JP2004277278A - Lower molding die for glass panel for cathode ray tube and method for producing glass panel for cathode ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by strong cooling at a periphery part with the heat insulation of the central part of a lower molding die in a pressure-molding step to produce a glass panel for a cathode ray tube. <P>SOLUTION: The lower molding die for the glass panel for the cathode ray tube has a glass-filling part shaped by a nearly rectangular bottom 2 and side walls 3 at four sides of the bottom and it cools the glass panel for the cathode ray tube 5 in the glass-filling part with a coolant supplied from the lower part of the bottom 2 to the central part of the bottom. The supercooling at the central part is prevented by having a vacant space 4 at the central part of the bottom 2 and then the cooling at the periphery part is strengthened. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a glass for a cathode ray tube capable of relatively strongly cooling the periphery of the bottom without overcooling the center of the bottom when cooling from below the bottom by providing a hollow layer inside the bottom. The present invention relates to a lower mold for forming a panel, and a method for producing a glass panel for a cathode ray tube using the lower mold for molding.

  Conventionally, when molding a glass panel for a cathode ray tube (hereinafter also simply referred to as a panel), a predetermined amount of molten glass lump (hereinafter referred to as a gob) is supplied to the lower mold, and then the upper mold is lowered to gob In general, the upper mold is raised after being pressed and then the molded panel is cooled in the lower mold, and then the panel is taken out. This method will be specifically described below with reference to the drawings.

  The above-described series of molding steps of the panel is usually obtained by a molding apparatus in which a plurality of lower molds 1 are arranged at equal intervals on a turntable 15 as shown in FIG. First, a predetermined amount of gob is supplied to the lower mold 1 on which an intermediate mold for molding the end of the panel is placed at the position a. The lower die loaded with the gob is subsequently moved to the pressure molding position b, and the upper die is lowered at the pressure molding position, and the gob is pressure molded into a hollow box type cathode ray tube glass panel.

  At this time, since the upper mold is relatively low in temperature as compared with the gob, the temperature of the gob in the lower mold rapidly decreases. And while the upper mold | type raises and the turntable 15 rotates intermittently further, the panel in a lower mold | type is cooled, and even after an intermediate mold | type is removed from a lower mold | type in e position, each cooling position f? Sequentially transferred to i and cooled sufficiently to the extent that deformation does not occur in subsequent handling. Thereafter, the cooled panel is taken out from the lower mold at the j position and sent to the next process. And the lower mold | type after taking out a panel is sent to the first gob supply position a in preparation for the next shaping | molding.

  In each cooling position, the outer surface of the panel in contact with the lower mold is cooled through the contact surface with the lower mold. Further, the inner surface of the panel is cooled by a coolant such as cooling air (hereinafter referred to as cooling air) blown out from a duct provided above each cooling position. At this time, a circular nozzle is installed at the bottom of each cooling position of the molding apparatus toward the bottom of the lower mold, and the lower mold is cooled by cooling air blown upward from the nozzle.

  FIG. 6 is a sectional view showing an apparatus for cooling the bottom of the lower mold. The lower mold 1 on which the panel 5 is placed as shown in the drawing is fixed to the turntable 15 via a mounting flange 8 by a plurality of legs 6 provided on the bottom 2 thereof. The bottom of the lower mold is cooled by the cooling air blown from the nozzle 11 disposed below. The cooling air from the nozzle 11 first collides with the center of the bottom through the space surrounded by the legs 6 and then flows to the periphery.

  Since this cooling air is a substantially circular collision jet directed toward the center of the bottom 2 of the lower mold 1, it has a mountain-shaped heat transfer coefficient distribution with the center stagnation point as a peak. Due to such a heat transfer coefficient distribution, the temperature of the bottom of the lower mold is low in the central part and high in the peripheral part, so that the cooling of the peripheral part of the panel 5 is relatively weak. Therefore, if the supply amount of the cooling air is increased in order to lower the temperature of the peripheral part of the lower mold 1, the temperature of the central part is lowered more than necessary to cause overcooling, which causes remarkable deterioration of moldability.

  In order to solve such a problem, in Japanese Patent Laid-Open No. 2000-351638, the shape of the outlet for supplying the cooling air toward the bottom of the lower die is made substantially rectangular so that the lower die is efficiently made. A method of cooling uniformly has been proposed.

However, the cooling air supplied from the outlet of the cooling device described in Japanese Patent Application Laid-Open No. 2000-351638 is a slit-like impinging jet directed toward the center of the bottom of the lower mold, so that the stagnation at the center It is still a mountain-shaped heat transfer coefficient distribution with a peak point, and it is difficult to eliminate the lack of cooling around the lower mold.
JP 2000-351638 A (see FIGS. 1 to 4)

  In recent years, flattening of the image display surface of a cathode ray tube has been progressing rapidly. In the cathode ray tube of the type having a shadow mask, the inner surface of the panel needs to have a spherical shape having a relatively large curvature because of its structure. Therefore, as shown in FIG. The part 13 may be designed so that the thickness of the peripheral part is more than twice the thickness of the central part. That is, the cross section of the face portion 13 has a slight difference in thickness distribution depending on the orientation such as the minor axis, the major axis, and the diagonal axis, but the thickness from the central portion 16 toward the peripheral portion 17 in any orientation. It becomes the uneven thickness shape which increases. Such a face panel is called an uneven thickness panel.

  Because of this uneven thickness shape, the peripheral portion of the thick panel is difficult to be cooled. Therefore, when the panel is cooled in the manufacturing process, the central portion 16 is overcooled and the peripheral portion 17 is insufficiently cooled. On the other hand, the temperature distribution of the lower mold tends to be relatively insufficiently cooled in the peripheral portion even if the bottom surface center portion is sufficiently cooled as described above.

  For this reason, when the panel in the lower mold is physically strengthened in this cooling step, a large difference in reinforcing stress value occurs between the peripheral portion 17 and the central portion 16 of the face portion 13. That is, the peripheral portion 17 of the face portion is less likely to be cooled from the inner surface due to the influence of the skirt portion 14 extending perpendicularly to the periphery of the face portion 13 and is relatively thicker than other portions. Since the lack of cooling further overlaps, the strengthening stress in the peripheral portion becomes relatively low. Further, as described above, the temperature of the peripheral portion of the bottom of the lower mold is considerably high due to insufficient cooling, so that there is a problem that the distribution of reinforcing stress is further increased.

  On the other hand, since the cathode ray tube is evacuated during use and the inside is in a reduced pressure state, tensile stress (hereinafter referred to as “tensile vacuum stress”) is generated in the envelope everywhere. The tensile vacuum stress varies in the magnitude and distribution of the stress value depending on the shape and thickness of the panel. When the magnitude and distribution of the tensile vacuum stress are viewed for the substantially rectangular face portion, the maximum is obtained at the peripheral portion of the outer surface of the face portion, particularly at the ends of the short axis and the long axis. Therefore, in order to allow the panel to withstand this maximum tensile vacuum stress, it is desirable to apply a relatively large reinforcing stress to the periphery of the face portion including the ends of the short axis and the long axis.

  However, with the conventional lower mold cooling technology, the cooling efficiency of the peripheral portion of the face portion is low as described above, so that the portion where the strongest physical strengthening is desired is insufficiently strengthened, and the desired physical strengthening is performed. It was difficult to manufacture the panel. In particular, it is extremely difficult to sufficiently and uniformly physically strengthen the peripheral portion of the panel having a flat outer surface of the face portion in a large size of 29 type or larger.

  The present invention uses a lower mold capable of relatively lowering the temperature distribution in the peripheral part of the bottom part of the lower mold, and the lower mold, in molding an uneven panel having a thick peripheral part of the face part. An object of the present invention is to provide a method for producing a glass panel for a cathode ray tube.

  The present invention has been made in order to solve the above-described problems, and in particular, when cooling the lower mold in the manufacturing process of the uneven thickness panel in which the peripheral part thickness of the face part is larger than the central part thickness, the lower mold The peripheral part is relatively strongly cooled without overcooling the center part of the bottom part.

That is, the present invention relates to a lower mold used in the molding process of a glass panel for a cathode ray tube, and by providing a hollow layer inside the bottom central portion of the lower mold, when cooling the lower mold, Provided is the following lower mold for molding a glass panel for a cathode ray tube, capable of relatively strongly cooling the bottom peripheral portion of the lower mold while suppressing heat conduction in the vertical direction and preventing overcooling.
(1) It has a glass filling portion formed by a substantially rectangular bottom portion and side wall portions provided on the four sides of the bottom portion, and the inside of the glass filling portion is cooled by a refrigerant supplied from below the bottom portion to the center portion of the bottom portion. A cathode ray tube glass panel lower mold for cooling the cathode ray tube glass panel, wherein a hollow layer is provided at the center of the bottom.
(2) The lower mold for molding a cathode ray tube glass panel according to 1 above, wherein the planar shape of the hollow layer is substantially circular.
(3) The lower mold for molding a cathode ray tube glass panel according to 1 or 2 above, wherein the planar shape shortest diameter D _S and longest diameter D _{L of the} hollow layer have a relationship of 0.25 ≦ D _S / D _L ≦ 1. .
(4) the area when the bottom and vertical projection and _{S B,} when the area of the planar shape of the hollow layer was _{S H,} above having _{0.01 ≦ S H / S B ≦} 0.25 the relationship Lower mold for molding 1, 2, or 3 cathode ray tube glass panels.
(5) The lower mold for molding a cathode ray tube glass panel according to any one of the above 1 to 4, wherein the thickness of the hollow layer at the center of the bottom is 0.1 to 20 mm.
(6) The lower mold for molding a cathode ray tube glass panel according to any one of the above 1 to 5, wherein the lower surface side of the central part where the hollow layer at the bottom is provided is convex.
further,
(7) Supply a refrigerant toward the bottom center of the bottom of the lower mold for forming a cathode ray tube glass panel formed by a substantially rectangular bottom and side walls provided on the four sides of the bottom; In the manufacturing method of the glass panel for cathode ray tubes which cools the filled glass, the hollow layer is provided in the center part of the bottom part of the said lower mold | type, The manufacturing method of the glass panel for cathode ray tubes characterized by the above-mentioned is provided.

  Since the present invention is configured as described above, in the conventional lower mold having no hollow layer, there is a problem that when the peripheral part is cooled, the central part is overcooled. In the lower mold, the cooling of the central portion of the bottom portion is suppressed and maintained by the hollow layer, so that the peripheral portion can be relatively cooled and strengthened without overcooling the central portion. Thereby, a desired reinforced compressive stress can be formed in the peripheral part of the face part.

  The present invention is particularly suitable for lower mold cooling of a large-sized cathode ray tube panel having a size of 29 or more, which has a thickness distribution in which the thickness of the peripheral portion of the face portion is significantly larger than the thickness of the central portion.

  In general, when cooling air is blown to the lower surface of the bottom center of the lower mold and the lower mold is cooled by the impinging jet, the heat transfer coefficient distribution at the bottom has a peak shape that peaks at the stagnation point of the bottom center as described above. become. Therefore, when it is desired to cool the peripheral portion of the bottom portion, it is technically important to install a heat insulating layer in order to avoid overcooling of the central portion. The present invention provides a hollow layer at the center of the bottom of the lower mold as a means for suppressing overcooling at the center of the bottom, that is, as a heat insulating means for adjusting the temperature distribution of the bottom of the lower mold. is there.

  For this purpose, the hollow layer is provided at the center of the bottom of the lower mold so as to obtain a predetermined heat insulating effect. Since the bottom of the lower mold is substantially the same rectangular shape as the face part shape of the panel, the center of the bottom of the lower mold is the center of this rectangular bottom, specifically the length of the rectangular bottom. This is a region within a predetermined range from the center of the bottom where the axis and the minor axis intersect. The present invention is characterized in that a hollow layer having a predetermined thickness is provided in this region along the bottom. When this hollow layer is provided in the bottom mold, it is preferably provided on the bottom surface of the bottom as much as possible. By setting the position of the hollow layer on the lower surface side of the bottom in this way, it is possible to reduce the burden when forming the hollow layer in the mold material. In addition, since the heat transfer surface of the cooling air is close to the hollow layer, it is possible to efficiently suppress the supercooling of the central portion of the bottom portion of the lower mold, and to cool the peripheral portion accordingly.

  In the present invention, the shape when the hollow layer is vertically projected is not limited. In the present invention, the planar shape of the hollow layer refers to this vertical projection shape. The planar shape may be a rectangular shape or a polygonal shape in addition to a circular or elliptical substantially circular shape. However, since the legs for mounting and fixing to the molding apparatus are generally arranged in a circular shape around the center of the bottom part on the lower surface of the bottom part of the lower mold, the substantially circular hollow is usually in the region surrounded by the legs. It is preferred to provide a layer. If the hollow layer is provided at the center of the bottom surrounded by the legs in this way, the hollow layer does not overlap the position of the legs, so that lowering of strength and deformation of the lower mold can be avoided, and formation of the hollow layer is easy. Become.

It is preferable that 0.25 ≦ D _S / D _L ≦ 1, where D _{S is} the shortest diameter of the planar shape of the hollow layer in the present invention and D _L is the longest diameter. If D _S / D _L is less than 0.25, an extreme difference occurs in cooling between the major axis and the minor axis of the rectangular face portion, which is not preferable. In particular, when the face portion of the panel is physically strengthened, this difference is not preferable because of a large bias in the degree of strengthening. On the other hand, the upper limit 1 is defined on the basis of insulating the directions of the major axis and the minor axis substantially uniformly, for example, like a circular hollow layer. It is preferably used.

  In the above, when the planar shape of the hollow layer is not a simple shape such as a substantially circular shape or a rectangular shape, the shortest diameter and the longest diameter can be determined by deriving a simple shape that approximates the hollow layer. it can. In addition, when the hollow layer is not circular, the major axis is usually matched with the major axis direction of the lower mold.

  In the present invention, the heat insulating region at the bottom of the lower mold is closely related to the size (area) of the planar shape of the hollow layer. As the area of the hollow layer increases, the lower mold heat insulating region also increases in proportion thereto. For this reason, in order to insulate the bottom of the lower mold so that a desired temperature distribution is obtained, it is necessary to provide the hollow layer so that the occupied area of the hollow layer is a predetermined ratio with respect to the area of the bottom of the lower mold. preferable.

The hollow As the area occupied by the hollow layer, area when were vertical projection (corresponding to a face portion of the panel to be molded) the bottom surface of the lower mold (hereinafter, the lower die area) as the S _B, provided in the lower die area of the planar shape of the layer (hereinafter, a hollow layer area) when the set to _{S H,} preferably from _{0.01 ≦ S H / S B ≦} 0.25, 0.05 ≦ S H / S B If it is ≦ 0.1, it is more preferable. When S _H / S _B is less than 0.01, only a very narrow range of the bottom of the lower mold is insulated, so it becomes difficult to reduce or eliminate the overcooling of the bottom. Conversely, when this value exceeds 0.25, a wide range is insulated from the central part to the peripheral part of the bottom part, so that the peripheral part requiring strong cooling is insulated more than necessary, and this part becomes insufficiently cooled. The lower mold may not be cooled to a desired temperature. As a result, it becomes difficult to sufficiently cool a part of the face portion.

  In the present invention, the hollow layer is usually formed with a uniform thickness at the center of the bottom of the lower mold. However, if it is desired to change the heat insulation characteristics of the bottom of the lower mold, it can be adjusted by changing the thickness, or When it is desired to adjust the heat insulation properties depending on the position of the bottom, the thickness of the hollow layer can be partially changed. For example, when it is desired to weaken the heat insulating effect in a specific orientation or the periphery of the hollow layer relative to the central portion, the thickness of the hollow layer in this region may be reduced.

  The thickness of the preferred hollow layer of the present invention is uniform or gradually decreasing from the center of the bottom portion toward the periphery, and is thus maximum at the center of the bottom portion. Therefore, by optimizing the thickness of the hollow layer at the center of the bottom portion, overcooling of the central portion of the face portion can be substantially prevented. The thickness of the hollow layer at the center of the bottom is preferably 0.1 to 20 mm. In the hollow layer having a thickness of less than 0.1 mm, since the heat insulating effect is not sufficient, it becomes difficult to eliminate the problem of supercooling in the center portion of the bottom. Further, a hollow layer having a thickness exceeding 20 mm is not preferable because it hinders the cooling necessary for molding the panel and reduces the strength of the bottom of the lower mold.

  In the present invention, such a hollow layer can be provided at the bottom of the lower mold by the following method. One of them is a method of forming a hollow layer by closing and closing the opening of a recess provided at the center of the bottom of the lower mold. Another method is to provide a hollow layer by attaching a hollow cover member to the lower surface of the central portion of the bottom. Thus, the hollow layer can be formed by a hollow member embedded in the bottom of the lower mold or provided in a convex shape on the bottom of the lower mold.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a plan view of a lower mold which is a preferred embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along a line AA in FIG. The lower mold 1 has a substantially rectangular glass filling portion (hollow portion) formed by a substantially rectangular bottom portion 2 and a side wall portion 3 extending in a direction perpendicular to the periphery of the bottom portion 2. When the panel is actually molded, an intermediate mold (not shown) is placed on the side wall 3 and used.

  On the lower surface 7 of the bottom portion 2, for example, four legs 6 are provided at fixed positions from the center portion of the bottom portion 2 in each of the major axis and the minor axis direction, that is, circular around the center of the bottom portion 2. The lower end of each leg is welded to the mounting flange 8. By screwing the mounting flange 8, the lower mold 1 can be fixed to the molding apparatus. The panel 5 placed on the glass filling portion of the lower mold 1 is first cooled at the bottom 2 by cooling air blown to the bottom 2 of the lower mold 1 through a hole 9 provided in the center of the mounting flange 8. The outer surface is cooled through the contact surface of the bottom 2.

  As shown in FIGS. 1 and 2, a circular hollow layer 4 having a radius of 100 mm and an overall thickness of 10 mm is provided in the central portion surrounded by the legs 6 of the bottom 2 of the lower mold 1. Specifically, a hollow having a thickness of 10 mm is formed by cutting a concave hole having a depth of 15 mm and a radius of 100 mm from the lower surface side in the center of the bottom portion 2 and closing the opening of the concave hole with a lid 10 having a thickness of 5 mm. Layer 4 is formed. In this case, the lid 10 can be fixed to the opening by a method of screwing the lid itself into a screw portion provided in the recess hole, a method of simply screwing the lid 10 or a method of welding. Thus, the hollow layer 4 can be formed inside the bottom 2 of the lower mold 1. In addition, as a material of the lid | cover 10, the same material as the lower mold | type 1 is preferable so that it can respond to the thermal expansion deformation at the time of use.

  FIG. 3 illustrates another embodiment of the present invention. In this example, the bottom 2 of the lower mold 1 is not cut to provide a hollow layer as shown in FIG. 2, but the umbrella-shaped member 12 is screwed or welded to the center of the bottom 2 of the lower mold. The hollow layer 4 is provided by attaching. That is, a space corresponding to the hollow layer 4 is formed inside the umbrella-shaped member 12, and the lower surface 7 and the umbrella-shaped member 12 are attached by attaching the umbrella-shaped member 12 to the lower surface 7 of the bottom 2 of the lower mold. The hollow layer 4 can be provided between the two. By attaching this umbrella-shaped member 12, the bottom 2 of the portion where the hollow layer 4 is provided is convex outward, and the thickness of the hollow layer 4 varies from the center to the periphery as shown in the figure. It is gradually decreasing.

  For this reason, the hollow layer 4 as in this example has a large thickness difference between the central part and the peripheral part, so that the central part having a larger thickness than the hollow layer having a uniform thickness as shown in FIG. The heat insulation characteristics of the Further, since the collision jet of the cooling air blown to the umbrella-shaped member 12 smoothly flows toward the periphery along the umbrella-shaped inclined surface, the center portion of the bottom portion 2 does not stagnate or is generated. However, it becomes slight and the supercooling in the center part of the bottom part 2 tends to be weakened. Due to both of these actions, the hollow layer of the present example is suitable when the cooling of the central portion of the bottom portion 2 is particularly concentrated and strongly suppressed. Although not shown, the umbrella-shaped member 12 may have a hemispherical shape or a flat disk shape. As described above, the hollow layer of the present invention can obtain the desired heat insulating effect by itself, but other heat insulating material can be loaded into the hollow layer as necessary.

  A molded body of a 34-inch cathode ray tube panel (see FIG. 7) was cooled using the lower mold 1 having the hollow layer 4 illustrated in FIGS. 1 and 2 (the planar shape is a circle with a radius of 100 mm and the thickness is 10 mm). . This panel has a substantially flat outer surface (curvature radius: 100000 mm), a thickness of about 15 mm at the center of the face, and a thickness of about 23 mm at the end of the major axis corresponding to the periphery of the face. The wall thickness at the end of the shaft has an uneven thickness distribution of about 30 mm.

On the other hand, the cooling for the lower mold uses a cooling device similar to that in FIG. 6, the inner diameter of the cooling air outlet is φ60 mm, the cooling air flow rate is about 100 m / s, from the start of air blowing per position to the stop of blowing. Was set to 20 seconds. Incidentally, the bottom surface area _{S B} of the lower mold for about 400000Mm ^2, the occupied area ratio of the hollow layer area _{S H} is about 8%. In addition, a lower mold having no conventional hollow layer is also prepared as a comparative example, and the lower mold of this comparative example is installed at another position of the molding apparatus to which the lower mold of the embodiment is attached. Molded with.

  And when the temperature of the lower mold was measured at the timing immediately after the panel was taken out, the temperature at the center of the bottom surface of the inner surface of the lower mold was 500 ° C. and the temperature of the long axis end was 510 ° C. In the comparative example, the temperature at the center of the bottom surface was 490 ° C., and the temperature at the end of the long axis was 550 ° C. From this, it was clarified that the present invention can obtain the effect of lowering the temperature of the peripheral part without lowering the temperature of the central part of the bottom surface.

  Furthermore, two 34 type | mold panels taken out from each lower type | mold of an Example and a comparative example were annealed continuously on the same conditions, and the compressive stress by the physical strengthening method was provided to the panel. And about these physically strengthened panels, the reinforced compressive stress in the outer surface of each face part was measured.

  In addition, the measurement of the said compressive stress was performed using the apparatus described in Unexamined-Japanese-Patent No. 11-281501. Specifically, a light source, a deflecting element, a slit, a first prism and a second prism, and a measuring unit including a light-shielding plate disposed between both prisms, a corrector, an analyzer, and an eyepiece are provided. In addition, a stress measuring device by a photoelastic method was used.

  FIG. 4 shows the measurement points of the reinforced compressive stress on the outer surface of the face part. The first measurement location is the central portion 18 (position where the minor axis 19 and the major axis 20 intersect) of the outer surface of the face portion 13, and the second measurement location is the major axis end of the outer surface of the face portion 13. This is the vicinity 21. Here, the long-axis end vicinity portion 21 indicates a position that enters 60 mm inside from the outermost peripheral position 22 of the long-axis end toward the central portion of the face portion 13.

  As a result, the panel molded with the lower mold of the embodiment of the present invention has a reinforced compressive stress of 15.0 MPa at the center portion of the face portion and 14.9 MPa at the vicinity of the major axis end, out of the peripheral portion of the face portion. In particular, it was confirmed that sufficient compressive stress was also formed in the vicinity of the long axis end where physical strengthening was difficult. On the other hand, in the panel molded with the conventional lower mold of the comparative example, the central part of the face part is 15.3 MPa, the vicinity of the long axis end is 10.1 MPa, and the central part of the face part has the same level of reinforced compression. Although stress was applied, the vicinity of the long axis end, which is difficult to physically strengthen, in the peripheral portion of the face portion was not sufficiently cooled, so that the desired reinforced compressive stress could not be applied.

The top view of the lower mold | type which is preferable embodiment of this invention. Sectional drawing in the AA part of FIG. Sectional drawing of the lower mold | type which is other embodiment of this invention. Explanatory drawing which shows the measurement location of the reinforced compressive stress of the glass panel for cathode ray tubes in an Example. Plane explanatory drawing of the molding apparatus of the glass panel for cathode ray tubes. Cross-sectional explanatory drawing of the lower mold | type cooling device of a prior art. Sectional drawing of the glass panel for cathode ray tubes.

Explanation of symbols

1: Lower mold 2: Bottom part 3: Side wall part 4: Hollow layer 5: Cathode ray Shenyang glass panel 6: Leg 7: Lower surface 8: Mounting flange 9: Hole 10: Lid 11: Nozzle 12: Umbrella member 13: Face part 14: Skirt 15: Turntable

Claims (7)

  A cathode ray tube in the glass filling portion having a glass filling portion formed by a substantially rectangular bottom portion and side wall portions provided on the four sides of the bottom portion, and supplied from a lower portion of the bottom portion to a central portion of the bottom portion. A lower mold for molding a cathode ray tube glass panel for cooling a glass panel, wherein a hollow layer is provided at a central portion of the bottom portion.   The lower mold for forming a cathode ray tube glass panel according to claim 1, wherein a planar shape of the hollow layer is substantially circular. 3. The lower mold for forming a cathode ray tube glass panel according to claim 1, wherein a shortest diameter D _S and a longest diameter D _L of the planar shape of the hollow layer have a relationship of 0.25 ≦ D _S / D _L ≦ 1. . The area when the vertical projection of the bottom and _{S B,} when the area of the planar shape of the hollow layer was _{S H,} claim 1 having _{0.01 ≦ S H / S B ≦} 0.25 the relationship, 4. A lower mold for molding a cathode ray tube glass panel according to 2 or 3.   The lower mold for forming a cathode ray tube glass panel according to any one of claims 1 to 4, wherein the thickness of the hollow layer at the center of the bottom is 0.1 to 20 mm.   The lower die for forming a cathode ray tube glass panel according to any one of claims 1 to 5, wherein a lower surface side of a central portion where the hollow layer of the bottom portion is provided is convex. A coolant is supplied toward the bottom center of the bottom of the lower mold for forming a cathode ray tube glass panel formed by a substantially rectangular bottom and side walls provided on the four sides of the bottom, and the lower mold is filled. In the manufacturing method of the glass panel for cathode ray tubes which cools glass,
A method for producing a glass panel for a cathode ray tube, wherein a hollow layer is provided at the center of the bottom of the lower mold.

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