TWI614541B - Method for manufacturing laminated optical film - Google Patents

Abstract

The present invention provides a method for manufacturing a laminated optical film in which a knurled portion of a laminated optical film is less likely to be wrinkled even when an optical film having a knurled portion is laminated with another film by a pair of bonding rollers.

In the present invention, the first optical film 2 is introduced between a pair of rotating bonding rollers 7a and 7b, and the first optical film 2 and the first optical film 2 are disposed on one side or both sides of the first optical film 2 through an adhesive layer or an adhesive layer. 2 optical film 3, 3, a method for manufacturing a laminated optical film bonded by pressing a pair of bonding rollers 7a, 7b to press the first optical film 2 and the second optical film 3, 3, wherein the first optical film 2 And at least one of the second optical film 3 has a knurled portion 3a, 3a at an edge portion in the width direction; and a pair of bonding rollers 7a, 7b avoids pressing the knurled portions 3a, 3a, and is bonded to the first Optical film 2 and second optical films 3,3.

Description

Manufacturing method of laminated optical film

The present invention relates to a method for manufacturing a laminated optical film.

Conventionally, a manufacturing method of a laminated optical film is known in which at least two optical films are laminated by a pair of bonding rollers through an adhesive layer or an adhesive layer (see, for example, Patent Document 1).

On the other hand, in order to prevent winding deviation and deformation when a long optical film is wound into a roll shape, minute irregularities called knurling are provided at both ends in the flow direction of the optical film. In a band shape (refer to, for example, Patent Document 2).

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-172290

[Patent Document 2] Japanese Patent Laid-Open No. 2014-218016

An optical film having a knurled portion (knurled portion). When a laminated optical film is produced by laminating a pair of bonding rollers with another film, wrinkles are easily generated in the knurled portion, and the quality of the laminated optical film is liable to decrease.

Therefore, the object of the present invention is to provide a laminated optical film that is less prone to wrinkles in the knurled portion of a laminated optical film manufactured when the optical film having a knurled portion is laminated with another film by a pair of bonding rollers. Production method.

The present invention is to introduce a first optical film between a pair of rotating bonding rollers, and a second optical film disposed on one or both sides of the first optical film with an adhesive layer or an adhesive layer interposed therebetween. At least one of the first optical film and the second optical film is produced in a widthwise edge portion by a method of manufacturing a laminated optical film that is laminated by pressing the first optical film and the second optical film with a pair of bonding rollers. The knurling part is provided, and a pair of bonding rollers is used to bond the first optical film and the second optical film while avoiding the pressure knurling part.

According to this manufacturing method, since the knurled portion is not pressurized by the bonding roller, wrinkles are less likely to occur in the knurled portion of the laminated optical film manufactured.

At least one of the pair of conforming rollers may be an elastic roller. The wrinkles that have conventionally occurred in the knurling section are prone to occur when the bonding roller is an elastic roller. Therefore, the present invention is suitably applied when the bonding roller is an elastic roller.

The first optical film and the second optical film are bonded via an adhesive layer, and the width of the adhesive layer in the extending direction of the pair of bonding rollers may be wider than the width of the first optical film. In this case, the first optical film and the second optical film can be adhered well.

In addition, a pair of bonding roller systems can bond the first optical film and the second optical film in a manner that avoids contact with the knurled portion. In this case, since the bonding roller does not contact the knurled portion, wrinkles are further prevented from occurring in the knurled portion.

According to the present invention, it is possible to provide a method for producing a laminated optical film in which a knurled portion of a laminated optical film is less likely to be wrinkled even when an optical film having a knurled portion is pressed against another film by a pair of bonding rollers.

1‧‧‧ laminated optical film

2‧‧‧The first optical film

3‧‧‧ 2nd optical film

3a‧‧‧Knurling Department

4‧‧‧ laminated body

5‧‧‧ Adhesive layer

7a‧‧‧Elastic roller (fitting roller)

7b‧‧‧metal roller (fitting roller)

FIG. 1 is a cross-sectional view in the width direction of a laminated optical film manufactured by the manufacturing method according to this embodiment.

Each of (A) to (C) in FIG. 2 is a cross-sectional view schematically showing an example of a knurled portion.

Fig. 3 is a view showing a state in which each film is bonded by a pair of bonding rollers.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3.

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that in the drawings, the same or corresponding parts are given the same reference numerals, and repeated descriptions are omitted.

As shown in FIG. 1, the laminated optical film 1 manufactured by the manufacturing method according to this embodiment includes a first optical film 2 and a second optical film 3 which is adhered on both sides thereof with an adhesive layer 5 interposed therebetween, 3. The laminated optical film 1 has a long shape and is wound into a roll shape and stored.

The second optical films 3 and 3 are equal in width to each other. One side of the widthwise edge portion has knurled portions 3a, 3a. The knurled portions 3 a and 3 a are provided in a strip shape along the direction (the front surface direction in the drawing) during the manufacture of the laminated optical film 1 and are provided in parallel with each other.

2 (A) to 2 (C) are cross-sectional views schematically illustrating side ends of a second optical film 3 as an example of a knurled portion 3a. Fig. 2 (A) is an example in which protrusions are provided on one side (upper in the figure), and depressions are provided on the opposite side (in the figure below) corresponding to the protrusions. Fig. 2 (B) is on a single side. The surface (upper in the figure) is provided with protrusions and depressions, the opposite surface (lower in the figure) is an example of a smooth surface, and the second figure (C) is an example in which protrusions and depressions are provided on both sides.

In this embodiment, the so-called knurling portion is connected to the side end portion of the second optical film 3, and the position from the innermost position to the outermost position is formed in the widthwise position where protrusions or depressions are formed on either of the two surfaces. So far it is called a knurling section. In this embodiment, the knurling portion 3a implemented in the second optical film 3 may be in any one of the forms (A) to (C) in FIG. 2, but is not limited to these forms. The width of the knurled portion 3a is not limited, but is about 0.5 to 5% of the width of the entire film in each side end portion, and is about 5 to 30 mm.

The shapes of the protrusions and depressions provided in the knurling portion 3a are trapezoidal in each of the examples in FIGS. 2A to 2C, but the trapezoidal shape may be a conical trapezoidal shape or a corner column trapezoidal shape. Examples of the shape other than a trapezoid include a cylinder, a prism, a cone, a pyramid, and the like, and the shape may be an irregular shape. Two or more shapes may be mixed.

In this embodiment, when the film is knurled, the knurling height is adjusted to 2 to 10 μm, and preferably 3 to 6 μm. Here, the knurling height refers to the thickness of the knurling portion 3a minus the non-knurling The value of the thickness of the machined portion is shown in each of the figures (A) to (C) in FIG. 2 by subtracting the thickness t 'of the knurled portion 3a from the thickness t' of the portion where the knurling is not performed. -t ". When the knurling height is too small, it is not possible to sufficiently suppress the defective appearance of the film from being taken up. When the knurling height is too large, the film may be easily broken during or after knurling. When there is a difference in thickness between the portions not subjected to the knurling process, the knurling height may be calculated using the average thickness, but in this case, the knurling height is preferably higher than the difference.

In addition, the thickness of the portion where the knurling process is not performed, that is, the thickness of the second optical film 3 is preferable from the viewpoint of thinning the laminated optical film 1. When the thickness is too thin, the strength is reduced and the workability is poor. It is preferably 5 to 90 μm, more preferably 5 to 60 μm, and even more preferably 5 to 50 μm.

By having the knurled portion 3a as described above, it is possible to prevent deformation such as winding offset and deformation when the long optical film is rolled into a roll, and curling at the end of the film when the optical film is transported. Although the height of the knurled portion 3a is only 2 to 10 μm, when the first optical film 2 and the second optical film 3 are bonded, when the knurled portion 3a is pressed from the roller, the unevenness of the knurled portion becomes The base point becomes prone to wrinkles.

The adhesive layer 5 exists in a width incorporated between the knurled portions 3 a and 3 a of the second optical film 3. That is, the width of the adhesive layer 5 is narrower than the width of the second optical film 3.

The width of the adhesive layer 5 is preferably wider than the width of the first optical film 2. In this case, the first optical film 2 and the second optical film 3 can be adhered well.

Here, the type and material of each member are illustrated. Make For example, when the first optical film 2 is a polarizer and the second optical film 3 is a protective film, it is a combination of optical films. At this time, the manufactured multilayer optical film 1 is a polarizing plate.

As the material of the polarizer, conventional materials used in the manufacture of polarizers can be used, and examples thereof include polyvinyl alcohol resins, polyvinyl acetate resins, ethylene / vinyl acetate (EVA) resins, and polyamides. Resin, polyester resin, etc. Among these, a polyvinyl alcohol-based resin is preferable. When forming into a film shape, it is preferable to dye a uniaxially stretched film with iodine or a dichroic dye and then perform a boric acid treatment.

The thickness of the polarizer is preferably 2 to 75 μm, more preferably 2 to 50 μm, and even more preferably 2 to 30 μm.

The protective film is a film that prevents the main surface and the ends of the polarizer from being cracked or damaged. Here, the "protective film" refers to a film that is physically laminated at the position closest to the polarizer among various films that can be laminated to the polarizer.

The protective film may be made of various transparent resin films known in the field of polarizing plates. For example, cellulose resins as representative examples of triethylfluorene cellulose, polyolefin resins as representative examples, polypropylene resins as representative examples, cyclic olefin resins as representative examples of norbornene resins, and polymethyl methacrylate Acrylic resins based on representative resins, polyester resins based on polyethylene terephthalate based resins, etc. are representative examples. Among these are cellulose resins.

The two protective films may be made of the same kind of material, or they may be made of different kinds of materials.

The protective film may be a film having no optical function, or a film incorporating optical functions such as a retardation film and a brightness enhancement film.

The thickness of the protective film is preferably 5 to 90 μm, more preferably 5 to 80 μm, and even more preferably 5 to 50 μm.

As the adhesive constituting the adhesive layer 5, various adhesives used in the manufacture of conventional polarizing plates can be used. For example, from the viewpoints of weather resistance, refractive index, and cation polymerizability, an epoxy resin having no aromatic ring in the molecule is preferable. Moreover, it is preferable to harden by irradiation of active energy rays (ultraviolet rays or hot rays).

As the epoxy resin, for example, a hydrogenated epoxy resin, an alicyclic epoxy resin, or an aliphatic epoxy resin is preferred. Polymerization initiators (e.g., photocationic polymerization initiators for polymerization by ultraviolet irradiation, thermal cationic polymerization initiators for polymerization by heating rays), and other additives (sensitizers, etc.) can be added to the epoxy resin to prepare coatings. An epoxy resin composition for cloth is used.

Further, as the adhesive, acrylic resins such as acrylamide, acrylate, amine acrylate, epoxy acrylate, and polyvinyl alcohol-based water-based adhesives can also be used.

The manufactured polarizing plate is a single-sided or double-sided one that is attached to a display unit (image display element) such as a liquid crystal cell. The polarizing plate may further include other optical layers laminated on the protective film. As other optical layers, for example, a reflective polarizing film that reflects polarized light of the opposite nature through a certain type of polarized light; a film having an uneven shape on the surface with an antiglare function; a film with an antireflection function on the surface; A reflective film with a reflective function; a semi-transparent reflective film with a reflective function and a transmissive function; a viewing angle compensation film.

The thickness of the polarizing plate composed of three layers of a polarizer and two protective films is preferably 10 to 500 μm, more preferably 10 to 300 μm, and even more preferably 10 to 200 μm.

As another combination of optical films, for example, the case where the first optical film 2 is the above-mentioned polarizing plate, and the second optical film 3 is a separation sheet or a temporary protective film. At this time, the adhesive layer is used instead of the adhesive layer 5, and the manufactured laminated optical film 1 is a “polarizing plate with a separator” or a “polarizing plate with a temporary protective film”.

The adhesive layer is a layer that functions when a polarizing plate is attached to another article (for example, a liquid crystal cell). The adhesive layer may be composed of an acrylic resin, a silicone resin, a polyester, a polyurethane, a polyether, or the like.

The thickness of the adhesive layer is preferably 2 to 500 μm, more preferably 2 to 200 μm, and even more preferably 2 to 50 μm.

As a method of laminating an adhesive on a polarizing plate, for example, a method of applying a solution containing the above resin and any additional components to the polarizing plate, or a method of forming an adhesive layer with the solution on a separating sheet and then laminating it on a protective film. method.

The separation sheet is a peelable film that is attached for the purpose of protecting the adhesive layer and preventing the adhesion of foreign matter, and is peeled off during use of the polarizing plate to expose the adhesive layer. The separator can be formed of, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate. Among them, a stretched film of polyethylene terephthalate is preferred.

The thickness of the separator is preferably 2 to 500 μm, and 2 to 200 μm is more preferred, and 2 to 100 μm is even more preferred.

The temporary protective film is a film that can be peeled from the polarizing plate, and is used to protect the surface of the polarizing plate laminated with the temporary protective film from damage and abrasion. As the material of the temporary protective film, the same as the above-mentioned protective film can be used. Among them, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene isophthalate are used. Better.

After temporarily protecting the polarizing plate, the protective film is laminated to the polarizing plate until the polarizing plate is used, and is peeled from the polarizing plate when the polarizing plate is used.

The thickness of the temporary protective film is preferably 2 to 500 μm, more preferably 2 to 200 μm, and even more preferably 2 to 100 μm.

Next, the manufacturing method concerning this embodiment is demonstrated. As shown in FIG. 3, the first optical film 2 and the second optical films 3 and 3 are introduced between a pair of rotating bonding rollers 7a and 7b while the films are being conveyed, and the bonding rollers 7a and 7b is pressed and bonded to each other. The two films to be bonded are transferred between the bonding rollers 7 a and 7 b to form the laminated body 4. In FIG. 3, the drawing of the adhesive layer 5 is omitted.

Here, the arrangement of the two films between the bonding rollers 7a, 7b is as shown in FIG. 4, and the existence width of the first optical film 2 is located between the two knurled portions 3a, 3a of the second optical film 3. The knurled portions 3a, 3a of the two second optical films 3, 3 face each other. Moreover, in FIG. 4, in order to make the drawing easier to see, the bonding rollers 7 a and 7 b are separated and drawn from the laminated body 4.

The adhesive layer 5 has a width that is included between the two knurled portions 3 a and 3 a of the second optical film 3 and is wider than the width of the first optical film 2. Then, two rolls of the second optical film 3 are enclosed in the adhesive layer 5. The flower portions 3a and 3a are located between the existing widths of the first optical film 2 in the inner portion. The adhesive layer 5 may be provided by applying the above-mentioned adhesive on the surface of the second optical film 3 opposite to the first optical film 2.

The pair of abutment rollers 7a, 7b is composed of an elastic roller 7a and a metal roller 7b in more detail. The "elastic roller" herein refers to a roller composed of an outermost layer of a roller, such as a rubber elastic body. The elastic roller 7a may be made of rubber as a whole, or may be made of metal at the center, and only the outermost layer may be made of rubber. Examples of the rubber material include nitrile butadiene rubber, urethane rubber, and silicone rubber.

The width of the elastic roller 7a (the extending width in a direction perpendicular to the conveying direction) is narrower (smaller) than the distance between the two knurled portions 3a, 3a of the second optical film 3 that is in contact with it. The width of layer 5 is also wide (large). Next, the elastic roller 7 a is arranged so as to be enclosed between the two knurled portions 3 a and 3 a and is arranged so as to include the width of the adhesive layer 5. Here, the width of the elastic roller 7a refers to the entire width of a portion that extends simultaneously while maintaining the same diameter as the portion that becomes an effective contact surface that facilitates bonding. For example, at the end portion of the elastic roller 7a, if a part having a width direction is reduced in diameter and not in contact with the second optical film 3, the width of the reduced diameter portion is set to the width of the elastic roller 7a. .

The width of the metal roller 7b is wider than the width of the second optical film 3 that is in contact with the metal roller 7b, and is located over the entire width of the second optical film 3 inside. At the time of bonding, the knurled portions 3a and 3a of the second optical film 3 are in contact with the metal roller 7b.

The pair of bonding rollers 7a and 7b presses (clamps) the first optical film 2 and the second optical film 3, 3 with the adhesive layer 5 interposed therebetween to bond the first optical film 2 and the first optical film 2 2 optical film 3,3. At this time, the knurled portions 3a of the two second optical films 3 and 3 are prevented from being pressurized. That is, the knurled portions 3a, 3a included in the second optical film 3 on the elastic roller 7a side do not contact the elastic roller 7a. On the other hand, the knurled portions 3a, 3a included in the second optical film 3 on the metal roller 7b side are in contact with the metal roller 7b, but the width of the elastic roller 7a side is not sufficient, so they are not pressurized.

At the time of lamination, a pair of laminating rollers 7a, 7b may not have a pressurizing film mechanism, instead, they can be pressed by a pair of pressing rollers arranged in contact with these to become a pressurizing film. .

The laminated body 4 produced by bonding is then hardened to complete the laminated optical film 1 shown in FIG. 1.

According to the manufacturing method described above, since the knurled portion 3a is not pressurized by the pair of bonding rollers 7a, 7b, the knurled portion 3a of the laminated optical film 1 is less likely to be wrinkled.

In addition, since the width of the adhesive layer 5 is wider than the width of the first optical film 2, the first optical film 2 and the second optical film 3 are adhered well. Moreover, since the elastic roller 7a is located in the existence width of the inner-coated adhesive layer 5, the first optical film 2 and the second optical film 3 can be adhered more favorably.

As mentioned above, although the preferred embodiment of this invention was described, this invention is not limited to the said embodiment. For example, in the above embodiment, the pair of conforming rollers 7a and 7b are shown as a combination of the elastic roller 7a and the metal roller 7b, but the pair of conforming rollers 7a and 7b can be replaced by two elastic rollers. The structure may be composed of two metal rollers.

In the above embodiment, the two second optical films 3 and 3 are shown as having the knurled portion 3a. However, the second optical film 3 may not have the knurled portion 3a.

In the above embodiment, the width of the metal roller 7b is wider than the width of the second optical film 3 in contact with the metal roller 7b. The metal roller 7b may be located within the entire width of the second optical film 3, and may be The width of the metal roller 7b is narrower than the distance between the two knurled portions 3a, 3a of the second optical film 3. The metal roller 7b is in a state of being enclosed between the two knurled portions 3a, 3a. In this case, the first optical film 2 and the second optical film 3 are bonded to the pair of bonding rollers 7a and 7b so as to avoid contact with the knurled portions 3a and 3a. Therefore, it is possible to further prevent the occurrence of wrinkles in the knurled portion 3a. .

Furthermore, in the embodiment described above, it is shown that the first optical film 2 does not have a knurled portion, and the first optical film 2 may have a knurled portion. In this case, the width of the elastic roller 7a is narrower than the distance between the knurled portions of the first optical film 2, and the elastic roller 7a is located between the knurled portions.

In addition, the magnitude relationship of the respective widths of the first optical film 2, the second optical film 3, and the adhesive layer 5 is not limited to the magnitude relationship of the embodiment described above, and may be any one of them.

Furthermore, in the above embodiment, a state where one piece of the first optical film 2 and two pieces of the second optical film 3 are bonded (three pieces of bonding) is shown, but it is also possible to combine one piece of the first optical film 2 with A state in which one piece of the second optical film 3 is bonded (two pieces of bonding).

Moreover, in the above embodiment, the display includes polarized light The element film is the first optical film 2, and the first optical film 2 may be an optical film that does not include a polarizing element.

2‧‧‧The first optical film

3‧‧‧ 2nd optical film

3a‧‧‧Knurling Department

4‧‧‧ laminated body

5‧‧‧ Adhesive layer

7a‧‧‧Elastic roller (fitting roller)

7b‧‧‧metal roller (fitting roller)

Claims (5)

A method for manufacturing a laminated optical film, wherein a first optical film is introduced between a pair of rotating bonding rollers, and the first optical film is disposed on one side or both sides of the first optical film through an adhesive layer or an adhesive layer. The second optical film is bonded by pressing the first optical film and the second optical film by the pair of bonding rollers, wherein at least one of the first optical film and the second optical film is The edge portion in the width direction has a knurled portion; the pair of bonding rollers is configured to bond the first optical film and the second optical film while avoiding pressure on the knurled portion. According to the method for manufacturing a laminated optical film according to item 1 of the scope of the patent application, wherein at least one of the aforementioned pair of bonding rollers is an elastic roller. The method for manufacturing a laminated optical film according to item 1 or 2 of the scope of the patent application, wherein the first optical film and the second optical film are bonded together via the adhesive layer; The width of the adhesive layer in the extending direction is wider than the width of the first optical film. The method for manufacturing a laminated optical film according to item 1 or 2 of the scope of the patent application, wherein the pair of bonding rollers are bonded to the first optical film and the second optical film to avoid contact with the knurled portion. The method for manufacturing a laminated optical film according to item 3 of the scope of the patent application, wherein the pair of bonding rollers are bonded to the first optical film and the second optical film to avoid contact with the knurled portion.