti-adhesive layer 16 from the
printable layer 18 so that only the layer 18 (and the
35 adhesive 26) remains on the substrate 24.
Steps b) and c) may be performed simultaneously or
one after the other. If performed one after the other,
the adhesive 26 is advantageously in the dry and/or
solidified state when the plastics film 14 is withdrawn.
At the end of step c), the face 22 of the printable
layer 18 is exposed, this face being smooth or ultrasmooth.
Nevertheless, a portion of the anti-adhesive layer
16 may remain on the face 22 of the printable layer 18
after the plastics film has been withdrawn.
The layer 18 is suitable for printing using any
suitable technique, the ink being deposited on the smooth
or ultra-smooth face 22 of the sheet 10.
In a variant, the substrate 24 may be made of a
coated or precoated paper, i.e. a paper with one of its
faces having deposited thereon a coating or precoating 33
that comprises one or more thermoplastic polymers or a
mixture of pigments and binder. This coating or
precoating 33 is for depositing on the above-mentioned
face 30 of the substrate, and it is advantageously
smoothed by calendering. It is for being bonded
subsequently on the face 28 of the printable layer 18.
Figure 2 shows a variant implementation of the
method of the invention that differs from the method
described above with reference to Figure 1 in particular
in that the multilayer structure 12' also includes an
additional layer 34 deposited on the top face 28 of the
printable layer 18.
A plurality of superposed additional layers 34 may
be deposited (simultaneously or successively) on the face
28 of the printable layer 18. Each of the additional
layers 34 may be printable or non-printable.
During step b), the bottom face 30 of the substrate
24 or the free top face 36 of the additional layer 34
(the layer farthest from the plastics film, when the
structure 12' has a plurality of additional layers) is
covered in adhesive 26. In a variant both of these faces
30 and 36 are covered in adhesive 26.
During step c), the multilayer structure 12' and the
substrate 24 are laminated so as to form a lined or
laminated product 32', and then the plastics film 14 and
the anti-adhesive layer are withdrawn, so as to expose
5 the smooth or ultra-smooth face 22 of the printable layer
18 of the sheet 10'.
As in Figure 1, the sheet of Figure 2 may include a
previously precoated substrate 24 on its face 30 in order
to increase its smoothness. The precoating 33 is of the
10 same type as that described with reference to Figure 1.
Figures 3 and 4 are diagrams showing means
implemented during the transfer step c) of the method of
the invention.
A first roller 40 serves to drive a continuous strip
15 of the multilayer structure 12 (made up of a plastics
film 14, an anti-adhesive layer 16, and a printable layer
18 - optionally together with one or more additional
layers 34). A second roller 42 that is parallel and
adjacent to the first roller 40 serves to drive a
20 continuous strip of the substrate 24.
The rollers 40 and 42 rotate in opposite directions
and they are spaced apart by a short distance so that the
multilayer structure 12 and the substrate 24 are forced
to pass between the rollers while being subjected to a
25 given level of pressure one against the other in order to
laminate them.
The adhesive 26 may be deposited on the multilayer
structure 12 and/or on the substrate 24, as mentioned
above, prior to this laminating step, or during this
30 laminating step. If the adhesive 26 is applied during
the laminating step, it may be injected between the
structure 12 and the substrate before they pass between
the rollers, as represented diagrammatically by the broad
arrow in Figure 3.
35 A third roller 44 drives the sheet 10 formed by the
substrate 24 and the printable layer 18 in one direction,
while the plastics film 14 and the anti-adhesive layer 16
are driven in another direction in order to separate them
from the sheet 10.
Figures 5 and 6 are images obtained by a scanning
electron microscope (SEB) showing respectively a face of
5 a base substrate or paper 24 and a smooth or ultra-smooth
face of a sheet 10 as fabricated by the method of the
invention.
The base paper (Figure 5) in this example is made of
mutually mixed cellulose fibers that define a rough face.
10 The roughness Sz of this face is about 19.7 pm, which
means that the maximum surface height from the highest
point to the deepest value is equal to 19.7 pm.
The sheet of the invention (Figure 6) has a smooth
or ultra-smooth face defined by its printable layer which
15 has roughness Sz of the order of 1.01 pm, with this being
comparable to that of a prior art paper covered in a
plastics film, having roughness Sz of the order of
1.5 pm.
This roughness value of 1.01 pm for the sheet of the
20 invention is given by way of indication and illustrates a
particular example of an embodiment of the invention.
Other examples illustrating the present invention
are described below.
25 Example 1: preparing an offset-printable smooth or ultrasmooth
sheet
A smooth or ultra-smooth sheet of the invention for
offset printing was prepared from a printable layer A
having the following composition:
The printable layer A had a final concentration of
50% by weight and a viscosity of 100 centipoise (cps)
measured with the help of a BrookfieldB viscosimeter.
5 The layer A was applied on one face of a PET
plastics film that had previously been covered in an
anti-adhesive layer based on chromic chloride stearate.
The layer A was deposited on the film at about 10 g/m2.
The layer A was then dried in an oven at 70°C. This
10 produced a multilayer structure constituted by a PET
plastics film, an anti-adhesive layer of chromic chloride
stearate, and the printable layer A.
The free face of the layer A, i.e. the face situated
on its side opposite from the plastics film, was pasted
15 with a Super-LokB 364 adhesive from the supplier National
Starch. The adhesive was deposited at 3 g/m2 on the layer
A. The pasted face of the layer A was applied against a
substrate formed by a 335 g/m2 Bristola paper fabricated
by the supplier Arjowiggins, and then the assembly was
20 dried in an oven at 70"~. Step b) of the method was then
terminated.
Thereafter plastics film and the anti-adhesive layer
were withdrawn (during step c)) so as to leave only the
printable layer A and the adhesive on the paper
25 substrate.
Composition of layer A
Pigments
Binder
Dispersant
Rheological modifier
Spreading agent
Calcium carbonate
HydrocanSB 60 OG (Omya)
Aqueous dispersion of n-butyl acrylateacrylonitrile-
styrene copolymer
AcronalB S504 (BASF)
Sulfoccinic acid - isooctyl ester, sodium salt
AgniqueB EHS 75E (Cognis)
Aqueous dispersion of acrylic copolymer
SterocollB FD (BASF)
Non-ionic surfactant
SurfynolB 420 (Safic-Alcan)
12489
3009
39
0.6g
0.29
The prepared sheet was suitable for offset printing.
It was not suitable for thermal transfer printing. This
was confirmed by a printing test performed on the sheet
obtained in Example 1 using a Canon Selphy CP800 thermal
5 transfer printer. Yellow, cyan, and magenta were
transferred poorly, and black was not transferred at all.
The final image was not acceptable.
Example 2: preparing an offset-printable smooth or ultra-
10 smooth sheet from a featherweight paper or a paper of
relatively large bulk
The printable layer A of Example 2 was prepared and
applied in the same manner and under the same conditions
as those described for Example 1 onto an ~lementa@ bulk
15 featherweight paper from the supplier Arjowiggins. That
paper had initial bulk of 1.4 (cm3/g).
Example 3: preparing an offset-printable smooth or ultrasmooth
sheet from a precoated support paper
20 The printable layer A of Example 3 was prepared and
applied in the same manner and under the same conditions
as those described for Example 1 onto a Maine Gloss@
precoated paper from the supplier Arjowiggins. That
paper had an initial Bekk smoothness of 400 s.
25
Example 4: preparing an offset-printable smooth or ultrasmooth
colored sheet
A smooth or ultra-smooth colored sheet of the
invention was prepared for offset printing from a
30 printable layer B having the following composition:
Composition of the printable layer B
Pigments
Binder
Calcium carbonate
HydrocarbB 60 OG (Omya)
Aqueous dispersion of n-butyl acrylateacrylonitrile-
styrene copolymer
AcronalB S504 (BASF)
12489
3009
The printable layer B had a final concentration of
50% by weight and viscosity of 100 cps, measured with the
help of a Brookfield@ viscosimeter.
5 The layer B was applied onto one face of a PET
plastics film that had previously been covered in an
anti-adhesive layer based on chromic chloride stearate.
The layer B was deposited on the film at about 10 g/m2.
The layer B was then dried in an oven at 70"~. This
10 produced a multilayer structure constituted by the PET
plastics film, an anti-adhesive layer of chromic chloride
stearate, and the printable layer B.
The free face of the layer B, i.e. the face situated
on the side opposite from the plastics film, was pasted
15 with a Super-Lok@ 364 adhesive from the supplier National
Starch. The adhesive was deposited at 3 g/m2 on the layer
B. The pasted face of the layer B was applied against a
substrate constituted by a 335 g/m2 BristolB paper
fabricated by the supplier Arjowiggins, and then the
20 assembly was dried in an oven at 70"~.
The plastics film and the anti-adhesive layer were
subsequently withdrawn so as to leave only the printable
layer B and the adhesive on the paper substrate.
The resulting paper had very uniform coloring.
25
Example 5: preparing an offset-printable smooth or ultrasmooth
sheet having low surface resistivity
A smooth or ultra-smooth sheet of the invention
having low surface resistivity and for offset printing
Dispersant
Rheological modifier
Spreading agent
Dye
Sulfoccinic acid - isooctyl ester, sodium salt
Agnique@ EHS 75E (Cognis)
Aqueous dispersion of acrylic copolymer
Sterocoll@ FD (BASF)
Non-ionic surfactant
Surfynol@ 420 (Safic-Alcan)
Bleu Levacell@ B liq (Bayer)
39
0.6g
0.29
0.1 g
was prepared from a printable layer C having the
following composition:
Composition of the printable layer C
Pigments
I acrylonitrile-styrene copolymer
Calcium carbonate
Binder
HydrocarbB 60 OG (Omya)
Aqueous dispersion of n-butyl acrylate-
Dispersant
I Clevios@ P (H. C. Starck)
Acronal@ S504 (BASF)
Sulfoccinic acid - isooctyl ester, sodium salt
Conductive additive
I
Rheological modifier I Aqueous dispersion of acrylic copolymer
AgniqueB EHS 75E (Cognis)
Aqueous dispersion of a conductive polymer
I Surfynol@ 420 (Safic-Alcan)
I
The printable layer C had a final concentration of
50% by weight and viscosity of 100 cps, as measured with
the help of a Brookfield@ viscosimeter.
The layer C was applied onto one face of a PET
plastics film that had previously been covered in an
10 anti-adhesive layer based on chromic chloride stearate.
The layer C was deposited on the film at about 10 g/m2.
The layer C was then dried in an oven at 70"~. A
multilayer structure was thus obtained constituted by the
PET plastics film, an anti-adhesive layer of chromic
15 chloride stearate, and the printable layer C.
The free face of the layer C, i.e. the face situated
on its side opposite from the plastics film, was pasted
with a Super-LokB 364 adhesive from the supplier National
Starch. The adhesive was deposited at 3 g/m2 on the layer
20 C. The pasted face of the layer C was applied against a
substrate constituted by 335 g/m2 Bristola paper
fabricated by the supplier Arjowiggins, and then the
assembly was dried in an oven at 70"~.
Spreading agent Non-ionic surfactant
The plastics film and the anti-adhesive layer were
subsequently withdrawn in order to leave only the
printable layer C and the adhesive on the paper
substrate.
5 The resistivity of the paper as obtained in that way
was relatively low, being of the order of 3x10'. This
resistivity is less than that of the paper of Example A
which was of the order of 1 ~ 1 a0pp~ro~xi mately.
10 Example 6: preparing a smooth or ultra-smooth sheet for
ink jet printing
A smooth or ultra-smooth sheet of the invention for
ink jet printing was prepared from a printable layer D
having the following composition:
15
The printable layer D had a final concentration of
14% by weight and viscosity of 50 cps, as measured with
the help of a Brookfield@ viscosimeter.
20 The layer D was applied onto one face of a PET
plastics film that had previously been covered in an
anti-adhesive layer based on chromic chloride stearate.
The layer D was deposited on the film at about 15 g/m2.
The layer D was then dried in an oven at 70°C. A
25 multilayer structure was then obtained constituted by the
PET plastics film, an anti-adhesive layer of chromic
chloride stearate, and the printable layer D.
The free face of the layer D, i.e. the face situated
on the side opposite from the plastics film, was pasted
30 with a Super-Lok@ 364 adhesive from the supplier National
Compounds
Pigments
Binder
Spreading agent
Alumina
Disperal HPl4-2 (Sasol)
Polyvinyl alcohol
Mo wiol4 7-88 (Seppic)
Non-ionic surfactant
Surfynol@ C T2 1 1 (Safic-Alcan)
1000g
1 009
1 g
Starch. The adhesive was deposited at 3 g/m2 on the layer
D. The pasted face of the layer D was applied against a
substrate formed by 335 g/m2 BristolB paper fabricated by
the supplier Arjowiggins, and then the assembly was dried
in an oven at 70'~.
The plastics film and the anti-adhesive layer were
then withdrawn in order to leave only the printable layer
D and the adhesive on the paper substrate.
Results: the various sheets prepared in Examples 1
to 6 were analyzed and the following parameters of each
sheet were measured: grammage, thickness, bulk,
smoothness, gloss, resistivity, and printability.
The measurements were performed as follows:
grammage was measured using the IS0 536 (1976)
standard, by means of Sartorius@ scales having a maximum
weight of 2220 grams (g) and with a precision of 0.1 g;
the thickness was measured using the IS0 534
(1988) standard by means of an MTS MI20 micrometer;
the bulk (or volume per unit weight) was measured
using the NFQ 03-017 standard;
the Bekk smoothness was measured using the IS0
5627 (1984) standard by means of a BuchelB 131 ED
appliance;
the gloss was measured at 75' using the TAPPIB
T480 om-92 method by means of a Byk-GardnerB micro-gloss
75" model 4553 appliance;
the surface resistivity was measured using the
ASTM D257-83 method by means of a Philips PM2525
Multimeter appliance;
the offset printability was evaluated by a
porometric ink absorption test using a CTP No. 9 method;
the "porometric ink" test serves to put a figure on the
absorption capacity of a paper and on the penetration
speed of the ink into the paper; it is based on
depositing a special ink, formulated using a black dye,
on the paper and on studying how it behaves over time;
and
the ink jet printing tests were performed with
Epson 2400 and Canon ip 8500 ink jet printers.
The table below summarizes all of the measurements
and analyses performed on the sheets of Examples 1 to 6.
I Porometric ink 1 15 s
I I I I I I I I I
x x x I V 0.36 1 V 0.33 1 V0.34 1 C 0.95 1 V 0.37 1 x
Grammage (g/m2)
Thickness (pm)
Bulk (cm3/g)
Bekk smoothness (s)
Gloss (at 75", in %)
Surface resisitivity
Maine Gloss@
paper
Support Examples
I contact time) 1 120 s
I I I x x x I V0.38 1 V0.32 1 V0.35 1 C1.04 1 V0.46 1 x
270
250
0.92593
60
x
x
tests (optical
density as a
function of
(x: parameters not measured)
Bristole
paper
Example 1 :
Layer A on
Bristol@
ElementaG3
bulk paper
Example 5:
Layer C on
BristolO
100
140
1.4
20
x
x
30 s
60 s
Example 6:
Layer D on
BristolB
Example 2
Layer A
Elementae
250
220
0.88
400
x
x
x
x
Example 3:
Layer A
Maine
Example 4:
Layer B on
Bristol@
304
273
0.9
7705
85.1
9.72x109
x
x
bulk
130
173
1.33
5035
86.3
x
x
x
Gloss@
290
240
0.83
9436
87
x
V 0.37
V 0.37
396
31 0
0.78
9532
85.9
2.47~10'~
V 0.30
V 0.31
31 1
314
1 .O1
6036
86.6
3.48~10'
V 0.33
V 0.34
294
334
1.14
996
85.4
x
C 1.22
C 1.06
V 0.41
V 0.40
x
X
The transfer of a printable layer (A to D) onto a
support increases the grammage and the thickness of the
support. The increase in grammage is about 30 g/m2 to
40 g/m2 for layer A, 126 g/m2 for layer B, 41 g/m2 for
5 layer C, and 24 g/m2 for layer D. The increase in
thickness is about 20 pm to 33 pm for layer A, 60 pm for
layer B, 64 pm for layer C, and 84 pm for layer D. The
increase in the grammage and the thickness of the support
is due essentially to the addition of adhesive and to the
10 transfer of the printable layer onto the support.
A paper is said to have relatively large bulk when
the value of its bulk is greater than or equal to
1.10 cm3/g. In the examples above, only the ElementaQ
bulk paper had large bulk (1.4 cm3/g) .
15 Depositing the printable layer A on a support
reduces its bulk. When the support initially had large
bulk, as with ElementaB bulk in Example 2, the transfer
of the layer A onto the support gave rise to a small
reduction in its bulk (about 5%). The bulk of the
20 ElementaQ bulk support having the layer A nevertheless
remained very large (1.33 cm3/g, i.e. greater than
1.10 cm3/g) .
Depositing the printable layer B on a support
reduced its bulk, whereas depositing the printable layer
25 C on a support had little influence on its bulk.
Depositing the printable D on a support increased its
bulk since the printable layer is an ink jet layer that
is very porous and thus of low density.
The BristolQ and ElementaQ bulk papers initially had
30 relatively poor smoothness, less than 100 s. By virtue
of its precoating based on calcium carbonate and styrene
butadiene latex, the precoated Maine Gloss@ layer
initially had relatively good smoothness of 400 s.
The transfer of a printable layer onto a support by
35 means of the method of the invention serves to confer a
smooth or ultra-smooth face to the support, as explained
above.
The transfer of the printable layer A onto a paper
support enables its smoothness to be increased
considerably. It should be observed that the printable
layer A enables a paper of large bulk to have very great
5 smoothness (5035 s in Example 2) imparted thereto. The
method of the invention thus makes it possible to provide
paper that presents both bulk and smoothness that are
large.
It should also be observed that the greater the
10 initial smoothness of the support, the greater the
smoothness of the support onto which the layer A is
transferred. The layer A transferred onto a Maine Gloss@
paper enables that paper to be given very great
smoothness of 9436 s.
15 Transferring the layer D onto a BristolB support
enables its smoothness to be increased to about 1000 s.
The sheets prepared in Examples 1 to 6 all presented
high gloss, greater than 80%. The method thus makes it
possible to prepare sheets presenting both smoothness and
20 gloss that are considerable.
The presence of a conductive additive in the layer C
serves to reduce the surface resistivity of the sheet
considerably. The sheet of Example 5 had surface
resistivity that was less than that of the sheets of
25 Examples 1 to 4 by a factor of about 1000. The additive
serves to increase the electrical conductivity of the
sheets, and thus makes it possible to envisage making
electrically conductive sheets.
Concerning the offset printability of the sheets
30 prepared in Examples 1 to 5, the test with porometric
inks shows that the papers had relatively satisfactory
optical density values after inking, even if density did
not increase over time, thus showing that absorption was
limited.
35 Concerning paper suitable for ink jet printing, as
prepared in Example 6, the tests performed on Epson and
Canon ink jet printers show results that are acceptable
in spite of low deposition.
Example 7: preparing a smooth or ultra-smooth printable
5 sheet including a printable resin or varnish
A smooth or ultra-smooth sheet of the invention was
prepared from a printable layer formed by an acrylic
printable resin or varnish E having the fowling
composition. The sheet was suitable for offset printing.
10
The printable varnish E had a final concentration of
50% by weight and viscosity of 50 cps, as measured with
the help of a BrookfieldB viscosimeter.
15 The varnish E was applied onto one face of a PET
plastics film that had previously been covered in an
anti-adhesive layer based on chromic chloride stearate.
The varnish was deposited on the film at about 5 g/m2.
The varnish was then dried in an oven at 70"~. A
20 multilayer structure was then obtained constituted by the
PET plastics film, an anti-adhesive layer of chromic
chloride stearate, and the acrylic varnish.
The free face of the varnish was pasted with a
Super-LokB 364 adhesive from the supplier National
25 Starch. The adhesive was deposited at 3 g/m2 onto the
varnish. The pasted face of the varnish was applied
Composition of printable varnish E
Binder
Dispersant
Rheological modifier
Spreading agent
Aqueous dispersion of n-butyl acrylateacrylonitrile-
styrene copolymer
AcronalB S305D (BASF)
Sulfoccinic acid - isooctyl ester, sodium salt
AgniqueB EHS 75E (Cognis)
Aqueous dispersion of acrylic copolymer
SterocollB FD (BA SF)
Non-ionic surfactant
SurfynolB 420 (Safic-Alcan)
3009
39
0.6g
0.29
against a substrate constituted by 335 g/m2 Bristola
paper fabricated by the supplier Arjowiggins, and then
the assembly was dried in an oven at 70°C. The plastics
film and the anti-adhesive layer were then withdrawn
5 (during step c)) in order to leave only the printable
varnish and the adhesive on the paper substrate.
The table below summarizes the measurements and
analyzes performed on the sheet prepared in Example 7.
Transferring the printable varnish E onto the
support produced little modification to the grammage,
thickness, and bulk of the support. The transfer enabled
15 a sheet to be prepared having smoothness (>10,000 s) and
gloss (99%) that are very high. Nevertheless, the
printability of the sheet was not as good as the
printabilities of the sheets prepared in Examples 1 to 6
because of the absence of pigments in the printable
20 layer.
Support
Grarnrnage (g/rn2)
Thickness (prn)
Bulk (crn3/g)
Bekk smoothness (s)
Gloss (at 75", in %)
Example 8: preparing smooth or ultra-smooth printable
sheets that are suitable for offset printing, indigo
Example 7:
Printable varnish E on Bristolo
280
260
0.93
> 10,000
99
printing, or printing using electrically conductive inks
25 .
In this example, each prepared sheet comprised two
printable layers AA, AB, or AC, a first layer (A, B, or
C) deposited (by kiss coating) on the anti-adhesive layer
of the multilayer structure, and a second layer (A)
deposited (by kiss coating) on the first layer. The
first layer, i.e. the layer closer to the plastics film
in the multilayer structure was the layer for directly
5 receiving inks during printing. It is the layer that
defines the printability depending on the printing
method. The second layer was a precoating providing the
first layer with good adhesion on the support and forming
a barrier against the adhesive (to prevent the adhesive
10 penetrating into the printable first layer).
The plastics film used was a PET film having a
thickness of 12 pm. The printable layers for preparing
an offset printable sheet were a first layer B and a
second layer A. The printable layers for preparing a
15 sheet suitable for HP indigo printing were a first layer
C and a second layer A. The printable layers for
preparing a sheet printable by electrically conductive
inks (printed electronics) were a first layer A and a
second layer A. The multilayer structures that were
20 prepared were of the type comprising: PET/anti-adhesive
layer/A&A or C&A or B&A layers. The layers A, B, and C
were deposited at 6 g/m2.
The compositions of those layers are set out in
detail in the following tables.
Composition of printable layer A
Pigments
Binder 1
Binder 2
Dispersant
Rheological modifier
Spreading agent
Composition of printable layer B
Pigments
Binder 1
Binder 2
Dispersant
Rheological modifier
Spreading agent
Calcium carbonate
Carbitala 95 (Imerys)
Aqueous dispersion of styrene-butadiene
copolymer
StyronalB 051 7 (BASF)
Aqueous dispersion of n-butyl acrylateacrylonitrile-
styrene copolymer
AcronalB S305 (BASF)
Sulfoccinic acid - isooctyl ester, sodium salt
AgniqueB EHS 75E (Cognis)
Aqueous dispersion of acrylic copolymer
SterocollB FD (BASF)
Non-ionic surfactant
SurfynolB 420 (Safic-Alcan)
475mL
190mL
94mL
39
0.6g
0.29
Calcium carbonate
CarbitalB 95 (Imerys)
Aqueous dispersion of styrene-butadiene
copolymer
StyronalB 05 1 7 (BA SF)
Aqueous dispersion of n-butyl acrylateacrylonitrile-
styrene copolymer
AcronalB S305 (BASF)
Sulfoccinic acid - isooctyl ester, sodium salt
AgniqueB EHS 75E (Cognis)
Aqueous dispersion of acrylic copolymer
SterocollB FD (BA SF)
Non-ionic surfactant
SurfynolB 420 (Safic-Alcan)
475mL
95mL
47mL
39
0.6g
0.29
Each of the three multilayer structures and 200 g/m2
OpaleB paper from the supplier Arjowiggins were coated in
5 a two-component polyurethane adhesive at 10 g/m2.
The resulting sheets presented good printability
depending on their applications, i.e. for offset
printing, for digital HP indigo printing, and for
conductive inks (printed electronics).

CLAIMS
1. A method of fabricating a printable sheet (10)
presenting at least one smooth face (22), the sheet
comprising a substrate (24), in particular made of paper,
5 having at least one face covered at least in part in a
layer or a plurality of superposed layers, the method
comprising the steps consisting in:
a) preparing or providing a multilayer structure
(12) comprising at least, or constituted by, a plastics
10 film (14), an anti-adhesive layer (16), and a printable
layer (18), the anti-adhesive layer being interposed
between the plastics film and the printable layer;
b) pasting adhesive on a face (30) of the substrate
and/or the face (28) of the multilayer structure situated
15 opposite from the plastics film, and applying said face
of the substrate against said face of the multilayer
structure so as to laminate the multilayer structure and
the substrate; and
c) withdrawing the plastics film from the printable
20 layer, the printable layer (18) defining said smooth face
(22) of the sheet.
2. A method according to claim 1, characterized in that
the printable layer (18) is in the solid state and/or dry
25 in step b) and/or step c).
3. A method according to claim 1 or claim 2,
characterized in that the substrate (24) is selected
from: paper; tracing paper; cardstock; and coated or
30 precoated paper.
4. A method according to claim 3, characterized in that
the paper has bulk greater than or equal to 1.10 cm3/g,
preferably greater than or equal to 1.2 cm3/g, and more
35 preferably greater than or equal to 1.3 cm3/g.
5. A method according to any preceding claim,
characterized in that, prior to step b), the said face of
the substrate is precoated with at least one smoothing
layer including one or more thermoplastic polymers or a
mixture of pigments and at least one binder.
6. A method according to claim 5, characterized in that,
prior to step b), the precoated layer of the substrate is
calendered in order to increase its smoothness.
7. A method according to any preceding claim,
characterized in that the plastics film (14) is a film
selected from films made of: polyethylene terephthalate
(PET); polyethylene (PE); polypropylene (PP); polymer
based on polylactic acid (PLA); or any polymer based on
cellulose.
8. A method according to any preceding claim,
characterized in that the anti-adhesive layer (16) is
based on: silicone (s) ; siloxane (s) ; polysiloxane (s) or
derivatives thereof; Werner complex(es), such as chromic
chloride stearates; or waxes of: polyethylene, propylene,
polyurethane, polyamide, polytetrafluoroethylene, or a
mixture thereof.
9. A method according to any one of claims 1 to 8,
characterized in that the anti-adhesive layer (16) is
withdrawn at least in part from the printable layer (18)
while withdrawing the plastics film (14) in step c).
10. A method according to any preceding claim,
characterized in that the anti-adhesive layer (16)
remains on the printable layer (18) when the plastics
film (14) is withdrawn in step c).
11. A method according to any preceding claim,
characterized in the that the printable layer (18)
comprises a mixture of pigments and at least one
printable varnish or binder, e.g. based on acrylic
polymer, polyurethane, polymethyl methacrylate, styrene
butadiene, vinyl acetate, polyamide, nitrocellulose or
5 any other cellulose, polyvinyl alcohol, starch, or a
mixture thereof.
12. A method according to any preceding claim,
characterized in that the multilayer structure (12')
10 comprises at least one additional layer (34) deposited on
the printable layer (18) on its side opposite from the
plastics film (14), the free face of said additional
layer or of the additional layer farthest from the
plastics film being for pasting and applying against said
15 face of the substrate during step b).
13. A method according to any preceding claim,
characterized in that it comprises an additional step
consisting in printing the sheet (10) with an ink having
20 electrical and/or optical properties.
14. A method according to any preceding claim,
characterized in that the smooth face (22) of the sheet
(10) has Bekk smoothness greater than about 900 sf or
25 greater than about 1000 s, preferably greater than
2000 sf and more preferably greater than 5000 s.
15. A method according to any preceding claim,
characterized in that the smooth face (22) of the sheet
30 (10) has gloss greater than 70% and preferably greater
than 80%.
16. A method according to any preceding claim,
characterized in that the printable layer (18) has a
35 thickness less than or equal to 30 pm, preferably less
than or equal to 15 pm, and more preferably less than or
equal to 10 pm, and/or grammage less than or equal to
30 g/m*, preferably less than or equal to 15 g/m2, and
more preferably less than or equal to 10 g/m2.
17. A method according to any preceding claim,
5 characterized in that it comprises, before step a), a
preliminary step consisting in making indented and/or
projecting patterns on the face of the plastics film that
is to receive the anti-adhesive layer and the printable
layer, e.g. by etching, the printable layer being for
10 fitting closely to the shape of these patterns so as to
include an imprint of the said face of the plastics film.
18. A method according to any preceding claim,
characterized in that the adhesive is deposited at least
15 on one face of the substrate in step b), and in that the
thickness of the deposited layer of adhesive is not less
than half the mean roughness of the face of the
substrate, and is preferably equal to said mean
roughness.
20
19. A printable sheet (10) presenting at least one smooth
face (22), the sheet comprising a substrate (24), in
particular a paper substrate, having at least one face
covered at least in part in a layer or a plurality of
25 superposed layer, including a printable layer (18)
defining said smooth face, the sheet being characterized
in that said smooth face has Bekk smoothness greater than
about 900 s, or greater than 1000 s, preferably greater
than 2000 s, and more preferably greater than 5000 s.
30
20. A printable sheet according to claim 19,
characterized in that its smooth face (22) has gloss
greater than 70%, and preferably greater than 80%.
35 21. A printable sheet according to claim 19 or claim 20,
characterized in that the printable layer (18) has
thickness less than or equal to 30 pm, preferably less
than or equal to 15 pm, and more preferably less than or
equal to 10 m , and/or gramrnage less than or equal to
30 g/m2, preferably less than or equal to 15 g/m2, and
more preferably less than or equal to 10 g/m2.
5
22. The use of a printable sheet according to any one of
claims 19 to 21, for making an electronic and/or optical
component, the sheet being printed by means of an ink
having electrical and/or optical properties.
10
23. The- use of a printable sheet according to any one of
claims 19 to 21, for printing a photographic image, for
making packaging, and/or for a casting application.