JP3328890B2 - Illuminated plastic optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical fiber that leaks light from all or a desired portion of a side surface of an optical fiber, and more particularly to an illuminated plastic optical fiber in which a sheath of the leaking portion is thinned.

[0002]

2. Description of the Related Art Plastic optical fibers leaking from the side are used for applications such as lighting, decoration, design, and display.

[0003] For the illuminated plastic optical fiber,
Conventionally, various fiber structures and manufacturing methods have been proposed. For example, a light leakage optical fiber is disclosed in Japanese Patent Publication No. 47-42534. The present invention
The total reflection portion of the optical fiber is selectively destroyed mechanically or thermally to form a light leakage portion, and this optical fiber is used as a fiber product and used as a surface light source. In addition to the above-mentioned conventional technology, a light leakage technology for leaking light transmitted through an optical fiber from a side surface includes a material having a characteristic in the material and configuration of the optical fiber, in which a transparent small piece is dispersed inside the optical fiber (Japanese Patent Publication No. SHO 51-51). No. -29551) and an optical fiber core using an elastomer as a sheath (cladding) material.
Leakage due to structural irregularities at the sheath interface (J. 60-1)
No. 12204), and a diffusion center such as a translucent or opaque material such as glass particles or a bubble is linearly dispersed in a core of the optical fiber, and the density of the diffusion center is preferably increased as the distance from the end of the optical fiber increases. (Japanese Patent Application Laid-Open No. 63-247705) to obtain a uniform illumination by increasing the height.

[0004] In addition, there are two types of cutting the optical fiber surface with a blade or the like, such as making a cut on the side surface of the rotating optical fiber with a blade (JP-A-50-83044). What is formed on the surface of an optical fiber
Japanese Patent Application Laid-Open No. 3-253903) and a device that forms a flaw at a specific position (Japanese Utility Model Laid-Open No. 4-18801).

[0005] Further, in the case where the surface of an optical fiber is roughened by heat treatment or a strain is formed, the synthetic fiber is heat-shrinked in a state where the synthetic fiber is spirally wound around the optical fiber, and the light leakage portion is formed. What forms (Japanese Patent Publication No. 52-325)
No. 82) and a method in which a heated projection is pressed against an optical fiber to form a light leakage recess at a predetermined interval (Japanese Patent Laid-Open No. 60-1).
59707) and a method in which a heated rough plate is pressed against an optical fiber to form fine irregularities on the surface (JP-A-63-293505, JP-A-63-3185).
No. 02, Japanese Utility Model Laid-Open No. 1-3803).

[0006] Twisting or mechanically pressing an optical fiber to form a strain or the like includes twisting the optical fiber to retain the strain (Japanese Patent Laid-Open No. 50-83049).
Forming fine irregularities on the surface by passing an optical fiber between a roller having fine projections
No. 3007), a device in which an optical fiber is twisted around a tension member (Japanese Patent Application Laid-Open No. 2-108007 and Japanese Patent Application Laid-Open No. 2-108008), and a wound / strain formed at a predetermined interval by passing the optical fiber between gears. (JP-A-3-123302 and JP-A-4-66904).

[0007]

The leaky optical fibers implemented and proposed in various prior arts leak a large amount of light from the side of the optical fiber, but the optical transmission loss is large, so that the practical fiber length is short. Alternatively, although light transmission loss is small and light is transmitted well in the core material, the amount of light leaking from the side of the optical fiber is effectively small, which is insufficient as a light leaking fiber. Further, there is also a problem that the amount of leaked light decreases as the distance from the optical fiber end on the light source side decreases, and it is difficult to obtain uniform illumination. The present invention has been made based on the above-described background, and an object of the present invention is to reduce the optical transmission loss, transmit light favorably in a core material, and increase the practical fiber length. Another object of the present invention is to provide an illuminated plastic optical fiber that is uniform in the length direction of the optical fiber and that can effectively leak light from the side of the optical fiber.

[0008]

The above objects are achieved by the illuminated plastic optical fiber of the present invention. That is, the illuminated plastic optical fiber of the present invention is composed of a core material having a high transparent substance, a sheath material described below , and a protective material having low transparency, and is a plastic optical fiber that leaks light from all or a desired portion of the side surface of the optical fiber. there are, are those wherein the sheath thickness of the desired portion to be light leakage is 2μm or less and thinner than 0.1 [mu] m, also the core -
An optical fiber having a sheath-protection structure and a sheath thickness of 3 μm or more
It is obtained by stretching.

The optical fiber used in the present invention is a plastic type having a highly transparent clad (sheath), a core, and a protective layer having a high refractive index. This is a step-index multimode optical fiber that changes stepwise. Core
Materials constituting the material include polymethyl methacrylate resin (PMMA, including a homopolymer and a copolymer of methyl methacrylate in this specification), deuterated PMMA, a polystyrene-based polymer, poly-4-methyl Penten-1, a silicon-based polymer, polycarbonate and the like can be used.

The cladding (sheath) material has a lower refractive index than the core material, and the material which can be used as the plastic optical fiber sheath material of the present invention includes the general formula (4):
General formulas (5) and (6) or copolymers thereof with vinyl monomers copolymerizable therewith may be mentioned.

Embedded image _{CH 2 = C (CH 3)} -COO- (CH 2) 2 (CF 2) n F ( wherein, n represents an integer of 5-12)

Embedded image CH ₂ ＣC (CH ₃ ) —COO—CH ₂ (CF ₂ ) _m X (where m is an integer of 1 to 4, and X represents H or F)

Embedded image CH ₂ ＣC (CH ₃ ) —COO—CY ((CF ₂ ) _a X) ((CF ₂ ) _b X) (where a and b are integers of 1 to 4, X is H or F and Y represent H or F)

Specific examples of the long-chain fluoroalkyl methacrylate represented by the general formula (4) used for producing the sheath used in the present invention include 1,1,2,2-tetrahydroperfluorooctyl methacrylate, 1,1,2,2-tetrahydroperfluorodecyl methacrylate, 1,1,2,2-
Tetrahydroperfluorododecyl methacrylate,
1,1,2,2-tetrahydroperfluorotetradecyl methacrylate and the like. These compounds may be used alone or as a mixture of two or more.

Specific examples of the short-chain fluoroalkyl methacrylate represented by the general formula (5) include trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3- Representative examples include pentafluoropropyl methacrylate and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate. These compounds may be used alone or as a mixture of two or more.

Specific examples of the monomer represented by the general formula (6) include, for example, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 1-trifluoro-2,2-difluoro , -3,3-difluoro, -4,4,4-trifluorobutyl methacrylate and the like can be shown as typical examples. These compounds may be used alone or as a mixture of two or more.

As other copolymerizable monomers, chain alkyl (meth) acrylates, methacrylic esters having a cyclic hydrocarbon group, and vinyl monomers capable of forming a hydrophilic polymer are used. As the chain alkyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate,
Examples thereof include isopropyl (meth) acrylate, n-butyl (meth) acrylate, and secondary butyl (meth) acrylate, with methyl methacrylate being preferred. Examples of the methacrylate having a cyclic hydrocarbon group include phenyl methacrylate, cyclohexyl methacrylate, adamantyl methacrylate, (iso) bornyl methacrylate, and tricyclomethacrylate [5.2.1.0 ^2.6 ] -dec-8-
Or the like is used.

Examples of the vinyl monomer capable of forming a hydrophilic polymer include (meth) acrylic acid, glycidyl methacrylate, methyl glycidyl methacrylate, acrylamide, 2-hydroxyethyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. And the like, but methacrylic acid is preferred.

The sheath constituting the illuminating optical fiber of the present invention comprises the compound represented by the general formula (4) in an amount of 30 to 50% by weight,
Compounds 20 to 50 selected from general formulas (5) and (6)
It is preferable to use a copolymer having 5% by weight, a compound having a hydrophilic group, particularly 10% by weight or less of methacrylic acid, another copolymerizable compound, particularly 5 to 50% by weight of methyl methacrylate. This copolymer has high transparency,
It has the characteristic of a low refractive index and is excellent in uniform stretching characteristics, and the formation of a very thin sheath layer of 0.1 to 2 μm, which is a feature of the present invention, can be performed by using another copolymer as a sheath material. It has the feature that it can be made more easily than in the case of forming a fiber.

The sheath thickness of the optical fiber used in the present invention is
The portion where the sheath thickness is reduced to 0.1 to 2 μm is the entire portion of the optical fiber or a desired portion to be leaked, and can be applied to an arbitrary portion.

The protective material is a polymer having a refractive index higher than the refractive index of the cladding material. Examples of the polymer which can be preferably used include polyethylene, polypropylene, polymethylpentene, nylon, polyester and the like. It is not limited only to polymers.

The illuminated plastic optical fiber of the present invention having the above-described structure exhibits the following functions and effects.
When light enters the sheath (refractive index n ₂ ) from the optical fiber core (refractive index n ₁ ), the incident angle θ _{c is} such that the refraction angle becomes 90 °.
(Critical angle), that is, sin θ _c = n ₂ / n ₁ (where n ₁
For light having an incident angle exceeding> n ₂ ), there is no refracted light, and the energy of the incident light is reflected 100% (total reflection) and transmitted through the core of the optical fiber. At that time, the incident light once enters the sheath, proceeds slightly along the boundary, and then returns to the core again. Depth Zd incident light has sunk in the sheath (core - depth field from the sheath surface becomes 1 / e) is, Z _d = λ / [2πn
₁ ｛sin ² θ ₁ − (n ₂ / n ₁ ) ² ｝ ^1/2 ] (where λ is the incident light wavelength and θ ₁ is the incident angle). The depth Z _d of penetration increases as approaching the critical angle theta _c. λ = 0.58
μm, θ ₁ = 70 °, n ₁ = 1.495, n ₂ = 1.402, Z _d
= 1 μm.

The sheath thickness of all or a desired portion of the plastic optical fiber including the core material, the sheath material, and the protective material is adjusted.
By making the film as thin as 0.1 to 2 μm, even if the light is totally reflected, the light seeps beyond the sheath due to the refractive index. Since the protective material is made of a material having a refractive index equal to or higher than the refractive index of the polymer constituting the sheath material, light that reaches the protective layer beyond the sheath layer enters the protective layer without being reflected, Due to the scattering of the light of the protective material itself or the scattering of the rough surface portion of the protective surface layer, the light always leaks from the side surface of the optical fiber.

At this time, by making the incident angle of light from the light source to the end of the optical fiber near 0 °, the incident angle θ _{1 of} the light transmitted through the optical fiber from the core to the sheath also becomes about 90 °. ,
Light leakage components from the side of the optical fiber can be suppressed. In accordance with yet progress of light transmitted through the optical fiber, the core - by bending irregularities and the optical fiber of the sheath interface, even less than 90 ° angle of incidence angle theta _1, i.e., become closer to the critical angle theta _c, light leakage component Increase.

Further, light transmitted through the optical fiber is absorbed by the core material and the sheath material, and the amount of transmitted light is attenuated. Therefore, the uniformity of the amount of leaked light in the longitudinal direction of the optical fiber is improved.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

[0024]

Example 1 Polymethyl methacrylate (refractive index n _D = 1.495) as a core material, 50 parts by weight of 1,1,2,2-tetrahydroperfluorooctyl methacrylate as a sheath material, 2,2,3,3,
Copolymer with 30 parts by weight of 3-pentafluoropropyl methacrylate, 15 parts by weight of methyl methacrylate, and 5 parts by weight of methacrylic acid (refractive index n _D = 1.402), polyethylene (n _D = 1.510) as a protective material, sheath A 5 μm thick plastic optical fiber was obtained. This was thermally stretched to a sheath thickness of 0.5 μm to obtain an illuminated plastic optical fiber. When white light was incident from one end face of the obtained plastic optical fiber, the side light leaked uniformly and brightly throughout the length of the optical fiber.

[0025]

Example 2 The same core material, sheath material and protective material as in Example 1 were used to obtain an eccentric plastic optical fiber having the thinnest sheath thickness of 0.5 μm. When white light was incident from one end face of the obtained plastic optical fiber, side light was leaked uniformly and brightly in the length direction so as to draw a streak on the optical fiber.

[0026]

Comparative Example 1 A plastic optical fiber having a sheath thickness of 5 μm was obtained in the same manner as in Example 1 until before the thermal drawing. This is sheath thickness 3
It was heat-stretched to μm to obtain an illuminated plastic optical fiber. When white light was incident from one end face of the obtained plastic optical fiber, the side light did not leak sufficiently.

[0027]

As demonstrated by the above embodiments, in the illuminated plastic optical fiber according to the present invention, the transmission loss is small, light can be transmitted well in the core material, and the practicable fiber length can be lengthened. At the same time, light can be uniformly and effectively leaked from the side of the optical fiber.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-34504 (JP, A) JP-A-57-2005 (JP, A) JP-A-50-131535 (JP, A) JP-A-50- 141332 (JP, A) Fully open sho 60-78004 (JP, U) Fully open sho 60-28702 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00 G02B 6 / 10 G02B 6/16-6/22 G02B 6/44

Claims (2)

(57) [Claims] 1. A core material, a compound 3 represented by the general formula (1)
0 to 70% by weight, selected from general formulas (2) and (3)
20 to 50% by weight of the compound, 0.5 to 0.5% of methacrylic acid
10% by weight, 5 to 50% by weight of methyl methacrylate
A polymer comprising a sheath material made of a copolymer and a protective material, wherein a sheath thickness of a desired portion to be leaked is 0.1 μm or more and 2 μm or less, and a polymer forming a protective layer has a refractive index of a polymer constituting the sheath. An illuminated plastic optical fiber comprising a polymer having a refractive index not less than the refractive index of CH ₂ ＣC (CH ₃ ) —COO— (CH ₂ ) ₂ (CF ₂ ) _n F (where n is an integer of 5 to 12) CH ₂ ＣC (CH _{3) -COO-CH 2 (CF} 2) m X ( wherein, m is an integer from 1 to 4, X is represents H or F) embedded image _{CH 2 = C (CH 3)} -COO-CY ( (CF ₂ ) _a X) ((CF ₂ ) _b X) (where a and b are integers of 1 to 4, X is H or F, and Y is
H or F is indicated) 2. It has a core-sheath-protection structure and a sheath thickness of 3 μm.
An illuminated plastic optical fiber, characterized in that the above optical fiber is stretched to form an optical fiber having a sheath thickness of 0.1 μm or more and 2 μm or less at a desired portion to be leaked.