JPH08264130A - Color cathode ray tube - Google Patents

Abstract

(57) [Summary] [Object] It is an object of the present invention to provide a color cathode ray tube with a shadow mask having a bridge between a scanning line of an electron beam and a horizontal arrangement of slits of the shadow mask. Another object of the present invention is to solve the problem of the prior art that moire fringes occur. [Structure] In a color cathode ray tube, slit holes of a color selecting porous electrode form a slit row at a constant pitch, and a first row of a bridge portion of the color selecting porous electrode is formed.
A second point located at a position closest to the center point of the first bridge portion of the slit row that is horizontally skipped in a row.
A color cathode ray tube, wherein a line connecting the center points of the bridge portions of the above and a scanning line scanned by the electron beam are parallel to each other. According to the present invention, it is possible to reduce moire generated between the bridge and the scanning line of the shadow mask by making the inclination of the arrangement of the bridges and the inclination of the scanning line with respect to the horizontal direction of the shadow mask the same. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube used for color image display, and more particularly to improvement of a color cathode ray tube having a color selection mechanism (hereinafter referred to as a shadow mask).

[0002]

2. Description of the Related Art Moire is formed by overlapping two grids and shifting them by a fine angle.

Two types of moire in a color cathode ray tube are known: interference between a video signal and a vertical periodic structure of slit holes in a shadow mask, and interference between a scanning line and a horizontal periodic structure of slit holes in a shadow mask. There is.

Here, a conventional example will be described as a countermeasure against moire due to interference between the scanning line and the lateral periodic structure of the slit holes in the shadow mask.

FIG. 3 is a schematic diagram of a cathode ray tube.
Is a panel, 10 is a funnel, 11 is a neck portion, 12 is a fluorescent screen (screen), 13 is a shadow mask, 14 is a magnetic shield, 15 is a deflection yoke, 16 is a purity adjusting magnet, 17 is a center beam static convergence adjusting magnet, 18 is a side beam static convergence adjustment magnet, 19 is an electron gun, and B
Is the electron beam.

A cathode ray tube (hereinafter referred to as a color cathode ray tube) used for displaying a color image is composed of a panel portion which is an image screen, a neck portion which houses an electron gun, and a funnel portion which connects the panel portion and the neck portion. A deflection device for scanning an electron beam emitted from an electron gun on a phosphor screen coated and formed on the inner surface of the panel is attached to the funnel portion.

The electron beam is deflected in the horizontal and vertical directions by the deflecting device provided in the funnel portion on the way from the electron gun to the fluorescent screen, and is sorted into each color by the shadow mask arranged inside the panel portion. The fluorescent screen emits light by hitting the fluorescent screen, and an image is formed on the fluorescent screen.

FIG. 4 shows a scanning screen. 20 is a scanning line formed by scanning an electron beam, 21 is a horizontal retrace line of the scanning line, and the electron beam is with respect to a horizontal axis (not shown). It is scanned with a certain angle. Further, the horizontal retrace line 21 does not cause the fluorescent screen to emit light.

Conventionally, the moire caused by the interference between the scanning line and the periodic structure of the slit holes in the shadow mask has been dealt with by changing the size of the slit.

FIG. 5 shows the ratio (λ / V) of the moire fringe wavelength (λ) to the vertical diameter (V) of the effective surface and the vertical diameter (P) of the vertical pitch (P) when the number of scanning lines in the effective surface is about 450. V)
It represents the ratio (P / V) to.

P2, P3, P4 and P5 are modes in which moire appears. By reducing λ / V and narrowing the pitch of moire, moire can be made inconspicuous.

Therefore, the moire appearing on the screen is made inconspicuous by taking a value near the intersection of the adjacent moire fringe modes, but it is difficult to obtain sufficient brightness when the pitch is narrow.

It is also conceivable to eliminate the bridge, but in this case, the strength is not sufficient with the shadow mask which is commonly used at present.

FIG. 6 shows an array of slits of a shadow mask in a conventional color cathode ray tube, which has bridges and slit holes in the vertical direction and is arranged at a constant pitch Pv to form a slit row. Further, 8 is the axis of the slit row connecting the bridge center points of the same slit row, and 7 is the horizontal axis of the shadow mask, and this horizontal axis is orthogonal to the slit axis. The lateral array is approximately parallel to the horizontal axis of the shadow mask.

When viewed from the panel side, the electron beam is scanned with a downward slope to the horizontal axis of the shadow mask. Therefore, moire fringes are generated between the horizontal arrangement of the slits of the shadow mask and the scanning line of the electron beam.

[0016]

As described above, the conventional color CRT equipped with a shadow mask having a bridge has bright and dark moire between the scanning line of the electron beam and the horizontal arrangement of the slits of the shadow mask. There was the problem of streaks.

An object of the present invention is to solve the problems that the above-mentioned conventional techniques have.

[0018]

To achieve the above object, the present invention comprises an evacuated envelope comprising a face plate and a neck portion and a funnel portion connecting these portions to each other. A screen of a mosaic color phosphor is formed on the inner surface of the face plate, and a shadow mask having a slit hole and a bridge portion is arranged apart from this screen to generate three electron beams at the neck portion. Then, an electron gun for projecting toward the screen is loaded, and the electron beam is deflected in both horizontal and vertical directions in the vicinity of the junction between the neck portion and the funnel portion to form a scanning raster on the screen. In the color cathode ray tube configured so that the deflection magnetic field region for drawing is set, the slit holes of the shadow mask have the same pitch. To form a slit row, and a second center located at a position closest to the first center point of the bridge portion of the shadow mask and the center point of the first bridge portion of the slit row skipped in one row horizontal direction. The line connecting the center points of the bridges and the scanning line for drawing the scanning raster were made parallel.

Alternatively, the slit holes of the shadow mask form the slit rows with the same pitch along the minor axis, and the slit rows of the slit row which are horizontally skipped with the first center point of the bridge portion of the shadow mask are formed. A line connecting the central points of the second bridge portions located closest to the central point of the first bridge portion and the scanning line for drawing the scanning raster line are parallel to each other.

Alternatively, a line connecting the first center point of the bridge portion of the shadow mask and the center point of the second bridge portion located at a position closest to the center point of the first bridge portion of the slit row which is skipped in a row. And the axes of the slit rows are orthogonal to each other.

[0021]

As described above, the inclination of the scanning line and the first center point of the bridge portion of the shadow mask and the second center portion of the slit row which is horizontally skipped are located at a position closest to the center point of the first bridge portion. By matching the inclination with the line connecting the center points of the bridge portions, it is possible to reduce moire caused by interference between the scanning line and the horizontal arrangement of the slits of the shadow mask.

[0022]

EXAMPLES The color cathode ray tube of the present invention will be specifically described below with reference to examples.

FIG. 1A is a plan view of a shadow mask showing an embodiment of the present invention, in which 1 is a shadow mask edge,
2 is a shadow mask slit forming surface.

FIG. 1 (b) is a partially enlarged view of FIG. 1 (a). 3 is a slit hole, 4 is a bridge between slits in the vertical direction, 41 is the center of the first bridge of an arbitrary slot row. The point, 42 is the center point of the second bridge located closest to 41, which is one slit row horizontally away from 41, and 5 is 4
An imaginary line passing through two points 1 and 42, 6 is a horizontal axis of the shadow mask, and θ is an angle between the imaginary line 5 and the horizontal axis 6 of the shadow mask.

Ordinary shadow mask slit hole pitch P
v is constant, and this embodiment is also applied to such a shadow mask. In the figure, there is a difference in inclination between the virtual line 5 and the horizontal axis of the shadow mask by an angle θ, and
The virtual line 5 and the scanning line of the electron beam have the same inclination.

Since the number of scanning lines on the panel effective surface of the color cathode ray tube differs depending on the region and model, the angle θ also changes accordingly.

The angle θ is generally expressed by fH being the horizontal frequency, fV being the vertical frequency, and the aspect ratio being a: b,

[0028]

[Equation 1]

It is derived by

For example, in the NTSC system with an aspect ratio of 4: 3, the number of scanning lines is 525, the frequency fH in the horizontal direction is about 15,734 Hz, the frequency fV in the vertical direction is about 59.94 Hz, and the scanning lines are about 59.94 Hz. The angle θ with respect to the horizontal
Becomes 0.164 °. Therefore, a line connecting the first center point of the bridge portion of the shadow mask and the center point of the second bridge portion located closest to the center point of the first bridge portion of the slit row that is horizontally skipped in one row Moire can be reduced by setting the inclination of the shadow mask with respect to the horizontal axis 6 to 0.164.

In the PAL system with an aspect ratio of 4: 3, the number of scanning lines is 625 and the frequency fH in the horizontal direction is about 1.
5,625 Hz, vertical frequency fV is about 50 Hz
Therefore, the angle θ of the scanning line with respect to the horizontal direction is 0.138 °. Therefore, a line connecting the first center point of the bridge portion of the shadow mask and the center point of the second bridge portion located closest to the center point of the first bridge portion of the slit row that is horizontally skipped in one row Moire can be reduced by setting the inclination of the shadow mask with respect to the horizontal axis 6 to 0.138 °.

FIG. 2 shows another embodiment, where 8 is the axis of the slit array. The imaginary line of the shadow mask is inclined downward to the right with respect to the horizontal axis when viewed from the panel side, and the slit holes are arranged so that the axis of the slit array is orthogonal to the imaginary line. Moire can also be reduced in this way.

In the embodiment, the aspect ratio is 4: 3, but similarly when the aspect ratio is 16: 9, the inclination of the array of bridges and the inclination of the scanning line with respect to the horizontal direction of the shadow mask should be the same. Thus, it is possible to reduce the moire generated between the bridge of the shadow mask and the scanning line.

[0034]

According to the present invention, the inclination of the array of bridges and the inclination of the scanning line with respect to the horizontal direction of the shadow mask are made equal to reduce the moire generated between the bridge and the scanning line of the shadow mask. You can Further, since it is not necessary to change the pitch of the slit holes, it is possible to reduce moire due to the scanning lines and the slit holes without deteriorating the brightness and the strength of the mask as compared with the conventional one.

[Brief description of drawings]

FIG. 1A is a plan view showing an embodiment of the present invention,
(B) is the elements on larger scale.

FIG. 2A is a plan view showing another embodiment of the present invention,
(B) is the elements on larger scale.

FIG. 3 is a cross-sectional view of a cathode ray tube.

FIG. 4 is a characteristic diagram of scanning lines of an electron beam.

FIG. 5 is a characteristic diagram of a moire pitch and a vertical pitch of a shadow mask.

FIG. 6 is a partially enlarged view of a conventional shadow mask.

[Explanation of symbols]

1 ... Shadow mask edge, 2 ... Shadow mask slit forming surface, 3 ... Slit hole, 4 ... Bridge between slits in vertical direction, 41 ... Center point of first bridge, 42 ... Center point of the second bridge, 5 ...
Virtual line passing through two points 41 and 42, 6 ... Horizontal axis of shadow mask, 8 ... Axis of slit array, 9 ... Panel, 12 ... Fluorescent screen, 13 ... Shadow mask, 1
4 ... Inner shield, 15 ... Deflection yoke, 1
9 ... Electron gun.

Claims (2)

[Claims] 1. A mosaic color phosphor screen is formed on an inner surface of the face plate, which includes an evacuated envelope including a face plate, a neck portion, and a funnel portion connecting the face plate and the neck portion to each other. A color selecting porous electrode having a slit hole and a bridge portion is arranged apart from the screen, and the color selecting porous electrode is provided on the neck portion.
An electron gun for generating an electron beam of a book and projecting it toward the screen is loaded, and the electron beams are deflected in both horizontal and vertical directions near the joint between the neck portion and the funnel portion. In a color cathode ray tube configured so that a deflection magnetic field region for drawing a scanning raster on the screen is set, the slit holes of the color selection porous electrode form a slit row with a constant pitch. Of the second bridge portion located closest to the first center point of the bridge portion of the color selection porous electrode and the center point of the first bridge portion of the slit row that is horizontally skipped in one row. A color cathode ray tube, wherein a line connecting center points and a scanning line scanned by the electron beam are parallel to each other. 2. The second center located at the position closest to the first center point of the bridge portion of the color selection porous electrode and the center point of the first bridge portion of the slit row that is skipped in a row. A color cathode ray tube, wherein a line connecting the center points of the bridge portions of the above and the axis of the slit row are orthogonal to each other.