JP6878894B2 - Glass material and its manufacturing method - Google Patents

Description

The present invention provides a glass material suitable for a magnetic optical element constituting a magnetic device such as an optical isolator, an optical circulator, and a magnetic sensor, a magnetic glass lens used for a digital camera, a glass sheet material used for a bandpass filter, and the like. Regarding the manufacturing method.

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 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.

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 light 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 50% or more (but not including 50%) of _{Pr 2} O _{3 in mol%.} The glass material of the present invention _{contains a large amount of Pr 2} O ₃ as described above, so that the absolute value of Verdet constant becomes large. As a result, a larger Faraday effect than before is exhibited. Further, 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. As described above, it is generally difficult to vitrify a glass material containing a _{large amount of Pr 2} O _3. However, according to the container-free floating method described later, even a composition that is difficult to vitrify can be easily vitrified.

Glass material of the present invention, further, in _{mol%, SiO 2 0~50%, B} 2 O 3 0~50%, Al 2 O 3 0~50%, by containing _P 2 O 5 _0~50% Is preferable. Since SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , and P ₂ O ₅ are components constituting the glass skeleton, vitrification can be performed relatively easily by containing these components.

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. In this way, the light extraction efficiency of the magneto-optical device in the low wavelength region can be improved.

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 in the air, and the glass raw material block is heated and melted to obtain molten glass. After that, it is characterized by including 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 Pr 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 the melting vessel.

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.

The glass material of the present invention can achieve both a high Faraday effect and a high light transmittance in a low wavelength region, and 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 preferably contains Pr ₂ O ₃ in a molar% of 50% or more (but not including 50%), and preferably contains 51% or more, 52% or more, and particularly 53% or more. If _{the content of Pr 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. On the other hand, _{if the content of Pr 2} O ₃ is too large, vitrification tends to be difficult. Therefore, it is preferably 80% or less, 77% or less, and particularly preferably 75% or less.

_{The content of Pr 2} O ₃ in the present invention is expressed by converting all Pr existing in the glass into trivalent oxides.

Regarding Pr, 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%.

_{In addition to Pr 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 "mol%" unless otherwise specified.

SiO ₂ , B ₂ O ₃ and P ₂ O _{5 form} a glass skeleton and are components that expand the vitrification range. However, since these components do 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 contents of SiO 2} , B ₂ O ₃ and P ₂ O ₅ are preferably 0 to 50% and 1 to 45%, respectively, particularly preferably 2 to 40%. The _{total amount of SiO 2} and B ₂ O ₃ is preferably 0 to 50%, 5 to 49%, 10 to 48%, 15 to 48%, and particularly preferably 20 to 47%. The _{total amount of B 2} O ₃ and P ₂ O ₅ is preferably 0 to 50%, 5 to 49%, 10 to 48%, 15 to 48%, and particularly preferably 20 to 47%. The _{total amount of SiO 2} , B ₂ O ₃ and P ₂ O ₅ is preferably 0 to 50%, 5 to 49%, 10 to 48%, 15 to 48%, and particularly preferably 20 to 47%.

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 50%, 0.1 to 40%, 1 to 30%, 1 to 20%, and particularly preferably 1 to 10%.

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, CaO, SrO and BaO have the effect of enhancing the stability and chemical durability of vitrification. 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%.

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, causing composition fluctuations and adversely affecting 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%.

_{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 optical isolator, an optical circulator, or a magnetic sensor. 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 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 irradiating device 13 irradiates the glass raw material block 12 with the laser light. As a result, the glass 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 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 ejection is continued, 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.

Since the glass material of the present invention has a high magnetic susceptibility, it can be used as an autofocus lens for a digital camera, a mobile phone with a camera, etc. by molding the glass material of the present invention into a lens shape by mold press molding or the like. Can be done. These cameras are provided with a drive device for changing the focal length of the camera, that is, for moving the autofocus lens to a predetermined position. Conventionally, the drive device has a lens for fixing the lens. It is equipped with a spring for moving the holder and lens holder. However, with a drive device provided with a lens holder and a spring, it is not possible to miniaturize a digital camera, a camera-equipped mobile phone type, or the like. However, by adopting a lens made of the glass material of the present invention having a high magnetic susceptibility that allows the lens itself to be moved by a magnet, a lens holder and a spring are not required, so that the camera and the like can be miniaturized. Become.

Further, the glass material of the present invention has a light transmittance in the wavelength range of 250 to 420 nm higher than the light transmittance in the wavelength range of 420 to 500 nm, and a light transmittance in the wavelength range of 500 to 550 nm of 550 to 620 nm. Higher than the rate, the light transmittance in the wavelength range of 620 to 950 nm is higher than the light transmittance in the wavelength range of 950 to 1200 nm. As described above, since it has a property of absorbing light in a specific wavelength range, it can be used as a bandpass filter by forming the glass material of the present invention into a sheet shape by polishing or the like.

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

Tables 1 and 2 show 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 glass raw material mass.

Next, the glass raw material mass was roughly pulverized in a mortar to obtain 0.05 to 1 g of small pieces. Using the obtained small pieces of the glass raw material mass, a glass material (diameter of about 1 to 8 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 in the air, and the raw material mass 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 400 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 10 had a Verdet constant of -1.71 to -2.01 at a wavelength of 405 nm, and had a large absolute value. The light transmittance at a wavelength of 405 nm was excellent at 58.4 to 75.6%. On the other hand, the glass material of the comparative example had a Verdet constant of −0.59 at a wavelength of 405 nm, and had a small absolute value.

The glass material of the present invention is suitable as a material for a magnetic optical element constituting a magnetic device such as an optical isolator, an optical circulator, a magnetic sensor, a magnetic glass lens used for a digital camera, a glass sheet used for a bandpass filter, and the like. is there.

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)

In mol%, Pr ₂ O ₃ is 50% or more (but 50% is not included) , Al ₂ O ₃ 0.1 to 20%, SiO ₂ , B ₂ O ₃ and P ₂ O ₅ are 20 to 20 in total. A glass material containing 49%. Furthermore, in _{mol%, SiO 2 0~ 49%,} B 2 O 3 0~ 49%, the glass material according to claim 1, characterized in that it contains _P 2 O 5 _0~ 49%. The glass material according to claim 1 or 2, 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 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 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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