Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to a lightsafe
masking film and, more specifically, to a composite, lightsafe
masking film to be used as an original copy having a transparent
pattern in the photomechanical reproduction process.
One known lightsafe masking film of this type is
composed of a plastic film substrate and a peelable, lightsafe
layer provided thereon. When a desired cutting line is formed
on the lightsafe layer manually or with a suitable automatic
cutting device and when the cut portion is removed by peeling,
there leaves a desired transparent pattern on the masking film.
Since the cutting line formed by means oE a cutting
blade or knife having a keen edge is very thin and, therefore,
is unclear and illegible, succeeding peeling works become
laborious and encounter a considerable difficulty.
The present invention has been made to overcome the
problem of the conventional lightsafe masking film and is
contemplated to provide a lightsafe masking film comprising a
substrate formed of a plastic material, and a lightsafe layer
peelably provided over the surface of said substrate and
containing a fluorescent substance so that a cutting line formed
on said lightsafe layer fluoresces under illuminated conditions
to form a legible pattern.
In another aspect, the present invention provides a
lightsafe masking film comprising a substrate formed of a
plastic material, a lightsafe layer peelably provided over said
substrate, and a fluorescent layer containing a fluorescent
substance and provided between said substrate and said lightsafe
layer or over said lightsafe layer, so that a cutting line
formed in the lightsafe layer fluoresces under illuminated
conditions to form a legible pattern.
The present invention will now be described in detail
below.
Lightsafe masking film according to the present
invention is comprised of a substrate formed of a plastic
material having provided thereon a peelable, lightsafe layer.
Any plastic material conventionally used in the
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substrate of known lightsafe masking film can be used for the
purpose of the present invention. Iransparent plastic films
such as polyethylene terephthalate films, polybutylene
terephthalate films, polyoxybenzoate films and polycarbonate
films may be suitably used as the substrate. Both stretched and
unstretched films may be used. The thickness of the film is
generally in the range of 20-300 ~m.
The substrate is overlaid with a peelable, lightsafe
layer. The lightsafe layer is generally comprised of (a) a
binder such as a synthetic rubber, e.g. a nitrile rubber, or a
synthetic resin, e.g. a vinyl chloride/vinylidene chloride
copolymer or a vinyl chloride/vinyl acetate copolymer, and (b) a
lightsafe or light-shading substance such as a colorant, e.g. an
organic or inorganic dye or pigment. The lightsafe substance is
preferably so selected as to provide a lightsafe layer capable
of preventing the passage of a light having wavelength of about
300-550 nm therethrough. Any binder and any lightsafe substance
customarily employed in lightsafe layers of known lightsafe
masking films may be used for the purpose of the present
invention. The lightsafe layer may further contain one or more
additives used in conventional masking films, if desired. The
lightsafe layer generally has a thickness of 20-50 ~m,
preferably 25-40 ~m.
In one embodiment according to the present invention,
a fluorescent substance is incorporated into the lightsafe
layer. By this, when the lightsafe layer is cut at the time of
the formation of a desired transparent pattern on the masking
film, the cut line becomes clear and legible under illuminated
conditions because of the fluorescence of the fluorescent
substance. The formation of the clear fluorescent line along
the cutting line is considered to be attributed (a) to an
increased intensity of a light to be absorbed by the fluorescent
substance because of irregular reflection on the edge of the
cutting line and (b) to an increased density, at the cutting
line, of the Eluorescent substance exposed to the light.
As the fluorescent substance, there may be used a
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substance capable of absorbing a visible or ultraviolet light
and of fluorescing a light with a wavelength of a visible
region, preferably a substance capable of absorbing purple, blue
or green visible light and of fluorescing a light with a longer
wavelength than the absorbed light. Organic or inorganic
fluorescent dyes or pigments may be suitably used. Illustrative
of suitable fluorescent substances are organic ones such as
Uranine-series, Eosine-series, Rhodamine-series, Thioflavine-
series, Trypaflavin-series, Auramine-series and coumarin-series
flurorescent dyes.
; The fluorescent substance is preferably used in the
form of a fine powder or a paste. The amount of the fluorescent
substance in the lightsafe layer is generally in the ragne of 2-
50 % by weight, preferably 5-30 ~ by weight. The by weight
ratio of the fluorescent substance to the lightsafe substance is
preferably in the range of 5:95 to 80:20, more preferably in
the range of 20:80 to 60:40. The masking film of the above
embodiment may be obtained by applying a coating composition
containing the binder, lightsafe substance, fluorescent
substance, etc. over the surface of the substrate, followed by
drying the coated layer.
In another embodiment according to the present
invention, rather than incorporating the fluorescent substance
into the lightsafe layer as in the above embodiment, a layer
containing such a fluorescent substance is formed as an overcoat
layer over the surface of the lightsafe layer or as an undercoat
layer ketween the substrate and the lightsafe layer. In this
embodiment,~too, when a cuting line is formed in the lightsafe
layer at the time of the formation of a transparent pattern on
the masking film, the cutting line fluoresces strongly to
permit easy recognition thereof, thereby making the succeeding
peeling and removing works easy.
The overcoat or undercoat layer may be composed of a
binder such as used in the lightsafe layer and the fluorescent
substance. The thickness of the undercoat or overcoat layer is
generally 0.5-25 um, preferably 2-20 ~m. The overcoat layer may
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be formed by applying a coating composition containing
fluorescent substance and the binder over the surface of the
lightsafe layer. The undercoat layer may be formed by applying
a similar coating composition over the surface of the substrate,
followed by the formation of the lightsafe layer over the
undercoat layer.
The following examples will further illustrate the
present invention.
Example 1
Preparation of Coatinq Composition:
A coating liquid having the composition shown in Table
below was prepared:
IngredientContent (part by weight)
Lightsafe substance *1 2
Fluorescent substance *2 2
Acrylonitrile-butadiene
rubber 6
Vinylchloride-vinylidene
chloride copolymer 20
Toluene 35
Methyl ethyl ketone 35
*1: OIL YELLOW 101 (Trademark) manufactured by Orient
~Chemical Industry Co., Ltd., Japan; color: yellow
*2, MPI-503 (Trademark) manufactured by Nihon Keiko
30Kagaku Kabushiki Kaisha, Japan; color: red
Preparation of Maskinq Film:
The above coating composition was applied over the
surface of a substrate of polyethylene terephthalate film
(thickness: 100 ,um) and dried to obtain a lightsafe layer having
a thickness of 25 um. The lightsafe layer was orange in color
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and was capable of preventing the passage of a light with a
wavelength of 300-490 nm therethrough. When the 1ightsafe layer
on the substrate was cut with a knife, the cutting line strongly
fluoresced and became pink, permitting easy identification of
the cutting line.
Example 2
A first coating liquid having the same composition as
that in Example 1 except that no fluorescent substance was
incorporated was prepared and applied in the same manner as in
Examle 1 over the surface of a polyethylene terephthalate film
substrate, thereby forming a peelable, lightsafe layer having a
thickness of 13 ~m on the surface of the substrate. Then, a
second coating liquid composed of 2 parts by weight of the
fluorescent substance used in Example 1, 6 parts by weight of a
acrylonitrile-butadiene rubber, 25 parts by weight of a vinyl
chloride/vinylidene chloride copolymer, 36 parts by weight of
toluene and 36 parts by weight of methyl ethyl ketone, was
applied to the surface of the lightsafe layer and dried to form
an overcoat layer having a thickness of 12 ~m. The resulting
masking film was capable of preventing the passage of a light
with a wavelength of 300-490 nm therethrough. When the
lightsafe layer was cut with a knife, the cutting line strongly
fluoresced and became pink, permitting easy identification of
the cutting llne.
Example 3
Over a polyethylene terephthalate film substrate, the
second coating liquid used in Example 2 was applied in the same
manner as that in Example 2 to form an undercoat layer having a
thickness of 12 ~m. Then the first coating liquid used in
Example 2 was applied on the surface of the undercoat layer to
form a lightsafe layer having a thickness of 13 ~m. The
resulting masking film was capable of preventing the passage of
- 35 a light with a wavelength of 300-490 nm therethrough. When the
lightsafe layer was cut with a knife, the cutting line strongly
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fluorescecl and became pink, permitting easy identification of
the cutting line.
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