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This invention relates to a light-shielding screen and a process for
producing the same. More particularly, the present invention is concerned
with a light-shielding screen which can be advantageously employed for
extraneous light rays-shielding in various image-indicating devices such
as television receivers, various displays having a CRT (cathode-ray tube)
and related to computers, various indicators such as indicators for
instruments, traffic signals and the like, and for shielding light rays in
the unnecessary direction emitted from various image-indicating devices,
thereby to adjust the visible angle range of the image from various
image-indicating devices.
Extraneous light rays are often incident on the faces of various
image-indicating devices and reflect therefrom, leading to the
deterioration of an image projected. In order to prevent the deterioration
of the projected image due to the reflection of extraneous light rays,
various light-shielding screens have heretofore been proposed. For
example, Japanese Patent Application Publication No. 55-7562 and U.S. Pat.
No. 2,053,173 disclose a light-shielding screen comprising a plurality of
transparent plastic layers, a plurality of light-reflecting layers and a
plurality of light-shielding layers which are put on top of each other.
Such light-shielding screens are produced by a process which comprises
superimposing transparent layers, light-reflecting layers and
light-shielding layers on top of each other to form a block consisting of
laminated layers and slicing the resulting block at a predetermined angle,
usually perpendicularly, relative to the laminated layers. Japanese Patent
Application Laid-Open Specification No. 53-78114 discloses a
light-shielding screen produced by a method which comprises piling up a
plurality of transparent sticks each having a hexagonal cross section and
having on its longitudinal side a light-absorbing or a light-reflecting
layer to form a block and slicing in a predetermined thickness the
resulting block perpendicularly relative to the longitudinal axis of the
piled sticks.
However, in the above-mentioned conventional light-shielding screens, the
width and thickness of the transparent layer and light-shielding layer are
not uniform from part to part since in slicing the block to form a
light-shielding screen the transparent layer and the light-shielding layer
undergo deformation. The uneven width and thickness of the transparent
layer and light-shielding layer lead to the uneven transmission of light
emitted from an image-indicating device through the light-shielding
screen, causing the image through the light-shielding screen to be
obscured.
On the other had, light-shielding screens having fine structures produced
from a photocurable resin have been proposed in, for example, Japanese
Patent Application Laid-Open Specification Nos. 55-139250/1980,
57-89701/1982, 57-165802/1982 and 57-189128/1982 and European Patent
Application Laid-Open Specification No. 0066745. The light-shielding
screens disclosed in the above-mentioned patent application laid-open
specifications are produced as follows. A photocurable resin composition
layer is provided on a substrate such as a transparent resin plate or a
transparent glass plate by the method in which a photocurable resin
composition is applied to the surface of the substrate or the method in
which a sheet of a photocurable resin composition is adhered to the
substrate. The photocurable resin composition layer is image-wise exposed
to actinic ray irradiation through an image-bearing transparency having
transparent portions and opaque portions which constitute a negative image
of a predetermined pattern comprising a plurality of lines arranged at
spaced intervals, thereby to convert the photocurable resin composition
layer to a modified layer having cured image portions and remaining
uncured portions. The uncured portions are removed by means of a
developer, thereby forming a plurality of relief lines corresponding to
the plurality of lines of the negative image. Then, the relief line
portions are dyed. Thus, there is produced a light-shielding screen
comprising a transparent plate and a light non-transmitting dyed relief
lines of a photocured resin composition and supported by the transparent
plate. However, in the above-mentioned method of producing a
light-shielding screen, the removal of the uncured portions from the
modified layer is effected with the support attached to one side of the
modified layer. Therefore, difficulties are encountered to sufficiently
remove the uncured portions by means of a developer, and a part of the
uncured portions remains unremoved at the corner where the relief portions
and the substrate meet. Particularly, in the case of a light-shielding
screen in which the relief lines formed on the substrate cooperate with
one another to form a striped or a lattice pattern, the narrower the
intervals of the relief lines and the higher the relief lines, the more
the amount of the uncured portions remaining unremoved. When the
light-shielding screen in which the uncured photocurable resin remains
unremoved at the corner where the relief portions and the substrate meet
is used for extraneous light rays-shielding in image-indicating devices or
for adjusting the visible angle range of the image from image-indicating
devices, the image through the light-shielding screen is a distorted one
and/or an obscured one.
It is possible to sufficiently remove the uncured photocurable resin by the
method in which in the step of removing the uncured photocurable resin the
developer is sprayed at a high pressure or the method in which the corner
at which the uncured photocurable resin have remained unremoved is
subjected to a strong brushing treatment by means of a developer-bearing
brush. However, in these methods, the relief lines tend to be deformed or
damaged. Therefore, the resulting light-shielding screens are poor in
extraneous light rays-shielding performance.
When in a light-shielding screen, the ratio of the intervals of the relief
lines to the height of the relief lines are limited to a low value, e.g.,
1:1.5 or less, in the step of producing it, the uncured photocurable resin
can be sufficiently removed without deformation or damage of the relief
lines. However, the light-shielding screen in which the ratio of the
intervals of the relief lines to the height of the relief lines is low,
e.g., 1:1.5 or less, is poor in extraneous light rays-shielding
performance and, hence, such light-shielding screen cannot be used for
applications where a high extraneous light rays-shielding performance is
required.
As is apparent from the foregoing, the conventional light-shielding screens
have a large room for improvement in respect of the quality of the image
through the light-shielding screen and the extraneous light rays-shielding
performance.
The present inventors have made extensive and intensive studies with a view
to eliminating the above-mentioned drawbacks of the conventional
light-shielding screens and to providing a light-shielding screen which is
not only excellent in the extraneous light rays-shielding performance but
also does not deteriorate the image emitted from image-indicating devices.
As a result, the present inventors have found that an excellent extraneous
light rays-shielding effect can be achieved without the deterioration of
an image emitted from an image-indicating device by using a
light-shielding screen comprising a light non-transmitting, photocured
resin composition layer and a plurality of hollow portions having their
respective upper and lower openings and passing through said composition
layer, each of said hollow portion having an inner wall extending from the
circumference of each upper opening to the circumference of each lower
opening substantially in parallel with the axis of said hollow portion.
Based on such a novel finding the present invention has been made.
Accordingly, it is an object of the present invention to provide a
light-shielding screen which is not only excellent in the extraneous light
rays-shielding performance but also does not deteriorate the image emitted
from image-indicating devices.
It is another object of the present invention to provide a process for
producing a light-shielding screen of the kind described above.
The foregoing and other objects, features and advantages of the present
invention will be apparent from the following description taken in
connection with the accompanying drawings in which:
FIG. 1 is a cross-sectional view of a conventional light-shielding screen;
FIG. 2 is a front view of one form of a light-shielding screen according to
the present invention;
FIG. 3 is a cross-sectional view taken on the line III--III of FIG. 2;
FIG. 4 is a schematic view illustrating the step of image-wise exposing a
photocurable resin composition layer to actinic radiation through an
image-bearing transparency to convert the photocurable resin composition
layer to a modified layer having photocured image portions and a plurality
of remaining uncured portions according to one mode of the process of the
present invention; and
FIG. 5 is a schematic view illustrating the step of applying a developer to
the modified layer formed in the step illustrated in FIG. 4 to form hollow
portions passing through the modified layer.
In FIGS. 1 to 5, like portions or parts are designated by like numerals.
In one aspect of the present invention, there is provided a light-shielding
screen comprising:
a light non-transmitting, photocured resin composition layer; and
a plurality of hollow portions passing through said resin composition
layer,
said resin composition layer cooperating with said hollow portions to form
a perforated structure,
said hollow portions having their respective upper and lower openings,
said upper openings being arranged in coplanar relationship on one surface
of said resin composition layer and said lower openings being arranged in
coplanar relationship on the other surface of said resin composition
layer,
each of said hollow portions having an inner wall extending from the
circumference of each upper opening to the circumference of each lower
opening substantially in parallel with the axis of said hollow portions,
said axis being defined by an imaginary straight line extending from the
center of each upper opening to the center of each lower opening.
The light-shielding screen of the present invention comprises a light
non-transmitting, photocured resin composition layer and a plurality of
hollow portions passing through the resin composition layer. The resin
composition layer cooperates with the hollow portions to form a perforated
structure. The hollow portions have their respective upper and lower free
openings. The upper free openings are arranged in coplanar relationship on
one surface of the resin composition layer and the lower free openings are
arranged in coplanar relationship on the other surface of the resin
composition layer. Each of the hollow portions has an inner wall extending
from the circumference of each upper opening to the circumference of each
lower opening substantially in parallel with the axis of the hollow
portions. The axis is defined by an imagiary straight line extending from
the center of each upper opening to the center of each lower opening.
Referring now to FIG. 1, there is shown a vertical cross-sectional view of
a conventional light-shielding screen, in which numeral 1 designates a
substrate, numeral 2 a relief of a photocured resin composition and
numeral 3 an uncured photocurable resin composition remaining unremoved.
In FIG. 2 is shown a plan view of one form of a light-shielding screen
according to the present invention, which comprises a light
non-transmitting, photocured resin composition layer 4 and hollow portions
5 having a square opening. In the present invention, the light
non-transmitting, photocured resin composition layer cooperates with a
plurality of hollow portions 5, thereby to form a preferred structure
consisting of hollow portions 5 and solid photocured resin portions 4. The
solid photocured resin portions 4 are in an interconnected form.
In FIG. 3 is shown a cross-sectional view taken on the line III--III of
FIG. 2, in which numeral 4 designates a light non-transmitting, photocured
resin composition layer and numeral 5 hollow portions. The hollow portions
5 have their respective upper openings 51 and lower openings 52. The upper
openings 51 are arranged in coplanar relationship on one surface of the
resin composition layer and the lower openings 52 are arranged in coplanar
relationship on the other surface of the resin composition layer. The
inner wall 53 of each of said hollow portions 5 extends from the
circumference of each upper opening 51 to the circumference of each lower
opening 52 substantially in parallel with the axis (an imaginary straight
line) of said hollow portion 5.
The shape of the upper and lower openings is not particularly critical, and
the upper and lower openings (hereinafter often referred to simply as
"openings") may have any shape. For example, the shape of the openings may
have any one of the shapes of openings disclosed in Japanese Patent
Application Laid-Open Specification Nos. 53-78114, 57-53703, 57-165802 and
57-205950, and may be circular, oval, triangular, square, rectangular,
rhombic, parallelogrammic or honeycomb (hexagonal). Generally, the shape
of the openings is circular, square, rectangular or hexagonal.
The widths of the openings are not critical and may vary depending on the
use of the light-shielding screen. However, in general, the widths of the
openings are in the range of 0.01 to 3 mm. The term "width of opening" as
used herein is intended to mean: the diameter in the case of a circular
opening; the length of the minor axis in the case of an oval opening; in
the case of a polygonal opening having sides in odd numbers, the minimum
distance between the vertexes and the sides opposite to the vertexes; and
in the case of a polygonal opening having sides in even numbers, the
minimum distance between the opposite sides.
The minimum distance between the circumferences of the nearest adjacent
openings and the thickness of the photocured resin composition layer are
not critical and may vary according to the use of the light-shielding
screen. Generally, however, the minimum distance between the
circumferences of the nearest adjacent openings and the thickness of the
photocured resin composition layer may be 0.005 to 0.5 mm and 0.05 to 6
mm, respectively.
In order to control light-shielding characteristics, the ratio of the width
of the opening to the thickness of the photocured resin composition layer
may be varied. Such ratio is not critical but may generally be varied from
1:0.2 to 1:5, preferably 1:0.6 to 1:5 according to use.
In the present invention, it is preferred that the surface of the modified
layer, at least the inner wall of each of the hollow portions have a
surface roughened. The roughened surface of the modified layer,
especially, the inner wall of each of the hollow portions serves to not
only scatter extraneous light rays but also scatter light rays emitted
from the image-indicating device and striking the modified layer, thereby
to prevent the reflection thereof. To form such a roughened surface of the
modified layer, it is preferred that the photocured resin composition
contain 0.1 to 20%, more preferably 0.5 to 10% by weight of a delustering
agent based on the photocured resin composition. The term "delustering
agent" as used herein is intended to mean a finely divided solid (which
will be described later) which can be dispersed uniformly into a
photocurable resin composition (which will be described later) without
undergoing any chemical or physical change such as chemical reaction or
dissolution.
According to the present invention, a further improved light-shielding
effect of the light-shielding screen can be attained by adopting a colored
surface of the modified layer, at least a colored surface of the inner
wall of each of the hollow portions. Dyes and pigments which may be used
and methods for coloring the surface of the modified layer and the surface
of the inner wall be described later.
In the present invention, the photocured resin composition is preferably
one obtained by photocuring a photopolymerizable resin composition which
will be mentioned later.
In another aspect of the present invention, there is provided a process for
producing a light-shielding screen which comprises:
(a) providing a photocurable resin composition layer;
(b) image-wise exposing the photocurable resin composition layer to actinic
radiation through an image-bearing transparency to convert the
photocurable resin composition layer to a modified layer having photocured
image portions and a plurality of remaining uncured portions, each of said
uncured portions extending from one surface of the layer to the other
surface of the layer; and
(c) applying a developer to said modified layer to remove said uncured
portions, thereby forming hollow portions passing through said modified
layer, said hollow portions having their respective upper and lower
openings, said upper openings being arranged in coplanar relationship on
one surface of said modified layer and said lower openings being arranged
in coplanar relationship on the other surface of said modified layer.
As a preferred example of the photocurable resin composition to be used in
the present invention, there may generally be mentioned a composition
comprising a compound having an additional polymerizable ethylenically
unsaturated group and a photopolymerization initiator. The compound may be
at least one member selected from the group consisting of prepolymers and
monomers. The composition may optionally contain a heat polymerization
inhibitor. As examples of the prepolymer, there may generally be mentioned
polymerization products such as unsaturated polyesters, alkyd resins,
unsaturated polyurethanes, oligomers of an ester-acrylate type,
unsaturated poly(meth)acrylates and various rubbers having a C-C bond. In
the present invention, the prepolymers may preferably have a number
average molecular weight of 500 to 100,000.
More illustrative examples of the above-mentioned prepolymers will be given
below:
(1) unsaturated polyesters prepared from at least one unsaturated
dicarboxylic acid such as maleic acid, fumaric acid or itaconic acid,
and/or its anhydride, and at least one polyhydric alcohol such as ethylene
glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin,
trimethylolpropane, pentaerythritol, 1,4-polybutadiene having terminal
hydroxyl groups, hydrogenated or non-hydrogenated 1,2-polybutadiene having
terminal hydroxyl groups, butadiene-styrene copolymer having terminal
hydroxyl groups or butadiene-acrylonitrile copolymer having terminal
hydroxyl groups; and unsaturated polyesters prepared from at least one
unsaturated dicarboxylic acid or its anhydride as mentioned above, at
least one polyhydric alcohol as mentioned above, and at least one
saturated polycarboxylic acid or its anhydride such as succinic acid,
adipic acid, phthalic acid, isophthalic acid, phthalic anhydride,
trimellitic acid or trimellitic acid anhydride;
(2) alkyd resins prepared by modifying the above-mentioned unsaturated
polyesters with at least one drying oil and/or at least one semidrying
oil;
(3) unsaturated polyurethanes having addition-polymerizable unsaturated
groups introduced by utilizing terminal isocyanate and/or hydroxyl groups
of polyurethanes derived from at least one polyol having two or more
terminal hydroxyl groups and at least one polyisocyanate, for example,
unsaturated polyurethanes which are prepared from (i) a polyurethane
having terminal isocyanate and/or hydroxyl groups and prepared from at
least one polyol such as a polyhydric alcohol as mentioned above,
polyester polyol or polyether polyol and at least one polyisocyanate such
as tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate or
hexamethylene diisocyanate and (ii) at least one unsaturated mono- or
di-carboxylic acid as mentioned above or its ester or polyester having
active hydrogen atoms derived from hydroxyl (reactive with the terminal
isocyanate) and/or carboxyl (reactive with both of the terminal isocyanate
and the terminal hydroxyl) and/or amino groups (reactive with the terminal
isocyanate), and unsaturated polyurethanes obtained by linking two or more
molecules of an unsaturated polyester as mentioned above with a
polyisocyanate; and
(4) oligomers of an ester-acrylate type obtained by the co-condensation of
an esterification reaction system composed of a polycarboxylic acid or its
anhydride and a polyhydric alcohol with acrylic acid and/or methacrylic
acid and having a number average molecular weight of about 200 to about
5,000, said number average molecular weight being controlled by choosing
an appropriate molar ratio of the raw materials, examples of said
polycarboxylic acid or its anhydride being adipic acid, isophthalic acid,
phthalic acid and phthalic anhydride, examples of said polyhydric alcohol
being ethylene glycol, propylene glycol, diethylene glycol, triethylene
glycol, glycerin, trimethylolpropane and pentaerythritol; epoxyacrylates,
for example, esters of acrylic acid or methacrylic acid and a compound
having epoxy groups obtained by condensation polymerization of a
polyhydric alcohol or polyhydric phenol with epichlorohydrin or an
alkylene oxide; and polymers having, in its side chains, carbon-carbon
double bonds capable of taking an active part in the addition
polymerization reaction, for example, polymers obtained by reacting an
unsaturated carboxylic acid or its anhydride with a polymer having
hydroxyl groups such as polyvinyl alcohol or cellulose, polymers obtained
by esterifying a homopolymer or copolymer of acrylic acid or methacrylic
acid having carboxyl groups with an unsaturated alcohol such as allyl
alcohol, glycidyl acrylate or glycidyl methacrylate, polymers obtained by
reacting a copolymer containing maleic anhydride monomer units with allyl
alcohol, a hydroxyalkyl acrylate and/or a hydroxyalkyl methacrylate, and
polymers obtained by reacting a copolymer having glycidyl acrylate and/or
glycidyl methacrylate monomer units with acrylic acid and/or methacrylic
acid. As the suitable rubber, there may be mentioned, for example, a
member (I) selected from the group consisting of 1,4-polybutadiene,
1,2-polybutadiene, a copolymer of butadiene and styrene, a copolymer of
butadiene and acrylonitrile and an EPDM; a member (II) selected from the
group consisting of a copolymer obtained by hydrogenating the member (I),
a copolymer of isobutylene and isoprene and a copolymer of ethylene and
propylene; and a modified rubber having an ethylenically unsaturated group
which may be obtained by incorporating the ethylenically unsaturated group
into the above-mentioned member (I) and member (II).
As stated above, the member (I) per se and also the modified rubber
obtained by incorporating an ethylenically unsaturated group into the
member (I) may be suitably employed in the present invention. In the case
where the latter polymer is employed, incorporation of an ethylenically
unsaturated group into the member (I) may be effectively carried out by
using a rubber of varied kind having a functional group at its chain
terminal. On the other hand, in the case of a rubber having a
1,2-polybutadiene segment, incorporation of an ethylenically unsaturated
group thereinto may be readily effected by utilizing an addition reaction
of maleic anhydride or the like to the 1,2-polybutadiene segment.
Moreover, ethylenically unsaturated polyamides, ethylenically unsaturated
polyimides and ethylenically unsaturated polyethers may be used as the
suitable prepolymer in the present invention.
Prepolymers other than those set forth above may also be suitably employed
in the present invention. As such other prepolymers, there may be
mentioned, for example, prepolymers having no ethylenically unsaturated
group which is capable of photocuring through the mechanism otherthan that
in which an addition reaction occurs between ethylenically unsaturated
double bonds. Examples of such prepolymers include a water-soluble nylon,
polyvinyl alcohol and derivatives thereof.
As the ethylenically unsaturated monomer which may be used in the
photopolymerizable resin composition, there may be mentioned commonly
known ethylenically unsaturated monomers as follows:
(1) unsaturated carboxylic acids such as acrylic acid and methacrylic acid,
or esters thereof, for example, alkyl acrylate, alkyl methacrylate,
cycloalkyl acrylate, cycloalkyl methacrylate, alkyl halide acrylate, alkyl
halide methacrylate, alcoxyalkyl acrylate, alcoxyalkyl methacrylate,
hydroxyalkyl acrylate, hydroxyalkyl methacrylate, aminoalkyl acrylate,
aminoalkyl methacrylate, tetrahyrofurfuryl acrylate, tetrahydrofurfuryl
methacrylate, allyl acrylate, allyl methacrylate, glycidyl acrylate,
glycidyl methacrylate, benzyl acrylate, benzyl methacrylate, phenoxy
acrylate, phenoxy methacrylate, mono- or di-acrylate of alkylene glycol,
mono- or di-methacrylate of alkylene glycol, mono- or di-acrylate of
polyoxyalkylene glycol, mono- or di-methacrylate of polyoxyalkylene,
trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
pentaerythritol tetraacrylate, pentadrythritol tetramethacrylate;
(2) acrylamides and methacrylamides, or derivatives thereof, for example,
an acrylamide N-substituted with an alkyl or hydroxyalkyl group, a
methacrylamide N-substituted with an alkyl or hydroxyalkyl group, an
acrylamide N,N'-disubstituted with alkyl and/or hydroxyalkyl groups, a
methacrylamide N,N'-disubstituted with alkyl and/or hydroxyalkyl groups,
diacetone acrylamide, diacetone methacrylamide,
N,N'-alkylene-bis-acrylamide, and N,N'-alkylene-bismethacrylamide;
(3) allyl compounds such as allyl alcohol, allyl isocyanate, diallyl
phthalate and triallyl cyanurate;
(4) maleic acid, maleic anhydride and fumaric acid, and esters thereof, for
example, mono- or di-alkyl maleate, mono- or di-alkyl fumarate, mono- or
di-haloalkyl maleate, mono- or di-haloalkyl fumarate, mono- or
di-alkoxyalkyl maleate, mono- or di-alkoxyalkyl fumarate; and
(5) other unsaturated compounds such as styrene, vinyltoluene,
divinylbenzene, N-vinylcarbazole and N-vinylpyrrolidone. They may be used
either alone or in combination. When they are employed in combination, an
azide compound may be incorporated into the ethylenically unsaturated
monomers. As such as azide compound, there may be mentioned
4,4'-diazidostilbene, p-phenylenebisazido, 4,4'-diazidobenzophenone,
4,4'-diazidodiphenylmethane, 4,4'-diazidochalcone,
2,6-di(4'-azidobenzal)-cyclohexanone,
4,4'-diazidostilbene-.alpha.-carboxylic acid, 4,4'-diazidodiphenyl,
disodium salt of 4,4'-diazidostilbene-2,2'-disulfonic acid and the like.
The amount of the ethylenically unsaturated monomer which may be
optionally incorporated into the above-mentioned prepolymer may usually be
200 parts or less by weight per 100 parts by weight of the prepolymer.
Various photopolymerization initiators as commonly used can be added to the
photocurable resin composition to be employed in the present invention.
Specific examples of such initiators include benzoin, benzoin alkyl ethers
such as benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl
ether and benzoin isobutyl ether, 2,2-dimethoxy-2-phenylacetophenone,
benzophenone, benzil, diacetyl, diphenyl sulfide, eosin, thionine,
9,10-anthraquinone, 2-ethyl-9,10-anthraquinone, Michler's ketone
[4,4'-bis-(dimethylamino)benzophenone] and the like. They may be used
either alone or in combination. The amount of any photopolymerization
initiator is such as will be effective for polymerization, i.e., 0.001 to
10% by weight based on the photocurable resin composition.
As the heat-polymerization inhibitor optionally added to the photocurable
resin composition to be employed in the present invention, there may be
mentioned, for example, hydroquinone, tert-butylhydroquinone,
benzoquinone, 2,5-diphenyl-p-benzoquinone, picric acid,
di-p-fluorophenylamine, p-methoxyphenol, 2,6-di-tert-butyl-p-cresol and
the like. They may be used either alone or in combination. Such
heat-polymerization inhibitors are added in the expectation of preventing
het-polymerization reactions (reactions in the darkness). Accordingly, the
amount of any heat-polymerization inhibitor is such as will be effective
for inhibiting heat-polymerization, i.e., 0.005 to 5.0% by weight based on
the prepolymer or the total weight of the prepolymer and the ethylenically
unsaturated monomer. Photocurable compositions other than those mentioned
above, for example, a composition comprising polyethylene, polythiol and a
photopolymerization initiator as disclosed in Japanese Patent Application
Publication No. 46-29525/1971 may also be employed in the present
invention. Moreover, as the photocurable composition other than those
mentioned above which may be employed in the present invention, there may
be mentioned, for example, diazo-type photocurable resin compositions such
as a diazo resin composition comprising an aromatic diazonium compound as
its major constituent and a composition comprising a diazide compound and
a rubber, photocurable resin compositions comprising cinnamic esters and
photocurable resin compositions as disclosed as disclosed in Japanese
Patent Application Publications No. 52-14277/1977 and No. 52-14278/1977
which each comprise a compound capable of releasing a Lewis acid by action
of light and an oxirane-containing compound.
In the present invention, roughening of the relief portions (photocured
resin portions), especially the side surfaces thereof, constituting the
photocured resin composition layer (modified layer) of the light-shielding
screen according to the present invention thereby to decrease the
reflectance of light rays from the relief portions is effective in
preventing the ghost phenomenon and light leakage. The above-mentioned
roughening of the relief portions may be advantageously attained by adding
a delustering agent to the photocurable resin composition.
As the delustering agent to be employed in the present invention, there may
be mentioned, for example, titanium oxide, mica, calcium carbonate, a
powdered glass such as Glass Pearl having a particle diameter of 5 to
15.mu. (trade name of a product manufactured and sold by Kyoritsu Ceramics
Co., Ltd., Japan), a finely divided silica such as Syloid having a
particle diameter of 0.5 to 20.mu. (trade name of a product manufactured
and sold by Fuji Davison Chemical Co., Ltd., Japan) and Aerosil having a
particle diameter of 0.5 to 20.mu. (trade name of a product manufactured
and sold by Nippon Aerosil Co., Ltd., Japan), aluminum powder, a powdered
clay and the like. The amount of the delustering agent to be added to the
photocurable resin composition in the present invention may generally be
in the range of 0.1 to 20% by weight, preferably 0.5 to 10% by weight
based on the photocurable resin composition. In general, in case the
amount of the delustering agent is less than 0.1% by weight based on the
photocurable resin composition, an effect for reflecting extraneous light
rays is not sufficient. Whereas, in case the amount of the delustering
agent is more than 20.0% by weight based on the photocurable resin
composition, the surface-roughening effect is not proportionally increased
but the transparency of the photocurable resin composition is rather
lowered, thereby causing the ultimate relief portions constituting the
photocured resin composition layer to exhibit a decreased resolution due
to the scattering of light rays. The suitable amount of the delustering
agent to be added may be determined on the basis of its side surface
roughening effect for the ultimate relief portions. For example, it is
preferred that the delustering agent be added to the photocurable resin
composition in an amount such that the reflectance as measured according
to the method described in Japanese Patent Application Laid-Open
Specification No. 57-189439/1982 (corresponding to U.S. patent application
Ser. No. 378,813) becomes 20% or less. Of the above-mentioned delustering
agents, a finely divided silica is most preferred from the standpoint of
good dispersion, good refractive index and the like.
A detailed explanation of the process of the present invention for
producing the above light-shielding screen will now be given. Referring to
FIG. 4, first, a photocurable resin composition is applied upon one flat
surface of a substrate 6 at a predetermined thickness to provide a
photocurable resin composition layer 7 on the substrate. Alternatively, a
sheet composed of a photocurable resin composition may be superimposed on
a substrate 6 while ensuring close contact therebetween to provide a
photocurable resin composition layer 7 on the substrate. Then, a
transparency 8 having a predetermined image is superimposed on the
photocurable resin composition layer 7. Next, the photocurable resin
composition layer 7 is irradiated through the image-bearing transparency 8
with an actinic light 9 selected from the solar light and the lights
emitted from an arc lamp, a mercury lamp, a xenon lamp, an ultraviolet
fluorescent lamp and the like to convert the photocurable resin
composition layer 7 to a modified layer having photocured image portions
and a plurality of remaining uncured portions. After the irradiation with
the actinic light, the image-bearing transparency 8 and substrate 6 are
removed. Thereafter, referring to FIG. 5, the unexposed, thus uncured
portions of the modified layer (photocured resin composition layer) 4' are
washed away with a developer 10, thereby forming hollow portions 5'
passing through the modified layer 4'. The hollow portions 5' have their
respective upper and lower openings, said upper openings being arranged in
coplanar relationship on one surface of the modified layer and said lower
openings being arranged in coplanar relationship on the other surface of
the modified layer 4'.
As the substrate 6 which may be used in the present invention, there may be
employed any substrate made of a material capable of being stripped off
the photocured resin composition layer. The form of the substrate is not
critical but a substrate in the form of film or sheet may preferably be
employed. As suitable examples of the substrate, there may be mentioned,
for example, films or sheets made of glass or synthetic resins such as
polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate,
polypropylene, polyethylene terephthalate, acetylcellulose,
polyacrylonitrile, polyamide, polyvinyl alcohol and the like. These may
also be employed metal sheets such as an aluminum sheet and steel sheet.
In the present invention, in order to facilitate the separation of the
photocured resin composition layer from the substrate, there may be
applied to the surface of the substrate a releasing agent such as a
silicon resin type releasing agent and a fluoroplastic type releasing
agent.
Whether the photocurable resin composition as liquid or solid, when the
photocurable resin composition which may be employed is tacky, it is
preferred that an interlayer film be provided between the image-bearing
transparency 8 and the layer of the photocurable resin composition 7 from
the standpoint of protection of the image-bearing transparency and
prevention of adhesion between the layer of the photocurable resin
composition and the image-bearing transparency. Examples of the interlayer
film include a transparent film such as polyethylene film, polypropylene
film, polycarbonate film, polyamide film, polyester film, acetyl cellulose
film, polyvinyl alcohol film and cellophane.
In the present invention, as mentioned above, the provision of a
photocurable resin composition layer may be effected by superimposing the
photocurable resin composition layer on a substrate, and the substrate may
be removed after exposing the photocurable resin composition layer to
actinic radiation, i.e., after step (b), and before applying a developer
to the resulting modified layer to remove the uncured portions, i.e.,
before step (c). Alternatively, in the present invention, the modified
layer may be subjected to the application of the developer with the
substrate attached to the modified layer and the substrate may be washed
away by the developer together with the uncured portions of the modified
layer. In this case, when water is used as the developer, a polyvinyl
alcohol substrate (water-soluble substrate) may be used as a suitable
substrate. When an organic solvent such as trichloroethane is used as the
developer, a polystyrene substrate may be used as a suitable substrate.
When dimethylsulfoxide is used as the developer, a polyacrylonitrile
substrate may be used as a suitable substrate.
When the photocurable resin composition is self-supporting, the
light-shielding screen may be prepared without using a substrate in the
following manner. A photocurable resin plate without any substrate is
subjected to exposure to actinic radiation through an image-bearing
transparency. The unexposed portions of the photocurable resin plate are
removed using a developer. In this case, as the photocurable resin plate,
there may be employed a plate which is obtained by (i) incorporating a
binder polymer into any one of the aforementioned photocurable resin
composition and (ii) subjecting the resulting resin composition to press
molding. As the binder polymer to be used in obtaining a photocurable
resin plate, there may be mentioned, for example, a polyamide, a polyvinyl
alcohol, a thermoplastic rubber, a butadiene-styrene block copolymer, a
polybutadiene, etc. The binder polymer may be incorporated into the resin
composition in an amount of 10 to 80% by weight based on the total amount
of the resulting plate. As the photocurable resin plate, there may also be
used a plate made of prepolymer of unsaturated polyamide, unsaturated
polyimide or unsaturated polymethacrylate.
According to the present invention, in removing the uncured portions of the
modified layer, as mentioned above, there is no substrate attached to the
modified layer, or the substrate may also be washed away together with the
uncured portions. Therefore, the uncured portions of the modified layer
are easily washed away by a developer to form a plurality of hollow
portions running from one side of the layer to the other side of the
layer. Consequently, the uncured photocurable resin composition does not
remain unremoved in the hollow portions. Therefore, a strong brushing to
remove uncured photocurable resin composition is not required, so that
deformation and damage of the photocured resin composition layer hardly
occurred. Moreover, the removal of the uncured portions can be performed
from not only one side of the layer but also the other side of the layer.
Further, the removal of the uncured portions can be effectively performed
from both sides of the photocured resin composition layer simultaneously.
The uncured portions may be removed by various conventional methods using a
developer. For example, the uncured portions may be removed, for example,
by spraying a developer on the modified layer having photocured image
portions and a plurality of remaining uncured portions to wash away the
uncured portions; by a brushing method in which the modified layer is
brushed with a developer-bearing brush, a sonication method in which the
modified layer is subjected to sonication in a developing solution; a
blowing method in which air is blown upon the modified layer; a sucking
method in which one side of the modified layer is evacuated to cause
pressure difference between one side of the modified layer and the other
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