Note: Descriptions are shown in the official language in which they were submitted.
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ADHESIVE TAPE AND METHOD FOR PREPARING THE SAME
Technical Field
The present invention relates to adhesive tapes for electromagnetic
interference
shielding useful in a variety of electronic application, and to methods of
preparing the
same.
Background
Electromagnetic radiation, which is generated in the circuits of various
electronic
devices, can, in some cases, disturb the functions of surrounding electronic
devices or
parts, reduce device performance, create environmental noise and interference,
damage
electronic images and reduce electronic device life spans.
To date, a variety of materials have been developed to shield electromagnetic
waves causing such problems. These materials include metal plates, metal
plated fabrics,
conductive paints, conductive tapes, conductive elastomers and the like.
In particular, conductive adhesive tapes are used mainly in miniaturized
electronic devices. Such conductive tapes are prepared by adding fine
conductive fillers,
such as carbon black, graphite, silver, copper, nickel, aluminum or the like
to an adhesive
polymer resin to impart conductivity to the resin. In order for such
conductive fillers to
impart conductivity to the adhesive polymer resin, the conductive filler
particles must
form a continuous conductive path in the adhesive polymer resin. For this
reason, a
relative excess of conductive filler is generally added to the adhesive
polymer resin.
When an excess of conductive filler is added, however, the melt
viscoelasticity of the
adhesive resin is reduced, allowing the filler particles to agglomerate
thereby increasing
the viscosity of the polymer resin. This viscosity increase, in turn, results
in an increase
in specific gravity and a deterioration in the physical properties, including
a reduction in
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impact and vibration absorbing properties. In addition, it is difficult to
control the
electrical conductivity of the conductive tapes using conventional methods of
manufacture.
Summary
Accordingly, the present inventors have made efforts to prepare a conductive
adhesive tape, which can shield electromagnetic waves without causing the
above-
mentioned problems.
In addition, the present inventors have made efforts to prepare an adhesive
tape
suitable for application in electronic devices, which gradually become
miniaturized and
slim.
As a result, the present inventors have found that, when flake conductive
filler is
used in adhesive polymer resin, it is possible to prepare an adhesive tape,
which has a very
small thickness while maintaining the adhesive properties and electrical
conductivity of
the resin.
Furthermore, the present inventors have found that, when a mask having a light-
shielding pattern formed thereon is attached to both sides of an adhesive
tape, and the
adhesive tape is irradiated with light, the movement of conductive filler can
be controlled
using the light-shielding pattern of the mask, thus making it possible to
prepare a
conductive adhesive tape having the desired electrical conductivity.
The present invention is based on such findings.
In one aspect, the present invention provides an adhesive tape, comprising: an
adhesive polymer resin; and flake conductive filler distributed in the
adhesive polymer
resin, wherein the flake conductive filler is electrically and continuously
arranged in the
adhesive polymer resin in the horizontal directions (x and y directions) and
thickness
direction (z direction) of the adhesive tape, and thus the adhesive tape shows
various
electrical conductivity.
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In another aspect, the present invention provides a method for preparing an
adhesive tape, comprising the steps of. (i) mixing a monomer for forming
adhesive
polymer resin with flake conductive filler; (ii) forming the mixture into a
sheet; (iii)
placing a mask on the surface of the sheet; and (iv) irradiating one side or
both sides of the
sheet with light to photopolymerize the monomer so as to form adhesive polymer
resin,
wherein the mask has a light-shielding pattern formed thereon, and the light
is radiated on
all or part of the surface of the sheet depending on the light-shielding
pattern.
Brief Description of the Drawings
FIG. 1(a) shows an adhesive tape, prepared in Example 1 of the present
invention, in which flake conductive filler is generally arranged in a network
configuration.
FIG. 1(b) shows an adhesive tape, prepared in Example 2 of the present
invention,
in which flake conductive filler is arranged from one surface of polymer syrup
to the inner
middle portion in the horizontal direction and the thickness direction.
FIG. 1(c) shows an adhesive tape, prepared in Example 3 of the present
invention,
in which flake conductive filler is arranged in the inner middle layer of
polymer syrup in
the horizontal direction.
FIGS. 2 and 3 schematically show that the arrangement of filler varies
depending
on the pattern of a mask, used in the light irradiation step of the inventive
method for
preparing the adhesive tape.
FIG. 4(a) is a scanning electron microscope ("SEM") photograph showing the
surface of an adhesive tape prepared according to Example 1 of the present
invention.
FIGS. 4(b) and 4(c) are scanning electron microscope ("SEM") photographs
showing the cross-sections of the adhesive tape prepared according to Example
1 of the
present invention.
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FIGS. 5(a) and 5(b) are scanning electron microscope ("SEM") photographs
showing both sides of an adhesive tape prepared according to Example 2 of the
present
invention, respectively.
FIG. 6 schematically shows a process of preparing an adhesive tape according
to
the present invention.
Detailed Description of Preferred Embodiments
Adhesive tapes according to the present invention generally have a structure
in
which flake conductive filler material is distributed in an adhesive polymer
resin. The
flake conductive filler material is arranged on the surface or inside (or
both) of the
adhesive tape in the horizontal direction and/or the thickness direction. Due
to such
ordered arrangement of the flake conductive filler material, the adhesive
tapes of the
invention exhibit improved electrical conductivity.
The flake conductive filler particles used in the present invention may be
substantially flatly arranged in the adhesive polymer resin. Alternatively,
the filler
particles may move differently from each other, due to the difference in
polymerization
initiation between portions of the polymer resin which results from the
presence of a light-
shielding pattern in the photopolymerization step.
A sheet-like adhesive tape according to one aspect of the invention can be
prepared, for example, by adding flake conductive filler to a syrup-like
polymer material
(hereinafter, referred to as "polymer syrup") that is not fully cured; forming
the mixture
into a sheet; placing a peelable release film on both sides of the sheet; and
irradiating both
sides of the sheet with light to photopolymerize the polymer syrup. By
arranging the
flake conductive filler material flatly (i.e., oriented in a plane) in the
horizontal directions
(x and y directions), an adhesive tape having a thickness of less than about
100 m can be
prepared. The step of forming the polymer syrup into a sheet may be carried
out at the
same time as the step of placing the release film on both sides of the sheet.
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Particularly, in the process of forming the polymer syrup into a sheet, the
light-
shielding patterned release film may be placed on both sides of the sheet. If
such a light-
shielding pattern is used, light irradiation is selectively conducted
depending on the light-
shielding pattern of the release film, and the photopolymerization of the
syrup surface is
selectively initiated. The flake conductive filler moves accordingly to the
portion of the
polymer syrup that is not yet polymerized, and this principle can be used to
control the
arrangement of the flake conductive filler material.
Specifically, if light is irradiated through a mask having a light-shielding
pattern
formed thereon, either the light cannot pass through the light-shielding
pattern region, or
the amount of light passed through that region will be significantly small.
Thus, in the
portion of the polymer syrup corresponding to the light-shielding pattern,
photopolymerization will not be initiated, or, if it is initiated, the
polymerization rate will
be very slow. Conversely, in the portion of the polymer syrup above which the
light-
shielding pattern is not placed, photopolymerization will be actively
initiated, and the
polymerization will progress towards the lower portion of the polymer syrup
via radicals
resulting from initiation of the photopolymerization.
In this manner, the flake conductive filler material present in the portion of
the
polymer syrup in which polymerization is initiated will move to other portions
in which
polymerization has not yet occurred. If photopolymerization progresses from
both sides
of the polymer syrup, polymerization will be initiated from the surface of the
polymer
syrup, and conductive filler present on the surface of polymer syrup will
migrate to the
interior portions of the polymer syrup in which the polymerization has not yet
occurred.
On the other hand, in the portion of the polymer syrup positioned below the
light-shielding
pattern, photopolymerization does not occur, and conductive filler present in
that portion
does not migrate or move to other portions. Using the movement properties of
the flake
conductive filler, various adhesive tapes according to the invention can be
made.
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One such embodiment is illustrated in FIG. 2. Polymer syrup 1 is placed
between masks 3 having no light-shielding pattern and is irradiated with light
4. In this
way, an adhesive tape is formed in which the flake conductive filler is
arranged in the
inner middle layer of the polymer syrup in the horizontal direction.
Another embodiment is illustrated in FIG. 3, where polymer syrup 1 is disposed
between masks 3 having a light-shielding pattern and is irradiated with light
4. In this
way, an adhesive tape is formed in which flake conductive filler 2 is arranged
in the
interior portion of the syrup above which the light-shielding pattern is not
placed.
Conversely, in that portion of the syrup above which the light-shielding
pattern is placed,
the flake conductive filler 2 remains on the surface of the polymer syrup
without any
significant movement or is present throughout the entire thickness direction
due to
photopolymerization initiated only by weak light. With this combination, the
flake
conductive filler 2 form a network structure which electrically connects one
side of the
tape to the other side.
In addition, where a light-shielding patterned mask is used only on one side
of the
polymer syrup, an adhesive tape can be made in which flake conductive filler
is arranged
from one side of the polymer syrup to the interior portion in both the
horizontal direction
and the thickness direction.
Adhesive tapes having different arrangements of flake conductive filler
according
to the invention can be used in various applications. For example, an adhesive
tape in
which flake conductive filler is arranged from one side of the adhesive tape
to the opposite
side to form a continuous network structure (as in the embodiment depicted in
FIG. 1(a)),
can be used as a double-sided adhesive tape for ground connectivity in all
directions (x, y
and z directions). An adhesive tape in which the flake conductive filler is
arranged
continuously from one side of the adhesive tape to the interior portion in the
thickness
direction and the horizontal directions (as in the embodiment depicted in FIG.
1(b)), can
be used as a double-sided adhesive tape for ground connectivity in the
horizontal
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directions (x and y directions) and insulation in the vertical, or thickness,
direction (z
direction). In addition, the adhesive tape, in which the flake conductive
filler is arranged
continuously in the interior portion of the adhesive tape in the horizontal
directions (as in
the embodiment depicted in FIG. 1(c)), can be used as a double-sided adhesive
tape for
insulation.
In the inventive adhesive tapes described above, arrangement of the flake
conductive filler can be controlled, unlike prior adhesive tapes in which
conductive filler
is irregularly dispersed. Thus, the inventive adhesive tapes can be prepared
to be used in
a variety of different applications requiring electrical conductivity.
Particularly,
according to the present invention, because a flake conductive filler material
is used, it is
possible to prepare an adhesive tape having a relatively small thickness
(e.g., around about
100 m). Accordingly, the adhesive tapes of the invention will typically have a
surface
resistance of about 0.1 Q /m2 or more and a vertical resistance of about 0.001
Q or
more.
In the adhesive tapes of the invention, the flake conductive filler is
introduced to
impart electrical conductivity and provide an ability to make the adhesive
tapes thinner.
Any material may be selected for use as the flake conductive filler as long as
it serves to
impart electrical conductivity and is flake in shape.
Examples of useful flake conductive filler materials in the present invention
include: flake metals, including: flake noble and non-noble metals; flake
noble and non-
noble metals plated with another noble or non-noble metal; noble metal- or non-
noble
metal-plated flake non-metals; flake conductive non-metals; and mixtures of
two or more
of these materials.
Specific examples of flake conductive filler materials include: noble metals
such
as gold, silver and platinum; non-noble metals such as nickel, copper, tin and
aluminum;
noble metal-plated noble and non-noble metals, such as silver-plated copper,
nickel,
aluminum, tin and gold; non-noble metal-plated noble and non-noble metals,
such as
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nickel-plated copper and silver; noble or non-noble metal-plated non-metals,
such as
silver- or nickel-plated graphite, glass, ceramics, plastics, elastomers and
mica; conductive
non-metals such as carbon black and carbon fiber; and mixtures of two or more
of any of
these materials.
The size of the flake conductive filler may vary depending on the type of
material
used. The size of the flake conductive filler is not specifically limited, but
in one
embodiment of the invention, if the flake conductive filler is square or
rectangular in
shape, it will generally have a thickness ranging from about 100 nm to about
25 m and a
side length of about 0.25-25 m.
The content of the flake conductive filler material in the adhesive tapes made
according to the invention will generally range from about 20-60 wt% based on
the total
weight of the adhesive tape. In one illustrative embodiment of the invention,
the content
of the adhesive polymer resin in the adhesive tape is about 40-80 wt%, and the
content of
the flake conductive filler is about 20-60 wt%.
In the present invention, an acrylic polymer resin can be used as the adhesive
polymer resin. In one embodiment, an acrylic polymer resin, which can be
prepared by
polymerizing a photopolymerizable monomer, may be used.
Photopolymerizable monomers useful to make such acrylic polymer resins include
alkyl acrylate ester monomers having a C1_14 alkyl group. Non-limiting
examples of such
alkyl acrylate ester monomers include: butyl(meth)acrylate,
hexyl(meth)acrylate, n-
octyl(meth)acrylate, isooctyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,
isononyl(meth)acrylate and the like. Other examples include isooctyl acrylate,
isononylacrylate, 2-ethyl-hexyl acrylate, decyl acrylate, dodecyl acrylate, n-
butyl acrylate,
hexylacrylate and the like.
Although alkyl acrylate ester monomers can be used alone to form an acrylic
adhesive polymer resins, they can also be copolymerized with other polar
copolymerizable
monomers to form acrylic adhesive polymer resins. One useful such resin can be
made
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from a copolymer of an alkyl acrylate ester monomer having a CI-14 alkyl group
with a
polar copolymerizable monomer. In this case, although the weight ratio of the
alkyl
acrylate ester monomer to the polar copolymerizable monomer is not
specifically limited,
it is preferably 99-50:1-50 in view of the physical properties of the
resulting adhesive
polymer resin.
Non-limiting examples of the polar copolymerizable monomer include acrylic
acid, itaconic acid, hydroxyalkyl acrylate, cyanoalkyl acrylate, acrylamide,
substituted
acrylamide, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylonitrile, vinyl
chloride, diallyl
phthalate and the like. Such polar copolymerizable monomers can serve to
impart
adhesiveness and cohesiveness to the polymer resin and improve adhesion.
The content of the adhesive polymer resin in the adhesive tapes made according
to
the invention will generally be about 40-80 wt% based on the total weight of
the adhesive
tape.
Also, in order for the adhesive tapes to possess physical properties required
in
products in which they are applied, the adhesive tapes of the invention may
further
comprise one or more additional fillers. Any such additional fillers can be
used, as long
as they do not impair the properties and usefulness of the adhesive tape. Non-
limiting
examples of such additional fillers include thermally conductive fillers,
flame retardant
fillers, antistatic agents, foaming agents and the like.
Such additional fillers will generally be used in an amount less than about
100
parts by weight, for example, about 10-100 parts by weight, based on 100 parts
by weight
of the adhesive polymer resin.
The adhesive tapes of the invention may further comprise additives, for
example,
polymerization initiators, crosslinkers, photoinitiators, pigments,
antioxidants, UV
stabilizers, dispersants, antifoaming agents, plasticizers and tackifying
resins. Such
additives may be added during the preparation process of the adhesive tape.
Hereinafter, a method for preparing the adhesive tape will be described in
detail.
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Adhesive tapes of the invention can be prepared by mixing either a monomer for
forming adhesive polymer resin or a prepolymer syrup of the monomer with flake
conductive filler for imparting electrical conductivity, adding additional
fillers or
additives, if used, and polymerizing the mixture.
Specifically, the adhesive tape of the present invention can be prepared by
carrying out the steps of. mixing a monomer for forming adhesive polymer resin
with
flake conductive filler; forming the mixture into a sheet; placing a mask on
the surface of
the sheet; and irradiating both sides of the sheet with light to
photopolymerize the
monomer for forming adhesive polymer resin. A mask having a light-shielding
pattern
formed on it may be used, and all or part of the sheet surface may be
irradiated with light
depending on the light-shielding pattern of the mask. In this case, the flake
conductive
filler present in the portion of the sheet in which polymerization is
initiated will move to
other portions in which polymerization has not yet occurred.
In one embodiment of the invention, the monomer for forming the adhesive
polymer resin is prepolymerized to prepare a polymer syrup, and the flake
conductive
filler and other necessary additives are added to the polymer syrup. This
method can be
used to uniformly disperse the flake conductive filler and facilitate the
initiation of
selective photopolymerization. More specifically, the step of mixing the
monomer for
forming the adhesive polymer resin with the flake conductive filler may
comprise the steps
of. partially polymerizing the monomer composition to prepare a polymer syrup
and
adding flake conductive filler to the polymer syrup. In one embodiment of the
invention,
the polymer syrup may have a viscosity of about 500 to about 20,000 cPs.
In a specific embodiment of the preparation method, a monomer for forming an
adhesive polymer resin, for example, a monomer for forming acrylic polymer
resin, is first
partially polymerized using a polymerization initiator under an oxygen-free
condition to
prepare a syrup having a viscosity of from about 500 to about 20,000 cPs. The
flake
conductive filler, crosslinker, photoinitiator and any other necessary
additives are added to
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the syrup, and the mixture is formed into a sheet. Light-transmitting release
films may be
used such that the polymer syrup sheet is disposed between two release film
layers. By
disposing the polymer syrup between the release films, a substantially oxygen-
free
condition can be maintained. If a light-shielding pattern is formed on one or
both of the
release films, the release films can serve as a mask on which a light-
shielding pattern is
formed. Thereafter, the polymer syrup may be polymerized and crosslinked under
a
substantially oxygen-free condition by directing irradiating light (preferably
UV light)
through the release films or other masks having a light-shield pattern. In
this step, the
light may be irradiated on all or part of the surface of the polymer syrup
depending on the
light-shielding pattern, so that photopolymerization is selectively initiated.
The flake
conductive filler present in the portion of the syrup in which the
polymerization is initiated
moves to other portions in which the polymerization has not yet occurred. As a
result,
the flake conductive filler is arranged three-dimensionally, and an adhesive
tape having a
desired electrical conductivity can be prepared.
During irradiation of the surface of the sheet with light, a decrease in the
content
of oxygen in the sheet can lead to an increase in the adhesion of the adhesive
polymer
resin, because unnecessary oxidation reactions in the adhesive tape are
avoided. The
blockage of oxygen can be achieved by disposing the polymer syrup between the
release
films as described above and forming the polymer syrup into a sheet. It is
also generally
preferable to initiate the photopolymerization through light irradiation in a
substantially
oxygen-free chamber, for example, a chamber having an oxygen concentration of
less than
about 1000 ppm. Doing so can more effectively block oxygen and prevent
oxidation
reactions. In some cases, the concentration of oxygen is more preferably less
than about
500 ppm.
In the photopolymerization step, in order for a only a selective portion of
the
surface of the sheet to be irradiated with light, a mask having a light-
shielding pattern may
be used, and in order for all the surface of the sheet to be irradiated with
light, a mask
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having no light-shielding pattern (that is, a transparent mask) may be used.
The mask
having a light-shielding pattern generally comprises a region through which
light can pass,
and a region through which light cannot pass or light passes in only a very
small amount.
Thus, the portion of the sheet above which the light-shielding pattern is
placed will not be
irradiated with light or will be irradiated with weak light, and the flake
conductive filler
present in that portion will remain on the surface of the sheet without any
substantial
movement. Conversely, the portion of the sheet above which the light-shielding
pattern
is not placed will be irradiated with light to initiate photopolymerization,
and the flake
conductive filler present in that portion will move to other portions in which
photopolymerization has not yet occurred. As a result, the flake conductive
filler can
form a network structure in the sheet. In addition, in order for the flake
conductive filler
to be arranged in the interior portion of the sheet, a mask having no light-
shielding pattern
may be used such that light can be irradiated on substantially all of the
surface of the
sheet.
Non-limiting examples of the mask include light-transmitting release films on
which a desired light-shielding pattern (such as a network structure or a
lattice structure) is
formed and light-transmitting release films having no light-shielding pattern.
A
transparent plastic film having a low surface area or on which a release layer
is coated
may be used as a light-transmitting release film. Examples of suitable light-
transmitting
release films include polyethylene films, polypropylene films, polyethylene
terephthalate
("PET") films and the like.
Any material capable of shielding about 10-100% of light reaching the light-
shielding pattern may be used to form the light-shielding pattern. Preferably,
a material
capable of shielding more than about 50% of light reaching the light-shielding
pattern is
used. In some embodiments of the invention, the light-shielding pattern can be
designed
such that it shields more than about 70% of incident light. If necessary, the
light-
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shielding pattern can also be designed such that it completely (100%) shields
incident
light.
There is no limitation on the method for forming the light-shielding pattern
on the
surface of the light-transmitting release film. Any method may be used that
deposits on
the surface of the light-transmitting release film a material for forming the
light-shielding
pattern that reduces or shields the passage of light. Printing methods, for
example, can
be applied for this purpose. Such printing methods are known in the art and
include, for
example, screen printing methods, printing methods that use heat transfer
paper, gravure
printing methods, etc. A black ink having good light-absorbing properties may
be used
to from the light-shielding pattern. The shape of the light-shielding pattern
formed on the
release film is not specifically limited and can be selected to coincide with
the particular
network structure desired for the conductive filler material.
In embodiments of the invention, the thickness of the release film may be
about 5
m to about 2 mm, but there is no particular limitation on the thickness of the
release film.
It is generally more difficult to form a light-shielding pattern and apply a
polymer syrup
on the release films having thicknesses of less than about 5 m. It can also
be difficult to
carry out the photopolymerization of the polymer syrup if the release film is
very thick
(e.g., more than about 2 mm).
Moreover, although the thickness of the adhesive tapes prepared according to
the
invention is not specifically limited, the adhesive tapes preferably have a
thickness of from
about 10-200 m. In some embodiments of the invention, the thickness of the
adhesive
tape is preferably from about 20-150 m, and more preferably from about 30-100
m, in
view of photopolymerization, the thickness and movement of the flake
conductive filler,
etc.
The intensity of light used to carry out the photopolymerization of the
polymer
syrup may be any intensity of light conventionally applied for
photopolymerization. In
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one embodiment of the invention, the intensity of light corresponding to that
of UV light is
preferred.
One or more crosslinkers or crosslinking agents may be used for crosslinking
the
adhesive polymer resin. Depending on the amount of crosslinker used, the
properties
(particularly the adhesive properties) of the adhesive polymer resin can be
controlled.
The crosslinker will generally be used in an amount of about 0.05-2 parts by
weight based
on 100 parts by weight of the adhesive polymer resin. Specific examples useful
crosslinkers and crosslinking agents include, but are not limited to,
multifunctional
actylates such as 1,6-hexanediol diacrylate, trimethylolpropane triacrylate,
pentaerythritol
triacrylate, 1,2-ethylene glycol diacrylate, 1,12-dodecanediol acrylate, and
the like.
In addition, one or more photoinitiators may be used in the preparation
process of
the adhesive tapes of the invention. Depending on the amount of photoinitiator
used, the
degree of polymerization of the polymer resin can be controlled. The
photoinitiator may
be used in an amount of about 0.01-2 parts by weight based on 100 parts by
weight of the
adhesive polymer resin. Specific examples of useful photoinitiators include,
but are not
limited to, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-
trimethylbenzoyl)phenylphosphine oxide, a,a-methoxy-a-hydroxyacetophenone, 2-
benzoyl-2(dimethylamino)- 1-[4-(4-morphonyl)phenyl]-l-butanone, 2,2-dimethoxy-
2-
phenylacetophenone, etc.
The adhesive tapes made according to the invention can be applied in various
electronic devices requiring electrical conductivity, since the arrangement of
the flake
conductive filler can be changed depending on the light-shielding pattern of
the mask so as
to change electrical conductivity.
Examples
The present invention will hereinafter be described in further detail with
reference
to examples and comparative examples. It will be understood that these
examples are
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offered for illustrative purposes only, and the scope of the present invention
is not to be
construed as limited thereto.
The term "parts" in the following examples means "parts by weight" relative to
100 parts by weight of adhesive polymer resin, which is formed by
polymerization of a
monomer.
Example 1
90 parts of 2-ethylhexyl acrylate as an acrylic monomer and 10 parts of
acrylic
acid as a polar copolymerizable monomer were placed in a 1-liter glass
reactor, and 0.1
parts of photoinitiator Irgacure 651 (a,a-methoxy-a-hydroxyacetophenone) and
0.1 parts
of crosslinker 1,6-hexanediol diacrylate ("HDDA") were added thereto. The
monomers
were partially polymerized by photoinitiation, thus preparing syrup having a
viscosity of
3000 cPs. To the syrup, 40 parts of flake silver as flake conductive filler
was added, and
the mixture was stirred, thus preparing a uniform polymer syrup.
Meanwhile, a lattice structure having a width of 350 m and an interval of 1
mm
was patterned on a release film made of a 75 m thicker transplant
polyethyleneterephthalate film ("PET") using black ink, thus preparing a mask
having a
light-shielding pattern.
As shown in FIG. 6, the polymer syrup was extruded from the glass reactor,
while
the patterned release film was placed on both sides of the polymer syrup using
a roll
coating machine, such that the thickness of the polymer syrup reached about 50
m. By
placing the release film on both sides of the polymer syrup, the polymer syrup
could be
prevented from coming into contact with air, particularly oxygen.
The polymer syrup was cured by irradiating both sides with UV light via the
release film at a energy dose of 4.5 mW/cm3 for 520 seconds using a metal
halide UV
lamp, thereby preparing an adhesive tape.
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Example 2
An adhesive tape was prepared in the same manner as in Example 1, except that
a
patterned release film was placed on the top side of the polymer syrup, and a
transparent
release film rather than the patterned release film was placed on the bottom
side.
Example 3
An adhesive tape was prepared in the same manner as in Example 1, except that
a
transparent release film rather than the patterned release film was placed on
both sides of
the polymer syrup.
Test Example 1: Resistance Measurement
The surface resistance and vertical resistance of each of the adhesive tapes
prepared in Examples 1 to 3 was measured by the surface probe method adapted
from Mil-
G-83528B using a Kietheley 580 micro-ohmmeter. The average value of
measurement
results are shown in Table 1 below.
Table 1
Vertical resistance (2) Surface resistance (Q /m2)
Top side Bottom side
Example 1 0.004 10.5 11.4
Example 2 - 10 -
Example 3 - - -
As can be seen in Table 1 above, the adhesive tapes prepared in Examples 1 to
3
had various electrical conductivities depending on the light-shielding
patterns of the
masks.
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CA 02709934 2010-06-17
WO 2009/085631 PCT/US2008/086363
Test Example 2: Adhesion Test
In accordance with ASTM D 1000, each of the adhesive tapes prepared in
Examples 1 to 3 was laminated with aluminum sheets, and then the adhesion of
each
adhesive tape to the top side and the bottom side in a 180 direction was
measured using a
Universal Test Machine ("UTM"). The measurement results are shown in Table 2
below.
Table 2
Top Side (kgf/in.) Bottom Side (kgf/in.)
Example 1 1.2 1.2
Example 2 1.41 1.15
Example 3 1.32 1.42
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