1. Field of the Invention
The present invention relates to a cathode ray tube, and more particularly, to a neck of a funnel and a stem sealed to the neck of a cathode ray tube.
2. Description of the Related Art
A cathode ray tube includes a phosphor layer on the inside thereof, a panel to which a shadow mask spaced from the phosphor layer is secured, a funnel having a neck and a cone portion connected to the panel, an electron gun housed in the neck for emitting an electron beam, a deflection yoke fixedly installed around the cone portion, and a stem sealed to one end of the neck for mounting the electron gun.
The cathode ray tube operates as follows. First, if a heater installed on the inside of a cathode of the electron gun generates heat, electrons are emitted from oxide coated on the top of the cathode. Then, the electrons emitted from the cathode pass through each electrode arranged at regular intervals to form the electron beam of the desired characteristics. The formed electron beam is deflected by a magnetic field produced by the deflection yoke, passes through the shadow mask, and collides with the phosphor layer coated on the inside of the panel to light up phosphors, thereby creating a screenful of an image.
To smoothly perform the operation as described above, the interior of the cathode ray tube must maintain a vacuum. To accomplish this, a stem having a plurality of stem pins for supplying voltages to the electron gun and an exhaust pipe for exhaustion is introduced into one end of the neck, and a portion at which the side of a stem flange contacts the inside of the neck is fused and sealed off. The interior of the cathode ray tube is evacuated through the exhaust pipe to a vacuum and the exhaust pipe is then fused and sealed.
The stem includes the stem flange formed in the shape of a flat disk whose diameter is smaller than the inside diameter of a sealing portion, the plurality of stem pins arranged in a round shape to pass through the stem flange for introducing signal voltages from an external circuit, and a plurality of stem mounds convexly built of glass, which is the material of the stem, for holding the plurality of stem pins and preventing the loss of vacuum, and the exhaust pipe formed in the central part of the stem flange for evacuating cathode ray tube to a vacuum. Here, the diameter of an inner stem pin circle of interior stem pins connected to the electrodes of the electron gun is equal to that of exterior stem pins connected to a socket for applying a predetermined voltage of each electrode of the electron gun.
As described above, the exterior stem pins are combined with the sockets installed in a chassis. For example, the stem used in the neck having a diameter of 22.5 mm (millimeters) is fit into a socket for 22.5 mm, and the stem used in the neck having a diameter of 29.1 mm is fit into a socket for 29.1 mm. However, this raises a problem in that a cathode ray tube having a neck of diameter 29.1 mm are not compatible with that having a neck of a diameter 22.5 mm since chassis for 29.1 mm has been chiefly manufactured in a market for monitors of 15 or more inches (diagonal measurement of screen).
Recently, an electric potential applied to a focusing electrode of an electron gun tends to increase due to a flat panel of a cathode ray tube and increased dynamic focusing modulation. Furthermore, current must be applied to coils of a deflection yoke to deflect electron beams emitted from the electron gun in a cathode ray tube. Since a smaller amount of current is consumed as the diameter of a neck decreases, the diameter of the neck tends to be less for low power consumption.
However, high electric potential and small diameter of a neck results in large spherical aberrations due to a decreased size of electrodes of an electron gun. To prevent this, the number of electrodes of an electron gun should be increased. Since the increased number of electrodes increases the number of stem pins accordingly, problems associated with a breakdown voltage may occur. To solve the breakdown voltage problems, one empty pin may be inserted on either side of a high voltage stem pin. However, since insertion of empty pins may result in the increased number of stem pins, a stem having a large stem pin circle is required.
Furthermore, to solve the breakdown voltage problems, the diameter of a neck may be made larger, and the diameter of a stem flange may be made larger to seal it to one end of the neck. However, the large diameter of the neck results in high power consumption and sealing the stem flange to the neck end may require an extra device and drop a yield rate.
It is more difficult to fuse and seal the stem having a large stem pin circle to a low deflection cathode ray tube having a narrow neck of a diameter 22.5 mm than to a cathode ray tube having a neck of a diameter 29.1 mm presently widely used. Furthermore, if a stem mount is formed very close to a connecting portion where the stem flange is fused and sealed to the end of the neck, cracks may occur easily at the connecting portion of the stem flange and the neck.
A neck of a cathode ray tube is disclosed in U.S. Pat. No. 6,078,134 issued to Nose et al. for Narrow-neck CRT having a Large Stem Pin Circle.
It is therefore an object of the present invention to provide a cathode ray tube having a stem compatible with a cathode ray tube having a neck of a different diameter, which simplifies a fabrication process and increases a yield rate by sealing the compatible stem to a neck with an existing sealing device.
It is another object of the present invention to provide a cathode ray tube having a stem-sealing region of a neck, where the inside diameter of the sealing region is increased so that it is easier to fuse and seal a stem having a large stem pin circle to the narrow neck of the cathode ray tube with low deflection.
Accordingly, to achieve the above and other objects, the present invention provides a cathode ray tube. The cathode ray tube includes a panel in which a phosphor layer is formed, a funnel connected to the panel, the funnel including a neck having a region for housing an electron gun and a region to which a stem is sealed, and a stem having a plurality of stem pins, each stem pin being supported by each stem mound for applying voltage to each electrode of the electron gun. The inside diameter of the stem sealing region of the neck is greater than that of the electron gun-housing region, the diameter of an inner stem pin circle formed by interior stem pins disposed on the inside of the neck is less than that of an outer stem pin circle formed by exterior stem pins disposed on the outside thereof, a horizontal length between an outer edge of the stem mound and an interior of the neck is in the range greater than or equal to 1.0 mm and less than or equal to 2.0 mm.
In another embodiment, a cathode ray tube includes a panel in which a phosphor layer is formed, a funnel connected to and tapered from the panel, and a neck connected to the funnel and including an electron gun-housing region and a stem sealing region, to which a stem having a plurality of stem pins arranged in an annular shape and passing therethrough for introducing signal voltages from an external circuit is sealed, wherein D1 is 22.5xc2x10.7 mm and D2 is in the range greater than D1 and less than or equal to 24.0 mm where the outside diameters of the electron gun-housing region and the stem sealing region are D1 and D2, respectively.
As described above, the cathode ray tube according to an embodiment of the present invention forms an outer stem pin circle greater than an inner stem pin circle, thereby achieving compatibility with cathode ray tubes having a neck of a different diameter. The stem is sealed to the inside of the neck by making the inside diameter of the sealing region of the neck larger than that of an electron gun-housing region, thereby increasing a yield rate without the need for a special device which is otherwise required for sealing a stem to one end of a neck. Furthermore, the stem is sealed at the stem-sealing region of the neck, thereby removing glass residues or foreign material and increasing a breakdown voltage.
The cathode ray tube according to another embodiment of this invention increases the outside diameter of a stem-sealing region of a narrow neck so that it is easier to fuse and seal the stem having a large stem pin circle to the narrow neck of the low deflection cathode ray tube. Furthermore, the cathode ray tube increases a distance between a stem mound on a stem flange and a connecting portion of the neck, thereby preventing occurrences of crack at the connecting portion.