JPH04305025A - Production of fluoride glass - Google Patents

Abstract

PURPOSE:To prevent the contamination of fluoride glass with carbon impurities and to produce the optically highly homogeneous fluoride glass. CONSTITUTION:A metallic complex as the starting material consisting of the metal elements and beta-diketone constituting fluoride glass is heated and vaporized, the formed gas current and a fluorine-contg. gas are introduced into a reaction system provided with a substrate, and the materials are subjected to reaction in the vapor phase or on the substrate in the reaction system to synthesize a fluoride glass. In this case, oxygen is introduced into the reaction system to prevent the fluoride glass from being contaminated with carbon impurities in the vapor-phase synthesis.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing optically highly homogeneous fluoride glass for use in optical fibers, laser glasses, lenses, etc.

0002

[Prior Art] Fluoride glass has been known to be optically highly homogeneous and ideal for optical fibers, laser glasses, lenses, etc., and has particularly excellent transmission characteristics in the infrared wavelength region. Therefore, it is attracting attention as a material with high potential for realizing ultra-low loss optical fibers in the infrared wavelength region.

[0003] Optical fibers made of this fluoride glass are expected to have a transmission loss of 10-2 dB/km or less, which exceeds that of quartz. It is considered the most promising glass material.

[0004] Conventionally, when manufacturing such fluoride glasses, a casting method has been adopted in which a glass melt produced by melting a batch of solid phase raw materials is poured into a mold and cooled to produce a glass rod. It had been. In addition, methods for manufacturing optical fiber preforms include the build-in casting method (see Japanese Patent Application Laid-Open No. 57-191240) and the two-layer melt method (see Japanese Patent Application Laid-Open No. 61-91032).
is proposed.

However, in these methods,
There are problems in that impurities of transition metals such as iron, nickel, copper, chromium, and cobalt are mixed in and moisture is adsorbed during weighing, pulverization, and mixing of raw materials. Since transition metal impurities have absorption in the infrared wavelength region, they cause a decrease in transmission characteristics in the infrared wavelength region. Moisture is mixed into the melt as an adsorbed impurity of the raw material, and due to the high temperature during melting, oxides are formed by dehydration condensation. This oxide precipitates as crystals during the cooling process and becomes a scatterer. Furthermore, there was also the problem that the container wall was corroded during the glass melting process and impurities were mixed in.

On the other hand, as a solution to these problems,
A metal complex consisting of a metal element and β-diketone that can constitute a fluoride glass is used as a starting material, and a gas flow obtained by heating and vaporizing the metal complex and a fluorine-containing gas are introduced into a reaction system provided with a substrate, and these are introduced into the reaction system. The present applicant has already proposed a gas phase reaction method (Japanese Unexamined Patent Publication No. 2-275726) in which fluoride glass is synthesized by reaction in the gas phase or on a substrate.

However, this method has a problem in that if the amount of fluorine-containing gas supplied is small, carbon produced by decomposition of the raw material will be mixed in as an impurity, causing coloration of the glass due to carbon. Furthermore, when the supply amount of fluorine-containing gas is increased,
There is a problem in that elements other than fluorine contained in this fluorine-containing gas mix into the glass and cause loss.

The present invention is intended to solve these problems, and aims to provide a method for producing optically highly homogeneous fluoride glass.

[0009]

[Means for Solving the Problems] A method for producing fluoride glass of the present invention to achieve the above-mentioned object uses a metal complex consisting of a metal element and β-diketone that can constitute fluoride glass as a starting material, Production of fluoride glass by introducing a gas stream obtained by heating and vaporizing the metal complex and a fluorine-containing gas into a reaction system provided with a substrate, and reacting them in the gas phase in the reaction system or on the substrate to synthesize fluoride glass. The method is characterized in that oxygen is introduced into the reaction system.

[0010] Furthermore, in the method for producing fluoride glass of the present invention, the fluorine-containing gas is fluorine, hydrogen, carbon, oxygen,
It is a compound gas of fluorine and at least one of boron, sulfur, nitrogen, chlorine, and bromine, and is characterized by being a mixed gas of one or more of fluorine or the compound gas.

[0011]

[Operation] A gas stream obtained by heating and vaporizing a metal complex consisting of a metal element and β-diketone and a fluorine-containing gas are introduced into a reaction system provided with a substrate, and oxygen is introduced into the reaction system to react in the gas phase or on the substrate. By synthesizing fluoride glass by doing this, it becomes possible to suppress the incorporation of carbon impurities by controlling the amount of oxygen added.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these embodiments in any way.

FIG. 1 shows a manufacturing apparatus for carrying out a method for manufacturing fluoride glass according to an embodiment of the present invention.

As shown in FIG. 1, reference numeral 1 denotes an aluminum chamber as a reaction system whose pressure is regulated under reduced pressure by an exhaust system consisting of a rotary pump, and is maintained at a pressure of 1 torr by the rotary pump. The entire chamber 1 is kept at 250°C by a heater 2, and a substrate (cylindrical tube) 3, which is a CaF2 plate, is installed inside the chamber 1 and heated to 250°C by the heater 2. .

[0015] This chamber 1 has inlet ports 1a and 1b formed therein. The insulating heater 6 is installed on the outer periphery of the inlet 1a.
Raw material supply pipes 7a to 7e equipped with a to 6e are connected to each raw material supply pipe 7a to 7e, and aluminum evaporators 8a to 8e are connected to the raw material supply pipes 7a to 7e. Heat retention heaters 9a to 9e are installed, and
Inside the evaporators 8a to 8e, a raw material organometallic complex 10 is provided.
is filled. On the other hand, a supply pipe 4 is connected to the inlet 1b, and a heat-retaining heater 5 is attached to the outer periphery. In this embodiment, a gas flow of an organometallic compound is introduced through the inlet 1a, and a fluorine-containing gas and oxygen are introduced through the inlet 1b.

(Example 1) In this example, a compound of Zr and CF3 -CO-CH-CO-CF3 and a compound of Ba and C2 F5 -CO-CH-CO-C were used as starting materials.
(CH3)3 compound (hereinafter referred to as Zr(hf
a) 4 , abbreviated as Ba (ppm) 2 ) was used. Then, Zr(hfa)4 is introduced from the inlet 1a of the chamber 1.
and Ba (ppm)2 are introduced.

Zr(hfa)4 and Ba(ppm)2
Ar gases are supplied as carrier gases, which are vaporized by keeping the temperature at 60° C. and 200° C., respectively. That is,
Zr(h
An evaporator 8 filled with fa)4 and Ba(ppm)2 is connected, and while heating this evaporator 8, Z
Ar is supplied into the chamber 1 by introducing Ar into r(hfa)4 and Ba(ppm)2. Note that the above-mentioned Zr(hfa)4 and Ba(ppm)2 are Ar
Each can be adjusted by adjusting the flow rate of the carrier gas. Note that the supply pipe 7 is kept at a temperature of 240° C. by a heat insulating heater 6 in order to suppress condensation of the gas.

Zr(
hfa)4 and Ba(ppm)2 react with NF3 in the gas phase or in the cylindrical tube 3 to form fluoride, which is deposited there as glass.

ZrF4 produced in the cylindrical tube 3 by the above reaction
Since the temperature of the cylindrical tube 3 is lower than the glass transition temperature, the mobility of BaF2 is small here, and the temperature of the cylindrical tube 3 is lower than the glass transition temperature.
frozen inside. Therefore, a non-equilibrium state can be realized in the same way as in the case of rapid cooling. By sequentially depositing them, it becomes possible to produce a glass film or bulk glass. At this time, organic components contained in the metal complex consisting of the metal element and β-diketone are decomposed by heat, and carbon is mixed into the glass as an impurity. Here, through the supply pipe 4, the inlet 1b
By introducing oxygen into the reaction system, carbon can be oxidized and removed from the system as CO2. Furthermore, if the temperature of the reaction system is 900° C. or lower, the reaction system described below is thermodynamically stable, and no oxygen is mixed into the glass unless the equilibrium partial pressure at each temperature is exceeded. Therefore, it is possible to produce a fluoride glass in which carbon is removed by the partial pressure of oxygen in the gas phase while limiting the amount of oxygen added. ZrO2 (s) + 2F2 (g) → ZrF4 (s)
+O2 (g)

In this example, Zr(hfa)4:2s
ccm, Ba(ppm)2:1sccm, NF3
:10~100sccm, O2 :1~200sccm
As a result of reaction for 2 hours under the conditions of m, 65ZrF4 −
A glass film with a thickness of 5 mm having a composition of 35BaF2 could be produced.

Regarding the glass thus produced,
Oxygen and carbon in the glass were analyzed by secondary ion mass spectrometry (SIMS). Figure 2 shows NF3 at 50 sccm.
The analysis results of oxygen and carbon in glass are shown when the oxygen concentration is changed from 0 to 100 sccm. As is clear from FIG. 2, when NF3 alone is used, about 10
0 ppm of carbon is mixed as an impurity, but carbon is reduced by adding oxygen, and when oxygen is 10 sccm or more, 1 ppm of carbon is mixed in as an impurity.
m or less. In addition, when oxygen is fixed at 50 sccm, carbon and oxygen 1 p at NF3: 50 sccm or more.
A glass having a particle diameter of 100 pm or less was obtained. As described above, NF3 alone could not suppress the incorporation of carbon into the glass, but carbon could be removed by introducing oxygen. Even a small amount of oxygen introduced is effective in removing carbon, and even if a large amount is added, the amount of oxygen mixed into the glass will not suddenly increase, but in order to reduce both oxygen and carbon to 1 ppm or less, [O2 ]/
[NF3] (molar ratio) = 0.01 to 0.5, 1000
To control the amount of oxygen mixed into glass down to ppm [O2
]/[NF3] (molar ratio)=0.5 to 5 is desirable.

As described above, by mixing oxygen into the fluorine-containing gas, while suppressing the mixing of carbon into the glass,
The oxygen concentration in the glass can be controlled.

(Example 2) In this example, a waveguide was used in the reaction system to supply microwaves of 2.45 GHz to generate plasma as an excitation source for the reaction.
, Ba(ppm)2 plus Al(hfa)3
Glass was synthesized in the same manner as in Example 1, except that a container filled with , Na (ppm), and La (ppm) 3 was connected and CF 4 was used as the fluorine-containing gas. Synthesis conditions are Zr(hfa)4:2sccm, Ba(ppm)
2: 1sccm, La (ppm) 3: 0.1sc
cm, Al(hfa)3:0.1sccm, Na(p
pm): 1sccm, CF4: 10-100sccm
, O2: 1~200sccm, Microwave output: 50
Synthesis was carried out using W and a pressure of 1 torr, and a glass film with a thickness of 2 mm was obtained in 3 hours.

FIG. 3 shows the results of SIMS analysis of the obtained glass. As is clear from Figure 3, when using CF4 alone, the amount of carbon due to the decomposition of the raw material and the decomposition of CF4 is 1000 ppm.
However, by introducing oxygen, it is possible to suppress the mixing of carbon, and by increasing the amount of oxygen introduced, it is possible to control the amount of oxygen mixed into the glass. In order to reduce both oxygen and carbon to 1 ppm or less, [
It is desirable that [O2]/[CF4] (molar ratio) = 0.05 to 1, and in order to control the amount of oxygen mixed up to 1000 ppm, [O2]/[CF4] (molar ratio) = 1 to 5.
is desirable. In addition, instead of CF4, C2 F6 , C
Similar effects can be obtained using 3F8 and CHF3.

(Example 3) In this example, fluoride glass was synthesized using the same apparatus as in Example 2 described above, except that SF6 was used instead of CF4. Synthesis was carried out under these conditions for 3 hours to obtain a glass film with a thickness of 2.5 mm. FIG. 4 shows the SIMS analysis results of the obtained glass. Figure 4
As is clear from the above, SF6 alone causes decomposition of the raw material and S
It can be seen that although carbon and sulfur are mixed in due to the decomposition of F6, this can be suppressed by adding oxygen. In addition, in order for carbon, oxygen, and sulfur to all be 1 ppm or less, [O2
]/[SF6] (molar ratio) = 0.05 to 1 is desirable, and to control the mixing of oxygen up to 1000 ppm, [O
2]/[SF6] (molar ratio) = 1 to 8 is desirable.

(Example 4) In this example, fluoride glass was synthesized using the same apparatus as in Example 2 described above, except that NF3 was used instead of CF4. Synthesis was carried out under these conditions for 3 hours to obtain a 3 mm thick glass film. Figure 5
The results of SIMS analysis of the glass obtained are shown below. As is clear from Fig. 5, NF3 alone causes decomposition of the raw material, NF3
It can be seen that although carbon contamination occurs due to the decomposition of carbon, it can be suppressed by adding oxygen. Also, in order for carbon and oxygen to all be 1 ppm or less, [O2]/[NF3]
(Mole ratio) = 0.01 to 3 is desirable, and 1000 ppm
To control the mixing of oxygen up to [O2 ]/[NF3
] (Molar ratio)=3 to 5 is desirable.

(Example 5) In this example, fluoride glass was synthesized using the same apparatus as in Example 4 described above, except that a low-pressure mercury lamp was used instead of the microwave plasma. Synthesis was carried out under these conditions for 3 hours to obtain a glass film with a thickness of 0.5 mm. FIG. 6 shows the SIMS analysis results of the obtained glass. As is clear from FIG. 6, when NF3 is used alone, the decomposition of the raw material and the contamination of carbon due to the decomposition of NF3 occur, but this can be suppressed by adding oxygen. In addition, in order for carbon and oxygen to all be 1 ppm or less, [O
2]/[NF3] (molar ratio) = 0.01 to 5 is desirable, and [O2]/[NF3] (molar ratio) = 5 to 10 is desirable to control the mixing of oxygen up to 1000 ppm.

(Example 6) In this example, glass was synthesized using the same apparatus as in Example 2 described above, except that BF3 was used as the fluorine-containing gas. The synthesis conditions were Zr(hfa
)4:2sccm, Ba(ppm)2:1scc
m, La (ppm)3: 0.1 sccm, Al (h
fa)3: 0.1sccm, Na (ppm): 1sc
cm, CF4: 10~100sccm, O2: 1~
200sccm, microwave output: 50W, pressure 1to
Synthesis was carried out using rr, and a glass film with a thickness of 2.5 mm was obtained in 3 hours. FIG. 7 shows the SIMS analysis results of the obtained glass. As is clear from Figure 7, when using BF3 alone, carbon due to decomposition of the raw material and boron due to decomposition of BF3 are 20pp.
However, by introducing oxygen, it is possible to suppress the mixing of carbon and boron, and by increasing the amount of oxygen introduced, it is possible to control the amount of oxygen mixed into the glass. In order to reduce both oxygen and carbon to 1 ppm or less, [O2]/[BF3] (molar ratio) = 0.0
The ratio is preferably 1 to 2, and in order to control the amount of oxygen mixed up to 1000 ppm, [O2]/[BF3] (molar ratio) is preferably 2 to 5.

(Example 7) In this example, fluoride glass was synthesized using the same apparatus as in Example 1 described above, except that HF was used instead of CF4. Under this condition 3
Time synthesis was performed to obtain a glass film with a thickness of 3 mm. FIG. 8 shows the SIMS analysis results of the obtained glass. As is clear from FIG. 8, when SF6 is used alone, carbon contamination occurs due to decomposition of the raw material, but it can be suppressed by adding oxygen. Also, in order for carbon to be 1 ppm or less, [O2]/
[HF] (molar ratio) = 0.05 to 0.5 is desirable, and 1
To control oxygen contamination up to 000 ppm [O2
]/[HF] (molar ratio)=3 to 8 is desirable.

(Example 8) In this example, fluoride glass was synthesized using the same apparatus as in Example 2 described above, except that ClF3 was used instead of CF4. Synthesis was carried out under these conditions for 3 hours to obtain a 3 mm thick glass film. FIG. 9 shows the SIMS analysis results of the obtained glass. As is clear from FIG. 9, when using ClF3 alone, carbon contamination occurs due to decomposition of the raw material, but this can be suppressed by adding oxygen. In addition, in order for all carbon to be below 1 ppm, [O
2]/[ClF3] (molar ratio) = 0.01 to 1 is desirable, and [O2]/[ClF3] (molar ratio) = 5 to 10 is desirable to control the mixing of oxygen up to 1000 ppm. Similar effects were obtained when BrF3 was used instead of ClF3.

(Example 9) In this example, fluoride glass was synthesized using the same apparatus as in Example 2 described above, except that OF2 was used instead of CF4. Synthesis was carried out under these conditions for 3 hours to obtain a glass film with a thickness of 1.5 mm. FIG. 10 shows the SIMS analysis results of the obtained glass. As is clear from FIG. 10, when OF2 is used alone, carbon contamination occurs due to decomposition of the raw material, but it can be suppressed by adding oxygen. Also, carbon and oxygen are all 1 ppm.
In order to achieve the following, it is desirable that [O2]/[OF2] (molar ratio) = 0.02 to 0.1, and to control the mixing of oxygen up to 1000 ppm, [O2]/[OF2]
(Molar ratio)=0.5-1 is desirable.

(Example 10) In this example, fluoride glass was synthesized using the same apparatus as in Example 2 described above, except that F2 was used instead of CF4. Synthesis was carried out under these conditions for 3 hours to obtain a glass film with a thickness of 3.5 mm. FIG. 11 shows the SIMS analysis results of the obtained glass. As is clear from Figure 10, even when F2 is used alone, no carbon is mixed in due to the decomposition of the raw material, and the amount of carbon mixed is 0.1 ppm.
It is as follows. Oxygen can be added to glass by adding oxygen, and to control oxygen contamination up to 1000 ppm, [O2]/[F2] (molar ratio) = 2
．． 5-5 is desirable.

[0033]

Effects of the Invention As described above in detail with reference to Examples, according to the method for producing fluoride glass of the present invention, a metal complex consisting of a metal element and β-diketone that can constitute a fluoride glass can be produced. In the process of synthesizing fluoride glass by introducing a heated and vaporized gas stream and a fluorine-containing gas as starting materials into a reaction system equipped with a substrate and reacting them in the gas phase of the reaction system or on the substrate, By introducing oxygen, it is now possible to suppress the incorporation of carbon impurities during the gas phase synthesis of fluoride glasses, which was difficult in the past, and to control the amount of oxygen added into the glass. Homogeneous fluoride glasses can be synthesized. As a result, by producing optical fibers using these glasses, it is possible to produce ultra-low loss optical fibers that have not been previously available.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a manufacturing apparatus for carrying out a method for manufacturing fluoride glass according to an embodiment of the present invention.

FIG. 2 is a graph showing the SIMS analysis results of the glass produced in Example 1.

FIG. 3 is a graph showing the SIMS analysis results of the glass produced in Example 2.

FIG. 4 is a graph showing the SIMS analysis results of the glass produced in Example 3.

FIG. 5 is a graph showing the SIMS analysis results of the glass produced in Example 4.

FIG. 6 is a graph showing the SIMS analysis results of the glass produced in Example 5.

FIG. 7 is a graph showing the SIMS analysis results of the glass produced in Example 6.

8 is a graph showing the SIMS analysis results of the glass produced in Example 7. FIG.

9 is a graph showing the SIMS analysis results of the glass produced in Example 8. FIG.

10 is a graph showing the SIMS analysis results of the glass produced in Example 9. FIG.

FIG. 11 is a graph showing the SIMS analysis results of the glass produced in Example 10.

[Explanation of symbols]

1 Chamber 1a Raw material inlet 1b Fluorine-containing gas and oxygen inlet 2 Heat retention heater 3 Substrate (cylindrical tube) 4 Fluorine-containing gas and oxygen supply pipes 5, 6 Raw material supply pipe heat retention heater 7 Raw material supply pipe 8a Zr (hfa) 4 filled evaporator 8b
Evaporator 8c La filled with Ba (ppm)2
(ppm) 3 evaporator 8d Al (hf
a) Evaporator 8e filled with 3 evaporator 9 filled with Na (ppm) Raw material heating heater 10 Raw material organometallic complex

Claims (2)

[Claims] Claim 1: A metal complex consisting of a metal element capable of constituting a fluoride glass and a β-diketone is used as a starting material, and a gas stream obtained by heating and vaporizing the metal complex and a fluorine-containing gas are introduced into a reaction system provided with a substrate. , a method for producing fluoride glass in which fluoride glass is synthesized by reacting these in a gas phase or on a substrate in a reaction system, the method comprising introducing oxygen into the reaction system. 2. The method for producing fluoride glass according to claim 1, wherein the fluorine-containing gas is a compound gas of fluorine or at least one of hydrogen, carbon, oxygen, boron, sulfur, nitrogen, chlorine, and bromine and fluorine. A method for producing fluoride glass, characterized in that the gas is one or a mixture of two or more of fluorine or said compound gas.