KR20200136891A - Manufacturing method of laminated film - Google Patents

Abstract

It provides a manufacturing method of a laminated film in which fracture of a film in a film bonding process was suppressed. In the manufacturing method of the present invention, the surface protective film is peeled from the stacked body while conveying the stacked body of the elongated first film having a breaking strength of 1.9 N/mm or less and the surface protection film laminated on one side of the first film to be manufactured. It includes bonding the 1st film and the 2nd film, and the protrusion width of the surface protection film in the width direction from the edge part of a 1st film at both ends of a laminated body is 1 mm or more and less than 20 mm.

Description

Manufacturing method of laminated film

The present invention relates to a method for producing a laminated film.

As a method for producing a laminated film containing a plurality of films, a method of efficiently producing a laminated film by continuously bonding to another film while conveying a long film is known. When the film is thinned in response to the recent demand for thinning of the laminated film, the breaking strength of the film is lowered, and as a result, the film may break in the bonding step.

Japanese Laid-Open Patent Publication No. 2018-36655

The present invention has been made in order to solve the above conventional problems, and its main object is to provide a method for producing a laminated film in which fracture of the film in the film bonding step is suppressed.

The manufacturing method of the laminated film of the present invention is a method of manufacturing a laminated film including a first film and a second film, and is laminated on one side of the elongated first film and the first film having a breaking strength of 1.9 N/mm or less. And peeling the surface protection film from the laminate while conveying the laminate with the obtained surface protection film to bond the first film and the second film, and at both ends of the laminate, the first film The protruding width of the surface protection film in the width direction from the end of the surface is 1 mm or more and less than 20 mm.

In one embodiment, the second film is a polarizing film, and the first film is a base film that functions as a protective layer of the polarizing film.

In one embodiment, the said 1st film and the said 2nd film are attached|attached through an adhesive agent.

In one embodiment, the said 1st film and the said 2nd film are attached|attached through an adhesive.

In one embodiment, the thickness of the first film is 30 μm or less.

In one embodiment, the said 1st film is a cycloolefin resin film, a cellulose resin film, or an acrylic resin film.

1 is a schematic cross-sectional view showing a method of manufacturing a laminated film according to an embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view of a laminate of a surface protection film and a base film cut along the width direction.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Manufacturing method of laminated film

1 is a schematic cross-sectional view showing a method of manufacturing a laminated film according to an embodiment of the present invention. The manufacturing method of the laminated film of this invention is a manufacturing method of a laminated film containing a 1st film and a 2nd film. This manufacturing method, while conveying the laminate 30 of the first film 10 and the surface protection film 20 laminated on one side of the first film 10 (Fig. 1 (a)), a laminate It includes peeling the surface protective film 20 from (30) (FIG. 1(b)) and bonding the 1st film 10 and the 2nd film 40 (FIG. 1(c)). Thereby, the laminated film 100 including the 1st film 10 and the 2nd film 40 is obtained. Typically, the surface protection film 20 is peeled while conveying the elongated laminate 30 in the longitudinal direction, and the surface protection film 20 peeling surface in the first film 10 and the so-called roll-to-roll The surface of the opposite side is continuously attached to the second film 40. The first film 10 is long and has a breaking strength of 1.9 N/mm or less. Fig. 1(a) is a schematic cross-sectional view when the laminate 30 is cut along the width direction. As shown in FIG. 1(a), the surface protection film 20 protrudes from the edge part of the 1st film 10 in the width direction in the laminated body 30 at both ends. The protruding width of the surface protection film 20 is 1 mm or more and less than 20 mm. The first film 10 can be protected by laminating the surface protection film 20 on the first film 10 until the first film 10 is provided for bonding with the second film 40. have. In addition, by using the surface protection film 20 that is wider than the first film 10, the protrusion width of the surface protection film 20 in the laminate 30 is 1 mm or more and less than 20 mm, so that the first film 10 ) Can be protected. As a result, after peeling the surface protection film 20 from the first film 10, fracture of the first film 10 before bonding the first film 10 and the second film 40 can be suppressed. have. The production method of the present invention can be used for production of a laminated film containing any first and second films.

In one embodiment, the 1st film and the 2nd film are attached|attached through an adhesive agent. In another embodiment, the 1st film and the 2nd film are bonded through an adhesive. As the adhesive and pressure-sensitive adhesive, any suitable adhesive and pressure-sensitive adhesive may be used, and representatively, a polyvinyl alcohol-based adhesive and an acrylic pressure-sensitive adhesive may be used. The thickness of the first film is preferably 30 μm or less. The first film is preferably a cycloolefin resin film, a cellulose resin film, or an acrylic resin film.

Any film can be used as the elongated first film and the second film having a breaking strength of 1.9 N/mm or less. In one embodiment, the 2nd film is a polarizing film, and the 1st film is a base film (polarizing film protective film) which can function as a protective layer of a polarizing film. In this case, the laminated film obtained is a polarizing plate including a polarizing film and a base film laminated on one side of the polarizing film.

Hereinafter, as an embodiment of the present invention, a method of manufacturing a polarizing plate in which the first film is a base film and the second film is a polarizing film will be described as an example.

B. Laminate

Fig. 2 is a schematic cross-sectional view of the laminate 30 of the surface protection film 20 and the base film 11 cut along the width direction. The laminate 30 includes a long base film 11 and a surface protection film 20 laminated on one side of the base film 11. The surface protective film protects the base film until the base film is provided for bonding with the polarizing film, and peels off at any appropriate time point before bonding the base film to the polarizing film. The laminated body is elongate and may be wound in a roll shape.

As shown in Fig. 2, at both ends of the laminate 30, the surface protection film 20 protrudes from the end of the base film 11 in the width direction, and the protrusion width of the surface protection film 20 is 1 mm or more. It is less than 20mm. When the protrusion width in the width direction of the surface protective film is 1 mm or more, fracture of the base film after peeling the surface protective film can be suppressed. Specifically, by protecting the end face of the base film by a surface protection film, cracks in the width direction at the ends of the base film, which may occur during transportation of the laminated disk or during operations such as winding and feeding of the laminated disk. Can be suppressed. As a result, after peeling the surface protective film, even when the base film is independently conveyed while applying tension in the longitudinal direction, it becomes possible to suppress fracture. In addition, when the protrusion width in the width direction of the surface protective film is less than 20 mm, a decrease in the handling property (transportability) of the laminate due to protrusion of the surface protective film can be suppressed. If the protrusion width is 20 mm or more, there may be a problem such as that the end of the surface protective film is wound around the end of the base film, so that the surface protective film becomes difficult to peel. However, if the protrusion width is less than 20 mm, such a problem can be avoided. I can. The protrusion width is preferably 3 mm to 18 mm, more preferably 5 mm to 16 mm, and particularly preferably 7 mm to 14 mm. The protrusion width at one end of the laminate and the protrusion width at the other end may be the same or different.

In one embodiment, the surface protection film is laminated on the base film via an adhesive layer. In another embodiment, the surface protective film is constituted by a self-adhesive film, and is laminated on a base film without interposing an adhesive layer.

As the pressure-sensitive adhesive used for lamination between the base film and the surface protection film, appropriately select a pressure-sensitive adhesive made of (meth)acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as the base polymer. It can be used. From the viewpoint of transparency, weather resistance, heat resistance, and the like, an acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is preferable. The thickness of the pressure-sensitive adhesive layer (dry film thickness) is determined according to the required adhesive strength. It is usually about 1 to 100 µm, preferably 5 to 50 µm.

B-1. Base film

The base film has a long shape as described above and has a breaking strength of 1.9 N/mm or less. The breaking strength of the base film is preferably 0.3 N/mm to 1.6 N/mm, more preferably 0.5 N/mm to 1.3 N/mm. The breaking strength of the base film can be measured, for example, by a tensile test according to JIS-K-7127.

The thickness of the base film is typically 30 μm or less, preferably 1 μm to 25 μm or less, and more preferably 3 μm to 20 μm.

The base film is formed from any suitable film that can function as a protective layer of a polarizing film. Specific examples of the material used as the main component of the film include cellulose resins such as cycloolefin resin films and triacetylcellulose (TAC), polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, and poly. And transparent resins such as ether sulfone, polysulfone, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. In addition, thermosetting resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone, such as polymethyl methacrylate (PMMA), or ultraviolet-curable resins may be mentioned. In addition to this, for example, glassy polymers such as siloxane polymers may be mentioned. In addition, the polymer film described in Japanese Unexamined Patent Publication No. 2001-343529 (WO01/37007) can also be used. The base film is preferably a cycloolefin resin film, a cellulose resin film, or an acrylic resin film.

The base film may be subjected to a surface treatment such as a hard coat treatment, an antireflection treatment, an anti-sticking treatment, and an anti-glare treatment as necessary.

The base film preferably has substantially optically isotropic properties. In the present specification, the term'substantially optically isotropic' means that the in-plane retardation Re (550) of the base film is 0 nm to 10 nm, and the retardation Rth (550) in the thickness direction is -10 nm to +10 nm. Re (550) is the in-plane retardation of the film measured with light having a wavelength of 550 nm at 23°C. Re(550) can be obtained by the formula: Re(550)=(nx-ny)×d. Rth(550) is the retardation in the thickness direction of the film measured with light having a wavelength of 550 nm at 23°C. Rth(550) can be obtained by the formula: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the slow axis direction, ny is the refractive index in the fast axis direction, nz is the refractive index in the thickness direction, and d is the thickness (nm) of the film.

B-2. Surface protection film

The thickness of the surface protection film is preferably 25 µm to 250 µm, more preferably 50 µm to 200 µm, and particularly preferably 70 µm to 150 µm. By using a surface protective film having sufficient thickness and rigidity, curling of the base film can be suppressed, and further, the transportability of the base film can be improved.

The surface protection film is preferably a transparent film having isotropic properties from the viewpoint of inspection properties and manageability.

Examples of the material constituting the surface protection film include polyester resins such as polyethylene terephthalate films, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, Polyolefin resin and acrylic resin are mentioned. Among these, polyester resins are preferred.

In the surface protective film, a peeling treatment layer can be provided on the surface opposite to the adhesive surface to the base film by a low-adhesion material such as silicone treatment, long chain alkyl treatment, or fluorine treatment.

C. Polarizing film

Any suitable polarizing film can be adopted as the polarizing film. For example, the resin film forming the polarizing film may be a single-layered resin film or a laminate of two or more layers.

Specific examples of a polarizing film composed of a single-layer resin film include polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and hydrophilic polymer films such as ethylene/vinyl acetate copolymer-based partial saponification films, such as iodine and dichroic dyes. A polyene-based oriented film, such as a dyeing treatment and a stretching treatment with a dichroic substance, a dehydration treatment product of PVA or a dehydrochloric acid treatment product of polyvinyl chloride, etc. are mentioned. Preferably, from the viewpoint of excellent optical properties, a polarizing film obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Moreover, you may dye it after drawing. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only can the contamination or blocking agent on the surface of the PVA-based film be washed, but also the PVA-based film is swelled to prevent staining and the like.

As a specific example of a polarizing film obtained by using a laminate, a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a PVA-based resin layer coated on the resin substrate and formed The polarizing film obtained by using the laminated body of is mentioned. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate, for example, a PVA-based resin solution is applied to the resin substrate and dried to form a PVA-based resin layer on the resin substrate. Obtaining a laminate of a PVA-based resin layer; It can be produced by stretching and dyeing the laminate to use the PVA-based resin layer as a polarizing film. In the present embodiment, stretching typically includes stretching by immersing the laminate in an aqueous boric acid solution. Further, the stretching may further include air stretching the laminate at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained laminate of the resin substrate/polarizing film may be used as it is (i.e., the resin substrate may be used as a protective layer of the polarizing film), the resin substrate is peeled from the laminate of the resin substrate/polarizing film, and the peeling surface is used for the purpose. Any suitable protective layer according to the above may be laminated and used. Details of a method for producing such a polarizing film are described in, for example, Japanese Laid-Open Patent Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

The thickness of the polarizing film is, for example, 30 µm or less, preferably 15 µm or less, more preferably 1 µm to 12 µm, still more preferably 3 µm to 12 µm, and particularly preferably 3 µm to 8 µm. . When the thickness of the polarizing film is within such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained.

The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is 43.0% to 46.0%, preferably 44.5% to 46.0% as described above. The polarization degree of the polarizing film is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. The measurement method and evaluation method of each characteristic are as follows. In addition, unless otherwise specified,'parts' and'%' in Examples and Comparative Examples are based on weight.

(1) thickness

It was measured using a dial gauge (manufactured by PEACOCK, product name'DG-205', dial gauge stand (product name'pds-2')).

(2) Breaking strength of the base film

The tensile test was performed according to JIS-K-7127. The measurement sample was performed at a chuck interval of 50 mm, a test piece width of 10 mm, and a test speed of 300 mm/min using a substrate film cut in the form of a test piece type 2 described in JIS-K-7127. In addition, the tester used for the measurement was an Instron-type tensile tester (manufactured by Shimadzu Corporation, Autograph). The strength when the sample broke in the tensile test was calculated as N/mm.

(3) Fracture of the base film

With respect to the polarizing plate (laminated film) of the base film/polarizing film of Reference Examples, Examples and Comparative Examples, it was confirmed whether or not the base film was broken.

(4) Handling

When the laminate of the surface protection film/substrate film of Reference Examples, Examples and Comparative Examples was conveyed at a conveyance speed of 20 m/min, the handling properties were evaluated based on the following criteria.

○... Folds and wrinkles did not occur in the laminate by transport, and the surface protective film could be easily peeled off.

×... Folds or wrinkles occurred in the layered product by transport, or it was difficult to peel the surface protective film.

[Production Example 1]

(Production of the polarizing film)

Amorphous IPA copolymerized PET film (thickness: 100 μm) having an absorption rate of 0.75% and a Tg of 75°C was subjected to corona treatment on one side of the substrate, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and aceto on the corona treated side 60℃ by applying an aqueous solution containing acetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Japan Synthetic Chemical Industries, brand name'Go Sepamer Z200') in a ratio of 9:1 By drying at, a 13 µm-thick PVA-based resin layer was formed on the resin substrate, and a laminate was produced.

The obtained laminate was uniaxially stretched at a free end 2.4 times in the longitudinal direction (length direction) between rolls having different circumferential speeds in an oven at 130°C (air auxiliary stretching treatment).

Next, the laminate was immersed for 30 seconds in an insolubilization bath having a liquid temperature of 40°C (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).

Next, it was immersed in a dyeing bath having a liquid temperature of 30°C while adjusting the concentration and immersion time of the dyeing solution (iodine: potassium iodide = 1:7 parts by weight) so that the single transmittance of the polarizer finally obtained was 42% (dye treatment). .

Next, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 40°C (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid) (crosslinking treatment).

Thereafter, uniaxial stretching was performed so that the total draw ratio was 5.5 times in the longitudinal direction (length direction) between rolls having different circumferential speeds while immersing the laminate in an aqueous boric acid solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70°C. Was carried out (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath having a liquid temperature of 20°C (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment).

Thereby, a laminated body (polarizer laminated body) of a resin base material and a 5 micrometers-thick polarizing film was produced.

[Reference Example 1]

1. Fabrication of a laminate of a surface protection film and a base film

A base film A was produced by forming a 2 µm-thick hard coat layer on one side of a film containing a cycloolefin-based resin as a main component (manufactured by Jeon Corporation, product name'ZD12', thickness 28 µm, width 1300 mm). The breaking strength of the base film A was 2.0 N/mm.

Subsequently, by bonding a surface protective film (manufactured by Toray Film Processing Co., Ltd., product name'#30 7832C', thickness 30 µm) to the side of the hard coat layer side of the base film A through an acrylic adhesive, the surface protection film/substrate film A laminated body of A was produced. At this time, at both ends of the laminate, the surface protection film was bonded so that the end portions of the surface protection film and the end portions of the base film A coincide (the protrusion width in the width direction of the surface protection film is 0 mm).

2. Fabrication of polarizing plate

While conveying the layered product of the surface protection film/substrate film A, peeling the surface protective film from the layered product, and conveying the substrate film A as it is, the side opposite to the hard coat layer of the substrate film A is applied with a PVA-based adhesive. A polarizing plate including the configuration of a base film/polarizing film laminate was obtained by continuously bonding the polarizing film laminate to the surface of the polarizing film side.

[Reference Example 2]

An acrylic resin film (thickness 40 µm, width 1330 mm) containing as a main component polymethyl methacrylate containing lactone rings, coated with a urethane-based easily adhesive layer on the surface, was used as the base film B. The breaking strength of the base film B was 4.3 N/mm.

Except having used the base film B, it carried out similarly to Reference Example 1, the laminated body of the surface protection film/base film B was produced, and the polarizing plate was produced using the said laminated body.

[Reference Example 3]

A laminate of a surface protection film/base film B was prepared in the same manner as in Reference Example 2, except that the base film B protrudes 5 mm from the end of the surface protection film in the width direction to bond the surface protection film, and the laminate was used. Thus, a polarizing plate was produced.

[Example 1]

A base film C was produced by forming a 2 µm-thick hard coat layer on one side of a film containing a cycloolefin-based resin as a main component (manufactured by Jeon Corporation, product name'ZF12', thickness 27 µm, width 1320 mm). The breaking strength of the base film C was 1.3 N/mm.

A laminate of a surface protection film/base film C was prepared in the same manner as in Reference Example 1 except that the base film C was used, and the surface protection film was bonded by making the surface protection film protrude 5 mm from the end of the base film C in the width direction. It was produced, and a polarizing plate was produced using the laminate.

[Example 2]

An acrylic resin film (20 µm in thickness, 1330 mm in width) mainly composed of polymethyl methacrylate containing lactone rings on the surface of which a urethane-based easily adhesive layer was applied was used as the base film D. The breaking strength of the base film D was 1.9 N/mm.

Except having used the base film D, it carried out similarly to Example 1, the laminated body of the surface protection film/base film D was produced, and the polarizing plate was produced using the said laminated body.

[Example 3]

A film containing a cycloolefin-based resin as a main component (manufactured by Jeon Corporation, product name'ZF14', thickness 13 µm, width 1330 mm) was used as the base film E. The breaking strength of the base film E was 0.9 N/mm.

Except having used the base film E, it carried out similarly to Example 1, the laminated body of the surface protection film/base film E was produced, and the polarizing plate was produced using the said laminated body.

[Example 4]

In the same manner as in Example 3, except that the surface protection film protrudes 1 mm from the end of the base film E in the width direction to bond the surface protection film, a laminate of the surface protection film/base film E was prepared, and the laminate was used. Thus, a polarizing plate was produced.

[Example 5]

In the same manner as in Example 3, except that the surface protection film protrudes 10 mm from the end of the base film E in the width direction to bond the surface protection film, a laminate of the surface protection film/base film E was prepared, and the laminate was used. Thus, a polarizing plate was produced.

[Comparative Example 1]

Surface protection film/base film D in the same manner as in Example 2, except that the surface protection film was bonded (the protrusion width in the width direction of the surface protection film is 0 mm) by making the end of the surface protection film coincide with the end of the base film D. A laminate of was prepared, and a polarizing plate was produced using the laminate.

[Comparative Example 2]

A layered product of a surface protection film/base film D was prepared in the same manner as in Example 2, except that the base film D protrudes 5 mm from the end of the surface protection film in the width direction to bond the surface protection film. Thus, a polarizing plate was produced.

[Comparative Example 3]

A laminate of the surface protection film/base film B was produced in the same manner as in Reference Example 2, except that the surface protection film protrudes from the end of the base film B by 20 mm in the width direction to bond the surface protection film.

Production of a polarizing plate was tested using the laminate, but the laminate had low handling properties, and the surface protective film was peeled off while conveying, and the base film and the polarizing film could not be bonded.

[Comparative Example 4]

A laminate of the surface protection film/base film C was produced in the same manner as in Example 1, except that the surface protection film was bonded to each other by making the end of the surface protection film coincide with the end of the base film C.

[Comparative Example 5]

A laminate of the surface protection film/base film E was produced in the same manner as in Example 3, except that the surface protection film was bonded to each other by making the end of the surface protection film coincide with the edge of the base film E.

With respect to the polarizing plates of Reference Examples, Examples, and Comparative Examples, the presence or absence of fracture of the base film and the handling property of the laminate were evaluated based on the above (3) and (4). Table 1 shows the results.

[Table 1]

In Reference Examples using a base film having a breaking strength of 2.0 N/mm or more, the base film did not break, but in Comparative Examples 1, 2, 4 and 5 using a base film having a breaking strength of 1.9 N/mm or less, the base film was broken. Has occurred. On the other hand, in Examples 1 to 5 in which the protrusion width of the surface protection film was 1 mm or more and less than 20 mm, fracture of the base film did not occur even though the base film having a breaking strength of 1.9 N/mm or less was used.

Industrial availability

The manufacturing method of the laminated film of this invention is used suitably as a manufacturing method of a polarizing plate.

10: first film
20: surface protection film
30: laminate
40: second film
100: laminated film

Claims (6)

As a method for producing a laminated film comprising a first film and a second film,
The first film by peeling the surface protection film from the laminate while conveying the laminate of the long-shaped first film having a breaking strength of 1.9 N/mm or less and a surface protection film laminated on one side of the first film. And bonding the second film together,
At both ends of the laminate, the protrusion width of the surface protection film in the width direction from the end of the first film is 1 mm or more and less than 20 mm. The method of claim 1,
The second film is a polarizing film,
The manufacturing method wherein the first film is a base film that functions as a protective layer of the polarizing film. The method according to claim 1 or 2,
A manufacturing method of bonding the first film and the second film through an adhesive. The method according to claim 1 or 2,
A manufacturing method of bonding the first film and the second film through an adhesive. The method according to any one of claims 1 to 4,
The manufacturing method in which the thickness of the first film is 30 μm or less. The method according to any one of claims 1 to 5,
The production method wherein the first film is a cycloolefin-based resin film, a cellulose-based resin film, or an acrylic resin film.

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