TW201734514A - Method for manufacturing laminated optical film - Google Patents

Abstract

The present invention provides a method for manufacturing a laminated optical film in which wrinkles are less likely to occur in the knurling portion of the laminated optical film even when an optical film having a knurling portion is pressure bonded to another film by a pair of bonding rolls. The method for manufacturing a laminated optical film in which a first optical film 2 and second optical films 3, 3 arranged on one side or both sides of the first optical film 2 with an adhesive layer or a pressure-sensitive adhesive layer are disposed between one pair of bonding rolls 7a and 7b, and the first optical film 2 and the second optical films 3, 3 are pressed and bonded together by a pair of bonding rolls 7a and 7b, wherein at least one of the first optical film 2 and the second optical films 3, 3 has knurling portions 3a, 3a at the edge portion in the width direction, and the pair of bonding rolls 7a and 7b laminate the first optical film 2 and the second optical films 3, 3 while avoiding pressurizing the knurling portions 3a, 3a.

Description

Method for manufacturing laminated optical film

The present invention relates to a method of producing a laminated optical film.

In the related art, a method for producing a laminated optical film in which at least two optical films are laminated by a pair of bonding rollers between the two of the optical films is described (see, for example, Patent Document 1).

On the other hand, in order to prevent winding deviation and deformation when the long optical film is wound into a roll shape, fine unevenness called knurling is imparted to both end portions in the flow direction of the optical film. It is formed into a strip shape (refer to, for example, Patent Document 2).

[Previous Technical Literature] [Patent Literature]

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

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

An optical film having a portion (knurling portion) imparted to the knurling When a laminated optical film is produced by press-bonding a pair of bonding rolls to another film, wrinkles are likely to occur in the knurled portion, and the quality of the laminated optical film is likely to be lowered.

Accordingly, an object of the present invention is to provide a laminated optical film in which a knurled portion of a laminated optical film to be produced is less likely to wrinkle even when an optical film having a knurled portion is pressed against another film by a pair of bonding rollers. Production method.

In the present invention, the first optical film is introduced between the pair of rotating rollers, and the second optical film is disposed on the one-side side or both sides of the first optical film via the adhesive layer or the adhesive layer. A method of producing a laminated optical film in which a first optical film and a second optical film are bonded together by a pair of bonding rollers, wherein at least one of the first optical film and the second optical film is at an edge portion in the width direction The knurling portion and the pair of bonding rollers prevent the pressure knurling portion from being bonded to the first optical film and the second optical film.

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

The pair of bonding rollers are at least one of the bonding rollers and may be elastic rollers. The wrinkles which have occurred in the knurling portion in the past are likely 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 to each other via the adhesive layer, and the width of the adhesive layer in the extending direction of the pair of bonding rollers can be wider than the width of the first optical film. In this case, the first optical film and the second optical film can be satisfactorily joined.

Further, the pair of bonding rollers can be bonded to the first optical film and the second optical film so as not to contact 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 the knurled portion of the laminated optical film to be produced is less likely to wrinkle even when the optical film having the knurled portion is pressed against another film by a pair of bonding rollers.

1‧‧‧Laminated optical film

2‧‧‧1st optical film

3‧‧‧2nd optical film

3a‧‧‧Knurling Department

4‧‧‧Layered body

5‧‧‧ adhesive layer

7a‧‧‧Flexible roller (fitting roller)

7b‧‧‧Metal roller (fitting roller)

Fig. 1 is a cross-sectional view in the width direction of a laminated optical film produced by the production method of the present embodiment.

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

Fig. 3 is a view showing a state in which the respective films are bonded by a pair of bonding rollers.

Fig. 4 is a sectional view taken along line IV-IV of Fig. 3.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are given to the same or corresponding parts, and the repeated description is omitted.

As shown in Fig. 1, the laminated optical film 1 produced by the production method of the present embodiment includes the first optical film 2, and the second optical film 3 which is adhered to the both surfaces of the first optical film 2 via the adhesive layer 5, 3. The laminated optical film 1 has a long shape and is wound in a roll shape and stored.

The second optical films 3 and 3 are equal in width to each other. Both sides of the edge portion in the width direction have knurled portions 3a, 3a. The knurling portions 3a and 3a are provided in a strip shape along the direction in which the laminated optical film 1 is conveyed (the front direction of the drawing) and are provided in parallel with each other.

FIGS. 2(A) to (C) are cross-sectional views schematically showing a side end portion of the second optical film 3 as an example of the knurling portion 3a. Fig. 2(A) shows a projection on one side (upper in the figure), and a recess on the opposite side (in the figure below) corresponding to the protrusion, and Fig. 2(B) is a single The surface (in the figure above) is provided with protrusions and depressions, and the surface on the opposite side (the lower side in the figure) is an example of a smooth surface, and the second drawing (C) is an example in which protrusions and depressions are provided on both sides.

In the present embodiment, the knurling portion is formed at 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 position in the width direction in which the projection or the depression is formed on either of the two surfaces. So far, it is called the knurling part. In the present embodiment, the knurling portion 3a implemented in the second optical film 3 may be in any one of the second drawings (A) to (C), but is not limited to the above. The width of the knurled portion 3a is not limited, but is about 0.5 to 5% of the width of the entire film at each end portion, and is about 5 to 30 mm.

The shape of the projections and recesses provided in the knurling portion 3a is trapezoidal in each of the second drawings (A) to (C), but the trapezoid may be a trapezoidal trapezoid or a trapezoidal pyramid. Further, examples of the shape other than the trapezoid include a column, a corner column, a cone, a pyramid, and the like, and may be indefinite. It is also possible to mix two or more shapes.

In the present embodiment, when the film is subjected to knurling, the knurl height is adjusted to 2 to 10 μm, preferably 3 to 6 μm. Here, the knurl height means that the knurling is not subtracted from the thickness of the knurled portion 3a. The value of the thickness of the processed portion is subtracted from the thickness t' of the knurled portion 3a by the thickness t' of the portion where the knurling is not performed, and "t' of the portion where the knurling is not performed, in each of the examples of Figs. 2(A) to (C). The value of -t". When the knurling height is too small, the film may not be sufficiently suppressed from being taken up, and when it is too large, the film may be easily broken during knurling or after processing. Further, when the portion where the knurling is not performed has a thickness difference, the knurl height may be calculated using the average thickness thereof, but at this time, the knurl height is preferably higher than the difference.

In addition, the thickness of the portion where the knurling is not performed, that is, the thickness of the second optical film 3 is preferably thinner from the viewpoint of thinning of the laminated optical film 1, and when it is too thin, the strength is lowered and the workability is poor. It is preferably 5 to 90 μm, more preferably 5 to 60 μm, still more preferably 5 to 50 μm.

By having the knurling portion 3a as described above, it is possible to prevent deformation such as winding deviation and deformation when the long optical film is wound into a roll shape, and curling at the end portion of the film during transport of the optical film. When 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 to each other, when the knurling portion 3a is pressed from the roller, the unevenness of the knurled portion becomes Basic points, it becomes easy to produce wrinkles.

The subsequent layer 5 is present in a width which is included between the knurled portions 3a, 3a attached to 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 subsequent 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 satisfactorily adhered to.

Here, the types and materials of the respective members are exemplified. Make The combination of the optical films may be, for example, when the first optical film 2 is a polarizer and the second optical film 3 is a protective film. At this time, the produced laminated optical film 1 is a polarizing plate.

As a material of the polarizer, a conventional material used for the production of a conventional polarizing plate can be used, and examples thereof include a polyvinyl alcohol resin, a polyvinyl acetate resin, an ethylene/vinyl acetate (EVA) resin, and a polyamide. Resin, polyester resin, etc. Among them, a polyvinyl alcohol-based resin is preferred. When it is formed into a film shape, it is preferred to carry out dyeing on a one-axis film by iodine or a dichroic dye, followed by boric acid treatment.

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

The protective film is a film that prevents cracking or damage of the main surface and the end portion of the polarizer. Here, the "protective film" refers to a film which is physically laminated to the position closest to the polarizer in various films which can be laminated on the polarizer.

The protective film may be composed of various transparent resin films known in the field of polarizing plates. For example, a cellulose-based resin represented by a representative example of a cellulose-based resin, a polyolefin-based resin which is a representative example of a polypropylene-based resin, a cyclic olefin-based resin which is a representative example of a norbornene-based resin, and a polymethyl methacrylate The resin is a representative example of an acrylic resin, and a polyethylene terephthalate resin is a representative example of a polyester resin. Among them, a cellulose resin is representative.

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

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

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

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

As the epoxy resin, for example, a hydrogenated epoxy resin, an alicyclic epoxy resin, an aliphatic epoxy resin or the like is preferable. A polymerization initiator (for example, a photocationic polymerization initiator for ultraviolet irradiation polymerization, a thermal cationic polymerization initiator for polymerization by heat irradiation), and other additives (sensitizing agents, etc.) may be added to the epoxy resin to prepare a coating. The cloth is used as an epoxy resin composition.

Further, as the adhesive, an acrylic resin such as acrylamide, an acrylate, an amine acrylate or an epoxy acrylate, or a polyvinyl alcohol-based aqueous adhesive can be used.

The polarizing plate to be produced is attached to one or both sides of 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. The other optical layer may, for example, be a reflective polarizing film that reflects a polarized light having opposite properties by a certain polarized light; an anti-glare film having an uneven shape on the surface; and a film having an anti-reflective function on the surface; A reflective film having a reflective function; a semi-transmissive reflective film having a reflective function and a transmissive function; a viewing angle compensation film and the like.

The polarizing plate composed of the polarizer and the three protective films has a thickness of preferably 10 to 500 μm, more preferably 10 to 300 μm, still more preferably 10 to 200 μm.

As another combination of the optical films, for example, the first optical film 2 is the above-mentioned polarizing plate, and the second optical film 3 is a separating piece or a temporary protective film. In this case, the adhesive layer is used in place of the adhesive layer 5, and the laminated optical film 1 produced is a "polarizing plate with a separator" or a "polarizing plate with a temporary protective film".

The adhesive layer is a layer that acts when a polarizing plate is attached to other articles such as a liquid crystal cell. The adhesive layer may be composed of an acrylic resin, a polyoxymethylene 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, still more preferably 2 to 50 μm.

As a method of laminating an adhesive layer on a polarizing plate, for example, a method of applying a solution containing the above resin and an optional additive component to a polarizing plate may be employed to form an adhesive layer on the separation sheet and then deposit the layer on the protective film. method.

The film which may be peeled off for the purpose of protecting the adhesive layer and preventing adhesion of foreign matter is peeled off during use of the polarizing plate to expose the adhesive layer. The separator may be composed 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 stretch film of polyethylene terephthalate is preferred.

The separator has a thickness of preferably 2 to 500 μm, preferably 2 to 200 More preferably μm, more preferably 2 to 100 μm.

The temporary protective film is a film which can be peeled off from the polarizing plate, and is used to protect the surface of the polarizing plate in which the temporary protective film is laminated from being damaged or worn. As the material of the temporary protective film, the same as the above protective film can be used, and a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polyethylene isophthalate is used. Preferably.

After the temporary protective film is laminated on the polarizing plate, it is bonded to the polarizing plate until the use of the polarizing plate, and is peeled off from the polarizing plate during use.

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

Next, a description will be given of a manufacturing method relating to the present embodiment. The first optical film 2 and the second optical film 3, 3 are conveyed as shown in Fig. 3, and are introduced between the pair of rotating bonding rollers 7a, 7b, and by the bonding roller 7a. 7b is pressed against each other and fits. The two bonded film systems are transferred between the rollers 7a and 7b to form the laminated body 4. Furthermore, in FIG. 3, the drawing of the adhesive layer 5 is omitted.

Here, the arrangement of the two films between the bonding rollers 7a and 7b is as shown in Fig. 4, and the width of the first optical film 2 is located in the two knurling portions 3a, 3a of the second optical film 3. The knurled portions 3a and 3a of the two second optical films 3 and 3 are opposed to each other. Further, in Fig. 4, the bonding rollers 7a, 7b are separated and drawn from the laminated body 4 in order to facilitate the drawing.

The adhesive layer 5 has a width which is included between the two knurled portions 3a and 3a of the second optical film 3 and is wider than the width of the first optical film 2. Then, the two layers of the second optical film 3 are wrapped in the adhesive layer 5 Between the flower portions 3a, 3a, and located in the presence width of the first optical film 2 is contained. The adhesive layer 5 can be provided by applying the above-mentioned adhesive to the surface of the second optical film 3 opposite to the surface of the first optical film 2.

The pair of bonding rollers 7a, 7b are composed of the elastic roller 7a and the metal roller 7b in more detail. Here, the term "elastic roller" means a roller composed of an elastic body such as rubber as the outermost layer of the roller. The elastic roller 7a may be made entirely of rubber, or the center portion may be made of metal, and only the outermost layer may be made of rubber. Examples of the material of the rubber include a nitrile butadiene rubber, an amine ester rubber, and a polyoxygen rubber.

The width of the elastic roller 7a (the extending width in the direction perpendicular to the conveying direction) is narrower (smaller) than the distance between the two knurling portions 3a, 3a of the second optical film 3 that is in contact therewith. The width of layer 5 is also wide (large). Then, the elastic roller 7a is disposed so as to be enclosed between the two knurling portions 3a, 3a, and is disposed so as to have the width of the adhesive layer 5 present. Here, the width of the elastic roller 7a means the same width as the portion which is the effective contact surface which contributes to the bonding, and the entire width of the portion which extends at the same time. For example, in the end portion side of the elastic roller 7a, when the portion having the width direction is reduced in diameter and the portion not in contact with the second optical film 3, the width of the portion where the reduced diameter is removed is set as 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 therewith, and is located at the entire width of the second optical film 3. 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 pressurize (clamp) the first optical film 2 and the second optical films 3 and 3 with the adhesive layer 5 interposed therebetween, and bond the first optical film 2 and the first optical film 2 and 2 optical film 3, 3. At this time, any of the knurled portions 3a of the two second optical films 3, 3 is prevented from being pressurized. In other words, the knurled portions 3a, 3a of the second optical film 3 on the side of the elastic roller 7a do not contact the elastic roller 7a. On the other hand, the knurled portions 3a and 3a of the second optical film 3 on the side of the metal roller 7b are in contact with the metal roller 7b, but the width of the elastic roller 7a is insufficient, so that it is not pressurized.

At the time of bonding, a pair of bonding rollers 7a, 7b may not have a mechanism for pressing the film, and instead, they may be pressed by being provided in contact with the pair of pressing rollers to become a pressurized film. .

The laminated optical body 1 shown in Fig. 1 is completed by bonding the laminated body 4 produced, and then curing the adhesive layer.

According to the above-described manufacturing method, 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 to be produced is less likely to wrinkle.

Further, 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 satisfactorily joined. Further, since the elastic roller 7a is located at the width of the adhesive inner layer 5, the first optical film 2 and the second optical film 3 can be more closely adhered.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the pair of bonding rollers 7a, 7b are combined with the elastic roller 7a and the metal roller 7b, but the pair of bonding rollers 7a, 7b can be made of two elastic rollers. The structure can also be composed of two metal rollers.

Further, in the above embodiment, the two second optical films 3, 3 are all provided with the knurled portion 3a, but the second optical film 3 of either of them may not have the knurled portion 3a.

Further, in the above embodiment, the width of the metal roller 7b is wider than the width of the second optical film 3 that is in contact therewith, and the metal roller 7b is located in 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, and the metal roller 7b is located between the two knurling portions 3a, 3a. In this case, the pair of bonding rollers 7a, 7b are bonded to the first optical film 2 and the second optical film 3 so as not to contact the knurling portions 3a, 3a, so that wrinkles in the knurled portion 3a can be further prevented. .

Further, in the above embodiment, the first optical film 2 is in a state in which the knurled portion is not provided, 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.

Further, 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 size relationship of the above-described embodiment, and may be any.

Further, in the above embodiment, the first optical film 2 and the two second optical films 3 are bonded together (three sheets are bonded), but one first optical film 2 may be used. A state in which one sheet of the second optical film 3 is bonded (two sheets of bonding).

Moreover, in the above embodiment, the display includes polarized light The film of the element 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‧‧‧1st optical film

3‧‧‧2nd optical film

3a‧‧‧Knurling Department

4‧‧‧Layered body

5‧‧‧ adhesive layer

7a‧‧‧Flexible roller (fitting roller)

7b‧‧‧Metal roller (fitting roller)

Claims (4)

A method for producing a laminated optical film, wherein a first optical film is introduced between a pair of rotating bonding rolls, and is disposed on one side or both sides of the first optical film via an adhesive layer or an adhesive layer The second optical film is bonded to 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, and the pair of bonding rollers prevent the first knurled portion from being pressed and the first optical film and the second optical film. The method for producing a laminated optical film according to claim 1, wherein the bonding roller of at least one of the pair of bonding rollers is an elastic roller. The method for producing a laminated optical film according to the first or second aspect, wherein the first optical film and the second optical film are bonded together via the adhesive layer; and the pair of bonding rollers The width of the above-mentioned adhesive layer in the extending direction is wider than the width of the first optical film. The method for producing a laminated optical film according to any one of the first to third aspect, wherein the pair of bonding rollers are bonded to the first optical film and the aforementioned The second optical film.