U.S. patent application number 09/794000 was filed with the patent office on 2001-09-13 for method of producing cathode ray tube and method of forming films.
This patent application is currently assigned to Sony Corporation. Invention is credited to Adachi, Takumi.
Application Number | 20010021410 09/794000 |
Document ID | / |
Family ID | 18587130 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021410 |
Kind Code |
A1 |
Adachi, Takumi |
September 13, 2001 |
Method of producing cathode ray tube and method of forming
films
Abstract
Disclosed is a method of forming a reflection film and a heat
absorbing film on the inner surface of a panel of a cathode ray
tube by using a vacuum vapor-deposition process. In the case of
using aluminum as the material for the reflection film, chromium is
used as the material for the heat absorbing film. Chromium has a
boiling point under a vacuum pressure at the time of
vapor-deposition, which is higher than that of aluminum. The
mixture of aluminum and chromium is supplied to a heater portion,
and is heated and vaporized by the heater portion to be deposited
on the inner surface of the panel. In this deposition, aluminum is
first vapor-deposited and then chromium is vapor-deposited.
Accordingly, the two kinds of films are formed in one
vapor-deposition step.
Inventors: |
Adachi, Takumi; (Saitama,
JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING
1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
Sony Corporation
|
Family ID: |
18587130 |
Appl. No.: |
09/794000 |
Filed: |
February 28, 2001 |
Current U.S.
Class: |
427/69 ;
427/294 |
Current CPC
Class: |
H01J 9/20 20130101; C23C
14/18 20130101; C23C 14/24 20130101; C23C 14/50 20130101; H01J
29/28 20130101 |
Class at
Publication: |
427/69 ;
427/294 |
International
Class: |
C23C 016/00; B05D
005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2000 |
JP |
P2000-068018 |
Claims
What is claimed is:
1. A method of producing a cathode ray tube, which is adapted to
form a reflection film and a heat absorbing film on the inner
surface of a panel by using a vacuum vapor-deposition process,
comprising the steps of: supplying a first material for forming the
reflection film and a second material for forming the heat
absorbing film to a heating source; and heating and vaporizing the
first and second materials by the heating source, thereby
depositing the first and second materials on the inner surface of
the panel; wherein the second material has a boiling point under a
vacuum pressure at the time of vapor-deposition, which is higher
than that of the first material.
2. A method of producing a cathode ray tube according to claim 1,
wherein the heating temperature at the time of vapor-deposition is
controlled to be switched on the basis of the boiling point of each
of the first and second materials.
3. A method of producing a cathode ray tube according to claim 1,
wherein the first and second materials are mixed to each other, and
the resultant mixture is supplied to the heating source.
4. A method of producing a cathode ray tube according to any one of
claims 1 to 4, wherein the first material is aluminum and the
second material is chromium.
5. A method of forming films, which is adapted to form two or more
films on a specific surface by a vacuum vapor-deposition process,
comprising the steps of: supplying two or more kinds of materials
to a heating source; and heating and vaporizing the two or more
kinds of materials by the heating source, thereby depositing the
two or more kinds of materials on the specific surface; wherein the
two or more kinds of materials are different from each other in
vacuum pressure at the time of vapor-deposition.
6. A method of forming films according to claim 5, wherein the
heating temperature at the time of vapor-deposition is controlled
to be switched on the basis of the boiling point of each of the two
or more kinds of materials.
7. A method of forming films according to claim 5, wherein the two
or more kinds of materials are mixed to each other, and the
resultant mixture is supplied to the heating source.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method of producing a
cathode ray tube, and particularly to a method of forming, on the
inner surface of a panel, a metal back film, that is, a reflection
film for improving the intensity of luminescence by a phosphor and
a heat absorbing film for reducing the degree of mislanding of an
electron beam due to thermal expansion of a mask used for color
selection, and a method of forming films suitable for forming a
reflection film and a heat absorbing film on the inner surface of a
panel.
[0002] In the step of producing a panel of a color cathode ray
tube, a phosphor film is formed on the inner surface of a panel and
then a reflection film made from aluminum is formed on the phosphor
film.
[0003] The phosphor film is formed by forming phosphors of red,
green, and blue on a black matrix film already formed on the inner
surface of the panel at specific positions corresponding to a
specific pattern, and forming an intermediate film for smoothening
the surfaces of the phosphors thereon.
[0004] The reflection film is formed by vapor-depositing aluminum
on the inner surface of the panel on which the phosphor film has
been formed.
[0005] In this way, as shown in FIG. 1, a phosphor film 2 and a
reflection film 3 are formed on the inner surface of the panel
1.
[0006] In a color cathode ray tube, generally, three electron beams
emitted from an electron gun are subjected to color selection by a
so-called mask such as an aperture grill or a shadow mask.
[0007] The three electron beams, which have passed through the
mask, collide with phosphors of the corresponding colors.
[0008] When irradiated with the electron beams, the mask generates
heat, with a result that the temperature of the mask is
increased.
[0009] The temperature of the mask is further increased due to the
fact that the radiation heat of the mask is reflected from the
reflection film formed on the phosphor film.
[0010] As a result, the thermal expansion of the mask becomes
significant, so that a deviation in landing position of each
electron beam when the electron beam reaches the phosphor.
[0011] The deviation in landing position of each electron beam is
called "mislanding" of the electron beam.
[0012] Such a phenomenon causes an inconvenience such as color
shift on an image displayed on a screen of the cathode ray
tube.
[0013] To reduce the degree of mislanding of electron beams, there
have been known methods of forming a heat absorbing film on a
reflection film already formed on the inner surface of a panel.
[0014] The heat absorbing film functions to absorb the radiation
heat generated by a mask.
[0015] The use of the heat absorbing film is thus effective to
suppress the thermal expansion of the mask.
[0016] According to the related art methods, the reflection film is
first formed by vapor-depositing aluminum on the inner surface of
the panel, and then the heat absorbing film is formed thereon.
[0017] For example, according to one of the related art methods, a
heat absorbing film is formed on the inner surface of a panel, on
which a reflection film has been formed, by coating the inner
surface of the panel with a suspension of graphite by spraying.
[0018] According to another related art method, aluminum is
vapor-deposited to form a reflection film, and subsequently
aluminum is again vapor-deposited at a vacuum pressure higher than
a vacuum pressure set at the time of forming the reflection film,
to form a heat absorbing film made from aluminum oxide on the
reflection film.
[0019] According to a further related art method, a heat absorbing
film is formed by vapor-depositing a blackened material other than
aluminum, for example, manganese or tin.
[0020] Each of the above-described related art methods, however,
requires independent two film formation steps for forming a
reflection film and a heat absorbing film on the inner surface of a
panel.
[0021] As a result, there occurs an inconvenience that the process
of producing a panel of a cathode ray tube is complicated.
SUMMARY OF THE INVENTION
[0022] An object of the present invention is to provide a method of
forming a reflection film and a heat absorbing film on the inner
surface of a panel of a cathode ray tube without complicating a
process of producing the cathode ray tube.
[0023] To achieve the above object, according to the present
invention, there is provided a method of producing a cathode ray
tube, which is adapted to form a reflection film and a heat
absorbing film on the inner surface of a panel by using a vacuum
vapor-deposition process, including the steps of: supplying a first
material for forming the reflection film and a second material for
forming the heat absorbing film to a heating source; and heating
and vaporizing the first and second materials by the heating
source, thereby depositing the first and second materials on the
inner surface of the panel; wherein the second material has a
boiling point under a vacuum pressure at the time of
vapor-deposition, which is higher than that of the first
material.
[0024] With this configuration, when the first and second materials
supplied to the heating source are heated by the heat source, the
first material lower in boiling pressure under a vacuum pressure at
the time of vapor-deposition is first vaporized to be deposited on
the inner surface of the panel, and then the second material is
vaporized to be deposited on the inner surface of the panel.
[0025] As a result, the reflection film and the heat absorbing film
are continuously formed in one vapor-deposition step.
[0026] This is effective to simplify the process of producing a
cathode ray tube and hence to reduce the production cost
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a sectional view of a panel of a cathode ray tube,
showing a positional relationship between a phosphor film and a
reflection film provided on the inner surface of the panel;
[0028] FIG. 2 is a sectional view of a structure of a cathode ray
tube to which the present invention is applied, showing a phosphor
film provided on the inner surface of a panel, a reflection film
provided on the phosphor film, a heat absorbing film provided on
the reflection film, and a mask provided adjacently to the heat
absorbing film;
[0029] FIG. 3 is a view of a vacuum vapor-deposition system used
for the present invention, showing an arrangement of a panel, a
vacuum chamber, and a heater for vapor-deposition;
[0030] FIG. 4 is a graph showing one example of a heating
temperature profile for vapor-deposition, which is used in a method
according to an embodiment of the present invention; and
[0031] FIG. 5 is a graph showing another example of the heating
temperature profile for vapor-deposition, which is used in the
method according to the embodiment of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0032] Hereinafter, an embodiment of the present invention suitable
for producing a cathode ray tube, particularly, a panel of a
cathode ray tube will be described with reference to the
drawings.
[0033] FIG. 2 is a sectional side view of a cathode ray tube
produced in accordance with a production method of the present
invention.
[0034] Referring to FIG. 2, a cathode ray tube main body 10
includes a glass made panel 11 and a funnel 12.
[0035] The end surface of an opening of the panel 11 is butted to
the end surface of an opening of the funnel 12 and is integrally
joined thereto with a sealant such as frit.
[0036] An electron gun 13, which functions as an electron beam
emission source, is contained in a neck portion of the funnel
12.
[0037] A phosphor film 14, a reflection film 15, and a heat
absorbing film 16 are formed on the inner surface of the panel
11.
[0038] A mask 17 for color selection, such as an aperture grill or
a shadow mask, is built in the cathode ray tube main body 10.
[0039] The mask 17 has a large number of slits or apertures for
color selection.
[0040] The mask 17 is disposed in the cathode ray tube main body 10
at a position near the inner surface of the panel 11.
[0041] An electron beam emitted from the electron gun 14 passes
through one of the slits or apertures of the mask 17 as shown by a
broken line in the figure, to reach the inner surface of the penal
11.
[0042] The electron beam, which has reached the inner surface of
the panel 11, makes the corresponding phosphor of the phosphor film
14 formed on the inner surface of the panel 11 luminous.
[0043] FIG. 3 is a schematic view of a vacuum vapor-deposition
system used for the present invention.
[0044] Referring to FIG. 3, a panel receiving base 19 is provided
on an upper portion of a vacuum chamber 18.
[0045] The panel 11 is placed on the panel receiving base 19 with
the phosphor film 14 formed on the inner surface of the panel 11
directed downwardly.
[0046] Two heater portions 20A and 20B as heating sources are
provided inside the vacuum chamber 18.
[0047] The two heater portions 20A and 20B are disposed in such a
manner as to be opposed to the phosphor film 14 formed on the inner
surface of the panel 11 placed on the panel receiving base 19.
[0048] The heater portions 20A and 20B may be heated by a
resistance heating method, an electron beam heating method, or a
high frequency induction heating method.
[0049] The number of the heater portions and the arrangement
thereof may be suitably set depending on the size and shape of the
panel 11 on which films are to be formed.
[0050] A method of forming a reflection film and a heat absorbing
film on the inner surface of the panel 11, that is, on the phosphor
film 14 by using the above-described vacuum vapor-deposition
system.
[0051] First, the panel 11 is placed on the panel receiving base 19
and materials are supplied to the heater portions 20A and 20B
disposed in the vacuum chamber 18.
[0052] At this time, the materials are put in crucibles provided on
the heater portions 20A and 20B.
[0053] Here, in the case of using aluminum as the material for
forming the reflection film 15, that is, as a first material, a
material having a boiling point under a vacuum pressure at the time
of vapor-deposition which is higher than that of aluminum and
exhibiting a desired heat absorbing function is used as the
material for forming the heat absorbing film 16, that is, as a
second material.
[0054] To be more specific, assuming that the vacuum pressure at
the time of vapor-deposition is 1.times.10.sup.-4 Torr
(1.33.times.10.sup.-2 Pa), the boiling point of aluminum under the
vacuum pressure is about 980.degree. C.
[0055] Accordingly, a material having a boiling point higher than
that of aluminum, for example, chromium having a boiling point of
1170.degree. C. under the vacuum pressure of 1.times.10.sup.-4 Torr
may be selected as the material for forming the heat absorbing film
16.
[0056] Powders of aluminum and chromium, which are selected as the
two kinds of materials satisfying the above requirement, are mixed,
for example, at a weight ratio of 1:1.
[0057] The resultant mixture may be compressed.
[0058] The mixture thus prepared is put in the crucibles on the
heater portions 20A and 20B.
[0059] The inside of the vacuum chamber 18 is then evacuated by
using a vacuum pump or the like.
[0060] The inner pressure of the vacuum chamber 18 is thus reduced
to a specific vacuum pressure.
[0061] The heater portions 20A and 20B are then operated.
[0062] The mixture is thus heated in accordance with a specific
temperature profile to be described later.
[0063] FIG. 4 shows a profile of a heating temperature at the time
of vapor-deposition.
[0064] It should be noted that the temperature profile shown in
FIG. 4 indicates the heating temperature of the material heated by
the corresponding one of the heater portions 20A and 20B with an
elapsed time.
[0065] Accordingly, the temperature of each of the heater portions
20A and 20B is controlled to a temperature slightly higher than the
above heating temperature of the material.
[0066] As is apparent from FIG. 4, the mixture is first subjected
to preliminary heating for 20 sec.
[0067] The temperature in the preliminary heating step is set to a
temperature lower than the above-described boiling point of
aluminum, that is, 980.degree. C., for example, set to 800.degree.
C. as shown in FIG. 4.
[0068] Next, the heating temperature is raised to a temperature
higher than 800.degree. C., and the mixture is subjected to main
heating at such a temperature for 45 sec.
[0069] The temperature in the main heating step is set to a
temperature higher than the above-described boiling point of
chromium, that is, 1170.degree. C., for example, set to
1200.degree. C. as shown in FIG. 4.
[0070] The mixture is thus heated by each of the heater portions
20A and 20B in accordance with the above-described temperature
profile.
[0071] Accordingly, aluminum lower in boiling point, that is, the
first material is first vaporized to be deposited on the inner
surface of the panel 11.
[0072] Subsequently, chromium higher in boiling point, that is, the
second material is vaporized to be deposited on the inner surface
of the panel 11.
[0073] As a result, the reflection film 15 made from aluminum and
the heat absorbing film 16 made from chromium are continuously
stacked on the inner surface of the panel 11, that is, on the
phosphor film 14.
[0074] By using such a production method, the reflection film 15
and the heat absorbing film 16 can be simultaneously formed on the
inner surface of the panel 11 in one vapor-deposition step.
[0075] The process of producing a cathode ray tube can be thus
simplified.
[0076] A time required for carrying out the film formation step for
forming the reflection film 15 and the heat absorbing film 16 can
be significantly reduced.
[0077] Since the mixture of powders of aluminum and chromium is
supplied to each of the heater portions 20A and 20B, chromium can
be efficiently heated with the aid of the thermal conduction of
aluminum previously melted.
[0078] This is effective to relatively easily evaporate chromium
having the high boiling point.
[0079] According to the present invention, however, it is not
necessarily required to supply the two materials in the form of the
mixture.
[0080] For example, a powder of aluminum and a powder of chromium
are weighed so that a weight ratio between the amounts of aluminum
and chromium becomes a specific weight ratio.
[0081] The powders of aluminum and chromium are supplied to the
heater portions 20A and 20B, respectively.
[0082] Alternatively, pellets of aluminum and pellets of chromium
may be supplied to the heater portions 20A and 20B,
respectively.
[0083] FIG. 5 shows another example of the heating temperature
profile at the time of vapor-deposition.
[0084] First, like the above-described temperature profile shown in
FIG. 4, the mixture is first subjected to preliminary heating at
800.degree. C. for 20 sec.
[0085] Next, the heating temperature is set to a temperature higher
than the boiling point of aluminum, that is, 980.degree. C. and
lower than the boiling point of chromium, that is, 1170.degree. C.,
for example, set to 1050.degree. C. as shown in FIG. 5.
[0086] The mixture is subjected to first main heating at
1050.degree. C. for 30 sec.
[0087] Next, the heating temperature is set to a temperature higher
than the boiling point of chromium, that is, 1170.degree. C., for
example, set to 1200.degree. C. as shown in FIG. 5.
[0088] The mixture is subjected to second main heating at
1200.degree. C. for 45 sec.
[0089] The two materials are thus heated by each of the heater
portions 20A and 20B in accordance with the temperature profile
shown in FIG. 5.
[0090] The two materials may be supplied in the form of the
mixture.
[0091] In such a temperature profile, the heating temperature at
the time of vapor-deposition is controlled to be switched on the
basis of the boiling point of each of the first and second
materials.
[0092] Accordingly, first, aluminum lower in boiling point is
evaporated by the first main heating to be deposited on the inner
surface of the panel 11.
[0093] Subsequently, chromium higher in boiling point is evaporated
by the second main heating to be deposited on the inner surface of
the panel 11.
[0094] As a result, the evaporation of aluminum and the evaporation
of chromium to the inner surface of the panel 11 can be separately
performed in accordance with one temperature profile.
[0095] In other words, it is possible to prevent aluminum and
chromium from being simultaneously evaporated.
[0096] Accordingly, each of the reflection film 15 and the heat
absorbing film 16 can be formed as a high purity film.
[0097] In the above-described embodiment, aluminum is used as the
first material and chromium is used as the second material;
however, the present invention is not limited thereto but may be
applicable to a combination of other materials (which may be other
than metals).
[0098] Further, in the above-described embodiment, the present
invention is applied to the process of producing a cathode ray
tube; however, the present invention is not limited thereto but may
be widely applicable to a method of forming two or more kinds of
films on a specific surface by using the vacuum vapor-deposition
process.
[0099] In this case, two or more kinds of materials different in
boiling point under a vacuum pressure at the time of
vapor-deposition are supplied to a heating source, and the two or
more kinds of materials are heated and evaporated by the heating
source to be deposited on the specific surface.
[0100] While the preferred embodiment of the present invention has
been described using the specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
* * * * *