JPS6350298B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Description of the Technical Field The present invention provides a method for producing a thin film of a fluorinated amorphous material that can be used as an infrared optical material. (B) Background of the Invention Single crystals of metal halides made by the molten salt method exhibit extremely good transmittance even in the infrared region, and are used as materials for optical equipment such as window materials, lenses, and filters. It has important uses. Many metal halides generally exhibit hygroscopic properties, but single metal fluorides such as BaF ₂ , CaF ₂ , and LiF have excellent heat resistance and moisture resistance, and are most commonly used as infrared optical materials. . However, the manufacturing cost required for growing a single crystal is high, and it is difficult to obtain a large-sized crystal. If these crystalline metal fluorides can be made into an amorphous (vitrified) state without grain boundaries that impede optical transparency, they can be used as good infrared transmitting materials. However, when a single metal fluoride melt is subjected to normal cooling and solidification operations, crystallization occurs.
It is not possible to obtain transparent amorphous materials.
Recently, multicomponent fluoride glasses containing BeF ₂ and ZrF ₄ as main components have been developed (for example, CM
Baldwin et al., Journal of Non-Crystalline
Solids, 1981, Volume 43, Page 309 and B. Bendov
et al., Applied Optics, 1981, Volume 20, 2875
(see page). Glass materials have great moldability and are different from single-crystal materials. but,
BeF ₂ glass is a deliquescent and highly toxic material. Furthermore, ZrF ₄ as a raw material is easily oxidized even in the atmosphere, and requires advanced technology in the manufacturing process. Furthermore, BeF ₂ and ZrF ₄ are expensive raw materials. From this point of view, it is desired to develop a fluoride-based amorphous material having an infrared transmitting function using an inexpensive manufacturing method. In particular, with rapid progress in optoelectronics, infrared optical materials are becoming increasingly important. (C) Purpose of the Invention In view of the above-mentioned points, the present invention provides a method for forming a melt of a multi-component metal fluoride into a thin film using a metal fluoride that is inexpensive as a raw material and chemically stable. The aim is to obtain an amorphous infrared transmitting material that has not been obtained so far by ultra-quenching it while rolling it. (D) Structure of the Invention Generally, the range of compositions that can be made into amorphous (glass) is limited. In particular, metal fluoride has excellent properties as an infrared transmitting material as described above, but it is a material that is easily crystallized. Therefore, discovering a material composition that can be made into an amorphous material is an important key point in material development. Furthermore, significantly increasing the cooling rate of the melt is also considered to be an effective means of achieving amorphousization. Therefore, an ultra-quenching device with a cooling rate of at least 10 ³ °C/sec or higher (for example, K. Nassau et al., Journal of
American Ceramic Society, 1979, Volume 62,
74 pages, T. Sekiya et al., Materials Research
Bulletin, 1984, vol. 19, p. 885 and Yasushi Torii et al., Book Science and Technology, 1983, vol. 24, p. 52). As a result of repeated searches for MF ₂ (M = Ba, Sr, Ca) - LiF - AlF ₃
In the composition system, by forming the melt into a thin film and ultra-quenching it, we were able to obtain amorphous infrared transmitting materials over a wide composition range. This is due to the fact that the melting point of the metal fluoride is lowered due to its multicomponent content, and its viscosity increases, which delays crystallization and reduces the probability that crystals with a specific composition will grow in the melt. It is thought that the amorphous state was achieved due to the combination of the following conditions: ultra-rapid cooling of the melt. The absorption edges of these infrared optical materials were 7 μm or more. The present invention has an advantage in terms of manufacturing cost because it does not require the labor of growing a single crystal, cutting out a crystal, etc. as in the prior art. (E) Examples of the invention Examples will be given and explained below. Barium fluoride (BaF ₂ ), strontium fluoride (SrF ₂ ), calcium fluoride (CaF ₂ ), lithium fluoride (LiF) and aluminum fluoride (AlF ₃ ) were used as starting materials as shown in Table 1. It was weighed to match the mixing ratio. A twin-roller ultra-quenching device was used to thin the amorphous amorphous film. this is,
It consists of a part that heats and melts the sample, and a twin metal roller part that rotates at 3000 revolutions per minute installed below it. A well-mixed raw material mixture is placed in a platinum nozzle container and melted at 600 to 1100℃, and the melt is sent between metal rollers and ultra-quenched to obtain a thin and uniform thin film (about 60μm thick). It will be done. Table 1 shows the results of the infrared transmission limit wavelength of the samples thus prepared. Here, the transmittance of the film is measured using an infrared spectrophotometer over the wavelength range of 2.5 to 50 μm, and the infrared transmittance limit wavelength is the wavelength at which the transmittance is 90% with a 60 μm thick film. stipulated. Further, FIG. 1 shows the infrared transmission spectra of Examples 3 and 7.

【table】

[Table] (F) Effects of the invention According to the above examples, materials within the scope of the present invention achieve a transparent amorphous state by ultra-quenching, transmit infrared rays well up to at least 7 μm, and can be used as infrared optical materials. It became clear that it could be done. Compared to conventional fluoride single-crystal materials for infrared optics, there is no difference in performance, and the melting temperature is lower due to the multi-component structure, which significantly reduces the need for large amounts of thermal energy and maintenance costs for heating furnace materials, etc. It has the advantage that a thin film can be obtained without crystal processing. Furthermore, the ultra-quenching method is an extremely economical process technology that can produce thin films at high speed. Therefore, the present invention can provide an infrared optical film material that is advantageous in various ways in terms of manufacturing cost, and has great industrial benefits.

[Brief explanation of the drawing]

FIG. 1 shows a typical example of an infrared transmission spectrum of a fluoride-based amorphous thin film (thickness: 60 μm) obtained according to the present invention. The numbers in the figure are the example numbers, and the compositions are as follows. 3: _0.4BaF2・0.4LiF・_0.2AlF2 , 7:
0.2BaF ₂・0.6LiF・0.2AlF ₃

Claims (1)

[Claims] 1 General formula xMF ₂・yLiF・zAlF ₃ (x+y+z=
In 1), the M component is at least one metal fluoride selected from barium, strontium, and calcium, x = 0.2 to 0.6, y =
Infrared transmittance, characterized by melting a composition mixture with a composition range of 0.2 to 0.6 and z = 0.1 to 0.4, inserting this melt between a metal cooling medium and rolling it into a thin film while ultra-quenching it. A method for producing amorphous materials.