MXPA98006994A - Cinescope of image of co - Google Patents

Abstract

The present invention relates to a color picture tube satisfying the following conditions. First, a value of df (r) / dr is zero in a first area on an inner surface of a panel that includes a point at which r = 0, and is negative on a second area from outside the first area to the point on the which r = Ld, where r denotes a radial distance from the Z axis, and f (r) denotes a position of a point on the inner surface of the panel in a direction of the Z axis, and the point at which r = Ld denotes an outermost point in a diagonal direction of the image display area. Second, a value of d2f (r) / dr2 is negative in a third area from the point where r = 0 inside a point where r = R2 being within the second area, is zero at the point where r = R2, and is positive in a fourth area from outside the point where r = R2 to the point where r = Ld. Third, a thickness of the panel in the second area in the direction of the Z axis is greater than that in the first area in the direction of the axis

Description

J *. 1 CINESCOPE OF COLOR IMAGE BACKGROUND OF THE INVENTION The present invention relates to a kinescope (tube) color image and, more specifically to a shape of a panel provided with a phosphor screen.

In a conventional color image kinescope (tube) a glass panel with a phosphor screen is commonly spherical for the purpose of making the kinescope (tube) of color image and the like light. However, because of the development of a technology In recent years, it has been possible to produce a panel in a substantially flat manner.

In a current color image kinescope (tube) that has a flat plate panel with surfaces In parallel, however, it is recognized that the portions of the ridges around the image of a screen appear to float to a greater degree with respect to a viewer than a portion of the image around a center of the screen so that an image of a human face shown on 5 the screen, for example, which should naturally be generally elliptical tends to look somewhat crescent shaped. It can be considered that the aforementioned phenomenon occurs for the following reason. As shown in Figure 9 schematically shows a vertical sectional view of conventional panel, an observer 30, observes around a center of a panel 3-1 at a substantially straight angle with respect to an outer surface of the panel 31. On the one hand , the viewer 30 looks around a flange of the panel 31 obliquely at an angle a with respect to an axis Z. Furthermore, if a thickness of the panel 31 around its center when viewed at a normal direction with respect to the center of an external surface 31b of the panel 31 is represented by TQ, it can be seen that a thickness T] _ of the panel 31 around its flange when viewed in an oblique direction at an angle a with respect to the Z axis, is greater than TQ. Accordingly, as a point being observed by the observer 30 approaches the edge of the screen, the apparent floating distortion of the image displayed in an image screen area on an inner surface 31a of the panel 31 (or a screen 32 of matches) becomes greater.

As a more specific example, it will be assumed that a refractive index n of glass constituting the panel 31 is 1,536, the size of the area of the screen and the image on the panel 31 in a diagonal direction is 260 [mm] and the observer 30 observes the phosphor screen from a position of 95 [mm] away from the outer surface 31b of the panel 31. Then, the phosphor screen recognized by the observer 30 would subsequently be seen as an apparent screen 33 as it is seen. it observes as if it were located closer to the observer 30 than the current phosphor screen 32, it is placed at a depth of Tg / n (= 2TQ / 3) from the outer surface 31b in e. center of the panel 31, that is, in a position of approximately T / 3 floating from the inner surface 31a in the center of the panel 31. As a point is being observed by the observer 30 it approaches a screen rim the Apparent floating distortion of the apparent screen 33, which is expressed by (Tg / 3 +? TD), becomes greater. Figure 10 shows graphs indicating the results of the calculations of a relation between the degrees of the angle of observation a with respect to the axis Z corresponding to a position of a point in the image screen area of the panel 31 and an increase? TD of the apparent floating distortion of the image. With reference to Figure 10, a radius of curvature of an outer surface of the panel is designated by RP [mm] and is calculated based on the premise that an inner surface of the panel is flat. However, similar results can be obtained if the outer surface of the panel is flat and the inner surface of the panel is curved. It is also assumed that in Figure 10 that the observer's eyes are placed at 95 [mm] away from the outer surface of the panel. The case in which RP = 90000 [mm] corresponds to the case in which the panel is a flat plate with parallel surfaces. In this case, it can be seen from Figure 10 that a portion of an image located at the observation angle of 50 degrees, for example, seems to be floating? TD, which is approximately 2.4 [mm], towards the observer, as compared to a portion of the image around the center of the phosphor screen.

BRIEF DESCRIPTION OF THE INVENTION The present invention has been made to solve the aforementioned problem associated with the conventional cathode ray tube. Therefore, it is an object of the present invention to provide a color image tube in which an apparent screen recognized by an observer becomes flat in such a way that it is capable of displaying a high quality image. According to one aspect of the present invention, a color picture tube has a panel, an inner surface which has an image display area, and a phosphor screen provided throughout the display, of image on the inner surface of the panel, to show an image when subjected to an irradiation of an electron beam. When a Z axis is superimposed on an axis of the tube that passes through a center of the panel and that is normal with respect to the panel, a direction from an internal part of the color image tube with respect to an observer is fixed to be in a positive direction of the Z axis, a radial distance from the Z axis is denoted by r, a point at which the Z axis intersects the internal surface of the panel, is denoted by a point at which r = 0, an outermost point at a diagonal direction of the image display area is denoted by a point at which r = L¿, and a position of a point on the internal surface of the panel in a Z axis direction is expressed by f (r) being a function of r, the following conditions are satisfied. First, a value of df (r) / dr which is a first derivative of f (r) is zero in a first area within the image display area, which includes a point at which r = 0, and is negative in a second area within the image display area from the outside of the first area with respect to the point at which r = L¿. Second, a value of d2f (r) / dr2 which is a second derivative of f (r) is negative in a third area within the image display area from the point where r = 0 relative to the interior of a point in which r = R2 being the second area, is zero at the point where r = R2 # and is positive in a fourth area within the image display surface from outside the point where r = R2 relative to the point where r = L¿. Third, a panel thickness in the second area in the direction of the Z axis is greater than a panel thickness in the first area in the direction of the Z axis. An apparent screen can be made flat so that the superior quality image can be visualized . Also, it is preferable that 0.4L ¿< R2 = 0. 85L ¿be satisfied. According to another aspect of the present invention, a color image tube has a panel, an inner surface which has an image display area, and a phosphor screen provided throughout the entire image display area. the internal surface of the panel, to show an image when subjected to an irradiation of an electron beam. When a Z axis is superimposed on an axis of the tube that passes through a center of the panel and that is normal with respect to the panel, a direction from an internal part of the color image tube with respect to an observer is fixed to be in a positive direction of the Z axis, a radial distance from the Z axis is denoted by r, a point at which the Z axis intersects the internal surface of the panel, is denoted by a point at which r = 0, an outermost point at a diagonal direction of the image display area is denoted by a point at which r = L¿, and a position of a point on the internal surface of the panel in a Z axis direction is expressed by f (r) being a function of r, the following conditions are satisfied. First, a value of df (r) / dr which is a first derivative of f (r) is zero in a first area within the image display area, which includes a point at which r = 0, is negative in a second area within the image display area from the outside of the first area with respect to the point where r = R ^ where R ^ is less than L¿, is zero at the point where r = R ^, and is positive in a third area within the image display area from outside the point where r = R * L with respect to a point at which r = L ^. Second, a value of d ^ f (r) / dr2 that is a second derivative of f (r) is negative in a fourth area within the image display area from the point where r = 0 relative to the interior of a point where r = R2 being the second area, is zero at the point where r = R2 and is positive in a fifth area within the image display surface from outside the point where r = R2 respect to the point where r = L¿. Third, a thickness of the panel in the second area in the direction of the Z axis is greater than a thickness of the panel in the first area in the direction of the Z axis. It is preferable that the following conditions are satisfied: 0.2Ld <; R2 = 0.65L ¿0.6L3 < Rl < 1.0L ¿Rl > R2 In addition, an outer surface of the panel may be of substantially flat shape with a curvature value of not less than 60000 [mm] or not greater than -6000 [mm]. In addition, the outer surface of the panel may be of a convex shape with a radius ^. ^ Of curvature below 60000 [mm]. In addition, a radius of curvature of the outer surface of the panel is greater than a radius of curvature about a center of the inner surface of the panel. Therefore, the apparent floating distortion of the apparent screen can be adjusted by means of not only the internal surface of the panel, but also the outer surface of the panel, thereby relaxing the design limitations of the panel. In addition, the inner surface of the panel can be rotationally symmetric with respect to the Z axis and the external surface of the panel can also be rotationally symmetric with respect to the Z axis. In addition, the inner surface of the panel can be rotationally asymmetric with respect to the Z axis and have different configurations between a cross section cut on a horizontal plane including the Z axis and a cross section cut on a vertical plane including the Z axis. Because the inner surface of the panel is rotationally asymmetric the panel can be adapted, for use with a shadow mask of a type of shadow grid, of which the vertical cross-section assumes a straight line shape and the horizontal transversal section It assumes a shape of a bow. In addition, the static resistance of the color image tube is increased, while at the same time the color image tube can be made light.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and wherein: Figure 1 is a vertical sectional view schematically showing a pipe of color image partially with its parts detached according to a first embodiment of the present invention; Figure 2 is a front view of the color image tube panel in > Figure 1; Figure 3 is an explanatory diagram showing a cross section taken along the diagonal line of the panel of the color image tube and indicating the conditions that are satisfied by an internal surface of the panel according to the first embodiment; Figure 4 is an explanatory diagram showing an apparent screen recognized by an observer according to the first mode; Figure 5 is an explanatory diagram showing a cross section taken along a diagonal line of a panel of a color image tube and indicating the conditions that are satisfied by an internal surface of the panel according to a second embodiment of the present invention; Figure 6 is an explanatory diagram showing a cross section taken along the diagonal line of a panel of a color image tube and indicating the conditions that are satisfied by an internal surface of the panel according to a third modality 'of the present invention; Figure 7 shows characteristic curves indicating a relationship between a radius of curvature about a center of the inner surface of the panel and an apparent floating distortion of an apparent phosphor screen, and a relationship between a radius of curvature about a center of the outer surface of the panel and an apparent floating distortion of the apparent phosphor screen; Figure 8 is an explanatory diagram showing a cross section taken along a diagonal line of a panel of a color image tube and indicating the conditions that are satisfied by an internal surface of a panel according to a fourth embodiment of the present invention; Figure 9 is a vertical sectional view schematically showing the conventional panel; and Figure 10 shows graphs indicating the results of the calculations of the relationship between the degrees of the observation angle α with respect to the Z axis and the increase to TD of the apparent floating distortion of the image.

DETAILED DESCRIPTION OF THE INVENTION The additional scope of application of the present invention will be apparent from the detailed description presented below. However, it should be understood that the detailed description and the specific examples, while indicating the preferred embodiments of the invention are given only by way of illustration, since various changes and modifications will be apparent to those skilled in the art from the description Detailed First Mode Figure 1 is a vertical sectional view schematically showing a color picture tube with its parts partially peeled according to a first embodiment of the present invention. As shown in Figure 1, the color image tube according to the first embodiment includes a panel 1, a funnel 2, and a phosphor screen 3 arranged on an internal surface of the panel 1, to show an image as it is subject to irradiation of a 5 electron beam. The color image tube further includes an electron gun 4 for emitting the electron beam 5, a deflection yoke 6 for scanning the electron beam 5 in the horizontal and vertical directions, a shadow mask 7 of a grid type of shadow in which a plurality of vertically elongated perforations are arranged in the horizontal direction and a film 8 which prevents the deflection provided on an external surface Ib of the panel 1 to obstruct the external reflected lights. Also, in the Figure 1, an observer is designated by a reference number 10. Figure 2 is a front view of the panel 1 shown in Figure 1. With reference to the Figure 2, a reference number 9 denotes an image display area on the inner surface of panel 1 (or on phosphor screen 3).

As seen from Figure 1 and Figure 2, a Z axis is superimposed on an axis of the tube that passes through a center of the panel 1 and that is normal with respect to the external surface Ib of the panel 1 in the center and a direction from inside the color image tube relative to an observer 10 is set to be in a positive direction of the Z axis. When a radial distance from the Z axis to a point in the normal image display area 9 relative to the Z axis is designated by r, a point in which the Z axis intersects the external surface of the panel 1 is denoted by a point where r = 0. In addition, a point more external in the diagonal direction (ie an address along the line D) of the image display area 9 is a point at which r = L¿, an outermost point in a vertical direction (i.e. an address along the line V) of the area 9 of the image display, is a point at which r = Lv, and a pu The outermost direction in a horizontal direction (ie an address along a line H) of the area 9 of the image display is a point at which r = LH- Figure 3 is an explanatory diagram showing a cross section taken along the diagonal line of the color image tube panel and indicating the conditions that are satisfied by the internal surface of the panel according to the first embodiment. The panel 1 in the color image tube according to the first embodiment is formed to be rotationally symmetric with respect to the Z axis and also to meet the requirements described below. When a position Z of a point on the internal surface of the panel 1 in the direction of the Z axis is expressed by an equation Z = f (r) as a function of a variable r, a value of a first derivative df (r) '/ dr of f (r) in the image display area 9 (not shown in Figure 3) on the inner surface of the panel 1 is zero in a first area 11 within the image display area 9 including the point where r = 0. Furthermore, a value of df (r) / dr is negative in a second area 12 within the image display area 9 from the outside of the first area 11 with respect to the point where r = L? Incidentally, in this mode, the first area 11 consists only of the point at which r = 0. The first area 11, however, may be greater than that in this mode.

In addition, a value of a second derivative d2f (r) / dr2 of f (r) in the image display area 9 on the internal surface of the panel 1 is negative in a third area 13 within the image display area 9 from the point where r = 0 relative to the interior of a point at which r = R2, where the point at which r = R2 is within the second area 12 (ie, from the point at which r = 0 to a point at which r = R2, but not including the point at which r = R2, where the point at which r = R2 is within the second area 12). A value of d2f (r) / dr2 is zero at the point at which r = R2, and positive at a fourth area 14 within the image display area 9 from outside the point at which r = 2 / a point where r = L¿ (that is, from the point where r = R2 but not including the point where r = R2, to the point where r = L¿). Further, when a thickness of the panel 1 in the second area 12 in the direction of the Z axis is represented by DR and a thickness of the panel 1 in the first area 11 in the direction of the Z axis direction is represented by TQ, DR / TQ > 1 is satisfied.

Still further, the outer surface Ib of the panel 1 is substantially flat, which means that a radius of curvature of the outer surface is not less than 60000 [mm] indicating a slightly convex surface and not greater than -60000 [mm] indicating a slightly concave surface The position of the point at which r = R2 satisfying the equation d2f (r) / dr2 = 0 is preferably set to meet a relation 0.4L¿ <; R2 = 0.85L¿. When a position of the center of the inner surface of that of panel 1 is expressed by the point where f (r) = 0, a shape of the inner surface of panel 1 can be expressed, for example, by the following equations: Z = f (r) = r2 (ar2 + b) a = 1.4787e-9 b = -6. 161e-5 The above equations indicate that the shape of the inner surface of the panel 1 is rotated substantially symmetrically with respect to the Z axis.

Now, it will be assumed that a thickness of the panel 1 at its center in the direction of the Z axis is represented by TQ, and a thickness of a ridge (in which r = L¿) of the panel 1 the diagonal direction is expressed by an equation TD = Tg +? TD. Then, if TQ is 13.0 [mm], for example,? TD becomes 0.675 [mm]. ? TD indicates an increase in thickness TQ from the center of panel 1 to the point at which r = L ?, and designated as a triangular prism. In this embodiment the internal surface of the panel 1 becomes non-spherical, being formed in such a way that the radius of the curvature around the center of the inner surface is approximately 8500 [mm] and the radius of curvature around the rim of the The inner surface is greater than 8500 [mm]. With this arrangement, the apparent floating distortion of the portion of the image around the rim of the inner surface of the panel 1 is greatly reduced, and at the same time, the floating of the portion resulting from the radius of curvature of about 8500 [mm] around the center of the inner surface of panel 1 can be recognized. By arranging the inner surface of the panel 1 to be non-spherical in this way, an apparent screen 15 can be made flatter, as shown by a chained line in Figure 4.

As described above, in the color picture tube according to the first embodiment, the internal surface of the panel 1 is configured to meet the requirements described above. Therefore, the apparent screen can be made flatter in such a way that a higher quality image can be displayed.

Second Mode Figure 5 is an explanatory diagram showing a cross section taken along a diagonal line of a panel of a color picture tube and indicating the conditions that are satisfied by an internal surface of the panel according to a second embodiment of the present invention. As shown in Figure 5 a shape of panel 1 of the color picture tube according to the second embodiment is formed to be rotationally symmetric with respect to the Z axis and also to satisfy the requirements that will be described later. With reference to Figure 1, Figure 2 and Figure 5, when a Z position of a point on the inner surface of the panel 1 in the direction of the Z axis is expressed by an equation Z = f (r) as a function of a variable r in the same maiera as in the first embodiment, a value of a first derivative df (r) / dr of f (r) over the image display area 9 (not shown in Figure 5) over the The internal surface of panel 1 is zero in a first area 21 within the image display area 9 including the point at which r = 0. Furthermore, the value of df (r) / dr is negative in a second area 22 within of the image display area 9 from the outside of the first area 21 to the interior of a point at which r = Ri fi being less than L¿ (ie from the outside of the first area 21 to a point at which = R * L, but not including the point at which r = R ^ and R j_ being less than L¿). Still further, the value of df (r) / dr is zero at the point where r = R ^, and is positive in a third area 23 within the image display area 9 from outside the point at which r = R] _ to the point at which r = L¿ (that is, from the point at which r = R ^ _, but not including the point at which r = R- ^, at the point at which r = Ld). Incident ally, in this mode, the first area 21 consists only of the point at which r = 0. The first area 21, however, may be greater than that in this mode.

In addition, a value of a second derivative d2f (r) / dr2 of f (r) in the image display area 9 on the internal surface of the panel 1 is negative in a fourth area 24 within the image display area 9 from the point where r 0 relative to the interior of a point where r = R2, is within the second area 22 (ie, from the point at which r = 0 to a point at which r = R2 / but not including the point at which r = R2) • The value of d2f (r ) / dr2 is zero at the point where r = R2, and is positive in a fifth area 25 within the image display area 9 from outside the point at which r = R2, at the point at which r = L¿ (that is, from the point where r = R2 but not including the point * where r = R2, to the point where r = L¿). Further, when a thickness of the panel 1 in the second area 22 in the direction of the Z axis is represented by DR and a thickness of the panel 1 in the first area 21 in the direction of the Z axis is represented by T, a condition DR / T0 >; 1 sat i s face. Still further, the outer surface Ib of the panel 1 is substantially flat, which means that a radius of curvature of the outer surface is not less than 60000 [mm] indicating a slightly convex surface and not greater than -60000 [mm] indicating a slightly concave surface The position of the point at which r = R2 satisfying the equation d2f (r) / dr2 = 0 is preferably set to meet a ratio 0.2Li = R2 < 0.65L, and the position of the point r = R] _ satisfying the equation df (r) / dr = 0 is preferably set to meet the condition 0.6L¿ < R ^ < 1.0 L? In addition, R] _ is greater than R2 • When a position of the center of the inner surface of panel 1 is expressed by an equation f (r) = 0, a shape of the inner surface of panel 1 can be expressed, for example , by means of the following equations: Z = f (r) = r2 (ar2 + b) a = 4.626e-9 b = -9.4096e-5 The above equations indicate that the shape of the inner surface of the panel 1 is rotationally symmetric with respect to the Z axis. Now, it is assumed that a thickness of the panel 1 at its center in the direction of the Z axis is represented by TQ, and a thickness of a flange (in which r = L) of panel 1 in the diagonal direction is expressed by an equation TD = TQ +? TD. Then, if TQ is 13.0 [mm], for example,? TD becomes 0.20 [mm]. ? TD indicates an increase in thickness TQ from the center of panel 1 to the point at which r = L¿, and designated as a triangular prism. Further, in the second embodiment the inner surface of the panel 1 becomes non-spherical, being formed in such a way that the radius of the curvature around the center of the inner surface is approximately 8500 [mm] and the radius of curvature around The flange of the inner surface is greater than 8500 [mm]. With this provision,. the apparent floating distortion of the portions of the image around the rim of the inner surface of the panel 1 is greatly reduced, and at the same time, the floating of the portion resulting from the radius of curvature of about 8500 [mm] around the center of the internal surface of panel 1 can be recognized. By arranging the inner surface of the panel 1 to be non-spherical in this way, an apparent screen recognized by the observer can become flatter.

As described above, in the color picture tube according to the second embodiment, the internal surface of the panel 1 is configured to meet the requirements described above. Therefore, the apparent screen can be made flatter in such a way that a higher quality image can be displayed.

Third Mode Figure 6 is an explanatory diagram showing a cross section taken along the diagonal line of a panel of a color picture tube and indicating the conditions that are satisfied by an internal surface of the panel in accordance with a third embodiment of the present invention. In Figure 6, structural elements that are identical or correspond to those in Figure 3 in the first embodiment are designated by the same reference numbers or characters. The color image tube according to the third embodiment is different from that described in the above according to the first embodiment only in that the outer surface Ib of the panel 1 is slightly convex and has the radius of curvature of 20000 [mm ] In the color image tube according to the third embodiment, the apparent screen can be made flat, so that a higher quality image can be displayed. Furthermore, the apparent floating distortion of the image can be corrected not only by the internal surface of the panel 1 but also by the outer surface Ib of the panel 1. Figure 7 shows the characteristic curves indicating a relationship indicated by the solid line 41 between a radius of curvature about a center of the inner surface of the panel and an apparent floating distortion of an apparent phosphor-screen, and a ratio indicated by the dotted line 42 between a radius of curvature about a center of the outer surface of the panel and an apparent floating distortion of an apparent phosphor screen. As seen from Figure 7, the inner surface is rotationally symmetric with the radius of curvature RP being 8500 [mm], for example, the apparent floating distortion is +0.56 [mm] in the direction of the Z axis. If the outer surface Ib is rotationally symmetric with the radius of curvature RP being 20000 [mm] for example, the apparent floating distortion is -0.24 [mm] in the direction of the Z axis. Consequently, in the center of panel 1 only, the Apparent floating distortion shall be a sum of +0.56 [mm] and -0.24 [mm], namely +0.32 [mm]. The characteristic curves in Figure 7 can be used to design the apparent screen to be flat. The third modality is identical to the first modality previously described in all those with respect to others than those previously explained.

Fourth Mode Figure 8 is an explanatory diagram showing a cross section taken along the diagonal line of a panel of an image tube - colored and indicating the conditions that are satisfied by an internal surface of the panel according to with a fourth embodiment of the present invention. In Figure 8, the structural elements that are identical or correspond to those in Figure 5 in the second embodiment are designated by the same numbers or characters. The color image tube according to the fourth embodiment is different from that of the second embodiment described above only in that the outer surface of the panel 1 is slightly convex "and has the radius of curvature of 20000 [mm]. In the color image tube according to the fourth embodiment, an apparent screen can be made flat, so that a higher quality image can be displayed. In addition, an apparent floating distortion of the image can be corrected not only by the internal surface of panel 1, but also by the external surface Ib of panel 1. In all aspects different from those discussed above, the fourth embodiment is identical to the second modality Fifth Mode In the first to fourth modes, a description has been directed to cases in which the inner surface of the panel 1 is rotationally symmetric with respect to the axis Z. The present invention, however, is not limited to this. The inner surface of the panel 1 can be rotationally asymmetric and have different configurations between a cross section cut on a horizontal plane including the Z axis and the horizontal H axis (shown in Figure 2) and a cross section cut of a vertical plane including the Z axis and the vertical V axis (shown in Figure 2), provided that the shape of the panel 1 is formed to meet the requirements described above. For example, a curvature of a cross section of the inner surface that is taken along the vertical axis V is smaller than that taken along the horizontal axis H (ie, the inner surface of the panel 1 is formed to be more flat), and the inner surface of the panel 1 is formed to be both both continuous and smooth. In this case a change of curvature R of the internal surface of the panel 1 in an area between the vertical axis V and the horizontal axis H, at an angle? with respect to the vertical axis V it can be calculated by means of the following equation: 1 / R2 = (eos2 T) / RV2 + (sin2 T) / RH2 wherein RV represents a radius of curvature of the cross section of the inner surface of the panel 1 taken along axis V, and RH represents a radius of curvature of the cross section of the inner surface of the panel 1 taken along of the horizontal axis H.

This rotationally asymmetric panel 1 is suitable for use with a shadow mask of a type of shadow grid the surfaces of which are straight when the shadow mask is cut vertically and are curved when cut horizontally. The internal surface of the panel 1 is designed based on a distance between the inner surface of the panel 1 and a shadow mask 7 (shown in Figure 2), a distance from a deflection center of an electronic beam to the screen of phosphor 3, a space of perforations in the mask 7 of shadow and imi lares. By forming the inner surface of the panel 1 to be rotationally asymmetric, the static resistance of the color picture tube increases, while at the same time the color picture tube can be made light. In this embodiment, a description has been addressed to the case in which the internal surface of panel 1 is formed to be rotationally asymmetric. The present invention is not limited to this. The outer surface of the panel Ib can be formed to be rotatably asymmetrically, alternatively.

In all other aspects different from those previously discussed, the fifth modality is identical to any of the first to the fourth modalities. The invention being described, it should be obvious that it can be varied in many ways. Such variations are not to be considered as a point of departure from the spirit and scope of the invention, and all modifications as will be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims (10)

1. A color image tube comprising: a panel (1), an internal surface (a) which has an image display area (9); and a phosphor screen (3) provided throughout the image display area (9) on the inner surface (la) of the panel (1), to show an image when subjected to irradiation of an electron beam ( 5); wherein: a Z axis is superimposed on an axis of the tube that passes through a center of the panel (1) and being normal with respect to such panel (1); an address from inside the color picture tube to an observer is set to be in a positive direction of the Z axis; A radial distance from the Z axis is denoted by r; a point at which the Z axis intersects the internal surface (la) of the panel (1) is denoted by a point at which r = 0; an outermost point in a diagonal direction of the image display area (9) is denoted by a point at which r = L¿; a position of a point on the internal surface (la) of the panel (1) in a direction of the Z axis is expressed by f (r) being a function of r, - a value of df (r) / dr which is a first derived from f (r) is zero in a first area within the image display area (11) (9) which includes a point at which r = 0, and is negative at a second area (12) within the area of image display (9) from the outside of the first area (11) to the point at which r = Ld; a value of d2f (r) / dr2 that is a second derivative of f (r) is negative in a third area (13) within the viewing area. of image (9) from the point where r = 0 inside a point where r = R2 being inside the second area (12), is zero at the point where r = R2 and is positive in the fourth area (14) within the image display surface '(9) from the outside of the point r = R2 to the point at which r = Ld; and a thickness (DR) of the panel (1) in the second area (12) in the direction of the Z axis is greater than a thickness (TQ) of the panel (1) in the first area (11) in the direction of the Z axis .

2. The color image tube according to claim 1, wherein the following condition is satisfied: 0. Ld < R2 = 0.85 L¿

3. A color image tube comprising: a panel (1), an internal surface (a) which has an image display area (9); and a match screen (3) provided throughout the image display area (9) on the inner surface (la) of the panel (1), to show an image when subjected to irradiation of an electron beam (5); wherein: a Z axis is superimposed on an axis of the tube that passes through a center of the panel (1) and being normal with respect to the panel (1); an address from inside the color picture tube to an observer is set to be in a positive direction of the Z axis; A radial distance from the Z axis is denoted by r; a point at which the Z axis intersects the internal surface (la) of the panel (1) is denoted by a point at which r = 0; an outermost point in a diagonal t direction of the image display area (9) is denoted by a point at which r - Ld; a position of a point on the inner surface 5 of the panel (1) in a direction of the Z axis is expressed by f (r) being a function of r; a value of df (r) / dr which is a first derivative of f (r) is zero in a first area (21) within the image display area (9) that includes a point at which r = 0, is negative in a second area (22) within the viewing area. image (9) from the outside of the first area "to the interior (21) of a point where r = R] _, where R ^ is less than Ld is zero at a point 15 where r = R * ] _ and is positive in a third area (23) within the image display area (9) from outside the point where r = R- ^ to a point where r = Ld; a value of df ( r) / dr2 which is a second derivative of f (r) is negative in a fourth area within the area (24) of visualization (9) of the image from the point where r = 0 inside a point in which r = R being within the second area (22), is zero at the point where 25 r = R2 and is positive in a fifth area within the area (25) of image display (9) from the outside from the point r = R2 to the point where r =

Ld; and a thickness (DR) of such panel (1) in the second area (22) in the direction of the Z axis is greater than a thickness (TQ) of the panel (1) in the first area (21) in the direction of the axis Z. The color image tube according to claim 3, wherein the following conditions are satisfied: 0.2Ld < R2 < 0.65Ld 0.6Ld < -L < 1.0Ld Rl > R2

5. The color image tube according to any of claims 1-4, wherein an outer surface (Ib) of the panel (1) is of a substantially planar shape with a radius of curvature of not less than 60000 [mm] or not greater than -60000 [mm].

6. The color image tube according to any of claims 1-4, wherein an outer surface (Ib) of the panel (1) is of a convex shape with a radius of curvature below 60000 [mm].

7. The color image tube according to claim 6, wherein the radius of curvature of the outer surface (Ib) of the panel (1) is greater than a radius of curvature about a center of the inner surface (the) of the panel (1).

8. The color image tube according to any of claims 1 to 4, wherein the inner surface (la) of the panel (1) is rotationally symmetrical with respect to the axis Z.

9. The color image tube with any of claims 1 to 4, wherein the outer surface (Ib) of the panel (1) is rotationally symmetrical with respect to the Z-axis.

10. The color image tube according to any of claims 1 to 4, wherein the inner surface (la) of the panel (1) is rotatably asymmetric with respect to the axis Z and has different configurations between a cross section cut on a horizontal plane including the Z axis and a cross section cut on a vertical plane including the Z axis.