Glass material

Abstract

To provide a glass material in which disadvantages, such as crystallization and a devitrified material, are less likely to occur while maintaining a desired optical characteristic.SOLUTION: A glass material has a refractive index of 1.8 or more, whose content of Al2O3 is more than 0 and not more than 500 ppm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a glass material used for optical elements such as cameras, microscopes, and endoscopes.

Background Art

[0002] In recent years, with the miniaturization and weight reduction of optical systems used in cameras, microscopes, endoscopes, etc., optical elements such as optical lenses used require optical characteristics of high refractive index and high dispersion. In order to make the glass used for optical elements have a higher refractive index, it is necessary to reduce the content of SiO2 and B2O3, which are the main skeletal components of the glass, and contain a large amount of rare earth oxides such as La2O3, Gd2O3, Ta2O5, or intermediate oxides such as Nb2O5 and TiO2. However, when the skeletal components are reduced and a large amount of intermediate oxides are contained, the glass-forming ability decreases and vitrification becomes difficult. General optical glass is produced by melting raw materials in a melting container such as a crucible and then cooling. Here, in the case of a glass composition with poor glass-forming ability, crystallization tends to proceed starting from the contact interface with the melting container in the conventional production method.

[0003] Even for a composition that is difficult to vitrify, vitrification can be achieved by eliminating contact with the melting container and increasing the cooling rate from the molten state. As such a method, a containerless floating method (containerless solidification method) in which raw materials are melted and cooled in a floating state is known. When using this method, the molten glass hardly contacts the melting container, and rapid cooling is possible, so even a composition that is difficult to vitrify as described above can be vitrified. For example, in Patent Document 1, a glass containing only TiO2 and BaO as a glass composition has been produced by the containerless floating method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Even when using the containerless floating method, crystallization may occur during the manufacturing process, making it impossible to obtain a glass material, or devitrified substances may occur in the obtained glass. In particular, this tendency is prominent in the case of compositions that are difficult to vitrify.

[0006] In order not to cause crystallization or devitrified substances, it is useful to add network-forming oxides. Generally, however, network-forming oxides have the effect of lowering the refractive index, and there is a risk of not being able to obtain the desired optical properties.

[0007] In view of the above, an object of the present invention is to provide a glass material that is less likely to have problems such as crystallization and the generation of devitrified substances while maintaining the desired optical properties.

Means for Solving the Problems

[0008] The glass material of the present invention is characterized in that the refractive index is 1.8 or more and the content of Al2O3 is more than 0 and up to 500 ppm.

[0009] In this way, since only an extremely small amount of Al2O3, more than 0 and up to 500 ppm, is contained as an essential component in the glass material, it is possible to suppress the occurrence of crystallization and devitrified substances without lowering the refractive index.

[0010] The glass material of the present invention contains, in mol%, more than 0 and up to 70% of La2O3 and more than 0 and less than 100% of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 + B2O3 + SiO2 + P2O5. In the present invention, “○+○+···” means the total content of each component. Here, it is not necessarily required to contain each component as an essential component, and there may be components that are not contained (0%).

[0011] According to the above configuration, a glass material having a refractive index of 1.8 or more can be easily obtained.

[0012] The glass material of the present invention is preferably used as an optical element.

[0013] The glass material of the present invention is preferably used for decoration.

[0014] The method for producing the glass material of the present invention is a method for producing any of the above glass materials, characterized in that, by ejecting gas from a gas ejection hole that opens to the molding surface of a mold, while floating and holding a raw material mass on the molding surface, after heating and melting the raw material mass to obtain molten glass, the molten glass is cooled.

Effects of the Invention

[0015] According to the present invention, it is possible to obtain a glass material in which defects such as crystallization and devitrification hardly occur while maintaining desired optical properties.

Brief Description of the Drawings

[0016]

Figure 1

Embodiments for Carrying Out the Invention

[0017] The glass material of the present invention has a refractive index (nd) of 1.8 or more, preferably 1.9 or more, particularly preferably 2.0 or more. In this way, it is suitable for use as an optical element or an ornament.

[0018] The glass material of the present invention contains Al2O3 as an essential component. Al2O3 is a component that suppresses crystallization during cooling of molten glass and the generation of devitrified substances in the glass. The content of Al2O3 is more than 0 to 500 ppm, preferably 0.5 to 400 ppm, more preferably 1 to 300 ppm, particularly preferably 3 to 250 ppm. If the content of Al2O3 is too small, it is difficult to obtain the above effects. On the other hand, if the content of Al2O3 is too large, the refractive index decreases and it becomes difficult to obtain desired optical properties.

[0019] The glass article of the present invention preferably contains, in mol%, more than 0% to 70% of La2O3 and more than 0% to less than 100% of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 + B2O3 + SiO2 + P2O5. The reasons for limiting the glass composition in this way will be explained below. In the following explanations regarding the content of each component, unless otherwise specified, "%" means "mol%".

[0020] La2O3 is a component that forms the glass skeleton and increases the refractive index without decreasing the light transmittance. It also has the effect of improving weather resistance. The content of La2O3 is preferably more than 0% to 70%, 5% to 68%, particularly 10% to 63%. If the content of La2O3 is too low, it becomes difficult to obtain the above effects. On the other hand, if the content of La2O3 is too high, it becomes difficult to vitrify.

[0021] Gd2O3, Y2O3, Yb2O3, Lu2O3, ZrO2, TiO2, Nb2O5, Ta2O5, WO3, Ga2O3, GeO2, B2O3, SiO2, and P2O5 are components that increase the refractive index or widen the vitrification range. The content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 + B2O3 + SiO2 + P2O5 is preferably more than 0%, 5% or more, 10% or more, 20% or more, particularly 30% or more. If the content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 + B2O3 + SiO2 + P2O5 is too low, it becomes difficult to obtain the above effects. On the other hand, the upper limit of the content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 + B2O3 + SiO2 + P2O5 is preferably less than 100%, 99% or less, particularly 95% or less, considering the content of other components. In addition, the combined amount of any two or more of the above components is also preferably within the above range.

[0022] The following will explain in detail each component of Gd2O3, Y2O3, Yb2O3, Lu2O3, ZrO2, TiO2, Nb2O5, Ta2O5, WO3, Ga2O3, GeO2, B2O3, SiO2, and P2O5.

[0023] Gd2O3 is a component that increases the refractive index. It also has the effect of improving weather resistance. However, if the content of Gd2O3 is too high, it becomes difficult to vitrify. Therefore, the content of Gd2O3 is preferably 0 - 40%, 1 - 35%, particularly 3 - 30%.

[0024] Y2O3 is a component that increases the refractive index. It also has the effect of improving weather resistance. However, if the content of Y2O3 is too high, it becomes difficult to vitrify. Therefore, the content of Y2O3 is preferably 0 - 30%, 1 - 25%, particularly 5 - 20%.

[0025] Yb2O3 is a component that increases the refractive index. However, if the content of Yb2O3 is too high, it becomes difficult to vitrify. Also, the raw material cost tends to increase. Therefore, the content of Y2O3 is preferably 0 - 30%, 1 - 25%, particularly 5 - 20%.

[0026] Lu2O3 is a component that increases the refractive index. However, if the content of Lu2O3 is too high, it becomes difficult to vitrify, and the raw material cost also tends to increase. Therefore, the content of Lu2O3 is preferably 0 - 20%, 1 - 15%, particularly 5 - 10%.

[0027] ZrO2 is a component that increases the refractive index. Also, as an intermediate oxide, it forms a glass skeleton, thus having the effect of broadening the vitrification range. However, if the content of ZrO2 is too high, it becomes difficult to vitrify, and the melting temperature becomes too high. Therefore, the content of ZrO2 is preferably 0 - 40%, 1 - 30%, 3 - 25%, particularly 5 - 20%.

[0028] TiO₂ is a component with a large effect of increasing the refractive index, and also has an effect of enhancing chemical durability. It also has an effect of broadening the vitrification range. The content of TiO₂ is preferably 0 to 90%, 5 to 85%, particularly preferably 10 to 80%. If the content of TiO₂ is too high, the absorption edge shifts to the long-wavelength side, so the transmittance of visible light (especially visible light in the short-wavelength region) tends to decrease. Also, it becomes difficult to vitrify.

[0029] Nb₂O₅ is a component with a large effect of increasing the refractive index, and also has an effect of broadening the vitrification range. The content of Nb₂O₅ is preferably 0 to 80%, 1 to 75%, 5 to 70%, particularly preferably 10 to 65%. If the content of Nb₂O₅ is too low, it becomes difficult to obtain the above effects. On the other hand, if the content of Nb₂O₅ is too high, it becomes difficult to vitrify.

[0030] Ta₂O₅ is a component with a large effect of increasing the refractive index. However, if the content of Ta₂O₅ is too high, it becomes difficult to vitrify, and the raw material cost also tends to increase. Therefore, the content of Ta₂O₅ is preferably 0 to 60%, 0.1 to 50%, 3 to 45%, particularly preferably 5 to 40%.

[0031] WO₃ is a component that increases the refractive index. However, if the content of WO₃ is too high, it becomes difficult to vitrify. Therefore, the content of WO₃ is preferably 0 to 30%, 1 to 25%, particularly preferably 5 to 20%.

[0032] Ga₂O₃ is a component that broadens the vitrification range because it forms a glass skeleton as an intermediate oxide. It also has an effect of increasing the refractive index. However, if the content of Ga₂O₃ is too high, it becomes difficult to vitrify, and the raw material cost also tends to increase. Therefore, the content of Ga₂O₃ is preferably 0 to 60%, 0 to 50%, 0 to 40%, particularly preferably 0 to 30%.

[0033] GeO₂ is a component that increases the refractive index and also has an effect of broadening the vitrification range. However, if the content of GeO₂ is too high, the raw material cost tends to increase. Therefore, the content of GeO₂ is preferably 0 to 10%, more preferably 0 to 5%.

[0034] B2O3 forms the glass skeleton and is a component that expands the vitrification range. It also lowers the glass transition point, making press molding easier. However, if the content of B2O3 is too high, the refractive index decreases, making it difficult to obtain the desired optical properties. Therefore, the content of B2O3 is preferably 0 to 50%, 0.1 to 40%, 3 to 38%, particularly 5 to 37%.

[0035] SiO2 forms the glass skeleton and is a component that expands the vitrification range. However, if the content of SiO2 is too high, the refractive index decreases, making it difficult to obtain the desired optical properties. Therefore, the content of SiO2 is preferably 0 to 40%, 0 to 30%, particularly 0.1 to 20%.

[0036] P2O5 is a component that constitutes the glass skeleton and has the effect of expanding the vitrification range. However, if its content is too high, it is likely to phase-separate. Therefore, the content of P2O5 is preferably 0 to 10%, more preferably 0 to 5%.

[0037] In addition, in order to obtain the optical properties of a high refractive index, it is preferable to adjust the content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2. The content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 is preferably 0% or more, more than 0%, 5% or more, 10% or more, 20% or more, particularly 30% or more. However, if the content of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2 is too high, it becomes difficult to vitrify, so it is preferably less than 100%, 99% or less, particularly 95%.

[0038] In addition, in order to facilitate vitrification, it is preferable to adjust the content of B2O3 + SiO2 + P2O5. The content of B2O3 + SiO2 + P2O5 is preferably 0% or more, more than 0%, preferably 0.1% or more, 3% or more, particularly preferably 5% or more. However, if the content of B2O3 + SiO2 + P2O5 is too high, the refractive index will decrease and it will be difficult to obtain the desired optical properties. Therefore, it is preferably 80% or less, 75% or less, particularly preferably 70% or less.

[0039] The glass article of the present invention contains components such as La2O3, Nb2O 5、 By actively containing components that broaden the vitrification range, such as TiO2 and B2O3, improper crystallization during glass production can be suppressed, and it becomes easier to increase the size of the glass article (for example, 2 mm or more, 3 mm or more, 4 mm or more, particularly 5 mm or more in diameter).

[0040] The glass article of the present invention can contain the following components in addition to the above.

[0041] MgO, CaO, SrO, BaO, and ZnO are components that broaden the vitrification range. These components can be contained in the range of 10% or less each. If the content of these components is too high, the refractive index will decrease and it will be difficult to obtain the desired optical properties.

[0042] By containing a coloring component composed of an oxide of V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Ce, Pr, or Er, the glass article can be adjusted to a desired color tone, which is suitable for decorative applications. These coloring components may be contained alone or in combination of two or more. The content of these oxides (total amount when containing two or more) is preferably 0 to 20%, 0.001 to 10%, 0.005 to 5%, particularly preferably 0.01 to 1%. Note that depending on the component to be contained, the coloring may become too strong and the visible light transmittance may easily decrease. As a result, the desired glow and fire may not be obtained, and it may be difficult to use as a decorative article. In that case, the content of the above oxides may be less than 1%, 0.5% or less, and further 0.1% or less.

[0043] Specific examples of the composition of the glass article include La2O3-Nb2O5 systems, La2O3-TiO2 systems, La2O3-Ta2O5 systems, and La2O3-B2O3 systems.

[0044] Examples of the La2O3-Nb2O5 system include those containing, in mol%, 5 to 80% (preferably 10 to 70%) of La2O3, 1 to 80% (preferably 20 to 70%) of Nb2O5, 0 to 80% (preferably 0 to 75%) of TiO2, 0 to 45% (preferably 0 to 40%) of Ta2O5, 0 to 20% (preferably 0 to 15%) of Gd2O3, 0 to 25% (preferably 0 to 20%) of ZrO2, 0 to 30% (preferably 0 to 20%) of WO3, 0 to 50% (preferably 0 to 40%) of B2O3, 0 to 40% (preferably 0 to 35%) of SiO2, 0 to 70% (preferably 0 to 60%) of Ga2O3, and 0 to 50% (preferably 0 to 40%) of ZnO.

[0045] Examples of the La2O3-TiO2 system include those containing, in mol%, 5 to 40% (preferably 10 to 35%) of La2O3, 40 to 85% (preferably 50 to 80%) of TiO2, 0 to 55% (preferably 0 to 50%) of Ta2O5, 0 to 20% (preferably 1 to 15%) of Gd2O3, 0 to 25% (preferably 5 to 20%) of ZrO2, 0 to 30% (preferably 0 to 20%) of WO3, 0 to 50% (preferably 0 to 40%) of B2O3, 0 to 40% (preferably 0 to 35%) of SiO2, 0 to 70% (preferably 0 to 60%) of Ga2O3, and 0 to 50% (preferably 0 to 40%) of ZnO.

[0046] Examples of the La2O3-Ta2O5 system include those containing, in mol%, 10 to 80% (preferably 20 to 70%) of La2O3, 5 to 70% (preferably 10 to 60%) of Ta2O5, 0 to 20% (preferably 0 to 15%) of Gd2O3, 0 to 25% (preferably 0 to 20%) of ZrO2, 0 to 30% (preferably 0 to 20%) of WO3, 0 to 50% (preferably 0 to 40%) of B2O3, 0 to 40% (preferably 0 to 35%) of SiO2, 0 to 70% (preferably 0 to 60%) of Ga2O3, and 0 to 50% (preferably 0 to 40%) of ZnO.

[0047] As for the La2O3-B2O3 system, in terms of mol%, it contains La2O3 20 to 75% (preferably 30 to 70%), B2O3 5 to 70% (preferably 10 to 60%), Gd2O3 0 to 20% (preferably 0 to 15%), ZrO2 0 to 25% (preferably 0 to 20%), WO3 0 to 30% (preferably 0 to 20%), SiO2 0 to 40% (preferably 0 to 35%), Ga2O3 0 to 50% (preferably 0 to 40%), ZnO 0 to 50% (preferably 0 to 40%).

[0048] As for the La2O3-Ga2O3 system, in terms of mol%, it contains La2O3 10 to 60% (preferably 20 to 55%), Ga2O3 5 to 75% (preferably 10 to 60%), Gd2O3 0 to 20% (preferably 0 to 15%), ZrO2 0 to 25% (preferably 0 to 20%), WO3 0 to 30% (preferably 0 to 20%), SiO2 0 to 40% (preferably 0 to 35%), ZnO 0 to 50% (preferably 0 to 40%).

[0049] The glass material of the present invention can be used for optical elements such as lenses and prisms, or for decorative purposes such as jewelry, artworks, and tableware.

[0050] FIG. 1 is an example of a schematic cross-sectional view of a manufacturing apparatus for manufacturing the glass material of the present invention. The manufacturing apparatus 1 of the glass material 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 gas ejection holes 10b that open to the molding surface 10a. A plurality of gas ejection holes 10b are provided. In this way, the raw material mass 12, the molten glass, and the glass material can be stably suspended. Note that a molding die having only one gas ejection hole 10b may also be used. The gas ejection holes 10b are connected to a gas supply mechanism 11 such as a gas cylinder. Gas is supplied from this gas supply mechanism 11 to the molding surface 10a via the gas ejection holes 10b. The type of gas is not particularly limited, and for example, it may be air or oxygen, or it may be nitrogen gas, argon gas, helium gas, carbon monoxide gas, carbon dioxide gas, or a reducing gas containing hydrogen.

[0051] To manufacture a glass material using the manufacturing apparatus 1, first, the raw material mass 12 is placed on the forming surface 10a. The raw material mass 12 includes those obtained by integrating glass raw material powders by press molding or the like, sintered bodies obtained by sintering after integrating glass raw material powders by press molding or the like, aggregates of crystals having a composition equivalent to the target glass composition, and the like. Further, those obtained by cutting or crushing the sintered body may be used as the raw material mass. Next, by ejecting gas from the gas ejection holes 10b, the raw material mass 12 is floated on the forming surface 10a. That is, the raw material mass 12 is held in a state of not being in contact with the forming surface 10a. In that state, laser light is irradiated from the laser light irradiation device 13 to the raw material mass 12. Thereby, the raw material mass 12 is heated and melted to obtain molten glass. Thereafter, the glass material can be obtained by cooling the molten glass. In the melting step and the cooling step, it is preferable to continue at least the ejection of gas and suppress the contact between the raw material mass 12, the molten glass, the glass material and the forming surface 10a. The heating method may be radiant heating in addition to the method of irradiating laser light.

[0052] Examples of the material of the mold include aluminum, aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-magnesium-silicon alloy, aluminum-magnesium-zinc alloy, metallic silicon, stainless steel, duralumin, platinum, platinum-rhodium alloy, tungsten, tungsten alloy, zirconium, titanium, titanium alloy, and the like. Among them, aluminum, aluminum-magnesium alloy, aluminum-silicon alloy, aluminum-magnesium-silicon alloy, and aluminum-magnesium-zinc alloy are preferable in terms of corrosion resistance and workability.

Example

[0053] Hereinafter, the present invention will be described based on examples, but the present invention is not limited to the following examples.

[0054] Tables 1 to 4 show Examples (No. 2 to 4, 7, 8, 11 to 13, 16, 17, 20 to 22, 25, 26, 29 to 31, 34, 35) and Comparative Examples (No. 1, 5, 6, 9, 10, 14, 15, 18, 19, 23, 24, 27, 28, 32, 33, 36) of the present invention.

[0055]

Table 1

[0056]

Table 2

[0057]

Table 3

[0058]

Table 4

[0059] 0.3 to 0.6 g of raw material powder prepared to have the glass compositions described in Tables 1 to 4 was press-molded and sintered at 900 to 1100 °C for 3 to 12 hours to produce raw material masses.

[0060] Using the raw material masses obtained above, substantially spherical glass materials with a diameter of about 5 to 7 mm were produced by a containerless floating method using the apparatus according to FIG. 1. As the heat source, 1 to 4 units of a 100 W CO2 laser oscillator were used. The gas flow rate was supplied in the range of 1 to 15 L / min. Twenty samples were prepared for each glass composition, and the occurrence probability of devitrification products and the refractive index (nd) were evaluated as follows.

[0061] Using a stereomicroscope (manufactured by Nikon Corporation, SMZ1000) and observing at 10 times magnification, the presence or absence of devitrification products inside the glass material was confirmed. The occurrence probability of devitrification products (the ratio of the number of samples in which defects occurred out of 20 samples) was defined as follows: ○ when 0 to 10%, △ when more than 10% to 20%, and × when more than 20%.

[0062] The refractive index was evaluated by the measured value with respect to the d line (587.6 nm) of a helium lamp using a KPR-2000 manufactured by Shimadzu Corporation after bonding the glass material onto a soda plate substrate with a thickness of 5 mm and performing right-angle polishing.

[0063] As is clear from Tables 1 to 4, the glass materials of the examples contained Al2O3 in the range of more than 0 to 500 ppm and were excellent in devitrification resistance. On the other hand, the glass materials of No. 1, 6, 10, 15, 19, 24, 28, and 33 that did not contain Al2O3 were inferior in devitrification resistance. Further, the glass materials of No. 5, 9, 14, 18, 23, 27, 32, and 36 that contained more than 500 ppm of Al2O3 had a slightly decreased refractive index and could not obtain the desired optical properties.

Claims

Claim 1 The refractive index is 2.0 or more, and in mol%, La ２ O ３ is 19.99 to 70%, Nb ２ O ５ is 5 to 80%, and it contains 49.97 to 80% of Gd2O3 + Y2O3 + Yb2O3 + Lu2O3 + ZrO2 + TiO2 + Nb2O5 + Ta2O5 + WO3 + Ga2O3 + GeO2, does not contain TiO2, and the content of Al ２ O ３ is 80 to 500 ppm, and is characterized as a glass material. Claim 2 in mol%, La ２ O ３ 19.99 to 70%, Gd ２ O ３ + Y ２ O ３ + Yb ２ O ３ + Lu ２ O ３ + ZrO ２ + TiO ２ + Nb ２ O ５ + Ta ２ O ５ + WO ３ + Ga ２ O ３ + GeO ２ + B ２ O ３ + SiO ２ + P ２ O ５ The glass material according to claim 1, characterized in that it contains 49.99 to 80%. Claim 3 The glass material according to claim 1 or 2, characterized in that it is used as an optical element. Claim 4 The glass material according to claim 1 or 2, characterized in that it is used as an ornament. Claim 5 A method for producing the glass material according to any one of claims 1 to 4, by ejecting gas from a gas ejection hole opening on the forming surface of a mold, floating and holding the raw material mass on the forming surface, heating and melting the raw material mass to obtain molten glass, and then cooling the molten glass. A method for producing a glass material, characterized by the above steps.

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