JP2015196601A - Production method of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method capable of improving greatly clarity of glass, in production of fluorophosphate glass.SOLUTION: A production method of optical glass comprising fluorophosphate glass has steps for: blending glass raw materials; obtaining molten glass 10 by melting the glass raw materials; clarifying the molten glass in a clarification tank 2; and molding the molten glass 10 after clarification. In the production method of the optical glass, moisture is added to the glass raw materials as much as 0.1-10 mass% to the 100 mass% glass raw materials.

Description

  The present invention relates to a glass production method capable of greatly improving the clarity of glass when producing a fluorophosphate glass.

  Fluorophosphate glass is a glass useful as an optical glass and is generally widely used. As a manufacturing method of a fluorophosphate glass, the method as proposed by patent documents 1-3 is mentioned, for example.

  By the way, when producing high-quality optical glass, it is required not only to control the optical characteristics to a desired value but also to produce the glass so that striae and bubbles do not occur in the obtained glass. In particular, air bubbles remaining in the glass can be removed in many cases by providing a clarification step, but it is general to add a component that acts as a clarifier to the glass raw material from the viewpoint of further improving the clarification.

  However, in the production of fluorophosphate glass, it has been common to melt without using a refining agent because of the lack of a suitable refining agent. Therefore, the clarity is still insufficient, and in order to obtain a high-quality fluorophosphate glass, improvement of the clarity has been desired.

JP 2005-060134 A Japanese Patent No. 4712290 Japanese Patent No. 4437807

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method which can improve the clarity of glass significantly in the case of manufacture of a fluorophosphate glass.

The gist of the present invention aimed at solving such problems is as follows.
[1] An optical glass manufacturing method comprising a fluorophosphate glass,
A step of preparing glass raw materials;
A step of melting the glass raw material to obtain a molten glass;
A step of refining the molten glass;
A step of forming molten glass after clarification,
A method for producing optical glass, wherein moisture is added to the glass raw material.

[2] The method for producing optical glass according to [1], wherein a water-containing material is used as the glass material.

[3] The method for producing optical glass according to [1] or [2], wherein moisture is added to the glass raw material in the blending step.

[4] A method for producing an optical element, wherein an optical glass is produced by the method according to any one of [1] to [3], and an optical element is produced using the optical glass.

  According to the production method of the present invention, the clarity of glass can be greatly improved when producing a fluorophosphate glass.

FIG. 1 schematically shows a cross section of a glass melting furnace used in a glass manufacturing method according to an embodiment of the present invention.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

  The optical glass manufacturing method according to the present embodiment is an optical glass manufacturing method made of fluorophosphate glass, a step of preparing a glass raw material, a step of melting the glass raw material to obtain a molten glass, and the above An optical glass manufacturing method comprising a step of refining molten glass and a step of forming molten glass after refining, and adding moisture to the glass raw material.

  According to such a production method, when producing a fluorophosphate glass, the clarity can be greatly improved, and a high-quality optical glass can be obtained. The reason why such an effect is obtained is not necessarily clear, but the present inventors presume as follows.

  In the present invention, by adding water to the glass raw material, it becomes easier to release gas from the molten glass as water vapor or other hydrolyzed components in the clarification process, thereby improving the clarity (bubble quality). I think that. That is, it is thought that the water | moisture content thrown into glass raw material works as a clarifier.

  In the conventional method for producing a fluorophosphate glass, it has been considered that moisture is avoided as much as possible in melting. For this reason, it is common to select a raw material with a low water content or to make the inside of the melting tank have a positive pressure so as to avoid the intrusion of outside air containing water vapor. This means that if there is moisture at the time of melting, it reacts with the fluoride in the raw material, becomes volatile HF gas, scatters, loses the raw material, and at the same time, the content of F that works to lower the refractive index fluctuates. This is because the refractive index of the glass is made unstable (see, for example, Patent Document 2).

  However, in the glass production method that avoids such moisture as much as possible, the clarity is poor and bubbles remain in the produced glass. Therefore, from the viewpoint of productivity improvement, product quality improvement, etc., it has been desired that the clarity (bubble quality) at the time of production is further improved.

  For such a problem, it is common to improve the foam quality by using a clarifying agent or the like, but in a fluorophosphate glass, there is no suitable refining agent. Further, chloride has a clarification effect, but if chloride is used, the platinum melting tank is eroded and platinum foreign matters are likely to be mixed into the glass. Therefore, conventionally, the method of melting without a clarifier has been the mainstream.

  In addition to the fining agent, there is a method to improve the foam quality by increasing the fining temperature and releasing dissolved gas easily. As a result, the fluctuation becomes large, and as a result, the target optical characteristics cannot be obtained. Therefore, such a method was not preferable.

  In addition to this, as a method for improving the foam quality, in the clarification process, the flow rate of the molten glass to be processed is reduced, the clarification time is lengthened, and the flow rate of the molten glass is not changed, and the width of the clarification tank is increased. However, there is a method to increase the surface area by reducing the depth, but because the former deteriorates productivity, the latter can not use existing facilities and requires new capital investment, so both methods are produced. This is not preferable because the cost increases.

  In order to solve such clarification problems, the present inventors pay attention to moisture that has been generally avoided in the past, and by using moisture as a clarifier, without using a special clarifier. Further, the inventors have found that excellent clarity can be obtained without increasing the production cost, and completed the present invention.

Hereinafter, the method for producing an optical glass according to the present invention will be described in detail. Can be implemented with changes. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic cross-sectional view showing an example of a melting furnace used in the manufacturing method according to an embodiment of the present invention.

The manufacturing method of the optical glass according to the present embodiment is preferably,
A process of preparing glass raw materials (preparation process);
A step of melting the glass raw material to obtain a molten glass (melting step);
A step of clarifying the molten glass (clarification step);
A step of forming the molten glass (molding step),
Water is added to the glass raw material.

  As a melting furnace used in such a manufacturing method according to the present embodiment, it is preferable to include a charging port 7, a melting tank 1, connection pipes 4 and 5, a clarification tank 2, and an outflow pipe 6. Other portions shown in FIG. 1 may be provided as necessary.

Hereinafter, each process will be described in detail.
<Mixing process>
In the blending step, raw materials and the like are blended so as to obtain a glass raw material so that optical glass having desired characteristics can be obtained.

  As the glass raw material, a batch raw material (prepared raw material) or a mixed cullet adjusted so as to obtain an optical glass having desired characteristics can be used.

  The batch raw material is obtained by weighing and blending raw materials corresponding to the glass components in a predetermined ratio according to the characteristics of the optical glass to be produced, and mixing them sufficiently.

  The raw material is not particularly limited, depending on the glass component, oxide, phosphoric acid, phosphate (polyphosphate, metaphosphate, pyrophosphate, etc.), boric acid, boric anhydride, carbonate Known glass raw materials such as nitrates, sulfates and hydroxides can be used.

  The mixed cullet can be obtained by blending a cullet-like glass (hereinafter simply referred to as “cullet”), which is obtained by virtue of rough melting (rough melt) of a batch raw material in advance at a predetermined ratio. In general, the cullet is preferably subjected to characteristic evaluation (for example, measurement of refractive index measurement) in advance. For example, when an optical glass having a predetermined refractive index is to be manufactured, a cullet having the same refractive index may be used as it is to form a mixed cullet, or the refractive index may be set to a predetermined refractive index after the main melting (remelting). A cullet having a high refractive index and a cullet having a low refractive index may be blended at a predetermined ratio to form a mixed cullet.

  The cullet is made of glass, but need not be homogeneous glass. Further, the cullet may contain bubbles. Furthermore, the raw material of a batch raw material may be included. When evaluating the composition and optical properties (eg, refractive index, Abbe number, etc.) of the cullet, a portion of the cullet is sampled and remelted to make a glass that is homogeneous and free of bubbles. Evaluation is made by measuring optical properties.

<Melting process>
In the melting step, the glass raw material prepared in the blending step is introduced from the inlet 7 into the melting tank 1 and melted.

  It is preferable to appropriately adjust the melting conditions according to the glass raw material and the glass composition. For example, melting is performed at a temperature that can sufficiently melt the mixed glass raw material. The upper limit of the melting temperature is not particularly defined, but it is desirable to melt at a temperature below the temperature at which the volatilization of the raw material in the melting tank 1 is suppressed and the desired glass quality is obtained. Generally, 800 ° C to 1000 ° C is preferable.

<Clarification process>
In the clarification process, the molten glass sufficiently melted in the melting process is fed into the clarification tank 2 and maintained at a predetermined temperature to perform a clarification process.

  It is preferable that the clarification conditions are appropriately adjusted according to the glass composition. For example, the temperature of the clarification tank can be adjusted within a range of 1100 ° C to 1400 ° C.

  In addition, you may provide a homogenization process after a clarification process as needed. The homogenization step can be performed by a known method.

<Molding process>
In the forming step, the molten glass that has undergone the refining step (and that has undergone the homogenization step as necessary) flows out of the outflow pipe 6 and is formed by a predetermined method.

  The molding method is not particularly limited, and examples thereof include a method of molding by casting into a mold and a step of press molding molten glass.

  In the cast molding, a long block-shaped glass, a rod-shaped glass, a gob-shaped glass, or the like can be formed. In press molding, the glass may be molded into a shape that approximates the shape of the optical element.

  The formed glass is transferred into an annealing furnace heated in advance to near the glass transition temperature and gradually cooled to room temperature. The obtained glass may be appropriately cut, ground, and polished to be reheated, softened, and used as a press forming material for press forming.

  In addition, although materials, such as the melting tank 1 used when manufacturing glass, are not specifically limited, the product made from a glassy carbon is preferable and it is also possible to use the melting tank made from platinum. However, when platinum is used, care must be taken to avoid mixing platinum inclusions into the glass.

  The glass manufacturing method according to the present embodiment is characterized in that, in the glass manufacturing method as described above, in particular, moisture is added to the glass raw material.

The method of adding moisture to the glass raw material is not particularly limited, and examples thereof include the following method.
(1) Water is added to the dried glass raw material at a predetermined ratio.
(2) Use raw materials or cullet with high water content.
(3) A combination of the above methods (1) or (2).

Method (1)
In the case of fluorophosphate glass, composition fluctuations (and hence characteristic fluctuations) occur when moisture is contained, and therefore, conventionally, a dry glass raw material has been generally used. Therefore, various raw materials prepared as a glass raw material have been widely used that have been heat-treated to such an extent that moisture can be removed. Also, when using cullet, it was common to use a cullet produced under conditions excluding moisture.

  However, in the method (1), a batch raw material or a raw material that has been heat-treated as usual or a cullet prepared under conditions excluding moisture is weighed and water is added at a predetermined ratio. Prepare mixed cullet.

  Thus, it is thought that the water | moisture content dissolved in the molten glass in a clarification process can be increased by adding a predetermined amount of water at the stage of a glass raw material, and clarification can be improved.

  Although it is preferable to adjust suitably according to a glass raw material, a glass composition, a melting time, a melting apparatus etc. as an addition amount of a water | moisture content, it is 0.1-10 mass% with respect to 100 mass% of glass raw materials, for example. be able to.

Method (2)
In the method (2), a glass raw material is prepared using a raw material or a cullet to which moisture is added instead of a dry raw material or a cullet produced under dry conditions that has been generally used conventionally.

  Examples of the raw material to which moisture has been added include raw materials that have not been dried. By using such raw materials, it is possible to omit the conventional drying process, so that the manufacturing process can be shortened and the production cost can be reduced. Moreover, since it is not necessary to maintain a dry state, storage of raw materials becomes easy. In addition, as a raw material to which moisture is added, for example, a raw material subjected to a humidification process can be used.

  In addition, the cullet to which moisture is added includes a cullet produced under conditions such that moisture is contained in the cullet. For example, a method of adding moisture to a raw material batch used for producing cullet, a method of positively introducing water vapor into a melting atmosphere, and the like can be mentioned. Such a cullet is also easy to store because it is not necessary to maintain a dry state.

  In the present embodiment, the above methods (1) or (2) can be combined as necessary. Moreover, in this embodiment, it is more preferable to perform the method of said (1) from a viewpoint which can control a water content appropriately.

  In addition, when adding water | moisture content to a glass raw material, while clarifying can be improved, it exists in the tendency for the component which volatilizes easily with a water | moisture content to volatilize more easily from molten glass. As a result, in the resulting optical glass, the glass composition deviates from the design composition, thereby causing a problem that the optical characteristics deviate from the expected values.

  Therefore, in the manufacturing method according to the present embodiment, it is preferable to grasp the ratio of composition variation with moisture addition in advance and adjust the composition considering the volatilization amount at the stage of the glass raw material. As such an adjustment method, for example, there is a method in which components that easily volatilize are roughly weighed in advance and the finished glass composition is corrected.

For glass composition below, unless otherwise specified, "%" of the cationic component represents a cation%, "%" in the anion component is an anion%. The cation% is a unit when the ratio of the content of a specific cation component to the total content of all cation components is expressed in mole percentage. Therefore, the total content of all cation components is 100 cation%. Moreover, anion% is a unit when the ratio of content of a specific anion component with respect to the total content of all anion components is expressed in mole percentage. Therefore, the total content of all anionic components is 100 anion%.

The optical glass according to the present embodiment is a fluorophosphate-based glass, and contains P ⁵⁺ , Al ³⁺ , an alkaline earth metal component, O ⁻ , and F ⁻ as essential components. It is preferable to contain Y ³⁺ as an optional component. The alkaline earth metal component is more preferably at least one component selected from Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ . A preferable glass composition in this embodiment will be described in detail below.

P ⁵⁺ is a basic component of a fluorophosphate glass, and is an important cationic component for obtaining devitrification resistance and a high refractive index. The content of P ⁵⁺ is preferably 0.5 to 50%, more preferably 3 to 45%. If the amount of P ⁵⁺ is too small, the glass becomes unstable and tends to devitrify. On the other hand, if the amount is too large, it is difficult to obtain low dispersion characteristics.

Al ³⁺ is an important component that improves the devitrification resistance of the fluorophosphate glass and suppresses thermal expansion. The Al ³⁺ content is preferably 3 to 50%, more preferably 6 to 45%. If Al ³⁺ is too much or too little, the glass becomes unstable and tends to devitrify.

Mg ²⁺ is an important cationic component that improves the devitrification resistance of the fluorophosphate glass, further reduces the specific gravity, lowers the degree of wear, and improves the workability. The content of Mg ²⁺ is preferably 0 to 15%, more preferably 0 to 10%. If Mg ²⁺ is too much or too little, the glass becomes unstable and tends to devitrify.

Ca ²⁺ is a cationic component that improves the devitrification resistance of the fluorophosphate glass and further reduces the degree of wear and improves the workability. The Ca ²⁺ content is preferably 0 to 40%, more preferably 0 to 35%. If Ca ²⁺ is too much or too little, the glass becomes unstable and tends to devitrify.

Sr ²⁺ is a cationic component that improves the devitrification resistance of the fluorophosphate glass and improves the refractive index. However, if the content of Sr ²⁺ exceeds 30%, the glass becomes unstable and the tendency to devitrification increases. Therefore, the content of Sr ²⁺ is preferably 0 to 30%, more preferably 0 to 25%.

Ba ²⁺ is a component that functions to improve the devitrification resistance and the refractive index. However, when the content of Ba ²⁺ exceeds 50%, the glass becomes unstable, the tendency to devitrification increases, the specific gravity increases, and the workability tends to decrease. Therefore, the Ba ²⁺ content is preferably 0 to 50%, more preferably 2 to 45%, and still more preferably 4 to 45%.

From the viewpoint of improving devitrification resistance, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferably 25 to 70%, more preferably 30 to 65%. .

Y ³⁺ is a cationic component that improves the refractive index of fluorophosphate glass and improves devitrification resistance and workability without impairing the abnormal partial dispersibility. However, when the content of Y ³⁺ is 4% or more, the liquidus temperature tends to increase. When the liquidus temperature rises, the glass forming temperature has to be made higher in order to avoid devitrification at the time of forming molten glass. As a result, volatilization from the molten glass increases and it becomes difficult to obtain a homogeneous glass. Moreover, the increase in volatility tends to fluctuate the optical properties of the glass obtained. In order to avoid such a problem, the content of Y ³⁺ is preferably less than 4%, more preferably 0 to 3%.

In addition, the optical glass according to the present embodiment includes Li ⁺ , Na ⁺ , K ⁺ La ³⁺ , Gd ³⁺ , Zn ²⁺ , Nb ⁵⁺ , Zr ⁴⁺ , B ³⁺ , Si as optional cation components. Various components such as ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , As ³⁺ and Sb ³⁺ may be contained.

Li ⁺ , Na ⁺ and K ⁺ are components that can be introduced for the purpose of adjusting the refractive index and Abbe number, improving devitrification resistance, adjusting thermal characteristics, and improving mechanical characteristics. When these components are contained, the total content of Li ⁺ , Na ⁺ and K ⁺ may be set to a range of 0 to 30% from the viewpoint of obtaining a low dispersion glass while maintaining devitrification resistance. Preferably, it is preferable to set it in the range of 0 to 25%.

La ³⁺ , Gd ³⁺ , Zn ²⁺ , Nb ⁵⁺ , Zr ⁴⁺ , B ³⁺ , Si ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , As ^3+, Sb, etc. have a refractive index / abbe It can be contained for the purpose of adjusting the number, improving devitrification resistance, adjusting thermal properties, improving mechanical properties, etc., but the total content is preferably less than 5%, more preferably 2 % Or less, more preferably 1% or less.

The content of O ²⁻ is preferably 0.5 to 90%, more preferably 5 to 85%. If O ²⁻ is too small, the glass becomes unstable and tends to devitrify, and if it is too large, it tends to be difficult to obtain low dispersion characteristics.

F ⁻ is an indispensable anion component that increases the Abbe number and improves the anomalous partial dispersibility. However, in order to weaken the glass structure, it is also a component that increases thermal expansion and increases the degree of wear. The content of F ⁻ is preferably 10 to 99.5%, more preferably 15 to 95%. If F ⁻ is too small, it is difficult to obtain low dispersion characteristics, and if it is too large, the glass becomes unstable and tends to devitrify.

The optical glass according to the present embodiment may contain Cl ⁻ , Br ⁻ , and I ⁻ as an optional anion component. When these components flow out of the molten glass, the effect of suppressing the molten glass from getting wet on the outer periphery of the platinum outflow pipe and reducing the homogeneity of the glass can be expected. Note that the total content of Cl ⁻ , Br ⁻ and I ⁻ is preferably in the range of 0.5% or less.

  In addition, the said component can be quantified by analyzing optical glass by ICP analysis etc.

Furthermore, the optical glass obtained by the production method according to the present invention contains OH ⁻ in addition to the above components. Such OH ⁻ can be quantified as βOH by measuring the spectral transmittance of the glass. βOH can be represented by the following formula (1).
βOH = − [ln (B / A)] / t (1)

Here, in the above formula (1), t represents the thickness (mm) of the glass used for measuring the external transmittance, and A represents a wavelength of 2500 nm when light is incident on the glass in parallel with the thickness direction. Represents the external transmittance (%), and B represents the external transmittance (%) at a wavelength of 2900 nm when light is incident on the glass in parallel to the thickness direction. In the above formula (1), ln is a natural logarithm. The unit of βOH is mm ⁻¹ . The value of βOH means that the larger the value, the more OH ⁻ is contained in the glass.

  The “external transmittance” is the ratio (Iout / Iin) of the intensity Iout of the transmitted light transmitted through the glass to the intensity Iin of the incident light incident on the glass, that is, the transmittance considering the surface reflection on the surface of the glass. The “internal transmittance” described later is the transmittance when there is no surface reflection on the surface of the glass (that is, the transmittance of the glass material itself constituting the glass). Each transmittance is obtained by measuring a transmission spectrum using a spectrophotometer.

The production method according to the present invention is characterized in that moisture is added to the glass raw material. Therefore, it is considered that the optical glass obtained by such a method contains more OH ^{− in the} glass than the optical glass obtained by the conventional production method in which moisture has been positively removed.

Characteristics of optical glass The optical glass obtained by the production method according to the present invention preferably has the following characteristics.

  The refractive index (nd) is preferably 1.40 to 1.65.

  The Abbe number (νd) is preferably 60 to 99.

Manufacture of an optical element In order to make an optical element using the optical glass obtained by the manufacturing method according to the present invention, a known method may be applied. For example, a glass material for press molding is produced by molding molten glass. Next, this glass material is reheated and press-molded to produce an optical element blank. Furthermore, it processes by the process including grinding | polishing of an optical element blank, and produces an optical element.

  Alternatively, a molten glass is formed to produce a glass material for press molding, and this glass material is heated and precision press molded to produce an optical element.

In each of the above steps, a molten glass may be molded to produce a glass molded body, and the glass molded body may be processed to produce a press-molding glass material.
Alternatively, molten glass is formed to produce a glass molded body, and this molded body is processed to produce an optical element.

  The optical functional surface of the manufactured optical element may be coated with an antireflection film, a total reflection film, or the like according to the purpose of use.

  Examples of the optical element include various lenses such as a spherical lens, an aspheric lens, a macro lens, and a lens array, a prism, and a diffraction grating.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement with a various aspect in the range which does not deviate from the summary of this invention. .

  Moreover, since the optical glass according to the present embodiment is suitable as a material for an optical element, it is preferably an amorphous glass. As a method of manufacturing a glass optical element, for example, there is a method of forming by heating and softening a glass material. Crystallized glass having a crystal phase dispersed in glass is not suitable for the molding method. In addition, the crystal phase in the crystallized glass may scatter light, thereby reducing the performance as an optical element. Amorphous glass does not have this problem.

  Hereinafter, the present invention will be described in more detail with reference to comparative examples, but the present invention is not limited to these examples.

Comparative Example 1
[Preparation of batch materials]
First, in producing an optical glass having desired characteristics, fluorides and metaphosphates corresponding to the respective constituents were prepared as dry powders as glass raw materials. Next, the raw materials were weighed and mixed well so that the glass composition of the optical glass finally obtained became the composition I shown in Table 1, and the batch raw material I was produced.

[Production of optical glass]
The batch raw material I prepared as described above is used as a glass raw material and charged into a melting tank 1 (platinum crucible) and heated and melted in an air atmosphere at 900 to 1000 ° C. to obtain a molten glass (melting step). .

  The molten glass in the melting tank 1 passed through the platinum connection pipe 4 and flowed into the platinum clarification tank 2. At this time, the temperature in the clarification tank 2 is set to be higher than the temperature in the melting tank 1, and the temperature of the molten glass flowing into the clarification tank 2 is raised to a range of 1050 to 1300 ° C. (clarification temperature). In this way, foam breakage was promoted (clarification process).

  Next, the molten glass in the clarification tank 2 flowed into the platinum homogenization tank 3 through the platinum connecting pipe 5. At this time, the temperature in the homogenization tank 3 is set to be lower than the temperatures of the melting tank 1 and the clarification tank 2, and the temperature of the molten glass flowing into the homogenization tank 3 is in the range of 650 to 800 ° C. (homogenization temperature). ). At that time, the molten glass 8 was stirred by rotating the platinum stirring device 8 inserted into the homogenizing tank 3 to promote homogenization of the molten glass (homogenization step).

  The molten glass homogenized in this way flows out from the platinum glass outflow pipe 6 attached to the bottom of the homogenization tank 3 in the air atmosphere (outflow process), and flows into a mold placed below the outflow pipe. Thus, a long glass block (width 130 mm × thickness 10 mm) was formed (molding step).

  Thereafter, the glass block is heated at a rate of + 100 ° C./hour in the air atmosphere, held at the vicinity of each glass transition temperature for 1.5 to 8 hours, and cooled at a rate of −10 ° C./hour. (Annealing step) An optical glass sample from which distortion was removed was obtained.

Example 1
In Example 1, instead of the dried fluoride used in the raw material used in Comparative Example 1, a fluoride mixed with water was prepared, and the glass raw material was considered in consideration of the composition variation when water was mixed into the raw material. An optical glass sample was obtained under the same conditions as in Comparative Example 1 except that it was prepared.

[Evaluation of optical glass]
[1] Glass composition An appropriate amount of each optical glass sample obtained as described above is collected, treated with acid and alkali, and inductively coupled plasma mass spectrometry (ICP-MS method) or ion chromatography method is used. The content of each component was measured by quantifying it, and it was confirmed that the content was consistent with the composition I.

[2] Refractive index nd and Abbe number νd
The molten glass that has been subjected to the homogenization process when producing the optical glass sample is scooped, cast into a mold, formed, held at a temperature near the glass transition temperature, and then cooled at a temperature decrease rate of −10 ° C./hour. A sample for measurement was prepared. About the obtained sample for a measurement, refractive index nd, ng, nF, nc was measured by the refractive index measuring method defined by Japan Optical Glass Industry Association standard. Furthermore, the Abbe number νd was calculated from the measured values of the refractive index.

  These characteristic values are characteristics resulting from the glass composition. Therefore, it was confirmed that the optical glass samples (Comparative Example 1 and Example 1) produced to have the same glass composition have substantially the same value. The results are shown in Table 1.

[3] Evaluation of residual bubbles An appropriate amount of each optical glass sample obtained as described above was collected, and the inside of the glass was magnified (100 times) using an optical microscope (magnification 20 to 100 times). The number of bubbles contained was counted and evaluated in five stages from the first grade to the fifth grade shown below. The smaller the number of bubbles, that is, the smaller the series, the better the clarity. The results are shown in Table 2.
First grade: 0 pieces / kg
Second grade: 1-2 pieces / kg
Grade 3: 3-4 / kg
Grade 4: 5-6 / kg
Grade 5: 6 or more / kg

  As shown in Table 2, it was confirmed that the evaluation of residual bubbles was second grade in the optical glass of fluorophosphate glass produced by the production method according to the comparative example of the present invention. On the other hand, according to the manufacturing method according to the embodiment of the present invention, by adding moisture to the glass raw material, the clarity is improved, and no residual bubbles are observed in the obtained optical glass. The evaluation was confirmed to be first grade.

Comparative Example 2
[Preparation of batch materials]
First, in producing an optical glass having desired characteristics, fluoride, metaphosphate, chloride, and oxide were prepared as glass raw materials. Next, the raw materials were weighed and mixed sufficiently so that the glass composition of the optical glass finally obtained became the composition II shown in Table 1, to prepare a batch raw material II.

[Production of optical glass]
The batch raw material II prepared as described above is used as a glass raw material in a melting tank 1 (platinum crucible), heated and melted in an air atmosphere at 900 to 1000 ° C. to obtain a molten glass (melting step) .

  Thereafter, the temperature of the clarification tank 2 was raised to the clarification temperature (range of 1100 to 1400 ° C.) and clarified (clarification step). Subsequently, the temperature of the homogenization tank 3 was lowered to the homogenization temperature (range of 800 to 1000 ° C.), and the mixture was stirred and homogenized with the stirring device 8 (homogenization step).

  The molten glass homogenized in this way flows out from the platinum glass outflow pipe 6 attached to the bottom of the homogenization tank 3 in the air atmosphere (outflow process), and flows into a mold placed below the outflow pipe. Thus, a long glass block (width 130 mm × thickness 10 mm) was formed (molding step).

  Thereafter, the glass block is heated at a rate of + 100 ° C./hour in the air atmosphere, held at the vicinity of each glass transition temperature for 1.5 to 8 hours, and cooled at a rate of −10 ° C./hour. (Annealing step) An optical glass sample from which distortion was removed was obtained.

Example 2
In Example 2, when preparing the batch raw materials, each raw material is weighed, and 1.0 g of water is added to and mixed with 100 g of the dried raw material, and the composition variation when water is mixed is taken into consideration. An optical glass sample was obtained under the same conditions as in Comparative Example 1 except that the glass raw material was prepared.

[Evaluation of optical glass]
[1] Glass composition An appropriate amount of each optical glass sample obtained as described above was collected and measured by quantifying the content of each component in the same manner as in Comparative Example 1 and Example 1, and composition II It was confirmed that it matches.

[2] Refractive index nd and Abbe number νd
Samples for measurement were prepared in the same manner as in Comparative Example 1 and Example 1, and predetermined measurements were performed to obtain the refractive index nd and Abbe number νd of the optical glasses according to Comparative Example 2 and Example 2. Since these optical glasses were also produced so as to have the same glass composition, it was confirmed that the respective characteristic values were substantially the same value. The results are shown in Table 3.

[3] Evaluation of Residual Bubbles An appropriate amount of each optical glass sample obtained as described above was collected, the residual bubbles were counted in the same manner as in Comparative Example 1 and Example 1, and the number density of residual bubbles was set to 1. Evaluation was made in 5 grades from grade 5 to grade 5. The results are shown in Table 4.

  As shown in Table 4, it was confirmed that the optical glass of fluorophosphate glass produced by the production method according to the comparative example of the present invention has many residual bubbles and is tertiary. On the other hand, according to the manufacturing method according to the embodiment of the present invention, by adding moisture to the glass raw material, the clarity is improved, and no residual bubbles are observed in the obtained optical glass. The evaluation was confirmed to be first grade.

Example 3
An optical lens was produced using the optical glass produced in Examples 1 and 2. Specifically, the glass is heated and softened, and press-molded into a shape that approximates the shape of the target lens. After press molding, the glass was annealed and finished into an optical lens by processing steps including a polishing step. In addition, what is necessary is just to apply a well-known method suitably for the press molding method of glass, the method of annealing, and a process process.

  It was confirmed that the optical lens thus obtained did not contain bubbles and had extremely high homogeneity.

Finally, the embodiments described so far are summarized.
The present embodiment is a method for producing an optical glass made of a fluorophosphate glass,
A step of preparing glass raw materials;
A step of melting the glass raw material to obtain a molten glass;
A step of refining the molten glass;
A step of forming molten glass after clarification,
It is a manufacturing method of optical glass which adds moisture to the above-mentioned glass material.

  The said form WHEREIN: It is preferable that it is a manufacturing method of optical glass which uses a water-containing raw material as said glass raw material.

  Moreover, in the said form, it is preferable that it is a manufacturing method of optical glass which adds a water | moisture content to a glass raw material in a preparation process.

Moreover, in the said form, it is preferable that it is the manufacturing method of optical glass which manufactures the fluorophosphate glass whose content of Y < ³⁺ > is 0 cation% or more and less than 4 cation%.

  Furthermore, another embodiment is a method for manufacturing an optical element, in which an optical glass is manufactured by the method of each aspect described above, and an optical element is manufactured using the optical glass.

DESCRIPTION OF SYMBOLS 1 ... Melting tank 2 ... Clarification tank 3 ... Homogenization tank 4, 5 ... Connection pipe 6 ... Outflow pipe 7 ... Input port 8 ... Stirrer 10 ... Melting Glass

Claims (4)

An optical glass manufacturing method comprising a fluorophosphate glass,
A step of preparing glass raw materials;
A step of melting the glass raw material to obtain a molten glass;
Clarifying the molten glass;
A step of forming molten glass after clarification,
The manufacturing method of optical glass which adds a water | moisture content to the said glass raw material.   The method for producing optical glass according to claim 1, wherein a water-containing raw material is used as the glass raw material.   The manufacturing method of the optical glass of Claim 1 or 2 which adds a water | moisture content to a glass raw material in a preparation process.   The manufacturing method of an optical element which produces optical glass by the method in any one of Claims 1-3, and produces an optical element using the said optical glass.

Images