JP2018062456A - Glass material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass material that is capable of exhibiting both a high Faraday effect and a high light transmittance in a short wavelength range and a method for producing the same.SOLUTION: A glass material contains, in mol%, PrO: 50% or more (excluding 50%), SiO: 0-50%, BO: 0-50%, AlO: 0-50%, PO: 0-50%; has a thickness of 1 mm and a light transmittance at a wavelength of 405 nm of 50% or more ; and is used as a Faraday rotation element. A method for producing a glass material includes the step of heating and melting a glass raw material lump, held in the state of floating in midair, to obtain molten glass; and thereafter, cooling the molten glass.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a glass material suitable for a material of a magneto-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. It relates to the manufacturing method.

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

  The optical rotation (rotation angle of the polarization plane) θ by 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 depending on the type of substance, and is called Verde's constant. The Verde constant is a positive value for a diamagnetic material and a negative value for a paramagnetic material. The greater the absolute value of the Verde constant, the greater the absolute value of the optical rotation, resulting in a large Faraday effect.

    θ = VHL

Conventionally, as a glass material showing the Faraday _{effect, SiO 2 -B 2 O 3 -Al} 2 O 3 -Tb 2 O 3 based glass material (see Patent Document _{1), P 2 O 5 -B} 2 O 3 -Tb 2 An O ₃ -based glass material (see Patent Document 2) or a P ₂ O ₅ -TbF ₃ -RF ₂ (R is an alkaline earth metal) -based glass material (see Patent Document 3) is known.

Japanese Patent Publication No.51-46524 Japanese Patent Publication No. 52-32881 Japanese Patent Publication No.55-42942

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

  In view of the above, an object of the present invention is to provide a glass material that can achieve both a high Faraday effect and a high light transmittance in a low wavelength region.

  As a result of intensive studies by the present inventors, it has been found that the above problems 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 has a large absolute value of the Verde constant due to containing a large amount of Pr ₂ O ₃ as described above. As a result, the Faraday effect which is larger than the conventional one is shown. In addition, Pr ₂ O ₃ basically exhibits no light absorption in a wavelength region of 420 nm or less (for example, 250 to 420 nm), and thus exhibits high transmittance in the wavelength region. As described above, glass materials containing a large amount of Pr ₂ O ₃ are generally difficult to vitrify. However, according to the containerless floating method described later, it is possible to easily vitrify even such a composition that is difficult to vitrify.

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 preferred. Since SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , and P ₂ O ₅ are components constituting a 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 at a wavelength of 405 nm of 50% or more. In this way, it is possible to improve the light extraction efficiency of the magneto-optical device in the low wavelength region.

  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 rotation element which is a kind of magneto-optical element. By using it for the above application, 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 glass material, and in a state where the glass raw material lump is suspended and held in the air, the glass raw material lump is heated and melted to obtain a molten glass. And 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 (melting method). However, the glass material of the present invention has a composition containing a large amount of Pr ₂ O ₃ that basically does not constitute a glass skeleton as described above, and is a material that is difficult to vitrify. Therefore, in a normal melting method, 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 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 melting vessel, crystallization starting from the interface with the melting vessel 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 rotation element of a magneto-optical device in a low wavelength region.

It is typical sectional drawing 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 in mol% of 50% or more (but not 50%), preferably 51% or more, 52% or more, particularly 53% or more. When the content of Pr ₂ O ₃ is too small, the absolute value of the Verdet constant is reduced, a sufficient Faraday effect is difficult to obtain. On the other hand, if the content of Pr ₂ O ₃ is too large, vitrification tends to be difficult, and 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 a representation in terms of Pr present in the glass to the oxide of any trivalent.

The magnetic moment that causes the Verde constant for Pr is larger in Pr ³⁺ than in Pr ⁴⁺ . Therefore, the larger the ratio of Pr ^{3+ in} the glass material, the greater the Faraday effect, which is preferable. Specifically, the ratio of Pr ^{3+ in} the total Pr is preferably 50% or more, 60% or more, 70% or more, 80% or more, 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 regarding the content of each component, “%” means “mol%” unless otherwise specified.

SiO ₂ , B ₂ O ₃ and P ₂ O ₅ are components that become a glass skeleton and widen the vitrification range. However, since these components do not contribute to the improvement of the Verde constant, if the content is too large, it is 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%, 1 to 45%, particularly 2 to 40%, respectively. Further, the total amount of SiO ₂ and _B 2 _{O 3} is 0-50%, 5-49%, 10-48%, 15-48%, 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%, 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%, particularly 20 to 47%.

Al ₂ O ₃ is a component that forms a glass skeleton as an intermediate oxide and widens the vitrification range. However, since Al ₂ O ₃ does not contribute to the improvement of the Verde 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%, particularly 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. However, if the content is too large, it becomes difficult to vitrify. Further, it 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 contribute to the improvement of the Verde constant. However, when the content is too large, it becomes difficult to vitrify. Further, it 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 all expressed by converting Dy, Eu, and Ce present in the glass into trivalent oxides.

  MgO, CaO, SrO, and BaO have the effect of increasing the vitrification stability and chemical durability. However, since it does not contribute to the improvement of the Verde constant, if the content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of these components is preferably 0 to 10%, particularly 0 to 5%.

Ga ₂ O ₃ has the effect of increasing the glass forming ability and expanding the vitrification range. However, when there is too much the content, it will become easy to devitrify. Further, since the Ga ₂ O ₃ it does not contribute to the improvement of the Verdet constant, when the content is too large, a sufficient Faraday effect difficult to obtain. Therefore, the Ga ₂ O ₃ content 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 its content is too large, it may volatilize during melting and cause composition fluctuations, or it may adversely affect the stability of vitrification. Therefore, the content of fluorine _{(F 2} equivalent) 0-10%, 0-7%, particularly preferably 0 to 5%.

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

  The glass material of the present invention preferably has a light transmission loss as small as possible when 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 containerless floating method. FIG. 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus for producing a glass material by a containerless floating method. Hereinafter, the manufacturing method of the glass material of this invention is demonstrated, referring FIG.

  The glass material manufacturing apparatus 1 has a mold 10. The mold 10 also serves as a melting container. The molding die 10 has a molding surface 10a and a plurality of gas ejection holes 10b opened in 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 lump 12 is arrange | positioned on the molding surface 10a. As the glass raw material block 12, for example, a raw material powder integrated by press molding or the like, a sintered body obtained by integrating raw material powder by press molding or the like, and a composition equivalent to the target glass composition are used. For example, an aggregate of crystals.

  Next, the glass raw material block 12 is floated on the molding surface 10a by ejecting gas from the gas ejection holes 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 this state, the glass material block 12 is irradiated with laser light from the laser light irradiation device 13. Thereby, the glass raw material lump 12 is heated and melted to be vitrified to obtain molten glass. Thereafter, the glass material can be obtained by cooling the molten glass. In the step of heating and melting the glass raw material lump 12 and the step of cooling until the temperature of the molten glass and further the glass material is at least the softening point or less, at least gas ejection is continued, and the glass raw material lump 12, molten glass, Furthermore, it is preferable to suppress contact between the glass material and the molding surface 10a. In addition, you may float the glass raw material lump 12 on the molding surface 10a using the magnetic force which generate | occur | produces by applying a magnetic field. In addition to the method of irradiating laser light, the method of heating and melting may be radiant heating.

  In addition, since the glass material of the present invention has a high magnetic susceptibility, the glass material of the present invention is used for autofocus lenses such as digital cameras and camera-equipped mobile phones by molding into a lens shape by mold press molding or the like. Can do. These cameras are provided with a driving device for changing the focal length of the camera, that is, for moving the autofocus lens to a predetermined position. Conventionally, the driving device has a lens for fixing the lens. A spring for moving the holder and the lens holder is provided. However, in a driving device including a lens holder and a spring, a digital camera, a camera-equipped mobile phone type, or the like cannot be downsized. 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 a camera or the like can be downsized. Become.

  Further, the glass material of the present invention has a light transmittance in the wavelength region of 250 to 420 nm higher than that in the wavelength region of 420 to 500 nm, and a light transmittance of 550 to 620 nm in the wavelength region of 500 to 550 nm. 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. Thus, since it has the property of absorbing light in a specific wavelength region, it can be used as a band-pass filter by forming the glass material of the present invention into a sheet shape by polishing or the like.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.

  Tables 1 and 2 show examples and comparative examples of the present invention.

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

Next, the glass raw material lump was coarsely pulverized in a mortar to obtain small pieces of 0.05 to 1 g. A glass material (diameter: about 1 to 8 mm) was produced by a containerless floating method using an apparatus according to FIG. 1 using small pieces of the obtained glass raw material lump. A 100 W CO ₂ laser oscillator was used as the heat source. Moreover, nitrogen gas was used as a gas for suspending the raw material lump in the air, and was supplied at a flow rate of 1 to 30 L / min.

  About the obtained glass material, the Verde constant was measured using the Kerr effect measuring device (the JASCO Corporation make, product number: K-250). Specifically, the obtained glass material was polished so as to have a thickness of about 1 mm, a Faraday rotation angle at a wavelength of 400 to 850 nm was measured in a magnetic field of 15 kOe, and a Verde 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 a wavelength of 405 nm from a light transmittance curve obtained by polishing the obtained glass material to a thickness of 1 mm and using a spectrophotometer (UV-3100, manufactured by Shimadzu Corporation). The light transmittance at was read. The light transmittance is an external transmittance including reflection.

  As apparent from Table 1, the glass materials of Examples 1 to 10 had Verde constants of −1.71 to −2.01 at a wavelength of 405 nm, and had large absolute values. Further, 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 Verde constant at a wavelength of 405 nm of −0.59 and a small absolute value.

  The glass material of the present invention is suitable as a material for a magneto 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 band pass filter, and the like. is there.

1: Glass material manufacturing apparatus 10: Mold 10a: Molding surface 10b: Gas ejection hole 11: Gas supply mechanism 12: Glass raw material block 13: Laser beam irradiation apparatus

Claims (6)

A glass material characterized by containing Pr ₂ O ₃ in a mol% of 50% or more (but not 50%). Furthermore, in _{mol%, SiO 2 0~50%, B} 2 O 3 0~50%, Al 2 O 3 0~50%, claim 1, characterized in that it contains _P 2 O 5 _0~50% The glass material as described in.   The glass material according to claim 1, 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 claim 1, 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 rotation element.   It is a method for manufacturing the glass material as described in any one of Claims 1-5, Comprising: In the state which floated and hold | maintained the glass raw material lump in the air, the said glass raw material lump was heat-melted and it was molten glass The manufacturing method of the glass material characterized by including the process of cooling the said molten glass after obtaining.