JP2979840B2 - Method for producing material for fluoride glass fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a material for a fluoride glass fiber using a chemical vapor deposition (CVD) method of a low-loss fluoride fiber used in, for example, an optical communication system.

[0002]

2. Description of the Related Art In recent years, the progress of optical communication systems has been remarkable, and as one of them, attempts have been made to realize long-distance communication systems using infrared optical fibers. To achieve this, a fiber having a low loss property far exceeding that of a silica-based optical fiber is indispensable. Candidate materials for these infrared optical fibers include fluoride glass, chalcogenide glass, and halide crystals. Among them, fluoride glass is considered most promising in terms of performance, difficulty in the production method, and the like. As a method for producing fluoride glass, a solid phase method in which a fluoride is melted and reacted using a crucible and various gas phase methods have been actively studied.In this method, impurities from the crucible are mixed into the glass. It is easy to use and there is no established manufacturing method. Of these, recently, the CVD method has attracted attention as an excellent method for synthesizing high-purity homogeneous glass, and many attempts have been made.

As the performance required of such a material for a fluoride fiber, low loss is the most important. Further, in terms of a manufacturing process, it can be easily manufactured at a high speed. In particular, in order to obtain a low loss, it is necessary to suppress the generation of impurities and microcrystals that cause optical transmission loss. From such a viewpoint, a CVD method that can easily purify an organometallic compound as a raw material by purification and easily suppress microcrystals by improving a raw material, a reaction gas, reaction conditions, and the like is a very important method for manufacturing the above material. Is advantageous. These are described in, for example, the publication {52th Annual Meeting of the Japan Society of Applied Physics, Proceedings No. 11a-ZK-9}.
And so on.

[0004]

However, despite the fact that it is most advantageous to manufacture by the CVD method, the fact that there is no material having a stable and good vaporization characteristic as a CVD material at present does not exist. This is a major problem that cannot take advantage of the advantages of the law. This is mainly due to C
This is because β-ketone-based dipivaloylmethane (DPM) compounds, which are frequently used as a raw material for VD, have poor vaporization characteristics due to heating and are easily thermally decomposed. This point is pointed out, for example, in the publication {The 52nd Annual Meeting of the Japan Society of Applied Physics, Proceedings No. 11a-ZK-8}, and is considered to be a drawback caused by the intrinsic instability of metal DPM compounds. Can be Due to such instability of the raw materials, in extreme cases, the raw materials have to be disposable and synthesized. Therefore, due to the drawbacks caused by the above-mentioned raw materials, a CVD technique for producing a fluoride fiber material having good performance and good production reproducibility has not been established.

That is, in the production of a material for a fluoride fiber by the conventional CVD method, it is impossible to stably transport the raw material to the CVD reaction section by heating at a low temperature due to the poor stability and vaporization of the raw material. Met. Therefore, there has been a great problem that it is difficult to control the composition of a multi-component system, and it is not possible to stably and quickly synthesize a fiber material having good characteristics. Furthermore, if the raw material is heated at a high temperature in order to increase the vaporization efficiency, the raw material is transported while being thermally decomposed, so that the incorporation of impurities into the sediment, the formation of microcrystals, and the composition shift are inevitable. Not only that,
There has also been a disadvantage that the above-mentioned raw materials must be disposable. Further, in the conventional method, when the vaporization rate is suppressed and the synthesis (reaction) time is lengthened, the vaporized state of the raw material changes with time, so that the composition in the thickness direction of the formed film becomes inhomogeneous. It was inevitable that the light loss would increase. Therefore, there is a strong demand for the development of a new raw material that can provide stable and good vaporization at a low temperature, but there is no progress on this at all.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a method for easily and rapidly producing a material for a fluoride glass fiber having good performance.

[0007]

According to the present invention, there is provided a method for producing a material for a fluoride glass fiber, comprising the steps of: evaporating a component raw material in which a metal atom belonging to Group IA or IVA of the periodic table is bonded to an organic group via an oxygen atom; A method in which at least one kind of vapor of dipivaloylmethane and tetrahydrofuran is brought into contact with the above-mentioned raw materials and then reacted.

[0008]

According to the present invention, IA to IV in the periodic table are used.
In the vaporization step of a compound raw material in which a group A metal atom is bonded to an organic group via an oxygen atom, by contacting at least one vapor of dipivaloylmethane and tetrahydrofuran, thermal decomposition of the raw material is suppressed. At the same time, the raw material can be transported to the reaction section more stably and at a higher speed by heating at a lower temperature than before, so that the raw material with good reproducibility can be vaporized.

[0009]

EXAMPLES The inventors of the present invention have studied in detail the volatility of a compound in which a metal atom is bonded to an organic group, such as the above-mentioned DPM compound, and as a result, among these compounds, in particular, the main component of fluoride fiber It has been found that the compounds of Group IA to Group IVA, such as Li, Na, Sr, Ba, Y, La, Zr, and Hf, have poor stability and poor vaporization. Therefore, it has been found that in the case of synthesizing a fluoride glass mainly containing an oxide of such a metal by a CVD method, it is inevitable that controllability to a target composition is particularly difficult. Thus, the present inventors, if these compounds can be stably vaporized without being thermally decomposed by heating at a lower temperature than before, the controllability of the composition is improved, and a fiber material having desired characteristics is obtained. They have found that they can be synthesized at high speed with good reproducibility, and have completed the present invention.

Embodiment 1 FIG. Using a normal hot wall type CVD apparatus having a pentagonal raw material heating system, 50ZrF ₄ -30BaF ₂ -10LaF ₃ -10YF ₃ which is a zirconium-based fluoride glass according to one embodiment of the present invention.
Was synthesized on a magnesium oxide substrate. As a raw material, a conventionally existing acetylacetonate derivative of each metal was used, and steam of dipivaloylmethane was flowed into and contacted with each of the quaternary raw materials during heating. As the synthesis conditions, the heating temperature of all the raw materials was set to 210 ° C., the carrier gas was argon, the reaction gas was carbon tetrafluoride, the pressure inside the reaction section (furnace) was 1 Torr, and the substrate temperature was 22 ° C.
The reaction was maintained at 0 ° C. for 120 minutes. After the reaction, the resultant was naturally cooled slowly to room temperature in a stream of carbon tetrafluoride. As a result, a fluoride glass having a thickness of about 3 μm according to one embodiment of the present invention was obtained. The light transmittance of the glass was measured using an infrared spectrophotometer, and was used as a rough index of infrared light transmission loss when a fiber was manufactured using the glass. Further, the film quality and crystal state of the glass fiber material were observed and investigated with an electron microscope.

Comparative Example 1 Using the same raw material and synthesis conditions as in Example 1, a material for a fluoride glass fiber having the same composition was synthesized by a conventional CVD method without mixing of tetrahydrofuran vapor. However, it was found that heating at 210 ° C. resulted in poor vaporization. Therefore, in the conventional method, the heating temperature of the raw materials is uniformly reset to 290 ° C., and the synthesis is performed for 120 minutes. As in the case of Example 1, the reaction is allowed to cool naturally to room temperature in a stream of carbon tetrafluoride. Thus, a film having a thickness of 1 μm was obtained. This film was also evaluated for film quality and light transmittance (light transmission loss) in the same manner as described above.

FIG. 1 is an infrared light loss characteristic diagram showing the infrared light loss characteristics of the two types of fluoride fiber glass materials obtained in Example 1 and Comparative Example 1 for comparing the present invention with the conventional example. In the figures, A1 indicates the characteristics of the fluoride fiberglass material of Example 1, and B1 indicates the characteristics of the fluoride fiberglass material of Comparative Example 1. As is apparent from FIG. 1, the fiber glass material according to one embodiment of the present invention has a lower loss over the entire infrared light region than that of the conventional manufacturing method, and is particularly intended as a wavelength of communication signal light. This tendency is remarkable at a wavelength around 2.55 μm. In the above experiment, both CVDs were used.
When the deposition rates in the synthesis of zirconium-based fluoride glass by the method were compared, it was found that, at the same heating (vaporization) temperature, the embodiment of the present invention was 50 to 100 times better than the conventional method. Further, according to the surface observation of both fiber glass materials, a microcrystalline structure was formed in some places according to the conventional method, whereas no formation was observed in the embodiment of the present invention. That is, according to the embodiment of the present invention, it has been found that the generation of microcrystals which causes light transmission loss can be suppressed. Therefore, according to the embodiment of the present invention, it is possible to synthesize a glass material for a fluoride fiber having excellent performance by the CVD method by heating at a much lower temperature than the conventional manufacturing method.

Embodiment 2 FIG. Using the same CVD apparatus as in Example 1, 50ZrF which is a zirconium-based fluoride glass
₄ -20BaF ₂ -5LaF ₃ -5AlF ₃ -20NaF magnesium oxide substrate was subjected to other examples the synthesis of the present invention. As a raw material, a dipivaloyl methanate derivative of each metal that has been widely used in the past is used as a raw material, and while these are all heated to 190 ° C., each is an organic solvent together with argon as a carrier gas in each. Tetrahydrofuran vapor was flowed in and brought into contact. The substrate temperature was set at 200 ° C. The reaction gas is hydrogen fluoride and the pressure inside the reactor (furnace) is 10 at 1 Torr.
The reaction was performed for 0 minutes. After the reaction, the resultant was naturally cooled slowly to room temperature in a hydrogen fluoride gas stream. As a result, a fluoride glass having a film thickness of about 5 μm according to another embodiment of the present invention was obtained. Light transmittance was measured as an index of infrared light loss of this glass material using an infrared spectrophotometer in the same manner as in Example 1. Further, the film quality and crystal state of the glass material were examined with an electron microscope.

Comparative Example 2 Using the same raw material and synthesis conditions as in Example 2, a glass material for a fluoride fiber having the same composition was synthesized by a conventional CVD method without mixing of tetrahydrofuran vapor. However, the deposition on the substrate was slight, and it was found that heating at 190 ° C. resulted in poor vaporization. Therefore, in the conventional method, the heating temperature of the raw materials is uniformly reset to 270 ° C., and the synthesis is performed for 120 minutes. After the reaction, the mixture is spontaneously released to room temperature in a hydrogen fluoride gas stream as in the other embodiments of the present invention. 2 μm after cooling
Was obtained. This film was similarly evaluated for film quality and light transmittance (light loss) on the same basis as in Example 2.

FIG. 2 is an infrared light loss characteristic diagram showing infrared light loss characteristics of the two kinds of fluoride fiber glass materials obtained in the above-mentioned Example 2 and Comparative Example 2 which compare the present invention with the conventional example. In the figures, A2 indicates the characteristics of the fluoride fiber glass material of Example 2, and B2 indicates the characteristics of the fluoride fiber glass material of Comparative Example 2. As is apparent from FIG. 2, the material according to the other embodiment of the present invention has a lower loss over the entire infrared light region, especially around 2.55 μm, as compared with the material according to the conventional manufacturing method used as the comparative example. The same result as in the case of Example 1 in which this tendency was remarkable at the wavelength of was obtained. Further, as a result of examining the film quality of the glass material with an electron microscope, it was found that microcrystals were formed in some places by the conventional method, as in the comparative example of Example 1. Further, when the deposition rates in the synthesis of the zirconium-based fluoride glass of both CVD methods were compared during the above experiment, the same heating (evaporation) temperature was observed in the case of the method of another embodiment of the present invention. It was found to be ~ 50 times better. Therefore, according to another embodiment of the present invention, it can be seen that a glass material for a fluoride fiber having good performance can be synthesized at a high speed by the CVD method by heating at a much lower temperature than the conventional manufacturing method. It became clear.

In Examples 1 and 2, the main reason why the performance of the material for glass fiber according to the conventional method used in the comparative example is not good is that the raw material is hardly vaporized by heating, and
Further, it is considered that the raw material was decomposed due to heating at a relatively high temperature, and it was difficult to stably transport the raw material to the reaction section. That is, the main reason why the properties of the sample obtained by the conventional method as a material for a fiber are not good is that the composition in the synthetic film caused by the formation of microcrystals and the unstable transport of each raw material as described in the Examples. It is presumed that heterogeneity has occurred.

[0017] Using the method of Example of the present invention, in the same manner as in Example 1 and 2 is not limited to the composition shown in _{Example, ZrF 4 -BaF 2 -LaF 3 -YF} 3 -AlF 3 -L
_{iF, ZrF 4 -HfF 4 -BaF 2} -LaF 3 -NaF-
_{AlF 3, ZrF 4 -BaF 2 -GaF} 3 -AlF 3, Zr
Materials for fluoride glass fibers such as F ₄ —BaF ₂ —LaF ₃ —NaF—AlF ₃ —InF ₃ were produced by a CVD method. As a result, it was found that, in each case, similarly to Examples 1 and 2 described above, a material for a fluoride glass fiber having better performance than the conventional method can be manufactured by the example of the present invention.

Various organic solvents were examined for the vapor to be brought into contact with the component raw materials according to the present invention. The vaporization by heating at a low temperature, which is an effect obtained by the present invention, was obtained for the organic solvents other than the two used in the examples. The effect of the improvement was not clear. Therefore, in the present invention, it is necessary to use at least one of dipivaloylmethane and tetrahydrofuran as the vapor to be brought into contact with the raw material. Although the details of this effect are not clear, from the above experimental results, decomposition of the raw material due to heating is suppressed, and by adding it to the conventional raw material, an adduct having a lower boiling point than the raw material is formed. At the same time
It is presumed that this adduct functions to be stably transported to the reaction section.

Further, the present invention is not limited to a method of bringing the vapors of dipivaloylmethane and tetrahydrofuran into contact in the vaporization step of the component raw materials. As a contact method, as in the example, the raw material may be brought into direct contact with the raw material at the time of heating, or the raw material may be brought into contact with the raw material together with a carrier gas. Confirmed by. The vaporization step in the present invention refers to the time when the liquid or solid raw material becomes gas and immediately after it becomes gas.

The component raw materials according to the present invention include Li, Nb belonging to groups IA to IVA of the periodic table.
a, Ba, Sr, Y, La, Al, Gd, Zr, Hf,
It was confirmed by experiments that the above-mentioned effect of the organic solvent was exhibited when the compound was a compound in which a metal atom was bonded to an organic group via an oxygen atom. Therefore, acetylacetonate, dipivaloylmethanate, alkoxide, hexafluoroacetylacetonate, pentafluoropropanoylpivaloylmethanate, cyclopentadienyl, and derivatives thereof of the above-mentioned metals are considered as meeting these conditions. And the like were used, and it was confirmed that the above-described vaporization promoting effect was exhibited in each case. Among these starting organometallic compounds, derivatives containing fluorine, such as hexafluoroacetylacetonate and pentafluoropropanoylpivaloylmethanate, are particularly convenient for synthesizing a fluoride glass. In the present invention, if a fluorine compound such as carbon tetrafluoride, hydrogen fluoride, or sulfur hexafluoride is used as the reaction gas as in the conventional method, it is not always necessary to use the above-mentioned fluorine-containing derivative. In the experiments of the present invention, it was confirmed by the same experiment as in the examples that no difference was caused in the performance of the synthesized fiberglass material even when any of the above-mentioned organometallic compounds was used as a raw material. did.

[0021]

According to the present invention, as described above, dipivaloylmethane is added to the raw material in the vaporizing step of the component raw material in which a metal atom belonging to Group IA or IVA of the periodic table is bonded to an organic group via an oxygen atom. By bringing at least one kind of vapor out of tetrahydrofuran into contact, and then reacting, a method for producing a material for a fluoride glass fiber having good performance can be obtained easily and at high speed.

[Brief description of the drawings]

FIG. 1 is an infrared light loss characteristic diagram of a fluoride fiber glass material comparing the present invention with a conventional example.

FIG. 2 is a graph showing infrared light loss characteristics of a fluoride fiber glass material comparing the present invention with a conventional example.

[Explanation of symbols]

 A1 Properties of the fluoride fiber glass material of Example 1 A2 Properties of the fluoride fiber glass material of Example 2 B1 Properties of the fluoride fiber glass material of Comparative Example 1 B2 Properties of the fluoride fiber glass material of Comparative Example 2

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhiro Imada 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi Mitsubishi Electric Corporation Materials and Devices Laboratory (72) Inventor, Hisao Watoi 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi No. Mitsubishi Materials Corporation Materials and Devices Research Laboratory (72) Inventor Takeshi Sato 8-1-1 Tsukaguchi Honcho, Amagasaki City Mitsubishi Electric Corporation Materials and Devices Laboratory (56) References JP-A-2-275726 (JP, A) JP-A-5-117855 (JP, A) JP-A-5-132776 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) C03B 8/04 C03B 37/018 C23C 16 / 18

Claims (1)

(57) [Claims] 1. In a vaporization step of a component material in which a metal atom belonging to Group IA or IVA of the periodic table is bonded to an organic group via an oxygen atom, at least one of dipivaloylmethane and tetrahydrofuran is added to the material. And a method for producing a material for a fluoride glass fiber to be reacted.