MOLD FOR MOLDING GLASS-MADE OPTICAL COMPONENT AND METHOD FOR MANUFUCTURING GLASS-MADE OPTICAL COMPONENT USING MOLD

Abstract

In the conventional direct press method, it was difficult to control the weight of molten glass gob when manufacturing a small precision glass component and thus the weight of the glass gob varies widely. Accordingly, the problem is that the precise molding cannot be expected stably. As a solution, the present invention provides a mold for molding a glass-made optical component and a manufacturing method using the mold, the mold comprising: a female mold which has a lower mold of a molding mold for molding the glass-made optical component on an outer peripheral portion of a concave surface of the female mold; a male mold which has a convex surface combined with the concave surface of the female mold; and a ring mold which is arranged on an outer peripheral portion of the male mold, the ring mold having an upper mold of the molding mold for molding the glass-made optical component, wherein molten glass gob introduced into the concave surface of the female mold is configured to be pressed from above by the male mold having the convex surface so that the molten glass gob is injected into a space formed between the lower mold and the upper mold of the molding mold.

Claims

1. A mold for molding a glass-made optical component having a precise and complicated three-dimensional shape, the mold comprising: a female mold which has a lower mold of at least one molding mold for molding the glass-made optical component on an outer peripheral portion of a concave surface of the female mold; a male mold which has a convex surface combined with the concave surface of the female mold; and a ring mold which is arranged on an outer peripheral portion of the male mold, the ring mold having an upper mold of the at least one molding mold for molding the glass-made optical component, wherein molten glass gob introduced into the concave surface of the female mold is configured to be pressed from above by the male mold having the convex surface so that the molten glass gob is injected into a space formed between the lower mold and the upper mold of the at least one molding mold.

2. The mold for molding the glass-made optical component according to claim 1, wherein a plurality of lower molds of the molding mold for molding the glass-made optical component is concentrically provided on the outer peripheral portion of the concave surface of the female mold centered around a center axis of the concave surface, a plurality of upper molds of the molding mold is concentrically provided on the ring mold so as to be aligned with positions of the lower molds which are concentrically provided, and a plurality of glass-made optical components can be molded by one press operation.

3. The mold for molding the glass-made optical component according to claim 1, wherein the lower mold of the molding mold for molding the glass-made optical component can be integrated with the female mold when the lower mold is fitted in the female mold, the upper mold of the molding mold can be integrated with the ring mold when the upper mold is fitted in the ring mold, the lower mold of the molding mold can be removed from the female mold, the upper mold of the molding mold can be removed from the ring mold, and the lower mold of the molding mold and the upper mold of the molding mold can be replaced according to the shape of the glass-made optical component.

4. The mold for molding the glass-made optical component according to claim 1, wherein the space formed between the lower mold and the upper mold of the molding mold for molding the glass-made optical component during a pressing process has a main space which has the shape corresponding to the shape of the glass-made optical component and an additional space which is formed outside the main space so that the molten glass gob can flow into the additional space.

5. The mold for molding the glass-made optical component according to claim 1, wherein the mold further comprises a mold lock mechanism which tightens the female mold and the ring mold with each other during a pressing process.

6. The mold for molding the glass-made optical component according to claim 1, wherein a bored hole is formed on at least one of the lower mold and the upper mold of the molding mold for molding the glass-made optical component so that air pressed by the molten glass gob is released from the main space which has the shape corresponding to the shape of the glass-made optical component during a pressing process.

7. The mold for molding the glass-made optical component according to claim 6, wherein an inner diameter of the bored hole is 0.1 mm or more and 0.5 mm or less.

8. A method of molding a glass-made optical component having a precise and complicated three-dimensional shape by using the mold for molding the glass-made optical component according to claim 1, the method comprising: (1) a process of introducing the molten glass gob into a central part of the concave surface of the female mold on which the lower mold of the molding mold for molding the glass-made optical component is provided at the outer peripheral portion; (2) a process of lowering the ring mold to be closely in contact with the female mold so that the upper mold of the molding mold formed on a lower surface of the ring mold is closely in contact with the lower mold of the molding mold formed on the outer peripheral portion of the female mold to form a main space in the molding mold, the main space having the shape corresponding to the shape of the glass-made optical component; (3) a process of pressing the molten glass gob introduced into the central part of the concave surface of the female mold from above by the male mold having the convex surface; (4) a process of further pressing the molten glass gob by the male mold so that the molten glass gob flows upward along an inner surface of the concave surface of the female mold and the molten glass gob is injected into the space formed in the molding mold through an inlet of the molten glass gob; (5) a process of pulling the male mold and then the ring mold upward after the temperature of the molten glass gob injected into the molding mold becomes equal to or lower than an annealing point of the molten glass and the molten glass is solidified; and (6) a process of removing a solidified glass molded body formed in the space of the female mold, the male mold, the ring mold and the molding mold and then cutting the molded glass-made optical component formed in the molding mold.

9. The method of molding a glass-made optical component having a precise and complicated three-dimensional shape according to claim 8, wherein the weight of the molten glass gob introduced in the concave surface of the female mold is 6 to 70 times heavier than the weight of the glass-made optical component formed in the molding mold.

10. The method of molding a glass-made optical component having a precise and complicated three-dimensional shape according to claim 8, wherein the weight of the molten glass gob introduced in the concave surface of the female mold is 8 to 70 times heavier than the weight of the glass-made optical component formed in the molding mold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 is a schematic diagram showing a mold for molding and a manufacturing method of a glass-made optical component of the present invention.

[0077] FIG. 2A shows an example of concentrically arranged molding molds. FIG. 2B shows an example of the molding molds arranged in parallel.

[0078] FIG. 3 shows an example of a detachable mechanism of the molding mold.

[0079] FIG. 4 shows an example of an additional space formed outside a space for the glass-made optical component of the molding mold.

[0080] FIG. 5 shows an example of a mold lock mechanism of a female mold a ring mold.

[0081] FIG. 6 shows an example of a bored hole formed in the molding mold.

[0082] FIG. 7 shows an example of a design drawing of the mold for molding of the present invention.

[0083] FIG. 8 shows an example of the glass-made optical component having a complicated shape formed by combining plural free-form surfaces and flat surfaces.

[0084] FIG. 9 shows an example of the glass-made optical component having a convex shape on both surfaces.

MODES FOR CARRYING OUT THE INVENTION

[0085] In the present invention, a mold 1 for molding a glass-made optical component 11 is produced by cutting and polishing a stainless steel according to a design drawing. A heat-resistant alloy having higher durability can be used for the molding mold 4 if required. As the design drawing (front view and plan view) of the mold concerning an embodiment of the present invention is shown in FIG. 7, the mold for molding the glass-made optical component of the present invention is comprised of a female mold 2, a molding mold 4, a ring mold 5 and a male mold 6. A concave surface 3 is formed on the female mold 2 to introduce a lump of molten glass (molten glass gob 7) made of a material of the glass-made optical component on the concave surface 3. Furthermore, a lower mold 4a of a molding mold 4 for molding a glass-made optical component 11 is formed on an outer peripheral portion of the female mold 2.

[0086] On the other hand, an upper mold 4b of the molding mold 4 is provided on a lower surface side of the ring mold 5 so that the upper mold 4b is located opposite to the lower mold 4a formed on the outer peripheral portion of the female mold 2. When the molten glass gob 7 is introduced into the concave surface 3 of the female mold 2, the ring mold 5 is first lowered and closely in contact with the female mold 2. Thus, a space sandwiched between the lower mold 4a of the molding mold 4 formed on the outer peripheral portion of the female mold 2 and the upper mold 4b of the molding mold formed on the lower surface portion of the ring mold 5 is formed. After the ring mold 5 is lowered, the male mold 6 having the convex surface is lowered. Thus, the molten glass gob 7 is pressed from above. The molten glass gob is raised upward along an inner surface of the concave surface 3 of the female mold 2 and reaches the outer peripheral portion while keeping sufficient fluidity, and the molten glass is injected into the space of the molding mold 4 sandwiched between the lower mold 4a and the upper mold 4b to form the glass-made optical component 11. At that time, the later described mold lock mechanism 13 is preferably used for certainly tightening the female mold 2 and the ring mold 5.

[0087] In the present invention, the mold 1 for molding the glass-made optical component 11 further has the features shown in FIGS. 2 to 6. The features will be explained by using each drawing.

[0088] FIG. 2A shows an example of the female mold 2 where four lower molds 4a of the molding mold 4 for forming the glass-made optical component 11 are concentrically provided on the outer peripheral portion of the concave surface 3 of the female mold 2 around a center axis of the concave surface 3. Four upper molds 4b of the molding mold 4 are concentrically provided on the lower surface side of the ring mold 5 so as to be aligned with positions of the four lower molds 4a. Thus, this mold has a structure capable of simultaneously molding four glass-made optical components 11 by one press operation. Similarly, the number of the molding molds 4 can be increased to six or eight, for example. The present invention can contribute to increase the productivity of the same optical components. In some cases, when the molding molds 4 having different shapes are provided, plurality kinds of optical components can be molded by one press operation.

[0089] FIG. 3 shows the upper mold 4b of the molding mold 4 provided on the lower surface side of the ring mold 5. The upper mold 4b is fixed to the ring mold 5 by bolt-tightening or the like and the upper mold 4b has a structure detachable from the ring mold 5. Similarly, the lower mold 4a of the molding mold 4 also has a structure detachable from the female mold 2 by an arbitrary method such as bolt-tightening (not illustrated). Thus, it is possible to mold the optical components having various shapes by replacing the lower mold 4a of the molding mold 4 and the upper mold 4b of the molding mold 4 while the female mold 2, the male mold 6 and the ring mold 5 are not replaced. The above described features shows that the present invention is suitable for mass production or multi-kind and small-quantity production.

[0090] FIG. 4 shows the mold structure having a space (main space) 9 sandwiched by the lower mold 4a and the upper mold 4b of the molding mold 4 (i.e., space 9 having the shape corresponding to the shape of the glass-made optical component 11) and further having an additional space 12 formed outside the space 9. If the additional space 12 is not provided, the glass-made optical component 11 may become a defective depending on the shape of the optical component since the molten glass gob 7 may not flow to the corners of the space 9 having the shape corresponding to the shape of the glass-made optical component 11 while forming a clearance. When the additional space 12 is provided, the molten glass gob 7 can be surely injected and filled to at least the corners of the space 9 having the shape corresponding to the shape of the glass-made optical component 11.

[0091] FIG. 5 shows that the mold structure has the mold lock mechanism 13 for tightening the female mold 2 and the ring mold 5 with each other. When the molten glass gob is injected, the space between the female mold 2 and the ring mold 5 is expanded and the clearance is easily formed. However, when the mold lock mechanism 13 is provided, occurrence of the dimensional defects of the glass-made optical component 11 can be prevented by suppressing the clearance.

[0092] FIG. 6 shows an example of the mold where a bored hole 14 is formed on the upper mold 4b of the molding mold 4 for releasing the air pressed by the molten glass gob 7 from the space 9 which has the shape corresponding to the shape of the glass-made optical component 11 during the pressing process. When the mold has the structure of releasing the air existed in the space 9 from the bored hole 14, it is expected that the occurrence of the shape defects can be prevented and the dimensional precision of the optical component can be increased. In FIG. 6, the inner diameter of the bored hole 14 is specified to 0.3 mm.

[0093] Next, the manufacturing method of the glass-made optical component concerning the present invention is the manufacturing method of molding a glass-made optical component having a precise and complicated three-dimensional shape by using the above described mold for molding the glass-made optical component. The explanation will be made by using FIG. 1 (and FIG. 4). A glass-made optical component having precise and complicated three-dimensional shape can be manufactured by: [0094] (1) introducing the molten glass gob 7 into a central part of the concave surface 3 of the female mold 2 on which the lower mold 4a of the molding mold 4 for molding the glass-made optical component 11 is provided at the outer peripheral portion; [0095] (2) lowering the ring mold 5 to be closely in contact with the female mold 2 so that the upper mold 4a of the molding mold 4 formed on a lower surface of the ring mold is closely in contact with the lower mold 4b of the molding mold 4 formed on the outer peripheral portion of the female mold to form a space 9 in the molding mold, the space 9 having the shape corresponding to the shape of the glass-made optical component 11; [0096] (3) pressing the molten glass gob 7 introduced into the central part of the concave surface 3 of the female mold 2 from above by the male mold 6 having the convex surface; [0097] (4) further pressing the molten glass gob 7 by the male mold 6 so that the molten glass gob 7 flows upward along an inner surface of the concave surface 3 of the female mold 2 and the molten glass gob 7 is injected into the space 9 formed in the molding mold (alternatively, space of both the space 9 and the additional space 12 formed outside the space 9) through an inlet 8 of the molten glass gob; [0098] (5) pulling the male mold 6 and then the ring mold 5 upward after the temperature of the molten glass gob injected into the molding mold 4 becomes equal to or lower than an annealing point of the molten glass and the molten glass is solidified; and [0099] (6) removing a solidified glass molded body 10 formed in the space of the female mold 2, the male mold 6, the ring mold 5 and the molding mold 4 and then cutting the molded glass-made optical component 11 formed in the molding mold.

[0100] In the above described processes, it is important that the pressing process is continued until the temperature of the molten glass gob 7 injected into the molding mold 4 becomes equal to or lower than the annealing point of the molten glass. A molded article having high dimensional precision can be obtained by the pressing the glass for 10 to 30 seconds, for example, for continuously applying the pressure to the glass until the glass is solidified. Since the article primary obtained by the above described method is the glass molded body 10 formed in the female mold 2, the male mold 6, the ring mold 5 and the molding mold 4, the process of cutting the glass-made optical component 11 from the molded body 10 as the final product is required. If required, grinding process and polishing process of the cut surface and end surface are performed after the cutting process in some cases.

[0101] In the method of manufacturing the glass-made optical component of the present invention, the weight of the molten glass gob 7 introduced in the concave surface 3 of the female mold 2 is preferably 6 to 70 times, more preferably 8 to 70 times, heavier than the weight of the glass molded body formed in the molding mold 4. When the weight ratio is specified as described above, the flow of the molten glass gob 7 can be kept sufficiently and the molten glass gob 7 can be surely injected into the space 9 (alternatively, the space of both the space 9 and the additional space 12 formed outside the space 9) for obtaining the glass-made optical component 11 through the inlet 8 of the molten glass gob. If the weight is less than 6 times, the flow cannot be kept sufficiently, and thus the glass-made optical component cannot be molded. If the weight exceeds 70 times, the molten glass gob flows out from the space between the ring mold and the male mold, and thus the pressing pressure becomes insufficient.

[0102] In the mold for molding the glass-made optical component and the manufacturing method of the present invention, the pressing between the female mold 2 and the male mold 6 is performed for making the molten glass gob 7 flow, and thus the molten glass gob 7 is injected into the space 9 formed by the molding mold 4 provided on the peripheral portion of the female mold 2 and the lower surface of the ring mold 5 to obtain the final product 11. In this respect, the present invention is completely different from the mold and the manufacturing method of the conventional direct press method where the final product is simply and directly pressed by the female mold and the male mold. However, with respect to the point that the molten glass gob 7 is pressed by the female mold 2 and the male mold 6, the present invention takes over the advantage of the direct press method where the cycle time of the pressing process is short. Thus, it can be said that the present invention is the manufacturing method suitable for mass producing a glass-made optical component having precise and complicated three- dimensional shape.

WORKING EXAMPLES

[0103] A glass-made optical component having a precise three-dimensional shape was molded by using the above described mold and the above described molding method. The working examples are shown in Table 1.

[0104] As for the glass, a general borosilicate glass having the thermal expansion coefficient of approximately 5510.sup.7/ C. was used. The temperature of the molten glass gob was approximately 1,000 C. when the molten glass gob was introduced into the female mold. Note that the annealing point of this glass is approximately 500 C.

TABLE-US-00001 TABLE 1 weight W1 of glass-made weight W2 of pressing pressing Working optical molten glass gob pressure time outer example component (g) (g) W2/W1 (Mpa) (sec) moldability appearance Group 1 complicated shape 3.1 combining plural insufficient insufficient free-form surfaces 100 7 23 injection shape and flat surfaces 200 13 23 good good 15 g 1 300 20 23 good good 500 33 25 good good 700 47 25 good good 15 g 900 60 25 good good 1100 73 27 X problem in X crack releasability Group 2 complicated shape 100 2 3.7 23 X injection combining plural impossible free-form surfaces 300 5 23 and flat surfaces insufficient insufficient 15 g 4 injection shape 500 8 25 good good 60 g 700 12 25 good good 900 15 25 good good 1100 18 27 good good Group 3 convex shape on 100 1 4.2 23 X both surfaces injection 15 g 8 impossible 300 3 23 insufficient insufficient injection shape 120 g 500 4 23 insufficient insufficient injection shape 700 6 25 good good 900 8 25 good good 1100 9 27 good good
The group 1 shows the molded result using the design drawing shown in FIG. 7. In this example, only one molding mold was provided and a glass-made optical component having a complicated shape formed by combining plural free-form surfaces and flat surfaces as shown in FIG. 8 was molded. A weight W1 of the molded glass-made optical component was approximately 15 g. As already described, the glass-made optical component can be obtained by removing the glass molded in the female mold, the male mold, the ring mold and the molding mold from these molds, and cutting the portion of the glass-made optical component (i.e., final product) from the molded glass removed from the molds. In a series of tests of the group 1, the moldability and the outer appearance of the molded glass-made optical component were evaluated by changing a weight W2 of the molten glass gob introduced into the concave surface of the female mold. The pressing pressure applied from the male mold to the molten glass gob was approximately 3.1 MPa, and the pressing time was approximately 23 to 27 seconds in accordance with the weight of the molten glass gob.

[0105] When the weight of the molten glass gob was 100 g (W2/W1 was approximately 7), although the molten glass gob reached the inlet 8 of the molten glass gob, the molding mold was not sufficiently filled with the molten glass gob. Therefore, the glass-made optical component could not be obtained. This is because the weight and the heat capacity of the molten glass gob was small and thus the heat was suddenly taken during the pressing process. Thus, fluidity was lost and the molten glass was solidified. On the contrary, when the weight of the molten glass gob was increased to 1,100 g (W2/W1 was approximately 73), the volume of the molten glass gob was too large with respect to the volume of the space formed by the female mold 2, the ring mold 5, the male mold 6 and the molding mold 4 for molding the glass molded body 10 when the molten glass gob was introduced and pressed by the male mold. Thus, the molten glass gob 7 entered in the clearance between the ring mold 5 and the male mold 6 and the lowering of the male mold 6 was obstructed. Therefore, the pressing could not be continued. In this case, since the male mold 6 could not be lowered to the predetermined position, the balance of the thickness of the glass molded body 10 was lost, and the problem occurred when removed from the molding mold. Consequently, crack occurred on the glass molded body 10 including the glass-made optical component 11. In five examples where the weight of the molten glass gob was 200 g to 900 g, there was no problem in the moldability and the outer appearance of the obtained glass-made optical component was good. Here, the weight of the molten glass gob was controlled to a predetermined weight by a furnace for feeding the molten glass. The weight of the introduced molten glass gob was calculated by measuring the solidified glass molded body 10 by a balance after the pressing process. The same can be applied to the following working examples.

[0106] Similar to the group 1, the group 2 shows a result of molding glass-made optical components having a complicated shape formed by combining plural free-form surfaces and flat surfaces. In the group 2, four glass-made optical components were manufactured by one press operation by using the molding mold using the female mold as shown in FIG. 2A. In this case, the total weight of the four glass-made optical components was 415 g=60 g. Table 1 shows the result where the test was performed in six standards of the weight of the molten glass gob from 100 g to 1,100 g. When the molten glass gob was 100 g (W2/W1 was approximately 2), the molten glass did not reach even to the inlet of the molten glass gob, and it was impossible to mold the glass-made optical component. This is also because the weight and the heat capacity of the molten glass gob was small and thus the heat was suddenly taken during the pressing process. Thus, fluidity was lost and the molten glass was solidified before the molten glass gob reaches the inlet. When the molten glass gob was 300 g (W2/W1=5), although the molten glass passed through the inlet of the molten glass gob and injected into the space for molding the glass-made optical component, the amount was insufficient and the glass-made optical component was incompletely molded. When the molten glass gob was 500 g or more (W2/W1 was approximately 8 or more), sufficient amount of the molten glass was raised upward along the concave surface of the female mold, reached the inlet of the molten glass gob, and injected into the space for molding the glass-made optical component to fill the space. Thus, the moldability was good. As a result, the outer appearance of the obtained glass-made optical component was the designed shape. In the group 2, even when the weight of the molten glass gob was 1,100 g, since 4 times as much as molten glass was injected into the molding mold through the inlet of the molten glass gob compared to the group 1, the pressing could be performed by the male mold without problems.

[0107] The group 3 shows an example of molding glass-made optical components (weight of one component is 15 g) having a convex shape on both surfaces as shown in FIG. 9. In the group 3, eight glass-made optical components were manufactured by one press operation by concentrically providing eight molding molds formed by the female mold and the ring mold. In this case, the total weight of the eight glass-made optical components was 815 g=120 g. Table 1 shows the result where the test was performed in six standards of the weight of the molten glass gob from 100 g to 1,100 g. When the molten glass gob was 100 g (W2/W1 was approximately 1), the molten glass did not reach even to the inlet of the molten glass gob, and it was impossible to mold the glass-made optical component. When the molten glass gob was 300 g (W2/W1 was approximately 3) and 500 g (W2/W1 was approximately 4), although the molten glass passed through the inlet of the molten glass gob and injected into the space for molding the glass-made optical component, the amount was insufficient and the glass-made optical component was incompletely molded. When the molten glass gob was 700 g or more (W2/W1 was approximately 6 or more), sufficient amount of the molten glass was raised upward along the concave surface of the female mold, reached the inlet of the molten glass gob, and injected into the space for molding the glass-made optical component to fill the space. Thus, the moldability was good. As a result, the outer appearance of the obtained glass-made optical component was the designed shape. In the group 3, even when the weight of the molten glass gob was 1,100 g, since 8 times as much as molten glass was injected into the molding mold through the inlet of the molten glass gob compared to the group 1, the pressing can be performed by the male mold without problems.

[0108] In the above described tests, the molding mold having the space for forming the glass-made optical component and the additional space formed outside as shown in FIG. 4 was used. It was confirmed that higher shape accuracy of the glass-made optical component could be obtained by adopting such a configuration.

[0109] In addition, when a bored hole of approximately 0.3 mm is formed on the molding mold for releasing air as shown in FIG. 6, the shape accuracy could be further improved.

[0110] From the above described results, in the manufacturing method of the glass-made optical component of the present invention using the molding mold of the present invention, the following processes are considered to be performed that the molten glass gob is pressed by the male mold in a state that the molten glass gob have sufficient temperature and fluidity, the molten glass is raised upward along the concave surface of the female mold and reaches the inlet of the molten glass gob, the molten glass gob passes through the inlet of the molten glass gob and injected into the molding mold while keeping sufficient temperature and fluidity, and heat of the glass is taken in the molding mold and the glass is solidified, and thus the glass-made optical component having a target shape can be obtained. After the glass-made optical component is solidified in the molding mold, the pressed molten glass gob existed in the concave surface of the female mold is solidified. Thus, it is considered that the moldability, the shape accuracy of the glass-made optical component and releasability become the appropriate condition. In order to do that, as shown in Table 1, the weight of the introduced glass gob with respect to the product weight, the pressing pressure and the pressing time should be appropriately adjusted.

[0111] Although the present invention is explained in detail according to the embodiments and working examples, the present invention is not limited to the contents of the embodiments and working examples. The present invention can be carried out in other various styles.

DESCRIPTION OF THE REFERENCE NUMERALS

[0112] 1: example of mold for molding glass-made optical component of present invention

[0113] 2: female mold

[0114] 3: concave surface of female mold

[0115] 4: molding mold

[0116] 4a: lower mold of molding mold

[0117] 4b: upper mold of molding mold

[0118] 5: ring mold

[0119] 6: male mold

[0120] 7: molten glass gob

[0121] 8: inlet of molten glass gob

[0122] 9: space formed in molding mold

[0123] 10: glass molded body

[0124] 11: glass-made optical component

[0125] 12: additional space formed outside space 9

[0126] 13: mold lock mechanism

[0127] 14: bored hole

[0128] 15: lock bar

[0129] 16: rotary hook

[0130] 17: lock plate

[0131] 18: molding mold fixing bolt