JP7606188B2 - Fabric surface treatment method - Google Patents

Description

The present invention relates to a method for surface treatment of fabric.

Processing techniques are known that process the surface of fabric to impart desired properties. For example, when processing the surface of fabric or the fibers that make up the fabric to impart water repellency or hydrophilicity, the surface of the fabric or fiber is subjected to a water repellent or hydrophilic treatment. As a water repellent or hydrophilic treatment, a chemical method is known in which the surface of the fabric or fiber is coated with a water repellent or hydrophilic agent. However, when coating the surface of the fabric or fiber with an agent, there is a risk that the coated agent will wear away or deteriorate and peel off. In addition, depending on the type of agent, there is a risk of adverse effects on the environment.

Other processing techniques include methods of physically processing the surface of fabrics or fibers. For example, Patent Document 1 (JP 2020-66824 A) discloses a method of forming a periodic structure on a fiber surface. In this method, an ultrashort pulse laser is irradiated onto the surface of the fiber while moving it relatively in the longitudinal direction of the fiber, thereby forming a periodic structure on the fiber surface by percussion processing. According to Patent Document 1, depending on the type of periodic structure, for example, it is possible to provide a fiber with superhydrophobicity or a fiber with superhydrophilicity.

JP 2020-66824 A

The method of Patent Document 1 is a technology for processing the surface of a single fiber with an ultrashort pulse laser. The surface of the fiber has fine irregularities, but from the perspective of focusing the laser, it can be said to be generally flat. Therefore, by focusing the laser on the surface of the fiber to be processed, the surface of the fiber can be processed into the desired periodic structure.

However, when this method is applied to processing the surface of a fabric, it may be difficult to perform the processing appropriately. The reason is as follows. Since the fabric is formed by bundling or twisting single fibers with a diameter of approximately 1 to 100 μm, the fabric has a thickness and its surface has unevenness in the thickness direction of approximately 1 to 1000 μm. In other words, even if the surface of the fiber itself is approximately flat, the surface of the fabric is not necessarily flat. For example, some of the multiple fibers exposed on the front side of the fabric are lined up on the surface, while others are located deep in the thickness direction from the surface of the fabric. That is, in addition to the fibers located on the shallow side of the thickness direction of the fabric (the surface or the side close to the surface), the multiple fibers exposed on the front side of the fabric also include fibers located on the deep side of the thickness direction of the fabric (the side farther from the surface).

On the other hand, the focal depth of the laser light used in laser processing is about 10 to several hundred μm. In other words, the unevenness of the surface of the fabric and the focal depth are in a dimensional region close to the thickness direction, making it difficult to uniformly process the fabric in its in-plane direction and thickness direction, i.e., in a three-dimensional region. The value obtained by dividing the pulse energy (J) of the laser light by the laser irradiation area (cm ² ) is called the fluence F (J/cm ² ), and in laser processing, a certain level of fluence is required to generate the ablation required for processing. Therefore, if the laser is focused on a fiber located on the shallow side of the thickness direction, the fluence on the fiber located on the deep side of the thickness direction becomes insufficient, making it difficult to process the fiber located on the deep side. On the other hand, if the laser is focused on a fiber located on the deep side, the fluence on the fiber located on the shallow side becomes insufficient, making it difficult to process the fiber located on the shallow side. As a result, there is a risk that unevenness will occur in the processing of the surface of the fabric, making it difficult to perform appropriate surface processing in a three-dimensional region.

The object of the present invention is to provide a surface processing method that uses a laser to perform an appropriate surface processing on fabric, thereby forming fabric with desired characteristics.

The method for surface treatment of fabric according to the present invention is as follows.
(1) A method for processing a surface of a fabric, the surface of which is composed of fiber bundles and has a thickness, using a short-pulse laser, the method including an adjustment step of adjusting the focal depth of the short-pulse laser so that the size of the unevenness of the surface of the fabric is within the range of the focal depth of the short-pulse laser.

In the present fabric surface processing method, in the adjustment process, the focal depth is adjusted so that the size of the unevenness of the fabric surface falls within the range of the focal depth of the short pulse laser. Specifically, for example, when the unevenness of the fabric surface is large, the focal depth range is adjusted to be expanded so that the unevenness of the surface is included. That is, the focal depth is not set to a dimensional range close to the unevenness of the fabric surface, but is set to a dimensional range equal to or wider than the depth in the thickness direction to be processed in the fabric (deeper than the unevenness of the fabric surface). As a result, after the adjustment process, the surface of the fiber can be processed with the laser light of the short pulse laser up to the depth in the thickness direction to be processed in the fabric. As a result, even if the surface of the fabric is not flat, the surface of the fabric located within the focal depth can be appropriately processed. At this time, for example, a fine structure can be imparted to the surface of the fiber by interference of laser light or multi-beam laser light (multi-beam interference), or interference between the light diffused by the laser light on the surface of the fabric and the laser light (surface wave interference). Due to the characteristics of its fine structure, not only fibers but also fabrics made from the fibers can exhibit various functions, including water repellency, hydrophilicity, and stain resistance.

(2) The method for processing the surface of the fabric described in (1) above, in which the concave, convex or concave-convex structure formed on the surface of the fabric by the processing is a fine structure in the micrometer range or less.

In this method for processing the surface of fabric, the concave, convex or concave-convex structure formed on the surface of the fabric by processing is a fine structure in the micrometer range or less. Here, the micrometer range is a square area with one side measuring 10 μm. Therefore, each convex or concave portion in the fine structure has a size that fits within a square area with one side measuring 10 μm. Such a fine structure can better express various functions, including water repellency, hydrophilicity and stain resistance, not only in fibers but also in fabrics composed of fibers.

(3) The method for processing the surface of fabric described in (1) or (2) above, in which at least a part of the processing is performed by an interference method using the laser light of the short pulse laser, and the interference method is a multi-beam interference method using at least two or more laser lights focused at the same focus, or a surface wave interference method.

In this method for processing the surface of fabric, at least a portion of the processing is performed by interference using the interference of laser light output from a short-pulse laser. The interference method is multi-beam interferometry or surface wave interferometry. As a result, in the area processed by interference, the surface of the fabric in the range of the laser light can be processed into a fine structure, and various functions can be more fully expressed not only in fibers but also in fabrics composed of fibers.

(4) The method for processing the surface of the fabric according to any one of (1) to (3) above, in which the structure processed on the surface of the fabric is a periodic microstructure, including periodically formed convex portions, and small convex portions and small concave portions periodically formed on the surface of the convex portions at a period smaller than the period of the convex portions.

In this method for surface treatment of fabric, the structure formed on the surface of the fabric is a periodic microstructure that includes periodically formed convex portions and small convex portions and small concave portions formed on the surface of the convex portions at a period smaller than the period of the convex portions. In other words, the periodic microstructure has two periodic structures. Due to the characteristics of this microstructure, various functions, particularly water repellency, can be expressed not only in fibers but also in fabrics composed of fibers.

(5) The method for surface processing of fabric described in any one of (1) to (4) above, in which the pulse interval of the laser light of the short pulse laser is widened by software, electronic circuitry, or mechanical means.

In this method of fabric surface processing, the pulse interval of the laser light of the short pulse laser is widened by software, electronic circuitry, or mechanically. In this way, by widening the pulse interval of the laser light and providing time for the heat stored in the fabric (fiber) by the laser light during processing to be dissipated, it is possible to more appropriately process the surface of the fabric while suppressing melting of the fabric (fiber). In other words, even for fabrics (fibers) that tend to store heat, it is possible to more appropriately process the surface of the fabric while suppressing melting of the fabric (fiber).

The present invention provides a surface processing method that uses a laser to perform an appropriate surface processing on fabric, thereby forming fabric with desired characteristics.

1 is a block diagram showing an example of the configuration of a processing device used in a fabric surface processing method according to an embodiment. FIG. FIG. 2 is a schematic diagram showing a laser light irradiation pattern in the surface processing method. FIG. 1 is a schematic diagram showing the relationship between the focal depth and the material in a surface processing method. FIG. 1 is a schematic diagram showing the relationship between the focal depth and the material in a conventional surface processing method. 1 is a schematic diagram showing the principle of surface wave interference processing in a surface processing method. 1 is a schematic diagram showing the principle of two-beam interference in a surface processing method. 1 is a block diagram showing an example of the configuration of a processing device used for multi-beam interference processing in a surface processing method. FIG. 2 is a schematic diagram showing a method for continuously processing a cloth in a surface processing method. 13 is a table showing the observation results of the surface condition of the fabric when pulsed with one light beam. 13 is a table showing the results of SEM observation of the surface state of a black substrate when pulsed with one light beam. 1 is a table showing the relationship between the contact angle and the surface state of a black substrate when pulsed with one light beam. 1 is a table showing the observation results of the surface state of the fabric after multi-beam interference processing. FIG. 1 is a diagram showing the surface state of a material used in multi-beam interference processing before processing. 13 is a table showing changes in contact angle over time due to multi-beam interference processing.

The surface processing method for fabric according to the embodiment will be described below with reference to the drawings. This surface processing method is a method for processing a three-dimensional area of the surface of a fabric that is composed of fiber bundles and has a thickness, using a short pulse laser. However, the present invention is not limited to the following embodiment, and it is possible to combine with other technologies, substitute, modify, etc. as appropriate within the scope that does not deviate from the purpose and intent of the present invention.

First, an example of the configuration of a processing device used in the surface processing method of the embodiment will be described. FIG. 1 is a block diagram showing an example of the configuration of a processing device used in the surface processing method. The processing device includes a laser 1 including a laser body 1a, an optical system 2, and a focal depth adjustment unit 3, a processing table 5, and a control device 6.

The laser body 1a is a laser oscillator capable of emitting a short-pulse laser light LB. The type of the laser body 1a is not particularly limited, and examples thereof include gas lasers such as carbon dioxide lasers and excimer lasers, solid-state lasers such as Yb:YAG lasers, Yb:KGW lasers, Yb:KYW lasers, and Ti:Al ₂ O ₃ (sapphire) lasers, semiconductor lasers, and fiber lasers. In this embodiment, the laser body 1a is a Yb:KGW laser.

From the viewpoint of ease of non-thermal processing (ablation processing), the pulse width of the laser light LB (short pulse) can be, for example, 1 femtosecond or more and less than 1000 picoseconds, preferably 10 femtoseconds or more and less than 1000 femtoseconds, and more preferably 100 femtoseconds or more and 500 femtoseconds or less. If the pulse width is too long, the fabric is easily thermally processed (photothermal processing) and non-thermal processing (ablation processing) becomes difficult. If the pulse width is too short, processing the fabric itself becomes difficult. In this embodiment, the pulse width of the laser light LB is 100 femtoseconds or more and less than 500 femtoseconds.

The wavelength of the laser light LB can be, for example, in the infrared region, visible light region, or ultraviolet region, with the visible light region and ultraviolet region being preferred. By making the wavelength of the laser light LB in the visible light region or ultraviolet region, the energy of the laser light LB can be more easily absorbed by the fibers that make up the fabric. This allows the laser light LB to process the fibers of the fabric more stably. In this embodiment, the wavelength of the laser light LB is 515 nm (green) in the visible light region.

Other conditions of the laser light LB can be appropriately selected according to the processing content of the material. In this embodiment, the respective conditions are as follows.
Average power (Pav): 0.1 to 5W
Repetition frequency (f): 1 to 60 kHz
Spot diameter (d): 1 to 50 μm
1 shot pulse energy (E): 0.01 to 50 μJ/shot
Peak power (Pp): 0.1 to 200 MW
Fluence (F): 0.1 to 50 J/ ^cm2
Intensity (I): 1.0×10 ¹¹ to 5×10 ¹⁵ W/cm ²

The optical system 2 forms an optical path that guides the laser light LB emitted from the laser body 1 to the focal depth adjustment unit 3. There are no particular limitations on the optical system 2, and examples include known devices such as mirrors, half mirrors, beam splitters, diffraction gratings, expanders, collimators, and combinations of these (the figure shows an example of a single mirror). It may also include a device (pulse picking device) that widens the interval between pulses of the laser light LB using software, electronic circuits, or mechanically.

The focal depth adjustment unit 3 adjusts the focal depth of the laser 1. There are no particular limitations on the means for adjusting the focal depth of the laser 1. Here, the theoretical focal depth Z is calculated by the following formula.
Z={2π・(d/2) ² }/(M ²・λ) …(A)
d=4M ²・λ・f/π・D・(exp) …(B)
The meaning of each parameter is as follows:
d: spot diameter of laser light LB ^M2 : beam quality λ: wavelength of laser light LB f: focal length of objective lens 4 D: diameter of laser light LB before focusing exp: 1
In this embodiment, the wavelength λ of the laser light LB is kept constant, and the focal depth adjustment unit 3 changes the focal depth of the laser 1 to a deeper or shallower depth by replacing the objective lens (condensing lens) 4 based on the unevenness of the surface of the fabric P.

The processing table 5 is a table on which the fabric P to be processed is placed and fixed, and may be, for example, a known X-Y table. The processing table 5 is moved so that the laser light LB irradiates the desired position on the fabric P when processing the fabric P. However, in order to have the laser light LB irradiate the desired position on the fabric P when processing the fabric P, the irradiation direction of the laser light LB may be moved (swept) by the optical system 2 including a laser scanning system.

The control device 6 is connected to at least the laser body 1, the optical system (equipment) 2, the focal depth adjustment unit 3, and the processing table 5 by wire and/or wirelessly (not shown). The control device 6 controls the operation of the laser body 1, the optical system 2, the focal depth adjustment unit 3, and the processing table 5 to perform surface processing of the fabric using a laser beam. The control device 6 is an information processing device such as a computer, a tablet terminal, or a smartphone. The control device 6 executes a computer program installed in the control device 6 to cause the control device 6 to realize multiple functions. The multiple functions include a function to control the laser body 1, the optical system 2, the focal depth adjustment unit 3, and the processing table 5. Note that the focal depth adjustment unit 3 may not be connected to the control device 6, and the objective lens 4 may be replaced by another means (e.g., manually).

Figure 2 is a schematic diagram showing the irradiation pattern of the laser light LB in the surface processing method. The upper side of Figure 2 (a) and Figure 2 (b) shows the irradiation pattern of the laser light LB perpendicular to the irradiation direction, and the lower side shows the energy distribution of the laser light LB (vertical axis: energy I, horizontal axis: time t). Figure 2 (c) shows an example of an irradiation pattern actually used to process the fabric P.

When a laser beam LB with a spot diameter d is irradiated onto fabric P, a circular irradiation pattern is formed on fabric P by one shot of laser beam LB. The energy distribution of the laser beam LB at that time is a curved line in which the energy is highest at the center of the circle formed by the laser beam LB and decreases toward the edge of the circle. Therefore, if the irradiation patterns of the laser beam LB are not overlapped with each other (FIG. 2(a)), the energy of the laser beam LB becomes extremely low in the area where the adjacent irradiation patterns contact each other, and an area where the processing of the fabric P is insufficient may occur. Therefore, when the laser beam LB is irradiated onto fabric P, the irradiation patterns of the laser beam LB are overlapped with each other (FIG. 2(b)). The degree of overlap, that is, the ratio of the overlap length τ of the diameters of adjacent circles to the spot diameter d, is defined as the overlap rate. Therefore, the overlap rate = τ/d (%). In the example of FIG. 2(a), the diameters of adjacent circles do not overlap, so the overlap rate is 0%. In the example of Figure 2(b), the diameters of adjacent circles overlap by 50%, so the overlap rate is 50%.

In the irradiation pattern actually used for processing the fabric P, the laser light LB is irradiated in the in-plane direction of the fabric P, i.e., in the xy direction. Therefore, there is an overlap rate in the x direction and an overlap rate in the y direction. In the example of FIG. 2(c), if the overlap length of the diameters of adjacent circles in the x direction is τ _x , the overlap rate τ _x /d (%) is 40%. On the other hand, if the overlap length of the diameters of adjacent circles in the y direction is τ _y , the overlap rate τ _y /d (%) is 50%. Each overlap rate can be changed as appropriate according to the processing content of the fabric.

Next, a method for processing the surface of fabric according to an embodiment will be described. This surface processing method includes an adjustment step for adjusting the focal depth so that the size of the unevenness of the surface of the fabric falls within the range of the focal depth of the short pulse laser. After adjusting the focal depth, the three-dimensional area of the surface of the fabric is surface processed using a short pulse laser, thereby allowing the desired processing to be performed on the surface of the fabric.

The focal depth can be adjusted by adjusting at least one of the wavelength λ of the laser light LB, the focal length f of the objective lens 4, and the diameter D of the laser light LB before focusing. In this embodiment, the focal depth adjustment unit 3 in the processing device of FIG. 1 selects and attaches an objective lens 4 having an appropriate focal length f from multiple objective lenses (focusing lenses) with different focal lengths f based on the magnitude of unevenness of the fabric P. This allows the focal depth of the laser 1 to be adjusted to a focal depth that allows the surface of the fabric P to be processed with the laser light LB.

Figure 3 is a schematic diagram showing the relationship between the focal depth and the fabric in a surface processing method, and Figure 4 is a schematic diagram showing the relationship between the focal depth and the fabric in a conventional surface processing method.

As shown in FIG. 4, the magnitude of unevenness in the thickness direction on the surface S1 of the fabric P (the surface exposed to the outside of the fabric P) is about D0. In other words, even if the surface of the fiber (including the case of a fiber bundle) Q itself is generally flat, the surface S1 of the fabric P in which the fiber Q is formed into a woven fabric, knitted fabric, etc. is not necessarily flat. Therefore, in conventional surface processing methods, the focal depth D2 of the laser (range of spot diameter d) is smaller than the magnitude D0 of unevenness in the thickness direction on the surface S1 of the fabric P. Therefore, in conventional surface processing methods, it is difficult to uniformly process the fabric P in its in-plane direction and thickness direction, i.e., in a three-dimensional area.

Therefore, as shown in FIG. 3, in the surface processing method of the fabric P in this embodiment, the focal depth (range of spot diameter d) of the laser 1 is adjusted in the adjustment process so that the size D0 of the unevenness in the thickness direction on the surface S1 of the fabric P falls within the range of the focal depth D1 of the laser 1. Specifically, for example, when the size D0 of the unevenness of the surface S1 of the fabric P is large, the range of the focal depth D1 is adjusted to be expanded so that the size D0 of the unevenness of the surface S1 is included. That is, instead of setting the focal depth D1 to a dimensional range close to the unevenness of the surface S1 of the fabric P, it is set to a dimensional range equal to or wider than the depth in the thickness direction to be processed in the fabric P (deeper than the unevenness of the surface S1 of the fabric P). That is, the unevenness of the surface S1 of the fabric P is contained within the focal depth. As a result, after the adjustment process, the surface of the fiber Q can be processed to the depth in the thickness direction to be processed in the fabric P with the laser light LB of the laser 1. Therefore, even if the surface S1 of the fabric P is not flat, the fabric P located within the focal depth can be appropriately surface-processed.

At this time, for example, a fine structure can be imparted to the surface of the fiber Q by the laser light LB, interference between the laser light LB and light scattered or diffusely reflected by the surface S1 of the fabric P (surface wave interference), or interference of multiple beams of laser light LB (multi-beam interference). Due to the characteristics of this fine structure, various functions can be expressed not only in the fiber Q but also in the fabric P composed of the fiber Q, including water repellency, hydrophilicity, and stain resistance.

In the surface treatment method for fabric in this embodiment, the concave, convex or concave-convex structure formed on the surface S1 of the fabric P is a fine structure in the micrometer range or less. Here, the micrometer range is a square area with one side measuring 10 μm. Therefore, each convex or concave portion in the fine structure has a size that fits within a square area with one side measuring 10 μm. Such a fine structure can better express various functions, including water repellency, hydrophilicity and stain resistance, not only in fibers but also in fabrics composed of fibers.

Next, we will explain surface wave interference. Figure 5 is a schematic diagram showing the principle of surface wave interference processing in a surface processing method. However, the diagram on the left shows the processing process of fabric P using laser 1, and the diagram on the right shows the state of fabric P after the processing process. The graph in the diagram on the left shows the relationship between the intensity I and time t for the laser light LB irradiated by laser 1.

As shown in the left figure, the laser 1 moves in the direction indicated by the straight arrow (y direction) at a predetermined moving speed, and irradiates the fabric P with laser light LB having an intensity equal to or greater than a predetermined threshold _I0 required for causing surface wave interference at a predetermined interval. Specifically, the laser 1 irradiates the fabric P with laser light LB so as to achieve a predetermined y-direction overlap ratio while moving in the y direction within a predetermined range from the front side to the back side (irradiation step). Next, the laser 1 moves a predetermined distance in the x direction so as to achieve a predetermined x-direction overlap ratio (movement step). These irradiation and movement steps are then repeated until the entire area to be processed on the fabric P is processed. As a result, the area to be processed on the fabric P is processed, for example, with an irradiation pattern as shown in FIG. 2(c).

In the irradiation process, the laser 1 further moves in the y direction while sweeping the laser light LB in a spiral shape on an elliptical orbit. However, the width of the ellipse is set to be approximately the size of the spot diameter in the x direction and smaller than the spot diameter in the y direction. At this time, the scattered light from the laser light LB scattered on the surface S1 of the fabric P interferes with the laser light LB, i.e., surface wave interference occurs, and interference fringes are formed. Then, by sweeping the laser light LB on an elliptical orbit, adjacent interference fringes caused by adjacent pulsed laser light LB can be synchronized with each other. This allows interference fringes to be generated uniformly on the surface S1, and a periodic microstructure can be formed on the surface S1 of the fabric P.

As shown in the figure, the following structure can be formed as a periodic microstructure on the surface S1 of the fabric P. That is, it is a microstructure that includes an uneven portion W1 having periodically formed concave and convex portions, and a small uneven portion W2 having small concave and small convex portions periodically formed on the surface of the convex portion with a period smaller than the period of the uneven portion W1.

Next, we will explain multi-beam interference. Figure 6 is a schematic diagram showing the principle of two-beam interference in the surface processing method. As shown in Figure 6, the laser light LB of the laser body 1a is incident on an optical system 10 including a half mirror 11 and mirrors 12a and 12b, and is split into laser lights LBa and LBb by the half mirror 11. The split laser lights LBa and LBb are reflected by mirrors 12a and 12b, respectively, and overlap and interfere with each other on the surface S1 of the fabric P, generating interference fringes. The interference fringes can form a periodic fine structure on the surface S1 of the fabric P. In this case, although not shown, the focal depth adjustment unit 3 is arranged, for example, behind the mirror 12a for the laser light LBa and behind the mirror 12b for the laser light LBb. In the case of multi-beam interference, for example, four-beam interference, the above-mentioned laser lights LBa and LBb are further split into two by half mirrors, and the four split laser lights are overlapped on the fabric, which can be realized.

Figure 7 is a block diagram showing an example of the configuration of a processing device used for multi-beam interference processing in a surface processing method. The laser light LB output from the laser body 1a passes through an optical system 20 including a Galilean expander 21, a polarizing beam splitter 22, a spatial light phase modulator 23, a collimator 24, and a Keplerian expander 25, and is irradiated onto the material P via a mask 26 and a focal depth adjustment unit 3 (objective lens 4). When this processing device is used in a surface processing method using two-beam interference, the optical system 10 in Figure 6 is disposed between the Keplerian expander 25 and the focal depth adjustment unit 3 (objective lens 4).

In this case, too, a periodic microstructure can be formed on the surface S1 of the fabric P, comprising an uneven portion having periodically formed recesses and protrusions, and a small uneven portion having small recesses and small protrusions periodically formed on the surface of the protrusions at a period smaller than the period of the uneven portion.

In the surface processing method of this embodiment, at least a portion of the processing is performed by an interference method that uses the interference of the laser light LB output from a short pulse laser. The interference method is the surface wave interference method or the multi-beam interference method as described above. As a result, in the area processed by the interference method, the surface S1 of the fabric P in the range of the laser light LB can be processed into a periodic microstructure, and various functions can be more fully expressed not only in the fiber Q but also in the fabric P composed of the fiber Q.

Here, in the surface processing method of this embodiment, the periodic microstructure formed on the surface S1 of the fabric P includes periodically formed convex portions, and small convex portions and small concave portions formed on the surface of the convex portions at a period smaller than the period of the convex portions. In other words, the periodic microstructure has two periodic structures. Due to the characteristics of this microstructure, various functions, particularly water repellency, can be expressed not only in fibers but also in fabrics composed of fibers.

In addition, in the surface processing method of this embodiment, the pulse interval of the laser light LB of the laser 1 can be widened by software or electronic circuitry. By widening the pulse interval of the laser light, it is possible to provide time for the heat stored in the fabric P (fiber Q) by the laser light LB during processing to be dissipated. This makes it possible to more appropriately process the surface S1 of the fabric P while suppressing melting of the fabric P (fiber Q). In other words, even for fabric P (fiber Q) that easily accumulates heat, it is possible to more appropriately process the surface S1 of the fabric P while suppressing melting of the fabric P (fiber Q).

In the above-mentioned method for fabric surface treatment, a first fabric contained in a product such as clothing may be prepared as the fabric for the above-mentioned adjustment process. Then, the above-mentioned surface treatment may be performed on the surface of the first fabric. In other words, this method for fabric surface treatment can also be applied as a post-processing step after the product is manufactured. In this way, a desired structure such as a microstructure can be imparted to the surface of any fabric in the product by performing a surface treatment in a post-processing step. Therefore, various functions required for the product can be imparted to the necessary parts of the product.

Figure 8 is a schematic diagram showing a continuous fabric processing method in a surface processing method. This figure shows a method of carrying out the surface processing method as shown in Figure 5 above on a continuous fabric P. In the example of this figure, a processing device 30 equipped with rolls 31 and 32 is used instead of the processing table 5. In this case, the direction of irradiation of the laser light LB is swept over the fabric P by an optical system 2 including a laser scanning system. The fabric P is stretched between the rolls 31 and 32, and is continuously sent out from the roll 31 and processed by the laser light LB. As a result, a periodic microstructure W is formed on the surface S1 of the fabric P.

(1) Pulse processing with one light beam Figure 9 is a table showing the observation results (optical microscope photographs) of the surface state of fabrics in pulse processing with one light beam. This figure shows the relationship between the surface state of each fabric that was subjected to surface processing using the processing device shown in Figures 1 and 5 and the fluence. However, the area where surface processing was attempted is shown by a two-dot chain line.

However, the characteristics of the fabric are as follows:
Fabric type/material/surface texture:
White fabric (TN) / Nylon 66 / Approx. 30 μm
Red fabric (KA) / Nylon 66 / Approx. 40 μm
Black fabric (N456-P) / Nylon 6 / Approx. 30 μm
The maximum surface unevenness was measured by SEM observation.

On the other hand, the processing conditions using the laser 1 are as follows.
Wavelength: 515 nm
Average power: 0.316W
Pulse width: 234 fs
Repetition frequency: 1.25 to 12.5 kHz
Spot diameter: 8 μm
1 shot pulse energy: 0.07 to 5.27 μJ/shot
Peak power: 0.3-22.5MW
Fluence: 0.1 to 10 J/ ^cm2
Strength: 6.0×10 ¹¹ to 4.5×10 ¹³ W/cm ²
Overlap rate: 50%
Lens specifications: Focal length: f40
Depth of focus: ±96.5μm

As shown in the figure, under the above conditions, it was confirmed that the surface of the fabric was processed in the area where surface processing was attempted, regardless of the type of fabric, despite the unevenness of the surface. It was also found that the higher the fluence, the more the surface processing of the fabric progresses and the change in the surface condition. Note that when using a lens with a focal length of f20 (depth of focus ±5 μm), the depth of focus is too narrow, making it difficult to process the fiber surface located outside the depth of focus.

Figure 10 is a table showing the results of SEM observations (SEM photographs) of the surface condition of black fabric when pulsed with one beam of light. This figure shows the relationship between the surface condition observed under magnification and the fluence for the black fabric in Figure 9.

As shown in the figure, it was confirmed that a microstructure with periodic concave and convex portions was formed on the black fabric by surface processing. It was also confirmed that by increasing the fluence, surface wave interference occurred and a finer uneven microstructure could be formed on the fiber surface of the black fabric. Although not shown, it was also confirmed that a microstructure with periodic concave and convex portions was formed on the white and red fabric by surface processing, just like the black fabric, and that by increasing the fluence, a finer uneven microstructure could be formed on the fiber surface of the white and red fabrics.

Fig. 11 is a table showing the relationship between the apparent contact angle and the surface condition of the black substrate in pulse processing with one light beam. This figure shows the relationship between the apparent contact angle and the surface condition for the black substrate in Fig. 10. However, the surface condition of the black substrate with a fluence of 0.5 J/ ^cm2 is approximately the same as that with a fluence of 0.2 J/ ^cm2 .

As shown in the figure, the black fabric surface-treated with a fluence of 0.5 J/ ^cm2 had a larger apparent contact angle (117°→125.2°) than the untreated black fabric, indicating that the water repellency was increased (similar at 0.2 J/ ^cm2 ). On the other hand, the black fabric surface-treated with a fluence of 1 J/ ^cm2 had a smaller apparent contact angle (117°→106.2°) than the untreated black fabric, indicating that the hydrophilicity was increased.

The reason for this is thought to be that in the black fabric whose surface was treated with a fluence of 0.5 J/ ^cm2 , a periodic microstructure (uneven structure) was created, improving water repellency. On the other hand, in the black fabric whose surface was treated with a fluence of 1.0 J/ ^cm2 , a structure effective in improving water repellency was not formed, and numerous grooves and gaps were created, increasing the contact area with water, which is thought to have increased hydrophilicity.

However, the apparent contact angle was measured under the following conditions.
Contact angle meter: Fully automatic contact angle meter DM-701 (manufactured by Kyowa Interface Science Co., Ltd.)
Measurement solvent: distilled water Volume: 2 μL
Gauge used: 28G, fluororesin Analysis method: Droplet method Measurement environment: 23°C, 30% RH
Specifically, 2 μL of distilled water was placed on the fabric to be measured using a contact angle meter, and the apparent contact angle was measured at five points on the fabric, and the left and right contact angles were measured at each point, giving a total of 10 measurement results, and the average value was taken as the contact angle.

(2) Multi-beam pulse processing Figure 12 is a table showing the observation results (optical microscope photographs) of the surface state of the fabric in multi-beam interference processing. This figure shows the surface state of the fabric subjected to two-beam interference processing and four-beam interference processing using the processing devices shown in Figures 7 and 8, respectively. Figure 13 is a diagram showing the surface state (unprocessed) of the fabric used in multi-beam interference processing, and shows an optical microscope photograph.

However, the characteristics of the fabric are as follows:
Fabric type/material/surface texture:
Refined cloth (N222) / nylon / approx. 50 μm
The maximum surface unevenness was measured by SEM observation.

On the other hand, the processing conditions using the laser 1 are as follows.
Wavelength: 515 nm
Average power: 1.68W (2 luminous flux), 1.75W (4 luminous flux)
Pulse width: 299 fs
Repetition frequency: 10 kHz x 1/50 (pulse picking) = 200 Hz
Spot diameter: about 140 μm
1 shot pulse energy: 29 to 31 μJ/shot
Peak power: 97-104MW
Fluence: 0.19 to 0.20 J/ ^cm2
Strength: 6.3×10 ¹¹ ~ 6.7×10 ¹¹ W/cm ²
Lens specifications: Focal length: f20
Depth of focus: ±25 μm

As shown in the figure, under the above conditions, it was confirmed that the surface of the fabric was processed in the area where surface processing was attempted, regardless of the surface unevenness, both with two and four beams. It was also found that the period of the periodic microstructure formed on the surface of the fabric changes depending on the number of beams. Specifically, the surface condition of the fabric was smooth before surface processing (Figure 13), but after two-beam interference processing, black line-like grooves like diagonal lines were formed by interference, and after four-beam interference processing, black dot-like recesses like dots arranged in a lattice pattern were formed by interference (Figure 12). Although not shown, if the focal depth was smaller than the above conditions, surface processing was not possible. Specifically, surface processing was not possible when the objective lens 4 had a focal length of f10 and a focal depth of ±11 μm.

Although not shown, if the surface of the fabric is processed without thinning out the pulses of the laser light LB, heat accumulates in the fabric during the surface processing, causing part of the fabric surface to melt. Therefore, in this embodiment, by thinning out the pulses of the laser light LB and performing the surface processing, it is possible to prevent the fabric surface from melting, as shown in the figure.

Figure 14 is a table showing the change over time in contact angle in multi-beam interference processing. This figure shows how the apparent contact angle changes over time for the unprocessed fabrics in Figures 12 and 13 and the fabrics that have been processed with two-beam interference processing and four-beam interference processing. Note that the contact angle was measured by placing 2 μL of distilled water on the fabric to be measured, starting measurement 1 second after the drop landed, and observing for 21 seconds.

As shown in the figure, the contact angle is significantly smaller with multi-beam interference processing compared to untreated fabric (114° → 46°, 52°: after 1 second), and therefore the hydrophilicity of the fabric is significantly increased. This is thought to be because the multi-beam interference processing creates numerous grooves and gaps on the surface of the fabric, increasing the area of contact with water and thus increasing hydrophilicity.

Q Fiber bundle P Fabric S1 Surface D0 Size of surface irregularities D1 Depth of focus

Claims (6)

A method for processing a surface of a fabric, the method comprising the steps of: processing a surface of a fabric that is made of fiber bundles and has a thickness, using a short pulse laser;
an adjustment step of adjusting the focal depth so that the size of the surface irregularities of the fabric falls within the range of the focal depth of the short pulse laser ;
The structure formed on the surface of the fabric by the processing is a periodic microstructure,
Periodically formed convex portions;
small convex portions and small concave portions are periodically formed on the surface of the convex portion at a period smaller than the period of the convex portion;
Including,
Fabric surface treatment method. The concave structure, convex structure or concave-convex structure formed on the surface of the fabric by the processing is a fine structure in the micrometer range or less;
A method for surface treatment of the fabric according to claim 1. At least a part of the processing is performed by wave interference using the laser light of the short pulse laser,
The interference method is a multi-beam interference method using at least two or more laser beams focused at the same focal point, or a surface wave interference method.
A method for surface treatment of the fabric according to claim 1 or 2. The pulse interval of the laser light of the short pulse laser is widened by software, electronic circuit, or mechanical means.
A method for treating the surface of a fabric according to any one of claims 1 to 3 . The angle of the laser beam of the short pulse laser to the surface of the fabric is perpendicular;
A method for treating the surface of a fabric according to any one of claims 1 to 4. The microstructure is formed in the fibers constituting the fabric along the longitudinal direction of the fibers.
A method for treating the surface of a fabric according to any one of claims 1 to 5.

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