Infrared transmissive glass, optical element, and infrared camera

Abstract

The present invention provides: infrared transmissive glass that has excellent infrared transmissivity and a high refractive index; an optical element; and an infrared camera. Provided is infrared transmissive glass comprising, in terms of at%, 50-90% S+Se+Te, 0.1-49.9% Al+Ga, 0.1-49.9% Si+Sn, 0-50% S, 0-25% Se, and 0% to less than 5% Ge.

Description

Infrared transmitting glass, optical elements and infrared cameras

[0001] The present invention relates to an infrared-transmitting glass, an optical element, and an infrared camera.

[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) 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, Si has a lower light transmittance in the infrared range than Ge, which is disadvantageous for improving the performance of infrared cameras.

[0004] Therefore, various infrared-transmitting glasses (chalcogenide glasses) have been proposed as materials to replace Ge and Si (Patent Document 1).

[0005] International Publication No. 2017 / 086227

[0006] Optical elements such as lenses are often used to correct aberrations by combining multiple materials with different optical constants. Therefore, infrared-transmitting materials, particularly chalcogenide glass, are required to have high infrared transmittance and a high refractive index in order to improve the degree of freedom in aberration correction.

[0007] In view of the above, an object of the present invention is to provide an infrared transmitting glass, an optical element, and an infrared camera that have excellent infrared transmittance and a high refractive index.

[0008] The following describes various aspects of an infrared transmitting glass, an optical element, and an infrared camera that solve the above problems.

[0009] The infrared transmitting glass of Aspect 1 is characterized by containing, in atomic %, 50% to 90% of S + Se + Te, 0.1% to 49.9% of Al + Ga, 0.1% to 49.9% of Si + Sn, 0% to 50% of S, 0% to 25% of Se, and 0% to less than 5% of Ge.

[0010] The infrared transmitting glass of embodiment 2 is the same as embodiment 1, and preferably contains, in atomic percent, 20% or more of Te.

[0011] The infrared transmitting glass of Aspect 3 is characterized by containing, in atomic %, 50% to 90% of Te, 0.1% to 49.9% of Al+Ga, 0.1% to 49.9% of Si+Sn, 0% to 50% of S, 0% to 25% of Se, and 0% to less than 5% of Ge.

[0012] The infrared transmitting glass of Aspect 4, in any one of Aspects 1 to 3, preferably contains, in atomic %, 0.1% to less than 15% of Al.

[0013] The infrared transmitting glass of Aspect 5 is any one of Aspects 1 to 4, and preferably contains 0.1% to 49.9% of Si.

[0014] The infrared transmitting glass of Aspect 6 is any one of Aspects 1 to 5, and preferably contains, in atomic %, 0 to 40% of Ag.

[0015] The infrared transmitting glass of Aspect 7 is any one of Aspects 1 to 6, and preferably contains, in atomic %, 0% to 40% of Cl+Br+I.

[0016] The infrared transmitting glass of Aspect 8 is any one of Aspects 1 to 7, wherein (Al+Ga) / (S+Se+Te) is preferably 0.01 to less than 1.

[0017] The infrared transmitting glass of Aspect 9 is any one of Aspects 1 to 8, wherein (Si+Sn) / (S+Se+Te) is preferably 0.01 to less than 1.

[0018] The optical element of Aspect 10 is preferably formed using the infrared transmitting glass of any one of Aspects 1 to 9.

[0019] The infrared camera of Aspect 11 preferably uses the optical element of Aspect 10.

[0020] According to the present invention, it is possible to provide an infrared transmitting glass, an optical element, and an infrared camera that have excellent infrared transmittance and a high refractive index.

[0021] The infrared-transmitting glass of the present invention is characterized by containing, in atomic percent, 50% to 90% of S + Se + Te, 0.1% to 49.9% of Al + Ga, 0.1% to 49.9% of Si + Sn, 0% to 50% of S, 0% to 25% of Se, and 0% to less than 5% of Ge. The infrared-transmitting glass of the present invention is also characterized by containing, in atomic percent, 50% to 90% of Te, 0.1% to 49.9% of Al + Ga, 0.1% to 49.9% of Si + Sn, 0% to 50% of S, 0% to 25% of Se, and 0% to less than 5% of Ge. The reasons for specifying the glass composition as described above and the content of each component are explained below. In the following description, unless otherwise specified, "%" means "atomic percent." In the present invention, "x + y + z + ..." means the total content of each component. Here, each component does not necessarily have to be contained as an essential component, and it is acceptable for some components not to be contained (0% content). Furthermore, "x + y + z + ... A% to B%" includes, for example, "x = 0%, y + z + ... A% to B%" and "x = 0%, y = 0%, z + ... A% to B%".

[0022] 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 50% to 90%. More specifically, the lower limit of the content of S + Se + Te is 50% or more, preferably 55% or more, and particularly 60% or more, and the upper limit of the content of S + Se + Te is 90% or less, preferably 88% or less, and particularly preferably 85% or less. 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 contents of each component are as follows:

[0023] S is a component that forms the glass skeleton, but it is also a component that easily reduces light transmittance at wavelengths of 10 μm or more. Therefore, from the viewpoint of improving light transmittance in the infrared region, the S content is 0% to 50%, and preferably 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, and particularly preferably substantially free of S. In this specification, "substantially free of S" means that it is not intentionally included in the raw materials, and does not exclude contamination at the impurity level. Objectively, this refers to a content of each component of less than 0.1%.

[0024] Se is a component that forms the glass skeleton, but is also a highly toxic component. Therefore, from the viewpoint of reducing the burden on the environment, the Se content is 0% to 25%, and preferably 20% or less, 10% or less, and particularly preferably substantially zero.

[0025] Te is a component that forms the glass skeleton and is particularly effective in increasing light transmittance in the wavelength range of 10 μm or more. The Te content is preferably 0% to 90%. More specifically, the lower limit of the Te content is preferably 0% or more, 10% or more, 20% or more, 30% or more, 40% or more, and particularly 50% or more, and the upper limit of the Te content is preferably 90% or less, 88% or less, and particularly 85% or less. From the viewpoint of increasing light transmittance particularly in the wavelength range of 15 μm or more, the lower limit of the Te content is preferably more than 50%, and particularly 60% or more.

[0026] Al and Ga are components that easily form a glass skeleton. The content of Al+Ga (total amount of Al and Ga) is 0.1% to 49.9%. More specifically, the lower limit of the content of Al+Ga is 0.1% or more, and preferably 1% or more, 2% or more, and particularly 3% or more, and the upper limit of the content of Al+Ga is 49.9% or less, and preferably 40% or less, 30% or less, 20% or less, and particularly 15% or less. If the content of Al+Ga is too low, vitrification becomes difficult. If the content of Al+Ga is too high, the internal transmittance tends to decrease. The preferred ranges of the contents of each component are as follows:

[0027] Al is a component that easily forms a glass skeleton and also a component that easily reduces the Abbe number and makes the glass highly dispersible. Furthermore, when Al is contained together with Si, it is easy to suppress light absorption by Si oxide impurities. The Al content is preferably 0% to 49.9%, and more preferably 0.1% to less than 15%. More specifically, the lower limit of the Al content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Al content is preferably 49.9% or less, 40% or less, 30% or less, 20% or less, 15% or less, less than 15%, 10% or less, 8% or less, 7% or less, 5% or less, and particularly preferably 4% or less. If the Al content is too high, the internal transmittance is likely to decrease.

[0028] Ga is a component that easily forms a glass skeleton and is also a component that easily suppresses a decrease in light transmittance at wavelengths of 10 μm or more. The Ga content is preferably 0% to 49.9%. More specifically, the lower limit of the Ga content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Ga content is preferably 49.9% or less, 40% or less, 30% or less, 20% or less, 15% or less, less than 15%, and particularly preferably 10% or less. If the Ga content is too high, vitrification becomes more difficult.

[0029] It is preferable that (Al+Ga) / (S+Se+Te) is 0.01 to less than 1. More specifically, it is preferable that the lower limit of (Al+Ga) / (S+Se+Te) is 0.01 or more, particularly 0.03 or more, and it is preferable that the upper limit of (Al+Ga) / (S+Se+Te) is less than 1, 0.8 or less, 0.5 or less, particularly 0.3 or less. When (Al+Ga) / (S+Se+Te) satisfies the above value, vitrification becomes easy. It should be noted that "(Al+Ga) / (S+Se+Te)" means the value obtained by dividing the total amount of Al and Ga by the total amount of S, Se, and Te.

[0030] Si and Sn are components that form a glass skeleton. The Si+Sn content (total amount of Si and Sn) is 0.1% to 49.9%. More specifically, the lower limit of the Si+Sn content is preferably 0.1% or more, 1% or more, 2% or more, and particularly 5% or more, and the upper limit of the Si+Sn content is preferably 49.9% or less, 40% or less, 30% or less, 25% or less, 22% or less, and particularly 20% or less. If the Si+Sn content is too low, vitrification becomes difficult. If the Si+Sn content is too high, the internal transmittance tends to decrease. The preferred ranges of the contents of each component are as follows. Among Si and Sn, it is preferable to contain Si, which is particularly likely to form a glass skeleton.

[0031] Si is a component that is particularly likely to form a glass skeleton and is also a component that tends to reduce the Abbe number and make the glass highly dispersible. The Si content is preferably 0% to 49.9%. More specifically, the lower limit of the Si content is preferably 0% or more, 0.1% or more, 1% or more, 2% or more, 5% or more, 8% or more, and particularly 10% or more, and the upper limit of the Si content is preferably 49.9% or less, 40% or less, 30% or less, 25% or less, 22% or less, and particularly 20% or less. If the Si content is too high, the internal transmittance tends to decrease.

[0032] Sn is a component that easily forms a glass skeleton and also easily increases the refractive index. The Sn content is preferably 0% to 49.9%. More specifically, the lower limit of the Sn content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Sn content is preferably 49.9% or less, 40% or less, 30% or less, 20% or less, and particularly preferably 15% or less. If the Sn content is too high, the internal transmittance is likely to decrease.

[0033] It is preferable that (Si + Sn) / (S + Se + Te) is 0.01 to less than 1. More specifically, it is preferable that the lower limit of (Si + Sn) / (S + Se + Te) is 0.01 or more, 0.05 or more, particularly 0.1 or more, and it is preferable that the upper limit of (Si + Sn) / (S + Se + Te) is less than 1, 0.5 or less, particularly 0.3 or less. When (Si + Sn) / (S + Se + Te) satisfies the above value, vitrification becomes easy. Here, "(Si + Sn) / (S + Se + Te)" means the value obtained by dividing the total amount of Si and Sn by the total amount of S, Se, and Te.

[0034] Ge is a component that forms the glass skeleton, but it is also a component that tends to increase the temperature coefficient of refractive index. It also tends to increase raw material costs. Therefore, the Ge content is 0% to less than 5%, preferably 3% or less, 1% or less, and particularly preferably substantially none.

[0035] From the viewpoint of obtaining desired optical properties, the lower limit of the content of S+Se+Te+Al+Ga+Si+Sn (total amount of S, Se, Te, Al, Ga, Si, and Sn) is preferably 50.2% or more, 51% or more, 60% or more, 70% or more, 80% or more, and particularly preferably 85% or more. The upper limit of the content of S+Se+Te+Al+Ga+Si+Sn is not particularly limited, but from the viewpoint of containing optional components, it may be 100% or less, 99% or less, 98% or less, and particularly preferably 95% or less.

[0036] The infrared transmitting glass of the present invention may contain the following optional components.

[0037] In is a component that easily increases the refractive index. The In content is preferably 0% to 49.8%. More specifically, the lower limit of the In content is preferably 0% or more, 0.1% or more, and particularly preferably 1% or more, and the upper limit of the In content is preferably 49.8% or less, 45% or less, 40% or less, 30% or less, 20% or less, 10% or less, and particularly preferably 5% or less. If the In content is too high, vitrification becomes difficult.

[0038] Ag is a component that increases the stability of the glass and also tends to suppress a decrease in light transmittance at wavelengths of 10 μm or more. The Ag content is preferably 0% to 40%. More specifically, the lower limit of the Ag content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Ag content is preferably 40% or less, 30% or less, 20% or less, 15% or less, and particularly preferably 10% or less. If the Ag content is too high, vitrification becomes difficult.

[0039] Cl, Br, and I are components that broaden the vitrification range and tend to improve the thermal stability of glass. The lower limit of the Cl + Br + I content (total amount of Cl, Br, and I) is preferably 0% or more, 1% or more, and particularly 2% or more, and the upper limit of the Cl + Br + I content is preferably 40% or less, 20% or less, 15% or less, and particularly 10% or less. If the Cl + Br + I content is too high, vitrification becomes difficult. Furthermore, weather resistance tends to decrease. The lower limit of the content of each of the Cl, Br, and I components is preferably 0% or more, 1% or more, and particularly 2% or more, and the upper limit of the content of each of the Cl, Br, and I components is preferably 20% or less, 15% or less, and particularly 10% or less.

[0040] Bi is a component that easily increases the refractive index. The Bi content is preferably 0% to 49.8%. More specifically, the lower limit of the Bi content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Bi content is preferably 49.8% or less, 45% or less, 40% or less, 30% or less, 20% or less, and particularly preferably 15% or less. If the Bi content is too high, vitrification becomes difficult.

[0041] Sb is a component that easily forms a glass skeleton and also easily increases the refractive index. The Sb content is preferably 0% to 49.8%. More specifically, the lower limit of the Sb content is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 2% or more, and the upper limit of the Sb content is preferably 49.8% or less, 45% or less, 40% or less, 30% or less, 20% or less, 15% or less, 10% or less, and particularly preferably 5% or less. If the Sb content is too high, vitrification becomes difficult.

[0042] Zn and Cu are components that broaden the vitrification range and tend to improve the thermal stability of glass. The Zn + Cu content (total amount of Zn and Cu) is preferably 0% to 49.8%. More specifically, the lower limit of the Zn + Cu content is preferably 0% or more, 0.1% or more, and particularly 1% or more, and the upper limit of the Zn + Cu content is preferably 49.8% or less, 45% or less, 40% or less, 30% or less, 20% or less, 10% or less, and particularly 5% or less. If the Zn + Cu content is too high, vitrification becomes difficult. Note that the contents of each of the Zn and Cu components are preferably 0% or more, 0.1% or more, and particularly 1% or more, and the upper limit of the Zn and Cu content is preferably 49.8% or less, 45% or less, 40% or less, 30% or less, 20% or less, 10% or less, and particularly 5% or less.

[0043] The infrared transmitting glass of the present invention may contain B, C, Cr, Mn, Ti, Fe, and the like. 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%. More specifically, the upper limit of the content of B+C+Cr+Mn+Ti+Fe is preferably 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 1% or less, and particularly preferably less than 1%. If the content of these components is too high, it may be difficult to obtain the desired optical properties. The lower limit of the content of B+C+Cr+Mn+Ti+Fe is not particularly limited, but may be 0% or more, or 0.1% or more. The upper limit of the content of each of B, C, Cr, Mn, Ti, and Fe is preferably 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 1% or less, particularly preferably less than 1%, and the lower limit of the content of each of B, C, Cr, Mn, Ti, and Fe is not particularly limited, but may be 0% or more, or 0.1% or more.

[0044] As is a component that enhances the thermal stability of glass. However, since As is a toxic component, from the viewpoint of reducing the burden on the environment, it is preferable that the As content be 0% to 30%, 25% or less, 20% or less, 10% or less, 5% or less, and particularly that As is not contained at all.

[0045] It is preferable that the material is substantially free of Cd, Tl, and Pb, which can minimize the environmental impact.

[0046] The infrared transmitting glass of the present invention preferably has a refractive index (n10) at 25°C and a wavelength of 10 μm of 2.3 or more, particularly 2.5 or more. By using an infrared transmitting glass having such a refractive index, optical elements exhibiting a relatively high refractive index in the infrared wavelength region can be produced. There is no particular upper limit to the refractive index, but in practice it is 4 or less, particularly 3.5 or less.

[0047] The infrared transmitting glass of the present invention has a temperature coefficient of refractive index (dn / dT) of 300×10 －６ Below, 200 x 10 －６ Below, especially 100 x 10 －６ It is preferable that the temperature coefficient of refractive index is equal to or less than 1×10. Here, the temperature coefficient of refractive index means the gradient of the change in the refractive index (n10) at a wavelength of 10 μm at temperatures between −40 and 80° C. By using an infrared transmitting glass having such a temperature coefficient of refractive index, it is possible to manufacture an optical element in which the change in refractive index in the infrared wavelength range with respect to temperature change is small. There is no particular lower limit to the temperature coefficient of refractive index, but in reality it is 1×10 －６ Above, especially 10x10 －６ That's all.

[0048] The infrared transmitting glass of the present invention preferably has an Abbe number (ν10) at a wavelength of 10 μm of 250 or less, 240 or less, and particularly preferably 230 or less. By using an infrared transmitting glass having such an Abbe number, it is possible to produce optical elements that exhibit relatively high dispersion in the infrared wavelength range. There is no particular lower limit to the Abbe number, but in practice it is 100 or more.

[0049] The infrared transmitting glass of the present invention preferably has an infrared absorption edge wavelength of 15 μm or more, particularly 18 μm or more. The larger the infrared absorption edge wavelength, the longer the infrared wavelength side the glass can transmit. 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.

[0050] The infrared transmitting glass of the present invention has excellent infrared transmittance and a high refractive index, and is therefore preferably used in optical elements such as filters and lenses used in infrared sensors, infrared cameras, etc. In other words, the optical element of the present invention is preferably made using the infrared transmitting glass described above. Furthermore, the infrared camera of the present invention is preferably made using the optical element described above.

[0051] 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 approximately 650°C to 1000°C for 6 to 12 hours. After that, the ampoule is rapidly cooled to room temperature, thereby obtaining the infrared transmitting glass.

[0052] The raw material may be an elemental raw material (Ga, Si, Te, Ag, I, etc.), or a compound raw material (Ga ２ Te ３ , AgI, etc.) may be used. These may also be used in combination.

[0053] The obtained infrared transmitting glass can be processed into a predetermined shape (disc, lens, etc.) to produce an optical element.

[0054] 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.

[0055] 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.

[0056] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0057] Tables 1-12 show Examples 1-103 of the present invention.

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] The 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 12 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 held for 6 to 12 hours. During this holding time, 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 refractive index and infrared absorption edge wavelength of the obtained sample were determined.

[0071] The refractive index n at 25°C and a wavelength of 10 μm was measured using a refractometer (infrared spectrorefractometer manufactured by Bunkoukeiki Co., Ltd.). １０ The refractive index was measured at temperatures from −40 to 80° C., and the temperature coefficient of the refractive index dn / dT was calculated.

[0072] The infrared absorption edge wavelength was determined by measuring the light transmittance of a 2 mm thick sample using a Fourier transform infrared spectrophotometer (Frontier, manufactured by PerkinElmer). The infrared absorption edge wavelength was the longest wavelength at which the light transmittance was 10% for a 2 mm thick sample in the infrared region with wavelengths of 1 μm or more.

[0073] As is clear from Tables 1 to 12, Examples 1 to 103 have a high infrared absorption edge wavelength of 18 μm or more and a refractive index n １０ The temperature coefficient of refractive index dn / dT was 165×10 －６ It became lower as follows.

[0074] 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 atomic percent, 50% to 90% of S+Se+Te, 0.1% to 49.9% of Al+Ga, 0.1% to 49.9% of Si+Sn, 0% to 50% of S, 0% to 25% of Se, and 0% to less than 5% of Ge.

2. The infrared transmitting glass according to claim 1, containing, in atomic percent, 20% or more of Tellurium.

3. An infrared transmitting glass containing, in atomic percent, 50% to 90% Te, 0.1% to 49.9% Al+Ga, 0.1% to 49.9% Si+Sn, 0% to 50% S, 0% to 25% Se, and 0% to less than 5% Ge.

4. The infrared transmitting glass according to any one of claims 1 to 3, containing, in atomic percent, 0.1% to less than 15% of Al.

5. An infrared transmitting glass according to any one of claims 1 to 3, containing, in atomic %, 0.1 to 49.9% of Si.

6. An infrared transmitting glass according to any one of claims 1 to 3, containing, in atomic %, 0 to 40% of Ag.

7. An infrared transmitting glass according to any one of claims 1 to 3, containing, in atomic %, 0% to 40% of Cl+Br+I.

8. An infrared transmitting glass according to any one of claims 1 to 3, wherein (Al+Ga) / (S+Se+Te) is 0.01 or more and less than 1.

9. An infrared transmitting glass according to any one of claims 1 to 3, wherein (Si+Sn) / (S+Se+Te) is 0.01 or more and less than 1.

10. An optical element comprising the infrared transmitting glass according to any one of claims 1 to 3.

11. An infrared camera using the optical element according to claim 10.