JP2005247658A - Method for producing precision press molding preform and method for producing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high-quality precision press molding preform from a fluorine-containing glass, especially, a fluorophosphate glass and to provide a method for producing a high-quality glass optical element from the preform. <P>SOLUTION: The method is one for producing a precision press molding preform from molten glass, wherein the preform is made by molding a melt of a fluorine-containing glass into a glass gob and etching the glass gob to remove its surface layer therefrom. The method for producing the optical element comprises heating the preform made by the above method and subjecting the heated preform to precision press molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a precision press-molding preform and a method for manufacturing an optical element. More particularly, the present invention relates to a method for producing a high-quality fluorine-containing glass preform, in particular a precision press-molding preform comprising a fluorophosphate glass, and a high-quality glass using said preform. The present invention relates to a method for manufacturing a manufactured optical element.

The demand for optical glass lenses is increasing rapidly with the spread of digital cameras and mobile phones. In order to meet this demand, attention is focused on precision press molding technology capable of manufacturing glass optical elements with high productivity.
The precision press molding method is a method of forming an optical functional surface by transferring the molding surface of a press mold that has been processed with high precision to the glass by press molding. For example, the polishing process requires enormous labor and cost. Can be mass-produced with high productivity. Such precision press molding requires a preform that has a smooth surface and is free of defects on both the inside and the surface.
In precision press molding, grinding and polishing of a press-molded product is limited to a minimum such as centering of a lens, or grinding and polishing are not performed. In addition, if there is a significant excess or deficiency in the weight of the preform, problems such as a decrease in the accuracy of the press-molded product and a glass that protrudes during press molding enter between the press molds. Therefore, the weight accuracy of the preform is precisely determined for each optical element to be manufactured.

By the way, as a preform manufacturing method, molten glass is cast into a mold, cooled to make a glass block or glass plate, cut and ground, and then polished to a smooth surface (referred to as cold working). Alternatively, a method is known in which molten glass flows out from a pipe to form a molten glass lump having a weight equivalent to one preform, and the preform is formed into a preform in the process of cooling the glass lump (referred to as hot forming). (For example, refer to Patent Document 1).
On the other hand, since cold working involves making a preform through many steps, there is a problem that it takes labor, time and cost, and there is also a problem in application to glass that is easily broken during polishing. In particular, in order to accurately adjust the weight of the preform to the target weight, more labor, time and cost are required.

Thus, the hot forming method has attracted attention as a method for improving productivity and a method for producing a preform with high weight accuracy.
Although the hot forming method is an excellent manufacturing method, the molten glass lump corresponding to one preform is separated from the molten glass, and the glass lump is directly formed into a preform. A glass lump with high surface accuracy and weight accuracy must be made.

By the way, with the downsizing, higher pixel count, and higher performance of digital cameras and digital video, the demand for lenses made of various optical glasses is increasing. One of the high demands is the low dispersion glass containing fluorine. There are lenses using glass, especially fluorophosphate glass.
There have been several attempts to mass-produce lenses made of fluorine-containing glass by precision press molding, but this has not been realized for the following reasons.

In precision press molding, a preform having a desired weight and shape must be prepared. However, if a preform is made by machining, it is not practical because it requires enormous labor and cost. On the other hand, when a preform is hot-formed, it is difficult to form a high-quality preform, and it has been considered difficult to realize. For this reason, lenses using fluorine-containing glass, particularly fluorophosphate glass, have been limited to polished lenses.
The reason why hot forming of a fluorine-containing glass preform is difficult is as follows. When hot forming a preform made of fluorine-containing glass, striae are observed on the surface of the formed preform. When this preform is examined in detail, it can be seen that striae are not recognized in the deep layer portion but are surface striae existing at a certain depth from the surface. One of the causes of surface stria can be presumed to be caused by the volatilization of fluorine in the glass from the surface until the molten glass lump is cooled and formed into a preform. In other words, it is considered that a small amount of fluorine occurs in the vicinity of the surface due to the volatilization of fluorine, which is observed as a surface striae.

Furthermore, fluorine-containing glass, particularly fluorophosphate glass, has a property that when the molten glass flows out of the pipe, it tends to get wet around the pipe periphery. Since the glass wetted on the pipe periphery is exposed to the atmosphere for a long time, easily volatile components such as fluorine are volatilized and deteriorated. Surface striae also occur when the altered glass is taken into the flowing glass surface.
When a preform having surface striae is precision press-molded in this way, striae remains on the surface of the obtained press-molded product, resulting in a defective product.
Further, when hot-forming a fluorine-containing glass, the glass surface is devitrified due to the reaction between water vapor and fluorine in the atmosphere, which causes a problem that it cannot be used as a preform.

Japanese Patent No. 2746567

  Under such circumstances, the present invention uses a method for producing a high-quality fluorine-containing glass preform, particularly a precision press-molding preform made of fluorophosphate glass, and the preform. It is an object of the present invention to provide a method for producing a high-quality glass optical element.

  As a result of intensive studies to achieve the above object, the inventors of the present invention formed molten glass composed of fluorine-containing glass into a glass lump, etched the glass lump, and removed the surface layer of the glass lump. Thus, it has been found that the purpose can be achieved by producing a precision press-molding preform, and the present invention has been completed based on this finding.

That is, the present invention
(1) In a method for producing a precision press-molding preform from molten glass,
A precision press characterized in that a molten glass made of fluorine-containing glass is formed into a glass lump, the glass lump is etched, and a surface layer of the glass lump is removed to produce a precision press-molding preform. Manufacturing method of preform for molding,
(2) A method for producing a precision press-molding preform as described in (1) above, wherein the glass is fluorophosphate glass;
(3) Fluorophosphate glass is expressed in terms of mol%, Al (PO ₃ ) ₃ 0-20%, Ba (PO ₃ ) ₂ 0-30%, Mg (PO ₃ ) ₂ 0-30%, Ca (PO _{3) 2 0~30%, Sr (} PO 3) 2 0~30%, Zn (PO 3) 2 0~30%, NaPO 3 0~15%, AlF 3 2~45%, ZrF 4 0~10% YF ₃ 0-15%, YbF ₃ 0-15%, GdF ₃ 0-15%, BiF ₃ 0-15%, LaF ₃ 0-10%, MgF ₂ 0-20%, CaF ₂ 2-45%, _{SrF 2 2~45%, ZnF 2 0~20} %, BaF 2 0~30%, LiF 0~10%, 0~15% NaF, KF 0~15%, Li 2 O 0~5%, Na 2 O _{0~5%, K 2 O 0~5%} , 0~5% MgO, CaO 0~5%, SrO 0~5%, Ba 0-5%, a method of manufacturing a preform for precision press molding according to the above (2) term is intended to include 0-5% ZnO,
(4) _A method for producing a precision press-molding preform as described in (1), (2) or (3) above, wherein the glass abrasion degree FA is 150 or more,
(5) The layer according to any one of (1) to (4) above, wherein a layer having a depth of 0.5 μm or more is removed from the surface by etching to produce a preform having a predetermined weight. Manufacturing method of precision press molding preform,
(6) The method for producing a precision press-molding preform according to any one of (1) to (5) above, wherein a glass lump or a spherical glass lump whose surface is constituted by curved surfaces having different curvatures is formed.
(7) The method for producing a precision press-molding preform according to any one of (1) to (6) above, wherein the glass lump is immersed in an etching solution for etching treatment,
(8) The process of forming molten glass into a glass lump is repeated to produce a plurality of glass lumps having a constant weight, and the plurality of glass lumps are etched under a certain condition to produce a plurality of preforms having a predetermined weight. (1) The manufacturing method of the precision press-molding preform according to any one of items (7) to (7),
(9) The method for producing a precision press-molding preform according to any one of (1) to (8) above, wherein the glass lump is annealed and then etched.
(10) Manufacturing of an optical element characterized by heating and precision press-molding a preform for precision press molding produced by the production method according to any one of (1) to (9) above. Method,
(11) The optical element manufacturing method according to (10) above, wherein a preform is introduced into a press mold, and the mold and the preform are heated together to perform precision press molding, and (12) preheated The method for producing an optical element according to (10) above, wherein the preform is introduced into a press mold and precision press molding is performed.
Is to provide.

According to the method for producing a precision press-molding preform of the present invention, a precision press-molding preform having good internal and surface quality can be obtained even when hot molding is performed using glass containing highly volatile fluorine. A method of manufacturing with high productivity can be provided.
In addition, high-quality preforms made of fluorophosphate glass with high utility value, such as low-dispersion glass or glass with color correction filter function for semiconductor image sensors that have been provided with infrared absorption characteristics by containing copper, have high productivity. It can also be manufactured.
Further, as large as wear-F _A is 150 or more, polishing can be a difficult glass, without polishing, can also be prepared into those of high productivity of high-quality preforms.
Moreover, since the surface layer of the glass lump is removed by the etching process, the surface layer having a depth corresponding to the above condition can be removed with good reproducibility by setting the etching conditions. If the defects on the glass surface are only the altered layer, the altered layer may be removed by washing or the like, but the surface stria extend to the deeper layer than the altered layer. Therefore, if the weight accuracy of the glass lump and the weight of the glass removed by the etching process are not accurate, the weight accuracy of the obtained preform is lowered. According to the present invention, a glass lump of a predetermined weight is formed by forming a molten glass lump, and the surface striation layer is removed by an etching process that can easily set the depth of surface removal accurately. High preforms can be manufactured with high productivity.

The surface striation layer may be removed by machining such as polishing, but the polishing process is limited to a flat or spherical surface. Therefore, it is difficult to remove the surface striae layer of the glass block whose surface is constituted by curved surfaces having different curvatures having high utility value as the shape of the precision press molding preform other than the sphere. On the other hand, according to the present invention, the surface layer can be uniformly removed by the etching process even if the glass block having the above shape is formed, and thus the preform having the above shape is also manufactured with high productivity. You can also. In addition, for the spherical glass lump, since the glass lump is spherically symmetric, the depth removed by the etching process becomes more uniform on the entire surface. Therefore, a spherical preform can be easily produced by etching treatment.
Furthermore, by immersing the glass block in an etching solution and performing an etching process, the entire surface of the glass block can be uniformly removed to a predetermined depth by a relatively easy method.
Also, by repeating the process of forming a glass lump from molten glass, a plurality of glass lumps having a constant weight are produced, and the plurality of glass lumps are etched under a certain condition to produce a preform having a predetermined weight. Thus, a high-quality and highly accurate preform can be manufactured with high productivity.

  Next, according to the method for producing an optical element of the present invention, since the preform made by the above method is precision press-molded, a high-quality optical element made of fluorine-containing glass can be produced with high productivity.

A method for manufacturing a precision press-molding preform and a method for manufacturing an optical element will be described in order.
[Precision press molding preform manufacturing method]
The method for producing a precision press-molding preform according to the present invention is a method for producing a precision press-molding preform from molten glass, wherein molten glass made of fluorine-containing glass is formed into a glass lump, and the glass lump is etched. Then, a precision press-molding preform is produced by removing the surface layer of the glass lump.
In this method, a sufficiently clarified and homogenized molten glass is prepared, and the molten glass is discharged from the pipe at a constant flow rate. And the molten glass lump of predetermined weight is isolate | separated from the molten glass which flows out. As a separation method, a molten glass is dropped from a pipe and separated into glass drops having a predetermined weight (referred to as a dropping method), the tip of the molten glass flow flowing out from the pipe is supported by a support, and the glass flow Make a constriction between the pipe side and the tip. Then, the support is rapidly lowered to separate the molten glass lump on the tip side from the constriction (referred to as descending cutting method), the molten glass flow flowing out from the pipe is cut with a cutting blade, and a molten glass lump having a predetermined weight is obtained. There is a method of separating (referred to as a mechanical cutting method). By keeping the glass outflow amount per unit time from the pipe constant, a molten glass lump of equal weight can be obtained if the separation interval is constant.

  Unlike the mechanical cutting method, the dropping method and the descending cutting method cannot form a cutting mark called a shear mark. In the present invention, since the surface of the hot-formed glass lump is removed by etching, if the shear mark is limited to a portion shallower than the depth to be removed by the etching process, the mechanical cutting method can also remove the shear mark by etching. You can make no preform. However, since the shear mark may extend deeper than the surface striae layer, it is preferable to separate the molten glass lump by a dropping method or a descending cutting method.

  The dropping method is suitable as a method for forming a glass lump in the range of 5 to 600 mg so that the weight tolerance based on the target weight is within ± 1%, and the descending cutting method is a glass lump in the range of 200 mg to 100 g. Is suitable as a method of molding so that the weight tolerance based on the target weight is within ± 2% (preferably within ± 1%). Therefore, when producing a glass lump, a production method can be selected based on the above range of weight and weight tolerance.

Next, the separated molten glass lump is received by a glass lump forming mold, or temporarily supported by a molten glass lump support, and then transferred to a glass lump forming mold to be formed into a glass lump having a predetermined shape. On the glass lump forming die, a method of forming while raising the glass by applying wind pressure (referred to as a floating forming method) is desirable.
For example, using a glass lump forming die provided with a recess provided with a port for jetting the gas for applying the wind pressure (called floating gas) to the bottom, the molten glass lump is supplied to the recess, and the glass is placed in the recess. A spherical glass lump can be formed by rotating up and down and rotating, and a recess or recess provided with a large number of gas ejection ports is made of a porous body, and a floating gas is ejected from the entire inner surface of the recess. Glass can be levitated and a glass lump can be formed into a shape along the shape of the recess.

The glass block is formed on a glass block forming mold, and then cooled to a glass transition temperature or a temperature lower than the above temperature, and then removed from the mold.
When the surface of the glass mass obtained in this way is magnified and observed with an optical microscope, striae is recognized over the entire glass mass. The striae are not recognized in the glass block obtained by removing the entire surface of the glass block to a predetermined depth by etching. Therefore, this striae is a surface stria localized near the surface. The alteration layer on the surface of the glass lump, such as burns, is limited to a portion having a depth of 0.1 μm or less from the surface, but the surface striae have reached a depth that can be recognized by visual observation using an optical microscope. It is desirable to perform an etching treatment from the glass lump surface to a depth of at least 0.5 μm or more.

  In the present invention, glass layers having different refractive indexes called striae on the glass surface are removed by etching. Among the striae, the surface striae present near the glass surface is a glass melt that has a difference in refractive index from the original glass due to a decrease in fluorine and boron with high vapor pressure among the glass components during glass melt molding. This is because Surface striae are usually observed as streaks. From this, it can be seen that the modified glass causing striae is distributed in the surface area of the original glass in a columnar and streak form. At this time, if the thickness of the modified glass has a diameter of φ0.5 μm or less, there is no influence on the image obtained when the glass is used as a lens due to the diffraction limit of visible light. That is, the problem as a lens is limited to a modified glass having a striae thickness of φ0.5 μm or more. Therefore, the striae cannot be completely removed unless the etching amount is at least 0.5 μm deep. A more preferable depth in the etching treatment is 1 μm or more, a further preferable depth is 10 μm or more, a still more preferable depth is 20 μm or more, and a particularly preferable depth is 50 μm or more. The etching process is performed to such a depth that an optically homogeneous glass mass having a predetermined weight with no striae is observed in the entire glass. Although there is no particular limitation on the upper limit of the depth of the etching process, it is not necessary to remove even the optically homogeneous glass, and therefore a depth of up to 5 mm may be used as a guide. Or you may manage the upper limit of the depth of an etching process with the ratio of preform weight / glass lump weight. In that case, the ratio of preform weight / glass lump weight is desirably 80% or more, and more desirably 85% or more. As described above, since the weight of the glass lump is slightly reduced by the etching treatment, it is preferable to mold the glass lump having a weight obtained by adding the weight reduction amount to the target weight so that a predetermined weight of the preform is obtained.

  Since the glass lump after the etching treatment has a smooth surface and is optically homogeneous, the glass lump after the etching treatment can be used as a precision press-molding preform. Note that if the hot-formed glass lump is etched without annealing, the glass may crack due to residual stress. For this reason, it is desirable to anneal the glass lump before the etching process to reduce or remove the residual stress inside the glass. The annealing process may be performed by holding the glass block at a temperature near the annealing point. Fluorine-containing glass, particularly fluorophosphate glass, has a large coefficient of thermal expansion, and stress tends to remain in the process of forming a glass block. Therefore, the annealing process is effective for preventing cracks during the etching process.

  Surface defect layers such as surface striae layers are removed by etching, but the depth at which surface defect layers exist is reduced as much as possible, or striae is reduced from the viewpoint of effective use of glass and improvement of productivity. It is desirable. In order to reduce the depth of the surface defect layer, gas flows along the outer periphery of the outflow pipe and in the glass outflow direction (vertically below) to reduce the wetting of the glass to the outer periphery of the outflow pipe, In order to reduce the reaction of the water vapor with the glass surface at a high temperature, it is preferable that the molten glass flows out in a dry atmosphere.

  The method of flowing gas along the outer periphery of the pipe is also effective in reducing the weight of the molten glass droplet obtained by the dropping method. In the dripping method, dripping occurs when the balance between the gravity acting on the glass and the surface tension at which the glass stays at the tip of the pipe is lost and the gravity increases. By constantly flowing a gas at a constant flow rate along the pipe periphery as described above, the downward force applied to the glass is increased, so that it is possible to drop a glass drop having a smaller weight than when no gas is flowed. it can. In addition, it is preferable to flow gas so that it may become a laminar flow near the pipe front-end | tip all over a pipe periphery.

The etching process on the surface of the glass lump uniformly removes the entire surface of the glass lump, so that the shape of the preform is similar to that of the glass lump. Therefore, a preform having a desired shape can be easily obtained by forming the glass block into a similar shape to the preform.
As optical elements manufactured by precision press molding, an optical element having a shape having one rotational symmetry axis such as a lens is overwhelmingly many. Therefore, the shape of the preform is also desired to be a spherical shape or a shape having one rotationally symmetric axis (for example, a spheroid, a shape obtained by extending a sphere in a certain axial direction, a crushed shape, or the like). In order to produce a preform having such a shape, a glass lump having a shape similar to the target preform shape may be formed and etched.

  In particular, a glass lump whose surface is constituted by curved surfaces with different curvatures, such as a shape having one rotational symmetry axis, which is obtained by removing a spherical glass lump from a glass lump whose entire surface is constituted by a curved surface, It is difficult to mechanically polish the entire surface of the glass block having such a shape to a uniform depth. However, according to the present invention, a preform made of glass having the above shape and optically uniform (uniform) can be easily manufactured by hot forming a glass lump of a desired shape and etching the glass lump. can do.

As such a shape having one rotationally symmetric axis, a shape having a smooth outline having no corners or depressions in a cross section including the rotationally symmetric axis, for example, an ellipse whose short axis coincides with the rotationally symmetric axis in the cross section. Some have contour lines. In addition, an arbitrary point on the outline of the glass lump in the cross section (which may be an arbitrary point on the outline of the preform) is connected to the center of gravity of the glass lump on the axis of rotational symmetry (may be the center of gravity of the preform). When the angle of one of the angles formed by the line and the tangent tangent to the contour line at a point on the contour line is θ, when the point moves on the contour starting from the rotational symmetry axis, θ Is preferably monotonically increasing from 90 ° and subsequently monotonously decreasing, and then monotonously increasing to 90 ° at the other point where the contour line intersects the rotational symmetry axis.
On the other hand, paying attention to the spherical symmetry of the spherical glass lump, the depth removed by the etching process becomes uniform on the entire surface due to the symmetry, and if the spherical glass lump is etched, a spherical preform can be easily produced. There is a merit.

Next, the glass used in the present invention will be described.
The glass used in the present invention contains fluorine that easily volatilizes during hot forming. Examples of such glasses include fluorophosphate glass, fluorine-containing silicate glass, fluorine-containing borosilicate glass, and fluorine-containing borate glass. Among these, fluorophosphate glass is a very important glass as a material for a low dispersion glass preform having an Abbe number (νd) of 65 or more. Moreover, by containing copper ions, it is a glass that imparts near-infrared absorption characteristics and is also useful as a color correction filter material for semiconductor imaging devices.

  Although it is such an important glass, there is a problem that high quality preforms cannot be hot-formed with high yield due to volatilization of fluorine and wetting of the glass around the pipe at the time of outflow. This has hindered hot forming of fluorophosphate glass preforms. However, according to the present invention, removal of surface striae and the like by etching treatment has opened the way for mass production by hot forming of a fluorine-containing glass preform, particularly a fluorophosphate glass preform.

Fluorophosphate glass has a relatively low glass transition temperature and is suitable for precision press molding. From the viewpoint of precision press moldability and hot formability, and from the viewpoint of imparting low dispersion characteristics with an Abbe number (νd) of 65 or more, a preferred fluorophosphate glass has Al, Ca and Sr as cation components and anion components. A particularly preferred fluorophosphate glass (hereinafter referred to as “glass A”) contains F and O as essential components. Al (PO ₃ ) _{30 to} 20%, Ba (PO ₃ ) _{2 in} terms of mol%. 0-30%, Mg (PO ₃ ) ₂ 0-30%, Ca (PO ₃ ) ₂ 0-30%, Sr (PO ₃ ) ₂ 0-30%, Zn (PO ₃ ) ₂ 0-30%, NaPO ₃ 0-15%, AlF ₃ 2-45%, ZrF ₄ 0-10%, YF ₃ 0-15%, YbF ₃ 0-15%, GdF ₃ 0-15%, BiF ₃ 0-15%, LaF _{3 0~10%,} MgF 2 0~2 _{%, CaF 2 2~45%, SrF} 2 2~45%, ZnF 2 0~20%, BaF 2 0~30%, LiF 0~10%, 0~15% NaF, KF 0~15%, Li 2 O 0-5%, Na ₂ O 0-5%, K ₂ O 0-5%, MgO 0-5%, CaO 0-5%, SrO 0-5%, BaO 0-5%, ZnO 0-5 % Is included.

The composition range will be described in detail. Unless otherwise specified, the content of each component is expressed in mol%.
Al (PO ₃ ) ₃ is a component constituting the glass network structure and is the most important component for improving the weather resistance of the glass. However, if its content exceeds 20%, the thermal stability of the glass decreases. The liquid phase temperature and the optical properties (dispersion becomes high) may be greatly deteriorated, so that the introduction amount is preferably limited to 20% or less. More preferably, it is 0.5 to 15% of range.

Ba (PO ₃ ) ₂ , Mg (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , and Sr (PO ₃ ) ₂ are components that constitute the glass network structure, similar to Al (PO ₃ ) ₃ , It is an important component that improves the weather resistance of glass. If the content exceeds 30%, the dispersion of the glass is increased, and the weather resistance is also deteriorated due to an increase in P ₂ O ₅ . Therefore, the amount of each introduced is preferably 30% or less. A more preferable content of each component of Ba (PO ₃ ) ₂ , Mg (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , and Sr (PO ₃ ) ₂ is in the range of 0 to 25%. In order to obtain a desired optical constant, the total amount of the above components (Mg (PO ₃ ) ₂ + Ca (PO ₃ ) ₂ + Sr (PO ₃ ) ₂ + Ba (PO ₃ ) ₂ ) should be 35% or less. Is preferable, and it is more preferable to set it as 32% or less.

Zn (PO ₃ ) ₂ is important as a component for improving the stability of the glass. However, when it is introduced in an amount exceeding 30%, the dispersion of the glass becomes high and the durability is deteriorated. Therefore, an introduction amount of 30% or less is desirable. NaPO ₃ is a component that improves the stability of the glass and improves the optical properties, but if it is introduced in an amount exceeding 15%, the durability is lowered. Therefore, it is desirable that the introduction amount is 15% or less.
AlF ₃ is a component that improves the stability of the glass and lowers the dispersion, but if its content is more than 45%, the stability of the glass is remarkably lowered and the solubility is also deteriorated. On the other hand, if it is less than 2%, the target optical characteristics cannot be obtained. Therefore, the introduction amount is preferably in the range of 2 to 45%, more preferably in the range of 4 to 40%.

ZrF ₄ is a component that constitutes the network structure of glass, and is a component that improves stability and improves durability, but when introduced in excess of 10%, not only the necessary optical properties cannot be obtained, Since excessive introduction also decreases the stability, the introduction amount is desirably 10% or less.

YF ₃ , YbF ₃ , GdF ₃ , BiF ₃ and LaF ₃ are highly effective in improving devitrification resistance by adding a small amount, but the amounts of YF ₃ , YbF ₃ , GdF ₃ and LaF ₃ are 15% and 15%, respectively. , 15%, 15%, and 10%, the glass becomes unstable and easily devitrified, so the amount of introduction is 0 to 15%, 0 to 15%, 0 to 15%, and 0 to 0%, respectively. It is desirable to suppress to 15% and 0 to 10%. More content of preferably YF ₃ 0 to 12%, and the content of YbF ₃ 0 to 12%, and the content of GdF ₃ 0 to 10%, and the content of BiF ₃ is 0-10%, of LaF ₃ The content is 0 to 7%, and the more preferable content of GdF ₃ is 0 to 8%.

MgF ₂ is a component that lowers the dispersion of the glass, but if introduced over 20%, the glass becomes unstable, so 20% or less is desirable.
CaF ₂ and SrF ₂ are components necessary for low dispersion while maintaining devitrification resistance. In particular, CaF ₂ plays a role of strengthening the glass structure in combination with AlF ₃ and is an indispensable component for stabilizing the glass. If the introduction amount of each of CaF ₂ and SrF ₂ is less than 2%, it cannot be said that the amount is sufficient from the viewpoint of improving the stability of the glass, and it becomes difficult to obtain a desired optical constant. Further, if both CaF ₂ and SrF ₂ are introduced in excess of 45%, there is a risk of destabilizing the glass. Therefore, both the amounts of CaF ₂ and SrF ₂ introduced should be in the range of 2 to 45%. Preferably, CaF ₂ is in the range of 5 to 40% and SrF ₂ is in the range of ₃ to 35%.

ZnF ₂ is effective in stabilizing the glass and increasing the durability, but if introduced in excess of 20%, the stability is lowered, so the introduced amount is desirably 20% or less.
BaF ₂ is effective in improving durability and reducing dispersion, but if introduced over 30%, the stability is lowered, so the amount introduced is preferably 30% or less.
LiF, NaF, and KF have the effect of improving the devitrification resistance and dispersibility of the glass by adding a small amount. However, when introduced excessively, the stability of the glass deteriorates rapidly and the durability deteriorates. , NaF and KF are preferably introduced in amounts of 0 to 10%, 0 to 15% and 0 to 15%, respectively. More preferable introduction amounts of LiF, NaF, and KF are 0 to 5%, 0 to 10%, and 0 to 10%, respectively.

Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO, ZnO are not essential components of the present invention, but the effect of improving the stability, weather resistance, and durability of the glass by introducing a small amount. However, since there is a possibility that the melting property of the glass may be deteriorated or the dispersibility may be deteriorated due to excessive introduction, each introduction amount is Li ₂ O 0-5%, Na ₂ O 0-5%, K _2. O 0-5%, MgO 0-5%, CaO 0-5%, SrO 0-5%, BaO 0-5%, ZnO 0-5%. More preferably _{Li 2 O 0~4%, Na 2} O 0~4%, K 2 O 0~4%, 0~4% MgO, CaO 0~4%, SrO 0~4%, BaO 0~4% ZnO 0 to 4%.

  In addition to the above components, it is also possible to introduce a small amount of a compound such as Cl or Br for the purpose of defoaming or adjusting the optical constant. However, it is desirable not to introduce a lead compound or an arsenic compound in consideration of environmental impact.

  Copper-containing fluorophosphate glass is also preferable as the glass used in the present invention. By introducing copper oxide based on fluorophosphate glass, near infrared absorption characteristics can be imparted. An optical element having near-infrared absorption characteristics can also be produced by precision press-molding a preform made of the above copper-containing fluorophosphate glass. The glass A can be exemplified as the base glass. Such an optical element can also be used as a color correction filter for a semiconductor image sensor such as a CCD or CMOS. For example, it can be formed into a thin plate to form the above filter, or a diffraction grating can be used to form an optical low-pass filter, or a lens can be formed into an optical element having both a color correction filter and a lens function. An optical element having both an optical low-pass filter function with a grating function, a lens function, and a color correction filter function can be provided.

Glass A is stable as glass, and after the glass melt is poured into a 40 × 70 × 15 mm carbon mold and allowed to cool to the glass transition temperature, it is annealed at the glass transition temperature for 1 hour. Even if it is further allowed to cool to room temperature, crystals that can be observed with a microscope do not precipitate.
When molding a glass lump made of glass A, after melting and refining at a temperature of 800 to 1100 ° C., oxygen gas is mixed in the atmosphere, in a dry atmosphere, or an inert gas such as nitrogen or a rare gas such as argon. In this case (in this case, the oxygen ratio is preferably 0.1 to 50% by volume), the glass is flowed out through a platinum alloy outflow pipe, and a glass lump is produced by the above-described float forming method.

  By using the glass having the above composition, it is made of an optical glass having an optical constant in the range of refractive index (nd) of 1.42 to 1.6 and Abbe number (νd) of 65 or more, preferably 65 to 97. A preform can be made. Moreover, in the said glass, it is more preferable to use the glass whose yield point (Ts) is 500 degrees C or less from the viewpoint of improving precision press moldability more.

Furthermore, many fluorine-containing glasses such as fluorophosphate glasses have a high degree of wear. Wear degree _{F A} is the amount that has been defined in the "method of measuring the wear of the optical glass" Japan Optical Glass Industry Association Standard JOGIS10-1994. _A glass having a higher degree of wear FA is not suitable for polishing because it is difficult to obtain a smooth surface by mechanical polishing or cracks during polishing. However, according to the present invention, a preform that is optically homogeneous and smooth on the entire surface can be produced without mechanical polishing. The glass to which the present invention is preferably applied is a glass having a wear degree F _A of 150 or more, more preferably a glass of 200 or more, and still more preferred glass is a glass having a wear degree F _A of 300 or more. The upper limit is not particularly preferred wear-F _A, it may be a guide 600 or less.

  Furthermore, it is preferable to use a glass having a high weather resistance having a haze value of 8% or less after being left for 350 hours under conditions of a temperature of 60 ° C. and a relative humidity of 90%. By using glass having high weather resistance, the surface of the preform produced by the above-described production method can be kept good for a long period of time, and the weather resistance of an optical element produced from the glass can also be improved. The haze value is an amount defined in Japan Optical Glass Industry Association Standard JOGIS07-1975 “Method for Measuring Chemical Durability of Optical Glass (Surface Method)”.

  Next, the glass lump etching process will be described. The etching process of the glass lump may be a dry etching process using an etching gas or a wet etching process using an etching solution, but the glass lump is immersed in the etching solution after removing the entire surface of the glass lump uniformly. It is preferable to immerse the entire glass block.

One of the advantages of the etching process over mechanical polishing is that the depth of the etching process (the depth removed by etching) can be made constant by making the etching process conditions constant. By combining this superiority and the superiority of hot forming, a high-quality and high-precision preform can be made from molten glass with high productivity. For example, a molten glass lump is separated from the molten glass flowing out, and a process of forming the glass lump is repeated to produce a plurality of glass lumps having a constant weight. Then, the plurality of glass lumps are etched under a certain condition to produce a preform having a certain weight. Since a certain amount of glass is removed under certain etching conditions, a large amount of preforms having a certain weight can be easily produced. This method is easy by making the time for immersing the glass block in the etching solution constant, or by immersing a plurality of glass blocks in the etching solution in a lump, and taking out from the etching solution after a predetermined time. It can be carried out. At this time, the temperature of the etching solution has the greatest influence on the etching rate. Therefore, in order to produce a preform with a high weight accuracy without impairing the high weight accuracy of the glass lump, the temperature of the etching solution is kept constant. Precise temperature control should be performed so that it can lean.
The weight and weight accuracy of the glass block and the preform are 5 to 600 mg when the dropping method is used, the weight tolerance based on the target weight is within ± 1%, and 200 mg to 10 g when the descending cutting method is used. The weight tolerance may be within ± 2% (preferably within ± 1%).

As the etching solution, an acid solution or an alkali solution can be used. Examples of the acid solution include HNO ₃ , HCl, H ₂ SO ₄ , HF, H ₂ SiF _{6 and the} like, or HNO ₃ , HCl, H ₂ SO ₄ , HF, and H ₂ SiF _6. The mixed solution which mixed the above acid can be illustrated. Examples of the alkaline solution include a solution of NaOH, KOH, Na ₂ CO ₃ or the like, or an alkaline solution in which two or more kinds of alkalis selected from NaOH, KOH, and Na ₂ CO ₃ are mixed. You may mix adjuvants, such as a chelating agent and surfactant, with the said acid solution or alkali solution. By adding a chelating agent to the etching solution, metal ions generated by melting the glass during the etching process can be taken in and the etching process can be performed more uniformly.

When a fluorophosphate glass containing an alkaline earth metal, such as glass A such as glass A, is etched with an H ₂ SO ₄ solution, a slightly soluble salt (such as BaSO _{4) is} formed on the glass lump surface by the reaction between the etchant and the glass. Sulfide) is formed. When such a salt accumulates on the glass lump surface, the progress of the etching is hindered, so it is desirable to stir the etching solution.

On the other hand, even when a fluorophosphate glass containing an alkaline earth metal, such as glass A, is etched with an HCl solution, the alkaline earth metal chloride is water-soluble, so it dissolves in the etching solution and does not hinder the progress of the etching. . From this point of view, the HCl solution is more preferable as the acid solution, and then the HNO ₃ solution is preferable.
On the other hand, it is also possible to utilize the generation of a hardly soluble salt. Since the hardly soluble salt precipitates in the solution, the etching solution is saturated and the etching rate is unlikely to decrease. Moreover, if a deposit is also removed, it can also be used repeatedly as etching liquid.
Using the fact that the etching rate increases with HCl solution and HNO _{3 solution,} the etching rate in H 2 SO ₄ solution is decreased, the mixed solution of HCl and _H 2 SO _4, mixing of HNO ₃ and _H 2 SO ₄ The etching rate can be adjusted by mixing solutions having different etching rates, such as a solution, a mixed solution of HCl, HNO ₃ , and H ₂ SO ₄ .
After the preform thus prepared is washed, a thin film such as a release film may be formed on the surface as necessary. Examples of the release film include a carbon-containing film and a self-assembled film.

[Method for Manufacturing Optical Element]
The optical element manufacturing method of the present invention is characterized in that a precision press-molding preform produced by the above-described manufacturing method is heated and precision press-molded.
Precision press molding is also called a mold optics molding method, which is already well known in the technical field to which the present invention belongs. A surface that transmits, refracts, diffracts, or reflects light rays of the optical element is called an optical functional surface. For example, taking a lens as an example, a lens surface such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens corresponds to an optical function surface. The precision press molding method is a method of forming an optical functional surface by press molding by precisely transferring a molding surface of a press mold to glass. That is, it is not necessary to add machining such as grinding or polishing to finish the optical functional surface.

According to the present invention, various lenses such as a spherical lens, an aspheric lens, and a micro lens, a diffraction grating, a lens with a diffraction grating, a lens array, various optical elements such as a prism, and applications include a digital camera and a camera with a built-in film. Various lenses such as lenses constituting imaging optical systems, imaging lenses mounted on camera-equipped mobile phones, and lenses for guiding light rays used for data reading and / or data writing on optical recording media such as CDs and DVDs An optical element can be manufactured. In addition, if a preform made of copper-containing glass is used, an optical element having a color correction function of a semiconductor imaging element can be produced.
These optical elements may be provided with an optical thin film such as an antireflection film, a total reflection film, a partial reflection film, or a film having spectral characteristics, if necessary.
Examples of the press mold used in the precision press molding method include known ones, for example, those having a release film on the molding surface of a mold material such as silicon carbide or cemented carbide material. preferable. As the release film, a carbon-containing film, a noble metal alloy film, or the like can be used, but a carbon-containing film is preferable from the viewpoint of durability and cost.
In the precision press molding method, it is desirable that the molding atmosphere be a non-oxidizing gas in order to keep the molding surface of the press mold in a good state. The non-oxidizing gas is preferably nitrogen or a mixed gas of nitrogen and hydrogen.

Next, a precision press molding method particularly suitable for the method for producing an optical element of the present invention will be described.
(Precision press molding method 1)
In this method, the preform is introduced into a press mold, the mold and the preform are heated together, and precision press molding is performed (referred to as precision press molding method 1).
In the precision press molding method 1, the temperature of the press mold and the preform is heated to a temperature at which the glass constituting the preform exhibits a viscosity of 10 ⁶ to 10 ¹² dPa · s to perform precision press molding. preferable.
In addition, the glass is cooled to a temperature at which the glass exhibits a viscosity of 10 ¹² dPa · s or more, more preferably 10 ¹⁴ dPa · s or more, more preferably 10 ¹⁶ dPa · s or more, and then the precision press-molded product is removed from the press mold. It is desirable to take it out.
Under the above conditions, the shape of the molding surface of the press mold can be accurately transferred with glass, and the precision press molded product can be taken out without being deformed.

(Precision press molding method 2)
In this method, after heating the preform, the preform is introduced into a press mold and precision press molding is performed. That is, the press mold and the preform are separately preheated, and the preheated preform is introduced into the press mold. Precision press molding (referred to as precision press molding method 2).
According to this method, since the preform is preliminarily heated before being introduced into the press mold, it is possible to manufacture an optical element with good surface accuracy free from surface defects while shortening the cycle time.
The preheating temperature of the press mold is preferably set lower than the preheating temperature of the preform. Thus, by lowering the preheating temperature of the press mold, the consumption of the mold can be reduced.
In addition, since it is not necessary to perform preform heating in the press mold, the number of press molds to be used can be reduced.

In the precision press molding method 2, it is preferable that the glass constituting the preform is preheated to a temperature exhibiting a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁵ to 10 ⁹ dPa · s.
The preform is preferably preheated while floating, and the glass constituting the preform is preferably 10 ^5.5 to 10 ⁹ dPa · s, more preferably 10 ^5.5 dPa · s to 10 ⁹ dPa · s. More preferably, it is preheated to a temperature showing a viscosity of less than s.
Moreover, it is preferable to start cooling the glass simultaneously with the start of pressing or in the middle of pressing.
The temperature of the press mold is adjusted to a temperature lower than the preheating temperature of the preform, and the temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s may be used as a guide.
In this method, it is preferable that after the press molding, the glass is cooled to a viscosity of 10 ¹² dPa · s or more and then released.
The precision press-molded optical element is taken out from the press mold and gradually cooled as necessary. Further, when the lens is molded, centering may be performed. Moreover, you may coat an optical thin film on the surface as needed.
In this way, a high-quality optical element made of fluorine-containing glass can be produced with high productivity.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.
(1) The compositions of the glasses used in Tables 1 to 4 are shown in Tables 1 to 4 together with optical constants (refractive index nd, Abbe number νd), transition temperature (Tg), and yield point (Ts). Although the optical constant changes only slightly depending on the temperature history, the composition, optical constant (refractive index nd, Abbe number νd), transition temperature (Tg), and yield point (Ts) are also different in preforms and optical elements. You can think of it as the same.

In order to make the glass, the corresponding oxides, carbonates, sulfates, nitrates, fluorides, hydroxides, etc. as the raw materials of each component, such as Al (PO ₃ ) ₃ , Ba (PO ₃ ) ₂ , 250 to 300 g is weighed to a predetermined ratio shown in Table 1 to Table 4 using AlF ₃ , YF ₃ , MgF ₂ , CaF ₂ , SrF ₂ , BaF ₂ , NaF, etc., and mixed well to form a preparation batch. Then, in an electric furnace kept at 1200 to 1450 ° C. in a platinum crucible, it is 0.1% in a gas called inert gas such as nitrogen, rare gas such as argon, or inert gas such as argon while stirring. Heating and melting were performed for 2 to 4 hours in an atmosphere mixed with ˜50 volume% oxygen gas. After melting, the molten glass is poured into a 40 × 70 × 15 mm carbon mold, allowed to cool to the glass transition temperature, immediately put into an annealing furnace, annealed for about 1 hour near the glass transition temperature, and then in the furnace Allowed to cool to room temperature. In the obtained glass, crystals that can be observed with a microscope were not precipitated.

The refractive index (nd), Abbe number (νd), transition temperature (Tg), and yield point (Ts) of the glasses shown in Tables 1 to 4 were measured as follows.
(A) Refractive index (nd) and Abbe number (νd)
The glass obtained by lowering the glass held at a temperature between the glass transition temperature and the yield point at a temperature lowering rate of −30 ° C./hour was measured.
(B) Transition temperature (Tg) and yield point (Ts)
The temperature increase rate was measured at 4 ° C./min with a thermomechanical analyzer from Rigaku Corporation.

In addition, Experiment No. About the glass of 1 and 2, the abrasion degree measured as follows was shown.
(C) Abrasion degree (F _A )
A sample with a measurement area of 9 cm ² is held at a fixed position of 80 mm from the center of a flat plate made of cast iron that rotates horizontally at 60 revolutions per minute, and 5 lapping solutions are prepared by adding 20 ml of water to 10 g of alumina abrasive grains having an average particle diameter of 20 μm. Supply uniformly for minutes and wrap with a load of 9.80N. Weigh the sample mass before and after lapping to determine the wear weight m. Similarly, the wear mass m ₀ of a standard sample (BSC 7) designated by the Japan Engineering Glass Industry Association is measured, and the wear degree (F _A ) is calculated by the following equation.

F _A = [(m / d) / (m ₀ / d ₀ )] × 100
(Where d is the specific gravity of the sample, and d ₀ is the specific gravity of the standard sample (BSC7))

(2) Next, molten glass from which the glasses shown in Tables 1 to 4 are obtained is melted in a large amount at a melting temperature of 800 to 1100 ° C., clarified and homogenized, and flows out from the platinum alloy outlet pipe at a constant flow rate. did.
The molten glass was discharged in the air, in a dry atmosphere, or in an inert gas atmosphere (nitrogen or argon, or a mixed gas of nitrogen and argon) containing 0.1 to 50% by volume of oxygen gas.
A molten glass lump of a predetermined weight was separated from the molten glass flowing out by a dropping method and received by a glass lump forming die that ejects gas, and the glass was moved up and down to form a spherical glass lump. By receiving the molten glass droplets dropped at regular time intervals one after another by the glass lump forming mold, the glass lump having a constant weight is formed one after another. After cooling to a temperature at which the glass block does not deform, it is removed from the mold. In this way, a plurality of spherical glass blocks made of the respective glasses shown in Tables 1 to 4 were produced.

  Moreover, it shows in Table 1-Table 4 by isolate | separating a molten glass lump by the fall cutting method, receiving with the glass lump shaping | molding die which has the recessed part formed with the porous, and ejecting gas from a porous fine hole. A glass lump made of each glass was formed. In this method as well, a plurality of glass blocks having a constant weight were produced by repeating the above steps with a constant separation time interval. The shape of the glass block formed by this method has one rotational symmetry axis, has a major axis and a minor axis, has a curved surface, and the surface in the present invention is configured by curved surfaces having different curvatures. This is a shape that approximates a flat sphere.

Any glass ingot thus formed is cooled to room temperature, then placed in an annealing furnace and annealed at a temperature about 10 ° C. lower than the glass transition temperature for 1 hour, at a rate of 30 ° C./hour. The temperature was lowered to room temperature to reduce distortion. A glass lump formed by any of the above methods has high weight accuracy. The weight tolerance of the obtained glass lump was within ± 1% based on the target weight.
When the surface of these glass lumps was magnified and observed with an optical microscope, fine surface striae were observed over the entire surface (see FIG. 1).

(3) Next, three types of etching solutions are prepared: 30% by weight nitric acid aqueous solution, 35% by weight hydrochloric acid, and 2% by weight H ₂ SiF ₆ aqueous solution. And the entire surface was etched to a depth of about 0.1 mm (100 μm) to remove the surface layer, and a glass lump with a predetermined weight was obtained. After the etching treatment, the glass lump was washed and dried, and the surface was magnified and observed with an optical microscope. As a result, no surface striae were observed. Furthermore, when the inside of the glass lump was observed, no striae was observed inside (see FIG. 1). An optically homogeneous glass lump was thus obtained, and this glass lump was used as a precision press-molding preform. The weight tolerance of the preform after the etching treatment was within ± 1% based on the weight of the target preform. Such an operation is repeated to obtain the relationship between the etching solution type, concentration, temperature, immersion time, glass composition, and etching depth.

  Next, a plurality of glass blocks of equal weight are immersed in the various etching solutions at the same time, and the entire surface of all the glass blocks is removed to a depth of 0.1 mm under the same conditions as the above etching conditions. A preform approximating the shape of the glass block before processing is prepared. All preforms thus produced were optically homogeneous, with no surface or internal striae, and no surface devitrification. Each preform has a predetermined weight, and a plurality of preforms with high weight accuracy could be produced simultaneously. The weight tolerance of each preform after the etching treatment was within ± 1% based on the weight of the target preform. A release film may be provided on the entire surface of the preform in order to improve the release property at the time of precision press molding. Examples of such a release film include a carbon film and a self-assembled film.

(4) The preform thus obtained was heated, and an aspheric lens was obtained by precision press molding (aspheric precision press) using the press apparatus shown in FIG. The details of precision press molding are as follows. The preform 4 was allowed to stand between the SiC lower mold 2 and the upper mold 1 having an aspherical shape, and then the quartz tube 11 was heated by energizing the heater 12 with the quartz tube 11 in a nitrogen atmosphere. . The temperature inside the molding die is set to a temperature at which the glass yield point is +20 to 60 ° C, and while maintaining the same temperature, the push rod 13 is lowered and the upper die 1 is pushed to perform the preform 4 in the press molding die. Was precision press-molded. A glass transition temperature in a state where the aspherical lens made of fluorophosphate glass formed by reducing the molding pressure after pressing, with the molding pressure of 8 MPa and the molding time of 30 seconds, is kept in contact with the lower mold 2 and the upper mold 1. It was gradually cooled to a temperature of −30 ° C. and then rapidly cooled to room temperature. Thereafter, the aspherical lens was taken out from the press mold and subjected to shape measurement and appearance inspection. The obtained aspherical lens was a highly accurate lens. Reference numeral 3 is a guide type, 9 is a support rod, 10 is a support base, and 14 is a thermocouple.

When the surface of this lens was magnified and observed with an optical microscope, it was confirmed that it was a high-quality lens with no surface or internal striae as in the preform used.
The aspherical lens made of a high-quality and high-precision fluorophosphate glass could be formed by introducing the preheated preform into a press mold and performing precision press molding.
The shape and dimensions of the preform may be appropriately determined depending on the shape of the precision press-molded product to be produced.

In the above embodiment, an aspherical lens is molded, but by using a press mold that matches the shape of the final product, various types such as a concave meniscus lens, a convex meniscus lens, a planoconvex lens, a biconvex lens, a planoconcave lens, a biconcave lens, etc. An optical element such as an aspherical lens or various spherical lenses, or a prism, a polygon mirror, or a diffraction grating can also be manufactured.
Also, various optical elements made of near-infrared absorbing glass can be produced by preparing a preform in the same manner using copper-containing fluorophosphate glass and precision press-molding in the same manner as described above. Such an optical element can be used as a color correction filter for a semiconductor imaging element.
In addition, an optical multilayer film such as an antireflection film or a high reflection film can be formed on the optical functional surface of each optical element obtained as necessary.

According to the method for producing a precision press-molding preform of the present invention, a precision press-molding preform having good internal and surface quality can be obtained even when hot molding is performed using glass containing highly volatile fluorine. It can be manufactured with high productivity.
Further, according to the method for producing an optical element of the present invention, since the preform made by the above method is precision press-molded, a high-quality optical element made of fluorine-containing glass can be produced with high productivity.

It is an optical microscope photograph figure of an example before the etching process of the glass lump which consists of fluorophosphate glass, and after an etching process. It is a schematic sectional drawing of one example of the precision press molding apparatus used in the Example.

Explanation of symbols

1 Upper mold 2 Lower mold 3 Guide mold (torso mold)
4 Preform 9 Support rod 10 Support base 11 Quartz tube 12 Heater 13 Push rod 14 Thermocouple

Claims (12)

In a method for producing a precision press-molding preform from molten glass,
A precision press characterized in that a molten glass made of fluorine-containing glass is formed into a glass lump, the glass lump is etched, and a surface layer of the glass lump is removed to produce a precision press-molding preform. A method for manufacturing a preform for molding.   The method for producing a precision press-molding preform according to claim 1, wherein the glass is fluorophosphate glass. Fluorophosphate glass is expressed in terms of mol%, Al (PO ₃ ) ₃ 0-20%, Ba (PO ₃ ) ₂ 0-30%, Mg (PO ₃ ) ₂ 0-30%, Ca (PO ₃ ) ₂ 0-30%, Sr (PO ₃ ) ₂ 0-30%, Zn (PO ₃ ) ₂ 0-30%, NaPO ₃ 0-15%, AlF ₃ 2-45%, ZrF ₄ 0-10%, YF _{3 0~15%, YbF 3 0~15%,} GdF 3 0~15%, BiF 3 0~15%, LaF 3 0~10%, MgF 2 0~20%, CaF 2 2~45%, SrF 2 2 _{~45%, ZnF 2 0~20%,} BaF 2 0~30%, LiF 0~10%, 0~15% NaF, KF 0~15%, Li 2 O 0~5%, Na 2 O 0~5 _{%, K 2 O 0~5%,} 0~5% MgO, CaO 0~5%, SrO 0~5%, BaO 0~ %, Precision press method for producing a molding preform according to claim 2 is intended to include 0 to 5% ZnO. Precision press method for producing a molding preform of claim 1, 2 or 3 wear-F _A glass is 150 or more.   The precision press-molding preform according to any one of claims 1 to 4, wherein a layer having a depth of 0.5 µm or more is removed by etching to produce a preform having a predetermined weight. Production method.   The method for producing a precision press-molding preform according to any one of claims 1 to 5, wherein a glass lump or a spherical glass lump whose surface is constituted by curved surfaces having different curvatures is formed.   The method for producing a precision press-molding preform according to any one of claims 1 to 6, wherein the glass block is immersed in an etching solution and etched.   The process of forming molten glass into glass lumps is repeated to produce a plurality of glass lumps having a constant weight, and the plurality of glass lumps are etched under a certain condition to produce a plurality of preforms having a predetermined weight. 8. A method for producing a precision press-molding preform according to any one of 7 above.   The method for producing a precision press-molding preform according to any one of claims 1 to 8, wherein the glass block is annealed and then etched.   A method for producing an optical element, comprising heating and precision press-molding a preform for precision press molding produced by the production method according to claim 1.   The method for manufacturing an optical element according to claim 10, wherein a preform is introduced into a press mold, and the mold and the preform are heated together to perform precision press molding.   The method of manufacturing an optical element according to claim 10, wherein a preform that has been preheated is introduced into a press mold and precision press molding is performed.

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