BACKGROUND OF THE INVENTION
Field of the Invention :
-
The present invention relates to a manufacturing method of a cathode-ray
tube, a manufacturing apparatus therefor and a cathode-ray tube.
Description of the Related Art:
-
FIG. 1 shows a schematic sectional view of a color cathode-ray tube.
-
This color cathode-ray tube 10 contains a fluorescent screen (not shown)
within a panel portion la of a cathode-ray tube body and a color selecting
electrode 3 is disposed with a predetermined gap to this fluorescent screen.
-
The color selecting electrode 3 comprises color selecting electrode thin
plates 7 containing a lot of tape-like grid structures 5 each having a slit-like
electronic beam aperture 4 which selectively allows mainly electron beams to pass
through and frames 6 (6a, 6b) for supporting this color selecting electrode thin
plates 7.
-
The color selecting electrode 3 introduces electron beams R emitted from
an electron gun 2 provided in a neck portion 1c of the cathode-ray tube body to the
fluorescent screen through the electronic beam apertures 4.
-
The panel portion 1a and a funnel portion 1b of the cathode-ray tube body
are formed of, for example, glass and both components are joined through a frit
portion 8 which is a sealing portion using, for example, frit glass.
-
Reference numeral 2a denotes a tip tube provided on a stem of the
electron gun 2 for exhausting air and reference numeral 9 denotes a conductive
film of carbon film or the like, formed on an inner wall of the funnel portion lb of
the cathode-ray tube body.
-
The color cathode-
ray tube 10 shown in FIG. 1 is produced through
predetermined processes. In processes carried out under a relatively high
temperature, usually, the following temperature conditions are applied.
- 1) Blackening of the color selecting electrode 3: about 450°C
- 2) Frit sealing process: about 450°C
The frit sealing process serves for burn-out of organic substances on the
fluorescent screen also. - 3) Exhausting process: 300°C-400°C
-
-
The above three processes are carried out in the order of 1)-3). The air-exhausting
process is carried out under such a condition that the panel portion la
and funnel portion 1b, and, the neck portion 1c and electron gun 2 are sealed.
-
That is, the panel portion 1a and funnel portion 1b are sealed by the frit
portion 8 usually with frit seal material and the neck portion 1c and electron gun 2
are sealed so as to make an interior of the cathode-ray tube body into an enclosed
space.
-
The panel portion la and the funnel portion 1b of the cathode-ray tube 10
require strength and air-tightness capable of enduring vacuum under a maximum
temperature (less than 400°C) of the exhausting process in order to exhaust air
from the cathode-ray tube 10 through the tip tube 2a.
-
For this purpose, the panel portion la and the funnel portion lb are sealed
using crystal frit glass as a frit sealing agent.
-
The crystal frit glass which crystallizes at more than 400°C is used by
selecting its material components.
-
Using the crystal frit glass which crystallizes at more than 400°C, the frit
sealing process is executed at the temperature of about 450°C as described above.
-
However, because a strong tension is applied to metallic material used for
the color selecting electrode 3, creep (plastic deformation) occurs at 450°C.
-
Particularly in the grid structure 5 of the thin color selecting electrode thin
plate 7 on which tension is applied, streak (twist) occurs.
-
If this creep occurs in the frit sealing process, the color selecting electrode
3 assembled so as to match with the position of the panel portion 1a is deformed,
so that a color shift may occur in the produced cathode-ray tube.
-
Thus, in the blackening process for the color selecting electrode 3, it was
necessary to make creep occur preliminarily by carrying out the blackening
process at a temperature higher than the frit sealing process in order to prevent an
occurrence of the creep (plastic deformation) in the frame 6 of the color selecting
electrode 3 and the color selecting electrode thin plate 7 due to a change of the
temperature in the subsequent frit sealing process.
-
Once the creep is made to occur by executing the blackening process at
more than 450°C, even if the same temperature is reached in the subsequent frit
sealing process, the quantity of the creep which occurs newly is relatively small.
-
However, if the blackening process is carried out at the temperature of
more than 450°C, the color selecting electrode thin plate 7 fixed to the frame 6 is
crept by a certain tension, so that the tension drops by about 30% relative to the
initial setting.
-
Thus, such a tension drop is expected preliminarily before the blackening
process, and in the initial setting of stretching the color selecting electrode thin
plates 7 on the frame 6 of the color selecting electrode 3, a stronger tension is set
up.
-
Thus, a strict frame 6 enduring such a strong tension is required and
therefore, the weight of the frame 6 is increased so that it is difficult to reduce the
weight of the cathode-ray tube 10.
SUMMARY OF THE INVENTION
-
To solve the above described problem, the present invention provides a
production method of a cathode-ray tube capable of reducing the temperature in
the blackening process and the like and manufacturing a cathode-ray tube whose
weight can be reduced, a production apparatus thereof and a cathode-ray tube
whose weight can be reduced.
-
According to the manufacturing method of the cathode-ray tube of the
present invention, a vacuum is created in the inside and outside of the cathode-ray
tube in an exhaust/sealing process for the cathode-ray tube, so as to exhaust air
from the cathode-ray tube.
-
According to the present invention described above, by creating a vacuum
in the inside and outside of the cathode-ray tube in the exhausting/sealing process,
the difference of pressure between the inside and outside of the cathode-ray tube
can be reduced. Thus, the load applied to the frit portion for joining the panel and
funnel can be also reduced.
-
In the manufacturing apparatus for the cathode-ray tube of the present
invention, the exhaust/sealing unit for the cathode-ray tube includes a means for
evacuating the frit portion of the cathode-ray tube from the outside.
-
According to the structure of the production apparatus of the present
invention described above, by providing with a means for creating a vacuum on
the outside of the frit portion, the inside and outside of the frit portion can be
evacuated in the exhaust/sealing process. Consequently, by reducing a difference
of pressure between the inside and outside of the frit portion, the load applied to
the frit portion can be reduced.
-
The cathode-ray tube of the present invention is formed by joining the
panel and funnel portion with amorphous frit glass.
-
According to the structure of the cathode-ray tube of the present invention,
by joining the panel and funnel with amorphous frit glass, the amorphous frit glass
possesses a characteristic of adhering to glass materials of the panel and funnel at
the temperature of less than 350°C. Therefore, the frit sealing process can be
carried out at this relatively low temperature so as to join the panel and funnel.
-
The cathode-ray tube of the present invention includes a color selecting
electrode subjected to blackening processing under a temperature of less than
350°C.
-
According to the structure of the cathode ray tube of the present invention,
the color selecting electrode subjected to the blackening processing under a
temperature of less than 350°C is provided. Thus, because the change of tension
between before and after the blackening processing for the cathode-ray tube is
small, the strength of the color selecting electrode may be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
-
- FIG. 1 is a schematic sectional view of a color cathode-ray tube;
- FIG. 2A is a diagram showing changes of tension between before and after the
blackening process at the processing temperature of 300°C in the blackening
process;
- FIG. 2B is a diagram showing changes of tension between before and after the
blackening process at the processing temperature of 350°C in the blackening
process;
- FIG. 3A is a diagram showing changes of tension between before and after the
blackening process at the processing temperature of 400°C in the blackening
process;
- FIG. 3B is a diagram showing changes of tension between before and after the
blackening process at the processing temperature of 450°C in the blackening
process;
- FIG. 4 is a diagram showing a relation between the temperature of the blackening
process and tension utilization ratio;
- FIG. 5 is a schematic structure diagram of a production apparatus for the cathode-ray
tube according to the present invention;
- FIG. 6 is a diagram showing a structure in which a furnace is provided outside the
production apparatus according to the present invention;
- FIG. 7A,B,C is a process diagram showing the first half of the process step by step
using the production apparatus of the cathode-ray tube according to the present
invention;
- FIG. 8A,B,C is a process diagram showing the latter half of the process step by
step using the production apparatus of the cathode-ray tube according to the
present invention ; and
- FIG. 9 is a schematic structure diagram of a production apparatus for the cathode-ray
tube according to another embodiment of the present invention.
-
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
-
The present invention concerns a manufacturing method of a cathode-ray
tube in which a vacuum is created on the inside and outside of the cathode-ray
tube to exhaust air from the cathode-ray tube in the exhaust/sealing process for the
cathode-ray tube.
-
The present invention concerns a manufacturing apparatus of the cathode-ray
tube including a means for creating a vacuum on a frit portion from the
outside, in an exhaust/sealing unit for the cathode-ray tube.
-
The present invention concerns a cathode-ray tube in which a panel and a
funnel are joined with amorphous frit glass.
-
The present invention concerns a cathode-ray tube including a color
selecting electrode subjected to blackening processing at less than 350°C.
-
An outline of the present invention will be described prior to a description
of a specific embodiment of the present invention.
-
The purpose of the blackening processing for the color selecting electrode
described above will be summarized in the following three points.
- A. Corrosion protection for the color selecting electrode (formation of a
blackening film)
- B. Prevention of light reflection in an exposure process for a fluorescent screen
- C. Avoiding changes of the color selecting electrode due to a temperature of frit
sealing process
-
-
Of the above described three points, the effects of A and B can be expected
by forming the blackening film. Thus, the processing temperature does not have
to be more than 450°C in order to obtain these effects.
-
The most prominent reason why the processing temperature of more than
450°C is required is to achieve a purpose of avoiding the above described point C,
that is, changes in the color selecting electrode 3.
-
If the color selecting electrode 3 changes, the aforementioned color shift
occurs.
-
Here, the changes in the color selecting electrode 3 will be described in
detail.
-
In the color cathode-ray tube 10, a color picture is displayed by mixing the
three primary colors of R(red), G(green) and B (blue).
-
By disposing the color selecting electrode 3 in front of the fluorescent
screen, the electron beam is mechanically cut off by grid structures 5 of the color
selecting electrode 3 and at the same time, the electron beams passing through
electronic beam apertures 4 between the grid structures 5 is irradiated on the
fluorescent screen, so that the electron beams corresponding to signals of R, G, B
are irradiated to the fluorescent materials of R, G, B.
-
Therefore, fluorescent material for respective colors are formed so as to
match with a position of each grid structure 5 of the color selecting electrode 3, so
that the fluorescent screen is constituted.
-
After an entire inner surface of the panel is coated with carbon stripe for
the fluorescent screen, red fluorescent material, green fluorescent material and
blue fluorescent material, only required places are exposed by the grid structures 5
of the color selecting electrode 3. Then, unnecessary places are removed so as to
form fluorescent material having a predetermined pattern.
-
That is, this fluorescent screen is produced by attaching or detaching the
color selecting electrode 3 for each color.
-
According to this method, an excellent performance fluorescent screen can
be obtained at a cheap price.
-
Unless positional relations between the fluorescent screen and color
selecting electrode obtained in the above described method is the same as when
the fluorescent screen is formed after the frit sealing process and exhausting
process are passed, a problem of the color shift described above occurs.
-
Thus, before the fluorescent screen is formed, the color selecting electrode
3 is subjected to blackening processing so as to generate a creep which will occur
in a subsequent process. Then, using the color selecting electrode 3 of that
condition, the fluorescent screen is formed.
-
However, the temperature in the blackening process is as high as 450°C
and severe for the material. The amount of change of tension between before and
after the blackening process reaches 30%.
-
Thus, the color selecting electrode 3 is produced in such a condition that
the tension is increased by about 30% and the strength needs to be increased
correspondingly to maintain such a high tension. As a result, the size of a frame 6
is increased so that the weight thereof also increases.
-
The reason why the temperature in the blackening process is raised is a
temperature condition for the frit sealing process.
-
This temperature condition for the frit sealing process is necessary for
satisfying a condition for the exhausting process in a subsequent stage.
-
The condition of the exhausting process is to keep a strength against a
difference of pressure between outside of the cathode-ray tube 10 and atmospheric
pressure when air is exhausted from the inside of the cathode-ray tube 10.
-
Because the inside of a product of the cathode-ray tube 10 is vacuum, it is
necessary to keep strength against difference of pressure with respect to the
atmospheric pressure outside.
-
That is, in the conventional exhausting process, the same strength as that
required for a product of the cathode-ray tube 10 was necessary.
-
In the exhausting process, in order to satisfy a sufficient service life
characteristic by suppressing generation of gas from a product, sufficient exhaust
is carried out in a condition heated up to 300-400°C as described above. If the
exhausting process is carried out at 200°C, the sufficient service life characteristic
cannot be satisfied.
-
Therefore, frit seal material of the frit portion 8 needs to have high strength
even at such a high temperature.
-
The crystal frit glass is stabilized by crystallizing. If the crystal frit glass is
employed as the frit sealing material, it is hardened with glass of a panel portion
la and a funnel portion 1b by crystallizing so as to keep strength.
-
If the crystal frit glass whose crystallizing temperature is as low as 350°C
for example, is used as the frit sealing material, it cannot keep sufficient strength
at 300-400°C in the exhausting process.
-
Amorphous frit glass also exists. If this amorphous frit glass is used as the
frit sealing material, a working temperature of the frit sealing process is set up so
as to keep strength when the frit glass adheres to glasses of the panel portion 1a
and funnel portion 1b.
-
However, because of the characteristic of the amorphous frit glass, the
working temperature becomes relatively low so that it cannot keep sufficient
strength under 300-400°C in the exhausting process. To secure sufficient strength
against the atmospheric pressure, the exhausting process must be carried out at a
temperature lower than the working temperature of the frit sealing process by
100°C-150°C. In that case, the service life characteristic of the cathode-ray tube
cannot be satisfied sufficiently.
-
For this reason, a crystal frit glass whose crystallizing temperature was
about 450°C was conventionally used as the frit sealing material and the frit
sealing process was carried out under the aforementioned working temperature
(about 450°C).
-
Changes of the tension between before and after the blackening process are
shown in FIGS. 2A, 2B and 3A, 3B as a result of investigation for every
processing temperature in the blackening process.
-
FIG. 2A shows the result when the processing temperature is 300°C,
FIG. 2B shows the result when the processing temperature is 350°C, FIG. 3A
shows the result when the processing temperature is 400°C, FIG. 3B shows the
result when the processing temperature is 450°C.
-
In every figure, the X-axis is set in the horizontal direction and a position
corresponding to the center of this diagram of the color selecting electrode 3 is set
up as a home position. Tension (initial) before the blackening process on each X-axis
coordinate (relative value) is indicated by □ while tension after the
blackening process is indicated by .
-
As indicated by FIGS. 2A, 2B, 3A and 3B, as the processing temperature
increases, the change of the tension between before and after the blackening
process increases and the change of the tension increases as it goes to a peripheral
portion of the screen off the center.
-
From results of FIGS. 2A, 2B, 3A and 3B, a mean value of ratio of the
tension after the blackening process with respect to the initial tension before the
blackening process is obtained, and then this is expressed as tension utilization
ratio (%). FIG. 4 shows relation between the tension utilization ratio and
processing temperature.
-
As evident from FIG. 4, the tension utilization ratio is high when the
processing temperature is less than 350°C, and if the processing temperature
exceeds 350°C, it is indicated that the tension utilization ratio drops suddenly.
-
Therefore, if the temperature of the blackening process is reduced to less
than 350°C, the change of the tension can be reduced. Thus, the initial tension can
be set to near the tension after the blackening process.
-
As a result, a necessity of forming a strict frame 6 while expecting a
change of the tension beforehand is eliminated, so that the structure of the frame 6
can be simplified and the weight of the color selecting electrode 3 can be reduced.
-
According to the present invention, the structure described above is used,
that is a production apparatus for the cathode-ray tube having a means for creating
a vacuum on the frit portion of the cathode-ray tube from the outside, provided in
the exhaust/sealing unit for the cathode-ray tube so that the temperature of the
blackening process can be less than 350°C. Using this production apparatus, a
vacuum is created inside and outside of the cathode-ray tube in the exhaust/sealing
process so as to exhaust air from the cathode-ray tube.
-
As a result, in the air exhaust/sealing process (exhausting process and
sealing process), a vacuum can be created on the inside and outside of the frit
portion 8 of the cathode-ray tube 10. Thus, a difference of pressure between the
inside and outside is eliminated so that the load on the frit portion 8 can be
reduced.
-
Therefore, such a necessity that the strength of the frit glass in the
exhausting process needs to be the same as the necessary strength of the cathode-ray
tube 10 can be eliminated.
-
Consequently, regardless of the temperature of the air exhausting process,
the frit portion 8 can be joined with amorphous frit glass or crystallizing frit glass
which can be crystallized at low temperature and therefore, the temperature of the
frit sealing process can be reduced. Thus, the blackening process temperature for
the color selecting electrode 3 can be reduced largely.
-
For example, if the amorphous frit glass whose working temperature is
300°C is used, the temperature of the blackening process for the color selecting
electrode 3 can be reduced to 300°C + α.
-
Because the temperature of the blackening process for the
color selecting
electrode 3 can be reduced by employing the above described structure, the
following advantages can be obtained.
- 1) The creep on metal which is generated upon the blackening can be reduced
largely. Furthermore, the streak(twist) of the grid structure 5 which is generated
upon the blackening can be avoided.
- 2) Because a change of tension between before and after the blackening process is
reduced largely, an initial tension for use in stretching a color selecting electrode
thin plate (color selecting mask) 7 can be reduced so as to be smaller than a
conventional excessive tension, so that it is possible to reach a necessary tension
in a completed cathode-ray tube 10.
As a result, the strength necessary for the frame 6 can be reduced.
Therefore, by reducing the stiffness of the frame 6, the structure thereof can be
simplified so as to achieve a reduction of the weight of the frame 6 as compared to
the conventional frame 6. For example, if the frit processing is carried out at
300°C, the weight thereof can be reduced by about 30%.
- 3) Because the processing temperatures of a blackening furnace and frit furnace
can be reduced, heating and lighting cost can be reduced. Because a load on the
furnace is reduced, consumption cost for the production apparatus can be also
reduced.
- 4) Because time until the inside of the furnace reaches a temperature for the
blackening process can be reduced, work efficiency can be improved.
-
-
Concerning the advantages of 3) and 4), because the temperature of the frit
sealing process is also reduced, the same effect is produced about the frit sealing
process also.
-
Next, an embodiment of the present invention will be described.
-
FIG. 5 shows a schematic structure diagram of the production apparatus for
the cathode-ray tube as an embodiment of the present invention.
-
This production apparatus 11 for the cathode-ray tube is employed for
producing a color cathode-ray tube 10 shown in FIG. 1, for example.
-
This production apparatus 1 has a first vacuum pump 13 which is a means
for creating a vacuum in the inside of the cathode-ray tube 10 like the
conventional production apparatus.
-
This first vacuum pump 13 is connected to a tip tube 2a of an electron gun
2 sealed in a neck portion 1c of the cathode-ray tube 10. As a result, a vacuum
can be created in the inside 15 of the cathode-ray tube 10 through the tip tube 2a.
-
According to this embodiment, a processing chamber 12 is provided so as
to cover entirely the cathode-ray tube 10 except a part of the neck portion 1c for
keeping air-tightness and a second vacuum pump 14 is provided as a means for
creating a vacuum on the outside of the cathode-ray tube 10.
-
Because the second vacuum pump 14 is connected to the processing
chamber 12, a vacuum can be created in the inside of the processing chamber 12,
that is, on the outside 16 of the cathode-ray tube 10.
-
Meanwhile, the outside 16 of the cathode-ray tube 10 does not have to be
made in a high vacuum state unlike the inside of the cathode-ray tube 10 and may
be in a sufficiently low pressure relative to the atmospheric pressure so that there
is a small difference of pressure between the inside 15 and outside 16 of the
cathode-ray tube 10.
-
Furthermore, as shown in FIG. 6, actually, a working chamber having a
heating means, for example, a heating furnace 18 is provided so as to cover the
cathode-ray tube 10 and the processing chamber 12.
-
Then, by heating an inside of the heating furnace 18, a temperature thereof
is raised to a predetermined working temperature necessary for the exhausting
process.
-
Furthermore, the heating furnace 18 may be used at the same time as a
heating furnace for use in other processes like the frit sealing process.
-
Although not shown, a structure in which the processing chamber is used
as the heating furnace (for example, a heating means such as a heater is provided
inside or just outside of the processing chamber) may be employed.
-
Next, a production process for the cathode-ray tube using the production
apparatus 11 of this embodiment will be described.
-
First, the color selecting electrode 3 shown in FIG. 1 is subjected to the
above described blackening processing under a temperature of less than 350°C.
-
Next, by carrying out exposure process using the color selecting electrode
3 subjected to the blackening processing, a fluorescent surface having a
fluorescent layer of a predetermined pattern is formed on an inside face of the
panel portion 1a.
-
Next, a metal back layer is formed through an intermediate film on the
fluorescent screen.
-
Then, the color selecting electrode 3 is attached to the panel portion la in
which the fluorescent screen and metal back layer are formed on the inside face
thereof.
-
Then, as shown in FIG. 7A, the panel portion la having the color selecting
electrode 3 formed in the above described manner and the funnel portion 1b are
prepared.
-
Next, as shown in FIG. 7B, the panel portion 1a and the funnel portion 1b
are joined together using amorphous frit glass or frit glass (not shown) which is
crystallized at less than 350°C for the frit portion 8 as a frit sealing material and
the frit sealing process is carried out at a predetermined temperature, for example,
350°C. At this time, organic substances in the fluorescent screen and intermediate
film on the inside face of the panel portion 1a are burnt out.
-
Meanwhile, after the frit sealing process is finished, the cathode-ray tube
10 is cooled gradually to the room temperature.
-
Subsequently, as shown in FIG. 7C, the electron gun 2 is inserted into the
neck portion Ic of the cathode-ray tube body subjected to frit sealing process and
then, the electron gun 2 is sealed by joining glass of the neck portion 1c to the
stem of the electron gun 2.
-
Next, as shown in FIG. 8A, the cathode-ray tube 10 in which the electron
gun 2 is sealed is accommodated in the production apparatus 1 shown in FIG. 5.
-
In this case, part of the neck portion Ic is exposed from the processing
chamber 12 and the tip tube 2a of the exposed stem of the electron gun 2 is
connected to the first vacuum pump 13.
-
Then, the inside 15 of the cathode-ray tube 10 is evacuated to a pressure of,
for example, 0.1 mPa using the first vacuum pump 13.
-
Further, the inside 16 of the processing chamber 12 is evacuated to a
pressure of, for example, 1 Pa using the second vacuum pump 14.
-
Consequently, a difference of pressure between the inside 15 and outside
16 of the cathode-ray tube 10 becomes about 1 Pa, which is much smaller than the
conventional data of 101 kPa.
-
Therefore, a pressure applied to the frit glass of the frit portion 8 can be
reduced.
-
By heating the cathode ray tube 10 and the entire inside of the processing
chamber 12 by means of a heating means such as the heating furnace 18 with a
small difference of pressure between the inside 15 and outside 16 of the cathode
ray tube 10, the temperature is raised to a predetermined working temperature, for
example, 300°C of the exhausting process.
-
Meanwhile, evacuation of the outside 16 of the cathode-ray tube 10 by the
second vacuum pump 14 may be started from a room temperature as described
above or may be started during heating. However, to keep strength of the frit glass.
the temperature when the evacuation is started must be set up.
-
If the temperature reaches the working temperature, the evacuation is
continued until temperature and air is exhausted from the inside 15 of the cathode-ray
tube 10 sufficiently.
-
Meanwhile, in this exhausting process, it is necessary to fix the panel and
funnel with fixture or the like to keep ordinary positions thereof upon the frit
sealing.
-
After a predetermined time elapses so that sufficient exhaust is carried out,
the temperature of the inside of the processing chamber 12 is lowered.
-
When the temperature of the processing chamber 12 drops to such a
temperature that the frit glass of the frit portion is capable of bearing the
atmospheric pressure, for example, 150°C, the evacuation of the second vacuum
pump 14 is stopped as shown in FIG. 8B to allow leak, so that the inside of the
processing chamber 12, that is, the outside 16 of the cathode-ray tube 10 is
brought into the atmospheric pressure.
-
At this time, a vacuum is kept in the inside 15 of the cathode-ray tube 10
by the first vacuum pump 13.
-
Next, the cathode-ray tube 10 is taken out of the processing chamber 12
and then, tip-off process is carried out by keeping vacuum in the inside 15 of the
cathode-ray tube 10.
-
More specifically, a heater is disposed around a position desired to be
sealed of the tip tube 2a and glass of the tip tube 2a is melted by heating by means
of the heater. Because the inside 15 of the cathode-ray tube 10 is a vacuum, the
molten glass is pulled in and adheres together so as to achieve sealing.
-
Consequently, as shown in FIG. 8C, an end of the tip tube 2a is sealed so
that the cathode ray tube 10 whose inside 15 is a vacuum is produced.
-
In this manner, the cathode-ray tube 10 whose inside 15 is evacuated and
sealed, can be produced.
-
Under the room temperature, the frit sealing material of the frit portion 8
which joins together the panel portion la and the funnel portion 1b has sufficient
strength, so that it can function as the cathode-ray tube 10.
-
According to this embodiment, a vacuum can be created both at the inside
15 and the outside 16 of the cathode-ray tube 10 by the first vacuum pump 13 and
second vacuum pump 14. Therefore, a difference of pressure between the inside
and outside of the cathode-ray tube 10 can be made small.
-
Consequently, particularly in the exhausting process, the load on the frit
sealing material of the frit portion 8 can be reduced. Thus, the amorphous frit
glass or frit glass which is crystallized under low temperature of, for example, less
than 350°C can be used as a frit sealing material, so that the frit sealing process
can be carried out at a low working temperature of, for example, less than 350°C.
-
Then, because the temperature of the frit sealing process can be reduced.
the temperature of the blackening process for the color selecting electrode 3,
which requires the same or higher temperature as the frit sealing process can be
reduced to less than 350°C, for example.
-
If the temperature of the blackening process is reduced, the change of the
tension between before and after the blackening process is reduced largely. As a
result, the initial tension when the color selecting electrode thin plate (color
selecting mask) 7 is stretched, can be reduced largely as compared to the
conventional excessive tension, so that the strength necessary for the frame 6 of
the color selecting electrode 3 can be reduced.
-
Therefore, the structure can be simplified by reducing the stiffness of the
frame 6, so that the weight of the color selecting electrode can be reduced so as to
achieve light weight of the cathode-ray tube.
-
Furthermore, because the temperatures of the blackening process and frit
sealing process are reduced, heating and lighting cost necessary for furnace
operation and updating the system and consumption cost of the production
apparatus can be reduced, and the time interval of a temperature cycle can be
reduced, so that the working efficiency can be improved.
-
Subsequently, another embodiment of the present invention will be
described.
-
This embodiment concerns a case in which a means for creating a vacuum
on the outside of the cathode-ray tube 10 is provided only near the frit portion 8.
-
FIG. 9 shows a schematic structure diagram of the production apparatus for
the cathode ray tube according to this embodiment of the present invention.
-
In this production apparatus 21, the processing chamber 22 covers a
portion near the frit portion 8 of the cathode-ray tube 10, that is, part of the funnel
portion 1b and panel portion 1a.
-
Then, the inside 23 of the processing chamber 22 is connected to the
second vacuum pump 14 like FIG. 1.
-
The other structural elements are the same as in the production apparatus
11 of the above described embodiment, and therefore, identical reference numerals
are attached and duplicated description thereof is omitted.
-
Because according to this embodiment, the processing portion 22 is
provided only near the frit portion 8, volume of the inside 23 is smaller.
-
Thus, the evacuation by the second vacuum pump 14 is facilitated and an
evacuated space is smaller, so that the structure of the processing chamber 22 can
be simplified.
-
The present invention is not restricted to the above described respective
embodiments which may be modified in various ways within a scope not
departing from the gist of the present invention.
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According to the above described present invention, the difference of
pressure between the inside and outside of the cathode-ray tube in the
exhaust/sealing process can be reduced. Therefore, the load applied to the frit
portion in which the panel and funnel are joined together can be reduced.
-
Thus, using amorphous frit glass or frit glass which is crystallized at low
temperature as sealing material, the frit sealing process can be carried out at low
working temperatures.
-
Furthermore, because the temperature of the frit sealing process can be
reduced, the temperature of the blackening process for the color selecting
electrode can be also reduced.
-
Consequently, the change of tension between before and after the
blackening process can be reduced largely. Thus, the initial tension can be
reduced largely as compared to the conventional excessive tension so that the
strength necessary for the frame of the color selecting electrode can be also
reduced.
-
Therefore, the structure can be simplified by reducing the stiffness of the
frame, so that the weight of the color selecting electrode can be reduced thereby
leading to reduction in the weight of the cathode-ray tube.
-
Having described preferred embodiments of the present invention with
reference to the accompanying drawings, it is to be understood that the present
invention is not limited to the above-mentioned embodiments and that various
changes and modifications can be effected therein by one skilled in the art without
departing from the scope of the present invention as defined in the appended
claims.
