JP7105485B2 - A method of forming a periodic structure on a fiber surface with an ultrashort pulse laser - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fiber having a periodic structure on its surface, and the fiber.

In 1965, Birnbaum accidentally discovered that a wavelength-sized periodic structure could be formed "instantaneously" on the bottom surface of laser processing marks (Non-Patent Document 1). This periodic structure is called surface wave interferometry because it is an ablation phenomenon in which the standing wave generated by the interference between the incident light and the plasma wave or scattered light generated on the surface selectively sublimates the material surface. In other words, there are two types of laser processing principles: conventional thermal processing and newly discovered ablation (sublimation). If the laser power is sufficient, only ablation occurs and no heat is generated. Insufficient laser power results in both ablation and thermal processing. And if the power of the laser is low, only thermal processing will occur. Which of these situations occurs depends on the pulse width in the case of a pulsed laser, as will be described later.

In the field of textiles as well, there has been a known technology that applies this principle to modify the surface of the fiber by irradiating it with a laser beam and imparting new functions to it. For example, Patent Document 1 describes a fiber surface modification method in which polyester fibers and aramid fibers are irradiated with Nd-YAG laser light. According to this fiber surface modification method, it is possible to change the chemical structure of the surface layer of polyester fibers and aramid fibers, change the ratio of constituent elements, and generate functional groups to increase activity.

In addition, Non-Patent Document 2 describes a technique of irradiating a synthetic fiber with a pulsed ultraviolet laser (excimer laser) to form a fine structure on the fiber surface. Furthermore, Non-Patent Document 3 describes formation of a fine surface structure and change in surface chemical structure by laser ablation by irradiating a PET resin fiber with a pulsed ultraviolet laser (excimer laser) of 20 ns. In addition, in Non-Patent Document 4, a pulsed ultraviolet laser (excimer laser) is irradiated to a polyester film or polyester fiber, and the difference between plasma treatment and electron beam treatment is examined with respect to dyeability and wettability.

JP-A-8-60534

Birnbaum M.: Semiconductor surface damage produced by ruby lasers, J. Appl. Phys., 36(11), 3688-3689 (1965) Thomas Bahners, Eckhard Schollmeyer: Die Angewandte Makromolekulare Chemie 151 (1987) 19-37 (Nr, 2509) Hirosa Watanabe, Tadahiko Takada, Tokai, Keiro, "Surface Changes of Poly(ethylene terefuthalate) Fibers by Laser Ablation" SEN-I GAKKAISHI Vol.49, No.4 (1993) p.157-162 Ichiro Enomoto, Hisashi Ito, Hidetoshi Yoshida, Hirokazu Yoshida, Yukihiko Kurita, "Effect of surface modification of polyester fabrics", Tokyo Metropolitan Institute of Industrial Technology Report No. 5 (2002) p.105-108

However, in the fiber surface modification method using a laser according to Patent Document 1, the fiber is continuously irradiated with the laser, so that the fiber is thermally processed. Also, in Non-Patent Document 3, the pulse width is in the region of several tens of nanoseconds. In a pulse oscillation laser, the pulse power P _p (W) is obtained by dividing the energy E (J) of one shot by the pulse width t (s). In other words, if the pulse width is several tens of nanoseconds, the pulse power is insufficient, and the workpiece is not only ablated but also thermally processed. Therefore, in these conventional processing methods, although we succeeded in processing only some polymer materials with high photodissociation, heat was conducted not only to the surface of the fiber but also to the inside of the fiber, causing the fiber to break and the fibers to break. However, there were various problems such as welding and deterioration of fibers, resulting in weakening of strength.

In addition, surface wave interferometry can form a fine structure with a periodicity (pitch) equal to the wavelength at once. Conversely, if only the surface wave interferometry method is used, the pitch of the periodic structure is determined by the wavelength. Since the wavelength of the laser that can cause the ablation phenomenon is about 1,080 nm or less, it was not possible to form a fine periodic structure with periodicity in the micrometer range.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to easily form a fine periodic structure in the nano-range to micrometer range on the surface of the fiber by laser irradiation, and cut and cut the fiber. The problem to be solved is to provide a production method that does not easily cause adhesion and deterioration of the inside of the fiber, and to provide a fiber having a fine periodic structure on the surface.

The present inventor first considered irradiating the fiber with an ultrashort pulse laser as a method of solving the first conventional problem, that is, cutting, welding, and deterioration of the fiber (referred to in this specification as "ultrashort laser “Pulse laser” refers to a pulse laser with a pulse width of 20 picoseconds or less). A laser with such a short pulse width sublimates the molecules that make up the fibers, so that no heat is generated and only the material near the surface of the fiber irradiated with the laser is removed. As a result, the heat-affected layer can be significantly reduced, and the risk of fiber cutting, welding, and alteration due to heat is extremely small. In addition, since an ultrashort pulse laser is used, surface wave interference can be caused on the fiber surface, which allows the periodic structure of the fiber surface to have a pitch of 100 micrometers or less and 100 nanometers or more depending on the wavelength of the laser. It can be a periodic structure with

Next, the present inventor considered the combination of percussion processing using an ultrashort pulse laser as a method of solving the second problem of the conventional art, that is, the formation of a fine periodic structure having a periodicity in the micrometer range. rice field. The percussion machining method is a machining method in which pulse machining is continuously repeated on the workpiece (work) at time intervals, fixed distance intervals, and shots using both. In the surface wave interference, the traces of the first processing are triggered, and the next periodic structure is continuously generated. Therefore, in the percussion processing method, by changing the processing distance interval with respect to the laser spot diameter (1 to 100 μm), the overlap rate of the processing range can be finely adjusted, and as a result, the degree of surface wave interference can be reduced. Suppress. In this way, a fine periodic structure is formed which has a pitch in the micrometer range, which is the processing pitch of percussion processing, and in which a fine pattern with a pitch smaller than that is also generated at the same time.

That is, in the method of forming a periodic structure on the fiber surface of the present invention, an ultrashort pulse laser is irradiated to the surface of the fiber while relatively moving in the longitudinal direction of the fiber to perform percussion processing, thereby forming a periodic structure on the fiber surface. It is characterized by

As a method of relatively moving the ultrashort pulse laser in the longitudinal direction of the fiber, there are methods such as moving the fiber, moving the irradiation position of the ultrashort pulse laser with a mirror, and changing the irradiation position of the fiber and the ultrashort pulse laser. A method of moving both can be adopted. By these operations, a fine periodic structure can be easily formed by causing surface wave interference in the longitudinal direction of the fiber. In addition, since an ultra-short pulse laser with a pulse width of 20 picoseconds or less is applied, it is difficult to weld the fibers together, and only the surface of the fibers can be processed, making it difficult for the interior of the fibers to deteriorate. For this reason, it is possible to process the surface shape of thin fibers with a thickness of several μm.

In the present invention, the type of fiber to be irradiated with an ultrashort pulse laser is not particularly limited, and synthetic fibers such as polyester and polypropylene, semi-synthetic fibers such as cellulose fibers and protein fibers, regenerated fibers such as rayon, glass fibers, Even inorganic fibers such as carbon fibers can form a fine periodic structure on the surface.

Further, the pulse width of the ultrashort pulse laser is preferably 20 picoseconds or less and 100 femtoseconds or more. With such an ultrashort pulse laser, it is relatively easy to obtain a pulse with a high peak power, so it is easy to use.

In the method of forming a periodic structure on the fiber surface of the present invention, the ultrashort pulse laser can be irradiated by a percussion processing method in which it is irradiated at predetermined distance intervals and predetermined time intervals. This makes it possible to easily adjust the overlap ratio of the spot diameter of the laser on the periodic structure formed on the fiber surface, thereby controlling the surface wave interference and the pitch of the periodic structure. easier.

In the method of forming a periodic structure on the fiber surface of the present invention, the periodic structure is a periodic structure in which a structure with a length approximately equal to the wavelength of the ultrashort pulse laser is repeatedly formed, and a predetermined distance interval for percussion processing. It can be a periodic structure. It is theoretically shown that the pitch a of the periodic structure produced by the surface wave interferometry changes according to the relationship a = λ/ (1 ± sin θ) depending on the laser wavelength λ and the incident angle θ. (See paper below).
Campbell EEB, Ashkenasi D, Rosenfeld A: Ultra-short-pulse laser irradiation and ablation of dielectrics, Materials Science Forum, 301, 123-144 (1999)
Sakabe S, Hashida M, Tokita S, Namba S, Okamuro K: Mechanism for self-formation of periodic grating structures on a metal surface by a femtosecond laser pulse, Physical Review B, 79, 33409-1-33409-4 (2009)

Also. In the step of relatively moving in the longitudinal direction, percussion processing can be performed while drawing an elliptical orbit having long sides and short sides.

The fiber obtained by the method of forming a periodic structure on the fiber surface of the present invention has a periodic structure in which a structure with a length approximately equal to the wavelength of the ultrashort pulse laser is repeatedly formed on the surface, and a predetermined distance interval for percussion processing. can be a fiber provided with a periodic structure equal to

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to easily form a fine periodic structure in the nano-range to the micrometer range on the surface of a fiber by irradiating it with an ultrashort pulse laser. Moreover, it is possible to suppress breakage and welding of the fibers and deterioration of the inside of the fibers. Therefore, for example, it is possible to provide fibers having superhydrophilicity and superhydrophobicity. In addition, it is possible to provide a fabric excellent in waterproofness, stain resistance, heat retention, heat retention, air permeability, high dyeability, high cushioning properties, and the like.

SEM photographs of polypropylene 1, 2 and polyester. It is a SEM photograph of polypropylene subjected to ultrashort pulse laser processing under various conditions. 1 is a diagram showing the surface microstructure and its measurement results in Example 1. FIG. FIG. 10 is a diagram showing the surface microstructure and its measurement results in Example 2; FIG. 10 is a diagram showing the surface microstructure and its measurement results in Example 3; It is a schematic diagram of percussion processing performed while drawing an elliptical orbit. FIG. 2 is a schematic diagram of a case where a beam splitter is used and an ultrashort pulse laser is applied to a fiber from various circumferential directions.

An embodiment embodying the present invention will be described below. However, the present invention is not limited to this example. Various modifications are also included in the present invention within the scope of those skilled in the art without departing from the scope of the claims.

<Example>
In this example, the surface of a polypropylene (PP) fiber was intermittently irradiated with an ultrashort pulse laser that was moved in the longitudinal direction of the fiber (that is, percussion processing was performed). The fibers used in the examples are the following fiber bundles.
Polypropylene (PP)
Mitsubishi Rayon W0056T30 75d(84T)10fil, fiber diameter 75 denier, single fiber diameter 60-90 μm
Detailed specifications of the above polypropylene are shown in Table 1, and a SEM photograph is shown in Fig. 1.

In addition, PHAROS SP manufactured by Light Conversion was used as an ultrashort pulse laser. Table 2 shows the specifications of this device.

The irradiation conditions of the ultrashort pulse laser were the conditions shown in Examples 1 to 9 (see Tables 3 and 4 below).
Here, in percussion processing, the distance interval when the ultrashort pulse laser is moved in the circumferential direction of the fiber and irradiated is the radial pitch, and the distance interval when the ultrashort pulse laser is moved in the longitudinal direction of the fiber and irradiated is the longitudinal direction. Pitch.

-Results-
SEM photographs were taken of the fibers processed by the ultrashort pulse laser as described above. The results are shown in FIG.

First, based on Fig. 2, the degree of occurrence of surface wave interference is examined, centering on the pulse power (W). Since the spot diameter of the ultrashort pulse laser is 30 μm, the overlap ratio is 0% when the longitudinal pitch is 40 μm, 33% when the longitudinal pitch is 20 μm, and 33% when the longitudinal pitch is 10 μm. The overlap ratio is 67%. Under the experimental conditions of this study, the fiber diameter of about 1,000 nm, which is almost the same as the wavelength of the ultrashort pulse laser, was used for all processing regardless of the pulse power at an overlap rate of 67%, and at a pulse power of 50 MW or more at an overlap rate of 33%. A morphological fine structure was observed, which was considered to be caused by surface wave interference. On the other hand, at an overlap rate of 0%, no fiber-shaped fine structure was observed at any pulse power. Therefore, if the pulse power is 50 MW or more and the overlap ratio is 33% or more, continuous surface wave interference occurs over the entire fiber surface. If satisfied (25 MW and 67%), surface wave interference was thought to occur.
On the other hand, when the overlap ratio was 0%, adjacent machining marks did not trigger the formation of a fine periodic structure with a longitudinal pitch equal to 40 μm. Even in that case, when the pulse power was 50 MW or more, a fiber-shaped fine structure with a diameter of about 1,000 nm was observed inside the circular processing marks when viewed from the top. Therefore, it was found that by adjusting the overlap ratio to a low level, a basic fine periodic structure in the micron-meter range can be produced, and a fine structure in the nanometer-range is formed in a complex manner inside it.

3 to 5 show the absolute values of the dimensions and shapes of these fine periodic structures measured with a laser microscope (OLS4000, manufactured by Olympus Corporation). At a peak power of 147 MW (170 fs) and a longitudinal pitch of 10 μm, the pitch of the fine periodic structure was τ ₁ = 10–42 μm in the longitudinal direction and τ ₂ = 6–22 μm in the circumferential direction. These fine periodic structures were formed by gathering fiber shapes with an average diameter of 1,010 nm. At a peak power of 147 MW (170 fs) and a longitudinal pitch of 20 μm, a hole (well) structure with a concave width of f ₂ = 11.8 μm was formed. At a peak power of 147 MW (170 fs) and a longitudinal pitch of 40 μm, the pitch of the fine periodic structure was τ ₁ = 40.1 μm in the longitudinal direction and τ ₂ = 20.4 μm in the circumferential direction, matching the percussion pitch.

From the above results, it was found that by controlling the power of the ultrashort pulse laser and the period in percussion processing, it is possible to easily form a fine periodic structure in the nanometer to micrometer range on the fiber surface. rice field. In addition, it was found that by controlling the output of the ultrashort pulse laser, it is possible to suppress adhesion between fibers and deterioration of the inside of the fibers. That is, by using the processing method of the present invention, for example, by forming fine irregularities in the fibers, it is possible to provide a fabric that is excellent in heat retention, breathability, high dyeability, high cushioning properties, touch, etc. can be done.

In the above embodiment, linear scanning is repeated in the step of relative movement in the longitudinal direction, but percussion processing may be performed while drawing an elliptical orbit having long and short sides (see FIG. 6). As a result, it is possible to more reliably lead to the formation of the next fine periodic structure using the previous working trace as a trigger, and to form the fine periodic structure on the entire fiber surface.

Also. In the above example, the axial direction of irradiation of the ultrashort pulse laser was only from one direction with respect to the fiber, but as shown in FIG. A beam splitter or the like may be used to irradiate the fiber from various circumferential directions (see FIG. 7). As a result, it becomes possible to apply fine shape processing to the entire circumferential direction of the fiber.

Claims (5)

An ultrashort pulse laser is applied to the surface of the fiber while relatively moving in the longitudinal direction of the fiber to perform percussion processing, and a periodic structure is formed on the fiber surface to form a periodic structure equal to the predetermined distance interval of the percussion processing. How to form. 2. The method of forming a periodic structure on a fiber surface according to claim 1, wherein the pulse width of said ultrashort pulse laser is 20 picoseconds or less and 100 femtoseconds or more. 3. The method of forming a periodic structure on a fiber surface according to claim 1 , wherein the fibers are chemical fibers , carbon fibers , or glass fibers. The percussion processing is performed by irradiating a pulsed laser at a predetermined distance interval, adjusting the overlap rate of the laser spot diameter to adjust the degree of occurrence of surface wave interference, resulting in a periodic structure 4. The method of forming a periodic structure on a fiber surface according to any one of claims 1 to 3, characterized in that the is adjusted. fiber length A periodic structure is formed on the fiber surface according to any one of claims 1 to 4, wherein the step of relatively moving in the hand direction performs percussion processing while drawing an elliptical orbit having a long side and a short side. Method.

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