JP2017181597A - Optical film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film capable of minimizing troubles associated with interlayer separation of a luminance enhancement film that may arise when peeling off a surface protection film.SOLUTION: An optical film 20 comprises a surface protection film 22 and a luminance enhancement film 21, and is characterized in that a peeling force required to peel the surface protection film off the luminance enhancement film is 10.0 N/25 mm or less and a rate of increase of the peeling force is less than 700% after being irradiated with an active energy ray amounting to a cumulative light intensity of 8000 mJ/cm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical film and a polarizing plate.

  A polarizing plate is an optical element having a function of absorbing linearly polarized light having a vibration plane parallel to the absorption axis direction and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis. It's being used.

  In the liquid crystal display device, two polarizing plates are used, one on each of the back side and the front side of the liquid crystal cell. By laminating a brightness enhancement film on the polarizing plate disposed on the back side, the brightness can be improved and the contrast of the liquid crystal display device can be improved. In portable devices such as small smartphones and tablet terminals, the amount of battery mounted is limited, so that the demand for a polarizing plate having a brightness enhancement film capable of obtaining a power saving effect is increasing.

  The brightness enhancement film is an optical element having a function of transmitting polarized light orthogonal to the reflection axis direction and reflecting parallel polarized light. For example, a plurality of polymer thin films having different refractive indexes are alternately laminated. What is formed is known.

  In order to protect the surface of the polarizing plate having the brightness enhancement film until it is bonded to the liquid crystal cell, the surface protection film is often temporarily bonded to the surface of the brightness enhancement film. This surface protective film is peeled off from the polarizing plate after the polarizing plate is bonded to the liquid crystal cell (see, for example, Patent Document 1).

  In recent years, in the commercialization process of attaching a polarizing plate to a touch panel, processing such as heating, UV irradiation, and force application is often performed to improve adhesion between films and cure liquid paste (for example, patents) Reference 2). Patent Document 2 describes a surface protective film having a reduced peel force. However, when the adherent member of the surface protective film is the above-described brightness enhancement film, the surface protective film described in Patent Document 2 is delaminated. Could not solve the problem.

JP 2004-258393 A JP-A-8-60111

  As described above, the brightness enhancement film is a laminate of two or more layers, and the adhesion between adjacent layers is not so high.

  For this reason, in a line for cutting a polarizing plate having a surface protective film and a brightness enhancement film into a predetermined shape, a potential crack is likely to occur on the end face of the brightness enhancement film, and the polarization plate is used as a liquid crystal cell for use as a product. When the surface protective film is peeled off after bonding, there is a problem that peeling occurs between the layers of each film in the brightness enhancement film, and a part of the brightness enhancement film is peeled off together with the surface protection film. This phenomenon is called delamination. In particular, as described in Patent Document 2, the peeling force of the surface protective film to the adherend tends to increase as the adhesive layer is altered by the treatment. In particular, the peeling force increases remarkably when irradiated with active energy rays in the ultraviolet region.

  The present invention has been made in consideration of the above points, and an object of the present invention is to provide an optical film and a polarizing plate that can suppress a problem that the brightness enhancement film is delaminated when the surface protective film is peeled off.

  One aspect of the present invention is an optical film provided with a surface protective film and a brightness enhancement film, and a cause force required when the surface protection film is peeled off from the brightness enhancement film after being irradiated with active energy rays. Is 10.0 N / 25 mm or less, and the rate of increase of the inducing force is less than 700%.

  In one aspect of the present invention, the surface protective film is laminated on the brightness enhancement film via an adhesive layer, and the adhesive layer has a transmittance of 5% or less for the active energy ray having a wavelength of 190 nm. It is good also as an optical film.

  One embodiment of the present invention provides a polarizing plate having the optical film of the above embodiment and a polarizing film.

  In the present specification, a laminate having a brightness enhancement film and a surface protective film may be simply referred to as an optical film.

  In this invention, the optical film and polarizing plate which can suppress the malfunction which a brightness improvement film delaminates at the time of peeling of a surface protection film can be provided.

1 is a diagram showing an embodiment of the present invention, and is a schematic cross-sectional view of a polarizing plate 50. FIG. It is a figure which shows the relationship between the distance at the time of causing the surface protection film 22 from the brightness enhancement film 21, and force. It is a top view at the time of measuring the cause force when peeling the surface protection film 22 in the polarizing plate 50 from a brightness enhancement film. It is sectional drawing at the time of measuring the cause force when peeling the surface protection film 22 from a brightness improvement film. It is a figure which shows the specification and evaluation of an Example, a comparative example, and a reference example. It is a schematic sectional drawing of the surface protection film in an Example, a comparative example, and a reference example. It is a figure which shows the relationship between the cause force and the delamination rate in the brightness enhancement film.

  Hereinafter, embodiments of the optical film and the polarizing plate of the present invention will be described with reference to FIGS.

<Polarizer>
FIG. 1 is a schematic cross-sectional view of the polarizing plate 50. The polarizing plate 50 has a configuration in which the polarizing film 10 and the optical film 20 are laminated. In the following description, as shown in FIG. 1, the side on which the optical film 20 is provided in the polarizing plate 50 is referred to as the upper side, and the side on which the polarizing film 10 is provided is referred to as the lower side. However, this merely defines the vertical direction for convenience of explanation, and does not limit the orientation when the optical film 20 and the polarizing plate 50 according to the present invention are used.

<Polarized film>
The polarizing film 10 is an absorptive polarizing film (hereinafter, absorptive polarizing film 10), and has a protective film 11 on the lower side. As the absorptive polarizing film 10, a film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film is usually used. The polyvinyl alcohol resin constituting the absorption polarizing film 10 can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acid, olefin, vinyl ether, unsaturated sulfonic acid, and acrylamide having an ammonium group. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehyde may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. Specific polyvinyl alcohol resins and dichroic dyes include, for example, polyvinyl alcohol resins and dichroic dyes exemplified in JP 2012-159778 A [Patent Document 3].

  What formed the polyvinyl alcohol-type resin into a film is used as a raw film of the absorption-type polarizing film 10. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is 150 micrometers or less. In consideration of easiness of stretching, the film thickness is preferably 3 μm or more, and preferably 75 μm or less.

  The absorptive polarizing film 10 is, for example, a step in which a polyvinyl alcohol-based resin film is stretched in a uniaxial stretch, a step in which the polyvinyl alcohol-based resin film is dyed with a dichroic dye, and the dichroic dye is adsorbed. A polyvinyl alcohol-based resin film on which a dye is adsorbed is manufactured by a process of treating with a boric acid aqueous solution and a process of washing with water after the treatment with the boric acid aqueous solution and finally drying. Moreover, the absorptive polarizing film 10 may be manufactured in accordance with, for example, a method described in JP 2012-159778 A. In this method, a polyvinyl alcohol resin layer that becomes the absorption polarizing film 10 can be formed by coating the base film with a polyvinyl alcohol resin. The thickness of the absorbing polarizing film 10 is usually 1 to 40 μm, preferably about 2 to 30 μm.

<Protective film>
As the protective film 11, for example, a thermoplastic film formed from a thermoplastic resin is used. The thickness of the thermoplastic resin film is usually 3 to 100 μm, preferably 5 to 50 μm. The thermoplastic resin film is preferably made of a resin excellent in transparency, uniform optical characteristics, mechanical strength, thermal stability, and the like. Specific examples of thermoplastic resins include cellulose resins such as triacetyl cellulose and diacetyl cellulose, polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, polymethyl (meth) acrylate, and polyethyl (meth) acrylate. (Meth) acrylic resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyimide resins, polyolefin resins such as polyethylene and polypropylene, and polynorbornene resins. Among these, a resin film formed from a cellulose resin, a polyester resin, a (meth) acrylic resin, a polycarbonate resin, and a polyolefin resin is preferable. Here, (meth) acrylate indicates that either methacrylate or acrylate may be used, and “(meth)” in the case of (meth) acrylic acid or the like is also the same.

  For these thermoplastic resin films, appropriate commercial products can be used. Examples of commercially available cellulose resin films are “Fujitac (registered trademark) TD80”, “Fujitac (registered trademark) TD80UF” and “Fujitac (registered trademark) TD80UZ” manufactured by FUJIFILM Corporation. “KC2UAW”, “KC8UX2M”, and “KC8UY” manufactured by Konica Minolta Co., Ltd.

  An appropriate commercial product can be used for the polyester resin film. Examples of commercially available polyester resin films are “Diafoil (registered trademark)” manufactured by Mitsubishi Plastics, “Lumirror (registered trademark)” manufactured by Toray Industries, Inc., and manufactured by Toyobo Co., Ltd. "Cosmo Shine (registered trademark)".

  An appropriate commercially available product can be used for the (meth) acrylic resin film. Examples of commercially available (meth) acrylic resin films include “Technoloy (registered trademark)” manufactured by Sumitomo Chemical Co., Ltd. and “Acryprene (registered trademark)” manufactured by Mitsubishi Rayon Co., Ltd. Can be mentioned.

  An appropriate commercial product can be used for the polycarbonate resin film. Examples of commercially available polycarbonate resin films include “Panlite (registered trademark)” manufactured by Teijin Chemicals Ltd. under the trade name.

  Examples of commercially available polyolefin resins are “Topas” manufactured by Topas Advanced Polymers GmbH and sold by Polyplastics Co., Ltd. “ARTON” (registered by JSR Corporation) Trademark), "ZEONOR (registered trademark)" and "ZEONEX (registered trademark)" sold by Nippon Zeon Co., Ltd., "Apel" (registered trademark) sold by Mitsui Chemicals, Inc. (All are trade names), and a film can be produced from these. Polyolefin-based resin films may also be used. For example, “Arton Film” (“Arton” is a registered trademark of the company) sold by JSR Corporation, “Sekisui Chemical Co., Ltd.” ESCINA ”(registered trademark),“ ZEONOR FILM ”(registered trademark) sold by Nippon Zeon Co., Ltd., and the like.

  In addition, as the absorption-type polarizing film 10, it is also possible to provide a protective film on the upper side in addition to the configuration having the protective film 11 on the lower side. Examples of the upper protective film include a brightness enhancement film and a laminate of the brightness enhancement film and a thermoplastic film.

<Brightness enhancement film>
As the brightness enhancement film 21, for example, a characteristic of reflecting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayered film of dielectrics or a multilayered laminate of layers having different refractive index anisotropies. Such as those exhibiting a cholesteric liquid crystal polymer or an alignment film of the cholesteric liquid crystal polymer supported on a film base material, and reflects either the left-handed or right-handed circularly polarized light and transmits the other light. An appropriate material such as a material exhibiting characteristics can be used. The types of layers constituting the multilayer laminate can be two or more. As the brightness enhancement film, for example, a material that generates a phase difference by stretching represented by polyethylene naphthalate, polyethylene terephthalate, polycarbonate, an acrylic resin represented by polymethyl methacrylate, “ARTON” (manufactured by JSR Corporation) A resin obtained by alternately uniaxially stretching a resin having a small phase difference expression amount such as a norbornene-based resin typified by (registered trademark) as a multilayer laminate can be used. Specific examples of brightness enhancement films include “DBEF” (registered trademark), “APF-V4” (product name), “APF-V3” (product name) and “APF-V2” (product name) manufactured by 3M. Etc. The thickness of the brightness enhancement film is usually 5 to 100 μm, preferably 10 to 50 μm.

<Brightness enhancement film / thermoplastic resin film laminate>
The laminated body of a brightness enhancement film and a thermoplastic resin film can be obtained by laminating these films via, for example, an adhesive or an adhesive. As the pressure-sensitive adhesive or adhesive, an appropriate known material may be selected. It is preferable to use a pressure-sensitive adhesive from the viewpoint of simplicity of bonding work and prevention of optical distortion. As the adhesive, for example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyether or the like as a base polymer can be employed. Among them, like acrylic pressure-sensitive adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, and has excellent adhesion to brightness enhancement films and thermoplastic resin films, and even better. It is preferable to select and use one that has heat resistance and does not cause peeling problems such as floating and peeling under a high temperature environment.

  The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive may contain fine particles for exhibiting light scattering properties as necessary, such as glass fibers, glass beads, resin beads, metal powders and other inorganic powders. It may contain a filler, a pigment, a colorant, an antioxidant, an ultraviolet absorber, and the like. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  The protective film 11 and the upper protective film may be provided with a hard code layer on the surface opposite to the bonding surface with the polarizing film. Thereby, scratches and the like that occur when processing the polarizing plate can be prevented. When providing a hard-coat layer, it is preferable that the thickness of a hard-coat layer is 1-8 micrometers from a viewpoint of making protection and flexibility compatible, and it is more preferable that it is 1-6 micrometers. When the thickness of the hard coat layer exceeds 8 μm, the flexibility becomes low, and there is a tendency that cracks are easily generated during bending. On the other hand, when the thickness of the hard coat layer is less than 1 μm, the flexibility is good, but sufficient characteristics are often not obtained from the viewpoint of in-plane uniformity.

  The hard coat layer can be formed of a resin coating layer. The resin material for forming the resin film layer has sufficient strength as a film after the resin film layer is formed, and a transparent material can be used without particular limitation. Examples of the resin include thermosetting resins, thermoplastic resins, ultraviolet ray curable resins, active energy ray curable resins such as electron beam curable resins, and two-component mixed resins. Among these, UV curable resins can be cured by UV irradiation, and can form a resin coating layer efficiently with a simple processing operation, as well as a light diffusion layer such as an antiglare treatment layer. Is preferable. Examples of the ultraviolet curable resin include various types such as polyester, acrylic, urethane, amide, silicone, and epoxy, and examples include ultraviolet curable monomers, oligomers, and polymers. Examples of the ultraviolet curable resin preferably used include those having an ultraviolet polymerizable functional group, particularly those containing an acrylic monomer or oligomer component having 2 or more, particularly 3 to 6 functional groups. It is done. Further, an ultraviolet polymerization initiator is blended in the ultraviolet curable resin.

  As a method for forming the resin coating layer, an appropriate known method can be adopted. For example, there is a method in which the resin (coating liquid) is applied to the protective film 5 and dried. When a curable resin is used, a curing process is performed thereafter. As the coating method of the coating solution, methods such as phanten, die coater, casting, spin coating, phanten metalling, and gravure can be adopted. In the coating, the coating solution may be diluted with a general solvent such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, ethyl alcohol, or the like. It can also be crafted.

  As a method of laminating the absorbing polarizing film 10 and the protective film, a method of adhering these films with an adhesive is usually employed. When a protective film is laminated on both surfaces of the absorption-type polarizing film 10, the same type of adhesive may be used, or different types of adhesives may be used.

  Examples of the adhesive include a water-based adhesive and a photocurable adhesive. The water-based adhesive is obtained by dissolving the adhesive component in water or dispersing the adhesive component in water, and can thin the adhesive layer. Examples of the water-based adhesive include those in which the main component of the adhesive (composition) is a polyvinyl alcohol resin or a urethane resin.

  Polyvinyl alcohol resin is modified such as partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol, etc. Polyvinyl alcohol resin may be used. When a polyvinyl alcohol resin is used as the adhesive component, the adhesive is often prepared as an aqueous solution of a polyvinyl alcohol resin. The density | concentration of the polyvinyl alcohol-type resin in an adhesive agent is about 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 1-5 weight part.

  In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to the adhesive containing a polyvinyl alcohol resin as a main component. Examples of water-soluble epoxy resins include polyamide polyamines obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a polycarboxylic acid such as adipic acid and epichlorohydrin. An epoxy resin can be mentioned. Commercially available products of such polyamide polyamine epoxy resins are “Smilease Resin (registered trademark) 650 (30)” and “Smilease Resin (registered trademark) 675” sold by Taoka Chemical Co., Ltd., respectively. “WS-525” sold by Seiko PMC Co., Ltd. can be used preferably. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness is reduced, while if the amount added is large, the adhesive layer tends to be brittle.

  The laminated body (absorption type polarizing film 10 and protective film) joined via the water-based adhesive is usually subjected to a drying treatment, and the adhesive layer is dried and cured. The drying process can be performed, for example, by blowing hot air. The drying temperature is appropriately selected from the range of about 40 to 100 ° C, preferably 60 to 100 ° C. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less. If the thickness of the adhesive layer becomes too large, the appearance of the polarizing plate tends to be poor.

  After the drying treatment, sufficient adhesive strength may be obtained by performing curing at a temperature of room temperature or higher for at least half a day, usually 1 day or longer. Such curing is typically performed in a state of being wound in a roll. A preferable curing temperature is in the range of 30 to 50 ° C, more preferably 35 ° C or more and 45 ° C or less. When the curing temperature exceeds 50 ° C., so-called “roll tightening” is likely to occur in the roll winding state. In addition, it is preferable to select suitably the humidity at the time of curing, for example so that a relative humidity may be in the range of 70% or less. The curing time is usually about 1 to 10 days, preferably about 2 to 7 days.

  Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator. Examples of the photocurable epoxy resin include alicyclic epoxy resins, epoxy resins having no alicyclic structure, and mixtures thereof. Moreover, what added the radical polymerization type initiator and / or the cationic polymerization type initiator to an epoxy resin, an acrylic resin, an okitacene resin, a urethane resin, a polyvinyl alcohol resin etc. as a photocurable adhesive agent can also be used.

The laminated body joined through the photocurable adhesive is cured by irradiating an active energy ray after the lamination. The active energy ray light source is preferably, for example, an active energy ray having a light emission distribution at a wavelength of 400 nm or less. Specifically, the low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultrahigh-pressure mercury lamp, chemical lamp, black light lamp, micro A wave excitation mercury lamp, a metal halide lamp, etc. are preferably used. The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 2500 mW. / Cm ² is preferable. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 2500 mW / cm ² or less, it is caused by heat radiated from the light source and heat generated when the photocurable adhesive is cured. There is little risk of yellowing of the epoxy resin and deterioration of the polarizing plate.

The light irradiation time to the photocurable adhesive is controlled for each photocurable adhesive to be cured, and the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10, It is preferably set to be 000 mJ / cm ² . When the cumulative amount of light to the photo-curable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and 10,000 mJ / cm ^2. In the case of the following, the irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less.

  When curing a photocurable adhesive by irradiation of active energy rays, the polarization degree of the polarizing film, the transmittance and the hue, and the polarizing plate such as the transparency of the transparent film such as an acrylic resin film, an optical compensation film and a protective film It is preferable to carry out the curing under the conditions that these functions do not deteriorate.

  Note that it is only when an appropriate surface protective film corresponding to Examples 1 to 3 described later is selected that a product can be manufactured with a high yield depending on the irradiation conditions of the active energy rays.

<Optical film>
The optical film 20 is configured by laminating a brightness enhancement film 21 and a surface protection film 22.

<Surface protection film>
FIG. 6 is a schematic cross-sectional view of the surface protective film 22. The surface protection film 22 is detachably attached to the surface of the member to be protected (brightness enhancement film 21) to protect the surface, and the substrate 1 and the brightness enhancement film 21 side of the substrate are provided. An adhesive layer 2 provided on a certain lower surface and a polymer layer 3 provided on an upper surface of the substrate are provided.

  As the base material 1, a synthetic resin made of polyethylene, polypropylene, polyester, polyimide, polycarbonate, or the like, and a laminate thereof can be used. In particular, considering transparency and heat resistance during use, An axially stretched polyethylene terephthalate film is preferred. The resin film may be non-stretched, uniaxially stretched, or biaxially stretched. Moreover, you may control the draw ratio of a resin film, and the orientation angle of an axial method to a specific value. In addition to the resin film, a film made of another resin can be used as long as it has necessary strength and optical suitability. Further, easy adhesion treatment such as corona treatment can be performed on the surface of these base materials.

  The film thickness of the substrate 1 is about 12 μm to 100 μm, and preferably 20 μm to 80 μm. This is because it is too thin that the film thickness of the substrate 1 is less than 12 μm, and it is difficult to protect the protective member due to dents caused by collision of foreign matter, and the protective member is wrinkled. It is difficult to perform the peeling operation of the surface protective film 22 because there is no stickiness or stiffness. Moreover, when the film thickness exceeds 80 μm, the rigidity of the base material is too large, and it is difficult to stick uniformly to the protective member without lifting, and the curl becomes large, resulting in difficulty in bonding to the touch panel. . Moreover, since the base material occupies a large ratio on the price structure of the surface protection film 22, the economical efficiency calculated | required by the said surface protection film 22A falls.

  The pressure-sensitive adhesive layer 2 is not particularly limited as long as it can be adhered to the base material 1 and can be easily peeled off after use, and does not easily contaminate the adherend surface. In view of optical durability, an acrylic pressure-sensitive adhesive is preferable. Moreover, the formation method of the adhesion layer 2 and the base material 1 is not specifically limited, It can form also by the well-known application | coating method and a melt extrusion method.

  As a hardening agent added to the adhesion layer 2, an isocyanate compound, an epoxy compound, a melamine compound, a metal chelate compound etc. are mentioned as a crosslinking agent which bridge | crosslinks a (meth) acrylate copolymer. Examples of the tackifier include rosin, coumarone indene, terpene, petroleum, and phenol.

  The polymer layer 3 is provided on the upper side of the substrate 1, and a release agent such as silicone or fluorine is used as a kind of acrylic resin, polyester resin, nylon resin, styrene / acrylonitrile resin, urethane resin, epoxy resin or the like. Alternatively, it is obtained by adding to two or more polymer compounds. Also, UV curable resins and thermosetting resins can be used in place of these polymer compounds.

 The polymer layer 3 preferably has a thickness of 0.003 μm to 3 μm, more preferably 0.02 μm to 1 μm, in order to satisfy a sufficient anti-staining function and printability.

  The polymer layer 3 has antistatic properties in the layer. Various surfactant-type charging methods such as cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, and nonionic antistatic agents can be used to impart (use and add) antistatic performance to the polymer layer. Use or add an inhibitor, or a conductive polymer such as polyaniline, polypyrrole, or polythiophene, or a conductive filler or whisker. In this embodiment, the rate of increase of the cause force can be controlled by adjusting the amount of the curing agent and the amount of the antistatic agent, but the amount of the antistatic agent is increased and added to the adhesive layer 2. This is preferable in that the amount of the curing agent to be reduced is reduced and the rate of increase in force can be reduced.

  The polymer layer 3 can also be constituted by mixing the above-mentioned silicon / acrylate comb-shaped graft polymer and a binder which is another polymer compound. The polymer layer 3 is composed of a silicon / acrylate-based comb graft polymer and another polymer compound. The weight ratio with a certain binder is 4: 1 to 1:20, preferably 1: 1 to 1:12. If the ratio of the silicon acrylate comb-shaped graft polymer is too large, the peeling force by the adhesive tape becomes too light, and the peeling operation of the surface protective film 22 by the cellophane adhesive film is hindered. On the other hand, if the ratio is too small, the water repellency and antifouling performance are insufficient, and delamination may occur in the brightness enhancement film 21, so the amount of release agent added to the polymer compound is adjusted appropriately. There is a need to.

  The polymer layer 3 may have a structure in which an antistatic layer is provided between the polymer layer 3 and the substrate 1 in addition to the structure having antistatic properties in the layer. The antistatic layer is coated with various types of surfactant type antistatic agents such as cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, nonionic antistatic agents, or binders such as polyester resins and acrylic resins. What was contained can be used. Also, conductive polymers such as polyaniline, polybilol, and polythiophene, and conductive fillers and whiskers dispersed in a binder can be used. Furthermore, a conductive compound composed of a resin having a phosphate group or a phosphate group and a polymer having an oxazoline group can be used as a polymer compound such as an acrylic, polyester, or polyurethane group. In the formation of the antistatic layer on the base material, the substance is dissolved in an organic solvent or the like to form a coating solution, and any known coating method such as gravure coating method, reverse coating method, roll coating method, etc. Can be formed. Further, it can be formed by a melt extrusion method.

  In addition, in the polarizing plate 50 in this embodiment, the adhesive layer 51 is provided on the lower surface of the protective film 11. The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer 51 only needs to satisfy various properties (transparency, durability, reworkability, etc.) used in the optical film. For example, the pressure-sensitive adhesive layer 51 is mainly composed of (meth) acrylic acid ester, An acrylic resin having a glass transition temperature (Tg) of 0 ° C. or less obtained by radical polymerization of a small amount of an acrylic monomer composition containing a (meth) acrylic monomer having a functional group in the presence of a polymerization initiator; An acrylic pressure-sensitive adhesive containing a crosslinking agent is used.

The surface protective film thus obtained has a triggering force of 10.0 N / 25 mm or less after irradiation with an active energy ray having an integrated light amount of 8000 mJ / cm ² in the UVB region (280 to 350 nm), preferably 8.0 N / 25 mm or less, more preferably 7.0 N / 25 mm or less, and even more preferably 5.0 N / 25 mm or less. The surface protective film thus obtained has a peel strength of preferably 3.0 N / 25 mm or less after irradiation with an active energy ray having an integrated light amount of 8000 mJ / cm ² in the UVB region (280 to 350 nm), More preferably, it is 1.0 N / 25 mm or less, More preferably, it is 0.5 N / 25 mm or less, Especially preferably, it is 0.2 N / 25 mm or less, Preferably it is 0.01 N / 25 mm or more. The irradiation intensity at this time can be set to 500 mW / cm ² . By setting the peeling force to 0.01 N / 25 mm or more, it is possible to prevent the surface protective film from being peeled off from the brightness enhancement film during conveyance.

Further, before and after irradiating the active energy ray having an integrated light amount of 8000 mJ / cm ² , the rate of increase of the causing force is less than 700%, preferably 600% or less. The transmittance at a wavelength of 190 nm of the surface protective film is preferably 10% or less, and more preferably 5% or less, in that the rate of increase of the causing force can be reduced.

  The polarizing plate of the present invention preferably has an end surface polished. By polishing, the dimensional accuracy of the outer shape of the polarizing plate can be improved, and further the cracking of the polarizer can be prevented. On the other hand, by polishing, the aspect ratio of the surface of the end face of the brightness enhancement film in the polarizing plate is increased, and when the surface protective film is peeled off after irradiation of active energy rays in that state, the brightness enhancement film is delaminated. It may be easier. According to the present invention, for example, even when the surface aspect ratio Str at the end face of the brightness enhancement film is 0.25 or more or 0.28 or more, delamination can be effectively suppressed. That is, according to the present invention, it is possible to achieve both improvement in the dimensional accuracy of the polarizing plate, prevention of cracking of the polarizer, and suppression of delamination.

  In order to perform such polishing, for example, an apparatus described in International Publication 2011/040636 can be used. The apparatus has a rotating body and a plurality of cutting blades provided on a disk-shaped installation surface perpendicular to the rotation axis of the rotating body. The end face of the polarizing plate is polished by being brought into contact with the substrate. In this embodiment, in order to keep the surface aspect ratio Str within a predetermined range, it is preferable to increase the number of cutting blades and decrease the rotational speed of the rotating body. For example, the number of cutting blades is 3 or more, Preferably, it is 5 or more, and the rotational speed of the rotating body is, for example, 10000 rpm or less, preferably 6000 rpm or less, more preferably 5000 rpm or less.

  In addition, when laminating and polarizing the polarizing plate, it is preferable that the end surface of the polarizing plate is brought into contact with the central portion of the disk-shaped installation surface in terms of being able to further suppress the occurrence of delamination. .

  On the opposite side of the liquid crystal cell (not shown) to which the polarizing plate 50 is bonded in the pressure-sensitive adhesive layer 51, the same kind of polarizing plate or a known polarizing plate can be laminated. The polarizing plate 50 provided with the pressure-sensitive adhesive layer 51 is preferably arranged on the back side (backlight side) in the liquid crystal display device, and is arranged so that the surface protective film 22 side is the backlight side. Is more preferable.

[Example]
EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “parts” expressed in terms of content or usage are based on weight unless otherwise specified.
[Sample creation method]
(End face treatment)
The end face processing was performed using the apparatus described in International Publication 2011/040636. A plurality of polarizing plates 50 are overlapped, and the laminated film is rotated on the peripheral surface of the laminated film aggregate in a state where the laminated film is sandwiched by a pair of resin sandwich members from the outer side of both outermost film surfaces. The blade surfaces of the blades face each other, and the circumferential surface of the laminated film aggregate was finished with the circumferential surface of the sandwiching member by the rotary blade. At this time, the rotational speed of the rotating body was 4800 rpm.
(Active energy ray irradiation)
Measuring equipment: [Fusion UV Systems Co., Ltd. Fusion UV B2-006]
Conveyor speed: 10 m / min, height: 50 mm, light intensity: 100%, bulb: D bulb, polarizing plate 50 bonded to soda glass, from surface protective film side, UVB region (280-315 nm) integrated light intensity in the so that the 8000 mJ / cm ^2, the irradiation intensity was irradiated with active energy rays 500 mJ / cm ^2.

[Evaluation method]
(Causing force)
Measuring instrument: [Peel test for peeling the surface protective film 22 from the brightness enhancement film 21 at a peel width of 25 mm, peel angle: 180 °, peel speed of 300 mm / min, using [Autograph AGS-50NX manufactured by Shimadzu] It was. FIG. 2 is a diagram showing the relationship between the distance and force when the surface protective film 22 is caused from the brightness enhancement film 21. As shown in FIG. 2, a large force is required to cause the surface protective film 22 to be peeled off from the brightness enhancement film 21, but the force is reduced after the peeling starts. In the present embodiment, the surface protective film 22 causes the maximum value until the surface protective film 22 is peeled off by 25 mm from the starting point, and the subsequent force is the peeling force.
· Causing force increase rate ... so that the accumulated amount of light in UVB region becomes 8000 mJ / cm ^2, increasing the lead force irradiation intensity was measured before and after irradiation with active energy rays 500 mJ / cm ² using the following formula The rate was calculated.
Rate of increase = [(N1-N0) / N0] x 100
Unit:%, N0: Cause force before UV irradiation, N1: Cause force after UV irradiation

  FIG. 3 is a plan view when measuring the cause force when the surface protective film 22 in the polarizing plate 50 is peeled from the brightness enhancement film. FIG. 4 is a cross-sectional view when measuring the cause force when the surface protective film 22 is peeled from the brightness enhancement film. In the peel test, the adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to a glass 70 as shown in FIGS. 3 and 4.

  The measurement of the motive force was performed using 10 samples, and the average value was taken. The measurement of the causing force was performed before and after irradiation of the active energy ray to the polarizing plate 50. After irradiation with active energy rays, the force was measured after leaving the sample in an environment of 25 ° C. and 55% RH to cool the sample to 23 ° C.

(Aspect ratio of cross section of brightness enhancement film 21)
Using a measuring instrument: [Model number: OLS4100 manufactured by Olympus Corporation], the surface roughness was measured in an ultra high speed mode with a magnification of 100 times. 3 cm was cut out from each of two end faces perpendicular to the stretching direction of the brightness enhancement film, and the width was measured at 5 points. The larger the aspect ratio, the more uneven the surface is and the rougher the surface is. It is considered that the smaller the aspect ratio, the more uniform the cross section, and no cracks or defects are generated.

[Sample preparation]
Samples of Examples 1 to 3, Comparative Examples 1 to 2, and Reference Examples 1 to 5 were produced according to the specifications shown in FIG.

[Example 1]
The polarizing plate 50 was produced as follows. First, a polyvinyl alcohol film having a thickness of 60 μm (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further, while maintaining a tension state, After immersing in pure water at 1 ° C. for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer having a thickness of 23 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film. Next, on one side of this polarizer, 3 parts of carboxyl group-modified polyvinyl alcohol [trade name “KL-318” obtained from Kuraray Co., Ltd.] is dissolved in 100 parts of water, and a water-soluble epoxy resin is added to the aqueous solution. Epoxy adhesive added with 1.5 parts of a certain polyamide epoxy additive [trade name “Smile Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30%] And a 40 μm-thick triacetyl cellulose film [trade name “KC4UY” manufactured by Konica Minolta Opto Co., Ltd.] is laminated as the transparent protective film 11, and the adhesive is used on the opposite side, and the thickness is Is a 26 μm brightness enhancement film 21 (made by 3M, trade name Advanced Polarized Film, Version 3) It was. A pressure-sensitive adhesive was applied to the surface on which the triacetylcellulose film (protective film 11) was bonded, and a polarizing plate 50 having a pressure-sensitive adhesive layer 51 was produced. SAT4038T15-JSL (manufactured by Sanei Kaken Co., Ltd.), which is a surface protective film 22 having a base material of a biaxially stretched polyester film having a thickness of 38 μm and an adhesive layer having a thickness of 15 μm and containing a curing agent and an antistatic agent, It bonded to the surface which bonded the improvement film 21 through the said adhesive. This surface protective film 22 had a transmittance of 5% or less with respect to the active energy ray having a wavelength of 190 nm.

The produced polarizing plate 50 with the brightness enhancement film 21 was laminated, and end face polishing was performed under the above conditions. The aspect ratio of the cross section of the brightness enhancement film 21 after the end face polishing was Str = 0.30. This sample was irradiated with an active energy ray having an integrated light amount of 8000 mJ / cm ² . After the adhesive seal 71 for peeling the surface protective film 22 is attached to the surface protective film 22, the end of one side (the right side in FIGS. 3 and 4) of the adhesive seal 71 is placed on the other side (FIG. 3 and FIG. The surface protective film 22 was caused by pulling it to the left of 4), and the cause force when peeling from the brightness enhancement film 21 was measured. The causing force when the surface protective film 22 was peeled from the brightness enhancement film was 4.8 N / 25 mm. In addition, the cause force before irradiation of the activation energy ray was 0.77 N / 25 mm.

[Example 2]
Samples were prepared in the same procedure as in Example 1 and subjected to the same treatment, but the surface protective film 22 protecting APF-V3 is a biaxially stretched polyester film having a thickness of 38 μm and an adhesive layer. SAT4538TF-JSL (manufactured by Sanei Kaken Co., Ltd.) having a thickness of 22 μm and containing a curing agent and an antistatic agent was used. The aspect ratio of the cross section of the brightness enhancement film 21 was Str = 0.30, and the cause force when peeling the surface protection film 22 from the brightness enhancement film 21 was 6.2 N / 25 mm. This surface protective film 22 had a transmittance of 5% or less with respect to the active energy ray having a wavelength of 190 nm.

[Example 3]
A sample was prepared in the same procedure as in Example 1 and subjected to the same treatment, but the surface protective film 22 protecting APF-V3 was a biaxially stretched polyester film having a thickness of 38 μm, and an adhesive layer SAT4238TF-JSL (manufactured by Sanei Kaken Co., Ltd.) having a thickness of 22 μm and containing a curing agent and an antistatic agent was used. The cross-sectional aspect ratio of the brightness enhancement film was Str = 0.30, and the cause force when peeling the surface protection film 22 from the brightness enhancement film 21 was 8.2 N / 25 mm. This surface protective film 22 had a transmittance of 5% or less with respect to the active energy ray having a wavelength of 190 nm.

[Comparative Example 1]
A sample was prepared in the same procedure as in Example 1 and subjected to the same treatment. However, the surface protective film for protecting APF-V3 was a biaxially stretched polyester film having a thickness of 38 μm, and an adhesive layer was formed. AS3-304 (made by Fujimori Kogyo Co., Ltd.) having a thickness of 20 μm was used as the surface protective film 22 shown in FIG. The aspect ratio of the cross section of the brightness enhancement film 21 was Str = 0.30, and the cause force when peeling the surface protective film from the brightness enhancement film 21 was 12.0 N / 25 mm. This surface protective film 22 had a transmittance of 5% or less with respect to the active energy ray having a wavelength of 190 nm.

[Comparative Example 2]
Samples were prepared in the same procedure as in Example 1 and subjected to the same treatment, but the surface protective film for protecting APF-V3 has the same configuration as the surface protective film 22A used in Comparative Example 1, AS3-501 (made by Fujimori Kogyo Co., Ltd.) having a base material of a biaxially stretched polyester film having a thickness of 38 μm and an adhesive layer having a thickness of 15 μm was used. AS3-501 differs from AS3-304 in the thickness and type of adhesive. The cross-sectional aspect ratio of the brightness enhancement film was Str = 0.30, and the cause force when peeling the surface protective film from the brightness enhancement film 21 was too large to be measured. This surface protective film 22 had a transmittance of 5% or less with respect to the active energy ray having a wavelength of 190 nm.

[Reference Example 1]
Samples were prepared and processed in the same procedure as in Example 1, but the active energy rays were not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end face polishing was Str = 0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to the glass 70. The causing force when the surface protective film 22 was peeled from the brightness enhancement film 21 was 0.77 N / 25 mm.

[Reference Example 2]
Samples were prepared and processed in the same procedure as in Example 2, but the active energy rays were not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end face polishing was Str = 0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to the glass 70. When the surface protective film 22 was peeled from the brightness enhancement film 21, the cause force was 2.6 N / 25 mm.

[Reference Example 3]
A sample was prepared in the same procedure as in Example 3 and subjected to the same treatment, but the active energy ray was not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end face polishing was Str = 0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to the glass 70. When the surface protective film 22 was peeled from the brightness enhancement film 21, the cause force was 1.4 N / 25 mm.

[Reference Example 4]
Samples were prepared and processed in the same procedure as in Comparative Example 1, but the active energy rays were not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end face polishing was Str = 0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to the glass 70. When the surface protective film 22 was peeled from the brightness enhancement film 21, the cause force was 1.2 N / 25 mm.

[Reference Example 5]
A sample was prepared and processed in the same procedure as in Comparative Example 2, but the active energy ray was not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end face polishing was Str = 0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into a strip shape was bonded to the glass 70. When the surface protective film 22 was peeled off from the brightness enhancement film 21, the cause force was 7.0 N / 25 mm.

  FIG. 7 is a diagram showing the relationship between the above-mentioned cause force and the delamination occurrence rate in the brightness enhancement film 21. In FIG. As shown in FIG. 7, it was confirmed that the delamination occurrence rate increased as the cause force increased. In this embodiment, as shown in FIG. 5, the case where the delamination occurrence rate is 0 to 10% or less is evaluated as ◯, the case where it exceeds 10% and 20% or less is Δ, and the case where it exceeds 20% is evaluated as ×. It was.

  On the other hand, when active energy ray irradiation is performed and the cause force exceeds 10.0 N / 25 mm, or when the increase rate of the cause force is 700% or more, the delamination occurrence rate is a result of x. However, if the cause force was 10.0 N / 25 mm or less and the rate of increase of the cause force was less than 700%, it was confirmed that the delamination occurrence rate was good or good with a good result.

  The preferred embodiments according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Polarizing film (absorption type polarizing film), 20 ... Optical film, 21 ... Brightness improving film, 22 ... Surface protective film, 50 ... Polarizing plate

Claims (3)

An optical film comprising a surface protective film and a brightness enhancement film,
After the active energy ray having an accumulated light amount of 8000 mJ / cm ² is irradiated, the cause force required for peeling the surface protective film from the brightness enhancement film is 10.0 N / 25 mm or less,
An optical film having an increase rate of the inducing force of less than 700%.   The optical film according to claim 1, wherein the surface protective film has a transmittance of 5% or less for the active energy ray having a wavelength of 190 nm.   A polarizing plate comprising the optical film according to claim 1 or 2 and a polarizing film.

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