JP6861953B2 - 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.

It is known that the Faraday effect is exhibited by applying a magnetic field to a magnetic material. 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 the Faraday effect, a SiO _2- B ₂ O _3- Al ₂ O _{3- Tb 2} O ₃ system glass material exhibiting paramagnetism (see Patent Document 1), P ₂ O _5- B ₂ O _3- Tb ₂ O ₃ type glass materials (see Patent Document 2), P ₂ O ₅ -TbF _3- RF ₂ (R is an alkaline earth metal) type glass material (see Patent Document 3), and the like are known. ing. Further, a PbO-SiO ₂ type glass material is known as a glass material exhibiting diamagnetism (see Non-Patent Document 1).

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

Properties of Glass, Volume 1, (1954), p.545

The paramagnetic glass material containing terbium as described above has a problem that the Faraday rotation angle fluctuates because the magnetic susceptibility changes depending on the temperature. On the other hand, it is known that the magnetic susceptibility of a diamagnetic glass material has a small temperature dependence. Therefore, by using the Faraday rotating glass made of a diamagnetic glass material, it is possible to provide a magneto-optical element in which the change in the Faraday rotation angle due to a temperature change is small.

However, the conventional diamagnetic glass material has a problem that the absolute value of Verdet constant is smaller than that of the paramagnetic glass material. In recent years, as magnetic devices have been miniaturized, further improvement of the Faraday effect is required so that even a small member can exhibit a sufficient optical rotation.

In view of the above, it is an object of the present invention to provide a diamagnetic glass material which exhibits a larger Faraday effect than the conventional one.

The glass material of the present invention is characterized by containing 73% or more of _{Yb 2} O _{3 in mass%.} As described above, the glass material of the present invention _{contains a large amount of Yb 2} O ₃ , so that the Verdet constant becomes positively large and exhibits diamagnetism. As a result, it exhibits a larger Faraday effect than the conventional diamagnetic glass material. Further, since Yb ₂ O ₃ has almost no light absorption at a wavelength of 300 to 900 nm, it also has a feature that it tends to show high transmittance even if it is contained in a large amount as described above. As described above, it is generally difficult to vitrify a glass material containing a _{large amount of Yb 2} O _3. However, according to the containerless floating method described later, even a composition that is difficult to vitrify can be easily vitrified.

Glass material of the present invention further contains, by _{mass%, B 2 O 3 0~27%} , P 2 O 5 0~27%, SiO 2 0~27%, by containing _Al 2 O 3 _0~27% Is preferable. Since B ₂ O ₃ , P ₂ O ₅ , SiO ₂ , and Al ₂ O ₃ are components constituting the glass skeleton, vitrification can be performed relatively easily by containing these components.

The glass material of the present invention _{preferably contains B 2} O ₃ + P ₂ O ₅ + SiO _{20 to} 27% by mass. In addition, in this specification, "○ + ○ + ..." means the total amount of each corresponding component.

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 a glass raw material block is suspended and held, and the glass raw material block is heated and melted to obtain molten glass. It is characterized by comprising a step of cooling the molten glass.

Generally, a glass material is produced by melting a raw material in a melting container such as a crucible and cooling it (melting method). However, the glass material of the present invention has a composition that basically _{contains a large amount of Yb 2} O ₃ that does not form a glass skeleton as described above, and is a material that is difficult to vitrify. There is a problem that crystallization proceeds from the contact interface with.

Even if the composition is difficult to vitrify, it can be vitrified by eliminating the contact at the interface with the melting vessel. As such a method, a containerless floating method in which a raw material is melted and cooled in a suspended state is known. When this method is used, since the molten glass hardly comes into contact with the molten container, crystallization starting from the interface with the molten container can be prevented and vitrification becomes possible.

According to the present invention, it is possible to provide a diamagnetic glass material that exhibits a larger Faraday effect than before.

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 is characterized by containing 73% or more _{of Yb 2} O _{3 in mass%.} If _{the content of Yb 2} O ₃ is too small, the absolute value of Verdet's constant becomes small, and it becomes difficult to obtain a sufficient Faraday effect. The content of Yb ₂ O ₃ is preferably 75% or more, particularly preferably 77% or more. On the other hand, _{if the content of Yb 2} O ₃ is too large, vitrification tends to be difficult, so that it is preferably 95% or less, 94% or less, and particularly 92% or less.

_{In addition to Yb 2} O ₃ , the glass material of the present invention can contain various components shown below. In the following description of the content of each component, "%" means "mass%" unless otherwise specified.

B ₂ O ₃ is a component that becomes the main glass skeleton and expands the vitrification range. However, since B ₂ O ₃ does not contribute to the improvement of Verdet's constant, if its content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of B 2} O ₃ is preferably 0 to 27%, 1 to 25%, and particularly preferably 2 to 20%.

P ₂ O ₅ is a component that forms a glass skeleton and expands the vitrification range. However, since P ₂ O ₅ does not contribute to Verdet's constant, if its content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of P 2} O ₅ is preferably 0 to 27%, 0 to 25%, 0 to 20%, 0 to 10%, particularly 0 to 10% (however, 0% is not included).

Al ₂ O ₃ is a component that forms a glass skeleton as an intermediate oxide and expands the vitrification range. However, since Al ₂ O ₃ does not contribute to the improvement of Verdet's constant, if the content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of Al 2} O ₃ is preferably 0 to 27%, 0 to 25%, 0 to 20%, 0 to 10%, particularly 0 to 10% (however, 0% is not included).

SiO ₂ is a component that forms a glass skeleton and expands the vitrification range. However, since SiO ₂ does not contribute to Verdet's constant, if its content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, _{the content of SiO 2} is 0-27%, 0-27% (27% is not included), 0-25%, 0-20%, 0-10%, especially 0-10% (but 0 is included). Not).

The content of SiO ₂ + B ₂ O ₃ is preferably 0 to 27%, 1 to 25%, and particularly preferably 2 to 20%. The content of B ₂ O ₃ + P ₂ O ₅ is preferably 0 to 27%, 1 to 25%, and particularly preferably 2 to 20%. The content of SiO ₂ + B ₂ O ₃ + P ₂ O ₅ is preferably 0 to 27%, 1 to 25%, and particularly preferably 2 to 20%.

MgO, CaO, SrO, and BaO have the effect of increasing the stability of vitrification and the effect of increasing the chemical durability. However, since it does not contribute to the improvement of Verdet's constant, if the content is too large, 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%.

Y ₂ O ₃ and La ₂ O ₃ have the effect of increasing the stability of vitrification, but if the content is too large, it becomes difficult to vitrify. Therefore, the content of each of these components is preferably 0 to 10%, particularly preferably 0 to 5%.

Ga ₂ O ₃ has the effect of increasing the glass forming ability and expanding the vitrification range. However, if the content is too large, devitrification is likely to occur. Further, since Ga ₂ O ₃ does not contribute to the improvement of Verdet's constant, if its content is too large, 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 to fluctuate the composition or affect the stability of vitrification. Therefore, the fluorine content (in _{terms of F 2} ) is preferably 0 to 10%, 0 to 7%, and particularly preferably 0 to 5%.

By having the above composition, the glass material of the present invention has a good Verdet constant and visible light transmittance. Specifically, the Verde constant of the glass material of the present invention is 0.25 min / Oe · cm or more, 0.28 min / Oe · cm or more, 0.30 min / Oe · cm or more, particularly 0.32 min / cm at a wavelength of 400 nm. It is preferably Oe · cm or more, and at a wavelength of 600 nm, 0.08 min / Oe · cm or more, 0.085 min / Oe · cm or more, 0.090 min / Oe · cm or more, 0.095 min / Oe · cm or more, in particular. It is preferably 0.100 min / Oe · cm or more. The visible light transmittance of the glass material of the present invention is preferably 50% or more, particularly 60% or more at a wavelength of 400 nm, and 60% or more, 70% or more, particularly 80% or more at a wavelength of 600 nm. preferable.

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 glass raw material block 12 is arranged on the molding surface 10a. The glass raw material mass 12 includes, for example, a raw material powder integrated by press molding or the like, a sintered body obtained by integrating the raw material powder by press molding or the like and then sintering, or a composition equivalent to the target glass composition. Examples thereof include an aggregate of crystals having.

Next, the glass raw material mass 12 is suspended on the molding surface 10a by ejecting gas from the gas ejection hole 10b. That is, the glass raw material block 12 is held in a state where it is not in contact with the molding surface 10a. In that state, the laser light irradiation device 13 irradiates the glass raw material block 12 with laser light. As a result, the glass raw material block 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 glass raw material block 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 gas is continuously ejected, and the glass raw material block 12, the molten glass, Further, it is preferable to suppress the contact between the glass material and the molded surface 10a. The glass raw material block 12 may be suspended on the molding surface 10a by utilizing the magnetic force generated by applying the magnetic field. Further, as the method of heating and melting, radiant heating may be used in addition to the method of irradiating laser light.

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 12 hours to prepare a glass raw material mass.

Next, the glass raw material mass was roughly pulverized in a mortar to obtain 0.05 to 0.5 g of small pieces. Using the obtained small pieces of the glass raw material mass, a glass material (diameter about 1 to 15 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, O 2} gas was used as a gas for suspending the raw material mass, and the raw material was supplied at a flow rate of 1 to 30 L / min.

The Verdet constant and transmittance of the obtained glass material were measured as follows.

Verdet's constant was measured using the rotary photon method. Specifically, the obtained glass material was polished to a thickness of 1 mm, the Faraday rotation angle at a wavelength of 400 to 1100 nm was measured in a magnetic field of 15 kOe, and the Verdet constant was calculated. The wavelength sweep rate was 6 nm / min.

The light transmittance was measured using a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation). Specifically, the obtained glass material is polished to a thickness of 1 mm, and the wavelengths of 400 nm, 500 nm, 600 nm, and 800 nm are obtained from the light transmittance curve obtained by measuring the transmittance at a wavelength of 300 to 1400 nm. The light transmittance in was read. The light transmittance is an external transmittance including reflection.

As is clear from Table 1, the Verdet constant of the glass materials of Examples 1 to 5 was 0.326 to 0.494 min / Oe · cm at 400 nm and 0.105 to 0.159 min / Oe · cm at 600 nm. It can be seen that the glass materials of Examples 1 to 5 are diamagnetic because the value of Verdet constant is positive. Further, the light transmittances exceeded 60% at a wavelength of 400 nm and exceeded 80% at a wavelength of 500 to 800 nm, showing good visible light transmittance.

On the other hand, the Verdet constant of the glass material of Comparative Example 1 was as small as 0.241 min / Oe · cm at 400 nm and 0.079 min / Oe · cm at 600 nm.

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: Glass raw material block 13: Laser light irradiation device

Claims (6)

A glass material containing 73% or more of Yb ₂ O _{3 and 1-27% of B 2} O _{3 by mass%.} Moreover, in _{mass%, P 2 O 5 0~27%} , the glass material according to claim 1, characterized in that it contains SiO 2 0-27%. The glass material according to claim 1 or 2, wherein the glass material contains B ₂ O ₃ + P ₂ O ₅ + SiO _{2 1-27% by mass.} The glass material according to any one of claims 1 to 3, wherein the glass material is used as a magneto-optical element. The glass material according to claim 4, 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 5, wherein the glass raw material block is heated and melted in a state where the glass raw material block is suspended and held to obtain molten glass. A method for producing a glass material, which comprises a step of cooling the molten glass after the glass material.

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