JP2006253001A - Glass bulb for cathode-ray tube, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid such a trouble that a defect due to an external injury on the outer surface of a bulb is developed to a crack by thermal stress by forming a proper physically strengthened compressive stress layer in the lower layer of a chemically strengthened compressive stress layer. <P>SOLUTION: A chemically strengthened compressive stress layer A formed by ion exchange. and a physically strengthened compressive layer B formed by cooling, which extends in the lower layer of the chemically strengthened layer A, are formed on the outer surface 2a of a glass panel part. The thickness of the physically strengthened compressive stress layer B is not less than 2.0 mm and less than 3.5 mm, and its compressive stress value is not less than 3.0 MPa and less than 8.5 MPa. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a glass bulb for a cathode ray tube and a manufacturing method thereof, and more particularly to a technique for optimizing internal stress in a glass bulb for a projection type cathode ray tube.

  Conventionally, as a cathode ray tube which is a constituent element of a television receiver or the like, a so-called direct-view type cathode ray tube and a projection type cathode ray tube are known. As shown in FIG. 6, a cathode ray tube glass bulb (hereinafter also simply referred to as a bulb) 1 serving as an envelope of these cathode ray tubes has a peripheral edge of a substantially rectangular face portion 2a constituting a front portion. A glass panel portion (hereinafter also simply referred to as a panel portion) 2 having a skirt portion 2b extending substantially perpendicularly toward the rear portion, and a large opening end and a small opening end are formed at one end and the other end in the tube axis direction, respectively. And a glass funnel portion (hereinafter also simply referred to as a funnel portion) 3 having a substantially funnel-shaped side wall portion 3a. The funnel portion 3 here means a glass article in which a neck tube 4 holding an electron gun is welded to a small opening end of the side wall portion (hereinafter the same).

  This type of valve, particularly the projection-type valve 1, has a seal edge surface formed at the opening end of the skirt portion 2 a of the panel that becomes the panel portion 2 and a large opening end of the side wall portion of the funnel that becomes the funnel portion 3. The formed seal edge surface is welded with a burner. Therefore, in the manufacturing process of this type of valve 1, due to the above-mentioned welding, strip-like tensile stress is applied to the outer surface of each part of the panel part 2 and the funnel part 3 separated from the welding part 1a by 10 to 15 mm. A layer is formed. Since the stress value of the tensile stress layer is extremely high, if the valve 1 in such a state is left as it is, a minute defect generated in the valve 1 itself, specifically, a geometrical defect such as a depression. The probability of occurrence of cracks is increased due to defects due to melt adhesion of glass powder or micro scratches caused by external influences. Therefore, in the valve 1 in such a state, the above-described tensile stress layer needs to be eliminated before the valve 1 is handled as a product.

  Therefore, such a valve 1 is introduced into a slow cooling furnace having a temperature gradient (gradient indicated by a temperature characteristic line T) as shown in FIG. 7 for the purpose of eliminating the above-described tensile stress layer. The distortion removal processing is performed by passing through. More specifically, as shown in the figure, this slow cooling furnace is a temperature at which the temperature of its internal space exceeds the slow cooling point as it moves sequentially from the zone (1) to the zone (18) downstream in the transport direction. The temperature is set so as to gradually decrease from a region (for example, about 550 ° C.) to about 120 ° C., and the time for one valve 1 to pass through the slow cooling furnace is about 60 minutes.

  When the valve 1 passes through the slow cooling furnace in which the temperature of the internal space is set in this way, the glass surface temperature of the valve 1 is once heated to the annealing point or higher, so that various residuals generated in the valve 1 Simultaneously with the relaxation of the stress, the tensile stress layer generated in the panel part 2 and the funnel part 3 disappears. Here, the annealing point is a value uniquely determined according to the type of glass, and if the glass is held at this annealing point for 15 minutes, the temperature at which the stress existing inside disappears. Is defined as

  The valve 1 subjected to such strain removal treatment has a compressive stress layer (hereinafter referred to as an ion-reinforced compressive stress layer) having a depth of less than 35 μm and a stress value of 4 MPa to 300 MPa on the outer surface of the panel portion 2. For the purpose of forming, a strengthening process by an ion exchange method (hereinafter referred to as an ion strengthening process) is performed.

That is, in order to obtain a large image, a projection type cathode ray tube has been widely used in a method for projecting and displaying an image displayed on a glass panel portion of a cathode ray tube on a large screen through an optical system. The image on the phosphor screen is required to be brighter in each stage than a normal direct-view cathode ray tube. Therefore, the projection type cathode ray tube has a high anode voltage and beam current density, and heat generated on the panel surface during operation is higher than that of the direct view type cathode ray tube. Therefore, tensile stress is generated on the outer surface of the panel part due to the thermal stress accompanying this heat generation, and if there are defects such as scratches, the probability of breakage starting from this will be significantly higher than that of the direct-view cathode ray tube. . For the purpose of reducing the damage, chemical strengthening by ion exchange treatment is performed by a technique such as Patent Documents 1 and 2 below.
JP-A-57-208042 Japanese Utility Model Publication No. 57-115155

  By the way, the valve | bulb 1 made into the annealing point or more during the distortion removal process in the annealing furnace mentioned above is cooled to room temperature to such an extent that glass is not damaged along the temperature gradient shown in FIG. However, since the cooling rate at this time is high and not complete slow cooling, the tensile stress layer generated in the panel portion 2 and the funnel portion 3 disappears, but the cooling temperature between the inner surface and the outer surface of the valve 1 is lost. New internal stresses arise due to the difference and the cooling rate difference.

  That is, in the cooling process in the slow cooling furnace, while the outer surface of the valve 1 is rapidly cooled, the inner surface is gradually cooled, and the outer surface side contracts rapidly while the inner surface side is Temporary strain is eased because the fluidity is still maintained, but when the inner surface side tries to shrink thereafter, the movement is limited by the already solidified outer surface side layer. As a result, the shrinkage of the glass on the outer surface side becomes smaller than that on the inner surface side, so that a situation occurs in which compressive stress remains on the outer surface and tensile stress remains on the inner surface. Such a situation becomes more prominent as the slow cooling rate is increased in a temperature region where the glass temperature is equal to or higher than the strain point (for example, about 450 ° C.) in order to improve productivity. Here, the strain point is a value uniquely determined according to the type of glass, and if the glass is held at this strain point for several hours (for example, 3 to 4 hours), it was present inside. The temperature is such that the stress disappears.

  And although the valve | bulb 1 which received the distortion removal process of such an aspect is given the chemical strengthening process by ion exchange as mentioned above, the temperature of the potassium nitrate molten salt used at that time is the slow temperature of glass. Between cold and strain points. For this reason, the compressive stress on the outer surface and the tensile stress on the inner surface formed by the above-described strain removal treatment are once relaxed, but the cooling rate in the cooling process of chemical strengthening by the subsequent ion exchange treatment, that is, the strain point Depending on the cooling speed condition until the temperature falls below the above-described principle, a new internal stress is generated due to the temperature difference and the cooling speed difference between the inner surface and the outer surface of the valve 1, particularly the panel portion 2, during cooling as described above.

  In the cooling process of chemical strengthening by ion exchange treatment, the cooling rate until the strain point is lowered is generally about 10 ° C. per minute at which the valve 1 is not damaged by thermal shock in the ion strengthening treatment furnace during cooling. It is done in

  However, in the conventional glass tube for a cathode ray tube thus manufactured, in the cooling process of chemical strengthening by ion exchange treatment, the compressive stress (hereinafter referred to as the following) formed on the outer surface of the glass, particularly the outer surface of the panel portion 2. Physically reinforced compressive stress layer) is not sufficiently crack-resistant against defects that break through the chemically reinforced compressive stress layer formed by chemical strengthening by ion exchange treatment, such as scratches and scratches. . In other words, depending on the degree of trauma, the wound part is the starting point for the thermal stress during the hot water cleaning process and exhaust process at a later tube maker, or mounting use by a set maker or end user, leading to the occurrence of cracks. The reality is that there are some troubles.

  The present invention has been made in view of the above circumstances, and by forming an appropriate physical strengthened compressive stress layer under the chemically strengthened compressive stress layer, a defect in which a wound defect on the outer surface of the valve extends into a crack due to thermal stress. It is a technical problem to avoid this.

In order to solve the above technical problem, the present invention includes a glass panel portion in which a substantially rectangular face portion and a skirt portion extending substantially perpendicular to the periphery thereof are formed, and a large opening end is welded to the skirt portion. A glass tube for a cathode ray tube comprising a substantially funnel-shaped side wall portion and a glass funnel portion having a glass neck portion welded to a small opening end of the side wall portion,
The outer surface of the glass panel part is formed with a chemically strengthened compressive stress layer formed by ion exchange and a physically strengthened compressive stress layer by cooling extending below the chemically strengthened compressive stress layer, The physical strengthening compressive stress layer has a thickness of 2.0 mm or more and less than 3.5 mm, and a compressive stress value of 3.0 MPa or more and less than 8.5 MPa. These two stress layers are constituted in duplicate from the surface of the glass panel.

  According to such a configuration, the compressive stress value of the physically strengthened compressive stress layer existing in the lower layer (inside) is sufficiently high even if it receives a defect or trauma that breaks through the ion strengthened compressive stress layer formed by the ion strengthening process. It will have excellent crack resistance. Within the range of the thickness and stress value of the physically strengthened compressive stress layer in the present invention, the thickness and the stress value are substantially correlated, the thickness of the physically strengthened compressive stress layer is less than 2.0 mm, and the stress value is 3. If it is less than 0 MPa, it is not possible to have sufficient anti-cracking properties against the extension of defects that break through the ion-reinforced compressive stress layer and the cracks of trauma. In addition, when the thickness of the physically strengthened compressive stress layer is 3.5 mm or more and the stress value is 8.5 MPa or more, the stress value of the tensile stress layer generated along with the formation of the compressive stress layer becomes too large and causes self-destruction. Invite this problem.

  In the above configuration, the thickness of the physical strengthening stress layer is more preferably 2.8 mm or more and less than 3.5 mm, and the compressive stress value is more preferably 7.0 MPa or more and less than 8.5 MPa.

  According to such a structure, it can have the outstanding crack resistance.

In addition, the method according to the present invention made to solve the above technical problem includes a seal edge surface of a glass panel in which a substantially rectangular face portion and a skirt portion extending substantially perpendicular to the periphery thereof are formed, and a tube shaft A glass bulb by welding a seal edge surface formed at the large opening end of the glass funnel having a substantially funnel-shaped side wall portion having a large opening end and a small opening end formed at one end and the other end in the direction, In the method for producing a glass bulb for a cathode-ray tube, the glass bulb is subjected to a distortion removal treatment, and then the ion exchange treatment of the glass bulb is performed.
After forming the chemically strengthened compressive stress layer on the outer surface of the glass panel by the ion exchange treatment, a cooling rate of 13 ° C./min to 20 ° C./min until the outer surface temperature of the glass panel falls below the strain point. It is characterized by cooling with.

  According to such a configuration, in the cooling process after the ion exchange treatment, the valve, in particular the panel, particularly the panel due to the temperature difference and the cooling rate difference between the inner surface and the outer surface of the panel until the strain point is lowered. A compressive stress layer is formed on the outer surface of the part by strong physical reinforcement. In addition, by increasing the cooling rate after completion of the ion strengthening process, the time required for the entire ion exchange process can be efficiently shortened, and the productivity can be improved.

  As described above, according to the present invention, both the chemically strengthened compressive stress layer formed by the ion strengthening treatment on the outer surface of the glass bulb, particularly the panel, and the lower layer through the cooling process of the ion strengthening treatment, the appropriate stress value is obtained. Because there is a physically reinforced compressive stress layer formed with the thickness of the stress layer, it has excellent crack resistance, and it is possible to prevent extension of cracks due to defects and trauma that break through the chemically reinforced compressive stress layer Become.

  On the other hand, according to the manufacturing method according to the present invention, after forming the chemically strengthened compressive stress layer by ion exchange treatment on the outer surface of the panel portion, until the outer surface temperature of the glass panel is lower than the strain point of the glass panel, Since cooling is performed at a cooling rate of 13 ° C./min or more and 20 ° C./min or less, it is possible to form a compressive stress layer by physical strengthening having an appropriate stress value excellent in crack resistance and a thickness of the stress layer. It becomes. In addition, by increasing the cooling rate after completion of the ion exchange process, the time required for the entire ion exchange process can be efficiently shortened, and productivity can be improved.

  Hereinafter, a projection cathode ray tube bulb (hereinafter simply referred to as a projection bulb) and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the projection bulb 1 according to this embodiment includes a panel portion 2 in which a skirt portion 2b is connected to a peripheral edge portion 2x of a face portion 2a at a substantially right angle, and a large portion at one end and the other end in the tube axis direction. The funnel part 3 which has the substantially funnel-shaped side wall part 3a in which the opening end and the small opening end were formed was sealed via the welding part 1a. As shown in FIG. 3, on the outer surface of the projection valve 1, in particular, on the outer surface of the panel portion 2, a chemically strengthened compressive stress layer A formed by ion exchange treatment and physical strengthening physical formed in the cooling process after ion exchange treatment. There is an extended portion B of the reinforced compressive stress layer (hereinafter referred to as a physical reinforced compressive stress layer B).

  Then, as shown in the figure, the central portion in the width direction in the region extending from the periphery of the peripheral portion 2x of the face portion 2a of the panel portion 2 to the periphery of the welded portion 1a of the funnel portion 3 through the skirt portion 2b. A piece 5 having a width t of 5 mm was cut out from (the central part in the direction along the long axis La), and the thickness and stress value of the compressive stress layer measured on the outer surface of the piece 5 by the Senarmon method are the above-mentioned ion-reinforced compressive stress layer. A has a thickness of 20 μm or more and less than 35 μm, and a compressive stress value of 4 MPa or more and 300 MPa or less, and the physical strengthened compressive stress layer B has a thickness of 2.0 mm or more and less than 3.5 mm and 3.0 MPa or more and 8.5 MPa. Compressive stress value of less than.

  The projection valve 1 is manufactured by the method described below. First, the panel and funnel molded in the molding step are welded by heating the seal edge surfaces of both to a burner. Thereafter, the welded projection valve is passed through a slow cooling furnace having the temperature gradient shown in FIG. Further, after that, only the outer surface of the panel portion 2 of the projection valve 1 that has been subjected to the distortion removal treatment is immersed in a molten potassium nitrate salt to perform an ion exchange treatment.

  In this ion exchange treatment, first, the liquid temperature of the potassium nitrate molten salt is set to the ion exchange temperature, and the outer surface of the panel 2 of the projection type bulb 1 is immersed in this and held for about 1 to 3 hours. In the subsequent cooling process, the temperature is decreased at a rate of 15 to 20 ° C./min until at least below the strain point, and then cooled to 380 ° C. at a conventional cooling rate of about 10 ° C./min, After that, let it cool naturally and bring it to room temperature. Thereby, the projection type valve | bulb 1 which has the chemical reinforcement | strengthening compression stress layer A and the physical reinforcement | strengthening compression stress layer B in the outer surface of the panel 2 as mentioned above is obtained. Here, as described above, the physical strengthening compressive stress layer B is 3.0 MPa or more and less than 8.5 MPa over a depth of 2.0 mm or more and less than 3.5 mm from the boundary with the adjacent chemical strengthening compressive stress layer A. It has a compressive stress value.

  Example 1 of the projection type valve according to the present invention has a temperature characteristic indicated by a broken line (large) in FIG. 2, that is, the temperature of the potassium nitrate molten salt, after the distortion removal after welding (processing based on the temperature gradient in FIG. 7). The ion exchange treatment is performed according to the characteristics or the temperature characteristics of the outer surface of the glass. More specifically, in Example 1, as a condition for performing the ion strengthening treatment, after being held at the ion exchange temperature for 1 to 3 hours immediately after the start, the sample is cooled at 13 ° C./min until it falls below the strain point. Then, after cooling to 380 ° C. at 10 ° C./min, it was naturally cooled.

  Example 2 of the projection-type bulb according to the present invention has a temperature characteristic indicated by a one-dot chain line in FIG. 2, that is, a temperature characteristic of potassium nitrate molten salt or an outer surface of glass after the distortion removal treatment after welding (same as above). The ion exchange treatment is performed according to the temperature characteristics. Specifically, in Example 2, as a condition for performing the ion exchange treatment, the ion exchange temperature is maintained at the ion exchange temperature for 1 to 3 hours immediately after the start thereof, and then cooled at 15 ° C./min until the strain point is lowered. Then, after cooling to 380 ° C. at 10 ° C./min, it was naturally cooled.

  Example 3 of the projection-type bulb according to the present invention has a temperature characteristic shown by a solid line in FIG. 2, that is, a temperature characteristic of potassium nitrate molten salt or a temperature of the outer surface of glass, after the distortion removal after welding (same as above). Ion exchange treatment was performed according to the characteristics. Specifically, in Example 3, as a condition for performing the ion exchange treatment, the ion exchange temperature is maintained at the ion exchange temperature for 1 to 3 hours immediately after the start, and then cooled at 20 ° C./min until the strain point is lowered. Then, after cooling to 380 ° C. at 10 ° C./min, it was naturally cooled.

  Comparative Example 1 (conventional example) shows the temperature characteristics indicated by the two-dot chain line in FIG. 2, that is, the temperature characteristics of the potassium nitrate molten salt or the temperature characteristics of the outer surface of the glass after the distortion removal treatment after welding (same as above). Therefore, an ion exchange treatment is performed. More specifically, in Comparative Example 1, as a condition for performing the ion exchange treatment, the ion exchange temperature is maintained at the ion exchange temperature for 1 to 3 hours immediately after the start, and then cooled at 10 ° C./min until the strain point is lowered. Then, after cooling to 380 ° C. at 10 ° C./min, it was naturally cooled.

  In Comparative Example 2, the ion exchange is performed according to the temperature characteristics indicated by the dotted line (small) in FIG. 2, that is, the temperature characteristics of the potassium nitrate molten salt or the temperature characteristics of the outer surface of the glass after the strain removal treatment after welding (same as above). It has been processed. Specifically, in Comparative Example 2, as a condition for performing the ion exchange treatment, the ion exchange temperature is maintained at the ion exchange temperature for 1 to 3 hours immediately after the start thereof, and then cooled at 25 ° C./min until the strain point is lowered. Then, after cooling to 380 ° C. at 10 ° C./min, it was naturally cooled.

  For the four projection-type valves subjected to the ion exchange processing of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2, pieces were cut out by the already described technique and the face portion 2a shown in FIG. The maximum compressive stress value and the thickness of the physically reinforced compressive stress layer and the chemically reinforced compressive stress layer on the outer surface of the skirt portion 2b from the outer surface of the skirt portion 2b were measured by the Senarmont method. In this example and the comparative example, the maximum compressive stress on the outer surface appears at the position a in FIG. 3 (a position 15 mm away from the outer surface of the skirt portion 2b. The results are shown in Table 1 below.

In addition, the projection type valves of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were cut as shown in FIG. 4, and the outer surface of the face portion 2a was scratched by # 320 sandpaper. After the application, a rubber plate having a heater H built in the inner surface of the face portion 2a was attached with heat-resistant tape. The cut projection type cathode ray tube was again attached with glass tape, and the wiring was connected from the neck portion 4. Then, as shown in FIG. 5, the projection type cathode ray tube is evacuated from the neck portion 4 using a rotary pump, and after reaching a certain degree of vacuum (10 ⁻³ Pa), a certain temperature rising schedule (4.5 ° C. / Min), the heater H was heated, and the outer surface temperature of the face portion 2a when a crack occurred from the scratched portion was recorded. The results are shown in Table 1 below.

  According to Table 1, the maximum compressive stress value of the physically strengthened compressive stress layer B is 5.5 MPa at the maximum in Example 1, the average value is 5.3 MPa, the maximum is 7.8 MPa in Example 2, and the average is 7 4 MPa, the maximum in Example 3 is 8.4 MPa and the average is 8.2 MPa, whereas in Comparative Example 1 (conventional example), the maximum is 2.9 MPa and the average is 2.8 MPa, and Comparative Example 2 Then, the maximum is 8.5 MPa, and the average is 8.5 MPa. Therefore, the compressive stress value of the physical reinforcing layer on the outer surface of the projection type valves according to Examples 1, 2, 3 and Comparative Example 2 of the present invention is conspicuous compared with the compressive stress value of the physical reinforcing layer of Comparative Example 1. It's big. However, in Comparative Example 2, the compressive stress value of the physical reinforcing layer on the outer surface of the panel is too large. As a result, the tensile stress on the inner surface increases, and cracks originated from minute defects (micro bubbles) on the inner surface of the valve after standing at room temperature. There was one out of four. From this, it was judged that 20 ° C. per minute is appropriate as the upper limit of the cooling rate to a temperature below the strain point.

  Further, according to the heat resistance test, the temperature at which cracks occur in the valve is 103 ° C. on average in Example 1, 110 ° C. on average in Example 2, and 114 ° C. on average in Example 3, whereas in Comparative Example 1, The average was 99.3 ° C., and in Comparative Example 2, the average was 126 ° C. However, in Comparative Example 2, since one of the four parts was damaged from the inner surface of the valve, the other three average temperatures were obtained. That is, in Comparative Example 2, it was confirmed that cracks are most likely to occur compared to Comparative Example 1, Example 1, Example 2, and Example 3. In consideration of this, the probability of occurrence of cracks is markedly reduced in the projection valves according to Examples 1, 2, and 3 of the present invention than in the projection valves according to Comparative Examples 1 and 2. I understand that. In particular, in the glass bulbs of Examples 2 and 3, the average fracture temperature difference ΔT was 11 ° C. and 15 ° C., respectively, compared with Comparative Example 1, and it was confirmed that they were significantly higher.

It is a perspective view which shows the principal part of the glass bulb for cathode ray tubes which concerns on embodiment of this invention. It is a graph which shows the process temperature schedule in the manufacturing method of the glass bulb for cathode ray tubes which concerns on embodiment of this invention. It is a front view which shows the piece of the glass bulb for cathode ray tubes which concerns on embodiment of this invention. It is a schematic front view which shows the implementation state of the durability experiment of the glass bulb for cathode ray tubes which concerns on embodiment of this invention. It is a schematic front view which shows the implementation state of the durability experiment of the glass bulb for cathode ray tubes which concerns on embodiment of this invention. 1 is a schematic front view showing a glass bulb for a cathode ray tube according to an embodiment of the present invention. It is a graph which shows the temperature schedule at the time of the distortion removal process in the manufacture process of the glass bulb for cathode ray tubes which concerns on embodiment of this invention.

Explanation of symbols

1 Bulb (glass bulb for cathode ray tube)
1a Welding part 2 Panel (glass panel)
2a Face part 2b Skirt part 2x Peripheral part 3 Funnel (glass funnel)
3a Side wall part 5 pieces A Chemically strengthened compressive stress layer B Physically strengthened compressive stress layer H Heater

Claims (2)

A glass panel portion having a substantially rectangular face portion and a skirt portion extending substantially perpendicularly to the periphery thereof, a substantially funnel-shaped side wall portion having a large opening end welded to the skirt portion, and a small opening end of the side wall portion In a glass bulb for a cathode ray tube comprising a glass funnel portion having a glass neck portion welded to
The outer surface of the glass panel part is formed with a chemically strengthened compressive stress layer formed by ion exchange and a physically strengthened compressive stress layer by cooling extending below the chemically strengthened compressive stress layer, A glass bulb for a cathode ray tube, wherein the physical strengthened compressive stress layer has a thickness of 2.0 mm or more and less than 3.5 mm and a compressive stress value of 3.0 MPa or more and less than 8.5 MPa. A sealing edge surface of a glass panel in which a substantially rectangular face portion and a skirt portion extending substantially perpendicular to the periphery thereof are formed, and a large opening end and a small opening end are formed at one end and the other end in the tube axis direction, respectively. A glass bulb having a funnel-shaped side wall is welded to the sealing edge surface formed at the large opening end to form a glass bulb, and the glass bulb is subjected to a strain removal treatment. In the method for manufacturing a glass tube for a cathode ray tube for performing an exchange process,
After forming the chemically strengthened compressive stress layer on the outer surface of the glass panel by the ion exchange treatment, cooling at 13 ° C./min to 20 ° C./min until the temperature of the outer surface of the glass panel falls below the strain point. A method for producing a glass bulb for a cathode ray tube, characterized by cooling at a speed.

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