Method for manufacturing a laminated optical film

Abstract

As a manufacturing method of a laminated optical film, a manufacturing method in which a transport line is not contaminated by a cut end of a film even when a liquid crystal coating type polarizing plate is used is provided. A first optical film (2) having a first optical functional layer (22) and a second optical functional layer (23), an adhesive layer (4), and a second optical film (3) are introduced into a pair of rotating bonding rollers (6a, 6b) in a state of being arranged in this order. At the time of bonding, the width (W1) of the second optical functional layer (23) is smaller than the width (W3) of the first optical functional layer (22). The width (W2) of the adhesive layer (4) is smaller than the width (W3) of the first optical functional layer (22) and larger than the width (W1) of the second optical functional layer (23). The adhesive of the adhesive layer (4) enters the first optical functional layer (22) side from both end portions of the second optical functional layer (23) so as to be in contact with the first optical functional layer (22).

Description

TECHNICAL FIELD

[0001] The present application relates to a method for manufacturing a layered optical film. BACKGROUND

[0002] In the past, a polarizing plate has been used in an image display device such as a liquid crystal display device or an organic EL display device. In a liquid crystal display device, a linear polarizing plate or a circular polarizing plate is used for image display or phase difference control, and in an organic EL display device, a circular polarizing plate is used for suppressing reflection of external light. As a polarizing plate layer that is a constituent element of a polarizing plate, a stretched film containing iodine as a dichroic dye is widely used, but in recent years, a liquid crystal coating type polarizing plate formed by coating a composition containing a dichroic dye and a liquid crystal compound has been studied (for example, Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2020 / 179864 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] A polarizing plate is a layered optical film in which optical films having various functions are laminated, and in the manufacture of a polarizing plate, the optical films are attached to or peeled from each other in a manner to become a desired layered configuration. This operation is usually performed while the optical films are transported using a transport line.

[0008] In the case where a liquid crystal coating type polarizing plate is adopted as a polarizing plate layer, a phenomenon in which a transport line is contaminated by a cut end of a film is seen more frequently than in the case where a conventional stretched film is adopted. According to the present inventor's investigation, it is known that the cut end is broken from an end portion in the width direction of a layered optical film during transport. Therefore, an object of the present application is to provide a manufacturing method in which a transport line is not contaminated by a cut end of a film even in the case where a liquid crystal coating type polarizing plate is adopted as a layered optical film.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] According to the present inventor's investigation, it is known that an end portion in the width direction of a layered optical film, in which an adhesive that bonds the optical films to each other does not spread, becomes an unfixed free end, and this portion easily breaks during transport to become a cut end. The thinner the thickness of the unfixed free end, the more easily it breaks. For example, even in the case where the adhesive does not spread to the end portion in the width direction, in the case where a film having a relatively thick thickness is included, the unfixed free end does not easily break, but in the case where the thick film is peeled during transport and only a thin film remains as an unfixed free end and is transported, the tendency of the unfixed free end to easily break becomes significant.

[0011] Therefore, the present invention provides a method for manufacturing a laminated optical film, wherein a first optical film, an adhesive layer, and a second optical film are introduced into the space between a pair of rotating bonding rollers in a sequentially arranged manner in a direction connecting a pair of bonding rollers, thereby bonding the first optical film and the second optical film. The first optical film sequentially includes a first optical functional layer and a second optical functional layer, the second optical functional layer being a polarizer layer including a liquid crystal coated polarizer. During bonding, the second optical functional layer side of the first optical film faces the adhesive layer side, and the width of the second optical functional layer is smaller than that of the first optical film. The width of the optical functional layer is such that the first optical functional layer is contained within the width of the second optical functional layer. The width of the adhesive layer is smaller than the width of the first optical functional layer and smaller than the width of the second optical film, but larger than the width of the second optical functional layer. The first optical functional layer and the second optical film are contained within the width of the adhesive layer. The adhesive layer is contained within the width of the second optical functional layer. The adhesive constituting the adhesive layer enters the first optical functional layer from both ends of the second optical functional layer and thus contacts the first optical functional layer.

[0012] If the first optical film and the second optical film are bonded together using an adhesive under the above conditions, the adhesive bypasses the end of the second optical functional layer and reaches the first optical functional layer, which is wider than the second optical functional layer. Therefore, the unfixed free ends are fixed by the adhesive, and almost no free movement occurs. Thus, during the subsequent transport of the laminated optical films, the breakage of the unfixed free ends from the first optical film is suppressed.

[0013] In this invention, the combined thickness of the first optical functional layer and the second optical functional layer can be 1 μm to 8 μm. If the unfixed free end has this thickness, it is particularly prone to breakage, thus making it suitable for application in this invention.

[0014] In this invention, the width of a pair of bonding rollers is greater than the width of either the first optical film or the second optical film, and the pair of bonding rollers can be present in such a way that they enclose the widths of the first and second optical films. Thus, the pressure from the bonding rollers is applied evenly to the entire bonded optical film.

[0015] In this invention, the liquid crystal coated polarizer can be a cured product of a polymeric liquid crystal composition comprising a dichroic pigment and a polymeric liquid crystal compound having at least one polymeric group.

[0016] In this invention, the first optical film may have a release substrate film on the side of the first optical functional layer opposite to the side of the second optical functional layer, and the first optical functional layer may be a hard coating formed on the release substrate film. In this case, even when the release substrate film is peeled off after bonding, the unfixed free end hardly moves, thus enabling the film to be transported without problems.

[0017] In this invention, the first optical film may further include an outer coating layer applied to the second optical functional layer. Furthermore, in this invention, the second optical film is composed of multiple layers, and these multiple layers may include a phase retardation layer.

[0018] In this invention, the adhesive is an active energy ray curing adhesive, which can have a curing process in which the adhesive is cured by irradiating the laminate between a pair of bonding rollers with active energy rays.

[0019] Invention Effects

[0020] According to the present invention, a method for manufacturing a laminated optical film can be provided, in which the transport line is not contaminated by the cut end of the film even when a liquid crystal coated polarizer is used. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a laminated optical film manufactured by the manufacturing method of this embodiment.

[0022] Figure 2 This is a diagram illustrating the manufacturing method of this embodiment.

[0023] Figure 3 yes Figure 2 The III-III cross-sectional view is a diagram showing the stacking state during bonding.

[0024] Figure 4 This is a cross-sectional view of a traditional stacked optical film.

[0025] Explanation of reference numerals in the attached figures

[0026] 1…Laminated optical film, 2, 2'…First optical film, 3…Second optical film, 4, 4'…Adhesive layer, 5…Coating machine, 6a, 6b…Laminating rollers, 7…UV irradiation device, 8…Laminated body, 10…Unfixed free end, 21…Putaway substrate film, 22…Hard coating (first optical functional layer), 23…Polarizer layer (second optical functional layer), 24…Outer coating, 31…Phase retardation layer (third optical functional layer), 32…Putaway substrate film, 100…Laminated optical film, W1…Width of polarizer layer, W2…Width of adhesive layer, W3…Width of hard coating, W4…Width of phase retardation layer, W… R1 W R2 …width of the bonding roller. Detailed Implementation

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the drawings, the same or corresponding parts are labeled with the same symbols, and repeated descriptions are omitted. Furthermore, the dimensional ratios of the drawings may not necessarily match the actual dimensional ratios; in particular, the thickness and width of the membrane are depicted exaggeratedly.

[0028] The method for manufacturing the laminated optical film in this embodiment is part of the manufacturing process of a circular polarizer having a polarizer layer, a hard coating layer, an outer coating layer, and a phase difference layer. Two optical films are bonded together with an adhesive by a pair of rotating bonding rollers to obtain a long strip of laminated optical film.

[0029] <Laminated Optical Films>

[0030] First, the composition of the stacked optical film will be explained. For example... Figure 1 As shown, the laminated optical film 1 manufactured by the manufacturing method of this embodiment is formed by bonding a first optical film 2 and a second optical film 3 together using an adhesive layer 4. The first optical film 2 sequentially comprises a release substrate film 21, a hard coating layer (first optical functional layer) 22, a polarizer layer (second optical functional layer) 23, and an outer coating layer 24. These layers are formed by coating a raw material resin onto the release substrate film 21 as a substrate. The release substrate film 21 is provided on the side of the hard coating layer 22 opposite to the polarizer layer 23 side. The second optical film 3 is composed of multiple layers and includes a release substrate film 32 and a retardation layer (third optical functional layer) 31. These layers are formed by coating a raw material resin of the retardation layer 31 onto the release substrate film 32 as a substrate. The first optical film 2 and the second optical film 3 are arranged such that the outer coating layer 24 and the retardation layer 31 face each other, and are bonded together using the adhesive layer 4.

[0031] In the first optical film 2, the release substrate film 21 and the hard coating layer 22 are of equal width and aligned at both ends. The width of the polarizer layer 23 is smaller than the width of the hard coating layer 22. The polarizer layer 23 and the outer coating layer 24 are of equal width and aligned at both ends. In the second optical film, the release substrate film 32 and the retardation layer 31 are of equal width and aligned at both ends. The adhesive layer 4 is smaller than the width of the hard coating layer 22 and smaller than the width of the retardation layer 31, but larger than the width of the polarizer layer 23. Furthermore, the adhesive layer 4 not only exists between the outer coating layer 24 and the retardation layer 31, but also extends beyond both ends of the outer coating layer 24, covering the side portions (thickness portions) of the outer coating layer 24 and the polarizer layer 23, and also reaches the hard coating layer 22. It should be noted that, in this specification, the "width" of each film or layer refers to the width in the direction orthogonal to the conveying direction of each film or layer during the manufacturing of the laminated optical film 1, i.e., the extension direction of the bonding roller. That is, Figure 1It is a cross-sectional view cut in a direction orthogonal to the conveying direction during manufacturing. In addition, the relative size relationship (width-narrow relationship) of the width of each membrane or layer is expressed as "large" and "small".

[0032] The central axes in the width direction of the release substrate film 21, hard coating 22, polarizer layer 23, outer coating 24, adhesive layer 4, phase retardation layer 31, and release substrate film 32 are approximately aligned. That is, in Figure 1 In the cross-sectional view shown, the stacked structure is roughly symmetrical from left to right.

[0033] Here, each membrane or layer is described.

[0034] (Peeling off the substrate film)

[0035] Various resin materials can be used as the release substrate films 21 and 32, such as polyethylene terephthalate (PET) resins, triacetyl cellulose (TAC) resins, polypropylene resins, and polycarbonate resins. The thickness of the release substrate films 21 and 32 is preferably 20 to 500 μm, more preferably 30 to 300 μm, and even more preferably 35 to 200 μm.

[0036] (Hard coating)

[0037] The hard coating 22 is provided to improve the surface hardness and scratch resistance of the polarizer layer 23. The hard coating 22 may contain a UV absorber. The hard coating 22 is, for example, a cured layer of a UV-curable resin. Examples of UV-curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. A method for forming the hard coating 22 is to apply a raw material resin to a release substrate film 21 and then cure it.

[0038] The thickness of the hard coating 22 can be 1μm to 20μm or 2μm to 7μm.

[0039] (Polarizing layer)

[0040] The polarizer layer 23 has at least a liquid crystal coated polarizer as a constituent element, and also has an alignment film. The alignment film is a film composed of a polymer compound and has an alignment constraint force that causes the polymeric liquid crystal compound to align in a desired direction.

[0041] In this embodiment, the polarizing layer is obtained by coating a composition (polymeric liquid crystal composition) containing a dichroic pigment and a polymeric liquid crystal compound having at least one polymeric group onto the surface of an alignment film, and then polymerizing the polymeric liquid crystal compound. Therefore, the polarizing layer is a cured product of the polymeric liquid crystal composition, and is a film in which the dichroic pigment is dispersed and aligned in a film composed of a polymer of the polymeric liquid crystal compound.

[0042] From the viewpoint of the orientation of polymerizable liquid crystal compounds, the thickness of the polarizing layer is preferably 0.5 μm to 3 μm, more preferably 1 μm to 3 μm. If the thickness of the polarizing layer is above the lower limit mentioned above, the polymerizable liquid crystal compound is difficult to align along the perpendicular orientation direction, thus tending to increase the orientation order. Conversely, if the thickness of the polarizing layer is below the upper limit mentioned above, the polymerizable liquid crystal compound is difficult to align randomly, thus tending to increase the orientation order. The thickness of the polarizing layer can be measured using an interferometer, laser microscope, or stylus-type thickness gauge.

[0043] Polymerizable liquid crystal compounds are compounds having at least one polymerizable group and exhibiting liquid crystal properties. A polymerizable group refers to a group that participates in a polymerization reaction, preferably a photopolymerizable group. Here, a photopolymerizable group refers to a group capable of participating in a polymerization reaction via active free radicals, acids, etc., generated by a photopolymerization initiator described later. Examples of polymerizable groups include vinyl, ethoxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, ethylene oxide, and oxetyl. Among these, acryloyloxy, methacryloyloxy, ethoxy, and oxetyl are preferred, and acryloyloxy is more preferred. The liquid crystal property can be thermotropic or lyotropic.

[0044] Dichroic pigments are pigments that exhibit different absorbance along their long axis and short axis. Preferably, dichroic pigments have an absorption maximum wavelength (λMAX) in the range of 300–700 nm. Examples of such dichroic pigments include acridine pigments, oxazine pigments, anthocyanins, naphthalene pigments, azo pigments, and anthraquinone pigments, with azo pigments being preferred. Examples of azo pigments include monoazo pigments, diazo pigments, triazo pigments, tetraazo pigments, and pizoazo pigments, with diazo and triazo pigments being preferred. Dichroic pigments can be used alone or in combination of two or more, but combinations of three or more are preferred. In particular, combinations of three or more azo compounds are more preferred.

[0045] Alignment films facilitate the alignment of polymeric liquid crystal compounds. The alignment states, such as horizontal alignment, vertical alignment, mixed alignment, and tilted alignment, vary depending on the properties of the alignment film and the polymeric liquid crystal compound, and their combinations can be arbitrarily selected. The alignment film is insoluble in the solvent used to form the polarizing layer on the alignment film, and preferably possesses heat resistance in heat treatments used for solvent removal and liquid crystal alignment. Examples of alignment films include alignment films made of oriented polymers, photo-alignment films, and groove alignment films, with photo-alignment films being preferred. The thickness of the alignment film is typically in the range of 10 nm to 500 nm, preferably in the range of 10 nm to 200 nm, and more preferably in the range of 30 nm to 100 nm.

[0046] In the first optical film 2, the total thickness of the layers other than the outermost release substrate film 21 is preferably 1 μm to 10 μm, and more preferably 2 μm to 8 μm. In particular, the total thickness of the hard coating layer 22 and the polarizer layer 23 is preferably 1 μm to 8 μm, and more preferably 2 μm to 6 μm. Even when the total thicknesses are as thin as these ranges, the laminated optical film 1 according to this embodiment is not prone to breakage when the release substrate film 21 is peeled off because the "unfixed free ends" are fixed by the adhesive layer 4, making it suitable for the manufacturing method of this embodiment.

[0047] (Outer coating)

[0048] The outer coating 24 is made of a material with low compatibility with the dichroic pigment contained in the polarizer layer, and functions to prevent the migration (diffusion) of the dichroic pigment. In addition, the outer coating 24 also provides protection for the polarizer layer 23 and imparts barrier properties against oxygen and moisture. The outer coating 24 can be provided on both sides of the polarizer layer 23 or on only one side. Figure 1 The diagram shows a configuration on one side. The outer coating 24 can be formed by coating the polarizer layer 23 with a material (composition) for forming the outer coating 24.

[0049] The outer coating 24 preferably possesses excellent solvent resistance, transparency, mechanical strength, thermal stability, opacity, and isotropy. The outer coating 24 disposed on one side of the polarizer layer 23 can be one layer or two or more layers. When there are two or more outer coating layers, the materials constituting each layer can be the same or different. Furthermore, when the outer coating 24 is disposed on both sides of the polarizer layer 23, each outer coating 24 can be formed of the same material or different materials. Examples of materials constituting the outer coating 24 include photocurable resins and water-soluble polymers.

[0050] Examples of photocurable resins include (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and silicone resins. Examples of water-soluble polymers include poly(meth)acrylamide polymers; vinyl alcohol polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, and (meth)acrylic acid or its anhydride-vinyl alcohol copolymers; carboxyvinyl polymers; polyvinylpyrrolidone; starches; sodium alginate; and polyethylene oxide polymers.

[0051] The thickness of the outer coating 24 is not particularly limited, but is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and can be 5 μm or less. In addition, it can be 0.05 μm or more, and can be 0.5 μm or more.

[0052] (Light transmittance of the first optical film)

[0053] Regarding the light transmittance of the first optical film 2, the transmittance of the first optical film 2 having the above-mentioned films or layers for ultraviolet light with a wavelength of 320 nm is preferably 10% to 90%.

[0054] (Phase difference layer)

[0055] The phase difference layer 31 can have one layer with phase difference, or it can have two or more layers with phase difference. When it has two or more layers, it can be a positive A plate or a positive C plate, such as a λ / 4 plate or a λ / 2 plate. When a positive C plate is included, the positive C plate can be stacked on the side closer to the polarizer layer 23, or it can be stacked on the side farther away from the polarizer layer 23.

[0056] One method for forming the phase retardation layer 31 is to first form an alignment film and then coat it with a polymeric liquid crystal compound constituting the phase retardation layer 31. When there are two or more layers with phase retardation, the separately formed phase retardation layers can be bonded together using an ultraviolet-curable adhesive. The alignment film can be either a horizontal alignment film or a vertical alignment film, depending on the type of phase retardation layer formed. A horizontal alignment film is an alignment film having an alignment restraint force that orients the polymeric liquid crystal compound constituting the phase retardation layer in a horizontal direction, while a vertical alignment film is an alignment film having an alignment restraint force that orients the polymeric liquid crystal compound constituting the phase retardation layer in a vertical direction.

[0057] The thickness of the phase retardation layer 31 is, for example, 0.1 μm to 10 μm, preferably 0.5 μm to 8 μm, and more preferably 1 μm to 6 μm.

[0058] (Light transmittance of the second optical film)

[0059] Regarding the light transmittance of the second optical film 3, the transmittance of the second optical film 3 having the above-mentioned films or layers for ultraviolet light with a wavelength of 320 nm is preferably less than 10%.

[0060] (Adhesive layer)

[0061] As the adhesive forming the adhesive layer 4, from the viewpoints of weather resistance, refractive index, and cationic polymerizability, an epoxy compound containing no aromatic ring within the molecule is preferred. The adhesive may contain a free radical polymerizable compound such as a compound having a (meth)acryloyl group. Furthermore, the adhesive is preferably an active energy radiation-cured adhesive that is cured by irradiation with active energy rays (ultraviolet light or thermal rays).

[0062] Preferred epoxy compounds include, for example, hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. A coating composition can be prepared by adding a polymerization initiator (e.g., a photocationic polymerization initiator for polymerization by ultraviolet irradiation, or a thermocationic polymerization initiator for polymerization by thermal irradiation) or further adding other additives (sensitizers, etc.).

[0063] Alternatively, water-based adhesives containing polyvinyl alcohol resins can also be used as adhesives.

[0064] The thickness of the adhesive layer 4 is preferably 0.1 μm to 5 μm, and more preferably 0.5 μm to 3 μm. It should be noted that the thickness of the adhesive layer 4 refers to the thickness at the overlapping portion of the polarizer layer 23 constituting the first optical film 2 and the second optical film 3.

[0065] <Manufacturing Method of Stacked Optical Films>

[0066] In the manufacturing method of the stacked optical film 1, such as Figure 2 and Figure 3 As shown, the first optical film 2, the adhesive layer 4, and the second optical film 3 are introduced into a pair of rotating bonding rollers 6a and 6b in a sequentially arranged direction between the bonding rollers 6a and 6b, thereby bonding the first optical film 2 and the second optical film 3. During bonding, the polarizer layer (second optical functional layer) 23 side of the first optical film 2 faces the adhesive layer 4 side.

[0067] Regarding the first optical film 2 and the second optical film 3, the optical films, which are manufactured separately, are conveyed and merged at the bonding rollers 6a and 6b. An applicator 5 for applying adhesive to the phase difference layer 31 of the second optical film 3 is disposed on the upstream side of the bonding rollers 6a and 6b.

[0068] Explain the manner in which each film or layer exists during lamination. For example... Figure 3As shown, the widths of each film or layer between the bonding rollers 6a and 6b satisfy the following relationship. It should be noted that in the following relationship, in the first optical film 2, the width of the release substrate film 21 is equal to the width of the hard coating layer 22; therefore, the width (W3) of the hard coating layer 22 has the same meaning as the width of the first optical film 2. Furthermore, in the second optical film 3, the width of the release substrate film 32 is equal to the width of the retardation layer 31; therefore, the width (W4) of the retardation layer 31 has the same meaning as the width of the second optical film 3.

[0069] The width W1 of the polarizer layer 23 is smaller than the width W3 of the hard coating layer 22. (W1 < W3)

[0070] The hard coating 22 exists with a width W1 of the inner polarizer layer 23.

[0071] The width W2 of the adhesive layer 4 is smaller than the width W3 of the hard coating layer 22. (W2 < W3)

[0072] The width W2 of the adhesive layer 4 is smaller than the width W4 of the phase retardation layer 31. (W2 < W4)

[0073] The width W2 of the adhesive layer 4 is greater than the width W1 of the polarizer layer 23. (W2 > W1)

[0074] The hard coating 22 and the phase difference layer 31 are present in a manner with a width W2 enclosing the adhesive layer 4.

[0075] • The adhesive layer 4 exists with a width W1 enclosing the polarizer layer 23.

[0076] • In the adhesive layer 4, the adhesive extends beyond both ends of the outer coating layer 24 and covers the side portions (thickness portions) of the outer coating layer 24 and the polarizer layer 23, and enters the hard coating layer 22 side, reaching the portion of the hard coating layer 22 that is wider than the polarizer layer 23.

[0077] Here, "inner enclosure" means that the two ends of the component on the wider side are located on the outer side in the width direction compared to the two ends of the component on the narrower side.

[0078] In addition, the width of each film or layer between the bonding rollers 6a and 6b also satisfies the following relationship, but it is not a necessary requirement.

[0079] • The width W4 of the retardation layer 31 is greater than the width W3 of the hard coating layer 22. (W4 > W3)

[0080] • Width (W) of a pair of bonding rollers 6a, 6b R1 W R2 They are equal to each other. (W) R1 =W R2 )

[0081] • Width (W) of a pair of bonding rollers 6a, 6b R1 W R2 It is larger than the width (W3) of the first optical film 2 and the width (W4) of the second optical film 3. R1 >W3, W R1 >W4, W R2 >W3, W R2 >W4)

[0082] • A pair of bonding rollers 6a and 6b exist in such a way that the width of the first optical film 2 (W3) and the width of the second optical film 3 (W4) are contained within them.

[0083] Here, "width of the bonding roller" refers to the total width of the portion that extends while maintaining the same diameter as the portion that serves as an effective contact surface for bonding. For example, if there is a portion of the bonding rollers 6a and 6b that is reduced in diameter in the width direction at the end side and does not contact the first optical film 2 or the second optical film 3, the width of the portion other than the reduced diameter portion is taken as the total width of the bonding rollers 6a and 6b.

[0084] Furthermore, the difference in width between the ends of each membrane or layer is preferably the distance between the ends (horizontal distance) shown below. When the central axes of each membrane or layer are aligned, the distance between the ends shown below is half the difference in width between each membrane or layer.

[0085] The horizontal distance between the end of the hard coating layer 22 and the end of the adhesive layer 4 is 0.1 mm to 50 mm, preferably 0.1 mm to 30 mm, and more preferably 0.1 mm to 15 mm.

[0086] • The horizontal distance between the end of the adhesive layer 4 and the end of the polarizer layer 23 is 0.1 mm to 50 mm.

[0087] • The horizontal distance between the end of the phase retardation layer 31 and the end of the hard coating layer 22 is 0 mm to 50 mm.

[0088] It should be noted that the values ​​mentioned above represent the distance between the ends when they are fitted together, but... Figure 1 The stacked optical films 1 shown also preferably have the same end-to-end distance.

[0089] The laminate 8 formed by bonding at the bonding rollers 6a and 6b is in an uncured state. Then, if the laminate that has passed through the bonding rollers 6a and 6b is irradiated with ultraviolet light from the ultraviolet irradiation device 7 located downstream of the bonding rollers 6a and 6b, the adhesive will cure and become solid. Figure 1The laminated optical film 1 shown (curing process). Here, when the ultraviolet transmittance of the first optical film 2 and the second optical film 3 meets the above-mentioned values, ultraviolet irradiation is preferably performed from the side of the first optical film 2.

[0090] Regarding the ultraviolet radiation exposure (cumulative light intensity in the UVA region (320–390 nm)), it is preferably set at 150 mJ / cm². 2 ~800mJ / cm 2 The irradiation is carried out in a specific manner. The irradiation can be performed in multiple stages, taking into account the degree of curing of the adhesive and the time required for curing. There are no particular limitations on the source of the ultraviolet light; ultraviolet light with a luminous distribution at wavelengths below 400 nm can be used, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

[0091] (Effect)

[0092] After the laminated optical film 1 is manufactured, further film bonding or peeling operations can be performed. For example, the release substrate film 21 can be peeled off, and a protective film can be laminated on the exposed hard coating 22. The protective film can be peelable from the hard coating 22.

[0093] In conventional methods for manufacturing laminated optical films, unfixed free ends are generated during the peeling of the release substrate film. That is, in conventional manufacturing methods, such as... Figure 4 As shown, after the first optical film 2 and the second optical film 3 are bonded together using an adhesive, forming a laminated optical film 100 from which the release substrate film 21 has been peeled off from the first optical film 2, if the width of the adhesive layer 4' is less than or equal to the width of the polarizer layer 23, the portion of the hard coating 22, polarizer layer 23, and outer coating 24 remaining after peeling that protrudes from the width of the adhesive layer 4 becomes a free end (unfixed free end 10). The unfixed free end 10 is not fixed and moves during transport, thus easily breaking and becoming a cut end during transport. The thinner the unfixed free end 10, the easier it is to break; therefore, this trend becomes significant when the combined thickness of the hard coating 22, polarizer layer 23, and outer coating 24 is thin. According to the inventors' research, it is known that when a liquid crystal coated polarizer is used, especially when the polarizer layer 23 becomes thinner, the unfixed free end 10 breaks into small pieces after the release substrate film 21 is peeled off, contaminating the transport line.

[0094] Even when a liquid crystal coated polarizer is used as the polarizer layer, as in this embodiment, unfixed free ends can still occur. However, in the manufacturing method of this embodiment, when the first optical film 2 and the second optical film 3 are bonded together using an adhesive, the adhesive bypasses the ends of the outer coating layer 24 and the polarizer layer 23 and reaches a wider surface of the hard coating layer 22. Therefore, the unfixed free ends are fixed by the adhesive, and almost no free-moving portions are generated. Thus, even after the release substrate film 21 is peeled off during the subsequent transport of the laminated optical film 1, breakage of the unfixed free ends can be suppressed. Therefore, according to the manufacturing method of this embodiment, even when a liquid crystal coated polarizer is used as the polarizer layer, the transport line will not be contaminated by the cut ends of the film during the transport of the laminated optical film.

[0095] The preferred embodiments of the present invention have been described above, but the present invention is not limited to any of the above embodiments. For example, the above embodiments show a configuration with an outer coating 24, but it is also possible to have a configuration without an outer coating 24, or to have other layers instead.

[0096] Industrial availability

[0097] This invention can be used in a method for manufacturing a polarizing plate having a liquid crystal coated polarizing film.

Claims

1. A method for manufacturing a laminated optical film, wherein, A first optical film, an adhesive layer, and a second optical film are introduced between a pair of rotating bonding rollers in a sequentially arranged manner in the direction connecting the pair of bonding rollers, thereby bonding the first optical film and the second optical film. The first optical film sequentially comprises a first optical functional layer and a second optical functional layer. The second optical functional layer is a polarizer layer containing a liquid crystal coated polarizer. When fitting, The second optical functional layer side of the first optical film faces the adhesive layer side. The width of the second optical functional layer is smaller than the width of the first optical functional layer. The first optical functional layer exists in such a way that it encloses the width of the second optical functional layer. The width of the adhesive layer is smaller than the width of the first optical functional layer and smaller than the width of the second optical film, but larger than the width of the second optical functional layer. The first optical functional layer and the second optical film are present in such a way that they enclose the adhesive layer. The adhesive layer exists in such a way that it encloses the width of the second optical functional layer, and the adhesive constituting the adhesive layer enters the first optical functional layer from both ends of the second optical functional layer to contact the first optical functional layer.

2. The manufacturing method according to claim 1, wherein, The combined thickness of the first optical functional layer and the second optical functional layer is 1 μm to 8 μm.

3. The manufacturing method according to claim 1 or 2, wherein, The width of the pair of bonding rollers is greater than the width of either the first optical film or the second optical film. The pair of bonding rollers are present in such a way that they enclose the width of the first optical film and the second optical film.

4. The manufacturing method according to claim 1 or 2, wherein, The liquid crystal coated polarizer is a cured product of a polymeric liquid crystal composition comprising a dichroic pigment and a polymeric liquid crystal compound having at least one polymeric group.

5. The manufacturing method according to claim 1 or 2, wherein, The first optical film has a release substrate film on the side of the first optical functional layer opposite to the side of the second optical functional layer. The first optical functional layer is a hard coating formed on the release substrate film.

6. The manufacturing method according to claim 1 or 2, wherein, The first optical film also has an outer coating layer applied to the second optical functional layer.

7. The manufacturing method according to claim 1 or 2, wherein, The second optical film is composed of multiple layers. The plurality of layers includes a phase difference layer.

8. The manufacturing method according to claim 1 or 2, wherein, The adhesive is an active energy radiation-cured adhesive. The manufacturing method includes a curing step in which the adhesive is cured by irradiating the laminated body that has passed between the pair of bonding rollers with active energy rays.

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