JP6926436B2 - Glass material and its manufacturing method - Google Patents

Description

The present invention relates to a glass material suitable for a magneto-optical element constituting a magnetic device such as an optical isolator, an optical circulator, and a magnetic sensor, and a method for manufacturing the same.

A glass material containing terbium oxide, which is a paramagnetic compound, is known to exhibit a Faraday effect, which is one of the magneto-optical effects. The Faraday effect is the effect of rotating a linearly polarized polarization plane that passes through a material placed in a magnetic field. Such effects are used in optical isolators, magnetic field sensors, and the like.

The optical rotation (angle of rotation of the plane of polarization) θ due to the Faraday effect is expressed by the following equation, where H is the strength of the magnetic field and L is the length of the substance through which the polarized light passes. In the formula, V is a constant that depends on the type of substance and is called Verdet's constant. The Verdet constant has a positive value in the case of a diamagnetic material and a negative value in the case of a paramagnetic material. The larger the absolute value of Verdet's constant, the larger the absolute value of optical rotation, resulting in a greater Faraday effect.

θ = VHL

Conventionally, as a glass material exhibiting a Faraday effect, a SiO _2- B ₂ O _3- Al ₂ O _3- Tb ₂ O ₃ system glass material (see Patent Document 1), P ₂ O _5- B ₂ O _3- Tb ₂ O _3- based glass materials (see Patent Document 2), P ₂ O _5- TbF _3- RF _2- (R is an alkaline earth metal) -based glass material (see Patent Document 3), and the like are known.

Special Publication No. 51-46524 Special Publication No. 52-32881 Special Publication No. 55-42942

The above glass material exhibits high transmittance in the visible region to the infrared region (for example, 450 to 1500 nm), but exhibits light absorption by the terbium element itself in the low wavelength region (for example, 450 nm or less). Therefore, there is a problem that the light transmittance is lowered in the low wavelength region and the light extraction efficiency of the magneto-optical device is inferior.

In view of the above, it is an object of the present invention to provide a glass material capable of achieving both a high Faraday effect and a high transmittance in a low wavelength region.

As a result of diligent studies by the present inventor, it has been found that the above problem can be solved by a glass material having a specific composition.

That is, the glass material of the present invention _{is characterized by containing Pr 2} O ₃ 25 to 50% (however, 25% is not included) and SiO ₂ 40 to 75% (however, 75% is not included) in mol%. And.

The glass material of the present invention contains _{Pr 2} O _3. Since Pr ₂ O ₃ basically does not show light absorption in the wavelength range of 420 nm or less (for example, 250 to 420 nm), it shows high transmittance in the wavelength range.

Furthermore, the present inventor has noted that the absolute value of the Verdet constant of the glass material increases in proportion to the Pr ion density. Therefore, they have found a glass composition in which the Pr ion density is increased, and have proposed the present invention.

The Pr ion density in the glass material is calculated by the following formula.

Pr ion density _{= (ρ × n × N A} ) / M
[rho: density of the glass material, n: Pr molar number of ion, _{N A:} Avogadro's number, M: molar mass of the glass material

As is clear from the above formula, in order to increase the Pr ion density, a method of increasing the density of the glass material, increasing the content of Pr ions, or decreasing the molar mass of the glass material can be considered. Among these, the present inventor paid attention to the molar mass of the glass material, and as a result of investigating various glass skeleton components added to the glass material, in order to reduce the molar mass of the glass material, SiO ₂ was used. Found to be effective. That is, since SiO ₂ has a small molecular weight of 60.08, it is difficult to reduce the Pr ion density even if it is contained in a large amount in the glass material. Therefore, in the glass material of the present invention, _{by containing a large amount of SiO 2} as described above, vitrification is facilitated while suppressing a decrease in the Faraday effect (decrease in the absolute value of Verdet constant).

Glass material of the present invention, further, in _mol%, preferably contains ₂ O 3 _0~25% B. In this way, vitrification becomes easier. However, since B ₂ O ₃ has a relatively large molecular weight of 69.62, the molar mass of the glass material becomes large and the Pr ion density tends to decrease relatively easily, so that the upper limit of the content is regulated as described above. ..

The glass material of the present invention further _{preferably contains Al 2} O _{30 to} 35% in mol%. In this way, vitrification becomes easier. However, since Al ₂ O ₃ has a large molecular weight of 101.96, the molar mass of the glass material becomes large and the Pr ion density tends to decrease relatively, so that the upper limit of the content is regulated as described above.

The glass material of the present invention preferably has a thickness of 1 mm and a light transmittance of 50% or more at a wavelength of 405 nm.

The glass material of the present invention can be used as a magneto-optical element. For example, the glass material of the present invention can be used as a Faraday rotating element, which is a kind of magneto-optical element. By using it for the above purposes, the effects of the present invention can be enjoyed.

The method for producing a glass material of the present invention is a method for producing the above-mentioned glass material, in which the raw material lump is suspended and held in the air, and the raw material lump is heated and melted to obtain molten glass. It is characterized by comprising a step of cooling the molten glass. Although the glass material of the present invention _{facilitates vitrification by containing a large amount of SiO 2} , it may be difficult to produce it by a normal melting method using a melting container because the melting point is relatively high. .. For example, among the melting containers (crucibles) used for ordinary melting, even a platinum container suitable for high-temperature melting has a melting point of about 1770 ° C., so it is difficult to manufacture a glass material having a melting point higher than that. .. However, according to the above method (container-free floating method), even if the glass material has a relatively high melting point, the molten glass basically does not come into contact with the molten container, so the starting point is the interface with the molten container. Crystallization can be prevented, and a glass material can be easily produced.

According to the present invention, it is possible to achieve both a high Faraday effect and a high transmittance in a low wavelength region, and it is particularly suitable as a Faraday rotating element for a magneto-optical device in a low wavelength region.

It is a schematic cross-sectional view which shows one Embodiment of the apparatus for manufacturing the glass material of this invention.

The glass material of the present invention _{contains Pr 2} O ₃ 25 to 50% (but does not contain 25%) and SiO ₂ 40 to 75% (but does not contain 75%) in mol%. The reason for limiting the glass composition range in this way will be described below. In the following description of the content of each component, "%" means "mol%" unless otherwise specified.

Pr ₂ O ₃ is a component that enhances the Faraday effect by increasing the absolute value of Verdet's constant. The content of Pr ₂ O ₃ is 25 to 50% (but not 25%), preferably 26 to 50% (but not 50%), more preferably 27 to 49%, even more preferably 30. ~ 48%. If _{the content of Pr 2} O ₃ is too small, it becomes difficult to obtain the above effect. On the other hand, _{if the content of Pr 2} O ₃ is too large, vitrification tends to be difficult. Although Pr exists in a trivalent or tetravalent state in glass, all of them are represented as _{Pr 2} O _{3 in the present invention.}

The magnetic moment that is the origin of Verdet's constant is larger in Pr ^{3+ than in Pr 4+. Therefore, the larger the proportion of Pr 3+ in} the glass material, the greater the Faraday effect, which is preferable. ^{Specifically, the proportion of Pr 3+} in all Pr is preferably 50% or more, 60% or more, 70% or more, 80% or more, and particularly 90% or more in mol%.

SiO ₂ is a component that forms a glass skeleton and expands the vitrification range. As a result, the diameter of the glass material can be easily increased. Further, as described above, since SiO ₂ does not easily reduce the Pr ion density in the glass material, it is possible to suppress the decrease in the Faraday effect when it is contained in a large amount. Further, SiO ₂ also has an effect of increasing the glass transition point to increase thermal stability, an effect of increasing mechanical strength, and an effect of increasing chemical durability. The content of SiO ₂ is 40 to 75% (however, 75% is not included), preferably 43% to 73%, and more preferably 45% to 70%.

In addition to the above components, the glass material of the present invention may contain various components shown below.

B ₂ O ₃ is a component that enhances the glass forming ability. By containing B ₂ O ₃ , it becomes easy to increase the diameter of the glass material. However, as described above, since B ₂ O ₃ has a _{higher molecular weight than SiO 2} , the Faraday effect is relatively likely to be reduced. In addition, it is a component that easily reduces thermal stability and hardness. Therefore, _{the content of B 2} O ₃ is preferably 0 to 25% (but not 25%), more preferably 0.1 to 23%, still more preferably 1 to 20%, and particularly preferably 2 to 15%. Is.

Al ₂ O ₃ is a component that forms a glass skeleton and expands the vitrification range. By containing Al ₂ O ₃ , it becomes easy to increase the diameter of the glass material. However, as described above, since Al ₂ O ₃ has a _{larger molecular weight than B 2} O ₃ , the Faraday effect is relatively likely to be reduced. Therefore, _{the content of Al 2} O ₃ is 0 to 35%, preferably 0 to 30%, more preferably 0.1 to 20%, and even more preferably 1 to 17%.

B ₂ O ₃ + Al ₂ O ₃ is preferably 0 to 35%, 0.1 to 30%, 1 to 28%, and particularly preferably 2 to 25%. Here, "B ₂ O ₃ + Al ₂ O ₃ " means the total amount of the contents of _{B 2} O ₃ and Al ₂ O _3.

La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , and Y ₂ O ₃ have the effect of improving the stability of vitrification, but if the content is too large, it becomes difficult to vitrify. It also causes a decrease in light transmittance. Therefore, _{the contents of La 2} O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , and Y ₂ O ₃ are each preferably 10% or less, particularly preferably 5% or less.

Dy ₂ O ₃ , Eu ₂ O ₃ , and Ce ₂ O ₃ improve the stability of vitrification and also contribute to the improvement of Verdet's constant. However, if the content is too large, it becomes difficult to vitrify. It also causes a decrease in light transmittance. Therefore, _{the contents of Dy 2} O ₃ , Eu ₂ O ₃ , and Ce ₂ O ₃ are each preferably 15% or less, particularly preferably 10% or less. The contents of Dy ₂ O ₃ , Eu ₂ O ₃ , and Ce ₂ O ₃ are expressed by converting all of Dy, Eu, and Ce existing in the glass into trivalent oxides.

MgO and CaO have the effect of stabilizing vitrification and increasing chemical durability. Further, since the molecular weight is relatively small, it is difficult to reduce the Pr ion density. However, if the content is too large, it becomes difficult to vitrify. Therefore, the content of each of these components is preferably 0 to 20%, particularly preferably 0 to 15%.

SrO and BaO have the effect of stabilizing vitrification and increasing chemical durability. However, since the molecular weight is relatively large, if the content is too large, the Pr ion density decreases, and it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of each of these components is preferably 0 to 10%, particularly preferably 0 to 5%.

GeO ₂ is a component that enhances the glass forming ability. However, since Geo ₂ has a relatively large molecular weight, if the content is too large, the Pr ion density decreases, and it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of GeO 2} is preferably 0 to 15%, 0 to 10%, and particularly preferably 0 to 9%.

P ₂ O ₅ is a component that enhances the glass forming ability. However, since P ₂ O ₅ has a relatively large molecular weight, if the content is too large, the Pr ion density decreases, and it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of P 2} O ₅ is preferably 0 to 7%, particularly preferably 0 to 5%.

Ga ₂ O ₃ has the effect of increasing the glass forming ability and expanding the vitrification range. However, since Ga ₂ O ₃ has a relatively large molecular weight, if the content is too large, the Pr ion density decreases, and it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of Ga 2} O ₃ is preferably 0 to 6%, particularly preferably 0 to 5%.

Fluorine has the effect of increasing the glass forming ability and expanding the vitrification range. However, if the content is too large, it may volatilize during melting, causing composition fluctuations or adversely affecting vitrification. Therefore, the fluorine content (in _{terms of F 2} ) is preferably 0 to 10%, 0 to 7%, and particularly preferably 0 to 5%.

_{Sb 2} O ₃ can be added as a reducing agent. However, in order to avoid coloring or in consideration of the load on the environment, _{the content of Sb 2} O ₃ is preferably 0.1% or less.

It is preferable that the glass material of the present invention has as little light transmission loss as possible, especially when it is used as a magneto-optical element such as an isolator. Therefore, the light transmittance of the glass material of the present invention is preferably 50% or more, 60%, particularly 70% or more at a wavelength of 405 nm.

The size of the glass material of the present invention is not particularly limited, but the larger the size, the higher the productivity, which is preferable. Specifically, when the glass material of the present invention has a spherical or ellipsoidal shape, its diameter (major diameter in the case of an ellipsoidal shape) is preferably 1 mm or more, 2 mm or more, and particularly preferably 3 mm or more.

The glass material of the present invention can be produced, for example, by a container-free floating method. FIG. 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus for manufacturing a glass material by a containerless floating method. Hereinafter, the method for producing the glass material of the present invention will be described with reference to FIG.

The glass material manufacturing apparatus 1 has a molding die 10. The molding die 10 also serves as a melting container. The molding die 10 has a molding surface 10a and a plurality of gas ejection holes 10b that are open to the molding surface 10a. The gas ejection hole 10b is connected to a gas supply mechanism 11 such as a gas cylinder. Gas is supplied from the gas supply mechanism 11 to the molding surface 10a via the gas ejection hole 10b. The type of gas is not particularly limited, and may be, for example, air or oxygen, or a reducing gas containing nitrogen gas, argon gas, helium gas, carbon monoxide gas, carbon dioxide gas, or hydrogen. good.

When manufacturing a glass material using the manufacturing apparatus 1, first, the raw material block 12 is arranged on the molding surface 10a. The raw material mass 12 has, for example, a material in which the raw material powder is integrated by press molding or the like, a sintered body in which the raw material powder is integrated by press molding or the like and then sintered, or a composition equivalent to the target glass composition. An aggregate of crystals and the like can be mentioned.

Next, the raw material mass 12 is suspended on the molding surface 10a by ejecting gas from the gas ejection hole 10b. That is, the raw material mass 12 is held in a state where it is not in contact with the molding surface 10a. In that state, the laser beam irradiation device 13 irradiates the raw material mass 12 with laser light. As a result, the raw material mass 12 is heated and melted to vitrify it, and molten glass is obtained. After that, the glass material can be obtained by cooling the molten glass. In the step of heating and melting the raw material mass 12 and the step of cooling the molten glass and further the glass material until the temperature of the glass material becomes at least the softening point or less, at least the gas is continuously ejected, and the raw material mass 12, the molten glass, and further It is preferable to suppress the contact between the glass material and the molded surface 10a. In addition to the method of irradiating the laser beam, the method of heating and melting may be radiant heating.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

Table 1 shows examples and comparative examples of the present invention.

Each sample was prepared as follows. First, the raw materials prepared so as to have the glass composition shown in the table were press-molded and sintered at 800 to 1400 ° C. for 6 hours to prepare a raw material mass.

Next, the raw material mass was roughly pulverized in a mortar to obtain 0.05 to 1.0 g of small pieces. Using the obtained small pieces of the raw material mass, a glass material (diameter about 1 to 10 mm) was prepared by a container-free floating method using an apparatus according to FIG. A 100 W CO ₂ laser oscillator was used as the heat source. Further, nitrogen gas was used as a gas for suspending the raw material mass, and the gas was supplied at a flow rate of 1 to 30 L / min.

The Verdet constant of the obtained glass material was measured using a Kerr effect measuring device (manufactured by JASCO Corporation, product number: K-250). Specifically, the obtained glass material was polished to a thickness of about 1 mm, the Faraday rotation angle at a wavelength of 350 to 850 nm was measured in a magnetic field of 15 kOe, and the Verdet constant at a wavelength of 405 nm was calculated. The wavelength sweep rate was 6 nm / min. The results are shown in Table 1.

The light transmittance is 405 nm from the light transmittance curve obtained by polishing the obtained glass material to a thickness of 1 mm and measuring it with a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation). The light transmittance in was read. The light transmittance is an external transmittance including reflection.

As is clear from Table 1, the glass materials of Examples 1 to 5 had a Verdet constant of −0.83 to −1.98 at a wavelength of 405 nm, and had a large absolute value. The light transmittance at a wavelength of 405 nm was as high as 80.9% or more. On the other hand, the glass materials of Comparative Examples 1 to 3 had a Verdet constant of −0.22 to −0.45 at a wavelength of 405 nm, which was a small absolute value.

The glass material of the present invention is suitable as a magneto-optical element constituting a magnetic device such as an optical isolator, an optical circulator, or a magnetic sensor.

1: Glass material manufacturing device 10: Molding mold 10a: Molding surface 10b: Gas ejection hole 11: Gas supply mechanism 12: Raw material mass 13: Laser light irradiation device

Claims (7)

In _{mole%, Pr 2 O 3 2 6} ~50%, glass material, characterized by containing SiO 2 4 2 ~7 4%. The glass material according to claim 1, further comprising B ₂ O _{30 to 25% in mol%.} Furthermore, in _mol%, the glass material according to claim 1 or 2, characterized in that it contains Al ₂ O 3 0~3 0%. The glass material according to any one of claims 1 to 3, wherein the glass material has a thickness of 1 mm and a light transmittance of 50% or more at a wavelength of 405 nm. The glass material according to any one of claims 1 to 4, wherein the glass material is used as a magneto-optical element. The glass material according to claim 5, wherein the glass material is used as a Faraday rotating element. The method for producing the glass material according to any one of claims 1 to 6, wherein the glass raw material block is heated and melted in a state where the glass raw material block is suspended and held in the air to melt glass. A method for producing a glass material, which comprises a step of cooling the molten glass after the glass material is obtained.

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