JP2901665B2 - Color cathode ray tube - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a shadow mask type color cathode ray tube, and more particularly to a color cathode ray tube in which a through hole arrangement of a shadow mask is less likely to cause moire. .

(Prior art) Generally, shadow mask type color cathode ray tubes are blue,
A shadow mask formed with a large number of through holes through which an electron beam passes is disposed in close proximity to and opposed to a phosphor screen formed of a three-color phosphor layer that emits green and red, and a three-electron beam emitted from an electron gun is provided. Are formed by using this shadow mask to display a color image on the phosphor screen.

In recent years, among such color cathode ray tubes, in particular, the through holes of the shadow mask have a substantially rectangular shape, and a plurality of the through holes are arranged linearly in a vertical direction via a bridge. A shadow mask arranged in a plurality of rows in the horizontal direction is used, and the fluorescent screen is formed in a stripe shape in the vertical direction corresponding to the through hole arrangement of the shadow mask.
Those composed of a color phosphor layer are generally used. In such a color cathode ray tube, an in-line type electron gun which emits three electron beams arranged in a line in the same horizontal plane as an electron gun is used. In particular, shadow masks in which the positions of bridges (or holes) are regularly shifted by 1/2 pitch between adjacent holes in order to ensure the mechanical strength required for color cathode-ray tubes are generally used. It is used regularly.

However, as mentioned above, the position of the bridge is
When a shadow mask shifted in pitch is used, there is a problem that moire is likely to occur on a screen.

It is generally known that when two patterns having light and dark stripes are superimposed, the two patterns interfere with each other to cause a moire phenomenon. In the case of a shadow mask type color cathode ray tube, one of the bright and dark fringes causing the moiré phenomenon is a plurality of scanning bright lines formed in the horizontal direction of the screen by scanning with an electron beam. The other is a light-dark fringe formed by a through hole and a bridge of a shadow mask. That is,
As described above, even if the bridges are regularly shifted by 1/2 pitch between adjacent through-hole arrays, the following bright and dark stripes are formed by the through-holes and the bridge.

That is, since the through holes of the shadow mask are generally formed by a photo etching process, FIG.
As shown in (1), the through hole actually formed even if the target is an accurate rectangle, is a substantially rectangular through hole (2) having semicircular portions (1) at both ends. As a result, the adjacent row of holes (3
In a shadow mask in which the bridge (4) is shifted by a half pitch between (a) and (3b), the following nine areas can be considered in terms of brightness.

(1) Combination area of rectangular part of through hole and bridge (10
1) (2) Combination area of rectangular part of through hole and semicircular part of through hole (102) (3) Combination area of rectangular part of through hole and rectangular part of through hole (103) (4) Combination area of semicircular part of through hole and rectangular part of through hole (104) (5) Combination area of bridge and rectangular part of through hole (10)
5) (6) Combined area of semicircular part of through hole and rectangular part of through hole (106) (7) Combined area of rectangular part of through hole and rectangular part of through hole (107) (8) Combined region of rectangular portion of through hole and semicircular portion of through hole (108) (9) Combined region of rectangular portion of through hole and bridge (10)
9) Therefore, the amount of transmission of the electron beam in each area is
As shown by the broken line (5) in FIG. 7B, the bright and dark fringes having the brightest part in the electron beam maximum transmission part (6) and the dark part in the minimum electron beam transmission part (7) are the same as the bright and dark stripes formed by the scanning bright line. Can be in any direction. Then, the light and dark fringes of the shadow mask and the light and dark fringes formed by the scanning bright lines interfere with each other to cause a moire phenomenon.

Obviously, in order to prevent the moire phenomenon of the color CRT, one of the two bright and dark fringes should be eliminated. However, if the vertical size of the screen and the broadcasting system are determined, the pitch of the bright and dark fringes formed by the scanning bright line is uniquely determined, and the bright and dark fringes cannot be eliminated. Therefore, as a means for preventing moiré of a color cathode ray tube, it is necessary to appropriately set the through-hole arrangement pitch and bridge width in the vertical direction of the shadow mask so that moiré does not become noticeable. However, in such a means for preventing moiré of a shadow mask, if the bridge width is reduced, the mechanical strength of the shadow mask becomes weaker, causing problems such as deformation and difficulty in shaping the shadow mask. Therefore, the pitch of the through holes in the vertical direction is a major factor in preventing moiré.

However, even if the shadow mask is designed as described above,
It is effective only for one broadcasting system, and a shadow mask designed optimally for another broadcasting system with a different number of scanning lines, for example, NTSC system, is not optimal for a PAL system with a different number of scanning lines, Moiré occurs. Therefore, in order to be able to be shared by both broadcasting systems, a compromise design must be made so that the moire does not become insignificant for either broadcasting system, and in some cases, unacceptable moiré may occur. , May not be shared. In addition, even in the case of the single broadcast system, there is a problem that even if an attempt is made to increase the pitch of the through holes in the vertical direction in order to improve the brightness, the pitch of the through holes cannot be freely increased due to the moire phenomenon.

There are various types of shadow masks conventionally improved to prevent the moiré phenomenon.

As one example, JP-A-51-40072 discloses that the position of the bridge (4) is irregularly changed by changing the length of the through-holes (2) in the through-hole row direction as shown in FIG. The shadow mask is shown shifted to the right.

The shadow mask in which the position of the bridge (4) is irregularly shifted in this manner is such that the interference with the bright and dark fringes formed by the scanning luminescent lines is diffused over the entire screen, the moiré becomes close to white noise, and the moiré phenomenon can be ignored. Becomes However, since the length of the through-holes (2) in the direction of the through-hole row is not constant in this shadow mask, particularly when a long light source is used and a stripe-shaped phosphor layer is formed through the shadow mask,
Cuts or narrow constrictions are formed in the phosphor layer, which tends to cause uneven brightness on the screen.

JP-A-51-11559 discloses a shadow having a parallelogram-shaped through hole (2) separated by a line (8) at 45 ° to the horizontal or vertical axis as shown in FIG. Combined with the same shape phosphor layer separated by lines in the same direction as the mask,
Shown is a color cathode ray tube with less noticeable moiré.

However, since the through holes (2) of the shadow mask are formed by the photo etching process as described above,
It is difficult for the shadow mask to form an angle of 45 ° at the bridge (4) portion, and the phosphor layer also has a partition, so that the brightness is lower than that of a color cathode-ray tube having a continuous stripe-shaped phosphor layer. Leads to a drop.

Further, as to the arrangement of the holes in the shadow mask, as shown in FIG. 7, the deviation amount of the bridge (4) between the adjacent holes (3a) and (3b) is Δy, and the adjacent holes (3a) It is conceivable that the arrangement pitch of the through holes (2) in (3b) is shifted by Δy = Pv / n, where Pv and n are integers. However, such a shadow mask does not eliminate light and dark stripes, but forms light and dark stripes in an oblique direction shown by a line (9), and the light and dark stripes in the oblique direction overlap with the light and dark stripes in the horizontal direction of the screen, and are extremely noticeable. Moiré with a strange feeling occurs.

As a supplement to such a problem of the shadow mask, Japanese Patent Application Laid-Open No. 52-125286 discloses, as shown in FIG. 8, the transparency of four adjacent through-hole arrays (3a) to (3d). Offset Δ of bridge (4) between hole arrays (3a) to (3d)
The arrangement of the through-hole arrays (3a) to (3d) is shown in which y is sequentially set as Δy ₁ = 1/2 · Pv Δy ₂ = 1/3 · Pv Δy ₃ = 1/3 · Pv.

This through-hole arrangement can prevent the formation of a dark portion in an oblique direction, and can make the moiré a level that cannot be visually recognized. However, such a through-hole arrangement still requires James P Wi
tte: Moir Considerations in Shadow-Mask Picture T
Another moiré occurs as described in ube.SID 87 DIGEST 18.5 P347-350 (1987).

In other words, no matter what cycle the bridge (4) is shifted to change Δy, as long as there is periodicity, local bright and dark parts are generated, and they appear with periodicity. When it overlaps with the light and dark fringes based on the scanning bright line, it is unavoidable to appear as point-like moiré.

There is a method in which Δy is determined by a uniform random number for the regularized through hole arrangement as described above, and the regularity is eliminated from the through hole arrangement.

However, even if the through-hole arrangement is set by a uniform random number, the following problem occurs. That is, as described above, moiré is 2
When m and n are positive integers, the scanning line interval is s, and the moire pitch of the mode (m, n) is Pm, n, 1 / Pm, n = | n / Moiré indicated by Pv-m / s | occurs.

As described above, a shadow mask of Δy = 1/2 is generally used, but this is performed so that the moiré of the mode (1, 1) is canceled out of phase so that the moire is not conspicuous. In the case of uniform random numbers, the value of Δy = 1/2 is relatively small, so that the moire of the mode (1, 1) having the strongest moire contrast is conspicuous, as shown in FIG. Then, the moiré can be seen running diagonally.

(Problems to be Solved by the Invention) As described above, a color cathode ray tube has a plurality of bright and dark fringes on a screen, in which a horizontal bright line obtained by horizontal scanning of an electron beam is a bright portion and a dark portion is between adjacent bright lines. Moire may occur on the screen due to interference between the light and dark fringes and the light and dark fringes generated from the arrangement of the holes in the shadow mask. In order to prevent this moiré, conventionally, means for eliminating bright and dark fringes generated from the arrangement of through holes in the shadow mask has been adopted. The light and dark fringes generated from the arrangement of the holes in the shadow mask are originally generated because the arrangement of the holes has some regularity. However, it does not have a through-hole arrangement that maintains the required screen quality and does not cause moiré. Actually, the arrangement pitch is such that moiré is unlikely to occur for each broadcasting system having a different number of scanning lines. In addition, the conventional shadow mask has a problem that it cannot be set freely even if the arrangement pitch is increased in order to improve the brightness. Further, there is a method of arranging the through holes by using a uniform random number in order to prevent moiré caused by such regular arrangement of the through holes. However, even if the through hole arrangement is set by uniform random numbers, moire in a partial oblique direction due to the mode (1, 1) is conspicuous, and moire cannot be sufficiently eliminated.

The present invention has been made in view of the above problems, and can make moiré inconspicuous enough, and the arrangement pitch of the through holes in the through hole row is arbitrarily large to reduce the length of the through holes. It is an object of the present invention to provide a color cathode-ray tube having a shadow mask that can improve characteristics by being set arbitrarily.

[Structure of the Invention] (Means for Solving the Problems) A substantially rectangular through-hole has a plurality of through-holes arranged in a first direction via a bridge, and the through-holes are aligned with the first direction. In a color cathode ray tube provided with a plurality of shadow masks arranged in a plurality of rows in the second direction orthogonal to each other, Δy is a positional deviation of the holes between the adjacent rows of holes, and Py is an arrangement pitch of the holes in the rows of the holes. Was set by random numbers according to a probability distribution with an average value of 0.5 Pv and a standard deviation of 0.3 Pv.

(Operation) As described above, the light and dark stripes of the shadow mask are generated because the arrangement of the through holes has some regularity. Therefore,
In order to eliminate the light and dark fringes, it is necessary to make the arrangement of the through holes irregular, but if the bridge width and the through hole length are irregular, it is difficult to form a striped phosphor layer without breaks or constrictions. Becomes Further, when the through holes are arranged by setting the shift amount Δy of the bridge between the adjacent through hole rows by a uniform random number, the transmission area of the electron beam included in a certain area over the entire shadow mask can be made constant. Brightness unevenness on the screen can be prevented.

However, in a through-hole array using uniform random numbers, 1 / 2Pv that cancels out the moiré mode (1,1) in opposite phase is required.
Other modes (2,1), (2,2), (3,1) ... (4,1) ...
For example, 1 / 3Pv, 1 / 4Pv ... are also required. But,
These higher-order modes have overlapping parts, and the higher the order, the smaller the difference in brightness even if they appear.
It is only necessary to cover up to about v. Therefore, if the central value of Δy by random numbers is 1 / 2Pv and the standard deviation is 0.3Pv, the appearance probability from 0.3Pv to 0.7Pv as the value of Δy is 60%.
%, It can cover 0.2Pv which is not so much needed, and even if it is a random number, it incorporates a lot of 1 / 2Pv which cancels the mode (1,1) in opposite phases, and from 1 / 5Pv to 4 / 5Pv
Can be set to cover up to.

Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

FIG. 3 shows the structure of a color cathode ray tube as one embodiment. This color cathode ray tube has an envelope consisting of a substantially rectangular panel (20) and a funnel-shaped funnel (21) integrally joined to the panel (20), and a fluorescent screen is provided on the inner surface of the panel (20). (22) is formed. The phosphor screen (22) is a striped three-color phosphor layer that emits blue, green, and red light extending in a direction parallel to the vertical axis of the panel (20). Then, a shadow mask (23) having the following through hole as an electron beam passing hole is mounted inside and facing the fluorescent screen (22). The tube axis (Z) is placed in the neck (24) of the funnel (21).
Center beam (25G) passing on the same horizontal plane
And a pair of side beams (25B) and (25R)
An electron gun (26) that emits an electron beam is provided,
The three electron beams (25
G), (25B), and (25R) scan a phosphor screen (22) via a shadow mask (23) to display a color image.

By the way, as shown in FIG. 1, the shadow mask (23) has a substantially rectangular through hole (27) having a certain size through a bridge (28) having a certain width b at a predetermined pitch PV and a vertical axis ( A plurality of linear through-hole rows (29) are arranged in the horizontal axis (X-axis) direction at a predetermined pitch PH in the horizontal axis (X-axis) direction. Usually, the arrangement pitch Pv in the vertical axis (Y axis) direction is about 0.3 to 1.5 mm, the width b of the bridge (28) is about 0.1 to 1.3 mm, and the arrangement pitch PH in the horizontal axis direction is a 21-inch class. It is about 0.6mm.

Moreover, as shown in FIG. 2, the shadow mask (23) shown in FIG. 2 has a through hole (27) as an accurate rectangle, and each of the through holes (29a) and (29b) between any two adjacent through hole rows (29a) and (29b). The hole (27) is misaligned, and the misalignment Δy is 0.5P
V, set by random numbers according to a probability distribution with a standard deviation of 0.3 PV. The probability distribution includes a normal distribution,
A distribution rule such as Poisson distribution or binomial distribution is applied, and Δy
Is between 0 and 1 Pv depending on the applied distribution rule.

By the way, if Δy is set by a uniform random number as described above, the through-hole arrangement is irregular and is an arrangement based on random numbers. Is constant, and uneven brightness on the screen can be prevented. Also, for moiré, by setting a random value according to a probability distribution with the central value of Δy being 0.5 PV and the standard deviation being 0.3 PV,
Introduces a lot of 1 / 2PV of the mode (1,1) that cancels out in opposite phases, and also incorporates higher-order modes with small contrast.
The appearance probability from 0.3PV to 0.7PV can be set to 60%, and the moiré phenomenon can be completely ignored. Also, since Δy is set by a uniform random number, there is no regularity in the oblique direction. Accordingly, no moire in the oblique direction occurs, and no complicated moire in the Δy value is generated. Furthermore, since the arrangement pitch Pv of the through holes (27) and the width b of the bridge (28) are the same, even if the phosphor layer is formed by exposure with a long light source, the phosphor layer is formed in a stripe shape without cuts and constrictions. can do.

In the above embodiment, the value of Δy is continuously changed from 0 to 1Pv, but the value of Δy is 1 / 2Pv,
It may be taken as a fraction like 1 / 3Pv, 2 / 3Pv, 1 / 4Pv to 3 / 4Pv, 1 / 5Pv to 4 / 5Pv. However, in higher-order modes other than the moiré mode (1, 1), there is an overlapping portion, and even if the higher-order modes appear, the difference in brightness becomes smaller, so that it is sufficient to cover up to about 1/5 Pv.

[Effects of the Invention] A substantially square through-hole has a plurality of through-holes arranged in a first direction via a bridge, and the plurality of through-holes are arranged in a second direction orthogonal to the first direction. For the arranged shadow masks, the positional deviation of the through-holes between adjacent through-hole rows is Δ
y, Δp, where Pv is the arrangement pitch of the through holes in the through hole row
When random numbers are set according to a probability distribution with an average value of 0.5 Pv and a standard deviation of 0.3 Pv, the arrangement of the holes becomes irregular, and the light and dark stripes of the shadow mask can be almost completely eliminated, and the light and dark on the screen Moire phenomenon due to interference with fringes can be prevented. When the shadow mask is configured as described above, the arrangement pitch Pv of the through holes and the width b of the bridge
Is constant, the through-hole area occupied in the constant area is constant, and uneven brightness on the screen can be eliminated. Further, a stripe-shaped phosphor layer having no cut or constriction can be easily formed using a long light source.

[Brief description of the drawings]

1 to 3 are explanatory views of an embodiment of the present invention. FIG. 1 is a view showing a through-hole arrangement of a shadow mask of a color CRT according to one embodiment, and FIG. FIG. 3 is a view showing a configuration of a color cathode ray tube according to an embodiment of the present invention; FIG. 3 (a) and FIG. 4 (b) are light and dark stripes of a shadow mask, respectively; FIGS. 5 to 9 are views showing the arrangement of through-holes in a conventional shadow mask which prevents the occurrence of light and dark fringes. 23: shadow mask, 27: through-hole 28: bridge, 29: through-hole row

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-50-744 (JP, A) JP-A-2-291645 (JP, A) JP-A-2-186536 (JP, A) JP-A-51- 107063 (JP, A) JP-A-2-103847 (JP, A) JP-A-51-40072 (JP, A) JP-B 8-24034 (JP, B2) JP-B-55-4924 (JP, Y2) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01J 29/00-29/07 H01J 9/14

Claims (1)

(57) [Claims] 1. A substantially square through-hole is formed through a bridge to a first hole.
A color cathode-ray tube having a plurality of through-hole arrays arranged in a plurality of directions, the plurality of through-hole arrays being arranged in a second direction orthogonal to the first direction, and a shadow mask arranged in a plurality of rows. The positional deviation of the through holes is Δy, and the arrangement pitch of the through holes in the through hole row is constant Pv.
A color cathode ray tube, wherein y is set by random numbers according to a probability distribution having an average value of 0.5 Pv and a standard deviation of 0.3 Pv.