KR100572334B1 - Method for manufacturing windshield for cathode ray tube - Google Patents

Abstract

The present invention relates to a method for manufacturing a front glass for a cathode ray tube, and more particularly, to a heat treatment method characterized by reducing the temperature difference for each part of the front glass in the manufacturing process of the front glass and at the same time having a uniform stress distribution. The method of manufacturing a front glass for a cathode ray tube according to the present invention is a heat treatment method for adjusting a temperature distribution present on a plane for uniform stress distribution in a section before a slow cooling process after a molding process in a process of manufacturing a front glass, and a center of the front glass face part. And a physical strengthening step of locally heating the region.

Description

Method for manufacturing windshield for cathode ray tube

The present invention relates to a method for producing a front glass for a cathode ray tube, and more particularly to a method for manufacturing a front glass comprising a physical strengthening step of the front glass.

The physical reinforcement of the conventional glass for cathode ray tube is press-molded at a temperature range of about 1000 ° C., and then cooled to below the slow cooling point while maintaining a large temperature difference between the surface and the inside of the front glass. To form a stress to relieve the stress inside the front glass to achieve a certain physical strengthening to obtain a compressive stress on the surface by heat treatment to a temperature that can be rearranged by the atoms constituting the glass in or outside the slow cooling furnace.

First, US Patent 4566893 maintains the compressive stress on the surface by maintaining a temperature of about 30 ℃ lower than the existing slow cooling temperature in the slow cooling furnace to have a minimum strain. U.S. Patent 2551591 not only applies compressive stress to the surface using an air cooling device in the pre-slow process for thickness reduction and flattening, but also increases the compressive stress by intensively cooling the crack-prone areas. have. Japanese Laid-Open Patent Publication No. 10-194766 increases the magnitude of the stress by partially cooling the corner portion where the compressive stress is smaller than other portions.

The front glass for the cathode ray tube has a face portion that largely displays an image, a skirt portion bonded to the back glass, and a blend R portion between the face portion and the skirt portion. Here, the face edge region adjacent to the blend R portion has a three-dimensional structure form connecting the skirt portion and the face portion, and the mold, shell, plunger and air former of the molding process are formed. It is influenced by the flow rate and position, and its thickness is thicker than the center area of the face, so that the cooling speed is slower than other areas, and the stress release is also large, so that the magnitude of stress in the front glass cross section is small and the surface temperature is high. . On the other hand, the cooling rate of the face center region is faster than the edge region, so that the compressive stress in the cross-sectional direction is large and the surface temperature is low. On the face surface where the hot edge region and the cold central region coexist, the surface temperature distribution difference ( T) becomes large and unnecessary plane tensile stress is generated in the face edge region. As a result, there is a problem that the compressive stress is unevenly distributed over the entire front glass and thus becomes vulnerable to external shocks and thus cannot be used as the front glass for cathode ray tube bulbs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a method for producing a front glass for cathode ray tubes that controls the temperature distribution of the front glass surface by a local heating method such that a relatively uniform compressive stress is formed on the front glass.

The method for manufacturing a front glass for a cathode ray tube according to the present invention is characterized by reducing the temperature difference for each region present on the plane by heating the central region of the front glass face in the section before the slow cooling process after the molding process during the manufacturing process of the front glass. .

Hereinafter, the preferable Example about the manufacturing method of the front glass for cathode ray tubes of this invention is demonstrated in detail.

1 shows a planar schematic showing the surface temperature change by position of the windshield. Referring to FIG. 1, in the center region Z1, the edge region Z2, and the corner region Z3 constituting the face portion in the conventional molding process of the front glass for cathode ray tube bulbs, planar tensile stresses appear widely, and high temperature The compressive stress in the cross-sectional direction was increased while lowering the surface temperature of the face edge region by cooling the edge region Z2 which is the region. On the contrary, the central region Z1, which is a low temperature region subjected to planar compressive stress, was locally heated to increase the surface temperature, thereby reducing the surface temperature difference for each region on the face surface, thereby reducing unnecessary plane tensile stress occurring in the edge region Z2. In addition, the stress was released at high temperature to reduce the magnitude of the compressive stress to achieve uniform stresses for the regions as a whole.

In the most ideal cooling curve, it is preferable that the temperature distribution curve of the front glass surface be minimized because the temperature drop curves distributed by the front glass areas in the molding process are almost the same, but there are many difficulties in controlling temperature variables such as molding fixtures. Therefore, the section in which the heat treatment conditions can be easily changed is until the molded front glass is introduced into the slow cooling furnace, and the method of controlling the temperature distribution is largely divided into two types. That is, in order to increase the compressive stress, a faster cooling method and a heating method for further relieving the stress by heating the part showing the excessive compressive stress.

The heat treatment diagrams of Comparative Example 1 are shown in FIG. 2A, and the heat treatment diagrams of Examples 1 and 2 are shown in FIGS. 2B and 2C. As shown in FIG. 1 and FIG. 2A, the temperature difference for each region before entering the slow cooling furnace between the temperature T1 of the central region Z1 and the temperature T2 of the edge region Z2 reaches about 80 ° C. .

In the present invention, the molded front glass was heat-treated to have a temperature drop curve as shown in FIGS. The area where the maximum vacuum tensile stress acts upon exhaustion was quenched locally to increase the compressive stress in the thickness direction and at the same time reduce the temperature difference distributed on the plane. In addition, by locally heating the stress in the face center region Z1 to be similar to the edge region Z2, the compressive stress in the thickness direction was alleviated and the temperature difference distributed on the plane was similarly reduced. After passing through the slow cooling furnace in this state, the center portion Z1 of the face portion maintains a temperature higher than the atmosphere of the slow cooling furnace, and then becomes lower and becomes the same. The face edge region Z2 becomes the slow cooling furnace at a temperature lower than the ambient temperature of the slow cooling furnace. It is equal to the ambient temperature of and ultimately cools down to room temperature with a uniform temperature distribution over the windshield plane.

In the case of local heating, a device capable of instantaneously raising the temperature to high temperature was used through a method such as a halogen lamp or induction heating. Since the temperature gradient changes a lot depending on the size of the heating coil, the heat flow is transferred to the surroundings by heating only the localized area rather than heating the entire face area. That is, the heat treatment was performed before the slow cooling process to adjust the cooling rate and the heating rate to be the same as the atmosphere set in the slow cooling furnace, and the work time for uniformizing the temperature distribution existing on the actual plane was shortened by the preliminary heat treatment operation.

When heating the face part center area | region Z1, the temperature T1 range of a center area | region shall be 450 degreeC <T1 <700 degreeC. When temperature T1 of center area | region Z1 becomes 700 degreeC or more, the shape of a front glass will be distorted by self weight, and when it is less than 450 degreeC, there will be no effect of stress relaxation. Preferably, the temperature T1 of the central region Z1 is preferably a slow cooling furnace holding temperature Ta &lt; T1 &lt; The slow cooling furnace holding temperature Ta is set so that the slow cooling furnace temperature may have a profile of temperature raising, holding, and lowering for the purpose of stress relaxation of the front glass.

The slow cooling furnace holding temperature Ta is preferably set to 480 ° C <Ta <520 ° C. In the case of Ta <480 ° C., the slow cooling furnace maintenance temperature Ta may be unstable front glass due to low temperature and insufficient stress uniformity, and much plane tensile stress. On the other hand, in the case of Ta> 520 ° C, the stress is largely released regardless of the heat treatment in the forming process, so that the effect of the compressive stress does not occur. The central zone Z1 is heated just before the slow cooling furnace is introduced or when passing through the slow cooling furnace. Particularly, in the slow cooling furnace, the central zone Z1 is locally heated by using a device insulated from the slow cooling atmosphere temperature. For example, when the face center region Z1 is 500 ° C. and the edge region Z2 is held at 490 ° C. for 30 minutes, the center region Z1 has a large degree of relaxation of the stress, and the edge region Z2. The stress is less relaxed. When heating proceeds prior to slow cooling furnace input, it is advantageous to do this, for example, in the process of pinning to support the shadow mask. In the Example of this invention, what is performed just before a slow cooling furnace is shown.

When cooling the face edge region Z2, the temperature T2 range of the edge region Z2 is cooled at the local heating start temperature Th <T2 <600 ° C. The local heating start temperature Th is the surface temperature in the face edge region Z2 at the start of heating the front glass face center region Zl in the section before the slow cooling process after the molding process in the process of manufacturing the front glass. Point to. In the case of Th> T2, the cooling of the edge region Z2 and the heating of the central region Zl proceed at the same time, and the effects of cooling and heating are canceled, so that stress is not uniform. When the temperature T2 of the edge region Z2 at the time of taking out of the mold after the shaping of the windshield is cooled to 610 占 폚 at 600 占 폚 <T2, locally cooling the edge region Z2 on the press for forming the windshield This is difficult to control due to temperature variables such as molding jig. Preferably, the local heating is preferably performed when the front glass begins to reheat with the flow of internal heat flow after the local cooling has proceeded above the glass transition temperature.

When the front glass is molded in the mold, the temperature distribution shape is as shown in FIG. 1, and the temperature T3 of the edge region Z3 is highest in the face portion, and the temperature Tl of the face central region Zl is lowest. Temperature. According to the temperature distribution, the product before the slow cooling furnace analysis is analyzed, and the face center region Zl is unstable in the plane compressive stress, and the face edge region Z2 is unstable in the plane tensile stress. You are vulnerable. When passing through the slow cooling process, the plane stresses appearing in the product disappear or become 1 to 2MFa. The greater the temperature difference on the plane of the windshield, the greater the stress on the plane, which can be easily broken in the process, making it impossible to use the product without passing through the furnace. In general, the area where the cooling occurs first occurs in the plane compressive stress and the other parts in the plane tensile stress is reduced by the local heating method by reducing the temperature difference by the position on the plane to reduce the plane tensile stress or planar compressive stress This was made to form.

EXAMPLE

Comparative Example 1 shows a nonuniform distribution of stress of the front glass and heat treatment conditions without local cooling and heating in the conventional front glass manufacturing process.

Example 1 shows the results of improving the distribution ratio of stress by measuring the temperature of each region of the front glass in the molding process and heating the center region Z1 having the lowest dual temperature.

Example 2 measures the temperature of each area of the front glass in the molding process, rapidly cools the face edge region Z2 where the widespread tensile stress is distributed, and then heats the face central region Z1 to reduce the temperature difference between the regions. After reducing, the result of improving the distribution ratio of the stress obtained by injecting into a slow cooling furnace is shown in Table 1.

TABLE 1

As shown in Comparative Example 1, the stress distribution of the conventional slow cooling product showed a difference of 6MPa or more in the order of T1> T2> T3. It can be seen that rather than Comparative Example 1, the difference in the stress distribution is reduced, thereby improving the stress distribution. Example 2 not only improved the overall stress distribution difference but also increased the magnitude of the compressive stress by increasing the stress of the required portion through partial cooling and then locally heating to reduce the stress (FIG. 3).

In addition, although the surface temperature difference (ΔT) after molding and just before the slow cooling injection does not show a big difference from 110 ° C to 80 ° C, the surface temperature difference can be reduced to 7 ° C through local heating, so that an unnecessary plane generated on the plane There is a great effect of reducing the tensile stress. It is possible to increase the magnitude of compressive stress in the thickness direction only with partial cooling, but blowing the air in a short time does not have a significant effect on reducing the actual plane temperature difference (Example 3). That is, in the case of only partial cooling, the surface temperature difference until immediately before the slow cooling furnace was about 70 ° C. was not much improved compared to Comparative Example 1, but the surface temperature difference could be reduced to 20 ° C. through the local heating method (FIG. 2C). .

As described above, the products that do not pass through the slow cooling furnace have a large temperature difference on the surface according to the temperature distribution for each region, thereby increasing the unnecessary plane tensile stress and thus cannot be used as a bulb for cathode ray tubes. However, it was possible to improve the physical reinforcement method of the front glass having a complicated shape unlike the plate glass by reducing the difference in the surface temperature of each region through the local heating method.

As explained above, according to the manufacturing method of the front glass for cathode ray tubes which concerns on this invention, the temperature distribution of the front glass surface can be controlled by a local heating system so that a comparatively uniform compressive stress may be formed in the front glass.

1 is a plan view schematically showing a windshield surface temperature change by position,

2a to 2c are graphs showing the change in temperature of each position of the windshield;

3 is a graph showing the distribution for each position of compressive stress.

♣ Explanation of symbols for the main parts of the drawing

Z1: windshield center area Z2: windshield edge area

Z3: Windshield corner area T1: Temperature of the windshield center area

T2: temperature of the windshield edge area

T3: temperature in the front glass corner area

Claims (6)

A method of manufacturing a front glass for a cathode ray tube, characterized in that the central region of the front glass face part is locally heated by a heat treatment method of controlling a temperature distribution present on the front glass in a section after the molding step in the manufacturing process of the front glass. The method for manufacturing a front glass for a cathode ray tube according to claim 1, wherein the heating is performed locally so that the temperature (T1) of the central region of the front glass face portion is 450 ° C &lt; T1 &lt; 700 ° C. The method of manufacturing a front glass for a cathode ray tube according to claim 2, wherein the heating is performed locally so that the temperature T1 of the center region of the front glass face portion is a slow cooling furnace holding temperature Ta &lt; T1 &lt; 4. The method for manufacturing a front glass for a cathode ray tube according to claim 3, wherein the slow cooling furnace holding temperature Ta satisfies 480 ° C <Ta <520 ° C. The method for manufacturing a front glass for a cathode ray tube according to claim 1, wherein in the slow cooling step of the manufacturing process of the front glass, the temperature of the central region of the front glass face portion is locally heated to be higher than the temperature of the edge region. 6. The method for manufacturing a front glass for a cathode ray tube according to claim 5, wherein the heating is performed locally so that the temperature T1 of the center portion of the face portion of the front glass is a slow cooling furnace holding temperature Ta &lt; T1 &lt;