Core, raw roll, and method for manufacturing raw roll

Abstract

To provide a winding core or the like capable of reducing a recess of a film due to a joint between buffer materials, and a step trace of the film due to a step on an end face in a longitudinal direction of the film.SOLUTION: A winding core 100 comprises a cylindrical body 10, a buffer layer 40 for covering an outer peripheral surface of the cylindrical body 10, and an adhesive member 30 arranged between the buffer layer 40 and the outer peripheral surface of the cylindrical body 10. The buffer layer 40 has a 25% compressive stress of 80 to 120 kPa, and the buffer layer 40 is a foaming resin layer containing an ethylene-vinyl acetate copolymer of 50 mass% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a core, a raw roll, and a method for manufacturing the raw roll. [Background technology]

[0002] When transporting or storing a long film or the like, it is common to wind the film around a cylindrical core to form a roll.

[0003] As a winding core to be used in such a case, as described in Patent Document 1, a winding core having a cylindrical body and a buffer material that covers the outer peripheral surface of the cylindrical body is known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3964892 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional winding cores, indentations may occur on the surface of the wound film due to the seams of the cushioning material on the outer surface of the cylindrical body, and step marks may occur on the portion wound on top of the film due to steps on the longitudinal end surfaces of the film.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a winding core or the like that can reduce indentations in the film caused by seams between cushioning materials and step marks in the film caused by steps on the longitudinal end surfaces of the film. [Means for solving the problem]

[0007] A winding core according to one aspect of the present invention includes a cylindrical body, a buffer layer covering the outer peripheral surface of the cylindrical body, and an adhesive member disposed between the outer peripheral surface of the cylindrical body and the buffer layer, wherein the 25% compressive stress of the buffer layer is 80 to 120 kPa and the buffer layer is a foamed resin layer containing 50 mass % or more of ethylene-vinyl acetate copolymer.

[0008] The thickness of the buffer layer may be, for example, 0.5 to 3 mm.

[0009] The pressure-sensitive adhesive member may be, for example, a single pressure-sensitive adhesive layer.

[0010] The pressure-sensitive adhesive member may have, for example, a pair of pressure-sensitive adhesive layers and a base layer disposed between the pair of pressure-sensitive adhesive layers.

[0011] The pressure-sensitive adhesive layer may be, for example, an acrylic pressure-sensitive adhesive layer.

[0012] A winding core according to one aspect of the present invention is used for winding an optical film, for example.

[0013] A raw roll according to one aspect of the present invention includes the above-described core and an optical film wound around the outer peripheral surface of the core.

[0014] A method for producing a raw roll according to one aspect of the present invention includes a step of winding an optical film on the outer peripheral surface of the core. [Effects of the Invention]

[0015] According to the present invention, a winding core or the like is provided that can reduce depressions in the film caused by seams between cushioning materials and step marks in the film caused by steps on the longitudinal end surfaces of the film. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of a winding core 100 according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the axial center of the winding core of FIG. [Figure 3] 3(a) and 3(b) are cross-sectional views showing examples of the adhesive member 30. FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view illustrating a depression YY caused by a seam Y of the laminate 50 in the film F wound around the core 100. As shown in FIG. [Figure 5] FIG. 5 is a schematic cross-sectional view illustrating a recess QQ caused by a corner Q at the inner peripheral end IE of the film F wound around the core 100. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Core) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a winding core 100 according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view of the axial center of the winding core.

[0018] The winding core 100 according to this embodiment mainly includes a cylindrical body 10, a laminate 50 (an adhesive member 30 and a buffer layer 40), and a boss member 20.

[0019] The cylinder 10 is a tube with a circular cross section. The outer diameter of the cylinder 10 can be, for example, 70 to 400 mm. The thickness of the cylinder 10 can be 2 to 10 mm. The axial length of the cylinder 10 can be adjusted appropriately according to the length of the film to be wound, but can be, for example, 300 to 2500 mm.

[0020] The material of the cylindrical body 10 is not particularly limited, but may be, for example, a metal such as an aluminum alloy; a fiber-reinforced resin; a polyvinyl chloride resin; or an ABS resin. An example of an aluminum alloy is an Al-Mg-Si alloy such as A6061. Examples of fibers in the fiber-reinforced resin include paper fiber, glass fiber, and carbon fiber. Examples of resins in the fiber-reinforced resin include epoxy resins and phenolic resins (Bakelite). These materials have a high Young's modulus and are lightweight yet strong.

[0021] The laminate 50 is wound around the outer circumferential surface of the cylindrical body 10 in the circumferential direction. The laminate 50 has an adhesive member 30 and a buffer layer 40 in this order from the cylindrical body 10 side.

[0022] The laminate 50 is wrapped around the cylinder 10 so as not to overlap each other, and the laminate 50 has a seam Y on the outer circumferential surface of the cylinder 10 where one end face and the other end face face each other. When no film is wrapped around it, the spacing of the seam Y, i.e., the spacing between the opposing end faces of the laminate 50, may be the same or different over the entire axial length of the cylinder 10.

[0023] The maximum spacing of the seam Y in the area where the film is wound can be 5 mm or less, preferably 2 mm or less, and more preferably 1 mm or less. Also, the spacing of the seam Y is preferably 0, but may be 0.3 mm or more, or 0.5 mm or more.

[0024] The buffer layer 40 is provided on the cylindrical body so as to cover the outer peripheral surface of the cylindrical body 10. The buffer layer has a buffering effect, that is, it has elasticity and has the effect of absorbing shock.

[0025] The buffer layer 40 is a foamed resin layer containing 50% or more by mass of ethylene vinyl acetate copolymer. The 25% compressive stress of the buffer layer 40 is 80 to 120 kPa. The buffer layer 40 may contain 70% or more by mass, or 80% or more by mass, of ethylene vinyl acetate copolymer.

[0026] The 25% compressive stress is the stress required to reduce the thickness of the buffer layer 40 by 25% of the total thickness. The 25% compressive stress can be controlled by the content of ethylene vinyl acetate copolymer, the foaming ratio, etc. The 25% compressive stress is measured in accordance with JIS K 6767.

[0027] There is no particular limitation on the thickness of the buffer layer 40, but it may be, for example, 0.3 to 10 mm, and more preferably 0.5 to 3 mm. The thickness is the value measured when the stress is 0.

[0028] The adhesive member 30 is disposed between the cylindrical body 10 and the buffer layer 40. The adhesive member 30 is releasable, and can be peeled off from the cylindrical body 10 together with the buffer layer 40.

[0029] 3(a) and 3(b) show examples of the adhesive member 30. FIG.

[0030] 3(a), the adhesive member 30 is a single adhesive layer 32. One surface of the adhesive layer 32 is in contact with the cylindrical body 10, and the other surface of the adhesive layer 32 is in contact with the buffer layer 40. Examples of the adhesive layer 32 include (meth)acrylic adhesives, urethane adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, polyether adhesives, fluorine-based adhesives, and rubber adhesives. Among these, (meth)acrylic adhesives are preferably used from the viewpoints of transparency, adhesive strength, reworkability, and the like. The thickness of the adhesive layer 32 can be set to, for example, 5 to 50 μm.

[0031] In (b) of FIG. 3, the PSA member 30 has a pair of PSA layers 32, 36, and a base layer 34 disposed between the pair of PSA layers 32, 36. The upper surface of the PSA layer 32 contacts the lower surface of the buffer layer 40, and the lower surface of the PSA layer 32 contacts the upper surface of the base layer 34. The upper surface of the PSA layer 36 contacts the lower surface of the base layer 34, and the lower surface of the PSA layer 36 contacts the outer peripheral surface of the cylindrical body 10. The thickness and material of the PSA layers 32, 36 in this embodiment can be the same as those of the PSA layer 32 in the embodiment of (a) of FIG. 3. The thickness and material of the PSA layers 32, 36 in the pair of PSA layers 32, 36 may be the same or different from each other.

[0032] The base material layer 34 may be made of, for example, polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene polymers; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; (meth)acrylic acid resins such as (meth)acrylic acid and polymethyl(meth)acrylate; cellulose ester resins such as triacetyl cellulose, diacetyl cellulose and cellulose acetate propionate; vinyl alcohol resins such as polyvinyl alcohol and polyvinyl acetate; polycarbonate resins; polystyrene resins; polyarylate resins; polysulfone resins; polyethersulfone resins; polyamide resins; polyimide resins; polyether ketone resins; polyphenylene sulfide resins; polyphenylene oxide resins, and mixtures and copolymers thereof.

[0033] The thickness of the base layer 34 may be 1 to 100 μm, and is preferably 20 to 50 μm.

[0034] When the adhesive member 30 is a single layer as in FIG. 3(a), the structure is simple, so that manufacturing is easy and the manufacturing cost of the core can be reduced.

[0035] On the other hand, when the adhesive member 30 has a three-layer structure as shown in Figure 3(b), a material that has strong adhesion to the buffer layer 40 can be used for the adhesive layer 32, and a material that has strong adhesion to the cylindrical body 10 can be used for the adhesive layer 36, making it easy to increase the adhesive strength between the buffer layer 40 and the cylindrical body 10. Furthermore, when peeling off the worn buffer layer 40 from the cylindrical body 10 after use of the core, the presence of the base layer 34 makes the buffer layer 40 less likely to tear, and the buffer layer 40 can be easily peeled off from the cylindrical body 10 together with the base layer 34. Therefore, it is easy to replace the buffer layer 40, and the cylindrical body 10 can be easily reused.

[0036] In Figure 1, boss members 20 are fitted into both axial ends of cylindrical body 10. Boss member 20 has a large-diameter cylindrical portion 22 housed within cylindrical body 10 and a small-diameter cylindrical portion 24 with an outer diameter smaller than that of the large-diameter portion. The outer diameter of large-diameter cylindrical portion 22 can be increased without changing the outer diameter of small-diameter cylindrical portions 24 of boss members 20 at both ends, allowing for a larger radius of curvature of the film in a wound state and making it easier to suppress curling and step marks on the film.

[0037] The material of the boss member 20 can be selected appropriately, similar to the cylindrical body.

[0038] (Manufacturing method of core) Next, an example of a method for manufacturing the winding core 100 will be described. A laminate 50 in which a buffer layer 40 and an adhesive member 30 are laminated, and a cylindrical body 10 are prepared. It is preferable that the outer adhesive surface of the adhesive member 30 of the laminate 50 is protected in advance with a release sheet. The laminate 50 is pre-cut to a size that is the length of one circumference of the outer circumferential surface of the cylindrical body 10 multiplied by the axial length of the cylindrical body.

[0039] The release sheet on the adhesive surface of the cut laminate 50 is peeled off, and the laminate 50 is attached to the outer peripheral surface of the cylindrical body 10. At this time, the laminate 50 is attached to the outer peripheral surface of the cylindrical body 10 so that the end faces of the laminates 50 face each other and the laminates do not overlap each other. In this manner, the winding core 100 can be manufactured.

[0040] Various types of films can be wound around the winding core 100 according to this embodiment. Examples of the films include optical films such as polarizing plates, retardation films, and protective films. The material of the protective film can be the same as that of the above-mentioned base layer 34. The thickness of the optical film can be, for example, 25 to 300 μm. The length of the film is, for example, 30 to 10,000 m.

[0041] By winding a film onto the outer peripheral surface of the buffer layer 40 of such a winding core 100, raw rolls of various films can be obtained.

[0042] (Action and effect) The core according to this embodiment has a foamed resin layer with a specific 25% compressive stress and a specific composition as a buffer layer, which reduces indentations in the film caused by the seams between buffer materials and step marks on the film caused by steps on the longitudinal end surfaces of the film.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0044] For example, there is no limitation on the shape of the cylinder, boss member, etc., and they can be modified appropriately to suit the supporting device for the winding core to be used. Also, the winding core does not need to have a boss member. [Example]

[0045] Example 1 An aluminum alloy cylinder with an outer diameter of 252 mm and a length of 1,360 mm was prepared. Boss members were fixed to both ends of the cylinder.

[0046] A foamed resin layer (sponge sheet: thickness 2 mm) containing 94% by mass of ethylene vinyl acetate copolymer was prepared as a buffer layer. The 25% compressive stress of the buffer layer was 100 kPa.

[0047] An acrylic adhesive layer (thickness: 20 μm) with a release sheet was attached to the buffer layer to obtain a laminate. The laminate was cut to fit the area of ​​the outer peripheral surface of a cylindrical body. The release sheet was peeled from the cut laminate, and the buffer layer was attached to the outer peripheral surface of the cylindrical body via the adhesive layer to obtain the winding core of Example 1. The gap at seam Y was 1 mm.

[0048] A 148 μm thick polarizing plate film of 1600 m was wound around the core to obtain a raw roll of polarizing plate film, which was then left to stand for 30 days.

[0049] Example 2 The procedure was the same as in Example 1, except that a foamed resin layer containing 60% by mass of ethylene vinyl acetate copolymer was used as the buffer layer. The 25% compressive stress of the buffer layer was 105 kPa.

[0050] (Comparative Example 1) The procedure was the same as in Example 1, except that a foamed resin layer containing 65% by mass of ethylene vinyl acetate copolymer was used as the buffer layer. The 25% compressive stress of the buffer layer was 130 kPa.

[0051] (Comparative Example 2) The procedure was the same as in Example 1, except that a foamed resin layer containing 60% by mass of ethylene vinyl acetate copolymer was used as the buffer layer. The 25% compressive stress of the buffer layer was 70 kPa.

[0052] (Comparative Example 3) The procedure was the same as in Example 1, except that a foamed resin layer containing 90% by mass of polyolefin was used as the buffer layer. The 25% compressive stress of the buffer layer was 34 kPa.

[0053] (evaluation) After leaving the film, the entire polarizing plate film was pulled out from the roll, and the condition of the surface of the inner peripheral edge of the film was visually inspected.

[0054] (Dent in the film caused by seam Y) Due to the seam Y of the buffer layer 40, linear depressions YY extending along the axial direction of the winding core 100 are formed in the film F at approximately regular intervals in the circumferential direction, as shown in Figure 4. These depressions YY are formed within a predetermined circumferential length range from the inner circumferential edge of the film F toward the outer circumferential edge of the winding. The circumferential length range in which the depressions YY were formed was visually confirmed and measured for each film of the examples and comparative examples. A mark of ◯ was given for a length less than 5 m, a mark of △ was given for a length between 5 m and 10 m, and a mark of × was given for a length of 10 m or more.

[0055] (Step marks) As shown in FIG. 5, the inner peripheral edge IE of the film F is fixed to the laminate 50 (buffer layer) with double-sided adhesive tape T. The film F wound onto the inner peripheral edge IE is pressed against a step (corner Q) on the end surface of the inner peripheral edge IE, causing the corner Q of the end surface to leave a linear mark (referred to as a step mark QQ) on the film F extending along the axial direction of the core. This step mark QQ is formed within a predetermined circumferential length from the inner peripheral edge of the film F to the outer peripheral edge of the winding. The circumferential length range in which the step mark QQ was formed was visually confirmed and measured for each film of the examples and comparative examples. A length of less than 5 m was marked with an ◯, a length of 5 m or more but less than 10 m with a △, and a length of 10 m or more with an X.

[0056] (Transformation) The film was visually inspected for deformation other than dents and step marks.

[0057] The case where there was no deformation of the film other than the dents and step marks was rated as ◯, the case where the pattern of the buffer layer was transferred to the film was rated as △, and the case where wrinkles were generated on the entire film was rated as x.

[0058] The results are shown in Table 1.

[0059] [Table 1]

[0060] According to the examples, it was confirmed that it is possible to reduce dents in the film caused by the seams between cushioning materials and step marks in the film caused by steps on the longitudinal end surfaces of the film, and that other deformations of the film are also less likely to occur. [Explanation of symbols]

[0061] 10... cylindrical body, 30... adhesive member, 32, 36... adhesive layer, 34... base material layer, 40... buffer layer, 20... boss member, 100... core, F... film.

Claims

1. A raw roll comprising a core and an optical film wound around an outer peripheral surface of the core, The winding core includes a cylindrical body and a laminated body, the laminate has a buffer layer covering an outer peripheral surface of the cylindrical body, and an adhesive member disposed between the outer peripheral surface of the cylindrical body and the buffer layer, The outer diameter of the cylindrical body is 70 to 400 mm, the laminate is wound around the outer circumferential surface of the cylindrical body in a circumferential direction, and the outer circumferential surface of the cylindrical body has a seam where one end surface and the other end surface face each other; The maximum distance between the joints is 0.3 mm or more and 2 mm or less, The thickness of the buffer layer of the core is 0.5 to 3 mm, the buffer layer has a 25% compressive stress of 100 to 120 kPa; the buffer layer is a foamed resin layer containing 50% by mass or more of an ethylene-vinyl acetate copolymer, The optical film has a thickness of 25 to 300 μm, The optical film is a polarizing plate film, a retardation film, or a protective film.

2. The raw roll according to claim 1 , wherein the adhesive member of the core is a single adhesive layer.

3. The raw roll according to claim 1 , wherein the adhesive member of the core has a pair of adhesive layers and a base layer disposed between the pair of adhesive layers.

4. The raw roll according to claim 2 or 3, wherein the pressure-sensitive adhesive layer of the core is an acrylic pressure-sensitive adhesive layer.

5. a step of winding an optical film around an outer peripheral surface of a core, The winding core includes a cylindrical body and a laminated body, the laminate includes a buffer layer covering an outer peripheral surface of the cylindrical body, and an adhesive member disposed between the outer peripheral surface of the cylindrical body and the buffer layer, The outer diameter of the cylindrical body is 70 to 400 mm, the laminate is wound around the outer circumferential surface of the cylindrical body in a circumferential direction, and the outer circumferential surface of the cylindrical body has a seam where one end surface and the other end surface face each other; The maximum distance between the joints is 0.3 mm or more and 2 mm or less, The thickness of the buffer layer of the core is 0.5 to 3 mm, the buffer layer has a 25% compressive stress of 100 to 120 kPa; the buffer layer is a foamed resin layer containing 50% by mass or more of an ethylene-vinyl acetate copolymer, The thickness of the optical film is 25 to 300 μm. The method for producing a raw roll, wherein the optical film is a polarizing plate film, a retardation film, or a protective film.

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