Note: Descriptions are shown in the official language in which they were submitted.
1 3 1 2466
HEAT-SENSITIVE STENCIL S~EET
BACKGROUND OF THE INVENTION
Field of the Art
This invention relates to a heat-sensitive stencil
sheet and a method for producing the same, more
particularly to a high performance heat-sensitive stencil
sheet and an economical method for producing the same.
~ackqround Art
The stencil printing system has heretofore been
broadly practiced as a simple printing system. According
to this stencil printing system, a laminate having a
thermoplastic film layer lam;nated on an appropriate
support (base) surface such as paper, etc. is used as the
heat-sensitive stencil sheet. By performing printing by
a heating printing means such as thermal heads on the
paper, the thermoplastic film layer is melted by heating
to form a perforated pattern corresponding to the printed
information for printing. In stencil printi~g, the film
layer side of the paper having printing thus effected
thereon, is superposed on a material to be printed such
as paper, etc. and a printing ink is fed in from the base
side.
The heat-sensitive stencil sheet to be used in the
heat-sensitive stencil printing system of the prior art
as described above is generally formed by laminating a
thin thermoplastic film layer of about several ~m on the
surface of a porous base such as paper, etc. with an
adhesive, etc. but the following problems are involved.
(1) Since the adhesive layer is also required to be
thermoplastic for enabling perforation with heat, no
strong adhesive such as a thermosetting adhesive can be
used, and therefore no sufficient adhesive force can be
obtained. Also, for the same reason, during printing,
the adhesive force will be lowered due to the solvent
components, etc. in the printing ink, whereby there is
the problem that poor print quality may occur if the
1312466
thermoplastic film peels off from the laver due to the thermal
head, etc. Thus, the heat-sensitive stencil sheet of the
prior art has the problem that it is not satisfactory
with respect to printing resistance.
(2) Since an organic solvent solution or emulsion of
a thermoplastic resin is generally used as the adhesive,
the required drying step and aging step make the process
cumbersome, and also increase the cost. Also, the heat
required in the drying and aging steps causes
thermoplastic film to be deformed to make a stable paper
product difficult to achieve. Further, a solvent system,
emulsion system adhesive, through impregnation into the
porous support will clog the voids in the porous base,
thereby having the drawback of being inferior in image
quality or image density.
(3) As the result of use of a porous material such
as paper, etc. as the base, it is necessary to enhance
the adhesive force to some extent in order to adhere both
sufficiently to ~ch other. ~owever, when the adhesive
force between the support and the film layer becomes
higher, the surface unevenness shape on the porous
support will be transferred onto the sur~ace of the thin
thermoplastic film layer, whereby there is the problem of
nonuniformity occurring on the printed image as caused by
the uneven shape during printing.
An object of the present invention is to solve the
drawbacks as described above, and provide an excellent
heat-sensitive stencil sheet economically.
S~MMARY OF THE INVENTION
The above object of the present invention can be
accomplished by the present invention as specified below.
More specifically, the present invention is a heat-
sensitive stencil sheet comprising a thermoplastic film
layer laminated through an adhesive layer on one surface
of a base, characterized in that the above adhesive layer
comprises an adhesive curable by ionizing radiation.
A
3 1 3 1 2466
Thus, in the present invention, by using an adhesive
curable by ionizing radiation as the adhesive for
adhering the porous support and the thermoplastic film of
the heat-sensitive stencil sheet, the support and the
thermoplastic film layer are adhered sufficiently to each
other, whereby an excellent printing resistance can be
exhibited during printing~
Since the adhesive curable by ionizing radiation is
of the non-solvent type, there is little impregnation of
the solvent into the porous support to give excellent
image quality and image density. Moreover, ionization
radiation curing is possible at low temperatures, and
therefore the sheet can be produced without causing any
deformation of the thermoplastic.
Also, since the adhesive to be used has great
adhesive force, the thermoplastic film and the base need
not be adhered under high pressure, whereby there is no
such drawback that the surface unevenness shape of the
support is transferred onto the thermoplastic film layer
side. Therefore, a printed matter with sharp images can
be given.
Further, in the heat-sensitive stencil sheet of the
present invention, drying and aging of the adhesive are
obviated by use of an adhesive curable by ionizing
radiation, and the adhesion step can be completed within
several seconds, and therefore the production steps can
be made continuous, and yet it is excellent in that a
heat-sensitive stencil sheet can be provided
economically.
.30 BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 and Fig. ~ are sectional views each showing
the constitution of the heat-sensitive stencil sheet of
the ~resent invention, and Fig. 3 and Fig. 4 are
sectional views each showing the steps for preparing the
heat-sensitive stencil sheet of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
4 1 3 1 2466
Referring now to pre~erred embodiments, the present
invention is described in more detail.
Fig. 1 and Fig. 2 illustrate schematically the
cross-sections of the heat-sensitive stencil sheet of the
present invention, and Fig. 3 and Fig. 4 illustrate
schematically the method of preparing the heat-sensitive
stencil sheet of the present invention.
As shown in the drawings, the heat-sensitive stencil
sheet according to the first invention is characterized
by a porous base 1 and a thermoplastic film layer 3 which
are adhered with an adhesive curable by ionizing
radiation 2, and the heat-sensitive stencil sheet
according to the present invention characterized by
forming further a sticking prevention layer 4 on the
surface of the thermoplastic film layer 3, and further
the third invention is characterized by first coating the
thermoplastic film layer 3 with the adhesive curable by
ionizing radiation 2 (Fig. 3), subsequently laminating
the porous base l thereon and thereafter curing the
adhesive 2 (Fig. 4) with the ionizing radiation ~the
arrowhead).
Porous base
-
The porous base 1 to be used in the present
invention is required to be a porous material so that
printing ink can pass therethrough during printing. For
example, any base which can be used as the base for the
heat-sensitive stencil sheet of the prior art can be used
in the present invention, such as various papers,
particularly porous papers such as Japanese paper,
synthetic papers comprising chemical fibers lsynthetic
fibers) such as rayon, vinylon, polyester, acrylonitrile,
etc., mixed papers made from chemical fibers and natural
fibers, etc. Although not particularly limited, papers,
synthetic Eibers, mixed papers, etc. having a basic
weight of, for example, about 8 to 1~ g/m2 can be used to
advantage.
1312~66
As the porous base to be used in the heat-sensitive
stencil sheet of the prior art, natural fibers have been
frequently used, but since natural fibers are generally
inferior in printing resistance, it has been proposed to
improve printing resistance by previously applying
viscose working on the support (e.g., Japanese Laid-Open
Patent Publications Nos. 92892/1987 and 156992/1987).
~owever, according to the study by the present inventors,
those having viscose working applied on a porous base
comprising natural fibers ensues a new problem that the
image density is lowered, and there are involved
drawbacks such as the problem of shrinkage at the viscose
worked portion and increases in production cost. The
present inventors have repeated experiments in view of
the above points to determine the following facts.
(a) Even when no viscose working or sizing treatment
is applied by making the wet tensile strength of the
material which becomes the base 200 g/15 mm or higher,
more preferably 300 g/15 mm or higher, a heat-sensitive
stencil sheet excellent in printing resistance and image
characteristics can be obtained without giving rise to
the accompanying drawbacks as described above. Thus, by
enhancing the wet tensile strength~ printing resistance
and particularly deformation of the image by elongation
of the paper can be effectively inhibited.
(b) In applying the viscose working, by use of a
mixed paper of natural fiber and synthetic fiber as the
support material, the wet tensile strength of the base
can be improved to 200 g/15 mm or higher, more preferably
300 g/lS mm or higher, whereby the same effect as in the
above la) can be obtained. At the same time, even if
viscose working may be applied, as different from the
case when only natural fibers are employed, shrinkage of
the paper can be reduced as far as possible to be
excellent in the point that lowering of the image density
can be prevented. Further, the mixed paper as mentioned
above has large wet tensile strength and can lower the
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cellulose concentration during the viscose working (e.g.
20% or less), and therefore it is also possible at this
point to effect reduction of the cost through increasing
the image density.
In the present invention, the "wet tensile stength"
as described above, means the strength at break obtained
by soaking a paper cut into a width of 15 mm and a length
of 250 mm in water of 20C for 10 minutes, then removing
excessive water with a blotting paper and performing the
tensile strength test before no change in moisture in the
test strip occurs. The tensile strength was performed at
a tensile speed of 50 mm~min. with a length between both
the grip ends upon the initiation of the test being 180
mm.
Thermoplastic film
The thermoplastic film layer 3 to be laminated on
the surface of the above support 1 is not particularly
limited, but any of those used is the heat-sensitive
stencil sheet of the prior art can be used, such as
polyvinyl chloride type film, vinyl chloride-vinylidene
chloride copolymer film, polyester film, polyethylene,
polyethyleneterephthalate (PET), polyolefin film such as
polypropylene, etc., polystyrene film, etc.
These thermoplastic film layers 3 should have a
thickness of 20 ~m or less, preferably 10 ~um or less,
more preferably 1 to 5 ~m, so that perforation can be
formed easily by the heating means of the thermal head,
etc.
Whereas, in the present invention, of the materials
as described above, as the material for the film layer 3,
a polyester film having a thickness of 1 to 10 ~m may be
preferably used. As one of the particularly preferable
polyester films, PET ilm may be mentioned, which has a
heat shrinkage of 3 to 30% at 150C and 15 min. and/or a
melting heat content of 5 to 10 cal/g and a melting point
of 270C or lower. In the following, the reason why such
7 1312466
PET film as mentioned above is preferable will be
explained.
Recently, for improvement of image quality of
printed matter, the printing system using thermal heads
has become the main stream, and the dot size tends to
become smaller. Accordingly, the heat content per dot
tends to become smaller, requiring that the stencil sheet
has higher sensitivity. Also, the stencil sheet using
polyethyleneterephthalate (PET) film as the thermoplastic
film has high crystallinity and thermal stability due to
the biaxially stretched PET film, and therefore has small
perforations in the stencil prepared to give an excellent
resolving power, but it has an insufficient density of
the printed matter. Further, it is generally difficult
to form the above polyvinyl chloride film or polyolefin
film into a thin film of several ~m, and it is also
defective in heat resistance, making it unsatisfactory in
both density and resoLving power.
In the present invention, by use of a PET film
having a heat shrinkage of 3 to 30~ at 150C and 15 min.
and/or a melting heat content of 5 to 10 cal/g, and a
melting point of 270C or lower, particularly as the
thermoplastic film, printing excellent in density and
resolving power can be realized.
Such PET film has a thickness of 1 to 10 ym,
preferably 1 to 4.5 ~m, a heat shrinkage at 150C and 15
min. preferably of 3 to 30%, more preferably 5 to 20%,
and also preferably its melting heat content of 5 to 10
cal/g, more preferably 6 to 9 cal/g, and a melting point
of 270C or lower.
If the thickness of the PET film is less than 1 ym,
the film itself is deficient in strength and also the
elasticity becomes too great to stand lamination working
or working during printing, while if the thickness
exceeds 10 ym, much energy is required during perforation
for melting the film and also the perforations become
8 1312~66
smaller to lower the density of the letters during
printing.
A preferable area for perforations formed by
perforation during stencil preparation may be 40 to 80%
of the area of the thermal head, more preferably 50 to
70~. Generally during printing, the size of one dot of
the printed matter becomes greater by 30 to 50~ than the
size of the above perforation. Accordingly, if the size
of perforations exceeds 80~ of the size of the thermal
head, the individual points of the printed matter will be
connected continuously to lower the resolution
remarkably. On the other hand, if it is less than 40%,
the individual points are too small, and a sharp image
cannot be obtained.
If the heat shrinkage exceeds 30%, the perforation
area after perforation in the thermal head becomes too
large, whereby the adjacent perforations become connected
continuously beyond the size of the thermal head to lower
the resolving power. On the other hand, if it is less
than 3%, the area of perforations after perforation is
too small, and sharp printing can be obtained.
If the melting heat content exceeds 10 cal/g, the
PET film has high crystallinity, whereby a large amount
of energy will be required for melting perforation.
Adhesive layer
The adhesive to be used for adhesion between the
above porous base 1 and the thermoplastic film 3
characterizes primarily the present invention, and an
adhesive curable by ionizing radiation 2 is used in the
present invention.
As the adhesive curable by ionizing radiation known
in the art, there may be included primarily polymers
having radical polymerizable double bonds in the
structure, for example, relatively lower molecular weight
polyester, polyether, acrylic resin, epoxy resin,
urethane resin, etc. containing ~meth)acrylate and
radical polymerizable monomer or polyfunctional monomer,
g 1312466
etc., further containing optionally a photopolymerizable
initiator to be crosslinked by polymerization with
electron beam or UV-ray, and these ~dhesives curable by
ionizing radiation, of the prior art can be all used in
the present invention.
However, those particularly preferred in the present
invention are those capable of forming an adhesive layer
which can retain heating meltability even after ionizing
radiation curing. Such adhesive layer can be formed from
an ionizing radiation curable adhesive having relatively
lower crosslinkability. Preferably, available ionizing
radiation curable adhesives contain a coating forming
component as the main component, and do not necessarily
require the presence of double bonds in the molecule,
having relatively lower molecular weights, for example,
containing a thermoplastic resin such as polyester resin,
polyvinyl acetate resin, ethylene-vinyl acetate copolymer
resin, chlorinated polypropylene, polyacrylate, terpene
resin, coumarone resin, indene resin, SBR, ABS,
polyvinylether, polyurethane resin having a molecular
weight of about 400 to several ten thousands as the main
component. These thermoplastic resins have been also
known in the art as the heat-sensitive adhesives, and
these heat-sensitive adhesive layers can be preferably
used in the present invention.
Further, in addition to the above components, for
improvement of the heating meltability of the adhesive
layer formed, a wa~ type polymer, oligomer having a
relatively lower melting point, for example, polyethylene
glycol, polypropylene glycol, paraffin, aliphatic
polyester, parablex, polyethylene sebacate, polyethylene
adipate, etc. may be also added, and these waxes can be
also used in place of the above thermoplastic resin.
In the present invention, since coatability during
formation of the adhesive layer is inferior with the
above thermoplastic resin and/or waxes alone, and also
the adhesive of the adhesive layer is deficient, it is
1312466
preferable to improve coatability by using a
monofunctional monomer such as vinyl type monomers, for
example, ~meth)acrylate, (meth)acrylamide, allyl
compound, vinyl -ethers, vinyl esters, vinyl heterocyclic
compounds, N-vinyl compounds, styrene (meth)acrylate,
crotonic acid, itaconic acid, etc. Further, in addition
to the above monofunctional monomer, bifunctional or more
monomers such as diethylene glycol di(meth~acrylate,
triethylene glycol di(meth)acrylate, tetraethylene glycol
di(meth)acrylate, trimethylolpropane tri(meth)acrylate,
pentaerythritol tetra~meth)acrylate, dipentaerythritol
hexa(meth)acrylate, tris(~-(meth)acryloyloxyethyl)-
isocyanurate, etc., but if these polyfunctional monomers
are used in large amounts, the thermal perforatability of
the adhesive layer is lowered, and therefore they should
not be used in large amounts. When used in small
amounts, for example, 10% by weight or less in the whole
monomers, preferably in an amount of 5% by weight or
less, excellent adhesive force and printing resistance
can be achieved without obstructing the thermal
perforatability of the adhesive layer.
Further, in the pre~ent invention, good thermal
perforatability can be also given to the adhesive layer
after curing by controlling increase in molecular weight
or crosslinking during curing of the adhesive layer by
adding a small amount of a known chain transfer agent
such as a mercaptan compound in the above adhesive.
The composition of the above ionizing radiation
curable adhesive to be used preferably in the present
invention may be preferably a composition which is non-
fluid having some adhesiveness (tackiness) at normal
temperature, and a fluidizable liquid having a viscosity
of about 500 to 2,000 cps under temperature elevation,
for example, at a temperature of 60 to 100C. For
example, a composition containing about 1 to 30 parts by
weight of a monomer based on 100 parts by weight of the
above thermoplastic resin and/or waxes.
1312466
11 -
~ s described above, as the ionizing radiation
curable adhesive of the present invention, it should
preferably consist of a composition containing la) a
thermoplastic resin and ~b) a monomer and/or a low
melting wax. Also, in the preferred embodiment of the
present invention, a composition containing a
thermoplastic resin having a molecular weight of about
1000 to 30,000, a monofunctional (meth)acrylate monomer
and a low melting wax having a melting point of 40 to
150C is preferred.
Ordinarily, a thermoplastic resin cannot be coated
unless diluted in a solvent. Accordingly, there are
problems that 11) lamination working can be done only with
difficulty, (2) the resin is impregnated into the porous
lS base to clog ~he ink passage holes, (3) the working speed
is slow, (4) the air is polluted with the solvent, (5)
the adhesive force during hole opening (namely during
formation of perforation pattern in the thermoplastic
layer) is low.
On the other hand, there has been also known an
adhesive comprising a wet curable type polyurethane, but
in this case, there are problems that (1) a long time is
required for curing, (2) the pot life is short, (3) hole
opening by the heat mode is difficult, and (4) coating
viscosity is high, whereby thin film coating is
difficult.
In the present invention, as described above, by
using a composition containing (a) a thermoplastic resin
and (b) a monomer and/or a low melting wax as the
ionizing radiation curable adhesive, the above problems
can be solved, and an adhesive with ~reat working speed,
easy lamination, having excellent printing resistance and
also hole opening by heat can be provided.
As the thermoplastic resin in this case, as
described above, a polymer such as polyester,
polyurethane, polycarbonate, epoxy resin, polyvinyl
acetate, polyacrylate, polystyrene, etc. can be used. It
,.,~
12 ~12466
is not preferable for the image that 2 or more double
bonds are contained in one molecule of these molecules.
The molecular weight should be preferably lower as about
1000 to ~everal ten thousands in working and image
characteristics. Also, for the purpose of improving the
heating meltability and easy lamination working, a wax
having a relatively lower melting point, for example, 40
to 150C, can be added.
Among the above thermoplastic resins, a polyester or
a polyurethane may be preferably employed, particularly
one which is solid at normal temperature and has no
crystallinity. Further, in the case of polyurethane, it
should preferably have a high agglomerating force and a
molecular weight of 400 to 10,000 in working
adaptability. Such low molecular weight i9 excellent in
fluidity during heating, and is also excellent in
agglomerating force during normal temperature.
on the other hand, as the monomer, a monofunctional
monomer, for example, (methy)acrylate, (meth)acrylamide
can be used. Printing resistance can be improved by
adding a bifunctional monomer to these monomers, but care
should be paid to~ add no excessive amount of such
monomer, because the image characteristics may be
considerably lowered thereby. Such polyurethane resin
can be synthesized by use of conventional isocyanates,
TDI, MDI, IPOI, etc. with various diols such as 1,4-
butane diol, polyester diol, polyether diol. At the
terminal ends, at most one acryloyl group may be also
introduced with 2-hydroxyethyl acrylate, N-
hydroxymethylacrylamide, etc.
The effects concerning the above embodiments may besummarized as followsi
(1) By use of a thermoplastic resin which has a low
molecular weight and is solid at normal temperature,
fluidity at high temperature can be exhibited to give
excellent perforatability. Also, the viscosity is low
during coating, and there is the advantage of easy
13 1312466
workability in this respect. For this purpose, the
polyurethane resin as described above i5 the most
preferred.
(~) In the case of~a wax with-a low melting point,
fluidity during heating can be improved to improve
perforatability, whereby adhesion between the above
thermoplastic film and the porous base becomes better
during preparation of the stencil of the present
invention.
(3) The monofunctional monomer controls the
viscosity during working, whereby not only working
adaptability is imparted, but it is also suitable for
imparting adhesiveness without imparting perforatability
during printing~ because it can be adequately impregnated
into the porous base.
(4) Because no solvent as in the prior art is
required to be used, where there i9 no problem of
pollution of the air, and also, since the amount
impregnated into the porous support can be reduced, the
pores in the porous base will not be clogged
unnecessarily.
(5) On account of the ionizing radiation curable
type, the production speed is extremely rapid, and also
curing at low temperatures is possible. For this reason,
as compared with the case when the adhesive of the prior
art is employed, the problems caused by heat (for
example, generation of curl) can be eliminated.
(6) On account of the ionizing radiation curable
type of adhesive, adequate crosslinking can be formed in
the adhesive layer. Accordingly, perforatability during
printing will not be impaired by the presence of the
adhesive layer, whereby a heat-sensitive stencil sheet
having excellent printing resistance can be provided.
Adhesion of porous support with thermoplastic film
The heat-sensitive stencil sheet of the present
invention can be obtained by adhering the above
14 1312466
thermoplastic film layer 3 with the base 1 with the above
ionizing-radiation-curable adhesive.
The above ionizin~-radiation-curable adhesive should
be coated rather on the thermoplastic layer 3 than on the
base 1 side. This is because if the ionizing-radiation
curable-adhesive given with adequate fluidity by heating
is applied on the porous base 1 side, the ionizing-
radiation-curable adhesive will be impregnated into the
- base 1, 50 that a good adhesiveness cannot be obtained.
The coating method itsel~ may be any of blade
coating, gravure coating, knife coating, reverse roll
coating, spray coating, ofEset gravure coating, kiss
coating, etc., and is not particularly limited.
The amount coated should be preferably a thickness
of, for example, about O.S to 5 ~m, because heat
perforatability during stencil preparation will be
lowered if the amount is too much, while problems occur
in the adhesive force if it is too small.
Of course, the above coating should preferably be
conducted at a temperature at which the adhesive has
sufficient coating characteristics, for example, under
temperature rises of about 50 to 10~C.
After coating of the above ionizing-radiation-
curable adhesive, the adhesive becomes non-fluid by
cooling, and said adhesive layer retains some
adhesivenes~ or tackiness due to the presence of the
monomer, and both are laminated under this state.
By curing the adhesive layer by irradiation of an
ionizing-radiation from the thermoplastic film layer 3
side or the base 1 side while performing lamination or
after lamination, the heat-sensitive stencil sheet
according to the first embodiment of the present
invention is obtained.
As the ionizing-radiation to be used, electron beam
and UV-ray may be préferably used, but when UV-ray is to
be used, it is necessary to formulate a
photopolymerization initiator in the above adhesive.
1312466
When electron beam is to be used, electron beam may
be irradiated from either surface of the above laminated
product, and when W-ray is to be used, at least one of
the base 1 and the thermoplastic ilm 3 is re~uired to be
transparent, and it is irradiated from the transparent
side.
For irradiation of radiation, the prior art
technique can be used as such. For example, in the case
of electron beam curing, there may be employed electron
beams having an energy of 50 to 1,000 KeV, preferably 100
to 300 KeV, released from various electron beam
accelerators such as the Cocklofwalton type, the
Vandegraph typer the cooscillation transformation type,
the insulatiny core transformer type, the linear type,
the electron curtain type, the dynamitron type, the high
frequency type, etc. In the case of UV-ray curing, W -
ray generated from a light source such as ultra-high
pressure mercury lamp, high pressure mercury lamp, low
pressure mercury lamp, carbon arc, xenon arc, metal
halide lamp, etc., can be utilized.
Although any irradiation method may be useful for
the present invention, electron beam irradiation is more
preferable for curing speed of the adhesive layer,
adhesiveness of the adhesive layer or other reasons.
Stickinq prevention laYer
In forming stencil holes by heating the
thermoplastic film layer 3 by a heating printing means
such as thermal head, etc., depending on the conditions,
there may be the fear that the thermal head may stick to
the thermoplastic film layer 3 to destroy the
thermoplastic film layer 3, or in the case of forming
stencil holes by exposure through a positive original
film, that the positive original film may be stuck.
The sticking prevention layer eliminates the above
drawbacks, and as shown in Fig. 2, a sticking prevention
layer 4 is formed on the thermoplastic film layer 3. The
sticking prevention layer 4 is required to be meltable by
16
1312466
heating and also non-sticky. As such resin meltable by
heating, for example, there can be employed fluorine
resins such as polytetrafluoroethylene,
polychlorotrifluoroethylene, tetrafluoroethylene-
5 hexafluoroethylene copolymer, polyvinylidene fluoride,etc ., epoxy resins , melamine resins , phenol resins ,
polyimide resins, polyvinyl acetal resins, polyvinyl
butyral resins, polyoxyethylene terephthalate,
polyPthylene oxide resins, etc. Further, for the purpose
10 of improving slidability of the sticking prevention layer
4 formed, a surfactant, for example, a fatty acid metal
salt such as a metal salt of stearic acid, palmitic acid,
lauric acid, oleic acid, etc. with lithium, potassium,
sodium, calcium, barium, aluminum, etc., a phosphate
15 ester type surfactant, a polyoxyethylene type surfactant,
or a surfactant such as mono-, di-alkyl phosphate,
tri(polyoxyethylene-alkylether)phosphate, etc. may be
preferably added at a proportion of about 10 to 200 parts
by weight per 100 parts by weight of the above resin to
20 form the sticking prevention layer 4.
The sticking prevention layer 4 comprising the above
resin (and the surfactant) may be formed by dissolving or
dispersing these materials in an organic solvent or water
to prepare a coating liquid and applying this onto the
25 surface of the thermoplastic film layer 3 according to
any desired method. The thickness of the sticking
prevention layer 4 should be preferably thinner, for
example, about 0.1 to 10 ~lm, since if it is too thick,
the heat sensitivity will be lowered to make formation of
30 perforations insufficient. The timing when the sticking
prevention layer 4 is formed is not particularly limited,
but may be ei'cher af ter or during formation of the heat-
sensitive stencil sheet of the above first invention, or
it may also be formed on the raw fabric of the
35 thermoplastic f ilm.
The above sticking prevention layer in the present
invention may preferably comprise a material which is
17 1312466
meltable by heating and has a melting point oE 40C or
higher.
In addition to the embodiments as described above,
the following embodiments can be particularly preferably
employed as the sticking prevention layer in the present
invention.
(1) One in which the sticking prevention layer
comprises a modified product of a silicone resin. Such
silicone modified resin has excellent effect in improving
lubricity, running performance, conveyability together
with the sticking prevention effect.
~ 2) One in which the sticking prevention layer
comprises a resin obtained by introducing urethane bonds,
ester bonds, ether bonds or amide bonds into a silicone
resin.
(3) One in which the sticking prevention layer
comprises a resin, preferably a crystalline polymer,
obtained by modifying a silicone resin with a polyester,
polycarbonate, polyether or epoxy resin.
zn Such modified resin improves adhesiveness with
PET film and solubility, and also has excellent effect in
reducing head dregs which are liable to be generated on
the thermal head. Also, for reducing head dregs, it is
effective to restrict the amount coated to 0.1 to 0.01
9/m2.
(4) One in which the sticking prevention layer has a
further antistatic property.
(5) One in which an antistatic layer is formed on
the sticking prevention layer.
Impartina of antistatic property
Ordinarily, the thermoplastic film layer oE a heat-
sensitive ~tencil sheet is liable to be charged, and
there may sometimes ensue the problem that the printing
paper sticks onto the paper after stencil preparation
during printing, so that smooth printing cannot be
performed.
18
1312466
The sticking prevention layer as described above has
antistatic effect to some extent, but when further
antistatic property iB demanded, it is possible to
formulate a surfactant which has been generally deemed to
have an antistatic effect, selected from among anionic
carboxylates, sulfonates, phosphoric acid derivatives,
cationic alkylamines, amideamines, quaternary ammonium
salts, nonionic polyhydric alcohols, polyhydric alcohol
esters, ethylene oxide adducts of higher alcohol,
alcoholphenol, fatty acid, amide, amine, etc., amphoteric
carboxylate type ~guanidine salt, betaine salt,
imidazoline type, amide type, diamine type, etc.), which
is solid at normal temperature (20C) at a proportion of
200 parts by weight or less based on 100 parts of the
above non-sticky sticking prevention layer. If it
exceeds 200 parts by weight, storage stability and
coatable gas will be undesirably lost.
The sticking prevention layer 4 composed mainly of
the above surfactant may be formed by dissolving or
dispersing these materials in an organic solvent or water
to prepare a coating liquid and applying this onto the
surface of the thermoplastic film layer 3 according to
any desired method.
Also, for imparting excellent antistatic property to
the paper, it is possible to form further an antistatic
layer on the sticking prevention layer 4. The antistatic
layer is formed of a surfactant having the above
antistatic effPct as the main component. Also, for
improvement of durability of that layer, a thermoplastic
resin or a modified product of silicone resin as
described for the sticking prevention layer can be used
with a binder of 100 parts by weight, mixed at a ratio of
200 parts by weight or less of the antistatic agent. The
thickness of such antistatic layer may be preferably
within the range of 0.01 ~m to 5 ~m. With a thickness
less than 0.10 ~mr there is substantially no antistatic
ability, while if it exceeds 5 ~m, stencil preparation
19 1312466
sensitivity will be lowered similarly as in the case of
the sticking prevention layer. Most preferably, the
thickness is in the range of 0.05 to 1 ~m.
In the following, the present invention is described
in more detail by referring to Examples, Comparative
Examples and Use Examples. In the sentences, parts or %
is based on weight unless otherwise noted.
Examples A-l to A-4
Polyurethane resin synthesized
from dipropylene glycol (1 mol),
TDI (2 mol), l-butanol (1.05 mol)
and 2-propanol (1.05 mol)O 7.25 parts
Acrylate monomer (Allonix M5700,
produced by Toa Gosei, Japan) 27.5 parts
The above components were melted and mixed at 85 to
90C to prepare an ionizing radiation curable adhesive
having a viscosity of 700 cps at 85C. The ionizing
radiation curable adhesive is non-fluidizable at 25C,
and has some tackiness.
The above adhesive curable by ionizing radiation was
applied on the surface of a PET film having various
properties shown below in Table 1 according to the direct
method at 80 to 90C at a ratio of 1.0 g/m2, and a porous
tissue paper (PVO39, produced by Krampton Co., 10.8 g/m2)
was laminated on the coated surface by means of a cooled
laminator, followed by ;rradiation of an electron beam of
5 Mrad to obtain a heat-sensitive stencil sheet of the
present invention.
On the opposite surface of the PET film used above,
a sticking prevention layer with a thickness of 0.1 ~m
comprising a mixture of a thermoplastic resin (Vyron 200,
produced by Toyobo, Japan) and a surfactant (Gafac RL-
210) at a weight ratio of ~3:67 was previously formed.
Example A-5
In place of the adhesive curable by ionizing
radiation in Example A-l, an adhesive curable by ionizing
radiation having the following composition was used, and
A
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following othersiwe the same procedure as in Example A-l,
a heat-sensitive stencil sheet of the present invention
was obtained.
Polyurethane resin synthesized from 1,3-
butanediol (1 mol), TDI (2 mol),
isopropanol (1.05 mol), l-butanol
(1.05 mol): 72.5 parts
Allonix M-5700 27.5 parts
viscosity 800 cps l8~C)
ExamPle A-6
In place of the adhesive --curable by ionizing
radiation in Example A-l, an adhesive curable by ionizing
radiation having the following composition was used, and
following otherwise the same procedure as in Example A-l,
a heat-sensitive stencil sheet of the present invention
was obtained.
Polyethylene resin synthesized from
polypropylene glycol MW 200 ~1 mol),
TDI (2 mol), isopropanol (1.18 mol) and
2-hydroxyethyl acrylate (0.25 mol): 80 parts
Allonix M-5600 20 parts
Comparative Examples A-l to A-3
Except for laminating with a porous tissue paper by
using a polyvinyl acetate emulsion type adhesive as the
adhesive at a coated amount of 2.0 g/m2, heat-sensitive
stencil sheets of the Comparative Examples were obtained
in the same manner as in Examples.
comParative Example A-4
Except for laminating with a porous tissue paper by
using a thermosetting urethane type resin as the adhesive
at a coated amount of 2.0 g/m2, the heat-sensitive
stencil sheet of the Comparative Example was obtained.
* trade mar~
21 1312466
Table 1
PET Film Properties
I m
ExampleA-l 2.0 5.6 2417.0
E~ample A-2 2.0 22.0 2609.5
Example A-3 1.5 4.0 2555.2
Example A-4 2.0 16.0 2336.7
E~ample A-5 2.0 ~.6 2417.0
Comp. Exsm.A-l2.0 1.5 2609.0
Comp. Exam. A-2 2.0 3.~ 260 11.0
Comp. Exam. A-3 2.0 5.6 241 7.0
Comp. E~am.A-42.0 ~.6 2417.0
I: thickness (~m)
II: heat shrinkage (%)
III: melting point (C)
IV: melting heat content (cal/g)
~5 Heating shrinkage was measured for a test strip of
200 mm x 200 mm under the conditisns oE 150C and 15
minutes, and represented as an average value of MD and
TD.
Use Example
The sheets of Examples and Comparative Examples were
perforated under the conditions shown below and stencil
printing was performed by use of the sheets to obtain the
results shown in Table 2.
Printing: running speed 3 msec./line, heat content
0.16 mJ
Printing machine:Ricoh Preport SS870, printing
speed 3 speeds
22 1312466
Evaluation was conducted according to the following
methods.
Density: Macbeth densitometer
.Optical.Density ~O.D.)
Resolving power: evaluation when 10 lines/mm of the
test chart of Society of
Electrophotography was printed:
O = discrimination of lines can be easily
performed
~ = discrimination is possible, although
lines are sometimes cut or run
together
x = no discrimination of lines is possible
Printing resistance: number of printed sheets
wherein no sticking appears
Pore area: pore area of printing paper when the area
of one dot of thermal head is made 100%
Overall evaluation: the above items are summarized
O = satisfactory a~ a whole
~ = partially unsatisfactory
x - unsatisfactory as a whole
23 1312466
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24
1 31 2466
Examvle B-l
Polyester resin (Polyester TP-219,
produced by ~ippon Gosei Kagaku,
Japan) 46.7 parts
Acrylate monomer (Allonix M5700,
produced by Toa Gosei, Japan) 23.2 parts
Aliphatic polyester oligomer
(Nipporane 4056, produced by
- Nippon Polyurethane, Japan) 30.0 parts
10 The above components were melted and mixed at 85 to
90C to prepare an adhesive curable by ionizing radiation
and having a viscosity at 85C of 1,250 cps. The
ionizing-radiation-curable adhesive is non-fluidizable at
25C, having some tackiness.
15 The above adhesive curable by ionizing radiation was
applied on the surface of a polyethylene terephthalate
film with a thickness of 2 ~m at 85 to 90C according to
the direct method at a ratio of 1.5 g/m2, then a stencil
paper K (produced by Nippon Shigyo, 10.5 g/m2) was
laminated on the coated surface by use of a cooled
laminator, and then an electron beam of 5 Mrad was
irradiated to ~ive a heat-sensitive stencil sheet of the
present invention.
With a black-and-white positive image film
superposed on the surface of the thermoplastic film layer
of the above heat-sensitive stencil sheet, a flash light
was irradiated to prepare a stencil, which was then
subjected to a stencil printer to give a printed matter
having sufficient printing resistance and resolving
power.
Examples B-2 to B-4 and Comparative Example B-1
~ eat-sensitive stencil sheets of the present
invention and Comparative Example were obtained in the
same manner as in Example B-l except for using an
ionizing-radiation-curable adhesive having the following
composition in place of the ionizing-radiation-curable
adhesive in Example B-l.
'~ ~
~.'
* trade mark
2~ 1312466
Example B-2
*
Polyester TP219 40 parts
Allonix M5700 20 parts
Nipporane 4056 30 parts
Diethyleneglycol dimethacrylate 1 part
Viscosity 800 cps (85C~
Example B-3
Polyester TP219 50 parts
Allonix M5700 50 parts
~-Mercaptopropionic acid0.005 part
Viscosity 900 cps (85C)
Example B-4
Polyester TP219 40 parts
Allonix M5700 20 p~rts
Aliphatic polyester oligomer
(~ipporane N4009, produced by
Nippon Polyurethane, Japan) 30 parts
Ethyleneglycol diacrylate0.5 part
Viscosity gO0 cps (85C)
Comparative Example B-l
Polyester TP219 50.0 parts
Allonix M5700 33.3 parts
Bifunctional urethane acrylate
(Diabeam UK6034, produced by
Mitsubishi Rayon, Japan)16.7 parts
Viscosity 900 cps (85C)
When stencil preparation and printing were performed
similarly as in Example B-l by use of the heat-sensitive
stencil sheets of the above Examples and Comparative
Example, the same excellent results as in Example B-l
were obtained in the case of Examples B-2 to B-4, but in
the case of Comparative Example B-l, because the adhesive
layer was highly crosslinked, its meltability by heating
was deficient, whereby the printed matter had the letters
blurred and also a low density.
Example B-5
A
* trade mark
~6
1 3 1 2466
on the thermoplastic film layer of the heat-
sensitive stencil sheet of the present invention obtained
in Example B-l, a sticking prevention layer with a
thickness of 0.1 to 0.2 g/m2 was formed from the
following composition to give a heat-sensitive stencil
sheet having a sticking prevention layer of the present
invention.
Polyvinyl butyral (Ethlec BX-l,
produced by Sekisui Kagaku, Japan) 50 parts
Surfactant (Plysurf 208, produced
by Daiichi Kogyo Yakuhin, Japan) 50 parts
Toluene 450 parts
Methyl ethyl ketone 450 parts
When stencil preparation and printing were performed
by means of Rocoh Reporter SS 870 by use of the above
heat-sensitive stencil sheet, there occurred no trouble
due to sticking of the thermal head, and a ~ood printed
matter could be obtained with excellent printing
resistance.
ExamDle B-6
On the thermoplastic film layer of the heat-
sensitive stencil sheet of the present invention obtained
in Example B-2, a sticking prevention layer with a
thickness of 0.1 to 0.2 g/m2 was formed from the
following composition to give a heat-sensitive stencil
sheet having a sticking prevention layer of the present
invention.
Acrylate ~Sumipeck B-MHO*
produced by Sumitomo
Kagaku, Japan) 50 parts
Surfactant (Electrostripper AC,
produced by Kao, Japan)50 parts
Toluene 450 parts
Methyl ethyl ketone 450 parts
When stencil preparation and printing were performed
by means of Rocoh Reporter SS 870 by use of the above
heat-sensitive stencil sheet, there occurred no trouble
* tl~e mark
27 1 31 2466
due to sticking of the thermal head, and a good printed
matter could be obtained with excellent printing
resistance.
Example B-7
On the thermoplastic film layer of the heat-
sensitive stencil sheet of the present invention obtained
in Example B-3, a sticking prevention layer with a
thickness of 0.1 to 0.2 g/m2 was formed from the
following composition to give a heat-sensitive stencil
sheet having a sticking prevention layer of the present
invention.
Acrylate ISumipeck B-M~O, produced
by Sumitomo Kagaku, Japan) 5Q parts
Surfactant ~Emulgen 108,
produced by Kao, Japan)50 parts
Toluene 450 parts
Methyl ethyl ketone 450 parts
~ hen stencil preparation and printing were performed
by means of Rocoh Reporter SS 870 by use of the above
heat-sensitive s~encil sheet, there occurred no trouble
due to sticking of the thermal head, and a good printed
matter could be obtained with excellent printing
resistance.
Examples D-l and D-3
~eat-sensitive stencil sheets of the present
invention were prepared in the same manner as in Example
B-5 except for using sticking prevention layers
comprising the following compositions in place of the
sticking prevention layer in Example B-5.
Exam~le D-l
Polyethylene glycol 6000 (produced
by Wako Junyaku Kogyo, Japan) 2 mol
Silicone type diol (X-22-160AS produced
by Shinetsu Kagaku Kogyo, Japan) 1 mol
4,4'-Diphenylmethane diisocyanate
(produced by Nippon Polyurethane
Kogyo, Japan) 2 mol
* trade mark
28 1312466
With the above formulation ratio, and by use of
dibutyltin laurate as the catalyst, the reaction was
carried out at 60C in methyl ethyl ketone, and then the
reaction mixture was diluted to 1.25 wt~ to provide a
sticking prevention agent. This was coated and dried on
a thermoplastic film by Myer bar No.10.
Example D-2
Polyester diol (PlaxelH-lP, produced
- by Dicel Kagaku Kogyo K.K., Japan) 1.3 mol
Silicone type diol 5X-22-160AS
produced by Shinetsu Kagaku
Kogyo X.K., Japan) 1.0 mol
4,4'-Diphenylmethane diisocyanate
(Produced by Nippon Polyurethane
Kogyo K.X., Japan) 1.15 mol
The same experiment as in Example D-l was practiced.
Example D-3
Preparation was performed in the same manner as in
Example D-2 except for adding 20 parts of ~ntistecks C-
200X as the antistatic agent per 100 parts to provide asticking prevention agent.
Reference ExamPles D-l to D-3
For the purpose of comparing the functions of the
sticking prevention layers, those having the sticking
prevention layers shown below were prepared, and their
characteristics were examined.
Reference Example 1
(no sticking prevention layer formed)
Reference Example 2
Stickinq prevention layer
Phosphate type surfactant
(Plysurf A208S, produced by Daiichi
Kogyo Seiyaku, Japan, m.p. 7C) 1 part
Toluene 40 parts
Methyl ethyl ketone 40 parts
(coating thickness on drying 0.1 ym)
Reference Example 3
A
* trade .nark
;
1312466
Gafac RL-210 1 part
Vyron 2000* 5 parts
~oluene 240 parts
Methyl ethyl ketone240 parts
(coating thickness on drying 0.1 ~m)
: 20
,~ * trade mark
1312466
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31 ~312466
The heat-sensitive stencil sheet of the present
invention can be applied widely as the heat-sensitive
stencil sheet to be used for the stencil preparation
method by use of a printing perforation system using a
heating printing means such as a thermal head.
