Note: Descriptions are shown in the official language in which they were submitted.
WO90/08653 PCT/NL90/0001l
20~4g
Screen cylinder and process for the production of such a
screen cylinder.
The invention relates in the first place to a
screen cylinder, comprising a smooth metal base cylinder
and a metal outer cylinder provided with perforations,
said cylinders being in tight contact with each other.
Such a screen cylinder Ls known from European
Patent Application 85200621.2 ~Publication
No. 0,160,341~ of Applicants.
The abo~e-mentioned patent application describes a
proces~ and a device for the production of a screen
roller in which a thin-walled metal ~creen printing
~tencil i9 disposed around the periphery of a smooth
cylindrical roller. ` ~ ~`
FLttin~ take~ place by first se~ling o~ with a
sealing agent the perorations of ~he ~reen printing
stencil to be u~ed and then, by means o a compressed
medium, slidinq the sealed cylinder thus formed onto the
smooth roller, which for that purpose is provided, at
the end where the sliding-on operation begins, with
outflow apertures for the compressed medium used.
Such screen rollers are used, for example, as ink
transfer rollers in printing systems.
Such a roller, which is therefore provided with a ~-
large number of cavities on the surface, is essentially -
brought into contact with the ink to be used, which is
in a reservoir and fills the cavities on this contact.
The excess ink is scraped off the surface of the screen
. ~ . . - ................ - .
roller using a doctor knife, so that ink only-remains in
the surf w e cavities of the roller.
The roller thus filled with ink is then brought
into contact, at a point which in the direction of
. ,, :.
SlJE~STlTlJTE SHE~ET
.. .,` .. , .. , .. `,.. , ~,.. , .,~ ~ . .. . . . . . . . .. . .. .. . .
WO90/086s3 PCT/NL90/000ll
2~S~2
rotation ~ollows the doctor knife, with a substrate
whlch has to be provided wit~ a screen-type ink coating
suc as, for example, the rubber blanket of an offset
machine or the surface of a flexographic roller used
The screen roller can also be used for the application
of an lnk or printing medium coating on the surface of a
movlng paper or textile web.
During use of the screen roller described above the
base cylinder and ~he outer cylinder are in tight
contact with each other, but are not connected to each
other.
Such an arrangement has the disadvantage that,
where inks with microscopically finely divided pigments
are used, in the course of time a pigment accumulation
can still take place between the dams o~ the outer
cylinder and the smooth metal base cylinder.
When the ink type ls changed, such pigment residues
coming from an ink used earlier can lead to pollution of
the ink uised on a subse~uent occasion, which is
undesirable.
Moreover, in the event o a heavy load, the outer
cylinder can shi~t relative to the base cylinder, so-
called "running".
The object of the p~esent invention is to produce a
solut1on to the above-mentionad problems, which is
characterized in that in the above-described screen
cylinder the base cylinder and the outer cylinder are
connected to each other by means of a soldered joint
As will be indicated more clearly here, it appears.
posslble according to the invention to apply a solder
selectiveIy on the inside of the dams of the outer
cylinder and on the outside of the base cylinder and,.
after bringing the base cylinder and the outer cylinder
into intimate contact with -each other, to actl;vate said
solder through a suitable temperature.treatment iD such
.,
~;iU ~3STllr~3Tg~ T
. ` , ` .
W090/OX6~3 PCT/NL90/000l1
2 0 ~ 8
a way that a soldered joint is produced between the -~
smooth base cylinder and the perforated outer cylinder.
The soldered joint thus formed acts as an absolu~e
seal, so that there is no longer any q~estion of any
form of pigment accumulation between the base cylinder
and the outer cylinder.
Another advantage found is that through the
provision of a soldered joint between the base cylinder
and the outer cylinder any "running" of the outer
cylinder relative to the base cylinder, such as that
which could occur during heavy mechanical loading of the
screen roller, can no longer occur.
Another advantage is that the soldered joint forms
an electrically conducting connection between th~ base
cylinder and the outer cylinder, which mean~ that - ag
will be discu~ed later - certain eLectrochemi~al
operations can be used on the assembly o~ base cylinder
and outer cylinder.
In particular, the soldered ~oint in the screen
cylinder according to the invention is a tin or a
tin/lead so~dered joint.
In the screen cy}inder according to the invention
.
the base cylinder is expediently selected from the group
comprising a solid metal cylinder, a thick-walled hollow
~5 cylinder and a thin-walled hollow cyiinder.
- Depending on the type of the base cylinder, the
screen cylinder according to the invention will be
suitable for certain applications.
If the base cylinder is a solid metal cylinder, the
screen:cylinder formed therewith will be extremely
suitable .as . an ink~transfer roller.
However-, such a screen cylinder can also be used as
a basis for the ormation of an e~ectro~orming mould.
For the formation of metal rotary screen printing
stencils, the starting point is a cylindrical roller in
SUBSTITIJTE S~EET
: ..`,,. ` . . ` . .. , . , . , ; - .. ~ :.., , ,`;
, . ` . ` .: . ` ` .. . . . . , - ~ ~ ... .... . . ; . . . .. .
WO 90~086~3 PC~/NL9o/
the surface of which cavities are formed, the
distribution of the cavities c~rresponding to the
perforation pattern in the rotary screen printing
stencil to be formed. The cavities in the roller are
filled with an electrically insulating resin which is
hardened. The roller thus provided with a pattern of
insula~ing places is placed, for the formation of a
rotary screen printing stencil, as the cathode in a bath
for the electrodeposition of metal, following which
metal is deposited on the roller. The deposited metal
will be deposited on the metal dams which lie between
the electrically insulating places and will possibly
spread over a part of the electrically insulating
places. On completion o~ the electrolytic process, the
deposit thus formed.can be removed from the cylindri~al
mould, thereby producing a rotary screen prlntin~
stencil. I
Therefore, if in the screen cylinder according to
the present invention the base cylinder is in the ~orm
of a solid metal cylinder, such a screen cylinder, aEter
filling o~ the cavities in the surface thereof with an
electrically insulating resin, will be very serviceable
as a mould for forming seamless metal screen printing
s;tencils, for example made of nickel.
2~ If the base cylinder is a hollow thick-walled
cylinder, after suitable clamping of such a cylinder
round a shaft by means of suitable end plates, the
screen cylinder will be usable as an ink transfer
roller. In this case also, on filling of the
perforations the screen cylinder will be usable as a
basic mould for forming, for example, rotary screen ~ .
printing stencils.
. , , . . ............. ; , ,,
If the base cylinder is a thin-walled hollow
cylinder, the screen cylinder formed will have to be
~5 fitted on a supporting cylinder before it can be used.
SU BSl~ U TI~ S~
,..
" . ' . ~' ` '''. . '" ',.' '. " ' .. '' .
WO90/08653 PCT/N W0/00011
20~5~8
The fitting of such a relatively thin-walled cylindrical
object round a supporting cylinder is known per se, and '
for carrying this out you are referred to European
Patent Application 85200621.2 of Applicants, mentioned
above.
In this form also, such a screen cylinder can be
used again as an ink transfer roller; for use of the
screen cylinder as a basis for forming an electrolysis
mould, an electricaLly conducting connection must be
formed between the cathode of the power source to be
used and the screen cylinder. If the carrier cylinder is
a metal cylinder, the electrically conducting connection
can be brought about between the carrier cylinder and
the screen cyLinder, while the cathode pole of the
direct current apparatus used is also connected to, ~?or
example, the shaft of the carrier c~linder.
For ~itting af the ~uter cylinder ~round the bas~
cylinder, if the base cyLinder i~ a solid or thick-
walled hollow cylinder, use can ~e made of the process
described in the European Patent Application with
publication number 0,160,340 mentioned above, i.e.
temporary sealing o~f of the perforations of the outer
cylinder and sliding it round the base cylinder by means
of a compressed medium. If the base cylinder is a hollow
thin-walled cylinder such as, for example, a thin-walled
nickel sleeve, the base cylinder can be brought into the
so-called kidney sbape, following which the outer
cylinder''can be slid around it.
When the base cylinder is released from being heLd
in a kidney shape, it`''resumes its original cylindrical
shape, and the outer surfa'ce of the base cylinder comes
to rest:against the inner'surface o~ thé outer cylinder
'' In all'cases the in'ternal diameter of? the outer
cylinder will be slightly smaller than the external
diameter of the base cylinder; however, the elongation
~3~ ?~
: ' ' "' ' ;'"'' ' ,';' " " ',': ~ ." ' "'' ` ' '"' ' ' ' ' '~'' "' " " ' '' ~ '' " '' "' "
wo9o/o86s3 PCT/NL90/0001l
~04~6A8
.
which the outer cylinder must exhibit for contac~ must
lie within the range of elasticity of the outer
cylinder.
The invention also relates to a process for the
production of a screen cylinder in which a smooth metal
base cylinder and a metal outer cylinder provided with
perforations are brought into tight contact with each
other.
Such a process is accordiny to the invention
characterized in that, prior to the assembly of the
screen cylinder, the inner surface of the outer cylinder
and/or the outer surface of the base cylinder are
provided with one or more metal layers which by
themselves or in combination can form a soldered joint,
and in that after bringing the ba~e cylinder and the
outer cylinder into contact with each okher the assembly
thus ~ormed iq subjected to A heat treatment at a
temperature which lies little above the melting point of
the soldered joint of the layer(sl.
The surface of the outer cylinder and/or the outer
surface o~ the base cylinder can be provided with metal
layers for the formation of a solderable intermediate
layer. For the formation of solderable layers, a single
layer of adequate thickness on one of the elements of
the screen cylinder is conceivable.
A metal layer can also be applied to each of the
elements of the s~creen cylinder to be formed.
The metal layer~s) can comprise a single metal or a
combination of metals. A metal layer can also be applied
to both the base cylinder and the outer cylinder, the
metals of the two layers being different, but in
combinatioi being capablè o forming a soldered ~oint.
The metal or the combination of metals must, however, be
such that a soldered joint is formed at a temperature
which does not exceed 250C.
~3~ 5'7'~
. : ~ . ,. '' ' : ' ,
W090/086~3 PCT/NL90/00011
2045~
In particular, prior to the formation o~ the
assembly of base cylinder and outer cylinder, a~ least
one of the metal layers applied is coated with a 1ux
compound.
Such flux ;~ompounds are generally known and are
used to obtain an improved flow behaviour of the solder
layer compouinds. Such ~Slux compounds can simply be
applied from a solution, by means of, for example, a
roller application system, to the layers applied for the
formation of a soldered joint; the flux layer compound
can, however, also be applied by spraying or brushing.
The solder layer materials used can be, for example, o~
tin or lead/tin; other solder compounds can also be
used. I the material o~ the outer cylinder i9 nickel,
for pràctical purposes the upper limit o~ the solder
temperature is set at 250C.
The soldering fLuxes to be used are generally
powdered or liquid compounds containing certain metal
salts, reisin components and wetting agents. The action
of such a flux is a reducing or conditioning action at
the soldering temperature. For a good adhesion of the
soldered joint layer both to the outer cylinder and to
the base cylinder, good degreasing of both elements
prior to the application of-the soldered metal layer,
combined with cleaning and activation' is very
desirable. Very good adhesion can also~be ensured by ~-
applying a so-cailed copper or nickel strike; this is an
electroplated copper or nickel layer with a maxi.~Sum
thickness o 1 micron. `
The heat treatment to be carried out is preferably
carried out in an oven in which there-is a protectiv~e
gas atmosphere which can be, for example, an inert gas
atmosphere or a slightly reducing gas atmosphere.
If the base cylinder is a so-called sleeve, i.e. a
relatively thin-walled metal cylinder, for carrying out
~ ~ ~ -~k~
. . . . . . . ` .
WO90/iD8653 PCT/NL90/00011
2 ~ 4 88
thé heat treatment the assembly of sleeve and outer
cy1inder in the form of a rotary screen printing stencil
is clamped on a cylinder, for example ln the manner
described in European patent publ1cation 1,160,341
mentioned earlier, with an internal heating
facility. The cylinder with the screen cylinder assembly
is then placed in a radiation oven which is provided
with, for example, quartz radiators.
After adding additional flux if necessary, the
programme ~or forming the soldered ~oint is gone
through, with a protective gas or a gas with ~lightly
reducing action being present in the oven as indicated.
After formation of the soldered joint, the assembly
of base cylinder and outer cylinder is expediently
co~led and washed for the removal of any excess 1ux
present.
Cooling take~ place very advantageou~ly to a
temperature o approximat~ly 35C, at which temperature
the washin~ operation i~ c~rried out.
During the carrying out of the process, metal
layers applied by electrodeposition can be used far the
application o the layer~si) which ha~e to ~orm the
subsequent soldered joint. Use can also be made of
electroless deposition of metal layers, while another
possibility is the application o~ a layer in which
suitable metal in powder form is incorporated in a
binder. The binder in such a case can expediently
contain a flux compound.
A heating o~en is expediently used for the
application of the heat treatment; other ~ethods of heat
supply such as induction heating, laser treat~ent etc.
are also possible.
If the base cylinder is a so-called sleeve, a
suitable carrier roller must be selected for the ~inal
use of the screen cylinder, in which case it can be a
c . ~ r ~ _ 5
.., . .,..
W090~086;3 PCT/NL90/000ll
2 0 ~ 8
rigid roller on which the sleeve with the stencil around
it can be sli~ using compressed air, while in the art
other tensionable rollers are also available. A major
advantage of the screen cylinder according to the
present invention Iies in the fact that through a
suitable choice of the perforated outer cylinder it is
possible to obtain a cavity volume per unit area which
can as desired deviate Erom the cavity volume per unit
area which can be obtained in the conventional screen
cylinder rollers.
The conventional screen cylinder rollers are
provided with their surface cavities by means of
mechanical working with a milling wheel or by etching.
As is also the case or the screen roller~ which
are described in Applicants' European Patent ApplLcation
85200621.2 and ~or the screen cylinders of the p,resent
application, it i~ or ~xample, pos~ible'to achieve
cavity volumes per unit area which are substantially
greater than the cavity volumes for screen rollers which
are manufactured in the conventional manner.
The invention will now be explained with re~erence
to the drawing, in which:
- Fig. 1 shows schematically a cross-section through a
part of the wall of a screen cylinder in which the base
cylinder is formed by a thick-walled hollow cylinderl
- Fig. 2 shows in cross-section of a part of the wall of a
screen cylinder in which the base cylinder is a thin-
walled hollow cylinder and the screen cylinder is fitted
on a thick-walled hollow cylinder; and
- ~ig. 3 shows a-cross-section through a part of the wall
of a screen cylinder accordin,~ to Fig. 1, which is used as
a mou]d for formi'ng rotary screen printing stencils through
electro~orming; '"'''''
- Fig. 4 shows schematically the combining of a thin-
walled base cylinder and a thin-walled outer cylinder.
Wo90~086~3 2 0 4 5 ~ ~ ~ PCT/NL90/~OOil
Fig. 1 shows the base cylinder 1 which is made of,
for example, thick-walled copper. The outer cylinder is
indicated by 2 and is formed by a rotary screen printing
stencil with a circumference of 64 cm, a length of 2
S metres, and a thickness of approximately 100
micrometres, and is made of nickel.
A tin layer is applied by electrodeposition both to
the base cylinder 1 and to the inside of the stencil 2,
both layers being approximately 15 micrometres thick.
Prior to the application of the two tin layers, a
so-called copper strike with a maximum thickness of 1
micrometre is used for improvement of the adhesion of
the subsequent soldered joint layer.
~ hrough treatment of the assembly of base cylinder
lS and outer cylinder 2, a soldered joint layer 4 i9
formedJ the heat treatment took place at a tempera~ure
of approximately 250C, the assembly of base cylinder
and outer cylinder being at this temperature eollowing
heatin~ up ~or a~prox. 5 minutes; the oven ui~ed h~d a
nitrogen atmosphere.
A~ter formation o~ the soldered joint, the screen
cylinder formed was cooled down to approx. 35C, after
which it was washed with water to remove the excess of
flux applied.
Fig. 2 shows the base cylinder formed by a seamless
nickel sleeve with a wall thickness of approx. 200
micrometres, a circumference of 64 micrometres, and a
length of approx. 2 m. The outer cylinder is a rotary
screen printing stencil with a fineness which can be
selected as desired, and which in particular can lie
between 100 and 250 mesh (mesh = number of holes per
linear inch), and the ~ineness of which in general can
lie between 60 and 500 mesh. , .,
After ~ormation of the screén cylinder, it is
~5 fitted by means o~ the air slide-on technique discussed
~ C5~ ~ uT~ ~ d
WO9O/OB653 PCT/NL9O/OOOll
2~ 8
earlier on the thick-walled hollow carrier cylinder 3.
It can be seen from Fig. 3 that a base cylinder 1
is provided with an outer cylinder 2 in the form of a
seamless metal rotary screen printing stencil. A
S soldered joint layer 4, which ensures adhesion of the
outer cylinder 2 to the base cylinder, is formed by
ca~rying out a heat treatment Reference number 5
indicates that the cavities in the outer cylinder are
filled up with an insuLating resin material; the surface
of the resin material lies flush with the top sides of
the dams of the screen material 2. If such a cylinder is
inserted as the cathode in, for example, an
electroplating nickel bath, metal is deposited on the
dams of the outer cylinder 2 and, depending on the
duration of electrolysis, will grow over the insulatin~
points 5. Through ~uitable pretreatment o~ such a mould
or example by applying chromium to the damq' o the
outer cylinder ~, a metal deposit such as a nickel
deposit deposited on the mould can be removed from the
mould using suitable equipment for the purpose as a
result o~ the proce5s conditions used during the ~rowing
operation.
Fiq. 4 shows the method of combining a thin-wallsd
base cylinder 1 and a thin-walled outer cylinder 2. The
base cylinder, such as a nickel sleeve, is brought into
the so-called kidney shape for the purpose. At great
lengths'of the outer cylinder the kidney shape is
brought about and maintained by means of equipment
suitable for-the purpose It'is also pointed out that
the screen cylinders'formed according to the inven~ion
can';be subjectèd to urther trëatments if desired by the ..
user f'or;'achieving desired end properties of the screen.
cylinder~ For instance, the finished screen cylinder can
be subjec~ed to an additional electrodeposition
operation in order to provide the surface thereof with a
`~ '~E ~
" ' ' ". . ' ., ' ." ' ' '.'. .';' ; ' :' . ' ' ' '. ' ' ' ` . '
'".'; " " ' .'', ' "''', '' ,' " ''' ' " ~ ' , ., ',,' ' '. ~'.,, .; , ' '' , '
woso/o86s3 PCT/NL90/00011
2 0 ~ 8
12
wear-resistant layer such as, for example, a ~in/nickel
layer, which is useful for reducing the wear as a result
of the action of a doctor knife during use of the
cylinder as an inking roller.
Such a screen cylinder can also be subjected to an
atching operation to change or to emphasize a particular
perforation form and/or, assuming a particular cavity
volume per unit area, to increa~e it further.
The screen cylinder can also be given a larger
cavity volume per unit area by coating the top side of
the dams of the screen with a metal which etches more
slowly, such as, e.g., Cu on an Ni screen, or is not
etched. In that case the dam height is retained, and so
is the dam width at the top; the dam flanks are,
however, strongly etched away, as a result o~ which a
large cavity volume i~ obtained. Through maintaining the
dam width, the tool Lie of ~he screen cylinder w1Ll,
however, remain unchanged. The ~tching operation
described above can, o~ course, also be carried out
20 before the outer cylinder i9 provided with a solder or
~older constituent. If the screen cylinder is to be used
as a mould, as described earlier, for forming, for
example, a screen printing stencil through
electroforming, the dam width can be reduced if desired
at the top by etching, as a result of which in
con~ection with the specifications o~ the stencils to be
~ormed an additional influencing parameter is obtained.
Through use of in particular the screen cylinder in
which the base cylinder is a thin-walled seamless metal
cyli~der and the outer cylinder is a sèamless metal
rotary screen printing stencil, a very rapid exchanging
facility is obtained, which makes it possible to vary as
desired the c~aracterlstic o~ a screen roller to-;be used
by simply exchanging the screen cylinder fitted on the -
carrier roller. . , "
-::
~` ~ ~ r
SlJE~ U ~
W090/08653 PCT/~L90/00011
204~8
The screen cylinder according to the inventian can
be split again into the base cylinder and the outer
cyLinder by heating to a temperature which lies above
the soldering temperature; the base cylinder is then
available againr~or re-use.
. . . ~
j, ,
