Infrared transmitting glass

Abstract

To provide glass which has high sensitivity to infrared light and is suitable for infrared sensor applications.SOLUTION: An infrared transmission glass contains, on a molar basis, greater than 0 to 50% of Ge, greater than 0 to 50% of Ga, 0 to 50% of Ag, 30 to 90% of Te, 0 to 40% of Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs, and 0 to 40% of F+Cl+Br+I. This glass is free from nodules with a long diameter of 500 μm or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an infrared transmitting glass for use in an infrared sensor or the like. [Background technology]

[0002] Infrared sensors used for detecting living organisms at night are installed in vehicle night vision and security systems. Infrared sensors detect infrared rays with wavelengths of approximately 8 to 14 μm emitted from living organisms, so optical elements such as filters and lenses that transmit infrared rays in that wavelength range are installed in front of the sensor unit.

[0003] Materials for such optical elements include Ge and ZnSe. These are crystalline materials, so they are difficult to process and are difficult to process into complex shapes such as aspherical lenses. This makes them difficult to mass-produce, and it is also difficult to miniaturize infrared sensors.

[0004] In view of this, chalcogenide glass has been proposed as a glassy material that transmits infrared rays with wavelengths of about 8 to 14 μm and is relatively easy to process (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Publication No. 1642870 Summary of the Invention [Problem to be solved by the invention]

[0006] The glass described in Patent Document 1 has poor sensitivity to infrared rays, and there is a risk that the infrared sensor will not function satisfactorily.

[0007] In view of the above, an object of the present invention is to provide a glass that has excellent sensitivity to infrared rays and is suitable for use as an infrared sensor. [Means for solving the problem]

[0008] As a result of various experiments, the inventors have discovered that Ga2O3 particles generated during melting cause multiple scattering, thereby reducing the infrared transmission characteristics.

[0009] The infrared transmitting glass of the present invention is characterized by containing, in mole percent, more than 0 to 50% Ge, more than 0 to 50% Ga, 0 to 50% Ag, 30 to 90% Te, 0 to 40% Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs, and 0 to 40% F+Cl+Br+I, and by being free of bumps with a major axis of 500 μm or more.

[0010] The infrared transmitting glass of the present invention is characterized by containing, in mole percent, Ge more than 0 to 50%, Ga more than 0 to 50%, Ag 0 to 50%, Te 30 to 90%, Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs 0 to 40%, and F+Cl+Br+I 0 to 40%, and having an internal transmittance of 90% or more at a wavelength of 12 μm. In this specification, "○+○+···" means the total content of at least one component arbitrarily selected from the corresponding components. For example, the above description means "the total content of at least one component selected from the group consisting of Si, Al, Ti, Cu, In, Sn, Bi, Cr, Sb, Zn, Mn, and Cs". It also includes a configuration that does not contain one or more components in the relevant constituent elements. In this case, for example, it may be described as Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs 0-40% (but Si is not included). In addition, the "internal transmittance" refers to the transmittance excluding the surface reflection loss on the entrance side and exit side of the sample. In addition, the "internal transmittance" in the present invention refers to the internal transmittance at a thickness of 2 mm, and specifically, it is calculated from the measured values ​​of the transmittance including the surface reflection loss at thicknesses of 2 mm and 10 mm.

[0011] It is preferable that the infrared transmitting glass of the present invention is substantially free of Cd, Tl and Pb.

[0012] The infrared transmitting glass of the present invention preferably has an infrared absorption edge wavelength of 20 μm or more at a thickness of 2 mm. In the present invention, the term "infrared absorption edge wavelength" refers to a wavelength at which the light transmittance is 20% in the infrared region of 8 μm or more.

[0013] The optical element of the present invention is characterized by using the infrared transmitting glass described above.

[0014] The infrared sensor of the present invention is characterized by using the above optical element. Effect of the Invention

[0015] The infrared transmitting glass of the present invention has excellent sensitivity to infrared rays and is suitable for use as an infrared sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The infrared transmitting glass of the present invention contains, in mole percent, more than 0 to 50% Ge, more than 0 to 50% Ga, 0 to 50% Ag, 30 to 90% Te, 0 to 40% Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs, and 0 to 40% F+Cl+Br+I. The reason for defining the glass composition in this way will be explained below. In the following description of the content of each component, "%" means "mol %" unless otherwise specified.

[0017] Ge is an essential component for forming a glass skeleton. The Ge content is more than 0 to 50%, and is preferably 2 to 40%, 4 to 35%, 5 to 30%, 7 to 25%, and particularly 10 to 20%. If the Ge content is too low, vitrification becomes difficult. On the other hand, if the Ge content is too high, Ge-based crystals are precipitated, making it difficult for infrared rays to transmit, and raw material costs tend to increase.

[0018] Ga is an essential component for increasing the thermal stability (vitrification stability) of glass. The Ga content is more than 0 to 50%, and is preferably 1 to 45%, 2 to 40%, 4 to 30%, 5 to 25%, and particularly preferably 5 to 20%. If the Ga content is too low, vitrification becomes difficult. On the other hand, if the Ga content is too high, Ga-based crystals are precipitated, making it difficult for infrared rays to transmit, and raw material costs tend to increase.

[0019] Ag is an essential component for increasing the thermal stability (vitrification stability) of glass. It is also a component that is highly effective in suppressing the generation of Te particles, which will be described later. The Ag content is 0 to 50%, and preferably 1 to 45%, 2 to 40%, 2 to 30%, 3 to 20%, and particularly preferably 3 to 10%. If the Ag content is too high, vitrification becomes difficult.

[0020] Te, a chalcogen element, is an essential component for forming a glass skeleton. The content of Te is 30 to 90%, preferably 40 to 89%, 50 to 88%, 60 to 86%, and particularly preferably 70 to 85%. If the content of Te is too low, vitrification becomes difficult. On the other hand, if the content of Te is too high, Te-based crystals are precipitated, making it difficult for infrared rays to pass through.

[0021] From the viewpoint of increasing the stability of vitrification, it is preferable that the total content of Ge, Ga, and Te is large. Specifically, it is preferable that Ge+Ga+Te is 50% or more, more preferably 60% or more, 70% or more, and particularly preferably 80% or more. However, in order to introduce other components, the upper limit of Ge+Ga+Te may be 98% or less, 96% or less, and particularly preferably 95% or less.

[0022] Si, Al, Ti, Cu, In, Sn, Bi, Cr, Sb, Zn, Mn, and Cs are components that enhance the thermal stability of glass without reducing the infrared transmission properties. The content of Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs is 0-40%, preferably 0-30%, 0-20%, and particularly 0.1-10%. If the content of Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs is too high, vitrification becomes difficult. The contents of each of Si, Al, Ti, Cu, In, Sn, Bi, Cr, Sb, Zn, Mn, and Cs are preferably 0-40%, 0-30%, 0-20%, and particularly 0.1-10%, respectively. Among them, it is preferable to use Sn because it has a particularly large effect of enhancing the thermal stability of glass. The content of Sn is preferably 0 to 40%, 0 to 30%, 0 to 20%, 0.1 to 15%, and particularly preferably 0.1 to 10%. On the other hand, if impurities (e.g., SiO2, Al2O3) resulting from these components are mixed in, the light transmittance in the infrared region may decrease. Therefore, from the viewpoint of avoiding the mixing of impurities, the contents of each of the components Si, Al, Ti, Cu, In, Sn, Bi, Cr, Sb, Zn, Mn, and Cs are preferably 5% or less, 3% or less, and 1% or less, respectively, and it is preferable that they are not substantially contained. Here, "substantially not contained" means that they are not intentionally contained in the raw material, and does not exclude the mixing at the impurity level. Objectively, the content of each component is preferably less than 0.1%.

[0023] F, Cl, Br, and I are also components that enhance the thermal stability of glass. The content of F+Cl+Br+I is 0-40%, preferably 0-20%, and particularly preferably 0.1-10%. If the content of F+Cl+Br+I is too high, vitrification becomes difficult and weather resistance is likely to decrease. The contents of each of the components F, Cl, Br, and I are preferably 0-40%, 0-20%, and particularly preferably 0.1-10%. Among them, I is preferable in that elemental raw materials can be used and the effect of enhancing the thermal stability of glass is particularly large. The content of I is preferably 0-40%, 0-20%, 0.1-15%, and particularly preferably 0.1-10%. On the other hand, from the viewpoint of obtaining glass with particularly high weather resistance, the contents of F+Cl+Br+I are preferably 5% or less, 3% or less, and 1% or less, respectively, and it is preferable that it is substantially not contained.

[0024] The infrared transmitting glass of the present invention may contain the following components in addition to the above components.

[0025] Se and As are components that expand the vitrification range and increase the thermal stability of glass. The content of each is preferably 0 to 10%, and more preferably 0 to 5%. However, since these substances are toxic, it is preferable to not substantially contain them from the viewpoint of reducing the impact on the environment and human body.

[0026] It is preferable that the infrared transmitting glass of the present invention is substantially free of the toxic substances Cd, Tl and Pb, thereby minimizing the impact on the environment.

[0027] The infrared transmitting glass of the present invention does not have any bumps with a major axis of 500 μm or more. Even if bumps are present in the infrared transmitting glass, their length is less than 500 μm, and is preferably 200 μm or less, 100 μm or less, 50 μm or less, and particularly 10 μm or less. In this way, it is possible to suppress the deterioration of infrared transmitting properties. Note that Ga2O3 generated by oxidation of Ga due to oxygen attached to the surface of the raw material is likely to become bumps, so it is preferable to suppress the generation of such bumps by the method described below.

[0028] The infrared transmitting glass of the present invention does not have Ga2O3 particles that cause multiple scattering, so the internal transmittance is likely to be high. Specifically, the internal transmittance at a wavelength of 12 μm is 90% or more, preferably 92% or more, 95% or more, 97% or more, and particularly preferably 99% or more. If the internal transmittance is too low, the sensitivity to infrared rays is poor, and the infrared sensor may not function sufficiently.

[0029] In addition, Te in glass is zero valence (Te 0 ) or -2V (Te 2- ), but Te in the glass can take the form of Te 0 When Te exists in this state, minute Te particles with a long diameter of about 1 μm tend to occur. Therefore, in order to further increase the internal transmittance, the Te in the glass should be 2- Specifically, the ratio of Te to the total Te is preferably 2- The abundance ratio of Te is preferably more than 0%, more preferably 1% or more, 5% or more, 10% or more, 15% or more, and particularly preferably 30% or more, in terms of mole percent. In this way, it becomes easier to suppress the generation of minute Te particles, and it becomes easier to further improve the internal transmittance. 2- The upper limit of the abundance ratio is practically 90% or less, 80% or less, 70% or less, and particularly 60% or less.

[0030] The infrared transmitting glass of the present invention is excellent in infrared transmittance at wavelengths of about 8 to 18 μm. The infrared absorption edge wavelength can be used as an index for evaluating the infrared transmittance. It can be determined that the larger the infrared absorption edge wavelength, the more excellent the sensitivity to infrared rays. The infrared transmitting glass of the present invention preferably has an infrared absorption edge wavelength of 20 μm or more, particularly 21 μm or more at a thickness of 2 mm.

[0031] The infrared transmitting glass of the present invention can be produced, for example, as follows. The raw materials are mixed to obtain the above glass composition, and a raw material batch is obtained. Next, the quartz glass ampoule is heated and evacuated, and then the raw material batch is placed in the quartz glass ampoule, and the quartz glass ampoule is sealed with an oxygen burner. Next, the sealed quartz glass ampoule is heated to 650-1000°C at a rate of 10-40°C / hour in a melting furnace, and then held for 6-12 hours. During the holding time, the quartz glass ampoule is turned upside down and the melt is stirred as necessary. In addition, by carrying out a reduction treatment during the manufacturing process, such as by firing the raw materials in a reducing gas in advance, Ga2O3 particles that deteriorate the infrared transmitting properties are less likely to be generated. Here, as the reducing gas, N2-H2 mixed gas, CO, H2S, N2O, SO2, NH3, etc. can be used, but it is preferable to use N2-H2 mixed gas because it is inexpensive and highly safe.

[0032] The quartz glass ampoule is then removed from the melting furnace and rapidly cooled to room temperature to obtain the infrared transmitting glass of the present invention.

[0033] The infrared transmitting glass thus obtained can be processed into a predetermined shape (disc, lens, etc.) to produce an optical element.

[0034] For the purpose of improving the transmittance, an anti-reflection film may be formed on one or both sides of the optical element. Examples of the method for forming the anti-reflection film include a vacuum deposition method, an ion plating method, and a sputtering method.

[0035] After the antireflection film is formed on the infrared transmitting glass, the glass may be processed into a predetermined shape. However, because the antireflection film is likely to peel off during the processing step, it is preferable to form the antireflection film after processing the infrared transmitting glass into a predetermined shape unless there are special circumstances.

[0036] The infrared transmitting glass of the present invention has excellent infrared transmittance and is therefore suitable for use as an optical element such as a cover member for protecting a sensor part of an infrared sensor or a lens for focusing infrared light on an infrared sensor part. EXAMPLES

[0037] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0038] Tables 1 to 3 show examples of the present invention and comparative examples, respectively.

[0039] [Table 1]

[0040] [Table 2]

[0041] [Table 3]

[0042] The samples of Examples 1 to 28 and Comparative Example 1 were prepared as follows. After evacuating a quartz glass ampoule while heating it, a raw material batch prepared to obtain the glass composition shown in the table after sintering in a reducing gas was placed in the quartz glass ampoule. Next, the quartz glass ampoule was sealed with an oxygen burner. Next, the sealed quartz glass ampoule was heated to 650 to 1000°C at a rate of 10 to 40°C / hour in a melting furnace, and then held for 6 to 12 hours. During the holding time, the quartz glass ampoule was turned upside down and the molten material was stirred. Next, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to obtain a sample.

[0043] The sample of Comparative Example 2 was obtained in the same manner as above, except that the step of calcining the raw material in a reducing gas was omitted.

[0044] The obtained samples were subjected to X-ray diffraction, and the diffraction spectrum was used to confirm whether or not they had been vitrified. In the table, samples that had been vitrified are indicated as "○" and samples that had not been vitrified are indicated as "×". In addition, the infrared absorption edge wavelength, internal transmittance, and graininess of each sample were measured or evaluated.

[0045] The infrared absorption edge wavelength was determined by measuring the light transmittance of each polished sample having a thickness of 2 mm±0.1 mm.

[0046] The internal transmittance was measured including the surface reflection loss for each polished sample having a thickness of 2 mm±0.1 mm and 10 mm±0.1 mm, and the internal transmittance at a wavelength of 12 μm was calculated from the obtained measured values.

[0047] The defects were evaluated as follows. The obtained samples were observed internally by the shadowgraph method using infrared light with a wavelength of 1 μm. Samples in which no defects with a major axis of 500 μm or more were observed were marked with an "O" and samples in which defects with a major axis of 500 μm or more were observed were marked with an "X".

[0048] In addition, Te present in the glass 2- The abundance ratio of was estimated by measuring XANES spectrum and performing linear fitting.

[0049] As shown in the table, it was confirmed that the samples of Examples 1 to 28 were vitrified, and no bumps with a major axis of 500 μm or more were observed. In addition, the infrared absorption edge wavelength was 24.1 to 24.4 μm, and the internal transmittance at a wavelength of 12 μm was high at 95% or more, showing good infrared transmission characteristics. In Examples 1 and 2, Te was Te 2- In the glass, it is present in a large amount of 48 to 50 mol % in this state. 2- It can be seen that the internal transmittance is superior to that of Example 6 in which the abundance ratio is 0%.

[0050] On the other hand, the sample of Comparative Example 1 was not vitrified and had a transmittance of almost 0% in the wavelength range of 2 to 24 μm. In the sample of Comparative Example 2, bumps with a major axis of 500 μm or more were observed, and the internal transmittance at a wavelength of 12 μm was low at 88%. [Industrial Applicability]

[0051] The infrared transmitting glass of the present invention is suitable for use as a cover member for protecting the sensor part of an infrared sensor, or as an optical element such as a lens for focusing infrared light on the sensor part.

Claims

1. An infrared transmitting glass comprising, in mole percent, more than 0 to 33.0% Ge, 17.5 to 50% Ga, 1 to 50% Ag, 30 to 90% Te, 0 to 40% Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs, and 0 to 40% F+Cl+Br+I, and having no bumps with a major axis of 500 μm or more.

2. An infrared transmitting glass comprising, in mole percent, more than 0 and up to 33.0% Ge, 17.5 to 50% Ga, 1 to 50% Ag, 30 to 90% Te, 0 to 40% Si+Al+Ti+Cu+In+Sn+Bi+Cr+Sb+Zn+Mn+Cs, and 0 to 40% F+Cl+Br+I, and having an internal transmittance of 90% or more at a wavelength of 12 μm.

3. 3. The infrared transmitting glass according to claim 1, which is substantially free of Cd, Tl and Pb.

4. 4. The infrared transmitting glass according to claim 1, wherein the infrared absorption edge wavelength at a thickness of 2 mm is 20 μm or more.

5. An optical element comprising the infrared transmitting glass according to any one of claims 1 to 4.

6. An infrared sensor comprising the optical element according to claim 5.

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