JP5443417B2 - Fluorophosphate glass, precision press-molding preform, optical element blank, optical element and production method thereof - Google Patents

Description

  The present invention relates to fluorophosphate glass suitable as an optical element material for lenses, prisms, filters, and the like, a precision press-molding preform made of the glass, an optical element blank, an optical element, and a method for producing the same.

  Fluorophosphate glass is in high demand because of its properties such as low dispersion, anomalous dispersion, and high light transmittance over a wide visible range. Low dispersion and anomalous dispersion are effective in correcting chromatic aberration, and excellent high light transmittance is not only for optical element materials that make up the imaging optical system, but also for guiding light of short wavelengths such as near ultraviolet light. It is also effective as an optical element material, and can contain a filter function for cutting near infrared light by containing copper ions, and is also effective as a color correction filter material for a semiconductor imaging element. Thus, the fluorophosphate glass is described in Patent Documents 1 and 2.

  In this way, fluorophosphate glass is a useful optical material, but since it exhibits remarkable volatility at high temperatures, striae is likely to occur when producing glass moldings from molten glass, and high-quality glass can be stably produced. Difficult to produce. Further, since volatile components are lost with time from the glass in the molten state, there is a problem that optical characteristics such as refractive index are easily changed.

In order to solve such a problem, Patent Document 2 discloses a method in which a volatile substance is sufficiently volatilized from molten glass, and the glass is obtained by rapid cooling when the volatilization of the substance is reduced.
This method achieves the required purpose by setting the difference in refractive index of the glass before and after remelting within a predetermined range.

JP-A-10-139454 JP 2007-76958 A

  The invention disclosed in Patent Document 2 is a very excellent technique for solving the problems inherent in fluorophosphate glass, but further improvements are desired from the following viewpoints.

In melting fluorophosphate glass, a platinum-based crucible having excellent corrosion resistance is used to reduce the melting of the melting vessel. However, even if platinum is used, the platinum container is slightly eroded by the molten glass, and platinum ions dissolve into the glass. In the process of melting the raw material and the process of clarifying the glass, the temperature of the glass is high, so platinum in the glass is dissolved as ions, but when the glass is cooled down to a temperature range suitable for outflow, the dissolved platinum ions become particles. As it begins to precipitate. Since fluorophosphate glass has low solubility of platinum ions, platinum particles are particularly likely to precipitate. The precipitated platinum particles become a foreign matter as a scattering source of light that passes through the glass, and deteriorates the performance as an optical element or becomes a starting point of glass breakage that occurs when strong light is applied.
In order to solve these problems, it is desired to suppress erosion in addition to reducing volatility.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a high-quality fluorophosphate glass, a precision press-molding preform made of the glass, an optical element blank, an optical element, and a method for producing them. .

In order to solve the above problems, the present invention
(1) An optical glass that does not contain ions having absorption in the visible region, contains a phosphorous component in terms of P ⁵⁺ , more than 3 cation% and not more than 30 cation%, in the vicinity of the ³¹ P reference frequency in the nuclear magnetic resonance spectrum Ri wherein the ratio ^{I (1) / I (0} ) is 0.08 der less of the intensity of the primary sideband peak resonance peak ^{I (1)} to the intensity of the resonant peak ^{I (0) occurring,} the content of ^{P 5+} The molar ratio O ²⁻ / P ⁵⁺ of the content of O ²⁻ with respect to is 3.5 or more,
In cation% display
P ⁵⁺ exceeding 3% and 30% or less,
Al ³⁺ 5-40%,
Mg ²⁺ 0-10%,
Ca ²⁺ 0-40%,
Sr2 ⁺ 0-30%,
Ba ²⁺ 0-30%,
(However, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 30% or more)
Li ⁺ 0-20%,
Na ⁺ 0-10%,
K ⁺ 0-10%,
Y ³⁺ 0-10%,
La ³⁺ 0-10%,
Gd ³⁺ 0-10%,
Yb ³⁺ 0-10%,
B ³⁺ 0-3%,
Zn ²⁺ 0-20%,
In ³⁺ 0-5%
As an anionic component,
F ^- 50-98%,
O ^2- 2~50%
Fluorophosphate glass which is characterized that you contain,
(2) An optical glass without the addition of ions having absorption in the visible ^region, and the molar ratio ^(O 2- ^{/ P 5+)} of ^{O 2-} content is 3.5 or more with respect to the content of ^{P 5+,}
In cation% display
P ⁵⁺ exceeding 3% and 30% or less,
Al ³⁺ 5-40%,
Mg ²⁺ 0-10%,
Ca ²⁺ 0-40%,
Sr2 ⁺ 0-30%,
Ba ²⁺ 0-30%,
(However, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 30% or more)
Li ⁺ 0-20%,
Na ⁺ 0-10%,
K ⁺ 0-10%,
Y ³⁺ 0-10%,
La ³⁺ 0-10%,
Gd ³⁺ 0-10%,
Yb ³⁺ 0-10%,
B ³⁺ 0-3%,
Zn ²⁺ 0-20%,
In ³⁺ 0-5%
As an anionic component,
F ^- 50-98%,
O ^2- 2~50%
Fluorophosphate glass, characterized by containing
(3) The fluorophosphate glass according to (1) or (2) above, containing 55 to 98 anion% of F ⁻ and ² to 45 anion% of O ²⁻ ,
(4) The fluorophosphate glass according to any one of (1) to (3), wherein the content of F ⁻ is 65 anion% or more.
(5) The fluorophosphate glass according to any one of (1) to (4), wherein the refractive index nd is 1.43 to 1.52.
(6) The fluorophosphate glass according to any one of (1) to (5) above, wherein the number density of metal particles having a particle size of 10 μm or more contained therein is less than 5 particles / cm ³ .
(7) Preform for precision press molding comprising the fluorophosphate glass according to any one of (1) to (6) above,
(8) An optical element blank comprising the fluorophosphate glass according to any one of (1) to (6) above,
(9) An optical element comprising the optical glass according to any one of (1) to (6) above,
(10) A method for producing an optical element in which the preform described in (7) above is heated and precision press-molded using a press mold,
(11) An optical element manufacturing method for grinding and polishing the optical element blank described in (8) above is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in optical homogeneity, and can provide the fluorophosphate glass which does not contain a foreign material, the precision press-molding preform which consists of the said glass, an optical element blank, an optical element, and those manufacturing methods.

It is a graph which shows the change of the refractive index variation | change_quantity ⁽ DELTA ⁾ nd of glass with respect to the change of intensity | strength ratio I ⁽¹⁾ / I ^{(0) in} a fluorophosphate glass, and the change of the number density of the metal particle with a particle size of 10 micrometers or more in glass. Fluorophosphate glass No. 1 of Example 1 of the present invention. 1 is a ³¹ P nuclear magnetic resonance spectrum of 1; Comparative fluorophosphate glass no. 1 is a ³¹ P magnetic resonance spectrum of 1; It is the schematic of the precision press molding apparatus used in Example 3 of this invention.

[Fluorophosphate glass]
First, the fluorophosphate glass of the present invention will be described.
Phosphate is generally used as a raw material for fluorophosphate glass, but in order to increase the amount of fluorine (F ⁻ ) introduced as an anion component as much as possible, as a phosphate, phosphorus (P ⁵⁺ ) 1 A metaphosphate (oxygen atom / phosphorus atom = 3) having a small ratio of oxygen (O ²⁻ ) atoms to atoms (oxygen atom / phosphorus atom) is used.

However, when glass is produced using metaphosphate, phosphoryl fluoride (POF ₃ ) is considered to be generated as a volatile component by reacting fluorine with metaphosphoric acid derived from the raw material in phosphorus in the molten glass. It is done. In contrast, when the atomic ratio of oxygen atoms per phosphorus atom in the molten glass is adjusted to 3.5 or more (oxygen atoms / phosphorus atoms ≧ 3.5), the amount of volatile components generated is greatly reduced. There was found. This is a phosphoric acid present in the molten glass than metaphosphoric acid, phosphorus (P ⁵⁺⁾ oxygen to ¹ atom (O ^2-) atomic ratio (oxygen atoms / phosphorus atoms) is 3, phosphorus (P ⁵⁺ ) It is considered that diphosphoric acid having a ratio of oxygen (O ²⁻ ) atoms to one atom (oxygen atom / phosphorus atom) of 3.5 is more stable.

By controlling the molar ratio O ²⁻ / P ⁵⁺ of the content of O ^{2− to} the content of P ⁵⁺ in the fluorophosphate glass to 3.5 or more, the generation of volatile components itself is suppressed, and the reaction of the molten glass And erosion can be reduced.

  It is considered that the glass, in which reactivity and erosion resistance are suppressed to extremely low levels as a fluorophosphate glass by such a method, is different in structure from the conventional glass.

Glass has an amorphous structure, and the structure is generally considered isotropic, but the presence of products that cause volatility and erosion is believed to cause slight anisotropy in the glass structure. In order to support this idea, a general nuclear magnetic resonance method was used as a method for analyzing the anisotropy of glass, and a ³¹ P nuclear magnetic resonance spectrum was measured. As a result, a clear difference was observed in the spectrum between the glass in which both the volatility and the erodibility were suppressed to a very low level and the conventional glass.

  In the nuclear magnetic resonance method, measurement is performed by rotating a glass sample. Depending on the magnitude of the anisotropy, the intensity ratio of the main peak of the obtained spectrum and the spinning sideband generated by the rotation of the sample changes.

  In order to obtain a fluorophosphate glass suitable for the object of the invention, a glass having nuclear magnetic resonance characteristics peculiar to a fluorophosphate glass with further suppressed volatility and erosion properties may be used.

That is, the fluorophosphate glass of the present invention contains a phosphorus component in terms of P ⁵⁺ and contains more than 3 cation% and 30 cation% or less, and the intensity I ^{(0) of the} resonance peak generated near the ³¹ P reference frequency in the nuclear magnetic resonance spectrum. The ratio I ⁽¹⁾ / I ⁽⁰⁾ of the intensity I ⁽¹⁾ of the primary sideband peak of the resonance peak with respect to is 0.08 or less.

The nuclear magnetic resonance spectrum is measured while rotating the glass sample at a constant speed around an axis orthogonal to the direction of the external magnetic field. In the fluorophosphate glass in which the phosphorus content is in the above range and neither volatile nor erosive property is suppressed, and in the fluorophosphate glass in which only the volatile property is suppressed and the erodible property is not suppressed, As a result, the intensity of the sideband peak increases, and the intensity ratio I ⁽¹⁾ / I ⁽⁰⁾ increases.

FIG. 1 shows how the volatility and the erodibility change as the intensity ratio I ⁽¹⁾ / I ⁽⁰⁾ increases or decreases. The horizontal axis in FIG. 1 is the intensity ratio I ⁽¹⁾ / I ⁽⁰⁾ , the left vertical axis is the refractive index change Δnd, and the right vertical axis is the number of metal particles having a particle size of 10 μm or more contained in the glass. Density. The refractive index change amount Δnd is the refractive index nd of the 200 g sample obtained by melting the raw material for 1 hour (referred to as nd (1h)) and the refractive index nd of the 200 g sample obtained by melting the raw material for 3 hours. nd (3h)), and the greater the Δnd, the higher the volatility. Moreover, the larger the number density of the metal particles, the higher the erodibility. From FIG. 1, when the intensity ratio I ⁽¹⁾ / I ⁽⁰⁾ is 0.08 or less, Δnd decreases rapidly and volatility is suppressed, and the number density of metal particles also decreases rapidly and corrodes. It can be seen that is also suppressed. Therefore, the strength ratio I ⁽¹⁾ / I ^{(0) is set} to 0.08 or less in order to suppress volatility and erosion. In order to further suppress volatility and erosion, the strength ratio I ⁽¹⁾ / I ⁽⁰⁾ is preferably 0.06 or less. The intensity ratio ^I a ^{(1) / I (0)} to 0.08 or less, the molar ratio ^(O 2- ^{/ P 5+)} of the content of ^{O 2-} to the content of ^{P 5+} reasons above 3.5 What is necessary is just to control above.

P ⁵⁺ is an important essential component that acts as a network former in glass. The content of P ⁵⁺ is set to more than 3% in order to obtain the volatility suppression and erosion suppression effects by the nuclear magnetic resonance characteristics while ensuring the stability of the glass. On the other hand, if it exceeds 30%, the molar ratio O ²⁻ / P ⁵⁺ is 3.5 or more, so that it is necessary to suppress the amount of fluorine introduced, and the required low dispersibility cannot be obtained. Therefore, the content of P ⁵⁺ exceeds 3% and falls within the range of 30%.

Preferred as fluorophosphate glass of the present invention ^is a fluorophosphate glass molar ratio ^(O 2- ^{/ P 5+)} of ^{O 2-} content is 3.5 or more with respect to the content of ^{P 5+,} the molar ratio ^{O 2-} The glass composition is controlled so that / P ⁵⁺ is 3.5 or more, thereby realizing the intensity ratio I ⁽¹⁾ / I ⁽⁰⁾ .

^{Increasing the} molar ratio O ²⁻ / P ⁵⁺ in the range of 3.5 or more is preferable from the viewpoint of suppressing volatility and erosion. However, when the content of F ⁻ increases, O ²⁻ which is the same anion component. The content of will be limited. As a result, F ^- for excessively increasing the molar ratio (O ^{2- /} P ⁵⁺⁾ in the glass is large content, there is a risk that not reach the required amount the content of P ^5+. Therefore, in a glass having an F ⁻ content of 65 anion% or more, it is better not to excessively increase the molar ratio if the molar ratio O ²⁻ / P ⁵⁺ is 3.5 or more.

  According to the present invention, not only the volatility but also the corrosiveness is sufficiently suppressed, so that the corrosion of platinum constituting the crucible, the pipe, the stirring rod, etc. used at the time of glass production is prevented, and the foreign material such as platinum is contained in the glass. Mixing can be prevented.

Next, the preferable composition range of the fluorophosphate glass of this invention is demonstrated.
A preferred embodiment of the present invention is as a cationic component,
P ⁵⁺ exceeding 3% and 30% or less,
Al ³⁺ 5-40%,
Mg ²⁺ 0-10%,
Ca ²⁺ 0-40%,
Sr2 ⁺ 0-30%,
Ba ²⁺ 0-30%,
(However, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 10% or more)
Li ⁺ 0-20%,
Na ⁺ 0-10%,
K ⁺ 0-10%,
Y ³⁺ 0-10%,
La ³⁺ 0-10%,
Gd ³⁺ 0-20%,
Yb ³⁺ 0-10%,
B ³⁺ 0-5%,
Zn ²⁺ 0-20%,
In ³⁺ 0-5%
As an anionic component,
F ^- 50-98%,
O ^2- 2~50%
It is characterized by containing.
Hereinafter, unless otherwise specified, the content and total content of each cation component are expressed as cation%, and the content and total content of each anion component are expressed as% anion.

P ⁵⁺ is an important essential component that acts as a network former in glass. The content of P ⁵⁺ is made more than 3% from the viewpoint of obtaining volatility suppression and erosion suppression effects by the nuclear magnetic resonance characteristics while ensuring the stability of the glass. On the other hand, if it exceeds 30%, the molar ratio O ²⁻ / P ⁵⁺ is 3.5 or more, so that it is necessary to suppress the amount of fluorine introduced, and the required low dispersibility cannot be obtained. Therefore, the content of P ⁵⁺ exceeds 3% and falls within the range of 30%. The preferable range of the content of P ⁵⁺ is 5 to 25%.

Al ³⁺ is an important component for enhancing stability in fluorophosphate glass, and if it is less than 5%, the glass tends to be unstable. On the other hand, if it exceeds 40%, the total amount of the other components becomes too small, so that it becomes unstable. Therefore, the content of Al ³⁺ is preferably in the range of 5 to 40%.

Alkaline earth metals such as Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ are components that increase the stability of the glass and increase the refractive index. By making the total amount 10% or more, an effect on stability is achieved. Becomes higher. However, if the amount of a specific alkaline earth metal component is too large, the balance with other components is lost, so it is preferable to introduce it uniformly, and at least two or more of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are introduced. Is preferred. Specifically, Mg ²⁺ is preferably 0 to 10%, Ca ²⁺ is 0 to 40%, Sr ²⁺ is 0 to 30%, and Ba ²⁺ is preferably 0 to 30%.

Alkali metals such as Li ⁺ , Na ⁺ , and K ⁺ are components that can lower the viscosity and glass transition temperature of the glass and facilitate glass production, but excessive introduction reduces stability. Therefore, it is preferable that the amount of Li ⁺ is 0 to 20%, the amount of Na ⁺ is 0 to 10%, and the amount of K ⁺ is 0 to 10%. Among the alkali metals, Li ⁺ has a large effect of increasing the stability, so it is more preferable to introduce 0.5% or more of Li ⁺ , more preferable to introduce 1% or more, and particularly preferable to introduce 5% or more. .

Rare earth elements such as Y ³⁺ , La ³⁺ , Gd ³⁺ , and Yb ³⁺ are components that increase the refractive index while maintaining the low dispersibility of the glass. However, excessive introduction increases the melting temperature and decreases the stability of the glass. End up. Therefore, the amount of each component is preferably 0 to 10%.

B ³⁺ is a component that improves the durability of the glass, but also has a tendency to volatilize as a fluoride during melting, and is also a component that decreases productivity. Therefore, the introduction amount is preferably 0 to 5%, more preferably 0 to 3%, and even more preferably not introduced.

Zn ²⁺ and In ³⁺ have the property that they can be easily introduced into glass like alkaline earth metals and can be expected to improve stability by introducing Zn ²⁺ and In ³⁺ into multiple components, but they are excessive. The introduction of is not preferred. For this reason, the amounts of Zn ²⁺ and In ³⁺ introduced are preferably 0 to 20% and 0 to 5%, more preferably 0 to 15% and 0 to 3%, respectively, and Zn ²⁺ is 0%. It is more preferable to set it to -10%, and it is particularly preferable not to introduce In ³⁺ .

  In addition, the fluorophosphate glass I has a property of high light transmittance in a wide range from a short wavelength to a long wavelength in the visible region, in addition to low dispersibility and abnormal partial dispersibility. Although it is suitable as a material for obtaining various optical elements such as lenses and prisms using such properties, in such applications, ions having absorption in the visible range, for example, Fe, Cu, Ni, Co It is desirable not to add ions of metal elements such as Cr, Mn, V, Nd, Ho, and Er.

Meanwhile, it is possible to impart the near infrared absorption properties by the addition of ^{Cu 2+,} when making a near-infrared absorbing glass, it is desirable to add ^{Cu 2+} outside split 0.5 to 13%. Cu ²⁺ -containing glass is suitable as a color correction filter material for semiconductor image sensors such as CCD and CMOS. The amount of Cu ²⁺ added may be appropriately determined within the above range in consideration of the thickness of the filter. Also in the case of Cu ²⁺ -containing glass, it is desirable not to add ions having absorption in the visible region other than Cu ²⁺ except for the case of adjusting the absorption characteristics.

Next, an anion component and an anion additive are demonstrated. The main anion components of the fluorophosphate glass of the present invention are F ⁻ and O ²⁻ . From the standpoint of realizing the required low dispersion characteristics and excellent glass stability, it is preferable to introduce 50 to 98% F ⁻ and ² to 50% O ²⁻ , 55 to 95% F ⁻ and O ^2−. It is more preferable to introduce 5 to 45%.

Further, when a small amount of Cl ⁻ , Br ⁻ , or I ⁻ is introduced, the fluorophosphate glass is less likely to get wet with platinum products such as platinum containers and platinum nozzles used during the production or outflow of glass. Can be easily manufactured. Excessive introduction of Cl ⁻ , Br ⁻ , and I ⁻ leads to refractive index fluctuations due to component volatilization and generation of platinum foreign matter, and therefore, the introduction amount is preferably 0 to 5% in total. Furthermore, from the above viewpoint, the total introduced amount of Cl ⁻ , Br ⁻ and I ⁻ is more preferably 4%, and further preferably 3%. Furthermore, the lower limit of the total introduction amount is more preferably 0.01%, further preferably 0.05%, and still more preferably 0.1%. Cl ^-, Br ^- and I ^- total content of the upper limit with any set preferably each range defined by the alignment Cl lower limit of ^-, Br ^- it can be said that total content of the preferred range ^- and I. Examples of such a range include a range in which the total introduction amount of Cl ⁻ , Br ⁻ and I ⁻ is 0 to 3% or 0.1 to 3%.

In order to achieve the object of the invention, the total amount of F ⁻ , O ²⁻ , Cl ⁻ , Br ⁻ and I ⁻ is preferably 98 anion% or more, more preferably 99 anion% or more. , 100 anion% is more desirable.

  The preferable range of the Abbe number νd in the fluorophosphate glass of the present invention is 75 to 97, and the more preferable range is 80 to 93.

  Moreover, the preferable range of the refractive index nd in the fluorophosphate glass of the present invention is 1.43 to 1.52, and the more preferable range is 1.45 to 1.51.

  In order to melt optically homogeneous glass, heat-resistant materials such as platinum and platinum alloys that are difficult to melt into the glass and the pipe that guides the glass in the process of homogenizing and flowing out the molten glass Consists of metal or alloy.

  Although these metal-based materials have the above properties, they tend to precipitate as metal particles in the glass as the temperature of the molten glass decreases as described above. In particular, fluorophosphate glass hardly dissolves metal ions, and such a problem is remarkable.

  According to the fluorophosphate glass of the present invention, it is difficult to corrode heat-resistant metal-based materials, so the amount of these metals mixed in the glass can be greatly suppressed, and a fluorophosphate glass with very few foreign substances can be obtained. it can.

In the fluorophosphate glass thus obtained, the number density of foreign matters having a particle diameter of 10 μm or more, for example, platinum particles or particles containing platinum, is less than 5 / cm ³ . The aforementioned particles become foreign substances that scatter light rays, for example, visible light, and deteriorate the performance of the optical element. According to the present invention, since the foreign matter that becomes the light scattering source is significantly reduced or does not exist, a high-quality optical glass can be provided. The preferred number density of foreign substances having a particle size of 10 μm or more contained in the glass is less than 5 / cm ³ , more preferably less than 2 / cm ³ .
The fluorophosphate glass of the present invention is an optical glass having anomalous dispersion, and is also suitable as a material for higher-order color correction optical elements.

Next, the manufacturing method of the fluorophosphate glass of this invention is demonstrated.
After preparing and melting a glass raw material, in order to obtain an optical glass by clarification and homogenization, the molar ratio of the total content of O ^{2− to} the total content of P ^{5+ in} the glass raw material is O ²⁻ / P ⁵⁺ is 3 .5 or more is used. Preferably, the molar ratio O ²⁻ / P ⁵⁺ is 3.51 or more, more preferably 3.55 or more, and still more preferably 3.6 or more. According to the present invention, since volatility of the molten glass is suppressed, the O ^2- content to the content of P ⁵⁺ in the glass molar ratio (O ^{2- /} P ⁵⁺⁾ and glass in the raw material of P ⁵⁺ of The molar ratio O ²⁻ / P ⁵⁺ of the total content of O ^{2− to} the total content is equal. However, the total content of O ^{2− in} the glass raw material is the amount of oxygen introduced into the glass, and it goes out of the melt as CO _X gas, NO _X gas, oxygen gas, water vapor, etc. during glass melting. Does not include the amount of oxygen to go. For example, when carbonates, nitrates, hydroxides, etc. are used as glass raw materials, carbonates, nitrates, hydroxides are decomposed by heating the glass raw materials to generate the above gases, and these gases are outside the glass melt. Therefore, oxygen contained in the gas does not contribute to the vitrification reaction. In addition, when bound water is present in the glass raw material, the bound water is desorbed by heating the glass raw material and flows out of the glass melt as water vapor, so oxygen in the water vapor does not contribute to the vitrification reaction. Therefore, the oxygen that goes out of the glass melt as the gas is excluded from the oxygen content. When carbonates, nitrates, and hydroxides are used, an oxide composed of a cation and oxygen as glass components contained in these compounds is considered, and the amount of oxygen contained in the compound is introduced into the glass as the oxide. Think of it as the amount of oxygen.
Here, the glass raw material includes a raw material prepared by mixing and mixing a plurality of kinds of compounds, so-called batch raw material, cullet and the like.

The total amount of oxygen and phosphorus contained in the glass raw material is converted into P ⁵⁺ amount and O ²⁻ amount so that the optical characteristics and the like become desired values, and the molar ratio of the amount of O ²⁻ with respect to the amount of P ⁵⁺ The glass raw material is prepared so that O ²⁻ / P ⁵⁺ is 3.5 or more, and the prepared glass raw material is melted. Thus, it is possible to control the molar ratio ^(O 2- ^{/ P 5+)} of ^{O 2-} content relative ^{P 5+} content in glass 3.5 or more.

From above to perform such control more reliably, oxygen contained in the glass raw materials, the total amount of phosphorus in terms of ^{P 5+} content and ^{O 2- quantities,} the molar ratio of ^{O 2-} in an amount relative to the amount of ^{P 5+ O 2-} / It is preferable to prepare the raw material so that P ⁵⁺ is 3.5 or more, more preferably to prepare the raw material so that it is 3.51 or more, and it is more preferable to prepare the raw material so that it is 3.55 or more, It is more preferable to prepare the raw material so as to be 3.6 or more.

When the raw material is prepared using only the metaphosphoric acid raw material and the fluoride raw material, the total amount of oxygen and phosphorus contained in the glass raw material is converted into P ⁵⁺ amount and O ²⁻ amount, and the mole of O ²⁻ with respect to the amount of P ^5+. The ratio O ²⁻ / P ⁵⁺ is 3, which does not reach 3.5 due to the lack of oxygen. Therefore, it is desirable to use an oxide or nitrate together so that oxygen can be introduced into the glass independently of phosphorus. Further, a part or all of the metaphosphate generally used as a phosphoric acid raw material may be replaced with a pyrophosphate. In the case of using pyrophosphate, it is desirable to use an oxide or nitrate together. According to the present invention, since the volatility of the molten glass is suppressed to a very low level, the optical glass having the tolerance of the refractive index nd within ± 0.00050, preferably within ± 0.00020 A method of manufacturing can be provided. Therefore, the tolerance of the refractive index nd of the optical glass constituting each article of precision press-molding preform, optical element blank, and optical element described later can be within the above range.

[Preform for precision press molding]
Next, the precision press molding preform of the present invention will be described.
The precision press-molding preform of the present invention is characterized by comprising the above fluorophosphate glass.

  Here, the precision press-molding preform means that a glass having a weight equal to the weight of the precision press-molded product is previously molded into a shape suitable for precision press molding.

  The precision press molding preform of the present invention is particularly suitable for precision press molding, and when used as a precision press molding preform, a release film such as a carbon film may be formed on the entire surface of the preform. preferable.

The following are two typical methods for manufacturing a precision press-molding preform.
The first method is a method in which molten glass is caused to flow out of a pipe, a molten glass lump having a desired weight is separated, and the glass lump is formed into a preform in the process of cooling the glass.

  In this method, first, molten glass is caused to flow out of a pipe. For example, molten glass is continuously discharged at a constant flow rate from a platinum alloy or platinum pipe heated to a predetermined temperature by an electric heating method, a high-frequency induction heating method, or a heating method that combines these two heating methods. Let

  Subsequently, the molten glass lump having a weight obtained by adding the weight of one preform or the weight of one preform added to the weight of the removal described later 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 as not to leave a cut mark. For example, the molten glass is dropped from the outlet of the pipe, or the molten glass flow tip flowing out is supported by the support. 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 molded into a preform having 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.

  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 of the mold and gradually cooled.

  Since many precision press-molded products (for example, optical elements) manufactured from a preform have a rotationally symmetric axis like a lens, the shape of the preform is preferably a shape having a rotationally symmetric axis. As a specific example, one having a sphere or one axis of rotational symmetry can be shown. A shape having one rotationally symmetric axis has a smooth outline with no corners or depressions in the cross section including the rotationally symmetric axis, for example, an ellipse whose short axis coincides with the rotationally symmetric axis in the cross section is defined as the outline. Examples of the shape include a flattened sphere (a shape in which one axis passing through the center of the sphere is defined and the dimension is reduced in the axial direction). A preform having such a shape is formed in a floated state (a preform having a rotationally symmetric axis and having a smooth outline having no corners or depressions in a cross section including the rotationally symmetric axis), It can be produced by rotating and molding molten glass droplets (forming a spherical preform).

  Furthermore, a preform having a shape having one rotational symmetry axis and having a depression on one or both of two mutually facing surfaces centering on two intersections of the rotational symmetry axis and the surface is also preferable. In this case, the center of the depression, that is, the center of the bottom of the depression is the intersection of the rotational symmetry axis and the depression. A preform having a depression on only one of the mutually facing surfaces is preferably used as a preform for producing a convex meniscus lens or a concave meniscus lens by precision press molding, and a preform having a depression on both of the surfaces facing each other. It is preferable as a preform used when a biconcave lens is produced by precision press molding. At the time of precision press molding, an upper mold and a lower mold are provided, and a preform is introduced into a press mold in which the molding surface of the upper mold and / or the lower mold is a convex surface. It is possible to hold the top of the molding surface of the lower mold and / or prevent the preform from being displaced when the preform is placed at the center position in the press mold and the press mold is moved. it can. Such a preform can be produced by press-molding a molten glass lump in a preform-forming lower mold. In this case, the molten glass lump is supplied to the preform molding lower mold, and the glass lump is kept floating until the glass has a viscosity suitable for press molding. When the glass has a viscosity suitable for press molding, the glass lump on the preform molding lower mold is pressed from above with the preform molding upper mold, and the preform molding lower mold and upper mold molding surface The shape is transferred to a glass block. The lower mold forming surface for preform molding is provided with a large number of gas outlets for ejecting gas for applying a wind pressure to the glass lump to float. During press molding, the gas ejection pressure is adjusted so that the glass does not enter the gas ejection port. By doing so, it is possible to prevent gas from entering the glass and mixing bubbles into the preform. After press molding, the upper mold for preform molding is separated from the glass, and the pressurization of the glass is finished.

  After that, the glass is cooled while blowing the gas from the gas outlet and applying air pressure to the glass to make it float, and the glass is taken out from the lower mold for forming the preform to obtain a preform. By doing so, even if wrinkles are generated on the glass surface by press molding, the glass surface is heated from the inside of the high-temperature glass by floating after press molding, and the wrinkles disappear and a smooth surface preform can be obtained. . In addition, when it is desired to form a depression on one of the opposed surfaces, one of the molding surfaces of the preform molding upper mold and the lower mold may be a convex surface and press molded. In that case, in order to stably float the glass and press molding, it is preferable that the lower mold forming surface for preform molding is a concave surface and the upper mold forming surface for preform molding is a convex surface. Moreover, when forming a dent in both the said opposing surfaces, it is preferable that both the preform lower mold surface and the preform upper mold surface are convex. As described above, when a high-temperature glass lump made of conventional fluorophosphate glass is levitated and held in a preform mold or press-molded, volatiles adhere to the mold and the gas outlet is clogged. There have been problems such as adherents adhering to the glass and contaminating the glass surface, and the accuracy of press molding is reduced, but according to the present invention, the volatility of the glass is suppressed. Can also be eliminated.

  The second method is a method in which molten glass is cast into a mold to produce a glass molded body, and the glass molded body is processed to produce a preform.

  Any known mold may be used as the mold according to the shape of the mold. For example, a mold having a flat bottom surface and three side walls surrounding the bottom surface from three directions and having one side opened is arranged below the pipe through which the molten glass flows out so that the bottom surface is horizontal. And the molten glass which flows out continuously from a pipe is poured on the bottom face of a casting_mold | template, and it shape | molds in plate shape, filling the glass with the part enclosed by the side wall. The molded glass is pulled out from the opening in the horizontal direction at a constant speed to obtain a glass plate having a constant width and a constant thickness. The drawn glass plate is annealed by passing through the annealing furnace at a slow speed. The annealed glass plate is cut perpendicular to the pulling direction to form a glass plate having a desired length.

Instead of the mold, a mold having a through-hole may be disposed below the outflow pipe so that the through-hole faces in the vertical direction, and molten glass may be continuously poured into the through-hole. The poured glass is rapidly cooled and formed into a rod shape, and is drawn downward at a constant speed from the lower end opening of the through hole. The glass rod pulled out from the mold passes through the atmosphere heated near the glass transition temperature, and after the operation of bringing the surface of the glass rod closer to the inside temperature, the glass rod is cut in the horizontal direction and has a desired length. It becomes.
The plate-like or rod-like glass molded body thus obtained is divided into glass pieces by cutting or cleaving, and these glass pieces are ground and polished to obtain a preform.

[Optical element blank]
Next, the optical element blank of the present invention will be described.
The optical element blank of the present invention is made of the above fluorophosphate glass.

  The optical element blank is a glass molded product that is finished into an optical element by grinding and polishing as described above, and has a shape obtained by adding a processing margin to be removed by grinding and polishing to the shape of the target optical element, that is, the optical element. It has a shape that approximates the shape.

There are two typical methods for manufacturing the optical element blank.
The first method is a method in which a glass gob for press molding made of the above fluorophosphate glass is heated and press molded.

  In this method, a powder release agent such as boron nitride is uniformly applied to the surface of the glass material prior to heating, placed on a heat-resistant dish and placed in a heat softening furnace, heated until the glass softens, and then pressed. It is introduced into a mold and press-molded. Next, the press-molded product is taken out from the mold, annealed to remove the distortion, and adjusted to have a desired optical property such as a refractive index. In this way, an optical element blank can be produced.

  The second method is a method in which a glass raw material is melted, the obtained molten glass is flowed out, the molten glass lump is separated from the molten glass stream, and the molten glass lump is press-molded.

  In this method, the homogenized molten glass flows out onto the lower mold forming surface uniformly coated with a powder release agent such as boron nitride, and the molten glass flow whose lower end is supported by the lower mold is sheared along the way. Cut with a so-called cutting blade. In this way, a molten glass lump having a desired mass is obtained on the lower mold surface. Next, the lower mold on which the molten glass lump is placed is transferred to a position just below the upper mold waiting in another position, and the molten glass lump is pressed with the upper mold and the lower mold to form an optical element blank shape. Next, the press-molded product is taken out from the mold, annealed to remove the distortion, and adjusted to have a desired optical property such as a refractive index. In this way, an optical element blank can be produced.

Both of the above two methods can be performed in the atmosphere. Known conditions and things can be used for the molding conditions, the material of the press mold, the heating and softening furnace, and the dish on which the preform is placed when heating and softening.
ADVANTAGE OF THE INVENTION According to this invention, the optical element blank which can produce the optical element without defects, such as striae, can be provided.

[Optical element and manufacturing method thereof]
Next, the optical element of the present invention will be described.
An optical element of the present invention is characterized by comprising the above fluorophosphate glass.
According to the optical element of the present invention, an optical element utilizing low dispersion characteristics can be provided.

  The type and shape of the optical element are not particularly limited, and examples include an aspherical lens, a spherical lens, a microlens, a lens array, a prism, a diffraction grating, a prism with a lens, and a lens with a diffraction grating. Specific examples of the aspherical lens and the spherical lens include a convex meniscus lens, a concave meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens.

From the viewpoint of application, optical elements constituting the imaging system, for example, a digital camera lens, a camera lens for a camera-equipped mobile phone, an optical pickup lens, a collimator lens, an optical communication lens, and the like can be given.
An optical thin film such as an antireflection film may be formed on the surface of the optical element as necessary.

Next, the manufacturing method of the optical element of this invention is demonstrated.
The method for producing an optical element of the present invention comprises two aspects.

  The first aspect of the optical element manufacturing method of the present invention (referred to as optical element manufacturing method I) is characterized in that the preform is heated and precision press-molded using a press mold. Precision press molding is also called mold optics molding, and is a well-known method in the art. In an optical element, a surface that transmits, refracts, diffracts, or reflects light is an optical functional surface (a lens surface such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens is taken as an example of a lens). It corresponds to the optical function surface), but according to precision press molding, the optical function surface can be formed by press molding by precisely transferring the molding surface of the press mold to glass, and the optical function surface is finished. Therefore, it is not necessary to add machining such as grinding and polishing.

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

  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. A carbon film is particularly preferable as the carbon-containing film from the viewpoint of durability and cost.

  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 embodiments of precision press molding used in the optical element manufacturing method I, two embodiments of precision press molding I and II are shown below.

(Precision press molding I)
In precision press molding I, a preform is introduced into a press mold, and the press mold and the preform are heated together to perform precision press molding.
In this precision press molding I, precision press molding can be performed by heating the temperature of the press mold and the preform to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ⁶ to 10 ¹² dPa · s. preferable.

In addition, after the glass is cooled to a temperature at which a viscosity of preferably 10 ¹² dPa · s or more, more preferably 10 ¹⁴ dPa · s or more, and even more preferably 10 ¹⁶ dPa · s or more, the precision press-molded product is pressed. It is desirable to remove from the mold.
Under the above conditions, the shape of the molding surface of the press mold can be accurately transferred with glass, and the precision press molded product can be taken out without being deformed.

(Precision press molding II)
In precision press molding II, a heated preform is introduced into a preheated press mold and precision press molding is performed.
According to this precision press molding II, since the preform is heated in advance before being introduced into the press mold, the optical element having good surface accuracy without surface defects can be obtained while shortening the cycle time for manufacturing the optical element. Can be manufactured.

  The preheating temperature of the press mold is preferably set lower than the preheating temperature of the preform. Thus, by lowering the preheating temperature of the press mold, it is possible to reduce the wear of the press mold.

In the precision press molding II, it is preferable that the glass constituting the preform is preheated to a temperature showing a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁹ dPa · s.
The preform is preferably preheated while floating, and more preferably preheated to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ^5.5 to 10 ⁹ dPa · s ^. It is more preferable to preheat to a temperature showing a viscosity of ⁵ dPa · s or more and less than 10 ⁹ dPa · s.
Moreover, it is preferable to start cooling the glass simultaneously with the start of pressing or in the middle of pressing.

The temperature of the press mold is adjusted to a temperature lower than the preheating temperature of the preform, and the temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s may be used as a guide.
In this method, it is preferable that after the press molding, the glass is cooled to a viscosity of 10 ¹² dPa · s or more and then released.

  The precision press-molded optical element is taken out from the press mold and gradually cooled as necessary. When the molded product is an optical element such as a lens, an optical thin film may be coated on the surface as necessary.

  The second aspect of the optical element manufacturing method of the present invention (referred to as optical element manufacturing method II) is an optical element manufacturing method for grinding and polishing the optical element blank.

  A known method may be applied to the grinding and polishing. The optical element manufacturing method II is suitable for manufacturing a large-diameter lens such as an optical element that can be easily processed by grinding and polishing such as a spherical lens and a prism, and a front lens of a telephoto lens.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1 and Comparative Example 1 (Production example of fluorophosphate glass)
Fluorophosphate glass No. 1 having each composition shown in Table 1-1 to Table 1-5. 1-17, comparative fluorophosphate glass no. In order to produce 1 and 2, raw materials such as phosphates such as diphosphate and fluoride corresponding to each glass component were weighed and mixed thoroughly. The ratio of the total content of O ^{2− to} the total content of P ⁵⁺ in each mixed raw material (O ²⁻ / P ⁵⁺ ), the total content of alkaline earth metal components, and the total content of rare earth components are determined for each glass. Table 1-1 to Table 1-5 together with the composition and characteristics of The mixed raw material was put into a platinum crucible, and the raw material was heated and melted for 1 to 3 hours with stirring in an electric furnace at 900 ° C., clarified and homogenized. 1-17 were obtained.

Fluorophosphate glass no. In preparation of the fluorophosphate glasses 1 to 17, the ratio of the total content of ^{O 2-} to the total content of ^{P 5+} as shown in Table 1-1 to Table 1-5 ^(O 2- ^{/ P 5+)} The optical glass having desired characteristics is obtained by controlling the volatility and erosion property to 3.5 or more and balancing the content of other components. Moreover, in the said manufacture example, phosphates, such as a diphosphate, and unvitrified raw materials, such as a fluoride, were used, but a cullet may be used and an unvitrified raw material and a cullet may be used together. . In addition, the amount of oxygen contained in the glass raw material, in particular, the unvitrified raw material is the amount of oxygen introduced into the glass. When carbonates, nitrates, and hydroxides are used, an oxide composed of a cation and oxygen as glass components contained in these compounds is considered, and the amount of oxygen contained in the compound is introduced into the glass as the oxide. Think of it as the amount of oxygen.

Fluorophosphate glass no. 1-17 and comparative fluorophosphate glass no. For each glass of 1-2, nuclear magnetic resonance occurring reference frequency near the ^{31 P} in the spectral intensity of the resonant peak I ⁽⁰⁾ and the intensity of the primary sideband peak I ^(1), the refractive index nd, Abbe number νd The number density of metal particles having a particle size of 10 μm or more contained in the glass was measured. Moreover, glass transition temperature Tg was measured about some glass among said 19 types of glasses. These measurement results are shown in Table 1-1 to Table 1-5.

The intensity I ⁽⁰⁾ , intensity I ⁽¹⁾ , refractive index nd, Abbe number νd, metal particle number density and glass transition temperature were measured by the following methods.
(1) Intensity I ⁽⁰⁾ and Intensity I ⁽¹⁾
Using Varian VXR-300S, the spectrum was measured under the conditions of an observation frequency of 121.4 MHz, a reference sample of 85% H ₃ PO ₄ , a magnetic field strength of H0 = 7.0T, and a sample rotation speed of 9.0 kHz. The peak intensity I ⁽¹⁾ of the spinning sideband appearing in the vicinity of I ⁽⁰⁾ and 70 ppm is calculated excluding the baseline, and the intensity ratio (I ⁽¹⁾ / I ⁽⁰⁾ ) is calculated.

Note that FIG. 1 ³¹ P nuclear magnetic resonance spectrum, FIG. 1 is a ³¹ P nuclear magnetic resonance spectrum of 1;
2 and 3, the horizontal axis represents the chemical shift (ppm unit), and the vertical axis represents the signal intensity (arbitrary unit). The highest peak in the center is the ³¹ P resonance peak (main peak), and the peak indicated by * is the spinning sideband. The spinning sideband near the main peak is the primary peak. Although there are two primary spinning sidebands, since the heights of the peaks are equal, either peak may be used when obtaining the intensity I ⁽¹⁾ .

(2) Refractive index nd and Abbe number νd
It measured about the optical glass obtained by making slow cooling temperature-fall rate -30 degreeC / hour.
(3) Number density of metal particles Magnified observation was performed 100 times using an optical microscope, the number of metal particles was counted, and the number density of metal particles was calculated from the volume in the observation area.
(4) Glass transition temperature Tg
The temperature was increased by a thermomechanical analyzer (Thermo Plus TMA 8310) manufactured by Rigaku Denki Co., Ltd. at a heating rate of 4 ° C./min.

  In addition, for each fluorophosphate glass, the refractive index nd of a 200 g glass sample obtained by melting the raw material for 1 hour is nd (1h), Abbe number νd is νd (1h), and the raw material is melted for 3 hours. The refractive index nd of the obtained 200 g glass sample is nd (3h), and the Abbe number νd is νd (3h). While measuring nd (1h) and nd (3h), νd (1h) and νd (3h) and the liquidus temperature LT were measured for some glasses. The results are shown in Table 1-1 to Table 1-5.

  Fluorophosphate glass no. Each of the glasses 1 to 17 had very little volatilization, and the number of metal particles having a particle diameter of 10 μm or more contained in the glass was extremely small. On the other hand, comparative fluorophosphate glass no. For 1 and 2, striae was recognized due to volatilization, and the number of metal particles having a particle diameter of 10 μm or more was large. Note that the metal particles contained in the glass are all platinum particles.

As shown in Table 1-1 to Table 1-5, fluorophosphate glass No. 1 was used. In Nos. 1 to 17, the absolute value of nd (3h) -nd (1h) was 0.00200 or less, and the refractive index change due to the difference in melting time of the raw materials was small. In 1-2, nd (3h) -nd (1h) was as large as 0.00400 or more.

  Further, the Abbe number was also measured using fluorophosphate glass No. 1. Nos. 1 to 5 had an absolute value of νd (3h) −νd (1h) within 0.4. In 1-2, the Abbe number change by the difference of 0.5 or more and the melting time of the raw material was also large.

  In the fluorophosphate glass of the present invention, since the difference in Abbe number due to the difference in melting time of the raw material is small, either νd (3h) or νd (1h) may be used as the Abbe number, but the Abbe number needs to be determined strictly. If there is, νd (1h) is the Abbe number of the fluorophosphate glass of the present invention.

In addition, each said fluorophosphate glass No.1. It is good also as a near-infrared absorptive glass by adding 0.5-13 cation% Cu < ²⁺ > to 1-17 on an external basis.
Fluorophosphate glass no. No striae was observed in any of the near-infrared-absorbing glasses in which 0.5 to 13 cation% Cu ²⁺ was added to these fluorophosphate glasses on an external basis, and they were extremely homogeneous optically.

Example 2 (Preparation Example of Preform for Precision Press Molding)
Fluorophosphate glass No. shown in Table 1-1 to Table 1-5. A molten glass composed of 1 to 17 is allowed to flow out at a constant flow rate from a platinum alloy pipe whose temperature is adjusted to a temperature range where stable outflow is possible without devitrification of the glass, and a glass lump is dropped. After supporting the molten glass flow front using the method or the support, the molten glass lump was separated by dropping the support and separating the glass lump. Each of the obtained molten glass ingots has a weight obtained by adding the weight of one of the objective preforms to the weight of the removal portion described later.

  Next, each of the obtained molten glass lumps was received by a receiving mold having a gas outlet at the bottom, and a gas was ejected from the gas outlet and molded while the glass lumps floated to prepare a precision press-molding preform. 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 had a smooth surface.

  Next, using a preform molding lower mold with a concave molding surface and a preform molding upper mold with a convex molding surface, the above support was separated on the molding surface of the preform molding lower mold. Supply molten glass lump, supply high-pressure gas to the back side of the lower mold molding surface made of porous material, jet the gas from the molding surface to float the molten glass lump, adjust the viscosity, then preform molding The glass lump on the lower mold was press-molded with the upper mold, and a preform having a depression on the upper surface was molded. Next, the upper mold was released from the upper surface, the glass was floated again, cooled, and then taken out from the lower mold, and a preform having a convex surface on one side and a depression on the other surface was produced. This preform was used for precision press molding of a convex meniscus lens and a concave meniscus lens described later. The upper and lower mold surfaces of the preform mold may be convex. In this case, a preform having a depression on both of the two opposing surfaces can be molded. This preform is suitable for precision press molding of a biconcave lens. In any of the moldings, there were no problems such as volatiles from the glass adhering to the preform molding die or clogging the gas ejection port.

  As another method, the entire surface of the molded spherical preform was polished by a known method, and the entire surface layer was removed to obtain an optically homogeneous preform.

Fluorophosphate glass Nos. Shown in Table 1-1 to Table 1-5. The molten glass consisting of each of 1 to 17 is caused to flow out at a constant flow rate from a platinum alloy pipe whose temperature is adjusted to a temperature range in which stable outflow is possible without devitrification of the glass, and continuously to the mold. While pouring, the glass plate molded from the opening on the side of the mold is pulled out at a constant speed in the horizontal direction, passed through an annealing furnace, annealed to remove strain, then cut to the desired length, and one after another Got. When the refractive indexes of the plurality of glass plates thus obtained were measured, the tolerance of the refractive index nd was within ± 0.00020, and the refractive index fluctuation was suppressed to an extremely small level for each fluorophosphate glass. It was confirmed. In addition, the glass which is a measuring object of a refractive index is gradually cooled at a cooling speed of 30 ° C./hour as described above.
Next, the glass plate was cut into a square shape to produce a plurality of glass pieces, and these glass pieces were ground and polished to obtain a preform having a smooth surface and an optically uniform surface.

Example 3 (Example of optical element production)
Each preform obtained as described above was precision press-molded using a press apparatus shown in FIG. 4 to obtain an aspheric lens.

That is, 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 heater 12 is energized with the inside of the quartz tube 11 as a nitrogen atmosphere. Then, the inside of the quartz tube 11 was heated. 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 the glass molded product was taken out of the mold and an aspherical lens was obtained. The obtained aspherical lens had extremely high surface accuracy.

In FIG. 4, reference numeral 9 is a support rod, reference numeral 10 is a lower mold / body holder, and reference numeral 14 is a thermocouple.
An aspherical lens obtained by precision press molding was provided with an antireflection film as required.

Next, the same preform as the above preforms was precision press-molded by a method different from the above method. In this method, first, the preform was preheated to a temperature at which the viscosity of the glass constituting the preform was 10 ⁸ dPa · s while the preform floated. On the other hand, a press mold having an upper mold, a lower mold, and a body mold is heated to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s, and the preheated preform is pressed. It was introduced into the mold cavity and precision press-molded at 10 MPa. Cooling of the glass and the press mold was started at the start of pressing, and the glass was cooled until the viscosity of the molded glass reached 10 ¹² dPa · s or more, and then the molded product was released to obtain an aspheric lens. The obtained aspherical lens had extremely high surface accuracy.
An aspherical lens obtained by precision press molding was provided with an antireflection film as required.
In this way, a glass optical element with high internal quality could be obtained with high productivity and high accuracy.

Example 4 (Example of manufacturing an optical element blank)
Fluorophosphate glass Nos. Shown in Table 1-1 to Table 1-5. The molten glass consisting of each of 1 to 17 is allowed to flow out at a constant flow rate from a platinum alloy pipe whose temperature is adjusted to a temperature range where stable outflow is possible without devitrification of the glass, and the molten glass is press-molded. It was supplied on the molding surface of the lower mold constituting the mold. A powder mold release agent such as boron nitride powder is uniformly applied on the lower mold surface before supplying the molten glass.

  Next, the molten glass flowing out is cut using a cutting blade called a shear to obtain a desired amount of molten glass lump on the lower mold surface.

  Next, the upper mold constituting the press mold is placed in a position where the molten glass lump is placed at the upper standby position, and the upper and lower molds are used to perform press molding while the glass lump is in a softened state. The press molded product thus obtained was released and taken out from the press mold to obtain an optical element blank. Next, the obtained blank was annealed to remove the strain, and the optical characteristics such as the refractive index were adjusted to be precisely equal to the desired value to obtain an optical element blank having a desired shape. In this way, lens blanks that approximate the shapes of various spherical lenses such as convex meniscus lenses, concave meniscus lenses, plano-convex lenses, plano-concave lenses, biconvex lenses, and biconcave lenses were produced.

  Next, each fluorophosphate glass No. shown in Table 1-1 to Table 1-5. The molten glass consisting of each of 1 to 17 is caused to flow out at a constant flow rate from a platinum alloy pipe whose temperature is adjusted to a temperature range in which stable outflow is possible without devitrification of the glass, and continuously to the mold. While pouring, the glass plate molded from the opening on the side of the mold is pulled out at a constant speed in the horizontal direction, passed through an annealing furnace, annealed to remove strain, then cut to the desired length, and one after another Got.

  Next, the glass plate is cut into a square shape to produce a plurality of glass pieces, and the glass pieces are barrel-polished to remove the edges of the glass pieces, and the surface is adjusted by adjusting the weight to a desired weight. A roughened preform was obtained.

  Then, powdered boron nitride was uniformly applied to the entire surface of the preform, placed on a heat-resistant dish, placed in a heating furnace, and heated and softened. The softened preform was introduced into a press mold and press molded to obtain an optical element blank.

  The optical element blank thus obtained was annealed to remove distortion, and the optical characteristics were adjusted so that the optical characteristics such as the refractive index were precisely equal to the desired values. In this way, lens blanks that approximate the shapes of various spherical lenses such as convex meniscus lenses, concave meniscus lenses, plano-convex lenses, plano-concave lenses, biconvex lenses, and biconcave lenses were produced.

Example 5 (Example of optical element production)
The optical element blank obtained in Example 4 was ground and polished to produce various spherical lenses such as a convex meniscus lens, a concave meniscus lens, a plano-convex lens, a plano-concave lens, a biconvex lens, and a biconcave lens.
In addition, the annealed glass plate produced in Example 4 was cut, ground, and polished to produce various spherical lenses and prisms such as a convex meniscus lens, a concave meniscus lens, a plano-convex lens, a plano-concave lens, a biconvex lens, and a biconcave lens. .
In this way, a glass optical element with high internal quality could be obtained with high productivity and high accuracy.

Example 6 (Example of optical element production)
Fluorophosphate glass No. 1 obtained in Example 1. A near-infrared absorbing glass to which 0.5 to 13 cation% Cu ²⁺ was added on 1 to 17 was sliced to form a flat plate, and the main surface of the flat plate was optically polished to produce a near-infrared absorbing filter.

  According to the present invention, a fluorophosphate glass with suppressed volatility and erodibility, a precision press-molding preform made of the glass, and an optical element blank and an optical glass that are base materials for optical elements such as various lenses An element can be manufactured.

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

Claims (11)

Resonance peak generated in the vicinity of the ³¹ P reference frequency in a nuclear magnetic resonance spectrum , which is an optical glass that does not add ions having absorption in the visible region, contains a phosphorous component in terms of P ^5+, and contains more than 3 cations% to 30 cations% the ratio ^{I (1) / I (0} ) is 0.08 der following the intensity ^{I (0)} the intensity of the primary side band peak of the resonance peaks for ^{I (1) Ri, O 2} to the content of ^{P 5+ -} and the content of the molar ratio ^(O 2- ^{/ P 5+)} is 3.5 or more,
In cation% display
P ⁵⁺ exceeding 3% and 30% or less,
Al ³⁺ 5-40%,
Mg ²⁺ 0-10%,
Ca ²⁺ 0-40%,
Sr2 ⁺ 0-30%,
Ba ²⁺ 0-30%,
(However, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 30% or more)
Li ⁺ 0-20%,
Na ⁺ 0-10%,
K ⁺ 0-10%,
Y ³⁺ 0-10%,
La ³⁺ 0-10%,
Gd ³⁺ 0-10%,
Yb ³⁺ 0-10%,
B ³⁺ 0-3%,
Zn ²⁺ 0-20%,
In ³⁺ 0-5%
As an anionic component,
F ^- 50-98%,
O ^2- 2~50%
The content to fluorophosphate glass, wherein Rukoto. An optical glass to which ions having absorption in the visible range are not added, ⁵⁺ O to the content of ^2- Molar ratio of the content of O ^2- / P ⁵⁺ Is 3.5 or more,
In cation% display
P ⁵⁺  More than 3% and less than 30%,
Al ³⁺  5-40%,
Mg ²⁺  0-10%,
Ca ²⁺  0-40%,
Sr ²⁺  0-30%,
Ba ²⁺  0-30%,
(However, Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ Total content of 30% or more)
Li ⁺  0-20%,
Na ⁺  0-10%,
K ⁺  0-10%,
Y ³⁺  0-10%,
La ³⁺  0-10%,
Gd ³⁺  0-10%,
Yb ³⁺  0-10%,
B ³⁺  0-3%,
Zn ²⁺  0-20%,
In ³⁺  0-5%
As an anionic component,
F ⁻  50-98%,
O ^2-  2-50%
Fluorophosphate glass comprising F ⁻ 55 to 98 anion%, O ^2- The fluorophosphate glass according to claim 1 or 2, comprising 2 to 45 anions. F ⁻ The fluorophosphate glass according to any one of claims 1 to 3, wherein the content of is at least 65 anions.   Refractive index nd is 1.43-1.52, The fluorophosphate glass in any one of Claims 1-4. The fluorophosphate glass according to any one of claims 1 to 5, wherein the number density of metal particles having a particle diameter of 10 µm or more contained therein is less than 5 particles / cm ³ .   A precision press-molding preform comprising the fluorophosphate glass according to any one of claims 1 to 6.   The optical element blank which consists of a fluorophosphate glass in any one of Claims 1-6.   An optical element made of the optical glass according to claim 1.   A method for manufacturing an optical element, wherein the preform according to claim 7 is heated and precision press-molded using a press mold. An optical element manufacturing method for grinding and polishing the optical element blank according to claim 8.

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