OPTICAL FIBER TAPE

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical fiber ribbon.BACKGROUND ART

[0002] Patent Literatures 1 and 2 each disclose a so-called intermittently coupled optical fiber ribbon. Patent Literature 1 discloses an optical fiber ribbon obtained by applying approximately the same amount of an adhesive member, which bonds optical fibers constituting the optical fiber ribbon, to both an upper side and a lower side of the optical fiber ribbon. Patent Literature 1 further discloses that by setting a thickness of the adhesive member for the optical fiber ribbon at "thickness = (√3 - 1) / 2 × D (D is fiber diameter)", optical fibers are prevented from coming into contact with the adhesive member of other optical fibers when densely stacked.

[0003] Also in the optical fiber ribbon of Patent Literature 2, an adhesive member is applied to both an upper side and a lower side of the optical fiber ribbon. Patent Literature 2 further discloses that a thickness of a part of the adhesive member is set at such a thickness that the adhesive member protrudes further than a tangent line passing through surfaces of coated optical fibers at least at a central portion of the adhesive member.

[0004] Patent Literature 3 relates to an optical fiber ribbon comprising three or more optical fibers arranged in parallel and connecting portions connecting the respective adjacent two optical fibers. The connecting portions are formed intermittently in each of a ribbon longitudinal direction and a ribbon width direction. The connecting portions have a specific split length.

[0005] Patent Literature 4 is concerned with a manufacturing method of an intermittently connected optical fiber ribbon in which stopping of application of ultraviolet curable resin which forms a connection part is good and less dripping of the resin occurs.

[0006] The method for manufacturing described in Patent Literature 5 yields a thin coated optical fiber of an optical fiber ribbon by which primary coated optical fibers are integrated with a little adhesive resin and fiber cord separation is facilitated.

[0007] The optical fiber ribbon described in Patent Literature 6 comprises first and second optical fibers arranged in parallel. At least one coupling member made of a resin material is present. The coupling member couples the first and second optical fibers by adhering the first and second optical fibers to each other intermittently in a longitudinal direction of the first and second optical fibers. The breaking elongation of the resin material constituting the coupling member is 200% to 500%.

[0008] Patent Literature 7 relates to a rollable optical fiber ribbon comprising a plurality of optical fibers and a ribbon body coupled to and supporting the plurality of optical fibers in an array. The ribbon body may comprise a plurality of discreet bridges located between adjacent pairs of optical fibers, wherein each of the discreet bridges are separated from each other in a longitudinal direction by a gap.

[0009] Patent Literature 8 provides an intermittent connection-type optical fiber tape core wire in which in a state where a plurality of optical fiber core wires are arranged in parallel between some or all of the plurality of optical fiber core wires, connection points in which adjacent optical fiber core wires are connected by a connecting resin and non-connection parts in which adjacent optical fiber core wires are not connected are provided intermittently in a longitudinal direction. At least a portion of the non-connection parts have a convex portion of the connecting resin having a tip of an acute angle in a cross-sectional view in a direction orthogonal to the longitudinal direction.CITATION LISTPATENT LITERATURE

[0010] Patent Literature 1: JP2016-133607A Patent Literature 2: JP2016-146003A Patent Literature 3: US 2015 / 049997 A1 Patent Literature 4: JP 2012 208312 A Patent Literature 5: JP 2003 241042 A Patent Literature 6: US 2017 / 090135 A1 Patent Literature 7: US 2019 / 049681 A1 Patent Literature 8: WO 2020 / 162501 A1 SUMMARY OF INVENTION

[0011] According to the present invention, there is provided an intermittently coupled optical fiber ribbon as defined in claim 1.BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 is a schematic plan view showing an optical fiber ribbon according to an embodiment. Fig. 2 is a schematic cross-sectional view of an optical fiber according to the embodiment. Fig. 3 is a schematic cross-sectional view of a bonded portion in the optical fiber ribbon according to the embodiment. Fig. 4 is a schematic side view of the bonded portion in the optical fiber ribbon according to the embodiment. DESCRIPTION OF EMBODIMENTSTECHNICAL PROBLEM

[0013] In the optical fiber ribbon described in Patent Literature 1, the same amount of an adhesive resin is provided on both sides of the optical fiber ribbon. The thickness of the adhesive resin is set at such a thickness that the adhesive resin does not come into contact with other optical fibers. For this reason, when a force is applied to roll and bend the optical fiber ribbon in a cross-sectional direction thereof at the time of housing the optical fiber ribbon in an optical cable, breakage of the bent adhesive resin on an outer side or peeling of the adhesive resin from optical fibers is likely to occur. As a result, the optical fibers may be separated.

[0014] In the optical fiber ribbon described in Patent Literature 2, since the thickness of a part of the bonded portion on both sides of the optical fiber ribbon is set at such a thickness that the bonded portion protrudes further than the tangent line passing through surfaces of coated optical fibers at least at the central portion of the bonded portion, a cross-sectional area of the optical fiber ribbon increases, which is disadvantageous to increasing a density of an optical cable.

[0015] An object of the present disclosure is to prevent an increase in a cross-sectional area of an optical fiber ribbon, make breakage of an adhesive resin or peeling between the adhesive resin and the optical fiber less likely to occur, and reduce a risk of separation of an optical fiber.ADVANTAGEOUS EFFECTS OF INVENTION

[0016] According to a configuration of the present disclosure, it is possible to prevent an increase in a cross-sectional area of an optical fiber ribbon, make breakage of the adhesive resin or peeling between the adhesive resin and the optical fiber less likely to occur, and reduce a risk of separation of an optical fiber.DESCRIPTIONS OF EMBODIMENTS

[0017] Embodiments of the present disclosure are listed and described.

[0018] According to an aspect of the present disclosure, there is provided an intermittently coupled optical fiber ribbon in which a bonded portion in which adjacent optical fibers are bonded by an adhesive resin and a non-bonded portion in which the adjacent optical fibers are not bonded by the adhesive resin are intermittently provided in a longitudinal direction among a part or all of a plurality of optical fibers arranged side by side in a width direction orthogonal to the longitudinal direction.

[0019] The bonded portion is provided on one side of the optical fiber ribbon.

[0020] A part of the bonded portion protrudes further than a tangent line passing through surfaces of the adjacent optical fibers on the one side.

[0021] In the longitudinal direction, at least one of longitudinal end portions of the bonded portion has a larger protrusion height than a central portion of the bonded portion.

[0022] The adhesive resin has a composite elastic modulus of 0.5 GPa or more and 6.0 GPa or less at 23°C.

[0023] In the longitudinal end portions of the bonded portion in the longitudinal direction, the adhesive resin generally has a smaller thickness than the central portion of the bonded portion in the longitudinal direction since the adhesive resin is interrupted when applied. In this case, the bonded portion is likely to break or be peeled from the longitudinal end portions where stress is easily concentrated. In the above configuration, since at least one of the longitudinal end portions of the bonded portion is thicker than the central portion of the bonded portion in the longitudinal direction, the bonded portion can be less likely to break or be peeled off from the longitudinal end portions, and a risk of separation of the optical fibers can be reduced. In addition, since the adhesive resin has a composite elastic modulus of 0.5 GPa or more, the adhesive resin can be less likely to break or the like, and since the composite elastic modulus is 6.0 GPa or less, transmission loss at low temperature can be reduced. In addition, since the adhesive resin is provided only on a surface on one side of the optical fiber ribbon, an increase in a cross-sectional area of the optical fiber ribbon can be prevented, thereby contributing to an increase in a density of an optical cable.

[0024] In the optical fiber ribbon, tear strength when tearing the bonded portion measured based on a tear test defined in JIS C 6838:2019 is preferably 0.005 N or more and 0.200 N or less.

[0025] According to this configuration, the tear strength for the bonded portion is set at 0.005 N or more, and thus the adhesive resin can be less likely to break or the like, and the risk of separation of the optical fibers can be further reduced. In addition, since the tear strength for the bonded portion is set at 0.200 N or less, the adhesive resin is less likely to remain on the optical fibers when an operator tears the bonded portion, and a decrease in workability in a subsequent step such as insertability of the optical fibers into a protective tube can be prevented.

[0026] In the optical fiber ribbon, a maximum value of the protrusion height of the bonded portion from the tangent line is preferably 10 µm or more and 100 µm or less.

[0027] According to this configuration, the maximum value of the protrusion height is set at 10 µm or more to increase the amount of the adhesive resin used and the cross-sectional area of the adhesive resin, and thus the adjacent optical fibers can be more firmly bonded. As a result, the adhesive resin can be less likely to break due to an external force or the like, and the risk of separation of the optical fibers can be further reduced. In addition, since the maximum value of the protrusion height is set at 100 µm or less, deterioration of transmission loss at low temperature can be reduced.

[0028] In the optical fiber ribbon, in the width direction, each of widthwise end portions of the bonded portion is preferably located outside relative to a center of a corresponding one of the adjacent optical fibers.

[0029] According to this configuration, a sufficient amount of the adhesive resin is used, and a contact area between the adhesive resin and the optical fibers is increased in the width direction. Accordingly, breakage of the adhesive resin or peeling between the adhesive resin and the optical fibers can be less likely to occur, and the risk of separation of the optical fibers can be further reduced.DETAILS OF EMBODIMENTS

[0030] Hereinafter, examples of the embodiments according to the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements are denoted by the same reference numerals even in different drawings, and redundant description will be appropriately omitted. In the drawings used for the following description, the scale is appropriately changed to make members recognizable.

[0031] First, an overview of an optical fiber ribbon 1 of the present disclosure and optical fibers 10 provided therein will be described with reference to Figs. 1 and 2. Fig. 1 is a schematic plan view showing the optical fiber ribbon 1 according to the present embodiment. The optical fiber ribbon 1 includes a plurality of (12 in this example) optical fibers 10 (including 10A and 10B). The plurality of optical fibers 10 are arranged side by side in a width direction W orthogonal to a longitudinal direction L. The optical fiber ribbon 1 is an intermittently coupled optical fiber ribbon in which a bonded portion 2, in which adjacent optical fibers 10 are bonded by an adhesive resin, and a non-bonded portion 3, in which the adjacent optical fibers 10 are not bonded by the adhesive resin, are intermittently provided along the longitudinal direction L.

[0032] In the optical fiber ribbon 1 shown in Fig. 1, every two independent optical fibers 10 are bonded by the adhesive resin. Alternatively, every three optical fibers 10 may be bonded. The optical fiber ribbon 1 may be constituted by a plurality of optical fibers each obtained by collectively coating a plurality of optical fibers 10 with a coating resin and coupling the plurality of coated optical fibers 10. Locations where the bonded portion 2 and the non-bonded portion 3 are intermittently provided may be provided among a part of the optical fibers 10 or among all optical fibers 10.

[0033] Fig. 2 is a schematic cross-sectional view of the optical fiber 10 according to the present embodiment. Fig. 2 is a schematic cross-sectional view of the optical fiber 10 shown in Fig. 1 cleaved along a plane including a thickness direction perpendicular to the longitudinal direction L and the width direction W.

[0034] The optical fiber 10 shown in Fig. 2 includes an optical fiber 11, a primary resin layer 12, a secondary resin layer 13, and a colored resin layer 14. An outer diameter of the optical fiber 10 is not particularly limited and may be, for example, about 200 µm or more or less.

[0035] The optical fiber 11 includes a core and cladding. The optical fiber 11 is, for example, a glass fiber. The primary resin layer 12 covers an outer periphery of the optical fiber 11. The primary resin layer 12 is formed of, for example, a soft ultraviolet curable resin having a relatively low Young's modulus. The secondary resin layer 13 covers an outer periphery of the primary resin layer 12. The secondary resin layer 13 is formed of, for example, a hard ultraviolet curable resin having a relatively high Young's modulus. The colored resin layer 14 covers an outer periphery of the secondary resin layer 13. The colored resin layer 14 is a layer for improving identification of the optical fiber 10, and is formed of, for example, a colored ultraviolet curable resin.

[0036] Next, the bonded portion 2 in the optical fiber ribbon 1 will be described in detail with reference to Figs. 3 and 4. Fig. 3 is a schematic cross-sectional view of the bonded portion 2 in the optical fiber ribbon 1 according to the present embodiment. Specifically, Fig. 3 is a schematic cross-sectional view when the optical fibers 10A and 10B and the bonded portion 2 provided between the optical fibers 10A and 10B shown in Fig. 1 are cleaved along a plane including the thickness direction. In Fig. 3, layers provided in the optical fibers 10A and 10B are not shown.

[0037] The bonded portion 2 is formed by curing an adhesive resin. A type of the adhesive resin is not particularly limited as long as a composite elastic modulus thereof satisfies the above definition, and for example, an acrylic ultraviolet curable resin or an epoxy ultraviolet curable resin may be used. The adhesive resin may be a thermosetting resin.

[0038] The composite elastic modulus of the adhesive resin at 23°C after curing is 0.5 GPa or more and 6.0 GPa or less. The composite elastic modulus is preferably 1 GPa or more, and more preferably 2 GPa or more from a viewpoint of making the adhesive resin less likely to break or the like. The composite elastic modulus is preferably 4.5 GPa or less, and more preferably 3.0 GPa or less from a viewpoint of further reducing transmission loss at low temperature. The composite elastic modulus of the adhesive resin may be adjusted by, for example, the type of the adhesive resin, a molecular weight of an oligomer, the number of functional groups contained in a monomer, and a blending ratio thereof. The composite elastic modulus in the present specification is a composite elastic modulus in the thickness direction measured by a test method based on ISO 14577.

[0039] As shown in Fig. 3, a part of the bonded portion 2 protrudes upward than a tangent line T passing through surfaces (contact point Q1, contact point Q2) of adjacent optical fibers 10A and 10B on one side. The protrusion may be provided, for example, by adjusting an application amount of the adhesive resin. Here, one side means one of an upper side and a lower side relative to a line connecting centers of adjacent optical fibers.

[0040] A maximum value H of a height of the protrusion of the bonded portion 2 from the tangent line T is preferably 10 µm or more and 100 µm or less, and more preferably 20 µm or more and 50 µm or less. The maximum value H of the height of the protrusion may be provided, for example, by adjusting the application amount of the adhesive resin.

[0041] The height of the protrusion is preferably maximum in a vicinity of a center of the bonded portion 2 in the width direction W. That is, the height of the protrusion is preferably maximum in a vicinity of a straight line P3 passing through a contact point between the optical fiber 10A and the optical fiber 10B. The bonded portion 2 is preferably gradually inclined in a curved shape from the vicinity of the center of the bonded portion 2 toward widthwise end portions 2a and 2b thereof in the width direction W.

[0042] In the width direction W, each of the widthwise end portions 2a and 2b of the bonded portion 2 is located outside relative to a center of a corresponding one of the adjacent optical fibers 10A and 10B. Specifically, the widthwise end portion 2a is located outside relative to a straight line P1 connecting a center point O1 of the optical fiber 10A and the contact point Q1. Similarly, the widthwise end portion 2b is located outside relative to a straight line P2 connecting a center point O2 of the optical fiber 10B and the contact point Q2. The outside refers to outside when the straight line P3 is a center. When three or more optical fibers 10 are bonded to form the bonded portion 2, the widthwise end portion 2a and the widthwise end portion 2b are formed between each of two outermost optical fibers 10 among the three or more optical fibers 10 and the optical fiber 10 located inside relative to a corresponding one of the two outermost optical fibers 10.

[0043] In the width direction W, a distance U between the widthwise end portion 2a and the center of the optical fiber 10A (distance between a straight line P4, which passes through the widthwise end portion 2a and is parallel to the straight line P1, and the straight line P1) is preferably equal to or greater than 1 / 10R (R is a radius of the optical fibers 10A and 10B), and more preferably equal to or greater than 1 / 5R, from the viewpoint of making the adhesive resin less likely to break or the like. From the viewpoint of reducing deterioration of transmission loss at low temperature, the distance U is preferably equal to or less than 2 / 3R, and more preferably equal to or less than 1 / 2R. The distance U may be controlled by, for example, adjusting a viscosity or the amount of the adhesive resin applied. The same applies to a distance between the widthwise end portion 2b and the center of the optical fiber 10B (distance between a straight line that passes through the widthwise end portion 2b and is parallel to the straight line P2 and the straight line P2).

[0044] Tear strength in the width direction W for the bonded portion 2 is preferably 0.005 N or more and 0.200 N or less, and more preferably 0.02 N or more and 0.10 N or less. The tear strength in the present specification is measured based on a tear test (IEC 60794-1-23:2019 ribbon tear test) defined in JIS C 6838:2019.

[0045] Fig. 4 is a schematic side view of the bonded portion 2 in the optical fiber ribbon 1 according to the present embodiment. In the longitudinal direction L, at least one of longitudinal end portions 2c and 2d of the bonded portion 2 preferably has a larger protrusion height than a central portion of the bonded portion 2. As in the example of Fig. 4, both of the longitudinal end portions 2c and 2d of the bonded portion 2 in the longitudinal direction L preferably have a larger protrusion height than the central portion of the bonded portion 2 in the longitudinal direction L. The protrusions of the longitudinal end portions 2c and 2d of the bonded portion 2 may be controlled by, for example, adjusting the application amount of the adhesive resin. The protrusion height of the bonded portion 2 from the central portion is preferably 20 µm or more and 100 µm or less.Examples

[0046] Hereinafter, the present disclosure will be described in more detail with reference to examples according to the present disclosure. The present disclosure is not limited to the following examples.

[0047] Structures and physical properties in the following production examples were measured by the following methods.Composite Elastic Modulus

[0048] A composite elastic modulus of a cured adhesive resin in a thickness direction was acquired by a test method based on ISO 14577 using a nanoindenter (Hysitron TI 950 Tribolndenter manufactured by Bruker). An indentation depth was set at 100 nm, and the measurement was performed using a Berkovich indenter.Presence And Absence of Protrusion, Height, and Position of End Portion

[0049] Presence and absence of the protrusion of the bonded portion 2 from the tangent line T in the width direction W, the maximum value H of the height of the protrusion, and positions of the widthwise end portions 2a and 2c were measured using a laser microscope. The same applies to presence and absence of the protrusions of the longitudinal end portions 2c and 2d of the bonded portion 2 in the longitudinal direction L.Separation Resistance

[0050] The optical fiber ribbon 1 was evaluated based on a twisting test defined in IEC 60794-1-2. Evaluation criteria are shown below. A: not separated even after 20 twists by 180°. B: separated after 15 twists or more and 20 twists or less by 180°. C: separated after 10 twists or more and 15 twists or less by 180°. D: separated after 5 twists or more and 10 twists or less by 180°. E: separated after 5 twists or less by 180°. Characteristics at Low Temperature

[0051] The optical fiber ribbon 1 was subjected to a heat cycle test in which one cycle of normal temperature (23°C) → -40°C → -60°C was repeated 6 times. An attenuation amount per unit distance when light having a wavelength of 1. 55 µm was incident on the optical fiber 11 provided in the optical fiber ribbon 1 was measured in environments of 23°C and -60°C, and characteristics of the optical fiber ribbon 1 were evaluated by a difference in measured value between two temperature environments. Evaluation criteria are shown below. A: difference in measured value was 0.05 dB / km or less B: difference in measured value was more than 0.05 dB / km and 0.1 dB / km or less C: difference in measured value was more than 0.1 dB / km and 0.3 dB / km or less D: difference in measured value is 0.3 dB / km or more Tear Strength

[0052] Tear strength was measured based on a tear test defined in JIS C 6838 (2019). In the tear test, a sample length was set at 150 mm (set such that a bonded portion was located at a central portion), a distance between chucks was set at 70 mm, and a pulling speed was set at 200 mm / min. A peak value was used as a measured value, and measured values of 5 samples were acquired for each of the production examples, and an arithmetic average thereof was used as the tear strength.Production Examples 1 to 42

[0053] The optical fiber ribbons 1 of Production Examples 1 to 42 were produced using 6 types of adhesive resins having different composite elastic modulus, and varied in presence and absence of a protrusion from the tangent line T and presence and absence of a protrusion of the bonded portion 2 at a longitudinal end portion. In Production Examples 1 to 42, the tear strength was about 0.03 N. The maximum value H of the height of a protrusion was about 30 µm. The distance U in the width direction W was in a range of 0 or more and 1 / 2R or less.

[0054] The optical fiber ribbons 1 of Production Examples 1 to 42 were evaluated for separation resistance and characteristics at low temperature. Results are shown in Table 1. In Table 1, Production Examples 8, 9, 14, 15, 20, 21, 26, 27, 32, 33, 38 and 39 are examples, and the other Production Examples are comparative examples. Table 1Bonded PortionSeparation ResistanceCharacteristics at Low TemperatureComposite Elastic Modulus (GPa)ProtrusionProtrusion at Longitudinal End PortionProduction Example 10.4YesNo (Flat)DBProduction Example 2Only One EndCBProduction Example 3Both EndsCBProduction Example 4NoNo (Flat)DBProduction Example 5Only One EndDBProduction Example 6Both EndsDBProduction Example 70.5YesNo (Flat)CBProduction Example 8Only One EndBBProduction Example 9Both EndsBBProduction Example 10NoNo (Flat)DBProduction Example 11Only One EndDBProduction Example 12Both EndsCBProduction Example 131.5YesNo (Flat)CBProduction Example 14Only One EndBBProduction Example 15Both EndsBBProduction Example 16NoNo (Flat)DBProduction Example 17Only One EndCBProduction Example 18Both EndsBBProduction Example 193.0YesNo (Flat)BBProduction Example 20Only One EndBBProduction Example 21Both EndsABProduction Example 22NoNo (Flat)CBProduction Example 23Only One EndCBProduction Example 24Both EndsCBProduction Example 254.5YesNo (Flat)BBProduction Example 26Only One EndABProduction Example 27Both EndsABProduction Example 28NoNo (Flat)BBProduction Example 29Only One EndBBProduction Example 30Both EndsBBProduction Example 316.0YesNo (Flat)ABProduction Example 32Only One EndABProduction Example 33Both EndsABProduction Example 34NoNo (Flat)BBProduction Example 35Only One EndABProduction Example 36Both EndsABProduction Example 376.5YesNo (Flat)ACProduction Example 38Only One EndACProduction Example 39Both EndsADProduction Example 40NoNo (Flat)BBProduction Example 41Only One EndABProduction Example 42Both EndsAC Production Examples 43 to 52

[0055] The optical fiber ribbons 1 of Production Examples 43 to 52 were produced using 6 types of adhesive resins having different composite elastic modulus, and varied in the tear strength for the bonded portion 2. In Production Examples 43 to 52, the protrusion of the bonded portion 2 from the tangent line T was "yes", and the distance U of the bonded portion 2 in the width direction W was in the range of 0 or more and 1 / 2R or less. The maximum value H of the height of a protrusion was about 30 µm. In addition, the longitudinal end portions 2c and 2d of the bonded portion 2 in the longitudinal direction L protruded further than the central portion of the bonded portion 2 in the longitudinal direction L. The optical fiber ribbons 1 of Production Examples 43 to 52 were evaluated for separation resistance. Results are shown in Table 2. Production Examples 43 to 52 are examples. Table 2Bonded PortionSeparation ResistanceComposite Elastic Modulus (GPa)Tear Strength (N)Production Example 430.50.005 to 0.200BProduction Example 44> 0.200BProduction Example 451.50.005 to 0.200BProduction Example 46> 0.200BProduction Example 473.00.005 to 0.200BProduction Example 48> 0.200AProduction Example 494.50.005 to 0.200BProduction Example 50> 0.200AProduction Example 516.00.005 to 0.200BProduction Example 52> 0.200A Production Examples 53 to 67

[0056] The optical fiber ribbons 1 of Production Examples 53 to 67 were produced using 6 types of adhesive resins having different composite elastic modulus, and varied in the maximum value H of the height of a protrusion of the bonded portion 2. In Production Examples 53 to 67, the protrusion of the bonded portion 2 from the tangent line T was "yes", and the distance U of the bonded portion 2 in the width direction W was in the range of 0 or more and 1 / 2R or less. The tear strength was about 0.03 N. In addition, the longitudinal end portions 2c and 2d of the bonded portion 2 in the longitudinal direction L protruded further than the central portion of the bonded portion 2 in the longitudinal direction L. The optical fiber ribbons 1 of Production Examples 53 to 67 were evaluated for separation resistance and characteristics at low temperature. Results are shown in Table 3. Production Examples 53 to 67 are examples. Table 3Bonded PortionSeparation ResistanceCharacteristics at Low TemperatureComposite Elastic Modulus (GPa)Protrusion Height (µm)Production Example 530.510C to BBProduction Example 54100BBProduction Example 55120BDProduction Example 561.510C to BBProduction Example 57100BBProduction Example 58120BDProduction Example 593.010C to BBProduction Example 60100ABProduction Example 61120ADProduction Example 624.510C to BBProduction Example 63100ABProduction Example 64120ADProduction Example 656.010C to BBProduction Example 66100ABProduction Example 67120AD Production Examples 68 to 87

[0057] The optical fiber ribbons 1 of Production Examples 68 to 87 were produced using 6 types of adhesive resins having different composite elastic modulus, and varied in the distance U in the width direction W. In Production Examples 68 to 87, the protrusion of the bonded portion 2 from the tangent line T was "yes". The tear strength was about 0.03 N. The maximum value H of the height of a protrusion was about 30 µm. In addition, the longitudinal end portions 2c and 2d of the bonded portion 2 in the longitudinal direction L protruded further than the central portion of the bonded portion 2 in the longitudinal direction L. The optical fiber ribbons 1 of Production Examples 68 to 87 were evaluated for separation resistance and characteristics at low temperature. Results are shown in Table 4. In Table 4, the distance U of less than 0R means that the widthwise end portion 2a of the bonded portion 2 in the width direction W is located inside relative to the straight line P1 and the widthwise end portion 2b is located inside relative to the straight line P2. Production Examples 68 to 87 are examples. Table 4Bonded PortionSeparation ResistanceCharacteristics at Low TemperatureComposite Elastic Modulus (GPa)Distance U (R)Production Example 680.5< 0CAProduction Example 690 or more and less than 1 / 5BAProduction Example 701 / 5 or more and 1 / 2 or lessABProduction Example 71> 1 / 2ACProduction Example 721.5< 0CAProduction Example 730 or more and less than 1 / 5BAProduction Example 741 / 5 or more and 1 / 2 or lessABProduction Example 75> 1 / 2ACProduction Example 763.0< 0CAProduction Example 770 or more and less than 1 / 5BAProduction Example 781 / 5 or more and 1 / 2 or lessABProduction Example 79> 1 / 2ACProduction Example 804.5< 0CAProduction Example 810 or more and less than 1 / 5BAProduction Example 821 / 5 or more and 1 / 2 or lessABProduction Example 83> 1 / 2ACProduction Example 846.0< 0CAProduction Example 850 or more and less than 1 / 5BAProduction Example 861 / 5 or more and 1 / 2 or lessABProduction Example 87> 1 / 2AC

[0058] Although the present invention is described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims. In addition, the number, positions, shapes, and the like of members described above are not limited to those in the above-described embodiments, and can be changed to the number, positions, shapes, and the like suitable for carrying out the present invention as defined in the claims.REFERENCE SIGNS LIST

[0059] 1: optical fiber ribbon 2: bonded portion 2a, 2b: widthwise end portion 2c, 2d: longitudinal end portion 3: non-bonded portion 10, 10A, 10B: optical fiber 11: optical fiber 12: primary resin layer 13: secondary resin layer 14: colored resin layer T: tangent line H: maximum value of height of protrusion L: longitudinal direction W: width direction U: distance O1, O2: center point P1, P2, P3, P4: straight line Q1, Q2: contact point R: radius

Claims

1. An intermittently coupled optical fiber ribbon (1) in which a bonded portion (2) in which adjacent optical fibers (10, 10A, 10B) are bonded by an adhesive resin and a non-bonded portion (3) in which the adjacent optical fibers (10, 10A, 10B) are not bonded by the adhesive resin are intermittently provided in a longitudinal direction (L) among a part or all of a plurality of optical fibers (10, 10A, 10B) arranged side by side in a width direction (W) orthogonal to the longitudinal direction (L), wherein the bonded portion (2) is provided only on a surface on one side of the optical fiber ribbon (1), a part of the bonded portion (2) protrudes further than a tangent line (T) passing through surfaces of the adjacent optical fibers (10, 10A, 10B) on the one side, in the longitudinal direction (L), at least one of longitudinal end portions (2c, 2d) of the bonded portion (2) has a larger protrusion height than a central portion of the bonded portion (2), and the adhesive resin has a composite elastic modulus of 0.5 GPa or more and 6.0 GPa or less at 23°C, wherein the composite elastic modulus is a composite elastic modulus in the thickness direction measured by a test method based on ISO 14577 using a nanoindenter, namely, a Berkovich indenter, while setting the indentation depth at 100 nm.

2. The optical fiber ribbon (1) according to claim 1, wherein tear strength when tearing the bonded portion (2) measured based on a tear test defined in JIS C 6838:2019 is 0.005 N or more and 0.200 N or less.

3. The optical fiber ribbon (1) according to claim 1 or 2, wherein a maximum value (H) of the protrusion height of the bonded portion (2) from the tangent line (T) is 10 µm or more and 100 µm or less.

4. The optical fiber ribbon (1) according to any one of claims 1 to 3, wherein in the width direction (W), each of widthwise end portions (2a, 2b) of the bonded portion (2) is located outside relative to a center of a corresponding one of the adjacent optical fibers (10, 10A, 10B).