JP4028878B2 - Cathode ray tube - Google Patents

Description

  The present invention relates to a cathode ray tube using a shadow mask, and more particularly to a technique for increasing the curved surface holding strength of a shadow mask.

  FIG. 10 shows a cross-sectional view of an example of a conventional cathode ray tube. The cathode ray tube 1 includes a vacuum envelope 2, various components attached to the vacuum envelope 2, and a deflecting device 12 disposed so as to surround the outer periphery of the vacuum envelope 2. The vacuum envelope 2 is formed by joining a funnel-shaped funnel 4 to a panel 3. The panel 3 includes a side wall 3b around the effective portion 3a formed on the curved surface, and a funnel 4 is joined to the side wall 3b. A phosphor screen 5 is provided on the inner surface of the effective portion 3 a of the panel 3. The phosphor screen 5 is formed of a black non-light emitting layer and a three-color phosphor layer formed so as to be embedded in a gap between the black non-light emitting layers.

  A substantially rectangular shadow mask 6 is disposed opposite to the phosphor screen 5. An electron gun 10 is disposed in the neck 8 of the funnel 4. The electron gun 10 emits three electron beams 9B, 9G, and 9R. The three electron beams 9B, 9G, and 9R are deflected by the deflecting device 12, and an image is displayed by scanning the phosphor screen 5 horizontally and vertically via the shadow mask 6.

  The shadow mask 6 is for selecting the three electron beams 9B, 9G, and 9R emitted from the electron gun 10 with respect to the three-color phosphor layers constituting the phosphor screen 5. The shadow mask 6 has a mask body 17 attached to a mask frame 18. The mask body 17 faces the phosphor screen 5 and has a curved effective surface in which a large number of electron beam passage holes are formed, a non-hole portion surrounding the outer periphery of the effective surface, and the non-hole portion over the entire periphery. It is formed in a substantially rectangular shape by a skirt portion bent at a substantially right angle. The mask frame 18 is attached to the skirt portion of the mask main body 17.

  As shown in FIG. 10, the wedge-shaped elastic support body 20 attached to each corner portion of the mask frame 18 is locked to the stud pin 21 provided at the corner portion of the side wall portion 3b of the panel 3, thereby shadowing. The mask 6 is detachably supported inside the panel 3.

  Since the trajectory of the electron beam changes due to the influence of the magnetic field, an inner shield 22 is attached to the mask frame 18 to extend to the electron gun 10 side and shield the external magnetic field.

  In general, in order to display an image without color misregistration on the phosphor screen 5 of the cathode ray tube, the three electron beams 9B, 9G, and 9R passing through the electron beam passage holes of the mask main body 17 form the three-color phosphor layer. It needs to be sorted to ensure correct landing. For this purpose, the positional relationship between the panel 3 and the shadow mask 6 is correct, and in particular, the distance between the inner surface of the effective portion 3a of the panel 3 and the effective surface of the mask body 17 needs to be within a predetermined allowable range.

  By the way, in recent years, in order to improve the visibility of the cathode ray tube, it is desired to increase the radius of curvature of the outer surface of the effective portion 3a of the panel 3 so as to be close to a plane. FIG. 10 shows an example in which the outer surface of the effective portion 3a of the panel 3 is substantially flat.

  In such a panel 3, it is necessary to increase the radius of curvature of the inner surface of the effective portion 3a from the viewpoint of the atmospheric pressure strength and visibility of the vacuum envelope, and as the radius of curvature of the inner surface of the effective portion 3a increases. In order to obtain an appropriate beam landing, it is necessary to increase the radius of curvature of the effective surface of the shadow mask 6.

However, if the radius of curvature of the effective surface of the shadow mask 6 is increased, the curved surface holding strength is reduced, and local deformation in the shadow mask 6 manufacturing process and thermal deformation in the cathode ray tube manufacturing process are likely to occur. Shift and color purity deterioration are likely to occur. As a technique for solving such a problem, Patent Document 1 proposes improving the curved-surface holding strength of a shadow mask by providing a reinforcing bead on an effective surface.
JP-A-7-161306

  However, if a reinforcing bead is provided on an effective surface having a large radius of curvature so that sufficient curved surface holding strength can be obtained, the spacing between the inner surface of the effective surface of the panel and the effective surface of the shadow mask locally deviates from the allowable range. An image of a step formed by providing the bead appears on the screen, and the image quality is significantly deteriorated. For this reason, the height of the reinforcing bead is usually limited to about 0.2 mm, and the curved surface holding strength is also limited.

  The present invention is intended to solve the above-described conventional problems, and provides a cathode ray tube capable of increasing the curved surface holding strength of a mask body to reduce a deviation in beam landing and prevent deterioration of color purity. With the goal.

In order to achieve the above object, a cathode ray tube according to the present invention includes a panel having a phosphor screen formed on an inner surface and a substantially flat outer surface, and a substantially rectangular shadow mask facing the phosphor screen. The shadow mask has a substantially rectangular mask body attached to a substantially rectangular mask frame, the mask body having an effective surface in which an electron beam passage hole is formed, and the effective mask. A non-peripheral portion surrounding the surface, the vertical axis of the screen passing through the tube axis of the cathode ray tube as the vertical axis, and the horizontal axis of the screen passing through the tube axis of the cathode ray tube as the horizontal axis. The main body is symmetrical with respect to the vertical axis and the horizontal axis, and has a dome-like curved shape as a whole. The curvature radius of the curve in the vertical axis direction of the effective surface of the mask main body is Ry, and the horizontal axis The curvature radius of the curve in direction and Rx, and Rk is calculated curvature radius Rk of the curved surface in the effective surface than Rk ² = Rx × Ry, the position of the effective surface of the mask body, the said horizontal axis vertical When expressed in a coordinate system with two axes as the axis, the central part is a square region 30 mm in the positive direction of the horizontal axis and 30 mm in the positive direction of the vertical axis from the origin, and the vicinity of the end of the diagonal axis is A square area of 30 mm in the negative direction of the horizontal axis from the end of the diagonal axis and 30 mm in the negative direction of the vertical axis is formed. A square area of 30 mm in the positive direction, the radius of curvature of the curved surface near the diagonal axis end of the effective surface is Rk (d), the radius of curvature of the curved surface near the horizontal axis end is Rk (h), and the curvature of the central curved surface When the radius is Rk (c), Rk (c) Rk (h), Rk (c)> Rk (d), and there is a portion where Rk (h) and Rk (d) satisfy a substantially identical relationship, and among the effective surfaces, among the symmetrical strip portion relative to the horizontal axis in width 30mm to the tube axis from the horizontal axis end, the horizontal axis on one side portion of the one side, the curvature in the vertical axis direction of the effective surface The distribution of the radius Rk includes a portion that becomes a concave curvature radius distribution having a minimum value or a portion that becomes a convex curvature radius distribution having a maximum value.

  According to the present invention, it is possible to increase the curved-surface holding strength of the shadow mask, and it is possible to prevent the deformation of the effective surface even when an impact is applied in the tube axis direction in the manufacturing process of the cathode ray tube or after the manufacturing is completed. Become. For this reason, it is possible to reduce the deviation of the beam landing and prevent the deterioration of the color purity.

  In the present invention, by satisfying each expression of the present invention, the curved surface holding strength of the mask body can be increased to reduce the deviation of the beam landing, and the deterioration of the color purity can be prevented.

In the concave or convex curvature radius distribution, the absolute value of the difference between the maximum value and the minimum value of the radius of curvature of the effective surface is preferably within 3000 mm.

  According to the preferred cathode ray tube of the present invention, the curved surface holding strength of the mask body can be further increased.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The basic structure of the cathode ray tube in the present embodiment is the same as that of the general cathode ray tube shown in FIG. For this reason, in this embodiment, a detailed description of elements other than the shadow mask is omitted.

  FIG. 1 is a perspective view showing a mask body of a shadow mask according to an embodiment of the present invention. FIG. 2A is a plan view showing a shadow mask in the embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along the line AA ′ in FIG. As described with reference to FIG. 10, the shadow mask performs color selection on three electron beams corresponding to R (red), G (green), and B (blue) emitted from the electron gun 10. It is an electrode which performs.

  In FIG. 1, the Z axis is the tube axis of the cathode ray tube, the Y axis is the vertical axis of the screen passing through the tube axis of the cathode ray tube, and the X axis is the horizontal axis of the screen passing through the tube axis of the cathode ray tube. This is the same in the following description.

  When viewed from the Z-axis direction, the mask main body 17 of the shadow mask 6 has an effective surface 14 and a non-porous portion 15 extending to the periphery of the effective surface 14. The effective surface 14 has a large number of slot-shaped and dot-shaped electron beam passage holes. Further, the non-hole portion 15 is bent to the electron gun 10 side at a substantially right angle over the entire circumference to form the skirt portion 16.

  When viewed from the Z-axis direction, the effective surface 14 and the non-hole portion 15 are formed in a substantially rectangular shape as shown in FIG. 2A, and as shown in FIG. A dome-shaped curved surface is formed. Further, as shown in FIG. 2B, the mask body 17 is held and fixed to a rectangular mask frame 18 via a skirt portion 16.

  Here, in recent years, in order to improve the visibility of the cathode ray tube, it is required to increase the radius of curvature of the outer surface of the effective portion of the panel so as to be close to a flat surface. The panel according to the present embodiment is based on the premise that the effective portion outer surface of the panel is substantially flat, that is, the panel has a radius of curvature of 10,000 mm or more on the effective portion outer surface of the panel.

  Such a panel needs to increase the radius of curvature of the inner surface of the effective portion from the viewpoint of the atmospheric pressure strength and visibility of the vacuum envelope. As the radius of curvature of the inner surface of the effective portion increases, in order to obtain an appropriate beam landing, the radius of curvature of the effective surface 14 of the mask body 17 needs to be increased.

  Generally, when the radius of curvature of the effective surface 14 of the mask body 17 is increased, the curved surface holding strength is lowered. For this reason, the mask main body 17 is likely to be locally deformed in the manufacturing process, and is likely to be deformed when an impact is applied even after the manufacturing is finished. If the mask main body 17 is deformed, the beam landing shift and the color purity are liable to occur.

  In addition, when the cathode ray tube receives an impact, the inertial force applied to the shadow mask increases in proportion to the weight of the mask body 17 from the portion where the inertial force is applied to the center of the mask body 17, that is, the area of the mask body 17. Become. In this case, an inertial force due to the weight of the entire effective surface 14 is applied near the periphery of the effective surface 14, and the inertial force is greater than that near the center. Further, in the vicinity of the periphery of the effective surface 14, inertial force is concentrated due to the mechanical strength difference between the material of the effective surface 14 and the non-hole portion 15, and deformation is likely to occur.

  On the other hand, the curved surface holding strength with respect to the inertial force of the effective surface 14 increases as the radius of curvature decreases. For this reason, it is usually necessary to make the radius of curvature near the periphery of the effective surface 14 smaller than that at the center. As will be described in detail below, the present invention is not limited to merely reducing the radius of curvature in order to improve the curved surface holding strength, but the short side (the side in the Y-axis direction) of the vicinity of the effective surface 14. ) Side curvature radius distribution.

  FIG. 3 is a diagram illustrating a region in which the radius of curvature of the curved surface of the effective surface 14 of the mask body 17 is defined in the present invention. This figure partially shows the mask main body 17, but the mask main body 17 is symmetric with respect to the X axis and the Y axis.

  Here, the mask main body 17 generally forms a dome-shaped curved surface by press-molding a mask having openings. At this time, the curved surface is slightly different from the original ideal curved surface due to variations in the press mold. For the confirmation, the displacement in the Z-axis direction between the mask body center and the measurement point (hereinafter referred to as “sag amount”) is measured at multiple points, and the degree of difference from the ideal curved surface is calculated. At the same time, it is determined how much the curvature radii of the vertical and horizontal curves are different from the ideal state.

  However, it is difficult to recognize the curvature radius distribution of the original curved surface only with the curvature radius of the curve, and the causal relationship between the curvature radius distribution of the effective surface of the shadow mask and the mask curved surface holding strength could not be confirmed. .

  In general, as a method for expressing the curvature radius of a curved surface, there is a method called total curvature or Gaussian curvature. In this case, the total curvature K is expressed by the following formula (1).

Formula (1) K = 1 / (R1 × R2)
In equation (1), the radii of curvature R1 and R2 are the maximum and minimum values at an infinite number of normal cuts with respect to a certain point on the curved surface.

  However, it is difficult to measure innumerable points on the mask curved surface, and the measurement time becomes longer due to the enormous measurement.

  Therefore, in this embodiment, the maximum value and the minimum value are simply assumed as the curvature radius Rx of the horizontal curve and the curvature radius Ry of the vertical curve, and the curvature radius Rk of the curved surface of the effective surface 14 is grasped. As a method to do this, the following formula (2) was used.

Formula (2) Rk ² = Rx × Ry
By using Equation (2), it is possible to efficiently confirm the curvature radius distribution of the curved surface, and to easily derive the curvature radius distribution of the curved surface that enhances the curved surface holding strength.

  Although details will be described later, it was found that the curved surface holding strength of the shadow mask can be increased by repeating the experiment confirmation and satisfying the following expressions (3), (4), and (5).

Formula (3) Rk (c)> Rk (h)
Formula (4) Rk (c)> Rk (d)
Formula (5) −800 ≦ Rk (h) −Rk (d) ≦ 800
In the above equations, Rk (c) is the radius of curvature (mm) of the curved surface at the center of the effective surface 14, Rk (d) is the radius of curvature (mm) of the curved surface near the diagonal axis end of the effective surface 14, and Rk ( h) is the radius of curvature (mm) of the curved surface in the vicinity of the end of the horizontal axis.

  The center portion is a square area of 30 mm in the positive direction of the X axis and 30 mm in the positive direction of the Y axis from the origin when the position of the mask body is expressed by XY coordinates. The vicinity of the diagonal axis is a square region 30 mm in the negative direction of the X axis from the diagonal axis end and 30 mm in the negative direction of the Y axis. The vicinity of the horizontal axis end means that the X axis extends from the horizontal axis end. This is a square area of 30 mm in the negative direction and 30 mm in the positive direction of the Y axis.

  Next, a description will be given using specific examples. For example, in an 86 cm type cathode ray tube having a screen aspect ratio of 16: 9, the size of the effective surface 14 of the mask body 17 is the distance in the Y axis direction with respect to the X axis (the length in the Y axis direction in the example of FIG. 3). The half width is approximately 200 mm, and the distance in the X-axis direction (half width of the length in the X-axis direction) with respect to the Y-axis is approximately 355 mm. In this case, the horizontal axis end is at a position of X = 355 mm and Y = 0, and the diagonal axis end is at a position of X = 355 mm and Y = 200 mm. In this cathode ray tube, the radius of curvature of the outer surface of the panel is approximately 100,000 mm.

  FIG. 4 shows the relationship between Rk (h) -Rk (d) of the above formula (5) and the curved-surface holding strength of the shadow mask in an 86 cm type cathode ray tube having a screen aspect ratio of 16: 9. In FIG. 3, when the intersection point of the X axis and the Y axis is the origin, the measurement position of Rk (h) is the position near the horizontal axis end of the effective surface 14, X = 350 mm, the position of Y = 0, Rk (d) The measurement positions are X = 350 mm and Y = 200 mm, which are positions near the end of the diagonal axis. Rk (h) -Rk (d) were set so as to satisfy the above equations (3) and (4), respectively, and the mask body used in this experiment was a dome-shaped curved surface as a whole.

  The curved surface holding strength of the vertical axis in FIG. 4 is 10%, which is a drop resistance strength in the tube axis direction on the neck side of the picture tube. It is desirable that the curved surface holding strength is 10G (100%) or more.

  In addition, an experiment was performed in which the amount of depression at the horizontal axis end and the vertical axis end of the effective surface 14 was constant, and the curvature radius was changed by varying the amount of depression at the diagonal axis end. In this case, as the amount of depression at the diagonal axis end increases, the radius of curvature at the diagonal axis end decreases and the absolute value of Rk (h) −Rk (d) also increases.

  Usually, the curved surface holding strength increases by bringing the curved surface of the mask body closer to a spherical surface. However, on the horizontal axis in FIG. 4, the curved surface holding strength decreases as it approaches both ends, and the curved surface holding strength increases even if the amount of depression at the diagonal axis end is increased and the curvature radius of the curved surface is reduced. is not.

  As can be seen from FIG. 4, the curved surface holding strength is the highest when Rk (h) −Rk (d) = 0, that is, when the curvature radius Rk of the curved surface near the horizontal axis end and the diagonal axis end is equal. Strength is high. As the absolute value of Rk (h) -Rk (d) increases, the curved surface holding strength decreases. However, if Rk (h) -Rk (d) is within ± 800 mm, the target curved surface holding strength (100%) Is realized. That is, it was found that the curved surface holding strength of the shadow mask can be ensured by satisfying the expressions (3), (4), and (5).

  It should be noted that the positions corresponding to Rk (h) and Rk (d) are selected within the square area of 30 mm on each side so as to satisfy the expressions (3), (4) and (5). Similar results were obtained.

  Although not shown here, the same phenomenon was confirmed when the amount of depression at the end of the vertical axis and the end of the diagonal axis was fixed and the amount of depression at the end of the horizontal axis was varied.

  Furthermore, various experiments were conducted to find effective conditions by improving the curved surface holding strength. As a result, in addition to satisfying the above equations (3), (4) and (5), the radius of curvature distribution in the Y-axis direction of the effective surface 14 in the shaded area shown in FIG. It was confirmed that the curved surface holding strength can be further improved by including a concave curvature radius distribution having a minimum value or a convex curvature radius distribution having a maximum value.

  More specifically, the band-shaped range indicated by the hatched portion in FIG. 3 is the X-axis of the band-shaped portion that is symmetric with respect to the X-axis with a width α of 30 mm from the X-axis end of the effective surface 14 in the Z-axis direction. Is a one-side part with one side.

  FIG. 5 shows the experimental results. FIG. 5 is a graph showing the relationship between the difference in radius of curvature and the curved surface holding strength in an 86 cm cathode ray tube having a screen aspect ratio of 16: 9. The curvature radius difference ΔRk on the horizontal axis in FIG. 5 is expressed by the following equation (6).

Formula (6) ΔRk = Rk (M) − (Rk (h) + Rk (d)) / 2
In Equation (6), Rk (M) is the radius of curvature of the curved surface at the intermediate position M where the radius of curvature is maximum or minimum between the vicinity of the horizontal axis end and the vicinity of the diagonal axis end of the effective surface 14. is there. The measurement positions of Rk (h) and Rk (d) are the same as those in FIG. 4, and the value of Rk (h) −Rk (d) is set to almost zero.

  That is, in the experiment which obtained the result of FIG. 5, the amount of sagging between the horizontal axis end and the diagonal axis end of the effective surface 14 is constant, and the value of Rk (h) −Rk (d) is almost zero. 4 shows the relationship between each value of the curvature radius difference ΔRk that changes with the amount of depression at the intermediate position M and the curved surface holding strength.

  Equation (6) is an equation representing the difference between the maximum value and the minimum value of the radius-of-curvature distribution in the Y-axis direction of the belt-like portion in FIG. 3, and (Rk (h) + Rk (d)) / 2 is Rk This corresponds to the minimum value when (M) is a maximum value or the maximum value when Rk (M) is a minimum value. In the experiment which obtained the result of FIG. 5, since the value of Rk (h) -Rk (d) is almost zero, the maximum value or the minimum value was set as the average value of Rk (h) and Rk (d).

  Further, Rk (M) at the intermediate position M is the minimum value or the maximum value of the curvature radius of the curved surface within the range from the vicinity of the horizontal axis end of the effective surface 14 to the vicinity of the diagonal axis end. Therefore, on the horizontal axis in FIG. 5, Rk (M) is a maximum value in the positive range (ΔRk> 0). In this case, between the vicinity of the horizontal axis end of the effective surface 14 and the vicinity of the diagonal axis end, there is a portion where the curvature radius distribution in the vertical axis direction is convex. In the negative range (ΔRk <0), Rk (M) is a minimum value, and there is a portion where the radius of curvature distribution in the vertical axis direction is concave.

  As shown in FIG. 5, when the absolute value of ΔRk is within 3000 mm, the curved surface holding strength can be secured at 100% or more. Further, the maximum value of the curved surface holding strength was about 160%, which greatly exceeded the result of FIG.

  FIG. 6 shows a curvature radius distribution of an example of the mask body used in the experiment of FIG. The example of FIG. 6 corresponds to P1 shown in FIG. 5, and in this example, it was confirmed that the curved surface holding strength was improved by about 57% with respect to the target value.

  In this embodiment, as shown in FIG. 6, the maximum value Rk (Max) of the curvature radius is 2478 mm, the curvature radius Rk (h) at the horizontal end is 1343 mm, and the curvature radius Rk (d) at the diagonal axis end is 1369 mm. Thus, the radius-of-curvature difference ΔRk at P1 is as follows according to the equation (6).

ΔRk = 2478− (1343 + 1369) / 2 = 1122 mm
FIG. 7 is a three-dimensional graph of the data shown in FIG. 6, and it is possible to grasp the curvature radius distribution of the entire curved surface. Moreover, it turns out that the edge part (right edge part of FIG. 7) of the horizontal direction (X-axis direction) of an effective surface is convex from this figure.

  Further, from the experimental result in which the horizontal axis in FIG. 5 is the negative side, the curvature radius distribution from the vicinity of the horizontal axis end of the effective surface 14 to the vicinity of the diagonal axis end is calculated. Even in the case of a concave curvature radius distribution in which Rk (M) at the intermediate position M within the range up to is a minimum value, the curved surface holding strength is further increased as in the case of the convex curvature radius distribution. You can see that it is raised.

  FIG. 8 shows the distribution of the curvature radius of an example of the mask body used in the experiment of FIG. The example of FIG. 8 corresponds to P2 shown in FIG. 5. In this example, it was confirmed that the curved surface holding strength was improved by about 50% with respect to the target value.

  In this embodiment, as shown in FIG. 8, the minimum value Rk (Min) of the radius of curvature is 1304 mm, the radius of curvature Rk (h) at the horizontal end is 2338 mm, and the radius of curvature Rk (d) at the diagonal end is 2376 mm. Thus, the radius-of-curvature difference ΔRk at P2 is as follows according to the equation (6).

ΔRk = 1304− (2338 + 2376) / 2 = −1053 mm
FIG. 9 is a three-dimensional graph of the data of FIG. 8, and it is possible to grasp the curvature radius distribution of the entire curved surface. Further, it can be seen from this figure that the end portion in the horizontal direction (X-axis direction) of the effective surface is concave (the right end portion in FIG. 9).

  As described above, in addition to satisfying the expressions (3), (4) and (5), the radius of curvature distribution in the Y-axis direction of the effective surface 14 in the shaded area shown in FIG. However, it was confirmed that the curved surface holding strength could be further increased by including a concave curvature radius distribution having a minimum value or a convex curvature radius distribution having a maximum value.

  This is considered to increase the curved surface holding strength because the stress applied during impact can be dispersed by forming the curvature radius distribution of the curved surface on the short side of the effective surface into a waveform. In this case, if the difference in the radius of curvature is too large as described above, the curved surface holding force is considered to be reduced due to stress concentration due to excessive waveform undulations.

  In addition, although each said Example demonstrated the example of the cathode ray tube of 86 cm type screen aspect ratio 16: 9, it has also confirmed that this invention was effective regardless of a screen size and a screen aspect ratio.

  According to the present invention, the curved surface holding strength of the mask main body can be increased to reduce the deviation of the beam landing and the deterioration of the color purity can be prevented, so that it is useful for, for example, a television receiver or a computer display.

The perspective view of the mask main body which concerns on one Embodiment of this invention. (A) The figure is a top view of the shadow mask which concerns on one Embodiment of this invention, (b) A figure is sectional drawing in the AA 'line of (a) figure. FIG. 6 is a plan view illustrating part of a shadow mask according to one embodiment of the present invention. The figure which shows the relationship between the curvature radius difference which concerns on one embodiment of this invention, and the curved-surface holding | maintenance intensity | strength of a shadow mask. The figure which shows the relationship between the curvature-radius difference which concerns on another example of one embodiment of this invention, and the curved-surface holding | maintenance intensity | strength of a shadow mask. The figure which shows distribution of the curvature radius of the effective surface which concerns on one embodiment of this invention. The figure which graphed distribution of the curvature radius of the effective surface of the shadow mask which concerns on an example of embodiment of this invention. The figure which shows distribution of the curvature radius of the effective surface which concerns on another example of one embodiment of this invention. The figure which graphed distribution of the curvature radius of the effective surface of the shadow mask which concerns on another example of embodiment of this invention. Sectional drawing of an example of the conventional cathode ray tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cathode ray officer 3 Panel 3a Effective part 5 Phosphor screen 6 Shadow mask 14 Effective surface 15 Non-perforated part 16 Skirt part 17 Mask body 18 Mask frame

Claims (2)

A cathode ray tube comprising a panel having a phosphor screen formed on the inner surface and a substantially flat outer surface, and a substantially rectangular shadow mask facing the phosphor screen,
The shadow mask is a substantially rectangular mask body attached to a substantially rectangular mask frame,
The mask body includes an effective surface in which an electron beam passage hole is formed, and a non-hole portion surrounding the effective surface,
When the vertical axis of the screen passing through the tube axis of the cathode ray tube is a vertical axis, and the horizontal axis of the screen passing through the tube axis of the cathode ray tube is the horizontal axis, the mask body is relative to the vertical axis and the horizontal axis. Is symmetrical, and is a dome-shaped curved surface as a whole,
The curvature radius of the curve in the vertical axis direction of the effective surface of the mask body is Ry, the curvature radius of the curve in the horizontal axis direction is Rx, and the curvature radius Rk of the curved surface in the effective surface is calculated from Rk ² = Rx × Ry. Rk,
When the position of the effective surface of the mask body is represented by a coordinate system in which the horizontal axis and the vertical axis are two axes, the central portion is 30 mm from the origin in the positive direction of the horizontal axis, and the vertical axis A square area of 30 mm in the positive direction, and the vicinity of the diagonal axis, a square area of 30 mm in the negative direction of the horizontal axis from the diagonal axis end and 30 mm in the negative direction of the vertical axis, and the vicinity of the horizontal axis end, From the horizontal axis end to a square area of 30 mm in the negative direction of the horizontal axis and 30 mm in the positive direction of the vertical axis,
When the radius of curvature of the curved surface near the diagonal axis end of the effective surface is Rk (d), the radius of curvature of the curved surface near the horizontal axis end is Rk (h), and the radius of curvature of the curved surface at the center is Rk (c).
Rk (c)> Rk (h),
Rk (c)> Rk (d),
And there is a portion where the Rk (h) and the Rk (d) satisfy a substantially identical relationship,
Of the effective surface, the width of the effective surface from the end of the horizontal axis to the tube axis direction is 30 mm and is symmetrical with respect to the horizontal axis. cathode lines distribution of the curvature radius Rk of the vertical axis, characterized in that it includes a portion to be portion to be a curvature radius distribution of the concave having a minimum value, or the curvature radius distribution of the convex having a maximum value tube.   2. The cathode ray tube according to claim 1, wherein in the concave or convex curvature radius distribution, an absolute value of a difference between a maximum value and a minimum value of the curvature radius of the effective surface is within 3000 mm.

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