JPH07142012A - Glass bulb for cathode-ray tube - Google Patents

Abstract

PURPOSE:To flatten and thin a face and at the same time to increase strength without increasing brightness difference. CONSTITUTION:Compressive stress layers 20, 21 are formed, which satisfy 1.0<=td/t0<=1.2 on the diagonal line of a face part and have the thickness of not less than t0/10 in the external surface and the internal surface of the face part when the thicknesses of glass in the center and in the vicinity of the end part of the face part 7 of a glass panel 3 are respectively t0 and td. Thereby, strength is increased and the development of a crack by impulse is stopped or rertarded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass bulb for a cathode ray tube (cathode ray tube) used in a television or the like, and more particularly to the construction of a glass panel constituting the display surface side thereof.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a cathode ray tube used in a television or the like. The cathode ray tube 1 basically includes a glass panel portion 3 on the image display surface side, a funnel-shaped funnel portion 4 that is hermetically joined to the glass panel portion 3, and a neck portion 5 that houses an electron gun 17. The glass bulb 2 is composed of The glass panel 3 is composed of a substantially rectangular face portion 7 which constitutes an image display surface, and a skirt portion 6 which extends from the peripheral portion of the face portion 7 in a substantially vertical direction.

An explosion-proof reinforcing band 8 is wound around the outer periphery of the skirt portion 6 for maintaining the panel strength and preventing scattering at the time of breakage. On the inner surface side of the face portion 7, a fluorescent film 12 that emits fluorescence due to an electron beam impact from an electron gun, and an aluminum film 13 for reflecting light emitted from the fluorescent film 12 to the rear of the cathode ray tube are laminated. A shadow mask 14 that defines the electron beam irradiation position is provided on the inner side. The shadow mask 14 is fixed to the inner surface of the skirt portion 6 by stud pins 15.

Such a glass panel portion 3 is a sealing portion 10.
It is hermetically joined to the funnel portion 4 by a sealing agent such as solder glass provided on the. Inside the funnel section 4,
An internal coating 16 is provided to prevent the shadow mask 14 from being highly charged by an electron beam and to be electrically grounded to the outside.

Since the glass bulb for a cathode ray tube having the above structure is used as a vacuum container, atmospheric pressure acts on the outer surface to generate stress. In this case, the glass bulb has an asymmetric structure different from the spherical shell, and due to this, the tensile stress region exists in a relatively wide range together with the compressive stress. For this reason, when some kind of mechanical shock is applied and a crack or breakage locally occurs, the crack or the like is instantly developed in order to release the stored strain energy, resulting in implosion.

In order to prevent such a danger, as described above, a metal reinforcing band 8 is attached to the skirt portion 6 of the glass panel 3 or the glass bulb is structured as close to a spherical shell as possible. Reduce the radius of curvature of the glass panel (for example, about 1R: here, 1R = 42.5 × V / 2
It is represented by 5.4 + 45.0, V is the diagonal diameter (mm) of the effective display surface, and thus the strength against impact was secured. Further, a method of increasing the strength by thickening the face portion of the glass panel has also been performed.

[0007]

However, in the above-mentioned conventional glass bulb for a cathode ray tube, if the radius of curvature of the glass panel is reduced in order to increase the strength against impact, the visibility becomes poor and the screen becomes difficult to see. For this reason, it is necessary to flatten the face, and it is necessary to flatten the screen to make it easier to see with a radius of curvature of about 1.5R to 2R.
However, when the face is flattened in this manner, there arises a problem that the face becomes weak against mechanical shock.

Further, when the above-mentioned reinforcing band is attached to the glass panel, the tightening force becomes non-uniform along the skirt portion at the peripheral edge of the face, the stable and highly reliable explosion-proof function cannot be obtained, and the face reinforcement is sufficiently achieved. There wasn't.

If the entire face portion is thickened for reinforcement, the weight becomes heavy and the handleability becomes poor. In order to deal with this point, a configuration is used in which the outer surface of the face portion is flattened and the radius of curvature of the inner surface is reduced to thicken the peripheral portion of the face, especially the four corner portions. With such a configuration, the weight of the entire face can be reduced, but the difference in the thickness between the central portion and the peripheral portion of the face causes a difference in the transmittance, resulting in a large difference in the luminance of the image and a reduction in the display quality. Cause problems.

The brightness B is B = ρT _m T _p V ^a I ^b
/ S. Where ρ is the luminous efficiency of the phosphor, T
_m is the transmittance of the mask, T _p is the transmittance of the glass panel, V
Is the anode voltage, I is the beam current, S is the screen area,
a and b are constants.

Further, the transmittance T of the glass panel is T =
It is represented by (1-R) ² · exp (−k · t). Here, R is the reflectance of the glass (4 to 4.5%), k is the extinction coefficient, and t is the glass wall thickness. The transmittance and extinction coefficient of two types of glass panel materials manufactured by Asahi Glass Co., Ltd. are shown in Table 1 below.
Shown in.

[0012]

[Table 1]

Further, in Table 2 below, regarding the glass panels of various sizes formed of the same glass material, the wall thicknesses at the center and peripheral portions of the face, their ratios and flatness,
And the transmittance and its ratio are shown.

[0014]

[Table 2]

In the size column of Table 2, the aspect ratio of the screen is shown in parentheses, and the aspect ratio of 4: 3 is not shown. As can be seen from this table, by changing the flatness according to the size, the thickness at the peripheral portion of the panel changes and the transmittance changes. This makes it possible to reduce the difference in transmittance between the center portion and the end portion of the face and bring the ratio close to 100% to make the luminance distribution uniform.

However, as described above, if flattening is performed while maintaining uniform wall thickness, the explosion-proof property is weakened, and it is easy to break even by a slight impact. If the thickness is increased to increase the strength, the weight increases and the handleability deteriorates. To reduce the weight, if the radius of curvature of the face inner surface is made small and the face center part is made thin and the end part is made thick, the brightness difference between the face center part and the end part becomes large and the visibility deteriorates. .

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and achieves flattening of the outer surface of the face and thinning of the entire glass panel without increasing the brightness difference between the central portion and the peripheral portion of the face. In addition, an object of the present invention is to provide a glass bulb for a cathode ray tube, which has improved strength against mechanical shock.

[0018]

In order to achieve the above object, according to the present invention, a substantially rectangular face portion forming a display screen and a skirt extending substantially vertically from the peripheral portion of the face portion. In a glass bulb for a cathode ray tube comprising a glass panel part consisting of a tube part, a funnel-shaped funnel part hermetically joined to the glass panel part, and a neck part at the base of the funnel part for housing an electron gun. Assuming that the glass thicknesses in the center of the effective screen portion of the face portion of the glass panel and in the vicinity of the end portions thereof are t ₀ and t _d , respectively, 1.0 ≦ t _d / t ₀ on the diagonal line of the face portion. Provided is a glass bulb for a cathode ray tube, wherein ≦ 1.2, and a compressive stress layer having a thickness of t _0/10 or more is formed on an outer surface and an inner surface of the face portion. To do.

In a preferred aspect of the present invention, when the stress value of the compressive stress layer is σ _c in a region including a diagonal line of the effective screen portion of the face portion, 60 k
It is characterized in that g / cm ² ≦ σ _c ≦ 200 kg / cm ² .

In the present invention, the compressive stress layer is formed by a cooling treatment after molding the glass panel.

The glass thickness t _{d in the} vicinity of the end portion of the face portion as referred to in the present invention substantially means the thickness of the end portion of the effective screen of the face portion. The effective screen end portion of the face portion refers to a contact portion between the inner curved surface of the panel face and the blend R (the tangent circle between the inner curved surface and the skirt).

[0022]

[Function] The difference in thickness between the central portion and the peripheral portion of the face of the glass panel is small, and the thickness is almost equal, and the glass is strengthened by the compressive stress layers formed on both inner and outer faces of the face.
It can be thin and flat.

That is, a compression layer having a stress value and a stress thickness sufficient to prevent or delay the progress of cracks is formed by physical strengthening on at least the face portion of the glass panel. As a result, while maintaining a flatness of about 1.5R to 2.0R, the weight is reduced, the brightness difference between the central portion and the end portion is reduced, and the glass for a cathode ray tube having a high strength capable of withstanding an impact is also provided. The valve becomes feasible.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a glass panel portion 3 of a glass bulb for a cathode ray tube according to an embodiment of the present invention. In this embodiment, the thickness of the central portion of the face portion 7 is t _0.
And the thickness of the peripheral portion is t _d , 1.0 ≦ t _d /
The glass panel is formed so that t ₀ ≦ 1.2. That is, the thickness difference between the central portion and the peripheral portion of the face is set to 1 or close to 1 to reduce the difference in thickness, thereby achieving equal thickness. By making the thickness equal, the light transmittance and the extinction coefficient of the glass are made substantially uniform over the entire face, the brightness difference between the central portion and the peripheral portion is reduced, and the screen is easy to see. FIG. 2 is a plan view of the face portion 7 of the glass panel 3. X and Y indicate central axes in the horizontal and vertical directions, respectively. The dotted line divides the screen into 16 parts. Since the radius of curvature of the inner surface of the face 7 is smaller than the radius of curvature of the outer surface, the glass thickness increases as the distance from the face center increases. Therefore, the four corners of the face 7 are thickest at the portions indicated by A, B, C, and D. In the glass panel according to the present invention, the four corners A, B,
On the diagonal line including C and D, it is desirable to satisfy the conditional expression 1.0 ≦ t _d / t ₀ ≦ 1.2 regarding the thickness.

In the above embodiment, as shown by the dotted line in FIG. 1, compressive stress layers 20 and 21 are formed on the outer surface and inner surface of the effective screen portion of the face portion 7. The thickness of the compressive stress layers 20 and 21 is t _0/10 or more. In addition, the stress values of these compressive stress layers 20 and 21 are expressed by σ _c
And 60 kg / cm ² ≦ σ _c ≦ 200 kg / c
It is preferably m ² .

As a method of forming the compressive stress layers 20 and 21, the molten glass is press-molded to form a glass panel, which is then cooled in a slow cooling furnace to be physically strengthened and compressed to the glass surface side. Form a stress layer. In this case, the magnitude of the generated stress depends on the time required for the glass surface to cool from the annealing temperature to the strain point,
The faster the cooling, the greater the difference in shrinkage with the inside,
After completion of cooling, a large compressive stress is generated on the surface. The presence of such a compressive stress layer enhances the mechanical strength of the glass surface.

In the physical strengthening referred to in the present invention, when the glass is rapidly cooled from a high temperature region near the softening point of the glass, the surface rapidly shrinks and solidifies, while the interior still retains sufficient fluidity and remains expanded. The temporary strain is instantly relieved by the flow. Upon further cooling, the interior will also try to shrink, but its movement is limited by the presence of the solidified surface layer. As a result, when the temperature of the glass falls to room temperature and reaches a sufficient equilibrium state, a large compressive stress layer is formed on the surface and a tensile stress layer is formed inside and remains as residual stress.

The magnitude of the stress generated at this time depends on the time required for the glass surface to drop from the annealing temperature to the strain point, and the faster the cooling, the greater the difference in shrinkage with the inside. Then, after slow cooling, a large compressive stress layer σ _c is generated on the surface. However, at the same time, a tensile stress with a magnitude of σ _t = −σ _c / 2 is inevitably formed in the inner center in a form of canceling this compressive stress.

Therefore, while the presence of the compressive stress layer on the surface enhances the strength, when the tensile stress in the inner center is too large, defects such as undissolved substances existing in the vicinity of the inner center trigger and are stored inside. There is a risk of self-destruction in an attempt to release the entrained tensile strain energy.

Considering thermal shock and the like in the normal cathode ray tube assembly process, in order to prevent self-destruction, 1
It was found from the thermal shock test of the glass bulb that it is necessary to suppress the tensile stress at the inner center within a range not exceeding 00 kg / cm ² . Therefore, from the relationship of σ _c = −2σ _t , it is necessary to set the compressive stress within a range not exceeding 200 kg / cm ² .

By providing the compressive stress layer by such physical strengthening, the glass panel can be flattened, thinned, and made to have an equal thickness, so that the visibility is improved and the transmittance is improved to make the face brightness uniform. Can be planned.

Table 3 shows the glass panels which were actually prepared by changing the conditions such as the radius of curvature of the face portion, the wall thickness and the transmittance.
Shows sample data for types.

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

Each of Samples 1 to 6 is a glass bulb used in a cathode ray tube for a color television.
A glass bulb having the characteristics shown in Table 1 and formed from a glass material having the composition shown in Table 5. The face portion of this glass bulb is for a 15-inch television having an aspect ratio of 4: 3 and an effective screen with a diagonal diameter of 36 cm. The cathode ray tube is assembled according to a normal manufacturing process. Is.

In Table 3, the data of the failure rate of the explosion-proof test is, as specified in the UL safety standard of the United States, the face part of the cathode ray tube glass panel is impacted with a steel ball at an energy of 7 J, and its Whether or not safety is judged is determined by the size of the glass that scatters significantly. in this case,
The impact position was set at a position 30 mm on the diagonal from the end of the effective screen, which is easily affected by the thickness distribution of the face portion with respect to the explosion-proof property.

(Sample-1) No compressive stress layer was formed. The outer and inner surfaces have small radii of curvature and are closest to the spherical shell structure in the sample. For this reason, it was strong against impact, and the wall thickness in the vicinity of the display end portion on the diagonal line could be made relatively thin as 12.5 mm without producing a product that failed the explosion-proof test. The light transmittance ratio between the center of the face and the upper end of the diagonal is 93%.
And good. However, the outer radius of curvature is 640 m
Since it is as small as m, the visibility is poor and the screen is difficult to see.

(Sample-2) The compressive stress layer is not formed. Visibility is improved by increasing the radius of curvature of the outer surface to 1200 mm. The ratio of the thickness of the face center portion to the thickness of the end portion of the effective screen portion is 1.10, and the equal thickness is good.
Further, the thickness of the end portion of the display surface was reduced to 11.0 mm to improve the light transmittance to 95.4%. However, since the thickness of the edge portion of the effective screen was thin, the strength was lowered and the rejection rate of the explosion-proof test was about 50% (9 out of 20 failed), which was extremely poor.

(Sample-3) Panel shape is sample-
Same as 2. In order to improve the explosion-proof strength, a compressive stress layer was formed on the panel surface by physical strengthening. The compressive stress value is 43 kg / cm ² at the center of the face and 40 kg / cm ² at the end of the face, which are distributed almost uniformly in the face effective display screen. The thickness of this compressive stress layer was 1.5 mm to 1.8 mm, which was 1/10 or more of the thickness of the central portion of the glass. By forming such a compressive stress layer, the strength against impact was increased, and the explosion-proof test result was improved as compared with Sample-2 having the same shape. However, a rejection rate of 10% has occurred.

(Sample-4) Panel shape is sample-
Same as 2. The stress value of the compressive stress layer was increased to about 1.5 times that of Sample-3 to 65 kg / cm ² at the center of the face and 63 kg / cm ² at the end of the face to enhance the explosion-proof strength. As a result, the pass rate of the explosion-proof test was 100%, and no defective product was generated.

(Sample-5) Sample shape is panel-
Same as 2. The stress value of the compressive stress layer was further increased from that of Sample-4 to 187 kg / cm ² at the center of the face,
The face edge was 183 kg / cm ² . In this case as well, the pass rate of the explosion-proof test was 100%, and no defective product was generated.

(Sample-6) The strength was increased without forming a compressive stress layer and the pass rate of the explosion-proof test was set to 100%. However, in this sample, the radius of curvature of the inner surface is small, and the thickness of the face end portion is large and the weight is large (4.2 kg), which makes the handling inconvenient. Further, the difference in thickness between the central portion and the end portion becomes large, which results in widening the difference in transmittance and deteriorating the visibility.

[0044]

As described above, in the glass bulb for a cathode ray tube according to the present invention, since the compressive stress layer having a predetermined thickness and a predetermined strength is formed on the glass panel face surface by physical strengthening, the strength is The development of cracks due to rising impact is prevented or delayed, and the occurrence of implosion is suppressed. In addition, while maintaining sufficient strength, it is possible to improve flatness and suppress the brightness difference in the display surface, improve visibility, and reduce the overall glass thickness and weight. .

[Brief description of drawings]

FIG. 1 is a sectional view of a glass panel according to an embodiment of the present invention.

FIG. 2 is a plan view of the glass panel shown in FIG.

FIG. 3 is a configuration diagram of a cathode ray tube to which the present invention is applied.

[Explanation of symbols]

 3: Glass panel 6: Skirt part 7: Face part 20, 21: Compressive stress layer

Claims (2)

[Claims] 1. A glass panel portion comprising a substantially rectangular face portion forming a display screen and a skirt portion extending from the peripheral portion of the face portion in a direction substantially perpendicular to the face portion, and with respect to the glass panel portion. In a glass bulb for a cathode ray tube constituted by a funnel-shaped funnel portion that is hermetically joined and a neck portion at the base of the funnel portion that houses an electron gun, the center of the effective screen portion of the face portion of the glass panel and its The glass thickness near the edge is t
₀ and t _d , 1.0 ≦ t _d / t ₀ ≦ 1.2 on the diagonal line of the face portion, and a thickness of t _0/10 or more on the outer surface and the inner surface of the face portion. A glass bulb for a cathode ray tube, characterized in that a compressive stress layer is formed. 2. When the stress value of the compressive stress layer is σ _c in a region including a diagonal line of the effective screen portion of the face portion, 60 kg / cm ² ≦ σ _c ≦ 200 kg / cm ²
The glass bulb for a cathode ray tube according to claim 1, wherein