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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating material used for antistatic high
refractive index film formation, as well as to an
antistatic/anti-reflection film covered transparent laminated body and an
antistatic/anti-reflection film covered cathode ray tube using this
coating material.
In particular, the present invention relates to coating material for
antistatic/high refractive index film formation which is useful as coating
material for transparent substrate surfaces requiring prevention of
electrostatic charge and/or prevention of reflection, such as, for
example, display screens of display apparatuses, covering materials for
these surfaces, window glass, glass for show windows, display screens of
TV Braun tubes, display screens of liquid crystal devices, covering glass
for gauges, covering glass for watches, windshield and window glass for
automobiles, and image display screens of cathode ray tubes, as well as to
antistatic/anti-reflection film covered laminated bodies composed of
antistatic/high refractive index films using this coating material and low
refractive index films, and to cathode ray tubes, at least the image
display of which comprises this transparent laminated body, and which are
provided with various functions such as antistatic functions,
electromagnetic wave shielding functions, anti-reflection functions, and
image contrast improvement functions and the like.
2. Background Art
Electrostatic charge builds up easily in transparent substrates for image
display, for example, in image display parts of TV Braun tubes, and as a
result of this electrostatic charge, a problem is known wherein dust
gathers on the display screen. Furthermore, problems are known wherein
external light is reflected in the image display screen, or external
images are reflected, and thus the images on the display screen become
unclear.
In order to to solve the above-described problems, conventionally, a fluid
in which finely powdered tin oxide doped with antimony (ATO) was dispersed
in a nonaqueous solvent such as the hydrolytic product of silicon alkoxide
(hereinbelow termed "silica gel") was applied and desiccated to form an
antistatic film on, for example, the surface of a transparent substrate,
and a low refractive index film having a refractive index lower than that
of the antistatic film was then formed on this antistatic film. That is to
say, using a coating material comprising a non-aqueous dispersion fluid
containing a mixture of the antimony doped tin oxide fine powder described
above and silica sol, an antistatic film was formed, and on this, a
coating material comprising a nonaqueous dispersion fluid of silica sol
was applied and a low refractive index film was formed.
Furthermore the cathode ray tube which forms the TV Braun tube or the
display of a computer or the like displays characters or images or the
like by causing an electron beam from an electron gun to impact a
fluorescent screen which emits red, green, and blue light. This cathode
ray tube radiates an electromagnetic wave as a result of the emission of
this high voltage electron beam, and there are cases in which undesirable
effects are exerted on human beings or machines in the vicinity thereof.
Furthermore, when the electron beam collides with the fluorescent body or
bodies, a static charge is generated on the front surface of the
faceplate.
Conventionally, in order to solve the above problems, a transparent and
electrically conductive oxide film comprising, for example, indium oxide
or the like, was formed by the sputtering method or the vapor deposition
method on a faceplate, and this faceplate was applied to the front surface
of the face panel and thus electromagnetic wave shielding was conducted;
alternatively, a transparent and electrically conductive film was formed
by coating the front surface of the face panel with a silica type binder
dispersion fluid containing antimony doped tin oxide and silica sol or the
like, and an antistatic effect was imparted to the front surface of the
face panel. Furthermore, as shown in the following formula, in order to
improve image contrast, cathode ray tubes were proposed in which colorants
such as pigments or the like were included in the antistatic coating
fluid, and thus antistatic effects and an increase in contrast were
achieved.
C.sub.r =(.pi.B/RT.sub.g L)+1
C.sub.r : contrast
B: fluorescent screen brightness
T.sub.g : light transmittance of glass
L: external light illumination
R: fluorescent screen reflectivity
Furthermore, cathode ray tubes have also been proposed in which colored
antistatic coating fluids are applied by being sprayed onto the display
screen, and a film with surface irregularities is thereby formed, thus
providing the cathode ray tube with an anti-reflection effect as a result
of light scattering.
The refractive index of the conventional antistatic film described above is
within a range of n=1.50 to 1.54, and the difference between this
refractive index and the refractive index of the low refractive index film
which is formed by means of the hydrolytic product of silicon alkoxide
(silica sol) is small, so that accordingly, the anti-reflection effect
created by means of the combining of such a conventional antistatic film
and a low refractive index film is insufficient, and such a product was
thus not suitable for practical application.
Furthermore, cathode ray tubes which were obtained by a method in which a
faceplate having formed thereon a transparent and electrically conductive
film such as, for example, indium oxide or the like, by means of the
sputtering method or vapor deposition method, was applied to a display
screen, are extremely expensive. Moreover, in cathode ray tubes having
applied thereto an antistatic/optical filter, obtained by a method in
which a colored antistatic fluid was coated thereon, possess insufficient
electric conductivity, so that sufficient electromagnetic shielding
effects could not obtained, and furthermore, in the case of cathode ray
tubes having applied thereto antistatic/optical filter/anti-reflection
functions formed by means of a method in which colored antistatic coating
fluid was applied by spraying, as a result of these surface irregularities
of the film which was thus formed, a problem existed in that as a result
of the surface irregularities of the film which was thus formed, the
degree of resolution of the images declined sharply.
SUMMARY OF THE INVENTION
The present invention was created in light of the above circumstances; it
has an object thereof to provide a coating material for formation of an
antistatic/high refractive index film possessing superior antistatic
effects, as well as an antistatic/anti-reflection film covered transparent
material laminated body provided with superior antistatic effects and
anti-reflection effects obtained by means of the use of this coating
material, and a cathode ray tube possessing this laminated body which is
provided with antistatic effects, electromagnetic wave shielding effects,
anti-reflection effects, and the effect of increase in contrast.
It was discovered that by mixing an antimony doped tin oxide fine powder
with a black colored electrically conductive fine powder, the problems
present in the background art described above could be solved, and based
on this discovery, the present invention was accomplished.
That is to say, the coating material for use in formation of an
antistatic/high refractive index film in accordance with the present
invention is characterized by comprising a dispersion fluid containing a
mixture of an antimony doped tin oxide fine powder and a black colored
electrically conductive fine powder.
Furthermore, the antistatic/anti-reflection film covered transparent
material laminated body in accordance with the present invention is
characterized by containing: a transparent substrate; an antistatic/high
reflective index film layer, formed by the application and the desiccation
of a coating material comprising a dispersion fluid containing a mixture
of antimony doped tin oxide fine powder and black colored electrically
conductive fine powder on the surface of the transparent substrate; and a
low refractive index film layer, which is formed on this antistatic/high
refractive index film layer and which possesses a refractive index which
is 0.1 or more lower than the refractive index of the antistatic/high
refractive index film layer.
Furthermore, in the cathode ray tube in accordance with the present
invention, the formation on at least the front surface thereof of a first
layer film containing a mixture of an antimony doped tin oxide fine
powder, and a black colored electrically conductive fine powder, and of a
second layer film, which is formed on the first layer film and which
contains silica sol which is obtained by the hydrolysis of silicon
alkoxide, was used as the means for the solution of the problems described
above.
According to the present invention, a black colored conductive fine powder,
for example, carbon black fine powder, which is light absorbing and
possesses a higher conductivity than antimony doped tin oxide fine powder,
is added to the antimony doped tin oxide fine powder; that is to say, a
conductive fine powder (ATO) and a black colored conductive fine powder
are mixed, in other words two types of conductive fine powder are added
together, and thereby, it is possible to produce an application fluid for
use in formation of an antistatic/high refractive index film possessing a
more superior two-type antistatic effect.
It is for this reason that the antistatic/high refractive index film layer
obtained by the use of the coating material for use in formation of an
antistatic/high refractive index film layer in accordance with the present
invention exhibits an extremely superior antistatic effect and
electromagnetic wave shielding effect. In addition, the antistatic/high
refractive index film layer exhibits a high refractive index.
In the transparent laminated body in accordance with the present invention,
the reflected light at the substrate surface is reduced, so that by
providing a low refractive index film having an index of refraction which
is more than 0.1, and preferably more than 0.15, less than that of the
antistatic/high refractive index film on the antistatic/high refractive
index film, it is possible to provide extremely superior anti-reflection
effects.
Accordingly, the laminated body of the present invention is extremely
useful in display screens of display devices, covering materials for the
surfaces thereof, window glass, show window glass, display screens of TV
Braun tubes, display screens of liquid crystal apparatuses, covering glass
for gauges, covering glass for watches, windshield and window glass for
automobiles, and front image screens of CRTs'.
Furthermore, when an antistatic/high refractive index film layer and a low
refractive index film layer obtained by means of the present invention are
combined into a single film and formed on a display screen of a Braun tube
or the like, the effects achieved are not merely those of an increase in
visibility resulting from the prevention of reflection and antistatic
effects, but rather, as the display screen possesses an antimagnetic wave
shielding effect, and as the display screen has a black color, image
contrast is improved, and visibility is further improved as a result
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing a cathode ray tube (TV Braun tube) in
accordance with Preferred Embodiments 16, 17, and 18 of the present
invention, from which a portion has been removed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinbelow, the present invention will be explained in detail.
First, the coating material for use in formation of an intistatic/high
refractive index film in accordance with the present invention will be
explained.
In the mixture of antimony doped tin oxide fine powder and black colored
electrically conductive fine powder which is used in the coating material
for formation of an antistatic/high refractive index film, the proportion
of the amount contained of the black colored electrically conductive fine
powder and the amount contained of the antimony doped tin oxide fine
powder should preferably be within a range of 1:99 to 30:70. If the amount
contained of black colored conductive fine powder exceeds 30 parts by
weight with respect to 100 parts per weight of the total of the black
colored electrically conductive fine powder and the antimony doped tin
oxide fine powder, the amount of black colored electrically conductive
fine powder will be excessive, and the transparency of the film layer
obtained will sharply decrease, and in the case in which such a laminated
film is formed on the display screen of a display apparatus, the
visibility will become extremely poor.
Furthermore, when the amount contained of the black colored electrically
conductive fine powder is less than 1 part per weight with respect to 100
parts per weight of the total of the black colored electrically conductive
fine powder and the antimony doped tin oxide fine powder then the
conductivity of the antistatic/high refractive index film layer which is
obtained will not increase, and furthermore, almost no light absorption is
generated, so that, even if a low refractive index film layer is formed on
the antistatic/high refractive index film layer, only antistatic and
anti-reflection effects which are identical to the conventional effects
can be obtained, and these effects are insufficient for such an antistatic
and anti-reflection film.
The black colored electrically conductive fine powder which is used in the
present invention may be of a black, gray, blackish gray, or blackish
brown shade, and must be a fine powder which possesses conductivity. For
example, fine powders which may be employed include, for example, oxide
fine powders, sulfide fine powders, or metallic fine powders, such as
carbon black, titanium black, metallic silicon, tin sulfide, mercury
sulfide, metallic cobalt, metallic tungsten, or the like. In particular,
carbon black fine powders such as kitchen black, furnace black, graphite
powder, and the like, are preferable.
In the case of the use of a carbon black fine powder, no special
restriction is made with respect to particle diameter; however, from the
point of view of dispersion stability of the coating material, it is
preferable that a powder having a particle diameter of less than 1
micrometer be employed.
In the antimony doped tin oxide fine powder which is used in the present
invention, the tin oxide may be produced by one of the previously known
methods: the gas phase method (wherein the appropriate compound is
gasified and then cooled and solidified in the gas phase), the CVD method
(wherein the component elements are gasified, reacted in the gas phase,
and the product is cooled and solidified), and the carbonate (or oxalate)
method (wherein carbonates or oxalates of the appropriate metallic
elements are converted in the gas phase, are cooled, and are. solidified).
Furthermore, an acid alkaline method in which an aqueous solution of
fluorides of the component elements and an aqueous solution of a basic
compound are mixed and reacted, and an ultra-fine grained sol of the
target compound is produced, or a hydrothermal method in which the solvent
is then removed, may be employed in the production of the antimony doped
tin oxide fine powder. In the above hydrothermal method, it is possible to
conduct the growth, spheroidizing, or surface reformation of the fine
particles. Furthermore, no separate restriction is made with the respect
to the form of these fine particles; a shape such as a spherical shape, a
needle shape, a plate shape, or a chain shape or the like may be employed.
No particular restriction is made with respect to the doping method of the
antimony with respect to the tin oxide. Furthermore, it is preferable that
the doped amount of antimony be within a range of 1 to 5 weight percent
with respect to the weight of the tin oxide. By means of this type of
antimony doping, the antistatic effects and electromagnetic wave shielding
effects of the tin oxide fine powder will be further increased.
Furthermore, with respect to the particle diameter of the antimony doped
tin oxide, it is preferable that the average particle diameter be within a
range of 1 to 100 nm. The reason for this is that if the average particle
diameter is less than 1 nm, the conductivity decreases, and as the
particles coagulate easily in the coating material, a uniform dispersion
becomes difficult, and furthermore, the viscosity thereof increases and
dispersion problems are caused, and as a result of increasing the
necessary amount of solvent in order to prevent such problems, the
concentration of the antimony doped tin oxide fine powder becomes too low.
Furthermore, when the average particle diameter exceeds 100 nm, the
antistatic/high refractive index film layer exhibits striking irregular
reflection of light as a result of Rayleigh scattering, and the degree of
transparency decreases so as to make the product white in appearance.
Furthermore, dispersants such as anionic surfactants, cationic surfactants,
ampholytic surfactants, and non-ionic surfactants may be used to disperse
the carbon black fine powder; a polymeric dispersant is preferably used.
In the case in which a polymeric dispersant is used in the coating material
for formation of an antistatic/high refractive index film of the present
invention, it is preferable to use a mixture in which 0.01 to 0.5 weight
percent of polymeric dispersant is added to 100 parts by weight of the
fine powder mixture comprising antimony doped tin oxide fine powder and
black colored electrically conductive fine powder. The reason for this is
that if the amount of polymeric dispersant exceeds 0.5 parts per weight,
the thickness of the adhesion layer of the dispersant becomes too large
and the contact between particles is hindered, and the conductivity of the
antistatic/high refractive index film layer which is obtained thereby
cannot be increased, and furthermore, even if a low refractive index film
layer is formed on this film layer, only those antistatic/anti-reflection
effects which were obtainable with the conventional technology can be
obtained. On the other hand, when the amount is less than 0.01 parts per
weight, the dispersion of the fine particles is insufficient, and the fine
particles coagulate, so that the conductivity of the antistatic/high
refractive index film layer which obtained cannot be increased, and
accordingly, even if a low refractive film index layer is formed on this
film layer, sufficient antistatic/anti-reflection effects cannot be
obtained; furthermore, as a result of the coagulation of the particles,
the degree of haze present in the film becomes high.
Anionic polymeric surfactants possessing carboxylic acid or sulfonic acid
groups, specific examples of which include polymeric polycarboxylate,
polystyrene sulfonate, and salts of naphthalene sulfonic acid condensates
may be used as the polymeric dispersant, and these polymeric dispersants
may be used singularly or in a mixture of two or more of the above. It is
also possible to use this type of polymeric dispersant concurrently with
the anionic surfactants which were conventionally employed; however with
only the anionic surfactants which were present is conventional detergents
and the like, the dispersion does not increase in comparison with the case
in which only polymeric dispersant is used, and as a result, it is
impossible to sufficiently achieve an increase in fineness and an increase
in refractive index of the first layer, and furthermore, bubbling becomes
strong and surface tension decreases excessively, so that during the
formation of the low refractive index film layer, wettability becomes
poor, and it is impossible to sufficiently obtain the object of the
present invention.
The dispersion fluid comprising the coating material for formation of an
antistatic/high refractive index film of the present invention may be a
mixture in which, in addition to solid components comprising an antimony
doped tin oxide fine powder and a black colored electrically conductive
fine powder, a solvent possessing a high boiling point and a high surface
tension is included.
It is preferable that the above-described solvent have a boiling point
above 150.degree. C. and a surface tension of 40 dyne/cm or greater.
It is preferable that the above solvent be selected from a group comprising
ethylene glycol, propylene glycol, formamide, dimethyl sulfoxide, and
diethylene glycol.
Examples of the high boiling point/high surface tension solvent used in the
present invention include, for example, ethylene glycol, propylene glycol,
formamide, dimethyl sulfoxide, diethylene glycol, and the like, and a
mixture of two or more of these solvents may also be used.
It is possible to concomitantly use other solvents; however it is necessary
to select and adopt an appropriate solvent, which will permit satisfactory
film formation without the loss of the conductivity and high refractive
index which comprise objects of the present invention, by means of
preparatory experiments in which the types of solvents present in the
dispersion fluid, or the proportions thereof, are varied.
In the dispersion fluid containing solid components comprising antimony
doped tin oxide fine powder and black colored conductive fine powder and a
solvent possessing a high boiling point and high surface tension, it is
preferable that the solvent having a high boiling point and a high surface
tension be present in the dispersion fluid in an amount within a range of
0.1 to 10 parts per weight with respect to 100 parts per weight of the
dispersion fluid. If the proportion of solvent possessing a high boiling
point and a high surface tension in the dispersion fluid exceeds 10 parts
per weight, there are cases in which the time required for vaporization of
the solvent becomes excessive, thus causing irregularities in desiccation.
For this reason, when a low refractive index film is applied on this film,
inter-layer mixing occurs, and film formation of the second layer film
cannot be conducted according to plan, so that sufficient conductivity and
anti-reflection characteristics cannot be obtained. On the other hand,
when the amount of this solvent is less than 0.1 parts per weight, the
attraction between particles is insufficient, and the filling of particles
within the film cannot be increased, so that the increase in fineness and
increase in refractive index of the film cannot be sufficiently achieved.
For this reason, the conductivity of the antistatic/high refractive index
film which is obtained cannot be increased, and even if the low refractive
index film is formed on top of this film, only those
antistatic/anti-reflection effects which were obtainable in the
conventional art can be obtained.
Furthermore, in order to fix the antimony doped tin oxide particles or the
carbon black particles on the substrate, an inorganic binder such as
silicon oil, silicon alkoxide hydrolytic product or the like, or an
organic binder such as acrylic resin, urethane resin, epoxy resin, or the
like, may be added. Furthermore, in such a case, in order to obtain the
conductivity which is an object of the present invention, it is necessary
to appropriately select such a binder by conducting preparatory tests in
which the weight ratio (binder)/(conductive powder) is varied.
The dispersants and binders may be used even in cases in which black
colored conductive fine powders other than carbon black are used.
The coating material for use in the formation of the first layer of film
described above is obtained by the mixing and dispersion of antimony doped
tin oxide fine powder and black colored conductive fine powder and a
dispersant and/or a solvent possessing a high boiling point and a high
surface tension, by means of a method in which mixing and dispersion is
conducted in water or in an organic solvent using an ultrasonic
homogenizer or a sand mill or the like.
Next, an explanation will be made of the antistatic/anti-reflection film
coated transparent material laminated body in accordance with the present
invention.
Examples of the transparent substrate which is used in the transparent
material laminated body include substrates selected from a group
consisting of glass materials, plastic materials and the like. The coating
material of the present invention is applied to this transparent
substrate, is desiccated to form an antistatic/high refractive index film
layer, and furthermore, on this antistatic/high refractive index film
layer, a low refractive index film layer is formed which has a refractive
index which is 0.1 or more less than the refractive index of the
antistatic/high refractive index film layer, and thereby, the transparent
material laminated body of the present invention is obtained.
The substrate for use in the laminated body of the present invention is
preferably of transparent material; however, the material for the
substrate is not limited thereto, and ferrous material, aluminum material
and other nonferrous metal material, or alloys thereof are also applicable
as the substrate as well as wood or concrete.
No particular limitation is made with respect to the thickness of the
antistatic/high refractive index film layer Which is formed on the
transparent substrate; however in general, a thickness in the range of
0.05 to 0.5 micrometers is preferable.
A low refractive index film layer is formed on the antistatic/high
refractive index film layer which is formed using the coating material of
the present invention. The low refractive index film layer fills the
cavities present in the antistatic/high refractive index film layer
surface, suppresses light scattering, and is effective in increasing the
resistance to abrasion.
It is possible to form the low refractive index film layer by applying a
coating material comprising a nonaqueous solution containing silicon
alkoxide to the antistatic/high refractive index film layer, desiccating
this, and subjecting this to a baking process.
The silicon alkoxide which is used in the coating material for the
formation of a low refractive index film described above may be selected
from a group comprising tetraalkoxy silane type compounds, alkyltrialkoxy
silane type compounds, dialkyldialkoxy silane type compounds, and the
like, and furthermore, the nonaqueous solvent may be selected from a group
containing alcohol type compounds, glycol-ether type compounds, ester type
compounds, and ketone compounds.
These compounds may be used singly, or in a mixture of two or more of the
above.
When the above-described coating material is applied to the antistatic/high
refractive index film layer, is desiccated, and is subjected to a baking
process, the silicon alkoxide hydrolytic product thereof is silica. The
index of refraction of silica is n=1.46, which is lower than the
refractive index of antimony doped tin oxide; however, in order to
increase the size of the difference in refractive index between the
antistatic/high refractive index film layer and the low refractive index
film layer, the concomitant use of a substance having a refractive index
which is lower than that of silicon and having high transparency is
preferable.
In the present invention, it is preferable to include magnesium fluoride
(n=1.38) fine powder in the coating material containing silicon alkoxide.
No particular limitation is made with respect to the percentage of
magnesium fluoride fine powder which is contained in the low refractive
index film layer, and it is possible to appropriately set this percentage
in accordance with the structure of the antistatic/high refractive index
film layer; however, in general, an amount within a range of 0.01 to 80
percent with respect to the weight of silicon alkoxide (SiO.sub.2
conversion) is preferable.
It is preferable that the magnesium fluoride fine powder which is used in
the formation of the low refractive index film layer have an average
particle diameter within a range of 1 to 100 nm. If the average particle
diameter exceeds 100 nm, in the low refractive index film layer which is
obtained, light will be irregularly reflected as a result of Rayleigh
scattering, and the low refractive index film layer will appear white, so
that the transparency thereof declines.
Furthermore, when the average particle diameter of the magnesium fluoride
fine powder is less than 1 nm, the fine particles coagulate easily, and
accordingly, uniform dispersion of the fine particles in the coating
material becomes difficult, and the viscosity of the coating material
becomes excessive. Furthermore, when the amount of solvent used is
increased in order to reduce the viscosity of the coating material, a
problem is caused in that the concentration of the magnesium fluoride fine
powder and the silicon alkoxide in the coating material is decreased.
The magnesium fluoride fine powder which is used in the present invention
may be produced by means of a previously known method, such as a gas phase
method, the CVD method, the carbonate or oxalate method, or the like.
Furthermore, it is possible to use an acid alkaline method, in which
aqueous solutions of fluorides of the component elements and aqueous
solutions of basic compounds are mixed and reacted, an ultrafine grained
sol of the target compound is produced, or to use a hydrothermal method,
in which the solvent is then removed, for the production of the magnesium
fluoride fine powder. In the above-described hydrothermal method, it is
possible to conduct the growth, spheroidizing, or surface reformation of
the fine particles. Furthermore, a spherical shape, a needle shape, a
plate shaped, or a chain shape are satisfactory shapes for these fine
particles.
In the present invention, no particular limitation is made with respect to
the thickness of the low refractive index film layer; however, a thickness
within a range of 0.05 to 0.5 micrometers is preferable. The reason for
this is that a low refractive index film layer having a thickness within
the above described range is comparatively thin, so that even if such a
film layer covers the antistatic/high refractive index film layer, as a
result of the conductivity of the antistatic/high refractive index film
layer, antistatic effects and electromagnetic wave shielding effects which
are sufficient for practical application can be exhibited.
Next, an explanation will be made of the creation of the
antistatic/anti-reflection film covered transparent material laminated
body of the invention
First, a first layer is created on a transparent substrate, using the
coating material for formation of an antistatic/high refractive index film
described above.
Next, a second layer film is formed on the first layer film which is thus
obtained, by use of the coating material for formation of a low refractive
index film described above.
Concrete examples of coating materials used in the second layer include,
for example, solvents in which a silicon alkoxide such as tetramethoxy
silane, tetraethoxy silane, methyl trimethoxy silane or the like, are
added to an alcohol such as methanol, ethanol, propanol, butanol, or the
like, an ester such as ethyl acetate, an ether such as diethyl ether or
the like, a ketone, an aldehyde, or one or a mixture of two or more
organic solvents such as ethyl cellosolve, and water, and acid such as
hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or the
like is added thereto, hydrolysis is carried out, and silica sol is
produced.
The spin coat method, the spray method, the dip method, or the like may be
used as the application method for the coating material which is used in
the formation of the first and second layers. In the case described below
in which this is applied to a cathode ray tube, it is preferable that the
spin coat method be employed in order to form a film having a uniform
thickness on the front surface.
In an antistatic/anti-reflection film coated transparent material laminated
body obtained in this manner, in the first layer antistatic/high
refractive index film layer, a black colored conductive fine powder having
a higher conductivity than the antimony doped tin oxide is added to the
antimony doped tin oxide, and thereby, in addition to the antistatic
effect, an electromagnetic wave shielding effect, and the effect of an
increase in screen contrast by means of light absorption, are exhibited.
Furthermore, on the first layer film, a low refractive index film layer
(second layer) having a lower index of refraction than the first layer
film is formed, and thereby, as a result of a combination of the first
layer and the second layer, an optical anti-reflection effect is
exhibited.
Furthermore, the transparent material laminated body described above may be
concretely employed in a cathode ray tube.
This cathode ray tube is comprised by forming a first layer high refractive
index film, containing a solid component in which antimony doped tin
oxide, and at least one of carbon black fine powder, graphite fine powder,
and titanium black fine powder, which have higher conductivity than
antimony doped tin oxide, is simultaneously present, on the image display
screen (face panel) of the front surface of a cathode ray tube, and on top
of this, forming a second layer low refractive index film containing
silica sol which is obtained by the hydrolysis of silicon alkoxide.
In the first layer film formed by means of the above-described coating
material, a black colored conductive fine powder having a higher
conductivity than antimony doped tin oxide is added to antimony doped tin
oxide, and by means of this, in addition to an antistatic effect, an
electromagnetic wave shielding effect, and an effect of an increase in
image contrast as a result of light absorption, can be achieved.
Furthermore, by forming a second layer film on top of the first layer
film, which second film has a lower index of refraction than the first
layer, it is possible to achieve an optical anti-reflection effect by
means of the combination of the first layer and the second layer.
Furthermore, a cathode ray tube in which a first layer high refractive
index film is formed from an aqueous dispersion fluid comprising antimony
doped tin oxide, and at least one of carbon black fine powder, graphite
fine powder, and titanium black fine powder, which have higher
conductivities than antimony doped tin oxide and absorb light, and
furthermore a polymeric dispersant selected from a group containing
polycarboxylic acid, polystyrene sulfonic acid, and naphthalene sulfonic
acid condensate salts, is formed, and on this, a second layer low
refractive index film containing silica sol obtained by the hydrolysis of
silicon alkoxide is formed.
Hereinbelow, the functions and effects obtained by the use of the
antistatic/high reflective index film layer of the present invention,
which contains the antimony doped tin oxide fine powder and black colored
conductive fine powder obtained as described above, will be explained.
In conventional coating materials for formation of antistatic films which
did not contain black colored conductive fine powder, the change in
conductivity and increase in index of refraction of the antistatic/high
refractive index film layer was determined solely by the antimony doped
tin oxide fine powder.
However, in the present invention, a black colored conductive fine powder,
for example, carbon black fine powder, which is light absorbing and
possesses a higher conductivity than antimony doped tin oxide fine powder,
is added to the antimony doped tin oxide fine powder; that is to say, a
conductive fine powder (ATO) and a black colored conductive fine powder
are mixed, in other words two types of conductive fine powder are added
together, and thereby, it is possible to produce an application fluid for
use in formation of an antistatic/high refractive index film possessing a
more superior two-type antistatic effect.
It is for this reason that the antistatic/high refractive index film layer
obtained by the use of the coating material for use in formation of an
antistatic/high refractive index film layer in accordance with the present
invention exhibits an extremely superior antistatic effect and
electromagnetic wave shielding effect. In addition, the antistatic/high
refractive index film layer exhibits a high refractive index within a
range of n=1.55 to 2.0.
Furthermore, in the coating material for formation of an antistatic/high
refractive index film comprising an aqueous dispersion fluid containing a
mixture of antimony doped tin oxide fine powder, black colored conductive
fine powder, and a polymeric dispersant, a polymeric dispersant is added
to antimony doped tin oxide fine powder and carbon black fine powder, so
that the polymeric dispersant adheres to the surfaces of the antimony
doped tin oxide fine powder and the carbon black fine powder, and it is
thereby possible to greatly improve the dispersion of these fine powders.
Accordingly, when this coating material is applied and desiccated, the
coagulation of the particles is prevented, the filling ratio of the film
is increased, and a state approaching maximum density filling is produced.
By means of this, the contact between particles is further improved, and a
superior antistatic effect can be obtained. Furthermore, by means of an
extreme reduction in gaps between particles, a high refractive index
within a ratio of n=1.6 to 2.0 is exhibited.
Furthermore, in a coating material comprising a dispersion fluid containing
a mixture of solid components comprising an antimony doped tin oxide fine
powder and a black colored conductor for fine powder and a solvent
possessing a high boiling point and high surface tension, in the
processing in which this coating material is applied on a substrate and
desiccated, even if other highly volatile solvents are present, after the
vaporization thereof, the solvent possessing a high boiling point and high
surface tension is present in the film until the point in time immediately
prior to desiccation. When this solvent is vaporized, as it possesses high
surface tension, the solvent draws the particles together, and by means of
this, the filling of the film is increased, and a state approximating
maximum density filling is produced. By means of this, the contact of the
particles can be improved. In addition, an effect is obtained of
strikingly reducing the gaps between particles. As a result, a film is
formed which is finely filled with solid components, and a film possessing
an antistatic effect and an increase in refractive index which are
superior to those of conventional examples is realized. As a result, the
antistatic/high refractive index film which is obtained by use of the
coating material for formation of an antistatic/high refractive index film
exhibits extremely superior antistatic effects and electromagnetic wave
shielding effects. In addition, the antistatic/high refractive index film
exhibits a high index of refraction within a range of n (index of
refraction)=1.6 to 2.0.
In the transparent laminated body in accordance with the present invention,
the reflected light at the substrate surface is reduced, so that by
providing a low refractive index film having an index of refraction which
is more than 0.1, and preferably more than 0.15, less than that of the
antistatic/high refractive index film on the antistatic/high refractive
index film, it is possible to provide extremely superior anti-reflection
effects. This is the case because the reflected light from the low
refractive index film surface and the reflected light from the
antistatic/high refractive index film boundary tend to cancel one another
out as a result of interference, and furthermore, as a result of the
carbon black particles present in the high refractive index film, the
external light which penetrates the antistatic/high refractive index film
is absorbed. By means of this, it is possible to increase the
anti-reflection effect to a level greater than that present in the
conventional art.
The above-described coating material for formation of antistatic/high
refractive index films makes possible the easy formation of a film layer
having superior antistatic properties and a high index of refraction on
the transparent substrate, and in particular, by means of combining an
antistatic/high refractive index film layer obtained by the use thereof
with a low refractive index layer, it is possible to provide an
antistatic/anti-reflection film covered transparent material laminated
body which is well suited to practical applications.
That is to say, by means of the use of a coating material containing
antimony doped tin oxide fine powder and black colored conductive fine
powder, that is to say, a coating material containing two types of
conductive particles, it is possible to obtain an antistatic/high
refractive index film layer possessing strong antistatic properties and a
high index of refraction. By means of combining this antistatic/high
refractive index film layer with a low refractive index layer, it is
possible to obtain an antistatic/anti-reflection film coated transparent
material laminated body possessing superior antistatic properties and
anti-reflection properties.
Because the laminated body of the present invention exhibits these types of
effects, it is extremely useful in display screens of display devices,
covering materials for the surfaces thereof, window glass, show window
glass, display screens of TV Braun tubes, display screens of liquid
crystal apparatuses, covering glass for gauges, covering glass for
watches, windshield and window glass for automobiles, and front image
screens of CRTs.
Furthermore, when an antistatic/high refractive index film layer and a low
refractive index film layer obtained by means of the present invention are
combined into a single film and formed on a display screen of a Braun tube
or the like, the effects achieved are not merely those of an | | |
