JPH0810583B2 - Color cathode ray tube - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an in-line type color cathode ray tube having a convergence characteristic suitable for use at a high horizontal deflection frequency or a plurality of horizontal deflection frequencies.

[Conventional technology]

There are currently few problems when using an in-line type color cathode ray tube for a color television receiver of a standard broadcasting system. For example, a horizontal scanning line is used as a disc play tube for a high definition video data terminal (VDT). When the number of electron beams is large and therefore the horizontal deflection frequency is high, the difference between the scanning area by the central beam, that is, the image reproduction area and the scanning area by the electron beams at the two ends of the three electron beams arranged on one horizontal plane is different. There was a problem of being noticeable.

The cause of this problem is presumed as follows. A cylindrical shield side wall that surrounds the three electron beams in order to shield the electron beams from the electrostatic charges charged on the inner wall surface of the glass bulb at the end of the electron gun on the fluorescent surface side that forms the three electron beams in-line And a bottomed cylindrical shield electrode made of a non-magnetic metal having a bottom surface having electron beam passage holes for each of the three electron beams on the side close to the cathode. On the other hand, the deflection yoke for generating the deflection magnetic field for deflecting the electron beam is arranged outside the funnel of the valve near the connection with the neck tube, but the end of the deflection magnetic field close to the cathode side is just shielded. Due to the relative position of the electrodes passing through the shield sidewall, the time-varying deflection magnetic field induces an eddy current in the electrically conductive shield sidewall, which weakens the original deflection magnetic field. At the horizontal deflection frequency of the standard broadcasting system, the effect of eddy current is small, and even if the scanning area by the central electron beam and the scanning area by the electron beams at both ends are different, there is no problem because the difference is small. However, in a high-definition display tube for VDT, for example, the number of horizontal scanning lines is much faster than the time rate of change of the horizontal deflection magnetic field as compared with the case of television broadcasting. It is believed that this is due to the fact that it has become much larger, and that its effects have become prominent.

Further, in Japanese Patent Laid-Open No. 56-76145, a magnetic field control element is provided on the bottom surface of the shield pole for increasing the horizontal deflection magnetic flux density acting on the central electron beam and lowering the horizontal deflection magnetic flux density acting on both side electron beams. Targeting an in-line type color cathode ray tube, one of the electron beams generated from the electron gun, whose deflection does not lag behind other electron beams in time, is introduced into the passage of the electron beam along with the temporal change of the horizontal deflection magnetic flux. It is disclosed to provide an eddy current inducing element that generates an eddy current. In order to prevent the horizontal deflection angle of the central electron beam from becoming small, the magnetic field control element (actually, a small cylindrical member made of a high magnetic permeability magnetic material) is provided above and below the central electron beam passage hole. By arranging them, the magnetic flux density of the deflection magnetic field acting on this beam is increased. Further, an annular body made of a magnetic material with high magnetic permeability is arranged around the electron beam passage holes on both sides to form a magnetic flux bypass that bypasses the beam passage holes so that the horizontal deflection magnetic field acting on the electron beams on both sides is weakened. I have to.

Further, eddy current inducing elements that project in the shape of eaves above and below the beam passage holes on both sides and are orthogonal to the horizontal deflection magnetic flux are provided. Therefore, four magnetic control elements and four eddy current inducing elements are arranged by welding or the like on the bottom surface of the shield electrode.

Next, in JP-A-60-86763 and JP-A-60-86737, in order to prevent the horizontal deflection magnetic field from being weakened by the eddy current, the eddy current intersects with the horizontal deflection magnetic field of the shield side wall, respectively. It is disclosed that a portion where a current is generated is cut out, and the height of the shield side wall is limited to 6.0 mm or less in order to reduce an area where the shield side wall intersects with the deflection magnetic field.

[Problems to be solved by the invention]

The present invention is conspicuous when an in-line type color cathode ray tube is used by increasing the number of horizontal scanning lines and increasing the horizontal deflection frequency in order to obtain high definition. To provide a color cathode ray tube which sufficiently suppresses defects, solves other problems, is simple and easy to manufacture, and sufficiently exhibits not only the original effect of the shield electrode but also the secondary effect. With the goal.

[Means for solving problems]

In the present invention, for example, a bottomed cylindrical shape which is made of metal and has a cylindrical shield side wall that shields the electron beam from the charging of the glass bulb wall surface by forming a bottom surface having three electron beam passage holes and opens toward the phosphor screen The metal material forming the shield side wall of the shield electrode has a large resistivity in the vertical direction and a low resistivity in the horizontal direction and other portions.

[Action]

The eddy current flowing on the shield side wall of the shield electrode due to the horizontal deflection magnetic flux increases as the resistance of the circuit through which the eddy current flows decreases, that is, the resistivity of the material forming the shield side wall decreases. Therefore, a material with a large resistivity is used as the material for the vertical portion of the shield sidewall where eddy currents acting on the central electron beam flow, and a material with a high resistivity is used as the material for the left and right portions of the shield sidewall where eddy currents acting on both sides of the beam flow. By using a small one, the action of the weakening magnetic field formed by the eddy current on the horizontal deflection magnetic field can be made equal for each electron beam in the in-line arrangement, and even if the horizontal deflection frequency is increased, the eddy current is increased. Misconvergence due to the current can be suppressed within a range that does not cause a problem.

〔Example〕

FIG. 1 (a) shows a shield electrode 1 of an embodiment of the color cathode ray tube of the present invention, 2 is a vertical side wall of the shield side wall, 3 is a lateral side wall, 4 and 6 are both-side beam passage holes, and 5 is a beam passage hole. The central beam passage hole. The horizontal deflection magnetic flux acting on the central beam intersects at the vertical side wall 2 of the shield side wall, and an eddy current flows there. As the horizontal deflection frequency increases, the deflection of the central beam becomes noticeable. Therefore, it is necessary to suppress the horizontal deflection magnetic field for deflecting the central beam from being weakened by the action of the eddy current. Therefore, the material of the vertical side wall 2 of the shield side wall is made of a material having a high resistivity, for example, nichrome, and the lateral side wall 3 where the horizontal deflection magnetic field that deflects the beams on both sides intersects the shield side wall is made of a material having a relatively low resistivity, for example, a usual Made of non-magnetic stainless steel. Actually, since each member of the electron gun is generally made of non-magnetic stainless steel, only the vertical side wall 2 of the shield electrode 1 may be made of a high resistivity material such as nichrome. At present, the parts of different materials can be easily welded by the laser welding method, so that nichrome and non-magnetic stainless steel can be easily joined by laser welding.
Further, FIG. 1 (b) shows another embodiment, which is constructed by lap welding. That is, the shield electrode 1a has a structure in which the end portions of the vertical side wall 2a and the horizontal side wall 3a are overlapped and welded to each other. Since nichrome is expensive and the range in which eddy current strongly flows is not so wide, it is not necessary to use nichrome for the entire height of the side wall of the shield.

〔The invention's effect〕

As described above, according to the present invention, it is possible to easily manufacture a high-definition tube in which misconvergence of an electron beam is suppressed to such an extent that it does not become a problem by using an in-line type electron gun.

[Brief description of drawings]

1 (a) and 1 (b) are plan views of a shield electrode of an embodiment of the color cathode ray tube of the present invention. 1,1a …… shield electrode, 2,2a …… upper side wall, 3,3a…
… Left and right side walls, 4,6 …… Both side beam passing holes, 5 …… Central beam passing hole.

Claims (1)

[Claims] 1. In an in-line type color cathode ray tube, an electron beam passage hole is formed at an end of a fluorescent screen of an electron gun for forming three electron beams arranged in parallel in one horizontal plane. The metal material forming the side wall of the cylindrical shield of the bottomed cylindrical shield electrode made of metal, which is composed of a cylindrical shield wall that shields the electron beam from the charging of the bottom surface and the glass bulb wall, and which is shielded from the electron beam is charged. A color cathode ray tube characterized in that a portion in a vertical direction with respect to the one horizontal plane has a higher resistivity than other portions.