JP2013199344A - Winding core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a winding core which does not cause a running-on level difference trace, and prevents occurrence of tightening or compression traces when a film to be wound is thin or even when an elastic modulus of a film is comparatively small.SOLUTION: A winding core 2 is provided with a cushioning layer 6 on the surface of a cylindrical body 4, and the cushioning layer is made of an elastic resin foaming body whose hardness (rubber hardness by a C type rubber hardness meter according to an SRIS standard) is 30-70, and an open cell rate is 70% or more.

Description

  The present invention relates to a winding core used for winding a highly functional film such as a functional film used in the information technology field.

  In recent years, with the development of the information technology field, films for liquid crystals, films for X-rays, films for printed circuit boards and copper foil laminate films thereof, and high-performance photographic paper have come to be frequently used as films for information equipment. Usually, these films are wound around a paper tube called a cylindrical core in the production and processing steps.

  In detail, these wound films are affected by the film thickness in the innermost layer, and are distorted due to “step-up steps”. That is, when the first layer of the innermost layer is wound and applied to the second layer, the second layer rides on the longitudinal end of the film, and the original flatness of the film on the second layer is impaired. As a result, internal distortion and unevenness are generated in the film as end face step marks, causing a problem that the film cannot be used in subsequent processes requiring surface flatness and precision. This internal distortion and unevenness are particularly likely to occur when the film after winding is left for a long time due to temporary stock or distribution.

  This distortion defect spreads further to the outer layer by overlapping windings, and the same defect is propagated and caused. Further, this distortion defect is particularly likely to occur when the film after winding is left for a long time due to temporary stock or distribution.

  These partial defects have been cut off and discarded at the stage of use, and expensive raw materials have been wasted, leading to increased costs.

  In order to solve this situation, in the field of rolled recording paper tube, in order to eliminate the end step generated in the core of recording paper for very thick image printing such as 0.2 mm or more, A foamed styrene sheet is wound around the outer periphery of the tube as a buffer layer, or a slit is provided in the core (for example, see Patent Document 1).

  However, especially in films for optical applications in the field of information equipment that require optical uniformity, such as liquid crystal films, X-ray films, and high-performance photographic paper, the films for printed circuit boards and their copper foil laminate films More uniformity is required, and this distortion defect is fatal.

In a film for applications that require such uniformity, as a means to eliminate distortion defects (climbing step traces) due to this “step-up step”, a buffer material is wound around the outer peripheral surface of the core material body, and the buffer material is wound around the buffer material. A winding core is disclosed in which a concave groove for dropping the film end in the length direction (axial direction) of the core is provided, and an adhesive sheet for fixing the film is fixed to the concave groove. ing. Moreover, it is said that this buffer material preferably has a rubber hardness H of 60 to 90 (see Patent Document 2).
Such a core has a complicated structure because it requires a concave groove, an adhesive sheet, and the like, and it takes a lot of time to perform an operation on the film core.

Alternatively, in a film for applications where such uniformity is required, a buffer layer is provided on the surface of a resin or metal cylindrical body as a means to eliminate distortion defects (climbing step traces) due to this “climbing step”. A wound core is disclosed (for example, see Patent Document 3). The sheet disclosed as this buffer layer is a closed cell sheet made of polyethylene or polypropylene having an apparent density of 0.03 to 0.2 gr / cm ³ and a compressive stress of 30 to 250 kPa at a strain of 25%.

  The use of such a core is effective in eliminating the “step-up step”. However, when the film to be wound is thin, or when the elastic modulus of the film is relatively small, the core is wound by the wound film layer. Since the tightening force is large, a so-called winding tightening that is compressed and deformed by the pressure tightened by the buffer layer is generated, resulting in a problem that the film winding shape collapses. Further, there may be a problem that a compression mark remains in the buffer layer after the film is unwound.

JP 2000-318930 A JP 2011-184152 A Japanese Patent No. 3964892

The present invention was made in view of the above problems, and when the film to be wound is as thin as 100 μm or less, or when the initial elastic modulus of the film is relatively small as 2 GPa or less, there is little occurrence of step marks. And it aims at providing the winding core which a winding tightening and a compression trace do not produce.

  The gist of the present invention is that a buffer layer is provided on the surface of a cylindrical body, and the buffer layer has a hardness (rubber hardness by a C-type rubber hardness meter according to SRIS standard) of 30 to 70, and an open cell ratio of 70%. As described above, the core is made of an elastic resin foam having a porosity of 20 to 50%.

  The elastic resin foam may be a polyurethane foam.

  According to the present invention, even when the film to be wound is as thin as 100 μm or less, or when the initial elastic modulus of the film is relatively small as 2 GPa or less, there is little generation of step marks and no winding or compression marks are generated. A core is provided.

The cross-sectional schematic diagram which shows the aspect of the core of this invention. The graph of the compressive force-strain curve of a foam. The graph of the compressive force-strain curve of a foam.

  As shown in FIG. 1, the core 2 of the present invention is formed by providing a buffer layer 6 on the surface of a cylindrical body 4. The buffer layer 6 is formed by winding a foamed resin sheet around the surface of the cylindrical body 4 in a spiral manner or with a seam parallel to the axial direction of the cylindrical body 4 and fixing it by adhesion or adhesion. Furthermore, the aspect by which the cylindrical body 4 was inserted in the cylindrical foamed resin sheet may be sufficient. The cylindrical body 4 is preferably made of hard resin or metal in view of dimensional stability.

  When the film is wound around the winding core, the film layer that is wound causes a force to tighten the winding core to cause winding tightening. However, when the hardness of the buffer layer 6 made of the foamed resin sheet decreases, the film layer is wound around the buffer layer 6. When deformation due to tightening occurs and the hardness of the buffer layer 6 increases, a step mark (hereinafter referred to as a step mark) runs on the film.

  The inventor of the present application has studied to eliminate this contradictory phenomenon, and as a result, by using an elastic resin foam having open cells (hereinafter referred to as a foam) as the buffer layer 6, no winding tightening occurs and a step mark is also generated. It has been found that no core is obtained.

  That is, in the core 2 of the present invention, the foamed resin sheet constituting the buffer layer 6 is made of a foam having open cells, and its hardness (rubber hardness by a C-type rubber hardness meter according to the SRIS standard) is 30 to 70. is there. It is preferable that the porosity of this foam is 20 to 50%. Moreover, it is preferable that the average diameter of the bubble of a foam is 1-100 micrometers. Moreover, it is preferable that an open cell rate is 70% or more.

  The winding core 2 of the present invention having such a configuration does not cause tightening even when a thin film having a thickness of 100 μm or less is wound, and the occurrence of a step mark that causes a problem in use is extremely small.

  Further, the core 2 of the present invention is not manifested as a defect when it occurs in a film for a printed substrate and its copper foil laminate film, but is manifested as a defect when it occurs in a film for optical use in the field of information equipment. Even if it is a level | step difference mark of the grade to perform, the generation | occurrence | production can be prevented. For example, it can be suitably used for winding a polarizing film for a liquid crystal panel.

  Since the foam has open cells, the foam is likely to be locally deformed and sinks into the foam when a large force is applied locally, such as a portion where a step mark is generated, which causes a step mark. It seems that the step at the edge of the film is easily absorbed. In contrast, when the foam has closed cells, the foam tends to support the entire surface of the foam when a large force is applied locally, such as a portion where a step mark is generated. In particular, it is difficult to be deformed, and it is difficult to sink into the foam.

  The buffer layer 6 is compressed and deformed by the pressure of the wound film. When the foam has open cells, the air in the bubbles escapes due to the compression and deformation of the buffer layer 6. As a result, as shown in FIG. 2, the stress when the foam is compressed increases as the amount of compression increases in the initial stage of compression (stage 1) until the amount of compression reaches 5%. When the compression amount is in the vicinity of over 5% and the compression amount is about 50% (stage 2), the slope of the compression amount-compression stress curve is smaller than one half of the compression amount-compression stress curve gradient in stage 1. That is, the gradient suddenly increases when the compression amount exceeds 50%. Due to the characteristics of the buffer layer 6, the step at the end of the film is absorbed by the deformation of the buffer layer 6 in the stage 2, and the step mark is less likely to occur. Further, when the film is wound, the buffer layer 6 is uniformly compressed, and the compressed state immediately after the film is wound is maintained, so that the film is less likely to be wrinkled.

On the other hand, when the pores of the foam are independent holes, the air in the bubbles is difficult to escape due to the compressive deformation of the buffer layer 6, and the stress when the foam is compressed as shown in FIG. However, the compression amount increases as the compression amount increases in the initial stage of compression up to about 10% (stage 1a), and compression starts when the compression amount exceeds 10% and the compression amount is about 40% (stage 2a). The gradient of the amount-compression stress curve is about one half of the gradient of the compression amount-compression stress curve in the stage 1a, and the gradient gradually increases when the compression amount exceeds 40%. Since the slope of the compression amount-compression stress curve is larger in the stage 2a than in the case of open cells, step marks due to the pressure of the film wound around the buffer layer 6 are likely to occur. In addition, since abnormal force exceeding the elastic deformation limit is easily applied to the bubble wall, the bubble wall is irreversibly creep deformed, and as a result, the entire buffer layer 6 is irreversibly deformed and compressed after the film is unwound. There is a strong tendency to leave marks. In addition, due to the creep deformation of the buffer layer 6 due to the deformation of the bubble wall, the buffer layer 6 is compressed and deformed immediately after the film is wound, and the buffer is displaced due to the time difference in the amount of compressive displacement from immediately after the film is wound. There is a tendency that a gap is formed between the layer 6 and the wound film layer or between the wound film layers, and the gap is absorbed to cause wrinkles in the film.

  2 is a compressive force-strain curve of a polyurethane foam (Nippon Hatsujo Co., Ltd., product number EXG, Asuka C hardness 55), and FIG. 3 is a polyethylene foam (Toray Industries, Ltd., product number 10020-AA00, foaming ratio 10 times). This is a compression force-strain curve.

  In the core 2 of the present invention, it is preferable that the foam has an Asker C hardness of SRIS 0101 standard of 30 to 70. When the hardness of the foam is less than 30, the buffer layer 6 is likely to be deformed by tightening, and when the hardness of the foam is more than 70, a step mark is generated on the film.

  The hardness of the foam can be set to a desired value by adjusting the elastic modulus of the elastic resin used for the foam, the porosity of the foam, and the diameter of the bubbles.

  On the other hand, if the average diameter of the foam bubbles exceeds 100 μm, a non-uniform step mark is likely to occur because a non-uniform force is applied to the wound film as a reaction force for tightening. When the average diameter of the bubbles in the foam is less than 1 μm, the step at the end of the film is hardly absorbed.

  The thickness of the buffer layer 6 is preferably 0.5 to 2 mm. If the thickness exceeds 2 mm, a shearing force is applied to the buffer layer in the direction opposite to the winding direction during winding, and the thickness is thick. As a result, the amount of absolute deformation of the buffer layer increases and wrinkles enter the surface of the buffer layer. May occur on film. If the thickness is less than 0.5 mm, step marks may be generated.

The open cell ratio was measured according to the ASTM-2856-94-C method. An air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.) was used as a measuring device, and the open cell ratio was calculated by the following formula.
Open cell ratio (%) = ((V−V1) / V) × 100
V: Apparent volume calculated from sample size (cm ³ )
V1: Sample volume (cm ³ ) measured using an air-comparing hydrometer

Regarding the average bubble diameter, the section of the foam was observed 100 times using SEM (scanning electron microscope), and the average value of the major and minor diameters of each bubble was taken as the bubble diameter, and the bubble diameter of an arbitrary range of bubbles was measured. The average bubble diameter was calculated.

The porosity ε is the ratio (%) of the volume of the space occupied by the bubbles to the apparent volume of the foam. From the apparent specific gravity ρ of the foam and the specific gravity ρ _{p of} the resin constituting the foam, ε = (1− (ρ / Ρ _p )) × 100 (%).

  Examples of the elastic resin (elastomer) used in the foam constituting the buffer layer 6 include styrene elastomers, olefin elastomers, urethane elastomers, polyester elastomers, polyamide elastomers, and acrylic elastomers. Two or more kinds of elastomers may be blended and used. Alternatively, these elastomer components may be copolymerized.

The elastic modulus of the elastic resin (tensile elastic modulus specified in JIS K7113: 1995) is preferably 5 to 200 MPa.

Examples of the styrene elastomer include a styrene-butadiene copolymer, a styrene-isoprene copolymer, a styrene-ethylene-butylene copolymer, and a styrene-ethylene-propylene copolymer. Styrene derivatives can be used in addition to styrene which is a part constituting the styrene elastomer.

Examples of the olefin elastomer include copolymers of α-olefins having 2 to 20 carbon atoms. Specifically, ethylene / α-olefin copolymer rubber, ethylene / α-olefin / non-conjugated diene copolymer rubber, propylene / α-olefin copolymer rubber, butene / α-olefin copolymer rubber, etc. Can be mentioned.

The polyester elastomer is obtained, for example, by polycondensation of dicarboxylic acid or a derivative thereof and a diol compound or a derivative thereof. For example, a multiblock copolymer having an aromatic polyester (for example, polybutylene terephthalate) portion as a hard segment component and an aliphatic polyester (for example, polytetramethylene glycol) portion as a soft segment component can be used.

Examples of the polyamide-based elastomer include a polyether block amide type and a polyether ester block amide type in which polyamide is used for the hard phase and polyether or polyester is used for the soft phase.

The acrylic elastomer has an acrylic ester such as ethyl acrylate or butyl acrylate as a main component, and glycidyl methacrylate, allyl glycidyl ether or the like is used as a crosslinking point monomer. Examples thereof include acrylonitrile-butyl acrylate copolymer, acrylonitrile-butyl acrylate-ethyl acrylate copolymer, acrylonitrile-butyl acrylate-glycidyl methacrylate copolymer, and the like.

  Examples of the elastomer further include isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), styrene isoprene butadiene rubber, and isoprene butadiene rubber.

  These elastomers can adjust the elastic modulus depending on the types, ratios, and molecular weights of the hard segment and the soft segment.

  As a component constituting the buffer layer 6, a softening agent for adjusting hardness and durability, and an inorganic additive such as clay, silica, barium sulfate, and calcium carbonate may be blended. In addition, flame retardant additives can be added to impart a high degree of flame retardancy.

  As an elastic resin used for the foam constituting the buffer layer 6, a urethane elastomer is preferable in terms of wear resistance and the like. Further, it is preferable because the open cell ratio and the cell size can be easily adjusted. The urethane elastomer is not particularly limited as long as it is a polymer in which a polyol and a diisocyanate are polymerized by a urethane bond. Moreover, what mixed the chain extender with the mixture of a polyol and diisocyanate and made it react can also be used. A polyurethane foam is obtained by adding a foaming agent to this mixture and foaming while reacting polyol, diisocyanate and chain extender. A polyurethane foam may be produced by blending the mixture with an auxiliary agent such as a foaming aid, a wrapping agent, or a catalyst that controls foaming properties as necessary.

  Moreover, the foam which has open cells can be obtained by the method illustrated in well-known Unexamined-Japanese-Patent No. 1999-322875, Unexamined-Japanese-Patent No. 2002-226829, and Unexamined-Japanese-Patent No. 2002-339844. The hardness of the foam, the average bubble diameter, the void ratio, and the open cell ratio can be kept within a predetermined range by selecting a resin and a foaming agent and setting molding conditions such as a blending ratio, molding temperature, and pressure.

  Moreover, the foam which has an open cell can be obtained by carrying out extrusion foam molding of the elastomer depending on the kind of elastic resin. The hardness of the foam, the average bubble diameter, the void ratio, and the open cell ratio can be kept within a predetermined range by selecting a resin and a foaming agent and setting molding conditions such as a blending ratio, molding temperature, and pressure. Extrusion foam molding is performed by mixing an auxiliary agent such as a surfactant and a cell regulator in the elastomer resin composition, and pressing the foaming agent to perform extrusion molding. As the foaming agent, for example, water, hydrocarbons, various chlorofluorocarbons, dimethyl ether, methyl chloride, ethyl chloride, inert gas, and the like can be used.

Example 1
The film was wound up using the core 2 having the configuration shown in FIG. The cylindrical body 4 is made of ABS (acryl-butadiene-styrene) resin, has an inner diameter of 152 mm, a wall thickness of 6 mm, and a length of 300 mm. The buffer layer 6 is made of a polyurethane (PU) foam sheet (manufactured by Nippon Hojo Co., Ltd .: product number EM30) and has a thickness of 2 mm.

The buffer layer 6 (polyurethane foam sheet) has an open cell ratio of 100%, an average cell diameter of 80 μm, and a porosity of 50%. The hardness is 65.

  Adhesion between the cylindrical body and the foamed resin sheet was performed by pasting the adhesive tape on the cylindrical body in a spiral shape using a double-sided adhesive tape. As the double-sided adhesive tape, one having a width of 50 mm manufactured by Nitto Denko Corporation was used.

The core 2 was mounted on a film winding device, a polyester film having a thickness of 30 μm was used as the film for winding, and the film was wound up at a winding tension of 70 N / cm ² and 10 m / min at a winding tension of 70 m / min. . No tightening was observed on the wound roll. After the wound roll is stored at 20 ° C. and 60% RH for 24 hours, it is unwound and the part where the end surface step traces at the beginning of winding are visually identified is specified, and the length of the film at the remaining part is identified. Was measured, and the ratio to the total film length was determined as the end face step mark residual ratio (%). The residual level difference on the end face step was as low as 4%.

Example 2
A core was manufactured using the same cylindrical body as used in Example 1. The thickness of the buffer layer 6 (polyurethane foam sheet, product number EXG manufactured by Nippon Hojo Co., Ltd.) is 1.25 mm, the open cell ratio is 100%, the average cell diameter is 50 μm, the porosity is 39%, and the hardness is 55.

  The film for winding similar to that used in Example 1 was used and wound up in the same manner as in Example 1. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the residual level difference on the end face step was as low as 3%.

Example 3
A winding core similar to that used in Example 1 was used, and a polyester film having a thickness of 15 μm (initial elastic modulus: 5 GPa) was used as the winding film. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the residual level difference on the end face step was as low as 1%.

Example 4
A winding core similar to that used in Example 1 was used, and a polyethylene film (initial elastic modulus: 1200 MPa) having a thickness of 15 μm was used as the film for winding. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, almost no end face step traces were observed.

Example 5
The core is the same as in Example 1 except that the buffer layer 6 (polyurethane foam sheet is manufactured by Nippon Kajo Co., Ltd., product number EXT (open cell ratio 100%, average cell diameter 30 μm, porosity 40%, hardness 65)) The film for winding was the same as that used in Example 1, and was wound up in the same manner as in Example 1. No tightening was observed on the wound roll. After storing at 24 ° C. for 24 hours at 60 ° C. and RH, the residual level difference on the end face step was as low as 3%.

Example 6
Example 1 except that a foam sheet (open cell ratio 70%, average cell diameter 50 μm, porosity 30%, hardness 50) using ethylene-propylene-diene rubber (EPDM) as the buffer layer 6 was used. A core was produced in the same manner. The film for winding similar to that used in Example 1 was used and wound up in the same manner as in Example 1. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the end face step mark residual ratio was as low as 3%.

Example 7
The same winding core as that used in Example 1 was used, and a polarizing film for liquid crystal manufactured by Nitto Denko Corporation was used as the film for winding. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, almost no end face step traces were observed.

Comparative Example 1
The sheet constituting the buffer layer 6 was the same as in Example 1 except that a polyurethane foam sheet having a thickness of 1 mm, an open cell ratio of 90%, an average cell diameter of 0.7 μm, a porosity of 15% and a hardness of 75 was used. And made a core. The film for winding similar to that used in Example 1 was used and wound up in the same manner as in Example 1. No tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the residual level difference on the end face step was as high as 20%.

Comparative Example 2
The sheet constituting the buffer layer 6 was wound in the same manner as in Example 1 except that a polyurethane foam sheet having a thickness of 2 mm, an open cell ratio of 100%, an average cell diameter of 120 μm, a porosity of 70% and a hardness of 25 was used. I made a wick. The film for winding similar to that used in Example 1 was used and wound up in the same manner as in Example 1. Tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the residual level difference on the end face step was as low as 3%.

Comparative Example 3
As the sheet constituting the buffer layer 6, a polyethylene (PE) resin foam resin sheet (manufactured by Toray: trade name Pef) having a thickness of 1 mm was used. This polyethylene resin foamed resin sheet has an apparent density of 0.1 gr / cm ³ and a hardness of 40. The bubbles are closed cells. The film for winding similar to that used in Example 1 was used and wound up in the same manner as in Example 1. Tightening was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the end face step mark residual ratio was as low as 3%. The buffer layer 6 after unwinding the wound film remained without recovering the dent deformation due to the tightening.

Comparative Example 4
The film was wound up in the same manner as in Comparative Example 3 except that the same film for winding as that used in Example 3 was used. Tightening was observed on the wound roll. After storing the wound roll at 20 ° C. and 60% RH for 24 hours, scars on the end face were hardly observed. The buffer layer 6 after unwinding the wound film remained without recovering the dent deformation due to the tightening.

Comparative Example 5
The film was wound up in the same manner as in Comparative Example 3 except that the same film for winding as used in Example 4 was used. Extreme winding was observed on the wound roll. After storing the wound roll at 20 ° C. and 60% RH for 24 hours, scars on the end face were hardly observed. The buffer layer 6 after unwinding the wound film remained without recovering the dent deformation due to the tightening.

Comparative Example 6
The film was wound up in the same manner as in Comparative Example 3 except that the same film for winding as that used in Example 7 was used. Extreme winding was observed on the wound roll. After the wound roll was stored at 20 ° C. and 60% RH for 24 hours, the end face step mark was as low as 3%. The buffer layer 6 after unwinding the wound film remained without recovering the dent deformation due to the tightening.

Table 1 summarizes the tightening and end surface step traces in the examples and comparative examples.

  Although the embodiment of the core of the present invention has been described above, the present invention can be carried out in various modifications, modifications and variations based on the knowledge of those skilled in the art without departing from the spirit thereof. All of these embodiments belong to the scope of the present invention.

  The core of the present invention is not limited to winding a film for optical applications in the field of information equipment, and can be widely applied to cores that need to have a buffer layer.

2: Core 4: Cylindrical body 6: Buffer layer

Claims (2)

A buffer layer is provided on the surface of the cylindrical body, and the buffer layer has a hardness (rubber hardness according to a C-type rubber hardness meter according to the SRIS standard) of 30 to 70, an open cell ratio of 70% or more, a porosity of 20 to 50%, A core made of an elastic resin foam. The core according to claim 1, wherein the elastic resin foam is a polyurethane foam.

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