JPS63215533A - Cathode-ray tube panel glass - Google Patents

Abstract

PURPOSE:To enable formation of a cathode-ray tube glass panel having high X-ray absorptivity and excellent browning resistance to X-rays and electron rays, by using a specific glass composition. CONSTITUTION:This cathode-ray tube panel glass has essentially the following composition, >=34cm<-1> X-ray absorption coefficient at 0.6Angstrom wavelength and resistance to browning by X-rays and electron rays with hardly any devitrification. 45.0-60.0wt.% SiO2, 0-4.0wt.% Al2O3, 0.5-3.0wt.% Li2O, 2.0-8.0wt.% Na2O, 3.0-10.0wt.% K2O, 0-4.0wt.% MgO, 0-4.0wt.% CaO, 3.0-14.0wt.% SrO, 8.0-20.0wt.% BaO, 5.0-12.0wt.% ZnO, 0-2.0wt.% ZrO2, 0-3.0wt.% TiO2, 0.1-2.0wt.% CeO2, 0-0.5wt.% Sb2O3 and 0-2.0wt.% P2O5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cathode ray tube panel glass mainly used for color television tubes.

[Prior art and its problems] A color television tube consists of a cathode, which is an electron emitting means, a funnel surrounding the cathode, and a panel on which an image is projected. An image is projected onto a panel by emitting light from a phosphor, but
At this time, brake X-rays are generated, and if they pass through the panel and leak out of the tube, it is dangerous to the human body, so the panel glass is required to have high X-ray absorption ability.

Currently, the X-ray absorption coefficient at a wavelength of 0.6λ is 28-291.
glass is used as panel glass, and this glass contains SrO, BaO, ZrO2 as X-ray absorbing components.
etc. are included. The X-ray absorption capacity of panel glass is
It is determined by the X-ray absorption coefficient of the glass and the thickness of the glass. In order to reduce the weight of the panel, it is necessary to reduce the thickness of the glass, in which case the X-ray absorption coefficient of the glass must be increased.

As an X-ray absorbing component, PbO has the highest absorption capacity, but glass containing PbO causes coloration called browning when exposed to electron beams and X-rays, which is undesirable. Therefore, glass containing PbO should be avoided. In order to further increase the X-ray absorption coefficient of SrO, BaO, Zr
Although it is necessary to contain a large amount of X-ray absorbing components such as O□,
On the other hand, if the content of these components is large, the glass tends to devitrify, the liquidus temperature increases, and the glass becomes difficult to mold.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and has high resistance to browning by 0° rays and electron beams.
Furthermore, it is an object of the present invention to provide a cathode ray tube panel glass which is resistant to devitrification and has a low liquidus temperature and thus has excellent melt formability.

[Structure of the Invention] The cathode ray tube panel glass according to the present invention has
The composition is limited from the viewpoint of browning resistance against radiation and electron beams, meltability, moldability, coefficient of thermal expansion, electrical properties, devitrification properties, etc. In particular, ZnO is 5.0 to 1
2. By limiting the content of Q% and ZrO2 (1 to 2.0%), the above objective of providing a glass that is less likely to devitrify and has a low liquidus temperature was achieved.

That is, the cathode ray tube panel glass of the present invention is characterized by essentially having the following composition expressed in weight percent.

SiO□ 45.0 ~ 60.0A I2
0. 0 ~ 4.0Li20
0.5 ~3.0Na20 2-0 ~
8.0 to 20 3.0 ~1000Mg0
0 ~ 4.0 Ca0 0 ~ 4.0 Sr0 3.0 ~ 14.0 BaO8,0
~ 20.0 Zn0 5.0 ~ 12.
0ZrO□ 0 ~ 2.0Ti
02 0 ~ 3.0Ce02
o, t ~ 2.0
Sb20. 0 ~ 0.5P2
050 to 2.0 or more preferably have the following composition.

SiO2 47.0 ~ 58.0AI203
1.11 ~ 3.0 L320 0.8 ~ 2.5Na20
2o from 3.0 to 7.0
3.5 ~ 9.0Mg0 θ ~
3.0Ca0 0 ~3.0 5r0 5.0 ~10,08a[10,
0 ~ 16.0 Zo0 5.0 ~ 10.0Zr02
0~1.9Ti020~2.
0 Ce02 0.1 ~ 1.0S
b20. o ~ 0.4
P205 0 to 1.0 The reason why the composition range of the cathode ray tube panel glass of the present invention is limited as described above is as follows.

SiO2 is a glass network former,
When it is less than 45.0%, the viscosity of the glass decreases and the chemical durability deteriorates. If it exceeds 60.0%, the viscosity of the glass becomes too high, making melt molding difficult.

^1□03 can be added to improve water resistance, but 4.0%
If the amount is more, the viscosity of the glass becomes too high and melt molding becomes difficult.

Li2O, Na2O, and 20 alkali metal oxides are contained as fluxing agents. If Li2O is less than 0.5%, it will not be effective as a fluxing agent,
When the amount is more than 3.0%, the glass tends to devitrify.

If Na2O is less than 2.0% and K2O is less than 3.0%, the viscosity of the glass will become too high and melt molding will be difficult, while if Na2O is more than 8.0% and K2O is more than 1000%, the glass will The coefficient of thermal expansion becomes too high.

MgO and CaO are each contained up to 4% mainly to adjust the viscosity curve of the glass.

SrO is important as a glass network modifier to obtain stable glass, and has high X-ray absorption ability, but if it is less than 3.0%, the above effect cannot be obtained, and if it is more than 14.0%, SrO is not preferred because crystals tend to precipitate, the liquidus temperature increases, and devitrification tends to occur during molding.

Like SrO, BaO is also contained as a network modifier of the glass and to increase the X-ray absorption ability of the glass, but if it is less than -8.0%, the above effect cannot be obtained, and if it is more than 20.0%. In this case, crystals tend to precipitate.

ZnO is effective in increasing the X-ray absorption ability of glass and suppressing the amount of alkali elution, but if it is less than 5.0%, SrO and BaO are added to maintain a high X-ray absorption coefficient.
, ZrO□ must be contained in large amounts, which increases the liquidus temperature and makes it difficult to mold the glass.If the content exceeds 12.0%, the devitrification temperature increases.

ZrO2 can be added to increase the X-ray absorption ability of glass, but if it is more than 2.0%, the surface devitrification temperature of the glass (
The liquidus temperature at the interface with air, platinum, and refractories becomes high, and devitrification tends to occur on the surface.

Moreover, if the surface devitrification temperature becomes high, it is not preferable because molding of the glass becomes difficult, similar to when the liquidus temperature inside the glass is high.

TiO□ can be added to prevent the glass from being colored by ultraviolet rays and X-rays, but if it exceeds 3.0%, the light transmittance of the glass decreases, which is not preferable.

CeO2 has an excellent effect of preventing coloring due to X-rays and is effective as a clarifying agent, but if it is less than 0.1%, the above effects cannot be obtained, and if it is more than 2.0%, it tends to devitrify. Also, the light transmittance in the short wavelength range of the visible region decreases, which is not preferable.

5b2o can be added as a glass fining agent, but 0.5b2o can be added as a glass fining agent.
If it exceeds 5%, the surface devitrification of the glass becomes significant.

P2O5 can be added to suppress the tendency of devitrification, but 2.
When the amount is more than 0%, a liquid phase separation phenomenon occurs, and conversely, devitrification tends to occur.

In addition to the above-mentioned components, the present invention also contains B2O3 to improve the solubility of the glass, and Nip and C to reduce the transmittance of the glass or adjust the coloring.

01Fe203. Coloring components such as MoO and Cr2O3 can also be added.

However, as mentioned above, pbo should not be introduced since it tends to cause coloring due to electron beams and X-rays.

[Example] Examples of the present invention will be described below along with comparative examples.

The following table shows the glass composition, X-ray absorption coefficient, and
It shows the thermal expansion coefficient, softening point, liquidus temperature, and surface devitrification temperature.

Below, blank samples Nos. 011 to 4 are examples of the glass of the present invention, and samples Nos. 5 and 6 are comparative examples.

Prepare samples No. 1 to 6 shown in the table as follows.

Raw material batches prepared to have the respective glass compositions of sample Nos. 1 to 6 were placed in a platinum crucible and melted at 1480° C. for 4 hours. Stir with a platinum stirring rod halfway to obtain a homogeneous glass.
After degassing by stirring for a minute, the mixture was poured into a mold to prepare a sample piece.

The X-ray absorption coefficients in the table are values at a wavelength of 0.6λ.

From the table, it can be seen that the glass of the present invention has a lower liquidus temperature than Samples No. 6 and 6, which are comparative examples, and a lower surface devitrification temperature than Samples No. 5 and 6, so it has superior melt formability. I understand.

[Effects of the Invention] As described above, the glass of the present invention has high X-ray absorption ability, is less colored by X-rays and electron beams, and has a low liquidus temperature and surface devitrification temperature, so it is easy to melt-form. Therefore, it is particularly suitable as cathode ray tube panel glass used in color television tubes.

Patent applicant: Nippon Electric Glass Co., Ltd. Representative Kishi 1) Kiyosaku

Claims (2)

[Claims] (1) Essentially the following composition in weight%: SiO_2 45.0-60.0 Al_2O_3 0-4.0 Li_2O 0.5-3.0 Na_2O 2.0-8.0 K_2O 3.0-10.0 MgO 0-4.0 CaO 0-4.0 SrO 3.0-14.0 BaO 8.0-20.0 ZnO 5.0-12.0 ZrO_2 0-2.0 TiO_2 0-3.0 CeO_2 0 .1 to 2.0 Sb_2O_3 0 to 0.5 P_2O_5 0 to 2.0, has an X-ray absorption coefficient of 34 cm or more at a wavelength of 0.6 Å, and is resistant to browning by X-rays and electron beams. A cathode ray tube panel glass that is characterized by high speed and low stall resistance. (2) Essentially the following composition in weight% SiO_2 47.0-58.0 Al_2_O_3 1.0-3.0 Li_2O 0.8-2.5 Na_2O 3.0-7.0 K_2O 3.5-9 .0 MgO 0-3.0 CaO 0-3.0 SrO 5.0-10.0 BaO 10.0-16.0 ZnO 5.0-10.0 ZrO_2 0-1.9 TiO_2 0-2.0 The cathode ray tube panel glass according to claim 1, having CeO_2 0.1-1.0 Sb_2O_3 0-0.4 P_2O_5 0-1.0.