JPH0794112A - Color cathode ray tube and its shadow mask - Google Patents

Abstract

PURPOSE:To provide a dot-type color cathode ray tube which prevents generation of any moire phenomenon and its shadow mask. CONSTITUTION:A shadow mask sets the vertical array pitches Pda, Pdb, Pdc of a number of electron beam passing-through dot-type holes Ga..., Gb... on an irregular basis and changes the shape and size of the holes in rows so that all shared area of the holes Ga..., Gb... in a given local area may be almost uniform in each of the same local areas all over the formed holes. A color cathode ray tube forms fluorescent dots Ba, Ga, Ra..., Gb... by using the shadow mask.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dot type color cathode ray tube which prevents the occurrence of moire phenomenon and its shadow mask.

[0002]

2. Description of the Related Art A shadow mask type color cathode ray tube has a phosphor screen composed of three phosphor layers of red, green and blue on the inner surface of a face panel, and a large number of electron beam transmitting through holes are arranged at a predetermined pitch in vertical and horizontal directions. The arrayed shadow masks are arranged close to and facing the fluorescent screen, and the electron beam emitted from the electron gun is selected by the shadow mask to display a color image on the fluorescent screen.

Among the above shadow mask type color cathode ray tubes, those requiring a high resolution such as a computer display, in particular, have a large number of blue, green and red fluorescent screens as shown in FIG. 2 (a). The phosphor dots (B), (G), (R), etc., each having a substantially circular shape with a diameter of 0.12 mm are regularly arranged at a predetermined pitch in the vertical and horizontal directions. For example, looking at the green phosphor dots (G) ..., the dots adjacent to each other are regularly arranged so as to form an equilateral triangle (A), and
The dot pitch (0.273 mm) in every other line in the vertical direction is the dot pitch (Pd). Also, blue and red phosphor dots (B)
The same applies to (R) ....

The phosphor dots (B) (G) (R) ...
Is formed by using a shadow mask having a large number of dot-shaped through holes, and although not shown, the phosphor slurry is first applied to the inner surface of the face panel and dried, and then the phosphor slurry is passed through the through holes of the shadow mask. After being exposed and cured, three different types of phosphor dots are exposed by changing the exposure angle to another two types and the red, green, and blue phosphor layers are formed.

Here, as shown in FIG. 2B, for example, when the phosphor dot (G) is irradiated with an electron beam (E) and the phosphor dot (G) emits light, the irradiated beam width is When the phosphor dot (G) is located at the center of (W), the emission brightness (La) shown by the hatched area in the drawing becomes maximum, and FIG.
As shown in (c), when the phosphor dot (G) is positioned at the edge of the irradiation beam width (W), the light emission luminance (Lb) shown by the diagonal lines in the figure is slightly lowered. On the other hand, as mentioned above,
Since the phosphor dots (G) are regularly arranged at a predetermined pitch, when the phosphor dots (B) (G) (R) ... )
The bright and dark portions of the luminance are repeatedly and regularly generated in the phosphor layer in accordance with the dot position with respect to, and regular light and dark fringes are generated. At the same time, when a plurality of scanning bright lines are formed in the horizontal direction of the screen by electron beam scanning, bright and dark fringes are formed with the scanning bright lines as the bright portion and the space between the scanning bright lines as the dark portion. Therefore, FIG.
As shown in (d), in particular, the dot pitch (Pd) and the scanning bright line pitch (Pb) {center-to-center distance of electron beam width (W)} are: mPd≈nPb (where m and n are integers) ...
When the condition (a) is satisfied, the phosphor dots (G) ... And the regular patterns of two bright and dark stripes due to the scanning bright lines overlap and interfere with each other, and a moire phenomenon occurs on the screen to generate visible light and shade.

As a measure for improving the moire phenomenon, the dot pitch (Pd) and the scanning bright line pitch (Pb) are set so as not to satisfy the expression (a), or the electron beam width (W) is thickened or the dots are set. It suffices to reduce the pitch (Pd) so that bright and dark stripes of the phosphor dots (G) ... Do not occur.

[0007]

The problem to be solved is to solve the moire phenomenon by solving the dot pitch (Pd) and the scanning bright line pitch (Pb) so as not to satisfy the expression (a).
Setting is effective when the number of scanning bright lines is constant like in a home receiver, but since there are many kinds of scanning bright line number modes in the display, it is not possible to prevent the moire phenomenon evenly in all modes. Is. Alternatively, as another moiré improving measure, if the electron beam width (W) is made thick or the dot pitch (Pd) is made small to prevent the occurrence of bright and dark stripes of the phosphor dots (G) ..., In the former case, the resolution is lowered. ,
In the latter case, there is a problem in that the cost is increased.

[0008]

According to the present invention, in a shadow mask, a large number of dot-shaped through holes for electron beam transmission, which are arranged in the vertical and horizontal directions, have an irregular arrangement pitch in the vertical direction, and the shadow mask has a predetermined pitch. It is characterized in that the shape and size of the through holes are changed for each row so that the total occupied area of a plurality of through holes in the local is substantially uniform over the entire surface of the through hole forming surface for each same local area.

A color cathode ray tube is characterized in that phosphor dots are formed by using the shadow mask.

[0010]

According to the above technical means, the phosphor dots of the dot type color cathode ray tube are formed by arranging them in the longitudinal direction irregularly by the dot type shadow mask in which a large number of through holes are irregularly arranged in the longitudinal direction. By making the light and dark stripe pattern of the phosphor dots irregular, interference with the light and dark stripe pattern of the scanning bright lines is prevented, and the moire phenomenon does not occur on the screen. In addition, the shape and size of the through holes are changed for each row so that the total occupied area of the plurality of through holes in a predetermined local area is substantially uniform over the entire surface where the through holes are formed. In a dot row with a small pitch interval where the density is large, the dot shape is small, and in a dot row with a large pitch interval where the phosphor dot density is small, when the dot shape is large, the brightness and color purity are substantially uniform over the entire screen. become.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the color cathode ray tube and its shadow mask according to the present invention will be described below with reference to FIG. First, FIG. 1A shows a phosphor dot (Ba) (Ga) (Ra) ... (Gb) showing an embodiment of a color cathode ray tube according to the present invention.
In the partial plan view of ..., the solid line part is green and the chain line parts are blue and red. At the same time, the solid line in the figure {phosphor dot (Ga)
(Portion (Gb) ...) is substantially the same as the through hole shape and size of the shadow mask according to the present invention. For example, when the green phosphor dots (Ga) ... The phosphor dots (Ba) (Ra) ... Are formed by exposing from the same through hole at different angles with respect to the exposure angle of the phosphor dots (Ga) as in the conventional case.

The above phosphor dots (Ba) (Ga) (R
a) ... (Gb) ... are arranged in the vertical and horizontal directions, and the pitch interval between the vertical dot rows on the phosphor screen (corresponding to the vertical pitch interval of the shadow mask through holes) is irregularly widened for each pitch. Alternatively, it is set to be narrow, and the vertical pitch interval (Pda) (Pdb) (P
dc) are different from each other.

At this time, if each dot shape is the same, in a row with a small pitch interval (Pdb), the dot density is increased and the brightness is locally increased, and the same electron beam (E) is emitted vertically. Phosphor dots (B
a) (Ga) (Ra) ... (Gb) ... overlap at the same time to reduce the color purity, and conversely, in a row with a large pitch interval (Pda), the dot density becomes small and the brightness locally decreases. . Therefore, the through hole shape and size are set so that the total occupied area of the plurality of through holes (Ga) ... Change every row.

For example, the diameter (Do) of a perfect circle (C) having the same shape as the conventional phosphor dot (G) shown by the dotted line is used as a reference value, and the pitch interval (Pda) with respect to the reference value (Do).
The size of the through hole (Ga) is set to be enlarged or reduced in the vertical direction with respect to the perfect circle (C) at the same ratio as (Pdb) (Pdc). That is, for example, in a row with a small pitch interval (Pdb) that is 0.8 times the reference value (Do), the dot shape is made smaller than that of the reference perfect circle (C), for example, phosphor dots (Gb) ... As shown in FIG.
The size is reduced to a horizontal elliptical shape having a size 0.8 times that of o).
Further, for example, in a row with a large pitch interval (Pda) that is 1.2 times the reference value (Do), the dot shape is made larger than that of the reference perfect circle (C), for example, phosphor dots (Ga) ... The dot vertical diameter (Da) is used as a reference value (D
It is enlarged and set to a vertical elliptical shape 1.2 times larger than o).

According to the above structure, phosphor dots (Ba)
Since (Ga) (Ra) ... (Gb) ... are arranged irregularly in the vertical direction, the equation (a) is not satisfied and the moire phenomenon does not occur. Also, the pitch interval (Pda) (Pd) between the dot rows
db) (Pdc), that is, the dot shape and size are adjusted to small and large in accordance with the size of the dot density, and the brightness is maintained substantially uniform over the entire screen. In particular, the same electron beam in a high-density dot row does not simultaneously overlap phosphor dots (Ba) (Ga) (Ra) ... (Gb) ... Which are vertically adjacent to each other, and the color purity is improved.

As for the dot shape, in addition to the above-mentioned longitudinal expansion or reduction, as in the enlargement example shown in FIGS. 1 (b) and 1 (c),
The entire circumference may be made uniform or the lateral diameter may be enlarged to form a perfect circle and a lateral ellipse, respectively.

[0017]

According to the present invention, in the dot type color cathode ray tube, the through holes of the shadow mask and the phosphor dots formed thereby are irregularly arranged in the vertical direction, and the dot density is adjusted according to the size. The size of the through holes and dots are set to be small and large, and the through hole shape is set so that the total occupied area of a plurality of through holes within a given local area is approximately uniform for each same local area over the entire surface where the through holes are formed. Since it is changed for each row, it is possible to prevent the occurrence of the moire phenomenon and the deterioration of the screen brightness and color purity.

[Brief description of drawings]

FIG. 1A is a plan view of through-holes and phosphor dot shapes showing an embodiment of a color cathode ray tube and a shadow mask thereof according to the present invention. (B) and (c) are plan views of through holes and phosphor dot shapes showing another embodiment of the color cathode ray tube and its shadow mask according to the present invention, respectively.

FIG. 2A is a plan view of through-holes and phosphor dot shapes showing an example of a conventional color cathode ray tube and its shadow mask. (B) is a plan view and a graph respectively showing phosphor dots irradiated with an electron beam and the emission brightness thereof. (C) is a schematic diagram showing a phosphor dot pitch and a scanning bright line pitch.

[Explanation of symbols]

 Ba, Ga, Ra Phosphor dot Ga Through hole Pda, Pdb, Pdc Pitch interval Da, Db Longitudinal diameter Do Reference value

Claims (4)

[Claims] 1. A color cathode line, comprising: a shadow mask having a large number of dot-shaped through holes for transmitting electron beams arranged in vertical and horizontal directions, wherein the pitch of the through holes in the vertical direction is irregularly set. Tube shadow mask. 2. The through-hole shape and size are changed for each row so that the total occupied area of a plurality of through-holes within a predetermined local area is substantially uniform over the entire surface of the through-hole forming surface for each same local area. The shadow mask according to claim 1, wherein: 3. The shape or size of the through hole is set to be enlarged or reduced in a vertical or horizontal direction with respect to a true circle having a diameter of the reference value at the same ratio as a pitch interval in the vertical direction with respect to the reference value. 2. A shadow mask for a color cathode ray tube as described in 2. 4. A color cathode ray tube comprising the shadow mask according to claim 1, 2 or 3, wherein phosphor dots are formed using the shadow mask.