WO2016067829A1

WO2016067829A1 - Curved plate glass molding method

Info

Publication number: WO2016067829A1
Application number: PCT/JP2015/078089
Authority: WO
Inventors: 森　弘樹; 松本　直之
Original assignee: 日本電気硝子株式会社
Priority date: 2014-10-31
Filing date: 2015-10-02
Publication date: 2016-05-06
Also published as: TW201623164A; JP6628151B2; JPWO2016067829A1

Abstract

In this invention, when obtaining a curved plate glass G2 by heating a plate glass G1 positioned over a lower mold 11 to mold the plate glass G1 by self-weight deformation, which accompanies the softening of the plate glass G1, the viscosity of the plate glass G is maintained at 10¹⁰ poises or greater during the interval from the start of the plate glass G1 heating until completion of the plate glass G1 molding.

Description

Method for forming curved plate glass

The present invention relates to a method for forming a curved plate glass, and more particularly to a method for forming a curved plate glass by bending the plate glass.

In recent years, portable electronic devices such as smartphones and tablet PCs are rapidly spreading. As a plate glass used for a touch panel of these devices, a flat plate glass conventionally used (hereinafter simply referred to as a flat glass) is generally used. Adoption of curved glass plates having a curved shape with a radius has been studied, and has actually begun to be adopted. In addition, the use of curved plate glass having a curved shape is also being considered for plate glass used in automobile displays such as car navigation systems.

As a method of forming this curved plate glass, a press method and a self-weight method are known roughly. Among these, the press method press-molds heat-softened flat glass using an upper mold and a lower mold having a curved molding surface (for example, see Patent Document 1). The method uses a lower mold having a curved molding surface and softens the flat glass placed on the lower mold by heating, so that the flat glass follows the molding surface of the lower mold by deformation due to its own weight. It shape | molds in a shape (for example, refer patent document 2).

JP-A-1-24034 JP-A-9-208244

However, since all of the above-described methods for forming a curved plate glass utilize the softening phenomenon associated with the heating of the flat glass, the marks (contact marks) generated when contacting the forming surface in the softened state are There is a problem that remains on the surface even after molding. That is, in the pressing method, the plate glass is heated to at least near the softening point, so that the surface of the plate glass is in a very soft state. Therefore, the surface of the plate glass tends to have contact marks with the molding surface. Above all, in the press method, the plate glass is sandwiched between the upper and lower forming dies with a suitable pressing force, so that contact marks with the forming surface are apt to be attached.

In the self-weight method, basically, since the plate glass is bent to a predetermined radius of curvature only by deformation due to its own weight (usually bending deformation), it is necessary to heat it to a temperature higher than that of press molding. Therefore, although the pressure applied to the molding surface is not strong as compared with the pressing method, the plate glass itself is soft, and the point that the contact mark with the molding surface remains is not solved. For example, window marks for automobiles (Patent Document 1, etc.), this type of contact mark was not a problem for conventional product applications, but display surfaces for high-definition display applications such as smartphones and automobile displays. The product value may be reduced.

In view of the above circumstances, in the present specification, the present invention provides a curved plate glass having a good surface quality by preventing the occurrence of contact marks with a mold as much as possible. As an objective.

The solution to the above problem is achieved by the method for forming a curved plate glass according to the present invention. That is, in this molding method, the plate glass placed on the lower mold is heated to obtain the curved plate glass by its own weight deformation accompanying the softening of the plate glass. It is characterized in that the viscosity of the glass sheet is maintained at 10 ¹⁰ poise or more until the molding is completed.

As described above, the present invention has been made by paying attention to the minimum viscosity of the plate glass during the heating process when the plate glass is formed into the curved plate glass using the so-called self-weight method. That is, in the conventional dead weight method, the plate glass is heated to near the softening point (the viscosity of the glass is about 10 ^7.65 poise) and sufficiently bent, and the bent plate glass is received by the molding surface. By this, the final curvature degree (for example, curvature radius) of plate glass was adjusted. On the other hand, the present invention is the minimum for heating the plate glass and causing the plate glass bent by its own weight deformation accompanying softening to undergo its own weight deformation until reaching the final shape (the shape of the curved plate glass as a molded product). The minimum required viscosity (minimum viscosity) was identified, and the minimum value of the viscosity between the start of heating and the completion of molding was defined. This prevents the situation where the molding surface and the sheet glass are in contact with each other more strongly than necessary, while forming the sheet glass into a desired shape, leaving a contact mark with the molding surface on the surface of the molded sheet glass (curved plate glass). Can be prevented as much as possible. Alternatively, even if contact marks remain, the extent (size, number, conspicuousness) can be minimized. Moreover, since the surface of a plate glass becomes so hard that plate glass is highly viscous, it can make it difficult to attach a contact trace with a shaping | molding surface also by this. In particular, by maintaining the viscosity of the plate glass at 10 ¹¹ poise or more from the start of heating to the plate glass until the formation of the plate glass, the curved plate glass is made more difficult to have contact marks with the molding surface. It is possible to further reduce the size, number, etc. of contact marks generated on the surface. Therefore, it becomes possible to shape | curve the curved plate glass which can satisfy | fill the high quality surface quality for smart phones, for example.

Further, in the method for forming a curved plate glass according to the present invention, the time during which the viscosity of the plate glass is 10 ¹³ poise or less is set to 60 minutes or less during the period from the start of heating to the plate glass until the forming of the plate glass is completed. May be set, preferably set to 30 minutes or less, more preferably set to 15 minutes or less. Further, from the viewpoint of increasing the forming accuracy, it is preferable to set the time for the viscosity of the plate glass to be 10 ¹³ poise or less to 1 minute or more.

As described above, the present invention regulates the minimum viscosity of the glass sheet during the process of forming the curved glass sheet by the self-weight method, thereby enabling high-precision curved molding and generating contact marks with the molding surface. In this case, in view of preventing the occurrence of contact traces on the surface of the plate glass with a higher probability, it is relatively possible even if the minimum viscosity is not reached. It is desirable to keep the low viscosity state (high temperature state) as short as possible. Therefore, by setting the minimum viscosity of the plate glass between the start of heating and the completion of molding as described above to 10 ¹⁰ poise or more and setting the time for the plate glass to be 10 ¹³ poise or less to 60 minutes or less, contact marks Can be prevented with higher probability, or the degree (number of occurrences, size, and conspicuousness) can be further suppressed.

Further, in the method for forming a curved plate glass according to the present invention, the time during which the viscosity of the plate glass is 10 ^14.5 poise or less is 90 minutes or less from the start of heating to the plate glass until the formation of the plate glass is completed. May be set, preferably 60 minutes or less, and more preferably 30 minutes or less. Further, from the viewpoint of improving the forming accuracy, it is preferable to set the time for the viscosity of the plate glass to be 10 ^14.5 poise or less to 5 minutes or more.

This configuration is also defined with the same concept as the configuration described above, and the minimum viscosity of the plate glass from the start of heating to the completion of molding is 10 ¹⁰ poise or more, and the viscosity of the plate glass is 10 ^14.5 poise. By setting the following time to 90 minutes or less, generation of contact traces can be prevented with higher probability, or the degree thereof can be further suppressed. Of course, in this case, it is possible to further prevent the occurrence of contact marks by setting the time during which the viscosity of the plate glass is 10 ¹³ poise or less to 60 minutes or less.

Also, the method for forming a curved plate glass according to the present invention may start heating the plate glass with a sheet softer than the lower die interposed between the lower die and the plate glass.

Thus, by interposing a sheet softer than the lower mold, the plate glass comes into contact with this sheet, and direct contact with the lower mold is avoided. Since this sheet is softer than the lower mold, even if it comes into contact with the glass sheet, it is difficult to be damaged (contact marks). Further, since it is a sheet, it is flexible with respect to deformation and easily follows the molding surface provided in the lower mold. Therefore, even if this sheet is interposed, there is no possibility that the forming accuracy of the curved plate glass is lowered.

Further, in the method for forming a curved plate glass according to the present invention, the plate glass is placed on the lower mold, and after forming the sealed space between the lower surface of the plate glass and the molding surface provided on the lower mold, the sealed space is decompressed. It may be a thing.

Thus, by reducing the pressure of the sealed space formed between the glass sheet and the molding surface provided in the lower mold, the pressure is higher on the upper surface side than the pressure in the space (sealed space) positioned on the lower surface side of the glass sheet. The air pressure in the space is relatively increased. Thereby, the plate glass which divides the said sealed space and the space located in the upper surface side is pressurized toward the shaping | molding surface from the space located in the upper surface side. Therefore, this pressing force boosts the deformation of the plate glass toward the forming surface, and the plate glass can be formed into a shape that follows the forming surface at a lower temperature (in a state where the viscosity is kept high). Therefore, it is possible to form the plate glass into a shape that more accurately follows the molding surface while preventing the occurrence of contact traces on the surface of the plate glass with a higher probability or further suppressing the degree thereof.

In this case, the method for forming a curved plate glass according to the present invention may further pressurize a space located on the upper surface side of the plate glass.

In this way, in addition to depressurizing the sealed space formed between the glass sheet and the molding surface, if the space located on the upper surface side of the glass sheet is pressurized, the pressure of the space located on the lower surface side of the glass sheet And the difference with the atmospheric | air pressure of the space located in the upper surface side can be enlarged, and a plate glass can be pressurized toward a shaping | molding surface with a bigger pressurization force. Therefore, even if the viscosity of the plate glass is maintained at a higher level, the plate glass can be formed into a shape that follows the forming surface. Therefore, it is possible to form the plate glass into a shape that more accurately follows the molding surface while preventing the occurrence of contact traces on the surface of the plate glass with a higher probability or further suppressing the degree thereof.

Further, the method for forming a curved plate glass according to the present invention may be one in which the curved plate glass is formed by heating the plate glass using a lower mold provided with a concave forming surface.

If a lower mold provided with a concave molding surface is used, for example, the sealed space can be easily formed between the lower surface of the glass sheet and the molding surface simply by placing the glass sheet on the lower mold. it can. Therefore, the above configuration is particularly effective when the space located on the upper surface side of the plate glass is relatively pressurized.

In addition, the method for molding a curved plate glass according to the present invention uses a lower mold provided with a concave molding surface and a convex molding surface, and after molding the curved plate glass by heating to the plate glass, Inverting the curved plate glass, placing the inverted curved plate glass on a lower mold provided with a molding surface having a shape corresponding to the lower surface of the inverted curved plate glass, and forming the curved plate glass by heating. Also good.

The above configuration is effective when a curved plate glass having a concavely curved portion and a convexly curved portion is formed. That is, when a curved plate glass having an uneven shape as described above is formed by the method according to the present invention, a forming surface corresponding to the lower surface shape of the curved plate glass to be formed, that is, a convex forming surface and a concave shape are formed. It is conceivable to use a lower mold provided with a molding surface. Here, when the plate glass is heated by the method according to the present invention (self-weight method) to form the curved plate glass, the end of the portion formed on the convex molding surface of the curved plate glass is raised. It has been found that it is difficult to accurately form a convexly curved portion.

Therefore, in the present invention, after the plate glass is placed on the lower mold and the curved plate glass is molded by heating, the curved plate glass is inverted, and a molding surface having a shape corresponding to the lower surface of the inverted curved plate glass is provided. The inverted curved plate glass was placed on the lower mold, and the curved plate glass was formed by heating. According to this method, the portion formed in a state where the end portion is lifted on the molding surface that is convex in the molding before reversal is deformed by its own weight due to heat softening on the molding surface that is concave in the molding after reversal. By this, it is re-molded into a final shape (a shape corresponding to a concave molding surface). Therefore, even a curved plate glass having a concavely curved portion and a convexly curved portion can be formed with high accuracy by correcting the lifting of the end portion.

Further, in this case, in the method for forming a curved plate glass according to the present invention, the lower mold used for forming after inversion may be the lower mold used for forming before inversion. Alternatively, the lower mold used for molding after inversion may be different from the lower mold used for molding before inversion.

When the smooth curved glass sheet to be formed is composed of a symmetric concave part and a convex part, the bottom surface shape of the curved plate glass after inversion is the same as the bottom surface shape of the curved plate glass before inversion. . Therefore, a common molding surface can be used before and after reversal, and even when reversing and further molding, only one lower mold is required. In addition, even in the case where the concave portion and the convex portion of the curved plate glass are asymmetrical shapes, the lower die used for molding after reversal is different from the lower die used for molding before reversal. Separately prepared, by forming the molding surface of the shape corresponding to the lower surface of the curved plate glass after reversal in the lower mold for the above reversal, the curved plate glass of the desired shape is molded by two moldings before and after reversal can do. Therefore, according to the molding method according to the present invention, even if it is a curved plate glass of any shape, the plate glass is accurately molded by using the lower mold provided with the molding surface of the corresponding shape before and after the reversing operation. It becomes possible to do.

Further, the method for forming a curved plate glass according to the present invention is provided by forming a concave forming surface on the lower mold, placing plate glasses having opposite two side lengths on the forming surface, and heating the plate glass to heat. When forming the sheet glass, the sheet glass is formed in a posture inclined with respect to the horizontal direction so that the relatively short side of the sheet glass is in contact with the forming surface above the relatively long side. It may be placed on the surface.

The shape of the plate glass before curve molding is usually rectangular, and the shape of the molding surface provided in the lower mold is often a semi-cylindrical shape. In this case, the sheet glass is formed on the molding surface in a state where the center line of the sheet glass having the same distance from the two opposite sides of the sheet glass is matched with the center line of the molding surface having the same distance from the two sides forming the peripheral edge of the molding surface. Place on top. At this time, the mounting position of the plate glass is horizontal. On the other hand, in recent years, from the viewpoint of design, there is an increasing need for the use of a plate glass that is not rectangular such as a trapezoidal shape, for example. However, when a plate glass having such a shape is placed in a horizontal posture on the molding surface of the lower mold as in the conventional case, the plate glass is curved asymmetrically (on the short side and the long side of the plate glass). Therefore, the value of the radius of curvature of the formed glass sheet is not stable, and it is difficult to form the curved glass sheet to the required accuracy.

On the other hand, in the present invention, a forming surface having a concave shape is provided in the lower mold, and plate glasses having different lengths of two opposite sides are placed on the forming surface and heated to form the curved plate glass. In doing so, the plate glass is placed on the molding surface in a posture inclined with respect to the horizontal direction so that the relatively short side of the plate glass is in contact with the molding surface above the relatively long side. I tried to put it. By placing the non-rectangular plate glass in an inclined posture on the molding surface in this way, the center of gravity of the non-rectangular plate glass is relatively compared to the case where it is placed in a horizontal posture as in the prior art. It will be in the state offset to the short side of plate glass. More specifically, when the non-rectangular plate glass is placed on the molding surface in a horizontal posture, the center line of the concave molding surface (here, for example, the distance from two sides forming the peripheral portion of the molding surface is equal) The center of gravity of the glass sheet is offset on the side that is longer than the center line. On the other hand, by placing the plate glass in an inclined posture so that the side that becomes the short side of the plate glass is relatively upward as described above, the center of gravity of the plate glass is shorter than the conventional side of the center line of the molding surface. It can be in an offset state. As a result, curved glass sheets can be molded while maintaining a balance between the short side and the long side, so that the degree of bending due to self-weight deformation is prevented as much as possible from the short side and the long side. As a result, it is possible to stably form a highly accurate curved plate glass.

Further, in this case, the method for forming the curved plate glass according to the present invention is such that the center of gravity of the plate glass is on the side where the short side of the plate glass is shorter than the center line of the forming surface where the distance from the two sides forming the peripheral portion of the forming surface is equal. The plate glass may be placed on the molding surface in a posture inclined with respect to the horizontal direction so as to be positioned.

As described above, by setting the position of the center of gravity of the plate glass relative to the molding surface, softening due to heating causes the gravity of the plate glass to be deformed so that the center of gravity of the plate glass faces the center line of the molding surface. This is because the short side of the plate glass has a small contact area with the molding surface and a small frictional resistance. Therefore, by placing the plate glass as described above, the variation in the degree of bending can be further reduced between the short side and the long side, and the curved plate glass can be formed with higher accuracy.

Further, in this case, the method for forming the curved plate glass according to the present invention is such that the offset amount of the center line of the plate glass having the same distance from the two sides of the plate glass to the short side of the plate glass with respect to the center line of the forming surface is It may be set to exceed 1 time and not more than 15 times the distance from the center line to the center of gravity.

As a result of verification by the present inventors on how much the offset of the center of gravity of the glass sheet is offset with respect to the center line of the molding surface, the present invention has a good influence on the molding accuracy. It has been found that very good results can be obtained when the distance from the center line of the plate glass to the center of gravity is set to be more than 1 time and 15 times or less. Therefore, by setting the offset amount to the short side of the plate glass with respect to the center line of the forming surface of the center line of the plate glass within the above range, the difference in curvature after bending between the short side and the long side is very In addition, it is possible to stably form a highly accurate curved glass sheet.

As described above, according to the present invention, it is possible to prevent the occurrence of contact marks with the mold as much as possible, and to provide a curved plate glass having a good surface quality.

It is principal part sectional drawing of the shaping | molding apparatus of the curved plate glass which concerns on 1st embodiment of this invention. It is the figure which planarly viewed the shaping | molding die shown in FIG. It is a figure for demonstrating the shaping | molding method of the curved plate glass which concerns on 1st embodiment of this invention, Comprising: It is principal part sectional drawing of the shaping | molding apparatus at the time of plate glass carrying out its own weight deformation by heating. It is a graph which shows the relationship between the heating time which concerns on 1st embodiment of this invention, and the viscosity of plate glass. It is principal part sectional drawing of the shaping | molding apparatus of the curved plate glass which concerns on 2nd embodiment of this invention. FIG. 6 is an AA cross-sectional view of the mold shown in FIG. 5. It is principal part sectional drawing of the shaping | molding apparatus of the curved plate glass which concerns on 3rd embodiment of this invention. It is the figure which planarly viewed the shaping | molding die shown in FIG. It is a figure for demonstrating the shaping | molding method of the curved plate glass which concerns on 3rd embodiment of this invention, Comprising: It is principal part sectional drawing of the shaping | molding apparatus at the time of plate glass carrying out its own weight deformation by the 1st heating. It is a figure for demonstrating the shaping | molding method of the curved plate glass which concerns on 3rd embodiment of this invention, Comprising: When the curved plate glass shape | molded in the shape shown in FIG. 9 was reversed and mounted in the shaping | molding die shown in FIG. It is principal part sectional drawing of this shaping | molding apparatus. It is principal part sectional drawing of the shaping | molding apparatus of the curved plate glass which concerns on 4th embodiment of this invention. It is the figure which planarly viewed the shaping | molding die shown in FIG. It is principal part sectional drawing of a shaping | molding die at the time of mounting plate glass in a horizontal attitude | position on the shaping | molding die shown in FIG.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a cross-sectional view of a principal part for explaining an outline of a curved sheet glass forming apparatus 10 according to a first embodiment of the present invention. The forming apparatus 10 houses a lower mold 11 for forming the sheet glass G1 into a predetermined curved shape, a heating apparatus 12 for heating the sheet glass G1 placed on the lower mold 11, and the lower mold 11 and the heating apparatus 12. A furnace chamber 13.

Here, the glass sheet G1 to be molded can have an appropriate composition according to its application, and the composition is not particularly limited. For example, in terms of mass%, SiO ₂ : 50 to 80 %, Al ₂ O ₃ : 5 to 25%, B ₂ O ₃ : 0 to 15%, Na ₂ O: 1 to 20%, K ₂ O: 0 to 10% Yes, it is possible to obtain a curved tempered glass plate by chemically strengthening it after being bent by the forming apparatus 10.

The dimension of the plate glass G1 is not particularly limited. For example, the thickness dimension may be 3.0 mm or less, preferably 2.5 mm or less, more preferably 1.5 mm or less. More preferably, it may be 1.0 mm or less. On the other hand, the lower limit may be 0.1 mm or more, preferably 0.5 mm or more, from the viewpoint of moldability. This is because if the thickness dimension is small, the curve can be easily formed even if the viscosity is relatively high.

The lower mold 11 has a molding surface 14 for molding the glass sheet G1 into a predetermined curved shape. In the present embodiment, the molding surface 14 is a concave curved surface, and as shown in FIG. 2, two opposing sides of the plate glass G1 placed on the lower mold 11 (here, the short sides G1a of the plate glass G1 having a rectangular shape, G1a) can be supported over the entire region in the width direction (here, the direction orthogonal to the bending direction; the same applies hereinafter). Further, the shape of the molding surface 14 is formed in a shape that extends linearly in the width direction and has a single radius of curvature over the entire bending direction. In the present embodiment, the bending direction is the direction along the long sides G1b and G1b of the plate glass G1, and the width direction is the direction along the short sides G1a and G1a of the plate glass G1 (FIG. 2).

Further, in the present embodiment, the sheet 15 is disposed between the plate glass G1 and the molding surface 14 provided on the lower mold 11. Therefore, in this case, heating to the plate glass G1 is started in a state where the sheet 15 is interposed between the plate glass G1 and the molding surface 14. Here, the sheet 15 is mainly for protecting the plate glass G1 from the lower mold 11 and is formed of a material softer than the lower mold 11. Specifically, glass, carbon, or a metal (such as stainless steel) that is softer than the material forming the lower mold 11 can be employed. These also have the tolerance with respect to the heating to the plate glass G1. The sheet 15 naturally has a sheet shape, and when placed on the molding surface 14, the sheet 15 is required to exhibit rigidity (degree of resistance to deformation as the sheet 15) that can be deformed following the molding surface 14. . In view of this point, for example, when the sheet 15 is formed of glass, the sheet 15 is formed of glass cloth. When the sheet 15 is formed of carbon, the sheet of carbon 15 is formed. When the sheet 15 is formed of stainless steel, the sheet 15 is formed of stainless steel cloth. It is good to form.

The lower mold 11 can be formed of any material without particular limitation as long as it can withstand the heating of the glass sheet G1 described later, and an example is mullite. Of course, the lower mold 11 can be formed of a material other than mullite, for example, alumina, zircon, or a mixture thereof (alumina zircon, zircon mullite, etc.).

The heating device 12 is for heating the glass sheet G1 placed on the lower mold 11 in the furnace chamber 13, for example, a radiant heating type such as an electric heater or a convection heating of the atmosphere 16 in the furnace chamber 13 with a burner. Alternatively, a type in which gas heated by a burner is supplied into the furnace chamber 13 and the atmosphere 16 in the furnace chamber 13 is convectively heated can be employed. In addition, in this embodiment, as shown in FIG. 1, the case where the heating apparatus 12 is arrange | positioned in the position which opposes the upper surface of the furnace chamber 13, more correctly, the upper surface G1c of the plate glass G mounted in the lower mold | type 11. Although illustrated, of course, other arrangement modes (arrangement position, number) can be adopted.

Next, an example of a method for forming a curved plate glass using the forming apparatus 10 having the above configuration will be described together with advantages of the present invention.

First, as shown in FIG. 1, sheet glass G1 to be molded is supplied into the furnace chamber 13 of the molding apparatus 10 and placed on the lower mold 11 (placement process). As shown in FIG. 1, when interposing the sheet | seat 15, the sheet | seat 15 is mounted in the lower mold | type 11, and the plate glass G1 is mounted from the top. In the state of being placed on the lower mold 11, the glass sheet G 1 has a shape before bending deformation (for example, a flat plate shape as shown in FIG. 1). At this time, the lower mold 11 may be preheated at a predetermined temperature (for example, 200 to 300 ° C.) in advance (preheating step). Preheating may be performed in the furnace chamber 13 or in a furnace chamber (preheating furnace) different from the furnace chamber 13.

Thus, after placing the glass sheet G1 on the lower mold 11, heating of the glass sheet G1 by the heating device 12 is started (heating process). As a result, the glass sheet G1 is softened, and the glass sheet G1 is made to conform to the molding surface 14 due to its own weight deformation accompanying the softening (downward deflection deformation in this embodiment) (in close contact with the molding surface 14 in a macro manner). Then, as shown in FIG. 3, it is molded into a shape according to the molding surface 14 (molding step). And if shaping | molding of the curved plate glass G2 is completed, the curved plate glass G2 will be taken out of the furnace chamber 13 from the lower mold | type 11 (extraction process). Through the above steps, the curved glass sheet G2 is obtained.

FIG. 4 shows the relationship between the heating time and the viscosity of the plate glass G1 during the heating step. As shown in FIG. 4, in this heating step, the temperature of the sheet glass G1 is raised with a constant gradient (usually, the temperature of the sheet glass G1 is estimated by the temperature of the atmosphere 16 in the furnace chamber 13 that can be easily measured), After the sheet glass G1 is heated to a predetermined temperature, a heat history for cooling the sheet glass G1 with a predetermined gradient is set. At this time, the thermal history is set so that the maximum temperature of the plate glass G1, that is, the minimum viscosity V _{min of the} plate glass G1 is 10 ¹⁰ poise or more. In other words, the viscosity of the plate glass G1 is maintained at 10 ¹⁰ poise or more from the start of heating to the plate glass G1 until the completion of molding. Thereby, while forming the plate glass G1 with high accuracy, the situation where the forming surface 14 and the plate glass G1 come into contact with each other more than necessary is avoided, and the surface of the formed plate glass G1 (curved plate glass G2) is formed on the surface of the forming glass 14. It is possible to prevent as much as possible a situation in which contact marks remain. Moreover, since the surface (lower surface G1d) of plate glass G1 becomes so hard that plate glass G1 is highly viscous, it can make it difficult to attach a contact trace with the molding surface 14 by this.

In the present embodiment, the time T ₁ during which the viscosity of the plate glass G1 is V ₁ = 10 ¹³ poise or less is set to 60 minutes or less from the start of heating to the completion of molding, and the viscosity of the plate glass G1 is V _The time T _{2 at} which ₂ = 10 ^14.5 poise or less was set to 90 minutes or less. Thus, even if the glass sheet G1 does not reach the minimum viscosity V _min , the occurrence of contact traces can be prevented with a higher probability, or to the extent (by that level) The number of occurrences, the size, the conspicuousness, etc.) can be further suppressed. Note that in the glass sheet G1 showing the composition of an example in this embodiment, the viscosity V ₁ was equivalent to the viscosity at the annealing point, the viscosity V ₂ corresponds to the viscosity at the strain point. From this, not only the minimum viscosity V _min of the glass sheet G1 is managed, but also the time T ₁ and T ₂ during which the glass sheet G1 is held at a temperature equal to or higher than the annealing point and the strain point is kept as short as possible. It can be understood that the present invention is very effective in preventing or suppressing the generation of marks as much as possible.

Incidentally, the minimum viscosity _{V min} these, predetermined viscosity _V 1, _{V 2} hereinafter become time _T 1, _{T 2} is preferably set as appropriate depending on the application of the curved plate glass G2. For example, in the case of high-definition display applications for automobile displays, considering that the thickness dimension is relatively large, for example, the time T when the minimum viscosity V _min of the glass sheet G1 is 10 ¹⁰ poise or more and the predetermined viscosity V ₁ or less _It is preferable to set ₁ to 60 minutes or less and a time T ₂ for which the predetermined viscosity V ₂ or less is set to 90 minutes or less. For high-definition display applications for smartphones, considering that the thickness dimension is relatively small, for example, the time T _{1 when} the minimum viscosity V _min of the glass sheet G1 is 10 ¹¹ poise or more and the predetermined viscosity V ₁ or less. Is set to 30 minutes or less, and the time T ₂ when the predetermined viscosity V ₂ or less is set to 60 minutes or less.

Further, in the present embodiment, the heating to the plate glass G1 is started in a state where the sheet 15 softer than the lower die 11 is interposed between the lower die 11 and the plate glass G1. Thereby, the plate glass G1 contacts with this sheet | seat 15, and the direct contact with the lower mold | type 11 is avoided. Since this sheet 15 is softer than the lower mold 11, even if it contacts with the glass sheet G1, scratches (contact marks) are less likely to occur. Further, since it is the sheet 15, it is flexible with respect to deformation and easily follows the molding surface 14 provided on the lower mold 11. Therefore, there is no possibility of adversely affecting the heat curve forming of the plate glass G1 by interposing this sheet 15, and there is no problem in terms of forming accuracy.

As mentioned above, although 1st embodiment of the shaping | molding method of the curved plate glass which concerns on this invention was described, this shaping | molding method can naturally take arbitrary forms within the scope of the present invention.

FIGS. 5 and 6 show an example (second embodiment of the present invention), and the molding apparatus 17 shown in these drawings shows the lower surface G1d of the sheet glass G1 in a state where the sheet glass G1 is placed on the lower mold 18. And a molding surface 14, a sealed space 19 is formed, and the sealed space 19 and a space 20 located on the upper surface G1c side of the plate glass G1 can be partitioned. Specifically, the lower mold 18 has a side portion 21 that defines a sealed space 19 together with the lower surface G1d of the glass sheet G1 and the molding surface 14 in a state where the glass sheet G1 is placed on the molding surface 14, thereby forming the molding surface. In the state in which the plate glass G1 is placed on the plate 14, the sealed space 19 can be formed on the lower surface G1d side of the plate glass G1.

Further, the lower mold 18 has a decompression device 22 that decompresses the sealed space 19 formed on the lower surface G1d side of the plate glass G1. Thereby, the sealed space 19 can be depressurized during part or all of the period during which the plate glass G1 is heated.

Thus, by reducing the pressure of the sealed space 19 formed between the glass sheet G1 and the molding surface 14, the pressure on the upper surface G1c is higher than the atmospheric pressure of the space (sealed space 19) located on the lower surface G1d side of the glass sheet G1. The atmospheric pressure in the space 20 is relatively increased. Thereby, the plate glass G1 which divides the sealed space 19 and the space 20 located on the upper surface G1c side is pressurized toward the molding surface 14 from the space 20 located on the upper surface G1c side. Therefore, the applied pressure pushes the deformation of the glass sheet G1 toward the molding surface 14, and the glass sheet G1 is shaped to follow the molding surface 14 at a lower temperature (in a state where the minimum viscosity _Vmin is kept high). Can be molded. Therefore, the generation of contact marks on the lower surface G1d of the plate glass G1 is prevented with a higher probability, or the plate glass G1 is formed into a shape that follows the molding surface 14 with higher accuracy while further suppressing the extent. Is possible. In this case, the minimum viscosity V _min of the plate glass G1 can be set to, for example, 10 ^11.5 poise or more.

Moreover, although illustration is abbreviate | omitted in said 2nd embodiment, you may further provide the pressurization apparatus for pressurizing the space 20 located in the upper surface G1c side of the plate glass G1. In addition to depressurizing the sealed space 19 formed between the plate glass G1 and the molding surface 14, if the space 20 positioned on the upper surface G1c side of the plate glass G1 is further pressurized, the lower surface G1d side of the plate glass G1 The difference between the air pressure in the space (sealed space 19) located and the air pressure in the space 20 located on the upper surface G1c side can be increased, and the plate glass G1 can be pressurized toward the molding surface 14 with a larger applied pressure. Therefore, it can be a state of maintaining further enhance the minimum viscosity V _min of the glass sheet G1 is formed into a shape conforming the sheet glass G1 the molding surface 14.

FIG. 7 is a cross-sectional view of the main part of the molding apparatus 23 according to the third embodiment of the present invention. As shown in FIG. 7, this molding apparatus 23 is different from the first and second embodiments in that it includes a lower mold 26 provided with a concave molding surface 24 and a convex molding surface 25. To do.

Here, both the concave molding surface 24 and the convex molding surface 25 have a constant radius of curvature, and in this embodiment, they are symmetrical around the boundary 27 between the molding surfaces 24 and 25 (rotation symmetry). ) In this case, the radius of curvature, the width dimension, and the dimension along the curve direction (dimension in the direction orthogonal to the width direction in FIG. 8) of each

molding surface

24, 25 are set to the same size.

Next, an example of a method for forming a curved plate glass using the forming apparatus 23 having the above configuration will be described together with advantages of the present invention.

First, as shown in FIG. 7, sheet glass G1 to be molded is supplied into the furnace chamber 13 of the molding apparatus 23 and placed on the lower mold 26 (placement step). At this time, as shown in FIG. 8, the glass sheet G1 is formed so that two opposing sides (short sides G1a, G1a) of the rectangular glass sheet G1 are supported by the molding surfaces 24, 25 over the entire width direction. Place on the

surfaces

24, 25. Although illustration is omitted, when the sheet 15 is interposed as in the first embodiment, the sheet 15 is placed on the lower mold 26, and the plate glass G1 is placed thereon.

Thus, after placing the plate glass G1 on the lower mold 26, the heating of the plate glass G1 by the heating device 12 is started (heating step). As a result, the glass sheet G1 is softened, and the glass sheet G1 is made to conform to the respective molding surfaces 24 and 25 (macro-adhered to the molding surfaces 24 and 25) by deformation due to its own weight as shown in FIG. Next, a curved sheet glass G3 having a concavely curved portion G3a and a convexly curved portion G3b, which is a shape conforming to the respective molding surfaces 24 and 25, is molded (molding step). At this time, the end portion G3b1 of the convexly curved portion G3b tends to be slightly lifted from the convex molding surface 25.

After forming the curved plate glass G3 in this way, the lower die, in which the curved plate glass G3 is inverted and provided with a molding surface having a shape corresponding to the lower surface G3c of the inverted curved plate glass G3, here, the first time The curved plate glass G3 is placed on the same one as the lower mold 26 used for the heat forming (FIG. 10). Since it is inverted, the concavely curved portion G3a of the curved glass sheet G3 is placed on the convex molding surface 25, and the convexly curved portion G3b is placed on the concave molding surface 24. It becomes a state. Thereafter, heating of the curved plate glass G3 by the heating device 12 is started (reheating process), the curved plate glass G3 is softened, and the curved plate glass G3 is deformed according to the molding surfaces 24 and 25 by its own weight deformation. Re-form into a new shape. At this time, the end portion G3b1 slightly raised from the convex molding surface 25 in the first heat molding is placed on the concave molding surface 24 after reversal, and its own weight is applied in a direction to cancel the floating. Works. Therefore, the convexly curved portion G3b including the end portion G3b1 is accurately reshaped into a shape corresponding to the molding surface 24 by the downward bending deformation in the second thermoforming.

Also in the present embodiment, by setting the thermal history so that the minimum viscosity V _min of the plate glass G1 (curved plate glass G3) during the first and second heating steps is 10 ¹⁰ poise or more, the plate glass While forming G1 (curved plate glass G3) with high accuracy, avoid the situation where the molding surfaces 24 and 25 and the plate glass G1 (curved plate glass G3) come into contact with each other more strongly than necessary, and form the plate glass G1 (curved plate glass). G3) It is possible to prevent as much as possible a situation in which contact marks with the molding surfaces 24 and 25 remain on the surface.

Of course, in addition to the minimum viscosity _{V min,} the time _{T 1} at which the viscosity of the glass sheet G1 (curved plate glass G3) is equal to or less than _V 1 ⁼ 10 13 poise set to 60 minutes or less, and the glass sheet G1 (curved plate glass G3) By setting the time T ₂ when the viscosity of V ₂ = 10 ^14.5 poise or less is set to 90 minutes or less, the relatively low viscosity state is kept as short as possible, and the occurrence of contact traces is more likely. It can be prevented, or the degree (number of occurrence, size, conspicuousness, etc.) can be further suppressed.

In the third embodiment, the case where the concave portion G3a and the convex portion G3b of the curved plate glass G3 to be formed are symmetric is exemplified. It is possible to apply. In that case, although not shown in the drawings, a lower mold used for molding after reversal is prepared separately from the lower mold 26 used for molding before reversal, and corresponds to the lower surface G3c of the curved plate glass G3 after reversal. By providing the shape-formed molding surface in the lower mold for after inversion, the curved plate glass G3 having a desired shape can be formed by forming twice before and after inversion.

In the third embodiment, the case where the curved glass sheet G3 to be formed has one concave portion G3a and one convex portion G3b, of course, of course, forms other than this It may be a plate glass G3. For example, although illustration is omitted, it is of course possible to form the curved plate glass G3 having a shape in which convex portions G3b are connected to both sides of the concave portion G3a by the method according to the third embodiment described above.

Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS.

FIG. 11 is a cross-sectional view of the main part of the molding apparatus 10 according to the fourth embodiment of the present invention. As shown in FIG. 11, the molding apparatus 10 is the same as the molding apparatus 10 used in the first embodiment. A different point exists in the shape of the plate glass G4 used as shaping | molding object, and its mounting aspect. Hereinafter, these points will be described in detail.

As shown in FIG. 12, the plate glass G4 to be molded in the present embodiment has a so-called non-rectangular shape in which the two opposite sides G4a1 and G4a2 have different lengths. In this illustrated example, since the two opposite sides G4a1 and G4a2 are parallel, the plate glass G4 has a trapezoidal shape with the short side G4a1 as the upper base and the long side G4a2 as the lower base.

And the plate glass G4 which makes the said shape is shape | molded with the attitude | position inclined with respect to the horizontal surface H so that the short side G4a1 side may contact the shaping | molding surface 14 above the long side G4a2 side, as shown in FIG. It is placed on the surface 14.

At this time, the center of gravity g (FIG. 12) of the glass sheet G4 is larger than the center line C1 (FIG. 12) of the molding surface 14 having the same distance from the two

sides

14a and 14a forming the peripheral edge of the molding surface 14. The mounting posture and position of the glass sheet G4 are set so as to be positioned on the short side G4a1 side (FIG. 11). More specifically, the offset amount of the center line C2 (FIG. 12) of the plate glass G4 having the same distance from the two sides G4a1 and G4a2 of the plate glass G4 to the short side G4a1 side of the plate glass G4 with respect to the center line C1 of the molding surface 14 S (FIG. 11) is set to be more than 1 time and not more than 15 times the distance d (FIG. 13) from the center line C2 of the glass sheet G4 to the center of gravity g. Note that the offset amount S here refers to the amount of deviation in the direction along the horizontal plane H of the center line C2 of the plate glass G4 with respect to the center line C1 of the forming surface 14, as shown in FIG.

After placing the plate glass G4 on the lower mold 11 as described above, heating to the plate glass G4 by the heating device 12 is started (heating step). As a result, the glass sheet G4 is softened, and the glass sheet G4 is made to conform to the molding surface 14 (macro-adhered to the molding surface 14) by deformation due to its own weight, and is formed into a shape according to the molding surface 14. (Molding process).

Here, in the present invention, the plate glass G4 is inclined with respect to the horizontal plane H so that the side of the plate glass G4 that is the relatively short side G4a1 is in contact with the molding surface 14 above the side that is relatively the long side G4a2. It was made to mount on the molding surface 14 with the attitude | position let it be (refer FIG. 11). By placing the non-rectangular plate glass G4 in an inclined posture on the molding surface 14 in this way, the center of gravity g of the non-rectangular plate glass G4 is compared with a case where the non-rectangular plate glass G4 is placed in a horizontal posture as in the prior art. Thus, the sheet glass G4 is relatively offset to the short side G4a1 side (see FIGS. 11 and 13). Specifically, when the non-rectangular plate glass G4 is placed on the molding surface 14 in a posture along the horizontal plane H, as shown in FIG. 13, the center line C1 (here, the concave molding surface 14) The center of gravity g of the plate glass G4 is offset to the side that becomes the longer side G4a2 than the center line having the same distance from the two

sides

14a and 14a forming the peripheral edge of the molding surface 14. On the other hand, by placing the plate glass G4 in an inclined posture so that the side that becomes the short side G4a1 of the plate glass G4 is relatively upward as described above, the center of gravity g of the plate glass G4 is more than that of the molding surface 14 than before. It can be in the state offset to the center line C1 side. As a result, the curved plate glass can be molded while balancing the short side G4a1 side and the long side G4a2 side, so the degree of bending due to its own weight deformation (in this embodiment, the radius of curvature after molding) is short. It is possible to prevent the situation where the side G4a1 side and the long side G4a2 side vary from each other as much as possible, and to stably form the curved plate glass with high accuracy.

In particular, in this embodiment, the center of gravity g of the glass sheet G4 is the side on which the short side G4a1 of the glass sheet G4 is located with respect to the center line C1 of the molding surface 14 having the same distance from the two

sides

14a and 14a forming the peripheral edge of the molding surface 14. The plate glass G4 was placed so as to be positioned at the position. More specifically, based on the verification result by the present inventors, the offset amount S of the center line C2 of the glass sheet G4 with respect to the center line C1 of the molding surface 14 is the distance d from the center line C2 of the glass sheet G4 to the center of gravity g. The position of the plate glass G4 was set so that it exceeded 1 time (FIG. 13) and 15 times or less. By placing in this way, due to the softening accompanying heating, the glass sheet G4 undergoes its own weight deformation (deflection deformation) so that the center of gravity g of the glass sheet G4 is directed toward the center line C1 of the molding surface 14. Therefore, by placing the plate glass G4 as described above, it is possible to further reduce the variation in the degree of bending between the short side G4a1 side and the long side G4a2 side, and it becomes possible to form the curved plate glass with higher accuracy. .

Also in the present embodiment, by setting the thermal history so that the minimum viscosity V _min of the plate glass G4 during the heating step is 10 ¹⁰ poise or more, the plate glass G4 is formed with high accuracy, while forming. It is possible to avoid the situation where the surface 14 and the plate glass G4 come into contact with each other more strongly than necessary, and to prevent as much as possible the situation in which the contact mark with the molding surface 14 remains on the surface of the formed plate glass G4.

Of course, in addition to the above minimum viscosity V _min , the time T ₁ when the viscosity of the plate glass G4 is V ₁ = 10 ¹³ poise or less is set to 60 minutes or less, and the viscosity of the plate glass G4 is V ₂ = 10 ^14.5. by setting poise or less and comprising a time T ₂ below 90 minutes, bear a relatively low viscosity state as much as possible in a short time, the occurrence of contact trace can be prevented at a higher probability, or the degree (generation number, Size, ease of conspicuousness, etc.) can be further suppressed.

In the fourth embodiment, the non-rectangular plate glass G4 is illustrated as having a trapezoidal shape, but the present invention can of course be applied to plate glasses having other forms. For example, although not shown, the present invention can also be applied to a non-trapezoidal plate glass such as a quadrangular shape in which two opposite sides are not parallel to each other. The term “side” as used herein means that the peripheral portion of the plate glass is linear when viewed as a whole, and not only the complete linear shape but also the peripheral portion that extends linearly with a slight curve. Including a part.

Moreover, regarding the molding surface 14 provided on the lower mold 11, in the first, second, and fourth embodiments, the glass sheets G1, G4 are molded into a shape having a single radius of curvature over the entire longitudinal direction. The shape is illustrated as an example, but it is not limited to this. The molding surface 14 may be configured with a plurality of curvature radii, whereby the glass sheets G1 and G4 can be molded into a curved shape having a plurality of curvature radii. Of course, part of the plate glasses G1 and G4 may be curved. Further, it is not necessary for the entire surface of the plate glasses G1 and G4 to be placed on the molding surface 14. For example, although not shown, a flat surface extending in the horizontal direction is provided around the molding surface 14, and the flat glass is provided on the flat surface. You may make it support the peripheral part of G1, G4.

In the first to fourth embodiments, one or a plurality of lower molds 11 are fixedly arranged in the furnace chamber 13, and the glass sheets G1 and G4 are placed on the lower mold 11 to perform molding at one time (so-called However, of course, the lower mold 11 and the sheet glasses G1 and G4 are passed through the heating furnace (furnace chamber 13) while being conveyed by a conveyor or the like, and are sequentially formed into the sheet glasses G1 and G4 that have passed therethrough. Processing may be performed (so-called continuous processing is performed).

Hereinafter, examples of the present invention will be described. First, experimental conditions (molding conditions, measurement conditions) will be described, and then the experimental results will be described.

(Molding condition)
In both the examples (Examples 1 to 4) and the comparative example, a plate glass having a long side of 160 mm, a short side of 80 mm, and a thickness dimension of 0.7 mm was used as a test piece. Then, this plate glass was placed on a molding surface having a concave curved shape of R1000 mm so as to bend along the long side, and molded into a shape following the molding surface by its own weight deformation accompanying heat softening. The thermal history at this time is as shown in Table 1.

(Measurement condition)
The number of contact marks remaining on the surface of the curved glass sheet formed as described above was measured. For any test piece, as a process before measurement, the surface of the curved plate glass was washed with pure water in a clean room to remove removable foreign matters, and the number of contact marks was visually measured. The measurement was performed in a clean room under two conditions of (1) illuminance 700 lx and (2) illuminance 1200 lx. The measurement results at this time are shown in Table 2. In addition, “innumerable” in Table 2 means that the number of contact marks that can be visually confirmed in the target test piece is large enough to exceed 100.

Thus, when the minimum viscosity of the plate glass during the heating step was less than 10 ¹⁰ poise (comparative example), innumerable contact traces at unacceptable levels were found on the surface of the formed plate glass (curved plate glass). On the other hand, when the minimum viscosity of the plate glass during the heating process was set to 10 ¹⁰ poise or more (Examples 1 to 4), the number of contact marks remaining on the surface of the curved plate glass was small. In particular, when the minimum viscosity of the plate glass is set to 10 ¹⁰ poise or more during the heating process (Example 1, Example 2), generation of contact traces is not observed at least under normal illuminance (under 700 lx), In particular, in this case, when the time when the viscosity of the plate glass is 10 ¹³ poise or less is set to 30 minutes or less and the time when the viscosity is 10 ^14.5 poise or less is set to 60 minutes or less (Example 1), The generation of contact marks was not observed at all under the condition where the illuminance was further increased (under 1200 lx), and a curved plate glass exhibiting excellent forming accuracy was obtained.

10, 17, 23

Molding device

11, 18, 26 Lower mold 12 Heating device 13 Furnace chamber 14 Molding surface 15 Sheet 19 Sealed space 22 Decompression device G1, G4 Sheet glass G2, G3 Curved sheet glass

Claims

In the method of forming a curved plate glass, heating the plate glass placed on the lower mold to obtain the curved plate glass by its own weight deformation accompanying the softening of the plate glass,
A method for forming a curved plate glass, wherein the viscosity of the plate glass is maintained at 10 10 poise or more after the heating of the plate glass is started until the forming of the plate glass is completed.
The curved plate glass according to claim 1, wherein the time during which the viscosity of the plate glass is 10 13 poise or less is set to 60 minutes or less between the start of heating of the plate glass and the completion of the forming of the plate glass. Molding method.
The time during which the viscosity of the plate glass is 10 14.5 poise or less is set to 90 minutes or less between the start of heating the plate glass and the completion of the forming of the plate glass. The shaping | molding method of curved sheet glass as described.
The method for forming a curved plate glass according to any one of claims 1 to 3, wherein heating to the plate glass is started in a state where a sheet softer than the lower die is interposed between the lower mold and the plate glass. .
5. The method according to claim 1, wherein the plate glass is placed on the lower mold to form a sealed space between a lower surface of the plate glass and a molding surface provided on the lower mold, and then the sealed space is decompressed. A method for forming a curved plate glass according to claim 1.
Furthermore, the shaping | molding method of the curved plate glass of Claim 5 which pressurizes the space located in the upper surface side of the said plate glass.
The method for forming a curved plate glass according to any one of claims 1 to 6, wherein the curved plate glass is formed by heating the plate glass using the lower mold provided with a concave forming surface.
After forming the curved plate glass by heating to the plate glass, using the lower mold provided with a concave forming surface and a convex forming surface,
The curved plate glass is inverted, the inverted curved plate glass is placed on a lower mold provided with a molding surface having a shape corresponding to the lower surface of the inverted curved plate glass, and the curved plate glass is molded by the heating. 5. The method for forming a curved plate glass according to claim 1, wherein the method is performed.
The method for forming a curved plate glass according to claim 8, wherein the lower mold used for the molding after the inversion is a lower mold used for the molding before the inversion.
The method for forming a curved plate glass according to claim 8, wherein the lower mold used for the molding after the reversal is different from the lower mold used for the molding before the reversal.
When forming the curved plate glass by forming the concave plate on the lower mold, placing the plate glasses having different lengths of two opposite sides on the molding surface, and heating the plate glass, The plate glass is placed on the molding surface in a posture inclined with respect to the horizontal direction so that the relatively short side of the plate glass is in contact with the molding surface above the relatively long side. The method for forming a curved plate glass according to any one of claims 1 to 4.
The plate glass is inclined with respect to the horizontal direction so that the center of gravity of the plate glass is located on the short side of the plate glass with respect to the center line of the forming surface having the same distance from two sides forming the peripheral edge of the forming surface. The method for forming a curved plate glass according to claim 11, wherein the glass plate is placed on the forming surface in a posture.
The amount of offset of the center line of the plate glass with the same distance from the two sides of the plate glass to the short side of the plate glass with respect to the center line of the forming surface is 1 of the distance from the center line of the plate glass to the center of gravity. The method for forming a curved sheet glass according to claim 12, wherein the method is set to be more than twice and not more than 15 times.