TW202106518A - Method for producing thin circularly polarizing plate - Google Patents

Abstract

The present invention provides a method for producing a thin circularly polarizing plate, said method exhibiting excellent travel ability during roll conveyance, while being suppressed in adhesive deformation defects due to tight winding during stagnation of the roll conveyance, thereby being suppressed in appearance defects of a film. A method for producing a circularly polarizing plate according to the present invention comprises: a step for forming a liquid crystal alignment fixing layer on the surface of a base material; a step for bonding the liquid crystal alignment fixing layer to the surface of a polarizing plate; a step for provisionally bonding a surface protective film to a surface of the polarizing plate in a removable manner, said surface being on the reverse side from the liquid crystal alignment fixing layer; a step for removing the base material from the liquid crystal alignment fixing layer; a step for forming an adhesive layer on the removal surface of the liquid crystal alignment fixing layer; and a step for provisionally bonding a separator to a surface of the adhesive layer in a removable manner, said surface being on the reverse side from the liquid crystal alignment fixing layer.

Description

Manufacturing method of thin circular polarizing plate

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

In image display devices such as LCD (Liquid Crystal Display) and Organic Electroluminescence Display (OLED), circular polarizing plates are used for the purpose of improving display characteristics or anti-reflection. The circular polarizing plate is typically laminated with a polarizing element and a retardation film (typically a λ/4 plate) such that the absorption axis of the polarizing element and the retardation axis of the retardation film form an angle of 45°. Furthermore, in accordance with the demand for the thinning of organic EL panels, the thinning of the circular polarizing plate is required.

However, in the previous manufacturing steps of thin circular polarizers, there are problems such as insufficient mobility during roller conveyance, and poor deformation of the adhesive caused by winding up during roller conveyance, and the appearance of the film bad. Prior art literature Patent literature

Patent Document 1: Japanese Patent No. 3325560

[The problem to be solved by the invention]

The present invention was completed to solve the above-mentioned previous problems, and its purpose 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. Production method. [Technical means to solve the problem]

The manufacturing method of the circular polarizing plate of the present invention includes: forming a liquid crystal alignment cured layer on the surface of a substrate; attaching the liquid crystal alignment cured layer to the surface of the polarizing plate; temporarily attaching the surface protection film to the The step of polarizing plate and the liquid crystal alignment cured layer on the opposite side; the step of peeling the substrate from the liquid crystal alignment cured layer; the step of forming an adhesive layer on the peeling surface of the liquid crystal alignment cured layer; and the separator can be peeled off The step of temporarily adhering to the adhesive layer on the opposite side of the liquid crystal alignment cured layer; and the thickness of the circular polarizing plate is 45 μm or less. In one embodiment, the said surface protective film contains a polyethylene resin or a polyethylene terephthalate resin. In one embodiment, the thickness of the surface protection film is 25 μm or more. In one embodiment, the polarizing plate and the liquid crystal alignment cured layer are bonded via a photocurable adhesive. In one embodiment, the liquid crystal alignment cured layer functions as a λ/4 plate. In one embodiment, it further includes the step of bonding another liquid crystal alignment cured layer to the opposite side of the liquid crystal alignment cured layer to the polarizing plate. In one embodiment, any one of the liquid crystal alignment cured layer and the other liquid crystal alignment cured layer functions as a λ/2 plate, and the other functions as a λ/4 plate. [Effects of Invention]

According to the present invention, in the manufacturing method of the thin circular polarizing plate, the liquid crystal alignment cured layer formed on the substrate is attached to the polarizing plate, and the surface protection film is temporarily adhered before peeling off the substrate, thereby obtaining the following The excellent effect described. That is, in the manufacturing process of the thin circular polarizing plate, the roll conveyance is excellent (for example, breakage is suppressed), and the deformation of the adhesive caused by the winding tightness during the stagnation of the roll conveying is suppressed, the adhesive dents, etc. , And suppress the poor appearance of the obtained circular polarizing plate (for example, the dirt on the visual recognition side).

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

A. Manufacturing method of circular polarizing plate 1(a) to (g) are schematic cross-sectional views for explaining the manufacturing method of the circular polarizing plate according to one embodiment of the present invention in the order of steps. Hereinafter, referring to FIGS. 1(a) to (g), each step of the method of manufacturing a circular polarizing plate will be described in detail.

A-1. Making of polarizing plate First, as shown in FIG. 1(a), a 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 arranged on both sides of the polarizing element. Preferably, as shown in the example in 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 suitable 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.

As a specific example of a polarizing element comprising a single-layer resin film, there may be mentioned hydrophilic polyvinyl alcohol (PVA, Polyvinyl Alcohol) film, partially formalized PVA film, ethylene-vinyl acetate copolymer partially saponified film, etc. Polyene-based oriented films such as dyeing treatments and stretching treatments using dichroic substances such as iodine or dichroic dyes, and polyene-based alignment films such as dehydrated PVA or dehydrochlorinated polyvinyl chloride. In terms of excellent optical properties, it is preferable to use a polarizing element obtained by dyeing a PVA-based film with iodine and performing uniaxial stretching.

The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching magnification of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be done after dyeing, or it can be stretched while dyeing. Also, dyeing may be performed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt or anti-blocking agent on the surface of the PVA-based film be cleaned, but it can also prevent the PVA-based film from swelling and uneven dyeing.

As a specific example of a polarizing element obtained using a laminate, 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 coating formation can be mentioned. The polarizing element obtained by the laminate of the PVA-based resin layer of the resin substrate. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, as follows: a PVA-based resin solution is applied to the resin substrate, and then dried. A PVA-based resin layer is formed on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is extended and dyed to form the PVA-based resin layer into a polarizing element. In the present embodiment, stretching typically includes stretching the laminate by immersing the laminate in an aqueous solution of boric acid. Furthermore, the stretching may further include stretching the laminated body at a high temperature (for example, 95°C or higher) in the air before stretching in a boric acid aqueous solution, if necessary. The obtained resin substrate/polarizing element laminate can be used directly (that is, the resin substrate can also be used as the protective layer of the polarizing element), or the resin substrate can be peeled from the resin substrate/polarizing element laminate, and Any appropriate protective layer for the peeling area layer is used according to the purpose. The details of the manufacturing method of this polarizing element are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of this gazette is incorporated into this specification as a reference.

When using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate to obtain a polarizing element, the thickness of the polarizing element is preferably 15 μm or less, more preferably 1 μm ~12 μm, more preferably 3 μm to 12 μm, particularly preferably 3 μm to 8 μm. When a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate is used to obtain a polarizing element, 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 of the polarizing element. Examples of materials for forming the resin film include (meth)acrylic resins, cellulosic resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norene-based resins, and polypropylene. Olefin resins, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins of these. Preferably it is a (meth)acrylic resin. In addition, the term "(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. The (meth)acrylic resin having a glutarimide structure (hereinafter also referred to as glutarimide resin) is described in, for example, Japanese Patent Laid-Open No. 2006-309033 and Japanese Patent Laid-Open No. 2006-317560 , Japanese Patent Application Publication No. 2006-328329, Japanese Patent Application Publication No. 2006-328334, Japanese Patent Application Publication No. 2006-337491, Japanese Patent Application Publication No. 2006-337492, Japanese Patent Application Publication No. 2006-337493 , Japanese Patent Application Publication No. 2006-337569, Japanese Patent Application Publication No. 2007-009182, Japanese Patent Application Publication No. 2009-161744, Japanese Patent Application Publication No. 2010-284840. These descriptions are cited in this specification as a reference.

The thickness of the protective layer is preferably 5 mm or less, more preferably 1 mm or less, still more preferably 1 μm to 500 μm, most preferably 5 μm to 150 μm. Furthermore, in the case of surface treatment, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

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

A-2. Formation of liquid crystal alignment cured layer Next, as shown in FIG. 1(b), the liquid crystal alignment cured layer 21 is attached to the surface of the polarizing plate 10 (the polarizing element 12 in the example of the figure). Specifically, the liquid crystal alignment cured layer 21 is formed on any appropriate substrate 30, and the laminate of the substrate 30 and the liquid crystal alignment cured layer 21 is bonded to the polarizing plate 10. The liquid crystal alignment cured layer and the polarizing plate are typically bonded via a photocurable adhesive. As a photocurable adhesive agent, an ultraviolet curable adhesive agent can be mentioned, for example.

The liquid crystal alignment cured layer is an alignment cured layer of liquid crystal compounds. The liquid crystal alignment cured layer 21 can be formed as follows: an alignment treatment is performed on the surface of the substrate 30, a coating liquid containing a liquid crystal compound is applied to the surface, and the liquid crystal compound is aligned in a direction corresponding to the above alignment treatment, And fix the alignment state. In one embodiment, the substrate is any suitable resin film. Preferably, a Triacetyl Cellulose (TAC) membrane is used.

By using the liquid crystal compound in the alignment cured layer, the difference between nx and ny of the obtained liquid crystal alignment cured layer can be significantly greater than that of the non-liquid crystal material, so the liquid crystal used to obtain the required in-plane phase difference can be significantly reduced The thickness of the alignment cured layer. As a result, the thickness and weight of the circular polarizing plate can be reduced. In this specification, the so-called "alignment cured layer" refers to a layer in which the liquid crystal compound is aligned in a specific direction in the layer, and the alignment state is fixed. Furthermore, the "alignment cured layer" includes the concept of an alignment cured layer obtained by curing a liquid crystal monomer as described later. In this embodiment, it is representative that the rod-shaped liquid crystal compound is aligned in the state of being aligned in the direction of the slow axis of the liquid crystal alignment cured layer (horizontal alignment).

As the liquid crystal compound, for example, a liquid crystal compound of a nematic phase (nematic liquid crystal) in a liquid crystal phase can be exemplified. As this liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for expressing the liquid crystallinity of the liquid crystal compound can be either liquid or thermophilic. The liquid crystal polymer and the liquid crystal monomer may 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 is that the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, curing) the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, if the liquid crystal monomers are polymerized or cross-linked with each other, the above-mentioned alignment state can be fixed thereby. Here, although a polymer is formed by polymerization and a three-dimensional network structure is formed by cross-linking, these are non-liquid crystalline. Therefore, the formed liquid crystal alignment solidified layer does not undergo transition to the liquid crystal phase, the glass phase, and the crystalline phase due to, for example, a temperature change specific to the liquid crystal compound. As a result, the liquid crystal alignment cured layer is not affected by temperature changes and has extremely excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs according to its kind. 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, the polymerizable mesogen compounds described in Japanese Patent Special Form 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. . As specific examples of the polymerizable mesogen compound, for example, the trade name LC242 from BASF, the trade name E7 from Merck, and the trade name LC-Sillicon-CC3767 from Wacker-Chem may be mentioned. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

As the above-mentioned alignment processing, any appropriate alignment processing can be adopted. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment can be cited. As specific examples of the mechanical alignment treatment, rubbing treatment and elongation treatment can be cited. As a specific example of the physical alignment treatment, magnetic field alignment treatment and electric field alignment treatment can be cited. As specific examples of the chemical alignment treatment, oblique vapor deposition and photo-alignment treatment may be mentioned. The processing conditions of various orientation processing can adopt any appropriate conditions according to the purpose.

The alignment of the liquid crystal compound is implemented 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 fixation of the alignment state is performed 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 polymerization treatment or crosslinking treatment.

Specific examples of the liquid crystal compound and details of the formation method of the alignment cured layer are described in Japanese Patent Laid-Open No. 2006-163343. The description of this publication is incorporated into this specification as a reference.

As another example of the liquid crystal alignment cured layer, a form in which the disc-shaped liquid crystal compound is aligned in any state of vertical alignment, mixed alignment, and oblique alignment can be cited. Among the discotic liquid crystal compounds, a representative one is that the disc surface of the discotic liquid crystal compound is aligned substantially perpendicular to the film surface of the alignment cured layer. The so-called discotic liquid crystal compound is substantially vertical means that the average value of the angle formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°, and further Preferably it is 85°-90°. The so-called discotic liquid crystal compound generally refers to a liquid crystal compound having a disc-shaped molecular structure such as benzene, 1,3,5-tris, calixarene, etc. The core is arranged in the center of the molecule, and linear alkyl groups, alkoxy groups, substituted benzyloxy groups, etc. are radially substituted as its side chains. As a representative example of disc-type liquid crystals, examples can be exemplified by the benzene derivatives, as described in Mol. Cryst. Liq. Cryst. Vol. 71, page 111 (1981) in the research report of C. Destrade et al. Benzene derivatives, indenobenzene derivatives, phthalocyanine derivatives; or cyclohexane derivatives described in Angew. Chem. Vol. 96, page 70 (1984) in the research report of B. Kohne et al. ; And J. Chem. Soc. Chem. Commun. in the research report of JM Lehn et al., page 1794 (1985), J. Am. Chem. Soc. 116 in the research report of J. Zhang et al., The azacorona or phenylacetylene giant ring described in page 2655 (1994). As further specific examples of the discotic liquid crystal compound, for example, the compounds described in Japanese Patent Laid-Open No. 2006-133652, Japanese Patent Laid-Open No. 2007-108732, and Japanese Patent Laid-Open No. 2010-244038 can be cited. . The descriptions in the above-mentioned documents and gazettes are cited as references in this specification.

As shown in FIG. 1(b), when the liquid crystal alignment cured layer includes a single layer, the thickness is preferably 0.5 μm-7 μm, more preferably 1 μm-5 μm. By using a liquid crystal compound, it can be significantly thinner than the thickness of the resin film to achieve the same in-plane phase difference as the resin film.

In the liquid crystal alignment cured layer, the typical refractive index characteristic shows the relationship of nx>ny=nz. The liquid crystal alignment cured layer is typically provided to impart anti-reflection properties to the polarizing plate, and when the liquid crystal alignment cured 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 cured layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and still more preferably 130 nm to 160 nm. Furthermore, "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be a situation of ny>nz or ny<nz within a range that does not impair the effect of the present invention.

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

The liquid crystal alignment cured layer can exhibit the reverse dispersion wavelength characteristic that the retardation value increases according to the wavelength of the measured light, and it can also exhibit the positive wavelength dispersion characteristic that the retardation value becomes smaller according to the wavelength of the measured light, and it can also show the phase. The difference is based on the flat wavelength dispersion characteristic that the wavelength of the measured light hardly changes. In one embodiment, the liquid crystal alignment cured layer exhibits reverse dispersion wavelength characteristics. In this case, the Re(450)/Re(550) of the liquid crystal alignment cured layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With this configuration, very excellent anti-reflection characteristics can be achieved.

The angle θ formed by the slow axis of the liquid crystal alignment cured layer and the absorption axis of the polarizing element is preferably 40°-50°, more preferably 42°-48°, and still more preferably about 45°. If the angle θ is within this range, by using the liquid crystal alignment cured layer as a λ/4 plate as described above, a circularly polarizing plate having extremely excellent circular polarization characteristics (and as a result, extremely excellent anti-reflection characteristics) can be obtained. Furthermore, the direction of the slow axis of the liquid crystal alignment cured 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 a step of attaching another liquid crystal alignment cured layer 22 to the liquid crystal alignment cured layer 21 on the opposite side of the polarizing plate 10. Specifically, it is as follows. First, in the same manner as described above, another liquid crystal alignment cured layer 22 is formed on the substrate 30. Next, similar to the above, the liquid crystal alignment cured layer 21 is formed on another substrate (not shown). At this time, each alignment treatment direction corresponds to the direction of the late phase axis of each alignment cured layer described later. Next, the liquid crystal alignment cured layer 21 is bonded to the other liquid crystal alignment cured layer 22 to produce a laminate having the liquid crystal alignment cured layer 21, the other liquid crystal alignment cured layer 22, and the substrate 30 in this order. Furthermore, the liquid crystal alignment cured layer 21 and the other liquid crystal alignment cured layer 22 are bonded via any appropriate adhesive. The obtained laminate was bonded to a polarizing plate in the same manner as described above. In this way, a laminate as shown in Fig. 1(c) can be obtained.

As shown in Figure 1(c), when the liquid crystal alignment cured layer 21 is bonded to another liquid crystal alignment cured layer 22, it is preferable that either the liquid crystal alignment cured layer and the other liquid crystal alignment cured layer is used as The λ/2 plate functions as a λ/4 plate while the other one functions as a λ/4 plate. Therefore, the thickness of the liquid crystal alignment cured layer and another liquid crystal alignment cured layer can be adjusted in such a way that the required in-plane phase difference of the λ/4 plate or the λ/2 plate can be obtained. For example, when the liquid crystal alignment cured layer functions as a λ/2 plate and the other liquid crystal alignment cured layer functions as a λ/4 plate, the thickness of the liquid crystal alignment cured layer is, for example, 2.0 μm to 3.0 μm, and the other liquid crystal alignment layer functions as a λ/4 plate. The thickness of the cured 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 cured layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and still more preferably 250 nm to 280 nm. The in-plane phase difference Re (550) of the other liquid crystal alignment cured layer is as described above for the single-layer alignment cured layer. The angle formed by the slow axis of the liquid crystal alignment cured layer and the absorption axis of the polarizing element is preferably 10°-20°, more preferably 12°-18°, and still more preferably about 15°. The angle formed by the slow axis of the other liquid crystal alignment cured layer and the absorption axis of the polarizing element is preferably 70°-80°, more preferably 72°-78°, and still more 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 cured layer and the other liquid crystal alignment cured layer, the method for forming the liquid crystal alignment cured layer and the liquid crystal alignment cured layer, and the optical properties are as described above for the single-layer alignment cured layer.

A-3. Temporary adhesion of surface protective film Next, as shown in FIG. 1(d), the surface protection film 40 is temporarily attached to the polarizing plate 10 on the opposite side of the liquid crystal alignment cured layer 21 so as to be peelable. 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 via the adhesive layer. Furthermore, in the following steps, the case where the liquid crystal alignment cured layer 21 is bonded to another liquid crystal alignment cured layer 22 will be described. Those skilled in the art naturally know that the same is true even if the liquid crystal alignment cured layer is a single layer.

The base film of the surface protection film 40 can be composed of any appropriate resin film. As the material for forming the resin film, olefin resins such as polyethylene resins, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as butene resins, and polyamide resins can be mentioned. , Polycarbonate resins, copolymer resins of these, etc. Preferably, it is a polyethylene resin or a polyethylene terephthalate resin. If this material is used in the manufacturing steps of the circular polarizing plate, the roll transport has excellent mobility, which can prevent the adhesive deformation caused by the winding up during the stagnation of the roll transport, and can suppress the appearance of the film.

The thickness of the base film is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm. With this thickness, it has the advantage that it is not easily deformed even if tension is applied during transportation and/or bonding.

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 modulus of the base film is within this range, in the manufacturing process of the circular polarizing plate, the roll transport has excellent mobility, which can prevent the adhesive from deforming due to tightness during stagnation during roll transport. And it can suppress the appearance of the film.

As the adhesive for forming the adhesive layer, any appropriate adhesive can be used. The matrix resin of the adhesive may, for example, be acrylic resin, styrene resin, or silicone resin. From the viewpoints of chemical resistance, adhesion for preventing penetration of the treatment liquid during immersion, and the degree of freedom to the adherend, an acrylic resin is preferred. As a crosslinking agent which can be contained in an adhesive, an isocyanate compound, an epoxy compound, and an aziridine compound are mentioned, for example. 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 protection film is preferably 25 μm or more, more 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 protection film refers to the total thickness of the base film and the adhesive layer.

A-4. Peeling off the substrate Next, as shown in FIG. 1(e), the substrate 30 is peeled off from the other liquid crystal alignment cured layer 22 in a state where the surface protective film 40 is temporarily adhered. In this way, the surface protection film is temporarily adhered before the substrate is peeled, so that in the manufacturing steps of the thin circular polarizing plate, the mobility during roll conveyance is excellent (for example, breakage is suppressed), and the winding up during stagnation during roll conveyance is suppressed This results in poor deformation of the adhesive, dents in the adhesive, etc., and suppresses poor appearance of the obtained circular polarizer (for example, dirt on the visual recognition side). Furthermore, if the thickness of the surface protection film is in the range described in A-3 above, this effect becomes remarkable.

A-5. Temporary adhesion of spacer 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 cured layer 22, and the spacer 60 is temporarily adhered to the adhesive layer 50 in a releasable manner.

The adhesive layer may typically contain an acrylic adhesive.

The thickness of the adhesive layer is preferably 50 μm or less, more preferably 30 μm or less, and still more 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 form a roll of a circular polarizing plate.

B. Circular polarizer When a circularly polarizing plate is actually used, the surface protective film 40 and the spacer 60 can be peeled off from the optical laminate 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 circular polarizer is 45 μm or less, preferably 40 μm or less. The lower limit of the thickness of the circular polarizer may be, for example, 10 μm. Furthermore, the so-called thickness of the circular polarizer refers to the total thickness from the polarizer to another liquid crystal alignment cured layer (that is, the thickness of the circular polarizer does not include the thickness of the surface protective film, the adhesive layer and the spacer) . Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by 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 case where the raw material sheet is observed to be broken during the movement of the roller, or the end of the polarizing plate is broken, broken and rolled up due to the fracture is marked as ×, and the case where no such phenomenon is observed is recorded For 〇. (2) Poor appearance The inspector makes the judgment by visual inspection. A circular polarizing plate was taken from the raw material sheet roll, the surface protective film was peeled off, and the case where visible dirt adhered to the visible side of the circular polarizing plate at this time was recorded as ×, and the case where there was no adhesion was recorded as ○. (3) Poor deformation of the adhesive caused by tight winding during stagnation The inspector makes the judgment by visual inspection. Store the raw sheet roll for 4 weeks. After discarding 3 turns of the outer roll, take a circular polarizer and attach it to a smooth blackboard (manufactured by Nitto Plastic Industry Co., Ltd., CLAREX). The unevenness of the adhesive will be recognized in the full-width view. It is ×, the case where the unevenness of the adhesive is visually recognized at a width of less than half is recorded as △, and the case where the unevenness of the adhesive is not visually recognized is recorded as ○.

[Example 1] 1. Production of polarizing element As the thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of about 75°C was used. Perform corona treatment on one side of the resin substrate. In a 9:1 mixture of polyvinyl alcohol (polymerization degree 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 resin, and the resultant 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 substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm to obtain a laminate. The obtained laminated body was uniaxially stretched to 2.4 times to the free end in the longitudinal direction (long side direction) between rollers with different peripheral speeds in an oven at 130°C (air-assisted stretching treatment). Then, the layered body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at 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 obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water), the monomer transmittance of the polarizing element finally obtained ( Ts) is changed to 43.0% or more, and the concentration is adjusted while immersing for 60 seconds (dyeing treatment). Then, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained 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) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). After that, while immersing the layered body in a boric acid aqueous solution (boric acid concentration of 4.0% by weight, potassium iodide concentration of 5.0% by weight) at a liquid temperature of 70°C, the total stretch magnification becomes 5.5 times in the vertical direction between rolls with different peripheral speeds. (Long side direction) Uniaxial extension (underwater extension treatment). After that, the layered body was immersed in a washing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 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 roller made of SUS (Steel Use Stainless, Japanese stainless steel standard) whose surface temperature was kept at 75°C for about 2 seconds (drying shrinkage treatment) . In this way, a polarizing element with a thickness of 5 μm is formed on the resin substrate.

2. Making of polarizing plate An acrylic film (surface refractive index: 1.50, 20 μm) was bonded as a protective layer to the surface of the polarizing element obtained above (the surface opposite to the resin substrate) via an ultraviolet curable adhesive. Specifically, it is applied so that the total thickness of the hardening adhesive becomes 1.0 μm, and is bonded using a roller press. After that, UV (Ultraviolet) rays are irradiated from the protective layer side to harden the adhesive. Then, after cutting both ends into strips, the resin substrate was peeled off to obtain a strip-shaped polarizing plate (width: 1300 mm) with a protective layer/polarizing element composition.

使用摩擦布摩擦三乙醯纖維素(TAC)膜(厚度80 μm)表面，實施配向處理。配向處理之方向設為當貼合於偏光板時，自視認側觀察相對於偏光元件之吸收軸之方向成為15°之方向。藉由於該配向處理表面藉由棒式塗佈機塗佈上述液晶塗佈液，於90℃加熱乾燥2分鐘而使液晶化合物配向。藉由對如此形成之液晶層使用金屬鹵素燈照射1 mJ/cm² 之光，使該液晶層硬化，從而於TAC膜上形成液晶配向固化層。 變更塗佈厚度、及將配向處理方向設為自視認側觀察相對於偏光元件之吸收軸之方向成為75°之方向，除此以外，與上述同樣地於另一TAC膜上形成另一液晶配向固化層。 其次，將液晶配向固化層貼合於另一液晶配向固化層，剝離TAC膜，製作依序具有液晶配向固化層、另一液晶配向固化層、及另一TAC膜之積層體。再者，液晶配向固化層與另一液晶配向固化層之貼合係經由上述2.中所使用之紫外線硬化型接著劑(厚度1.0 μm)進行。其次，將所獲得之積層體經由上述2.中所使用之紫外線硬化型接著劑(厚度1.0 μm)貼合於上述偏光板。如此，獲得具有偏光板/液晶配向固化層/另一液晶配向固化層/基材(另一TAC膜)之構成之積層體。3. The formation of a liquid crystal alignment cured layer and another liquid crystal alignment cured layer will show a nematic liquid crystal phase polymerizable liquid crystal (manufactured by BASF Corporation: trade name "Paliocolor LC242", represented by the following formula) 10 g, and the polymerization 3 g of a photopolymerization initiator (manufactured by BASF Corporation: trade name "Irgacure 907") of a liquid liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [化1]

A rubbing cloth was used to rub the surface of a triacetyl cellulose (TAC) film (thickness 80 μm) to perform an alignment treatment. The direction of the alignment treatment was set to a direction of 15° with respect to the absorption axis of the polarizing element when viewed from the viewing side when it was attached to the polarizing plate. The liquid crystal compound is aligned by coating the liquid crystal coating liquid on the surface due to the alignment treatment by a bar coater, and heating and drying at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with 1 mJ/cm ² light using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment cured layer on the TAC film. Except for changing the coating thickness and setting the alignment treatment direction to a direction of 75° with respect to the absorption axis of the polarizing element when viewed from the viewing side, another liquid crystal alignment was formed on another TAC film in the same manner as above. Cured layer. Secondly, the liquid crystal alignment cured layer is attached to another liquid crystal alignment cured layer, and the TAC film is peeled off to produce a laminate having a liquid crystal alignment cured layer, another liquid crystal alignment cured layer, and another TAC film in sequence. Furthermore, the bonding of the liquid crystal alignment cured layer and another liquid crystal alignment cured layer is performed 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 laminate having the composition of a polarizing plate/liquid crystal alignment cured layer/another liquid crystal alignment cured layer/substrate (another TAC film) is obtained.

4. Production of circular polarizing plate In the laminate obtained above, a surface protective film (E-MASK RP109F, manufactured by Nitto Denko) is temporarily adhered to the side of the polarizing plate opposite to the liquid crystal alignment cured layer. After that, another TAC film as a base material was peeled off from the other liquid crystal alignment cured layer. An adhesive layer (acrylic adhesive, thickness: 50 μm) is formed on the peeling surface of the other liquid crystal alignment cured layer. In the step of forming the adhesive layer, the evaluation of (1) above was performed. The spacer is temporarily adhered to the adhesive layer on the opposite side of the liquid crystal alignment cured layer in a peelable and temporary manner. In this way, an optical laminate having a surface protective film/polarizer/liquid crystal alignment cured layer/another liquid crystal alignment cured 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 protection film is 2.0×10 ⁹ Pa. The obtained optical laminate was used for the evaluation of (2) to (3) above. The results are shown in Table 1. Furthermore, the thickness (excluding the adhesive) of the circular polarizing plate obtained by peeling off the surface protection film and the spacer from the optical laminate was 31 μm.

[Example 2] Except that E-MASK RP149C (manufactured by Nitto Denko Corporation) was used for the surface protective film, an optical laminate was obtained in the same manner as in Example 1. 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 protection film is 2.0×10 ⁹ Pa. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

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

[Example 4] Except that Toretec 7832C (manufactured by Toray Corporation) was used as the surface protection film, an optical laminate was obtained in the same manner as in Example 1. The thickness of the base film of the surface protection film and the thickness of the surface protection film are 30 μm. The tensile elastic modulus of the surface protection film is 3.0×10 ⁸ Pa. The obtained optical laminate 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 cycloolefin-based unstretched film with a hard coat layer (manufactured by Zeon Corporation, thickness: 27 μm) was used instead of the acrylic-based stretched film, except that it was obtained in the same manner as in Example 1. An optical laminate with a long retardation layer and a hard-coated polarizing plate. The obtained optical laminate was subjected to the same evaluation as in Example 1. Furthermore, the thickness of the circular polarizing plate obtained by peeling off the surface protection film and the separator from the optical laminate except for the adhesive was 38 μm.

[Comparative Example 1] Except not using a surface protective film, it carried out similarly to Example 1, and obtained the optical laminated body. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2] Except not using a surface protective film, it carried out similarly to Example 5, and obtained the optical laminated body. The obtained optical laminate 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 modulus of elasticity (Pa) 2.0×10 ⁹ 2.0×10 ⁹ 3.0×10 ⁸ 3.0×10 ⁸ 2.0×10 ⁹ - - The thickness of the base film of the surface protection film (μm) 38 50 25 30 38 - - Thickness of surface protection film (μm) 48 60 25 30 48 - - Migration 〇 〇 〇 〇 〇 X X bad apperance 〇 〇 〇 〇 〇 X X Poor deformation of the adhesive caused by tight winding during stagnation 〇 〇 △ △ 〇 X X

[Evaluation] According to Table 1, it can be seen that the optical laminate obtained by the examples of the present invention has excellent mobility during roll conveyance, suppresses poor deformation of the adhesive caused by winding tightness during stagnation during roll conveyance, and suppresses poor appearance of the film. Furthermore, it can be seen that by using a thicker surface protection film, it is possible to suppress poor deformation of the adhesive due to winding up during stagnation (comparison of Examples 1 and 2 with Examples 3 and 4). [Industrial availability]

The circular 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 electroluminescence display devices (OLED).

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

1(a) to (g) are schematic cross-sectional views for explaining the manufacturing method of the circular polarizing plate according to one embodiment of the present invention in the order of steps. Fig. 2 is a schematic cross-sectional view of a circular polarizing plate obtained by the manufacturing method of one embodiment of the present invention.

10: Polarizing plate

11: protective layer

12: Polarizing element

21: Liquid crystal alignment cured layer

22: Another liquid crystal alignment cured layer

30: Substrate

40: Surface protective film

50: Adhesive layer

60: spacer

Claims (11)

A method for manufacturing a circular polarizing plate, which includes: The step of forming a liquid crystal alignment cured layer on the surface of the substrate; The step of attaching the liquid crystal alignment cured layer to the surface of the polarizing plate; The step of temporarily adhering the surface protection film on the opposite side of the polarizing plate and the liquid crystal alignment cured layer in a peelable manner; The step of peeling off the substrate from the liquid crystal alignment cured layer; The step of forming an adhesive layer on the peeling surface of the liquid crystal alignment cured layer; and A step of temporarily attaching a spacer to the adhesive layer on the opposite side of the liquid crystal alignment cured layer in a peelable manner; and The thickness of the circular polarizer is 45 μm or less. The method for manufacturing a circular polarizing plate of claim 1, wherein the surface protective film contains a polyethylene resin or a polyethylene terephthalate resin. The method for manufacturing a circular polarizing plate of claim 1, wherein the thickness of the surface protection film is 25 μm or more. The method for manufacturing a circular polarizing plate of claim 1, wherein the thickness of the surface protection film is 25 μm or more. The method for manufacturing a circular polarizing plate according to any one of claims 1 to 4, wherein the polarizing plate and the liquid crystal alignment cured layer are bonded via a photo-curing adhesive. The method for manufacturing a circularly polarizing plate according to any one of claims 1 to 4, wherein the liquid crystal alignment cured layer functions as a λ/4 plate. The method for manufacturing a circularly polarizing plate according to claim 5, wherein the liquid crystal alignment cured layer functions as a λ/4 plate. The method for manufacturing a circular polarizing plate according to any one of claims 1 to 4, which further includes a step of attaching another liquid crystal alignment cured layer to the opposite side of the liquid crystal alignment cured layer to the polarizing plate. According to claim 5, the method for manufacturing a circular polarizing plate further includes a step of attaching another liquid crystal alignment cured layer to the opposite side of the liquid crystal alignment cured layer to the polarizing plate. The method for manufacturing a circularly polarizing plate according to claim 8, wherein any one of the liquid crystal alignment cured layer and the other liquid crystal alignment cured layer functions as a λ/2 plate, and the other functions as a λ/4 plate. The method for manufacturing a circularly polarizing plate according to claim 9, wherein any one of the liquid crystal alignment cured layer and the other liquid crystal alignment cured layer functions as a λ/2 plate, and the other functions as a λ/4 plate.

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