JP2021086057A - Illumination plastic optical fiber and manufacturing method thereof, illumination plastic optical fiber bundle, optical fiber illumination device, optical fiber sensor, optical fiber sheet, optical fiber woven fabric, optical fiber knitted fabric, plastic optical fiber cord, and medical equipment - Google Patents

Abstract

To provide an illumination plastic optical fiber that has enough resistance to bending and emits light uniformly in a lengthwise direction.SOLUTION: A plastic optical fiber is provided that has a core and a cladding, and emits light from a fiber side face. In the illumination plastic optical fiber, an average value of a line roughness Ra(S) of a cladding surface at a position of 5 cm from one end of the plastic optical fiber in a lengthwise direction and a line roughness Ra(E) of the cladding surface at a position of 5 cm from the other end in the direction is 1 to 10 μm.SELECTED DRAWING: None

Description

The present invention relates to an illuminated plastic optical fiber, a method for manufacturing the same, and an application thereof.

A plastic optical fiber generally used for optical transmission has a core (inner layer) and a clad (outer layer) made of a transparent resin formed in a concentric circular shape. In a plastic optical fiber having such a configuration, light incident from one end is efficiently transmitted to the other end while repeating total internal reflection at the interface between the core and the clad, so that it is used for medical endoscopes and industrial use. It is effectively used as an optical transmission material for lighting such as for automobiles.

All of these are means for transmitting the light received from one end to the other end without leaking the light in the middle, but the light is leaked from the middle (side surface) in the longitudinal direction to function as a linear illuminant. If possible, it can be used for indoor and outdoor lighting applications, alternative applications for neon signs and electric displays, other decorative applications, and even sensor applications.

As such a plastic optical fiber for side light emission, a method of sandblasting to damage the clad and leak light has been proposed (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 11-84135 Special Table 2001-502438 Gazette

However, when the sandblasting treatment is performed, the core of the plastic optical fiber may be damaged in some cases, and there is a problem that the optical fiber is easily broken when bent. Further, in Patent Document 2, it is proposed to adjust the brightness uniformity by adjusting the density of scratches in the longitudinal direction, but depending on the sandblasting conditions, a singular point where the brilliance becomes stronger (this is called a "bright spot"). ) Occurred. Even if such illuminated plastic optical fibers are bundled and coated with a coating cord of transparent, translucent, white or other colors, the brightness at the bright spot is inevitably increased. There was a problem of poor uniformity.

Therefore, an object of the present invention is to provide an illuminated plastic optical fiber that is resistant to bending and emits light uniformly in the longitudinal direction.

That is, the present invention is a plastic optical fiber having a core and a clad and illuminating from the side surface of the fiber, and the line roughness Ra of the clad surface at a position 5 cm from one end in the longitudinal direction of the plastic optical fiber ( It is an illuminated plastic optical fiber in which the average value of S) and the line roughness Ra (E) of the clad surface at a position 5 cm from the other end is 1 to 10 μm.

According to the present invention, it is possible to provide an illuminated plastic optical fiber that is resistant to bending and emits light uniformly in the longitudinal direction.

Hereinafter, preferred embodiments of the illuminated plastic optical fiber and the like according to the present invention will be specifically described, but the present invention is not limited to the following embodiments and may be variously modified according to an object and an application. Can be carried out.

The plastic optical fiber in the present invention has a two-layer structure formed of a transparent resin of a core (inner layer) and a clad (outer layer), and has a round cross section.

(core)
In the illuminated plastic optical fiber according to the embodiment of the present invention, the transparent resin used for the core includes polymethylmethacrylate (PMMA), a copolymer containing methylmethacrylate as a main component, polystyrene, polycarbonate, and polyorganosiloxane (silicone). , Norbornen and the like. Among them, polymethylmethacrylate is a preferable resin as an optical fiber in terms of transparency, refractive index, bending characteristics and heat resistance.

(Clad)
In the illuminated plastic optical fiber according to the embodiment of the present invention, the transparent resin used for the cladding is preferably a polymer obtained by polymerizing a polymerization component containing 70% by weight or more of vinylidene fluoride.

Examples of the polymerization component containing 70% by weight or more of vinylidene fluoride include vinylidene fluoride alone, vinylidene fluoride / tetrafluoroethylene, vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene, vinylidene fluoride / hexafluoroacetone, and the like. Examples thereof include polymerization components in which a copolymer containing the above is synthesized.

When a polymer obtained by polymerizing a polymerization component containing 70% by weight or more of vinylidene fluoride is used as a clad, the core is not easily scratched even when sandblasted, and the plastic optical fiber is not easily broken when bent. Become.

The elastic modulus of the clad is preferably 500 to 1200 MPa. If it is 500 MPa or more, even if sandblasted, the clad is hard, so that the core is protected and it becomes difficult to break. When it is 1200 MPa or less, the clad becomes flexible and easy to bend. More preferably, it is 600 to 1000 MPa.

Here, the elastic modulus indicates a flexural modulus and is a value measured by ASTM D790. As a typical test piece of ASTM D790, one having a size of 127 mm × 13 mm × 3.1 mm is used. The unit of measurement of ASTM D790 is MPa, and the flexural modulus is obtained from the slope at the point where the slope is the largest at the initial stage of stress application in the stress-bending displacement curve, that is, the tangent line at that place.

Regarding the refractive index of the core and the clad, the numerical aperture (NA) represented by the formula (1) is preferably 0.45 or more and 0.65 or less.

The theoretical numerical aperture is expressed by the difference in refractive index between the core and the clad as shown in the following equation.
Numerical aperture = ((refractive index of core) ^2- (refractive index of first clad) ² ) ^1/2 equation (1).

The numerical aperture of the plastic optical fiber with PMMA as the core, which has been put into practical use so far, is 0.45 to 0.65. Compatibility with peripheral parts such as elements can be maintained.

The thickness of the clad layer of the fiber is preferably 3.0 μm to 15.0 μm, and more preferably 4.0 μm to 13.0 μm.

Further, the melt flow rate (hereinafter, may be abbreviated as MFR) value of the clad used in the illuminated plastic optical fiber according to the embodiment of the present invention is generally 5 to 100 g / 10 minutes (condition: temperature 230 ° C.). , The load is 3.8 kg, the orifice diameter is 2 mm, and the length is 8 mm).

The clad used for the illuminated plastic optical fiber according to the embodiment of the present invention has a line roughness Ra (S) on the clad surface at a position 5 cm from one end in the longitudinal direction and a position 5 cm from the other end. The average value with the line roughness Ra (E) of the clad surface (hereinafter, this is referred to as “the average value of Ra”) is 1 to 10 μm. When the average value of Ra is 1 to 10 μm, side emission can be efficiently obtained while maintaining the bending characteristics of the fiber. If the average value of Ra is less than 1 μm, the side emission is not sufficient, and if it exceeds 10 μm, the fiber is easily broken. The average value of Ra is preferably 2 to 8 μm.

The line roughness Ra of the clad surface at a position 5 cm from the end means a value measured by the following measuring method. The fiber is observed under a microscope at each of the 5 cm positions and captured in an image, and Ra is measured in a range of 5 mm on each side with the 5 cm position as the center. The number of measurements is taken by rotating 1/3 each around the longitudinal direction of the fiber, measuring once in each region and a total of three times at one end, and taking the average value thereof. The “average value of Ra” is the average value of Ra (S) and Ra (E) measured in this way. The above measurement can be performed, for example, by using the line roughness software mounted on the KEYENCE microscope VHX-6000. In addition, the conditions and the like not specified here regarding the Ra measurement method are based on "JIS B0601: 2013".

The clad used in the illuminated plastic optical fiber according to the embodiment of the present invention preferably has a value obtained by dividing the average value of Ra by the thickness of the clad of 0.1 to 1.

When the value obtained by dividing the average value of Ra by the clad thickness is 0.1 or more, the brightness of the side emission of the plastic optical fiber can be improved. Further, when it is 1 or less, the bending resistance can be improved.

The clad thickness is obtained from the clad thickness obtained from SEM observation and three points within a range of 5 cm from the other end at any three points within a range of 5 cm from one end in the longitudinal direction. The average value of 6 points of the total clad thickness obtained is shown. As the measurement conditions for SEM observation, the image is adjusted so that the edge of the portion to be read becomes clear at an acceleration voltage of 10 kV and a magnification of 5000 times, and the thickness of the clad is measured using the length measurement function of the SEM.

As for the clad used for the illuminated plastic optical fiber according to the embodiment of the present invention, the line roughness Ra (A) of the clad at a position 5 cm from the end on the illuminated plastic optical fiber side coupled to the light source is the other end. It is preferable to connect the light source so that the value is smaller than the line roughness Ra (B) of the clad at a position 5 cm from the portion. By doing so, the brightness uniformity can be improved.

In the illuminated plastic optical fiber of the present invention, when the illuminated plastic optical fiber is evenly divided into five in the longitudinal direction, the line roughness Ra of the clad surface for each division increases from one end to the other. It is preferable that the size increases in order. By setting Ra in this way, the brightness uniformity in the longitudinal direction can be improved. Here, Ra for each division is a value obtained by measuring Ra at the center in the longitudinal direction in each divided region by a method according to the measurement method of Ra (S) and Ra (E) described above.

The brighter the illuminated plastic optical fiber, the better, but the more the brightness attenuation factor is suppressed, the better the decorativeness. That is, it is preferable that the luminance attenuation factor is small even if the luminance is small, rather than the luminance being large and the luminance attenuation factor being large. The brightness attenuation factor is a value obtained by dividing the difference between the brightness at a position 5 cm from the light source and the brightness at a position 5 cm before the end on the opposite side of the light source by the difference in length.

It is preferable that the brightness attenuation rate of the illuminated plastic optical fiber according to the embodiment of the present invention is 30 cd / m or less. It is more preferably 20 cd / m or less, and even more preferably 10 cd / m or less. By doing so, the brightness uniformity is further enhanced and the decorativeness is improved.

(Manufacturing method of illuminated plastic optical fiber)
Next, an example of a method for manufacturing an illuminated plastic optical fiber according to an embodiment of the present invention will be described.

The plastic optical fiber that is the basis of the illuminated plastic optical fiber of the present invention can be easily manufactured by a composite spinning method using a core-sheath composite spinneret. Further, in the optical fiber produced by this composite spinning method, the cross-sectional shape of the core and the clad can be exactly the same in any cross section in the longitudinal direction.

Subsequently, for the purpose of improving the mechanical properties, a general 1.2 to 3 times stretching treatment is performed to obtain a plastic optical fiber. The outer diameter of the plastic optical fiber of the present invention is usually 0.1 mm to 3 mm and may be appropriately selected depending on the intended purpose, but from the viewpoint of handleability and the like, 0.25 mm to 1.5 mm is preferable. ..

The clad of the obtained plastic optical fiber is sandblasted to scratch the surface of the clad. The sandblasting process has a method of fixing a nozzle for ejecting media or changing the nozzle. When the nozzle is fixed, a uniform illuminated plastic optical fiber in the longitudinal direction can be produced by varying the speed of the fiber transmission and adjusting the density of scratching the clad along the longitudinal direction. .. For example, there is a method of gradually slowing down the speed of the fiber to change the speed of the fiber transmission line so that the density of scratches increases in the distance from the end face where the light is incident. By doing so, it is possible to manufacture an illuminated plastic optical fiber having excellent brightness uniformity in the longitudinal direction. On the other hand, when the fiber is fixed, the speed of the nozzle may be variable so that the density of scratches increases in the direction far from the end face where the light is incident. Further, the nozzle may be movable in the longitudinal direction with respect to the fiber, or may be movable in the vertical direction.

In addition, as a method of sandblasting, sandblasting is performed while translating the illuminated plastic optical fiber at a variable speed, or sandblasting is performed by changing the distance from the illuminated plastic optical fiber toward the illuminated plastic optical fiber traveling at a constant speed. The method is preferred. When sandblasting while translating the illuminated plastic optical fiber at a variable speed, the speed on the light source side is high, and by slowing down the speed as it goes in the longitudinal direction, Ra on the light source side is small and Ra in the longitudinal direction is large. It is possible to improve the brightness uniformity. In addition, when sandblasting by changing the distance from the optical fiber toward the illuminated plastic optical fiber that travels at a constant speed, the light source side is farther from the optical fiber, and as it goes in the longitudinal direction, the optical fiber and the optical fiber By shortening the distance between the two, Ra on the light source side is small, Ra in the longitudinal direction can be increased, and brightness uniformity can be improved.

The material of the projection material used for sandblasting may be an inorganic material such as glass, alumina or silica. More preferably, it is alumina. By using alumina, the sandblasting treatment time can be shortened.

The size of the projection material is preferably 10 to 700 μm. When it is 10 μm or more, the takt time can be shortened. Further, when it is within 700 μm, it is possible to appropriately scratch the clad. More preferably, it is 100 to 600 μm.

The illuminated plastic optical fiber of the present invention is a side-illuminated fiber suitable as various sensors for decorative applications such as illumination and clothing, industrial use, household lighting application, industrial / medical / environmental use, etc., and is incident on the end face of the fiber. The light is leaked from the side of the fiber, and the indoor and outdoor areas are colored with light, the shape and existence of objects are shown, the destination and direction are shown, various other decorations, various lighting, etc., temperature and pressure. It is used as a sensor to detect such things.

(Illuminated plastic fiber optic bundle)
The illuminated plastic optical fiber according to the embodiment of the present invention is usually used as a sheet or a bundle of a plurality of optical fibers. Here, the "bundle shape" refers to a state in which a plurality of plastic optical fibers are simply assembled, a state in which they are twisted in a rope shape or a string shape, a state in which they are aligned in a sheet shape, and a state in which the above-mentioned fiber aggregate is further assembled. Further, the state of collecting and bundling and the state of twisting these are included. The number of optical fiber bundle bundles is arbitrary and can be appropriately selected and changed according to the purpose. For example, 5 to 1000 plastic optical fibers are used for one bundle.

Further, such an optical fiber bundle is preferably used as an aggregate in which a plurality of optical fibers are bundled, and the plastic optical fiber is divided into a plurality of groups of bundles, and these bundles are twisted 1 to 20 times / number of times. It is more preferable that the mixture is twisted at a ratio of m. The plastic optical fiber bundle having such a structure can further improve the illumination efficiency of the plastic optical fiber by microbending, and can be made into a high-brightness illumination device.

In the optical fiber bundle according to the embodiment of the present invention, the optical fiber bundle may be inserted into a transparent tube or coated with a transparent resin for the purpose of protection. The material of the transparent tube is, for example, a transparent, colorless or colored material made of soft or flexible plastic, and specifically, vinyl chloride resin, acrylic resin, polycarbonate resin, polyester resin, poly. There are vinyl acetate resin, ethylene-vinyl acetate copolymer resin and the like. Secondary materials such as plasticizers and auxiliaries may be added to these main components as appropriate.

(Optical fiber illumination device)
Further, the illuminated plastic optical fiber according to the embodiment of the present invention is used in an optical fiber illumination device by optically connecting a light source to the end face of at least one end thereof. As the preferred light source in the present invention, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, an LED, or the like having particularly high brightness is used. It should be noted that the mounting of the reflector and the lens, the shape of the lamp, the power consumption, and the like can be appropriately changed according to the purpose of use.

When the plastic optical fiber is divided into five in the longitudinal direction, the line roughness Ra of the clad surface for each division increases in order from one end to the other, and the light source is the clad. It is preferable that the surface is optically connected to one end on the side where the line roughness Ra is small.

(Optical fiber sensor)
The plastic optical fiber according to the embodiment of the present invention can be used as a sensor having at least a part thereof. Specific examples of the center include sensors that can be used to measure temperature and pressure, and to measure the environment of ammonia, humidity, oxygen, alkanes, gasoline vapor, and the like. Examples of the sensor configuration include an optical fiber sensor in which light entering from the side surface of the optical fiber is reflected inside the fiber in the dark and the light is sensed by a photoelectric sensor attached to the end surface.

(Optical fiber sheet, optical fiber woven fabric, optical fiber knit)
Further, the plastic optical fiber according to the embodiment of the present invention may be used as a sheet, a woven fabric, and a knitted fabric having at least a part thereof, and can be used as a pressure sensor or a decorative application.

The optical fiber sheet is formed by arranging optical fibers in a plane and adhering or fusing them together.

Further, when used as an optical fiber woven fabric, generally, an optical fiber is used as a warp, and a woven fabric woven so as to hold the optical fiber by threads and wefts arranged between the optical fibers is known. .. In addition to these woven fabrics, an optical fiber knitted fabric in which an optical fiber is used as a monofilament and knitted so as to hold the optical fiber by warp knitting may be used.

The above-mentioned optical fiber may be used as the optical fiber, and a thread having a finer fineness and flexibility than that of the optical fiber may be used as the thread for holding the optical fiber. As the yarn, it is preferable to use synthetic fibers whose fineness and mechanical properties can be easily adjusted, but natural fibers other than synthetic fibers, regenerated fibers or semi-synthetic fibers may be used. Examples of synthetic fibers include olefin-based synthetic fibers, aliphatic polyamide-based synthetic fibers typified by nylon, polyester-based synthetic fibers typified by polyethylene terephthalate (PET), and the like.

Further, it may be a plastic optical fiber cord which is a cord in which one or a plurality of illuminated plastic optical fibers are bundled and coated with a resin. By doing so, the amount of incident light can be increased, and by using the translucent coating resin, the brightness of the side emission can be increased.

It may also be used in medical devices that have at least a portion of an illuminated plastic optical fiber. For example, it can be expected to have a sterilizing effect by ensuring the brightness of the surgical site and using blue by emitting light in a wide range by side emission.

Hereinafter, the present invention will be described in more detail with reference to Examples. The evaluation was performed by the following method.

-Fiber side brightness (luminance attenuation rate): A halogen lamp (12V100W) is used as the light source, and a brightness meter <Minolta T-1M> is used at a position 5 cm from the light source on the surface of a 1 m long plastic optical fiber. The brightness (luminance B) and the brightness (luminance C) at a position 5 cm before the end opposite to the light source (that is, a position 95 cm from the light source) are measured, and the difference between the brightness is the length. The brightness attenuation rate per unit length was calculated by dividing by the difference (90 cm).

-Number of breaks and bends: A load of 500 g is applied to one end of a plastic optical fiber, supported by a mandrel having a diameter of 20 mmφ, and the other end of the fiber is continuously bent at an angle of 90 ° around the support point to cut the fiber. The number of times until it was done was measured. (Average value of n = 5)
-Refractive index: The measurement was carried out in an atmosphere at room temperature of 25 ° C. using an Abbe refractive index meter (DR-M2 manufactured by Atago Co., Ltd.) as a measuring device.

-Bending elastic modulus: The measurement method of ASTM D790 was used. The size of the test piece was 127 mm × 13 mm × 3.1 mm. The unit of measurement of ASTM D790 was MPa, and the flexural modulus was determined from the slope at the point where the slope was the largest at the initial stage of stress application in the stress-bending displacement curve, that is, the tangent line at that place.

-Core diameter / clad thickness: Measured at room temperature of 25 ° C. with a small measuring microscope (STM6 manufactured by Olympus Corporation) as a measuring device.

-The line roughness Ra (μm) was measured by the line roughness software mounted on the KEYENCE VHX-6000 microscope. Ra (S) and Ra (E) were measured at a position 5 cm from one end of the plastic optical fiber and 5 cm from the other end, respectively, by the methods described herein. In addition, Ra1 to Ra5 divide a plastic optical fiber having a length of 1 m into five regions evenly in the longitudinal direction, and position the center of the divided regions (10 cm, 30 cm, 50 cm, 70 cm and 90 cm in order from the front). Each of the positions) was measured by the method described in the present specification.

-Bright spot: Light was incident on a plastic optical fiber having a length of 1 m and visually observed in a dark room. If there was a bright spot, it was considered that there was a bright spot.

In the examples and comparative examples, the substances constituting the core and the clad are described as follows.
-PMMA: Polymethylmethacrylate-VDF: Vinylidene fluoride-TFE: Tetrafluoroethylene-HFP: Hexafluoropropylene.

[Example 1]
As a clad material, VdF / TFE = 75/25 (refractive index: 1.404) having the composition shown in Table 1 was supplied to the composite spinning machine. Further, PMMA (refractive index 1.492) produced by continuous soul polymerization is supplied to the composite spinning machine as a core material, and the core and clad are composite melt-spun with a core and a sheath at a temperature of 220 ° C., and the fiber diameter is 1000 μm (core). A plastic optical fiber having a diameter of 980 μm and a clad thickness of 10.0 μm) was obtained. The obtained plastic optical fiber was sandblasted. The conditions for sandblasting are that the length of the plastic optical fiber is 1 m, the alumina particle diameter is 320 μm, the wind pressure is 0.25 MPa, the time is 2 seconds, the distance between the fiber and the nozzle is 15 cm at first, and the nozzle is 5 cm after 2 seconds. It was moved at a constant speed in the direction perpendicular to the longitudinal direction.

The plastic optical fiber having a length of 1 m thus obtained was evaluated by the above-mentioned evaluation method, and the results are shown in Tables 1 and 2. The number of breaks and bends and the uniformity of brightness were good.

[Examples 2 to 8 and Comparative Examples 1 to 3]
A plastic optical fiber was obtained in the same manner as in Example 1 except that the particle size of the clad material and the alumina used for the sandblasting treatment was changed as shown in Table 1. The same evaluation as in Example 1 was performed using these plastic optical fibers, and the results are shown in Tables 1 and 2. In Comparative Example 3, the sandblasting process was not performed.

Claims (15)

A plastic optical fiber having a core and a clad and illuminating from the side surface of the fiber, the line roughness Ra (S) of the clad surface at a position 5 cm from one end in the longitudinal direction of the plastic optical fiber, and the other. An illuminated plastic optical fiber having an average value of 1 to 10 μm with the line roughness Ra (E) of the clad surface at a position 5 cm from the end. The illuminated plastic optical fiber according to claim 1, wherein the clad has an elastic modulus of 500 to 1200 MPa. Claim 1 or 2 in which when the plastic optical fiber is evenly divided into five in the longitudinal direction, the line roughness Ra of the clad surface for each division increases in order from one end to the other. Illuminated plastic optical fiber according to. The illuminated plastic optical fiber according to any one of claims 1 to 3, wherein the brightness attenuation rate in the longitudinal direction of the plastic optical fiber is 30 cd / m or less. An illuminated plastic optical fiber bundle comprising a plurality of illuminated plastic optical fibers according to any one of claims 1 to 4. An optical fiber illuminating device comprising the illuminated plastic optical fiber according to any one of claims 1 to 4 and a light source optically connected to at least one end of the illuminated plastic optical fiber. When the plastic optical fiber is divided into five in the longitudinal direction, the line roughness Ra of the clad surface for each division increases in order from one end to the other, and the light source becomes the clad surface. The optical fiber illumination device according to claim 6, wherein the optical fiber illumination device according to claim 6 is optically connected to one end on the side having a small line roughness Ra. An optical fiber sensor having at least a part of the illuminated plastic optical fiber according to any one of claims 1 to 4. An optical fiber sheet having at least a part of the illuminated plastic optical fiber according to any one of claims 1 to 4. An optical fiber woven fabric having at least a part of the illuminated plastic optical fiber according to any one of claims 1 to 4. An optical fiber knit having at least a part of the illuminated plastic optical fiber according to any one of claims 1 to 4. A plastic optical fiber cord, which is a cord obtained by bundling one or a plurality of illuminated plastic optical fibers according to any one of claims 1 to 4 and coating the resin. A medical device having at least a part of the illuminated plastic optical fiber according to any one of claims 1 to 4. The method for producing an illuminated plastic optical fiber according to any one of claims 1 to 13, wherein the clad is sandblasted. 14. Claim 14: Sandblasting is performed while translating the illuminated plastic optical fiber at a variable speed, or sandblasting is performed toward the illuminated plastic optical fiber traveling at a constant speed by changing the distance from the optical fiber. The method for manufacturing an illuminated plastic optical fiber according to.