JPH0784128A - Illumination device - Google Patents

Abstract

PURPOSE:To enable the effective leakage of light from the flank of a plastic optical fiber having the sheath thickness of the part to be subjected to light leakage uniformly in the longitudinal direction of the optical fiber by connecting a light source of a numerical aperture of a specific value or below to the light incident side of the optical fiber. CONSTITUTION:The sheath thickness of the entire part or desired part of the plastic optical fiber consisting of a core material, sheath material and protective material is reduced as small as 0.1 to 2mum by which even the light to be totally reflected in relation to a refractive index is bled out beyond the sheath and the light leakage from the flank of the optical fiber is generated. The similar materials are respectively used for the core material and sheath material to be used here. The optical fiber is coated with a polyethylene as the protective material, by which the plastic optical fiber having the sheath thickness of 5mum is obtd. This plastic optical fiber is thermally elongated to the sheath thickness of 0.5mum to form the lighting plastic optical fiber. A white source of the numerical aperture of 0.3 is connected to one end face of the resulted plastic optical fiber and light is made incident thereon, by which the bright flank leaking light free from unevenness over the entire part is uniformly obtd. in the longitudinal direction of the optical fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device using a plastic optical fiber which leaks light from all or a desired part of the side surface of an optical fiber, and more particularly, it is an opening for an illuminating plastic optical fiber having a thin sheath. The present invention relates to an illumination device in which light sources of 0.3 or less are combined.

[0002]

2. Description of the Related Art Plastic optical fibers that leak light from the side are used in applications such as lighting, decoration, design, and displays.

For illuminated plastic optical fibers,
Conventionally, various fiber structures and manufacturing methods have been proposed. For example, Japanese Patent Publication No. 47-42534 discloses a leaky optical fiber. This invention
The total reflection portion of the optical fiber is selectively destroyed mechanically or thermally to form a light leakage portion, and the optical fiber is used as a fiber product and used as a surface light source. In addition to the above-mentioned conventional technique, as a light leakage technique for leaking light transmitted through the optical fiber from the side surface, one characterized by the material and configuration of the optical fiber is one in which transparent particles are dispersed inside the optical fiber (Japanese Patent Publication No. -29951) and an elastomer as a sheath (clad) material, and an optical fiber core-
Light leakage caused by structural irregularities at the sheath interface
12204) and a translucent or opaque material such as glass particles or a diffusion center such as a bubble is linearly dispersed in the core of the optical fiber, and preferably the diffusion center density is increased as the distance from the end of the optical fiber increases. There is a method (Japanese Unexamined Patent Publication No. 63-247705) in which the illumination is increased to obtain uniform illumination.

[0004] Further, the one in which a cut is formed on the surface of the optical fiber with a blade or the like, the one in which the side surface of the optical fiber being swung is cut with a blade (Japanese Patent Laid-Open No. 83044/50), and the one with a specific shape What is formed on the surface of an optical fiber
No. 253903), and one that forms a scratch at a specific position (Actual Kaihei 4-1801).

Further, in the case where the surface of the optical fiber is heat-treated to roughen or form strain, the synthetic fiber is heat-shrinked in a state that the synthetic fiber is spirally wound around the optical fiber, and the light leakage part is formed. What is formed (Japanese Patent Publication Sho-52-325)
No. 82), and a heated protrusion is pressed against an optical fiber to form light leakage concave portions at predetermined intervals (Japanese Patent Laid-Open No. 60-1).
59707) and a heated rough plate pressed against an optical fiber to form fine irregularities on the surface (JP-A-63-293505, JP-A-63-3185).
No. 02, and Japanese Utility Model Laid-Open No. 1-3803).

Those which twist or mechanically press down an optical fiber to form a strain or the like, twist the optical fiber to leave the strain (Japanese Patent Laid-Open No. 50-83049).
And an optical fiber is formed between the rollers having fine protrusions to form fine irregularities on the surface (JP-A-1-27).
No. 3007), a method in which an optical fiber is twisted around a tension member (Japanese Patent Laid-Open No. 2-108007, Japanese Patent Laid-Open No. 2-108008), and scratches and strains are formed at predetermined intervals through the optical fiber between gears. (Japanese Patent Application Laid-Open No. 3-123302, Japanese Patent Application Laid-Open No. 4-66904).

[0007]

Although light leaking optical fibers have been implemented and proposed by various prior arts, although these leak light in large amounts from the side surface of the optical fiber,
The optical transmission loss is large and the practical fiber length is short, or the optical transmission loss is small and the light is transmitted satisfactorily in the core material, but it does not effectively leak from the side of the optical fiber and is a side leaking fiber. Is still not enough. There is also a drawback that the amount of light leakage decreases as the distance from the end of the optical fiber on the light source side decreases, and it is difficult to obtain uniform illumination.

The present invention has been made on the basis of the above background, and an object of the present invention is to achieve good light leakage in the core material with a small optical transmission loss, although the side light leakage is good. Providing an illuminated plastic optical fiber that can transmit and extend the practical fiber length, is uniform in the length direction of the optical fiber, and can effectively leak light from the side of the optical fiber, improving illumination efficiency The purpose of the present invention is to provide an illuminating device.

[0009]

The above problems can be solved by an illuminating device using the illuminated plastic optical fiber of the present invention, and the gist thereof is to provide a core material and a sheath material having high transparency. The optical fiber provided with the protective layer according to 1., the numerical aperture is 0.3
The illumination device is characterized by combining the following light sources.

The optical fiber used in the present invention is a plastic type having a highly transparent clad (sheath), a core (or core), and optionally a protective layer, and its structure has a graded refractive index. It is a step-index multimode optical fiber that changes dynamically.

As the material constituting the core material, polymethylmethacrylate (hereinafter referred to as PMMA, including homopolymer and copolymer of methyl methacrylate in this specification), deuterated PMMA, polystyrene-based Polymers, poly-4-methylpentene-1, silicone polymers, polycarbonates and the like can be used.

The clad (sheath) material has a smaller refractive index than the core material, and the materials that can be preferably used as the plastic optical fiber sheath material of the present invention are represented by the general formula (1), the general formula (2) and the general formula (2). Formula (3) or a copolymer with a vinyl monomer copolymerizable therewith may be mentioned.

[Chemical 1]

[Chemical 2]

[Chemical 3]

Specific examples of the long-chain fluoroalkylmethacrylate represented by the general formula (1) used for producing the sheath material used in the present invention include 1,1,2,2-tetrahydroperfluorooctylmethacrylate, 1,1,2,2-tetrahydroperfluorodecyl methacrylate, 1,1,2,2-
Tetrahydroperfluorododecyl methacrylate,
1,1,2,2-tetrahydroperfluorotetradecyl methacrylate and the like can be mentioned. These compounds may be used alone or in combination of two or more.

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

Specific examples of the monomer represented by the general formula (3) include, for example, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate and 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 in combination of two or more.

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

Vinyl monomers capable of forming a hydrophilic polymer include (meth) acrylic acid, glycidyl methacrylate, methylglycidyl methacrylate, acrylamide, 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Etc., but methacrylic acid is preferred.

The sheath constituting the optical fiber for illumination of the present invention comprises 30 to 50% by weight of the compound represented by the general formula (1),
Compounds 20 to 50 selected from general formula (2) and general formula (3)
It is preferable to use a copolymer having a weight percentage of 5% by weight, a compound having a hydrophilic group, particularly 10% by weight or less of methacrylic acid, and another copolymerizable compound, especially 5 to 50% by weight of methyl methacrylate. This copolymer has high transparency,
It has a characteristic that the refractive index is low, and also has excellent uniform stretching characteristics. The formation of an extremely thin sheath layer of 0.1 to 2 μm, which is a characteristic of the present invention, is performed by using another copolymer as a sheath material. It has a feature that it can be easily manufactured as compared with the case of forming a fiber.

The sheath thickness of the optical fiber used in the present invention is
By setting the thickness to 0.1 to 2 μm, the light leakage characteristics are improved, and the portion where the sheath thickness is made thin is the whole of the optical fiber or a desired portion where light is to be leaked, and it can be applied to any portion.

The protective material is preferably composed of a polymer having a refractive index higher than that of the clad material,
Materials that can be preferably used as the plastic optical fiber protective material of the present invention include, for example, polyethylene, polypropylene, polymethylpentene, nylon and polyester, but are not limited to these polymers.

The illuminated plastic optical fiber used in the present invention having the above structure exhibits the following operational effects. Light from the optical fiber core (refractive index n ₁ ) to the sheath (refractive index n ₁ )
incident angle θ _c (critical angle) such that the refraction angle becomes 90 ° when incident on n ₂ ), that is, when the incident angle exceeds sin θ _c = n ₂ / n ₁ (where n ₁ > n ₂ ). There is no refracted light, and 100% of the energy of incident light is reflected (total reflection) and transmitted through the core of the optical fiber. At that time, the incident light once enters the sheath, slightly advances along the boundary, and then returns to the core again. Depth Z _d (incident core)
The depth from the sheath interface where the electric field becomes 1 / e) is Z _d = λ / [2
πn 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 penetration depth Zd increases as it approaches the critical angle θ _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 consisting of the core material, the sheath material, and the protective material is set.
By thinning the thickness to 0.1 to 2 μm, even light that is totally reflected due to the refractive index will exude beyond the sheath and leak light from the side surface of the optical fiber.

Further, when the protective material having a refractive index higher than that of the sheath material is coated, the light which reaches the protective layer beyond the sheath layer enters the protective layer without being totally reflected, and the light of the protective material itself is scattered. ,
Alternatively, because the transparency is not high due to the rough surface of the protective surface layer, the light is scattered and efficiently leaks from the side surface of the optical fiber.

At this time, in order to uniformly leak light from the illuminated plastic optical fiber according to the present invention in the length direction of the optical fiber, the numerical aperture of the incident light from the light source to the end of the optical fiber is set.
It should be 0.3 or less. As a result, the incident angle θ ₁ from the core to the sheath in the optical fiber is also close to 90 °, and the light leakage component from the side surface of the optical fiber is suppressed, so that light can be leaked over a long distance. Further, the light transmitted through the optical fiber becomes closer to the angle of incidence θ _{1 of} 90 ° or less, that is, the critical angle θ _c due to the irregularity of the core-sheath interface or the bending of the optical fiber, and the light is separated from the light source. The light leakage component increases even in the portion, and the illumination device having a uniform light leakage property can be obtained. Here, the light transmitted through the optical fiber is absorbed by the core material and the sheath material, and the transmitted light amount is attenuated. Therefore, the light leakage amount is more uniform in the length direction of the optical fiber.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0026]

Example 1 Polymethylmethacrylate (refractive index n _D = 1.495) as a core material, 1,1,2,2-tetrahydroperfluorooctylmethacrylate 50 parts by weight as a sheath material, 2,2,3,3,
Using a copolymer (refractive index n _D = 1.402) of 30 parts by weight of 3-pentafluoropropyl methacrylate, 15 parts by weight of methyl methacrylate, and 5 parts by weight of methacrylic acid, a plastic optical fiber having a sheath thickness of 5 μm was obtained. This optical fiber has a sheath thickness of 0.5
It was heat-stretched to μm to obtain an illuminated plastic optical fiber. The numerical aperture on one end surface of the obtained plastic optical fiber
When a white light source of 0.3 was connected and light was incident, side light was uniformly and uniformly leaked over the entire length of the optical fiber.

[0027]

[Example 2] The same core material and sheath material as in Example 1 were used, and polyethylene (refractive index n _D = 1.51) was used as a protective material.
0) was coated to obtain a plastic optical fiber having a sheath thickness of 5 μm. This was heat-drawn to a sheath thickness of 0.5 μm to obtain an illuminated plastic optical fiber. When a white light source with a numerical aperture of 0.3 was connected to one end surface of the obtained plastic optical fiber and light was incident on the side surface, the side surface was uniform and uniform in the length direction of the optical fiber, and the side light was leaked brightly and uniformly.

[0028]

[Example 3] Example 2 as a core material, a sheath material, and a protective material
Use the same one used in, and the thinnest sheath thickness is 0.5μ.
An eccentric plastic optical fiber of m was obtained. A white light source with a numerical aperture of 0.3 was connected to one end face of the obtained plastic optical fiber, and when light was incident, side light was uniformly and brightly leaked in the length direction so as to draw a line on the optical fiber.

[0029]

Comparative Example 1 When a white light source with a numerical aperture of 0.5 was connected to one end surface of an illuminated plastic optical fiber obtained in the same manner as in Example 1 and light was incident, the amount of light leakage increased on the white light incident side. It showed non-uniform side light leakage along the length.

[0030]

Comparative Example 2 When a white light source with a numerical aperture of 0.5 was connected to one end surface of an illuminated plastic optical fiber obtained in the same manner as in Example 2 and light was incident, the amount of light leakage increased on the white light incident side. It showed non-uniform side light leakage along the length.

[0031]

COMPARATIVE EXAMPLE 3 Using the same material as that used in Example 1,
A plastic optical fiber having a sheath thickness of 5 μm was obtained in the same manner as in Example 1. This was heat-drawn to a sheath thickness of 3 μm to obtain an illuminated plastic optical fiber. When a white light source with a numerical aperture of 0.3 was connected to one end surface of the obtained plastic optical fiber and light was incident, the amount of side light leakage was insufficient.

[0032]

Comparative Example 4 A plastic optical fiber having a sheath thickness of 5 μm was obtained in the same manner as in Example 2, and this was thermally stretched to a sheath thickness of 3 μm to obtain an illuminated plastic optical fiber. When a white light source with a numerical aperture of 0.3 was connected to one end surface of the obtained plastic optical fiber and light was incident, the amount of side light leakage was insufficient.

[0033]

As demonstrated by the above embodiments, in the illumination device according to the present invention, the transmission loss is small, the light is well transmitted in the core material, and the fiber length that can be practically used as the side leakage type illumination device is long. In addition, the light can be uniformly and effectively leaked from the side surface of the optical fiber.

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[Procedure amendment]

[Submission date] October 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

Title: Illumination device

Claims (1)

[Claims] 1. An optical fiber comprising a transparent core material and a sheath material, wherein a desired portion to be leaked has a sheath thickness of 0.1 μm or more and 2 μm or less. A plastic optical fiber has a numerical aperture of 0.3. An illuminating device characterized in that the following light sources are connected.