JP7356482B2 - cable - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to cables.

Cables covered with a sheath (outer jacket) are sometimes printed with markings for identification purposes, and in recent years, a technology called laser marking has become popular as a printing technology.
The mainstream of laser marking is to use laser irradiation to foam a resin material to change it to a color such as white, or to burn the resin material by laser irradiation to change it to a color such as black.

An example of a cable compatible with laser marking technology is disclosed in Patent Document 1.
According to the technique disclosed in Patent Document 1, the outer covering is divided into a first covering part and a second covering part, and a coloring agent for laser marking is added only to one covering part, and a coloring agent for laser marking is added to the other covering part. has a structure in which the coloring agent is not added, and attempts are made to minimize cost increases and changes in the properties of the entire jacket.

JP2019-215970A

By the way, when a resin material is foamed and turned white by laser irradiation, printing may not be possible even after adjusting the laser irradiation conditions, and the cause of this has not yet been investigated.
A main object of the present invention is to provide a cable that can be printed using laser marking technology, and that can be printed within a range that does not require adjustment of laser irradiation conditions or can be adjusted.

When the inventor investigated the reason why printing could not be performed even if the laser irradiation conditions were adjusted, he discovered that there is a certain relationship between the transmission density per unit thickness and the printing condition. It's arrived.
That is, according to the present invention,
A twisted pair core made by twisting multiple insulated core wires together,
an inner sheath covering the twisted pair core;
and an outer sheath covering the inner sheath,
The outer sheath contains a polyurethane resin and a colorant,
A cable is provided, wherein the outer sheath has a transmission density D/t per unit thickness of 5.4 to 13.2 mm ^-1 .

According to the present invention, it is possible to provide a cable that does not require adjustment of laser irradiation conditions or can print within an adjustable range.

FIG. 2 is a cross-sectional view schematically showing a cable. FIG. 3 is a schematic diagram for explaining calculation of transmission density per unit thickness. 7 is a diagram showing actual printing states of samples 3, 6, and 8. FIG. FIG. 3 is a schematic diagram for explaining the relationship between transmission density per unit thickness and printing state.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In this specification, "~" indicating a numerical range includes the upper limit and the lower limit.

As shown in FIG. 1, the cable mainly includes a twisted pair core 10 in which a pair of insulated core wires 3a and 3b are twisted together, an inner layer sheath 20 that fully covers the twisted pair core 10, and an outer layer that covers the inner layer sheath 20. It is composed of a sheath 30.

The insulated core wire 3a has a configuration in which a stranded conductor 1a is covered with an insulator 2a, and the insulator 2a is colored red.
The insulated core wire 3b has a structure in which a stranded conductor 1b is covered with an insulator 2b, and the insulator 2b is colored black.

The stranded conductors 1a and 1b are stranded conductors made by twisting a plurality of thin wires together. Each thin wire is made of annealed copper wire plated with tin or silver.
The stranded wire conductors 1a and 1b are preferably made by twisting together a plurality of tin-plated annealed copper wires (thin diameter strands) with a constant diameter, and have an outer diameter of AWG 18 to 30.

The insulators 2a and 2b are made of polyethylene resin.
The polyethylene resin constituting one insulator 2a is blended with a coloring agent for coloring it red, and the polyethylene resin constituting the other insulator 2b is blended with a coloring agent for coloring it black. There is.
The thickness of the insulators 2a, 2b is preferably 0.10 to 0.30 mm.
The insulators 2a and 2b are formed by extrusion coating polyethylene resin onto the stranded conductors 1a and 1b, and then irradiating (crosslinking) with an electron beam.

The inner sheath 20 is made of polyvinyl chloride resin and contains a black colorant (carbon, etc.).
The inner sheath 20 is formed by extrusion coating the twisted pair core 10 with the black polyvinyl chloride resin.

The outer sheath 30 is made of polyurethane resin and contains a black colorant (carbon, etc.).
The black polyurethane resin has a low temperature embrittlement temperature of -60°C or lower according to JIS K 6301, preferably -68°C or lower. The tensile strength according to JIS K 7311 is 40 MPa or more, preferably 42 MPa or more, the tensile elongation is 450% or more, preferably 500% or more, and the 100% modulus is 5.0 MPa or less, preferably 4.9 MPa or less. be.
The black polyurethane resin preferably has a cold resistance of -75°C or more according to JIS K 6301, a tensile strength of 50 MPa or less, a tensile strength of 600% or less, and a 100% modulus of 4.0 MPa or more according to JIS K 6723. preferable.
In addition to the colorant, the black polyurethane resin may contain additives such as antioxidants, ultraviolet absorbers, heat aging inhibitors, fillers, processing aids, and lubricants, if necessary.
The thickness of the outer sheath 30 is preferably 0.10 to 0.30 mm.
The outer sheath 30 is formed by extruding and coating the inner sheath 20 with the black polyurethane resin.

In the cable according to this embodiment, the transmission density D/t per unit thickness of the outer sheath 30 is 5.4 to 13.2 mm ^-1 , preferably 7.1 to 8.8 mm ^-1 .
The transmission density D/t per unit thickness of the outer sheath 30 is calculated as follows.
The outer sheath 30 is peeled off from the cable, pressed while heating, and processed into a film shape with a thickness of about 0.3 mm. Thereafter, using a transmission densitometer, the transmission density D=-log10 (Eo/Ei) is measured from the luminous flux of the outgoing Eo and the incident Ei (see FIG. 2). At the same time, the thickness t [mm] is measured using a dial thickness gauge, and the transmission density D/t [mm ⁻¹ ] per unit thickness is calculated.

According to the present embodiment described above, the transmission density D/t per unit thickness of the outer sheath 30 is 5.4 to 13.2 mm ⁻¹ , so adjustment of the laser irradiation conditions is not necessary or is possible within a range. (See examples below).

Note that the cable according to this embodiment is preferably used for bicycles, and can be applied to communication purposes thereof, as well as to power supply purposes.

(1) Preparation of sample (1.1) Sample 1
Ninety-five tin-plated annealed copper wires each having a diameter of 0.05 mm were twisted together to prepare two stranded wire conductors of AWG25 (outer diameter 0.56 mm).

One stranded wire conductor was coated with high-density polyethylene mixed with a red masterbatch by extrusion and irradiated with an electron beam to form a red insulator with a thickness of 0.17 mm. An insulated core wire of No. 1 was obtained.
The other stranded wire conductor was coated with the same high-density polyethylene mixed with a black masterbatch by extrusion and irradiated with an electron beam to form a black insulator with a thickness of 0.17 mm. 2 insulated core wires were obtained.
The mass mixing ratio of each masterbatch and high-density polyethylene was 1:30 for both the red insulator and the black insulator.

Thereafter, while the first insulated core wire and the second insulated core wire are twisted together to form a twisted pair core, black polyvinyl chloride resin (PVC) is extruded and coated on top of the twisted core. Then, a black polyurethane resin was extrusion coated to form an outer layer sheath with a thickness of 0.23 mm, and a cable with an outer diameter of about 2.3 mm was manufactured.

Thereafter, laser marking was performed on the cable using a general-purpose laser marking device. The laser irradiation conditions (specifications) of the laser marking device are as follows.
Oscillator average output: 20W
Pulse period: 5~50μs
Scan speed: max. 12,000mm/s

(1.2) Samples 2 to 10
In Sample 1, the carbon concentration and thickness of the outer sheath were varied.
Other than that, it was manufactured and laser printed in the same manner as Sample 1.

(2) Evaluation of samples The following processing was performed on each sample, and the relationship between the transmission density D/t per unit thickness and the printing state was evaluated.
The polyurethane resin sheath was peeled off and pressed while heating to form a film with a thickness of approximately 0.3 mm. Thereafter, using a transmission densitometer (X-Lite 301 manufactured by X-Lite), the transmission density D=-log10 (Eo/Ei) was measured from the luminous flux of the outgoing Eo and the incident Ei through a 3 mm diameter aperture ( (see Figure 2). In addition, the thickness t [mm] was measured using a dial thickness gauge (anvil diameter 10 mm), and the transmission density D/t [mm ^-1 ] per unit thickness was calculated.
Table 1 shows the relationship between the transmission density D/t per unit thickness and the printing condition.

In Table 1, the evaluation criteria for "◎", "○", "△", and "×" are as follows.
"◎": Equivalent to the standard sample, no adjustment of laser irradiation conditions is required "○": Equivalent to the standard sample, fine adjustment of laser irradiation conditions is required "△": Difference from the standard sample However, it can be made equivalent to the standard sample by adjusting the laser irradiation conditions and increasing the number of irradiations. "×": Printing cannot be recognized even if the laser irradiation conditions and number of irradiations are increased.

(3) Summary As shown in Table 1 and Figure 3, in samples 3 to 10, the printing condition is ◎, ○, or △, and the transmission density D/t per unit thickness is 5.4 to 13.2 mm ^-1 It turned out to be useful. In particular, it was found that samples 4 to 7 had a printing condition of ◎ or ○, and that it was useful that the transmission density D/t per unit thickness was 7.1 to 8.8 mm ^-1 .
The relationship between the transmission density D/t per unit thickness and the printing condition was estimated as follows.
As shown in Figure 4, when the transmission density D/t per unit thickness is 5.4 to 13.2 mm ^-1 , gas bubbles are generated within the polyurethane resin layer due to the heat of the laser, and the bubbles are formed on the surface. white bumps (phenomenon: foaming). On the other hand, if the transmission density D/t per unit thickness is less than 5.4 mm ^-1 , the laser will pass through the polyurethane resin layer and gas bubbles will not be sufficiently generated (phenomenon :Transparent). If the transmission density D/t per unit thickness is excessive, exceeding 13.2 mm ^-1 , the laser energy will be absorbed in a very shallow part of the surface of the polyurethane resin layer, resulting in an excessive amount of heat. The state of the gas bubbles cannot be maintained and they disappear (phenomenon: gas bubble disappearance).

1a, 1b twisted wire conductor 2a, 2b insulator 3a, 3b insulated core wire 10 twisted core 20 inner layer sheath 30 outer layer sheath

Claims (2)

A twisted pair core made by twisting multiple insulated core wires together,
an inner sheath covering the twisted pair core;
and an outer sheath covering the inner sheath,
The outer sheath contains a polyurethane resin and a colorant,
A cable characterized in that the outer sheath has a transmission density D/t per unit thickness of 5.4 to 13.2 mm ^-1 . The cable according to claim 1,
A cable characterized in that the outer sheath has a transmission density D/t per unit thickness of 7.1 to 8.8 mm ^-1 .