JP5727417B2 - Optical glass, optical element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a high refractive index low dispersion optical glass having a refractive index nd of 1.86 or more and an Abbe number νd of 38 or more, a glass molded body made of the optical glass, an optical element made of the optical glass, and a method for producing them. About.

  In an imaging optical system such as a camera lens, a technique of correcting chromatic aberration by combining a lens made of high dispersion glass and a lens made of low dispersion glass is often used. An example of the low dispersion glass is disclosed in Patent Document 1.

By the way, in order to correct chromatic aberration with a more compact configuration, it is desirable to increase the refractive index of the low dispersion glass while increasing the Abbe number difference between the high dispersion glass and the low dispersion glass. By increasing the refractive index, it is possible to produce a lens with a reduced refractive index of the optical functional surface while obtaining a required refractive power.
In order to achieve the above object, an optical glass having a refractive index nd of 1.86 or more and an Abbe number νd of 38 or more is desired.

  However, glass that satisfies the above optical properties contains a large amount of rare earth components, and the content of the network-forming components of the glass is relatively reduced, so that the devitrification resistance is lowered, and the glass is heated and softened when it is molded. There is a problem of being easily devitrified.

The invention disclosed in Patent Document 1 contains a large amount of Ta ₂ O ₅ in order to solve the above problem, but since Ta ₂ O ₅ is a rare and expensive raw material, the manufacturing cost increases. End up. As a result, there has been a problem in that the use is limited even though the glass is useful.

JP 54-90218 A

  Under such circumstances, the present invention provides a high refractive index and low dispersion optical glass excellent in devitrification resistance, a glass molded body and an optical element made of the optical glass, and the glass molded body. An object of the present invention is to provide a method for manufacturing an optical element.

  As a result of intensive studies to achieve the above object, the present inventors can achieve the object with an optical glass having a specific glass composition and having a refractive index and an Abbe number of a certain value or more. Based on this finding, the present invention has been completed.

That is, the present invention
(1) In mass% display,
1 3-23% of B ₂ O ₃ and SiO ₂ in a total amount _(however, the content of B 2 _{O 3} is 7-17%, the content of SiO ₂ is from 6 to 12%),
La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ are 58 to 80% in total (provided that the content of La ₂ O ₃ is 30 -50%, Gd ₂ O ₃ content is 1-30% , Y ₂ O ₃ content is 0-10%, Yb ₂ O ₃ content is 0-5%, WO ₃ content is 0 ~ 6%),
La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ in a total amount of 50 to 70%,
The ZrO ₂ 2~10%,
Nb ₂ O ₅ and 1-7%,
ZnO 0-6%,
Ta ₂ O ₅ is 0% or more and less than 13%,
0 to 5% of TiO ₂ (however, the total content of TiO ₂ and alkaline earth metal oxide is 5% or less),
Li ₂ O 0-1%,
Contains, does not contain Pb,
The ratio of Ta ₂ O ₅ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ is 0.23 or less,
The ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O _{3 to} the total content of B ₂ O ₃ and SiO ₂ is 2 . 4 to 3.6, a refractive index nd of 1.86 or more, and an Abbe number νd of 38 or more, an optical glass ,
(2) The optical glass according to (1) above, wherein the glass transition temperature Tg is 674.9 ° C. or higher .
(3 ) A rod-shaped glass molded body (hereinafter referred to as a glass molded body I) comprising the optical glass according to the above (1) or (2 ),
( 4 ) It is characterized by comprising an optical glass having a refractive index nd of 1.86 or more, an Abbe number νd of 38 or more, and a difference between the crystallization peak temperature Tx and the glass transition temperature Tg (Tx−Tg) of 110 ° C. or more. A rod-shaped glass molded body (hereinafter referred to as a glass molded body II),
( 5 ) In the optical glass, the rod-shaped glass molded body according to the above ( 4 ), wherein the content of Ta ₂ O ₅ is 0% or more and less than 13% by mass,
(6) In the optical _glass, the ratio of _{La 2 O 3, Gd 2 O} 3, Y 2 O 3, Yb 2 O 3, ZrO 2, Nb 2 O 5 and the content _{of Ta} 2 _{O 5} to the total content of WO ₃ The rod-shaped glass molded article according to the above ( 4 ) or ( 5 ), wherein is 0.23 or less,
(7) an optical glass is represented by mass%, _Nb 2 _{O 5} 0 to 15%, the containing ZrO ₂ 2 to 10% and ZnO 0-15% (4) ~ (6) any one of Items 1 The rod-shaped glass molded body according to item,
(8) an optical glass is represented by _mass%, B 2 _{O 3} and with containing 12-30% of SiO ₂ in a total _{amount, La 2 O 3, Gd 2} O 3, Y 2 O 3, Yb 2 O 3, ZrO ₂ , Nb ₂ O ₅ and WO ₃ are contained in a total amount of 55 to 80%, and La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O with respect to the total content of B ₂ O ₃ and SiO ₂ The rod-shaped glass molded body according to any one of the above ( 4 ) to ( 7 ), wherein the ratio of the total content of ₃ is 2 to 4 ,
( 9 ) The rod-shaped glass molded body according to any one of ( 4 ) to ( 8 ) above, wherein the side surface is a surface formed by solidifying glass in a molten state.
( 10 ) In the method for producing a glass molded body, in which a molten glass obtained by heating and melting a glass raw material is poured into a mold to form a glass molded body made of optical glass.
Using a mold having a through hole, forming while continuously pouring molten glass into the through hole, and continuously drawing the molded glass from the through hole,
The molten glass is cooled by contacting the inner wall of the through hole so as to surround the molten glass moving in the through hole, and a glass molded body made of the optical glass described in the above (1) or (2) is produced. A method for producing a glass molded body (hereinafter referred to as production method I),
( 11 ) In the method for producing a glass molded body, in which a molten glass obtained by heating and melting a glass raw material is poured into a mold to form a glass molded body made of optical glass.
Using a mold having a through hole, forming while continuously pouring molten glass into the through hole, and continuously drawing the molded glass from the through hole,
The molten glass is cooled by contacting the inner wall of the through hole so as to surround the molten glass moving in the through hole, the refractive index nd is 1.86 or more, the Abbe number νd is 38 or more, the crystallization temperature Tx and the glass transition temperature Tg. A glass molded body made of an optical glass having a difference (Tx−Tg) of 110 ° C. or higher (hereinafter referred to as Manufacturing Method II),
( 12 ) An optical element comprising the optical glass according to (1) or (2 ) above,
( 13 ) A method for producing an optical element, comprising a step of heating and softening a glass material made of the optical glass as described in (1) or (2 ) above, and ( 14 ) above ( 10 ) ) Or ( 11 ) a method for producing an optical element comprising a step of producing a glass material from a glass molded body produced by the method according to item 11 and heating and softening the glass material.
Is to provide. Said ( 3 )-( 11 ), ( 14 ) is a reference aspect.

According to the present invention, there are provided a high refractive index and low dispersion optical glass excellent in devitrification resistance, a glass material for heating softening and an optical element comprising the optical glass, and a method for producing the glass material and the optical element. Can do.
Further, the above effect can be obtained without using a large amount of expensive Ta ₂ O ₅ .

It is explanatory drawing which shows an example of the manufacturing method of the glass forming body of this invention. It is explanatory drawing which shows an example of the method of controlling the taking-out speed | rate of the glass from a through-hole. It is explanatory drawing which shows the specific example of the isolation | separation method of a glass molded object. It is explanatory drawing which shows the specific example of the isolation | separation method of a glass molded object. It is explanatory drawing which shows the specific example of the isolation | separation method of a glass molded object. It is explanatory drawing which shows an example of the side pressure cutting method. It is explanatory drawing which shows the other example of the side pressure cutting method.

First, the optical glass of the present invention will be described.
[Optical glass]
The optical glass of the present invention, represented by _mass%, B 2 _{O 3} and 12 to _30% of SiO ₂ in a total _{amount, La 2 O 3, Gd 2} O 3, Y 2 O 3, Yb 2 O 3, ZrO 2 , Nb ₂ O ₅ and WO ₃ in a total amount of 55-80%, ZrO ₂ 2-10%, Nb ₂ O ₅ 0-15%, ZnO 0-15%, Ta ₂ O ₅ 0% or more The ratio of Ta ₂ O ₅ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ is 0. .23 or less, the ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O _{3 to} the total content of B ₂ O ₃ and SiO ₂ is 2 to 4 and refraction The ratio nd is 1.86 or more, and the Abbe number νd is 38 or more.

  In the present invention, unless otherwise specified, the content or total content of each component is displayed in mass%, and the ratio between the content or total content is expressed in mass ratio.

In the optical glass of the present invention, both B ₂ O ₃ and SiO ₂ function as network forming components. If the total content of B ₂ O ₃ and SiO ₂ (B ₂ O ₃ + SiO ₂ ) is less than 12%, the devitrification resistance decreases, and if it exceeds 30%, the refractive index decreases, so B ₂ O ₃ + SiO ₂ is 12 to 30%. A preferred lower limit is 14%, a more preferred lower limit is 16%, and a still more preferred lower limit is 17%. On the other hand, the preferable upper limit is 28%, the more preferable upper limit is 26%, the still more preferable upper limit is 25%, and the more preferable upper limit is 24%.

In an embodiment in which the total content of alkaline earth metal oxide and TiO ₂ described below is 5% or less, the more preferable upper limit of B ₂ O ₃ + SiO ₂ is 23%, the still more preferable upper limit is 22%, and still more preferable The upper limit is 21%, the particularly preferred upper limit is 20%, and the most preferred upper limit is 19%.

La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ are all components that increase the refractive index and suppress the content of Ta ₂ O _5. However, in order to obtain a required refractive index, it is necessary to contain 55% or more in total. However, if it exceeds 80%, devitrification resistance decreases, so the total content is set to 55 to 80%. In an embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the preferable lower limit is 58%, the more preferable lower limit is 60%, and the further preferable lower limit is 62%. On the other hand, the preferable upper limit is 76%, the more preferable upper limit is 74%, and the more preferable upper limit is 72%.

However, in the embodiment in which the total content of alkaline earth metal oxide and TiO ₂ exceeds 5%, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ The preferable lower limit of the total content of WO ₃ and WO ₃ is 56%, the more preferable lower limit is 58%, and the further preferable lower limit is 60%. On the other hand, the preferable upper limit is 76%, the more preferable upper limit is 74%, and the more preferable upper limit is 72%.

Of these, ZrO ₂ can be introduced in a small amount, so that the stability of the glass can be increased, so 2% or more is introduced. However, if introduced in excess of 10%, the dispersion increases, so the content is 2-10%. To do. In an embodiment where the total content of alkaline earth metal oxide and TiO ₂ is 5% or less, the preferred lower limit is 3%, the more preferred lower limit is 4%, the still more preferred lower limit is 5%, and the more preferred lower limit is 5.2%. An even more preferable lower limit is 5.5%. On the other hand, the preferable upper limit is 8.5%, the more preferable upper limit is 7.5%, and the more preferable upper limit is 6.8%.

By introducing an appropriate amount of Nb ₂ O ₅ , devitrification resistance when heating and softening and molding (referred to as devitrification resistance during reheating) is improved. However, when it exceeds 15%, the devitrification resistance is lowered. Also, the dispersion becomes large. Therefore, the content is made 0 to 15%.

In the glass of the present invention, Nb ₂ O ₅ has unique properties among the high refractive index imparting components, and the devitrification resistance at the time of reheating is improved by substitution with Ta ₂ O ₅ . As a measure of devitrification resistance during reheating, it can be considered that the larger the difference between the crystallization peak temperature Tx and the glass transition temperature Tg (Tx−Tg), the better the devitrification resistance. When the amount of Ta ₂ O ₅ is reduced while maintaining the high refractive index characteristics, the substitution from Ta ₂ O ₅ to Nb ₂ O ₅ is most preferable for maintaining a large Tx-Tg. Substitution from Ta ₂ O ₅ to MgO, CaO, SrO, BaO, ZnO is not as effective as substitution to Nb ₂ O ₅ , but is effective in maintaining devitrification resistance during reheating. On the other hand, substitution of Ta ₂ O _{5 with} rare earth oxides is not preferable from the viewpoint of maintaining devitrification resistance during reheating. Therefore, in order to improve the devitrification resistance at the time of reheating, it is preferable to set the content of Nb ₂ O ₅ in the range of 1 to 15%. In an embodiment in which Nb ₂ O ₅ is introduced as an essential component, in an embodiment in which the total content of alkaline earth metal oxide and TiO ₂ is 5% or less, the content of Nb ₂ O ₅ is 1 to 8%. Is more preferable, it is more preferable to set it as 2-8% of range, it is more preferable to set it as 2.5-8%, and it is still more preferable to set it as 3-8%. The upper limit of the content of nb ₂ O _5, preferably 7% or less, more preferably 6% or less, further preferably 5% or less.

In an embodiment where the total content of the alkaline earth metal oxide and TiO ₂ exceeds 5%, the upper limit of the Nb ₂ O ₅ content is preferably 6%, more preferably 5%, and more preferably 4% More preferably.

  ZnO is a component that acts to lower the glass transition temperature while maintaining high refractive index characteristics. However, if introduced over 15%, the devitrification resistance decreases and the dispersion also increases, so the content thereof is reduced to 0. ~ 15%. The preferred upper limit is 12%, the more preferred upper limit is 9%, the still more preferred upper limit is 7%, and the more preferred upper limit is 6%. On the other hand, the preferred lower limit is 0.1%, the more preferred lower limit is 0.5%, the still more preferred lower limit is 1%, and the more preferred lower limit is 2%.

Ta ₂ O ₅ is a high refractive index imparting component, but the raw material cost is significantly higher than that of the high refractive index imparting component. Moreover, since it is also a rare substance, its content is set to less than 13%. The conventional glass required 15% or more of Ta ₂ O ₅ in order to achieve the same characteristics as the optical characteristics of the glass of the present invention. In the present invention, the content of each component is balanced as described later. by, while maintaining the desired optical characteristics by replacing Ta ₂ O ₅ to other high refractive index-imparting components, to achieve a weight loss of Ta ₂ O _5. From the above viewpoint, a preferable range of the Ta ₂ O ₅ content is 0 to 12%, a more preferable range is 0 to 11%, and a further preferable range is 0 to 10%.

In order to further reduce the amount of Ta ₂ O ₅ while maintaining various properties of the glass, the total content of the alkaline earth metal oxide and TiO ₂ is preferably more than 5%, 6% More preferably. A more preferable range of the total content is 6 to 10%. In an embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is high, the loss resistance during reheating is replaced by replacing Ta ₂ O ₅ with at least one component of the alkaline earth metal oxide and TiO _2. Improves permeability, but further improves the resistance to devitrification during reheating by replacing Ta ₂ O ₅ with Nb ₂ O ₅ and introducing 1% or more of Nb ₂ O _5. be able to. In this embodiment, the preferable range of the Ta ₂ O ₅ content is 0 to 11%, and the more preferable range is 0 to 10%.

In order to maintain the required refractive index while maintaining Ta ₂ O ₅ in the above range, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO The ratio of the Ta ₂ O ₅ content to the total content of ₃ (Ta ₂ O ₅ / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + WO ₃ )). 23 or less. A preferable range of the ratio is 0.22 or less, a more preferable range is 0.21 or less, a further preferable range is 0.2 or less, a more preferable range is 0.17 or less, and a still more preferable range is 0.16 or less.

The optical glass of the present invention is a glass having a refractive index nd of 1.86 or more and an Abbe number νd of 38 or more. La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb with respect to the total content of B ₂ O ₃ and SiO ₂ as network forming components in order to keep the devitrification resistance good while maintaining the optical characteristics. The ratio of the total content of ₂ O ₃ ((La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is set in the range of 2 to 4. Among the high refractive index imparting components, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ serve to increase the refractive index while keeping the dispersion low. Therefore, if the ratio is smaller than 2, it is difficult to maintain the optical characteristics, and if it is larger than 4, the devitrification resistance is lowered. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the preferable lower limit of the ratio is 2.4, the more preferable lower limit is 2.6, and the more preferable lower limit is 2.8. A preferred upper limit of the ratio is 3.8, a more preferred upper limit is 3.6, and a more preferred upper limit is 3.5. On the other hand, in an embodiment in which the total content of alkaline earth metal oxide and TiO ₂ exceeds 5%, the preferred lower limit of the ratio is 2.5, the more preferred lower limit is 2.7, and the more preferred lower limit is 2.9. . A preferable upper limit of the ratio is 3.9, a more preferable upper limit is 3.7, and a more preferable upper limit is 3.6.

WO ₃ is a component for imparting a high refractive index, but when it is introduced excessively, devitrification resistance at the time of reheating is lowered. Therefore, the content is preferably 15% or less, and more preferably 10% or less. However, in the embodiment using Nb ₂ O ₅ as an optional component, the effect of improving devitrification resistance at the time of reheating due to the introduction of Nb ₂ O ₅ cannot be obtained, so the amount of WO ₃ should be 0 to 6%. Is preferred. Moreover, since the glass tends to be colored by the introduction of WO ₃ , the content is more preferably 0 to 4%, more preferably 0 to 2% regardless of the presence or absence of Nb ₂ O _5. Preferably, the content is 0 to 1%, more preferably 0 to 0.5%, and particularly preferably not introduced.

It is preferable that the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O _3, and Yb ₂ O ₃ is 30 to 70% in view of providing the optical characteristics and improving the stability as glass. In an embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the preferable lower limit of the total content is 45%, the more preferable lower limit is 46%, the still more preferable lower limit is 47%, and the more preferable lower limit is 48%, a more preferred lower limit is 49%, and a still more preferred lower limit is 50%. On the other hand, a preferable upper limit of the total content is 70%, a more preferable upper limit is 69%, a further preferable upper limit is 68%, a more preferable upper limit is 67%, a still more preferable upper limit is 66%, a still more preferable upper limit is 65%, An even more preferred upper limit is 64%.

In an embodiment where the total content of alkaline earth metal oxide and TiO ₂ exceeds 5%, the preferred lower limit of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ is 47% The more preferred lower limit is 48%, the still more preferred lower limit is 49%, the still more preferred lower limit is 50%, the still more preferred lower limit is 51%, and the still more preferred lower limit is 52%. On the other hand, a preferable upper limit of the total content is 70%, a more preferable upper limit is 69%, a further preferable upper limit is 68%, a more preferable upper limit is 67%, a still more preferable upper limit is 66%, a still more preferable upper limit is 65%, An even more preferred upper limit is 64%.

Among the network forming components, B ₂ O ₃ functions to improve the meltability and lower the glass transition temperature. In order to acquire such an effect, it is preferable to make it contain 5% or more, but in order to raise a refractive index more, it is preferable to suppress the content to 25% or less. Therefore, the preferable range of the content of B ₂ O ₃ is 5 to 25%. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the preferable range of the B ₂ O ₃ content is 5 to 20%. _A preferable lower limit of the content of B 2 _{O 3} 7%, more preferred lower limit is 8%, more preferred lower limit is 9%. On the other hand, the preferable upper limit is 19%, the more preferable upper limit is 18%, and the more preferable upper limit is 17%.

In the embodiment in which the total content of alkaline earth metal oxide and TiO ₂ exceeds 5%, the preferred range of B ₂ O ₃ content is 8-25%. _{Incidentally,} B 2 _{O 3} preferably lower limit of the content is 10%, and more preferable lower limit is 11%, more preferred lower limit is 12%. On the other hand, a preferable upper limit is 24%, a more preferable upper limit is 23%, and a further preferable upper limit is 22%.

SiO ₂ functions to improve devitrification resistance and to increase the viscosity when molding molten glass. In order to obtain such an effect, the content is preferably 1% or more, but in order to further increase the refractive index, the content is preferably suppressed to 14% or less. Therefore, the preferable range of the content of SiO ₂ is 1 to 14%. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the preferred range of the SiO ₂ content is 2 to 14%. A preferable lower limit of the SiO ₂ content of 4%, more preferable lower limit is 5%, more preferable lower limit is 6%. On the other hand, the preferable upper limit is 12%, the more preferable upper limit is 10%, and the more preferable upper limit is 8%. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ exceeds 5%, the preferred range of the SiO ₂ content is 1 to 10%. The preferable lower limit of the SiO ₂ content is 1.5%, the more preferable lower limit is 2%, and the more preferable lower limit is 2.5%. On the other hand, the preferable upper limit is 9%, the more preferable upper limit is 8%, and the more preferable upper limit is 7%.

La ₂ O ₃ is a component that imparts a high refractive index and low dispersion property as described above, but its devitrification resistance may be reduced by excessive introduction, so its content should be 30 to 60%. Is preferred. A preferred lower limit is 35%, and a more preferred lower limit is 38%. On the other hand, the preferable upper limit is 55%, the more preferable upper limit is 50%, and the more preferable upper limit is 47%. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the more preferable lower limit of the La ₂ O ₃ content is 40%. In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ exceeds 5%, the more preferable upper limit of the La ₂ O ₃ content is 45%.

Gd ₂ O _{3 is} also a component that imparts high refractive index and low dispersion characteristics. However, since there is a possibility that devitrification resistance may be reduced due to excessive introduction, the content is preferably 0 to 30%. A preferred lower limit is 1%, a more preferred lower limit is 3%, and a still more preferred lower limit is 5%. On the other hand, the preferred upper limit is 25%, the more preferred upper limit is 22%, the still more preferred upper limit is 20%, and the more preferred upper limit is 19%.

Y ₂ O _{3 is} also a component that imparts high refractive index and low dispersion characteristics. However, since there is a possibility that devitrification resistance may be reduced due to excessive introduction, the content is preferably 0 to 10%. A preferred lower limit is 1%, a preferred upper limit is 8%, a more preferred upper limit is 6%, and a more preferred upper limit is 5%.

Yb ₂ O _{3 is} also a component that imparts high refractive index and low dispersion characteristics. However, since there is a possibility that devitrification resistance may be reduced due to excessive introduction, the content is preferably 0 to 5%. A preferred upper limit is 3%, a more preferred upper limit is 2%, and a more preferred upper limit is 1%.

Sb ₂ O ₃ functions as a fining agent when added in an appropriate amount. The addition amount is preferably 0 to 1% on an external basis, more preferably 0 to 0.5%, further preferably 0 to 0.3%, and 0 to 0.2%. It is more preferable to do.
In addition, as can be introduced as an optional _component, it may be exemplified _{MgO, CaO, SrO, BaO,} GeO 2, Li 2 O, Na 2 O, K 2 O, a _{Bi 2} O 3, TiO 2.

MgO, CaO, SrO, and BaO function to improve the meltability, and can also be introduced as a carbonate raw material or a nitrate raw material, so that the defoaming effect is enhanced. It is also a component that is relatively easy to maintain devitrification resistance during reheating by replacement with Ta ₂ O ₅ . However, since the refractive index may be lowered due to excessive introduction or the stability as glass may be impaired, MgO, CaO, SrO and BaO are preferably 0 to 20% in total content. It is more preferably 10%, further preferably 0 to 7%, and further preferably 0 to 5%.

As for MgO, CaO, SrO, and BaO, it is easier to maintain the optical characteristics within a required range by replacing Ta ₂ O ₅ with B ₂ O ₃ or SiO ₂ instead of replacing with MgO, CaO, SrO, or BaO. Therefore, in order to acquire the said effect, you may introduce | transduce 0.5% or more of MgO, CaO, SrO, and BaO in a total content within the said range.

  From the above viewpoint, the preferable range of MgO is 0 to 8%, the more preferable range is 0 to 4%, the still more preferable range is 0 to 2%, and the more preferable range is 0 to 1%.

  The preferable range of CaO is 0 to 10%, the more preferable range is 0 to 5%, the still more preferable range is 0 to 3%, and the more preferable range is 0 to 1%.

  A preferable range of SrO is 0 to 15%, a more preferable range is 0 to 8%, a further preferable range is 0 to 5%, and a more preferable range is 0 to 2%.

  The preferable range of BaO is 0 to 20%, and the more preferable range is 0 to 10%.

  In an embodiment in which the total content of the alkaline earth metal oxide and TiO2 is 5% or less, the more preferable range of the BaO content is 0 to 5%, and the more preferable range is 0 to 3%. On the other hand, in the embodiment in which the total content of the alkaline earth metal oxide and TiO2 exceeds 5%, the more preferable range of BaO is 0 to 10%, and the more preferable range is 1 to 8%. Since BaO has the strongest function of increasing the refractive index among the alkaline earth metal oxides suitable as a component constituting the optical glass, it is preferably introduced positively.

GeO ₂ is an arbitrary component having a network forming function and having a larger function of increasing the refractive index than SiO ₂ and B ₂ O ₃ . However, if it is introduced excessively, the refractive index is lowered and the manufacturing cost increases because it is a very expensive component. Therefore, the content is preferably 0 to 15%, more preferably 0 to 5%, and even more preferably not introduced.

When a small amount of Li ₂ O, Na ₂ O, or K ₂ O is introduced, the meltability is improved, the glass transition temperature and the softening temperature are lowered, and the annealing temperature and the molding temperature can be lowered. However, since the refractive index decreases or the devitrification resistance deteriorates due to excessive introduction, the Li ₂ O content is preferably 0 to 1%, more preferably 0 to 0.6%. Preferably, it is 0 to 0.4%, more preferably 0 to 0.2%. The content of Na ₂ O, preferably set to 0 to 2%, more preferably to 0 to 1.2%, more preferably to 0 to 0.8%, 0 to 0.4 % Is more preferable. The content of K ₂ O is preferably 0 to 3%, more preferably 0 to 2%, further preferably 0 to 1.5%, and 0 to 1%. Even more preferable.

Bi ₂ O ₃ works to reduce the glass transition temperature and softening temperature and increase the refractive index when introduced in a small amount, but the glass is strengthened by excessive introduction and the devitrification resistance is reduced. The content is preferably 0 to 6%, more preferably 0 to 4%, further preferably 0 to 3%, and still more preferably 0 to 2%.

TiO ₂ increases the refractive index by introducing an appropriate amount, but dispersion increases, glass is colored, and devitrification resistance decreases by excessive introduction. Therefore, its content is 0 to 12%, preferably 0. -10%, more preferably 0-8%, still more preferably 0-7%. TiO ₂ has a high single bond strength and is considered to play a role as a modified oxide as well as to form a network by replacing a part of the network forming component. When the glass is stabilized by TiO ₂ are involved in network formation can be considered. However, since the coloration of the glass by the introduction of TiO ₂ is able to increase, will either introduce TiO ₂ colored glass, such as stability, which specifications may be determined by considering whether the priority. When TiO ₂ is introduced, the amount is 0.1% or more within the above range, preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and still more preferably 2%. That's it. On the other hand, when priority is given to color reduction, it is preferable not to introduce TiO ₂ .

In the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, the TiO ₂ content is preferably 0 to 5%, more preferably 0 to 3%, and 0 to 2 % Is more preferable, and 0 to 1% is even more preferable.

On the other hand, in the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ exceeds 5%, the TiO ₂ content is preferably 1 to 12%, more preferably 2 to 10%. It is more preferable to set it as 5 to 9%, and it is still more preferable to set it as 3 to 8%.

In addition, in order to make the above various characteristics better, B ₂ O ₃ , SiO ₂ , La, in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less or more than 5%. ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , Ta ₂ O ₅ , MgO, CaO, SrO, BaO, Li ₂ O, Na ₂ O The total content of K ₂ O and TiO ₂ is preferably 95% or more, more preferably 96% or more, still more preferably 98% or more, and even more preferably 99% or more. 100% is even more preferable.

Further, B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , Ta ₂ O ₅ , MgO, CaO, The total content of SrO, BaO and TiO ₂ is preferably 95% or more, more preferably 96% or more, still more preferably 98% or more, and even more preferably 99% or more, Even more preferably 100%.

Among them, in an embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ is 5% or less, B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb The total content of ₂ O ₅ , Ta ₂ O ₅ , MgO, CaO, SrO and BaO is preferably 95% or more, more preferably 96% or more, still more preferably 98% or more, It is more preferable to set it to 99% or more, and it is more preferable to set it to 100%. In particular, the total content of B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ is preferably 95% or more. 96% or more, more preferably 98% or more, still more preferably 99% or more, and even more preferably 100%.

On the other hand, in the embodiment in which the total content of the alkaline earth metal oxide and TiO ₂ exceeds 5%, B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb The total content of ₂ O ₅ , Ta ₂ O ₅ , MgO, CaO, SrO, BaO and TiO ₂ is preferably 95% or more, more preferably 96% or more, and 98% or more. More preferably, it is more preferably 99% or more, and even more preferably 100%. In particular, the sum of B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , MgO, CaO, SrO, BaO and TiO ₂ The content is preferably 95% or more, more preferably 96% or more, still more preferably 98% or more, even more preferably 99% or more, and even more preferably 100%. preferable.
In any of the preferred embodiments, SB ₂ O ₃ may be added within the above range on an external basis.
Pb, As, Cd, Cr, Th, and U are preferably not introduced because they are toxic and radioactive.

  Hf, Lu, Sc, Ga, and In can also be introduced. However, the glass of the present invention can achieve the object of the invention without introducing these components. And since all the said components are expensive, it is preferable not to introduce Hf, Lu, Sc, Ga, and In from the viewpoint of cost.

In addition, SnO ₂ can be introduced in an amount of 1.0% or less in order to enhance the clarification effect. However, since the introduction of SnO ₂ is not essential, it is not necessary to introduce SnO ₂ .

  Although it is possible to introduce F if the amount is small, it is preferable not to introduce it because it shows volatility and may cause a variation of striae and optical constant.

  The optical glass of the present invention is produced by rapidly cooling a molten glass obtained by heating, melting, clarifying and homogenizing a glass raw material. As a glass raw material, an oxide, boric acid, carbonate, nitrate or the like corresponding to a glass component may be appropriately weighed and a prepared raw material obtained by sufficiently stirring may be used. The raw material thus prepared is roughly melted to make a cullet raw material, and the cullet raw material is prepared so as to obtain the required optical characteristics, and then melted, clarified and homogenized to make a molten glass, The molten glass may be produced by directly introducing an unvitrified raw material such as a powder raw material or a pellet raw material into a melting vessel without undergoing rough melting, and heating, melting, clarifying, and homogenizing.

  The optical glass of the present invention has excellent devitrification resistance at the time of reheating, but the refractive index is not high because it is a glass having a relatively small amount of network-forming components due to the provision of high refractive index and low dispersion characteristics. The liquidus temperature is higher than that of glass, and the glass will be devitrified unless the temperature at the time of molding the molten glass is increased. As a result, the viscosity of the molten glass at the time of molding becomes low, and striae are likely to occur in the glass molded body. In order to solve such a problem, it is desirable that the flow of the molten glass at the time of molding is made as straight as possible so that the outer flow and the inner flow of the molten glass do not mix. In addition, it is desirable to rapidly cool the glass by making the surface area of the molten glass as large as possible from the viewpoint of preventing devitrification when forming the molten glass, and by quickly depriving the glass of heat by bringing the mold into contact with the glass. As satisfying these conditions, it is desirable to form a rod-shaped glass molded body.

  In the optical glass of the present invention, the glass transition temperature Tg can be set to 730 ° C. or lower, and the crystallization peak temperature described later can be set to 810 ° C. or higher. However, in the same glass, since Tx-Tg can be taken as large as 110 ° C. or more, the devitrification resistance at the time of reheating can be made excellent.

  A preferred range of the glass transition temperature Tg is 720 ° C. or less, a more preferred range is 710 ° C. or less, a preferred range of the crystallization peak temperature is 815 ° C. or more, a more preferred range is 820 ° C. or more, and a further preferred range is 825 ° C. or more. A more preferable range is 830 ° C. or higher.

  In addition, a preferable range of Tx-Tg is 120 ° C. or higher, a more preferable range is 125 ° C. or higher, a further preferable range is 130 ° C. or higher, a more preferable range is 135 ° C. or higher, a still more preferable range is 140 ° C. or higher, and a still more preferable range. Is 145 ° C or higher, and an even more preferable range is 150 ° C or higher.

Next, the glass molded body of the present invention will be described.
[Glass compact]
The glass molded body of the present invention has two embodiments of glass molded bodies I and II. The glass molded body I is a rod-shaped glass molded body made of the optical glass of the present invention. According to the glass molded body of the present invention, the above-mentioned effects can be obtained, and it is not necessary to forcibly reduce the viscosity at the liquidus temperature in order to prevent striae and devitrification. It is possible to set the composition of the glass with an emphasis on the point of making it more favorable.

  The glass molded body II focuses on such points, and has a refractive index nd of 1.86 or more and an Abbe number νd of 38 or more, and a difference between the crystallization peak temperature Tx and the glass transition temperature Tg (Tx -Tg) is 110 ° C. or higher, preferably 120 ° C. or higher, more preferably 125 ° C. or higher, more preferably 130 ° C. or higher, more preferably 135 ° C. or higher, still more preferably 140 ° C. or higher, even more preferably 145 ° C. or higher. Still more preferably, it is a rod-shaped glass molded body made of optical glass at 150 ° C. or higher. Also with this glass molded body II, the same effect as that of the glass molded body I can be obtained.

  The crystallization peak temperature is determined as follows. In differential scanning calorimetry, an endothermic peak appears when the glass sample is heated, and an exothermic peak appears when the temperature is further raised. The point at which this exothermic peak begins to occur is the crystallization peak temperature Tx.

  In differential scanning calorimetry, a differential scanning calorimetric curve (DSC curve) is obtained with the horizontal axis representing temperature and the vertical axis representing the amount corresponding to the exothermic endotherm of the sample. In this curve, when the exothermic peak appears from the base line, the intersection of the tangent and the base line at which the slope becomes maximum is defined as the crystallization peak temperature Tx.

  The crystallization peak temperature Tx can be measured using a sample obtained by sufficiently pulverizing glass with a mortar, for example, using a high-temperature differential scanning calorimeter “Thermo Plus 2 / DSC8270” manufactured by Rigaku Corporation. .

  The glass transition temperature Tg can be measured by preparing a cylindrical glass sample having a diameter of 5 mm and a length of 20 mm and using, for example, a thermomechanical analyzer “TMA4000s” manufactured by Bruker AXS. .

  When a glass material is heated and softened and formed into a required shape, the glass material needs to be heated to a temperature higher than the glass transition temperature. Since the glass becomes devitrified when the temperature of the glass at the time of forming reaches a temperature range where the glass is crystallized, a glass having a small Tx-Tg is disadvantageous in forming while preventing devitrification. Therefore, in the present invention, Tx−Tg is in the above range. When the composition is set so that Tx-Tg is increased in the high refractive index and low dispersion glass, the degree of freedom in setting the composition for increasing the viscosity at the liquidus temperature is restricted, so even a glass having a low viscosity at the liquidus temperature is optical. Tx-Tg can be made a required value or more by using a glass molded body having a uniform shape and a large surface area.

As the optical glass constituting the glass molded body II of the present invention, it is preferable that the content of Ta ₂ O ₅ is 0% or more and less than 13% by mass because of the reason described in the explanation of the optical glass of the present invention. , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and the ratio of Ta ₂ O ₅ content to the total content of WO ₃ is 0.23 or less Some are preferred. Furthermore, in terms of mass%, Nb ₂ O ₅ is contained in an amount of 0 to 15%, ZrO ₂ is contained in an amount of ₂ to 10%, ZnO is contained in an amount of 0 to 9%, and B ₂ O ₃ and SiO ₂ are added in a total amount of 12 to 30%. And containing La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ in a total amount of 55 to 80%, and containing B ₂ O ₃ and SiO ₂ The ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O _{3 to} the total content of is preferably 2 to 4.
In any of the embodiments of the glass molded body of the present invention, it is preferable that the side surface is a surface formed by solidifying molten glass.

Next, the manufacturing method of the glass forming body of this invention is demonstrated.
[Method for producing glass molded body]
The method for producing a glass molded body of the present invention has two embodiments, production methods I and II.
The method I for producing a glass molded body is a method for producing a glass molded body in which a molten glass obtained by heating and melting a glass raw material is poured into a mold to form a glass molded body made of optical glass.
Using a mold having a through hole, forming while continuously pouring molten glass into the through hole, and continuously drawing the molded glass from the through hole,
The molten glass is cooled by contacting the inner wall of the through hole so as to surround the molten glass moving in the through hole, and a glass molded body made of the optical glass of the present invention is produced.

On the other hand, the manufacturing method II of the glass molded body is a method for manufacturing a glass molded body that forms a glass molded body made of optical glass by pouring a molten glass obtained by heating and melting a glass raw material into a mold.
Using a mold having a through hole, forming while continuously pouring molten glass into the through hole, and continuously drawing the molded glass from the through hole,
The molten glass is cooled by contacting the inner wall of the through hole so as to surround the molten glass moving in the through hole, the refractive index nd is 1.86 or more, the Abbe number νd is 38 or more, the crystallization temperature Tx and the glass transition temperature Tg. The glass molding which consists of optical glass whose difference (Tx-Tg) is 110 degreeC or more is produced. This production method II corresponds to a method for producing the glass molded body II of the present invention.
Hereinafter, the preferable aspect regarding the manufacturing method of a glass forming body is demonstrated.

  In the said aspect, using the casting_mold | template which has a through-hole, the molten glass which flows out out of a pipe is poured continuously into the inlet of the said through-hole, and it takes out continuously from the outlet of the said through-hole, and shape | molds it into solid glass. In at least a partial region (cooling region) in the through-hole, the glass side surface in the through-hole is brought into contact with the inner wall of the through-hole to remove heat from the side surface, and the central portion of the glass And bring the temperature of the side closer.

  In this method, a mold having a through hole is used, and molten glass flowing out from a pipe is continuously poured into the inlet of the through hole, and continuously taken out from the outlet of the through hole to be formed into a solid glass.

  In order to form an optically homogeneous glass molded body, it is important not to disturb the flow of the molten glass even in the mold. In order to form a hollow glass, a mechanism for partially blocking the flow of the glass is provided in the mold so that the molten glass does not flow into the hollow portion, that is, the portion not filled with the glass. For example, when it is desired to form the central axis portion of the rod-shaped glass molded body into a hollow shape, a highly heat-resistant rod is arranged along the central axis of the mold, like the mold, and molten glass is poured so as to surround the rod. At that time, a mechanism for preventing the glass from filling the hollow portion corresponding to the rod disturbs the flow of the molten glass. For the purpose of obtaining an optically homogeneous glass molded body, the glass molded body is therefore a solid glass molded body having no hollow portion.

  The mold to be used has a through hole, and the through hole has an inlet for pouring the molten glass and an outlet for taking out the solid glass, and the molten glass flowing out from the molten glass outflow pipe is used as the inlet of the through hole. Pour continuously. And in at least a partial region (cooling region) in the through hole, a side surface of the glass from the melted state until at least the surface is solidified, that is, a surface facing the direction perpendicular to the direction in which the glass moves as a whole. By bringing the glass into contact with the inner wall of the through hole, the heat of the glass is taken from the side surface. This can reduce or prevent the occurrence of striae in glass that is likely to generate striae, particularly in glass that has a low viscosity when flowing out. In particular, the glass can be efficiently cooled by bringing the entire circumference of the side surface into contact with the inner wall of the through hole so that no gap is generated between the side surface and the inner wall of the through hole.

  As will be described later, in order to prevent devitrification of the glass, it is preferable that the temperature of the molten glass that flows out from the pipe and flows into the through-hole inlet is equal to or higher than the liquid phase temperature. Specifically, the surface temperature of the molten glass poured into the through-hole inlet is preferably in the range of (liquid phase temperature + 10 ° C.) to (liquid phase temperature + 100 ° C.). The surface temperature of the molten glass flow flowing into the through-hole inlet can be regarded as the same as the temperature at the lower end of the outflow pipe, and the temperature at the lower end of the outflow pipe can be measured with a thermocouple. Moreover, the temperature of the center part of the molten glass poured into the through-hole inlet can be measured by inserting a thermocouple into the molten glass. The temperature difference between the surface temperature of the molten glass flow measured in this way and the temperature at the center is preferably within 120 ° C, more preferably within 60 ° C, and even more preferably within 50 ° C. preferable.

  The temperature of the mold (through hole inner wall) is preferably determined in consideration of (1) the glass does not melt, (2) the molten glass spreads in the through hole without any gap. The mold may be provided with a heater or a cooler as necessary for temperature control. When the temperature of the surface of the glass molded body at the outlet of the through hole is too high, the mold is cooled by air cooling or by providing a water-cooled plate, and when the temperature is too low, it is heated by a heater. Can be adjusted.

  The temperature of the upper inner wall of the through hole in the cooling region can be, for example, 50 to 150 ° C. lower than the glass transition temperature of the glass to be formed. As will be described later, when the entire glass flow path in the through hole is used as a cooling region, the temperature of the inner wall of the through hole can be 20 to 50 ° C. lower than the glass transition temperature of the glass to be formed in the vicinity of the inlet. When using a molding furnace, the temperature is 100 to 400 ° C. lower than the glass transition temperature in the vicinity of the outlet, and the temperature near the inlet is equal to or higher than the temperature near the outlet in the intermediate portion between the inlet and the outlet. be able to. The temperature of the inner wall of the through hole can be measured by making a hole in the mold and inserting a thermocouple as close as possible to the inner wall of the through hole.

  In this way, in the cooling region, the glass side surface is brought into contact with the inner wall of the through hole to remove heat, thereby promoting the cooling of the glass and preventing or reducing the occurrence of striae. However, as explained above, particularly in a glass having a low viscosity at the time of outflow, if the temperature difference between the inside and the surface of the glass taken out from the mold is excessively large, the glass may be broken or broken by internal stress. . Therefore, by passing the glass that has passed through the cooling region in an environment that is 150 ° C. lower than the glass transition temperature (Tg) (Tg−150 ° C.) or more, the temperature of the center and side surfaces of the glass is increased. It is desirable that Thereby, the glass rapidly cooled in the cooling region to reduce or prevent striae can be prevented from being broken or broken by internal stress after passing through the cooling region.

  The cooling region may be the entire glass channel in the through hole. In this case, the environment above (Tg−150 ° C.) can be an atmosphere to which the glass taken out from the through hole outlet is exposed. Thus, when the glass taken out from the through-hole outlet is passed through an atmosphere of (Tg−150 ° C.) or higher to bring the temperature of the central portion and the side of the glass closer, the glass taken out from the through-hole outlet is It is preferable to immediately put in the atmosphere.

  In addition, the inside of the through hole is roughly divided into two regions, the inlet side and the outlet side, and the glass side is brought into contact with the inner wall of the through hole in the region on the inlet side and the operation of taking the heat of the glass from the side is performed. It is also possible to control the inner wall temperature of the through hole in the region to a temperature lower than the glass transition temperature Tg by 150 ° C. (Tg−150 ° C.) or higher. In this case, the environment above (Tg−150 ° C.) is the temperature-controlled outlet side region. Here, the region on the inlet side and the region on the outlet side may be insulated to facilitate the temperature control in both regions.

  In any of the above cases, the operation of bringing the temperature of the central portion and the side surface of the glass closer is preferably performed by passing the glass under an environment of 100 ° C. lower than the glass transition temperature (Tg-100 ° C.) or more. It is more preferable to carry out by passing the glass under an environment of 50 ° C. lower than the transition temperature (Tg−50 ° C.) or more, and it is more preferred to carry out by passing the glass under the environment of the glass transition temperature Tg.

  If the temperature in the environment is too low, the furnace must be lengthened when an operation for bringing the temperature at the center and side of the glass closer is performed in the molding furnace. In addition, when performing an operation for bringing the temperature of the central portion and the side surface of the glass closer in the mold, the mold must be made long. As a result, a large space is required, and it becomes difficult to control the glass extraction speed from the through hole outlet.

  Moreover, when cleaving a glass molded object, since the Young's modulus of glass will increase when the temperature of glass becomes low too much, it will become difficult to cleave. In the present invention, the glass is a continuous body from the molten glass to the glass molded body, and when the glass molded body is cleaved with a large force, the impact reaches the molten glass in the mold and disturbs the flow of the glass. There is a possibility of causing a problem in obtaining a simple glass molded body. Although cutting with a wire saw or a grindstone is possible, the glass must be cooled to near room temperature, and such cooling requires a space for slow cooling as long as several tens of meters. Therefore, it is not preferable. In order to perform the cleaving of the glass molded article satisfactorily, the glass temperature is preferably not higher than the transition temperature, more preferably 150 ° C. lower than the transition temperature and lower than the transition temperature, more preferably lower than the transition temperature. Further, it is more preferable that the temperature be 100 ° C. or lower and the transition temperature or lower, more preferably 50 ° C. or lower and the transition temperature or lower than the transition temperature, and particularly preferably near the transition temperature. Considering the above points, in the present invention, the operation of bringing the temperature of the central portion and the side surface of the glass closer is performed in an environment of (Tg−150 ° C.) or higher. After the operation to bring the temperature of the center and side of the glass closer, that is, after reducing the distortion, the glass molded body is cleaved or cut to separate the glass molded body without damaging it at a desired position. Can do.

  The upper limit of the temperature for performing the operation of bringing the temperature of the inside and the side of the glass closer to the temperature may be a temperature at which the outer diameter shape of the glass formed by rapid cooling of the glass side surface (cross-sectional shape perpendicular to the take-out direction) does not deform, Preferably it is below the softening temperature of glass, more preferably below the softening temperature.

  When the above operation is performed in an atmosphere, a furnace called a molding furnace is connected to the outlet of the through hole, and the glass continuously taken out from the outlet of the through hole advances into the furnace as it is, and the temperature of the center and the side approaches. You should just go out of the furnace when it reaches the state. In addition, the time for passing through the furnace may be a time that can reduce the internal stress of the glass molded body to such an extent that no explosive destruction occurs or to the extent that it does not break due to slight thermal shock or mechanical shock. . For this purpose, the length of the forming furnace along the glass take-out direction may be determined appropriately by experiments or the like in consideration of the glass take-out speed and the passage time in the furnace. The atmospheric temperature control in the furnace can be performed, for example, by controlling the current value flowing through the heater arranged in the furnace or the time during which the current flows.

As described above, the temperature difference between the glass central portion and the side surface is made to be, for example, 0 to 150 ° C., preferably 0 to 100 ° C., more preferably 0 to 50 by performing the operation of bringing the temperature of the central portion and the side surface of the glass closer. It can be set to ° C. Note that the operation of bringing the temperature of the central portion and the side surface of the glass closer to each other is different from annealing, which is an operation of gradually cooling the glass to near room temperature, and ends when the temperature of the glass is considerably higher than room temperature.
Next, the mold to be used will be described.

  From the viewpoint of preventing glass fusion, spreading, bending, etc., the ratio of the inner diameter to the length of the through hole (inner diameter / length) in the mold is preferably in the range of 1/50 to 3 times. More preferably, it is a range of 1/20 to 2 times. The inner diameter of the through hole should be determined in consideration of the outer diameter of the glass molded body to be obtained, and can be set to, for example, 10 to 100 mm. However, it is not intended to limit to this dimension.

  In order not to obstruct the movement of the glass in the mold, the cross-sectional shape perpendicular to the glass movement direction of any portion through which the glass of the mold passes is made equal to the cross-sectional shape perpendicular to the movement direction of the glass molding. It is desirable. If the temperature distribution of the mold is not controlled, the temperature on the inlet side of the mold during molding will be higher than the temperature on the outlet side. Sometimes the inner diameter of the through hole along the moving direction of the glass does not become constant. In this method, the inner diameter of the through-hole is increased from the inlet to the outlet, and thermal expansion is performed so that the inner diameter becomes constant along the moving direction of the glass during molding or slightly expands toward the outlet. In consideration of the above, it is preferable that the through hole is tapered and the inclination of the taper is determined. In particular, when molding glass with low viscosity at the time of outflow or when using a mold made of a material with high glass wettability, it is desirable to increase the inclination of the taper in order to prevent the glass from sticking to the mold. .

  The material of the mold is preferably a heat-resistant metal such as carbon, casting or nickel. Moreover, it is preferable to perform the process which produces a glass molded object from molten glass in an inert atmosphere from a viewpoint of preventing deterioration of a casting_mold | template.

  In the case where the atmosphere affects the quality of the glass molded body, it is preferable to surround the path of the molten glass between the pipe outlet and the through hole inlet and control the atmosphere therein. In this method, the area of the surface exposed to the atmosphere of the high-temperature glass is not large as in the conventional molding method, so even if the pipe tip and the entire molding apparatus are sealed and the atmosphere inside is not replaced, If the inner atmosphere is replaced with a desired gas so as to surround the minimum necessary narrow range as described above, the purpose of the atmosphere control can be achieved. In order to suppress the volatilization from the high temperature glass surface, reduce or prevent the glass wetting to the outer peripheral surface of the pipe tip and improve the quality of the glass molded body, the above atmosphere is a dry atmosphere, an inert gas atmosphere, Alternatively, a dry inert gas atmosphere is preferable.

  In this method, the glass that has passed through the cooling region is passed through an environment having a temperature of 150 ° C. lower than the glass transition temperature or higher, regardless of the presence or absence of an operation for bringing the temperature at the center and side of the glass closer, When forming a molded object from the glass containing a volatile component, for example, a boric acid component, it is suitable as a method of reducing and preventing striae.

  A more preferable embodiment in this embodiment is a method using a mold having a through hole in which an inlet and an outlet communicate linearly. In this method, it is preferable to place the mold so that the inlet is positioned higher than the outlet and to pour the molten glass so that the height of the molten glass liquid surface in the through hole is constant.

  An example of the preferred embodiment is shown in FIG. As shown in FIG. 1, a molten glass 9 flowing down in a pipe 1 is poured into a mold 2 and formed into a glass molded body 11 in the process of moving the glass from a high position to a low position. As shown in FIG. 1, if the portion where the poured glass passes is a through hole that linearly connects the inlet and the outlet, the flow of the molten glass becomes smoother in the mold and the flow is disturbed. As a result, an optically homogeneous glass molding can be more stably produced.

  In this method, as shown in FIG. 1, it is preferable to arrange the mold 2 so that the central axis of the through hole is vertical (matches the vertical line). However, the central axis may be inclined with respect to the vertical line. When the mold 2 is arranged with the central axis being vertical, the flow of the molten glass 9 flowing down vertically in the pipe 1 proceeds in the mold 2 toward the outlet without changing the overall flow direction. The disturbance of the flow in the mold is further reduced, and the striae reducing effect can be further enhanced.

  Moreover, a straight glass molded body can be obtained by pouring the molten glass 9 into a through hole in which the inlet and the outlet are linearly connected. A straight glass molded body is convenient for processing a glass molded body to produce a glass material for press molding or for producing an optical element. In order to obtain a glass molded body having a straight central axis and having the same cross-sectional shape and dimensions perpendicular to the central axis at an arbitrary position, a through-hole that linearly connects the inlet and the outlet It is desirable that the glass 2 taken out from the mold 2 is uniformly cooled. By performing uniform cooling, the shrinkage of the glass can be made uniform and the straightness of the glass molded body can be maintained. Moreover, in this invention, there also exists an advantage that the rectilinearity of a glass molded object can be improved by performing operation which brings the temperature of the center part and side surface of glass close as mentioned above.

In order to stabilize the molding conditions, it is preferable to make the height of the liquid surface of the molten glass 9 in the through hole constant. For that purpose, the outflow amount of the molten glass 9 from the pipe 1 may be made constant and the speed at which the glass is taken out from the outlet may be made constant. However, since the outflow amount of the molten glass may slightly vary with time, it is desirable to control the speed at which the glass is taken out from the mold 2 so that the height of the liquid surface is always constant.
Next, glass removal from the through hole outlet will be described.

  In this method, the glass can be taken out from the through-hole outlet by downward movement due to its own weight, pulling out the glass from the through-hole outlet, gravity applied to the glass, and pulling out the glass by applying a pulling force. It is also possible to use the extraction method. Moreover, since glass hardly extends by taking out, the glass taking-out speed corresponds to the moving speed of the taken-out glass molded body 11. The control of the take-out speed is to control the force for pulling out the glass molded body so that the take-out speed becomes a desired speed, or when the glass moves downward at a speed larger than the desired speed by its own weight, glass forming is performed. This means that a force that decelerates the body is applied to control the take-out speed to a desired speed.

  If the glass extraction speed from the through-hole exit is too large or too small, the height of the liquid surface of the molten glass 9 in the through-hole is not constant, and a gap is formed between the inner wall of the through-hole and the glass. The dimensions of are not stable. In an extreme case, the molten glass 9 overflows from the mold 2 or the shape of the glass molded body becomes defective. Therefore, it is preferable to control the extraction speed.

  As an example of control of the taking-out speed of the glass molded body, as shown in FIG. 1, the glass molded body 11 is held by holding the surface (side surface) 6 formed by the inner wall of the through-hole of the glass taken out from the through-hole outlet. The method of controlling the speed taken out from the outlet of the can be mentioned. For example, in a state where the side surface 6 of the glass molded body 11 is sandwiched between the plurality of rollers 3 so that the roller 3 and the glass molded body side surface 6 do not slip, the rotational speed of the roller 3 is controlled to control the glass molded body. Controls the downward movement speed. It is desirable that a plurality of sets of the plurality of rollers 3 are arranged along the movement path of the glass molded body, and the gravity acting on the glass molded body is dispersed and supported by the plurality of sets of rollers. By doing in this way, it can prevent more reliably that the glass forming body 11 slips between the rollers 3 and control of taking-out speed becomes impossible. The roller 3 is preferably disposed in the molding furnace 7. The distortion of the glass molded body that has passed through the molding furnace 7 is reduced, and the glass molded body below the roller 3 is suspended by being held by the roller 3. Therefore, even if the glass molded body below the roller 3 is separated from the upper glass, the glass take-out speed is not adversely affected. Further, since the distortion of the glass molded body exiting the molding furnace 7 is reduced, the glass is not damaged by the separation of the glass molded body. Furthermore, if the annealed glass molded body is cut or cleaved at a position after passing through the holding position, it is advantageous because the pouring of the molten glass into the mold does not have to be interrupted. In this way, since the weight of the glass molded body to be held does not have to be excessive, it is advantageous in terms of controlling the glass take-out speed, and the glass molded body separated while molding the glass molded body is advantageous. It can be sent to the next step, and the productivity of the glass molded body can be increased.

  On the other hand, in the method of controlling the take-out speed while holding the glass side surface, if the force for sandwiching the glass is excessively increased, the glass is damaged, and thus a force exceeding a predetermined force cannot be applied. Therefore, when the weight of the glass molded body increases, the glass molded body slides between the rollers, and speed control becomes difficult. In order to avoid such a situation, a method of controlling the glass extraction speed from the through hole by supporting the tip of the glass extracted from the outlet of the through hole may be used. An example is shown in FIG. Unlike the method of holding the side surfaces, this method does not hold the glass molded body by frictional force, and is suitable for molding a large-weight glass molded body.

  In any of the above take-out speed control methods, the take-out speed is controlled by monitoring the liquid level of the molten glass 9 in the mold 2 with the liquid level sensor 4, and the liquid level is higher than the reference height based on the monitor signal. If the liquid level is higher, the take-out speed can be increased, and if the liquid level is lower than the reference height, the take-out speed can be reduced. For example, the monitor signal is input to the take-out speed controller 5, the reference height is compared with the monitored liquid level in the controller 5, and the result is fed back to the take-out speed. In the method of controlling the take-out speed by sandwiching the glass side surface with the roller 3 (see FIG. 1), the control signal output from the controller 5 is input to the controller of the motor that rotates the roller 3, and the rotation speed of the roller 3 is controlled. Can do. In the method of controlling the extraction speed by supporting the tip of the glass taken out from the outlet of the through hole (see FIG. 2), a control signal output from the controller 5 is output to the actuator of the mechanism (support mechanism 8) that supports the tip. By inputting, it is possible to control so that the moving speed of the member supporting the glass front end becomes a desired speed. The method of monitoring the height of the molten glass liquid surface in the mold is not particularly limited, and examples thereof include a method using a thermometer, a laser sensor, or the like.

By the way, if the angle formed by the central axis of the through hole and the vertical line is increased, the frictional force between the mold through hole and the side surface of the glass molded body increases. Even with the holding method, the take-out speed can be controlled. Therefore, when a heavy glass molded body is formed from a glass whose viscosity at the time of outflow is not extremely low, the mold can be arranged with the central axis of the through hole inclined with respect to the vertical line.
Next, a method for separating the glass molded body being taken out will be described.

  The glass taken out from the outlet of the through-hole is reduced in internal stress by the operation of bringing the temperature of the inside and the side close to each other, and the risk of explosive breakage or breakage due to slight thermal shock or mechanical shock is eliminated. Furthermore, in order to cool this glass to room temperature, the glass must be drawn out of the mold for a long time. For this purpose, a large space may be required below the mold, or the weight of the glass molded body may be excessive, and it may be difficult to precisely control the removal speed. Therefore, it is desirable to separate the glass molded body when the temperature of the glass molded body is near the glass transition temperature.

  Specific examples of the separation method are shown in FIGS. As shown in FIG. 3, a marking line is formed on a part of the side surface of the glass molded body at a predetermined position by a scribing process in a direction perpendicular to the take-out direction of the glass molded body. Place a fulcrum that locally supports the side surface opposite to the position on which the scribe processing is performed across the central axis of the glass, while restricting the movement of the glass molded body above the fulcrum by the fulcrum, A method is preferred in which pressure is applied in the horizontal direction below the scribe processing position, and the glass molded product is broken by breaking the glass molded product from the scribe-processed portion around the fulcrum as shown in FIG.

  Further, when cleaving a glass molded body having a large outer diameter, a metal jacket having a water channel formed therein is locally brought into contact with the scribe portion as shown in FIG. A crack that goes from the inside of the glass to the inside of the glass is generated, and the side opposite to the marking line is supported by a fulcrum across the central axis of the glass molding, and the force is applied to the glass molding below the marking line, and the crack is the fulcrum. It is preferable to crush the glass molded body by applying a torque so that it grows toward the portion supported by.

  The magnitude of the internal stress generated in the cooling process varies depending on the shape and size of the glass molded body. For example, in the case of an extremely thin glass molded body such as an optical fiber, it is difficult to make a temperature difference between the inside and the surface. Further, even in a sheet-like glass having a very thin thickness, it is difficult to make a temperature difference between the inside and the surface. Conversely, a rod-like glass having a large outer diameter or a thick plate-like glass has a large temperature difference between the inside and the surface, and a large internal stress is likely to occur during the cooling process. As such a glass molded body, there is a plate-like glass having a thickness of 3 mm or more, or a rod-like glass having an outer diameter of 3 mm or more. Therefore, the present invention is suitable for forming a sheet glass having a thickness of 3 mm or more, and more preferable for forming a sheet glass having a thickness of 5 mm or more. Further, it is suitable for molding rod-shaped glass having an outer diameter of 3 mm or more, suitable for molding rod-shaped glass having an outer diameter of 5 mm or more, and further suitable for molding rod-shaped glass having an outer diameter of 10 mm or more. It is more suitable for forming a rod-shaped glass having an outer diameter of 10 mm or more.

  In this specification, “rod glass” refers to a circle, an ellipse, a square, or a cross-sectional shape such as a rectangle or polygon whose ratio of long side to short side (long side / short side length) is 2 or less. A glass molded body having The “plate glass” refers to a glass plate having a ratio of width to thickness (width / thickness) exceeding 2.

  The outer diameter of the rod-shaped glass means the length of the thinnest portion of the glass in a cross section perpendicular to the central axis of the rod-shaped glass. For example, in cylindrical glass, the cross section perpendicular to the central axis of the cylinder is a circle, so the outer diameter is the diameter of the circle, and in elliptical column glass, the cross section perpendicular to the central axis is oval. The outer diameter is the minor axis of the ellipse, and in the case of regular square columnar glass, the cross section perpendicular to the central axis is a square, so the outer diameter is the length of one side of the square. The rectangular columnar glass having a rectangular cross section perpendicular to the central axis has an outer diameter corresponding to the length of the short side of the rectangle.

In the method described so far, the molten glass flowing out from the pipe is continuously poured into the mold without interruption, and by placing one mold below the outlet of the pipe flowing out of the molten glass, The molded body can be continuously formed.
Next, the aspect using a some casting_mold | template is demonstrated.

  In the present invention, while preparing a plurality of the molds, one of them is arranged below the pipe, and molten glass is continuously poured into the mold arranged below the pipe to form a glass molded body, Stopping the pouring of the molten glass into the mold, unloading the mold into which the molten glass has been poured from below the pipe, taking out the glass molded body from the unloaded mold, and after the unloading, the molten glass is poured It is also possible to repeatedly carry out a process in which a casting mold different from the casting mold is carried and arranged below the pipe and the molten glass is poured into the carried casting mold.

  This method is suitable for forming a large-sized glass molded body made of glass having low viscosity at the time of outflow. This method requires a plurality of molds, a mechanism for sequentially moving the molds below the pipe, and a mechanism for interrupting the pouring of the molten glass into the mold. There is an advantage that it is not necessary to simultaneously perform an operation of completely removing the glass molded body from the same mold. Therefore, when the length of the glass molded body reaches a predetermined length, the pouring of the molten glass into the mold is interrupted, and the glass molded body is taken out together with the mold from below the pipe to cut and cleave the glass molded body. Without removing from the mold. Therefore, since the speed at which the glass molded body is taken out can be controlled by supporting the tip (lower end) of the glass molded body, unlike the method of holding the side surface of the glass molded body using frictional force, The take-out speed of the glass molded body can be controlled with high accuracy.

  In order to interrupt the flow of molten glass, for example, a cutting blade consisting of a single blade suitable for cutting a molten glass flow having a low viscosity at the time of outflow is inserted between the outlet of the pipe and the inlet of the through hole. What is necessary is just to cut | disconnect the flow of glass flow and to retreat pouring of molten glass by retracting a cutting blade at the time of carrying out and carrying out of a mold. In this method, the molten glass flowing out from the pipe is preferably poured into the mold without interruption, except for the interruption of the molten glass.

  For example, two molds are used, and the molds are alternately carried into and out of the pipe outlet, and three or more molds are mounted on a mechanism that synchronously transfers a plurality of molds such as a turntable. The above table can be rotated by indexing so that the molds are sequentially retained below the pipe outlet.

  In any of the method using a single mold and the method using a plurality of molds, the pipe is arranged vertically, and the center of the molten glass liquid surface in the mold is positioned vertically below the center of the pipe outlet. It is preferable to arrange a mold. By doing so, the molten glass can be flowed through the mold in a state where the molten glass is aligned from the inlet side toward the outlet side, which is advantageous in obtaining an optically homogeneous glass molded body.

  This glass molded body production method is suitable as a method for producing a glass molded body made of glass having a viscosity at a liquidus temperature (hereinafter referred to as “liquid phase viscosity”) of less than 100 dPa · s. In order not to devitrify the glass, it is necessary to flow out the molten glass at a temperature higher than the devitrification temperature range and rapidly cool the glass. The devitrification temperature range of the glass does not necessarily exactly match the liquidus temperature, but as a guide, the vicinity of the liquidus temperature can be considered as the lower limit of the outflow temperature at which the glass does not devitrify. Therefore, in order to flow out without devitrifying a glass having a liquid phase viscosity of less than 100 dPa · s, the viscosity at the time of outflow needs to be less than 100 dPa · s. For this reason, low-viscosity glass flows out, and the application of this method becomes effective.

  There is also an effect of preventing the devitrification of the glass by increasing the ratio of the contact area with the inner wall of the through hole of the glass and quickly taking away the heat of the glass.

  When the main objective is to reduce or prevent striae of the glass molded body, use a mold with a straight through hole center axis (inlet and outlet in linear communication), and vertically align the center axis of the mold through hole. Thus, it is effective to arrange the mold and continuously pour molten glass from the inlet of the mold through-hole to produce a glass molded body. The above-mentioned conditions can be applied as they are for the shape and dimensions of the mold through-hole and the material of the mold. And in a through-hole, it is preferable to make the perimeter of a glass side surface contact a through-hole inner wall, and take the heat of glass from the said side surface. Also in this aspect, as described above, it is desirable to make the pipe that flows out of the molten glass vertical. By doing in this way, the flow of the glass in a pipe, the moving direction of the glass in a casting_mold | template, and the direction of the gravity which acts on glass can be arrange | equalized. Thereby, the glass surface and the inside can be prevented from being mixed, and striae reduction and prevention effects can be improved. From the viewpoint of reducing striae and improving the prevention effect, it is preferable to pour molten glass by adjusting the positional relationship between the pipe and the mold so that the central axis of the pipe and the central axis of the mold through hole coincide.

According to the above method, striae can be localized in the surface layer of the glass molded body, and an optically homogeneous glass molded body having no striae inside can be obtained over a large volume. The glass molded body thus obtained is processed into a press-molding glass material, processed into an optical element, heated to the above-mentioned press-molding glass material, and press-molded as described later. Or an optical element, or the optical element blank can be processed to produce an optical element.
Thus, according to the said method, it can manufacture based on high productivity, without damaging an optically homogeneous glass molded object.

Next, the optical element of the present invention and the method for producing the optical element will be described.
[Optical element]
The optical element of the present invention is an optical element made of the optical glass of the present invention. The optical element of the present invention has the excellent characteristics of the optical glass described above. Examples of the optical element of the present invention include various lenses such as a spherical lens, an aspherical lens, and a microlens, and a prism. In terms of usage, it is suitable for interchangeable lenses for single-lens reflex cameras, lenses for digital still cameras, lenses for digital video cameras, lenses for projectors, and the like.
If necessary, an optical thin film such as an antireflection film may be formed on the surface of these optical elements.

[Method for Manufacturing Optical Element]
The method for producing an optical element of the present invention is a method for producing an optical element comprising a step of heating and softening and molding a glass material made of the optical glass.

  Another aspect of the method for producing an optical element of the present invention includes a step of producing a glass material from the glass molded body produced by the method I or II for producing a glass molded body, and heating and softening the glass material. It is a manufacturing method of the optical element provided.

  In any manufacturing method, glass with excellent devitrification resistance during reheating is used as a raw material, so that it is possible to prevent the glass from devitrifying during molding by reheating while being a high refractive index and low dispersion glass. And an optical element can be manufactured with high productivity.

  The molding method in the process of heating and softening the glass material includes press molding the softened glass material using a press mold, and using a plurality of rollers, the glass material is placed between rotating rollers. For example, a method of sandwiching and pressing to form a rod-shaped glass molded body can be exemplified.

  The press molding method can be further divided into two modes. In the first method, the glass material is heated and softened, introduced into a press mold, press molded, the press molded product is cooled slowly, and then ground. This is a method of polishing to finish an optical element. In this method, the glass material is press-molded into a shape obtained by grinding or polishing the shape of the optical element. The process from heating, softening to slow cooling can be performed in the atmosphere. In this method, a glass material whose entire surface is roughened by barrel polishing or the like is used, and a powder release agent such as boron nitride is uniformly applied to the entire surface of the glass material. And it introduce | transduces in a heating furnace, heats and softens, and introduce | transduces into a press mold. Then, after forming by pressing with the upper mold and the lower mold, the mold is opened, the press-molded product is taken out, and placed in a slow cooling furnace to reduce distortion and precisely match the refractive index of the glass with the target value. After the molded product is cooled to room temperature, the optical element is finished by grinding and polishing using well-known methods for grinding and polishing for producing a glass optical element. In this way, various optical elements such as a spherical lens and a prism are manufactured. If necessary, an optical multilayer film such as an antireflection film may be formed on the surface of the optical element.

  The second method is a method of manufacturing an optical element by heating a glass material having a smooth surface and precision press molding. Precision press molding is also called mold optics molding, which uses a press mold that has a mold member with a precisely machined molding surface and the mold member is assembled with high precision, and shapes the entire optical element. The molding surface is precisely transferred to glass to form an optical functional surface. In this method, the positional accuracy of a plurality of optical function surfaces can be formed with high accuracy. For example, it is possible to mold the lens while suppressing the tilt (tilt) of the central axis of the optical functional surfaces on both surfaces of the lens and the shift (decenter) of the central axis. In the second method, the optical functional surface, that is, the surface of the optical element that refracts, diffracts, reflects, or transmits light can be formed without machining such as grinding or polishing. Optical elements, which are troublesome and costly in machining such as spherical lenses, can be manufactured with high productivity. Precision press molding may be performed according to a known method. For example, a film having a function of improving the releasability of the carbon film or the like on the entire surface of the glass material for press molding and improving the slip between the glass and the molding surface is formed, and the glass material is used in a non-oxidizing atmosphere. Heat and precision press mold in the same atmosphere. Next, the press mold is opened, the press molded product is taken out, and gradually cooled to obtain an optical element. If necessary, the optical element thus obtained may be subjected to machining such as centering of a portion around the optical functional surface, for example, a lens. By such a method, optical elements such as an aspherical lens, a spherical lens, a lens array, a microlens, a diffraction grating, and a prism can be manufactured with high productivity. If necessary, an optical multilayer film such as an antireflection film may be formed on the surface of the optical element.

  The optical element of the present invention can be manufactured by the above manufacturing method, but may be manufactured as follows. The glass molded body is precisely annealed, the refractive index is precisely adjusted to a desired value and the distortion in the glass is reduced, and the glass molded body is cut or cut to produce a cut piece. Examples of the shape of the glass molded body include the rod-shaped glass described above. When the glass is cleaved perpendicular to the central axis of the rod-shaped glass, it is desirable to apply a side pressure cutting method.

Next, the cut piece is ground to produce an optical element blank in which a margin is added to the shape of the optical element, and the blank is polished to finish the optical element.
When using a rod-shaped glass molded body, it is preferable that the outer diameter of the rod-shaped glass molded body is equal to the outer diameter of the optical element, or is molded to an outer diameter obtained by adding a grinding margin or a polishing margin to the outer diameter of the optical element. .

  In this way, various optical elements such as lenses, prisms, and filters can be manufactured with high productivity. An optical multilayer film such as an antireflection film may be formed on the surface of the optical element.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
The raw materials were weighed appropriately using raw materials such as oxides, hydroxides, carbonates, and nitrates so as to have the compositions shown in Tables 1 and 3. After mixing the prepared raw materials, it was melted in a platinum crucible. The glass of the example was melted at 1300 to 1450 ° C. After stirring and clarifying the glass, it was poured out into an iron plate to form a block. The glass block was transferred to a furnace heated to near the glass transition temperature and annealed to room temperature. Samples for various measurements were cut out from the obtained glass block and measured as follows.

The refractive index nd and Abbe number νd were measured based on the Japan Optical Glass Industry Association Standard JOGIS-01.
The degree of coloring was also measured based on Japan Optical Glass Industry Association Standard JOGIS-02. In Table 1, the degree of coloring is indicated by λ70 and λ80. Measurements of λ70 is compliant with the standard, First, a glass sample optically polished parallel sided thickness 10 mm, incident measurement light vertically intensity I _in one of the optically polished face, the other The intensity I _out of the light emitted from the optical polishing surface is measured. The wavelength at which the external transmittance (I _out / I _in ) in the visible region becomes 70% is defined as λ70. In the visible range longer than λ70, the external transmittance exceeds 70%. When a sample having a thickness of 10 mm cannot be prepared, a method may be used in which external transmittance is measured at a predetermined thickness, and the result is converted to calculate λ70. λ80 is measured in the same manner as the measurement method of λ70, and the wavelength at which the external transmittance is 80% is set. The other points are the same as λ70.

  The glass transition temperature Tg was measured by preparing a cylindrical glass sample having a diameter of 5 mm and a length of 20 mm and using a thermomechanical analyzer TMA4000s manufactured by Bruker AXS.

The crystallization peak temperature Tx was measured using a high-temperature differential scanning calorimeter “Thermo Plus 2 / DSC8270” manufactured by Rigaku Corporation using a sample obtained by sufficiently pulverizing glass with a mortar.
The measurement results are shown in Tables 2 and 4.

In this way, while suppressing the content of Ta ₂ O ₅ to less than 13% by mass, it is excellent in devitrification resistance during reheating, has a refractive index nd of 1.86 or more, and an Abbe number νd of 38 or more. Low dispersion glass was obtained.

[note]
Total amount A: Total amount of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ Ratio A: Ta ₂ O ₅ / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + WO ₃ )
Ratio B: (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )

[Note] The total amount A, the ratio A, and the ratio B are the same as the footnotes in Table 2.

Example 2
The glass raw materials were weighed so that the same optical glass as the optical glass produced in Example 1 was obtained, mixed well, then introduced into a melting vessel, heated and melted. Next, a sufficiently clarified and homogenized molten glass is continuously flowed out from a pipe outlet arranged vertically, at a constant outlet speed, and the center of the inlet of the through hole provided in the carbon mold arranged at the position shown in FIG. It was poured continuously without interruption. The inner diameter of the mold through hole was φ20 mm, the center axis of the through hole was made to coincide with the vertical direction, and the center axis of the pipe was made to coincide with the center axis of the through hole. The length of the mold through-hole was set to several hundred mm, and a band heater (not shown) was wound around the mold and heated so that good molding was possible, and the temperature of the inner wall of the through-hole was appropriately controlled. The side surface of the round bar-shaped glass taken out from the outlet of the through hole was sandwiched between two rollers to control the speed of taking out the round bar-shaped glass. A motor that monitors the molten glass liquid level in the mold through-hole using a laser sensor, inputs a monitor signal output from the sensor to a roller controller, and rotates the roller so that the liquid level is constant. Controlled electrical input to. In this embodiment, the take-out speed of the round bar glass is controlled as follows. That is, feedback is applied to the rotational speed of the roller in accordance with the fluctuation of the liquid level, so that the liquid level is kept constant.

  In this manner, a round glass rod having a diameter of 20 mm was continuously taken out from the outlet of the through hole. A molding furnace was placed directly under the mold, and the round glass bar taken out from the mold was immediately moved into the molding furnace. A heater (not shown) was placed in the molding furnace, and the temperature of the furnace atmosphere was maintained in a temperature range in which the round bar glass was not damaged. The roller was placed in a molding furnace. The round bar-shaped glass passes through the molding furnace over time, but since the temperature of the center and surface of the round bar-shaped glass approaches in the meantime, internal stress that explosively destroys the round bar-shaped glass itself is not generated. In addition, a round bar glass could be formed without damaging the glass.

  Next, a scribing line was formed on a part of the side surface of the round bar-like glass coming out of the forming furnace by a scribing process in a direction perpendicular to the central axis of the round bar-like glass. And the metal jacket which poured the water to the internal water channel was made to contact the marking line so that the part which formed the marking line might be cooled locally, and a crack might extend toward the center from a marking line. At this time, the metal jacket was made to follow the movement of the round bar-shaped glass so as to keep in contact with the marking line. When the crack grows, support the part opposite to the part where the marking line is formed with respect to the central axis of the round bar glass, and press the side of the glass molded body below the marking line to form the marking line. The lower round bar glass was separated from the round bar glass above the height. In addition, since the round glass of the present example has a relatively thin outer diameter of 20 mm, it was possible to perform satisfactory separation without applying a thermal shock by contacting a metal jacket.

At the time of separation, the side surface of the round bar-shaped glass to be separated was held by a robot arm, and after the separation, the round bar-shaped glass was transferred to the continuous slow cooling furnace inlet placed on the side of the mold and the molding furnace. A belt conveyor for conveying the heater and the glass was placed in a continuous slow cooling furnace, and the glass was gradually cooled while moving the round bar glass placed on the belt in a furnace with a controlled temperature distribution to remove distortion.
When the round glass bar taken out from the continuous annealing furnace was cut, the cut surface was polished and the inside was observed, the striae was found only in the very shallow layer from the surface, and striae was observed in the deeper part. There wasn't. That is, most of the round bar glass was optically homogeneous.

Example 3
A glass material for press molding was produced using each round bar-like glass that had been slowly cooled, produced in Example 2. First, a scribing line was formed by scribing on the cleaved portion of the side surface of the round bar glass. Then, insert the round bar glass into the high pressure vessel so that the part where the marking line is formed is located in the center of the container, and chuck the round bar glass with the rubber seal to the container opening so as not to limit the movement in the central axis direction, Water was poured into the container, and the container was filled with water so that bubbles did not enter.
In this state, the water pressure in the container was increased, and the glass was cut perpendicularly to the central axis of the round bar glass at the position of the marking line. In this way, the round bar-shaped glass was cleaved at a predetermined interval to produce cut pieces.
Next, the cut piece was barrel-polished to adjust the weight to be equal to the weight of the target press-molded product, and the sharp edge was rounded to roughen the surface to obtain a press-molding glass material.
Further, the cut piece was ground and polished to produce a precision press-molding glass material having a smooth surface.

Example 4
A powder mold release agent composed of boron nitride was uniformly applied to the entire surface of the glass material for press molding produced in Example 3, and was heated and softened in the atmosphere while being transferred into the heating furnace. .
The softened glass material is introduced into a press mold consisting of an upper mold, a lower mold, and a body mold, press-molded in the atmosphere, the mold is opened, the press-molded product is taken out, placed in a slow cooling furnace, and precision annealed to room temperature. It cooled and it was set as the optical element blank.
Next, the blank was ground and polished to produce a spherical lens made of each optical glass. There was no devitrification or striae inside the lens, and an optically homogeneous optical element could be obtained.

Example 5
A carbon film is formed on the entire surface of the precision press-molding glass material produced in Example 3, heated in a mixed gas atmosphere of nitrogen and hydrogen, and a carbon film as a release film on the molding surface of the SiC mold material. Precision press molding was performed using a press molding die with a mark. Subsequently, the precision press-molded product was gradually cooled to obtain an aspheric lens made of each optical glass.
There was no devitrification or striae inside the lens, and an optically homogeneous optical element could be obtained.

Example 6
The precision annealed round bar glass produced in Example 2 was cut perpendicularly to the central axis by a side pressure cutting method to produce a cut piece. Next, the cut piece was ground and polished to produce a spherical lens made of each optical glass. There was no devitrification or striae inside the lens, and an optically homogeneous optical element could be obtained.

The optical glass of the present invention is a high refractive index and low dispersion optical glass excellent in devitrification resistance. By using this optical glass, a glass material for heating and softening molding and an optical element can be provided.
Further, the optical glass having the above properties can be obtained without using a large amount of expensive Ta ₂ O ₅ .

DESCRIPTION OF SYMBOLS 1 Pipe 2 Mold 3 Roller 4 Liquid level sensor 5 Controller 6 Glass side surface 7 Molding furnace 8 Support mechanism 9 Molten glass 10 Solid glass 11 Glass molded body 12 High pressure vessel 13 Liquid inlet 14 Seal

Claims (4)

In mass% display,
1 3-23% of B ₂ O ₃ and SiO ₂ in a total amount _(however, the content of B 2 _{O 3} is 7-17%, the content of SiO ₂ is from 6 to 12%),
La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ are 58 to 80% in total (provided that the content of La ₂ O ₃ is 30 -50%, Gd ₂ O ₃ content is 1-30% , Y ₂ O ₃ content is 0-10%, Yb ₂ O ₃ content is 0-5%, WO ₃ content is 0 ~ 6%),
La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ in a total amount of 50 to 70%,
2-10% of ZrO ₂
Nb ₂ O ₅ and 1-7%,
ZnO 0-6%,
Ta ₂ O ₅ is 0% or more and less than 13%,
0 to 5% of TiO ₂ (however, the total content of TiO ₂ and alkaline earth metal oxide is 5% or less),
Li ₂ O 0-1%,
Contains, does not contain Pb,
The ratio of Ta ₂ O ₅ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and WO ₃ is 0.23 or less,
The ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O _{3 to} the total content of B ₂ O ₃ and SiO ₂ is 2 . 4 is to 3.6, and a refractive index nd of 1.86 or more, an optical glass, wherein the Abbe number νd is 38 or more. The optical glass according to claim 1, wherein the glass transition temperature Tg is 674.9 ° C. or higher . Optical element characterized by comprising the optical glass according to claim 1 or 2. The process according to claim 1 or 2 heating a glass material formed of the optical glass according to an optical element which comprises a step of molding softened.

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