Note: Descriptions are shown in the official language in which they were submitted.
1049389
The present invention relates to a novel masking fiIm and a method
for preparing the same.
The present invention provides a masking film which has opacity to
light that is active to expose photo-sensitive materials and which has trans-
parency to other visible light, which comprises: a) a substantially trans-
parent supporting plastic film, at least one surface having been treated by
roughening or oxidation; b) a coloured resin layer adhered on said treated
surface through an adhesive undercoating; and c) a strippable film having at
least one strippable surface adhered to said coloured resin layer through a
pressure-sensitive adhesive.
Purthermore, the present invention provides a laminate which is an
intermediate for the above described masking film which has opacity to light
that is active to expose photo-sensitive materials and which has transparency
to other visible light, which comprises a substantially transparent supporting
plastic film in which at least one surface is roughened or oxidized, and a
coloured resin layer adhered on said surface through an adhesive undercoating.
The objects and advantages of the invention will become apparent
in light of the following explanation.
The masking film which is provided by the present invention is
useful in photoengraving. Photoengraving is generally conducted by a plate-
making process wherein artwork is transferred to a photo original plate
having masking properties.
One of the masking films of the prior art provided a laminate which
was prepared by applying a rubber pressure-sensitive adhesive agent upon a
strippable sheet of glassine paper, wax paper or vinyl chloride resin. The
masking film carried a nitrocellulose lacquer as a masking layer (e.g. United
States Patent No, 2,576,491). Another prior art development comprised a poly-
ethyleneterephthalate film applied to a vinyl chloride resin containing a dye.
Formerly such masking films had the disadvantage that they were
subject to variance of their dimensions under the influence of temperature
and humidity in the ambient atmosphere. Furthermore, they exhibited an un-
desired expansion and contraction due to the heat of the light source which
1~ ~ -1- ~
~0d~9389
is generally used in the preparation of a photo original plate. The masking
films of the prior art suffered from a lack of thermal and hygroscopic
dimensional stability. Exact duplication of a picture, using the masking
- la -
~ql
1049389
film of the prior ar~ results in a poor resolution of the image due to the
comparatively thick nitrocellulose layer. Also, the pattern which is separ-
ated from the strippable layer is easily broken and lengthened.
The masking film of the prior art comprising a polyethylenetere-
phthalate film carrying a vinyl chloride resin containing a dye, suffers from
the fact that it is difficult to adhere the vinyl chloride resin layer on
artwork, a silk screen, or a photographic plate Furthermore, there was a
problem in the lack of durability of the stripped layer.
The present invention seeks to provide a novel masking film which
has opacity to the light of a wave length which is active to expose photo-
sensitive materials and which has transparency to other visible light and
overco~es the trawbacks of the prior art.
The masking film of the invention is prepared by laminating to the
treated surface of a substantially transparent supporting plastic film, in
which at least one surface is roughened or oxidized, a colored resin layer
through an adhesive undercoating, and adhering to the resin layer a stripp-
able surface of a film having at least one strippable surface through a
pressure-sensitive adhesive layer.
The main characteristic of the masking film of the invention is
its excellent dimensional stability, such as thermal dimensional stability,
hygroscopic dimensional stability, dimensional stability on standing, and the
like~ Hhile it is sasy to remove the release film ti.e. the strippable
surface) from the masking film, the remainir.g film will retain its shape
and adherence properties. The masking film of the present invention is
suitable for re-use for purposes of amendment, such as arrangement of ca~era
ready art, or other objects. Furthermore, the masking film of the invention
is useful in the exact reproduction of artwork. In addition, the film hss
the industrial advantage that it ~ay be easily manufactured using commercially
available machi~es.
The supporting plastic film to be used in accordance with the
present inventi~n may be oriented or non-oriented polyester or polyether
films such as polyethyleneterephthalate, polybutyleneterephthalate, poly-
--2--
.
1049389
terephthalate, poloxybenzoate or polyisobutyleneoxide film and the like; homo-
polymeric or copoly~eric films such as polycarbonate, polystyrene, nylon-6,
nylon-66, nylon-10, nylon-ll or nylon-12 film and the like; polyethylene, poly-
propylene, polybuten-l or poly(4-~ethylpentene-1) film or copolymeric film in
which the main components are these polyolefines.
It is desirable to use as the supporting plastic fil~ a biaxially
oriented polypropylene, polyethyleneterephthalate or a nylon~-12 film which is
sbout 6-200 microns in thickness, most preferably 9-50 microns, which is sub-
stantially transparent.
These plastic films are used according to the invention after a con_
ventional roughening or oxidizing treatment on at least one surface of the film.The film surface ~ay be oxidized by a corona discharge treatment or a roughen_
ed using a sand-blasting or a solvent etching treatment.
The colored resin layer is adhered on the treated surface of the ;.
above mentioned pl~stic film with an adhesive undercoating.
The undercoatings which may be used in carrying out the invention
are those which strongly adhere to both the plastic supporting film and the
i colored resin layer, are transparent and not coloret, ant have good thermal
ant hygroscopic stability.
The following have been found to be suitable adhesive undercoatings;
a mixturo of an isophthalic polyester, butyl-etherified melamine and a small
amount of sulfuric acid; a mixture of an isophthalic polyester and a prelimin-
ary condensate of a polyol and a diisocyanate having remaining active isocyan-
ate groups; and a mixture of a copolymer of vinyl chloride and vinyl acetate
with a preliminary condensate of a polyol with a diisocyanate having remaining
active isocyanate groups.
When a polyolefine, polystyrene, polyester or polyether plastic film
is used as the supporting plastic film it is desirable to use a mixture of an
isophthalic polyester, butyl-etherified melamine and a small amount of sulfuric
acid as the adhesive undercoating.
The isophthalic polyester in the above mixture is a condensate of
isophthalic acid with a diol, in which the diol may be a saturated alcohol,
such as ethylene glycol, propylene glycol or the like or an unsaturated
*Trademark 3
1049389
alcohol such as butenediol, hexenediol or the liko
The butyl-etherified melamine is obtained by reacting ~elamine
with formaldehyde to giVR a melamine-formaldehyte condensate ant subsequently
butyl-etherifying this product with a large amount of butanol. The resulting
product is soluble in benzene. The product is used as a solution in a ~ol-
vent mixed with toluene and ethyl acetate by replacing the ~edium of butyl-
etherification with said solvent.
The preferred weight ratio of isophthalic polyester to butyl-
etherified melamine is from about 2:8 to 9:1, most desirably from about 6:q
to 8:2. Sulfuric acid is added to said mixture as a hardening catalyst in
an amount from about 0.5 to 1 part per 100 parts by weight of the butyl-
etherified melamine. This results in a well hardened coat at the temperature
of 80-150 C.
It is possible to add to the undercoating other ingredients such as
an antistatic agent, antioxidant, ultraviolet ray absorbent, heat stabilizer,
dye or pigment, waxes or inorganic fine powders as an antiblocking agent or
lubricant, as long as they will not have any unfavorable influence on the
binding ability of the undercoating. Such undercoating shoult be applied
as tbin as possible, preferably in the thickness of about 0.5-3 microns.
The reSinQ used for the formation of the coloret resin layer may
.
be nitrocellulose, cellulose acetate, cellulose acetate propionate, cellulose
acetate butylate, ethoxy cellulose, viny~ chloride resin, styrene resin,
acrylic acid or acrylic ester resin, polyester resin, polyurethane resin,
polyamide resin, amino resin, aminoalkyd resin and the like. Colorants, in
the form of colored lacquer or ink, are added to the resins.
The opacity of the masking film to the light that is active to
photo-sensitive materials and has transparency to other visible light may be
adjusted by the colored resin layer. For exa~ple, to mask for blue sensitive
material, the colored resin layer should be deep blue, deep green, deep yellow-
orange or deep red. Por an ortho sensitive material, the resin layer shoultbe deep orange or deep red. For a semi-panchro~atic material, the resin layer
should be deep green.
--4--
~q
~049389
The most preferred resin used 85 the colored resin layer is nitro-
cellulose, such as a conventional nitrocellulose lacquer (SS type cotton or
RS type cotton) having a viscosity from 1/8 to 120 seconds. When a nitro-
cellulose having a ~iscosity less than 1/8 second is used, the layer coated
from the nitrocellulose lacquer is brittle. When the viscosity is over 120
seconds, application of the lacquer becomes difficult.
As colorants for nitrocellulose dyes or a mixture of dyes and pig-
ments may be used. Dyes are not limited in their color tone or structure,
so long as they are oil soluble and compatible wi~h nitrocellulose ~or other
resin used) and have minimized variance of color tone as a result of exposure
to heat ultraviolet rays. However the pigment must have sufficient masking
properties for the masking film to be preparod.
An organic or inorganic pigment may also be used if it does not have
any unfavorable influence on the transparency of the nitrocellulose coating
for light of a desired wave length range The extinction of light as it passes
through the colored resin layes ~ay be controllet by both the amount of dye in
this resin layer and the thickness of the resin layer.
It i5 possible to add other ingredients to the colored lacquer used
to fo D the coloret resin layer, such as an antioxidants, heat stabilizers,
ultraviolot ray absorbers, antistatic agents, plasticizers, antiblocking agents
and lubricants when thoy are neeted. The method for applying said lacquer may
be any method, such as using a rotogravure printing machine, roll coater, bar
coater, spray gun or dipping coater. A coloret lacquer of nitrocellulose is
adhered to the roughenet or oxidized surface of the plastic film through the
undercoating, When other resins are used, colored lacquers may be prepared
in a maMer analogous to nitrocellulose,
It is desirable to apply the colored resin layer as thinly as
possible, e.g. the thickness of the layer after evaporation of solvent should
be 3-10 microns. Accordingly, the concentration of the colorant in the
lacquer should be high. For example, the colorant may be preferably from
about 80-120 parts by weight per 100 parts by weight of resin.
The undercoating to be uset in the invention improves the adhesion
~.~
1049389
between the plastic film and the colored resin layer. In addition, when the
masking film is used for photoengraving, there is no problem resulting from a
shift of the masked wave length range by reason of color change in the colored
layer or other layers. The plastic film set on said ~ndercoating is excellent
in thermal resistance, resistance to weathering, hot water resistance and the
like.
A pressure-sensitive adhesive layer may be applied to said colored
resin layer. Suitable pressure-sensitive adhesives which may be used, are
rubber or other transparent pressure-sensitive adhesives, which may contain
the same dyes or pigments as are used in coloring the nitrocellulose lacquer,
unless they give an unfavorable influence on pressure-sensiti~o adhesiveness.
A laminate having masking properties may be prepared by pressing
and adhering the adhesive surface of the pressure-sensitive adhesive surface
of the masking film of the invention to the strippable surface of a stripp-
able plastic film.
Altornatively, the laminate may be prepared by apply~ng and trying
a pressure-sensitive adhesive layer on a transparent strippable film and then
laminating this to the coloret resin layer of the masking film of the
invention,
The transparent strippable film has as its base a film which is
similar to the plastic film used as the support in the invention as explained
above has on at least one side a strippable proporty. The strippable property
is obtainet by using a release agent, which ~ay be a silicone resin, a cop-
olymer of methacrylic acit or acrylic acid having a long side chain such as
polystearyl acrylate or waxes ~e.g. wax release agent referred to in Japanese
Patent Publication No. 3382/1959), or any other agent that gives a transparent
strippable coat. Ho~ever, it is especially preferred to use a vinylsilane
silicone resin along with an organic peracid fro~ the viewpoints of the
strippable property and transparency. It is recom~ended to apply, dry and
cure this combinat~on on the strippable plastic fil~ by which silicone resin
crosslinking is carried out.
In the masking film of the invention it is preferable that the
--6--
~/
., -- - , ~
1049389
thickness of all layers, excluding the transparont strippable film, is about
15-70 ~icrons, desirably about 15-35 microns. The thickness of the layers,
excluding the strippable fil~ and the support fil~, is most preferably in ~he
range of about 5 5-20 microns.
The invention will be illustrated by the following Examples, without
being limited to them.
Example 1
An isotactic polypropylene film, having a melt index of 2.0 and
being oriented in machine tirection and transverse direction seven times to
give a biaxially oriented polypropylene film having thickness of 18 microns,
was subject to a corona-discharged to obtain a film having a contact angle of
the discharged treatment surface to water of 70C.
The resulting film was coated with the following composition:
Isophthalic polyester 50 parts
Butyl-etherified melamine 50 parts
Sulfuric acid 0.5 parts
Ethyl acetate 420 parts
Toluene 210 parts
Methyl ethyl ketone 210 parts
Methyl alcohol 58.4 parts
Stearic acid amide 1.0 parts
Fine silica powder 0.1 parts
taverage dia~eter: 0.3y)
The coating was applied using a gravure coater and the coated film
was dried for about 1.5 min. in an oven at 120C to give a film in which the
thickness of the coated layer was ly. The thickness of both layers was l9y.
Said film showed transmission of 90%. There was no noticeable change in its
adhesiveness and appearance after being dipped in boiling water for 30 min.
The film was not discolored after irradiation for 150 hrs. with ultraviolet
rays.
The following composition was prepared as the colored nitrocellulose
lacquer:
-
10493~9
Nitrocellu~ose (SS, 1/2 second)150 parts
Red dye (Neozaphon red) 75 parts
Yellow dye tNeozaphon yellow) 75 parts
Methyl ethyl ketone 460 parts
Isopropyl alcohol 40 parts
Toluene 200 parts
The nitrocellulose lacquer was applied to the undercoating of thepolypropylene film by a gravure coater and driet to remove the solvent re-
sulting in a deep red film in which the thickness of the coated nitrocellulose
layer was S~ and the total thickness was 24~. The transmission of said film,
using a Beckmann spectrophotometer, was 0~ at a wave length from 200 to 590
millimicrons. The passage of light was recorte~ at a wave length greater
than 590~.
On the surface of said red nitrocellulose layer an acrylic adhesive
was applied so as to provide a dried athesive layer 7~ thick The resulting
prossure-sensitive masking film hat a total thickness of 31~.
Urethane wax was applied on a biaxially oriented polypropylene base
fil~ to provide a coated layer 0.2~ thick. The resulting strippable fil~
having a total thickness o 110~. The masking film and the strippable film
were laminatod together by pressing the strippable film against the pressure-
sensitivo athesive surface of the masking film, with the urethane wax layor
therebetween. It was found that said laminate possossod excellent hygroscopic
dimensional stability, since variance in its di~ension was ~ 0.001~ turing a
change in relative humidity from 0~ to 90~ (or 90~ to 0~ reversely) at ~0C
as measured by a cathetometer.
The laminate was then heated in an oven at different temperatures
for 10 min. and its thermal dimensional stability was measured relati~e to
variances of dimension before and after heat treatment, as reported belo~;
~ Variance rate of dimension
.
50C ~ 0.00
60C ~ 0.01~
70C ~ 0.02%
-8-
1049389
The pressur~-sensitive adhesive ~asking film of the laminate was
peeled from the strippable film to prepare a strip 15 ~D x lS0 mm which showed
a tensile serength of 4,5 Kg/~ and an elongation of 12~ a~ measured with a
tensile tester.
The la~inste was put on an artwork and the ~asking layer was cut in
the shape of the artwork. Those parts of the masking layer not corresponding
to the artwork were re~oved from the laminate to give a masking film having
a pattern idontical to the artwork on a transparent strippable film.
The laminate carrying the pattern was closely attached to "Fuji
lith-ortho film type F" of Fu~i Photo F~lm Co., Ltd. and development was con-
ducted after exposing it for l min, to the light of a xenon lamp, It was
found that the film possessed an excellent shading property, with no photo-
sensitive development on the part corresponding to the pattern in the masking
fil~,
Example 2
A solution containing vinylsilane silicone resin and a small amount
of benzoyl peroxide as a hardening agent was applied to a biaxially osientet
polypropylene film of 120~ and dried and curet for 3 min, at 130C to obtain
a transparent strippable film in which the thicknoss of the driet coatet
29 layer was 0,1~ ant the total thickness was 120~, This transparent strippable
film was laminated to the masking film of Example 1 in the same way as in
Examplo 1.
The masking layer of sait laminate was cut in the outline of an art-
work and the resulting masking pattern was, utilizing its adhesiveness, adhered
to PS plate under the trademark of "PLANOSUPPER POSITIVE GRENC~AT" of Fuji
Photo F~lm Co., Ltd. which was exposed for 6 min. to a xenon lamp and etched,
It was found that no photo image was formed on the part corresponding to the
pattern in the ~asking film,
Peeling tests were conducted by adhering the masking layer from this
Exa~ple and the masking film cut from the laminate of Example 1 to the photo-
sensitive emulsion face of a photo-sensitive film and allowing them to stand
for 24 hrs, at room te~porature and then stripping off the ~asking layers. It
,~1
iO49389
was found that the ~asking film of this Example was more easily stripped than
that of Exa~ple 1, The peeling strength at 90C of the masking film of this
Example was 1~0 g/ 25 ~m, while that of the ~asking film of Exa~ple 1 was
320 g~ 25 ~,
Examples 3-9
The fol~owing undercoating compositions were applied to the treated
surface of a biaxially orientet polyethyleneterephthalate film which hat been
subj0ct to corona-tischarging or sand-blasting treat~ent, using a gravure
printing ~achine set on gravurecylinder of line numbers being 150 lines ant
teepness of cell being 35~. The thickness of the undercoating was 2~ in each
product,
-TABLE I
TEST THICKNESS OP PRE-TReATMENT UNDERCOATING
NO. POLYETHYLENE COMPOSITION
TEREPHTHALATE
PILM
1 6~ corona-discharge A 100 parts S 400 parts
B 10 parts
2 6~ corona-discharge C 100 parts S 400 parts
B 15 parts
3 9p corona-dischasge A 100 parts S 400 parts
B 10 parts
4 9~ corona-discharge C 100 parts S 400 parts
B 15 parts
12~ corona-discharge A 100 parts S 400,'parts
B 10 parts
6 12~ sant-blast on C 100 parts S 400 parts
one surface B 10 parts
7 20~ sand-blast on A 100 parts S 400 parts
both surfaces B 10 parts
Notes:
"S" means a ~ixture of methyl ethyl ketone and toluen~
"A" ~eans VINYLITE VAGH a trade mark for a copoly~er of vinyl ~,
chloride/ ~inyl acetate/ vinyl alcohol in weight ~atio of 91:4:5 of Union
Carbide Co " Ltd,
- "C" means TOYOBO STER RESIN a trade Mark for a polyester resin
of Toyobo Co., Ltd.
- 10-
.. .. . . :
1049389
"B" means a condensate of toluenediisocyanate and hexantriol of
Japan Polrurethane Co,, Ltd. haYing a trade mark of CORONATE L.
The following co~position was prepared a~ a vinyl chlorite color
lacquer:
VINYLITE VMCH 150 (parts by weight)
Ret dye (Neozaphon ret) 75 (parts by weight)
Yellow tye tNeozaphon yellow)75 (parts by weight)
Methyl ethyl ketone 460 tparts by weight)
Toluene 240 tparts by weight~
~VINYLITE VMCH is a trade mark for a copolymer of vinyl chloride/vinyl
acetateAmaleic acit in weight ratio or 86:13:1 of Union Carbide Co., Ltt.
Deep ret films having a thickness of 5~ were prepared by applying
the above color lacquer on each of the undercoatet films of Test Nos, 1-7
and trying them for 30 seconds in an oven at 70C to evaporate the solvent.
The characteristics of the resultant red films were as follo~s:
TABLE II
Example Base Film Adhesive- Appearance Variance Rate in
No. ness of Dimension t60C)
Color
Lacquer
Control No pre-treat- Non- Red ~ 0.01 t~)
ment ~ under- athesion transparent
coating 12
of PET
3 Test No. 1 film Excellent Red _ 0.05 (%)
transparent
4 Test No. 2 film Excellent Red - 0.05 t%)
transparent
Test No. 3 film Excellent Red ~ 0,02 t~)
transparent
6 Test No. 4 film Excellent Red ~ 0,02 t%)
transparent
7 Test No. 5 film Excellent Red 1 0.01 t%)
transparent
8 Test No. 6 fil~ Excellent Red ~ 0.01 t%)
transparent
9 Test No. 7 film Excellent Red se~ 0.005 (~)
transparent
- --11--
~q
1049389
Note:
~PET~ is a biaxially orientet polyethyleneterephthalate fil~.
Transparency of the red films was measured using a Beckmann spec-
trophoto~eter. Their transparency was 0~ in the wave len~th range from 200
to 590 m~ while light passed through the film at wave lengths greater than
590 m~.
Then lamina~es ~ere prepared by applying an acrylic adhesive on
the surface coated with the vinyl chloride lacquer so as to provide a 7~
thick dried coated layer, and pressing each of the resulting masking films
having pressure-sensi~ive adhesiveness with a strippable film of 125~ thick-
ness which was obtained by applying a urethane wax on a biaxially oriented
polyethyleneterephthalate film as a base film to provide a coated wax layer of
about 0.2~ of thickness.
Among these lsminates, the colored layers in the films of Examples
3-6 could be cut easily with a razor in the outline of an artwork to give a
pattern. Also, the colored layers in the films of Exa~ples 7-9 could be
smoo~hly cut with a ruby or diamond cutter.
It was possible to write or draw ~pon the film of Example 9 with
a pencil before cutting because the outer surface of the support film was
roughened.
The colored layers, except for Examples 3 and 4, were easy to handle
and could adhere to an object to be masked and then peeled away.
Example 10
A colored film was prepared by applying the colorant as used in
Example 3, using the undercoating of Test No. 2 in Table I, on a cast nylon-12
which film has been subject to corona-discharge, having a thickness of 18~.
The film was made from a polymer having an average molecular weight of 100,000
obtained by polymerization of laurolactam. A transparent strippable film
having a total thickness of 120~ was prepared by applying a solution contain-
ing vinylsilane silicone resin as the main component and a small amount ofbenzoyl peroxide as hardening agent on a biaxially oriented polypropylene film
of 120~ and drying and curing for 3 min. at 130C.
. ~ ,
10493~S9
A laminate ~as prepared by applying the following pressure-sensitive
adhesive co~position to said transparent ~trippable film so as to provide a
coated layer of 7~ thickness after drying, and pressing the thus-coated poly-
propylene film over the above coloret nylon-12 film:
ALLON S-1602 (acrylic adhesi~e, 100 parts by weight
Toa Chem, Ind. Co., Ltd.)
CORONATE HL 2 parts by weight
Methyl ethyl ketone 100 parts by weight
No
"CORONATE HL" is a preliminary condensate of urethane prepared
from hexamethylene-diisocyanate,
The laminate was easily separated into a transparent strippable
film layer and a pressure-sensitive adhesi~e masking film layer, the latter
of which possessed the following characteristics:
TABLE III
Control Exa~ple 10
Pre-treat~ent no corona-discharge
Undercoating no Test No. 2 composition
in Examples 3-9
Athesi~eness of poor excellent
Colored Lacquer
Variance Rate in 60C ~ 0.02 ~ 0.02
Dimension of
Masking film layer 70C ~ 0.07 ~ 0.07
80C - 0.10 -0.10
The masking layer of said laminate was cut in the form of an art-
~ork and the resulting masking pattern was adhered to a PS plate as describet
in Example 2, which was exposed for 6 min. to a xenon lamp and etched. No
photo-image was formed on the part corresponding to the pattern of the
~asking film.
Trademark
_13-
,rl
