TWI877441B - Take-up roll and optical film roll wound on the take-up roll - Google Patents

Abstract

The subject of the present invention is to provide a take-up roller that can significantly suppress the occurrence of pressure marks on the film being rolled up. The solution is a take-up roller in the embodiment of the present invention, which has a cylindrical rubber core and a smoothing layer composed of a resin film wound around the core.

Description

Take-up roll and optical film roll wound on the take-up roll

The present invention relates to a take-up roll and an optical film roll wound on the take-up roll.

Films can be used for a wide range of purposes. Examples of such films include optical films used in image display devices and packaging films used in food-related applications. In most cases, films can be stored and transported in the form of a film roll wound on a roll-up roll. In recent years, the thinning of films has been progressing significantly. As the thinning of films has progressed, embossing, which was not a problem in the past, has gradually become a problem. Such problems are particularly prominent in optical films that have strict tolerance standards for defects, etc. Prior Art Literature Patent Literature

Patent document 1: Japanese Patent Publication No. 2011-184152

Problem to be solved by the invention The present invention is completed to solve the above-mentioned previous problems, and its main purpose is to provide a winding roller that can significantly suppress the occurrence of pressure marks on the rolled film.

Means for solving the problem The take-up roll of the embodiment of the present invention has a cylindrical rubber core and a smoothing layer composed of a resin film wound on the core. In one embodiment, the hardness of the take-up roll is less than 100g by a BC value measured by a roll hardness tester. In one embodiment, the thickness of the resin film is more than 15μm. In one embodiment, the resin film is selected from polyethylene terephthalate film, polyethylene film, biaxially oriented polypropylene film and cyclic olefin resin film. According to another aspect of the present invention, an optical film roll is provided. The optical film roll is formed by winding an optical film on the take-up roll. In one embodiment, the optical film includes a polarizing plate. In one embodiment, the thickness of the polarizing plate is less than 500 μm.

Effect of the invention According to the embodiment of the present invention, by configuring the take-up roller to have a rubber core and a smoothing layer of a resin film wound on the core, a take-up roller that can significantly suppress the occurrence of pressure marks on the film being rolled up can be realized.

Hereinafter, the specific implementation forms of the present invention will be described with reference to the attached drawings, but the present invention is not limited to the said implementation forms. In addition, the drawings are schematically shown for the convenience of viewing, and the ratios of length, width, thickness, etc., as well as angles, height differences, etc. in the attached drawings are different from the actual ones.

A. Take-up Roller FIG. 1 is a schematic cross-sectional view of a take-up roll in an embodiment of the present invention in a direction perpendicular to the length direction (the width direction of the film being rolled up); FIG. 2 is a schematic three-dimensional view of the take-up roll of FIG. 1 . The take-up roll 100 shown in the figure has a cylindrical core 10 and a smoothing layer 20 composed of a resin film 22 wound around the core 10. The core 10 is typically made of rubber. As described above, by forming a smoothing layer by winding a resin film around a soft rubber core, the occurrence of pressure marks on the rolled film can be significantly suppressed. More details are as follows. Conventionally, rolls made of only a hard core (e.g., fiber reinforced plastic (FRP), metal) are widely used as roll-up rolls. Such rolls have the problem of causing pressure marks (called roll-up pressure marks) on the film in a roll state. In order to solve the above problem, it is known that after the core (actually the roll) is made soft, it is easy to cause damage such as scratches on the core itself, and the softness will cause wrinkles or unevenness on the surface, which will cause pressure marks to occur, and as a result, the pressure marks cannot be fully suppressed. The inventors conducted an in-depth discussion on the relationship between the structure of the take-up roller and the indentation, and found that by winding a predetermined resin film on a soft core to form a smoothing layer, any problem of a hard core (essentially a roller) or a soft core (essentially a roller) can be solved, thus completing the present invention.

As an indicator of hardness, the BC value of the take-up roll measured by a roll hardness tester is preferably less than 100g, preferably 27g~80g, more preferably 30g~75g, and particularly preferably 40g~70g. If the BC value is within the above range, the occurrence of indentation can be better suppressed. In addition, as a roll hardness tester, for example, "RQP" manufactured by Tapio Technologies can be cited.

The core 10 is typically made of rubber as described above. As the rubber, any appropriate rubber can be used as long as the effect of the embodiment of the present invention can be obtained. As representative examples of rubber, nitrile rubber, ethylene propylene rubber, silicone rubber, butyl rubber, urethane, etc. can be cited. Nitrile rubber or urethane is preferred. These are low-priced and easily available, and have the advantage of being soft.

The hardness of the rubber constituting the core 10 (measured by a type A durometer) is preferably 10 to 100, more preferably 15 to 95. If the hardness is within the above range, it has the advantage of being less likely to cause indentation.

The length of the core 10 can be appropriately set according to the width of the film to be rolled. For example, the length of the core can be more than 1000 mm, and for example, it can be 1000 mm to 4000 mm, and for example, it can also be 1300 mm to 2000 mm. The diameter of the core 10 can be appropriately set according to the length of the core, the amount of film to be rolled, etc. The diameter of the core can be, for example, 20 mm to 400 mm, and for example, it can also be 25 mm to 300 mm.

As the resin film 22 constituting the smoothing layer 20, any appropriate resin film can be used as long as the effect of the embodiment of the present invention can be obtained. Examples of the resin film include polyethylene terephthalate (PET) film, polyethylene (PE) film, biaxially oriented polypropylene (OPP) film, and cyclic olefin resin (COP) film. The resin film can also be a film formed by a combination of the constituent resins of these films (blends, copolymers, etc.). PET film is preferred. This is because it is easily available and has an excellent effect in preventing indentations.

The tensile modulus of the resin film is preferably 1000MPa~8000MPa, more preferably 1500MPa~5000MPa. If the tensile modulus is within the above range, it has the advantages of being difficult to break during the roll manufacturing step and easy to transport.

The thickness of the resin film is preferably 15 μm or more, more preferably 22 μm or more, more preferably 27 μm or more, and particularly preferably 35 μm or more. If the thickness of the resin film is within the above range, the above-mentioned desired BC value can be achieved, and the occurrence of indentation can be suppressed more effectively. The upper limit of the thickness of the resin film can be, for example, 500 μm. If the resin film is too thick, it may be difficult to form, and the cost may increase.

The winding amount of the resin film can be appropriately set according to the diameter of the core, etc. The winding amount of the resin film is preferably more than 3m, more preferably more than 10m, more preferably more than 20m, and particularly preferably more than 25m. If the winding amount of the resin film is within the above range, the desired smoothing layer can be formed. As a result, the above-mentioned desired BC value can be achieved, and the occurrence of indentation can be better suppressed. Even if the winding amount of the resin film is excessively increased, the effect will not change substantially, so from the perspective of cost, the upper limit of the winding amount can be, for example, 200m.

In the cross section perpendicular to the length direction of the core (winding roll), the thickness T of the smoothing layer in the diameter direction of the core is preferably 1 mm to 200 mm, more preferably 1 mm to 100 mm, and more preferably 2 mm to 80 mm. The ratio (T/D) of the thickness T of the smoothing layer to the diameter D of the core is preferably 1% to 100%, more preferably 1% to 50%, more preferably 1% to 40%, and particularly preferably 2% to 30%. With the above-mentioned structure, the above-mentioned desired BC value can be achieved, and the occurrence of indentation can be better suppressed.

The smoothing layer is a flat and smooth surface without ripples, wrinkles, bumps, roughness, etc. If it is the above structure, the occurrence of indentation can be better suppressed. The smaller the variation of the thickness of the smoothing layer, the better. Specifically, the variation (difference between the maximum and minimum values) of the thickness of the smoothing layer measured at any 10 points of ^1m2 is preferably 5μm or less, preferably 3μm or less, and more preferably 1μm~2μm.

As the film rolled up by the take-up roll, any appropriate film can be cited. As a representative example, a single film of a resin film or a laminated film including a resin film can be cited. As a specific example of the film to be rolled up, any appropriate industrial film (such as an optical film, a packaging film, a base film for a tape) can be cited. An optical film is preferably used. The permissible criteria for defects of optical films are strict, so the effect brought about by the embodiment of the present invention is remarkable. The optical film has an optical function, and can be representatively any appropriate film that can be applied to an image display device. Specific examples of optical films include polarizers, phase difference films, polarizing plates (representatively, a laminate of a polarizer and a protective film), conductive films for touch panels, surface treatment films, and laminates appropriately laminated according to the purpose (e.g., circular polarizing plates for anti-reflection, polarizing plates with conductive layers for touch panels). In one embodiment, the optical film includes a polarizing plate. The thickness of the polarizing plate may be, for example, less than 500 μm, or 30 μm to 300 μm, or 50 μm to 170 μm. As described above, the permissible standards for defects of optical films are strict, and as optical films become thinner, embossing that was not a problem in the past becomes a problem. Therefore, in the thin optical film (such as a polarizing plate), the effect of the embodiment of the present invention is remarkable. In addition, the thickness of the polarizing plate refers to the total thickness of the polarizer, the protective film, and the adhesive or adhesive used to laminate them, and does not include the thickness of the adhesive used to attach the polarizing plate to the image display panel. In addition, the polarizing plate can be a single polarizing plate or a polarizing plate included in a laminate (such as a circular polarizing plate for anti-reflection, a polarizing plate with a conductive layer for a touch panel).

B. Optical film roll The optical film can be rolled up on a roll-up roll of an embodiment of the present invention to form an optical film roll. Therefore, the optical film roll is also included in the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an optical film roll of an embodiment of the present invention in a direction orthogonal to the width direction (the length direction of the roll-up roll). The optical film roll 200 shown in the figure is formed by rolling up the optical film 120 on the roll-up roll 100 shown in FIG. 1 and FIG. 2. The optical film roll of the embodiment of the present invention has significantly suppressed embossing, so it can be used in the form of a final product up to the end of the length direction of the optical film. That is, the optical film roll of the embodiment of the present invention has a high product yield, which can suppress costs. More details are as follows. In most cases, the indentation of the rolled film will occur in the center of the film roll (i.e., the surrounding portion close to the roll-up roller). According to the embodiment of the present invention, the indentation of the optical film in the surrounding portion close to the roll-up roller can be significantly suppressed, so that the optical film can be used in the form of a final product up to the end of the length direction, and the yield rate can be improved.

The optical film roll can be manufactured by any appropriate method. In one embodiment, as shown in FIG. 4 , the optical film roll can also be manufactured continuously from the manufacture of the take-up roller of the embodiment of the present invention. Specifically, the winding of the resin film 22 onto the core 10 and the winding of the optical film 120 can also be performed continuously. At this time, the resin film 22 and the optical film 120 are mounted by any appropriate means. As mounting means, for example, adhesive tape and adhesive can be cited. In an embodiment not shown in the figure, the optical film roll can also be formed by rolling the optical film 120 on the take-up roller 100 having the core 10 and the smoothing layer 20.

Embodiments The present invention is specifically described below by embodiments, but the present invention is not limited to these embodiments. The evaluation items of the embodiments are as follows.

(1) Hardness of the take-up roll The take-up rolls produced in the examples and comparative examples were measured with a roll hardness tester (manufactured by Tapio Technologies, product name "RQP") at 1,300 points in the longitudinal direction (width direction of the rolled film) at a distance of 1 mm, and the average value was taken as the hardness. (2) Surface condition of the take-up roll The surface condition of the take-up rolls produced in the examples and comparative examples was observed with the naked eye and evaluated according to the following criteria. ○ (Good): No scratches or indentations larger than 1 mm were found × (Poor): Scratches and/or indentations larger than 1 mm were found (3) Number of defects in optical film rolls A 5-meter central portion (the portion surrounding the take-up roll) was cut out of the optical film rolls produced in the embodiments and comparative examples, and the number of indentations and defects was counted with the naked eye and converted into the number per 1 ^m2 . Evaluation was performed according to the following criteria. ◎ (Excellent): No indentations or defects were found (the total was zero) ○ (Good): The total number of indentations and defects was 1 to 10 △ (Acceptable): The total number of indentations and defects was 11 to 20 × (Poor): The total number of indentations and defects was 21 or more

<Example 1> A cylindrical rubber core having a diameter of 152.4 mm (6 inches) and a length of 1600 mm was prepared. A 5 m PET film having a thickness of 50 μm was wound around the core and a smoothing layer was formed to produce a roll. The BC value of the obtained roll was 49 g. In addition, the surface condition of the obtained roll was good.

A polarizing plate having a structure of triacetate cellulose (TAC) protective film (thickness 25 μm)/polarizer (thickness 5 μm)/acrylic protective film (thickness 20 μm)/adhesive layer (20 μm)/separator was prepared by conventional methods. The polarizing plate was rolled up 1000 m onto the above-obtained roll to produce an optical film roll (polarizing plate roll). The evaluation of defects of the obtained optical film roll was excellent.

<Examples 2-3> A take-up roll was prepared in the same manner as in Example 1 except that the PET film was wound around the core at the winding amount shown in Table 1. An optical film roll was prepared in the same manner as in Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

<Examples 4 to 12> A take-up roll was prepared in the same manner as in Example 1 except that a PET film of the thickness shown in Table 1 was wound around a core at a winding amount shown in Table 1. An optical film roll was prepared in the same manner as in Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

<Comparative Example 1> The core of Example 1 was directly used as a take-up roll. That is, a take-up roll was produced in the same manner as Example 1 except that the PET film was not wound. An optical film roll was produced in the same manner as Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

<Comparative Example 2> A take-up roll was prepared in the same manner as in Example 4 except that a cylindrical FRP core having a diameter of 152.4 mm (6 inches) and a length of 1600 mm was used. An optical film roll was prepared in the same manner as in Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

<Comparative Examples 3-4> A take-up roll was prepared in the same manner as in Comparative Example 2 except that the PET film was wound around the core at the winding amount shown in Table 1. An optical film roll was prepared in the same manner as in Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

<Comparative Example 5> The core of Comparative Example 2 was directly used as a take-up roll. That is, a take-up roll was produced in the same manner as Comparative Example 2 except that the PET film was not wound. An optical film roll was produced in the same manner as Example 1 except that the take-up roll was used. Table 1 shows the BC value and surface condition of the obtained take-up roll, and the evaluation of defects of the obtained optical film roll.

[Table 1]

<Evaluation> It is obvious from Table 1 that compared with the comparative example, the embodiment of the present invention can more significantly suppress the pressure marks and defects of the optical film roll.

Industrial Applicability The winding roll of the embodiment of the present invention can be used for winding any appropriate film, and is particularly suitable for winding optical films.

10: Core 20: Smoothing layer 22: Resin film 100: Take-up roll 120: Optical film 200: Optical film roll D: Core diameter T: Smoothing layer thickness

FIG. 1 is a schematic cross-sectional view of a take-up roll in a direction perpendicular to the length direction of an embodiment of the present invention. FIG. 2 is a schematic three-dimensional view of the take-up roll in FIG. 1. FIG. 3 is a schematic cross-sectional view of an optical film roll in a direction perpendicular to the width direction of an embodiment of the present invention. FIG. 4 is a schematic three-dimensional view illustrating an example of a manufacturing process of an optical film roll in an embodiment of the present invention.

10: Core

20: Smoothing layer

22: Resin film

100: Roller

D: Core diameter

T: Thickness of smoothing layer

Claims (5)

A take-up roller having a cylindrical rubber core and a smoothing layer composed of a resin film wound on the core; the thickness of the resin film is 20μm~50μm; the hardness of the take-up roller is 32g~68g as measured by a roller hardness tester; in a cross section perpendicular to the length direction of the core, the thickness T of the smoothing layer in the diameter direction of the core is 1mm~200mm. The take-up roll as claimed in claim 1, wherein the resin film is selected from polyethylene terephthalate film, polyethylene film, biaxially oriented polypropylene film and cyclic olefin resin film. An optical film roll is formed by rolling the optical film on a winding roll as in claim 1 or 2. As in claim 3, the optical film roll, wherein the optical film comprises a polarizing plate. As in claim 4, the optical film roll, wherein the thickness of the polarizing plate is less than 500 μm.