Resin coating device and resin coating method

Abstract

A resin coating device comprises: a point having a point hole; a first die having a first die hole; a first resin supply passage; a second die having a second die hole; and a second resin supply passage. The axial deviation in the radial direction of a first reference axis passing through the first die hole along the direction of travel of a glass fiber and a second reference axis passing through the second die hole along the direction of travel is 3 μm or less. The second die hole has a second reduced diameter part, the diameter of which narrows downward from the inlet in the direction of travel. When the tilt angle of the second reduced diameter part is from 2 degrees to less than 6 degrees or from 8 degrees to 15 degrees, the height of the second reduced diameter part in the direction of travel is from 1 mm to 5 mm, and when the tilt angle of the second reduced diameter part is from 6 degrees to less than 8 degrees, the height of the second reduced diameter part in the direction of travel is from 1 mm to 3 mm.

Description

Resin application device and resin application method

[0001] This application claims priority to Japanese Patent Application No. 2024-118739, filed on July 24, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses an optical fiber resin coating device for forming a coating on the surface of an optical fiber.

[0003] Japanese Patent Application Publication No. 10-226540

[0004] A resin application device for passing a glass fiber and applying resin to a surface of the glass fiber includes: a point having a point hole through which the glass fiber is passed; a first die disposed directly below the point and having a first die hole through which the glass fiber is passed; a first resin supply passage connected to a first inlet located between the point and the first die; a second die disposed directly below the first die and having a second die hole through which the glass fiber is passed; and a second resin supply passage connected to a second inlet located between the first die and the second die. A first reference axis extending along the traveling direction of the glass fiber and passing through the first die hole and a second reference axis extending along the traveling direction and passing through the second die hole have a radial misalignment of 3 μm or less. The second die hole has a second tapered portion whose diameter narrows downward from the inlet in the traveling direction. When the inclination angle of the second reduced diameter portion is 2 degrees or more and less than 6 degrees or 8 degrees or more and 15 degrees or less, the height of the second reduced diameter portion in the direction of travel is 1 mm or more and 5 mm or less, and when the inclination angle of the second reduced diameter portion is 6 degrees or more and less than 8 degrees, the height of the second reduced diameter portion in the direction of travel is 1 mm or more and 3 mm or less.

[0005] Fig. 1 is a schematic cross-sectional view of a resin application apparatus according to a first embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of a first die of the resin application apparatus. Fig. 3 is a schematic cross-sectional view of a second die of the resin application apparatus. Fig. 4 is an enlarged cross-sectional view of a second die hole of the second die.

[0006] If an attempt is made to form a thinner coating layer, there is a risk that uneven thickness may occur.

[0007] An object of the present disclosure is to provide a resin application device that can reduce uneven thickness when applying a thin layer of resin to a glass fiber.

[0008] According to the present disclosure, it is possible to provide a resin application device that reduces uneven thickness when applying a thin layer of resin to a glass fiber.

[0009] First, embodiments of the present disclosure will be described. (1) A resin application device according to one aspect of the present disclosure is a resin application device that applies resin to a surface of a glass fiber by passing the glass fiber through the resin application device, the resin application device comprising: a point having a point hole through which the glass fiber is inserted; a first die disposed directly below the point and having a first die hole through which the glass fiber is inserted; a first resin supply passage connected to a first inlet located between the point and the first die; a second die disposed directly below the first die and having a second die hole through which the glass fiber is inserted; and a second resin supply passage connected to a second inlet located between the first die and the second die. A first reference axis extending along the traveling direction of the glass fiber and passing through the first die hole and a second reference axis extending along the traveling direction and passing through the second die hole have a radial misalignment of 3 μm or less. The second die hole has a second tapered portion whose diameter narrows downward from the inlet in the traveling direction. When the inclination angle of the second reduced diameter portion is 2 degrees or more and less than 6 degrees or 8 degrees or more and 15 degrees or less, the height of the second reduced diameter portion in the direction of travel is 1 mm or more and 5 mm or less, and when the inclination angle of the second reduced diameter portion is 6 degrees or more and less than 8 degrees, the height of the second reduced diameter portion in the direction of travel is 1 mm or more and 3 mm or less.

[0010] If the inclination angle of the second tapered portion is less than 2 degrees, thickness unevenness tends to occur in the second resin. If the inclination angle of the second tapered portion is more than 15 degrees, thickness unevenness tends to occur in the second resin.

[0011] When the inclination angle of the second tapered portion is 7 degrees, the resin pressure inside the second die hole is at its maximum. If the height of the second tapered portion is approximately 5 mm, the pressure inside the second die hole becomes too high, making it easy for deformation to occur in the primary layer made of the first resin. According to the present disclosure, when the inclination angle of the second tapered portion is 6 degrees or more and less than 8 degrees, the height of the second tapered portion in the traveling direction of the glass fiber is 1 mm or more and 3 mm or less. Therefore, deformation of the primary layer is unlikely to occur, and thickness unevenness is unlikely to occur in the secondary layer made of the second resin.

[0012] When the inclination angle of the second tapered portion is 2 degrees or more and less than 6 degrees, or 8 degrees or more and 15 degrees or less, and the height of the second tapered portion is 1 mm or more, thickness unevenness is unlikely to occur in the second resin. When the height of the second tapered portion is about 7 mm, the pressure of the second resin becomes too high, making it likely that deformation of the primary layer will occur. According to the present disclosure, when the inclination angle of the second tapered portion is 2 degrees or more and less than 6 degrees, or 8 degrees or more and 15 degrees or less, the height of the second tapered portion in the traveling direction of the glass fiber is 1 mm or more and 5 mm. Therefore, deformation of the primary layer is unlikely to occur, and thickness unevenness is unlikely to occur in the secondary layer.

[0013] (2) In the above (1), the first die may further include a first die lower surface that is a tapered surface rotationally symmetric about the first reference axis. The second die may further include a second die upper surface that abuts the first die lower surface and is a tapered surface rotationally symmetric about the second reference axis. An inclination angle of the first die lower surface with respect to the first reference axis and an inclination angle of the second die upper surface with respect to the second reference axis may be the same.

[0014] According to the present disclosure, the inclination angle of the lower surface of the first die relative to the first reference axis is the same as the inclination angle of the upper surface of the second die relative to the second reference axis, which makes it easy to align the positions of the first die holes with the positions of the second die holes and to keep the axial misalignment between the first reference axis and the second reference axis in the radial direction of the glass fiber to 3 μm or less, thereby making it difficult for deformation to occur in the primary layer and for thickness deviation to occur in the secondary layer.

[0015] Note that the phrase "the inclination angles are the same" does not only mean that the inclination angles are exactly the same, but also means that the difference between the inclination angles is sufficiently small and the inclination angles are evaluated as being substantially the same. The smaller the difference between the inclination angles, for example, ±0.1 degrees, ±0.05 degrees, or ±0.02 degrees, the easier it is to align the positions of the first die holes and the second die holes, and the smaller the amount of axial misalignment can be.

[0016] (3) A resin coating method according to one aspect of the present disclosure uses the resin coating device described in (1) or (2) above, and includes: a first resin coating step of inserting the glass fiber through the first die hole and coating a first resin onto the inserted glass fiber; and a second resin coating step of inserting the glass fiber through the second die hole located directly below the first die hole and coating a second resin onto the first resin on the inserted glass fiber, wherein a maximum resin pressure inside the second die hole is 60% or less of a maximum resin pressure inside the first die hole.

[0017] According to the present disclosure, the maximum resin pressure inside the second die hole is 60% or less of the maximum resin pressure inside the first die hole, so that deformation of the primary layer is unlikely to occur.

[0018] (4) In the above (3), the average coating thickness of the first resin may be 5 μm or more and 40 μm or less, and the average coating thickness of the second resin may be 5 μm or more and 30 μm or less.

[0019] According to the present disclosure, thickness unevenness is unlikely to occur, and the first resin and the second resin can be applied thinly to the glass fiber.

[0020] (Details of an embodiment of the present disclosure) Specific examples of a resin application device 1 according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0021] 1 is a schematic cross-sectional view of a resin application device 1 according to a first embodiment of the present disclosure. The resin application device 1 is configured to pass a glass fiber G1 through the resin application device 1 and apply a resin to the surface of the glass fiber G1. The diameter of the glass fiber G1 is, for example, φ80 μm or more and φ125 μm or less. As illustrated in FIG. 1 , the resin application device 1 includes a point 10, a first die 20, a second die 30, a first resin supply path 40, and a second resin supply path 50.

[0022] The point 10 is disposed at the entrance of the resin coating device 1. The point 10 is disposed directly above the first die 20 in the traveling direction D1 of the glass fiber G1. The point 10 is formed of an ultra-rigid member. The point 10 has a point lower surface 11 and a point hole 19. The point hole 19 is formed to allow the glass fiber G1 to pass through. The cross section of the point hole 19 in a plane perpendicular to the traveling direction D1 is circular.

[0023] In this embodiment, "up" includes a direction toward the upstream side of the traveling direction D1 of the glass fiber G1, and is the same as "up" with respect to the paper surface of Fig. 1. In this embodiment, "down" includes a direction toward the downstream side of the traveling direction D1 of the glass fiber G1, and is the same as "down" with respect to the paper surface of Fig. 1.

[0024] The second die 30 is disposed at the outlet of the resin coating device 1. The second die 30 is disposed directly below the first die 20 in the traveling direction D1 of the glass fiber G1. The second die 30 is formed of an ultra-rigid member. The ultra-rigid member is mainly composed of, for example, tungsten carbide (WC) and cobalt (Co). The second die 30 has a second die upper surface 31 and a second die hole 39. The second die hole 39 is formed to allow the glass fiber G1 to pass through. The cross section of the second die hole 39 in a plane perpendicular to the traveling direction D1 is circular.

[0025] The first die 20 is disposed between the point 10 and the second die 30 in the traveling direction D1 of the glass fiber G1. The first die 20 is formed of an ultra-rigid member. The first die 20 has a first die upper surface 21, a first die lower surface 22, and a first die hole 29. The first die upper surface 21 is formed to abut against the point lower surface 11. The first die lower surface 22 is formed to abut against the second die upper surface 31. The first die hole 29 is formed to allow the glass fiber G1 to pass through. The cross section of the first die hole 29 in a plane perpendicular to the traveling direction D1 is circular.

[0026] 1 , the first die upper surface 21 and the point lower surface 11 abutting against the first die upper surface 21 are tapered surfaces that are rotationally symmetrical about a first reference axis A1 that extends along the advancing direction D1 of the glass fiber G1 and passes through the first die hole 29. For example, the diameters of the first die upper surface 21 and the point lower surface 11 both gradually decrease downward in the advancing direction D1. Both the first die upper surface 21 and the point lower surface 11 have an inclination angle θ1 (see FIG. 2 ) with respect to the first reference axis A1.

[0027] 2 is a schematic cross-sectional view of the first die 20. As illustrated in FIG. 2, the "inclination angle" in this embodiment is the angle formed when an imaginary extension line of the tapered surface intersects with a reference axis, and is an angle that extends rotationally symmetrically around the reference axis. The inclination angle θ1 is, for example, 2 degrees or more and 30 degrees or less.

[0028] The first die lower surface 22 is a tapered surface that is rotationally symmetric about a first reference axis A1 that extends along the traveling direction D1 of the glass fiber G1 and passes through the first die hole 29. For example, the diameter of the first die lower surface 22 gradually increases downward in the traveling direction D1. The first die lower surface 22 has an inclination angle θ2 with respect to the first reference axis A1. The inclination angle θ2 is, for example, equal to or greater than 2 degrees and equal to or less than 30 degrees.

[0029] 3 is a schematic cross-sectional view of the second die 30. As illustrated in FIG. 3, the second die upper surface 31 is a tapered surface that is rotationally symmetrical about a second reference axis A2 that extends along the traveling direction D1 of the glass fiber G1 and passes through the second die hole 39. For example, the diameter of the second die upper surface 31 gradually increases downward in the traveling direction D1. The second die upper surface 31 has an inclination angle θ3 with respect to the second reference axis A2. The inclination angle θ3 is, for example, equal to or greater than 2 degrees and equal to or less than 30 degrees.

[0030] In this embodiment, the amount of axial misalignment between the first reference axis A1 and the second reference axis A2 in the radial direction of the glass fiber G1 is 3 μm or less.

[0031] The inclination angle θ2 of the first die lower surface 22 with respect to the first reference axis A1 and the inclination angle θ3 of the second die upper surface 31 with respect to the second reference axis A2 are the same.

[0032] Note that "the tilt angles are the same" does not only mean the case where the tilt angles are exactly the same, but also includes the case where the difference between the two is sufficiently small and evaluated to be substantially the same. The smaller the difference between the two is, for example, ±0.1 degrees, ±0.05 degrees, or ±0.02 degrees, the smaller the amount of axial misalignment between the first reference axis A1 and the second reference axis A2 in the radial direction of the glass fiber G1 can be.

[0033] As illustrated in FIG. 1 , the first resin supply path 40 is connected to a first inlet 41 located between the point 10 and the first die 20. The first inlet 41 is connected to the outlet of the point hole 19 and to the inlet of the first die hole 29 in the traveling direction D1 of the glass fiber G1. The first resin supply path 40 is formed to supply the primary resin to be applied to the surface of the glass fiber G1 to the first die hole 29. The primary resin is, for example, a urethane acrylate-based ultraviolet-curable resin. The primary resin is an example of a first resin.

[0034] The second resin supply path 50 is connected to a second inlet 51 located between the first die 20 and the second die 30. The second inlet 51 is connected to the outlet of the first die hole 29 and to the inlet of the second die hole 39 in the traveling direction D1 of the glass fiber G1. The second resin supply path 50 is formed to supply a secondary resin, which is different from the primary resin, to the second die hole 39. The secondary resin is applied onto the primary resin that covers the surface of the glass fiber G1. The secondary resin is, for example, a urethane acrylate-based ultraviolet-curable resin. The secondary resin is an example of a second resin.

[0035] Next, the second die hole 39 will be described in detail. Fig. 4 is an enlarged cross-sectional view of the second die hole 39. As illustrated in Fig. 4, the second die hole 39 has a second reduced diameter portion 391 and a second land portion 392.

[0036] The second tapered portion 391 is disposed at the entrance of the second die 30. The diameter of the second tapered portion 391 narrows downward from the entrance in the traveling direction D1 of the glass fiber G1. The second land portion 392 is disposed directly below the second tapered portion 391 and is connected to the second tapered portion 391. The diameter of the second land portion 392 is constant in the traveling direction D1 of the glass fiber G1. The second tapered portion 391 and the second land portion 392 are each part of the second die hole 39.

[0037] The cross section of the second reduced diameter portion 391 and the cross section of the second land portion 392 in a plane perpendicular to the traveling direction D1 of the glass fiber G1 are both circular.

[0038] The second reduced diameter portion 391 has a tapered surface 3911 that is rotationally symmetric about the second reference axis A2. The tapered surface 3911 has an inclination angle θ4 with respect to the second reference axis A2. The inclination angle θ4 is equal to or greater than 2 degrees and equal to or less than 15 degrees.

[0039] When the inclination angle θ4 of the second reduced diameter portion 391 is 2 degrees or more and less than 6 degrees, or 8 degrees or more and 15 degrees or less, the height H of the second reduced diameter portion 391 in the traveling direction D1 of the glass fiber G1 is 1 mm or more and 5 mm or less. When the inclination angle θ4 of the second reduced diameter portion 391 is 6 degrees or more and less than 8 degrees, the height H of the second reduced diameter portion 391 in the traveling direction D1 is 1 mm or more and 3 mm or less.

[0040] Next, a resin coating method using the resin coating apparatus 1 will be described. In other words, a resin coating method using the above-mentioned point 10, first die 20, and second die 30 will be described. The resin coating method includes a point insertion step, a first resin coating step, and a second resin coating step. In the point insertion step, the glass fiber G1 is inserted into the point hole 19 of the point 10 located at the entrance of the resin coating apparatus 1. The glass fiber G1 inserted into the point hole 19 is then inserted into the first die 20.

[0041] In the first resin application step, the glass fiber G1 inserted from the point 10 passes through the first die hole 29 of the first die 20. At this time, the primary resin is supplied into the first die hole 29 of the first die 20 from the first resin supply path 40. By inserting the glass fiber G1 into the first die hole 29 to which the primary resin has been supplied, the primary resin is applied onto the surface of the glass fiber G1. After passing through the first die hole 29, the glass fiber G1 is inserted into the second die 30.

[0042] In the second resin application process, the glass fiber G1 coated with the primary resin passes through the second die hole 39 of the second die 30. At this time, the secondary resin is supplied to the second die hole 39 of the second die 30 from the second resin supply path 50. The maximum resin pressure inside the second die hole 39 is 60% or less of the maximum resin pressure inside the first die hole 29. By inserting the glass fiber G1 through the second die hole 39 to which the secondary resin has been supplied, the secondary resin is applied onto the primary resin of the glass fiber G1. In this manner, the resin application device 1 applies the primary resin and the secondary resin to the glass fiber G1 to form a primary layer made of the primary resin and a secondary layer made of the secondary resin. The average coating thickness of the primary layer is 5 μm or more and 40 μm or less. The average coating thickness of the secondary layer is 5 μm or more and 30 μm or less.

[0043] As described above, the second die 30 of this embodiment has the second tapered diameter portion 391. When the inclination angle θ4 of the second tapered diameter portion 391 is less than 2 degrees, or when the inclination angle θ4 of the second tapered diameter portion 391 is greater than 15 degrees, thickness unevenness is likely to occur in the secondary layer. When the inclination angle θ4 of the second tapered diameter portion 391 is 7 degrees, the resin pressure inside the second die hole 39 is maximized. In this case, if the height H of the second tapered diameter portion 391 is approximately 5 mm, the pressure in the second die hole 39 becomes too high, and deformation of the primary layer is likely to occur.

[0044] In the present embodiment, when the inclination angle θ4 of the second tapered portion 391 is equal to or greater than 6 degrees and less than 8 degrees, the height H of the second tapered portion 391 in the traveling direction D1 of the glass fiber G1 is equal to or greater than 1 mm and equal to or less than 3 mm, which makes it difficult for the primary layer to deform and the secondary layer to have uneven thickness.

[0045] When the inclination angle θ4 of the second tapered diameter portion 391 is 2 degrees or more and less than 6 degrees, or 8 degrees or more and 15 degrees or less, and the height H of the second tapered diameter portion 391 is 1 mm or more, thickness unevenness is unlikely to occur in the secondary layer. When the height H of the second tapered diameter portion 391 is about 7 mm, the pressure of the second resin becomes too high, making it likely that deformation of the primary layer will occur. According to the present disclosure, when the inclination angle θ4 of the second tapered diameter portion 391 is 2 degrees or more and less than 6 degrees, or 8 degrees or more and 15 degrees or less, the height H of the second tapered diameter portion 391 in the traveling direction D1 of the glass fiber G1 is 1 mm or more and 5 mm. Therefore, deformation is unlikely to occur in the primary layer, and thickness unevenness is unlikely to occur in the secondary layer.

[0046] In the resin coating apparatus 1 of this embodiment, the first die 20 has a first die lower surface 22, which is a tapered surface rotationally symmetric about the first reference axis A1. The second die 30 abuts the first die lower surface 22 and has a second die upper surface 31, which is a tapered surface rotationally symmetric about the second reference axis A2. The inclination angle θ2 of the first die lower surface 22 relative to the first reference axis A1 and the inclination angle θ3 of the second die upper surface 31 relative to the second reference axis A2 are generally the same. This makes it easy to align the positions of the first die hole 29 and the second die hole 39, and makes it easy to keep the axial misalignment between the first reference axis A1 and the second reference axis A2 in the radial direction of the glass fiber G1 to 3 μm or less. This makes it difficult for thickness deviations to occur in the primary layer and the secondary layer.

[0047] In the resin coating method using the resin coating apparatus 1, the maximum resin pressure inside the second die hole 39 is 60% or less of the maximum resin pressure inside the first die hole 29. Therefore, deformation of the primary layer is unlikely to occur.

[0048] (Evaluation Experiment) Hereinafter, the present embodiment will be described in more detail by showing the results of evaluation tests using examples and comparative examples according to the present embodiment. Note that the present disclosure is not limited to these examples.

[0049] In the evaluation experiment, the inclination angle θ4 and height H of the second tapered portion 391 shown in FIG. 4 were evaluated. More specifically, multiple types of second die holes 39 were prepared, and simulations and experiments were conducted. In the simulation, the maximum resin pressure inside the first die hole 29 and the maximum resin pressure inside the second die hole 39 were calculated. In the experiment, a primary layer and a secondary layer were formed on the surface of the glass fiber G1 using the first die 20 and multiple types of second dies 30. The primary layer was then visually inspected for deformation and the thickness uniformity of the secondary layer was determined. In both the simulation and the experiment, the radial misalignment between the first reference axis A1 passing through the first die hole 29 and the second reference axis A2 passing through the second die hole 39 was 3 μm or less. The diameter of the first die hole 29 was, for example, 200 μm. The diameter of the second land portion 392 of the second die hole 39 was, for example, 300 μm.

[0050] The presence or absence of deformation of the primary layer was confirmed by visually inspecting the cross section of the glass fiber G1 by cutting the glass fiber G1 on which the primary layer and secondary layer were formed perpendicularly to the longitudinal direction. In this evaluation experiment, the "thickness-free ratio" refers to the percentage obtained by dividing the minimum thickness of the secondary layer in the radial direction of the glass fiber G1 at the cross section of the glass fiber G1 by the maximum thickness of the secondary layer at the maximum thickness. For example, if the thickness of the secondary layer is uniform, the thickness-free ratio is 100%. The greater the difference between the minimum and maximum thicknesses due to deformation of the secondary layer, the lower the thickness-free ratio. In this evaluation experiment, samples with a thickness-free ratio of more than 50% were designated as examples, and samples with a thickness-free ratio of 50% or less were designated as comparative examples. The evaluation results are shown in Table 1.

[0051] Samples No. 2 to No. 4, No. 6, No. 7, and No. 9 to No. 14 are examples, while Samples No. 1, No. 5, No. 8, and No. 15 to No. 17 are comparative examples.

[0052] As examples, in Samples No. 2 to No. 4, the inclination angle θ4 of the second reduced diameter portion 391 is 2 degrees. In Sample No. 2, the height H of the second reduced diameter portion 391 is 1 mm. In Sample No. 3, the height H of the second reduced diameter portion 391 is 3 mm. In Sample No. 4, the height H of the second reduced diameter portion 391 is 5 mm.

[0053] In Samples No. 6 and No. 7, the inclination angle θ4 of second reduced diameter portion 391 is 7 degrees. In Sample No. 6, the height H of second reduced diameter portion 391 is 1 mm. In Sample No. 7, the height H of second reduced diameter portion 391 is 3 mm.

[0054] In Samples No. 9 to No. 11, the inclination angle θ4 of second reduced diameter portion 391 is 12 degrees. In Sample No. 9, the height H of second reduced diameter portion 391 is 1 mm. In Sample No. 10, the height H of second reduced diameter portion 391 is 3 mm. In Sample No. 11, the height H of second reduced diameter portion 391 is 5 mm.

[0055] In Samples No. 12 to 14, the inclination angle θ4 of the second reduced diameter portion 391 is 15 degrees. In Sample No. 12, the height H of the second reduced diameter portion 391 is 1 mm. In Sample No. 13, the height H of the second reduced diameter portion 391 is 3 mm. In Sample No. 14, the height H of the second reduced diameter portion 391 is 5 mm.

[0056] As a comparative example, in Sample No. 1, the inclination angle θ4 of the second reduced diameter portion 391 is 0 degrees, and the height H of the second reduced diameter portion 391 is 0 mm. In Sample No. 5, the inclination angle θ4 of the second reduced diameter portion 391 is 2 degrees, and the height H of the second reduced diameter portion 391 is 7 mm. In Sample No. 8, the inclination angle θ4 of the second reduced diameter portion 391 is 7 degrees, and the height H of the second reduced diameter portion 391 is 5 mm. In Samples No. 15 to No. 17, the inclination angle θ4 of the second reduced diameter portion 391 is all 18 degrees. In Sample No. 15, the height H of the second reduced diameter portion 391 is 1 mm. In Sample No. 16, the height H of the second reduced diameter portion 391 is 3 mm. In Sample No. 17, the height H of the second reduced diameter portion 391 is 5 mm.

[0057] First, the simulation results confirmed that when the maximum pressure inside the first die 20 is 3.5 MPa, if the maximum resin pressure inside the second die hole 39 exceeds 60% of the maximum resin pressure inside the first die hole 29, the resin pressure inside the second die hole 39 is too high and deformation of the primary layer occurs (Sample No. 5 and Sample No. 8). On the other hand, it was confirmed that if the maximum resin pressure inside the second die hole 39 is 60% or less of the maximum resin pressure inside the first die hole 29, no deformation of the primary layer occurs. Note that the simulation was performed using FLOW3D (registered trademark), a general-purpose three-dimensional thermal fluid analysis software from Flow Science Japan, Inc.

[0058] As shown in Sample No. 1 in Table 1, when the inclination angle θ4 of the second reduced diameter portion 391 was less than 2 degrees, the thickness-free rate of the secondary layer was 40%, and thickness unevenness of the secondary layer was confirmed. Furthermore, as shown in Samples No. 15 to No. 17, when the inclination angle θ4 of the second reduced diameter portion 391 exceeded 15 degrees, the thickness-free rate of the secondary layer was 40%, and thickness unevenness of the secondary layer was confirmed. From the above, it was confirmed that when the inclination angle θ4 of the second reduced diameter portion 391 was 2 degrees or more and 12 degrees or less, thickness unevenness did not occur in the secondary layer.

[0059] Simulations and experiments have shown that when the inclination angle θ4 of the second tapered portion 391 is 7 degrees, the resin pressure inside the second die hole 39 is at its maximum. It has also been found that the longer the height H of the second tapered portion 391, the greater the resin pressure inside the second die hole 39. However, if the resin pressure inside the second die hole 39 is too high, the resin pressure in the second die hole 39 may crush the primary layer, causing deformation of the primary layer. For example, as shown in Sample No. 8, when the inclination angle θ4 of the second tapered portion 391 is 7 degrees and the height H of the second tapered portion 391 is 5 mm, it was confirmed that deformation of the primary layer occurred.

[0060] As shown in Sample No. 6 in Table 1, when the inclination angle θ4 of the second tapered portion 391 was 7 degrees and the height H was 1 mm, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the thickness-free rate was 78%, confirming that no deformation occurred in the secondary layer. Furthermore, as shown in Sample No. 7, when the inclination angle θ4 of the second tapered portion 391 was 7 degrees and the height H was 3 mm, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the thickness-free rate was 85%, confirming that no deformation occurred in the secondary layer. From the above, it was confirmed that when the inclination angle θ4 of the second tapered portion 391 was 6 degrees or more and less than 8 degrees and the height H of the second tapered portion 391 was 1 mm or more and 3 mm or less, no deformation occurred in the primary layer and no thickness-free rate occurred in the secondary layer.

[0061] As shown in Sample No. 2 in Table 1, when the inclination angle θ4 of the second tapered portion 391 was 2 degrees and the height H was 1 mm, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the thickness-free rate was 64%, confirming that no deformation occurred in the secondary layer. As shown in Sample No. 3, when the inclination angle θ4 of the second tapered portion 391 was 2 degrees and the height H was 3 mm, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the thickness-free rate was 80%, confirming that no deformation occurred in the secondary layer. As shown in Sample No. 4, when the inclination angle θ4 of the second tapered portion 391 was 2 degrees and the height H was 5 mm, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the thickness-free rate was 88%, confirming that no deformation occurred in the secondary layer. From the above, it was confirmed that if the inclination angle θ4 of the second reduced diameter portion 391 is 2 degrees or more and less than 6 degrees, and the height H of the second reduced diameter portion 391 is 1 mm or more and 5 mm or less, no deformation occurs in the primary layer and no thickness deviation occurs in the secondary layer.

[0062] Furthermore, as shown in Samples No. 9 to No. 11 in Table 1, when the inclination angle θ4 of the second tapered portion 391 was 12 degrees and the height H was 1 mm or more and 5 mm or less, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the non-uniform thickness rate was 70% or more, and no deformation occurred in the secondary layer. As shown in Samples No. 12 to No. 14 in Table 1, when the inclination angle θ4 of the second tapered portion 391 was 15 degrees and the height H was 1 mm or more and 5 mm or less, it was confirmed that no deformation occurred in the primary layer. Furthermore, in this case, the non-uniform thickness rate was 60% or more, and no deformation occurred in the secondary layer. From the above, it was confirmed that when the inclination angle θ4 of the second tapered portion 391 was 8 degrees or more and 15 degrees or less and the height H of the second tapered portion 391 was 1 mm or more and 5 mm or less, no deformation occurred in the primary layer and no non-uniform thickness occurred in the secondary layer.

[0063] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0064] It should be understood that at least one configuration or feature described in each embodiment or example can be combined with other embodiments or examples, or can be modified in various ways.

[0065] 1 Resin application device 10 Point 11 Point lower surface 19 Point hole 20 First die 21 First die upper surface 22 First die lower surface 29 First die hole 30 Second die 31 Second die upper surface 39 Second die hole 391 Second reduced diameter portion 3911 Tapered surface 392 Second land portion 40 First resin supply path 41 First inlet 50 Second resin supply path 51 Second inlet G1 Glass fiber D1 Traveling direction θ1, θ2, θ3, θ4 Inclination angle A1 First reference axis A2 Second reference axis H Height

Claims

1. A resin application device for passing a glass fiber and applying resin to the surface of the glass fiber, comprising: a point having a point hole through which the glass fiber is passed; a first die located directly below the point and having a first die hole through which the glass fiber is passed; a first resin supply path connected to a first inlet located between the point and the first die; a second die located directly below the first die and having a second die hole through which the glass fiber is passed; and a second resin supply path connected to a second inlet located between the first die and the second die, wherein the radial axial deviation between a first reference axis that runs along the traveling direction of the glass fiber and passes through the first die hole and a second reference axis that runs along the traveling direction and passes through the second die hole is 3 μm or less, the second die hole has a second tapered portion whose diameter narrows as it goes downward from the inlet in the traveling direction, and when the inclination angle of the second tapered portion is 2 degrees or more and less than 6 degrees or 8 degrees or more and 15 degrees or less, the height of the second tapered portion in the traveling direction is 1 mm or more and 5 mm or less, When the inclination angle of the second reduced diameter portion is equal to or greater than 6 degrees and less than 8 degrees, the height of the second reduced diameter portion in the traveling direction is equal to or greater than 1 mm and equal to or less than 3 mm.

2. The resin application device described in claim 1, wherein the first die further has a first die lower surface which is a tapered surface that is rotationally symmetrical about the first reference axis, and the second die further has a second die upper surface which abuts the first die lower surface and is a tapered surface that is rotationally symmetrical about the second reference axis, and the inclination angle of the first die lower surface relative to the first reference axis and the inclination angle of the second die upper surface relative to the second reference axis are the same.

3. A resin application method using the resin application device described in claim 1 or claim 2, comprising: a first resin application step of inserting the glass fiber through the first die hole and applying a first resin onto the inserted glass fiber; and a second resin application step of inserting the glass fiber through the second die hole located directly below the first die hole and applying a second resin onto the first resin on the inserted glass fiber, wherein the maximum resin pressure inside the second die hole is 60% or less of the maximum resin pressure inside the first die hole.

4. A resin application method according to claim 3, wherein the average coating thickness of the first resin is 5 μm or more and 40 μm or less, and the average coating thickness of the second resin is 5 μm or more and 30 μm or less.

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