U.S. patent application number 10/652169 was filed with the patent office on 2004-02-26 for crt funnel of a non beam-index type.
This patent application is currently assigned to NIPPON ELECTRIC GLASS CO., LTD.. Invention is credited to Komori, Hiroshi, Yamazaki, Hiroki.
Application Number | 20040038798 10/652169 |
Document ID | / |
Family ID | 26606496 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040038798 |
Kind Code |
A1 |
Komori, Hiroshi ; et
al. |
February 26, 2004 |
CRT funnel of a non beam-index type
Abstract
A CRT funnel of a non beam-index type is made of a lead glass
which contains 10-30 mass % of PbO and has an X-ray absorption
coefficient of 40 cm.sup.-1 or more at 0.6 .ANG.. The lead glass
further contains Sb.sub.2O.sub.3 and an additive including at least
one of CeO.sub.2 and SnO.sub.2. In case where the additive includes
CeO.sub.2, it is preferable that the content of CeO.sub.2 is not
smaller than 0.01 mass % and is smaller than 0.5 mass %. In case
where the additive includes SnO.sub.2, the content of SnO.sub.2
preferably falls within a range of 0.001-2 mass %.
Inventors: |
Komori, Hiroshi; (Otsu-shi,
JP) ; Yamazaki, Hiroki; (Koga-gun, JP) |
Correspondence
Address: |
Collard & Roe, P.C.
1077 Northern Boulevard
Roslyn
NY
11576
US
|
Assignee: |
NIPPON ELECTRIC GLASS CO.,
LTD.
|
Family ID: |
26606496 |
Appl. No.: |
10/652169 |
Filed: |
September 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10652169 |
Sep 2, 2003 |
|
|
|
10034071 |
Dec 20, 2001 |
|
|
|
6642163 |
|
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Current U.S.
Class: |
501/60 ;
501/62 |
Current CPC
Class: |
H01J 29/863 20130101;
C03C 4/087 20130101; C03C 3/105 20130101 |
Class at
Publication: |
501/60 ;
501/62 |
International
Class: |
C03C 003/102; C03C
003/105 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2000 |
JP |
392405/2000 |
Oct 10, 2001 |
JP |
312949/2001 |
Claims
What is claimed is:
1. A CRT funnel of a non beam-index type, made of a lead glass
which contains 10-30 mass % of PbO, which has an X-ray absorption
coefficient of 40 cm.sup.-1 or more at 0.6 .ANG., and which
contains Sb.sub.2O.sub.3 and an additive comprising at least one of
CeO.sub.2 and SnO.sub.2.
2. The CRT funnel according to claim 1, wherein the content of PbO
falls within a range of 15-27 mass %.
3. The CRT funnel according to claim 1, wherein the content of
Sb.sub.2O.sub.3 falls within a range of 0.01-1 mass %.
4. The CRT funnel according to claim 1, wherein said additive
solely comprises CeO.sub.2, the content of CeO.sub.2 being not
smaller than 0.01 mass % and being smaller than 0.5 mass %.
5. The CRT funnel according to claim 4, wherein the content of
CeO.sub.2 falls within a range of 0.01-0.45 mass %.
6. The CRT funnel according to claim 1, wherein said additive
solely comprises SnO.sub.2, the content of SnO.sub.2 falling within
a range of 0.001-2 mass %.
7. The CRT funnel according to claim 6, wherein the content of
SnO.sub.2 falls within a range of 0.001-1.5 mass %.
8. The CRT funnel according to claim 1, wherein said additive
comprises CeO.sub.2 and SnO.sub.2, the content of CeO.sub.2 being
not smaller than 0.01 mass % and being smaller than 0.5 mass %, the
content of SnO.sub.2 falling within a range of 0.001-1.5 mass
%.
9. The CRT funnel according to claim 8, wherein the content of
CeO.sub.2 falls within a range of 0.01-0.45 mass % while the
content of SnO.sub.2 falls within a range of 0.001-1.5 mass %.
10. The CRT funnel according to claim 1, wherein said glass further
contains, in mass %, 48-58% SiO.sub.2, 0.5-6% Al.sub.2O.sub.3, 0-5%
MgO, 0-6% CaO, 0-9% SrO, 0-9% BaO, 3-9% Na.sub.2O, 4-11% K2O, 0-5%
ZnO, and 0-2% ZrO.sub.2.
11. The CRT funnel according to claim 10, wherein the content of
SiO.sub.2 falls within a range of 49-57 mass %.
12. The CRT funnel according to claim 10, wherein the content of
Al.sub.2O.sub.3 falls within a range of 1-5 mass %.
13. The CRT funnel according to claim 10, wherein the content of
MgO is 4 mass % or less.
14. The CRT funnel according to claim 10, wherein the content of
CaO falls within a range of 1-5 mass %.
15. The CRT funnel according to claim 10, wherein the content of
SrO is 7 mass % or less.
16. The CRT funnel according to claim 10, wherein the content of
BaO is 7 mass % or less.
17. The CRT funnel according to claim 10, wherein the content of
Na.sub.2O falls within a range of 4-8 mass %.
18. The CRT funnel according to claim 10, wherein the content of
K2O falls within a range of 5-10 mass %.
19. The CRT funnel according to claim 10, wherein the content of
ZnO is 4 mass % or less.
20. The CRT funnel according to claim 10, wherein the content of
ZrO.sub.2 falls within a range of 0-1.5 mass %.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a funnel for use in a CRT (cathode
ray tube) of a non beam-index type.
[0002] An envelope of a CRT comprises a panel portion for
projecting video images, a tubular neck portion with an electron
gun arranged therein, and a flare-shaped funnel portion connecting
the panel portion and the neck portion. Electron beams emitted from
the electron gun excite phosphors arranged on an inner surface of
the panel portion to emit light so that the video images are
projected on the panel portion. At this time, X-rays bremsstrahlung
are produced inside the CRT. Therefore, the envelope of the type is
required to have a high X-ray absorbability.
[0003] A funnel glass is used for the funnel portion. The funnel
glass used for the envelope of the CRT is generally referred to as
a CRT funnel glass.
[0004] In view of the above, the funnel glass is made of a lead
glass which contains 10-30 mass % of PbO high in X-ray
absorbability and which has an X-ray absorption coefficient of 40
cm.sup.-1 or more at 0.6 .ANG..
[0005] Such CRTs are classified broadly into a non beam-index type
and a beam-index type. In recent years, following the increase in
production amount and size of the CRT of the non beam-index type,
there arises a shortage of glass parts. In particular, the funnel
glass tends to be broken during an assembling process of the CRT.
Therefore, the shortage is serious for the funnel glass as compared
with other parts and the increase in production amount is in a
strong demand.
[0006] In order to increase the production amount, an additional
melting furnace must be newly installed. However, such new
installation of the additional melting furnace results in a high
cost and is not preferable.
[0007] In view of the above, it is proposed to increase a glass
pull rate in an existing melting furnace without newly installing
the additional melting furnace. However, if the glass pull rate is
increased, a residence time of a glass within the melting furnace
is shortened so that the glass is formed into a glass product
without being subjected to sufficient fining within the melting
furnace. In this event, the number of seeds in the glass product is
increased and a product yield or a production efficiency is
degraded.
[0008] In order to increase the glass pull rate in the melting
furnace and to reduce the number of seeds in the glass product, the
content of Sb.sub.2O.sub.3 as a fining agent for a CRT glass must
be increased. However, since Sb.sub.2O.sub.3 is a high
environmental load substance, a greater content than that used at
present is unfavorable.
[0009] In view of the above, proposal is made of a technique of
reducing the number of seeds in the glass by addition of CeO.sub.2
to Sb.sub.2O.sub.3. For example, Japanese Unexamined Patent
Publication No. 8-31342 (JP 8-31342 A) discloses a CRT funnel made
of a lead glass containing Sb.sub.2O.sub.3 and CeO.sub.2. However,
the funnel disclosed therein is for use in a beam-index type CRT.
In the CRT of this type, coloring of a funnel glass by X rays
produced in the CRT results in reduction in indexing beams detected
by a photodetector device so that the performance of the CRT is
deteriorated. The addition of CeO.sub.2 in the above-mentioned
publication aims to solve such problem due to the X-ray coloring
inherent to the beam-index type CRT funnel. Thus, the glass
disclosed therein contains a large amount of CeO.sub.2. In
addition, the CRT funnel of the beam-index type is a small-sized
model not greater than 6 inches and is very small in quantity of
production. Therefore, the glass pull rate is small so that the
residence time of the glass in the melting furnace is extended. As
a result, irrespective of the amount of the fining agent,
sufficient fining is performed. In this connection, the
above-mentioned publication does not suggest an appropriate type
and an appropriate type of the fining agent in case where the glass
pull rate is increased.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of this invention to provide a CRT
funnel of a non beam-index type having an excellent seed free grade
by enabling the increase in glass pull rate in a production process
without requiring the increase in content of Sb.sub.2O.sub.3.
[0011] Other objects of the present invention will become clear as
the description proceeds.
[0012] According to an aspect of this invention, there is provided
a CRT funnel of a non beam-index type, made of a lead glass which
contains 10-30 mass % of PbO, which has an X-ray absorption
coefficient of 40 cm.sup.-1 or more at 0.6 .ANG., and which
contains Sb.sub.2O.sub.3 and an additive comprising at least one of
CeO.sub.2 and SnO.sub.2.
[0013] CeO.sub.2 and SnO.sub.2 have following characteristics. In
CeO.sub.2, change in valence causes a reaction represented by
2CeO.sub.2->Ce.sub.2O.sub.3+1/2O.sub.2 to gradually produce an
oxygen gas in a temperature range from about 1000.degree. C. to
about 1500.degree. C. In SnO.sub.2, change in valence number causes
a reaction represented by SnO.sub.2->SnO+1/2O.sub.2 in a
temperature range higher than the above-mentioned temperature range
in CeO.sub.2 to produce an oxygen gas in a temperature range from
about 1400.degree. C. to about 1600.degree. C. Therefore, by the
use of Sb.sub.2O.sub.3 and at least one of CeO.sub.2 and SnO.sub.2
in combination as a fining agent, a fining gas is increased in a
wide temperature range. As a consequence, even if a residence time
of the glass in a melting furnace is short, a high fineness is
kept.
[0014] PbO is a component which improves the X-ray absorption
coefficient of the glass. However, if the content of PbO is less
than 10 mass %, the X-ray absorbability is insufficient. On the
other hand, if the content is greater than 30 mass %, the viscosity
of the glass is excessively low so that formation is difficult.
Preferably, the content of PbO falls within a range of 15-27 mass
%.
[0015] Sb.sub.2O.sub.3 is essential as a fining agent. However, if
the content is greater than 2 mass %, the glass tends to be
devitrified. Preferably, the content of Sb.sub.2O.sub.3 falls
within a range of 0.01-1 mass %.
[0016] CeO.sub.2 is a component required to compensate the shortage
of the fining gas in case where the glass pull rate is increased.
However, if the content is less than 0.01 mass %, a sufficient
effect can not be obtained. On the other hand, the content of 0.5
mass % or more brings about no substantial change in fineness and
does not provide the effect corresponding to the increase in raw
material cost but the number of seeds may be increased to the
contrary. In case where the above-mentioned additive comprises
CeO.sub.2 alone, the content of CeO.sub.2 preferably falls within a
range of 0.01-0.45 mass %.
[0017] SnO.sub.2 is also a component required to compensate the
shortage of the fining gas in case where the glass pull rate is
increased. If the content is less than 0.001 mass %, a sufficient
effect can not be obtained. On the other hand, if the content is
greater than 2 mass %, the glass tends to be devitrified. In case
where the above-mentioned additive comprises SnO.sub.2 alone, the
content of SnO2 preferably falls within a range of 0.001-1.5 mass
%.
[0018] In case where the above-mentioned additive comprises
CeO.sub.2 and SnO.sub.2, it is preferable that the content of
CeO.sub.2 is not smaller than 0.01 mass % and is smaller than 0.5
mass % and that the content of SnO.sub.2 falls within a range of
0.001-2 mass %.
[0019] In addition, the lead glass may further contain, in mass %,
48-58% SiO.sub.2, 0.5-6% Al.sub.2O.sub.3, 0-5% MgO, 0-6% CaO, 0-9%
SrO, 0-9% BaO, 3-9% Na2O, 4-11% K.sub.2O, 0-5% ZnO, and 0-2%
ZrO.sub.2.
[0020] SiO.sub.2 is a component serving as a network former of the
glass. If the content is less than 48 mass %, the viscosity of the
glass is excessively low so that the formation becomes difficult.
If the content is more than 58 mass %, the coefficient of thermal
expansion of the glass is excessively low and fails to match the
coefficient of thermal expansion of a neck glass. Preferably, the
content of SiO.sub.2 falls within the range of 49-57 mass %.
[0021] Al.sub.2O.sub.3 is also a component serving as a network
former of the glass. If the content is smaller than 0.5 mass %, the
viscosity of the glass is excessively low so that the formation
becomes difficult. If the content is greater than 6 mass %, the
coefficient of thermal expansion of the glass is excessively low
and fails to match the coefficient of thermal expansion of a neck
glass. Preferably, the content of Al.sub.2O.sub.3 falls within a
range of 1-5 mass %.
[0022] MgO is a component serving to facilitate melting of the
glass and to adjust the coefficient of thermal expansion and the
viscosity. If the content is greater than 5 mass %, the glass tends
to be devitrified so that the formation becomes difficult.
Preferably, the content of MgO is 4 mass % or less
[0023] CaO, like MgO, is a component serving to facilitate melting
of the glass and to adjust the coefficient of thermal expansion and
the viscosity. If the content is greater than 6 mass %, the glass
tends to be devitrified so that the formation becomes difficult.
Preferably, the content of CaO falls within a range of 1-5 mass
%.
[0024] Each of SrO and BaO is a component serving to facilitate
melting of the glass, to adjust the coefficient of thermal
expansion and the viscosity, and to improve the X-ray
absorbability. If the content of each of SrO and BaO is greater
than 9 mass %, the glass tends to be devitrified so that the
formation becomes difficult. Preferably, the content of each of SrO
and BaO is 7 mass % or less.
[0025] Na.sub.2O is a component to adjust the coefficient of
thermal expansion and the viscosity. If the content is less than 3
mass %, the coefficient of thermal expansion is excessively low and
fails to match the coefficient of thermal expansion of the neck
glass. If the content is more than 9 mass %, the viscosity is
excessively low so that the formation is difficult. Preferably, the
content of Na.sub.2O falls within the range of 4-8 mass %.
[0026] K.sub.2O, like Na.sub.2O, is a component to adjust the
coefficient of thermal expansion and the viscosity. If the content
is smaller than 4 mass %, the coefficient of thermal expansion is
excessively low and fails to match the coefficient of thermal
expansion of the neck glass. If the content is greater than 11 mass
%, the viscosity is excessively low so that the formation is
difficult. Preferably, the content of K.sub.2O falls within the
range of 5-10 mass %
[0027] ZnO is a component to improve the X-ray absorption
coefficient of the glass and to suppress alkali elution. If the
content is greater than 5 mass %, generation of devitrifying stones
is increased due to volatilization and agglomeration of ZnO.
Preferably, the content of ZnO is 4 mass % or less.
[0028] ZrO.sub.2 is a component to improve the X-ray absorption
coefficient of the glass. If the content is greater than 2 mass %,
the glass tends to be devitrified so that the formation becomes
difficult. Preferably, the content of ZrO.sub.2 falls within the
range of 0-1.5 mass %.
[0029] In addition to the above-mentioned components, other
components such as P.sub.2O.sub.5 and B.sub.2O.sub.3 may be added
up to 1 mass % as far as the characteristics of the glass are not
degraded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a view for describing a method of preparing each
sample upon measurement of the ratio of seeds remaining in a glass;
and
[0031] FIG. 2 is a view showing a cut face of the sample.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] Now, a CRT funnel of a non beam-index type according to an
embodiment of this invention will be described in detail in
conjunction with specific examples.
[0033] The CRT funnel is made of a lead glass selected from
examples (Samples Nos. 1-8) which are shown in Tables 1 and 2
together with comparative examples (Samples Nos. 9-11). The sample
No. 9 shows an existing funnel composition.
1 TABLE 1 Examples composition (mass %) No. 1 No. 2 No. 3 No. 4 No.
5 No. 6 SiO.sub.2 52.5 55.55 50.67 52.8 52.5 53.2 Al.sub.2O.sub.3
3.3 1.0 4.8 3.0 3.3 2.0 PbO 22.8 20.0 19.0 22.0 22.8 20.0 MgO 1.9
0.5 2.0 1.5 1.9 2.5 CaO 3.8 4.0 3.0 4.0 3.8 3.5 SrO 0.6 4.0 3.0 1.0
0.6 -- BaO 0.8 -- 1.0 1.0 0.8 4.0 Na.sub.2O 6.3 5.0 5.5 6.5 6.3 6.0
K.sub.2O 7.6 9.0 8.5 7.5 7.6 8.0 ZnO 0.1 0.4 2.2 -- 0.1 --
ZrO.sub.2 -- -- -- -- -- 0.2 Sb.sub.2O.sub.3 0.2 0.1 0.3 0.5 0.2
0.1 CeO.sub.2 0.1 0.45 0.03 0.2 -- -- SnO.sub.2 -- -- -- -- 0.1 0.5
Ratio (%) of seeds 7 7 6 5 8 7 remaining in the glass X-ray
absorption co- 66 65 63 63 66 61 efficient (0.6
.ANG.,cm.sup.-1)
[0034]
2 TABLE 2 Examples Comparative Examples composition (mass %) No. 7
No. 8 No. 9 No. 10 No. 11 SiO.sub.2 54.8 52.5 52.6 53.6 55.9
Al.sub.2O.sub.3 1.0 3.3 3.3 2.0 1.0 PbO 20.0 22.8 22.8 20.0 20.0
MgO 0.5 1.9 1.9 2.5 0.5 CaO 4.0 3.8 3.8 3.5 4.0 SrO 4.0 0.6 0.6 --
4.0 BaO -- 0.8 0.8 4.0 -- Na.sub.2O 5.0 6.3 6.3 6.0 5.0 K.sub.2O
9.0 7.6 7.6 8.0 9.0 ZnO 0.4 0.1 0.1 -- 0.4 ZrO.sub.2 -- -- -- -- --
Sb.sub.2O.sub.3 0.3 0.2 0.2 -- -- CeO.sub.2 -- 0.1 -- 0.4 --
SnO.sub.2 1.0 0.1 -- -- 0.2 Ratio (%) of seeds 4 5 10 11 13
remaining in the glass X-ray absorption co- efficient (0.6 .ANG.,
cm.sup.31 1) 65 66 66 61 66
[0035] Each of the samples given in Tables was prepared in the
following manner.
[0036] At first, a material batch in an amount of 100 g prepared to
have a glass composition as defined in the Tables was put into a
platinum conical crucible and melted at about 1550.degree. C. for
20 minutes. Next, a molten glass was removed from the crucible and
gradually cooled to obtain a glass 1 illustrated in FIG. 1. The
glass thus prepared was cut into a piece having a thickness of 5
mm. A cut face was subjected to mirror-polishing to obtain the
sample having a polished cut face. FIG. 2 shows the cut face of the
sample. In the figure, a reference numeral 2 represents seeds
remaining in the glass.
[0037] For each sample obtained as mentioned above, the ratio of
seeds remaining in the glass and the X-ray absorption coefficient
were calculated. The results are shown in the Tables.
[0038] The ratio of seeds remaining in the glass is calculated in
the following manner. An image of the polished cut face of each
sample was picked up and was supplied to a computer. By image
processing, the ratio of seeds with respect to a sectional area was
calculated. A smaller ratio represents quicker seed free and a
higher fineness.
[0039] The X-ray absorption coefficient was obtained by calculating
the absorption coefficient at 0.6 .ANG. with reference to the glass
composition and the density.
[0040] As is obvious from the Tables, it is understood that, in the
samples Nos. 1 through 8 as the examples of this invention, the
ratio of seeds remaining in the glass was as small as 7% or less
and the seeds were quickly released because these samples contain
CeO.sub.2 and/or SnO.sub.2 in addition to Sb.sub.2O.sub.3. Since
the content of PbO is 19% or more, the X-ray absorption coefficient
was as high as 61 to 66 cm.sup.-1.
[0041] On the other hand, in the samples Nos. 9 through 11 as the
comparative examples, the ratio of seeds remaining in the glass was
as high as 10% or more because one of Sb.sub.2O.sub.3, CeO.sub.2
and SnO.sub.2 was solely used as a fining agent.
[0042] Based on the above-mentioned results, the glass was melted
in a practical melting furnace to manufacture a funnel. Then, the
number of seeds in a resultant product was counted.
[0043] At first, by the use of a glass material having the
composition of Sample No. 9 which does not contain CeO.sub.2 and
SnO.sub.2, the funnel was manufactured at a glass pull rate of 100
kg/hr within the melting furnace. In this event, the number of
seeds was 0.5/kg. After the glass pull rate was changed into 110
kg/hr, the number of seeds was remarkably increased. Next, the
glass pull rate was kept at 110 kg/hr, 0.1% of CeO.sub.2 was added
to the composition of No. 9 which is thereby modified into the
composition of Sample No. 1. In this state, the funnel was
manufactured. Then, the number of seeds was decreased to
0.5/kg.
[0044] In the similar manner, the funnel was produced after the
composition of No. 9 was changed into the composition of No. 5.
Then, the number of seeds was 0.5/kg.
[0045] Since the lead glass described above has a high fineness,
the funnel having a seed free grade equivalent or superior to that
of the existing funnel can be manufactured even if the glass pull
rate is increased. Therefore, it is possible to solve the problem
of shortage of funnels resulting from the increase in production
amount or in size.
[0046] The CRT funnel of the non beam-index type according to this
invention can be obtained by preparing a material batch having a
composition within the above-mentioned range, melting the material
batch at about 1500.degree. C. to produce a molten glass, forming a
glass gob from the molten glass, supplying the glass gob into a
molding die, and press forming the glass gob.
* * * * *