JPH04284335A - Color picture tube - Google Patents

Abstract

PURPOSE:To reduce moire pattern appearing on a color picture tube. CONSTITUTION:Each of the electron beam transmission holes 11 of a shadow mask 10 is a substantially rectangular shape and separated from each other by a first bridge 12 with its width of 0.120-0.150mm and a second bridge with its width of 0.050-0.090mm narrower than that of the first bridge. In the area defined by the bridge 12, there are three electron beam transmission holes 11 to form an electron beam transmission hole group 14. The electron beam transmission hole groups 14 are so arranged as forming a transmission hole row 15. In which large number of holes are aligned at vertical direction intervals of about 1.15mm or a pitch PGV with their longitudinal directions parallel to the vertical axis, while these transmission hole rows 15 are arranged in a large number is horizontal direction at a horizontal pitch PH of about 0.8-0.9mm. The electron beam transmission hole groups 14 are staggered by 1/2PGV between adjacent transmission hole rows.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Field of Application] The present invention relates to a color picture tube.
In particular, it relates to the electron beam transmission hole pattern of the shadow mask.

0002

2. Description of the Related Art In general, a shadow mask type color picture tube is composed of an envelope consisting of a substantially rectangular panel 1 and a funnel 2, as shown in FIG.
On the inner surface of the phosphor screen 3, there is a phosphor screen 3 consisting of a group of striped phosphors that emit red, green, and blue light without any break in the vertical direction (Y direction), and a large number of slit-shaped electron beam transmission holes close to and facing the phosphor screen 3. A shadow mask 4 formed thereon is disposed, and three electron beams BR, BG, arranged in a line in alignment with the horizontal axis (X-axis) are placed inside the neck 5 of the funnel 2.
An in-line electron gun 6 that emits BB is installed inside.

Further, as shown in FIG. 10, the electron beam transmission hole 7 of the shadow mask 4 has a substantially rectangular shape.
A large number of through holes are arranged in a direction parallel to the vertical axis (Y-axis) via bridges 8, and this row of permeable holes is arranged in the horizontal direction (Y-axis).
They are arranged in multiple rows in the X direction). Then, the phosphor screen is formed using an exposure method using a long light source through the electron beam transmission hole 7 of the shadow mask 4, so that the shadow of the bridge 8 of the shadow mask 4 is not formed on the inner surface of the panel. In addition, the positions of the electron beam transmission holes 7 are regularly shifted by 1/2 pitch (PV/2) between adjacent transmission hole rows to ensure the necessary strength as the shadow mask 4. Common.

By the way, in the above-mentioned shadow mask type color picture tube, the electron beam is scanned in the horizontal direction to form a scanning line, but the image has a bright and dark striped pattern due to the beat caused by the shadow of the electron beam due to the scanning line and the shadow mask. arise,
Image quality may be significantly impaired. Generally, this is called Moire fringes, and the vertical spacing PV of the electron beam transmission holes of the shadow mask and the width b of the bridge are designed so that the Moire fringes do not become noticeable.

In general, if the vertical pitch of the electron beam transmission holes in the transmission hole row is PV, and the scanning line interval on the shadow mask is S, then the electron beam transmittance of the transmission hole row A(y
) and the brightness waveform B(y) of the scanning line are expressed by the following equations.

[0006]

[Math 1]

[0007]

##EQU00002## From this, the brightness I(y) of the scanning line transmitted through the transmission hole array is expressed by the following equation.

[0008]

[Math 3]

The last term in equation (3) represents moiré. This depends on the values of n and m, (n, m)
One is determined when is determined. Therefore, there is (n, m)
The moire fringes corresponding to the set of are referred to as mode (n, m) moire. Equation (3) is an orthogonal function, and mode (n, m)
The moiré term can be treated as a single term, so

0010

It can be treated as [Equation 4]. Un,m (y) is the mode (n,
m) is a function in the y direction representing moiré. The moiré pitch Pn,m is

[0011]

[Math 5] Also, the modulation degree Mn,m of brightness and darkness is

0012

It is expressed as [Equation 6]. Usually, the electron beam transmission holes are shifted by 1/2 pitch between adjacent transmission hole rows, and this is due to the following reason. In equation (2), if the shadow mask pitch PV deviates by Δy,

[0013]

[Equation 7] The moiré term of the brightness I'(y) of the scanning line transmitted through such an electron beam transmission aperture is

[0014]

[Math. 8] Therefore,

[0015]

[Formula 9] In equation (4)', in order to have the opposite phase of equation (4),
Since 2πΔyn/PV caused by the pitch deviation Δy only needs to be π, 3π, 5π..., Δy=PV/
2, n=1, 3, 5, . . . and if adjacent transmission hole rows are shifted by 1/2 pitch, they will cancel each other out when n is an odd number mode.

Therefore, as mentioned above, if adjacent transmission hole rows are shifted by 1/2 pitch, the mode that occurs as moiré fringes is the mode where n is an even number, and is generally (2, 1
) , (2,2) , and (2,3) are said to be well recognized as moire fringes. Therefore,
Designs have been made to adjust the vertical pitch PV so that the intensity of the moiré fringes in each mode does not increase.

However, when attempting to share different broadcasting systems (for example, sharing PAL and NTSC systems), since the number of scanning lines is different between the two systems, it is necessary to set the moire fringes to a level that does not become noticeable in both systems. This results in a compromise design, and if either is at an unacceptable level, sharing becomes impossible.

Furthermore, when a still image is displayed on a general consumer VTR, the number of scanning lines is halved compared to general broadcasting. In this case as well, a compromise design is made, but general broadcasting may take priority and still images may end up being secondary. By the way, various improvements have been made regarding such moire fringes.

The most commonly seen method is to change the positional deviation Δy of the vertical arrangement of adjacent electron beam transmission holes, for example, as described in Japanese Patent Publication No. 57-50338 and Japanese Patent Application Laid-Open No. 52-125268. There is something like that. However, when Δy is shifted regularly, diagonal moire fringes occur, and even when several types of Δy are used, partial moire fringes occur. On the other hand, in recent years, as color picture tubes have become larger and the performance of electron guns has improved, the brightness and darkness of horizontal scanning lines have become more distinct, and moiré fringes have become more noticeable.

Now, basically, these moiré fringes will not occur if the vertical length of the electron beam transmission hole is smaller than the vertical diameter of the electron beam passing through it. It does not occur even if the vertical length is very large. That is, unless a shadow of the electron beam is created by the shadow mask, moiré fringes will not occur. However, there are the following problems.

[0021] The shadow mask covers the entire screen with red, green,
The curved surface is formed so that the electron beam hits the blue phosphor stripe well. Usually, press processing is used for this processing. This press process is applied to the shadow mask.
Plastic working is performed by applying a force of 5 to 25 kgf/mm2. However, if the width of the bridge is narrow, the bridge will stretch during this pressing and not only will a good curved surface not be obtained, but the bridge may break. Furthermore, if the vertical length of the electron beam transmission hole is made smaller, the bridge width cannot be made thinner than a certain point, as mentioned above, and the shadow mask transmittance of the electron beam deteriorates.
Screen brightness cannot be obtained. On the other hand, if the vertical length of the electron beam transmission hole is very large, the lateral connection of the entire shadow mask becomes rough, and the above-mentioned pressing cannot be performed.

[0022] Therefore, curved surface forming is not done by plastic working.
This results in a stretching method that pulls the periphery of the shadow mask outward in a planar manner. In the case of the stretching method,
The curved surface of the shadow mask is limited to a flat or cylindrical shape, the valve cost is high to maintain vacuum strength, and the stretching method itself is complicated and expensive for the shadow mask structure, so overall, the tube cost is very high. It ends up being expensive.

Therefore, Japanese Patent Application Laid-Open No. 55-124930 discloses a method of reducing the occurrence of moire fringes by making the width of the bridge different at predetermined positions while maintaining the mechanical strength of the shadow mask. It describes what to do.

However, Japanese Patent Application Laid-Open No. 55-124930
Even in the case described in the above publication, the positions at which the bridge widths are made to differ are determined to some extent by the broadcasting system. Therefore, we are trying to share the different broadcasting methods mentioned above (for example, PA
When attempting to share the L system and the NTSC system, the number of scanning lines is different between the two systems, so it is necessary to set the settings to a level that does not cause significant moiré fringes in both systems, resulting in a compromise design where either one is unacceptable. If the level
Sharing becomes impossible.

Therefore, as mentioned above, if adjacent transmission hole rows are shifted by 1/2 pitch, the mode that occurs as moiré fringes is the mode where n is an even number, and is generally (2, 1
) , (2,2) , and (2,3) are said to be well recognized as moire fringes. Therefore,
Designs have been made to adjust the vertical pitch PV so that the brightness and darkness of the moiré fringes in each mode do not increase.

However, as mentioned above, as color picture tubes have become larger and electron guns have become more sophisticated, the brightness and darkness of moiré fringes have increased, which has not been seen in the past (4, 1). Higher-order modes such as (4,2) and (4,3) are also becoming a problem.

[0027]

[Problems to be Solved by the Invention] Ultimately, as mentioned above, it is difficult to maintain the current screen quality and obtain an electron beam transmission aperture pattern for a shadow mask that is not affected by moiré fringes. With the increase in size and the improvement of focus quality, the current situation has become even more difficult, and the current structure basically relies on a compromise design. In view of the above problems, the present invention provides a color picture tube that basically eliminates moiré fringes. [Structure of the invention]

[0028]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a transmission hole row in which a plurality of electron beam transmission holes are arranged in a first direction, and the transmission hole row is arranged in a first direction. In a color picture tube equipped with a plurality of shadow masks arranged in a plurality of rows in a second direction perpendicular to the first direction, the transmission hole row includes an electron beam transmission hole group consisting of at least two electron beam transmission holes. The electron beam transmission holes are separated by bridges 1 and arranged at a predetermined pitch in the first direction, and the electron beam transmission hole groups are shifted by 1/2 pitch between adjacent transmission hole rows, and the electron beam transmission within the transmission hole groups is The second delimiting the hole
The width and height of the bridge are smaller than those of the first bridge.

[0029]

[Function] By configuring the shadow mask as described above, it has the strength to withstand mask forming by pressing, and the vertical length of the electron beam transmission hole can be set by separating the screen brightness, allowing electrons to be freely controlled. It becomes possible to vary the diameter according to the vertical diameter of the beam, and it becomes possible to set the moiré phenomenon to a level where it is virtually unnoticeable.

On the other hand, according to the present invention, in addition to the transmission hole group corresponding to the conventional design, there is a transmission hole pattern within the transmission hole group. The vertical pitch of the small holes in the group of holes and the shape of the holes in the group of holes can be designed to improve moiré, which increases the degree of design freedom and allows for high-order A color picture tube with improved mode moiré can be achieved.

[0031]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Other than the electron beam transmission hole pattern of the shadow mask, it is similar to a conventional color picture tube, and consists of an envelope consisting of a substantially rectangular panel and a funnel. A phosphor screen consisting of a group of striped phosphors that emit light in the vertical direction (Y direction) with no breaks, and a shadow mask in which a large number of slit-shaped electron beam transmission holes are formed are arranged close to and opposite to this phosphor screen. A horizontal axis (X
An in-line electron gun is installed that emits three electron beams arranged in a line in line with the main axis.

As shown in FIG. 1, the electron beam transmission hole 11 of the shadow mask 10 has a substantially rectangular shape, and has a first bridge 12 and a second bridge 13 having a smaller width than the first bridge 12. are separated from each other by This shadow mask 10 has a plate thickness of 0.10 to 0.30 mm.
It is made of low carbon steel or low expansion material such as invar. The first bridge has a width w1 of 0.1
20 to 0.150 mm, and there are three electron beam transmission holes 11 within the space separated by this first bridge 12, forming an electron beam transmission hole group 14. The individual electron beam transmission holes 11 in the electron beam transmission hole group 14 have a width of about 0.050 to 0.090 mm w.
It is delimited by a second bridge 13 with 2.

A large number of electron beam transmission holes 14 are arranged at vertical intervals, that is, pitches PGV, with their longitudinal directions parallel to the vertical axis, forming transmission hole rows 15, which are arranged horizontally at horizontal pitches. A large number of them are arranged at intervals of PH. Then, in the adjacent transmission hole row, electron beam transmission hole group 1
4 is off by 1/2 PGV. For example, 29 inch 1
In a 10° deflection color picture tube, PGV is approximately 1.15 mm, and PH is set to approximately 0.8 to 0.9 mm. Furthermore, in the aforementioned 29-inch 110° deflection color picture tube, the vertical length lV of the electron beam transmission holes 11 in the electron beam transmission hole group 14 is set to 0.28 mm; The pitch PVS of the electron beam transmission holes 11 is 0.36 mm.

Further, a vertical cross section of the shadow mask according to the present invention is shown in FIG. 2(a). The first bridge 12 has a width w1 and a height h1 equal to the thickness of the shadow mask, whereas the second bridge 13 has a width w2 and a height h2 equal to the height of the first bridge 12. It is about half. With such a configuration, deterioration of the electron beam transmittance caused by the second bridge 13 can be suppressed. In other words, if both the first and second bridges 12 and 13 have a height equivalent to the thickness of the shadow mask, the transmittance of the electron beam incident on the transmission hole group is reduced by the side wall of the second bridge. do. However, by reducing the height h2 of the second bridge 13 as shown in FIG. 2, it is possible to reduce the influence of the bridge side wall, which causes a decrease in electron beam transmittance. A shadow mask having such a cross section can be formed by etching. In other words, when forming an electron beam transmission hole, etching is performed from both the screen side and the electron gun side, where the opening diameter is large, but since the second bridge has a small width, it is removed during etching and the plate thickness is reduced. It will be about half.

In the present invention, in addition to the transmission hole group corresponding to the design of a conventional color picture tube, the transmission hole group has a predetermined transmission hole pattern, so that it is possible to deal with the above-mentioned higher-order mode moiré. be. The effect of higher-order modes on moiré will be explained below. That is, Figure 3(a
), when there are two transmission holes in the transmission hole group, as shown schematically in FIG. 3(b), considering the transmittance of the slit in this case,

[0036]

[Math. 10] However, PGV=PV1+PV2 At this time,

[0037]

[Formula 11] However, μ=PV1/(PV1+PV2), where (6
), if an = 0, then Mn,m = 0. The contrast ratio C, which indicates the intensity of the brightness of the moiré fringes, is

[0038]

If Mn,m = 0, then C = 1, and moiré fringes cannot be recognized. (8) In order for an = 0 in the formula, cosnπμ=
0, nπμ=π/2, 3π/2π, 5π/2, . . . n
In even mode, when n=4, μ=1/8, 3/8 (μ=5/8 and 3/8 are the same), when n=6, μ=1/12, 3/12, 5/12, μ
By balancing the values of PV1 and PV2, it is possible to prevent high-order moiré fringes.

Next, the case where there are three transmission holes in the transmission hole group will be explained. The transmission hole pattern is shown in FIG. 4(a). This is the case when one transmission hole group has two large transmission holes and two small transmission holes. The transmittance pattern in such a case is as shown in Fig. 4(b), where the length of the large transmission hole is q, and the vertical pitch of the transmission hole group is PGV.
Then, the occupation ratio of large permeation holes q/PGV is on the horizontal axis,
If the contrast ratio is taken as the vertical axis and the curves for each mode of n=2, 4, and 6 are taken, the result will be as shown in FIG. 4(c). however,
Each mode was standardized so that q/PGV=0 was the same. When q/PGV is 0.5, the contrast ratio of each mode of n=2 and n=6 can be made 1, but the contrast ratio of the mode of n=4 becomes maximum. Moreover, when q/PGV is 0.36, each mode of n=2 and n=4 is small, and n=6 is slightly large. Therefore, it is possible to select and respond to q/PGV depending on the pattern of the moire fringe that appears. In the pattern shown in FIG. 1, q/PGV=0.
24, and from FIG. 4(c), each mode of n=4 and n=6 is small, and n=2 is slightly large.

The case where a shadow mask constructed as described above is used will be explained by taking a 29-inch 110° deflection color picture tube as an example and comparing it with a conventional one. Note that a conventional color picture tube with PV = 1.15 mm and bridge width of 0.15 mm was used. The number of scanning lines is N
In the case of the TSC method, the number is 525, and the number of effective scanning lines including image signals is 485. Furthermore, since images are displayed with a 108% overscan in a consumer picture tube, a 29-inch color picture tube has a vertical screen size of 412 mm, so the scanning line spacing is 1.09 mm. On the other hand, the vertical diameter of the electron beam is changed by the anode current flowing through the color picture tube through the anode. In other words, if you increase the anode current to make the screen brighter, the electron beam will become larger,
The vertical diameter also increases. Therefore, increasing the anode current changes the scanning line width. As shown in Figure 5, the characteristics of the anode current Ib per color and the scanning line width Sw when a white signal is input to the screen are as follows: In a 29-inch color picture tube, Ib = 10 μA and Sw = 0.8 mm. and Ib=
At 100 μA, Sw=1.3 mm.

Now, when the color picture tube of the present invention was compared with the conventional color picture tube, no moiré fringes could be discerned in either case at an anode current Ib=10 μA. However, in the case of a one-field image, such as a still image of a video, in which the number of scanning lines is halved and the spacing between scanning lines is widened, conventional color picture tubes can Moiré fringes occur toward the edges, but they did not occur in the color picture tube according to the present invention.

Similar experiments were also carried out using various electron guns in which the shape of the electron beam was flattened so that the vertical diameter of the electron beam was small. As a result, for a normal white signal, in a conventional color picture tube, anode Ib = 10 μA and scanning line width Sw = 0.6.
In the case of Sw=0.4 mm, moire fringes as shown in FIG. 6(b) appear, but in the present invention, no moire fringes were observed even in the case of Sw=0.4 mm. However, Sw=0.4
In the case of a one-field image of mm, moire fringes as shown in FIG. 6(b) described above were observed. This is considered to be due to the appearance of moiré fringes that could not be confirmed due to the small contrast ratio.

As described above, the present invention can accommodate various moiré fringes by changing the pattern within the group of transmission holes. Therefore, next, a more improved embodiment is shown in FIG. The transmission hole group 24 separated by the first bridge 22 has a small transmission hole 21a and a large transmission hole 21b, and between the transmission holes is a second bridge whose width is smaller than that of the first bridge 22. Separated by 23. Small transmission hole 2
A small bridge 23 is set at 0.125 PGV from the center of 1a. Therefore, the length of the small transmission hole 21a is 0.29 m.
m, the length of the large transmission hole 21b is 0.32 mm.

In a color picture tube with such a configuration, Sw=
Even with a scanning line width of 0.4 mm, no moiré fringes could be observed in the field image. As mentioned above, the length of the center transmission hole shown in Fig. 4(c) is 0.25 with respect to the length of the transmission hole group, and each mode of n=4 and n=2 is suppressed. It depends on what happened.

Combining the embodiments shown in FIGS. 1 and 7 above, in the present invention, since there is a second bridge with a small width, a decrease in brightness of about 10% is unavoidable, but in practice, it is difficult to avoid using fluorescent materials. At low currents, the shape of the electron beams striking the is separated into individual beams, as shown in Figure 8(a), but as the anode current exceeds Ib = 1 mA, the shape of the electron beams changes as shown in Figure 8(b). The electron beams that were separated by the second bridge begin to connect. Furthermore, as mentioned above, the height of the second bridge is smaller than the height of the first bridge, so the brightness at the peak is 5% compared to conventional color picture tubes.
The brightness deterioration can be kept to a certain extent.

In each of the above embodiments, the number of electron beam transmission holes in the electron beam transmission hole group was explained as three, but based on the explanation of FIGS. 3 and 4 above, It goes without saying that the present invention can be practiced as long as there are two or more beam transmission holes.

[0047]

As described above, according to the present invention, moiré fringes can be effectively reduced, deterioration of brightness can be minimized, and design parameters are increased.
It becomes possible to respond according to the situation.

[Brief explanation of the drawing]

FIG. 1 is a partial schematic diagram of a shadow mask showing an embodiment of the present invention.

FIG. 2 is a vertical partial cross-sectional view for explaining the bridge of the shadow mask in FIG. 1;

FIG. 3 is a diagram for explaining the operation of the present invention.

FIG. 4 is a diagram for explaining the operation of the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the anode current of an electron beam and the scanning line width.

FIG. 6 is a schematic diagram of moiré fringes appearing on a color picture tube.

FIG. 7 is a partial schematic diagram showing another embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating an electron beam image passing through a shadow mask according to the present invention.

FIG. 9 is a sectional view showing the general configuration of a color picture tube.

FIG. 10 is a partial schematic diagram showing an electron beam transmission hole pattern of a shadow mask in a conventional color picture tube.

[Explanation of symbols]

4, 10...Shadow mask 11, 21a, 21b...Electron beam transmission hole 12, 22
...First bridge 13, 23 ...Second bridge 14, 24 ...Electron beam transmission hole group PGV ...Vertical pitch PH ...Horizontal pitch

Claims (1)

[Claims] 1. A transmission hole array in which a plurality of electron beam transmission holes are arranged in a first direction, and a plurality of transmission hole arrays are arranged in a second direction perpendicular to the first direction. In the color picture tube equipped with a shadow mask, the transmission aperture row includes an electron beam transmission hole group consisting of at least two electron beam transmission holes separated by a first bridge and arranged at a predetermined pitch in the first direction. The electron beam transmission hole groups are arranged with a 1/2 pitch shift between adjacent transmission hole rows, and the width and height of the second bridge that separates the electron beam transmission holes in the transmission hole group are equal to the width and height of the second bridge that separates the electron beam transmission holes in the transmission hole group. A color picture tube characterized by being smaller than the bridge of 1.