JPH0372016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for molding optical parts, and more particularly to a method for melting and press-molding glass raw materials.

[Prior Art of the Invention] As a method for manufacturing optical lenses such as camera lenses and pick-up lenses for compact discs,
There are two methods: a cutting-polishing process and a press-molding method in which the glass is placed in a mold member. The press molding method has many problems that need to be solved, such as material selection for mold parts, processing of the mold surface, and temperature control of the mold and glass, but it has advantages in terms of manufacturing costs and the ability to easily mold lenses with complex shapes. Development has been progressing in recent years.

[Problems with the prior art] In the press molding method, a preformed semi-finished lens (hereinafter referred to as a blank) is placed in a mold member, the blank and the mold member are heated simultaneously or separately to a press temperature, and the mold is formed by press forming. There is a method of molding a lens by press-transferring an optically functional surface formed on a member, and a method of melting a glass raw material and then putting an appropriate amount of it into a mold member and press-molding it.

A molding method using the aforementioned blank is disclosed in Japanese Patent Publication No. 61-32263, and a method of molding from raw materials is disclosed in Japanese Patent Publication No. 56-378.

The significance of glass press molding in a glass mold member is that the press of the mold member allows molding by pressure transfer of the mold surface of the same mold onto the glass, making it possible to produce a large number of lenses with the same precision in a short time. Therefore, compared to the conventional cutting-polishing method, manufacturing time can be shortened and costs can be reduced. In the case of an aspherical lens, there are problems with the polishing tool, polishing time, etc. for polishing the aspherical surface.

In addition, in the case of glass press molding, in the case of the method using the blank described above, it is necessary to make the shape of the blank and the shape and precision of the final product on the surface of the blank, and the equipment and equipment required for blank processing are required.
It is difficult to pursue cost benefits due to process and blank processing time.

Furthermore, a method of heating and press forming by melting glass raw materials is also disclosed in the aforementioned Japanese Patent Publication No. 56-378, but this invention maintains the temperature of the metal mold constant above the transition point and below the softening point of the glass to be formed. , a molding method characterized by placing the fluid glass in the metal mold, molding it under pressure, and maintaining this state for 20 seconds or more until the temperature distribution of the molded glass becomes uniform. It is.

In this molding method, the mold temperature of the mold member is heated above the transition point of the glass and the fluid glass is pressure molded, so the high mold temperature causes the problem that the glass fuses to the mold surface. Because the mold temperature during pressure molding is extremely high, for example, when molding a lens with a thick center wall, there is a problem in removing distortion when the lens is cooled down after being pressed at high temperature, and it is also difficult to withstand the high temperatures mentioned above. There are problems such as material selection for the mold member to be obtained and shortening of the mold life of the mold member. This invention also discloses a "molding method for high-precision lens materials," which is a method for eliminating sink marks and obtaining lens materials with a tolerance of 3/100 mm or less, and is suitable for lenses with surface precision on the wavelength order, such as photographic lenses. There is no disclosure of a method for obtaining directly from molten glass raw materials.

[Problems to be Solved by the Present Invention] The present invention proposes a molding method that solves the above-mentioned problems. In particular, glass powder raw materials are heated and melted, and the molten glass is put into a mold and press-molded. By doing so, it is possible to directly obtain high-precision optical parts such as photographic lenses without post-processing, and we propose a molding method that can be expected to be effective in mass production.

Furthermore, the present invention prevents the glass from adhering to the mold surface when molten glass is put into a mold member and press-molded, and the temperature range of the glass and mold is set so that the same mold member can be repeatedly press-molded. suggest something.

[Means for Solving the Problems] The present invention is characterized by passing through the following steps in order to solve the above-mentioned problems. First, (a) glass raw materials are heated to melt the glass. In this step, when the final product is, for example, a lens for a single-lens reflex camera, powder of a glass raw material suitable for glass for the lens is placed in a crucible and heated to melt. During this melting process, air bubbles in the molten glass are defoamed and stirred to create a highly homogeneous glass without bubbles.

(b) Next, adjust the mold temperature. The mold members are made of materials such as cemented carbide, and are used as an upper mold, a lower mold, and depending on the shape of the lens, a body mold located on the side of the upper mold and the lower mold, and when the mold is closed, the spatial shape lens inside the mold is The inner surface of the mold is mirror-finished to form the optically functional surface of the lens. The precision of the optically functional surface of the mold is that the optically functional surface of the mold is pressed against the glass and the precision of the mold surface is transferred to the glass surface to become the lens surface, so it is equivalent to or higher than the required surface precision of the lens. Finish. The temperature of the mold member is adjusted within the range of the glass transition point of the glass raw material and a temperature 100°C lower than the glass transition point.

When liquefied glass is placed in a mold member adjusted to the above temperature, the glass is rapidly cooled and the glass temperature drops, while the surface temperature of the mold member, especially the mold, rises, the mold temperature rises, and the temperature difference between the glass and the mold rapidly decreases. to shrink.

(c) In the process of placing glass in a mold and rapidly reducing the surface temperature of the glass, primary pressure is applied to either the upper mold, the lower mold, or both the upper mold and the lower mold. In this pressurizing process, the surface temperature of the glass rapidly decreases, which prevents the phenomenon of fusion with the mold.Also, the surface deterioration layer can be suppressed to an optically acceptable range, and the glass flows due to the pressurization of the mold members. The molten glass changes shape to follow the spatial shape of the mold, forming a lens shape. This primary pressurization is performed until the glass temperature reaches a viscosity of 10 ^{8.5 to 11} poise, and the glass is pressed to a shape similar to the final product so that the wall thickness is 5% or more larger than that of the final product.

If the glass is formed into an approximate shape until the glass temperature reaches a temperature that indicates a viscosity of ^{108.5 to 11} poise, it will take a short time to process the glass into a shape that is 5% thicker than the final product. It was preferable for deformation due to

Here, as mentioned above, glass produces sink marks as it cools, but by pressurizing the glass to a temperature at which it exhibits a viscosity of ^{108.5 to 11} poise, it is possible to significantly reduce the sink marks. The present inventors have found that the remaining sink marks can be sufficiently eliminated by leaving 5% or more, preferably 1% or more, and pushing out the remaining push margin in the next step described below. A possible way to further reduce sink marks is to raise the mold temperature, but the mold temperature is the glass transition point (Tg, 10 ¹³ poise) of the glass to be formed.
If molding was started at a temperature higher than that, fusion tended to occur, and conversely, if molding was started at a mold temperature of Tg-100°C or lower, sink marks became large and could not be eliminated in the next process. For the above reasons, it is preferable to set the mold temperature at the start of molding to Tg - 100°C from the glass transition temperature (Tg) of the glass to be molded. Furthermore, by keeping the mold temperature at the above-mentioned temperature, it is not only effective in preventing sink marks and fusion, but also keeps the mold temperature at the temperature required for molding (10 ^{8.5 to} 10 ¹¹ poise depending on the viscosity of the glass to be molded) during pressurization. Since the temperature does not rise above (corresponding to the temperature of

(d) Further, following the above-mentioned primary pressurization, pressure is applied to the mold member to mold the glass into the final product shape.

The glass temperature at the end of the first pressurization mentioned above is 10 ^8.5
The temperature indicates a viscosity of ^~11 poise, but the temperature at the time of pressurization of the final product shape is the temperature of the members constituting the mold member,
That is, while maintaining the temperature of the member in contact with the glass within a temperature range in which the glass exhibits a viscosity of ^{108.5 to 11} poise, the temperature difference between the mold members is at least 20 poise.
The temperature of the mold member is controlled so that it converges within ℃. As a result, the glass temperature inside the mold member is 10 ^8.5
kept within a temperature range exhibiting a viscosity of ^~11 poise,
Furthermore, at the end of the second pressurizing process, the temperature difference inside the glass is kept within 20°C, and the final product shape is formed.

If the viscosity of the glass in the second pressing step was less than 10 ^8.5 , excellent surface transferability could not be obtained due to deformation of the glass under its own weight and increase in sink marks during cooling. On the other hand, if the viscosity of the glass was greater than 10 ¹¹ , the time required for molding would be enormous, and the glass would partially recover its elasticity after pressing, making it impossible to obtain a good surface. Furthermore, if there is a temperature difference between the members of the mold, especially the mold member having an optical function surface, at the end of the second pressurizing step, a similar temperature difference will occur in the glass that is in contact with the mold member. For this reason, due to the difference in thermal expansion inside the glass,
Warping occurs during cooling shrinkage to room temperature, which causes deterioration of the precision of the optical functional surface of the glass.However, by the end of the second pressurizing process, the temperature difference between the mold members should be kept within 20°C, and the following steps described below should be carried out. The present inventors have found that by performing the cooling step of the process, the warpage caused in the second pressurizing step can be eliminated.

(e) When the above-mentioned pressure molding of the final product shape is completed, a cooling process begins in which the mold member is cooled and the product in the pressure molded shape is taken out from the mold member. This cooling step has the meaning of a preparatory step for the annealing operation for removing internal strain and adjusting the refractive index of the final product glass.

The temperature of the glass and mold during the second pressurization was 10 ^8.5
Since the temperature is between ¹¹ poise and 11 poise, if the molded product is removed from the mold at this temperature, the shape of the molded product will be deformed and distortion will occur as it cools. For this reason, the molded product is cooled together with the mold to prevent deformation, but favorable results were obtained in the annealing process by keeping the mold member and glass temperature approximately the same and cooling at the same rate in the cooling process before the annealing process. . Therefore, the present inventor considered dividing the cooling process after the above-mentioned secondary pressurization process into two processes. That is, in the first step of cooling, the temperature of the glass within the range of glass viscosity ^{108.5 to 11} poise and the mold are controlled to be the same temperature. Furthermore, as a second step, the glass and the mold are kept at the same temperature and cooled to the take-out temperature or annealing temperature.

A particularly important condition is that during the primary cooling, the temperatures of the glass and mold members are controlled to almost the same temperature while the temperature of the glass and mold is cooled from the glass viscosity of ^{108.5 to} 11 poise to the temperature of the glass transition point. Thereafter, the mold member and the glass were cooled at the same cooling rate from the glass transition point to the glass viscosity of ^1014.5 poise.

For optical parts molded without performing such a cooling step, if the next step of fine annealing is performed to obtain the desired refractive index, the shape obtained up to the second pressurizing step, especially the optical function surface, will change. There was a deviation of ±5 or more Newton rings in the surface accuracy,
Optical parts molded through the cooling process have almost no residual strain due to molding or cooling, and even if the fine annealing is performed, the shape and surface precision obtained up to the cooling process will not be impaired. I stopped talking.

[Description of Examples] Example 1 Nd= suitable for a camera lens, for example, a single-lens reflex camera lens manufactured and sold by the present applicant.
A lens having the shape shown in FIG. 4 was molded using a glass raw material equivalent to F8 having properties of 1.59551 (refractive index) and νd = 39.2 (Atsube number). First, the glass raw material is placed in a crucible 17 shown in FIG. 1A.
Heat to 1400℃ to vitrify the glass raw material into a molten state. The molten glass is cooled to around 1300°C, and stirred and defoamed.

FIG. 2 shows a molding apparatus used in the present invention.

In the figure, numerals 1 and 2 indicate a lower mold and an upper mold, which are made of materials such as tungsten carbide and cemented carbide. The lower mold 1 and the upper mold 2 are provided with recesses 1a and 2a that form a spatial shape that becomes a lens shape on the mating surfaces when the molds are closed, and the surfaces of the recesses 1a and 2a form the optically functional surfaces of the lens. surface roughness
Finish to R _nax 0.01μm. Reference numerals 3 and 4 indicate heaters for adjusting the temperature of the lower mold 1 and the upper mold 2, which are wound around each mold member or through heater insertion holes appropriately provided in the mold member.

Reference numerals 5 and 6 denote holding members for holding the lower mold and upper mold, and opening and closing operations of the lower mold 1 and the upper mold 2 are performed by moving the holding members upward and downward. 7 and 8 are each mold member 1,
2 shows a temperature sensor for measuring the temperature of No. 2, and output signal lines 7a and 8a of the temperature sensor are input to controllers 9 and 10. controller 9,1
Reference numeral 0 denotes a meter that controls the mold temperature of the lower mold and the mold temperature of the upper mold, respectively, and input signals from the measuring devices 7 and 8 and power to the heaters 3 and 4 are output to each controller. 9 and 10 are provided with a program for controlling the supply of electricity to the heaters 3 and 4 based on the signals from the temperature detectors 7 and 8 so as to follow the temperature curve shown in FIG.

Depending on the shape of the optical component to be molded, a body mold may be provided in the mold member shown in FIG.

The temperature of the mold member is adjusted before pouring the molten glass, which has been stirred and defoamed at a temperature of around 1300°C, into the mold member. As shown in FIG. 3, the temperatures of the mold members 1 and 2 are adjusted within the range between the glass transition point (Tg=445°C) of the glass raw material F8 and a temperature 100°C lower than the glass transition point (Tg-100°C). As an example, the inventor set the mold temperature to 440°C. Lower mold 1 after controlling the mold temperature to 440℃
The glass melting temperature is adjusted when glass 14 is placed on the optically functional surface 1a. When putting the molten glass 14 into the lower mold, the glass 14 shown in FIG. This is not desirable and it is necessary to make it into a suitable lump state.
Furthermore, when the glass temperature is high, bubbles may be drawn into the glass or striae may be generated when the glass flows out from the tip of the nozzle 11 of the crucible to the lower mold. Therefore, when the molten glass flows out from the nozzle 11 into the lower mold, good results were obtained by setting the temperature of the glass clay to 10 ^4.2 poise, or 860°C in terms of temperature. In the case of print and crown materials such as F8, it is preferable to adjust the glass outflow temperature to a temperature range in which the glass viscosity is 10 ^3.5 to ^5.5 poise to prevent the formation of lumps and bubbles in the outflow cut glass mentioned above. In the case of lanthanum-based glass materials, a temperature range with a glass viscosity of 10 ^0.5 to ^3.5 poise was suitable. After the glass is poured into the lower mold and cut, the upper mold is placed over the glass and the glass is pressed and molded by the lower mold and the upper mold. (See Figure 1 B) When the glass 14 is poured onto the lower mold, the temperature change of the glass 14 is caused by a curve G as shown in Figure 3 due to the temperature difference between the lower mold temperature of 440°C and the glass temperature of 860°C. Glass viscosity as shown as ₁
The temperature decreases rapidly from 10 ^4.2 poise to 10 ^9.0 ~ ^9.2 poise, and on the contrary, the temperature of the mold part changes to the curve M ₁ (lower mold) M ₂
As shown in (upper mold), the temperature rises rapidly from 440℃.
Since the lower mold 1 comes into contact with the glass before the upper mold 2, the temperature starts to rise first. After the glass was placed in the mold, the press operation consisted of primary pressing in the first pressing step shown in FIG. 3 and secondary pressing in the second pressing step. In the first pressurization, the lower mold of the upper mold was closed and the press pressure was gradually increased over 6 seconds until it reached a maximum of 30 kg/cm ² . As a result of this operation, as described above, the glass temperature is rapidly lowered and the mold temperature is rapidly raised, and the glass is formed into a shape by the recesses 1a and 2a of the upper and lower molds. The press operation of the upper and lower molds for the first pressurization is performed so that the center thickness of the thick portion of the molded glass remains approximately 5% larger than the lens thickness of the final product.

Further, secondary pressurization is subsequently performed. In the secondary pressurization, a press pressure of 60 kg/cm ² is applied for about 60 seconds, and as shown in the second pressurization process in Figure 3, during this secondary pressurization, the temperature distribution between each member of the mold member is variation of
While converging to within 20℃, the glass temperature at the end of the second pressing was 520℃ as shown at point ₁ in Figure 3.
The heaters 3 and 4 are operated by the controllers 9 and 10 shown in Fig. 2 so that the clay becomes 10 ^9.3 poise. At the end of the second pressurization operation, the glass has a shape formed by the concave parts of the lower and upper molds, and the 5% margin left at the end of the first pressurization is compressed (see Figure 1C). ). Upon completion of the pressing operation, the glass 14 is shaped into a lens. The temperature of the formed glass is as high as 520°C, and it is cooled to make it into a product. In order to cool a glass lens at a high temperature of 520°C, it is necessary to maintain the shape at the end of pressurization while suppressing changes in the lens shape and distortion.

In this example, as shown in Fig. 3, the cooling curve G ₃ of the glass lens and the cooling curve M ₄ of the mold member are set as shown in the figure. The heaters were controlled by controllers 9 and 10 so that the temperature difference between the mold members remained within 5°C. After that, the temperature of the glass lens and mold member was set to 425℃ as shown at point g2 in Figure 3.
(glass viscosity 10 ^14.5 poise) along the same cooling curve. The cooling speed of cooling curve g ₄ is 5
℃/min, the cooling speed of cooling curve G ₃ is approximately 10℃/min.
I did it at min.

The temperature of the mold member and glass lens is g ₂ as shown in Figure 3.
When this point was reached, the lower mold of the upper mold was immediately opened, the glass lens was taken out, and the glass lens was left to cool to room temperature. When we measured the accuracy of the glass lens at this point, we found that the external dimensions were within the tolerances shown in Figure 4, and the surface accuracy of the lens surface was asymmetry, which is the accuracy required for photographic lenses. The irregularity (partial deviation of the R component) was within 0.5 Newton (0.63/4 μm deviation), and the surface roughness was within R _nax 0.02 μm. Furthermore, fine annealing was performed to return the refractive index of this glass lens to the predetermined refractive index (nd = 1.59551).After that, the accuracy was measured in the same manner as above, and the above-mentioned asperities, curls, and surface roughness also changed. There was no difference in the curvature of the lens surface, and the deviation in the curvature of the lens surface was within ±2 lines (±0.63 μm) with the Newton link.
The surface change layer was also less than 400 Å, and could be used as a photographic lens as is.

Example 2 A biconvex lens using the same glass raw material equivalent to F8 as in Example 1, with an outer diameter of 25 mm, a central wall thickness of 11 ± 0.05 mm, and a curvature of the optical functional surface of R ₁ = 20 mm and R ₂ = 40 mm, respectively. The molding process was carried out. The mold used for this molding consists of an upper mold and a lower mold whose internal shape corresponds to the lens, and the mold surface corresponding to the optical functional surface has a surface roughness R _nax of 0.01 μm or more. I finished it.

First, set the temperature of the upper and lower molds to 350℃ (glass transition point 445
The molten glass obtained in the same manner as in Example 1 was heated to 840℃ (glass viscosity lower than 95℃).
Place it between the upper and lower molds at a temperature of 10 ^4.4 poise, and
Gradually increase the press pressure over a period of seconds to a maximum of 30Kg/cm ²
The first pressurization was performed so that the center wall thickness of the formed glass remained approximately 2% of the lens wall thickness of the final product.

Further, secondary pressurization was subsequently performed. In the secondary pressurization, a press pressure of 50Kg/cm ² was applied for about 50 seconds, and at the end of the second pressurization process, the glass temperature was 510℃ (clay 10 ^9.5 poise), and the mold temperatures of the upper mold and lower mold were 510℃±5, respectively. The temperature was adjusted to ℃. After that, the pressure is released, and while the glass lens is still placed between the molds, the mold temperature is controlled at a cooling rate of about 10℃ per minute so that the temperature difference between the glass lens and each mold converges to within 2℃. Cooled to glass transition point (445℃) and further cooled at 5℃ per minute
Cooling speed of 425℃ (glass viscosity 10 ^{to 14.5} poise) so that there is no temperature difference between the glass lens and each mold.
Cooled to . Thereafter, the glass lens was removed from the mold and fine annealed to adjust the refractive index. Furthermore, when similar measurements were performed for Example 1, the deviation in the curvature of the optical functional surface was within ±2 lines for the Newton ring, and for both the ask and the Newton rings.
The surface roughness was within R _nax 0.02, and the performance was equivalent to or better than that of conventional polished lenses.

Example 3 A lens with the same shape as Example 1 (see Figure 4) was
nd=1.77250, νd=49.6 Glass point transition point Tg=700℃
Molding was carried out using a glass raw material equivalent to lanthanum-based glass L _a SF016, which has the following properties. The mold member used for this molding was the same as in Example 1.

First, the temperature of the mold member was adjusted to 650°C (50°C lower than the glass transition point of 700°C), and then the molten glass obtained in the same manner as in Example 1 was heated to 900°C (glass viscosity: 10 ^2.9
Poise), the press pressure is gradually increased over 5 seconds until it reaches a maximum of 45 kg/cm ² , and the center wall thickness of the molded glass is approx. 1st so that 5% remains
Pressure was applied.

Further, secondary pressurization was subsequently performed. In the secondary pressurization, a press pressure of 80 kg/cm ² was applied for about 120 seconds, and at the end of the second pressurization process, the glass temperature was 718℃ (viscosity 10 ^10.2
Poise) Mold temperature of upper mold and lower mold is 716℃±3 respectively
The temperature was adjusted to ℃. After that, the pressure was released, and the glass lens was cooled at a cooling rate of about 5℃ per minute with the glass lens placed between the molds until the temperature difference between the glass lens and each mold was 1℃.
While controlling the mold temperature so that it converges within the glass transition point (700℃), the temperature is further reduced to 685℃ (glass viscosity 10 to ^14.5 poise). Thereafter, the glass lens was removed from the mold and fine annealed to adjust the refractive index. Furthermore, when similar measurements were performed on Example 1, the deviation of the curvature of the optical functional surface was within ±2 lines for the Newton ring, within 0.5 lines for both the ask and Newton rings, and the surface roughness was R _nax 0.02 or less. can be,
Its performance was equivalent to or better than that of conventional polished lenses.

[Effects of the Invention] As explained above, by carrying out the process according to the present invention, it is possible to achieve high precision as typified by photographic lenses (outer diameter tolerance within 5/100 mm, asperity and curl within 0.5 Newton ring). , the variation in curvature deviation is within ±2 Newton rings) Grinding optical parts,
It has become possible to directly mold glass raw materials from molten liquid without the need for post-processes such as polishing.
The following points can be cited as effects of the present invention.

(1) It is possible to obtain optical components with high precision, especially local changes in curvature within 0.63/4 μm, without sink marks or warpage during cooling, by direct molding from melted raw materials.

(2) The cost is less than 2/1 compared to conventional methods using grinding and polishing or molding using reheat press.

(3) Efficient mass production can be expected because the range of mold temperature variation is small and the mold temperatures before and after molding are close, making it easy to use the mold repeatedly.

(4) Since high-temperature glass is placed in a low-temperature mold, the surface of the glass is quickly cooled, so the deterioration layer on the glass surface can be kept to a level that does not pose a practical problem.

(5) Since the mold temperature is low, not only is there no flexibility even when high-temperature glass is used, but the life of the mold is greatly extended because the mold temperature does not exceed the temperature required for actual molding.

[Brief explanation of drawings]

FIGS. 1A to 1C are diagrams explaining the molding process according to the present invention. FIG. 1A is an explanatory diagram of inserting molten glass into the mold member from the nozzle 11, and FIG. 1B is an explanation of the first pressurization. Figure 1C is an explanatory diagram of the second pressurization,
FIG. 2 is an explanatory diagram of an apparatus used in the process of the present invention, FIG. 3 is a temperature curve diagram according to Example 1 of the present invention, and FIG. 4 is a diagram showing the shape of a lens to be molded. 1...Lower mold, 2...Upper mold, 3, 4...Heater,
5, 6...Mold holding member, 7, 8...Temperature detector,
9, 10... Controller, 11... Nozzle, 1
2... Outflow glass, 13a, 13b... Cutting blade, 1
4, 15, 16... Glass to be formed, 17... Crucible, 18, 19... Heater, 1a, 2a... Optical functional surface, 7a, 8a... Temperature output signal line.

Claims (1)

[Claims] 1. A method for heating and melting a glass raw material and pressing it to form an optical component includes the following steps: (a) A first step of heating the glass raw material to form a glass solution.
process. (b) It has a mold member consisting of an upper mold and a lower mold having an optically functional surface for pressing the glass solution, and the mold temperature of the mold member is 100°C lower than the glass transition point of the glass raw material and the glass transition point. The second step is to adjust the temperature to a temperature range between the temperatures. (c) The glass from the first step is placed in the mold member whose temperature has been controlled by the second step, and the glass temperature is
10 The first pressurizing step of pressing into an approximate shape so that the wall thickness is 5% or more preferably 1% or more than the final product when the temperature reaches a temperature indicating clay of ^{8.5 to 11} poise. (d) following the first pressing step, pressing the mold member into the final optical component shape while maintaining the temperature of the mold member within a temperature range where the glass exhibits a clay of 10 ^8.5 to ¹¹ poise; By the end of the press,
A second pressurizing step in which the mold member is pressed while controlling its temperature so that the temperature difference between the molds converges within 20°C. (e) After the second pressurizing step, there is a step of cooling the molded optical component and the mold member, and the cooling step is performed until the glass temperature reaches the glass transition point. A first cooling step in which the optical components are cooled to keep the temperature difference within 5 degrees Celsius, and after the first cooling, the temperature difference between the upper mold and the lower mold in contact with the glass is kept to a slight difference to remove the strain from the glass to the lower limit. A second cooling step to cool down to.