KR20090031834A - Preform for precision press forming, forming die, glass compact manufacturing method using the die, and optical element manufacturing method - Google Patents

Abstract

A preform for molding find press is provided not to destroy glass without making volume of the preform comparing to volume of lens drastically and to produce efficiently optical element having predetermined face precision. A preform for molding find press includes a rotation symmetry shaft, two end surfaces intersecting with the rotation symmetry shaft and one side connecting to circumference of the two end surfaces. The two end surfaces are independently a convex surface or a concave surface. A side of the preform for molding find press is a side formed by solidifying glass of melting state.

Description

PREFORM FOR PRECISION PRESS FORMING, FORMING DIE, GLASS COMPACT MANUFACTURING METHOD USING THE DIE, AND OPTICAL ELEMENT MANUFACTURING METHOD}

TECHNICAL FIELD This invention relates to the preform for precision press molding, a shaping | molding die, the manufacturing method of the glass molded object using this shaping | molding die, and the manufacturing method of an optical element.

Precision press molding method (mold press method) as a method of heating an optical glass material (also referred to as a preform) made of optical glass, press molding to precisely transfer the shape of the mold's molding surface to glass, and producing optical elements such as aspherical lenses. Also known as). Since optical elements such as lenses have a rotationally symmetrical shape, the shape of the preform is also rotationally symmetrical, and the preform is pressed from the symmetry axis direction to spread the glass evenly in the press-molding die. Patent Documents 1 and 2 describe an example of a method for manufacturing an optical element by such a preform and a precision press molding method.

In the method of directly making a preform from molten glass disclosed in Patent Documents 1 and 2, in order to mold a glass having a smooth surface, the glass is molded in a state in which the glass mass is floated and floated on the molding die, and after the molding is finished, The glass molded body is taken out from the molding die, and the molten glass mass is again supplied to the empty mold to perform molding. By arranging several shaping | molding dies on a turntable and index-rotating a table, glass molded bodies can be produced one after another from the molten glass which flows out continuously.

By the way, in recent years, the demand of the lens whose at least one optical function surface among concave meniscus lens, a biconcave lens, a flat concave lens etc. is concave shape is increasing. Patent documents 3 and 4 disclose the manufacturing method of the lens whose one or both optical functional surfaces are concave-shaped. Patent Document 3 describes a method of manufacturing a meniscus-shaped optical element by press molding a glass under heating using a pair of molding dies comprising a first mold member and a second mold member. This method is a glass material for optical element molding, and heats a cylindrical glass having a flat surface as a mirror surface at a temperature equal to or higher than the yield point of the glass in an atmosphere of 10 ³ Pa or less, and has one side convex by self-weight deformation. It is characterized by using what was thermally deformed so that the other surface may become concave shape. Patent Document 4 describes a method of forming an optical element by press molding a glass material under heating using a pair of molding dies each having a first mold and a second mold facing each other, and the glass materials have different diameters. Two or more other cylindrical glass materials are formed by overlapping between the two molds and press-molding them.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2007-99529

[Patent Document 2] Japanese Unexamined Patent Publication No. 2003-40632

[Patent Document 3] Japanese Patent Application Laid-Open No. 9-295817

[Patent Document 4] Japanese Patent Application Laid-Open No. 9-249424

As mentioned above, the demand of the lens whose at least one optical function surface is concave shape among the concave meniscus lens, both concave lenses, a flat concave lens, etc. is increasing. Such a lens has a higher proportion of the volume of the entire lens than that of the biconvex lens or the flat convex lens in a portion (a peripheral portion of the lens) away from the optical axis than in the vicinity of the optical axis. That is, when molding such a lens, the space in the mold is narrow near the central axis of the mold (which coincides with the optical axis of the lens to be molded) and becomes wider as it is separated from the axis. If the glass is to be spread and widened in this space, the glass does not widen along the forming surface, and falls out in the lateral direction. As a result, the glass does not spread widely throughout the molding surface, and a lens having high surface precision is not obtained over the whole optical functional surface. This tendency becomes particularly remarkable at the periphery of the concave optical functional surface.

In order to produce a lens having excellent surface accuracy for a concave meniscus lens or the like having a problem as described above, for example, a method of processing a preform into a shape approximating the lens shape and then performing precision press molding is considered. (First method). However, in this method, unless the shape of the pre-pressed surface of the preform, that is, the surface pressed by the molding die during precision press molding is precisely processed, an atmospheric gas is trapped between the glass and the molding surface (called a gas trap). In this part, since the shape of the molding surface cannot be transferred to the glass, there is a problem that the surface precision is lowered.

As another method, a method of using a preform having a large center thickness is conceivable (second method). This method is a method of spreading the glass widely throughout the molding surface by actively increasing the amount of glass deformation during precision press molding, thereby transferring the entire molding surface to the glass. However, in this method, the volume of the preform must be greatly increased compared to the volume of the lens, and the glass (called a residue) that is projected on the outside of the molding surface is bound to be large. When the molded article with a large amount of such residue is cooled, the crushing phenomenon increases the volume shrinkage of the residue portion, deforms a portion close to the residue on the optical function surface, and deteriorates the surface precision of the lens.

In addition, when the residual portion is large, the inner diameter of the sleeve forming the press-molding die must be increased to accommodate the press-molded article, and the entire press-molded die must be made large. However, when the press molding die is enlarged, the cracking property of the die is lowered, and the surface accuracy of the lens cannot be sufficiently increased. In addition, since the press-molding die is made of expensive materials such as SiC and cemented carbide, the enlargement of the die leads to an increase in the mold cost. In addition, by increasing the size of the mold, the processing cost also increases.

In addition, a large amount of residues increases the time required for deep odor processing, thereby increasing the production cost. In addition, from the viewpoint of increasing the utilization rate of glass, which is one of the features of the precision press molding method, it cannot be said that molding with many residues is preferable.

In addition, since the preform volume must be made larger than the lens volume, the time required for heating the preform or cooling the precision press-molded product must be lengthened, resulting in a decrease in throughput.

In view of such circumstances, when the methods described in Patent Documents 3 and 4 are examined, the method described in Patent Document 3 is a method using free deformation by heating, and therefore, the thickness cannot be largely taken for a diameter. Therefore, the method described in patent document 3 is not suitable for the said 2nd method. In addition, since it is a method using free deformation, it is also difficult to produce a glass material having a shape very close to the lens shape, and therefore it is not suitable for the first method.

In the method described in Patent Document 4, when the number of glasses overlapping each other is increased, the labor and cost during polishing are increased, and when the amount is small, the residue during precision press molding is increased, so that the surface precision of the lens is reduced, The labor and cost of the is increased.

An optical element, in particular a meniscus lens, having a predetermined surface precision, without precisely processing the shape of the surface pressurized by the mold during precision press molding, and without significantly increasing the preform volume relative to the volume of the optical element. Although a new technique for efficiently producing an optical element having a concave optical functional surface such as both concave lenses is required, it is a phenomenon that such a technique does not exist.

In the lens having the concave optical functional surface as described above, it is preferable to use a glass having a high refractive index in view of the optical design. As the high refractive index glass, such as B ₂ O ₃ -La may be a high refractive index and high dispersion glass as typified by ₂ O ₃ based glass which is represented by a refractive index medium and low dispersion glass, phosphoric acid-based glass.

Since the high refractive index medium-low dispersion glass has a narrow temperature range corresponding to the viscosity suitable for precision press molding, temperature control at the time of press molding is difficult. If the temperature is too low, necessary surface precision of the lens may not be obtained, or gaps or cracks may occur. On the other hand, when temperature is too high, it will fuse | melt with a press molding die.

The high refractive index high dispersion glass has high reactivity with the press-molding mold, and is easy to cause fusion with the mold. Moreover, radial flaws which are considered to be due to reaction with a mold tend to occur on the lens surface. In order to suppress the reaction of glass and a mold, it is desired to lower the reactivity by lowering the temperature at the time of press molding.

In order to eliminate such troubles (the occurrence of fusion and radiation defects), it is preferable to keep the temperature of the glass at the time of precision press molding as low as possible. Therefore, the glass of high viscosity state is pressed. As described above, when minute defects such as grinding traces are present on the surface of the preform, defects such as glass breakage are likely to occur during precision press molding. In the polishing of glass, polishing is performed while applying a liquid such as water to the glass surface. However, in the case of phosphate glass, in particular, a deterioration layer such as a hydration layer is easily formed on the surface. It promotes fusion with the mold forming surface.

This tendency becomes remarkable when the glass transition temperature (Tg) exceeds 540 ° C. or higher and the refractive index nd becomes 1.75 or higher in the high refractive index medium-low dispersion glass, and in the high refractive index high dispersion glass, the refractive index nd is 1.75. If it becomes abnormal, it will become remarkable.

In any case, when obtaining an optical element with high surface accuracy, it is necessary to reliably prevent damage to the glass.

The present invention has been made to solve this problem,

(1) without precisely processing the shape of the surface pressurized by the molding die during precision press molding,

(2) without significantly increasing the preform volume compared to the lens volume,

(3) without breaking the glass,

(4) The optical element having a predetermined surface precision can be efficiently produced.

It is an object of the present invention to provide a preform for precision press molding and to provide a molding die that can be used to manufacture such a precision press molding preform.

Moreover, an object of this invention is to provide the manufacturing method of the optical element using the said preform for precision press molding.

Moreover, an object of this invention is to provide the manufacturing method of the molded object which can be used as a base material of the preform for precision press molding using the said shaping | molding die, or the preform for precision press molding.

The present invention is a glass preform for precision press molding, which has a rotational symmetry axis, and has two end faces intersecting the rotation symmetry axis and one side surface connected to an outer circumference of the two end faces.

The two end faces are the pressed surface and are independently convex or concave,

Assuming a virtual circumference having an axis coinciding with the axis of rotation symmetry and circumscribing the preform, the ratio (ø / h) of the diameter ø to the height h of the circumference is 1 or more and 3 or less,

A ratio (V / V ₀ ) of the volume V of the preform to the volume V ₀ of the circumference is 68% or more, and relates to a preform for precision press molding (claim 1).

Moreover, this invention relates to the manufacturing method of the optical element containing precision press molding the said preform for precision press molding of the said invention using a press molding die (claim 24).

Moreover, this invention is a shaping | molding die used for shaping | molding a molten glass lump while cooling in a floating state, and obtaining a glass molded object,

The said shaping | molding die is provided with the concave glass shaping | molding part which has a bottom part and the side wall installed so that the circumference | surroundings of the bottom part may be provided,

The bottom portion has a plurality of gas ejection openings for ejecting a gas for floating by applying wind pressure to the glass mass.

It relates to a molding die, characterized in that (claim 10).

In addition, the present invention is a method for producing a glass molded body obtained by flowing out the molten glass to separate the molten glass lump, and forming the glass lump by cooling while cooling the glass lump in a glass forming unit provided in the molding die,

As the shaping mold, by using the shaping mold of the present invention and holding the molten glass lump in a floating state in the glass shaping portion of the shaping mold, two pieces having a rotational symmetry axis and intersecting the rotational symmetry axis, respectively, It relates to a method for producing a glass molded body comprising a glass molded body having an end face and one side surface connected to the outer circumference of the two end faces (claim 18).

Moreover, this invention is the manufacturing method of the preform for precision press molding which manufactures a glass molded object by the method of the said invention, and grind | polishing at least one part of the said molded object (claim 23).

Moreover, this invention is a manufacturing method of the optical element containing precision press molding the glass molded object or the preform for precision press molding obtained by the manufacturing method of the said invention using a press molding die (claim 26).

According to the present invention, it is possible to provide a preform for precision press molding for efficiently producing an optical element with high precision and a method for producing an optical element using the preform.

Moreover, according to this invention, the shaping | molding die used for manufacturing the preform for precision press molding for producing a high precision optical element efficiently can be provided. Moreover, according to this invention, the manufacturing method of the molded object which can be used as a base material of the preform for precision press molding or the preform for precision press molding using the said shaping | molding die can be provided. Moreover, according to this invention, the manufacturing method of the optical element using the preform for precision press molding manufactured by the said manufacturing method can be provided.

In this invention, when describing a range below and specifying a range, an upper limit shall be included in the said range, and as described above, when specifying a range, a minimum shall be included in the said range.

<Preform for Precision Press Forming>

The precision press molding preform for glass according to the present invention has a rotational symmetry axis, and has two end faces intersecting the rotation symmetry axis and one side surface connected to the outer periphery of the two end faces. Preform. In addition, the two end faces of the preform of the present invention are a pneumatic surface and are independently convex or concave surfaces. In addition, the preform of the present invention has an axis coinciding with the axis of rotation symmetry, and when a virtual circumference circumscribes the preform is assumed, the ratio (ø / h) of the diameter ø to the height h of the circumference is 1 or more. And 3 or less. Further, the ratio (V / V ₀ ) of the volume V of the preform to the volume V ₀ of the circumference is 68% or more.

The preform of this invention has the axis of rotation symmetry, and has two end surfaces which respectively intersect the said rotation symmetry axis, and one side surface connected to the outer periphery of the said two end surfaces.

In order to shape an optical element having a rotational symmetry having a very high optical functional surface like a lens, it is appropriate to use a preform having a rotational symmetry axis. For an operation of rotating by an arbitrary angle around the axis of rotation symmetry, the contours of the preforms before and after rotation can overlap each other. However, this rotational symmetry does not need to be geometrically rigid, and it should just be a grade which can manufacture a desired optical element by precision press molding.

Typical shapes of the preform of the present invention are cylindrical, but not only purely cylindrical, but one or both of the two end faces may be convex. In addition, it may be any of the case where the side is parallel to the axis of rotation symmetry and non-parallel.

In order to spread and widen the glass evenly by precision press molding, and to obtain an optical element with less knitting, the surface facing the direction of the rotational symmetry axis, that is, the end surface is taken as the pressed surface during precision press molding. The end face may be convex or concave. For example, both end faces may be convex, two end faces and concave, or one of the two end faces may be convex and the other concave. What is necessary is just to determine whether an end surface is convex or concave, considering the shape of optical elements, such as a lens to shape | mold, For example, when forming a concave meniscus lens or a convex meniscus lens, two end surfaces Both of them are convex, or one of the two end faces is convex and the other is concave. When forming both concave lenses, the two end faces are both convex or both end faces are concave. It is preferable to set it as one, or to make one of two end surfaces convex, and the other as a concave surface. And by determining the curvature of an end surface according to the shape of the shaping | molding surface of a press molding die, the gas trap at the time of precision press molding can be prevented.

If the end face is convex or concave, the curvature is appropriately determined in consideration of the spherical surface if the press-molded surface is spherical, and the aspherical reference curvature of the aspherical surface if the molded surface is aspheric. Can be. The curvature of the two end faces may be the same or different.

Moreover, the said convex surface may be provided with the recessed part in the area | region containing the intersection with the axis of rotation symmetry of a convex surface. The size of the concave portion (ratio to the convex surface) can be appropriately determined in consideration of the curvature of the spherical surface if the optical functional surface of the lens is spherical, and the aspheric reference curvature of the aspherical surface of the aspherical surface. For example, if the diameter of the optical functional surface of the lens is d, the diameter of the concave portion can be in the range of d / 3 to d / 2. The depth of the recess can be appropriately determined in consideration of the texture of the lens and the like. For example, if the height h is used, the depth of the recess can be h / 5 to h / 4.

In addition, when the end surface (the pressed surface) is a convex surface, a concave portion is formed in an area including an intersection with the rotational symmetry axis of the end surface, so that the pressed surface is pressed when the pressed surface is formed on the convex forming surface. It is easier to align the center of the preform and the center of the preform. In addition, during mass production of the precision press-molded product, the preform is introduced into the press-molding die, and the press-form into which the preform is introduced is moved even if the concave portion of the pressed surface is pressed at the top of the convex-shaped molding surface. It is also possible to keep the position of the preform fixed. This effect can be obtained even when the end surface is a concave surface, and the center of the concave surface, i.e., the recessed portion, is an area including an intersection with the axis of rotational symmetry of the end surface.

Two outer periphery of the side surface of the preform of this invention connect to each of the outer peripheries of two end surfaces. The connection portion may form an angle or a curved surface. Alternatively, a connection surface may be formed between the two outer peripheries of the side faces and the outer periphery of the end faces, respectively, to connect the two outer peripheries of the side faces and the outer peripheries of the end faces.

The side surface of the preform of the present invention may be a shape that approximates the lateral shape of the circumference or the lateral shape of the circumference, or a shape that approximates the lateral shape of the shingled cone or the side shape of the shingled cone. According to this preform having such a shape, it is possible to further increase the filling factor (V / V _0). The lateral shape of the circumference means that the diameter of the circumferential cross section is equal at any position of the cross section, and the surface of the side face is a smooth curved surface (curved flat surface) based on the smooth circumference. On the other hand, a shape that approximates the lateral shape of the circumference is not strictly a lateral shape of the circumference from the geometrical point of view, such as when the side of the preform has a groove to be described later. Means a shape which can be regarded as equivalent to the lateral shape of the circumference. Specifically, the shape approximating the lateral shape of the circumference has irregularities and grooves (waveform structure) on the surface of the lateral surface, but the diameter of the circle circumscribed or inscribed to these irregularities and grooves of the circumferential cross section is equal at any position in the cross section. It means shape. The shape and dimensions of the irregularities and the grooves can be appropriately determined in consideration of the volume of the preform to be molded and the ratio of the diameter ø to the height h of the circumference and the curvature of the lower surface side. By having irregularities and grooves (and mountain ranges) on the side of the preform, it is possible to prevent the side of the preform from becoming a gas trap in the post-forming molding step, or to deform in comparison with a smooth curved surface (curved flat surface). The resistance to is increased, which is effective in suppressing residue formation.

Further, the lateral shape of the ashhead cone decreases or increases in diameter of the circumferential cross section from one end face to the other end face, and the surface of the side face is a smooth curved surface (curved flat surface) based on the smooth circumference. The degree of reduction or increase in the diameter of the circumferential cross section is appropriately determined in consideration of the shape required for the preform, but the range of 4 ° to 6 ° is assumed for the right angle (full width 2α) of the virtual cone having the side of the ash cone as a part of the side. It is suitable from the viewpoint of making it easy to take out in the slow cooling process of a preform. Also, α is an angle (inner angle) formed by the central axis of the imaginary cone and the mother ship.

In addition, the shape approximating the side shape of the ash column is not exactly the side shape of the column in the shape of the ash column, such as the case where the side of the preform has a groove to be described later. It means the shape which can be regarded as equivalent to the lateral shape of the circumferential column from the viewpoint. Specifically, as in the case of a shape that approximates the lateral shape of the circumference, the surface of the lateral surface has irregularities or grooves (waveform structure), but the diameter of the circle circumscribed or inscribed to these irregularities or grooves of the circumferential cross section is one end surface. From toward the other end face, means a decreasing or increasing shape. The shape and dimensions of the unevenness and the groove can be appropriately determined in consideration of the ease of taking out the slow cooling step of the preform. By having irregularities and grooves (and ridges) on the side surfaces of the preforms, it is possible to prevent the side surfaces of the preforms from becoming gas traps in the post-processing molding process, or in the case of smooth curved surfaces (curved flat surfaces), The resistance to deformation increases, which is effective in suppressing residue formation.

Even when the glass is pulled out in a direction orthogonal to the press direction, that is, when the glass is uniformly widened in the orthogonal direction when pressed, and the glass does not spread widely on the forming surface, it is a factor that lowers the surface precision of the optical element. do. In terms of suppressing the behavior of the glass at the time of pressing, a preform in which a plurality of grooves formed from one side of the two end faces toward the other side is formed. Since the grooves are located on the side surface, the glass spreads on the mold-forming surface and widens in the space in the press-molding surface at the time of pressing, so that an optical element having high surface precision can be manufactured more easily. It is preferable that the some groove | channel of the side surface is arrange | positioned at equal intervals. By doing so, it is possible to control the widening of the glass isotropically about the rotational symmetry axis of the preform during precision press molding. The grooves may be formed parallel to the rotational symmetry axis, or may be formed in a constant direction with respect to the rotational symmetry axis, but during precision press molding, after the glass is controlled isotropically around the rotational symmetry axis, The groove is preferably formed parallel to the axis of rotation symmetry. In addition, the said groove | channel can be obtained by the method mentioned later.

In precision press molding, high viscosity glass is pressed at high pressure. And since the deformation | transformation amount at the time of press is large in the preform of this invention, when grinding traces or a flaw exist in the surface of a preform, the glass will be easy to break from the part as a starting point. After preventing such trouble, preferably, at least the side surface of the preform is obtained by solidifying the glass in the molten state, and more preferably, two end surfaces (pipress surface) besides the side surface are also obtained by the solidification of the glass in the molten state. It is done. The surface obtained by solidifying the molten glass means the glass surface obtained when the whole glass molded object used as the whole preform or the base material of a preform is produced by cooling and solidifying molten glass, and the below-mentioned heating polishing surface, ie, a glass surface, It differs from the surface obtained by solidifying after heating and remelting a bay. Since cold working such as grinding and polishing is not performed on the surface obtained by solidifying the molten glass, no grinding traces or polishing scratches exist, and no starting point of the breakage exists. Particularly preferred is a preform in which the entire surface is a surface obtained by solidifying the glass in the molten state from the viewpoint. Moreover, since the grinding | polishing trace and a grinding | wound flaw are repaired by remelting, and the heat-polishing surface obtained by cooling and solidifying after remelting a glass surface becomes a microscopically smooth surface, the origin of the said destruction does not exist.

The heated polishing surface is obtained by a method called fire polish. However, since the glass surface is reheated at a high temperature on the heat-polishing surface, there is a fear that the glass surface is deteriorated. In particular, in the glass containing an easy-to volatile components such as B ₂ O _3, alkali metals, fluorine, chlorine, tends to deteriorate the glass surface by the volatilization at the time of fire policy. In addition, since the glass once formed into a desired shape is reheated and remelted, the glass is deformed from the desired shape. For this reason, the latter is remarkably superior when the heated polished surface and the surface obtained by solidifying the molten glass are compared. The mirror polished surface is a polished surface after a lapping process such as rough polishing or sand blasting. There are a large number of grinding marks and abrasive scratches on the wrapped surface, which are the starting point of the breakdown. In the mirror polished surface, the larger one of these origins is removed, but since there is a very small flaw called a latent image, the preform having the mirror polished surface is composed of the entire surface by the surface obtained by solidifying molten glass or the heated polishing surface. The fracture resistance is lower than that of the preform. Since the etching trace also removes grinding traces and polishing defects by etching, the preform whose surface is an etching surface is also excellent in fracture resistance. However, when the surface with a latent flaw is etched, fracture resistance may deteriorate because a flaw is present. Either way, it is remarkably preferable to set it as the surface obtained by solidifying the glass of a molten state.

Moreover, as an example of the surface obtained by solidifying the glass of a molten state, the free surface, the mold transfer surface obtained by transferring a mold shaping surface to a molten glass, etc. are mentioned. The free surface can be formed, for example, by forming a molten glass mass while floating. The mold transfer surface can be formed by pressing the glass by a press molding die or by introducing molten glass into the mold.

In the preform of the present invention, the shape is adjusted so that the ratio (? / H) of the diameter? To the height h of the imaginary circumference circumscribed to the preform is 1 or more and 3 or less. If the ratio (? / H) is less than 1, the side portion or the boundary portion between the side surface and the end surface (piped surface) enters the effective diameter of the lens, and the possibility of deteriorating the quality of the lens surface increases. On the other hand, when the ratio (? / H) is larger than 3, the amount of deformation of the glass at the time of precision press molding becomes small, and it becomes difficult to spread the glass widely throughout the molding surface. In addition, the preform may be biased in the press-molding mold, causing the lens to be skewed and eccentric. Therefore, the ratio (? / H) is set as the above range, but the preferred range of the ratio (? / H) is 1 to 2.6, more preferably 1 to 2.4, and still more preferably 1 to 2.0.

The shape of the preform of the present invention is also preferable from the point of producing a preform which is a surface obtained by solidifying the glass in the molten state. In preparation of the preform which is the surface obtained by solidifying the glass of a molten state, it shape | molds while applying a wind pressure to a molten glass mass and floats, as mentioned later. At this time, although the wind pressure which blows out a gas on the bottom of a glass lump and raises it is acquired, when ø / h is too big | large, it will become difficult for the said gas to fall out along the side surface from the bottom of a glass lump, and it will become difficult to float a glass lump stably. On the other hand, when ø / h is too small, it becomes difficult to float the glass mass only by the wind pressure applied to the bottom of the glass mass. Since ø / h is in the range of the present invention, the glass mass can be molded while stably floating. In addition, the preferable range of (phi) / h becomes a range mentioned above also from a viewpoint of stabilization of the floating of a glass lump.

In this way, precision after securing the amount of deformation of the glass at the time of press forming, from the viewpoint of reducing, inhibiting the amount coming out becomes empty from the forming surface of the glass, a preform for a volume V ₀ of the cylindrical volume V of the ratio (V / V ₀ ) is made 68% or more. The ratio (V / V ₀ ) is an amount that can also be referred to as the filling rate of glass in the virtual circumference, and can be considered as an index for reducing the amount of glass to be used while improving the surface accuracy of the entire optical functional surface. In terms of increasing the effective, non-(V / V ₀₎ to be not less than 69% is preferred, more preferably to the preferred, more than 71% from not less than 70%, of more than 72% It is more preferable. The upper limit of the filling rate (V / V ₀ ) is about 96%, and considering the reduction in filling rate due to the grooves or end faces of the side surfaces described later, the upper limit of the filling rate is preferably 94%, and is 92%. It is more preferable to set it, it is further more preferable to set it as 90%, and it is further more preferable to set it as 88%.

When the preform is a spheroid, the filling rate (V / V ₀ ) is 2/3 (66.7%), and even when the preform is a sphere, the filling rate (V / V ₀ ) is 2/3 (66.7%). Therefore, in these preforms, even when scaled up to increase the amount of deformation of the glass during precision press molding, the filling rate (V / V ₀ ) is constant, so that even if the amount of deformation of the glass can be increased, it is protruded from the molding surface. The amount of glass, ie the amount of residue, also increases. As a result, the surface accuracy of the lens is lowered due to crushing of the residue part. In addition, if the residue portion is large, the sleeve type for accommodating the glass is also large, and the entire press-molded type also becomes large, so that the cracking property of the mold decreases, making it difficult to make an optical element with high surface precision over the whole optical functional surface. do.

On the other hand, in the present invention, since the ratio (ø / h) is 1 or more and 3 or less and (V / V ₀ ) is 68% or more, press molding with little residue is possible, and as a result, the optical functional surface Optical elements with high surface accuracy can be obtained over the whole area. In addition, since the enlargement of the press-molding die can be suppressed with respect to a predetermined optical element, it is possible to reduce the mold cost and the processing cost of the mold. In addition, while reducing the amount of glass removed by the deep odor processing, the time required for the deep odor processing can be shortened, and the utilization rate of the glass can be increased. In addition, the throughput required for heating the preform or cooling the precision press-molded product can be shortened to increase throughput.

When ø is used with a preform smaller than the diameter when the molding surface is viewed in a plane, the side surface of the preform may become an optical functional surface by precision press molding. Even in that case, by making a side surface into a mirror surface, the optical functional surface which is smooth and has high surface precision can be shape | molded. However, in order to form a smooth and highly functional optical functional surface and to reduce and prevent breakage of the glass during precision press molding, the corner where the p-pressed surface and the side surface intersect is a curved surface, and the curved surface is also a mirror surface. It is desirable to do so. However, from the point of forming a smooth and highly functional optical functional surface, it is preferable that? Is larger than the diameter when the molding surface is viewed in a plane.

In addition, it is preferable to make the maximum height Ry of the pressed surface smaller than the maximum height Ry of the side surface (by JIS B0601-1994) in terms of forming a smooth optical function surface. Specifically, the maximum height Ry of the side surface is preferably 1 µm or less and approximately 0.3 µm to 1 µm, and the maximum height Ry of the end surface that is the pressed surface is 0.02 µm or less and approximately 0.01 µm to 0.02 µm. It is a range.

In addition, the preform of this invention can be manufactured by the method of mentioning later, and can also be produced by the method of grinding and polishing glass, and can also be produced by the method of grinding and polishing after press-molding glass.

The preform of the present invention can be suitably used for molding concave meniscus lenses, convex meniscus lenses, and both concave lenses, and is particularly preferable for forming concave meniscus lenses and both concave lenses.

Glass preferred as materials for concave meniscus lenses, convex meniscus lenses, biconcave lenses and the like is glass containing B ₂ O ₃ and La ₂ O ₃ as the glass component. Such glass is high refractive index low dispersion glass or high refractive index medium dispersion glass. As mentioned above, the temperature range from which the viscosity suitable for precision press molding is obtained is narrow, and the glass transition temperature is also high. Therefore, only a slight fluctuation in the press molding temperature is likely to cause fracture from the origin of fracture present on the side of the preform. In addition, the glass having a high glass transition temperature has a high preform heating temperature and a press molding heating temperature at the time of precision press molding, but the preform is reduced in preventing and preventing the consumption of the release film formed on the press molding mold or the mold molding surface. It is preferable to suppress both heating temperatures of the press-molding die as low as possible. In response to these demands, high-viscosity glass is pressed in precision press molding with a large amount of glass deformation. At this time, if it is the said preform in which the above-mentioned breakdown origin does not exist on a surface, optical elements, such as a concave meniscus lens, a convex meniscus lens, a biconcave lens, can be shape | molded.

As a 1st specific example of the preform of this invention, the preform comprised by the optical glass whose glass transition temperature (Tg) is 540 degreeC or more, More preferably, the preform comprised by the optical glass whose glass transition temperature (Tg) is 570 degreeC or more. More preferably, it is a preform comprised with glass whose glass transition temperature (Tg) is 590 degreeC or more, More preferably, it is a preform comprised with glass whose glass transition temperature (Tg) is 600 degreeC or more. However, when the glass transition temperature Tg becomes too high, precision press molding may become difficult. Therefore, it is preferable to make glass transition temperature Tg below 690 degreeC.

As glass which comprises the preform for precision press molding of this invention, the following optical glasses are preferable, for example.

The preform of the present invention is suitable for molding lenses having concave lens surfaces such as meniscus lenses and biconcave lenses, but among them, for molding lenses having negative refractive power such as concave meniscus lenses and biconcave lenses. desirable. Such a lens is suitable for color erasing in combination with a lens having a positive refractive power, and it is preferable to use a glass having a low dispersion rather than a glass constituting a lens having a positive refractive power. In addition, glass having a high refractive index is preferred in that the compactness of the optical system and the absolute value of the curvature of the lens surface are reduced to facilitate mold processing and precision press molding of the precision press molding.

From this point of view, as the glass constituting the preform of the present invention, in the range where the Abbe's number νd is 35 or more, the optical glass having the refractive index nd that satisfies the following formula 1 in the range where the refractive index nd is 1.70 or more and the Abbe's number νd is less than 35: Is preferred.

More preferably, glass having a refractive index nd of 1.75 or more within the above range is preferable.

However, if the refractive index is further increased while maintaining low dispersion, the glass stability is lowered. Therefore, it is preferable that the optical property within the above range is within a range satisfying the following Equation 2. More preferred.

(week)

Equation 1 is a straight line connecting nd = 1.90, νd = 25 and nd = 1.7, νd = 35

Equation 2 is a straight line connecting nd = 2.00, νd = 45 and nd = 1.7, νd = 65

Equation 3 is a straight line connecting nd = 2.00, νd = 35 and nd = 1.7, νd = 60

In addition to the optical properties, glass that exhibits a relatively low glass transition temperature is preferable for glass for precision press molding. As glass which realizes such a property, in mol% display, as a glass component,

B₂O₃ 5 to 70%,

SiO₂ 0-50%,

ZnO 1-50%,

La₂O₃ 5-30%,

Gd₂O₃ 0-22%,

Y₂O₃ 0-10%,

Yb₂O₃ 0-10%,

Li ₂ O 0-20%,

Na ₂ O 0-10%,

K ₂ O 0-10%,

MgO 0-10%,

CaO 0-10%,

SrO 0-10%,

BaO 0-10%,

ZrO₂ 0-15%,

Ta₂O₅ 0 to 20%,

WO₃ 0 to 20%,

Nb₂O₅ 0-15%,

TiO₂ 0-40%,

Bi₂O₃ 0-10%,

GeO₂ 0-10%,

Ga₂O₃ 0-10%,

Al₂O₃ 0-10%

The optical glass containing the can be illustrated.

The optical glass will be described below. In addition, unless otherwise specified, the quantity of each component shall be represented by mol%.

B ₂ O ₃ is an essential component and serves as an oxide to form a glass mesh. When high refractive index components such as La ₂ O ₃ are introduced, B ₂ O ₃ is introduced in order to form 5% or more of B ₂ O _{3 so as} to form a main network component, while providing sufficient stability against devitrification and Although it is necessary to maintain meltability, when it exceeds 70%, the refractive index of glass will fall and it will become unsuitable for the objective of obtaining high refractive index glass. Therefore, the amount of B ₂ O ₃ introduced is 5 to 70%, preferably 10 to 65%, more preferably 10 to 60%, still more preferably 15 to 60%.

SiO ₂ is an optional component and La ₂ O ₃ For glass containing a large amount of rare earth oxide components such as glass, the liquidus temperature of the glass is lowered, the high temperature viscosity is improved, and the stability of the glass is greatly improved, but the refractive index of the glass is lowered by the introduction of excess. In addition, the glass transition temperature becomes high, making precise press molding difficult. Therefore, the amount of SiO ₂ introduced is 0 to 50%, preferably 0 to 40%, more preferably 0 to 30%, still more preferably 0 to 25%.

ZnO is an essential component, lowers the melting temperature, the liquidus temperature, and the transition temperature of the glass, and is indispensable to the adjustment of the refractive index. If the content is less than 1%, the above effect is weak. If the content is more than 50%, the dispersion is increased, the stability against devitrification is deteriorated, and the chemical durability is also lowered. Therefore, the amount of introduction is in the range of 1 to 50%, The preferred range is 3 to 45%, more preferably 5 to 40%, and still more preferably 10 to 35%.

La ₂ O _{3 is} also an essential component, and the chemical index is improved by increasing the refractive index without lowering the stability to devitrification of the glass or increasing the dispersion. However, if it is less than 5%, a sufficient effect is not obtained, and if it exceeds 30%, the stability against devitrification significantly deteriorates, so that the amount of introduction is 5-30%, preferably 5-25%, more preferably 5-5. It is 22%, More preferably, it is 5 to 20%.

Like La ₂ O ₃ , Gd ₂ O ₃ is a component that improves the refractive index and chemical durability of glass without deteriorating the stability and low dispersibility of the glass. When Gd ₂ O ₃ is introduced in excess of 22%, the stability against devitrification deteriorates, and the glass transition temperature increases, so that the precision press formability tends to deteriorate, so the introduction amount is 0 to 22%, preferably 0. 20%, More preferably, it is 0-18%, More preferably, you may be 0-15%.

Y ₂ O ₃ and Yb ₂ O ₃ are arbitrary components that realize high refractive index and low dispersion glass. When a small amount is introduced, Y ₂ O ₃ and Yb ₂ O ₃ increase the stability of the glass and improve chemical durability. It greatly impairs the stability to the glass and raises the glass transition temperature or yield point temperature. Thus, Y ₂ 0 - 10% and a content of the content of, Yb ₂ O ₃ of O ₃ is set at 0-10%.

Although Li ₂ O has a great effect of lowering the glass transition temperature, the refractive index decreases due to excessive introduction, and the glass stability also decreases. Therefore, the amount of Li ₂ O is 0 to 20%, preferably 0 to 15%, more preferably 0 to 10%, still more preferably 0 to 8%. In addition, when the priority given to the low-temperature softening sex are to the amount of Li ₂ O less than 0.1%.

Na ₂ O and K ₂ O have a function of improving meltability. However, since the refractive index and the glass stability decrease due to excessive introduction, each amount of introduction is made 0 to 10%.

MgO, CaO, and SrO also have a function of improving meltability. However, since the refractive index and the glass stability decrease due to excessive introduction, each amount of introduction is made 0 to 10%.

Although BaO functions to increase the refractive index, the glass stability is lowered due to excessive introduction, so that the amount of introduction is made 0 to 10%.

ZrO ₂ is an essential component used to realize high refractive index glass and to maintain low dispersion of glass. By introducing ZrO ₂ , the effect of improving the viscosity of the glass and the stability to devitrification can be obtained without lowering the refractive index of the glass, but when it is introduced in excess of 15%, the liquidus temperature rises rapidly and the stability to devitrification also deteriorates. The introduction amount is 0 to 15%, preferably 0 to 12%, more preferably 0 to 10%, still more preferably 0 to 8%.

Ta ₂ O ₅ is an optional component that realizes high refractive index and low dispersion glass. By introducing Ta ₂ O ₅ , there is an effect of improving the stability to high temperature viscosity and devitrification without lowering the refractive index of the glass, but when it is introduced in excess of 20%, the liquidus temperature rises rapidly and dispersion increases. The introduction amount is 0 to 20%, preferably 0 to 17%, more preferably 0 to 14%, still more preferably 0 to 10%.

WO ₃ is a component which is suitably introduced in order to improve the stability and meltability of the glass and to improve the refractive index. However, when the amount is more than 20%, the dispersion becomes large and the necessary dispersion characteristics are not obtained, and the coloring of the glass is increased. Therefore, the introduction amount is 0 to 20%, preferably 0 to 18%, more preferably 0 to 16%, still more preferably 0 to 14%.

Nb ₂ O ₅ is an optional component which increases the refractive index while maintaining the stability of the glass, but since dispersion is increased by excessive introduction, the amount of introduction is 0 to 15%, preferably 0 to 13%, more preferably 0 to 10 %, More preferably, you may be 0 to 8%.

TiO ₂ is an optional component that can be introduced to improve the refractive index of the glass, but the dispersion is increased by excessive introduction, so that the desired optical constant cannot be obtained, or the coloring of the glass is increased, so that the amount of introduction is 0 to 40%. Preferably it is 0 to 35%, More preferably, it is 0 to 30%, More preferably, you may be 0 to 25%.

Bi ₂ O ₃ is an optional component that increases the refractive index of the glass and improves the stability of the glass. However, excessive introduction of the glass reduces the stability of the glass and raises the liquidus temperature. Therefore, the introduction amount shall be 0 to 10%.

GeO ₂ is an optional component which increases the refractive index of the glass and improves the stability of the glass, and the amount of introduction thereof is preferably 0 to 10% and preferably 0 to 8%. However, it is more preferable not to introduce | transduce, since it is expensive at the drastic difference compared with another component.

Ga ₂ O _{3 is} also an optional component which increases the refractive index of the glass and improves the stability of the glass, and the amount of introduction thereof is preferably 0 to 10% and preferably 0 to 8%. However, it is more preferable that it is not introduced because it is expensive with a significant difference compared to other components.

Al ₂ O ₃ is an optional component that increases the high temperature viscosity of the glass, lowers the liquidus temperature, improves moldability of the glass, and also improves chemical durability. However, since the refractive index decreases due to excessive introduction and the stability against devitrification also decreases, the introduction amount is made 0 to 10%.

In addition, although Sb ₂ O ₃ is arbitrarily added as a defoamer, when the amount of Sb ₂ O ₃ added exceeds 1% by weight based on the total content of all glass components, the molding surface of the press-molded die is damaged during precision press molding. It is preferable to add 0 to 1% by weight, more preferably 0 to 0.5% by weight, more preferably 0 to 0.1% by weight of Sb ₂ O _3, based on the total content of all glass components. More preferred.

On the other hand, it is preferable not to introduce | transduce as a glass component, PbO is mentioned as an example. When PbO is harmful and the preform made of glass containing PbO is precisely press-molded in a non-oxidizing atmosphere, lead precipitates on the surface of the molded body and the transparency as an optical element is impaired, or the deposited metal lead is press-molded. Problem arises.

Lu ₂ O ₃ can be introduced at a small amount of 0 to 3%. However, in general, as the component of the optical glass, the frequency of use is less than that of other components, the scarcity value is high, and the optical glass raw material is expensive.

It is preferable not to introduce toxic elements such as elements such as cadmium and tellurium which are environmental problems, radioactive elements such as thorium, and arsenic. Moreover, it is preferable not to introduce fluorine from a problem, such as volatilization at the time of glass melting.

What is necessary is just to determine the introduction amount of each component within the said composition range in order to acquire desired optical characteristic in the above-mentioned range.

As described above, in the case of precise press molding of glass having a high refractive index, when the temperature of the mold or the temperature of the glass increases, the components in the glass, in particular, the high refractive index imparting component and the molding surface of the mold, or the components and the preform surface The coated film causes a chemical reaction, causing problems such as cloudiness or scratches on the surface of the glass or sticking to the mold. In order to avoid such a trouble, it is desired to suppress the temperature of the shaping | molding die and glass at the time of press molding, ie, press-molding glass with a comparatively high viscosity. Therefore, the above-mentioned glass has a narrower allowable temperature range at the time of press molding compared to glass having a low refractive index.

Moreover, compared with glass with a low refractive index, the said glass has a large viscosity change with respect to temperature change, a viscosity rises significantly only by the temperature being slightly reduced, and hard glass is pressed, and a crack and a crack easily occur.

In addition, in the present invention, since the deformation amount of the glass in the precision press molding is large, cracks and cracks are more likely to occur. Therefore, it is desired to reduce or prevent gaps and cracks by removing flaws and latent flaws on the surface of the preform.

As described above, the glass containing the high refractive index imparting component is required to lower the glass transition temperature (Tg) in order to suppress the chemical reaction with the mold forming surface or the chemical reaction with the film coating the preform surface. . The preferable range of glass transition temperature is 650 degrees C or less, More preferably, it is 630 degrees C or less. In addition, as mentioned above, since the said glass contains a high refractive index provision component, in the optical glass for precision press molding, glass transition temperature is comparatively high and the transition temperature becomes 520 degreeC or more as a target. In glass with a higher refractive index or glass with a lower dispersion, the glass transition temperature is higher, and the glass transition temperature is 540 ° C or higher, depending on the glass, 550 ° C or higher, and further 580 ° C or higher and 600 ° C or higher.

As the sheet of glass, in mol _{percentages, B 2 O 3 20~43%,} La 2 O 3 5 to 24%, ZnO 22 to 42%, Li ₂ O 0 to 15%, Gd ₂ O ₃ 0 to 20%, SiO ₂ 0 to 20%, ZrO ₂ 0-10%, Ta ₂ O ₅ 0-10%, WO ₃ 0-10%, Nb ₂ O ₅ 0-10%, TiO ₂ 0-10%, Bi ₂ O ₃ 0-10%, GeO ₂ 0-10%, Ga ₂ O ₃ 0-10%, Al ₂ O ₃ 0-10%, BaO 0-10%, Y ₂ O ₃ 0-10%, Yb ₂ O ₃ 0-10%, Sb ₂ O ₃ The glass containing 0 to 1% can be illustrated.

As described above, optical elements such as concave meniscus lenses and biconcave lenses made of high refractive index and low dispersion glass are subjected to precision press molding by the preform using optical glass having a high glass transition temperature as described above. It can be produced with high precision.

The said glass is preferable as glass which implement | achieves the optical characteristic whose refractive index nd is 1.75 or more and Abbe's number (vd) is 25-55.

Phosphate glass can be mentioned as a 2nd specific example of the glass which comprises the preform of this invention. To obtain high refractive index and high dispersion characteristics, P ₂ O ₅ In addition, phosphate glass containing Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , WO ₃ , Li ₂ O, P ₂ O ₅ , Nb ₂ O ₅ , Bi ₂ O ₃ , phosphate glass containing Li ₂ O Phosphoric acid glass containing P ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , Li ₂ O, P ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , WO ₃ , Li ₂ O Phosphate glass etc. can be illustrated. Since these phosphate glasses contain high refractive index high dispersion imparting components such as Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , and WO ₃ , the phosphate glass reacts with the press-molding mold and, as described above, the fusion of the glass and the mold, and optical Radial flaws on the surface of the device are likely to occur.

In order to eliminate such troubles (the occurrence of fusion and radiation defects), it is preferable to keep the temperature of the glass at the time of precision press molding as low as possible. Therefore, the glass of high viscosity state is pressed. As described above, when minute defects such as grinding traces are present on the surface of the preform, defects such as glass breakage are likely to occur during precision press molding. In the polishing of glass, polishing is performed while applying a liquid such as water to the glass surface. However, in the case of phosphate glass, in particular, a deterioration layer such as a hydration layer is easily formed on the surface. It promotes fusion with the molding surface. According to the present invention, the side of the preform, preferably one of the two end faces in addition to the side, more preferably the side and two end faces, more preferably the entire surface to the surface formed by solidifying the molten glass Thereby, the problem at the time of the precision press molding by the said grinding trace and a deterioration layer can be reduced and eliminated.

Moreover, phosphate glass is preferable as glass which implement | achieves the optical characteristic whose refractive index nd is 1.75 or more and Abbe's number (nud) is less than 25.

<Molding>

Next, the shaping | molding die of this invention used in order to obtain a glass molded object by shape | molding while cooling a molten glass lump in a floating state is demonstrated. The shaping | molding die of this invention is equipped with the concave glass shaping | molding part which has the bottom part and the side wall installed so that the circumference | surroundings of the bottom part may be provided, and the said bottom part has a some which blows out the gas for floating by applying wind pressure to the said glass mass. It is characterized by having a gas outlet.

As mentioned above, the shaping | molding die of this invention is a shaping | molding die suitable for shape | molding one aspect in the molded object, such as the preform which has a specific shape, for example, the preform for precision press molding of this invention. Such a molded article is a glass molded article having an axis of rotational symmetry, and having two end faces each intersecting the axis of rotation symmetry and one side surface connected to the outer periphery of the two end faces. In addition, this molded article has two end faces independently convex or concave, and the side face is made of a surface obtained by solidifying molten glass, and has an axis coinciding with the axis of rotation symmetry, and an external circumference of the preform. Assuming a circumferential circumference, the ratio (ø / h) of the diameter ø to the height h of the circumference is 1 or more and 3 or less, and the ratio of the volume V of the preform to the volume V ₀ of the circumference (V / V It is preferable that ₀ ) is 68% or more. This molded article will be described later.

The shaping | molding die of this invention is provided with the concave glass shaping | molding part which has the bottom part and the side wall installed so that the circumference | surroundings of the bottom part may be provided. Moreover, the bottom part of a glass shaping | molding part has a some gas blowing port which blows out the gas for floating by applying wind pressure to the said glass lump.

Also in the shaping | molding die used for floating-molding glass molded objects, such as a preform known until now, it is providing the bottom part which has a gas outlet, and the concave glass shaping | molding part of the structure in which the side wall is continued as it is from the bottom, for example. For example, patent document 2 has description. However, the shaping | molding die of this invention is characterized by including the concave-glass shaping | molding part which has a plurality of gas ejection openings provided in the bottom part, and has a side wall installed so as to surround the said bottom part, and shaping | molding provided with such a glass shaping part The brother is unknown.

The bottom portion having the plurality of gas blowing holes may be made of, for example, a porous material having air permeability. Alternatively, the non-porous material may be provided with gas outlets regularly or irregularly. The shaping | molding die for floating molding which has several gas ejection opening is known until now.

Specifically, the bottom of the glass molded part is made of a porous body, and a high pressure gas is supplied to the rear surface of the porous body, that is, the surface facing the glass mass, and the gas is passed from the surface facing the glass mass by passing the porous body. It is preferable to eject. By doing in this way, gas can be ejected evenly from the whole surface which faces the bottom glass mass, and an upward wind pressure can be applied to the lower surface of a glass mass relatively uniformly. Therefore, the wind pressure by gas blowing is concentrated in the local part of the lower surface of the glass lump of a low viscosity state, and it can prevent that the unevenness | corrugation generate | occur | produces on the lower surface of the glass lump.

In the said shaping | molding die, since the wind pressure for floating a glass lump is obtained by the gas which blows out from the gas injection port provided in the bottom part, it is preferable to blow out a gas evenly on the glass surface which faces a bottom part. In order to perform such a gas blowing, it is preferable to form a bottom part with a porous body, and it is preferable to provide the gas flow path for supplying gas to the back surface of a porous body. By supplying a high pressure gas to the back surface of the porous body and permeating the porous body, the gas can be ejected from the surface evenly.

Similarly to the bottom surface, the side wall is formed of a porous body, and when a high-pressure gas is supplied to the rear surface of the porous body, the way that the ejected gas escapes from the bottom is easily blocked by the gas ejected from the side surface. As a result, there is a possibility that sufficient wind pressure on the bottom surface cannot be obtained and the floating state of the glass is deteriorated. Therefore, it is preferable to form the gas ejection opening only in the bottom face among the bottom face and the side wall. By forming the gas blowing holes only on the bottom surface, the glass mass can be stably floated.

The shape of the bottom portion is preferably a shape in which the shape of the bottom surface of the preform base material processed on the pressed surface or the pressed surface of the preform, which is a molded body, or a shape approximating the above shape.

In addition, when the shape of the bottom of the glass molded part is a concave surface, the glass mass becomes easy to shake without the sidewalls of the shape, but according to the present invention, even when the shape of the bottom is a concave surface, the glass mass can be stably floated. have.

The shape of the side wall may be either of a side shape of the circumference, a side shape of the ash cone, a shape approximating the side shape of the circumference, or a shape approximating the side shape of the ash ash cone. Here, the shape that approximates the lateral shape of the circumference and the shape that approximates the lateral shape of the ash cone is because a groove or a convex part may be formed in the side wall as described above. The side wall functions to suppress the shaking of the glass lump or the glass molded body. However, the side wall may be a shape approximating the lateral shape of the circumference or a shape approximating the lateral shape of the ash cone in the range of exhibiting such a function.

In order to mold a preform having a large filling rate, a molding die having a sidewall vertical or near vertical is preferable. In such a shaping mold, it is preferable that the sidewall is opened upward, that is, the shape of the sidewall is approximated to the side shape or the shape of the ash cone, so that the preform can be taken out smoothly from the glass forming part, and the opening is made larger than the bottom part. . By doing in this way, the preform can be taken out smoothly from a glass molding part.

It is preferable that the side wall has a gas flow path through which gas ejected from a gas ejection port flows toward the opening direction of the glass molding part. Specifically, the gas flow passage may be a plurality of grooves extending perpendicularly or obliquely to the direction of the opening of the glass molding portion from the bottom, and the surface of the side wall having the gas flow passage is a waveform consisting of a continuous surface or an intermittent surface. Can be. A wave formed by a continuous plane is a shape in which grooves and a mountain range without angles appear alternately, while a wave formed by intermittent surfaces is a shape in which grooves and a mountain range appear alternately, and a tangent between the groove and the mountain range forms an angle. It is a shape. The intermediate shape (for example, a waveform consisting of an intermittent surface and a shape in which the angle between the groove and the mountain range is rounded) may be used.

The shaping | molding die of this invention has a rotational symmetry axis | shaft as mentioned above, and has a 2 end surface which mutually intersects the said rotational symmetry axis | shaft, and one side surface which connects to the outer periphery of the said 2nd end surface, in order to shape | mold the glass molded object Is used. One end face of the molded body is in particular shaped into a shape corresponding to the bottom of the mold, and the side face is molded into a shape corresponding to the side wall of the mold. The molding die of the present invention has a gas flow path on the side wall, whereby at least a part of the gas blown out from the gas jet port reaches the opening via the gas flow path, thereby making it possible to stably maintain the glass mass in the glass molding part. . In addition, the gas passing through the gap between the gas flow passage and the sidewalls other than the gas flow passage and the glass mass can avoid or alleviate the contact between the glass mass and the sidewall, and the side surface of the glass molded body can be a surface obtained by solidifying the molten glass. have.

The shaping | molding die of this invention is further demonstrated based on FIG.

Shown in FIG. 1A is a molding die 10 which is an embodiment of the molding die of the present invention. The shaping | molding die 10 is comprised from the bottom base member 11, the bottom formation part 12 comprised by the porous material formed in the opening part of the center of the bottom base member 11, and the side wall structural member 13. As shown in FIG. The side wall constituent member 13 has an inner wall constituting the side wall of the molded part. In addition, the side wall constituent member 13 can be divided into a plurality of parts, and when taken out of the glass molded body after molding, as shown in FIG. can do.

Shown in Fig. 2A is a molding die 20 which is an embodiment of the molding die of the present invention. The shaping | molding die 20 is comprised from the bottom base member 21, the bottom formation part 22 comprised by the porous material formed in the opening part of the center of the bottom base member 21, and the side wall structural member 23. As shown in FIG. In the side wall constituent member 23, the inner wall constitutes the side wall of the molded part. The lower part of the side wall constituting member 23 has a shape corresponding to the recess formed in the upper portion of the bottom base member 21, and can be assembled by being detachably assembled into the recess. In addition, a magnet 24 may be provided inside the recess formed in the upper portion of the bottom base member 21 to fix the side wall constituting member 23. Moreover, the gas flow path which consists of the groove | channel cut | disconnected in the longitudinal direction is shape | molded in the surface 23a which comprises the side wall inside the opening of the side wall structural member 23. As shown in FIG. In addition, as shown in Fig. 2C, the inside of the opening of the sidewall constitution member 23 has a back ash cone shape (virtual vertex above the sidewall constitution member 23) in which the lower opening is larger than the upper opening. Angle α corresponding to 1/2 of the right angle of the cone, so that the glass molded bodies are not separated from each other when the side wall member 23 is separated from the bottom base member 21 after molding. In consideration of the size of, it can be appropriately determined, for example, it can be in the range of 2 to 3 °. In addition, the said virtual vertex means the vertex of the virtual cone which makes the side of the said ashhead cone a part of a side, and the right angle of a cone means the right angle of the said virtual cone. At the time of taking out the glass molded object after shaping | molding, as shown to (b), the side wall structural member 23 can be removed and the glass molded object can be easily carried in after that.

3A is a molding die 30 which is an embodiment of the molding die of the present invention. The shaping | molding die 30 is comprised from the bottom base member 31 and the bottom formation part 32 comprised with the porous material formed in the opening part of the center of the bottom base member 31. As shown in FIG. As for the upper part of the bottom part formation part 32 of the bottom base member 31, an inner wall comprises the side wall of a shaping | molding part. The inside of the inner wall 33 of the bottom base member 31 has a ash head conical shape (virtual vertex is above the inner wall 33) in which the inner diameter of the lower side is smaller than the opening of the upper side, and of the right angle of the cone. The angle α, which corresponds to 1/2, can be appropriately determined in consideration of the size of the molded body so as not to become a resistance due to engagement when the glass molded body is taken out vertically upwards, and may be, for example, in a range of 2 to 3 °. have. FIG. 3B shows a cross-sectional shape of the bottom base member 31 at X-X '. The unevenness | corrugation of the gas flow path which consists of the groove | channel formed in the longitudinal direction inside the inner wall 33 is shown.

The side wall has a rotation axis symmetry shape or a substantially rotation axis symmetry shape, but the bottom surface is also a rotation axis symmetry shape so that the axis of symmetry of the side wall and the symmetry axis of the bottom surface become a common axis, that is, the shape of the glass molded part is also rotation axis symmetry shape or approximately rotation axis symmetry. It is preferable to set it as a shape.

By doing in this way, the shape of a glass molded object can also be set as rotation axis symmetry shape or substantially rotation axis symmetry shape. When the glass molded body is polished and processed into a preform for precision press molding, that is, when the glass molded body is used as the preform base material, the glass molded body can be used as a preform for precision press molding having a rotation axis symmetry, a rotation axis symmetry shape, or a substantially rotation axis symmetry shape. It is preferable to process.

When producing the optical element of the rotation axis symmetry shape represented by a lens etc. by precision press molding, it is preferable that the shape of a preform is also rotation axis symmetry shape. By pressing the preform from the direction of the symmetry axis, the glass can be symmetrically stretched around the axis to make the optical element typified by a lens with little or no knitting.

It is preferable that the shape of the bottom of the glass molded part is a concave surface, so that the gas ejected from the gas ejection port formed at the bottom flows smoothly through the opening of the glass molded part from the gap between the bottom and the glass, the gap between the side wall and the glass. While gravity acting on the glass mass attempts to close the gap, the gas ejected from the gas outlet tries to form the gap, so that the upward wind pressure acts on the glass mass.

As mentioned above, since the side wall of a glass shaping | molding part rises, the molten glass mass in a glass shaping | molding part is controlled by the side wall, and is largely deviated from the droplet shape. In such a state, due to the surface tension, the molten glass lump is intended to be in the form of droplets, so that the gap between the glass and the sidewall is narrowed, and the gas ejected from the bottom is less likely to fall out between the glass and the sidewall. In order to eliminate such a state, it is preferable to use the shaping | molding die which provided the groove | channel in the opening direction toward the glass molding part from the bottom face side on the side wall. Since the glass is difficult to enter the groove by the surface tension, a gap in which the gas flows in the groove is likely to occur. By making the part which gas tends to fall locally locally, glass becomes hard to enter into that part, and the clearance gap between the glass and side walls which become a gas flow path is ensured stably. As a result, the gas can stay between the glass and the glass molded portion, thereby deforming the shape of the glass molded body or preventing the glass from taking unstable behavior.

The preferable shape of the side wall is provided with a plurality of grooves extending from the bottom side of the glass molding portion toward the opening of the glass molding portion, and the grooves are arranged at regular intervals so that the width and depth of each groove are equal to each other, and each groove is mutually Parallel shapes are more preferred. In this case, the cross-sectional shape of the side wall orthogonal to the axis of symmetry is a shape in which grooves equal in depth and width are formed on the circumference at equal intervals. By making the side shape such a shape, since the gas ejected from the bottom of the shaping die does not flow to any part of the glass lump side surface, the axial symmetry of the glass molded body or the preform does not decrease, or the filling rate (V / V ₀ ) The effect that this does not fall can be acquired.

In the case where the groove is formed on the side wall as described above, the side of the glass molded body is formed with an uneven portion or a wave shape reflecting the shape of the groove. When there are a plurality of grooves on the side wall, a plurality of convex portions are formed on the side surfaces of the glass molded body, and grooves are formed between these convex portions. The convex portion of the glass molded body functions to further suppress the shaking of the glass molded body by fitting into the grooves of the sidewalls of the mold.

<Method of Manufacturing Glass Molded Body>

Hereinafter, the manufacturing method of the glass molded object of this invention is demonstrated.

The manufacturing method of the glass molded object of this invention is a method of obtaining a glass molded object by flowing molten glass, isolate | separating a molten glass mass, and shape | molding the said glass mass while cooling in a floating state in the glass molding part provided in the shaping | molding die. The method of obtaining a glass molded object in such a process is well known. However, this invention has a rotational symmetry axis | shaft by using the shaping | molding die of this invention as said shaping | molding die, and hold | maintains the said molten glass lump in the floating state in the glass shaping | molding part of the shaping | molding die, and also has the said rotational symmetry axis | shaft. It is characterized by forming a glass molded body having two end faces each intersecting with each other and one side surface connected to the outer circumference of the two end faces. Moreover, one aspect in the preform for precision press molding of this invention can be manufactured by the manufacturing method of the glass molded object of the said invention.

First, after heating and melting a glass raw material in a heat resistant container, it is lightening and homogenizing, molten glass flows out continuously at a constant speed from the pipe connected to the said container. On the other hand, a plurality of shaping dies are arranged on the circumference around the axis of rotation of the table on a turntable for index rotation, and each shaping die repeats commutation at a plurality of positions including directly below the pipe. To rotate in the right direction.

The molten glass mass is supplied to the mold when the mold is rectified to a position directly below the pipe (called a cast position), and the glass mass is transferred to the mold before the mold is rounded and returned to the cast position by the rotation of the table. It is molded into a molded body and taken out from the molded mold. The above-described process is repeated by transferring and rectifying the molded die, which has been emptied by taking out the glass molded body, to the cast position. By performing the same operation with respect to several shaping | molding dies, glass molded bodies are manufactured one after another from the molten glass which flows out continuously.

An example of supply of the molten glass lump to a shaping | molding die is as follows. The mold is raised to the cast position, close to the lower end of the pipe flowing out of the molten glass flow, the lower end of the molten glass flow is received as a mold, and a concave part is formed in the middle of the molten glass flow. It dives to separate the lower molten glass from the concave portion to obtain a molten glass mass on the mold. The amount of molten glass lump can be adjusted to a desired amount by adjusting the distance between the lower end of the pipe and the forming die when receiving the lower portion of the molten glass flow, the timing of descent of the forming die, and the like. In addition, the said method is an example and the other well-known method of isolate | separating a molten glass lump can be used suitably.

In supplying the molten glass mass to the shaping mold, the molten glass mass is filled in the glass forming portion to a height above the lower end of the side wall, for example, to a height between the lower end and the upper end of the side wall. Then, the gas is blown out from the gas outlet of the bottom, and the glass is lumped and cooled while applying upward wind pressure to the glass mass. By doing so, the side of the glass mass is molded in a state surrounded by the side wall.

In the manufacturing method of the present invention, the molten glass lump is held in the molded glass molding portion in a floating state, thereby having two axes of rotational symmetry and connected to the outer periphery of the two end surfaces and the two end surfaces intersecting the axes of rotational symmetry, respectively. The glass molded object provided with one side surface is shape | molded. As mentioned above, one end surface of a molded object is shape | molded especially in the shape corresponding to the bottom part of a shaping | molding die, and the side surface is shape | molded in the shape corresponding to the side wall of a shaping | molding die. When the ratio of the volume of the glass lump to the volume of the glass molded part of the shaping mold is not less than a certain range, the side surface of the molded body is molded into a shape corresponding to the sidewall of the shaping mold. Although this ratio changes also with the planar area of the bottom of a shaping | molding die, it is suitable for the volume of the glass lump to be about 40% or more of the volume of a glass shaping | molding part, for example. However, even if the volume of the glass lump is less than about 40% of the volume of the glass molded part, depending on the planar area of the bottom of the molded part, the side surface may be molded into a shape corresponding to the sidewall of the molded part.

Moreover, when the said ratio is less than 40%, a shaping | molding die will become large unnecessarily, and the problem that an excessive burden is added to the up-down movement mechanism and the transfer mechanism of a die | dye also arises. Moreover, when the volume of a glass molding part is enlarged, a glass molding part will deepen. As a result, when the molten glass flowing out of the outflow pipe is supplied to the glass forming part, the outflow pipe tip must be inserted into the glass forming part. However, in order to keep the viscosity of glass in a suitable range, the pipe is attached with a heating device or is insulated with a heat insulating material, so it is difficult to insert the pipe tip into the glass forming part. Therefore, it is preferable to solve this problem by making the said ratio 40% or more. On the other hand, when the said ratio exceeds 65%, since it becomes difficult to stably float a glass lump in a glass molding part, it is preferable to make the said ratio 65% or less.

The amount of gas ejected from the bottom of the molding die is adjusted by starting the preform or glass molded body by adjusting the flow rate of the gas stepwise, and the curvature of the surface facing the bottom side of the molding die is obtained from the two end faces of the obtained prototype. Whether or not it is within a desired range is examined, and when it is out of the range, the gas flow rate is adjusted to an appropriate range, and the production is performed by maintaining the gas blowing amount corresponding to the gas flow rate. In addition, since the gas ejection amount does not significantly differ from the gas ejection amount required to float the glass lump in the conventional forming mold having no sidewalls and the entire glass forming portion having a bottom composed of a porous body. If the gas ejection amount is started and the gas ejection amount is adjusted as described above, desired molding can be performed.

Since the molten glass has low viscosity, in the floating state, the glass is deformed along the bottom and sidewalls of the glass forming portion, and a thin gas layer made of the gas is formed between the bottom and the sidewalls. In this state, the side surface of a glass lump becomes enclosed by the side wall of a glass molding part, and a glass lump is hold | maintained, maintaining a floating state in a glass molding part. Therefore, even when a large acceleration acts on the glass mass in the horizontal direction, the glass mass is supported by the sidewalls of the glass forming portion having the lateral shape of the circumference or the side shape of the ash cone, so that the glass lump can be suppressed from shaking.

In the conventional mold, since there is no sidewall of the shape which suppresses the shaking of the glass mass, when the glass mass is subjected to large acceleration in the horizontal direction, the glass mass is shaken on the mold. In particular, when the turntable is index-rotated, periodic acceleration is applied to the glass mass, but when the acceleration and the shaking of the shaped glass mass resonate, the shaking of the glass mass is further increased. On the other hand, in the present invention, since the side wall functions to suppress the shaking of the glass mass, the shaking does not increase even when the periodic acceleration is applied to the glass mass.

As described above, the molten glass lump in the glass molded part is restricted by the sidewall of which the glass molded part is raised, and is greatly deviated from the droplet shape. In such a state, due to the surface tension, the molten glass lump is intended to be in the form of droplets, so that the gap between the glass and the sidewall is narrowed, and the gas ejected from the bottom is less likely to fall out between the glass and the sidewall. If a molding die having a gas flow path formed on the side wall from the bottom face side toward the opening direction of the glass molding part is used, glass is unlikely to enter the groove by surface tension, so that a gap in which the gas flows in the groove easily occurs. By making the part which gas tends to fall locally locally, glass becomes hard to enter into that part, and the clearance gap between the glass and side walls which become a gas flow path is ensured stably. As a result, the gas can stay between the glass and the glass molded portion, thereby deforming the shape of the glass molded body, or preventing the glass from taking unstable behavior.

The shape of the top surface of the glass lump held in the glass molding portion is a shape obtained by cooling and solidifying the shape determined by the balance of the surface tension of the molten glass lump and its own weight, etc., but in the case of changing the top surface shape to a desired shape. The upper surface of the glass lump held in the glass molding portion may be pressed to form a desired shape. In particular, since the shape determined by the balance of the surface tension of the molten glass lump and its own weight becomes a smooth convex surface, the upper surface is concave, or when the recess is formed near the intersection of the rotational symmetry axis of the glass mass and the upper surface. The method is valid. An upper surface is a surface which becomes one side of the end surface (Pipress surface) of a glass molded object, and the shape is as above-mentioned. The press is performed while the shaped glass is in a softened state. For example, the upper surface of the glass can be formed into a concave surface by press molding the glass from above from a press type having a convex forming surface. The shape of the other pressed surface is molded into a shape in which the bottom surface of the shaping portion is inverted. By making the bottom face of the molded part a concave surface, the other pipped surface can be molded into a convex surface, and by making the bottom face of the molded part a convex surface, the other p-pressed surface can be molded into a concave surface. After pressing, if the press die is separated from the glass, the glass (formed on the preform) rises again, and even if the glass surface is quenched by the press and wrinkles are formed, the glass surface is reheated by the heat inside the glass, and the wrinkle is caused. Can be eliminated to produce a preform having a smooth surface. In this method, when the said gas blowing pressure is high, it is preferable to adjust the gas blowing pressure at the time of a press so that gas does not enter a glass at the time of a press, and glass does not enter a porous body. However, the glass may be floated, and when the gas does not enter the glass at the time of pressing and the glass does not enter the porous body, the gas blowing pressure may not be adjusted at the time of pressing.

As described above, the glass molded body molded in the mold is taken out from the mold. The extraction from the mold is preferably carried out by adsorbing and retaining the upper surface of the glass molded body and taking it out of the mold in the upward direction, rather than pinching and taking out the glass molded body in view of the shape of the molded mold having sidewalls. Do. According to this method, the glass molded body can be taken out without interruption of the glass molded body by the side wall.

Alternatively, as shown in Figs. 1 and 2, the bottom and sidewalls of the mold are formed of separate members, and when the molten glass mass is accommodated or the glass is being molded, the bottom and sidewalls are combined to form the glass molding portion. When the preform is taken out, the bottom portion and the sidewall on which the preform is loaded may be separated to take out the preform.

At this time, as shown in Fig. 1, the side wall is composed of a plurality of members, and when the molten glass lump is accommodated or when the glass is molded, the members are combined to form a glass molding portion, and the preform is taken out. At this time, the member may be separated in the horizontal direction to take out the preform. Alternatively, as shown in Fig. 2, the bottom part and the side wall are separated in the vertical direction, but in order to leave the preform on the bottom part, the shape of the side wall is made to be a shape that approximates the side shape of the ash cone or the shape, and the opening is made smaller than the bottom part. That is, it is preferable that the side wall is made into an open shape below. In this way, the preform can be smoothly extracted from the sidewall.

The glass molded product taken out from the molding die is cooled to room temperature after annealing.

Moreover, the preform for precision press molding of this invention can be manufactured by the manufacturing method of the glass molded object of this invention.

<Glass molded body>

The shape of the glass molded object obtained by the manufacturing method of this invention is equivalent to the shape of the preform for precision press molding of the said invention. The upper surface of the glass molded body (the surface facing upward while being in the glass molded part) becomes a free surface unless it presses or exhales gas, and becomes a smooth convex surface rising from the center part. In order to control the curvature even if the upper surface is flat, concave, or convex, the upper surface may be pressed when the glass is deformable, or gas may be blown out into a desired shape. In the precision press molding, the upper surface and the bottom surface are the pressed surfaces to be pressed by the press forming mold.

In precision press molding, high viscosity glass is pressed at high pressure. And since the molded object obtained by the manufacturing method of this invention has a big deformation | transformation amount at the time of a press, when grinding traces or a flaw exist in the surface of a molded object, a glass will be easily broken by the part. In order to prevent such a trouble, at least the side surface of the molded body is a surface obtained by solidifying the glass in the molten state, and preferably two end surfaces (pipeless surface) besides the side surface are also surfaces obtained by the solidification of the glass in the molten state. The surface obtained by solidifying the molten glass means the glass surface obtained when the molten glass is cooled and solidified for the whole glass molded object used as the whole body or the base material of a preform, and the below-mentioned heat-polished surface, ie, a glass surface, It differs from the surface obtained by solidifying after heating and remelting a bay. Since cold working such as grinding and polishing is not performed on the surface obtained by solidifying the molten glass, there are no grinding marks or polishing traces, and thus there is no origin of the breakage. In particular, the molded object which is a surface obtained by solidifying the glass of molten state from the said viewpoint is preferable. Moreover, since the grinding | polishing trace and the grinding | polishing trace are repaired by remelting, and also the heat-polishing surface obtained by cooling and solidifying after remelting a glass surface becomes a micro surface smoothly, the origin of the said destruction does not exist.

The heated polishing surface is obtained by a method called fire polish. However, since the glass surface is reheated at a high temperature on the heat-polishing surface, there is a fear that the glass surface is deteriorated. In particular, in the glass containing an easy-to volatile components such as B ₂ O _3, alkali metals, fluorine, chlorine, tends to deteriorate the glass surface by the volatilization at the time of fire policy. In addition, since the glass once formed into a desired shape is reheated and remelted, the glass is deformed from the desired shape. For this reason, the latter is remarkably superior when the heated polished surface is compared with the surface obtained by solidifying the molten glass. The mirror polished surface is a polished surface after a lapping process such as rough polishing or sand blasting. There are a large number of grinding marks and polishing marks on the wrapped surface, which are the starting point of the breakdown. In the mirror polished surface, a larger one of these origins is removed, but since a very fine flaw called a latent flaw exists, the molded body having the mirror polished surface is composed of a surface obtained by solidifying molten glass or a heated polished surface. The fracture resistance is lower than that of the molded article. Since etching traces and grinding traces are removed by etching, the molded body of the etching surface of the surface is also excellent in fracture resistance. However, when the surface with a latent flaw is etched, fracture resistance may deteriorate because a flaw is present. Either way, it is remarkably preferable to set it as the surface obtained by solidifying the glass of a molten state.

Moreover, as an example of the surface obtained by solidifying the glass of a molten state, the mold transfer surface etc. which are obtained by transferring a free surface and a shaping | molding die surface to a molten glass are mentioned. The free surface can be formed, for example, by forming a molten glass mass while floating. The mold transfer surface can be formed by pressing the glass by a press molding die or by introducing molten glass into the mold.

The shape of the molded article of the present invention is also favorable in that a molded article which is a surface obtained by solidifying the glass in the molten state is produced. In preparation of the molded object whose whole surface is the surface obtained by solidifying the glass of a molten state, it shape | molds while applying a wind pressure to a molten glass lump and floats, as mentioned later. At this time, although the wind pressure which blows out a gas and floats on the bottom surface of a glass lump is obtained, when ø / h is too big | large, it will become difficult for the said gas to fall out along the side surface from the bottom of a glass lump, and it becomes difficult to float a glass lump stably. On the other hand, when ø / h is too small, it becomes difficult to float the glass mass only by the wind pressure applied to the bottom of the glass mass. Since ø / h is in the range of the present invention, the glass mass can be molded while stably floating. In addition, the preferable range of (phi) / h becomes a range mentioned above also from a viewpoint of stabilization of the floating of a glass lump.

The molded article of the present invention can be suitably used as a preform for molding concave meniscus lenses, convex meniscus lenses, and both concave lenses, and is particularly preferable for forming concave meniscus lenses and biconcave lenses.

A concave meniscus lens, a convex methoxy varnish preferred glass as a material, such as coarse lens, biconcave lens, a glass containing B ₂ O ₃ and La ₂ O ₃ as a glass component. Such glass is suitable for glass constituting the preform for precision press molding of the present invention B ₂ O ₃ -La ₂ O ₃ It is the same as containing glass. In addition, phosphate glass, for example, phosphate glass having optical characteristics having a refractive index nd of 1.75 or more and Abbe number vd of less than 25 is also preferable.

<Method for Manufacturing Optical Element>

Next, the manufacturing method of the optical element of this invention is demonstrated. The manufacturing method of the optical element of this invention is roughly divided into two aspects.

<The manufacturing method of the optical element Ⅰ>

According to a first aspect of the method for manufacturing an optical element of the present invention (hereinafter referred to as manufacturing method I of the optical element), the production of an optical element for precise press molding the preform for precision press molding of the present invention using a press molding die It is a way.

The press-molding die includes, for example, a press-shape for receiving the pressing die and the pressing die, which face each other, for pressing the preform, and for guiding the pressing die during pressing. When one of the pairs of pressing dies is the upper die and the other is the lower die, the preform is rotated so that one side of the prepress surface of the preform faces the upper die forming surface, and the other side of the prepress face faces the lower die forming surface. The preform is placed in the press forming die so that the axis of symmetry is parallel to the pressing direction and coincides with the center of the upper and lower forming faces.

As described above, the lesser residue can reduce the adverse effect due to crushing of the residue portion. However, even if the glass is not protruded from the upper and lower molding surfaces, the entire molding surface can be accurately transferred to the glass. It becomes difficult. Therefore, it is preferable to form a space for accommodating the glass, that is, the residue portion protruding from the forming surface, on the outside of the upper and lower forming surfaces inside the sleeve. However, if this space is made larger than necessary, the whole press-molding die becomes large, which is not preferable in terms of cracking the die. Therefore, it is preferable to reduce the space for accommodating the residue portion.

This invention is suitable for manufacture of a lens, especially a concave meniscus lens, a convex meniscus lens, and a biconcave lens, and especially the manufacture of a concave meniscus lens and a biconcave lens. Lenses in which at least one optical function surface becomes a concave surface, especially in a lens with a thick thickness of a peripheral portion called a board thickness, such as a concave meniscus lens or a double concave lens, are moved from the center to the periphery. Therefore, it is difficult to accurately transfer the molding surface, but according to the present invention, the entire molding surface can be accurately transferred to the glass, and the degradation of the surface accuracy due to crushing in the subsequent cooling process can be reduced and prevented. have. Therefore, a preferable aspect of the present invention is a method for producing such an optical element, wherein the forming surface of at least one of the opposing mold members for forming a press forming die and pressing the preform is a convex surface.

In this method, it is preferable to form a recessed part in the center of the pressed surface of a preform, and to press the said pressed surface to the convex shaping surface. When the convex surface of the pressed surface is pressed into the convex forming surface, the preform escapes from an appropriate position and direction in the press forming die, and the rotational symmetry axis between the pressing direction and the preform is displaced, or the rotation symmetry axis between the center of the forming surface and the preform This shift may cause the rearing and eccentricity. According to the above preferred embodiment, such a problem can be prevented. However, in order to prevent a gas trap, it is preferable to make the absolute value of the curvature radius of a convex shaping surface smaller than the absolute value of the curvature radius of the recessed part of a preform press surface.

In addition, in order to prevent the preform from shifting from an appropriate position and direction when the preform is set in the press forming mold and transported, the concave portion of the preform pressed surface is formed into a convex forming surface by the self weight of the upper mold or the self weight of the upper mold and the preform. It may be pressed.

As the press-molding die, a film formed by using a cemented carbide mold such as SiC mold, tungsten carbide, cement mold, or the like, and having appropriately formed a film containing a noble metal alloy film such as a carbon-containing film or a platinum alloy as a release film on the molding surface is used. Although what is necessary, it is preferable to use the SiC formulation which has high heat resistance, and it is preferable to form the carbon containing film in the shaping | molding surface. In a process in which the press molding die is exposed to high temperatures in a series of processes of precision press molding, it is preferable to perform the above steps in a non-oxidizing atmosphere such as a forming gas in order to prevent deterioration due to oxidation of the press molding die.

Next, the precision press molding method especially preferable for the manufacturing method I of an optical element is demonstrated.

<Precision Press Forming Method 1>

In this method, a preform is introduced into a press molding die, and both the press molding mold and the preform are heated, and the precision press molding is called (precision press molding method 1). In the precision press molding method 1, it is preferable to perform precision press molding by heating both the press molding die and the temperature of the said preform to the temperature which the glass which comprises a preform shows the viscosity of 10 <^6> -10 <^12> dPa * s. Further, the glass is cooled to a temperature exhibiting 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-molding die. It is preferable. According to the above conditions, the shape of the press-molded surface can be accurately transferred by glass, and the precision press-molded product can be taken out without deformation.

<Precision Press Forming Method 2>

This method is characterized by introducing a preform preheated to a press molding die and precisely press molding (called the precision press molding method 2). In this method, it is preferable to preheat separately the press-molding die and the preform for press molding, and to introduce the pre-heated preform into the press-molding die and to perform precise press molding. According to this method, since the preform is heated before introduction into the press-molding die, it is possible to manufacture an optical element having good surface precision without surface defects while shortening the cycle time.

It is preferable to make the preheating temperature of the press molding die lower than the preheating temperature of the preform. Such preheating can suppress the heating temperature of the press-molding die to be low, thereby reducing the consumption of the press-molding die. In the precision press molding method 2, the glass constituting the preform is preferably preheated to a temperature exhibiting a viscosity of 10 ⁹ dPa · s or less, more preferably 10 ⁹ dPa · s. In addition, it is preferable to preheat while raising the preform, and the glass constituting the preform exhibits a viscosity of 10 ^5.5 to 10 ⁹ dPa · s, more preferably 10 ^5.5 dPa · s or more and less than 10 ⁹ dPa · s. It is more preferable to preheat with temperature.

Moreover, it is preferable to start cooling of glass simultaneously with press start or from the middle of a press.

In addition, although the temperature of a press molding die | dye is adjusted to temperature lower than the preheating temperature of the said preform, what is necessary is just to aim at the temperature which the said glass shows the viscosity of 10 <^9> -10 <^12> dPa * s.

In this method, after press molding, the glass is preferably released after cooling to a viscosity of 10 ¹² dPa · s or more.

The precision press-molded optical element is taken out from the press-molding die and slowly cooled as necessary. In the case where the molded article is an optical element such as a lens, an optical thin film may be coated on the surface as necessary.

<The manufacturing method of the optical element II>

The second aspect of the method for manufacturing the optical element of the present invention (hereinafter referred to as manufacturing method II of the optical element) is obtained by grinding a preform or molded article for precision press molding comprising the molded product obtained by the production method of the present invention by polishing or the like. It is a manufacturing method of the optical element which precision-preforms the preform for precision press molding using a press molding die.

The press-molding die includes, for example, a press-shape for receiving the pressing die and the pressing die, which face each other, for pressing the preform, and for guiding the pressing die during pressing. When one of the pairs of pressing dies is the upper die and the other is the lower die, the preform is rotated so that one side of the prepress surface of the preform faces the upper die forming surface, and the other side of the prepress face faces the lower die forming surface. While the axis of symmetry is parallel in the pressing direction, the preform is placed in the press forming die so as to coincide with the center of the forming surface of the upper and lower dies.

As described above, the lesser residue can reduce the adverse effect due to crushing of the residue portion, but the entire molding surface can be precisely applied to the glass even if the glass is not protruded from the upper and lower molding surfaces. It becomes difficult to transcribe. Therefore, it is preferable to form a space for accommodating the glass, that is, the residue portion protruding from the forming surface, on the outside of the upper and lower forming surfaces inside the sleeve. However, if this space is made larger than necessary, the whole press-molding die becomes large, which is not preferable in terms of cracking the die. Therefore, it is preferable to reduce the space for accommodating the residue portion.

The present invention is preferable for the production of concave meniscus lenses, convex meniscus lenses and both concave lenses among the lenses, and particularly for the production of concave meniscus lenses and biconcave lenses. Lenses in which at least one optical function surface becomes a concave surface, especially in a lens with a thick thickness of a peripheral portion called a board thickness, such as a concave meniscus lens or a double concave lens, are moved from the center to the periphery. Therefore, it is difficult to accurately transfer the molded surface, but according to the present invention, the entire molded surface can be accurately transferred to the glass, and the degradation of the surface precision due to crushing in the subsequent cooling process can be reduced and prevented. . Therefore, a preferable aspect of the present invention is a method for producing such an optical element, which constitutes a press molding die and is a method in which at least one molding surface of the opposing mold member for pressing the preform is a convex surface.

In this method, it is preferable to form a recessed part in the center of the pressed surface of a preform, and to press the said pressed surface to the convex shaping surface. When the convex surface of the pressed surface is pressed to the convex forming surface, the preform is ejected from the proper position and direction in the press forming die, and the rotational symmetry axis of the pressing direction and the preform is displaced, or the center of the forming surface and the preform There is a possibility that the axis of rotation symmetry may be misaligned and cause knitting and eccentricity. According to the above preferred embodiment, such a problem can be prevented. However, in order to prevent a gas trap, it is preferable to make the absolute value of the curvature radius of a convex shaping | molding surface smaller than the absolute value of the curvature radius of the recessed part of a preform press surface.

In addition, in order to prevent the preform from shifting from an appropriate position and direction when the preform is set in the press forming mold and transported, the concave portion of the preform pressed surface is formed into a convex forming surface by the self weight of the upper mold or the self weight of the upper mold. It may be pressed.

As the press-molding die, a die formed of a cemented carbide, such as SiC or tungsten carbide, a cement or the like is used, and a film formed by appropriately forming a noble metal alloy film such as a carbon-containing film or a platinum alloy on the forming surface as a release film. Although what is necessary, it is preferable to use the SiC formulation which has high heat resistance, and it is preferable to form the carbon containing film in the shaping | molding surface. In a process in which the press molding die is exposed to high temperatures in a series of processes of precision press molding, it is preferable to perform the above steps in a non-oxidizing atmosphere such as a forming gas in order to prevent deterioration due to oxidation of the press molding die.

Particularly preferred precision press molding methods in the production method II of the optical element are the above-mentioned precision press molding method 1 and the precision press molding method 2. The reason is the same as that of the manufacturing method I of an optical element.

The precision press-molded optical element is taken out from the press-molding die and slowly cooled as necessary. In the case where the molded article is an optical element such as a lens, an optical thin film may be coated on the surface as necessary.

<Example>

Next, the present invention will be described in more detail with reference to Examples.

<Example 1>

4, the cross-sectional shape (left) when the preform of the present invention is cut in the plane including the axis of rotation symmetry, the cross-sectional shape (right) of the preform formed by forming a conventional molten glass lump in a floating state, and these preforms The cross-sectional shape (middle) of the press-formed product (aspherical concave meniscus lens) obtained by precision press molding is shown. The outline shown by the broken line of the press-molded product corresponds to the residue part.

These preforms supply a desired amount of molten glass lumps to the glass forming portion by using a forming die in which grooves are formed at equal intervals on the side wall shown in FIG. 2, and blow off gas from the bottom of the glass forming portion formed of a porous body. The glass lumps are stably floated and molded.

Shown in Fig. 2A is a molding die 20 which is an embodiment of the molding die of the present invention. The shaping | molding die 20 is comprised from the bottom base member 21, the bottom formation part 22 comprised by the porous material formed in the opening part of the center of the bottom base member 21, and the side wall structural member 23. As shown in FIG. In the side wall constituent member 23, the inner wall constitutes the side wall of the molded part. The lower part of the side wall constituting member 23 has a shape corresponding to the recess formed in the upper portion of the bottom base member 21, and can be assembled by being detachably assembled into the recess. In addition, a magnet 24 may be provided inside the recess formed in the upper portion of the bottom base member 21 to fix the side wall constituting member 23. Moreover, the gas flow path which consists of the groove | channel cut | disconnected in the longitudinal direction is shape | molded in the surface 23a which comprises the side wall inside the opening of the side wall structural member 23. As shown in FIG. In addition, as shown in Fig. 2C, the inside of the opening of the sidewall constitution member 23 has a back ash cone shape (virtual vertex of the sidewall constitution member 23) in which the lower opening is larger than the upper opening. Angle α, which corresponds to the half of the cone's right angle, so that the glass molded bodies are not separated from each other when the sidewall constituent member 23 is separated from the bottom base member 21 after molding. In consideration of the size of the molded body, it can be appropriately determined and can be, for example, in the range of 2 to 3 °. In addition, the said virtual vertex means the vertex of the virtual cone which makes the side of the said ashhead cone a part of a side, and the right angle of a cone means the right angle of the said virtual cone. At the time of taking out the glass molded object after shaping | molding, as shown to (b), the side wall structural member 23 can be removed and a glass molded object can be easily carried in after that.

The supply of molten glass lumps to the glass forming part flows out of the molten glass flow at a constant flow rate from the outlet pipe in which the blue and homogenized molten glass is temperature-controlled, and the glass forming part of the mold is brought close to the glass outlet of the pipe and flows out. The lower end is supported, the middle part is formed by the surface tension in the middle of the molten glass flow, and the mold is dropped at a predetermined timing to separate the molten glass from the part which is the middle part by the surface tension of the glass, The molten glass lump below was obtained from the separation part by the method of obtaining a glass shaping | molding part.

When taking out the molded preform from the molding die, when the glass molding portion is widened upward, the upper surface of the preform is sucked and held up, and is immediately lifted up and taken out.

When the glass molding is widened downward, the molding is divided into a sidewall portion and a bottom portion, and the preform is removed from the sidewall by moving the sidewall portion upwards or moving the bottom portion downwards thereon. The preform remaining on the bottom is sucked out and taken out. The preform taken out is annealed, washed, and a carbon-containing film, for example, a hydrogenated carbon film, is formed on the surface as required and sent to a precision press molding step.

In addition, the groove | channel omitted in the figure is formed in the preform side surface in parallel at multiple intervals and the rotation symmetry axis at equal intervals. This groove serves to control the kneading of the glass in the precision press molding.

Table 1 below shows the mass, volume, specific gravity of the glass constituting the preform, diameter, height, volume, and filling rate of the virtual circumference circumscribed to the preform.

In the above method, a glass molded body (preform) was prepared for each glass of phosphate glass 1 having glass numbers 1 to 11 and specific gravity of 4.421 and phosphate glass 2 having a specific gravity of 5.11 shown in Table 2 below. In addition, the viscosity curves of the glass of numbers 5, 9, and 12 are shown in the glass shown in Table 2 in FIG.

When the heating temperature of the press-formed mold or the preform is set so that the viscosity of the glass during precision press molding becomes 10 ⁷ dPa · s, for example, as is apparent from FIG. 5, the absolute value of the ratio of the viscosity change with respect to the temperature change. The absolute value of the inclination of the graph is larger in the glass of the numbers 5 and 9 than in the glass of the number 12. That is, the glass of numbers 5 and 9 has the property that a viscosity changes drastically only by a slight change of temperature. Therefore, the glass of Nos. 5 and 9 has a narrower temperature range at the time of precision press molding than the glass of No. 12, and the application of the present invention is more preferable in that it reduces and prevents gaps and cracks during molding. It can be said.

These preforms are placed in a mold in which the lower mold face is concave and the upper mold face is convex, followed by precise press molding, followed by annealing to remove the residue by chamfering to remove the aspherical concave meniscus lens and aspheric face convex. Various aspherical lenses of meniscus lenses and aspherical biconcave lenses were obtained.

After installing the preform obtained by the said method between the lower mold | type and upper mold | type which comprise a press molding die, the inside of a quartz tube was energized by the heater as nitrogen atmosphere, and the inside of a quartz tube was heated. The temperature inside the press-molding die is set to a temperature at which the glass to be molded exhibits a viscosity of 10 ⁶ to ^{10 10} dPa · s, while maintaining the same temperature, the pressure bar is lowered and the upper die is pressed to press the preform set in the mold. It was. The pressure of the press was 8 MPa, and the press time was 30 seconds. After pressing, the pressure of the press was released, and the press-formed glass molded product was brought into contact with the lower mold and the upper mold to slowly cool to a temperature at which the viscosity of the glass became 10 ¹² dPa · s or more, and then rapidly cooled to room temperature to manufacture the glass molded article. Was taken out from the mold to obtain an aspherical lens. The lower mold and the upper mold are aligned by the sleeve type, and the movement of the upper mold and the lower mold is guided by the sleeve.

In this way, aspherical concave meniscus lenses and aspherical biconcave lenses were produced. The said lens was preferable as a lens which comprises an imaging optical system. The surface accuracy of each of these lenses was a result within a standard of 0.25 µm or less in the center and 0.35 µm or less in the peripheral portion in the P-V value. In Table 1, the surface precision of the aspherical concave meniscus lens obtained by using each preform is shown as P-V value in the center part and P-V value in the periphery part. The PV value is a difference between the (x, y) coordinates obtained by actually measuring the aspherical surface of the lens formed by the theoretical (x, y) coordinates expressed by the aspherical equation (design formula) with respect to the aspherical surface of the aspherical lens. Corresponds to the difference between the best and the deepest fan point. In addition, when shaping these lenses, breakage of the glass did not occur. Moreover, the result similar to an aspherical concave meniscus lens was also obtained about an aspherical biconcave lens. Here, when molding an aspherical concave meniscus lens, the lower mold surface is concave, the upper mold surface is convex, and when aspheric both concave lenses are molded, the lower mold surface and the upper mold surface are convex. .

Comparative Example

On the other hand, when the same lens was produced using a preform having a filling rate of 66.7%, the surface precision was 0.25 µm or less at the center of the P-V value, but 0.4 µm and the decrease in surface accuracy were observed at the periphery. The glass numbers 1-11 shown in Table 2, each glass of phosphate glass 1, phosphate glass 2, and obtained by the precision press molding of the preform whose filling rate is less than 68%, or the ratio ((ø / h) more than 3) Surface precision of the aspherical concave meniscus lens is shown as the PV value at the center portion and the PV value at the peripheral portion. The results are shown in Table 3. These lenses had a P-V value of 0.25 µm or less in the center portion at the center portion, but a decrease in surface accuracy was observed at 0.4 µm or more in the peripheral portion. In addition, the aspherical biconcave lens also had the same result as that of the aspherical concave meniscus lens.

<Example 2>

In the same manner as in Example 1, the preforms shown in Table 4 were prepared using the glasses Nos. 1 to 11 shown in Table 2, glass of phosphate 1 and glass of phosphate 2. However, in the present Example, the glass on the shaping | molding part of a shaping | molding die was pressed into the upper mold which has the convex shaping | molding surface from upper direction, while the glass was in the softening state, and the upper surface of the preform was shape | molded into the concave surface. After press molding, the glass was cooled while floating again. The side surface and the lower surface of the preform are the same shapes as those of the first embodiment. Table 4 shows the data for each of the preforms thus obtained. As shown in Table 4, the preform in which one of the press surfaces is a convex surface and the other surface of the press surface is a concave surface is heated, and the upper mold having the convex molding surface and the lower mold having the concave molding surface and the sleeve type are heated. Precision press-molding was carried out by the press-molding die provided with, to obtain an aspherical concave meniscus lens. The surface precision of each lens is shown in Table 4 by the same technique as in Example 1. In precision press molding, the preform is introduced into the press forming mold so that the upper surface of the preform, that is, the concave surface, and the lower surface of the preform, that is, the convex surface faces the lower mold side, and at the top of the upper mold surface, the upper surface of the preform, The center was pressed to prevent the preform from deviating from the center position of the press forming die. In addition, when pressing the center of a preform upper surface, ie, the concave surface at the top part of an upper mold shaping | molding surface, the force applied to a preform was made into the self weight of an upper mold only. In this state, both the preform and the press molding die were heated to perform precise press molding. In addition, the press-molding dies were replaced with those for press molding of aspherical biconcave lenses to produce aspherical biconcave lenses. Aspherical biconcave lenses, as well as the aspherical concave meniscus lenses, a lens with good surface accuracy could be obtained.

<Example 3>

In the same manner as in Example 2, a preform in which both of the pressed surfaces were concave surfaces was obtained by press molding. In the present Example, the shaping | molding part of a preform shaping | molding die was made into convex surface. Thus, the preform was produced using the glass numbers 1-11 shown in Table 2, each glass of phosphate glass 1, and phosphate glass 2. The data concerning each preform thus obtained is approximately equivalent to the data shown in Table 4. Next, the preform whose two p-pressed surfaces are both concave surfaces was heated, and it was press-molded precisely by the press shaping | molding die provided with the upper mold | type and lower mold | type which have convex formation surface, and the aspherical biconcave lens was obtained. Surface precision of each lens was the same as in Example 2. In the precision press molding, the center of the upper and lower surfaces of the preform was pressed at the top of the upper and lower mold surfaces so that the preforms did not deviate from the center position of the press molding mold. In addition, when the center of the pre-press surface of the preform was pressed at the top of the upper and lower mold-formed surfaces, the force applied to the preform was only the upper weight of the upper die. In this state, both the preform and the press molding die were heated to perform precise press molding. In this way, an aspherical biconcave lens having good surface accuracy could be obtained.

In addition, in Examples 1-3, since the whole surface of the preform was made into the surface obtained by solidifying the glass of a molten state, the preform was not damaged from shaping | molding a preform until precision press molding. In addition, even if the preform was pressed into the upper mold in Examples 2 and 3, the preform was not damaged.

INDUSTRIAL APPLICABILITY The present invention is useful in the field of producing molded articles such as molding dies suitable for producing preforms for precision press molding and preforms for precision press molding using the molding dies.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows one aspect of the shaping | molding die of this invention.

2 is a view showing one embodiment of a molding die of the present invention.

3 is a view showing one embodiment of a molding die of the present invention.

4 is a cross-sectional shape (left view) when the preform of the present invention is cut in a plane including a rotational symmetry axis, a cross-sectional shape (right view) of a preform in which a conventional molten glass lump is molded in a floating state, and these The figure which shows the cross-sectional shape (center) of the precision press molded article (aspherical lens) obtained by precision press molding a preform.

FIG. 5 shows the viscous curves of the glasses of numbers 5, 9 and 12 in the glass shown in Table 2. FIG.

<Explanation of symbols for the main parts of the drawings>

10, 20, 30: molding

11, 21, 31: bottom foundation member

12, 22, 32: bottom formation part

13, 23: side wall member

24: magnet

33: inner wall

Claims (27)

A preform for glass precision press forming, having a rotational symmetry axis, and having two end faces intersecting the rotation symmetry axis and one side surface connected to an outer circumference of the two end faces, The two end faces are the pressed surface and are independently convex or concave, Assuming a virtual circumference having an axis coinciding with the axis of rotation symmetry and circumscribing the preform, the ratio (ø / h) of the diameter ø to the height h of the circumference is 1 or more and 3 or less, A preform for precision press forming, wherein the ratio (V / V ₀ ) of the volume V of the preform to the volume V ₀ of the circumference is 68% or more. The method of claim 1, The said side surface is a precision press molding preform which consists of the surface obtained by solidifying the glass of a molten state. The method according to claim 1 or 2, The glass for precision press molding of the glass transition temperature (Tg) of 540 ℃ or more. The method of claim 1, The preform for precision press molding whose refractive index (nd) of the said glass is 1.75 or more. The method of claim 1, One or both of said two end surfaces consists of a surface obtained by solidifying molten glass, Preform for precision press molding. The method of claim 1, One or both of said two end surfaces are convex, and the recessed part is provided in the area | region containing the intersection with the axis of rotation symmetry of the said convex surface, The precision press molding preform characterized by the above-mentioned. The method of claim 1, The said side surface has the shape approximating the side shape of a circumference, or the side shape of a circumference, or the shape approximating the side shape of a ash head cone or the side shape of a ash head cone. The method of claim 1, Preform for precision press molding used for shape | molding any one of a concave meniscus lens, a convex meniscus lens, and both concave lenses using the shaping | molding die whose at least an image forming surface is convex shape. The method of claim 1, In the said side surface, the preform for precision press molding in which the some groove | channel formed formed toward the other side from one side of two end surfaces is formed. As a shaping | molding die used for shaping | molding a molten glass mass while cooling in a floating state, and obtaining a glass molded object, The said shaping | molding die is provided with the concave glass shaping | molding part which has a bottom part and the side wall installed so that the circumference | surroundings of the bottom part may be provided, The bottom portion has a plurality of gas ejection openings for ejecting a gas for floating by applying wind pressure to the glass mass. Molding type, characterized in that. The method of claim 10, And the side wall has a gas flow path through which gas ejected from the gas ejection port flows in an opening direction of the glass molding part. The method of claim 11, And the gas flow path is a plurality of grooves extending perpendicularly or inclined to the direction of the opening of the glass molding portion from the bottom portion. The method of claim 12, The shaping | molding die whose surface of the side wall which has the said gas flow path is a waveform which consists of a wave form which consists of a continuous surface, or an intermittent surface. The method of claim 10, The bottom part which has the said some gas blowing opening is a shaping | molding die comprised with the porous material which has air permeability. The method of claim 10, The said glass molding is a shaping | molding die which is a base material of the preform for precision press molding, or the preform for precision press molding. The method of claim 10, The glass molded body has a rotational symmetry axis, and has two end faces intersecting the rotation symmetry axis and one side surface connected to an outer circumference of the two end faces. The method of claim 16, A side face of the glass molded body is molded by sidewalls of the glass molded part. In the method for producing a glass molded body obtained by flowing out the molten glass to separate the molten glass lump, and forming the glass lump by cooling while cooling the glass lump in a floating state formed in the glass mold, By using the molding die according to claim 10 as the molding die, and holding the molten glass mass in a floating state in the glass molding portion of the molding die, two end faces each having a rotational symmetry axis and intersecting the rotational symmetry axis, respectively And a glass molded body having one side surface connected to the outer circumferences of the two end faces, wherein the glass molded body is molded. The method of claim 18, The said glass molded object is a manufacturing method of the glass molded object which is a base material of the preform for precision press molding, or the preform for precision press molding. The method of claim 18 or 19, A volume of the glass lump is in the range of 40 to 65% of the volume of the glass molded part, the method for producing a glass molded body. The method of claim 18, The manufacturing method of the glass molded object containing pressing the upper surface of the glass lump held by the glass molding part. The method of claim 18, In the glass molded body, two end faces are independently convex or concave, The side surface is made of a surface obtained by solidifying the glass in the molten state, Assuming a virtual circumference having an axis coinciding with the axis of rotation symmetry and circumscribing the preform, the ratio (ø / h) of the diameter ø to the height h of the circumference is 1 or more and 3 or less, Process for producing a volume V of the ratio (V / V ₀₎ is a glass molded body 68% or more of the preform to the volume V ₀ of the circumference. The manufacturing method of the preform for precision press molding which manufactures a glass molded object by the method of Claim 18, and grinds at least one part of the said molded object. The manufacturing method of the optical element containing precision press molding the preform for precision press molding of Claim 1 using a press molding die. The method of claim 24, The manufacturing method of the optical element which shape | molds any one of a concave meniscus lens, a convex meniscus lens, and both concave lenses using the shaping | molding die whose at least an image forming surface is convex. The manufacturing method of the optical element containing precision press molding the glass molded object obtained by the manufacturing method of Claim 18, or the preform for precision press molding using a press molding die. The method of claim 26, At least one molding surface of an opposing mold member for constituting a press molding die and for pressing the preform is a convex surface.

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