Glass molding and its manufacturing method

Abstract

To provide a glass molding useful for manufacturing an optical element: and to provide a production method thereof.SOLUTION: A glass molding has a liquid phase temperature, and has any shape between a circular column, a regular n prism and an approximately regular n prism constituted of glass whose viscosity at the liquid phase temperature is 5×103 dPa-s or less. The glass molding comprises such glass that an area of a cross section vertical to a side face is 1.0×103 mm2 or more, and that the stria measure following Japan Optical Glass Industry Association Specification JOGIS11-1975 is first to third grade.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a glass molded body and a method for producing the same. [Background technology]

[0002] One conventional method for producing optical glass lenses involves first forming a striae-free plate-shaped glass, cutting it, and then press-molding and polishing the cut glass pieces to obtain optical glass lenses. However, this method has the problem that a large amount of glass is discarded at the stage of obtaining the glass pieces. As a method for reducing such glass waste, for example, there is a method in which optical glass is molded into a cylindrical shape rather than a plate shape and then cut.

[0003] As a method for forming cylindrical glass, Patent Documents 1 and 2 disclose a method in which molten glass is directly poured into a cylindrical mold and formed. These documents disclose that cylindrical glass having an outer diameter of 20 to 30 mm was obtained.

[0004] Furthermore, Patent Document 3 discloses a method for molding and producing optical glass having a relatively large volume, in which molten glass is poured into a mold with an open top to mold a plate-shaped glass having a width of 200 mm to 240 mm and a thickness of 10 mm to 15 mm. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-089275 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-052109 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-001391 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, optical glass has also been used in thin plate-shaped elements such as light guide plates used in goggle-type displays. Such thin plate-shaped glass elements, such as light guide plates, are sometimes required to have a side length at least longer than the distance between the human pupils, necessitating the use of relatively large glass elements. In the mass production of such thin optical glass elements, a disk-shaped wafer made of optical glass is processed into one or more elements by dicing or other methods, similar to a semiconductor element production line. The wafer is made by slicing a cylindrical glass, which corresponds to an ingot in the production of semiconductor elements, or by cutting it out of a glass sheet. Therefore, the optical glass corresponding to the wafer is required to be a thin glass sheet with a large side length and a specified area. Another method for efficiently manufacturing a large number of optical elements such as lenses is to produce a disk-shaped thin glass plate by thinly slicing a glass molded body, press it using precision press molding dies 101 and 102 to produce pressed glass 201, create a large number of lenses, and stack and cut these to produce an optical element 401 equipped with a large number of lenses, as shown in FIG. For the sake of efficiency and reducing the amount of glass waste, it is preferable to extract glass members from disk-shaped glass with a relatively large area for many optical glass elements. Therefore, it is desirable to manufacture cylindrical glass with a relatively large cross-sectional area from which multiple large disk-shaped glass can be extracted.

[0007] However, the cross-sectional area of ​​the cylindrical glass in Patent Documents 1 and 2 is insufficient, and a glass molded product with a larger diameter is preferred. Moreover, the plate-shaped glass in Patent Document 3 cannot be said to have a shape suitable for obtaining an optical glass element for a light guide plate. An object of the present invention is to provide a glass molded body useful for producing optical elements and a method for producing the same. [Means for solving the problem]

[0008] That is, the present invention encompasses the following production method. [1] A method for producing a glass molded body from a three-dimensional glass, comprising: placing the solid glass in the mold so that it contacts the bottom of the mold; a step of heating the three-dimensional glass together with the mold to raise the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; a step of deforming the three-dimensional glass at the molding temperature to form a glass molded body having a shape corresponding to the internal shape of the mold; and removing the glass molded body from the mold after cooling to obtain the glass molded body. [2] A method for producing a glass molded body from a three-dimensional glass, comprising: placing the three-dimensional glass on a base; a step of covering the placed three-dimensional glass with a tube from an open end thereof and placing the tube so that the end thereof contacts the base; heating the three-dimensional glass with the tube covered, raising the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; a step of deforming the three-dimensional glass at the molding temperature to form a glass molded body having a shape corresponding to the internal shape of the tube; and after cooling, removing the glass molded body from the cylinder to obtain the glass molded body. [3] The manufacturing method according to [1] or [2], wherein the deformation of the three-dimensional glass is caused by its own weight. [4] The method according to [1] or [2], wherein the glass molded body has a cylindrical shape. [5] A method for producing plate glass, comprising producing a glass molded body by the method according to [1] or [2], and slicing the glass molded body into thin plates. [6] A liquidus temperature, and a viscosity at the liquidus temperature is 5×10 3A glass molded body having the shape of a cylinder, a regular n-gonal prism, or a nearly regular n-gonal prism, which is made of glass having a viscosity of 1000 dPa·s or less, The area of ​​the cross section perpendicular to the side is 1.0 x 10 3 mm 2 That's all, A glass molded body (where n is an integer of 5 or more) made of glass having striae of grades 1 to 3 as measured in accordance with Japan Optical Glass Industry Association Standard JOGIS11-1975. [7] The glass molded body according to [6], wherein the length from one end to the other end of the shape is 2 cm or more. [8] A method for producing plate glass, comprising slicing the glass molded body according to [6] or [7] into thin plates. [9] A method for producing an optical element, which comprises forming one or more optical elements from a plate glass obtained by the method described in [8]. [Effects of the Invention]

[0009] The glass molded product of the present invention, for example, a glass molded product made of glass having predetermined properties produced by the manufacturing method of the present invention, has a viscosity of 5×10 at the liquidus temperature. 3 Although it is a glass with a relatively low viscosity of dPa·s or less, it has a low degree of striae and a cross-sectional area of ​​1.0×10 3 mm 2 Since the glass molded body has the shape of a cylinder, a regular n-sided prism, or an approximately regular n-sided prism (where n is an integer of 5 or more) having the above cross section, optical glass of the desired shape and with the desired properties can be efficiently extracted from the glass molded body. Furthermore, according to the method for producing a glass molded body of the present invention, even if a glass has a relatively low viscosity, a glass molded body having a large cross-sectional area can be produced without the occurrence of striae. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a manufacturing process of a general camera module. [Figure 2]FIG. 2 is a diagram showing the manufacturing steps according to the manufacturing method of the first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the manufacturing steps according to the manufacturing method of the second embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the differential thermal analysis of a common optical glass. [Figure 5] FIG. 5 is a diagram showing the relationship between the ratio of the volume of cylindrical glass to the volume of a regular n-rectangular prismatic glass molded body (volume of cylindrical glass / volume of regular n-rectangular prismatic glass molded body). DETAILED DESCRIPTION OF THE INVENTION

[0011] [Glass molding] The glass molded body of the present invention has a liquidus temperature and a viscosity of 5×10 at the liquidus temperature. 3 A glass molded body having the shape of a cylinder, a regular n-prism, or a nearly regular n-prism, which is made of glass with a viscosity of 1.0×10 dPa·s or less, and has a cross-sectional area perpendicular to the side surface of 1.0×10 3 mm 2 The glass molded article is made of glass having striae of grades 1 to 3 as measured in accordance with the Japan Optical Glass Industry Association standard JOGIS11-1975 (where n is an integer of 5 or more).

[0012] The glass molded article of the present invention has a shape of any one of a cylinder, a regular n-sided prism, and a substantially regular n-sided prism (where n is an integer of 5 or more), and has a cross-sectional area perpendicular to the side surface of 1.0 × 10 3 mm 2 It is characterized by having the above. Here, the cylindrical shape includes not only a rod shape with a circular cross section perpendicular to the side surface, but also a disk shape (with a short distance between both ends). Furthermore, the terms "regular n-gonal prism shape" and "approximately regular n-gonal prism shape" include not only rod-shaped shapes whose cross section perpendicular to the side surface is a regular n-gon or an approximately regular n-gon, but also regular n-gonal plate-shaped shapes (where the distance between both ends is shorter than the diameter of the circumscribing circle of the regular n-gon) and approximately regular n-gonal plate-shaped shapes (where the distance between both ends is shorter than the diameter of an imaginary circle that includes all of the vertices of the approximately regular n-gon on or within its circumference). A cylindrical glass can be produced by processing the side surface of a prismatic glass molded body by grinding, polishing, etc. If the cross section perpendicular to the side surface of the prismatic shape is a regular n-gon or a nearly regular n-gon (n is 5 or more), the amount of glass to be removed when producing the cylindrical glass can be reduced. When producing cylindrical glass from a regular n-rectangular prismatic glass molded body, the relationship between the volume ratio of the cylindrical glass to the volume of the regular n-rectangular prismatic glass molded body (volume of cylindrical glass / volume of regular n-rectangular prismatic glass molded body) is shown in Figure 5. This ratio is called the yield of cylindrical glass. When n = 4, the yield is less than 80%, but when n is 5 or more, the yield increases significantly. n is preferably 6 or more, more preferably 7 or more, even more preferably 8 or more, even more preferably 9 or more, and even more preferably 10 or more. The glass molded body of the present invention can be obtained, for example, by the method for producing a glass molded body of the present invention, and the cross-sectional area perpendicular to the side surface is preferably 2.0×10 3 mm 2 More preferably, 2.5 × 10 4 mm 2 More preferably, 3.0 × 10 4 mm 2 This is because the larger the cross-sectional area, the more efficiently the desired optical glass element can be obtained.

[0013] The glass constituting the glass molded product of the present invention has a liquidus temperature (exists a liquidus temperature). Here, the liquidus temperature is the lowest temperature at which no crystalline solid is formed from the glass melt when maintained at a certain temperature for a certain period of time. That is, the glass molded product of the present invention has a viscosity of 5×10 3 Extremely stable glasses that do not precipitate crystalline solids even in the high viscosity range exceeding dPa·s are excluded.

[0014] The glass molded body of the present invention has a viscosity of 5×10 at the liquidus temperature. 3 The viscosity at the liquidus temperature is 5×10 dPa·s or less. 3The glass of the present invention is intended to have a low viscosity near the molding temperature (near the temperature at which the glass melt is molded), such as a viscosity of 1×10 dPa·s or less. 3 dPa·s or less, and more preferably 1×10 2 It is dPa·s or less.

[0015] The glass molded article of the present invention is made of glass having striae of grades 1 to 3 as measured in accordance with the Japan Optical Glass Industry Association standard JOGIS11-1975. Generally, the viscosity at the liquidus temperature is 5×10 3 It is difficult to directly manufacture glass bodies with large cross-sectional areas from molten glass with a viscosity of dPa·s or less (low-viscosity glass). This is thought to be because when low-viscosity glass is molded, after the glass is cast (after the molten glass is poured into a mold), the low-temperature glass part on the glass surface (the glass near the surface whose temperature has dropped first) penetrates into the interior of the glass, which is still hot, making the glass prone to becoming non-uniform. However, the glass molding of the present invention is formed by deforming a three-dimensional glass having striae of grades 1 to 3 by heating, and therefore the viscosity at the liquidus temperature is 5×10 3 Even with glass having a viscosity of less than dPa·s, it is possible to obtain glass molded bodies with a large cross-sectional area. Here, three-dimensional glass refers to solidified glass having a shape that can be placed inside a mold, preferably glass with a flat and / or convex curved surface. When forming glass molded bodies, the glass is molded in a high viscosity state, making it difficult for new striae to form. Therefore, even with glass molded bodies with a large cross-sectional area, glass molded bodies with striae of grades 1 to 3 can be obtained. Here, striae refers to portions where optical properties such as refractive index are non-uniform. The glass shaped body of the present invention is preferably a glass shaped body having first or second grade striae, and more preferably a glass shaped body having first grade striae.

[0016] The length from one end to the other end of the glass molded article of the present invention is not limited, but is, for example, 2 cm or more, preferably 5 cm or more, and more preferably 10 cm or more. Here, the length from one end to the other end of the glass molded body corresponds to the height in the case of a cylindrical glass, and corresponds to the thickness in the case of a disk-shaped glass.

[0017] [Method of manufacturing glass molded body] (Embodiment 1) A first embodiment of the method for producing a glass molded article of the present invention is as follows: A method for producing a glass molded body from three-dimensional glass, comprising the steps of: placing the three-dimensional glass in a mold so that the three-dimensional glass is in contact with the bottom of the mold; heating the three-dimensional glass together with the mold to raise the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; deforming the three-dimensional glass at the forming temperature to form a glass molded body having a shape corresponding to the internal shape of the mold; and cooling and removing the glass molded body from the mold to obtain the glass molded body. This embodiment may further include a step of supporting the three-dimensional glass and a step of placing the three-dimensional glass together with the mold in a heating furnace while the three-dimensional glass is supported. This will be explained in detail below with reference to FIG. In addition, in embodiment 1 and embodiment 2 described later, cylindrical glass shaped bodies are produced, but the glass shaped bodies obtained by these production methods are not limited to cylindrical shapes; glass shaped bodies of various shapes can be produced, such as glass shaped bodies whose cross section perpendicular to the side surface is a circle, ellipse, triangle, rectangle, polygon with pentagons or more, equilateral triangle, square, or regular polygon with pentagons or more. Therefore, the three-dimensional shape of the glass shaped bodies obtained in embodiment 1 and embodiment 2 can be a cylindrical shape, a prismatic shape, or the like.

[0018] First, the three-dimensional glass piece 1 is placed on the bottom surface 32 of the mold 3, which has a recess. The three-dimensional glass piece 1 can be a rectangular parallelepiped glass piece with a rectangular cross section, as shown in Figure 2, or a cylindrical or other shape. It is preferable that the surface of the three-dimensional glass piece be flat and / or convexly curved. If a three-dimensional glass piece has a cavity inside or a recess on its surface that is deeper than the opening diameter, the surface of the three-dimensional glass piece (including the internal surface of the glass surrounding the cavity) will remain inside the glass molded body, reducing the optical homogeneity of the glass molded body. Therefore, it is not recommended to use three-dimensional glass piece with a cavity or a recess on its surface that is deeper than the opening diameter. The three-dimensional glass piece 1 is solid as glass. The three-dimensional glass piece 1 is placed so that its long side is perpendicular to the bottom surface 32 of the mold 3. The cross-sectional area of ​​the three-dimensional glass piece 1 is smaller than the cross-sectional area of ​​the internal shape 31 of the mold 3 (the area of ​​the internal shape in a plane parallel to the bottom surface 32). This is because the three-dimensional glass piece needs to be placed so that it is in contact with the bottom surface 32.

[0019] The mold 3 has an internal shape 31 that corresponds to the shape of the glass molded body 21. In other words, the internal shape 31 is the shape of the recess in the mold 3. In FIG. 2, in order to obtain a glass molded body 21 with a large diameter, the mold 3 has an internal shape 31 (i.e., a cylindrical shape) that corresponds to that shape. In order to prevent the glass from overflowing from the mold 3, the volume of the internal shape 31 of the mold 3 (the mold volume) is made larger than the volumes of the three-dimensional glass 1 and the glass molded body 21. The material of the mold 3 is not particularly limited as long as it is fire-resistant, and examples thereof include ceramics and silica earth.

[0020] If the cross-sectional area of ​​the three-dimensional glass 1, which is the material, is small and the volume of the glass molding 21 is large, the long side of the three-dimensional glass 1 needs to be very long relative to the cross-section. In this case, as shown in Figure 2, a support 5 can be used to hold the three-dimensional glass 1 so that it does not fall over. In Figure 2, a support 5 is used to support the three-dimensional glass 1 from above, but the support method is not particularly limited, and a method such as clamping from the side can also be used.

[0021] Next, as shown in Figure 2(b), the 3D glass 1 and mold 3 (and, if necessary, support 5) are placed in a heating furnace 4, and the furnace is set so that the 3D glass 1 can be heated to the forming temperature. The forming temperature is above the temperature at which the 3D glass 1 deforms under its own weight but below the crystallization temperature. If the temperature is below the temperature at which the 3D glass 1 deforms under its own weight, the glass is difficult to deform, and the 3D glass 1 cannot be deformed into the desired shape. If the temperature is above the crystallization temperature, the glass becomes molten at a low viscosity, which may result in the formation of striae. In the manufacturing method of the present invention, the glass is not brought to a low-viscosity molten state. If the glass is brought to a low-viscosity molten state, if the glass is unstable, it will pass through the glass crystallization point during the subsequent cooling stage, causing crystals to form in or on the glass surface. The present invention allows the production of cylindrical glass molded bodies with a large cross-sectional area perpendicular to the length direction without crystallization, even from unstable glasses prone to crystallization. In the present invention, the lower limit of the forming temperature is the temperature at which the glass deforms under its own weight. The temperature at which the glass deforms under its own weight is essentially the yield point Ts. The yield point (Ts) is the temperature at which expansion apparently stops on a thermal expansion curve. The yield point Ts is determined, for example, by JIS R 3103-3 Part 3: Transition temperature measurement method by thermal expansion method. It should be noted that this cessation of expansion does not represent the essential thermal expansion characteristics of the glass, but is caused by deformation due to the load applied to the glass sample and its own weight. In the present invention, the lower limit of the preferred forming temperature is a temperature above the yield point. In this specification, the crystallization temperature is the temperature at the Tc portion, which is the maximum endothermic peak, in FIG. 4, which shows a graph of differential thermal analysis of a typical optical glass.

[0022] The heating furnace 4 may be at room temperature when the three-dimensional glass 1 is inserted, or the temperature may be raised to a certain level before the three-dimensional glass 1 is inserted and heated, or the heating furnace 4 may be heated to the desired temperature beforehand and the three-dimensional glass 1 is inserted into it.

[0023] The 3D glass piece 1 is inserted into the heating furnace 4, and when the temperature of the 3D glass piece 1 reaches a temperature close to the forming temperature, the glass softens. The softened glass spreads within the mold 3 due to its own weight, and is finally formed into the internal shape 31 of the mold 3. After that, by cooling, a solidified glass molded body 21 having a shape corresponding to the internal shape 31 of the mold 3 is obtained.

[0024] The cooling rate is preferably slow so as not to crack the resulting glass shaped body, but is not particularly limited and can be determined appropriately depending on the glass composition and shape of the glass shaped body 21 .

[0025] (Embodiment 2) The second embodiment of the method for producing a glass molded body is as follows: A method for manufacturing a glass molded body from three-dimensional glass, comprising the steps of: placing the three-dimensional glass on a base; covering the open end of the placed three-dimensional glass with a tube and placing the tube so that the end is in contact with the base; heating the three-dimensional glass with the tube covered to raise the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; deforming the three-dimensional glass at the forming temperature to form a glass molded body having a shape corresponding to the internal shape of the tube; and obtaining the glass molded body by cooling and removing it from the tube. The three-dimensional glass with the tube covered may be placed in a heating furnace together with the base and the tube, and the temperature of the three-dimensional glass in the heating furnace may be raised to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight but lower than the crystallization temperature, and the forming temperature may be maintained. This will be described in detail below with reference to FIG.

[0026] As shown in Figure 3, embodiment 2 is more effective than embodiment 1 when obtaining a glass molded body in which the length from one end to the other end of the glass molded body is longer (long and slender) than the outer diameter of the end face. It differs from embodiment 1 in that a base such as a dish 6 can be used instead of a mold. The base does not have to be a dish 6, but may be a fireproof plate, or the mold 3 as in embodiment 1 may be used. In embodiment 2, the bottom surface 61 of the dish 6 is used as the base. Furthermore, by using the dish 6 as the base, glass will not contaminate anything other than the apparatus when it leaks from the tube 7.

[0027] In embodiment 2, the three-dimensional glass 1 is placed on the bottom surface 61 of the dish 6, and then the tube 7 is placed on the dish 6 so as to cover the three-dimensional glass 1. In embodiment 2, the open end of the tube 7 is placed over the three-dimensional glass 1, which is standing vertically on the dish 6, and the tube 7 is also placed vertically on the dish 6. The length of the tube 7 is preferably longer than the length of the long side of the three-dimensional glass 1, but may be shorter than the length of the long side of the three-dimensional glass 1 as long as it does not affect the production of the glass molded body 22. If necessary, the tube 7 may be supported by a support to prevent it from falling over.

[0028] The shape of the glass shaped body 22 obtained in the second embodiment corresponds to the internal shape of the cylinder 7, so the cylinder 7 is selected so that a glass shaped body having the desired internal shape can be obtained. For example, a tube having an inner diameter of about 20 to 180 mm and a length of about 100 to 700 mm can be used as the cylinder 7. The material of the cylinder is not particularly limited as long as it is fire-resistant, and examples thereof include ceramic and diatomaceous earth.

[0029] Next, the three-dimensional glass 1, the dish 6, and the tube 7 are placed in the heating furnace 4, and the furnace is set up so that the three-dimensional glass 1 can be heated to the forming temperature. At this time, the three-dimensional glass 1 may lean against the tube 7 inside the tube 7, as long as the tube 7 is positioned perpendicular to the bottom surface of the dish 6. The forming temperature and the temperature setting of the heating furnace 4 are omitted because they are the same as those in the first embodiment.

[0030] The 3D glass 1 is inserted into the heating furnace 4, and when the 3D glass 1 reaches a temperature close to the forming temperature, the glass softens. The softened glass spreads downward inside the cylinder 7 due to its own weight, and is finally formed into the internal shape of the cylinder 7. After that, by cooling, solidified glass having a shape corresponding to the internal shape of the cylinder 7 is obtained. The cooling rate can be set appropriately, as in the first embodiment.

[0031] In both embodiments 1 and 2, the three-dimensional glass 1 is deformed by its own weight, but this is not limited to this. The glass may be pressurized from above using a press or the like, or a weight may be placed on the three-dimensional glass to apply load to the glass, thereby shaping it. [Example]

[0032] The present invention will be further described below with reference to examples, although the present invention is not limited to these examples.

[0033] [Making cylindrical molded glass] Glass raw materials were mixed and melted at 900 to 1450°C depending on the glass state. In other words, the glass raw materials were heated and melted in the range of 1300 to 1450°C. After casting into a mold, the glass was annealed at a temperature 50 to 100°C higher than the glass transition temperature (Tg) of each glass, yielding seven types of plate-shaped glasses 1 to 7 (stria grades 1 to 3). The glass transition temperatures, melting temperatures, liquidus temperatures, and holding temperatures of Glasses 1 to 7 are shown in Table 1, and the viscosity, yield point, and crystallization temperature at the liquidus temperature are shown in Table 2. The glass transition temperature (transition point) Tg was determined according to JIS R 3103-3 Part 3: Transition temperature measurement method using thermal dilatometry. The liquidus temperature was determined as follows. The volume of each glass shown in Table 1 is 10 cm 3The glass sample was placed in a platinum crucible and held in a glass melting furnace set at the melting temperature shown in Table 1 for 20 minutes to fully melt the glass sample into a molten state. The platinum crucible was then removed from the glass melting furnace and the glass sample was allowed to cool in the platinum crucible until its temperature reached 500°C or less. The platinum crucible was then placed in a glass melting furnace set at a temperature of T [°C] and held there for 2 hours. After being removed from the furnace, the platinum crucible containing the glass sample was immediately (within 8 seconds) placed on a refractory material (e.g., bricks) at room temperature, and the glass sample was cooled to room temperature. Room temperature here was in the range of -10 to 80°C. The surface and interior of the glass sample were then visually inspected to determine whether or not crystals were present. The above experiment was repeated by changing the temperature T in 10°C increments within the holding temperature range shown in Table 1, and the lowest temperature at which no crystals were observed on the surface or inside of the glass sample was taken as the liquidus temperature LT. The viscosity at the liquidus temperature can be calculated from the approximation curve obtained by measuring the viscosity at the liquidus temperature, a temperature 50°C higher than the liquidus temperature, a temperature 100°C higher than the liquidus temperature, a temperature 150°C higher than the liquidus temperature, and the glass transition temperature Tg, using, for example, a rotational viscometer. The approximation curve can be calculated from the data obtained at five points. The methods for measuring the yield point Ts and crystallization temperature are as described above.

[0034] [Table 1] [Table 2]

[0035] Next, glass strips were obtained by cutting the glass plates 1 to 7. The glass strips had a rectangular shape of 25 mm x 59 mm x 300 mm.

[0036] (Examples 1 to 7) The obtained glass strips 1 to 7 were processed under the following conditions by the method of embodiment 1 (with support) to obtain cylindrical (disk-shaped) glass having a diameter of 150 mm and a height of 25 mm. The striae were grades 1 to 3. Mold: Ceramic Mold interior shape: Cylindrical Inner diameter of mold (bottom): 150mm The height of the inner shape of the mold is 30mm Molding temperature: yield point (Ts) +20℃~100℃

[0037] (Examples 8 to 14) Glasses 1 to 7 shown in Table 1 were similarly prepared in the form of strips of 25 mm x 44 mm x 300 mm, and each glass was formed into a cylindrical glass piece with a diameter of 53 mm and a length of 150 mm under the following conditions by the method of embodiment 2. The striae were grades 1 to 3. Cylinder: Ceramic tube Inner diameter of barrel: 53mm Cylinder length: 300mm Molding temperature: yield point (Ts) +20℃~100℃ Base: Ceramic dish (bottom diameter 150mm) In the above example, seven cylindrical glass pieces made of each of Glasses 1 to 7 were produced using a cylindrical ceramic tube. Instead of the cylindrical ceramic tube, a ceramic tube with a regular pentagonal cross section, a regular hexagonal cross section, or a regular octagonal cross section could be used to produce a regular pentagonal prism-shaped glass molded body, a regular hexagonal prism-shaped glass molded body, and a regular octagonal prism-shaped glass molded body, respectively. In this way, seven regular pentagonal prism-shaped glass pieces made of each of Glasses 1 to 7, seven regular hexagonal prism-shaped glass pieces made of each of Glasses 1 to 7, and seven regular octagonal prism-shaped glass pieces made of each of Glasses 1 to 7 were produced. Next, the side surfaces of each of these prismatic glass pieces were processed to produce cylindrical glass pieces inscribed in the cross section of the prism. That is, in this way, cylindrical glass was produced from each prismatic glass, having a length equal to that of the prismatic glass and a thickness (diameter of the circular cross section) equal to or approximately equal to the diameter of the circle inscribed in a cross section perpendicular to the axis of each prismatic glass.

[0038] Example 15 Each glass molded body produced in Examples 1 to 14 was sliced ​​by a known method to produce circular thin glass sheets made of multiple sheets of various glasses. A number of light guide plates for use in goggle-type displays were formed on these thin glass sheets by a known method, and each light guide plate was separated by dicing to efficiently produce multiple light guide plates. No crystals or striae were observed in each light guide plate, confirming its high quality. It is also possible to manufacture optical elements other than light guide plates using known methods.

[0039] (Comparative Example 1) The glass melt from which the glasses used in Examples 1 to 14 were obtained was cast into a mold described in Patent Documents 1 and 2 to form a glass having a cross-sectional area of ​​1.0 × 10 3 mm 2 When the obtained glass was observed, significant striae were observed, and it was not possible to obtain a glass molding having striae of grades 1 to 3.

[0040] Explanation of symbols 1. 3D glass 21, 22 Glass molding Type 3 31 Inside the model 32 bottom 4 Furnace 5 Support 6 plates 7 tubes

Claims

1. A method for producing a glass molded body from three-dimensional glass, the glass molded body having any one of a cylindrical shape, a regular n-gonal prism shape, and a substantially regular n-gonal prism shape, for obtaining a plurality of optical elements, comprising: placing the solid glass in the mold so that it contacts the bottom of the mold; a step of heating the three-dimensional glass together with the mold to raise the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; a step of deforming the three-dimensional glass at the molding temperature to form a glass molded body having a shape corresponding to the internal shape of the mold; and after cooling, removing the glass molded body from the mold, thereby obtaining the glass molded body (where n is an integer of 5 or more).

2. A method for producing a glass molded body from a three-dimensional glass, comprising: placing the three-dimensional glass on a base; a step of covering the placed three-dimensional glass with a tube from an open end thereof and placing the tube so that the end thereof contacts the base; heating the three-dimensional glass with the tube covered, raising the temperature of the three-dimensional glass to a forming temperature that is equal to or higher than the temperature at which the three-dimensional glass deforms under its own weight and lower than the crystallization temperature, and maintaining the forming temperature; a step of deforming the three-dimensional glass at the molding temperature to form a glass molded body having a shape corresponding to the internal shape of the tube; and after cooling, removing the glass molded body from the cylinder to obtain the glass molded body, The glass of the glass molded body has a liquidus temperature and a viscosity of 5×10 ３ dPa·s or less.

3. The manufacturing method according to claim 1 or 2, wherein the deformation of the three-dimensional glass is caused by its own weight.

4. The method according to claim 1 or 2, wherein the glass molded body has a cylindrical shape.

5. A method for producing sheet glass, comprising producing a glass shaped body by the method according to claim 1 or 2, and slicing the glass shaped body into thin sheets.

6. a liquidus temperature, and a viscosity at the liquidus temperature of 5×10 ３ A glass molded body having any one of a cylindrical shape, a regular n-gonal prism, and a substantially regular n-gonal prism, which is made of glass having a viscosity of 1000 dPa s or less, The area of ​​the cross section perpendicular to the side is 2.0 x 10 ３ mm ２ That's all, A glass molding made of glass having striae of grades 1 to 3 as measured in accordance with Japan Optical Glass Industry Association Standard JOGIS11-1975 (where n is an integer of 5 or more).

7. 7. The glass molded article according to claim 6, wherein the length from one end to the other end of the shape is 2 cm or more.

8. A method for producing sheet glass, comprising slicing the glass molded product according to claim 6 or 7 into thin sheets.

9. A method for producing an optical element, comprising forming one or more optical elements from a glass plate obtained by the method according to claim 8.

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