KR101196274B1 - Optical glass, precision press-molding preform and optical element - Google Patents

Abstract

It is possible to provide high quality optical glass that is optically uniform and free of streaks when producing precision press molded preforms. This optical glass is an optical glass which is a fluorine-containing glass which has refractive index nd ⁽¹⁾ , and this fluorine-containing glass is remelted for 1 hour at 900 degreeC of nitrogen atmosphere, and it cools to the glass transition temperature, and is 30 degreeC / h When the refractive index of the fluorine-containing glass after cooling to 25 ° C. at the temperature drop rate of is nd ⁽²⁾ , the refractive index nd ⁽¹⁾ and the refractive index nd ⁽²⁾ are substantially the same.

Optical glass, optical element, precision press molding, preform

Description

OPTICAL GLASS, PRECISION PRESS-MOLDING PREFORM AND OPTICAL ELEMENT}

1 is a schematic view of a precision press forming apparatus used in the embodiment.

The present invention relates to an optical glass, a precision press molding preform made of optical glass, a manufacturing process of the preform, an optical element made of optical glass, and a manufacturing process of the optical element.

As a method of manufacturing optical elements made of glass by press molding without grinding or polishing, precision press molding is known. This method accurately transfers the shape of the inner surface of the press-forming mold to each glass material to be molded, and can mass-produce optical elements that are not easily made by grinding and polishing, such as aspherical lenses, micro lenses, diffraction gratings, etc. with high productivity. .

The glass material to be molded by precision press molding is called a preform, which is a glass molded body made of glass having a weight exactly equal to that of the press molded article. Looking at the steps from melting the glass to forming the optical element as a series of processes, the productivity of the process as a whole can be further improved if the preform can be formed directly from the molten glass.

On the other hand, fluorine-containing glass such as fluorinated phosphate glass or the like is a very useful optical glass such as low dispersion glass, and the glass described in JP 3-500162 is known as such fluorinated phosphate optical glass.

Precision press-formed preforms (hereinafter also referred to as "glass shaped bodies") are made by molding molten glass obtained by heating and melting a glass raw material, and fluorine-containing glass such as conventional fluorinated phosphate glass is formed through a high temperature glass surface. The fluorine in the volatilized preform as a final product has optical irregularities of streaes in the layer around the surface.

The preform has a problem that can be used as a material for manufacturing an optical element only when the surface layer of the preform is removed in some way.

In addition, apart from the production of the preform, the shaping of plate-like glass or rod-shaped glass from molten glass causes a problem that volatilization of the highly volatile material through the hot glass surface causes streaks.

As described above, there is a problem that the optical uniformity of the glass is impaired when the fluorine-containing glass is made by heating and melting the glass raw material.

The present invention has been made to overcome the above-mentioned problems. It is an object of the present invention to provide an optically uniform and high quality fluorine containing optical glass. Another object of the present invention is to provide a precision press-formed preform made of the optical glass and a manufacturing process thereof. Still another object of the present invention is to provide an optical element made of the optical glass and a manufacturing process thereof.

In order to achieve the above object, the present invention provides the following (1) to (17).

(1) An optical glass which is a fluorine-containing glass having a refractive index nd ⁽¹⁾ , wherein the fluorine-containing glass is remelted at 900 ° C. for 1 hour in a nitrogen atmosphere, and cooled to the glass transition temperature thereof, followed by 30 ° C./h of When the refractive index of the fluorine-containing glass after cooling to 25 ° C at a temperature drop rate is nd ⁽²⁾ , the refractive index nd ⁽¹⁾ and the refractive index nd ⁽²⁾ are substantially the same as each other.

(2) The optical glass according to the above (1), wherein the absolute value of nd ⁽²⁾ -nd ⁽¹⁾ is 0.00300 or less.

(3) The optical glass according to (1) or (2), wherein the fluorine-containing glass is fluorophosphate glass.

(4) In the above (3), the fluorinated phosphate glass is% cation,

5 to 50% P ⁵⁺

0.1 to 40% Al ³⁺

0 to 20% Mg ²⁺

0-25% Ca ²⁺

0 to 30% Sr ²⁺

0 to 30% Ba ²⁺

0-30% Li ⁺

0-10% Na ⁺

0 to 10% K ⁺

0 to 10% Y ³⁺

0 to 5% La ³⁺

0 to 5% Gd ³⁺

     Optical glass containing a.

(5) In the above (3) or (4), F ^- content molar ratio of the (F ^{- -} / (F ^- + O ^2-)) and O compared to the total content of F ² of 0.25 ~ 0.95 of the optical glass .

(6) The optical glass as described in any one of said (3)-(5) containing 2-30 cation% of Li ⁺ .

(7) The optical glass according to any one of the above (1) to (6), wherein the refractive index nd ⁽¹⁾ is 1.40000 to 1.60000 and Abbe's number (vd) is 67 or more.

(8) The optical glass according to the above (3), wherein the fluorophosphate glass contains Cu ²⁺ .

(9) In the above (8), as cation%

11 to 45% P ⁵⁺

0 to 29% Al ³⁺

The sum of Li ⁺ , Na ⁺ and K ⁺ is 0 to 43%

The sum of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ is 14-50%

0.5 to 13% Cu ²⁺

≪ / RTI >

Optical glass containing 17 to 80% F ⁻ as anion%.

(10) The optical glass according to (1) or (2), wherein the fluorine-containing glass is fluoroborate glass or fluorosilicate glass.

(11) Precision press molding preform made of optical glass in any one of (1) to (10) above

(12) The precision press-formed preform according to the above (11), which is a surface formed by solidification of the glass surface in a molten state.

(13) flowing out the molten glass of the optical glass in any one of (1) to (10) above, separating the molten glass mass and forming the glass mass into a preform during cooling of the glass; Manufacturing process of precision press forming preforms.

(14) An optical element made of optical glass in any one of (1) to (10).

(15) heating the precision press molding preform in the above (11) or (12) or the precision press molding preform obtained by the process in (13), and precision press molding the precision press molding preform in a press forming mold. Manufacturing process of the optical element comprising the step.

(16) The optical element manufacturing process according to the above (15), wherein the precision press molding preform is injected into the press molding mold, and the precision press molding preform and the press molding mold are heated together to perform precision press molding.

(17) The optical element manufacturing process according to the above (15), wherein the precision press molding preform heated separately is injected into a heated press molding mold to perform precision press molding.

When melting the glass raw material to produce a preform made of fluorine-containing glass such as fluorinated phosphate glass, strong volatilization occurs through the molten glass surface, and the volatilization causes streaks around the preform surface. When the easily volatilized material in the glass used to make the preform is reduced in some way, it can be expected to overcome the striped problem because volatilization is suppressed. When the content of easily volatilized material is reduced, the required glass can be changed in the composition itself.

The inventors of the present invention have found several facts by studying how to overcome the striped problem by reducing the concentration of volatiles in the glass while realizing the required glass composition. The inventors found out the following.

(1) A volatile substance and a nonvolatile substance are considered to exist in the molten glass obtained by heating and melting a glass raw material.

(2) In glass, volatiles are generated when the glass raw material is heated and melted, and the amount of volatiles is no longer generated or generated thereafter, but the amount is based on the amount of volatiles generated when the raw material is heated and melted. I think it is negligible.

(3) In order to reduce the concentration of the volatile substance, it is sufficient to volatilize the volatile substance from the molten glass accumulated in the container. It is necessary to prevent the glass from spilling before the concentration of volatiles is sufficiently reduced.

(4) A molten glass having a reduced concentration of volatiles is molded to form a preform, and the preform is gradually cooled and then heated to melt. In this case, since the glass formation from the raw material has already been completed by the initial melting, it is considered that the concentration of the volatile substance does not increase. Indeed, even when the glass having a reduced concentration of volatiles as described above is remelted, volatiles are hardly observed.

(5) It is not easy to determine whether the concentration of volatiles has been reduced to the extent that the stripes are sufficiently reduced. It is theoretically conceivable to use a method of identifying and measuring volatiles or measuring volatiles volatilized from re-melted glass in quantities per unit volume of glass and confirming based on the amount. However, such methods are not practical.

The glass of the present invention is fortunately optical glass, so the refractive index is determined very precisely.

The refractive index of the glass reflects its composition, and the refractive index changes with the change of the composition. A change in the concentration of volatiles means a very small change in its composition. In optical glass in which the refractive index is determined very precisely, such a very small change can be detected by the change in the refractive index. For example, measuring the refractive index before and after remelting the glass indicates that a large amount of volatile material is in the glass to be remelted when the difference between the refractive index before remelting and the remelting after remelting is large. A small difference indicates a small amount of volatiles.

(6) The difference between the refractive index before remelting and the refractive index after remelting is related to overcoming the stripe problem, in which the refractive index before remelting and after remelting become substantially the same, more specifically the refractive index before remelting and The absolute value of the difference between the refractive indices after melting becomes equal to or less than a constant value, thereby providing an optical glass which can overcome the problem of stripes.

Based on the above inference, the present inventors measure the refractive indices before and after remelting the glass to determine the refractive index difference and adjust the absolute value of the refractive index difference to be below a certain value thereby overcoming the striping problem found during the molding of the glass. It was.

The present invention is described in detail below.

[Optical glass]

The optical glass of the present invention is a fluorine-containing glass having a refractive index nd ⁽¹⁾ , and the fluorine-containing glass is remelted for 1 hour at 900 ° C in a nitrogen atmosphere, and cooled to its glass transition temperature, and then 30 ° C / h. When the refractive index of the fluorine-containing glass after cooling to 25 ° C. at the temperature drop rate is nd ⁽²⁾ , the refractive index nd ⁽¹⁾ and the refractive index nd ⁽²⁾ are substantially the same.

The fact that nd ⁽¹⁾ and nd ⁽²⁾ are substantially identical to each other means that nd ⁽¹⁾ and nd ⁽²⁾ are so close to each other that the optical glass does not have stripes.

In the optical glass of the present invention ^, the absolute value of nd ⁽²⁾ -nd ⁽¹⁾ is preferably 0.00300 or less. If the absolute value of nd ⁽²⁾ -nd ⁽¹⁾ exceeds 0.00300, streaks occur on the surface of the preform when the molten glass is molded into the preform. If the absolute value is 0.00300 or less, a glass material capable of preventing the generation of streaks can be provided. The absolute value is preferably 0.00200 or less, more preferably 0.00150 or less, and more preferably 0.00100 or less. In fluorine-containing glass, fluorine is a component that reduces the refractive index of the glass relatively, so that the values of nd ⁽²⁾ -nd ⁽¹⁾ are generally positive.

As an atmosphere in which remelting is performed to measure nd ⁽²⁾ , a nitrogen atmosphere is used to prevent the influence on the refractive index of the glass due to the reaction between the glass and the atmosphere. Remelting is carried out under predetermined conditions including the conditions of heating at 900 ° C. for 1 hour, and the remelted glass is cooled to its glass transition temperature. Since the value of nd ⁽²⁾ is also affected by the temperature drop rate during cooling, cooling takes place at a predetermined temperature drop rate of 30 ° C./h and the remelted glass is cooled to 25 ° C.

The refractive index can be measured by a known method, and the measurement is preferably made with a precision of up to 6 significant digits (5 decimal places or less). The measurement of the refractive index can use the "Method of Measurement of Reflactive Index of Optical Glass" of the Japan Optical Glass Industry Association standard JOGIOS 01-1994.

When the glass has a volume such as the shape of a certain shape or a small or thin lens, there are some cases where the glass cannot be processed to have the shape and dimensions defined in the above standard. In such a case, the glass is heated to soften, press molded and heat treated so that the glass has a prism shape where the two surfaces meet at a predetermined angle. And the refractive index of glass is measured based on the same principle as the said standard. The temperature for press-molding the glass into the prism form is the highest glass softening temperature, and this heating temperature is considerably lower than the temperature at which the glass is melted, so that the effect of heating on the concentration of volatiles is negligible and before The amount of change from the refractive index to the refractive index after the heating becomes negligible.

To reduce or overcome the streaks of glass, it is effective to reduce the concentration of volatiles as well as to lower the molding temperature.

Preferred embodiments of the optical glass of the present invention are described below.

The optical glass of the present invention is made of fluorine-containing glass, and specific examples of the optical glass include fluorinated phosphate glass, fluorinated boric acid glass and fluorinated silicate glass. Hereinafter, the optical glass which is fluorinated phosphate glass is called "optical glass I", and the optical glass which is fluorinated boric acid glass or fluorosilicate glass is called "optical glass II".

The first preferred embodiment of the optical glass I (hereinafter referred to as "optical glass I-A") which is fluorinated phosphate glass is an optical glass containing the following cation.

5 to 50% P ⁵⁺

0.1 to 40% Al ³⁺

0 to 20% Mg ²⁺

0-25% Ca ²⁺

0 to 30% Sr ²⁺

0 to 30% Ba ²⁺

0-30% Li ⁺

0-10% Na ⁺

0 to 10% K ⁺

0 to 10% Y ³⁺

0 to 5% La ³⁺

0 to 5% Gd ³⁺

In the optical glass Ⅰ-A, as an anion component F ^- and O ^2- content ratio of the ^F-molar ratio of the content of the ^- O and F compared to the total amount of ^{2- (F - / (F -} + O 2-)) is It is preferable that it is 0.25-0.95. When the content ratio of the anionic component is determined as described above, the glass may have low dispersion characteristics.

The above-mentioned optical glass I-A can have the optical characteristic of refractive index nd ⁽¹⁾ of 1.40000-1.60000 and Abbe number (vd) of 67 or more. Although the upper limit of Abbe's number ((nu) d) is not specifically limited, Preferably an upper limit of 100 or less becomes a target for the stable production of glass.

The free I-A preferably comprises at least two of Ca ²⁺ , Sr ²⁺ and Ba ²⁺ as the divalent cation component (R ²⁺ ).

In the optical glass I-A, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ as the divalent cation component (R ²⁺ ) is preferably at least 1 cation%, and Mg ²⁺ , Ca More preferably, the content of ²⁺ , Sr ²⁺ and Ba ²⁺ is at least 1 cation%.

The composition of the said optical glass I-A is demonstrated below. Hereinafter, the% content of the cationic component represents the content by the cation% according to the molar ratio, and the% content of the anionic component represents the content by the anion% according to the molar ratio.

P ⁵⁺ is a network former of glass and is basically a cationic component. When the P ⁵⁺ content is less than 5%, the stability of the glass is lowered. When the P ⁵⁺ content exceeds 50%, it is necessary to inject P ⁵⁺ in the form of an oxide raw material, thereby increasing the content of oxygen in the glass, which leads to unintended optical properties. The P ⁵⁺ content is therefore limited to 5-50%, more preferably 5-40%, particularly preferably 5-35%. When P ⁵⁺ is injected, it is not suitable to use PCl ₅ because this corrodes the platinum and volatilizes violently to prevent stable production. Injection of P ⁵⁺ is preferably in the form of phosphates.

Al ³⁺ is a component that improves the stability of fluorinated phosphoric acid. When the content of Al ³⁺ is less than 0.1%, the stability of the glass is lowered. When the content of Al ³⁺ exceeds 40%, the glass transition temperature (T _g ) and the liquidus temperature (LT) greatly increase, so that the molding temperature increases and streaks are strongly generated due to surface volatilization during molding. Thus, it is no longer possible to obtain a uniform glass forming material, in particular a press formed preform. Therefore, the content of Al ³⁺ is limited to 0.1 to 40%, more preferably 5 to 40%, particularly preferably 10 to 35%.

Injecting Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ as the divalent cation component (R ²⁺ ) improves the stability of the glass. However, when these components are excessively injected, the glass stability is lowered. Therefore, the contents of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are preferably limited to the following ranges.

First of all, the content of Mg ²⁺ is preferably 0 to 20%, more preferably 1 to 20%, more preferably 5 to 15%, and particularly preferably 5 to 10%.

The content of Ca ²⁺ is preferably 0 to 25%, more preferably 1 to 25%, more preferably 5 to 20%, particularly preferably 5 to 16%.

The content of Sr ²⁺ is preferably 0 to 30%, more preferably 1 to 30%, more preferably 5 to 25%, particularly preferably 10 to 20%.

The content of Ba ²⁺ is preferably 0 to 30%, more preferably 1 to 30%, more preferably 1 to 25%, more preferably 5 to 25%, particularly preferably 8 to 25 percent.

Injecting at least two components of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferred to injecting only one of them, and at least two of Ca ²⁺ , Sr ²⁺ and Ba ²⁺ More preferred is to inject the component. In order to further improve the effect caused by the divalent cation component (R ²⁺ ), it is preferable to adjust the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ to 1 cation% or more. In addition, if the content of any one of these exceeds this upper limit, the stability is sharply lowered. Ca ²⁺ and Sr ²⁺ can be injected in relatively large amounts, while Mg ²⁺ and Ba ²⁺ are particularly unstable when injected in large quantities. However, Ba ²⁺ is a component that realizes a high refractive index when low dispersion is maintained, so that a relatively large amount of Ba ²⁺ is preferably injected unless stability is impaired.

Li ⁺ is a component that reduces the glass transition temperature (T _g ) without compromising stability. However, when the content exceeds 30%, the durability of the glass is impaired, and at the same time, the workability is also lowered. Therefore, the content of Li ⁺ is limited to 0 to 30%, preferably 0 to 25%, more preferably 0 to 20%.

However, when it is particularly necessary to lower the glass transition temperature for glass use in precision press molding, it is desirable to adjust the content of Li ⁺ to 2 to 30%, and to adjust the content to 5 to 25%. It is more preferable, and it is more preferable to adjust the content to 5-20%.

Na ⁺ and K ^+, such as Li ⁺ has an effect to lower the glass transition temperature (T _g). At the same time, however, they increase the coefficient of thermal expansion when compared to Li ⁺ . NaF and KF have a high solubility in water as compared to LiF, thus degrading the waterproofness of the glass, so that the content of Na ⁺ and K ^+, respectively, is limited to 0-10%. The content of each of Na ⁺ and K ⁺ is preferably 0 to 5%, more preferably none of them are injected.

Y ³⁺ , La ³⁺ and Gd ³⁺ have the effect of improving the stability and durability of the glass and increasing the refractive index. When the content of Y ³⁺ exceeds 10% or the content of each of La ³⁺ and Gd ³⁺ exceeds 5%, on the contrary, the stability decreases and the glass transition temperature increases significantly, so that the content of Y ³⁺ is 0 Is limited to ^˜10 %, and the content of each of La ³⁺ and Gd ³⁺ is limited to 0-5%. The content of Y ³⁺ is preferably in the range of 0 to 5%. The content of each of La ³⁺ and Gd ³⁺ is preferably in the range of 0 to 3%.

For stable production of high quality glass, the total content of P ⁵⁺ , Al ³⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Y ³⁺ , La ³⁺ and Gd ³⁺ It is desirable to control more than 95% cation. The total content is more preferably greater than 98%, more preferably greater than 99%, and even more preferably 100%.

In addition to the above cationic component, the optical glass I-A may include a cationic component such as Ti, Zr, Zn, a lanthanide element, and B, unless it is contrary to the object of the present invention.

To obtain an optical glass to achieve high stability at the same time and the intended optical properties, the ratio of the anionic component is F ^- and O ^2- total content compared to the ^F-content in the molar ratio, i.e., F ^- / (F ^- + O ^2-) Is determined to be 0.25-0.95.

Optical glass I-A is excellent not only as glass for optical element manufacture by grinding and polishing but also as glass for optical element manufacture by precision press molding.

The optical glass I-A includes an embodiment of optical glass (hereinafter referred to as "optical glass I-Aa") containing 2 to 30 cations% of Li ⁺ . In this optical glass I-Aa, the viscosity can be reduced at the liquidus temperature, and the molding (molding) temperature can be reduced. By injecting Li ^{+ of} at least 2 cations, the shaping temperature and glass transition temperature of the glass can be further reduced, and the volatilization from the surface of the preform can be further reduced. When the content of Li ⁺ exceeds 30 cations%, the durability and workability of the glass are deteriorated. In addition, since the temperature for precision press molding can be dropped by the injection of Li ⁺ , the time required to heat the preform and the time required to cool the press molded article can be reduced, so that the overall processing time can be reduced to increase the throughput. Improvements can be made. In addition, since the press molding temperature is reduced, the reaction between the glass and the press molding die can be suppressed, thereby improving the surface state of the press molded article and extending the life of the press molding die.

Optical glass I of the present invention, which is a fluorinated phosphate glass, exhibits high transmittance in the visible light region except when a colorant is included. By preparing a 10 mm thick sample with two flat surfaces parallel to each other made of optical glass I and injecting light perpendicular to the two surfaces, optical glass I is measured at the sample surface when measured at a wavelength in the range of 400 to 2000 nm. The transmittance excluding the reflection loss is at least 80%, preferably at least 95%.

The optical glass I-Aa having the above-described content of Li ⁺ has a glass transition temperature (Tg) of 470 ° C or less, preferably 430 ° C or less.

In addition, the optical glass I-Aa actively contains Li ⁺ in alkali metal ions, so that the optical glass I-Aa has a relatively small coefficient of thermal expansion and a relatively good water resistance. Thus, the glass can be polished and molded into a press-formed preform or molded into an optical element having a high quality and smooth glass surface by polishing.

The optical glass I-A (including the optical glass I-A-a) exhibits excellent water resistance and chemical durability, so that even if the precision press-molded preform is stored and stored for a long time before being press-molded, the preform surface does not deteriorate. In addition, since the surface of the optical element is not easily deteriorated, the optical element can be used without surface blur for a long time.

In addition, in the optical glass I-Aa, the glass melting point can be controlled to a temperature about 50 ° C. lower than the melting point of the glass which does not contain Li while having an optical constant equivalent to that of the optical glass I-Aa. It is possible to reduce or eliminate defects such as coloring of glass caused by dissolution, generation of bubbles and formation of streaks.

In general, fluorophosphate glass has a high viscosity when it flows out, so that when a lump of molten glass having a predetermined weight is separated from the outflowing molten glass and molded to prepare a preform, the fluorophosphate glass has a thin solid line. And a portion such as a thin solid line remains on the surface of the glass gob and has a defect of forming a protrusion. In order to reduce the glass viscosity at the time of outflow and to remove the defect, it is necessary to increase the temperature at which the glass is outflowed, and as described above, the volatilization of fluorine increases from the surface of the glass and the generation of streaks becomes more severe. Will occur.

In order to lower the temperature suitable for forming molten glass in order to solve the above problem, the glass composition of the optical glass I-Aa is such that a fluorinated phosphate glass having a temperature at which the glass exhibits a predetermined viscosity has such a viscosity. It is determined to be lower than the temperature indicated. The glass transition temperature is much lower than the temperature for forming the molten glass into the preform, but the molding temperature of the glass with the low glass transition temperature can also be reduced, such that the glass composition has a high glass transition temperature that forms streaks and solid lines during molding. Is adjusted to fall within the above range to reduce or overcome the problem.

In addition, by lowering the glass transition temperature, the temperature for heating the glass for press molding, in particular for precision press molding preforms, can be reduced, as already described, so that the reaction between the glass and the press forming mold is alleviated and The effect may be to prolong life.

Therefore, the said optical glass I-Aa is suitable as a glass material for press molding, especially the precision press molding, and also as a glass material for manufacturing an optical element by grinding and polishing. Preferred embodiments of the optical glass I-Aa are the same as those of the optical glass I-A except that the content of Li ⁺ is limited to the above-mentioned range.

Optical glass I, which is a fluorinated phosphate glass, includes a second preferred embodiment (hereinafter referred to as "optical glass IB"), which is a fluorinated phosphate glass containing Cu ²⁺ , which acts as a near infrared absorbing glass. Optical glass IB is suitable as a color correction filter for semiconductor image pickup devices, such as CCD or CMOS. When optical glass IB is used for this purpose, it is preferable to adjust the content of Cu ²⁺ to 0.5 to 13 cation%.

It is preferable that optical glass I-B has especially the following composition as% cation.

11 to 45% P ⁵⁺ ,

0 to 29% Al ³⁺ ,

The total content of Li ⁺ , Na ⁺ and K ⁺ is 0-43%,

14 to 50% total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺

0.5 to 13% Cu ²⁺

And as anion% 17 ~ 80% F ⁻

In the above composition, the other anion components are all O ^{2 −} , and it is preferable that there are no other anions except O ^2- .

In this composition, P ⁵⁺ is a basic component of fluorinated phosphate glass and an important component for absorption in the infrared region by Cu ²⁺ . When the content of P ⁵⁺ is less than 11%, the color of the glass is changed to turn green. If the content exceeds 45%, the weather resistance and devitrification resistance of the glass deteriorate. Therefore, the content of P ⁵⁺ is preferably limited to 11 to 45%, more preferably 20 to 45%, and 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 fluorinated phosphate glass. However, when the Al ³⁺ content exceeds 29%, the near infrared absorption characteristic of the glass is poor. Therefore, the content of Al ³⁺ is preferably limited to 0 to 29%, more preferably 1 to 29%, more preferably 1 to 25%, and even more preferably 2 to 23%.

Li ⁺ , Na ⁺ and K ⁺ are components that improve the melt and devitrification resistance of the glass and improve the transmittance in the visible light region. However, if the total content of these components exceeds 43%, the durability and workability of the glass deteriorate. Therefore, the total content of Li ⁺ , Na ⁺ and K ⁺ is preferably limited to 0 to 43%, preferably 0 to 40%, more preferably 0 to 36%.

Li ⁺ in the alkali component is excellent in the above functions, it is more preferable to adjust the component of Li ⁺ to 15 to 30%, more preferably to 20 to 30%.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ are useful components to improve the devitrification resistance, durability and processability of the glass. However, when these are injected in excess, the devitrification resistance of the glass deteriorates. Therefore, it is preferable to adjust the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to 14 to 50%, more preferably to 20 to 40%.

The content of Mg ²⁺ is preferably in the range of 0.1 to 10%, more preferably 1 to 8%.

The content of Ca ²⁺ is preferably in the range of 0.1 to 20%, more preferably 3 to 15%.

The content of Sr ²⁺ is preferably in the range of 0.1 to 20%, more preferably 1 to 15%.

The content of Ba ²⁺ is preferably in the range of 0.1 to 20%, more preferably 1 to 15%, and even more preferably 1 to 10%.

Cu ²⁺ has the property of absorbing near infrared rays. When the content of Cu ²⁺ is less than 0.5%, the near infrared absorption is small. When the content exceeds 13%, the devitrification resistance of the glass deteriorates. Therefore, the content of Cu ²⁺ is preferably 0.5 to 13%, more preferably 0.5 to 10%, more preferably 0.5 to 5%, and more preferably 1 to 5%.

F ⁻ is an important anion component in optical glass IB, which lowers the melting point of the glass and improves the weather resistance of the glass. Since the optical glass IB contains F ⁻ , the melting point of the glass is lowered and the reduction of Cu ²⁺ is suppressed so that the desired optical properties can be obtained. When the content of F ⁻ is less than 17%, the weather resistance of the glass becomes poor. When the content exceeds 80%, the content of O ^2- decreases and coloring of about 400 nm occurs due to the monovalent ion Cu ⁺ . Therefore, the content of F ⁻ is preferably adjusted to 17 to 80%. In order to further improve the above properties of the glass, it is more preferable to adjust the content of F ⁻ to 25 to 55%, more preferably to 30 to 50%.

O ^2- is an important anion component in the optical glass IB, and O ² preferably constitutes the entire anion component except F ⁻ . Accordingly, the component of O ^2- becomes the content of the range obtained by subtracting the F ⁻ content of any one of the above preferred ranges from 100%. When the content of O ² is too small, the divalent ions Cu ²⁺ are reduced to Cu ⁺ so that absorption is amplified in the short wavelength region, especially about 400 nm, and the color of the glass turns green. When the content is too large, the viscosity of the glass increases and the melting point increases so that the transmittance of the glass falls.

Since Pb and As have a very detrimental effect, it is preferable not to use either.

It is preferable that optical glass I-B has the following transmittance | permeability characteristics.

When optical glass IB has a predetermined thickness showing 50% transmittance at 615 nm in spectral transmittance at 500 nm to 700 nm, optical glass IB has the following spectral transmittance characteristics at wavelengths of 400 to 1200 nm. Has

The transmittance at a wavelength of 400 nm is 78% or more, preferably 80% or more, more preferably 83% or more, and more preferably 85% or more.

The transmittance at a wavelength of 500 nm is at least 85%, preferably at least 88%, more preferably at least 89%.

The transmittance at a wavelength of 600 nm is at least 51%, preferably at least 55%, more preferably at least 56%.

The transmittance at a wavelength of 700 nm is 12% or less, preferably 11% or less, more preferably 10% or less.

The transmittance at a wavelength of 800 nm is 5% or less, preferably 3% or less, more preferably 2.5% or less, more preferably 2.2% or less, and still more preferably 2% or less.

The transmittance at a wavelength of 900 nm is 5% or less, preferably 3% or less, more preferably 2.5% or less, still more preferably 2.2% or less, and still more preferably 2% or less.

The transmittance at a wavelength of 1000 nm is 7% or less, preferably 6% or less, more preferably 5.5% or less, more preferably 5% or less, and still more preferably 4.8% or less.

The transmittance at a wavelength of 1100 nm is 12% or less, preferably 11% or less, more preferably 10.5% or less, and still more preferably 10% or less.

The transmittance at a wavelength of 1200 nm is 23% or less, preferably 22% or less, more preferably 21% or less, and still more preferably 20% or less.

As such, the absorption of near-infrared light is large at the wavelength of 700 to 1200 nm, and the absorption of visible light is small at the wavelength of 400 to 600 nm. As used herein, in a glass sample having two flat surfaces that are parallel to each other and optically polished, light is incident on the glass sample perpendicularly to the flat surface through any one of the flat surfaces, such that It is a value obtained by dividing the intensity of light emitted through the other by the intensity of light before entering the sample. This transmittance is also referred to as "external transmittance".

According to the above characteristics, excellent color correction for semiconductor imaging devices such as CCD, CMOS, and the like is achieved.

The optical glass of the present invention includes optical glass (optical glass II) which is boric fluoride glass or fluorosilicate glass.

Optical glass II also contains fluorine, boron or silicon as a component of the glass raw material, so that a substance which tends to volatilize is generated by heating and melting the glass raw material. Thus, as in the case of optical glass I, which is fluorinated phosphate glass, the molten glass is substantially removed by volatilization (volatiles) prior to production into a preform, whereby by volatilization of volatiles during molding It is possible to reduce or prevent the variation of the refractive index and the generation of streaks generated. In optical glass II, the target of glass substantially free of volatilized material is a glass having a refractive index nd ⁽¹⁾ and a refractive index nd ⁽²⁾ , the two refractive indices being substantially equal to each other, more specifically nd ^{(2 )} -the absolute value of nd ⁽¹⁾ is 0.00300 or less, where the refractive index nd ⁽²⁾ is remelted for 1 hour at 900 ° C. in a nitrogen atmosphere, cooled to its glass transition temperature, and then at a rate of 30 ° C./h. It is the refractive index of the glass after cooling to 25 degreeC, and refractive index nd ⁽¹⁾ is the refractive index of the glass before the process mentioned above. The method of measuring the refractive index, the remelting condition, and the preferable range of the absolute value are the same as those described for the optical glass I.

In the optical glasses I and II, the volatiles of each glass are removed or reduced so that a large portion of the material portion removed by volatilization is introduced when preparing the glass raw material for the glass composition. The glass composition is adjusted such that the absolute value of nd ⁽²⁾ -nd ⁽¹⁾ is adjusted to a predetermined value or less and at the same time nd ⁽¹⁾ becomes a desired value. A typical component whose content is reduced by volatilization is fluorine. For other components the glass composition can be adjusted according to the criteria according to the final glass composition.

The optical glass of the present invention is produced by melting a glass raw material by heating in a container, and then reducing the concentration of volatiles in the container, and then pouring the glass to form it. The conditions for remelting can be determined as required so that the absolute value of nd ⁽²⁾ -nd ⁽¹⁾ is no greater than 0.00300.

During molding, the high temperature glass is likely to react with the water in the atmosphere, and the reaction deteriorates the quality of the glass. Therefore, it is preferable that the glass flows out and is molded in a dry atmosphere. The moisture content in the dry atmosphere is preferably such that the dew point temperature is -30 ° C or less. As the atmosphere, an inert gas such as nitrogen, argon or the like may be used.

The glass molding material thus obtained is subjected to machining, such as cutting, grinding, polishing, etc., to make press-formed glass materials or precision press-formed preforms, which will be described in detail below, or to make optical elements such as lenses, prisms, filters, and the like. .

[Precision Press Forming Preform and Its Manufacturing Process]

The precision press-formed preform of the present invention is characterized by being made of the optical glass of the present invention. The precision press molding preform herein refers to a material obtained by preforming the glass having the same weight as that of the press-formed product into a form suitable for precision press molding.

Fluorinated phosphate glass is characterized by having a large friction and a large coefficient of thermal expansion compared to other general optical glass. These properties are not suitable for polishing. When the degree of friction is large, the accuracy of the finish is inferior, and polishing flaws tend to remain on the glass surface. Polishing is performed while spraying the polishing liquid on the glass. When the polishing liquid is sprinkled on the glass whose temperature has risen by polishing or when the glass having polishing flaws on the surface is immersed in the cleaning liquid whose temperature has risen during ultrasonic cleaning, the glass is exposed to a large temperature change. Fluorinated phosphate glass having a large coefficient of thermal expansion is likely to have a problem of being broken due to thermal shock. Therefore, it is desirable to produce either a precision press-molded preform or an optical element by a method based on polishing. From this point of view, it is preferable that the entire surface of the precision press-molded preform is a surface formed by solidification of the glass in the molten state, and the optical element is preferably manufactured by precision press molding.

When the entire surface of the preform is made by solidification of the molten glass, breakage of the preform can be prevented or reduced when the preform is cleaned or heated before precision press molding.

The manufacturing process of the press-formed preform provided in the present invention will be described below.

The manufacturing process of the press-formed preform provided in the present invention comprises a first embodiment including flowing molten glass out of a pipe, separating the molten glass mass and forming the molten glass mass into a preform during cooling of the glass. Examples (hereinafter referred to as "preform manufacturing process I") are included.

In the preform manufacturing process I and the preform manufacturing process II to be described below, the molten glass can be prepared by the same method as the above manufacturing process of the optical glass of the present invention. The molten glass with reduced volatile concentration is continuously discharged at a constant rate from the platinum alloy or platinum pipe heated to a predetermined temperature. The molten glass mass having the weight of one preform or the total weight of one preform and the portion to be removed as described below is separated from the outflowing molten glass. When separating the molten glass mass, it is preferable not to use a cutting blade so that cutting flaws do not remain. For example, a method of dropping molten glass from an outlet of a pipe or a tip of an outflowing molten glass flow with a support member, and when the mass of molten glass having a predetermined weight becomes separable, the support member is quickly moved down. It is preferable to use a method of moving to separate the molten glass mass from the tip of the molten glass flow using the surface tension of the molten glass.

The separated molten glass mass is molded into the desired shape on / on the recess of the preform mold during cooling of the glass. In this case, in order to prevent breakage, such as cracking of the glass, or formation of wrinkles on the surface of the preform during cooling of the glass, it is preferable to mold the glass mass in a floating state by applying gas pressure upward to the glass mass. In this case cooling of the surface of the glass mass by blowing a gas to the surface is preferred to eliminate or reduce the occurrence of streaks.

After lowering the temperature of the glass to a temperature range in which no external force deforms the preform, the preform is removed from the mold and gradually cooled.

In order to further reduce volatilization from the glass surface, it is preferable to form the preform by flowing the glass in a dry atmosphere (dry nitrogen atmosphere, dry air atmosphere, dry mixed gas atmosphere of nitrogen and oxygen, etc.) as described above.

The second embodiment of the manufacturing process of the press-formed preform provided in the present invention (hereinafter referred to as "preform manufacturing process II") is a step of forming a molten glass into a glass molding material and machining the glass molding material to machine the present invention. Preform manufacturing process comprising the step of producing a preform made of optical glass.

The molten glass is prepared as already described. In the preform manufacturing process II, first, molten glass is continuously discharged from the pipe to a forming mold positioned below the pipe. The mold has a flat bottom, three side walls standing around the bottom, and one opening. Adjacent to the opening, the two sidewalls standing at the side edges of the bottom face parallel to each other, the center of the bottom surface is positioned below the pipe vertically, the mold is arranged and fixed so that the bottom surface is horizontal, and spilled into the mold The molten glass is sprinkled so as to have a uniform thickness to the area surrounded by the side wall, and after the molten glass is cooled, the glass is removed from the opening at a constant speed in the horizontal direction. The removed glass is transferred to a heat treatment furnace and heat treated. In this way, a plate-shaped glass molding material made of the optical glass of the present invention having a constant width and a constant thickness is obtained. In this way, a glass molding material can be obtained with reduced or suppressed surface streaks.

Thereafter, the plate-shaped glass molding material is cut or separated into a plurality of pieces of glass called cut pieces, and these pieces of glass are ground and polished to finish with press-formed preforms each having an intended weight.

Alternatively, a cylindrical mold having a through hole is placed vertically fixed below the pipe vertical such that the center axis of the through hole is vertical. In this case, the mold is preferably arranged such that the center axis of the through hole is vertically below the pipe. Then, the molten glass flows from the pipe to the through hole of the mold to fill the through hole with the glass, and the solidified glass is pulled out of the opening of the lower end of the through hole vertically downward at a constant speed and gradually cooled to form a cylindrical rod-shaped glass. A molded body is obtained. The glass molded body thus obtained is heat treated, and the heat-treated glass is cut or separated perpendicular to the central axis of the cylindrical rod-shaped glass molded body. Thereafter, the glass pieces are ground and polished to finish with press-formed preforms each having an intended weight. Also in this method, it is preferable to flow out molten glass and shape | molding in a dry atmosphere as already mentioned above. In this method, it is also effective to increase the cooling of the glass by blowing gas to the glass surface in order to reduce and prevent the occurrence of streaks.

Preform manufacturing processes I and II are both suitable as manufacturing processes for precision press molding preforms, since high quality preforms with high weight accuracy can be produced.

In the preform manufacturing step II, the glass molded body is processed so that 100% of the glass molded body is not used as the preform. However, since the surface streaks of the glass molded body can be reduced or suppressed, the effective use volume of the glass molded body can be increased. The material cost of the fluorinated phosphoric acid in the optical glass is expensive, and the manufacturing cost of the preform and the optical element can be reduced by the effective use of the glass.

The preform can be produced from any of the optical glasses I and II of the present invention depending on the end use.

[Optical device and manufacturing process thereof]

The optical element of the present invention is characterized by being made of the optical glass of the present invention. The optical element of the present invention is made of the optical glass of the present invention, and has the advantage of low dispersion characteristics. In addition, the optical element of the present invention is made of glass excellent in water resistance and chemical durability, according to the present invention can make an optical element free of defects such as cloudy on the surface even when used for a long time.

The optical element is not particularly limited in its kind and shape, but is not limited to aspherical lens, spherical lens, micro lens, lens array, prism, diffraction grating, prism with lens, lens with diffraction grating, etc. Suitable.

In view of the application, the optical element is suitable for an optical element constituting an imaging device such as a lens for an optical camera, an optical pickup lens, a collimator lens, or the like of a digital camera or a mobile phone with a camera.

If necessary, an optical thin film such as an antireflection film can be formed on the surface of the optical element.

The manufacturing process of the optical element provided by the present invention will be described below.

The manufacturing process of the optical element provided by the present invention comprises the steps of heating the precision press forming preform of the present invention or the precision press forming preform made by the preform manufacturing process of the present invention and the step of precision press forming the preform in a press forming mold. It includes.

Such precision press molding is also referred to as "mold optics" and is well known in the art. In the optical element, the surface for transmitting, refracting, diffraction, or reflecting light is called an optical functional surface (for example, an aspherical surface of an aspherical lens, a spherical surface of a spherical lens, etc.). According to the precision press molding, the optical functional surface can be made by precisely transferring the molding surface shape of the press forming mold to glass, and does not require processing processes such as grinding, polishing, etc. to finish the optical functional surface.

The manufacturing process of the optical element provided by the present invention is suitable for manufacturing optical elements such as lenses, lens arrays, diffraction gratings, prisms, and the like, and is particularly suitable for producing aspherical lenses with high productivity.

According to the manufacturing process of the optical element provided by the present invention, since the optical element having the above optical characteristics can be obtained, and the glass has a low glass transition temperature (T _g ), the press forming temperature can be lowered, so that the press forming mold Damage on the molding surface of the mold can be reduced and can extend the life of the mold. In addition, since the glass constituting the preform has high stability, devitrification is effectively prevented at the stage of reheating and pressing. In addition, a series of steps that begin with melting of the glass and end with obtaining the final product can be performed with high productivity.

As a press molding mold used in precision press molding, a known press molding mold such as a press molding mold obtained by forming a mold release film on a molding surface of a molding die material made of refractory ceramic such as silicon carbide, zirconia, alumina, or the like can be used. Can be. Above all, a press mold made of silicon carbide is preferred, and a carbon-containing film or the like can be used as the mold release film. In view of durability and cost, carbon films are preferred.

In precision press molding, it is preferable to use a non-oxidizing gas atmosphere for molding so that the molding surface of the press molding die is maintained in good condition. The non-oxidizing gas is preferably selected from nitrogen or a mixture of hydrogen and nitrogen.

Precision press molding for use in the manufacturing process of the optical element provided by the present invention includes two embodiments of precision press molding 1 and precision press molding 2 described below.

(Precision press forming 1)

Precision press molding 1 is a method of injecting a preform into a press mold and heating the preform and the press mold together to perform precision press molding.

In the precision press molding 1, it is preferable to heat the press forming mold and the preform together to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ⁶ to 10 ¹² dPa · s in order to perform precision press molding.

In addition, the press-formed product is cooled to a temperature where the glass preferably exhibits a viscosity of at least 10 ¹² dPa · s, more preferably at least 10 ¹⁴ dPa · s, more preferably at least 10 ¹⁶ dPa · s. It is preferable to take out from a press molding die after that.

Under the above conditions, not only the shape of the forming surface of the press forming die can be accurately transferred to glass, but also the precision press molded product can be pulled out without any deformation.

(Precision press forming 2)

Precision press molding 2 is a method of precise press molding by pre-injecting the pre-heated preform into a pre-heated press forming mold.

In precision press molding 2, the preforms are preheated before being injected into the mold to make the optical elements with excellent surface accuracy without surface defects despite the reduced process time.

The preheating temperature for the press forming die is preferably set lower than the preheating temperature of the preform. By thus setting the preforming temperature for the press forming die, wear of the press forming die can be reduced.

In the precision press molding 2, the preform is preheated to a temperature at which the glass constituting the preform preferably exhibits a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁹ dPa · s.

In addition, it is preferable to heat the preform while the preform is floating, and more preferably, the glass constituting the preform is preheated to a temperature exhibiting a viscosity of 10 ^5.5 to 10 ⁹ dPa · s while the preform is floating, More preferably, it is preheated to a temperature exhibiting a viscosity of less than 10 ^5.5 to 10 ⁹ dPa · s.

It is also desirable to start the cooling of the glass at the same time as the start of pressurization or after a certain time.

While the temperature of the press forming mold is adjusted to a temperature lower than the preheating temperature of the preform, a temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s may be used as an index.

In this method, it is preferred to cool the precision press molded product to a temperature at which the glass exhibits a viscosity of 10 ¹² dPa · s or less before withdrawing the precision press molded product.

The optical element obtained by the precision press molding is taken out of the press forming mold and gradually cooled as required. If the precision press molded product is an optical device, the optical thin film may be coated on the surface as desired.

Although the manufacturing process of the optical element provided by the present invention is as described above, the optical element of the present invention can also be produced by other methods. For example, the molten glass may be spilled to form a glass molded body, the glass molded body may be heat treated, and then processed to make the optical device. Further, optical elements such as various lenses are made by thinly slicing the previously described cylindrical rod-shaped glass molded body perpendicular to the main axis, and grinding and polishing the cylindrical rod-shaped glass pieces.

For the optical elements, any one of the optical glasses I and II can be used according to the purpose.

[Example]

The invention is described in more detail with reference to the following examples, which, however, are not intended to limit the scope of the invention.

Example 1 (Example of Preparation of Optical Glass)

As a glass raw material, phosphates, fluorides, etc. corresponding to the glass component are prepared, and the glass raw materials are weighed and thoroughly mixed to obtain a glass having the composition shown in Table 1 or 2.

The raw materials are melted in a platinum crucible at 850 ° C. for 1 hour and the melt is rapidly cooled and pulverized to obtain coarse melt glass shavings. 10 kg of coarse melt glass shavings are introduced into a platinum crucible, the crucible is tightly sealed with a lid, and then heated to 900 ° C. to melt the glass shavings. Thereafter, a sufficiently dried gas is injected into a platinum crucible, and the molten glass is purified at 1,100 ° C. for 2 hours while a dry atmosphere is maintained. The dry gas may be selected, for example, from an inert gas such as nitrogen, a mixed gas of oxygen and inert gas, or oxygen.

After purification, the glass temperature is lowered to 850 ° C., lower than the purification temperature, and then the glass is flowed out through a pipe connected to the bottom of the crucible. The gas injected into the crucible is purged through the filter and discharged out. In each of the above steps, the glass in the crucible is stirred for uniform glass.

The molten glass thus obtained is injected into a carbon mold in a dry nitrogen atmosphere. The injected glass is cooled to the glass transition temperature and immediately thereafter the glass is placed in a heat treatment furnace, heat treated at a temperature near the glass transition temperature for 1 hour and gradually cooled to a room temperature in the heat treatment furnace. In this way, optical glass Nos. 1 to 11 in Tables 1 and 2 were obtained.

Thus obtained optical glass No. 1 to No. 11 was magnified through a microscope to confirm that there were no precipitated crystals or unmelted raw materials.

Thus obtained optical glass No. 1 to No. The refractive index (nd), Abbe's number (νd), and glass transition temperature (T _g ) of 11 were measured as follows. Tables 1 and 2 show the measurement results.

(1) refractive index (nd) and Abbe's number (νd)

The refractive index (nd) and Abbe number (νd) of the optical glass obtained at the gradual cooling rate of -30 ° C / h were measured.

Regarding the refractive index (nd), the optical glass No. 1 to No. The value obtained by measuring 11 was made into nd ⁽¹⁾ . Optical glass no. 1 to No. 11 was remelted and cooled, and the refractive index nd ⁽²⁾ was measured as follows.

30 g of optical glass was added to a glass carbon crucible in a quartz glass chamber with a volume of 2 L and a dry nitrogen gas injected at a rate of 2 L / min. The glass was remelted for hours. The glass is then cooled in the chamber to a temperature near the glass transition temperature and again to room temperature at a rate of temperature drop of -30 ° C / h. Optical glass No. obtained by this method. 1 to No. The refractive index nd ⁽²⁾ was measured for 11.

Tables 1 and 2 show optical glass Nos. 1 to No. Show the values of nd ⁽²⁾ -nd ⁽¹⁾ for 11 and their absolute values.

(2) glass transition temperature (T _g )

The glass transition temperature (T _g ) of each glass was measured at the temperature increase rate of 4 degree-C / min using the apparatus for thermomechanical analysis of Rigaku Corporation.

As shown in Tables 1 and 2, all optical glass Nos. Of the present invention. 1 to No. 11 had preferable refractive index, Abbe number, and glass transition temperature, showed the outstanding low temperature softening characteristic, and meltability, and was suitable as optical glass for press molding.

Also, both the values of nd ⁽²⁾ -nd ⁽¹⁾ and their absolute values were less than 0.00300.

Example 2 (Example of Preparation of Optical Glass)

As the glass raw material, phosphates, fluorides, oxides, and the like corresponding to the glass composition were prepared, and the glass raw materials were weighed and mixed sufficiently to obtain glass having compositions Nos. 12 to 13 as shown in Table 3. The glass materials thus obtained were filled into a platinum crucible and the crucible was tightly sealed. While stirring the glass raw material in an electric furnace of 790-850 degreeC, the raw material was heated and melted as in Example 1, the melt was refine | purified and cooled, and the molten glass began to flow out. The gas discharged from the crucible was purified through a filter and discharged out.

The molten glass thus obtained was injected into a carbon mold and the resultant glass could be cooled to the glass transition temperature. Immediately thereafter the glass was placed in a heat treatment furnace, heat treated for 1 hour near the glass transition temperature and gradually cooled to room temperature. In this way, optical glass Nos. 12 and 13 in Table 3 were obtained. Table 3 shows the glass transition temperatures (T _g ) and the transmittances at typical wavelengths of optical glasses Nos. 12 and 13. The transmittance is a value obtained when an optical glass having a predetermined thickness exhibits a transmittance of 50% at a wavelength of 615 nm. The thickness of the optical glass No. 12 was 1.0 mm, and the thickness of the optical glass No. 13 was 0.45 mm. Transmittance measurements were also performed with a spectrophotometer on samples with two opposing surfaces, each in the form of a flat plate and optically polished.

The optical glass with respect to No.12 and 13, nd ⁽²⁾ - The value of nd ⁽¹⁾ is small and than 0.00300, nd ⁽²⁾ - smaller than the absolute value of nd ⁽¹⁾ 0.00300 also.

(Reference) R ⁺ represents the total content of Li ⁺ , Na ⁺ and K ⁺ .

R ' ²⁺ represents the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ .

R ″ ²⁺ represents the total content of R ′ ²⁺ and Zn ²⁺ .

Comparative Example 1

The glass raw material was melted to obtain the glass of Comparative Example 1 in Table 4 without any dry inert gas flowing into the crucible. In addition, a continuous melting furnace having a volume of 50 liters was used. The melting temperature was set at 1,100 ° C. and the glass was placed in the furnace for 20 hours before melting began and the molten glass flowed. When producing glass from the molten glass thus prepared in the same manner as in the above procedure, nd ⁽²⁾ increases significantly compared to nd ⁽¹⁾ , and as shown in Table 4, the absolute of nd ⁽²⁾ -nd ⁽¹⁾ The value was greater than 0.00300.

(Reference) R ⁺ represents the total content of Li ⁺ , Na ⁺ and K ⁺ .

R ' ²⁺ represents the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ .

Example 3 (Example of Preparation of Preform)

From the molten glass of optical glass Nos. 1-11 and the comparative example 1 glass, the precision press molding preform was manufactured as follows. The molten glass flows out at a constant speed out of the temperature-controlled platinum pipe to a temperature range in which the molten glass can flow stably without any devitrification, or a method of dropping or supporting the tip of the molten glass flow as a support and fastening the support. The molten glass mass having the weight of the intended preform was separated by moving down to separate the glass mass. Thereafter, the molten glass mass was received by a receiving mold having a gas outlet at the bottom, and the gas was ejected from the gas outlet to form a preform in the state of floating the glass mass. The preforms thus obtained had the form of spheres or compressed spheres by adjusting or setting the spacing of the molten glass mass separation. The preform thus obtained had a weight exactly equal to the set point, and each entire surface became a smooth surface formed by the solidification of the glass in the molten state.

And the inside of the preform was observed. Although no streaks were found in the optical glass Nos. 1 to 11 of the present invention, clear streaks were found radially on the surface of the glass of Comparative Example 1.

Separately preforms were made from molten glass as follows. The molten glass was injected into a casting mold, and a dry gas was blown to the glass surface to form a glass plate or a cylindrical rod-shaped glass while promoting the cooling of the glass, and the formed glass was heat treated and cut to obtain a glass piece. The cut pieces were ground and polished to obtain a preform with a smooth overall surface. In this case, streaks were not found on the surface of the plate glass or cylindrical rod-shaped glass obtained by casting the molten glass obtained by replacing the atmosphere, but streaks were found on the surface of the glass obtained without replacing the atmosphere.

Example 4 (Example of Manufacturing Optical Device)

The preform obtained in Example 3 made of optical glass Nos. 1 to 11 was precisely press-molded with the press apparatus shown in Fig. 1 to make an aspherical lens. In particular, a press forming mold having an upper forming die member 1, a lower forming die member 2, and a sleeve 3 is prepared, and the preform 4 is placed in the lower forming die member 2 and the upper forming die member 1. ). Thereafter, a nitrogen atmosphere was supplied into the quartz tube 11, and a power was supplied to the heater 12 to heat the inside of the quartz tube 11. The temperature inside the press mold is set to a temperature at which the molded glass exhibits a viscosity of 10 ⁸ to 10 ¹⁰ dPa · s, while the pressure rod 13 is moved downwards while the temperature is maintained, thereby allowing the upper mold member 1 to Press to pressurize the preform in the mold. Pressurized at a pressure of 8 Mpa for 30 seconds. Thereafter, the pressure was removed and the glass molded body obtained by press molding contacted the lower mold frame member 2 and the upper mold frame member 1 to a temperature at which the glass exhibited a viscosity of at least 10 ¹² dPa · s. Gradually cooled. Thereafter, the glass molded body was rapidly cooled to room temperature and removed from the mold to obtain an aspherical lens. The aspherical lens obtained by this method has a remarkably high surface accuracy.

In Fig. 1, reference numeral “9” denotes a support rod, “10” denotes a lower mold frame member and a sleeve holder, and “14” denotes a thermocouple.

As required, an antireflection film was formed on each of the aspherical lenses obtained by precision press molding.

Example 5 (Example of Manufacturing Optical Element)

The preform made from optical glass Nos. 1 to 11 obtained in Example 3 was subjected to precision press molding by the following method different from the method in Example 4. In this method, the preform was first preheated to a temperature at which the glass constituting the preform exhibited a viscosity of 10 ⁸ dPa · s while the preform was floating. Separately, the press forming mold having the upper mold member, the lower mold member and the sleeve is heated to a temperature at which the glass constituting the preform has a viscosity of 10 ⁹ to 10 ¹² dPa? S, and the preheated preform is pressed. It is injected into the space of the mold and precisely press molded at a pressure of 10 MPa. The glass and the press mold are cooled simultaneously with the start of pressurization, and cooling is continued until the shaped glass has a viscosity of at least 10 ¹² dPa · s. Thereafter, the molded product is taken out of the mold to obtain an aspherical lens. Aspheric lenses of the above method have a remarkably high surface accuracy.

As required, an antireflection film was formed on each of the aspherical lenses obtained by precision press molding. In this way, optical elements made of optical glass having high internal quality are produced with high productivity and high accuracy.

Example 6 (Example of Preparation of Plate Glass and Optical Element)

Each of molten glass of optical glass Nos. 1 to 11 was separately injected from a pipe into a molding mold continuously and molded into a plate glass in a dry nitrogen atmosphere, and the molded glass was gradually cooled. When observing the inside of each of these glasses, no streaks were found.

Thereafter, the plate-shaped glass was cut, ground and polished to prepare a press-forming material. These materials were heated to soften and press molded to obtain an optical element blank. The blanks were gradually cooled, ground and polished to obtain spherical lenses.

An anti-reflection film was formed on each of the optical elements or a near-infrared reflecting film was coated.

Example 7

Preform, plate-shaped glass and cylindrical rod-shaped glass made of the optical glasses Nos. 12 and 13 were prepared by the methods described in Examples 3, 6 and the like. Thereafter, the plate-shaped glass made of optical glass No. 12 was thinly cut and processed into a flat plate shape, and the major surfaces parallel to each other were optically polished to obtain a near infrared absorption filter having a thickness of 1.0 mm. The NIR filter thus obtained is attached to a quartz plate (the major surfaces parallel to each other are optically polished) and two optical glass (borosilicate glass BK-7) plates to function as a NIR filter and a low-pass filter. We created a complex filter with all the functions of). This composite filter was integrated into the imaging device.

Similarly, the plate glass made of optical glass No. 13 was thinly cut, and both surfaces of the obtained glass pieces were optically polished to obtain a 0.45 mm thick flat plate. Such a plate can be attached to a quartz plate and an optical glass (borosilicate glass) plate to make a composite filter.

The composite filter thinly cuts cylindrical rod glass made of optical glass No. 12 or 13, optically polishes both surfaces of the glass pieces thus obtained, and the resultant flat plate, quartz plate and optical glass (borosilicate glass BK-7) plate Can be stacked up.

Thereafter, preforms made of optical glass Nos. 12 and 13 were press molded to obtain aspherical lenses having a function of near infrared absorption.

The various optical elements by the above methods were all optically uniform and streaked.

According to the present invention, fluorine-containing optical glass without stripes can be obtained. In addition, it is possible to obtain an optical glass having low dispersion characteristics, a low glass transition temperature, and softening characteristics at a low temperature such that precision press molding is achieved, and optical elements such as precision press molding preforms and various lenses are used. Can be made from

According to the present invention, it is possible to provide a fluorine-containing optical glass which is suitable for producing high quality precision press-formed preforms from molten glass, and which is also suitable for precise press-molding the preforms thus obtained to produce optical elements.

According to the present invention, it is also possible to provide a precision press-formed preform made of the optical glass and a manufacturing process thereof, and to provide an optical element made of the optical glass and a manufacturing process thereof.

In addition, since the content of volatile materials in the optical glass is reduced, it is possible to provide an optical glass that does not change much of optical properties such as refractive index when melted and molded.

Claims (17)

An optical glass which is a fluorine-containing glass having a refractive index nd ⁽¹⁾ , wherein the fluorine-containing glass is remelted for 1 hour at 900 ° C. in a nitrogen atmosphere, and cooled to its glass transition temperature, followed by a temperature drop rate of 30 ° C./h. When a la 25, the refractive index of the fluorine-containing glass nd ⁽²⁾ after it has been cooled to ℃, nd ⁽²⁾ - the optical glass, characterized in that the absolute value of nd ⁽¹⁾ is not more than 0.00300. delete The optical glass according to claim 1, wherein the fluorine-containing glass is fluorinated phosphate glass. The method of claim 3, wherein the fluorinated phosphate glass is cation%, 5 to 50% P ⁵⁺ 0.1 to 40% Al ³⁺ 0 to 20% Mg ²⁺ 0-25% Ca ²⁺ 0 to 30% Sr ²⁺ 0 to 30% Ba ²⁺ 0-30% Li ⁺ 0-10% Na ⁺ 0 to 10% K ⁺ 0 to 10% Y ³⁺ 0 to 5% La ³⁺ 0 to 5% Gd ³⁺      An optical glass comprising a. The optical glass according to claim 3, wherein the molar ratio (F ⁻ / (F ⁻ + O ^{2 −} )) of the content of F ⁻ to the total content of F ⁻ and O ^{2 −} is 0.25 to 0.95. The optical glass according to claim 3, which contains 2 to 30 cation% of Li ⁺ . The optical glass according to claim 1, wherein the refractive index nd ⁽¹⁾ is 1.40000 to 1.60000 and Abbe's number (vd) is 67 or more. 4. The optical glass according to claim 3, wherein the fluorophosphate glass contains Cu ²⁺ . The method according to claim 8, wherein as cation% 11 to 45% P ⁵⁺ 0 to 29% Al ³⁺ The sum of Li ⁺ , Na ⁺ and K ⁺ is 0 to 43% The sum of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ is 14-50% 0.5 to 13% Cu ²⁺ &Lt; / RTI &gt; Optical glass containing 17-80% F <^-> as anion%. The optical glass according to claim 1, wherein the fluorine-containing glass is fluorinated boric acid glass or fluorosilicate glass. Precision press-formed preform made of optical glass according to claim 1. 12. The precision press-formed preform according to claim 11, wherein the entire surface is a surface formed by solidification of the glass surface in a molten state. A method for producing a precision press-formed preform, comprising: flowing out the molten glass of the optical glass according to claim 1, separating the molten glass mass and forming the glass mass into a preform during cooling of the glass. An optical element made of optical glass according to claim 1. An optical device comprising the steps of heating the precision press-molded preform according to claim 11 or 12 or the method of claim 13 and precision press-molding the precision press-formed preform in a press-forming mold. Manufacturing method. 16. The method of claim 15, wherein the precision press molding preform is injected into the press molding mold, and the precision press molding preform and the press molding mold are heated together to perform precision press molding. 16. The method of claim 15, wherein the separately heated precision press molding preform is injected into a heated press molding mold for precision press molding.

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