Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
1998-07-07
2002-06-25
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
Reexamination Certificate
active
06411028
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conductive anti-reflection film that functions as an anti-reflection film and prevents AEF (Alternative Electric Field) from taking place and to a cathode ray tube that suppresses light from reflecting on an outer surface of a face panel and thereby prevents the AEF from taking place.
2. Description of the Related Art
An electron gun and a deflection yoke of a cathode ray tube such as a TV Braun tube, a computer monitor, or the like generate electromagnetic waves.
So far, the possibility of which electromagnetic waves that leak out from a cathode ray tube adversely affects adjacent electronic devices has been pointed out.
To prevent the electromagnetic waves (electric field) of a cathode ray tube from leaking out, a method for decreasing the surface resistance of the face panel of the cathode ray tube has been proposed.
For example, Japanese Patent Laid-Open Application Nos. 61-118932, 61-118946, and 63-160140 disclose various surface treatment methods for preventing a face panel from being charged. With these methods, the AEF has been prevented. As methods for forming a conductive layer with a low surface resistance on a face panel, gas phase methods such as PVD method, CVD method, and spattering are known. For example, Japanese Patent Laid-Open Application No. 1-242769 discloses a method for forming a transparent low-resistance conductive layer using spattering method.
Generally, the refractive index of a conductive layer is high. Thus, it is difficult to have a sufficient anti-reflection effect with only a conductive layer. Consequently, to satisfy both properties of conductivity and anti-reflection and to protect a conductive layer, the conductive layer of the conductive anti-reflection film is covered with an anti-reflection layer containing SiO
2
and having a low refractive index. However, the surface resistance of the anti-reflection layer that contains SiO
2
and has a low refractive index is high. When the conductive layer is covered with the anti-reflection layer, the anti-reflection layer does not have conductivity.
To allow an anti-reflection layer of a cathode ray tube to be conductive, the following structures have been proposed.
(1) To allow a conductive layer
3
that structures a conductive anti-reflection film
2
formed on a face panel
8
to be conductive, a conductor portion
5
that pierces the anti-reflection layer
4
and contacts the conductor layer
3
is formed. Thereafter, the conductor portion
5
is filled with a special solder
6
(see FIG.
2
).
(2) An area for a conductor portion
5
is formed in a conductor layer
3
. An anti-reflection layer
4
is not formed in the conductor portion
5
(see FIG.
3
).
(3) An anti-reflection layer
4
that is a porous layer is covered on a conductive layer
3
. A part of the conductive layer
3
is exposed as a conductive portion.
However, when a conductive portion that pierces an anti-reflection layer is formed so as to allow a conductive anti-reflection film to be conductive and the conductive portion is filled with solder, the structure of the conductive anti-reflection film becomes complicated. In addition, since the number of fabrication steps increases, the productivity of the conductive anti-reflection film decreases.
On the other hand, when a conductive layer is covered with an anti-reflection layer that is a porous layer, the strength of the anti-reflection layer decreases. Thus, the durability of the conductive anti-reflection film remarkably decreases.
As a method for forming a conductive layer on a substrate such as a face panel, a solution of which conductive oxide particles or metal particles have been dispersed is coated on a substrate by coating method or wetting method. The resultant coated film is dried or baked and thereby a conductive layer is obtained.
In this method, a plurality of layers are formed on the substrate in such a manner that the refractive index of an inner layer of (adjacent to) the substrate is higher than the refractive index of an outer layer of (apart from) the substrate. In other words, the refractive index of the outermost layer is the lowest.
However, since the refractive index of a layer with higher conductivity is higher than the refractive index of a layer with lower conductivity, when a conductive layer is formed as an outermost layer disposed against the substrate, the characteristic for protecting the conductive anti-reflection film from reflecting light deteriorates or vanishes.
An anti-reflection layer that contains SiO
2
and that has a low refractive index is formed on a conductive layer so as to prevent light from reflecting. In this case, the anti-reflection layer functions as a capacitor. Thus, the surface resistance of the conductive anti-reflection film cannot be sufficiently decreased. Consequently, a conductive portion cannot be formed on the front surface of the conductive anti-reflection film.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a conductive anti-reflection film that completely prevents the AEF (Alternating Electric Field) from taking place and light from reflecting and, allows the front surface thereof to be conductive, and has high productivity and durability.
Another object of the present invention is to provide a cathode ray tube that has such a conductive anti-reflection film and that can displays a high quality picture for a long service life.
According to the present invention, a layer of the front surface (an outermost layer against the substrate) of a conductive anti-reflection film contains SiO
2
and conductive particles so as to allow the front surface thereof to be conductive. Thus, a conductive portion can be easily formed on the front surface of the conductive anti-reflection film.
A first aspect of the present invention is a conductive anti-reflection film, comprising a first layer containing first conductive particles, and a second layer disposed for covering the first layer, the second layer containing SiO
2
and second conductive particles.
According to the conductive anti-reflection film of the present invention, the first layer containing conductive particles is covered with the second layer containing SiO
2
and conductive particles. Thus, the refractive index of the second layer becomes smaller than the refractive index of the first layer. In addition, the surface resistance of the second layer can be decreased. Thus, the second layer prevents light from reflecting. In addition, a conductive portion can be disposed on the second layer.
A second aspect of the present invention is a cathode ray tube, comprising a face plate having a first surface containing a phosphor substance, a first layer disposed on a second surface opposite to the first surface of the face plate, the first layer containing first conductive particles, and a second layer disposed for covering the first layer, the second layer containing SiO
2
and second conductive particles.
According to the cathode ray tube of the present invention, the first layer containing conductive particles is disposed on the second surface opposite to the first surface containing a phosphor substance. The first layer is covered with the second layer containing SiO
2
and conductive particles. Thus, the refractive index of the second layer becomes smaller than the refractive index of the first layer. In addition, the surface resistance of the second layer can be decreased. Consequently, the second layer can prevent light from reflecting and electrically contact with desired conductivity.
The conductive particles contained in the first layer may be the same as or different from the conductive particles contained in the second layer.
Examples of the conductive particles used in the present invention are super fine particles of at least one substance selected from the group consisting of gold, silver, silver compound, copper, copper compound, tin compound, and titanium compound. Examples of the silver compound are silver oxide, sliver nitrate, silver acetate
Abe Michiyo
Chigusa Hisashi
Matsuda Hedemi
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