Infrared transmitting glass

Abstract

To provide an infrared transmitting glass having excellent light transmission properties in an infrared region.SOLUTION: An infrared transmitting glass contains, in terms of mol%, 20-90% of S+Se+Te, greater than 0% and not greater than 40% of Ge, greater than 0% and not greater than 50% of Al+Si, and 0.01-20% of Mg+Ca.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an infrared-transmitting glass. [Background technology]

[0002] Development of infrared cameras for use in in-vehicle night vision and security systems is progressing. Infrared cameras are designed by combining optical elements such as filters and lenses that transmit infrared light.

[0003] Materials such as germanium (Ge), chalcogenide glass, and silicon (Si) are often used for the optical elements. However, Ge is an expensive material, which is disadvantageous for reducing the cost of optical elements. Furthermore, chalcogenide glass and Si generally have lower optical transmittance in the infrared range than Ge, which is disadvantageous for improving the performance of infrared cameras.

[0004] Therefore, chalcogenide glass with excellent light transmittance in the infrared region has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 105719 [Patent Document 2] International Publication No. 2017 / 086227 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when oxygen is mixed into chalcogenide glass, the constituent elements of the glass combine with the oxygen to form oxide impurities, which can cause infrared absorption, which can significantly degrade the optical properties of optical elements.

[0007] As a method for suppressing infrared absorption caused by oxide impurities, for example, Patent Document 2 discloses a method of adding Ti to chalcogenide glass. However, since there are oxide impurities for which Ti does not sufficiently suppress infrared absorption, other means for suppressing infrared absorption have been sought.

[0008] In view of the above, an object of the present invention is to provide an infrared transmitting glass having excellent light transmission properties in the infrared region. [Means for solving the problem]

[0009] The infrared transmitting glass of the present invention is characterized by containing, in mole percent, 20% to 90% of S+Se+Te, more than 0% to 40% of Ge, more than 0% to 50% of Al+Si, and 0.01% to 20% of Mg+Ca.

[0010] The infrared transmitting glass of the present invention preferably contains, in mole percent, more than 0% to 50% of Al.

[0011] The infrared transmitting glass of the present invention preferably contains, in mole %, more than 0% to 90% of Te.

[0012] The infrared transmitting glass of the present invention preferably contains, in mole percent, 0% to 40% of Zn+Ga+In+Sn+Sb+Bi, 0% to 40% of Cu+Ag, 0% to 40% of F+Cl+Br+I, and 0% to 40% of B+C+Cr+Mn+Ti+Fe.

[0013] The infrared transmitting glass of the present invention preferably has an As content of 30% or less.

[0014] In the infrared transmitting glass of the present invention, the ratio of the content of the group 13 elements to the content of S+Se+Te, (B+Al+Ga+In) / (S+Se+Te), is preferably 0.7 or less.

[0015] In the infrared transmitting glass of the present invention, the ratio of the content of Group 14 elements to the content of S+Se+Te, (C+Si+Ge+Sn) / (S+Se+Te), is preferably 0.7 or less.

[0016] The optical element of the present invention is characterized by using the infrared transmitting glass described above.

[0017] The infrared sensor of the present invention is characterized by using the optical element described above.

[0018] The infrared camera of the present invention is characterized by using the optical element described above. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an infrared transmitting glass having excellent light transmission properties in the infrared region. DETAILED DESCRIPTION OF THE INVENTION

[0020] The infrared transmitting glass of the present invention is characterized by containing, in mole percent, 20% to 90% of S + Se + Te, more than 0% to 40% of Ge, more than 0% to 50% of Al + Si, and 0.01% to 20% of Mg + Ca. The reasons for specifying the glass composition in this way and the content of each component are explained below. In the following explanation, "%" means "mol percent" unless otherwise specified.

[0021] S, Se, and Te are components that form the glass skeleton. The content of S+Se+Te (total amount of S, Se, and Te) is 20% to 90%, preferably 30% to 89%, 40% to 89%, 50% to 85%, 50% to 80%, and particularly preferably 50% to 75%. If the content of S+Se+Te is too low, vitrification becomes difficult. If the content of S+Se+Te is too high, S-based, Se-based, or Te-based crystals are precipitated, which tends to reduce light transmittance. The preferred ranges of the content of each component are as follows:

[0022] The S content is preferably 0% to 90%, 10% to 90%, 20% to 89%, 30% to 89%, 40% to 88%, 50% to 88%, 50% to 80%, and particularly preferably 50% to 75%. However, S is a component that tends to reduce light transmittance at wavelengths of 10 μm or more. Therefore, from the perspective of improving light transmittance in the infrared region, the S content is preferably 30% or less, 20% or less, 10% or less, and particularly preferably 5% or less.

[0023] The Se content is preferably 0% to 90%, 10% to 90%, 20% to 89%, 30% to 89%, 40% to 88%, 50% to 88%, 50% to 80%, and particularly preferably 50% to 75%. However, Se is a toxic component. Therefore, from the perspective of reducing the burden on the environment, it is preferable that the Se content be 40% or less, 30% or less, 20% or less, or 10% or less, and particularly preferably substantially free of Se. In this specification, "substantially free of Se" means that Se is not intentionally included in the raw materials and does not exclude the presence of impurity levels. Objectively, this refers to a content of each component being less than 0.1%.

[0024] The Te content is preferably 0% to 90%, more than 0% to 90%, 10% to 90%, 20% to 89%, 30% to 89%, 40% to 88%, 50% to 88%, 50% to 80%, and particularly preferably 50% to 75%. If the Te content is too high, vitrification becomes difficult. Furthermore, Te-based crystals are likely to precipitate, resulting in a decrease in light transmittance.

[0025] It is sufficient that at least one of S, Se, and Te is contained, but it is particularly preferable that Te is contained, as this tends to reduce the effect on light transmittance at wavelengths of 8 μm to 14 μm.

[0026] Ge is a component that forms the glass skeleton. The Ge content is more than 0% to 40%, and is preferably 0.1% to 39%, 1% to 30%, 2% to 25%, 3% to 20%, and particularly preferably 4% to 20%. If the Ge content is too low, vitrification becomes difficult. If the Ge content is too high, Ge-based crystals are precipitated, which tends to reduce light transmittance. In addition, raw material costs tend to increase.

[0027] Al and Si are components that form the glass skeleton. They are also components that tend to decrease the Abbe number of the glass. The Al+Si content (total amount of Al and Si) is more than 0% to 50%, and is preferably 0.1% to 50%, 3% to 45%, 5% to 35%, and particularly preferably 8% to 25%. If the Al+Si content is too low, vitrification becomes difficult. If the Al+Si content is too high, Al-based or Si-based crystals are precipitated, and light transmittance is likely to decrease. The preferred ranges of the content of each component are as follows:

[0028] The Al content is preferably 0% to 50%, more than 0% to 50%, 0.1% to 40%, 3% to 40%, and particularly preferably 3% to 30%.

[0029] The Si content is preferably 0% to 50%, more than 0% to 50%, 0.1% to 40%, 3% to 40%, and particularly preferably 3% to 30%.

[0030] Both Al and Si oxide impurities have optical absorption in the infrared region. Specifically, Si oxide impurities (Si-O) absorb light with a wavelength of approximately 9 μm. Furthermore, Al impurities (Al-O) absorb light with a wavelength of approximately 16 μm. Therefore, the presence of these oxide impurities affects light transmittance in the infrared region. For example, Si oxide impurities tend to have a significant effect on light transmittance in the wavelength range (e.g., wavelengths of 8 μm to 14 μm) often used in infrared sensors. Furthermore, Al is more easily oxidized than Si. Therefore, Al oxide impurities are easily generated and difficult to remove. Furthermore, when Si and Al are simultaneously introduced into glass, Al is likely to be preferentially oxidized over Si from a thermodynamic standpoint. The infrared absorption by these oxide impurities can be suppressed by introducing Mg and Ca, as described below.

[0031] Mg and Ca are components that are highly effective in suppressing infrared absorption caused by oxidized impurities. Specifically, Mg and Ca are more likely to be oxidized than the aforementioned components (Al, Si, Ge, S, Se, and Te), and therefore are more likely to suppress infrared absorption caused by these oxidized impurities. On the other hand, Mg oxidized impurities and Ca oxidized impurities do not absorb light in the aforementioned infrared wavelength range. Therefore, adding Mg or Ca can easily reduce the effect on light transmittance in the aforementioned wavelength range. The total content of Mg and Ca (the total amount of Mg and Ca) is 0.01% to 20%, preferably 0.01% to 15%, 0.01% to 10%, 0.01% to 8%, 0.01% to 5%, 0.05% to 5%, 0.1% to 5%, and particularly preferably 0.3% to 5%. If the amount of Mg and Ca is too small, infrared absorption may not be sufficiently suppressed. If the amount of Mg+Ca is too large, Mg-based or Ca-based crystals will precipitate, which tends to reduce light transmittance.

[0032] From the viewpoint of thermodynamics, it is preferable to use Ca rather than Mg because it reacts easily with oxygen and has a particularly large effect of suppressing infrared absorption.

[0033] The infrared transmitting glass of the present invention may contain the following optional components in addition to the above components.

[0034] Zn, Ga, In, Sn, Sb, and Bi are components that tend to broaden the vitrification range and improve the thermal stability of glass. The content of Zn+Ga+In+Sn+Sb+Bi (the total content of Zn, Ga, In, Sn, Sb, and Bi) is preferably 0% to 40%, more than 0% to 40%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, and particularly 0.1% to 5%. If the content of Zn+Ga+In+Sn+Sb+Bi is too high, vitrification becomes difficult. The contents of each of the Zn, Ga, In, Sn, Sb, and Bi components are preferably 0% to 40%, 0% to 40%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, and particularly 0.1% to 5%.

[0035] Cu and Ag are components that tend to broaden the vitrification range and improve the thermal stability of glass. The Cu+Ag content (total amount of Cu and Ag) is preferably 0% to 40%, more than 0% to 40%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, and particularly preferably 0.1% to 10%. If the Cu+Ag content is too high, vitrification becomes difficult. The contents of each of the Cu and Ag components are preferably 0% to 40%, 0% to 40%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, and particularly preferably 0.1% to 10%.

[0036] F, Cl, Br, and I are components that tend to broaden the vitrification range and increase the thermal stability of glass. The content of F+Cl+Br+I (total amount of F, Cl, Br, and I) is preferably 0% to 40%, 0% to 30%, 0% to 20%, and particularly preferably 0% to 10%. If the content of F+Cl+Br+I is too high, vitrification becomes difficult. Furthermore, weather resistance tends to decrease. The content of each of the components F, Cl, Br, and I is preferably 0% to 40%, 0% to 30%, 0% to 20%, and particularly preferably 0% to 10%.

[0037] In addition to the above components, B, C, Cr, Mn, Ti, Fe, etc. may be contained. The content of B+C+Cr+Mn+Ti+Fe (the total content of B, C, Cr, Mn, Ti, and Fe) is preferably 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, 0% to 1%, and particularly preferably 0% to less than 1%. If the content of these components is too high, it may be difficult to obtain the desired optical properties. The content of each of B, C, Cr, Mn, Ti, and Fe is preferably 0% to 10%, 0% to 5%, 0% to 1%, and particularly preferably 0% to less than 1%.

[0038] The total content of the above-mentioned optional components, Zn+Ga+In+Sn+Sb+Bi+Cu+Ag+F+Cl+Br+I+B+C+Cr+Mn+Ti+Fe, is preferably 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, and particularly preferably 0.1% to 5%. In the present invention, "Zn+Ga+In+Sn+Sb+Bi+Cu+Ag+F+Cl+Br+I+B+C+Cr+Mn+Ti+Fe X% to Y%" includes, for example, "Fe=0%, Ga+In+Sn+Sb+Bi+Cu+Ag+F+Cl+Br+I+B+C+Cr+Mn+Ti+Fe X% to Y%" and "Fe=0%, Ti=0%, In+Sn+Sb+Bi+Cu+Ag+F+Cl+Br+I+B+C+Cr+Mn+Ti+Fe X% to Y%".

[0039] As is a component that enhances the thermal stability of glass. However, because As is a toxic component, from the viewpoint of reducing the burden on the environment, the As content is preferably 30% or less, 25% or less, 20% or less, 10% or less, 5% or less, and particularly preferably substantially zero.

[0040] It is preferable that the material is substantially free of Cd, Tl, and Pb, which can minimize the environmental impact.

[0041] The ratio (B+Al+Ga+In) / (S+Se+Te) of the total content (mol %) of Group 13 elements (B, Al, Ga, In) to the total content (mol %) of chalcogen elements (S, Se, Te) is preferably 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, and particularly preferably 0.2 or less. The lower limit is preferably, for example, 0.01 or more. When the ratio of the content of Group 13 elements to the content of chalcogen elements satisfies the above range, vitrification becomes easier.

[0042] The ratio (C+Si+Ge+Sn) / (S+Se+Te) of the content of Group 14 elements (C, Si, Ge, Sn) to the content of chalcogen elements (S, Se, Te) is preferably 0.7 or less, 0.6 or less, 0.5 or less, particularly 0.4 or less. The lower limit is preferably, for example, 0.01 or more. When the content ratio of Group 14 elements to chalcogen elements satisfies the above range, vitrification becomes easier.

[0043] The infrared transmitting glass of the present invention preferably has an infrared absorption edge wavelength of 15 μm or more, 16 μm or more, particularly 17 μm or more. The larger the infrared absorption edge wavelength, the longer the infrared wavelength side that can be transmitted. Here, the infrared absorption edge wavelength means the longest wavelength side at which light transmittance is 10% at a thickness of 2 mm in the infrared region of wavelengths of 1 μm or more.

[0044] The infrared transmitting glass of the present invention can be produced, for example, as follows. First, raw materials are mixed to obtain the desired composition. Next, the mixed raw materials are placed in a quartz glass ampoule that has been heated and evacuated, and the ampoule is sealed with an oxygen burner while evacuating. Next, the sealed quartz glass ampoule is kept at about 650°C to 1000°C for 6 to 12 hours. After that, the ampoule is rapidly cooled to room temperature to obtain the infrared transmitting glass.

[0045] The raw materials may be elemental raw materials (Ge, Ga, Si, Te, Ag, I, etc.), compound raw materials (GeTe4, Ga2Te3, AgI, etc.), or a combination of these.

[0046] The obtained infrared transmitting glass can be processed into a predetermined shape (disk, lens, etc.) to produce an optical element.

[0047] For the purpose of improving transmittance, an anti-reflection film may be formed on one or both surfaces of the optical element. Examples of methods for forming the anti-reflection film include vacuum deposition, ion plating, and sputtering.

[0048] After forming the antireflection coating on the infrared-transmitting glass, the glass may be processed into a predetermined shape. However, because the antireflection coating is likely to peel off during the processing step, it is preferable to form the antireflection coating after processing the infrared-transmitting glass into a predetermined shape, unless there are special circumstances.

[0049] Thus, the infrared transmitting glass of the present invention has a composition containing, in mole percent, 20% to 90% of S + Se + Te, more than 0% to 40% of Ge, more than 0% to 50% of Al + Si, and 0.01% to 20% of Mg + Ca. The infrared transmitting glass having this composition is likely to suppress infrared absorption by oxide impurities and exhibit excellent light transmission properties in the infrared region. [Example]

[0050] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0051] Tables 1 to 4 show Examples 1 to 26 of the present invention and Comparative Examples 27 and 28.

[0052] [Table 1]

[0053] [Table 2]

[0054] [Table 3]

[0055] [Table 4]

[0056] The samples of the examples and comparative examples were prepared as follows. First, a quartz glass ampoule was heated and evacuated, and then raw materials were mixed to obtain the glass compositions shown in Tables 1 to 4 and placed in the quartz glass ampoule. Next, the quartz glass ampoule was sealed using an oxygen burner. Next, the sealed quartz glass ampoule was placed in a melting furnace, where the temperature was raised to 650 to 1000°C at a rate of 10 to 40°C / hour and then maintained for 6 to 12 hours. During this period, the quartz glass ampoule was turned upside down to stir the melt. Finally, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to obtain a sample. The light transmittance of the obtained sample in the infrared range was measured to determine whether or not it had infrared absorption.

[0057] Using a sample with a thickness of 2 mm, the light transmittance in the infrared region of wavelengths from 8 μm to 14 μm was measured. In the obtained transmittance spectrum, wavelength regions where the transmittance decreased by 10% or more from the light transmittance at a wavelength of 10 μm were judged to be oxidation absorption, and the corresponding section in Tables 1 to 4 was marked with "Yes." If the wavelength region was 13 μm to 14 μm, it was judged to be Ge oxidation absorption, and if it was 14 μm to 18 μm, it was judged to be Al oxidation absorption. If no absorption was observed, it was marked with "No."

[0058] As is clear from Tables 1 to 4, by adding Mg or Ca, it is possible to suppress infrared absorption caused by bonding of Ge, Al with oxygen. [Industrial Applicability]

[0059] The infrared transmitting glass of the present invention can be suitably used for optical elements such as filters and lenses used in infrared sensors, infrared cameras, etc.

Claims

1. An infrared transmitting glass containing, in mole percent, 20% to 90% of S + Se + Te, more than 0% to 40% of Ge, more than 0% to 50% of Al + Si, and 3% to 20% of Mg + Ca.

2. 2. The infrared transmitting glass according to claim 1, containing, in mole percent, more than 0% to 50% of Al.

3. 3. The infrared transmitting glass according to claim 1, containing, in mole percent, more than 0% to 90% of Te.

4. 4. The infrared transmitting glass according to claim 1, comprising, in mole percent, 0% to 40% of Zn+Ga+In+Sn+Sb+Bi, 0% to 40% of Cu+Ag, 0% to 40% of F+Cl+Br+I, and 0% to 40% of B+C+Cr+Mn+Ti+Fe.

5. 5. The infrared transmitting glass according to claim 1, wherein the As content is 30% or less.

6. 6. The infrared transmitting glass according to claim 1, wherein a ratio of the content of the Group 13 elements to the content of S+Se+Te, (B+Al+Ga+In) / (S+Se+Te), is 0.7 or less.

7. 7. The infrared transmitting glass according to claim 1, wherein a ratio of the content of the Group 14 elements to the content of S+Se+Te, (C+Si+Ge+Sn) / (S+Se+Te), is 0.7 or less.

8. An infrared transmitting glass containing, in mole percent, 20% to 90% of S + Se + Te, more than 0% to 40% of Ge, more than 0% to 50% of Al + Si, and 0.01% to 20% of Ca.

9. An optical element using the infrared transmitting glass according to any one of claims 1 to 8.

10. An infrared sensor using the optical element according to claim 9.

11. An infrared camera using the optical element according to claim 9.

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