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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an anti-reflection member and manufacturing
method thereof, and relates to a cathode ray tube having a front panel
applied with such anti-reflection member.
2. Description of Related Art
For example for conventional cathode ray tubes (CRT), a picture displayed
on the cathode ray tube is not viewed clearly because external light is
reflected on the panel surfacel; that is a problem of conventional cathode
ray tubes. On the other hand, the potential of the panel surface changes
because of high voltage applied on the fluorescent screen formed on the
inside surface of the panel of the cathode ray tube. As a result, dust
adheres on the panel surface and the panel causes an electric discharge to
an approching human body. To prevent such phenomena, it is required to
provide an antistatic function on the panel surface. In addition, it is
also important to provide an electromagnetic radiation shielding function
so as not to release electromagnetic waves from the cathode ray tube. As a
method for solving all the technical problems as described herein above, a
technique in which an anti-reflection member having conductivity is
applied on the panel surface has been known.
Such an anti-reflection member comprises a laminate composed of a
substrate, a hard coat layer, and a multilayered reflection preventing
optical thin film. The substrate consists of, for example,
polyethyl-eneterephthalate (PET) or polycarbonate (PC). A hard coat layer
consists of, for example, polymethyl-methacrylate (PMMA), and is formed on
the surface of the substrate because the surface is susceptible to
touching. In the case that it is not necessary to provide an antistatic
function and an electromagnetic radiation shielding function to an
anti-reflection member, at least two layers of dielectric thin film
consisting of SiO, SiO.sub.2, TiO.sub.2, ZrO.sub.2, Ta.sub.2 O.sub.5, and
Y.sub.2 O.sub.5, for example, and a high refractive index film/low
refractive index film/high refractive index/low refractive index film . .
. ) are formed on the hard coat layer. Materials having high refractive
index (having a refractive index of 1.8 to 2.7 at around the wave length
of 550 nm) such as TiO.sub.2, ZrO.sub.2, Ta.sub.2 O.sub.5, and Y.sub.2
O.sub.5 are excellent in adhesion with hard coat layers consisting of
polymethyl-methacrylate.
On the other hand, in the case that it is necessary to provide an
antistatic function and an electromagnetic radiation shielding function to
an anti-reflection member, it is preferable to structure a reflection
preventing optical thin film by laminating a transparent conductive oxide
film and a thin film (referred as to low refractive index film
hereinafter) consisting of a material having lower refractive index than
that of the material used for the transparent conductive oxide film. By
structuring the reflection preventing optical thin film as described
herein, not only is antistatic function and electromagnetic radiation
shielding function due to transparent conductive oxide film provided to
the anti-reflection member but also an anti-reflection function due to the
high refractive index film/low refractive index film structure is provided
simultaneously. Thereby the structure of a reflection preventing optical
thin film is simplified. An example of the transparent conductive oxide
film includes ITO (I.sub.2 O.sub.3 doped with Sn) film (refractive index
is 1.9 to 2.0). On the other hand, examples of the low refractive index
film include SiO.sub.2 film (refractive index=1.46 at 550 nm) and
MgF.sub.2 film (refractive index =1.38 at 550 nm).
Usually, by repeating the film forming process, namely, ITO film/low
refractive index film/ITO film/low refractive index film . . . on a hard
coat layer formed on a substrate, an anti-reflection member is provided
with an anexcellent anti-reflection function in the wide wave length range
from 450 to 650 nm. A schematic partial cross-sectional view of the
anti-reflection member having such structure is shown in FIG. 4A. In FIG.
4A, a reflection preventing optical thin film having a four layer
structure is shown; the first layer and third layer consist of ITO film,
and the second and fourth layer consist of low refractive index film.
Usually, ITO film is formed by spattering using a target of oxide ITO. An
ITO film is formed under the spattering condition that the composition of
such ITO target is, for example, In.sub.2 O.sub.3 /SnO.sub.2 =90 parts by
weight/10 parts by weight, target current density is 2 W/cm.sup.2, and
others are Ar/O.sub.2 =50 volume %/50 volume %, and 0.2 Pa.
It is reported that the crystallization temperature of ITO ranges from
150.degree. to 200.degree. C. Therefore, to improve the adhesion (adhesion
strength) to a hard coat layer, it is desirable to heat the substrate to a
temperature of 120.degree. C. or higher. However, such heating of a
substrate can cause thermal damage such as deformation of the substrate
consisting of plastic material. Heating of a hard coat layer consisting of
polymethyl-methacrylate to a temperature of 100.degree. C. or higher can
cause the reduction of the hardness.
Recently, ITO film formed on a color filter was used as a transparent
electrode for a flat panel display of liquid crystal display devices. Such
an ITO film is formed by DC magnetron spattering using ITO target. ITO
film formed by such method is excellent in resistivity, wet etching
performance, and reproducibility of characteristics. However, an ITO film
formed on a hard coat layer by DC magnetron spattering using an ITO target
is insufficient in adhesion strength to the hard coat layer.
The inventors of the present invention proposed a new anti-reflection
member comprising a laminate of a substrate, a hard coat layer, and a
multilayered reflection preventing optical thin film in Japanese Patent
Application Hei 7-170925 (application date: Jul. 6, 1995). A schematic
partial cross-sectional view of the anti-reflection member having such
structure is shown in FIG. 4B. The substrate of the anti-reflection member
consists of, for example, polyethylene-terephthalate (PET) and
polycarbonate (PC). A hard coat layer consists of, for example,
polymethyl-methacrylate (PMMA) an is formed thereon. To provide an
antistatic function and an electromagnetic radiation shielding function to
the anti-reflection member, the anti-reflection member has the first layer
of the reflection preventing optical thin film comprising a conductive
light absorbing film, and the second layer of the reflection preventing
optical thin film consisting of a material having lower refractive index
than that of the material used to structure the first layer.
The conductive light absorbing film consists of a material selected from
the group composed of Ag, Au, TiN.sub.X (X=0.3 to 1), TiO.sub.X N.sub.Y
(wherein X=0.3 to 1, Y<1, and Y.ltoreq.X), TaN.sub.X (wherein X=0.2 to 1),
Pt, Al, Cu, Ta, Ni-Cr, Cu-Al, Cu-Zn-Al, Cu-Ni-Al and Cu-Sn-Al, and the
thickness ranges from 4 to 40 nm. On the other hand, the second layer of
the reflection preventing optical thin film consists of SiO.sub.2 or
MgF.sub.2. The above-mentioned material to be used for the conductive
light absorbing film has a characteristic that light absorption
coefficient changes dependently on wave length. Reflection is prevented
for a wide range of wave length (430 to 650 nm). This is possible even if
the reflection preventing optical thin film has a two layer structure. The
light transmittance of these materials ranges from 70 to 90%, however,
because the two layer structure can be used for the reflection preventing
optical thin film, the low light transmittance of the conductive light
absorbing film does not cause any problem.
However, it was found that the adhesion (adhesion strength) of such
conductive light absorbing film to a hard coat consisting of
polymethyl-methacrylate was insufficient.
Therefore, it is the object of the present invention to provide an
anti-reflection member provided with an antistatic function and an
electromagnetic radiation shielding function which has a reflection
preventing optical thin film excellent in adhesion to a hard coat layer,
and a manufacturing method thereof. In addition, a cathode ray tube having
a front panel applied with such anti-reflection member is provided.
SUMMARY OF THE INVENTION
A anti-reflection member in accordance with the first embodiment of the
present invention for achieving the above mentioned object is the
anti-reflection member comprising a laminate of substrate, hard coat
layer, and reflection preventing optical thin film having at least two
layers, wherein
the first layer of the reflection preventing optical thin film in contact
with the hard coat layer consists of transparent conductive oxide film
formed by reactive physical vapor phase deposition, and
the second layer of the reflection preventing optical thin film consists of
a material having a lower refractive index than that of the first layer.
A manufacturing method of an anti-reflection member in accordance with the
first embodiment of the present invention for achieving the
above-mentioned object is the manufacturing method of an anti-reflection
member comprising a laminate of substrate, hard coat layer, and reflection
preventing optical thin film having at least two layers, wherein
the first layer of the reflection preventing optical thin film in contact
with the hard coat layer consists of transparent conductive oxide film,
and
the second layer of the reflection preventing optical thin film consists of
a material having a lower refractive index than that of the first layer,
and
the transparent conductive oxide film is formed by reactive physical vapor
phase deposition.
Wherein, the "transparent" of the transparent conductive oxide film means
the absorption coefficient .alpha. based on Lambert's law of 0 to 0.3,
preferably, 0 to 0.2 when a light with a wave length of 550 nm is
transmitted. The "conductive" of the transparent conductive oxide film
means the value of resistance measured by eddy current method of
1.times.10 to 1.times.10.sup.4 .OMEGA./.quadrature., preferably,
1.times.10 to 5.times.10.sup.3 .OMEGA./.quadrature..
In the anti-reflection member, or the manufacturing method thereof, in the
first embodiment of the present invention, examples of the reactive
physical vapor phase deposition, namely, physical vapor phase deposition
(PVD, Physical Vapor Deposition) accompanying chemical reaction between at
least partial material to be deposited on the hard coat layer and the
material used for the hard coat layer, include;
(A) various vacuum deposition such as electron beam heating, resistance
heating, and flush deposition,
(B) plasma deposition,
(C) various spattering such as bipolar spattering, DC spattering, DC
magnetron spattering, high frequency spattering, magnetron spattering,
ion-beam spattering, and bias-spattering, and
(D) various ion-plating such as DC method, RF method, multi-cathode method,
activation reaction method, HCD method, electric field deposition, high
frequency ion-plating, and reactive ion-plating,
wherein among these methods, reactive spattering using a metal or alloy
target, in detail, DC magnetron spattering is preferably used. In this
case, a target material consisting of Sn, Zn, In, or In-Sn alloy is
preferably used. When Sn is used as a target, a transparent conductive
oxide film obtained by reactive physical vapor phase deposition consists
of SnO.sub.2. When Zn is used as a target, a transparent conductive oxide
film obtained by reactive physical vapor phase deposition consists of ZnO.
When In is used as a target, a transparent conductive oxide film obtained
by reactive physical vapor phase deposition consists of In.sub.2 O.sub.3.
Further, when In-Sn is used as a target, a transparent conductive oxide
film obtained by reactive physical deposition consists of ITO. Spattering
is carried out in an O.sub.2 atmosphere for the reactive spattering. On
the other hand, spattering is carried out in an Ar+O.sub.2 (content of
O.sub.2 is 0 to 30 volume %) atmosphere for conventional spattering using
an oxide target.
To improve the adhesion to a hard coat layer, it is preferable that an
element (referred to as element B) having the same or higher affinity with
oxygen as an element (referred to as element A hereinafter) which
constitutes the transparent conductive oxide film is contained in the
transparent conductive oxide film. In general, the affinity of an element
to oxygen can be estimated from the standard free energy of formation of
the oxide. In other words, an oxide having smaller standard free energy of
formation forms oxide easier. Though it depends on the element A, an
example of the element B includes an element selected from the group
composed of Ti, Zr, Al, Mg, Si, Cr, W, Fe, and Mn. Examples of combination
of the element A and element B are listed in Table 1. The ratio element
B/(element A+element B) (in atomic ratio) is 0.001 to 0.1, preferably
0.005 to 0.05.
TABLE 1
______________________________________
Element A Element B
______________________________________
Sn Cr, Ti, Al, Zr
Zn Cr, Ti, Al, Zr
In Cr, Ti, Al, Zr
In and Sn Cr, Ti, Al, Zr
______________________________________
In the manufacturing method of the anti-reflection member in accordance
with the first embodiment of the present invention, a material consisting
of the second layer of the reflection prevention optical thin film may be
a material having a refractive index of about 1.7 or smaller, examples
include SiO.sub.2, SiO, MgF.sub.2, CaF.sub.2, LaF.sub.3, Na.sub.3
AlF.sub.6, Na.sub.5 Al.sub.3 Fl.sub.4, NdF.sub.3, LaF.sub.3, CeF.sub.3,
BaF.sub.2, NaF, SrF.sub.2, and Al2 O.sub.3, among these materials,
SiO.sub.2 or MgF.sub.2 is preferably used.
It is preferable that the hard coat layer consists of a material which
contains oxygen as a constituent element. In detail, the hard coat layer
may be an organic film consisting of a resin-based material selected from
the group composed of silicon-based material, polyfunctional
acrylate-based material or urethane resin-based material, melamine
resin-based material, and epoxy resin-based material, and may be an
organic-inorganic film. Examples of silicon-based material include
co-hydrolysates of tetra-alcoxysilane or alkyl-trialcoxysilane and silane
coupling agent having functional group such as epoxy group or methacryl
group. Examples of polyfunctional acrylate-based material include, for
example, polyol-acrylate, polyester-acrylate, urethane-acrylate, and
epoxyacrylate. Furthermore, an example of urethane resin-based material
includes, for example, melamine-polyurethane. The hard coat layer consists
preferably of acryl-based material, specifically, polymethyl-methacrylate
(PMMA). An example of an organic-inorganic film includes acryl-silicon.
Otherwise, the hard coat layer of organic-inorganic film may be formed
from colloidal silica in a form of hydrophylic sol or lipophilic sol. The
hard coat layer may be formed by various methods for coating a material
such as dipping coating, spin coating, spray coating, and flow coating
followed by drying and thermosetting or ultraviolet ray curing.
In the manufacturing method of the light reflection prevention member in
accordance with the first embodiment of the present invention, the
anti-reflection member may be manufactured continuously by a process in
which the substrate comprises a roll film, the film on which a hard coat
layer had been formed previously is unwound, the first layer comprising a
transparent conductive oxide film formed on the hard coat layer by
reactive spattering using a metal or alloy target therefor. Subsequently,
the second layer of an reflection preventing optical thin film is formed
on the first layer by spattering, then the film comprising the reflection
preventing optical thin film formed on the hard coat layer is wound.
In the manufacturing process of the anti-reflection member in accordance
with the first embodiment of the present invention, a SnO.sub.2 layer, ZnO
layer, I.sub.2 O.sub.3 layer, or ITO layer is formed on the second layer
of the reflection preventing optical thin film, thereon a SiO.sub.2 layer
or MgF.sub.2 layer is formed, further, these two layers may be laminated
one above another alternately. In detail, for example, the reflection
preventing optical thin film may have a structure such as ITO
layer/SiO.sub.2 layer/ITO layer/SiO.sub.2 layer/ . . . /ITO
layer/SiO.sub.2 layer, SnO.sub.2 layer/SiO.sub.2 layer/SnO.sub.2
layer/SiO.sub.2 layer/ . . . /SnO.sub.2 layer/SiO.sub.2 layer, or ZnO
layer/SiO.sub.2 layer/ZnO layer/SiO.sub.2 layer/ . . . /ZnO
layer/SiO.sub.2 layer. Otherwise, the structure may comprise m-th layers
(m is odd numbers) consisting of the same or different materials selected
from the group composed of SnO.sub.2, ZnO, I.sub.2 O.sub.3, and ITO, and
n-th layers (n is even numbers) consisting of the same or different
materials selected from the group composed of SiO.sub.2 and MgF.sub.2 (for
example, SnO.sub.2 layer/SiO.sub.2 layer/ITO layer/SiO.sub.2 layer). In
this case, a SnO.sub.2, ZnO layer, I.sub.2 O.sub.3 layer, or ITO layer of
(2N--l)th layer (wherein 1<N) may be formed by, for example, either
reactive spattering or conventional spattering using an oxide target.
The anti-reflection member in accordance with the second embodiment of the
invention for achieving the above-mentioned object comprises a laminate of
substrate, hard coat layer, and reflection preventing optical thin film
having at least three layers, wherein
the first layer of the reflection preventing optical thin film in contact
with the hard coat layer consists of transparent oxide film formed by
reactive physical vapor phase deposition, and
the second layer of the reflection preventing optical thin film consisting
of conductive light absorbing film, and
the third layer of the reflection preventing optical thin film consists of
a material having a lower refractive index than that of the second layer.
The manufacturing method of the anti-reflection member in accordance with
the second embodiment of the present invention for achieving the
above-mentioned object is the manufacturing method of an anti-reflection
member comprising a laminate of a substrate, hard coat layer, and
reflection preventing optical thin film having at least three layers,
wherein
the first layer of the reflection preventing optical thin film in contact
with said hard coat layer consists of transparent oxide film, and
the second layer of the reflection preventing optical thin film consisting
of conductive light absorbing film, and
the third layer of the reflection preventing optical thin film consists of
a material having a lower refractive index than that of the second layer,
and
the transparent oxide film is formed by reactive physical vapor phase
deposition.
Wherein, the "transparent" of the transparent conductive oxide film means
the absorption coefficient .alpha. based on Lambert's law of 0 to 0.3,
preferably, 0 to 0.2 when a light with a wave length of 550 nm is
transmitted. The "conductive" of the transparent conductive oxide film
means the value of resistance measured by eddy current method of
1.times.10 to 1.times.10.sup.4 .OMEGA./.quadrature., preferably,
1.times.10 to 5.times.10.sup.3 .OMEGA./.quadrature.. Further, the "light
absorptive" of the conductive light absorbing film means the absorption
coefficient of 0 to 0.5 when a light of 550 nm is transmitted, preferably
0.1 to 0.3.
In the anti-reflection member or the manufacturing method thereof in
accordance with the second embodiment of the present invention, the same
reactive physical vapor phase deposition as described in the
anti-reflection member or the manufacturing method thereof in accordance
with the first embodiment of the present invention may be used, among
these methods, reactive spattering using a metal or alloy target, in
detail, DC magnetron spattering is preferably used.
The thickness of the transparent oxide film may be arbitrary as far as the
thickness does not influence adversely on the anti-reflection effect. But
generally, the thickness is 1 to 20 nm in average provided on a hard coat
layer. The transparent oxide film is formed only to improve the adhesion
between the second layer of the reflection preventing optical thin film
and the hard coat layer.
In the anti-reflection member or the manufacturing method thereof in
accordance with the second embodiment of the present invention, the
transparent oxide film consists preferably of at least one material
selected from the group composed of ZrO.sub.2, TiO.sub.2, SiO.sub.X
(wherein X=1 to 2), SiO.sub.X N.sub.Y (wherein X=.sub.1 to 2, Y=0.2 to
0.6), and CrO.sub.X (wherein X=0.2 to 1.5). When reactive spattering is
used as the reactive physical vapor phase deposition, a target consisting
of Zr is used for forming ZrO.sub.2 film, a target consisting of Ti is
used for forming TiO.sub.2 film, a target consisting of Si is used for
forming SiO.sub.X (wherein X=1 to 2) film or SiO.sub.X N.sub.Y (wherein
X=1 to 2, and Y=0.2 to 0.6), and a target consisting of Cr is used for
forming CrO.sub.X film. The transparent oxide film may be provided with
conductivity. For providing conductivity, the transparent oxide film may
consist of SnO.sub.2, ZnO, In.sub.2 O.sub.3, or ITO, and the film formed
by reactive physical vapor deposition in the same manner as described in
the description of the anti-reflection member or the manufacturing method
thereof in accordance with the first embodiment of the present invention.
To improve the adhesion to a hard coat layer, it is preferable that an
element (referred to as element D hereinafter) having the same or higher
affinity with oxygen as an element (referred to as element C hereinafter)
which constitutes the transparent oxide film is contained in the
transparent oxide film. Though it depends on the element C, examples of
the element D includes an element selected from the group composed of Ti,
Zr, Al, Mg, Be, Si, Cr, W, Fe, Mn, and Sn. Examples of the combination of
the element C and element D are listed in Table 2. The ratio element
D/(element C+element D) (in atomic ratio) is 0.001 to 0.1, preferably
0.005 to 0.05.
TABLE 2
______________________________________
Element C Element D
______________________________________
Zr Mg, Be
Ti Al, Zr, Be
Si Ti, Al, Zr, Be
Cr Si, Ti, Al, Zr, Be
______________________________________
In the anti-reflection member or the manufacturing method thereof in
accordance with the second embodiment of the present invention, the
conductive light absorbing film consists preferably of metal, alloy, metal
nitride or metal oxide-nitride. Wherein, nitrides of alloy and
nitride-oxides of alloy are included in the term "metal nitride" and
"metal oxide-nitride". In detail, examples of material to be used for the
conductive light absorbing film include materials selected from the group
composed of Ag, Au, TiNX (X=0.3 to 1), TiO.sub.X N.sub.Y (wherein X=0.3 to
1, Y<1, and Y.ltoreq.X), TaN.sub.X (wherein X=0.2 to 1), Pt, Al, Cu, Ta,
Ni-Cr, Cu-Al, Cu-Zn-Al, Cu-Ni-Al and Cu-Sn-Al. Oxygen and Nitrogen happen
to be trapped occasionally during forming of the conductive light
absorbing film consisting of metal or alloy, however herein, this
conductive light absorbing film is defined as the conductive light
absorbing film consisting of metal or alloy.
In the anti-reflection member or the manufacturing method thereof in
accordance with the second embodiment of the present invention, examples
to be used for the third layer of the reflection preventing optical thin
film include SiO.sub.2, MgF.sub.2, CaF.sub.2, LaF.sub.3, Na.sub.3
AlF.sub.6, NdF.sub.3, LaF.sub.3, and Al.sub.2 O.sub.3, among these
materials, SiO.sub.2 or MgF.sub.2 is preferably used. The hard coat layer
may consist of the same material as described in the description of the
reflection preventing member or the manufacturing method thereof in
accordance with the first embodiment of the present invention, among these
materials, in detail, the hard coat layer consists preferably of
polymethyl-methacrylate (PMMA).
In the manufacturing method of the light reflection prevention member in
accordance with the second embodiment of the present invention, the
anti-reflection member may be manufactured continuously by a process in
which a substrate comprises a roll film, the film on which a hard coat
layer had been formed previously is unwound, the first layer comprising
the transparent oxide film is formed on the hard coat layer by reactive
spattering using a metal or alloy target, subsequently the second layer of
reflection preventing optical thin film comprising the conductive light
absorbing film is formed on the first layer by spattering, then the third
layer of the reflection preventing optical thin film is formed on the
second layer by spattering, finally the film comprising the reflection
preventing optical thin film formed on the hard coat layer is wound.
In the present invention, the substrate may consist of any material as far
as the material transmits light. A material to be used for the substrate
may be selected dependently on required specification and application
field of the anti-reflection member, and may be selected from plastic
materials or glass materials. When plastic material is selected to form
the substrate, examples include, polyethyleneterephthalate (PET),
polycarbonate (PC), polypropylene (PP), polymethyl-methacrylate and
copolymer thereof, unsaturated polyester, acrylonitrile-styrene copolymer,
vinylchloride, polyurethane, epoxy resin, and cellulose-based resin such
as triacetyl-cellulose and diacetyl-cellulose, among these materials,
polyethyleneterephthalate (PET) or polycarbonate (PC) is preferably used.
The form of the substrate may be film, sheet, or plate dependently on
required specification and application. The thickness of the substrate is
not limited, and may be selected dependently on required specification and
application. A hard coat layer may be formed on the back side (the side on
which the reflection preventing optical thin film is not formed) of the
anti-reflection member dependently on application of the anti-reflection
member.
Examples of application of the anti-reflection member in accordance with
the first embodiment and the second embodiment of the present invention
include, for example, application on the panel surface of cathode ray
tubes, and the surface of picture display portions of liquid crystal
displays, plasma displays, and EL displays, and for example, application
as filter to be provided in front of a cathode ray tube and application on
the surface of various optical lenses. For example, on the back side (the
side on which the hard coat layer is not formed) of the anti-reflection
member in accordance with the first embodiment and the second embodiment
of the present invention, an adhesive layer or pressure sensitive adhesive
layer is formed, and the anti-reflection member may be applied on the
panel surface of a cathode ray tube with interposition of such adhesive
layer or pressure sensitive adhesive layer. When, by applying the
anti-reflection member with pressing thereon in vacuum, trapping of air
between the anti-reflection member and the panel surface of the cathode
ray tube is prevented. Further, ultraviolet-curing resin adhesives are
also used effectively.
On the uppermost layer of the reflection preventing optical thin film, a
layer consisting of fluorine-based material such as
polytetrafluoroethylene, tetrafluoroethylene-perfluoro-alkylvinyl-ether
copolymer, polychloro-trifluoroethylene, tetrafluoroethylene-ethylene
copolymer, chlorotrifluoroethylene-ethylene copolymer,
polyvinylidenefluoride, and polyvinyl-fluoride may be formed to prevent
staining with fingerprints. In this case, the thickness of the layer may
be 3 to 100 nm so as not to influence adversely on the reflection
preventing effect.
Film thickness of the first layer and the second layer of the reflection
preventing optical thin film of the anti-reflection member in accordance
with the first embodiment of the present invention, or film thickness of
the second layer and the third layer of the reflection preventing optical
thin film of the anti-reflection member in accordance with the second
embodiment of the present invention may be determined according to the
film thickness determining method based on two layered structure with
V-shape structure and W-shaped structure comprising what is called
(.lambda./4-.lambda./2) film or the film thickness determining method
based on three layered structure comprising what is called
(.lambda./4-.lambda./2-.lambda./4) film.
In conventional art, an ITO layer is formed by spattering using a target of
oxide ITO. On the other hand, in the anti-reflection member or the
manufacturing method thereof in accordance with the first embodiment of
the present invention, the transparent conductive oxide film which is the
first layer of the reflection preventing optical thin film in contact with
the hard coat layer is formed by reactive physical vapor phase deposition.
When reactive spattering using a metal or alloy target is used as reactive
physical vapor phase deposition, the spattering is carried out under a
spattering condition of insufficient oxygen unlike conventional spattering
technique in which a oxide target is used. In this case, when spattered
particles are deposited on a hard coat layer, completely oxidized
particles are not deposited on a hard coat layer, but partially active
metal or alloy spattered particles are deposited on a hard coat layer and
react with oxygen atoms in molecules which forms the hard coat layer, thus
the reaction results in chemical strong adhesion. As a result, the
adhesion (adhesion strength) between the transparent conductive oxide film
and hard coat layer is improved. In the anti-reflection member in
accordance with the first embodiment of the present invention, the
combination of the transparent conductive oxide film with the second layer
leads to the effective prevention of light reflection, on the other hand,
transparent conductive oxide film provides antistatic function and
electromagnetic radiation shielding function to the anti-reflection
member.
In the case that elements which form the conductive light absorbing film
have no or little affinity with oxygen in molecules which form the hard
coat layer, adhesion between the conductive light absorbing film and hard
coat layer is considered to be insufficient. On the other hand, in the
anti-reflection member or the manufacturing method thereof in accordance
with the second embodiment of the present invention, the transparent oxide
film which is the first layer of the reflection preventing optical thin
film in contact with the hard coat layer is formed by reaction physical
vapor phase deposition. When reactive spattering using a metal or alloy
target is used as reactive physical vapor phase deposition, the spattering
is carried out under a spattering condition of insufficient oxygen unlike
conventional spattering technique in which a oxide target is used. In this
case, when spattered particles are deposited on a hard coat layer,
completely oxidized particles are not deposited on a hard coat layer, but
partially active metal or alloy spattered particles are deposited on a
hard coat layer and react with oxygen atoms in molecules which forms the
hard coat layer, thus the reaction results in chemical strong adhesion. As
a result, the adhesion (adhesion strength) between the transparent oxide
film and hard coat layer is improved. In the anti-reflection member in
accordance with the second embodiment of the present invention, the
combination of the conductive light absorbing film with the third layer
leads to the effective prevention of light reflection, on the other hand,
conductive light absorbing film provides antistatic function and
electromagnetic radiation shielding function to the anti-reflection
member. The transparent oxide film is provided with anti-reflection
function by adjusting the film thickness of the transparent oxide film.
The transparent oxide film is provided with antistatic function and
electromagnetic radiation shielding function by using a conductive
transparent oxide film.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic partial cross-sectional view of the anti-reflection
member of Example 1.
FIG. 2 is a schematic partial cross-sectional view of the anti-reflection
member of Example 2.
FIG. 3 is a schematic diagram of a spattering equipment suitable for
continuous manufacturing of the anti-reflection member of the present
invention.
FIGS. 4A and 4B are a schematic partial cross-sectional view of a
conventional anti-reflection member, and a schematic partial
cross-sectional view of the anti-reflection member proposed by the
applicant of the present invention in Japanese Patent Application Hei
7-170925 (1995).
DETAIL DESCRIPTION OF PREFERRED EXAMPLE
The present invention will be described in detail hereinafter based on
examples referring to the drawings.
EXAMPLE 1
Example 1 relates to the anti-reflection member and the manufacturing
method thereof in accordance with the first embodiment of the present
invention. In Table 3, target materials and film forming conditions for
reactive spattering (in detail, DC magnetron spattering) are shown. A
schematic partial cross-sectional view of the obtained anti-reflection
member is shown in FIG. 1. In FIG. 1, the first layer of the reflection
preventing optical thin film is a transparent conductive oxide film
(thickness is 15 nm) formed by reactive DC magnetron spattering. The
second layer of the reflection preventing optical thin film is a SiO.sub.2
film with a thickness of 20 nm formed by conventional spattering using a
target of oxide. The third layer of the reflection preventing optical thin
film is a transparent conductive oxide film (thickness is 100 nm) formed
by reactive DC magnetron spattering under the same conditions for forming
the first layer. The fourth layer of the reflection preventing optical
thin film is a SiO.sub.2 film with a thickness of 85 nm formed by
conventional spattering. The hard coat layer consists of PMMA. The
substrate consists of PET. Film forming spattering conditions for forming
the second layer and the fourth layer are shown herein under.
______________________________________
Target SiO.sub.2
Power density 5 W/cm.sup.2
Atmosphere gas Ar
Atmospheric pressure 0.2 Pa
______________________________________
A anti-reflection member having the same structure was prepared by
conventional method. In detail, as to the conventional method shown in
Table 3, the first layer of the reflection preventing optical thin film is
a transparent conductive oxide film (thickness is 15 nm) formed by DC
magnetron spattering using a target of oxide. The second layer of the
reflection preventing optical thin film is a SiO.sub.2 film with a
thickness of 20 nm formed by conventional spattering using a target of
oxide. The third layer of the reflection preventing optical thin layer is
a transparent conductive oxide film (thickness is 100 nm) formed by DC
magnetron spattering using a target of oxide. The fourth layer of the
reflection preventing optical thin film is a SiO.sub.2 film with a
thickness of 85 nm formed by conventional spattering using a target of
oxide. The substrate consists of PET. The same film forming conditions as
used in Example 1 were used for forming the second layer and fourth layer.
Film forming conditions for forming the third layer by spattering are
shown herein under.
______________________________________
Target ITO
Power density 5 W/cm.sup.2
Atmosphere gas Ar
Atmospheric pressure 0.2 Pa
______________________________________
TABLE 3
__________________________________________________________________________
Target
Atmospheric gas
Atmos-
Transparent
power
concentration
pheric
Rating of
conductive
density
(volume %)
pressure
adhesion
Example
Target material
oxide film
(W/cm.sup.2)
Ar O.sub.2
(Pa)
strength
__________________________________________________________________________
1 In-Sn alloy
ITO 4 0 100 0.2 4
In-Sn alloy
ITO 4 30 70 0.2 4
In-Sn alloy
ITO 2 0 100 0.2 4
In-Sn alloy
ITO 2 30 70 0.2 5
Sn metal
SnO.sub.2
4 0 100 0.2 5
Sn metal
SnO.sub.2
4 30 70 0.2 5
Sn metal
SnO.sub.2
2 0 100 0.2 5
Sn metal
SnO.sub.2
2 30 70 0.2 5
Zn metal
ZnO 4 0 100 0.2 3
Zn metal
ZnO 4 30 70 0.2 3
Zn metal
ZnO 2 0 100 0.2 3
Zn metal
ZnO 2 30 70 0.2 0
Conven-
ITO oxide
ITO 4 0 100 0.2 0
tional
ITO oxide
ITO 4 50 50 0.2 0
method
ITO oxide
ITO 2 0 100 0.2 0
ITO oxide
ITO 2 50 50 0.2 0
__________________________________________________________________________
Sliding test was carried but for evaluation of adhesion (adhesion
strength). The sliding test includes following procedures. Four pieces of
cotton cloth impregnated with ethyl alcohol are wound on a steel ball with
a diameter of 20 mm, 3 kgf of load is loaded on the steel ball and the
loaded steel ball is brought into a contact with the uppermost layer of a
reflecting preventing optical thin film placed flat, and the steel ball is
reciprocated horizontally between 10 cm distance. The number of
reciprocation until the steel ball causes delamination of the reflection
preventing optical thin film is measured for rating of adhesion (adhesion
strength).
The rating result of adhesion (adhesion strength) is shown in Table 3. The
adhesion strength rating of "0" represents the delaminating within 5
cycles of reciprocation. The adhesion strength rating of "1" represents
the delamination in the reciprocation cycle range from 5 to 10. The
adhesion strength rating of "2" represents the delamination in the
reciprocation cycle range from 10 to 20. The adhesion strength rating of
"3" represents the delamination in the reciprocation cycle range from 20
to 30. The adhesion strength rating of "4" represents the delamination in
the reciprocation cycle range from 30 to 40. The adhesion strength rating
of "5" represents no delamination until 50 reciprocation cycles. All
delamination of the reflection preventing optical thin films was caused
between the first layer and hard coat layer.
From the Table 3, it is obvious that the adhesion (adhesion strength)
between the first layer and hard coat layer is greatly improved for the
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