JPS6162009A - Plastic group light transmitting resin - Google Patents

Abstract

PURPOSE:To suppress transmission loss due to thread diameter spot and unmatching of structure by constituting a projection layer of polymer having a glass transfer temperature higher than that of polymer constituting a core material layer and specifying a drawing temperature and its magnification. CONSTITUTION:In a temperature area setting up a temperature close to Tg of the protection layer polymer as the lower limit of the condition of drawing and a temperature higher than the Tg by 60 deg.C as its upper limit, the drawing is controlled at the magnification of 1.05-20 and a string is instantaneously cooled at the outlet of the drawing part. If drawing is executed at a temperature lower than the Tg of the protection layer polymer, transmission loss based upon the unmatching of the structure is increased in addition to the increase of thread diameter spots. When the drawing is executed at a temperature higher than the Tg by >=60 deg.C, the bending property of the obtained light transmitting resin is reduced. It is preferable to control the magnification of drawing in the range of 1.2-10. If the magnification of drawing is smaller than 1.05, bent resisting property is not improved, and if exceeds 20, troubles such as the sharp increase of the thread diameter spot and the cut of the string may be generated.

Description

[Detailed description of the invention] [Field of invention] TECHNICAL FIELD The present invention relates to glass-based optically transmitting fibers.

[Prior art]

Conventionally, inorganic glass-based optical fibers have been known as optical fibers that have excellent optical transmission properties over a wide range of wavelengths, but synthetic resins have been used because they have poor workability, are susceptible to bending stress, and are expensive. Optical transmitting fibers based on these materials have been developed. Optical transmitting fibers made of synthetic resin have a core-sheath structure, with a core made of a polymer that has a high refractive index and good light transmission, and a sheath made of a transparent polymer that also has a low refractive index. It can be obtained by producing fibers with The polymer useful as a core component with high light transparency is preferably an amorphous material, and polymethyl methacrylate, polycarbonate, or polystyrene is generally used.

Among these, polymethyl methacrylate has excellent mechanical properties, thermal properties, weather resistance, etc. as well as transparency, and is used industrially as a core material for high-performance plastic optical fibers.

However, the refractive index of this polymethyl methacrylate is 1.4.
8 to 1,50, which is relatively small. Therefore, when this polymer is used for the core, it is necessary to use a polymer with a particularly small refractive index as the sheath component. Examples of polymers with a small refractive index include Japanese Patent Publication No. 43-8978 and Japanese Patent Publication No. 56-832.
1, Special Publication No. 56-8322, Special Publication No. 56-8323
Polymerized esters consisting of methacrylic acid and fluorinated alcohols as described in Japanese Patent Publication No. 53-60243, etc., and Japanese Patent Publication No. 53-42
A copolymer of vinylidene fluoride and tetrafluoroethylene as described in No. 260 is known.

None of these fluorine-containing polymers are general-purpose, special, and very expensive. In addition, the properties that the sheath component polymer should have, adhesiveness with the core component, preferred formability to ensure a uniform and smooth core-sheath interface structure, mechanical performance that can withstand friction and bending, usage environment, and processing. Many of them are insufficient in terms of heat resistance, chemical resistance, etc. that can withstand the conditions. On the contrary, at present, no polymer for the sheath component that can completely satisfy these properties is known.

As methods for producing light transmitting fibers having a core-sheath structure, the following two methods can be mentioned in terms of the method of covering the sheath component. One is to mix the core and sheath components and the protective layer component in a molten state using a special nozzle and discharge them to form the core.
This is a method of imparting a sheath structure, and is a so-called composite spinning method. The other method is a so-called coating method in which a core component is first shaped into a predetermined fiber, and then a sheath component dissolved in an appropriate solvent is coated on the core component, and the solvent is removed to obtain a light transmitting fiber.

When comparing the two, the composite spinning method has high productivity and is a labor-saving and energy-saving process that can simplify the equipment. Furthermore, it has advantages such as being able to manufacture optically transmitting fibers with a wide range of thicknesses and easy process control, making it an extremely advantageous method from an industrial perspective. Manufacture is possible.

However, the composite spinning method is technically more difficult than the coating method, and requires advanced technology in nozzle design, polymer selection, etc. in order to maintain uniform smoothness at the core-sheath interface. In particular, in addition to selecting the polymer for each layer, it is important to optimize the spinning conditions and stretching conditions in order to improve the properties necessary for practical use, especially mechanical properties such as transmission loss, heat resistance, and bending resistance. Therefore, selecting the optimal spinning conditions and stretching conditions has become an extremely important technical issue.

[Purpose of the invention]

The purpose of the present invention is to suppress the increase in transmission loss caused by yarn diameter unevenness and structural irregularities, alleviate the internal stress strain of the core material layer, sheath material layer, and protective layer, and reduce the increase in transmission loss during heating exposure. It is an object of the present invention to provide a plastic light transmitting fiber which can be kept low and has excellent mechanical properties such as bending resistance.

The glass-based optically transmitting fiber of the present invention, which has been found to achieve the above object, is a plastic shaped by stretching a fiber whose basic constituent units are a core material layer, a sheath material layer, and a protective layer. The protective layer is made of a polymer having a glass transition temperature higher than the glass transition temperature of the polymer constituting the core material layer, and the stretching is performed near the glass transition temperature of the protective layer. It is characterized in that it is carried out at a ratio of 1.05 to 200 in a temperature range with a lower limit and an upper limit of 60° C. higher than the glass transition temperature of the protective layer, and is rapidly cooled at the exit of the stretching section.

Hereinafter, the glass transition temperature Tg will be referred to as 0 [Embodiment] The structure of the glass-based optically transmitting fiber of the present invention is shown in a cross-sectional view as an example in FIG. Sheath material layer 2 and protection 1! ! 3 as a basic structural unit, and a fourth layer, a fifth layer, etc. are formed around the protective layer 3 depending on the purpose of use.
... may be provided, or a tension member 6 such as a polymer fiber or metal wire, a film, a paper-like material, etc. may be interposed outside the protective layer.

Figure 1 (a) shows an optical fiber with a three-layer structure, (b) shows an optical fiber with a four-layer structure, (C) shows an optical fiber with a five-layer structure, and (d) shows an optical fiber with a three-layer structure! - is an optical fiber cable in which a fourth coating layer is provided on the outer periphery via a tension member 6, and (e) is an optical fiber cable in which a plurality of three-layered optical fibers are bundled and coated.

Examples of the amorphous polymer used as a component of the core layer 1 include methacrylic polymers, polycarbonates, polystyrene, styrene-methacrylic acid ester copolymers, or polymers in which all or part of the hydrogen atoms of these polymers are polymerized. Transparent non-grade thermoplastic resins such as deuterated polymers substituted with hydrogen atoms can be used, and of course other transparent amorphous polymers and blends can also be used. Amorphous polymers particularly preferably used in the present invention include methacrylic polymers and polycarbonates.

Among these, the methacrylic polymer is, for example, a homopolymer or copolymer of methyl methacrylate (70% of the starting monomer
It is preferable that methyl methacrylate accounts for at least 1 weight % and 30 weight % or less of other monomers copolymerizable with methyl methacrylate. Examples of the monomer copolymerizable with methyl methacrylate include vinyl monomers such as methyl acrylate and ethyl acrylate. ), copolymers of methacrylic acid esters such as cyclohexyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, fer methacrylate, and monomers copolymerizable with these, etc. can be mentioned. this house,
Homopolymers and copolymers of methyl methacrylate are preferred.

In addition, suitable polycarbonates have the general formula
fO-T? Examples include aromatic polycarbonates represented by -0-C-3n and the like.

In addition, these and 4,4'-dioxydiphenyl nityl, ethylene glycol, p-xylylene glycol, 1
．． Copolymers with dioxy compounds such as 6-hexanediol can also be used, but from the viewpoint of heat resistance, those with a heat distortion temperature of 120° C. or higher are preferred.

Here, the heat distortion temperature is ASTMT) -648, load 4
．． 6 refers to the measured value at &/ctn''.

As the sheath material layer 2, a substantially transparent polymer having a refractive index 0.01 or more lower than that of the core component is used, but usually the difference in refractive index from the core component is 0.01 or more. 01-0.15
It is best to choose from those within this range. There is no particular restriction on the type of polymer constituting the sheath material layer, and conventionally known polymers may be used.

Specific examples include the following.

Polymethyl methacrylate (n=1.49), styrene/methyl methacrylate coprimer (n=1.50-1
．． 58), 4-methylpentene 1 (n = 1.46), ethylene-acetic acid picopolymer (n = 1.46-1.50),
Polycarbonate (n=1.50-1.57).

Contains fluorine? rimether methacrylate (n -1,38~1
．． 45) Vinylidene fluoride? Rimmer (n=1.38~
1.42), vinylidene fluoride/hexafluoroglobylene copoly-r-(n = 1.38-1.42)l methyl methacrylate/styrene, vinyltoluene or α
- Methylstyrene/maleic anhydride ternary or quaternary copolymers (n=1.50-1.58), etc. These polymers use unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid to improve the delamination strength in the basic structural units.

Unsaturated glycidyl monomers such as glycidyl acrylate or methacrylate, β-methylglycidyl acrylate or methacrylate, hydrophilic monomers such as acrylamide, methacrylamide and derivatives thereof, hydroxyalkyl acrylate or methacrylate may be copolymerized.

Among these polymers, the most versatile ones are:
Methacrylic polymers such as polymethyl methacrylate, and, for example, Japanese Patent Publication No. 43-8978, Japanese Patent Publication No. 56-8
321, Special Publication No. 56-8322, Special Publication No. 56-83
Polymerized esters of methacrylic acid and fluorinated alcohols as disclosed in No. 23 and JP-A No. 53-60243 can be used. Specific examples of these esters include, for example, methacrylic acid 2
．． 2.2-) Lifluoroethyl, methacrylic acid 2゜2
．． 3.3-tetrafluoropropyl, methacrylic acid 2,
Examples include 2,3,3,3-pentafluorozologyl and the like. Furthermore, using one or more of these fluorine-containing methacrylic esters, for example,
Fluorine-containing methacrylic acid ester, vinyl monomer copolymerizable with this ester, and vinyl monomer capable of forming a hydrophilic homopolymer, as described in No. 7311, Japanese Patent Application No. 57-230436, etc. A copolymer consisting of a polymer may also be used.

Although the thickness of the sheath material layer used in the present invention is not particularly limited, it is preferably in the range of 2 to 50 μm in order to further improve the adhesion between the layers and the bending resistance of the fibers.

The polymer used for the protective layer 3 is T of the core layer polymer.
It is a polymer having a Tg higher than g, and includes, for example, polycarbonate, polysulfone, heat-resistant methyl methacrylate copolymer, polyether sulfone, polyester carbonate, and the like.

In addition, the high Tg polymer used for the protective layer 3 has a car?
black, talc, glass fiber, aromatics, t? )) It is also possible to fill with inorganic or organic fillers such as amide fibers and carbon fibers.

The undrawn yarn of the plastic light transmitting fiber of the present invention can be produced using a composite spinning method or a coating method.

Manufactured using a cable covering method, etc. For example, in the composite spinning method, it is manufactured by a composite spinning machine including a core peripheral component melt extruder, a sheath material layer component melt extruder, and a retainer layer component melt extruder. The core component is melted by a melt extruder and fed in fixed amounts to the spinning head using a metering pump, and the sheath component and the protective layer component are each fed to the spinning head in the same way.

For example, with a spinneret with a structure as shown in Fig. 2 in the spinning head,
It is shaped into a layered structure and discharged. In FIG. 2, the base material layer component is supplied from (A), the sheath material layer component is supplied from (B), and the protective layer component is supplied from (C), and is discharged from (D).

The extrudate having a three-layer structure discharged in step 1- is cooled by leaving it to cool or by forced cooling using an appropriate cooling means such as a refrigerant or gas blowing. The cooled yarn may be further drawn and wound continuously through a take-up machine, or it may be wound as an undrawn yarn and then drawn in a separate step.

In the present invention, the stretching conditions are controlled at a stretching ratio of 1.05 to 20 in a temperature range where the lower limit is near the Tg of the protective layer polymer and the upper limit is 60°C higher than the Tg of the protective layer polymer. Furthermore, the yarn is rapidly cooled at the exit of the drawing section. Various stretching methods can be used for the stretching device, such as a hot air circulation type heating surface using air or inert gas, a hot plate heating surface, an infrared heating surface, an induction heating surface, and a heat medium heating surface.The stretching temperature depends on these heating atmospheres. The yarn temperature can be arbitrarily controlled and set by the temperature setting. Further, the stretching ratio is arbitrarily set by the speed ratio of the feed row 2 and the take-up roller.

In the present invention, if the stretching is carried out at a temperature lower than the Tg of the protective layer polymer, not only will the yarn diameter increase but also the transmission loss due to structural irregularities will increase. Also, the protective layer polymer T
If the stretching is performed at a temperature 60° C. or more higher than g, the flexibility of the obtained light transmitting fiber will decrease. Furthermore, in the present invention, the stretching ratio is in the range of 1.05 to 20, more preferably 1.2.
It is necessary to control the stretching ratio within a range of 1.0 to 10. If the stretching ratio is smaller than 1.05, the improvement in the bending resistance of the light transmitting fiber, which is the objective of the present invention, will not be achieved. Further, if the stretching ratio exceeds 20, the yarn diameter becomes extremely large, which may cause problems such as yarn breakage.

In the present invention, the heated and drawn yarn is rapidly cooled at the exit of the drawing section and then taken off to become a light transmitting fiber. The light transmitting fiber obtained by rapid cooling shows no increase in transmission loss even when heated to a temperature higher than the Tg of the core layer polymer, whereas the light transmitting fiber obtained by cooling naturally without rapid cooling shows no increase in transmission loss. When optically transmitting fibers are heated to a temperature higher than the Tg of the core layer polymer, dithering occurs in the sheath layer, resulting in an extremely large increase in transmission loss.

The cause of this is not clear, but it is thought that the strain inside the fiber during stretching and cooling has a large effect.

As a practical and suitable means for cooling the yarn at the exit of the drawing section, blowing of a gas such as air, nitrogen gas, argon gas, carbon dioxide gas, etc., or water.

Examples include passing through a liquid such as ice water, antifreeze, and liquid nitrogen, or bringing it into contact with a solid such as ice and dry ice. The temperature of these cooling media is preferably below room temperature, and the threads coming out of the cooling section are preferably cooled to a temperature lower than at least the Tg of the core layer polymer, preferably below about room temperature. The cooling section is preferably set as close to the exit of the stretching section as possible, preferably within 1° crI1, more preferably within several meters.

Core material layer 1 in the plastic light transmitting fiber of the present invention
The thickness and thickness of the sheath material layer 2 and the protective layer 3 are appropriately set depending on the intended use of the optically transmitting fiber. For example, in the spinneret shown in FIG. 2, the thickness and diameter can be controlled by changing the diameter and length of the orifice at each feed port.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Note that parts in the examples indicate parts by weight.

The optical transmission performance was evaluated by measuring the optical transmission loss of the obtained optically transmitting fiber using the apparatus shown in FIG. 4 of JP-A-58-7602.

Example 1 Using the apparatus schematically shown in FIG. 3, a glass-based optically transmitting fiber of the present invention was obtained. 100 parts of methyl methacrylate and 0.0 parts of t-butyl mercaptan were produced by continuous bulk polymerization using a volatile matter separator consisting of a reaction tank equipped with a spiral lean stirrer and a twin-screw one-vent extruder.
Part 40, G-T-Pucirno! -Oxide 0.0017
The polymerization temperature was 155°C, and the average residence time was 4.0 hours. The volatile part was separated as 4.5 Hg, and the core component polymer (Tg=xos°C) was supplied to a core-sheath protective layer three-component composite spinning head at 230°C via a gear pump section maintained at 230°C.

On the other hand, 100 parts of 2.2,3.3.3-pentafluoropropyl methacrylate prepared from methacrylic acid chloride and 2.2,3.3°3-pentafluoropropanol and 1 part of methacrylic acid were mixed with azobisisobutyropropanol. Polymerization was performed using nitrile as a catalyst in the presence of a small amount of n-octylmercazotane to obtain a sheath component polymer with a refractive index of 1.417. This sheath component polymer was supplied to a composite spinning head at 230°C via a gear pump in a screw melt extruder set at 200°C.

On the other hand, as a polymer for the protective layer, polycarbonate (Tg
A polymer obtained by melt-kneading 3.0 inches of Cardiff Black at 145°C) was supplied to a composite spinning head at 250°C via a gear pump in a screw melt extruder set at 230°C.

The molten polymers of the core material layer, sheath material layer and protective layer were supplied at the same time using a spinneret (nozzle diameter 3 mm) 201,
It was discharged at 230°C.

The yarn 202 discharged from the nozzle 201 has a temperature of 25°C 0.2
Quench device 203 with air flow of m/aee
It was cooled in a 2 m long circulating hot air furnace 206 heated to 165° C. and then taken up by a first nip roller 204 at a speed of 3.0 m/1 nin.

6. It is stretched and passes through a guide 208 in a 10°C cold water tank (20 holes in length) 207 installed 2 ctn from the outlet of the hot air circulation furnace 206. It was taken up by the second Nitsuno roller 205 and wound up by the winding machine 209 at a speed of Q m/m+n.

The resulting three-layer optically transmitting fiber has a core diameter of 300 μm.
, sheath material thickness: 10 μm, protective layer thickness: 90 μm.

The outer diameter was approximately 500 μm, and microscopic observation revealed that the core material layer, sheath material layer, and protective layer were perfect circles with concentric circles, and no air bubbles or foreign matter were observed. Thread diameter unevenness and transmission loss of the optically transmitting fiber thus obtained.

Transmission loss after heating: 1 on the mandrel in 110111nl
The winding light amount retention rate when the film was wound 0 times was evaluated, and the results are shown in Table 1.

Examples 2 to 11 Comparative Examples 1 to 6 Light transmitting fibers were obtained in the same manner as in Example 1, except that the stretching temperature, stretching ratio, and quenching conditions were changed as shown in Tables 1 and 2.

The same characteristics evaluation as in Example 1 was performed and the results are shown in Tables 1 and 2.

Wrapping light intensity retention rate Inject 650 nm parallel light into one end of the fiber and fix it. Measure.

Examples 12 to 13 Optical transmitting fibers were obtained in the same manner as in Example 1, except that the polymers as components of the core layer and protective layer were changed to those shown in Table 1. The same characteristics evaluation as in Example 1 was performed, and the results are shown in Table 1.

[Brief explanation of the drawing]

Figures 1 (,) to (,) are cross-sectional views of the optically transmitting fiber of the present invention; Figure 2 is a cross-sectional view showing an example of the structure of a spinneret for producing a three-layer optically transmitting fiber; The figure is a schematic diagram of an apparatus showing an example of a process for manufacturing the optically transmitting fiber of the present invention. 1: Core material layer, 2: Sheath material layer, 3: Covering layer, A, E: Core material layer component outlet, B: Sheath material layer component outlet, C, E: Protective layer component outlet, D: Discharge port, 201 : Spinning nozzle, 202: Light transmitting fiber, 203: Spinning quench device, 204: First nip roller, 205: Second nip roller, 206: Hot air circulation stretching device, 207: Quenching water tank, 208 Ni guide, 20
9: Winder.

Claims (1)

[Claims] (1) A plastic light transmitting fiber shaped by drawing a fiber whose basic constituent units are a core layer, a sheath layer, and a protective layer, wherein the protective layer constitutes the core layer. A polymer comprising a polymer having a glass transition temperature higher than the glass transition temperature of the polymer, and at which the stretching temperature is such that the lower limit is near the glass transition temperature of the protective layer and the upper limit is 60° C. higher than the glass transition temperature of the protective layer. 1 in the area
．． 1. A plastic light transmitting fiber characterized by being drawn at a stretching ratio of 0.05 to 20 and rapidly cooled at the exit of the drawing section.