JP6218536B2 - Optical element and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical element and a method for manufacturing the same.

  As a method of manufacturing an optical element such as a glass lens, a method of press-molding a molding material (hereinafter referred to as “a glass material for press molding” or “preform”) using an upper mold and a lower mold having opposed molding surfaces. It has been known.

  When molding a glass optical element by press molding, the glass material for press molding and the molding surface of the molding die adhere to each other under high temperature conditions, so that a chemical reaction occurs at the interface between them, so that fusion, spider, scratches, etc. Reaction traces or the like may occur, and the optical performance of the optical element obtained by press molding may deteriorate.

  Conventionally, as a means for preventing the occurrence of the reaction mark, it has been proposed to provide a coating film on the surface of a glass material for press molding to suppress the reaction between the mold and the glass (for example, Patent Document 1). reference). Patent Document 2 proposes to provide a hydrogen capture film on the surface of a glass material for press molding in order to suppress the generation of linear marks.

JP 2011-1259 A JP 2004-250295 A

By the way, as a result of the study by the present inventors, it has been clarified that, in the production of a glass optical element by press molding, the homogeneity of the optical element is lowered due to generation of minute bubbles in the glass after press molding. In order to provide an optical element having high optical performance, it is desired to suppress foaming in glass.
Therefore, the present inventors have intensively studied the cause of generation of bubbles in order to find a means for suppressing foaming in glass. As a result, we found an unexpected phenomenon that bubbles generated in the optical element after press molding contain a lot of oxygen even when press molding is performed in a non-oxidizing atmosphere (oxygen content is several ppm). It was. Since the cause of oxygen generation in press molding in a non-oxidizing atmosphere is only oxide glass, it is considered that oxygen derived from oxide glass is involved in the generation of bubbles.

  One embodiment of the present invention provides a method of manufacturing an optical element capable of suppressing the generation of bubbles in the optical element after press molding.

One embodiment of the present invention provides:
Oxide glass,
A coating film covering at least part of the surface of the oxide glass;
Have
The above-described coating film is a metal oxide film in which oxygen is lost from the stoichiometric composition, and the metal oxide film is included in the oxide glass at a temperature equal to or higher than the glass transition temperature of the oxide glass. An optical element in which an oxygen atom is incorporated at a rate faster than a rate at which a metal atom contained in the metal oxide film diffuses into the oxide glass;
About.

A further aspect of the present invention provides:
A step of preparing a glass material for press molding having an oxide glass and a coating film that covers at least a part of the surface of the oxide glass and is a metal oxide film in which oxygen is lost from the stoichiometric composition; ,
A press process for forming a press-molded body by press-molding a glass material for press molding;
With
The press-molded body described above includes the above-described coating film that has undergone a pressing process, and the coating film that has undergone the pressing process is a metal oxide film having a higher oxygen content than the coating film before the pressing process. Device manufacturing method,
About.

As a result of intensive studies in order to suppress the foaming of the glass due to oxygen derived from the oxide glass, the inventors have provided the above-described coating film on the surface of the glass material for press molding.
A metal oxide film in which oxygen is deficient from the stoichiometric composition is in a state where oxygen is easily taken up. Therefore, with the metal oxide film in this state, oxygen that causes foaming during press molding can be removed from the inside of the glass, and generation of bubbles can be suppressed.
However, during press molding, between the coating film and the oxide glass, the movement of oxygen atoms from the oxide glass to the coating film (incorporation) and the movement of metal atoms from the coating film to the oxide glass ( Diffusion) can also occur. In the metal oxide film in which the diffusion rate of the metal atoms is faster than the rate at which oxygen atoms are taken into the coating film, the diffusion proceeds in preference to the uptake. For this reason, a remarkable reduction in film thickness or disappearance of the film occurs due to press molding, and it is difficult to suppress foaming inside the oxide glass. On the other hand, since the above-mentioned coating film takes in oxygen atoms in preference to the diffusion of metal atoms, it efficiently takes in oxygen atoms that cause generation of bubbles from oxide glass and suppresses foaming. Can do.
In the optical element thus obtained, the above-described coating film that has undergone a pressing step is present. The coating film included in this optical element takes oxygen from the oxide glass during press molding,
The oxygen atom content relative to the metal atoms is higher than that contained in the glass material for press molding. However, as a result of the examination by the present inventors, it has become clear that the coating film included in the optical element is still in a state in which oxygen is lost from the stoichiometric composition.

According to one embodiment of the present invention, it is possible to provide a method for manufacturing an optical element capable of suppressing the generation of bubbles in glass during press molding.
Furthermore, according to one embodiment of the present invention, it is possible to provide a homogeneous optical element that does not generate bubbles.

FIG. 1 shows an example of a press molding apparatus. In FIG. 2, the optical microscope photograph of the lens (core glass: I-1 in Table 1) produced in Example 1 is shown. In FIG. 3, the optical microscope photograph which expanded and image | photographed a part of lens (core glass: I-1 in Table 1) produced by the comparative example 2 is shown. FIG. 4 shows the depth direction analysis result of secondary ion intensity by TOF-SIMS after pressing (lens) regarding Example 1. FIG. 5: shows the depth direction analysis result of the secondary ion intensity by TOF-SIMS before the press (unpressed goods) regarding Example 1. FIG. FIG. 6 shows the result of comparison of the secondary ion intensity ratio of ZrO ₂ / ZrO in FIGS. FIG. 7 shows the depth direction analysis result of the secondary ion intensity by TOF-SIMS of the lens produced in Comparative Example 2. FIG. 8 shows a result of superimposing the result of Example 1 shown in FIG. 4 and the result of Comparative Example 2 shown in FIG. FIG. 9 shows the depth direction analysis result of the secondary ion intensity by TOF-SIMS after pressing (lens) regarding Comparative Example 1. FIG. 10 shows the depth direction analysis result of the secondary ionic strength by TOF-SIMS before pressing (unpressed product) in Comparative Example 1.

  Hereinafter, a method for manufacturing an optical element according to one embodiment of the present invention will be described in more detail. Hereinafter, specific embodiments may be described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.

In the optical element manufacturing method described above, press molding is performed using a glass material for press molding having a metal oxide film in which oxygen is lost from the stoichiometric composition as a coating film covering at least part of the surface of the oxide glass. I do. And the above-mentioned coating film has the above-mentioned press-molding glass material in which the content of oxygen atoms relative to metal atoms is also present in at least a part of the surface of the press-molded body obtained by press-molding this press-molding glass material. Is included as a metal oxide film that is higher than the coating film of the film.
As described above, according to the new findings discovered by the inventors' extensive studies, it is assumed that bubbles generated in the optical element after press molding are oxygen derived from oxide glass. In contrast, a metal oxide film in which oxygen is deficient from the stoichiometric composition is considered to be in a state where oxygen can be easily taken in so as to approach the stoichiometric composition, which is a more stable state. Therefore, by applying at least a part of the surface of the oxide glass with a metal oxide film in which oxygen is deficient from the stoichiometric composition, the oxygen that causes foaming during the press is converted from the oxide glass to the metal. Since it can be taken into the oxide film, it is possible to provide a high-quality optical element in which the generation of bubbles after press molding is suppressed. Since the metal oxide film remaining on the surface of the press-molded body (optical element) thus formed contains oxygen atoms taken from the oxide glass, the press-molding glass before press molding has it. It contains more oxygen atoms than the metal oxide film. That is, the press-molded body has a metal oxide film having a content rate of oxygen atoms with respect to metal atoms higher than that of the coating film of the press-molding glass material on at least a part of the surface.

In order to obtain a press-molded body in which the metal oxide film in the above-described state exists after press molding, the metal oxide film is converted into oxide glass at a temperature equal to or higher than the glass transition temperature of the oxide glass. The rate at which oxygen atoms are incorporated (hereinafter also referred to as “oxygen atom incorporation rate”) is the rate at which metal atoms contained in the metal oxide film diffuse into the oxide glass (hereinafter, “metal atom diffusion rate”). )) A faster metal oxide film should be formed.
As described above, during press molding, between the oxide glass and the coating film that coats the oxide glass, oxygen atoms move (take in) from the oxide glass to the coating film and are oxidized from the coating film. Migration (diffusion) of metal atoms into the material glass can also occur. Since press molding is usually performed at a temperature equal to or higher than the glass transition temperature, the speed at which the above-described metal oxide film takes in oxygen atoms in the oxide glass during press molding depends on whether the metal atoms in the metal oxide film are oxides. Faster than the speed taken into the glass. In the case of a coating film having such properties, uptake of oxygen atoms into the coating film during pressing proceeds in preference to the diffusion of metal atoms into the oxide glass. Therefore, after press molding, the metal oxide film in the above-described state can be present on the press-molded body. On the other hand, in a metal oxide film in which the diffusion rate of metal atoms into the oxide glass is faster than the rate at which oxygen atoms are incorporated into the coating film, diffusion proceeds in preference to the incorporation. For this reason, a remarkable reduction in film thickness or disappearance of the film occurs due to press molding, and it is difficult to suppress foaming inside the oxide glass. The above effect can be achieved if the oxygen atom uptake rate is larger than the metal atom diffusion rate, and therefore the difference between the oxygen atom uptake rate and the metal atom diffusion rate is not particularly limited. .

As described above, the glass material for press molding suitably used in the method for manufacturing an optical element according to one aspect of the present invention includes an oxide glass and a coating film that covers at least a part of the surface of the oxide glass. In this case, the metal oxide film is in a state where oxygen is deficient from the stoichiometric composition, and the oxygen atom uptake rate and the metal atom diffusion rate satisfy the above relationship. The optical element obtained through the step of press molding the glass material for press molding also has a metal oxide film in which the oxygen atom uptake rate and the metal atom diffusion rate satisfy the above-described relationship. However, the metal oxide film present on the optical element has a higher oxygen atom content to metal atoms than the metal oxide film before press molding. This is because oxygen atoms are taken from the oxide glass in press molding.
Hereinafter, the above-described glass material for press molding will be described in more detail.

Coating film (metal oxide film)
The coating film covering the oxide glass may be formed by a film formation method capable of forming a metal oxide film in which oxygen is lost from the stoichiometric composition. For example, sputtering, vacuum deposition, CVD (Chemical Vapor Deposition) in a non-oxidizing atmosphere using a metal as a target on the surface of a glass lump made of oxide glass (hereinafter also referred to as “core glass”) By forming the film by a known film formation method such as the method, the above-described coating film can be formed. The lower limit of the film forming temperature (core glass temperature) is preferably 150 ° C. or higher, and more preferably 200 ° C. or higher. The upper limit is preferably less than the glass transition temperature of the core glass. The upper limit temperature is, for example, 450 ° C. or less.
As a specific embodiment, a plurality of core glasses formed in a predetermined shape are arranged in a tray and placed in a vacuum chamber, and the core glass is heated to about 300 ° C. by a heater while evacuating the vacuum chamber. To do. After evacuating until the degree of vacuum in the vacuum chamber becomes 1 × 10 ⁻⁵ Torr or less, Ar gas is introduced, the atmosphere gas in the vacuum chamber is replaced with Ar gas, and then a high frequency is applied to the target substrate. The raw material is turned into plasma, and a coating film is formed on the surface of the core glass. The film thickness of the coating film can be controlled to a desired film thickness by adjusting the pressure (vacuum degree) in the vacuum chamber, the power source power, and the film formation time. In addition, the coating film should just cover at least one part of the surface of core part glass. Therefore, the core glass after coating film formation may be in a state where a part of the surface is uncoated or the entire surface may be covered. In one embodiment, when the optical element is formed by press-molding a glass material for press molding, at least a portion of the core glass that will form the optical functional surface of the optical element can be covered. An optical functional surface means a region within an effective diameter in an optical lens, for example. However, it is not limited to the above-described embodiment because oxygen atoms can be taken from the core glass if the above-described coating film is present in at least a part of the surface of the glass material for press molding. .

  As the metal constituting the coating film, a metal that can form a metal oxide film in which the oxygen atom uptake rate and the metal atom diffusion rate satisfy the above-described relationship may be used. Specific examples of such metals include zirconium, titanium, niobium, tungsten, and tantalum. However, even if the metal is not exemplified here, a preliminary experiment is performed as appropriate to confirm that the oxide film satisfying the above relationship can be formed by the oxygen atom uptake rate and the metal atom diffusion rate. It is possible to determine a metal that can form a metal oxide film that satisfies the above relationship. As a target in the above-described film forming method, it is preferable to use these metals alone. The film thickness of the coating film is preferably 0.5 nm or more and more preferably 1.5 nm or more in order to efficiently take in oxygen from the oxide glass. From the viewpoint of preventing spiders, the thickness of the coating film is preferably 15 nm or less, and more preferably 10 nm or less.

As described above, the coating film described above is in a state where oxygen is lost from the stoichiometric composition. For example, in the case of zirconium oxide, since the stoichiometric composition is ZrO ₂ , when the coating film is a zirconium oxide film, the composition is ZrOx (x <2). Here, x is not particularly limited as long as it is less than 2. The same applies to other metal oxide films.

Oxide glass (core glass)
Examples of the core glass whose surface is at least partially covered by the above-described coating film include optical glasses having various compositions that are usually used for producing optical elements. Specific examples of such optical glass include boric acid-rare earth glass such as lanthanum borate glass, phosphate glass, and silicate glass.

By the way, as a composition in which foaming tends to be caused by pressing in the optical glass, an oxide glass containing a relatively large amount of Nb ₂ O ₅ , TiO ₂ , WO ₃ , and Ta ₂ O ₅ as high refractive index imparting components. Can be mentioned. In the method for producing an optical element according to one aspect of the present invention, for example, one or more high refractive index imparting components selected from the group consisting of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Ta ₂ O ₅ are included, and the high refractive index The oxide glass having a total content (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Ta ₂ O ₅ ) of the rate-imparting component of 10% by mass or more is used as the core glass, and the above-mentioned coating film is provided on the core glass. Can be press molded. Thereby, a homogeneous optical element in which the generation of bubbles after pressing is suppressed can be obtained. The total content (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Ta ₂ O ₅ ) is more preferably 15% by mass or more. The total content (N _b O ₅ + TiO ₂ + WO ₃ + Ta ₂ O ₅ ) is 50% by mass or less, which suppresses an increase in press temperature due to a significant increase in the glass transition temperature Tg and the yield point Ts. Moreover, it is preferable from the viewpoint of easiness of vitrification, and more preferably 45% by mass or less.

Since the pressing temperature is usually performed at a temperature equal to or higher than the glass transition temperature of the core glass, the higher the glass transition temperature, the higher the pressing temperature tends to be. On the other hand, a significant increase in the press temperature may promote the generation of bubbles. Therefore, as a preferable specific embodiment of the core glass, an oxide glass containing an appropriate amount of one or more glass components having an action of lowering the glass transition temperature can be exemplified. Examples of the glass component having an action of lowering the glass transition temperature include ZnO and an alkali metal oxide selected from the group consisting of Li ₂ O, Na ₂ O and K ₂ O. The total content of ZnO and alkali metal oxide (ZnO + Li ₂ O + Na ₂ O + K ₂ O) is preferably 5% by mass or more, and more preferably 10% by mass or more. On the other hand, from the viewpoint of ease of vitrification, the total content (ZnO + Li ₂ O + Na ₂ O + K ₂ O) is preferably 25% by mass or less, and more preferably 20% by mass or less. Specific examples of the core glass include optical glass having a refractive index nd of 1.70 to 2.10 and an Abbe number νd of 20 to 55 from the viewpoint of the usefulness of the optical element. Further, as another specific embodiment, as an excellent glass with excellent press moldability, in particular, precision press moldability, an optical glass satisfying one or both of glass transition temperature Tg of 630 ° C. or lower and yield point Ts of 680 ° C. or lower. Can also be illustrated. However, the method for manufacturing an optical element according to one embodiment of the present invention is not limited to the specific embodiment described above.

  More specific embodiments of the optical glass that can be the core glass include, for example, the following glasses I, II, and III. However, the core glass may be an oxide glass, and the composition thereof is not particularly limited. Glasses I, II, and III are all suitable as optical glasses for producing optical elements. According to one embodiment of the present invention, such an optical glass can be press-molded to provide a high-quality optical element free from bubbles in the glass.

<Glass I>
In cation% display,
B ³⁺ and Si ⁴⁺ in total 5 to 60% (however, B ³⁺ is 5 to 50%),
Zn ²⁺ and Mg ²⁺ in total 5% or more,
La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ in total 10 to 50%,
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ in total ⁶ to 45% (provided that the total content of Ti ⁴⁺ and Ta ⁵⁺ exceeds 0% and W ⁶⁺ Content over 5%),
Including
The cation ratio of the Si ⁴⁺ content to the B ³⁺ content (Si ⁴⁺ / B ³⁺ ) is 0.70 or less,
Ti ⁴⁺ and Ta ⁵⁺ content of the cation ratio of Ta ⁵⁺ to the total content of ^{(Ta 5+ / (Ti 4+ +} Ta 5+)) is not less 0.23 or more,
The cation ratio of the W ⁶⁺ content to the total content of Nb ⁵⁺ and W ⁶⁺ (W ⁶⁺ / (Nb ⁵⁺ + W ⁶⁺ )) is 0.30 or more,
Cation ratio of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ^{3+ to} the total content of B ³⁺ and Si ⁴⁺ ((Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ + Bi ³⁺ ) / (B ³⁺ + Si ⁴⁺ )) is more than 0.37 and not more than 3.00,
Cation ratio of the total content of Zn ²⁺ , Mg ²⁺ and Li ^{+ to} the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ ((Zn ²⁺ + Mg ²⁺ + Li ⁺ ) / ( La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )) is 0.40 or more,
The refractive index nd is 1.90 to 2.00, and the Abbe number νd is the following formula (1):
25 ≦ νd <(3.91−nd) /0.06 (1)
An oxide glass that meets the requirements.

Although the glass I is a high refractive index glass, it can exhibit a low glass transition temperature, and thus is suitable as a glass for precision press molding. In a preferred embodiment of the optical glass according to one embodiment of the present invention, the glass transition temperature is 650 ° C. or lower. Optical glass having a glass transition temperature of 650 ° C. or lower can maintain the glass temperature during precision press molding in a relatively low temperature range, suppresses the reaction between the glass during press molding and the press molding surface, and is precise. The press formability can be maintained in a good state. From such a viewpoint, the glass transition temperature is preferably 640 ° C. or less, more preferably 630 ° C. or less, further preferably 620 ° C. or less, further preferably 610 ° C. or less, 600 ° C. It is still more preferable to make it below.
In addition, when the glass transition temperature is excessively decreased, the stability of the glass decreases or the refractive index tends to decrease. Therefore, the glass transition temperature is preferably 500 ° C. or higher, and is preferably 520 ° C. or higher. More preferably, it is 540 degreeC or more, More preferably, it is 560 degreeC or more, It is still more preferable to set it as 570 degreeC or more.

<Glass II>
B comprises ₂ O _3, La ₂ O ₃ and ZnO, by _{mol%, B 2 O 3 20~60%,} SiO 2 0~20%, ZnO 22~42%, La 2 O 3 5~24%, Gd ₂ O ₃ 0-20% (however, the total amount of La ₂ O ₃ and Gd ₂ O ₃ is 10-24%), ZrO ₂ 0-10%, Ta ₂ O ₅ 0-10%, WO ₃ 0 10%, Nb ₂ O ₅ 0-10%, TiO ₂ 0-10%, Bi ₂ O ₃ 0-10%, GeO ₂ 0-10%, Ga ₂ O ₃ 0-10%, Al ₂ O ₃ 0 10%, BaO 0 to 10%, Y ₂ O ₃ 0 to 10% and Yb ₂ O ₃ 0 to 10%, and an Abbe number (ν _d ) of 40 or more and substantially free of lithium Glass.

Concerning Glass II, “substantially free of lithium” means that the amount of Li ₂ O introduced is suppressed to a level that does not cause spiders or burns that hinder the use of the glass surface as an optical element. It is. Specifically, it means that the content is reduced to less than 0.5 mol% in terms of the amount of Li ₂ O. Since the risk of spider and burns can be reduced as the amount of lithium is reduced, the amount of Li ₂ O is preferably suppressed to 0.4 mol% or less, and more preferably to 0.1 mol% or less. Preferably, no introduction is more preferable.

Glass II is suitable for precision press molding, and it is preferable that the transition temperature (T _g ) is low in order to prevent wear of the press mold and damage to the release film formed on the molding surface of the mold. The temperature (T _g ) is preferably 630 ° C. or lower, and more preferably 620 ° C. or lower. On the other hand, in order to prevent spiders and burns on the glass surface, the amount of lithium in the glass is limited as described above. Therefore, if the transition temperature (T _g ) is excessively decreased, the refractive index decreases or the glass Problems such as a decrease in stability of the product are likely to occur. Therefore, the transition temperature (T _g ) is more preferably 530 ° C. or higher, and further preferably 540 ° C. or higher.

  JP, 2006-137661, A paragraphs 0013-0039 can be referred to for details of glass II.

<Glass III>
In mol%
SiO ₂ 0-20%,
B ₂ O ₃ 5-40%,
SiO ₂ + B ₂ O ₃ = 15-50%,
Li ₂ O 0-10%,
ZnO 12-36%,
However, 3 × Li ₂ O + ZnO ≧ 18%,
La ₂ O ₃ 5-30%,
Gd ₂ O ₃ 0-20%,
Y ₂ O ₃ 0-10%,
La ₂ O ₃ + Gd ₂ O ₃ = 10 to 30%,
La ₂ O ₃ / ΣRE ₂ O ₃ = 0.67 to 0.95%,
(However, ΣRE ₂ O ₃ = La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Sc ₂ O ₃ + Lu ₂ O ₃ )
ZrO ₂ 0.5-10%,
Ta ₂ O ₅ 1-15%,
WO ₃ 1-20%,
Ta ₂ O ₅ / WO ₃ ≦ 2.5 (molar ratio)
Nb ₂ O ₅ 0-8%,
TiO ₂ 0-8%
Including
Refractive index nd is 1.87 or more,
An oxide glass having an Abbe number νd of 35 or more and less than 40.

  Glass III exhibits low-temperature softening properties with a glass transition temperature of 650 ° C. or lower. A more preferable range of the glass transition temperature of the glass III is 640 ° C. or less, more preferably 630 ° C. or less, more preferably 620 ° C. or less, and still more preferably 610 ° C. On the other hand, if the glass transition temperature is excessively decreased, it is difficult to achieve higher refractive index and lower dispersion and / or the stability and chemical durability of the glass tend to decrease. Is preferably 510 ° C. or higher, preferably 540 ° C. or higher, more preferably 560 ° C. or higher, and even more preferably 580 ° C. or higher.

  Further, the preferred range of the yield point (Ts) of the glass III is 700 ° C. or less, more preferably 690 ° C. or less, further preferably 680 ° C. or less, more preferably 670 ° C. or less, and still more preferably 660 ° C. or less. . When the yield point (Ts) is excessively decreased, it is difficult to further increase the refractive index and the dispersion, and / or the stability and chemical durability of the glass tend to decrease. Therefore, the yield point (Ts) is preferably 550 ° C. or higher, more preferably 580 ° C. or higher, even more preferably 600 ° C. or higher, and even more preferably 620 ° C. or higher.

  JP, 2008-201661, A paragraphs 0016-0065 can be referred to for the details of glass III.

Core Glass Molding Core glass can be formed into a known shape as a preform for optical element molding using oxide glass by a known method as a preform molding method. Regarding the shape of the core glass and the forming method, reference can be made, for example, to paragraphs 0087 to 0106 of JP2011-1259A and description of examples, and paragraphs 0040 to 0044 of JP2004-250295A and description of examples.

Arbitrary coating The glass material for press molding used in the method for producing an optical element according to one embodiment of the present invention is obtained by performing a film forming process for coating the above-described metal oxide film on the core glass described above. be able to. The glass material for press molding thus obtained has a structure in which the metal oxide film is in direct contact with the surface of the core glass. On the glass material for press molding having this configuration, one or more layers can be arbitrarily formed. Such a coating is effective for enhancing the mold releasability of the glass from the mold during press molding.

  A carbon-containing film can be given as an embodiment of the above-mentioned arbitrary coating. The carbon-containing film provides sufficient slipperiness with the mold when the glass material is supplied to the mold prior to pressing so that the glass material can move smoothly to a predetermined position (center position) of the mold. At the same time, when the glass material is softened and deformed by the press, the glass material is stretched according to the glass deformation on the surface of the glass material, and the glass material can be spread on the mold surface. Furthermore, it is useful in that the glass is easily separated from the surface of the mold when the molded body is cooled to a predetermined temperature after pressing, thereby assisting the mold release. In addition, laminating a carbon-containing film on the above-described metal oxide film is also effective in suppressing the occurrence of cracking in press molding.

  The carbon-containing film is preferably a film containing carbon as a main component, but may contain a component other than carbon such as a hydrocarbon film. As a method for forming the carbon-containing film, a known film forming method such as vacuum deposition using a carbon raw material, sputtering, ion plating method, or plasma CVD (Chemical Vapor Deposition) can be used. Further, a carbon-containing film may be formed by thermal decomposition of a carbon-containing material such as hydrocarbon.

  Moreover, as an arbitrary film, the film described as the 1st surface layer and the 2nd surface layer in Unexamined-Japanese-Patent No. 2011-1259 can also be formed, for example. For the details thereof, the same publication can be referred to.

Production of optical element The glass material for press molding described above is prepared, and then the press molded body obtained by press molding itself or by subjecting the press molded body to a post-process such as film formation. An optical element according to one embodiment can be obtained.

  The press molding can be performed by a known press molding method as a molding method of the optical element. Hereinafter, although a specific aspect is demonstrated, this invention is not limited to the following aspect.

  As a mold used for press molding, a precise material made of a dense material having sufficient heat resistance and rigidity can be used. Examples include metals such as silicon carbide, silicon nitride, tungsten carbide, aluminum oxide, titanium carbide, and stainless steel, or those whose surfaces are coated with a film of carbon, refractory metal, noble metal alloy, carbide, nitride, boride, etc. be able to. As the film covering the molding surface, a film containing carbon is preferable from the viewpoint that a glass material for press molding can be molded into a glass optical element without fusing, spidering, scratching, or the like. JP, 2011-1259, A paragraph 0116 can be referred to about a carbon content film. By using a molding die having a carbon-containing release film on the molding surface as the molding die, there is an advantage that the slipperiness between the molding surface and the glass material is increased and the moldability is further improved.

  FIG. 1 shows an example of a press molding apparatus. In press molding, as shown in FIG. 1, press molding glass in which a core glass 1 is coated with the above-described coating film 2 in a molding die 6 including an upper die 3, a lower die 4 and a barrel die 5. The material PF is supplied and the temperature is raised to a temperature range suitable for pressing.

For example, the heating temperature is appropriately set according to the type of oxide glass constituting the core glass 1, but the glass material PF and the mold 6 are temperatures at which the viscosity of the glass material PF becomes 10 ⁵ to 10 ¹⁰ dPa · s. When it is in the region, it is preferable to perform press molding. The pressing temperature is more preferably, for example, a temperature at which the oxide glass constituting the core glass 1 is 10 ⁶ to 10 ⁸ dPa · s before and after 10 ^7.2 dPa · s, and the core glass 1 is equivalent to 10 ^7.2 dPa · s. It is more preferable to set the temperature so that Usually, the press temperature is set to a temperature equal to or higher than the glass transition temperature of the core glass. At such a temperature, the core glass is covered with a metal oxide film in which oxygen is deficient from the stoichiometric composition and the oxygen atom uptake rate and the metal atom diffusion rate satisfy the above relationship. By performing press molding of the glass material for press molding, it is possible to prevent bubbles from being generated in the press-molded body obtained by press molding by incorporating oxygen atoms that cause foam generation into the metal oxide film. . Note that the press temperature and the heating temperature related to the press refer to the temperature of the atmosphere in which press molding is performed. Press molding can be performed by lowering the press head 7 and applying a predetermined load.

The glass material PF may be supplied to the mold 6 and the glass material PF and the mold 6 may be heated to a predetermined range, or the glass material PF and the mold 6 may be heated to a predetermined temperature range. Therefore, the glass material PF may be disposed in the mold 6. Further, the glass material PF is heated to a temperature corresponding to a viscosity of 10 ⁵ to 10 ⁹ dPa · s, the mold 6 is heated to a temperature corresponding to a glass viscosity of 10 ⁹ to 10 ¹² dPa · s, and the glass material PF is placed in the mold 6. Then, a method of immediately press forming may be employed. In this case, since the mold temperature can be relatively lowered, the temperature increase / decrease cycle time of the molding apparatus can be shortened, and deterioration of the mold 6 due to heat can be suppressed, which is preferable. In either case, cooling is started at the start or after the start of press molding, and the temperature is lowered while applying an appropriate load application schedule and maintaining the adhesion between the molding surface and the glass. Then, it molds and takes out a molded object. The mold release temperature is preferably 10 ^12.5 to 10 ^13.5 dPa · s.

  In the released glass molded body, the metal oxide film provided on the glass material for press molding has taken in oxygen atoms from the core glass, so that the coating film has a higher oxygen content than before press molding. That is, there is a metal oxide film in which the content of oxygen atoms with respect to metal atoms is higher than the coating film of the glass material for press molding before press molding. This metal oxide film has been found by the present inventors to be in a state where oxygen is deficient rather than the stoichiometric composition.

The obtained glass molded body can be shipped as an optical element as a final product as it is, or post-processing such as centering and film formation for forming an optical functional film such as an antireflection film on the surface. It can also be made into a final product after application. For example, a desired antireflection film can be formed by appropriately forming a film such as Al ₂ O ₃ , ZrO ₂ —TiO ₂ , MgF ₂ or the like on the glass molded body having the surface layer as a single layer or a laminated layer. Can be formed. The antireflection film can be formed by a known method such as vapor deposition, ion-assisted vapor deposition, ion plating, or sputtering. For example, in the case of the vapor deposition method, the vapor deposition material is heated by an electron beam, direct energization or arc in a vacuum atmosphere of about 10 ⁻⁴ Torr using a vapor deposition apparatus, and the material generated by evaporation and sublimation from the material is used. The antireflection film can be formed by transporting the vapor onto the substrate and condensing / depositing it. The substrate heating temperature can be about room temperature to about 400 ° C. However, when the glass transition temperature (Tg) of a base material is 450 degrees C or less, it is preferable that the upper limit temperature of base-material heating shall be Tg-50 degreeC.

  An optical element according to one embodiment of the present invention is a small-diameter, thin-walled small-mass lens, for example, a small imaging system lens, a communication lens, an optical pickup objective lens, a collimator lens, and the like mounted on a portable imaging device. be able to. The lens shape is not particularly limited, and various shapes such as a convex meniscus lens, a concave meniscus lens, a biconvex lens, and a biconcave lens can be taken.

  Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to the embodiment shown in the examples.

The glass transition temperature and yield point described below are values measured at a heating rate of 4 ° C./min with a thermomechanical analyzer of Rigaku Corporation.
The refractive index (nd) and the Abbe number (νd) were measured for the optical glass obtained at a slow cooling rate of −30 ° C./hour.

[Example 1]
(1) Production of glass material for press molding Optical glass I-1 belonging to glass I described in Table 1 and optical glass II- belonging to glass II as optical glass to be core glass 1 of glass material PF for press molding 1 was used to form a zirconia oxide film on the surface by the following process.
First, the optical glass to be the core glass 1 was dropped and cooled from a molten state onto a receiving mold, and a glass lump having a shape in which one side was a convex surface and the other side was a concave surface was preformed. A coating film (film thickness: about 5 nm) was formed on the preformed glass block by sputtering at a film forming temperature of 300 ° C. in an atmosphere of Ar 100% using metal zirconium (Zr) as a target. . The film thickness was adjusted according to the sputtering conditions. The press-molding glass material thus obtained had an outer dimension of 10 to 11 mm and a center thickness of 7 to 8 mm.

(2) Production of Press Molded Body by Precision Press Molding Next, the glass material PF for press molding produced in the above (1) was press molded in a nitrogen gas atmosphere by a mold press molding apparatus. In other words, a SiC upper and lower mold in which a carbon-containing release film is formed on the molding surface by a sputtering method, and a molding mold comprising a barrel mold, and the atmosphere in the chamber of the molding apparatus is filled with non-oxidizing N ₂ gas. The core glass was heated to a temperature at which the viscosity of the core glass was 10 ^7.2 dPa · s, and supplied to a mold heated to a temperature equivalent to 10 ^8.5 dPa · s as the viscosity of the core glass. Immediately after the supply, the glass material is pressed between the upper and lower molds (press temperature: 675 ° C.), cooled to a temperature below the annealing temperature of the core glass while maintaining the close contact between the glass and the upper and lower molds, and molded from within the mold. The body (optical lens) was taken out. The molded body had an outer diameter of 20.0 mm and a center thickness of 0.70 mm. Next, the outer periphery of the press-molded body was centered by grinding to obtain a concave meniscus aspheric glass lens with a diameter of 18 mm.

[Example 2]
In the production of the glass material for press molding (1), a coating film having a film thickness of about 5 nm was formed on each of the core glass I-1 and II-1 using metal titanium (Ti) instead of metal zirconium. Otherwise, a concave meniscus aspheric glass lens was obtained in the same manner as in Example 1.

[Example 3]
In the production of the glass material for press molding (1), a coating film having a film thickness of about 5 nm was formed on each of the core glass I-1 and II-1 using metal tantalum (Ta) instead of metal zirconium. Otherwise, a concave meniscus aspheric glass lens was obtained in the same manner as in Example 1.

[Example 4]
Example of production of press-molding glass material (1), except that metal tungsten (W) was used instead of metal zirconium, and a coating film having a film thickness of about 5 nm was formed on core glass II-1. A concave meniscus aspheric glass lens was obtained in the same manner as in Example 1.

[Example 5]
In the production of the glass material for press molding (1), except that metal niobium (Nb) was used instead of metal zirconium, a coating film having a film thickness of about 5 nm was formed on the core glass II-1. A concave meniscus aspheric glass lens was obtained in the same manner as in Example 1.

[Comparative Example 1]
In the production of the glass material for press molding (1), Example 1 except that a coating film having a thickness of about 5 nm was formed on the core glass I-1 using metal yttrium (Y) instead of metal zirconium. Similarly, a concave meniscus aspheric glass lens was obtained.

[Comparative Example 2]
Except that the ZrO ₂ film and the SiO ₂ film, which are the surface layers in Examples 1 to 6 of JP 2011-1259 A, were formed in this order on the surface of the core glass I-1, the same as in Example 1. A concave meniscus aspheric glass lens was obtained. The thicknesses of the ZrO ₂ film and the SiO ₂ film were each about 5 nm.

<Evaluation of presence / absence of bubbles>
Each lens produced in Examples and Comparative Examples was observed with an optical microscope at a magnification of 50 times to confirm the presence or absence of bubbles in the lens. No bubbles were observed in the lenses produced in Examples 1 to 4. . As a representative example, FIG. 2 shows an optical micrograph of the lens (core glass: I-1 in Table 1) produced in Example 1. It can be confirmed that a homogeneous lens having high transparency without bubbles is obtained.
On the other hand, in the lenses produced in Comparative Examples 1 and 2, many bubbles having a diameter of 50 μm or more were confirmed. In FIG. 3, the optical microscope photograph which expanded and image | photographed a part of lens (core glass: I-1 in Table 1) produced by the comparative example 2 is shown. It can be confirmed that many bubbles are generated.
In Comparative Example 2, the coating film covering the core glass is a film having a stoichiometric composition such as a ZrO ₂ film. Such a metal oxide film permeates oxygen liberated from the oxide glass at the time of press molding and is considered not to be taken into the film. Oxygen that has permeated the membrane is confined in the press mold and is not released to the outside. As a result, it is presumed that the film again passes through the film and returns to the glass, thereby causing foaming in the glass.

<Confirmation of gas composition in foam>
When the gas composition in the bubbles in the lens (core glass: glass 1-1) produced in Comparative Example 2 was analyzed by mass spectrometry, N _{2 was} 89% and O _{2 was} 11%. Yes, oxygen exceeding 10% was detected even though press molding was performed in a nitrogen gas atmosphere. This result confirms that the oxygen derived from the oxide glass is the cause of the generation of bubbles, as described above.

<Confirmation of coating film state before and after press molding (Example 1, Comparative Example 2)>
About the glass produced in Example 1 and Comparative Example 2 using glass I-1 as the core glass and the glass for press molding produced under the same conditions as the glass material for press molding used in this molding, the following method is used. Composition analysis in the depth direction from the surface was performed by TOF-SIMS (Time-of-flight secondary ion mass spectrometer).
Depth direction analysis by TOF-SIMS Depth direction measurement was performed using TOF-SIMS300 manufactured by ION-TOF. TOF-SIMS is a technique for irradiating pulsed primary ions and detecting the generated secondary ions. In the depth direction analysis of TOF-SIMS, (i) irradiation with primary ions, (ii) measurement of generated secondary ions, (iii) irradiation with sputtered ions, and data is repeated by repeating steps (i) to (iii) below. get.
Bi ₃ ⁺⁺ was used as the primary ion source, and the voltage applied to the column of the primary ion source was 25 kV. The measurement was performed with the primary ion source current set to 0.2 pA. The irradiation area of the primary ion source (= measurement region for detecting secondary ions) was 100 μm square, and negative ions were detected as secondary ions.
Cs was used for the sputter ion source. The acceleration of the sputter ion source was adjusted to 1 kV and the current value was adjusted to 75.4 nA. Sputtering was performed with a sputter ion source area of 400 μm square.

FIG. 4 shows the depth direction analysis result of secondary ion intensity by TOF-SIMS after pressing (lens) regarding Example 1. FIG. 5: shows the depth direction analysis result of the secondary ion intensity by TOF-SIMS before the press (unpressed goods) regarding Example 1. FIG. In the figure, the unit of secondary ionic strength is an arbitrary unit. The same applies to the drawings described later.
The film thickness of the zirconium oxide formed as the coating film on the core glass in Example 1 is about 5 nm. In the figure, ZrO and ZrO ₂ are described as secondary ions derived from zirconium oxide in each sample. Although not shown in the figure, Zr alone is detected in each sample. Since Zr ₂ has not been detected, it is considered that the single Zr is not derived from the metal Zr but derived from the zirconium oxide. Therefore, the coating films before and after pressing are all zirconium oxide. In the analysis results of ZrO and ZrO ₂ before pressing shown in FIG. 5, two peaks are recognized in the vicinity of the surface. The present inventors presume that the first peak near the surface is a natural oxide film, and the second peak is caused by reaction with glass during film formation. SiO ₂ detected by the depth direction analysis of the secondary ionic strength by TOF-SIMS is derived from SiO ₂ contained in the glass. In each sample, the reason why the SiO ₂ strength is increased in the vicinity of the surface is considered to be because a slight amount of contaminants (for example, siloxane) is present on the surface.
Figure 6 is a ZrO _2/2 ion intensity ratio of ZrO (hereinafter. Referred to as "ZrO ₂ / ZrO intensity ratio") result of comparison in FIGS. The ZrO ₂ / ZrO intensity ratio is an index indicating the degree of oxidation in the zirconium oxide film. However, the range of about 2 nm from the surface of the zirconium oxide cannot be discussed because of the influence of the natural oxide film. In the result shown in FIG. 6, the ZrO ₂ / ZrO intensity ratio from the depth range of about 2 nm to about 5 nm is higher after pressing than before pressing. From this result, it can be confirmed that the oxidation of zirconium oxide was promoted by the press.

When the above-mentioned coating film before press molding is a zirconium oxide film, the ZrO ₂ / ZrO strength ratio described above is, for example, in the range of 0.5 to 1.9 before pressing. The covering film can be a zirconium oxide film having a ZrO ₂ / ZrO intensity ratio in the range of 2.0 to 2.3, for example, after pressing. Higher ZrO ₂ / ZrO means that it is oxidized and contains more oxygen. When a ZrO ₂ film is formed, the ZrO ₂ / ZrO intensity ratio of this film can usually take a value of about 2.4 to 3.2.

In FIG. 7, the depth direction analysis result of the secondary ion intensity by TOF-SIMS of the lens produced in the comparative example 2 is shown. FIG. 8 shows a result of superimposing the result of Example 1 shown in FIG. 4 and the result of Comparative Example 2 shown in FIG. Comparative Example 2 has a SiO ₂ / ZrO ₂ / glass structure, and it has been confirmed in advance that SiO ₂ and ZrO ₂ have a stoichiometric composition before and after pressing. In FIG. 7, in the depth notation of Comparative Example 2, the interface between SiO ₂ and ZrO ₂ is 0, and the SiO ₂ portion is indicated by minus.
When attention is paid to the region (depth 0 to 5 nm) showing ZrOx in FIG. 8, the ZrO ₂ / ZrO intensity ratio after pressing in Example 1 is smaller than that in Comparative Example 2. From this result, it can be seen that the degree of oxidation by the press of Example 1 is lower than that of Comparative Example 2. That is, it can be confirmed that the zirconium oxide after pressing in Example 1 is deficient in oxygen as compared with ZrO ₂ having a stoichiometric composition in Comparative Example 2. In Comparative Example 2, since the SiO ₂ film was formed on the outermost surface of the press-molding glass material, it is not necessary to consider the influence of the natural oxide film. However, in Example 1, the region of about 2 nm from the surface is the natural oxide film. It is affected and cannot be the subject of discussion.

That is, from the results shown in FIGS. 4 to 8, in Example 1, the zirconium oxide film had a composition in which oxygen was lost from the stoichiometric composition ZrO ₂ before and after pressing, but after pressing, It can be confirmed that the oxygen content of the zirconium oxide film is higher than that before pressing.

<Confirmation of coating film state before and after press molding (Comparative Example 1)>
With respect to the lens produced in Comparative Example 1 using glass I-1 as the core glass and the glass for press molding produced under the same conditions as the glass material for press molding used in this molding, the above method was used for TOF-SIMS. The depth direction analysis of the secondary ionic strength was performed.
FIG. 9 shows the depth direction analysis result of the secondary ion intensity by TOF-SIMS after pressing (lens) regarding Comparative Example 1. FIG. 10 shows the depth direction analysis result of the secondary ionic strength by TOF-SIMS before pressing (unpressed product) in Comparative Example 1. From the results shown in FIGS. 9 and 10, it can be confirmed that the yttrium oxide film disappears after pressing. This is because the yttrium oxide film formed on the core glass in Comparative Example 1 is included in the yttrium oxide film than the rate at which the yttrium oxide film takes in oxygen atoms contained in the core glass during press molding. It is a result which shows that the speed | rate which a metal atom (Y) diffuses into core part glass is quick.

  Each metal oxide film produced on the core glass in Examples 2 to 5 is also in a state where oxygen is lost from the stoichiometric composition before and after pressing by the same method. It was confirmed that the oxygen content was higher than before pressing.

  For glass III-1 shown in Table 2 below corresponding to oxide glass III, press molding was performed in the same manner as in Example 1 to confirm that a homogeneous lens without bubbles was obtained.

As described above, according to one embodiment of the present invention, generation of bubbles after pressing can be suppressed. Preferably, when observed with an optical microscope at a magnification of 10 to 50 times, bubbles with a diameter of 50 μm or more are less than 1 bubble, bubbles with a diameter of 25 μm or more are less than 2 bubbles, or bubbles with a diameter of 10 μm or more are 5 And the total of the diameters of the bubbles does not exceed 50 μm can be used as an index that is a homogeneous optical element in which the generation of bubbles is suppressed. More preferably, when observed with an optical microscope at a magnification of 10 to 50, the number of bubbles having a diameter of 25 μm or more is less than one, or the number of bubbles having a diameter of 10 μm or more is less than 3, and the total diameter of the bubbles That does not exceed 25 μm can be used as an index that is a homogeneous optical element without bubbles. All the lenses manufactured in the above-described examples satisfy the preferable index and the more preferable index. Here, the total diameter of the bubbles is, for example, 100 μm if there are two mills having a diameter of 50 μm. In addition, the diameter here refers to the diameter when the bubble is a circular bubble, the distance in the longitudinal direction when the bubble is elliptical, and the longest possible distance when the bubble is irregular. To do.
In the examples, almost the entire surface of the core glass surface was coated with a metal oxide film, but even if a portion was uncoated, oxygen was deficient from the stoichiometric composition and the oxygen atom uptake rate. Needless to say, the same effect can be obtained if a metal oxide film in which the diffusion rate of metal atoms and the diffusion rate of metal atoms satisfy the above-described relationship exists on the surface of the core glass.

  Finally, the above-described aspects are summarized.

According to one aspect,
A step of preparing a glass material for press molding having an oxide glass and a coating film that covers at least a part of the surface of the oxide glass and is a metal oxide film in which oxygen is lost from the stoichiometric composition; ,
A press process for forming a press-molded body by press-molding a glass material for press molding;
With
The press-molded body described above includes the above-described coating film that has undergone a pressing process, and the coating film that has undergone the pressing process is a metal oxide film having a higher oxygen content than the coating film before the pressing process. Device manufacturing method,
Is provided.

  According to the method for manufacturing an optical element described above, it is possible to provide a homogeneous optical element in which the generation of bubbles is suppressed. In addition, according to the method for manufacturing an optical element described above, an oxide glass and a coating film that covers at least a part of the surface of the oxide glass are included, and the coating film has a stoichiometric composition. The rate at which the metal oxide film takes in oxygen atoms contained in the oxide glass at a temperature higher than the glass transition temperature of the oxide glass in a state where oxygen is more deficient is that the metal atoms contained in the metal oxide film It is possible to provide an optical element that is a metal oxide film faster than the speed of diffusion into oxide glass.

  In one aspect, the metal oxide described above is an oxide of a metal selected from the group consisting of zirconium, titanium, niobium, tungsten, and tantalum.

  In one embodiment, the metal oxide film of the press-molded body obtained by press molding is in a state where oxygen is deficient from the stoichiometric composition.

In one aspect, the above-mentioned oxide glass contains one or more high refractive index imparting components selected from the group consisting of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Ta ₂ O ₅ . The total content (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Ta ₂ O ₅ ) of the high refractive index imparting component is preferably 10% by mass or more and 50% by mass or less.

In one embodiment, the above oxide glass contains one or more selected from the group consisting of ZnO and alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O). Preferably, the total content of ZnO and alkali metal oxide (ZnO + Li ₂ O + Na ₂ O + K ₂ O) is 5% by mass or more and 25% by mass or less.

  In one embodiment, heating during press molding is performed at a heating temperature of 650 ° C. or higher. According to the manufacturing method of the above-mentioned optical element, generation | occurrence | production of the bubble in such high temperature press can be suppressed.

  In one embodiment, the oxide glass and a coating film covering at least a part of the surface of the oxide glass, the coating film described above is in a state in which oxygen is lost from the stoichiometric composition, In addition, at a temperature equal to or higher than the glass transition temperature of the oxide glass, the rate at which the metal oxide film takes in oxygen atoms contained in the oxide glass is faster than the rate at which the metal atoms contained in the metal oxide film diffuse into the oxide glass. A glass material for press molding which is a metal oxide film is also provided. This glass material for press molding is suitably used in the method for producing an optical element according to the above-described embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is useful in the field of manufacturing optical elements such as glass lenses.

Claims (5)

Oxide glass,
A coating film covering at least part of the surface of the oxide glass;
Have
The coating film is a metal oxide film in which oxygen is lost from the stoichiometric composition, and the metal oxide film is formed on the oxide glass at a temperature equal to or higher than the glass transition temperature of the oxide glass. The optical element, wherein the oxygen atom contained therein is incorporated at a speed higher than the speed at which the metal atom contained in the metal oxide film diffuses into the oxide glass. The optical element according to claim 1, wherein the metal oxide is an oxide of a metal selected from the group consisting of zirconium, titanium, niobium, tungsten, and tantalum. An oxide glass and a metal oxide film that covers at least part of the surface of the oxide glass and lacks oxygen from the stoichiometric composition, and the metal at a temperature equal to or higher than the glass transition temperature of the oxide glass The oxide film takes in oxygen atoms contained in the oxide glass, and the coating film is a metal oxide film faster than the speed at which the metal atoms contained in the metal oxide film diffuse into the oxide glass ; Preparing a glass material for press molding having
A press step of press-molding the press-molding glass material to form a press-molded body; and
With
The press-molded body includes the coating film that has undergone the pressing process, and the coating film that has undergone the pressing process is a metal oxide film having a higher oxygen content than the coating film before the pressing process. A method for manufacturing an optical element. A step of preparing a glass material for press molding comprising oxide glass, and a coating film that covers at least a part of the surface of the oxide glass and is a metal oxide film in which oxygen is lost from the stoichiometric composition; ,
A press step of press-molding the press-molding glass material to form a press-molded body; and
With
The metal oxide, zirconium, titanium, niobium, tungsten, and oxides der of a metal selected from the group consisting of tantalum is,
The press-molded body includes the coating film that has undergone the pressing step, and
The method for producing an optical element, wherein the coating film that has undergone the pressing step is a metal oxide film having a higher oxygen content than the coating film before the pressing step. 5. The method for producing an optical element according to claim 3, wherein the metal oxide film of the press-molded body is in a state where oxygen is deficient from the stoichiometric composition.