JP6788816B2 - Infrared transmissive glass - Google Patents

Description

The present invention relates to infrared transmissive glass used for infrared sensors and the like.

In-vehicle night vision and security systems are equipped with infrared sensors used for biological detection at night. Since the infrared sensor senses infrared rays having a wavelength of about 8 to 14 μm emitted from a living body, an optical element such as a filter or a lens that transmits infrared rays in the wavelength range is provided in front of the sensor unit.

Examples of the material for the optical element as described above include Ge and ZnSe. Since these are crystals, they are inferior in processability, and it is difficult to process them into a complicated shape such as an aspherical lens. Therefore, there is a problem that it is difficult to mass-produce and it is also difficult to miniaturize the infrared sensor.

Therefore, chalcogenide glass has been proposed as a vitreous material that transmits infrared rays having a wavelength of about 8 to 14 μm and is relatively easy to process (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-161374

Since the glass described in Patent Document 1 has a significantly reduced infrared transmittance at a wavelength of 10 μm or more, it is particularly inferior in sensitivity to infrared rays emitted from a living body, and the infrared sensor may not function sufficiently.

In view of the above, it is an object of the present invention to provide a glass having excellent infrared transmittance and suitable for infrared sensor applications.

As a result of diligent studies by the present inventors, it has been found that the chalcogenide glass having a specific composition can solve the above-mentioned problems.

That is, the infrared transmissive glass of the present invention has Ge 0 to 50% (but does not contain 0%), Te 4 to 80%, Sn + Ag + Cu + Bi + Sb 0 to 50% (but does not contain 0%), and F + Cl + Br + I in mol%. It is characterized by containing 0 to 50%. In this specification, "○ + ○ + ..." Means the total amount of the contents of each corresponding component.

The infrared transmissive glass of the present invention preferably contains substantially no Cd, Tl and Pb.

The infrared transmissive glass of the present invention preferably has a 30% light transmissive wavelength of 20 μm or more at a wavelength of 8 to 22 μm at a thickness of 2 mm.

The optical element of the present invention is characterized by using the above-mentioned infrared transmissive glass.

The infrared sensor of the present invention is characterized by using the above optical element.

According to the present invention, it is possible to provide a glass having excellent infrared transmittance and suitable for infrared sensor applications.

It is a graph which shows the light transmittance curve of the infrared transmittance glass produced in Example 1. FIG.

The infrared transmissive glass of the present invention is Mol%, Ge 0 to 50% (but not including 0%), Te 4 to 80%, Sn + Ag + Cu + Bi + Sb 0 to 50% (but not including 0%), and F + Cl + Br + I 0 to 0. It is characterized by containing 50%. The reason for defining the glass composition in this way will be described below. In the following description of the content of each component, "%" means "mol%" unless otherwise specified.

Ge is an essential component for forming a glass skeleton. The content of Ge is 0 to 50% (but not including 0%), preferably 1 to 40%, more preferably 2 to 30%, and further preferably 5 to 25%. preferable. If the content of Ge is too small, it becomes difficult to vitrify. On the other hand, if the content of Ge is too large, Ge-based crystals tend to precipitate and the raw material cost tends to increase.

The chalcogen element Te is an essential component that forms the glass skeleton. The content of Te is 4 to 80%, preferably 10 to 75%, and more preferably 20 to 70%. If the content of Te is too small, it becomes difficult to vitrify, while if it is too large, Te-based crystals tend to precipitate.

Sn, Ag, Cu, Bi, and Sb are components that enhance the thermal stability of glass. The content of Sn + Ag + Cu + Bi + Sb is 0 to 50% (but not including 0%), preferably 1 to 40%, more preferably 2 to 30%, and further preferably 3 to 25%. It is preferably 5 to 20%, and particularly preferably 5 to 20%. If the content of Sn + Ag + Cu + Bi + Sb is too small or too large, it becomes difficult to vitrify. The content of each component of Sn, Ag, Cu, Bi, and Sb is 0 to 50%, preferably 0 to 50% (but not including 0%), and is preferably 1 to 40%. It is more preferably 2 to 30%, particularly preferably 3 to 25%, and most preferably 5 to 20%. Of these, Ag and Sn are preferably used because they have a particularly large effect of increasing the thermal stability of glass.

F, Cl, Br, and I are also components that enhance the thermal stability of glass. The content of F, Cl, Br, I is 0 to 50%, preferably 1 to 40%, more preferably 1 to 30%, still more preferably 1 to 25%. It is particularly preferably 1 to 20%. If the content of F + Cl + Br + I is too large, it becomes difficult to vitrify and the weather resistance tends to decrease. The content of each component of F, Cl, Br, and I is 0 to 50%, preferably 1 to 40%, more preferably 1 to 30%, and 1 to 25%, respectively. Is more preferable, and 1 to 20% is particularly preferable. Among them, it is preferable to use I because an elemental raw material can be used and the effect of enhancing glass stability is particularly large.

In addition to the above components, the infrared transmissive glass of the present invention may contain the following components.

Zn, In, Ga and P are components that widen the vitrification range and enhance the thermal stability of glass. The content thereof is preferably 0 to 20%, more preferably 0.5 to 10%. If the content of these components is too high, it becomes difficult to vitrify. Since Ga has a high cost, its content is preferably 10% or less, 5% or less, and particularly preferably not contained.

Se and As are components that widen the vitrification range and enhance the thermal stability of glass. The content thereof is preferably 0 to 10%, more preferably 0.5 to 5%. However, since these substances are toxic, it is preferable not to contain them from the viewpoint of reducing the influence on the environment and the human body.

It is preferable that the infrared transmissive glass of the present invention does not substantially contain toxic substances Cd, Tl and Pb. In this way, the impact on the environment can be minimized. Here, "substantially not contained" means that it is intentionally not contained in the raw material, and does not exclude contamination at the impurity level. Objectively, it means that the content of each component is less than 0.1%.

The infrared transmissive glass of the present invention has excellent infrared transmittance at a wavelength of about 8 to 22 μm. As an index for evaluating the infrared transmittance at a wavelength of about 8 to 22 μm, a 30% transmission wavelength in the infrared region can be mentioned. It can be judged that the larger the 30% light transmission wavelength at a wavelength of 8 to 22 μm, the better the infrared transmission. The 30% transmission wavelength (thickness 2 mm) in the infrared region of the present invention is preferably 20 μm or more, and more preferably 21 μm or more.

The infrared transmissive glass of the present invention can be produced, for example, as follows. First, the raw materials are prepared so as to have a desired composition. Put the raw material in a quartz glass ampoule that has been evacuated while heating, and seal it with an oxygen burner while evacuating. The infrared transmissive glass of the present invention can be obtained by holding the sealed quartz glass ampoule at about 650 to 800 ° C. for 6 to 12 hours and then quenching it to room temperature.

As the raw material, an elemental raw material (Ge, Te, Ag, Cu, I, etc.) may be used, or a compound raw material (GeTe ₄ , AgI, CuI, etc.) may be used. It is also possible to use these in combination.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

Tables 1 and 2 show examples and comparative examples of the present invention, respectively.

Each sample was prepared as follows. The raw materials were mixed so as to have a predetermined composition ratio, and a raw material batch was obtained. After vacuum exhausting the quartz glass amplifier washed with pure water while heating, the raw material batch was put in, and the quartz glass amplifier was sealed with an oxygen burner while vacuum exhausting.

The sealed quartz glass ampoule was heated to 650 to 800 ° C. at a rate of 10 to 20 ° 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 every 2 hours to stir the melt. Then, the quartz glass ampoule was taken out from the melting furnace and rapidly cooled to room temperature to obtain a sample.

The obtained sample was subjected to X-ray diffraction, and it was confirmed from the diffraction spectrum whether or not it was vitrified. In the table, those that are vitrified are marked with "○" and those that are not vitrified are marked with "x". In addition, the light transmittance at a thickness of 2 mm was measured for each sample, and the 30% transmitted wavelength in the infrared region having a wavelength of 8 to 22 μm was measured. Note that FIG. 1 shows the light transmittance curve of the sample of Example 1.

As shown in Table 1, the samples of Examples 1 to 10 are vitrified, have a 30% transmission wavelength of 21.0 to 21.7 μm, and have good light transmittance in the infrared region near a wavelength of 8 to 22 μm. Was shown.

On the other hand, as shown in Table 2, the samples of Comparative Examples 1 to 5 were not vitrified, and the light transmittance was almost 0% in the wavelength range of 2 to 24 μm.

The infrared transmissive glass of the present invention is suitable as an infrared transmissive optical element used in an infrared sensor or the like.

The infrared transmissive glass of the present invention can be used as a cover member for protecting the sensor portion of an infrared sensor or as an optical element such as a lens for condensing infrared light on the sensor portion.

Claims (5)

In mol%, it contains Ge 5 to 25%, Te 60 to 80%, Sn + Ag + Cu + Bi + Sb 1 to 25% (but including Ag and / or Sn), and F + Cl + Br + I 0 to 20 %, and does not contain Se and As. Infrared transmissive glass as a feature. The infrared transmissive glass according to claim 1, which is substantially free of Cd, Tl and Pb. The infrared transmissive glass according to claim 1 or 2, which is a chalcogenide glass. An optical element according to any one of claims 1 to 3, wherein the infrared transmissive glass is used. An infrared sensor according to claim 4, wherein the optical element is used.