JP2005310597A - Color picture tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color picture tube in which reflecting beams generated when a part of electron beams emitted from an electron gun collide into an aperture edge or aperture inner wall does not make an unnecessary phosphor emit light. <P>SOLUTION: The shadow mask 7 is constructed of a main mask 12 in which apertures for defining the shape of electron beams are formed and an auxiliary mask 22 which is fixed overlapping the phosphor screen side throughout the all regions of the porous part of the main mask 12 and in which apertures are formed corresponding to the location of the apertures of the main mask 12. The apertures of the main mask 12 and the auxiliary mask 22 are constructed of communicating holes in which small holes 16, 26 formed on the surface of the electron gun side and large holes 17, 27 formed on the surface of the phosphor screen side are communicated. The minor axis side aperture edge 29 of the small hole 27 of the auxiliary mask 22 is positioned on the screen periphery side than the minor axis side aperture edge 19 of a corresponding large hole 17 of the main mask 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color picture tube applied to a television receiver, a computer display, and the like, and more particularly to the structure of a shadow mask used therefor. More particularly, the present invention relates to a color picture tube that has high contrast and high color purity and does not emit unnecessary phosphors.

  In general, in a color picture tube, a rectangular shadow mask for restricting the arrival position of an electron beam emitted from an electron gun is arranged facing a phosphor screen formed on the inner surface of a rectangular panel. ing. This shadow mask is fixed to the mask frame via a skirt formed by bending at the outer periphery. A large number of apertures are formed in a predetermined arrangement on the effective surface of the shadow mask facing the phosphor screen, and R (red), G (green), and B (blue) emitted from the electron gun. The three electron beams corresponding to the respective colors are subjected to color selection by the respective openings of the shadow mask and are incident on the three-color phosphors constituting the phosphor screen.

  There are roughly two types of shadow mask apertures: circular and rectangular. For display tubes that display characters and graphics, shadow masks with circular apertures are mainly used. A shadow mask having a rectangular opening is mainly used for a consumer color picture tube used at home. In any of the shadow masks, the opening basically consists of a communication hole in which a small hole formed on the surface on the electron gun side and a large hole formed on the surface on the phosphor screen side communicate with each other. The diameter at the communicating portion between the small hole and the large hole substantially defines the opening diameter.

  Since the opening of the shadow mask is formed by etching from both the electron gun side surface and the phosphor screen side surface, the inner wall thereof is rounded. During the operation of the color picture tube, a part of the electron beam incident on the shadow mask collides with the inner wall of the small hole, and the inner wall of the small hole is rounded as described above. The electron beam that collided with is reflected in all directions (hereinafter, the electron beam that collided with the inner wall of the small hole and reflected was referred to as a “reflected beam”). As a result, the reflected beam that has escaped from the large hole portion of the shadow mask toward the phosphor screen reaches the phosphor screen, causing unnecessary phosphors to emit light, causing deterioration in contrast and color purity.

  Further, when a white bar pattern is displayed on the periphery of the screen, the phosphor on the short axis side than the pattern emits light unnecessarily over a wide range. This is because a reflected beam is generated in all the apertures in the area on the shadow mask corresponding to the position where the white bar pattern is displayed, and these reflected beams travel in opposite directions due to the large incident angle of the electron beam. This is because the amount increases.

  As a technique for solving the above-mentioned problems with a shadow mask having a rectangular aperture shape, the shadow mask aperture is arranged on the phosphor screen side surface with respect to the small holes formed on the electron gun side surface. It has been proposed to make the formed large hole an eccentric hole by shifting the large hole in the width direction or the direction in which both the width direction and the longitudinal direction of the electron beam pass (see, for example, Patent Documents 1 and 2).

  Further, as a technique for suppressing a reflected beam generated when a part of an electron beam incident on a shadow mask collides with an inner wall of a small hole, as shown in FIG. The angle α formed between the tangent line 45 drawn along the electron beam 43 passing through and the perpendicular 46 passing through the center of the aperture is formed to be larger than the angle β formed between the trajectory of the electron beam 43 and the perpendicular 46. It has been proposed (see, for example, Patent Document 3).

  By the way, recently, the use ratio of a flat panel display is increasing as a terminal of a personal computer and an engineering workstation (EWS). However, a large number of display tubes are still used as a desktop. On the other hand, as a color picture tube for general home use, a flat square tube having a flat screen with little reflection of external light and little image distortion has become the mainstream from the ergonomic viewpoint in the direction of enlargement. ing. In addition, recently, a completely flat tube in which an outer surface of a panel for displaying an image has a substantially perfect flat shape similar to that of a plate glass has gained popularity.

  In general, the effective face of the shadow mask facing the phosphor screen is formed in a shape corresponding to the inner shape of the panel, and the shadow mask of the flat square tube has a smaller curvature than the shadow mask of the conventional color picture tube, A completely flat tube shadow mask has a smaller curvature and a flat shape. For this reason, in the case of a complete flat tube, the incident angle of the electron beam incident on the opening in the peripheral portion of the effective surface of the shadow mask is further increased as compared with the case of the flat square tube. As a result, the above-described problem becomes remarkable in a complete flat tube or the like in which the incident angle of the electron beam incident on the aperture of the shadow mask is large, and the image quality is greatly deteriorated.

  Further, in recent years, a shadow mask for high resolution has been required to have a small aperture pitch. However, the smaller the aperture pitch, the greater the number of apertures, so that the generation ratio of the reflected beam increases. The problem is more serious.

  On the other hand, a shadow mask configured by laminating and joining a plurality of flat mask plates has been proposed (see, for example, Patent Documents 4 and 5).

  Also, in a shadow mask constructed by laminating and joining a plurality of flat mask plates, the positional relationship of the apertures of each flat mask plate to prevent the electron beam from colliding with the inner walls of the small holes It has been proposed that the taper amount of the large hole is made appropriate (see, for example, Patent Document 6).

In addition, in a shadow mask constructed by laminating and joining a plurality of flat mask plates, the aperture width of the flat mask plate on the electron gun side is eliminated in order to eliminate variations in the electron beam passage area due to shadow mask assembly errors. And the ratio of the aperture width of the flat mask plate on the phosphor screen side to 1.4 to 1.8 has been proposed (see, for example, Patent Document 7).
Japanese Patent Laid-Open No. 50-142160 JP-A-57-57449 JP-A-7-65737 JP-A-2-172142 JP-A-2-123645 JP-A-3-67440 Japanese Patent Laid-Open No. 9-22664

  As described above, in Patent Documents 1 and 2, in order to prevent a part of the electron beam incident on the shadow mask from colliding with the opening edge or the inner wall of the opening, the opening of the shadow mask is arranged on the electron gun side. By shifting the large holes formed on the phosphor screen side surface in the width direction or in the direction in which both the width direction and the longitudinal direction exit the electron beam, the eccentric holes are formed. However, when this configuration is adopted, the incident angle of the electron beam incident on the aperture of the shadow mask becomes larger in a completely flat tube. As a result, the amount of the reflected beam going to the screen increases, and the contrast and color purity of the entire screen deteriorate, and the image quality deteriorates. Furthermore, in the shadow mask with a small aperture pitch that has been required in recent years, the generation ratio of the reflected beam increases as described above, and this problem becomes more serious.

  In addition, as described above, in Patent Document 3, in order to suppress the reflected beam generated when a part of the electron beam incident on the shadow mask collides with the inner wall of the small hole, the cross-sectional shape of the inner wall of the small hole is changed. Although it has been proposed to have a knife edge shape, when this configuration is adopted, the generation rate of the reflected beam can be reduced as the height of the inner wall of the small hole is reduced. The etching rate when the small holes communicate with each other increases, and the control of the opening width becomes extremely difficult.

  On the other hand, in Patent Document 4, a plurality of flat mask plates are laminated and joined, the opening width of the small holes of the flat mask plate on the electron gun side is 150 μm, and the opening width of the large holes of the flat mask plate on the electron gun side Is set to 280 μm, the aperture width of the small hole of the flat mask plate on the phosphor screen side is set to 280 μm, and the aperture width of the large hole of the flat mask plate on the phosphor screen side is set to 420 μm. The shadow mask disclosed in Document 4 has a double structure for the purpose of suppressing local doming. The aperture width as described above is set in order to prevent the passage area of the electron beam from being reduced due to the positional deviation when the flat mask plates are overlapped. No consideration is given to the effect of the mask plate shielding the reflected beam.

  Further, in Patent Document 5, a plurality of flat mask plates are laminated and joined, the opening width of the small holes in the flat mask plate on the electron gun side is 150 μm, and the opening width of the large holes in the flat mask plate on the electron gun side Is set to 280 μm, the aperture width of the small hole of the flat mask plate on the phosphor screen side is set to 270 μm, and the aperture width of the large hole of the flat mask plate on the phosphor screen side is set to 420 μm. Similarly to the shadow mask disclosed in Patent Document 4, the shadow mask disclosed in Document 5 has a double structure for the purpose of suppressing local doming. In addition, as with the shadow mask disclosed in Patent Document 4, the aperture width as described above is also used to prevent the electron beam passage area from being reduced due to the positional deviation when the flat mask plates are overlapped. It is set, and no consideration is given to the effect of the flat mask plate on the phosphor screen side blocking the reflected beam. The distance between the center position of the small hole of the flat mask plate on the electron gun side and the large hole of the flat mask plate on the electron gun side and the short axis side opening edge of the small hole of the flat mask plate on the phosphor screen side is Both are 120 μm, and the effect of shielding the reflected beam cannot be obtained depending on the small hole side surface of the flat mask plate on the phosphor screen side.

  In addition, as described above, in Patent Document 6, in order to prevent the electron beam from colliding with the inner wall of the small hole by laminating and joining a plurality of flat mask plates, It has been proposed that the positional relationship and the taper amount of the large hole be appropriate, but when this configuration is adopted, the reflected light beam collides with the inner wall of the small hole of the flat mask plate on the electron gun side when this configuration is adopted. This phenomenon cannot be prevented, and Patent Document 6 does not take into consideration the relationship between the method of shielding the generated reflected beam and the aperture width of each flat mask plate.

  Also, as described above, in Patent Document 7, in order to eliminate the variation in the electron beam passage area due to the assembly error of the shadow mask by laminating and joining a plurality of flat mask plates, the flat mask plate on the electron gun side is opened. Although it has been proposed to set the ratio of the hole width to the hole width of the flat mask plate on the phosphor screen side to 1.4 to 1.8, the shadow mask disclosed in Patent Document 7 In order to improve the above, a double structure is used. Further, the above aperture ratio: 1.4 to 1.8 is set to prevent the passage area of the electron beam from being reduced due to the positional deviation when the flat mask plates are overlapped. There is no consideration given to the effect of the flat mask plate on the phosphor screen side blocking the reflected beam. Moreover, in the color picture tube in which the generation ratio of the reflected beam is increased with the recent flattening of the outer surface of the panel and the reduction of the aperture pitch, the aperture ratio as described above: 1.4 to 1.8. Even if the shadow mask is used, a sufficient shielding effect of the reflected beam cannot be obtained.

  The present invention has been made in order to solve the above-described problems in the prior art, and is caused by a part of the electron beam emitted from the electron gun colliding with the aperture edge or the inner wall of the aperture of the shadow mask. An object of the present invention is to provide a color picture tube that does not emit phosphors that do not require a beam.

  In order to achieve the above object, the color picture tube according to the present invention comprises a bulb comprising a panel having a phosphor screen made of phosphors of a plurality of colors on the inner surface and a funnel connected to the rear of the face panel. The electron gun built in the neck portion of the funnel, and the phosphor screen arranged at a predetermined position facing the phosphor screen, perpendicular to each other and perpendicular to the tube axis, A color picture tube comprising a rectangular shadow mask having a short axis, wherein the shadow mask includes a main mask having an aperture through which an electron beam passes, and the entire perforated portion of the main mask. The auxiliary mask is fixed to overlap with the phosphor screen and has an opening formed in accordance with the position of the opening of the main mask. The opening of the main mask and the auxiliary mask A small hole formed on the surface on the electron gun side and a large hole formed on the surface on the phosphor screen side communicated with each other, and the short axis side opening edge of the small hole of the auxiliary mask Is located on the peripheral side of the screen with respect to the opening edge on the short axis side of the large hole corresponding to the main mask.

  In the color picture tube of the present invention, the distance from the center of the long axis of the perforated part to the end along the long axis is L, and the width of the large hole of the main mask is D. 'main, where the width of the small hole corresponding to the auxiliary mask is Dsub, and the offset amount of the center position of the corresponding small hole of the auxiliary mask with respect to the center position of the large hole of the main mask is Z, It is preferable that the relationship of the following formula (1) is satisfied at any position where the distance along the major axis from the center of the major axis is in the range of 0.7L to 1L.

Dsub ≦ 0.2D′main + 2Z (1)
In the configuration of the color picture tube of the present invention, it is preferable that the radius of curvature of the outer surface of the panel is 10,000 mm or more.

  According to the configuration of the color picture tube of the present invention, when the electron beam emitted from the electron gun enters the main mask, a part of the inner wall of the small hole on the surface of the main mask opening on the electron gun side It is possible to prevent an unnecessary phosphor from emitting light by a reflected beam generated by colliding with the light. As a result, it is possible to improve contrast and color purity.

  Further, in the configuration of the color picture tube of the present invention, according to the preferable example satisfying the relationship of the above formula (1), the reflected beam can be effectively shielded, so that a high-quality color picture tube is provided. It becomes possible to do.

  In the configuration of the color picture tube of the present invention, according to a preferred example in which the radius of curvature of the outer surface of the panel is 10000 mm or more, the reflected beam can be shielded more effectively.

  Hereinafter, the present invention will be described more specifically using embodiments.

  FIG. 1 is a cross-sectional view including a horizontal axis (X axis) of a screen showing the overall configuration of a color picture tube according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view including a vertical axis (Y axis) of the screen. .

  As shown in FIGS. 1 and 2, the color picture tube of the present embodiment includes a rectangular panel 1 formed of glass or the like having a horizontal axis (X axis) as a major axis, and a side wall portion 2 of the panel 1. A valve (vacuum envelope) comprising a funnel 3 formed of glass or the like having a funnel-like shape and a neck portion 4 that is integrated with the funnel 3 and extends rearward. The electron gun 10 is provided. On the inner surface of the panel 1, there is formed a phosphor screen 5 composed of a dot- or stripe-shaped three-color phosphor layer that emits R (red), G (green), and B (blue) and a black light shielding layer. Yes. Here, the electron gun 10 emits in-line three electron beams 9R, 9G, and 9B composed of a center beam and a pair of side beams that pass on the same horizontal plane toward the phosphor layer of the phosphor screen 5. Is an electron gun. In addition, a shadow mask structure 6 for restricting the arrival positions of the electron beams 9R, 9G, and 9B emitted from the electron gun 10 is disposed at a predetermined position in the bulb so as to face the phosphor screen 5. Yes. The funnel 3 has a vertical deflection coil and a horizontal deflection coil on the outer periphery of the neck portion 4 side for deflecting the electron beams 9R, 9G, and 9B emitted from the electron gun 10 in the vertical direction and the horizontal direction. A deflection yoke 11 is mounted.

  In the color picture tube having the above-described configuration, the electron beams 9R, 9G, and 9B emitted from the electron gun 10 are deflected in the horizontal direction and the vertical direction by the horizontal deflection magnetic field and the vertical deflection magnetic field generated by the deflection yoke 11. The image is displayed by passing through the shadow mask structure 6 and scanning the phosphor screen 5 horizontally and vertically.

  The shadow mask structure 6 includes a shadow mask 7 that is a color selection electrode in which a large number of openings serving as electron beam passage holes are formed, and a mask frame 8 having an L-shaped cross section that fixes the periphery of the shadow mask 7 and a rectangular mask frame 8. An elastic support (not shown) provided on the side wall of the mask frame 8 is engaged with a stud pin (not shown) embedded in the side wall 2 of the panel 1, so that the inner surface of the panel 1 is fixed. It is supported. Incidentally, the opening as the electron beam passage hole of the shadow mask 7 is formed in a rectangular shape or a circular shape depending on the application.

  Taking a 32-inch (76 cm) wide color picture tube with an aspect ratio of 16: 9 as an example, the outer surface shape of the panel 1 is substantially flat with a radius of curvature of 100,000 mm. The inner surface has a radius of curvature of about 7000 mm along the horizontal axis (X axis) and a radius of curvature of about 1500 mm along the vertical axis (Y axis).

  Next, the structure of the shadow mask 7 of this Embodiment is demonstrated using FIGS. 3 is a cross-sectional view including a horizontal axis (X-axis) of a screen showing a shadow mask in one embodiment of the present invention, and FIG. 4 is a cross-sectional view including a vertical axis (Y-axis) of the screen showing the shadow mask. 5 is a cross-sectional view including the horizontal axis (X axis) of the screen showing the aperture shape of the shadow mask.

  As shown in FIGS. 3 and 4, the shadow mask 7 of the present embodiment includes a main mask 12 in which an opening defining the shape of the electron beam is formed, and a phosphor over the entire perforated portion of the main mask 12. The auxiliary mask 22 is fixed on the screen 5 in an overlapping manner and has an opening formed in accordance with the position of the opening of the main mask 12. As described above, the shadow mask 7 of the present embodiment has a double-layer structure on the entire mask surface. In this specification, the shadow mask plate positioned on the electron gun 10 side is referred to as a “main mask”, and the fluorescence mask The shadow mask plate located on the body screen 5 side is referred to as “auxiliary mask”.

  Hereinafter, the configurations of the main mask 12 and the auxiliary mask 22 will be described in more detail.

  The two shadow mask plates (the main mask 12 and the auxiliary mask 22) are fixed in a flat state after the positional relationship is determined using positioning openings formed in each of them. This is for ensuring the positional accuracy of the opening as the electron beam passage hole. In order not to prevent the passage of the electron beam, the positions of the openings of both shadow mask plates need to be strictly matched. If each shadow mask plate is molded into a curved shape by press processing and if the positions of the holes in both shadow mask plates are adjusted, if the molding position shifts during pressing, it will also cause a shift in the aperture position. It becomes difficult to make the apertures of the shadow mask plates coincide. Moreover, since both shadow mask plates come to have a curved shape after press molding, it is extremely difficult to match the positions of both.

  For the above reasons, in the present embodiment, both shadow mask plates are positioned and fixed in a flat state before press molding, and then press molded.

  The auxiliary mask 22 is fixed to the main mask 12 by laser welding the perforated portion 23 and the non-porous portion 24 to the main mask 12. Laser welding of the perforated part 23 is performed by irradiating a laser from the auxiliary mask 22 side. At that time, the laser is irradiated to the region between the aperture rows extending substantially linearly along the vertical axis (short axis) direction.

  The auxiliary mask 22 is fixed to the main mask 12 in a state in which the perforated portion 23, the non-perforated portion 24, and the skirt portion 25 overlap the perforated portion 13, the non-perforated portion 14 and the skirt portion 15 of the main mask 12, respectively. Thus, the entire surface of the shadow mask 7 has a double structure.

  As the material of each of the main mask 12 and the auxiliary mask 22, a metal material such as an invar material (Fe-36% Ni alloy) known as an iron material or a low thermal expansion material having a plate thickness of about 0.1 to 0.25 mm is used. be able to. It is desirable that the material constituting the auxiliary mask 22 has a thermal expansion coefficient close to that of the material constituting the main mask 12, and ideally, the material having the same thermal expansion coefficient is desirable. Since the shadow mask 7 receives heat of about 400 ° C. during the manufacturing process of the color picture tube, if the thermal expansion coefficient differs greatly between the main mask 12 and the auxiliary mask 22, the shadow mask 7 becomes bimetallic and undergoes heat treatment. This is because even if the mask 7 is deformed or not completely deformed, the shape of the shadow mask 7 varies.

  Each aperture of the main mask 12 and the auxiliary mask 22 is formed in a rectangular shape with the horizontal axis (X-axis) direction of the perforated portions 13 and 23 as a width direction, and a plurality of apertures are formed in the perforated portions 13 and 23. A plurality of aperture rows arranged linearly in the vertical axis (Y-axis) direction via the bridge portion are arranged at a predetermined arrangement pitch PH in the horizontal axis (X-axis) direction.

  As shown in FIG. 5, each opening of the main mask 12 and the auxiliary mask 22 is formed in the small hole 16 (26) formed on the surface on the electron gun 10 side and on the surface on the phosphor screen 5 side. The shadow mask 7 has a communication hole that communicates with the large hole 17 (27), and the shadow mask 7 has a center position of the large hole 17 (27) relative to a center position of the small hole 16 (26) as it goes to the periphery of the screen. It is a so-called “offset mask” that is offset to the periphery of the screen. Further, the center position of the small hole 26 of the auxiliary mask 22 is offset toward the periphery of the screen so as to match the incident angle of the electron beam with respect to the center position of the small hole 16 of the main mask 12. Further, the short axis (vertical axis) side opening edge 29 of the small hole 26 of the auxiliary mask 22 is positioned closer to the screen periphery than the short axis side opening edge 19 of the corresponding large hole 17 of the main mask 12. .

  Next, the effect brought about by the shadow mask 7 of the present embodiment having the above structure will be described with reference to FIGS.

  As shown in FIG. 6A, when a conventional single-layer shadow mask 35 (corresponding to the main mask 12 of this embodiment) is used, a part of the incident beam 30 incident on the shadow mask 35 is used. Collides with the inner wall of the small hole on the surface of the electron gun 10 side of the aperture, and the reflected beam 31 generated thereby passes from the large hole portion to the phosphor screen 5 side and reaches the phosphor screen 5. Since the energy density of light is inversely proportional to the square of the distance, as shown in FIG. 7A, the energy density of the reflected beam 31 generated in one aperture and reaching the phosphor screen 5 (hereinafter referred to as “inner wall reflection”). The distribution of 34 (referred to as “energy density”) has a maximum value at a certain position, and becomes a mountain-shaped distribution that decreases from the position of this maximum value to the periphery. In FIG. 7A, the horizontal axis partially shows the irradiation position of the reflected beam on the corresponding phosphor screen 5 for one aperture, and the vertical axis shows the energy density (this is described below). The same applies to FIGS. 7B to 7D described in FIG. Although each inner wall reflection energy density 34 is small, when a white bar pattern is displayed, the reflected beam 31 is generated in all apertures in the region on the shadow mask 35 corresponding to the position where the pattern is displayed. When many of them gather and overlap, it becomes a large amount of energy and promotes visible light emission. This causes unnecessary phosphors to emit light, causing deterioration in contrast and color purity.

  Further, as shown in FIG. 6B, when the conventional single-layer shadow mask 35 is used, the amount of the reflected beam 31 reflected toward the screen center increases around the screen. The deterioration of color purity is further increased. Then, the distribution of the inner wall reflection energy density 34 in this case is a distribution in which the maximum value of the energy density is moved to the screen center side as shown in FIG. 7B.

  On the other hand, as shown in FIG. 6C, when the shadow mask 7 of the present embodiment is used, the reflected beam 31 tends to advance toward the vicinity of the end of the large hole of the main mask 12. Since the reflected beam 31 is shielded by the small hole side surface of the auxiliary mask 22, the distribution of the inner wall reflection energy density 34 is as shown in FIG. 7C, and the energy near the large hole end of the main mask 12. The density is almost zero. In this case, since the lateral width of the distribution is small, the influence of the superposition of the inner wall reflection energy density is small. As a result, unnecessary phosphors can be prevented from emitting light and the contrast and color purity can be improved.

  In addition, when the shadow mask 7 of the present embodiment is used, the above-described effect around the screen is further increased. As shown in FIG. 5 and FIG. 6D, in the shadow mask 7 of the present embodiment, the center position of the small hole 26 of the auxiliary mask 22 relative to the center position of the small hole 16 of the main mask 12 is set around the screen. Since the offset is made to the screen peripheral side in accordance with the incident angle (deflection angle) of the incident beam 30, the short-axis side opening edge 29 of the small hole 26 of the auxiliary mask 22 and the corresponding large hole 17 of the main mask 12. The distance from the short axis side opening edge 19 is inevitably long, and the reflected beam 31 that is going toward the center of the screen can be shielded more effectively. In this case, the distribution of the inner wall reflection energy density 34 is a distribution obtained by cutting a portion having a high energy density, as shown in FIG.

  As described above, by using the shadow mask 7 of the present embodiment having the above-described structure, when the incident beam 30 is incident on the main mask 12, a part of the incident mask 30 is an opening of the main mask 12. The reflected beam 31 generated by colliding with the inner wall of the small hole on the surface on the electron gun 10 side can be prevented from causing unnecessary phosphors to emit light. As a result, it is possible to improve contrast and color purity.

  Furthermore, in the shadow mask 7 of the present embodiment, the distance from the center of the horizontal axis (long axis) of the perforated portions 13 and 23 to the end along the horizontal axis (long axis) is L, the main mask The width of the 12 large holes 17 is D'main, the width of the corresponding small hole 26 of the auxiliary mask 22 is Dsub, and the center position of the corresponding small hole 26 of the auxiliary mask 22 with respect to the center position of the large hole 17 of the main mask 12 When the offset amount is Z, at any position where the distance along the horizontal axis (long axis) from the center of the horizontal axis (long axis) is in the range of 0.7L to 1L, the following formula (1) It is desirable to satisfy this relationship.

Dsub ≦ 0.2D′main + 2Z (1)
This is due to the following examination results.

  First, the brightness of the phosphor that emits light due to the reflected beam 31 was measured when a conventional shadow mask 35 having a single structure as shown in FIGS. 6A and 6B was used. In the experiment, a white bar pattern 32 is displayed on the periphery of the phosphor screen 5 by using a 32-inch color picture tube equipped with a single shadow mask 35, and on the vertical axis (short axis) side of this pattern. The measurement was performed by measuring the luminance of unnecessary light emission 33 generated due to the reflected beam 31 (see FIG. 9A). FIG. 8A shows the experimental results. 8A, the horizontal axis indicates the distance along the horizontal axis (long axis) from the end on the short axis side of the white bar pattern 32, and the vertical axis is unnecessary for the luminance at the center of the white bar pattern 32. The luminance ratio of the light emission 33 is shown (this is the same for FIG. 8B described below).

  As can be seen from FIG. 8 (a), when the single shadow mask 35 is used, the luminance of the unnecessary light emission 33 is the horizontal axis (long axis) from the short axis side end of the white bar pattern 32. ) Has a maximum value at a position where the distance along 10) is 10 mm. This means that unnecessary light emission 33 as shown in FIG. 9A is generated centering on a position where the distance along the horizontal axis (long axis) from the end of the short axis side of the white bar pattern 32 is 10 mm. It means that Thus, if the luminance of the unnecessary light emission 33 has a maximum value at a position away from the white bar pattern 32, the unnecessary light emission 33 is easily recognized, and the image quality is significantly impaired. Such a phenomenon occurred at a position where the distance along the horizontal axis (long axis) from the center of the horizontal axis (long axis) was in the range of 0.7L to 1L.

  Next, the auxiliary mask 22 is overlapped and fixed on the main mask 12 as in the present embodiment, thereby shielding the reflected beam 31 that is going to travel toward the center of the screen where the inner wall reflection energy density 34 is large. I examined that. FIG. 10 shows a schematic diagram for explanation.

  As shown in FIG. 10, the distribution of the inner wall reflection energy density 34 along the phosphor screen 5 is now made to correspond to the large holes of the main mask 12. At this time, the ratio α of the amount of the reflected beam 31 that is going to advance toward the center of the screen with respect to the total amount of the reflected beam 31 generated in one aperture is expressed as the following formula (2). be able to.

α = [(D′ main−Dsub) / 2 + Z] / D′ main (2)
Here, assuming that the maximum value of the inner wall reflection energy density 34 is at the center of the large hole of the main mask 12, if α is 0.5, the inner wall reflection energy density 34 advances toward the maximum value. Since the reflected beam 31 to be shielded can be shielded, the reflected beam 31 can be effectively shielded. However, in reality, as described above, the distribution of the inner wall reflection energy density 34 is a distribution in which the maximum value is closer to the center of the screen, so that the inner wall reflection energy density 34 tends to increase toward the maximum. A value smaller than 0.5 should be sufficient to shield the reflected beam 31 that is transmitted. Therefore, the following experiment was conducted.

  When the above equation (2) is modified, the following equation (3) is obtained.

Dsub = (1-2α) D′ main + 2Z (3)
In the experiment, an auxiliary mask 22 having Dsub with α being 0.3 and 0.4 is prepared for one type of main mask 12, and the same method as in the case of the shadow mask 35 having a single structure described above. went. FIG. 8B shows the experimental results. As can be seen from FIG. 8B, in the case of the shadow mask 7 in which α is 0.3, the luminance of unnecessary light emission is reduced as compared with the case of the shadow mask 35 having a single sheet structure, but still remains. Has a local maximum.

  On the other hand, as can be seen from FIG. 8B, in the case of the shadow mask 7 having α of 0.4, the luminance of unnecessary light emission is further reduced, and the luminance of unnecessary light emission is reduced to the white bar pattern. It decreases monotonously with increasing distance from 32. In the case of such a luminance distribution, unnecessary light emission (33 in FIG. 9A) is not recognized as shown in FIG. 9B, and the image quality is extremely good. confirmed.

  Based on the above examination results, when α is 0.4 or more, the relationship of the above equation (1) is derived from the above equation (3). And by satisfy | filling the relationship of said Formula (1), since the reflected beam 31 can be shielded effectively, it becomes possible to provide a high quality color picture tube.

  In general, it can be recognized that the outer surface of the panel 1 has a radius of curvature of 10,000 mm or more is flat, but in such a color picture tube having the flat outer surface of the panel 1, the structure of the shadow mask is With the structure described in the above embodiment, the reflected beam can be shielded more effectively.

  The color picture tube of the present invention is not limited to the one described in the above embodiment, and can be variously modified within the scope of the present invention. For example, in the above-described embodiment, the color picture tube with the shadow mask 7 having a rectangular opening has been described as an example, but the present invention has been mounted with a shadow mask having a circular opening. The present invention can also be applied to a color picture tube, and in this case, the same effect as described above can be obtained. In the case of a circular opening, the “width” of the opening in the present invention is the “diameter in the major axis direction”. In the above embodiment, the case where one auxiliary mask 22 is used has been described as an example. However, the number of auxiliary masks is not limited to one, and a plurality of auxiliary masks may be used.

  According to the present invention, it is possible to shield the reflected beam generated by the collision at the inner wall of the aperture and prevent unnecessary emission of the phosphor. And since the said effect in the periphery of a screen becomes still larger, this invention is especially useful for a wide type color picture tube.

Sectional drawing containing the horizontal axis (X-axis) of the screen which shows the whole structure of the color picture tube in one embodiment of this invention Sectional drawing including the vertical axis (Y-axis) of the screen which shows the whole structure of the color picture tube in one embodiment of this invention Sectional drawing containing the horizontal axis (X-axis) of the screen which shows the shadow mask in one embodiment of this invention Sectional drawing containing the vertical axis (Y-axis) of the screen which shows the shadow mask in one embodiment of this invention Sectional drawing containing the horizontal axis (X-axis) of the screen which shows the aperture shape of the shadow mask in one embodiment of this invention Schematic diagram for explaining a reflected beam in an embodiment of the present invention ((a) is a schematic diagram in the vicinity of the center of the screen when there is no auxiliary mask, (b) is a schematic diagram around the screen when there is no auxiliary mask. (C) is a schematic diagram in the vicinity of the screen center when the auxiliary mask is fixed to the main mask. (D) is a schematic diagram in the vicinity of the screen when the auxiliary mask is fixed to the main mask. The schematic diagram which shows distribution of the inner wall reflection energy density in one embodiment of the present invention ((a) is a schematic diagram in the vicinity of the center of the screen when there is no auxiliary mask, (b) is in the periphery of the screen when there is no auxiliary mask. (C) is a schematic diagram around the center of the screen when the auxiliary mask is fixed to the main mask, (d) is a schematic diagram around the screen when the auxiliary mask is fixed to the main mask) In an embodiment of the present invention, the distance along the horizontal axis (major axis) from the short axis end of the white bar pattern and the ratio of the luminance of unnecessary light emission to the luminance of the center of the white bar pattern (A) is a characteristic diagram in the case of a single-layer shadow mask, (b) is a characteristic when α is 0.3 and 0.4 when the auxiliary mask is fixed to the main mask. (Figure) The schematic diagram for demonstrating unnecessary light emission at the time of displaying a white bar pattern in the peripheral part of the phosphor screen in one embodiment of the present invention ((a) is a schematic diagram when there is no auxiliary mask, ( b) Schematic diagram when the auxiliary mask is fixed to the main mask) The schematic diagram for demonstrating shielding of the reflected beam in one embodiment of this invention Sectional drawing which shows the hole shape of the shadow mask in a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Panel 5 Phosphor screen 6 Shadow mask structure 7 Shadow mask 8 Mask frame 9R, 9G, 9B Electron beam 10 Electron gun 12 Main mask 22 Auxiliary mask 13, 23 Perforated part 14, 24 Non-perforated part 15, 25 Skirt part 16 , 26 Small holes 17, 27 Large holes 19 Short axis (vertical axis) side opening edge 29 of main mask large hole Short axis (vertical axis) side opening edge 30 of auxiliary mask small hole Incident beam 31 Reflected beam 32 White bar pattern 33 Unnecessary light emission 34 Inner wall reflection energy density

Claims (3)

A panel having a phosphor screen made of phosphors of a plurality of colors on the inner surface, and a funnel connected to the back of the face panel;
An electron gun built into the neck of the funnel;
A color which is disposed at a predetermined position in the bulb so as to face the phosphor screen, and includes a rectangular shadow mask having two major axes which are perpendicular to each other and perpendicular to the tube axis. A picture tube,
The shadow mask is fixed to the main mask having an aperture through which an electron beam passes and the phosphor screen side over the entire perforated portion of the main mask, and is fixed at the position of the aperture of the main mask. It consists of an auxiliary mask in which holes are formed together,
The opening of the main mask and the auxiliary mask comprises a communication hole in which a small hole formed on the surface on the electron gun side and a large hole formed on the surface on the phosphor screen side communicate with each other.
A color picture tube characterized in that the short axis side opening edge of the small hole of the auxiliary mask is located on the screen peripheral side with respect to the short axis side opening edge of the corresponding large hole of the main mask. . The distance from the center of the major axis of the perforated part to the end along the major axis is L, the width of the large hole of the main mask is D'main, and the width of the corresponding small hole of the auxiliary mask And Dsub, where Z is the offset amount of the center position of the small hole corresponding to the auxiliary mask with respect to the center position of the large hole of the main mask, the distance along the long axis from the center of the long axis is The color picture tube according to claim 1, which satisfies the relationship of the following formula (1) at any position within a range of 0.7L to 1L.
Dsub ≦ 0.2D′main + 2Z (1) The color picture tube according to claim 1 or 2, wherein a radius of curvature of an outer surface of the panel is 10,000 mm or more.

Images