Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Record Carrier for Electro-Erosion Printers, and ~Sethod of
~laking Same
The invention relates to a record carrier for electro-erosion
printers with a base material coated ~ith a lacquer layer
containing pigments, and covered by a thin metal layer con-
sisting oE aluminum or containing aluminum as main component,
and a method of making such a record carrier.
Record carriers of this type have been known for quite some
time. In the production of record carriers that are vapor-
0 deposited with aluminum, or coated therewith it is necessaryfor various reasons, especially in view of the necessary
dullness, the copying charac-teristics after prlnting, and
the correct burnishing during printing that the surface shows
a certain roughness. This is obtained in that to the lacquer
layer beneath the aluminum layer fillers are admixed which more
or less protrude from the surface. The dullness increases
with the amount of admixed fillers since -the light diffusion
increases through the closely packed arrangement of -the
pigment bodies, i.e. the density of peaks per surface unit.
However, there also increases the sensitivity to abrasion
and scratching traces as during printing the electrodes merely
slide over the peaks of the pigment grains, and tear the
aluminum layer there. ~ith an increasing filler proportion,
the sharpness of the protruding pigment grain contours
increases, too, since the grains have scarcely any surrounding
lacuqer let. Furthermore, highly filled lacquers are always
less stable and therefore show a chalking tendency.
There exist various methods of reducing the abrasion and
scratching traces by means of the lacquer composition selected
a) Low pigment-content, high-gloss lacquers with soft pigments
as e.g. carbon black or CaCO3 are used. Such record carriers
have a high degree of brightness of 40 ~ to 50 %. As a cali-
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brating standard a planar, polished hlack glass plate is usedhaving a degree oE brightness of 100%~ With a degree of
brightness of 40~, the copying characteristics are still
rather poor. On the other hand, the electrode abrasion is
low. The characteristics wit~l respect to abrasion or scratching
traces, however, can substantially be improved in that a
gliding layer on the basis of a metallic soap in accordance
with a metallic soap, such as that of applicant's German
patent application serial no. P30 32 2237, is used, to which
10 10 to 30~ by weight of a multi-functional, aliphatic,
saturated or unsaturated alcohol are admixed. A thus modified
metallic soap is preferably applied to the aluminum layer
surface by rubbing on, rubbing in, and polishing.
b) Very hard fillers (e.g. quartz powder) are used which
cannot be destroyed by the print electrodes. The lacquers
are highly filled, too, with the filler ha~ing merely to be
firmly embedded in the lacquer to avoid chalking. These
lacquers have a very low degree of brightness of up to 10%
and have thus very positive copying characteristics. They
can also show an extremely low amount of abrasion traces
- since the electrodes slide only on the peaks of the pigment
grains but cannot destroy them. The only but rather important
disadvantage of such a pigmenting is the extremely high
electrode abrasion.
Here, too, the abrasion traces can be reduced by using metal-
lic soaps, or a modified metallic soap in accordance with
`~ the above mentioned German patent application.
In all cases, however, a maximum adhesion of the aluminum
layér over the entire surface is an essential condition for
a low amount of abrasion or scratching traces.
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Highly-filled lacquers with few abrasion traces are to
contain hard pigments since with soft pigments there is a
too high surface damage which in turn causes strong abrasion
traces.
The quality of the polymer used for the lacquer is of course
very important, too, but even the hardest and toughest
polymer, with a high filling with soft pigments will always
show quite strong abrasion traces. This is due to the sharp
surface contours of the prctruding pigments, and to the
destruction of the pigments by the electrodes, as well as to
the high surface pressure by the electrodes caused by the
form of the pigments.
Quite generally it can be said that highly filled lacquers
practically show an angular or acicular waviness of the
surface, and that thus the necessary dullness or the
necessary degree of brightness are easily achieved. For
high copying characteristics, degrees of brightness of 20~
to 25% are required. Experience has shown that a degree of
brightness of less than 20~ involves a too high greying of
the aluminum layer which can be explained by the increased
light absorption at the sharp edges. With a degree of
brightness of 10% to 12% the paper is visibly grey.
With low pigment content-lacquers the situation is
different, i.e. the electrode slides only over a few pigment
grains which furthermore are coated with a rather khick
lacquer layer and thus protected. The surface pressure of
the electrodes is high, too, but the contours of the
protruding pigments are of a soft waviness. So the polymer
is exposed to very high strain at the few points of contact.
Since this waviness is of a very low frequency the dullness
is low, too.
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So the hitherto available lacquers do not permit a perfeet
solution for ~he problem of abrasion traees, even when speei-
fieally modified metallic soaps are used.
The object of the invention can thus be defined as follows.
~ surface of the lacquer layer and consequently of its cover-
ing and very thin aluminum layer is to be provided, with the
following properties:
1. a high frequency of the waviness,
2. a soft waviness,
3. a high mechanic strength and toughness through thick
laequer layers on the pigment grains,
4. a high dullness,
5. a low greying,
6. a low electrode abrasion, and
' 15 7. a homogeneous adhesion of the aluminum layer to the
laequer layer.
Preferably, the following characteristics are to be achieved,
e.g.
8. a low surface pressure of the electrodes, and
9. a low strain on the lacquer layer.
These demands which had formerly been considered contradietory
can, however, be aehieved by a record carxier of the above
mentioned type as composed in accordance with the invention,
in that the roughness of the metal layer surface caused by
the pigmenting of the lacquer layer shows a high frequency,
a low amplitude and a soft, rounded-off waviness praetically
without edges or steps. The arrangement is preferably of
such a design that the laequer layer consists of two super-
imposed layers, that the first layer over the base material
eonsists of a lacquer highly filled with soft pigments, the
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grain size of the pigments being such that the surface shows
a roughness of more than approximately 5 ~m, and that the
second layer consists of a low pigment-content lacquer con-
taining only fine, sof-t pigments with the grain size of less
than 1 um to approximately 2 ,um. On the other hand, it is
also highly advantageous to proceed such that the lacquer laye~
consists of two superimposed layers, that the first layer over
the base material consists of a lacquer highly filled with
soft pigments, the grain size of the pigments being such that
10 the surface shows a roughness of more than approximately 5 ~m,
and that the second layer consists of a lacquer which instead
of the pigments contains a soluble dye. It is of particular
advantage if the first and second lacquer layer are composed
on the basis of the same polymer.
Such a record carrier can be produced in accordance with the
invention in that the first lacquer layer consists of an
~ % to 12 % solution of a highly molecular cellulose acetate
butyrate in ethyl acetate which also contains 15 to 20 %
by weight CaC03 with a granulation of 10 jum to 15 tum, 2 to 3 %
by weight by fine or coarse grain carbon black, and 2 % by
weight plasticizer, and that the second lacquer layer consists
of an 8 % to 12 % solution of a highIy molecular cellulose
acetate butyrate in ethyl acetate which furthermore contains
O to 1 % by weight CaC03 with a granulation of 1 -~m to 2 ~m
maximum, 2 to 3 % by weight fine carbon black with a granu-
lation of 1 ~um to 2 ~m maximum, and 2 % by weight plasticizer,
or that instead of 2 to 3 % by weight of fine-grain carbon
black the second lacquer contains a quantity of an equally
effective soluble dye. Advantageously, a first polymeric
lacquer layer highly filled with pigments is provided on the
base material, said lacquer layer containing only soft pigments
with a grain size of more than 5 ~m, and ther~_ypon another
polymeric lacquer layer is provided which contains either only
fine, soft pigments with a grain size of less than 1 ~m to
approximately 2 ~m, or a soluble dye.
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The invention will now be described in detail with reference
to two embodiments referring to the enclosed drawings.
The drawincJs show the following:
Fig. 1 considerably enlarged a cross-section of a ~eco~d
carrier, and over it a schematical representa-
tion of a recording electrode, this record
carrier containing a highly filled lacquer with
an angular and acicular waviness of the surface
with h~gh frequency, thus realizing the necess-
ary dullness and the necessary degree of
brightness, respectively,
~ig. 2 a considerably enlarged schematical representation
of a record carrier, where the lacquer is of
a low pigment-content only so that the electrod~
of ~lhich only the contours are given slides
over few pigment grains only which are coated
with a thick polymeric layer, and
Fig. 3 a considerably enlarged cross-section of a
record carrier composed in accordance with
0
the inventlon.
~s shown in Fig. 3 which is used to explain the inventive idea,
a first lacquer layer 2 is applied on a base material, as
e.g. paper 1. This lacquer contains only soft pigments which
consequcntly cause a low electrode abrasion only. The grain
size of these pigments is such that on the surface of the
lacquer layer, and consequently on the surface of aluminum
layer 4 covering it there is a roughness, i.e. a distance
betwcen highest peaks and lowest valleys of more than
approximately 5 um. Furthermore~ this lacquer is so highly
filled that it has an extremely low degree of brightness of
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less than 5%~ After a vapor deposition of an aluminum
layer, this lacquer would be of a very grey appearance,
and furthermore there would be considerable chalking. Also
shown are the contours of a writing electrode 5.
Covering the first lacquer layer 2, a second lacquer layer
6 is provided. This lacquer layer 6 contains only fine and
soft pigments 7 with a diameter of less than 1 ~m to approx-
imately 2 ~m. This lacquer layer 6 shows a very low filling.
Although in exceptional cases different polymers can be
used for lacquer layers 2 and 6, provided they are compatible,
the same polymer will mostly be used for both lacquer layers.
Owing to this second lacquer layer 6 a very soft and rounded-
off waviness of high frequency is obtained, superimposed with
a micro-roughness of the ~ine pigments in the second lacquer
layer 6. As shown strictly schematically, pigment grains 7
close to the surface are surrounded with a stable lacquer
layer, i.e. there is no more chalklng.
Below, two embodiments will be given for the necessary
lacquer composition, cellulose acetates monobutyrates being
used as polymer for the lacquer substrate.
Example 1
Lacquer 1: A highly molecul.r cellulose acetate butyrate
(Cellit* BF 900) in an 8~ solution in ethyl acetate is mixed
with 15~ by weight CaCO3 with a granulation of 10 ~m to 15 ~m
as an approximately 20~ fraction. Furthermore, 2% by weight
carbo~ black in fine or coarse granulation, and 2% plasti-
cizer are admixed.
Lacquer 2: For the second lacquer layer, the same highly
molecular cellulose acetate butyrate (Cellit BF 900) is used
in an 8% solution in ethyl acetate with an admixture of 2~ by
weight carbon black with a granulation of maximum 1 ~m to
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* Trade Mark
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2 ~m, or instead with an admixture of a soluble dye without
pigment, and 2% by weight plasticizer.
Example 2
Lacquer 1: A highly molecular cellulose acetate butyrate
(Cellit BL 700) is prepared in a 12% solution in ethyl
acetate, and mixed with 20% by weight CaCO3 with a granulation
of approximately 10 ~m to 15 ~m as an approximately 20%
fraction. Furthermore, 3~ by weight carbon black in fine
or coarse granulation and 2% by weight plasticizer are
added.
Lacquer 2: Highly molecular cellulose acetate butyrate
(Cellit BL 700) is mixed in a 12% solution in ethyl acetate
with 1% by weight CaC03 with a granulation of maximum 1 ~m
to 2 ~m, with 3% by weight carbon black with a granulation
f maximum 1 um to 2 ~m, or instead with a soluble dye
without pgiments, and with 2% by weight plasticizer.
With these lacquer compositions for the first and the second
lacquer layer, excellent results could be achieved, parti-
cularly if an adhesion promoter is used between carrier
material and lacquer layer. However, instead of the polymers
used here for the first and second lacquer layer it is also
possible to use stable, temperature-resistant lacquers on
the basis of cellulose acetomonobutyrate, where a cellulose
acetomonobutyrate is mixed with a polyvinyl ester copolymer
with side branches consisting of long aliphatic chains, at
a ratio of 65 to 90% by weight to 10 to 35% by weight before
being processed into the finished lacquer, with fillers
and/or pigments being added.
It can equally be of considerable advantage when polymerized,
heat-resistant lacquers of high carbon black compatibility
and high pigment absorption on cellulose acetate basis are
used.
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The lacquers of high carbon black compatibility and high
pigment absorption mentioned there are produced in that two
polymers of different melting point, e.g. a solvent-free
cellulose acetate and a highly polymeric, solvent-free
ethylene vinyl acetate copolymerisate are processed
together. Both components are processed into a
copolymerisate in a kneader at approximately the mean
softeniny temperature. This lacquer which can be produced
e.g. of powdery or granular cellulose acetate, or granular
or powdery polyvinyl acetate, or granular or powdery
ethylene vinyl acetate copolymerisate, is expected to yield
even better results in combination with the new record
carrier, i.e. when used for both lacquer layers.
These ]acquers generally do not require an adhesion promoter
between the lacquer layer and the base material.
It can thus be concluded that by means of the present
invention it is possible to obtain a lacquer surface and
consequently a surface of a record carrier coated or
vapor-deposited with a very thin aluminium layer, which more
than satisfies all demands made above. This new lacquer
surface has been found to have a high frequency of waviness,
a soft, rounded-off waviness, a high mechanical strength and
toughness through thick polymer layers on the pigment
grains, as well as a high dullness. Furthermore, there is
much less greying, and electrode abrasion could be kept low;
and the vapor-deposited aluminum layer shows excellent
adhesion. There is furthermore a low surface pressure of
the electrodes, and a low strain on the lacquer polymer.
GE9-80-038
