JPH05279077A - Fluoride glass - Google Patents

Abstract

PURPOSE:To provide a fluoride glass having excellent water resistance and low refractive index compared to ZrF4 glass and lower casting temp. and cooling temp. compared with AlF3 glass so that an optical fiber coated org. resin can be easily produced. CONSTITUTION:This fluoride glass contains, by mol%, 5-23% ZrF4, 10-19.9 AlF3, 0-19% YF3, 0-18% CaF2, 5-30% BaF2, 5-28% ZnF2, and 0-23% NaF, satisfying that the total amt. of these components is >=75%. For example, by constituting the glass of 16% ZrF4, 18% AlF3, 11% YF3, 15% CaF2, 15% BaF2, 20% ZnF2, and 5% NaF, the obtd, glass has 322 deg.C glass transition temp., 407 deg.C crystallization temp., 550 deg.C melting point of crystal, and 1.4689 refractive index.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluoride glass useful as a material for a mid-infrared window material, an infrared energy transmission fiber, and an optical communication fiber.

[0002]

2. Description of the Related Art Fluoride glass that transmits mid-infrared rays having a wavelength of 2 to 6 .mu.m is drawing attention as a material for mid-infrared window materials, infrared energy transmission fibers and optical communication fibers. Fluoride glasses that have been reported so far are roughly classified into two types. That is, they are ZrF ₄ system (for example, JP-A-61-183144) and AlF ₃ system (for example, JP-A-62-175039).

[0003]

Although a composition stable to crystallization has been reported in ZrF ₄ type glass, it cannot be used only in a very limited place or method due to its poor water resistance. However, the refractive index of the glass is around 1.5, and there is a drawback that the coupling loss becomes high when it is connected to a silica-based fiber of around 1.45.

On the other hand, AlF ₃ type glass shows higher water resistance than ZrF ₄ type glass,
Since the slow cooling temperature is 150 to 200 ° C. higher than that of the ZrF ₄ system, it is very difficult to work in a glove box used for keeping the atmosphere of an inert gas during glass melting, and for example, When Teflon resin is jacketed in advance on glass processed into a columnar shape to form a fiber, there is a problem that the molding temperature is too high and the resin material is easily decomposed by heat.

[0005]

The fluoride glass of the first invention which solves the problems of the above-mentioned conventional fluoride glass is ZrF ₄ : 5 to 23% AlF ₃ : 10 to 19.9% in terms of mol%. _{YF 3: 0~19% CaF 2:} 0~18% BaF 2: 5~30% ZnF 2: 5~28% NaF: 0~23% and the total amount of these components is 75% or more.

That is, in the present invention, the content of AlF ₃ is made relatively high to improve the water resistance of the glass, and B
The main purpose was to lower the casting and slow cooling temperatures of the glass melt by adjusting the contents of fluorides of a, Zn and Na.

The ZrF ₄ content is 5 to 25 mol%, preferably 10 to 20 mol%. If the ZrF ₄ content exceeds this range, the rate of crystal precipitation in the melt during the cooling process becomes high. However, it becomes difficult to obtain a homogeneous glass.

The minimum content of AlF ₃ is 10 mol%, and if it is lower than this lower limit, not only the melt tends to become milky white but also the water resistance of the glass deteriorates. The upper limit is 19.
It is 9 mol%, and if it exceeds this upper limit, the melting temperature and casting temperature of the glass become high, which not only makes it difficult to work in the glove box, but also increases the rate of crystal precipitation in the melt during the slow cooling process. Therefore, it becomes difficult to obtain a homogeneous glass.

YF ₃ is a component for improving the water resistance of the glass as well as the casting of the glass melt and the control of the slow cooling temperature, and the content thereof is 0 to 19 mol%, preferably 5%.
Is about 13 mol%. When the content of YF ₃ is less than the above lower limit, the glass melt tends to become milky white in the cooling process,
On the other hand, when the amount is more than the upper limit, compositional change occurs during melting due to boiling of the melt, and even if boiling is suppressed, it is difficult to obtain a homogeneous glass because the crystal precipitation rate is high.

CaF ₂ , BaF ₂ , ZnF ₂ and NaF are components that act to modify the network structure of the glass, and are in the above-mentioned limited range, preferably CaF ₂ is 5 to 17 mol%, Ba
F ₂ is 8 to 23 mol%, ZnF ₂ is 10 to 23 mol%,
When NaF exceeds the range of 4 to 16 mol%, the rate of crystal precipitation in the melt during the cooling process becomes high, and it becomes difficult to obtain a homogeneous glass. Further, when NaF exceeds the upper limit of the above-mentioned limited range, the water resistance of the glass decreases.

Further, the fluoride glass of the second invention for solving the above-mentioned conventional problems is ZrF ₄ , AlF ₃ , YF ₃ and CaF.
₂ , a mixture of BaF ₂ , ZnF ₂ and NaF, and LiF, TlF, MgF ₂ and Sr as additional components.
F ₂ , PbF ₂ , GaF ₃ , InF ₃ , LaF ₃ , Yb
F _{3, GdF 3,} adding at least one kind of HfF _4, ZrF proportion of each component in mol% _{4: 5~23% AlF 3: 10~19.9} % YF 3: 0~19% _{CaF 2: 0~18% BaF 2:} 5~30% ZnF 2: 5~28% NaF: 0~23% LiF: 0~6% TlF: 0~10% MgF 2: 0~5% SrF 2: 0 _{~20% PbF 2: 0~10% GaF} 3: 0~5% InF 3: 0~5% LaF 3: 0~5% YbF 3: 0~8% GdF 3: 0~5% HfF 4: 0~ 10%, and the total amount of the additional components is 0.5 to 25 mol%.
Is.

The ZrF ₄ content is 5 to 25 mol%, preferably 10 to 20 mol%. When the ZrF ₄ content exceeds this range, the rate of crystal precipitation in the melt during the cooling process is high. It becomes difficult to obtain homogeneous glass.

The content of AlF ₃ is 10 to 19.9 mol%, preferably 14 to 19 mol%. When the content of AlF ₃ is lower than the lower limit, not only the melt tends to become milky white but also the water resistance of glass is high. The sex becomes worse. _{On the} other hand, when the content of AlF ₃ exceeds the upper limit, the melting and casting temperatures of glass become high, and the rate of crystal precipitation in the melt during the cooling process becomes high.

YF₃Is the glass melt casting, slow cooling temperature
Not only to adjust the glass, but also to improve the water resistance of the glass
And its content is 0 to 19 mol%, preferably
Is 5 to 13 mol%, YF₃Content is below this lower limit
When the amount is low, the glass melt tends to become milky white during the cooling process.
If it exceeds the upper limit, it is melting due to boiling of the melt.
Change of composition occurs in the crystal, and even if the boiling is suppressed, the crystal
Uniform due to high exit speed Hard to get a good glass
It

CaF ₂ , BaF ₂ , ZnF ₂ and NaF are components that act to modify the network structure of the glass, and are in the above-mentioned respective limiting ranges, preferably CaF ₂ : 5 to 17 mol%, B
aF _2: 8~23 mol%, ZnF _2: 10~23 mol%,
When the content of NaF exceeds 4 to 16 mol%, the rate of crystal precipitation in the melt during the cooling process becomes high, and it becomes difficult to obtain a homogeneous glass. Further, when NaF exceeds the upper limit of the above-mentioned limited range, the water resistance of the glass decreases.

Further, LiF, TlF, MgF ₂ , Sr
F ₂ , PbF ₂ , GaF ₃ , InF ₃ , LaF ₃ , YbF ₃ ,
GdF ₃ and HfF ₄ are additives useful for controlling the optical and thermal properties of the glass, and they can be added within the above-mentioned limited range, but their total amount is 25 mol%.
If the amount is larger, crystals tend to precipitate during the process of cooling the glass melt.

[0017]

EXAMPLES The present invention will now be described in more detail with reference to specific examples. <Example 1> As shown in Table 1, the composition of the obtained glass is expressed in mol%, and ZrF is 4: 16% and AlF is 3:18.
%, YF3: 11%, CaF2: 15%, BaF2: 1
5%, ZnF2: 20%, NaF: 5%,
A total of 50 g was weighed and melted at 900 ° C. for 2 hours at 650 ° C. for 1 hour in a platinum crucible under an inert gas atmosphere, and then poured into a mold having a diameter of 10 mm and a length of 100 mm, and then heated at 300 ° C. It was put in an electric furnace and gradually cooled.

The compound of the above composition obtained is colorless and transparent.
It was. In the differential thermal analysis, the glass transition point 322
℃, crystallization start point 407 ℃ (crystallization peak is 485
℃), a melting point of 550 ° C was observed, and X-ray diffraction
A halo pattern peculiar to amorphous Or did it not appear
The obtained compound was determined to be glass.

Further, when the outer circumference of the obtained glass was optically polished and a heat shrinkable Teflon FEP tube was jacketed to form a fiber, the preform surface temperature was 36.
A fiber having an outer diameter of 125 μm could be stably spun at 5 ° C., and thermal decomposition of Teflon was not observed. When the refractive index of this glass was measured with a Pulfrich refractive index measuring device, it was 1.4689 in the wavelength band of sodium d-line.

Further, the above glass is 4 × 5 × 16 mm
The glass block (the surface was polished to JIS standard abrasive grain size 400) was used, and the weight loss was measured when the glass block was immersed in distilled water at 100 ° C. and a 1 / 100N nitric acid aqueous solution for 2 hours. , 0.8% by weight for distilled water,
In the case of a 1 / 100N nitric acid aqueous solution, it was 1.1% by weight.

<Examples 2 to 22> Compounds having the compositions shown in Table 1 were prepared in the same manner as in Example 1. All the compounds were colorless and transparent, and had a glass transition point and a crystal in differential thermal analysis. It was determined that the substance was glass, because a crystallization peak and a crystalline melting point were observed, and only a halo pattern peculiar to amorphous appeared even in X-ray diffraction.

<Comparative Examples 1-8> Compounds having the compositions shown in Table 2 were prepared in the same manner as in Example 1. All of the compounds were white opaque materials, and in addition to the halo pattern in X-ray diffraction, Since a sharp peak peculiar to the crystal appeared, it was determined to be a mixture of crystalline and glassy.

<Comparative Example 9> The composition of the obtained glass is molar.
%, ZrF_Four: 47.5%, AlF₃: 4.5% , YF
₃: 2.0%, LaF₃: 2.5%, BaF₂: 23.5
%, NaF: Weigh 50 g in total so as to be 20%
And melting and annealing in the same manner as in Example 1
A colorless transparent glass body was obtained. This differential thermal analysis
At a glass transition point of 272 ° C. and a crystallization start temperature of 475 ° C.
there were.

On the other hand, the refractive index of the obtained glass at the sodium d-line was 1.4943, which was higher than that of the material of Example 1 by 0.025 or more. Further, when the same dissolution test as in Example 1 was conducted, as shown in Table 3, the value was about 5 times larger than that of the material of Example 1.

<Comparative Example 10> The composition of the obtained glass is expressed in mol%, ZrF ₄ : 10.2.%, AlF ₃ : 300.1.
%, YF ₃ : 8.3%, BaF ₂ : 10.6%, NaF:
3.8%, MgF ₂ : 3.5%, CaF ₂ : 20.3%,
A total amount of 50 g was weighed so that SrF _{2 was} 13.2%, and melted, cast, and gradually cooled in the same manner as in Example 1 to obtain a colorless transparent glass body.

When the glass was subjected to differential thermal analysis, the glass transition point was 393 ° C., the crystallization start temperature was 466 ° C., and the crystal melting temperature was 660 ° C. The outer periphery of the obtained glass rod was optically polished, and an attempt was made to form a fiber by the same method as in Example 1. However, it was necessary to raise the glass surface temperature to 430 ° C. or higher, and the Teflon resin foamed and could not be formed into a fiber. It was

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

As is apparent from the above-mentioned examples, the fluoride glass of the present invention has a lower refractive index and a higher chemical durability than the conventionally known ZrF ₄ type glass, and AlF.
It is suitable for optical communication fiber, infrared energy transmission fiber, and mid-infrared window material because it has a lower melting and casting temperature than ₃ type glass and is easily made into fiber.

Claims (2)

[Claims] 1. ZrF ₄ : 5 to 23% AlF ₃ : 10 to 19.9% YF ₃ : 0 to 19% CaF ₂ : 0 to 18% BaF ₂ : 5 to 30% ZnF ₂ : 5 ~ 28% NaF: 0-23%, and a fluoride glass in which the total amount of these components is 75% or more. 2. ZrF ₄ , AlF ₃ , YF ₃ , CaF ₂ , B
A mixture of aF ₂ , ZnF ₂ and NaF is added to LiF, TlF, MgF ₂ , SrF ₂ and Pb as additional components.
F ₂ , GaF ₃ , InF ₃ , LaF ₃ , YbF ₃ , GdF ₃ ,
At least one kind of HfF ₄ is added, and the proportion of each of these components is expressed in mol% ZrF ₄ : 5 to 23% AlF ₃ : 10 to 19.9% YF ₃ : 0 to 19% CaF ₂ : 0 to 18 _{% BaF 2: 5~30% ZnF 2} : 5~28% NaF: 0~23% LiF: 0~6% TlF: 0~10% MgF 2: 0~5% SrF 2: 0~20% PbF 2: _{0~10% GaF 3: 0~5% InF} 3: 0~5% LaF 3: 0~5% YbF 3: 0~8% GdF 3: 0~5% HfF 4: 0-10% and A fluoride glass in which the total amount of the additional components is 25% or less.