KR20000019963A - Shadow mask for color braun tube - Google Patents

Abstract

PURPOSE: Many slots of shadow mask for a color braun tube are arranged in proportion to a horizontal pitch, a vertical pitch of the slot and arranged in inverse proportion to a radius of curvature in order to provide a stable color purity. CONSTITUTION: Many slots are arranged having a regular rate of distance increase in the effective surface of the shadow so that an electron beam impacted against a fluorescent surface have a regular distance. But if the tilt of an electron beam is occurred, the distance between nearby electron beams is decreased and purity redundancy is diminished. So many slots are arranged in proportion to a horizontal pitch, a vertical pitch of the slot and arranged in inverse proportion to a radius of curvature to have a regular distance among the electron beams even the tilt.

Description

Shadow Mask for Color CRT

The present invention relates to a color CRT, and more particularly to a shadow mask for a CRT, which serves as color screening of an electron beam emitted from an electron gun.

FIG. 1 is a side view showing a general color CRT in a partial cross section, in which red, green, and blue phosphors are applied to an inner surface of a panel 1 to form a fluorescent film 2, and a neck portion behind the panel 1 The funnel 3 in which the electron gun 4 is enclosed in 3a is fused by glass.

The shadow mask 6, which serves as color screening of the electron beam 5 emitted from the electron gun 4, is fixed to the frame 7 at a portion adjacent to the fluorescent surface 2 formed by coating on the inner surface of the panel 1. The frame 7 is fitted to the stud pin 9 fixed to the side wall of the panel 1 by a spring 8 fixed to the frame to maintain the suspended state.

In addition, an inner shield 10 is coupled to one side of the frame 7 to protect the electron beam 5 moving to the fluorescent surface 2 side from the external magnetic field when the CRT is operated by a fixing spring 11. A reinforcing band 12 is wound around the outer circumferential surface of the CRT to prevent firecrackers caused by external impact during operation of the CRT.

A deflection yoke 13 is provided on the outer circumferential surface of the neck of the funnel 3 to deflect the electron beam in the horizontal and vertical directions of the screen.

Therefore, when the heater built in the cathode (not shown) receives power from the stem pin and generates heat, electrons are emitted from the cathode by heat generated in the heater and a voltage difference applied to a plurality of electrodes adjacent to the cathode. The electron beam 5 is accelerated and focused while passing through holes of a plurality of electrodes positioned at regular intervals vertically from the cathode in the screen direction, and then deflected in the vertical and horizontal directions by a deflection yoke 13 installed on the outer circumferential surface of the neck portion. Will move to the state.

The electron beam thus moved passes through the slot 6a of the shadow mask 6 provided in close proximity to the fluorescent surface 2 and strikes the phosphor coated on the inner surface of the panel 1 accurately, thereby reproducing the screen.

FIG. 2 is a perspective view showing the shadow mask in FIG. 1, wherein the shadow mask 6 is welded and fixed to an effective surface 6b having numerous circular thin slots 6a and a support frame 7. It is composed of a skirt 6c having a constant length so that it can be.

3 is an enlarged front view of a portion of the effective surface of the shadow mask, in which the electron beam 5 emitted from the electron gun 4 is applied to the inner surface of the panel 1 on the effective surface 6b of the shadow mask 6. The slots 6a are arranged horizontally and vertically of the shadow mask 6 so as to maintain a constant interval so that the electron beam 5 impinging on the fluorescent surface when they collide with the fluorescent surface 2 to emit light.

As shown in FIG. 4, the shadow mask 6 has slots 6a, which are electron beam passing holes, arranged in the same size from the center to the end of the diagonal axis with respect to the X and Y axes of the shadow mask, or from the center of the shadow mask 6 It is formed with a constant rate of increase as a function of the distance between the X and Y axes.

In recent years, the most difficult and difficult technical problem that arises as the inner surface of the panel 1 is flit is to secure the purity margin.

However, as shown in Equation 1 and Equation 2, the purity margin decreases the purity margin because the distance between adjacent electron beams is reduced.

This not only adversely affects the color purity quality of the white uniformity of the color CRT, but also adversely affects the production of the CRT.

Where T is the distance between the electron beam centers

T ₀ : Distance between electron beam centers when the electron beam tilt angle is "0"

θ: electron beam tilt angle

δ: distance reduction amount between electron beams by electron beam tilt

Where S: black matrix (BM) dot size of the fluorescent surface

B: size of electron beam

Mb: Movement amount of electron beam when 1mm movement of deflection yoke

As shown in Equation 2, among the several factors that determine the color purity margin, the color purity margin greatly depends on the distance between the electron beam centers (T) and the electron beam size (B).

However, since the distance T between the centers of the electron beams is determined by the electron beam tilt generated by the geometrical factors of the color CRT, artificial adjustment is impossible.

Therefore, adjusting the electron beam size (B) is used as a way to secure the color purity margin.

Also, designing the electron beam size B to be equal to the distance between the closest screen dots is most advantageous for color purity margin and luminance.

However, since the conventional shadow mask slot size is defined only as a function of the distance change on the X axis and the Y axis at the center (CL: Center Line) of the shadow mask 6 as in Equation 3 and Equation 4, the electron beam tilt Since the electron beam size (B) at the periphery of the screen in question is not arbitrarily adjusted, there is a limit in solving the color purity margin problem due to the electron beam tilt.

m = mo × (1 ± aX ^{n One} ) × (1 ± bY ^{n 2} )

Where mo is the shadowmask slot size at the center of the screen

a, b: increase factor of the shadow mask slot size

X, Y: horizontal and vertical distance of the screen

B = μm

Where B is the electron beam size

μ: electron beam expansion coefficient

The present invention has been made to solve such a problem in the prior art, and aims to provide a more stable color purity quality by minimizing the tilt phenomenon caused by the reduction of the overall length of the color CRT and the fleet of the panel.

According to an aspect of the present invention for achieving the above object, in the shadow mask which is installed in close proximity to the inner surface of the panel, the number of slots are formed in the shadow mask innumerably proportional to the horizontal and vertical pitch of the slot and the curvature of the inner surface of the panel There is provided a shadow mask for a color CRT tube, which is formed to have a functional relationship inversely proportional to the radius.

1 is a side view showing a typical color CRT in some cross-section

Figure 2 is a perspective view showing the shadow mask in Figure 1

3 is an enlarged front view of a portion of an effective surface of a shadow mask;

4 is a graph illustrating a change in slot size in a conventional shadow mask.

5 is a state diagram showing an electron beam arrangement by a conventional shadow mask

6A and 6B are graphs illustrating a change in slot size in a shadow mask of the present invention.

Figure 7 is a state diagram showing the electron beam arrangement by the shadow mask of the present invention

8 is a graph comparing color purity by shadow masks applied to the prior art and the present invention.

Explanation of symbols for main parts of the drawings

1 panel 6: shadow mask

6a: slot

Hereinafter, the present invention will be described in more detail with reference to FIGS. 6 to 8 as an embodiment.

6A and 6B are graphs showing a change in slot size in the shadow mask of the present invention, FIG. 7 is a state diagram showing the arrangement of electron beams by the shadow mask of the present invention, and FIG. 8 is a color purity by the shadow mask applied to the prior art and the present invention. In the present invention, a vertical axis (Y) and a horizontal axis in the center of the screen are represented by variables of the pitch between slots and the radius of curvature of the inner surface of the panel as variables of the number of slots 6a formed in the shadow mask 6. It is characteristic to form while varying the dimension toward the outside of (X).

As described above, it is most advantageous to design the distance between adjacent screen dots equal to the size B of the electron beam to improve color purity margin and luminance.

Accordingly, the distance between adjacent screen dots may be expressed by the horizontal and vertical pitches Sh and Sv of the screen, which may be expressed by Equation 5.

Sh = κMh, Sv = κMv

Where Sh, Sv: the horizontal and vertical pitch of the screen

Mh, Mv: Horizontal and vertical pitch of shadow mask

α: pitch expansion coefficient

The electron beam size B when the electron beam 5 radiated from the electron gun 4 enclosed in the neck portion 3a of the funnel 3 passes through the slot 6a of the shadow mask 6 to reach the screen. Derived from the relationship with the slot diameter of the shadow mask (6) can be expressed as shown in equation (6).

Where m is the slot diameter of the shadow mask

Q: Distance from inside of panel to inside of shadow mask

ζ: magnification of the electron beam

According to Equations 1, 5, and 6, the size of the slot diameter m of the shadow mask for making the most ideal size B of the electron beam may be represented by Equation 7 as follows.

m = T- [2 × Q × tan (ζ × π / 180)] = T ₀ × δ- [2 × Q × tan (ζ × π / 180)]

Where T is the distance between the electron beam centers

T ₀ : Distance between electron beam centers when the electron beam tilt angle is "0"

δ: amount of reduction in distance between electron beams due to tilt

Q: Distance from the inside of the panel to the inside of the shadow mask

ζ: electron beam expansion coefficient

In Equation 7, T is a function of the screen pitch determined by the shadow mask 6, δ is a function of the electron beam tilt angle, the tilt angle is the main factor is the curvature of the inner surface of the panel (1).

Accordingly, the optimum shadow mask slot size is a function of shadow mask pitch and panel curvature, which is directly proportional to the pitch of the shadow mask and inversely proportional to the curvature of the panel, thus adjusting the electron beam size at any point. It is understood that the problem of purity margin due to the reduction of the distance between adjacent screen dots due to the cause is solved.

Where ε is a constant

R: Panel curvature

As described above, the present invention can not avoid the tilt phenomenon of the electron beam coming from the curved surface of the panel 1 and the shadow mask 6, but has a functional relationship according to the horizontal and vertical pitch of the slot 6a and the curvature of the inner surface of the panel. By changing the size of the slot, it is possible to form an optimal electron beam diameter at any point, thereby improving the margin of purity because it is possible to secure a much longer distance than the conventional hitting the phosphor of a different color.

Claims (2)

In the shadow mask that is installed close to the inner surface of the panel, a myriad of slots formed in the shadow mask is formed so as to have a functional relationship proportional to the horizontal and vertical pitch of the slot and inversely proportional to the radius of curvature of the inner surface of the panel Shadow mask for color CRT. The method of claim 1, The functional relationship is A shadow mask for color CRT tubes, which is satisfied by.