JP2000086276A - Neck glass for cathode-ray tube reduced in lead elution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the absorption coefficient of X rays above a specified value and to drastically reduce the lead elution by specifying the contents of PbO and Fe2O3. SOLUTION: This neck glass for a cathode-ray tube contains, by weight, 20-40% PbO and 0.06-10% Fe2O3, and the absorption coefficient of the X rays of 0.6 Å wavelength is controlled to >=80 cm-1. The glass contg. 38-58% SiO2, 0-5% Al2O3, 20-40% PbO, 0-5% MgO, 0-6% CaO, 0-95% SrO, 0-9% BaO, 0-5% Na2O, 6-15% K2O, 0-1% Sb2O3 and 0.06-10% Fe2O3 is preferably used as such a glass. The lead elution is reduced while maintaining the X-ray absorptivity without decreasing the PbO content. This neck glass is appropriate as the one constituting the envelope of a color cathode-ray tube.

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 with less lead elution, and more particularly to a neck glass used for an envelope of a color cathode ray tube.

[0002]

2. Description of the Related Art An envelope of a cathode ray tube comprises a panel on which an image is projected, a neck on which an electron gun is mounted, and a funnel connecting the panel and the neck. These members constituting the envelope are made of glass having characteristics according to each operation.

In a color cathode ray tube, when an applied voltage is applied to an anode, electrons jump out of an electron gun serving as a cathode, and the electrons hit a phosphor provided on an inner surface of the panel to emit light, thereby displaying an image on the panel. At this time, braking X-rays are emitted. However, if the X-rays pass through the envelope and leak out of the tube, it is dangerous for the human body. Therefore, each member constituting the envelope is made of glass having a large X-ray absorbing ability. It is made with. For example, the neck is made of glass containing 20 to 40% by weight of PbO having a large X-ray absorption capacity and having an absorption coefficient of 80 cm ^-1 or more for X-rays having a wavelength of 0.6 Å.

[0004]

In recent years, cathode ray tubes have been crushed and buried in the ground as one of the methods for disposing of cathode ray tubes. However, PbO contained in glass has been used for many months. May elute into the ground. Lead is harmful to the human body, and there is concern that the eluted lead will pollute the environment.

An object of the present invention is to provide a neck glass for a cathode ray tube in which lead is less likely to elute than conventional glasses.

[0006]

In order to reduce the amount of lead eluted, the content of PbO in the glass may be reduced.
If PbO is reduced by a certain amount or more, a sufficient X-ray absorption capacity cannot be obtained. In order to compensate for this, it is conceivable to add a large amount of SrO or BaO having relatively high X-ray absorption capability to the glass. However, in this method, the liquidus temperature of the glass increases, and the glass tends to be devitrified. Becomes difficult.

Therefore, the present inventor has conducted various experiments and found that, by including a certain amount of Fe ₂ O ₃ in lead glass, a neck glass for a cathode ray tube in which lead is hardly eluted can be produced. It led to the proposal of the invention.

That is, the neck glass for a cathode ray tube having a low lead elution according to the present invention has a PbO content of 20 to 40% by weight and an absorption coefficient for X-rays having a wavelength of 0.6 angstroms of 80 cm ^-1 or more. in the neck glass, characterized by containing a Fe ₂ O ₃ 0.06-10 wt%.

[0009]

The neck glass for a cathode ray tube according to the present invention is made of Fe ₂ O ₃
By 0.06 to 10% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, thereby maintaining a high X-ray absorption capacity without reducing the PbO content. Meanwhile, it is possible to significantly reduce the amount of lead eluted.

[0010] Fe ₂ O ₃ does not pollute the environment even if it elutes into the ground. The reason for limiting the content as described above is that if it is less than 0.06% by weight, significant lead elution occurs. Is not obtained, and if it is more than 10% by weight, molding becomes difficult due to devitrification of the glass. Further F
As the amount of e ₂ O ₃ increases, the infrared transmittance of the molten glass decreases, and particularly when the glass is melted in a large tank, the melting property of the glass deteriorates, and lumps and the like are easily generated. desirable.

In the neck glass of the present invention, the content of PbO is 2
It contains 0 to 40% by weight and exhibits a high absorption coefficient of 80 cm ^-1 or more for X-rays having a wavelength of 0.6 Å.
If the content of PbO is less than 20% by weight, sufficient X-ray absorbing ability cannot be obtained, while if it is more than 40% by weight, the viscosity of the glass becomes too low and molding becomes difficult, which is not preferable. If the absorption coefficient for X-rays having a wavelength of 0.6 Å is less than 80 cm ⁻¹ , the amount of X-rays transmitted becomes too large and adversely affects the human body, so that it cannot be used as a neck glass for a cathode ray tube.

[0012] As such a neck glass for a cathode ray tube, 38 to 58% by weight of SiO ₂ and Al ₂ O ₃
0-5%, PbO 20-40%, MgO 0-5
%, CaO 0-6%, SrO 0-9%, BaO 0
_{~9%, Na 2 O 0~5%} , K 2 O 6~15%, Sb
_{2 O 3 0~1%, Fe 2} O 3 0.06~10% by weight, more _{SiO 2 40~55%, Al 2 O} 3 0.5
-4%, PbO 25-38%, MgO 0-3%, C
aO 0-4%, SrO 0-7%, BaO 0-7%,
_{Na 2 O 0~4%, K 2} O 8~14%, Sb 2 O 3 0
0.6%, a glass having a composition of Fe ₂ O ₃ 0.5 to 5% are preferred.

Further, in the present invention, in addition to the above components, it is possible to include glass in a range that does not impair the properties of the glass. For example, ZrO ₂ , CeO ₂ , TiO ₂ , V ₂ O
_Although components such as ₅ may be contained up to 3% by weight in total,
When the glass is buried in the ground, the addition of components such as Cr ₂ O ₃ , CdO and As ₂ O ₃ which may pollute the environment should be avoided.

[0014]

EXAMPLES Hereinafter, the neck glass for a cathode ray tube of the present invention will be described in detail based on examples and comparative examples.

Table 1 shows examples of the present invention (samples No. 1 to No. 1).
5) and a comparative example (sample No. 6).

[0016]

[Table 1] (% by weight)

Each sample was prepared as follows.

First, a raw material batch prepared to have the 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. Then, the sample was produced by pouring the molten glass into a mold and gradually cooling it.

For each of the samples thus obtained, the X-ray absorption coefficient and the lead elution amount were determined and are shown in the table.

As can be seen from the table, No. 1 of the embodiment of the present invention. Each of samples 1 to 5 had an X-ray absorption coefficient of 89.8.
cm ^-1 or more and lead elution amount is 0.3 to 1.1 mg / l
And few. On the other hand, in Comparative Example No. Sample No. 6 had a high X-ray absorption coefficient of 101.8 cm ^-1 , but had a large lead elution amount of 1.4 mg / l. However, the coefficient of thermal expansion of each sample at 30 to 380 ° C was 92 to 9
It was 8.times.10.sup.- ⁷ / .degree. C., which was equivalent to that of the existing neck glass for color cathode ray tubes.

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

The lead elution amount was determined as follows.

First, a glass sample was crushed and classified, and only the crushed material which passed through a sieve having an opening of 420 microns but did not pass through a sieve having an opening of 250 microns was taken out. Next, the crushed product was washed with water, transferred to a beaker, and dried in a dryer. Further, 10 g of the crushed product was put into an Erlenmeyer flask together with 100 ml of pure water, and autoclaved at 121 ° C. for 60 minutes. Then, the Pb in this solution was converted to ICP
-Quantification was performed by the AES method, and the amount of lead eluted was determined.

The coefficient of thermal expansion is a value obtained by measuring the average coefficient of thermal expansion at 30 to 380 ° C. using a dilatometer.

[0025]

As described above, the neck glass for a cathode ray tube of the present invention contains PbO in an amount of 20 to 40% by weight while containing FbO.
Because comprising the e ₂ O _3, while having an X-ray absorption coefficient equivalent to conventional glass are those of lead elution amount is very small, the neck glass, especially constituting the envelope of the color cathode-ray tube It is suitable as.

Continued on the front page F-term (reference) 4G062 AA03 BB01 BB04 DA05 DA06 DB01 DB02 DB03 DC01 DD01 DE01 DF04 DF05 EA01 EB01 EB02 EB03 EC03 EC04 ED01 ED02 ED03 EE01 EE02 EE03 EF01 EF02 EF01 FG01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 EF01 FG01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM25 MM12 NN40 5

Claims (2)

[Claims] 1. A cathode ray tube neck glass having a PbO content of 20 to 40% by weight and an absorption coefficient of not less than 80 cm ^-1 for X-rays having a wavelength of 0.6 Å, wherein Fe ₂ O ₃ is 0.06%. A neck glass for a cathode ray tube with little lead elution, characterized by containing 10 to 10% by weight. 2. The composition according to claim 2, wherein the weight percentage of SiO _{2 is} 38-58.
_{%, Al 2 O 3 0~5%} , PbO 20~40%, Mg
O 0-5%, CaO 0-6%, SrO 0-9%,
BaO 0-9%, Na ₂ O 0-5%, K ₂ O 6-1
_{5%, Sb 2 O 3 0~1} %, Fe 2 O 3 0.06~10%
2. The neck glass for a cathode ray tube according to claim 1, wherein said glass has a low lead elution.