JPH035336A - Production of infrared glass image fiber - Google Patents

Abstract

PURPOSE:To obtain a flexible infrared glass image fiber having a small transmission loss by putting plural glass fibers in tubularly molded glass and drawing the resulting preform under prescribed conditions. CONSTITUTION:Plural glass fibers 1 having a core-clad structure are put in tubularly molded glass 2 to obtain a preform. This preform is vertically set in a cylindrical crucible 7 having a bottom nozzle 7a, only the bottom of the crucible 7 is heated and the preform is continuously drawn while keeping the bottom at such a temp. that the viscosity of the preform is regulated to 10<3->10<7.5>P.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a flexible infrared glass image fiber with excellent light transmittance.

[Prior Art] Chalcogenide glass is an optical material with excellent infrared transmittance, chemical stability, and heat resistance, and is already used in infrared transmitting windows, filters, and the like. If this chalcogenide glass can be molded into an image fiber, it can be applied to waveguides for image transmission, which have already been implemented using silica glass fibers, especially waveguides for transmission of thermal images near room temperature.

Generally, it is desirable for an optical fiber to have a core-clad structure in which the outer periphery of a core material is covered with a cladding material having a certain finite thickness and a refractive index lower than that of the core. This is necessary not only to reduce the transmission loss of the fiber, but also to improve the mechanical strength and weather resistance of the fiber. In the case of a chalcogenide glass fiber, since the wavelength range of transmitted light is in the infrared region, it is preferable that the cladding material is also a material that transmits infrared rays, such as chalcogenide glass. The rod-in-tube method (P) is used as a method for producing a fiber with a core-clad structure using chalcogenide glass.

H, Roth, and R, D, Rock, Op
t, Eng, 2Ei (1987) 88), double crucible method (T, anamori V, Teru-
numa, S., Takahashi and T.
Hiyashita, J., Lightwave T.
ech, LT-2 (1984) 607), rod-in-tube method using a crucible (J, N15hii,
T, Yamashi-ta and T,
Yamagishi, Appl, Phys
, Lett, 53 (198g) 55
3) etc. have been reported, but there is no example of creating a chalcogenide glass image fiber using these methods.

[Problem to be solved by the invention] Saito et al. reported that they created an image fiber using Teflon clad As-8 (H, 5ait0
．． 2kg/cm H, Takizawa, S, Sa
kuragi and FTanei, Appl,
Oat, 24 (1985) 2304). However, according to Arai et al., Teflon-clad Δs-3 fiber has high transmission loss due to absorption of Teflon in the wavelength region of 2 μm or more (■^rai, H
, nikuchi, S, Sakuragi, H,
5aito and H, Takizawa, Proc.
, of 5PIE, 5γ6 (In2) 24)
.

Saito et al. also pointed out this in their paper,
He says that using a cladding material that is transparent in the infrared region reduces fiber loss and allows images to be transmitted more efficiently. On the other hand, Krosek et al.
We propose to create image bundles by bundling b-8e fibers (P, Klocek H, R
oth and R, DRock, Opt, Eng,
, 26 (1987) 88).

However, the mechanical strength of chalcogenide glass is generally 175 or less than that of oxide glasses such as silica glass, so
It is considered that the fibers are easily broken and it is extremely difficult to bundle multiple fibers in a well-aligned manner. Furthermore, in the case of this fiber, strong oxide absorption appears around 8 μm, and transmission loss is high (5 dB/m or more) over the entire wavelength range of 3-11 μm, so efficient image transmission cannot be expected. Conceivable.

-Manyo previously reported that low-loss chalcogenide glass fibers with a core-clad structure could be produced by the rod-in-tube method using a crucible (J.
N15hii T, Yamashita and T
, Yamagishi, Appl, Phys, L
ett, 53 (1988) 553), it was not possible to directly produce an image fiber using this method. Therefore, no example has yet been reported in which an image fiber is made of a glass fiber that is transparent in the infrared region and has a core-clad structure.

[Means for Solving the Problems] The method for manufacturing an infrared image fiber according to the present invention includes a preform in which a plurality of glass fibers having a core-clad structure are inserted into a glass molded into a tube shape. The crucible is placed vertically into a cylindrical crucible with a nozzle installed at the bottom, and only the vicinity of the nozzle of the crucible is heated locally, and the temperature is increased so that the viscosity of 737.5 ohm is in the range of io-io poise. The feature is that the preform is continuously drawn while maintaining the .

In the method of the present invention, heating the preform in the crucible,
The gas pressure in the gap between the tube and the plurality of fibers in the tube during drawing is 10 −1 torr or less, and the gas pressure around the outer periphery of the tube is 0.2 K.
'J/ci or more is preferable.

When the pressure inside the crucible is lower than 0.2 to 9/ci, it is difficult for the glass to flow out from the nozzle, and when the pressure is lower than 10 g/c
When it exceeds ti, the amount of glass flowing out from the crucible increases, which not only makes it difficult to control the fiber diameter, but also
Air bubbles are easily trapped in the resulting fiber.

The glass material that can be spun in the method of the present invention is not particularly limited as long as it can transmit infrared rays, but chalcogenide glass is most preferred. This is because chalcogenide glass has higher thermal stability than other glass materials, so devitrification during spinning is less likely to occur.

When the glass material is chalcogenide glass, it is preferable to replace the inside of the crucible and the vicinity of the nozzle with an inert gas. This is because when chalcogenide glass is heated above its glass transition point, it tends to react with oxygen and moisture present around the glass.

[Examples] Next, the method of the present invention will be explained in more detail based on Examples.

FIG. 1 shows a cross-sectional view of an apparatus for carrying out the method of the present invention, in which a local heating heater 15, an atmosphere adjustment box 10, a fiber wire diameter measuring device 11, and a resin coater are placed below a crucible 7 with a nozzle 7a installed at the bottom. 12, an ultraviolet irradiation box 13, a print roller 14, and a winding drum 16 are arranged. The upper part of the crucible 7 is covered with a lid 3 that connects a pressurizing inert gas inlet 8 via a connecting resin tube 4. In the case of FIG. 1, a vacuum suction port 17 is provided in the lid 3, a suction resin tube 6 is connected to the lid 3, and a glass fiber 1 having a core clad structure is inserted into the lower end via the connection resin tube 5. It is connected to the glass tube 2.

Example 1 An infrared image glass fiber was manufactured using the apparatus shown in FIG.

AS: 40 mol%, Se: 2 mol%, S: 58 mol%,
Core diameter 1 consisting of a core consisting of a composition of and a cladding consisting of a composition of As: 38 mol% and S: 62 mol%
1500 glass fibers of 50μm, cladding diameter 200μm, length 150, inner diameter 9#, outer diameter 12.5
M, length 160 m, composed of AS: 38 mol%, S: 62 mol%, inserted into tube 2,
It was vertically installed in a crucible 7 with an inner diameter of 13M and a nozzle 7a with a diameter of 2M at the bottom.

Before starting spinning, argon gas was flowed in for 30 minutes at a flow rate of 300 cc#n in from the pressurizing inert gas port 8, the depressurizing suction port 1γ, and the inert gas inlet port 9 of the atmosphere adjustment box 10. . Thereafter, the supply of argon gas from the inert gas port 8 for pressurization and the suction port 11 for depressurization is stopped, and only the vicinity of the lower end of the crucible is heated using the heater 1 for local heating.
5 to a temperature at which the viscosity of tube 2 and fiber 1 was about 106 voices.

Tube 2 and fiber ~1 are fused together, and tube 2
After it is uniformly fused around the nozzle 7a at the lower end of the crucible, real carbon gas is supplied from the pressurizing inert gas port 8 again to pressurize the area around the tube 2 at a pressure of 9/cti to 5.0. At the same time, the gap between the tube 2 and the fiber 1 is removed from the vacuum suction port 17 via the resin tube 6 for suction.
The pressure was reduced to O-2 torr. Through these operations, the tube 2 and fiber 1 near the local heating heater 15 are completely integrated, and the outer diameter is 100 to 1000 mm from the nozzle 7a.
It was possible to continuously spin .mu.m fibers at a speed of 0.5 to 10'rrL/min.

After this core bar passed through an atmosphere adjustment box 10 and a fiber wire diameter measuring device 11, it was immediately coated with an ultraviolet curable acrylic resin in a resin coater 12.

After the resin was cured in the ultraviolet irradiation box 13, it was wound onto a drum 17 via a print roller 14. The transmission loss of the obtained image fiber is shown in FIG. The minimum loss was 0.5 dB/m near the wavelength of 2.5 μya, and the minimum bending radius was less than 50 m for a fiber with an outer diameter of 800 μm.

Example 2-3 An image fiber having the composition shown in Table 1 was used as an example.
The fibers were continuously spun using the same method as in 1. When the transmission loss of the obtained image fiber was measured, it was found to be 0.86 B/m at a wavelength of around 5.5 μm for the material of Example-2.
In addition, in the material of Example-3, the wavelength is 1.1 at around 8.5 μm.
It was dB/m. In addition, the minimum bending radius in the case of a core bar with an outer diameter of 800 μm was 100 bends or less in all cases.

Table 1 Comparative Example An infrared image fiber made of glass having the same composition as in Example 1 was manufactured using the apparatus shown in FIG. However, the spinning was performed while maintaining the interior of the crucible 7 and the gap between the tube 2 and the 77 bar 1 inside the tube with argon gas at atmospheric pressure. With this method, the outer diameter is 400μ.
It was possible to obtain a fiber with a diameter of 100 mm, but when the cross section of the fiber was observed under a microscope, bubbles with a neck diameter of 10 to 50 μm were observed, and the outer fiber was easily broken when bent to a radius of 200 μm or less.

[Effects of the Invention] According to the method of the present invention, glass fibers with a core-clad structure, particularly chalcogenide glass fibers, which have been difficult to manufacture in the past, have no internal irregularities, have high mechanical strength, and have low transmission loss. It is possible to produce image fibers with low image quality.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the core bar manufacturing apparatus used in the example, and FIG. 2 is a transmission loss spectrum of the image fiber obtained in Example 1. 1... Glass fiber 2... Glass tube, 3... Lid for crucible with nozzle, 4.・5...
Resin tube for connection, 6...Resin tube for suction,
7a... Nozzle, 8... Inert gas inlet for pressurization,
9...Inert gas inlet, 10...Atmosphere adjustment box,
11... Fiber wire diameter measuring device, 12... Resin coater 13... Ultraviolet irradiation box, 14... Print roller 15... Local heating heater 16...
Winding drum, 17... suction port for decompression. Non-Oxide Glass Research and Development Co., Ltd.

Claims (1)

[Claims] 1. A preform in which a plurality of glass fibers having a core-clad structure are inserted into a tube-shaped glass is vertically placed in a cylindrical crucible with a nozzle at the bottom. The crucible is heated locally near the nozzle until the viscosity of the preform reaches 10^3-10^7.
^． A method for manufacturing an infrared glass image fiber, characterized by continuously drawing a preform while maintaining a temperature within a range of ^5 poise. 2 The pressure of the gas in the gap between the tube and the plurality of fibers in the tube when heating and drawing the preform in the crucible is 10^-^1 torr or less, and the pressure of the gas around the outer periphery of the tube is 0. 2. The method for producing an infrared glass image fiber according to claim 1, wherein the infrared glass image fiber is .2 kg/cm^2 or more and 10 kg/cm^2 or less. 3. The method of manufacturing an infrared glass image fiber according to claim 1, wherein the preform is made of chalcogenide glass that is transparent in the infrared wavelength region. 4. The method for producing an infrared glass image fiber according to claim 1 or 3, wherein the inside of the crucible and the vicinity of the nozzle are replaced with an inert gas when spinning the preform.