Infrared transmitting glass

Abstract

To provide an infrared transmitting glass that has excellent light transmitting properties in an infrared region and also has high dispersion characteristics.SOLUTION: An infrared transmitting glass contains, in mol%, S+Se+Te of 20% to 90%, Ge of more than 0% to 40%, and Al+Si of more than 0% to 50%.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 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 Summary of the Invention [Problem to be solved by the invention]

[0006] Generally, optical elements such as lenses are often used to correct aberrations by combining multiple materials with different optical constants. Therefore, there is a demand for an increased variety of glass materials for infrared-transmitting materials, particularly chalcogenide glass, in order to improve the degree of freedom in aberration correction.

[0007] The chalcogenide glass described in Patent Document 1 has a relatively large Abbe number and low dispersion, and therefore there has been a demand for chalcogenide glass that has infrared transmission properties equivalent to those of the above chalcogenide glass and also has high dispersion.

[0008] In view of the above, an object of the present invention is to provide an infrared transmitting glass having excellent light transmission characteristics in the infrared region and high dispersion characteristics. [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, and more than 0% to 50% of Al+Si.

[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 percent, more than 0% to 50% of Al and more than 0% to 50% of Si.

[0012] The infrared transmitting glass of the present invention preferably contains, in mole %, more than 0% to 90% of Te.

[0013] 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.

[0014] The infrared transmitting glass of the present invention preferably has an As content of 30% or less.

[0015] 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 0.4 or less.

[0016] 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.

[0017] The infrared transmitting glass of the present invention preferably has an infrared absorption edge wavelength of 15 μm or more.

[0018] The infrared transmitting glass of the present invention preferably has an Abbe number ν10 at a wavelength of 10 μm of 200 or less.

[0019] The infrared transmitting glass of the present invention preferably has a refractive index n10 at a wavelength of 10 μm of 2.2 or more.

[0020] The optical element of the present invention is characterized by using the infrared transmitting glass described above.

[0021] The infrared sensor of the present invention is characterized by using the optical element described above.

[0022] The infrared camera of the present invention is characterized by using the optical element described above. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide an infrared transmitting glass having excellent light transmission characteristics in the infrared region and high dispersion characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0024] 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, and more than 0% to 50% of Al + Si. The reasons for specifying the glass composition in this way and the contents of each component are explained below. In the following explanation, "%" means "mol percent" unless otherwise specified.

[0025] 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:

[0026] 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.

[0027] 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%.

[0028] 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.

[0029] It is sufficient that at least one of S, Se and Te is contained, but it is particularly preferable that Te is contained, since it has little absorption in the far infrared region.

[0030] 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.

[0031] Al and Si are components that form the glass skeleton and reduce the Abbe number, thereby making the glass highly dispersible. 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, the Abbe number increases, which tends to result in low dispersion. If the Al+Si content is too high, Al-based or Si-based crystals precipitate, which tends to reduce light transmittance. The preferred ranges for the content of each component are as follows:

[0032] 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%.

[0033] 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%.

[0034] While it is sufficient for the glass to contain at least one of Al and Si, it is particularly preferable for the glass to contain Al. This helps to reduce the impact of oxide impurities on light transmittance in the wavelength range of 8 μm to 14 μm. Specifically, Si oxide impurities (Si—O) absorb light with a wavelength of approximately 9 μm, which tends to significantly affect light transmittance in the wavelength range (8 μm to 14 μm) often used in infrared sensors. On the other hand, Al impurities (Al—O) absorb light with a wavelength of approximately 16 μm, which tends to reduce the impact on light transmittance in the above wavelength range. From the perspective of obtaining a high-dispersion glass, it is particularly preferable for the glass to contain both Al and Si. This makes it easier to obtain an infrared-transmitting glass with even higher dispersion.

[0035] The infrared transmitting glass of the present invention may contain the following optional components in addition to the above components.

[0036] 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%.

[0037] 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%.

[0038] 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%.

[0039] 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%.

[0040] The total content of the above-mentioned optional components, Zn+Ga+In+Sn+Sb+Bi+F+Cl+Br+I+Ag+Cu+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%.

[0041] 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.

[0042] It is preferable that the material is substantially free of Cd, Tl, and Pb, which can minimize the environmental impact.

[0043] 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 0.4 or less, 0.3 or less, particularly 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.

[0044] 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.

[0045] 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.

[0046] The infrared transmitting glass of the present invention preferably has an Abbe number (ν10) at a wavelength of 10 μm of not more than 200, not more than 190, not more than 180, not more than 170, particularly not more than 160. There is no particular upper limit to the Abbe number, but in practice it is 10 or more.

[0047] The infrared transmitting glass of the present invention preferably has a refractive index (n10) at a wavelength of 10 μm of 2.2 or more, 2.4 or more, 2.6 or more, 2.8 or more, particularly 3.0 or more. There is no particular upper limit to the refractive index, but in practice it is less than 4.5.

[0048] 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.

[0049] 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.

[0050] The obtained infrared transmitting glass can be processed into a predetermined shape (disk, lens, etc.) to produce an optical element.

[0051] 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.

[0052] 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.

[0053] As described above, 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, and more than 0% to 50% of Al + Si. The infrared transmitting glass having this composition has excellent light transmission characteristics in the infrared range, a small Abbe number, and high dispersion. Therefore, it is suitable as a new glass material for optical elements, and can increase the degree of freedom in aberration correction. [Example]

[0054] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0055] Tables 1 to 3 show Examples 1 to 20 of the present invention and Comparative Examples 21 to 23.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] 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 3 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 infrared absorption edge wavelength, refractive index, and Abbe number of the obtained sample were determined.

[0060] Using a 2 mm thick sample, the light transmittance in the infrared region was measured to determine the infrared absorption edge wavelength, which was the longest wavelength at which the light transmittance reached 10% in the infrared region of wavelengths 1 μm or more.

[0061] The refractive indices n8, n10, and n12 at wavelengths of 8 μm, 10 μm, and 12 μm were measured using a refractometer. The Abbe number (ν10) at a wavelength of 10 μm was calculated using the following formula:

[0062] Abbe number (ν10)={(n10-1) / (n8-n12)}

[0063] As is clear from Tables 1 to 3, the samples of the examples had infrared absorption edge wavelengths of 16 μm or more and Abbe numbers ν10 of 114 to 197. On the other hand, the samples of the comparative examples had Abbe numbers ν10 of 242 to 257. [Industrial Applicability]

[0064] 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 mol %, 20% to 90% of S + Se + Te, more than 0% to 40% of Ge, 0.1% to 50% of Al, and 0.1% to 50% of Si, and having an Abbe number ν10 at a wavelength of 10 μm of 200 or less.

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

3. 3. The infrared transmitting glass according to claim 1 or 2, containing, 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.

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

5. 5. 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 0.4 or less.

6. 6. 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.

7. 7. The infrared transmitting glass according to claim 1, wherein the infrared absorption edge wavelength is 15 μm or more.

8. 8. The infrared transmitting glass according to claim 1, which has a refractive index n10 at a wavelength of 10 μm of 2.2 or more.

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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