JPH02248339A - Method for bending plate glass - Google Patents

Abstract

PURPOSE:To reduce the working time by interposing a mold release agent consisting of the spheroidal particles having specified diameter and volume ratio between two plate glasses placed on a bender, heating the glasses closes to their softening points and bending the glass. CONSTITUTION:The mold release agent consisting of the spheroidal particles of silica gel, etc., substantially incapable of being wetted with the plate glass at the bending temp. of 500-700 deg.C, having <=150mum diameter and >=50% volume ratio of >=10mum-diameter grains and having a gently sloping surface is sprinkled between the two plate glasses placed on a bender at 20-500 units/mm<2> density. The glasses are heated close to their softening points, hung down by gravity, and bent. The bent glasses are annealed, discharged, washed and dried. An intermediate laminating film made of synthetic resin such as polyvinyl butyral is interposed between the two bent glasses to laminate the glasses, and a laminated glass is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for bending sheet glass, particularly two sheets of glass for laminated glass suitable for automobile windshields.

[Prior Art] Bent laminated glass for automobile windshields and the like is generally made by cutting a plurality of glass sheets to a predetermined size, usually two glass sheets stacked one on top of the other, and forming a bent mold on a trolley to have a desired contoured surface. This bending mold is placed on a trolley, and the trolley is sent into a heating chamber, where the glass plate is heated to around its softening point temperature, and the glass plate is allowed to hang under its own weight, and the molded contour surface of the bending mold is Then, after passing through an annealing chamber to slowly cool the glass, it is taken out, washed as necessary, dried, etc., and then a synthetic resin membrane such as polyvinyl butyral is placed between the two bent glass plates. It is manufactured by sandwiching an interlayer film, heat-pressing it, and processing it together.

FIGS. 3A and 3B schematically show the state in which two glass plates are placed on a bending mold and the state in which they are bent by heating. 1 is a glass plate, and 2 is a contour bending die for self-weight bending. The bending die 2 generally consists of a central portion 2A and side portions 2B, 2C which are hinged to each other. These side parts 2B, 2C have hinges 3
A counterweight 4 is attached so that the glass plate can be easily bent into a predetermined shape by pivoting upward around the glass plate. When bending using this bending die 2, a flat glass plate is bent between the center portion 2A of the bending die 2, or the side portions 2B and 2G, or between the center portion 2A and the side portions 2.
Support it with B and 2C and put it into the heating furnace.

When the glass plate is heated in the heating furnace to near the softening temperature, the center part of the glass plate bends due to its own weight and bends into the center part 2A of the mold.
At the same time, the side parts 2B and 2C on both sides of the bending mold are rotated upward about the hinge as shown in the figure by the action of the counterweights 4 attached to the side parts. movement, thereby bending both sides of the glass plate.

In such a bending method, two sheets of glass stacked one on top of the other are heated to near their softening point, so there is a risk that they will fuse together. Therefore, conventionally, baking soda,
It has been common practice to interpose particles of Celite or the like with a particle size of around 1 μm as a mold release agent between two sheets of glass before joining them together.

[Problems to be Solved by the Invention] One of the typical defects when two sheets of glass are bent by the method described above is perspective distortion due to local minute deformation of the glass. The reason for this is that when bending is performed with a fine particle of foreign matter trapped between two sheets of glass, the sheet glass is heated to near its softening point, causing minute deformation around the foreign object due to its own weight. has been done.

Conventionally, in order to prevent the occurrence of perspective distortion, methods such as washing the glass sheets with running water before stacking them were used, but it is extremely difficult to completely remove foreign matter, and it is difficult to completely eliminate the occurrence of perspective distortion. It was difficult to prevent this.

[Means for Solving the Problems] The present invention was made to solve the above-mentioned problems, and involves heating two sheets of glass placed on a bending mold to around the softening point temperature, and then bending the glass sheets by their own weight. In a sheet glass bending method in which sheet glass is bent by hanging, a mold release agent is placed between the two sheets of glass in advance so that it does not substantially get wet with the sheet glass under the temperature conditions during bending. Particles with a diameter of 10 μm or more account for 50% by volume
The object of the present invention is to provide a method for bending sheet glass, which is characterized by interposing particles having a smooth surface and having a particle size of 150 μm or less.

Figure 2 (A) is a conceptual cross-sectional view showing the presumed mechanism of optical distortion caused by foreign matter in the past. 5 is a foreign matter that cannot be washed away, and 6 is a microparticle used as a mold release agent. be. In this way, since the foreign matter 5 is much larger than the mold release agent 6, a fairly wide area of the glass plate l is supported at the point of contact with the foreign matter 5, and it is thought that stress concentration occurs at that contact point. . Therefore, when the plate glass l is heated to near its softening point during bending and becomes susceptible to plastic deformation, it undergoes steep plastic deformation around the foreign object, as shown in Figure 2 (B). It is presumed that this causes optical distortion.

Although it is difficult to determine the size of foreign particles that cause such optical distortion, large particles tend to stick to the eyes (and are easier to clean), and small particles tend to get into the spaces between the laminated glass. Taking these factors into consideration, we can imagine that it is a relatively small object that cannot be completely cleaned.It is difficult to remove such a large foreign object by normal cleaning, and if it is done, it will be necessary to clean the environment etc. It is necessary to take very large-scale measures, which is not easy in terms of cost and other factors.

The present invention is characterized by using particles that are much larger than the particles around IILm that have been conventionally used as a mold release agent.

FIG. 1 is a conceptual cross-sectional view showing the presumed mechanism by which optical distortion can be prevented from occurring according to the present invention. 7 is a particle larger than the conventional one used in the present invention.

In the present invention, unlike the conventional method, the foreign matter 5 enters between the particles 7. Therefore, the plate glass l is not a foreign object 5 (,2
It is supported by a large number of particles 7 dispersed between the sheets of glass, and no stress concentration occurs heretofore. Therefore, even if sheet glass is heated to around its softening point during the bending process, plastic deformation never occurs in the past.

The material of the particles is 5 when bending plate glass.
A material that is heat resistant at the bending temperature of 50°C to 700°C and does not substantially wet the sheet glass, that is, a material that can be separated without damaging the two glass sheets after bending, is fine. It is more desirable if it is stable enough to be used as a molding agent and does not get wet with glass. Furthermore, if a material undergoes large plastic deformation during bending, there is little point in using large particles, so it is desirable that the plastic deformation is small.In addition, it is desirable that the plastic deformation is small and that it can be easily removed in the subsequent cleaning process. Silica gel and the like are examples of materials having the following properties.This material is highly desirable because it is relatively easy to obtain a desirable substantially spherical shape as described below, and also has favorable deformability.

The shape of the particles may be one with a smooth surface without any corners that would cause major damage to the two sheets of glass, but a spherical shape is preferable because it is more difficult to scratch.

Further, the particle size is preferably 150 μm or less.

If the particle size is larger than this, if the particle distribution is not uniform, the particles themselves may cause local deformation of the glass plate. In addition, the particle size distribution is 10 μm
It is preferable that the volume ratio of the above substances is 50% or more. If the number of particles smaller than this is large, the effect of suppressing the occurrence of optical distortion due to the above-mentioned foreign matter will be small. Regarding this particle size distribution, the smaller the variation, the greater the effect of suppressing the occurrence of optical distortion, but in that sense, the particularly desirable range of particle size distribution is that particles with a diameter of 30 to 100 μm account for 30% or more by volume. and has a particle size of 100 μm or less.

A very simple method for dispersing the particles is to scatter the particles sorted through a sieve with a specific mesh onto a predetermined plate glass. Of course, the method is not limited to this method (other methods such as dispersing particles in a solvent, spraying, and then evaporating the solvent may also be used).

The distribution of the particles is preferably as uniform as possible. The uniformity is related to the density of scattering, and it is difficult to understand it quantitatively, but when seen with the naked eye, the unevenness is not noticeable, and when seen with a microscope, particles do not stick together (peck each other). It is best to leave it in a state where there are no gathered parts.

Regarding the dispersion density, it can be used in a fairly wide range depending on the thickness of the plate glass, but it is 20 to 500 pieces/1.
It is better to set it to about ``srrr''.

As for the bending method and the method for manufacturing laminated glass, conventionally used methods can be used.

The above explanation describes the case of manufacturing two sheets of laminated glass with a relatively simple shape, but it can also be used when manufacturing laminated glass with a more complex shape or bending three or more sheets. Of course, it can also be applied. In particular, in cases where sharp bending is to be performed, the bending process may be performed by providing local heating means along the bending line instead of just heating the entire body as described above.

[Example] Using a bending die as shown in FIG. 3, two sheets of glass were overlapped and bent at the same time. When stacking, place a particle with a maximum particle size of 100μ on the lower glass plate in advance.
Particles having a particle diameter of 30 to 100 μm and containing approximately 40% by volume were dispersed and arranged using a sieve, and then the upper glass was placed.

The particles were approximately spherical particles made of quartz gel, and the scattering density was approximately 100 particles/II.2.

A laminated interlayer film of polyvinyl butyral was sandwiched between these two glass plates, and the laminate was degassed in a vacuum bag, and then
The pieces were preliminarily bonded by heating to 00°C, and then taken out from the bag and laminated in an autoclave at 150°C for 1 hour.

The obtained laminated glass had almost no optical distortion and was in good condition.

[Effects of the Invention] According to the present invention, it is possible to prevent local glass deformation due to foreign matter during bending and to prevent the occurrence of optical distortion, and to obtain a good laminated glass.

Additionally, glass can be bent at higher temperatures and for longer periods of time, making it possible to mold complex shapes. Furthermore, since the temperature during bending can be increased, there is also the effect of shortening the bending time.

[Brief explanation of drawings]

FIG. 1 is a conceptual sectional view showing the mechanism of the present invention, FIG. 2 is a conceptual sectional view showing the conventional mechanism, and FIG. 3 is a schematic diagram showing a typical sheet glass bending method. 1 is a glass plate, 2 is a mold, 5 is a foreign substance, 6 is a mold release agent, and 7 is a particle larger than the conventional one used in the present invention. No. 11￥1 No. 2 1￥1 (lI) C8ノ

Claims (3)

[Claims] (1) In a sheet glass bending method in which two sheets of glass placed on a bending die are heated to around the softening point temperature of the sheet glass and bent by allowing the sheet glass to hang down by its own weight, the above two sheets are bent in advance. As a mold release agent between the plate glass, it does not substantially wet the plate glass under the temperature conditions during bending, has a volume ratio of 50% or more of particles with a particle size of 10 μm or more, and has a particle size of 150 μm or less. A method for bending plate glass characterized by interposing particles having a gentle surface. (2) The method for bending sheet glass according to claim 1, wherein the particles are substantially spherical particles. (3) The method for bending plate glass according to claim 1 or 2, wherein the particles are silica gel.