TWI813536B - Optical film and polarizing plate - Google Patents

Abstract

Provided is an optical film capable of suppressing a problem of delamination of brightness enhancement film during delamination of surface protective film.

Provided is an optical film 20 provided with a surface protection film 22 and a brightness enhancement film 21, wherein the pulling force required peeling the surface protection film off the brightness enhancement film is 10.0N/25 mm or less after being irradiated with an active energy ray with an accumulated light amount of 8000 mJ/cm², and the increasing rate of the pulling force is less than 700%.

Description

Optical films and polarizing plates

The present invention relates to optical films and polarizing plates.

A polarizing plate is an optical element that has the function of absorbing linearly polarized light with a vibration surface parallel to its absorption axis and transmitting linearly polarized light with a vibration surface orthogonal to the absorption axis. For example, it can be used in liquid crystal display devices. .

In the liquid crystal display device, two polarizing plates are used and one is disposed on the back side and the front side of the liquid crystal unit. The brightness enhancement film is laminated on the polarizing plate disposed on the back side to increase the brightness, thereby improving the contrast of the liquid crystal display device. In mobile devices such as small smartphones and tablet terminals, the battery capacity is limited, so there is an increasing demand for polarizing plates with brightness enhancement films that can achieve power-saving effects.

The so-called brightness enhancement film is an optical element that has the function of transmitting polarized light perpendicular to the direction of its reflection axis and reflecting parallel polarized light. For example, there is known a film in which two types of polymer films with different refractive index are alternately formed. Formed by accumulation of layers.

Before the polarizing plate with the brightness enhancement film is attached to the liquid crystal cell, in order to protect the surface of the brightness enhancement film, the brightness enhancement film is often placed on the polarizer. The surface where the film enters is temporarily covered with a surface protective film. The surface protective film is peeled off and removed from the polarizing plate after the polarizing plate is attached to the liquid crystal cell (for example, see Patent Document 1).

In recent years, in the production process of laminating a polarizing plate and a touch panel, in order to improve the adhesion between films or harden the liquid paste, treatments such as heating, UV irradiation, and application of force are often performed (for example, refer to Patent Document 2 ). Although Patent Document 2 describes a surface protective film with reduced peeling force, the surface protective film described in Patent Document 2 cannot solve the problem of interlayer peeling when the adhered member of the surface protective film is the aforementioned brightness enhancement film.

[Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2004-258393

[Patent Document 2] Japanese Patent Application Publication No. 8-60111

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

Therefore, in a production line that cuts a polarizing plate having a surface protection film and a brightness enhancement film into a predetermined shape, potential cracks are likely to occur on the end face of the brightness enhancement film. When the surface protective film is peeled off after being combined with the liquid crystal cell, peeling will occur between the film layers in the brightness enhancement film, leaving a portion of the brightness enhancement film There is a problem of parts peeling off together with the surface protective film. This phenomenon is called interlaminar peeling. In particular, as described in Patent Document 2, the peeling force of the surface protective film from the adherend tends to increase due to the deterioration of the adhesive layer due to the aforementioned treatment. Especially when irradiated with active energy rays in the ultraviolet region, the peeling force increases significantly.

The present invention was completed in consideration of the above-mentioned circumstances, and an object thereof is to provide an optical film and a polarizing plate that can suppress the defect of interlayer peeling of the brightness enhancement film when peeling off the surface protective film.

One aspect of the present invention provides an optical film, which has a surface protective film and a brightness enhancing film, and has a pulling force required to peel off the surface protective film from the brightness enhancing film after irradiation with active energy rays. It is 10.0N/25mm or less, and the aforementioned pull-up force increase rate does not reach 700%.

In one aspect of the present invention, the surface protective film is laminated on the brightness enhancement film through an adhesive layer, and the adhesive layer can also have a transmittance of 5% or less for the active energy rays with a wavelength of 190 nm. optical film.

One aspect of the present invention provides a polarizing plate having the above-mentioned optical film and polarizing film.

In this specification, a laminated body having a brightness enhancement film and a surface protection film may be simply called an optical film.

The present invention can provide an optical film and a polarizing plate that can suppress the defect of interlayer peeling of a brightness enhancement film when peeling off a surface protective film.

1:Substrate

2:Adhesive layer

3:Polymer layer

10: Polarizing film (absorptive polarizing film)

11: Protective film

20: Optical film

21:Brightness enhancing film

22:Surface protective film

50:Polarizing plate

51: Adhesive layer

70:Glass

71: Then seal the slide

FIG. 1 is a diagram showing an embodiment of the present invention, and is a schematic cross-sectional view of the polarizing plate 50 .

Figure 2 is a diagram showing the relationship between the distance and the applied force when the surface protective film 22 is pulled up from the brightness enhancement film 21.

FIG. 3 is a plan view when measuring the pulling force when peeling off the surface protective film 22 of the polarizing plate 50 from the brightness enhancement film.

Fig. 4 is a cross-sectional view when measuring the pulling force when the surface protective film 22 is peeled off from the brightness enhancement film.

Figure 5 is a diagram showing specifications and evaluations of Examples, Comparative Examples, and Reference Examples.

Figure 6 is a schematic cross-sectional view of the surface protective film in the Example, Comparative Example, and Reference Example.

FIG. 7 is a graph showing the relationship between the pulling force and the occurrence rate of delamination of the brightness enhancement film 21 .

Embodiments of the optical film and polarizing plate of the present invention will be described below with reference to Figures 1 to 7 .

〈Polarizing plate〉

Figure 1 is a schematic cross-sectional view of the polarizing plate 50 . The polarizing plate 50 has a laminated structure in which the polarizing film 10 and the optical film 20 are laminated. In the following description, as shown in FIG. 1 , the polarizing plate 50 is provided with the optical film 20 The side on which the polarizing film 10 is provided is called the upper side, and the side on which the polarizing film 10 is provided is called the lower side. However, this term is only defined in the up and down direction for convenience of explanation, and does not limit the orientation of the optical film 20 and the polarizing plate 50 of the present invention when used.

〈Polarizing 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, one in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin film is usually used. The polyvinyl alcohol-based resin constituting the absorptive polarizing film 10 is obtained by saponifying polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate. 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 degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin can be further modified. For example, aldehyde-modified polyvinyl formaldehyde or polyvinyl acetal can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. Specific examples of polyvinyl alcohol-based resins and dichroic dyes include those listed in Japanese Patent Application Laid-Open No. 2012-159778 [Patent Document 3].

The polyvinyl alcohol-based resin formed into a film is used as the embryonic film of the absorptive polarizing film 10 . The method of forming a polyvinyl alcohol-based resin film is not particularly limited, and the film can be formed by a known method. The thickness of the embryonic membrane composed of polyvinyl alcohol-based resin is not particularly limited, but is, for example, 150 μm or less. Taking into consideration the ease of stretching, etc., the film thickness is preferably 3 μm or more, and more preferably 75 μm or less.

The absorptive polarizing film 10 is, for example, a polyvinyl alcohol-based resin film that is stretched in a uniaxial stretching step, and then undergoes a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye. , the steps of treating the polyvinyl alcohol-based resin film adsorbed with the dichroic pigment with a boric acid aqueous solution, and the steps of washing with water after being treated with the boric acid aqueous solution, and finally drying. In addition, the absorptive polarizing film 10 can be produced according to the method described in Japanese Patent Application Laid-Open No. 2012-159778, for example. In this method, a polyvinyl alcohol-based resin layer as the absorptive polarizing film 10 can be formed by coating a polyvinyl alcohol-based resin on a base film. The thickness of the absorptive 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 of a thermoplastic resin can be 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 composed of a resin that is excellent in transparency, uniform optical properties, mechanical strength, thermal stability, etc. Specific examples of thermoplastic resins include cellulose-based resins such as cellulose triacetate and cellulose diacetate, such as polyethylene terephthalate, polyethylene isophthalate, and polyterephthalate. Polyester resins such as butylene glycol, (meth)acrylic resins such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polycarbonate resins, polyether resins, polyurethane Resin, polyimide resin, polyolefin resin such as polyethylene, polypropylene, polynorbornene resin. In particular, a resin film formed of a cellulose resin, a polyester resin, a (meth)acrylic resin, a polycarbonate resin, or a polyolefin resin is preferred. Here, (meth)acrylate means either methacrylate or acrylate, and the same applies to "(meth)" when referring to (meth)acrylic acid and the like.

Appropriate commercially available products can be used as these thermoplastic resin films. Examples of commercially available cellulose resin films, each represented by a trade name, include "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF" and "Fujitac (registered trademark)" manufactured by Fujifilm Co., Ltd. Trademark) TD80UZ", "KC2UAW", "KC8UX2M" and "KC8UY" made by Konica Minolta Co., Ltd., etc.

Appropriate commercially available products can be used as the polyester resin film. Examples of commercially available polyester resin films, each represented by a trade name, include "Diafoil (registered trademark)" manufactured by Mitsubishi Plastics Co., Ltd. and "Lumirror (registered trademark)" manufactured by Toray Co., Ltd. , "Cosmoshine (registered trademark)" manufactured by Toyobo Co., Ltd., etc.

Appropriate commercially available products can be used for the (meth)acrylic resin film. Examples of commercially available (meth)acrylic resin films, each represented by a trade name, include "Technolloy (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd. and "Acryplen (registered trademark) manufactured by Mitsubishi Rayon Co., Ltd. Registered trademark)" etc.

Appropriate commercial products can be used for the polycarbonate resin film. Examples of commercially available polycarbonate resin films are represented by trade names. Examples include "Panlite (registered trademark)" manufactured by Teijin Kasei Co., Ltd. and the like.

Examples of commercially available polyolefin-based resins include "Topas" manufactured by Topas Advanced Polymers GmbH and sold by Polyplastics Co., Ltd., "ARTON" (registered trademark) sold by JSR Co., Ltd., "ZEONOR (registered trademark)" and "ZEONEX (registered trademark)" sold by Japan ZEON Co., Ltd., "Apel" (registered trademark) sold by Mitsui Chemicals Co., Ltd. (the above are all trade names), etc. Films can be made from these. In addition, polyolefin-based resin films may also be used, and examples thereof include "Arton Film" sold by JSR Co., Ltd. ("Arton" is a registered trademark of the same company) and "Esushina" sold by Sekisui Chemical Industry Co., Ltd. "(registered trademark), "ZeonorFilm" (registered trademark) sold by Japan ZEON Co., Ltd., etc.

In addition, in addition to having the protective film 11 on the lower side, the absorptive polarizing film 10 may also have a protective film on the upper side. Examples of the upper protective film include a brightness enhancement film, a laminate of a brightness enhancement film and a thermoplastic film, and the like.

〈Brightness enhancing film〉

As the brightness enhancement film 21 , for example, a multilayer film of a dielectric or a multilayer laminate having layers with different refractive index anisotropies can be used. Reflective properties; or, like an alignment film of a cholesteric liquid crystal polymer or its alignment liquid crystal layer supported on a film substrate, it can reflect either counterclockwise or clockwise circularly polarized light and allow other light to penetrate Those with suitable characteristics. The types of layers constituting the multilayer laminate may be two or more. As the brightness enhancement film, for example, materials that generate a phase difference due to stretching, such as polyethylene naphthalate, polyethylene terephthalate, and polycarbonate, and polymethacrylic acid can be used. Resins that exhibit a small amount of phase difference, such as acrylic resins represented by methyl ester and norbornene-based resins represented by "Arton" (registered trademark) manufactured by JSR Co., Ltd., are alternately stretched along one axis. Multi-layered laminated body. Specific examples of the brightness enhancing film include "DBEF" (registered trademark), "APF-V4" (product name), "APF-V3" (product name) and "APF-V2" (product name) manufactured by 3M Company. )wait. 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 laminate of the brightness enhancement film and the thermoplastic resin film may be obtained by laminating these films through, for example, an adhesive or an adhesive. As the adhesive or adhesive, it is sufficient to select an appropriate known one. From the viewpoint of ease of joining work and prevention of optical distortion, it is preferable to use an adhesive. As the adhesive, for example, those using acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyethers, etc. as the base polymer can be used. In particular, it is preferable to use an adhesive that has excellent optical transparency like an acrylic adhesive, maintains moderate wettability or cohesion, has excellent adhesion to brightness enhancement films and thermoplastic resin films, and has good heat resistance. It is durable and will not cause peeling problems such as warping or peeling in high temperature environments.

The adhesive layer formed by the adhesive may contain fine particles to exhibit light scattering properties if necessary, and may also contain fillers, pigments, and colorants such as glass fiber, glass beads, resin beads, metal powder, or other inorganic powders. materials, antioxidants, UV absorbers, etc. Examples of ultraviolet absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel azide salt compounds, and the like.

The protective film 11 and the upper protective film may be provided with a hard coat layer on the surface opposite to the bonding surface of the polarizing film. This can prevent scratches etc. that may occur during processing of the polarizing plate. When providing a hard coat layer, from the viewpoint of both protection and flexibility, the thickness of the hard coat layer is preferably 1 to 8 μm , more preferably 1 to 6 μm . When the thickness of the hard coat layer exceeds 8 μm , the bending flexibility becomes low and cracks tend to easily occur when bending. On the other hand, when the thickness of the hard coat layer is less than 1 μm , although the bending property is good, sufficient characteristics tend not to be obtained from the viewpoint of in-plane uniformity.

The hard coat layer can be formed using a resin coating layer. The resin material used to form the resin film layer is not limited as long as the film formed by the resin film layer has sufficient strength and transparency. Examples of the resin include thermosetting resins, thermoplastic resins, active energy ray-curing resins such as ultraviolet curing resins and electron beam curing resins, and two-liquid mixed resins.

In particular, ultraviolet curable resins are suitable because they can harden the resin by irradiation with ultraviolet rays and can efficiently form a resin coating layer with simple processing operations. They can also form light diffusion layers such as anti-glare treatment layers. . Examples of UV-curable resins include polyester-based, acrylic-based, urethane-based, amide-based, polysilicone-based, epoxy-based, and the like, including UV-curable monomers and oligomers. , polymers, etc. Preferably usable ultraviolet curable resins include, for example, those having ultraviolet polymerizable functional groups, and examples thereof include acrylic monomers having 2 or more such functional groups, particularly 3 to 6 such functional groups, or Oligomer components. In addition, ultraviolet curable resin contains an ultraviolet polymerization initiator.

The resin coating layer can be formed by an appropriate known method, such as a method of applying the aforementioned resin (coating liquid) to the protective film 5 and drying it. When using curable resin, perform hardening treatment afterwards. The coating method of the aforementioned coating liquid may be fountain, die-slit coater, casting, spin coating, fountain metaling, gravure, or the like.

In addition, when painting, the aforementioned coating liquid can be diluted with general solvents such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, ethyl alcohol, etc. It can also be applied directly without dilution.

As for the method of laminating the absorbing polarizing film 10 and the protective film, a method of bonding these films with an adhesive is usually used. When the protective films are laminated on both sides of the absorbing polarizing film 10, the same type of adhesive or different types of adhesives can be used.

Examples of the adhesive include water-based adhesives, photocurable adhesives, and the like. Water-based adhesives are those in which the adhesive components are dissolved or dispersed in water, so that the adhesive layer can be made thinner. Examples of water-based adhesives include adhesives (compositions) whose main component is polyethylene. Alcohol-based resin or urethane resin is used as a preferred adhesive.

Polyvinyl alcohol-based resins can be partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, as well as graft-modified polyvinyl alcohol, acetyl-acetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, amine-based Modified polyvinyl alcohol-based resin such as modified polyvinyl alcohol. When polyvinyl alcohol-based resin is used as an adhesive component, the adhesive is often prepared with an aqueous solution of polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight relative to 100 parts by weight of water.

In order to improve the adhesiveness, it is preferable to add a curing component such as glyoxal or a water-soluble epoxy resin or a cross-linking agent to an adhesive containing a polyvinyl alcohol-based resin as a main component. Examples of water-soluble epoxy resins include polyamide polyamines obtained by reacting polyalkylene polyamines such as diethylenetriamine and triethylenetetramine with dicarboxylic acids such as adipic acid, and Polyamide polyamine epoxy resin obtained from the reaction of epichlorohydrin. Commercially available products of this polyamide polyamine epoxy resin, represented by trade names, are "Sumirez Resin (registered trademark) 650 (30)" and "Sumirez Resin (registered trademark) sold by Tagoka Chemical Industry Co., Ltd. Trademark) 675", "WS-525" sold by Starlight PMC Co., Ltd., etc., can be used appropriately. The amount of the curing component or cross-linking agent added is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin. When the added amount is small, the adhesion-improving effect becomes smaller. On the other hand, when the added amount is large, the adhesive layer tends to become brittle.

The laminate (the absorptive polarizing film 10 and the protective film) joined by a water-based adhesive is usually subjected to a drying process to dry and harden the adhesive layer. The drying process can be performed by blowing hot air, for example. The drying temperature can be appropriately selected from the range of 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 dried adhesive layer is usually about 0.001 to 5 μm , preferably 0.01 μm or more, and preferably 2 μm or less, more preferably 1 μm or less.

When the thickness of the adhesive layer becomes too large, the appearance of the polarizing plate is likely to be poor.

After drying, sufficient bonding strength can be obtained by aging at a temperature above room temperature for at least half a day, usually for more than one day. This aging is typically carried out in a rolled state. A preferable aging temperature is in the range of 30 to 50°C, more preferably 35°C or more and 45°C or less. When the aging temperature exceeds 50°C, so-called "winding tightness" is likely to occur in the roll state. In addition, the humidity during aging is preferably appropriately selected such that the relative humidity falls within a range of 70% or less, for example. The maturation 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 that do not have an alicyclic structure, and mixtures thereof.

Moreover, as a photocurable adhesive, a radical polymerization initiator added to an epoxy resin, an acrylic resin, an oxetane resin, a urethane resin, a polyvinyl alcohol resin, etc. can be used. and/or cationic polymerization initiator.

The photocurable adhesive can be cured by irradiating active energy rays after lamination of the laminates joined through a photocurable adhesive. The light source of the active energy ray is preferably an active energy ray having a luminescence distribution at a wavelength of 400 nm or less. Specifically, it is preferable to use a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, or a black light lamp. , microwave excited mercury lamp, metal halide lamp, etc. The intensity of light irradiation to the photocurable adhesive can be appropriately determined according to the composition of the photocurable adhesive and is not particularly limited. However, the irradiation intensity in the wavelength region in which activation of the polymerization initiator is effective is preferably 0.1 to 2500mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time will not be too long, and when it is 2500 mW/cm ² or less, the epoxy resin will be damaged due to the heat radiated from the light source and the heat generated when the photocurable adhesive hardens. There is less risk of yellowing or polarizing plate deterioration.

The light irradiation time of the photocurable adhesive is controlled according to each photocurable adhesive to be cured, but it is preferably set so that the cumulative light amount represented by the product of the above irradiation intensity and the irradiation time becomes 10 to 10,000 mJ/ cm ² . When the cumulative light intensity of the photocurable 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 when it is 10,000 mJ/cm ² or less, The irradiation time will not be too long and good productivity can be maintained. In addition, the thickness of the adhesive layer after active energy ray irradiation is usually about 0.001 to 5 μm , preferably 0.01 μm or more, and preferably 2 μm or less, more preferably 1 μm or less.

When the photocurable adhesive is cured by irradiation with active energy rays, it is preferable that the polarization degree, transmittance, and It is cured under conditions such as hue, transparency of acrylic resin films, optical compensation films, protective films and other transparent films and various functions of the polarizing plate.

In addition, products that can be manufactured with excellent yield under the above-mentioned active energy ray irradiation conditions are limited to the case where an appropriate surface protective film is selected in accordance with Examples 1 to 3 described below.

〈Optical film〉

The optical film 20 is formed by laminating a brightness enhancement film 21 and a surface protection film 22 .

〈Surface protective film〉

FIG. 6 is a schematic cross-sectional view of the surface protective film 22 . The surface protection film 22 is peelably attached to the surface of the protected member (brightness enhancement film 21) to protect the surface. The surface protection film 22 includes: a base material 1, and a brightness enhancement film provided on the base material. The adhesive layer 2 on the lower surface of the promotion film 21 side, and the polymer layer 3 provided on the upper surface of the base material.

As the base material 1, synthetic resins using polyethylene, polypropylene, polyester, polyimide, polycarbonate, etc. as raw materials and laminates thereof can be used. In consideration of transparency and heat resistance during use, a relatively Preferably it is a biaxially stretched polyethylene terephthalate film. The resin film may be non-stretched, uniaxially stretched, or biaxially stretched.

In addition, the stretching ratio of the resin film and the alignment angle of the axis method can be controlled to specific values. In addition to the above-mentioned resin films, films made of other resins may also be used as long as they have the necessary strength and optical properties. again, Corona treatment and other adhesion-facilitating treatments may also be performed on the surface of these substrates.

The film thickness of the substrate 1 is about 12 μm to 100 μm , preferably 20 μm to 80 μm . When the film thickness of the base material 1 is less than 12 μm , if it is too thin, nicks etc. may be generated due to the collision of foreign matter, making it difficult to protect the aforementioned protective member, and it is difficult to protect the protective member without causing wrinkles. or it is difficult to peel off the surface protective film 22 due to lack of toughness. In addition, when the film thickness exceeds 80 μm , the rigidity of the base material is too high, making it difficult to adhere the protective member uniformly without floating, and the curl becomes large, making it difficult to bond the touch panel. In addition, in terms of the price structure of the surface protection film 22, since the base material accounts for a large proportion, the economical efficiency required for the surface protection film 22A is reduced.

The adhesive layer 2 can be adhered to the base material 1 and can be easily peeled off after use. It is not particularly limited as long as it is an adhesive layer that is not easy to stain the adhered surface. Taking into account the effects under high temperature/humid heat conditions. For optical durability, acrylic adhesive is preferred. In addition, the formation method of the adhesive layer 2 and the base material 1 is not particularly limited, and can also be formed by a known coating method or a melt extrusion method.

Regarding the curing agent added to the adhesive layer 2, examples of the crosslinking agent that crosslinks the (meth)acrylate copolymer include isocyanate compounds, epoxy compounds, melamine compounds, metal chelate compounds, and the like. Examples of the tackifier include rosin-based, coumarone-indene-based, terpene-based, petroleum-based, and phenol-based agents.

The polymer layer 3 is provided on the upper side of the base material 1, and a release agent such as a polysilicone type or a fluorine type is added to an acrylic resin or a polyester resin or a resistant resin. It is obtained from one or more polymer compounds such as polyester resin, styrene/acrylonitrile resin, urethane resin, epoxy resin, etc. Moreover, UV curing resin and thermosetting resin can also be used instead of these polymer compounds.

In order to satisfy sufficient contamination prevention function and printability, the polymer layer 3 is preferably 0.003 μm to 3 μm , more preferably 0.02 μm to 1 μm .

In addition, the polymer layer 3 has antistatic properties within the layer. As a method of imparting (using, adding) antistatic properties to the polymer layer, various surfactant-type antistatic agents such as cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, and nonionic antistatic agents are used/added. Electrostatic agents, or conductive polymers such as polyaniline, polypyrrole, and polythiophene, conductive fillers, and whiskers. In this embodiment, the increase rate of the pull-up force can be controlled by adjusting the amount of the hardener and the amount of the antistatic agent. However, it is possible to increase the amount of the antistatic agent and reduce the amount of the hardener added to the adhesive layer 2. It is better to reduce the increase rate of pulling force.

The polymer layer 3 can also be formed by mixing the aforementioned silicon/acrylate comb-shaped graft polymer and other adhesives that are polymer compounds. The silicon/acrylate comb-shaped graft polymer and other polymer compounds are The weight ratio of the compound to the adhesive 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 generated by the adhesive tape will be too weak, and the peeling operation of the surface protective film 22 using a cellophane adhesive film will also cause problems. hinder. On the other hand, if the ratio is too small, the water repellency or contamination prevention performance will be insufficient, and interlayer delamination may occur in the brightness enhancement film 21, so it is necessary to appropriately adjust the polymerization. The amount of release agent added to the compound.

唑啉基的聚合物所構成之導電性化合物。於基材形成抗靜電層時，可藉由使前述物質溶解於有機溶劑等中形成塗裝液，並使用公知之任意的塗布方法，例如凹版塗佈法或逆向塗佈法、滾筒塗佈法等而形成。 In addition, the polymer layer 3 may have an antistatic layer between the polymer layer 3 and the base material 1 in addition to having antistatic properties within the layer. The antistatic layer can use various surfactant-type antistatic agents such as cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, nonionic antistatic agents, or polyester resins, acrylic resins, etc. Adhesive person. Alternatively, conductive polymers such as polyaniline, polypyrrole, and polythiophene, conductive fillers, and whiskers dispersed in an adhesive may be used. Furthermore, it can also be used in polymer compounds such as acrylic type, polyester type, and polyurethane type, which are composed of a resin having a phosphate group or a phosphate group and a resin having a phosphate group.

A conductive compound composed of oxazoline-based polymers. When forming an antistatic layer on a substrate, the aforementioned substances can be dissolved in an organic solvent to form a coating liquid, and any known coating method can be used, such as gravure coating, reverse coating, and roller coating. etc. formed.

And it can also be formed by melt extrusion.

In addition, in the polarizing plate 50 of this embodiment, the adhesive layer 51 is provided on the lower surface of the protective film 11 . The adhesive forming the adhesive layer 51 can be any one that satisfies various characteristics (transparency, durability, heavy workability, etc.) used in the optical film. For example, an acrylic adhesive containing an acrylic resin and a cross-linking agent can be used. This acrylic resin is an acrylic monomer composition containing (meth)acrylate as a main component and a small amount of (meth)acrylic monomer having a functional group, and is subjected to radical polymerization in the presence of a polymerization initiator. It is polymerized and has a glass transition temperature (Tg) below 0°C.

The surface protective film obtained in this way has a pulling force of 10.0N/25mm or less, preferably 8.0N/25mm or less after being irradiated with active energy rays with a cumulative light intensity of 8000mJ/ ^cm2 in the UVB region (280 to 350nm). , preferably 7.0N/25mm or less, and more preferably 5.0N/25mm or less. The peeling force of the surface protective film obtained in this way after being irradiated by active energy rays with a cumulative light intensity of 8000mJ/ ^cm2 in the UVB region (280 to 350nm) is preferably 3.0N/25mm or less, and more preferably 1.0N/ 25mm or less, more preferably 0.5N/25mm or less, particularly preferably 0.2N/25mm or less, and more preferably 0.01N/25mm or more. The irradiation intensity at this time can be set to 500mW/cm ² . By setting the peeling force to 0.01N/25mm or more, the surface protective film can be prevented from peeling off from the brightness enhancement film during transportation.

In addition, before and after irradiation with active energy rays with a cumulative light intensity of 8000 mJ/cm ² , the rate of increase in the pulling force is less than 700%, and preferably less than 600%. In order to reduce the rate of increase of the pulling force, the transmittance of the surface protective film at a wavelength of 190 nm is preferably 10% or less, more preferably 5% or less.

The polarizing plate of the present invention is preferably one whose end surface is ground. By performing grinding processing, the dimensional accuracy of the polarizing plate shape can be improved and the polarizing plate can be prevented from cracking. On the other hand, due to the polishing process, the aspect ratio of the surface of the polarizing plate, especially the end surface of the brightness enhancement film, becomes large, and when the surface protective film is peeled off after irradiating active energy rays in this state, brightness may easily occur. Promote film delamination. According to the present invention, for example, even if the aspect ratio Str of the surface of the end surface of the brightness enhancement film is 0.25 or more or 0.28 or more, delamination can be effectively suppressed. That is to say, through the present invention, it is possible to simultaneously improve the dimensional accuracy of the polarizer, prevent cracks of the polarizer, and suppress interlayer peeling.

When performing such grinding processing, for example, the apparatus described in International Publication No. 2011/040636 can be used. This device has a rotary body and a plurality of cutting edges provided on a disc-shaped installation surface perpendicular to the rotation axis of the rotary body. The device is configured to contact the cutting edge with the end surface of the polarizing plate while rotating the rotary body. , and those who grind the end surface of the polarizing plate.

In this embodiment, in order to control the surface aspect ratio Str within a predetermined range, it is preferred to increase the number of cutting edges and reduce the rotation speed of the rotating body. For example, it is preferred that the number of cutting edges be 3 or more. It is 5 or more, and the rotation speed of the rotating body is, for example, 10,000 rpm or less, preferably 6,000 rpm or less, and more preferably 5,000 rpm or less.

In addition, in order to further suppress the occurrence of interlayer delamination, when the polarizing plates are laminated and polished, it is preferred that the end surfaces of the polarizing plates come into contact with the center portion of the disc-shaped installation surface.

In the adhesive layer 51, on the opposite side to the liquid crystal cell (not shown) bonded to the polarizing plate 50, a polarizing plate of the same type or a known polarizing plate may be laminated. In addition, the polarizing plate 50 provided with the adhesive layer 51 is preferably disposed on the back side (backlight side) of the liquid crystal display device, and more preferably is disposed so that the surface protective film 22 side becomes the backlight side.

(Example)

The following examples will be cited to illustrate the present invention in more detail, but the present invention is not limited to these examples. Unless otherwise stated in the examples, "%" and "parts" expressed in content or usage are based on weight.

[Sample preparation method]

(End face treatment)

The end surface treatment was performed using the device described in International Publication No. 2011/040636.

A plurality of polarizing plates 50 are stacked on top of each other, and the laminated film is held between the two outermost film surfaces by a pair of resin clamping members, with the blade surface of the rotating blade facing the side of the laminated film. The peripheral surface of the assembly is precisely cut by the rotating blade together with the peripheral surface of the clamping member. At this time, the rotation speed of the rotating body is 4800 rpm.

(active energy ray irradiation)

Measuring machine: [Fusion UV B2-006 manufactured by Fusion UV Systems Co., Ltd.]

Set the conveyor belt speed: 10m/min, height: 50mm, light intensity: 100%, valve: D valve, and for the polarizing plate 50 attached to the soda-lime glass, start from the surface protective film side so that the UVB area (280 to 315nm ), active energy rays with an irradiation intensity of 500 mJ/cm ² are irradiated so that the accumulated light amount becomes 8000 mJ/cm ² .

[Evaluation method]

(pull force)

Measuring machine: Using [Shimadzu Corporation's universal testing machine AGS-50NX], the surface protective film 22 is peeled off from the brightness enhancement film 21 using a peeling width of 25 mm, a peeling angle of 180°, and a peeling speed of 300 mm/min. Experiment. Figure 2 is a diagram showing the relationship between distance and force when the surface protection film 22 is pulled up from the brightness enhancement film 21. As shown in FIG. 2 , in the initial stage of peeling off the surface protective film 22 from the brightness enhancement film 21 , a large force is required to pull up, but the pulling force becomes smaller after the peeling starts. In this embodiment, the maximum value until the surface protective film 22 is peeled off by 25 mm from the starting point is defined as the pulling force, and the force thereafter is defined as the peeling force. ‧The rate of increase in the pull-up force...The pull-up force measured before and after irradiating active energy rays with an irradiation intensity of 500 mJ/cm ² so that the cumulative light amount in the UVB region becomes 8000 mJ/cm ² is calculated using the following formula Rise rate.

Rise rate = [(N1-N0)/N0] × 100 Unit: %, N0: Pulling force before UV irradiation, N1: Pulling force after UV irradiation

FIG. 3 is a plan view when measuring the pulling force when peeling off the surface protective film 22 of the polarizing plate 50 from the brightness enhancement film. FIG. 4 is a cross-sectional view when measuring the pulling force when peeling the surface protective film 22 from the brightness enhancement film. In the peeling test, the adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into long strips is bonded to the glass 70 as shown in Figures 3 and 4.

The pull-up force was measured using 10 samples, and the average value was calculated. The pull-up force was measured before and after irradiating the polarizing plate 50 with active energy rays. After irradiation with active energy rays, place it in an environment of 25°C and 55% RH. After the temperature of the sample cools to 23°C, the pull-up force is measured.

(Aspect ratio of the cross section of the brightness enhancement film 21)

Using a measuring machine: [Olympus Co., Ltd. model: OLS4100], the surface roughness was measured in ultra-high-speed mode with a magnification set to 100 times. Cut out 3cm each time from two end surfaces in the direction perpendicular to the extending direction of the brightness enhancement film, and measure the width at 5 points each time. When the aspect ratio is larger, the cross section will have uneven unevenness and a rough texture. The smaller the aspect ratio, the cross-section is uniform and no cracks or defects occur.

[Sample production]

According to the specifications shown in Figure 5, samples of Examples 1 to 3, Comparative Examples 1 to 2, and Reference Examples 1 to 5 were produced.

[Example 1]

The polarizing plate 50 is produced in the following manner. First, a polyvinyl alcohol film with a thickness of 60 μm (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) is uniaxially stretched to about 5 times by dry stretching, and then, while maintaining the tensile state, is immersed in 60 °C pure water for 1 minute, and then immersed in an aqueous solution with 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 with a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72° C. for 300 seconds. Then, it was washed with pure water at 26° C. for 20 seconds, and then dried at 65° C. to obtain a 23 μm thick polarizer with iodine adsorbed and aligned on the polyvinyl alcohol film. Next, an epoxy-based adhesive is applied to one side of the polarizer, wherein the epoxy-based adhesive is dissolved in 100 parts of water with 3 parts of carboxyl-modified polyvinyl alcohol [trade name obtained from Kuraray Co., Ltd. "KL-318"], and add a polyamide epoxy additive as a water-soluble epoxy resin [trade name "Sumirez Resin (registered trademark) 650(30) obtained from Tagoka Chemical Industry Co., Ltd. ", an aqueous solution with a solid concentration of 30%] 1.5 parts, and then laminated to a 40 μm thick cellulose triacetate film [trade name "KC4UY" manufactured by Konica Minolta Opto Co., Ltd.] as the transparent protective film 11 , and the brightness enhancement film 21 (manufactured by 3M, trade name Advanced Polarized Film, Version 3) with a thickness of 26 μm is bonded to the opposite side using the aforementioned adhesive. An adhesive is applied to the surface on which the cellulose triacetate film (protective film 11 ) is laminated, thereby producing a polarizing plate 50 having an adhesive layer 51 . The base material is a biaxially stretched polyester film with a thickness of 38 μm , the thickness of the adhesive layer is 15 μm , and SAT4038T15-JSL (Sun A. Kaken Co., Ltd.) containing a hardener and an antistatic agent is used as the surface protection film 22. Co., Ltd.), and is bonded to the surface where the brightness enhancement film 21 is bonded through the aforementioned adhesive. The surface protective film 22 has a transmittance of 5% or less for the aforementioned active energy rays with a wavelength of 190 nm.

The produced polarizing plate 50 with the brightness enhancement film 21 was laminated, and end surface polishing was performed under the above conditions. The aspect ratio of the cross section of the end-face-polished brightness enhancement film 21 is Str=0.30. This sample was irradiated with active energy rays with a cumulative light intensity of 8000 mJ/cm ² . After attaching the adhesive seal 71 for peeling off the surface protective film 22 to the surface protective film 22, pull the end of one side of the adhesive seal 71 (the right side in Figures 3 and 4) to the other side. One side (the left side of Figures 3 and 4) was used to pull up the surface protective film 22, and the pulling force when peeled off from the brightness enhancement film 21 was measured. The pulling force when peeling off the surface protective film 22 from the brightness enhancement film was 4.8N/25mm.

In addition, the pulling force before activation energy ray irradiation is 0.77N/25mm.

[Example 2]

Samples were made using the same process as in Example 1, and the same treatment was performed, except that the surface protective film 22 to protect APF-V3 was used: the base material was a biaxially stretched polyester film with a thickness of 38 μm , and the thickness of the adhesive layer was SAT4538TF-JSL (manufactured by Sun A. Kaken Co., Ltd.) that is 22 μm and contains a hardener and an antistatic agent. The aspect ratio of the cross section of the brightness enhancement film 21 is Str=0.30, and the pulling force when peeling off the surface protection film 22 from the brightness enhancement film 21 is 6.2N/25mm. The surface protective film 22 has a transmittance of 5% or less for the aforementioned active energy rays with a wavelength of 190 nm.

[Example 3]

Samples were made using the same process as in Example 1, and the same treatment was performed, but the surface protective film 22 to protect APF-V3 was used: the base material was a biaxially stretched polyester film with a thickness of 38 μm , and the thickness of the adhesive layer was SAT4238TF-JSL (manufactured by Sun A. Kaken Co., Ltd.) that is 22 μm and contains a hardener and an antistatic agent. The aspect ratio of the cross section of the brightness enhancement film is Str=0.30, and the pulling force when peeling off the surface protection film 22 from the brightness enhancement film 21 is 8.2N/25mm. The surface protective film 22 has a transmittance of 5% or less for the aforementioned active energy rays with a wavelength of 190 nm.

[Comparative example 1]

Samples were made using the same process as in Example 1, and the same treatment was performed, except that the surface protective film to protect APF-V3 used a biaxially stretched polyester film with a thickness of 38 μm as the base material and a thickness of the adhesive layer of 20 μm . AS3-304 (manufactured by Fujimori Industries, Ltd.) is used as the surface protective film 22 as shown in Fig. 6 . The aspect ratio of the cross section of the brightness enhancement film 21 is Str=0.30, and the pulling force when peeling off the surface protective film from the brightness enhancement film 21 is 12.0N/25mm. The surface protective film 22 has a transmittance of 5% or less for the aforementioned active energy rays with a wavelength of 190 nm.

[Comparative example 2]

Samples were prepared using the same process as in Example 1, and were subjected to the same treatment. However, the surface protective film to protect APF-V3 was made with the same structure as the surface protective film 22A used in Comparative Example 1, that is, the base material had a thickness of 38 µm biaxially stretched polyester film and the thickness of the adhesive layer is 15 µm AS3-501 (manufactured by Fujimori Industrial Co., Ltd.). AS3-501 and AS3-304 are different in thickness and type of adhesive. The aspect ratio of the cross section of the brightness enhancement film is Str=0.30, and the pulling force when peeling off the surface protective film from the brightness enhancement film 21 is too large and cannot be measured. The surface protective film 22 has a transmittance of 5% or less for the aforementioned active energy rays with a wavelength of 190 nm.

[Reference example 1]

A sample was prepared using the same process as in Example 1, and the same treatment was performed, but no active energy rays were irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end surface grinding is Str=0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into strips is bonded to the glass 70 . The pulling force when peeling off the surface protective film 22 from the brightness enhancement film 21 is 0.77N/25mm.

[Reference example 2]

A sample was prepared using the same process as in Example 2, and the same treatment was performed, but no active energy rays were irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end surface grinding is Str=0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into strips is bonded to the glass 70 . The pulling force when peeling off the surface protective film 22 from the brightness enhancement film 21 was 2.6N/25mm.

[Reference example 3]

A sample was prepared using the same process as in Example 3, and the same treatment was performed, but no active energy rays were irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end surface grinding is Str=0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into strips is bonded to the glass 70 . The pulling force when peeling off the surface protective film 22 from the brightness enhancement film 21 is 1.4N/25mm.

[Reference Example 4]

A sample was prepared using the same process as Comparative Example 1, and the same treatment was performed, except that the active energy rays were not irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end surface grinding is Str=0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into strips is bonded to the glass 70 . The pulling force when peeling off the surface protective film 22 from the brightness enhancement film 21 is 1.2N/25mm.

[Reference Example 5]

A sample was prepared using the same process as Comparative Example 2, and the same treatment was performed, except that no active energy rays were irradiated. The aspect ratio of the cross section of the brightness enhancement film 21 after end surface grinding is Str=0.30. The adhesive layer 51 of the polarizing plate 50 with the brightness enhancement film 21 cut into strips is bonded to the glass 70 . The pulling force when peeling off the surface protective film 22 from the brightness enhancement film 21 is 7.0 N/25mm.

FIG. 7 is a graph showing the relationship between the above-mentioned pulling force and the occurrence rate of delamination of the brightness enhancement film 21 . As shown in Figure 7, it was confirmed that the greater the pulling force, the greater the occurrence rate of interlaminar delamination. In this embodiment, as shown in Figure 5, the case where the occurrence rate of interlaminar delamination is 0 to 10% or less is evaluated as ○, the case where it exceeds 10% and 20% or less is evaluated as △, and the case where it exceeds 20% is evaluated as ○. is ×.

On the other hand, when active energy ray irradiation is carried out, if the pull-up force exceeds 1.0N/25mm or the increase rate of the pull-up force is 700% or more, the result of the occurrence rate of delamination is shown as ×, but as long as the pull-up force If it is 10.0N/25mm or less and the pull-off force increase rate is less than 700%, it can still be confirmed that the occurrence rate of delamination is a good result of ○ or △.

The above content describes suitable embodiments of the present invention with reference to the appended drawings, but it goes without saying that the present invention is not limited to these examples. The various shapes or combinations of the constituent components shown in the above examples are only examples, and shall not deviate from the gist of the present invention. Various changes can be made based on design requirements, etc.

10: Polarizing film (absorptive polarizing film)

11: Protective film

20: Optical film

21:Brightness enhancing film

22:Surface protective film

50:Polarizing plate

51: Adhesive layer

Claims (8)

An optical film having a surface protection film and a brightness enhancement film, and after being irradiated with active energy rays with a cumulative light intensity of 8000mJ/ ^cm2 , the pulling force is 7.0N when the surface protection film is peeled off from the brightness enhancement film /25mm or less, where the pull-up force is the maximum value within 25 mm from the starting point of peeling, and the pull-up force measured before and after the irradiation of the active energy ray is used to calculate the increase rate of the pull-up force using the following formula Less than 700%, rising rate = [(N1-N0)/N0]×100 N0: Pulling force before irradiation of active energy rays, N1: Pulling force after irradiation of active energy rays. An optical film comprising a surface protective film and a brightness enhancing film with a thickness of 50 μm or less, and after being irradiated with active energy rays with a cumulative light quantity of 8000 mJ/cm ² and peeling off the surface protective film from the brightness enhancing film, The pulling force is 10.0N/25mm or less, where the pulling force is the maximum value within 25mm of peeling from the starting point, and the pulling force measured before and after irradiation of the active energy ray is calculated using the following formula The rising rate of force does not reach 700%, rising rate = [(N1-N0)/N0]×100 N0: the pulling force before irradiation of active energy rays, N1: the pulling force after irradiation of active energy rays. An optical film, the end surface of which is processed by grinding. The aforementioned optical film has a surface protection film and a brightness enhancement film. After being irradiated with an active energy ray with a cumulative light amount of 8000mJ/ ^cm2 , the aforementioned surface protection film is improved from the aforementioned brightness. When the film is peeled off, the pulling force is 10.0N/25mm or less, where the pulling force is the maximum value within 25mm from the starting point until the film is peeled off, and the pulling force measured before and after irradiation of the aforementioned active energy rays is used. The rise rate of the pull-up force calculated by the following formula does not reach 700%. The rise rate = [(N1-N0)/N0]×100 N0: the pull-up force before irradiation of active energy rays, N1: the pull-up force after irradiation of active energy rays Get up. An optical film, which has a surface protection film and a brightness enhancement film. The aspect ratio Str of the brightness enhancement film on the surface of the end surface is more than 0.25. After the above optical film is irradiated with active energy rays with a cumulative light amount of 8000mJ/ ^cm2 , When peeling off the surface protective film from the brightness enhancing film, the pulling force is 10.0 N/25 mm or less, where the pulling force is the maximum value within 25 mm from the starting point, and will be before and after irradiation of the active energy rays. The measured pull-up force was calculated using the following formula, and the increase rate of the pull-up force did not reach 700%. The increase rate = [(N1-N0)/N0] × 100 N0: the pull-up force before irradiation of active energy rays, N1: Pulling force after irradiation with active energy rays. The optical film according to any one of items 1 to 4 of the patent application, wherein the surface protection film is peeled off from the brightness enhancement film after being irradiated with active energy rays with a cumulative light intensity of 8000 mJ/cm ² . The required peeling force is 0.11N/25mm or less. The optical film according to claim 5, wherein the increase rate of the peeling force is 95% or less. The optical film according to any one of items 1 to 4 of the patent application, wherein the transmittance of the surface protective film to the active energy rays with a wavelength of 190 nm is 5% or less. A polarizing plate having the optical film described in any one of items 1 to 7 of the patent application scope and a polarizing film.