Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1998-10-19
2001-12-04
Kalafut, Stephen (Department: 1745)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192230, C204S192260, C204S192280, C204S298110, C204S298230, C204S298250
Reexamination Certificate
active
06325901
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for manufacturing a cathode ray tube, in which a predetermined film is formed on a face of a panel.
BACKGROUND OF THE INVENTION
FIG. 1
schematically shows the construction of a general cathode ray tube. As shown in the drawing, a panel
12
and a funnel
13
are formed integral to constitute a cathode ray tube
11
. The inner space of these panel
12
and funnel
13
is held at a high vacuum. In order to allow the cathode ray tube to maintain a high resistance to implosion, a reinforcing metal band
14
, which is called an explosion-proof band, is wound about the outer circumferential surface of the panel
12
, with a Braun tube-holding metal tool
14
a
interposed therebetween, such that the panel
12
is fastened by the band
14
. Also, the outer wall of the funnel
13
is coated with dag
15
consisting of an organic conductive material layer in order to obtain an electrical conductivity on the surface.
Further, an anti-reflection film of a multi-layer structure (not shown) is formed on the face
12
a
of the panel
12
. A Braun tube equipped with an anti-reflection film, which serves to suppress reflection of the outer light, is used in recent years in mainly color TV receivers, terminal apparatuses of an electronic computer, etc.
Various methods such as a spinning method, a spraying method, a sputtering method and a vapor deposition method have been tried to date in an attempt to form a multi-layered anti-reflection film
16
on the face
12
a
of the panel
12
. However, these methods have been found advantageous in some aspects and defective in other aspects. For example, the wet spinning method and spraying method permit forming the anti-reflection film at a relatively low cost and are suitable for mass production. However, the film is rendered thick, resulting in failure to obtain a desired reflectance.
On the other hand, a dry sputtering method or vapor deposition method permits forming a thin film, however, a large vacuum apparatus and, in some cases, a heating device are required, leading to a marked increase in the facility cost. Also, since a thin film is formed under vacuum in these methods, the atmosphere around a thin film-forming region must be discharged to establish a desired vacuum state, in this case, it takes a long time to establish the desired vacuum state, resulting in failure to improve the productivity.
FIG. 2
schematically shows a thin film-forming apparatus using a conventional sputtering method. As shown in the drawing, the apparatus comprises a vacuum chamber
18
. The cathode ray tube
11
on which a thin film is to be formed is arranged within the vacuum chamber
18
. A target
19
made of a desired material of the thin film is also arranged within the vacuum chamber
18
to face the cathode ray tube
11
. The target
19
is disposed on a support member
20
which also acts as a cooling water pipe.
Each of the support member
20
and an annular body
21
arranged to surround the panel
12
of the cathode ray tube
11
is connected to a high frequency power source device or a DC power source device
22
. Also, a magnet
23
is mounted to the support member
20
positioned behind the target
19
. In this apparatus, a free space in which a magnetic field and an electric field intersect each other at right angles is formed by the magnet
23
and the DC power source device
22
in front of the surface of the target
19
. An inert gas is introduced into the particular free space and a voltage is applied to the inert gas so as to bring about discharge.
A plasma
24
of a high density is generated by the discharge. It should be noted that a large amount of ions within the plasma
24
are accelerated by a bias voltage generated in the vicinity of the target
19
so as to bombard the target
19
. As a result, atoms forming the target material are ejected from the target
19
. In other words, a sputtering phenomenon takes place. The ejected atoms are deposited on the face
12
a
of the panel
12
of the cathode ray tube
11
positioned apart from the target
19
so as to form a thin film on the face
12
a
acting as a workpiece of the panel
12
.
Where, for example, the target
19
is formed of zirconium oxide (ZrO
2
) and sputtering is performed under an argon gas (Ar) atmosphere, a thin film of zirconium oxide is formed on the face
12
a
of the cathode ray tube
11
. Then, the material of the target
19
is changed into silicon, and sputtering is carried out under a mixed gas atmosphere consisting of an argon gas and an oxygen gas (O
2
) so as to form a thin film of silicon dioxide (SiO
2
) on the zirconium oxide thin film. In this fashion, different layers collectively forming the anti-reflection film
16
are successively formed on the face
12
a
of the panel
12
, with the result that the face
12
a
is enabled to exhibit a desired reflectance.
In the conventional method of forming a thin film, however, the entire cathode ray tube
11
is disposed within the vacuum chamber
18
for forming the thin film. Naturally, the vacuum chamber
18
is required to have a large inner volume. Also, it takes much time to establish a vacuum state within the vacuum chamber
18
, leading to a low efficiency. It should be noted that the high vacuum within the vacuum chamber
18
is broken every time the cathode ray tube
11
is put into and taken out of the vacuum chamber
18
. In other words, the vacuum chamber
18
must be evacuated frequently. It follows that the evacuation to produce a vacuum condition within the vacuum chamber
18
takes much time, leading to a low productivity.
The outer surface of the funnel
13
except the face
12
a
of the panel
12
of the cathode ray tube
11
is coated with the organic conductive material layer
15
. Where the cathode ray tube
11
is used as an electron tube under an ordinary condition, the organic conductive material layer
15
functions for ensuring an electrical conductivity on the surface and, thus, is useful. However, several problems are generated by the organic conductive material layer
15
where the cathode ray tube
11
is disposed under a vacuum environment. First of all, since a gas is contained in the organic conductive material layer
15
, it takes a longer time for evacuating the vacuum chamber
18
.
For shortening the evacuating time, it is conceivable to heat, for example, the cathode ray tube
11
. If the cathode ray tube
11
is heated, however, a new problem is brought about that the organic conductive material layer
15
tends to peel off. The organic conductive material layer
15
peeling off the outer surface of the funnel
13
is accumulated within the vacuum chamber
18
and scattered in the evacuating step so as to be attached to the face
12
a
of the panel
12
of the cathode ray tube
11
. It follows that the product cathode ray tube
11
is rendered defective.
Further, as described previously, the band
14
is wound about the panel
12
for fastening the panel
12
in order to allow the cathode ray tube
11
to maintain a high resistance to implosion. It should be noted in this connection that, if the cathode ray tube
11
is put in the vacuum chamber
18
held at a high vacuum, the pressure difference between the outer space and the inner space of the cathode ray tube
11
is diminished, with the result that the cathode ray tube
11
tends to be swollen and the band
14
is pushed radially outward. Then, if the cathode ray tube
11
is taken out of the vacuum chamber
18
, the cathode ray tube
11
is caused to shrink by the atmospheric pressure, leading to a weakened fastening force of the band
14
. It follows that the cathode ray tube
11
tends to fail to exhibit a sufficient resistance to implosion.
SUMMARY OF THE INVENTION
As described above, various problems remain unsolved in the conventional method of manufacturing a cathode ray tube. First of all, since the entire cathode ray tube is put in a vacuum chamber held at a high vacuum for forming a thin film, it took much time to produce a vacuum condit
Aramaki Yoshimitsu
Chigusa Hisashi
Hirayama Kazumasa
Iijima Hisashi
Ito Takeo
Kabushiki Kaisha Toshiba
Kalafut Stephen
Mercado Julian A.
Pillsbury & Winthrop LLP
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