JPS5815448B2 - Method for manufacturing phosphoric acid glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing glass that is a constituent material of an optical transmission line;
In particular, it relates to a method for producing glass containing a phosphoric acid compound.

Glass used for optical transmission lines, especially high-quality optical fibers, is required to have high purity.

However, "high purity" here means that the content of unintended impurities is extremely small, for example, several ppm or less.

As a method for obtaining high-purity glass as described above, a halide of an element that becomes a glass-forming oxide, such as 5iC1
4, using GeC1, TiC1, etc. as a starting material,
It is already well known to oxidize this raw material in the gas phase to give glass-forming oxides.

With this method, the starting materials are already of fairly high purity, so if care is taken with the purity of other reaction gases (H2, 02, etc.), glass-forming oxides of extremely high purity can be produced. .

However, the conventional well-known glass synthesis method described above,
This method is suitable for mass production because it uses a tube or rod-shaped body as a support and deposits glass-forming oxide (hereinafter referred to as soot) deposited in powder form from the gas phase on the inner wall of the tube or the surface of the rod-shaped body. There is a disadvantage of scarcity.

In addition, one of the present inventors proposed a method in which soot precipitated from the gas phase is once collected in a quartz container and heated from outside the container to vitrify it.

However, since the conventional glasses for optical transmission lines were mainly silicic acid-based glasses containing SiO2 as the main component, the temperature required for vitrification and melting of the soot was high, making it difficult to melt in a quartz crucible. To lower the alkali (
For example, if Na2O, etc.) is added, there is a problem that the quartz container will be eroded in the heated state.

Quartz (Sin2) is originally slightly acidic,
It is easily attacked by alkalis, but not easily attacked by weakly acidic substances.

Phosphorus pentoxide (PO
5) is well known, but P2O5 itself is highly chemically active and particularly absorbs moisture from the air.

Furthermore, since P2O5 is easily evaporated, it evaporates in large quantities at high temperatures during vitrification, resulting in the disadvantage that the amount of P2O3 contained in the resulting glass is considerably smaller than the amount initially mixed. .

As a countermeasure against this, it is desirable to use a phosphate in the form of MPO4 (M is a positive element such as a metal) instead of P2O5, but in the conventional manufacturing method of phosphate, it is used as a raw material for glass for optical transmission lines. Phosphate of high purity cannot be obtained.

Furthermore, in order to prevent the evaporation of easily evaporable P2O5, a method has been proposed in which a halogenated phosphorus compound such as POCl3 and a halogenated germanium compound such as GeCl4 are mixed in the gas phase and the mixed gas is oxidized.

Although this method can significantly reduce the evaporation of P2O5, the produced glass has a strong affinity for water and easily absorbs moisture from the air, so it has the drawback that it cannot be used as it is.

The present invention has been made in view of the above-mentioned points, and involves obtaining a phosphate glass raw material that forms a phosphate of the group (I) element through a gas phase chemical reaction between a compound of the group (I) element and a phosphorus compound, and adding other types of phosphoric acid to this raw material. It is an object of the present invention to provide a method for producing phosphoric acid glass in which a phosphoric acid compound is melted and vitrified in a mixed state.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Gallium (Ga), a type of group element, is associated with phosphoric acid and GaP.
It is well known to make a salt of the composition O4.

However, the conventional method for producing GaPO4 is gallium trioxide (
This is a method in which Ga20 and phosphoric acid (H3PO,) are reacted at high temperatures, and as described above, it is not possible to obtain a highly pure phosphate.

Furthermore, GaPO4 has a high melting point (approximately 1670° C.) and is not easily vitrified when used alone.

Therefore, the present inventors obtained a powdery reaction product, that is, soot, by subjecting a mixed vapor of gallium trichloride (GaC13) and phosphorus oxychloride (POC'13) to flame hydrolysis.

As will be explained later, this suit is small (mostly GaP
It was confirmed that it was O4.

The schematic structure of the apparatus used for this reaction is shown in the attached drawing.

In the figure, container 1 contains liquid POCl3, and container 2 contains liquid GaCl3.

Introducing pipes 3 and 4 for bubbling gas, such as argon (Ar), are inserted into both containers 1 and 2, and the vapors of POCl3 and GaCl3 are supported on Ar by bubbling, and are discharged from reaction gas outlet pipes 5 and 6, respectively. Extracted from the container.

Note that the POCl3 container 1 is maintained at 40° C., and the GaCl3 container 2 is maintained at 140° C. in a constant temperature bath (not shown).

Ar carrying the raw materials, which are led out from the reaction gas lead-out pipes 5 and 6, are mixed along the way, and further combined with 02 introduced from the oxygen lead-in pipe 7, and passed through the single mixed gas lead-in pipe 8 to the torch. Enter 9.

In addition to Ar and 02 carrying the above raw materials, 02 and H2 are introduced into the torch 9 from introduction pipes 10 and 11, respectively, and ignited to generate an oxyhydrogen flame 12.

The high heat of the oxyhydrogen flame causes a hydrolysis reaction of POCl3 and GaCl3, and the reaction product, soot 13, is precipitated, which is received by the crucible 14 and accumulated therein.

As a result of inspecting the soot 13 using an X-ray recovery method, it was found that all or most of it was gallium phosphate (GaPO4).

As is well known, extremely high purity GaCl3, POCl3, etc. used in the semiconductor industry are available, so the soot obtained as described above has an extremely low content of unnecessary components and is suitable for optical transmission lines. Suitable as a material for glass.

Based on the results of this experiment, the present inventors conducted a trial production experiment of glass for optical transmission lines according to the embodiment described below.

Example ■ GaP0. , P2O5 and G
The composite oxide soot with eO2 was mixed at a weight ratio of 36:64, and was melted and vitrified.

However, as mentioned above, the above composite oxide contains P and G.
It is obtained by mixing and oxidizing the halogen compound of e in the gas phase, and the mixing ratio is 40:60 in terms of P2O5:GeO2, and even when it is in a soot state, P
The present inventors have already confirmed that the amount of decrease in 2O5 is very small.

Now, GaP0. Temporarily 1/2 (Ga203+P2O5)
Considering this, the ratio of Ga2O3 is 57% by weight and P2O5 is 43% by weight, so the composition of the above glass is P2O5: 24%, GeO2: 56%, Ga2O
3: corresponds to 20%.

This glass is vitrified by melting it at approximately 1,500°C, and has a refractive index of 1,588, an optical transmission loss of 3.8 dB/km, and good water resistance, making it suitable as a constituent material for optical transmission lines. Fully usable.

Example 2 In this example, 53% by weight of GaPO4 soot and 47% by weight of a composite oxide soot of P2O5 and GeO2 were mixed, melted, and vitrified.

The composition of the glass thus obtained was P2O5: 42% by weight
, GeO2: 28% by weight, and Ga2O3: 30% by weight, and the refractive index was 1.574, which was about 1% lower than that of Example (2).

Further, the water resistance of this glass was as good as in Example (2).

From the above results, when a coated optical fiber is manufactured using the glass of Example I as the core glass and the same glass of Example 2 as the cladding glass, the numerical aperture is 0.
It is theoretically clear that 21 products can be obtained.

In the above embodiments, GaP0. was synthesized by flame hydrolysis, but similar results can be obtained by gas-phase oxidation without using hydrogen.

In addition, the raw materials are not limited to GaCl3 and POCl3,
Generally, it is thought that equivalent effects can be obtained if the reaction is carried out in the gas phase using a vaporizable compound of Ga and P.

According to the manufacturing method according to the present invention explained above, it is possible to manufacture a highly pure phosphoric acid compound, so it is extremely advantageous to apply to the manufacturing of optical transmission line glass and other high-purity glasses. problems arising from chemical activity and easy evaporation can be avoided.

Furthermore, if a composite oxide of Si or Ge is mixed and melted into a phosphoric acid compound of group (I) element obtained by a gas phase chemical reaction,
A glass with good optical properties and water resistance can be obtained, and this glass can be sufficiently vitrified at temperatures around 1500° C. Moreover, since it does not contain alkali, it is convenient for spinning in a quartz container, and various other advantages can be obtained.

[Brief explanation of drawings]

The accompanying drawing is a schematic system diagram for explaining the manufacturing process of a gallium phosphate compound in one embodiment of the manufacturing method of the present invention. 1: POCl3 container, 2: GaCl3 container, 3 and 4
: Gas introduction tube for bubbling, 5 and 6: Reaction gas outlet tube, 7: 0□ introduction tube, 8: Mixed gas introduction tube, 9: Torch, 10: 02 introduction tube to the torch, 11: Same<H2 introduction tube , 12: Oxyhydrogen flame, 13: Ga phosphorus oxide soot, 14
: Crucible.

Claims (1)

[Claims] 1. A method for producing phosphate glass, which comprises vitrifying a gallium phosphate compound obtained by reacting a gallium compound and a phosphorus compound in a gas phase together with a composite oxide of germanium and phosphorus.