JP2008081383A - Method for manufacturing optical glass, glass base stock for press forming, and method for manufacturing the glass base stock for press forming, and method for manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing optical glass, by which the incorporation of a platinum or platinum-alloy foreign matter into glass can be reduced in the case that the optical glass composed of fluorophosphate glass is manufactured by a melting method. <P>SOLUTION: The method for manufacturing the optical glass composed of fluorophosphate glass using a phosphate raw material and a fluoride raw material includes a first process for obtaining phosphate glass by melting the phosphate raw material in a vessel made of a nonmetal material and a second process for further melting the obtained phosphate glass in a molten state or melting after solidifying the melt of the phosphate glass together with the fluoride raw material in a vessel made of platinum or a platinum alloy. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing optical glass, a glass material for press molding, a method for producing a glass material for press molding, and a method for producing an optical element.

  Fluorophosphate glass is very useful as a low-dispersion glass. For example, fluorophosphate glass into which copper ions are introduced is widely used as near-infrared absorbing glass.

  As a method for producing optical glass made of the above fluorophosphate glass, there is known a method in which a glass obtained by heating and melting a phosphate raw material and a fluoride raw material is clarified and homogenized in a molten state (hereinafter referred to as melting). It is known as an effective method for producing a large amount of glass.

  In the above melting method, the melting of the glass raw material and the clarification and homogenization of the glass are usually carried out in a platinum or platinum alloy crucible having erosion resistance so that impurities do not melt into the molten glass in an extremely high temperature state. Is called.

However, since fluorophosphate glass has a very strong erodibility, even if a crucible made of platinum or a platinum alloy is used, the crucible is eroded and its constituent components are taken into the glass. Platinum or a platinum alloy mixed in the glass is deposited as a foreign substance, and becomes a light scattering source, thereby degrading the quality of the optical glass (see, for example, Patent Document 1).
JP 2002-128528 A (fourth line from the lower right column of the second page to two lines from the upper left column of the third page)

  Under such circumstances, the present invention provides a method for producing an optical glass that can reduce the mixing of foreign substances into the glass when an optical glass made of fluorophosphate glass is produced by a melting method. The second object is to provide a glass material for press molding comprising the optical glass produced by the above method, and the glass material for press molding and the optical material produced from the optical glass produced by the above method. It is a third and fourth object of the present invention to provide a method for manufacturing each element.

As a result of examining the mechanism by which foreign matter is mixed in the fluorophosphate glass when the present inventor made a fluorophosphate glass by a melting method using a phosphate raw material and a fluoride raw material, the following (a) to ( It came to acquire the knowledge of b).
(A) When the phosphate raw material is melted and vitrified, the platinum or platinum alloy crucible is eroded and the platinum or platinum alloy is taken into the glass.
(B) When a silica crucible is used instead of a platinum or platinum alloy crucible in order to prevent erosion by the phosphate raw material, the silica crucible is eroded by the fluoride raw material, and the silica from the crucible is The glass is taken into the glass, and the optical properties of the glass such as the refractive index are greatly deviated from the desired values.

Based on the above knowledge, the present inventors further examined. First, a phosphate raw material was melted in a non-metallic container such as a silica crucible to obtain a phosphate glass, and then the obtained phosphate glass Is melted in a platinum or platinum alloy container together with the fluoride raw material after the melt is solidified or after being melted, so that the silica crucible is prevented from being eroded by the fluoride raw material. The present inventors have found that not only the above optical characteristics can be imparted, but also the amount of platinum or platinum alloy mixed into the fluorophosphate glass can be reduced, and the amount of precipitation as foreign matters can be reduced.

That is, the present invention
(1) A method for producing an optical glass comprising a fluorophosphate glass using a phosphate raw material and a fluoride raw material,
The first step of melting phosphate raw material in a non-metallic container to obtain phosphate glass, and the obtained phosphate glass as a melt or after solidifying the melt, fluoride A second step of melting in a container made of platinum or a platinum alloy together with a raw material, and a method for producing optical glass,
(2) A glass material for press molding, comprising an optical glass obtained by the method described in (1) above,
(3) The glass material for press molding according to (2), which is a preform for precision press molding,
(4) The molten glass made of the optical glass obtained by the method described in (1) above is allowed to flow out, the molten glass lump is separated, and formed into a precision press-molding preform in the process of cooling the molten glass lump. A method for producing a glass material for press molding, characterized by:
(5) A press molding characterized in that molten glass made of optical glass obtained by the method described in (1) above is cast into a mold to produce a glass molded body, and then the glass molded body is machined. Manufacturing method for glass materials,
(6) A method for producing an optical element, wherein the press-molding glass material according to (3) or the press-molding glass material obtained by the method according to (4) is precision press-molded,
(7) An optical element blank is formed by press-molding the glass material for press molding according to (2) or (3) above or the glass material for press molding obtained by the method according to (4) or (5) above. Producing, grinding and polishing the blank, a method for producing an optical element,
(8) A method for producing an optical element comprising a step of grinding and polishing a glass molded body made of optical glass obtained by the method described in (1) above, and (9) In (1) above An optical element manufacturing method is provided, wherein molten glass made of optical glass obtained by the method described above is flowed out and press-molded to produce an optical element blank, and then the blank is ground and polished To do.

  According to the present invention, when an optical glass made of fluorophosphate glass is prepared by a melting method using a phosphate raw material and a fluoride raw material, not only can the desired optical properties be imparted to the optical glass, It is possible to provide a method for producing an optical glass capable of reducing contamination of platinum or a platinum alloy foreign material. Further, according to the present invention, it is possible to provide a glass material for press molding composed of the optical glass produced by the above method, and further produce a glass material for press molding and an optical element from the optical glass produced by the above method, respectively. A method can be provided.

[Method for producing optical glass]
First, the manufacturing method of the optical glass of this invention is demonstrated.
The method for producing an optical glass of the present invention is a method for producing an optical glass comprising a fluorophosphate glass using a phosphate raw material and a fluoride raw material,
The first step of melting phosphate raw material in a non-metallic container to obtain phosphate glass, and the obtained phosphate glass as a melt or after solidifying the melt, fluoride And a second step of melting in a platinum or platinum alloy container together with the raw material.

In the present invention, the phosphate raw material means various metal phosphates such as Al (PO ₃ ) ₃ , Ba (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , Sr (PO ₃ ) ₂ in the glass production process. And the reaction product of each of the above-mentioned phosphate itself, H ₃ PO ₄ , P ₂ O _5, etc., and an oxide such as an alkali metal or an alkaline earth metal. Further, in the present invention, the fluoride raw _material, means AlF _3, MgF _2, CaF 2, SrF fluoride or the like _2, a mixture of this such fluorides. These glass raw materials can be appropriately selected according to the glass composition to be obtained.

  As the non-metallic container for melting the phosphate raw material, a container composed of one or more selected from silica, alumina, graphite, silicon carbide, vitrified carbon and the like is preferable.

  In the method of the present invention, the first step is a step of obtaining a phosphate glass by melting a phosphate raw material in the non-metallic container. The heating temperature at the time of melting is preferably 900 to 1300 ° C, more preferably 900 to 1200 ° C. The heating time is preferably 30 to 240 minutes, more preferably 60 to 180 minutes. The atmosphere is preferably a non-oxidizing atmosphere, and examples of the non-oxidizing atmosphere include a nitrogen atmosphere, a rare gas atmosphere such as argon, and a vacuum atmosphere. By making the atmosphere at the time of melting into a non-oxidizing atmosphere, it becomes possible to use a container made of a material having low fire resistance.

  The phosphate raw material is melted at least until the raw material is melted and vitrified. Further, the glass may be homogenized by continuing the heating, but considering that the glass homogenizing process is performed in a platinum or platinum alloy container, which will be described later, the heating process is performed when the raw material is vitrified. It is preferable to end.

  As described above, the fluoride raw material erodes a container made of silica, which is a non-metallic container, but in the present invention, only the phosphate raw material is melted in the non-metallic container, so the structure of the silica container It becomes possible to prevent or reduce components from being incorporated into the glass.

  In the method of the present invention, the second step is a step of melting the obtained phosphate glass in a molten or platinum or platinum alloy container together with a fluoride raw material after the molten material is solidified. .

  In the melting in the second step, the non-metallic container and the platinum or platinum alloy container are connected by a pipe, so that the phosphate glass produced in the non-metallic container is placed in the platinum or platinum alloy container. The glass body obtained by once cooling and solidifying the phosphate glass prepared in a nonmetallic container may be reheated and then reheated in a platinum or platinum alloy container. You may go.

  Examples of the platinum alloy constituting the container include platinum / zirconia alloy, platinum / gold alloy, platinum / iridium alloy, and platinum / rhodium alloy.

The melting temperature in the second step is preferably 800 to 1200 ° C, more preferably 900 to 1100 ° C. High-temperature glass tends to react with moisture in the atmosphere, and this reaction lowers the quality of the glass. Therefore, the atmosphere during melting is preferably a dry atmosphere. The moisture content in the dry atmosphere is preferably equivalent to a dew point of −30 ° C. or lower, and examples of the gas include inert gases such as nitrogen and argon.
Moreover, it is preferable to homogenize the glass by performing a stirring process together with the melting process.

  As described above, the phosphate raw material erodes the platinum or platinum alloy container when vitrified, but in the present invention, the phosphate raw material is melted and vitrified in a non-metallic container. Since melting is performed in a container made of platinum or a platinum alloy, it is possible to prevent or reduce mixing of constituent components of the container made of platinum or a platinum alloy into the glass.

Next, optical glass made of fluorophosphate glass obtained by the method of the present invention will be described.
As a preferable first aspect (hereinafter referred to as optical glass I) of the optical glass made of fluorophosphate glass, P ⁵⁺ 5-50%, Al ³⁺ 0.1-40%, Mg ²⁺ 0-20 in terms of cation%. %, Ca ²⁺ 0-25%, Sr ²⁺ 0-30%, Ba ²⁺ 0-30%, Li ⁺ 0-30%, Na ⁺ 0-10%, K ⁺ 0-10%, Y ³⁺ 0-10% , La ³⁺ 0 to 5%, and Gd ³⁺ 0 to 5%.

In the optical glass I, the anion component F ^- and ^{O 2-} allocations, F ^- and ^{O 2-} F to the total amount of ^- the molar ratio of the content of ^{F - / (F - + O} 2-) 0.25 It is preferable to be in the range of ˜0.95. By setting the amount of the anion component as described above, low dispersion characteristics can be imparted to the glass.

  According to the optical glass I, it is possible to realize optical characteristics having a refractive index value nd of 1.40000 to 1.60000 and an Abbe number (νd) of 67 or more. The upper limit of the Abbe number (νd) is not particularly limited, but it is preferable to set the Abbe number (νd) to 100 or less from the viewpoint of stably producing the glass.

In the optical glass I, 2 divalent cationic components ^{(R 2+)} as ^Ca 2+, those containing two or more of ^{Sr 2+} and ^{Ba 2+} preferred.

The optical glass I preferably has a total content of 1% or more of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ which are divalent cation components (R ²⁺ ), Mg ²⁺ , Ca ²⁺ , Sr. More preferably, the contents of ²⁺ and Ba ²⁺ are each 1% or more.

  Hereinafter, the composition of the optical glass I will be described in detail. The content ratio (%) of each cation component means the cation% based on the molar ratio, and the content ratio (%) of each anion component is also based on the molar ratio. % Of anion.

P ⁵⁺ is an important cation component as a glass network former. If it is less than 5%, the stability of the glass is lowered, and if it exceeds 50%, P ⁵⁺ needs to be introduced as an oxide raw material, so the oxygen ratio increases. Does not meet the target optical characteristics. Therefore, the amount is 5% to 50%, more preferably 5% to 40%, and particularly preferably 5% to 35%. When introducing P ^5+, the use of PCl ₅ is not appropriate because it erodes platinum and is volatile, which hinders stable production and is preferably introduced as a phosphate.

Al ³⁺ is a component that improves the stability of fluorophosphate glass. If it is less than 0.1%, the stability decreases, and if it exceeds 40%, the glass transition temperature (Tg) and the liquidus temperature (LT) increase greatly. As a result, the molding temperature rises and striae due to surface volatilization during molding occurs strongly, making it impossible to obtain a homogeneous glass molded body, particularly a press molding preform. Therefore, the amount is 0.1% to 40%, more preferably 5% to 40%, and particularly preferably 10% to 3%.
5%.

Introduction of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ , which are divalent cation components (R ²⁺ ), contributes to improvement of the stability of the glass. However, since the stability as glass decreases due to excessive introduction, it is preferable to set Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ in the following ranges.

First, the preferable content of Mg ²⁺ is 0 to 20%, more preferably 1 to 20%, still more preferably 5 to 15%, and particularly preferably 5 to 10%. The preferable content of Ca ²⁺ is 0 to 25%, more preferably 1 to 25%, still more preferably 5 to 20%, and particularly preferably 5 to 16%. The preferable content of Sr ²⁺ is 0 to 30%, more preferably 1 to 30%, still more preferably 5 to 25%, and particularly preferably 10 to 20%. The preferable content of Ba ²⁺ is 0 to 30%, more preferably 1 to 30%, still more preferably 1 to 25%, still more preferably 5 to 25%, and particularly preferably 8 to 25%.

It is preferable to introduce two or more of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , rather than introducing each singly, and more than two of Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are introduced. preferable. In order to further enhance the effect of introducing the divalent cation component (R ²⁺ ), the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferably 1% or more. Moreover, when it introduces exceeding each upper limit, stability will fall rapidly. Ca ²⁺ and Sr ²⁺ can be introduced in a relatively large amount, but Mg ²⁺ and Ba ²⁺ particularly lower the stability. However, since Ba ²⁺ is a component capable of realizing a high refractive index while maintaining low dispersion, it is preferably introduced in a large amount within a range not impairing stability.

Li ⁺ is a component that lowers the glass transition temperature (Tg) without impairing the stability. However, if it exceeds 30%, the durability of the glass is impaired and at the same time the workability is lowered. Therefore, the amount is 0-30%. A preferable range is 0 to 25%, and a more preferable range is 0 to 20%.

However, when it is desired to lower the glass transition temperature particularly for precision press molding applications, the amount of Li ⁺ is preferably 2 to 30%, more preferably 5 to 25%, and more preferably 5 to 20%. More preferably.

Na ⁺ and K ⁺ have the effect of lowering the glass transition temperature (Tg), respectively, like Li ⁺ , but at the same time, the thermal expansion coefficient tends to be larger than that of Li ⁺ . Moreover, since NaF and KF have a very high solubility in water as compared with LiF, the water resistance is also deteriorated. Therefore, the amounts of Na ⁺ and K ⁺ are 0 to 10%, respectively. A preferable range for both Na ⁺ and K ⁺ is 0 to 5%, and it is more preferable not to introduce them.

Y ³⁺ , La ³⁺ and Gd ³⁺ have the effect of improving the stability and durability of the glass and increasing the refractive index. However, if it exceeds 5%, the stability deteriorates and the glass transition temperature (Tg) is large. In order to increase, the amount is set to 0 to 5%. A preferable range is 0 to 3%.

From the viewpoint of stably producing high-quality optical glass, the total amount of P ⁵⁺ , Al ³⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ and Y ³⁺ , La ³⁺ , Gd ³⁺ is used as a cation. % Is preferably over 95%, more preferably over 98%, further preferably over 99%, and even more preferably 100%.

  The optical glass I can contain a lanthanoid such as Ti, Zr and Zn in addition to the cation component described above and a cation component such as B and a cation component such as B as long as the object of the present invention is not impaired.

Ratio of anionic components, while realizing the desired optical properties, in order to obtain an optical glass having excellent stability, F ^- and O ^2-F to the total amount of ^- the molar ratio of the content of F ^- / ( F ⁻ + O ²⁻ ) is set to 0.25 to 0.95.

  The optical glass I is an excellent glass both as a glass for producing an optical element by precision press molding and as a glass for producing an optical element by grinding and polishing.

A preferred second embodiment of the optical glass made of fluorophosphate glass (hereinafter referred to as optical glass II) is made of fluorophosphate glass containing Cu ²⁺ , and this glass functions as near-infrared absorbing glass. The optical glass II is particularly suitable as a color correction filter for a semiconductor image sensor such as a CCD or CMOS, and when used for the above-mentioned purposes, the Cu ²⁺ content is preferably 0.5 to 13 cation%. .

A particularly preferred composition of the optical glass II is expressed in terms of cation%, P ⁵⁺ 11 to 45%, Al ^{3+ 0 to} 29%, Li ⁺ , Na ⁺ and K ⁺ in a total of 0 to 43%, Mg ²⁺ , Ca ²⁺ , sr ^{2+, 14 to 50%} in total of ^{Ba 2+} and ^{Zn 2+,} wherein the Cu 2+ 0.5 to 13%, further anionic% ^display, F - is intended to include 17 to 80%.

In the above composition, the remaining amount of the anionic component is preferably O ²⁻ .
Hereinafter, the composition of the optical glass II will be described in detail. As in the description of the composition of the optical glass I, the content ratio (%) of each cation component means the cation% based on the molar ratio. The content ratio (%) of each anion component also means% anion based on the molar ratio.

In the above composition, P ⁵⁺ is a basic component of fluorophosphate glass and an important component that brings about absorption of Cu ^{2+ in} the infrared region. If the content of P ⁵⁺ is less than 11%, the color deteriorates to be greenish. Conversely, if it exceeds 45%, the weather resistance and devitrification resistance deteriorate. Therefore, the content of P ⁵⁺ is preferably 11 to 45%, more preferably 20 to 45%, and still more preferably 23 to 40%.

Al ³⁺ is a component that improves the devitrification resistance, heat resistance, thermal shock resistance, mechanical strength, and chemical durability of fluorophosphate glass. However, if it exceeds 29%, the near infrared absorption characteristics deteriorate. Therefore, the content of Al ³⁺ is preferably 0 to 29%, more preferably 1 to 29%, still more preferably 1 to 25%, and even more preferably 2 to 23%. .

Li ⁺ , Na ⁺ and K ⁺ are components that improve the meltability and devitrification resistance of the glass and improve the transmittance in the visible light region, but if the total amount exceeds 43%, the durability of the glass, Workability deteriorates. Therefore, the total content of Li ⁺ , Na ⁺ and K ⁺ is preferably 0 to 43%, more preferably 0 to 40%, and still more preferably 0 to 36%.

Among the alkali components, Li ⁺ is excellent in the above action, and the amount of Li ⁺ is preferably 15 to 30%, more preferably 20 to 30%.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ^2+, and Zn ²⁺ are useful components that improve the devitrification resistance, durability, and workability of the glass. However, since the devitrification resistance decreases due to excessive introduction, Mg The total amount of ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ is preferably 14 to 50%, more preferably 20 to 40%.

A preferable range of the Mg ²⁺ content is 0.1 to 10%, and a more preferable range is 1 to 8%. A preferable range of the Ca ²⁺ content is 0.1 to 20%, and a more preferable range is 3 to 15. A preferable range of the Sr ²⁺ content is 0.1 to 20%, and a more preferable range is 1 to 15%. A preferable range of the Ba ²⁺ content is 0.1 to 20%, a more preferable range is 1 to 15%, and a further preferable range is 1 to 10.

Cu ²⁺ is a bearer of near-infrared light absorption characteristics. If the amount is less than 0.5%, the near-infrared absorption is small. Therefore, the content of Cu ²⁺ is preferably 0.5 to 13%, more preferably 0.5 to 10%, still more preferably 0.5 to 5%, and even more preferably 1 to 5%.

F ⁻ is an important anion component that lowers the melting point of the glass and improves the weather resistance in the optical glass II. By containing F ⁻ , the optical glass II can lower the melting temperature of the glass, suppress the reduction of Cu ²⁺ , and obtain the required optical characteristics. When the content of F ⁻ is less than 17%, the weather resistance deteriorates. On the other hand, when the content of F ⁻ exceeds 80%, the content of O ²⁻ decreases, so that coloring near 400 nm is caused by monovalent Cu ⁺ . Therefore, the content of F ⁻ is preferably 17 to 80. In order to further improve the above characteristics, the amount of F ⁻ is more preferably 25 to 55%, and further preferably 30 to 50%.

O ²⁻ is an important anion component in the optical glass II, and it is preferable that the entire remaining amount excluding F ^{− of the} total anion component is composed of the O ²⁻ component. Therefore, the preferable amount of O ²⁻ is a range obtained by subtracting the preferable amount of F ⁻ from 100%. If the amount of O ²⁻ is too small, divalent Cu ²⁺ is reduced to monovalent Cu ⁺ , so that the absorption in the short wavelength region, particularly near 400 nm, becomes large, and the color becomes green. On the other hand, if the amount is excessive, the viscosity of the glass is high and the melting temperature is high, so that the transmittance is deteriorated.
Note that Pb and As are not harmful because they are highly harmful.

  The preferable transmittance characteristics of the optical glass II are the following characteristics when the spectral transmittance at a wavelength of 500 to 700 nm is converted to a thickness at which the wavelength showing a transmittance of 50% is 615 nm, and the spectral transmittance at a wavelength of 400 to 1200 nm is as follows: Is shown.

  78% or more at a wavelength of 400 nm, preferably 80% or more, 85% or more at a wavelength of 500 nm, preferably 88% or more, 51% or more at a wavelength of 600 nm, preferably 55% or more, 12% or less at a wavelength of 700 nm, preferably 11% Hereinafter, 5% or less at a wavelength of 800 nm, preferably 3% or less, 5% or less at a wavelength of 900 nm, preferably 3% or less, 7% or less at a wavelength of 1000 nm, preferably 6% or less, preferably 12% or less at a wavelength of 1100 nm, preferably 11% or less, 23% or less at a wavelength of 1200 nm, preferably 22% or less.

  That is, absorption of near-infrared light having a wavelength of 700 to 1200 nm is large, and absorption of visible light having a wavelength of 400 to 600 nm is small. Here, the transmittance is assumed to be a glass sample having two planes that are parallel to each other and optically polished, and when light is incident on one of the planes perpendicularly, the intensity of the light emitted from the other of the planes is expressed as follows. It is a value divided by the intensity of the incident light before entering the sample, and is also called external transmittance.

  The optical glass II can satisfactorily perform color correction of a semiconductor image sensor such as a CCD or a CMOS due to such characteristics.

[Glass material for press molding]
The glass material for press molding of the present invention is characterized by comprising an optical glass obtained by the method for producing an optical glass of the present invention.

  Optical glass made of fluorophosphate glass has properties that it has a higher degree of wear and a larger thermal expansion coefficient than other general optical glasses, and such properties are not preferable for polishing. When the degree of wear is large, processing accuracy is lowered, and scratches during polishing are likely to remain on the glass surface. Polishing is performed while the cutting fluid is applied to the glass. However, if the cutting fluid is applied to the glass whose temperature has been increased by polishing, or if glass having scratches due to polishing on the surface is added to the cleaning liquid whose temperature has increased during ultrasonic cleaning, the glass A fluorophosphate glass that is exposed to a large temperature change and has a large coefficient of thermal expansion is likely to break the glass due to thermal shock. Therefore, it is desirable to manufacture the glass material for press molding by a method not based on polishing. From such a viewpoint, the glass material for press molding is preferably a precision press molding preform. Here, the precision press-molding preform means that a glass having a weight equal to the weight of the press-molded product is previously molded into a shape suitable for precision press-molding.

  As a precision press-molding preform, the entire surface is preferably formed by solidifying molten glass, and the entire surface of the preform is formed by solidifying molten glass; and By doing so, it is possible to prevent or reduce damage to the preform when the preform is washed or heated prior to precision press molding.

[Method for producing glass material for press molding]
Next, the manufacturing method of the glass material for press molding is demonstrated.
In the method for producing a glass material for press molding according to the present invention, the first aspect (hereinafter referred to as “Glass Material Production Method I”) is to let molten glass made of optical glass obtained by the method for producing optical glass of the present invention flow out. The molten glass lump is separated and formed into a precision press-molding preform in the course of cooling the molten glass lump.

Hereinafter, the manufacturing method I of a glass raw material is demonstrated based on a preferable specific example.
The molten glass is continuously discharged at a constant flow rate from a platinum or platinum alloy pipe heated to a predetermined temperature. A molten glass lump having a weight equivalent to one preform is separated from the molten glass that has flowed out. When separating the molten glass lump, it is desirable to avoid the use of a cutting blade so that no cut marks remain. It is preferable to use a method in which the molten glass lump is separated from the front end of the molten glass flow by using the surface tension of the molten glass by suddenly dropping the support at a timing at which the molten glass lump of the target weight can be separated.

  The separated molten glass lump is formed into a desired shape in the process of cooling the glass on the recess of the preform mold. At that time, in order to prevent wrinkles on the preform surface or breakage in the glass cooling process called can cracking, it is preferable to mold the glass lump in a state of being lifted by applying upward wind pressure to the glass block. In that case, it is preferable to spray the gas on the surface of the glass lump to promote the cooling of the surface from the viewpoint of reducing and preventing the occurrence of striae.

  After the temperature of the glass is lowered to a temperature range that does not deform even when an external force is applied to the preform, the preform is taken out from the preform mold and gradually cooled.

  In order to reduce the volatilization of the glass component from the glass surface, it is preferable to perform glass outflow and preform molding in a dry atmosphere (dry nitrogen atmosphere, dry air atmosphere, dry mixed gas atmosphere of nitrogen and oxygen, etc.). .

  In the glass material production method I, a high-quality and highly accurate preform can be produced, which is suitable as a method for producing a precision press-molding preform.

  In the method for producing a glass material for press molding according to the present invention, a second aspect (hereinafter referred to as glass material production method II) uses a molten glass made of optical glass obtained by the method for producing optical glass of the present invention as a mold. A glass molded body is produced by casting, and then the glass molded body is machined.

  As a preferable specific example in the production method II of the glass material, first, the molten glass is continuously discharged from the pipe and poured into a mold disposed below the pipe. As the mold, a flat bottom and a side wall that surrounds the bottom from three sides and one side of which is open are used. The side walls that sandwich the opening side and bottom from both sides face each other in parallel, and the mold is placed, fixed, and poured into the mold so that the center of the bottom is positioned vertically below the pipe and the bottom is horizontal. The molten glass is spread so as to have a uniform thickness in the region surrounded by the side walls, and after cooling, the glass is drawn out horizontally from the opening on the side surface of the mold at a constant speed. The drawn glass molded body is sent into an annealing furnace and annealed. In this way, a plate-like glass molded body having a certain width and thickness and having reduced and suppressed surface striae is obtained.

  Next, the plate-like glass molded body is cut or cleaved and divided into a plurality of glass pieces called cut pieces, and these glass pieces are ground and polished to finish a preform for press molding with a target weight.

Another preferred specific example is as follows.
A mold having a cylindrical through hole is placed and fixed vertically below the pipe so that the central axis of the through hole faces the vertical direction. At this time, it is preferable to arrange | position a casting_mold | template so that the central axis of a through-hole may be located in the vertically downward direction of a pipe. Then, molten glass is poured from the pipe into the mold through-hole at a constant flow rate, the glass is filled into the through-hole, and the solidified glass is drawn vertically downward at a constant speed from the lower end opening of the through-hole, gradually cooled, A cylindrical rod-shaped glass molded body is obtained. After annealing the glass molded body thus obtained, a plurality of glass pieces are obtained by cutting or cleaving from a direction perpendicular to the central axis of the cylindrical bar. Next, the glass piece is ground and polished to finish a preform for press molding with a desired weight. Also in these methods, it is preferable to perform the outflow and shaping of the molten glass in a dry atmosphere as described above. Furthermore, also in these methods, it is effective to reduce and prevent striae by accelerating cooling by blowing a gas onto the glass surface during molding.

[Method of manufacturing optical element]
Next, the manufacturing method of the optical element of this invention is demonstrated.
The first aspect of the optical element manufacturing method of the present invention (hereinafter referred to as optical element manufacturing method I) is obtained by the press molding glass material or glass material manufacturing method I of the present invention as a precision press molding preform. The press-molding glass material is precision press-molded.

  The precision press molding is also called mold optics molding, and is a well-known method in the technical field. According to precision press molding, an optical functional surface can be formed by press molding by precisely transferring the molding surface of a press mold to glass, and machining such as grinding and polishing is performed to finish the optical functional surface. There is no need to add.

  Therefore, the optical element manufacturing method I of the present invention is suitable for the production of optical elements such as lenses, lens arrays, diffraction gratings, and prisms, and is particularly suitable as a method for producing aspherical lenses with high productivity. Yes.

According to the optical element manufacturing method I of the present invention, since the glass transition temperature (Tg) constituting the preform is low, the press molding temperature can be lowered, and the molding surface of the press mold is damaged. Can be reduced and the life of the mold can be extended. Further, since the glass constituting the preform has high stability, devitrification of the glass can be effectively prevented even in the reheating and pressing steps. Furthermore, a series of steps for obtaining a final product from glass melting can be performed with high productivity.

  As a press mold used for precision press molding, known molds such as silicon carbide, zirconia, alumina and other heat-resistant ceramic molds provided with a release film can be used. A silicon press mold is preferable, and a carbon-containing film or the like can be used as the release film. In view of durability and cost, a carbon film is particularly preferable.

  In precision press molding, it is desirable that the molding atmosphere be a non-oxidizing gas in order to keep the molding surface of the press mold in a good state. The non-oxidizing gas is preferably nitrogen or a mixed gas of nitrogen and hydrogen.

  As a preferable aspect in the manufacturing method I of the optical element of the present invention, a glass material is introduced into a press mold and both are heated together to perform precision press molding, or a glass material heated separately in a preheated press mold And an embodiment in which precision press molding is introduced.

  The precision press-molded optical element is taken out from the press mold and gradually cooled as necessary.

  The second aspect of the optical element production method of the present invention (hereinafter referred to as optical element production method II) is the above-mentioned press molding glass material of the present invention or the above-mentioned glass material production method II. An optical element blank is produced by press-molding a glass material, and the blank is ground and polished.

  The weight of the glass material is preferably a weight obtained by adding the weight to be removed by grinding and polishing to the weight of one optical element to be obtained. As a grinding and polishing method, a conventionally known method is used. Can be used.

  The third aspect of the optical element manufacturing method of the present invention (hereinafter referred to as optical element manufacturing method III) is to grind and polish a glass molded body made of optical glass obtained by the optical glass manufacturing method of the present invention described above. Including the step of performing.

  As a specific embodiment of the optical element manufacturing method III, for example, there is a method in which molten glass is flowed out to form a glass molded body, annealed, and then subjected to mechanical processing such as cutting, grinding, polishing and the like to manufacture an optical element. It is done. For example, an optical element such as various lenses can be manufactured by slicing the cylindrical rod-shaped glass molded body described above from a direction perpendicular to the cylinder axis, and grinding and polishing the obtained cylindrical glass. .

  According to a fourth aspect of the optical element manufacturing method of the present invention (hereinafter referred to as optical element manufacturing method IV), a molten glass made of the optical glass obtained by the above-described optical glass manufacturing method of the present invention is allowed to flow out and pressed. An optical element blank is produced by molding, and then the blank is ground and polished.

  The weight of the optical element blank is preferably a weight obtained by adding the weight to be removed by grinding and polishing to the weight of one optical element to be obtained. As a grinding and polishing method, a conventionally known method is used. Can be used.

When the optical element obtained by each of the above production methods is a lens or the like, an antireflection film may be formed on the surface or a near infrared light reflection film may be coated as necessary.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1 (Production Example of Optical Glass I)
No. shown in Table 1 and Table 2. The raw materials corresponding to each component were weighed and mixed sufficiently so as to obtain a glass having a composition of 1 to 11. At this time, the mixture was divided into two raw material groups so as not to mix the phosphate raw material and the fluoride raw material.
The prepared raw material containing the phosphate raw material was put in a silica crucible and melted for 1 hour with stirring at 1200 ° C., and then rapidly cooled and pulverized to obtain cullet. In this melting process, nitrogen gas was continuously supplied into the silica crucible to keep the atmosphere in a non-oxidizing atmosphere.

  Next, 10 kg of this cullet was put into a platinum crucible sealed with a lid, and at the same time, 15 kg of a blended raw material containing fluoride was put into it, heated to 900 ° C., stirred and melted. Next, a sufficient amount of dry gas was introduced into the platinum crucible and the molten glass was clarified at 1100 ° C. for 2 hours while maintaining a dry atmosphere. Examples of the dry gas include an inert gas such as nitrogen, a mixed gas of an inert gas and oxygen, oxygen, and the like.

After clarification, the temperature of the glass was lowered to 850 ° C., which is lower than the temperature at the time of clarification, and then the molten glass was poured out from the pipe connected to the bottom of the crucible, cast into a mold, and formed into a glass block.
The gas introduced into the silica crucible and the platinum crucible was cleaned through a filter and then discharged to the outside.

  When light was incident on each glass block obtained and the optical path of the light in the glass was observed from the side, light scattering by the platinum foreign matter was hardly observed, and it was confirmed that platinum foreign matter could be prevented from entering the glass block. did. A photograph taken by arbitrarily selecting one of the obtained glass blocks is shown in FIG. 2 (white spots on the glass block in FIG. 2 are caused by dust adhering to the glass surface).

  In addition, the obtained optical glass No. For 1 to 11, the refractive index (nd), Abbe number (νd), and glass transition temperature (Tg) were measured as follows. The measurement results are shown in Tables 1-2.

(1) Refractive index (nd) and Abbe number (νd)
It measured about the optical glass obtained by making slow cooling temperature-fall rate -30 degreeC / hour.
(2) Glass transition temperature (Tg)
The glass transition temperature (Tg) was measured using a thermomechanical analyzer manufactured by Rigaku Corporation with a heating rate of 4 ° C./min.

Example 2 (Production Example of Optical Glass II)
No. shown in Table 3 The raw materials corresponding to each component were weighed and mixed well so as to obtain a glass having a composition of 12-13. At this time, the mixture was divided into two raw material groups so as not to mix the phosphate raw material and the fluoride raw material.
Next, in the same manner as in Example 1, optical glass No. 12-13 were produced. When light was incident on each optical glass obtained and the optical path of the light in the glass was observed from the side, light scattering by the platinum foreign matter was hardly observed, and it was confirmed that platinum foreign matter mixing into the glass block could be prevented. did.

  The obtained optical glass No. About 12-13, the refractive index (nd), Abbe number ((nu) d), and glass transition temperature (Tg) were measured like Example 1, and the transmittance | permeability in a typical wavelength was measured. The results are shown in Table 3.

  The transmittance is a value at a thickness at which the transmittance is 50% at a wavelength of 615 nm. Optical glass No. 12, the thickness is 1.0 mm. In 13, the thickness is 0.45 mm. The transmittance was measured with a spectrophotometer using a flat plate-like sample in which the opposing surfaces were optically polished in parallel with each other.

Comparative Example 1 (Optical glass production comparative example)
No. shown in Table 1 and Table 2. The raw materials corresponding to each component were weighed and mixed sufficiently so as to obtain a glass having a composition of 1 to 11. At this time, the sample was prepared by mixing the phosphate raw material and the fluoride raw material without mixing them.
25 kg of the above prepared raw materials were put into a platinum crucible sealed with a lid, and heated at 1200 ° C. for 1 hour to melt the raw materials. Next, the molten glass was clarified over 1 hour at 900 ° C. with stirring while introducing a sufficient drying gas into the platinum crucible and maintaining a dry atmosphere.
After clarification, the temperature of the glass was lowered to 850 ° C., which is lower than the temperature at the time of clarification, and then the molten glass was poured out from the pipe connected to the bottom of the crucible, cast into a mold, and formed into a glass block.
The gas introduced into the platinum crucible was cleaned through a filter and then discharged to the outside.

  When a light beam is incident on the obtained glass block made of each optical glass and the optical path of the light beam in the glass is observed from the side, the light path is clearly observed by light scattering by a platinum foreign material, and a large number of platinum is contained in the glass block. It was confirmed that foreign matter was mixed. FIG. 3 shows a photograph taken by arbitrarily selecting one of the obtained glass blocks.

Example 3 (Production example of lens preform by glass material production method I)
Each molten glass obtained from Example 1 and made of optical glass Nos. 1 to 11 has a constant flow rate from a platinum pipe whose temperature is adjusted to a temperature range where stable outflow is possible without causing the glass to devitrify. The molten glass lump having the weight of the target preform was separated by a method in which the molten glass flow tip was supported by dropping or supporting the molten glass using a support and then rapidly dropping the support to separate the glass lump. Next, each of the obtained molten glass lumps is received in a receiving mold having a gas outlet at the bottom, and the glass bulge is formed by floating gas from the gas outlet, and is formed of optical glass No. 1-11. A lens preform for press molding was prepared. The shape of the preform was made spherical or flat spherical by adjusting and setting the separation interval of the molten glass. The weights of the obtained preforms precisely matched the set values, and all of the preforms were smooth and the surfaces were formed by solidification of the molten glass.
Subsequently, when the inside of the preform was observed, no striae were observed in any of them.

Example 4 ( Example of manufacturing lens preform by glass material production method II)
Each molten glass made of optical glass Nos. 1 to 11 obtained in Example 1 is fixed to a mold from a platinum pipe whose temperature is adjusted to a temperature range in which stable outflow is possible without devitrification of the glass. The glass was cast by flowing out at a flow rate of 5 mm, and formed into a sheet glass while spraying a dry gas on the glass surface to promote cooling. Also in this case, no striae were found on the surface of the sheet glass. After the annealing treatment, the surface of the glass piece obtained by cutting each obtained plate glass was ground and polished to obtain a precision press-molding lens preform with a smooth entire surface.

Example 5 (Manufacturing Examples of Various Lenses by Optical Element Manufacturing Method I)
Each preform obtained in Example 3 and Example 4 was precision press-molded using the press apparatus shown in FIG. 1 to obtain various lenses. Specifically, after the preform 4 is placed between the lower mold 2 and the upper mold 1 of the press mold composed of the upper mold 1, the lower mold 2 and the body mold 3, the inside of the quartz tube 11 is placed in a nitrogen atmosphere to form a heater 12. Was energized to heat the inside of the quartz tube 11. The temperature inside the press mold is set to a temperature at which the glass to be molded exhibits a viscosity of 10 ⁸ to 10 ¹⁰ dPa · s, and while maintaining the same temperature, the push bar 13 is lowered and the upper mold 1 is pressed to form. The preform set in the mold was pressed. The press pressure was 8 MPa, and the press time was 30 seconds. After pressing, the pressure of the press is released, and the glass molded product that has been press-molded is kept in contact with the lower mold 2 and the upper mold 1 until the viscosity of the glass reaches 10 ¹² dPa · s or more. It was cooled and then rapidly cooled to room temperature, and various lenses were removed from the mold.

  In FIG. 1, reference numeral 9 is a support rod, reference numeral 10 is a lower mold, a barrel holder, and reference numeral 14 is a thermocouple. Further, the shape of the molding surface of the upper mold 1 and the lower mold 2 shown in FIG. 1 was appropriately changed according to the obtained lens shape.

  By the above method, lenses having various shapes such as a concave meniscus lens, a convex meniscus lens, a biconcave lens, a biconvex lens, a planoconvex lens, and a planoconcave lens were produced. Each of the obtained lenses had extremely high surface accuracy. The various lenses were provided with an antireflection film as required.

Example 6 (Manufacturing examples of various lenses by optical element manufacturing method II)
Each molten glass made of optical glass Nos. 1 to 11 obtained in Example 1 was cast into a mold and formed into a sheet glass. After annealing the obtained plate-like glass, it was cut into a plurality of glass pieces in the shape of a lattice, and the surface was roughened by barrel polishing, and the glass pieces were made to have a desired weight to obtain a glass material.
Next, a powder release agent such as boron nitride was applied to the entire surface of the glass material, heated and softened in the air, and press-molded to produce lens blanks having shapes approximate to various lens shapes. After the obtained lens blank was annealed, it was ground and polished to produce various lenses made of optical glass Nos. 1-11.
By the above method, lenses having various shapes such as a concave meniscus lens, a convex meniscus lens, a biconcave lens, a biconvex lens, a planoconvex lens, and a planoconcave lens were produced. The various lenses were provided with an antireflection film as required.

Example 7 ( Examples of various lenses manufactured by optical element manufacturing method III)
Each molten glass made of optical glass Nos. 1 to 11 obtained in Example 1 was continuously poured from a pipe into a mold, formed into a sheet glass in a dry nitrogen atmosphere, and slowly cooled. Next, when the inside of the glass was observed, no striae was observed.
This plate-like glass was cut into a required size, ground and polished, and various lenses made of optical glass Nos. 1 to 11 were produced.
By the above method, lenses having various shapes such as a concave meniscus lens, a convex meniscus lens, a biconcave lens, a biconvex lens, a planoconvex lens, and a planoconcave lens were produced. The various lenses were provided with an antireflection film as required.

Example 8 ( Example of production of near-infrared absorbing filter by optical element production method III)
Each molten glass made of optical glass Nos. 12 to 13 obtained in Example 2 was continuously poured from a pipe into a mold, formed into a glass block in a dry nitrogen atmosphere, and slowly cooled. Next, when the inside of the glass was observed, no striae was observed.
Each glass block was sliced, the surface was ground and polished, processed into a thin plate, and a near infrared absorption filter was produced.

Example 9 ( Examples of various lenses manufactured by optical element manufacturing method IV)
Each molten glass made of optical glass No. 1 to 11 obtained in Example 1 was continuously flowed out from the platinum pipe, received on the lower press mold waiting under the pipe, and the molten glass flow was cut. The required amount of molten glass ingot was obtained. The lower mold on which the molten glass block was placed was retracted from below the pipe, and the molten glass block was press-molded using the upper mold facing the lower mold to obtain a lens blank.
These series of steps were sequentially repeated by using a plurality of lower molds to obtain a plurality of lens blanks.
Each lens blank was annealed and then ground and polished to obtain various lenses made of optical glass Nos. 1-11.
By the above method, lenses having various shapes such as a concave meniscus lens, a convex meniscus lens, a biconcave lens, a biconvex lens, a planoconvex lens, and a planoconcave lens were produced. The various lenses were provided with an antireflection film as required.

  According to the present invention, when optical glass made of fluorophosphate glass is produced by a melting method, not only can desired optical properties be imparted to the optical glass, but also contamination of platinum or platinum alloy foreign matter into the glass can be reduced. The manufacturing method of the optical glass which can be provided can be provided. Further, according to the present invention, it is possible to provide a glass material for press molding composed of the optical glass produced by the above method, and further produce a glass material for press molding and an optical element from the optical glass produced by the above method, respectively. A method can be provided.

It is the schematic of the precision press molding apparatus used in the Example of this invention. It is a photograph which shows the glass block obtained in the Example of this invention. It is a photograph which shows the glass block obtained by the comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Upper type | mold 2 ... Lower type | mold 3 ... Body type | mold 4 ... Preform 9 ... Support rod 10 ... Lower type | mold, barrel type | mold holder 11 ... Quartz tube 12 ... Heater 13 ... Push rod 14 ... Thermocouple

Claims (9)

A method for producing an optical glass comprising a fluorophosphate glass using a phosphate raw material and a fluoride raw material,
The first step of melting phosphate raw material in a non-metallic container to obtain phosphate glass, and the obtained phosphate glass as a melt or after solidifying the melt, fluoride And a second step of melting in a container made of platinum or a platinum alloy together with the raw material.   A glass material for press molding comprising the optical glass obtained by the method according to claim 1.   The press-molding glass material according to claim 2, which is a precision press-molding preform.   The molten glass made of the optical glass obtained by the method according to claim 1 is allowed to flow out, the molten glass lump is separated, and is molded into a precision press-molding preform in the course of cooling the molten glass lump. A method for producing a glass material for press molding.   A glass material for press molding characterized in that a molten glass made of optical glass obtained by the method according to claim 1 is cast into a mold to produce a glass molded body, and then the glass molded body is machined. Production method.   A method for producing an optical element, wherein the press-molding glass material according to claim 3 or the press-molding glass material obtained by the method according to claim 4 is precision press-molded.   The glass material for press molding according to claim 2 or 3 or the glass material for press molding obtained by the method according to claim 4 or 5 is press-molded to produce an optical element blank, and the blank is ground and polished. A method for manufacturing an optical element.   A method for producing an optical element, comprising a step of grinding and polishing a glass molded body made of optical glass obtained by the method according to claim 1.   An optical element blank is produced by causing molten glass comprising optical glass obtained by the method according to claim 1 to flow out and press-molding, and then grinding and polishing the blank. Production method.