Glass manufacturing method

Abstract

To provide a production method of glass capable of suppressing oxidation and enhancing productivity.SOLUTION: A production method of glass includes the steps of: producing a melt 11 from a raw material 6 put in a vessel 1; homogenizing the melt 11; and removing gas from the melt 11. At least one of the step of producing the melt 11 from the raw material 6 and the step of homogenizing the melt 11 is conducted under an inert gas or reductive gas atmosphere. In the step of removing the gas from the melt 11, the inert gas or the reductive gas is removed by setting the temperature of the melt 11 lower than the temperature in the step of homogenizing the melt 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing glass. [Background technology]

[0002] In recent years, chalcogenide glass has been known as a material that is preferably used in the field of infrared optics. Chalcogenide glass is not only transparent to infrared rays, but also has advantages in terms of mass productivity and cost reduction due to its applicability to mold presses.

[0003] When manufacturing optical members such as lenses, for example, molten glass is quenched and cast to produce a glass ingot, which is then ground, polished, and cleaned to produce a glass preform, which is then molded by press molding or the like to produce an optical member such as a lens.

[0004] An example of a method for manufacturing a glass article is disclosed in the following Patent Document 1. In this manufacturing method, glass is obtained by melting glass raw materials in a vacuum-sealed ampoule. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 06-183779 Summary of the Invention [Problem to be solved by the invention]

[0006] When forming glasses such as chalcogenide glasses, it is necessary to suppress oxidation. In the method described in Patent Document 1, while oxidation can be suppressed, it is necessary to destroy the ampoule when taking out the glass. Therefore, it is difficult to sufficiently increase productivity.

[0007] An object of the present invention is to provide a method for producing glass that can suppress oxidation and increase productivity. [Means for solving the problem]

[0008] The method for producing glass according to the present invention includes a step of converting raw materials placed in a container into a melt, a step of homogenizing the melt, and a step of degassing the melt, and is characterized in that at least one of the steps of converting the raw materials into a melt and homogenizing the melt is carried out in an inert gas or reducing gas atmosphere, and in the step of degassing the gas from the melt, the temperature of the melt is set lower than the temperature in the step of homogenizing the melt, thereby degassing the inert gas or reducing gas.

[0009] In the step of degassing the melt, it is preferable to reduce the pressure inside the vessel.

[0010] It is preferable that both the step of melting the raw materials and the step of homogenizing the melt are carried out in an inert gas or reducing gas atmosphere.

[0011] It is preferable that the method further comprises, after the step of degassing the melt, a step of heating the melt and causing the melt to flow out of the container.

[0012] It is preferable that at least one of the steps of turning the raw material into a melt and homogenizing the melt is carried out under an atmosphere of one of an inert gas and a reducing gas, and that the step of causing the melt to flow out of the container is carried out inside the container under an atmosphere of the other of an inert gas and a reducing gas.

[0013] Preferably, the glass is a chalcogenide glass. Effect of the Invention

[0014] According to the present invention, it is possible to provide a method for producing glass that can suppress oxidation and increase productivity. [Brief description of the drawings]

[0015] [Figure 1] 1(a) to 1(c) are schematic cross-sectional views illustrating a step of melting raw materials in a method for producing glass according to one embodiment of the present invention. [Diagram 2] 1(a) and 1(b) are schematic cross-sectional views illustrating the process of homogenizing the melt and subsequent processes in a glass manufacturing method according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a temperature profile in a method for producing glass according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in the drawings, components having substantially the same functions may be referred to by the same reference numerals.

[0017] (Glass manufacturing method) The present embodiment is characterized by a step of degassing an inert gas or a reducing gas from a melt obtained by melting raw materials. The manufacturing method of the present embodiment will be described below with reference to the drawings.

[0018] Fig. 1(a) to Fig. 1(c) are schematic cross-sectional views for explaining a step of making the raw material into a melt in a method for producing glass according to one embodiment of the present invention. Fig. 2(a) and Fig. 2(b) are schematic cross-sectional views for explaining a step of homogenizing the melt and subsequent steps in a method for producing glass according to one embodiment of the present invention. Fig. 3 is a diagram showing a temperature profile in a method for producing glass according to one embodiment of the present invention. For convenience, coil 10A or coil 10B is omitted in some of the drawings. The temperature profile in Fig. 3 is an example, and is not limited thereto.

[0019] The manufacturing method of this embodiment is a method for manufacturing chalcogenide glass as one example of the present invention, although the method of the present invention can also be applied to the manufacture of glasses other than chalcogenide glass.

[0020] As shown in Fig. 1(a), in this embodiment, a crucible is used as the container 1. The container 1 has a bottom 2 and a side wall 3. The container 1 is preferably made of quartz glass. This allows glass to be formed suitably in the following steps.

[0021] A pipe 4 is connected to the bottom 2 of the container 1. An outer tube 5 is disposed so as to surround the pipe 4. The pipe 4 passes through the outer tube 5. In this embodiment, the pipe 4 is made of quartz glass. The outer tube 5 is made of Pt. However, the outer tube 5 may be made of any suitable metal.

[0022] As shown in FIG. 1(a), glass raw material 6 is placed in container 1. In this embodiment, raw material 6 is a mixture containing components that constitute chalcogenide glass. In this embodiment, raw material 6 may contain metal. In the present invention, "metal" includes metal elements, semimetal elements, alkali metal elements, alkaline earth metal elements, and the like. Details of raw material 6 will be described later. It is preferable to melt a small amount of raw material 6 in advance to make a small amount of molten liquid, and to allow a small amount of molten liquid to flow into pipe 4. The small amount of molten liquid is cooled in pipe 4 and becomes a solidified material (solid glass). This allows plug 12 to be formed. By forming plug 12, raw material 6 can be stably placed even if pipe 4 is connected to bottom 2 of container 1.

[0023] Next, as shown in Fig. 1(b), a lid 7 is placed on the side wall 3 of the container 1. A gas supply pipe 8 and a gas exhaust pipe 9 are connected to the lid 7. Gas is exhausted from the container 1 through the gas exhaust pipe 9 to reduce the pressure. Next, an inert gas or reducing gas is supplied into the container 1 through the gas supply pipe 8. By repeating this process, the inside of the container 1 is filled with an inert gas atmosphere or a reducing gas atmosphere.

[0024] As the inert gas, for example, nitrogen, helium, argon, etc. can be used. As the reducing gas, for example, hydrogen, carbon monoxide, hydrocarbon gas, etc. can be used.

[0025] When forming chalcogenide glass, it is necessary to prevent the heated raw material 6 or the melt described later from reacting with oxygen or moisture. In this embodiment, the air in the container 1 is replaced with an inert gas or a reducing gas, so that oxygen and moisture are removed from the container 1. Therefore, chalcogenide glass can be suitably formed without using a sealed container kept in a vacuum state. In this embodiment, as described later, the melt is made to flow out of the container 1 from the pipe 4, and then glass is formed. Therefore, it is not necessary to destroy the container 1 to take out the formed glass, and the container 1 can be reused.

[0026] Incidentally, as shown in FIG. 1(c), the coil 10A is arranged so as to surround at least a part of the side wall 3 of the container 1. Specifically, the coil 10A is arranged so as to surround the part of the container 1 where the raw material 6 is arranged. The raw material 6 is induction-heated by passing a current through the coil 10A. Specifically, an induced magnetic field generated by passing a current through the coil 10A generates an induced current. The raw material 6 contains a metal, and the metal has an internal resistance. Therefore, when an induced current flows through the metal, the metal contained in the raw material 6 becomes a heat source, and the entire raw material 6 is heated. This induction heating turns the raw material 6 into a melt 11 as shown in FIG. 2(a). The melt 11 is heated to a temperature a° C., which will be described later, and a reaction proceeds. This makes it possible to make the melt 11 homogenous.

[0027] Furthermore, an induced magnetic field and an induced current are generated by passing a current through coil 10A, and a Lorentz force is applied to melt 11. Melt 11 can also be made homogenous by stirring it with this Lorentz force. In this manner, in this embodiment, melt 11 can be made homogenous without using a means for stirring melt 11 by directly contacting a member therewith, such as a stirrer. However, melt 11 may be stirred with a stirrer or the like to efficiently homogenize it.

[0028] As described above, a part of the melt 11 flows into the pipe 4. The melt 11 in the pipe 4 is cooled and solidifies (solid glass). This forms the plug 12. Therefore, a small amount of the melt 11 sufficient to form the plug 12 flows into the pipe 4, but the outflow of the remaining melt 11 is stopped by the plug 12. However, a lid, a plunger, or the like may be used instead of the plug 12.

[0029] As indicated by the double-headed arrow A in FIG. 3, in this embodiment, the step of homogenizing the melt 11 is performed at a° C. For example, a=600° C. to 1000° C. After the step of homogenizing the melt 11, the inert gas or reducing gas is degassed from the melt 11. More specifically, after the step of homogenizing the melt 11, the melt 11 is cooled to a temperature (b° C.) lower than a° C., thereby degassing the gas. For example, as indicated by the double-headed arrow B in FIG. 3, the degassing is performed at b=300° C. to less than 700° C.

[0030] Next, the melt 11 is heated to a temperature (c° C.) suitable for forming. For example, c is less than 400° C. to 700° C. Thereafter, the inside of the container 1 is made to have an inert gas atmosphere or a reducing gas atmosphere, and the melt 11 is caused to flow out of the container 1.

[0031] Here, as shown in FIG. 2(b), a coil 10B is disposed around the outer tube 5. By passing a current through the coil 10B, the outer tube 5 is induction heated. The pipe 4 and the plug 12 in the pipe 4 are heated by radiant heat from the outer tube 5. Note that the plug 12 is solid glass and does not contain a simple metal or alloy, and is therefore not induction heated. The plug 12 melts due to the heating caused by the radiant heat, and the molten liquid 11 flows out of the container 1.

[0032] It should be noted that the methods shown in Figures 1(a) to 1(c) and Figures 2(a) and 2(b) and the temperatures shown in Figure 3 are merely examples, and the methods and temperatures in the process of turning the raw material 6 into melt 11, the process of homogenizing the melt 11, and the process of causing the melt 11 to flow out of the container 1 are not limited to those described above.

[0033] The melt 11 that has flowed out is poured into, for example, an appropriate mold. Next, the melt 11 is cooled in the mold to form glass. This glass can be ground, polished, and washed to produce a preform glass. In addition, optical members such as lenses can be produced by subjecting the preform glass to mold press molding or the like. Note that optical members such as lenses may be produced directly from the above glass without producing a preform glass.

[0034] The feature of this embodiment is that after melting the raw material 6 under an inert gas or reducing gas atmosphere and homogenizing the melt 11, in the process of degassing the gas from the melt 11, the inert gas or reducing gas is degassed by setting the temperature lower than the temperature in the process of homogenizing the melt 11. Since the process of turning the raw material 6 into the melt 11 and the process of homogenizing the melt 11 are performed under an inert gas or reducing gas atmosphere, oxidation can be suppressed. Furthermore, since degassing is performed at a low temperature, degassing can be performed more reliably. More specifically, the solubility of gas often increases as the temperature decreases. On the other hand, the solubility of the inert gas and reducing gas in the melt 11 decreases as the temperature decreases. Therefore, in this embodiment, degassing from the melt 11 can be performed more reliably, and foaming in the melt 11 can be suppressed when forming glass. Therefore, the formed glass can be more reliably suppressed from containing bubbles, and the productivity of glass can be increased.

[0035] At least one of the steps of turning the raw material 6 into the melt 11 and homogenizing the melt 11 may be performed in an inert gas or reducing gas atmosphere. However, it is preferable to perform both the steps of turning the raw material 6 into the melt 11 and homogenizing the melt 11 in an inert gas or reducing gas atmosphere. This makes it possible to more reliably suppress oxidation.

[0036] In the step of degassing the melt 11, it is preferable to reduce the pressure inside the container 1 as in this embodiment. This allows for effective degassing. However, it is not always necessary to reduce the pressure when degassing.

[0037] In this embodiment, after the step of degassing melt 11, melt 11 is heated and melt 11 is caused to flow out of container 1. In this manner, it is preferable that the temperature of melt 11 in the step of degassing melt 11 is lower than the temperature of melt 11 in the step of causing melt 11 to flow out of container 1. This allows degassing to be performed more reliably.

[0038] It is preferable that at least one of the step of making the raw material 6 into the melt 11 and the step of homogenizing the melt 11 is performed under an atmosphere of one of an inert gas and a reducing gas, and the step of making the melt 11 flow out of the container 1 is performed under an atmosphere of the other of an inert gas and a reducing gas. Specifically, for example, when the step of making the melt 11 homogenous is performed under an inert gas atmosphere, it is preferable to make the step of making the melt 11 flow out of the container 1 under a reducing gas atmosphere. Alternatively, for example, when the step of making the melt 11 homogenous is performed under a reducing gas atmosphere, it is preferable to make the step of making the melt 11 flow out of the container 1 under an inert gas atmosphere. In this way, the amount of gas in the melt 11 can be easily reduced.

[0039] The temperature (a°C) in the step of homogenizing melt 11 is preferably 600°C to 1000°C, 700°C to 1000°C, or 750°C to 1000°C, particularly preferably 800°C to 950°C. If the temperature in the step of homogenizing melt 11 is too low, the viscosity of melt 11 increases, making it difficult to homogenize melt 11. In addition, productivity is likely to decrease. If the temperature in the step of homogenizing melt 11 is too high, container 1 is likely to deteriorate. In addition, raw material 6 is likely to volatilize.

[0040] The temperature (b°C) in the degassing step is preferably 300°C to less than 700°C, 300°C to less than 600°C, and particularly preferably 300°C to less than 500°C. If the temperature in the degassing step is too low, the viscosity of melt 11 increases, making degassing more difficult. Also, melt 11 is more likely to devitrify. If the temperature in the degassing step is too high, degassing is more likely to be insufficient.

[0041] The temperature (c°C) suitable for molding is appropriately adjusted to obtain a viscosity suitable for the desired molding means, and is preferably from 400°C to less than 700°C, from 450°C to 650°C, and particularly preferably from 500°C to 650°C.

[0042] The temperature (b° C.) in the degassing step is preferably lower than the temperature (c° C.) suitable for molding, which makes it easier to degas the inert gas or reducing gas sufficiently.

[0043] The ratio of materials contained in raw material 6 of this embodiment is adjusted so as to obtain glass having the following composition. In the explanation of the glass composition, "%" means "mol %." For example, the total content of A, B, and C may be expressed as "content of A+B+C" or "A+B+C."

[0044] The glass formed by the method of the present embodiment has a glass composition containing, in molar ratios, from more than 0% to 50% Ge, from more than 0% to 50% Ga, from 30% to 90% Te, from more than 0% to 40% Ag+Al+Ti+Cu+In+Sn+Bi+Cr+Zn+Mn, and from 0% to 50% F+Cl+Br+I.

[0045] Ge is a component for forming a glass skeleton. Ge is a semimetal element. The Ge content is more than 0% to 50%, preferably 2% to 40%, more preferably 4% to 35%, even more preferably 5% to 30%, even more preferably 7% to 25%, and even more preferably 10% to 20%. If the Ge content is too low, vitrification becomes difficult. On the other hand, if the Ge content is too high, Ge-based crystals tend to precipitate easily and the raw material cost tends to increase.

[0046] Ga is a component for increasing the thermal stability (vitrification stability) of glass. Ga is a metal element. The Ga content is more than 0% to 50%, preferably 1% to 45%, more preferably 2% to 40%, even more preferably 4% to 30%, even more preferably 5% to 25%, and even more preferably 10% to 20%. If the Ga content is too low, vitrification becomes difficult. On the other hand, if the Ga content is too high, Ga-based crystals tend to precipitate easily and the raw material cost tends to increase.

[0047] Te, a chalcogen element, is a component that is essential for forming a glass skeleton. Te is also a metalloid element. The content of Te is 30% to 90%, preferably 40% to 89%, more preferably 50% to 88%, even more preferably 60% to 86%, and even more preferably 70% to 85%. If the content of Te is too low, vitrification becomes difficult. On the other hand, if the content of Te is too high, Te-based crystals are likely to precipitate.

[0048] Ag+Al+Ti+Cu+In+Sn+Bi+Cr+Zn+Mn are metal elements. The glass contains the above metal elements, which can enhance thermal stability. The content of Ag+Al+Ti+Cu+In+Sn+Bi+Cr+Zn+Mn is 0% to 40%, preferably more than 0% to 30%, more preferably more than 0% to 20%, and even more preferably 0.1% to 10%. If the content of Ag+Al+Ti+Cu+In+Sn+Bi+Cr+Zn+Mn is too low or too high, vitrification becomes difficult. The contents of each of Ag, Al, Ti, Cu, In, Sn, Bi, Cr, Zn, and Mn are each 0% to 40%, preferably 0% to 30% (at least one of them is more than 0%), more preferably 0% to 20% (at least one of them is more than 0%), and even more preferably 0.1% to 10%. Among these, it is preferable to use Ag and / or Sn, since they have a particularly large effect of increasing the thermal stability of the glass.

[0049] The glass formed in this embodiment may contain, in addition to the above components, the following components, for example.

[0050] F, Cl, Br, and I are also components that enhance the thermal stability of glass. The content of F+Cl+Br+I is 0% to 50%, preferably 1% to 40%, more preferably 1% to 30%, even more preferably 1% to 25%, and particularly preferably 1% to 20%. If the content of F+Cl+Br+I is too high, vitrification becomes difficult and weather resistance is easily reduced. The contents of each of F, Cl, Br, and I are each 0% to 50%, preferably 1% to 40%, more preferably 1% to 30%, even more preferably 1% to 25%, and particularly preferably 1% to 20%. Among them, it is preferable to use I, since elemental raw materials can be used and the effect of enhancing glass stability is particularly large.

[0051] By including Si, Sb, and Cs, the thermal stability can be improved. Here, Si and Sb are semimetals. Si+Sb+Cs is preferably 0% to 40%, more preferably 0% to 30%, even more preferably 0% to 20%, and even more preferably 0.1% to 10%. The content of each of the components Si, Sb, and Cs is 0% to 40%, preferably 0% to 30%, more preferably 0% to 20%, and particularly preferably 0.1% to 10%.

[0052] S is a component that expands the vitrification range and tends to increase the thermal stability of glass. Its content is preferably 0% to 30%, more preferably 0% to 20%, further preferably 0% to 10%, and particularly preferably 0% to 3%. If the S content is too high, the transmittance of infrared rays having a wavelength of 10 μm or more tends to decrease.

[0053] Se and As are components that expand the vitrification range and increase the thermal stability of glass. The content of each of these elements is preferably 0% to 10%, more preferably 0% to 5%, and particularly preferably 0.5% to 5%. However, since these substances are toxic, it is preferable that they are not substantially contained from the viewpoint of reducing the impact on the environment and human body, as described above.

[0054] It is preferable that the glass does not substantially contain the toxic substances Cd, Tl and Pb, where "substantially not containing" means that the content is 0.1% or less.

[0055] The ratio of metal in the raw material 6 is preferably 80% or more, 85% or more, particularly 90% or more, by volume. In this way, the raw material 6 can be easily melted by induction heating. Therefore, the temperature can be increased or decreased more easily and quickly than by heating by radiation, and productivity can be improved. The upper limit is not particularly limited, but can be, for example, 100% or less, 99% or less, particularly 98% or less. [Explanation of symbols]

[0056] 1…Container 2…Bottom 3…Side wall 4. Piping 5...Mantle tube 6...Raw materials 7…Lid 8...Gas supply pipe 9...Gas exhaust pipe 10A…Coil 10B…Coil 11…Melted liquid 12…Seal

Claims

1. A method for producing glass, comprising the steps of: forming a melt from the raw material placed in the container; homogenizing the melt; degassing the melt; Equipped with At least one of the steps of converting the raw material into the melt and homogenizing the melt is carried out in an inert gas or reducing gas atmosphere; In the step of degassing the gas from the melt, the temperature of the melt is lowered to a temperature lower than the temperature in the step of homogenizing the melt, thereby degassing the inert gas or reducing gas; The method further includes a step of heating the melt and causing the melt to flow out of the container after the step of degassing the gas from the melt, At least one of the steps of converting the raw material into the melt and homogenizing the melt is carried out in an atmosphere of one of an inert gas and a reducing gas; In the step of causing the melt to flow out of the container, the step is performed under an atmosphere of the other of an inert gas and a reducing gas; The method for producing glass, wherein the glass is a chalcogenide glass.

2. The method for producing glass according to claim 1 , wherein the pressure inside the vessel is reduced in the step of degassing the gas from the melt.

3. 3. The method for producing glass according to claim 1, wherein both the step of converting the raw materials into the melt and the step of homogenizing the melt are carried out in an inert gas or reducing gas atmosphere.

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