TW202225382A - Manufacturing method of optical film capable of providing an optical film having a coating layer with fewer defects and excellent uniformity - Google Patents

Abstract

The present invention provides a method for producing an optical film in which a laminate (8) is obtained by clamping and bonding a long film substrate (1) and a protective film (2) with a pair of clamping rollers (41, 42). The laminate is transported to a peeling section (10) along the longitudinal direction by rollers. In the peeling section, the protective film is peeled off from the first main surface of the film substrate, and then the coating liquid is applied to the first main surface of the film substrate. By this method, an optical film having a coating layer with fewer defects and excellent uniformity can be provided. Preferably, the two rollers constituting a pair of clamping rollers are of electrical conductivity.

Description

Manufacturing method of optical film

The present invention relates to a manufacturing method of an optical film.

A thin coating film is used as an optical film having functions such as optical compensation for liquid crystal display devices, and anti-reflection of external light for organic EL (Electroluminescence) elements. Films with smaller thicknesses have low self-sustainability and are difficult to handle alone. Therefore, a solution is applied on a support such as a plastic film to form a coating, and the coating is dried and processed in a state where the coating is in close contact with the support.

For example, Patent Document 1 discloses a method in which a resin solution is applied on a support to form a resin coating layer, and a laminated body of the support and the coating layer is stretched to produce a laminated retardation film. Patent Document 2 discloses a method of fabricating an aligned liquid crystal layer by using a stretched film as a support, coating a liquid crystal composition thereon, and aligning the liquid crystal compound along the plane along the extending direction (alignment direction) of the film. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-46068 [Patent Document 2] No. WO2016/121856

[Problems to be Solved by Invention]

In the method of forming a coating by transporting the film substrate as a support in the longitudinal direction by a roll-to-roll method and applying a solution thereon to form a coating, if there are scars on the film substrate, the scars will be transferred to the film substrate. Defects such as coating, or poor alignment of liquid crystal molecules. In addition, since the surface state of the film base material may lead to poor coating, the film thickness or optical properties of the coating layer may become uneven. [Technical means to solve problems]

One embodiment of the present invention is a method for producing an elongated optical film, wherein a coating layer is formed on the first main surface of the elongated film substrate having a first main surface and a second main surface.

First, by sandwiching the elongated film base material and the protective film with a pair of nip rolls and laminating them, a laminate in which the protective film is releasably attached to the first main surface of the film base material is obtained (lamination step ). Both the first roll and the second roll constituting a pair of nip rolls have electrical conductivity.

The laminate of the film base material and the protective film is roll-conveyed to the peeling section along the longitudinal direction (first conveying step), and in the peeling section, the protective film is peeled off from the first main surface of the film base material (protective film peeling step) . The film base material after peeling off the protective film is conveyed from the peeling part to the coating part along the longitudinal direction of the film base material (second conveying step), and in the coating part, the first main surface of the film base material is coated A coating solution (coating step) is used to obtain a laminate having a coating layer on the first main surface of the film substrate.

The coating liquid may also be a liquid crystal composition containing a liquid crystal compound. The liquid crystal composition may further contain a photocurable liquid crystal compound. After coating the liquid crystal composition containing the photocurable liquid crystal compound on the film substrate, the liquid crystal compound may be photocured.

The film substrate may be one having an alignment limiting force that aligns liquid crystal molecules in a specific direction. The film substrate may be, for example, a stretched film whose molecular alignment is not parallel to the longitudinal direction, or an oblique stretched film.

The optical film may be one with other optical layers layered on the coating in a roll-to-roll roll-up. The optical layer laminated on the coating may also include a polarizing element. The optical film can be a circular polarizing plate formed by laminating a coating and a polarizing element. [Effect of invention]

Since the protective film is temporarily adhered until immediately before the coating liquid is applied to the film substrate, the occurrence of scratches on the film substrate caused by the roller conveyance is suppressed. In addition, by sandwiching the film base material and the protective film with two conductive rollers and bonding them together, internal electrification of the laminate is less likely to occur, and the occurrence of coating defects due to electrification of the film base material and the like is suppressed. Therefore, a coating with fewer defects such as scratches, streaks, etc. caused by the film substrate can be obtained.

[Outline of Steps] In the present invention, a coating is formed by coating the solution on one main surface of the elongated film substrate. FIG. 1 is a cross-sectional view of an optical film 9 in which a coating layer 3 is provided on the first principal surface 1A of a film substrate 1 . FIG. 2 is a cross-sectional view of a laminate 8 in which the protective film 2 is releasably attached to the first main surface 1A of the film substrate 1 .

FIG. 3 : is a conceptual diagram which shows the outline of the bonding apparatus and bonding process for bonding the film base material 1 and the protective film 2 to obtain the laminated body 8. FIG. In FIG. 3 , the winding body 28 obtained by winding the long protective film 2 into a roll shape is wound around the unwinding roller 29 . The protective film unwound from the winding body 28 is continuously conveyed to the downstream side along the conveyance path formed by the conveyance rollers 44 and 45 , and is conveyed to the bonding portion 40 .

The bonding portion 40 includes a pair of nip rolls 41 and 42 . The film base material 1 and the protective film 2 are separated by sandwiching the film base material 1 and the protective film 2 conveyed from the upstream side (the left side of the figure) up and down with a pair of nip rolls including the first roll 41 and the second roll 42. By bonding, the laminated body 8 to which the protective film 2 is releasably adhered on the film base material 1 is obtained (bonding step). As described in detail below, the first roll 41 in contact with the film substrate 1 and the second roll 42 in contact with the protective film 2 are both conductive rolls.

The laminate of the film substrate 1 and the protective film 2 is continuously conveyed to the downstream side along the conveyance path formed by the conveyance rollers 46 and 47, and is wound up by the take-up roller 49, whereby a long film of the laminate 8 is obtained. The rolled body 80 obtained by winding into a roll shape.

FIG. 4 is a conceptual diagram showing an outline of a film forming apparatus and a film forming step for forming the coating layer 3 on the film substrate 1 . In FIG. 4 , the winding body 80 of the laminated body 8 is wound around the unwinding roller 81 . The laminated body 8 unwound from the winding body 80 moves continuously to the downstream side along the conveyance path formed by the conveyance rollers 83, 85, and 87, and is conveyed to the peeling part 10 (first conveyance step).

In the peeling part 10, the protective film 2 is peeled off from the film base material 1 (peeling process). By peeling off the protective film 2, the 1st main surface 1A of the film base material 1 is exposed. The film base material 1 after peeling the protective film is conveyed from the peeling part 10 to the coating part 30 (second conveyance step). In the coating section 30, the coating liquid is coated on the first main surface 1A of the film substrate 1 (coating step).

The laminated body 9 (optical film) which formed the coating layer 3 on the 1st main surface 1A of the film base material 1 is wound up by the winding roll 91, and the winding body 90 of the elongate optical film can be obtained by this. Between the coating part 30 and the take-up roll 91, the heating part 50 can also be used for heating. When the coating liquid contains a photopolymerizable component such as a photopolymerizable liquid crystal compound, photocuring may be performed on the cured portion 60 .

When the solution is applied on one side of the film substrate while being transported by roll-to-roll, due to the contact and friction with the transport roller, flaws along the longitudinal direction are likely to be generated on the film substrate. If there are scratches on the film substrate, when a coating is formed thereon, the scratches on the film substrate will be transferred to the coating, possibly resulting in optical defects. In addition, when the liquid crystal composition is coated on the film substrate, the liquid crystal molecules are easily aligned along the extending direction of the flaws, which may lead to poor alignment defects.

In the embodiment of the present invention, the protective film 2 is releasably attached to the first main surface 1A of the film substrate 1 . Since the protective film 2 is attached to the first main surface 1A of the film base 1 during the period from the unwinding roller 81 to the peeling part 10 (first conveyance step), in the first conveyance step, the film base The first main surface 1A of 1 does not come into direct contact with the conveyance roller 87 . Since the coating liquid is applied on the first main surface 1A of the film substrate 1 immediately after the protective film 2 is peeled off from the film substrate 1, it is possible to prevent the first main surface of the film substrate from contacting with the conveying roller 87. The generation of scratches can inhibit the transfer of the scratches to the coating layer 3 or the poor alignment of the liquid crystal molecules.

In this embodiment, since the coating is performed immediately after the protective film 2 is peeled off from the film substrate 1, the peeling part 10 and the coating part 30 are arranged close to each other, so that the conveying path of the film substrate in the second conveying step is short. . Therefore, the bonding state of the film substrate and the protective film, and the static electricity when the protective film is peeled off from the film substrate in the peeling portion 10 may sometimes affect the application of the coating liquid in the coating portion 30 . Specifically, a region with a small coating thickness is formed in a stripe shape extending in the width direction, and when the optical film is applied to an image display device, the stripe-shaped unevenness may be recognized and recognized.

In one embodiment of the present invention, one of the bonding film base material 1 and the protective film 2 has electrical conductivity to the nip rolls 41 and 42, thereby suppressing the occurrence of stripe-like unevenness extending in the width direction as described above. .

When the coating solution was applied on the film substrate immediately after peeling off the protective film, the samples with uneven streaks on the coating were analyzed, and no uneven thickness or physical properties were found on the film substrate after peeling off the coating. deformed. Therefore, it is considered that the stripe-like thickness unevenness of the coating layer formed on the film substrate is caused by the shrinkage caused by the electrification of the film substrate when the coating liquid is applied on the surface of the film substrate.

The reason for the electrification of the film substrate includes peeling electrification when peeling off the protective film, but even if the film substrate after peeling the protective film is destaticized with an antistatic bar, the aforementioned streak-like unevenness is not sufficiently eliminated. In order to further study the electrification of the film substrate, a carbon powder test in which carbon powder was adhered to the film surface was carried out. As a result, it was confirmed in both the laminate formed by laminating the protective film on the film substrate and the individual film substrate. The toner adheres in the form of a line extending in the width direction. According to this result, when the laminate of the film substrate and the protective film is charged, even after the protective film is peeled off, the charged state of the film substrate (internal electrification) is maintained, which causes the shrinkage of the coating liquid and causes the coating on the coating to shrink. Streaks are formed.

In the embodiment of the present invention, since the first roll 41 and the second roll 42 constituting a pair of nip rolls have electrical conductivity, when the film substrate 1 and the protective film 2 are laminated in the laminating section 40, the nip roll can be prevented from being sandwiched. The electrification of the layered body 8 is caused by electrification of the rollers. Therefore, even after the protective film 2 is peeled off, the inside of the film base 1 is less charged, and shrinkage when the coating liquid is applied on the first main surface 1A of the film base 1 is suppressed, and it is considered that the coating defect can be prevented The resulting stripes are uneven in thickness.

[Material] Hereinafter, each material used in this embodiment will be described.

<Coating liquid> The coating liquid applied on the film substrate 1 is a solution containing a solid content (solute) constituting the coating layer 3, and a solvent for dissolving and dispersing the solid content. As the solid content, various resin materials or liquid crystal materials can be used.

Examples of the resin material for the coating layer include cellulose-based resins such as acetyl cellulose, polyester-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, maleic diamides Imine-based resins, polyolefin-based resins, (meth)acrylic resins, cyclic polyolefin resins (noralkene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, poly Silica resin, etc.

A liquid crystal composition containing a liquid crystal compound is coated on the film substrate 1, so that the liquid crystal compound is aligned in a specific direction, and then the alignment state is fixed, thereby forming a coating layer (liquid crystal layer) in which the liquid crystal molecules are aligned in a specific direction. ).

As a liquid crystal compound, a rod-shaped liquid crystal compound, a discotic liquid crystal compound, etc. are mentioned. The liquid crystal compound is preferably a rod-like liquid crystal compound from the viewpoint of easy alignment along the plane due to the alignment restraining force of the film substrate. The rod-shaped liquid crystal compound may be a main chain type liquid crystal or a side chain type liquid crystal. The rod-shaped liquid crystal compound may be a liquid crystal polymer or a polymer of a polymerizable liquid crystal compound. If the liquid crystal compound (monomer) before polymerization exhibits liquid crystallinity, it may not exhibit liquid crystallinity after polymerization.

The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystallinity by heating. The thermotropic liquid crystal undergoes phase transition of crystal phase, liquid crystal phase and isotropic phase with the change of temperature. The liquid crystal compound contained in the liquid crystal composition may be any of a nematic liquid crystal, a smectic liquid crystal, and a cholesteric liquid crystal. A chiral agent can also be added to the nematic liquid crystal to make it have cholesteric alignment.

Examples of rod-like liquid crystal compounds exhibiting thermotropic properties include methylimines, oxyazos, cyanobiphenyls, cyanophenyl esters, benzoates, and cyclohexanecarboxyphenyl esters , cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldiethanes, diphenylacetylenes, alkenylcyclohexylbenzonitrile class etc.

Examples of the polymerizable liquid crystal compound include: a polymerizable liquid crystal compound capable of fixing the alignment state of the rod-shaped liquid crystal compound using a polymer binder; a polymerizable liquid crystal compound having a polymerizable functional group capable of fixing the alignment state of the liquid crystal compound by polymerization Liquid crystal compounds, etc. Among them, a photocurable liquid crystal compound having a photocurable functional group is preferable.

The photocurable liquid crystal compound (liquid crystal monomer) has a mesogen group and at least one photocurable functional group in one molecule. The temperature (liquid crystal phase transition temperature) at which the liquid crystal monomer exhibits liquid crystallinity is preferably 40 to 200°C, more preferably 50 to 150°C, and further preferably 55 to 100°C.

As the mesogen group of the liquid crystal monomer, biphenyl group, phenyl benzoate group, phenylcyclohexane group, oxyazophenyl group, methylimino group, azophenyl group, phenyl group can be mentioned. Ring structures such as pyrimidinyl, diphenylethynyl, diphenylbenzoate, bicyclohexyl, cyclohexylphenyl, and bitriphenyl. These cyclic units may have substituents such as cyano groups, alkyl groups, alkoxy groups, halogen groups, and the like at the ends.

As a photocurable functional group, a (meth)acryloyl group, an epoxy group, a vinyl ether group, etc. are mentioned. Among them, a (meth)acryloyl group is preferred. The photocurable liquid crystal monomer preferably has two or more photocurable functional groups in one molecule. By using a liquid crystal monomer containing two or more photocurable functional groups, a crosslinked structure is introduced into the liquid crystal layer after photocuring, so that the durability of the optical film tends to be improved.

As the photocurable liquid crystal monomer, any appropriate liquid crystal monomer can be used. For example, International Publication No. 00/37585, US Patent No. 5211877, US Patent No. 4388453, International Publication No. 93/22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, Japanese Patent Laid-Open No. 2017-206460, International Publication No. 2014/126113, International Publication No. 2016/114348, International Publication No. 2014/010325, Japanese Patent Laid-Open No. 2015-200877, Japanese Patent Laid-Open No. 2010-31223, International Publication No. 2011/050896, Japanese Patent Laid-Open No. 2011-207765, Japanese Patent Laid-Open No. 2010-31223, Japanese Patent Laid-Open No. 2010-270108, International Publication Compounds described in No. 2008/119427, Japanese Patent Laid-Open No. 2008-107767, Japanese Patent Laid-Open No. 2008-273925, International Publication No. 2016/125839, Japanese Patent Laid-Open No. 2008-273925, and the like. By selecting the liquid crystal monomer, the appearance of birefringence or the wavelength dispersion of retardation can also be adjusted.

In the liquid crystal composition, in addition to the liquid crystal monomer, a compound for controlling the alignment of the liquid crystal monomer to a specific direction may also be included. For example, the liquid crystal compound (monomer) can be vertically aligned by making the liquid crystal composition contain a side chain type liquid crystal polymer. Moreover, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically aligned.

The liquid crystal composition may contain a photopolymerization initiator. In the case of curing the liquid crystal monomer by ultraviolet irradiation, in order to promote photocuring, the liquid crystal composition preferably contains a photopolymerization initiator (photoradical generator) that generates radicals by light irradiation. Depending on the type of the liquid crystal monomer (the type of the photocurable functional group), a photocation generator or a photoanion generator may be used. The usage-amount of a photopolymerization initiator is about 0.01-10 weight part with respect to 100 weight part of liquid crystal monomers. In addition to the photopolymerization initiator, a sensitizer and the like can be used.

A liquid crystal composition can be prepared by mixing a liquid crystal monomer, various alignment control agents as needed, a polymerization initiator, and the like with a solvent.

(Solvent) The solvent of the coating liquid is not particularly limited as long as it can dissolve the solute and does not corrode the substrate (or has low corrosivity). Examples include: chloroform, dichloromethane, carbon tetrachloride, dichloroethane, Halogenated hydrocarbons such as tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene; phenols such as phenol, p-chlorophenol; benzene, toluene, xylene, methoxybenzene, 1,2 - Aromatic hydrocarbons such as dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidine Ketone-based solvents such as ketones; ester-based solvents such as ethyl acetate and butyl acetate; tertiary butanol, glycerol, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol , dipropylene glycol, 2-methyl-2,4-pentanediol and other alcohol solvents; dimethylformamide, dimethylacetamide and other amine solvents; acetonitrile, butyronitrile and other nitrile solvents; diethyl ether , dibutyl ether, tetrahydrofuran and other ether solvents; A mixed solvent of two or more solvents may also be used.

The solid content concentration of the coating liquid is usually about 5 to 60% by weight. The coating liquid may also contain additives such as surfactants and leveling agents.

<Film base material> By using the long film base material 1 as a substrate, a series of steps from the application of the coating liquid to the drying can be carried out by roll-to-roll. When the coating liquid is a liquid crystal composition, operations such as alignment treatment or photohardening of the liquid crystal molecules after coating can also be performed on the film substrate 1 as a series of steps. In addition, the step of laminating the coating layer 3 formed on the film substrate 1 to another substrate can also be carried out by roll-to-roll, so that the productivity of the optical film can be improved.

The width of the film substrate 1 is preferably 30 cm or more, and may be 50 cm or more, 80 cm or more, 100 cm or more, or 120 cm or more. From the viewpoint of the productivity of the optical film, the larger the width of the film substrate 1, the better, and it is usually 500 cm or less, and may be 400 cm or less or 300 cm or less. The length of the film substrate is preferably 100 m or more, and may be 300 m or more, 500 m or more, 800 m or more, 1000 m or more, or 1200 m or more. The upper limit of the length of the film substrate 1 is not particularly limited, but is usually 10,000 m or less, and may be 7,000 m or less or 5,000 m or less. The thickness of the film substrate 1 is preferably about 10 to 200 μm.

The resin material constituting the film base 1 is not particularly limited as long as it does not dissolve in the solvent of the coating solution and can withstand drying, alignment treatment, curing, and other treatments, and examples include polyethylene terephthalate, polyethylene terephthalate, Polyesters such as polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as noralkene-based polymers; cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; Acrylic polymers; styrene polymers; polycarbonate, polyamide, polyimide, etc.

Films containing hydrophobic resin materials such as polyolefins, cyclic polyolefins, and acrylic polymers tend to be internally charged when they are attached to the protective film 2, which may lead to poor coating when the coating solution is applied after peeling off the protective film. . As described above, one of the bonding film base material 1 and the protective film 2 has electrical conductivity to the nip rolls 41 and 42 , thereby suppressing the charging of the laminate 8 . Therefore, even if a hydrophobic resin film is used as the film base material 1 In this case, coating defects can also be prevented.

The film substrate 1 may also have an alignment restricting force for aligning liquid crystal molecules in a specific direction. For example, the film base 1 may be provided with an alignment film on the first main surface. The alignment film may be appropriately selected according to the type of the liquid crystal compound, the material of the substrate, and the like. As an alignment film for aligning liquid crystal molecules along a surface in a specific direction, what is obtained by subjecting a polyimide-based or polyvinyl alcohol-based alignment film to a rubbing treatment can be exemplified. Moreover, a photo-alignment film can also be used. The resin film may be subjected to rubbing treatment without providing an alignment film.

The film substrate 1 may also include an alignment film for vertically aligning liquid crystal molecules. As an alignment agent for forming a vertical alignment film (vertical alignment film), lecithin, stearic acid, cetyltrimethylammonium bromide, octadecylamine hydrochloride, Monocarboxylate chromium complexes, silane coupling agents or organosilanes such as siloxane compounds, perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, and the like.

A stretched film can also be used as the film substrate 1 . In the stretched film, the resin material (polymer) constituting the film is aligned in the stretched direction, and the stretched film has the function of aligning the liquid crystal molecules along the stretched direction. By using the stretched film, even when the alignment film is not formed on the film substrate, the alignment restraint force for aligning the liquid crystal molecules in a specific direction can be provided. Since there is no need to form an alignment film, the manufacturing cost of the optical film can be reduced. In addition, by not providing an alignment film, contamination and poor alignment due to frictional gas can be prevented.

The extending direction of the stretched film (the orientation direction of the polymer) is not particularly limited, and may or may not be parallel to the longitudinal direction of the film substrate. By using a stretched film whose molecular alignment is not parallel to the longitudinal direction, a liquid crystal layer whose liquid crystal molecular alignment is not parallel to the longitudinal direction can be formed as the coating layer 3 .

The stretching ratio of the stretched film should just be such that the alignment restricting force can be exerted, and it is, for example, about 1.1 times to 5 times. The stretched film may also be a biaxially stretched film. Even if it is a biaxially stretched film, as long as the longitudinal and transverse stretch ratios are different, the liquid crystal molecules can be aligned in the direction with the larger stretch ratio.

The stretched film may also be an oblique stretched film. The diagonally stretched film has an orientation axis in a direction that is neither parallel nor orthogonal to the longitudinal direction (for example, a direction of 10 to 80° with respect to the longitudinal direction), so by using the diagonally stretched film as the film substrate 1, it can be formed The liquid crystal molecules are aligned in the liquid crystal layer in a direction neither parallel nor orthogonal to the lengthwise direction.

<Protective film> The protective film 2 temporarily adhered to the first main surface 1A of the film substrate 1 is shown in FIG. 2 , and preferably has an adhesive layer 292 on one surface of the core material 291 . The protective film 2 may also have an antistatic layer (not shown) on the back surface of the core material 291 (the surface opposite to the surface on which the adhesive layer is formed).

(Core Material) The material of the core material 291 of the protective film 2 is not particularly limited as long as it has flexibility, and a metal foil, a resin film, or the like can be used. A resin film is preferable because the material is inexpensive and the processability is excellent. As a specific example of the resin material which comprises the core material 291, what was mentioned above as the resin material of the film base material 1 can be mentioned. The core material 291 can also be a stretched film. The thickness of the core material 291 is not particularly limited. From the viewpoint of having both self-sustainability and flexibility, the thickness of the core material 291 is preferably about 10-100 μm.

(Adhesive Layer) The adhesive layer 292 may be formed of an adhesive used in a general adhesive tape or the like as long as it can be attached to the film base material 1 and can be peeled off from the film base material 1 . As the protective film 2, a self-adhesive film can also be used, which is obtained by integrally molding the resin material constituting the core material 291 and the resin material of the adhesive layer 292 by multi-layer extrusion.

The composition of the adhesive constituting the adhesive layer 292 is not particularly limited, and can be appropriately selected from acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, Polymers such as vinyl acetate/vinyl chloride copolymers, modified polyolefins, epoxy-based, fluorine-based, natural rubber, synthetic rubber and other rubber-based polymers are used as the base polymer. In particular, since it is easy to adjust the adhesive force (peeling force) and there is less paste residue on the film substrate 1 as the adherend, an acrylic polymer based on an acrylic polymer can be preferably used. adhesive.

As the acrylic base polymer, a polymer having a monomer unit of an alkyl (meth)acrylate as a main skeleton is suitably used. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group is suitably used. The content of the alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more with respect to the total amount of monomer components constituting the base polymer. The acrylic polymer may be a copolymer of a plurality of alkyl (meth)acrylates. The arrangement of the constituent monomer units may be random or block.

The acrylic base polymer preferably contains a monomer component having a functional group capable of crosslinking as a copolymerization component. As the monomer having a functional group capable of crosslinking, a hydroxyl group-containing monomer or a carboxyl group-containing monomer may, for example, be mentioned. Among them, as a copolymerization component of the base polymer, hydroxyl-containing monomers such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferably contained. The hydroxyl or carboxyl group of the base polymer becomes a reaction point for reaction with the crosslinking agent. By introducing a cross-linked structure into the base polymer, the cohesive force of the adhesive is improved, and a moderate adhesion force to the film substrate as an adherend is exhibited, and the peeling force when the protective film 2 is peeled off from the film substrate 1 is reduced. trend.

The molecular weight of the base polymer is appropriately adjusted so that the adhesive layer 292 has the desired adhesive force. For example, the weight average molecular weight in terms of polystyrene is about 50,000 to 2,000,000, preferably about 70,000 to 1.8 million. , more preferably about 100,000 to 1,500,000, and still more preferably about 200,000 to 1,000,000. Furthermore, in the case of introducing a cross-linked structure into the base polymer, it is preferable that the molecular weight of the base polymer before the introduction of the cross-linked structure is in the above-mentioned range.

For the purpose of adjusting the adhesive force of the adhesive layer 292 or the like, a cross-linked structure may be introduced into the base polymer. For example, a cross-linked structure is introduced by adding a cross-linking agent to the solution obtained by polymerizing the base polymer and heating if necessary.

As the crosslinking agent, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, and a metal chelate may, for example, be mentioned. Compound cross-linking agent, etc. Among them, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are preferred from the viewpoint that the reactivity with the hydroxyl group or the carboxyl group of the base polymer is high and the crosslinking structure is easily introduced. The usage-amount of the crosslinking agent may be appropriately adjusted according to the composition and molecular weight of the base polymer, target adhesion properties, and the like. The amount of the crosslinking agent to be used is preferably 0.5 parts by weight relative to 100 parts by weight of the base polymer from the viewpoint of making the adhesive have moderate cohesion and adjusting the peeling force when peeling off the protective film from the adherend to an appropriate range Above, more preferably 1 part by weight or more, still more preferably 1.5 part by weight or more. From the viewpoint of having moderate adhesion to the adherend, the amount of the crosslinking agent used is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and more preferably 10 parts by weight relative to 100 parts by weight of the base polymer. copies or less.

By introducing a cross-linked structure into the base polymer, the gel fraction of the adhesive increases, and the peeling force when peeling off the protective film from the adherend tends to decrease as the adhesive behavior decreases. The gel fraction of the adhesive layer 292 is preferably 70.0% or more, more preferably 80.0% or more, and still more preferably 90.0% or more. If the gel fraction of the adhesive layer 292 is too large, the wettability to the adherend may decrease, and the adhesive force may become insufficient. Therefore, the gel fraction of the adhesive layer 292 is preferably 99% or less, more preferably 98% or less. The gel fraction can be obtained as the insoluble content in a solvent such as ethyl acetate. The weight fraction of the previous sample (unit: wt%). Generally, the gel fraction of a polymer is equal to the degree of crosslinking, and the more crosslinked parts in the polymer, the greater the gel fraction becomes.

The adhesive layer 292 may also contain additives such as silane coupling agents, adhesion imparting agents, plasticizers, softeners, anti-deterioration agents, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents.

The thickness of the adhesive layer 292 is not particularly limited. From the viewpoint of taking into account both the adhesive force to the adherend and the peelability from the adherend, the thickness of the adhesive layer 292 is preferably 1-50 μm, more preferably 2 to 40 μm, more preferably 3 to 35 μm. The smaller the thickness of the adhesive layer 292 is, the more the peelability from the adherend tends to be improved.

The peeling force when peeling off the protective film 2 from the film substrate 1 is preferably 1.5 N/50 mm or less, more preferably 1.0 N/50 mm or less or 0.8 N/50 mm or less. The peeling force is a value measured in a peeling test in which the protective film is peeled off from the film substrate under the conditions of a peeling angle of 180° and a tensile speed of 10 m/min. By reducing the peeling force, the zipper phenomenon (zipping) when peeling the protective film from the film base material can be suppressed. In addition, since the vibration of the film base 1 caused by the peeling force of the protective film 2 is reduced, the moving state of the film base 1 on the coating section 30 (on the backup roll 31 ) is stabilized, and the application of the coating liquid can be suppressed. uneven.

From a viewpoint of suppressing a zipper phenomenon (Zipping) and coating unevenness, it is preferable that the peeling force of the protective film 2 is small. On the other hand, when the peeling force is too small, when the laminated body of the film base material and the protective film is conveyed by the rollers, the protective film may be unintentionally peeled off from the film base material, resulting in poor conveyance. Therefore, the peeling force when peeling the protective film from the film substrate is preferably 0.05 N/50 mm or more, and may be 0.1 N/50 mm or more, 0.15 N/50 mm or more, or 0.2 N/50 mm or more.

(Anti-static layer) The protective film 2 can also have an anti-static layer on the back of the core material 291 . By having the antistatic layer, the surface resistance of the back surface 2A of the protective film 2 is reduced, and the charging when the film substrate 1 and the protective film 2 are bonded together can be suppressed more effectively. In addition, by providing the protective film 2 with an antistatic layer, the film base 1 can be prevented from being charged when the protective film 2 is peeled off from the film base 1, and dust can be prevented from adhering to the film base 1 due to static electricity or coating failure.

As an antistatic layer, the layer formed by containing an antistatic component in a binder resin is mentioned, for example. As the binder resin, various types of resins, such as thermosetting resins, ultraviolet curing resins, electron beam curing resins, and two-component mixing resins, can be used. As an antistatic component, an organic or inorganic conductive substance, various antistatic agents, etc. are mentioned. Examples of the organic conductive substance include conductive polymers such as polyaniline, polypyrrole, polythiophene, polyethylenimine, and allylamine-based polymers. As the inorganic conductive substance, various metals, alloys, and conductive metal oxides may, for example, be mentioned. The inorganic conductive substance is preferably contained in the antistatic layer in the form of fine particles having a particle diameter of 0.1 μm or less (typically 0.01 μm to 0.1 μm). The antistatic component may be a cationic antistatic agent, an anionic antistatic agent, a zwitterionic antistatic agent, a nonionic antistatic agent, and the like.

The surface resistance of the back surface 2A of the protective film 2 may be 1×10 ¹⁰ Ω/sq or less, 5×10 ⁹ Ω/sq or less, 1×10 ⁹ Ω/sq or less, or 5×10 ⁸ Ω/sq or less. The surface resistance is generally 1×10 ³ Ω/sq or more, and may be 1×10 ⁴ Ω/sq or more, or 1×10 ⁵ Ω/sq or more. The smaller the surface resistance of the back surface 2A of the protective film 2 is, the more likely it is that charging tends to be suppressed when the film substrate 1 and the protective film 2 are attached to each other and when the protective film 2 is peeled off from the film substrate 1 .

[Fabrication of Optical Film] The adhesive layer 292 of the protective film 2 is attached to one surface of the film substrate 1 to form the laminate 8 , the protective film 2 is peeled off from the film substrate 1 of the laminate 8 , and the protective film 2 is placed on the first side of the film substrate 1 The coating layer 3 is formed on the one main surface 1A, whereby a laminate (optical film) 9 having the coating layer 3 on the film substrate 1 can be obtained. Hereinafter, each step will be described focusing on the case where an aligned liquid crystal layer is formed as the coating layer 3 using a liquid crystal composition containing a liquid crystal compound as a coating liquid.

<Lamination step> As shown in FIG. 3 , the film substrate 1 and the protective film 2 are respectively transported by rollers, and the film substrate 1 and the protective film are sandwiched by a pair of nip rollers 41 and 42 in the laminating section 40 . 2 are bonded together to form the layered body 8 . The bonding step may be performed continuously with the production step of the film substrate 1 . For example, when the film base 1 is a stretched film, the protective film 2 may be bonded to the film base 1 by roll-to-roll before the stretched film is wound into a roll. By carrying out the bonding of the protective film 2 continuously with the manufacturing process of the film base 1, the number of times of contact between the roller and the first main surface 1A of the film base 1 can be reduced, and the occurrence of scratches can be suppressed.

As described above, both the first roll 41 and the second roll 42 constituting a pair of nip rolls have electrical conductivity. As a conductive roll, a metal roll, a conductive rubber roll, etc. are mentioned. The conductive roller may be a coated roller formed by coating the outer peripheral surface of an insulating material with a conductive material as long as the contact surface with the film substrate 1 and the protective film 2 has conductivity. The surface resistance of the conductive roller is, for example, 1×10 ¹⁰ Ω/sq or less, or 1×10 ⁹ Ω/sq or less, 1×10 ⁸ Ω/sq or less, or 1×10 ⁷ Ω/sq or less.

The metal roll may be obtained by applying metal coating to the outer peripheral surface of an insulating material (eg, a resin material). The conductive rubber roller may be one in which the outer peripheral surface of a metal roller or a resin-made roller is covered with conductive rubber. Examples of the conductive rubber material constituting the conductive rubber roller include kneading carbon black with rubber materials such as natural rubber, butadiene rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. and other conductive materials.

The first roll 41 in contact with the film substrate 1 and the second roll 42 in contact with the protective film 2 may be the same type of roll, or may be different types of rolls. For example, both of the nip rolls 41 and 42 may be metal rolls, or both may be conductive rubber rolls, or one may be a metal roll and the other may be a conductive rubber roll. From the viewpoint of suppressing poor bonding such as air bubbles at the bonding interface, it is preferable that at least one of the rolls 41 and 42 is a conductive rubber roll. Both the rollers 41 and 42 may be conductive rubber rollers. Silicone rubber is particularly preferred as the rubber material for the conductive rubber roller, since it is easy to adjust the hardness and to uniformize the pressure distribution in the width direction.

<First Conveying Step> The layered body 8 formed by bonding the protective film 2 to the first main surface 1A of the film base material 1 is temporarily wound up into a roll-shaped roll body 80 and set on the unwinding roll 81 . The layered body 8 unwound from the winding body 80 provided on the unwinding roller 81 moves continuously to the downstream side along the conveyance path formed by the conveyance rollers 83 , 85 and 87 , and is conveyed to the peeling section 10 .

In addition, in FIGS. 3 and 4, the laminated body 8 of the film base material 1 and the protective film 2 is temporarily wound into a roll-shaped roll, but the laminated body 8 is formed by laminating the film base material 1 and the protective film 2 together. The step (the above-mentioned bonding step) and the first conveying step may be carried out continuously. For example, after the film base material 1 and the protective film 2 are bonded together, the laminated body 8 may be directly conveyed to the peeling part 10 without winding up.

<Peeling step> In the peeling step, the protective film 2 is peeled off from the laminated body 8 conveyed to the peeling section 10 to expose the first main surface 1A of the film base material 1 . The peeling method of the protective film is not particularly limited, but is usually a method of peeling on the peeling roll 11 . If the wrapping angle of the protective film 2 with respect to the peeling roller 11 is larger than the wrapping angle of the film substrate 1 with respect to the peeling roller 11, the conveying rollers 13 and 23 downstream of the peeling roller 11 can be arranged so that the film can be removed from the film on the peeling roller 11. The base material 1 peels off the protective film 2 . The peeling roll may be a pair of nip rolls that sandwich the laminated body 8 up and down. The protective film 2 peeled from the 1st main surface of the film base material 1 is conveyed along the conveyance path formed by conveyance rollers 23 and 25, and is wound up by the winding-up roller 21 into the wound body 20.

<Second conveyance step> In the second conveyance step, the film substrate 1 after peeling the protective film 2 is conveyed to the coating unit 30. The first main surface 1A of the film base 1 is exposed while the film base 1 is conveyed from the peeling part 10 to the coating part 30 after the protective film 2 is peeled off in the peeling part 10 . In this embodiment, the conveying path of the film base 1 in the second conveying step is short, and the contact chance between the first main surface 1A of the film base 1 and the conveying roller is less, so the film base in the second conveying step The scars on the wood are very rare.

During conveyance of the film base material 1 from the peeling section 10 (peeling roll 11 ) to the coating section 30 (backup roll 31 ), if the conveying roll is not brought into contact with the first main surface 1A of the film base material 1 , it is possible to prevent the In the second conveyance step, scratches are generated on the first main surface 1A of the film substrate 1 .

As shown by the dotted line in FIG. 4 , in the second conveyance step, the roller 15 may also be in contact with the first main surface 1A of the film base 1 . By bringing the roller 15 into contact with the first main surface 1A of the film base 1 , a force pressing from the first main surface side (lower side in the figure) to the upper side in the figure acts on the film base 1 . Therefore, vibration of the film substrate 1 due to the peeling force of the protective film 2 is reduced, and uneven application of the coating liquid can be suppressed.

In the conveyance path (second conveyance step) of the film base material 1 in the period from the peeling of the protective film 2 in the peeling part 10 to the time when the coating liquid is applied in the coating part 30 , the first main part of the film base material 1 The roller 15 with which the surface 1A is in contact can function as a "pressing roller" for the film substrate 1 .

The pressing roller should just be able to suppress vibration of the film base material 1 by peeling of the protective film 2 in the peeling part 10, and does not need to be in contact with the whole width direction of the film base material 1. The pressing roller may only contact both ends in the width direction of the film substrate 1 without contacting the central part in the width direction. For example, the barbell-shaped roller 151 schematically shown in FIG. 5 can be used as the pressing roller 15 which is in contact with the first main surface 1A of the film substrate 1 .

The roller 151 has cylindrical rollers 15R and 15L at both ends, and the rollers 15R and 15L at both ends are connected via a connecting shaft 15C having a diameter smaller than those of the rollers. When this roller 151 is used, the roller 151 is only in contact with both ends in the width direction of the film base material, and does not contact with the center in the width direction of the film base material.

In the second conveying step, there are cases where scars are formed on the first main surface of the film substrate due to contact with the rollers 15 at both ends in the width direction of the film substrate (regions where the rollers 15R, 15L contact the rollers 15R, 15L). If this area is regarded as a non-product area, and only the center in the width direction which is not in contact with the roll 15 is regarded as a product area, an optical film (coating layer 3 ) with few defects caused by scratches of the film substrate 1 can be obtained. For example, if the coating liquid is applied only to the center in the width direction of the film substrate 1 and no coating is formed on both ends of the film substrate in the width direction, only the center in the width direction becomes the product area. In addition, by punching the film at an appropriate stage after the coating is formed, or cutting the ends into long strips, etc., the regions of both ends can be removed from the product, so that only the center of the film substrate in the width direction can be cut. part as the product area.

As described above, in the second conveying step, when the roller is in contact with the first main surface 1A of the film substrate 1, it is preferable that the first main surface 1A at both ends in the width direction is in contact with the pressing roller, The central portion in the width direction is not in contact with the roller with respect to one main surface. In this form, the vibration of the film substrate 1 caused by the peeling of the protective film 2 can be suppressed, the coating unevenness of the coating layer 3 can be reduced, and a coating with fewer defects caused by the scratches of the film substrate 1 can be obtained. Layer 3.

At both ends of the film substrate 1, the width of the portion where the film substrate is in contact with the pressing roller is, for example, 1 to 50 cm, respectively. When the width of the portion of the film base material in contact with the pressing roller is too small, the vibration suppression effect of the film base material may be insufficient, or the mobility of the film base material may decrease. When the width of the portion of the film substrate in contact with the pressing roller is too large, the width of the non-product area of the optical film is large, resulting in a decrease in production efficiency or yield. The width of the portion of the film substrate in contact with the pressing roller may be 2 cm or more, 3 cm or more, or 5 cm or more, and may also be 30 cm or less, 25 cm or less, 20 cm or less, 15 cm or less, or 10 cm or less.

The pressing roller may be arranged so as to protrude outward from both ends in the width direction of the film substrate 1 , or may be arranged on the inner side of both ends in the width direction. When the pressing roller is arranged more inward than both ends in the width direction of the film substrate 1, the distance from one end of the width direction of the film substrate to the pressing roller can be within 30 cm, within 20 cm, or within 15 cm within 10 cm, within 5 cm, within 3 cm, or within 1 cm.

During the period after the protective film 2 is peeled off in the peeling section 10 until the coating liquid is applied in the coating section 30, the pressing roller in contact with the first main surface 1A of the film substrate 1 only needs to be able to press both ends of the film substrate. It is sufficient to suppress the vibration of the film base material, and its shape is not limited to the barbell shape shown in FIG. 5 . For example, two rolls may be arranged separately from both ends in the width direction. The pressing roller in contact with the first main surface 1A of the film substrate 1 may also be paired with the roller in contact with the second main surface 1B of the film substrate 1 to be a nip roll for pinching the film substrate 1 . Between the peeling part 10 and the coating part 30, two or more pressing rolls which contact the 1st main surface 1A of the film base material 1 may be provided.

In the second conveyance step, the member that presses the film base material from the first principal surface 1A side of the film base material 1 to suppress the vibration of the film base material does not necessarily have to be a rotating body. For example, between the peeling part 10 and the coating part 30 , an ejector pin or the like that presses the film base material from the first main surface side (lower side in the figure) toward the second main surface side may be arranged as a film pressing mechanism.

In the second conveyance step, both ends of the film substrate may be held by tenter clips. In this case, it is also possible to press the regions of both ends in the width direction of the film substrate from both the first main surface and the second main surface without bringing the rollers or the like into contact with the widthwise center portion of the film substrate, thereby suppressing protection from Vibration of the film substrate 1 caused by the peeling of the film 2 . In this case, the jig under contact with the first main surface side of the film substrate functions as a film pressing mechanism.

As shown in FIG. 4 , in the second conveyance step between the peeling part 10 and the coating part 30 , by bringing the roller 13 into contact with the second main surface 1B of the film base 1 , the second main surface 1B can also be Since the film base material 1 is pressed sideways, the vibration of the film base material 1 caused by the peeling force of the protective film 2 can be suppressed more effectively.

The roller 13 in contact with the second main surface 1B of the film base 1 may be in contact with only both ends of the film base, or may be in contact with the entire width direction of the film base. From the viewpoint of conveyability of the film base material, etc., it is preferable that the roll 13 is in contact with the entire width direction of the second main surface of the film base material.

<Coating step> The coating liquid is coated on the first main surface 1A of the film substrate 1 conveyed to the coating section 30 . In the form shown in FIG. 4 , in a state where the second main surface 1B of the film substrate 1 is in contact with the backup roll 31 , the first main surface 1A of the film substrate 1 is coated with the film ejected from the die nozzle 33 . coating liquid.

The method of applying the coating liquid on the film substrate 1 is not particularly limited. As a coating method, in addition to die coating, contact roll coating, gravure coating, reverse coating, spray coating, Meyer bar coating, knife roll coating, and air knife coating may be mentioned. Wait. The coating thickness of the coating liquid is preferably adjusted so that the thickness of the coating layer 3 after drying the solvent becomes about 0.1 to 20 μm.

In the present embodiment, since the protective film 2 is temporarily adhered to the first main surface 1A of the film substrate 1 immediately before the coating step to be protected, the first main surface of the film substrate 1 caused by the roller conveyance is protected. The generation of scratches on the surface 1A is suppressed. In addition, by sandwiching the film base material 1 and the protective film 2 with two conductive rollers 41 and 42 and sticking them together, the internal electrification of the laminate 8 is less likely to occur, so that the film base material 1 is charged after peeling off the protective film 2. The occurrence of coating defects caused by etc. is suppressed. Therefore, the coating layer 3 with few defects such as scratches and streaks caused by the film substrate 1 can be formed.

<Steps after coating> The film substrate 1 after the coating liquid is coated may also be heated by the heating unit 50 . The heating unit 50 includes, for example, a heating furnace 55 , and heats the film substrate 1 and the coating liquid applied thereon while the film substrate 1 is being conveyed in the heating furnace 55 . For example, the solvent of the coating liquid can be removed by heating.

When the coating liquid is a liquid crystal composition and the liquid crystal compound contained in the liquid crystal composition is a thermotropic liquid crystal, the liquid crystal composition layer is heated to become a liquid crystal phase, whereby the liquid crystal compound is aligned in a specific direction. Specifically, the liquid crystal composition applied on the film substrate is heated to the N (nematic phase)-I (isotropic liquid phase) transition temperature or higher, and the liquid crystal composition is brought into an isotropic liquid state. Then, if necessary, slow cooling is performed so that a nematic phase is formed. At this time, it is preferable to temporarily maintain the temperature at which the liquid crystal phase is present, and to grow the liquid crystal phase domain into a single domain. Alternatively, after coating the liquid crystal composition, the temperature can be maintained within a temperature range in which a nematic phase is exhibited for a certain period of time to align the liquid crystal molecules in a specific direction.

The heating temperature at the time of aligning the liquid crystal compound in a specific direction may be appropriately selected according to the type of the liquid crystal composition, and it is usually about 40 to 200°C. When the heating temperature is too low, the transition to the liquid crystal phase tends to be insufficient, and when the heating temperature is too high, alignment defects may increase. The heating time may be adjusted so that the liquid crystal phase region can sufficiently grow, and it is usually about 30 seconds to 30 minutes.

After aligning the liquid crystal compound by heating, it is preferable to cool to the temperature below the glass transition temperature. The cooling method is not particularly limited, and may be taken out from a heating atmosphere to room temperature, for example. Forced cooling such as air cooling and water cooling can also be performed.

When the liquid crystal compound has curability, it is preferable to use the hardening part 60 for hardening. For example, when the liquid crystal compound has photocurability, photocuring is performed in a state in which the photocurable liquid crystal compound (liquid crystal monomer) has liquid crystal regularity. The irradiation light from the light source 61 may polymerize the photocurable liquid crystal compound, and generally, ultraviolet rays or visible light having a wavelength of 250 to 450 nm are used. In the case where the liquid crystal composition contains a photopolymerization initiator, it is only necessary to select light with a wavelength of which the photopolymerization initiator has sensitivity. As the irradiation light source, a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED (Light Emitting Diode), a black light lamp, a chemical lamp, etc. can be used. In order to promote the photohardening reaction, the light irradiation is preferably performed in an inert gas atmosphere such as nitrogen.

During photohardening, the liquid crystal compound can also be aligned in a specific direction by utilizing polarized light in a specific direction. As described above, when the liquid crystal compound is aligned by the alignment control force of the film substrate 1, the irradiation light may be non-polarized light (natural light).

The irradiation intensity may be appropriately adjusted according to the composition of the liquid crystal composition, the addition amount of the photopolymerization initiator, and the like. The irradiation energy (cumulative irradiation light amount) is usually about 20 to 10000 mJ/cm ² , preferably 50 to 5000 mJ/cm ² , and more preferably 100 to 800 mJ/cm ² . In order to promote the photohardening reaction, light irradiation may also be performed under heating conditions.

The polymer after photohardening the liquid crystal monomer is non-liquid crystalline, and will not cause the transition of liquid crystal phase, glass phase and crystal phase due to temperature change. Therefore, it is difficult for the liquid crystal layer obtained after photohardening in the state of aligning the liquid crystal monomer in a specific direction to change the molecular alignment due to the temperature change. Also, the birefringence of the liquid crystal layer is significantly greater than that of films comprising non-liquid crystal materials, so that the thickness of the optically anisotropic element with the desired retardation can be significantly reduced.

The optical properties of the coating layer (liquid crystal layer) 3 are not particularly limited. The front retardation and the thickness direction retardation of the coating layer 3 may be appropriately set according to the application and the like. When there are liquid crystal molecules aligned along the plane, the front retardation of the coating layer 3 is, for example, about 20-1000 nm. When the coating layer 3 is a quarter wave plate, the front retardation is preferably 100-180 nm, more preferably 120-150 nm. When the coating layer 3 is a 1/2 wavelength plate, the front retardation is preferably 200-340 nm, more preferably 240-300 nm. When the liquid crystal is vertically aligned, the in-plane retardation of the coating layer 3 is about 0 (eg, less than 5 nm, preferably less than 3 nm), and the absolute value of the retardation in the thickness direction is about 30-500 nm.

The retardation of the coating 3 such as the liquid crystal layer is proportional to the thickness. When a coating liquid is applied, if a portion with a small local thickness is formed due to the shrinkage of the surface of the film substrate, etc., the retardation of this portion becomes small, thereby causing optical unevenness in the display device. As described above, in this embodiment, the film base material and the protective film are bonded by sandwiching the film base material with the nip rolls composed of two conductive rolls, so that the internal electrification during bonding is less likely to occur, and coating defects caused by coating defects are suppressed. The resulting stripes are uneven in thickness. Therefore, it is difficult to generate retardation unevenness due to thickness unevenness of the optical film (coating layer), and the optical uniformity is excellent.

The alignment direction of the liquid crystal molecules in the coating layer (liquid crystal layer) 3 may or may not be parallel to the longitudinal direction (roll-to-roll conveyance direction) of the film substrate 1 . As described above, by utilizing the alignment restraining force of the obliquely stretched film or the like, a liquid crystal layer in which the alignment of the liquid crystal molecules is not parallel to the longitudinal direction can be formed. When the alignment of the liquid crystal molecules is not parallel to the longitudinal direction, if there are scars along the longitudinal direction on the film substrate, the liquid crystal molecules in the liquid crystal layer formed thereon are aligned in the longitudinal direction along the scars, resulting in Poor alignment. As described above, by coating the liquid crystal composition on the film substrate 1 immediately after peeling off the protective film 2 temporarily adhered to the film substrate 1, it is possible to suppress the occurrence of scratches on the film substrate and reduce the misalignment of the liquid crystal layer.

<Processing of Optical Film> By winding the layered body 9 (optical film) having the coating layer 3 formed on the first main surface 1A of the film substrate 1 with the take-up roll 91, a roll of a long optical film can be obtained Around the body 90. This laminated body 9 can be used as an optical film as it is. Since the regions of both ends in the width direction of the film base material 1 are non-product regions, it is also possible to perform the period from the formation of the coating layer 3 until the winding by the winding roller 91 or after the winding by the winding roller 91. At an appropriate stage, the area is removed by cutting through the strip. Moreover, the film may be punched out so that the region of both ends in the width direction may not be included, and a single-piece product may be cut out.

The layered body 9 in which the coating layer 3 is formed on the first main surface 1A of the film substrate 1 may be used as an optical film as it is, or the film substrate 1 may be peeled off and only the coating layer 3 may be used as an optical film. When the coating layer 3 is a resin layer, the laminate of the film substrate 1 and the coating layer 3 may be extended to impart optical anisotropy to the coating layer 3 .

Other layers may also be laminated on the coating layer 3 . For example, by bonding the optical layer 4 on the coating layer 3 via the adhesive layer 5, the laminated body 96 shown in FIG. 6 can be obtained.

The optical layer 4 laminated on the coating layer 3 is not particularly limited, and an optically isotropic or optically anisotropic film generally used as an optical film can be used without particular limitation. Specific examples of the optical layer 4 include transparent films such as retardation films and polarizer protective films, functional films such as polarizers, viewing angle widening films, viewing angle limiting (privacy) films, and brightness enhancement films. The optical layer 4 may be a single layer or a laminate. The optical layer 4 can also be a liquid crystal layer. The optical layer 4 can also be a polarizing plate formed by laminating a transparent protective film on one side or both sides of the polarizing element. When the polarizing plate is provided with a transparent protective film on one side, the polarizing element can be attached to the coating layer, and the transparent protective film can also be attached to the coating layer.

The material of the adhesive constituting the adhesive layer 5 is not particularly limited as long as it is optically transparent, and examples thereof include epoxy resin, polysiloxane, acrylic resin, polyurethane, polyamide, and polyether. , polyvinyl alcohol, etc. The thickness of the adhesive layer 5 is appropriately set according to the type of the adherend, the material of the adhesive, and the like. In the case of using a hardening type adhesive that exhibits adhesiveness by a crosslinking reaction after coating, the thickness of the adhesive layer 5 is preferably 0.01 to 5 μm, more preferably 0.03 to 3 μm.

As the adhesive, various types of adhesives such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used. Among them, a water-based adhesive or an active energy ray-curable adhesive is preferable from the viewpoint that the thickness of the adhesive layer can be reduced. .

The coating layer 3 and the optical layer 4 are laminated through the adhesive layer 5 by applying an adhesive to one or both sides of the surface of the coating layer 3 and the surface of the optical layer 4 and hardening. The curing of the adhesive may be appropriately selected according to the type of the adhesive. For example, the water-based adhesive can be hardened by heating. The active energy ray hardening adhesive can be hardened by irradiation with active energy rays such as ultraviolet rays.

The laminate 96 formed by laminating the optical layer 4 on the coating layer 3 on the film substrate 1 via the adhesive layer 5 can be directly used as an optical film. In this case, the film substrate 1 constitutes a part of the optical film. As shown in FIG. 7 , the film base material may also be peeled off from the coating layer 3 . As also shown in FIG. 8 , an appropriate adhesive layer 6 can be laminated on the surface of the coating layer 3 exposed by the peeling of the film substrate.

The adhesive constituting the adhesive layer 6 is not particularly limited, and can be appropriately selected from acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyethers, and fluorine-based polymers. materials, rubber-based polymers, etc. as the adhesive of the base polymer. Particularly preferred are adhesives such as acrylic adhesives and rubber-based adhesives, which are excellent in transparency, exhibit moderate wettability, cohesion, and adhesiveness, and are excellent in weather resistance, heat resistance, and the like. The thickness of the adhesive layer is appropriately set according to the type of the adherend, etc., and is usually about 5 to 500 μm.

When the adhesive layer 6 is laminated on the coating layer 3 , for example, it is performed by sticking an adhesive previously formed in a sheet shape on the surface of the coating layer 3 . The adhesive layer 6 can also be formed by applying the adhesive composition on the coating layer 3 , and then performing solvent drying, cross-linking, photohardening, and the like. In order to improve the adhesive force (grip force) between the coating layer 3 and the adhesive layer 6, the surface of the coating layer 3 can also be subjected to surface treatment such as corona treatment, plasma treatment or the like, or an easy-adhesive layer is formed and then the adhesive layer 6 is laminated. .

Preferably, the spacer 7 is temporarily adhered to the surface of the adhesive layer 6 . The spacer 7 protects the surface of the adhesive layer 6 before attaching the optical film to other members. As the constituent material of the separator, plastic films such as acrylic resin, polyolefin, cyclic polyolefin, polyester, etc. can be suitably used. The thickness of the spacer is usually about 5-200 μm. Preferably, the surface of the separator is subjected to mold release treatment. As a mold release agent, a polysiloxane type material, a fluorine type material, a long-chain alkyl type material, a fatty acid amide type material, etc. are mentioned.

On the exposed surface of the coating layer 3 after peeling off the film substrate 1, other optical layers may also be laminated through an appropriate adhesive layer or adhesive layer. For example, other optical layers can also be laminated on the coating layer 3 through an appropriate adhesive layer, and an adhesive layer can also be further laminated thereon.

The optical film provided with the coating layer can be used, for example, as an optical film for an image display device. As an example of the optical film formed by laminating the other optical layers 4 on the coating layer 3, a circular polarizing plate formed by laminating the alignment liquid crystal layer as the coating layer 3 and a polarizing plate can be exemplified.

The polarizing plate may be composed of only one layer of polarizing elements, or as described above, a transparent protective film may be attached to one side or both sides of the polarizing element. As polarizers, hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films may, for example, adsorb iodine or dichroic dyes. Dichroic substances and uniaxially stretched; polyene-based alignment films such as dehydration-treated products of polyvinyl alcohol or dehydrochlorination-treated products of polyvinyl chloride.

Among them, it is preferable to adsorb dichroic substances such as iodine and dichroic dyes to a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol in terms of having a high degree of polarization The polyvinyl alcohol (PVA) is a polarizing element that is aligned in a specific direction. For example, a PVA-based polarizing element is obtained by subjecting a polyvinyl alcohol-based film to iodine dyeing and stretching. A PVA-based resin layer can also be formed on the resin substrate, and iodine dyeing and stretching can be performed in the state of a laminate.

In the circular polarizing plate having the polarizing plate and the liquid crystal layer laminated, preferably at least one layer of the liquid crystal layer has liquid crystal molecules aligned along the plane. In the circular polarizer, the alignment direction of the liquid crystal molecules in the liquid crystal layer in which the liquid crystal molecules are aligned along the plane and the direction of the absorption axis of the polarizer are arranged in a manner that is neither parallel nor orthogonal.

For example, when the circular polarizer has only one liquid crystal layer, the liquid crystal layer as the coating layer 3 is a 1/4 wavelength plate, and the direction of the absorption axis of the polarizing element and the alignment direction of the liquid crystal molecules (generally the slow axis direction) is set to 45°. The angle formed by the absorption axis direction of the polarizing element and the alignment direction of the liquid crystal molecules may be 35-55°, 40-50°, or 43-47°.

In the structure in which the polarizing plate 4 and the coating layer 3, which is a quarter-wave plate, are laminated in such a way that the angle formed by the optical axes of the two is 45°, it is also possible to further have a homeotropic alignment with respect to the substrate surface. ) has a liquid crystal layer with liquid crystal molecules. By sequentially laminating the coating layer 3 as a quarter-wave plate and the vertical liquid crystal layer functioning as a positive C plate on the polarizing plate, a circular polarizing plate that can shield reflected light from external light from an oblique direction can be formed. The vertical alignment liquid crystal layer (positive C plate) and the surface alignment liquid crystal layer (as the 1/4 wavelength plate of the positive A plate) can also be sequentially laminated on the polarizer.

In a circular polarizer formed by laminating a plurality of liquid crystal layers on a polarizing plate, the liquid crystal layers may also be all oriented liquid crystal layers. In this case, the liquid crystal layer disposed on the side close to the polarizer 4 is preferably a 1/2 wavelength plate, and the liquid crystal layer disposed on the side away from the polarizer 4 is preferably a 1/4 wavelength plate. In this laminated structure, it is preferable that the angle formed by the direction of the retardation axis of the 1/2 wavelength plate and the direction of the absorption axis of the polarizer is 75°±5°, and the direction of the retardation axis of the 1/4 wavelength plate and the polarized light are 75°±5°. The angle formed by the direction of the absorption axis of the element is arranged in a manner of 15°±5°. The circular polarizing plate formed by such a laminated layer functions as a circular polarizing plate in a wide wavelength range of visible light, thus reducing the chromatic aberration of the reflected light.

As described above, in the embodiment of the present invention, since the protective film is temporarily adhered on the surface of the film substrate until just before the coating liquid is applied, the occurrence of scratches on the film substrate is suppressed, and the scars on the film substrate are The resulting coating defects are less. In addition, even when the coating layer is an aligned liquid crystal layer, and the alignment of the liquid crystal molecules is not parallel to the longitudinal direction of the film substrate, there are fewer misalignment defects. Furthermore, since coating defects caused by lamination of the film substrate and the protective film are suppressed, the in-plane uniformity of the coating layer becomes high, and favorable display characteristics can be realized.

1: film substrate 1A: first main surface of film substrate 1B: second main surface of film substrate 2: protective film 2A: backside of protective film 3: coating layer (liquid crystal layer) 4: optical layer (polarizing plate ) 5: Adhesive layer 6: Adhesive layer 7: Separator 8: Laminated body 9, 96, 97, 98: Laminated body (optical film) 10: Peeling part 11: Peeling roller 13: Conveying roller 15: Pressing roller 15C : connecting shaft 15R: roller 15L: roller 20: winding body 21: winding roller 23: conveying roller 25: conveying roller 29: unwinding roller 30: coating unit 31: backup roller 33: die nozzle 40: bonding unit 41, 42: Pinch rolls 44, 45, 46, 47: Conveying rolls 49: Winding rolls 50: Heating section 55: Heating furnace 60: Hardening section 61: Light source 71, 73, 75, 77, 79: Conveying rolls 80: Winding body 81: Unwinding rollers 83, 85, 87: Conveying roller 91: Winding roller 151: Pressing roller 291: Core material 292: Adhesive layer

Figure 1 is a cross-sectional view of an optical film with a coating on a film substrate. Figure 2 is a cross-sectional view of a laminate with a protective film temporarily adhered to the film substrate. Fig. 3 is a diagram showing the outline of the steps of laminating the film substrate and the protective film. FIG. 4 is a diagram showing the outline of a film forming apparatus and a film forming step for forming a coating layer on a film substrate. Fig. 5 is a perspective view showing an example of the shape of the pressing roller. 6 is a cross-sectional view of an optical film of one embodiment. 7 is a cross-sectional view of an optical film of one embodiment. 8 is a cross-sectional view of an optical film of one embodiment.

1: film substrate

2: Protective film

8: Laminate

28: winding body

29: Unwinding roller

40: Fitting department

41,42: Pinch rollers

44, 45, 46, 47: Conveyor Rollers

49: take-up roll

80: winding body

Claims (10)

A manufacturing method of an optical film, which is a manufacturing method of an elongated optical film, the manufacturing method comprising: a laminating step, which has a first principal surface and a The long film substrate on the second main surface and the protective film are laminated to obtain a laminate with the protective film attached to the first main surface of the film substrate releasably; the first conveying step is to combine the above The layered body is transported to the peeling part along the longitudinal direction of the film base material; The protective film peeling step is in the peeling part, and the protective film is peeled off from the first main surface of the film base material; The second conveying step , which is that the above-mentioned film base material after peeling the above-mentioned protective film is transported from the above-mentioned peeling part to the coating part along the longitudinal direction of the above-mentioned film base material; The coating solution is applied on the first main surface of the base material to obtain a laminate having a coating layer on the first main surface of the film base material; and both the first roll and the second roll have electrical conductivity. The method for producing an optical film according to claim 1, wherein at least one of the first roll and the second roll is a conductive rubber roll. The method for producing an optical film according to claim 1 or 2, wherein the coating liquid is a liquid crystal composition containing a liquid crystal compound. The manufacturing method of the optical film of claim 3, wherein the liquid crystal composition comprises a photocurable liquid crystal compound, and the manufacturing method has a step of further photocuring the liquid crystal compound after the coating step. The method for producing an optical film according to claim 1 or 2, wherein the film base is a stretched film whose molecular orientation is not parallel to the longitudinal direction. The manufacturing method of the optical film of Claim 1 or 2 whose roller does not contact the center part of the width direction of the 1st main surface of the said film base material in the said 2nd conveyance process. The method for producing an optical film according to claim 6, wherein in the second conveying step, the film pressing mechanism is in contact with both ends in the width direction of the first principal surface of the film substrate at least once, and the film pressing mechanism It does not contact the center part of the width direction of the 1st main surface of the said film base material. The method for producing an optical film according to claim 7, wherein the film pressing mechanism is a pressing roller that contacts only both ends in the width direction of the first main surface of the film substrate. The manufacturing method of the optical film of claim 1 or 2, which comprises the step of laminating other optical layers on the above-mentioned coating layer by roll-to-roll. The method for producing an optical film according to claim 9, wherein the optical layer includes a polarizing element.

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