U.S. patent application number 09/966215 was filed with the patent office on 2002-07-11 for silica layers and antireflection film using same.
Invention is credited to Ichimura, Koji, Nakajima, Tatsuji.
Application Number | 20020090521 09/966215 |
Document ID | / |
Family ID | 27344799 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020090521 |
Kind Code |
A1 |
Nakajima, Tatsuji ; et
al. |
July 11, 2002 |
Silica layers and antireflection film using same
Abstract
A silica layer is provided which is usable as a low refractive
index undergoing no change in its refractive index. Further, a
silica layer is provided which is highly productive and usable as a
medium or high refractive index layer undergoing neither reduction
in transmittance nor change in spectral colors. Still further, an
antireflection film using these silica layers is provided. These
silica layers are: a silica layer composed of an organic silicon
compound, which has a refractive index of not less than 1.40 and
not more than 1.46 (.lambda.=550 nm), and whose composition is
represented by SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0); a
carbon-containing silica layer, which has a refractive index of not
less than 1.55 and less than 1.80 (.lambda.=550 nm), and whose
composition is represented by Sio.sub.aC.sub.b (a=0.7 to 1.7, b=0.2
to 1.4); and a silica layer containing carbon, which has a
refractive index of not less than 1.80 and not more than 2.50
(.lambda.=550 nm), and whose composition is represented by
SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0). These silica layers
are used to form the antireflection film.
Inventors: |
Nakajima, Tatsuji;
(Tokyo-to, JP) ; Ichimura, Koji; (Tokyo-to,
JP) |
Correspondence
Address: |
Richard J. Streit
Ladas & Parry
Suite 1200
224 South Michigan Avenue
Chicago
IL
60604
US
|
Family ID: |
27344799 |
Appl. No.: |
09/966215 |
Filed: |
September 28, 2001 |
Current U.S.
Class: |
428/446 ;
428/702 |
Current CPC
Class: |
C23C 28/04 20130101;
C23C 30/00 20130101; C23C 16/401 20130101; C23C 16/30 20130101;
G02B 1/115 20130101; Y10T 428/24942 20150115 |
Class at
Publication: |
428/446 ;
428/702 |
International
Class: |
B32B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2000 |
JP |
P2000-298728 |
Sep 29, 2000 |
JP |
P2000-298729 |
Nov 2, 2000 |
JP |
P2000-336287 |
Claims
What is claimed is:
1. A silica layer comprising an organic silicon compound, which has
a refractive index of not less than 1.40 and not more than 1.46
(.lambda.=550 nm), and whose composition is represented by
SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0).
2. A silica layer according to claim 1, wherein infrared absorption
due to C--H stretching vibrations ranges from 0.1 to 1 cm.sup.-1and
infrared absorption due to O--H stretching vibrations ranges from 1
to 30 cm.sup.-1.
3. A silica layer according to claim 1, wherein the refractive
index has a change by 0.01 or less after a humidity/heat resistance
test.
4. A silica layer according to claim 1, which is formed by a plasma
CVD method using an organic silicone as a raw material.
5. A carbon-containing silica layer, which comprising a refractive
index of not less than 1.55 and less than 1.80 (.lambda.=550 nm),
and whose composition is represented by SiO.sub.aC.sub.b (a=0.7 to
1.7, b=0.2 to 1.4).
6. A silica layer according to claim 5, wherein a ratio of
silicon-silicon (Si--Si) bonds to all Si atoms' bonds in the silica
layer is 1% or less.
7. A silica layer according to claim 5, which is formed by a plasma
CVD method using an organic silicone as a raw material.
8. A carbon-containing silica layer, which comprising a refractive
index of not less than 1.80 and not more than 2.50 (.lambda.=550
nm), and whose composition is represented by SiO.sub.dC.sub.e
(d=0.5 to 0.9, e=1.0 to 2.0).
9. A silica layer according to claim 8, wherein a ratio of
silicon-silicon (Si--Si) bonds to all Si atoms' bonds in the silica
layer is 1% or less.
10. A silica layer according to claim 8, which is formed by a
plasma CVD method using an organic silicone as a raw material.
11. An antireflection film comprising at least a substrate film and
an antireflection multilayered article provided on the substrate
film, wherein the antireflection multilayered article contains any
of: (A) a silica layer composed of an organic silicon compound,
which has a refractive index of not less than 1.40 and not more
than 1.46 (.lambda.=550 nm), and whose composition is represented
by SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0); (B) a
carbon-containing silica layer, which has a refractive index of not
less than 1.55 and less than 1.80 (.lambda.550 nm), and whose
composition is represented by SiO.sub.aC.sub.b (a=0.7 to 1.7, b=0.2
to 1.4); and (C) a carbon-containing silica layer, which has a
refractive index of not less than 1.80 and not more than 2.50
(.lambda.=550 nm), and whose composition is represented by
SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0).
12. An antireflection film according to claim 11, wherein an
outermost layer of the antireflection multilayered article is the
silica layer (A), and wherein at least one of the silica layer (B)
and the silica layer (C) is formed internally from the outermost
layer.
13. An antireflection film according to claim 11, wherein the
antireflection multilayered article comprises the silica layer (B),
the silica layer (C), and the silica layer (A), in order from a
side of the substrate film.
14. An antireflection film according to claim 11, wherein the
antireflection multilayered article comprises a silica layer (C), a
silica layer (A), another silica layer (C), and another silica
layer (A), in order from a side of the substrate film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a silica layer comprising
an organic silicon compound and a carbon-containing silica layer
containing carbon, and also to an antireflection film having an
antireflection multilayered article formed of these silica
layers.
[0003] 2. Related Art
[0004] Transparent boards made of glass, plastic, etc. are used in
various displays including liquid-crystal displays, plasma
displays, and CRTs for computers, word processors, television sets,
and indicating panels, etc. Such transparent boards are also used
in indicators for instrumentation, etc., and rear-view mirrors,
goggles, windowpanes, etc. When trying to read characters, symbols
and other information through these transparent boards, one may
have difficulty doing so due to reflection of light on their
transparent surface.
[0005] To overcome this difficulty, one technique available today
is to arrange an antireflection multilayered article having layers
of different refractive indices superposed on a substrate film to
form an antireflection film, and then to adhere the antireflection
film to the surface of a transparent board, for prevention of light
reflection.
[0006] It is known to be preferable to provide a small refractive
index layer as the outermost layer (substantially opposite to the
substrate of the antireflection film) of the antireflection
multilayered article for efficient prevention of light reflection,
and a silica layer is suitably used as this small refractive index
layer. It is also known to be preferable to provide a plurality of
layers inward of the outermost layer (i.e., between the substrate
and the outermost layer of the antireflection film), which have
refractive indices greater than that of the outermost layer.
[0007] However, due to the fact that the density of a silica layer
is generally proportional to its refractive index, to decrease the
refractive index of a silica layer used as the outermost layer, low
density silica layer must be used. However, in the low density
silica layer, there are many voids, and when this silica layer is
used for a long period of time and/or under high temperature and
high humidity, these voids are subjected to inversion of water
molecules to change the reflective index of the silica layer.
[0008] Further, in many antireflection multilayered articles of
conventional antireflection films, their outermost layer is formed
of a silica layer, but the layers other than the outermost layer
(i.e., the layers having refractive indices different from that of
the outermost layer) are made from materials other than silica. For
example, in many antireflection multilayered articles having a low
refractive index layer, a medium refractive index layer, and a high
refractive index layer superposed on a substrate film, a silica
layer is used as the low refractive index layer which is the
outermost layer, and titanium oxide layers are used as the medium
and high refractive index layers. Further, these medium and high
refractive index layers are usually formed by sputtering, etc.
SUMMARY OF THE INVENTION
[0009] Therefore, to form the conventional antireflection
multilayered articles, thin layers having different refractive
indices, such as medium and high refractive index layers, need to
be formed separately with using different materials, by sputtering,
etc., thereby causing problems of low yield, high cost, and poor
adhesion between layers.
[0010] Under these circumstances, to overcome the above problems,
some medium and high refractive index layers are formed of silica
layers. This is because the refractive index of a silica layer can
be increased by setting x in SiO.sub.x (i.e., the number of oxygen
atoms bonded to a single silicon atom) to a value smaller than 2
(stoichiometric mixture ratio), whereby the acidity of the silicon
atom can be adjusted to control the refractive index of the silica
layer. In this way, the use of a silica layer as a medium or high
refractive index layer permits continuous formation of an
antireflection film using the same raw material and system as
formation of a silica layer used as a low refractive index
layer.
[0011] However, when the refractive index is adjusted by setting x
of SiO.sub.x forming the silica layer to a smaller value as
mentioned above, absorption of light by the silica layer gradually
increases in the visible range. As a result, the silica layer, when
used as an optical layer, causes problems such as a reduction in
transmittance and a change in spectral colors. These problems are
assumed to be caused by the fact that Si--Si bonds absorbing
radiation in the visible range would increase to increase the
extinction coefficient of the silica layer.
[0012] It should be noted that the low refractive index layer, the
medium refractive index layer, and the high refractive index layer
which are thin layers for forming the antireflection multilayered
article are names given to distinguish one layer from others when
they are compared relatively in terms of their index of refraction.
A layer having a comparatively high refractive index is denoted as
a high refractive index layer, a layer having a comparatively low
refractive index as a low refractive index layer, and a layer
having a refractive index between those of the high and low
refractive index layers as a medium refractive index layer.
Generally, layer having a refractive index of 1.80 or more may be
high refractive index layer, layer having a refractive index
between 1.55 and less than 1.80 may be medium refractive index
layer, and layer having a refractive index of less than 1.55 may be
low refractive index layer. Therefore, these names are used in the
above sense throughout this specification.
[0013] The present invention has been accomplished under the above
problems, and a first object thereof is to provide a silica layer
usable as a low refractive index layer, whose low refractive index
undergoes no change even when used for a long period of time and
under high temperatures and high humidities.
[0014] Further, a second object of the present invention is to
provide a silica layer usable as a medium refractive index layer or
a high refractive index layer, which is a thin layer for use in the
antireflection multilayered article of an antireflection film,
which is formable from a silicon compound that is the same raw
material as that of a known silica layer as the outermost layer,
highly productive, and undergoing no reduction in transmittance and
no change in spectral colors.
[0015] Still further, a third object of the present invention is to
provide an antireflection film exhibiting high productivity and
excellent transparency and antireflection characteristics.
[0016] To achieve the above objects, a silica layer according to
the present invention comprises an organic silicon compound, which
has a refractive index of not less than 1.40 and not more than 1.46
(.lambda.=550 nm), and whose composition is represented by
SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0) (hereinafter,
referred to as "silica layer (A)" whenever applicable).
[0017] When the refractive index of the silica layer is set to any
value within the above range, the silica layer can be used as a low
refractive index layer exhibiting excellent optical properties, and
can thus be utilized as the outermost layer, etc. of an
antireflection multilayered article in an antireflection film.
Further, when the silica layer comprises an organic silicon
compound having a composition represented by SiO.sub.xC.sub.y:H
(x=1.6 to 1.9, y=0.2 to 1.0), the silica layer contains a linkage
with an organic group such as a methyl group (CH.sub.3--), in
addition to the silicon atom (Si) and the oxygen atoms (O), which
are its essential constituents. As a result, the silica layer can
have a low refractive index.
[0018] To decrease the refractive index, voids had to be provided
in the conventional silica layers to decrease their density. As a
result, these silica layers allow the inversion of water molecules
into the voids when used for a long period of time and/or under
high temperatures and humidities, and this would in turn change
their refractive index. However, since the silica layer of the
present invention comprises an organic silicon compound, its
refractive index can be decreased by controlling its composition.
Therefore, there is no need to provide voids in the silica layer,
and thus the refractive index of the silica layer undergoes no
change even when the silica layer is used for a long period of time
and/or under high temperatures and humidities.
[0019] A silica layer of the present invention as one preferred
embodiment may be that has an infrared absorption due to C--H
stretching vibrations in the range 0.1-1 cm.sup.-1 and infrared
absorption due to O--H stretching vibrations in the range 1-30
cm.sup.-1.
[0020] The silica layer having such an absorption spectrum as above
could exhibit the above-mentioned property of the present invention
(the ability of a silica layer to have a low refractive index
without providing voids therein, due to the fact that the silica
layer is made of an organic silicon compound) more effectively.
[0021] Further, a silica layer of the present invention as another
preferred embodiment has a change in its refractive index by 0.01
or less after a humidity/heat resistance test.
[0022] Here, the humidity/heat resistance test means a test in
which a silica layer is stood at 80.degree. C. and 90% relative
humidity for 1000 hours. The refractive index of the silica layer
of the present invention can possess a change by 0.01 or less even
after the test. Therefore, the silica layer which expresses such a
moderate change with respect to the refractive index after the test
would be sufficiently practicable.
[0023] A silica layer of the present invention as another preferred
embodiment is a layer which is formed by a plasma CVD method using
an organic silicone as raw material.
[0024] The plasma CVD method permits comparatively easy control
over the conditions for forming the silica layer of the present
invention. Also, as a feature, the silica layer of the present
invention comprises an organic silicon compound. To form a layer
from such a raw material containing an organic ingredient, the
plasma CVD method using gaseous raw materials is most
preferable.
[0025] Further, to achieve the above objects, a silica layer
according to the present invention comprises carbon-containing
silica layer, and has a refractive index of not less than 1.55 and
less than 1.80 (.lambda.=550 nm), and a composition represented by
SiO.sub.aC.sub.b (a=0.7 to 1.7, b=0.2 to 1.4) (hereinafter referred
to as "silica layer (B)" whenever applicable).
[0026] When the refractive index of the silica layer is set to a
value within the above range, the silica layer can be suitably used
as a medium refractive index layer in the antireflection
multilayered article of an antireflection film. Also, the
composition of the silica layer is represented by above, whereby
the silica layer can have a desired refractive index (not less than
1.55 and less than 1.80 (.lambda.=550 nm)). As a result, when used
as one of the layers forming the antireflection multilayered
article of an antireflection film, the silica layer, because of its
being similar to the silica layer as a low refractive index layer
of the antireflection multilayered article, can improve yield and
reduce cost in forming the antireflection multilayered article.
[0027] A silica layer of the present invention as one preferred
embodiment is such that the ratio of Si--Si bonds to all Si atoms'
bonds in the layer is 1% or less.
[0028] When the refractive index of the silica layer is adjusted by
setting x of SiO.sub.x to a smaller value in order to form a silica
layer as a medium refractive index layer in the known technique,
the proportion of the Si--Si bonds grows larger within the layer,
thereby causing the silica layer to gradually increase the
absorption of light in the visible range and to sometimes reduce
its transmittance and change its spectral colors. However, when the
ratio of Si--Si bonds to all Si atoms' bonds in the silica layer is
confined to 1% or less, the layer is assumed to contain few Si--Si
bonds, thus making itself hardly influenced by optical absorption
due to the Si--Si bonds. As a result, its extinction coefficient
can be set to 0.018 (.lambda.=550 nm) or less.
[0029] It should be noted that the extinction coefficient means an
imaginary number of a complex refractive index, which is calculated
from the equation h=.alpha..lambda./4.pi. (wherein a is the
absorption coefficient and .lambda. is the wavelength of light).
The smaller its extinction coefficient, the better its
transparency.
[0030] Further, a silica layer of the present invention as another
preferred embodiment is formed by a plasma CVD method using an
organic silicone as raw material.
[0031] The plasma CVD method permits comparatively easy control
over the conditions for forming the silica layer of the present
invention. Further, when an organic silicone is used as a raw
material for forming the silica layer of the present invention by
the plasma CVD method, the silica layer can be formed
efficiently.
[0032] A silica layer of the present invention as one preferred
embodiment is carbon-containing silica layer , and which has a
refractive index of not less than 1.80 and not more than 2.50
(.lambda.=550 nm), and has composition represented by
SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0) (hereinafter,
referred to as "silica layer (C)" whenever applicable).
[0033] When the refractive index of the silica layer is set within
the above range, the silica layer can be suitably used as a high
refractive index layer in the antireflection multilayered article
of an antireflection film. Also, when the composition of the silica
layer can be represented by above, the silica layer can have a
desired refractive index (from 1.80 to 2.50 (.lambda.=550 nm)).
[0034] Further, a silica layer of the present invention as another
preferred embodiment is such that the ratio of Si--Si bonds to all
Si atoms' bonds in the layer is 1% or less.
[0035] When the refractive index of the silica layer is adjusted by
setting x of SiO.sub.x to a smaller value in order to form a silica
layer as a medium refractive index layer in the known technique,
the proportion of the Si--Si bonds grows larger within the layer,
thereby causing the silica layer to gradually increase the
absorption of light in the visible range, and to sometimes reduce
its transmittance and change its spectral colors. However, when the
ratio of Si--Si bonds to all Si atoms' bonds in the silica layer is
regulated to 1% or less, the layer is assumed to contain few Si--Si
bonds, thus making itself hardly influenced by optical absorption
due to the Si--Si bonds. As a result, its extinction coefficient
can be set to 0.018 (.lambda.=550 nm) or less.
[0036] Further, a silica layer of the present invention as another
preferred embodiment is the layer which is formed by a plasma CVD
method using an organic silicone as raw material.
[0037] The plasma CVD method permits comparatively easy control
over the conditions for forming the silica layer of the present
invention. Further, by using an organic silicone as a raw material
for forming the silica layer of the present invention by the plasma
CVD method, the silica layer can be formed efficiently.
[0038] An antireflection film of the present invention as one
preferred embodiment comprises at least a substrate film and an
antireflection multilayered article provided on the substrate film,
the antireflection multilayered article containing any of the
silica layer (A), the silica layer (B), and the silica layer
(C).
[0039] Since the antireflection multilayered article is formed of
any of the silica layer (A), the silica layer (B), and the silica
layer (C), the antireflection film can be provided with an
excellent antireflection function.
[0040] Further, an antireflection film of the present invention as
another preferred embodiment comprises at least a substrate film
and an antireflection multilayered article provided on the
substrate film, wherein the outermost layer of the antireflection
multilayered article is the silica layer (A), and wherein at least
one of the silica layer (B) and the silica layer (C) is formed as
layer(s) located inwardly from the outermost layer.
[0041] The antireflection film of the present invention uses the
silica layer (A) (the silica layer composed of an organic silicon
compound) as the outermost layer of its antireflection multilayered
article, i.e., as the layer provided at the side opposite to the
another side faced to the substrate in the antireflection
multilayered article. Thus, by forming the outermost layer of the
low refractive index silica layer, the silica layer contains
linkages to organic groups such as a methyl group (CH.sub.3--), in
addition to the linkages between silicon atoms (Si) and oxygen
atoms (O) which are essential constituents of silica layer, and
hence can have a low refractive index.
[0042] Further, an antireflection film of the present invention is
formed of at least one of the silica layer (B) and the silica layer
(C) (the carbon-containing silica layers) as a layer located
inwardly from the outermost layer, i.e., as a layer interposed
between the substrate and the outermost layer in the antireflection
multilayered article. This is because the carbon-containing silica
layer can have a larger refractive index than the organic silicon
compound used as the outermost layer of the antireflection
multilayered article, and thus the carbon-containing silica layer
can be suitably used as the layer located inwardly from the
outermost layer, i.e., as a medium or high refractive index layer
when the outermost layer is formed of a low refractive index layer.
Also, when this silica layer is used as a medium or high refractive
index layer, all layers in the antireflection multilayered article
can be formed by silica layers, including the outermost layer,
whereby the transparency of the entire antireflection multilayered
article and adhesion between layers can be improved.
[0043] Further, an antireflection film of the present invention as
another preferred embodiment comprises at least a substrate film
and an antireflection multilayered article superposed on the
substrate film, the antireflection multilayered article comprising
the silica layer (B), the silica layer (C), and the silica layer
(A), in order from the side of the substrate.
[0044] Further, an antireflection film of the present invention as
another preferred embodiment comprises at least a substrate film
and an antireflection multilayered article superposed on the
substrate film, the antireflection multilayered article comprising
the silica layer (C), the silica layer (A), the silica layer (C),
and the silica layer (A), in order from the side of the
substrate.
[0045] When the layers of the antireflection multilayered article
are comprised as mentioned above, the antireflection multilayered
article can perform the antireflection function efficiently as a
whole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a schematic sectional view showing an example of
an antireflection film of the present invention;
[0047] FIG. 2 is a schematic sectional view showing another example
of an antireflection film of the present invention; and
[0048] FIG. 3 is a schematic sectional view of a plasma CVD system
for producing silica layers and an antireflection film of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Silica Layers
[0050] Three types of silica layers of the present invention will
now be described. The three types of silica layers of the present
invention are:
[0051] <1> a silica layer comprising an organic silicon
compound and functioning as a low refractive index layer;
[0052] <2> a silica layer containing carbon and functioning
as a medium refractive index layer; and
[0053] <3> a silica layer containing carbon and functioning
as a high refractive index layer.
[0054] <1> Silica Layer Comprising an Organic Silicon
Compound and Functioning as a Low Refractive Index Layer
[0055] A silica layer comprising an organic silicon compound, which
is one type of silica layer of the present invention, has features
enumerated below.
[0056] (1) Its refractive index ranges from 1.40 to 1.46, and its
composition is represented by SiO.sub.xC.sub.y:H (x=1.6 to 1.9,
y=0.2 to 1.0).
[0057] (2) Its infrared absorption due to C-H stretching vibrations
is in the range 0.1-1 cm.sup.-1, and its infrared absorption due to
O--H stretching vibrations is in the range 1-30 cm.sup.-1.
[0058] (3) Its refractive index undergoes a change by 0.01 or less
after a humidity/heat resistance test.
[0059] The above features (1) to (3) will be described
concretely.
[0060] Feature (1):
[0061] The silica layer composed of an organic silicon compound of
the present invention has the feature that its refractive index
ranges from 1.40 to 1.46 and that its composition is represented by
SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0).
[0062] As to the silica layer composed of an organic silicon
compound of the present invention, because of its main intended use
as the outermost layer of an antireflection multilayered article of
which an antireflection film is made together with a substrate, the
smaller its refractive index, the more desirable it is. If its
refractive index is within the above range, the silica layer
composed of an organic silicon compound of the present invention
can be used as a low refractive index layer, and hence as the
outermost layer of the antireflection multilayered article.
[0063] Also, the composition of this silica layer is represented by
SiO.sub.xC.sub.y:H (x=1.6 to 1.9, y=0.2 to 1.0). That is, the
silica layer is not a layer comprising simple silicon oxide
(SiO.sub.x), but a layer comprising a silicon compound containing
organic moiety(containing carbon (C) and hydrogen (H)) (i.e., an
organic silicon compound).
[0064] Here, the numeral x of oxygen atoms (O) bonded to the
silicon atom (Si) in the silica layer ranges from 1.6 to 1.9. This
is because, when the numeral x greater than 1.6, the refractive
index of the silica layer increases so as to disqualify the silica
layer as a low refractive index layer and hence make it unsuitable
for the outermost layer of the antireflection multilayered article
in the antireflection film. On the other hand, it may be impossible
to increase the number x in excess of 1.9 in terms of the atomic
structure of silicon. Therefore, in this silica layer, the number x
of oxygen atoms (O) bonded to the silicon atom (Si) is set to 1.6
to 1.9.
[0065] Further, the numeral y of carbon atoms (C) bonded to the
silicon atom (Si) in this silica layer ranges from 0.2 to 1.0. The
reason is as follows. When the numeral of carbon atoms is smaller
than 0.2, it is impossible to decrease amply the refractive index
of the silica layer only by its inherent composition. As the result
in such case, to decrease the refractive index (i.e., to form the
silica layer as a low refractive index layer) so that the silica
layer can be used as the outermost layer of the antireflection
multilayered article, voids must be provided in the silica layer.
When the silica layer containing voids is used under high
temperature, high humidity, etc., its refractive index does change
(its refractive index increases), and hence such a silica layer is
not suitable to achieve the objects of the present invention. On
the other hand, if the numeral y is increased in excess of 1.0, the
silica layer thus formed becomes brittle as a whole, making it
impossible to form the layer itself.
[0066] Thus, the silica layer is formed using an organic silicon
compound so that its refractive index ranges from 1.40 to 1.46 and
so that its composition is represented by SiO.sub.xC.sub.y:H (x=1.6
to 1.9, y=0.2 to 1.0), whereby the silica layer can have a low
refractive index without need for providing voids therein.
Therefore, the refractive index of the silica layer undergoes no
change even when the silica layer is used for a long period of time
and/or under high temperature and high humidity. Further, due to
its low refractive index, the silica layer can be suitably used as
the outermost layer of the antireflection multilayered article in
the antireflection film.
[0067] Feature (2):
[0068] This silica layer has the feature that its infrared
absorption due to C--H stretching vibrations is in the range 0.1-1
cm.sup.-1, and that its infrared absorption due to O--H stretching
vibrations is in the range 1-30 cm.sup.-1.
[0069] As mentioned above, this silica layer includes bondings to
the organic moiety (carbon (C) and hydrogen (H)), in addition to
the bondings between silicon atoms (Si) and the oxygen atoms (O).
In this silica layer, the structure of organic moiety to be bonded
is not limited. Any organic residue having any structure may be
acceptable, as long as the resultant refractive index of the silica
layer as a whole is in the 1.40-1.46 range and its composition
satisfies the above-mentioned range.
[0070] However, of any silica layer having the composition
satisfying the range mentioned in (1) above, particularly, a silica
layer exhibiting an infrared absorption due to C--H bond stretching
vibrations in the 0.1-1 cm.sup.-1 range and an infrared absorption
due to O--H bond stretching vibrations in the l-30 cm.sup.-1 range
is preferable, and further a silica layer exhibiting an infrared
absorption due to C--H bond stretching vibrations in the 0.3-1
cm.sup.-1 range and an infrared absorption due to O--H bond
stretching vibrations in the 3-15 cm.sup.-1 range is more
preferable.
[0071] Here, the above infrared absorptions are measured by a known
transmission type IR spectroscopy, and the value of
.intg.(.alpha./f)df in the infrared absorption due to each type of
stretching vibrations is caluculated (wherein a is the absorption
coefficient and f is the frequency). The infrared absorption due to
C--H bond stretching vibrations is caluculated from an read
absorbance at the wave number range 2800-3100 cm.sub.-1 in obtained
absorption spectrum. The infrared absorption due to O--H bond
stretching vibrations is caluculated from an read absorbance at the
wave number range 3000-3800 cm.sup.-1 in obtained absorption
spectrum.
[0072] It is obvious that any silica layer in which its infrared
absorption due to C--H bond stretching vibrations and its infrared
absorption due to O--H bond stretching vibrations are within the
above ranges includes bonds to organic moieties, and hence it can
be said that such a silica layer has a low refractive index as well
as humidity/heat resistance.
[0073] Feature (3):
[0074] This silica layer has the feature that its refractive index
undergoes a change by 0.01 or less after a humidity/heat resistance
test.
[0075] Here, the humidity/heat resistance test according to the
present invention is carried out by standing a silica layer in an
environmental test machine at 80.degree. C. and 90% relative
humidity for 1000 hours.
[0076] Since this silica layer has characteristics such as
mentioned above, its refractive index underwent a change by 0.01 or
less when a comparison was made with respect to the refractive
index before and after the test, and hence it can be said that the
silica layer would be sufficiently practicable.
[0077] <2> Silica Layer Containing Carbon and Functioning as
a Medium Refractive Index Layer
[0078] Next, a silica layer containing carbon and functioning as a
medium refractive index layer, which is one type of the silica
layer of the present invention, will be described.
[0079] The silica layer of the present invention which contains
carbon and functions as a medium refractive index layer has
features enumerated below.
[0080] (1) Its refractive index is not less than 1.55 and less than
1.80 (.lambda.=550 nm), and its composition is represented by
SiO.sub.aC.sub.b (a=0.7 to 1.7, b=0.2 to 1.4).
[0081] (2) The ratio of Si--Si bonds to all Si atoms' bonds in the
layer is 1% or less.
[0082] The above features (1) and (2) will be described
specifically.
[0083] Feature (1):
[0084] The carbon-containing silica layer of the present invention
has the feature that its refractive index ranges from 1.55 to less
than 1.80 (.lambda.=550 nm), and that its composition is
represented by SiO.sub.aC.sub.b (a=0.7 to 1.7, b=0.2 to 1.4).
[0085] As to the carbon-containing silica layer of the present
invention, because of its main intended use as a medium refractive
index layer of an antireflection multilayered article of which an
antireflection film is made together with a substrate, it is
preferable that its refractive index ranges from 1.55 to less than
1.80 (.lambda.=550 nm). Therefore, by setting the refractive index
within the above range, the carbon-containing silica layer of the
present invention can be used as a medium refractive index layer in
the antireflection film.
[0086] Further, the composition of this silica layer is represented
by SiO.sub.aC.sub.b (a=0.7 to 1.7, b=0.2 to 1.4). That is, the
silica layer is not a layer composed of simple silicon oxide
(SiO.sub.x), but is a carbon (C) containing silica layer. Thus, due
to the possessing of carbon component, the silica layer can have a
desired refractive index.
[0087] Here, the numeral a of oxygen atoms (O) in this silica layer
ranges from 0.7 to 1.7. This is because the numeral of bonded
oxygen atoms smaller than 0.7 would make the refractive index of
this silica layer so large that the silica layer is no longer a
medium refractive index but will become a high refractive index
layer. On the other hand, the numeral of oxygen atoms greater than
1.7 reduces its refractive index to that (1.46 to 1.47) of a simple
silica layer (SiO.sub.2), thereby making this silica layer
unsuitable for a medium refractive index layer for forming the
antireflection multilayered article.
[0088] Further, the numeral b of carbon atoms (C) in this silica
layer ranges from 0.2 to 1.4. This is because the numeral of carbon
atoms in the silica layer smaller than 0.2 reduces its refractive
index to that (1.46 to 1.47) of the simple silica layer
(SiO.sub.2), thereby making this silica layer unsuitable for a
medium refractive index layer for forming the antireflection
multilayered article. On the other hand, the numeral of carbon
atoms greater than 1.4 would make the refractive index of this
silica layer so large that the silica layer is no longer a medium
refractive index but will become a high refractive index layer.
[0089] Feature (2):
[0090] This silica layer containing carbon has the feature that the
ratio of Si--Si bonds to all Si atoms' bonds in the layer is 1% or
less.
[0091] This is because the Si--Si bonds in the silica layer absorb
light in the visible range and an abundance of these bonds would
reduce the light transmittance of the layer and/or change its
spectral colors. Here, "the ratio of Si--Si bonds to all Si atoms'
bonds" refers to the percentage of Si--Si bonds in all of Si--Si
bonds, Si--O bonds and Si--C bonds.
[0092] In the present invention, the percentage of Si--Si bonds in
the silica layer is obtained based on waveform separation in
electron spectroscopy. Specifically, the percentage was obtained by
measuring a Si(2p) spectrum using an photoelectron spectrometer
(ESCALAB 220i-XL manufactured by VG Scientific) under the following
conditions. It should be noted that the measurement was made after
etching the silica layer to about several nanometers using Ar ions,
through correction of bonding energy was done so as to the is peak
of C--C bond is 284.6 eV. Further, the spectrum was subjected to
waveform separation using the Si--O binding energy of 103.5 eV, the
Si--Si binding energy of 99.0 eV, and the Si--C binding energy of
100.5 eV.
[0093] (Measurement Conditions)
[0094] X-ray source: Monochromatized Al K.alpha. radiation
[0095] X-ray output: 10 kV, 20 mA
[0096] Area for measurement: 0.7 mm in diameter
[0097] Escape depth of photoelectron: 90.degree.
[0098] <3> Silica Layer Containing Carbon and Functioning as
a High Refractive Index Layer.
[0099] Next, a silica layer containing carbon and functioning as a
high refractive index layer, which is one type of silica layer of
the present invention, will be described.
[0100] The silica layer of the present invention containing carbon
and functioning as a high refractive index layer has features
enumerated below.
[0101] (1) Its refractive index ranges from 1.80 to not more than
2.50 (.lambda.=550 nm), and its composition is represented by
SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0).
[0102] (2) The ratio of Si--Si bonds to all Si atoms' bonds in the
layer is 1% or less.
[0103] The above features (1) and (2) will be described
specifically.
[0104] Feature (1):
[0105] The carbon-containing silica layer of the present invention
has the feature that its refractive index is not less than 1.80 and
not more than 2.50 (.lambda.=550 nm), and that its composition is
represented by SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0).
[0106] As to the carbon-containing silica layer of the present
invention, because of its main intended use as a high refractive
index layer of an antireflection multilayered article of which an
antireflection film is made together with a substrate, it is
preferable that its refractive index is not less than 1.80 and not
more than 2.50 (.lambda.=550 nm). Therefore, by setting the
refractive index within the above range, the carbon-containing
silica layer of the present invention can be used as a high
refractive index layer in the antireflection film.
[0107] Further, the composition of this silica layer is represented
by SiO.sub.dC.sub.e (d=0.5 to 0.9, e=1.0 to 2.0). That is, the
silica layer is not a layer composed of simple silicon oxide
(SiO.sub.x), but a carbon (C) containing silica layer. Thus, due to
the possessing of carbon component, the silica layer can have a
desired refractive index.
[0108] Here, the numeral d of oxygen atoms (O) in the silica layer
ranges from 0.5 to 0.9. This is because the numeral of oxygen atoms
smaller than 0.5 increases the percentage of a silicon atom (Si)
bonding to another silicon atom (Si), i.e., the percentage of
Si--Si bonds, thereby increasing the extinction coefficient, and as
a result, the transparency of the silica layer is impaired to make
the silica layer unsuitable for one of the layers in the
antireflection multilayered article of the antireflection film. On
the other hand, the numeral of oxygen atoms greater than 0.9 would
decrease the refractive index so that the silica layer will become
a medium refractive index layer.
[0109] Further, the numeral e of carbon atoms (C) in this silica
layer ranges from 1.0 to 2.0. This is because the numeral of carbon
atoms smaller than 1.0 would decrease the refractive index so that
the silica layer will become a medium refractive index layer. On
the other hand, the numeral of carbon atoms greater than 2.0
impairs the transparency of the silica layer to make the silica
layer unsuitable for one of the layers in the antireflection
multilayered article of the antireflection film. In addition, the
internal stress of the silica layer grows larger, leading to
cracking and delamination of the silica layer.
[0110] Feature (2):
[0111] This carbon-containing silica layer has the feature that the
ratio of Si--Si bonds to all Si atoms' bonds in the layer is 1% or
less.
[0112] Since this feature is similar to that of the aforesaid
silica layer containing carbon and functioning as a medium
refractive index layer, its description is omitted here.
[0113] Antireflection Film
[0114] Next, an antireflection film made of the above-described
three types of silica layers of the present invention will be
described.
[0115] FIG. 1 is a schematic sectional view showing an example of
an antireflection film of the present invention. As shown in FIG.
1, the antireflection film 1 comprises a substrate 2 and an
antireflection multilayered article 3. Depending on the
predetermined use, etc. of the antireflection film 1, a hard
coating layer 7 may be interposed between the substrate 2 and the
antireflection multilayered article 3, or a stainproof layer 8,
etc. may be provided on the antireflection multilayered article
3.
[0116] The components of the antireflection film 1 of the present
invention will be described in detail below.
[0117] <1> Antireflection Multilayered Article
[0118] The antireflection multilayered article 3 in the
antireflection film 1 of the present invention is characterized by
the fact of containing any of the silica layer composed of an
organic silicon compound described in <1> above, the
carbon-containing silica layer described in <2> above, and
the carbon-containing silica layer described in <3> above.
Therefore, in the antireflection multilayered article of the
antireflection film of the present invention, as long as the
multilayered article 3 contains one of the silica layer composed of
an organic silicon compound described in <1> above, the
carbon-containing silica layer described in <2> above, and
the carbon-containing silica layer described in <3> above, it
is not necessary to form the entire antireflection multilayered
article of these silica layers. As the high refractive index layer,
for example, a titanium oxide layer may be used. As the medium
refractive index layer, for example, any layer formed by dispersing
fine particles of Al.sub.2O.sub.3, SiN, SiON, ZrO.sub.2, SiO.sub.2,
or ZnO.sub.2 into an organic silicon compound, etc. may also be
used. Further, it is not necessary to provide single medium
refractive index layer 6, but a plurality of different layers may
be layered to provide a medium refractive index layer that has the
above-mentioned refractive index as a whole. Still further, as the
low refractive index layer, any layer of SiO.sub.2, MgF.sub.2, etc.
may be used.
[0119] This is because, by forming the above-mentioned three types
of silica layers of the present invention in the antireflection
multilayered article, each of these silica layers yields such
positive effects as to form an excellent antireflection film. In
this case, it is preferable to use the silica layer composed of an
organic silicon compound described in <1> above as a low
refractive index layer for the outermost layer of the
antireflection multilayered article. It is preferable to use the
carbon-containing silica layer described in <2> above as a
medium refractive index layer. Further, it is preferable to use the
carbon-containing silica layer described in <3> above as a
high refractive index layer.
[0120] The antireflection multilayered article 3 in the
antireflection film 1 of the present invention shown in FIG. 1 has
a feature that a silica layer 4 composed of an organic silicon
compound of the present invention (the silica layer described in
<1> above) is formed as its outermost layer, and that at
least one of the silica layers respectively containing carbon and
functioning as medium and high refractive index layers (the silica
layers denoted by reference numerals 6 and 5 in FIG. 1 and
described in <2> and <3> above) is formed the layer
located inwardly from the outermost layer. Here, the outermost
layer of the antireflection multilayered article 3 means a layer
arranged at the outermost location in the antireflection
multilayered article 3 formed of optical layers (layers formed to
prevent reflection), i.e., the layer located opposite to the
substrate 2. Here, the antireflection multilayered article 3 does
not contain any other layers than the optical layers, the other
layers being the hard coating layer 7 and the stainproof layer 8,
for example.
[0121] The outermost layer of the antireflection multilayered
article 3 in the antireflection film 1 is formed of the silica
layer 4 composed of an organic silicon compound, whereby the
outermost layer can have a small refractive index. Further, the
carbon-containing silica layers 5 and 6 are formed inward of the
silica layer 4, whereby these layers 5 and 6 can be suitably used
as high and medium refractive index layers in the antireflection
multilayered article.
[0122] How the layers are arranged in the antireflection
multilayered article of the antireflection film of the present
invention is not particularly limited, as long as the outermost
layer is a silica layer composed of an organic silicon compound, or
at least one of carbon-containing silica layers is formed as an
internal layer. These layers may be layered as one desires so as to
provide antireflection effects.
[0123] Among others, it is preferable to arrange the layers of the
antireflection multilayered article of the present invention as
shown in FIG. 1. That is, for the outermost layer, the silica layer
4 composed of an organic silicon compound is used as a low
refractive index layer; for the layer directly thereunder (the
layer next to the outermost layer in the direction of the
substrate), the above-mentioned carbon-containing silica layer 5 is
used as a high refractive index layer; and for the layer directly
under the high refractive index layer, the carbon-containing silica
layer 6 is used as a medium refractive index layer.
[0124] It is also preferable to arrange the layers of the
antireflection multilayered article as shown in FIG. 2. That is,
for the outermost layer, the silica layer 4 composed of an organic
silicon compound is used as a low refractive index layer; for the
layer directly thereunder (the layer next thereto in the direction
of the substrate), the above-mentioned carbon-containing silica
layer 5 is used as a high refractive index layer; and for the layer
directly under the high refractive index layer, the silica layer 4
composed of an organic silicon compound is used; and for the layer
directly thereunder, the carbon-containing silica layer 5 is used
as a high refractive index layer.
[0125] This is because, by arranging the layers of the
antireflection multilayered article 3 as mentioned above,
antireflection can be achieved efficiently, and all layers in the
antireflection multilayered article can be formed of silica layers,
whereby adhesion between layers can be improved.
[0126] The thickness of the silica layer 4 composed of an organic
silicon compound used as a low refractive index layer is not
particularly limited, but any thickness may be acceptable as long
as antireflection effects can be provided. However, in general,
thicknesses in the 10-1000 nm range are preferable, and thicknesses
in the 50-150 nm range are particularly preferable, because
thicknesses thinner than the above would be ineffective to provide
antireflection effects, and thicknesses thicker than the above
would embrittle the entire layer to impair its
film-formability.
[0127] Further, the thickness of the carbon-containing silica layer
5 used as a high refractive index layer is not particularly
limited, either, and any thickness maybe acceptable as long as
antireflection effects can be provided. Among others, thicknesses
in the 0.005-0.3 .mu.m range are particularly preferable, and
thicknesses in the 0.01-0.15 .mu.m range are more preferable, in
general. Because thicknesses thinner than 0.005 .mu.m provide
little antireflection effects, and thicknesses thicker than 0.3
.mu.m cause deformation of the substrate and delamination of the
layer due to stresses of the layer.
[0128] Still further, as to the carbon-containing silica layer 6
used as a medium refractive index layer, thicknesses in the
0.005-0.3 .mu.m range are particularly preferable, and thicknesses
in the 0.01-0.15 .mu.m range are more preferable for a similar
reasons as mentioned above as to a high refractive index layer.
[0129] <2> Substrate
[0130] Next, the substrate 2 will be described. In the
antireflection film 1 of the present invention, the substrate 2 is
located opposite to the antireflection multilayered article 3, and
provides the base portion for the antireflection film 1. The
substrate 2 is not particularly limited, as long as it may be any
high molecular material film which is transparent in the visible
range.
[0131] The high molecular material film includes triacetylcellulose
film, diacetylcellulose film, cellulose acetate butylate film,
polyether sulfone film, polyacrylic film, polyurathane film,
polyester film, polycarbonate film, polysulfone film, polyether
film, trimethylpentene film, polyetherketone film, acrylonitrile
film, and methacrylonitrile film. Further, colorless film may be
more preferably used. Among others, uniaxially or biaxially
stretched polyester film is suitably used because of its good
transparency and heat resistance. Particularly, polyethylene
terephthalate (PET) film is preferable. Also, triacetylcellulose is
suitably used due to the absence of optical anisotropy. The high
molecular material film typically of about 6-188 .mu.m in thickness
is suitably used.
[0132] <3> Hard Coating Layer
[0133] Still further, in the antireflection film 1 of the present
invention, the hard coating layer 7 may also be arranged, in
addition to the previously mentioned antireflection multilayered
article 3 and substrate 2.
[0134] The hard coating layer 7 used in the present invention is
formed in order to give mechanical strength to the antireflection
film 1. Therefore, this layer 7 is not always necessary, depending
on the intended use of the antireflection film 1.
[0135] The material for the hard coating layer 7 is not
particularly limited, as long as it is similarly transparent in the
visible range and can give strength to the antireflection film. For
example, a UV cure acrylic hard coating or a thermoset silicone
hard coating may be used. Further, the thickness of this hard
coating layer is typically in the 1-30 .mu.m range, and such a hard
coating layer 7 can be manufactured by any ordinary coating method
and which is not particularly limited.
[0136] Further, the hard coating layer 7 is preferably arranged at
a location separated from the silica layer 4 composed of an organic
silicon compound as the outermost layer, and thus preferably
located directly on the substrate 2, because it is arranged to give
strength to the antireflection film 1, not to improve the
antireflection function.
[0137] <4> Other Layers
[0138] In the antireflection film 1 of the present invention, other
layers may be arbitrarily superposed, depending on the desired use,
etc. of the antireflection film, in addition to the previously
mentioned antireflection multilayered article 3, substrate 2, and
hard coating layer 7.
[0139] For example, when the antireflection film is used at the
display of a computer, the stainproof layer 8 may be provided for
protection of the display surface from dirt. The stainproof layer 8
may be made from a fluoroalkyl group-containing organic silicon
compound, an alkyl group-containing organic silicon compound,
etc.
[0140] Method of Manufacturing Silica Layers and an Antireflection
Film Using the Same:
[0141] Next, a method of manufacturing the antireflection film of
the present invention will be described.
[0142] In the present invention, as long as an antireflection
multilayered article such as mentioned above can be formed, the
method of manufacturing the antireflection film is not particularly
limited. For example, one can employ any method, such as a vacuum
evaporation method, a sputtering method, a thermal CVD method, or
wet coating based on a sol-gel method, etc.
[0143] Among the above methods, it is preferable to use the plasma
CVD method for manufacturing the silica layers and the
antireflection film of the present invention.
[0144] Here, the plasma CVD method refers to a film-forming method
utilizing a phenomenon in which a plasma is generated within a
reaction chamber into which a predetermined gas is introduced, to
generate atomic or molecular radical species, which are then
adhered to the solid surface and further desorb volatile molecules
through their surface reaction in many cases, to be incorporated on
the solid surface. By forming the antireflection film of the
present invention with the plasma CVD method, a plurality of layers
can be collectively formed efficiently. In terms of power
application, the plasma CVD method comes in two types: a plasma CVD
method based on capacitive coupled plasma, and a plasma CVD method
based on inductive coupled plasma, either of which can be employed
in the present invention.
[0145] Here, of the above types of the plasma CVD method, it is
particularly preferable to use a plasma CVD system such as shown in
FIG. 3, because this plasma CVD system permits serial manufacture
of the antireflection film of the present invention, and accurate
control over the temperature of the polymeric film, which is the
substrate.
[0146] The plasma CVD system 30 shown in FIG. 3 is a plasma CVD
system based on capacitive coupled plasma where a web-like
polymeric film 31 is rolled off from a substrate roll-off section
32 for feeding into reaction chambers (a, b, c) in a vacuum
container 33. Then, predetermined layers are formed on a
layer-forming drum 34 within the respective reaction chambers, and
the thus layer-formed substrate is then rewound by a substrate
rewinding section 36.
[0147] This plasma CVD system 30 has a feature that a plurality
(three) of reaction chambers are arranged. The respective reaction
chambers (a, b, c) are formed while partitioned by partition walls
35. Here, for purposes of explanation to be given below, the three
reaction chambers are denoted as the reaction chamber a, the
reaction chamber b, and the reaction chamber c from the right-hand
end. The reaction chambers are provided with electrode plates a1,
b1, c1 and source gas inlets a2, b2, c2, respectively. The reaction
chambers (a, b, c) are provided along the outer periphery of the
layer-forming drum 34. This is because the polymeric film for
forming the antireflection multilayered article is supplied into
the reaction chambers in synchronism with the rotation of the
layer-forming drum 34 for formation of the antireflection
multilayered article on the layer-forming drum, whereby the
respective layers can be layered serially when such a layout is
adopted.
[0148] According to a plasma CVD system such as mentioned above, by
feeding different source gases into the respective chambers, the
layers can be formed independently inside the respective
chambers.
[0149] For example, in the antireflection film 1 shown in FIG. 1,
first, the hard coating layer 7 is formed on, for example, a PET
film 2 as the substrate by a conventional wet coating technique,
and the medium and high refractive index layers 6 and 5, both of
which are carbon-containing silica layers, and the silica layer 4
composed of an organic silicon compound as the outermost layer can
be formed thereafter by the plasma CVD system 30. That is, by
feeding silicon-containing gases as raw materials for the
respective layers into the reaction chambers a, b, c, the
antireflection film 1 can be formed, in which the silica layers as
medium and high refractive index layers and the silica layer (low
refractive index layer) as the outermost layer are formed on the
polymeric film 31, by the time the polymeric film 31 passing over
the layer-forming drum 34 is rewound onto the substrate rewinding
section 46.
[0150] In manufacturing the antireflection film 1 of the present
invention using the plasma CVD system shown in FIG. 3, organic
silicones are preferable as the raw materials for forming the
silica layers (low, medium, and high refractive index layers)
constituting the antireflection multilayered article 3.
Specifically, these raw materials include hexamethyldisiloxane
(HMDSO), tetramethyldisiloxane (TMDSO), methyltrimethoxysilane
(MTMOS), methylsilane, dimethylsilane, trimethylsilane,
diethylsilane, propylsilane, phenylsilane, tetramethoxysilane,
octamethylcyclotetrasiloxane, tetraethoxysilane, etc.
[0151] It should be noted that the present invention is not limited
to the above-mentioned antireflection film and its manufacturing
method. The above embodiments are illustrative, and therefore, any
embodiment having substantially the same arrangement as and
providing similar effects and advantages to the technical scope
recited in the appended claims will be included in the technical
scope of the present invention.
EXAMPLES
[0152] The present invention will be described in detail with
reference to examples thereof.
[0153] Silica Layer Composed of an Organic Silicon Compound and
Functioning as a Low Refractive Index Layer
Example 1
[0154] A silica layer was formed on a substrate using the system of
FIG. 3 as an example of the present invention. For its formation,
only the reaction chamber a was used, because the layer to be
formed is only a silica layer composed of an organic silicon
compound and functioning as a low refractive index layer. The
conditions under which the silica layer was formed are shown
below.
[0155] (Layer-forming Conditions)
[0156] Source gas:
(CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3+O.sub.2
[0157] Plasma generation means: RF wave at 13.56 MHz
[0158] Substrate: PET film (trade name: "Lumirror T60" manufactured
by Toray)
[0159] Under the above conditions, the silica layer having the
following properties was formed on the substrate.
[0160] Refractive index: 1.43
[0161] Composition: SiO.sub.1.6C.sub.0.5:H
[0162] Infrared absorption due to C--H stretching vibrations: 0.7
cm.sup.-1
[0163] Infrared absorption due to O--H stretching vibrations: 5.2
cm.sup.-1
[0164] It should be noted that a photoelectron spectrometer was
used for the composition analysis, that an infrared spectrometer
was used for the measurement of infrared absorptions, and that an
ultraviolet-visible spectrometer and an ellipsometer were used for
the measurement of optical properties.
[0165] Then, the refractive index of the above silica layer was
measured again after the layer was stood at 80.degree. C. and 90%
relative humidity for 1000 hours (humidity/heat resistance test)
using an environmental test machine. The result is shown below.
[0166] Refractive index after the humidity/heat resistance test:
1.43
Comparative Example 1
[0167] As a comparative example to the present invention, a silica
layer was formed using a known vacuum evaporation system, under the
following conditions.
[0168] (Layer-forming Conditions)
[0169] Evaporation source: SiO.sub.2
[0170] Means for vaporizing the source: Electron gun
[0171] Substrate: PET film (Trade name: "Lumirror T60" manufactured
by Toray)
[0172] Under the above conditions, the silica layer having the
following properties was formed.
[0173] Refractive index: 1.42
[0174] Composition: SiO.sub.1.8C.sub.0.1:H
[0175] Infrared absorption due to C--H stretching vibrations: 0
cm.sup.-1
[0176] Infrared absorption due to O--H stretching vibrations: 7
cm.sup.-1
[0177] It should be noted that the photoelectron spectrometer was
used for the composition analysis, that the infrared spectrometer
was used for the measurement of infrared absorptions, and that the
ultraviolet-visible spectrometer and the ellipsometer were used for
the measurement of optical properties.
[0178] Then, the refractive index of the above silica layer was
measured again after the layer was stood at 80.degree. C. and 90%
relative humidity for 1000 hours (humidity/heat resistance test)
using the environmental test machine. The result is shown
below.
[0179] Refractive index after the humidity/heat resistance
test:1.44
[0180] From the above results, it has become clear that the example
of the present invention exhibits a low refractive index and is
thus preferable as the outermost layer of an antireflection
multilayered article in an antireflection film, and even has
humidity/heat resistance. On the other hand, the comparative
example exhibits a lower refractive index than the example of the
present invention before the humidity/heat resistance test, but the
silica layer of the comparative example is very porous compared to
the silica layer of the example of the present invention, and hence
has no practicability as an antireflection film. Further, the
refractive index of the comparative example underwent a change by
0.02 after the humidity/heat resistance test.
[0181] Carbon-containing Silica Layer Functioning as a High or
Medium Refractive Index Layer
Example 2
[0182] A silica layer was formed using the system of FIG. 3 as an
example of the present invention. For its formation, only the
reaction chamber a was used, because the layer to be formed is only
a carbon-containing silica layer. The conditions under which the
silica layer was formed are shown below.
[0183] (Layer-forming Conditions)
[0184] Source gas: HMDSO((CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3),
O.sub.2, He
[0185] Plasma excitation frequency: 40 kHz
[0186] Substrate: PET film (trade name "Lumirror T60" manufactured
by Toray)
[0187] HMDSO flowrate: 1 slm
[0188] O.sub.2 gas flowrate: 1 slm
[0189] He gas flowrate: 0.5 slm
[0190] Power: 1 kW
[0191] Layer-forming pressure: 9.3 Pa
[0192] Layer-forming rate: 1.2 .mu.m.multidot.m/min
Example 3
[0193] A silica layer of the present invention was formed similarly
to Example 2 except for the following conditions.
[0194] (Layer-forming Conditions Different from Those of Example
2)
[0195] O.sub.2 gas flowrate: 0.5 slm
[0196] Power: 1.5 kW
[0197] Layer-forming pressure: 6.7 Pa
Example 4
[0198] A silica layer of the present invention was formed similarly
to Example 2 except for the following conditions.
[0199] (Layer-forming Conditions Different from Those of Example
2)
[0200] O.sub.2 gas flowrate: 0 slm
[0201] Power: 3 kW
[0202] Layer-forming pressure: 2.7 Pa
Example 5
[0203] A silica layer of the present invention was formed similarly
to Example 2 except for the following conditions.
[0204] (Layer-forming Conditions Different from Those of Example
2)
[0205] O.sub.2 gas flowrate: 0.2 slm
[0206] Power: 2 kW
[0207] Layer-forming pressure: 3.3 Pa
Comparative Example 2
[0208] A silica layer of a comparative example to the present
invention, was formed similarly to Example 2 except for the
following conditions. (Layer-forming conditions different from
those of Example 2)
[0209] Source gas: TMS (tetramethylsilane), O.sub.2, He
[0210] TMS flowrate: 1 slm
[0211] O.sub.2 gas flowrate: 0.2 slm
[0212] Power: 3 kW
[0213] Layer-forming pressure: 4.0 Pa
Comparative Example 3
[0214] A silica layer of a comparative example to the present
invention, was formed similarly to Example 2 except for the
following conditions.
[0215] (Layer-forming Conditions Different from Those of Example
2)
[0216] Source gas: TMOS (tetramethoxysilane), O.sub.2, He
[0217] TMOS flowrate: 1 slm
Comparative Example 4
[0218] A silica layer of a comparative example to the present
invention was formed under the following conditions using a known
winding type sputtering system.
[0219] (Layer-forming Conditions)
[0220] Target: p-Si
[0221] Feed gases: O.sub.2, Ar
[0222] O.sub.2 gas flowrate: 50 sccm
[0223] Ar gas flowrate: 450 sccm
[0224] Power: 3 kW
[0225] Layer-forming pressure: 3 mTorr
[0226] Layer-forming rate: 20 nm.multidot.m/min
[0227] As to the thus formed silicon layers of the present
invention which are Examples 2 to 5 and Comparative Examples 2 to
4, their compositions, refractive indices n (.lambda.=550 nm), and
extinction coefficients k (.lambda.=550 nm) are shown in Table 1
below. It should be noted that the photoelectron spectrometer was
used for the composition analysis, that the infrared spectrometer
was used for the understanding of chemical bonding in the silica
layers, and that the ultraviolet-visible spectrometer and the
ellipsometer were used for the measurement of optical
properties.
1 TABLE 1 Composition (SiO.sub.xC.sub.y) Value of x Value of y
(number of (Number of Refractive Extinction oxygen atoms) carbon
atoms) index n coefficient k Example 2 1.6 0.3 1.55 0.00089 Example
3 1.6 1.0 1.64 0.0045 Example 4 0.5 1.8 2.45 0.017 Example 5 0.5
1.0 1.97 0.014 Comparative 0.3 1.0 2.22 0.052 Example 2 Comparative
1.8 0.1 1.46 0.00021 Example 3 Comparative 1.0 1.0 1.95 0.034
Example 4
[0228] As can be understood also from Table 1, the silica layers
according to Examples 2 and 3 have refractive indices suitable for
medium refractive index layers, and so do the silica layers
according to Examples 4 and 5 for high refractive index layers. It
is also understood that each of the silica layers according to
Examples 1 to 4 has an extinction coefficient of 0.018 or less, and
hence has an excellent transparency.
[0229] On the other hand, it is understood that the silica layer
according to Comparative Example 2 has a refractive index which is
within the preferable range as a high refractive index layer, but
that the number of oxygen atoms in its composition is as small as
0.3. Therefore, the percentage of Si--Si bonds in the layer is so
large that its extinction coefficient is 0.018 or more. Hence, it
has become clear that this silica layer lacks transparency.
[0230] Further, it is understood that the silica layer according to
Comparative Example 3 has a number of carbon atoms C in its
composition which is as small as 0.1. Therefore, this silica layer
is analogous to a layer of pure silicon dioxide (SiO.sub.2) having
a small refractive index. Hence, it has become clear that a layer
is usable neither as a medium nor high refractive index layer.
[0231] Still further, the silica layer according to Comparative
Example 4 was formed by using the winding type sputtering system,
and thus its refractive index is within the preferable range as a
high refractive index layer, but its extinction coefficient is
0.018 or more, which makes it clear that this silica layer lacks
transparency.
[0232] Antireflection Film Using Silica Layers
Example 6
[0233] The antireflection film 1 shown in FIG. 1 was formed as an
example of the present invention using the system of FIG. 3. For
its formation, the carbon-containing silica layer 6 as a medium
refractive index layer was formed in the reaction chamber a, the
carbon-containing silica layer 5 as a high refractive index layer
was formed in the reaction chamber b, and the silica layer composed
of an organic silicon compound as a low refractive index layer was
formed in the reaction chamber a, whereby the three layers were
sequentially layered at a time. The conditions inside the
respective reaction chambers are shown below.
[0234] (Reaction Chamber a: Formation of the Silica Layer as a
Medium Refractive Index Layer)
[0235] Source gas:
(CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3+O.sub.2
[0236] source gas flowrate: 1 slm
[0237] O.sub.2 gas flowrate: 0.3 slm
[0238] He gas flowrate: 1.0 slm
[0239] Power: 1 kW
[0240] Pressure: 3 Pa
[0241] Plasma generation means: RF waves at 13.56 MHz
[0242] (Reaction Chamber b: Formation of the Silica Layer as a High
Refractive Index Layer)
[0243] Source gas:
(CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3+O.sub.2
[0244] source gas flowrate: 1 slm
[0245] O.sub.2 gas flowrate: 0 slm
[0246] He gas flowrate: 1 slm
[0247] Plasma generation means: RF waves at 13.56 MHz
[0248] (Reaction Chamber c: Formation of the Silica Layer as a Low
Refractive Index Layer)
[0249] Source gas:
(CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3+O.sub.2
[0250] source gas flowrate: 1.0 slm
[0251] O.sub.2 gas flowrate: 3.0 slm
[0252] Layer-forming rate: 0.25 .mu.m.multidot.m/min
[0253] Plasma generation means: RF waves at 13.56 MHz
[0254] Further, a PET film (trade name: "Lumirror T60" manufactured
by Toray) was used as the substrate 2, and a hard coating layer was
layered on the substrate by wet coating before superposing the
antireflection multilayered article using the plasma CVD
system.
[0255] (Properties of the Antireflection Film)
[0256] The antireflection film 1 shown in FIG. 1 was formed under
the above conditions.
[0257] The silica layer 4 composed of an organic silicon compound
(layered at the reaction chamber c) as the outermost layer of the
antireflection multilayered article 3 in the antireflection film 1
has the following properties.
[0258] Refractive index: 1.43
[0259] Composition: SiO.sub.1.6C.sub.0.5:H
[0260] Infrared absorption due to C--H stretching vibrations: 0.7
cm.sup.-1
[0261] Infrared absorption due to O--H stretching vibrations: 5.2
cm.sup.-1
[0262] The photoelectron spectrometer was used for the composition
analysis, the infrared spectrometer was used for measurement of
infrared absorptions, and the ultraviolet-visible spectrometer and
the ellipsometer were used for the measurement of optical
properties.
[0263] Then, the refractive index of the silica layer 4 composed of
an organic silicon compound was measured again after the
antireflection film 1 was stood at 80.degree. C. and 90% relative
humidity for 1000 hours (humidity/heat resistance test) using the
environmental test machine. The result is shown below.
[0264] Refractive index after the humidity/heat resistance
test:1.43
[0265] From the above, it has become clear that the silica layer 4
composed of an organic silicon compound as the outermost layer of
the antireflection multilayered article 3 in the antireflection
film 1 of the present invention exhibits a small refractive index
and thus suitable for the outermost layer, and even has
humidity/heat resistance.
[0266] Further, the carbon-containing silica layer 6 (layered at
the reaction chamber a) as a medium refractive index layer in the
antireflection multilayered article 3 of the antireflection film 1
has the following properties.
[0267] Refractive index: 1.76 (.lambda.550 nm)
[0268] Composition: SiO.sub.0.9C.sub.1.2
[0269] Extinction coefficient: 0.0042
[0270] The photoelectron spectrometer was used for the composition
analysis, the infrared spectrometer was used for the understanding
of chemical bonding in the silica layer, and the
ultraviolet-visible spectrometer and the ellipsometer were used for
the measurement of optical properties.
[0271] From the above results, it has become clear that the
carbon-containing silica layer 6 formed in this example has a
refractive index suitably usable as a medium refractive index layer
of the antireflection multilayered article in the antireflection
film, and is excellent in transparency due to its small extinction
coefficient.
[0272] Further, the carbon-containing silica layer 5 (stacked in
the reaction chamber b) as a high refractive index layer in the
antireflection multilayered article 3 of the antireflection film 1
has the following properties.
[0273] Refractive index: 2.10 (.lambda.550 nm)
[0274] Composition: SiO.sub.0.7C.sub.1.5
[0275] Extinction coefficient: 0.0008 (.lambda.550 nm)
[0276] It should be noted that the photoelectron spectrometer was
used for the composition analysis, that the infrared spectrometer
was used for the understanding of chemical bonding in the silica
layer, and that the ultraviolet-visible spectrometer and the
ellipsometer were used for the measurement of optical
properties.
[0277] From the above results, it has become clear that, similarly
to the silica layer 6 as a medium refractive index layer, the
carbon-containing silica layer 5 formed in this example has a
refractive index suitably usable as a high refractive index layer
of the antireflection multilayered article in the antireflection
film, and is excellent in transparency due to its small extinction
coefficient.
[0278] Further, by using a silica layer to form every layer of the
antireflection multilayered article 3 in the antireflection film 1
as in the above example, an antireflection film exhibiting good
antireflection performance, transparency, and adhesion between
layers was obtained.
[0279] In the antireflection multilayered article of the
antireflection film of the present invention, a silica layer
composed of an organic silicon compound is used as its outermost
layer, and at least one carbon-containing silica layer is formed
internally from the outermost layer, whereby the outermost layer
has bondings to organic moieties, such as methyl group
(CH.sub.3--), in addition to bondings between silicon atoms (Si)
and oxygen atoms (O) which are its essential constituents, and
hence the outermost layer can have a small refractive index without
providing voids therein. Further, due to the absence of voids, the
silica layer of the present invention has superior performance with
respect to humidity/heat resistance.
[0280] Further, the carbon-containing silica layer forming the
antireflection multilayered article can be used as the so-called
medium or high refractive index layer by setting its refractive
index between 1.55 and 2.50 (.lambda.=550 nm). Still further, this
carbon-containing silica layer is made from the same silicon oxide
(SiO.sub.x) as that of the silica layer used as the outermost
layer, and hence can improve the yield of forming the
antireflection multilayered article, reduce cost, and can even
improve adhesion between the layers forming the antireflection
multilayered article. Also, this carbon-containing silica layer has
an extinction coefficient of 0.018 (.lambda.550 nm) or less, and
thus is sufficiently transparent, whereby it can be suitably used
as a layer in an antireflection multilayered article for forming an
antireflection film applied to various displays, such as
liquid-crystal displays, and plasma displays, for example.
[0281] The entire disclosure of Japanese Patent Applications Nos.
2000-298728 filed on Sep. 29, 2000; 2000-298729 filed on Sep. 29,
2000; and 2000-336287 filed on Nov. 2, 2000, including their
specifications, claims, drawings and summaries is incorporated
herein by reference in its entirety.
* * * * *