Electrospinning apparatus

Abstract

To provide an electrospinning device which can make discharge rate of a polymer solution become uniform.SOLUTION: An electrospinning device is assembled with a tank 13 for storing a raw material liquid 11 and a nozzle 20 which includes a discharge port 15 at its tip, is provided in a manner that a suction port 17 of base end is in contact with the raw material liquid 11, and moves the raw material liquid 11 to the discharge port 15 by capillary phenomenon, wherein the raw material liquid 11 discharged from the discharge port 15 is made finer by applying electric voltage between the nozzle 20 and a sheet-like substrate 21 and is deposited on the sheet-like substrate 21 in a state of an ultrafine fiber.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to an electrospinning device.

Background Art

[0002] In the electrospinning device of Patent Document 1, a circular spinning hole is formed in a tubular storage tank for storing a spinning solution. The electrospinning device discharges the stored spinning solution from the spinning hole to a collection member by applying a voltage, and laminates a fiber aggregate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above electrospinning device, as a means for supplying the spinning solution to the spinning holes, the spinning solution pressurized by a pump is fed into the storage tank from one end in the length direction of the storage tank. In such a supply structure, the internal pressure at the center in the length direction of the storage tank is lower than the internal pressure at one end in the length direction of the storage tank. Due to this non-uniform internal pressure, the amount of the discharged spinning solution was not uniform in all the spinning holes. This disclosure has been completed based on the above circumstances, and an object thereof is to make the discharge amount of the raw material liquid for electrospinning uniform.

Means for Solving the Problems

[0005] The electrospinning device of this disclosure is a tank for storing a raw material liquid, [[ID=4,7]] a nozzle having a discharge port at the tip and provided such that a suction port at the base end is in contact with the raw material liquid, and moving the raw material liquid to the discharge port by capillary action. By applying a voltage between the nozzle and the sheet-like substrate, the raw material liquid discharged from the discharge port is atomized into ultrafine fibers and deposited onto the sheet-like substrate. [Effects of the Invention]

[0006] The electrospinning apparatus of this disclosure supplies the raw material liquid to the discharge port by capillary action, thereby enabling uniform discharge of the raw material liquid. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of an electrospinning apparatus according to Embodiment 1. [Figure 2] This is a plan view of the retaining plate according to Embodiment 1. [Figure 3] This is a schematic diagram of an electrospinning apparatus according to Embodiment 2. [Figure 4] This diagram shows the operation flow of the lifting device disclosed herein. [Figure 5] This is a schematic diagram of the electrospinning apparatus according to Embodiment 3. [Figure 6] This diagram shows the operation flow of the replenishment device disclosed herein. [Figure 7] This is a schematic diagram of an electrospinning apparatus according to Embodiment 4. [Figure 8] This is a schematic diagram of an electrospinning apparatus according to Embodiment 5. [Modes for carrying out the invention]

[0008] Herein, we present a preferred example of the present disclosure. Any combination of the following embodiments, provided they do not contradict each other, is also included in the embodiments for carrying out the invention.

[0009] In this disclosure, it is preferable to have a retaining plate that holds multiple nozzles, the retaining plate being in surface contact with the raw material liquid and keeping the suction ports in contact with the raw material liquid. Because the retaining plate is kept in contact with the surface of the raw material liquid, the suction ports of the nozzles do not move away from the liquid surface, so that the raw material liquid can be discharged uniformly from each discharge port. In addition, because the retaining plate covers a wide area of ​​the raw material liquid, drying of the raw material liquid can be prevented.

[0010] In this disclosure, it is preferable that the retaining plate is held in contact with the liquid surface of the raw material liquid solely by the buoyancy of the raw material liquid. Since the retaining plate can be kept in contact with the liquid surface by buoyancy, a device for holding the retaining plate and nozzle is unnecessary.

[0011] In this disclosure, it is preferable that the electrospinning apparatus has a holding plate made of a conductive material, and that a power supply for applying a voltage between the sheet-like substrate and the holding plate is connected to the holding plate. Since the voltage is applied over the entire arrangement area of ​​the multiple nozzles, the charge level of the raw material liquid becomes uniform at all nozzles.

[0012] In this disclosure, it is preferable that the electrospinning apparatus includes a lifting device that raises and lowers the tank according to the height of the liquid level of the raw material in the tank. By raising and lowering the tank, the nozzle discharge port can be kept at a constant height, thereby maintaining a constant distance between the discharge port and the sheet-like substrate, and stabilizing the thickness (basis weight) of the ultrafine fibers in the sheet-like substrate.

[0013] In this disclosure, it is preferable that the electrospinning apparatus is equipped with a replenishment device that replenishes the raw material liquid in a tank according to the amount of raw material liquid discharged from the discharge port. By replenishing the raw material liquid according to the amount of raw material liquid discharged, the liquid level of the raw material liquid in the tank can be kept at a constant height, and the height of the discharge port can be kept at a constant height. Since the distance between the discharge port and the sheet-like substrate can be kept constant without raising or lowering the nozzle or tank, the thickness (basis weight) of the ultrafine fibers in the sheet-like substrate can be stabilized without providing a lifting device.

[0014] In the present disclosure, it is preferable that a plurality of discharge ports are arranged side by side in a two-dimensional direction. Since the plurality of discharge ports are arranged side by side in the two-dimensional direction, ultrafine fibers can be deposited on the sheet-like base material over a wide range.

[0015] In the present disclosure, it is preferable that a plurality of discharge ports are arranged in a staggered pattern. Since the plurality of nozzles are arranged in a staggered pattern, interference of the electric field between adjacent nozzles can be avoided and suppressed.

[0016] In the present disclosure, it is preferable to include a nozzle block provided so as to contact the raw material liquid, and a plurality of nozzles in a penetrating form are integrally formed in the nozzle block, and the proximal ends of the nozzles are in contact with the raw material liquid. Since the nozzles in the nozzle block are difficult to deform, the discharge of the raw material liquid is stabilized.

[0017] In the present disclosure, it is preferable that the nozzle block is made of a conductive material, and a power source for applying a voltage between the nozzle block and the sheet-like base material is connected to the nozzle block. Since the inner peripheral surfaces of all the nozzles are constituted by the nozzle block, the amount of charge of the raw material liquid becomes uniform in all the nozzles.

[0018] In the present disclosure, it is preferable that the proximal end of the nozzle opens at the bottom surface inside the tank. As the level of the raw material liquid surface drops, it is not necessary to raise and lower the nozzle or the tank. Therefore, even without a lifting device, the thickness (basis weight) of the ultrafine fibers on the sheet-like base material is stabilized.

[0019] Figures 1 - 8 are diagrams related to the electrospinning device of the present disclosure. In each figure, "front side" is represented by "F", "upper side" by "U", and "right side" by "R".

[0020] <Embodiment 1> [Configuration of the electrospinning device 10] As shown in FIG. 1, the electrospinning device 10 according to the first embodiment has a raw material liquid 11, a tank 13, a nozzle 20, a holding plate 30, a sheet-like base material 21, a collecting electrode 24, and an electrode charging unit 25.

[0021] [Raw material liquid 11] The raw material solution 11 is prepared by dissolving or dispersing a resin material that forms ultrafine fibers as a solute in a volatile solvent. Examples of solutes include synthetic resins such as polyacrylonitrile (PAN), polypropylene (PP), and polyethylene (PE). Examples of solvents include compounds such as N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), and tetrahydrofuran (THF).

[0022] [Tank 13] As shown in Figure 1, the tank 13 stores the raw material liquid 11. The tank 13 has a rectangular parallelepiped shape with the top open, formed by the bottom surface 31 and the inner wall surface 33.

[0023] [Nozzle 20] As shown in Figure 1, the nozzle 20 draws up the raw material liquid 11 stored in the tank 13 through capillary action from the suction port 17 opening at its base end and moves it to the discharge port 15. The nozzle 20 has a cylindrical tubular shape. As shown in Figure 2, a tubular hole 23 for discharging the raw material liquid 11 is provided inside the nozzle 20. The tubular hole 23 for discharging the raw material liquid 11 penetrates between the discharge port 15, which is the end of the nozzle 20 on the sheet-like substrate 21 side, and the suction port 17, which is the end of the nozzle 20 on the tank 13 side (base end). The opening of the tubular hole 23 for discharging the raw material liquid 11 on the sheet-like substrate 21 side becomes the discharge port 15.

[0024] The outer diameter of the nozzle 20 (or the diameter if the nozzle 20 is cylindrical) is, for example, 0.2 mm. Reducing the outer diameter makes it easier for electric field concentration to occur near the discharge port 15 of the nozzle 20. When electric field concentration occurs near the discharge port 15 of the nozzle 20, the strength of the electric field formed between the nozzle 20 and the sheet-like substrate 21 can be increased. Therefore, the voltage applied by the electrode charging section 25 can be reduced. In other words, the driving voltage can be reduced.

[0025] The inner diameter of the discharge port 15 is, for example, 0.1 mm. The inner diameter of the discharge port 15 can be appropriately changed according to the cross-sectional dimensions of the ultrafine fibers to be produced. The inner diameter of the suction port 17 of the nozzle 20 is, for example, 0.1 mm. The tubular hole 23 is formed with a constant inner diameter from the suction port 17 to the discharge port 15. The inner diameter of the tubular hole 23 can be appropriately changed according to the cross-sectional dimensions of the ultrafine fibers to be produced, the surface tension of the raw material liquid 11, the specific gravity of the raw material liquid 11, the wettability of the inner surface of the nozzle 20, etc. The suction port 17 is in contact with the raw material liquid 11 stored in the tank 13. The raw material liquid 11 moves from the suction port 17 to the discharge port 15 via the tubular hole 23 by capillary action. In detail, when the suction port 17 of the tubular nozzle 20 is brought into contact with the raw material liquid 11, the raw material liquid 11 rises along the inner surface of the tubular hole 23 by capillary action and reaches the discharge port 15.

[0026] [Holding plate 30] The electrospinning apparatus 10 of this embodiment 1 is equipped with a holding plate 30. The holding plate 30 is made of a conductive material and is a member that covers the entire surface A of the raw material liquid 11 in the tank 13. The holding plate 30 is in the shape of a roughly rectangular parallelepiped and is, for example, about 0.1 mm smaller than each side that forms the inside of the tank 13. The holding plate 30 has a nozzle housing hole 32 for holding the nozzle 20. The outer diameter of the nozzle housing hole 32 is approximately the same shape as the outer diameter of the nozzle 20. The nozzle housing hole 32 penetrates the upper and lower surfaces of the holding plate 30. The height of the suction port 17 of the nozzle 20 coincides with the lower end of the nozzle housing hole 32 (the lower surface of the holding plate 30).

[0027] As shown in Figure 2, in a plan view of the holding plate 30 from above, the discharge ports 15 of the nozzle 20 are arranged in a staggered pattern. A staggered pattern means that in two parallel adjacent rows of discharge ports 15, the discharge ports 15 of one row are offset from the discharge ports 15 of the other row in the length direction of the row. The amount of the offset is half the pitch between the discharge ports 15 in each row.

[0028] The outer surface of the retaining plate 30 has a gap between it and the inner wall surface 33 of the tank 13 when it is fixed to the tank 13. When the retaining plate 30 is housed in the tank 13, it is held to float in contact with the liquid surface A of the raw material liquid 11 solely by the buoyancy of the liquid material 11. Since the retaining plate 30 can be kept in contact with the liquid surface A by buoyancy, there is no need for a device to hold the retaining plate 30 and the nozzles 20 so that they do not sink into the raw material liquid 11. When the retaining plate 30 is housed in the tank 13, the lower end of the retaining plate 30 is in surface contact with the raw material liquid 11, and the opening of the suction port 17, which is the suction port, is kept in contact with the raw material liquid 11. The retaining plate 30 covers, for example, more than 90% of the upper surface of the raw material liquid 11. As a result, the openings of the suction ports 17 of all nozzles 20 do not leave the liquid surface A, so the raw material liquid 11 can be discharged from all discharge ports 15. Furthermore, since the holding plate 30 covers a wide area of ​​the raw material liquid 11, drying of the raw material liquid 11 can be prevented.

[0029] [Sheet-like base material 21] The sheet-like substrate 21 is a component that deposits solute (hereinafter also referred to as fibrous component) in the raw material liquid 11 discharged from the nozzle 20. The sheet-like substrate 21 is discharged from the feed roller 34 in a horizontally extended state and is also wound onto the winding roller 35. The area of ​​the sheet-like substrate 21 that is horizontally extended between the two rollers 34 and 35 is designated as the collection area. The fibrous aggregate consisting of fibrous component discharged from the nozzle 20 is laminated in a sheet-like manner on the lower surface of the collection area of ​​the sheet-like substrate 21.

[0030] [Collection electrode 24] The collection electrode 24 is made of a metallic conductive material and has a rectangular parallelepiped shape. As shown in Figure 1, the collection electrode 24 is positioned between the feed roller 34 and the winding roller 35. The collection electrode 24 is positioned to face the upper surface of the collection area of ​​the sheet-like substrate 21.

[0031] [Electrode charging section 25] The electrode charging unit 25 is a power source for applying voltage, electrically connected to the conductive retaining plate 30 and the collection electrode 24, respectively. The conductive retaining plate 30 is connected to the positive electrode of the electrode charging unit 25. The collection electrode 24 is connected to the negative electrode of the electrode charging unit 25.

[0032] [Effects of the electrospinning apparatus 10 of Embodiment 1] The operation and effects of the electrospinning apparatus 10 will now be explained. The electrospinning apparatus 10 includes a tank 13 for storing raw material liquid 11, a nozzle 20, a retaining plate 30 for holding the base end of the nozzle 20, a sheet-like base material 21, and an electrode charging section 25. The nozzle 20 has a discharge port 15 at its tip and a suction port 17 at its base end that is in contact with the raw material liquid 11.

[0033] The raw material liquid 11 moves from the suction port 17 of the nozzle 20 of the electrospinning apparatus 10 to the discharge port 15 by capillary action. When the raw material liquid 11 has moved to the discharge port 15, a voltage is applied to the holding plate 30 and the collection electrode 24 by the electrode charging unit 25, and the raw material liquid 11 in contact with the holding plate 30 becomes positively charged. The positively charged raw material liquid 11 is attracted by electrostatic force from the discharge port 15 toward the collection electrode 24. During this time, the solvent contained in the droplets of the raw material liquid 11 volatilizes and is stretched. As a result, the ultrafine components are refined into ultrafine fibers and spun. The ultrafine fibers thus spun accumulate on the lower surface of the sheet-like substrate 21 to form a nonwoven fabric.

[0034] The raw material liquid 11 stored in the tank 13 rises along the inner surface of the narrow bore 23 by capillary action and reaches the discharge port 15. The force that causes the raw material liquid 11 to rise within the narrow bore 23 is not obtained by applying external pressure to the raw material liquid 11 in the tank 13, but rather by capillary action that occurs individually in each nozzle 20 without being affected by other nozzles 20. Since all nozzles 20 are identical parts, the force that causes the raw material liquid 11 to rise is the same for all nozzles 20. In this way, the discharge amount from each nozzle 20 is constant, so the thickness of the nonwoven fabric can be kept constant. Furthermore, as shown in Figure 2, the electrospinning apparatus 10 of this disclosure has the discharge ports 15 of multiple nozzles 20 arranged in a staggered pattern, so interference of electric fields between adjacent nozzles 20 can be avoided and suppressed.

[0035] <Embodiment 2> A second embodiment of the present disclosure, the electrospinning apparatus 40, will be described with reference to Figure 3. The electrospinning apparatus 40 of this second embodiment is equipped with a lifting device 51 for maintaining the height of the liquid surface A of the raw material liquid 41 within a certain range. The other configurations are the same as those of the first embodiment, so the same configurations will not be described, and the same effects and advantages as in the first embodiment will also not be described.

[0036] The electrospinning apparatus 40 of Embodiment 2 is equipped with a lifting device 51 that raises and lowers the tank 42 according to the height of the liquid level A of the raw material liquid 41 in the tank 42. In Embodiment 2, the raw material liquid 41, the tank 42, the nozzle 44, the holding plate 55, the sheet-like substrate (not shown), the collection electrode (not shown), and the electrode charging section (not shown) are the same as in Embodiment 1. The lifting device 51 includes a liquid level sensor 43, a lifting control device 49, a motor 46, a screw shaft 47, a nut 48, a lifting member 45, and a lifting frame 59. The raw material liquid 41 stored in the tank 42 rises through the nozzle 44 by capillary action and is uniformly discharged from all discharge ports 57.

[0037] [Liquid level sensor 43] The liquid level sensor 43 detects the position of the liquid level A of the raw material liquid 41 stored in the tank 42, and is, for example, an electrode-type level sensor.

[0038] [Lifting control device 49] The lifting control device 49 is a device that raises and lowers a lifting member 45 according to the position of the liquid level A of the raw material liquid 41, which changes according to the discharge rate of the raw material liquid 41. The liquid level sensor 43 and the lifting control device 49 are electrically connected by a wire. Information on the height of the liquid level A from the liquid level sensor 43 is transmitted to the lifting control device 49 via a cord as an electrical signal.

[0039] [Motor 46] The motor 46 is a component that serves as the drive source for the lifting device 51. The motor 46 is electrically connected to the lifting control device 49. The motor 46 operates or stops in response to instructions from the lifting control device 49.

[0040] [Screw shaft 47, nut 48] The screw shaft 47 rotates in conjunction with the motor 46 and is a component that raises and lowers the lifting member 45. The screw shaft 47 is cylindrical and has a male thread 52 formed on its outer circumference. The nut 48 has a female thread (not shown) formed on the inside and is attached to the screw shaft 47.

[0041] [Lifting frame 59] The lifting frame 59 consists of a roughly rectangular plate-shaped base 56 installed on the floor, a support column 54 extending upward from the rear edge of the base 56, and a pair of upper and lower brackets 53a and 53b positioned on the front of the support column 54. A screw shaft 47 with a nut 48 attached is positioned between the brackets 53a and 54b.

[0042] [Lifting / lowering member 45] The lifting member 45 is roughly rectangular in shape and is the member on which the tank 42 is placed. The lifting member 45 is connected to a nut 48. As the motor 46 rotates, the lifting member 45 that supports the nut 48 rises, pulling the tank 42 up to a predetermined height. The nut 48 moves up and down between the lower end of the bracket 53a and the upper end of the bracket 53b as the screw shaft 47 rotates.

[0043] [Operation flow of the lifting device 51] Figure 4 is a diagram showing the operation flow of the lifting device 51 of this disclosure. First, the liquid level sensor 43 detects the liquid level of the raw material liquid 41 in the tank 42 (step S301). Next, the lifting control device 49 determines whether the detected liquid level is below a predetermined level (step S302).

[0044] If the lifting control device 49 determines that the detected liquid level is not below a predetermined level (step S302, No), the liquid level sensor 43 detects the liquid level again (step S301). On the other hand, if the lifting control device 49 determines that the detected liquid level has fallen below a predetermined level (step S302, Yes), the lifting control device 49 instructs the motor 46 to operate (step S303). The tank 42 rises as a result of the motor 46 operating (step S304).

[0045] While the motor 46 is operating, if the liquid level sensor 43 determines that the liquid level is below a predetermined value (step S305, Yes), the lifting control device 49 instructs the motor 46 to continue operating (S303). On the other hand, if the detected liquid level is determined to have risen to a predetermined level (step S305, No), the lifting control device 49 instructs the motor 46 to stop, thereby stopping the rise of the tank 42 (step S306). These adjustments to the liquid level A of the raw material liquid 41 are performed continuously. By raising and lowering the tank 42 according to the liquid level A of the raw material liquid 41, the liquid level A of the raw material liquid 41 in the tank 42 can be kept at a constant height, and the height of the discharge port 57 of the nozzle 44 can be kept at a constant height. As a result, the electrospinning apparatus 40 of Embodiment 2 can stabilize the thickness (basis weight) of the ultrafine fibers in the sheet-like substrate.

[0046] <Embodiment 3> An electrospinning apparatus 60 of Embodiment 3, which embodies the present disclosure, will be described with reference to Figure 4. The electrospinning apparatus 60 of Embodiment 3 is equipped with a replenishment device 75 for maintaining the height of the liquid level A of the raw material liquid 63 within a certain range. The other configurations are the same as those of Embodiment 1, so the same configurations will not be described, and the same effects and advantages as in Embodiment 1 will also not be described.

[0047] As shown in Figure 5, the electrospinning apparatus 60 of Embodiment 3 is equipped with a replenishment device 75 that replenishes the raw material liquid 63 in the tank 64 according to the amount of raw material liquid 63 discharged from the discharge port 61. The raw material liquid 63, tank 64, nozzle 70, holding plate 66, sheet-like substrate (not shown), collection electrode (not shown), and electrode charging unit (not shown) in Embodiment 3 are the same as in Embodiment 1. The replenishment device 75 is equipped with a liquid level sensor 67, inflow control device 68, pump 69, storage container 73, and pipe 71. The liquid level sensor 67 in Embodiment 3 is the same as in Embodiment 2. The raw material liquid 63 stored in the tank 64 rises through the nozzle 70 by capillary action and is discharged uniformly from all discharge ports 61.

[0048] [Inflow control device 68] The inflow control device 68 is a device that causes the raw material liquid 63 to flow in from the storage container 73 according to the position of the liquid level A of the raw material liquid 63, which changes according to the discharge rate of the raw material liquid 63. The liquid level sensor 67 and the inflow control device 68 are electrically connected by a wire. Information on the height of the liquid level A from the liquid level sensor 67 is transmitted to the inflow control device 68 via a code as an electrical signal.

[0049] [Pump 69] The pump 69, in response to instructions from the inflow control device 68, draws up the raw material liquid 63 from the storage container 73 and flows it into the tank 64. The pump 69 is electrically connected to the inflow control device 68. The pump 69, the storage container 73, and the tank 64 are connected via a pipe 71.

[0050] [Pipe 71] Pipe 71 is a flow path for the raw material liquid 63 to flow into the tank 64. Pipe 71 is connected from the storage container 73, via the pump 69, to the tank 64. The tank-side end 72 of pipe 71 is open.

[0051] [Operation flow of the replenishment device 75] Figure 6 is a diagram showing the operation flow of the replenishment device 75 of this disclosure. First, the liquid level sensor 67 detects the liquid level of the raw material liquid 63 in the tank 64 (step S401). Next, the inflow control device 68 determines whether the detected liquid level is below a predetermined level (step S402).

[0052] If the inflow control device 68 determines that the detected liquid level is not below a predetermined level (step S402, No), the liquid level sensor 67 detects the liquid level again (step S401). On the other hand, if the inflow control device 68 determines that the detected liquid level has fallen below a predetermined level (step S402, Yes), the inflow control device 68 instructs the pump 69 to operate (step S403). The operation of the pump 69 causes the raw material liquid 63 to flow from the storage container 73 into the tank 64 (step S404).

[0053] While the pump 69 is operating, if the liquid level sensor 67 determines that the liquid level is below a predetermined value (step S405, Yes), the lifting control device 49 instructs the pump 69 to continue operating (S403). On the other hand, if the detected liquid level is determined to have risen to a predetermined level (step S405, No), the inflow control device 68 instructs the pump 69 to stop, thereby stopping the inflow of the raw material liquid 63 (step S406). These adjustments to the liquid level A of the raw materials are performed at all times. By replenishing the raw material liquid 63 according to the discharge rate of the raw material liquid 63, the liquid level A of the raw material liquid 63 in the tank 64 can be kept at a constant height, and the height of the discharge port 61 can be kept at a constant height. Since the distance between the discharge port 61 and the sheet-like substrate can be kept constant without raising or lowering the nozzle 70 or the tank 64, the thickness (basis weight) of the ultrafine fibers in the sheet-like substrate can be stabilized without providing a lifting device.

[0054] <Embodiment 4> A 4th embodiment of the present disclosure, an electrospinning apparatus 80, will be described with reference to Figure 7. The 4th embodiment of the electrospinning apparatus 80 is equipped with a nozzle block 90 in place of the nozzle 20 and holding plate 30 of the 1st embodiment. The other configurations are the same as those of the 1st embodiment, so the same configurations will not be described, and the same effects and advantages as in the 1st embodiment will also not be described.

[0055] As shown in Figure 7, the electrospinning apparatus 80 of Embodiment 4 has a nozzle block 90 provided so as to be in contact with the raw material liquid 81. The nozzle block 90 has a plurality of nozzle holes 82 integrally formed therein, which penetrate the nozzle block 90 in the vertical direction. The nozzle holes 82 function as nozzles 91 for discharging the raw material liquid 81. The suction port 92 at the lower end of the nozzle holes 82 opens to the lower surface of the nozzle block 90 and is in contact with the raw material liquid 81. The raw material liquid 81, the tank 83, the sheet-like substrate 84, the collection electrode 85, the feed roller 86, and the winding roller 87 are the same as in Embodiment 1. The raw material liquid 81 stored in the tank 83 rises through the nozzle holes 82 by capillary action and is uniformly discharged from all discharge ports 89.

[0056] [Nozzle Block 90] The nozzle block 90 is made of a conductive material and is a component that covers the opening on the top surface of the tank 83. The nozzle block 90 is a thick, roughly rectangular plate. One side of the outer circumference of the nozzle block 90 is, for example, about 0.1 mm smaller than each side that forms the inner surface of the tank 83. The nozzle block 90 has a plurality of nozzle holes 82. The cross-sectional shape of the nozzle holes 82 is circular, and the diameter is, for example, about 0.1 mm. The nozzle holes 82 open on both the upper and lower surfaces of the nozzle block 90. ​​The part of the nozzle block 90 other than the nozzle holes 82 is defined as the block base material 88. The discharge ports 89 of the nozzle holes 82 open on the top surface of the nozzle block 90 and are arranged in a staggered pattern in a plan view. When the nozzle block 90 is fixed to the tank 83, there is a small gap between the outer circumference of the nozzle block 90 and the inner surface of the tank 83. The nozzle block 90 is made of a material with a specific gravity lower than the raw material liquid 81, such as a conductive resin. When the nozzle block 90 is housed in the tank 83, the nozzle block 90 is held in contact with the liquid surface A of the raw material liquid 81 by buoyancy alone, without sinking into the raw material liquid 81. The end (base end) of the nozzle 91 on the bottom surface of the tank 83 is in contact with the raw material liquid 83. Since the nozzle block 90 can be kept afloat by buoyancy, a device to hold the nozzle block 90 is unnecessary. The lower surface of the nozzle block 90 is in surface contact with the raw material liquid 81, and the suction port 92 is kept in contact with the raw material liquid 81. The nozzle block 90 covers, for example, 90% or more of the upper surface of the raw material liquid 81.

[0057] [Electrode charging section 95] The electrode charging unit 95 is a power source for applying voltage to the conductive nozzle block 90 and the collection electrode 85, respectively, through electrical connection. The conductive nozzle block 90 is connected to the positive electrode of the electrode charging unit 95. The collection electrode 85 is connected to the negative electrode of the electrode charging unit 95.

[0058] [Effects of the electrospinning apparatus 80 of Embodiment 4] The operation and effects of the electrospinning apparatus 80 of this fourth embodiment will now be described. The raw material liquid 81 moves from the lower end of the nozzle hole 82 of the nozzle block 90 to the discharge port 89 at the upper end by capillary action. When the raw material liquid 81 has moved to the upper end of the nozzle hole 82, a voltage is applied to the nozzle block 90 and the collection electrode 85 by the electrode charging unit 95, and the raw material liquid 81 becomes positively charged within the nozzle hole 82. The positively charged raw material liquid 81 is attracted toward the collection electrode 85 by electrostatic force. At this time, the solvent contained in the droplets volatilizes and is stretched. As a result, the fiber components are refined and spun into ultrafine fibers. The ultrafine fibers thus spun accumulate on the lower surface of the sheet-like substrate 84 to form a nonwoven fabric. The block substrate 88 in which the nozzle hole 82 is formed is a large metal block, so the inner wall surface of the nozzle hole 82 is difficult to deform. Therefore, the discharge amount from each nozzle 91 becomes constant, and the thickness of the nonwoven fabric can be kept constant.

[0059] <Embodiment 5> A field spinning apparatus 100 of Embodiment 5, which embodies the present disclosure, will be described with reference to Figure 8. The field spinning apparatus 100 of Embodiment 5 has a nozzle 101 with a different configuration from Embodiment 1. The other configurations are the same as those of Embodiment 1, so the same configurations will not be described, and the same effects and advantages as in Embodiment 1 will also not be described.

[0060] As shown in Figure 8, in Embodiment 5, the electrospinning apparatus 100 has a suction port 102 at the base end of the nozzle 101 that opens at the bottom surface 103 inside the tank 105. The raw material liquid 104, the tank 105, the holding plate 106, the sheet-like substrate 107, the collection electrode 108, the electrode charging section 109, the feed roller 111, and the winding roller 112 are the same as in Embodiment 1. The holding plate 106 is housed inside the tank 105 and fixed to the inner wall surface 114 of the tank 105.

[0061] [Nozzle 101] As shown in Figure 8, multiple nozzles 101 are fixed to a retaining plate 106 in a manner that penetrates the retaining plate 106 vertically. The nozzles 101 draw up the raw material liquid 104 stored in the tank 105 through the suction port 102 by capillary action and move it to the discharge port 110. The nozzles 101 have a narrow tube shape with a circular cross-section. Inside the nozzles 101, there is a narrow tube hole 113 for discharging the raw material liquid 104. The narrow tube hole 113 penetrates from the upper end to the lower end of the nozzle 101. The opening at the end (upper end) of the nozzle 101 (narrow tube hole 113) on the side of the collection electrode 108 functions as the discharge port 110. The base end (lower end) of the nozzle 101 (narrow tube hole 113) functions as the suction port 102. The suction port 102 is positioned so as to be in close proximity to the horizontal bottom surface 103 inside the tank 105 and facing it in the vertical direction. The distance between the suction port 102 of the nozzle 101 and the bottom surface 103 is, for example, approximately 1.0 cm.

[0062] The diameter of the nozzle 101 is, for example, 0.2 mm. Reducing the diameter makes it easier for electric field concentration to occur near the discharge port 110 of the nozzle 101. When electric field concentration occurs near the discharge port 110 of the nozzle 101, the strength of the electric field formed between the nozzle 101 and the sheet-like substrate 107 can be increased. Therefore, the voltage applied by the electrode charging unit 109 can be reduced. In other words, the driving voltage can be reduced.

[0063] The inner diameter of the discharge port 110 is, for example, 0.1 mm. The inner diameter of the discharge port 110 can be appropriately changed according to the cross-sectional dimensions of the ultrafine fibers to be formed. The inner diameter of the suction port 102 of the nozzle 101 is, for example, 0.1 mm. The tubular hole 113 is formed in a straight line from the suction port 102 to the discharge port 110. The suction port 102 of the nozzle 101 is in contact with the raw material liquid 104 stored in the tank 105. The raw material liquid 104 moves from the suction port 102 of the nozzle 101 to the discharge port 110 by capillary action through the tubular hole 113. In detail, when the suction port 102 of the nozzle 101, which has a cylindrical tubular shape, is brought into contact with the raw material liquid 104, the raw material liquid 104 rises along the inner surface of the tubular hole 113 by capillary action and reaches the discharge port 110.

[0064] [Effects of the electrospinning apparatus 100 of Embodiment 5] The operation and effects of the electrospinning apparatus 100 of this embodiment 5 will now be described. The raw material liquid 104 moves from the opening of the suction port 102 located on the bottom surface 103 inside the tank 105 of the electrospinning apparatus 100 to the upper end of the nozzle 101 by capillary action. When the raw material liquid 104 has moved to the upper end of the capillary hole 113, a voltage is applied to the holding plate 106 and the collection electrode 108 by the electrode charging unit 109, and the raw material liquid 104 becomes positively charged within the capillary hole 113. The positively charged raw material liquid 104 is attracted toward the collection electrode 108 by electrostatic force. At this time, the solvent contained in the droplets of raw material liquid 104 volatilizes and is stretched. As a result, the fiber components are refined and spun into ultrafine fibers. The ultrafine fibers thus spun are accumulated on the lower surface of the sheet-like substrate 107 to form a nonwoven fabric. In the electrospinning apparatus 100 of Embodiment 5, there is no need to raise or lower the nozzle 101 or tank 105 as the liquid level A of the raw material liquid 104 decreases. Therefore, even without a lifting device, the thickness (basis weight) of the ultrafine fibers in the sheet-like substrate 107 remains stable.

[0065] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments, for example, are also included in the technical scope of the present invention. (1) The electrospinning apparatus 10 of Embodiment 1 is equipped with a holding plate 30 that holds a plurality of nozzles 20, and the holding plate 30 is in surface contact with the raw material liquid 11, and the suction port 17 is kept in contact with the raw material liquid 11. The electrospinning apparatus may not have a holding plate, and the suction ports of the nozzles may be in contact with the raw material liquid. (2) In Embodiment 1, the holding plate 30 is held in contact with the liquid surface A of the raw material liquid 11 solely by the buoyancy of the raw material liquid 11. The electrospinning apparatus may be configured such that the holding plate 30 is fixed to the tank 13 using a fixing jig, and is not held solely by the buoyancy of the raw material liquid 11. (3) The holding plate 30 in Embodiment 1 is made of a conductive material and is connected to the positive electrode of the electrode charging section 25. The spinning electric field device may also use a tank made of a conductive material and connect the tank to the positive electrode of the electrode charging section. (4) In the electrospinning apparatus 10 of Embodiment 1, the multiple discharge ports 15 are arranged in a two-dimensional direction. The multiple discharge ports do not have to be arranged in a two-dimensional direction. Arrangement in a two-dimensional direction means, for example, that multiple rows of parallel discharge ports are provided, and the pitch of the discharge ports in all rows is substantially the same. (5) The discharge ports 15 of the nozzle 20 in this embodiment 1 are arranged in a staggered pattern. The discharge ports do not have to be arranged in a staggered pattern. (6) The nozzle 20 of Embodiment 1 is a cylindrical tubular shape with an inner diameter of approximately 0.1 mm. The inner diameter of the nozzle may be 0.01 mm or more and 1.0 mm or less. (7) The narrow tube bore 23 in this embodiment 1 is formed so that its inner diameter is constant from the suction port 17 to the discharge port 15. The narrow tube bore may be made so that its inner diameter decreases from the base end to the discharge port. (8) In Embodiment 1, the retaining plate 30 covers 90% or more of the upper surface of the raw material liquid 11. The retaining plate only needs to cover 70% or more of the upper surface of the raw material liquid. (9) In Embodiment 1, the nozzle 20 moves the raw material liquid 11 from the bottom to the top by capillary action. If the movement is to be carried out by capillary action, the nozzle may also be configured to move the raw material liquid from the top to the bottom. (10) The replenishment device 75 of Embodiment 2 uses a liquid level sensor 43. The replenishment device may replenish the raw material liquid from another storage container to the tank in accordance with the weight of the raw material liquid that has flowed out of the tank. (11) The replenishment device 75 of Embodiment 2 uses an electrode-type sensor as the liquid level sensor 43. The liquid level sensor may also be a capacitive-type level sensor or a microwave-type level sensor. (12) The lifting device 51 of Embodiment 3 is equipped with a liquid level sensor 67 and a lifting control device 49. The lifting device may raise the tank by manually operating the motor. (13) In Embodiment 5, the base end of the nozzle 101 is open at the bottom surface 103 inside the tank 105. The base end of the nozzle may be spaced far away from the bottom surface. [Explanation of symbols]

[0066] 10, 40, 60, 80, 100... Electrospinning machines 11,41,63,81,104…raw material liquid 13, 42, 64, 83, 105… Tanks 15,57,61,110…Discharge port 17,92,102… Inlet 20, 44, 70, 91, 101… nozzles 21,84,107…Sheet-like substrate 30,55,66,106…Retaining plate 75…Supply device 90... Nozzle block 31,103…Bottom part

Claims

1. A tank for storing the raw material liquid, A nozzle having a discharge port at its tip and a suction port at its base that is positioned to come into contact with the raw material liquid, which moves the raw material liquid to the discharge port by capillary action, A retaining plate that holds multiple nozzles, A liquid level sensor for detecting the position of the liquid level of the raw material liquid stored in the tank, The system includes a lifting device that raises and lowers the tank according to the height of the liquid level of the raw material liquid inside the tank, The holding plate is maintained in surface contact with the surface of the raw material liquid and with the suction port in contact with the raw material liquid solely by the buoyancy of the raw material liquid. An electrospinning apparatus that applies a voltage between the nozzle and the sheet-like substrate to atomize the raw material liquid discharged from the discharge port into ultrafine fibers and deposit them onto the sheet-like substrate.

2. The retaining plate is made of a conductive material, The electrospinning apparatus according to claim 1, wherein a power supply for applying a voltage between the sheet-like substrate and the holding plate is connected to the holding plate.

3. The electrospinning apparatus according to claim 1 or claim 2, further comprising a supplying device for supplying the raw material liquid to the tank in accordance with the amount of raw material liquid discharged from the discharge port.

4. The electrospinning apparatus according to claim 1 or claim 2, wherein the plurality of discharge ports are arranged in a two-dimensional direction.

5. The electrospinning apparatus according to claim 4, wherein the plurality of discharge ports are arranged in a staggered pattern.

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