JP4919942B2 - Manufacturing method of glass molded body, precision press molding preform and optical element - 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 relates to a method for efficiently producing a glass molded body, which is a base material for producing a high-quality glass article such as a precision press-molding preform, with high productivity. The present invention relates to a method for producing a precision press-molding preform from a glass molded body, and a method for producing an optical element from the obtained 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

  However, this method has the following problems. When the glass lump is rapidly cooled at the time when the glass starts to solidify in the liquid, the glass lump may be broken or cracked due to rapid volume shrinkage. Such breaks and cracks are called cans and cracks, but even if they do not break, they can cause a phenomenon called sinking due to rapid cooling, resulting in a part of the glass lump surface being depressed or vacuum bubbles being generated in the glass lump. there were.

  The present invention has been made under such circumstances, and a glass molded body as a base material for producing a high-quality glass article such as a precision press-molding preform is efficiently manufactured with high productivity. It is an object of the present invention to provide a method for producing well, a method for producing a precision press-molding preform from the obtained glass molded body, and a method for producing an optical element from the obtained preform.

  The inventors of the present invention have intensively studied in order to achieve the above object, and have completed the present invention.

That is, the present invention
(1) In a method for producing a solid glass molded body from molten glass,
A molten glass lump is dropped into a liquid, cooled in the liquid, molded, and then the entire surface is polished to produce a precision press-molding preform made of glass, such as the molten glass lump. A glass molded body having a mass is obtained. As the liquid, a boiling point BP at 1 atm is 30 to 200 ° C., a constant pressure specific heat is Cp [J / (g · K)], and a heat of vaporization is Q [J / g]. The following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
The use of a liquid filling, as well,
Cooling the circulating liquid, maintaining the liquid temperature constant, flowing the glass droplets that have reached the liquid level with the circulating flow of liquid, shifting from the position when the liquid level is reached, preventing the glass droplets from sticking together,
A method for producing a glass molded body, characterized by
(2) When mass-producing a glass molded body by repeating the steps of dropping the molten glass droplet into the liquid, cooling and molding in the liquid, the temperature of the liquid is a predetermined temperature within a range of 0 to 200 ° C. ± 10 ° C. The method for producing a glass molded body according to claim 1, wherein the glass molded body having a constant thermal history is mass-produced.
(3) The manufacturing method of the glass molded object as described in said (1) or (2) term which shape | molds the glass whose average linear expansion coefficient in 100-300 degreeC is 50 * 10 < ^-7 > K < ^-1 > or more,
(4) The method for producing a glass molded article according to any one of (1) to (3) above, wherein the liquid contains a fluorine compound.
(5) In a method for producing a solid glass molded body from molten glass,
A molten glass lump is poured into a liquid, cooled in the liquid, molded, and then the entire surface is polished to produce a precision press-molding preform made of glass, such as the molten glass lump, etc. Obtaining a glass molded body of mass, and
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] as the liquid, the following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
Using a liquid that satisfies
The liquid is CF ₃ (CF ₂ ) ₅ CF ₃ and / or CF ₃ CH ₂ OCF ₂ CF ₂ H;
A method for producing a glass molded body, characterized by
(6) The method for producing a glass molded body according to the above (5 ), wherein the molten glass lump is charged into the liquid by dropping a molten glass droplet into the liquid from the outlet of the nozzle.
(7) The method for producing a glass molded body according to any one of (1) to (4) and (6) above, wherein a molten glass droplet having a mass of 100 mg or less is dropped.
(8) and wherein said (1) to prepare a glass shaped material by the method described in to (7) any one of claim to prepare a preform by polishing the entire surface of the glass shaped material Manufacturing method for precision press molding preforms,
(9) The glass molded body is mass-produced by the method described in any one of the above items (1) to (7), and the entire surface of the mass-produced many glass molded bodies is simultaneously polished to produce a preform. A method for producing a precision press-molding preform, and
(10) A method for producing an optical element, characterized in that a preform is produced by the method described in (8) or (9) above, and the preform is heated and precision press-molded.
Is to provide.

  According to the present invention, a method for efficiently producing a glass molded body as a base material for producing a high-quality glass article such as a precision press-molding preform with high productivity, and the obtained glass It is possible to provide a method for producing a precision press-molding preform from a molded body, and a method for producing an optical element from the obtained preform.

First, the manufacturing method of the glass forming body of this invention is demonstrated.
[Method for producing glass molded body]
The method for producing a glass molded body of the present invention is a method for producing a solid glass molded body from molten glass. The molten glass lump is poured into a liquid and cooled in the liquid, and after molding, the entire surface is polished. A preform for producing a glass precision press-molding preform, obtaining a glass molded body having the same mass as the molten glass lump, and having a boiling point BP of 30 to 200 at 1 atm as the liquid. The following relational expression (1) where Cp [J / (g · K)] and constant heat of vaporization are Q [J / g]
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
It is characterized by using the liquid which satisfy | fills.

  Cans, cracks, and vacuum bubbles generated when a molten glass lump is formed in a liquid are due to the glass lump being rapidly cooled. Therefore, in order to prevent cans, cracks, and vacuum bubbles, the liquid in contact with the glass lump is boiled by the heat of the glass lump to gasify it, and the surface of the glass lump is covered with the gas layer. What is necessary is just to reduce the cooling speed. However, even if the glass lump surface is covered with the gas layer, it is difficult to completely eliminate the above-described problems unless the heat insulation effect by the gas layer is sufficient. In particular, when glass having a large expansion coefficient is formed, volume shrinkage during cooling increases, and therefore a gas layer must be formed so as to obtain a sufficient heat insulating effect.

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

Next, the liquid used in the present invention will be described.
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)
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. This amount of heat was used as an index A of the ease of gasification of the liquid, and as a result of an experimental investigation of the relationship between this index and the effect of preventing cans, cracks, and vacuum bubbles, in the present invention, as a molding liquid, (1)
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
It has been found that good results can be obtained by using a liquid that satisfies the above.
Table 1 shows BP, Cp, Q, and A for some liquids.

このように、液体により指標Ａの値には大きな差がある。フッ化炭化水素やハイドロフルオロエーテルのように指標Ａが所定値以下になっている液体では、液体がガス化しやすく、ガス層による十分な断熱効果が得られるが、水やエチレングリコールのように指標Ａが大きい液体では、ガス層による十分な断熱効果が得られにくい。

Thus, there is a large difference in the value of the index A depending on the liquid. For liquids with index A below the specified value, such as fluorinated hydrocarbons and hydrofluoroethers, the liquid is easy to gasify, and a sufficient heat insulation effect can be obtained by the gas layer. In a liquid having a large A, it is difficult to obtain a sufficient heat insulating effect by the gas layer.

  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 the present invention, from the viewpoint of obtaining a sufficient heat insulating effect due to gas layer formation, it is necessary to use a liquid having an index A of 900 J / g or less as the molding liquid, preferably 700 J / g or less, more preferably Is preferably 400 J / g or less, more preferably 250 J / g or less.

  As for the boiling point of the liquid, if the boiling point is too high, the boiling of the liquid stops with cooling of the glass lump, the gas necessary for gas layer formation is not supplied, and the glass lump cannot be cooled slowly.

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, a liquid having a boiling point of 30 to 200 ° C. is used as the molding liquid. The boiling point of the preferred liquid is 60 to 150 ° C, more preferably 80 to 120 ° C.

In addition, a glass having a larger expansion coefficient has a larger volume shrinkage during cooling, and can easily form cans, cracks, and vacuum bubbles. Therefore, the present invention is suitable for molding a glass having a large expansion coefficient, and is suitable for molding a glass having an average linear expansion coefficient at 100 to 300 ° C. of 50 × 10 ⁻⁷ K ⁻¹ or more, and 80 × 10 ^−7. It is more suitable for forming glass of K ⁻¹ or higher.

  In the present invention, a liquid that satisfies the above-mentioned various conditions is used. As such a liquid, a liquid containing a fluorine compound is preferable. However, since the fluorine compound generates hydrofluoric acid by thermal decomposition, it is generated by boiling or gasification of the liquid. Hydrofluoric acid alters the surface of the glass molded body, and an altered layer called burn is easily formed. However, the obtained glass molded body is a base material for polishing the entire surface to produce a precision press-molding preform, and the altered layer on the surface is surely removed by the polishing.

When a liquid containing a fluorine compound is used as the molding liquid, a basic such as calcium hydroxide, sodium hydroxide or potassium hydroxide is optionally used to neutralize the hydrofluoric acid generated by thermal decomposition as described above. The substance can be added to a liquid containing a fluorine compound. In this case, the addition amount of the basic substance is usually 1 to 10 parts by mass, preferably 3 to 7 parts by mass with respect to 100 parts by mass of the liquid, although it depends on the type of the basic substance and the molding liquid. .
(Effects of the method of the present invention)
In the method for producing a glass molded body of the present invention, it is desirable that the molten glass lump is poured into the liquid by dropping molten glass droplets into the liquid from the nozzle outlet. In such a method, the molten glass lump is poured into the liquid by dropping molten glass droplets into the liquid from the nozzle outlet, but the temperature of the nozzle is kept constant and the molten glass is continuously supplied at a constant flow rate. When it flows out, the dropping time interval becomes constant, and the mass of the molten glass droplet becomes constant.

  The amount of molten glass that flows out per unit time is called the pulling amount, but in the production of optical glass, if the pulling amount changes, the residence time of the molten glass in the melting vessel changes, so the clarification conditions may deviate from the optimum state. When the staying time becomes long, a material such as platinum constituting the container is dissolved in the glass, and the coloring of the glass becomes strong. In order to obtain molten glass droplets with a desired mass while avoiding such problems, the pulling amount is kept constant and the time interval of dropping is adjusted.

  According to the present invention, since it is not necessary to transfer the molding die to the lower part of the nozzle one after another for dropping glass as in the prior art, the drop interval is shortened to increase the production amount of the glass molded body per unit time. Can do. The smaller the mass of the molten glass droplet, the shorter the dropping interval, and the greater the merit that can be enjoyed.

  In combination with the use of the liquid that is easily gasified, the present invention is suitable for forming a lightweight glass molded body, particularly suitable for dropping a molten glass droplet having a mass of 100 mg or less, and dropping a molten glass droplet having a mass of 50 mg or less. Is more preferable.

In addition, in the method by dripping a molten glass drop, since the surface tension of a glass drop becomes dominant as a factor which determines the shape of a glass molded object, there exists a merit which can shape | mold a glass drop spherically. A spherical glass molded body is easy to polish and can be said to be preferable from the viewpoint of efficiently producing a preform.
(Liquid temperature control method)
In the present invention, when mass-producing a glass molded body by repeating the steps of dropping a molten glass droplet into the liquid, cooling and molding in the liquid, the temperature of the liquid is a predetermined temperature ± 10 in the range of 0 to 200 ° C. By carrying out the control to maintain at ° C., the glass molded body can be mass-produced efficiently.

  That is, even when the glass is slowly cooled in the liquid using a liquid having a small heat of vaporization, the amount of consumption of the liquid can be reduced. 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.

When the predetermined temperature of the liquid maintained in the range of ± 10 ° C. is Tliq [° C.], a method for controlling the liquid to Tliq [° C.] is a method capable of maintaining the liquid uniformly at the temperature. Although there is no particular limitation, for example, there is a control method for forming an external circulation flow path for liquid and for providing a heat exchanger in the flow path to cool the circulating liquid and maintain the liquid temperature constant. preferable. 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.

Next, the manufacturing method of the precision press molding preform of this invention is demonstrated.
[Precision press molding preform manufacturing method]
The method for producing a precision press-molding preform (hereinafter sometimes simply referred to as a preform) of the present invention is to prepare a preform by polishing the entire surface of the glass molded body produced by the above-described method. It is characterized by.

  In production of a glass optical element, a glass corresponding to a desired optical characteristic is selected from a variety of optical glasses, and a preform having an amount corresponding to the mass of the optical element is made. Under such circumstances, in order to respond quickly to the demand from the user, it is necessary to prepare a large number of preforms having various masses for each type of glass. However, such a method is not preferable because it always requires unnecessary inventory of preforms.

  According to the present invention, even in the above situation, it is possible to respond quickly and efficiently to user demand as follows. An equal-mass glass molded body is formed to make a lot consisting of a plurality of glass molded bodies. The mass of one glass molded body is changed for each lot, and a plurality of lots having different masses are produced. Specifically, a lot of glass molded products having a mass α obtained by adding the mass of the polishing preform to the minimum mass of the preform required, and adding a mass β of the polishing margin to the maximum mass of the preform required. One type or a plurality of types of lots composed of a glass molded body having a mass and a glass molded body having a mass between masses α and β are produced. In this way, a lot made of a glass molded body having several stages of mass is prepared. When a preform with a specific mass is required according to demand, a lot consisting of a glass molded body having a mass larger than the specific mass and closest to the mass is selected, and the entire surface of the glass molded body contained in the lot Is polished to prepare a preform having the above-mentioned mass. By doing so, a preform having a desired mass can be efficiently manufactured by adjusting the polishing margin.

Examples of the fluorine compound that satisfies the formula (1) and generates a small amount of fluorine by thermal decomposition include CF ₃ (CF ₂ ) ₅ CF ₃ , CF ₃ CH ₂ OCF ₂ CF ₂ H, and the like. . Among hydrofluoroethers, CF ₃ CH ₂ OCF ₂ CF ₂ H, unlike CF ₃ (CH ₂ ) ₃ OCH ₃ [manufactured by Sumitomo 3M Co., Ltd., trade name “Novek”], generates less fluorine, and 30% of the Novec Since the generated amount can be suppressed to a certain level, the minimum polishing margin can be set small.
(Polishing process)
In the present invention, the entire surface of the glass molded body obtained as described above is polished to produce a desired preform. As the polishing process, the following method can be used.

  Place the spherical glass molded body in the groove of the polishing machine with a cross-section of the groove on the circular arc, and sandwich the glass molded product with another polishing machine, and apply the liquid called slurry mixed with abrasive to form the glass. The entire surface of the glass molded body is uniformly polished while rolling the body along the groove. In this way, a spherical preform having a high sphericity can be produced. In such a method, a preform having a shape similar to that of a glass molded body can be obtained. Therefore, a preform having a target mass can be made relatively simply by adjusting the polishing margin while measuring the diameter of the sphere. The mass of the glass that is reduced by the polishing treatment can be easily calculated from the specific gravity, the diameter, and the reduction amount of the diameter of the glass.

  In the polishing treatment of the spherical glass molded body, it is desirable to place an equal mass of the glass molded body in the groove of the polishing disk and polish it simultaneously. In this way, an equal pressure is applied to each workpiece, the polishing margin for each workpiece can be made uniform, and a large number of preforms with extremely small mass tolerances can be produced simultaneously.

  The method for producing a precision press-molding preform according to the present invention including such an embodiment is a method for producing a preform by polishing the entire surface of a glass molded body produced by the above method. As a polishing method, a known method can be used in addition to the above method. Prior to the polishing treatment, the glass molded body may be annealed as necessary. Since distortion is reduced by annealing, an effect of preventing damage in the polishing process can be obtained.

  In addition, according to this invention, since the glass lump can be cooled slowly in a liquid, generation | occurrence | production of the crack which is hard to understand visually as well as the crack understood visually can be prevented. If a glass molded body containing minute cracks is overlooked and subjected to a polishing process, the cracks will grow rapidly during the polishing process. As described above, since a large number of glass moldings are simultaneously polished, if even one piece of glass is broken, the broken pieces will damage other glass surfaces, resulting in a large number of defective products. As described above, according to the present invention, such troubles can be avoided.

Next, the manufacturing method of the optical element of this invention is demonstrated.
[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 preform for precision press molding 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 aforementioned preform is introduced into a press mold, the mold and the preform are heated together, and precision press molding is performed.

In this precision press molding method 1, both the temperature of the press mold and the preform are heated to a temperature at which the glass constituting the preform exhibits a viscosity of about 10 ⁶ to 10 ¹² dPa · s to perform precision press molding. It is 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 preform, it is introduced into a press mold and precision press-molded, that is, the press mold and the preform are separately preheated, and the preheated preform is introduced into the press mold. And precision press molding.

  According to this method, since the preform 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.

  The preheating temperature of the press mold is preferably set lower than the preheating temperature of the preform. Thus, by lowering the preheating temperature of the press mold, the consumption of the mold can be reduced.

  Further, according to this method, since it is not necessary to perform preform heating in the press mold, the number of press molds to be used can be reduced.

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

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

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

The temperature of the press mold is adjusted to a temperature lower than the preheating temperature of the preform. 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 preform is supplied onto the lower mold and pressed. Molding can be performed. According to the present invention, by using the preform, the optical element can be produced with high productivity without causing problems such as a gas trap even if a press mold having different molding surface shapes of the upper mold and the lower mold is used. It can be manufactured originally.

  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, if a preform made of copper-containing glass is used, an optical element having a color correction function of a semiconductor imaging element can be produced. 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) Production of glass molded body A lanthanum borate-containing glass having a refractive index nd of 1.806 and an Abbe number νd of 40.7 was melted at 1200 ° C, and passed through a platinum outlet pipe whose temperature was controlled at 1050 ° C. Molten glass was dropped from a platinum outflow nozzle whose temperature was controlled at 1000 ° C. A glass with a mass smaller than the mass of a platinum nozzle with an outer diameter of 0.8 mm and an inner diameter of 0.6 mm, with nitrogen gas flowing constantly at a flow rate of 0.8 l / min vertically below the outer diameter of the nozzle, and dropping by the nozzle tip. Drops were obtained. The mass was 20 mg and the dropping interval was 0.2 seconds.

The glass dropped from the nozzle was perfluorocarbon [manufactured by Sumitomo 3M, trade name “Fluorinert FC-84”, characteristic CF ₃ (CF ₂ ) ₅ CF ₃ , A = 143 J / g, BP = 80 ° C.]. It took about 4 seconds to fall into the container (inner diameter 80 mm, liquid level 800 mm, cylindrical container) and reach the bottom of the container from the liquid level. The temperature of the liquid was controlled by an external circulation type cooling device equipped with a Stirling cooler, and was controlled within a range of 20 ± 5 ° C. An open / close valve was provided at the bottom of the container, and opened and closed every 5 minutes to take out the glass molded body. The finished glass molded body was a sphere having an average diameter of 2.03 mm and a roundness of 50 μm or less, and contained no defects due to rapid cooling such as cans, cracks, and vacuum bubbles. 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 was measured using a roundness measuring machine (“RA-2100” manufactured by Mitutoyo Corporation).
(2) Manufacture of preforms The glass base material obtained in (1) above was taken and polished with a white 100 μm to a diameter of 1.83 mm. As a result, a spherical preform lot with no defects on the surface was obtained. . The time required for the polishing treatment 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 annealed under the condition of cooling to room temperature in 1 hour to obtain an aspheric lens. The obtained aspherical lens had good thickness accuracy [variation of edge thickness within ± 0.005 mm (measured by measuring the edge thickness once with a laser displacement meter)].
Example 2
(1) Manufacture of glass molded body A heavy furin glass having a refractive index nd of 1.82 and an Abbe number νd of 24 is melted at 1100 ° C., passed through a platinum outflow pipe whose temperature is controlled to 950 ° C., and then heated to 900 ° C. Molten glass was dropped from a temperature-controlled platinum outflow nozzle. A glass droplet with a platinum nozzle outer diameter of 0.8 mm and an inner diameter of 0.7 mm, with nitrogen gas flowing constantly at a flow rate of 0.5 liters / min. Got. The mass was 40 mg, and the dropping interval was 0.25 seconds.

The glass droplets dropped from the nozzle were made of hydrofluoroether [Asahi Glass Co., Ltd., trade name “Asahiklin AE3100”, characteristic formula CF ₃ CH ₂ OCF ₂ CF ₂ H + ethanol, A = 246 J / g, BP = 54 ° C.] It took about 6 seconds to drop into the container (inner diameter 100 mm, liquid level 1200 mm) and reach the bottom of the container from the liquid level. The temperature of the liquid was controlled by an external circulation device equipped with a Stirling cooler, and was controlled within a range of 20 ± 5 ° C. An open / close valve was provided at the bottom of the container, and the glass formed body was taken out by opening and closing every 10 minutes. The finished glass molded body was a spherical body having an average diameter of 2.76 mm and a roundness of 100 μm or less, and did not contain any defects due to rapid cooling such as cans, cracks, and vacuum bubbles. When the surface was observed with an electron microscope, the fluorine component of the hydrofluoroether and the glass reacted with each other, resulting in slight white burn.
(2) Manufacture of preform The glass preform obtained in (1) above was taken and polished with a white 150 μm to a diameter of 2.46 mm, and a spherical preform lot with no defects on the surface was obtained. . The time required for the polishing treatment was 12 hours.
(3) Manufacture of optical element About 100,000 ball preforms in the ball preform lot obtained in (2) above, precision press molding was performed in the same manner as in Example 1, and precision press molded products were obtained. After being heated to 350 ° C. in a batch type annealing furnace, maintained at that temperature for 2 hours, and then annealed under the condition of cooling to room temperature in 1 hour to obtain an aspheric lens. The obtained aspherical lens had good thickness accuracy (the variation in edge thickness was within ± 0.005 mm).

  According to the method for producing a glass molded body of the present invention, a glass molded body that is a base material for producing a high-quality glass article such as a precision press-molding preform is efficiently manufactured with high productivity. be able to. Moreover, a precision press-molding preform can be manufactured using the glass molded body, and various optical elements can be manufactured from the precision press-molding preform.

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 (10)

In a method for producing a solid glass molded body from molten glass,
A molten glass drop is dropped into a liquid, cooled in the liquid, molded, and then the entire surface is polished to produce a glass precision press-molding preform, such as the molten glass lump, etc. A glass molded body having a mass is obtained. As the liquid, a boiling point BP at 1 atm is 30 to 200 ° C., a constant pressure specific heat is Cp [J / (g · K)], and a heat of vaporization is Q [J / g]. The following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
The use of a liquid filling, as well,
Cooling the circulating liquid, maintaining the liquid temperature constant, flowing the glass droplets that have reached the liquid level with the circulating flow of liquid, shifting from the position when the liquid level is reached, preventing the glass droplets from sticking together,
A method for producing a glass molded body characterized by the above. When mass-producing a glass molded body by repeating the steps of dropping the molten glass droplet into the liquid, cooling and molding in the liquid, the temperature of the liquid is maintained at a predetermined temperature ± 10 ° C in the range of 0 to 200 ° C. The manufacturing method of the glass forming body of Claim 1 which controls and mass-produces the glass forming body with a fixed heat history. The manufacturing method of the glass molded object of Claim 1 or 2 which shape | molds the glass whose average linear expansion coefficient in 100-300 degreeC is 50 * 10 < ^-7 > K < ^-1 > or more. The method for producing a glass molded body according to any one of claims 1 to 3, wherein the liquid contains a fluorine compound. In a method for producing a solid glass molded body from molten glass,
A molten glass lump is poured into a liquid, cooled in the liquid, molded, and then the entire surface is polished to produce a precision press-molding preform made of glass, such as the molten glass lump, etc. Obtaining a glass molded body of mass, and
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] as the liquid, the following relational expression (1)
Cp × (BP−20 ° C.) + Q ≦ 900 J / g (1)
Using a liquid that satisfies
  The liquid is CF ₃ (CF ₂ ) ₅ CF ₃ And / or CF ₃ CH ₂ OCF ₂ CF ₂ Being H,
A method for producing a glass molded body characterized by the above. The method for producing a glass molded body according to claim 5 , wherein the molten glass lump is charged into the liquid by dropping a molten glass droplet into the liquid from an outlet of the nozzle. The method for producing a glass molded body according to any one of claims 1 to 4, wherein a molten glass droplet having a mass of 100 mg or less is dropped. To prepare a glass shaped material by the method according to any one of claims 1 to 7 precision press-molding preform, characterized in that by polishing the entire surface of the glass shaped material to produce the preform Manufacturing method. A precision press characterized in that a glass molded body is mass-produced by the method according to any one of claims 1 to 7, and a preform is prepared by simultaneously polishing the entire surface of a large number of mass-produced glass molded bodies. A method for manufacturing a preform for molding. A method for producing an optical element , comprising producing a preform by the method according to claim 8 or 9 , and heating and precision-pressing the preform.

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