JP2020007194A - Production method of glass plate - Google Patents

Abstract

To provide a production method of a glass plate capable of precisely producing a glass plate of a predetermined shape.SOLUTION: A production method of a glass plate includes a heating and molding step for bending a glass plate put on a ring-shaped molding tool by heating to the vicinity of the softening point of the glass plate, and an annealing step for annealing the bent glass plate in the vicinity of softening point of the glass plate. The glass plate has a first region within 50 mm from the outer peripheral edge of the glass plate, a second region within 100 mm from the center of gravity of the glass plate, and a third region between the first region and the second region. The third region contains a bending promotion region that is cooled before the glass plate reaches the annealing point in the annealing step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a glass plate.

  An automotive window glass generally includes a windshield, a rear glass, a side glass, a sunroof glass, and the like. As a type of a glass sheet for a window glass for an automobile, in addition to a normal single-sheet glass sheet, two glass sheets are mutually bonded to a windshield with a plastic interlayer film made of PVB (polyvinyl butyral) interposed therebetween. Laminated glass is used. Such an automotive window glass may be manufactured in a curved shape depending on the body line of an automobile or a design requirement.

  As a method for bending a glass plate, one or two flat glass plates are placed on a forming die having a bent forming surface corresponding to a desired curved surface, and the forming die is placed in this state. The glass sheet is carried into a heating furnace, the glass sheet is heated to a temperature close to the glass softening temperature, a bend is formed along the forming die by the weight of the glass sheet, and then the bent glass sheet is gradually cooled in an annealing zone. Methods for cooling to below are known.

  For example, Patent Document 1 discloses that a temperature distribution is formed in each region of a glass plate in a heating furnace in order to bend the glass plate into a desired shape.

JP 2001-089172 A

  In the heating furnace, the glass sheet bent after forming the temperature distribution on the glass sheet is gradually cooled in the annealing zone. However, if a temperature distribution exists in the glass sheet, a temperature difference occurs between adjacent regions in the plane of the glass sheet. As a result, at the time of slow cooling, the actual bending amount of the glass plate may be different from the target bending amount, and there is a concern that the glass plate does not have a desired shape.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a method for manufacturing a glass plate that can accurately form a glass plate into a desired shape.

  The method for producing a glass sheet of the present invention includes a heating step of heating and bending a glass sheet placed on a ring-shaped mold to near the softening point of the glass sheet, A slow cooling step of gradually cooling the glass sheet of claim 1, wherein the glass sheet is a first region within 50 mm from the outer edge of the glass sheet, and within 100 mm from the center of gravity of the glass sheet. A second region, and a third region between the first region and the second region, a bending acceleration region in the third region, the slow cooling step, the Cooling the bend-promoting area before reaching the annealing point of the glass sheet.

  According to the present invention, a glass plate can be accurately formed into a desired shape.

FIG. 1A is a schematic side view of a glass sheet manufacturing apparatus according to the embodiment, and FIG. 1B is a schematic plan view of the glass sheet manufacturing apparatus according to the embodiment. FIG. 2 is a plan view illustrating an example of a region of the glass plate. FIG. 3 is an explanatory diagram for explaining deformation of a bending region and a peripheral region during slow cooling. FIG. 4 is a graph in which the shape of the glass plate is plotted with the vertical dimension (mm) as the vertical axis and the horizontal dimension (mm) as the horizontal axis. FIG. 5 is a graph comparing the shapes of two glass plates with and without cooling. FIG. 6 is a graph in which the shape of the glass plate is plotted with the vertical dimension (mm) as the vertical axis and the horizontal dimension (mm) as the horizontal axis. FIG. 7 is a graph showing a change in mismatch due to cooling of the inner glass sheet.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is described by the following embodiments. However, changes can be made in many ways without departing from the scope of the invention, and other embodiments other than the embodiments can be used. Accordingly, all modifications within the scope of the present invention are included in the appended claims. Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

  Hereinafter, a preferred embodiment of a method for manufacturing a glass plate will be described with reference to the drawings. In the present embodiment, the characteristics of the glass such as the softening point and the annealing point will be described, and a case of soda lime glass will be described as an example of the type of the glass plate. However, the characteristics derived from the type of glass described in the following description in the present specification are not limited to this embodiment, and may be appropriately changed according to the type of glass.

  FIG. 1A is a schematic configuration diagram of an apparatus for manufacturing a glass sheet according to the embodiment, and FIG. 1B is a schematic plan view of an apparatus for manufacturing a glass sheet according to the embodiment. The glass sheet manufacturing apparatus 10 is an apparatus for manufacturing a glass sheet for laminated glass.

  The glass sheet manufacturing apparatus 10 includes a heating furnace 12 for heating and forming the glass sheet G, and an annealing furnace 14 provided at a stage subsequent to the heating furnace 12. The glass plate G represents one or two glass plates, and the number is not limited. In the embodiment, the glass plate G illustrates a case where two glass plates are stacked.

  The heating furnace 12 heats and bends the flat glass sheet G before bending. The heating furnace 12 includes a cart 16 and a ring-shaped mold 18 having a desired curved surface mounted on the cart 16. The heating furnace 12 includes therein a plurality of heaters (not shown) for heating the glass plate G and forming a predetermined temperature distribution. The heaters are arranged in a matrix, and the plurality of heaters can adjust the temperature for each area of the glass plate G. The heater can heat the glass sheet G to near the softening point temperature (for example, in the range of 580 ° C. to 750 ° C.). By heating, the glass sheet G is bent into a shape along the mold 18 by its own weight. The cart 16 and the forming die 18 are made of a heat-resistant material that can withstand the forming temperature of the glass sheet G of the heating furnace 12. The carriage 16 is moved in the heating furnace 12 by an arbitrary transfer device (not shown).

  The annealing furnace 14 is provided outside the heating furnace 12 and is continuously provided at a subsequent stage, and gradually cools the glass sheet G heated to around the softening point formed by bending. Slow cooling means that the temperature is gradually lowered to the target temperature. In FIG. 1, the lehr 14 has a wall surface to define an internal space. The annealing furnace 14 includes a transfer device that transfers the forming die 18 on which the glass plate G is placed. In the annealing furnace 14 of the embodiment, a nozzle 22 is arranged as a cooling device near the carry-in entrance 20. As shown in FIG. 1 (A), the nozzles 22 are arranged above, below, and behind the glass plate G, respectively. As shown in FIG. 1B, the nozzles 22 are respectively arranged with a virtual center line passing through the center of gravity of the glass plate G parallel to the transport direction. Therefore, a total of eight nozzles 22 are arranged in the annealing furnace 14. “Up” and “down” are determined based on the direction of gravity, and “front” and “rear” are determined based on the transport direction of the glass sheet G.

  The glass sheet G carried into the annealing furnace 14 is divided into regions as shown in FIG. A indicates the outer peripheral edge of the glass plate G. The outer peripheral edge A indicates the side of the outer edge of the glass plate G. The two-dot chain line B is a line connecting a portion of 50 mm inward from the outer peripheral edge A of the glass plate G. A portion surrounded by the outer peripheral edge A and the two-dot chain line B is a first region G1. The first area G1 is an area within 50 mm from the outer peripheral edge A. A two-dot chain line C is a line connecting a portion of 100 mm from the center of gravity CG of the glass plate G. The inside of the two-dot chain line C within 100 mm from the center of gravity CG is the second region G2. In the glass plate G, a region between the first region G1 and the second region G2 is a third region G3. In the glass plate G, a region surrounded by a two-dot chain line D is a bending acceleration region G4. In FIG. 2, four bending acceleration regions G4 are located in the third region G3.

  The bending acceleration region G4 will be described. When bending the glass sheet G, the glass sheet G is heated in the heating furnace 12 to near the softening point. At this time, a bent area in the glass sheet G where a large amount of bending (a deep bending amount) or a small radius of curvature is required is heated to a high temperature as compared with a peripheral area of the bending area. The temperature distribution (temperature difference) is, for example, about 30 ° C. to 70 ° C. When bent, the glass sheet G having a temperature distribution is transferred to the annealing furnace 14.

  As shown in FIG. 3, the glass sheet G conveyed to the annealing furnace 14 includes, in the plane of the glass sheet G, a bent area DA that is a high-temperature area and a peripheral area around the bent area DA and lower than the high-temperature area. An area SA exists. Usually, the slow cooling of the slow cooling furnace 14 is performed by natural cooling (also referred to as standing or natural standing). As a result, the peripheral area SA reaches the annealing point earlier than the bending area DA, and the peripheral area SA does not deform. On the other hand, since the bending area DA reaches the annealing point later, it is deformed by heat shrinkage and is pulled toward the peripheral area SA. As a result, the inventor has found that the relative distance between the bending area DA and the peripheral area SA is reduced, and the bending amount of the bending area DA may be insufficient.

  The inventor specifies, in the plane of the glass sheet G, a region in which the amount of bending is insufficient with respect to a target amount of bending, which is caused by the magnitude of the temperature distribution, that is, the temperature difference, as a bending acceleration region G4 ( The present inventors have found that, by cooling at least a part of the bending acceleration region G4 in the annealing furnace 14 before reaching the annealing point, the bending amount of the bending acceleration region G4 can be increased, and the present invention has been achieved.

  The bending promotion area G4 is often located in any of the third areas G3, as shown in FIG. The first region G1 is an edge region of the glass sheet G and has a small bending amount, so that the bending amount is unlikely to be insufficient. The second region G2 is located substantially at the center of the glass plate G, and is easily bent by gravity when the glass plate G is placed on the ring-shaped forming die 18. Therefore, in the second region G2, the shortage of the bending amount of the glass plate G is less likely to occur. The bending promoting region G4 located in the third region G3 is an important region for accurately forming the glass sheet G into a desired shape.

  As shown in FIG. 2, a dashed line E passing through the center of gravity CG of the glass plate G and connecting the upper side and the lower center, and a dashed line F passing through the center of gravity CG of the glass plate G and orthogonal to the dashed line E are drawn. In this case, the bending acceleration region G4 is the third region G3, and is located in a region surrounded by the two-dot chain line B, the one-dot chain lines E and F. That is, the bending promotion region G4 is located at the corner of the third region, and four bending promotion regions G4 are located as a whole. The four bending promotion regions G4 at the corners of the third region G3 are regions where the amount of bending of the glass sheet G is likely to be insufficient. The reason for this is that, like the second region G2, it is easily bent by gravity on the dashed lines E and F.

The “slow cooling point” refers to a temperature at which the viscosity of the glass becomes 10 ¹³ dPa · s, and is determined by the composition of the glass. The annealing point of soda lime glass is typically around 550 ° C. At a temperature lower than the annealing point, the glass sheet is hardly thermally deformed.

The “softening point” refers to a temperature at which the viscosity of the glass becomes 10 ^7.65 dPa · s, and is determined by the composition of the glass and the like. The softening point of soda lime glass is typically about 750 ° C. The bending temperature of the glass sheet is set to the same temperature as the softening point or a temperature slightly lower than the softening point.

  The manufacturing method of the glass sheet of the embodiment will be described by taking a glass sheet for laminated glass used for a windshield for an automobile as an example. First, a flat glass plate is cut into a glass plate G having a required shape by a manufacturing apparatus (not shown).

  A ring shape having a desired curved surface in a state where two glass plates G, a glass plate G (inner glass plate) disposed inside the vehicle and a glass plate G (external glass plate) disposed outside the vehicle, are overlapped. Is placed on the molding die 18. The single glass plate G has a thickness in the range of, for example, 1.5 mm to 3.0 mm.

  In the heating and forming step, the two glass plates G before bending are placed on a molding die 18 placed on a carriage 16 and carried into the heating furnace 12 by an arbitrary transport means. While passing through the heating furnace 12, the glass sheet G is heated by a plurality of heaters (not shown) to a temperature near the softening point higher than the annealing point (for example, in the range of 580 ° C. to 750 ° C.). The plurality of heaters form a temperature distribution in the plane of the glass sheet G in order to set the glass sheet G to a target bending amount. The glass plate G is bent by the inner surface of the glass plate G being flexed by its own weight while being supported along the bent shape of the molding die 18 by softening due to heating. As a result, the two flat glass plates G are bent into a glass plate G having a desired curved surface.

  In the slow cooling step, the two glass sheets G near the softening point formed by bending are transported from the heating furnace 12 to the slow cooling furnace 14 by the transport means together with the carriage 16 and the forming die 18. The two glass plates G are gradually cooled in the annealing furnace 14 from near the softening point to the annealing point or lower. The two glass plates G are manufactured through a heating forming step and a slow cooling step.

  On the other hand, in the annealing furnace 14, a total of eight nozzles 22 are arranged near the carry-in port 20 as a cooling device in addition to a transfer device that transfers the forming die 18 on which the glass plate G is placed.

  A gas is blown from a nozzle 22 disposed on an upper side to a bending promotion area G4 (not shown) of the glass sheet G, which is an inner glass sheet located on the upper side of the two glass sheets G. A gas is blown from a nozzle 22 disposed on a lower side to a bending promotion area G4 (not shown) of the glass sheet G, which is an outer glass sheet located on the lower side of the two glass sheets G. That is, in the slow cooling step, the two glass sheets G are simultaneously cooled before reaching the slow cooling point in at least a part of each bending acceleration region G4. By blowing the gas until the glass sheet G reaches the annealing point, the bending amount of the bending acceleration region G4 can be increased. It is preferable that the timing at which the gas is blown onto the glass sheet G is immediately after the glass sheet G is conveyed to the annealing furnace 14. That is, it is preferable that at least a part of the bending acceleration region G4 be cooled as soon as the glass sheet G is carried into the lehr 14. This is because the temperature difference at the stage when the temperature of the glass plate G is high and reaches the annealing point can be widened. In addition, since two glass sheets G are simultaneously cooled before at least part of each bending acceleration area G4 reaches the annealing point, the difference in shape (mismatch) between the two glass sheets G can be reduced. A laminated glass obtained by bonding two glass plates G via an intermediate film has a more desired shape, and is preferable. The term “immediately” is not limited to cooling immediately after the glass sheet G is carried into the lehr 14, but also includes cooling within 30 seconds after the glass sheet G is carried into the lehr 14.

  As the gas blown from the nozzle 22, air, an inert gas, or the like can be suitably used. For example, the temperature of the gas is preferably from 100 ° C to 350 ° C. Further, the wind speed is preferably from 5 m / sec to 15 m / sec. Further, the cooling rate is preferably 2.8 ° C./sec or more and 6.6 ° C./sec or less. Further, the cooling time is preferably from 10 seconds to 60 seconds. By setting it in the above range, it becomes possible to eliminate the shortage of the bending amount. These numerical values can be appropriately set according to the size, shape, and bending amount of the glass plate G.

  By the way, wind-cooling strengthening is known, in which air is blown onto a glass sheet heated from about 600 ° C. to about 700 ° C. to rapidly cool the glass sheet to physically strengthen the glass sheet. In air cooling, air is blown over the entire surface of the glass plate, and the air velocity is 100 m / sec to 200 m / sec. However, in the cooling performed on the bending acceleration region G4, a compressive stress is hardly applied to the surface (2 MPa or less), which is different from the air cooling strengthening.

  In the embodiment, the nozzle 22 that blows the gas is illustrated as the cooling device, but the configuration of the cooling effect is not particularly limited. The annealing furnace 14 may include a radiation cooling device instead of the nozzle 22.

  Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. However, the present invention is not limited to these examples. The temperature is a value measured by a radiation thermometer. Using a thermo tracer (6T63 manufactured by NEC Sanei) as a radiation thermometer, a photograph was taken from above and measured between the molding zone and the slow cooling zone.

<Test 1>
The shape change of the glass plate according to the presence or absence of cooling in the slow cooling step was confirmed. When the two glass plates for laminated glass are placed on a forming die in a superposed state, the heating molding step and the slow cooling step are performed, and the cooling is not performed in the slow cooling step (no cooling), and A glass plate was produced under the condition of cooling (with cooling). Without cooling, the glass plate was gradually cooled at 2.7 ° C./sec. With cooling, the entire glass plate was gradually cooled, and a gas was blown onto each of the bending promotion regions of the two glass plates (the inner glass plate and the outer glass plate) for 30 seconds to be cooled at 3.7 ° C./second. The effect of cooling on the glass plates was quantified by measuring the shape of the inner and outer glass plates.

  FIG. 4 is a graph in which the shape of the glass plate is plotted with the vertical dimension (mm) as the vertical axis and the horizontal dimension (mm) as the horizontal axis. In the graph, the lowest point of the glass plate G was set as the origin (0, 0). As shown by the arrow in FIG. 4, the shape of the glass plate was measured from a point 300 mm horizontally from the origin to a position from the lower side to the upper side. On the line of the arrow, there are two cooled bend promoting regions.

  In the upper graph of FIG. 5, the left vertical axis is the shape (depth) of the glass plate (depth) (mm), and the horizontal axis is the vertical coordinate (mm) of the glass plate. It is the graph which plotted the shape of the inner plate glass in the case. The right vertical axis is the shape difference, and the difference (cooling-less shape-cooling shape) (mm) is plotted.

  In the lower graph of FIG. 5, the left vertical axis represents the shape (depth) of the glass sheet, and the horizontal axis represents the vertical coordinates of the glass sheet. It is the graph which plotted the shape. The right vertical axis is the shape difference, and the difference (cooling-less shape-cooling shape) (mm) is plotted.

  As shown in the two graphs of FIG. 5, when the shape with cooling and the shape without cooling are compared, the shape is large (deep) in the two bending promotion regions of the shape with cooling. It can be understood that is larger.

  By cooling in the slow cooling step, the amount of bending could be increased in the bending promotion regions of both the inner glass and the outer glass.

<Test 2>
The shape change of the glass plate due to the cooling time in the slow cooling step was confirmed. When the two glass plates for laminated glass are placed on a forming die in a superposed state, the heating molding step and the slow cooling step are performed, and the cooling is not performed in the slow cooling step (no cooling), and A glass plate was produced under the condition of cooling (with cooling).

  In the slow cooling step, the entire glass plate is gradually cooled, and a gas is applied at 3.7 ° C./sec to the right side surface and the left side surface of the two glass plates in the bending acceleration region for 10 seconds. , 20 seconds, and 30 seconds.

  FIG. 6 is a graph in which the shape of the glass plate is plotted with the vertical dimension (mm) as the vertical axis and the horizontal dimension (mm) as the horizontal axis. In the graph, the lowest point of the glass plate G was set as the origin (0, 0). As shown by the arrows in FIG. 6, the shape of the glass plate was measured from the point 300 mm (right side) laterally from the origin and -300 mm (left side) laterally from the origin, from the lower side to the upper side. I went there. On each arrow line, there are two cooled bend promoting regions.

  In the upper graph of FIG. 7, the vertical axis represents the mismatch (mm), the horizontal axis represents the distance (mm) from the lower side, and the right side has no cooling (reference: ref), 10 seconds (10 seconds), and 20 seconds. The mismatch of each cooling time of seconds (20 sec) and 30 seconds (30 sec) was plotted.

  In the lower graph of FIG. 7, the vertical axis represents the mismatch (mm), the horizontal axis represents the distance (mm) from the lower side, and the left side has no cooling (reference: ref), 10 seconds (10 seconds), The mismatch between the cooling times of 20 seconds (20 seconds) and 30 seconds (30 seconds) was plotted.

  The mismatch means a shape difference between the inner glass sheet and the outer glass sheet, and the smaller the numerical value, the smaller the shape difference.

  Comparing ref, 10 sec, 20 sec, and 30 sec at 300 mm and 700 mm on the horizontal axis of the graph in FIG. 7, it can be understood that the longer the time, the smaller the value of the mismatch. By lengthening the cooling, the amount of bending of the inner glass could be increased, and the mismatch was reduced.

DESCRIPTION OF SYMBOLS 10 Glass plate manufacturing apparatus, 12 Heating furnace, 14 Slow-cooling furnace, 16 carts, 18 Molds, 20 Carry-in, 22 nozzles, G glass plate, G1 1st area, G2 2nd area, G3 3rd area, G4 Bending acceleration Area, DA bending area, SA peripheral area

Claims (9)

A glass plate placed on a ring-shaped mold, a heating forming step of bending and forming by heating to near the softening point of the glass plate,
A slow cooling step of slowly cooling the glass sheet near the softening point formed by bending,
A method for manufacturing a glass plate, comprising:
The glass plate includes a first region within 50 mm from an outer peripheral edge of the glass plate, a second region within 100 mm from the center of gravity of the glass plate, and a third region between the first region and the second region. Including
Having a bending promoting region in the third region;
The method of manufacturing a glass sheet, wherein the slow cooling step includes cooling at least a part of the bending acceleration region of the glass sheet before reaching a slow cooling point of the glass sheet.   The method for manufacturing a glass sheet according to claim 1, wherein in the annealing step, at least a part of the bending promotion region is cooled as soon as the glass sheet is transferred to the annealing furnace.   The method for manufacturing a glass sheet according to claim 2, wherein at least two of the bending promotion regions located in the third region are cooled.   The method for manufacturing a glass sheet according to claim 3, wherein four bending promotion regions located at corners of the third region are cooled.   The method for producing a glass sheet according to any one of claims 1 to 4, wherein a cooling rate in the slow cooling step is 2.8 / sec or more and 6.6 / sec or less.   The method for producing a glass sheet according to claim 5, wherein a cooling time in the slow cooling step is 10 seconds or more and 60 seconds or less.   The method for manufacturing a glass sheet according to any one of claims 1 to 6, wherein two glass sheets are placed on the ring-shaped mold in an overlapping manner.   The method for manufacturing a glass sheet according to claim 1, wherein the bending promotion region is cooled by blowing a gas.   The method for manufacturing a glass sheet according to claim 1, wherein the bending promotion region is cooled by radiation cooling.

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