阅读说明：本技术 红外线透过性透镜的制造方法、红外线透过性透镜和红外线摄像机 (Method for manufacturing infrared-transmitting lens, and infrared camera ) 是由 松下佳雅 佐藤史雄 于 2017-04-24 设计创作，主要内容包括：本发明提供表面品质优异的红外线透过性透镜的制造方法。特征在于,将硫属玻璃的预制件在不活泼气体气氛下进行烧制,得到烧制体之后,对上述烧制体进行热压成型。(The invention provides a method for manufacturing an infrared-transmitting lens with excellent surface quality. Characterized in that a chalcogenide glass preform is fired in an inert gas atmosphere to obtain a fired body, and then the fired body is hot press molded.)

1. A method for manufacturing an infrared-transmitting lens, comprising:

and firing the chalcogenide glass preform in an inert gas atmosphere to obtain a fired body, and then carrying out hot press molding on the fired body, wherein the softening point of the chalcogenide glass is 250-370 ℃.

2. The method for manufacturing an infrared-transmitting lens according to claim 1, comprising:

and firing the prefabricated member at a temperature which is 0-50 ℃ lower than the yield point.

3. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the preform was fired under nitrogen atmosphere.

4. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the fired body is hot-press molded at a temperature of the chalcogenide glass at a yield point or higher and a softening point or lower.

5. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the fired body is hot-press molded in an inert gas atmosphere.

6. The method for manufacturing an infrared-transmitting lens according to claim 5, wherein:

the fired body was hot-press molded in a nitrogen atmosphere.

7. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the chalcogenide glass contains S, Se and Te.

8. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the chalcogenide glass contains 30 to 80 mol% of S + Se + Te.

9. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

and firing the prefabricated member for 6-12 hours.

10. The method for manufacturing an infrared-transmitting lens according to claim 1 or 2, wherein:

the chalcogenide glass is substantially free of As.

11. An infrared-transmitting lens produced by the method for producing an infrared-transmitting lens according to claim 1 or 2, characterized in that:

the infrared-transmitting lens is formed of a chalcogenide glass, and the number of recesses having a diameter of 2.5 [ mu ] m or more and 100 [ mu ] m or less per unit area of the surface is 100 or less, and the unit area is 1mm × 1 mm.

12. An infrared camera, characterized by:

the lens according to claim 11, which is formed by using the infrared-transmitting lens.

Technical Field

The present invention relates to a method for manufacturing an infrared-transmitting lens used for an infrared sensor, an infrared camera, and the like.

Background

An infrared sensor for detecting a living body at night is provided in a vehicle-mounted night vision system, a security system, or the like. Since the infrared sensor detects 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 include Ge and ZnSe. They are crystalline and therefore have poor processability and are difficult to process into complex shapes such as aspherical lenses. Therefore, there are problems that mass production is difficult and miniaturization of the infrared sensor is also difficult.

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

The chalcogenide glass can be molded, and an optical element such as an aspherical lens can be obtained by sandwiching the chalcogenide glass between an upper mold and a lower mold and hot-pressing the chalcogenide glass. (see, for example, patent document 2)

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-161374

Patent document 2: japanese laid-open patent publication No. H06-211540

Disclosure of Invention

Technical problem to be solved by the invention

The chalcogenide glass has a problem that a recess is generated on the surface of an optical element of a lens obtained by molding due to heating at the time of pressing, and the surface quality of the lens is degraded. When a large number of concave portions are formed on the surface of the optical element, the image is distorted or disordered when the optical element is used as a lens of a camera.

The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing an infrared-transmitting lens having excellent surface quality.

Means for solving the technical problem

The present inventors have made various studies and, as a result, have obtained the following findings, and have made the present invention. During the hot press molding of chalcogenide glass, the surface of chalcogenide glass adsorbs water and reacts with the components in chalcogenide glass to generate gas. For example, in a sulfide-based chalcogenide glass containing a large amount of sulfur, water adsorbed on the surface of the glass reacts with sulfur in the glass to generate H from the surface of the glass₂And S. If this gas is generated at the interface between the chalcogenide glass and the mold, a depression is likely to be generated on the surface of the lens after hot press molding, and the surface quality is likely to be degraded. Thus, when the chalcogenide glass preform is fired in an inert gas atmosphere before hot press molding, water adsorbed on the surface of the glass can be removed, so that gas is less likely to be generated when the chalcogenide glass preform is hot press molded, and dishing is less likely to occur on the surface of the lens after hot press molding.

The method for producing an infrared-transmitting lens of the present invention is characterized in that a chalcogenide glass preform is fired in an inert gas atmosphere to obtain a fired body, and then the fired body is hot-press molded.

In the method for producing an infrared-transmitting lens of the present invention, the preform is preferably fired at a temperature lower than the yield point by 0 to 50 ℃.

In the method for manufacturing an infrared-transmitting lens of the present invention, the preform is preferably fired in a nitrogen atmosphere.

In the method for producing an infrared-transmitting lens of the present invention, the fired body is preferably hot-press molded at a temperature of not lower than the yield point and not higher than the softening point of the chalcogenide glass.

In the method for producing an infrared-transmitting lens of the present invention, the fired body is preferably hot-press molded in an inert gas atmosphere.

In the method for producing an infrared-transmitting lens of the present invention, the fired body is preferably hot-press molded in a nitrogen atmosphere.

In the method for producing an infrared-transmitting lens of the present invention, the chalcogenide glass preferably contains S, Se and Te.

In the method for producing an infrared-transmitting lens of the present invention, the chalcogenide glass preferably contains 30 to 80% by mol of S + Se + Te.

The infrared-transmitting lens of the present invention is characterized by being formed of a chalcogenide glass, and the number of recesses having a diameter of 2.5 [ mu ] m or more and 100 [ mu ] m or less per unit area (1mm × 1mm) of the surface is 100 or less.

The infrared camera of the present invention is formed by using the above infrared-transmitting lens.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a method for producing an infrared-transmitting lens having excellent surface quality can be provided.

Drawings

FIG. 1 is a photograph showing the surface state of the lens obtained in the example.

Fig. 2 is a photograph showing the surface state of the lens obtained in the comparative example.

Detailed Description

The method for producing an infrared-transmitting lens of the present invention is characterized in that a chalcogenide glass preform is fired in an inert gas atmosphere to obtain a fired body, and then the fired body is hot-press molded. Hereinafter, the method for manufacturing the infrared-transmitting lens of the present invention will be described in detail.

First, a chalcogenide glass preform is obtained, for example, by the following operation. The composition of the chalcogenide glass will be described later. The raw materials were mixed to obtain a desired glass composition, and a raw material master batch was obtained. Subsequently, the quartz glass ampoule was evacuated while heating, and then the raw material master batch was added to seal the quartz glass ampoule with an oxygen burner while evacuating. And (3) heating the sealed quartz glass ampoule in a melting furnace to 650-1000 ℃ at a speed of 10-20 ℃/h, and then keeping for 6-12 hours. During the holding time, the quartz glass ampoule was turned upside down as needed to stir the melt. Then, the quartz glass ampoule was taken out from the melting furnace and quenched to room temperature, thereby obtaining a chalcogenide glass. The obtained chalcogenide glass is cut, polished, and processed to obtain a chalcogenide glass preform.

The obtained preform is fired to obtain a fired body. This can suppress the generation of gas from the glass surface as described above.

The firing atmosphere is preferably an inert atmosphere, preferably a nitrogen, argon or helium atmosphere. From the viewpoint of low cost, a nitrogen atmosphere is particularly preferable. When firing is performed without atmosphere control, the glass is oxidized, and the infrared transmission characteristics tend to be lowered. The firing temperature is preferably 0 to 50 ℃ lower than the yield point of the glass, more preferably 0 to 40 ℃ lower, and particularly preferably 0 to 20 ℃ lower. If the firing temperature is too high, the surface adsorbs water and the components in the chalcogenide glass react with each other during firing to generate gas, thereby deteriorating the surface quality of the fired body. On the other hand, if the firing temperature is too low, water adsorbed on the surface of the glass cannot be completely removed, and gas is generated during hot press molding, which tends to degrade the surface quality after molding.

The obtained fired body was hot-press molded with a mold to obtain an external-ray permeable lens. The hot-pressing atmosphere is preferably an inert atmosphere, such as a nitrogen, argon or helium atmosphere. From the viewpoint of low cost, a nitrogen atmosphere is particularly preferable. When firing is performed without atmosphere control, the glass is oxidized, and the infrared transmission characteristics tend to be lowered. Further, the mold is oxidized and deteriorated, and the service life of the mold is shortened, which tends to increase the manufacturing cost. The pressing temperature is preferably a temperature of not lower than the yield point and not higher than the softening point of the glass, more preferably a temperature of 0 to 50 ℃ higher than the yield point of the glass, still more preferably a temperature of 0 to 30 ℃ higher than the yield point of the glass, and particularly preferably a temperature of 0 to 20 ℃ higher than the yield point of the glass. If the pressing temperature is too low, the glass may not be softened and deformed, and may be damaged by the pressing pressure. In addition, if the pressing temperature is too high, the amount of gas generated during pressing increases, and the surface quality of the molded lens tends to decrease. The mold preferably has an optically polished surface. In addition, the lens shape is preferably a meniscus shape.

The infrared-transmitting lens produced by the present invention has excellent surface quality. Specifically, the number of recesses having a diameter of 2.5 μm or more and 100 μm or less per unit area (1mm × 1mm) is preferably 100 or less, more preferably 50 or less, still more preferably 30 or less, and particularly preferably 10 or less. The infrared-transmitting lens produced by the present invention has excellent surface quality, and is therefore suitable as an optical element such as a lens for condensing infrared light in an infrared sensor section of an infrared camera.

The chalcogenide glass used in the present invention will be described below.

The chalcogenide glass preferably contains S, Se and Te. S, Se and Te, which are chalcogens, are components forming the glass skeleton. The content of S + Se + Te (the total amount of S, Se and Te) is preferably 30 to 80% by mol, more preferably 35 to 70% by mol. When the content of S + Se + Te is too small, vitrification is difficult, while when too large, weather resistance may be deteriorated.

In addition, as the chalcogen element, S or Te is preferably selected from the environmental viewpoint.

The following components may be contained in addition to the above components.

Ge. Ga, Sb, Bi and Sn are components for widening the vitrification range and improving the thermal stability of the glass, and the contents thereof are preferably 0 to 50%, more preferably 0 to 40%, in mol%. When the content of these components is too large, vitrification becomes difficult.

Zn, In and P are components for widening the vitrification range, and the contents thereof are preferably 0 to 20% by mol, respectively. When the content of these components is too large, vitrification becomes difficult.

Cl, F and I are components for broadening the transmission wavelength range of infrared rays, and the content thereof is preferably 0 to 20% by mole. When the content of these components is too large, the weather resistance tends to be lowered.

Further, it is preferable that As, Cd, Tl and Pb As toxic substances are not substantially contained. In this way, the influence on the environment can be minimized. Here, "substantially free" means not intentionally contained in the raw materials, and does not exclude mixing at an impurity level, and objectively means that the content of each component is less than 1000 ppm.

The yield point of the chalcogenide glass is preferably 200-400 ℃, and particularly preferably 220-340 ℃. The softening point is preferably 230 to 430 ℃, and particularly preferably 250 to 370 ℃.

Examples

(examples)

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The lenses of the examples were made as follows. The raw materials were blended so that S61%, Ge 5%, Bi 1%, and Sb 33% were in mol% to obtain a raw material master batch. Subsequently, the quartz glass ampoule washed with pure water was heated while evacuating, and then the raw material master batch was added to seal the quartz glass ampoule with an oxygen burner while evacuating.

And (3) heating the sealed quartz glass ampoule in a melting furnace to 650-1000 ℃ at a speed of 10-20 ℃/h, and then keeping for 6-12 hours. During the holding time, the quartz glass ampoule was turned upside down every 2 hours, and the melt was stirred. Then, the quartz glass ampoule was taken out from the melting furnace and quenched to room temperature, thereby obtaining a chalcogenide glass (yield point 240 ℃ C., softening point 270 ℃ C.).

The resulting chalcogenide glass is processed into a preform shape. After the processing, firing is performed for 6 to 12 hours at a temperature 10 to 20 ℃ lower than the yield point in a nitrogen atmosphere, and water attached to the surface of the glass is removed.

And heating the fired prefabricated member to a temperature higher than the yield point by 10-20 ℃ under a nitrogen atmosphere, and performing hot press molding by using a mold with an optical grinding surface to form the prefabricated member into a concave-convex lens shape to obtain the lens. The surface of the obtained lens was observed with a digital microscope. Fig. 1 shows a photograph of the surface state of the lens. The number of concave portions having a diameter of 2.5 μm or more and 100 μm or less per unit area (1mm × 1mm) of the lens surface was 6, and the surface quality was good.

Comparative example

Lenses were obtained in the same manner as in examples, except that hot press molding was performed without firing the preform. Fig. 2 shows a photograph of the surface state of the lens. The number of concave portions having a diameter of 2.5 μm or more and 100 μm or less per unit area (1mm × 1mm) of the lens surface was 162, and the surface quality was poor.

Industrial applicability of the invention

The infrared-transmitting lens produced in the present invention is suitable as an optical element such as a lens for condensing infrared light in an infrared sensor section of an infrared camera.