Technical Field
[0001] This invention relates to a method of easily and economically producing watermark
paper which is exquisite and has high gradation by utilizing a lace.
Background Art
[0002] As production methods of watermark paper, there have heretofore been employed (a)
a method which fits a pattern shape such as figures or characters on a face wire of
a cylinder mould or a dandy roll, (b) a method which paints out the meshes of the
face wire in a pattern with a resin or the like, and (c) a method which hammers the
face wire itself into a corrugation pattern.
[0003] According to the methods (a) and (b), the meshes of the wire of the pattern portion
are closed and the passage of fibrous materials through them is impeded. As a result,
a wet web is not formed at that portion or even if it is formed, its thickness is
reduced, so that a watermark pattern comes into view. If the size of the meshes of
the face wire closed by the pattern shape is by far greater than a fiber length in
this case, holes are formed in the wet web and renders a practical problem. Therefore,
limitations must be imposed on the shape, size and distribution of the pattern shape
or multi-layered papermaking must be carried out in order to prevent the formation
of the holes. The operations of forming this pattern shape and fitting it to the wire
and the operations of painting out the meshes of the wire in match with the pattern
need an extremely high level of technique and skill and the production time necessary
for such operations is extremely long, as well. The proposals described in Japanese
Patent Publication Nos. 12202/1972, 21248/1974, 24483/1979 and 28486/1979 attempt
to solve such problems and to easily produce a pattern shape or a wire cloth having
the pattern shape by utilizing a photo-sensitive resin.
[0004] Since the method (c) hammers the pattern as the corrugation of the wire, the meshes
of the wire are not closed. Therefore, the watermark pattern is generated due to the
difference of drainage rate depending on the height of the corrugation of the wire,
its depth, the angle of a slope, and so forth. In comparison with the methods (a)
and (b), this method (c) is more excellent in so-called "gradation" which represents
a delicate difference of density of the watermark pattern, has the smaller possibility
of holes at which the fiber does not at all exist, and has a smaller limitation to
the design of the watermark pattern. However, the production of the wire for the method
(c) needs a higher level of technique and skill than the methods (a) and (b). Moreover,
there is a problem that the corrugation pattern itself of the wire is likely to undergo
deformation or breakage during the paper making operation.
[0005] The production methods of watermark paper described above exhibit the watermark pattern
by forming low and high densities in the fiber distribution during the paper making
process. Unlike these methods, a method which prints an arbitrary pattern by a transparentizing
agent (Japanese Patent Publication No. 3802/1975) and a method using a resin which
becomes transparent by hot press and then makes the pattern portion transparent by
hot press to obtain a watermark-like pattern (Japanese Patent Laid-Open No. 275500/1986)
have been proposed.
[0006] Japanese Patent Publication Nos. 7725/1972 and 12846/1974 propose a production method
of watermark paper having a deep corrugation pattern by using a fourdrinier wire providing
a pattern. This method however involves the problem that since the fourdrinier wire
providing a pattern rotates while keeping in contact with a large number of rollers
and receiving a hign tension, the expensive fourdrinier wire providing a pattern is
worn out and its travelling stability is not satisfactory.
[0007] The various problems with the above-described conventional methods are summarized
as follows.
1) An extremely high level of technique and skill are required for the conventional
production method of the patterned wire and moreover, an extremely long period of
time is necessary for the production thereof. Thus, there remain the problems that
mass-producibility of watermark paper is impeded and the production cost is high.
2) According to the method (a) which fits the pattern mould such as figures and characters
to the face wire and the method (b) which paints out the meshes of the wire in the
pattern form, the design of the watermark pattern is limited in order to prevent the
holes that are likely to occur when the meshes of the wire are closed. So-called "gradation"
which represents a delicate difference of density of the watermark pattern is not
sufficient, either.
3) The method (c) which hammers the pattern form in corrugation in the wire itself
is superior to the methods (a) and (b) in the aspect of gradation, but this method
involves the problem that the corrugated pattern itself is likely to undergo deformation
and breakage during the papermaking process.
Disclosure of the Invention
[0008] It is therefore an object of the present invention to provide a method which can
solve the problems of the conventional methods described above, can freely watermark
even a complicated pattern with high gradation and can moreover easily and economically
produce watermark paper.
[0009] Namely, the method producing watermark paper in accordance with the present invention
is characterized in that a lace is fixed and bonded to a wire cloth for papermaking
to form a patterned wire, this patterned wire is fitted as a face wire to a cylinder
mould of a cylinder-vat machine or a dandy roll, and papermaking is conducted by using
the cylinder mould or the dandy roll to which the patterned wire is fitted.
[0010] The lace used in the present invention is a generic name of those products which
are formed by yarn in a predetermined texture and express a through-hole-like pattern
by the density of gaps between the yarns, and includes a fabric lace formed by making
an embroidery on a base cloth such as a fabric, a knitted fabric and the like. (Refer
to "Modern World Encyclopedia", Vol. 3, page 944 (1972), published by Kodansha.)
[0011] Materials of the yarn for producing the lace are not particularly limitative in the
present invention and metal fibers such as bronze fibers or stainless steel fibers,
synthetic fibers such as nylon or polyester and natural fibers such as cotton, hemp
or wool can be used.
[0012] When the lace is integrally fixed and bonded to the wire cloth for papermaking, arbitrary
means such as soldering, sewing, bonding by an adhesive and the like, can be selected
depending on the materials of the lace.
[0013] Appearance of the pattern of watermark paper in the present invention is based on
diversity of the lace texture such as the combination of the thickness of the yarns
of the lace constituting the face wire, the density of gaps between the yarns, the
variety of the thickness of the pattern portions formed by the degree of overlap of
the yarns, and so forth. Accordingly, it is possible to obtain watermark paper having
a complicated and exquisite pattern and excellent gradation that the conventional
methods have not been able to obtain.
Brief Description of Drawings
[0014]
Fig. 1 is a perspective view of a dandy roll having a patterned wire fitted thereto
which is used in the present invention; and
Fig. 2 is a perspective view of a cylinder mould for a cylinder-vat machine having
a patterned wire fitted thereto which is used in the present invention.
Best Mode for Carrying Out the Invention
[0015] Fig. 1 shows a dandy roll 1 which is used when the method of the present invention
is practiced by a fourdrinier machine. This dandy roll 1 is produced by fitting a
patterned wire, which is formed by fixing and bonding a lace 2 to a wire cloth 3 for
papermaking, to a frame 4 of the dandy roll.
[0016] Fig. 2 shows a cylinder mould 10 used when the method of the present invention is
practiced by a cylinder-vat machine. This cylinder mould 10 is produced by fitting
a patterned wire, which is formed by fitting and bonding a lace 20 to a wire cloth
30 for papermaking, to a frame 40 of the cylinder.
[0017] When the present invention is practiced, the dandy roll 1 shown in Fig. 1 is disposed
and slidably rotated in the process in which wet web is formed on the wire part of
the fourdrinier machine or the like, so as to execute paper making, and the resulting
wet web is dried in a customary manner. In the case of the cylinder mould 10 for the
cylinder-vat machine shown in Fig. 2, the cylinder mould 10 is disposed at a predetermined
position inside a vat of the cylinder-vat machine and papermaking may be carried out
in a customary manner. The cylinder-vat machine includes specific cylinder-vat machines
such as a roto-former, a ultra-former, a Stevens former, and so forth.
[0018] In the present invention, as the lace for forming the patterned wire, a lace can
be used as it is. However, in order to further improve gradation of the watermark
pattern, it is possible to use those laces part of the mesh of which is painted out
with a resin by printing, or those laces part of which is thickend with a resin.
Example 1
[0019] A patterned wire was produced by fixing and bonding integrally a lace obtained by
knitting polyester filaments and having a flower pattern to a 90-mesh wire cloth made
of bronze by using an epoxy type adhesive (trade name "Araldite 106", a product of
CIBA-GEIGY Co.), and this patterned wire was fitted as a face wire to a cylinder mould.
Then, watermark paper having a basis weight of 120 g/m² was produced using paper stock
having the following composition (per beater):

[0020] As a result, an exquisite and complicated lace pattern was watermarked and watermark
paper having high gradation could be obtained.
Example 2
[0021] Part of the pattern of a lace knitted by polyester filaments was painted out by screen
printing using an epoxy resin ("Araldite 106", a tradename) and part thereof was further
thickened with the resin.
[0022] The lace obtained in this manner was integrally fixed and bonded to a wire cloth
made of bronze by an adhesive (the same epoxy resin as described above) to produce
a patterned wire and this patterned wire was fitted as a face wire to a dandy roll.
The dandy roll was placed on a wire part of a fourdrinier machine and was brought
into rolling contact with wet web (dry basis weight: 110 g/m²) having the same paper
stock composition as in Example 1. Thereafter, paper was dried in a customary manner.
[0023] As a result, there could be obtained watermark paper having gradation due to a delicate
watermark pattern formed by the lace pattern and a clear watermark pattern formed
by the thickened resin portion and the paint-out portion by screen printing.
[0024] The effects obtained by the production method of watermark paper in accordance with
the present invention described above can be summarized as follows.
1) In the production of the patterned wire for watermarking, fixing and bonding of
the lace and the wire cloth are the main operations. Therefore, a high level of technique
and skill, that have been necessary in the conventional method, are not necessary.
2) The production time of the patterned wire for watermarking inclusive of the lace
production time can be reduced drastically by use of a mechanical knit lace. According
to the expriments carried out by the inventors of the present invention, the production
time of the patterned wire could be reduced to about 1/100 in comparison with the
conventional method (a) which fits a pattern shape such as figures or characters.
3) The watermark pattern is exhibited by the texture of the yarns constituting a lace.
Therefore, in comparison with the method which closes the meshes of the wire and has
been employed mainly in the past to exhibit the watermark pattern, the method of the
present invention is more excellent in the representation of gradation. Furthermore,
since the possibility of occurrence of holes in the web due to the watermark pattern
does not exist, there is no limitation to the design of the watermark pattern.
4) In the conventional method (c) which directly hammers the watermark pattern as
corrugation of the wire, there is a great danger that the corrugation pattern gradually
undergoes deformation or is worn out during the papermaking process. In this respect,
the patterned wire used in the present invention which is obtained by fixing and bonding
the lace and the wire cloth is more superior in the aspect of durability during the
papermaking process.
5) The above explanation describes mainly the effects of the present invention in
comparison with the conventional methods. Furthermore, the lace used in the present
invention can be produced by converting the design of the lace into digital information
by an electronic scanner or the like, and producing the lace by an automatic knitting
or weaving machine. Therefore, even a lace having a complicated design can be produced
within a short time.
6) Due to the effects described above, the present invention makes it possible to
produce a variety of watermark paper having various designs in a limited quantity.