TWI820331B - Manufacturing method of thin circular polarizing plate - Google Patents

Abstract

The present invention provides a method for manufacturing a thin circularly polarizing plate that has excellent mobility during roller conveyance, suppresses adhesive deformation defects caused by tight winding during stagnation during roller conveyance, and suppresses poor appearance of the film. The manufacturing method of the circularly polarizing plate of the present invention includes: the steps of forming a liquid crystal alignment solidified layer on the surface of a substrate; the step of bonding the liquid crystal alignment solidified layer to the surface of the polarizing plate; and temporarily adhering a surface protective film to the surface of the polarizing plate in a peelable and detachable manner. The steps of placing the polarizing plate on the opposite side to the liquid crystal alignment solidified layer; the steps of peeling off the base material from the liquid crystal alignment solidified layer; the steps of forming an adhesive layer on the peeling surface of the liquid crystal alignment solidified layer; and peeling off the spacer. The step of temporarily adhering to the side of the adhesive layer opposite to the liquid crystal alignment solidified layer.

Description

Manufacturing method of thin circular polarizing plate

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

In image display devices such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs), circular polarizing plates are used for the purpose of improving display characteristics or anti-reflection. Typically, a circularly polarizing plate laminates a polarizing element and a retardation film (typically a λ/4 plate) so that the absorption axis of the polarizing element and the slow axis of the retardation film form an angle of 45°. Furthermore, in response to the demand for thinning organic EL panels, there is a demand for thinning circularly polarizing plates.

However, the previous manufacturing process of thin circular polarizers had problems such as insufficient mobility during roller conveyance, poor deformation of the adhesive due to tight winding during stagnation during roller conveyance, and the appearance of a film. bad. Prior technical literature patent documents

Patent Document 1: Japanese Patent No. 3325560

[Problem to be solved by the invention]

The present invention was completed in order to solve the above-mentioned previous problems, and its object is to provide a thin circular polarizing plate that has excellent mobility during roller conveyance, suppresses winding up during stagnation during roller conveyance, and suppresses poor appearance of the film. Manufacturing method. [Technical means to solve problems]

The manufacturing method of the circularly polarizing plate of the present invention includes: the steps of forming a liquid crystal alignment solidified layer on the surface of a substrate; the step of bonding the liquid crystal alignment solidified layer to the surface of the polarizing plate; and temporarily adhering a surface protective film to the surface of the polarizing plate in a peelable and detachable manner. The steps of placing the polarizing plate on the opposite side to the liquid crystal alignment solidified layer; the steps of peeling off the base material from the liquid crystal alignment solidified layer; the steps of forming an adhesive layer on the peeling surface of the liquid crystal alignment solidified layer; and peeling off the spacer. The step of temporarily adhering to the adhesive layer on the opposite side to the liquid crystal alignment solidified layer; and the thickness of the circular polarizing plate is less than 45 μm. In one embodiment, the surface protective film contains polyethylene resin or polyethylene terephthalate resin. In one embodiment, the thickness of the surface protective film is 25 μm or more. In one embodiment, the polarizing plate and the liquid crystal alignment solidified layer are bonded together via a photocurable adhesive. In one embodiment, the liquid crystal alignment solidified layer functions as a λ/4 plate. In one embodiment, the method further includes the step of bonding another liquid crystal alignment solidified layer to the side of the liquid crystal alignment solidified layer opposite to the polarizing plate. In one embodiment, any one of the liquid crystal alignment solidified layer and the other liquid crystal alignment solidified layer functions as a λ/2 plate, and the other functions as a λ/4 plate. [Effects of the invention]

According to the present invention, in the manufacturing method of a thin circular polarizing plate, the liquid crystal alignment solidified layer formed on the base material is bonded to the polarizing plate, and a surface protective film is temporarily adhered before peeling off the base material, so that the following can be obtained. The excellent results described. That is, in the manufacturing process of thin circular polarizing plates, the mobility during roller conveyance is excellent (for example, breakage is suppressed), and the adhesive deformation defects, adhesive dents, etc. caused by winding during stagnation during roller conveyance are suppressed. , and suppress the appearance defects of the obtained circular polarizing plate (for example, dirt on the viewing side).

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

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

A-1. Production of polarizing plate First, as shown in FIG. 1(a) , the polarizing plate 10 is prepared. The polarizing plate 10 typically includes a polarizing element and a protective layer disposed on at least one side of the polarizing element. The protective layer can also be disposed on both sides of the polarizing element. Preferably, as shown in the example of the figure, the protective layer 11 is disposed on one side of the polarizing element 12 .

A-1-1. Polarizing element As the polarizing element of the polarizing plate, any appropriate polarizing element can be used. For example, the resin film forming the polarizing element may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizing element including a single-layer resin film include hydrophilic polyvinyl alcohol (PVA, Polyvinyl Alcohol)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films. Polyene-based alignment films such as those made by dyeing and stretching using dichroic substances such as iodine or dichroic dyes, dehydrated PVA or dehydrochlorinated polyvinyl chloride, etc. In order to have excellent optical properties, it is preferable to use a polarizing element obtained by dyeing a PVA-based film with iodine and uniaxially stretching it.

The above-described dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be done after dyeing, or you can stretch while dyeing. In addition, dyeing may be performed after stretching. If necessary, the PVA film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA film in water and washing it before dyeing, not only can the dirt or anti-adhesive agent on the surface of the PVA film be washed away, but also the PVA film can be prevented from swelling and causing uneven dyeing.

Specific examples of polarizing elements obtained using a laminate include a laminate using a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and a coating. A polarizing element obtained by laminating a PVA resin layer on the resin base material. A polarizing element obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be produced, for example, as follows: a PVA-based resin solution is applied to the resin base material and dried. A PVA-based resin layer is formed on the resin base material to obtain a laminated body of the resin base material and the PVA-based resin layer; the laminated body is stretched and dyed to make the PVA-based resin layer into a polarizing element. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching. Furthermore, if necessary, the stretching may further include stretching the laminate in the air at a high temperature (for example, 95° C. or higher) before stretching in a boric acid aqueous solution. The obtained laminated body of the resin base material/polarizing element can be used directly (that is, the resin base material can also be used as a protective layer of the polarizing element), or the resin base material can be peeled off from the laminated body of the resin base material/polarizing element, and Any appropriate protective layer may be used on the peeling area layer depending on the purpose. Details of the manufacturing method of this polarizing element are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of this publication is incorporated into this specification by reference.

When a polarizing element is obtained using a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, the thickness of the polarizing element is preferably 15 μm or less, more preferably 1 μm. ~12 μm, more preferably 3 μm ~ 12 μm, particularly preferably 3 μm ~ 8 μm. When a polarizing element is obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material, the thickness of the polarizing element is preferably more than 15 μm and 40 μm or less.

A-1-2. Protective layer The protective layer is formed of any suitable film that can be used as a protective layer for the polarizing element. Examples of materials for forming the resin film include: (meth)acrylic resin, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norvinyl resin, and polypropylene. Olefin resins, ester resins such as polyethylene terephthalate resin, polyamide resins, polycarbonate resins, and copolymer resins thereof. (Meth)acrylic resin is preferred. In addition, "(meth)acrylic resin" means 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 described in, for example, Japanese Patent Application Laid-Open No. 2006-309033 and Japanese Patent Application Laid-Open No. 2006-317560 , Japanese Patent Laid-Open No. 2006-328329, Japanese Patent Laid-Open No. 2006-328334, Japanese Patent Laid-Open No. 2006-337491, Japanese Patent Laid-Open No. 2006-337492, Japanese Patent Laid-Open No. 2006-337493 , Japanese Patent Laid-Open No. 2006-337569, Japanese Patent Laid-Open No. 2007-009182, Japanese Patent Laid-Open No. 2009-161744, and Japanese Patent Laid-Open No. 2010-284840. These descriptions are incorporated into this specification as references.

The thickness of the protective layer is preferably 5 mm or less, more preferably 1 mm or less, further preferably 1 μm to 500 μm, and most preferably 5 μm to 150 μm. Furthermore, when 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 bonded to the polarizing element through any appropriate bonding layer (adhesive layer, adhesive layer).

A-2. Formation of liquid crystal alignment solidified layer Next, as shown in FIG. 1(b) , the liquid crystal alignment solidified layer 21 is bonded to the surface of the polarizing plate 10 (the polarizing element 12 in the illustrated example). Specifically, the liquid crystal alignment solidified layer 21 is formed on any appropriate base material 30 , and the laminate of the base material 30 and the liquid crystal alignment solidified layer 21 is bonded 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 the photocurable adhesive include ultraviolet curable adhesives.

The liquid crystal alignment solidified layer is an alignment solidified layer of liquid crystal compound. The liquid crystal alignment solidified layer 21 can be formed as follows: subjecting the surface of the base material 30 to alignment treatment, applying a coating liquid containing a liquid crystal compound to the surface, and aligning the liquid crystal compound in a direction corresponding to the alignment treatment. and fix the alignment state. In one embodiment, the base material is any suitable resin film. It is preferable to use triacetyl cellulose (TAC) membrane.

By using a liquid crystal compound for the above-mentioned alignment solidified layer, the difference between nx and ny of the obtained liquid crystal alignment solidified layer can be significantly larger than that of non-liquid crystal materials, so the amount of liquid crystal used to obtain the required in-plane phase difference can be significantly reduced. The thickness of the alignment solidified layer. As a result, the circular polarizing plate can be made thinner and lighter. In this specification, the so-called "alignment solidified layer" refers to a layer in which liquid crystal compounds are aligned in a specific direction within the layer, and the alignment state is fixed. In addition, the "alignment hardened layer" is a concept including the alignment hardened layer obtained by hardening a liquid crystal monomer as mentioned later. In this embodiment, it is typical that the rod-shaped liquid crystal compounds are aligned in the slow axis direction of the liquid crystal alignment solidified layer (horizontal alignment).

Examples of the liquid crystal compound include nematic liquid crystal compounds of the liquid crystal phase series (nematic liquid crystal). As this liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for expressing liquid crystallinity of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer can be used individually 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. The reason for this is that the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, if the liquid crystal monomers are polymerized or cross-linked, the alignment state can be fixed. 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 alignment solidified layer does not undergo transition to a liquid crystal phase, a glass phase, or a crystal phase due to temperature changes unique to liquid crystal compounds. As a result, the liquid crystal alignment solidified layer is not affected by temperature changes and has extremely excellent stability.

The temperature range in which a liquid crystal monomer exhibits liquid crystallinity differs depending on its 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.

As the above-mentioned liquid crystal monomer, any appropriate liquid crystal monomer can be used. For example, polymerizable liquid crystals described in Japanese Patent Publication No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. primordial compound . Specific examples of the polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferred.

As the above-mentioned alignment treatment, any appropriate alignment treatment can be adopted. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of the mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment processing include magnetic field alignment processing and electric field alignment processing. Specific examples of the chemical alignment treatment include oblique evaporation and photo-alignment treatment. The processing conditions for various alignment treatments can be any appropriate conditions depending on the purpose.

Alignment of the liquid crystal compound is performed by processing at a temperature that exhibits a liquid crystal phase according to the type of the liquid crystal compound. By performing this temperature treatment, the liquid crystal compound acquires a liquid crystal state, and the liquid crystal compound is aligned according to the direction of the alignment treatment on the surface of the substrate.

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 alignment state is fixed by subjecting the liquid crystal compound aligned 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 solidified layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated into this specification as a reference.

Another example of the liquid crystal alignment solidified layer is a form in which a disk-type liquid crystal compound is aligned in any of vertical alignment, mixed alignment, and tilt alignment. Typical examples of disc-type liquid crystal compounds are those in which the disc surface of the disc-type liquid crystal compound is aligned substantially vertically with respect to the film surface of the alignment solidified layer. The so-called disc-type liquid crystal compound is substantially vertical, which means that the average angle between the film surface and the disc surface of the disc-type liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°, and further Preferably it is 85°~90°. The so-called disc-type liquid crystal compound generally refers to a liquid crystal compound having a disc-shaped molecular structure such as benzene, 1,3,5-trifluorocarbon, calixarene, etc. The core is arranged in the center of the molecule, and linear alkyl groups, alkoxy groups, substituted benzyloxy groups, etc. are substituted radially as side chains. Typical examples of disc-type liquid crystals include benzene derivatives and dihydric compounds described in the research report of C. Destrade et al., Mol. Cryst. Liq. Cryst. Vol. 71, page 111 (1981). Diphenyl derivatives, indenacene derivatives, phthalocyanine derivatives; or cyclohexane derivatives described in the research report of B. Kohne et al., Angew. Chem. Volume 96, Page 70 (1984) ; and the research report by J. M. Lehn et al., J. Chem. Soc. Chem. Commun., page 1794 (1985), the research report by J. Zhang et al., J. Am. Chem. Soc. Volume 116, The azacorona system or the giant ring of the phenylacetylene system described on page 2655 (1994). Further specific examples of the disk-type liquid crystal compound include compounds described in Japanese Patent Application Laid-Open Nos. 2006-133652, 2007-108732, and 2010-244038. . The descriptions in the above-mentioned documents and gazettes are incorporated into this specification by reference.

As shown in Figure 1(b), when the liquid crystal alignment solidified layer includes a single layer, its thickness is preferably 0.5 μm to 7 μm, and more preferably 1 μm to 5 μm. By using a liquid crystal compound, an in-plane retardation equivalent to that of the resin film can be achieved significantly thinner than the thickness of the resin film.

In the liquid crystal alignment solidified layer, the typical refractive index characteristic shows the relationship nx>ny=nz. The liquid crystal alignment solidified layer is typically provided to provide anti-reflective properties to the polarizing plate. When the liquid crystal alignment solidified layer is a single layer, it can function as a λ/4 plate. In this case, the in-plane phase difference Re(550) of the liquid crystal alignment solidified layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and further preferably 130 nm to 160 nm. Furthermore, "ny=nz" here includes not only the situation where ny and nz are completely equal, but also the situation where they are substantially equal. Therefore, the situation of ny>nz or ny<nz may exist within the scope that does not impair the effect of the present invention.

The Nz coefficient of the liquid crystal alignment solidified layer is preferably 0.9-1.5, more preferably 0.9-1.3. By satisfying this 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 solidified layer can exhibit inverse wavelength dispersion characteristics in which the phase difference value becomes larger according to the wavelength of the measured light. It can also exhibit positive wavelength dispersion characteristics in which the phase difference value becomes smaller depending on the wavelength of the measured light. It can also exhibit phase dispersion characteristics. The difference is based on the measurement of flat wavelength dispersion characteristics with little change in the wavelength of light. In one embodiment, the liquid crystal alignment solidified layer exhibits reverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the liquid crystal alignment solidified layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. If constructed in this way, very excellent anti-reflection properties can be achieved.

The angle θ formed by the slow axis of the liquid crystal alignment solidified layer and the absorption axis of the polarizing element is preferably 40° to 50°, more preferably 42° to 48°, and further preferably about 45°. If the angle θ is within this range, by using the liquid crystal alignment solidified layer as a λ/4 plate as described above, a circularly polarizing plate having very excellent circular polarization properties (and, as a result, very excellent antireflection properties) can be obtained. Furthermore, the direction of the slow axis of the liquid crystal alignment solidified layer can correspond to the above-mentioned alignment treatment direction.

In another embodiment, the manufacturing method of the present invention is shown in FIG. 1(c) and further includes the step of bonding another liquid crystal alignment solidified layer 22 to the side of the liquid crystal alignment solidified layer 21 opposite to the polarizing plate 10 . Specifically, it is as follows. First, in the same manner as described above, another liquid crystal alignment solidified layer 22 is formed on the base material 30 . Next, in the same manner as above, the liquid crystal alignment solidified layer 21 is formed on another base material (not shown). At this time, each alignment processing direction corresponds to the slow axis direction of each alignment solidified layer described later. Next, the liquid crystal alignment solidified layer 21 is bonded to another liquid crystal alignment solidified layer 22 to prepare a laminate having the liquid crystal alignment solidified layer 21 , another liquid crystal alignment solidified layer 22 , and the base material 30 in sequence. Furthermore, the liquid crystal alignment solidified layer 21 and another liquid crystal alignment solidified layer 22 are bonded together via any appropriate adhesive. The obtained laminated body was bonded to a polarizing plate in the same manner as above. In this way, a laminated body as shown in Fig. 1(c) can be obtained.

As shown in FIG. 1(c) , when the liquid crystal alignment solidified layer 21 is bonded to another liquid crystal alignment solidified layer 22 , it is preferable that either one of the liquid crystal alignment solidified layer and the other liquid crystal alignment solidified layer serves as The λ/2 plate functions while the other functions as a λ/4 plate. Therefore, the thickness of the liquid crystal alignment solidified layer and the other liquid crystal alignment solidified layer can be adjusted in a manner to obtain the required in-plane phase difference of the λ/4 plate or the λ/2 plate. For example, when the liquid crystal alignment solidified layer functions as a λ/2 plate and the other liquid crystal alignment solidified layer functions as a λ/4 plate, the thickness of the liquid crystal alignment solidified layer is, for example, 2.0 μm to 3.0 μm, and the other liquid crystal alignment solidified layer functions as a λ/4 plate. The thickness of the solidified layer is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane phase difference Re(550) of the liquid crystal alignment solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and further preferably 250 nm to 280 nm. The in-plane phase difference Re (550) of another liquid crystal alignment solidified layer is as described above for the single-layer alignment solidified layer. The angle formed by the slow axis of the liquid crystal alignment solidified layer and the absorption axis of the polarizing element is preferably 10° to 20°, more preferably 12° to 18°, and further preferably about 15°. The angle formed by the slow phase axis of the other liquid crystal alignment solidified layer and the absorption axis of the polarizing element is preferably 70° to 80°, more preferably 72° to 78°, and further preferably about 75°. With this configuration, characteristics close to ideal reverse wavelength dispersion characteristics can be obtained, and as a result, very excellent anti-reflection characteristics can be achieved. Regarding the liquid crystal compound constituting the liquid crystal alignment solidified layer and another liquid crystal alignment solidified layer, the liquid crystal alignment solidified layer and the formation method, optical properties, etc. of the liquid crystal alignment solidified layer, are as described above for the single-layer alignment solidified layer.

A-3. Temporary adhesion of surface protective film Next, as shown in FIG. 1(d) , the surface protective film 40 is releasably and temporarily adhered to the side of the polarizing plate 10 opposite to the liquid crystal alignment solidified layer 21 . In more detail, the surface protection film 40 includes a base film and an adhesive layer, and the surface protection film 40 and the polarizing plate 10 are bonded together via the adhesive layer. Furthermore, in the following steps, the bonding of the liquid crystal alignment solidified layer 21 and another liquid crystal alignment solidified layer 22 will be described. Those skilled in the art will naturally know that the same is true even if the liquid crystal alignment solidified layer is a single layer.

The base film of the surface protective film 40 can be composed of any appropriate resin film. Examples of materials for forming the resin film include olefin resins such as polyethylene resins, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norvinyl resins, and polyamide resins. , polycarbonate resins, copolymer resins, etc. Preferred are polyethylene-based resins or polyethylene terephthalate-based resins. If this material is used, in the manufacturing process of circularly polarizing plates, it has excellent mobility during roll conveyance, can suppress adhesive deformation defects caused by winding up during stagnation in roll conveyance, and can suppress poor appearance of the film.

The thickness of the base film is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm. This thickness has the advantage of being less likely to deform even if tension is applied during transportation and/or lamination.

The tensile elastic 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 elastic modulus of the base film is within this range, in the manufacturing process of the circularly polarizing plate, the mobility during roller conveyance will be excellent, and the adhesive deformation defects caused by winding up during stagnation during roller conveyance can be suppressed. And it can suppress the poor appearance of the film.

As the adhesive forming the adhesive layer, any appropriate adhesive can be used. Examples of the matrix resin of the adhesive include acrylic resin, styrene resin, and silicone resin. From the viewpoints of chemical resistance, adhesion to prevent penetration of treatment liquid during immersion, and degree of freedom to the adherend, an acrylic resin is preferred. Examples of the cross-linking agent that may be contained in the adhesive include isocyanate compounds, epoxy compounds, and aziridine compounds. The adhesive may also 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 the thickness is, for example, 0.1 μm.

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

A-4. Peeling off the base material Next, as shown in FIG. 1(e) , the base material 30 is peeled off from the other liquid crystal alignment solidified layer 22 with the surface protective film 40 temporarily adhered. In this way, since the surface protective film is temporarily adhered before the base material is peeled off, the mobility during roll conveyance in the manufacturing process of the thin circular polarizing plate is excellent (for example, breakage is suppressed), and the stagnation during roll conveyance due to winding tightness is suppressed. It causes poor adhesive deformation, adhesive dents, etc., and suppresses poor appearance of the obtained circular polarizing plate (for example, dirt on the visible side). Furthermore, when the thickness of the surface protective film is in the range described in A-3 above, this effect becomes remarkable.

A-5. Temporary adhesion of isolation parts Next, as shown in FIGS. 1(f) and (g) , an adhesive layer 50 is formed on the peeling surface of the other liquid crystal alignment solidified layer 22 , and the spacer 60 is peelably and temporarily adhered to the adhesive layer 50 .

The adhesive layer may typically include an acrylic adhesive.

The thickness of the adhesive layer is preferably 50 μm or less, more preferably 30 μm or less, further preferably 20 μm or less. The lower limit of the thickness of the adhesive layer may be, for example, 1 μm.

The spacer protects the adhesive layer before actual use and can be formed into a roll of circularly polarizing plates.

B. Circular polarizing plate When a circularly polarizing plate is actually used, the surface protective film 40 and the spacer 60 can be peeled off from the optical laminated body shown in FIG. 1(g) obtained by the above-mentioned manufacturing method. In this way, the circular polarizing plate 100 as shown in FIG. 2 can be 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 may be, for example, 10 μm. Furthermore, the so-called thickness of the circularly polarizing plate refers to the total thickness from the polarizing plate to another liquid crystal alignment solidified layer (that is, the thickness of the circularly polarizing plate does not include the thickness of the surface protective film, adhesive layer and spacer) . Example

Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to these examples. In addition, the measurement and evaluation methods in the Examples are as follows.

(1) Migration In the step of forming the adhesive layer, the situation where the raw sheet is broken when the roller is moved, or the end of the polarizing plate is broken, broken or rolled up due to breakage is marked as ×, and the situation where no such phenomenon is observed is recorded as is 0. (2)Poor appearance Inspectors make judgments by visual inspection. Take a circular polarizing plate from the raw sheet roll, peel off the surface protective film, and mark the case where visible dirt adheres to the visible side of the circular polarizing plate as ×, and mark the case where it does not adhere as 0. (3) Deformation of the adhesive caused by tight rolling during stagnation Inspectors make judgments by visual inspection. Keep the raw sheet roll for 4 weeks, discard 3 outer rolls, use a circular polarizing plate, and attach it to a smooth blackboard (CLAREX, manufactured by Nitto Plastic Industry Co., Ltd.). The unevenness of the adhesive will be visible with full-width viewing. It is marked as ×, and the case where the adhesive unevenness is visible at less than half the width is marked as △, and the case where the adhesive unevenness is not visually recognized is marked as 0.

[Example 1] 1. Production of polarizing elements As the thermoplastic resin base material, a long amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of approximately 75°C was used. Perform corona treatment on one side of the resin substrate. A PVA system made from a 9:1 mixture of polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetyl acetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") 13 parts by weight of potassium iodide was added to 100 parts by weight of the resin, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned 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 with a thickness of 13 μm, thereby producing a laminated body. The obtained laminate was uniaxially extended to 2.4 times the free end in the longitudinal direction (long side direction) between rollers with different circumferential speeds in an oven at 130°C (air-assisted stretching treatment). Next, the laminated body was immersed in an insolubilization bath (a boric acid aqueous solution prepared by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) with a liquid temperature of 40° C. for 30 seconds (insolubilization treatment). Then, in a dyeing bath with a liquid temperature of 30° C. (an iodine aqueous solution prepared by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water), the monomer transmittance of the finally obtained polarizing element was measured ( Ts) becomes 43.0% or more, and immerse for 60 seconds (dyeing process) while adjusting the concentration. Next, it was immersed in a crosslinking bath (a boric acid aqueous solution prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) of a liquid temperature of 40° C. for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminated body in a boric acid aqueous solution with a liquid temperature of 70°C (boric acid concentration 4.0% by weight, potassium iodide concentration 5.0% by weight), it was stretched longitudinally between rolls with different circumferential speeds so that the total stretching ratio became 5.5 times. (long side direction) uniaxial stretching (water stretching treatment). Thereafter, the laminated body was immersed in a cleaning bath (an aqueous solution prepared by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) with a liquid temperature of 20° C. (washing treatment). Thereafter, while drying in an oven maintained at 90°C, it is brought into contact with a heated roller made of SUS (Steel Use Stainless, Japanese stainless steel standard) whose surface temperature is kept at 75°C for about 2 seconds (drying shrinkage treatment) . In this way, a polarizing element with a thickness of 5 μm was formed on the resin substrate.

2. Production of polarizing plates An acrylic film (surface refractive index 1.50, 20 μm) was bonded to the surface of the polarizing element obtained above (the surface opposite to the resin base material) via an ultraviolet curable adhesive as a protective layer. Specifically, the curable adhesive is applied so that the total thickness becomes 1.0 μm and bonded using a roller. Thereafter, UV (Ultraviolet, ultraviolet) light is irradiated from the protective layer side to harden the adhesive. Then, both ends were cut into long strips, and the resin base material was peeled off to obtain a long strip-shaped polarizing plate (width: 1300 mm) having a protective layer/polarizing element structure.

3. Formation of a liquid crystal alignment solidified layer and another liquid crystal alignment solidified layer. 10 g of polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula), and 10 g of polymerizable liquid crystal for this polymerization 3 g of a photopolymerization initiator of a flexible liquid crystal compound (manufactured by BASF: trade name "Irgacure 907") was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [Chemical 1] The surface of the triacetyl cellulose (TAC) film (thickness 80 μm) was rubbed with a rubbing cloth to perform alignment treatment. The direction of the alignment treatment is set to a direction that is 15° relative to the direction of the absorption axis of the polarizing element when viewed from the viewing side when it is attached to the polarizing plate. The liquid crystal compound was aligned by applying the above-mentioned liquid crystal coating liquid to the alignment-treated surface with a rod coater and heating and drying it at 90° C. for 2 minutes. The thus formed liquid crystal layer is irradiated with light of 1 mJ/cm ² using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer on the TAC film. Another liquid crystal alignment was formed on another TAC film in the same manner as above except that the coating thickness was changed and the alignment treatment direction was set to a direction of 75° with respect to the direction of the absorption axis of the polarizing element when viewed from the viewing side. solidified layer. Next, the liquid crystal alignment solidified layer is bonded to another liquid crystal alignment solidified layer, the TAC film is peeled off, and a laminate having the liquid crystal alignment solidified layer, another liquid crystal alignment solidified layer, and another TAC film in sequence is produced. Furthermore, the bonding between the liquid crystal alignment solidified layer and another liquid crystal alignment solidified layer is carried out through the ultraviolet curable adhesive (thickness 1.0 μm) used in 2. above. Next, the obtained laminate was bonded to the above-mentioned polarizing plate via the ultraviolet curable adhesive (thickness: 1.0 μm) used in 2. above. In this way, a laminated body having the composition of polarizing plate/liquid crystal alignment solidified layer/another liquid crystal alignment solidified layer/base material (another TAC film) is obtained.

4. A circularly polarizing plate was produced in the laminate obtained above, and a surface protective film (E-MASK RP109F, manufactured by Nitto Denko Co., Ltd.) was releasably and temporarily adhered to the side of the polarizing plate opposite to the liquid crystal alignment solidified layer. Thereafter, another TAC film as a base material is peeled off from another liquid crystal alignment solidified layer. An adhesive layer (acrylic adhesive, thickness: 50 μm) is formed on the peeling surface of the other liquid crystal alignment solidified layer. In the step of forming the adhesive layer, the evaluation of (1) above was performed. The spacer is peelably and temporarily adhered to the side of the adhesive layer opposite to the liquid crystal alignment solidified layer. In this way, an optical laminated body having the composition of surface protective film/polarizing plate/liquid crystal alignment solidified layer/another liquid crystal alignment solidified layer/adhesive layer/separator is obtained. The thickness of the base film of the surface protection film is 38 μm, and the thickness of the surface protection film is 48 μm. The tensile elastic modulus of the surface protective film is 2.0×10 ⁹ Pa. The obtained optical laminated body was subjected to the evaluation of the above (2) to (3). The results are shown in Table 1. Furthermore, the thickness (excluding adhesive) of the circularly polarizing plate obtained by peeling off the surface protective film and the spacer from the optical laminate was 31 μm.

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

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

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

[Example 5] As the protective layer of the polarizing plate, a cyclic olefin-based unstretched film with a hard coat layer (manufactured by Nippon Zeon Co., Ltd., thickness: 27 μm) was used instead of the acrylic-based stretched film. The procedure was carried out in the same manner as in Example 1 to obtain a product. An optical laminate with a polarizing plate attached to a long retardation layer and a hard coat layer. The obtained optical laminated body was subjected to the same evaluation as in Example 1. Furthermore, the thickness of the circularly polarizing plate excluding the adhesive obtained by peeling off the surface protective film and the spacer from the optical laminate was 38 μm.

[Comparative example 1] An optical laminated body was obtained in the same manner as in Example 1 except that a surface protective film was not used. The obtained optical laminated body was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative example 2] An optical laminated body was obtained in the same manner as in Example 5 except that a surface protective film was not used. The obtained optical laminated body was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Comparative example 2 Tensile elastic modulus (Pa) 2.0×10 ⁹ 2.0×10 ⁹ 3.0×10 ⁸ 3.0×10 ⁸ 2.0×10 ⁹ - - Thickness of base film of surface protective film (μm) 38 50 25 30 38 - - Thickness of surface protective film (μm) 48 60 25 30 48 - - migration 〇 〇 〇 〇 〇 × × Poor appearance 〇 〇 〇 〇 〇 × × Poor deformation of the adhesive caused by tight rolling during stagnation 〇 〇 △ △ 〇 × ×

[evaluation] As can be seen from Table 1, the optical laminate obtained by the Examples of the present invention has excellent mobility during roll transportation, suppresses poor deformation of the adhesive due to winding during stagnation during roll transportation, and suppresses poor appearance of the film. Furthermore, it was found that the use of a thicker surface protective film can further suppress the deformation defects of the adhesive caused by tight winding during stagnation (Comparison between Examples 1 and 2 and Examples 3 and 4). [Industrial availability]

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

10:Polarizing plate 11:Protective layer 12:Polarizing element 21: Liquid crystal alignment solidified layer 22: Another liquid crystal alignment solidified layer 30:Substrate 40:Surface protective film 50:Adhesive layer 60:Isolation piece 100: Circular polarizing plate

1(a) to 1(g) are schematic cross-sectional views for explaining a step-by-step method for manufacturing a circularly polarizing plate according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a circularly polarizing plate obtained by a manufacturing method according to an embodiment of the present invention.

10:Polarizing plate

11:Protective layer

12:Polarizing element

21: Liquid crystal alignment solidified layer

22: Another liquid crystal alignment solidified layer

30:Substrate

40:Surface protective film

50: Adhesive layer

60:Isolation piece

Claims (11)

A method for manufacturing a circularly polarizing plate, which sequentially includes: the steps of forming a liquid crystal alignment solidified layer on the surface of a substrate; the steps of bonding the liquid crystal alignment solidified layer to the surface of the polarizing plate; and temporarily adhering the surface protective film to the surface in a peelable manner. The steps of placing the polarizing plate on the opposite side to the liquid crystal alignment solidified layer; the steps of peeling off the base material from the liquid crystal alignment solidified layer; the steps of forming an adhesive layer on the peeled surface of the liquid crystal alignment solidified layer; and placing the spacer The step of releasably and temporarily adhering to the adhesive layer on the opposite side to the liquid crystal alignment solidified layer; and the thickness of the circular polarizing plate is less than 45 μm. The method of manufacturing a circularly polarizing plate according to claim 1, wherein the surface protective film contains polyethylene resin or polyethylene terephthalate resin. The method for manufacturing a circularly polarizing plate according to claim 1, wherein the thickness of the surface protective film is 25 μm or more. The method for manufacturing a circularly polarizing plate according to claim 2, wherein the thickness of the surface protective film is 25 μm or more. The manufacturing method of a circularly polarizing plate as claimed in any one of claims 1 to 4, wherein the above-mentioned polarizing plate and The liquid crystal alignment solidified layer is bonded via a photocurable adhesive. The method for manufacturing a circularly polarizing plate according to any one of claims 1 to 4, wherein the liquid crystal alignment solidified layer functions as a λ/4 plate. The method for manufacturing a circularly polarizing plate according to claim 5, wherein the liquid crystal alignment solidified layer functions as a λ/4 plate. The manufacturing method of a circularly polarizing plate according to any one of claims 1 to 4, which further includes the step of bonding another liquid crystal alignment solidified layer to the side of the liquid crystal alignment solidified layer opposite to the polarizing plate. The manufacturing method of a circularly polarizing plate as claimed in claim 5 further includes the step of bonding another liquid crystal alignment solidified layer to the side of the liquid crystal alignment solidified layer opposite to the polarizing plate. The method of manufacturing a circularly polarizing plate according to claim 8, wherein either one of the liquid crystal alignment solidified layer and the other liquid crystal alignment solidified layer functions as a λ/2 plate, and the other functions as a λ/4 plate. The method of manufacturing a circularly polarizing plate according to claim 9, wherein either one of the liquid crystal alignment solidified layer and the other liquid crystal alignment solidified layer functions as a λ/2 plate, and the other functions as a λ/4 plate.