JP2000040476A - Glass panel for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance mechanical strength, and to improve safety by forming compression stress layers having a thickness of a specific value equivalent to a specific value of a glass thickness on the inside surface and the outside surface of a glass panel, and setting a compressive stress of these compressive stress layers and a tensile stress of a tensile stress layer formed between the compressive stress layers of the inside/outside surfaces in the specific relations. SOLUTION: A stress of a tensile stress layer inside glass is restrained while maintaining a high compression stress by setting the thickness of compression stress layers formed on the inside surface and the outside surface to 5/100 to 13/100 of a glass thickness. Even if the surface of a glass panel is flawed, there is a rare posibility of thrusting through the compression stress layers being strengthening layers. A compression stress of the compression stress layers and a tensile stress of the tensile stress layer formed between the compression stress layers of the inside/outside surfaces, are set so as to satisfy an expression I, II (here, the compression stress of the compression stress layers C is denoted by σc and the tensile stress of the tensile stress layer formed between the compression stress layer C of the inside/outside surfaces is denoted by σt).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As shown in FIG. 3, a glass panel for a cathode ray tube has a substantially rectangular face portion 1a on which an image is projected.
And a skirt portion 1b extending over the entire circumference of the face portion 1a. By attaching the funnel 2 and the neck 3 to the glass panel 1, a glass bulb for a cathode ray tube is formed. The glass bulb for a cathode ray tube is used as a vacuum container by exhausting the inside.

In a glass bulb for a cathode ray tube whose inside is evacuated, stress is generated by applying an atmospheric pressure to an outer surface thereof. Therefore, a sufficient mechanical strength is required for the glass bulb, which is insufficient. If this is the case, it will not be able to withstand the stress load due to the atmospheric pressure and will be destroyed.

Since the glass bulb for a cathode ray tube has a non-spherical shape, the stress distribution generated on the bulb surface due to the atmospheric pressure when the inside is evacuated, as shown in FIG. Although there is an area where compressive stress and tensile stress outward exist, the glass structure is generally strong against compressive stress and weak against tensile stress. In the valve,
Breakage or implosion is likely to occur starting from the area of the glass panel 1 where the area where the maximum tensile stress is generated.

In order to solve such a problem, a glass panel for a cathode ray tube, in which a compressive stress layer is formed on a glass surface by chemical strengthening or air cooling, has been conventionally used.
In general, it is known that compressive stress for glass makes it difficult for the glass to be scratched and breaks the glass,
In the case of chemical strengthening, a compressive stress layer is formed by exchanging small alkali ions (Na ions) on the surface layer of a glass panel for a cathode ray tube into large alkali ions (K ions). In the case of tempering, the temperature inside the glass of the CRT glass panel is considerably high, that is, at a temperature higher than the strain point temperature, and the surface is rapidly cooled to utilize the temperature difference between the surface layer and the inside of the glass. Thus, a compressive stress layer is formed on the glass surface.

[0006]

In a conventional glass panel for a cathode ray tube, the stress value of a compressive stress layer formed on the surface is high, but there are the following problems.

In a conventional glass panel for a cathode ray tube by ion exchange, as shown in FIG.
Since only a compressive stress layer C having a thickness of several tens of μm is formed on both surfaces of the glass, when a deep scratch is made on the glass surface,
There is a problem that the scratch easily penetrates through the compressive stress layer C.

On the other hand, in the conventional glass panel for a cathode ray tube strengthened by air cooling, as shown in FIG. 6, the stress distribution is shown on both surfaces of the glass so that the thickness is about 1/6 to 1/5 of the glass thickness. A compressive stress layer C is formed, and a tensile stress layer T is formed between the compressive stress layers with a stress value of の of the compressive stress value (absolute value). Therefore, in such a glass panel, the compressive stress layer C on the glass surface is thick, but there is a disadvantage that the stress value of the internal tensile stress layer T is large. That is, in a glass bulb using such a glass panel, since the thickness of the compressive stress layer C on the surface of the glass panel is deep, there is little possibility that the surface of the glass panel may be damaged even if the surface is damaged. Once a fine crack originating from such a scratch penetrates the compressive stress layer C and reaches the internal tensile stress layer T, the stress of the tensile stress layer T is released at a stretch, and the glass is broken into small pieces and scattered. There is a risk. In particular, in a glass bulb for a cathode ray tube having a vacuum inside, since implosion occurs due to instantaneous intense air flow, scattering of glass pieces becomes a serious problem.

Accordingly, an object of the present invention is to reduce the possibility that a scratch on the surface of glass penetrates the compressive stress layer on the glass surface, and that a crack originating from the scratch reaches the internal tensile stress layer. However, an object of the present invention is to provide a glass panel for a cathode ray tube capable of suppressing scattering of glass pieces due to implosion and imparting high mechanical strength and safety to the glass bulb for a cathode ray tube.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems and objects, and has an approximately rectangular face portion having an effective screen portion on which an image is projected, and an entire periphery of the face portion. In a glass panel for a cathode ray tube comprising a skirt portion extending over the glass panel, an inner surface and an outer surface of the glass panel have a thickness of 5/100 to 13/100 of the glass thickness.
Is formed, and the compressive stress value σ _c of the compressive stress layer and the tensile stress value σ _t of the tensile stress layer formed between the compressive stress layers on the inner and outer surfaces are σ _t <1/3 | σ
_c | and | σ _t | <2000 psi.

[0011]

According to the glass panel for a cathode ray tube of the present invention, the thickness of the compressive stress formed on the inner surface and the outer surface is set to 5/100 to 13/100 of the thickness of the glass, so that the conventional glass panel is strengthened by air cooling. While maintaining the same high compressive stress value as that of the glass panel for a cathode ray tube, the stress value of the tensile stress layer inside the glass is suppressed. Further, since the thickness of the compressive stress is 5/100 to 13/100 of the thickness of the glass, even if the surface of the glass panel is damaged, there is little possibility that the glass panel will penetrate the compressive stress layer which is the reinforcing layer.

The thickness of the compressive stress is 5/10 of the thickness of the glass.
When it is less than 0, when the surface of the glass panel is scratched, the scratch easily penetrates the compressive stress layer, and when it is 15/100 or more of the glass thickness, a desired high compressive stress value is maintained. However, it is difficult to suppress only the stress value of the tensile stress layer.

The tensile stress value σ _t of the tensile stress layer inside the glass formed between the compressive stress layers on the inner and outer surfaces is σ _t
By <1/3 | σ _c |, even when a crack originating from a surface flaw of glass reaches the internal tensile stress layer, scattering of glass fragments due to implosion can be suppressed.

Further, the absolute value of the tensile stress value σ _t is set to 2000
What is less than psi is 2000 psi or more,
Even in the range of the tensile stress value σ _t of σ _t <1/3 | σ _c |, if the crack reaches the tensile stress layer inside the glass, the risk of the glass being broken into small pieces and scattering is increased. It is.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a glass panel for a cathode ray tube according to the present invention will be described based on embodiments.

(Embodiment) FIG. 1 is an explanatory view of a glass panel for a cathode ray tube of the present invention, and FIG. 2 is a glass panel 1 for a cathode ray tube.
FIG. 4 is an explanatory diagram showing a stress distribution at the center of the face portion 1a.

The 29-inch cathode ray tube glass panel 1 of this embodiment has a thickness of 13 mm at the center of the face portion 1a.
Thus, a compressive stress layer C is formed on the inner surface and the outer surface. The compressive stress layer C is, for example, about 1.3 mm at the center of the face portion and is 10/100 of the glass thickness, and its stress value is 2000 psi. Also,
The stress value of the tensile stress layer in the center of the glass is 400 psi
It is.

The glass panel 1 for a cathode ray tube was manufactured in the following manner.

After the molten glass is pressed by a molding die to form a glass panel 1 for a cathode ray tube, the inner surface and the outer surface of the glass panel 1 are air-cooled for 10 to 20 seconds before being carried into an annealing furnace. . At this stage, the temperature of the inner and outer surface layers of the glass panel 1 is cooled to 473 ° C., which is the strain point of the glass panel 1, and the temperature inside the glass is kept at or above the strain point. The glass panel 1 was loaded into a lehr where the above-mentioned strain point was set to the highest temperature, passed through a lehr process for a predetermined time, and then was discharged from the lehr.

Comparative Example 1 A glass panel similar to the glass panel for a cathode ray tube used in the present example was immersed in a KNO ₃ solution tank maintained at about 480 ° C. for about 2 to 3 hours, and the surface layer of the glass panel was immersed. Was subjected to an ion exchange treatment to produce a glass panel for a cathode ray tube having a compressive stress layer having a compressive stress value of 14000 psi and a thickness of about 20 μm formed on the inner surface and the outer surface. The stress value of the tensile stress layer in the center of the inside of the glass of such a glass panel is 20 psi.

(Comparative Example 2) A glass panel similar to the glass panel for a cathode ray tube used in the present embodiment was subjected to a conventional ordinary air-cooling strengthening treatment, so that a compressive stress value was 5000 ps.
i. A glass panel for a cathode ray tube having a compressive stress layer having a thickness of about 2.2 mm formed on the inner surface and the outer surface was prepared. The stress value of the tensile stress layer at the center of the inside of the glass of such a glass panel is 2500 psi.

Using each of the above-mentioned glass panels for a cathode-ray tube, a glass bulb for a cathode-ray tube whose inside was evacuated was produced and subjected to an impact test. Due to the small thickness of the layer, the scratch penetrated the compressive stress layer only by making a scratch on the face portion with a diamond cutter.

On the other hand, in the glass bulb using the glass panel of the present embodiment and the comparative example 2, the thickness of the compressive stress layer of the glass is large, so that the glass bulb has a thickness sufficient to prevent the crack from spreading from the scratch. there were.

However, once the flaws have reached the tensile stress layer inside the glass, the glass bulb using the glass panel of the present embodiment has a small stress value in the glass inside the glass. In comparison with No. 2, the scattering of the small glass pieces was small, and good results were obtained.

[0025]

As described above, according to the glass panel for a cathode ray tube of the present invention, there is no possibility that the surface flaw of the glass penetrates the compressive stress layer which is the strengthening layer and the crack originating from the surface flaw of the glass. Can prevent the scattering of glass fragments due to implosion even when it reaches the internal tensile stress layer, and has an excellent effect of imparting high mechanical strength and safety to the glass bulb.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a glass panel for a cathode ray tube according to the present invention.

FIG. 2 is an explanatory view showing a stress distribution of a glass panel for a cathode ray tube according to the present invention.

FIG. 3 is an explanatory view of a glass bulb for a cathode ray tube.

FIG. 4 is an explanatory view showing a distribution of stress generated in a glass bulb for a cathode ray tube.

FIG. 5 is an explanatory diagram showing a stress distribution of a conventional glass panel for a cathode ray tube.

FIG. 6 is an explanatory diagram showing a stress distribution of a conventional glass panel for a cathode ray tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass panel for cathode ray tubes 1a Face part 1b Skirt part 2 Funnel 3 Neck C Compressive stress layer T Tensile stress layer

Claims (1)

[Claims] In a glass panel for a cathode ray tube comprising a substantially rectangular face portion on which an image is projected and a skirt portion extending over the entire circumference of the face portion, an inner surface and an outer surface of the glass panel are provided. , 5/10 of glass thickness
A compressive stress layer having a thickness of 0 to 13/100 is formed. A compressive stress value σ _c of the compressive stress layer and a tensile stress value σ of a tensile stress layer formed between the compressive stress layers on the inner and outer surfaces are formed. _t
Is σ _t <１ ／ | σ _c |, and | σ _t | <20
A glass panel for a cathode ray tube, which has a pressure of 00 psi.