JP5020027B2 - Manufacturing methods for glass moldings, precision press-molding preforms, and optical elements - Google Patents

Description

  The present invention relates to a method for producing a glass molded body, a method for producing a precision press-molding preform, and a method for producing an optical element. More specifically, the present invention is a method for producing a glass molded body that efficiently and stably mass-produces a glass molded body suitable as a preform for producing a precision press molding preform or preform with a small mass tolerance, And a method for manufacturing the preform, and a method for manufacturing an optical element using the preform.

  A precision press molding method is known as a method for mass-producing glass optical elements such as aspherical lenses. In this method, a required amount of glass is preformed into a compact called a preform prior to precision press molding. Then, the preform is heated and softened and press-molded using a press mold, and the molding surface is precisely transferred to glass to form the optical functional surface of the optical element.

The precision press molding method is a method having excellent productivity. However, in order to further improve the productivity, the point is how efficiently the preform is produced. In order to meet these demands, several preform production methods have been proposed. As an example, as described in Patent Document 1, a method is known in which molten glass droplets are dropped into a liquid and molded into a preform while cooling.
Japanese Patent Laid-Open No. 10-291824

  When the preform is mass-produced by the method disclosed in Patent Document 1, since the high-temperature glass is continuously introduced into the liquid, the temperature of the liquid rises. If a liquid with a low heat of vaporization is used, the liquid is consumed rapidly, and production must be continued while constantly replenishing the liquid. If a liquid with a large heat of vaporization is used to eliminate such inconvenience, the glass is rapidly cooled in the liquid, causing damage such as cans and cracks, or the volume of the glass shrinks while the glass surface is solidified. Vacuum bubbles are generated.

  Small preforms molded from molten glass droplets are used in the manufacture of small optical elements. However, the manufacture of such small optical elements can be difficult to process after precision press molding, such as centering, and requires labor and cost. Therefore, it is desirable to complete the optical element by precision press molding. For example, when making a lens without centering, it is necessary to distribute the glass in the press mold without excess or deficiency. If the amount of glass is too large, the glass enters between the barrel mold and the lower mold, and between the barrel mold and the upper mold, and a molding beam is generated or the mold is damaged. On the other hand, if the amount of glass is small, the molding surface will not be sufficiently transferred to the glass, resulting in a lens with poor surface accuracy, or the molding of the edge of the lens that will be the positioning reference surface when fixing the lens will be insufficient. . In order to make a polishing-free and centering-free optical element in this way, a preform with high mass accuracy is required.

  In order to make a small preform with high mass accuracy, the mass tolerance must be kept small. In such a case, as an operation for making the mass of the glass droplet constant, it may not be sufficient to make the molten glass flow rate and the dropping interval constant. In such a case, a method of polishing a glass molded body obtained from molten glass droplets and finishing it into a preform having a small mass tolerance is effective.

  In order to reduce the mass tolerance by polishing, for example, a method of forming a spherical glass molded body and polishing it so as to obtain a spherical preform having a constant diameter can be considered. That is, the mass is managed by the diameter by making the mass of the preform correspond to the diameter. This method is effective if the assumption is that the density of all glass moldings is constant, but if the temperature of the liquid to which the glass is dropped is not constant, the thermal history of the glass moldings will vary, and the density of the moldings will be reduced. Variation will also occur. As a result, it becomes difficult to suppress the mass tolerance even when polishing so that the diameter is constant.

  The present invention has been made to solve these problems, and is capable of efficiently and stably mass-producing a precision press-molding preform having a small mass tolerance or a glass molded body suitable as a base material for producing a preform. An object of the present invention is to provide a method for producing a glass molded body, a method for producing the preform, and a method for producing an optical element using the preform.

  The inventors of the present invention have made extensive studies in order to solve the above problems, and have completed the present invention.

That is, the present invention
(1) A method for producing a glass molded body for mass-producing a glass molded body by dropping molten glass droplets into a liquid, cooling and molding the liquid in the liquid,
When the boiling point at 1 atm is BP [° C.], the constant pressure specific heat is Cp [J / (g · K)], and the heat of vaporization is Q [J / g], the following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 1200 J / g (1)
Using a liquid that satisfies
A method for producing a glass molded body, characterized in that the temperature of the liquid is controlled to be maintained at a predetermined temperature in a range of 0 to 200 ° C., and a solid glass molded body is mass-produced.
(2) A method for producing a glass molded body as described in (1) above, wherein a molten glass droplet having a mass of 100 mg or less is dropped into a spherical glass molded body.
(3) The external circulation channel for the liquid is formed, and a heat exchanger is provided in the channel to cool the circulating liquid, and control for maintaining the liquid temperature at a predetermined temperature is performed (1) or ( The method for producing a glass molded body according to item 2),
(4) The method for producing a glass molded body according to (3) above, wherein the molten glass droplets are dropped one after another while causing a flow by circulation of the liquid on the liquid surface where the molten glass droplets are dropped,
(5) The method for producing a glass molded body according to any one of (1) to (4) above, wherein a glass molded body for polishing is produced,
(6) (5) above to prepare a Riga lath shaped body by the method according to claim a method for producing a precision press-molding preform, which comprises grinding the resulting glass shaped material and, (7 ) A method for producing an optical element for heating and precision press molding a glass preform,
(1) to (5) to produce a trigger lath shaped body by the method according to any one of clauses, or to produce a descriptor remodeling by the method described in (6) section, obtained A method for producing an optical element, characterized in that a heated glass molded body or preform is subjected to precision press molding,
Is to provide.

  According to the present invention, a precision press-molding preform having a small mass tolerance or a method for producing a glass molded body for efficiently and stably mass-producing a glass molded body suitable as a base material for producing a preform, and the above A method for producing a preform and a method for producing an optical element using the preform can be provided.

First, the manufacturing method of the glass forming body of this invention is demonstrated.
[Method for producing glass molded body]
In the method for producing a glass molded body of the present invention, when the glass molded body is mass-produced by repeating the steps of dropping a molten glass droplet into a liquid and cooling and molding in the liquid, the temperature of the liquid is set to 0 to 200 ° C. The solid glass molded body is mass-produced by performing control to maintain a predetermined temperature in the range.

  The predetermined temperature of the liquid is Tliq [° C.], the temperature at the time of dropping the molten glass droplet is Tglass [° C.], the constant heat of the glass per unit mass is Cp [J / (kg · K)], Mass m [kg], the dropping interval of the molten glass droplets is t [seconds], and when the glass droplets are finally cooled to Tliq [° C.], the amount of heat that the liquid obtains by heat exchange with the molten glass droplets per unit time It can be estimated that (Tglass−Tliq) × Cp × m / t.

  Therefore, the temperature of the liquid is controlled so that the temperature of the liquid is maintained at Tliq while the liquid is cooled using a heat exchanger having a cooling capacity per unit time that is at least higher than the above-mentioned heat quantity.

  By doing so, the amount of consumption of the liquid can be reduced even when the glass is slowly cooled in the liquid by using the liquid having a small heat of vaporization. Further, during the mass production of glass molded bodies, a glass molded body having a constant thermal history can be mass-produced by keeping the liquid temperature constant, and a preform having a very small mass tolerance can be made by polishing.

  Furthermore, by stabilizing the quality of the glass molded body, it is possible to make the progress of polishing constant when simultaneously polishing a large number of glass molded bodies, and by polishing a glass molded body with uniform quality, It is also possible to reduce or prevent glass breakage during polishing.

  As described above, the present invention is suitable for mass production of glass preforms that become small preforms or become small preforms by polishing. In particular, it is preferable to drop a molten glass droplet having a mass of 100 mg or less to form a spherical glass molded body, and more preferably 50 mg or less.

Furthermore, it is suitable for mass production of preforms whose mass tolerance per 1000 pieces is within ± 0.5%.
(Liquid temperature control method)
In the present invention, the method for controlling the liquid to Tliq [° C.] is not particularly limited as long as the liquid can be uniformly maintained at the above temperature. For example, an external circulation channel for the liquid is formed. In addition, a control method is preferred in which a heat exchanger is provided in the flow path to cool the circulating liquid and to keep the liquid temperature constant. At that time, it is more desirable to drop the molten glass droplets one after another while causing a flow by circulation of the liquid on the liquid surface where the molten glass droplets are dropped. If the dropping distance is short, the glass droplets do not stick in the air even if the dropping interval t is short, but when the glass droplet reaches the liquid level, it rapidly decelerates. May stick to glass drops. By adopting the above configuration, glass droplets that have reached the liquid level can be caused to flow by the circulating flow of the liquid, and this problem can be avoided by not swiftly shifting from the position at the time of reaching the liquid level. As a method, there are a method of maintaining a constant liquid temperature by immersing a heat exchanger in a liquid, a method of maintaining a constant liquid temperature by cooling a container containing the liquid from the surroundings, and the like.

  In any method, measure the temperature of the liquid, compare the measurement result with the set value of the liquid temperature, and if the liquid temperature is higher, increase the cooling of the liquid by the heat exchanger, and if the liquid temperature is lower, the heat exchanger Reduce or stop liquid cooling by. From the viewpoint of performing such feedback control, it is preferable to use a measuring device that converts temperature data into an electrical signal, such as a thermocouple, for the temperature of the liquid. For the feedback control, a known control method using a microcomputer or the like may be employed.

  The temperature of the liquid is more preferably maintained within a predetermined temperature range of ± 10 ° C. from the viewpoint of achieving the object of the invention.

Tliq is set to a temperature higher than the melting point of the liquid used in the operating environment.
The glass molded body thus obtained can be used as a preform as it is or as a glass molded body for polishing. In the case of a glass molded body for polishing, the glass molded body is used as a preform after being polished.

In the present invention, since the liquid is used to produce a glass molded body in the liquid, it is also referred to as a “forming liquid”.
(Liquid for molding)
In order to mold molten glass droplets in a liquid so that they do not cause canning, cracking or vacuum bubbles, the liquid is heated and evaporated by the heat of the molten glass droplets to gasify, and this gas surrounds the glass. To. By doing so, the glass is slowly cooled and formed without causing breakage, cracks or vacuum bubbles.

  As a liquid used in such a method, it is desired that the liquid is a normal temperature and a normal pressure, that the specific heat and the heat of vaporization are both small, and that the boiling point is not so high (for example, lower than the glass transition temperature).

  As such a liquid, when the boiling point BP at 1 atm is 30 to 200 ° C., the constant pressure specific heat is Cp [J / (g · K)], and the heat of vaporization is Q [J / g], the following relational expression ( It is preferable to use a liquid that satisfies 1).

Cp × (BP−20 ° C.) + Q ≦ 1200 J / g (1)
The amount of heat required for 1 g of 20 ° C. liquid to boil by contacting the glass lump surface and gasify is expressed as Cp × (BP−20 ° C.) + Q. Using this amount of heat as an index A of the ease of gasification of a liquid, and investigating the relationship between this index and the effect of preventing cans, cracks, and vacuum bubbles, it is preferable to use a liquid that satisfies the above formula (1). It was found that results were obtained.

  In particular, when the mass of the molten glass lump is small, for example, when a molten glass drop is dropped onto a liquid, a sufficient gas layer is formed by using a liquid with a small index A but a small amount of heat. be able to.

  In order to obtain a sufficient heat insulating effect due to gas layer formation, it is preferable to use a liquid having an index A of 1200 J / g or less, more preferably a liquid having 1000 J / g or less, and a liquid having 900 J / g or less. More preferably, it is more preferable to use a liquid of 400 J / g or less.

On the other hand, if the boiling point is too low, the liquid is consumed significantly and the liquid must be constantly replenished.
Therefore, in the present invention, it is preferable to use a liquid having a boiling point of 30 to 200 ° C., and a more preferable boiling point of the liquid is 60 to 150 ° C., more preferably 80 to 120 ° C.

Examples of the liquid satisfying such conditions include perfluorocarbon [CF ₃ (CF ₂ ) ₅ CF ₃ , BP = 80 ° C., A = 143 J / g], hydrofluoroether [manufactured by Sumitomo 3M, trade name “Fluorinert FC” -84 ”, CF ₃ CH ₂ OCF ₂ CF ₂ H + ethanol, BP = 54 ° C., A = 246 J / g], hydrofluoroether [CF ₃ (CH ₂ ) ₃ OCH ₃ , BP = 76 ° C., A = 194 J / g], pentafluorobutane [CF ₃ CH ₂ CF ₂ CH ₃ , BP = 40 ° C., A = 155 J / g], ethyl acetate [BP = 77 ° C., A = 515 J / g], ethanol [BP = 78 ° C., A = 978 J / g], isopropyl alcohol [BP = 83 ° C., A = 828 J / g] and the like.

  Among these liquids, an organic fluorine compound-containing liquid is preferable from the viewpoints of BP, A value and low flammability. However, since the organic fluorine compound generates hydrofluoric acid by thermal decomposition, the liquid is boiled and gasified. The hydrofluoric acid generated by the above changes the surface of the glass molded body, and an altered layer called burn is easily formed. However, when the glass base material made of the obtained glass molded body is subjected to polishing treatment to produce a precision press-molding preform, the altered layer on the surface of the glass base material is surely removed by the above polishing treatment. However, in the present invention, by adding a basic substance to the liquid containing the organic fluorine compound, the hydrofluoric acid generated during the gasification of the fluorine compound is neutralized, and the glass surface is corroded by the hydrofluoric acid. Can be prevented. As the basic substance, calcium hydroxide, sodium hydroxide, potassium hydroxide and the like can be used.

Next, the manufacturing method of the precision press molding preform of this invention and the manufacturing method of an optical element are demonstrated.
[Precision press molding preform manufacturing method]
In the method for producing a precision press-molding preform of the present invention, a precision press-molding preform is prepared by polishing the glass molding for polishing obtained by the method for producing a glass molded body described above.

  In addition, when grinding | polishing the said glass molded object, it is preferable to anneal beforehand to reduce the distortion in this glass molded object so that a damage may not arise in a grinding | polishing process.

  In this polishing treatment, it is preferable that a plurality of glass moldings are collectively polished to produce an equal mass precision press-molding preform in order to facilitate mass matching or volume matching of each preform. .

  In order to use the precision press-molding preform thus obtained or the above-described glass molded body (hereinafter, these may be collectively referred to as a glass gob) as a glass material for molding an optical element, The shape is preferably a sphere.

Used for micro optical elements such as glass lenses mounted on camera-equipped mobile phones, glass lenses constituting optical systems for writing / reading data to / from optical disks, and optical systems that optically connect each element in optical communication In precision press molding of a glass lens, it is preferable to use a spherical glass gob. This is because the volume of the glass gob used in these optical elements is required to exactly match the design value. When the glass gob glass is insufficient, the glass cannot be filled and transferred over the entire molding surface of the press mold, and a high-precision optical element cannot be produced. On the other hand, when the glass gob glass is excessive, the glass enters between the mold members constituting the press mold and becomes a molding burr, or the glass cannot be pressed to a predetermined state. When a spherical glass gob is used, it is easy to control its volume.
[Method for Manufacturing Optical Element]
In the method for producing an optical element of the present invention, an optical element is produced by precision press-molding the “glass molded body or preform for precision press molding” (glass gob) produced by the above-described method. The precision press molding method and conditions may be optimized according to each case by applying known methods and conditions.

  Precision press molding is also called a mold optics molding method, and is a method of forming the shape of an optical functional surface by press molding, and is already well known in the technical field. A surface that transmits, refracts, diffracts, or reflects light rays of the optical element is called an optical functional surface. For example, taking a lens as an example, a lens surface such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens corresponds to an optical function surface. The precision press molding method is a method of forming an optical functional surface by press molding by precisely transferring a molding surface of a press mold to glass. That is, it is not necessary to add machining such as grinding or polishing to finish the optical functional surface.

  As a press mold used in the precision press molding method, a known mold, for example, a mold having a release film on a molding surface of a mold material such as silicon carbide or super hard material can be used. Among these, it is preferable to use a press mold made of silicon carbide. As the release film, a carbon-containing film, a noble metal alloy film, or the like can be used. From the viewpoint of durability and cost, it is preferable to use a carbon-containing film.

  In the precision press molding method, it is desirable that the molding atmosphere be a non-oxidizing gas atmosphere in order to keep the molding surface of the press mold in a good state. As the non-oxidizing gas, it is preferable to use nitrogen, a mixed gas of nitrogen and hydrogen, or the like.

Next, a precision press molding method particularly suitable for the method for producing an optical element of the present invention will be described.
(Precision press molding method 1)
In this method, the glass gob described above is introduced into a press mold, the mold and the glass gob are heated together, and precision press molding is performed.

In this precision press molding method 1, precision press molding is performed by heating the temperature of the press mold and the glass gob to a temperature at which the glass constituting the glass gob exhibits a viscosity of about 10 ⁶ to 10 ¹² dPa · s. preferable.

Further, after the glass is cooled to a temperature showing 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, the precision press-molded product is removed from the press mold. It is desirable to take it out.

Under the above conditions, the shape of the molding surface of the press mold can be accurately transferred with glass, and the precision press molded product can be taken out without being deformed.
(Precision press molding method 2)
In this method, after heating the above-mentioned glass gob, it is introduced into a press mold and precision press-molded. That is, the press mold and the glass gob are separately preheated, and the preheated glass gob is introduced into the press mold and precision press-molded. It is to be molded.

  According to this method, since the glass gob is heated in advance before being introduced into the press mold, it is possible to manufacture an optical element with good surface accuracy free from surface defects while shortening the cycle time.

  It is preferable to set the preheating temperature of the press mold lower than the preheating temperature of the glass gob. Thus, by lowering the preheating temperature of the press mold, the consumption of the mold can be reduced.

  Moreover, according to this method, since it is not necessary to perform glass gob heating within a press mold, the number of press molds to be used can be reduced.

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

The glass gob is preferably preheated while floating, and the glass constituting the glass gob is preferably 10 ^5.5 to 10 ⁹ dPa · s, more preferably 10 ^5.5 dPa · s to less than 10 ⁹ dPa · s. It is more preferable to preheat to a temperature showing the viscosity of

  Moreover, it is preferable to start cooling the glass simultaneously with the start of pressing or in the middle of pressing.

The temperature of the press mold is adjusted to a temperature lower than the preheating temperature of the glass gob. The temperature at which the glass exhibits a viscosity of 10 ⁹ to 10 ¹² dPa · s may be used as a guide.

In this method, it is preferable that after the press molding, the glass is cooled to a viscosity of 10 ¹² dPa · s or more and then released.

  In the present invention, a press mold having at least an upper mold and a lower mold, wherein the shape of the upper mold molding surface and the shape of the lower mold molding surface are different, and a preheated glass gob is supplied onto the lower mold to press mold. It can be performed. According to the present invention, by using the glass gob, the optical element can be made highly productive without causing problems such as gas traps even when press molds having different upper and lower mold surface shapes are used. And can be manufactured.

  The precision press-molded optical element is taken out from the press mold and gradually cooled as necessary. Further, when the lens is molded, centering may be performed.

  Thus, according to the present invention, various lenses such as spherical lenses, aspherical lenses, and micro lenses, diffraction gratings, lenses with diffraction gratings, various optical elements such as lens arrays and prisms, and digital cameras as applications Guides light used for data reading and / or data writing on optical recording media such as lenses that constitute imaging optical systems for cameras with built-in cameras and cameras, camera-equipped mobile phones, and CDs and DVDs Therefore, various optical elements such as lenses can be manufactured. In addition, when a glass gob made of copper-containing glass is used, an optical element having a color correction function of a semiconductor imaging element can be produced. Among them, it is suitable as a method for producing a lens mounted on a digital camera.

  These optical elements may be provided with an optical thin film such as an antireflection film, a total reflection film, a partial reflection film, or a film having spectral characteristics, if necessary.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1
(1) Manufacture of glass molded body A lanthanum borate glass having a refractive index of nd: 1.806 and an Abbe number νd: 40.7 was melted at 1200 ° C, and passed through a platinum outflow pipe whose temperature was controlled at 1100 ° C. Molten glass was dropped from a platinum outflow nozzle whose temperature was controlled at 1050 ° C. The platinum nozzle had an outer diameter of 0.8 mm, an inner diameter of 0.6 mm, and nitrogen gas was allowed to flow vertically below the outer diameter portion of the nozzle at a rate of 0.8 L / min. The mass was 20 mg and the dropping interval was 0.1 seconds.

The glass dropped from the nozzle is a container (inner diameter: 80 mm, liquid level: 800 mm) containing perfluorocarbon [manufactured by Sumitomo 3M, trade name “Fluorinert FC-3283”, characteristic CF ₃ (CF ₂ ) ₇ CF ₃ ]. It took about 4 seconds from the liquid level to the bottom of the container. The temperature of the liquid was controlled with a circulation type cooling device, and was controlled within a range of 20 ± 5 ° C. The cooling efficiency of the circulation cooling device was an output of 200 W as an execution value, and the circulation flow rate was set to 5 L / min.

  In addition, when the liquid does not circulate, when the molten glass droplet enters the liquid surface, the surroundings of the glass are covered with a liquid vapor film. Became extremely slow. As a result, when the next glass droplet falls at a short interval of 0.1 seconds, the glass droplets come into contact with each other and become a sphere having twice the mass. It was not obtained.

  However, when it was circulated, the glass flow could be quickly displaced from the position at the time of reaching the liquid surface by the circulation flow, and this problem could be avoided.

  The finished glass molding was spherical with an average diameter of 2.03 mm and a roundness of 50 μm or less. Production was continued for 8 hours, and 288,000 glass molded bodies were produced. When the specific gravity of the finished glass molding was measured, it was within the range of 4.590 ± 0.002.

If the temperature of the liquid is not controlled, there is a difference in the heat history when the glass droplet is formed, and the specific gravity is 4.590 ± 0.01. In addition, since the liquid evaporates one after another, it is necessary to supply a liquid of about 200 cm ³ every 10 minutes.

By this method, a glass base material lot made of a glass molded body with less quality variation than before was obtained. When the quality of the glass molding was inspected, there were no defects such as cans and cracks. When the surface was observed with an electron microscope, the fluorine component of the perfluorocarbon and the glass reacted, resulting in slight white burn. The roundness is a value obtained by a roundness measuring device RA-2100 manufactured by Mitutoyo Corporation (hereinafter the same).
(2) Manufacture of preform When the glass base material lot obtained in the above (1) was polished with a white 100 μm to a diameter of 1.83 mm, a spherical preform lot having no defects on the surface was obtained. . The time required for polishing was 12 hours.
(3) Manufacture of optical elements 100,000 spherical preforms in the spherical preform lot obtained in (2) above are precision press molded with a press mold as shown below, and an aspheric lens Produced.

Each spherical preform shown in FIG. 1 is placed between an upper die 1 and a lower die 2 made of SiC having a carbon-containing film (diamond-like carbon film) on the molding surface, and then the inside of the quartz tube 11 is nitrogenated. The quartz tube 11 was heated by energizing the heater 12 as an atmosphere. After the temperature in the mold is set to a temperature at which the viscosity of the ball preform 4 to be molded is about 10 ⁵ to 10 ⁹ dPa · s, the upper die 1 is lowered by maintaining the temperature and lowering the push bar 13. The molded ball preform 4 in the mold was pressed by pressing from above. The press pressure was 5 to 15 MPa, and the press time was 10 to 300 seconds. After pressing, the pressure of the press is released, and the aspherical press-molded glass molded body is gradually cooled to the glass transition temperature in contact with the upper mold 1 and the lower mold 2 and then rapidly cooled to near room temperature. The glass formed into an aspherical surface was taken out from the mold. In FIG. 1, reference numeral 3 is a guide type, 10 is a support base, 9 is a support rod, and 14 is a thermocouple.

  The obtained precision press-molded product was heated to 380 ° C. in an annealing furnace, maintained at that temperature for 2 hours, and then cooled to room temperature in 1 hour to obtain an aspheric lens. The obtained aspherical lens had good thickness accuracy (average thickness deviation within ± 5 μm).

The average thickness deviation was determined as follows.
<Average thickness deviation>
The edge thickness of the lens was measured over the entire circumference using a laser dimension measuring instrument LS-5000 manufactured by Keyence Corporation.
Example 2
(1) Manufacture of a glass molded body A heavy flint glass having a refractive index of nd: 1.82 and an Abbe number νd: 24 is melted at 1100 ° C., passes through a platinum outlet pipe whose temperature is controlled at 1000 ° C., and reaches 950 ° C. Molten glass was dropped from a temperature-controlled platinum outflow nozzle. The platinum nozzle had an outer diameter of 0.8 mm, an inner diameter of 0.7 mm, and nitrogen gas was flowed vertically down the outer diameter portion of the nozzle at a rate of 0.5 L / min to obtain a glass droplet smaller than the natural dripping mass. The mass was 40 mg, and the dropping interval was 0.20 seconds.

  The glass droplet dropped from the nozzle dropped into a container containing ethanol (inner diameter 100 mm, liquid level 1200 mm), and it took about 6 seconds to reach the bottom of the container from the liquid level. The structure of the container was a double tube structure, and the temperature of the liquid was controlled in the range of 20 ± 5 ° C. by cooling the container. Cooling was performed by circulating a heat medium through the double pipe section, and the cooling efficiency of the cooling device was an output of 200 W as an effective value.

  By rotating the container (moving along a φ20 orbit), the position where the glass droplet reached the liquid level was shifted from the previous glass droplet. Thereby, the contact of glass droplets can be prevented.

  The finished glass molded body was spherical with an average diameter of 2.76 mm and a roundness of 100 μm or less. Production was performed continuously for 12 hours, and 216,000 glass molded bodies were produced. When the specific gravity of the finished glass was measured, it was within the range of 3.690 ± 0.002.

If the temperature of the liquid is not controlled, there is a difference in the heat history when the glass droplet is formed, and the specific gravity is 3.690 ± 0.01. In addition, since the liquid evaporates one after another, it is necessary to supply a liquid of about 200 cm ³ every 10 minutes.

By this method, a glass base material lot made of a glass molded body with less quality variation than before was obtained. When glass quality was inspected, there were no defects.
(2) Manufacture of preforms Of these glass base material lots, 100,000 pieces were polished with a white 150 μm to a diameter of 2.46 mm, and a spherical preform lot having no defects on the surface was obtained. . The time required for polishing was 12 hours.
(3) Manufacture of optical element About 50,000 ball preforms in the ball preform lot obtained in (2) above, precision press molding was carried out in the same manner as in Example 1 to produce precision press molded products. After heating to 350 ° C. in an annealing furnace, the temperature was maintained for 2 hours, and then cooled to room temperature over 1 hour to obtain an aspherical lens. The obtained aspherical lens had good thickness accuracy (average thickness deviation within ± 5 μm).

  According to the method for producing a glass molded body of the present invention, it is possible to efficiently and stably mass-produce a preform for precision press molding with a small mass tolerance or a glass molded body suitable as a base material for producing a preform. it can.

It is a schematic sectional drawing of one example of the precision press molding apparatus used in the Example.

Explanation of symbols

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

Claims (7)

A method for producing a glass molded body for mass-producing a glass molded body by dropping a molten glass droplet into a liquid, cooling and molding the liquid in a liquid,
When the boiling point at 1 atm is BP [° C.], the constant pressure specific heat is Cp [J / (g · K)], and the heat of vaporization is Q [J / g], the following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 1200 J / g (1)
Using a liquid that satisfies
A method for producing a glass molded body, wherein the temperature of the liquid is controlled to be maintained at a predetermined temperature in a range of 0 to 200 ° C., and a solid glass molded body is mass-produced.   The method for producing a glass molded body according to claim 1, wherein a molten glass droplet having a mass of 100 mg or less is dropped to form a spherical glass molded body.   The glass according to claim 1 or 2, wherein an external circulation flow path for liquid is formed, and a heat exchanger is provided in the flow path to cool the circulating liquid and to control the liquid temperature at a predetermined temperature. Manufacturing method of a molded object.   The manufacturing method of the glass forming body of Claim 3 which drops a molten glass drop one by one, producing a flow by the circulation of a liquid on the liquid level which drops a molten glass drop.   The manufacturing method of the glass forming body of any one of Claims 1-4 which produces the glass forming body for grinding | polishing. 5. manufactured Riga lath shaped body by the method according to the obtained method for producing a precision press-molding preform, which comprises polishing the glass molded body. A method for manufacturing an optical element for heating and precision press molding a glass preform,
To prepare Riga lath shaped body by the method according to any one of claims 1 to 5 or prepared descriptor remodeling by the method of claim 6, the resulting glass shaped body or flop, A method for producing an optical element, characterized in that the reform is heated and precision press-molded.

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