U.S. patent application number 11/675991 was filed with the patent office on 2007-08-23 for pressure sensitive adhesive for sticking an electromagnetic wave-shielding film and an optically functional film, and a display panel filter element containing same.
This patent application is currently assigned to Lintec Corporation. Invention is credited to Mikihiro Kashio, Shin Koizumi, Tadashi MATANO.
Application Number | 20070196646 11/675991 |
Document ID | / |
Family ID | 38428582 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070196646 |
Kind Code |
A1 |
MATANO; Tadashi ; et
al. |
August 23, 2007 |
PRESSURE SENSITIVE ADHESIVE FOR STICKING AN ELECTROMAGNETIC
WAVE-SHIELDING FILM AND AN OPTICALLY FUNCTIONAL FILM, AND A DISPLAY
PANEL FILTER ELEMENT CONTAINING SAME
Abstract
A pressure sensitive adhesive for sticking together an
electromagnetic wave-shielding film and an optically functional
film, wherein a storage elastic modulus at 70.degree. C. is
7.00.times.10.sup.4 Pa or more; and a display panel filter element
comprising (1) an electromagnetic wave-shielding film, the film
being a laminate of a transparent substrate film, an adhesive for a
metal foil, which is applied on one surface of the transparent
substrate film, and a metal foil mesh formed on the adhesive for a
metal foil, (2) a layer of the pressure sensitive adhesive
according to (1), which is applied so as to cover the metal foil
mesh of the electromagnetic wave-shielding film, and (3) an
optically functional film provided on the pressure sensitive
adhesive, are provided. The pressure sensitive adhesive exhibits a
sufficient adhesive strength, can be filled into the inside of the
pores of the metal foil mesh, and does not generate bubbles in a
heating treatment.
Inventors: |
MATANO; Tadashi;
(Urayasu-shi, JP) ; Koizumi; Shin; (Tokyo, JP)
; Kashio; Mikihiro; (Saitama-shi, JP) |
Correspondence
Address: |
HESLIN ROTHENBERG FARLEY & MESITI PC
5 COLUMBIA CIRCLE
ALBANY
NY
12203
US
|
Assignee: |
Lintec Corporation
Tokyo
JP
|
Family ID: |
38428582 |
Appl. No.: |
11/675991 |
Filed: |
February 16, 2007 |
Current U.S.
Class: |
428/355AC ;
427/96.3; 428/343; 428/355CN; 428/355R; 428/411.1 |
Current CPC
Class: |
Y10T 428/28 20150115;
B32B 27/306 20130101; B32B 15/20 20130101; B32B 27/36 20130101;
C09J 133/08 20130101; C09J 2301/302 20200801; Y10T 428/2891
20150115; B32B 15/08 20130101; B32B 2307/412 20130101; B32B 7/12
20130101; B32B 2405/00 20130101; H01J 11/10 20130101; B32B 27/308
20130101; B32B 2307/51 20130101; C09J 133/26 20130101; B32B
2307/212 20130101; H05K 9/0096 20130101; H01J 11/44 20130101; Y10T
428/31504 20150401; Y10T 428/2887 20150115; B32B 3/266 20130101;
Y10T 428/2852 20150115; C08F 220/1804 20200201; B32B 2457/20
20130101; B32B 2457/204 20130101; H01J 2211/446 20130101; B32B
2307/40 20130101; C08F 220/1804 20200201; C08F 220/14 20130101;
C08F 220/20 20130101; C08F 220/58 20130101; C08F 220/1804 20200201;
C08F 220/14 20130101; C08F 220/20 20130101; C08F 220/58
20130101 |
Class at
Publication: |
428/355AC ;
428/343; 428/355.R; 428/355.CN; 428/411.1; 427/96.3 |
International
Class: |
B05D 5/12 20060101
B05D005/12; B32B 7/12 20060101 B32B007/12; B32B 15/04 20060101
B32B015/04; B32B 9/04 20060101 B32B009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2006 |
JP |
2006-040281 |
Nov 13, 2006 |
JP |
2006-306241 |
Claims
1. A pressure sensitive adhesive for sticking together an
electromagnetic wave-shielding film and an optically functional
film, wherein a storage elastic modulus at 70.degree. C. is
7.00.times.10.sup.4 Pa or more.
2. The pressure sensitive adhesive according to claim 1, wherein a
storage elastic modulus at 23.degree. C. is 1.00.times.10.sup.5 Pa
or more.
3. The pressure sensitive adhesive according to claim 1, wherein a
peak temperature of loss tangent (tan .delta.) is -15.degree. C. or
more.
4. The pressure sensitive adhesive according to claim 1, comprising
an acrylic copolymer containing (meth)acrylic alkyl ester monomers
as a comonomer.
5. The pressure sensitive adhesive according to claim 4, comprising
the acrylic copolymer further containing nitrogen-containing vinyl
monomers as a comonomer.
6. The pressure sensitive adhesive according to claim 4, wherein
said acrylic copolymer does not contain an acid comonomer.
7. The pressure sensitive adhesive according to claim 5, wherein
said acrylic copolymer does not contain an acid comonomer.
8. A display panel filter element comprising (1) an electromagnetic
wave-shielding film, said film being a laminate of a transparent
substrate film, an adhesive for a metal foil, which is applied on
one surface of said transparent substrate film, and a metal foil
mesh formed on said adhesive for a metal foil, (2) a layer of said
pressure sensitive adhesive according to claim 1, which is applied
so as to cover said metal foil mesh of said electromagnetic
wave-shielding film, and (3) an optically functional film provided
on said pressure sensitive adhesive.
9. The display panel filter element according to claim 8, wherein a
storage elastic modulus at 23.degree. C. of said pressure sensitive
adhesive is 1.00.times.10.sup.5 Pa or more.
10. The display panel filter element according to claim 8, wherein
a peak temperature of loss tangent (tan .delta.) of said pressure
sensitive adhesive is -15.degree. C. or more.
11. The display panel filter element according to claim 8, wherein
said pressure sensitive adhesive comprises an acrylic copolymer
containing (meth)acrylic alkyl ester monomers as a comonomer.
12. The display panel filter element according to claim 11, wherein
said pressure sensitive adhesive comprises the acrylic copolymer
further containing nitrogen-containing vinyl monomers as a
comonomer.
13. The display panel filter element according to claim 11, wherein
said acrylic copolymer does not contain an acid comonomer.
14. The display panel filter element according to claim 12, wherein
said acrylic copolymer does not contain an acid comonomer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a pressure sensitive
adhesive for sticking an electromagnetic wave-shielding film and an
optically functional film, and a display panel filter element
containing the same. The pressure sensitive adhesive according to
the present invention can be used for the manufacture of a display
panel filter element constituting, for example, a plasma display
panel or the like.
[0003] 2. Description of the Related Art
[0004] It is believed that an electromagnetic wave emitted from an
electromagnetic device such as a plasma display affects not only
other electromagnetic devices, but also the human body.
Particularly, an electromagnetic wave having a frequency of 30 MHz
to 130 MHz is emitted from a plasma display, and may affect
computers and computer peripherals positioned therearound.
Accordingly, the emitted electromagnetic wave should be prevented
from leaking toward the outside. An electromagnetic wave may be
shielded, for example, by a method of covering an emitting source
with a case formed from a highly conductive material, or a method
of applying a conductive net on the emitting source. However, an
apparatus such as a plasma display, which must be observed,
requires transmittability, and the above methods cannot be
adopted.
[0005] Therefore, in a plasma display or the like, an
electromagnetic wave-shielding sheet composed of a transparent
substrate film and a metal foil mesh carried thereon via an
adhesive layer is used as a means having not only transmittability
but also a property of shielding an electromagnetic wave. The metal
foil mesh is formed by mounting a metal foil on the transparent
substrate film via the adhesive layer, and forming pores by etching
the metal foil. The electromagnetic wave-shielding film, which is a
laminate of the transparent substrate film, the adhesive layer, and
the metal foil mesh, can provide a required shielding property by
appropriately adjusting a thickness of the metal foil or a size of
the mesh pores, even if the strength of an emitted electromagnetic
wave is high as in a plasma display. Further, it also has a
sufficient transparency to assure a visibility of the display
screen (see, for example Patent Document No. 1).
[0006] The electromagnetic wave-shielding film is stuck together
with various optically functional films, such as a near infrared
light-absorbing film, an ultraviolet light-absorbing film, or an
antireflective film by a pressure sensitive adhesive applied onto
the metal foil mesh on the surface of the electromagnetic
wave-shielding film. After sticking together the electromagnetic
wave-shielding film and the optically functional film, an
autoclaving treatment is generally carried out under a pressure of
about 0.3 to 1.5 MPa at about 40 to 80.degree. C. In the
autoclaving treatment as above, the inside of the pores of the
metal foil mesh having a fine concave-convex surface structure is
entirely filled with the pressure sensitive adhesive under
pressure, to entirely exclude bubbles; this property will be
hereinafter sometimes referred to as the "filling-in property".
Further, the pressure sensitive adhesive used in the above sticking
must have a sufficient adhesive strength between the metal foil
mesh on the surface of the electromagnetic wave-shielding film and
the optically functional film, and a sufficient adhesive strength
between the optically functional film and the adhesive layer (for
the metal foil) exposed in the pores of the metal foil mesh so that
a separation of the electromagnetic wave-shielding film from the
optically functional film is prevented. [0007] [Patent Document No.
1] Japanese Unexamined Patent Publication No. 2003-188576.
SUMMARY OF THE INVENTION
[0008] However, pressure sensitive adhesives conventionally used to
stick together the electromagnetic wave-shielding film and various
optically functional films have defects in that the adhesive
strength is insufficient, it does not entirely fill the inside of
the pores of the metal foil mesh under pressure, or bubbles are
generated during a heat treatment.
[0009] The inventors of the present invention found that, in the
particular application of a pressure sensitive adhesive for
sticking together an electromagnetic wave-shielding film and an
optically functional film, a high adhesive strength can be obtained
by adjusting viscoelastic parameters of the pressure sensitive
adhesive within a particular scope.
[0010] Accordingly, the object of the present invention is to
provide a pressure sensitive adhesive which exhibits a sufficient
adhesive strength, can be entirely filled into the inside of the
pores of the metal foil mesh under pressure, and does not generate
bubbles during a heat treatment, in the sticking together of an
electromagnetic wave-shielding film and various optically
functional films.
[0011] Other objects and advantages of the present invention will
be apparent from the following description.
[0012] In accordance with the present invention, there is provided
a pressure sensitive adhesive for sticking together an
electromagnetic wave-shielding film and an optically functional
film, wherein a storage elastic modulus at 70.degree. C. is
7.00.times.10.sup.4 Pa or more.
[0013] In accordance with a preferable embodiment of the pressure
sensitive adhesive of the present invention, a storage elastic
modulus at 23.degree. C. is 1.00.times.10.sup.5 Pa or more.
[0014] In accordance with another preferable embodiment of the
pressure sensitive adhesive of the present invention, a peak
temperature of loss tangent (tan .delta.) is -15.degree. C. or
more.
[0015] In accordance with still another preferable embodiment of
the pressure sensitive adhesive of the present invention, it
comprises an acrylic copolymer containing (meth)acrylic alkyl ester
monomers, and optionally further containing nitrogen-containing
vinyl monomers, as comonomers. In accordance with still another
preferable embodiment, the acrylic copolymer does not contain an
acid comonomer.
[0016] Further, the present invention also relates to a display
panel filter element comprising [0017] (1) an electromagnetic
wave-shielding film, the film being a laminate of a transparent
substrate film, an adhesive for a metal foil, which is applied on
one surface of the transparent substrate film, and a metal foil
mesh formed on the adhesive for a metal foil, [0018] (2) a layer of
the pressure sensitive adhesive, which is applied so as to cover
the metal foil mesh of the electromagnetic wave-shielding film, and
[0019] (3) an optically functional film provided on the pressure
sensitive adhesive.
[0020] The pressure sensitive adhesive of the present invention can
be entirely filled into the inside of the pores of the metal foil
mesh under heating and pressed, and has a durability under an
elevated temperature and a high humidity condition, by adjusting
the storage elastic modulus at an autoclaving treatment of
70.degree. C. within a particular scope.
[0021] The pressure sensitive adhesive of the present invention
also has a higher storage elastic modulus at a normal temperature
of 23.degree. C. in comparison with conventional pressure sensitive
adhesives, and therefore, exhibits good adhesive properties to the
surface of the metal foil mesh on the electromagnetic
wave-shielding film.
[0022] Further, the pressure sensitive adhesive of the present
invention has an excellent corrosion resistance, and therefore, the
metal foil mesh is not corroded when applied on the electromagnetic
wave-shielding film.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] A pressure sensitive adhesive has viscoelasticity, and thus
shows a viscous behavior and an elastic behavior. As viscoelastic
parameters quantitatively representing viscoelasticity, the storage
elastic modulus (G'), loss elastic modulus (G''), and loss tangent
(tan .delta.) are widely used. The storage elastic modulus is
defined as a ratio of elastic stresses at the same phase of strain,
and is associated with a capability of the material to elastically
store an energy. The loss elastic modulus is a ratio at a different
phase of strain, and corresponds to a capability of the material to
dissipate a stress as heat. Further, the ratio (G''/G') of the
above elastic moduli is defined as a loss tangent (tan .delta.),
and represents a ratio of a viscous component to an elastic
component in the material. These viscoelastic parameters can be
determined by an apparatus for measuring dynamic
viscoelasticity.
[0024] The storage elastic modulus at 70.degree. C. of the pressure
sensitive adhesive of the present invention is 7.00.times.10.sup.4
Pa or more, preferably 8.00.times.10.sup.4 Pa or more, more
preferably 9.00.times.10.sup.4 Pa or more. The temperature of
70.degree. C. is a typical temperature at which an electromagnetic
wave-shielding film and an optically functional film are stuck
together in an autoclave. If the storage elastic modulus (G') at
70.degree. C. is less than 7.00.times.10.sup.4 Pa, durability in
the particular application according to the present invention may
be deteriorated under an elevated temperature and a high humidity.
An upper limit of the storage elastic modulus (G') at 70.degree. C.
does not exist. In the particular application according to the
present invention, however, if the pressure sensitive adhesive
becomes too hard, the pressure at the autoclaving treatment must be
increased so that the pressure sensitive adhesive is applied over
the metal foil mesh on the surface of the electromagnetic
wave-shielding film, and the inside of the pores of the metal foil
mesh having a fine concave-convex surface structure is entirely
filled with the pressure sensitive adhesive. In this regard, the
upper limit of the storage elastic modulus at 70.degree. C. may be
preferably 1.00.times.10.sup.6 Pa.
[0025] The storage elastic modulus (G') at 23.degree. C. of the
pressure sensitive adhesive of the present invention is preferably
1.00.times.10.sup.5 Pa or more, more preferably 1.50.times.10.sup.5
Pa or more, most preferably 2.00.times.10.sup.5 Pa or more. If the
storage elastic modulus (G') at 23.degree. C. is less than
1.00.times.10.sup.5 Pa, the adhesive strength between the
electromagnetic wave-shielding film and the optically functional
film may be insufficient in the particular application according to
the present invention. There is not a particular upper limit of the
storage elastic modulus (G') at 23.degree. C. In the particular
application according to the present invention, however, if the
storage elastic modulus at 23.degree. C. (G') becomes too high, the
sticking abilities are reduced. In this regard, the upper limit of
the storage elastic modulus at 23.degree. C. may be preferably
1.00.times.10.sup.6 Pa.
[0026] The peak temperature of loss tangent (tan .delta.) of the
pressure sensitive adhesive of the present invention is preferably
-15.degree. C. or more, more preferably -12.degree. C. or more. If
the peak temperature is less than -15.degree. C., it might be
difficult to obtain a desired adhesive strength. There is not a
particular upper limit of the peak temperature of loss tangent (tan
.delta.). However, if the peak temperature of loss tangent becomes
too high, sticking abilities are reduced. In this regard, the upper
limit of the peak temperature of loss tangent may be preferably
30.degree. C.
[0027] The adhesive strength of the pressure sensitive adhesive of
the present invention is preferably 20 to 50 N/25 mm, more
preferably 22 to 45 N/25 mm, under the conditions shown in Examples
as mentioned below.
[0028] A preferable example of the pressure sensitive adhesive of
the present invention is an acrylic copolymer containing
(meth)acrylic alkyl ester monomers as a comonomer, particularly an
acrylic copolymer containing (meth)acrylic alkyl ester monomers and
nitrogen-containing vinyl monomers as a comonomer. A ratio of the
nitrogen-containing vinyl monomers to all the comonomers contained
the acrylic copolymer is preferably 0.1-30.0% by mass, more
preferably 3-30% by mass, most preferably 4-25% by mass.
Hereinafter, a mixture of monomers constituting the acrylic
copolymer is referred to as a monomer mixture. If an amount of the
nitrogen-containing vinyl monomers used is less than 0.1% by mass,
the adhesive strength may become extremely low. If an amount of the
nitrogen-containing vinyl monomers used is more than 30% by mass,
the filling-in property may be deteriorated.
[0029] The (meth)acrylic alkyl ester monomer is, for example, an
alkyl acrylate or alkyl methacrylate containing an alkyl ester
moiety having 1 to 20 carbon atoms, preferably 1 to 12 carbon
atoms. Specifically, there may be mentioned methyl(meth)acrylate,
ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate,
iso-butyl(meth)acrylate, t-butyl(meth)acrylate,
pentyl(meth)acrylate, hexyl(meth)acrylate,
cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,
isooctyl(meth)acrylate, decyl(meth)acrylate, dodecyl(meth)acrylate,
myristyl(meth)acrylate, palmityl(meth)acrylate, or
stearyl(meth)acrylate. The (meth)acrylic alkyl ester monomer as
above may be used alone or in combination thereof.
[0030] One or more of the (meth)acrylic alkyl ester monomer as
above may be used at an amount of preferably 70-97% by mass, more
preferably 75-95% by mass, in the monomer mixture. If the amount of
the (meth)acrylic alkyl ester monomer is less than 70% by mass, the
filling-in property may be deteriorated. If an amount of the
(meth)acrylic alkyl ester monomer is more than 97% by mass, the
adhesive strength may become extremely low.
[0031] It is preferable that the monomer mixture, which is a
mixture of constitutional components of the acrylic copolymer,
further contains monomers containing one or more cross-linking
functional groups in a molecule. The cross-linking functional group
may be, for example, a hydroxyl group, an amide group, an amino
group, a carboxyl group, or a carbon-carbon unsaturated bond. A
hydroxy group, an amide group, an amino group or a carboxyl group
is reacted with a cross-linking agent to form a cross-linked
structure, whereas an addition reaction of carbon-carbon
unsaturated bonds forms a cross-linked structure. As the monomer
containing a cross-linking functional group in a molecule, there
may be mentioned, for example, a hydroxyalkyl(meth)acrylate, such
as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,
3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate,
3-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate; an
acrylamide, such as acrylamide, methacrylamide, N-methyl
acrylamide, N-methylmethacrylamide, N-methylolacrylamide,
N-methylolmethacrylamide a monoalkylaminoalkyl(meth)acrylate, such
as monomethylaminoethyl(meth)acrylate,
monoethylaminoethyl(meth)acrylate,
monomethylaminopropyl(meth)acrylate,
monoethylaminopropyl(meth)acrylate n ethylenic unsaturated
carboxylic acid, such as acrylic acid, methacrylic acid, crotonic
acid, maleic acid, itaconic acid, citraconic acid. The monomer
containing a cross-linking functional group in a molecule as above
may be used alone or in a combination thereof. The group containing
one or more carbon-carbon unsaturated bonds is for example a
(meth)acryloyl group. Preferably, the cross-linking functional
group-containing monomer does not contain an acid component, from a
standpoint of a suppression of corrosion of the metal foil mesh,
and thus, hydroxyalkyl (meth)acrylate is particularly
preferable.
[0032] The cross-linking functional group-containing monomer can be
used at an amount of, preferably 0-10% by mass, more preferably
0.2-5% by mass, in the monomer mixture.
[0033] As the nitrogen-containing vinyl monomer, there may be
mentioned, for example, (meth)acrylamide, N-tert-butylacrylamide,
N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-diethylacrylamide,
N,N-dimethylaminopropylacrylamide, N-isopropylacrylamide,
N-phenylacrylamide, dimethylaminopropylacrylamide,
N-vinylcaprolactam, acryloyl morpholine, dimethylaminoethyl
acrylate, or acryloylpiperidine.
[0034] Of these vinyl monomers as above, it is preferable to use a
nitrogen-containing vinyl monomer having a glass-transition
temperature (Tg) of 80.degree. C. or more, more preferably
110.degree. C. or more as a glass-transition temperature of a
corresponding homopolymer. As an example of such a
nitrogen-containing vinyl monomer, there may be mentioned
acrylamide (119.degree. C.), methacrylamide (171.degree. C.),
N-tert-butylacrylamide (135.degree. C.), N,N-dimethylacrylamide
(119.degree. C.), N,N-dimethylaminopropylacrylamide (119.degree.
C.), N-isopropylacrylamide (134.degree. C.), N-phenylacrylamide
(160.degree. C.), acryloyl morpholine (145.degree. C.), or
acryloylpiperidine (116.degree. C.), and acryloyl morpholine, or
N,N-dimethylacrylamide is particularly preferable. The temperature
shown in brackets is a glass-transition temperature of the
corresponding homopolymer.
[0035] The nitrogen-containing vinyl monomer also may be the
cross-linking functional group-containing monomer.
[0036] The acrylic copolymer may optionally contain other monomers
such as vinyl acetate or styrene, as a comonomer.
[0037] The acrylic copolymer can be prepared, for example, by any
known polymerization methods, such as a solution polymerization or
a mass polymerization from the monomer mixture containing the
(meth)acrylic alkyl ester monomers and the nitrogen-containing
vinyl monomers. The weight-average molecular weight thereof is
preferably about 200 to 1800 thousands, more preferably 500 to 1500
thousands.
[0038] Preferably, the acrylic copolymer is cross-linked with a
cross-linking agent. As the cross-linking agent, there may be
mentioned, for example, a polyisocyanate compound, a metal chelate
compound, or an epoxy compound, and the polyisocyanate compound is
preferable. As the polyisocyanate compound, there may be mentioned,
for example, a compound containing two or more isocyanate groups,
such as, tolylene diisocyanate or a hydride thereof, an adduct of
tolylene diisocyanate with trimethylolpropane, triphenylmethane
triisocyanate, methylene-bis-di-phenylisocyanate or a hydride
thereof, hexamethylene diisocyanate, an adduct of hexamethylene
diisocyanate with trimethylolpropane, xylylenediisocyanate, an
adduct of xylenediisocyanate with trimethylolpropane,
4,4'-dicyclohexylmethane diisocyanate, or polymerization product
thereof. An amount of the cross-linking agent used is not
particularly limited, but generally, is 0.01 to 10 parts by mass
with respect to 100 parts by mass of the acrylic copolymer.
[0039] The pressure sensitive adhesive of the present invention may
contain, in addition to the acrylic copolymer as above, for
example, a tackifier resin such as petroleum resin, terpene resin,
rosin resin, coumarone-indene resin or phenol resin, antioxidant,
ultraviolet absorber, light stabilizer, softening agent,
anticorrosive agent, or silane coupling agent or filler, or other
appropriate additives, so long as the object of the present
invention is not inhibited.
[0040] Further, the pressure sensitive adhesive of the present
invention can contain a near infrared ray adsorbing agent, a neon
light shielding agent, dyestuff, pigment or the like to prevent or
alleviate an emission of various optical radiations, such as near
infrared ray or neon light, from the plasma display.
[0041] As the near infrared ray adsorbing agent, there may be
mentioned, for example, a colorant, such as a colorant of cyanines,
thiols, metal complexs, an azo compound, polymethines, diphenyl
methanes, triphenyl methanes quinines or diimmonium salt. Two or
more agents as mentioned above can be generally used in combination
in accordance with the wavelengths of two or more near infrared
rays emitted from the plasma display. As the neon light shielding
agent, there may be mentioned, for example, a cyanine compound, a
squalium compound, an azomethine compound, a xanthene compound, or
an oxonol compound.
[0042] The pressure sensitive adhesive of the present invention is
used for sticking together the electromagnetic wave-shielding film
and the optically functional film, as mentioned above. The
electromagnetic wave-shielding film may be a laminate of [0043] (1)
a transparent substrate film, [0044] (2) an adhesive for a metal
foil, which is applied on one surface of the transparent substrate
film, and [0045] (3) a metal foil mesh formed on the adhesive for a
metal foil. As the transparent substrate film, a film of an acrylic
resin, a polycarbonate resin, a polypropylene resin, a polyethylene
resin, a polystyrene resin, a polyester resin, a cellulose resin, a
polysulfone resin, a polyvinyl chloride resin or the like may be
used. Generally, it is preferable to use a film of a polyester
resin such as polyethylene terephthalate resin, in view of its
excellent mechanical strength and high transparency. The thickness
of the transparent substrate film is not particularly limited, but
preferably is about 50 .mu.m to 200 .mu.m in view of the mechanical
strength and a high resistance to bending. If necessary, on one
side or both sides of the transparent substrate film, a corona
discharge treatment can be carried out or one or two easy-to-adhere
pressure sensitive adhesive layers can be provided.
[0046] The electromagnetic wave-shielding film can be prepared, for
example, by a method comprising placing a metal foil on one surface
of a transparent substrate film carrying thereon an adhesive for a
metal foil, and etching the metal foil to form a metal foil mesh.
As a metal foil, there may be mentioned a foil of a metal such as
copper, iron, nickel, or chromium, or an alloy thereof, or an alloy
containing one or more above-mentioned metals as main components.
The metal foil is not particularly limited, but a copper foil is
preferable because an electromagnetic wave can be effectively
shielded, an etching procedure can be easily conducted, and the
workability is good.
[0047] The thickness of the metal foil is preferably 1 .mu.m to 100
.mu.m, more preferably 5 .mu.m to 20 .mu.m. If the thickness is
less than 1 .mu.m, an electromagnetic wave cannot be sufficiently
shielded. If the thickness is more than 100 .mu.m, side-etching
proceeds and cannot be ignored, and thus, it is difficult to form
pores in an accurate manner. The metal foil may have a blackened
layer formed by a blackening treatment on the side of the
transparent substrate film, to impart not only an anticorrosive
property but also an anti-reflective property. A chromate treatment
can be carried out on the blackened layer as an anticorrosive
treatment. When a metal foil without a pre-blackening treatment is
used, a blackening treatment can be carried out at any one of the
subsequent steps. The blackened layer also can be formed by forming
a photosensitive resin layer, which may be a resist layer, from a
black-colored composition, carrying out an etching, and allowing
the resist layer to remain. Alternatively, a metal plating can be
used to form a black coating.
[0048] When a film of an ethylene-vinyl acetate copolymer resin
having a high thermofusibility or a thermofusible resin such as an
ionomer resin is used alone or in combination with another resin
film as a laminate, the transparent substrate film and the metal
foil can be laminated without an adhesive layer therebetween. In
general, however, the lamination is carried out by a dry laminate
method or the like, using an adhesive. As the adhesive for a metal
foil forming the adhesive layer for a metal foil, there may be
mentioned, for example, an adhesive, such as an acrylic resin, a
polyester resin, a polyurethane resin, a polyvinyl alcohol resin, a
vinyl chloride/vinyl acetate copolymer resin, or a ethylene/vinyl
acetate copolymer resin. In addition, a thermosetting resin or a
radiation-curable resin, such as a ultraviolet ray-curable resin,
an electron radiation-curable resin can be used.
[0049] The metal foil on the resulting laminate is etched to form
thick pores, whereby a mesh is formed. Thus, an electromagnetic
wave-shielding film, which is a laminate of the transparent
substrate film, the adhesive layer, and the metal foil mesh can be
obtained.
[0050] In the electromagnetic wave-shielding film, the metal foil
mesh, which is one of the subjects to be stuck with the pressure
sensitive adhesive of the present invention, is required to have a
transmittability, and an aperture ratio of the metal foil mesh used
is generally 65 to 95%. The aperture ratio means a ratio of a
transmittable portion without the metal foil to an area of the
metal foil mesh. The thickness of the metal foil mesh is preferably
1 .mu.m to 100 .mu.m, more preferably 5 .mu.m to 20 .mu.m.
[0051] The pressure sensitive adhesive of the present invention can
be applied on the side of the metal foil mesh of the
electromagnetic wave-shielding film or the surface of the optically
functional film by any known methods, to thereby form a film
carrying the pressure sensitive adhesive. The pressure sensitive
adhesive can be applied, for example, by a method comprising
forming a layer of the pressure sensitive adhesive of the present
invention on a releasable surface of the release sheet by a known
applying method, and laying the layer of the pressure sensitive
adhesive on the side of the metal foil mesh or the surface of the
optically functional film to transfer the layer thereto, or a
method comprising applying the pressure sensitive adhesive on the
side of the metal foil mesh or the surface of the optically
functional film by a known applying method. The applying method may
be, for example, a roll coater, a knife coater, a die coater, a
blade coater, a gravure coater, a screen printing, or the like.
[0052] After the pressure sensitive adhesive of the present
invention is applied on the side of the metal foil mesh of the
electromagnetic wave-shielding film or the surface of the optically
functional film, it is subjected to an autoclaving treatment in the
state that it is stuck to the metal foil mesh side and the
optically functional film surface. The autoclaving treatment can be
carried out by a known method, for example, at 40 to 80.degree. C.,
under the pressure of 0.3 to 1.5 MPa. Preferably, the pressure
sensitive adhesive is applied at a thickness such that it can
entirely cover the metal foil mesh. The thickness of the resulting
pressure sensitive adhesive after the autoclaving treatment is
preferably 20 .mu.m to 100 .mu.m, more preferably 20 .mu.m to 40
.mu.m.
[0053] As the optically functional film, there may be mentioned,
for example, a film absorbing a near infrared or infrared light, a
film absorbing a neon light, a film absorbing an ultraviolet light,
a film preventing or alleviating a leakage of an electromagnetic
wave in addition to the metal foil mesh, a film inhibiting a
reflection of an outside light, or a film adjusting a color tone.
Further, a film protecting a glass surface of a display panel, or a
film preventing a glass from shattering also can be stuck. A
substrate of the optically functional film may be a film of
polyethylene terephthalate, polymethyl methacrylate, polycarbonate
or the like. The thickness of the substrate is about 20 .mu.m to
300 .mu.m.
[0054] The display panel filter element according to the present
invention comprises [0055] (1) the electromagnetic wave-shielding
film, the film being a laminate of [0056] (a) the transparent
substrate film, [0057] (b) the adhesive for a metal foil, the
adhesive (b) being applied on one surface of the transparent
substrate film(a), and [0058] (c) the metal foil mesh formed on the
adhesive (b) for a metal foil, [0059] (2) the pressure sensitive
adhesive, which is applied so as to cover the metal foil mesh of
the electromagnetic wave-shielding film, and [0060] (3) the
optically functional film provided on the pressure sensitive
adhesive.
[0061] The display panel filter element can be used as a component
of a plasma display panel or the like.
EXAMPLES
[0062] The present invention will now be further illustrated by,
but is by no means limited to, the following Examples.
Example 1
[0063] To 200 parts by mass of ethyl acetate, 64.5 parts by mass of
n-butyl acrylate, 30 parts by mass of methyl acrylate, 0.5 part by
mass of 2-hydroxyethyl acrylate, and 5 parts by mass of acryloyl
morpholine as monomer components, and 0.2 parts by mass of
azobisisobutyronitorile as an initiator were added. The whole was
stirred at 60.degree. C. for 17 hours to obtain a solution of
acrylate ester copolymer having a weight-average molecular weight
of 850 thousand. To the resulting copolymer solution, a
trifunctional adduct based on xylenediisocyanate [TD-75:
manufactured by Soken Chemical & Engineering Co., Ltd.] was
added as a cross-linking agent at an amount of 0.5 part by mass
with respect to 100 parts by mass of solid content of the copolymer
solution. The whole was diluted with 2-butanone to a solution
having a concentration of 25% by mass, to thereby obtain a solution
of a pressure sensitive adhesive. A glass-transition temperature of
acryloyl morpholine homopolymer was 145.degree. C.
[0064] The resulting solution of the pressure sensitive adhesive
was coated on a releasable surface of a release film [SP-PET3811:
manufactured by LINTEC Corporation] by a knife coater, and dried at
90.degree. C. for one minute to obtain a layer of the pressure
sensitive adhesive with a thickness of 25 .mu.m. A polyethylene
terephthalate film [CosmoshineA4300: manufactured by Toyobo Co.,
Ltd.] with a thickness of 100 .mu.m was laminated as a substrate of
an optically functional film to obtain a film carrying the pressure
sensitive adhesive.
Example 2
[0065] The procedure of Example 1 was repeated, except that 59.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 850 thousand.
Example 3
[0066] The procedure of Example 1 was repeated, except that 54.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 15 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 850 thousand.
Example 4
[0067] The procedure of Example 1 was repeated, except that 49.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 20 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 850 thousand.
Example 5
[0068] The procedure of Example 1 was repeated, except that 64.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 5 parts
by mass of N,N-dimethyl acrylamide were used as monomer components,
to obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand. A glass-transition temperature of the
homopolymer of N,N-dimethyl acrylamide was 119.degree. C.
Example 6
[0069] The procedure of Example 1 was repeated, except that 59.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of N,N-dimethyl acrylamide were used as monomer components,
to obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 7
[0070] The procedure of Example 1 was repeated, except that 54.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 15 parts
by mass of N,N-dimethyl acrylamide were used as monomer components,
to obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 8
[0071] The procedure of Example 1 was repeated, except that 49.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, and 20 parts
by mass of N,N-dimethyl acrylamide were used as monomer components,
to obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 9
[0072] The procedure of Example 1 was repeated, except that 59
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 1 part by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 10
[0073] The procedure of Example 1 was repeated, except that 58
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 2 parts by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 11
[0074] The procedure of Example 1 was repeated, except that 57
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 3 parts by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Example 12
[0075] The procedure of Example 1 was repeated, except that 54
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 1 part by mass of 2-hydroxyethyl acrylate, and 10 parts
by mass of acryloyl morpholine were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Comparative Example 1
[0076] The procedure of Example 1 was repeated, except that 49.5
parts by mass of n-butyl acrylate, 30 parts by mass of methyl
acrylate, 20 parts by mass of methyl methacrylate, and 0.5 part by
mass of 2-hydroxyethyl acrylate were used as monomer components, to
obtain a film carrying a pressure sensitive adhesive. A
weight-average molecular weight of the resulting acrylate ester
copolymer was 800 thousand.
Comparative Example 2
[0077] The procedure of Example 1 was repeated, except that 79
parts by mass of n-butyl acrylate, 20 parts by mass of methyl
acrylate, and 1 part by mass of 2-hydroxyethyl acrylate were used
as monomer components, to obtain a film carrying a pressure
sensitive adhesive. A weight-average molecular weight of the
resulting acrylate ester copolymer was 900 thousand.
[Evaluation of Properties]
(1) Preparation of a Laminate Film of a Copper Mesh
[0078] A copper mesh-laminated film was prepared as an
electromagnetic wave-shielding film to be used in the following
evaluation of properties, as follows:
[0079] A polyethylene terephthalate film [Cosmoshine A4100:
manufactured by Toyobo Co., Ltd.] with a thickness of 100 .mu.m was
stuck to a copper foil having a blackened surface [BW-S:
manufactured by Furukawa Circuit Foil Co., Ltd] with a thickness of
10 .mu.m on the surface opposite to the blackened side, with an
adhesive based on a polyurethane resin [mixture of Takelac A310
(main component)/Takenate A10 (curing agent)/ethyl acetate=12/1/21
(mass ratio): manufactured by Takeda Pharmaceutical Co., Ltd.] for
a metal foil, to obtain a laminate of the polyethylene
terephthalate film/the layer of the adhesive for a metal foil/the
copper foil.
[0080] A resist solution containing casein as a main ingredient was
coated on the copper foil side of the resulting laminate and dried
to form a photosensitive resin layer. A mask with a pattern was
used to conduct a contact exposure with an ultraviolet ray. Then,
the laminate was developed with water, cured, and baked at
100.degree. C. to form a resist pattern. The mask used had a
pattern with pitches of 300 .mu.m and line widths of 10 .mu.m. The
laminate with the resulting resist pattern was etched on the resist
pattern side by spraying a ferric chloride solution (Baume
degree=42; temperature=30.degree. C.), and washed with water. After
the resist was removed with an alkali solution, the laminate was
washed and dried to obtain a copper mesh laminate, i.e., an
electromagnetic wave-shielding film, composed of the polyethylene
terephthalate film/the layer of the adhesive for a metal foil/the
copper mesh. The aperture ratio of the copper foil was 80%, and the
thickness of the copper foil was 10 .mu.m.
(2) Method of Measuring an Adhesive Strength to the Copper Mesh
[0081] A sample having a width of 25 mm and a length of 240 mm was
cut from each of the films carrying the pressure sensitive
adhesive. After a release film was peeled therefrom, the film
carrying the pressure sensitive adhesive was stuck to the copper
mesh laminate on the copper mesh side. The whole was pressed in an
autoclave (manufactured by Kurihara Manufactory Inc.) under 0.5 MPa
at 70.degree. C. for 30 minutes, and then allowed to stand at
23.degree. C. under a relative humidity of 50% for 24 hours.
Thereafter, an adhesive strength was measure by a tensile strength
tester (Tensilon: manufactured by Orientec Co., Ltd.) at a peeling
rate of 300 mm/min and a peeling angle of 180.degree.. In all films
prepared in Examples 1 to 12 and Comparative Examples 1 and 2, the
peeling occurred at an interface between the pressure sensitive
adhesive and the copper mesh.
(3) Method of Measuring an Adhesive Strength to a Glass
[0082] The procedure of the above item "(2) Method of measuring an
adhesive strength to the copper mesh" was repeated, except that a
non-alkali glass (1727: manufactured by Corning Inc.) was used
instead of the copper mesh laminate as the adherend.
(4) Method of Measuring a Storage Elastic Modulus (G') and a Loss
Elastic Modulus (G'')
[0083] A specimen having a cylindrical layer (diameter=8 mm and
thickness=3 mm) of the pressure sensitive adhesive on a release
sheet was prepared by successively laminating thereon layers of the
pressure sensitive adhesive released from a release film carrying
thereon a layer (thickness=25 .mu.m) of the pressure sensitive
adhesive. Then, a storage elastic modulus (G') and a loss elastic
modulus (G'') were measured by a torsional shear testing method
under the following conditions: [0084] Measuring apparatus: an
apparatus for measuring a dynamic viscoelasticity [DYNAMIC ANALYZER
RDAII: manufactured by Rheometric Co., Ltd.] [0085] Frequency: 1 Hz
[0086] Temperature: 23.degree. C., and 70.degree. C.
(5) Method of Calculation of a Loss Tangent (tan .delta.)
[0087] A loss tangent (tan .delta.) can be calculated from a
storage elastic modulus (G') and a loss elastic modulus (G'') by
the following equation:
loss tangent=loss elastic modulus/storage elastic modulus
(6) Existence or Nonexistence of Bubbles
[0088] A sample having a width of 50 mm and a length of 120 mm was
cut from each of the films carrying the pressure sensitive
adhesive. After a release film was peeled therefrom, the film
carrying the pressure sensitive adhesive was stuck to the copper
mesh laminate on the copper mesh side. The whole was pressed in an
autoclave (manufactured by Kurihara Manufactory Inc.) under 0.5 MPa
at 70.degree. C. for 30 minutes, and then the existence or
nonexistence of bubbles was visually observed. The results were
evaluated as follows:
[0089] .smallcircle.: No defect in appearance;
[0090] x: bubbles existed at an interface between the pressure
sensitive adhesive layer and the copper mesh.
(7) Method of Evaluating Durability
[0091] A sample having a width of 50 mm and a length of 120 mm was
cut from each of the films carrying the pressure sensitive
adhesive. After a release film was peeled therefrom, the film
carrying the pressure sensitive adhesive was stuck to the copper
mesh laminate on the copper mesh side. The whole was pressed in an
autoclave (manufactured by Kurihara Manufactory Inc.) under 0.9 MPa
at 70.degree. C. for 60 minutes, and then allowed to stand at
23.degree. C. under a relative humidity of 90% for 24 hours, and
further, at 80.degree. C. under a relative humidity of 50% for 24
hours. Thereafter, the appearance was visually evaluated as
follows:
[0092] No defect in appearance;
[0093] .smallcircle.: No bubble having a maximum diameter of 100
.mu.m or more was observed;
[0094] .times.: Bubble having a maximum diameter of 100 .mu.m or
more was observed.
(8) Method of Evaluating Corrosion Resistance
[0095] A sample having a width of 50 mm and a length of 120 mm was
cut from each of the films carrying the pressure sensitive
adhesive. After a release film was peeled therefrom, the film
carrying the pressure sensitive adhesive was stuck to the copper
mesh laminate on the copper mesh side. The whole was pressed in an
autoclave (manufactured by Kurihara Manufactory Inc.) under 0.5 MPa
at 70.degree. C. for 30 minutes (pressure conditions 1), or under
0.9 MPa at 70.degree. C. for 60 minutes (pressure conditions 2) to
obtain specimens for evaluation. Before and after the specimen was
allowed to stand at 60.degree. C. under a relative humidity of 90%
for 500 hour, transmittances at a wave length of 700 nm were
measured by a spectrophotometer [MPC3100: manufactured by Shimadzu
Corp.], and a difference of transmittance rate (.DELTA.Y) of the
specimen was calculated. When .DELTA.Y was not more than 1.5%, a
corrosion resistance was good.
(9) Results of Evaluation
[0096] The results of the evaluation are shown in the following
Table 1.
TABLE-US-00001 TABLE 1 Peak Corrosion resistance Corrosion
resistance Adhesive Storage elastic temperature (Pressure
conditions 1) (Presssure conditions 2) strength (N/25 mm) modulus
(Pa) of tan .delta. .DELTA.Y (%) 700 nm .DELTA.Y (%) 700 nm on
copper mesh on glass 23.degree. C. 70.degree. C. (.degree. C.)
Bubbles Durability 60.degree. C. 90% RH 500 h 60.degree. C. 90% RH
500 h Example 1 22.8 23.0 2.82 .times. 10.sup.5 1.02 .times.
10.sup.5 -10.0 .largecircle. .largecircle. 0.28 0.28 Example 2 25.0
25.0 3.15 .times. 10.sup.5 1.26 .times. 10.sup.5 -1.5 .largecircle.
.largecircle. 0.40 0.41 Example 3 29.0 34.0 4.56 .times. 10.sup.5
1.56 .times. 10.sup.5 5.0 .largecircle. .largecircle. 0.31 0.33
Example 4 36.3 36.0 7.47 .times. 10.sup.5 1.33 .times. 10.sup.5
15.0 .largecircle. .largecircle. 0.66 0.66 Example 5 22.0 23.0 2.11
.times. 10.sup.5 7.67 .times. 10.sup.4 -11.0 .largecircle.
.largecircle. 0.34 0.34 Example 6 28.0 25.0 2.19 .times. 10.sup.5
8.34 .times. 10.sup.4 -3.0 .largecircle. .largecircle. 0.52 0.55
Example 7 37.5 34.0 3.27 .times. 10.sup.5 9.66 .times. 10.sup.4 2.7
.largecircle. .largecircle. 0.48 0.51 Example 8 41.7 36.0 6.79
.times. 10.sup.5 1.42 .times. 10.sup.5 10.1 .largecircle.
.largecircle. 0.51 0.51 Example 9 27.5 20.5 2.55 .times. 10.sup.5
1.12 .times. 10.sup.5 -2.0 .largecircle. .circleincircle. 0.25 0.26
Example 10 29.0 19.5 2.74 .times. 10.sup.5 1.32 .times. 10.sup.5
-1.0 .largecircle. .circleincircle. 0.22 0.21 Example 11 41.5 20.5
2.67 .times. 10.sup.5 9.61 .times. 10.sup.5 4.9 .largecircle.
.circleincircle. 0.34 0.35 Example 12 31.0 28.0 4.86 .times.
10.sup.5 1.56 .times. 10.sup.5 17.0 .largecircle. .circleincircle.
0.35 0.37 Comparative 25.0 25.0 1.43 .times. 10.sup.5 5.54 .times.
10.sup.4 -3.0 X X 0.38 0.41 Example 1 Comparative 13.4 12.0 8.28
.times. 10.sup.4 4.46 .times. 10.sup.4 -25.0 X X 0.52 0.55 Example
2
[0097] The pressure sensitive adhesive of the present invention can
be used, for example, in the manufacture of a display panel filter
element constituting a plasma display panel or the like, and in the
manufacture of a display using the same.
[0098] As above, the present invention was explained with reference
to particular embodiments, but modifications and improvements
obvious to those skilled in the art are included in the scope of
the present invention. (24)
* * * * *