JPH0362658B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to an infrared transmitting halide glass useful for transmitting infrared rays. b. Prior Art The optical transmission bodies conventionally used have been mainly oxide glasses mainly composed of quartz (SiO ₂ ).
However, the glass has Si and O that form the network.
Due to the strong coupling between the two, infrared absorption occurs due to lattice vibrations, and the drawback is that only infrared light with wavelengths up to about 2 μm can be transmitted. Therefore, materials with transparent windows in the infrared region with wavelengths of 2 μm or more are being developed. If the materials that have been reported to date are roughly divided into glasses and crystalline materials, glass materials include fluoride glasses such as zirconium fluoride (ZrF ₄ )-based and beryllium fluoride (BeF ₂ )-based glasses, and zinc chloride (ZnCl). ₂ ), bismuth chloride (BiCl ₃ ), cadmium chloride (CdCl ₂ ), cadmium iodide,
Non-fluoride halide glasses such as lead bromide-based or sodium chloride (ThCl ₄ )-based glasses, and chalcogen glasses containing arsenic, germanium, etc., are known. On the other hand, crystalline materials include thallium halide (TlBr-TlI) and silver halide (AgCl-
Polycrystals such as AgBr) and single crystals such as potassium chloride (KCl), cesium bromide (CsBr), and cesium iodide (CsI) are known. However, fluoride glass has the disadvantage that its infrared transmission wavelength range is limited to about 4 μm because it absorbs infrared light due to lattice vibration at wavelengths of 4 μm or more. Therefore, non-fluoride halide glass
It is considered the most promising candidate as an infrared transmitting material because it transmits well even infrared rays with wavelengths of 10 μm or more. However, glasses whose main components are ZnCl ₂ or BiCl ₃ are extremely deliquescent, making them impractical, and
Glasses mainly composed of CdCl ₂ , CdI ₂ and PbBr ₂ also had the disadvantage of being impractical due to the toxicity of Cd, Pb, etc. Chalcogen glass also contains a large amount of toxic components such as arsenic and selenium, and has many structural defects, so it has the disadvantage of high absorption of infrared rays. On the other hand, when it comes to crystalline materials, polycrystalline materials have a large scattering of light at grain boundaries due to their polycrystalline nature, and single-crystalline materials have a high rate of growth per minute. 1~
It had the disadvantage of being small at 2 cm and extremely poor productivity. c. Purpose of the Invention The purpose of the present invention is to provide a glass that transmits infrared rays from the near-infrared to mid-infrared region extremely well, is neither deliquescent nor toxic, and has excellent productivity. d Structure of the Invention The present invention is characterized in that the proportion of cationic components constituting the glass is 50 to 77 mol% silver and 23 to 50 mol% cesium, and the proportion of anionic components constituting the glass is 5 to 80 mol% bromide ions. This is an infrared transmitting halide glass characterized by having an iodide ion content of 20 to 95 mol%. Next, the reason for limiting the composition to this range will be described. The present inventors have investigated the AgBr-CsBr system and the AgI-
We discovered that CsI-based halide compositions form glass. Furthermore, it was discovered that the crystal precipitation tendency could be significantly controlled by replacing bromine (Br) in the AgBr-CsBr glass composition with iodine (I) and by replacing iodine with bromine in the AgI-CsI glass composition. . When bromine in AgBr-CsBr glass is replaced with iodine, if the mole fraction of the substituted iodine is less than 0.20, the effect of substitution on suppressing crystal precipitation is small;
Moreover, when the iodine molar fraction exceeded 0.95, the crystal precipitation tendency increased. From this, it became clear that the appropriate value for the molar fraction of iodine was 0.20 to 0.95. On the other hand, when iodine in AgI-CsI glass was replaced with bromine, the effect was small if the bromine molar fraction of the substitution was less than 0.05, and the tendency for crystal precipitation increased when it exceeded 0.80. Therefore, it has become clear that the appropriate ratio of the mole fraction of bromine for substitution is 0.05 to 0.80. AgX−CsX containing bromine and iodine
In the system glass (X=Br+I), when AgX was less than 50 mol% or exceeded 77 mol%, the tendency for crystal precipitation increased. From this, the appropriate amount of AgX is 50 to 77
Similarly, it has been found that the appropriate amount of CsX is 23 to 50 mol%. The components of the present invention are composed of AgX and CsX (X = Br + I), but in order to adjust the properties of the glass, such as the refractive index and expansion coefficient, other halogen compounds may be added to the extent that they do not significantly increase the tendency of crystal precipitation. It is okay to add it. Next, the present invention will be explained in more detail based on examples. e Examples Example 1 Proportions of AgBr26.4, AgI39.6, CsBr13.6 and CsI20.4 mol% - that is, AgX66, CsX34 mol%
5 g of mixed powder prepared so that Br ^- / (Br ^- + I ^- ) = 0.40- was placed in a highly pure and anhydrous transparent quartz container and heated at 100°C for 17 hours in a vacuum dryer. Ta. After that, nitrogen gas vaporized from a liquid nitrogen cylinder was filled into a vacuum dryer and the temperature was raised to 300℃.
Heat and melt for 10 minutes. After cooling, the quartz container was transferred to a melting furnace inside a glove box flowing nitrogen gas, and heated at 400℃ for 30 minutes until the sample thickness was 0.4~
It was poured into a brass mold designed to have a thickness of 0.5 mm. The sample thus prepared was examined for the presence or absence of crystals using a polarizing microscope and X-ray diffraction. As a result, it was confirmed that no crystals were present in any of the methods. FIG. 1 shows the X-ray diffraction pattern of the glass. This figure shows that there are no sharp peaks characteristic of crystals, and only halos characteristic of glass are present. Furthermore, FIG. 2 shows the infrared transmission characteristics of the glass. However, the sample was melted in the same manner as described above, but molded in a brass mold designed to yield a sample with a thickness of 1 mm. wavelength is
Although there is some absorption due to OH groups at 2.8 μm and 6.25 μm and some absorption thought to be caused by oxides around 18 μm, it shows extremely high transmittance in the mid-infrared region of the measurement range of 2.5 to 25 μm. Examples 2 and 3 Mixed powders with the same composition as Example 1, that is, AgX66, CsX34 mol%, Br ^- / (Br ^- + I ^- ) = 0.40, but with a different raw material blending ratio - Table 1 Examples 2 and 3 The compounding ratio shown in - was prepared and melting was carried out in the same manner as in Example 1. The determination of vitrification and infrared transmission properties of the obtained glass were investigated, and the results were as shown in Example 1.
It was the same. In Table 1, the results of the vitrification determination in Examples are expressed as ○ and ×. Here, the ○ marks in the table indicate non-existence in both the polarizing microscope and X-ray diffraction evaluation methods.

【table】

[Table] Items judged to be of good quality. Examples 4 to 48 Each raw material formulation and each composition glass shown in Examples 4 to 48 in Table 1 was melted in the same manner as in Example 1. The results of the judgment of vitrification of the obtained sample are
As shown in the table, all the X-ray diffraction results had the same shape as in FIG. In addition, the infrared transmission characteristics are basically the same as those shown in FIG. 2, and in both cases, extremely high transmission characteristics were exhibited in the mid-infrared region with a wavelength of 2.5 μm to 25 μm. Comparative Examples 1 to 11 Glasses having the raw material formulations and compositions shown in Comparative Examples 1 to 11 in Table 1 were prepared in the same manner as in Example 1. The presence of crystals in each glass was confirmed by observation with the naked eye or with a polarizing microscope. Here, Comparative Examples 1 to 3 have a small amount of Ag and a large amount of Cs. On the contrary, Comparative Examples 4 and 5 are examples in which the amount of Ag is large and the amount of Cs is small. Moreover, Comparative Examples 7 and 8 had a small amount of bromine and a large amount of iodine. Examples 9 to 11 are examples in which the amount of bromine is large and the amount of iodine is small. Glasses containing crystals are indicated by an x in the column of vitrification determination in Table 1. f Effect of the invention The glass according to the invention is mainly composed of Ag, Cs, Br.
and I. Infrared absorption due to lattice vibration of these components is at a wavelength around 40 to 50 μm,
In the mid-infrared region of 2.5 to 25 μm, there is no absorption due to internal factors. Moreover, ZnCl ₂ or
It does not have the deliquescent properties found in BiCl ₃ glass, and does not contain any toxic components. For these reasons, it can be said that the glass of the present invention can be applied to fibers for ultra-low loss optical communication, fibers for infrared thermometers, window materials for infrared lasers, lens materials for infrared convergence or divergence, and the like.

[Brief explanation of drawings]

FIG. 1 is an X-ray diffraction diagram of the glass obtained in Example 1, and FIG. 2 is an infrared transmission characteristic diagram of the same glass.

Claims (1)

[Claims] 1 The ratio of cationic components that make up the glass is silver 50
-77 mol%, cesium 23-50 mol%, and the proportion of anion components constituting the glass is 5-80 mol% bromide ions and 20-95 mol% iodide ions. halide glass.