JPS6288245A - Color cathode-ray tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to color cathode ray tubes having an aperture mask and, more particularly, to improvements in internal magnetic shields for such cathode ray tubes.

Color cathode ray tubes (color picture tubes) for color television that use an aperture mask are affected by external magnetic fields, especially the earth's magnetic field, which causes the trajectory of the electron beam to shift undesirably, causing raster distortion and deterioration of color purity and convergence. easy.

For example, a rightward or leftward shift of the beam trajectory causes landing errors in picture tubes with vertical fluorescent stripes. In other words, the beam lands on the right or left side of the intended landing point on the stripe.

For this reason, acceptable performance requires that such color picture tubes be effectively shielded from external magnetic fields, and it is common practice to incorporate internal magnetic shields within color picture tubes for this purpose.

Because the influence of the earth's magnetic field depends on the installation location and orientation of the pipe,
For optimal magnetic shielding, it is necessary to remagnetize the magnetic shield after moving the tube so that the magnetic domains can realign. Therefore, magnetic shields are typically made of soft magnetic materials, such as low carbon steel, which can be easily remagnetized each time the television device is turned on.

The shape of the magnetic shield is generally determined by the requirement to shield as much tube volume as possible without interfering with tube operation. For example, extending the shield too far into the funnel can tend to interfere with the deflection field of the electron beam and create interceptors or "clipping" of the deflected beam. Additionally, for cost reasons, The shape can be determined as simple as possible.

In US Pat. No. 3,867,668, the magnetic shield is constructed from two curved sheets of magnetic material, making it convenient and easy to manufacture, store, transport and assemble. Furthermore, an external shield is used to cover the gap formed by the opening between the two curved sheets, resulting in "complete shielding".
has been achieved.

The influence of the earth's magnetic field on beam landing can be described in terms of two components: an east-west (left-right) influence determined by the transverse horizontal magnetic field, and a south-north (top-bottom) influence determined by the axial horizontal magnetic field. is common. The magnitude of these effects is the difference between the beam landing errors when the picture tube is oriented east and west and when it is oriented north and south. Additionally, each face of the tube is generally described based on the dial of an analog clock. That is, the upper side is 12
The base is 6 o'clock, the right side (as seen from the observer) is 3 o'clock, and the left side is 9 o'clock.

It is an object of the present invention to provide an internal magnetic shield for a color picture tube that has an improved shielding effect and is easy to manufacture with current manufacturing technology.

The present invention provides an internal magnetic shield in a color picture tube.
a bowl-shaped hole having at least one slot-like hole extending in the direction of the axis of rotation of the tube or the Z-axis in each of the 6 o'clock side wall and the 12 o'clock side wall and having a large opening surrounding the Z-axis through which the electron beam passes; It is characterized by being composed of a structure.

In a preferred embodiment of the present invention, the 6 o'clock side wall of the shield and the 12
The side wall is provided with a pair of centrally located slot holes facing each other above and below the Z-axis.

In the present invention, such a shield is constructed by first cutting slot holes into a thin sheet of soft magnetic material such as low carbon steel;
The sheet is then pressed onto a bowl-shaped mold to curve and crimp the sheet into a bowl-shaped structure. Next, cut this shield to form an opening.

The invention will be explained with reference to the drawings.

FIG. 1 shows a color cathode ray tube (color picture tube) for color television having a tube 13 in which a face panel part 15, a funnel part 17, and a neck part 19 are integrated. A cathodoluminescent screen 21 consisting of an array of individual fluorescent elements is provided on the interior surface of the face panel 15. Inside the neck portion 19 is a mount 22 that includes an electron gun that directs three electron beams toward the screen 21.
is placed. An aperture mask 25 is placed adjacent to the screen 21 to allow the electron beam to reach desired fluorescent elements on the screen. The aperture mask 25 is supported by a frame member 29, and this frame member is supported by a stand 29 embedded in the side wall of the panel 15.

An internal magnetic shield 31 is attached to this mask frame 29. The magnetic shield has a bowl-shaped structure 39 having a slot 41 in the center of its upper and lower walls aligned with the central axis or Z-axis of the tube and aligned above and below, and an opening 47 surrounding the Z-axis. Consists of.

1, the bowl-shaped structure 39 of the shield 31 extends along the funnel 17 from the periphery of the mask 25 in the direction of the mount 22, generally following the contour of the funnel wall and connecting the mask and the mount. terminating midway between to define an opening 47. Further elongation of the shield improves the shielding effect, but it also risks interfering with the beam deflection field generated by an external deflection device (not shown) located at the funnel-neck transition. A loop occurs that intercepts (clipped) the electron beam.

FIG. 2 shows a plan view of the shield 31 viewed from the rear of the tube in the direction of the Z axis. Following the conventional notation of considering the screen panel as the face of an analog clock and representing the various sections of the tube, the top, left, bottom and right sides of the shield are designated as 12 o'clock, 3 o'clock and 6 o'clock, respectively. Described as side and 9 o'clock side. As is clear from FIG. 2, the slot 41
a and 41b are located at the center of the 6 o'clock side and the 12 o'clock side.

These slots are located at the openings 47 on the 6 o'clock and 12 o'clock sides.
It can also be located off-center within a central area within 40% of the length of .

Although two or more slots can be provided in one side wall, it is preferable that each side wall has the same number of slots. Furthermore, the slots need not be aligned one above the other as shown, but can also be offset from one another within the central area.

These slots extend from the rim 48 to the straight edge 49 of the opening 47.
The shield has a height h of about 50-95% of the height H of the shield up to, and a width W of about 1-10% of the length at the rim 48 of the shield.

The aperture 47 is rectangular in shape with a length-to-width ratio of approximately 1.7 to 2.1, with a central portion defined by a straight edge 49 and two end portions defined by curved edges 50. shall have the following.

As shown in detail in FIGS. 1 and 3, the center of this opening is located in a plane perpendicular to the Z-axis, and both ends are located in an upwardly curved plane. It has a curved side shape as shown in the figure.

The opening 47 is approximately 49 mm wide of the width Wr of the shield at the rim 48.
It has a width of ~51% as well as a length of about 65~6
It has a length La of 9%. Additionally, the degree of upward curvature of the end of the opening caused by the intersection of the bowl-shaped sidewall and the rectangular opening is represented by the height Hc of the shield from the rim 48 to the exterior 52 of the curved edge 50; Approximately 8 of height Hl
It can be within the range of 5 to 90%.

Within the size range described above, aperture 47 has a length-to-width ratio that is greater than the length-to-width ratio of certain conventional designs of shield apertures (approximately 2:1.3). This change in aperture size improves north-both speed screening, but slightly reduces east-fourth speed screening. However, the east-fourth gear deflection effect is at least partially restored by centering slots in the 6 o'clock and 12 o'clock side walls.

- As an example, 19V mini-neck color display tubes having a shielding body of the present invention and a conventional shielding body were manufactured, and the differences in registration were compared.

The shield of the present invention has a rectangular opening with slots at the 6 o'clock and 12 o'clock sides and an upwardly curved edge, as shown in the figure, and the dimensions of each part (in inches) are: I, = 4.0, L, =15.0, W.

=10.9, Hc=3.75, Wr=5.3
7, L, =10.75.

W=0.3 and h=3.9. The conventional shielding body has no slot, and its opening is located entirely in a plane perpendicular to the Z axis, and the dimensions of each part are +1. =3.0.

=15.0, Wr=10.9. Rei = 7.4 and = 9.6. Registration (the difference between the strike position and the actual beam landing position, also known as beam landing error) was measured and averaged for several sample tubes of each type of shield. . Measurements were made on the four corners of each sample picture tube's screen, facing south, east, north, and west in sequence. The difference in registration between north and south facing was approximately 1.2 mil on average with conventional shielding;
It was less than about 0.6 mil for the shield of the present invention. The difference in registration between east and west orientation averaged about 0.5 mil for the conventional shield, while it was about 0.6 mil for the shield of the present invention. This significant improvement in north-both direction deflection at the slight sacrifice of east-fourth deflection results in beneficial shielding of the effects of external magnetic fields, resulting in an overall improvement in tube performance.

Another feature of the invention is that the shield is fabricated from a thin sheet of soft magnetic material, such as low carbon steel. The sheet is pressed onto a mold, curved and crimped to form the desired shape. Crimp is represented by irregularly distributed wavy lines in the diagram.

Preferably, the slots are formed before molding, for example by cutting or punching. This is because after molding, the slots must be formed on a curved surface, which is more difficult than forming them on a flat surface. Because the slots are located in portions of the sheet that will be significantly curved during forming, it is important to adhere to the dimensions and other limitations mentioned above for these slots to avoid tearing the sheet and deforming the slots during forming. . For the same reason, it is advantageous to form the apertures after molding.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it goes without saying that various modifications and changes can be made.

[Brief explanation of drawings]

1 is a cross-sectional view of a color display tube incorporating the internal magnetic shield of the present invention; FIG. 2 is a rear plan view showing the slots and openings of the shield of FIG. 1; and FIG. FIG. 2 is a side view showing the outline of one edge of the opening of the shield shown in FIG. 1; 11... Color cathode ray tube 13... Tube 15...
・Face panel part 17...Funnel part 19...
・Neck part 21...Cathode luminescence screen 22...Electron gun mount 25...Aperture mask 27...
・Stud 29...Frame member 31...
・Internal magnetic shield 39...bowl-shaped structure 41a,
41b...Slot 47...Aperture 48...Rim 49...Straight edge 50...Curved edge Patent Applicant: North American Philips Consumer Electronics Corporation

Claims (1)

[Scope of Claims] 1. A glass tube integrating a faceplate portion, a funnel portion, and a neck portion; and a fluorescent screen consisting of an array of individual fluorescent elements deposited on the inner surface of the faceplate. at least one electron gun disposed within the neck portion to direct and generate an electron beam toward the screen; an aperture mask disposed adjacent to the screen for directing the electron beam to a desired fluorescent element on the screen; a mask; and an electron gun, both forward of the neck and having a rim extending around the periphery of the mask and a side wall extending from the rim along the inner surface of the funnel in the direction of the neck. a color cathode ray tube comprising an internal magnetic shield consisting of a bowl-shaped structure terminating in an aperture defining an aperture for passing the electron beam through the mask and screen; In a color cathode ray tube having an upper side, a right side, a lower side, and a left side surrounding the Z-axis, respectively called 12 o'clock side, 3 o'clock side, 6 o'clock side, and 9 o'clock side when viewed from the viewer, the shielding A color cathode ray tube, characterized in that the body has at least one slot-like hole extending in the direction of the Z-axis of the tube on each of the 6 o'clock side and the 12 o'clock side of the bowl-shaped structure. 2. The bowl-shaped structure has a pair of slot holes, a first
The slot hole is located at the center of the 12 o'clock side surface above the Z axis, and the second slot hole is located at the center of the 6 o'clock side surface below the Z axis, facing the first slot hole. The color cathode ray tube according to claim 1, characterized in that the color cathode ray tube is 3. The color cathode ray tube according to claim 2, wherein the bowl-shaped structure has a 6 o'clock side surface and a 12 o'clock side surface extending more toward the neck than the 3 o'clock side and 9 o'clock side. . 4. The opening is defined by straight edges on the 6 o'clock and 12 o'clock sides and outwardly curved and upwardly curved edges on the 3 o'clock and 9 o'clock sides, and extends in a plane perpendicular to the Z axis. 4. The color cathode ray tube according to claim 3, wherein the color cathode ray tube is formed into a rectangular opening having a central portion and two end portions located in a plane curved upward from the vertical plane. 5. The shield has a height H_s from the rim to the straight edge of the opening and a length L_r at the rim, and the slot has a height h of about 50-95% of H_s and about 1 of L_r.
5. The color cathode ray tube according to claim 4, wherein the color cathode ray tube has a width w of ~10%. 6. The shield has a width W_r at the rim, and the opening has a width W of about 49-51% of the width W_r of the shield.
_a and a length L_a of about 65 to 69% of the length L_r of the shielding body.
Color cathode ray tube as described. 7. The shielding body extends from the rim to the curved edge of the opening,
A height H_ of about 85 to 90% of the height H_s of the shielding body
A color cathode ray tube characterized in that it has c. 8. The opening has a length L_a to width W_ of about 1.7-2.1
A color cathode ray tube having a ratio of a. 9. A color cathode ray tube according to claim 8, wherein said bowl-shaped structure comprises a crimped sheet of soft magnetic material. 10. In manufacturing an internal magnetic shield for a color cathode ray tube, first form at least one pair of slots in a thin sheet of soft magnetic material, and then press the sheet onto a bowl-shaped mold to form a bowl. A method for manufacturing an internal magnetic shield for a color cathode ray tube, which is characterized by curve-molding into a shaped structure. 11. The manufacturing method according to claim 10, characterized in that an opening is formed in the bowl-shaped structure after the structure is formed.