Coating processes – Electrical product produced – Fluorescent or phosphorescent base coating
Reexamination Certificate
1999-06-24
2002-10-08
Beck, Shrive P. (Department: 1762)
Coating processes
Electrical product produced
Fluorescent or phosphorescent base coating
C427S066000, C427S068000
Reexamination Certificate
active
06461668
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a cathode ray tube, particularly, to formation of a phosphor screen of a cathode ray tube.
As shown in
FIGS. 1
to
3
, a phosphor screen
5
consisting of a black film
2
, three phosphor films
3
a
,
3
b
,
3
c
of green, blue and red, and an aluminum film
4
formed to cover the black film
2
and the phosphor films is formed on the inner surface of a panel
1
of a cathode ray tube. Incidentally,
FIG. 1
is a side cross sectional view of the panel
1
,
FIG. 2
is a front view of the panel
1
, and
FIG. 3
is a cross sectional view showing in a magnified fashion a part of the panel
1
.
As shown in
FIG. 4
, a phosphor screen-forming apparatus
8
for forming the phosphor screen on the inner surface of the panel
1
comprises a black film-forming section
8
a
for forming the black film, a phosphor film-forming section
8
b
for forming the three phosphor films
3
a
,
3
b
,
3
c
, and an aluminum film-forming section
8
c
for forming the aluminum film to cover the black film and the phosphor films by vacuum vapor deposition.
In the phosphor screen-forming apparatus
8
, it is difficult to achieve 100% of yield in each section and, thus, defective articles are unavoidably generated. To be more specific, a panel
1
A defective in the black film is generated in the black film-forming section
8
a
. Also, a panel
1
B defective in the phosphor films is generated in the phosphor film-forming section
8
b
. Further, a panel
1
C defective in the aluminum film is generated in the aluminum film-forming section
8
c.
The defect is derived from the shadow mask used in combination with the panel for the pattern formation and from the panel itself. Since the black film or the phosphor film is formed by directly coating the inner surface of the panel with the film material, the black film or the phosphor film is rendered defective if dust or a foreign matter is attached to the inner surface of the panel in the coating step.
Also, if the development and the drying are insufficient, it is impossible to form the black film or the phosphor film in a desired pattern making the formed film defective. It is also possible for the three kinds of phosphors to be mixed with each other and for the phosphor particles to fail to be attached strongly to the inner surface of the panel, leading to the defective phosphor film. For example, the green light-emitting phosphor may possibly be mixed with the red or blue light-emitting phosphor to make the formed phosphor film defective.
The defective aluminum film includes typically a film defective in thickness and a film containing dust or a foreign matter.
The defective film is also derived from the defectiveness of the shadow mask including the defective pore size of the shadow mask and deformation of the shadow mask. Since the panel is exposed to light through the shadow mask that is kept in tight contact with the panel, a satisfactory phosphor film cannot be formed no matter how many times the phosphor coating, light exposure and development may be repeated, unless the shadow mask itself is corrected. Where the shadow mask cannot be corrected, it is necessary to return to the preceding step to replace the shadow mask and to align the shadow mask with the panel.
For forming the phosphor screen
5
, the inner surface of the panel
1
is washed in general as a pretreatment of the phosphor screen-forming step. Specifically, an industrial water, hydrofluoric acid and pure water are successively sprayed against the inner surface of a new panel to remove the foreign matter, dust, etc. attached to the inner surface of the new panel, followed by drying the panel and subsequently coating the washed inner surface of the panel with resist to form a primary coat for forming the black film
2
.
On the other hand, the defective panels
1
A,
1
B,
1
C are loaded again in the phosphor screen-forming apparatus
8
shown in
FIG. 4
like the new panel. Within the phosphor screen-forming apparatus
8
, the defective aluminum film
4
, the defective phosphor film
3
and the defective black film
2
are washed away by a panel washing device. Then, the film forming steps are redone starting with the initial step of the black film-forming step, like the new panel.
In the conventional phosphor screen-forming apparatus, the panels having the films formed thereon are inspected at the outlets of the black film-forming section
8
a
, the phosphor film-forming section
8
b
and the aluminum film-forming section
8
c
, and the defective panels are manually rejected from the manufacturing line so as to be transferred by a transfer means such as a carriage and supplied again to the black film-forming section. However, normal panels transferred from the upstream steps must be supplied into the black film-forming section, making it difficult to control the loading of the rejected panels at the inlet of the black film-forming section
8
a
. It is also difficult to control the recovery of the defective panels.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of manufacturing a cathode ray tube that makes it possible to form again a phosphor screen on a panel once rejected as a defective panel so as to manufacture a cathode ray tube efficiently while decreasing the manual labor requirement.
Another object of the present invention is to provide an apparatus for manufacturing a cathode ray tube that makes it possible to form again a phosphor screen on a panel once rejected as a defective panel so as to manufacture a cathode ray tube efficiently while decreasing the manual labor requirement.
According to an aspect of the present invention, there is provided a method of manufacturing a cathode ray tube, in which an untreated panel for a cathode ray tube is supplied to a phosphor screen-forming line including a black film-forming step for forming a black film, a phosphor film-forming step for forming a phosphor film, and an aluminum film-forming step for forming an aluminum film to form a patterned phosphor screen consisting of the black film, the phosphor film and the aluminum film on the inner surface of the panel, comprising the steps of rejecting from the phosphor screen-forming line at least one defective panel selected from the group consisting of the panel defective in the black film formed in the black film-forming step, the panel defective in the phosphor film formed in the phosphor film-forming step, and the panel defective in the aluminum film formed in the aluminum film-forming step, recycling the rejected defective panel to the starting point of the phosphor screen-forming line, and forming again a pattern of a phosphor screen consisting of the black film, the phosphor film and the aluminum film on the inner surface of the panel recycled to the phosphor screen-forming line, wherein, where the untreated panel for the cathode ray tube conflicts with the rejected defective panel at a starting point of the phosphor screen-forming line, the defective panel is supplied in preference to the untreated panel to the phosphor screen-forming line.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a cathode ray tube, comprising a phosphor screen-forming device including a black film-forming section for forming a black film, a phosphor film-forming section for forming a phosphor film and an aluminum film-forming section for forming an aluminum film and serving to form a pattern of a phosphor screen consisting of the black film, the phosphor film and the aluminum film on the inner surface of an untreated panel for a cathode ray tube, an untreated panel transfer device for transferring the untreated panel for the cathode ray tube to a region near the phosphor screen-forming device, a first delivery device for delivering the untreated panel for the cathode ray tube from the untreated panel transfer device onto the phosphor screen-forming device, a rejecting device for rejecting from the phospho
Hirayama Kazumasa
Sasaki Yuzuru
Beck Shrive P.
Cleveland Michael
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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