JP2013028510A - Method of molding glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of efficiently molding a glass in a state that the surface of the glass is smooth.SOLUTION: The method of molding the glass includes: a step of molding a rod-shaped glass by solidifying a molten glass flowing from an outflow nozzle; a step of heating the rod-shaped glass to the temperature at which the rod-shaped glass can be press-molded; and a step of pressing the side surface of the heated rod-shaped glass by using a molding surface of a die to mold the heated rod-shaped glass into a desired shape.

Description

  The present invention relates to a glass forming method, and more particularly to a glass forming method used as a casing of an electronic device such as a portable terminal.

  Generally, resin or metal is used for a housing of a mobile terminal such as a smartphone (Smart Phone) or a monitor such as an LCD (Liquid Crystal Display) from the viewpoint of processability and cost. However, in recent years, design properties are often required for a housing, and it has been proposed to use glass for the housing (for example, Patent Document 1). In patent document 1, it is proposed to color the back surface glass of the transparent solar cell mounted on the back surface of the mobile phone into a favorite color.

  Incidentally, an electronic component, a liquid crystal panel or the like (hereinafter referred to as an electronic component or the like) is accommodated in the electronic device. For this reason, the shape of the housing | casing of an electronic device becomes a box shape or the shape close | similar to a box shape, and the space which accommodates an electronic component etc. is ensured inside.

  Thus, as a method of processing glass into a box shape or a shape close to a box shape, a thick plate glass or a block glass (gob) is prepared, and this glass is cut into a box shape or a shape close to a box shape (for example, In general, machining with a cutting bit) or chemical machining with an etching solution is generally performed. However, when processing thick glass or block glass with a cutting tool or etching solution, the processing amount per unit time is low, and it is necessary to form a recess for accommodating electronic components, so the processing amount is large and the productivity is high. There is a problem that it is low.

  For this reason, it has been proposed to process the glass into a box shape or a shape close to the box shape by press molding, for example, by pressing a block glass formed into a desired weight with a mold, Processing glass into a shape close to a box shape is performed. In recent years, there has also been proposed a molding method in which a sheet glass is heated to a temperature at which press molding can be performed, and the heated sheet glass is pressed with a mold (for example, Patent Document 2).

JP 2005-129987 A US Publication No. 2010-0126222

  However, when a massive glass molded to a desired weight is pressed with a mold, a shear mark (scissor trace) is generated in the massive glass when the massive glass is molded to a desired weight. Since this shear mark cannot usually be removed by press molding, it must be removed by cutting or polishing after press molding. In this case, since the number of steps necessary for manufacturing the casing increases by the amount of cutting and polishing, the manufacturing cost increases. In addition, in some electronic devices, there are cases in which the casing has a curved shape in order to provide design properties. In this case, since the shear mark generated on the curved surface, not the flat surface, must be removed, cutting or polishing is required. Becomes difficult.

  Moreover, in the method of pressing a plate glass with a mold, it is necessary to fold the plate glass into a box shape or a shape close to a box shape. However, when the bending angle is deep (large), there is a possibility that “wrinkles” occur in the bent portion and the design is impaired. Further, in order to prevent wrinkles from occurring in the bent portion, it can be considered that the bent portion is bent while being stretched. However, in general, a plate glass is thin because it is manufactured by a fusion method. For this reason, when a bending part is extended, there exists a possibility that the thickness of a bending part may become thin too much and required intensity | strength may not be ensured.

  In addition, the float method, in which molten glass is floated on a float bath containing molten metal having a specific gravity higher than that of glass, can produce thick plate glass, but is a production method for mass production. It is not suitable for the housing of electronic devices that are often produced in small quantities. In addition, in the roll-out method in which the molten glass is passed between two horizontal rolls and then cooled and cut, it is difficult to produce a glass with a smooth surface. Not suitable for body use. Although it is conceivable to polish the glass surface, the manufacturing cost increases because the number of steps required for manufacturing the housing increases.

 An object of this invention is to provide the shaping | molding method of the glass which can be shape | molded efficiently in the state where the glass surface is smooth.

  The glass molding method of the present invention includes a step of solidifying molten glass flowing out from an outflow nozzle to form a rod-shaped glass, a step of heating the rod-shaped glass to a temperature at which press molding is possible, and a heated rod shape Pressing the side surface of the glass with the molding surface of the mold, and molding the heated rod-shaped glass into a desired shape.

  According to the present invention, a glass rod obtained by solidifying molten glass flowing out from an outflow nozzle is heated to a temperature at which press molding can be performed, and a fired surface of the heated glass rod is pressed by a molding surface of a mold to obtain a desired shape. Therefore, it is possible to provide a glass molding method capable of efficiently molding the glass surface in a smooth state.

The block diagram of the shaping | molding apparatus of 1st glass. The block diagram of the shaping | molding apparatus of a 2nd glass. The figure which shows the glass molded object shape | molded by the glass shaping | molding apparatus which concerns on embodiment.

(Embodiment)
FIG. 1 is a configuration diagram of a first glass forming apparatus 10. FIG. 2 is a configuration diagram of the second glass forming apparatus 20. A glass forming apparatus 1 according to this embodiment (hereinafter simply referred to as a glass forming apparatus 1) melts a glass raw material, flows out a molten glass G from an outflow nozzle and solidifies it to form a rod-shaped glass ( The first glass molding apparatus 10 (see FIG. 1) to be molded into a glass rod) and the glass rod R are heated to a temperature at which press molding is possible and molded into a box shape or a shape close to a box shape with a mold. The second glass molding apparatus 20 (see FIG. 2). Hereinafter, with reference to FIG.1 and FIG.2, the glass shaping | molding apparatus 1 which concerns on embodiment is demonstrated.

(First Glass Forming Apparatus 10)
As shown in FIG. 1, the first glass molding apparatus 10 includes a melting furnace 101, a clarification tank (refiner) 102, a stirring means 103, a molding container 104, a roller 105, and a slow cooling apparatus 106. .

The melting furnace 101 heats and melts silica sand, soda ash, limestone, and the like, which are glass materials. The clarification tank 102 removes bubbles generated in the molten glass G due to gas such as H ₂ O, CO ₂ , O ₂ generated by vitrification reaction or air entrained during melting.

  The stirring means 103 includes a stirring tank 103a that stores the glass G in a molten state, a rotating shaft 103b that is driven and rotated by a motor (not shown), and a melting shaft that is attached to the rotating shaft 103b and is stored in the stirring tank 103a. And a stirring blade 103c for stirring the glass G in a state. The agitation means 103 agitates and homogenizes the clarified glass G delivered from the clarification tank 102.

  The forming container 104 includes a cylindrical container 104a that accommodates the molten glass G that has been stirred by the stirring means 103, and an outflow nozzle 104b that is provided at the bottom of the container 104a. The molten glass G accommodated in the container 104a flows out from the outflow nozzle 104b. The outlet of the outflow nozzle 104b has a circular shape, and the molten glass G in the container 104a flows out of the outflow nozzle 104b in a columnar shape, that is, a bar shape. The glass G that has flowed out of the outflow nozzle 104b is gradually deprived of heat in the air and changes from a molten state to a softened state.

  The roller 105 flows out of the outflow nozzle 104b of the molding container 104 and is rotated by a motor (not shown) in a state where the roller 105 is in contact with a part of the side surface of the softened bar-shaped glass G. It sends out to the below-mentioned slow cooling apparatus 106 at a fixed speed.

  The slow cooling device 106 gradually cools the softened glass G fed from the roller 105. The softened glass G is gradually cooled and solidified by the slow cooling device 106 to obtain a glass rod R that is a rod-shaped glass. By slowly cooling, the thermal strain generated between the vicinity of the surface of the glass G and the inside thereof is alleviated.

(Second Glass Forming Device 20)
As shown in FIG. 2, the second glass forming apparatus 20 includes a cutting unit 201, a heating unit 202, a forming unit 203, and a removing unit 204. The cutting means 201 cuts the glass rod R obtained by the first glass forming apparatus 10 into a predetermined length. An appropriate cutting method can be used for cutting the glass rod R. In the following description, the glass rod R cut to a predetermined length is referred to as a glass blank B.

The heating means 202 is, for example, a gas burner, and heats the glass blank B to a temperature at which press molding can be performed (for example, a softening point temperature). In the present invention, the temperature at which press molding is possible refers to the temperature of glass exhibiting the viscosity necessary for starting glass molding. Specifically, the viscosity η (dPa · s) of the glass is 3 to 5 (η = 1 × 10 ³ to 1 × 10 ⁵ dPa · s).

  The molding unit 203 includes a mold 203a having a molding surface processed into a desired shape (in this embodiment, the shape of the casing of the electronic device), and a glass blank heated to a temperature at which press forming can be performed by the heating unit 202. A pressing unit 203b that presses the mold 203a against the side surface of B and pressurizes the side surface to a predetermined pressure;

  The shape of the molding surface of the mold 203a is transferred to the glass blank B by pressing the mold 203a against the side surface of the glass blank B heated to a temperature at which press molding is possible and pressurizing to a predetermined pressure. A glass molded body C formed into the above is obtained. In addition, when pressing the metal mold | die 203a against the side surface of the glass blank B, attention is paid so that the cut surface of the glass blank B may not contact the molding surface of the metal mold | die 203a. The removing means 204 removes the excess portion from the glass molded body C, that is, the portion that protrudes from the molding surface of the mold 203a.

  FIG. 3 is a view showing the shape of a glass molded body C molded by the glass molding apparatus 1 according to the embodiment. FIG. 3A is a top view of the glass molded body C. FIG. FIG. 3B is a cross-sectional view taken along line I-I in FIG.

Next, glass forming in the forming unit 203 will be described.
Since the glass blank B at the time of molding is in a softened state, even the minute surface shape of the mold 203a is not transferred to the glass blank B by molding. That is, the smoothness of the surface of the glass molded body C depends on the smoothness of the surface of the glass blank B before molding, not the smoothness of the surface of the mold 203a.

  In particular, in a non-isothermal press in which pressing is performed in a state where the temperature of the mold 203a is lower than the temperature of the glass blank B, the glass 203 is deprived of heat from the moment the softened glass blank B touches the mold 203a. The extensibility of the rod R decreases. For this reason, the surface of the glass blank B cannot follow the minute surface shape of the mold 203a. That is, the smoothness of the surface of the glass molded body C after molding is influenced by the smoothness of the surface of the glass blank B before molding, not the smoothness of the molding surface of the mold 203a. In this embodiment, the glass blank B is formed into a desired shape by pressing the side surface of the glass blank B, that is, the fire-making surface excellent in smoothness, with the molding surface of the mold 203a.

  For this reason, in order to obtain the smoothness of the surface of the glass molded body C after molding, it is not necessary to polish the surface of the glass molded body C, and a glass molded body used as a casing of an electronic device is efficiently produced. be able to. Moreover, it shape | molds so that the cut surface of the glass blank B may not contact the shaping | molding surface of the metal mold | die 203a. For this reason, even if a cut surface is a rough surface, the smoothness of the molding surface of the glass molded body C is not affected.

  In addition, because thick glass blank B is used as the molding target, unlike the case of forming plate glass, “wrinkles” occur in the bent part, or the thickness of the bent part becomes too thin to ensure the required strength. The possibility of not being able to be reduced can be reduced.

(About surface roughness)
Here, the surface roughness in the present invention will be described. The surface roughness of the side surface of the rod-shaped glass formed by the first glass forming apparatus 10 described with reference to FIG. 1 is such that the center line average roughness (Ra) defined by JIS B0601 is 1 μm or less. Preferably there is. By setting the center line average roughness (Ra) to 1 μm or less, a glass molded body C having a smooth surface can be obtained after press molding.

  And since the glass molded object C with the smooth surface can be obtained, it is not necessary to grind the surface of the glass molded object C after press molding, and the glass of high productivity can be formed. When the surface roughness of the side surface of the rod-shaped glass exceeds 1 μm in the center line average roughness (Ra), a glass molded body C having a smooth surface cannot be obtained after press molding. In this case, a polishing step for polishing and smoothing the surface of the glass molded body C is required, which is not preferable because the number of manufacturing steps increases.

  The surface roughness of the side surface of the glass is within the above range (centerline average roughness (Ra) is 1 μm or less) by heating the rod-shaped glass to a temperature higher than the temperature at which press molding is possible and then press molding. Even if it is not, a smooth surface can be obtained after press molding. However, in this case, more time and energy are required for heating the glass, and the productivity is significantly deteriorated. For this reason, it is preferable that the surface roughness of the side surface of the glass be in the above range (centerline average roughness (Ra) is 1 μm or less).

  The side surface of the rod-shaped glass is a fire-making surface having excellent smoothness, and means an outer surface parallel to the axial direction of the rod-shaped glass. Further, as described above, when the glass rod R is cut into the glass blank B having a predetermined length, the cut surface can be made into a mirror surface by cutting using the cleaving. As such a cutting method, for example, there is a side pressure cutting method, but not limited thereto, a known method can be used. Thus, if the cut surface is a mirror surface, that is, if the surface roughness is in the above range (centerline average roughness (Ra) is 1 μm or less), the cut surface can also be formed by a press. For example, a surface whose surface roughness is not 1.5 μm or less in terms of centerline average roughness (Ra) is defined as a rough surface.

  In addition, when the glass molded body C molded by the glass molding apparatus 1 is used as a casing of an electronic device such as an information terminal such as a smartphone or an LCD ((Liquid Crystal Display)), it is damaged due to a drop impact during use or a long period of time. High strength is required in consideration of contact scratches caused by the use of Therefore, the surface of the glass molded body C may be strengthened.

  As a strengthening treatment method for increasing the strength of glass, a method of forming a compressive stress layer on the glass surface is generally known. Typical methods for forming a compressive stress layer on the glass surface include a wind-cooling strengthening method (physical strengthening method) in which the glass plate surface heated to the vicinity of the softening point is rapidly cooled by air cooling, and the glass transition point and below. Alkali metal ions (typically Li ions, Na ions) having a small ionic radius on the surface of the glass plate by ion exchange at a temperature are changed to alkali ions (typically, Na ions or K for Li ions). There is a chemical strengthening method in which ions are exchanged for Na ions and K ions).

The chemical strengthening method is, for example, by immersing soda lime glass in a molten potassium nitrate salt heated to about 380 ° C., so that ion exchange of alkali ions (sodium ions (Na ⁺ ), which are glass components) has a larger ionic radius. This is a method of forming a compressive stress on the glass surface by performing potassium ion (K ⁺ ) in the molten salt, and imparting high strength to the glass molded body C.

(Glass composition)
As the glass used in the glass molding method of the present invention, SiO ₂ (silicon dioxide) is 55 to 80%, Al ₂ O ₃ (aluminum oxide) is ₃ to 16%, B ₂ O ₃ (boron oxide) 0-12%, Na ₂ O (sodium oxide) 5-16%, K ₂ O (potassium oxide) 0-4%, MgO (magnesium oxide) 0-15%, 0 to 3% CaO (calcium oxide), ΣRO (R is Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), Zn (zinc)) 0 to 18%, ZrO ₂ ( It is preferable to use a glass containing 0 to 1% of zirconium oxide).

Hereinafter, although each composition of the said glass is demonstrated, unless indicated otherwise, it demonstrates using mol percentage display content. SiO ₂ is a component constituting the glass skeleton and an essential component. If the content of SiO ₂ is less than 55%, the stability or weather resistance as glass is lowered. For this reason, the lower limit of the content of SiO ₂ is preferably 60% or more, and more preferably 65% or more. On the other hand, if the SiO ₂ content exceeds 80%, the viscosity of the glass increases, and the meltability is significantly reduced. For this reason, the upper limit of the content of SiO ₂ is preferably 75% or less, and more preferably 70% or less.

Al ₂ O ₃ is a component that improves the weather resistance and chemical strengthening properties of glass, and is an essential component. When the content of Al ₂ O ₃ is less than 3%, the weather resistance is lowered. Therefore, the lower limit of the content of Al ₂ O ₃ is preferably 4% or more, and more preferably 5% or more. On the other hand, if the content of Al ₂ O ₃ exceeds 16%, the viscosity of the glass becomes high and homogeneous melting becomes difficult. Therefore, the upper limit of the content of _Al 2 _{O 3} is preferably 14% or less, and more preferably 12% or less.

B ₂ O ₃ is a component for improving the weather resistance of glass, but not necessarily can be contained if necessary. If the content of B ₂ O ₃ is less than 4%, a significant effect may not be obtained for improving weather resistance. Therefore, the lower limit of the content of B ₂ O ₃ is preferably 5% or more, more preferably 6% or more. Further, if the content of B ₂ O ₃ exceeds 12%, striae due to volatilization may occur and the yield may be reduced. For this reason, the upper limit of the content of B ₂ O ₃ is preferably 11% or less, and more preferably 10% or less.

Na ₂ O is a component that improves the meltability of the glass, and is an essential component for forming a surface compressive stress layer by ion exchange. When the content of Na ₂ O is less than 5%, the meltability is poor, and it becomes difficult to form a desired surface compressive stress layer by ion exchange. For this reason, the lower limit of the content of Na ₂ O is preferably 7% or more, and more preferably 8% or more. Further, when the content of Na ₂ O exceeds 16%, the weather resistance is lowered. Therefore, the upper limit content of Na 2 _O is preferably 15% or less, and more preferably 14% or less.

K ₂ O is a component that improves the meltability of the glass and has the effect of increasing the ion exchange rate in chemical strengthening. For this reason, although it is not essential, it is a preferable component to contain. When the content of K ₂ O is less than 0.01%, there is a possibility that a significant effect cannot be obtained for improving the meltability or the ion exchange rate. Therefore, the lower limit of the content of _{K 2} O is preferably 0.3% or more. Further, if the content of K ₂ O exceeds 4%, the weather resistance is lowered. For this reason, the upper limit of the content of K ₂ O is preferably 3% or less, and more preferably 2% or less.

  MgO is a component that improves the meltability of the glass, and is not essential, but can be contained as necessary. If the content of MgO is less than 3%, there is a possibility that a significant effect for improving the meltability cannot be obtained. For this reason, it is preferable that the minimum of content of MgO is 4% or more. Further, if the content of MgO exceeds 15%, the weather resistance is lowered. For this reason, the upper limit of the content of MgO is preferably 13% or less, and more preferably 12% or less.

  CaO is a component that improves the meltability of the glass, and is not essential, but can be contained as necessary. If the content of CaO is less than 0.01%, a significant effect cannot be obtained for improving the meltability. For this reason, it is preferable that the minimum of content of CaO is 0.1% or more. Further, when the content of CaO is more than 3%, the chemical strengthening characteristics are deteriorated. For this reason, the upper limit of the CaO content is preferably 1% or less, and more preferably 0.5% or less.

  RO (R is Mg, Ca, Sr, Ba, Zn) is a component that improves the meltability of the glass, and is not essential, but can contain one or more as required. If ΣRO (R is Mg, Ca, Sr, Ba, Zn) is less than 1%, a significant effect on improving the meltability cannot be obtained. For this reason, the lower limit of ΣRO is preferably 3% or more, and more preferably 5% or more. Further, when ΣRO (R is Mg, Ca, Sr, Ba, Zn) exceeds 18%, the weather resistance is lowered. For this reason, the upper limit of ΣRO is preferably 15% or less, more preferably 13% or less, and even more preferably 11% or less. Note that ΣRO indicates the total amount of MgO, CaO, SrO, BaO, and ZnO.

ZrO ₂ is a component that increases the ion exchange rate and is not essential, but may be contained as necessary. If the content of ZrO ₂ exceeds 1%, the meltability may deteriorate and remain in the glass as an unmelted product. For this reason, the content of ZrO ₂ is preferably 1% or less.

(SiO ₂ + Al ₂ O ₃ + B ₂ O ₃ ) / (ΣR ₂ O + CaO + SrO + BaO) represents the ratio between the total amount of network oxides forming the glass network and the total amount of main modifying oxides. If the ratio is less than 4, there is a possibility that the probability of breaking when the impression is made after the chemical strengthening treatment is increased. For this reason, the lower limit of this ratio is preferably 4.2 or more, and more preferably 4.4 or more. Moreover, when this ratio exceeds 6, the viscosity of glass will increase and meltability will fall. For this reason, the upper limit of this ratio is preferably 5.5 or less, and more preferably 5 or less. Note that ΣR ₂ O indicates the total amount of Na ₂ O, K ₂ O, and Li ₂ O.

  SrO (strontium oxide) is a component for improving the meltability of glass, and is not essential, but can be contained as necessary. If the content of SrO is less than 1%, there is a possibility that a significant effect cannot be obtained for improving the meltability. For this reason, the lower limit of the SrO content is preferably 3% or more, and more preferably 6% or more. On the other hand, if the SrO content exceeds 15%, the weather resistance and chemical strengthening properties may be deteriorated. For this reason, the upper limit of the content of SrO is preferably 12% or less, and more preferably 9% or less.

  BaO (barium oxide) is a component for improving the meltability of the glass, and is not essential, but can be contained as necessary. If the content of BaO is less than 1%, a significant effect may not be obtained for improving the meltability. For this reason, the lower limit of the content of BaO is preferably 3% or more, and more preferably 6% or more. Further, if the content of BaO exceeds 15%, the weather resistance and chemical strengthening characteristics may be deteriorated. For this reason, the upper limit of the content of BaO is preferably 12% or less, and more preferably 9% or less.

  ZnO (zinc oxide) is a component for improving the meltability of the glass, and is not essential, but can be contained as necessary. If the content of ZnO is less than 1%, there is a possibility that a significant effect cannot be obtained for improving the meltability. For this reason, the lower limit of the ZnO content is preferably 3% or more, and more preferably 6% or more. Further, if the ZnO content exceeds 15%, the weather resistance may be lowered. For this reason, the upper limit of the ZnO content is preferably 12% or less, and more preferably 9% or less.

In addition, Sb ₂ O ₃ , Cl, F, and other components may be contained as glass refining agents as long as the purpose is not impaired. When such components are contained, the total content of these components is preferably 1% or less, and more preferably 0.5% or less.
In addition, you may contain the following components in glass.

SO ₃ (sulfur oxide) is a component that acts as a fining agent, and although it is not essential, it can be contained as necessary. If the content of SO ₃ is less than 0.005%, the expected clarification action cannot be obtained. For this reason, the lower limit of the content of SO ₃ is preferably 0.01% or more, more preferably 0.02% or more, and further preferably 0.03% or more. On the other hand, when the content of SO ₃ exceeds 0.5%, it becomes a generation source of bubbles, and there is a possibility that the glass melts slowly or the number of bubbles increases. For this reason, the upper limit of the content of SO ₃ is preferably 0.3% or less, and more preferably 0.2% or less. More preferably, it is 0.1% or less.

SnO ₂ (tin oxide) is a component that acts as a fining agent, and although it is not essential, it can be contained as necessary. If the SnO ₂ content is less than 0.005%, the expected clarification action cannot be obtained. For this reason, the lower limit of the content of SnO ₂ is preferably 0.01% or more, and more preferably 0.05% or more. On the other hand, if the content of SnO ₂ exceeds 1%, it becomes a generation source of bubbles, and there is a possibility that the glass melts slowly or the number of bubbles increases. For this reason, the upper limit of the content of SnO ₂ is preferably 0.8% or less, more preferably 0.5% or less, and further preferably 0.3% or less.

TiO ₂ (titanium oxide) is a component that improves the weather resistance of the glass, and is not essential, but can be contained as necessary. If the content of TiO ₂ is less than 0.005%, a significant effect may not be obtained for improving weather resistance. For this reason, the lower limit of the content of TiO ₂ is preferably 0.01% or more, and more preferably 0.1% or more. If the content of TiO ₂ exceeds 1%, the glass becomes unstable and devitrification may occur. Therefore, the upper limit of the content of TiO ₂ is preferably 0.8% or less, and more preferably 0.6% or less.

Li ₂ O (lithium oxide) is a component for improving the meltability of the glass, and is not essential, but can be contained as necessary. If the content of Li ₂ O is less than 1%, a significant effect may not be obtained for improving the meltability. Therefore, the lower limit of the Li 2 _O content is preferably 3% or more, more preferably 6% or more. Further, if the content of Li ₂ O exceeds 15%, the weather resistance may be lowered. Therefore, the upper limit of the Li 2 _O content is preferably 12% or less, and more preferably 9% or less.

  Further, for the purpose of coloring glass, as a coloring component, Co, Mn, Fe, Ni, Cu, Cr, V, Bi, Er, Sn, Ce, Pr, Eu, Nd, Ag, from the group consisting of metal oxides You may contain 0.1 to 10% of the selected at least 1 component by the molar percentage display of an oxide basis.

  It is preferable that the maximum value of the thickness of the glass shape | molded with the shaping | molding method of the glass of this invention is 1.5 mm or more. According to this, since the glass thickness can be press-molded to a certain level or more in applications where high strength is required, such as a case of a mobile terminal such as a smartphone, there are few restrictions on the shape of the glass molded body, and glass molding A desired shape and high strength can be imparted to the body.

(Other embodiments)
As described above, the present invention has been described in detail based on the above embodiment, but the present invention is not limited to the above embodiment, and various modifications and changes can be made without departing from the scope of the present invention. is there. For example, in the said embodiment, although the glass blank B which cut | disconnected the glass rod R with the 2nd glass shaping | molding apparatus 20 is shape | molded with the metal mold | die 203a, the front-end | tip part of the glass rod R is heated, and the metal mold | die 203a is formed. After molding, the glass molded body C may be separated from the glass rod R.

  Further, as a modification of the first glass forming apparatus 10, a rod-shaped glass may be formed by a downdraw method or a bellows method. Since the glass molded into a rod shape by these methods has a side surface that is a fire-making surface, the surface of the glass molded body C after press molding can be made smooth.

  In addition, as described above, the glass molded body formed by the glass forming method of the present invention has applications such as a housing of a mobile terminal such as a smartphone, but is not limited thereto. For example, it can be used as a method of forming a cover glass of a touch panel used for a display device of a portable terminal into a shape other than a flat plate shape. Examples of the shape other than the flat plate shape include a curved surface shape, an uneven shape, a corrugated shape, and a stepped shape. Thereby, a cover glass with a special shape can be applied to a device provided with a touch panel.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to these Examples.

In this example, commonly used glass materials such as oxides, hydroxides, carbonates and nitrates were appropriately selected so that the composition of the glass was as follows. The glass composition in this example is expressed in mole percentage, SiO ₂ is 62.1%, Na ₂ O is 12.0%, K ₂ O is 3.9%, MgO is 10.1%, Al ₂ O ₃ Is 7.7%, ZrO ₂ is 0.5%, Co ₃ O ₄ is 0.38%, Fe ₂ O ₃ is 3.2%, and SO ₃ is 0.38%. The content of SO _{3 is} the content of residual SO ₃ remaining in the glass after the addition of bow glass (Na ₂ SO ₄ ) to the glass raw material to decompose the bow glass, and is calculated from the molar ratio. Value.

  In this example, the following two samples (Sample A (Example) and Sample B (Comparative Example)) were prepared. Hereinafter, Sample A and Sample B will be described.

(Sample A)
A glass rod R having the above composition is formed using the first glass forming apparatus 10 described with reference to FIG. 1, and the glass rod R is cut into a predetermined length by a side pressure cutting method. Sample B (Example) was designated as B.

(Sample B)
The glass raw material mixture was put into a platinum crucible, heated and melted, defoamed, poured into a preheated box-shaped mold, and slowly cooled, and a glass blank having the above composition was used as Sample B (Comparative Example).

  Next, the surface roughness (centerline average roughness Ra) before press molding was measured for the sample A and the sample B. The measurement position of the surface roughness before press molding was the surface (scheduled molding surface) in contact with the mold during press molding. Note that a laser microscope (manufactured by Keyence Corporation, shape measurement laser microscope VK-X100) was used for measurement of the surface roughness (centerline average roughness Ra).

  Next, using the second glass molding apparatus 20 described with reference to FIG. 2 (however, excluding the heating means), a glass molded body was prepared from the sample A and the sample B. In addition, the metal mold | die used for press molding provided the chromium plating in the glass contact surface, and the surface was a mirror surface state. Moreover, the conditions (temperature, pressure, etc.) of press molding are the same for both sample A and sample B.

  About the glass moldings of Sample A (Example) and Sample B (Comparative Example), the surface roughness (centerline average roughness) of the surface (the same location as measured with a glass blank) in contact with the mold by press molding Ra) was measured using the stylus type surface roughness measuring instrument. Moreover, about the sample A and the sample B, the surface state of the press molding surface of a glass molded object was observed visually.

Table 1 shows the measurement results of the surface roughness of Sample A (Example) and Sample B (Comparative Example). The surface roughness is an average value of the surface roughness measured at five locations for both sample A and sample B.

  From the results in Table 1, it can be seen that a smooth press-formed surface can be obtained if the surface roughness of the surface of the glass blank before press forming is 1 μm or less in terms of the center line average roughness. On the other hand, when the surface roughness of the molding surface before press molding exceeds 1 μm in the center line average roughness, even if the surface state of the mold used for press molding is smooth, the smooth press molding surface is It turns out that it cannot be obtained.

 The glass molding method of the present invention can be efficiently molded in a state where the glass surface is smooth, so that glass for which design is required, for example, a glass used for a housing of a mobile terminal such as a smartphone or a monitor such as an LCD. Suitable for molding.

  DESCRIPTION OF SYMBOLS 1 ... Glass shaping | molding apparatus, 10 ... 1st glass shaping | molding apparatus, 20 ... 2nd glass shaping | molding apparatus, 101 ... Melting kiln, 102 ... Clarification tank, 103 ... Agitation means, 103a ... Agitation tank, 103b ... Rotation Shaft, 103c ... stirring blade, 104 ... molding container, 104a ... container, 104b ... outflow nozzle, 105 ... roller, 106 ... slow cooling device, 201 ... cutting means, 202 ... heating means, 203 ... molding means, 203a ... mold , 203b ... pressing means, 204 ... removing means, B ... glass blank, C ... glass molding, R ... glass rod.

Claims (7)

Solidifying molten glass flowing out from the outflow nozzle to form a rod-shaped glass;
Heating the rod-shaped glass to a temperature at which it can be press-formed,
Pressing the side surface of the heated rod-shaped glass with a molding surface of a mold, and molding the heated rod-shaped glass into a desired shape; and
A glass forming method characterized by comprising:   2. The glass forming method according to claim 1, wherein the side surface has a center line average roughness (Ra) of 1 μm or less.   3. The method according to claim 1, further comprising a step of removing the glass protruding from the molding surface of the mold when the side surface of the heated rod-shaped glass is pressed by the molding surface of the mold. The glass forming method described in 1.   4. The method according to claim 1, further comprising a step of cutting the rod-shaped glass into a predetermined length before the step of heating the rod-shaped glass to a temperature at which press molding is possible. The glass molding method according to Item 1.   The glass molding method according to any one of claims 1 to 4, wherein the maximum thickness of the glass molded into the desired shape is 1.5 mm or more.   The glass forming method according to any one of claims 1 to 5, further comprising a step of tempering the glass formed into the desired shape.   An electronic apparatus comprising a glass formed by the forming method according to any one of claims 1 to 6 in at least a part of a housing.

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