JP2005330154A - Optical glass, glass base material of preform for precision press molding and its manufacturing method, preform for precision press molding, optical element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass having a refractive index (n<SB>d</SB>) of 1.72 or more and an Abbe number (ν<SB>d</SB>) of 45 or less and having good solubility and also capable of precision press molding at a relatively low temperature. <P>SOLUTION: In the optical glass having the refractive index (n<SB>d</SB>) of 1.72 or more and the Abbe number (ν<SB>d</SB>) of 45 or less, the optical glass contains 16-27% B<SB>2</SB>O<SB>3</SB>, more than 0% and 7.5% or less SiO<SB>2</SB>, 10-45% La<SB>2</SB>O<SB>3</SB>, more than 10% and 35% or less ZnO, 4-28% WO<SB>3</SB>(wherein a ratio of WO<SB>3</SB>content to ZnO content WO<SB>3</SB>/ZnO is more than 0.37), more than 0% and 5% or less Li<SB>2</SB>O, 0-6% TiO<SB>2</SB>, 0-8.5% Nb<SB>2</SB>O<SB>5</SB>, 0-10% Ta<SB>2</SB>O<SB>5</SB>, 0-6% ZrO<SB>2</SB>by weigh % and glass transition temperature (T<SB>g</SB>) is 560°C or lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is relatively low in precision press molding can be B ₂ O ₃ -La ₂ O ₃ based precision press-molding preform formed of the optical glass and the glass and its manufacturing method, and an optical element made from the glass for their preparation .

Glass is a method for mass-producing optical elements with high productivity without grinding or polishing by precisely transferring the optical function surfaces of optical elements such as lens surfaces of aspherical lenses to the molding surface of the press mold. The precision press molding method (also called mold optics molding method) is known. A glass material for precision press molding is required to have a property of softening at a relatively low temperature. As a glass material for precision press molding having a high refractive index characteristic with an Abbe number (νd) of 45 or less, B ₂ O ₃ —La ₂ O ₃ glass disclosed in Patent Documents 1 and 2 is known. Yes.

JP 2002-362938 JP-A-6-305769

By the way, in the conventional B ₂ O ₃ —La ₂ O ₃ based glass, there is a problem that when a sufficiently high refractive index and excellent glass stability are imparted, the glass transition temperature rises and the press molding temperature rises. It was. Even if the press molding temperature is high, if an appropriate press mold and release film are combined, an optical element can be produced with sufficiently high productivity. The use of a press mold requires a high level of technology.
In recent years, due to demands for high precision, light weight, and miniaturization of optical systems, the precision press molding method has made it difficult to mold complex surface shaped optical elements and large shaped optical elements. Manufacturing needs to be done.
For this purpose, the glass transition temperature (T _g ) and yield point (T _s ) are reduced from the viewpoint of further suppressing damage to the release film and expanding the choices of usable press molds and release films. It is desired to make it as low as possible.
Furthermore, as an optical glass for precision press molding, good meltability is also required.

The present invention has been made in order to solve the above problems, and has a refractive index (n _d ) of 1.72 or more, an Abbe number (ν _d ) of 45 or less, a good solubility, and a comparison. It is a first object to provide an optical glass capable of precision press molding at a low temperature.
Another object of the present invention is to provide a glass base material for producing a precision press-molding preform made of the glass and a manufacturing method thereof, and a precision press-molding preform made of the glass and a manufacturing method thereof.
Furthermore, it is a third object to provide an optical element made of the optical glass and a method for producing the same.

As a means for solving the above problems, the present invention provides:
(Claim 1)
In an optical glass having a refractive index (n _d ) of 1.72 or more and an Abbe number (ν _d ) of 45 or less,
In weight% display
B ₂ O ₃ 16-27%,
SiO ₂ more than 0% and 7.5% or less,
La ₂ O ₃ 10-45%,
ZnO more than 10% and 35% or less,
WO ₃ 4-28%
(However, the ratio _WO 3 / ZnO in the content of WO ₃ with respect to the content of ZnO 0.37 greater),
Li ₂ O over 0% and 5% or less,
TiO ₂ 0-6%,
Nb ₂ O ₅ 0-8.5%,
Ta ₂ O ₅ 0-10%,
ZrO ₂ 0-6%,
And an optical glass characterized by having a glass transition temperature (T _g ) of 560 ° C. or lower.
(Claim 2)
The optical glass according to claim 1, wherein the optical glass is used for a glass material for precision press molding.
(Claim 3)
In a glass base material for producing a precision press-molding preform,
A glass base material comprising the optical glass according to claim 1.
(Claim 4)
In the manufacturing method of a glass base material for producing a precision press-molding preform,
The glass base material according to claim 3, wherein molten glass is flown out of a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are heated and press-molded. The manufacturing method of the glass base material characterized by manufacturing.
(Claim 5)
In the manufacturing method of a glass base material for producing a precision press-molding preform,
The glass mother body according to claim 3, wherein molten glass is flown out of a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are ground and / or polished. A method for producing a glass base material, comprising producing a material.
(Claim 6)
A precision press-molding preform comprising the optical glass according to claim 1.
(Claim 7) The precision press-molding preform according to claim 6, wherein the volume is 1.3 cm ³ or more.
(Claim 8)
In the manufacturing method of a precision press-molding preform made of optical glass,
A method for producing a precision press-molding preform, wherein a preform is produced by smoothing a surface of a glass base material produced by the method according to claim 4 in a process including polishing.
(Claim 9)
In the manufacturing method of a precision press-molding preform made of optical glass,
A method for producing a precision press-molding preform, wherein a molten glass lump is separated from an outflowing molten glass, and the preform is molded into the optical glass preform according to claim 1 or 2 in the course of cooling of the glass. .
(Claim 10)
An optical element comprising the optical glass according to claim 1.
(Claim 11)
In a method for manufacturing an optical element that heats a glass preform and performs precision press molding with a press mold,
A method for producing an optical element, wherein the preform is produced by the method according to claim 8 or 9.
(Claim 12)
The method for producing an optical element according to claim 11, wherein a preform is introduced into a press mold, the mold and the preform are heated together, and precision press molding is performed.
(Claim 13)
The method for producing an optical element according to claim 11, wherein a heated preform is introduced into a press mold and precision press molding is performed.
(Claim 14)
14. The method of manufacturing an optical element according to claim 11, wherein a lens having a diameter of 12 mm or more is manufactured.
Is to provide.

According to the present invention, an optical glass having a refractive index (n _d ) of 1.72 or more and an Abbe number (ν _d ) of 45 or less and capable of precision press molding at a relatively low temperature can be provided.
Further, it is possible to provide a glass base material for producing a precision press-molding preform made of the glass and a manufacturing method thereof, and a precision press molding preform made of the glass and a manufacturing method thereof.
Furthermore, the optical element which consists of said optical glass, and its manufacturing method can be provided.
As a result, optical elements made of glass having the above optical characteristics can be mass-produced with high productivity, and restrictions on press molds used for precision press molding are relaxed, and the life of the press molds is reduced. It can be extended.

[Optical glass]
The optical glass of the present invention is an optical glass having a refractive index (n _d ) of 1.72 or more and an Abbe number (ν _d ) of 45 or less.
B ₂ O ₃ 16-27%,
SiO ₂ more than 0% and 7.5% or less,
La ₂ O ₃ 10-45%,
ZnO more than 10% and 35% or less,
WO ₃ 4-28%
(However, the ratio _WO 3 / ZnO in the content of WO ₃ with respect to the content of ZnO 0.37 greater),
Li ₂ O over 0% and 5% or less,
TiO ₂ 0-6%,
Nb ₂ O ₅ 0-8.5%,
Ta ₂ O ₅ 0-10%,
ZrO ₂ 0-6%,
And has a glass transition temperature (T _g ) of 560 ° C. or lower.
Hereinafter, unless otherwise specified, the content of the glass component is expressed in weight%.

In a range that satisfies the above characteristics,
Na ₂ O 0~5%,
K ₂ O 0-5%,
MgO 0-5%,
CaO 0-5%,
BaO 0-5%,
Y ₂ O ₃ 0-10%,
Gd ₂ O ₃ 0-10%,
Can be introduced as an optional component.

Effective components to a decrease in the glass transition temperature in the above ingredients, _ZnO, is a WO 3, Li ₂ O, since inter alia WO ₃ is that an effect of increasing the refractive index, by introducing a WO ₃ actively The optical glass of the present invention realizes a further decrease in the glass transition temperature while maintaining a high refractive index. Further, excellent glass stability is realized by adjusting the balance of the above components.

Hereinafter, the reasons for limiting the composition range will be described in detail.
B ₂ O ₃ is an essential component and a glass network forming component. If the content is too small, the stability of the glass is lowered, and the refractive index is lowered by excessive introduction, so the content is made 16 to 27%. A preferred range is 17-26%.

SiO _{2 is} also an essential component, and if not introduced, the glass stability is lowered. However, the refractive index decreases due to excessive introduction, the glass transition temperature rises, and the meltability deteriorates, so the content is made more than 0% and 7.5% or less. A preferable range is 1 to 6%, and a more preferable range is 1 to 5.5%.

La ₂ O ₃ is an essential component for realizing the optical constant of the present invention. However, since the liquid phase temperature becomes high due to excessive introduction and molding becomes difficult, the content is 10 to 45%. To do. A preferable range is 15 to 40%, and a more preferable range is 17 to 38%.

  ZnO is an essential component from the viewpoint of lowering the glass transition temperature, but it becomes difficult to vitrify when introduced excessively, so its content is made to exceed 10% and not more than 35%. A preferable range is 11 to 35%, and a more preferable range is 12 to 32%.

WO ₃ is an essential component and has a function of increasing the refractive index and lowering the glass transition temperature. However, excessive introduction deteriorates the glass devitrification resistance and increases the tendency to color the glass. ˜28%. A preferable range is more than 10% and 25% or less, and a more preferable range is 10.5 to 25%.
However, in order to increase the refractive index and lower the glass transition temperature, the ratio WO ₃ / ZnO (weight ratio) of the WO ₃ content to the ZnO content is set to exceed 0.37. A preferable range of the ratio is 0.4 or more.

Li ₂ O is an essential component for lowering the glass transition temperature. However, since the devitrification resistance of the glass is lowered and the liquidus temperature is also raised by excessive introduction, the content exceeds 0% and 5%. The following. A preferable range is 0.5 to 4%.

The above are the essential components in the optical glass of the present invention. Next, optional components will be described.
TiO ₂ and Nb ₂ O ₅ are optional components to be introduced for obtaining a desired optical constant. However, since the glass transition temperature is prevented from being lowered by excessive introduction, the content of TiO ₂ is set to 0 to 6% and the content of Nb ₂ O ₅ is set to 0 to 8.5%. A preferred range for TiO ₂ is 0.5-4%, a preferred range for Nb ₂ O ₅ is 0-8%, and a more preferred range is 1-8%.

Ta ₂ O ₅ is an optional component that can be introduced from the viewpoint of improving the stability of the glass and increasing the refractive index, but the liquid phase temperature rises due to excessive introduction. Moreover, since it is an expensive raw material, excessive introduction is not preferable from the viewpoint of cost. Therefore, the content is made 0 to 10%. A preferred range is 1-8%.

ZrO ₂ is an optional component that can be introduced to improve the stability of the glass. However, since the excessive introduction prevents the glass transition temperature from being lowered, the content is made 0 to 6%. A preferred range is 1 to 5%.

In addition to the above components, a clarifying agent can be added. As a clarifier, known substances such as Sb ₂ O ₃ and As ₂ O ₃ can be added in a total amount of 0 to 1%, preferably 0 to 0.5%. However, it is desirable not to use As ₂ O _{3 because} of environmental influences, so it is desirable to use Sb ₂ O ₃ .
In order to achieve the above object, the total amount of the above components is preferably 95% or more, more preferably 98% or more, and further preferably 100%.

Furthermore, the following components can be introduced as long as the object of the invention is not impaired.
Na ₂ O and K ₂ O function to lower the glass transition temperature and adjust the optical constant. However, even if the introduction amount is increased, the refractive index is lowered and the desired optical characteristics cannot be obtained. In this case, 0 to 5% is introduced.

MgO, CaO, and BaO can be introduced in a small amount for adjusting the optical constant, but introduction of a component that lowers the glass transition temperature due to excessive introduction is limited. And
Y ₂ O ₃ and Gd ₂ O ₃ can also be introduced in an amount of 0 to 10% for adjusting the optical constant.

With the above composition, the glass transition temperature (T _g ) can be reduced to 560 ° C. or less, and the heat resistance limitation required for the press mold can be greatly relaxed. In addition, the preferable range of the glass transition temperature ( _Tg ) of the optical glass of this invention is 550 degrees C or less. Although there is no restriction | limiting in particular about the minimum of glass transition temperature, What is necessary is just to make 450 degreeC or more into a standard.
Since the glass transition temperature is thus low, the glass is suitable as a glass material for precision press molding.
The preferred range of the refractive index of the present invention _{(n d)} is 1.72 to 1.86, preferable range of the Abbe number ([nu _d) is 30-45.
The optical glass of the present invention can be produced by molding a molten glass obtained by heating, melting, clarifying, and homogenizing a glass raw material by a conventional method.

[Glass base material for manufacturing precision press-molding preform and its manufacturing method]
The glass base material for producing the precision press-molding preform of the present invention is characterized by comprising the above optical glass. The glass base material is smoothed by a process including polishing to form a precision press-molding preform (hereinafter referred to as a preform). Since the preform requires high weight accuracy, it is desirable to make the glass base material with high weight accuracy.
There are roughly two methods for producing the glass base material. In the first method, molten glass is flown out of a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are heated and pressed to form a glass base material. It is a method of producing. A method such as cutting or cleaving can be used for dividing the glass molded body. The press molding can be performed in the air by applying a powdery mold release agent to the surface of the glass piece.

In the second method, molten glass is discharged from a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are ground and / or polished to obtain a glass mother. This is a method for producing a material.
These methods require a number of steps compared to the method of directly forming a preform from molten glass (called hot forming method), and there is a problem that processing waste is generated. The restriction on the viscosity and temperature of the glass at the time of molding is relaxed rather than the case. Therefore, the glass transition temperature can be further lowered.

The glass molded body is preferably annealed to reduce residual strain before machining such as cutting, cleaving, grinding, and polishing.
[Preform for precision press molding and its manufacturing method]
The preform of the present invention is characterized by comprising the above optical glass. The weight accuracy of the preform is preferably within ± 2%, more preferably within ± 1%, based on the target weight. The preform has an optically homogeneous internal quality, and also has a high surface quality that is smooth and free from scratches and alterations.

  There are roughly two methods for manufacturing such a preform. The first method is to prepare the preform by smoothing the surface of the glass base material in a process including polishing, and the second method is called a hot forming method, and the molten melt flows out. A molten glass lump is separated from the glass and formed into a preform made of optical glass in the process of cooling the glass. In the hot forming method, it is important to increase the weight accuracy of the molten glass lump, and therefore, the outflow speed of the molten glass flowing out from the pipe is made constant, and the molten glass lump is separated at a constant time interval (period). Separation method includes dropping glass from the outlet of the pipe, receiving the lower end of the molten glass flowing out by the support, causing constriction in the middle of the molten glass flow, and lowering from the constricted part due to the surface tension of the glass There is a method of separating the glass. In this method, the glass can be separated by removing the support at a predetermined timing or weakening the support force. In any of the methods, the glass is separated without using a cutting blade, so that it is possible to prevent cutting marks from being generated in the preform.

The separated molten glass block is formed into a preform while being floated by applying upward wind pressure on the mold. After the temperature of the glass is lowered to near the glass transition temperature or lower than that, the preform is taken out from the mold and gradually cooled. In this way, a preform can be produced directly from the molten glass.
When a relatively large optical element is precision press-molded, the force that must be applied at the time of pressing increases because the area of the molding surface is large. Since the above-mentioned preform has a low transition temperature of 560 ° C. or lower, it exhibits a lower viscosity than conventional glass at the conventional press molding temperature. Therefore, even if the pressing pressure is relatively low, the glass spreads sufficiently in the mold cavity, and a highly accurate optical element can be easily obtained.

From the above viewpoint, the preform of the present invention is suitable for molding a relatively large optical element, and its volume is desirably 1.3 cm ³ or more. According to the preform of the present invention, a preform is made from optical glass excellent in meltability, so that a large-sized optically homogeneous preform having no striae can be realized.

In order to manufacture a preform having a volume of 1.3 cm ³ or more, the above first and second methods may be applied. From the viewpoint of productivity, molten glass is poured out to make one preform at a time. The first method is more advantageous than the second method. In particular, when the volume is 3.5 cm ³ or more, it becomes difficult to manufacture the preform by the second method. Therefore, the preform is manufactured by the first method. Is preferred.
The shape of the preform may be a shape that makes it easy to mold the target optical element. However, when molding a rotating body such as a lens, the shape of the preform should be a spherical body or a rotating body with one rotational symmetry axis. Is preferred.

[Optical element and manufacturing method thereof]
The optical element of the present invention is made of the above optical glass.
The optical element manufacturing method of the present invention is characterized in that the preform produced by the above method is heated and precision press-molded with a press mold.
Examples of such an optical element include a spherical lens, an aspherical lens, a microlens, a lens array, various lenses such as a lens with a diffraction grating, a diffraction grating, and a prism. Further, a multilayer film such as an antireflection film may be provided on the surface of the optical element as necessary.
There are two modes for the method of manufacturing the optical element. In the first aspect, a preform is introduced into a press mold, and the mold and the preform are heated together to perform precision press molding. In the second aspect, a preform heated in the press mold is used. Introduced and precision press-molded.
In any method, since a preform for optical glass having a glass transition temperature of 560 ° C. or lower is used, the press molding temperature can be set low. Therefore, it is possible to extend the life of the press mold, and to use a press mold using a mold made of a super hard material such as tungsten carbide and a press mold having a release film made of a noble metal or a noble metal alloy on the molding surface. It can also be used, and the limitation of the press mold used is relaxed.
In addition, what is necessary is just to apply a well-known method and conditions about the heating process of a preform, precision press molding conditions, the slow cooling process of a precision press molded product, etc.
Since the optical element of the present invention is made of glass having a refractive index (n _d ) of 1.72 or more and excellent in precision press moldability, it is suitable for a lens having a diameter of 12 mm or more and from a medium diameter to a large diameter.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
(Examples 1-31)
So that the glass composition shown in Tables 1 to 4, oxides respectively corresponding as raw materials, carbonates, sulfates, nitrates, hydroxides such as, for _{example, SiO 2, H 3 BO 3} , La 2 O 3, ZnO , ZnCO ₃ , ZrO ₂ , Li ₂ CO ₃ , 250 to 300 g are weighed, mixed well to form a blended batch, placed in a platinum crucible, and kept in a 1200 to 1250 ° C. electric furnace. After melting and refining, the mixture was stirred and homogenized, and then the molten glass was poured into a 40 × 70 × 15 mm carbon mold. Then, after cooling to the glass transition temperature, it was immediately put into an annealing furnace, annealed for about 1 hour in the glass transition temperature range, and then allowed to cool to room temperature in the furnace. 31 to 31 optical glasses were obtained, and optical glasses of Examples 1 to 31 were obtained. In each of the obtained optical glasses, crystals that can be observed with a microscope were not precipitated.
Moreover, since each glass is excellent in meltability, defects such as unsettled raw materials and striae were not observed in each glass.

In addition, the characteristic of optical glass was measured by the method shown below. The results are shown in Tables 1-4.
(1) Refractive index (n _d ) and Abbe number (ν _d )
The optical glass held at a temperature between the transition temperature (T _g ) and the yield point (T _s ) was measured for the optical glass obtained at a temperature drop rate of −30 ° C./hour.
(2) Transition temperature (T _g ) and yield point (T _s )
The temperature rise rate was measured at 4 ° C./min with a thermomechanical analyzer TMA8310 manufactured by Rigaku Corporation.

(Comparative Examples 1-3)
Comparative Examples 1 and 2 correspond to Examples 19 and 22 in Patent Document 1, and Comparative Example 3 corresponds to an example in Patent Document 2 and Table 4 shows the characteristics of the obtained optical glass. . Glass is the refractive index of Comparative Examples 1 and 2 corresponding to Patent Document 1, while in the same range as the embodiments of the Abbe numbers present invention, the ratio WO 3 _/ ZnO in the content of WO ₃ with respect to the content of ZnO 0. Since it is 37 or less, the glass transition temperature exceeds 560 ° C. as shown in Table 4, and when optical products such as lenses are produced by precision press molding using this glass as a material, clouding occurs on the surface and cloudiness occurs. However, it was inappropriate as an optical product.
In addition, since the glass of Comparative Example 3 corresponding to Patent Document 2 has a high SiO ₂ content, unmelted material remains in the glass when melted in the same manner as in the examples of the present invention, which is not suitable as an optical glass. Appropriate quality.

（実施例３２）
次に清澄、均質化された熔融ガラスを白金合金製のパイプから底部が平坦で一方の側面が開口した鋳型に一定流量で流し込み、鋳型の開口部から平板状に成形されたガラスを一定の速度で引き出して実施例１の光学ガラスからなる一定の幅と厚みを備えたガラス板を製造した。
次に上記ガラス板をアニールし、所定の寸法に切断してカットピースと呼ばれる六面体のガラス片を複数個作製し、これらカットピースをバレル研磨して目的重量にしてから、大気中で加熱、軟化して金型を用いてプレス成形してプリフォーム用のガラス母材を得た。上記目的重量は、プリフォームの重量にガラス母材の研磨しろに相当するガラスの重量を加えたものとすればよい。また金型の成形面の形状は目的とするプリフォームの形状に近似する形状とすればよい。

(Example 32)
Next, clarified and homogenized molten glass is poured from a platinum alloy pipe into a mold with a flat bottom and one side open at a constant flow rate, and the glass formed into a flat plate shape from the mold opening at a constant speed. A glass plate having a certain width and thickness made of the optical glass of Example 1 was produced.
Next, the glass plate is annealed and cut into predetermined dimensions to produce a plurality of hexahedral glass pieces called cut pieces. These cut pieces are barrel-polished to the target weight and then heated and softened in the atmosphere. Then, it was press-molded using a mold to obtain a preform glass preform. The target weight may be the weight of the preform plus the weight of glass corresponding to the polishing margin of the glass base material. The shape of the molding surface of the mold may be a shape that approximates the shape of the target preform.

Next, the entire surface of the glass base material was polished to produce a precision press-molding preform made of the optical glass of Example 1. The volume of these preforms was 2.0 cm ³ and the weight tolerance was within ± 1% based on the target weight.
For each glass of Examples 2-31, a preform having a volume of 2.0 cm ³ and a weight tolerance within ± 1% based on the target weight was prepared in the same manner.

  If necessary, a film can be formed on the preform surface to prevent the glass from spreading into the mold by preventing fusion with the mold during precision press molding. Examples of such films include carbon-containing films and self-assembled films. As the carbon-containing film, a hydrogenated carbon film, a carbon film, or the like is desirable.

(Example 33)
Next, the clarified and homogenized molten glass flows down continuously from the platinum alloy pipe at a constant flow rate, receives the tip of the molten glass flow with a preform mold, and the timing when the molten glass lump of a predetermined weight is separated from the tip The mold was lowered rapidly to separate the molten glass lump. The separated glass lump was molded into a spherical preform made of the optical glass of Example 1 while floating on the mold. The volume of the obtained preform was 2.0 cm ³ and the weight tolerance was within ± 1%.
In each of the above embodiments, a spherical preform was formed. However, a preform having a flattened sphere (one axis passing through the center of the sphere and having a dimension reduced in the axial direction) is produced. You can also
The entire surface of the preform thus produced was formed by solidification of the molten glass and was a free surface. Further, no defects such as striae, devitrification, cracks and bubbles were observed on the surface and inside.
For each glass of Examples 2-31, a preform having a volume of 2.0 cm ³ and a weight tolerance within ± 1% based on the target weight was prepared in the same manner.
If necessary, a film can be formed on the surface of the preform to prevent the glass from spreading into the mold by preventing fusion with the mold during precision press molding. Examples of such films include carbon-containing films and self-assembled films. As the carbon-containing film, a hydrogenated carbon film, a carbon film, or the like is desirable.

(Example 34)
Next, an optical element was precision press-molded using each preform obtained in Examples 32 and 33.
The preform is heated to a temperature at which the viscosity of the glass constituting the preform is 10 ⁹ to 10 ¹¹ dPa · s, together with a WC press mold having a platinum alloy film on the molding surface, and in a nitrogen atmosphere The preform was precision press molded using a press mold. The obtained precision press-molded product was annealed to obtain an aspheric lens having a diameter of 15 mm. The refractive index (n _d ) and Abbe number (ν _d ) of the obtained lens coincide with the values in the optical glass forming the preform. In order to precisely adjust the optical characteristics to a desired value, the annealing conditions of the optical element, such as the annealing rate, may be appropriately adjusted. In addition, what is necessary is just to set suitably press conditions, such as press time and a press pressure, in the well-known range according to the shape and dimension of a molded article.
By such a method, the shape of the press mold and the weight of the preform are appropriately determined, and various lenses such as a spherical lens, a micro lens, a lens array, and a lens with a diffraction grating, a diffraction grating, a prism, a prism with a lens, and a polygon mirror An optical element such as was produced. As the aspherical lens and the spherical lens, lenses having various shapes including a biconvex shape, a biconcave shape, a planoconvex shape, a planoconcave shape, a convex meniscus shape, and a concave meniscus shape can be made.
The shape accuracy of the obtained optical element was sufficiently high, and no defects were recognized inside and on the surface.
In this example, a WC press mold having a platinum alloy release film on the molding surface was used, but the same molding can be performed using an SiC press mold having a carbon release film on the molding surface. Is possible.

(Example 35)
Next, using the preforms obtained in Examples 32 and 33, the preform is preheated to a temperature at which the viscosity of the glass constituting the preform exhibits a viscosity of 10 ⁹ to 10 ¹¹ dPa · s. The preheated preform was introduced into a WC press mold having a platinum alloy release film provided on the molding surface preheated to a temperature lower than the temperature of the mold, and the preform was used in a nitrogen atmosphere. Was precision press-molded. In addition, what is necessary is just to set suitably press conditions, such as press time and a press pressure, in the well-known range according to the shape and dimension of a molded article. The obtained precision press-molded product was annealed to obtain an aspheric lens having a diameter of 15 mm. The refractive index (n _d ) and Abbe number (ν _d ) of the obtained lens coincide with the values in the optical glass forming the preform. In order to precisely adjust the optical characteristics to a desired value, the annealing conditions of the optical element, such as the annealing rate, may be appropriately adjusted.

  By such a method, the shape of the press mold and the weight of the preform are appropriately determined, and various lenses such as a spherical lens, a microlens, a lens array, and a lens with a diffraction grating, a diffraction grating, a prism, a prism with a lens, and a polygon mirror An optical element such as was produced. In addition, as an aspherical lens and a spherical lens, lenses having various shapes including a biconvex shape, a biconcave shape, a planoconvex shape, a planoconcave shape, a convex meniscus shape, and a concave meniscus shape can be made. The shape accuracy of the obtained optical element was sufficiently high, and no defects were recognized inside and on the surface.

  In this example, a WC press mold having a platinum alloy release film on the molding surface was used, but the same molding can be performed using an SiC press mold having a carbon release film on the molding surface. Is possible.

  According to the present invention, an optical glass having a desired refractive index and Abbe number, good meltability and capable of precision press molding at a relatively low temperature is obtained, and the optical glass is used. As a result, optical elements can be mass-produced with high productivity.

Claims (14)

In an optical glass having a refractive index (n _d ) of 1.72 or more and an Abbe number (ν _d ) of 45 or less,
In weight% display
B ₂ O ₃ 16-27%,
SiO ₂ more than 0% and 7.5% or less,
La ₂ O ₃ 10-45%,
ZnO more than 10% and 35% or less,
WO ₃ 4-28%
(However, the ratio _WO 3 / ZnO in the content of WO ₃ with respect to the content of ZnO 0.37 greater),
Li ₂ O over 0% and 5% or less,
TiO ₂ 0-6%,
Nb ₂ O ₅ 0-8.5%,
Ta ₂ O ₅ 0-10%,
ZrO ₂ 0-6%,
And an optical glass characterized by having a glass transition temperature (T _g ) of 560 ° C. or lower.   The optical glass according to claim 1, wherein the optical glass is used for a glass material for precision press molding. In a glass base material for producing a precision press-molding preform,
A glass base material comprising the optical glass according to claim 1. In the manufacturing method of a glass base material for producing a precision press-molding preform,
The glass base material according to claim 3, wherein molten glass is flown out of a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are heated and press-molded. The manufacturing method of the glass base material characterized by manufacturing. In the manufacturing method of a glass base material for producing a precision press-molding preform,
The glass mother body according to claim 3, wherein molten glass is flown out of a pipe to form a glass molded body, the glass molded body is divided to produce a plurality of glass pieces, and the glass pieces are ground and / or polished. A method for producing a glass base material, comprising producing a material.   A precision press-molding preform comprising the optical glass according to claim 1. The precision press-molding preform according to claim 6, wherein the volume is 1.3 cm ³ or more. In the manufacturing method of a precision press-molding preform made of optical glass,
A method for producing a precision press-molding preform, wherein a preform is produced by smoothing a surface of a glass base material produced by the method according to claim 4 in a process including polishing. In the manufacturing method of a precision press-molding preform made of optical glass,
A method for producing a precision press-molding preform, wherein a molten glass lump is separated from an outflowing molten glass, and the preform is molded into the optical glass preform according to claim 1 or 2 in the course of cooling of the glass. .   An optical element comprising the optical glass according to claim 1. In a method for manufacturing an optical element that heats a glass preform and performs precision press molding with a press mold,
A method for producing an optical element, wherein the preform is produced by the method according to claim 8 or 9.   12. The method of manufacturing an optical element according to claim 11, wherein a preform is introduced into a press mold, the mold and the preform are heated together, and precision press molding is performed.   The method of manufacturing an optical element according to claim 11, wherein a heated preform is introduced into a press mold and precision press molding is performed.   The method for manufacturing an optical element according to claim 11, wherein a lens having a diameter of 12 mm or more is manufactured.