Note: Descriptions are shown in the official language in which they were submitted.
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~his invention relates to a method of making metallized
paper webs and more particularly to making metallized paper
webs having a smooth and therefore specularly reflective
surface.
Paper webs have surfaces which are matt so that when
1 5 they are metallized by vacuum (vapour) deposition the metal-
j lized surface has a matt ash-coloured surface and lacks
¦ metallic lustre. To obtain a shiny finish a relatively
¦ thick coat of a synthetic resin is applied to the paper and
¦ is solidified on the paper. In order to obtain a suitably
reflective surface for metallizing, it may be necessary to
apply two or more coats of synthetic resin. If a very thin
J film of a resinous coating agent is applied by a conventional
¦ coating technique, the coating acquires a surface corres-
¦- ponding to the surface of the underlying paper substrate.
When a relatively thick coating of resin is applied the
coated paper tends to curl and also becomes difficult to fold.
The present invention provide~ a method of overcoming these
difficulties.
¦ ~he present invention accordingly provides a method
of making a metallized paper web characterised i~ that the
process comprises the steps of:
depositing a film of a synthetic resin coating agent in
a flowable condition onto a continuously running band
having a release surface;
continuously feeding a web of paper towards the said
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release surface so as to enga~e therewith;
pressing the paper web against the release surface
coated wiuh the coating agent whereby the paper is coated
with a coherent layer of coating agent having a surface
determined by the contour of the release surface;
¦ 5 releasing the release surface fr~m the paper web and
the coherent layer of coating agent adherent thereto; and
subsequently metallizing the coated paper web.
The principal distinction between the products of the
¦ prior art and those of the present invention is that,
¦ 10 whereas in the prior art the configuration of the metallized
¦ surface ls determined primarily by the surface of the paper
web substrate, in the present in-~ention the configuration of
the metallized surface is determined primarily by the
contour or surface condition of the release surface and not
by that of the paper web substrate.
Preferably the release surface is specularly smooth by
which we mean that the surface is mirror-like where the
underlying material is itself reflective e.g. stainless
steel or is similarly smooth where the material is itself
non-reflective e.g. plastics films. If desired the surface
may be engraved e.g. with a decorative pattern or identi-
fying symbols or words. Where the release surface is
engraved it is still preferred that at least the remainder
of the surface be specularly smooth, i.e. the une~graved
areas.
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Use of an engraved and specularly smooth release surface
gives a metalli~ed product with an embossed but still
mirror-like finish. The engraved areas may be specularly
smooth or matt. In the latter case it increases the
contrast of the embossed areas.
The synthetic resin coating agent can be either thermo-
plastic or thermosetting. The agent can be deposited onto
the transfer surface in solution either in water or a non-
aqueous e.g. organic solvent, as an emulsion or plastisol
or in the liquid form e.g. as with hot-melt coatings. Where
a hot-melt coating is employed it may be applied in powder
form and melted in situ on the release surface. The amount ~ -
of coating agent used in the present invention is typically -
from 1 to 15 grams per square metre of paper web substrate.
This is, very approximately equivalent to a coating having
an average thickness of from l,u to 15,u which is much less
than is necessary for a self supporting film especially of
"as cast" synthetic resin materials. If less than 1 g/m ;~
of coating agent is used the eventual metallized surface may
be more like the surface of the paper web substrate than
that of the release surface. Preferably the coating weight
is in the range 3-5g/m2. Use of more than 5 g/m2 does not
generally bring any substantial further improvement and, as is
mentioned above, with large amounts of coating agent such as
25g/m2 or above the product loses its paper properties and ~
becomes more difficult to handle. ;
In applying the coating agent to the paper it is
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; important to ensure that the coating agent is set, solid-
ified or cured sufficiently by the time it is released from
the release surface to ensure that the coating retains the
surface characteristics of the release surface. Where the
coating agent is used in the form of a solution or emulsion
it is ad~antageous if at least a part of the solvent or
continuous phase is removed e.g. by evaporation before the
film of coating agent and paper web are brought together.
I This reduces possible problems of the paper absorbing fluid
¦ and allows the coating agent to form at least a partially
coherent film having a surface complimentary to that of the
release surface before coming into contact with the paper
web. In any event by the time the film of coating agent,
adhering to the paper, is removed from the release surface
the coating agent must be in the form of a coherent and
¦ 15 substantially non-flowable film. This generally means that
, the coating agent is,by that time, solid. With hot melt
¦ coating agents this can be achieYed by cooling the film of
agent in contact with the paper, if necessary having previ-
ously thermally activated the hot melt coating agent. With
coating agents in solution or emulsion form it will be
necessary to remove the solvent or emulsion continuous phase
if this has not been completed before bringing the paper web
and film of coating agent together. This can conveniently
be done by heating e.g. by passing the paper web in contact
with the film of coating agent on the release surface
between a set of heated rolls. Subsequently the paper web
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and coatlng a~gent are cooled to ensure satisfactory coherence
of the coating agent.
The invention will be described further with reference
. ~ to the accompanying drawings in which:
d ~ r~
Figure 1 illustrates, ir a dia~'rammio way, a process
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according to an embodiment of the invention;
Fig. 2 is a diagramatical view illustrating a process
of a further embodiment of the invention;
Figs. 3 and 4 are enlarged diagramatical views showing
the main parts of the above embodiments;
Fig. 5 is a diagramatical view showing a process of a still
further embodiment of the invention;
Fig. 6 is a lO0 x enlarged photograph showing an
untreated paper surface;
Fig. 7 is a photograph in the same magnification, showing
a paper surface treated by a conventional coating method; and
Fig. 8 is a photograph in the same magnification, showing
a paper surface treated by the process of the invention.
Throughout the drawings, similar steps~ parts and elements
are shown by similar reference numerals and letters.
Referring now to Figs. 1, 3 and 4, the numeral 1 designates
a coating station including a bath 2 containing a synthetic
resin coating agent A, and rolls 3 and 4 for applying the
coating agent to an endless belt 5. The method of coating the
agent A on the endless belt 5 may be any known one, for example,
rotogravure coating, roll coating or hot-melt coating. The
coating agent A is either thermo-plastic or thermo-setting
synthetic resin, which may be water-soluble, solvent-soluble
or emulsive.
Said endless belt 5 has an outer surface easily releasable
from the coating agent A when the latter
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thin resilient steel such as stainless steel strip which is
given a mirror-like finish known in the art as "super-~inish".
Alternatively, the belt can be a plastics strip having a
suitably smooth sur~ace e.g. polyolefine sand polyesters such
as terephthalate esters. The release properties of the surf-
! 5 ace can be improved by coating the sur~ace with a smooth layer
of a substance having particularly good release properties
such as fluorinated polymeric hydrocarbonsespecially poly-
tetrafluoroethylene e.g. Teflon (Trade Mark) and silicones.
Where the release surface is a plastics material it can be
ln supported or reinforced by, for example, glass fibre cloth.
¦ The endless belt 5 may be engraved with a predetermined
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pattern in its outer surface. However, the cm~oosc~ surface
should be finished microscopically smooth.
Said endless belt 5 is supported and t:cavelled by means
¦ 15 of roll~ 6,7 and 8 and a cooling roll 9.
The numeral 10 is a paper web, the uncoiled extension of
which is adapted to pass, while being pressed against the
outer surface of the endless belt 5, through a heating roll
11 and a cooling roll 12 which are opposed to the rolls 8
and 9 respectively. The numeral 13 designates a treated web
being coiled. The numerals 14 and 15 illustrate a drying
zone and cooling zone respectively,
In operation, at the coating station 1 the coating agent
A is applied to the outer smooth surface of the endless belt
5' which then travels along the drying zone 14 to dry the
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coating agent. The paper web 10~ which is uncoiled and fed
towards the rolls 8 and 11, is engaged and pressed against
the outer surface of the endless belt 5 between the roll 8
and heating roll 11~ whereby the paper web is adhered to
the coating agent A on the outer surface of the endless belt
5.
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Thereafter the endless belt 5 together with the paper web
passes through the coolingjzone 15 to solidify the coating
agent A, which is now securely lamina~ed as a synthetic resin
film on the paper web, which is then parted from the endless
belt 5 at the opposed cooling rolls 9 and 12 thereby causing
said synthetic resin film on the paper web to release from the
outer surface of the endless belt 5, as seen from Figs. 3 ~nd
4. This release can be smoothly performed without iri~ing
the synthetic resin film (coating agent) since the outer sur-
face of the endless belt 5 has a property easily releasable
from a synthetic resin (coating agent) film which ~ras pressed
and securely engagcd with the surface of the paper web by
means of the rolls 8 and 11. In case that the coating agen-t
is thermo-setting it is cured at the heating roll 11.
In the above operation, if the surface of the endless
belt 5 is flat, then the synthetic resin film having the same
surface is formed on the paper web, while if the surface cf
the endless belt 5 has an embossed pattern, the synthetic resin
film having the complementary pattern is laminated on the
paper web. In any case the paper web is gi~en a controlled
smooth surface suitable for metallizing Also in the above
operation, if the hot-melt coating is employed at the coating
station 1, a synthetic resin of hot-melt type can be used as
a coating agent. In this case the drying zone 14 is replaced
by a cooling zone. The other steps are the same. In any
~ype of coating agent, it is possible to mix flllers, extender
pigments, color pigments, dyes or like substances.
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As shown by the dot-dash lines in Fig. 1, instead of
the ~ndiess belt 5 may be used a roll of sheet or film B
having a surface condition similar to the endless belt 5 and
having a length sufficient for treating the paper web. The
extension of the sheet B travels through the rolls 6, 7, 8
and 9, and is then coiled at C departing from the paper web.
As will be understood, since the endless be]t 5 or the
sheet B serves as a support for the synthetic resin film
(coating agent), even a very thin film can readily be treated
without tear, and the treatment of the paper web can be per--
formed by a single and continuous process. After the treatment,
the paper web is metallized by vacuum evaporation to present
an excellent metallic luster owing to the smoothness of the
controlled surface of synthetic resin film on the paper, which
was given by the identically controlled surface of the endless
belt 5 or sheet B (see Fig. 8, hereinafter explained).
Fig. 2 shows another embodiment of the invention. In
the figure, the numeral 16 is a laminating station including
opposed pressing rolls 17 and 1~. The numer~ 19 is a heating
roll. Other parts and elements are the same as the previous
embodiment.
In operation, at the coating station 1 the endless belt
5 is coated with the coating agent A. Then at the laminating
station 16 the uncoiled paper web is pressed against the endless
belt 5 the outer surface of which was coated with the coating
agent A, which is thus secured to the paper web. The endless
belt 5 together with the paper web travels towards the roll 7.
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during passing along the drying ~one 14 and the heating roll
19 the coating agent is dried, which is in turn cooled to
solidify during passing through the cooling zone 15. There-
after the paper web with the synthetic resin film (coating
agent) secured thereto is released from the endless belt 5 at
the opposed cooling rolls 9 and 12, and is then coiled at 13.
Various modifications similar to the first embodiment can also
be applied to the present embodiment. The hot-melt coating
may be employed at the coating station 1. Fillers, dyes and
like substances can be mixedin the coating agent A.
Fig. 5 shows a still further embodiment of the invention.
In the figure a cylindrical drum 20is provided with an outer
surface of a property easily releasable from the coating agent
A when solidified. For the purpose the drum 20 is covered
therearound with the synthetic resin material referred to in
the first embodimentj and more particularly, for example, with
Teflon (Trademark). In another example, the outer periphery
of the drum 20 of hard metal is given a mirrorlike finish.
In operation, at the coating statîon 1 the coating
agent A is coated on the outer periphery of said drum 20 being
rotated. The coating agent A on the drum 20 is dried during
passing along a drying zone 21, and thereafter at a pressing
roll 22 the paper fed from the paper web 10 is pressed against
the outer periphery of the drum 20. As the paper adhered on
the drum 20 passes through a cooling zone 23, the coating
agent A is cooled to solidify. The paper with the synthetic
resin film (coating agent) secured thereto is released from
the outer periphery of the dr~m 20 at a roll 24j and is then
coiled at 1~. If required, a heating zone 25 and/or heating
and pressing rolls 26 can be provided so as to improve adhesion
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of the paper against the coat,ing agent. Also a heating zone
27 and/or hqating and pressing rolls 28 can be provided for
`~ the further improvement of the surface of synthetic resin film
on the paper. The paper web thus treated is metallized by
vacuum evaporation.
The following are examples aocording to the prooess of
the first embodiment (Fig. 1).
EXAMPLE 1 '
, Endless belt 5: 0.6mm thick mirrorlike finished stainless
steel plate
Coating agent: vinyl and acrylic resin mixture (ratio 7:3j,
-solid content: 25%
(Dai-Nippon Ink Co., Ltd., Japan article
number AF-400~
Coating weight: lg, 2g, 3g, 4g, 5g per square meter in
the state dri'ed on the paper web~
Condition of drying at 14: hot air, temperature: 150C
Lamination temperature at roll 11:170C
Running speed of endless belt: 30m/min.
The results are as follows:-
Coating weight Lus-ter after metallizing with all~inium
lg ' pretty good but lacking in uniformity
2g - ditto -
3g uniform and good luster
4g - ditto -
g - ditto -
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EXAMPLE 2
Roll of film B: O.Ol?mm thick polyethylene- j
terephthalate film
Coating agent: one component thermo-setting acrylic resin
emulsion,
solid content: 40%
(Hoechst Gosei Co., Ltd., Japan, Trademark:
MOWINYL, article number ~9000)
Coating weight: 3g per square meter, dried on the paper
web
Condition of drying at 14: hot air and infrared heater,
temperature: 150jC
Lamination temperature at roll 11: 150 to 160C
Running speed: 30m/min.
By the above EXAMPLE 2, the metalllzed paper having a good
- luster similar to the EXAMPLE 1 has been obtained.
Fig. 6 shows a surface conditio~ of an untreated paper.
As appears, the surface is very rough. Fi`g. 7 shows a surface
condition in which a synthetic resin coating agent of 5g/m2
(dried) was applied to the paper of Fig. 6 by a conventional
coating method. As seen, the surface is still rough, and when
metallized it presents ash color due to the diffused relfection
of light. On the other hand, Fig. 8 shows a surface condition
of the paper with a synthetic resin film formed by the process
according to the EXAMPLE 1, the coating weight being 3g/m2(dried)
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much less th~n the previous conventional method of Fig. 7.
As appears, the .surface is much improved, and therefore is
suitable for metallizing or printing. By any conventiGnal
method it is impossible to ob-tain a smoo-th surface by such
an extremely thin synthetic resin film layer. According to
the present invention, therefore, the propertie.s of a paper
will be little injured by an applied coating agent. ~lr-ther-
more the present invention makes it possible to obtain a con-
trolled surface of a paper by a single continuous process
thereby improving the productivity.
The process of the invention can be applied to any paper
by using any kind of`synthetic resin as a coating agent. The
only thing to be considered is that the endless belt 5, sheet
B or drum 20 should have a controlled smooth surface having
a better releasability with respect to the coating agent as
compared with the paper web to be filmed by the coating agent.
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