Glass material

Abstract

Provided is a glass material that has a high light transmittance in the short wavelength range and is able to be easily produced.　The glass material is characterized by containing, in mol%, less than 5-30% of Pr2O3 and 0.1-95% of B2O3.

Description

[Technical Field]

[0001] The present invention relates to a glass material suitable for use as a material for magneto-optical elements constituting magnetic devices such as optical isolators, optical circulators, and magnetic sensors, magnetic glass lenses used in digital cameras, and glass sheets used in bandpass filters. [Background technology]

[0002] Glass materials containing paramagnetic compounds are known to exhibit the Faraday effect, a magneto-optical effect that rotates the plane of polarization of linearly polarized light passing through a material placed in a magnetic field. This effect is used in optical isolators and magnetic sensors.

[0003] The angle of rotation θ (the angle of rotation of the plane of polarization) due to the Faraday effect is expressed by the following formula, where H is the strength of the magnetic field, L is the length of the material through which the polarized light passes, and V is the Verdet constant. The Verdet constant is a constant that depends on the type of material, and is positive for diamagnetic materials and negative for paramagnetic materials. The larger the absolute value of the Verdet constant, the larger the absolute value of the angle of rotation, meaning that it indicates a larger Faraday effect.

[0004] θ=VHL

[0005] Known examples of glass materials that exhibit the Faraday effect include SiO2-B2O3-Al2O3-Tb2O3-based glass materials (Patent Document 1), P2O5-B2O3-Tb2O3-based glass materials (Patent Document 2), and P2O5-TbF3-RF2 (R is an alkaline earth metal)-based glass materials (Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 51-46524 [Patent Document 2] Special Publication No. 52-32881 [Patent Document 3] Special Publication No. 55-42942 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the above glass materials exhibit high light transmittance in the visible to infrared range, the light transmittance decreases in the wavelength range shorter than the visible range (short wavelength range) due to absorption by Tb2O3. Therefore, when magneto-optical elements using such glass materials are used in the short wavelength range, there is a risk of a decrease in light extraction efficiency and breakage due to heat generation.

[0008] In view of the above, an object of the present invention is to provide a glass material that has high light transmittance in the short wavelength range and is easy to manufacture. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the above problems can be solved by using a glass material having a specific composition.

[0010] That is, the glass material of the present invention is characterized by containing, in mole percent, 5 to less than 30% of Pr2O3 and 0.1 to 95% of B2O3.

[0011] The glass material of the present invention exhibits high transmittance in the short wavelength range due to the inclusion of Pr2O3 as described above. As a result, it is possible to suppress a decrease in light extraction efficiency in the short wavelength range and damage to magneto-optical elements due to heat generation. Furthermore, the inclusion of B2O3 as an essential component facilitates vitrification and makes the material easy to manufacture.

[0012] The glass material of the present invention preferably further contains, in mol %, SiO20 to 90% and P2O50 to 90%.

[0013] The glass material of the present invention preferably further contains, in mol %, 30 to 50% Al2O.

[0014] The glass material of the present invention preferably contains 20% or more of B2O3+SiO2+P2O5.

[0015] The glass material of the present invention preferably has a light transmittance of 50% or more at 355 nm when it has a thickness of 1 mm.

[0016] The glass material of the present invention is preferably used as a magneto-optical element.

[0017] The glass material of the present invention is preferably used as a Faraday rotator. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a glass material that has high light transmittance in the short wavelength range and is easy to manufacture. DETAILED DESCRIPTION OF THE INVENTION

[0019] The glass material of the present invention contains, in mole percent, 5 to less than 30% of Pr2O3 and 0.1 to 95% of B2O3. The reasons for limiting the composition of the glass material as described above are explained below. In the following explanation of the content of each component, "%" means "mol%" unless otherwise specified.

[0020] Pr2O3 is an essential component that increases the absolute value of the Verdet constant and enhances the Faraday effect. It also contributes to improving the magnetic susceptibility of the glass material. Furthermore, because Pr2O3 has no optical absorption peak in the short wavelength region (e.g., 250 to 420 nm), it is also a component that allows for obtaining a glass material with high optical transmittance in this wavelength region. The Pr2O3 content is 5 to less than 30%, and is preferably more than 5% to less than 30%, 6 to less than 30%, 10 to less than 30%, more than 10% to less than 30%, 12 to less than 30%, 15 to less than 30%, 15 to 29%, 15 to 27%, 15 to 24%, or particularly preferably 15 to 22%. If the Pr2O3 content is too low, the absolute value of the Verdet constant becomes small, making it difficult to obtain a sufficient Faraday effect. On the other hand, if the Pr2O3 content is too high, vitrification becomes difficult. Furthermore, the absorption edge on the short wavelength side of the glass is likely to shift to the long wavelength side, and the light transmittance in the short wavelength region is likely to decrease. Note that the Pr2O3 content in the present invention is expressed by converting all Pr present in the glass into trivalent oxide.

[0021] The magnetic moment that gives rise to the Verdet constant is Pr 4+ than Pr 3+ Therefore, the Pr in the glass material 3+ The larger the ratio of Pr to the total Pr, the greater the Faraday effect, which is preferable. 3+ The proportion of is preferably 50% or more, 60% or more, 70% or more, 80% or more, particularly preferably 90% or more, in mole percent.

[0022] B2O3 forms the glass skeleton and is an essential component for expanding the vitrification range and facilitating vitrification. It is also a component that tends to shift the short-wavelength absorption edge of glass to the short-wavelength side. However, because B2O3 does not contribute to improving the Verdet constant, if its content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the B2O3 content is 0.1 to 95%, preferably 10 to 90%, 20 to 90%, 25 to 90%, 30 to 90%, 40 to 88%, 50% to 85%, more than 50% to 85%, and particularly preferably 51 to 85%.

[0023] In addition to the above components, the glass material of the present invention may contain various components shown below.

[0024] SiO2 forms the glass skeleton and is a component that easily expands the vitrification range. However, because SiO2 does not contribute to improving the Verdet constant, if the SiO2 content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the SiO2 content is preferably 0 to 90%, 0 to 70%, 0 to 60%, 0 to 50%, 0 to less than 40%, 0 to 39%, 0.1 to 37%, and particularly preferably 1 to 35%.

[0025] P2O5 is a component that forms the glass framework and easily expands the vitrification range. It is also a component that easily shifts the short-wavelength absorption edge of glass to the short-wavelength side. However, because P2O5 does not contribute to improving the Verdet constant, if its content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the P2O5 content is preferably 0 to 90%, 0 to 70%, 0 to 50%, 0 to 30%, 0 to 20%, 0 to 10%, 0 to 5%, 0.1 to 5%, and particularly 1 to 5%.

[0026] To further expand the vitrification range, SiO2+P2O5 is preferably 0-90%, 0-80%, 0-50%, 0.1-40%, and particularly preferably 1-35%. If the SiO2+P2O5 content is too high, it becomes difficult to obtain a sufficient Faraday effect. Note that "SiO2+P2O5" refers to the combined content of SiO2 and P2O5.

[0027] It is preferable that B2O3+SiO2+P2O5 is 20% or more, 30% or more, 40% or more, 50% or more, 51% or more, 53% or more, and particularly 55% or more. This facilitates vitrification. The upper limit of B2O3+SiO2+P2O5 is, for example, 95% or less, and particularly 90% or less. Note that "B2O3+SiO2+P2O5" refers to the total content of B2O3, SiO2, and P2O5.

[0028] Al2O3 forms the glass skeleton and is a component that easily expands the vitrification range. However, because Al2O3 does not contribute to improving the Verdet constant, if its content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the Al2O3 content is preferably 0 to 50%, 0 to 45%, 0.1 to 45%, 0.1 to 40%, 0.1 to 35%, 0.1 to 30%, 0.1 to 25%, 1 to 25%, and particularly preferably 1 to 20%.

[0029] Tb2O3 is a component that increases the absolute value of the Verdet constant and enhances the Faraday effect. It also increases the magnetic susceptibility of the glass material. However, if the content is too high, vitrification becomes difficult. Furthermore, light transmittance in the short wavelength region tends to decrease. Therefore, the Tb2O3 content is preferably 0 to less than 25%, 0 to 24%, 0 to 20%, 0 to 15%, 0 to 10%, 0 to 5%, 0 to 3%, and particularly preferably 0 to 1%. The Tb2O3 content is expressed by converting all Tb present in the glass into trivalent oxide.

[0030] Dy2O3 is a component that increases the absolute value of the Verdet constant and enhances the Faraday effect. It also increases the magnetic susceptibility of the glass material. However, if the amount is too high, vitrification becomes difficult. Also, light transmittance in the short wavelength range tends to decrease. Therefore, the Dy2O3 content is preferably 0 to less than 15%, 0 to 14%, 0 to 10%, 0 to 5%, 0 to 3%, and especially 0 to 1%. The Dy2O3 content is expressed by converting all Dy present in the glass into trivalent oxide.

[0031] Ce2O3, La2O3, Gd2O3, Yb2O3, and Y2O3 are components that tend to increase the stability of vitrification, but if their contents are too high, vitrification becomes more difficult. Also, light transmittance tends to decrease. Therefore, the contents of Ce2O3, La2O3, Gd2O3, Yb2O3, and Y2O3 are each preferably 0 to 10%, and particularly preferably 0 to 5%.

[0032] MgO, CaO, SrO, and BaO are components that tend to improve vitrification stability and chemical durability. However, these components do not contribute to improving the Verdet constant, so if their content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of these components is preferably 0 to 20%, 0 to 15%, and particularly preferably 0 to 10%, respectively.

[0033] Li2O, K2O, and Na2O are components that increase the stability of vitrification and tend to lower the melting temperature of the glass. However, these components do not contribute to improving the Verdet constant, so if their content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the contents of these components are preferably 0 to 30%, 0 to 25%, 0 to 20%, 0 to 15%, and particularly 0 to 10%, respectively.

[0034] Ga2O3 is a component that easily widens the vitrification range. However, if its content is too high, devitrification is likely to occur. Furthermore, since Ga2O3 does not contribute to improving the Verdet constant, if its content is too high, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the Ga2O3 content is preferably 0 to 35%, 0 to 20%, 0 to 10%, 0 to 5%, or less than 0 to 5%, and particularly preferably 0 to 4%.

[0035] Fluorine is a component that enhances glass-forming ability and easily widens the vitrification range. However, if the fluorine content is too high, it may volatilize during melting, causing striae, making it difficult to obtain a homogeneous glass. Therefore, the fluorine content (calculated as F2) is preferably 0 to 10%, 0 to 7%, 0 to 5%, and particularly preferably 0 to 4%.

[0036] Sb2O3 can be added as a reducing agent, but considering the environmental impact, the Sb2O3 content is preferably 0.5% or less.

[0037] As described above, the glass material of the present invention exhibits high light transmittance in the short wavelength region (e.g., 250 to 420 nm), and can therefore be suitably used in magneto-optical elements used in this wavelength region, such as optical isolators, optical circulators, and magnetic sensors. In this case, the light transmittance at a wavelength of 355 nm at a thickness of 1 mm is preferably 50% or more, 60% or more, 70% or more, and particularly 80% or more. Note that this light transmittance is the external transmittance, including reflection.

[0038] Furthermore, the glass material of the present invention has the above composition, and therefore has a good magnetic susceptibility (for example, 1×10 -4 emu / mol or more, especially 2 × 10 -4 emu / mol or more). Therefore, the glass material of the present invention may be molded into a lens shape by mold press molding or the like and used as an autofocus magnetic glass lens for digital cameras, camera-equipped mobile phones, and the like. Typically, these cameras are equipped with a lens holder for fixing the lens and an elastic body for moving the lens holder as a driving device for changing the focal length, making it difficult to reduce the size. Therefore, a method has been proposed in which the lens (magnetic glass lens) is moved by a magnet instead of the above-mentioned driving device. As described above, the glass material of the present invention has good magnetic susceptibility, so that an autofocus magnetic glass lens that moves sufficiently even when a small magnet is used can be manufactured, which can contribute to the miniaturization of cameras and the like.

[0039] Furthermore, the glass material of the present invention may be formed into a glass sheet by polishing or the like and used as a bandpass filter. In this case, for example, the light transmittance in the wavelength range of 250 to 420 nm is preferably higher than the light transmittance in the wavelength range of 420 to 500 nm. Also, for example, the light transmittance in the wavelength range of 500 to 550 nm is preferably higher than the light transmittance in the wavelength range of 550 to 620 nm. Furthermore, for example, the light transmittance in the wavelength range of 620 to 950 nm is preferably higher than the light transmittance in the wavelength range of 950 to 1200 nm.

[0040] The glass material of the present invention is preferably produced by melting glass raw materials in a melting vessel such as a crucible and cooling them. As described above, the glass material of the present invention has a Pr2O3 content limited to less than 30%, which facilitates vitrification and allows for stable production of the glass material. Furthermore, this production method can melt a larger amount of glass raw materials at one time compared to a production method in which glass raw materials are melted and cooled in a levitated state (containerless levitation method), and therefore allows for efficient production of larger glass materials. [Example]

[0041] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0042] Tables 1 to 3 show examples of the present invention and comparative examples.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] Examples 1 to 8 and Comparative Examples 1 and 3 were prepared as follows. First, raw material powders were weighed to obtain the glass compositions shown in the tables and thoroughly mixed to prepare glass raw materials. Next, approximately 100 g of the glass raw material was placed in a platinum crucible and melted in an electric furnace at 1200°C to 1500°C while stirring with a platinum stirring rod to refine and homogenize it. Finally, the molten glass was poured onto a carbon plate and shaped to prepare a glass material.

[0047] Comparative Example 2 was prepared as follows. First, raw material powders were weighed to obtain the glass composition shown in the table and thoroughly mixed to prepare a glass raw material. Next, approximately 0.5 g of the glass raw material was press-molded and sintered at 800°C for 6 hours to prepare a glass raw material lump. Finally, the glass raw material lump was placed in a containerless levitation device, levitated using nitrogen gas, melted by CO2 laser irradiation, and then cooled to prepare a glass material.

[0048] The Verdet constant at a wavelength of 355 nm and the light transmittance at a wavelength of 355 nm were measured for the obtained glass materials. In addition, the glass transition temperature (Tg) and crystallization temperature (Tc) were measured for Examples 1 to 8 and Comparative Example 2. Each measurement was carried out as follows.

[0049] The Verdet constant at a wavelength of 355 nm was measured using a Faraday rotation measurement device (manufactured by JASCO Corporation). Specifically, the obtained glass material was polished to a thickness of 1 mm, and then the Faraday rotation angle at a wavelength of 355 nm was measured in a magnetic field of 12.5 kOe, and the Verdet constant was calculated.

[0050] The light transmittance at a wavelength of 355 nm was measured using a spectrophotometer (Shimadzu UV-3100). Specifically, the obtained glass material was polished to a thickness of 1 mm, and then the light transmittance at wavelengths of 300 to 400 nm was measured. The light transmittance at 355 nm was read from the light transmittance curve. Note that the light transmittance is the external transmittance, including reflection.

[0051] The glass transition temperature (Tg) and crystallization temperature (Tc) were measured using a macro-type differential thermal analyzer. Specifically, in a chart obtained by measuring up to 1100°C using the macro-type differential thermal analyzer, the value of the first inflection point was taken as the glass transition temperature, and the value of the strong exothermic peak was taken as the crystallization temperature. The difference between the glass transition point and the crystallization temperature was taken as ΔT, and was used as an index of the ease of vitrification. The larger ΔT means that vitrification is easier.

[0052] As is clear from Tables 1 and 2, the glass materials of Examples 1 to 8 had Verdet constants of 0.255 to 1.668 at a wavelength of 355 nm, and high light transmittances of 50% or more at a wavelength of 355 nm. On the other hand, the glass material of Comparative Example 1 was not vitrified by a molding method involving melting and pouring in a platinum crucible. The glass material of Comparative Example 2 was vitrified by the containerless levitation method, but the light transmittance at a wavelength of 355 nm was low at 45.2%, indicating low light transmittance in the short wavelength range. The glass material of Comparative Example 3 had a low light transmittance at a wavelength of 355 nm of 39.6%, indicating low light transmittance in the short wavelength range.

[0053] Furthermore, as is clear from Table 3, the glasses of Examples 4, 5, 7, and 8 had large ΔT of 181 to 263°C, while the glass of Comparative Example 2 had a small ΔT of 112°C. [Industrial Applicability]

[0054] The glass material of the present invention is suitable as a material for magneto-optical elements constituting magnetic devices such as optical isolators, optical circulators, and magnetic sensors, magnetic glass lenses used in digital cameras, and glass sheets used in bandpass filters.

Claims

1. In mole percent, Pr ２ O ３ 5 to less than 30%, B ２ O ３ 0.1-90%, Tb ２ O ３ 0 to less than 25%, Dy ２ O ３ 0 to less than 15%, SiO ２ 0 to less than 40%, Al ２ O ３ A glass material containing 0.1 to 8%.

2. Further, in mol%, P ２ O ５ The glass material according to claim 1, containing 0 to 90% of ZnO.

3. B ２ O ３ +SiO ２ +P ２ O ５ The glass material according to claim 1 or 2, wherein the content of SiO 2 is 20% or more.

4. B ２ O ３ +SiO ２ +P ２ O ５ The glass material according to claim 3, wherein the ratio of the porosity of the glass to the total porosity of the glass is 70% or more.

5. 5. The glass material according to claim 1, which has a light transmittance of 50% or more at 355 nm when the glass material has a thickness of 1 mm.

6. The glass material according to any one of claims 1 to 5, which is used as a magneto-optical element.

7. The glass material according to claim 6, which is used as a Faraday rotator.

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