JPS59111104A - Optical transmission fiber - Google Patents

Abstract

PURPOSE:To obtain an optical transmission fiber having excellent adhesion and heat resistance and the numerical aperture approximate to a theoretical numerical aperture by covering a core component consisting of a polymethyl methacrylate polymer with a sleeve component consisting of a specific resin compsn. CONSTITUTION:(A) 90-10wt% copolymer of >=60mol% polyvinyldene fluoride or vinyldene fluoride and >=40mol% tetrafluoroethylene or hexafluoropropylene and (B) 10-90wt% a copolymer of >=60wt% fluoroalkyl methacrylate expressed by the formula I or formula II (X is F, H; Z is H, CH3; m is 1-5; n is 1-10) and 40-0wt% a vinyl monomer (e.g.; styrene) are blended and a sleeve component consisting of a resin compsn. is obtd. The core component obtd. by spinning a polymethyl methacrylate polymer is coated with the above-mentioned sleeve component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission fiber having a core-sheath structure and comprising a novel sheath component.

Although optical transmission fibers made of plastic are inferior in optical transmission loss and heat resistance compared to inorganic glass, they have a large diameter, a large numerical aperture, are lightweight, and have extremely excellent flexibility.
Among these, optical transmission fibers containing methyl methacrylate as a core component are beginning to be used for short-distance optical transmission applications.

The present applicant, Tokusho, has shown that an optical transmission fiber whose core is polymethyl methacrylate and whose sheath is a copolymer of vinylidene fluoride and tetrafluoroethylene exhibits excellent performance! J-2/4
No. 60.

However, although vinylidene fluoride copolymers have good adhesion to the core material and excellent processability, they are essentially crystalline polymers and easily crystallize when heated or cooled, forming spherulites. As a result, light passing through the core material is scattered by the crystallized state of the sheath, resulting in a reduction in light transmission performance. On the other hand, the parable is
-Fluorinated alkyl methacrylate as shown in No.g32/? The main component polymer is essentially a non-grade polymer, and although it maintains good transparency when used as a sheath material for optical transmission fibers, it has poor adhesion to the core material and has poor processability. It has the disadvantage of being inferior.

The present inventors conducted intensive research on methods to improve the drawbacks of conventional sheath materials as described above, and as a result, a blend of a vinylidene fluoride copolymer and a polymer whose main component is fluorinated alkyl methacrylate was developed. Surprisingly, it was discovered that a blended material can be easily produced and can be used as a sheath material that has excellent adhesion to the core material while maintaining its quality, and the present invention V has been achieved. That is, the gist of the present invention is that the core component is mainly a polymer such as polymethyl methacrylate, and polyvinylidene fluoride or polyvinylidene fluoride units'f
The light transmitting fiber is characterized in that the sheath component is a vegetable oil composition made by blending a vinylidene fluoride copolymer containing tAO mol% or more and a polymer whose main component is fluorinated argyl methacrylate.

In the polyvinylidene fluoride material used in the sheath material of the present invention, the vinylidene fluoride copolymer and the polymer mainly composed of methyl methacrylate have good compatibility with each other, and a wide range of blending ratios can be achieved. The properties of the polymer can be changed depending on the ratio.For example, when the purpose is to improve the Ax properties and processability of the core component, the ratio of the vinylidene fluoride copolymer component is increased, and the transparent When the purpose is to improve the properties and heat resistance, a blend with the desired performance can be easily obtained by increasing the proportion of the 111 compound containing fluorinated alkyl methacrylate as the main component.

For example, the glass transition temperature I, which is one of the characteristics of blends,
The temperature (Tg) is the Tg of vinylidene fluoride copolymer ~ -g5
The Tg of the fluorinated alkyl methacrylate yarn polymer can be varied from C to 1100 C by changing the blending ratio.

The sheath component of the present invention maintains the excellent bud property and processability of the vinylidene fluoride copolymer to the core component, while also possessing the heat resistance and light property of the fluorinated alkyl methacrylate yarn polymer. Due to these characteristics, it is possible to provide an optical transmission fiber that takes into account the excellent characteristics of both.

The composition of the vinylidene fluoride polymer used as the sheath component in the present invention needs to contain 46 mol % or more of vinylidene fluoride units. This is because if the vinylidene fluoride level is less than 10 mol %, the compatibility with the fluorinated alkyl methacrylate is insufficient and uniform blending becomes difficult.

Monomers to be copolymerized with vinylidene fluoride include trifluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, methyl methacrylate, /, /, /
-) Refluoro t' Vinyl monomers such as vinyl acetate and isobutylene can be used, and special V (fluorine-containing monomers such as tetrafluoroethylene and hexafluoropropylene have a low refractive index, so they have a large aperture (high light). Preferred for obtaining transmission fibers.

Tetrafluoroethylene, hexafluoropropylene, methyl methacrylate, /, /, / as the J component
-) It is also possible to copolymerize vinyl monomers such as vinyl refluoroacetate, chlorotrifluoroethylene, and imbutylene in an amount of 20 mol % or less.

In addition, the dlJ-alkyl methacrylate used as the sheath component in the present invention has the basic structural formula (%) 1 cit, =c 0-C-(CF2)yuX CF.

The one shown is used. Specific examples include co, -1 difluoroethyl methacrylate (-FM), λ, λ,
Coat trifluoroethyl methacrylate (?
FM), ,2.2. J, 3-tetrafluorobrobyl methacrylate <yFM), 2+
2.3. ．． 3.3-pentafluoropropyl methacrylate
Shi - To (5FM), 2 * -1
+ J + J + da, lI-hexafluorobutyl methacrylate (AFM), 2, co, 3. ．． 3. 'I-l! ,! , S-octa7fluoropentyl methacrylate (g F M ), /, /-di(trifluoromethyl) J + -” + '-trifluoroethyl methacrylate) (9FM), or homopolymers of these 6θ fluorinated alkyl methacrylate
A copolymer containing at least % by weight of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, t
Examples include copolymers in which vinyl monomers such as -butyl methacrylate, lauryl methacrylate, nonyl methacrylate, methyl acrylate, butyl acrylate, λ ethylhexyl acrylate, and styrene are combined with ON and θ weight and M%.

Among them, methyl methacrylate is particularly preferred as the second component. Copolymers of fluorinated alkyl methacrylate 6θ richness% or more and vinyl monomers O to lIo% must be produced by conventional emulsion polymerization, 1M turbidity polymerization, bulk polymerization, and solution polymerization. However, in order to obtain a highly pure copolymer, it is preferable to employ the bulk type method.

As the polymerization initiator, there can be used conventional polymerization initiators such as organic peroxides such as di-tevt-butyl peroxide and dicumyl peroxide, methyl 2.
Examples include azo compounds such as λ'-azobisisobutyrate and λ,21-azobisisobutypnitrile, and ordinary alkyl mercaptans are used as chain transfer agents.

When mixing a vinylidene fluoride copolymer and a polymer whose main component is alkyl fluoride methacrylate, acetic acid ethyl ester, N,N'-dimethylformamide, dimethyl sulfoxide, dimethyl acetamide, etc. are used to ensure uniform mixing. After dissolving in a solvent, a mixed polymer can be obtained by melt blending at a temperature higher than the melting point of the crystalline polymer, for example, by mixing at a temperature higher than 2,000.

When performing the above mixing, if the vinyl fluoride IJ-dens fiber copolymer in the composition is 99 trillion yen percent or more, the optical transmission fiber manufactured using the composition as a sheath material will be heat resistant because the sheath material will crystallize. It is undesirable due to its poor properties and transparency. In addition, if the copolymer mainly composed of fluorinated alkyl acrylate is 99% or more, the layering properties between the sheath material and the core material will decrease, causing a peeling phenomenon at the interface and reducing the transmission performance. This is not preferable because it lowers the temperature. Therefore, a polymer consisting of vinylidene fluoride copolymer 99% to 99% by weight and alkyl fluoride methacrylate as the main component.
Weight%, preferably vinylidene fluoride copolymer 90-1
70 to 90 weight % of a polymer mainly composed of o heavy magnet and fluorinated alkyl methacrylate, preferably 10 to 10 weight % of a vinylidene fluoride polymer go-co ohm % and fluorinated alkyl methacrylate From the viewpoint of performance balance, it is preferable that the composition be as follows.

As the core component polymer used in the present invention, polymethyl methacrylate is particularly preferred from the viewpoint of optical transmission performance, but a poly(11) polymer containing 80 mol% or more of methyl methacrylate may also be used. Co-metallic components include acrylic acid esters such as methyl acrylate, 11-layer ethyl acrylate, propyl methacrylate, acrylic [W-butyl, 6s-ethylhexyl acrylic], cyclohexyl methacrylate, benzyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples include monomers such as methacrylic esters of propyl and butyl methacrylate. For example, the core component to be used is 10
Is it manufactured by continuous bulk polymerization method as shown in No. n? It is preferable to use

The optical transmission fiber of the present invention has a sheath made of ethyl acetate by a conventional method.
A method of dissolving the fiber in a solvent such as dimethylformamide or dimethylacetamide and coating it with a sheath material on the surface of the fiber of the core component made of a polymer mainly composed of polymethyl methacrylate using a dipping method, or using a core-sheath type composite spinning nozzle. It can be manufactured by a method in which the core component is spun and the sheath part is extruded and shaped at the same time. The spinning temperature may be set appropriately taking into account the melting temperatures of the core component and sheath component.
'-u, j OC is preferable.

When a composite filament is produced by melt-coextruding the fluorine-based resin composition of the present invention as a sheath component together with a core component using a core-sheath spinneret, the molding temperature ranges over a wide range from /Sθ to -θC. No abnormal phenomena such as foaming or whitening were observed in the sheath component, and the numerical aperture, which is an important measurement value that is influenced by the interface state between the sheath and core in optical transmission fibers, was determined by the refractive index of the core and sheath. The numerical aperture is very close to the theoretical numerical aperture of It is thought that when used, both adhesion and heat resistance are improved, and disturbances at the core-sheath interface are suppressed. The reason for this is that, as mentioned above, the fluorinated alkyl methacrylate polymer inhibits the crystallization 2 of the vinylidene fluoride copolymer, improves quality, and has good compatibility with the core component polymethyl methacrylate. This is thought to be because better adhesion can be obtained in relation to the vinylidene chloride thread copolymer.

The present invention will be specifically explained below using Examples.

In addition, all parts in the examples are parts by weight, and all percentages are weight Jt.
Indicates i%.

Here, the performance of the optical transmission fibers obtained in Examples and Comparative Examples was evaluated using the following method. (1) Evaluation of optical transmission loss The transmission loss of the optical transmission fibers obtained is shown in Figure 1. Measured using the equipment shown.

The light emitted from a halogen lamp (10λ) driven by a stabilized power source (/θl) is made into parallel light by a lens (loJ), then monochromated by an interference filter (lθ), and then connected to an optical transmission fiber (ioθ). It is focused at the focal point of a lens (10S) with equal numerical aperture.

Adjustment is made so that the incident end surface (iot) of the optical transmission fiber is located at this focal point, and the light is made to enter the optical transmission fiber <io. The light incident from the input end face (106) is attenuated and passes through the output end face (106).
Shoot from IO'l). This emitted light is converted into a current by a photodiode C/(M) with a sufficiently large area, amplified by a current-to-torque conversion type amplifier (toq), and then measured by a voltmeter (//). Read as a value.

Measurement of transmission loss shall be carried out using the following procedure.

First, make the optical transmission fiber (10!) long.
Both end faces are cut at right angles to the fiber axis, finished to have a smooth surface, and the input end face (104) and the output end face (i
o7) is attached so that it does not move during measurement. Read the reading on the voltmeter in a dark room.

Let this voltage value be . Next, turn on one indoor light, remove the output end face (lθri) from the device, and cut the optical transmission fiber (100’ft) from this end face at the point (///) of length l◎Then, attach it to the device. Finish the end face of the other optical fiber so that it is perpendicular to the fiber axis, as before, and attach it to the device as the new output end face. During these operations, care must be taken not to move the incident end face (104) in order to keep the incident optical paper constant. Return to the dark room, read the reading on the voltmeter, and call this value ■.

(to the original transmission loss) is calculated by the following formula.

71 here! Length of two optical fibers Km) 1, , I
2: Light amount (voltmeter reading value) Note that the measurement conditions in the present invention (
Well, it is as follows.

Interference filter (+, wavelength): AdaA nm10c Total length of optical fiber): 15m1 (Cut length of optical fiber): /QmD (Bobbin diameter): /
Here, the bobbin is used to make the device compact, and the remaining optical fibers are attached to the bobbin (not shown) so that the distance between the input end face (106) and the output end face (LO) is approximately /m. ).

(λ) Measurement of Numerical Aperture of Optical Transmission Fiber The numerical aperture of the optical transmission fiber was measured using the measuring device shown in FIG. (1) is a parallel light source with a built-in herogen lamp. The output light of the light source has a center wavelength A 3'
After passing through an interference filter (λ) of 0 + n and half value ILIM J -1 to make it monochromatic, the parallel light beams are focused by a lens (3) whose numerical aperture is larger than that of the optical transmission fiber, and the optical transmission fiber is (lI) is made incident on one end surface (j). The end face ←) is cut perpendicular to the fiber axis of the optical transmission fiber and finished smooth, and the fiber axis and optical axis (7) are fixed using the fixture (A).
Fixed so that they match. After the incident light passes through a light transmission fiber having a total length of /jm, it exits from the other end face <g>. The end surface <g>, which is finished with a smooth surface perpendicular to the fiber axis, is aligned with the central axis of the fixed shaft (9), and the fixed shaft ( 9
).

(ll) is a rotary arm that rotates around the central axis of the fixed shaft (9), and the rotation angle θ can be read.

(/2) is a photomultiplier tube that detects light, and it is installed in the case (13) and passes through the hole (/lI). is located at a distance of 511 m from the central axis with a diameter of lS.The distribution of the emitted light is measured by the relationship between the rotation angle θ of the rotating arm and the current of the photomultiplier tube using a device configured as shown in Figure 1. An example of this is shown in Fig. 3.If the maximum current Imax is the angle width θW in which Imax decreases to %, the numerical aperture (NA) can be found from the equation.

NA=sin Ow・1. - (3) Heat resistance test of sheath component polymer The obtained sheath component polymer 7 was heated at 20θC using a 3A ton heating press! ; Create a film with a uniform thickness of 50 μm under a load of Okg/crl-10θkq/c-, and perform AST
Total light transmittance and haze value were measured using an integrating sphere haze meter in accordance with M-D/θ03-A/. This film was exposed to gSC in a thermostatic cypress for IOθ hours to grow crystals, and the total light transmittance and haze value were determined as heat resistance test results using an integrating sphere haze meter similar to the above.

←) Dense layer property test The obtained film of the sheath component polymer was placed on a methacrylic resin plate with a thickness of 3 mm, heat laminated using a -〇〇〇 heat press, and then cooled to room temperature in accordance with JIS 3; 1I00. The adhesion test according to Method V was evaluated by the riless cut method. First, 100 squares were made, adhesive tape was attached, and the degree of density enhancement was evaluated based on the number of squares.〇◎ Each cut was thin and both sides were smooth, and the intersection of the cuts and the square There is no peeling in the eyes ○ There is peeling on both sides of the cut and the intersection, and the defective area is within /j% Δ There is peeling on both sides of the cut and the intersection, and the defective area is within 6S%. Example 1 λll coquat trifluoroethyl methacrylate gθ portion, methyl methacrylate co. azobisisobutyronitrile θ"t'z as a polymerization initiator.
fs and n-octyl mercaptan θθ were added to the ampoule tube, and the tube was sealed under reduced pressure after repeated degassing. This sealed ampoule was polymerized by heating at 70C for 11 hours to obtain a transparent resin body. Further heating for 1joc for 3 hours to achieve a polymerization conversion rate of 99%? ! 4 □Take out the obtained 'r:, Polymer C hereinafter referred to as Polymer A] and dilute it to a concentration of 3 in ethyl acetate.
It was dissolved to a concentration of 0%. On the other hand, vinylidene fluoride-tetrafluoroethylene (1107,
1□) (mole ratio) (hereinafter referred to as copolymer B) was similarly adjusted to a 30% ethyl acetate bath solution, and mixed with the solution of the above 2,2-trifluoroethyl methacrylate spinning wheel copolymer. After thoroughly removing the solvent by deaerating the solvent, the obtained solid material was pulverized using a Claracy and JIS-Z-480/Standard/A mesh bath 3.
+2 mesh fraction K was separated and shaped into pellets using a 2S dragon φ vent type extruder (manufactured by Osaka Seiki Co., Ltd.). The refractive index of the obtained polymer was /daOO. The total light transmittance (T t ) of a film obtained by molding this polymer into a film having a thickness of 50 μm was %D and S% haze. The heat resistance test result is the total light transmittance ('l'
t) K'7% and haze value SS%, which were good.

Core - Using a silk spinneret, use polymethyl methacrylate as the core component and the above N (coalescence) as the sheath component.
A composite filament with a K diameter of 80 μm was obtained. Observation using Microscope 4 revealed that the core-sheath interface was perfectly round and no air bubbles or foreign matter were observed.

The wavelength of the filament is A! ; The transmission loss due to Onrn light is 11.1θd f3 /K m,! 70
4t for nm light; t OdB/Krn% 320 nm
In the case of light, it was Da J OdB/Km. In addition, this filament (D l]iJ D' k is OdaS, and the theoretical numerical aperture (N,
The value was close to A-r=shoulder-1)-osit.

Examples Ω to IO Ndl composition of l+'4 component polymer acid, polymer B, and mixing of polymer A and polymer B in Example/; 1
The performance of the sheath component polymer and the transmission characteristics of the optical transmission fiber were evaluated in the same manner as in Example/, except that the I/I ratio was changed as shown in Table 1.71:o The evaluation results are summarized in Table 7. Indicated.

Comparative Example/~3 As shown in Table 1, when only Polymer B was used as the sheath component polymer (Comparative Example/), i Table 1 shows the performance of the sheath component polymer and the transmission characteristics of the optical transmission fiber. 7.

As shown in each Example, when Polymer A and Polymer B are mixed and used, a sheath component with good heat resistance and core-sheath adhesion can be obtained, whereas in Comparative Examples, a sheath component with good heat resistance and good core-sheath adhesion is obtained. The heat resistance of the resin was poor, the contact with the methacrylic resin plate was poor, and the performance was insufficient.

l Figure 1) A detailed explanation of 11 Figure 1 shows the equipment 11 for measuring the transmission loss of an optical transmission fiber.
Figures 6 and 2 are schematic diagrams of a device l''i for measuring the numerical aperture of optical transmission fibers, and Figure 3 is an explanatory diagram of an example of numerical aperture measurement. Lens da...no C
Sending fibers s, g...End face 12 of optical transmission fiber...Photomultiplier tube 10θ...Optical transmission fiber lθ6...Incidence end face 10
7... Output end face

Claims (1)

[Scope of Claims] 1. A light transmitting fiber characterized in that its sheath component is a resin composition obtained by blending a polymer whose main component is polymethyl methacrylate. λ Vinylidene fluoride yarn copolymer is a copolymer consisting of 10 mol% or more of vinylidene fluoride units and 40 mol% or less of tetrafluoroethylene units.
Optical transmission fiber described in Section 1. 3 Vinylidene fluoride yarn copolymer is at position 24+ of vinylidene fluoride
t, o mol% or more and hexafluorohiropropylene units are 7
The optical transmission fiber according to claim 1, which is a copolymer consisting of 0 mol% or less.