JPH0331655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for sharply bending glass sheets.

As a method for sharply bending a glass plate, a heater wire is arranged at a predetermined distance from the surface of the glass plate on the bending line where the glass plate is to be sharply bent, and the heater line is heated by electricity to bend the glass plate along the bending line. A method is known in which the glass plate is sharply bent along the bending line by heating the portion to a temperature equal to or higher than the softening point of the glass plate. This method is superior in terms of appearance because the heater filaments do not come into contact with the glass plate surface, so no traces of the heater filaments remain on the curved portion of the glass plate. However, if the bending line on which the glass plate is to be sharply bent is curved or bent, the heater wires must be wired along the bending line when bending the glass plate sharply using the above method. , it takes time and cost to manufacture a jig to maintain the wiring state during bending, and the bending line of the glass plate is It became difficult to heat only a portion locally, and there was a drawback that it was impossible to bend the glass plate sharply, for example, to make the curvature of the bent portion less than 30R.

The present invention improves these drawbacks, allows easy bending along curved or curved lines, and reduces the curvature of the outer surface of the bent portion of the glass plate.
It is possible to bend sharply to 30R or less,
Furthermore, it was invented as a result of studies with the aim of providing a method for bending a glass plate that does not leave traces of heater filaments on the bent curved portion of the glass plate. A heater wire is arranged along the bending line to be bent, and the heating wire is heated with electricity to heat the bending line portion of the glass plate to a temperature equal to or higher than the softening point of the glass plate, and the heating line is heated along the bending line. In the method of sharply bending a glass plate, a mold release agent layer is disposed on the surface of the glass plate along the bending line of the glass plate, and a heater filament is further placed in contact thereon, and the heater filament is This invention relates to a method for sharply bending a glass plate, which is characterized by overlaying a heat-resistant fiber sheet on top of the glass plate to suppress heater streaks.

The present invention will be explained in more detail below.

1 and 3 are perspective views of a sharply bent glass plate according to the present invention, and FIG.
A glass plate cut to produce the glass plate of FIG. 1 is shown, and FIG. 4 shows a glass plate cut to produce the glass plate of FIG. 3. In the figure, 1 indicates a glass plate to be bent, 2 indicates a glass plate molded body subjected to the bending process, and 3 indicates a bending line for sharply bending the glass plate.

When sharply bending a glass plate by the method of the present invention, the glass plate is cut into a predetermined size and shape. A heater strip is arranged along the bending line where the cut glass plate is to be bent sharply. A mold release agent is applied to the curved portion of the glass plate where the heater wire comes into contact with the heater wire to prevent the heater wire from welding to the glass plate and leaving traces when the heater wire is energized and heated. It is formed. As this mold release agent, one is used that maintains its performance even at the heating temperature of the heater strip, for example, 800°C to 1000°C. For example, as the mold release agent, heat-resistant inorganic ones such as calcium carbonate, sodium chloride, boron nitride, and carbon can be preferably used.

On the surface of the glass plate where the heater stripes are arranged along the desired sharp bending line, a heat-resistant fiber sheet is overlaid to cover at least the bent line portion where the heater stripes are arranged to suppress the heater stripes. . Thereby, it is possible to ensure that the heater wires are wired along the bending line where the glass plate is sharply bent, to prevent the heater wires from shifting during bending, and to perform the desired bending process.

This heat-resistant fiber sheet has sufficient heat resistance against the heating temperature of the heater wire, for example, 800°C to 1000°C, and also has flexibility that is suitable for bending glass. used. For example, quartz glass fiber, various glass fibers, heat-resistant ceramic fibers made of asbestos, etc. can be used. Among them, quartz glass defibers have sufficient heat resistance and excellent chemical and physical stability, so they are most suitable as the heat-resistant fiber sheet used in the present invention.

In the present invention, the heat-resistant fiber sheets that are stacked to suppress heater filaments arranged along the bending line of the glass plate to be bent need only cover at least most of the bending line of the glass plate. The sheet may be sized to cover only the bent line portion of the glass plate, or may be sized to cover the entire glass plate including the bent line portion to be bent. The heater strips are usually arranged on the inner corner side of the glass plate that is to be bent sharply, so the thickness of the heat-resistant fiber sheet is set to 30R, for example, so that it can be bent sharply without any problems. It is preferable that it be thin so that it can be bent sharply with the following curvature. The most practical thickness is approximately 0.2 mm to 2 mm, including ease of handling. Of course, if the curvature is greater than 30R, a material with a thickness greater than 2 mm can also be used.
If such a heat-resistant fiber sheet is used, it can be bent at the same time and in the same way as the glass plate.
Moreover, it is optimal because it does not cause any defects to the glass plate.

Such a heat-resistant fiber sheet is placed on the side that forms the inner corner of the glass plate where the heater filaments are normally sharply bent. A heat-resistant fiber sheet is placed on the top side of the glass plate to be bent, and in the case of a method in which the sleeve part of the glass plate is bent sharply downward by self-weight bending, the bottom side of the glass plate to be bent is A heat-resistant fiber sheet will be placed on the

Furthermore, a cover glass plate can be further stacked on top of the heat-resistant fiber sheet to suppress the heat-resistant fiber sheet, thereby further reliably preventing the heater filaments from shifting from their predetermined positions. Similar to the heat-resistant fiber sheet, the cover glass plate to be stacked on top of such a heat-resistant fiber sheet only needs to cover at least the bent line portion of the glass plate, and should be of a size that covers only the bent line portion of the glass plate. It may be a glass plate of a size that covers the entire glass plate including the bending line portion to be bent. The heater strips are usually arranged on the side that forms the internal angle of the glass plate that is to be bent sharply, so the thickness of the cover glass plate should be 30R or less, for example, in order to avoid any problems in bending the glass plate sharply. It is preferable that it be thin so that it can be bent sharply with a curvature of . The most practical thickness of the plate is approximately 1 mm to 2 mm, including ease of handling. Of course, if the curvature is greater than 30R, a plate thicker than 2 mm can be used.

A release agent layer is formed on the desired bending line of the glass plate to be bent, a heater wire is placed on top of it so as to match the bending line, and a heat-resistant fiber sheet is layered on top of the heater wire. The assembly, in which the strips are held down and, if necessary, a cover glass is layered on top of a heat-resistant fiber sheet, can be subjected to gravity bending, for example, with a contour designed to obtain a glass sheet molded body with a predetermined shape. Place the glass plate on a bending die, place it in a heating furnace, and heat the entire glass plate to a temperature above its strain point and below its softening point, e.g.
Heat to a temperature of about 450℃ to 600℃. If heated to a temperature higher than 600°C, there is a risk of undesirable deformation of the glass plate, such as doubling. or,
If the temperature is lower than 450°C, the temperature will become non-uniform during subsequent heating by the heater wire, and there is a risk of thermal cracking, which is not preferable. In addition, if complicated bending is required and heating to a higher temperature is advantageous, use 650
It is also possible to heat the glass plate to a temperature higher than °C.

When the glass plate reaches the above temperature, a voltage is applied to the heater wires, the heater wires are electrically heated to a temperature of 650°C or higher, preferably 750°C to 800°C, and a release agent is applied to the heater wires. The curved line portion of the glass sheet that is in contact with the glass sheet is locally heated to a temperature near or above the softening point of the glass sheet, for example, to a temperature of about 680°C to 750°C.
When the bending line portion of the glass plate reaches a temperature near or above the softening point of the glass plate, the glass plate is sharply bent into a predetermined shape by a self-weight bending mechanism.

The heater wire used in the present invention is usually heated to 650°C to 850°C, preferably
A conductive material that generates heat at a temperature of about 750°C to 800°C and is stable above this temperature is selected. As for the shape of the heater wires, the heater wires are arranged along the bending line of the glass plate to be bent, and even if they are suppressed by the cover glass plate at the same time, the heater wires are placed along the bending line of the glass plate. It is ribbon-shaped or linear and has a thickness of 0.5 mm to prevent it from digging into the heater or leaving marks from the heater stripes.
mm or less, preferably 0.05 mm to 0.2 mm. The most suitable material is nickel-chromium alloy, iron-chromium alloy, stainless steel, tantalum, platinum, molybdenum, or the like.

In the above example, we explained an example in which the self-weight bending method was applied as a method for sharply bending the glass plate along the bending line, but the method is not limited to the self-weight bending method. Glass plate bending methods can be used as well.

After the bending process, the glass plate sharply bent by the method of the present invention can be subjected to a strengthening treatment or an annealing treatment, if necessary.

In addition, in the present invention, the bending of the glass plate is used in order to hide the optical distortion of the curved line portion of the glass plate that is sharply bent, or to make the traces of heater filaments less noticeable. A colored band can be formed in the line portion. This colored band is
They may be provided inside or outside the sharply bent corners of the glass plate. Further, this colored band may be formed before the glass plate is sharply bent, or may be formed after this bending process is performed. A typical example of this colored band is ceramic color frit, and when this is used, it is usually printed in a band shape on the inside or outside of the bending line of the glass plate, and the ceramic color frit is printed inside the bending line. Once formed, a release agent is then applied to the surface of the glass plate, and the ceramic color frit is baked onto the curved portion of the glass plate by bending it in the manner described above.

Next, embodiments of the present invention will be described with reference to FIGS. 5 to 10.

Example 1 As shown in Figure 7, a rectangular soda lime glass plate 10 with a thickness of 4 mm (vertical dimension: 500 mm, horizontal dimension: 300 mm)
A powder layer of calcium carbonate is formed as a release agent layer 12 along the bending line 11 which is sharply bent (mm), and then a powder layer of calcium carbonate is formed thereon along the bending line 11 as shown in FIG. , a heater wire 14 (Ro=
1.15 Ω/m), and on the top surface of the glass plate 10 on which the heater filaments 14 are arranged, silica glass (trade name of quartz glass fiber manufactured by Japan Inorganic Fibers Co., Ltd., 1 mm thick) of the same size as the glass plate is placed. ) were stacked on top of each other to hold down the heater filaments 14. The assembly prepared in this way is placed on a bending die 15 for self-weight bending as shown in FIG. The heater wire was heated to 750℃ by applying 180W of power to the glass plate, and the bent portion of the glass plate was heated to 680℃ and softened by the heater wire, and the glass plate was attached to the bent portion of the gravity bending mold 15. Using the moment of the counterweight 16, the glass plate was sharply bent along its bending line. The bending die is a self-weight bending die having a ring whose upper surface is the forming surface as shown in FIG. The part corresponding to the middle part of the glass plate 10 is the non-movable part 1.
7, and the glass plate 10 is placed on the line connecting the pair of hinges connecting the movable part 16 and the non-movable part 17.
The bending lines of the movable part 16 and the non-movable part 17 were designed to form an angle of 85 degrees.

After bending the glass plate 10, it was taken out from the heating furnace, the heat-resistant fiber sheet was removed, and air-cooled strengthening was performed.

The glass plate that is sharply bent in this way has an angle of 85° between the sleeve part and the center part, and an inner curvature of 5R at the bent part.
There were no traces of heater filaments left on the curved portion of the glass plate, and the appearance was good.

Example 2 Soda cubes cut into the shape and dimensions shown in Figure 8.
Lime glass plate 10 (plate thickness: 5 mm, a = 530 mm,
A heavy metal powder layer is formed as a release agent layer 12 as shown in FIG. 8 along the sharply bent bent line 11 (b=400mm, c=150mm, d=500mm), and then as shown in FIG. Thickness along bend line 11 on top
A heater wire made of ribbon-like nichrome (Ro=1.15Ω/m) with a width of 0.2 mm, a width of 4 mm, and a length of 1300 mm is arranged, and the glass plate and A heat-resistant fiber sheet 13 made of the same glass as in Example 1 with the same dimensions is stacked to suppress the heater filaments, and a cover glass plate 15 with a thickness of 2 mm and the same size and shape as the glass plate to be bent is further stacked on top of it. Ta. The assembly prepared in this way is placed on a bending die as shown in Figure 9 with the heat-resistant fiber sheet facing down, and this is placed in a heating furnace to heat the entire glass plate to 500℃. Then, 600W of power was applied to the heater wires to increase the heater wires to 700W.
℃, and the bent line 11 portion of the glass plate 10 was heated to 650° C. by the heater wire to soften it, and the sleeve portion of the glass plate 10 was made to hang downward at a right angle. Next, after performing a slow cooling treatment, the cover glass plate was removed to obtain a sharply bent glass plate as shown in FIG. The angle between the sleeve part and the center part of this glass plate is 80°, and the inner curvature of this bent part is
10R, no traces of heater streaks were left on the bent portion of the glass plate, and the appearance was good.

As described above, according to the present invention, the heater filaments are suppressed by a heat-resistant fiber sheet and, if necessary, by a cover glass plate. When sharply bending a glass plate into a curved line, a combination of curved and straight lines, or an S-shaped bending line, the wiring position of the heater wire should be adjusted along the bending line of the glass plate. It can be held securely without shifting until the sharp bending process is completed, and the bending process of a predetermined shape can be performed accurately. Since the heating wire is electrically heated to locally heat the curved portion of the glass plate, the curvature of the inner and outer portions of the curved portion of the glass plate can be reduced. For example, according to the present invention, it is possible to reduce the curvature of the bent portion of the glass plate to 5R. Moreover, since a layer of mold release agent is formed between the bending line of the glass plate to be bent and the heater filament, there are no traces of the heater filament left on the bend of the glass plate, resulting in an excellent appearance. Can be bent.

In addition, as a method of sharply bending the glass plate,
Conductive frit paste such as silver paste is printed in a line along the curved line where the glass plate is to be bent sharply, and this printed line is used as an electrical heater for local heating of the curved line of the glass plate. Methods are also known, but for example, in the case of silver paste, the melting point of silver is approximately 960°C, so heating up to 800°C is the practical limit, and in the case of conductive frit paste, it is difficult to heat up to the desired level. In order to obtain the desired resistance value, the thickness is usually made as thin as 20 to 30 μ, so it has the disadvantage of being easily cut and not being able to apply high power, which limits local heating of the curved portion of the glass plate. Therefore, it is difficult to make the curvature of the bending line lower than 15R. On the other hand, since the method of the present invention uses heater wires, it is possible to locally heat the curved portion of the glass plate to a higher temperature than in the method using the conductive frit paste described above. It is possible to bend sharply to a curvature of 5R. Further, in the method using the conductive frit paste described above, the printed lines remain on the bent part of the glass plate after bending, but in the case of the present invention, no printed lines remain on the bent part of the glass plate. There are also advantages.

[Brief explanation of drawings]

1 and 3 are perspective views of a glass sheet sharply bent according to the present invention, FIG. 2 is a plan view of a glass sheet cut to form the glass sheet of FIG. 1, and FIG. are plan views of the glass plate cut to form the glass plate shown in Fig. 2; Figs. 5 to 10;
The figure is an explanatory diagram for explaining the method of the present invention. 1, 10; glass plate, 3, 11; bending line, 1
2; release agent layer; 13; heat-resistant fiber sheet; 14; heater filament.

Claims (1)

[Scope of Claims] 1. A heater wire is arranged along the curved line where the glass plate is to be bent sharply, and the heater wire is energized and heated to bend the curved line portion of the glass plate above the softening point of the glass plate. In the method of sharply bending a glass plate along the bending line by heating the glass plate to a temperature of A method for sharply bending a glass plate, which is characterized by contacting and arranging the heater filaments and suppressing the heater filaments by overlaying a heat-resistant fiber sheet on top of the heater filaments. 2. Claim 1, wherein the heat-resistant fiber sheet is a heat-resistant ceramic fiber sheet.
A method for sharply bending a glass plate as described in Section 1. 3. A method for sharply bending a glass plate according to claim 1, wherein the heat-resistant fiber sheet is flexible. 4. The method for sharply bending a glass plate according to claim 1, wherein the heat-resistant fiber sheet is a quartz glass fiber sheet. 5. A method for sharply bending a glass plate according to claim 1, characterized in that a ceramic color frit layer is formed along the bending line of the glass plate. 6. A method for sharply bending a glass plate according to claim 1, characterized in that a cover glass plate is further stacked on the heat-resistant fiber sheet stacked on the heater filament.