JP2022107291A - Manufacturing method of glass molding tool and manufacturing method of optical element - Google Patents

Abstract

To provide a manufacturing method of a glass molding tool capable of manufacturing the glass molding tool by transferring a surface shape of a master mold at a high precision.SOLUTION: There is provided a manufacturing method of a glass molding tool having a concave shaped or a convex shaped molding surface. The manufacturing method includes the steps of: pressing a glass raw material heated to a temperature of Ta in a state of being in contact with a master mold surface; cooling the glass raw material at the contacted state; and releasing the contacted state after cooling to form the molding surface. A release of the contacted state is performed when a temperature of the glass raw material is a contacted state release allowable temperature Tb or lower. Tb is calculated by Tb=Tg-200°C where Tg is a glass transition temperature (unit:°C) of the glass raw material. A temperature of the master mold is Tk when a temperature of the glass raw material during cooling is Tc. Tk is calculated by Tk=Tc-A, where A is more than 0°C.SELECTED DRAWING: None

Description

The present invention relates to a method for manufacturing a glass molding mold and a method for manufacturing an optical element.

As a method for manufacturing an optical element such as a lens, a method of press-molding a material to be molded by a molding die is widely used. Patent Document 1 discloses a glass molding mold as a molding mold that can be used in such a manufacturing method.

JP-A-2019-127425

Conventionally, metal or ceramic molding dies have been used for manufacturing optical elements. As a method for producing a molding die from metal or ceramics, a method of cutting out a molding die from a base material by machining such as cutting or grinding is usually adopted. However, it takes a lot of cost and time to produce a molding die having a molding surface that can be used for manufacturing an optical element by such machining.

On the other hand, as for the glass molding mold, the molding mold in which the surface shape of the master mold is transferred can be manufactured by press-molding the glass material softened by heating with the master mold. If a master mold having a desired surface shape can be prepared and the surface shape of the master mold can be accurately transferred to a glass material, it is easy to mass-produce a molding mold having a molding surface that can be used for manufacturing an optical element. On the other hand, when the material to be molded is actually press-molded using a glass molding die and provided as an optical element, if the surface shape of the master mold cannot be transferred to the glass molding die with high accuracy, the required optical performance can be obtained. It is difficult to manufacture an optical element having a glass.

In view of the above, one aspect of the present invention is to provide a method for manufacturing a glass mold, which can transfer the surface shape of the master mold with high accuracy to manufacture a glass mold. ..

One aspect of the present invention is
A method for manufacturing a glass molding mold having a concave or convex molding surface.
Pressing the glass material heated to temperature Ta in contact with the surface of the master mold,
Cooling the glass material in the contacted state,
After the above cooling, the state of being in contact with the above is released.
Including forming the molding surface by
The release of the contacted state is performed when the temperature of the glass material is equal to or lower than the allowable temperature for releasing the contacted state Tb.
Tb is
Tb = Tg-200 ° C
Tg is the glass transition point (unit: ° C.) of the above glass material.
During the cooling, when the temperature of the glass material is Tc, the temperature of the master mold is Tk.
Tk = Tc-A
When A is more than 0 ° C. and the temperature of the glass material is Tb or more and less than Tc, the temperature of the master mold is lower than the temperature of the glass material.
In the entire temperature range above Tb and below Tc
When the molded surface to be formed has a concave shape, the master mold and the glass material are described by the following formula 1:
(Equation 1)
-1.00 ≤ β _TK -β _TG ≤ 0.01
The filling,
When the molded surface to be formed has a convex shape, the master mold and the glass material are described by the following formula 2:
(Equation 2)
-0.01 ≤ β _TK -β _TG ≤ 1.00
The filling,
Tc is less than Tb and less than Ta, and Tc = Tg + (Ts-Tg) × B
B is more than 0 and less than 1, and Ts is the yield point (unit: ° C.) of the glass material.
In the above formula,
β _TK is a value indicating the shrinkage rate (unit:%) at the temperature (TA) based on the length at the temperature Ta of the master type in no unit.
β _TG is a value indicating the shrinkage rate (unit:%) at the temperature T based on the length of the glass material at the temperature Ta in no unit.
T is a method for manufacturing a glass molding mold, which is Tb or more and less than Tc.
Regarding.

The present inventor has made it possible to transfer the surface shape of the master mold with high accuracy by suppressing the occurrence of abnormal mold release during cooling by satisfying the above formula between the glass material and the master mold. We thought that it could contribute, and came up with the above-mentioned manufacturing method.

According to one aspect of the present invention, it is possible to manufacture a glass molding mold by transferring the surface shape of the master mold with high accuracy. Further, according to one aspect of the present invention, it is also possible to provide a method for manufacturing an optical element using the glass molding die thus manufactured.

It is schematic cross-sectional view which shows an example of the manufacturing apparatus for an optical element including a glass molding die. It is the schematic sectional drawing which shows an example of the manufacturing apparatus of a glass molding mold. The evaluation results regarding the combination of the glass material 1 and the master mold 1 and the combination of the glass material 2 and the master mold 2 are shown. The evaluation results regarding the combination of the glass material 3 and the master mold 1 and the combination of the glass material 4 and the master mold 2 are shown. The evaluation result regarding the combination of the glass material 5 and the master mold 1 is shown. The evaluation result regarding the combination of the glass material 6 and the master mold 1 is shown.

[Manufacturing method of glass molding]
Hereinafter, the method for manufacturing the above-mentioned glass molding mold will be described in more detail. Hereinafter, the present invention may be described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.

<Structure of glass molding mold>
FIG. 1 is a schematic cross-sectional view of an example of a manufacturing apparatus for an optical element provided with a glass molding die. The optical element manufacturing apparatus 10 of FIG. 1 manufactures an optical element 20 from a material 21 to be molded by press molding, and includes an upper mold 11 and a lower mold 12 which are glass molding molds. The upper mold 11 and the lower mold 12 are supported so as to be relatively movable in the guide mold 13, and the distance between them can be changed. Both the upper mold 11 and the lower mold 12 may be a movable type that can be moved, or a fixed type in which one is movable and the other is non-movable.

The upper mold 11 and the lower mold 12 have a molding surface 14 and a molding surface 15 on opposite sides to each other. Specifically, the optical element 20 is a biconvex lens having aspherical surfaces on both sides, and the molded surface 14 and the molded surface 15 are concave surfaces (aspherical surfaces) having a shape corresponding to each convex surface (aspherical surface) of the optical element 20. Is. That is, the shapes of the molding surface 14 and the molding surface 15 are transferred by press molding to form a convex surface of the optical element 20. However, the embodiment shown in FIG. 1 is an example, and the molding surface of the glass molding mold manufactured by the above manufacturing method has a convex shape in one form and a concave shape in the other form.

Coatings 16 and 17 are formed on the molding surfaces 14 and 15, respectively. The coating films 16 and 17 can be coating films generally called a release film, and can play a role of suppressing fusion of the material to be molded, for example, a carbon film or the like. The coatings 16 and 17 shown in FIG. 1 have a single-layer structure, but a coating having a multi-layer structure having different compositions can also be provided. Alternatively, a configuration in which the molding surfaces 14 and 15 are exposed without the coatings 16 and 17 can be selected.

A heater (not shown) is provided on the outside of the guide mold 13. At the time of molding, the material to be molded 21 can be heated with a heater to a molding temperature at which it softens.

In the present invention and the present specification, the "glass molding mold" refers to a portion provided with a molding surface. For example, in FIG. 1, the entire portion of the upper mold 11 and the lower mold 12 except for the coatings 16 and 17 may be made of glass. Alternatively, only a part of the upper mold 11 and the lower mold 12 including the molding surface 14 and the molding surface 15 is made of glass, and a base portion made of another material such as metal is joined to the glass portion to form the upper mold. 11 and the lower mold 12 can also be configured.

<Glass material>
The glass molding mold can be manufactured by press molding a glass material with a master mold. The glass material is not particularly limited, and a glass material having various compositions and physical properties can be used. As the glass material, commercially available glass may be used, or a glass material produced by a known method may be used.

Regarding the glass composition of the glass material, for example, a composition satisfying one or more of the following (A) to (G) can be mentioned. As an example, the glass material can be an aluminosilicate-based glass and / or a glass material made of glass corresponding to the silicate-based glass. In the present invention and the present specification, the "aluminosilicate-based glass" means a glass in which at least SiO ₂ and Al ₂ O ₃ are contained in the glass composition represented by the oxide standard for the cationic component of the glass. The “silicate-based glass” refers to a glass in which at least SiO ₂ is contained in the glass composition represented by the oxide standard for the cation component of the glass. As the glass composition of the aluminosilicate glass and / or the glass corresponding to the silicate glass, for example, a composition satisfying one or more of the following (A) to (F) can be mentioned. However, the following compositions are merely examples, and glass materials having various compositions can be used as the glass material.
(A) In the glass composition represented by mol%, the total content of SiO ₂ and Al ₂ O ₃ is 60.0% or more.
(B) In the glass composition represented by mol%, the SiO ₂ content is 51.0 to 79.0%, the Al ₂ O ₃ content is 8.0 to 24.0%, and the total of MgO, CaO, SrO and BaO. In the (C) mol%-denominated glass composition having a content of 1.0 to 35.0%, the MgO content is 1.0 to 30.0%, the CaO content is 0.0 to 15.0%, and the like. SrO content is 0.0 to 12.0%, BaO content is 0.0 to 12.0%, ZnO content is 0.0 to 10.0%, and Li _2O content is 0.0 to 8 0.0%, total content of Na ₂ O and K ₂ O is 0.0 to 4.25%, ZrO ₂ content is 0.0 to 10.0%, TiO ₂ content is 0.0 to 6 The total content of 0.0%, La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ is 0.0 to 4.0%.
(D) In the glass composition expressed in mole%, the molar ratio of the total content of Li ₂ O, Na ₂ O, K ₂ O to the total content of SiO ₂ , Al ₂ O ₃ , and Mg O (Li ₂ O + Na ₂ O + K). ₂ O) / (SiO ₂ + Al ₂ O ₃ + MgO) is in the range of 0.000 to 0.050.
(E) In the glass composition represented by mol%, the total content of SiO ₂ , B ₂ O ₃ , P ₂ O ₅ and Al ₂ O ₃ is 10.0 to 90.0%.
(F) In the glass composition represented by mol%, the SiO ₂ content is 0.0 to 80.0%, preferably 1.0 to 70.0%, and the B ₂ O ₃ content is 0.0 to 80.0. %, preferably 1.0 to 70.0%, P ₂ O ₅ content is 0.0 to 80.0%, preferably 1.0 to 70.0%, Al ₂ O ₃ content is 0.0. It is ~ 30.0%.
In the glass composition represented by (G) mol%, the MgO content is 0.0 to 60.0%, the CaO content is 0.0 to 60.0%, and the SrO content is 0.0 to 60.0%. BaO content is 0.0 to 60.0%, ZnO content is 0.0 to 60.0%, Li ₂ O content is 0.0 to 60.0%, and Na ₂ O and K ₂ O Total content is 0.0-60.0%, ZrO ₂ content is 0.0-20.0%, La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O The total content of ₅ and HfO ₂ is 0.0-70.0%.

Further, as an example, the following (1) to (3) can be exemplified as the physical characteristics of the glass, and the glass material can have one or more of the following (1) to (3). However, the following physical properties are merely examples, and a glass material having various physical properties can be used as the glass material. The following average coefficient of thermal expansion α is a value measured using a thermomechanical analyzer (TMA; Thermomechanical Analysis). The method for measuring the glass transition point Tg and the yield point Ts will be described later.
(1) The glass transition point Tg is 650 ° C. or higher, 670 ° C. or higher, or 700 ° C. or higher (for example, 900 ° C. or lower).
(2) The yield point Ts is 700 ° C. or higher, 720 ° C. or higher, or 750 ° C. or higher (for example, 950 ° C. or lower).
(3) The average coefficient of thermal expansion α at 100 ° C to 300 ° C is 10 × ^10-7 / ° C to 70 × ^10-7 / ° C, 20 × ^10-7 / ° C to 60 × ^10-7 / ° C, or 25. It is × 10 ^-7 / ° C. to 55 × 10 ^-7 / ° C.

<Press molding of glass material>
In the above manufacturing method, a glass molding mold having a concave or convex molding surface is manufactured by pressing the glass material with a master mold to mold the glass material.

FIG. 2 is a schematic cross-sectional view of an example of a glass molding mold manufacturing apparatus (hereinafter, also referred to as “mold molding apparatus”). The mold manufacturing apparatus of FIG. 2 includes an upper mold (master mold) 31 having a convex molding surface 34, a lower mold 32, and a guide mold 33. The glass material 41 is pressed between the upper mold 31 and the lower mold 32, and the surface shape of the upper mold molding surface 34 is transferred to the glass material 41, whereby a glass molding mold having a concave molding surface is obtained. Be done. The surface shape of the lower mold 32 may be a planar shape, a convex shape, or a concave shape, and is not particularly limited. Further, in the molding mold manufacturing apparatus of FIG. 2, the master mold for transferring the surface shape to the glass material to form the molding surface of the glass molding mold is the upper mold, but the master mold is arranged as the lower mold. You can also do it.

The upper die 31 and the lower die 32 are supported in a guide die (generally also referred to as a "sleeve") 33 so as to be relatively movable, and the distance between the upper die 31 and the lower die 32 can be changed. Both the upper mold 31 and the lower mold 32 may be a movable type that can be moved, or may be a fixed type in which one is movable and the other is non-movable.

A heater (not shown) is provided on the outside of the guide mold 33. At the time of molding, the glass material 41 can be heated with a heater to a molding temperature Ta where the glass material 41 softens. Ta may be set according to the type of glass material, and may be, for example, in the range of 700 to 1000 ° C, preferably in the range of 750 to 950 ° C. Further, in one form, Ta = Ts ± 50 ° C. can be set. In the molding die manufacturing apparatus of FIG. 2, the upper die, the lower die, and the guide die are heated together with the glass material by the heater provided on the outside of the guide die 33.

The glass material heated to the temperature Ta is pressed in contact with the surface of the master mold (molding surface 34 of the upper mold 31 in FIG. 2). The glass material 41 can be pressed by applying a pressing load to the glass material 41 via the upper mold 31 and / or the lower mold 32.

After that, the glass material 41 is cooled in a state of being in contact with the surface of the master mold, and then the state of contact with the surface of the master mold is released. In this way, the glass material 41 is press-molded to obtain a glass molding mold having a concave molding surface formed by transferring the surface shape of the master mold surface (molding surface 34 of the upper mold 31 in FIG. 2). can. Here, the above-mentioned release of the contact state is performed when the temperature of the glass material is equal to or less than the allowable contact release temperature Tb. Tb is determined according to the glass transition point Tg of the glass material, and is "Tb = Tg-200 ° C.". It can be said that Tb is a temperature at which the hardening of the glass is sufficiently progressing. Tb is preferably well below the strain point of the glass, and from this point of view, for example, Tg-150 ° C or lower, preferably Tg-160 ° C or lower, more preferably Tg-180 ° C or lower, still more preferably Tg-200. It can be below ° C. Tb is, for example, 20 ° C. or higher, 50 ° C. or higher, 70 ° C. or higher, 100 ° C. or higher, 150 ° C. or higher, 200 ° C. or higher from the viewpoint of facilitating the temperature of the glass molding mold and / or master mold to follow the cooling rate. , 250 ° C. or higher, 300 ° C. or higher, 350 ° C. or higher, or 400 ° C. or higher. Further, the Tb is preferably sufficiently lower than the Tg of the glass molding mold, and from this viewpoint, for example, 900 ° C. or lower, 800 ° C. or lower, 700 ° C. or lower, 600 ° C. or lower, 550 ° C. or lower, 500 ° C. or lower, 400. It can be ℃ or less, 350 ℃ or less, or 300 ℃ or less. While cooling from Ta to Tb, a pressing load may be continuously applied to the glass material 41 via the upper mold 31 and / or the lower mold 32, or the load may be only the weight of the mold itself.

According to the molding die molding apparatus of FIG. 2, a glass molding die having a concave molding surface can be obtained. On the other hand, if the surface shape of the molding surface of the master mold is concave, a glass molding mold having a convex molding surface can be obtained by transferring the concave shape to the glass material. Mold The glass mold taken out from the molding apparatus can be optionally subjected to one or more of known post-processes such as annealing and film formation.

In the above manufacturing method, a master mold having a temperature of Tk ° C. when the glass material has a temperature of Tc is used. Here, Tc is less than Tb and less than Ta, and "Tc = Tg + (Ts-Tg) x B", B is more than 0 and less than 1, and Ts is the yield point (unit: ° C.) of the glass material. Is. For Tk, "Tk = TA", where A is above 0 ° C. That is, the temperature of the master mold when the glass material is cooled to the temperature Tc is more than 0 ° C. lower than that of Tc. Further, when the temperature of the glass material is Tb or more and less than Tc, the temperature of the master mold is lower than the temperature of the glass material. It is considered that the glass material cooled from the temperature Ta ° C. starts to harden when the temperature falls below the temperature Tc specified by the above formula, and if abnormal mold release occurs here, the accuracy of transferring the surface shape of the master mold is high. It is presumed that it will drop significantly. A is more than 0 ° C. and varies depending on the thermal characteristics of the glass material and master mold, cooling conditions, volume of the glass material, etc., and may be, for example, 1 ° C. or higher, 30 ° C. or higher, 50 ° C. or higher, or 60 ° C. or higher. It can also be, for example, 300 ° C. or lower, 200 ° C. or lower, or 150 ° C. or lower. Normally, A tends to increase as the cooling rate increases, and tends to decrease as the cooling rate decreases. For example, A tends to increase to, for example, 70 ° C., 75 ° C., 80 ° C., 85 ° C., etc. by increasing the cooling rate. Further, A tends to decrease to 65 ° C., 60 ° C., 55 ° C., ..., For example, by slowing down the cooling rate. The temperature of the master mold is defined as the temperature of the surface of the master mold that comes into contact with the glass material. The cooling rate is an average cooling rate from Ta to Tb, which will be described later, and is −0.1 ° C./min or more from the viewpoint of increasing the productivity of the glass molding mold and / or suppressing the thermal deterioration of the master mold. -0.3 ° C / min or higher, -0.5 ° C / min or higher, -1.0 ° C / min or higher, -3.0 ° C / min or higher, -5.0 ° C / min or higher, -10.0 ° C It can be ≥/ min or -15.0 ° C / min or higher, and -100.0 ° C / min or lower, -50.0 ° C / min or lower, -30.0 ° C / min or lower, -25. 0 ° C / min or less, -20.0 ° C / min or less, -18.0 ° C / min or less, -16.0 ° C / min or less, -14.0 ° C / min or less, -12.0 ° C / min or less , -10.0 ° C./min or less, -5.0 ° C./min or less, -3.0 ° C./min or less, or -1.0 ° C./min or less.

In the above manufacturing method, as a combination of the master mold and the glass material, a combination satisfying the following temperature relationship is used. That is, in the entire temperature range of Tb or more and less than Tc, when the formed molding surface has a concave shape, the master mold and the glass material satisfy the following formula 1, and when the formed molding surface has a convex shape, the master mold is used. The glass material satisfies the following formula 2.

(Equation 1)
-1.00 ≤ β _TK -β _TG ≤ 0.01
(Equation 2)
-0.01 ≤ β _TK -β _TG ≤ 1.00

β _TK is a value indicating the shrinkage rate (unit:%) at the temperature (TA) based on the length at the temperature Ta of the master type in no unit, and β _TG is the temperature of the glass material. It is a value showing the shrinkage rate (unit:%) at the temperature T based on the length in Ta in no unit, and T is Tb or more and less than Tc.

In the present invention and the present specification, the above-mentioned shrinkage rate is a value obtained by the following method.
A measurement sample is cut out from the master mold or glass material, or a measurement sample composed of the same material as the master mold or glass material is prepared. When the master mold and / or the glass material has a film (for example, a release film) on the surface of the base material, the above shrinkage rate is composed of the same material as the measurement sample or the base material part cut out from the base material part. Obtain the sample for measurement. The sample for measurement is a round bar having a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. In the following, the length of the measurement sample will be referred to as _LRT . The thermal expansion characteristics of each sample are measured by a method according to JOBIS08-2003. Specifically, a graph obtained by heating a sample at a heating rate of 4 ° C./min with a load of 98 mN applied and measuring the amount of elongation (unit: mm) with respect to temperature every second (so-called heat). From the expansion curve), the amount of elongation ΔL _Ta at the temperature Ta and the amount of elongation ΔLT at an arbitrary temperature _T are obtained. The difference (ΔL _Ta − ΔL _T ) between the elongation amount ΔL _Ta and ΔLT thus obtained is defined as the shrinkage amount (unit: mm) at the temperature _T based on the length at the temperature Ta, and this is measured at the temperature Ta. The shrinkage rate (unit:%) is obtained by dividing the length of the sample to be used by L _RT + ΔL _Ta (unit: mm). Further, regarding the glass material, the temperature corresponding to the intersection of the extension of the linear portion of the low temperature region and the high temperature region in the above graph is the glass transition point Tg, and the temperature at which the expansion apparently stops in the above graph, that is, the temperature increases as the temperature rises. Let the temperature of the turning point at which the temperature changes from increasing to decreasing be the yield point Ts.

In the above formulas 1 and 2, regarding the shrinkage rate of the master type and the shrinkage rate of the glass material, the shrinkage rate of the master type compared with the shrinkage rate of the glass material at the temperature T is the shrinkage rate at the temperature (TA). be. As a combination of the glass material and the master mold, the present inventor has a heat diffusion characteristic between the glass material and the master mold when the glass material is pressed at Ta ° C. and then cooled in contact with the surface of the master mold. It is considered that using a combination that satisfies the above formula in consideration of the difference in temperature caused by the difference contributes to making it possible to transfer the surface shape of the master mold with high accuracy and manufacture a glass molding mold. ing. This is because, according to the combination satisfying the above formula, the master mold surface (molded surface) is abnormally released from the glass material because the degree of shrinkage of the master mold greatly exceeds the degree of shrinkage of the glass material during cooling. It is presumed that it can be suppressed. Here, the reason why the temperature range satisfying the above formula is set to the entire temperature range of Tb or more and less than Tc is considered to be that the glass material cooled from the temperature Ta starts to harden when the temperature becomes less than the temperature Tc specified by the above formula. This is because it is presumed that if abnormal mold release occurs here, the accuracy of transferring the surface shape of the master mold will be significantly reduced. Regarding the temperature Tc, as described above, Tc = Tg + (Ts−Tg) × B, and B is 0 or more and 1 or less. From the viewpoint of further improving the transfer accuracy, B is preferably 0.1 or more, more preferably 0.2 or more. From the same viewpoint, B is preferably 0.7 or less, more preferably 0.5 or less.

The lower limit of the formula 1 is −1.00 or higher, preferably −0.50 or higher, and more preferably −0.20 or higher. The upper limit of the formula 1 is 0.01 or less, preferably 0.005 or less, and more preferably 0 or less. The lower limit of the formula 2 is −0.01 or higher, preferably −0.005 or higher, and more preferably 0 or higher. The upper limit of the formula 2 is 1.00 or less, preferably 0.50 or less, and more preferably 0.20 or less.

The master type material is not particularly limited. From the viewpoint of heat resistance, durability and the like, a master type made of silicon carbide (SiC), glass or the like is preferable. The master mold can be produced by a known method.

[Manufacturing method of optical element]
One aspect of the present invention relates to a method for manufacturing an optical element, which comprises manufacturing a glass molding die by the above-mentioned manufacturing method and press-molding a material to be molded by the manufactured glass molding die.

As for the method for manufacturing the optical element, a known technique for manufacturing the optical element by press molding can be applied except that the glass mold manufactured by the method for manufacturing the glass molding mold described above is used. An example of the optical element manufacturing apparatus that can be used for press molding is the optical element manufacturing apparatus of FIG. 1 described above.

Examples of the optical element include various lenses such as a spherical lens, an aspherical lens, and a microlens, a prism, and the like. Further, the material to be molded can be a glass material, and the optical element can be a glass optical element.

For example, using the above glass molding mold, a glass block processed for press molding (hereinafter, referred to as “glass material for press molding”) can be press-molded. Examples of glass materials for press molding include preforms for precision press molding, glass materials for obtaining optical element blanks by press molding (glass gobs for press molding), and other glass ingots having a mass corresponding to the mass of press-molded products. Can be mentioned. The glass material for press molding is produced through a process of processing a glass molded body. The glass molded body can be produced by heating and melting the glass raw material and molding the obtained molten glass. Examples of the processing method for the glass molded body include cutting, grinding, and polishing. The optical element blank is a glass molded body having a shape similar to the shape of the optical element to be manufactured. The optical element blank can be produced by a method of molding glass into a shape in which a processing allowance to be removed by processing is added to the shape of the optical element to be manufactured. For example, an optical element is subjected to a method of heating and softening a glass material for press molding and press molding (reheat pressing method), a method of supplying a molten glass ingot to a press molding mold and press molding by a known method (direct press method), and the like. A blank can be made.

For example, the shape accuracy of the molding surface of a molding die for precision press molding is desired to be several times higher than the shape accuracy required for an optical element. According to the method for manufacturing a glass mold described above, the surface shape of the master mold can be transferred with high accuracy to manufacture a glass mold. The glass molding die thus obtained is suitable as a molding die for precision press molding. However, since it is preferable in various press moldings that the shape accuracy of the molded surface is excellent, the glass molding mold manufactured by the above manufacturing method is not limited to the molding mold for precision press molding, and is molded for various press moldings. Suitable as a mold.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the embodiments shown in the examples.

<Glass material>
As the glass material, 6 kinds of glass materials (glass materials 1 to 6) were prepared. Glass materials 1 to 6 are made of aluminosilicate glass and / or glass corresponding to silicate glass, and are glass materials satisfying one or more of (A) to (F) exemplified above. ..

<Master type>
As the master mold, a master mold 1: SiC master mold and a master mold 2: glass master mold (glass: glass type name M-TAFD305 manufactured by HOYA Corporation) were prepared.

The glass transition point Tg, the yield point Ts, and the average coefficient of thermal expansion α at 100 ° C. to 300 ° C. of the above glass material were measured by the methods described above. For each glass material, Tc was calculated as "Tc = Tg + (Ts-Tg) x B" from the values of Tg and Ts. Here, B = 1/3. The measured or calculated values are shown in Table 1.
The temperature Ta at the time of molding each glass material was the temperature shown in Table 1.

For the glass materials 1 to 5, the master mold 1 having a convex or concave molding surface is used as the upper mold, and for the glass material 6, the master mold 2 having the convex or concave molding surface is used as the upper mold. Using this, press molding was performed by the molding mold manufacturing apparatus shown in FIG. With the temperature Ta as the temperature shown in Table 1, a load is applied and pressed while the glass material is in contact with the surface of the master mold, and the cooling rate is -10 ° C / min to the temperature Tb calculated from the Tg of each glass material. Then, after cooling to about room temperature in the mold molding apparatus, the contact state with the master mold is released, and the surface shape of the master mold is transferred to form a glass molding mold. Was taken out from the mold manufacturing apparatus. As a result of measurement with a non-contact thermometer, A = 70 ° C for glass materials 1 to 4 and master mold 1, A = 150 ° C for glass material 5 and master mold 1, and glass material 6 and master mold 2 for. A = 30 ° C., and in any combination of the glass material and the master mold, the temperature of the master mold was lower than the temperature of the glass material when the temperature of the glass material was Tb or more and less than Tc.

For each combination of the above glass material and the master mold, three glass molding molds were manufactured.
Regarding the manufactured glass molding mold, the concave shape accuracy (transfer accuracy) of the glass molding mold formed by transferring the convex shape of the master mold, and the glass molding mold formed by transferring the concave shape of the master mold. The convex shape accuracy (transfer accuracy) of the above was evaluated by the following method and the following evaluation criteria.
(Evaluation method)
The shape of the molding surface of the glass molding mold was measured using an ultra-high precision coordinate measuring machine (UA3P) manufactured by Panasonic, and the BESTFIT shape error was calculated. The measurement was performed twice in total by changing the measurement direction for each molded surface. The BESTFIT shape error was calculated based on the radius of curvature of the master mold surface (spherical surface).
(Evaluation criteria)
〇: The shape error after BEST FIT is 0.04 μm or less in all the molding surfaces of the three glass molding dies.
X: Within the molding surface of the three glass molding dies, there is a portion having a shape error of more than 0.04 μm after BEST FIT.

For each glass material and master mold, the shrinkage rate was determined by the method described above, and a curve of the shrinkage rate with respect to temperature was created. For the master type, a curve (curve 1) of the shrinkage rate with respect to each temperature and a curve (curve 2) in which the curve 1 was shifted to the right by A ° C. were also created. For each combination of the glass material and the master type, a difference curve between the master type curve 2 and the shrinkage rate curve of the glass material (curve 3) was created. From the difference curve, it can be determined whether or not the combination of the glass material and the master mold satisfies Equations 1 and 2.

The above results are shown in FIGS. 3 to 6.

Among the combinations shown in FIGS. 3, 4 and 6, precision is achieved by using a glass molding die having a concave shape made from a combination of a glass material satisfying Equation 1 and a master die as an upper die and a lower die. Press molding was performed to produce a glass optical element (biconvex lens).

Among the combinations shown in FIG. 3, precision press molding is performed using a glass molding mold having a convex shape produced from a combination of a glass material satisfying Equation 2 and a master mold as an upper mold and a lower mold, and glass is performed. An optical element (both concave lenses) manufactured by the same manufacturer was manufactured.

The surface shape of the optical element produced above was evaluated by the above evaluation method performed on the molding surface of the glass molding mold, and the BEST FIT shape error was obtained based on the radius of curvature of the master mold surface (spherical surface). It was confirmed that the shape error after BEST FIT within the effective diameter of the lens was 0.04 μm or less, which sufficiently satisfied the shape accuracy required for the optical element.

Finally, each of the above aspects will be summarized.

According to one aspect, a method for manufacturing a glass molding mold having a concave or convex molding surface, in which a glass material heated to a temperature Ta is pressed in contact with the surface of the master mold. The glass material is cooled in the contacted state, and after the cooling, the contacted state is released to form the molded surface, and the contacted state is released. Is performed when the temperature of the glass material is equal to or less than the allowable temperature for releasing the contact state Tb, Tb is Tb = Tg-200 ° C., and Tg is the glass transition point (unit: ° C.) of the glass material. The temperature of the master mold when the temperature of the glass material is Tc during the cooling is Tk, Tk = Tc−A, A is more than 0 ° C., and the temperature of the glass material is When the temperature is Tb or more and less than Tc, the temperature of the master mold is lower than the temperature of the glass material, and when the formed surface is concave in the entire temperature range of Tb or more and less than Tc, the master mold and the glass When the material satisfies the above formula 1 and the formed molding surface has a convex shape, a method for producing a glass molding mold is provided in which the master mold and the glass material satisfy the above formula 2.

According to the above manufacturing method, a glass molding mold can be manufactured by transferring the surface shape of the master mold with high accuracy.

In one form, the temperature A can be 1 ° C. or higher and 300 ° C. or lower.

In one form, the Tb can be 50 ° C. or higher and 500 ° C. or lower.

In one embodiment, the cooling can be performed at a cooling rate of −0.1 to −100.0 ° C./min.

According to one aspect, there is provided a method for manufacturing an optical element, which comprises manufacturing a glass molding die by the above manufacturing method and press molding a material to be molded by the manufactured glass molding die.

In one form, the optical element can be a glass optical element.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.
For example, it is of course possible to arbitrarily combine two or more of the forms described as examples or preferred ranges in the specification.

Claims (6)

A method for manufacturing a glass molding mold having a concave or convex molding surface.
Pressing the glass material heated to temperature Ta in contact with the surface of the master mold,
Cooling the glass material in the contacted state,
After the cooling, the abutting state is released.
Including forming the molding surface by
The release of the contacted state is performed when the temperature of the glass material is equal to or lower than the allowable temperature for releasing the contacted state Tb.
Tb is
Tb = Tg-200 ° C
Tg is the glass transition point (unit: ° C.) of the glass material.
During the cooling, when the temperature of the glass material is Tc, the temperature of the master mold is Tk.
Tk = Tc-A
When A is more than 0 ° C. and the temperature of the glass material is Tb or more and less than Tc, the temperature of the master mold is lower than the temperature of the glass material.
In the entire temperature range above Tb and below Tc
When the molded surface to be formed has a concave shape, the master mold and the glass material have the following formula 1:
(Equation 1)
-1.00 ≤ β _TK -β _TG ≤ 0.01
The filling,
When the molded surface to be formed has a convex shape, the master mold and the glass material are referred to by the following formula 2:
(Equation 2)
-0.01 ≤ β _TK -β _TG ≤ 1.00
The filling,
Tc is less than Tb and less than Ta, and Tc = Tg + (Ts-Tg) × B
B is more than 0 and less than 1, and Ts is the yield point (unit: ° C.) of the glass material.
In the above formula,
β _TK is a value indicating the shrinkage rate (unit:%) at the temperature (TA) based on the length at the temperature Ta of the master type without a unit.
β _TG is a value indicating the shrinkage rate (unit:%) at the temperature T based on the length of the glass material at the temperature Ta in no unit.
T is a method for manufacturing a glass molding mold, which is Tb or more and less than Tc. The method for manufacturing a glass molding mold according to claim 1, wherein A is 1 ° C. or higher and 300 ° C. or lower. The method for producing a glass molding mold according to claim 1 or 2, wherein the Tb is 50 ° C. or higher and 500 ° C. or lower. The method for producing a glass molding mold according to any one of claims 1 to 3, wherein the cooling is performed at a cooling rate of −0.1 to −100.0 ° C./min. Manufacturing a glass molding die by the manufacturing method according to any one of claims 1 to 4, and press molding a material to be molded by the manufactured glass molding die.
A method for manufacturing an optical element, including. The method for manufacturing an optical element according to claim 5, wherein the optical element is a glass optical element.

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