TW202247988A - Manufacturing method for plastic optical fiber - Google Patents

Abstract

This manufacturing method is for a plastic optical fiber that comprises: a first layer formed by a first resin material including a fluorine-containing resin; and a second layer which is formed by a second resin material and is in contact with the first layer. This manufacturing method includes (A) performing a heat treatment on a linear body including a first layer and a second layer disposed in contact with the first layer at a temperature which is lower than or equal to a first glass transmission temperature Tg1 of the first resin material and lower than or equal to a glass transition temperature Tg2 of the second resin material. The first resin material and the second resin material have a peeling strength of at least 1 kN/m. Here, the peeling strength pertains to a joined body of a first sheet made of the first resin material and a second sheet made of the second resin material, and is the peeling strength of the second sheet with respect to the first sheet as measured by SAICAS.

Description

Manufacturing method of plastic optical fiber

The invention relates to a manufacturing method of plastic optical fiber.

The plastic optical fiber has a core at the center as a portion for transmitting light, and a cladding covering the outer periphery of the core. The core is formed of a resin material with a high refractive index. In order to keep light inside the core, the cladding is formed of a resin material having a lower refractive index than that of the core. As the resin material for the core and the cladding, for example, from the viewpoint of reducing the transmission loss of the plastic optical fiber, a fluorine-containing resin can be used (for example, Patent Document 1).

The plastic optical fiber further includes, for example, a coating layer disposed on the outer periphery of the coating portion. With the coating, the mechanical strength of the plastic optical fiber can be improved. prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2001-302935

[Problem to be solved by the invention]

According to the research of the inventors of the present invention, regarding a plastic optical fiber having a layer formed of a fluorine-containing resin (hereinafter referred to as a "layer containing a fluorine-containing resin"), there is a difference between the layer containing a fluorine-containing resin and the difference over time. The tendency for interfacial delamination to occur between adjacent layers. If interfacial peeling occurs, microbending occurs in which the central axis of the core is slightly shifted, which may increase the transmission loss of the plastic optical fiber.

Therefore, an object of the present invention is to provide a method for producing a plastic optical fiber capable of suppressing interfacial peeling between a layer containing a fluorine-containing resin and an adjacent layer due to changes over time. [Technical means to solve the problem]

The present invention provides a method for manufacturing plastic optical fiber, which comprises a first layer formed of a first resin material containing fluorine-containing resin, and a second layer formed of a second resin material and in contact with the first layer. layer, and the above-mentioned manufacturing method includes (A) at a temperature below the first glass transition temperature Tg ₁ of the above-mentioned first resin material and below the glass transition temperature Tg ₂ of the above-mentioned second resin material, for the above-mentioned first layer, and The linear body of the second layer arranged in contact with the first layer is heat-treated, and the first resin material and the second resin material have a peel strength of 1 kN/m or more. Wherein, the above-mentioned peel strength refers to the peel strength of the second sheet relative to the first sheet measured as follows, that is, the first sheet containing the above-mentioned first resin material with a thickness of 50 μm, and the above-mentioned second sheet. The second sheet of resin material with a thickness of 50 μm was stacked to obtain a laminate, and the above-mentioned laminate was pressed with a hand roller along the lamination direction of the above-mentioned laminate at 270°C to produce the above-mentioned first sheet and the above-mentioned second. The bonded body of the sheets was measured by Surface And Interfacial Cutting Analysis System (SAICAS, Surface Interface Cutting Analysis System) to obtain the peel strength of the second sheet relative to the first sheet. [Effect of Invention]

According to the present invention, it is possible to provide a method for producing a plastic optical fiber capable of suppressing interfacial peeling between a layer containing a fluorine-containing resin and an adjacent layer due to changes over time.

Hereinafter, an embodiment of a method for producing a plastic optical fiber (hereinafter referred to as "POF") of the present invention will be described. The following description is not intended to limit the invention to specific embodiments.

The production method of the present embodiment is a production method of a POF comprising a first layer formed of a first resin material containing a fluorine-containing resin, and a layer formed of a second resin material in contact with the first layer. tier 2. The manufacturing method of this embodiment includes: (A) at a temperature below the first glass transition temperature Tg ₁ of the above-mentioned first resin material and below the glass transition temperature Tg ₂ of the above-mentioned second resin material, for the above-mentioned first layer, And the linear body of the above-mentioned second layer arranged in contact with the above-mentioned first layer is heat-treated. In the production method of this embodiment, the first resin material and the second resin material have a peel strength of 1 kN/m or more.

Here, the peel strength of the first resin material and the second resin material refers to the peel strength measured using a bonded body of the first sheet made of the first resin material and the second sheet made of the second resin material. Specifically, the aforementioned peel strength refers to the peel strength of the second sheet relative to the first sheet measured by combining the first sheet with a thickness of 50 μm including the first resin material, and the second sheet including the second sheet. The second sheet of resin material with a thickness of 50 μm is stacked to obtain a laminate, and the laminate is pressed with a hand roller along the lamination direction of the laminate at 270°C to produce the first sheet and the second sheet The bonded body was measured using SAICAS to obtain the peel strength of the second sheet with respect to the first sheet. In addition, the pressure applied to the laminate by a hand roller is, for example, 5 to 20 kPa.

The first sheet including the first resin material and the second sheet including the second resin material were produced by the following methods, respectively. The first sheet is to heat the first resin material in the range of glass transition temperature Tg ₁ +80~Tg ₁ +150℃ of the first resin material, and apply a pressure of 2~20 MPa to form a sheet with a thickness of 50 μm . The second sheet is to heat the second resin material in the range of the glass transition temperature Tg ₂ +80 ~ Tg ₂ +150°C of the second resin material, and apply a pressure of 2 ~ 20 MPa to form a sheet with a thickness of 50 μm .

The above-mentioned peel strength is determined by the following formula (1), for example. The measurement mode of SAICAS is constant speed mode. The cutting speed was 10 μm/sec. In the formula (1), P is the peel strength [kN/m]. FH is the horizontal cutting stress [N] when a SAICAS diamond cutting edge (manufactured by Daipla, rake angle: 40°) is moved horizontally at the interface between the first layer and the second layer. W is the cutting edge width of SAICAS [m]. Furthermore, SAICAS is a registered trademark of Daipla Co., Ltd. P=FH/W...(1)

In a POF having a layer containing a fluorine-containing resin (that is, corresponding to the first layer in the production method of this embodiment), there are layers adjacent to the layer containing a fluorine-containing resin due to changes over time (that is, Corresponds to the tendency of interfacial peeling to occur between the second layer in the production method of this embodiment. In contrast, in the manufacturing method of this embodiment, the first resin material and the second resin material having a peel strength of 1 kN/m or more are used to form the first layer and the second layer, respectively, and are placed on the POF as described above. During production, the above-mentioned heat treatment of (A) can be performed to suppress the occurrence of interfacial peeling between the first layer and the second layer due to changes over time. It eases the process of producing the linear body (for example, for The residual stress generated in the linear body in the cooling process of cooling and solidifying the linear body in the molten state, and the elongation process of the linear body, etc.). It is considered that by such relaxation of residual stress, the adhesive strength between the first layer and the second layer can be maintained, and peeling at the interface between the first layer and the second layer due to changes over time can be suppressed.

If the first resin material and the second resin material have a peel strength of 1 kN/m or more, the interface between the first layer and the second layer due to changes over time can be suppressed by the heat treatment of the above (A) The occurrence of stripping. In order to more reliably suppress the occurrence of interfacial peeling between the first layer and the second layer by the manufacturing method of this embodiment, the first resin material and the second resin material preferably have a peel strength of 1.5 kN/m or more, More preferably, it has a peel strength of 2 kN/m or more. The upper limit of the peel strength of the 1st resin material and the 2nd resin material is not specifically limited. However, when the peeling strength of the first resin material and the second resin material is high, it is difficult to cause interfacial peeling between the first layer and the second layer due to changes over time. The effect of suppressing interfacial peeling by the heat treatment of (A) above, the peeling strength of the first resin material and the second resin material may be, for example, 20 kN/m or less, 10 kN/m or less, or 5 kN/m m or less, may be less than 2.5 kN/m, or less than 2.3 kN/m.

The linear body to be subjected to the heat treatment of (A) above may be obtained, for example, by a melt spinning method in which the first resin material and the second resin material are heated and melted to form fibers, and the resulting The shaped body is obtained by cooling and solidifying. The linear body obtained by this method usually produces residual stress when it is cooled and solidified. Therefore, by performing the heat treatment of (A) above on such a linear body, the residual stress of the linear body can be effectively relaxed, and the gap between the first layer and the second layer that occurs due to changes over time can be effectively suppressed. Interface peeling. For example, the production method of this embodiment may include the following operations before the above (A): heating and melting the first resin material and the second resin material to form a fiber shape, and cooling and solidifying the obtained molded body to obtain 1st and 2nd layer of linear bodies.

In addition, the linear body subjected to the heat treatment of (A) above may also be stretched. Residual stress is usually generated on the stretched linear body. Therefore, by performing the heat treatment of (A) above on such a linear body, the residual stress of the linear body can be effectively relaxed, and interfacial peeling due to changes over time can be effectively suppressed. The manufacturing method of this embodiment may include, for example, the operation of stretching the linear body including the first layer and the second layer before the above (A).

As mentioned above, the heat treatment temperature T of the linear body in (A) is not more than the first glass transition temperature Tg ₁ of the first resin material and not more than the glass transition temperature Tg ₂ of the second resin material. By heat-treating the linear body at a temperature below Tg ₁ and below Tg ₂ , for example, the adhesive strength between the first layer and the second layer can be maintained, and the residual stress of the linear body can be relaxed. Therefore, the heat treatment of the above (A) can effectively suppress the interfacial peeling between the first layer and the second layer due to the temporal change. Also, for example, when the linear body is stretched, by heat-treating the linear body at a temperature below Tg ₁ and below Tg ₂ , it is possible to maintain the alignment of the resin material produced during stretching along the stretching direction. , to ease the residual stress. Therefore, the above-mentioned heat treatment of (A) can maintain the strength and flexibility of the POF improved by the alignment of the resin material, and can suppress interfacial peeling between the first layer and the second layer due to changes over time.

The heat treatment temperature T in the above (A) is preferably Tg ₁ -65°C or higher and Tg ₂ -65°C or higher. By heat-treating the linear body at a temperature of Tg ₁ -65° C. or higher and Tg ₂ -65° C. or higher, the residual stress of the linear body can be efficiently and effectively relaxed. In order to more efficiently and effectively relax the residual stress of the linear body, the heat treatment temperature T in the above (A) is more preferably Tg ₁ -45°C or higher and Tg ₂ -45°C or higher.

Based on the above reasons, the heat treatment temperature T of the linear body in (A) above preferably satisfies Tg ₁ -65°C≦T≦Tg ₁ and Tg ₂ -65°C≦T≦Tg ₂ . The heat treatment temperature T of the linear body is more preferably satisfying Tg ₁ -45°C≦T≦Tg ₁ °C and Tg ₂ -45°C≦T≦Tg ₂ °C.

In this specification, the glass transition temperature refers to the intermediate point glass transition temperature (T _mg ) calculated based on the regulation of JIS K7121:1987.

The heat treatment time in (A) above is preferably at least 10 minutes, more preferably at least 1 hour. By setting the heat treatment time to 10 minutes or more, the residual stress of the linear body can be sufficiently relaxed, and interfacial peeling due to changes over time can be more reliably suppressed.

The heat treatment time in (A) above may be, for example, 75 hours or less, may be 24 hours or less, may be 18 hours or less, or may be 12 hours or less. The heat treatment in the above (A) can sufficiently relax the residual stress of the linear body for less than 75 hours, and more reliably suppress the interfacial peeling caused by the change over time.

There are no particular limitations on the method of performing the heat treatment of (A) above, and any method can be used as long as it can expose the linear body including the first layer and the second layer to a desired temperature range for a required time. For example, the above-mentioned heat treatment of (A) may be performed on the above-mentioned linear body in the state of being wound up on a bobbin, and the linear body may be placed on a belt conveyor, for example, while passing through a heating furnace, and continuously Carry out heat treatment. The heating means used in the heat treatment is also not particularly limited, and known heating means such as a heater can be used.

The POF manufactured by the manufacturing method of this embodiment can be, for example, POF10 as shown in FIG. Covering layer 13. In the POF 10 , the clad part 12 is in contact with the core part 11 , and the clad part 13 is in contact with the clad part 12 .

When POF 10 is manufactured by the manufacturing method of this embodiment, any one of core portion 11, cladding portion 12, and coating layer 13 is the first layer, and is in contact with the first layer and opposite to the first layer. A configuration in which the layer has a peel strength of 1 kN/m or more serves as the second layer. For example, the core 11 or the cladding 12 may be the first layer. When the core 11 is the first layer, the core 11 is formed of a first resin material including a fluorine-containing resin, and the cladding 12 is a second layer formed of a second resin material. In this case, the resin contained in the second resin material is not particularly limited as long as it has high transparency. As the resin contained in the second resin material, for example, acrylic resins such as fluorine-containing resins and methyl methacrylate, styrene resins, and carbonate resins may, for example, be mentioned. Among them, fluorine-containing resins are suitably used from the point of view that small transmission loss can be realized in a wider wavelength region. When the cladding part 12 is the first layer, the cladding part 12 is formed of the first resin material containing fluorine-containing resin, and the core part 11 or the cladding layer 13 becomes the second layer formed of the second resin material. When the core part 11 is the second layer, the resin contained in the second resin material may, for example, be fluorine-containing resin, acrylic resin such as methyl methacrylate, styrene resin, and carbonate Department of resin, etc. As described above, a fluorine-containing resin can realize a small transmission loss in a wider wavelength region, so it is suitably used as the resin contained in the core 11 . When the covering layer 13 is the second layer, the resin contained in the second resin material may, for example, be various engineering plastics such as polycarbonate, cycloolefin polymers, cycloolefin copolymers, polyesters, polyolefins, etc. , and copolymers of monomers forming these polymers, polytetrafluoroethylene (PTFE), modified PTFE, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), etc. When the covering layer 13 is the second layer, the second resin material does not need to contain fluorine-containing resin. In general, the adhesiveness between fluorine-containing resins and resins other than fluorine-containing resins such as polycarbonate is not high. Therefore, when the covering layer 13 is formed of the second resin material that does not contain a fluorine-containing resin, it is easy to cause a gap due to time-lapse between the coating portion 12 formed of the first resin material containing a fluorine-containing resin. Interfacial peeling caused by changes. However, even with such a combination of resins, according to the production method of this embodiment, by performing the heat treatment of (A) above, it is possible to suppress the interface that occurs between the clad portion 12 and the coating layer 13 due to changes over time. Peeling, so the increase in transmission loss is suppressed.

Regarding the POF manufactured by the manufacturing method of this embodiment, for example, a plurality of layers can be used to constitute the clad part. For example, the POF manufactured by the manufacturing method of this embodiment can be a POF 20 of a modified example as shown in FIG. The coating layer 13 on the outer periphery. In the POF 20, the cladding portion 22 has a two-layer structure, that is, a double cladding structure. The two-layer structure includes a first cladding layer 221 arranged in contact with the core 11, and a first cladding layer 221 arranged on a lower layer than the first cladding layer. The cladding layer 221 is closer to the second cladding layer 222 on the outer peripheral side. In the POF 20 , the covering layer 13 is in contact with the second covering portion 222 . In addition, although the example in which the covering part 22 has a 2-layer structure is shown in FIG. 2, the number of layers contained in the covering part 22 is not limited to this, and may include 3 or more layers.

When manufacturing POF 20 by the manufacturing method of this embodiment, any one of the core 11, the first cladding layer 221, the second cladding layer 222, and the cladding layer 13 is the first layer, and The configuration in which the first layer is in contact with the first layer and has a peel strength of 1 kN/m or more becomes the second layer. For example, the core part 11, the first cladding part 221, or the second cladding part 222 may be the first layer. When the core part 11 is the first layer, the core part 11 is formed of the first resin material including fluorine-containing resin, and the first covering part 221 becomes the second layer formed of the second resin material. When the first covering part 221 is the first layer, the core part 11 or the second covering part 222 becomes the second layer formed of the second resin material. When the second covering part 222 is the first layer, the first covering part 221 or the covering layer 13 becomes the second layer formed of the second resin material. When the second layer is the core part 11, the first cladding part 221, or the second cladding part 222, the resin contained in the second resin material only needs to be a resin with high transparency, and No particular limitation. In these cases, as the resin contained in the second resin material, for example, acrylic resins such as fluorine-containing resins and methyl methacrylate, styrene resins, and carbonate resins may, for example, be mentioned. Among them, fluorine-containing resins are suitably used from the point of view that small transmission loss can be realized in a wider wavelength region. When the covering layer 13 is the second layer, as the resin contained in the second resin material, as in the case of POF10, various engineering plastics such as polycarbonate, cycloolefin polymer, PTFE, modified PTFE, and PFA, etc. When the covering layer 13 is the second layer, the second resin material does not need to contain fluorine-containing resin. As described above, even in the case where the coating layer 13 is formed of the second resin material that does not contain a fluorine-containing resin, according to the manufacturing method of this embodiment, by performing the above-mentioned heat treatment of (A), it is possible to suppress the deterioration caused by time. Interfacial debonding between the second cladding portion 222 and the coating layer 13 due to the change can be suppressed from increasing the transmission loss.

The POF manufactured by the manufacturing method of this embodiment is, for example, a refractive index distribution (GI) type POF.

Hereinafter, each configuration of the POF 10 will be described in more detail by taking a case where the POF 10 is manufactured by the manufacturing method of this embodiment as an example.

(core 11) The core 11 is the region where light is transmitted. The core 11 has a higher refractive index than the cladding 12 . With this configuration, the light incident on the core 11 is confined inside the core 11 by the cladding 12 and propagates in the POF 10 .

The core 11 contains resin. The resin used for the core 11 is not particularly limited as long as it has high transparency. As resin used for the core part 11, acrylic resin, such as a fluorine resin and methyl methacrylate, a styrene resin, and carbonate resin etc. are mentioned, for example. Among them, fluorine-containing resins are suitably used from the point of view that small transmission loss can be realized in a wider wavelength region.

The core 11 preferably contains a fluorine-containing resin. The core 11 may contain a fluorine-containing resin as a main component. Here, the fact that the core 11 contains a fluorine-containing resin as a main component means that the component most contained in the core 11 in terms of mass ratio is the fluorine-containing resin. The core part 11 may contain 80 mass % or more of fluororesins, may contain 90 mass % or more, and may contain 95 mass % or more.

The core 11 may further contain additives in addition to the resin. The additive is, for example, a refractive index adjuster. That is, the core portion 11 can be formed of a resin composition containing a resin and additives such as a refractive index adjuster. As a refractive index adjuster, the well-known refractive index adjuster used for the material of the core part 11 of POF10 can be used, for example. The material of the core 11 may also contain other additives other than the refractive index adjuster.

When the POF 10 of the present embodiment is, for example, a GI type, the core 11 has a refractive index distribution in which the refractive index changes with respect to the radial direction. Such a refractive index distribution can be formed, for example, by adding a refractive index adjuster to the resin and diffusing the refractive index adjuster in the resin (for example, by thermal diffusion).

As described above, the resin constituting the core portion 11 is preferably a fluorine-containing resin including a fluorine-containing polymer. Hereinafter, the fluorine-containing resin contained in the core part 11 will be described as a first fluorine-containing resin, and the fluorine-containing polymer contained in the first fluorine-containing resin will be described as a first fluorine-containing polymer.

From the viewpoint of suppressing light absorption due to stretching energy of the C-H bond, the first fluoropolymer contained in the first fluororesin preferably does not substantially contain hydrogen atoms, and is particularly preferably bonded to carbon atoms. All hydrogen atoms of the junction are replaced by fluorine atoms. That is, the first fluoropolymer preferably does not substantially contain hydrogen atoms and is perfluorinated. In this specification, a fluoropolymer containing substantially no hydrogen atoms means that the content of hydrogen atoms in the fluoropolymer is 1 mol % or less.

The first fluoropolymer preferably has a fluorinated alicyclic structure. The fluorinated alicyclic structure may be included in the main chain of the fluoropolymer, or may be included in the side chain of the first fluoropolymer. The first fluoropolymer has, for example, a structural unit (A) represented by the following structural formula (1). [chemical 1]

In formula (1), R _ff ¹ to R _ff ⁴ each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 7 carbons, or a perfluoroalkyl ether group having 1 to 7 carbons. R _ff ¹ and R _ff ² may be connected to form a ring. "Perfluorinated" means that all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. In formula (1), the carbon number of the perfluoroalkyl group is preferably 1-5, more preferably 1-3, still more preferably 1. The perfluoroalkyl group may be linear or branched. As a perfluoroalkyl group, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, etc. are mentioned.

In formula (1), the carbon number of the perfluoroalkyl ether group is preferably 1-5, more preferably 1-3. The perfluoroalkyl ether group may be linear or branched. The perfluoroalkyl ether group may, for example, be a perfluoromethoxymethyl group or the like.

When R _ff ¹ and R _ff ² are linked to form a ring, the ring may be a 5-membered ring or a 6-membered ring. As this ring, a perfluorotetrahydrofuran ring, a perfluorocyclopentane ring, a perfluorocyclohexane ring and the like may, for example, be mentioned.

As a specific example of a structural unit (A), the structural unit represented by following formula (A1)-(A8) is mentioned, for example. [Chem 3]

The structural unit (A) is preferably a structural unit (A2) among the structural units represented by the above formulas (A1) to (A8), that is, a structural unit represented by the following formula (2). [Chem 2]

The first fluoropolymer may contain one or more structural units (A). In the first fluoropolymer, the content of the structural unit (A) is preferably at least 20 mol %, more preferably at least 40 mol %, based on the total of all structural units. There exists a tendency for a 1st fluoropolymer to have higher heat resistance by containing 20 mol% or more of structural units (A). When the structural unit (A) is included in 40 mol% or more, the first fluoropolymer tends to have higher transparency and higher mechanical strength in addition to higher heat resistance . In the first fluoropolymer, the content of the structural unit (A) is preferably at most 95 mol %, more preferably at most 70 mol %, based on the total of all structural units.

The structural unit (A) is derived from, for example, a compound represented by the following formula (3). In formula (3), R _ff ¹ to R _ff ⁴ are the same as formula (1). In addition, the compound represented by formula (3) can be obtained by the well-known manufacturing method represented by the manufacturing method disclosed in Japanese Patent Application Publication No. 2007-504125, for example. [chemical 4]

Specific examples of the compound represented by the formula (3) above include compounds represented by the following formulas (M1) to (M8). [chemical 5]

The fluorine-containing polymer may further contain other structural units in addition to the structural unit (A). As other structural units, the following structural units (B)-(D) are mentioned.

The structural unit (B) is represented by the following formula (4). [chemical 6]

In formula (4), R ¹ to R ³ each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. R ⁴ represents a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Part of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

The fluorine-containing polymer may contain one kind or two or more kinds of structural units (B). In the fluoropolymer, the content of the structural unit (B) is preferably 5 to 10 mol% based on the total of all structural units. The content of the structural unit (B) may be 9 mol% or less, or may be 8 mol% or less.

The structural unit (B) is derived from, for example, a compound represented by the following formula (5). In formula (5), R ¹ to R ⁴ are the same as formula (4). The compound represented by formula (5) is a fluorine-containing vinyl ether such as perfluorovinyl ether. [chemical 7]

The structural unit (C) is represented by the following formula (6). [chemical 8]

In formula (6), R ⁵ to R ⁸ each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Part of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

The fluorine-containing polymer may contain one kind or two or more kinds of structural units (C). In the fluoropolymer, the content of the structural unit (C) is preferably 5 to 10 mol% based on the total of all structural units. The content of the structural unit (C) may be 9 mole % or less, or may be 8 mole % or less.

The structural unit (C) is derived from, for example, a compound represented by the following formula (7). In formula (7), R ⁵ to R ⁸ are the same as formula (6). The compound represented by formula (7) is a fluorine-containing olefin such as tetrafluoroethylene and chlorotrifluoroethylene. [chemical 9]

The structural unit (D) is represented by the following formula (8). [chemical 10]

In formula (8), Z represents an oxygen atom, a single bond, or -OC(R ¹⁹ R ²⁰ )O-, and R ⁹ to R ²⁰ each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 5 carbons, or Perfluoroalkoxy group having 1 to 5 carbon atoms. Part of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms. s and t are each independently 0 to 5, and s+t represents an integer of 1 to 6 (wherein, when Z is -OC(R ¹⁹ R ²⁰ )O-, s+t may be 0).

The structural unit (D) is preferably represented by the following formula (9). Furthermore, the structural unit represented by the following formula (9) is the case where Z is an oxygen atom, s is 0, and t is 2 in the above formula (8). [chemical 11]

In formula (9), R ¹⁴¹ , R ¹⁴² , R ¹⁵¹ , and R ¹⁵² each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 5 carbons, or a perfluoroalkoxy group having 1 to 5 carbons. Part of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Part of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms.

The fluorine-containing polymer may contain one kind or two or more kinds of structural units (D). In the fluoropolymer, the content of the structural unit (D) is preferably from 30 to 67 mol% based on the total of all structural units. The content of the structural unit (D) is, for example, 35 mol % or more, may be 60 mol % or less, or may be 55 mol % or less.

The structural unit (D) is derived from, for example, a compound represented by the following formula (10). In formula (10), Z, R ⁹ to R ¹⁸ , s and t are the same as in formula (4). The compound represented by formula (10) is a fluorine-containing compound that has two or more polymerizable double bonds and is capable of cyclopolymerization. [chemical 12]

The structural unit (D) is preferably derived from a compound represented by the following formula (11). In formula (11), R ¹⁴¹ , R ¹⁴² , R ¹⁵¹ , and R ¹⁵² are the same as formula (9). [chemical 13]

Specific examples of the compound represented by formula (10) or formula (11) include the following compounds. CF ₂ =CFOCF ₂ CF=CF ₂ CF ₂ =CFOCF(CF ₃ )CF=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CF=CF ₂ CF ₂ =CFOCF ₂ CF(CF ₃ )CF=CF ₂ CF ₂ =CFOCF (CF ₃ )CF ₂ CF=CF ₂ CF ₂ =CFOCFClCF ₂ CF=CF ₂ CF ₂ =CFOCCl ₂ CF ₂ CF=CF ₂ CF ₂ =CFOCF ₂ OCF=CF ₂ CF ₂ =CFOC(CF ₃ ) ₂ OCF= CF ₂ CF ₂ =CFOCF ₂ CF(OCF ₃ )CF=CF ₂ CF ₂ =CFCF ₂ CF=CF ₂ CF ₂ =CFCF ₂ CF ₂ CF=CF ₂ CF ₂ =CFCF ₂ OCF ₂ CF=CF ₂ CF ₂ = CFOCF ₂ CFClCF=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CCl=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CF=CFCl CF ₂ =CFOCF ₂ CF(CF ₃ )CCl=CF ₂ CF ₂ =CFOCF ₂ OCF=CF ₂ CF ₂ =CFOCCl ₂ OCF=CF ₂ CF ₂ =CClOCF ₂ OCCl=CF ₂

The first fluoropolymer may further include structural units other than structural units (A) to (D), but preferably does not substantially contain structural units other than structural units (A) to (D). Furthermore, the so-called fluorine-containing polymer does not substantially contain other structural units other than structural units (A) to (D), which means that relative to the total of all structural units in the fluorine-containing polymer, the structural units (A) to (D) The total of (D) is 95 mol% or more, preferably 98 mol% or more.

The polymerization method of the first fluorine-containing polymer is not particularly limited, and for example, general polymerization methods such as radical polymerization can be used. As for the polymerization initiator used to polymerize the fluoropolymer, perfluorinated compounds may be used.

The first fluoropolymer constitutes the first fluororesin that can be used as the resin constituting the core 11 . The glass transition temperature of the first fluorine-containing resin is not particularly limited, and is, for example, 100°C to 140°C, may be 105°C or higher, or may be 120°C or higher.

The refractive index of the core portion 11 is not particularly limited as long as it is higher than the refractive index of the clad portion 12 . In POF 10 , in order to realize a high numerical aperture, it is preferable that the difference between the refractive index of the core 11 and the refractive index of the clad 12 is larger for the wavelength of light used. For example, the refractive index of the core portion 11 may be set to 1.340 or higher, or may be set to 1.360 or higher for the wavelength of light used (for example, a wavelength of 850 nm). The upper limit of the refractive index of the core is not particularly limited, and is, for example, 1.4000 or less.

(coating part 12) The covering part 12 contains resin. The resin used for the covering portion 12 is not particularly limited as long as it has high transparency. As a resin used for the covering part 12, acrylic resins, such as fluororesin and methyl methacrylate, a styrene resin, and carbonate resin etc. are mentioned, for example. Among them, fluorine-containing resins are suitably used from the point of view that small transmission loss can be realized in a wider wavelength region.

The covering part 12 preferably contains a fluorine-containing resin. The covering part 12 may contain a fluorine-containing resin as a main component. Here, the term that the covering part 12 contains a fluorine-containing resin as a main component means that the most abundant component in terms of mass ratio in the covering part 12 is the fluorine-containing resin. The coating part 12 may contain 80 mass % or more of fluororesins, may contain 90 mass % or more, and may contain 95 mass % or more. The covering portion 12 may be composed only of fluorine-containing resin. The coating part 12 may further contain an additive in addition to the resin.

As described above, the resin constituting the covering portion 12 is preferably a fluorine-containing resin including a fluorine-containing polymer. Hereinafter, the fluorine-containing resin contained in the coating portion 12 is described as a second fluorine-containing resin, and the fluorine-containing polymer contained in the second fluorine-containing resin is described as a second fluorine-containing polymer.

Examples of the fluorine-containing resin that can be used as the second fluorine-containing resin are the same as those exemplified as the fluorine-containing resin that can be used as the first fluorine-containing resin. That is, examples of the fluoropolymer that can be used as the second fluoropolymer are the same as those exemplified as the fluoropolymer that can be used as the first fluoropolymer.

The second fluoropolymer constitutes a second fluororesin that can be used as the resin constituting the covering portion 12 . The glass transition temperature of the second fluorine-containing resin is not particularly limited, and is, for example, 100°C to 140°C, may be 105°C or higher, or may be 120°C or higher.

The resin constituting the cladding portion 12 may be different from the resin constituting the core portion 11 , and preferably has an affinity with the resin constituting the core portion 11 . For example, the resin constituting the cladding portion 12 may contain the same polymerized units as those contained in the resin constituting the core portion 11 , or may be the same as the resin constituting the core portion 11 . Thereby, separation is less likely to occur at the interface between the core portion 11 and the cladding portion 12, for example, transmission loss can be kept low.

The refractive index of the cladding portion 12 is not particularly limited as long as it is designed according to the refractive index of the core portion 11 . The cladding part 12 may have a refractive index of 1.310 or less at the wavelength of light used (for example, a wavelength of 850 nm), or may have a refractive index of 1.300 or less.

(coating layer 13) The coating layer 13 is provided to increase the mechanical strength of the POF 10 . For the coating layer 13 , for example, materials and structures used as coating layers in known POFs can be applied. As the material of the covering layer 13, for example, various engineering plastics such as polycarbonate, cycloolefin polymers, cycloolefin copolymers, polyesters, polyolefins, and copolymers of monomers forming these polymers, PTFE , modified PTFE, and PFA, etc.

The glass transition temperature of the material constituting the coating layer 13 is not particularly limited, and is, for example, 100°C to 140°C, may be 105°C or higher, or may be 120°C or higher.

Next, an example of a method of manufacturing POF 10 will be described.

POF10 is produced, for example, using a melt spinning method. That is, an example of the manufacturing method of POF10 includes: Melting and extruding the core material into a fibrous shape, thereby producing a fibrous molded body comprising the above-mentioned core material; Melting the cladding material and extruding to coat the surface of the molded body, thereby producing a first laminate in which the core material and the cladding material are concentrically laminated; The coating layer material is melted and extruded so as to cover the surface of the above-mentioned second molded body, thereby producing a second molded product in which the above-mentioned core material, the above-mentioned cladding material, and the above-mentioned cladding material are laminated concentrically. Laminated body; cooling and solidifying the above-mentioned second laminate to obtain a linear body comprising a core, a covering, and a covering layer; and The above-mentioned heat treatment of (A) is performed on the above-mentioned linear body.

FIG. 3 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture the POF 10 described above. Hereinafter, an example of the manufacturing method of POF10 using this manufacturing apparatus is demonstrated.

The apparatus 100 shown in FIG. 3 is equipped with the 1st extrusion apparatus 101a for core part formation, the 2nd extrusion apparatus 101b for clad part formation, and the 3rd extrusion apparatus 101c for coating layer formation. The device 100 further includes a first chamber 110 and a second chamber 120 . The first chamber 110 and the second chamber 120 are arranged vertically downward in this order.

The first extruding device 101a has a first storage part 102a for storing the core material 1a, and a first extrusion part 103a for extruding the core material 1a stored in the first storage part 102a from the first storage part 102a . The first extruder 101a may further be provided with a heating unit such as a heater (not shown), so that the core material 1a can be melted in the first housing portion 102a, and then the molten state can be maintained until the core material after melting 1a until formed. In this case, for example, the rod-shaped core material (preform) 1a is inserted into the first housing portion 102a through the upper opening of the first housing portion 102a, and heated in the first housing portion 102a, This makes it melt.

In the first extruding device 101a, the core material 1a is extruded from the first housing part 102a through the first extruding part 103a to form the core part 2 through the first extruding part 103a, for example, by gas extrusion. The core material 1 a extruded to form the core 2 through the first extrusion part 103 a then moves vertically downward and is supplied to the first chamber 110 and the second chamber 120 in sequence.

The second extruding device 101b has a second storage part 102b for storing the coating part material 1b, and a second extrusion part for extruding the coating part material 1b stored in the second storage part 102b from the second storage part 102b 103b. The second extrusion device 101b extrudes the molten coating material 1b so as to cover the outer periphery of the core 2 formed by the core material 1a extruded from the first extrusion device 102a. Specifically, the coating part material 1b extruded from the 2nd extruder 101b is supplied to the 1st chamber 110. As shown in FIG. In the first chamber 110, by covering the core 2 formed of the core material 1a with the cladding material 1b, the cladding 3 covering the outer periphery of the core 2 can be formed. The laminate formed of the core 2 and the cladding 3 covering the outer periphery of the core 2 moves from the first chamber 110 to the second chamber 120 .

The third extruder 101c includes, for example, a third housing portion 102c for housing the coating layer material 1c, a screw 104 arranged in the third housing portion 102c, and a hopper 105 connected to the third housing portion 102c. In the third extruder 101c, for example, the granular coating layer material 1c is supplied into the third housing portion 102c through the hopper 105 . The covering layer material 1c supplied into the third housing portion 102c is softened and made fluid by kneading with the screw 104 while being heated, for example. The softened coating layer material 1c is extruded from the third housing portion 102c by the screw 104 .

The coating layer material 1 c extruded from the third extrusion device 101 c is supplied into the second chamber 120 . In the second chamber 120, the surface of the layered body formed by the core 2 and the cladding 3 is covered with the cladding layer material 1c, and the cladding layer 4 covering the outer periphery of the cladding 3 can be formed.

The laminated body 5 formed by laminating the core 2 , the cladding 3 , and the covering layer 4 concentrically moves from the second chamber 120 to the diffuser 130 arranged vertically below the second chamber 120 . For example, a heater (not shown) for heating the laminate may be arranged in the diffusion pipe 130 . In the diffusion pipe 130, for example, the temperature and viscosity of the laminated body 5 passing inside can be adjusted appropriately. The diffusion tube 130 can diffuse dopants such as a refractive index adjuster contained in the laminated body 5 passing through the inside of the diffuser tube 130 in the laminated body 5 .

The diffuser 130 is connected to the inner flow path of the nozzle 140 . That is, the opening below the diffuser 130 is connected to the inlet of the nozzle 140 , and the laminate 5 after passing through the diffuser 130 flows into the internal flow path through the inlet of the nozzle 140 . The laminated body 5 is reduced in diameter by passing through the internal flow path, and is ejected in a fibrous form from the ejection port of the nozzle 140 .

The positional relationship between the second chamber 120 and the diffusion pipe 130 can be exchanged. which is. It can be configured as a device in which the diffusion pipe 130 is arranged below the first chamber 110, the second chamber 120 is arranged below it, and the nozzle 140 is further arranged below the second chamber.

The fibrous laminate 5 ejected from the outlet of the nozzle 140 flows into the inner space 151 of the cooling pipe 150 , is cooled while passing through the inner space 151 , and is released from the opening to the outside of the cooling pipe 150 . The laminated body 5 released from the cooling pipe 150 passes between the two rollers 161 and 162 of the nip roller 160, and then passes through the guide rollers 163 to 165 to form a linear structure including the core part, the cladding part, and the coating layer. The form of body 6 is taken up to take-up roll 166 . Further, a displacement meter 170 for measuring the outer diameter of the linear body 6 may be provided near the take-up roller 166 , for example, between the guide roller 165 and the take-up roller 166 .

The above-mentioned heat treatment of (A) is performed on the linear body 6 including the core portion, the cladding portion, and the coating layer. Regarding the heat treatment of the linear body 6, for example, the linear body 6 can be wound up to a heat treatment reel (not shown), and the linear body 6 in the state of being wound up to the reel can be heat treated; The linear body 6 pulled out by the take-up roller 166 is placed on, for example, a belt conveyor (not shown), and the heat treatment is continuously performed while the linear body 6 is passed through the heating furnace. The conditions such as the temperature of the heat treatment of the above-mentioned (A) at this time are as above. [Example]

Hereinafter, the present invention will be described in more detail with examples and comparative examples, but the present invention is not limited thereto.

(Example 1) [Production of fluorine-containing resin for core and cladding] Prepare a polymer of perfluoro-4-methyl-2-methylene-1,3-dioxolane (the compound of the above formula (M2), "PFMMD") as a core and cladding of fluorine-containing resins. Perfluoro-4-methyl-2-methylene-1,3-dioxolane is synthesized by first synthesizing 2-carboxymethyl-2-trifluoromethyl-4-methanol base-1,3-dioxolane, make it fluorinated, and decarboxylate the resulting carboxylate. Perfluorobenzoyl peroxide was used as a polymerization initiator in the polymerization of perfluoro-4-methyl-2-methylene-1,3-dioxolane.

Below, the synthesis of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane, 2-carboxymethyl-2-trifluoromethyl-4-methyl Fluorination of yl-1,3-dioxolane, synthesis of perfluoro-4-methyl-2-methylene-1,3-dioxolane, and perfluoro-4-methanol The details of the polymerization of yl-2-methylene-1,3-dioxolane will be described.

<Synthesis of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane> Prepare a 3 L three-necked flask equipped with a water-cooled condenser, a thermometer, a magnetic stirrer, and Using an isobaric dropping funnel, 139.4 g (1.4 moles in total) of a mixture of 2-chloro-1-propanol and 1-chloro-2-propanol was put into the flask. The flask was cooled to 0°C, and methyl trifluoropyruvate was slowly added thereto, followed by further stirring for 2 hours. 100 mL of dimethylsulfoxide (DMSO) and 194 g of potassium carbonate were added thereto over 1 hour, and stirring was continued for 8 hours to obtain a reaction mixture. The resulting reaction mixture was mixed with 1 L of water, the aqueous phase was separated and extracted with dichloromethane, the dichloromethane solution was mixed with the organic reaction mixture, the The solution is dried. After removal of solvent, 245.5 g of crude product were obtained. This crude product was subjected to fractional distillation under reduced pressure (12 Torr) to obtain 230.9 g of a purified product of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane. The boiling point of the refined product is 77-78°C, and the yield is 77%. Furthermore, it was confirmed by HNMR (H Nuclear Magnetic Resonance, H Nuclear Magnetic Resonance) and ¹⁹ FNMR ( ¹⁹ F Nuclear Magnetic Resonance, ¹⁹ F Nuclear Magnetic Resonance) that the obtained purified product was 2-carboxymethyl-2-trifluoromethyl -4-methyl-1,3-dioxolane.

HNMR(ppm): 4.2-4.6, 3.8-3.6 (CHCH ₂ , multiplet, 3H), 3.85-3.88 (COOCH ₃ , multiplet, 3H), 1.36-1.43 (CCH ₃ , multiplet, 3H) ¹⁹ FNMR( ppm): -81.3 (CF ₃ , s, 3F)

<Fluorination of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane> Inject 4 L of 1,1,2-trichlorotrifluoroethane into a 10 L stirred reaction tank. In the stirred reaction tank, nitrogen gas was flowed at a flow rate of 1340 cc/min, and fluorine gas was flowed at a flow rate of 580 cc/min, and placed under a nitrogen/fluorine atmosphere. After 5 minutes, dissolve 290 g of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane prepared in advance in 750 mL of 1,1,2-tris Chlorotrifluoroethane solution, the solution was added to the reaction tank at a rate of 0.5 ml/min. The reaction tank was cooled to 0°C. After all the dioxolane had been added over 24 hours, the fluorine flow was stopped. After nitrogen flushing, aqueous potassium hydroxide solution was added until weakly basic.

After removing volatile matter under reduced pressure, the surroundings of the reaction tank were cooled, and then dried under reduced pressure at 70° C. for 48 hours to obtain a solid reaction product. Dissolve the solid reaction product in 500 mL of water, add excess hydrochloric acid, and separate into an organic phase and an aqueous phase. The organic phase was separated and distilled under reduced pressure to obtain perfluoro-2,4-dimethyl-1,3-dioxolane-2-carboxylic acid. The boiling point of the main distillate is 103°C to 106°C/100 mmHg. The yield of fluorination was 85%.

<Synthesis of perfluoro-4-methyl-2-methylene-1,3-dioxolane> The distillate above was neutralized with an aqueous potassium hydroxide solution to obtain perfluoro-2,4- Dimethyl-2-carboxylate potassium-1,3-dioxolane. The potassium salt was vacuum dried at 70°C for 1 day. The salt is decomposed at 250°C-280°C under nitrogen or argon atmosphere. It was condensed in a freeze trap cooled to -78°C to obtain perfluoro-4-methyl-2-methylene-1,3-dioxolane in a yield of 82%. The boiling point of the product is 45°C/760 mmHg. The product was identified using ¹⁹ FNMR and GC-MS (Gas Chromatograph-Mass Spectrometer, gas chromatography-mass spectrometry).

¹⁹ FNMR: -84 ppm (3F, CF ₃ ), -129 ppm (2F, =CF ₂ ) GC-MS: m/e244 (molecular ions) 225, 197, 169, 150, 131, 100, 75, 50.

＜Polymerization of perfluoro-4-methyl-2-methylene-1,3-dioxolane＞ 100 g of perfluoro-4-methyl-2-methylene-1,3-dioxolane obtained by the above method and 1 g of perfluorobenzoyl peroxide were sealed in a glass tube. For the glass tube, the oxygen in the system was removed by freezing and degassing, then filled with argon, and heated at 50°C for several hours. Although the content became solid, if it was further heated at 70° C. overnight, a 100 g transparent rod-shaped product was obtained.

The resulting transparent rod was dissolved in Fluorinert FC-75 (manufactured by Sumitomo 3M Co., Ltd.), and the resulting solution was poured on a glass plate to obtain a polymer film. The obtained polymer had a glass transition temperature of 117°C and was completely amorphous. The transparent stick was dissolved in hexafluorobenzene, and chloroform was added thereto to cause precipitation, whereby the product was purified. The glass transition temperature of the refined polymer is about 131°C. This polymer is used as a fluorine-containing resin for the core and the cladding.

[Refractive index modifier] Chlorotrifluoroethylene oligomer (manufactured by Daikin Co., Ltd.) was used as a refractive index adjuster.

[core material] The fluorine-containing resin produced by the above-mentioned method and the above-mentioned refractive index adjuster were melt-mixed at 260° C. to produce a resin composition. The concentration of the refractive index adjuster in the resin composition was 12% by mass. This resin composition was used as a core material.

[cover material] The fluorine-containing resin produced by the above-mentioned method was used as the material of the covering part.

[cover material] Xylex 7200 (manufactured by SABIC, glass transition temperature: 113° C.) was used as the coating layer material.

[Production of POF] A POF having the same configuration as POF 10 shown in FIG. 1 was produced by the melt spinning method using the core material, cladding material, and cladding layer material prepared by the method described above. The manufacturing apparatus 100 shown in FIG. 3 is used when manufacturing the linear body including a core part, a cladding part, and a coating layer. The melting temperature of the core material is 250°C, the melting temperature of the covering material is 255°C, and the melting temperature of the covering layer material is 220°C. The heat treatment of the linear body including the core, the cladding, and the covering layer is to wind the linear body into a spool for heat treatment, and perform 1 at 90°C on the linear body in the state wound up on the spool hour, 12 hour, or 24 hour heat treatment.

In the obtained POF, the outer diameter of the core was 80 μm, the outer diameter of the cladding was 100 μm, and the outer diameter of the cladding layer (that is, the outer diameter of the POF) was 470 μm.

In the POF of this embodiment, the covering portion corresponds to the first layer, and the covering layer corresponds to the second layer.

[Determination of peel strength] The peel strength of the fluorine-containing resin of the covering part material, that is, the polymer of PFMMD produced by the above method, and the covering layer material, that is, Xylex7200, was measured by SAICAS.

First, a 50-μm-thick first sheet made of a polymer of PFMMD and a 50-μm-thick second sheet made of Xylex7200 were produced. The first sheet is made by heating the polymer of PFMMD at 220°C for 7 minutes, keeping it at 220°C and pressing it with a pressure of 10 MPa for 5 minutes, and then pressing it at 220°C with a pressure of 20 MPa 5 minutes. The second sheet is made by heating the pellets of Xylex7200 at 225°C for 5 minutes, keeping the temperature at 225°C and pressing with a pressure of 2 MPa for 2 minutes, and then pressing at 225°C with a pressure of 10 MPa for 2 minutes. minute. Then, the produced first sheet and the second sheet were superimposed on each other to obtain a laminate, and pressure was applied to the obtained laminate with a hand roller along the lamination direction of the laminate at 270°C to produce the first sheet and the second sheet. A bonded body of the second sheet. This joined body was used as a test piece.

In SAICAS (manufactured by Daipla, product name: DN-20), the cutting edge is pressed against the surface of the second sheet of the test piece with a specific rake angle, and the cutting edge is pushed along while applying a specific load to the cutting edge. Move horizontally to cut the second sheet. Then, after the cutting edge reached the interface between the second sheet and the first sheet, the diamond cutting edge (manufactured by Daipla, rake angle: 40°) was moved only in the horizontal direction to measure the horizontal cutting stress FH. The assay was performed in constant rate mode. The cutting speed was 10 μm/sec. From the measurement results, the peel strength P was determined according to the formula (1). The results are shown in Table 1.

[Evaluation of interface peeling] After the produced POF was placed in an atmosphere of 23°C and 50%RH for 30 days, the POF was observed with an ultrasonic microscope (observation field of view: 6 mm×6 mm) to evaluate whether there is separation between the coating part and the coating layer. The evaluation results are shown in Table 1. In Table 1, "〇" indicates that interfacial peeling was observed, and "×" indicates that interfacial peeling was not observed.

(comparative example 1) [Production of POF] A POF was fabricated in the same manner as in Example 1, except that the linear body including the core, the cladding, and the coating layer was not heat-treated. In the manufactured POF, the outer diameter of the core is 80 μm, the outer diameter of the cladding is 100 μm, and the outer diameter of the reinforcing layer (that is, the outer diameter of the POF) is 470 μm. In the POF of this comparative example, the coating part corresponds to the first layer, and the coating layer corresponds to the second layer.

[Determination of peel strength] The measured values in Example 1 were used as the peel strength of the fluorine-containing resin that is the material of the coating part, that is, the polymer of PFMMD produced by the above method, and Xylex7200 that is the material of the coating layer.

[Evaluation of interface peeling] The prepared POF was evaluated for interfacial peeling in the same manner as in Example 1. The evaluation results are shown in Table 1.

(comparative example 2) [Production of POF] DURABIO T-7450 (manufactured by Mitsubishi Chemical Co., Ltd., glass transition temperature: 129°C) was used as the coating material, the melting temperature of the coating material was set to 220°C, and the core, cladding, and coating were not included. The linear body is heat treated. A POF was produced in the same manner as in Example 1 except for the above. In the manufactured POF, the outer diameter of the core is 80 μm, the outer diameter of the cladding is 100 μm, and the outer diameter of the reinforcing layer (that is, the outer diameter of the POF) is 470 μm. In the POF of this comparative example, the coating part corresponds to the first layer, and the coating layer corresponds to the second layer.

[Determination of peel strength] The peel strength of the fluorine-containing resin of the cladding material, that is, the PFMMD polymer produced by the above method, and the cladding layer material, that is, DURABIO T-7450, was measured by SAICAS. First, a 50-μm-thick first sheet made of a polymer of PFMMD and a 50-μm-thick second sheet made of DURABIO T-7450 were prepared. The first sheet is made by heating the polymer of PFMMD at 220°C for 7 minutes, keeping it at 220°C and pressing it with a pressure of 10 MPa for 5 minutes, and then pressing it at 220°C with a pressure of 20 MPa 5 minutes. The second sheet is made by heating the granules of DURABIO T-7450 at 210°C for 3 minutes, keeping it at 210°C and pressing it with a pressure of 2 MPa for 2 minutes, and then at 210°C with a pressure of 10 MPa. Press down for 2 minutes. Then, the produced first sheet and the second sheet were superimposed on each other to obtain a laminate, and pressure was applied to the obtained laminate with a hand roller along the lamination direction of the laminate at 270°C to produce the first sheet and the second sheet. A bonded body of the second sheet. This bonded body was used as a test piece, and the peel strength was measured by SAICAS. The measurement sequence and measurement conditions of SAICAS are the same as those in Example 1. The results are shown in Table 1.

[Evaluation of interface peeling] The prepared POF was evaluated for interfacial peeling in the same manner as in Example 1. The evaluation results are shown in Table 1.

(comparative example 3) [Production of POF] DURABIO T-7450 (manufactured by Mitsubishi Chemical Co., Ltd., glass transition temperature: 129° C.) was used as the coating layer material, and the melting temperature of the coating layer material was set to 220° C. A POF was produced in the same manner as in Example 1 except for the above. In the manufactured POF, the outer diameter of the core is 80 μm, the outer diameter of the cladding is 100 μm, and the outer diameter of the reinforcing layer (that is, the outer diameter of the POF) is 470 μm. In the POF of this comparative example, the coating part corresponds to the first layer, and the coating layer corresponds to the second layer.

[Determination of peel strength] The measured value of Comparative Example 2 was used as the peel strength of the fluorine-containing resin that is the material of the coating part, that is, the polymer of PFMMD produced by the above method, and the material of the coating layer, that is, DURABIO T-7450.

[Evaluation of interface peeling] The prepared POF was evaluated for interfacial peeling in the same manner as in Example 1. The evaluation results are shown in Table 1.

(comparative example 4) [Production of POF] POF was produced in the same manner as in Example 1 except for the following. ･Polymethyl methacrylate (PMMA (glass transition temperature: about 102°C)) is used instead of PFMMD as the resin for the core and cladding. ･Set the melting temperature of the core material to 240°C. ･Set the melting temperature of the coating material to 240°C. ･The linear body including the core, cladding, and coating layer is not heat-treated.

In the manufactured POF, the outer diameter of the core is 80 μm, the outer diameter of the cladding is 100 μm, and the outer diameter of the reinforcing layer (that is, the outer diameter of the POF) is 470 μm.

In the POF of this comparative example, the coating part corresponds to the first layer, and the coating layer corresponds to the second layer.

[Determination of peel strength] The peel strength of PMMA, which is the cover material, and Xylex7200, which is the cover layer material, was measured by SAICAS. First, a 50-μm-thick first sheet made of PMMA and a 50-μm-thick second sheet made of Xylex7200 were prepared. The first sheet was produced by heating the PMMA at 220°C for 5 minutes, keeping it at 220°C and pressing it with a pressure of 2 MPa for 2 minutes, and then pressing it at 220°C for 2 minutes at a pressure of 10 MPa. The second sheet is made by heating the pellets of Xylex7200 at 225°C for 5 minutes, keeping the temperature at 225°C and pressing with a pressure of 2 MPa for 2 minutes, and then pressing at 225°C with a pressure of 10 MPa for 2 minutes. minute. Then, the produced first sheet and the second sheet were superimposed on each other to obtain a laminate, and pressure was applied to the obtained laminate with a hand roller along the lamination direction of the laminate at 270°C to produce the first sheet and the second sheet. A bonded body of the second sheet. This bonded body was used as a test piece, and the peel strength was measured by SAICAS. The measurement sequence and measurement conditions of SAICAS are the same as those in Example 1. The results are shown in Table 1.

[Evaluation of interface peeling] The prepared POF was evaluated for interfacial peeling in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Table 1] Coating material/coating material Peel strength [kN/m] heat treatment interface peeling no heat treatment heat treatment 1 h Heat treatment for 12 h Heat treatment for 24 hours Example 1 PFMMD polymer/Xylex 2.29 have - 〇 〇 〇 Comparative example 1 PFMMD polymer/Xylex 2.29 none x - - - Comparative example 2 PFMMD polymer/DURABIO 0.93 have - x x x Comparative example 3 PFMMD polymer/DURABIO 0.93 none x - - - Comparative example 4 PMMA/Xylex >20 none 〇 - - -

In the POFs of Example 1 and Comparative Example 1, the coating material (corresponding to the first resin material) and the covering layer material (corresponding to the second resin material) have a peel strength of 1 kN/m or more. In the POF having the cladding part and coating layer formed by the combination of such materials, interfacial peeling occurred in Comparative Example 1, which was not subjected to heat treatment at 90°C, but was subjected to 1 h, 12 h, and 24 h at 90°C. In Example 1 of the heat treatment of h, the occurrence of interfacial peeling was suppressed.

In the POFs of Comparative Examples 2 and 3, the peeling strengths of the cover material (corresponding to the first resin material) and the covering layer material (corresponding to the second resin material) were less than 1 kN/m. In the POF having the clad part and the clad layer formed by the combination of such materials, interfacial peeling occurred in Comparative Example 3, which was not heat-treated at 90°C, even after 1 h, 12 h, and In Comparative Example 2 of heat treatment for 24 h, the occurrence of interfacial peeling was also confirmed. That is, when the peeling strength is less than 1 kN/m, the interfacial peeling cannot be suppressed by heat treatment at 90°C.

In the POF of Comparative Example 4, the covering material (corresponding to the first resin material) and the covering layer material (corresponding to the second resin material) had a large peel strength exceeding 20 kN/m. In this case, since the adhesive force between the coating part and the coating layer is high, even when the heat treatment at 90° C. is not performed, interfacial peeling does not occur. However, the POF of Comparative Example 4 did not use a fluorine-containing resin as the resin constituting the core portion and the cladding portion. Therefore, it is considered that the transmission loss on the long wavelength side of the POF of Comparative Example 4 is larger than that of the POFs of Example 1 and Comparative Examples 1 to 3 using a fluorine-containing resin. [Industrial availability]

The POF manufacturing method of the present invention is suitable for manufacturing POF for high-speed communication.

1a: Core material 1b: Coating material 1c: Coating material 2: Core 3: Coating 4: Coating layer 5: laminated body 6: linear body 10:POF 11: Core 12: cladding department 13: Coating layer 20:POF 22: cladding department 100: Manufacturing device 101a: the first extrusion device 101b: The second extrusion device 101c: the third extrusion device 102a: Containment Unit 1 102b: Containment Unit 2 102c: Containment Section 3 103a: The first extrusion part 103b: The second extrusion part 104: screw 105: Hopper 110: Room 1 120: Room 2 130: Diffusion tube 140: Nozzle 150: Cooling pipe 151: Internal space 160: nip roller 161,162: roll 163, 164, 165: guide roller 166: take-up roller 170: Displacement gauge 221: 1st cladding layer 222: Second coating layer

FIG. 1 is a schematic view showing an example of a cross-sectional structure of a plastic optical fiber manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a schematic view showing another example of the cross-sectional structure of a plastic optical fiber manufactured by the manufacturing method according to the embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture plastic optical fibers.

10:POF

11: Core

12: cladding department

13: Coating layer

Claims (11)

A method of manufacturing a plastic optical fiber, the plastic optical fiber comprising a first layer formed of a first resin material containing a fluorine-containing resin, and a second layer formed of a second resin material and in contact with the first layer, and The above-mentioned manufacturing method includes (A) at a temperature of not more than the first glass transition temperature Tg1 of the above-mentioned _first resin material and not more than the glass transition temperature Tg2 of the above-mentioned _second resin material. The above-mentioned second-layer linear body arranged in one layer in contact with each other is heat-treated, and the above-mentioned first resin material and the above-mentioned second resin material have a peel strength of 1 kN/m or more, wherein the above-mentioned peel strength is measured as follows The peel strength of the second sheet with respect to the first sheet, that is, the first sheet with a thickness of 50 μm containing the above-mentioned first resin material and the second sheet with a thickness of 50 μm containing the above-mentioned second resin material Overlap each other to obtain a laminated body, apply pressure to the laminated body with a hand roller along the lamination direction of the laminated body at 270°C to make a bonded body of the first sheet and the second sheet, using Surface And Interface Cutting Analysis System (SAICAS) measured the bonded body to obtain the peel strength of the second sheet with respect to the first sheet. Such as the manufacturing method of claim 1, wherein The above-mentioned plastic optical fiber has a core, the cladding part disposed on the outer periphery of the above-mentioned core part, and the covering layer disposed on the outer periphery of the covering portion, and The core portion or the cladding portion is the first layer. Such as the manufacturing method of claim 2, wherein The above-mentioned coating part is the above-mentioned first layer. Such as the manufacturing method of claim 3, wherein The above-mentioned core part contains a fluorine-containing resin. Such as the manufacturing method of claim 3 or 4, wherein The above-mentioned covering layer is the above-mentioned second layer, The above-mentioned second resin material does not contain a fluorine-containing resin. The manufacturing method according to any one of claims 1 to 5, wherein The above-mentioned linear system is obtained by heating and melting the above-mentioned first resin material and the above-mentioned second resin material to form a fibrous shape, and cooling and solidifying the obtained molded body. The manufacturing method according to any one of claims 1 to 6, wherein The aforementioned linear body is extended. The production method according to any one of claims 1 to 7, wherein in the above (A), the temperature T of the heat treatment of the linear body satisfies: Tg ₁ -65°C≦T≦Tg ₁ , and Tg ₂ -65 °C≦T≦Tg ₂ . The manufacturing method according to any one of claims 1 to 8, wherein In said (A), the time of the said heat treatment of the said linear body is 10 minutes or more and 75 hours or less. The production method according to any one of claims 1 to 9, wherein the above-mentioned fluorine-containing resin contained in the above-mentioned first resin material contains a polymer having a structural unit represented by the following formula (1), [Chem. 1]

(In formula (1), R _ff ¹ to R _ff ⁴ independently represent a fluorine atom, a perfluoroalkyl group with 1 to 7 carbons, or a perfluoroalkyl ether group with 1 to 7 carbons, R _ff ¹ and R _ff ² can be joined to form a ring). Such as the production method of claim 10, wherein the above-mentioned structural unit is represented by the following formula (2), [Chem. 2]

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