JP2633303B2 - Color picture tube - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube using a rectangular shadow mask having a large number of slots as a color selecting means, and improves the efficiency of the shadow mask by increasing the electron beam transmittance. And the occurrence of local doming is prevented.

2. Description of the Related Art In general, a rectangular shadow mask having a large number of slots (hereinafter simply referred to as a mask) is shown in FIG.
Each slot is configured as shown in FIG. 10, and each slot has a major axis in a direction substantially parallel to the long side direction of the mask (X direction).
It is formed in an oval or rectangular shape having a major axis in a direction substantially parallel to the short side direction (Y direction) of the mask. That is,
The surface on the electron gun side has an oval small-diameter opening 1, and the phosphor screen side has a rectangular large-diameter opening 2. A bridge portion 3 is provided between the Y-directional arrangements of the slots, and an inclined side wall portion 4 is provided between the small-diameter opening 1 and the large-diameter opening 2.
There is. An edge 40 of the side wall 4 on the side of the small opening is a knife edge.

Of the two long side portions of the side wall portion 4, the long side portion along the electron beam 5 emitted from the electron gun, that is, the long side portion far from the mask short side direction axis passing through the center of the mask is tapered outward. Part 41, the other long side part is an inner tapered part 42
The inclination angle φ ₀ of the outer tapered portion 41 is formed to be larger than the incident angle θ ₀ of the electron beam 5 as disclosed in Japanese Patent Application Laid-Open No. 59-86135. . Such slots can be obtained by performing photo-etching from both front and back sides of a steel plate as a mask material.

In recent years, as the color picture tube has become larger and the degree of flatness of the face surface and the mask has been increased, local doming has been more likely to occur on the mask. This is thermal deformation caused by the electron beam having a high current density hitting the mask.To prevent this, the thickness of the steel plate as the mask material is increased from 0.15 to 0.18 mm to 0.2 to 0.3 mm. Or to improve the heat conduction.

However, when the plate thickness is increased, the inclination angle φ ₀ for securing the incident angle θ ₀ of the electron beam must be further increased,
Then, the width of the large-diameter opening 2 and the side wall 4 also increases, and the substantial plate thickness decreases. In addition, the press pressure during molding of the mask increases as the mask becomes thicker and larger, so if the edge 40 is a knife edge like a conventional thin mask, the edge 40 will be damaged during formation. The small-diameter opening 1 deforms irregularly as if the blade spilled. In such a case, not only does the quality of the mask deteriorate, but also the quality of the phosphor screen formed by exposure using the mask as an optical mask decreases significantly.

Therefore, the etching conditions at the time of forming the slots of the mask are controlled, and as shown in FIG.
And a step of edges 43 and 44 connecting the small-diameter opening 1 from the inclined surface to the small-diameter opening 1 side, and increasing the thickness at the same edge to increase the mechanical strength. Is increasing. The bridge portion 3 is for maintaining the mechanical strength at the time of forming the curved surface of the mask, and is preferably as small as possible in order to increase the transmittance of the electron beam. The bridge width required for stable press forming is about 1 /
2

On the other hand, even if the slot is located in the peripheral area in the Y direction of the mask, the incident angle of the electron beam with respect to the slot is considerably large. desirable. However, such an inclination cannot be provided because the beam transmittance is reduced, and the slot located in the mask peripheral area is
It is formed in a shape as shown in FIG. 12 to FIG. In this case, the height of step 6 formed by both end edges 43 and 44 on the small-diameter opening 1 side becomes the lowest at the center of the long side where the etching progress rate is high as shown in FIG. About half of the plate thickness due to the relationship with the bridge part 3.
Stand up to the position. Since the outer tapered portion 31 of the bridge 3 has a steeper slope than the inner tapered portion 32, the transmittance of the electron beam can be increased.

Referring to FIG. 15 and FIGS. 16 to 18 showing the cross-sectional shapes thereof, an edge 43 at the center of a long side having a low step height is shown.
The electron beam 5 that has passed through is not cut (17th
Figure) You can head to the phosphor screen. But,
In each of the cross sections A ₁ -A ₁ and A ₂ -A ₂ , the outer tapered portion 31 of the bridge portion 3 is larger than the inner tapered portion 32 as shown in FIGS. The step height at 45,46 is lower than the step height at edges 47,48.
However, in the formation of the slot by applying the chemical etching method, each step height of the edges 45, 46, 47, 48 is reduced to a height corresponding to about 1/2 of the plate thickness in relation to the bridge portion 3. Since it rises, a part of the electron beam 5 is cut by the edges 45 and 47. For this reason, the shape of the beam spot generated by the electron beam that has passed through the small-diameter opening portion 1 and reached the phosphor screen is changed into shadow portions 51 and 52.
19, the beam is cut at the end of the longer side farther from the mask short side direction axis (Y direction center axis) passing through the center of the mask, and as shown in FIG.
become.

Since the inclination of the outer tapered portion 31 is larger than that of the inner tapered portion 32, the portion where the beam spot 7 is cut is:
The portion 54 closer to the mask long side direction axis (the central axis in the X direction) passing through the center of the mask is larger than the portion 53 closer to the mask. When the beam spot 7 is distorted in this manner, the effective central axis 72 of the luminance with respect to the central axis 71 of the original electron beam becomes Δχ.
Only to the center axis side in the Y direction. In particular, in the case of a 110 ° wide-angle deflection color picture tube having a face with high flatness using a mask with a thickness of 0.25 mm, the angle of incidence θ ₀ of the electron beam on the mask becomes large, so the amount of Δχ is very large. 30μ
m.

In the case of a color picture tube of the black matrix system, the effective beam center position with respect to the phosphor screen always shifts by Δχ toward the Y axis center axis due to the shift of the effective luminance center. The beam landing allowance is smaller than the beam landing allowance in the opposite direction. Moreover, in reality, the spacing (pitch) between the red (R), green (G), and blue (B) phosphor stripes shown in FIG. 20 and the corresponding red (R), green (G), Since the pitch of the blue (B) beam spot is not the same, when the beam landing position deviates greatly, especially when local doming occurs,
Irradiation unevenness of the three colors R, G and B is caused, and the color purity is remarkably reduced. The reduced amount of the beam landing margin corresponds to the effective shift amount Δχ of the luminance center.

Problems to be Solved by the Invention As described above, local doming is likely to occur in a mask in a color picture tube having a face surface with a high degree of flatness, and although the thickness of the mask is increased as a countermeasure, when forming a slot, The resulting steps are higher and the edges of the beam spot are cut off, reducing the beam landing latitude.

Accordingly, it is an object of the present invention to provide a color picture tube that can achieve both the thickening of the masks and the improvement of the beam landing tolerance, which are incompatible with each other, as described above.

Means for Solving the Problems A color picture tube according to the present invention comprises an electron gun, a phosphor screen, and a slot provided between the electron gun and the phosphor screen in close proximity to the phosphor screen. A rectangular shadow mask having a short-axis direction substantially parallel to the mask long-side direction and a long-axis direction substantially parallel to the mask short-side direction. A portion having a large-diameter opening on the surface on the phosphor screen side, and a step inclined from the large-diameter opening toward the small-diameter opening and a step extending from the inclined surface to the small-diameter opening. In the color picture tube formed by etching the side wall portion, of the intersection lines where the inclined surface intersects with the step, the intersection line that is farthest from the mask short side direction axis passing through the center of the rectangular shadow mask. The long side of the line is gradually bent in a direction away from the mask short side axis as going from the center to at least one end.

In the color picture tube configured as described above, even if the electron beam is cut at the step portion of the slot of the mask, the diameter of the small-diameter opening on the side that cuts the electron beam is enlarged. The shape of the beam spot generated when the electron beam after passing through the phosphor screen reaches the phosphor screen as a projection of the slot is no longer cut at the end into a persimmon seed shape. A beam spot can be obtained. For this reason, the geometric center axis of the beam spot and the effective brightness center axis can be matched, and the beam landing tolerance can be increased.

Embodiments Next, the present invention will be described in detail together with illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which, of two intersecting lines at which the inclined portion and the step 6 intersect, the longer side, which is farther from the mask short side axis (Y direction center axis), has this long side. From the center of the side to one end, it is gradually bent in a direction away from the mask short side direction axis. A- in FIG.
Referring to FIG. 2 showing the cross section A, since the step height of the edge 43 is relatively low, the electron beam 5 passing through the short diameter W of the small-diameter opening 1 is not cut off to the phosphor screen. You can head. In addition, the third section showing the BB section
Referring to the figure, the minor axis of the small-diameter opening 1 is W + dW, which is wider than the central minor axis W by dW, so that the relationship between the amount of enlargement at the small-diameter opening and the edge 43 is the step height. Is ts and the incident angle of the electron beam 5 is θ ₀ , the minor diameter of the small-diameter opening 9 at the long side end position B is determined so that dW = ts tan θ ₀ (1). . Here, even if the electron beam is cut at the edge 47 at the long side end position B, the required width W of the electron beam can be ensured, so that the electron beam passing through the small-diameter opening is projected onto the phosphor screen. The shape of the beam spot, which is the projection of, is not a persimmon seed shape but has good left-right symmetry, and it is possible to match the geometric center axis of the beam spot with the effective brightness center axis .

When a mask with a plate thickness of 0.28 mm was incorporated in a 29 inch 110 ° deflection type color picture tube having a highly flat face, the incident angle (X-axis direction component) of the electron beam on the mask was θ ₀ = At 34 degrees, it was confirmed that by setting the dW to 0.06 mm, a beam spot with good symmetry was obtained on the phosphor screen, and the beam landing tolerance could be improved.

FIG. 5 and FIG. 6 show a slot near the center axis in the X direction in a conventional mask and a beam spot by an electron beam passing through the slot. And
7 and 8, which are drawn in comparison with both figures, show another embodiment of the present invention, in which a mask having a thickness of 0.28 mm is used. When the incident angle (X-axis direction component) of the electron beam is 27 degrees, the minor diameter enlargement amount dW at the enlarged end 47 of the small-diameter opening.
When dW was 0.03 mm, a beam spot with good left-right symmetry was obtained.

The amount of dW depends on the radius of curvature and the step height of the mask, but it is sufficient if the amount is not more than 1/2 of the plate thickness.

Effect of the Invention According to the present invention, a thick mask having a curved surface with a high flatness is used, and the shape of the beam spot by the electron beam that reaches the phosphor screen through the slot is changed with good symmetry. It is possible to match the effective luminance central axis with the geometric central axis. For this reason, the beam landing tolerance can be increased, and a decrease in color purity can be suppressed even in dynamic characteristics such as when local doming occurs. In designing the etching pattern, it is not necessary to consider that the electron beam is cut, so that a color picture tube having a high design latitude can be provided. Further, since the shape of the beam spot can be controlled by the slot shape of the mask, when forming a slot in a thick mask by etching,
There is no need to deeply etch the tapered portion near the bridge portion, and the shape of the step is formed by a gentle curve, so that there is an advantage that the etching is facilitated.

[Brief description of the drawings]

FIG. 1 is an enlarged plan view of a part of a mask used in a color picture tube embodying the present invention, and FIG.
A sectional view, FIG. 3 is a BB sectional view of the same, and FIG. 4 is a CC of the same.
FIG. 5 is a plan view in which a part of a conventional mask is enlarged, FIG. 6 is a plan view of a beam spot obtained by a color picture tube using the mask, and FIG. 7 is another embodiment of the present invention. , FIG. 8 is a plan view of a ghost spot obtained by the color picture tube of the embodiment, FIG. 9 is a perspective view of a part of a conventional mask, FIG.
10 is a sectional view taken along line AA of FIG. 9, FIG. 11 is a perspective view of a part of the conventional mask, FIG. 12 is a plan view of a part of the conventional mask, and FIG. 13 is BB of FIG. Sectional view, FIG. 14 is AA
FIG. 15 is a plan view of a part of a conventional mask, and FIG.
Figure A ₁ -A ₁ section view of Figure 15, Figure 17 is the A ₀ -A ₀ cross section ,, FIG. 18 the A ₂ -A ₂ section view, FIG. 19 is a conventional color picture tube Plan view of the beam spot obtained by
The figure shows the relationship between the phosphor screen and the beam spot during local doming of the color picture tube. 1 ... small diameter opening, 2 ... large diameter opening, 3 ... bridge, 4 ... side wall, 5 ... electron beam, 6 ... step.

Claims (1)

(57) [Claims] An electron gun, a phosphor screen, and a rectangular shadow mask having a slot disposed between the electron gun and the phosphor screen in close proximity to the phosphor screen; Has a minor diameter axis substantially parallel to the mask long side direction and a major diameter axis substantially parallel to the mask short side direction, and has a small-diameter opening in the surface on the electron gun side, and a surface on the phosphor screen side. A large-diameter opening, and an inclined surface inclined from the large-diameter opening toward the small-diameter opening and a side wall having a step from the inclined surface to the small-diameter opening, each formed by etching. In the color picture tube, the longer side of the intersection line that intersects the inclined surface and the step and that is farther from the mask short side direction axis passing through the center of the rectangular shadow mask is at least from the center thereof. Color picture tube, characterized in that gradually bent in a direction away from the mask short side axis in accordance One of going to the end.