JPH03291833A - Shadow mask - Google Patents

Abstract

PURPOSE: To shorten a moire wavelength and to reduce a moire phenomenon by setting a variation range for a pitch in the vertical direction of an electron beam passing hole in a shadow mask. CONSTITUTION: When Py represents a pitch in the vertical direction of an electron beam passing hole 5 in a shadow mask set according to a broadcasting mode while Ps represents a scanning line pitch, a moire wavelength is represented by the following expression: a moire wavelength = 1/(|2/Py-n/2 Ps|)=1/(|fa-fs|). In this relationship expression, a variation range Δx of the vertical pitch when (n) is a positive integral number 3 or 4 is found, and this variation range Δx is added/subtracted to/from the predetermined vertical pitch Py, and on the basis of this pitch, the electron beam passing hole 5 is bored. In this relationship expression, fa represents a shadow mask pitch frequency, while fs represents a scanning frequency.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a shadow mask for a color cathode ray tube.
In particular, the present invention relates to a shadow mask in which the arrangement pattern of electron beam transmission holes is designed to reduce moiré.

[Conventional technology]

The structure of a shadow mask type color cathode ray tube will be explained based on FIG. After being deflected by the deflection magnetic field of W16, the inner surface of the panel 1 (hereinafter referred to as "screen surface") 2 passes through the electron beam transmission hole 5 of the shadow mask 3.
The three primary color phosphors 4 of red, green, and blue coated on the surface are irradiated.

The shape of the three primary color phosphors 4 corresponds to the shape of the electron beam transmission hole 5, and the mutual arrangement of the three primary color phosphors 4 irradiated with the three electron beams 7 transmitted through one electron beam transmission hole 5 forms three units. This corresponds to the arrangement of the electron guns 9.

Further, the arrangement of the three primary color phosphors 4 on the screen surface 2 is determined according to the arrangement of the electron beam transmission holes 5 in the shadow mask 3.

The shapes of the electron beam transmission holes 5 can be broadly classified into circular and rectangular shapes, and the rectangular electron beam transmission holes 5 are usually arranged as shown in FIG.

The electron beam transmission hole 5 has a bridge (bridl; 1e) 1 having a width for each vertical pitch Py perpendicular to the scanning direction.
0, and the vertical deviation of the electron beam transmission holes 5 between adjacent rows of electron beam transmission holes in the scanning direction is Δy.

As shown in FIG. 5A, the transmittance of the electron beam passing through the electron beam transmission hole array is maximum when the scanning line 11 passes through the center of the electron beam transmission hole 5 in the vertical direction. As shown in FIG. B, the minimum value is reached when the center position between two vertically adjacent scanning lines 11 coincides with the vertical center of the electron beam transmission aperture 5.

Due to interference between the vertical arrangement of the electron beam transmission holes 5 of the shadow mask 3 and the scanning line arrangement, a phenomenon in which a ripple pattern or a grain pattern appears on the screen surface 2, that is, moire occurs.

Various studies have been carried out to date to reduce such moiré phenomena.

One of them is a technique described in U.S. Pat. No. 4,210,842, in which the vertical pitch of electron beam transmission holes is set to reduce the moire pitch by a broadcasting method, and a mask that obtains a moire phase difference is used. The moiré pattern is scattered by determining a pattern and randomly arranging the vertical pitch of the shadow mask.

[Problem to be solved by the invention]

However, when the moire patterns are arranged randomly based on this US patent, not only the moire phenomenon is further increased, but also various problems occur in the manufacturing process of the shadow mask.

Although the technique of designing a dedicated shadow mask for NTSClPAL and SESAM slightly improves moiré due to the difference in broadcasting formats, since the vertical pitch of the shadow mask is constant, the moiré cannot be significantly degraded, and Since the overscan difference of the set and the deviation in the size of the electron beam could not be solved, it was necessary to manufacture a shadow mask with improved moiré.

The present invention has been made in view of these points, and by setting the change range of the vertical pitch of the shadow mask and implementing a shadow mask to which this is applied, the moiré wavelength can be shortened and the moiré wavelength can be reduced. The purpose of the present invention is to provide a shadow mask that can reduce the phenomenon.

[Means to solve the problem]

In order to achieve the above object, according to claim 1, the shadow mask of the present invention is characterized in that the size of the bridge of the electron beam transmission space is constant, and the length of the predetermined electron beam transmission hole is variable. In a shadow mask in which electron beam transmission holes are arranged, when the vertical pitch of the electron beam transmission holes of the shadow mask set by the broadcasting method is Py, and the scanning line pitch is ps, In the relational expression expressed by the frequency (where fa is the scanning frequency), the range of change Δx of the vertical pitch at a positive integer n=3.4 is determined, and the range of change Δx is expressed as the predetermined vertical pitch. The electron beam transmission hole is characterized in that the electron beam transmission hole is drilled at an angle corresponding to Py.

According to claim 2, in the shadow mask, the vertical arrangement of the electron beam transmission holes of the shadow mask is such that the sum of two types of vertical pitches is constant; It is characterized in that electron beam transmission holes are arranged alternately in the vertical direction.

Furthermore, according to claim 3, the shadow mask is characterized in that the electron beam transmission holes of the shadow mask are vertically arranged alternately with vertical pitches of Py-Δx and py+Δx.

Furthermore, according to claim 4, in the shadow mask, the electron beam transmission holes of the shadow mask have a vertical pitch of Py+Δx−sin(r).

It is characterized by an alternating vertical arrangement as Py+Δx-cos(r), where r is an arbitrary vertical distance of the screen.

Furthermore, according to claim 5, the shadow mask has a vertical pitch change range Δx of 0.03≦Δx≦0.
It is characterized by having 05 shoes.

Furthermore, according to claim 6, the shadow mask has an arrangement of electron beam transmission holes in the shadow mask, in which electron beam transmission holes have a relatively large vertical opening size, and electron beam transmission holes have a relatively large vertical opening size. The electron beam transmission hole is formed adjacent to the electron beam transmission hole.

(Function) The shadow mask of the present invention recited in claims 1 to 6 is based on a characteristic diagram of the relationship between the vertical pitch of the shadow mask, the scanning line pitch, and the moiré wavelength determined by the broadcasting system. In this method, the variation range of the vertical pitch of the electron beam transmission apertures of the shadow mask is set to a point where the macroscopic moiré wavelength appears small, and the set variation range of the vertical pitch is maximized to transmit the electron beam. Shadow masks are formed by varying the actual vertical pitch of the holes and the vertical opening length.

Therefore, in the shadow mask of the present invention, the electron beam transmission holes are arranged with an appropriate vertical pitch to minimize moire, so the moire wavelength is shortened and the moire phenomenon is reliably reduced. An extremely clear and high-quality image is reproduced on the screen of the color cathode ray tube.

[Example] Hereinafter, the present invention will be described in detail with reference to FIGS. 1 and 2. The same parts as the conventional one are given the same reference numerals.

First, the present invention will be explained in detail.

FIG. 2 is a characteristic diagram for explaining the relationship between the vertical pitch of the electron beam transmission aperture and the moiré wavelength, which is illustrated by the following relational expression.

The moiré frequency fc is expressed by the following formula.

fc=1fa-fsl...11)
Here, fa is the mask pitch frequency and fs is the scanning frequency.

On the other hand, if the moiré wavelength is λ, then f-1/λ...(2)
Therefore, the moiré wavelength λ is expressed by the following formula.

Here, Py is the vertical pitch of the electron beam transmission holes of the shadow mask, Ps is the scanning line pitch, and n is a positive integer.

As shown in equation (3) above, moiré is a phenomenon caused by interference between the scanning line and the vertical pitch of the electron beam transmission holes of the shadow mask.

The fundamental factors contributing to the moiré phenomenon are the vertical pitch and scanning lines of the electron beam transmission holes in the shadow mask, but one scanning line is fixed by the broadcasting system. Therefore, moiré can be minimized by optimizing the vertical pitch of the other shadow mask.

The shadow mask according to the present invention is based on the principle analyzed above, and by variably arranging the vertical pitch of the electron beam transmission holes within a set range, the moire wavelength can be shortened and the moire pattern can be scattered. This is to reduce moiré.

In FIG. 2, the vertical axis is the magnitude of the moiré wavelength λ,
The horizontal axis is the vertical pitch size of the electron beam transmission holes.

The smaller the moiré wavelength, the less moiré will appear visually.
If the moire wavelength, which is the standard of moire visibility at which moire appears visually, is set to 5-, a positive integer n for moire that appears in an intermittent array will determine the vertical pitch change range at 3 and 4. Can be done.

In other words, the intersections of two graphs intersecting at integers n=3 and n=4 are points A and B, but point B is not considered because the moire phenomenon does not appear visually due to the small moiré wavelength. Point A is applied to the present invention because the moiré wavelength appears visually.

2 of the A intersection at the point where the moiré wavelength is 5
If the vertical pitch change range between two graphs is 2Δx, then Δx is the vertical axis of the intersection A and the graph (n=4 or n
= 3).

That is, it is most preferable to maximize the vertical pitch change range Δx, but the specific range is 0.03≦Δx.
It is preferable to set it to ≦0.05MM.

The larger the Δx, the more the moire is scattered, so the moire phenomenon appears less.

By adjusting the variation range Δx set in this way and applying it to the vertical arrangement of the electron beam transmission holes, the moiré pattern can be dispersed.

First example FIG. 1A shows a first embodiment of the invention.

In this embodiment, the variation range Δx of the vertical pitch of the electron beam transmission apertures 5 determined as described above is applied, and the vertical pitches S1 and S2 of the electron beam transmission apertures 5 are set to 51=Py− The electron beam transmission hole 5 is arranged so that Δx and 52=PV+Δx.

At this time, the bridge 10 between the vertically adjacent electron beam transmission holes 5 is usually made to have the same size b as the conventional one.

The above-mentioned Py is the vertical pitch of the electron beam transmission holes 5 of the shadow mask 3 set according to the broadcasting system.

To further explain, since the vertical pitch Py of the electron beam transmitting holes 5 has a predetermined value, the vertical arrangement of the electron beam transmitting holes 5 of the shadow mask 3 according to the present invention has two different vertical pitches S1 and S1. 82, Sl, S2. Sl.

S2... are arranged alternately. As a result, the vertical pitch of the electron beam transmission apertures 5 of the present invention is as shown in FIG.
1. :I3, the two elements Sl and 82 are alternately arranged vertically.

If a color cathode ray tube equipped with a shadow mask 3 in which electron beam transmission holes 5 are arranged in this manner is used, the moire pattern that appears visibly will be scattered in the vertical direction, so the moire phenomenon can be greatly reduced. can.

In order to maximize the scattering of the moire pattern, the electron beam transmission hole 5 adjacent to the electron beam transmission hole 5 having a relatively small vertical opening size is formed to have a relatively large opening size.

In this way, the color cathode ray tube equipped with the shadow mask 3 in which the electron beam transmission holes 5 are vertically arranged can have the effect of reducing visible margins of moiré, and thus can obtain improved image quality.

Second example FIG. 1B shows a second embodiment of the invention.

In this embodiment, the vertical pitches S1 and S2 of the electron beam transmission holes 5 are 51=Py+Δx 5in(r
') and 52=Py+Δx-cos(r), and assuming that the bridge 10 between the vertical electron beam transmission holes 5 has a predetermined size b, 81
and 82 are arranged alternately.

The variable r in the above trigonometric function is the arbitrary vertical distance of the screen.

The shadow mask 3 arranged in this manner has two vertical pitches 81.32 as in the first embodiment, and in order to maximize the scattering of the moiré pattern, the shadow mask 3 has an electron beam with a small aperture size. The electron beam transmission holes adjacent to the beam transmission hole 5 are arranged to have a large opening size.

A color cathode ray tube equipped with such a shadow mask 3 can also be expected to have similar effects as described above.

As explained above, according to the present invention, the variation range Δx of the vertical pitch of the electron beam transmission holes for reducing moiré is set, and this Δx is applied to change the vertical pitch of the electron beam transmission holes of the shadow mask. By adjusting the length of the openings and arranging them, it is possible to disperse the moire pattern and expect an effect of reducing moire.

〔Effect of the invention〕

Since the shadow mask of the present invention is configured and operates as described above, by setting the variation range of the vertical pitch of the shadow mask and implementing a shadow mask to which this is applied, the moiré wavelength can be shortened. At the same time, it is possible to greatly reduce the 7-area phenomenon, and the image quality of a color cathode ray tube equipped with this shadow mask becomes extremely high quality.

[Brief explanation of drawings]

1A and 1B are enlarged views of a shadow mask pattern illustrating an array of electron beam transmission holes, showing a first embodiment and a second embodiment of the shadow mask of the present invention, respectively, and FIG. 2 is a vertical view of the electron beam transmission holes. FIG. 3 is a schematic perspective view illustrating the main parts of a color cathode ray tube to which the present invention is applied, and FIG. 4 is a characteristic diagram for explaining the relationship between pitch and moiré wavelength. FIGS. 5A and 5B are explanatory diagrams illustrating the relationship between the electron beam transmission holes and the scanning lines, respectively. FIGS. DESCRIPTION OF SYMBOLS 1... Panel, 2... Screen surface, 3... Shadow mask, 4... Three primary color phosphor, 5... Electron beam transmission hole, 6... Deflection device, 7... Electron beam, 8
...3 electron gun, 9...unit electron gun, 10...bridge, 11...scanning line.

Claims (1)

[Scope of Claims] 1) In a shadow mask in which the size of the bridge of the electron beam transmission space is constant and the length of the predetermined electron beam transmission hole is varied and the electron beam transmission holes are arranged, it is set according to the broadcasting method. When the vertical pitch of the electron beam transmission holes of the shadow mask is Py and the scanning line pitch is Ps, Moire wavelength = 1/|(2/py)-(n/2ps)|=
1/|fa-fs| (where fa is the shadow mask pitch frequency and fs is the scanning frequency), the vertical pitch change range Δx for positive integers n=3, 4 , and the electron beam transmission holes are formed by adjusting the range of change Δx to the predetermined vertical pitch Py. 2) The vertical arrangement of electron beam transmission holes in the shadow mask is
Claim 1, characterized in that the sum of two types of vertical pitches is constant, and the electron beam transmission holes are arranged such that the two types of vertical pitches alternate in the vertical direction. Shadow mask as described. 3) The shadow mask according to claim 1, wherein the electron beam transmission holes of the shadow mask are vertically arranged alternately with vertical pitches of Py-Δx and Py+Δx. 4) The vertical pitch of the electron beam transmission holes of the shadow mask is Py+Δx・sin(r), Py
Shadow masks according to claim 1, characterized in that they are vertically arranged alternately as +Δx·cos(r), where r is an arbitrary vertical distance of the screen. 5) The shadow mask according to claim 1, 3 or 4, characterized in that the vertical pitch change range Δx is 0.03 mm≦Δx≦0.05 mm. 6) The electron beam transmission holes of the shadow mask are arranged such that electron beam transmission holes having small vertical opening dimensions are adjacent to electron beam transmission holes having relatively large vertical opening dimensions. The shadow mask according to any one of claims 1 to 4, characterized in that: