U.S. patent application number 10/922938 was filed with the patent office on 2005-05-05 for electromagnetic wave shielding laminate and display device employing it.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. Invention is credited to Morimoto, Tamotsu, Yanagisawa, Tohru.
Application Number | 20050095449 10/922938 |
Document ID | / |
Family ID | 34208995 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050095449 |
Kind Code |
A1 |
Yanagisawa, Tohru ; et
al. |
May 5, 2005 |
Electromagnetic wave shielding laminate and display device
employing it
Abstract
An electromagnetic wave shielding laminate comprising a
transparent substrate and an electromagnetic wave shielding film
formed thereon, characterized in that the electromagnetic wave
shielding film has, sequentially from the substrate side, a first
high refractive index layer made of a material having a refractive
index of at least 2.0, a first oxide layer containing zinc oxide as
the main component, an electroconductive layer containing silver as
the main component, and a second high refractive index layer made
of a material having a refractive index of at least 2.0.
Inventors: |
Yanagisawa, Tohru; (Tokyo,
JP) ; Morimoto, Tamotsu; (Chiba, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Tokyo
JP
100-8405
|
Family ID: |
34208995 |
Appl. No.: |
10/922938 |
Filed: |
August 23, 2004 |
Current U.S.
Class: |
428/689 ;
428/701; 428/702 |
Current CPC
Class: |
H05K 9/0096 20130101;
H01J 2211/446 20130101 |
Class at
Publication: |
428/689 ;
428/701; 428/702 |
International
Class: |
B32B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2003 |
JP |
2003-208674 |
Claims
What is claimed is:
1. An electromagnetic wave shielding laminate comprising a
transparent substrate and an electromagnetic wave shielding film
formed thereon, characterized in that the electromagnetic wave
shielding film has, sequentially from the substrate side, a first
high refractive index layer made of a material having a refractive
index of at least 2.0, a first oxide layer containing zinc oxide as
the main component, an electroconductive layer containing silver as
the main component, and a second high refractive index layer made
of a material having a refractive index of at least 2.0.
2. The electromagnetic wave shielding laminate according to claim
1, wherein the electromagnetic wave shielding film has a second
oxide layer between the electroconductive layer and the second high
refractive index layer.
3. The electromagnetic wave shielding laminate according to claim 1
or 2, wherein the first or second high refractive index layer is a
layer containing niobium oxide as the main component.
4. The electromagnetic wave shielding laminate according to claim
1, 2 or 3, wherein the content of silver in the electroconductive
layer is at least 99.8 atomic %.
5. The electromagnetic wave shielding laminate according to any one
of claims 2 to 4, wherein the second oxide layer is an oxide layer
containing zinc oxide as the main component.
6. The electromagnetic wave shielding laminate according to any one
of claims 1 to 5, wherein at least three such electromagnetic wave
shielding films are laminated from the substrate side.
7. An electromagnetic wave shielding laminate comprising a
transparent substrate and at least two electromagnetic wave
shielding films laminated thereon, characterized in that each
electromagnetic wave shielding film has, sequentially from the
substrate side, a first high refractive index layer made of a
material having a refractive index of at least 2.0, a first oxide
layer containing zinc oxide as the main component, an
electroconductive layer containing silver as the main component,
and a second high refractive index layer made of a material having
a refractive index of at least 2.0, and the first high refractive
index layer and the second high refractive index layer which are in
direct contact each other between the electromagnetic wave
shielding films, are made of a single layer formed all
together.
8. The electromagnetic wave shielding laminate according to claim
7, wherein each electromagnetic wave shielding film has a second
oxide layer between the electroconductive layer and the second high
refractive index layer.
9. The electromagnetic wave shielding laminate according to claim 7
or 8, wherein the first or second high refractive index layer is a
layer containing niobium oxide as the main component.
10. A display device characterized by comprising a display screen
to display images and an electromagnetic wave shielding laminate as
defined in any one of claims 1 to 9, provided on the viewer's side
of the display screen.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electromagnetic wave
shielding laminate having a plurality of layers laminated on a
substrate and a display device provided with such an
electromagnetic wave shielding laminate.
[0003] 2. Discussion of Background
[0004] Electromagnetic waves are emitted from a luminescent screen
of a plasma display panel (PDP). Such electromagnetic waves are
influential over electronic equipment located nearby to cause
malfunction thereof. Therefore, for the purpose of shielding such
electromagnetic waves, it has heretofore been known to install on
the front surface of the luminescent screen one having a
transparent electroconductive film covered on a substrate of e.g.
glass.
[0005] For example, a laminate wherein titanium oxide and a metal
layer are alternately laminated, or a protecting plate for PDP
coated with a multilayer conductive film, wherein an oxide layer
containing, as the main component, zinc oxide (ZnO) containing at
least one metal, and a metal layer containing silver (Ag) as the
main component are alternately laminated in a total of (2n+1)
layers (wherein n is a positive integer) from the substrate side,
has been proposed (Patent Documents 1 and 2).
[0006] Such an electromagnetic wave shielding film is usually
required to have a high visible light transmittance and a low
resistivity. With an electromagnetic wave shielding film having an
oxide layer and a metal layer alternately laminated, it is commonly
known to increase the number of metal layers laminated or to make
metal layers thick, in order to lower the resistivity.
[0007] Patent Document 1: WO98/13850
[0008] Patent Document 2: JP-A-2000-246831
[0009] In prior art disclosed in the above Patent Document 1,
palladium is doped to a silver layer in order to improve the
moisture resistance of silver. There has been a problem that the
resistivity thereby increases. If the number of laminated metal
layers is increased in order to lower the resistivity, there has
been another problem that the visible transmittance will thereby
decrease.
[0010] Whereas, in prior art disclosed in Patent Document 2,
titanium oxide being a material having a high refractive index, is
used as an oxide layer. If a material having a high refractive
index like titanium oxide, is used, there will be a merit such that
even when the number of laminated layers is increased, the decrease
in transmittance will be small. However, the laminate having
titanium oxide and silver alternately laminated, has had a problem
that the moisture resistance is poor. By adding palladium to
silver, the moisture resistance may be improved, but there has been
a problem that the resistivity will increase by the addition of
palladium.
SUMMARY OF THE INVENTION
[0011] In view of the above-mentioned problems of the prior art,
the present invention is intended to provide a low cost
electromagnetic wave shielding laminate which has a high visible
light transmittance and which also has low resistivity and high
moisture resistance, and a display device employing it.
[0012] The present invention provides an electromagnetic wave
shielding laminate comprising a transparent substrate and an
electromagnetic wave shielding film formed thereon, characterized
in that the electromagnetic wave shielding film has, sequentially
from the substrate side, a first high refractive index layer made
of a material having a refractive index of at least 2.0, a first
oxide layer containing zinc oxide as the main component, an
electroconductive layer containing silver as the main component,
and a second high refractive index layer made of a material having
a refractive index of at least 2.0.
[0013] The present invention also provides an electromagnetic wave
shielding laminate comprising a transparent substrate and at least
two electromagnetic wave shielding films laminated thereon,
characterized in that each electromagnetic wave shielding film has,
sequentially from the substrate side, a first high refractive index
layer made of a material having a refractive index of at least 2.0,
a first oxide layer containing zinc oxide as the main component, an
electroconductive layer containing silver as the main component,
and a second high refractive index layer made of a material having
a refractive index of at least 2.0, and the first high refractive
index layer and the second high refractive index layer which are in
direct contact each other between the electromagnetic wave
shielding films, are made of a single layer formed all
together.
[0014] Further, the present invention provides a display device
characterized by comprising a display screen to display images and
the electromagnetic wave shielding laminate of the present
invention provided on the viewer's side of the display screen.
[0015] The electromagnetic wave shielding laminate and the display
device of the present invention are a low cost electromagnetic wave
shielding laminate which has a high visible light transmittance and
which also has low resistivity and high moisture resistance, and a
display device employing it.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic cross-sectional view illustrating one
embodiment of the electromagnetic wave shielding laminate of the
present invention.
DESCRIPTION OF SYMBOLS
[0017] 1: Electromagnetic wave shielding laminate
[0018] 2: Substrate
[0019] 31: First high refractive index layer
[0020] 32: First oxide layer
[0021] 33: Electroconductive layer
[0022] 34: Second oxide layer
[0023] 35: Second high refractive index layer
[0024] 100: Electromagnetic wave shielding film
[0025] 200: High refractive index layer formed all together
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS ELECTROMAGNETIC
WAVE SHIELDING LAMINATE
[0026] Now, an example of an electromagnetic wave shielding
laminate according to one embodiment of the present invention will
be described in detail with reference to the drawing.
FIRST EMBODIMENT
[0027] FIG. 1 illustrates an electromagnetic wave shielding
laminate 1 according to the first embodiment of the present
invention. The dimensional proportions in FIG. 1 are different from
the actual ones for the sake of convenience for illustration. This
electromagnetic wave shielding laminate 1 comprises a transparent
substrate 2 and electromagnetic wave shielding films 100 formed
thereon. This embodiment takes a construction wherein four
electromagnetic wave shielding films 100 are laminated.
[0028] Substrate
[0029] The material for the substrate 2 may be any material so long
as it is smooth and transparent and capable of transmitting visible
light. For example, plastics or glass may be mentioned.
[0030] The plastics include, for example, polyethylene
terephthalate, polycarbonate, triacetylcellulose, polyether sulfone
and polymethyl methacrylate.
[0031] The thickness of the substrate 2 may suitably be selected
depending upon the particular application. For example, it may be a
film or a plate. Further, the substrate 2 may be constituted by a
single layer or may be a laminate of a plurality of layers.
[0032] The substrate 2 may be used as bonded to a separate glass
plate, plastic plate or the like by means of an adhesive or the
like. For example, a substrate 2 of a thin plastic film may be
bonded to a separate plastic plate, a glass plate or the like, or a
substrate 2 made of a glass plate may be bonded to a separate glass
plate, a plastic plate or the like.
[0033] Electromagnetic Wave Shielding Films
[0034] Each of the electromagnetic wave shielding films 100 formed
on the substrate 2 basically comprises a first high refractive
index layer 31, a first oxide layer 32 formed on the first high
refractive index layer 31, an electroconductive layer 33 formed on
the first oxide layer 32, and a second high refractive index layer
35 formed on the electroconductive layer 33. In this embodiment, a
second oxide layer 34 is further formed between the
electroconductive layer 33 and the second high refractive index
layer 35, so that the electromagnetic wave shielding film 100
comprises a first high refractive index layer 31, a first oxide
layer 32, an electroconductive layer 33, a second oxide layer 34
and a second high refractive index layer 35.
[0035] High Refractive Index Layers
[0036] Each of the first high refractive index layers 31 and the
second high refractive index layers 35 is made of a material having
a refractive index of at least 2.0. The refractive index is
preferably at least 2.0 and at most 2.7. By adjusting the
refractive index of the first high refractive index layers 31 or
the second high refractive index layers 35 to a level of at least
2.0, it is possible to maintain the visible light transmittance at
a high level even if the laminated number of electromagnetic wave
shielding films 100 is increased.
[0037] In this specification, the refractive index (n) is meant for
the refractive index at a wavelength of 550 nm.
[0038] The material for the first high refractive index layers 31
or the second high refractive index layers 35 may, for example, be
niobium oxide (n: 2.35), titanium oxide (n: 2.45) or tantalum oxide
(n: 2.1 to 2.2). Among them, niobium oxide or titanium oxide is
preferred, and niobium oxide is particularly preferred. By making
the first high refractive index layers 31 or the second high
refractive index layers 35 to be layers containing niobium oxide as
the main component, it is possible to reduce the penetration amount
of water and to improve the moisture resistance of the
electromagnetic wave shielding films 100. It is particularly
preferred that the first high refractive index layers 31, or the
second high refractive index layers 35 are layers containing
niobium oxide as the main component, since the above effect is
thereby large.
[0039] Further, the first high refractive index layers 31 or the
second high refractive index layers 35 may be crystalline or
amorphous. However, they are preferably amorphous. By making the
first high refractive index layers 31 or the second high refractive
index layers 35 to be amorphous, it is possible to reduce
penetration of water via crystal grains and thereby to further
improve the moisture resistance of the electromagnetic wave
shielding films 100.
[0040] The geometrical film thickness of each of the first high
refractive index layers 31 is preferably from 20 to 50 nm, more
preferably from 30 to 40 nm. Further, the geometrical film
thickness of each of the second high refractive index layers 35 is
preferably from 20 to 50 nm, more preferably from 30 to 40 nm.
[0041] This embodiment takes a construction such that four
electromagnetic wave shielding films 100 are laminated on a
transparent substrate 2, whereby the first high refractive index
layer 31 in the electromagnetic wave shielding film 100 of the
second laminated layer is laminated directly on the second high
refractive index layer 35 in the electromagnetic wave shielding
film 100 of the first laminated layer. In this case, the second
high refractive index layer 35 and the first high refractive index
layer 31 have the same composition. In FIG. 1, the second high
refractive index layer 35 and the first high refractive index layer
31 are shown to be a high refractive index layer 200, as they are
put together and formed all together. Further, if necessary, the
first high refractive index layer 31 and the second high refractive
index layer 35 may be formed in two or more operations.
[0042] With a view to reducing the visible light reflectance and
broadening the wavelength zone wherein a low reflectance is
obtainable, the thickness of each of the first high refractive
index layer 31 of the first laminated layer and the second high
refractive index layer 35 of the finally laminated layer, is
preferably thinner (by about 1/2) than the thickness of the high
refractive index layers 200. Further, the thicknesses of the
respective layers may suitably be adjusted in order to adjust the
overall optical characteristics inclusive of the substrate.
[0043] The method for forming the first high refractive index
layers 31 or the second high refractive index layers 35, may, for
example, be a method of forming them by a sputtering method
employing a reduced type target of a metal oxide, an ion plating
method, a vapor deposition method or a CVD method. Among them, a
method of forming them by a sputtering method employing a reduced
type target of niobium oxide is advantageous in that at the time of
forming a niobium oxide layer on an electroconductive layer 33, it
is possible to prevent oxidation of the electroconductive layer 33
and to form the layer uniformly over a large area at a high
speed.
[0044] The reduced type target of niobium oxide to be used here, is
a target deficient in oxygen as compared with the stoichiometrical
composition of niobium oxide. Specifically, it is more preferably
one having a composition represented by the formula Nb.sub.2O.sub.x
(0<X<5) and having electroconductivity, which can be
discharged by a DC sputtering method to form a film. Further, it is
also possible to employ a method of sputtering in an oxygen
atmosphere by using metallic niobium as a target.
[0045] When a reduced type target is employed, it is preferred to
use an inert gas containing from 5 to 20 vol % of an oxidizing gas,
as the sputtering gas. As such an oxidizing gas, oxygen gas may
usually be used. However, it is also possible to use, for example,
nitrogen monoxide, nitrogen dioxide, carbon monoxide, carbon
dioxide or ozone.
[0046] Oxide Layers
[0047] First Oxide Layers
[0048] The first oxide layers 32 are made of a material containing
zinc oxide as the main component. The material containing zinc
oxide as the main component has its crystal structure which is
close to the crystal structure of silver constituting the
electroconductive layers 33. Accordingly, if silver is laminated on
the oxide layer made of the material containing zinc oxide as the
main component, silver having good crystallinity may be obtained.
With the silver having good crystallinity, it is considered
possible to reduce migration. Thus, by making the first oxide
layers 32 from the material containing zinc oxide as the main
component, it is possible to suppress migration of silver and to
maintain the adhesion between the first oxide layer 32 and the
electroconductive layer 33. By maintaining the adhesion, it is
possible to prevent penetration of moisture into the grain
boundaries, whereby the moisture resistance of silver will be good.
When the electromagnetic wave shielding film 100 in the present
invention contains the second oxide layer (made of the material
containing zinc oxide as the main component), the adhesion can
similarly be maintained at the interface between the
electroconductive layer 33 made of silver having good
crystallinity, and the second oxide layer 34 (made of a material
containing zinc oxide as the main component), whereby the moisture
resistance will further be improved.
[0049] Here, migration of silver means that silver will be diffused
and agglomerated. If silver is agglomerated, the moisture
resistance will be poor, and at the same time, the agglomerated
portion will be whitened to show a poor outer appearance.
[0050] The material containing zinc oxide as the main component
means that zinc oxide is contained in an amount of at least 80
atomic %, preferably at least 90 atomic %. Specifically, it may be
one composed substantially solely of zinc oxide (ZnO), or it may,
for example, be an oxide (hereinafter referred to as AZO) which
comprises zinc oxide as the main component and aluminum oxide
(Al.sub.2O.sub.3) or an oxide (hereinafter referred to as GZO)
which comprises zinc oxide as the main component and gallium oxide
(Ga.sub.2O.sub.3). Among them, AZO or GZO is preferred from the
viewpoint of the durability of the oxide layer, and AZO is most
preferred, since it is close to the crystal structure of
silver.
[0051] Aluminum contained in AZO formed into a film, is preferably
from 1 to 10 atomic %, more preferably from 2 to 6 atomic %, based
on the total amount of aluminum oxide and zinc oxide. Generally, a
film formed of a simple substance of zinc oxide has a large
internal stress. If the internal stress is large, cracks are likely
to be formed in the first oxide layers 32, and moisture is likely
to penetrate through such cracked portions.
[0052] By controlling the content of aluminum oxide to be at least
1 atomic %, it is possible to reduce the internal stress of the
first oxide layers 32 and thereby to minimize the possibility of
cracking. By controlling the content of aluminum oxide to be at
most 10 atomic %, it is possible to maintain the crystal structure
of zinc oxide.
[0053] The geometrical thickness of each of the first oxide layers
32 is preferably from 2 nm to 10 nm, more preferably from 3 nm to 6
nm. By controlling the geometrical thickness of each of the first
oxide layers 32 to be at most 10 nm, the effects of the adjacent
first high refractive index layers 31 will not be impaired, such
being desirable.
[0054] In the electroconductive layers 33, in order to obtain
silver having good crystallinity, the influence of the undercoating
will be substantial, and accordingly it is preferred that the
geometrical thickness of each of the first oxide layers 32 is
large. In a case where the electromagnetic wave shielding laminate
of the present invention has a second oxide layer, the geometrical
thickness of the first oxide layer 32 is preferably larger than the
geometrical thickness of the second oxide layer 34.
[0055] The method for forming the first oxide layers 32 may, for
example, be a physical vapor deposition method such as a vacuum
vapor deposition method, a reactive vapor deposition method, an ion
beam assisted vapor deposition method, a sputtering method or an
ion plating method, or a chemical vapor deposition method such as a
plasma enhanced CVD method. Among them, a DC sputtering method is
preferred, since control of the film thickness is thereby
relatively easy, a practical film strength can be obtained even
when it is formed on a low temperature substrate, a film formation
over a large area is easy, or formation of a laminated film is easy
if a so-called inline installation is employed.
[0056] Second Oxide Layers
[0057] The second oxide layers 34 are made of a material containing
a metal oxide as the main component. The metal oxide may preferably
be, for example, a material containing zinc oxide as the main
component, a material containing titanium oxide as the main
component, or a material containing indium oxide as the main
component. In a case where the material containing zinc oxide as
the main component, is used for the second oxide layers 34, like in
the case of the interface between the first oxide layer and the
electroconductive layer 33 made of silver, it is possible to
maintain the adhesion at the interface between the
electroconductive layer 33 made of silver having good crystallinity
and the second oxide layer 34 made of a material containing zinc
oxide as the main component, whereby the moisture resistance will
be further improved, such being preferred.
[0058] As the second oxide layers 34, titanium oxide, AZO, GZO or
an oxide comprising indium oxide as the main component and tin
oxide (SnO.sub.2), may more preferably be mentioned. Among them,
AZO or GZO is preferred from the durability of the oxide layer, and
AZO is most preferred, since it is closer to the crystal structure
of silver.
[0059] Aluminum contained in AZO formed into a film is preferably
from 1 to 10 atomic %, more preferably from 2 to 6 atomic %, based
on the total amount of aluminum oxide and zinc oxide. Generally,
the film formed from a simple substance of zinc oxide has a large
internal stress. If the internal stress is large, cracks are likely
to form in the second oxide layers 34, and moisture is likely to
penetrate through such cracked portions.
[0060] By controlling the content of aluminum oxide to be at least
1 atomic %, it is possible to reduce the internal stress of the
second oxide layers 34 and thereby to minimize the possibility of
cracking. By controlling the content of aluminum oxide to be at
most 10 atomic %, it is possible to maintain the crystal structure
of zinc oxide.
[0061] The geometrical thickness of each of the second oxide layers
34 is preferably from 1 nm to 6 nm, more preferably from 2 nm to 4
nm.
[0062] The method for forming the second oxide layers may, for
example, be a physical vapor deposition method such as a vacuum
vapor deposition method, a reactive vapor deposition method, an ion
beam assisted vapor deposition method, a sputtering method or an
ion plating method, or a chemical vapor deposition method such as a
plasma enhanced CVD method. Among them, a DC sputtering method is
preferred, since control of the film thickness is relatively easy,
a practical film strength can be obtained even when the film is
formed on a low temperature substrate, film formation over a large
area is easy, and formation of laminated films is easy if a
so-called inline installation is employed.
[0063] Electroconductive Layers
[0064] The electroconductive layers 33 are made of a material
containing silver as the main component. Here, the material
containing silver as the main component means that the content of
silver is at least 99.8 atomic % based on the total metal contained
in the material. As the material containing silver as the main
component, a simple substance of silver, or an alloy having at
least one metal selected from palladium platinum, gold, iridium,
rhodium, copper and bismuth incorporated to silver, may be
mentioned. By controlling the content of silver to be at least 99.8
atomic %, it is possible to lower the resistivity of the
electromagnetic wave shielding laminate 1 even if the thickness of
the conductive layers 33 is made thin. Further, the resistivity can
be made low even if the number of electromagnetic wave shielding
films 100 laminated, is small, whereby it is possible to obtain an
electromagnetic wave shielding laminate 1 which has a low
resistivity and a high visible light transmittance.
[0065] The content of silver in the electroconductive layers 33 is
preferably at least 99.8 atomic %, and further, a simple substance
of silver of at least 99.9 atomic % is most preferred also from the
viewpoint of the cost.
[0066] The geometrical thickness of each of the electroconductive
layers 33 is preferably from 5 to 20 nm. The geometrical
thicknesses of the respective electroconductive layers 33 may be
the same or different.
[0067] Formation of the electroconductive layers 33 may be carried
out by various methods such as a sputtering method and a vapor
deposition method. It is particularly preferred to form them by a
DC sputtering method, whereby the film forming speed is high, and a
layer having a uniform thickness and a uniform quality can be
formed over a large area.
[0068] The laminated number of electromagnetic wave shielding films
100 laminated on the substrate 2 is preferably at least 2 in order
to provide a sufficient electromagnetic wave-shielding ability.
When the laminated number is at least 2, an adequate
electromagnetic wave shielding performance can be obtained.
Further, it is more preferred that at least 3 such films are
laminated. Further, it is preferred that the laminated number of
electromagnetic wave shielding films 100 is at most 8, whereby a
high visible light transmittance can be maintained. From such a
viewpoint, the laminated number is most preferably from 3 to 6.
[0069] Display Device
[0070] Now, the display device according to another embodiment of
the present invention will be described in detail.
SECOND EMBODIMENT
[0071] The display device according to the second embodiment of the
present invention comprises a display screen to display images and
an electromagnetic wave shielding laminate provided on the viewer's
side of the display screen.
[0072] Such a display device may, for example, be a plasma display
panel (PDP), a liquid crystal display device (LCD), an
electroluminescence display (ELD) or a cathode ray tube display
device (CRT).
[0073] The viewer's side of the display screen to display images is
usually constituted by a transparent substrate such as a glass
substrate or a plastic substrate. The electromagnetic wave
shielding laminate is not particularly limited so long as it is the
electromagnetic wave shielding laminate of the present invention.
For example, it is possible to employ the electromagnetic wave
shielding laminate 1 according to the first embodiment.
[0074] The electromagnetic wave shielding laminate may be bonded
directly to the viewer's side surface of the display screen by
means of e.g. an adhesive, or may be installed with a space from
the display screen.
[0075] Otherwise, on the viewer's side of the display screen, a
front plate made of glass, plastic or the like may be installed
afresh, and on the viewer's side or display's side of the front
plate, the electromagnetic wave shielding laminate may be directly
bonded. Or, on the viewer's side or display's side of the front
plate, the electromagnetic wave shielding laminate may be installed
with a space from the front plate.
THIRD EMBODIMENT
[0076] The display device according to the third embodiment of the
present invention comprises a display screen to display images and
an electromagnetic wave shielding film formed on the surface of the
viewer-side of the display screen.
[0077] Such a display device may, for example, be:
[0078] (1) A display device wherein the electromagnetic wave
shielding film has, sequentially from the viewer's side surface of
the display screen, a first high refractive index layer made of a
material having a refractive index of at least 2.0, a first oxide
layer containing zinc oxide as the main component, an
electroconductive layer containing silver as the main component,
and a second high refractive index layer made of a material having
a refractive index of at least 2.0;
[0079] (2) A display device wherein such an electromagnetic wave
shielding film has a second oxide layer between the
electroconductive layer and the second high refractive index
layer;
[0080] (3) A display device wherein the first or second high
refractive index layer of such an electromagnetic wave shielding
film is a layer containing niobium oxide as the main component;
[0081] (4) A display device wherein the content of silver in the
electroconductive layer in such an electromagnetic wave shielding
film is at least 99.8 atomic %; or
[0082] (5) A display device wherein at least three such
electromagnetic wave shielding films are laminated from the
substrate side.
[0083] In this case, the viewer's side of the display screen is
usually constituted by a transparent substrate such as a glass
substrate or a plastic substrate.
[0084] Further, as such an electromagnetic wave shielding film, the
electromagnetic wave shielding film 100 according to the first
embodiment may, for example, be used. In such a case, on the
viewer's side surface of the display screen, a first high
refractive index layer 31, a first oxide layer 32, an
electroconductive layer 33, a second oxide layer 34 and a second
high refractive index layer 35 are laminated sequentially.
[0085] The electromagnetic wave shielding film may be formed
directly on the viewer's side surface of the display screen by e.g.
a vapor deposition method or a sputtering method.
[0086] Now, the present invention will be described in further
detail with reference to Examples.
EXAMPLE 1
[0087] As a transparent substrate, a polyethylene terephthalate
film (hereinafter referred to as PET, thickness: 100 .mu.m) was
used which is a high transmittance film for optical use.
[0088] For film forming by sputtering, a Web coater film forming
apparatus (manufactured by Hirano Koon K.K.) was used.
[0089] The size of the target was 50 mm.times.195 mm, and
transportation of a substrate was carried out by a roll-to-roll
system wherein a long rolled-up film substrate was dispensed and
via a guide roll, sputtered at a can roll position and rolled up
again via a guide roll. With respect to the sputtering power
source, film forming was carried out by DC discharge (MDX-10K,
manufactured by AE Company, RPG-100, manufactured by ENI
Company).
[0090] On the film substrate, four electromagnetic wave shielding
films were formed in the order of high refractive index layer
(1)/oxide layer (1)/electroconductive layer/oxide layer (2)/high
refractive index layer (2)/oxide layer (1)/electroconductive
layer/oxide layer (2)/high refractive index layer (2)/oxide layer
(1)/electroconductive layer/oxide layer (2)/high refractive index
layer (2)/oxide layer (1)/electroconductive layer/oxide layer
(2)/high refractive index layer (1), from the substrate side.
[0091] Detailed film forming conditions are shown in Table 1.
1 Electro- magnetic Sputtering Film wave shielding Target gas
(Ar/O.sub.2 Sputtering Sputtering thick- film material
cm.sup.3min.sup.-1) power pressure ness High refractive NS-NBO 93/7
0.50 kW 0.399 Pa 32 nm index layer (1) Oxide layer (1) AZO 100/0
0.10 kW 0.798 Pa 5 nm Electro- Ag 100/0 0.15 kW 0.798 Pa 16 nm
conductive layer Oxide layer (2) AZO 100/0 0.10 kW 0.798 Pa 2 nm
High refractive NS-NBO 93/7 0.50 kW 0.399 Pa 64 nm index layer
(2)
[0092] The high refractive index layer (1) and the high refractive
index layer (2) were formed by DC discharge by using niobium oxide
(NS-NBO, manufactured by ASAHI GLASS CERAMICS CO., LTD.) as a
target. The oxide layer (1) and the oxide layer (2) were formed by
DC discharge by using one having 3 mass % of aluminum oxide added
to zinc oxide (manufactured by ASAHI GLASS CERAMICS CO., LTD.) as a
target. Further, the electroconductive layer was formed by DC
discharge by using silver having a purity of 99.9 atomic %, as a
target.
[0093] Further, the contents of zinc and aluminum in the oxide
layers in the obtained electromagnetic wave shielding laminate were
substantially the same as the contents of zinc and aluminum
contained in the target. Adjustment of the film forming speed was
carried out by the transportation speed of the substrate, and in
the case of a material whereby the film forming speed was slow,
reciprocating film forming was repeated a few times to obtain the
desired thickness. The film thickness was measured by means of a
feeler type film thickness meter (Dektak3.sup.st distributor of
ULVAC Company). The results of the film thicknesses thus obtained
are shown in Table 1.
[0094] Evaluation
[0095] (1) Visible Light Transmittance
[0096] The visible light transmittance of the obtained
electromagnetic wave shielding laminate was measured by using Model
304 transmittance meter manufactured by Asahi Spectra Co., Ltd. The
results of the measurement of the visible light transmittance are
shown in the following Table 2.
[0097] (2) Resistivity
[0098] The resistivity of the obtained electromagnetic wave
shielding laminate was measured by using 717 conductance monitor
manufactured by DELCOM Company. The results of the measurement of
the resistivity are shown in the following Table 2.
[0099] (3) Moisture Resistance
[0100] A NaCl test was used for evaluation of the moisture
resistance. Firstly, 1 .mu.l of a 2 mass % NaCl aqueous solution
was dropped on an electromagnetic wave shielding film of an
electromagnetic wave shielding laminate and then dried. Thereafter,
a PET film (thickness: 100 .mu.m) provided with an adhesive
material (ADC2 manufactured by Poratechno Company or PTR 2500
manufactured by Arisawa Seisakusho K.K., thickness: 25 .mu.m) was
bonded on the electromagnetic wave shielding film, followed by
storage for 100 hours in a constant temperature and humidity tank
at a temperature of 60.degree. C. with a relative humidity of 95%,
whereupon the assembly was taken out, and the PET film was peeled.
The area of the portion which was deteriorated and peeled was
measured by a slide gauge. The results of the measurement of the
deteriorated area are shown in the following Table 2.
COMPARATIVE EXAMPLE 1
[0101] Without forming an oxide layer (1) on a high refractive
index layer (1), an electroconductive layer was formed directly on
the high refractive index layer (1) under the same film forming
conditions as in Example 1. Otherwise, the operation was carried
out in the same manner as in Example 1 to obtain an electromagnetic
wave shielding laminate.
[0102] With respect to the obtained electromagnetic wave shielding
laminate, the visible light transmittance, the resistivity and the
moisture resistance were evaluated by the same methods as in
Example 1. The results of the measurement of the visible light
transmittance, the resistivity and the moisture resistance will be
shown in the following Table 2.
COMPARATIVE EXAMPLE 2
[0103] Without forming an oxide layer (1) and an oxide layer (2),
an electroconductive layer was formed directly between the high
refractive index layer (1) and the high refractive index layer (2)
under the same film forming conditions as in Example 1. Otherwise,
the operation was carried out in the same manner as in Example 1 to
obtain an electromagnetic wave shielding laminate.
[0104] With respect to the obtained electromagnetic wave shielding
laminate, evaluation of the visible light transmittance, the
resistivity and the moisture resistance was carried out by the same
methods as in Example 1. The results of measurements of the visible
light transmittance, resistivity and the moisture resistance will
be shown in the following Table 2.
2 TABLE 2 Transmittance Resistivity Deteriorated (%) (.OMEGA.) area
(mm.sup.2) Ex. 1 57.3 0.69 17 Comp. Ex. 1 54.8 0.76 109 Comp. Ex 2
51.8 0.78 657
[0105] When the results of Example 1 and Comparative Example 1 are
compared, it is evident that in the visible light transmittance and
the resistivity, Example 1 is substantially equal to Comparative
Example 1 and thus confirmed to be a good electromagnetic wave
shielding laminate. Further, with respect to the deteriorated area
by the NaCl test, the deteriorated area in Example 1 is 1/6 of the
deteriorated area in Comparative Example 1, and thus, it was
confirmed that Example 1 was excellent in moisture resistance.
Further, from these results, it was confirmed that the moisture
resistance of the electromagnetic wave shielding film was improved
by forming an oxide layer (1) between the high refractive index
layer (1) and the electroconductive layer.
[0106] Then, when the results of the Example 1 and Comparative
Example 2 are compared, it is evident that in the visible light
transmittance and the resistivity, Example 1 is substantially equal
to Comparative Example 2, but with respect to the deteriorated area
by the NaCl test, the deteriorated area in Example 1 is {fraction
(1/38)} of the deteriorated area in Comparative Example 2. Thus, it
was confirmed that Example 1 was excellent in moisture resistance.
From these results, it was confirmed that the presence of the oxide
layer (1) and the oxide layer (2) contributed substantially to the
improvement of the moisture resistance of the electromagnetic wave
shielding film.
[0107] From the foregoing results, it was confirmed that the
electromagnetic wave shielding laminate obtained in Example 1 is an
electromagnetic wave shielding laminate which has a high visible
light transmittance and a low resistance and which is excellent
also in the moisture resistance.
EXAMPLE 2
[0108] An electromagnetic wave shielding laminate was prepared in
the same manner as in Example 1 except that the film forming
conditions were as shown in Table 3.
[0109] With respect to the obtained electromagnetic wave shielding
laminate, evaluation of the moisture resistance was carried out in
the same manner as in Example 1. The result of the measurement of
the moisture resistance is shown in Table 6.
3TABLE 3 Electro- magnetic Sputtering wave gas Film shielding
Target (Ar/O.sub.2 Sputtering Sputtering thick- film material
cm.sup.3min.sup.-1) power pressure ness High NS-NBO 85/15 0.50 kW
0.399 Pa 30 nm refractive index layer (1) Oxide AZO 100/0 0.10 kW
0.798 5 nm layer (1) Electro- Ag 100/0 0.15 kW 0.798 16 nm
conductive- layer Oxide AZO 100/0 0.10 kW 0.798 2 nm layer (2) High
NS-NBO 85/15 0.50 kW 0.399 60 nm refractive index layer (2)
EXAMPLE 3
[0110] An electromagnetic wave shielding laminate was prepared in
the same manner as in Example 1 except that the film forming
conditions were as shown in Table 4.
[0111] The high refractive index layers (1) and (2) were formed by
DC discharge by using reduced type titanium oxide (TXO) target
(manufactured by ASAHI GLASS CERAMICS CO., LTD.).
[0112] With respect to the obtained electromagnetic wave shielding
laminate, evaluation of the moisture resistance was carried out in
the same manner as in Example 1. The result of the measurement of
the moisture resistance is shown in Table 6.
4TABLE 4 Electro- magnetic Sputtering wave gas shielding Target
(Ar/O.sub.2 Sputtering Sputtering Film film material
cm.sup.3min.sup.-1) power pressure thickness High TXO 93/7 10.0 kW
0.399 Pa 30 nm refractive index layer (1) Oxide AZO 100/0 0.10 kW
0.798 Pa 5 nm layer (1) Electro- Ag 100/0 0.15 kW 0.798 Pa 16 nm
conductive layer Oxide AZO 100/0 0.10 kW 0.798 Pa 2 nm layer (2)
High TXO 93/7 10.0 kW 0.399 Pa 60 nm refractive index layer (2)
COMPARATIVE EXAMPLE 3
[0113] An electromagnetic wave shielding laminate was prepared in
the same manner as in Example 1 except that the film forming
conditions were as shown in Table 5, and AZO layers (refractive
index: 1.93) (1) and (2) were used instead of the high refractive
index layers (1) and (2).
[0114] AZO layers (1) and (2) were formed by DC discharge by using
one having 3 mass % of aluminum oxide added to zinc oxide
(manufactured by ASAHI GLASS CERAMICS CO., LTD.) as a target.
[0115] Further, the contents of zinc and aluminum in the oxide
layers of the obtained electromagnetic wave shielding laminate were
substantially the same as the contents of zinc and aluminum
contained in the target.
[0116] With respect to the obtained electromagnetic wave shielding
laminate, evaluation of the moisture resistance was carried out in
the same manner as in Example 1. The result of the measurement of
the moisture resistance is shown in Table 6.
5TABLE 5 Electro- magnetic Sputtering wave gas shielding Target
(Ar/O.sub.2 Sputtering Sputtering Film film material
cm.sup.3min.sup.-1) power pressure thickness AZO layer AZO 97/3
0.50 kW 0.399 Pa 30 nm (1) Oxide AZO 100/0 0.10 kW 0.798 Pa 5 nm
layer (1) Electro- Ag 100/0 0.15 kW 0.798 Pa 16 nm conductive layer
Oxide AZO 100/0 0.10 kW 0.798 Pa 2 nm layer (2) AZO layer AZO 97/3
0.50 kW 0.399 Pa 60 nm (2)
[0117]
6 TABLE 6 Deteriorated area (mm.sup.2) Example 2 8.2 Example 3 21.7
Comparative 71.9 Example 3
[0118] In Example 2 employing niobium oxide as the material for the
high refractive index layer and in Example 3 employing titanium
oxide as the material for the high refractive index layer, only a
peripheral portion where NaCl was dropped, was deteriorated, and
the deteriorated area was small. When niobium oxide and titanium
oxide are compared, the deteriorated area was smaller with niobium
oxide, and thus the durability was superior. In Comparative Example
3 wherein AZO layer was used instead of the high refractive index
layer, not only the peripheral portion where NaCl was dropped, was
deteriorated, but cracks were formed over a wide area of the formed
film surface extending from the dropped portion, and the
deteriorated area was large.
INDUSTRIAL APPLICABILITY
[0119] The electromagnetic wave shielding laminate of the present
invention is useful as a filter for e.g. a display device.
[0120] The entire disclosure of Japanese Patent Application No.
2003-208674 filed on Aug. 25, 2003 including specification, claims,
drawings and summary is incorporated herein by reference in its
entirety.
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