JP7619266B2 - Method for manufacturing film laminate - Google Patents

Description

The present invention relates to a film laminate having a surface protective film laminated thereon. More specifically, the present invention relates to a film laminate that can effectively utilize the width direction of the film and reduce waste.

A transfer method in which a functional layer formed on a substrate film is transferred is known as a method for providing a functional layer having various functions on an object, and in recent years, the transfer method has been used in many fields. Examples of functional layers include surface decoration layers such as printed layers and metal deposition layers, optical functional layers such as anti-glare layers, anti-reflection layers, polarizing layers, and retardation layers, thin film layers, thin film substrate layers of circuits such as ceramic layers, circuit layers, catalyst layers for fuel cells, and barrier layers.

In these fields, functional layers are required to be increasingly thinner and more precise, and therefore the surface of the release substrate film on which the functional layer is formed is also required to have high precision and smoothness.

Generally, these release substrate films are manufactured and used as long rolls. In order to stably wind the film into a roll, the film surface needs to have a certain degree of roughness, but the film to which the functional layer is transferred needs to be highly smooth, and this smoothness can make winding difficult.

As a method for making it easier to wind up a film and preventing it from shifting or becoming scratched on the surface, knurling applied to the widthwise ends of the film, as shown in Patent Document 1, is known.

In addition, when a film with a retardation layer or polarizing layer made of liquid crystal compounds on a base film is stored in roll form, extremely high pressure can be applied to the film on the core side at areas where the thickness has increased slightly due to slight thickness unevenness in the film or at steps at the beginning of the roll, which can disrupt the orientation of the liquid crystal compounds that make up the retardation layer or polarizing layer. To prevent this, knurling is sometimes used.

When providing a functional layer on a base film, especially when providing a functional layer on a release base film, if the base film is knurled, the knurled area can become an obstacle to processing processes such as coating, transfer, and vapor deposition, as well as transportation, so the knurled area was slit and removed before being processed.

Furthermore, release substrate films provided with functional layers are often knurled before being wound up, and when multiple functional layers are provided, the knurled portions are repeatedly removed, which requires the preparation of release substrate films that are significantly wider than the width of the final product, and also results in a large amount of waste due to the slitting and removal of the knurled portions, which is not only economically disadvantageous but also undesirable in terms of environmental protection.

JP 2011-248198 A

The present invention has been made in light of the above-mentioned problems. The object of the present invention is to provide a film laminate for transfer to provide a functional layer on an object, which reduces waste, prevents problems during winding, and allows for the provision of a functional layer with fewer defects, as well as a method for producing the same and a method for transferring a functional layer to an object.

The film laminate of the present invention, which has achieved the above-mentioned objectives, its manufacturing method, and the method for transferring a functional layer to an object, have the following features:

[1] A long film laminate in which a base film and a surface protective film are laminated, characterized in that knurling is applied to both ends of the surface protective film in the width direction.

[2] A film laminate as described in [1], in which the base film has not been subjected to knurling.

[3] A film laminate described in [1] or [2] in which a functional layer is disposed between the base film and the surface protective film.

[4] A film laminate described in [3], wherein the base film is a release film and the functional layer is a transferable thin-film optical element.

[5] A film laminate according to [4], wherein the thin film optical element is an oriented liquid crystal compound layer.

[6] A method for producing a film laminate, comprising the steps of preparing the film laminate described in [1], peeling a surface protective film from a base film of the film laminate, providing a functional layer on the surface of the base film on which the surface protective film was laminated, and bonding a surface protective film to the surface on which the functional layer is provided.

[7] A method for transferring a functional layer, comprising the steps of producing a film laminate by the production method described in [6], peeling a surface protective film from the film laminate, bonding the functional layer surface of the film laminate to an object to be transferred, and peeling the base film from the object to be transferred.

By using the film laminate of the present invention, it is possible to reduce the amount of waste when providing a functional layer on an object, prevent problems during winding, and provide a functional layer with fewer defects on the object.

1 is a cross-sectional view of a film laminate according to one embodiment of the present invention. 2 shows a plan view of the film laminate of FIG. 1 as viewed from the surface protection film side. 1 is a cross-sectional view of a substrate film according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of a substrate film according to another embodiment of the present invention. FIG. 2 is a cross-sectional view of a substrate film according to yet another embodiment of the present invention. 2 illustrates a cross-sectional view of a film stack according to another embodiment of the present invention. 1 is a cross-sectional view of a functional layer laminate film according to one embodiment of the present invention. 3 shows a cross section of a functional layer laminate film according to another embodiment of the present invention. 3 illustrates a cross-sectional view of a film laminate according to yet another embodiment of the present invention.

The present invention will be described below based on the embodiments and with reference to the drawings, but the present invention is of course not limited to the embodiments below, and can of course be implemented with appropriate modifications within the scope of the intent described above and below, all of which are included in the technical scope of the present invention. In addition, hatching and component symbols may be omitted in each drawing for convenience, but in such cases, reference should be made to the specification or other drawings. Also, the dimensions of components in the drawings may differ from the actual dimensions.

A film laminate 1 according to an embodiment of the present invention will be described with reference to Figures 1 to 6. Figure 1 shows a cross-sectional view in the thickness direction of a film laminate 1 according to one embodiment of the present invention, and Figure 2 shows a plan view of the film laminate 1 in Figure 1 as viewed from the surface protective film 4 side. Figure 3 shows a cross-sectional view in the thickness direction of a substrate film 2 according to one embodiment of the present invention, Figure 4 shows a cross-sectional view in the thickness direction of a substrate film 2 according to another embodiment of the present invention, and Figure 5 shows a cross-sectional view in the thickness direction of a substrate film 2 according to yet another embodiment of the present invention. Also, Figure 6 shows a cross-sectional view in the thickness direction of a film laminate 1 according to another embodiment of the present invention.

The film laminate 1 is a long film in which a base film 2 and a surface protective film 4 are laminated, and knurling is applied to both ends of the surface protective film 4 in the width direction, and the surface protective film 4 has knurled portions 4b at both ends in the width direction.

The film laminate 1 has a longitudinal direction (MD) and a width direction (TD) perpendicular to the longitudinal direction, and the base film 2 and the surface protective film 4 have the same longitudinal direction (MD) and width direction (TD) as described above. In addition, the film formation direction when the film laminate 1, the base film 2, and the surface protective film 4 are formed coincides with the longitudinal direction (MD).

[Base film]
The base film 2 serves as a base material on which the functional layer 3 described below is laminated, and preferably has a release surface 2a with releasability so that the functional layer 3 can be peeled off after being bonded to an object.

There are no particular limitations on the resin used for the base film 2 as long as it maintains its strength as a base film, but among these, polyester, polycarbonate, polystyrene, polyamide, polypropylene, cyclic polyolefin, triacetyl cellulose, and polyfluoroethylene are preferred, with polyethylene terephthalate, cyclic polyolefin, and triacetyl cellulose being particularly preferred.

The substrate film 2 may be a single layer or a multi-layer structure. In the case of a multi-layer structure, it may be formed by co-extrusion. As shown in Figs. 3 to 5, examples of the multi-layer structure include a release surface 2a side layer 20A/back surface side layer 20B, a release surface 2a side layer 20A/intermediate layer 20C/release surface 2a side layer 20A, and a release surface 2a side layer 20A/intermediate layer 20C/back surface side layer 20B. The release surface 2a side layer 20A has releasability, and the back surface side layer 20B does not have to have releasability. Here, having releasability means that when the functional layer 3 provided on the substrate film 2 is transferred to an object, the peel strength between the functional layer 3 and the substrate film 2 is such that the functional layer 3 is transferred without remaining on the substrate film 2. The peel strength between the functional layer 3 and the base film 2 varies depending on various conditions such as the adhesive strength between the functional layer 3 and the object, the film strength of the functional layer 3, and the surface strength of the object, but is preferably 10 N/25 mm or less, and more preferably 8 N/25 mm or less. The peel strength between the functional layer 3 and the base film 2 is preferably 0.05 N/25 mm or more, but must exceed the peel strength between the surface protective film 4 and the functional layer 3 described later.

The thickness of the base film 2 is preferably 5 μm or more, more preferably 7 μm or more. Also, it is preferably 80 μm or less, more preferably 60 μm or less.

The base film 2 may be a stretched film or an unstretched film. In the case of a stretched film, it may be uniaxially stretched, weakly biaxially stretched (stretched in two directions, but weakly in one direction), or biaxially stretched.

As shown in FIG. 6, the base film 2 may have a release layer 20a on the base film base layer 20. However, if the base film 2 itself has low adhesion to the functional layer 3 and has sufficient releasability without providing the release layer 20a, the release layer 20a may not be provided. If the adhesion is too low, the adhesion may be adjusted by performing a corona treatment on the surface. The release layer 20a can be formed using a known release agent, and preferred examples include alkyd resin, amino resin, long-chain acrylic acrylate, silicone resin, and fluororesin. These can be selected appropriately according to the adhesion with the functional layer.

The base film 2 may be provided with an antistatic layer, an oligomer or monomer precipitation prevention layer, a surface smoothing layer, etc. The thickness of the release layer, antistatic layer, precipitation prevention layer, surface smoothing layer, etc. is preferably 10 μm or less, more preferably 7 μm or less. Also, it is preferably 0.1 μm or more, and particularly preferably 0.3 μm or more. When referring to the base film 2 without any particular specification, it is assumed that the release layer, antistatic layer, precipitation prevention layer, surface smoothing layer, etc. are also included.

It is preferable that the release surface 2a (surface of the release surface layer 20A) of the substrate film 2 is smooth. In the present invention, the "release surface 2a" of the substrate film means the surface of the substrate film on which the functional layer to be transferred is intended to be provided. When an antistatic layer, a deposition prevention layer, a flattening coating layer, a release layer, etc. are provided, if a functional layer is provided thereon, the surfaces of these layers (surfaces in contact with the functional layer) are the "release surface 2a" of the substrate film.

The lower limit of the three-dimensional arithmetic mean roughness (SRa) of the release surface 2a of the substrate film 2 is preferably 1 nm, and more preferably 2 nm. If it is less than the above, it may be difficult to achieve the numerical value in reality. Furthermore, the upper limit of the SRa of the release surface 2a of the substrate film 2 is preferably 30 nm, more preferably 25 nm, even more preferably 20 nm, particularly preferably 15 nm, and most preferably 10 nm.

The lower limit of the three-dimensional ten-point average roughness (SRz) of the release surface 2a of the base film 2 is preferably 5 nm, more preferably 10 nm, and even more preferably 13 nm. The upper limit of the SRz of the release surface 2a of the base film 2 is preferably 200 nm, more preferably 150 nm, even more preferably 120 nm, particularly preferably 100 nm, and most preferably 80 nm.

The lower limit of the maximum height (SRy: maximum peak height SRp of the release surface + maximum valley depth SRv of the release surface) of the release surface 2a of the base film 2 is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of SRy of the release surface 2a of the base film 2 is preferably 300 nm, more preferably 250 nm, even more preferably 150 nm, particularly preferably 120 nm, and most preferably 100 nm.

The base film 2 is industrially supplied in the form of a wound film roll. The lower limit of the roll width is preferably 300 mm, more preferably 500 mm, and even more preferably 600 mm. The upper limit of the roll width is preferably 5000 mm, more preferably 4000 mm, and even more preferably 3000 mm.

The lower limit of the roll length is preferably 100 m, more preferably 500 m, and even more preferably 1000 m. The upper limit of the roll length is preferably 100,000 m, more preferably 50,000 m, and even more preferably 30,000 m.

[Surface protection film]
A surface protective film 4 is attached to the release surface 2a of the base film 2, and the film is wound into a roll. Knurling is applied to the ends in the width direction of the surface protective film 4. By attaching the surface protective film 4, it is possible to prevent the release surface 2a of the base film 2 from being scratched, and by applying knurling to the surface protective film 4, it is possible to prevent wrinkles from occurring, making it easier to wind up, and also to prevent the film from shifting during storage, transportation, etc. in the wound state.

As shown in Figure 6, the surface protective film 4 may have an adhesive layer 40a provided on the surface protective film base layer 40.

Examples of the surface protection film base layer 40 include resin films and paper, with resin films being preferred. Suitable examples of resins used in the resin film include polyolefins, polyesters, polyamides, polyurethanes, etc., with polyolefins being preferred being polypropylene and polyethylene, and polyesters being preferred being polyethylene terephthalate. These may be copolymerized to adjust various physical properties such as the flexibility of the film. The resin film may be an unstretched film or a stretched film. In the case of a stretched film, it may be uniaxially stretched or biaxially stretched.

The adhesive layer 40a of the surface protection film 4 can use conventional adhesives such as rubber-based, acrylic-based, and polyolefin-based. Examples of rubber-based adhesives include natural rubber, butadiene rubber, isoprene rubber, and styrene-based block copolymer elastomers such as SBS, SIS, SEBS, and SEPS. Examples of acrylic-based adhesives include crosslinked copolymers of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, metal chelating agents, and compounds containing multiple double bonds.

Examples of polyolefin-based rubbers include ethylene-propylene rubbers such as EPM and EPDM, and those that use these as soft segments with polyethylene or polypropylene as hard segments, as well as blends of ethylene-propylene rubber with polyethylene or polypropylene.

These adhesives may contain various adhesion regulators and stabilizers, such as tackifiers, fatty acid esters, fatty acid bisamides, polyglycerin, silicone oil, and silicone resins.

The adhesive can be applied by coating it on the surface protective film substrate layer 40, or by co-extruding the resin of the substrate and the resin that will become the adhesive layer when forming the surface protective film substrate layer 40.

The peel strength of the surface protective film 4 is preferably 0.01 N/25 mm or more, more preferably 0.03 N/25 mm or more, and even more preferably 0.05 N/25 mm or more. The peel strength is preferably 2.0 N/25 mm or less, more preferably 1.5 N/25 mm or less, even more preferably 1.0 N/25 mm or less, particularly preferably 0.7 N/25 mm or less, and most preferably 0.5 N/25 mm or less. The adhesive strength of the surface protective film 4 is the adhesive strength when the surface protective film 4 is peeled off from a film laminate 1 consisting of a base film 2 and a surface protective film 4, or a film laminate 1 having a functional layer 3 between the base film 2 and the surface protective film 4. The adhesive strength of the surface protective film 4 can be adjusted by the composition and thickness of the adhesive.

By setting the peel strength at or above the above level, problems such as inadvertent peeling of the surface protective film 4 are less likely to occur during the winding process, unwinding process, the process of peeling the surface protective film 4 from the base film 2 and providing the base film 2 with the functional layer 3, and the process of peeling the surface protective film 4 from the base film 2 with the functional layer 3 laminated thereon and attaching it to an object. Furthermore, by setting the peel strength at or below the above level, a high processing speed can be ensured in each process that requires peeling of the surface protective film 4, reducing problems such as the functional layer 3 being taken up by the surface protective film 4 and making it easier to perform stable processing.

The total thickness of the surface protective film 4 is preferably 5 μm or more, and more preferably 10 μm or more. The total thickness of the surface protective film 4 is preferably 100 μm or less, and more preferably 80 μm or less.

The thickness of the adhesive layer 40a is preferably 1 μm or more, more preferably 2 μm or more, and is preferably 50 μm or less, and more preferably 30 μm or less. However, the thickness of the adhesive layer 40a is preferably 70% or less of the thickness of the surface protective film 4, more preferably 50% or less, and is preferably 5% or more, and more preferably 10% or more.

[Knurling]
The surface protection film 4 has knurled portions 4b at both ends in the width direction. The width of the knurled portions 4b is preferably 5 mm or more, more preferably 7 mm or more, and particularly preferably 10 mm or more. The width of the knurled portions 4b is preferably 50 mm or less, more preferably 40 mm or less, and particularly preferably 30 mm or less.

The knurling may be performed from the end of the surface protection film 4 in the width direction, but it is preferable that the knurling is performed at a distance of 2 mm or more inward from the end, and more preferably at a distance of 3 mm or more. The distance between the knurled portion 4b and the end of the surface protection film 4 is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. By providing the above distance, the knurling can be performed reliably.

The height of the knurling is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 1.5 μm or more. The height of the knurling is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 12 μm or less.

By setting the width, distance from the outermost end, and height of the knurled portion 4b within the above ranges, stable winding can be achieved and winding slippage can be effectively prevented. In addition, if an oriented liquid crystal compound layer 30 is provided as the functional layer 3 on the base film 2, the oriented state of the oriented liquid crystal compound layer 30 can be maintained.

Methods for performing knurling include (1) a method of passing a surface protective film 4 between a pair of knurls with protrusions and matching recesses to impart a wavy shape, (2) a method of passing a surface protective film 4 between a knurl with protrusions and a flat knurl to provide a raised portion pushed aside by the protrusions around the recesses, (3) a method of irradiating with a laser to provide a raised portion around the recesses, and (4) a method of providing a convex portion using a hot melt resin or an ultraviolet irradiated resin. In knurling using knurling, the knurling may be heated or the portion of the film to which the knurls are to be applied may be irradiated with infrared rays to make it easier to perform the knurling.

The shape of the knurled convex or concave portion may be any shape, such as a circle, ellipse, triangle, square, rhombus, trapezoid, pentagon, hexagon, or any polygon with more than one side. It may also be a combination of two or more of these shapes.

The distance between adjacent convex or concave portions is preferably 100 μm or more, more preferably 200 μm or more, and is preferably 5 mm or less, and even more preferably 3 mm or less, with the closest distance between adjacent convex or concave portions being 100 μm or more, and even more preferably 200 μm or more.

The arrangement of the convex and concave portions may be aligned vertically and horizontally, or may be a staggered arrangement in which adjacent concave and convex arrangements are shifted by half a period, or a diagonal arrangement in which adjacent concave and convex arrangements are shifted by 1/3 or 1/4. The convex portions formed by knurling are preferably provided on the surface of the surface protection film 4 that is not bonded to the base film 2 or the functional layer 3.

The knurling may be performed in advance during the manufacture of the surface protection film 4, or may be performed immediately before unrolling the surface protection film 4 that has not been knurled and laminating it to the base film 2. Alternatively, the knurling may be performed only on the surface protection film 4 in a state where the base film 2 and the surface protection film 4 are laminated together. In this case, the above methods (2), (3), and (4) are preferred.

It is preferable that the base film 2 is not subjected to knurling. By not subjecting the base film 2 to knurling, the functional layer 3 can be provided on the base film 2 by effectively utilizing the entire width of the base film 2, thereby improving productivity and reducing waste.

It is preferable that the width of the surface protection film 4 is in the range of -30 to +30 mm relative to the width of the base film 2, more preferably -20 to +20 mm, and particularly preferably -10 to +10 mm. Most preferably, the width of the surface protection film 4 is the same as the width of the base film 2.

In addition, it is preferable to adjust the knurling position of the surface protection film 4 to match the width of the base film 2.

[Functional layer]
It is preferable that a functional layer 3 is disposed between the substrate film 2 and the surface protective film 4. The functional layer 3 will be described with reference to Fig. 7 and Fig. 8. Fig. 7 shows a cross-sectional view of a functional layer laminate film 5 according to one embodiment of the present invention, and Fig. 8 shows a cross-sectional view of a functional layer laminate film 5 according to another embodiment of the present invention.

A film laminate 1 consisting of a base film 2 and a surface protective film 4 wound into a roll is unwound, the surface protective film 4 is peeled off, and a functional layer 3 is provided on the surface of the base film 2 on which the surface protective film 4 was laminated, i.e., the release surface 2a, to obtain a functional layer laminate film 5 as shown in Figure 7.

Examples of the functional layer 3 include surface decoration layers such as printed layers and metal deposition layers, thin-film optical elements such as anti-glare layers, anti-reflection layers, polarizing layers, and retardation layers, thin-film substrate layers of circuits such as thin-film layers and ceramic layers, circuit layers such as metals, electrode surface (catalyst) layers of fuel cells, primary batteries, and secondary batteries, and barrier layers. It is preferable that the functional layer 3 is a thin-film optical element. In particular, it is preferable that the functional layer 3 is an oriented liquid crystal compound layer 30, and among these, a polarizing layer or a retardation layer is suitable as the functional layer 3. Since the substrate film 2 has releasability, it is possible to transfer the functional layer 3 such as the oriented liquid crystal compound layer 30 to an object.

The functional layer 3 may be provided directly on the base film 2, or, as shown in Figure 8, an orientation control layer 3a may be further provided on the base film 2 and the functional layer 3 may be provided on the orientation control layer 3a.

As the polarizing layer, an absorptive polarizing layer using a liquid crystal compound and a dichroic dye, a circular polarizing layer (circularly polarized reflective layer) using a cholesteric liquid crystal compound, and a retardation layer using a liquid crystal compound are preferred. As the retardation layer using a liquid crystal compound, a λ/4 retardation layer or a λ/2 retardation layer is preferred. For the retardation layer, a material suited to the respective functions and a forming method suited to the material are used, and examples of the method include wet coating, and dry film formation such as vapor deposition, sputtering, and CVD. For wet coating, heating for crosslinking and radiation curing may be performed after drying.

The following describes a preferred embodiment of the oriented liquid crystal compound layer 30 of the present invention, an absorptive polarizing layer and a retardation layer using a liquid crystal compound.

(Absorptive polarizing layer)
The absorptive polarizing layer is preferably made of a liquid crystal compound and a dichroic dye, which is a dye having different absorbance in the long axis direction and the short axis direction of the molecule.

The dichroic dye preferably has a maximum absorption wavelength (λ _MAX ) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, and among these, azo dyes are preferred. Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbene azo dyes, and bisazo dyes and trisazo dyes are preferred. The dichroic dyes may be used alone or in combination, but it is preferred to combine two or more types in order to adjust the color tone to an achromatic color. It is more preferred to combine three or more types, and it is particularly preferred to combine three or more types of azo compounds.

From the viewpoint of achieving good orientation of the dichroic dye, the content of the dichroic dye in the absorptive polarizing layer is preferably 0.1 to 30 mass%, more preferably 0.5 to 20 mass%, even more preferably 1.0 to 15 mass%, and particularly preferably 2.0 to 10 mass%.

The absorptive polarizing layer preferably contains a liquid crystal compound for efficiently orienting the dichroic dye. The liquid crystal compound is preferably a polymerizable liquid crystal compound for fixing the orientation state. The polymerizable liquid crystal compound is a compound that has a polymerizable group and exhibits liquid crystallinity. The polymerizable group means a group involved in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group that can undergo a polymerization reaction by an active radical or acid generated from a photopolymerization initiator described later. As the polymerizable group, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The compound exhibiting liquid crystallinity may be a thermotropic liquid crystal or a lyotropic liquid crystal, and among thermotropic liquid crystals, it may be a nematic liquid crystal or a smectic liquid crystal. Among them, a smectic liquid crystal compound is preferable, and a high-order smectic liquid crystal compound is more preferable. When the liquid crystal layer formed by the polymerizable liquid crystal compound has a high-order smectic phase, an absorptive polarizing layer having a higher degree of orientational order can be produced.

Specific preferred polymerizable liquid crystal compounds include those described in, for example, JP 2002-308832 A, JP 2007-16207 A, JP 2015-163596 A, JP 2007-510946 A, JP 2013-114131 A, WO 2005/045485 A, Lub et al. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996), and the like.

From the viewpoint of increasing the orientation of the polymerizable liquid crystal compound, the content of the polymerizable liquid crystal compound in the absorptive polarizing layer is preferably 70 to 99.5% by mass, more preferably 75 to 99% by mass, even more preferably 80 to 97% by mass, and particularly preferably 83 to 95% by mass.

The absorptive polarizing layer can be provided by applying a composition paint to the substrate film 2. The composition paint may contain a solvent, a polymerization initiator, a sensitizer, a polymerization inhibitor, a leveling agent, a polymerizable non-liquid crystal compound, a crosslinking agent, etc.

The composition paint may be applied onto a substrate film 2 or onto an orientation control layer 3a described in detail below, and then dried, heated and cured as necessary.

The thickness of the polarizing film formed from the composition paint is 0.1 to 5 μm, preferably 0.3 to 3 μm, and more preferably 0.5 to 2 μm.

(Retardation Layer)
The retardation layer, which is another preferred example of the oriented liquid crystal compound layer 30 of the present invention, is a layer in which a liquid crystal compound is oriented. As the liquid crystal compound, a discotic liquid crystal compound, a rod-shaped liquid crystal compound, etc. are used. The liquid crystal compound used in the retardation layer is also preferably a polymerizable liquid crystal compound.

The retardation layer may be of various types depending on the purpose, such as a positive or negative A plate, a positive or negative C plate, or an O plate. The orientation is also selected according to the type of retardation layer and the type of liquid crystal compound, such as in-plane horizontal orientation, vertical orientation, tilted orientation, or orientation in which the tilt angle of the tilted orientation changes in the thickness direction. For example, for a circular polarizer, a λ/4 retardation layer with a retardation of 120 to 150 nm for the A plate or a λ/2 retardation layer with a retardation of 240 to 300 nm is selected.

Examples of retardation layers can be found in JP 2008-149577 A, JP 2002-303722 A, WO 2006/100830 A, JP 2015-64418 A, etc.

The retardation layer may be provided by applying a retardation composition paint, and the retardation composition paint may contain a solvent, a polymerization initiator, a sensitizer, a polymerization inhibitor, a leveling agent, a polymerizable non-liquid crystal compound, a crosslinking agent, etc.

The phase difference composition paint may be applied onto the substrate film 2 or onto the orientation control layer 3a described in detail below, and then dried, heated and cured as necessary.

The thickness of the retardation layer is 0.1 to 10 μm, preferably 0.3 to 7 μm, and more preferably 0.5 to 5 μm.

(Orientation Control Layer)
As described above, the oriented liquid crystal compound layer 30 such as a polarizing layer or a retardation layer may be provided directly on the substrate film 2, but an orientation control layer 3a may be provided on the substrate film 2, and the oriented liquid crystal compound layer 30 may be provided on the orientation control layer 3a. In the present invention, the polarizing layer, retardation layer, circularly polarized light reflective layer, etc. may contain an orientation control layer.

The orientation control layer 3a controls the orientation direction of the liquid crystal compound, allowing for the provision of a polarizing layer, phase difference layer, circularly polarized light reflective layer, etc. with higher precision.

The alignment control layer 3a may be any alignment control layer that can bring the oriented liquid crystal compound layer 30 into a desired alignment state. Methods for imparting alignment control ability to the alignment control layer 3a include, for example, rubbing treatment on the surface, oblique deposition of an inorganic compound, and formation of a layer with microgrooves. In addition, a method of forming an optical alignment control layer that generates an alignment function by orienting molecules by irradiating polarized light is also preferred. Below, a rubbing treatment alignment control layer and an optical alignment control layer are described as examples of preferred alignment control layers 3a.

Examples of polymer materials used for the orientation control layer 3a formed by rubbing treatment include polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resins, polysiloxane derivatives, etc. The orientation control layer 3a can be produced by applying a rubbing treatment orientation control layer coating liquid containing these polymer materials onto a release film 2, followed by heating and drying, etc., and then rubbing the coating surface with a rubbing roller made of raised fabric of fibers such as nylon, polyester, or acrylic.

The thickness of the rubbing treatment orientation control layer is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and particularly preferably 0.1 to 1 μm.

It is also possible to give the surface of the base film 2 the function of an orientation control layer by performing a rubbing treatment directly on the base film 2.

Another preferred example of the orientation control layer 3a is a photo-alignment control layer, which is an alignment film provided with an orientation control ability by applying a coating liquid containing a polymer or monomer having a photoreactive group and a solvent to the substrate film 2 and irradiating the coating with polarized light, preferably polarized ultraviolet light. The photoreactive group is a group that generates liquid crystal alignment ability by light irradiation. Specifically, it generates a photoreaction that is the origin of liquid crystal alignment ability, such as molecular orientation induction or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction, which occurs by light irradiation. Among such photoreactive groups, those that cause a dimerization reaction or photocrosslinking reaction are preferred in terms of excellent orientation control ability and maintaining the liquid crystal state of the aligned liquid crystal compound layer 30. As the photoreactive group that can cause the above reaction, a group containing an unsaturated bond, especially a double bond, is preferred, and a group having at least one selected from the group consisting of a C=C bond, a C=N bond, an N=N bond, and a C=O bond is particularly preferred.

Among these, photoreactive groups capable of causing a photodimerization reaction are preferred, with cinnamoyl and chalcone groups being preferred because they require a relatively small amount of polarized light irradiation for photoalignment and because they are capable of easily obtaining a photoalignment control layer that is excellent in thermal stability and stability over time. Furthermore, as polymers having photoreactive groups, those having cinnamoyl groups such that the terminals of the polymer side chains form cinnamic acid structures are particularly preferred. Examples of main chain structures include polyimide, polyamide, (meth)acrylic, and polyester.

Specific examples of the optical alignment control layer include those described in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, and JP-A-2009 Examples of the alignment control layers include those described in JP-A-109831, JP-A-2002-229039, JP-A-2002-265541, JP-A-2002-317013, JP-T-2003-520878, JP-T-2004-529220, JP-A-2013-33248, JP-A-2015-7702, and JP-A-2015-129210.

By irradiating the thus obtained pre-orientation optical alignment control layer with polarized light in a predetermined diagonal direction with respect to the longitudinal direction of the base film 2, an optical alignment control layer is obtained in which the orientation control direction is diagonal with respect to the longitudinal direction of the long base film 2. By adjusting the angle of the irradiated polarized light, the orientation control direction of the optical alignment control layer can be adjusted as desired.

[Production method]
The present invention also provides a method for producing the transfer film laminate 1. The production method according to the embodiment of the present invention includes the steps of preparing the film laminate 1, peeling the surface protective film 4 from the base film 2 of the film laminate 1, providing a functional layer 3 on the surface of the base film 2 on which the surface protective film 4 was laminated, and bonding the surface protective film 4 or another surface protective film to the surface on which the functional layer 3 is provided.

The film laminate 1 is obtained as a long object and wound up as a roll. At this time, the surface protective film 4 is attached and wound up, which prevents damage to the surface of the base film 2 to which the functional layer 3 is attached. The surface protective film is knurled, which prevents problems such as wrinkles during winding and prevents misalignment during storage, transportation, etc. in the wound state.

The surface protective film 4 is peeled off from the substrate film 2 of the film laminate 1, and the functional layer 3 is provided on the surface of the substrate film 2 on which the surface protective film 4 was laminated. Since the surface of the substrate film 2 on which the functional layer 3 is provided is protected by the surface protective film 4, it is possible to provide a high-performance functional layer 3.

It is preferable that the side of the base film 2 on which the functional layer 3 is laminated is not knurled. By not applying knurling to the side of the base film 2 on which the functional layer 3 is laminated, the knurled portion can be used without slitting or removing it in the process of transferring the functional layer 3 to an object or in the next process when a further functional layer is provided on the functional layer 3.

A surface protective film is laminated to the surface on which the functional layer 3 is provided, and a film laminate 1 having the functional layer 3 is obtained as shown in Figure 9. The surface protective film in this case may be the surface protective film 4 that was included in the original film laminate 1, or may be a different surface protective film. Even if it is a different surface protective film, it is preferable that the surface protective film laminated to the functional layer 3 has been subjected to knurling processing in the same manner as the surface protective film 4.

By laminating a knurled surface protection film, it is possible to prevent damage to the functional layer 3, and to prevent problems such as wrinkles during winding, and misalignment during storage and transportation in a wound state. Furthermore, when the functional layer 3 is a porous body or a liquid crystal compound layer, it is possible to prevent deterioration of the functional layer 3 caused by localized high pressure on the winding core side.

The length and width of the film laminate 1 on which the functional layer 3 is laminated are the same as the preferred length and width of the base film 2, and the length and width of the surface protective film 4 are also the same as above.

[Transfer Method]
The present invention further provides a method for transferring the functional layer 3. The transfer method according to the embodiment of the present invention includes the steps of producing a film laminate 1 having a functional layer 3 laminated thereon by the above-mentioned production method, peeling off a surface protective film from the film laminate 1, bonding the functional layer 3 surface of the film laminate 1 to an object to be transferred, and peeling off the base film 2 from the object to be transferred.

In the process of transferring the functional layer 3 to an object, the roll of film laminate 1, on which the functional layer 3 with the surface protective film bonded thereto, is unwound from the roll and the surface protective film is peeled off. An adhesive or pressure-sensitive adhesive is applied to the functional layer 3 from which the surface protective film has been peeled off, and after it has been bonded to the object, the base film 2 is peeled off.

The object is not particularly limited, but is preferably a long object such as a film or sheet processed by roll-to-roll. For example, for optical applications, examples include transparent films, polarizing plates, retardation films, and circular polarizing plates. For optical applications, the object provided with the functional layer 3 is used as, for example, an anti-reflection film, an anti-glare film, a polarizing plate, a retardation plate, a circularly polarized reflector, a polarizing plate with an optical compensation layer, a circular polarizing plate, a brightness enhancement film, a polarizing plate with a brightness enhancement layer, or a circular polarizing plate with a brightness enhancement layer.

This application claims the benefit of priority based on Japanese Patent Application No. 2019-148470, filed on August 13, 2019. The entire contents of the specification of Japanese Patent Application No. 2019-148470, filed on August 13, 2019, are incorporated by reference into this application.

The present invention will be described below with reference to the following examples. The present invention is not limited to the following examples, and can of course be modified as appropriate within the scope of the above and below-mentioned aims, and all such modifications are within the technical scope of the present invention.

The characteristics in the examples were evaluated using the following methods.

(1) Height of knurling Using a Handy-0.1 thickness meter manufactured by Fuji Work, the knurled parts at both ends of the surface protection film were measured at 5 locations every 3 cm, for a total of 10 locations, and the average value was taken as the thickness of the knurled part. The film thickness was measured at a location 1 cm from the center of the knurled parts at both ends, and the average value of the 10 locations was taken as the film thickness. The value obtained by subtracting the film thickness from the thickness of the knurled part was taken as the height of the knurling.

(2) Three-dimensional surface roughness SRa, SRz, and SRy
Using a stylus-type three-dimensional roughness meter (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.), measurements were taken over a measurement length of 1 mm in the longitudinal direction of the film with a cutoff value of 0.25 mm and a needle feed rate of 0.1 mm/sec under conditions of a needle radius of 2 μm and a load of 30 mg, and the film was divided into 500 points at a pitch of 2 μm, and the height of each point was captured in a three-dimensional roughness analyzer (SPA-11). The same operation was performed continuously 150 times at intervals of 2 μm in the width direction of the film, that is, over a width of 0.3 mm in the width direction of the film, and the data was captured in the analyzer. Next, the center surface average roughness (SRa), ten-point average roughness (SRz), and maximum height (SRy) were determined using the analyzer.

(3) Peel strength of surface protective film The laminates of surface protective film/substrate film and the laminates of surface protective film/functional layer/substrate film obtained in the examples and comparative examples were cut to a width of 25 mm and a length of 160 mm to prepare samples. The longitudinal direction of the sample was the width direction of the substrate film.

The substrate film surface of the sample was attached to an acrylic plate of the same width and length as the 1 mm thick sample using double-sided tape. The surface protection film was peeled off from a portion of one end of the sample, approximately 20 mm in length, and a biaxially oriented polyester film of 25 mm in width, 160 mm in length, and 50 μm in thickness was attached to the peeled portion of the surface protection film using double-sided tape. The substrate film or the functional layer/substrate film laminate of the portion where the surface protection film was peeled off was held together with the acrylic plate by the lower chuck of a tensile tester, and the end of the opposite side to the biaxially oriented polyester film surface protection film attached was held by the upper chuck, and the peel strength was measured when peeled off at 180 degrees at a speed of 300 mm/min. The tester used was Shimadzu Corporation's "Autograph (registered trademark)" (AG-X), and the average value was calculated from 2 seconds to 25 seconds after the start of peeling. The measurement was performed on five samples, and the average value was taken as the peel strength. The temperature in the measurement room was 24°C. The sample was left for 24 hours in a room at 24° C. and a relative humidity of 50% after the surface protection film was attached.

[Example]
(Manufacture of surface protection film)
An antistatic surface protection film having a width of 100 cm was prepared, which had an acrylic adhesive layer of 7 μm on an unstretched polypropylene (CPP) film substrate having a thickness of 32 μm.

(Production of Base Film)
Polyethylene terephthalate (PET) resin pellets with an intrinsic viscosity of 0.62 dl/g were dried under reduced pressure (1 Torr) at 135° C. for 6 hours, then fed to an extruder and melted at 285° C. This molten polymer was filtered through a stainless steel sintered filter medium (nominal filtration accuracy of 10 μm particles, 95% cut), extruded from a die in the form of a sheet, and then wound around a casting drum with a surface temperature of 30° C. using an electrostatic casting method, cooled and solidified to produce an unstretched film.

The unstretched film was introduced into a tenter stretching machine, and while holding the ends of the film with clips, it was introduced into a hot air zone at a temperature of 125°C and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, it was heat-set at a temperature of 210°C for 10 seconds, and further subjected to a 3.0% relaxation treatment. Thereafter, both ends of the film cooled to 130°C were cut with a shear blade, and the ears were cut off with a tension of 0.5 kg/ ^mm2 , and then wound up to obtain a uniaxially oriented PET film (width 100 cm) with a film thickness of 50 μm. A surface protective film was attached to one side to obtain a film roll (film laminate 100a) with a length of about 500 m.

(Knurl processing)
Just before laminating the surface protection film to the base film, knurling was performed using a heated knurling machine (180°C) for knurling, which had a quadrangular pyramid shape on the surface of the surface protection film opposite to the surface to which the base film was laminated. The knurling was performed as follows. The back roll of the heated knurling machine was a roll that had been surface-treated with a fluororesin.
<Knurl processing>
Height: 4.7 μm
Distance between recesses: 1.0 mm
Distance from film edge: 5 mm
Width: 15mm

The adhesive strength of the surface protection film to the base film was 0.11 N/25 mm.

The surface roughness of the release surface of the base film (the surface to which the surface protective film was attached) was as follows.
Center surface average roughness (SRa): 2 nm
Ten-point average roughness (SRz): 11 nm
Maximum height (SRy): 17 nm

(Coating of functional layer)
The film laminate 100a was unwound from the roll of the film laminate 100a, the surface protective film was peeled off, and then a coating material for an orientation control layer having the following composition was applied to the surface of the substrate film to which the surface protective film had been attached using a bar coater, and the coating material was dried at 80° C. for 5 minutes to form a film having a thickness of 200 nm. The surface of the obtained film was then treated with a rubbing roll wrapped with a nylon napped cloth to obtain a substrate film laminated with an orientation control layer. Rubbing was performed at an angle of 45° to the film roll unwinding direction (longitudinal direction (MD)).
Completely saponified polyvinyl alcohol (weight average molecular weight 800) 2 parts by weight Ion-exchanged water 100 parts by weight Surfactant 0.5 parts by weight

Subsequently, a solution for forming a retardation layer (liquid crystal compound layer) having the following composition was applied to the surface that had been subjected to the rubbing treatment by a bar coating method. The solution was dried at 110° C. for 3 minutes and cured by irradiation with ultraviolet light to form a λ/4 retardation layer on the substrate film, thereby obtaining a functional layer laminate film 100.
Rod-shaped liquid crystal compound (LC242 manufactured by BASF) 92 parts by weight Trimethylolpropane triacrylate 5 parts by weight Irgacure 379 3 parts by weight Surfactant 0.1 parts by weight Methyl ethyl ketone 250 parts by weight

The orientation control layer and λ/4 retardation layer were coated at intervals of approximately 10 mm from both ends of the substrate film in the width direction.

A surface protection film other than the film laminate 100a was bonded to the λ/4 phase difference layer surface of the obtained functional layer laminate film 100, and a film roll (film laminate 100b) having a length of approximately 500 m was obtained.

Just before laminating the surface protection film, the surface protection film was subjected to knurling using the same equipment as described above. The knurling was performed as follows.
<Knurl processing>
Height 5.3 μm
Distance between recesses: 1.0 mm
Distance from film edge: 5 mm
Width: 10mm

The adhesive strength of the surface protective film to the functional layer laminate film 100 was 0.17 N/25 mm.

(Transfer of functional layer)
The film laminate 100b was unwound and the surface protective film was peeled off, and then an ultraviolet-curing adhesive was applied to the functional layer surface (coating width 980 mm), which was then attached to a polarizing plate (width 1000 mm), cured by irradiation with ultraviolet light, and then wound into a roll. The polarizing plate was a Cosmoshine SRF (R) manufactured by Toyobo Co., Ltd., which had an anti-reflection layer as a protective film on one side of a 5 μm-thick polarizer made of polyvinyl alcohol (PVA) with iodine adsorbed thereon, and the functional layer was attached to the polarizing plate surface.

The obtained roll-shaped laminate is a laminate of polarizer protective film/polarizer/λ/4 retardation layer/orientation control layer/substrate film, and the substrate film can be peeled off to use it as a circular polarizing plate. Specifically, for example, after peeling off the substrate film, an optical adhesive sheet is laminated on the orientation control layer surface, the widthwise end is slit by 20 mm and removed, cut to the required length, and attached to the surface of the organic EL panel, whereby an anti-reflection circular polarizing plate can be provided on the organic EL display device. In this case, the original substrate film width was 1000 mm, while the final circular polarizing plate width is 960 mm, and the substrate film can be used efficiently.

The peel strength when peeling the base film from the laminate was 1.2 N/25 mm. The peel strength was measured by attaching the polarizer protective film surface of the laminate to an acrylic plate and measuring the peel strength of the surface protective film.

(Disturbance in the retardation layer on the core side)
The film laminate 100b was unwound, and two samples of 10 cm x 10 cm were cut out from the part directly above the end of the film at the beginning of the winding at the 5th turn from the winding core. After peeling off the surface protection film of the sample, the two samples were aligned and overlapped, sandwiched between two polarizing plates arranged in parallel Nicol, and light was irradiated from below to observe the extinction state. There was no unevenness in the extinction state, and no disturbance of the retardation layer due to local pressure on the winding core side caused by knurling was observed.

[Comparative Example]
(Production of Base Film)
The substrate film was prepared in the same manner as in the example, but when the substrate film was wound up, knurling was performed using a heated knurling machine (270°C) for knurling in which a quadrangular pyramid shape was provided on the substrate film. The knurling process is as follows. The back roll of the heated knurling machine is a roll that has been subjected to mirror finishing. The substrate film was wound up without laminating a surface protective film (film 200a).
<Knurl processing>
Height 4.5 μm
Distance between recesses: 1.0 mm
Distance from film edge: 5 mm
Width: 10mm

(Coating of functional layer)
The film 200a was unwound from the above-mentioned roll body, and the knurled portions on both ends were slit to a width of 20 mm and removed.Then, an orientation control layer and a retardation layer were provided on the knurled surface of the film 200a in the same manner as in the example, and the film was wound into a roll to obtain the functional layer laminated film 200.

Just before winding, the wire was knurled using the same equipment as above. The knurling process is as follows.
<Knurl processing>
Height 5.0 μm
Distance between recesses: 1.0 mm
Distance from film edge: 5 mm
Width: 10mm

(Transfer of functional layer)
The functional layer laminate film 200 was unwound, and the knurled portions at both ends were slit to a width of 20 mm and removed, and then the film was attached to a polarizing plate in the same manner as in the example and wound into a roll. The width of the adhesive application was 900 mm, and the width of the polarizing plate was 920 mm.

The obtained roll-shaped laminate can be used as a circular polarizing plate by peeling off the base film as in the examples, but when the end in the width direction is slit by 20 mm and removed after laminating with an optical adhesive sheet as in the examples, the width of the final circular polarizing plate is 880 mm, which is not an efficient use of the base film.

1: Film laminate 2: Base film 2a: Release surface 20A: Release surface side layer 20B: Back surface side layer 20C: Intermediate layer 20: Base film base layer 20a: Release layer 3: Functional layer 3a: Orientation control layer 30: Aligned liquid crystal compound layer 4: Surface protective film 4b: Knurled portion 40: Surface protective film base layer 40a: Adhesive layer 5: Functional layer laminate film

Claims (2)

A method for producing a film laminate, comprising the steps of:
A step of preparing a long-length film laminate in which a base film and a surface protective film are laminated, the material constituting the base film being at least one selected from the group consisting of polyester, polycarbonate, polystyrene, polyamide, polypropylene, cyclic polyolefin, triacetyl cellulose, and polyfluoroethylene, the surface protective film being knurled at both ends in the width direction, and the base film not being knurled;
peeling the surface protective film from the base film of the film laminate;
providing a functional layer on the surface of the base film on which the surface protective film was laminated;
and a step of attaching a surface protection film to the surface on which the functional layer is provided. A method for transferring a functional layer, comprising the steps of:
Producing a film laminate by the method of claim 1 ;
peeling the surface protective film from the film laminate;
A step of bonding a functional layer surface of the film laminate to an object to be transferred;
and peeling the base film from the object to be transferred.

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