JPS62260728A - Production of glass preform for optical transmission - Google Patents

Abstract

PURPOSE:To efficiently add fluorine and improve the fluorine yield, by exposing a porous silica deposit formed by a flame hydrolysis method to an atmosphere containing silicon oxyfluoride before melting the porous silica deposit to provide transparent glass. CONSTITUTION:A silicon compound is subjected to flame hydrolysis to deposit fine silica particles and afford a porous silica deposit, which is then exposed to silicon oxyfluoride or an atmosphere containing the silicon oxyfluoride. The exposed silica deposit is then melted while heating to provide transparent glass.

Description

[Detailed description of the invention] 3. Review of the invention and ◆1 explanation +t! The present invention relates to a method for manufacturing a glass base material for transmission, and a method for manufacturing a glass base material for transmission containing a fluorine atom as a dopant.

(Prior art) Quartz material, which is the original transmission glass base material, is produced by flame hydrolysis of silicon compounds such as silicon tetrachloride, and fine powder of silica is deposited on a support. It is well known that transparent vitrification can be obtained by heating and melting a porous glue deposit.

However, this optical transmission glass base material usually has a central part called a core with a high refractive index through which light passes, and an outer peripheral part called a cladding with a different polar refractive index. In order to increase the refractive index, when a JT layer is made by force deposition, Cre ('E1, etc.) is added to the silicon compound in order to increase the refractive index.
A method of lowering Q□ with a dopant has been adopted, but this
Since OeCl (OeCl, etc.) is expensive and resource-intensive, a method of using a low-refractive material as the glass base material for the cladding has also been adopted. Boron and fluorine are known as dopants to reduce the iF% ratio of the glass base material, but boron is not preferable because it has infrared absorption in the long wavelength range. Although fluorine is preferred, OF4. eel, F, , SiF
Even if an attempt is made to make a silica stack by mixing a fluorine compound such as fluorine compound, the amount contained in the fluorine-containing silica deposit will be extremely small, so this method is problematic in practice.

On the other hand, regarding doping of the glass base material, it is also known to obtain dopants obtained by fire hydrolysis of silicon compounds or to add dopants such as those mentioned above during the transparent vitrification of liquefied deposits, and to dope them during heat treatment. However, in this case, it is necessary to remove the dopant that has a large overaxis with respect to 11"l':tC, and when using a fluorine compound as the dopant, the glass component is SiF4. carbon atoms present in fluorine compounds [
Therefore, there is a disadvantage that SiO□ as a glass component is reduced by 5ill and volatilized, and furthermore, oxygen defects are generated by this carbon atom C2.

(Explanation Q) The present article is concerned with the production of a fluorine-doped glass base material for transmission that solves this disadvantage, and this is a method for producing a glass base material for transmission by flame hydration of a silicon compound. Generate with +f solution or Rika a
After depositing the powder and forming a porous silica shell into a shape, it is heated in an atmosphere containing silicon oxyfluoride (or exposed to an atmosphere containing silicon oxyfluoride), and is then thermally melted. It is characterized by being transparent or lathed.

In other words, the present inventors have described a method for producing a fluorine-doped optical transmission glass base material from a porous LA glue deposit obtained from a silicon compound. In glass 1: By efficiently adding fluorine, a high fluorine yield can be obtained, and as a result, a glass base material doped with fluorine can be obtained efficiently. Since this silicon oxyfluoride compound can be manufactured as a high-purity product, we confirmed that it is possible to avoid the presence of impurities such as carbon (two disadvantages). The present invention was completed by conducting research on the types of silicon compounds and the amount to be removed.

The structure of the porous silica structure in the method of the present invention can be carried out by the published method. Therefore, the general formula
RmSlx4-m, R is a methyl group, an ethyl group,
A monovalent hydrocarbon group such as a propyl group, χ is a halogen atom such as chlorine or fluorine, an alkoxy group such as a methquine group or an ethoxy group, and m is an atom of O to 4.
Compounds such as 5iC1,, 8i, (i'4. H81
C1,,5iF(4,C)(,5iC1,.

CH,51(OCH,+,, 5itOOH,+4.
Glasses containing 5i (OC, H, +4, etc. as main components) are fed into a flame such as an acidic water flame to cause a flame 110 water decomposition reaction. The manufacturing method for these four silica deposits is as follows: [Deposit fine silica powder on a rotatable support, and then use it to deposit this L-nof-Fα form. The outer periphery of the heat-resistant support in the axial direction (which is twisted in row 7 by the shaft attached to it, which is made of stone or carbonaceous material) (while the car is reciprocating) ,
It may also be performed by an external method of depositing fine silica particles.

The density IW of the 7-reforced product obtained in this way is Q,
1~Q, -1p/C This porous body absorbs and bonds moisture, hydroxyl groups, and chlorine that sometimes occur, and serves as a support for original transmission. By removing the quartz rod that forms the core of the quartz rod, it becomes the base material for the original transmission base material.

In the method of the present invention, the porous glue deposit thus obtained is heated and melted in the presence of an oxyfluorosilicon compound to form the original transmission glass base material. The silica deposits are converted to oxyfluoride silicon.
Alternatively, the silica pellet may be treated in advance at a temperature of 1,000 to 1,300°C in an atmosphere containing A, and then melted at 1,300 to 1,600°C to form transparent glass. 1,300-1.
Although it may be heated to 600° C. for 770°C to melt and form transparent glass, the latter method is preferred for high 1 kK doping because the volatilization of fluorine during transparent vitrification is less per pl. Since this transparent vitrification is carried out in the presence of a silicon oxyfluoride compound, it also provides the advantage that the fluorine doping and simultaneous reaction (also known as Eryu water reaction) are carried out. The atmosphere containing the compound may be one in which a silicon oxyfluoride compound is diffused in a gas such as helium, argon, nitrogen, # element, etc., but if this fl'J I: is too low, fluorine doped C : The effect of lowering the elasticity is insufficient, and if the temperature is too high, γ2 will remain so that bubbles remain in the glass base material, so this JUj is preferably 0.01 to 10 mol%. Q, 1 to 5 mol% of the shaft valve is often found, and this process f
! '! 8% F:'+J is! Iη should always be 1 to 3 o'clock ttn.

The O-1-silicon fluoride compound used for this is 1#
Q formula 5inOn-, represented by F2n+2, where n is 1 to 10
If the number of V is six, and if a part of this F is replaced with Cl, the boiling point is low.
The spirit is also '8 easy.
i, OF, , octafluorotrizoloki+ySi, O,
F, Decafluorotetrasilochitin s1t's"+.

be preferred.

3.These silicon oxyfluoride compounds can be prepared by converting silicon tetraruride into partial n0 with a mixture of ethyl ether and water, for example.
Water splitting method a (J, Az, chem, Soc
, .

72, 3178 (1950)], a method for fluorination of chlorosilochitins with SbF using 5bC1s as a catalyst [J, Am, Cbem, Soc,
h7.1092 (1945) [Kateru] Derizo T. 7, Si, OF, can be obtained by fluorinating 5i20CI, but in this fluorination process, l1M1l I'tE T 5L20 F2O3
, Si, OF1''1, etc. can also be used in the present invention, but they can be easily obtained in high grade by distillation or other means.

Tsuki (two i1) Akira's implementation (raise yjl.

Example 1 Manjo 411-tube burner (25il14430m1
1 minute, 8210 g/min, 02161/min to form an oxyhydrogen flame. In addition, a porous 0-silicon blowing body was grown!

Next, this porous S/liquid volume was heated at 1.200°C for 2 hours in a helium gas atmosphere containing 13 mol % of hekitofluorology/roxane S1□OF, and then heated from helium gas alone. When heated for 111-:p in an inert gas atmosphere at 1.500°C and melted to form transparent glass, the OH group-containing F/I was 50 ppb and the refractive index was 0.3 compared to that of silica glass. % low yield rate quartz, Galanuka 1
The glass filtration ratio at this time was an extremely low value of 2%.

In addition, when quartz glass was made in the same manner as above except that the e degree of hexafluorodisiloxane was changed to 0 to 8 mol%, and the refractive index of the obtained quartz glass was measured, it was as shown in Figure 1. I got some good results.

1; Good: ;1mi Example 2 The porous G silica obtained by the method of Example 1 was loaded with 5 mol% of octafluorotrisoloxane Si, 0. Fs
Put the helium gas into the gas furnace, and 1.000
- From C to 1,500'C 5"07 minutes ← Wakuko・
Heat it to 110℃ with a μ pull, heat and treat for about 2b, then 14i.
A quartz glass matrix was obtained in January, and −j, O
H content is 30 ppb and quartz galanu C has two effects, Q, 6
% low refractive index, and the glass volatilization rate of this umbrella was 3%, which was less than Fl.

[Brief explanation of drawings]

Figure 1 is a box graph showing the relationship between the mole percent of hexafluorocysilochitin and the refractive index of the quartz glass tube in Example 1 (-). Applicant Shin-Etsu Chemical Co., Ltd. Agent Patent attorney Mr. Yamamoto Sales - Figure 1 0 5
1゜S: 20F6 Wandering% ~・1

Claims (1)

[Claims] 1. After depositing silica particles produced by flame hydrolysis of a silicon compound to form a porous silica deposit, this is exposed to an atmosphere containing silicon oxyfluoride or to a silicon oxyfluoride atmosphere. A method for producing a glass base material for optical transmission, which is then heated and melted to form transparent glass.