Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
2001-06-25
2003-09-09
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S407000, C313S408000
Reexamination Certificate
active
06617776
ABSTRACT:
REFERENCE TO RELATED APPLICATIONS
The present application is the national stage under 35 U.S.C. §371 of international application PCT/JP99/07266, filed Dec. 14, 1999 which designated the United States, and which application was not published in the English language.
1. Technical Field
This invention concerns a shadow mask material for use in a color picture tube, a shadow mask and a color picture tube incorporating the same. More specifically it relates to a mask material for use in a color picture tube having excellent tensile strength and high temperature creep strength, a shadow mask and a color picture tube incorporating the same.
2. Background Art
In recent years, in shadow mask type color picture tubes, so-called flat face cathode ray tubes have been adopted, which are attached by welding to a frame having a slightly curved mask surface. The flat face cathode ray tube has a remarkable effect of greatly reducing random reflection of illumination light or the like and moderating fatigue of eyes.
For the shadow mask material adapted in the existent system as described above, it has been attached an importance, for example, to press moldability and shape retainability keeping the shape upon pressing as it is so as to be attached by welding to a frame having a slightly curved mask surface.
However, when the flattening for the cathode-ray tube is advanced further in the shadow mask system, it may be a worry that the flattening can not be attained with a slightly curved mask surface adopted in existent cathode ray tubes.
In view of the above, it has been demanded for the development of a shadow mask material capable of completely flattening the mask surface in a shadow mask type cathode ray tube known so far and capable of coping therewith.
A subject of this invention is to provide a shadow mask material for use in a color picture tube capable of coping with a completely flat face cathode ray tube as described above, a shadow mask, and a color picture tube incorporating the same and, further, a shadow mask material for use in a color picture tube having excellent tensile strength and high temperature creep strength, a shadow mask and a color picture tube incorporating the same.
DISCLOSURE OF THE INVENTION
A shadow mask material for use in a color picture tube according to the invention is characterized by comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu and from 0.001 to 0.4% by weight of P.
A shadow mask material according to the invention is characterized by comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu, from 0.001 to 0.4% by weight of P and from 0.01 to 1.75% by weight of Ni.
A shadow mask material according to the invention is characterized by comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu and from 0.001 to 0.4%by weight of P.
A shadow mask for use in a color picture tube according to the invention is characterized by comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu, from 0.001 to 0.4% by weight of P and from 0.01 to 1.75% by weight of Ni.
A color picture tube according to the invention is characterized by incorporating a shadow mask for use in a color picture tube comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu and from 0.001 to 0.4% by weight of P.
A color picture tube according to the invention is characterized by incorporating a shadow mask for use in a color picture tube comprising a low carbon steel containing from 0.05 to 2.5% by weight of Cu, from 0.001 to 0.4% by weight of P and from 0.01 to 1.75% by weight of Ni.
A color picture tube according to the invention is characterized in that a shadow mask applied with tension is attached to a frame. The tension in the picture tube is desirably in either upper or lower direction or in both directions of the frame.
A shadow mask material according to the invention is characterized in that elongation is 0.1% or less when applied with a load stress of 20 kgf/mm
2
and kept at 450° C.×60 min.
BEST MODE FOR PRACTICING THE INVENTION
The shadow mask material according to this invention is welded to a frame in a state loaded with a large tension in the vertical direction and has a sufficient creep strength also at a high temperature such that the shadow mask applied with tension is kept in a tension—loaded state with no slacking of the shadow mask also in the subsequent heat treatment step.
Accordingly, extremely low carbon steel used as the material for the shadow mask according to this invention is preferably decarbonized and denitrated using a vacuum degasing method to reduce carbide and nitrides in the steel and promoted for the growth of the crystal grains in the steps of hot rolling or hot rolling and heat treatment (primary heat treatment and secondary heat treatment)
At first, the elements to be added to the steel used for the material of the shadow mask according to this invention and the reason for limiting the addition amount thereof are to be explained.
Referring to C, it is desirably as low as possible since carbides increase to hinder the growth of crystal grains as amount C in steel sheets after cold rolling is more. Therefore, the upper limit for the C content is preferably 0.01% by weight. The lower limit is preferably as low as possible providing that it can be reduced practically by a vacuum degasing treatment.
With reference to Mn, Mn has to be added for bonding with S in the steel to fix the S content in the steel as MnS to prevent hot shortness but lesser addition amount is preferred for improving the magnetic property and it is added by an amount of 0.5% by weight or less.
Si is preferably as less as possible since it deteriorates the adhesion of blackened film and the content is defined to 0.3% by weight or less. Since S greatly hinders the etching property, it is preferably as less as possible and the content is defined as 0.05% by weight or less. Further, since also N forms nitrides to hinder the growth of crystal grains, it is preferred as less as possible and restricted to 0.05% by weight or less.
Regarding Cu, it has an effect of increasing the precipitation amount of &egr;-phase in the precipitation heat treatment (secondary heat treatment) along with increase of the addition amount to greatly improve the yield strength, tensile strength and creep strength. However, no sufficient effect for the improvement of the strength can be obtained when the addition amount is insufficient. It is preferably, 0.05% by weight or more, more preferably, 0.5% by weight or more and, further preferably, 1% by weight or more.
On the other hand, if the addition amount is excessive, precipitates are increased and deteriorates the mechanical property such as tensile strength and creep strength. It is preferably 2.5% by weight or less, more preferably, 2% by weight or less and, further preferably 1.5% by weight or less.
P is effective for increasing the strength by solid solution strengthening and since the tensile strength and the creep strength increase remarkably by the addition amount of P, solid solution strengthening by P can be combined with strengthening based on the precipitation heat treatment by the addition of Cu as an object of this invention.
The amount of P added is preferably 0.001% or more, more preferably, 0.01% by weight or more and, further preferably, 0.1% by weight or more.
When the addition amount is excessive, mixed grains are formed by segregation and this also results in embrittlement, it is preferably 0.4% by weight or less, more preferably, 0.25% by weight or less and, further preferably, 0.15% by weight or less.
Ni has a remarkable effect of preventing hot shortness caused by the addition of Cu and has a great effect of improving the yield in the manufacturing step for the shadow mask material applied with tension in accordance with this invention. Further, quality can be stabilized since this suppresses segregation of Cu and tensile strength and creep strength are improved by solid solution hardening of Ni. Since the effect of Ni can be attained sufficie
Ide Tsuneyuki
Miyazaki Takahiko
Okayama Hironao
Sigemasa Susumu
Tahara Yasuo
Browdy and Neimark PLLC
Patel Nimeshkumar D.
Phinney Jason
Toyo Kohan Co. Ltd.
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