KR100540038B1 - Cladding composition containing layered silicate clay - Google Patents

Abstract

The present invention relates to a cladding composition comprising 0.01 to 20 parts by weight of layered silicate clay with respect to 100 parts by weight of fluoro acrylate monomer.

The clad prepared by the cladding composition according to the present invention exhibits excellent performance as a cladding material for optical fibers and image fibers because the heat-resistant property is improved due to the layered silicate clay and there is no decrease in transparency and an increase in refractive index.

Description

Cladding composition containing layered silicate clay {CLADDING COMPOSITION CONTAINING LAYERED SILICATE CLAY}             

1 is a graph showing the refractive index of the clad prepared in Examples 1 to 3.

Figure 2 is a graph showing the glass transition temperature of the clad prepared in Examples 1 to 3.

Figure 3 is a wide angle X-ray diffraction (WAXD) graph showing the degree of dispersion of the layered silicate clay in the clad prepared in Examples 1 to 3.

FIG. 4 is a TEM photograph showing a state in which a layered silicate clay is peeled and dispersed in a nano size in a clad prepared in Example 3. FIG.

The present invention relates to a cladding composition containing a layered silicate clay, and more particularly, to a plastic optical fiber having a high numerical aperture while maintaining a high numerical aperture by dispersing the layered silicate clay nanoscale in a fluoro acrylate monomer. And a cladding composition for an image fiber.

Quartz-based optical fibers have high transparency and excellent heat resistance, but have a disadvantage in that the production cost is high due to the lack of flexibility and the complicated processing process. However, since plastic optical fibers have high flexibility, easy handling and good workability, and low production cost, demand for these optical fibers is increasing.

Plastic optical fiber (hereinafter referred to as "POF") has a slightly lower optical transmission efficiency than conventional quartz or glass optical fibers, but has advantages in terms of bending characteristics, ease of connection, and production cost. It is emerging as an alternative material for optical fiber. POF is mainly used for local area networks, communication media inside cars, and home networking.

Plastic image fibers (hereinafter referred to as "PIF") include image guides, endoscopes for endoscopes, multi-core fibers that are distinct from structural single-core fibers, and fiber bundles. It is called as bundle, and it is used for medical endoscope, industrial endoscope, outdoor billboard, image sensor, communication and lighting.

The cladding in POF or PIF allows the light incident on the core layer to totally reflect inside the core and primarily to protect the core layer. In particular, since PIF needs to transmit an image, the optical loss must be reduced as much as possible. This requires a large refractive index difference from the core layer. In addition, in order to have thermal stability at the actual temperature used must have a high glass transition temperature.

Currently, as the material of POF or PIF, acrylic resin, polycarbonate resin, polystyrene resin, perfluorinated resin, etc. are mainly used. Especially, polymethyl methacrylate (PMMA) among acrylic resins is widely used because of its excellent optical properties. have.

Meanwhile, as the plastic optical fiber cladding composition, as disclosed in Korean Patent Application Nos. 1998-0003201, 1996-7006648, and 1994-7002828, etc., methyl methacrylate / fluoroacrylate-based copolymer, methyl methacrylate / Vinylidene fluoride copolymers, fluoroacrylates, and the like are used. The cladding composition used at this time generally has a low refractive index (1.35 to 1.45) compared to the refractive index (1.49) of the core material (PMMA). By introducing such a fluoro-based compound into the cladding composition can be prepared clad having a low refractive index, the problem of heat resistance, that is, the glass transition temperature is lower than the use temperature range occurs.

Accordingly, a technical object of the present invention is to provide a cladding composition for plastic optical fibers and image fibers containing layered silicate clay while improving the heat resistance temperature and having no decrease in transparency and an increase in refractive index.

In order to achieve the above technical problem, the present invention provides a cladding composition comprising 0.01 to 20 of the layered silicate clay with respect to 100 parts by weight of the fluoro acrylate monomer.

In the cladding composition of the present invention, it is preferable that 0.01 to 20 parts by weight of the layered silicate clay, 1 to 10 parts by weight of the polymerization initiator and 10 parts by weight or less of the emulsifier based on 100 parts by weight of the fluoroacrylate monomer.

In the cladding composition of the present invention, the fluoro acrylate monomers are trifluoroethyl methacrylate, tetrafluoropropylalphafluoroacrylate, pentafluoropropyl methacrylate, perfluorodecyl methacrylate, perfluoro It is preferable that they are lococtyl methacrylate, heptadecafluorodecyl methacrylate, and hexafluorobutyl methacrylate.

In order to achieve the above another technical problem, the present invention provides a clad obtained by emulsion polymerization of the cladding composition, the refractive index is 1.43 or less and the glass transition temperature is 70 ℃ or more.

Hereinafter, the cladding composition containing the layered silicate clay of this invention is demonstrated more concretely.

The present invention is to provide a clad for POF and PIF having a low refractive index and a high glass transition temperature. Polymethyl methacrylate (PMMA) is commonly used as a core material of POF and PIF. The refractive index is 1.492 and the glass transition temperature is about 117 ° C. Commonly used as clad material is a fluoro acrylate compound, specific examples include trifluoroethyl methacrylate, tetrafluoropropyl alpha fluoroacrylate, pentafluoropropyl methacrylate, purple Fluorodecyl methacrylate, perfluorooctyl methacrylate, heptadecafluorodecyl methacrylate, and hexafluorobutyl methacrylate.

Although the refractive index of the fluoro acrylate compound is in the range of 1.35 to 1.43, the glass transition temperature is lower than 40 to 70 DEG C, which is not suitable for use as a clad material of POF and PIF.

Accordingly, the present inventors have developed a clad composition comprising adding a layered silicate clay to a polymerization composition including a fluoro acrylate monomer, a polymerization initiator, an emulsifier, and the like to increase the glass transition temperature.

The content of the layered silicate clay with respect to 100 parts by weight of the fluoro acrylate monomer is preferably 0.01 to 20 parts by weight. When the content is less than 0.01 parts by weight, the effect of addition is hardly observed. Is not good because it is not good. In addition, the polymerization initiator is preferably added 1 to 10 parts by weight with respect to 100 parts by weight of the fluoro acrylate monomer, but when added to less than 1 part by weight can not be expected to effect the polymerization, more than 10 parts by weight This is undesirable because the molecular weight of the polymer decreases. The emulsifier is preferably added in an amount of 10 parts by weight or less with respect to 100 parts by weight of the fluoroacrylate monomer, but when it is added in excess of 10 parts by weight, the emulsifier is difficult to remove, which is not preferable.

The layered silicate clay added to the cladding composition of the present invention is present in a layered structure in the composition, and when each layer is peeled off, it is separated into a layer having a thickness of several nm. Instead of layered silicate clay, organic particles such as polystyrene (PS) or polymethylmethacrylate (PMMA), or inorganic particles such as silica can be used as heat-resistant additives, the diameter of which is used when such monodisperse organic and inorganic particles are used. It is preferable that it is 50 nm or less.

)가 휘도(brightness)의 중요한 요소이기 때문에 개구수가 가능한 커야 하며 이를 위해서는 코어의 굴절율(n₁)과 클래드의 굴절률(n₂)의 차이가 더욱 커야만 한다. PIF의 개구수를 고려한 클래드의 굴절률은 1.43 이하인 것이 바람직하며, 유리전이온도는 PIF의 사용온도를 고려할 때 70℃ 이상인 것이 바람직하다. Especially in the case of PIF, numerical aperture (NA)

Since () is an important factor of brightness, the numerical aperture must be as large as possible, and for this purpose, the difference between the refractive index n _{1 of the} core and the refractive index n ₂ of the clad must be larger. The refractive index of the clad in consideration of the numerical aperture of PIF is preferably 1.43 or less, and the glass transition temperature is preferably 70 ° C. or more in consideration of the temperature of use of PIF.

When the refractive index of the clad exceeds 1.43, the numerical aperture (NA) decreases, which is not preferable, and when the glass transition temperature is lower than 70 ° C, the glass transition of the clad occurs in a range lower than the normal use temperature of POF or PIF. I can't.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the protection scope of the present invention is not limited by these examples.

Examples 1 to 3

30g of trifluoroethyl methacrylate (TFEMA), 250g of deionized water, Potassium persulfate (KPS), 99% purity, Aldrich Co., Ltd.) 0.1g, and 2g of Lauryl sulfate (SDS), 99% purity, manufactured by Aldrich Co., Ltd. to prepare a polymerization composition, and the polymerization composition prepared as described above in each of three 500 ml three-neck flasks. After the three compositions were prepared, 0.3, 0.9 and 1.5 g of layered montmorillonite were added to the polymerization composition, respectively, and the emulsions were polymerized at 80 rpm for 6 to 8 hours.

The emulsion-polymerized polymer was finely cut and placed in a spacer having a thickness of 0.5 mm, and then compression molded to prepare a specimen. In order to reduce the contact angle between the compression molded specimen and the refractometer, use a bromobenzene (refractive index 1.559) to closely adhere the specimen to prevent light from leaking from the sample holder of the refractometer, and then use the ABBE refractometer to adjust the refractive index of the specimen. Measured. The measurement results are shown in Table 1 and FIG. 1. As shown in Figure 1, even if the clay content in the clad composition increases it can be seen that little change in the refractive index.

In addition, a glass transition temperature measuring instrument (TA Instrument, model name: Dupont 2010 DSC) was used to measure the glass transition temperature of the polymer. The rate of temperature rise was 20 ° C./min and the glass transition temperature was determined by half-height method after two measurements for accuracy. The results are shown in Table 1 and FIG. 2. As shown in Figure 2, it can be seen that the glass transition temperature is increased when the clay content in the clad composition increases.

In addition, the sample was precipitated with an alcohol solvent, washed with deionized water, separated with a centrifugal separator and dried using a freezed dryer, and the WAXD measurement was performed using the powder obtained. Shown in As shown in FIG. 3, it can be seen that the laminar clay montmorillonite is effectively dispersed in the polymer clad polymerized by the embodiment of the present invention.

4 is a 5 wt% TEM photograph of the clad to determine whether the layered silicate clay is substantially and effectively dispersed within the polymer clad.

Examples 4-6

A clad was prepared in the same manner as in Example 1, except that 30 g of perfluorodecyl methacrylate (PFDMA) was added instead of trifluoroethyl methacrylate as a polymerization monomer. Physical properties were measured.

Comparative Example 1

The clad was polymerized in the same manner as in Example 1 except that layered montmorillonite was not added, and physical properties were measured.

Comparative Example 2

The clad was polymerized in the same manner as in Example 4 except that layered montmorillonite was not added, and physical properties were measured.

Table 1 shows the measurement results of the physical properties of the clad obtained in the above Examples and Comparative Examples.

Monomer Clay content (wt%) Refractive index T _g (℃) Example 1 A One 1.419 85 Example 2 3 1.419 92 Example 3 5 1.422 95 Comparative Example 1 0 1.415 76 Example 4 B One 1.369 71 Example 5 3 1.369 80 Example 6 5 1.372 85 Comparative Example 2 0 1.369 62

In Table 1, A is trifluoroethyl methacrylate (2,2,2-trifluoroethyl methacrylate, TFEMA), and B is perfluorodecyl methacrylate (1,1,2,2-perfluoro decylmethacrylate, PFDMA). to be.

As shown in Table 1, in the case of the comparative example, the glass transition temperature was relatively lower than that of each of the examples using the same type of monomer because no layered silicate clay was added.

On the other hand, in the case of the embodiment, it can be seen that the refractive index does not change significantly but the glass transition temperature increases significantly as the amount of the layered silicate clay (montmorillonite) is increased. This point can also be confirmed from FIG. 1 and FIG. 2.

Embodiments of the present invention show that by peeling and dispersing the layered silicate clay in the cladding composition to a nano size in the emulsion polymerization process, it is possible to improve the glass transition temperature without lowering the transparency or increasing the refractive index.

As described above, according to the present invention, by cladding and dispersing the layered silicate clay in the cladding composition to a nano-size, it is possible to produce a clad with improved heat resistance characteristics without lowering the transparency or increase in the refractive index.

Claims (4)

Cladding composition comprising 0.01 to 20 parts by weight of the layered silicate clay with respect to 100 parts by weight of the fluoro acrylate monomer. The method of claim 1, A cladding composition comprising 0.01 to 20 parts by weight of layered silicate clay, 1 to 10 parts by weight of a polymerization initiator and 10 parts by weight or less of an emulsifier, based on 100 parts by weight of a fluoro acrylate monomer. The method of claim 1, Fluoro acrylate monomers include trifluoroethyl methacrylate, tetrafluoropropylalphafluoroacrylate, pentafluoropropyl methacrylate, perfluorodecyl methacrylate, perfluorooctyl methacrylate, hepta Decafluorodecyl methacrylate, hexafluorobutyl methacrylate, The cladding composition, characterized in that. A clad with a refractive index of 1.43 or less and a glass transition temperature of 70 ° C. or more, obtained by emulsion polymerization of the cladding composition according to claim 1.

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