Glass bulb for a cathode ray and a method of producing the same

Abstract

A glass panel 3 for a glass tube for a cathode ray tube has a flat panel face portion 7 and a reduced thickness while maintaining a sufficient strength without increasing a difference of brightness, and with less shrinking deformation due to the cooling and solidification of the glass panel. Compressive stress layers 20, 21 having a thickness of to/10 or more are formed in outer and inner surfaces of the face portion 7 of the glass panel 3 respectively. The relation to the wall thickness td of the central portion of the face portion to the wall thickness to of a portion near an edge portion on a diagonal line is 1.0</=td/to</=1.2. Compressive stress layers 22, 23 are formed in outer and inner surfaces of a skirt portion 6 wherein the compressive stress value of the face portion 7 is larger than the compressive stress value of the skirt portion, and the compressive stress value of the outer surface 20 of the face portion is larger than that of the inner surface 21.

What is claimed is: 
     
       1. A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular .Iadd.flat .Iaddend.face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom in substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion.Iadd., the radius of curvature of the inner portion of the face portion is smaller than the radius of the curvature of the outer surface.Iaddend..   
     
     
       2. The glass bulb for a cathode ray tube according to claim 1, wherein the glass wall thickness t d  near an edge portion of the face portion and on a diagonal line of the face portion is in a relation of 1.0≦t d  /t o  ≦1.2. 
     
     
       3. The glass bulb for a cathode ray tube according to claim 1, wherein 60 kg/cm 2  ≦|σ c  | where σ c  is the stress value of the compressive stress layers in a region including the diagonal line of the effective picture surface portion of the face portion. 
     
     
       4. The glass bulb for a cathode ray tube according to claim 2, wherein the radius of curvature R G  of the outer surface of the face portion is 1.5 R or more when R =42.5×V/25.4+45.0 (mm) and V is the length of a diagonal line of the effective displaying surface. 
     
     
       5. The glass bulb for a cathode ray tube according to claim 2, wherein the compressive stress layers in the outer and inner surfaces of the face portion are substantially uniformly formed in the entire of the face portion. 
     
     
       6. The glass bulb for a cathode ray tube according to claim 1, wherein the compressive stress layers are extended to the skirt portion of the glass panel portion. 
     
     
       7. The glass bulb for a cathode ray tube according to claim 6, wherein the stress value of the compressive stress layers of the face portion is larger than that of the skirt portion. 
     
     
       8. The glass bulb for a cathode ray tube according to claim 7, wherein the stress value of the compressive stress layer in the outer surface of the face portion is equal to or larger than that of the inner surface. .Iadd. 
     
     
       9.  A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are substantially uniformly formed in the outer surface and the inner surface of the entire face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass portion, the radius of curvature of the inner portion of the face portion is smaller than the radius of curvature of the outer surface. .Iaddend..Iadd.   
     
     
       10.  A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface wherein the radius of curvature of the inner portion of the face portion is smaller than the radius of curvature of the outer surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion and wherein the compressive stress layers extend to the skirt portion of the glass panel portion. .Iaddend..Iadd.   
     
     
       11.  A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion, .Iaddend.   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are substantially uniformly formed in the outer surface and the inner surface of the entire face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion. .Iadd.12. A glass bulb for a cathode ray tube which comprises:   a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface wherein the radius of curvature of the inner portion of the face portion is smaller than the radius of curvature of the outer surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion and wherein the compressive stress layers extend to the skirt portion of the glass panel portion. .Iaddend..Iadd.13. A glass bulb for a cathode ray tube which comprises:   a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion, the radius of curvature of the inner portion of the face portion is smaller than the radius of curvature of the outer surface and wherein the glass wall thickness t d  near an edge portion of the face portion and on a diagonal line of the face portion is in a relation of 1.0≦t d  /t o  ≦1.2.   
     
     
        .Iaddend..Iadd.  .  A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular, face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion, wherein the radius of curvature R G  of the outer surface of the face portion is 1.5 R or more where R=42.5×V/25.4+40.5 (mm and V is the length of a diagonal line of the   
     
     
        effective displaying surface. .Iaddend..Iadd.15.  A glass bulb for a cathode ray tube which comprises: a glass panel portion having a substantially rectangular, face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion and wherein the compressive stress layers extend to the skirt portion of the glass panel portion and the stress values of the compressive stress layers of the face portion is larger than that of the skirt portion. .Iaddend..Iadd.16. The glass bulb for a cathode ray tube according to claim 15, wherein the radius of curvature of the inner portion of the face portion is smaller than the radius of curvature of the outer surface. .Iaddend..Iadd.17. The glass bulb for a cathode ray tube according to claim 16, wherein the glass wall thickness t d  near and edge portion of the face portion and on a diagonal line of the face portion is in a relation to 1.0≦t d  /t o  ≦1.2. .Iaddend..Iadd.18. The glass bulb for a cathode ray tube according to claim 15, wherein 60 kg/cm 2  ≦/σ c  / where σ c  is the stress value of the compressive stress layers in a region including the diagonal line of the effective picture surface portion of the face portion. .Iaddend..Iadd.19. The glass bulb for a cathode ray tube according to claim 15, wherein the radius of curvature R G  of the outer surface of the face portion is 1.5 R or more where R=42.5×V/25.4+45.0 (mm) and V is the length of a diagonal line of the effective displaying surface. .Iaddend..Iadd.20. The glass bulb for a cathode ray tube according to claim 15, wherein the compressive stress layers in the outer and inner surfaces of the face portion are substantially uniformly formed in the entire of the face portion. .Iaddend..Iadd.21. The glass bulb for a cathode ray tube according to claim 15, wherein the stress value of the compressive stress layer in the outer face of the face portion is equal to or larger than that of the inner surface. .Iaddend..Iadd.22. A glass bulb for a cathode ray tube which comprises:   a glass panel portion having a substantially rectangular, flat face portion constituting a picture displaying surface and a skirt portion contiguous to the circumferential portion of the face portion and extending therefrom in substantially perpendicular to the face portion,   a funnel portion in a funnel-like form which is airtightly connected to the glass panel portion, and   a neck portion disposed at the root of the funnel portion and containing therein an electron gun, wherein compressive stress layers each having a thickness of t o  /10 or more are formed in the outer surface and the inner surface of the face portion where t o  is the wall thickness at the central portion of the effective picture surface portion of the face portion of the glass panel portion, where (1) the stress, σ c , is 60 kg/cm 2  ≦/σ c  / in the compressive stress layers in a region including the diagonal line of the effective picture surface portion of the face portion, (2) the compressive stress layers extend to the skirt portion of the glass panel portion (3) the radius of the curvature of the inner portion of the face portion is smaller than the radius of the curvature of the outer surface, (4) the radius of curvature R G  of the outer surface of the face portion is 1.5 R or more where R=42.5×V/25.4+45.0 (mm) and V is the length of a diagonal line of the effective displaying surface and (5) the glass wall thickness t d  near an edge portion of the face portion and on a diagonal line of the face portion is in a relation of 1.0≦t d  /t o  ≦1.2. .Iaddend..Iadd.23. The glass bulb for a cathode ray tube according to claim 22, wherein the compressive stress layers in the outer and inner surfaces of the face portion are substantially uniformly formed in the entire of the face portion. .Iaddend..Iadd.24. The glass bulb for a cathode ray tube according to claim 22, wherein the stress value of the compressive stress layer in the outer surface of the face portion is equal to or larger than that of the inner surface of the face portion. .Iaddend.