Glass optical component molding dies

Abstract

In a mold structure in which a pressed molten glass gob rises up the concave surface of a barrel mold and is directly injected into the mold, there are problems with low yield and productivity in obtaining glass optical components that match the shape of the mold. In addition, when changing the mold shape, there is a problem of high costs, such as the need to manufacture a new barrel mold from scratch. [Solution] A glass flow path mold is formed, which is composed of a lower mold provided on the body mold and an upper mold provided on the ring mold, so as to connect a body mold, a ring mold, and a molding die composed of a lower mold and an upper mold into which a molten glass gob is poured. The lower mold of the glass flow path mold can be integrated with the body mold and is removable, and the upper mold of the glass flow path mold can be integrated with the ring mold and is removable. The glass flow path mold can also be integrated with the molding die. These features can significantly improve yield and productivity.

Description

[Technical field]

[0001] The present invention relates to a mold for molding glass optical components, which is used to efficiently manufacture glass optical components having precise and complex three-dimensional shapes, specifically glass optical components having precise and complex three-dimensional shapes such as double-sided aspherical glass lenses and irregular shaped lenses. [Background technology]

[0002] In recent years, with the shift to LED and LD light sources, lens-shaped products and optical components are becoming smaller, more precise, and more complex in shape, and there is a demand for molds for molding glass optical components that can accommodate these changes.

[0003] Conventionally, the main methods that have been tried to produce molding dies for glass products having small three-dimensional shapes, such as optical components, and molding methods using those dies are the direct press method, mold press method, reheat press method, and injection molding method.

[0004] The direct press method is the most typical pressing technique in which a molten glass gob is directly put into a mold and pressed with a press. It is called the direct press method because the glass gob is directly molded into the shape of the mold between a barrel mold, an arrow mold, and a ring mold. In mass production, a molten glass gob (a lump of molten glass) that has been shear-cut (cut with a blade) to a nearly constant weight according to the product weight from the molten glass flowing out of a melting furnace is generally put directly into a barrel mold (the lower concave mold of a pair of molds) and pressed with an arrow mold (the upper convex mold of a pair of molds) to form it into the shape of the mold.

[0005] In this case, a ring die is placed around the outer periphery of the arrow die. When the arrow die descends to press the glass gob, the ring die descends slightly earlier than the arrow die to fit into the barrel die and guide the arrow die while forming the edge of the pressed glass product.

[0006] Conventional direct press technology has the following drawbacks: (1) In manufacturing small precision glass parts, it is difficult to keep the weight of the molten glass gob constant, and the weight of the glass gob varies widely, making it difficult to perform stable precision molding. In other words, this molding method requires that the fluctuation in the weight of the glass gob be absorbed directly by the fluctuation in the thickness of the product, making it difficult to mold products with high shape accuracy. (2) When trying to obtain small, thin-walled glass optical components, the molten glass gob loses heat rapidly as it stretches through the narrow gap of the mold during pressing, causing the glass to solidify before it can be fully stretched. Furthermore, in the case of small-sized glass optical components, the original molten glass gob itself does not have much heat capacity, so the molten glass gob cools quickly during pressing, causing the glass to crack or break during press molding, making it extremely difficult to mold glass optical components with complex shapes that have thin or narrow parts. (3) Because a molten glass gob at about 1,000°C is molded in a mold at about 500°C, fusion between the glass and the mold is prevented. However, the surface of the molten glass gob in contact with the mold is rapidly cooled and solidified, while the inside of the glass shrinks and solidifies later. This causes a type of molding defect (defects in shape and size) caused by volumetric shrinkage called "sink," and high shape precision cannot be obtained.

[0007] In order to overcome these drawbacks of the direct pressing method, a mold for molding glass optical components has been disclosed (Patent Document 1), which is characterized in that it comprises a body mold having at least a pair of lower molds for molding glass optical components provided on the outer edge of a concave portion, an arrow mold having a convex portion that combines with the concave portion of the body mold, and a ring mold arranged on the outer periphery of the arrow mold and having at least a pair of upper molds for molding glass optical components, wherein a molten glass gob is introduced into the concave portion of the body mold and pressed from above by the arrow mold having the convex portion, thereby injecting the molten glass gob into a space formed between the lower and upper molds of the at least a pair of molding dies.

[0008] On the other hand, molds other than the direct pressing method have also been proposed. Patent Document 2 disclosed by Angle et al. can be considered as a technology that combines the mold pressing method with the injection molding method, in which a carbon mold is used, heated and pressed in a non-oxidizing atmosphere, and the glass molded product is left in the carbon mold without being released, and the temperature is lowered slowly for a sufficient period of time while maintaining the heating and pressure until the temperature drops below the glass transition point, thereby producing a three-dimensional glass optical component. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2019 / 202816 issue [Patent Document 2] U.S. Patent No. 3,844,755 Summary of the Invention [Problem to be solved by the invention]

[0010] In the conventional molds described in Patent Document 1, when changing the shape of a glass optical component to be manufactured, a pair of upper and lower molding dies are replaced, but it was found that if only the molding dies are replaced, the way in which the molten glass gob enters the molding dies changes, resulting in problems such as a deterioration in shape precision and a decrease in manufacturing yield. Therefore, when replacing the molding dies, it was often necessary to remake the entire barrel die or ring die.

[0011] On the other hand, the method disclosed in Patent Document 2 has the problems that it requires the use of a special carbon mold and that, although it is possible to mold small optical components such as simple lenses, it is not possible to mold glass optical components having complex three-dimensional shapes as is the objective of the present invention. [Means for solving the problem]

[0012] An object of the invention according to the present application is to provide a novel mold for molding glass optical components, which is capable of molding glass optical components having precise and complex three-dimensional shapes efficiently and with a high yield.

[0013] In order to solve the above-mentioned problems, the present invention provides a mold for molding a glass optical component having a precise and complex three-dimensional shape, the mold comprising: a barrel mold having a lower mold for molding the glass optical component provided on the outer edge of a concave portion; an arrow mold having a convex portion that combines with the concave portion of the barrel mold; and a ring mold arranged on the outer periphery of the arrow mold and provided with an upper mold for molding the glass optical component, wherein a molten glass gob inputted into the concave portion of the barrel mold is pressed from above by the arrow mold having the convex portion, thereby injecting the molten glass gob into a space surrounded by the lower mold and the upper mold of the molding mold. The mold for molding a glass optical component is characterized in that a glass flow path mold is formed, the glass flow path mold consisting of a lower mold provided on the periphery of the concave portion of the barrel mold and an upper mold provided on the ring mold, so as to connect the barrel mold, the ring mold, and the molding mold, in order to inject the molten glass gob into the molding mold as the mold is pressed.

[0014] Here, glass optical components having precise and complex three-dimensional shapes refer to double-sided aspherical lenses, irregular lenses, optical components having complex three-dimensional shapes, etc., and the present invention can provide a mold capable of molding glass optical components that are far more difficult to mold than simple concave or convex lenses, for example, those that have almost no flat surfaces and have grid-like grooves formed on both sides. These glass optical components having precise and complex three-dimensional shapes will be exemplified later together with examples of molds for molding glass optical components.

[0015] The structure and function of the glass optical component molding die of the present invention will be described with reference to FIG. 1. The glass optical component molding die 1 of the present invention is composed of a barrel mold 2, a molding die 4, a ring mold 5, an arrow mold 6, and a glass flow path die 12. A lump of molten glass (molten glass gob), which is the material of the glass optical component, is poured into the concave surface 3 of the barrel mold 2. Meanwhile, the arrow mold 6 has a convex surface and is used to pressurize the molten glass gob from above. Unlike the conventional direct pressing method, the present invention does not directly transfer the shapes of the barrel mold 2 and the arrow mold 6 to obtain a molded product, but when the molten glass gob poured into the barrel mold 2 is pressed by the arrow mold 6, it rises along the concave surface 3 of the barrel mold to reach the peripheral portion, and through the glass flow path die 12 consisting of a lower mold and an upper mold, molten glass is poured and filled into the space between the lower mold 4a of the molding die 4 provided at the outer edge and the upper mold 4b of the molding die provided on the lower surface of the ring mold 5, thereby forming a glass optical component.

[0016] The main part of the body mold 2 is the concave portion 3, and a lower mold 12a of the glass flow path mold is provided on the periphery of the concave portion of the body mold, a lower mold 4a of the forming mold is provided on the outer edge of the concave portion of the body mold, and an upper mold 12b of the glass flow path mold and an upper mold 4b of the forming mold are provided on the underside of the ring mold 5. In a conventional direct press mold, a final molded product is press-molded between the body mold and the arrow mold, or between the body mold, the arrow mold, and the ring mold, whereas in the present invention, pressing by the body mold 2 and the arrow mold 6 causes a flow in the molten glass gob, so that a molten glass gob is injected through the glass flow path mold 12 into a space 9 formed by the forming mold 4 consisting of a lower mold provided on the outer edge of the concave portion of the body mold and an upper mold of the forming mold provided on the underside of the ring mold, thereby obtaining a final product between the forming molds, which is completely different from a conventional direct press mold.

[0017] Here, the glass flow path mold is composed of a lower mold of the glass flow path mold formed inside the molding die so as to be connected to the lower mold provided on the outer edge of the body mold, and an upper mold of the glass flow path mold formed inside the molding die so as to be connected to the upper mold of the molding die provided on the underside of the ring mold. The molding die is formed on the outer edge of the concave part of the body mold, but the glass flow path mold is formed inside the molding die and in a place that overlaps with the concave part of the body mold, so this part is called the peripheral part.

[0018] The glass flow passage mold 12 will be described with reference to Fig. 1. In the glass optical component molding mold 1, points A and B are defined as follows. Point A: The end point of the center line on the glass flow channel surface of the lower mold of the glass flow channel mold on the body side. Point B: The end point of the center line of the glass flow channel surface of the lower mold of the glass flow channel mold on the molding die side. The areas SA and SB at the end points of the glass flow path mold are defined as follows: When the body mold is placed horizontally, the areas SA and SB are perpendicular to a vertical section including the center line of the glass flow path surface of the lower mold of the glass flow path mold, SA: Area of ​​the vertical cross section (CA) of the glass flow passage space passing through point A (cross-sectional area of ​​the glass flow passage mold on the glass inlet side) SB: Area of ​​the vertical cross section (CB) of the glass flow passage space passing through point B (cross-sectional area of ​​the glass flow passage mold on the glass outflow side) It is defined as:

[0019] In the present invention, it has been found that when the ratio (SA / SB) of the cross-sectional area SA on the glass inflow side of the glass flow path space to the cross-sectional area SB on the glass outflow side of the glass flow path space is in the range of 1.7 to 19.7, the shape accuracy of the glass optical component is excellent.

[0020] The lower die 4a of the molding die 4 for molding the glass optical component can be integrated with the barrel die 2 by being fitted into the barrel die, and the upper die 4b of the molding die 4 can be integrated with the ring die 5 by being fitted into the ring die, and the lower die 4a of the molding die is structured so as to be removable from the barrel die 2, and the upper die 4b of the molding die is structured so as to be removable from the ring die 5, so that the lower die 4a of the molding die 4 and the upper die 4b of the molding die 4 can be replaced according to the shape of the glass optical component. This is because it is possible to manufacture various optical components using the same barrel die 2, arrow die 6 and ring die 5. For the same reason, lower die 12a of glass flow path mold 12 for molding glass optical components can be integrated with barrel mold 2 by being fitted into it, and upper die 12b of glass flow path mold 12 can be integrated with ring mold 5 by being fitted into it, and lower die 12a of glass flow path mold 12 is structured so as to be removable from barrel mold 2, and upper die 12b of glass flow path mold 12 is structured so as to be removable from ring mold 5, so that lower die 12a of glass flow path mold 12 and upper die 12b of glass flow path mold 12 can be replaced to match the shape of the glass optical component.

[0021] Furthermore, once the shapes of the molding die 4 and the glass flow path die 12 have been determined, as shown in Fig. 2, the molding die 4 and the glass flow path die 12 can be integrated to form a glass flow path die integrated molding die 13. The glass flow path die integrated molding die 13 is composed of a lower die 13a of the glass flow path die integrated molding die and an upper die 13b of the glass flow path die integrated molding die.

[0022] The space 9 formed between the lower mold 4a and the upper mold 4b of the molding die 4 for molding a glass optical component is a space corresponding to the shape of the glass optical component to be formed, but in addition, it is desirable to have an additional space outside the space into which the molten glass gob can flow, since this ensures that the molten glass gob can be injected into the space 9. This is because it is possible to prevent the formation of voids in the space 9, which would result in a defective shape of the glass optical component.

[0023] In addition, at least one of the lower mold 4a and the upper mold 4b of the molding die 4 for molding the glass optical component is preferably provided with a perforation for removing air pushed out by the molten glass gob from a space corresponding to the shape of the glass optical component during press molding. This is because, when the molten glass gob is injected into the space through the molten glass inlet, the air existing in the space is removed through the perforation, and this is expected to improve the dimensional accuracy of the optical component. In this case, it is preferable that the inner diameter of the perforation is 0.1 mm or more and 0.5 mm or less. This is because the diameter is sufficient to remove air and is small enough for the molten glass to flow in. Effect of the Invention

[0024] According to the present invention, a new mold for molding glass optical components can be used to mold glass optical components having precise and complex three-dimensional shapes that could not be obtained with conventional molds with good yield and high productivity. Furthermore, in the basic embodiment, not only does it not require special mold materials and a non-oxidizing atmosphere as in the mold press method, but it also enables mass production or small-lot production of a wide variety of products, making a great contribution to the development of the industry. [Brief description of the drawings]

[0025] [Figure 1] 1 is an example of a mold for molding a glass optical component according to the present invention. [Diagram 2] This is an example of the glass optical component molding die of the present invention in which the molding die and the glass flow passage die are integrated. [Diagram 3] FIG. 1 is a diagram showing an example of a glass optical component manufactured using the molding die for the glass optical component of the present invention, and a cross-sectional area SA on the glass inflow side and a cross-sectional area SB on the glass outflow side of the flow path space of the glass flow path die in this case. [Figure 4] FIG. 2 is an enlarged view of an example of a lower die of a glass channel die. [Diagram 5] 1 is an example of a glass optical part obtained using the glass optical part molding die of the present invention. [Figure 6]1 is another example of a glass optical component obtained using the glass optical component molding die of the present invention. [Figure 7] 1 is yet another example of a glass optical component obtained using the glass optical component molding die of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The glass optical component molding die 1 of the present invention can be manufactured by cutting and grinding stainless steel according to design drawings. For the molding die 4, a heat-resistant alloy with higher durability may be used as necessary. The glass optical component molding die of the present invention is composed of a body mold 2, a molding die 4, a ring mold 5, an arrow mold 6, and a glass flow path die 12. The body mold 2 is formed with a concave portion 3 into which a lump of molten glass (molten glass gob) made of the material of the glass optical component is poured, and a lower mold 4a of the molding die 4 for molding the glass optical component is provided on the outer edge of the concave portion 3, and further, a lower mold 12a of the glass flow path die is provided on the peripheral portion connecting the inclined surface of the concave portion of the body mold and the lower mold 4a of the molding die.

[0027] On the other hand, the upper die 4b of the molding die 4 is provided on the lower surface side of the ring die 5 so as to face the lower die 4a provided on the outer edge of the concave surface of the body die 2, and further the upper die 12b of the glass flow path die is provided at a position facing the lower die 12a of the glass flow path die. When a molten glass gob is poured into the concave surface 3 of the body die 2, the ring die 5 first descends and comes into close contact with the body die 2, forming a space sandwiched between the lower die 12a of the glass flow path die on the periphery of the concave surface of the body die 2, the lower die 4a of the molding die 4, the upper die 12b of the glass flow path die on the lower surface of the ring die 5, and the upper die 4b of the molding die. Following the descent of the ring die 5, an arrow die 6 having a convex surface descends, and the molten glass gob is pressurized from above. The molten glass gob, while maintaining sufficient fluidity, rises along the inner surface of the concave portion 3 of the body mold 2, reaches the peripheral edge, reaches end point A of the lower mold 12a of the molten glass flow path mold, and as its cross-sectional area decreases (thus increasing the inflow speed of the molten glass gob), reaches end point B of the lower mold 12a of the glass flow path mold (equal to the inlet of the lower mold 4a of the molding mold 4), and is injected into the space sandwiched between the lower mold 4a and upper mold 4b of the molding mold 4, to form a glass optical component.

[0028] The effect of the glass flow path mold is considered to be that it is useful for appropriately adjusting the shape of the molten glass gob and its speed of movement toward the molding die as the molten glass gob pressed by the arrow die 6 climbs up the inclined surface of the barrel die and finally fills the molding die. The cross-sectional area of ​​the glass gob's flow path is large at the entrance (point A) of the glass flow path mold, and becomes smaller as it moves toward the molding die. According to the law of conservation of mass, it is considered that the smaller the cross-sectional area, the faster the movement speed. Therefore, it is considered that the molten glass gob flows faster at the exit (point B) of the glass flow path mold than at the entrance (point A), so that it fills the space inside the molding die evenly.

[0029] The upper die 4b of the molding die 4 can be fixed to the ring die 5 by, for example, bolting, and has a mold structure that allows it to be attached and detached. Similarly, the lower die 4a of the molding die 4 in the body die 2 also has a mold structure that allows it to be attached and detached by any method such as bolting (not shown), and it is possible to mold optical components of various shapes by replacing the lower die 4a of the molding die 4 and the upper die 4b of the molding die 4 while using the same body die 2, arrow die 6, and ring die 5. As with the molding die, the lower die 12a and upper die 12b of the glass flow path die can also be fixed to the body die and ring die, respectively, by bolting, and can naturally be attached and detached. These characteristics indicate that it is suitable for small-lot, high-mix production.

[0030] Fig. 3-1 shows a glass molded body 14 produced using the glass optical component molding die 1 of the present invention, and a glass optical component 15 formed at its end. Fig. 3-2 shows a cut at the outlet CB of the glass flow path die, and the cross-sectional area of ​​CB is SB. Meanwhile, Fig. 3-3 shows a cut at the inlet CA of the glass flow path die, and the cross-sectional area of ​​CA is SA. The portion of the glass molded body from CA to CB corresponds to the shape of the flow path of the glass flow path die.

[0031] Fig. 4 shows only the lower mold of the glass flow path mold. Fig. 4-1 is an overall view, and Fig. 4-2 is a cross-sectional view taken along the center line of the glass flow path surface. It can be seen that the glass flow path space narrows toward the molding die. When the center line of the glass flow path surface is drawn, the point where it intersects with the body side end of the glass flow path mold is point A, and the point where it intersects with the molding die side end is point B. In the present invention, it was found that the shape precision of glass optical components is excellent when the ratio (SA / SB) of the cross-sectional area SA of the glass flow path space on the glass inflow side to the cross-sectional area SB of the glass flow path space on the glass outflow side is in the range of 1.7 to 19.7. EXAMPLES

[0032] Table 1 lists the product sizes of various glass optical components manufactured using the glass optical component molding die of the present invention, as well as the inlet cross-sectional area SA and outlet cross-sectional area SB of the glass flow channel die. X, Y, and Z are the maximum dimensions of the product in each direction.

[0033] [Table 1]

[0034] If SA / SB is less than 1.7, molding defects called insufficient flow will occur frequently. This is a phenomenon in which the molten glass gob does not reach every corner of the space inside the forming die. This is thought to be because the cross-sectional area does not change significantly between the entrance (point A) and exit (point B) of the glass flow path die, which slows the inflow speed of the molten glass gob into the space inside the forming die and reduces the inflow pressure, so the molten glass gob cannot fully fill the space inside the forming die.

[0035] On the other hand, if SA / SB exceeds 19.7, cracks and breaks occur frequently in the product. This is thought to be because the cross-sectional area at point B in the flow path of the molten glass gob is significantly smaller than the cross-sectional area at point A, i.e., the glass flow path space narrows sharply toward the forming die, so that the inflow speed of the molten glass gob into the space in the forming die becomes too fast and the inflow pressure becomes too high, so that a large pressure is applied to the glass that has flowed into the forming die space, causing the generation of cracks and breaks.

[0036] Fig. 5 shows a lens for an in-vehicle sensing system with a cylindrical surface on one side and an aspherical surface on the back side, Fig. 6 shows a lens for a projector with three surfaces, one of which has three spherical surfaces and the remaining two are cylindrical surfaces, with the three surfaces each having a different shape, and Fig. 7 shows a lens for an in-vehicle headlamp with a free-form surface shape on the front and back sides. None of these could be molded using conventional methods, and even the method shown in Patent Document 1 made molding difficult and it was not possible to mold with a good yield, but the present invention achieved excellent molding precision and productivity. [Explanation of symbols]

[0037] 1...An example of a mold for molding a glass optical component of the present invention. 2. Body type 3... Concave part of the body 4. Molding tool 4a...Lower die of molding die 4b: Upper part of molding die 5. Ring type 6. Arrow type 9. Space formed between molding dies 12. Glass flow channel mold 12a: Lower mold of glass flow channel mold 12b: Upper mold of glass flow channel mold 13. Integrated mold in which molding mold and glass flow path mold are integrated 13a...Lower die of integrated die 13b: Upper die of integrated die 14. Glass molding 15. Glass optical components

Claims

1. A mold for molding a glass optical component having a precise and complex three-dimensional shape, comprising: a body mold having a lower mold for molding the glass optical component provided on the outer edge of a concave portion thereof; an arrow mold having a convex portion which fits into the concave portion of the body mold; and a ring mold disposed on the outer periphery of the arrow mold and provided with an upper mold for molding the glass optical component, wherein a molten glass gob is poured into the concave portion of the body mold and pressed from above by the arrow mold having the convex portion, thereby injecting the molten glass gob into a space surrounded by the lower mold and the upper mold of the molding mold. a glass flow path mold including a lower mold provided on the periphery of the concave portion of the body mold and an upper mold provided on the ring mold so as to connect the body mold, the ring mold, and the molding mold in order to inject the molten glass gob into the molding mold during the pressing, and wherein when points A, B, SA, and SB are defined as follows, a ratio (SA / SB) of a cross-sectional area SA on the glass inflow side of a glass flow path space surrounded by the glass flow path mold to a cross-sectional area SB on the glass outflow side of the glass flow path space is in the range of 1.7 to 19.

7. Point A: End point of the center line on the glass flow path surface of the lower mold of the glass flow path mold on the body mold side. Point B: End point of the center line on the glass flow path surface of the lower mold of the glass flow path mold on the molding mold side. SA: the area of ​​a vertical cross section (CA) of a glass flow path space which is perpendicular to a vertical cross section including the center line of the glass flow path surface of the lower mold of the glass flow path mold and passes through point A when the body mold is placed horizontally (cross-sectional area of ​​the glass inflow side of the glass flow path space). SB: the area of ​​a vertical cross section (CB) of the glass flow path space which is perpendicular to a vertical cross section including the center line of the glass flow path surface of the lower mold of the glass flow path mold and passes through point B when the body mold is placed horizontally (cross-sectional area of ​​the glass outflow side of the glass flow path space).

Images