JPH0649582B2 - Method for forming deep-drawn glass product having smooth surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for forming a deep-drawn glass product having a smooth surface,
In particular, the present invention relates to a method for forming a deep-drawn glass product, such as a display front panel for a flat-screen television, which partially has a smooth surface.

[Prior Art] Generally, for a front panel of a cathode ray tube, for example, a method in which a molten glass gob is press-molded into a predetermined mold and then a portion where a smooth surface is required is polished, or a glass plate is molded. There is a method of placing on a mold, heating, and then vacuum forming.

[Problems to be Solved by the Invention] However, among the conventional molding methods for this purpose, in the method of press-molding the gob, the glass gob melted during molding by the molding die is pressed against the surface of the molding die. ,
Since the surface of the glass product suffered from a flaw, it was necessary to polish the portion requiring a smooth surface after molding. As a result, there is a problem that the number of steps is increased, the production efficiency is reduced, and the cost is increased.

On the other hand, in the vacuum forming method, the force that contributes to the deformation of the glass plate is only the vacuum force, so it is necessary to raise the temperature of the deformed part of the glass plate. There is a problem that the plate thickness of the deformed portion having a high deformation becomes extremely thin, and that the glass plate portion near the deformed portion has a flaw due to contact with the molding die.

Further, in the vacuum forming method as well as the method of forming by sandwiching the glass plate between the male mold and the female mold, when the glass plate is placed on the concave mold and heated, the flat portion of the glass plate is bent due to its own weight. Things couldn't bloom.

On the other hand, in the method of heat forming by sandwiching a glass plate between a male mold and a female mold, a shearing force always acts on the glass plate, and when deep drawing is performed, the glass plate part forming the side surface is pulled. There is a problem that the glass plate is stretched and the thickness of the glass plate becomes thin, which causes a problem in strength, and is limited to the molding of a shallow small article such as a fluorescent display tube.

[Means for Solving the Problem] The present invention has been made to solve such conventional problems, and to reduce the thickness of the side wall of a deep-drawn molded product having no flaws on the smooth surface. It is an object of the present invention to provide a molding method capable of efficiently molding at low cost.

In order to achieve this object, the present invention is formed in the inner dimension of the glass product, and put the glass plate on the convex mold contacting the inner peripheral edge portion, the outer peripheral portion to be deformed of the glass plate, The glass product is heated to a temperature higher than the central portion of the glass plate, which is a smooth surface, and is deformed by its own weight on the convex mold, and then is deformed by a concave mold formed to the outer dimension of the glass product. A method for forming a deep-drawn glass product having a smooth surface for pressing a formed glass plate, wherein the temperature of the glass in the central portion of the glass plate during press forming is a viscosity indication (log
η and η are the poises of 14.5 or less and 11.5 or more, and the temperature of the outer peripheral portion of the glass plate to be deformed is 7.5 or more in the viscosity display, and after the press molding. At the start of slow cooling or cooling, once the glass temperature of the central portion of the glass plate is 14.5 or less in the viscosity display 1
A method of forming a deep-drawn glass product having a smooth surface, characterized in that the temperature difference between the central portion and the outer peripheral portion of the glass plate is set to 30 ° C. or less at a temperature of 2.4 or more.

In the present invention, when the glass product becomes large in size, it can be supported on a middle crosspiece which comes into contact with the central portion of the glass plate with a width of 2 mm or less at a key part of the convex molding die.

[Operation] In the present invention, while the central portion of the glass plate forming the smooth surface is kept at a temperature relatively lower than the outer peripheral portion of the glass plate forming the side wall, the part forming the side wall is preliminarily weighted by itself. Then, the central part of the glass plate is press-molded by controlling the central part within a predetermined temperature range and the outer peripheral part at a predetermined temperature or higher without contacting the central part of the glass plate with the molding die, and further performing slow cooling or cooling. At the start, the central part of the glass plate is within the specified temperature range, and the temperature difference between the central part and the outer peripheral part of the glass plate is below the specified temperature.Therefore, there is almost no decrease in the wall thickness, and it is pressed against a smooth surface. It is possible to efficiently mold a deep-drawing molded product having a high flatness smooth surface with no scratch and no warpage from a glass plate.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of a molded product according to the present invention, and FIG. 2 is a sectional view taken along the line AA ′ of FIG. In forming such a deep-drawn molded product from a glass plate, first, a support plate (1
The glass plate (G) is placed on the mold (11) attached to 0), and the entire glass plate is heated to a temperature about 100 ° C. lower than the strain point or higher. At this time, the mold is formed to the internal size of the molded product, or a support tool of similar size is used and transferred to a regular mold before press molding,
Either is fine.

Then, the outer peripheral portion (E) of the glass plate to be deformed is heated to a temperature at which the viscosity is displayed (log η, η is poise) to 7.5 (about 740 ° C. for soda lime silica glass) and the smooth surface of the molded article is heated. The constituent part (C) is 1 in the viscosity display.
4.5 (about 492 ° C) or less, preferably 13.5 (about 5)
Selectively heat up to 30 ° C. or lower to 12.4 (about 560 ° C.) or higher.

At this time, the temperature of the part constituting the smooth surface is 1 in the viscosity display.
If the temperature is not higher than 4.5, the glass may be cracked or broken during the pre-molding, and molding may not be sufficiently performed. Further, when the size of the glass plate is large, when the temperature is not less than 12.4 in the viscosity display, the glass plate is bent during heating, and it is difficult to obtain a clear smooth surface. In order not to leave any impression on the glass surface, it is preferable to keep the temperature of the portion C below the temperature at which the viscosity is 13.5.

Further, in order to substantially prevent the flexural deformation of the glass plate during heating, the glass cross-supporting middle bar (1
Providing 2) is particularly effective when the glass plate is large. If the middle crosspiece (12) is not provided, the supporting interval of the glass plate becomes long, so that when the temperature rising speed of the local heating is slow, the glass plate is likely to be flexibly deformed as the temperature rises.

At this time, the width of the portion of the middle rail (12) that comes into contact with the glass is 2
It should be less than mm, preferably less than 1 mm. When the width of the inner bar is wider than 2 mm, when the glass plate at room temperature is placed on the forming die, the temperature difference between the glass plate which is preheated in advance and the glass plate is locally rapidly heated and is not in contact. May cause thermal cracking, which is a problem.

The glass plate locally heated at the portion (E) to be deformed as described above is deformed by its own weight as shown in FIG. At this time, there is almost no change in the thickness of the glass plate in the deformed portion. When the glass plate is pressed with the concave mold (13) and the convex mold (10, 11) in such a state, the deformed portion of the glass plate which has been heated to a temperature suitable for the above-mentioned molding easily deforms, and the side wall. The deep-drawn glass product is molded while avoiding the problems associated with the reduction of the wall thickness.

If the glass product molded in this way is cooled as it is, there is a large temperature difference of more than 100 ° C. between the outer peripheral part and the inner part of the Galau plate, so warping occurs when it is cooled to room temperature or residual strain occurs during cooling. There is a risk of damage. Therefore, in the method of the present invention, the glass molded article is kept at a strain point of glass or higher (a temperature at which the temperature of the viscosity is 14.5 or higher), and the temperature difference inside the glass molded article is 30. Reduce to below ℃. At this time, in order to reduce the residual strain remaining in the glass product, the glass temperature should be set to a temperature of 13.5 or lower and 12.4 or higher in the viscosity display (about 530 ° C. or higher and 560 ° C. or lower for soda lime silica glass). Is preferred. If the temperature difference is reduced at a temperature below the strain point, there is no effect in reducing the residual strain.
At high temperatures such as 2.4 or less, the glass easily deforms,
The process becomes complicated. Further, if the temperature difference is larger than 30 ° C., the warp remaining in the molded product becomes large, which is not suitable for precision molded products.

In such a method of the present invention, there is almost no decrease in the thickness of the side wall, and the wall of the glass plate is not formed by the conventional method of setting glass between the concave and convex molds and heat forming, which is impossible by vacuum forming. It has become possible to secure a thickness of 85% or more of the thickness and to perform deep drawing with a depth of 20 mm or more or 4 times or more the thickness of the glass plate.

In this case, the feature of the present invention is preferably exerted when the ratio h / x of the protrusion (X) (FIG. 2) from the smooth side surface and the inner surface height (h) (FIG. 2) is 1.5 or more, usually 4.
This is the time of molding a molded product having a sharp shape of 5 or more.

The present inventors use a 4 mm float glass plate and have a flat surface dimension of 290 × 218 and an inner surface height (h) of 80 mm and a ratio (h / x) to the side surface of the protrusion of 5.67. Was molded by the above method to obtain a molded product having a side wall thickness of 3.7 mm and a ratio to the raw plate of 0.9 or more. There was no impression on the smooth surface of this molded product, and the warpage was about 100 μm, which was reduced to about ⅓ of that in the case without the middle crosspiece (12). Also,
The size of the smooth surface is 930 x 610 and the inner surface height (h) is 44.
In the case of a molded product having a ratio (h / x) of 1.5 in mm, the side surface is 3.8.
mm (blank plate ratio 0.95) or more, and the warp was 500 μm or less.

[Effects of the Invention] As described above, according to the method of the present invention, it is possible to form a highly flat three-dimensional glass molded body with almost no reduction in the thickness of the side wall of the glass plate. It is possible to obtain a glass molded product which is strong and suitable for a flat-panel television container and the like which is light in weight.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a perspective view of a deep-drawn glass product, FIG. 2 is a sectional view taken along the line AA 'in FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing a state in which a glass plate is placed, and FIG. 4 is a cross-sectional view of a glass plate and a concave forming die which are heated and deformed by heating on a convex forming die. C: Part that constitutes the smooth surface of the glass product E: Part that becomes the peripheral part of the glass product G: Glass plate 10: Support plate of convex mold, 11: Convex mold 12: Middle bar of convex mold, 13: Concave mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Eto 4-8-8 Doshomachi, Higashi-ku, Osaka City, Osaka Prefecture Nihon Sheet Glass Co., Ltd. (56) Reference JP-A-51-62810 (JP, A) JP-A-SHO 61-227932 (JP, A) Japanese Patent Sho 50-36850 (JP, B2)

Claims (2)

[Claims] 1. A glass plate is placed on a convex mold which is formed to have an inner size of the glass product and is in contact with the inner peripheral edge of the glass product, and the outer peripheral portion of the glass plate to be deformed is a smooth surface of the glass product. Which is heated to a temperature higher than the central portion of the glass plate to be deformed by its own weight on the convex molding die, and then the deformed glass plate is pressed by a concave molding die formed to the outer dimension of the glass product. 13. A method for forming a deep-drawn glass product having a smooth surface, wherein the temperature of the glass in the central portion of the glass plate during press forming is a viscosity display (log η, η is poise).
5 or less and 11.5 or more, and the temperature of the outer peripheral portion of the glass sheet to be deformed is 7.5 or more in the viscosity display, and after the press molding, the gradual cooling or cooling is started. , The temperature at which the glass temperature of the central portion of the glass plate is 14.5 or less and 12.4 or more in the viscosity display, and the temperature difference between the central portion and the outer peripheral portion of the glass plate is 30 ° C.
A method for forming a deep-drawn glass product having a smooth surface, characterized in that: 2. A middle bar, which is in contact with the central portion of the glass plate, is provided at a key part of the convex mold, and a width of the middle bar, which contacts the glass plate, is 2 mm or less. A method for forming a deep-drawn glass product having a smooth surface according to the item.