JPH0312337A - Panel glass of cathode-ray tube - Google Patents

Abstract

PURPOSE:To suppress the tinting of glass by X-rays, electron beams and UV, to lower the temp. of the liq. phase, to nearly prevent devitrification and to improve the resistance to browning by electron beams, the meltability and moldability by specifying the components, compsn. and X-ray absorption coefft. of the glass. CONSTITUTION:A batch of starting materials so prepd. as to obtain a desired glass compsn. is charged into a crucible and melted by heating at about 1,450 deg.C for about 4hr. The resulting melt is defoamed, poured into a metallic mold and slowly cooled to form glass. This glass is released from the mold and polished to obtain the glass having >=34cm<-1> X-ray absorption coefft. (0.6Angstrom ) and consisting of, by weight, 45.0-60.0% SiO2, 0-4.0% Al2O3, 0.2-3.0% LiO2, 1.0-5.5% Na2O, 6.0-13.5% K2O, 0-4.0% MgO, 0-4.0% CaO, 3.0-14.0% SrO, 8.0-20.0% BaO, 5.5-12.0% ZnO, 0-2.0% ZrO2, 0-3.0% TiO2, 0.1-2.0% CeO2, 0-0.5% Sb2O3 and 0-2.0% P2O5. In the compsn., the weight ratio of Na2O to Na2O+K2O is 0.14-0.28.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to cathode ray tube panel glass used in color television tubes, projection tubes, and the like.

[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 the wavelength of 0.6 people is 28-29c
m glass is used as panel glass,
This glass contains 5rO1BaO5Z as an X-ray absorbing component.
Contains r02 etc. The X-ray absorption capacity of panel glass 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 further enhanced. As an X-ray absorption component, PB
Although PbO is the component with the highest absorption capacity, glass containing PbO is not preferable because it causes discoloration called browning when irradiated with electron beams and X-rays. Therefore, PbO
In order to further increase the X-ray absorption coefficient of the glass by avoiding the inclusion of This causes a problem in that the glass tends to devitrify as it rises, making it difficult to mold the glass.

[Object of the invention] The object of the invention is to obtain an X-ray absorption coefficient of 34 at a wavelength of 0.6
01 or above, has little coloring due to X-rays, electron beams, and ultraviolet rays, has high resistance to the browning phenomenon caused by electron beams, and has low liquidus temperature, so it is difficult to devitrify and has excellent melt moldability. The present invention provides cathode ray tube panel glass.

[Structure of the Invention] While conducting research on glasses that are particularly resistant to browning caused by electron beams, the present inventors discovered that the coloring of glass by electron beams is not limited to the components constituting the glass, but also includes Na2O. It was also found that the mixing ratio of the two components has a large effect.

The cathode ray tube panel glass according to the present invention has excellent resistance to browning caused by electron beams, X-ray absorption ability,
The ratio of each component and the mixing ratio of 20% with Na2O are strictly regulated, taking into consideration the browning resistance due to radiation and ultraviolet rays, meltability, moldability, coefficient of thermal expansion, electrical properties, devitrification properties, etc. SiO□ has essentially the following composition in weight %: 45.0 to 60. OA1□03
0 ~ 4.0 Li20 0.2 ~ 3.
0Na20 1.0 ~ 5
．． 5 to 20 6.0 to 1
3.5Mg0 Q ~
4.0Ca0 0
〜4.0Sr0 3.0〜
14.0Ba0 8.0
~ 20.0Zn0 5.5
~ 12.0ZrO□ 0
~ 2.0Ti0□ 0 ~
3.0Ce02 o, 1
~ 2.0Sb203 0 ~
0.5 pzo5 9 ~
2.0=0.14-0.28, 0% by weight K2
0% by weight) = 0.14 to 0.28.

More preferably, it has the composition essentially as follows: 5i02 47.0 to 58.0AI203
1.0 ~3.0Li20 0
．． 5 ~ 2.5 Na20 2.0 ~ 5.0
13.0 3.0 3.0 ■090 16.0 1O00 1,9 2,0 1,0 0,4 20% by weight in 1,0) K2O7,0~ MgOO~ CaOO~ SrO5,0~ BaO10,0 ~Zn0 5.5 ~ZrO□
0 ~TiO20~ CeO□ 0.1 ~S'b20.
Q ~ P20.
0 ~ = 0.14 ~ 0.28, and 0% by weight = 0.19 ~
It is characterized by being 0.2♂.

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.

5i02 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.

A.I. 0. 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 is a component that suppresses browning caused by electron beams, improves the meltability of glass, and increases the coefficient of thermal expansion, but if it is less than 0.2%, the above effects cannot be obtained. When the amount is more than 3.0%, the glass tends to devitrify, and since the Li2O raw material itself is expensive, it is not preferable to contain a large amount from the cost standpoint.

Na2O and 20 are also components that improve the meltability of glass along with Li2O, but if Na2O is less than 1.0% and 20 is less than 6.0%, the viscosity of the glass becomes too high and melt molding becomes difficult. Become. In addition, in the present invention, in order to reduce coloring due to electron beams, Na2O weight %/(Na2
The condition is that K20% by weight is 0.14 to 0.28, but if Na2O is more than 5.5%, it becomes difficult to satisfy this range, and K2O is 13.5%.
If the amount is more than that, the coefficient of thermal expansion of the glass becomes too high.

M[0 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 important. is not preferred because crystals tend to precipitate and the liquidus temperature increases, making it easier to devitrify during molding.

Like SrO, BaO9 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%, BaO9 is contained. crystals tend to precipitate.

Zoo is effective in increasing the X-ray absorption ability of glass and suppressing the amount of alkali elution, but if it is less than 5.5%, SrO, Ba is added to maintain a high X-ray absorption coefficient.
It becomes necessary to contain large amounts of O and ZrO2, which increases the liquidus temperature and makes it difficult to mold the glass.
．． When the amount is more than 0%, the devitrification temperature becomes high.

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 as in the case where the liquidus temperature inside the glass is high.

TiO2 can be added to prevent the glass from being colored by ultraviolet rays and X-rays, but if it is more than 3.0%, it is not preferable because the light transmittance of the glass decreases.

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.
If the amount is more than 0%, a liquid phase separation phenomenon occurs and devitrification tends to occur.

In addition to the above components, the present invention also uses B2O3 and F to improve the meltability of the glass, and Nip, Coo, Fe2O3, MoO, and Cr to adjust the color tone of the glass.
It is possible to add coloring ingredients such as 2O3.

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 of Examples and Comparative Examples, Na2O weight%
/(20% by weight Na), X-ray absorption coefficient, electron beam coloring, liquidus temperature, and surface devitrification temperature.

Sample Nos. I to 5 in the margin table below are examples of the present invention, and sample Nos. 6 to 9 are comparative examples.

Samples No. I to 9 shown in the table were prepared as follows.

A raw material batch prepared to have the glass composition of each sample was placed in a platinum crucible and melted at about 1450° C. for 4 hours. In order to obtain a uniform glass, the glass was stirred for 5 minutes with a platinum stirring rod to defoam, and then poured into a mold and formed into a plate. After cooling slowly, it was removed from the mold and polished to 20X.
A sample piece with dimensions of 30×5 ml was prepared, and the X-ray absorption coefficient, electron beam coloring, liquidus temperature, and surface devitrification temperature were measured using this sample piece.

As a result, a sample in which Na2O weight %/(20 weight % Na 20 weight %) is greater than 0.28! It was found that the electron beam coloring of lJ[L6 and 7 was 38 and 51, respectively, and there was a high possibility that the browning phenomenon caused by the electron beam would occur.

In addition, sample No. 8 containing 0.5% of Z(10) and 4.0% of ZrO□ had poor melt formability due to its high liquidus temperature and surface devitrification temperature, and further contained 3.5% of PbO. Sample N
[19] has an electron beam coloring of 75, and it is known that the browning phenomenon caused by the electron beam is most likely to occur.

On the other hand, samples Nos. 1 to 5, which are examples of the present invention, have a small electron beam coloring of 6 to IO, so there is little possibility of browning caused by the electron beam, and the liquidus temperature is 849.
℃ or less, and the surface devitrification temperature was as low as 882°C or less, so it had excellent melt moldability.

The method for measuring electron beam coloring is as follows.

After vapor-depositing aluminum to a thickness of 3now on each sample glass whose transmittance was measured in advance and fixing it to the shadow mask of a color television tube with a wire, an applied voltage of 30 kV from an electron gun and an electron beam current density of 3 μA/crn were applied. The sample glass was irradiated with an electron beam for 50 hours under the following conditions.
Remove the sample glass from the wire, remove the evaporated aluminum, measure the transmittance, and measure the wavelength of 400n before and after irradiation.
The transmittance difference in m was determined and the values are shown in the table.

The method for measuring the liquidus temperature and surface devitrification temperature is as follows.

First, each sample glass was crushed, and only the crushed material that passed through a 32-mesh sieve but not a 48-mesh sieve was taken out, washed with water, dried, and transferred into a platinum boat. This platinum boat was placed in an electric furnace with a temperature gradient of 700 to 1200° C., and after heat treatment for 48 hours, the platinum boat was taken out, allowed to cool, and then the sample glass was taken out from the platinum boat. Next, this sample glass is observed with a polarizing microscope to find the boundary between the area where crystals are precipitated and the area where the crystals are not precipitated, approximately 2 mm above the bottom of the glass, and an electric furnace corresponding to the position of the boundary is found. The temperature was determined and taken as the liquidus temperature. In the same way, the boundary between the area where crystals were precipitated and the area where the crystals were not precipitated was found on the surface of the glass, and the temperature in the electric furnace where that position was located was determined and determined as the surface devitrification temperature.

[Effects of the Invention] As described above, the glass of the present invention has high X-ray absorption ability, high resistance to the browning phenomenon caused by electron beams, and low liquidus temperature and surface devitrification temperature. Since it is easy to melt and mold, it is suitable for color television tubes and projection panel glass.

Claims (2)

[Claims] (1) Essentially the following composition in weight%: SiO_245.0-60.0 Al_2O_30-4.0 Li_2O0.2-3.0 Na_2O1.0-5.5 K_2O6.0-13.5 MgO0-4.0 CaO0~4.0 SrO3.0~14.0 BaO8.0~20.0 ZnO5.5~12.0 ZrO_20~2.0 TiO_20~3.0 CeO_20.1~2.0 Sb_2O_30~0.5 P_2O_50~ 2.0, Na_2O wt%/(Na_2O wt% + K_
2O weight %) = 0.14 to 0.28, and an X-ray absorption coefficient of 34 cm^-^1 or more at a wavelength of 0.6 Å. (2) Essentially the following composition in weight%: SiO_247.0-58.0 Al_2O_31.0-3.0 Li_2O0.5-2.5 Na_2O2.0-5.0 K_2O7.0-13.0 MgO0-3 .0 CaO0~3.0 SrO5.0~10.0 BaO10.0~16.0 ZnO5.5~10.0 ZrO_20~1.9 TiO_20~2.0 CeO_20.1~1.0 Sb_2O_30~0.4 P_2O_50~1.0, Na_2O wt%/(Na_2O wt%+K_
2O weight%) = 0.19 to 0.28, and 0.6 Å
The cathode ray tube panel glass according to claim 1, wherein the cathode ray tube panel glass has an X-ray absorption coefficient of 34 cm^-^1 or more at a wavelength of .