JPH0213456Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Industrial Application Field) The present invention relates to a mold used when forming a glass plate by vacuum forming, press forming, or a combination thereof. (Prior art) As a method for molding cathode ray tubes (CRTs), fluorescent display tubes, plasma displays, etc., a glass plate placed on a mold is conventionally heated to near its softening point.
A method is known in which the glass plate is formed by evacuating it through a suction hole formed in the mold, or by pressing it with a press mold placed above the mold, so as to follow the molding area of the mold. Here, the material for the mold has traditionally been FC.
Metal materials such as alloys, stainless steel, heat-resistant cast steel, and superalloys are used. These metal materials do not have good wettability with glass, and the glass fuses during molding, making it impossible to release the mold. Therefore, the glass plate must be coated with a mold release agent before molding. I try to do this. (Problem that the invention aims to solve) However, when molding cathode ray tubes, etc., a part of the glass plate will be stretched significantly during molding, and even if the glass plate is coated with a mold release agent before molding. Even if the mold release agent is not able to follow the elongation of the glass plate, the greatly elongated part will come into direct contact with the bottom of the mold without the release agent, and if the mold temperature is 550℃ or higher. When the glass and the mold are fused together, it becomes impossible to release the mold. Therefore, it has been considered to use a material that has good wettability with glass, that is, amorphous carbon or graphite, which has no affinity with glass and does not cause glass adhesion, as a material constituting the mold. However, amorphous carbon and graphite deteriorate when they come into contact with oxygen at high temperatures, so the entire atmosphere of the heating furnace that houses the mold must be an inert gas atmosphere such as nitrogen gas. The heating furnace itself must have an airtight structure, which complicates the structure and takes time to create a predetermined atmosphere, reducing production efficiency. (Means for Solving the Problems) In order to solve the above problems, the present invention makes the bottom part of the mold forming part, which is in contact with the most extended part of the glass plate and has a low degree of contact with the outside air, with an amorphous shape. It is made of carbon, graphite, or boron nitride. (Example) An example of the present invention will be described below based on the accompanying drawings. FIG. 1 is a longitudinal cross-sectional view of a mold according to the present invention, and FIG. 2 is a plan view of the same mold. The mold 1 has an inverted pyramid-shaped (funnel-shaped) molding part 2 that opens upward. The upper part 2a and middle part 2b of this molding part 2 are formed by the first mold part 3, and the bottom part 2c of the molding part 2 is formed by the second mold part 4. The first mold part 3 is made of a metal material with excellent mechanical strength such as FC alloy, stainless steel, heat-resistant cast steel, or superalloy, and the second mold part 4 is made of a material with good wettability with glass. In other words, materials such as amorphous carbon, graphite, or boron nitride, which have no affinity with glass that has been heated to near its softening point and are difficult to fuse with, are used, and this is processed using hot pressing methods. Obtain by twisting and shaping. The second mold part 4 has a vacuum suction hole 5.
is installed. Further, the material of the second mold part 4 is the same as that of the first mold part 3.
Since the coefficient of linear expansion is smaller than the material of It is preferable that there be no gaps between the parts. Further, when boron nitride is used as the material for the second mold part 4, the content of boron nitride is preferably 75 wt% or more, particularly 90 wt% or more. A method of molding the glass plate G using the mold 1 as described above will be described below. First, a glass plate G coated with a mold release agent is placed on a mold 1, and the glass plate G is heated to near its softening point. In this case, when amorphous carbon or graphite is used as the material for the second mold part 4, the vacuum suction hole 5 is used to prevent deterioration due to contact with oxygen at high temperatures. It is preferable that a small amount of inert gas such as nitrogen gas be blown into the bottom 2c of the molding section 2. When the glass plate G is heated to near its softening point, the glass plate G is pushed more than halfway into the molding part 2 using a press mold (not shown), and the glass plate G is sucked through the vacuum suction hole 5. A glass plate G is molded into a shape that follows the molding part 2. In this case, the part of the glass plate G that contacts the bottom part 2c of the molding part 2 is stretched the most, so the mold release agent cannot follow this elongation, but the second mold part 4 that forms the bottom part 2c is As described above, since it is made of a material with excellent wettability, the glass will not be fused. Next, an example will be described with specific numerical values. First, SUS403 was used as the material for the first mold part 3, a boron nitride sintered body with a boron nitride content of 95 wt% was used as the material for the second mold part 4, and soda was used as the glass plate G.・Prepare 3 mm thick lime silica glass, coat this glass plate with boron nitride fine powder as a mold release agent to a thickness of about 30 μm, and then
The mold was heated to 830°C and the mold was heated to approximately 800°C, and molding was performed using a combination of press molding and vacuum forming. In addition, the length L of the short side of the upper end opening of the mold 1 used for molding was 13 mm, and the first mold part 3
The depth H of the upper part 2a and the middle part 2b of the molded part 2 formed by the molding part 2 was varied variously during molding. The results are shown in [Table].

[Table] As is clear from this [Table], H/L>1.25
In this case, glass adheres to the intermediate part 2b of the molding part formed by the first mold part 3, and H/L≦
At 1.25, no adhesion occurred. In addition, the material of the second mold part 4, the components of the glass plate G, the molding temperature,
Even in experiments conducted by changing the dimensions of the molded part 2, substantially the same results as above were obtained. Therefore, it is preferable to determine the dimensions of the second mold part 4 so as to satisfy the relationship H/L≦1.25. Furthermore, in the case where the second mold is made of amorphous carbon or graphite, even if an inert gas such as nitrogen gas is not ejected when the mold is heated,
Since the second mold is located at the bottom of the molding section,
The degree of contact with outside air was small and there was no major deterioration. (Results of the invention) As explained above, according to the invention, in a mold for forming a glass plate, the bottom of the mold that contacts the most stretched part of the glass plate is made of amorphous carbon.
Since it is made of graphite or boron nitride, it can be easily released from the mold without glass fusing (adhesion). Furthermore, since the entire mold is not made of graphite, etc., the entire heating furnace can be easily removed. It does not require a nitrogen gas atmosphere, does not complicate the entire device and does not increase costs, and has many effects such as maintaining the rigidity of the entire mold.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a glass molding mold according to the present invention, FIG. 2 is a plan view of the same mold, and FIG. 3 is a longitudinal sectional view of the mold during molding. In the drawings, 1 is the mold, 2 is the molding part, 2a is the upper part of the molding part, 2b is the middle part of the molding part, 2c is the bottom of the molding part, 3 is the first mold part, and 4 is the second mold part. mold part,
5 is a vacuum suction hole, and G is a glass plate.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a mold for molding a glass plate, the molding part of the mold opens upward, and the bottom part of the molding part is in contact with the most extended part of the glass plate. A glass molding mold characterized by being made of amorphous carbon, graphite, or boron nitride. (2) The depth of the molded part made of a metal material that does not use amorphous carbon, graphite, or boron nitride is H, and the length of the short side of the opening of the molded part is L.
The glass molding mold according to claim 1, which is a utility model, and is characterized in that the mold satisfies the relationship H/L≦1.25.