JP7257907B2 - Manufacturing method of thin circularly polarizing plate - Google Patents

Description

The present invention relates to a method for manufacturing a thin circularly polarizing plate.

BACKGROUND ART In image display devices such as liquid crystal display devices (LCD) and organic electroluminescence display devices (OLED), circularly polarizing plates are used for the purpose of improving display characteristics and preventing reflection. A circularly polarizing plate is typically a polarizer and a retardation film (typically a λ/4 plate), and the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45°. It is layered in this way. Furthermore, due to the demand for thinner organic EL panels, thinner circularly polarizing plates are required.

However, in the conventional manufacturing process for thin circularly polarizing plates, there are problems such as insufficient runnability during roll transport, defective deformation of the adhesive due to tight winding during stagnation in roll transport, and poor appearance of the film. There is

Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and the purpose thereof is to provide excellent running performance during roll transport, suppress winding tightening during stagnation in roll transport, and improve the appearance of the film. An object of the present invention is to provide a method for manufacturing a thin circularly polarizing plate in which defects are suppressed.

The method for producing a circularly polarizing plate of the present invention includes the steps of forming a liquid crystal alignment fixed layer on the surface of a substrate, bonding the liquid crystal alignment fixed layer to the surface of a polarizing plate, and the liquid crystal alignment fixed layer of the polarizing plate. a step of releasably temporarily attaching a surface protective film to the opposite side, a step of peeling the base material from the liquid crystal alignment fixed layer, and a step of forming a pressure-sensitive adhesive layer on the peeling surface of the liquid crystal alignment fixed layer; temporarily attaching a separator releasably to the side of the pressure-sensitive adhesive layer opposite to the liquid crystal alignment solidified layer, wherein the thickness of the circularly polarizing plate is 45 μm or less.
In one embodiment, the surface protective film contains a polyethylene-based resin or a polyethylene terephthalate-based resin.
In one embodiment, the surface protective film has a thickness of 25 μm or more.
In one embodiment, the polarizing plate and the liquid crystal alignment fixed layer are bonded together via a photocurable adhesive.
In one embodiment, the liquid crystal alignment fixed layer functions as a λ/4 plate.
In one embodiment, it further includes bonding another liquid crystal alignment fixed layer to the opposite side of the liquid crystal alignment fixed layer to the polarizing plate.
In one embodiment, one of the liquid crystal alignment fixed layer and the separate liquid crystal alignment fixed layer functions as a λ/2 plate, and the other functions as a λ/4 plate.

According to the present invention, in the method for producing a thin circularly polarizing plate, the liquid crystal alignment fixed layer formed on the substrate is attached to the polarizing plate, and the surface protective film is temporarily attached before the substrate is peeled off. The following excellent effects are obtained. That is, in the manufacturing process of a thin circularly polarizing plate, it has excellent running properties during roll transport (for example, breakage is suppressed), and adhesive deformation defects, adhesive dents, etc. due to tight winding during stagnation in roll transport are suppressed. At the same time, poor appearance of the obtained circularly polarizing plate (for example, contamination on the viewing side) is suppressed.

1(a) to 1(g) are schematic cross-sectional views for explaining a method for manufacturing a circularly polarizing plate according to an embodiment of the present invention in order of steps. It is a schematic sectional drawing of the circularly-polarizing plate obtained by the manufacturing method of one Embodiment of this invention.

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

A. Method for Manufacturing Circularly Polarizing Plate FIGS. 1(a) to 1(g) are schematic cross-sectional views for explaining a method for manufacturing a circularly polarizing plate according to an embodiment of the present invention in order of steps. Hereinafter, each step of the method for manufacturing a circularly polarizing plate will be described in detail with reference to FIGS.

A-1. Preparation of Polarizing Plate First, as shown in FIG. 1(a), a polarizing plate 10 is prepared. Polarizing plate 10 typically includes a polarizer and a protective layer disposed on at least one side of the polarizer. Protective layers may be placed on both sides of the polarizer. Preferably, protective layer 11 is disposed on one side of polarizer 12, as shown.

A-1-1. Polarizer Any appropriate polarizer can be adopted as the polarizer of the polarizing plate. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. In addition, oriented polyene films such as those dyed with dichroic substances such as iodine and dichroic dyes and stretched, and dehydrated PVA and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used because of its excellent optical properties.

The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending|stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-based film be washed away, but also the PVA-based film can be swollen to remove uneven dyeing. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is obtained, for example, by applying a PVA-based resin solution to the resin base material and drying the resin base material. forming a PVA-based resin layer thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, stretching may further include stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained resin substrate/polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate. Then, any appropriate protective layer may be laminated on the release surface according to the purpose. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The publication is incorporated herein by reference in its entirety.

The thickness of the polarizer is preferably 15 μm or less when the polarizer is obtained using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate. , more preferably 1 μm to 12 μm, still more preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. The thickness of the polarizer is preferably more than 15 μm and 40 μm or less when the polarizer is obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. be.

A-1-2. Protective Layer The protective layer is formed of any suitable film that can be used as a protective layer for a polarizer. Materials for forming the resin film include, for example, (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, and polyethylene terephthalate resins. ester-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. A (meth)acrylic resin is preferred. In addition, "(meth)acrylic resin" refers to acrylic resin and/or methacrylic resin.

In one embodiment, a (meth)acrylic resin having a glutarimide structure is used as the (meth)acrylic resin. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are disclosed, for example, in JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328329, and JP-A-2006-328329. 2006-328334, JP 2006-337491, JP 2006-337492, JP 2006-337493, JP 2006-337569, JP 2007-009182, JP 2009- No. 161744 and Japanese Patent Application Laid-Open No. 2010-284840. These descriptions are incorporated herein by reference.

The thickness of the protective layer is preferably 5 mm or less, more preferably 1 mm or less, even more preferably 1 μm to 500 μm, most preferably 5 μm to 150 μm. In addition, when the surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

The protective layer is attached to the polarizer via any appropriate adhesive layer (adhesive layer, adhesive layer).

A-2. Formation of Liquid Crystal Alignment Fixed Layer Next, as shown in FIG. 1B, a liquid crystal alignment fixed layer 21 is adhered to the surface of the polarizing plate 10 (the polarizer 12 in the illustrated example). Specifically, the liquid crystal alignment fixed layer 21 is formed on any appropriate base material 30 , and the laminate of the base material 30 and the liquid crystal alignment fixed layer 21 is attached to the polarizing plate 10 . The liquid crystal alignment solidified layer and the polarizing plate are typically bonded together via a photocurable adhesive. Examples of photocurable adhesives include ultraviolet curable adhesives.

The liquid crystal alignment fixed layer is a liquid crystal compound alignment fixed layer. The liquid crystal alignment fixed layer 21 is formed by subjecting the surface of the substrate 30 to an alignment treatment, coating the surface with a coating liquid containing a liquid crystal compound, and aligning the liquid crystal compound in a direction corresponding to the alignment treatment. It can be formed by fixing the orientation state. In one embodiment, the substrate is any suitable resin film. Preferably, a triacetylcellulose (TAC) film is used.

By using a liquid crystal compound for the alignment fixed layer, the difference between nx and ny of the obtained liquid crystal alignment fixed layer can be remarkably increased compared to a non-liquid crystal material. The thickness of the liquid crystal alignment fixed layer can be remarkably reduced. As a result, the thickness and weight of the circularly polarizing plate can be reduced. As used herein, the term "fixed alignment layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction and the alignment state is fixed. In addition, the "alignment fixed layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the liquid crystal alignment fixed layer (homogeneous alignment).

Examples of liquid crystal compounds include liquid crystal compounds whose liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. Either lyotropic or thermotropic mechanism may be used to develop the liquid crystallinity of the liquid crystal compound. The liquid crystal polymer and liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, the alignment state can be fixed by polymerizing or cross-linking the liquid crystal monomers. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by cross-linking, but these are non-liquid crystalline. Therefore, the formed liquid crystal orientation fixed layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a change in temperature, which is peculiar to liquid crystalline compounds. As a result, the liquid crystal alignment fixed layer is not affected by temperature changes and is extremely stable.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

Any appropriate liquid crystal monomer can be employed as the liquid crystal monomer. For example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such polymerizable mesogenic compounds include LC242 (trade name) available from BASF, E7 (trade name) available from Merck, and LC-Sillicon-CC3767 (trade name) available from Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

Any appropriate alignment treatment may be adopted as the alignment treatment. Specific examples include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of physical orientation treatment include magnetic orientation treatment and electric field orientation treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photo-alignment treatment. Arbitrary appropriate conditions can be adopted as the processing conditions for various alignment treatments depending on the purpose.

Alignment of the liquid crystal compound is performed by treatment at a temperature at which a liquid crystal phase is exhibited depending on the type of liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is aligned in accordance with the orientation treatment direction of the surface of the base material.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the alignment fixed layer are described in JP-A-2006-163343. The description of the publication is incorporated herein by reference.

Another example of the liquid crystal alignment fixed layer includes a form in which a discotic liquid crystal compound is aligned in any one of vertical alignment, hybrid alignment, and tilt alignment. A discotic liquid crystal compound typically has a discotic surface aligned substantially perpendicularly to the film surface of the alignment fixing layer. When the discotic liquid crystal compound is substantially perpendicular, the average angle between the film surface and the disk surface of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°. , more preferably 85° to 90°. Discotic liquid crystal compounds generally have a cyclic mother nucleus such as benzene, 1,3,5-triazine, or calixarene at the center of the molecule, and a linear alkyl group, alkoxy group, or substituted benzoyl A liquid crystal compound having a discotic molecular structure in which oxy groups and the like are radially substituted as side chains. Representative examples of discotic liquid crystals include C.I. Destrade et al., Mol. Cryst. Liq. Cryst. 71, 111 (1981), benzene derivatives, triphenylene derivatives, truxene derivatives and phthalocyanine derivatives; Kohne et al., Angew. Chem. 96, 70 (1984) and cyclohexane derivatives described in J. Am. M. In the report of Lehn et al., J. Am. Chem. Soc. Chem. Commun. , 1794 (1985); In the report of Zhang et al., J. Am. Am. Chem. Soc. 116, 2655 (1994), azacrown-based and phenylacetylene-based macrocycles. Further specific examples of discotic liquid crystal compounds include compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The descriptions in the above documents and publications are incorporated herein by reference.

When the liquid crystal alignment fixing layer is composed of a single layer as shown in FIG. 1(b), its thickness is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using a liquid crystal compound, it is possible to realize an in-plane retardation equivalent to that of a resin film with a thickness much thinner than that of a resin film.

The liquid crystal alignment fixed layer typically exhibits a refractive index characteristic of nx>ny=nz. The liquid crystal alignment fixed layer is typically provided to impart antireflection properties to the polarizing plate, and when the liquid crystal alignment fixed layer is a single layer, it can function as a λ/4 plate. In this case, the in-plane retardation Re(550) of the liquid crystal alignment fixed layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, still more preferably 130 nm to 160 nm. Here, "ny=nz" includes not only the case where ny and nz are completely equal but also the case where they are substantially equal. Therefore, ny>nz or ny<nz may be satisfied within a range that does not impair the effects of the present invention.

The Nz coefficient of the liquid crystal alignment fixed layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained circularly polarizing plate is used in an image display device, a very excellent reflection hue can be achieved.

The liquid crystal alignment fixed layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, or exhibits a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. Alternatively, it may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes even with the wavelength of the measurement light. In one embodiment, the liquid crystal alignment fixed layer exhibits reverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the liquid crystal alignment fixed layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection properties can be achieved.

The angle θ between the slow axis of the liquid crystal alignment fixed layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably about 45°. . If the angle θ is in such a range, by using the liquid crystal alignment fixed layer as a λ / 4 plate as described above, it has very excellent circularly polarized light properties (as a result, very excellent antireflection properties). A circular polarizer can be obtained. In addition, the slow axis direction of the liquid crystal alignment fixed layer can correspond to the alignment treatment direction.

In another embodiment, the manufacturing method of the present invention further includes bonding another liquid crystal alignment solid layer 22 to the opposite side of the liquid crystal alignment solid layer 21 to the polarizing plate 10 as shown in FIG. 1(c). . Specifically, it is as follows. First, another liquid crystal alignment fixed layer 22 is formed on the substrate 30 in the same manner as described above. Next, the liquid crystal alignment fixed layer 21 is formed on another substrate (not shown) in the same manner as described above. At this time, each orientation processing direction corresponds to the slow axis direction of each orientation fixed layer described later. Next, the liquid crystal alignment fixed layer 21 is bonded to another liquid crystal alignment fixed layer 22 to produce a laminate having the liquid crystal alignment fixed layer 21, another liquid crystal alignment fixed layer 22, and the substrate 30 in this order. Note that the liquid crystal alignment fixed layer 21 and another liquid crystal alignment fixed layer 22 are bonded together via any appropriate adhesive. The laminate thus obtained is attached to a polarizing plate in the same manner as described above. Thus, a laminate as shown in FIG. 1(c) is obtained.

When the liquid crystal alignment fixed layer 21 and another liquid crystal alignment fixed layer 22 are laminated together as shown in FIG. /2 plate and the other as a λ/4 plate. Therefore, the thickness of the liquid crystal alignment fixed layer and the separate liquid crystal alignment fixed layer can be adjusted so as to obtain the desired in-plane retardation of the λ/4 plate or the λ/2 plate. For example, when the liquid crystal alignment fixed layer functions as a λ/2 plate and another liquid crystal alignment fixed layer functions as a λ/4 plate, the thickness of the liquid crystal alignment fixed layer is, for example, 2.0 μm to 3.0 μm. The thickness of the liquid crystal alignment fixed layer is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re(550) of the liquid crystal alignment fixed layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, still more preferably 250 nm to 280 nm. The in-plane retardation Re(550) of the alternative liquid crystal alignment fixed layer is as described above for the single layer alignment fixed layer. The angle formed by the slow axis of the liquid crystal alignment fixed layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, still more preferably about 15°. The angle formed by the slow axis of another liquid crystal alignment fixed layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably about 75°. be. With such a configuration, it is possible to obtain characteristics close to ideal reverse wavelength dispersion characteristics, and as a result, very excellent antireflection characteristics can be realized. The liquid crystal compounds constituting the liquid crystal alignment fixed layer and another liquid crystal alignment fixed layer, the method of forming the liquid crystal alignment fixed layer and the liquid crystal alignment fixed layer, the optical characteristics, etc. are as described above for the single-layer alignment fixed layer. .

A-3. Temporary attachment of surface protection film
Next, as shown in FIG. 1(d), a surface protective film 40 is temporarily adhered to the opposite side of the polarizing plate 10 from the liquid crystal alignment solidified layer 21 so as to be peelable. More specifically, the surface protective film 40 includes a base film and an adhesive layer, and the surface protective film 40 and the polarizing plate 10 are attached via the adhesive layer. In the subsequent steps, the case where the liquid crystal alignment fixed layer 21 and another liquid crystal alignment fixed layer 22 are bonded together will be described, but it will be understood by those skilled in the art that the liquid crystal alignment fixed layer is the same even if the liquid crystal alignment fixed layer is a single layer. is self-evident.

A base film of the surface protection film 40 may be composed of any appropriate resin film. Materials for forming the resin film include olefin resins such as polyethylene resins, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, polyamide resins, polycarbonate resins, and copolymers thereof. Resin etc. are mentioned. A polyethylene-based resin or a polyethylene terephthalate-based resin is preferable. With such a material, in the manufacturing process of the circularly polarizing plate, the runnability during roll transport is excellent, adhesive deformation defects due to tight winding during stagnation in roll transport are suppressed, and poor appearance of the film can be suppressed. .

The thickness of the base film is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm. With such a thickness, there is an advantage that deformation is less likely to occur even if tension is applied during transportation and/or lamination.

The tensile modulus of the base film is preferably 1.0×10 ⁸ Pa to 5.0×10 ⁹ Pa, more preferably 2.0×10 ⁸ Pa to 3.0×10 ⁹ Pa. If the tensile modulus of the base film is within such a range, in the manufacturing process of the circularly polarizing plate, the running property during roll transport is excellent, and deformation defects of the adhesive due to tight winding during stagnation in roll transport are suppressed. Poor appearance of the film can be suppressed.

Any appropriate pressure-sensitive adhesive may be employed as the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer. Examples of base resins for adhesives include acrylic resins, styrene resins, and silicone resins. Acrylic resins are preferred from the viewpoints of chemical resistance, adhesiveness for preventing infiltration of the treatment liquid during immersion, flexibility to the adherend, and the like. Cross-linking agents that can be contained in the adhesive include, for example, isocyanate compounds, epoxy compounds, and aziridine compounds. The adhesive may contain, for example, a silane coupling agent. The formulation of the adhesive can be appropriately set according to the purpose.

The thickness of the adhesive layer is preferably 3 µm or less, more preferably 1 µm or less. The lower limit of thickness is, for example, 0.1 μm.

The thickness of the surface protection film is preferably 25 μm or more, more preferably 30 μm or more, and still more preferably 35 μm or more. The upper limit of the thickness of the surface protective film may be, for example, 100 μm. In addition, the thickness of the surface protection film refers to the total thickness of the base film and the pressure-sensitive adhesive layer.

A-4. Detachment of Substrate Next, as shown in FIG. 1(e), the substrate 30 is detached from the liquid crystal alignment solidified layer 22 with the surface protective film 40 temporarily attached. Thus, by temporarily attaching the surface protective film before peeling off the base material, excellent running properties during roll transport in the manufacturing process of the thin circularly polarizing plate (for example, breakage is suppressed), and during roll transport Defective deformation of the adhesive and dents of the adhesive due to tight winding during stagnation are suppressed, and poor appearance of the obtained circularly polarizing plate (for example, contamination on the viewing side) is suppressed. Furthermore, when the thickness of the surface protection film is within the range described in A-3 above, such effects become remarkable.

A-5. Temporary attachment of separator Next, as shown in FIGS. 1( f ) and ( g ), an adhesive layer 50 is formed on the release surface of another liquid crystal alignment fixed layer 22 , and the separator 60 can be peeled off from the adhesive layer 50 . to wear temporary clothes.

The pressure-sensitive adhesive layer can typically be composed of an acrylic pressure-sensitive adhesive.

The thickness of the adhesive layer is preferably 50 µm or less, more preferably 30 µm or less, and even more preferably 20 µm or less. The lower limit of the thickness of the pressure-sensitive adhesive layer can be, for example, 1 μm.

The separator protects the pressure-sensitive adhesive layer until it is actually used, and enables roll formation of the circularly polarizing plate.

B. Circularly Polarizing Plate When the circularly polarizing plate is actually used, the surface protective film 40 and the separator 60 can be peeled off from the optical layered body shown in FIG. 1(g) obtained by the above manufacturing method. Thus, a circularly polarizing plate 100 as shown in FIG. 2 is obtained. The thickness of the circularly polarizing plate is 45 μm or less, preferably 40 μm or less. The lower limit of the thickness of the circularly polarizing plate can be, for example, 10 μm. The thickness of the circularly polarizing plate refers to the total thickness from the polarizing plate to another liquid crystal alignment fixed layer (that is, the thickness of the circularly polarizing plate does not include the thickness of the surface protective film, the adhesive layer and the separator. ).

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The measurement and evaluation methods in the examples are as follows.

(1) Runnability In the process of forming the adhesive layer, X was given when the raw material was broken during roll running, and the polarizing plate was bent, torn, or turned over, leading to breakage.
(2) Poor Appearance Determined visually by an inspector. When the circularly polarizing plate was collected from the raw fabric roll and the surface protective film was peeled off, the case where visible dirt adhered to the viewing side of the circularly polarizing plate was evaluated as ×, and the case where there was no dirt was evaluated as ◯.
(3) Adhesive Deformation Defects Due to Tight Winding During Stagnating This was determined visually by an inspector. After storing the original roll for 4 weeks and discarding 3 outer windings, the circularly polarizing plate was collected and pasted on a smooth blackboard (manufactured by Nitto Jushi Kogyo Co., Ltd., CLAREX). The case where the unevenness of the adhesive was visually recognized was evaluated as Δ, and the case where the unevenness of the adhesive was not visually recognized was evaluated as ◯.

[Example 1]
1. Fabrication of Polarizer As a thermoplastic resin substrate, an amorphous isophthalate-copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of about 75° C. was used. . Corona treatment was applied to one side of the resin substrate.
Polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z410") mixed at 9:1: 100 weight of PVA-based resin 13 parts by weight of potassium iodide was added to parts by weight, and dissolved in water to prepare an aqueous PVA solution (coating solution).
The above PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Then, the finally obtained polarizer is added to a dyeing bath (iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 43.0% or more (dyeing treatment).
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 40°C (an aqueous solution of boric acid obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, the laminate is immersed in an aqueous solution of boric acid (boric acid concentration: 4.0% by weight, potassium iodide concentration: 5.0% by weight) at a liquid temperature of 70 ° C., and is moved between rolls with different peripheral speeds in the longitudinal direction (longitudinal direction). direction) was uniaxially stretched so that the total draw ratio was 5.5 times (underwater stretching treatment).
After that, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (washing treatment).
After that, while drying in an oven kept at 90° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75° C. for about 2 seconds (drying shrinkage treatment).
Thus, a polarizer having a thickness of 5 μm was formed on the resin substrate.

2. Preparation of polarizing plate On the surface of the polarizer obtained above (the surface opposite to the resin base material), an acrylic film (surface refractive index 1.50, 20 μm) as a protective layer, and an ultraviolet curable adhesive is applied. pasted together through Specifically, the curable adhesive was applied so as to have a total thickness of 1.0 μm, and was bonded using a roll machine. After that, UV rays were applied from the protective layer side to cure the adhesive. Next, after slitting both ends, the resin substrate was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of protective layer/polarizer.

トリアセチルセルロース（ＴＡＣ）フィルム（厚み８０μｍ）表面を、ラビング布を用いてラビングし、配向処理を施した。配向処理の方向は、偏光板に貼り合わせる際に偏光子の吸収軸の方向に対して視認側から見て１５°方向となるようにした。この配向処理表面に、上記液晶塗工液をバーコーターにより塗工し、９０℃で２分間加熱乾燥することによって液晶化合物を配向させた。このようにして形成された液晶層に、メタルハライドランプを用いて１ｍＪ/ｃｍ^２の光を照射し、当該液晶層を硬化させることによって、ＴＡＣフィルム上に液晶配向固化層を形成した。
塗工厚みを変更したこと、および、配向処理方向を偏光子の吸収軸の方向に対して視認側から見て７５°方向となるようにしたこと以外は上記と同様にして、別のＴＡＣフィルム上に別の液晶配向固化層を形成した。
次に、液晶配向固化層を別の液晶配向固化層に貼り合わせ、ＴＡＣフィルムを剥離し、液晶配向固化層と別の液晶配向固化層と別のＴＡＣフィルムとをこの順に有する積層体を作製した。なお、液晶配向固化層と別の液晶配向固化層との貼り合わせは、上記２．で用いた紫外線硬化型接着剤（厚み１．０μｍ）を介して行った。次に、得られた積層体を上記２．で用いた紫外線硬化型接着剤（厚み１．０μｍ）を介して上記偏光板に貼り合わせた。このようにして、偏光板／液晶配向固化層／別の液晶配向固化層／基材（別のＴＡＣフィルム）の構成を有する積層体を得た。 3. Formation of liquid crystal alignment fixed layer and another liquid crystal alignment fixed layer Polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name “Paliocolor LC242”, represented by the following formula) 10 g and light for the polymerizable liquid crystal compound A liquid crystal composition (coating liquid) was prepared by dissolving 3 g of a polymerization initiator (trade name “Irgacure 907” manufactured by BASF) in 40 g of toluene.

The surface of a triacetyl cellulose (TAC) film (thickness: 80 μm) was rubbed with a rubbing cloth for orientation treatment. The direction of the orientation treatment was set to be 15° from the direction of the absorption axis of the polarizer when viewed from the viewing side when attached to the polarizing plate. The above liquid crystal coating solution was applied to the alignment-treated surface using a bar coater, and dried by heating at 90° C. for 2 minutes to align the liquid crystal compound. The thus formed liquid crystal layer was irradiated with light of 1 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a liquid crystal alignment fixed layer on the TAC film.
Another TAC film was prepared in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was set to be 75° from the viewing side with respect to the direction of the absorption axis of the polarizer. Another liquid crystal alignment fixing layer was formed thereon.
Next, the liquid crystal alignment fixed layer was laminated to another liquid crystal alignment fixed layer, the TAC film was peeled off, and a laminate having the liquid crystal alignment fixed layer, another liquid crystal alignment fixed layer, and another TAC film in this order was produced. . The bonding of the liquid crystal alignment fixed layer and another liquid crystal alignment fixed layer is the same as in 2. above. It was performed through the ultraviolet curable adhesive (thickness 1.0 μm) used in . Next, the laminate thus obtained is subjected to the above 2. was attached to the polarizing plate via the ultraviolet curable adhesive (thickness: 1.0 μm) used in . Thus, a laminate having a configuration of polarizing plate/solidified liquid crystal alignment layer/another fixed layer for liquid crystal alignment/substrate (another TAC film) was obtained.

4. Preparation of Circularly Polarizing Plate In the laminate obtained above, a surface protective film (E-MASK RP109F, manufactured by Nitto Denko) was temporarily adhered releasably to the opposite side of the polarizing plate to the liquid crystal alignment fixed layer. After that, another TAC film as a substrate was peeled off from another liquid crystal alignment solidified layer. A pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive, thickness: 50 μm) was formed on the release surface of the separate liquid crystal alignment solidified layer. In the process of forming the pressure-sensitive adhesive layer, the above (1) was evaluated. A separator was temporarily adhered releasably to the side of the pressure-sensitive adhesive layer opposite to the liquid crystal alignment solidified layer. Thus, an optical laminate having a structure of surface protective film/polarizing plate/solidified liquid crystal alignment layer/another fixed layer for liquid crystal alignment/adhesive layer/separator was obtained. The thickness of the base film of the surface protection film was 38 μm, and the thickness of the surface protection film was 48 μm. The tensile elastic modulus of the surface protective film was 2.0×10 ⁹ Pa. The obtained optical layered body was subjected to the evaluations (2) to (3) above. Table 1 shows the results. The thickness of the circularly polarizing plate obtained by peeling off the surface protective film and the separator from the optical layered body (excluding the adhesive) was 31 μm.

[Example 2]
An optical laminate was obtained in the same manner as in Example 1, except that E-MASK RP149C (manufactured by Nitto Denko Corporation) was used as the surface protective film. The thickness of the base film of the surface protective film was 50 μm, and the thickness of the surface protective film was 60 μm. The tensile elastic modulus of the surface protective film was 2.0×10 ⁹ Pa. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 3]
An optical laminate was obtained in the same manner as in Example 1, except that Toraytec 7832E (manufactured by Toray Industries, Inc.) was used as the surface protective film. The thickness of the base film of the surface protection film and the thickness of the surface protection film were 25 μm. The tensile elastic modulus of the surface protective film was 3.0×10 ⁸ Pa. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 4]
An optical laminate was obtained in the same manner as in Example 1, except that Toraytec 7832C (manufactured by Toray Industries, Inc.) was used as the surface protective film. The thickness of the base film of the surface protection film and the thickness of the surface protection film were 30 μm. The tensile elastic modulus of the surface protective film was 3.0×10 ⁸ Pa. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 5]
In the same manner as in Example 1, except that a cycloolefin-based unstretched film with a hard coat layer (manufactured by Nippon Zeon Co., Ltd., thickness: 27 μm) was used instead of the stretched acrylic film as the protective layer of the polarizing plate. An optical laminate, which is a polarizing plate with a retardation layer and a hard coat layer, was obtained. The obtained optical layered body was subjected to the same evaluation as in Example 1. The thickness of the circularly polarizing plate excluding the pressure-sensitive adhesive obtained by peeling off the surface protective film and separator from the optical layered body was 38 μm.

[Comparative Example 1]
An optical laminate was obtained in the same manner as in Example 1, except that no surface protection film was used. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Comparative Example 2]
An optical laminate was obtained in the same manner as in Example 5, except that no surface protection film was used. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[evaluation]
As is clear from Table 1, the optical laminates obtained in the examples of the present invention are excellent in running properties during roll transport, suppress adhesive deformation defects due to tight winding during stagnation in roll transport, and improve film quality. It can be seen that the poor appearance is suppressed. Furthermore, it can be seen that the use of a thick surface protection film suppresses poor adhesive deformation due to tight winding during stagnation (comparison between Examples 1 and 2 and Examples 3 and 4).

The circularly polarizing plate obtained by the manufacturing method of the present invention is suitably used for image display devices such as liquid crystal display devices (LCD) and organic electroluminescence display devices (OLED).

REFERENCE SIGNS LIST 10 polarizing plate 11 protective layer 12 polarizer 21 liquid crystal alignment fixed layer 22 another liquid crystal alignment fixed layer 30 substrate 40 surface protective film 50 adhesive layer 60 separator 100 circularly polarizing plate

Claims (7)

A method for manufacturing a circularly polarizing plate,
A step of forming a liquid crystal alignment fixed layer on the substrate surface;
a step of bonding the liquid crystal alignment solidified layer to the surface of a polarizing plate;
a step of temporarily attaching a surface protective film to the opposite side of the polarizing plate from the liquid crystal alignment solidified layer in a peelable manner;
a step of peeling the substrate from the liquid crystal alignment solidified layer;
forming a pressure-sensitive adhesive layer on the release surface of the liquid crystal alignment solidified layer;
temporarily attaching a separator to the side of the pressure-sensitive adhesive layer opposite to the liquid crystal alignment solidified layer in a releasable manner ,
The thickness of the circularly polarizing plate is 45 μm or less,
A method for manufacturing a circularly polarizing plate. 2. The method for producing a circularly polarizing plate according to claim 1, wherein the surface protection film contains a polyethylene-based resin or a polyethylene terephthalate-based resin. 3. The method for producing a circularly polarizing plate according to claim 1, wherein the surface protective film has a thickness of 25 [mu]m or more. 4. The method for producing a circularly polarizing plate according to claim 1, wherein said polarizing plate and said liquid crystal alignment fixed layer are bonded together via a photocurable adhesive. 5. The method for producing a circularly polarizing plate according to claim 1, wherein said liquid crystal alignment fixed layer functions as a λ/4 plate. 5. The method for producing a circularly polarizing plate according to claim 1, further comprising bonding another liquid crystal alignment fixed layer to the opposite side of the liquid crystal alignment fixed layer to the polarizing plate. 7. The method for producing a circularly polarizing plate according to claim 6, wherein one of said liquid crystal alignment fixed layer and said another liquid crystal alignment fixed layer functions as a [lambda]/2 plate, and the other functions as a [lambda]/4 plate.

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