JP2022107529A - Glass molding die for optical element molding, and method for producing optical element - Google Patents

Abstract

To provide a glass molding die having elasticity with low temperature dependency.SOLUTION: The present invention pertains to a glass molding die for optical element molding. The glass is aluminosilicate glass. In the glass composition of the glass expressed by mol%, the total content of SiO2 and Al2O3 is 60% or more, and the molar ratio of the total content of Li2O, Na2O and K2O to the MgO content (Li2O+Na2O+K2O)/MgO is 0.000-0.400.SELECTED DRAWING: None

Description

The present invention relates to a glass molding die for forming an optical element and a method for manufacturing the 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

When the material to be molded is press-molded by a molding die to mass-produce optical elements, usually, press-molding of a plurality of materials to be molded is repeated using one molding die. It is desirable that the shape variation of the optical elements mass-produced in this way is small in order to stably supply the optical elements having the desired optical performance to the market. In this regard, the present inventor has obtained new findings that a glass molding die having a small elasticity temperature dependence is desirable as a glass molding die. When the material to be molded is press-molded, the glass molding mold is subjected to a temperature raising process and a temperature lowering process together with the material to be molded. If the elastic change of the glass molding mold is large in such a process, the molding surface shape of the glass molding mold changes significantly, and the surface shape of the optical element formed by transferring the molding surface varies. Because.

In view of the above, one aspect of the present invention is to provide a glass molding mold having a small elasticity temperature dependence.

As a result of diligent studies, the present inventor has determined the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / MgO of the total content of Li ₂ O, Na ₂ O and K ₂ O to the MgO content in the aluminosilicate glass. It was newly found that by setting the range from 0.000 to 0.400, it is possible to suppress a large change in the elasticity of the glass depending on the temperature, and more specifically, it is possible to suppress the temperature dependence of the Young rate.

That is, one aspect of the present invention is
A glass molding mold for forming optical elements.
The above glass is aluminosilicate glass,
In the glass composition of the above glass in terms of mol%,
The total content of SiO ₂ and Al ₂ O ₃ is 60% or more, and the molar ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the Mg O content (Li ₂ O + Na ₂ O + K ₂ O) / MgO Is in the range of 0.000 to 0.400, the above-mentioned glass molding mold,
Regarding.

Further, one aspect of the present invention relates to a method for manufacturing an optical element, which comprises press-molding a material to be molded by the glass molding die.

According to one aspect of the present invention, it is possible to provide a glass molding die for molding an optical element, which has a small elasticity temperature dependence. Further, according to one aspect of the present invention, it is also possible to provide a method for manufacturing an optical element using the above-mentioned glass molding mold.

It is schematic cross-sectional view which shows an example of the optical element manufacturing apparatus which includes a glass molding die. It is the schematic sectional drawing which shows an example of the manufacturing apparatus of a glass molding mold.

[Glass molding mold for forming optical elements]
Hereinafter, the 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 an optical element manufacturing apparatus provided with a glass molding die. The optical element manufacturing apparatus 10 of FIG. 1 manufactures an optical element 20 from a material to be molded 21 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 glass molding mold having the above composition can be the upper mold 11 in one form and the lower mold 12 in the other form. Further, in another form, the upper mold 11 and the lower mold 12 can both be glass molding molds having the above composition. The glasses constituting the upper mold 11 and the lower mold 12 can be the same glass in one form and different glasses in the other form. In a preferred form, both the upper mold 11 and the lower mold 12 can be glass molding molds having the above composition, and in a more preferable form, the glass constituting the upper mold 11 and the lower mold 12 is the same glass. There can be.

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 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 lower mold 12 can also be configured.

The glass constituting the glass molding mold will be described in more detail below.

<Glass composition>
In the present invention and the present specification, the glass composition is expressed on an oxide basis with respect to the cationic component of the glass. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials into those that are decomposed at the time of melting and exist as oxides in glass. Unless otherwise specified, the glass composition is expressed on a molar basis (molar%, molar ratio).
The various components constituting the glass contain elements contained in the glass by known methods such as inductively coupled plasma emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The amount (mass% of element) can be quantified. By dividing the content of this element (mass% of the element) by the atomic weight, the content of each element in mol% can be obtained.
Further, in the present invention and the present specification, the content of the constituent component is 0% or not contained or introduced, which means that the constituent component is substantially not contained, and the constituent component is at an unavoidable impurity level. It is permissible to be included.

The glass is aluminosilicate glass. In the present invention and the present specification, the "aluminosilicate glass" refers to 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. In the above glass, the total content of SiO ₂ and Al ₂ O ₃ (SiO ₂ + Al ₂ O ₃ ) is 60.0% or more. It is considered that the total content (SiO ₂ + Al ₂ O ₃ ) of 60.0% or more contributes to the reduction of the temperature dependence of elasticity (specifically, the temperature dependence of Young's modulus, the same applies hereinafter). From this point of view, the total content (SiO ₂ + Al ₂ O ₃ ) is preferably 65.0% or more, and in addition to the above viewpoint, the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding step is performed. It is preferably 66.0% or more from the viewpoint of increasing the temperature, and in addition to these viewpoints, it is preferably 68.0% or more from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). In addition to the viewpoint, from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is preferably 70.0% or more.
On the other hand, the total content (SiO ₂ + Al ₂ O ₃ ) is preferably 91.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, a normal press molding step is usually performed. It is preferably 90.5% or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at temperature, and 90.5 from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to these viewpoints. % Or less, and in addition to these viewpoints, from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is preferably 89.5% or less.

The molar ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the MgO content ((Li ₂ O + Na ₂ O + K ₂ O) / MgO) is 0. It is 400 or less, preferably 0.300 or less, and in addition to the above viewpoint, it is 0.200 or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed. Preferably, it is 0.150 or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to those viewpoints, and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example, α described later). Is low), it is preferably 0.100 or less. The molar ratio ((Li ₂ O + Na ₂ O + K ₂ O) / MgO) is 0.000 or more and can be 0.000 or more than 0.000.

The molar ratio of MgO content to the total content of MgO + CaO + SrO + BaO (MgO / (MgO + CaO + SrO + BaO)) can be, for example, 1.000 or less. The molar ratio (MgO / (MgO + CaO + SrO + BaO)) is preferably 0.500 or more from the viewpoint of further reducing the temperature dependence of elasticity. From the viewpoint of increasing the rigidity (for example, Young's modulus), it is preferably 0.550 or more, and in addition to these viewpoints, it is preferably 0.600 or more from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). Preferably, it is 0.650 or more from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to those viewpoints.

The total content of Li ₂ O + Na ₂ O + K ₂ O (Li ₂ O + Na ₂ O + K ₂ O) can be, for example, 0.0% or more or more than 0.0%. The total content (Li ₂ O + Na ₂ O + K ₂ O) can be, for example, 4.25% or less. The total content (Li ₂ O + Na ₂ O + K ₂ O) is preferably 4.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, a normal press molding step is usually performed. It is preferably 3.0% or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at temperature, and 2.0 from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to these viewpoints. % Or less, and in addition to these viewpoints, 1.0% or less is preferable from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

The total content of Na ₂ O and K ₂ O (Na ₂ O + K ₂ O) can be, for example, 0.0% or more or more than 0.0%. The total content (Na ₂ O + K ₂ O) can be, for example, 4.25% or less. The total content (Na ₂ O + K ₂ O) is, for example, 4.0% or less, 3.0% or less, 2 from the viewpoint of further reducing the temperature dependence of elasticity or not increasing the coefficient of thermal expansion too much. It can be 0.0% or less, 1.0% or less, or 0.5% or less.

The total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) can be, for example, 35.0% or less. The total content (MgO + CaO + SrO + BaO) is preferably 32.5% or less from the viewpoint of further reducing the temperature dependence of elasticity. For example, from the viewpoint of increasing Young's modulus), it is preferably 30.0% or less, and in addition to these viewpoints, it is 27.5% or less from the viewpoint of increasing the heat resistance of glass (for example, glass transition temperature). Preferably, it is 25.0% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to those viewpoints.
The total content (MgO + CaO + SrO + BaO) can be, for example, 0.0% or more or 1.0% or more. The total content (MgO + CaO + SrO + BaO) is preferably 8.0% or more from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (MgO + CaO + SrO + BaO) For example, from the viewpoint of increasing Young's modulus), it is preferably 8.5% or more, and in addition to these viewpoints, from the viewpoint of increasing the heat resistance of glass (for example, glass transition temperature), it is 9.0% or more. Preferably, it is 9.5% or more from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to those viewpoints.

The total content of MgO and CaO (MgO + CaO) can be, for example, 32.5% or less. The total content (MgO + CaO) is preferably 30.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (MgO + CaO) For example, from the viewpoint of increasing Young's modulus), it is preferably 27.5% or less, and in addition to these viewpoints, it is 25.0% or less from the viewpoint of increasing the heat resistance of glass (for example, glass transition temperature). Preferably, it is 22.5% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to those viewpoints.
The total content (MgO + CaO) can be, for example, 0.0% or more or 1.0% or more. The total content (MgO + CaO) is preferably 8.0% or more from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (MgO + CaO) For example, from the viewpoint of increasing Young's modulus), it is preferably 8.5% or more, and in addition to these viewpoints, from the viewpoint of increasing the heat resistance of glass (for example, glass transition temperature), it is 9.0% or more. Preferably, it is 9.5% or more from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to those viewpoints.

The total content of SiO ₂ , Al ₂ O ₃ and Mg O (SiO ₂ + Al ₂ O ₃ + MgO) can be, for example, 100.0% or less or less than 100.0%. Further, the total content (SiO ₂ + Al ₂ O ₃ + MgO) can be, for example, 80.0% or more. The total content (SiO ₂ + Al ₂ O ₃ + MgO) is preferably 85.0% or more from the viewpoint of further reducing the temperature dependence of the elasticity, and in addition to the above viewpoint, a normal press molding step is usually performed. It is preferably 86.0% or more from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at temperature, and 87.0 from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to these viewpoints. % Or more is preferable, and in addition to these viewpoints, 88.0% or more is preferable from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

The total content of Li ₂ O, Na ₂ O, K ₂ O, SrO and BaO (Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO) can be, for example, 0.0% or more or more than 0.0%.
Further, the total content (Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO) can be, for example, 4.5% or less, and may be 3.5% or less from the viewpoint of further reducing the temperature dependence of the elasticity. Preferably, in addition to the above viewpoints, it is preferably 3.0% or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the press molding step is usually performed, and in addition to these viewpoints, the heat resistance of the glass. From the viewpoint of increasing (for example, glass transition temperature), it is preferably 2.0% or less, and in addition to these viewpoints, 1.0 from the viewpoint of improving the thermal expansion characteristics of glass (for example, α described later is low). % Or less is preferable.

The total content of SiO ₂ , Al ₂ O ₃ , MgO, CaO, ZrO ₂ and TiO ₂ (SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO ₂ + TiO ₂ ) shall be, for example, 100.0% or less or less than 100.0%. Can be done. Further, the total content (SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO ₂ + TiO ₂ ) can be, for example, 85.0% or more, and is 90.0% or more from the viewpoint of further reducing the temperature dependence of the elasticity. In addition to the above viewpoints, it is preferably 91.0% or more from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the press molding process is usually performed, and in addition to these viewpoints, the glass. From the viewpoint of increasing the heat resistance (for example, glass transition temperature), it is preferably 92.0% or more, and in addition to these viewpoints, from the viewpoint of improving the thermal expansion characteristics of glass (for example, α described later is low). It is preferably 93.0% or more.

The molar ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of MgO and CaO ((Li ₂ O + Na ₂ O + K ₂ O) / (MgO + CaO)) is, for example, 0.000 or more or It can be greater than 0.000. Further, the molar ratio ((Li ₂ O + Na ₂ O + K ₂ O) / (MgO + CaO)) can be, for example, 2.000 or less, and is 0.150 or less from the viewpoint of further reducing the temperature dependence of the elasticity. In addition to the above viewpoints, it is preferably 0.100 or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the press molding process is usually performed. From the viewpoint of increasing the heat resistance (for example, the glass transition temperature), it is preferably 0.050 or less, and in addition to these viewpoints, from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is 0. It is preferably 030 or less.

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 + MgO ((Li ₂ O + Na ₂ O + K ₂ O) / (SiO ₂ + Al ₂ O ₃ + MgO)) is, for example, It can be greater than or equal to 0.000 or greater than or equal to 0.000. Further, the molar ratio ((Li ₂ O + Na ₂ O + K ₂ O) / (SiO ₂ + Al ₂ O ₃ + MgO)) can be, for example, 0.050 or less, from the viewpoint of further reducing the temperature dependence of the elasticity. Is preferably 0.040 or less, and in addition to the above viewpoints, it is preferably 0.030 or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the press molding process is usually performed. From the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), it is preferably 0.020 or less, and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example, α described later is low). From the viewpoint of, it is preferably 0.010 or less.

Molar ratio of the total content of Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO to the total content of SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO _{2 +} TiO ₂ ((Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO) / (SiO ₂ + Al ₂ O ₃ + TiO + ₂ )) can be 0.000 or more or more than 0.000. Further, the molar ratio ((Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO) / (SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO ₂ + TiO ₂ )) can be, for example, 0.100 or less, further reducing the temperature dependence of elasticity. It is preferably 0.090 or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed, and preferably 0.080 or less. In addition to these viewpoints, the temperature is preferably 0.060 or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example, α described later). From the viewpoint of (low), it is preferably 0.050 or less.

Total content of La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ (La ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Ta ₂ O ₅ + Nb ₂ O ₅ + HfO ₂ ) can be greater than or equal to 0.000% or greater than or equal to 0.000%. Further, the total content (La ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Ta ₂ O ₅ + Nb ₂ O ₅ + HfO ₂ ) can be, for example, 5.0% or less, and the temperature dependence of elasticity can be increased. From the viewpoint of further reduction or not to reduce the specific elastic modulus too much, it is preferable in the order of 4.0% or less, 3.0% or less, 2.0% or less, and 1.0% or less.

SiO ₂ is a skeleton component of glass and is a useful component for reducing the temperature dependence of elasticity. The SiO ₂ content is preferably 51.0% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, further reducing the temperature dependence of elasticity. It is preferably 55.0% or more from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed, in addition to the above viewpoint. It is preferable that the temperature is 57.0% or more from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to those viewpoints, and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example, which will be described later). From the viewpoint of low α), it is preferably 58.0% or more.
Further, the SiO ₂ content is preferably 79.0% or less from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and the temperature dependence of elasticity is further increased. From the viewpoint of further reduction, it is preferably 76.0% or less, and in addition to the above viewpoint, it is 75.0% or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed. In addition to these viewpoints, it is preferably 74.0% or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example). For example, from the viewpoint of low α, which will be described later), it is preferably 73.0% or less.

Al ₂ O ₃ is a skeleton component of glass and is a useful component for reducing the temperature dependence of elasticity. The Al ₂ O ₃ content is preferably 8.0% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and the temperature dependence of the elasticity is further increased. From the viewpoint of further reduction, it is preferably 10.0% or more, and in addition to the above viewpoint, it is 11.0% or more from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed. In addition to these viewpoints, it is preferably 12.0% or more from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), and in addition to these viewpoints, the thermal expansion characteristics of the glass are improved (for example). For example, α is low, which will be described later), and it is preferably 12.5% or more.
Further, the Al ₂ O ₃ content is preferably 24.0% or less from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and the temperature dependence of the elasticity. From the viewpoint of further reducing the amount of glass, it is preferably 22.0% or less, and in addition to the above viewpoint, it is 21.0% from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed. It is preferably 20.5% or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to those viewpoints, and in addition to these viewpoints, the thermal expansion characteristics of the glass. From the viewpoint of improvement (for example, α described later is low), it is preferably 20.0% or less.

B ₂ O ₃ is a component that can be arbitrarily contained in the glass, for example, for adjusting the viscosity of the glass. The B ₂ O ₃ content can be, for example, 0.0% or more or more than 0.0%, from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass mold. , 0.1% or more, 0.3% or more, 0.5% or more or 1.0% or more.
Further, the B ₂ O ₃ content is preferably 2.0% or less from the viewpoint of further reducing the temperature dependence of the elasticity, and in addition to the above viewpoint, the glass at a temperature at which the normal press molding step is performed. It is preferably 2.0% or less from the viewpoint of increasing the rigidity (for example, Young's modulus), and 2.0% or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to these viewpoints. In addition to these viewpoints, it is preferably 2.0% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

MgO is a component that can contribute to an increase in Young's modulus of glass, a decrease in specific gravity (and an increase in specific elastic modulus by reducing the specific gravity), and / or a decrease in α described later. The MgO content can be 0.0% or more, more than 0.0% or 1.0% or more, and the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. From the viewpoint, it is preferably 6.0% or more, and from the viewpoint of further reducing the temperature dependence of elasticity, it is preferably 8.0% or more. From the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass, it is preferably 8.5% or more, and in addition to these viewpoints, 9.0% from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). The above is preferable, and in addition to these viewpoints, it is preferably 9.5% or more from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).
Further, the MgO content can be, for example, 30.0% or less, and is 24.0% or less from the viewpoint of suppressing the generation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferable that it is 22.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding step is performed. It is preferably 21.0% or less from the viewpoint of increasing the temperature, and in addition to these viewpoints, it is preferably 20.5% or less from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). In addition to the viewpoint, it is preferably 20.0% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

The CaO content can be greater than or equal to 0.0% or greater than 0.0%. CaO is a component that can contribute to an increase in Young's modulus and a decrease in specific gravity (and an improvement in specific elastic modulus by reducing the specific gravity) of glass, and is preferably used in combination with MgO.
The CaO content can be, for example, 15.0% or less, from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and from the viewpoint of suppressing a decrease in the glass transition temperature. Is preferably 10.0% or less, preferably 8.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, at a temperature at which a normal press molding step is performed. From the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass, it is preferably 7.0% or less, and in addition to these viewpoints, from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), it is 6.0% or less. In addition to these viewpoints, it is preferably 5.5% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

The SrO content can be 0.0% or higher or greater than 0.0%. SrO is a component that can contribute to adjusting the meltability of glass, and is also a component that can contribute to further reducing the temperature dependence of elasticity by substituting with an alkaline component.
The SrO content can be, for example, 12.0% or less, from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and the viewpoint of suppressing the decrease in Young's modulus of the glass. From the viewpoint, it is preferably 6.0% or less, and from the viewpoint of further reducing the temperature dependence of elasticity, it is preferably 5.0% or less. From the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass, it is preferably 4.0% or less, and in addition to these viewpoints, 3.5% from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). It is preferably 3.0% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to these viewpoints.

The BaO content can be 0.0% or higher or greater than 0.0%. BaO is a component that can contribute to adjusting the meltability of glass, and is also a component that can contribute to further reducing the temperature dependence of elasticity by substituting with an alkaline component.
The BaO content can be, for example, 12.0% or less, from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold, and the viewpoint of suppressing the decrease in Young's modulus of the glass. From the viewpoint, it is preferably 8.0% or less, and from the viewpoint of further reducing the temperature dependence of elasticity, it is preferably 5.0% or less. It is preferably 4.5% or less from the viewpoint of increasing the rigidity (for example, Young's modulus) of the glass in the above, and 4.0% from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature) in addition to these viewpoints. It is preferably 3.8% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low) in addition to these viewpoints.

The ZnO content can be 0.0% or higher or greater than 0.0%. Reducing the ZnO content to a certain amount or less can contribute to suppressing a decrease in the glass transition temperature and / or a decrease in the specific elastic modulus.
The ZnO content can be, for example, 10.0% or less, and is 5.0% or less from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold and from the above viewpoint. It is preferably 4.0% or less from the viewpoint of further reducing the temperature dependence of the elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (for example, Young's modulus). ) Is preferably 3.5% or less, and in addition to these viewpoints, 3.0% or less is preferable from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). From the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is preferably 2.5% or less.

The Li ₂ O content can be 0.0% or higher or greater than 0.0%. Reducing the Li ₂ O content below a certain amount may contribute to further reducing the temperature dependence of elasticity, suppressing the decrease in the glass transition temperature, and / or suppressing the decrease in Young's modulus. ..
The Li ₂ O content can be, for example, 8.0% or less, and is 3.0% from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold and from the above viewpoint. It is preferably 2.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is usually performed (for example). From the viewpoint of increasing Young's modulus), it is preferably 1.5% or less, and in addition to these viewpoints, it is preferably 1.0% or less from the viewpoint of increasing the heat resistance of glass (for example, glass transition temperature). In addition to these viewpoints, it is preferably 0.5% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

The Na ₂ O content can be 0.0% or higher or greater than 0.0%. Reducing the Na ₂ O content below a certain amount may contribute to further reducing the temperature dependence of elasticity, suppressing the decrease in the glass transition temperature, and / or suppressing the decrease in Young's modulus. ..
The Na ₂ O content is preferably 3.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (for example, From the viewpoint of increasing Young's modulus), it is preferably 2.0% or less, and in addition to these viewpoints, it is preferably 1.0% or less from the viewpoint of increasing the heat resistance of glass (for example, the glass transition temperature). In addition to these viewpoints, it is preferably 0.5% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

_The K2O content can be 0.0% or higher or greater than 0.0%. Keeping the _K2O content below a certain amount can contribute to further reducing the temperature dependence of elasticity, suppressing the decrease in the glass transition temperature, and / or suppressing the decrease in Young's modulus. ..
The K ₂ O content is preferably 3.0% or less from the viewpoint of further reducing the temperature dependence of elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (for example, From the viewpoint of increasing Young's modulus), it is preferably 2.0% or less, and in addition to these viewpoints, it is preferably 1.0% or less from the viewpoint of increasing the heat resistance of glass (for example, the glass transition temperature). In addition to these viewpoints, it is preferably 0.5% or less from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low).

ZrO ₂ is a component that can be arbitrarily contained in the glass, for example, in order to improve Young's modulus. The ZrO ₂ content can be, for example, 0.0% or more or more than 0.0%. The ZrO ₂ content can be, for example, 10.0% or less, and 4.0% or less from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. Is preferable, and from the viewpoint of further reducing the temperature dependence of elasticity, it is preferably 2.0% or less, and in addition to the above viewpoint, the rigidity (for example, Young's modulus) of the glass at the temperature at which the normal press molding process is performed From the viewpoint of increasing, it is preferably 2.0% or less, and in addition to those viewpoints, from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature), it is preferably 1.0% or less, and these viewpoints. In addition, from the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is preferably 0.5% or less.

TiO ₂ is a component that can be optionally contained in the glass, for example, in order to improve Young's modulus and / or suppress the generation of bubbles in the glass molding die. The TiO ₂ content can be, for example, 0.0% or more or more than 0.0%. The TiO ₂ content is 0.1% or more, 0.3% or more, 0.5% or more or 1 from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. It can be 0.0% or more.
Further, the TiO ₂ content can be, for example, 6.0% or less, and is 5.0% or less from the viewpoint of suppressing the generation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferably 4.0% or less from the viewpoint of further reducing the temperature dependence of the elasticity, and in addition to the above viewpoint, the rigidity of the glass at the temperature at which the normal press molding step is performed (for example, Young's modulus). ) Is preferably 3.0% or less, and in addition to these viewpoints, 2.0% or less is preferable from the viewpoint of increasing the heat resistance of the glass (for example, the glass transition temperature). From the viewpoint of improving the thermal expansion characteristics of the glass (for example, α described later is low), it is preferably 1.0% or less.

The La ₂ O ₃ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. Is even more preferable. The La ₂ O ₃ content can be 0.0%, 0.0% or more or more than 0.0%.

The Y ₂ O ₃ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. Is preferable. The Y ₂ O ₃ content can be 1.0% or less or 0.5% or less, and is 0.0% (ie, not contained), 0.0% or more or more than 0.0%. You can also do it.

The Yb ₂ O ₃ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. Is even more preferable. The Yb ₂ O ₃ content can be 1.0% or less or 0.5% or less, and is 0.0% (ie, not contained), 0.0% or more or more than 0.0%. You can also do it.

The Ta ₂ O ₅ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. Is even more preferable. The Ta ₂ O ₅ content can be 1.0% or less or 0.5% or less, and is 0.0% (ie, not contained), 0.0% or more or more than 0.0%. You can also do it.

The Nb ₂ O ₅ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. Is even more preferable. The Nb ₂ O ₅ content can be 1.0% or less or 0.5% or less, and is 0.0% (ie, not contained), 0.0% or more or more than 0.0%. You can also do it.

The HfO ₂ content is preferably 4.0% or less, more preferably 3.0% or less, and more preferably 2.0% or less, from the viewpoint of reducing the temperature dependence of elasticity. More preferred. The HfO ₂ content can be 1.0% or less or 0.5% or less, and can be 0.0% (ie, not contained), 0.0% or more or more than 0.0%. can.

SnO ₂ is a component that can be optionally contained in the glass, for example, in order to improve Young's modulus and / or suppress the generation of bubbles in the glass molding die. The SnO ₂ content can be, for example, 0.0% or more or more than 0.0%. The SnO ₂ content is 0.05% or more, 0.3% or more or 0.5% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. be able to.
Further, the SnO ₂ content is preferably 3.0% or less, preferably 2.0% or less, from the viewpoint of suppressing the generation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferably 1.5% or less, preferably 1.0% or less, and preferably 0.5% or less. The SnO ₂ content can be 0.2% or less or 0.1% or less, and can be 0.0% (ie, not contained), 0.0% or more or more than 0.0%. can.

CeO ₂ is a component that can be optionally contained in the glass, for example, in order to improve Young's modulus and / or suppress the generation of bubbles in the glass molding die. The CeO ₂ content can be, for example, 0.0% or more or more than 0.0%. The CeO ₂ content is 0.05% or more, 0.3% or more or 0.5% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. be able to.
The CeO ₂ content is preferably 3.0% or less, preferably 2.0% or less, from the viewpoint of suppressing the generation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferably 1.5% or less, preferably 1.0% or less, and preferably 0.5% or less. The CeO ₂ content can be 0.2% or less or 0.1% or less, and can be 0.0% (ie, not contained), 0.0% or more or more than 0.0%. can.

Sb ₂ O ₃ is a component that can be arbitrarily contained in the glass, for example, in order to improve Young's modulus and / or suppress the generation of bubbles in the glass molding die. The Sb ₂ O ₃ content can be, for example, 0.0% or more or more than 0.0%. The Sb ₂ O ₃ content is 0.05% or more, 0.1% or more, 0.3% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. , 0.5% or more or 1.0% or more.
The Sb ₂ O ₃ content is preferably 3.0% or less, preferably 2.0% or less, from the viewpoint of suppressing the generation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferably 1.5% or less, preferably 1.0% or less, and preferably 0.5% or less.

Fe ₂ O ₃ is a component that can be arbitrarily contained in the glass, for example, in order to improve Young's modulus and / or suppress the generation of bubbles in the glass molding die. The Fe ₂ O ₃ content can be, for example, 0.0% or more or more than 0.0%. The Fe ₂ O ₃ content is 0.05% or more, 0.3% or more or 0.5% or more from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. Can be.
The Fe ₂ O ₃ content is preferably 2.0% or less, preferably 1.0% or less, from the viewpoint of suppressing the formation of bubbles, veins and / or undissolved substances in the glass molding mold. It is preferably 0.5% or less, preferably 0.2% or less, and preferably 0.01% or less.

<Glass properties>
In one form, the glass constituting the glass molding mold can have one or more of the glass physical characteristics described below.

(Glass transition temperature Tg, yield point Ts)
In the present invention and the present specification, the glass transition temperature Tg and the yield point Ts of the glass constituting the glass molding mold are values obtained by the following methods.
A glass sample is cut out from a glass mold, or a glass sample composed of the same material as the glass mold is prepared. The thermal expansion characteristics of each glass sample are measured by a method according to JOBIS08-2003. Specifically, the 1st digit of the Tg (unit: ° C) of the glass is rounded to the nearest 10 ° C to set the annealing temperature, and the glass sample is placed in an annealing furnace that can raise the temperature to this temperature. The temperature is raised from room temperature (about 25 ° C.) to the above set temperature in 1 to 2 hours, held for 2 hours, cooled at a cooling rate of -30 ° C./hour for 4 hours, and then kept at room temperature (about 25 ° C.) in the furnace. The allowed-chilled glass sample is processed into a cylindrical glass sample having a diameter of 4.0 to 5.0 mm and a length of 10 mm to 20 mm. A graph (so-called thermal expansion) obtained by heating this glass 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. Create a curve). 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 defined as the glass transition point Tg, and in the above graph, the temperature at which the expansion apparently stops, that is, the elongation increases from increases to decrease as the temperature rises. Let the temperature of the turning point be the yield point Ts.
In order for the glass molding die to be a molding die suitable for press molding at a higher temperature, the glass transition temperature Tg of the glass is preferably 755 ° C. or higher, and more preferably 760 ° C. or higher. It is more preferably 765 ° C. or higher, and even more preferably 770 ° C. or higher. The glass transition temperature Tg of the glass can be, for example, 860 ° C or lower, 855 ° C or lower, 850 ° C or lower, 845 ° C or lower, or 840 ° C or lower.
Further, in order for the glass molding die to be a molding die suitable for press molding at a higher temperature, the yield point Ts of the glass is preferably 830 ° C. or higher, preferably 835 ° C. or higher. More preferably, it is more preferably 840 ° C. or higher, and even more preferably 845 ° C. or higher. Further, the yield point Ts of the glass can be, for example, 940 ° C or lower, 935 ° C or lower, 930 ° C or lower, 925 ° C or lower, or 920 ° C or lower.

(Average coefficient of linear expansion α)
For example, as shown in FIG. 1, a glass molding die can be combined with a guide die to form an optical element manufacturing apparatus. From the viewpoint of stress control received by the glass molding mold in the optical element manufacturing apparatus when combined with such a constituent member such as a guide mold, it is preferable to adjust the thermal expansion characteristics of the glass constituting the glass molding mold. In one form, the thermal expansion characteristics of the glass constituting the glass molding mold are preferably 23.5 × 10 ^-7 / ° C or higher as the average linear expansion coefficient α in the temperature range of 100 to 300 ° C. It is more preferably 24.0 × 10 ^-7 / ° C. or higher, further preferably 24.5 × 10 ^-7 / ° C. or higher, and even more preferably 25.0 × 10 ^-7 / ° C. or higher. .. The average coefficient of linear expansion α of the glass is preferably 48.0 × 10 ^-7 / ° C or less, more preferably 47.0 × 10 ^-7 / ° C or less, and 46.0 ×. It is more preferably ^10-7 / ° C. or lower, further preferably 45.0 × ^10-7 / ° C. or lower, and even more preferably 44.0 × ^10-7 / ° C. or lower.
The average coefficient of linear expansion α is calculated by the formula: α = d / (L × T). d is the amount of change in sample length (mm) in the temperature range of 100 to 300 ° C., L is the initial length of the sample (mm), and T is the temperature difference (K) (300 ° C.-100 ° C. = 200 ° C.). .. As a device for measuring the coefficient of linear expansion, a thermomechanical analyzer (TMA; Thermomechanical Analysis) or a dilatometer can be used.
The average coefficient of linear expansion α can be obtained by, for example, the following method.
Tg (unit: ° C.) of glass using a thermomechanical analyzer (TMA; Thermomechanical Analysis) for a glass sample cut out from a glass mold or a glass sample composed of the same material as the glass mold. The 1st place of the glass is rounded to the nearest 10 ° C, and the temperature is set as the annealing temperature. A glass sample having a diameter of 4.0 to 5 is obtained by raising the temperature to the above-mentioned set temperature over time, holding it for 2 hours, slowly cooling it at −30 ° C./hour for 4 hours, and then allowing it to cool to room temperature (about 25 ° C.) in the furnace. Process into a cylindrical glass sample of 0.0 mm x 10 mm to 20 mm in length. A graph obtained by heating this glass 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 thermal expansion). From the curve), the average linear expansion coefficient α can be obtained.

In one form, the constituent member of the manufacturing apparatus for an optical element such as a guide type can be a member made of silicon carbide (SiC). The average coefficient of linear expansion α of SiC is about 37 × 10 ^-7 / ° C. When α of the glass constituting the glass molding mold is “A × ^10-7 / ° C.”, the fact that X calculated by the formula: X = A-37 is a negative value means that the optical element is manufactured. It is preferable from the viewpoint of suppressing the fall of the optical element from time to time. From this point of view, X calculated by the above formula of the glass is preferably -13.5 or more, more preferably -13.0 or more, and further preferably -12.5 or more. , -12.0 or more is more preferable. Further, the X can be, for example, 11.0 or less, 10.0 or less, 9.0 or less, 8.0 or less, or 7.0 or less, and is preferably less than 0.0 from the above viewpoint. ..
Further, from the viewpoint of suppressing the glass molding mold from receiving stress from the SiC member in the optical element manufacturing apparatus, the absolute value | X | of X is preferably 13.0 or less, and 12. It is more preferably 5 or less, further preferably 12.0 or less, and even more preferably 11.5 or less. Further, the absolute value | X | is preferably 0.0 or more, and more preferably more than 0.0.

(specific gravity)
From the viewpoint of adjusting the specific elastic modulus described later, it is preferable that the specific gravity of the glass is small. The specific gravity of the glass is preferably 2.98 or less, more preferably 2.93 or less, further preferably 2.88 or less, and even more preferably 2.83 or less. Further, the specific gravity of the glass can be, for example, 2.35 or more, 2.37 or more, 2.40 or more, or 2.43 or more, and can be lower than the value exemplified here. The specific gravity of the glass can be determined by the Archimedes method for a measuring glass sample cut out from a glass molding die or for a measuring glass sample composed of the same material as the glass molding die.

(Young's modulus)
From the viewpoint of suppressing deformation of the glass molding die, it is preferable that the Young's modulus of the glass constituting the glass molding die is high. From this point of view, the Young's modulus of the glass is preferably 87 GPa or more, more preferably 88 GPa or more, further preferably 89 GPa or more, and further preferably 90 GPa or more. Further, the Young's modulus of the glass can be, for example, 120 GPa or less, 110 GPa or less, 101 GPa or less, 100 GPa or less, 99 GPa or less, 98 GPa or less, or 97 GPa or less, or can exceed the values exemplified here. The Young's ratio of the glass is determined by JIS at a measurement temperature of 25 ° C. ± 5 ° C. for a measurement glass sample cut out from a glass mold or a measurement glass sample composed of the same material as the glass mold. It can be obtained by the ultrasonic pulse method described in R1602: 1995. The size of the glass sample for measurement can be appropriately set to a size equal to or larger than the minimum dimension described in JIS R1602: 1995.

For the glass constituting the glass molding die, it is preferable that the rigidity of the glass at the temperature at which the press molding process is usually performed is high. From this point of view, the Young's modulus of the glass at the measurement temperature of 590 ° C. is preferably 80 GPa or more, more preferably 85 GPa or more, further preferably 88 GPa or more, and further preferably 90 GPa or more. It is more preferably 91 GPa or more, and even more preferably 92 GPa or more. The Young's modulus of the glass at a measurement temperature of 590 ° C. can be, for example, 118 GPa or less, 107 GPa or less, 102 GPa or less, 100 GPa or less, 98 GPa or less, 97 GPa or less, or 96 GPa or less, or the values exemplified here. It can also be exceeded.
From the above viewpoint, the Young's modulus of the glass at the measurement temperature of 650 ° C. is preferably 80 GPa or more, more preferably 84 GPa or more, further preferably 87 GPa or more, and 89 GPa or more. Is even more preferable, 90 GPa or more is even more preferable, and 91 GPa or more is even more preferable. The Young's modulus of the glass at a measurement temperature of 650 ° C. can be, for example, 117 GPa or less, 106 GPa or less, 101 GPa or less, 99 GPa or less, 97 GPa or less, 96 GPa or less, or 95 GPa or less, or the values exemplified here. It can also be exceeded.
The Young's modulus at the measurement temperature of 590 ° C. or 650 ° C. can be determined by the above-mentioned Young's modulus measurement method except that the measurement temperature is set to 590 ° C. or 650 ° C.

(Specific elastic modulus)
The specific elastic modulus is the Young's modulus of glass divided by the density. Here, the density can be considered as a value obtained by adding a unit of g / cm ³ to the specific gravity of glass. A molding die made of glass having a higher specific elastic modulus can be said to be a molding die that is lighter but less likely to be deformed. From this point of view, the specific elastic modulus of the glass is preferably 31.0 MNm / kg or more, more preferably 32.0 MN m / kg or more, and further preferably 33.0 MN m / kg or more. It is more preferably 33.5 MNm / kg or more. The specific elastic modulus of the glass is, for example, 41.0 MNm / kg or less, 40.5 MN m / kg or less, 40.0 MN m / kg or less, 39.5 MN m / kg or less, or 39.0 MN m / kg or less. It can, and can exceed the values illustrated here.

(Rigidity)
The rigidity of the glass represents the difficulty of deformation with respect to the shearing force, and from the viewpoint of suppressing the deformation of the glass molding mold, it is preferable that the glass forming the glass molding mold has a high rigidity. From this point of view, the rigidity of the glass can be 33.0 GPa or more, and is preferably 34.0 GPa or more, 35.0 GPa or more, and 36.0 GPa or more in that order. The rigidity of the glass can be, for example, 42.0 GPa or less, 41.5 GPa or less, 41.0 GPa or less, 40.5 GPa or less, or 40.0 GPa or less.
The rigidity of the glass is determined by JIS at a measurement temperature of 25 ° C. ± 5 ° C. for a glass sample for measurement cut out from a glass mold or for a glass sample for measurement made of the same material as the glass mold. It can be obtained by the ultrasonic pulse method described in R1602: 1995. The size of the glass sample for measurement can be appropriately set to a size equal to or larger than the minimum dimension described in JIS R1602: 1995.

(Poisson's ratio)
The Poisson's ratio of glass is a unitless parameter obtained from the ratio of Young's modulus and rigidity. The Poisson's ratio of the glass can be, for example, 0.190 or more, and is preferably 0.195 or more, 0.200 or more, 0.205 or more, and 0.210 or more in that order. The Poisson's ratio of the glass can be, for example, 0.333 or less, and is preferably 0.300 or less, 0.290 or less, 0.280 or less, 0.270 or less, and 0.260 or less in that order.
The Poisson's ratio of the glass is determined by JIS at a measurement temperature of 25 ° C. ± 5 ° C. for a measurement glass sample cut out from a glass mold or a measurement glass sample composed of the same material as the glass mold. It can be obtained by the ultrasonic pulse method described in R1602: 1995. The size of the glass sample for measurement can be appropriately set to a size equal to or larger than the minimum dimension described in JIS R1602: 1995.

(Liquid phase temperature LT)
As an index of the meltability of glass, the liquid phase temperature LT can be mentioned. From the viewpoint of improving the meltability of the glass, the liquidus temperature LT of the glass constituting the glass molding mold is preferably 1440 ° C. or lower, more preferably 1420 ° C. or lower, and 1400 ° C. or lower. More preferably, it is more preferably 1380 ° C. or lower, and even more preferably 1360 ° C. or lower. Further, the liquidus temperature LT of the glass can be, for example, 1150 ° C. or higher, 1170 ° C. or higher, 1200 ° C. or higher, or 1230 ° C. or higher, and can be lower than the value exemplified here.

The "liquid phase temperature" in the present invention and the present specification refers to the measurement glass sample cut out from the glass mold or the measurement glass sample composed of the same material as the glass mold by the following method. Desired.
Approximately 20 cc of glass (for example, 50 g for glass with a specific gravity of 2.5 g / cc) is placed in a platinum crucible and heated in a furnace with an atmospheric temperature of 1400 ° C to 1600 ° C for 15 to 30 minutes to bring it into a molten state. After that, the glass transition temperature is cooled to Tg or less. The cooled glass is moved into a furnace having an atmospheric temperature T in the furnace and kept in the furnace for 16 hours, and then the presence or absence of crystal precipitation is determined by observation with an optical microscope (magnification: 100 times).
For different T (in increments of 10 ° C.), the presence or absence of crystal precipitation is determined by the above method. The lowest temperature of T at which no crystal precipitation is observed is defined as the liquidus temperature.

<Manufacturing method of glass molding>
The glass molding mold can be manufactured as a glass molding mold having a concave or convex molding surface by pressing a glass material for the glass molding mold with a master mold.

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. The cooling rate C in the cooling step is an average cooling rate from Ta to Tb, which will be described later, and is −0.1 from the viewpoint of increasing the productivity of the glass molding mold and / or suppressing the thermal deterioration of the master mold. ° C / min or higher, -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, It can be -10.0 ° C./min or higher or -15.0 ° C./min or higher, and also -100.0 ° C./min or lower, -50.0 ° C./min or lower, -30.0 ° C./min. Below, -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. It can be 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 one embodiment, the press load and / or cooling rate may be switched at a temperature Tm below Tb> Ta from the standpoint of increasing productivity. The cooling rate C at this time is based on the cooling rate Ca (unit: ° C./min) of Ta to Tm and the cooling rate Cb (unit: ° C./min) of Tm to Tb.
C (unit: ° C./minute) = (Ta-Tb) / {(Ta-Tm) / Ca + (Tm-Tb) / Cb}
Can be obtained as.

After the above cooling, the contact state with the master mold surface 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. The release of the contact state can be performed at a temperature Tb where the hardening of the glass is sufficiently advanced. Tb can be, for example, a temperature near or below Tg. 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.

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 press-molding a material to be molded by the 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 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, a specific example of a method for obtaining an optical element made of glass by press molding will be described.
A carbon film is coated on the molding surface of the glass molding die as a release film and arranged in the optical element manufacturing apparatus. After the glass material for press molding (glass material to be molded) is supplied into the optical element manufacturing apparatus, the glass material to be molded is heated and softened to a temperature equivalent to 10 ⁸ dPa · s to 10 ¹² dPa · s. Then, by pressing this with the molding die, the molding surface of the glass molding die is transferred to the glass material to be molded. The set temperature of the device at this time is called the press temperature. In order to prevent oxidation of the molded surface, it is preferable that the atmosphere at the time of molding is non-oxidizing. After that, while applying an appropriate load application schedule (for example, -50 ° C / min, etc.) to the glass molding mold and the glass material to be molded, while maintaining the close contact between the molding surface and the glass element to be molded, the glass to be molded After cooling to the vicinity of the glass transition temperature of the glass constituting the material, the optical element manufacturing apparatus can be opened (disassembled) and the molded body (optical element) can be taken out.

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.

[Examples 1 to 20, Comparative Example 1]
<Glass material for glass moldings>
A glass material having the glass composition shown in Table 1 was prepared by the following method.
Various oxides, boric acid, carbonates, and sulfates were used as raw materials for introducing each component so as to have the glass composition shown in Table 1, and the raw materials were weighed and sufficiently mixed to prepare a blending raw material. At this time, a total of 200 g of raw materials were used in terms of oxides. The crucible containing the compounding raw material was placed in a glass melting furnace, the glass was melted, clarified and homogenized at 1600 ° C. for 3 hours, and the molten glass was poured from the crucible into a preheated mold to form a mold. Next, the molded glass was taken out from the mold and placed in an annealing furnace set to a furnace temperature of 750 ° C., and annealed at a slow cooling / lowering rate of −30 ° C./hour to obtain a glass material.

<Master type>
As a master mold, a SiC master mold was prepared.

<Making a glass mold by press molding>
Each glass material was press-molded by the method described above by the molding die manufacturing apparatus having the configuration shown in FIG. The temperature Ta is set to a temperature in the range of 780 ° C to 900 ° C, a load is applied and pressed while the glass material is in contact with the surface of the master mold, and the temperature Tb is set to a temperature in the range of 450 ° C to 650 ° C. C (average cooling rate from temperature Ta to Tb) is cooled in the range of −5.0 ° C./min to -30.0 ° C./min, and then allowed to cool to about room temperature in a molding die molding apparatus. The contact state with the master mold was released, and the glass molding mold on which the surface shape of the master mold was transferred to form the molding surface was taken out from the molding mold manufacturing apparatus.
In this way, a glass molding mold having a concave molding surface was produced.

[Evaluation of glass molding]
<Glass properties>
For each of the glass molding dies of Examples 1 to 20 and Comparative Example 1, the various glass physical characteristics shown in Table 3 were obtained by the methods exemplified above, and are shown in Table 2. The Young's modulus shown in Table 2 is the Young's modulus at a measurement temperature of 25 ° C. ± 5 ° C.

<Evaluation of temperature dependence of elasticity (Young's modulus)>
For each of the glass moldings of Examples 1 to 20, the Young's modulus at each measurement temperature was measured at the measurement temperatures of 590 ° C, 650 ° C, 700 ° C and 750 ° C, respectively, by the methods exemplified above.
For the glass molding mold of Comparative Example 1, Young's modulus at each measurement temperature was measured at the measurement temperatures of 590 ° C. and 650 ° C. by the methods exemplified above, respectively.
In Table 3, E (590), E (650), E (700), and E (750) each indicate the Young's modulus at the measurement temperature of the value in parentheses. The unit is "GPa".
From the measurement results, an approximate straight line is created by the minimum square method with the Young rate as the vertical axis and the measurement temperature as the horizontal axis, and the slope of this approximate straight line is shown in Table 3 as the "slope of the Young rate". The unit of slope of Young's modulus is "GPa / ° C.".
It can be determined that the smaller the absolute value of the slope of Young's modulus obtained in this way, the smaller the temperature dependence of Young's modulus of the glass molding die. From the results shown in Table 3, it can be confirmed that the glass molding dies of Examples 1 to 20 have a smaller temperature dependence of Young's modulus than the glass molding dies of Comparative Example 1. In one form, the gradient of Young's modulus calculated as described above from the Young's modulus at four measurement temperatures of 590 ° C., 650 ° C., 700 ° C. and 750 ° C. is preferably −0.0100 GPa / ° C. or higher. , -0.0090 GPa / ° C. or higher, more preferably -0.0080 GPa / ° C. or higher, further preferably -0.0070 GPa / ° C. or higher, and -0.0060 GPa / ° C. or higher. Is even more preferably -0.0050 GPa / ° C. or higher, even more preferably -0.0045 GPa / ° C. or higher, and even more preferably -0.0040 GPa / ° C. or higher. Even more preferable. The slope of Young's modulus can be, for example, −0.0010 GPa / ° C. or lower or −0.0020 GPa / ° C. or lower, or can exceed the value exemplified here.

[Manufacturing and evaluation of optical elements]
It is considered that the smaller the shape change of the molding surface of the glass molding mold when mass-producing the optical element by press molding, the more the occurrence of the shape variation of the optical element can be suppressed. The degree of change in the molding surface shape of the glass molding mold when mass-producing optical elements by press molding can be evaluated by the following method.
The glass molding die is exposed to a press temperature environment in one lens molding cycle, heated, and then cooled to near the glass transition temperature. It is considered that the shape change of the molding surface of the glass molding mold mainly occurs at a high press temperature in one lens molding cycle, and the change increases as the number of presses increases. The number of Newtons is calculated from the shape of the glass molding die used for lens molding and the shape before use for a certain number of times (number of shots) X or more (for example, 50 shots or more) at a certain press temperature.
The number of Newtons can be obtained by the following method.
The shape of the molding surface of the glass molding mold is measured at room temperature (about 25 ° C.) using a shape measuring device. Examples of the shape measuring device include an interferometer, a three-dimensional measuring machine (for example, UA3P manufactured by Panasonic Production Engineering Co., Ltd.) and the like. Here, UA3P manufactured by Panasonic Production Engineering Co., Ltd. was used. From the value of the radius of curvature R of the molded surface (near axis R for the aspherical molded surface) measured by the shape measurement, the number of Newton rings when the measurement wavelength is 546.1 nm is calculated.
The value D / X obtained by dividing the difference D (after use-before use) of the number of Newtons before and after use by the number of shots X is defined as the amount of change ΔN of Newtons per shot, and by multiplying this by 100, per 100 shots. Find the Newton change amount of 100 D / X. The lower limit of the value of the number of presses X for obtaining ΔN is set to 50 or more in consideration of the measurement error of ΔN. Regarding the upper limit of X, if X is increased until the shape of the glass molding mold does not change, the apparent ΔN becomes small and may not be suitable for evaluation. Therefore, the upper limit of X is preferably 100 or less. , 80 or less, more preferably 60 or less.
For example, the Newton change amount ΔN per shot at 590 ° C. is described first from the shape of the glass molding mold used for lens molding and the shape before use for a certain number of times X (50 ≦ X ≦ 100) at a press temperature of 590 ° C. The number of Newtons calculated by the above method was calculated, and D / X, which is the value obtained by dividing the difference D (after use-before use) of the number of Newtons before and after using the lens molding by the number of shots X, is "1 at 590 ° C." It can be obtained as "Newton change amount ΔN per shot". It can be evaluated that the smaller the value obtained in this way, the smaller the shape change of the molding surface of the glass molding mold when mass-producing optical elements by press molding.
For Examples 7, 11, 12 and Comparative Example 1, the glass molding dies having the above concave shapes are used as the upper and lower dies, respectively, and are shown in FIG. 1 by the method of the specific example described above. The number of shots is X (50 ≦), where the press temperature is 590 ° C. It was repeated as X ≦ 60). Then, 100 D / X obtained by multiplying ΔN = D / X obtained by the above method by 100 is calculated, and is shown in Table 4 as “a value obtained by multiplying the Newton change amount ΔN per shot at 590 ° C by 100”. The "value obtained by multiplying the Newwon change amount ΔN per shot at 590 ° C. by 100" can be 0.00 or more or more than 0.00, and preferably 1.00 or less, preferably 0.90. Hereinafter, it is more preferable in the order of 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, and 0.30 or less. In Comparative Example 1, since the shape of the molding surface of the molding die changed significantly and press molding could not be performed up to the number of shots X, Table 4 shows “press impossible”.

As shown in Table 3, the glass molding mold of the example composed of the glass having the composition described above has a small temperature dependence of Young's modulus. The results shown in Table 4 show that the glass molding die having such a small Young's modulus temperature dependence has little change in the shape of the molding surface of the glass molding die when mass-producing optical elements by press molding. There is.

Finally, each of the above aspects will be summarized.

According to one aspect, it is a glass molding mold for forming an optical element, and the glass is an aluminosilicate glass, and the total content of SiO ₂ and Al ₂ O ₃ in the glass composition of the glass in terms of mol%. Is 60% or more and the molar ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the MgO content (Li ₂ O + Na ₂ O + K ₂ O) / MgO is in the range of 0.000 to 0.400. A glass mold is provided.

The glass molding die is a glass molding die for an optical element, and can be a glass molding die having a small elasticity temperature dependence.

In one form, the molar ratio of MgO to the total content of MgO, CaO, SrO and BaO (MgO / (MgO + CaO + SrO + BaO)) can be 0.500 or more in the glass composition expressed in mole% of the glass.

In one form, in the molar% representation of the glass composition of the glass, Li ₂ O, Na ₂ O, K ₂ O, SrO with respect to the total content of SiO ₂ , Al ₂ O ₃ , MgO, CaO, ZrO ₂ and TiO ₂ And the molar ratio of the total content of BaO ((Li ₂ O + Na ₂ O + K ₂ O + SrO + BaO) / (SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO ₂ + TiO ₂ )) can be in the range of 0.000 to 0.100.

In one form, the MgO content is 1.0 to 30.0%, the CaO content is 0.0 to 15.0%, and the SrO content is 0.0 to 12 in the molar%-denominated glass composition of the glass. 0.0%, BaO content 0.0 to 12.0%, ZnO content 0.0 to 10.0%, Li ₂ O content 0.0 to 8.0%, Na ₂ O and K The total content with ₂ O is 0.0 to 4.25%, the ZrO ₂ content is 0.0 to 10.0%, the TiO ₂ content is 0.0 to 6.0% and La ₂ O ₃ , The total content of Y ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ can be 0.0-4.0%.

In one form, the Young's modulus of the glass at a measurement temperature of 590 ° C. can be 80 GPa or more.

In one form, the Young's modulus of the glass at a measurement temperature of 650 ° C. can be 80 GPa or more.

According to one aspect, there is provided a method for manufacturing an optical element, which comprises press-molding a material to be molded by the 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 (8)

A glass molding mold for forming optical elements.
The glass is aluminosilicate glass and
In the glass composition of the glass in terms of mole%,
The total content of SiO ₂ and Al ₂ O ₃ is 60% or more, and the molar ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the Mg O content (Li ₂ O + Na ₂ O + K ₂ O) / MgO The glass molding die in the range of 0.000 to 0.400. In the glass composition of the glass in terms of mole%,
The glass molding mold according to claim 1, wherein the molar ratio of MgO (MgO / (MgO + CaO + SrO + BaO)) to the total content of MgO, CaO, SrO and BaO is 0.500 or more. In the glass composition of the glass in terms of mole%,
The molar ratio of the total content of Li ₂ O, Na ₂ O, K ₂ O, SrO and BaO to the total content of SiO ₂ , Al ₂ O ₃ , MgO, CaO, ZrO ₂ and TiO ₂ ((Li ₂ O + Na ₂ ). The glass molding mold according to claim 1 or 2, wherein O + K ₂ O + SrO + BaO) / (SiO ₂ + Al ₂ O ₃ + MgO + CaO + ZrO ₂ + TIO ₂ )) is in the range of 0.000 to 0.100. In the glass composition of the glass in terms of mole%,
MgO content 1.0-30.0%,
CaO content is 0.0-15.0%,
SrO content is 0.0-12.0%,
BaO content is 0.0-12.0%,
ZnO content is 0.0-10.0%,
Li ₂ O content is 0.0-8.0%,
The total content of Na ₂ O and K ₂ O is 0.0-4.25%,
ZrO ₂ content is 0.0-10.0%,
The TiO ₂ content is 0.0 to 6.0%, and the total content of 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. ~ 4.0%,
The glass molding mold according to any one of claims 1 to 3. The glass molding mold according to any one of claims 1 to 4, wherein the Young's modulus of the glass at a measurement temperature of 590 ° C. is 80 GPa or more. The glass molding mold according to any one of claims 1 to 5, wherein the Young's modulus of the glass at a measurement temperature of 650 ° C. is 80 GPa or more. Press-molding the material to be molded by the glass molding die according to any one of claims 1 to 6.
A method for manufacturing an optical element, including. The method for manufacturing an optical element according to claim 7, wherein the optical element is a glass optical element.

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