JP2002060244A - Neck glass for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neck glass for a cathode-ray tube having high X-ray absorbing performance and less liable to crack. SOLUTION: The neck glass comprises, by mass, 30-40% PbO, 38-58% SiO2, 0-5% Al2O3, 0-5% MgO, 0-0.1% CaO, 0-5% SrO, 0-5% BaO, 0-5% ZnO (MgO+ CaO+SrO+BaO+ZnO <=5%), 0-5% Na2O, 6-15% K2O, 0-2% Sb2O3, 0 to <1.2% TiO2 and 0-10% Fe2O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neck glass for a cathode ray tube.

[0002]

2. Description of the Related Art An envelope of a cathode ray tube has a panel portion on which an image is projected, a tubular neck portion on which an electron gun is mounted, and
It consists of a funnel-shaped funnel that connects the panel and the neck, and when the electron gun is mounted on the neck tube, the electron gun is fixed at the center of the neck tube in the neck tube welded to one end of the funnel. After inserting a metal pin and an electron gun attached to a stem to which an exhaust pipe has been previously welded, welding is performed by welding the open end of the neck tube and the stem. Usually, this welding is performed by heating a burner frame with a burner.

The electron beam emitted from the electron gun causes a phosphor provided on the inner surface of the panel portion to emit light to project an image on the panel portion. At this time, a braking X-ray is generated in the tube, and this is transmitted through the envelope. Leakage outside the tube has a negative effect on the human body.
This type of envelope is required to have high X-ray absorption capability.

[0004] In particular, the neck tube is required to have a high X-ray absorbing ability because the wall thickness of the tube wall is smaller than that of the panel or the funnel (the average thickness of a general neck tube is about 2.4 mm). . Therefore, unlike a tube glass for lighting made of soda glass or borosilicate glass, a lead tube containing about 35% by mass of PbO, which is a component for maximizing the X-ray absorptivity of glass, is contained in a neck tube or a stem glass. A system glass is used.

[0005]

However, lead-based glass has a lower crack resistance than soda-based glass and borosilicate glass, and has a metal pin for fixing the electron gun when the electron gun is mounted in the neck tube. The inner wall of the neck tube may be rubbed and scratched. The damaged neck tube was damaged during welding of the neck tube and the stem glass, during vacuum baking, and breakdown occurred when a high voltage was applied, thereby reducing production efficiency and safety.

An object of the present invention is to have a high X-ray absorption capacity,
An object of the present invention is to provide a neck glass for a cathode ray tube which is hardly damaged.

[0007]

As a result of repeating various experiments, the present inventors have found a composition that does not easily damage even lead-based glass, and propose the present invention.

That is, the glass for a cathode ray tube according to the present invention is, in terms of mass percentage, 30 to 40% of PbO and 38 to 5 of SiO ₂ .
_{8%, Al 2 O 3 0~5} %, 0~5% MgO, CaO
0 to 0.1%, SrO 0 to 5%, BaO 0 to 5
%, ZnO 0-5%, MgO + CaO + SrO + Ba
O + ZnO 0-5%, Na ₂ O 0-5%, K ₂ O 6
_{~15%, Sb 2 O 3 0~2} %, TiO 2 0~1.2
%, Fe ₂ O ₃ 0 to 10%.

[0009]

The lead glass has lower crack resistance and is more easily damaged than soda glass and borosilicate glass, but the lead glass of the present invention, the neck glass for a cathode ray tube, is more easily damaged. MgO and Ca are components that increase
By suppressing the total amount of O, SrO, BaO, and ZnO to 5% or less, and particularly to suppressing CaO to 0.1% or less, the crack resistance of the glass is increased and the glass is hardly damaged.

The reasons for limiting the composition of the glass in the present invention as described above are as follows.

The amount of PbO is a component that enhances the X-ray absorption coefficient of the glass. If it is less than 30%, the X-ray absorption coefficient is sufficient for glass for a cathode ray tube, that is, the absorption coefficient for X-rays having a wavelength of 0.6 Å. Does not exceed 90 cm ^−1, and the amount of transmitted X-rays becomes too large, which may adversely affect the human body. Conversely, the PbO content is 40% by mass.
If it is larger, the viscosity of the glass becomes too low, and it becomes difficult to form the glass into a neck tube. Preferably 31 to
39%.

[0012] SiO ₂ is a component that serves as a network former of glass. If it is less than 38%, the viscosity of the glass becomes low and molding becomes difficult. If it is more than 58%, the thermal expansion coefficient of the glass becomes low. It becomes too inconsistent with the coefficient of thermal expansion of the funnel glass. Preferably 4
0 to 56%.

[0013] Al ₂ O ₃ is also a component that becomes a network former of the glass, when more than 5%, the glass is easily devitrified, hard spots by reaction with refractory is easily generated. Preferably it is 0-4%.

MgO is a component that makes the glass easy to melt and adjusts the coefficient of thermal expansion and viscosity. Is reduced. Preferably 0
4%.

CaO is a component that facilitates melting of the glass and adjusts the coefficient of thermal expansion and viscosity. However, since the crack resistance of the glass is remarkably reduced, its content should be suppressed to 0.1% or less. Is important, and it is preferable not to contain it.

SrO and BaO are both components that facilitate melting of the glass, adjust the coefficient of thermal expansion and viscosity, and further enhance the X-ray absorption ability. Resistance decreases. Preferably each is 0 to 4.5%. More preferably, SrO is 2.5
%, BaO is less than 1%.

ZnO is a component that makes the glass easy to melt and adjusts the coefficient of thermal expansion and viscosity. Is reduced. Preferably 0
4%.

MgO, CaO, SrO, BaO, ZnO
Is a component that adjusts the coefficient of thermal expansion and viscosity. However, if the total amount of these components is more than 5%, the crack resistance of the glass is significantly reduced, which is not preferable. MgO + CaO + S
The preferable content of rO + BaO + ZnO is 0 to 4.5.
%.

Na ₂ O is a component that adjusts the coefficient of thermal expansion and the viscosity. If it is more than 5%, the viscosity becomes too low, making molding difficult, and the volume resistivity of the glass becomes low. Too much and the electrical insulation deteriorates. Preferably 0
~ 4%.

K ₂ O, like Na ₂ O, is also a component that adjusts the coefficient of thermal expansion and viscosity. If it is less than 6%, the coefficient of thermal expansion will be too low, and if it is more than 15%, the viscosity will be low. It becomes too difficult to mold. Preferably it is 7-14%.

The value of Na ₂ O / (Na ₂ O + K ₂ O) is set to 0.115 to 0.500 (preferably 0.120 to 0.520).
When it is in the range of 0.435), the volume electric resistivity of the glass is increased, and the electrical insulation is improved.

TiO ₂ is a component that suppresses the elution of PbO in the glass when the glass is crushed, buried in the ground and disposed of, but the cost is considerably high when 1.2% or more. Get higher. The preferred range of TiO ₂ is 0 to 1%.

Sb ₂ O ₃ can be used as a fining agent,
If it is more than 2%, the glass tends to be devitrified, and molding is difficult. Preferably it is 0-1%.

Fe ₂ O ₃ is a component that lowers the infrared transmittance of glass, and can be added, for example, when performing infrared heating described below. However, the content of Fe ₂ O ₃ is 1
If it is more than 0%, the glass tends to be devitrified, and molding is difficult. Preferably it is 0 to 7%.

When an electron gun having low heat resistance is mounted, if the transmittance at a wavelength of 1050 nm in the thickness direction of the neck glass is set to 85% or less (preferably 70% or less), the neck tube and the stem of the infrared lamp are used. Local heating of the glass can be performed, and oxidation of the cathode material can be prevented.

85% transmittance at a wavelength of 1050 nm
In order to reduce the content to below, the content of Fe ₂ O ₃ in the glass composition may be set to 0.03% or more (preferably 0.05% or more). Further, a reducing agent such as metal Si is used in an amount of 0.002 to 0.1.
When the content is 5%, the proportion of Fe ²⁺ increases, and it becomes possible to reduce the light transmittance in the infrared region while maintaining the light transmittance in the visible region of the glass.

The average thickness of the neck tube, which is generally widely used, is 2.4 mm. However, the neck glass for a cathode ray tube of the present invention is not limited to this. Needless to say, a neck glass for a cathode ray tube having a small average thickness (for example, 1.0 mm) or a small average thickness (for example, 1.0 mm) is included.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The neck glass for a cathode ray tube of the present invention will be described below in detail with reference to embodiments.

Table 1 shows examples of the present invention (samples No. 1 to No. 1).
4) and Table 2 shows comparative examples (samples Nos. 5 to 8).

[0030]

[Table 1]

[0031]

[Table 2]

Each sample in the table was prepared as follows.

First, a raw material batch prepared so as to have the glass composition shown in the table was placed in a platinum crucible and melted at about 1480 ° C. for 4 hours. In order to obtain a homogeneous glass, degassing was performed by stirring for 3 minutes using a platinum stirring rod on the way. afterwards,
After the molten glass was formed into a predetermined shape, it was gradually cooled.

The crack resistance and X-ray absorption coefficient of each sample thus obtained were measured and are shown in the table.

The crack resistance is determined by the method proposed by Wada et al. (M. Wada et al. Proc., The
Xth ICG, vol. 11, Ceram. So
c. , Japan, Kyoto, 1974, p39). In this method, a sample glass is placed on the stage of a Vickers hardness tester, and a diamond-shaped diamond indenter is pressed against the surface of the sample glass with various loads for 15 seconds. After unloading, the number of cracks generated from the four corners of the indentation by 15 seconds is counted, and the maximum number of cracks (4
C) is determined, and this is defined as the crack occurrence rate. The load at which the crack occurrence rate becomes 50% is defined as “crack resistance”. A large crack resistance means that a crack is hardly generated even under a high load, that is, it has excellent crack resistance. The crack occurrence rate was measured 20 times with the same load, and the average value was obtained. The measurement was performed at a temperature of 25 ° C. and a humidity of 30%.

The X-ray absorption coefficient is obtained by calculating the absorption coefficient for a wavelength of 0.6 Å based on the glass composition and the density.

As is clear from the table, the sample No. Nos. 1-4 have an X-ray absorption coefficient of 100 cm ^-1 or more, and CaO, a component that reduces crack resistance,
And MgO, CaO, SrO,
Since the total content of BaO and ZnO was as low as 3.5% or less, the crack resistance was as high as 300 mN or more, and thus the glass was suitable as a neck glass for a cathode ray tube.

On the other hand, the sample No. 5-
7 has a total content of MgO, CaO, SrO, BaO, and ZnO of 3.7% or less, but contains 0.2% or more of CaO, which is a component that most reduces crack resistance,
The crack resistance is as low as 190 mN or less, and it is considered that cracks are likely to occur in the manufacturing process.

The sample No. No. 8 does not contain CaO, which is the component that most deteriorates crack resistance, but has a low crack resistance of 180 mN because the total amount of MgO, CaO, SrO, BaO, and ZnO is as high as 5.2%, and is thus low. It seems that cracks are likely to occur in the process.

[0040]

As described above, in the neck glass for a cathode ray tube of the present invention, the content of CaO is suppressed to 0.1% or less,
Since the total amount of O, CaO, SrO, BaO, and ZnO is limited to 5% or less, it has excellent crack resistance. Moreover, since it has a high X-ray absorption coefficient, it is suitable as a neck glass for a cathode ray tube.

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Claims (1)

[Claims] 1. PbO 30 to 40% by mass,
_{SiO 2 38~58%, Al 2 O} 3 0~5%, MgO
0-5%, CaO 0-0.1%, SrO 0-5%,
BaO 0-5%, ZnO 0-5%, MgO + CaO
+ SrO + BaO + ZnO 0 to 5%, Na ₂ O 0 to 0%
_{5%, K 2 O 6~15%} , Sb 2 O 3 0~2%, TiO 2
Less than 0 to 1.2%, cathode-ray tube neck glass, which is a Fe ₂ O ₃ 0~10%.