JPH0422042A - Manufacture of shadow mask structure for cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent the deterioration in color purity by putting a peripheral part of a shadow mask on a mask frame, so as to pressurize the vicinity of and around the two parts to be fixed together, and by irradiating a laser beam on the parts, so as to fix them together through laser welding. CONSTITUTION:A shadow mask 6 put on a mask frame 5 is sandwiched between heaters 14a and 14b vertically, while a heater is heated up to 120 C, and the shadow mask 6 is not prevented from being heat-expanded and is extended horizontally, while it is held in such a manner that the mask is not relaxed vertically. A point 16 of a moving part 16 is in contact at a certain pressure with the center of a peripheral part of the shadow mask 6 which is forced out from an upper heater 14a to the outside. Point-welding is carried out on the entire circumference of the shadow mask 6 at multiple points by laser, and homogeneous tensile force is generated at a room temperature. When the image including a bright screen and the part of extremely high brightness is to be displayed, deterioration in color purity is not easily generated.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a uniform tension in the shadow mask when it is used, and even when the temperature of the shadow mask increases, its thermal expansion is suppressed by the tension. A shadow for a color cathode ray tube that absorbs by relaxation and maintains the correspondence between the electron beam passing hole of the shadow mask and each primary color phosphor on the phosphor surface disposed opposite thereto. The present invention relates to a method for manufacturing a mask structure.

[Prior Art] In a shadow mask type color cathode ray tube, three electron beams emitted from electron guns dedicated to each primary color, emitting red, green, and blue light, strike one electron at a scanning position on a shadow mask. After passing through the beam passage hole, the electron beams for each primary color collide with the dots or stripes of the red, green and front wall light bodies arranged facing each other on the inner surface of the panel, respectively, and are excited and emit light. There is.

Therefore, in order to achieve good color display, it is necessary to have a large number of electron beam passing holes in the shadow mask, and red, green, and front wall light dots arranged facing each other on the inner surface of the panel in correspondence with each of these electron beam passing holes. or stripes must maintain a predetermined correct relative position.

However, the time that the electron beam passes through the electron beam passage hole of the shadow mask is shorter than the time that the electron beam collides with the shadow mask, and the mask transmittance of the electron beam is usually 15 to 20. It is only about %. When the electron beam impinges on the shadow mask, it increases the temperature there, causing thermal expansion. If there is a bright screen or a very bright area on the screen, the beam current will increase, causing the shadow mask in that area to expand. The correspondence relationship between the dots and stripes of the phosphor deviates from the predetermined correct relative position, resulting in deterioration of color purity.

One way to prevent the shadow mask from heating and expanding due to electron beam impact and the resulting deterioration of color purity is to fix the shadow mask to the mask frame with uniform tension applied in advance to prevent the shadow mask from rising in temperature. Even though
It has been proposed that the tension is simply relaxed without actually causing expansion and deformation.

Furthermore, a method for fixing a shadow mask to a mask frame while applying uniform tension to the shadow mask is disclosed in Japanese Patent Application Laid-Open No. 62-11912, for example.
Japanese Patent No. 51130 discloses that while the periphery of a flat shadow mask, including the electron beam passage hole, to which a uniform predetermined tension is applied, is held between a mask frame and a ribbon-shaped frame, the ribbon-shaped A method is disclosed in which a pulsed laser beam that is sent intermittently from above the frame is irradiated to fix the ribbon between the frames.

However, when the inventors tried this method, it was difficult to perform good laser welding so that the shadow mask, the frame, and the ribbon-like frame were completely brought into close contact with each other over the entire circumference. In reality, uneven tension occurred, and color purity was observed to deteriorate due to heating expansion of the shadow mask by the electron beam during use.

[Problems to be Solved by the Invention] The above-mentioned conventional techniques do not take into account the fact that the peripheral edge of the shadow mask to be welded and the mask frame are in complete contact with each other over the entire circumference, and therefore there is a slight gap between the two. If gaps remain, the laser welding method will not be able to achieve a good adhesion in those areas, and it will not be possible to apply uniform tension, that is, the same tension in all directions, resulting in deterioration of color purity. A problem arose.

In the present invention, laser welding is performed after the shadow mask and mask frame are always kept in perfect contact with each other, so that a good adhesion state is achieved over the entire circumference between the two, and a uniform tension is applied to the shadow mask. An object of the present invention is to provide a method for manufacturing a shadow mask structure for a cathode ray tube that prevents deterioration of color purity from appearing.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a shadow mask under uniform tension is fixed to a mask frame parallel to the shadow mask surface at its peripheral edge. In the method of manufacturing a shadow mask structure for a cathode ray tube, the peripheral edge of the shadow mask is placed on the mask frame, and while applying pressure to at least the vicinity of the portions of the two to be fixed to each other to ensure contact, The parts were irradiated with a laser beam and the two were fixed together by laser welding.

In order to easily carry out the above method, the present invention includes a member that slides relative to the shadow mask while applying pressure to the vicinity of the parts to be fixed to each other, and a member for the parts to be fixed to each other. It was decided to use a laser welding means equipped with a mechanism for holding the laser beam focusing lens in a predetermined relative position.

Furthermore, the shape of the end of the welding means that contacts the shadow mask of the member that slides relative to the shadow mask is such that the laser beam is the central axis, and the end is at the contact surface with the shadow mask that intersects with this axis. The part that transitions from the end contact surface of the sliding member to the non-contact area has a surface shape that is smooth in the sliding direction and easy to slide while applying pressure. It was formed like this. This also prevents scratches from occurring on the surface of the shadow mask.

In addition, in order to apply uniform tension to the shadow mask at room temperature, the shadow mask is held at a predetermined relative temperature higher than that of the mask frame, and the shadow mask is placed and fixed on the mask frame, so that the temperature of both is maintained. When they are equal, the force that causes the shadow mask itself to contract is applied as tension.

[Effects] If the above-mentioned measures are taken, the peripheral edge of the shadow mask and the mask frame will be in perfect contact with each other at the location and time of laser welding due to the pressure, contact, and sliding members of the laser welding means. Because of this, good adhesion can be obtained by laser welding. In laser welding, the influence of the gap between objects to be welded on the welding state is extremely large, and the allowable value is said to be 10% or less of the plate thickness of the objects to be welded. Therefore,
When welding a thin plate, for example, about 25 μm, which is the object of the present invention, there is almost no clearance between the plate and the mask frame.

In addition, the lens for condensing the laser beam is
Since it is always held in a predetermined relational position to the part to be welded which is in complete contact with the sliding member, the convergence state of the laser beam on the shadow mask of this part is always as desired. A good and uniform welding condition can be obtained all around the shadow mask.

When the shadow mask is placed on the mask frame with no tension applied to the shadow mask and with the shadow mask held at a predetermined relative temperature higher than the mask frame, there is no tension between the shadow mask and the mask frame, even if it is completely Even if a good adhesion state is not achieved, the welding means according to the present invention can provide a good adhesion state, and moreover, it is possible to generate an almost completely uniform tension relatively easily.

[Example 5] Fig. 5 is a side sectional view of a color cathode ray tube using a shadow mask structure manufactured according to the present invention. In the figure, 1 is a panel, 2 is a panel skirt, and 3 is a shadow embedded in the panel skirt. A stud for supporting the mask; 4 is a leaf spring that is fixed to the mask frame and engages with the stud through a hole drilled therein to support the shadow mask; 5 is a mask frame having a flat surface around the opening; 6 is plate thickness 0.025
A planar shadow mask made of mild steel with a diameter of 0.080 mm drilled at a pitch of 175 mm on the inner effective surface, 7 an electron gun, 8 an electron beam, 9 a deflection coil, and 1o a panel inner surface. A color phosphor surface is made up of a group of three primary color phosphors arranged in the form of a large number of regularly arranged dots or stripes, and numeral 11 is the face plate of the panel. As is well known, the arrangement of the holes in a shadow mask is such that if the lines connecting the centers of the holes intersect at an angle of 60 degrees, all the holes will be equally spaced.

On the other hand, from the electron gun 7, the face plate 1 is placed at a mutual spacing of 5,5 mm.
Three electron beams 8 emitted so as to be concentrated at the center of the inner surface of the color fluorescent surface 10 are deflected over the entire surface of the color fluorescent surface 10 by a deflection coil 9. When the shadow mask 6 is heated by the impact of most of the electron beam 8, the temperature of the shadow mask increases and expands, and the position where the electron beam passes through the hole of the shadow mask and lands on the color fluorescent surface 10 is determined. Displace from a given position. That is, a landing error occurs. As described above, in order to reduce this error as much as possible, tension is generated in the shadow mask in advance, and the expansion is absorbed by relaxing the tension. However, sufficient effects cannot be obtained unless the tension is generated uniformly. FIG. 3 is a perspective view of the shadow mask structure viewed from the fluorescent surface side. FIG. 4 is a perspective view of the shadow mask structure seen from the electron gun side. As shown in FIG.
Spot welding is performed by pulsed laser irradiation at a large number of points on the welding line 13 shown by the dotted chain line.

FIG. 1 is a sectional view for explaining laser welding means according to the present invention. The shadow mask 6 placed on the mask frame 5 is heated by two heaters 14a.

14b is sandwiched from above and below. Here, each of these heaters is 1
The shadow mask 6 is heated to 20° C., and is held so as not to prevent the shadow mask 6 from thermally expanding and spreading laterally, and to prevent it from loosening in the vertical direction. A condensing lens 15 is arranged so that the laser beam is irradiated approximately at the center of the periphery of the shadow mask 6 that protrudes outward from the upper heater 14a, and a movable part 16 integrated with the condensing lens 15 is arranged so that the entire circumference of the shadow mask is It is supported by a robot 17 so that it can be welded.

A shadow mask 6 extends outward from the upper heater 14a.
The tip 16a of the movable part 16 is in contact with approximately the center of the peripheral edge of the movable part 16 with a predetermined pressure. FIG. 2 shows an enlarged view of the tip 16a of the movable part. Providing a balancer 18 between the movable part 16 and the robot 17 makes it easier to set the pressure. The optimum value of this pressure is determined depending on the plate thickness and material of the shadow mask 6, the contact area of the tip 16a of the movable part, etc., but in the case of the shadow mask of the mild steel layer with a plate thickness of 0.025n* in this embodiment. is the area 2. of the hollow cylindrical portion of the tip 16a of the movable portion.
10 to 500 g is appropriate for 4+om2. Actually, in this example, the pressure was set at 100 g in consideration of adhesion and not damaging the shadow mask.

A condensing lens 15 is connected to a pulse laser source 19 by an optical fiber 20.

On the other hand, the mask frame 5 is cooled by air blown out from the air outlet 21 so that the temperature does not rise during the welding operation.

As described above, by performing spot welding at a large number of points over the entire circumference of the shadow mask 6 using a laser, a shadow mask structure having uniform tension at room temperature can be obtained.

In this embodiment, a case has been described in which the shadow mask 6 is welded in a heated and expanded state without applying tension to the shadow mask 6 during laser welding. However, the present invention exhibits exactly the same effect even when using other methods, such as laser welding with mechanical tension applied to the shadow mask 6.

Further, in the above embodiment, the case where spot welding is performed is explained, but the effect is the same when seam welding is performed. Although the embodiments of the present invention described above are cases in which a planar shadow mask is used, the laser welding means according to the present invention can also be used when developing a shadow mask in a cylindrical shape. In the case of a cylindrical surface, this method does not have to be applied to the entire circumference, but may be applied only to the top and bottom or left and right sides.

[Effects of the Invention] As explained above, according to the present invention, a shadow mask under uniform tension is fixed at its peripheral edge to a mask frame parallel to the shadow mask surface,
A shadow mask structure for a cathode ray tube in which deterioration of color purity is unlikely to occur even when displaying a bright screen or an image including a very high luminance part can be simply and easily produced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining the laser welding means according to the present invention, FIG. 2(a) is an enlarged side cross-sectional view of the tip of the movable part of the laser welding means according to the present invention, and FIG. 2(b) 3 is an enlarged bottom view of the tip of the movable part, FIG. 3 is a perspective view of the shadow mask structure according to the present invention, seen from the fluorescent surface side, and FIG. 4 is a perspective view of the same shadow mask structure, seen from the electron gun side. FIG. 5 is a side sectional view of a color cathode ray tube using a shadow mask structure manufactured according to the present invention. 1...Panel, 2...Panel skirt, 3.
... Stud, 4... Leaf spring, 5... Mask frame. 6...shadow mask, 7...electron gun, 8...
・Electron beam, 9...deflection coil, 10・
... Color fluorescent surface, 11 ... Panel face plate,
12... Outer edge of shadow mask, 13... Welding line, 14a, 14b... Heater, 15... Condensing lens, 16... Movable part, 16a... Tip of movable part, 17... robot. 18... Balancer, 19... Pulse laser source,
20... Optical fiber, 21... Air outlet.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a shadow mask structure for a cathode ray tube, in which a shadow mask under uniform tension is fixed at its peripheral portion to a mask frame parallel to the surface of the shadow mask, The peripheral edge of the shadow mask is placed on the mask frame, and while applying pressure to at least the vicinity of the parts to be fixed to each other to ensure contact, the parts are irradiated with a laser beam to laser weld the two parts together. 1. A method for manufacturing a shadow mask structure for a cathode ray tube, characterized in that the structure is fixed by a method. 2. A member that slides relative to the shadow mask while pressurizing the vicinity of the parts to be fixed to each other, and a mechanism for holding the laser beam condensing lens in a predetermined relative position with respect to the parts to be fixed to each other. 2. The method of manufacturing a shadow mask structure for a cathode ray tube according to claim 1, wherein a laser welding means is used. 3. The shape of the end of the member that slides relative to the shadow mask that contacts the shadow mask is such that the laser beam is the central axis and the end is cut at the contact surface with the shadow mask that intersects with this axis. 3. The method of manufacturing a shadow mask structure for a cathode ray tube according to claim 2, wherein the structure has a hollow cylindrical shape. 4. The part of the member that slides while applying pressure in contact with the shadow mask has a surface shape that is smooth in the sliding direction and makes it easy to slide while applying pressure from the end contact surface to the non-contact area. 4. The method of manufacturing a shadow mask structure for a cathode ray tube according to claim 3, further comprising: 5. Claims 1 to 4 characterized in that the shadow mask is placed and fixed on the mask frame while the shadow mask is maintained at a predetermined relative temperature higher than that of the mask frame without applying tension to the shadow mask. any one of
A method for manufacturing a shadow mask structure for a cathode ray tube according to 2.