U.S. patent application number 11/768309 was filed with the patent office on 2008-08-21 for protective film temporarily lamination to electromagnetic wave shielding sheet, method for producing the same, and electromagnetic wave shielding sheet.
Invention is credited to Akiko GOTOU, Hironori KAMIYAMA.
Application Number | 20080200333 11/768309 |
Document ID | / |
Family ID | 39707195 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080200333 |
Kind Code |
A1 |
GOTOU; Akiko ; et
al. |
August 21, 2008 |
PROTECTIVE FILM TEMPORARILY LAMINATION TO ELECTROMAGNETIC WAVE
SHIELDING SHEET, METHOD FOR PRODUCING THE SAME, AND ELECTROMAGNETIC
WAVE SHIELDING SHEET
Abstract
The present invention is to provide an electromagnetic wave
shielding sheet with a protective film that is temporarily
laminated on a copper mesh layer for shielding electromagnetic
waves, the electromagnetic wave shielding sheet is not discolored
even after long-term use, especially at high temperature and high
humidity, while the protective film exhibits appropriate adhesion
properties. To achieve the object, there is provided an
electromagnetic wave shielding sheet comprising a transparent
substrate, at least a copper mesh layer provided on one surface of
the transparent substrate and a protective film temporarily
laminated to the copper-mesh-layer-side surface, the protective
film comprises a support and an adhesive layer containing a polymer
having repeating units derived from an acrylic ester and/or a
methacrylic ester on the support, and the amount of free organic
acids in the adhesive layer is an amount which makes 10 or less the
color difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface of the electromagnetic wave shielding sheet before and
after the adhesive layer surface is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%.
Inventors: |
GOTOU; Akiko; (Tokyo-to,
JP) ; KAMIYAMA; Hironori; (Tokyo-to, JP) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Family ID: |
39707195 |
Appl. No.: |
11/768309 |
Filed: |
June 26, 2007 |
Current U.S.
Class: |
503/225 |
Current CPC
Class: |
Y10T 428/1462 20150115;
H05K 9/0096 20130101; Y10T 428/24868 20150115; B32B 15/20 20130101;
H05K 9/0086 20130101; Y10T 428/1471 20150115; B32B 15/08 20130101;
Y10T 428/14 20150115 |
Class at
Publication: |
503/225 |
International
Class: |
B41M 5/00 20060101
B41M005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2006 |
JP |
2006-179105 |
Claims
1. A protective film for temporary lamination to an electromagnetic
wave shielding sheet in which at least a copper mesh layer is
provided on one surface of a transparent substrate, wherein the
protective film is for temporary lamination to a
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet, wherein the protective film comprises a support
and an adhesive layer containing a polymer having repeating units
derived from an acrylic ester and/or a methacrylic ester on the
support, and wherein an amount of free organic acids in the
adhesive layer is an amount that makes 10 or less a color
difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface of the electromagnetic wave shielding sheet before and
after the adhesive layer surface is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%.
2. The protective film for temporary lamination to an
electromagnetic wave shielding sheet according to claim 1, wherein
the repeating units derived from an acrylic ester and/or a
methacrylic ester in the adhesive layer comprise repeating units
derived from urethane acrylate and/or urethane methacrylate.
3. A protective film for temporary lamination to an electromagnetic
wave shielding sheet, wherein the protective film comprises a
support and an adhesive layer containing a polymer having repeating
units derived from an acrylic ester and/or a methacrylic ester on
the support, and wherein 20 ng/cm.sup.2 or less is a total amount
of acetic acid and formic acid extracted upon testing the
protective film by a test method in which the adhesive layer
surface of the protective film is extracted at 23.degree. C. for 15
minutes with ultrapure water and the resulting extract is measured
for an amount of extracted acetic acid and an amount of extracted
formic acid by ion chromatography.
4. The protective film for temporary lamination to an
electromagnetic wave shielding sheet according to claim 3, wherein
the repeating units derived from an acrylic ester and/or a
methacrylic ester in the adhesive layer comprise repeating units
derived from urethane acrylate and/or urethane methacrylate.
5. A protective film for temporary lamination to an electromagnetic
wave shielding sheet, wherein the protective film comprises a
support and an adhesive layer containing a polymer having repeating
units derived from urethane acrylate and/or urethane methacrylate
on the support.
6. An electromagnetic wave shielding sheet comprising: a
transparent substrate; at least a copper mesh layer provided on one
surface of the transparent substrate; and a protective film
temporarily laminated to a copper-mesh-layer-side surface, wherein
the protective film comprises a support and an adhesive layer
containing a polymer having repeating units derived from an acrylic
ester and/or a methacrylic ester on the copper mesh layer side of
the support, and wherein an amount of free organic acids in the
adhesive layer is an amount that makes 10 or less a color
difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface of the electromagnetic wave shielding sheet before and
after the adhesive layer surface is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%.
7. The electromagnetic wave shielding sheet according to claim 6,
wherein the repeating units derived from an acrylic ester and/or a
methacrylic ester in the adhesive layer of the protective film
comprise repeating units derived from urethane acrylate and/or
urethane methacrylate.
8. The electromagnetic wave shielding sheet according to claim 6,
wherein delamination resistance of the adhesive layer of the
protective film is from 0.05 to 1.3 N/25 mm with respect to the
copper-mesh-layer-side surface.
9. The electromagnetic wave shielding sheet according to claim 6,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is, when a
roughness profile is used as a profile of the surface, a ten-point
average roughness "Rz JIS" (JIS B0601 (1994)) of the profile from
0.5 to 5.0 .mu.m.
10. The electromagnetic wave shielding sheet according to claim 6,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is a center line
average roughness "Ra" (JIS B0601 (1994)) of fine irregularities on
the surface from 0.1 to 3.0 .mu.m.
11. An electromagnetic wave shielding sheet comprising: a
transparent substrate; at least a copper mesh layer provided on one
surface of the transparent substrate; and a protective film
temporarily laminated to a copper-mesh-layer-side surface, wherein
the protective film comprises a support and an adhesive layer
containing a polymer having repeating units derived from an acrylic
ester and/or a methacrylic ester on the support; the protective
film is temporarily laminated to the copper-mesh-layer-side surface
through the adhesive layer; and 20 ng/cm.sup.2 or less is a total
amount of acetic acid and formic acid extracted upon testing the
protective film by a test method in which the adhesive layer
surface of the protective film is extracted at 23.degree. C. for 15
minutes with ultrapure water and the resulting extract is measured
for an amount of extracted acetic acid and an amount of extracted
formic acid by ion chromatography.
12. The electromagnetic wave shielding sheet according to claim 11,
wherein the repeating units derived from an acrylic ester and/or a
methacrylic ester in the adhesive layer of the protective film
comprise repeating units derived from urethane acrylate and/or
urethane methacrylate.
13. The electromagnetic wave shielding sheet according to claim 11,
wherein delamination resistance of the adhesive layer of the
protective film is from 0.05 to 1.3 N/25 mm with respect to the
copper-mesh-layer-side surface.
14. The electromagnetic wave shielding sheet according to claim 11,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is, when a
roughness profile is used as a profile of the surface, a ten-point
average roughness "Rz JIS" (JIS B0601 (1994)) of the profile from
0.5 to 5.0 .mu.m.
15. The electromagnetic wave shielding sheet according to claim 11,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is a center line
average roughness "Ra" (JIS B0601 (1994)) of fine irregularities on
the surface from 0.1 to 3.0 .mu.m.
16. An electromagnetic wave shielding sheet comprising: a
transparent substrate; at least a copper mesh layer provided on one
surface of a transparent substrate; and a protective film
temporarily laminated to a copper-mesh-layer-side surface, wherein
the protective film comprises a support and an adhesive layer
containing a polymer having repeating units derived from urethane
acrylate and/or urethane methacrylate on the copper mesh layer side
of the support.
17. The electromagnetic wave shielding sheet according to claim 16,
wherein delamination resistance of the adhesive layer of the
protective film is from 0.05 to 1.3 N/25 mm with respect to the
copper-mesh-layer-side surface.
18. The electromagnetic wave shielding sheet according to claim 16,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is, when a
roughness profile is used as a profile of the surface, a ten-point
average roughness "Rz JIS" (JIS B0601 (1994)) of the profile from
0.5 to 5.0 .mu.m.
19. The electromagnetic wave shielding sheet according to claim 16,
wherein surface roughness of the copper-mesh-layer-side surface to
which the protective film is temporarily laminated is a center line
average roughness "Ra" (JIS B0601 (1994)) of fine irregularities on
the surface from 0.1 to 3.0 .mu.m.
20. A method for producing a protective film for temporary
lamination to a copper-mesh-layer-side surface of an
electromagnetic wave shielding sheet in which at least the copper
mesh layer is provided on one surface of a transparent substrate,
the method comprising the steps of: selecting an adhesive in which
an amount of free organic acids is an amount that makes 10 or less
a color difference .DELTA.E.sub.L*a*b* of the
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet before and after the adhesive is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%, from adhesives containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, and therewith forming an adhesive layer on a support.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electromagnetic wave
shielding sheet to shield electromagnetic waves produced from
displays such as cathode-ray tubes (CRT) or plasma display panels
(PDP.) In particular, the present invention relates to a protective
film that causes no discoloration of an electromagnetic wave
shielding sheet even after long-term storage at high temperature
and high humidity, a method for producing the protective film, and
an electromagnetic wave shielding sheet with the protective
film.
[0003] 2. Description of the Related Art
[0004] With the sophistication of function and the increasing use
of electrical and electronic devices in recent years,
electromagnetic interference (ERI) has increased and displays such
as cathode-ray tubes and plasma display panels produce
electromagnetic waves. To shield the electromagnetic waves,
electromagnetic wave shielding sheets to be disposed on the front
face of a display is known. Such electromagnetic wave shielding
sheets are demanded to have optical transparency as well as
electromagnetic wave shielding capability. Accordingly,
electromagnetic wave shielding sheets provided with optical
transparency by using a transparent substrate such as a resin film
or a glass plate as a substrate and forming thereon a conductive
mesh layer of metal such as copper are known.
[0005] Sometimes optical filters such as an antireflection filter
and a near-infrared filter are mounted on the front face of a
display so that in many cases an electromagnetic wave shielding
sheet is laminated to the optical filters through an adhesive layer
and disposed on the front surface of a display as a composite
filter. For example, Japanese Patent Application Laid-Open (JP-A)
No. 11-126024 discloses a front surface plate of a display panel in
which an antireflection film is attached to a filter film for
shielding electromagnetic waves through a tacky adhesive layer.
[0006] Sometimes a protective film is temporarily laminated to the
electromagnetic wave shielding sheet to protect the mesh layer
until the electromagnetic wave shielding sheet is disposed on the
front face of a display or laminated to other optical filters, etc.
JP-A No. 2003-188576 discloses an electromagnetic wave shield sheet
comprising a protective film to protect a transparent base film or
an electromagnetic wave shielding layer in handling or production
of the products.
SUMMARY OF THE INVENTION
[0007] As aforementioned, during the time between forming a
conductive mesh layer on a transparent substrate and treating the
mesh layer surface with various post-processes such as providing an
adhesive layer that will function as a planarizing layer of the
mesh layer and laminating the adhesive layer to another optical
film or a display, preferably a protect film is temporarily
laminated to the mesh layer surface to keep the concave of the
conductive mesh layer free of dust or to make mesh lines of the
conductive mesh layer having an extremely narrow width of about 10
.mu.m free from contamination or breaking. In order to laminate a
protective film directly to such a mesh layer surface, the
protective film is required to have appropriate adhesion properties
that allow the protective film to directly adhere to and easily
peel off the conductive mesh layer, and use of a film having an
adhesive layer has been studied. However, at the time of peeling
off a protective film, some adhesives cause problems such that a
blackened layer that is further laminated on a copper mesh layer is
partially peeled off together with the protective film and adhesive
residue is left behind. In the case where a film having an adhesive
layer is temporarily laminated to a conductive mesh layer such as a
copper mesh layer, some adhesives cause a problem of blue-green
discoloration of the copper mesh layer when the electromagnetic
wave shielding sheet is stored for a longtime, especially at high
temperature and high humidity. Such discoloration of a copper mesh
layer causes blue discoloration of the electromagnetic wave
shielding sheet and the color reproducibility of a display is
adversely affected. This problem also occurs when a blackened layer
comprising a thin film of cooper-cobalt alloy particles, nickel
sulfide particles or the like is formed on a copper mesh and an
adhesive layer is laminated thereon.
[0008] The present invention has been achieved in light of the
above-stated problems. The object of the present invention is
firstly to provide a protective film for temporary lamination to an
electromagnetic wave shielding sheet, which film leaves no adhesive
residue behind when peeled off and causes no partial peeling of a
blackened layer and the like if the blackened layer and the like
are further laminated on the copper mesh layer, while the film
having appropriate adhesion properties that involves easy adhesion
and easy peelability in a balanced manner with respect to a copper
mesh layer of the electromagnetic wave shielding sheet. Especially,
the present invention is to provide a protective film for temporary
lamination to an electromagnetic wave shielding sheet that causes
no discoloration of the electromagnetic wave shielding sheet even
after long-term use, especially at high temperature and high
humidity.
[0009] The object of the present invention is secondly to provide
an electromagnetic wave shielding sheet with a protective film that
is temporarily laminated on a copper mesh layer for shielding
electromagnetic waves, the protective film leaves no adhesive
residue behind when peeled off and causes no partial peeling of a
blackened layer and the like if the blackened layer and the like
are further laminated on the copper mesh layer, while the copper
mesh layer and the protective film exhibit easy adhesion and easy
peelability. Especially, the present invention is to provide an
electromagnetic wave shielding sheet that does not discolor even
after long-term use, especially at high temperature and high
humidity.
[0010] In order to achieve the first object, the present invention
provides a protective film for temporary lamination to an
electromagnetic wave shielding sheet in which at least a copper
mesh layer is provided on one surface of a transparent substrate,
wherein the protective film is for temporary lamination to a
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet; the protective film comprises a support and an
adhesive layer containing a polymer having repeating units derived
from an acrylic ester and/or a methacrylic ester on the support;
and an amount of free organic acids in the adhesive layer is an
amount that makes 10 or less a color difference .DELTA.E.sub.L*a*b*
of the copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet before and after the adhesive layer surface is
laminated on the copper-mesh-layer-side surface and they are left
for 200 hours in an atmosphere of a temperature of 60.degree. C.
and a relative humidity of 95%.
[0011] In order to achieve the first object, the present invention
also provides a protective film for temporary lamination to an
electromagnetic wave shielding sheet, wherein the protective film
comprises a support and an adhesive layer containing a polymer
having repeating units derived from an acrylic ester and/or a
methacrylic ester on the support; and 20 ng/cm.sup.2 or less is a
total amount of acetic acid and formic acid extracted upon testing
the protective film by a test method in which the adhesive layer
surface of the protective film is extracted at 23.degree. C. for 15
minutes with ultrapure water and the resulting extract is measured
for an amount of extracted acetic acid and an amount of extracted
formic acid by ion chromatography.
[0012] In order to achieve the first object, the present invention
further provides a protective film for temporary lamination to an
electromagnetic wave shielding sheet, wherein the protective film
comprises a support and an adhesive layer containing a polymer
having repeating units derived from urethane acrylate and/or
urethane methacrylate on the support.
[0013] Further, the present invention provides a method for
producing a protective film for temporary lamination to a
copper-mesh-layer-side surface of an electromagnetic wave shielding
sheet in which at least the copper mesh layer is provided on one
surface of a transparent substrate, the method comprising the steps
of: selecting an adhesive in which an amount of free organic acids
is an amount that makes 10 or less a color difference
.DELTA.E.sub.L*a*b* of the copper-mesh-layer-side surface of the
electromagnetic wave shielding sheet before and after the adhesive
is laminated on the copper-mesh-layer-side surface and they are
left for 200 hours in an atmosphere of a temperature of 60.degree.
C. and a relative humidity of 95%, from adhesives containing a
polymer having repeating units derived from an acrylic ester and/or
a methacrylic ester, and therewith forming an adhesive layer on a
support.
[0014] In order to achieve the second object, the present invention
provides an electromagnetic wave shielding sheet comprising: a
transparent substrate; at least a copper mesh layer provided on one
surface of the transparent substrate; and a protective film
temporarily laminated to a copper-mesh-layer-side surface, wherein
the protective film comprises a support and an adhesive layer
containing a polymer having repeating units derived from an acrylic
ester and/or a methacrylic ester on the copper mesh layer side of
the support, and an amount of free organic acids in the adhesive
layer is an amount that makes 10 or less a color difference
.DELTA.E.sub.L*a*b* of the copper-mesh-layer-side surface of the
electromagnetic wave shielding sheet before and after the adhesive
layer surface is laminated on the copper-mesh-layer-side surface
and they are left for 200 hours in an atmosphere of a temperature
of 60.degree. C. and a relative humidity of 95%.
[0015] Also, in order to attain the second object, the present
invention provides an electromagnetic wave shielding sheet
comprising: a transparent substrate; at least a copper mesh layer
provided on one surface of the transparent substrate; and a
protective film temporarily laminated to a copper-mesh-layer-side
surface, wherein the protective film comprises a support and an
adhesive layer containing a polymer having repeating units derived
from an acrylic ester and/or a methacrylic ester on the copper mesh
layer side of the support; the protective film is temporarily
laminated to the copper-mesh-layer-side surface through the
adhesive layer; and 20 ng/cm.sup.2 or less is a total amount of
acetic acid and formic acid extracted upon testing the protective
film by a test method in which the adhesive layer surface of the
protective film is extracted at 23.degree. C. for 15 minutes with
ultrapure water and the resulting extract is measured for an amount
of extracted acetic acid and an amount of extracted formic acid by
ion chromatography.
[0016] In order to attain the second object, the present invention
also provides an electromagnetic wave shielding sheet comprising: a
transparent substrate; at least a copper mesh layer provided on one
surface of a transparent substrate; and a protective film
temporarily laminated to a copper-mesh-layer-side surface, wherein
the protective film comprises a support and an adhesive layer
containing a polymer having repeating units derived from urethane
acrylate and/or urethane methacrylate on the copper mesh layer side
of the support.
[0017] According to the present invention, since the protective
film comprises an adhesive layer containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, and the amount of free organic acids in the adhesive layer
is an amount that makes 10 or less a color difference
.DELTA.E.sub.L*a*b* of the copper-mesh-layer-side surface of the
electromagnetic wave shielding sheet before and after the adhesive
layer surface is laminated on the copper-mesh-layer-side surface
and they are left for 200 hours in an atmosphere of a temperature
of 60.degree. C. and a relative humidity of 95%, the following
effects can be produced. While the copper mesh layer and the
protective film appropriately exhibit easy adhesion and easy
peelability, the protective film leaves no adhesive residue behind
when peeled off and causes no partial peeling of a blackened layer
and the like that are further laminated on the copper mesh layer.
In addition, the protective film causes no discoloration of the
copper mesh layer even after long-term use, especially at high
temperature and high humidity.
[0018] According to the present invention, since the protective
film comprises an adhesive layer containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, and 20 ng/cm.sup.2 or less is the total amount of acetic
acid and formic acid extracted upon testing the protective film by
the above-specified test method, the following effects can be
produced. While the copper mesh layer and the protective film
appropriately exhibit easy adhesion and easy peelability, the
protective film leaves no adhesive residue behind when peeled off
and causes no partial peeling of a blackened layer and the like
that are further laminated on the copper mesh layer. In addition,
the protective film causes no discoloration of the copper mesh
layer even after long-term use, especially at high temperature and
high humidity.
[0019] In the present invention, since the protective film
comprises an adhesive layer containing a polymer having repeating
units derived from urethane acrylate and/or urethane methacrylate,
the following effects can be produced. While the copper mesh layer
and the protective film exhibit easy adhesion and easy peelability,
the protective film leaves no adhesive residue behind when peeled
off and causes no partial peeling of a blackened layer and the like
that are further laminated on the copper mesh layer.
[0020] In the electromagnetic wave shielding sheet of the present
invention, delamination resistance of the adhesive layer of the
protective film is preferably from 0.05 to 1.3 N/25 mm with respect
to the copper-mesh-layer-side surface from the viewpoint of
appropriate adhesion that allows the protective film to directly
adhere to and easily peel off the copper mesh layer.
[0021] In the electromagnetic wave shielding sheet of the present
invention, surface roughness of the copper-mesh-layer-side surface
to which the protective film is temporarily laminated is preferably
a ten-point average roughness "Rz JIS" (JIS B0601 (1994)) of the
profile from 0.5 to 5.0 .mu.m when a roughness profile is used as a
profile of the surface, and a center line average roughness "Ra"
(JIS B0601 (1994)) of fine irregularities on the surface from 0.1
to 3.0 .mu.m from the viewpoint of appropriate adhesion and
removability when combined with an adhesive specified in the
present invention, that is, the protective film leaves no adhesive
residue behind when peeled off and causes no partial peeling of a
blackened layer and the like if the blackened layer and the like
are further laminated on the copper mesh layer, while having easy
adhesion and easy peelability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In the accompanying drawings,
[0023] FIG. 1 is a sectional view illustrating an example of a
protective film for temporary lamination to an electromagnetic wave
shielding sheet according to the present invention.
[0024] FIG. 2A is a sectional view illustrating an example of the
electromagnetic wave shielding sheet according to the present
invention.
[0025] FIG. 2B is a sectional view illustrating an example of the
electromagnetic wave shielding sheet according to the present
invention.
[0026] FIG. 2C is a sectional view illustrating an example of the
electromagnetic wave shielding sheet according to the present
invention.
[0027] FIG. 3 is a perspective view of an example (FIG. 2C) of the
electromagnetic wave shielding sheet according to the present
invention.
[0028] FIG. 4A is a sectional view taken along the line A-A of FIG.
3.
[0029] FIG. 4B is a sectional view taken along the line B-B of FIG.
3.
[0030] FIG. 5 is a diagram illustrating a laminating machine to
temporarily laminate the electromagnetic wave shielding sheet and
the protective film of the present invention.
[0031] FIGS. 6A to 6D are diagrams illustrating an example of
producing the electromagnetic wave shielding sheet according to the
present invention.
[0032] The numerical symbol in each figure refers to the following:
1. support; 2. adhesive layer; 11. transparent substrate; 12.
conductor layer; 13. conductive treating layer; 14. copper mesh
layer; 15. copper plated layer; 17. blackened layer; 18. metal
layer; 20, 30, 40. laminate; 21. first paper feed member; 22.
second paper feed member; 23. first release film wind-up roller;
24. second release film wind-up roller; 25. first laminating unit;
26. second laminating unit; 27. wind-up roller; 100.
electromagnetic wave shielding sheet; 101. mesh area; 103. opening;
and 104. line
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] The present invention relates to a protective film for
temporary lamination to an electromagnetic wave shielding sheet and
an electromagnetic wave shielding sheet. Hereinafter, a protective
film for temporary lamination to an electromagnetic wave shielding
sheet and an electromagnetic wave shielding sheet will be described
in this order.
[0034] A. Protective Film for Temporary Lamination to
Electromagnetic Wave Shielding Sheet
[0035] Now, the protective film for temporary lamination to the
electromagnetic wave shielding sheet of the present invention is
described.
[0036] The first protective film for temporary lamination to an
electromagnetic wave shielding sheet of the present invention is a
protective film for temporary lamination to an electromagnetic wave
shielding sheet in which at least a copper mesh layer is provided
on one surface of a transparent substrate, wherein the protective
film is for temporary lamination to a copper-mesh-layer-side
surface of the electromagnetic wave shielding sheet; the protective
film comprises a support and an adhesive layer containing a polymer
having repeating units derived from an acrylic ester and/or a
methacrylic ester on the support; and an amount of free organic
acids in the adhesive layer is an amount that makes 10 or less a
color difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface of the electromagnetic wave shielding sheet before and
after the adhesive layer surface is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%.
[0037] The second protective film for temporary lamination to an
electromagnetic wave shielding sheet of the present invention is a
protective film for temporary lamination to an electromagnetic wave
shielding sheet, wherein the protective film comprises a support
and an adhesive layer containing a polymer having repeating units
derived from an acrylic ester and/or a methacrylic ester on the
support, and 20 ng/cm.sup.2 or less is a total amount of acetic
acid and formic acid extracted upon testing the protective film by
a test method in which the adhesive layer surface of the protective
film is extracted at 23.degree. C. for 15 minutes with ultrapure
water and the resulting extract is measured for an amount of
extracted acetic acid and an amount of extracted formic acid by ion
chromatography.
[0038] The third protective film for temporary lamination to an
electromagnetic wave shielding sheet is a protective film for
temporary lamination to an electromagnetic wave shielding sheet,
wherein the protective film comprises a support and an adhesive
layer containing a polymer having repeating units derived from
urethane acrylate and/or urethane methacrylate on the support.
[0039] Temporarily laminating a temporary protective film to the
copper mesh layer surface of the electromagnetic wave shielding
sheet has advantages such that during the time until the next
process, the concave portion of the conductive mesh layer can be
kept free of dust and the mesh lines can be free from breaking or
contamination upon handling or storage. In the case of temporarily
laminating a film having an adhesive layer to a copper mesh layer,
however, some adhesives cause problems such that adhesive residue
is left behind when a temporarily laminated protective film is
peeled off and a blackened layer and the like that are further
laminated on the copper mesh layer are partially peeled off
together with the protective film. An other problem is that the
copper mesh layer discolors after the electromagnetic wave
shielding sheet is stored for a long time, especially at high
temperature and high humidity.
[0040] In this regard, since the protective film of the present
invention uses an adhesive layer containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, especially a polymer having repeating units derived from
urethane acrylate and/or urethane methacrylate for the adhesive to
form an adhesive layer, the protective film leaves no adhesive
residue behind when peeled off and causes no partial peeling of a
blackened layer and the like that are further laminated on the
copper mesh layer. In addition, the protective film has good
adhesion and removability.
[0041] Since the protective film comprises an adhesive layer
containing a polymer having repeating units derived from an acrylic
ester and/or a methacrylic ester and the amount of free organic
acids in the adhesive layer is an amount that makes 10 or less the
color difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface before and after the above-specified test in a high
temperature and high humidity environment, the protective film
leaves no adhesive residue behind when peeled off and causes no
partial peeling of a blackened layer and the like that are further
laminated on the copper mesh layer, while the copper mesh layer and
the protective film exhibit appropriate adhesion properties. In
addition, the protective film allows no discoloration of the
electromagnetic wave shielding sheet even after long-term use,
especially at high temperature and high humidity. It is noted the
term "free organic acids" refers to organic compounds having a
carboxyl group that is present in uncombined form and examples of
the free organic acids include acetic acid and formic acid.
[0042] Alternatively, since the protective film comprises an
adhesive layer containing a polymer having repeating units derived
from an acrylic ester and/or a methacrylic ester and 20 ng/cm.sup.2
or less is the total amount of acetic acid and formic acid
extracted from the adhesive layer surface upon testing the
protective film by the above-specified test method, the protective
film leaves no adhesive residue behind when peeled off and causes
no partial peeling of a blackened layer and the like that are
further laminated on the copper mesh layer, while the copper mesh
layer and the protective film exhibit appropriate adhesion
properties. In addition, the protective film allows no
discoloration of the electromagnetic wave shielding sheet even
after long-term use, especially at high temperature and high
humidity.
[0043] The reasons that the copper mesh layer of the
electromagnetic wave shielding sheet and the protective film
exhibit appropriate adhesion properties and the protective film
used in the present invention causes no discoloration of the
electromagnetic wave shielding sheet even after long-term use,
especially at high temperature and high humidity, are considered as
follows.
[0044] An adhesive layer containing a polymer having repeating
units derived from an acrylic ester and/or a methacrylic ester,
especially an adhesive layer containing a polymer having repeating
units derived from urethane acrylate and/or urethane methacrylate,
is found suitable and selected as one having good adhesion and
removability, i.e. one that hardly leaves adhesive residue behind
when peeling off a protective film and causes no partial peeling of
a blackened layer and the like that are further laminated on the
copper mesh layer, while having appropriate adhesion properties
that allows the adhesive layer to directly adhere to and easily
peel off the conductive mesh layer. On the other hand,
discoloration of the copper mesh layer after long-term storage at
high temperature and high humidity is attributed to that the
presence of protons dissociated from acids and so on and water
contained in the adhesive layer renders the copper surface
sensitive to oxidation so that compounds containing copper ions
such as copper complex is produced by oxidation, thereby
discoloring the copper surface to blue or similar color.
[0045] It seems that in general carboxyl groups or acid components
can be present in an adhesive layer containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester.
[0046] To the contrary, while the adhesive layer of the protective
film of the present invention is an adhesive layer containing a
polymer having repeating units derived from an acrylic ester and/or
a methacrylic ester, the amount of free organic acids in the
adhesive layer is as small as an amount that makes 10 or less the
color difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface before and after the above-specified test in a high
temperature and high humidity environment.
[0047] Also, while the adhesive layer of the protective film of the
present invention is an adhesive layer containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, the total amount of acetic acid and formic acid extracted
from the adhesive layer surface in a test conducted by the
above-specified test method is as small as 20 ng/cm.sup.2 or
less.
[0048] As aforementioned, among the acid components contained in
the adhesive layer, the present invention focuses on free organic
acids that are capable of readily transferring to the adhesive
layer surface to be in contact with the electromagnetic wave
shielding sheet or specific free organic acids that are present on
the adhesive layer surface. It is presumed that reducing the amount
of the free organic acids allows to decrease the presence of
protons dissociated from the adhesive layer surface to be in
contact with the electromagnetic wave shielding sheet so as to
control the oxidation-sensitive state of the copper surface even in
high temperature and high humidity environment. Consequently, it
seems possible to obtain an electromagnetic wave shielding sheet
that does not discolor even after long-term use, especially at high
temperature and high humidity, by using the above-described
adhesive layer as an adhesive layer to be in contact with the
copper mesh layer surface of the electromagnetic wave shielding
sheet.
[0049] (Layer Configuration)
[0050] FIG. 1 is a sectional view showing a basic embodiment of the
protective film for temporary lamination to the electromagnetic
wave shielding sheet according to the present invention.
[0051] FIG. 1 shows a configuration of a protective film 10 for
temporary lamination to an electromagnetic wave shielding sheet, in
which an adhesive layer 2 containing a polymer having repeating
units derived from an acrylic ester and/or a methacrylic ester is
laminated on a support 1.
[0052] A release layer (not shown in FIG. 1) may be further
laminated on the surface of the support 1, on which the adhesive
layer 2 is not laminated. Also, the release layer may be laminated
to the adhesive layer 2 until the protective film for temporary
lamination to an electromagnetic wave shielding sheet is actually
laminated to an electromagnetic wave shielding sheet.
[0053] The embodiments of the protective film for temporary
lamination to the electromagnetic wave shielding sheet of the
present invention are not limited by the above-mentioned examples.
Any that has the substantially same essential features as the
technical ideas described in claims of the present invention and
exerts the same effects and advantages is included in the technical
scope of the present invention.
[0054] Hereinafter, the protective film of the present invention
will be described.
[0055] (Support)
[0056] The support is a layer having strength to support the
adhesive layer having low mechanical strength and to protect the
mesh surface of the electromagnetic wave shielding sheet.
Consequently, there is no particular limit to the support and as
far as it has strength to support the adhesive layer and to protect
the mesh surface, and suitable properties for storage. It may be
appropriately selected for use depending on storage conditions.
Concrete examples of the support include a film or sheet of organic
material such as resin. Such film or sheet is suitable for use
since it is sufficiently thin, lightweight, flexible and
strong.
[0057] Resins used to form the film or sheet of organic material
include, for example, polyester resin such as polyethylene
terephthalate, polybutylene terephthalate, polyethylene
naphthalate, copolymer of terephthalic acid, isophthalic acid and
ethylene glycol, copolymer of terephthalic acid,
cyclohexanedimethanol and ethylene glycol; polyamide resin such as
nylon 6; polyolefin resin such as polyethylene, polypropylene,
polymethylpentene; polyvinyl chloride; and so on.
[0058] There is no particular limit to the thickness of the support
as far as it meets the storage conditions of the electromagnetic
wave shielding sheet. The thickness is normally from 25 to 70
.mu.m, preferably from 40 to 60 .mu.m. The support having a
thickness less than the range is insufficient in mechanical
strength and may break. The support having a thickness exceeding
the range is excess in performance and expensive. In addition, it
is difficult to wind for storage.
[0059] A resin film or sheet is a preferable material for the
support. Among resins, polyolefins such as polyethylene,
polypropylene are particularly preferable since they are excellent
in transparency, easy to peel for its balance between elasticity
and flexibility, and inexpensive. Especially, polypropylene is
preferable since it does not stretch easily and hardly causes
curling or partial detachment of the protective film after
adhesion. In addition, for these reasons, the selection tolerance
of delamination resistance of the adhesive is widened.
[0060] (Adhesive Layer)
[0061] The adhesive layer provided with the protective film of the
present invention needs to have the above-mentioned excellent
adhesion and removability. Further, the copper mesh layer surface
(especially, a thin and rough or porous blackened layer) to which
the protective film will adhere is required not to peel off with
the adhesive. As a result of considering various resins, an acrylic
polymer, that is, one containing a polymer having repeating units
derived from an acrylic ester and/or a methacrylic ester is found
excellent. The adhesive layer provided with the protective film of
the present invention may contain a compound such as an additive
(e.g. antioxidant) as needed. Rubber adhesives are generally
excellent to prevent discoloration of copper. However, in this
case, since the copper mesh layer surface (especially, the
blackened layer) is liable to peel off with the adhesive layer at
the time of peeling off the protective film, they are not suitable
for the application in which such peeling of the copper mesh layer
surface is not desired.
[0062] The term "adhesive" as used herein refers to a kind of
bonding agent which allows adhesion by simply applying an
appropriate, light hand pressure with only surface stickiness given
by the bonding agent. In general, the adhesive requires no physical
energy or action such as heat, humidity or radiation irradiation
(e.g. ultra violet or electron-beam irradiation) to exhibit its
adhesion force. In addition, no chemical reaction such as
polymerization reaction is required. The adhesive can keep a
certain adhesion force that is capable of adhesion and removability
over time. As the adhesive used in the present invention, an
acrylic adhesive which mainly comprises repeating units derived
from an acrylic ester and/or a methacrylic ester and is a polymer
obtained by copolymerizing copolymerizable monomers as needed since
the adhesive leaves no adhesive residue behind when peeling off the
protective film and causes no partial peeling of a blackened layer
and the like that are further laminated on the copper mesh layer,
while having appropriate adhesion properties.
[0063] In the case where such an acrylic adhesive is used as an
adhesive layer, discoloration of a copper mesh layer may easily
occur. However, in the adhesive layer provided with the protective
film of the present invention, the amount of free organic acids in
the adhesive layer is an amount that makes 10 or less the color
difference .DELTA.E.sub.L*a*b* of the copper-mesh-layer-side
surface, the color difference .DELTA.E.sub.L*a*b* is based on
chromaticities a*, b*, and a luminance L* (defined by International
Commission on Illumination or CIE) of the copper-mesh-layer-side
surface measured before and after the adhesive layer surface is
laminated on the copper-mesh-layer-side surface of the
electromagnetic wave shielding sheet and left for 200 hours in an
atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%. Preferably, the amount of free organic acids in
the adhesive layer is an amount that makes the color difference
.DELTA.E.sub.L*a*b* 5 or less. More preferably, it is an amount
that makes the color difference .DELTA.E.sub.L*a*b* 1 or less. From
the viewpoint of ensuring adhesion to the copper mesh layer, a
certain amount of free organic acids may remain in the adhesive
layer as far as the color difference .DELTA.E.sub.L*a*b* is 10 or
less and 0.1 or more. Color difference .DELTA.E.sub.L*a*b* is
calculated by the following equation:
.DELTA.E.sub.L*a*b*={(.DELTA.L*).sup.2+(.DELTA.a*).sup.2+(.DELTA.b*).sup.-
2}.sup.1/2
[0064] It is noted that .DELTA.L*, .DELTA.a* and .DELTA.b*
respectively refer to the difference of values of L*, a* and b* of
the copper-mesh-side surface of the electromagnetic wave shielding
sheet, before and after the sheet is left to stand in the
above-specified environment for the above-specified hours. L*, a*
and b* are values in L*a*b* color system recommended by the
International Commission on Illumination (CIE) in 1976 and also
defined in JIS Z8729.
[0065] when the copper mesh layer has a color tone of the copper or
a color tone of the blackened layer on the copper surface, and the
mesh shape and size of the copper mesh layer is in the ranges of
those as will be described, a color difference .DELTA.E.sub.L*a*b*
of 10 or less is almost invisible and practically unnoticeable in
the case of the electromagnetic wave shielding sheet comprising the
copper mesh disposed on the front face of a normal image display.
Especially, a color difference .DELTA.E.sub.L*a*b* of less than the
range of 0.6 to 1.0, which range is generally regarded as the
visually differentiable threshold range, is more preferable since
no discoloration of the copper mesh layer surface can be visually
differentiated.
[0066] The adhesive layer to be provided with the protective film
of the present invention hardly causes discoloration of the copper
mesh layer since an adhesive layer in which the total amount of
acetic acid and formic acid obtained by extracting the adhesive
layer surface at 23.degree. C. for 15 minutes with ultrapure water
measures 20 ng/cm.sup.2 or less by ion chromatography, is selected
as the adhesive layer of the present invention. More particularly,
a color difference .DELTA.E.sub.L*a*b* of 10 or less, more
preferably 5 or less, still more preferably 1 or less, is
achievable in the case where the adhesive layer surface of the
protective layer of the present invention is laminated to the
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet; a test in a high temperature and high humidity
environment is performed thereon (i.e., they are left in an
environment with a temperature of 60.degree. C. and a relative
humidity of 95% for 200 hours); and chromaticities a*, b*, and a
luminance L* (defined by International Commission on Illumination
or CIE) are measured for the copper-mesh-layer-side surface before
and after the test to obtain a color difference
.DELTA.E.sub.L*a*b*. The total amount of acetic acid and formic
acid extracted from the adhesive layer is more preferably 10
ng/cm.sup.2 or less, still more preferably 3 ng/cm.sup.2 or less.
From the viewpoint of ensuring adhesion to the copper mesh layer, a
certain total amount of acetic acid and formic acid may remain in
the adhesive layer after the extraction. If the total amount of
acetic acid and formic acid extracted from the adhesive layer in
the above-mentioned test is 20 ng/cm.sup.2 or less, 0.5 ng/cm.sup.2
or more, or further, 1 ng/cm.sup.2 or more of acetic acid and
formic acid may be contained in the adhesive layer.
[0067] Extraction of the adhesive layer surface at 23.degree. C.
for 15 minutes with ultrapure water has to be performed in a clean
booth disposed with a chemical filter. The elution amount
(ng/cm.sup.2) of acetic acid or formic acid per unit area can be
obtained by multiplying the concentration of acetic acid/forming
acid in the resulting extract (ng/mL) by the amount of the
resulting extract (mL) and then dividing the result by the
extraction area (cm.sup.2.) The total of the amounts obtained by
the calculation is the total elution amount of acetic acid or
formic acid.
[0068] As the acrylic ester and/or a methacrylic ester used to form
a polymer having repeating units derived from an acrylic ester
and/or a methacrylic ester, monomers such as (meth) acrylic acid
alkyl ester, urethane (meth)acrylate obtained by the reaction of
hydroxyl group-containing (meth)acrylic acid ester with isocyanates
may be suitably used. Also, (meth)acrylic acid alkoxyalkyl ester or
the like may be used. It should be noted acrylic acid and/or
methacrylic acid is referred to herein as (meth)acrylic acid for
brevity. Acrylate and/or methacrylate is referred to herein as
(meth)acrylate.
[0069] Examples of the (meth)acrylic acid alkyl ester monomer used
herein include methyl (meth)acrylate, ethyl (meth)acrylate,
n-propyl (meth)acrylate, sec-propyl (meth)acrylate, n-butyl
(meth)acrylate, sec-butyl (meth)acrylate, tert-butyl
(meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate,
cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, undecyl
(meth)acrylate, and lauryl (meth)acrylate.
[0070] As the hydroxyl group-containing (meth) acrylic acid ester
used for urethane (meth)acrylate obtained by the reaction of
hydroxyl group-containing (meth)acrylic acid ester with
isocyanates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl
(meth)acrylate, and so on are suitably used. A compound having in
the molecule thereof at least one isocyanate group may be used as
the isocyanates, and divalent isocyanates such as tolylene
diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate,
4,4'-diphenylmethane diisocyanate, hydrogenated tolylene
diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate,
lysine diisocyanate methyl ester, 2,2,4-trimethyl hexamethylene
diisocyanate and xylylene diisocyanate are preferable. Multimers
thereof (e.g. dimers or monomers) or adducts thereof may be
used.
[0071] Preferable examples of urethane (meth)acrylate include
urethane (meth)acrylate obtained by the reaction of 2-hydroxyethyl
(meth)acrylate with tolylene diisocyanate and urethane
(meth)acrylate obtained by the reaction of 2-hydroxypropyl
(meth)acrylate with tolylene diisocyanate. Especially, urethane
methacrylate obtained by the reaction of 2-hydroxyethyl
methacrylate with tolylene diisocyanate is suitably used.
[0072] Examples of the (meth)acrylic acid alkoxyalkyl ester include
2-methoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate,
2-methoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate,
2-methoxybutyl (meth)acrylate, 4-methoxybutyl (meth)acrylate,
2-ethoxyethyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate and
4-ethoxybutyl (meth)acrylate.
[0073] Especially, the polymer having repeating units derived from
an acrylic ester and/or a methacrylic ester used in the present
invention preferably has repeating units derived from urethane
(meth)acrylate as the repeating units derived from an acrylic ester
and/or a methacrylic ester. In this case, it is more achievable
that the amount of free organic acids in the adhesive layer is an
amount that makes 10 or less the color difference
.DELTA.E.sub.L*a*b* of the copper-mesh-layer-side surface before
and after the above-specified test in a high temperature and high
humidity environment and the total amount of acetic acid and formic
acid extracted by the above-specified test measures 20 ng/cm.sup.2
or less,
[0074] while the adhesive layer has appropriate adhesion properties
that allow the adhesive layer to leave less adhesive residue behind
and cause no partial peeling of a blackened layer and the like that
are further laminated on the copper mesh layer of the
electromagnetic wave shielding sheet, when the protective film is
peeled off from the electromagnetic wave shielding sheet.
[0075] Preferable and concrete examples of the polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester used in the present invention include but are not limited to:
(1) a copolymer having repeating units derived from urethane
(meth)acrylate obtained by the reaction of 2-hydroxyethyl
(meth)acrylate with tolylene diisocyanate and repeating units
derived from methyl (meth)acrylate; (2) a copolymer having
repeating units derived from urethane (meth)acrylate obtained by
the reaction of 2-hydroxyethyl (meth)acrylate with tolylene
diisocyanate, repeating units derived from butyl (meth)acrylate,
repeating units derived from 2-ethylhexyl (meth)acrylate, and
repeating units derived from ethyl (meth)acrylate; and (3) a
copolymer having repeating units derived from urethane
(meth)acrylate obtained by the reaction of 2-hydroxyethyl
(meth)acrylate with tolylene diisocyanate and repeating units
derived from ethyl (meth)acrylate.
[0076] Besides the above, the polymer having repeating units
derived from an acrylic ester and/or a methacrylic ester used in
the present invention may be copolymerized with a monomer having a
functional group as far as the amount of contained free organic
acids, the total amount of the extracted acetic acid and formic
acid, and appropriate adhesion properties are not adversely
affected. Example of monomers having a functional group include a
monomer having a hydroxyl group such as 2-hydroxyethyl
(meth)acrylate, 2-hydroxypropyl (meth)acrylate, and allyl alcohol;
a monomer having an amide group such as (meth) acrylamide, N-methyl
(meth)acrylamide, and N-ethyl (meth)acrylamide; a monomer having an
amide group such as N-methylol (meth) acrylamide, and dimethylol
(meth)acrylamide, and a methylol group; a monomer having a
functional group such as a monomer having an amino group such as
aminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and
vinylpyridine; a monomer having an epoxy group such as allyl
glycidyl ether, and glycidyl ether (meth)acrylate. Besides these
monomers, fluorine-substituted (meth)acrylic acid alkyl ester,
(meth)acrylonitrile, a vinyl group-containing aromatic compound
such as styrene and methylstyrene, vinyl acetate, and a halogenated
vinyl compound are included.
[0077] Besides the aforementioned monomers having a functional
group, the acrylic adhesive used in the present invention may be
copolymerized with other monomers having an ethylene double bond.
Examples of the monomers having an ethylene double bond include
.alpha.,.beta.-unsaturated dibasic acid diesters such as dibutyl
maleate, dioctyl maleate, and dibutyl fumarate; vinyl ether; a
vinyl aromatic compound such as styrene, .alpha.-methylstyrene and
vinyl toluene; and (meth)acrylonitrile.
[0078] Besides the aforementioned monomers having an ethylene
double bond, a compound having two or more ethylene double bonds
may be used in combination. Examples of such compounds include
divinylbenzene, diallyl maleate, diallyl phthalate, ethylene glycol
di(meth)acrylate, trimethylolpropane tri(meth)acrylate, methylene
bis(meth)acrylamide.
[0079] In the polymer having repeating units derived from an
acrylic ester and/or a methacrylic ester used for the adhesive
layer of the present invention, the ratio of repeating units
derived from one or two or more kinds of acrylic esters and/or
methacrylic esters to the total number of repeating units of all
monomers in a copolymer is preferably 50 mol % or more, more
preferably 80 mol % or more, still more preferably 90 mol % or
more. A copolymer comprising only repeating units derived from two
or more kinds of acrylic esters and/or methacrylic esters is also
suitably used.
[0080] As a commercial product of the resin film having an adhesive
layer containing a polymer having repeating units derived from an
acrylic ester and/or a methacrylic ester, for example, C-200 and
C-300 (product name; manufactured by: Nitto Denko Corporation);
A-1330 (product name; manufactured by: Hitachi Chemical Co., Ltd.)
are suitably used.
[0081] The adhesive layer of the present invention may contain an
antioxidant, a curing agent (a cross-linking agent) such as an
isocyanate compound or the like, a tackifier, a silane coupling
agent, a filler, and so on if required as far as the effects of the
present invention can be obtained.
[0082] The thickness of the adhesive layer of the protective film
of the present invention is not particularly limited as far as it
is appropriately determined in order to appropriately control the
adhesion properties of the adhesive layer with respect to the
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet. In general, the thickness of the adhesive layer is
from 2 to 10 .mu.m.
[0083] As a measure of the adhesion of the adhesive layer of the
protective film of the present invention to the electromagnetic
wave shielding sheet, the delamination resistance of the adhesive
layer evaluated in the following manner is preferably from 0.05 to
1.3 N/25 mm. It is measured in such a manner that by means of a
roller the adhesive layer of the protective film is allowed to
adhere to non-mesh forming portion of a surface of an electrolytic
copper foil having a thickness of 11 .mu.m (product name: TC;
manufactured by: Furukawa Circuit Foil Co., Ltd.), in which the
surface has a "Rz JIS" (JIS B0601 (1994)) from 3 to 4.3 .mu.m and a
center line average roughness "Ra" (JIS B0601 (1994)) of fine
irregularities on which part of the surface from 0.2 to 0.6 .mu.m;
the resulting sheet is cut to a size of 150 mm long by 25 mm wide;
and the protective film was measured using a tensile testing
machine such as "Tensilon" (product name; manufactured by: Toyo
Seiki Seisaku-sho, Ltd.) by stretching the protective film and the
electrolytic copper foil surface in a direction such that they make
an angle of 180.degree. at a pulling speed of 300 mm/min and in an
environment of 20 to 25.degree. C.
[0084] (Release Layer)
[0085] The protective film of the present invention may further
have a release layer so that during storage the adhesive layer does
not adhere to the support surface on which no adhesive layer is
laminated and can be stored in rolled or stacked form. The release
layer may be laminated on the support surface on which no adhesive
layer is laminated. Moreover, the release layer may be laminated to
the adhesive layer until the protective film for temporary
lamination to an electromagnetic wave shielding sheet is actually
and temporarily laminated to the electromagnetic wave shielding
sheet. An easily peelable PET film subjected to a silicone
treatment, for example, is suitably used as the release layer. An
easily peelable paper may be the release layer that is laminated on
the adhesive layer until the protective film for temporary
lamination to an electromagnetic wave shielding sheet is actually
and temporarily laminated to the electromagnetic wave shielding
sheet.
[0086] (Method for Producing Protective Film)
[0087] The method for producing the protective film for temporary
lamination to an electromagnetic wave shielding sheet of the
present invention is a method for producing a protective film for
temporary lamination to a copper-mesh-layer-side surface of an
electromagnetic wave shielding sheet in which at least the copper
mesh layer is provided on one surface of a transparent substrate,
the method comprising the steps of: selecting an adhesive in which
an amount of free organic acids is an amount that makes 10 or less
a color difference .DELTA.E.sub.L*a*b* of the
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet before and after the adhesive is laminated on the
copper-mesh-layer-side surface and they are left for 200 hours in
an atmosphere of a temperature of 60.degree. C. and a relative
humidity of 95%, from adhesives containing a polymer having
repeating units derived from an acrylic ester and/or a methacrylic
ester, and therewith forming an adhesive layer on a support.
[0088] Such a production method enables to produce a protective
film that leaves no adhesive residue behind when peeled off and
causes no partial peeling of a blackened layer and the like even in
the case where the blackened layer and the like are further
laminated on the copper mesh layer, while having appropriate
adhesion properties that involves easy adhesion and easy
peelability in a balanced manner with respect to a copper mesh
layer of the electromagnetic wave shielding sheet; moreover, the
protective film causes no discoloration of the electromagnetic wave
shielding sheet even after long-term use, especially at high
temperature and high humidity.
[0089] B. Electromagnetic Wave Shielding Sheet
[0090] Now, the electromagnetic wave shielding sheet of the present
invention is described.
[0091] The first electromagnetic wave shielding sheet of the
present invention is an electromagnetic wave shielding sheet
comprising: a transparent substrate; at least a copper mesh layer
provided on one surface of the transparent substrate; and a
protective film temporarily laminated to a copper-mesh-layer-side
surface, wherein the protective film comprises a support and an
adhesive layer containing a polymer having repeating units derived
from an acrylic ester and/or a methacrylic ester on the
copper-mesh-layer-side surface of the support, and an amount of
free organic acids in the adhesive layer is an amount that makes 10
or less a color difference .DELTA.E.sub.L*a*b* of the
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet before and after the adhesive layer surface is
laminated on the copper-mesh-layer-side surface and they are left
for 200 hours in an atmosphere of a temperature of 60.degree. C.
and a relative humidity of 95%.
[0092] The second electromagnetic wave shielding sheet of the
present invention is an electromagnetic wave shielding sheet
comprising: a transparent substrate; at least a copper mesh layer
provided on one surface of the transparent substrate; and a
protective film temporarily laminated to a copper-mesh-layer-side
surface, wherein the protective film comprises an adhesive layer
containing a polymer having repeating units derived from an acrylic
ester and/or a methacrylic ester; the protective film is
temporarily laminated to the copper-mesh-layer-side surface through
the adhesive layer; and 20 ng/cm.sup.2 or less is a total amount of
acetic acid and formic acid extracted upon testing the protective
film by a test method in which the adhesive layer surface of the
protective film is extracted at 23.degree. C. for 15 minutes with
ultrapure water and the resulting extract is measured for an amount
of extracted acetic acid and an amount of extracted formic acid by
ion chromatography.
[0093] The third electromagnetic wave shielding sheet of the
present invention is an electromagnetic wave shielding sheet
comprising: a transparent substrate; at least a copper mesh layer
provided on one surface of a transparent substrate; and a
protective film temporarily laminated to a copper-mesh-layer-side
surface, wherein the protective film comprises an adhesive layer
containing a polymer having repeating units derived from urethane
acrylate and/or urethane methacrylate.
[0094] Temporarily laminating a temporary protective film to a
copper mesh layer surface after forming the copper mesh layer
surface on a transparent substrate by etching or plating has
advantages such that during the time until the next process, the
concave portion of the conductive mesh layer can be kept free of
dust and the mesh lines can be free from contamination upon
handling or storage. In the case of temporarily laminating a film
having an adhesive layer to a copper mesh layer, however, some
adhesives cause problems such that adhesive residue is left behind
when a temporarily laminated protective film is peeled off and a
blackened layer and the like are partially peeled off together with
the protective film if the blackened layer and the like are further
laminated on the copper mesh layer. An other problem is that the
copper mesh layer discolors after the electromagnetic wave
shielding sheet is stored for a long time, especially at high
temperature and high humidity.
[0095] In this regard, according to the present invention, since
the protective film uses an adhesive layer containing a polymer
having repeating units derived from an acrylic ester and/or a
methacrylic ester, especially a polymer having repeating units
derived from urethane acrylate and/or urethane methacrylate for the
adhesive to form an adhesive layer, the protective film leaves no
adhesive residue behind when peeled off and causes no partial
peeling of a blackened layer and the like that are further
laminated on the copper mesh layer. In addition, the protective
film has good adhesion and removability.
[0096] Further, since the amount of free organic acids in the
adhesive layer of the protective film is an amount that makes 10 or
less the color difference .DELTA.E.sub.L*a*b* of the
copper-mesh-layer-side surface before and after the above-specified
test in a high temperature and high humidity environment, or since
20 ng/cm.sup.2 or less is the total amount of acetic acid and
formic acid extracted upon testing the protective film by the
above-specified test method, an electromagnetic wave shielding
sheet that does not discolor even after long-term use, especially
at high temperature and high humidity, can be obtained.
[0097] It appears that due to the same reasons as in "A. Protective
film for temporary lamination to electromagnetic wave shielding
sheet," the protective film used in the present invention does not
discolor even after long-term use, especially at high temperature
and high humidity, while the copper mesh layer and the protective
film exhibit appropriate adhesion properties.
[0098] (Layer Configuration)
[0099] FIGS. 2A to 2C are a sectional view of the electromagnetic
wave shielding sheet of the present invention, showing an example
of a basic embodiment.
[0100] FIG. 2A shows the configuration of an electromagnetic wave
shielding sheet 100 in which a copper mesh layer 14 is formed on a
transparent substrate 11 and a protective film 10 provided with an
adhesive layer 2 and a support 1 is temporarily laminated to the
copper mesh layer 14 surface through the adhesive layer 2.
[0101] An electromagnetic wave shielding sheet may be further
provided with other layers. In the electromagnetic wave shielding
sheet of the present invention, from the viewpoint of improving
visibility of a display image by reducing light reflectance and
enhancing contrast, a blackened layer 17 is preferably provided on
the copper mesh layer 14 as shown in FIG. 2B.
[0102] In the configuration of FIGS. 2A and 2B, the copper mesh
layer 14 may be laminated on the transparent substrate 11 through
an adhesive layer (not shown.)
[0103] FIG. 2C shows an example of a layer configuration of an
electromagnetic wave shielding sheet in the case where the
electromagnetic wave shielding sheet is formed by an electrolytic
plating method, in which configuration a conductive treating layer
13 is formed on the transparent substrate 11, the copper mesh layer
14 and the blackened layer 17 are further laminated thereon in this
sequence, and the protective film 10 provided with the adhesive
layer 2 and the support 1 is temporarily laminated to the blackened
layer 17 surface through the adhesive layer 2.
[0104] FIG. 3 is a perspective view only showing the transparent
substrate layer 11, the conductive treating layer 13 and the copper
mesh layer 14 of the electromagnetic wave shielding sheet in FIG.
2C. The conductive treating layer 13 and the copper mesh layer 14
(herein after, the both layers and other conductive layers are
correctively referred to as a "conductor layer 12") are in the form
of a mesh with densely aligned openings 103. The mesh 101 consists
of a combination of mesh lines 104 and openings 103. The blackened
layer 17 (not shown) that is further laminated on the copper mesh
layer 14 is incorporated with the conductor layer 12 to form the
mesh 101.
[0105] FIG. 4A is a sectional view taken along the line A-A of FIG.
3. FIG. 4B is a sectional view taken along the line B-B of FIG. 3.
FIG. 4A shows a section of the openings, in which the openings 103
and the mesh lines 104 are formed alternately. FIG. 4B shows a
section of the mesh line 104, in which the mesh line 104 comprising
the copper mesh layer 14 and the conductive treating layer 13 is
continuously formed. The sectional views of the electromagnetic
wave shielding sheet of FIGS. 2A to 2C correspond to a sectional
view taken along to the line A-A.
[0106] The embodiments of the electromagnetic wave shielding sheet
of the present invention are not limited by the above-mentioned
examples. As far as the protective film is laminated with its
adhesive layer to the copper-mesh-layer-side surface of an
electromagnetic wave shielding sheet, other protective films may be
further laminated to the transparent substrate surface on which no
copper mesh layer is laminated of the electromagnetic wave
shielding sheet. The electromagnetic wave shielding sheet of the
present invention may be in a form such that single- or
multi-layered optical filters are preliminarily laminated to the
transparent substrate surface on which no copper mesh layer is
laminated of the electromagnetic wave shielding sheet. Examples of
the optical filters include, for example, an antireflection layer,
a near-infrared absorbing layer, and an anti-glare layer. Any that
has the substantially same essential features as the technical
ideas described in claims of the present invention and exerts the
same effects and advantages is included in the technical scope of
the present invention.
[0107] Hereinafter, layers of the electromagnetic wave shielding
sheet of the present invention will be described, starting from a
transparent substrate. The same protective film as the
above-mentioned one of the present invention may be used for the
protective film of the electromagnetic wave shielding sheet of the
present invention. Thus, an explanation for the protective film of
the electromagnetic wave shielding sheet of the present invention
is omitted herein.
[0108] (Transparent Substrate)
[0109] A transparent substrate is a layer to reinforce a copper
mesh layer with low mechanical strength. Accordingly, with
appropriate consideration of heat resistance properties, insulation
properties and so on, one with mechanical strength and optical
transparency may be selected to use depending on the application.
Specific Examples of the transparent substrate include, for
example, a plate and a sheet (or film) made of organic material
such as resin, and a plate made of inorganic material such as
glass.
[0110] Examples of transparent resins used for the above-mentioned
plate and sheet of organic material include, for example, polyester
resins such as polyethylene terephthalate, polybutylene
terephthalate, polyethylene naphthalate, a copolymer of
terephthalic acid, isophthalic acid and ethylene glycol, a
copolymer of terephthalic acid, cyclohexanedimethanol and ethylene
glycol, polyamide resins such as such as nylon 6, polyolefin resins
such as polypropylene and polymethylpentene, acrylic resins such as
polymethylmethacrylate, styrene resins such as polystyrene, a
copolymer of styrene and acrylonitrile, cellulose resin such as
triacetyl cellulose, imide resins, and polycarbonate resins.
[0111] As a resin material, these resins are used solely or in
combination (i.e. a mixed resin or a polymer alloy.) They are used
as a single layer or a laminate composed of multiple layers. In the
case where they are used as a resin sheet, they are preferably used
as a uniaxially oriented sheet or a biaxially oriented sheet from
the viewpoint of mechanical strength.
[0112] The resins may appropriately contain an additive such as an
ultra violet absorber, a filler, a plasticizer, an antistatic agent
as needed.
[0113] Examples of the glass used for the above-mentioned glass
plate include quartz glass, borosilicate glass, and soda-lime
glass. Alkali-free glass or the like is more preferable, which has
a low thermal expansion coefficient, is excellent in dimensional
stability and workability at heat-treatment at an elevated
temperature, and contains no alkaline component. A glass plate of
such a glass may be used at the same time as an electrode substrate
that will be used as a front substrate of a display.
[0114] The thickness of the transparent substrate is not
particularly limited and may be determined according to the
application. In the case of a transparent substrate made of a
transparent resin, the thickness is generally from 12 to 1,000
.mu.m, more preferably from 50 to 500 .mu.m. If a transparent
substrate is a glass plate, a glass plate having a thickness from 1
to 5 mm is generally preferable. Any of the materials having a
thickness less than the range is insufficient in mechanical
strength so as to cause warpage, loosening or breaking. Any of the
materials having a thickness exceeding the range is excess in
performance and expensive; moreover, thinning the electromagnetic
wave shielding sheet becomes difficult.
[0115] The transparent substrate may be used as a front substrate
that is a component of a display device comprising a front
substrate and a back substrate. In the embodiment in which the
electromagnetic wave shielding sheet is used as a front filter to
be disposed in front of a front substrate, a sheet is more
excellent than a plate in terms of thinness and lightness. In terms
of durability, a resin sheet is more excellent than a glass
plate.
[0116] For the above-mentioned reasons, a resin sheet is a
preferred material for a transparent substrate. Among resin sheets,
a polyester resin sheet of, for example, polyethylene terephthalate
or polyethylene naphthalate is particularly preferable in terms of
transparency, heat resistance, costs, and so on. Further, a
biaxially oriented polyethylene terephthalate sheet is most
preferable. Higher transparency is better for the transparent
substrate, and an optical transparency having a visible light
transmission of 80% or more is preferable.
[0117] A conventionally known adhesion-enhancing treatment such as
a corona discharge treatment, a plasma treatment, an ozone
treatment, a flame treatment, a primer treatment, a preheating
treatment, a dust removal treatment, a vapor deposition treatment,
and an alkali treatment may be appropriately performed on the
surface of the transparent substrate.
[0118] (Copper Mesh Layer)
[0119] The copper mesh layer is a conductive layer that functions
to shield electromagnetic waves. The copper mesh layer itself is
non-transparent; however, it involves electromagnetic wave
shielding properties and optical transparency in a balanced manner
since it is in the form of a mesh and provided with openings.
[0120] A layer that is conductive and functions to shield
electromagnetic waves may consist of a copper mesh layer only or a
combination of a copper mesh layer and other layers of conductive
materials. Examples of the other layers of conductive materials
include, for example, a thin conductive layer which is to be used
as a base layer for copper plating (herein after referred to as a
conductive treating layer) and a conductive blackened layer, and
they are collectively referred to as a conductor layer. In FIG. 2C,
for example, if the blackened layer 17 is conductive, a conductor
layer means the conductive treating layer 13, the copper mesh layer
14 and the blackened layer 17. If the blackened layer 17 is not
conductive, a conductor layer means the conductive treating layer
13 and the copper mesh layer 14.
[0121] The copper mesh layer of the invention is a mesh layer
containing copper. Examples of the copper mesh layer of the present
invention include a mesh layer made of a copper alloy such as
brass, bronze, phosphor bronze, cupronickel, and
phosphorus-containing copper.
[0122] The conductor layer including the copper mesh layer may be
any shape and there is no particular limit. The opening is
typically square-shaped. The opening may be in a polygonal shape
including a triangular shape such as an equilateral triangular
shape, a quadrangular shape such as a square shape, a rectangular
shape, a diamond shape, a trapezoidal shape, a hexagonal shape; or
in a spherical shape or an ellipsoidal shape. The mesh has multiple
openings in any of the above-mentioned shapes so as to be formed
into a grid of lines between the openings, each of which lines
generally has a uniform width. In general, the openings and the
mesh lines of the entire copper mesh layer are the same in shape
and size, respectively. More specifically, in consideration of the
aperture ratio and the non-visibility of the mesh, the width of the
mesh lines 104 between the openings (i.e., the line width "W") is
preferably 40 .mu.m or less, more preferably 20 .mu.m or less.
However, in order to exhibit the electromagnetic wave shielding
effect and prevent breaking, it is preferable for the mesh lines to
ensure a line width of at least 5 .mu.m or more. The width of the
openings can be represented by: (the line pitch "P")-(the line
width "W"), and it is preferably 150 .mu.m or more, more preferably
200 .mu.m or more in the present invention in terms of optical
transparency and that air bubbles hardly remain in the openings
when laminated to an optical filter as will be described below. In
order to exhibit the shielding effect of electromagnetic waves in
the range of MHz to GHz, it has to be 3,000 .mu.m at the
maximum.
[0123] The height of the mesh lines 104 is approximately from 1 to
100 .mu.m, preferably from 2 to 20 .mu.m. If the thickness is far
less than the range, the electrical resistance increases so that it
becomes difficult to obtain a sufficient electromagnetic wave
shielding performance. If the thickness exceeds the range, it
becomes difficult to obtain a highly precise mesh pattern so that
the uniformity of the mesh pattern decreases. The height of the
mesh lines is the total thickness of, among the conductor layer 12
and non-conductive layers that are further laminated on the
conductor layer 12, all layers which are provided with the openings
and thus form the mesh lines 104. The bias angle of the mesh, which
is an angle made by the meeting of the mesh lines of the mesh and
the outer periphery of the electromagnetic wave shielding sheet,
may be appropriately set at an angle that hardly produces moire
patterns, in consideration of the pixel pitch or light emission
properties of a display.
[0124] The method for forming the copper mesh layer is not
particularly limited. Various conventionally known methods of
forming an optically transparent electromagnetic wave shielding
sheet may be appropriately employed, including the following four
methods for example.
[0125] (1) A method in which a pattern is printed on a transparent
substrate with an electric conductive ink, and a metal plating is
applied on the electric conductive ink layer (see, for example,
JP-A 2000-13088.)
[0126] (2) A method in which an electric conductive ink or a
photosensitive coating liquid containing a catalyst for chemical
plating is entirely applied on a transparent substrate, the applied
layer is formed into a mesh by a photolithography method, and a
metal plating is applied on the mesh (see, for example,
"Photosensitive Catalyst for Electro-less Plating with Fine
Pattern", Advanced Materials Research Group New Technology Research
Laboratory Sumitomo Osaka Cement Co., Ltd., on Sumitomo Osaka
Cement Co., Ltd. Web Page,
http://www.socnb.com/product/hproduct/display.html, accessed on
Jan. 7, 2003.)
[0127] (3) A transparent substrate is laminated to a metal foil
with an adhesive, and then the metal foil is formed into a mesh by
a photolithography method (see, for example, JP-A 11-145678.)
[0128] (4) A transparent substrate is prepared in which a metal
thin film is formed by sputtering or the like on one surface of the
transparent substrate to form a conductive treating layer and on
the conductive treating layer a metal layer is formed by
electrolytic plating as a metal plating layer. The metal plating
layer of the metal plating transparent substrate and the conductive
treating layer are formed to be mesh like by a photolithography
method (see, for example, Japanese Patent No. 3502979, JP-A
2004-241761.)
[0129] (Blackened Layer)
[0130] In order to absorb outside light incident on the
electromagnetic wave shielding sheet and improve the visibility of
an image on a display, a blackened layer is preferably provided on
the electromagnetic wave shielding sheet of the present invention
in terms of enhancing contrast. Some blackened layer can increase
adhesion due to its rough surface.
[0131] The blackened layer may be a layer which is in dark color
such as black and satisfies the basic properties such as adhesion,
and conventionally known blackened layers may be appropriately
used. The blackened layer is not necessarily required to have
conductivity.
[0132] Consequently, inorganic materials such as metal or organic
materials such as black-colored resin may be used to form the
blackened layer.
[0133] In the case of using inorganic materials, a metallic layer
of a metal, an alloy, a metallic compound such as a metal oxide or
metal sulfide is formed as the blackened layer. As a method for
forming a metallic layer, various conventionally known blackening
treatments may be appropriately used. Especially, blackening
treatment by a plating method is preferably in terms of
adhesiveness, uniformity, and simplicity. Materials used for
plating include, for example, metals such as copper, cobalt,
nickel, zinc, molybdenum, tin and chromium, and metallic compounds.
Plating with these materials is more excellent than using cadmium
or the like for plating in terms of adhesiveness, blackness and so
on.
[0134] Materials including Black chromium, black nickel (nickel
sulfide) and nickel alloys are preferably used to form the
blackened layer. The nickel alloys include an alloy of nickel and
zinc, an alloy of nickel and tin, and an alloy of nickel, tin and
copper. In general, particles of the blackened layer are needle
shaped so that they are easily deformed by external force and
change their appearance. A blackened layer of a nickel alloy has
advantages such that particles are hardly deformable and their
appearance hardly changes in a post-process. In the case of using a
blackened layer of nickel sulfide, there is an advantage of high
productivity. In this case, however, there is a problem that
discoloration of the blackened layer can easily occur due to an
adhesive of the protective layer. The present invention can solve
the problem. When a nickel alloy is used as the material of a
blackened layer, the method for forming the blackened layer may be
a conventionally known electrolytic or electroless plating. A
nickel alloy may be formed after conducting a nickel plating.
[0135] Plating methods suitable as a blackening treatment include a
cathodic electrodeposition plating method in which a conductor
layer of copper is subjected to cathodic electrolysis in an
electrolyte of such as sulfuric acid, copper sulfate, or cobalt
sulfate, thereby depositing cationic particles on the conductor
layer. According to this method, the cationic particles deposited
on the conductor layer blacken the conductor layer and at the same
time roughen the surface of the conductor layer. As the cationic
particles, particles of copper or copper-alloy may be used. As the
particles of copper alloy, copper and cobalt alloy particles are
preferable. The average particle diameter of the alloy particles is
preferably from 0.1 to 1 .mu.m. By using copper and cobalt alloy
particles, a blackened layer comprising a copper-cobalt alloy
particle layer can be obtained. The cathodic electrodeposition
plating method is also preferable in terms that the average
particle diameter of cationic particles to be deposited can be
controlled from 0.1 to 1 .mu.m. If the average particle diameter
exceeds the range, the density of the deposited particles
decreases. Thus, the blackness of the blackened layer decreases,
becomes uneven, and detachment of the particles may easily occur.
On the other hand, even if the average particle diameter is less
than the range, the blackness of the blackened layer decreases.
When conducting the cathodic electrodeposition at high current
density, the surface of the copper mesh layer becomes cathodic and
is activated by reducing hydrogen so that significantly improved
adhesion can be obtained between the copper surface and the
cationic particles.
[0136] The black density of the blackened layer is preferably 0.6
or more. Measurement of black density is carried out by means of
COLOR CONTROL SYSTEM GRETAG SPM100-11 (product name; manufactured
by: Kimoto Co., Ltd.) with an angle of observation field of 100 and
observation light source D50. Illumination type is set to density
standard ANSIT. A specimen is subject to measurement after white
calibration. The light reflectance of the blackened layer is
preferably 5% or less. Light reflectance is measured by means of
Haze Meter HM150 (product name; manufactured by: Murakami Color
Research Laboratory Co., Ltd.) in accordance with JIS-K7105, or it
may be expressed by a reflectance value "Y" using a
color-difference meter. In this case, "Y" is preferably 15 or
less.
[0137] In the electromagnetic wave shielding sheet of the present
invention, surface roughness of the copper-mesh-layer-side surface
to which the protective film is temporarily laminated is preferably
a ten-point average roughness "Rz JIS" (JIS B0601 (1994)) of the
profile from 0.5 to 5.0 .mu.m when a roughness profile is used as a
profile of the surface, and a center line average roughness "Ra"
(JIS B0601 (1994)) of fine irregularities on the surface from 0.1
to 3.0 .mu.m from the viewpoint that the protective film can have
adhesion and removability of the protective film when combined with
an adhesive specified in the present invention, that is, the
protective film leaves no adhesive residue behind when peeled off
and causes no partial peeling of a blackened layer and the like if
the blackened layer and the like are further laminated on the
copper mesh layer.
[0138] (Lamination of Protective Film)
[0139] There is no particular limit to the method for temporarily
laminating the above-mentioned protective film to a
copper-mesh-layer-side surface of the electromagnetic wave
shielding sheet in which at least the copper mesh layer is provided
on one surface of a transparent substrate.
[0140] Any laminator such as a roll laminator or a flat bed
laminator may be used as far as it can apply pressure to an optical
filter and an electromagnetic wave shielding sheet. A roll
laminator is preferable since it corresponds to roll to roll
lamination method and enables continuous production.
[0141] Lamination pressure is not particularly limited. For
example, in the case of using a roll laminator, a linear pressure
from 1 to 20 kgf/cm is preferable. The temperature of a pressure
member of a laminator is not particularly limited.
[0142] FIG. 5 shows an example of a process for laminating an
electromagnetic wave shielding sheet to a protective film by means
of a laminator. A roll of an electromagnetic wave shielding sheet
is set in a first paper feed member 21 of a laminator. A roll of a
laminate sheet comprising a release film and a protective film (an
adhesive layer and a support) is set in a second paper feed member
22. While the electromagnetic wave shielding sheet is fed from the
first paper feed member 21, the laminate sheet is fed from the
second paper feed member 22. At the same time, the release film is
wound up onto a wind-up roller 24. A copper mesh layer side of the
electromagnetic wave shielding sheet and the adhesive layer side of
the protective film are faced to each other. They are laminated to
each other by means of a first laminating unit 25 at a lamination
pressure of approximately 10 kgf/cm, and then again by a second
laminating unit 26 at a lamination pressure of approximately 10
kgf/cm. The lamination result is wound onto a wind-up roll 27, thus
obtaining a laminate sheet comprising the electromagnetic wave
shielding sheet and the protective film (the adhesive layer and the
support.) Two laminating unit are used in FIG. 5; however, only one
laminating unit may be used to laminate if it can provide a good
lamination result.
[0143] The electromagnetic wave shielding sheet with the protective
film of the present invention may be distributed in the form of a
continuous band (roll) or separate sheets. There is no particular
limit to the means for separating the sheet into separate sheets.
Any kind of cutting means for filters may be used.
[0144] As described above, the protective film for temporary
lamination to an electromagnetic wave shielding sheet of the
present invention can provide an effect that the protective film
leaves no adhesive residue behind when peeled off and causes no
partial peeling of a blackened layer and the like even in the case
where the blackened layer and the like are further laminated on the
copper mesh layer, while having appropriate adhesion properties
that involves easy adhesion and easy peelability in a balanced
manner with respect to a copper mesh layer of the electromagnetic
wave shielding sheet. Especially, if the amount of a specific acid
in the adhesive layer is less than the specified amount, the
protective film provides an additional effect that if causes no
discoloration of the electromagnetic wave shielding sheet even
after long-term use, especially at high temperature and high
humidity.
[0145] The electromagnetic wave shielding sheet of the present
invention is an electromagnetic wave shielding sheet with a
protective film that is temporarily laminated on a copper mesh
layer for shielding electromagnetic waves, which sheet provides an
effect that the protective film leaves no adhesive residue behind
when peeled off and causes no partial peeling of a blackened layer
and the like even in the case where the blackened layer and the
like are further laminated on the copper mesh layer, while the
copper mesh layer and the protective film exhibit easy adhesion and
easy peelability. Especially, if the amount of a specific acid in
the adhesive layer of the protective film is less than the
specified amount, the protective film provides an additional effect
that if causes no discoloration of the copper mesh layer even after
long-term use, especially at high temperature and high
humidity.
[0146] The method for producing the protective film for temporary
lamination to an electromagnetic wave shielding sheet of the
present invention can provide effects that can obtain the
protective film, in which the protective film leaves no adhesive
residue behind when peeled off and causes no partial peeling of a
blackened layer and the like even in the case where the blackened
layer and the like are further laminated on the copper mesh layer,
while having appropriate adhesion properties that involves easy
adhesion and easy peelability in a balanced manner with respect to
a copper mesh layer of the electromagnetic wave shielding sheet;
moreover, the protective film causes no discoloration of the
electromagnetic wave shielding sheet even after long-term use,
especially at high temperature and high humidity.
[0147] The present invention is not limited by the above-mentioned
embodiments. The above-mentioned embodiments are examples, and any
that has the substantially same essential features as the technical
ideas described in claims of the present invention and exerts the
same effects and advantages is included in the technical scope of
the present invention.
EXAMPLES
[0148] Hereinafter, the present invention will be explained further
in detail with reference to examples. The scope of the present
invention may not be limited to the following examples. Herein,
"part(s)" refers to "part(s) by weight" if not particularly
mentioned.
(Tests)
[0149] Each of the adhesive layer surfaces of the following
protective films "A" to "D" was extracted at 23.degree. C. for 15
minutes with ultrapure water. In particular, each protective film
was cut into a size of 10 cm.times.10 cm and the adhesive layer of
the cut out film was entirely immersed in 500 ml of ultrapure water
and left at 23.degree. C. for 15 minutes while.
[0150] The amounts of acetic acid and formic acid were measured for
the resulting extract of each cut out film by ion chromatography.
Said extraction was performed in a clean booth with a chemical
filter. The elution amount (ng/cm.sup.2) of each component per unit
area was obtained by multiplying the concentration of acetic
acid/forming acid in the resulting extract (ng/mL) by the amount of
the resulting extract (mL) and then dividing the result by the
extraction area (cm.sup.2.)
[0151] Protective film A: An adhesive layer of the protective film
A comprises an acrylic copolymer formed by copolymerizing urethane
methacrylate, which is obtained by reaction of 2-hydroxyethyl
methacrylate with tolylene diisocyanate, with methyl methacrylate.
The thickness of the adhesive layer is 6 .mu.m. The total thickness
of the protective film A is 60 .mu.m.
[0152] Protective film B: An adhesive layer of the protective film
B comprises an acrylic copolymer formed by copolymerizing urethane
methacrylate, which is obtained by reaction of 2-hydroxyethyl
methacrylate with tolylene diisocyanate, with butyl acrylate,
2-ethylhexyl acrylate, and ethyl acrylate. The thickness of the
adhesive layer is 6 .mu.m. The total thickness of the protective
film B is 60 .mu.m.
[0153] Protective film C: An adhesive layer of the protective film
C comprises an acrylic polymer formed by copolymerizing butyl
acrylate with 2-ethylhexyl acrylate. The thickness of the adhesive
layer is 6 .mu.m. The total thickness of the protective film C is
60 .mu.m.
[0154] Protective film D: An adhesive layer of the protective film
D comprises a rubber copolymer comprising a styrene-isobutylene
copolymer. The thickness of the adhesive layer is 6 .mu.m. The
total thickness of the protective film D is 60 .mu.m.
[0155] Ion chromatography measurement condition was given as
follows.
[0156] Apparatus: DX-600 (product name; manufactured by: Nippon
Dionex K.K.)
[0157] Column: AG11-HC+AS11-HC
Eluent: KOH
[0158] Eluent concentration: 1 to 35 mM (Gradient)
(Test Results of the Amounts of Acetic Acid and Formic Acid) Table
1 shows the amounts of acetic acid and formic acid obtained by the
measurement. It is thus found that the protective film A and the
protective film B could be used as the protective film for
temporary lamination to an electromagnetic wave shielding sheet of
the present invention.
TABLE-US-00001 TABLE 1 Extracted Amount of Each Acid per Unit Area
(ng/cm.sup.2) Acetic Acid Formic Acid Protective Film A 1.2 0.7
Protective Film B 1.6 1.1 Protective Film C 86 16 Protective Film D
Below Below detectable detectable limit limit
Example 1
[0159] An electromagnetic wave shielding sheet 100 shown in FIG. 2C
was produced as follows.
[0160] As a transparent substrate 11, a color less, transparent,
biaxially-stretched polyethylene terephthalate film in the form of
a continuous belt was prepared. The polyethylene terephthalate film
had a thickness of 100 .mu.m and a polyester resin primer layer on
one surface thereof.
[0161] On the primer layer of the transparent substrate, a 0.1
.mu.m thick nickel-chromium alloy layer and a 0.2 .mu.m thick
copper layer were provided in this sequence by a sputtering method
so as to prepare a conductive treating layer 13.
[0162] On the conductive treating layer surface, a 2.0 .mu.m thick
copper plated layer 15 was provided by an electrolytic plating
method using a copper sulfate bath (herein after, the conductive
treating layer 13 and the copper plated layer are referred to as a
metal layer 18 in combination.) As a result of forming the metal
layer 18 on the transparent substrate, there was produced a
copper-clad laminate sheet 20 as shown in FIG. 6A, in which the
metal layer 18 was directly formed on the transparent substrate
without an adhesive layer in between.
[0163] Next, the laminate sheet 20 was etched using the
photolithographic method for the conductor layer 12 to form a mesh
comprising openings 103 and mesh lines 104 as shown in FIG. 6B,
thereby obtaining a laminate 30.
[0164] In etching, using a production line for a color TV shadow
mask, a process from masking to etching was consistently performed
on the continuous belt-shaped laminate sheet. A photosensitive
etching resist was applied to the entire surface of the conductor
layer surface of the laminate sheet and then a desired mesh pattern
was transferred by contact exposure, followed by development,
film-hardening treatment, and baking, so that the resist layer was
patterned such that the resist layer remains on portions
corresponding to mesh lines and no resist layer remains on portions
corresponding to openings of the mesh. Next, the conductor layer
was etched and removed in an aqueous ferric chloride to form mesh
openings, followed by water washing, resist stripping, cleaning and
drying in this sequence.
[0165] The mesh pattern of the mesh area had square openings and
mesh lines having a line width of 10 .mu.m, a line distance (pitch)
of 300 .mu.m, and a line height of 2.3 .mu.m. When the mesh is cut
in the form of a rectangular sheet, the bias angle, which is
defined as an inferior angle to the long side of the rectangular
sheet, is 49 degrees.
[0166] Next, a blackened layer 17 was formed on a metal layer 18 of
the laminate 30. In particular, using a nickel plate as an anode,
the laminate sheet in which the mesh-shaped conductor layer was
formed on the transparent substrate was immersed in a plating bath
of a mixture of a nickel ammonium sulfate solution, a zinc sulfate
solution, and a sodium thiocyanate solution for a blackening
treatment. The exposed surface of the conductor layer was entirely
covered with the blackened layer 17 made of a nickel-zinc alloy,
thus obtaining a laminate 40 as shown in FIG. 6C, in which the
conductor layer 12 comprising the conductive treating layer 13, the
copper mesh layer 14, and the blackened layer 17 was laminated.
[0167] To the copper mesh side of the laminate 40, using a roll
laminator, the protective film A in which an acrylic adhesive layer
was laminated to a 50 .mu.m thick polyethylene film support was
laminated by pressing them between a pair of pressure rollers
comprising a rubber coated steel core, at a roller pressure (total
pressure) of 0.2 MPa and a processing speed of 15 meters per
minute, thus producing an electromagnetic wave shielding sheet 100
of Example 1 as shown in FIG. 6D, having a structure comprising:
the transparent substrate, the conductor layer 12 (comprising the
conductive treating layer 13, the copper mesh layer 14, and the
blackened layer 17,) and a protective film A 10 (comprising the
adhesive layer 2 and a polyethylene film 1) in sequence.
Example 2
[0168] An electromagnetic wave shielding sheet was produced as in
Example 1, except that the protective film A was changed to the
protective film B.
Comparative Example 1
[0169] An electromagnetic wave shielding sheet was produced as in
Example 1, except that the protective film A was changed to the
protective film C.
Comparative Example 2
[0170] An electromagnetic wave shielding sheet was produced as in
Example 1, except that the protective film A was changed to the
protective film D.
(Evaluation)
[0171] Examples and Comparative Examples were evaluated on the
following points. The results are shown in Table 2.
(1) Discoloration Property 1
[0172] Firstly, chromaticities a*, b*, and a luminance L* (defined
by the International Commission on Illumination (CIE)) were
measured for the copper mesh side surface of the electromagnetic
wave shielding sheets of Examples and Comparative Examples. After
the electromagnetic wave shielding sheets were exposed to an
atmosphere of high temperature and high humidity (60.degree. C.,
95% RH) for 200 hours, chromaticities a*, b*, and a luminance L*
were measured again for the copper mesh side surface of the
electromagnetic wave shielding sheets. From results of the
measurements, a color difference .DELTA.E before and after exposed
to an atmosphere of high temperature and high humidity was
obtained. In Table 2, the marking "x" indicates
.DELTA.E.sub.L*a*b*>10 (i.e., the case where a color difference
is above a narrow margin by visual examination and discoloration is
clearly and visually observed.) The marking ".DELTA." indicates
1<.DELTA.E.sub.L*a*b*.ltoreq.10 (i.e., the case where a color
difference is below a narrow margin by visual examination.) The
marking "o" indicates .DELTA.E.sub.L*a*b*.ltoreq.1 (i.e., the case
where a color difference is below a differential threshold of
discoloration by visual examination.)
(2) Discoloration Property 2
[0173] The electromagnetic wave shielding sheets were exposed to a
dry atmosphere of high temperature (80.degree. C.) for 200 hours to
measure chromaticities a*, b*, and a luminance L of the copper mesh
side surface. From results of the measurements, a color difference
.DELTA.E.sub.L*a*b* was obtained. The color difference
.DELTA.E.sub.L*a*b* of the copper mesh side surface of each
electromagnetic wave shielding sheet was evaluated in accordance
with the standard mentioned in "(1) Discoloration property 1."
(3) Delamination Resistance (Adhesion)
[0174] Each electromagnetic wave shielding sheet to which each
corresponding protective film was temporarily laminated was cut to
a size of 150 mm long by 25 mm wide. The cut-off protective film
was measured using a tensile tester (product name: Tensilon;
manufactured by: Toyo Seiki Seisaku-sho, Ltd.) by stretching the
protective film and the copper-mesh-layer-side surface in a
direction such that they make an angle of 180.degree. at a
stretching speed of 300 mm/min and in an atmosphere of a
temperature from 20 to 25.degree. C.
(4) Adhesive Residue
[0175] In the evaluation of delamination resistance, it was
visually determined if adhesive residue was left on the
copper-mesh-layer-side surface or not when the protective film was
peeled off. The marking "o" indicates that no adhesive was left on
the copper-mesh-layer-side surface, and "x" indicates that adhesive
was left on the copper-mesh-layer-side surface.
(5) Peeling of Blackened Layer
[0176] In the evaluation of delamination resistance, it was
visually determined if partial peeling of the blackened layer
occurred and the peeling adhered to the adhesive layer surface of
the protective film when the protective film was peeled off. The
marking "o" indicates no peeling of the blackened layer occurred,
and "x" indicates that part of the blackened layer was peeled off
and adhered to the adhesive layer surface.
TABLE-US-00002 TABLE 2 Delamination Peeling of Protective
Discoloration Discoloration Resistance Adhesive Blackened Film
property 1 property 2 (N/25 mm) Residue Layer Example1 Protective
.largecircle. .largecircle. 0.49 .largecircle. .largecircle. Film A
Example2 Protective .largecircle. .largecircle. 1.1 .largecircle.
.largecircle. Film B Comparative Protective X X 0.69 .largecircle.
.largecircle. Example 1 Film C Comparative Protective .largecircle.
.largecircle. 0.12 X X Example 2 Film D
(Results)
[0177] The above-described Examples and Comparative Examples result
in the following findings.
[0178] The electromagnetic wave shielding sheets of Examples 1 and
2 are such that the protective film left no adhesive residue behind
when peeled off and caused no partial peeling of a blackened layer
and the like that were further laminated on the copper mesh layer,
while the copper mesh layer and the protective film exhibited
appropriate easy adhesion and easy peelability. Moreover, the
electromagnetic wave shielding sheets did not discolor even after
long-term use, especially at high temperature and high
humidity.
[0179] On the other hand, the electromagnetic wave shielding sheet
of Comparative Example 1, in which the amounts of acetic acid and
formic acid extracted from the adhesive layer were large, had
adequate adhesion properties; however, discoloration was observed
after long-term storage, especially at high temperature and high
humidity. In Comparative Example 2 using a rubber adhesive layer,
discoloration of the copper mesh was not a problem and in a
favorable state; however, the protective film left adhesive residue
behind and caused partial peeling of the blackened layer when
peeled off.
* * * * *
References