JP-7856101-B2 - Film manufacturing method and film

Inventors

• 森井 里誌
• 中江 葉月
• 南條 崇

Assignees

• コニカミノルタ株式会社

Dates

Publication Date

20260511

Application Date

20220315

Priority Date

20210629

Claims (10)

1. The process of preparing a strip-shaped base film, The process includes applying a knurling composition to both ends in the width direction of the surface of the strip-shaped base film, and then drying or curing it to form knurled portions. The knurling portion is The base film includes a plurality of protrusions arranged in the width direction, The volume of the protrusion on the widthwise end side of the base film is smaller than the volume of the protrusion on the widthwise central side, and The height of the protrusion on the widthwise end side of the base film is smaller than the height of the protrusion on the widthwise central side. In a cross-section passing through the plurality of protrusions along the width direction of the base film, The slope of the line connecting the vertex of the protrusion closest to the widthwise end of the base film and the vertex of the protrusion closest to the widthwise center is 5 × 10⁻⁵ to 3 × 10⁻³ mm/mm. A method for manufacturing film.
2. The height of the plurality of protrusions decreases as they approach the widthwise edge of the base film. A method for manufacturing a film according to claim 1 .
3. The average spacing between the multiple protrusions in the width direction of the base film is 500 to 5000 μm. A method for manufacturing a film according to claim 1 or 2 .
4. The knurling composition comprises a thermoplastic resin and a solvent. A method for manufacturing a film according to any one of claims 1 to 3 .
5. The thermoplastic resin is a cycloolefin resin or a (meth)acrylic resin. A method for manufacturing a film according to claim 4 .
6. The concentration of the thermoplastic resin is 1 to 10% by mass relative to the knurling composition. A method for manufacturing a film according to claim 4 or 5 .
7. The aforementioned base film is a resin film. A method for manufacturing a film according to any one of claims 1 to 6 .
8. The thickness of the base film is 10 to 40 μm. A method for manufacturing a film according to any one of claims 1 to 7 .
9. A film comprising a base film and knurling portions arranged at both ends in the width direction of the surface of the base film, The knurling portion is The base film includes a plurality of protrusions arranged in the width direction, The volume of the protrusion on the widthwise end side of the base film is smaller than the volume of the protrusion on the widthwise central side, The height of the protrusion on the widthwise end side of the base film is smaller than the height of the protrusion on the widthwise central side. In a cross-section passing through the plurality of protrusions along the width direction of the base film, The slope of the line connecting the vertex of the protrusion closest to the widthwise end of the base film and the vertex of the protrusion closest to the widthwise center is 5 × 10⁻⁵ to 3 × 10⁻³ mm /mm. film.
10. The aforementioned base film is a resin film. The film according to claim 9 .

Description

This invention relates to a method for manufacturing a film and to a film. Resin films, primarily composed of cycloolefin resins and (meth)acrylic resins, possess excellent transparency and dimensional stability, making them suitable for use as optical films, such as polarizing plate protective films. Optical films are typically stored or transported in roll form for ease of handling and manufacturing efficiency. When film rolls are stored or transported in a rolled state, significant deformation of the rolls, sticking of films together, or damage can lead to a decrease in film quality. This increases waste in the polarizing plate manufacturing process and increases the labor costs for quality inspections, ultimately leading to higher product prices. To suppress quality degradation due to deformation of film rolls, a textured surface called embossing is usually applied to both ends of the film in the width direction (see, for example, Patent Document 1). However, the embossed areas formed by embossing are easily crushed, and sometimes the adhesion between films cannot be sufficiently suppressed. In contrast, a method is known in which knurled sections are formed on both ends of the base film in the width direction by a coating method (see, for example, Patent Document 2). Figure 4A is a plan view of a conventional film, and Figure 4B is a cross-sectional view taken along line 4B-4B in Figure 4A. As shown in Figures 4A and 4B, Patent Document 2 discloses a method for forming knurled portions 2 by applying a knurling solution in a strip to both ends in the width direction of a base film 1 and then drying it. The knurled portions 2 formed by this application are said to have higher strength and be less prone to crushing compared to the uneven structure formed by embossing, thus effectively suppressing adhesion between films. Japanese Patent Publication No. 2016-89110Japanese Patent Publication No. 2012-206312 Figure 1A is a plan view of the film according to this embodiment, and Figure 1B is a cross-sectional view taken along the line 1B-1B in Figure 1A.Figure 2A is a partially enlarged plan view of the dotted line portion of Figure 1A, and Figure 2B is a cross-sectional view taken along the line 2B-2B in Figure 2A.Figures 3A and 3B are partial cross-sectional views showing modified versions of Figure 2B.Figure 4A is a plan view of a conventional film, and Figure 4B is a cross-sectional view taken along the line 4B-4B in Figure 4A.Figure 5 is a partial perspective view showing the state of curling in a conventional film. The reason why curling occurs at the edges of the base film 11 when applying and forming the knurling composition is not clear, but it is presumed to be as follows. In other words, when the knurling composition applied to the surface of the base film 11 is dried or cured, the force of shrinkage caused by the drying or curing of the knurling composition is transmitted to the base film 11, making it easily deformed. In particular, the edges of the base film 11 are more easily deformed than the central part (because they have less weight and a higher degree of freedom), so it is thought that curls occur at the edges of the base film 11, causing them to bend towards the side to which the knurling composition was applied (see Figure 5). In contrast, the present invention involves 1) forming a knurling composition in a plurality of island-like (protrusions) in the width direction of the base film, and further, 2) providing a distribution in the volume (preferably height) of these protrusions; specifically, making the volume (preferably height) of the protrusions on the width direction end side of the base film smaller than the volume of the protrusions on the width direction center side. This reduces the contact area between the base film and the protrusions, while making the shrinkage force generated on the width direction end side smaller than the shrinkage force generated on the width direction center side. This suppresses curling at the edges of the base film. Furthermore, when transporting a thin base film with a low elastic modulus, compressive forces (buckling stress) are easily generated in the width direction of the base film, which tends to cause wrinkles in the center of the width direction. In contrast, by providing the above-described distribution of heights for multiple protrusions in the width direction of the base film, an expanding effect (expander effect) can be achieved, which expands the base film in the width direction. This further suppresses wrinkles caused by buckling stress. The configuration of the present invention will now be described. 1. Film Manufacturing Method Figure 1A is a plan view of a strip-shaped film 10 according to this embodiment, and Figure 1B is a cross-sectional view taken along line 1B-1B in Figure 1A. Figure 2A is a partially enlarged plan view of the dotted line portion 2A in Figure 1A, and Figure 2B is a partially enlarged cross-sectional view of the