molds for molding glass optical components

Abstract

In molds where pressed molten glass gobs rise up the concave section of the mold body and are directly injected into the molding die, there were problems with low yield and productivity in obtaining glass optical components that matched the shape of the molding die. Furthermore, changing the shape of the molding die required the manufacture of a new mold body, resulting in high costs. [Solution] A glass flow channel mold is formed, consisting of a lower mold provided on the body mold and an upper mold provided on the ring mold, so as to connect the molding die, which consists of a body mold, a ring mold, and a lower mold and an upper mold into which molten glass gobs are injected. The lower mold of the glass flow channel mold can be integrated with and detached from the body mold, and the upper mold of the glass flow channel mold can be integrated with and detached from the ring mold. The glass flow channel mold can also be integrated with the molding die. These features significantly improve yield and productivity.

Description

Technical Field

[0001] The present invention relates to a mold for forming a glass optical component having a precise and complex three-dimensional shape, specifically, a glass optical component having a precise and complex three-dimensional shape such as a glass double-sided aspherical lens or an irregular lens, for efficiently manufacturing the same.

Background Art

[0002] With the LED and LD conversion of various light sources in recent years, the miniaturization, high-precision, and complex shaping of lens-shaped products and optical components have been progressing, and there is a demand for molds for forming glass optical components corresponding to these.

[0003] Conventionally, as a molding die for a glass molded product having a small three-dimensional shape such as an optical component and a molding method using the molding die, mainly the direct press method, the mold press method, the reheat press method, and the injection molding method have been tried.

[0004] The direct press method is the most typical press technique in which a molten glass gob is directly put into a mold and press molding is performed by a press machine. Since the glass gob is directly formed into the shape of the mold between the body mold, the arrow mold, and the ring mold, it is called the direct press method. As a mass production method, from the molten glass flow flowing out of the melting furnace, a molten glass gob (a lump of molten glass) that has been shear-cut (cut with a blade) to have a substantially constant weight according to the product weight is directly put into the body mold (the concave mold on the lower side of the pair of molds), and pressed with the arrow mold (the convex mold on the upper side of the pair of molds) to form the shape of the mold.

[0005] In this case, a ring mold is arranged on the outer peripheral portion of the arrow mold. The ring mold descends slightly earlier than the arrow mold and fits into the body mold when the arrow mold descends to press the glass gob, and plays a role of forming the edge of the glass product to be pressed while guiding the arrow mold.

[0006] The conventional direct press technique had the following drawbacks. (1) In the manufacture of small, precision glass parts, it is difficult to control the weight of the molten glass gob to be constant, and the weight variation of the glass gob becomes large, which makes it difficult to achieve stable precision molding. In other words, because the molding method has to absorb the weight fluctuations of the glass gob directly through fluctuations in the thickness of the product, it is difficult to mold products with high shape accuracy. (2) When attempting to obtain small, thin-walled glass optical components, there was a problem in that during pressing, the molten glass gob rapidly lost heat to the mold as it stretched through the narrow gaps, causing the glass to solidify before it could stretch thinly enough. Furthermore, in the case of even smaller glass optical components, the initial heat capacity of the molten glass gob itself was low, so the molten glass gob cooled down quickly during pressing, causing the glass to crack or break during press molding. This made it extremely difficult to mold glass optical components with complex shapes that have thin or narrow sections. (3) Because molten glass gobs at a temperature of around 1,000°C are formed in a mold at a temperature of around 500°C, fusion between the glass and the mold is prevented. However, the surface of the molten glass gob in contact with the mold cools and solidifies rapidly, while the inside of the glass shrinks and solidifies more slowly. This results in a type of molding defect (defects in shape and dimensions) caused by volume shrinkage called "sink marks," and high shape accuracy could not be obtained.

[0007] To overcome the drawbacks of the direct press method, a mold for molding glass optical components has been disclosed (Patent Document 1). The mold comprises a body mold with at least one 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 is combined with the concave portion of the body mold, and a ring mold positioned on the outer circumference of the arrow mold and provided with at least one pair of upper molds for molding glass optical components, wherein a molten glass gob placed in the concave portion of the body mold is pressed from above by the arrow mold having the convex portion, thereby injecting the molten glass gob into the space formed between the lower and upper molds of the at least pair of molding dies.

[0008] On the other hand, molds that deviate from the direct press method have also been proposed. Patent document 2 disclosed by Angle et al. can be seen as a technology that combines the mold press method with the injection molding method. It uses a carbon mold, heats and presses it in a non-oxidizing atmosphere, and then, without demolding, leaves the glass molded product inside the carbon mold and slowly cools it down to below the glass transition point while maintaining heating and pressurization for a sufficient amount of time, thereby manufacturing three-dimensional glass optical components. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] WO2019 / 202816 issue [Patent Document 2] U.S. Patent No. 3844755 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In the conventional mold described in Patent Document 1, when changing the shape of the glass optical component being manufactured, a pair of upper and lower molding dies are replaced. However, it was found that simply replacing the molding dies alters how the molten glass gob enters the molding die, resulting in a deterioration of shape accuracy and a decrease in manufacturing yield. Therefore, when replacing the molding dies, it was often necessary to remake the entire body mold or ring mold.

[0011] On the other hand, the method disclosed in Patent Document 2 has the drawbacks of requiring the use of a special carbon mold and being able to mold small optical components such as simple lenses, but not being able to mold glass optical components with complex three-dimensional shapes as targeted by the present invention. [Means for solving the problem]

[0012] The object of the invention described in this application is to provide a novel mold for molding glass optical components that can efficiently mold glass optical components having precise and complex three-dimensional shapes with a high yield.

[0013] To solve the aforementioned conventional problems, the present invention provides a mold for molding a glass optical component having a precise and complex three-dimensional shape, comprising: a body mold with 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 is combined with the concave portion of the body mold; and a ring mold arranged on the outer circumference of the arrow mold and provided with an upper mold for molding the glass optical component, wherein a molten glass gob placed in the concave portion of the body mold is pressed from above by the arrow mold having a convex portion, thereby injecting the molten glass gob into the space enclosed by the lower mold and the upper mold of the molding die, characterized in that, in order to inject the molten glass gob into the molding die in conjunction with the pressing, a glass flow channel mold is formed, consisting of 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 die.

[0014] Here, glass optical components having precise and complex three-dimensional shapes refer to double-sided aspherical lenses, irregularly shaped lenses, and other optical components having complex three-dimensional shapes. According to the present invention, it is possible to provide a mold that can mold glass optical components that are far more difficult to mold than simple concave or convex lenses, such as those that have almost no flat surfaces and have grid-like grooves formed on both sides. Examples of these glass optical components having precise and complex three-dimensional shapes will be illustrated later, along with examples of molds for molding glass optical components.

[0015] The structure and function of the mold for molding glass optical components of the present invention will be explained with reference to Figure 1. The mold 1 for molding glass optical components of the present invention consists of a body mold 2, a molding die 4, a ring mold 5, an arrow mold 6, and a glass flow channel mold 12. A lump of molten glass (molten glass gob), which is the material for the glass optical component, is placed into the concave portion 3 of the body mold 2. On the other hand, the arrow mold 6 has a convex portion and is used to pressurize the molten glass gob from above. Unlike the conventional direct press method, the present invention does not obtain a molded product by directly transferring the shape of the molds of the body mold 2 and the arrow mold 6. Instead, when the molten glass gob placed into the body mold 2 is pressed by the arrow mold 6, it rises along the concave portion 3 of the body mold and reaches the periphery, and through the glass flow channel mold 12, which consists of a lower mold and an upper mold, molten glass is injected 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 a concave portion 3, but the lower mold 12a of the glass flow dies is provided on the periphery of the concave portion of the body mold, and the lower mold 4a of the molding die is provided on the outer edge of the concave portion of the body mold, and the upper mold 12b of the glass flow dies and the upper mold 4b of the molding die are provided on the lower side of the ring mold 5. Conventional direct press dies press-form the final molded product between the body mold and the arrow die, or between the body mold, arrow die and ring mold. In contrast, in the present invention, the pressing by the body mold 2 and the arrow die 6 generates flow in the molten glass gob, and as a result, the molten glass gob is injected through the glass flow dies 12 into the space 9 formed by the molding die 4, which consists of the lower mold of the molding die provided on the outer edge of the concave portion of the body mold and the upper mold of the molding die provided on the lower surface of the ring mold, thereby obtaining the final product between the molding dies. This is completely different from conventional direct press dies.

[0017] Here, the glass channel mold consists of a lower glass channel mold formed inside the molding die so as to connect to the lower mold of the molding die provided on the outer edge of the body mold, and an upper glass channel mold formed inside the molding die so as to connect to the upper mold of the molding die provided on the lower surface of the ring shape. The molding die is formed on the outer edge of the concave portion of the body mold, but the glass channel mold is formed inside the molding die and overlaps with the concave portion of the body mold, so this portion is called the peripheral portion.

[0018] The glass flow channel mold 12 will be explained using Figure 1. In the mold 1 for molding glass optical components, points A and B are defined as follows. Point A: The end point on the body side of the center line on the glass channel surface of the lower mold of the glass channel mold. Point B: The end point on the mold side of the center line on the glass channel surface of the lower mold of the glass channel mold. Furthermore, the areas SA and SB at the endpoints of the glass flow channel mold are defined as follows: That is, when the body mold is placed horizontally, the area is perpendicular to the vertical cross-section that contains the center line of the glass flow channel surface of the lower mold of the glass flow channel mold within the plane. SA; Area of ​​the vertical cross-section (CA) of the glass channel space passing through point A (cross-sectional area on the glass inlet side of the glass channel mold) SB; Area of ​​the vertical cross-section (CB) of the glass channel space passing through point B (cross-sectional area on the glass outflow side of the glass channel mold) This is how it is defined.

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

[0020] Incidentally, the lower die 4a of the molding die 4 for molding the glass optical component can be integrated with the body die 2 by being fitted into the body 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. Further, the lower die 4a of the molding die is structured to be removable from the body die 2, and the upper die 4b of the molding die is structured to be removable from the ring die 5. The lower die 4a of the molding die 4 and the upper die 4b of the molding die 4 can be exchanged according to the shape of the glass optical component. This enables the production of various optical components while using the same body die 2, arrow die 6, and ring die 5. For the same reason, the lower die 12a of the glass flow path die 12 for molding the glass optical component can be integrated with the body die 2 by being fitted into the body die, and the upper die 12b of the glass flow path die 12 can be integrated with the ring die 5 by being fitted into the ring die. Also, the lower die 12a of the glass flow path die 12 is structured to be removable from the body die 2, and the upper die 12b of the glass flow path die 12 is structured to be removable from the ring die 5. The lower die 12a of the glass flow path die 12 and the upper die 12b of the glass flow path die 12 can be exchanged according to the shape of the glass optical component.

[0021] Furthermore, if the shapes of the molding die 4 and the glass flow path die 12 are determined, as shown in FIG. 2, the molding die 4 and the glass flow path die 12 can be integrated into a glass flow path die integrated molding die 13. The glass flow path die integrated molding die 13 comprises 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] Incidentally, the space 9 formed between the lower die 4a and the upper die 4b of the molding die 4 for molding the glass optical component corresponds to the shape of the glass optical component. In addition, it is desirable to have an additional space outside this space into which the molten glass gob can flow, as this ensures the injection of the molten glass gob into the space 9. This is because it can prevent the formation of voids in the space 9 and deterioration of the 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 discharging the air extruded 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 present in the space escapes through the perforation, and an improvement in the dimensional accuracy of the optical component can be expected. In this case, it is desirable that the inner diameter of the perforation is 0.1 mm or more and 0.5 mm or less. This is because it has a diameter sufficient to discharge the air and is small enough for the molten glass to flow in.

Effects of the Invention

[0024] According to the present invention, with a novel molding die for glass optical components, it is possible to mold a glass optical component having a precise and complex three-dimensional shape that could not be obtained with conventional dies, with good yield and high productivity. Further, in the basic embodiment, it does not require a special mold material or a non-oxidizing atmosphere such as the mold press method, and it is possible to perform mass production or small-lot and multi-variety production, which greatly contributes to the development of the industry.

Brief Description of the Drawings

[0025] [Figure 1] This is an example of the molding die for glass optical components of the present invention. [Figure 2] This is an example in which the molding die and the glass flow path die are integrated in the molding die for glass optical components of the present invention. [Figure 3] This is a diagram showing an example of a glass optical component manufactured using the molding die for glass optical components of the present invention, and the cross-sectional area SA on the glass inflow side and the 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] This is an enlarged view of an example of the lower mold of the glass flow path die. [Figure 5] This is an example of a glass optical component obtained using the molding die for glass optical components of the present invention. [Figure 6]This is another example of a glass optical component obtained using the mold for molding glass optical components of the present invention. [Figure 7] This is yet another example of a glass optical component obtained using the mold for molding glass optical components of the present invention. [Modes for carrying out the invention]

[0026] The mold 1 for molding glass optical components in the present invention can be manufactured by cutting and grinding stainless steel according to the design drawings. For the molding die 4, a more durable heat-resistant alloy may be used as needed. The mold for molding glass optical components in the present invention consists of a body mold 2, a molding die 4, a ring mold 5, a arrow mold 6, and a glass flow channel mold 12. The body mold 2 has a concave portion 3 into which a lump of molten glass (molten glass gob) made of the material for the glass optical component is introduced. The 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 the lower mold 12a of the glass flow channel mold is provided on the peripheral edge connecting the slope of the concave portion of the body mold and the lower mold 4a of the molding die.

[0027] On the other hand, on the lower side of the ring-shaped mold 5, the upper mold 4b of the molding die 4 is positioned opposite the lower mold 4a provided on the outer edge of the concave portion of the body mold 2, and the upper mold 12b of the glass flow path mold is positioned opposite the lower mold 12a of the glass flow path mold. When molten glass gob is introduced into the concave portion 3 of the body mold 2, the ring-shaped mold 5 descends first and comes into close contact with the body mold 2, forming a space between the lower mold 12a of the glass flow path mold at the periphery of the concave portion of the body mold 2, the lower mold 4a of the molding die 4, and the upper mold 12b of the glass flow path mold and the upper mold 4b of the molding die on the lower side of the ring-shaped mold 5. Following the descent of the ring-shaped mold 5, the arrow-shaped mold 6 having a convex portion 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, reaching the periphery, and then reaches the endpoint A of the lower mold 12a of the molten glass flow channel mold. As its cross-sectional area decreases (and thus the inflow velocity of the molten glass gob increases), it reaches the endpoint B of the lower mold 12a of the glass flow channel mold (which is equal to the entrance of the lower mold 4a of the molding die 4), and is injected into the space sandwiched between the lower mold 4a and the upper mold 4b of the molding die 4, thereby forming a glass optical component.

[0028] The effect of the glass channel mold is thought to be that it helps to appropriately regulate the shape and speed of the molten glass gob toward the molding die as it rises up the slope of the body mold and ultimately fills the molding die, after being pressed by the arrow mold 6. At the inlet (point A) of the glass channel mold, the cross-sectional area of ​​the glass gob in the channel path is large, and it decreases as it moves toward the molding die. And, according to the law of conservation of mass, it is thought that the speed of movement increases as the cross-sectional area decreases. Therefore, it is thought that the flow of molten glass gob is faster at the outlet (point B) of the glass channel mold than at the inlet (point A), and that it fills the space inside the molding die more evenly.

[0029] Furthermore, the upper mold 4b of the molding die 4 can be fixed to the ring mold 5 by, for example, bolt fastening, and has a mold structure that allows for attachment and detachment. Similarly, in the body mold 2, the lower mold 4a of the molding die 4 has a mold structure that allows for attachment and detachment by any method such as bolt fastening (not shown), and by changing the lower mold 4a and the upper mold 4b of the molding die 4 while using the same body mold 2, arrow mold 6 and ring mold 5, it is possible to mold optical components of various shapes. Similar to the molding die, the lower mold 12a and upper mold 12b of the glass flow channel mold can also be fixed to the body mold and ring mold, respectively by bolt fastening, and are, of course, detachable. These features indicate that it is suitable for small-batch, high-mix production.

[0030] Figure 3-1 shows a glass molded body 14 manufactured using the glass optical component molding die 1 of the present invention, and a glass optical component 15 formed at its end. Figure 3-2 is a cross-section of the glass flow channel mold at the outlet CB, where the cross-sectional area of ​​CB is SB. On the other hand, Figure 3-3 is a cross-section of the glass flow channel mold at the inlet CA, where 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 channel of the glass flow channel mold.

[0031] Figure 4 shows only the lower mold of the glass channel mold. Figure 4-1 is an overall view, and Figure 4-2 is a cross-sectional view when cut along the center line of the glass channel surface. It can be seen how the glass channel space narrows towards the molding die. When the center line of the glass channel surface is drawn, point A is the point where it intersects with the end of the body mold of the glass channel mold, and point B is the point where it intersects with the end of the molding die. In the present invention, it has been found that when the ratio (SA / SB) of the cross-sectional area SA on the glass inlet side of the glass channel space to the cross-sectional area SB on the glass outlet side of the glass channel space is in the range of 1.7 to 19.7, the shape accuracy of the glass optical component is excellent. [Examples]

[0032] Table 1 summarizes the product sizes of various glass optical components manufactured using the glass optical component molding die of the present invention, along with 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 their respective directions.

[0033] [Table 1]

[0034] When the SA / SB ratio is less than 1.7, molding defects known as under-extrusion become frequent. This is a phenomenon where the molten glass gob does not reach every corner of the mold cavity. This is thought to be because the cross-sectional area does not change significantly between the inlet (point A) and outlet (point B) of the glass flow channel mold, resulting in a slow inflow rate and low inflow pressure of the molten glass gob into the mold cavity, preventing the molten glass gob from adequately filling the mold cavity.

[0035] On the other hand, when the SA / SB ratio exceeds 19.7, cracks and fractures frequently occur 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 becomes significantly smaller than the cross-sectional area at point A, meaning the glass flow path space narrows rapidly towards the molding die. As a result, the inflow velocity of the molten glass gob into the molding die space becomes too fast, and the inflow pressure becomes too high. This puts great pressure on the glass that has entered the molding die space, causing cracks and fractures to occur.

[0036] Figure 5 shows an automotive sensing lens with one side being a cylindrical surface and the other side being an aspherical surface; Figure 6 shows a projector lens with three spherical surfaces on one of its three faces and two cylindrical surfaces, each with a different shape; and Figure 7 shows an automotive headlight lens with free-form surfaces on both the front and back surfaces. None of these could be molded using conventional methods, and even the method shown in Patent Document 1 was difficult to use, resulting in low yields. However, the present invention offers superior molding accuracy and productivity. [Explanation of Symbols]

[0037] 1. This is an example of a mold for molding glass optical components according to the present invention. 2...Body type 3. Concave section of the body 4. Molding die 4a..Lower mold for molding die 4b..Upper mold of the molding die 5...Ring type 6...Arrow shape 9. Space formed between the molding dies. 12. Glass flow channel mold 12a...Lower mold for glass flow channel mold 12b...Upper mold for glass flow channel 13. Integrated mold in which the molding die and the glass flow channel die are combined. 13a...Lower mold for integrated mold 13b... Upper mold for integrated mold 14. Glass molded body 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 with 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 is combined with the concave portion of the body mold; and a ring mold positioned on the outer circumference of the arrow mold and provided with an upper mold for molding the glass optical component, wherein a molten glass gob placed in the concave portion of the body mold is pressed from above by the arrow mold having a convex portion, thereby injecting the molten glass gob into the space enclosed by the lower mold and the upper mold of the molding die, characterized in that, in order to inject the molten glass gob into the molding die in conjunction with the pressing, a glass flow channel mold is formed, consisting of 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 die.

2. The glass channel mold is provided on the periphery of the concave portion of the body mold so as to connect to the lower mold of the molding die provided on the outer edge of the concave portion of the body mold, and the lower mold of the glass channel mold can be integrated with the body mold by being fitted into the body mold and is removable from the body mold, and further, the upper mold of the glass channel mold is provided on the ring mold so as to connect to the upper mold of the molding die, and the upper mold of the glass channel mold can be integrated with the ring mold by being fitted into the ring mold and is removable from the ring mold, and the lower and upper molds of the glass channel mold can be replaced as a pair to match the shape of the glass optical component, as described in claim 1.

3. The mold for molding glass optical components according to claim 1, characterized in that, when points A, B, SA, and SB are defined as follows, the ratio (SA / SB) of the cross-sectional area SA on the glass inflow side of the glass channel space surrounded by the glass channel mold to the cross-sectional area SB on the glass outflow side of the glass channel space is in the range of 1.7 to 19.

7. Point A: The endpoint on the body side of the center line on the glass channel surface of the lower mold of the glass channel mold. Point B: The endpoint on the molding die side of the center line on the glass channel surface of the lower mold of the glass channel mold. SA: When the body mold is placed horizontally, the area of ​​the vertical cross-section (CA) of the glass channel space passing through point A, which is perpendicular to the vertical cross-section containing the center line of the glass channel surface of the lower mold of the glass channel mold (the cross-sectional area on the glass inflow side of the glass channel space). SB: When the body mold is placed horizontally, the area of ​​the vertical cross-section (CB) of the glass channel space passing through point B, which is perpendicular to the vertical cross-section containing the center line of the glass channel surface of the lower mold of the glass channel mold (the cross-sectional area of ​​the glass outflow side of the glass channel space).

4. The lower mold of the glass channel mold, which is formed to connect the body mold and the molding die, is integrated with the lower mold of the molding die for molding the glass optical component and is provided on the periphery of the concave portion of the body mold, and the upper mold of the glass channel mold is integrated with the upper mold of the molding die for molding the glass optical component and is provided on the ring mold, and the integrated lower mold and the integrated upper mold are provided as a pair, the integrated lower mold can be integrated with the body mold by being fitted into the body mold and is removable from the body mold, and the integrated upper mold can be integrated with the ring mold by being fitted into the ring mold and is removable from the ring mold, and the mold for molding a glass optical component according to claim 1, characterized in that an integrated lower mold, which is formed by integrating the lower mold of the molding die for molding the glass optical component with a pair of the lower molds of the glass channel mold, and an integrated upper mold, which is formed by integrating the upper mold of the molding die with a pair of the upper molds of the glass channel mold, can be exchanged as a pair to match the shape of the glass optical component.

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