JPH02103847A - Shadow mask type color cathode-ray tube - Google Patents

Abstract

PURPOSE:To avoid generation of moire stripes and lessen conspicuousness by putting the bridge parts at every slot row of a shadow mask in completely irregular arrangement within the specific range, and making it specified slot arrangement pitch. CONSTITUTION:The shifting amounts 1- 7 of bridge parts 9 at every slot row of a shadow mask 7 are put in completely irregular arrangement within the range of >=BW (but, BW shows the width of the bridge part and shows the shifting amount of bridge part between adjacent slot rows), and the pitch PV of the slot 8 in the direction V is made 0.3mm<=PV<=1.5mm. Hereby, the optical interference between the shadow of the bridge part 9 projected on a fluorescent face and the stripe of brightness by the scanning line of electron beams changes finely at every slot row, so not only the generation of moire stripe can be avoided as far as possible, but also the moire stripes which arise slightly can be made hard to be conspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shadow mask type color cathode ray tube in which the arrangement pattern of slots in the shadow mask is improved.

[Prior Art] Fig. 2 is a schematic cross-sectional view showing the structure of a shadow mask type color cathode ray tube. A vertically continuous striped fluorescent film (3) is mounted in a direction perpendicular to the scanning line of the beam spot. (4)
is a roughly conical funnel connected to panel (1);
(5) is a tubular neck part with three electron guns (
2) are installed in an in-line arrangement. (6)
is a deflection yoke with a funnel (4) and a tubular neck (
5) is placed on the outer periphery near the connection with the electron gun (2).
deflects the electron beam emitted from the Reference numeral (7) denotes a shadow mask, which is disposed opposite to the fluorescent film (3) and has a slot (8) through which electron beams are selectively transmitted.

Next, the operation of this color cathode ray tube will be explained.

Three electron beams emitted from the electron gun (2) are deflected by the horizontal deflection magnetic field and the vertical deflection magnetic field formed by the deflection yoke (6) and are scanned over the entire surface of the fluorescent screen of the fluorescent film (3), forming a shadow mask. (7) through the slots (8) and hit the phosphor stripes of the respective corresponding colors;
The phosphor is excited and emitted light to emit a predetermined amount of light, thereby forming a color image.

FIG. 3 is an enlarged view of a part of a conventional shadow mask (7) in a color cathode ray tube. (
(See Japanese Patent Application Laid-open No. 53-56964) As is clear from the figure, the shadow mask (7) has a rectangular slot (
8) are arranged at a constant pitch (Pv) in the vertical direction of the screen (hereinafter referred to as the ``V direction'') in large numbers almost parallel to each other regularly in the horizontal direction (hereinafter referred to as the ``H direction''). ) in array 1. It is structured in a mosaic pattern.

(9) is a bridge portion that constitutes a non-perforated portion existing between each slot (8) in the slot row.

The V-direction opening dimensions (text) of each slot (8) are all constant, and each slot row is generally such that the position of the bridge portion (8) of the adjacent slot row is relative to the other slot (8) in the V direction. In other words, the above pitch (
They are arranged so as to be alternately shifted by 1/2 of Pv).

When an electron beam is scanned in the H direction on a shadow mask (7) having such an array pattern of slots (8), the electron beam scans the slots (8) of each slot row.
) and the slot (8), so a shadow is projected onto the fluorescent screen of the fluorescent film (3). This shadow is spaced by α ((1/2) Pv) in the H direction, which is the value obtained by multiplying the amount of deviation (1/2) Pv by the dimensional expansion rate (α) determined by the trajectory of the electron beam. projected on.

By the way, the number of scanning lines of the electron beam is 5 in the NTSC system.
25 trees, and 625 trees in the PAL system. Furthermore, since the electron beam itself has a certain size, shadows are created between the scanning lines when the fluorescent screen is scanned, and bright and dark stripes are generated by the electron beam.

FIG. 4 is a diagram showing the state of an electron beam contributing to light emission when a scanning line passes through a shadow mask (7) having an array pattern of slots (8) as shown in FIG. In the same figure, (IOa) indicates that the electron beam is at the bridge part (8).
The scanning line (10c) is the scanning line when the electron beam overlaps the bridge part (8), and the part with the maximum current density at the center of this scanning line is the bridge part (9). It's getting heavy. (IOb) is a scanning line when a part of the electron beam overlaps with the bridge portion (9). Comparing these scanning lines (lQa) to (IOc), it is found that in the case of scanning line (10a), the shaded phosphor screen (3) has the largest and brightest light emitting area; In the case of (10c), the light emitting area of the phosphor screen (3) and the area of the bridge part (9) are in a ratio of 1:l, and the brightness y of the phosphor screen (3) is the same as that of the scanning line (10a). It is halved in comparison. The regular repetition of brightness and darkness caused by such scanning lines becomes a moiré pattern.

As a result, the bridge part (8) of the shadow mask (7)
) and the bright and dark fringes caused by the scanning line optically interfere, resulting in Moiré fringes. In order to make these moire fringes as inconspicuous as possible, the pitch (Pv) of the slots (8) of the shadow mask (7) in the V direction is generally adjusted.
It has been selected like Haggi.

That is, as is well known, the pitch (Pv) of the slot (8) in the V direction is the dimension (
1/2 of Pvl) is (PA), the vertical interval of scanning lines is (PS), and the repetition interval of moiré fringes on the phosphor screen (3) (hereinafter referred to as "moiré fringe pitch") is (PM). ), where m and n can be expressed as integers. These moire fringes vary depending on the values of m and n, and when a predetermined mode (m, n) is determined, one pattern is determined.

One of the conditions under which moiré fringes become noticeable and unsightly is that the moiré fringes pitch (PM) becomes large, and for this purpose, 2 m PS -n PA must become a small value. That is, the condition is that 2mPS=nPA approximately holds true.

In the past, in a conventional shadow mask type color cathode ray tube, the slot was Set the pitch (Pv),
For any mode of moire fringes, care is usually taken to ensure that the moire fringe pitch (spatial period) (P)l) does not become large.

Figure 5 shows the slot pitch (Pv) and the moiré fringe pitch (P
It is a characteristic diagram showing the relationship with M). In this figure, both the vertical and horizontal axes represent the scanning line pitch P in the NTSC system.
Standardized by NTSC.

- Generally speaking, among moire fringes, the ones that are actually noticeable are PM(1,3) and PM(1), according to experimental results.

4) and PM(1,5).

However, if we take the case of a two-finch type 110° deflection color cathode ray tube as an example, moire fringes are least noticeable at a standardized slot pitch of 1.28 x 10 mm, which is PM (1°4); The pitch (Pv) is 0.91 mm.

In this case, in order to reduce moire fringes, it is sufficient to increase (PA) and to decrease PM (m, n) in formula 1, and for that purpose, it is sufficient to increase the slot pitch (Pv). , it is desirable that the shadow mask (7) is formed into a substantially convex spherical shape.
) is restricted to Pv≦1.5 mm due to moldability problems.

On the other hand, from the viewpoint of transmittance of the electron beam to the shadow mask (7), it is preferable that the pitch (Pv) of the slots (8) be as large as possible. From the above points, the slot pitch (Pv) is selected to be as large as possible within the range of 1.5 mm or more, and to a value that makes moiré fringes inconspicuous. However, if Pv≦1.5 mm, that is, the standardized slot pitch≦2. In the range of I XIO mm, it is impossible to completely eliminate moiré fringes.

Another method for reducing the occurrence of moiré fringes is to reduce the width (Bw) of the bridge portion (9), but in this case as well, if the pitch (Pv) of the slot (8) is increased Similarly, it is not preferable from the viewpoint of moldability of the shadow mask (7), and from the viewpoint of maintaining the mechanical strength of the shadow mask (7), it is usually 0.1 mm≦Bw≦3.
A value in the range of 15 mm is required.

The influence of the width (B w) by the size of the shadow on the phosphor screen of this bridge part (9) increases in proportion to the deflection angle of the electron beam, and the width of the shadow part of the scanning line increases as the width of the shadow of the electron beam increases. The better the focus performance is, the larger the value tends to be.

In particular, a deflection yoke (
In color cathode ray tubes that improve focusing performance over the entire surface of the phosphor screen by applying a modulation voltage synchronized to the deflection current (3), the bright and dark stripes of the scanning lines on the phosphor screen become clearer. Moiré stripes are easily noticeable. Furthermore, if the shape of the panel (1) forming the phosphor screen is aspheric, as is often used in recent color cathode ray tubes, the spacing between the scanning lines at each position on the phosphor screen changes, causing moiré. The striped pattern also becomes very complex.

[Problems to be Solved by the Invention] In the conventional shadow mask type color cathode ray tube configured as described above, as long as there is a bridge portion of finite width between the slots, bright and dark stripes caused by the scanning lines are eliminated. There is a problem in that the occurrence of moire fringes due to optical interference between the light and dark fringes of the bridge portion is unavoidable, and the moire fringes are very conspicuous.

In order to solve this problem, various proposals have been made regarding the arrangement method of the bridge parts (9), but all proposals have a certain degree of regularity in the arrangement of the bridge parts (9). Even if it were possible to theoretically find conditions for the scanning line spacing (Ps) and the arrangement method of the bridge section (8) to make moiré fringes less noticeable to a certain extent, during operation of a color cathode ray tube, it is mainly due to the characteristics of the drive circuit, etc. from,
It is difficult to always keep the scanning line spacing (Ps) constant within the entire screen. For this reason, even if we find a theoretical condition for the arrangement of the bridge section (9) that makes moire fringes less noticeable, it is extremely difficult to make moire fringes less noticeable in an actual color cathode ray tube on the entire screen. Have difficulty.

This invention was made to solve these problems, and it is possible to avoid the occurrence of moire fringes as much as possible, and to make the generated moire fringes very difficult to stand out, thereby making it possible to obtain high-quality reproduced images. The purpose of the present invention is to provide a shadow mask type color cathode ray tube.

[Means for Solving the Problems] A shadow mask type color cathode ray tube according to the present invention has the following features:
The position of the bridge part for each slot row arranged horizontally on the shadow mask is completely determined within the range of Δ≧Bw (where Bw is the width of the bridge part, and Δ is the amount of shift of the bridge part between adjacent slot rows). Irregular array, and slot array pitch (PV) of 0.3 mm≦Pv≦1.5
It is characterized by being set to mm.

[Operation] According to the present invention, the horizontal slot row is Although minute moire fringes determined by the arrangement pitch are generated, since the moire fringes are randomly shifted for each slot row, the moire fringes are hardly noticeable as a whole.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is an enlarged view of a portion of a shadow mask (7) in a shadow mask type color cathode ray tube according to an embodiment of the present invention. As is clear in the figure,
Slot rows are formed by connecting vertically long continuous slots (8) in the direction perpendicular to the scanning line (V direction) at a constant pitch (Pv) via bridge parts (9), and each slot row is connected horizontally. The configuration in which slots are arranged in parallel at equal intervals in the direction (H direction) is similar to the conventional example shown in FIG. 3, but the arrangement of each slot row is different as follows.

That is, the amount of shift (Δ) of the bridge portions (9) between adjacent slot rows in the horizontal direction is set completely randomly. Specifically, for example, in FIG.
The amount of shift (△1) between the first column and the second column is 0.4 Pv
, the straight line (Δ2) between the second and third rows is Q, 7
5Pv, amount of shift between the 3rd and 4th columns (Δ3)
is 0.5 Pv, the amount of shift between the 4th and 5th columns
(△4) is 0.6P, the amount of shift between the 5th and 6th columns (△5) is 0.35Pv, and the amount of shift between the 6th and 7th columns (Δ6) is Q , Ei5Pv, 7th and 8th columns
The arrangement is completely irregular, with a shift amount (△7) of 0.3Pv from the column.

In this manner, the random shift amount (Δ) is determined by irregular statistical processing using a random number generator.

Also, each smoothing amount (Δ) is two slots (8)
, (8) The width of the bridge part (8) between (Bw)
When Δ≧Bw. It has been experimentally confirmed that this is preferable in terms of moldability of the shadow mask (7).

A shadow mask (7) having such an array pattern of slots (8) has bright and dark stripes due to the shadow of the bridge part (9) projected onto the fluorescent screen (3) in FIG. 2 for each slot row, Fine moiré fringes determined by the array pitch in the H direction are generated due to optical interference with the bright and dark fringes caused by the scanning line of the electron beam, but since the moire fringes cause a pitch shift for each slot row, the overall It is possible to make moire fringes almost inconspicuous.

Furthermore, since it is possible to reduce the conspicuousness of moiré fringes as described above, it is preferable to make the pitch (Pv) of the slots (8) in the V direction as large as possible from the viewpoint of electron beam transparency. Considering the moldability of 7), it is preferable to set the value between 0.3 mm≦Pv≦1.5 mm. This has also been confirmed experimentally.

Furthermore, since the pitch (Pv) of the slots (8) in the ■ direction is constant, when forming the continuous striped fluorescent film (4) in the ■ direction, the well-known photolithography technique is used as in the conventional example. It can be easily formed.

[Effects of the Invention] As described above, according to the present invention, the bridge portions of each slot row of the shadow mask are arranged completely irregularly within the range of Δ≧Bw, and the slot row arrangement pitch (P v) is set to 0.
．． By setting 3 mm≦Pv≦1.5 mm, the optical interference between the shadow of the bridge portion projected on the phosphor screen and the bright and dark stripes caused by the scanning line of the electron beam changes finely for each slot row, thereby preventing moiré. Not only can the occurrence of stripes be avoided as much as possible, but even the slightest occurrence of moire fringes can be made less noticeable. Therefore, it is possible to significantly improve the quality of reproduced images.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of a portion of a shadow mask in a shadow mask type color cathode ray tube according to an embodiment of the present invention;
The figure is a schematic cross-sectional view of a shadow mask type color cathode ray tube, Figure 3 is an enlarged view of a portion of a shadow mask in a conventional shadow mask type color cathode ray tube, and Figure 4 is a diagram showing a scanning line passing through the shadow mask in Figure 3. FIG. 5 is a characteristic diagram showing the relationship between the standardized slot pitch and the moiré fringe pitch in the NTSC system. (+)... Panel, (2)... Electron gun, (3)...
・Fluorescent film, (7)...Shadow mask, (8)...
- Slot, (9)...Bridge part. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 8 Nislot Figure Figure Figure

Claims (1)

[Claims] (1) Three electron guns arranged in-line, and vertically elongated slots perpendicular to the scanning line of the electron beam spot from these electron guns are arranged at a constant pitch (P
v) A shadow mask type color cathode ray tube comprising a shadow mask in which continuous slot rows are arranged horizontally in parallel, and a striped phosphor screen disposed opposite to the shadow mask and continuous in the vertical direction. The bridge part for each slot row of the shadow mask is Δ≧Bw
(However, Bw is the width of the bridge part, Δ is the shift amount of the bridge part between adjacent slot rows), and the slot row arrangement pitch Pv is 0.3 mm≦
A shadow mask type color cathode ray tube characterized in that Pv≦1.5mm.