JP2010105830A - Method for producing optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold a glass material at a reduced pressure accomplished by endowing a glass with a high fluidity. <P>SOLUTION: There is provided a method for producing an optical device by disposing a glass material 20 between a pair of a cope 25 and a drag 26 opposed to each other and subjecting the glass material to heat press, which method comprises the heating step of heating the temperatures of the cope 25, the drag 26, and the glass material 20 to the same temperature so that the temperature lies between the yield point and below the softening point, the heat retention step of retaining them at the temperature for a specified time T (min) or longer till the fluidity of the glass material 20 becomes uniform after the temperatures of the cope 25 and the drag 26 and the glass material 20 are equalized, and the press step of press molding the glass material 20 after it is retained at the specified temperature for the specified tim (min) or longer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical element, in which a glass material is disposed between a pair of opposed molds and heated and pressed to manufacture an optical element.

  Conventionally, in order to shorten the molding cycle time and improve productivity and to obtain a highly accurate molded product, when the molding material reaches a desired temperature, it immediately enters the pressing process and molding is performed with a high load. It was. However, when a high pressing force is applied to the molding material in a state where the fluidity is poor, the shape that can be molded is restricted, and cracks and internal stress are generated.

In order to solve this problem, for example, Patent Document 1 proposes a technique in which a heated glass material is formed by its own weight, then the upper mold is removed, and then a molded product is taken out.
JP-A-1-257140

  However, in Patent Document 1, it must be heated to a temperature at which it is deformed by its own weight. That is, the temperature of the glass material must be raised to a temperature at which the glass material is deformed by its own weight. There was a problem that a desired shape could not be obtained unless it was used.

  The present invention has been made to solve such a problem, and by forming a glass material at a low pressure after imparting high fluidity to the glass, the shape of the molded product is greatly different and a large amount of deformation is required. An object of the present invention is to provide a method for manufacturing an optical element corresponding to the above.

In order to achieve the object, the invention according to claim 1
In the method of manufacturing an optical element in which an optical element is manufactured by placing a glass material between a pair of opposingly arranged molds and heating and pressing,
A heating step of heating the mold and the glass material to the same temperature so that the temperature is above the yield point and below the softening point;
After the temperature of the mold and the glass material reaches the isothermal temperature, a heating and holding step of maintaining the isothermal temperature for a predetermined time or more until the flowability of the glass material is uniform,
And a pressing step of pressing the glass material after holding for the predetermined time or more.

The invention according to claim 2 is the method of manufacturing an optical element according to claim 1,
The glass material has a shape having at least one of a side and a diameter,
Among the linear dimensions of at least one of the sides and the diameter, the shortest dimension is d (mm),
When the predetermined time is T (min),
T (min) = 3.4615d-4.1026
It has the relationship of these.

The invention according to claim 3 is the method of manufacturing an optical element according to claim 1,
The minimum thickness dimension of the glass material is d (mm),
When the predetermined time is T (min),
T (min) = 3.4615d-4.1026
The invention according to claim 4 is characterized in that in the method of manufacturing an optical element according to any one of claims 1 to 3,
The shape of the glass material is a cylindrical shape.

The invention according to claim 5 is the method for manufacturing an optical element according to any one of claims 1 to 3,
The glass material has a spherical shape.

  According to the present invention, a glass material can be formed at a low pressure by imparting high fluidity to glass. Accordingly, it is possible to cope with a case where the shape of the molded product is greatly different and a large amount of deformation is required.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of an optical element manufacturing apparatus.
The manufacturing apparatus 10 includes a molding chamber 12 whose periphery is covered with a casing 11, and a press mechanism 15 that is disposed in the molding chamber 12 and presses a mold set 14. The molding chamber 12 is provided with a carry-in port and a carry-out port (not shown) through which the mold set 14 is carried in and out.

  A heater 18 is embedded in the side wall of the housing 11 that covers the molding chamber 12. The heat from the side wall is moved by convection and radiation to uniformly heat the indoor atmosphere and the mold set 14. Thus, the heater 18 can set the temperature of the mold set 14 and the glass material 20 inside thereof to the same temperature (equal temperature). The heating device is not limited to heating by the heater 18, but may be any device that can heat the mold set 14 and the glass material 20 at the same temperature.

Further, a gas inlet 22 and a gas outlet 23 are provided on the upper wall of the housing 11. A non-oxidizing gas such as nitrogen gas (N ₂ gas) is introduced from the gas inlet 22, and the atmosphere in the molding chamber 12 can be filled with nitrogen gas. Thus, contact between the mold set 14 and the glass material 20 and oxygen is cut off, and oxidation of the glass material 20 and the like can be prevented.

  The press mechanism 15 has an air cylinder 16 and a pressure plate 17 fixed to the tip of the operating rod 16a. The pressure plate 17 is driven in the vertical (opposite) direction by the air cylinder 16. Then, by the lifting and lowering operation of the pressure plate 17 by the air cylinder 16, operations such as clamping and clamping of the mold set 14 are performed.

Next, the configuration of the mold set 14 will be described.
The mold set 14 includes an upper mold (molding mold) 25, a lower mold (molding mold) 26, and a cylindrical sleeve (body mold) 27. The upper mold 25 and the lower mold 26 are fitted and inserted from both ends of the sleeve 27 so that the molding surfaces of the upper mold 25 and the lower mold 26 face each other. The upper mold 25 is slidable in the axial direction of the sleeve 27. Further, the glass material 20 described above is arranged between the molding surface of the upper mold 25 and the molding surface of the lower mold 26. The upper mold 25, the lower mold 26, and the sleeve 27 are finished by polishing a cemented carbide such as tungsten carbide (WC).

  In the present embodiment, as the glass material 20 described above, a commercially available cylindrical optical glass that is inexpensive and has high weight accuracy is used. This is because, if the shape is cylindrical, the management dimensions are two, that is, the diameter and the height, and therefore volume management is easier compared to a rectangular parallelepiped. However, the glass material 20 is not limited to a cylindrical shape.

2A to 2G are diagrams illustrating an example of the appearance of the glass material 20.
The shape of the glass material 20 ₁ shown in FIG. 2 (A), the dimensions of height (side) b than dimensions of diameter a is longer elongated cylindrical shape. The glass material 20 ₁ side and the shortest dimension in the diameter (minimum thickness) d of, the diameter a.

The shape of the glass material 20 ₂ shown in FIG. 2 (B) is a thin-walled cylindrical short dimension of height (side) b than the size of the diameter a. The glass material 20 ₂ sides and the shortest dimension in the diameter (minimum thickness) d of, a height b.

Furthermore, the shape of the glass material 20 ₃ shown in FIG. 2 (C), and the dimensions of the height (side) b of the diameter a of equal cylindrical shape. The glass material 20 _third side and the shortest dimension in the diameter (minimum thickness) d of, may be set to either the diameter a, the height b.

The shape of the glass material 20 ₄ shown in FIG. 2 (D), the long dimension of the width (side) dimension and depth (side) g dimensions are equal and height than the width dimension e of e (sides) f It is a rectangular parallelepiped (square prism shape). The shortest dimension in the glass material 20 ₄ sides (minimum thickness) d of, may be set to either the width e, depth g.

The shape of the glass material 20 ₅ shown in FIG. 2 (E), the width (side) depth than the size of the e (side) dimension of g is short and the depth (side) g Dimensions height than the (side) It is a rectangular parallelepiped (square column shape) with a short dimension of f. The shortest dimension in the glass material 20 ₅ sides (minimum thickness) d of, the height f.

Furthermore, the shape of the glass material 20 ₆ shown in FIG. 2 (F), the width (side) Dimensions and height of e (sides) f dimension and depth (side) g dimensions and are all equal cubes (cubes shape) It is. The shortest dimension (minimum thickness) in the sides of the glass material 20 ₆ d, the width e, height f, may be set to any depth g.

The shape of the glass material 20 ₇ shown in FIG. 2 (G) is a spherical shape with a diameter h. The glass material 20 ₇ of the shortest dimension in the diameter (minimum thickness) d of, the diameter h. The glass material 20 may have a polyhedral shape.

  The glass material 20 having such a shape is disposed between the molding surfaces of the upper mold 25 and the lower mold 26. In the present embodiment, in consideration of the stability of the glass material 20 on the lower mold 26, the cylindrical plane of the glass material 20 is placed on the molding surface of the lower mold 26.

Next, the manufacturing process of this embodiment will be described.
In FIG. 1, the inside of the molding chamber 12 is first replaced with nitrogen gas (N ₂ gas), and the air cylinder 16 is set in a retracted state so that no load is applied to the glass material 20 other than the weight of the upper mold 25. .

Next, the heater 18 is energized, and the mold set 14 and the glass material 20 are heated to the same temperature so that the temperature is higher than the yield point and lower than the softening point.
Here, the yield point is used to mean a temperature at which expansion stops apparently in a thermal expansion curve, for example. This is regarded as a temperature corresponding to a viscosity of approximately 10 ¹⁰ to 10 ¹¹ dPa · s. The softening point is used, for example, to mean a temperature at which glass begins to significantly soften and deform due to its own weight, and is regarded as a temperature corresponding to a viscosity of about 10 ^7.6 dPa · s (http: /// /Www.hoya-opticalworld.com/japan/PD/pd5_term/t004.html).

  Thus, by heating the atmosphere in the molding chamber 12 with the heater 18, it is possible to heat evenly without causing temperature unevenness. Note that the order of the replacement of the nitrogen gas in the molding chamber 12 and the energization of the heater 18 can be selected first as necessary.

  Here, a good molded product cannot be obtained at such a high temperature that the shape of the glass material 20 is deformed by its own weight or is deformed by the weight of the upper mold 25. This is because if the heating temperature is too high, temperature unevenness is likely to occur in the glass material 20, and since the glass material 20 is deformed first after being softened, the gas is trapped and a desired shape cannot be obtained. Similarly, even if the mold set 14 and the glass material 20 reach the same temperature and immediately shift to the pressing process, a good molded product cannot be obtained.

At that time, the soaking is not yet promoted, and the fluidity of the glass material 20 is not uniform as a whole.
Next, after the temperature of the mold set 14 and the glass material 20 reaches the same temperature, the temperature is held for a predetermined time T (min) or more. In the present embodiment, the glass material 20 can be obtained with good fluidity (consistent in fluidity) by being held for a predetermined time or more after the glass material 20 reaches the same temperature.

  That is, if the temperature is not maintained for a predetermined time or more at the same temperature, for example, a gas reservoir is formed between the flat portion of the end surface of the columnar glass material 20 and the concave molding surface (see FIG. 1) of the upper mold 25 facing this. May occur. On the other hand, by providing a holding time of a predetermined time or more, this gas accumulation does not occur, and press molding can be performed at a low pressure.

The predetermined time T (min) described above varies depending on the minimum thickness dimension d of the glass material 20. However, as a result of the experiment, it has been found that good results can be obtained with respect to the fluidity of the glass material 20 if it is maintained for a predetermined time T (min) or more shown in Table-1.

FIG. 3 shows the relationship between the minimum thickness d (mm) of the glass material 20 shown in Table 1 and the predetermined time T (min).
From FIG. 3, the following relationship can be derived between the minimum thickness dimension d (mm) and the predetermined time T (min). That is, when the minimum thickness dimension of the glass material 20 is d (mm), the predetermined time T (min) has a relationship of T = 3.4615d−4.1026.

  Thus, the fluidity | liquidity of the glass raw material 20 can be accelerated | stimulated by heating the glass raw material 20 to isothermal temperature, and hold | maintaining it for the predetermined time T or more (fluidity becomes uniform). That is, if the glass material 20 is maintained at a constant temperature for a predetermined time T or more, the fluidity of the glass material 20 is maintained in a stable state.

  That is, when the glass material 20 is heated, heat is transferred from the outer periphery to the inside, and there is no temperature difference between the outer periphery and the inside (center) of the glass material 20, and the fluidity of the glass material 20. Becomes stable.

  Therefore, the minimum thickness dimension d along the direction in which heat is transferred earliestly from the outer peripheral portion of the glass material 20 to the inside (center) is related to the time until the fluidity of the glass material 20 is stabilized. That is, the shorter the minimum thickness dimension d of the glass material 20, the sooner the fluidity of the glass material 20 becomes stable.

  Note that the fluidity of the glass material 20 is improved even within the predetermined time T (min), but at this point, the glass material 20 is in a state of being hardly deformed even if the weight of the upper mold 25 is added.

  Therefore, after maintaining the predetermined time T (min) or more until the fluidity of the glass material 20 is improved, the pressure plate 17 is lowered by the air cylinder 16 and the glass material 20 is pressed and deformed. Thereby, a good optical element without cracks can be obtained. Further, the optical element to be manufactured is not limited to a mirror surface that does not require a polishing step, but can also be used for manufacturing an optical element material provided with a polishing allowance.

  In the present embodiment, when the glass material 20 is heated, the weight of the upper mold 25 is added to the glass material 20, but the glass material can be obtained by integrally connecting the pressure plate 17 and the upper mold 25. The weight of the upper die 25 may not be added to 20. This makes it easier to control the heating of the glass material 20.

  FIG. 4 is a diagram showing a relationship (comparative example) between the heating temperature of the normal glass material 20, the molding pressure, and the holding time. Moreover, FIG. 5 is a figure which shows the relationship between the heating temperature of the glass raw material 20 by this embodiment, forming pressure, and holding time.

In the comparative example of FIG. 4, after the glass material 20 reaches the set temperature, the molding is performed immediately at the molding pressure P ₁ in order to shorten the cycle time after holding for T ₁ hour. On the other hand, according to FIG. 5, after the glass material 20 reaches the set temperature, the glass material 20 is molded at the molding pressure P ₂ after being held for a relatively long T ₂ time.

T ₁ times of the comparative example, the time to wait until the temperature of the glass material 20 is a set temperature. On the other hand, T ₂ time of this embodiment is time for waiting until the fluidity | liquidity of the glass raw material 20 becomes good, and is corresponded to the holding time more than predetermined time T (min) mentioned above.

Moreover, in the comparative example, the molding is first performed at a high molding pressure P ₁ and then molded at the next lowest pressure P ₁ ′. Therefore, there is a possibility that cracking or distortion occurs when molding the glass material 20 at a high molding pressure P _1. In contrast, in the present embodiment, the molding at a low constant molding pressure P ₂ than the molding pressure P ₁ was held long T ₂ hours than T ₁ times. Moreover, molding pressure _{P 2} was 1/10 or less of the molding pressure _{P 1.}

4 and 5, the molding pressure is still applied after the heating temperature is lowered in order to maintain the pressed state until the shape of the glass material 20 is determined to some extent.
According to FIG. 5, it can be seen that if the glass material 20 is heated to an equal temperature and then molded after a certain long holding time (T ₂ ), it can be molded at a low pressure (P ₂ ).

  In the single-piece apparatus configuration shown in FIG. 1, the holding time longer than the predetermined time (Tmin) described above becomes longer, which affects the molding cycle time. For this reason, an apparatus capable of forming a large number of pieces at a time is used, or a plurality of mold sets 14 are preheated in accordance with a forming interval, and are sequentially formed as the holding time ends for a predetermined time (Tmin) or more. By taking the configuration to perform, molding can be performed efficiently.

  According to this embodiment, the temperature of the mold set 14 and the glass material 20 is heated to an equal temperature so as to be equal to or higher than the yield point and lower than the softening point, and the glass material 20 is held at the temperature for a predetermined time Tmin or longer. The glass material 20 can be formed at a low pressure with high fluidity. Accordingly, it is possible to perform complicated deformation at low pressure while suppressing unevenness of the material, and it is possible to obtain a good optical element free from cracks and internal distortion generated by molding at high pressure.

It is a figure which shows the whole structure of the manufacturing apparatus of an optical element. (A)-(G) is a figure which shows the external appearance of a glass raw material, respectively. It is the figure which made the relationship between the thickness of a glass raw material, and predetermined time a graph. It is a figure which shows the relationship (comparative example) of the heating temperature of a normal glass raw material, forming pressure, and holding time. It is a figure which shows the relationship between the heating temperature of a glass raw material by this embodiment, forming pressure, and holding time.

Explanation of symbols

Manufacturing apparatus 10 the optical element 11 the housing 12 forming chamber 14 type set 15 press mechanism 16 the air cylinder 16a actuating rod 17 the pressure plate 18 heater 20 glass material ₂₀ 1 to 20 ₆ the glass material 22 gas inlet 23 gas outlet 25 Upper mold 26 Lower mold 27 Sleeve

Claims (5)

In the method of manufacturing an optical element in which an optical element is manufactured by placing a glass material between a pair of opposingly arranged molds and heating and pressing,
A heating step of heating the mold and the glass material to the same temperature so that the temperature is above the yield point and below the softening point;
After the temperature of the mold and the glass material reaches the isothermal temperature, a heating and holding step of maintaining the isothermal temperature for a predetermined time or more until the flowability of the glass material is uniform,
And a pressing step of press-molding the glass material after holding for the predetermined time or longer. The glass material has a shape having at least one of a side and a diameter,
Among the linear dimensions of at least one of the sides and the diameter, the shortest dimension is d (mm),
When the predetermined time is T (min),
T (min) = 3.4615d-4.1026
The method for manufacturing an optical element according to claim 1, wherein: The minimum thickness dimension of the glass material is d (mm),
When the predetermined time is T (min),
T (min) = 3.4615d-4.1026
The method of manufacturing an optical element according to claim 1, wherein: The method of manufacturing an optical element according to claim 1, wherein the glass material has a cylindrical shape. The method of manufacturing an optical element according to claim 1, wherein the glass material has a spherical shape.