Note: Descriptions are shown in the official language in which they were submitted.
G4767
The present invention relates to a method
of applying patterned designs upon paper surfaces by screen
printing.
The present method relates to the first
step of the dry transfer process, that is, to the step of
printing on the paper substrate; it relates, generally,
to printing on paper, in which ink is to be absorbed.
Designs orpatterns are frequentlyprintedon
paperas a method stepin providing designs orpatterns on textile
material. In dry transfer printing, several types of known
; coloring materials are used in order to print, or dyej patterns
on textiIe fabrics which may be woven or knit, and made of
acetate, polyesterj polyamide, polyacrylic, polyvinylchloride,
polyurethane, or other similar man-made fibers. ~ispersion dyes
or inks or colors are particularly used in such dyeing or patter-
ning. Some inks or dyes customarily used have the property to sub-
limate at a temperature of about 150C or higher, that is, to
change from fixed to gaseous phase without passing through a
liquid phase. This characteristic of the dye is used in the
dry transfer process. The pattern to be applied to the textile
material, rather than being applied directly thereto is first
printed on paper which is then continuously, or in steps,
brought into contact with the textile material to which the
pattern is to be applied. Heat and pressure is applied, so
that the dye on the paper changes to gaseous phase and con-
denses on the textile fibers and thereby also diffuses to the
fibers. This transfer process, also referred to as dye transfer
itself, is a portion of the entire patterning process. Printing
on the paper and transfer from the major step of the dry transfer
process. The paper and the textile substrate are brought to-
gether usually in a suitable calendar, or under a pressure
blade or apparatus in a continuously moving process; they may
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also be brought together in batch processes in stationary
: presses. This method of applying designs may replace con~en-
tional textile printing methods, such as flat or rotary screen
printing or raised roller printing, in which the designs are
directly applied to the textile substrate.
Beside these processes, a wet transfer
process lS
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known in which dye~ also applied to paper are transferred to the
fabric unaer influence of vapor, ty~ically hot water vàpor, or
steam, so that the textile substrate is suitably patterned. ~hi~
process is mentioned onl.y for completeness of various textile
patterni-ng processes; the present invention is not generally
directed to the wet transfer Process, rather to the dry transfer
~rocess .
The dr~ transfer process has some advantages with re~pect
to the conventional direct textile printing in that additional
~tep9 have to be carried out on the fabric in the latter proce~s.
~o fix the ink, or dye, in the direct printing process on the fabric
it must be subjected to s-teamS to maintain the hand o~ the fabric,
as well as render the material laundry and wash-safe, the printed
fabric must be washed first. ~he dry transfer print process avoids
the additional treatment steps of the fabric and thus is less
expensive in its application,
~ he trans~er paper which is printed in the dry transfer
process may have the dge or ink applied by various pr~nting
processes, such a~ raised rotary printing, offset printing, flat b~d
~20~ print mg, rotary film printing or flexo-printing. ~he qualitatively
bèst results are obtained ~n photogravure- and flexo-printing.
Paper pri-nted bg means o~ offset processes or flat film print~ng
are not used to great extent in industrg; rotary screen printing
applied to the paper is increasingly used due to the low price of
-the te~tile sub~trate when completely pat-terned. Heretoforelhowever,
rotary screen printing could not compare in quality with roller
printing. Photogravure-printing produces excellent printed results;
rotary screen proce~se~, however, heretofore required compromises
either with res-pect to price or quali-ty.
~eduction in quality of printing when using rotary screen
printing proceese~ with respect to roller printing will be
1~64767
no-ticeable primarily in that in the photogravure-printing
comparatively large uniform areas of a particular color could be
printed to have absolutely uniform color distribution; when
adjacent colored surfaces were printed of dif~erent color, or hue,
the slight overlap which is required due to the e-ngraving of the
rollers did not lead to smear, or diffusion of one color or ink
into the other. The positioning or geometric main-tenance of the
pattern being applied is excellent when using roller printing;
,
tendency o~ the ink to flow to an adjacent zone, or to an adjacent
zone o~ a different color is low. Transfer of i-nk from still wet
~aper, that is, from paper still wet with ink, into the i~k of the
subsequent printing form is practically ex~luded.
With respect to quali-ty~ pho~o~ravure-printin~ thus has
`` substantial advanta~es, one o~ which being that, ~rimaril~, dry
paper is used for printing. All print applications are fir~t dried l;
in the drying chamber, associated with the particular printing
pattern or form before it i~ printed on the second pattern, by the
second color, or by covering ink. The second ink application may
be by rotary screens, ~'or example~
The photogravure-printing process thus relates to a "wet-
~' to-dry" printing method; rotary screen printing i9~ however, a
~` "wet-to-wet" prin~inig methoQ. ~he dif~erence i~ easi~y seen;screen printing~ and particularly rotary ~creen pri-nting, was first
I developed ~or direct printing textile materials, which,~due to
their excellent absorption of ink, are particularly suitable for a
"wet-t~-wet" printing process. There was no nece 9 sity to con~truct
drying chambers in combination with rotary screen printing machines.
`~ If, then, paper is to be patterned or printed with rotary screen
printing machine3, in order to apply the dry transfer prin-ting
process to tex-tiles, it would be desirable -to use the existing
screen pri~ting machinery without incurring the expense of
~ubsequent construction o~ intermediate drying chambers, although
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11)647~;7
it would -theoretica~ly be possible to 90 reconstruct the rotary
screen printing m~chines which are already in existence.
Some basic difficulties arise when using rotary screen
printing machines to print on paper: if a predetermined quantity of
ink is applied to the paper, in accordance with.pa-ttern, then the
quantity of ink must be carefully metered to have an exact relation
to the absorption capacity of the transfer pa~er A quantati~e
absorption problem thus arises in that the quantity of ink which is
available must be such that a closed film of ink can always be
applied, 90 that the absorption capability of the paper is over-
loaded with respect to the quantity of ink actually available; in
other word~, the applied quantity of ir~ can be absorbed into the
paper only in part, the rest remaining on the sur~ace. ~hus, the
first oolor of ir~ may smear with respect to the second, since an
unabsorbed film of ir~ floats on the surface of the paper web which
mixes on the paper with the subsequent color of ink merging at the
edge, or ~uperimposed thereon. ~his smearing and mixing process i9
additionally anhanced by the mechanical loading placed on the paper
during the screen prin-ting, that is~ due to the compre~sion o~ the
paper which had the first coating of ink applied at the next
~ubsequent screen printing stencil roller.
An additional diffioulty ari~es: the ink which is first
printed on the stencil can penetrate into the ~creen openings o~
the next subsequent stencil, ~o that:a portion of the fir~t printing
ink is transferred to and through the surface of the sub~eque~t
patterning ~tencil. If~this occurs in one of the open portions o~
the screen vf the subsequent stencil, that is, in a region where
the ~econd ink was to print, then there will be inter-mi~ture of
the ink -.~rom the first printing into the interior of the stencil
of the second color, to be there mixed with the ink o~ the second
color, thu~ undesirably affecting the purity of the color, or hue,
of the second ink.
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~esides smear of the ink, suxfaces of paper
on which ink is applied which is not absorbed within the paper
are difficult to be printed on with subsequent patterns. The
second color ink is apt to flow into the first colored ink;
this phenomena has been referred to as insufficient stability
of the ink.
After a paper web has been printed with
ink, it must be dried so tha-t -the paper can be rolled without
smearing. If the pattern provides areas which are not printed,
that is, the natural surface of the paper, then, upon drying,
; the unprinted portions of the paper are excessively heated
and the intense drying heat, to vaporize the volatile portions
of the ink, is substantial. The zones which have been printed
can just barely give off their volatile contents while the un-
printed surfaces are over-heated. This difference in moisture
between the printed and unprinted portions of the paper needs
:
to localize tension within the paper so that it buckles, or
forms bubbles and bulges; upon subsequent transfer printing,
- these bubbles or bulges cause problems.
The absorption problems so far discussed
generally relate to the quantity of ink being applied; quali-
tative difficulties also arise. Any surfaces to be inked must
have a uniform depth of color, or hue; within a particular
pattern areas of a particular color, adjacent zones must have
the same hue and the unifirmity of application of color must
be such that the naked eye cannot recognize any differences
in color saturation of the printed surfaces.
The capability of absorption of ink by the
paper is thus of substantial importance and the way and manner
of the absorption of the ink must be controlled. In this type
of rotary screen printing it is necessary that the film of ink
applied to the paper sinks uniformly within the surface of the
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~ 6~767
paper; the uniformity of absorption is determined by the paper
it3elf. If the capability o~ ab~orption is uniform, then th~
ink will be accepted e~sentially uniform--with respect to the
depth of penetration of the ink within the paper substrate.
The quantity of ink being applied of course also affects the
absorption of the ink. If, for example, a quantity of ink is
used which can saturate the paper through to the back surface
thereof, then any non-uniformitie~ within the paper it~elf will
have greater e~fect than with shallower penetration ~ince any
differences in absorption within the paper will be effective on
the ink throughout the entire tranæverse dimension of the paper
rather than merely through a portion thereof.
It is an object of the present invention to pro~ide
a pro¢es~, particularly adapted to the dry transfer process of
printing pattern3 on paper which is inexpensive and which results
in printed paper ~heets or webs of high quality.
According to the present invention, there i~ provided
a method of applying patterned de~ upon a sub3trate9 compri-
sing the steps of:
~ - providing a rotary screen stencil formed with openlng~
thexethrough,
- placing said rotary screen stencil over a ~urface of
; said 3ubstrate,
- placing a predetermined coverage pattern correspondi~g
to pattern areas of design on the ~creen stencil at the obver3e
side thereof with respect to the side of 3aid ~creen stencil facing
said subs~rate,
- applying a predetermined quantity of ink to ~aid rotary
screen ste~cil, said ink being applied by taking into consideration
the flow-de~ormation properties of said ink,
- pressing by ~queegee means said ink through said ope-
nings of ~aid rotary screen stencil onto the surface of the subs-
trate, and,
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- giving to ~aid ~queegee means a predetermined angle
0~ inclinat~on in order to transfer the necessary amount o~ ink
from the rotary screen stencil onto the substrate in form of
~ingle dots.
: In the prior art, the
~)64767
problems of quantative and qualitative ab~orption are usually
cau~ed by uncontrolled, most frequently excessive application
of ink to the paper web. Under ordinary circumstances, much
too much ink is applied in form of a continuous film of ink.
It ii3~ then, necessary to sub3tantially reduce -the amount of
ink-paste ~hich is being applied. ~his, however, i2 no-t 90
ea~i~y carried out since the requisite minimvm of ink cannot
be obtained by mechanical control of the printing apparatus
itself. It is no-t possible therefore to reduce the quantity
of ink by merely changing the pattern of the screen, the -type
of doctor blade7 the doctor blade angle, or the like; if thi~
i9 done, insufficient ink is applied in certain location~ and
prohlems of application of any ink in selec-ted zones will occur.
The film of ink will be complete, and may even be excessive in
some zone3 while, at other zones, it i~ in~ufficient or may not
print at all. Thus, the ink pattern on the paper it2elf may
already be defective.
In accordance with the -teaching2 of the present
invention, the ~i~m of ink being applied is not a closed film
~ at all; rather, the necessary small quantity o~ ink being applied
~` i9 selected and controlled b~ considering the flow propertie~,
or flow-deformat~on properties of -the ink, as well as angle of
doctor blade~ and type of doctor blade, but, then in addi-tion
i ~ thereto to print only the pattern of the 2tencil itsel~; in
o-ther words, it is the screen pattern of the screen stencil
which is printed, in accordance with the particular coverage
pattern de~ired -to be transferred to the ~aper. ~hu~, the
actual application of ink to the paper will be in form of
adjacent dot~, in accordance with the raster as determined by
the screen ~tencil.
In accordance with the prior ar-t, it is cu~-tomary to
print closed zones of films of ink on paper or-fabri.c ~lthough
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1064767
printing in dot patterns in known, eventually, a closed film
or surface of ink has been applied; the dot pattern was
however speci~ically arranged in accordance with the pattern
itself. Rather than printing a closed film of ink, applying
a dot pattern on the paper transer web has substantial advan-
tages in rotary screen processes. It is to be noted that
printing in accordance with the matrix pattern is not known.
The pattern to be printed is thus provided
in single dots of ink. The surface of the paper adjacent these
dots thus provides a reserve for ink absorption. Quantitative
absorption problems thus are solved. Smear of the first ink
into a subsequently colored ink is not a problem anymore since
the inked surface is broken up into single points or dots or
ink, based on stencil and formation, and occurs only in the zone
or region of one of the dots themselves. Any remaining smears
~ at interfaces will be so small that 1hey can be neglected due
; to the minute extent of the smear itself. The absorption capa-
bility of the specific paper is thus exhausted only after three
or four subsequent applications of ink are made to the paper;
in conventional printing, that is, in printing in accordance
with the prior art when a closed continuous filament of ink
is printed, first application of ink usually already completely
exhausted the absorption capability of this paper substrate.
Since all the ink applied to the paper substrate
can be absorbed, there will be no more transfer of ink already
applied to the paper to a subsequent screen stencil. No free or
floating portion of ink will remain on the surface since each
application is in a dot only. Thus, there will be no running in
of one color into the other. The dimensional or geometric sta-
bility of the ink on the paper is enhanced.
The total quantity of ink being used is subs-
tantially less than before and thus the drying time in drying
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1S~6~767
requirements are substantially reduced. Buckling of paper upon
drying is thu~
3L06476';9
: effectively avoided, since the printed ink dots, in general, are
usually surrounded at least at some point~ by unprinted paper,
~ he quality of the pattern being printed, directly, and
upon transfer is much better than heretofore, that i9, when
continuous closed films of ink were printed, since the.ink itself"
is usually located only at the outer surface of the paper web~
and does not penetrate clear through the paper web. Structural
differences within the interior of the paper web thus have little
or no influence on the absorption of ink. Since the ink is
generally locatea at the outer portion of the cross-sectional area ~,
of the paper9 transfer o~ the i-nk to the textile fabric, which i~
to be ..patterned upon hea-ting can be easily accomplished since it
i9 not necessary that the ink must pass in gaseous phase, through
the entire cross-section o~ the paper ~eb.
Requirements on paper,quality can be reduced since the
uniformity of the paper throughout it; cross-section is no longer
a serious problem. Thus, cheaper paper can be used for the
proce 9S . . . [
~he process in accordance with the present invention i~ -
applicable not only to paper web but also the webs of other
materials which may include plastics, or plastic-coated paper
or otherwise coated webs o~ fle~ible material on which printing ,:
can be carried out.
.~he process i~ part1cularly applicable for the, dry
tran~er process of printing; it can be used, generally~ ,,t,o,,
apply ink in a pattern on a paper sheet or,web for any use,
for example to print wallpaper or the like.
~he invention will be described by ~.way of example with
reference to the accompanying drawing, wherein the ~igure is a
highly ~chematic cros~-sectional view through a screen ~tencil
and a paper web having dots of ink printed thereon.
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~L0~4767
Paper web or sub~trate 10 has dots of ink 11 applied
there-to by a ~creen stencil, i.e. as shown in -the ~igure a
rotary screen stencil 12. ~he ink 13 fed to the inner side of
the screen stencil 12 i~ pressed through interstices 14 by a squegee
or doctor blade 15 on to the substrate 10. Not the whole ink
corre~ponding to the volume o~ one interstice 1~ is deposited on
to the substrate 10, but only a part thereof.. ~his i9
schematically shown in 16 and 17 by a separation ~rocess, whereby
a part 18 of the ink remains in the interstices.
~he dots ll of ink deposited on the surface of the
substrate 10 will "~ink" into the substrate. ~he ~Isinking~
depth h is small and the i~k remain~ partly on the surface of the
substrate in wet condition.
~ ow, printing of further dots of another ink in the next ¦-
printing ~tation of the machine will re~ul~t in a considerabl~
smearing of the first i-nk wi-th the second ink, ~ince mo~t of the
second dots are printed in the intervals between the first dots.
After the printing o~ dots is finished, the substrate is
dried and is ready for use.
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