U.S. patent application number 09/789068 was filed with the patent office on 2001-09-13 for pressure-sensitive adhesive sheets and method of fixing functional film.
Invention is credited to Kishioka, Hiroaki, Ohura, Masahiro, Yoshikawa, Takao.
Application Number | 20010021452 09/789068 |
Document ID | / |
Family ID | 18573797 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021452 |
Kind Code |
A1 |
Kishioka, Hiroaki ; et
al. |
September 13, 2001 |
Pressure-sensitive adhesive sheets and method of fixing functional
film
Abstract
A pressure-sensitive adhesive sheets comprising a layer of a
crosslinked pressure-sensitive adhesive, which is formed by an
acrylic polymer made of a homopolymer or copolymer of a monomer
containing a (meth)acrylate as a principal component, a silane
coupling agent and a crosslinking agent, wherein a sol component of
the crosslinked pressure-sensitive adhesive has a weight-average
molecular weight of not less than 300,000 and a proportion of a
low-molecular component having a molecular weight of not more than
100,000 in the sol component is not more than 15% by weight in the
measurement of the molecular weight by the gel permeation
chromatography method, which the sheet cause neither lifting nor
formation of bubbles at the bonding interface even when exposed to
severe conditions such as high temperature or high temperature and
humidity in case a functional film is bonded/fixed to a display
device, thus making it possible to maintain good appearance for a
long period.
Inventors: |
Kishioka, Hiroaki; (Osaka,
JP) ; Ohura, Masahiro; (Osaka, JP) ;
Yoshikawa, Takao; (Osaka, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
18573797 |
Appl. No.: |
09/789068 |
Filed: |
February 20, 2001 |
Current U.S.
Class: |
428/343 ;
156/94 |
Current CPC
Class: |
C08G 2170/40 20130101;
C09J 2433/00 20130101; C08G 18/809 20130101; C09J 7/10 20180101;
Y10T 428/28 20150115; Y10T 428/31612 20150401; C09J 7/385 20180101;
C09J 2301/302 20200801; C08G 18/6254 20130101 |
Class at
Publication: |
428/343 ;
156/94 |
International
Class: |
B32B 035/00; B32B
007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2000 |
JP |
2000-52243 |
Claims
What is claimed is:
1. A pressure-sensitive adhesive sheet comprising a layer of a
crosslinked pressure-sensitive adhesive, which is formed by an
acrylic polymer made of a homopolymer or copolymer of a monomer
containing a (meth)acrylate as a principal component, a silane
coupling agent and a crosslinking agent, wherein a sol component of
the crosslinked pressure-sensitive adhesive has a weight-average
molecular weight of not less than 300,000 and a proportion of a
low-molecular component having a molecular weight of not more than
100,000 in the sol component is not more than 15% by weight in the
measurement of the molecular weight by the gel permeation
chromatography method.
2. The pressure-sensitive adhesive sheet according to claim 1,
wherein the amount of the silane coupling agent is within a range
from 0.001 to 5 parts by weight based on 100 parts by weight of the
acrylic polymer.
3. The pressure-sensitive adhesive sheet according to claim 1 or 2,
wherein a sol fraction of the sol component of the layer of the
crosslinked pressure-sensitive adhesive agent is within a range
from 5 to 60% by weight.
4. The pressure-sensitive adhesive sheet according to any one of
claims 1 to 3, wherein the adhesive strength to glass is not less
than 300 g/20 mm width.
5. A method of fixing a functional film, which comprises
bonding/fixing the functional film to a display device through the
pressure-sensitive adhesive sheets of any one of claims 1 to 4.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to sheet- or tape-shaped
pressure-sensitive adhesive sheets, which are used to fix a
functional film to a display device.
[0003] 2. Description of the Related Art
[0004] Pressure-sensitive adhesive sheets have recently been
utilized in various fields because of good bonding operation
properties. Among these, pressure-sensitive adhesive sheets
comprising, as a base component, a homopolymer or copolymer of a
monomer containing, as a base, an acrylic polymer (i.e. an alkyl
(meth)acrylate) are superior in durability performances such as
weathering resistance, heat resistance, deterioration resistance
and the like. Therefore, they are used particularly preferably in
the fields where these durability performances are required.
[0005] As one of uses of pressure-sensitive adhesive sheets, for
example, there has been known a use of bonding/fixing functional
films such as conductive film, antiglare film and the like to a
display device (glass surface thereof). In view of use such as
display device to which severe requirements on the appearance is
made, it is required for these pressure-sensitive adhesive sheets
to cause neither lifting nor formation of bubbles at the bonding
interface when exposed to severe conditions such as high
temperature or high temperature and humidity (e.g. inside of
automobiles or warehouses in the summer season) for a long time,
not to mention at the beginning of standing after bonding/fixing,
thus making it possible to maintain good appearance.
[0006] To resolve these requirements, it is suggested to use
acrylic pressure-sensitive adhesive sheets comprising an acrylic
polymer, as a base component, and a silane coupling agent
incorporated into the acrylic polymer, thereby to improve the
adhesion to the glass surface. Although use of the
pressure-sensitive adhesive sheets improves the adhesion to glass
to some extent, there still remains such a problem that lifting and
formation of bubbles occur at the bonding interface when exposed to
severe conditions such as high temperature or high temperature and
humidity (e.g. inside of automobiles or warehouses in the summer
season) for a long time, thus making it hard to maintain good
appearance.
SUMMARY OF THE INVENTION
[0007] In light of the circumstances described above, an object of
the present invention is to provide pressure-sensitive adhesive
sheets for fixing a functional film to a display device, having
excellent weathering resistance which cause neither lifting nor
formation of bubbles at the bonding interface even when exposed to
severe conditions such as high temperature or high temperature and
humidity (e.g. inside of automobiles or warehouses in the summer
season) for a long time, thus making it possible to maintain good
appearance.
[0008] As a result of an intensively study about the object
described above, the present inventors have found that
pressure-sensitive adhesive sheets having excellent weathering
resistance, wherein the pressure-sensitive adhesive has a
crosslinked structure, are obtained by incorporating a silane
coupling agent into an acrylic polymer and crosslinking the acrylic
copolymer, and a sol component of the crosslinked
pressure-sensitive adhesive having a specific molecular weight
distribution with less low-molecular component, and that, when a
functional film is bonded/fixed to a display device using the
resulting pressure-sensitive adhesive sheets, neither lifting nor
formation of bubbles occurs at the bonding interface even during
the weathering evaluation test, thus making it possible to maintain
good appearance for a long period, whereby the present invention
has been completed.
[0009] That is, the present invention is directed to a
pressure-sensitive adhesive sheet comprising a layer of a
crosslinked pressure-sensitive adhesive, which is formed by an
acrylic polymer made of a homopolymer or copolymer of a monomer
containing a (meth)acrylate as a principal component, a silane
coupling agent and a crosslinking agent, wherein a sol component of
the crosslinked pressure-sensitive adhesive has a weight-average
molecular weight of not less than 300,000 and a proportion of a
low-molecular component having a molecular weight of not more than
100,000 in the sol component is not more than 15% by weight in the
measurement of the molecular weight by the gel permeation
chromatography method. Also the present invention is directed to a
method of fixing a functional film, which comprises bonding/fixing
the functional film to a display device through the
pressure-sensitive adhesive sheets with the constitution described
above.
[0010] As used herein, the sol component of the layer of the
crosslinked pressure-sensitive adhesive refers to a sol component
which is a soluble polymer dissolved in ethyl acetate when a
predetermined amount Mo (about 0.5 g) of the above layer is covered
with a fluororesin film having numerous pores (diameter: 0.2
.mu.m), followed by dipping in ethyl acetate at 20.degree. C. for
240 hours. The sol fraction thereof is determined by calculating
from the formula: (Mt/Mo).times.100 (% by weight) where Mt is an
amount of the sol component and Mo is an initial weight before
dipping.
[0011] Using the above soluble polymer (sol component), the
weight-average molecular weight of the sol component and the
proportion (% by weight) of the low-molecular component having a
molecular weight of not more than 100,000 were determined from a
molecular weight distribution curve by the gel permeation
chromatography method (hereinafter referred to as the GPC method).
The measuring conditions of the molecular weight distribution curve
by the GPC method are as follows: concentration of sample; 1 mg/ml,
amount of sample introduced; 500 mg, column temperature; 40.degree.
C., and flow rate; 1.0 ml/minute.
[0012] As used herein, the term "pressure-sensitive adhesive
sheets" is a general term for pressure-sensitive adhesive tapes and
various adhesive products (e.g. pressure-sensitive adhesive labels)
having the shape which resembles closely to that of the
pressure-sensitive adhesive tapes.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The acrylic polymer used as the base polymer in the present
invention is a homopolymer or copolymer of a monomer containing an
alkyl (meth)acrylate as a principal component, and the other
monomer, capable of copolymerizing with the alkyl (meth)acrylate,
can be used in combination with the alkyl (meth)acrylate.
[0014] The alkyl (meth)acrylate is a monomer represented by the
following general formula: 1
[0015] wherein R.sup.1 is a hydrogen atom or a methyl group, and
R.sup.2 is an alkyl group having 1 to 18 carbon atoms. Specific
examples thereof include methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl
(meth)acrylate, lauryl (meth)acrylate and the like.
[0016] The copolymerizable monomer, for example, there can be used
any of various monomers, which are known as a monomer for
modification of an acrylic pressure-sensitive adhesive, such as
vinyl acetate, styrene, (meth)acrylonitrile, (meth)acrylamide,
(meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl
(meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycidyl
(meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate and the like.
These copolymerizable monomers are usually used in the proportion
of not more than 50% by weight based on the total amount of the
alkyl (meth)acrylate and the copolymerizable monomer.
[0017] Such an acrylic polymer is preferably a polymer which
exhibits a proper molecular weight distribution before
crosslinking, particularly the low-molecular component exhibits a
molecular weight smaller than as usual, so that the sol component
has a weight-average molecular weight of not less than 300,000,
preferably not less than 500,000 (usually up to 5,000,000), and the
amount of a low-molecular component having a molecular weight of
not more than 100,000 is not more than 15% by weight, preferably
not more than 10% by weight by weight in the measurement of the
molecular weight by the gel permeation chromatography method after
forming a crosslinked structure by the acrylic polymer, the silane
coupling agent and the crosslinking agent. The molecular weight
constitution of the sol component after crosslinking can be easily
set within the above range by using the acrylic polymer with such a
constitution to a proper crosslinking treatment.
[0018] Before crosslinking, the acrylic polymer with the above
constitution can be obtained, for example, by polymerizing due to a
solution polymerization method, an emulsion polymerization method
or a bulk polymerization method using a polymerization initiator
such as azo compound or peroxide, or photopolymerizing due to
irradiation with light using a photopolymerization initiator, or
polymerizing due to irradiation with radiation to obtain an acrylic
polymer, adding an organic solvent capable of dissolving on a
low-molecular component, and removing only the low-molecular
component with separating; or adding a required additive to the
polymer, forming the mixture into a tape, and treating the tape
with the same organic solvent as described above, thereby to elute
the low-molecular component.
[0019] According to alternative method of forming the acrylic
polymer with the above constitution, an acrylic polymer with less
low-molecular component can be obtained by using a polymerization
solvent having a small chain transfer coefficient in the solution
polymerization and polymerizing at the temperature as low as
possible due to an increase of the monomer concentration, or
employing the photopolymerization method using a
photopolymerization initiator, that is, selecting the operation
conditions on polymerization. The polymerization operation and the
operation of removing the low-molecular component after
polymerization may be appropriately used in combination.
[0020] In the present invention, examples of the silane coupling
agent to be incorporated into the acrylic polymer include
vinyltrichlorosilane, vinyltris (.beta.-methoxyethoxy)silane,
vinyltriethoxysilane, vinyltrimethoxysilane,
[0021] .gamma.-methacryloxypropyltrimethoxysilane,
[0022] .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
[0023] .gamma.-glycidoxypropyltrimethoxysilane,
[0024] .gamma.-glycidoxypropyltriethoxysilane,
[0025] N-.beta.
(aminoethyl).gamma.-aminopropyltrimethoxysilane,
[0026] N-.beta.
(aminoethyl).gamma.-aminopropylmethyldimethoxysilane,
[0027] .gamma.-aminopropyltriethoxysilane,
[0028] N-phenyl-.gamma.-aminopropyltrimethoxysilane,
[0029] .gamma.-chloropropyltrimethoxysilane and the like.
[0030] The amount of the silane coupling agent is usually within a
range from 0.001 to 5 parts by weight, and preferably from 0.01 to
1 parts by weight, based on 100 parts by weight of the acrylic
polymer. When the amount of the silane coupling agent is too small,
the adhesion to the display device (glass) can not be sufficiently
improved. On the other hand, when the amount is too large, an
adverse influence is likely to be exerted on the bonding
properties, which is not preferred.
[0031] In the present invention, in case the silane coupling agent
is incorporated into the acrylic polymer and the acrylic polymer is
crosslinked with the crosslinking agent, the kind and amount of the
crosslinking agent are appropriately selected so that the sol
fraction after crosslinking, that is, the proportion of the soluble
polymer is usually within a range from 5 to 60% by weight, and
preferably from 10 to 40% by weight, and the weight-average
molecular weight with respect to the sol component after
crosslinking and the proportion of the lower-molecular component
having a molecular weight of not more than 100,000, which are
determined by the measurement of the molecular weight by the gel
permeation chromatography method, are within the above range.
[0032] The crosslinking agent include conventionally known
crosslinking agents, a polyfunctional melamine compound and/or a
polyfunctional epoxy compound are particularly preferred. Specific
examples thereof include methylatedmethylolmelamine, butylated
hexamethylolmelamine, diglycidylaniline, glycerin diglicidyl ether
and the like. The amount of the crosslinking agent is usually
within a range from 0.001 to 10 parts by weight, and preferably
from 0.01 to 5 parts by weight, based on 100 parts by weight of the
acrylic polymer.
[0033] Use of a polyfunctional isocyanate compound is also
preferred, and examples of such a compound include tolylene
diisocyanate, hexamethylene diisocyanate, polymethylenepolyphenyl
isocyanate, diphenylmethane diisocyanate,
trimethylolpropanetolylene diisocyanate, polyether polyisocyanate,
polyester polyisocyanate and the like. The amount of such a
compound is usually within a range from 0.01 to 20 parts by weight,
and preferably from 0.05 to 15 parts by weight, based on 100 parts
by weight of the acrylic polymer.
[0034] The pressure-sensitive adhesive sheets of the present
invention has a layer of the pressure-sensitive agent crosslinked
with the crosslinking agent, which usually has a thickness within a
range from 5 to 500 .mu.m, and preferably from 10 to 100 .mu.m.
This layer may be formed into a sheet or tape by forming on one or
both surfaces of a transparent substrate made of a plastic film
having a thickness within a range from 10 to 1,000 .mu.m, or may be
formed into the same form described above with no substrate by
forming on a proper release liner.
[0035] These pressure-sensitive adhesive sheets have an adhesive
strength to glass of not less than 300 g/20 mm width, and
preferably not less than400 g/20 mm width (usually preferably not
more than 2000 g/20 mm width), and are used particularly preferably
as an adhesive fixing material for fixing composite films having
various functions, which usually have a thickness within a range
from about 50 to 200 .mu.m (for example, functional films such as
conductive film, antiglare film, heat ray screening film,
anti-reflective sheet, etc.) to a display device (glass surface
thereof).
[0036] In the present invention, in order to fix the above
functional film to the display device, the both are bonded/fixed
through the pressure-sensitive adhesive sheets. Usually, the
pressure-sensitive adhesive sheets are applied to the functional
film and the resultant is applied to the display device (glass
surface thereof). Whereby, the functional film can be fixed with
good adhesive strength without causing lifting and formation of
bubbles at the bonding interface when exposed to severe conditions
such as high temperature or high temperature and humidity (e.g.
inside of automobiles or warehouses in the summer season) for a
long time, not to mention at the beginning of standing after
bonding, thus making it possible to maintain good appearance for a
long term.
[0037] The reason why such an effect is exerted is not apparent,
necessarily. The present inventors consider the reason as follows.
That is, an improvement in adhesion to the adherend (display
device: glass, etc.) due to incorporation of the silane coupling
agent and the constitution of the polymer wherein the amount of the
low-molecular component in the sol component after is reduced after
crosslinking with the crosslinking agent exerts an action of
inhibiting a gas evolved from the pressure-sensitive adhesive
sheets, the functional film or the like from causing formation of
bubbles and lifting.
EXAMPLES
[0038] The present invention will be described in more detail by
way of the following Examples. In the Examples, parts are by weight
unless otherwise stated. Acrylic polymer solutions A to C used in
the following Examples and Comparative Examples are prepared by the
following manners.
[0039] <Acrylic polymer solution A>
[0040] 70 Parts of 2-ethylhexyl acrylate, 25 parts of n-butyl
acrylate, 5 parts of acrylic acid, 0.06 parts of 3-hydroxypropyl
acrylate, and 45 parts of ethyl acetate as a polymerization solvent
were charged in a three-necked flask, followed by stirring while
introducing a nitrogen gas for two hours. After removing oxygen in
the polymerization system, 0.2 parts of benzoyl peroxide was added
and the mixture was reacted by heating to 60.degree. C. for ten
hours, then reacted by heating to 75.degree. C. for two hours. To
the reaction solution, ethyl acetate was added to obtain an acrylic
polymer solution A having a solid content of 45% by weight.
[0041] <Acrylic polymer solution B>
[0042] To 100 parts of the acrylic polymer solution A, 120 parts of
n-heptane was added dropwise while stirring over six hours. After
left to stand for 24 hours, the supernatant was separated. To the
polymer solution after separating the supernatant, toluene was
added and dissolved and, furthermore, the operation of adding 120
parts of n-heptane and separating the supernatant in the same
manner as described above was repeated five times. To the final
polymer solution thus obtained, 80 parts of toluene was added,
followed by concentration to obtain an acrylic polymer solution B
having a solid content of 25% by weight.
[0043] <Acrylic polymer solution C>
[0044] The acrylic polymer solution A and the acrylic polymer
solution B were mixed in a weight ratio of 1:1 to obtain an acrylic
polymer solution C having a solid content of 35% by weight.
Example 1
[0045] To 100 parts of the acrylic polymer solution B, 1.5 parts of
tolylene diisocyanate and 0.09 parts of
.gamma.-glycidoxypropyltrimethoxy- silane were added to prepare a
pressure-sensitive adhesive solution. This solution was spread over
a substrate made of a polyethylene terephthalate film having a
thickness of 188 .mu.m so that the thickness after drying becomes
25 .mu.m, dried with heating at 130.degree. C. for three minutes
and then aged at 50.degree. C. for 72 hours to form a
pressure-sensitive adhesive sheet for measurement of the adhesive
strength, which has a layer of a crosslinked pressure-sensitive
adhesive. In the same manner as described above, a
pressure-sensitive adhesive sheet for measurement of the weathering
resistance, comprising a release liner made of a polyethylene
terephthalate film having a thickness of 38 .mu.m and a layer
having a thickness of 25 .mu.m of a crosslinked pressure-sensitive
adhesive formed on the release liner was produced.
Example 2
[0046] To 100 parts of the acrylic polymer solution C, 3 parts of
diphenylmethane diisocyanate and 0.12 parts of
.gamma.-methacryloxypropyl- trimethoxysilane were added to prepare
a pressure-sensitive adhesive solution. In the same manner as in
Example 1, a pressure-sensitive adhesive sheet for measurement of
the adhesive strength and a pressure-sensitive adhesive sheet for
measurement of the weathering resistance were produced.
Comparative Example 1
[0047] To 100 parts of the acrylic polymer solution C, 0.8 parts of
trimethylolpropanetolylene diisocyanate and 0.15 parts of
.beta.-(3,4-epoxycyclohexyl) trimethoxysilane were added to prepare
a pressure-sensitive adhesive solution. In the same manner as in
Example 1, a pressure-sensitive adhesive sheet for measurement of
the adhesive strength and a pressure-sensitive adhesive sheet for
measurement of the weathering resistance were produced using the
resulting pressure-sensitive adhesive solution.
Comparative Example 2
[0048] To 100 parts of the acrylic polymer solution B, 3 parts of
trimethylolpropanetolylene diisocyanate was added to prepare a
pressure-sensitive adhesive solution. In the same manner as in
Example 1, a pressure-sensitive adhesive sheet for measurement of
the adhesive strength and a pressure-sensitive adhesive sheet for
measurement of the weathering resistance were produced using the
resulting pressure-sensitive adhesive solution.
[0049] With respect to the pressure-sensitive adhesive sheets for
measurement of the adhesive strength and pressure-sensitive
adhesive sheets for measurement of the weathering resistance of
Examples 1 and 2 and Comparative Examples 1 and 2, the adhesive
strength test and weathering evaluation test were performed in the
following procedures. These results are as shown in Table 1. In
Table 1, the presence or absence of the silane coupling agent in
the pressure-sensitive adhesive solution as well as the sol
fraction, the weight-average molecular weight as measured by the
GPC method and the proportion of the low-molecular component having
the molecular weight of not more than 100,000 with respect to the
sol component of the layer of the crosslinked pressure-sensitive
adhesive are also shown for reference.
[0050] <Adhesive strength test>
[0051] Specimens having a width of 20 mm and a length of 120 mm
were made from the pressure-sensitive adhesive sheet for
measurement of the adhesive strength. Each of these specimens was
laminated on a glass plate by moving rollers (2 kg) back and forth
once under the atmosphere at 23.degree. C., and then the peel
strength was measured at the same temperature using a Tensilon type
peeling tester at a peeling rate of 300 mm/minute.
[0052] <Weathering evaluation test>
[0053] Samples were made by laminating the pressure-sensitive
adhesive sheet for measurement of the weathering resistance on a
polyethylene terephthalate film having a thickness of 125 .mu.m and
fixing the laminate to glass. The weathering evaluation test was
performed by exposing each of the resulting samples to the
atmosphere at a temperature of 80 or 60.degree. C. and a humidity
of 95% RH for each 500 hours. After the completion of the
weathering evaluation test, samples where any of appearance defects
such as formation of bubbles and lifting is not visually observed
at the bonding interface were rated "O", whereas, samples where
formation of bubbles and lifting are slightly observed were rated
"X".
1 TABLE 1 Com- Com- para- para- tive tive Ex- Ex- Ex- Ex- ample 1
ample 2 ample 1 ample 2 Silane coupling agent con- con- con- none
tained tained tained Sol Sol fraction 15 10 15 29 component (% by
weight) Weight-average 58 47 49 58 molecular weight (.times.
10,000) Low-molecular 6 12 25 6 component (% by weight) Adhesive
strength test 550 590 620 500 (g/20 mm width) Weathering evaluation
test .largecircle. .largecircle. .times. .times.
[0054] As is apparent from Table 1, the pressure-sensitive adhesive
sheets of Examples 1 and 2 according to the present invention
exhibit good adhesive strength according to the molecular weight
constitution of the sol component in the layer of the crosslinked
pressure-sensitive adhesive, and also exhibit excellent weathering
resistance because any of formation of bubbles and lifting does not
occur at the bonding interface after the weathering evaluation
test. On the other hand, the pressure-sensitive adhesive sheet of
Comparative Example 1 wherein the molecular weight constitution of
the sol component is not within the scope of the present invention,
and the pressure-sensitive adhesive sheet which has a molecular
weight constitution of the sol component within the scope of the
present invention but contains no silane coupling agent of
Comparative Example 2 are inferior in weathering resistance.
[0055] As described above, pressure-sensitive adhesive sheets
having excellent weathering resistance, wherein a sol component
having a specific molecular weight distribution with less
low-molecular component, are obtained by incorporating a silane
coupling agent into an acrylic polymer and crosslinking the acrylic
copolymer. When a functional film is bonded/fixed to a display
device using the resulting pressure-sensitive adhesive sheets,
neither lifting nor formation of bubbles occurs at the bonding
interface even during the weathering evaluation test, thus making
it possible to maintain good appearance for a long period.
* * * * *