Plastic optical fiber cable and method of transmitting signal

1. A plastic optical fiber cable comprising:

a bare plastic optical fiber comprising a core and a clad layer formed around the core, the clad layer being formed of one or plural layers; and

a coating layer around the bare plastic optical fiber,

wherein

the core comprises polymethyl methacrylate or a copolymer containing a methyl methacrylate unit;

the clad layer comprises a layer comprising a fluorine-containing olefin resin comprising a tetrafluoroethylene unit in at least an outermost layer of the clad layer, the fluorine-containing olefin resin having a heat of crystal fusion of 40 mJ/mg or less as measured using differential scanning calorimetry (DSC);

the coating layer comprises a light-shielding coating layer, a first functional coating layer (C) and a second functional coating layer (D), the light-shielding layer is present on an opposite side from the bare plastic optical fiber, the first functional coating layer (C) is present on the light-shielding layer, and the second functional coating layer (D) is present on the first functional coating layer (C);

the light-shielding coating layer comprises a resin composition comprising at least one nylon resin of nylon 11 and nylon 12, a total content of a monomer and an oligomer of the nylon resin is 1.5% by mass or less;

one of the first functional coating layer (C) and the second functional coating layer (D) comprises a first resin composition (I) and the other comprises a second resin composition (II);

the first resin composition (I) comprises a polybutylene terephthalate resin or an ethylene-vinyl alcohol copolymer;

the second resin composition (II) comprises a nylon resin composition having a crystalline melting point in a range of 240° C. or more and 280° C. or less as measured using differential scanning calorimetry (DSC), and an oxygen transmission rate P (cm 3 ·cm/(cm 2 ·sec·Pa)) as measured employing a method defined in ISO14663-2:1999 (Annex C) at a temperature T (K), said P satisfying the following general formula (1):

P< 8×10 −2 ×exp(−560 /T )  (1),

and the nylon resin composition is colorless or colored with an inorganic pigment;

when the first functional coating layer (C) comprises the resin composition (I) and the second functional coating layer (D) comprises the resin composition (II), the thickness c (μm) of the first functional coating layer (C) and the thickness d (μm) of the second functional coating layer (D) satisfy the following general formula (2):

0.39 ≦c /( c+d )≦0.9  (2);

when the first functional coating layer (C) comprises the resin composition (II) and the second functional coating layer (D) comprises the resin composition (I), the thickness c (μm) of the first functional coating layer (C) and the thickness d (μm) of the second functional coating layer (D) satisfy the following general formula (3):

0.15 ≦c /( c+d )≦0.7  (3);

a total thickness of the coating layer is 500 μm or more and 660 μm or less; and

a thickness of the light-shielding coating layer is 200 μm or more and 350 μm or less.

2. The plastic optical fiber cable according to claim 1 , further comprising a protective coating layer presented between the bare plastic optical fiber and the light-shielding coating layer,

wherein the protective coating layer comprises at least one resin selected from the group consisting of a methyl (meth)acrylate resin, a styrene resin, a vinylidene fluoride homopolymer, a polybutylene terephthalate resin, and a copolymer containing an ethylene unit and a vinyl alcohol unit.

3. The plastic optical fiber cable according to claim 1 , wherein the second resin composition (II) comprises nylon 66.

4. The plastic optical fiber cable according to claim 2 , wherein the second resin composition (II) comprises nylon 66.

5. The plastic optical fiber cable according to claim 2 , wherein a thickness of the protective coating layer is 10 μm or more and 100 μm or less.

6. The plastic optical fiber cable according to claim 2 , wherein the thickness of the light-shielding coating layer is 140 μm or more and 300 μm or less.

7. The plastic optical fiber cable according to claim 2 , wherein ratio b/a of the thickness b of the light-shielding coating layer to a thickness of the protective coating layer is 1.5 or more and 30 or less.

8. The plastic optical fiber cable according to claim 2 , wherein a ratio (b+c+d)/a of the total thickness of the thickness b of the light-shielding coating layer, the thickness c of the first functional coating layer (C) and the thickness d of the second functional coating layer (D) to a thickness a of the protective coating layer is 5.5 or more and 70 or less.

9. The plastic optical fiber cable according to claim 1 , wherein an outer diameter of the bare plastic optical fiber is 900 μm or more and 1100 μm or less.

10. A method for transmitting a signal by using the plastic optical fiber cable as recited in claim 1 in combination with a visible light emitting diode having an emission center wavelength in a range of 500 nm or more and 600 nm or less.

11. A method for transmitting a signal by using the plastic optical fiber cable as recited in claim 2 in combination with a visible light emitting diode having an emission center wavelength in a range of 500 nm or more and 600 nm or less.

12. A method for transmitting a signal by using the plastic optical fiber cable as recited in claim 3 in combination with a visible light emitting diode having an emission center wavelength in a range of 500 nm or more and 600 nm or less.

13. A method for transmitting a signal by using the plastic optical fiber cable as recited in claim 4 in combination with a visible light emitting diode having an emission center wavelength in a range of 500 nm or more and 600 nm or less.