Method and apparatus for producing fiber sheet

Abstract

To provide a method and apparatus for producing a fiber sheet, capable of forming the fiber sheet well by precisely depositing fibers at a desired position on a base material layer while producing the fibers by an electrospinning method.SOLUTION: The method for producing a fiber sheet in which a raw material liquid is discharged from a nozzle and fibers produced from the raw material liquid are deposited on a base material layer by an electrospinning method, includes arranging the substrate layer while spaced apart from the nozzle, placing a counter electrode on a surface of the substrate layer opposite to the nozzle, and applying voltage to make the nozzle and the counter electrode have different polarity from each other to form an electric field between the nozzle and the counter electrode, for a spinning step of spinning the raw material liquid discharged from the nozzle as a fiber in the electric field. In the spinning step, the counter electrode has, on a side of the substrate layer, a top part including a flat part in contact with the substrate layer and a portion configured to have no corners in an outward direction of the flat part in a planar direction. In the spinning step, the flat part and the substrate layer are brought into contact with each other to generate a potential difference between the nozzle and the flat part, and the spun fibers are deposited on an area of the substrate layer that has been brought into contact with the flat part.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing a fibrous sheet. [Background technology]

[0002] As a method for producing a fiber sheet, the electrospinning method is known. In the electrospinning method, a high voltage is applied to a raw material liquid (a solution or melt of a resin that is the raw material of the fiber) to spin and deposit ultrafine fibers (for example, fibers on the nanometer order) to form a fiber sheet. Several techniques related to this electrospinning method have been proposed so far. For example, the manufacturing method described in Patent Document 1 describes a technique for controlling the deposition state of fibers by changing the distance A between a collector electrode disposed opposite to the ejection portion of the raw material liquid and the substrate. The technique also describes a configuration in which the top of the collector electrode is curved, such as hemispherical. The manufacturing method described in Patent Document 2 describes a technique for changing the flying direction of the spinning dope by moving a counter electrode facing the spinning start part. From the viewpoint of controlling the flying direction, a configuration is described in which an acute-angled protrusion is provided on the collector side of the counter electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-167641 A [Patent Document 2] JP 2013-019073 A Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, the method for producing a fiber sheet by electrospinning utilizes the action of voltage. Specifically, electric charges gather on the surface of the liquid droplets at the tip of the nozzle, and the droplets are stretched by the electric repulsive force of the charges, deforming into a cone shape called a Taylor cone. When the electric repulsive force of the charges exceeds the surface tension of the liquid, the cone-shaped liquid is discharged from the tip of the nozzle and gradually stretched in a spiral, and spun toward the target area of ​​the substrate layer. However, since the fibers collected and deposited on the base layer and the fibers spun before deposition are charged with the same polarity, charge repulsion between them may occur. For example, when a positively charged raw material liquid L is discharged from a nozzle 1 and spun into fibers 8A (FIG. 13(A)), a positively charged collected fiber 8B is deposited at a target landing point 49 on the base layer 4 (FIG. 13(B)). Furthermore, since the fiber 8A spun thereafter is charged with the same positive polarity, charge repulsion occurs between the collected fiber 8B (FIG. 13(C)). This phenomenon may cause the fibers to be deposited outside the desired area on the base layer (for example, FIG. 13(C)), and it is therefore necessary to suitably control the deposition position.

[0005] In view of the above, the present invention relates to a method and an apparatus for producing a fiber sheet, which can produce fibers by an electrospinning method and deposit them accurately at desired positions on a base material layer to form a good fiber sheet. [Means for solving the problem]

[0006] The present invention provides a method for producing a fiber sheet by ejecting a raw material liquid from a nozzle and depositing fibers generated from the raw material liquid by an electrospinning method on a base material layer, the method comprising the steps of: disposing a counter electrode on a surface of the base material layer opposite the nozzle, the base material layer being disposed at a distance from the nozzle; applying a voltage to cause the nozzle and the counter electrode to have different polarities to each other, forming an electric field between the nozzle and the counter electrode; and performing a spinning process in which the raw material liquid ejected from the nozzle is spun into fibers by the electric field, the counter electrode has a top portion on the base material layer side, the top portion including a flat portion in contact with the base material layer and a portion configured so as not to have a corner on the outer side in a planar direction of the flat portion; and in the spinning process, the flat portion and the base material layer are brought into contact with each other to generate a potential difference between the nozzle and the flat portion, and the spun fibers are deposited in the abutted area of ​​the base material layer.

[0007] The present invention also provides an apparatus for producing a fiber sheet, comprising a nozzle for ejecting a raw material liquid, and a counter electrode arranged opposite to but spaced from the nozzle and generating an electric field between the nozzle, the apparatus having a means for applying a voltage so as to make the nozzle and the counter electrode have different polarities, and a space is provided between the nozzle and the counter electrode into which a base material layer can be introduced, the counter electrode having a top portion on the base material layer side, the top portion having a flat portion in contact with the base material layer, and a portion configured so as not to have any corners on the outer side of the flat portion in the planar direction. Effect of the Invention

[0008] According to the fiber sheet manufacturing method of the present invention, the fibers are generated by the electrospinning method and deposited with high accuracy at desired positions on the base material layer to form a fiber sheet. Furthermore, according to the fiber sheet manufacturing apparatus of the present invention, the above manufacturing method can be suitably carried out. [Brief description of the drawings]

[0009] [Figure 1]FIG. 2 is a schematic diagram illustrating a preferred embodiment of a manufacturing apparatus used in the method for manufacturing a fiber sheet according to the present embodiment. [Diagram 2] 1A is a side view showing a counter electrode together with a base material layer, and FIG. 1B is a plan view of the counter electrode. [Diagram 3] 1A is a side view showing an example in which the top of the opposing electrode is configured so as to have no corners on the outer side of the flat portion in the planar direction, and is made up of a combination of straight lines, and FIG. 1B is a plan view of the same example. [Figure 4] FIG. 13 is a partially enlarged side view showing another example in which the portion configured to have no corners is formed by combining straight line portions. [Diagram 5] FIG. 13 is a partially enlarged side view showing yet another example in which the portion configured to have no corners is formed by combining straight line portions. [Figure 6] FIG. 2 is a perspective view that illustrates an example of spinning fibers in an area of ​​a base material layer that is in contact with a flat portion of a counter electrode, according to the method for producing a fiber sheet of the present embodiment. [Figure 7] FIG. 13 is a perspective view showing an example of a nozzle moving mechanism and a state in which the nozzle is moved based on the mechanism. [Figure 8] FIG. 13 is a perspective view illustrating an example of a counter electrode moving mechanism. [Figure 9] FIG. 1A is an explanatory diagram showing a schematic diagram of the relationship between the process in which the electric potential of the collected fiber increases depending on the spinning time of the fiber and the process in which the absolute value of the voltage applied to the counter electrode is increased depending on the spinning time while spinning, and FIG. 1B is an explanatory diagram showing a schematic diagram of the state in which the potential difference is kept constant by increasing the absolute value of the voltage applied to the counter electrode. [Figure 10] FIG. 2 is a perspective view showing a schematic diagram of a preferred embodiment in which a plurality of nozzles are used to perform a plurality of spinning operations at once in the method for producing a fiber sheet according to the present embodiment. [Figure 11] FIG. 2 is a perspective view showing a ring electrode and a side electrode, which are preferably used when a plurality of nozzles are used to perform a plurality of spinning operations at once in the fiber sheet manufacturing method of the present embodiment, together with the nozzles. [Figure 12] 12 is an explanatory diagram illustrating an example of the action of the side electrode illustrated in FIG. 11. [Figure 13] 1(A) and 1(B) are explanatory diagrams that typically show a fiber spinning process in a method for producing a fiber sheet using a conventional electrospinning method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a preferred embodiment of the method and apparatus for producing a fibrous sheet according to the present invention will be described. The method for producing a fiber sheet according to the present embodiment involves ejecting a raw material liquid from a nozzle, and depositing fibers produced from the raw material liquid by an electrospinning method on a substrate layer. Specifically, the method involves the following spinning step. That is, a counter electrode is placed on the surface of the base material layer opposite the nozzle, the surface being spaced apart from the nozzle, and a voltage is applied to make the nozzle and the counter electrode have different polarities, thereby forming an electric field between the nozzle and the counter electrode, and a spinning process is performed in which the raw material liquid discharged from the nozzle is spun into fibers by the electric field.

[0011] In the fiber sheet manufacturing method of this embodiment, the counter electrode has a top portion including a flat portion in contact with the base layer and a portion configured to have no corners on the outer side of the flat portion in the planar direction of the flat portion, as described later. Using this counter electrode, in the spinning process, the flat portion and the base layer are brought into contact with each other to generate a potential difference between the nozzle and the flat portion. Then, the spun fiber is deposited in the abutted area of ​​the base layer. As described later, the potential difference with the nozzle is the largest at the position where the flat portion and the base layer are brought into contact with each other, and the spun fiber is likely to be concentrated at that position. This allows the fiber to be generated by the electrospinning method while being deposited with precision at a desired position on the base layer, thereby forming a fiber sheet in a good condition. The details of the counter electrode will be described later.

[0012] A preferred embodiment of a manufacturing apparatus for carrying out the manufacturing method of the fiber sheet of the present embodiment is, for example, as shown in Fig. 1. However, the apparatus is not limited to that shown in Fig. 1, and other apparatus configurations can be appropriately changed as long as they include the configuration of the counter electrode 2 and the arrangement of the counter electrode 2 and the base material layer 4 described below.

[0013] 1 (hereinafter, also referred to as electrospinning apparatus 100) includes a nozzle 1 that ejects a raw material liquid L, and a counter electrode 2 that is disposed facing the nozzle 1 while being spaced apart from the nozzle 1 and generates an electric field between the nozzle 1 and the counter electrode 2. The manufacturing apparatus 100 also includes a means (voltage application device) 3 for applying a voltage so that the nozzle 1 and the counter electrode 2 have different polarities, and includes a space 5 between the nozzle 1 and the counter electrode 2 into which a base material layer 4 can be introduced.

[0014] The discharged raw material liquid L is a raw material for fibers to be spun by the electrospinning method. For example, it may be a resin solution in which a resin is dissolved in a solvent, or a resin melt in which a resin is melted to a temperature equal to or higher than its melting point. The resin and solvent used in the resin solution may be any of various resins commonly used in electrospinning. For example, the resin may include one or more resins selected from polyester resin, acrylic resin, polystyrene resin, polyvinyl butyral resin, polyurethane resin, polyamide resin, polyimide resin, polyamideimide resin, etc. The polyester resin may contain one or more selected from polylactic acid, polyethylene terephthalate, polybutylene terephthalate, and the like. The acrylic resin may include one or more resins selected from polyacrylonitrile resin, polymethacrylic acid resin, and the like. The polyamide resin may include one or more selected from nylon and the like. Examples of the solvent include water, methanol, ethanol, 1-propanol, 2-propanol, hexafluoroisopropanol, 1-butanol, isobutyl alcohol, 2-butanol, 2-methyl-2-propanol, tetraethylene glycol, triethylene glycol, dibenzyl alcohol, 1,3-dioxolane, 1,4-dioxane, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-hexyl ketone, methyl-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, acetone, hexafluoroacetone, phenol, formic acid, methyl formate, ethyl formate, propyl formate, methyl benzoate, ethyl benzoate, propyl benzoate, and acetic acid. The solvent may include one or more selected from methyl, ethyl acetate, propyl acetate, dimethyl phthalate, diethyl phthalate, dipropyl phthalate, methyl chloride, ethyl chloride, methylene chloride, chloroform, o-chlorotoluene, p-chlorotoluene, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, dichloropropane, dibromoethane, dibromopropane, methyl bromide, ethyl bromide, propyl bromide, acetic acid, benzene, toluene, hexane, cyclohexane, cyclohexanone, cyclopentane, o-xylene, p-xylene, m-xylene, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, pyridine, and the like. The resin used in the resin molten liquid is a thermoplastic resin, and may include, for example, one or more selected from polyolefin resins, polyester resins, polyamide resins, vinyl polymers, acrylic polymers, nylon polymers, polyvinyl acetate, polyvinyl acetate-ethylene copolymers, and the like. The polyolefin resin may include one or more selected from polyethylene, polypropylene, ethylene-α-olefin copolymer, and the like. The polyester resin may contain one or more selected from polyethylene terephthalate, polybutylene terephthalate, polylactic acid, liquid crystal polymer, and the like. The vinyl polymer may include one or more selected from polyvinyl chloride, polyvinylidene chloride, polystyrene, and the like. The acrylic polymer may include one or more selected from polyacrylic acid, polyacrylic acid esters, polymethacrylic acid, polymethacrylic acid esters, and the like. The nylon-based polymer may include one or more selected from nylon 6, nylon 66, and the like. The resin solution or the resin melt may contain various additives. The raw material liquid L is held in a raw material supplying section (not shown) and can be supplied to the nozzle 1 in a constant amount in the raw material supplying section.

[0015] The nozzle 1 and the counter electrode 2 are made of a conductive material such as metal. The nozzle 1 can be of various structures and shapes that can be normally adopted, and the diameter of the tip of the nozzle 1 can be appropriately set as an outlet for the raw material liquid L according to the fiber diameter (for example, on the order of nanometers) of the fiber to be spun. The counter electrode 2 can also be of various structures that can be normally adopted, for example, a cylindrical metal rod. The voltage application device 3 has a voltage application unit 31 such as a DC high-voltage power supply and an electric wire 32, and the voltage application unit 31 is electrically connected to the nozzle 1 and the counter electrode 2 by the electric wire 32. In addition, the counter electrode 2 is grounded. This allows the nozzle 1 and the counter electrode 2 to have different polarities from each other by applying a voltage. Making the polarities different from each other means, for example, that when the polarity of the voltage applied to one is positive, the polarity of the voltage applied to the other is negative, or that the polarity is zero, i.e., no positive or negative.

[0016] In the manufacturing apparatus 100 shown in FIG. 1, a positive voltage is applied to the nozzle 1, and a negative voltage is applied to the counter electrode 2. However, the manufacturing method and manufacturing apparatus for a fiber sheet of the present invention are not limited to this, and various application forms can be adopted as described above. For example, a negative voltage may be applied to the nozzle 1, and a positive voltage may be applied to the counter electrode 2. Also, a positive or negative voltage may be applied to the nozzle 1, and the counter electrode 2 may have zero polarity, or vice versa. The zero polarity is achieved, for example, by grounding the nozzle 1 or the counter electrode 2 in the manufacturing apparatus 100 of FIG. 1.

[0017] In the manufacturing apparatus 100, the voltage application device 3 applies a voltage to make the nozzle 1 and the counter electrode 2 have different polarities, thereby forming an electric field in the space 5 between the nozzle 1 and the counter electrode 2. This space 5 is an area into which the base material layer 4 can be introduced, and is an area in which the raw material liquid L discharged from the nozzle 1 is spun into fibers.

[0018] In the space 5 where an electric field is formed (hereinafter, also referred to as the electric field space), a potential difference is generated between the nozzle 1 and the counter electrode 2. At the tip of the nozzle 1, charges are collected on the surface of the droplets of the raw material liquid L, and the droplets are stretched by the electric repulsive force of the charges, and are deformed into a cone shape called a Taylor cone. When the electric repulsive force of the charges exceeds the surface tension of the raw material liquid L, the cone-shaped raw material liquid L is discharged from the tip of the nozzle 1 into the electric field space 5. The discharged raw material liquid L is charged, and is attracted toward the counter electrode 2 by an electric attraction (electrostatic attraction) based on the potential difference in the electric field space 5. At that time, the discharged raw material liquid L is influenced by various forces such as an electric self-repulsive force within the charged raw material liquid L in addition to an external electric attraction based on the potential difference in the electric field space 5, and is gradually drawn in a spiral and repeatedly stretched, and is spun toward the base layer 4 on the counter electrode 2. In this way, the above-mentioned spinning process in the manufacturing method of the fiber sheet of this embodiment can be performed.

[0019] 2(A) and 2(B), the counter electrode 2 used in the spinning process has a flat portion 21 on the side of the base layer 4 that contacts the base layer 4, and a top portion 23 that has a portion configured to have no corners on the outer side in the planar direction of the flat portion 21 (hereinafter also referred to as the edge portion) 22. Here, the "flat" of the flat portion 21 refers to a shape that can come into planar contact with the base layer 4. As long as it meets this definition, it is considered to be flat even if it has fine (e.g., micrometer) irregularities such as surface roughness.

[0020] 2(B), in the counter electrode 2, the flat portion 21 in contact with the base material layer 4 is located in the center of the area of ​​the top portion 23 when viewed in plan on the base material layer 4 side. At the outer edge portion 22 in the planar direction, the above-mentioned portion configured to have no corners is disposed so as to surround the flat portion 21. This counter electrode 2 generates a potential difference between the flat portion 21 and the nozzle 1. Usually, in an electric field, the edge of a general counter electrode is a corner, and this part is likely to concentrate the electric field like a lightning rod, and the charge is likely to be biased. If the fibers gather at the corner where the electric field is likely to concentrate, it may be difficult to control the collection at the targeted position. In contrast, the counter electrode 2 used in this embodiment is arranged at the edge 22 on the outer side of the flat part 21 in the planar direction, so that the electric field is prevented from concentrating at the edge 22. In addition, the flat part 21 has a constant distance from the nozzle 1, and the potential difference with the nozzle 1 is likely to be larger and more uniform in the top 23. The part configured to have no corners can be of various shapes that can avoid the concentration of the electric field as described above. For example, as shown in FIG. 2(A), it can be a curved part whose outer surface is curved away from the base layer 4.

[0021] The above-mentioned "corner" refers to a portion on the surface of the apex 23 that protrudes outward at an angle sufficient to concentrate the electric field. The "portion configured to have no corner" is a portion that does not include the above-mentioned portion that protrudes outward, and preferably extends at the edge 22 so as to move away from the base layer 4 at a gentle angle. The portion that is configured to have no corners may be made up of a curved surface that is smoothly connected to the flat portion 21, as shown in FIG. 2(A), or may be made up of a combination of straight line portions when viewed from the side. When the "portion configured to have no corners" is configured by combining straight line portions, the intersections between the straight line portions (corresponding to the change points that change the straight line portions described below) do not protrude outward or the angle at which they protrude outward exceeds 90°. In this case, the intersections may include those that protrude inward. The intersections also include intersections with flat portion 21. If the intersections do not protrude outward at an acute angle of 90° or less, they do not act as lightning rods, and unexpected discharges can be avoided.

[0022] An example of a case where straight lines are combined to form the "portion configured to have no corners" is shown in Fig. 3. In Fig. 3, there is a change point K at which straight line portion 22A changes so as to move away from base layer 4 as it moves outward from straight line portion 21A on the surface of flat portion 21. The magnitude θ of the change point K (the intersection angle between the straight line portions) is preferably 175° or less, more preferably 160° or less, and even more preferably 150° or less, from the viewpoint of preventing the distance between the base layer 4 and portions other than the flat portion 21 from becoming too close and controlling the collection of fibers at a targeted position. Moreover, the magnitude θ of the change point K is preferably 95° or more, more preferably 110° or more, and even more preferably 120° or more, from the viewpoint of preventing the concentration of fibers at the change point K and forming a nanofiber sheet without collection unevenness. The change point K may be a plurality of change points K1, K2, etc., which are formed by changing the straight line as the straight line portion 22A moves outward as shown in Fig. 4. In this case, the magnitudes θ1, θ2 of the change points K are preferably within the range of the magnitude θ described above. Also, as shown in FIG. 5, after a change point K is formed once, a straight line portion 22B may proceed parallel to a straight line portion 21A on the surface of the flat portion 21, and a change point K may be formed again. Furthermore, when there are a plurality of change points K, the intersections with the flat portion 21 do not have to be the change points K, and the change points K may be gentle curves.

[0023] As described above, at the top 23 of the counter electrode 2, the flat portion 21 and the base material layer 4 are in contact with each other. Therefore, charges of a polarity different from that of the nozzle 1 tend to flow in this contact region (hereinafter, the contact region) 41. On the other hand, in a region 42 other than the contact region 41 of the base material layer 4, there is no electric field concentration at the edge portion, and the region 42 tends to be charged with the same polarity as the fibers 8. In other words, charge repulsion tends to occur between the fibers 8 and the region 42. As a result, the contact region 41 becomes the region that exerts the strongest electric attraction with respect to the electric field space 5 among the planar regions of the base material layer 4. In this way, in the spinning process described above, the flat portion 21 and the base layer 4 are brought into contact with each other to generate a potential difference between the nozzle 1 and the flat portion 21. By carrying out the spinning described above while maintaining this contact state, the fibers 8 can be concentrated in the planar region of the contact region 41 of the base layer 4. In the region 42 of the base layer 4 other than the contact region 41, the deposition of the fibers 8 can be prevented by the charge repulsion described above. Furthermore, since the charge of the flat portion 21 is most strongly applied to the contact region 41 of the base layer 4, the charge of the fibers 8 having a different polarity (the charge of the nozzle 1) is easily neutralized, and the potential difference between the nozzle 1 and the base layer 4 can be easily maintained. As a result, even if the orientation of the Taylor cone of the raw material region L generated at the tip of the nozzle 1 changes, or even if there is charge repulsion between the deposited fibers 8 and the spun fibers 8 before deposition, the spun fibers 8 can be more strongly drawn into the contact region 41 of the base layer 4. As a result, the deposition position of the fibers 8 can be suitably controlled with the contact region 41 as the target region for spinning (see, for example, FIG. 6).

[0024] In this manner, according to the fiber sheet manufacturing method of the present embodiment, the fibers 8 are generated by electrospinning and deposited with precision at desired positions on the base material layer to favorably form the fiber sheet 10. Furthermore, the fiber sheet manufacturing apparatus 100 of the present embodiment can favorably implement the above manufacturing method.

[0025] In the fiber sheet manufacturing method and manufacturing device of this embodiment, the nozzle 1 and the counter electrode 2 are opposed to each other in the vertical direction, and spinning is performed from top to bottom, but this is not limited to the above. For example, the positions of the nozzle 1 and the counter electrode 2 may be reversed to perform spinning from bottom to top, or the nozzle 1 and the counter electrode 2 may be opposed to each other along the horizontal direction to perform spinning in the horizontal direction. Also, the nozzle 1 and the counter electrode 2 may be opposed to each other along a direction intersecting the vertical and horizontal directions, and spinning may be performed in that direction.

[0026] In the fiber sheet manufacturing method and manufacturing apparatus of this embodiment, the space 5 is formed by the distance between the nozzle 1 and the counter electrode 2, and can be set as appropriate from the viewpoint of optimally performing spinning by the above-mentioned electrical attraction. For example, the distance between the tip of the nozzle 1 and the surface of the flat portion 21 of the counter electrode 2 is preferably 30 mm or more, more preferably 50 mm or more, and even more preferably 80 mm or more, from the viewpoint of performing good stretching for fiberization. In addition, the distance between the tip of the nozzle 1 and the surface of the flat portion 21 of the counter electrode 2 is preferably 300 mm or less, more preferably 250 mm or less, and even more preferably 200 mm or less, from the viewpoint of forming a good electric field and suitably depositing the spun fibers 8 at the desired position of the base material layer 4.

[0027] From the viewpoint of improving the chargeability of the raw material liquid L, the potential difference between the nozzle 1 and the flat portion 21 of the counter electrode 2 is preferably 1 kV or more, more preferably 10 kV or more, and even more preferably 15 kV or more. Moreover, from the viewpoint of preventing discharge, the potential difference is preferably 100 kV or less, more preferably 50 kV or less, and even more preferably 30 kV or less.

[0028] In a plan view from the top 23 side of the counter electrode 2, the planar shape of the flat portion 21 is not limited to the circle shown in FIG. 2(B) and can be various shapes. For example, an ellipse, a polygon, etc. can be mentioned. However, from the viewpoint of suppressing uneven distribution of the electrode in the flat portion 21 at the top 23 and distributing the charge widely and evenly, the planar shape of the flat portion 21 is preferably a shape without corners on the outer edge and the outer edge is represented by a closed curve, and a circle is more preferable. If the planar shape of the flat portion 21 is a circle, the charge can be distributed radially and evenly, which is preferable. In addition, in a plan view from the top 23 side of the counter electrode 2, the part (e.g., a curved surface part) configured to have no corners is preferably arranged so as to border the outer edge of the flat portion 21. It is preferable that the outer surface of the connection part between the part configured to have no corners and the flat portion 21 has no corners such as a step and is a gently curved surface. The radius of curvature R of the curved surface when viewed from the side is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more, from the viewpoint of preventing electric field concentration on the curved surface and forming a nanofiber sheet without collection unevenness. Moreover, the radius of curvature R of the curved surface is preferably 18 mm or less, more preferably 15 mm or less, and even more preferably 12 mm or less, from the viewpoint of better controlling the deposition position of the fibers 8.

[0029] The proportion of the flat portion 21 in the area of ​​the top 23 of the counter electrode 2 when viewed in a plane is preferably 15% or more, more preferably 30% or more, and even more preferably 45% or more, from the viewpoint of increasing the contact area with the base material layer 4 and promoting the de-electrification of the charged electric charge. Moreover, from the viewpoint of better controlling the deposition position of the fibers 8, the proportion of the flat portion 21 is preferably 85% or less, more preferably 75% or less, and further preferably 65% ​​or less.

[0030] In plan view from the top 23 side of the counter electrode 2, the planar area of ​​the flat portion 21 can be set to various values ​​by appropriately controlling the deposition position described above. For example, the planar area of ​​the flat portion 21 is set to 15 mm from the viewpoint of increasing the contact area with the base layer 4 and promoting the removal of the charged electric charge. 2 More than 40mm is preferable.2 More preferably, 70 mm or more 2 The above is more preferable. In addition, the planar area of ​​the flat portion 21 is set to 7500 mm from the viewpoint of better controlling the deposition position of the fibers 8. 2 Less than 2000mm is preferable. 2 Less than 300mm is preferable. 2 The following is even more preferred:

[0031] In the fiber sheet manufacturing method and manufacturing device of this embodiment, it is preferable to perform spinning while moving the nozzle 1 relative to the counter electrode 2. This makes it possible to set the region (contact region) 41 that abuts against the flat portion 21 of the base layer 4 as the target region for spinning, deposit the fibers 8 more accurately over the entire contact region 41, and satisfactorily manufacture a fiber sheet 10 with a more uniform basis weight. In addition, the areas of the flat portion 21 and the contact region 41 can be enlarged to widen the movement range of the nozzle 1, and a larger fiber sheet 10 can be satisfactorily manufactured. Furthermore, by appropriately setting the movement range of the nozzle 1, a partial target region can be set within the contact region 41 of the base layer 4, and fiber sheets 1 of any of a variety of planar shapes can be satisfactorily manufactured. As a mechanism for moving the nozzle 1, various mechanisms that are commonly used in this type of manufacturing method can be adopted. For example, as shown in Fig. 7, there is a nozzle moving mechanism 6 having a support part 61, a rail part 62 supported by the support part 61, and a movable part 63 movable along the rail part 62 and to which the nozzle 1 is fixed. By moving the movable part 63 along the rail part 62, the nozzle 1 can be moved within the contact region 41 of the base layer 1. At that time, it is more preferable that the rail part 62 is movable along the support part 61.

[0032] In the fiber sheet manufacturing method and manufacturing device of this embodiment, it is preferable to move the nozzle 1 and the counter electrode 2 and spin one following the other. In this case, the region (contact region) 41 of the base material layer 4 where the flat portion 21 of the counter electrode 2 abuts moves along with the movement of the counter electrode 2. Therefore, the target region for spinning in the base material layer 4 can be set to an area larger than the contact region 41 before the movement. This allows for the successful production of larger fiber sheets 10 with various planar shapes. For example, the counter electrode 2 may follow the location where the nozzle 1 has moved, or the nozzle 1 may follow the location where the counter electrode 2 has moved. The coordinate P of the following location does not need to be completely the same as above, and may change relative to the planar direction of the counter electrode 2. The amount of deviation of the coordinate P of the following location is preferably 30 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less, from the viewpoint of better controlling the deposition position of the fiber 8. This is possible because the counter electrode 2 has a flat portion 21 and a portion configured to have no corners at its edge, and the flat portion 21 abuts against the base layer 4, so that the deposition position can be suitably controlled. That is, as described above, the strong electric attraction in the abutment region 41 of the base layer 4 causes the fiber 8 to follow the flat portion 21 of the counter electrode 2 and be deposited on the base layer 4. Therefore, even if the operation of the nozzle 1 and the operation of the counter electrode 2 are not completely synchronized, it is possible to deposit the fiber 8 to be spun at a desired position with high accuracy, as described above. Moreover, it is more preferable to move the nozzle 1 and the counter electrode 2 coaxially in the axial direction of the spinning direction, so that the two move synchronously and the fiber deposition at the desired position can be performed with higher accuracy. When moving them coaxially, the center position of the nozzle 1 and the center position of the counter electrode 2 do not necessarily have to be the same, and they may be operated with an offset. From the viewpoint of better control of the deposition position of the fiber 8, the offset amount is preferably 30 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less. As a mechanism for moving both the nozzle 1 and the counter electrode 2, various mechanisms that are commonly used in this type of manufacturing method can be adopted. For example, as shown in FIG. 8, in addition to the nozzle movement mechanism 6 described above, a counter electrode movement mechanism 7 having a support part 71, a rail part 72 supported by the support part 71, and a movable part 73 that can move along the rail part 72 and has the counter electrode 2 fixed thereto can be combined. The counter electrode movement mechanism 7 preferably operates in the same manner as the nozzle movement mechanism 6 described above. This mechanism allows the spun fiber 8 to be deposited on the base layer 4 with greater accuracy while moving both the nozzle 1 and the counter electrode 2. In the example shown in FIG. 8, if the flat part 21 of the counter electrode 2 has an area smaller than that shown in FIG. 7, the linearity of the spinning direction between the nozzle 1 and the counter electrode 2 that move relative to each other can be further improved, and spinning can be suitably controlled, which is preferable.

[0033] In the example shown in FIG. 8, only the nozzle 1 may be moved as shown in FIG. 7, or only the counter electrode 2 may be moved. When only the counter electrode 2 is moved, the production apparatus 100 may have a configuration including only the counter electrode moving mechanism 7 without the nozzle moving mechanism 6 (not shown). When only the counter electrode 2 is moved, the spinning can be controlled in the same manner as when only the nozzle 1 is moved as shown in FIG. 7, and larger fiber sheets 10 of various planar shapes can be produced satisfactorily. From the viewpoint of satisfactorily producing larger fiber sheets 10 of various planar shapes, it is more preferable to move both the nozzle 1 and the counter electrode 2, as described above.

[0034] In the fiber sheet manufacturing method and manufacturing device of this embodiment, it is preferable to perform spinning while increasing the absolute value of the voltage (collection voltage) applied to the nozzle 1 or the counter electrode 2 according to the spinning time. When the voltage applied to the nozzle 1 or the counter electrode 2 is of zero polarity, it is preferable to set it to zero polarity only at the start of spinning, and increase the absolute value of the voltage of the opposite polarity to the voltage applied to the opposing counter electrode 2 or nozzle 1 with the spinning time. For example, as shown in FIG. 9(A), even if the potential of the collected fibers increases as the fibers 8 are deposited in the contact area 41 of the base layer 4, the absolute value of the voltage of the opposite polarity to the fibers 8 is increased with respect to the counter electrode 2 according to the spinning time. This makes it possible to control the potential difference to be kept constant even if a large amount of fibers 8 carrying the same polarity as the nozzle 1 are deposited in the contact area 41 of the base layer 4 and the potential difference with the nozzle 1 is reduced (FIG. 9(B)). This prevents the balance between the supply amount of the raw material liquid L and the electrostatic attraction force, which may occur when the potential difference is reduced and the electrostatic attraction force that draws the raw material liquid L is weakened. This prevents the occurrence of the drop of droplets of the raw material liquid L (droplets that cannot become fibers) that may be caused by the balance being destroyed. This makes it possible to stabilize good spinning. In addition, since the potential difference can be kept constant, the straightness of the fibers 8 moving from the nozzle 1 toward the counter electrode 2 can also be maintained. This makes it possible to more suitably control the deposition position of the fibers 8 to be spun, and to manufacture a better fiber sheet 10 with a higher yield. The above voltage control is preferably carried out as follows. The spinning time is calculated from the movement trajectory data inputted to the movement mechanism of the nozzle 1 or the counter electrode 2 described above. It is preferable that the voltage values ​​at the start and end of spinning are preset to predetermined values, and the voltage values ​​are changed continuously based on the spinning time. Alternatively, it is preferable to divide the voltage increase from the start to the end of spinning and the above-mentioned spinning time into multiple times, and control the voltage in stages. In the fiber sheet manufacturing method and manufacturing apparatus of this embodiment, it is preferable that the absolute value of the voltage (collection voltage) be increased according to the spinning time by the counter electrode 2, since the absolute value of the voltage value of the counter electrode 2 is lower than that of the nozzle 1 and from the viewpoint of reducing the risk of discharge with the apparatus.

[0035] In the fiber sheet manufacturing method and manufacturing device of the present embodiment, the aforementioned counter electrode 2 is used, so that the deposition position of the fiber 8 to be spun can be suitably controlled. Therefore, it is also possible to arrange a plurality of counter electrodes 2 in the planar region of the base layer 4, set target regions for spinning in a plurality of locations, and satisfactorily manufacture a plurality of fiber sheets 10. In this case, it is preferable to arrange a plurality of counter electrodes 2 spaced apart from each other with respect to the base layer 4 from the viewpoint of ensuring the straightness of spinning. This makes it possible to spin into a plurality of target regions in one spinning cycle. That is, it becomes possible to efficiently form a pattern (pattern spinning) in which a plurality of fiber sheets spaced apart from each other are arranged in a predetermined planar region of the base layer 4. In addition, a plurality of nozzles 1 may be arranged to face a plurality of counter electrodes 2 in a one-to-one relationship. This makes it possible to spin a plurality of fibers at once (pattern spinning). At this time, it is preferable that the number of counter electrodes 2 and the nozzles 1 are the same, but the number of nozzles 1 may be less than the number of counter electrodes 2, and a spinning batch using a plurality of nozzles 1 may be performed a plurality of times to form fiber sheets 10 in a number corresponding to the number of counter electrodes 2. In this pattern spinning, the individual target regions corresponding to the counter electrodes 2 may be contact regions 41 where the counter electrodes 2 are fixed without moving (e.g., FIG. 6), or may be wider regions formed by the contact regions 41 moving with the movement of the counter electrodes 2 (e.g., FIG. 8). The target region for spinning may be a region set within the movement range of the nozzles 1 as shown in FIG. 7.

[0036] The base material layer 4 may be a sheet having a predetermined dimension, or a long continuous sheet unwound from a roll of raw material. The continuous sheet is repeatedly conveyed and stopped in the machine direction (MD), and the base material layer is conveyed intermittently, so that pattern spinning can be performed at multiple locations on the continuous sheet. Various materials commonly used in this type of article can be used as the material for the base layer 4. Examples include nonwoven fabric, film, sponge, woven fabric, knitted fabric, paper, mesh sheet, and laminates thereof.

[0037] In particular, in the case of a continuous sheet, it is preferable to use the above-mentioned multiple counter electrodes 2, or multiple counter electrodes 2 and multiple nozzles 1. In this case, multiple target regions can be set within a predetermined region extending in the machine flow direction and the cross direction (Cross Direction; CD) perpendicular to the machine flow direction, and pattern spinning can be performed. This allows a set number of fiber sheet patterns to be quickly and satisfactorily formed within a predetermined planar region of the continuous sheet 46. Moreover, this can be repeatedly performed along the longitudinal direction of the continuous sheet 46. For example, a spinning batch in which spinning is performed on multiple target regions at once can be repeatedly performed in the machine flow direction.

[0038] When the base layer 4 is a continuous sheet and a spinning batch in which multiple nozzles 1 are used to spin multiple target regions at once is repeatedly performed in the machine flow direction, it can be, for example, as shown in Figure 10. In the specific example shown in Figure 10, the nozzle moving mechanism 6 has a nozzle aggregation plate 63A on the movable part 63, and nine nozzles 1 are attached to this nozzle aggregation plate 63A. In addition, nine counter electrodes 2 are arranged. Hereinafter, the nine nozzles 1 are referred to as the nozzle 1 group, and the nine counter electrodes 2 are referred to as the counter electrode 2 group. In the specific example shown in Fig. 10, a group of nine nozzles 1 faces a group of nine counter electrodes 2 on a continuous sheet 46 unwound from a raw roll 45, and spins the continuous sheet 46 at a time in a plurality of target regions (performs a spinning batch). At this time, by moving a nozzle aggregation plate 63A attached to a movable part 63, a fiber sheet of a predetermined area and shape can be formed for each target region, as shown in Fig. 7. Alternatively, as shown in Fig. 8, the nozzles 1 and the counter electrodes 2 may be moved so that one follows the other while spinning.

[0039] In the specific example shown in FIG. 10, two spinning batches are performed for a predetermined planar area of ​​the continuous sheet using a first group of nine nozzles and a second group of nine counter electrodes. The two spinning batches are performed for different target areas in the first and second spinning batches by moving the rail part 62 of the nozzle moving mechanism 6 along the support part 61 while the conveyance of the continuous sheet 46 is temporarily stopped. As a result, a pattern of 18 fiber sheets 10 is formed within the predetermined planar area of ​​the continuous sheet 46. The number of spinning batches for a predetermined planar area of ​​the continuous sheet is not limited to the above two times, and may be one spinning batch or three or more spinning batches. This can be appropriately set depending on the size of the predetermined planar area that divides the pattern of the fiber sheets 10 in the continuous sheet 46, the number of fiber sheets 10, and the number of nozzles 1 and counter electrodes 2. In the specific example shown in Fig. 10, after the patterns of 18 fiber sheets 10 have been formed, a predetermined planar area of ​​the continuous sheet 46 proceeds to the next laser cutting process. In the laser cutting process, the fiber sheet 10 and the material of the continuous sheet 46 (base layer 4) are cut out together at the outer edge of the fiber sheet 10 by, for example, a laser cutter 91. The cut-out laminated sheet of the fiber sheet 10 and the base layer 4 is transported to a product outlet. The remaining continuous sheet 46 is trimmed and collected. This series of steps is repeated while the continuous sheet 46 is being transported.

[0040] In the fiber sheet manufacturing method and apparatus of this embodiment, when multiple nozzles 1 are opposed to multiple counter electrodes 2 in a one-to-one relationship to spin at the same time as described above, it is more preferable to perform the spinning in the following configuration. 11, it is preferable to arrange a ring electrode 81 so as to surround the tip of each nozzle 1. It is preferable that the ring electrode 81 is charged with a voltage of the same polarity as the nozzle 1 and the raw material liquid L to be discharged. This can improve the straightness of spinning that directs the raw material liquid L to be discharged toward the counter electrode 2. 11, the electric field space 5 between the multiple nozzles 1 and the counter electrode 2 may be surrounded by a side electrode 82. The side electrode 82 is also preferably charged with a voltage of the same polarity as the nozzles 1 and the discharged raw material liquid L. This makes it possible to correct the trajectory of the fibers that tend to spread outward due to charge repulsion, as shown in FIG. 12, and improve the straightness of the spinning. The above-mentioned ring electrode 81 and side electrodes 82 can be used whether the base material layer 4 is a single sheet or a continuous sheet.

[0041] In the pattern spinning in which a plurality of fiber sheets 10 are formed spaced apart from one another as described above, the fiber sheets are formed not on the entire surface of the base layer 4 but on a portion of the base layer 4, leaving a margin. Therefore, the fiber sheet manufacturing method of the present embodiment can effectively utilize the margin. That is, before transitioning to regular spinning to start the fiber sheet manufacturing method of this embodiment, it is preferable to perform end-cut spinning (sacrificial spinning) in a margin (non-deposition area) other than the target area where the fibers 8 are deposited. This allows spinning in the target area to be performed with improved stability in the discharge of the raw material liquid L from the nozzle 1. This stabilizes the spinning. [Explanation of symbols]

[0042] 1 nozzle 2 Counter electrode 21 Flat area 23 Top 3. Means for applying voltage (voltage application device) 4 Base material layer 8. Fiber 10 Fiber sheet 100 Fiber sheet manufacturing equipment L Raw material liquid

Claims

1. A method for producing a fiber sheet, comprising: discharging a raw material solution from a nozzle; and depositing fibers generated from the raw material solution by an electrospinning method on a substrate layer, the method comprising: The substrate layer is disposed at a distance from the nozzle. a counter electrode is disposed on a surface of the substrate layer opposite to the nozzle; By applying a voltage, the nozzle and the counter electrode are made to have different polarities, thereby forming an electric field between the nozzle and the counter electrode; In the spinning step of spinning the raw material liquid discharged from the nozzle into fibers in the electric field, The counter electrode a flat portion on the base layer side that contacts the base layer; The flat portion has a top portion on the outer side in the planar direction thereof, and a portion configured to have no corners, In the spinning step, a potential difference is generated between the nozzle and the flat portion while the flat portion and the base material layer are in contact with each other; depositing the spun fibers in the abutted area of ​​the substrate layer; A method for manufacturing a fiber sheet.

2. The method for producing a fiber sheet according to claim 1 , wherein the corner-free portion is a curved portion whose outer surface is curved away from the base material layer.

3. The method for producing a fiber sheet according to claim 1 or 2, wherein the spinning is performed while the nozzle is moved relative to the counter electrode.

4. The method for producing a fiber sheet according to claim 1 or 2, wherein the nozzle and the counter electrode are moved, one following the other, during spinning.

5. 3. The method for producing a fiber sheet according to claim 1, wherein spinning is performed while increasing the absolute value of the voltage applied to the nozzle or the counter electrode according to the spinning time.

6. The method for producing a fiber sheet according to claim 5, wherein spinning is carried out while increasing the absolute value of the voltage applied to the counter electrode according to the spinning time.

7. A fiber sheet manufacturing apparatus comprising: a nozzle for discharging a raw material liquid; and a counter electrode disposed opposite to the nozzle at a distance from the nozzle, for generating an electric field between the nozzle and the counter electrode, a means for applying a voltage to the nozzle and the counter electrode so that the polarities of the voltages are different from each other; a space between the nozzle and the counter electrode into which a base material layer can be introduced; The counter electrode is a flat portion on the base layer side that contacts the base layer; a top portion having a portion configured to have no corners outward in a plane direction of the flat portion; Fiber sheet manufacturing equipment.

8. The fiber sheet manufacturing apparatus according to claim 7 , further comprising a mechanism that enables fibers to be spun to be deposited on the substrate layer while moving one or both of the nozzle and the counter electrode.

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