JP2019020718A - Optical sheet - Google Patents

Abstract

To provide an optical sheet less likely causing such a problem (multi-sheet picking) that upon picking an optical sheet one by one from a stack where optical sheets are stacked, a plurality of optical sheets are picked at one picking operation.SOLUTION: The optical sheet has a surface protective film, a polarizing plate and a release film, in this order, in which a coefficient of dynamic friction between the surface protective film and the release film is 0.40 or less. It is preferable that the surface of the release film opposite to the polarizing plate has an abundance of silicon atoms of 3% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical sheet.

  The polarizing plate is widely used in image display devices such as liquid crystal display devices, particularly in various mobile devices such as smartphones in recent years. Conventionally, a polarizing plate has been used in which a protective film is bonded to one or both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film.

  The polarizing plate is marketed as an optical sheet with a peelable surface protective film (also called a protect film) and a peelable film (also called a separate film) attached to the surface to prevent the surface from becoming dirty or scratched. It is common to be done.

  When the polarizing plate is bonded to a display element such as a liquid crystal cell, the optical sheets are taken out one by one from the laminate in which a plurality of the optical sheets are stacked. And a peeling film is peeled from an optical sheet, and it bonds to a display element through the exposed adhesive layer.

  Patent Document 1 proposes automating the removal of an optical sheet by a machine in order to efficiently perform the process of removing the optical sheet (Patent Document 1). When the optical sheet is automatically taken out in this way, there is a problem that a plurality of optical sheets are taken out by one take-out (hereinafter, sometimes referred to as multiple taking).

  In addition, when the polarizing plate is thick, the optical sheet is separated by the weight of the optical sheet including the polarizing plate, so that it is difficult to take multiple sheets, but recently there is an increasing demand for thinning the polarizing plate. Multiple actions are likely to occur because the action is small.

JP 2006-308912 A

  An object of the present invention is to provide an optical sheet that is unlikely to be subjected to multiple taking when an optical sheet is taken out one by one from a laminate in which a plurality of optical sheets are stacked.

[1] It has a surface protective film, a polarizing plate, and a release film in this order,
An optical sheet having a dynamic friction coefficient between the surface protective film and the release film of 0.40 or less.
[2] The optical sheet according to claim 1, wherein the surface of the release film opposite to the polarizing plate has a silicon atom content of 3% or more.
[3] The release film has a marking on the surface opposite to the polarizing plate,
The optical sheet according to claim 1 or 2, wherein a ratio of the area of the marking to the area of the release film is 2% or less.

  When taking out an optical sheet from a laminated body in which a plurality of optical sheets are stacked one by one, it is possible to provide an optical sheet in which multiple taking is unlikely to occur.

It is a schematic sectional drawing which shows an example of the layer structure which the optical sheet of this invention has. It is a schematic sectional drawing which shows an example of the laminated body with which the optical sheet of this invention overlapped two or more. It is the schematic plan view which looked at the optical sheet of this invention from the peeling film side. It is the schematic which shows an example of marking.

<Optical sheet>
FIG. 1 is a schematic sectional view showing an example of the optical sheet of the present invention. An optical sheet 10 shown in FIG. 1 is a laminated film having a surface protective film 2, a polarizing plate 1, and a release film 3 in this order. In the optical sheet 10, the surface protective film 2, the polarizing plate 1, and the release film 3 are preferably laminated in this order. In the optical sheet 10, the surface protective film 2 and the release film 3 are preferably members that constitute the outermost surface of the optical sheet.

  The optical sheet 10 may be obtained by manufacturing a long optical sheet by roll-to-roll while conveying each member constituting the optical sheet 10 and cutting the optical sheet, or each of the predetermined shapes. You may obtain by preparing each member and laminating sequentially.

  The shape of the optical sheet is not particularly limited, but may be a polygon such as a rectangle or a triangle, a circle, an ellipse, or a combination thereof.

Area of the optical sheet is not particularly limited, for example, is preferably 18600～2500Mm ^2, more preferably 12600~6870mm ^2. When the area of the optical sheet is smaller than 18600 mm ² , it is difficult to separate into individual optical sheets by its own weight as described above, and thus the effect of the present invention is remarkable. When the area of the optical sheet is larger than 2500 mm ² , it is easy to adjust the frictional force as described later.

  From the same viewpoint, when the optical sheet has a rectangular shape having a long side and a short side, the length of the long side is preferably 17.3 to 6.6 cm, and preferably 15.5 to 11.0 cm. More preferably, the length of the short side is preferably 10.8 to 3.7 cm, and more preferably 8.7 to 6.2 cm.

  In the present invention, the dynamic friction coefficient between the surface protective film and the release film is 0.40 or less, and preferably 0.30 or less. On the other hand, when the surface protective film or the like is peeled off using the release tape, the dynamic friction coefficient is preferably 0.10 or more from the viewpoint of enhancing the adhesion between the release tape and the surface protective film. It may be 20 or more. The method for measuring the dynamic friction coefficient follows the method described in Examples described later.

  As will be described later, the dynamic friction coefficient can be controlled by the existence ratio of silicon atoms on the surface of the release film, the surface resistivity of the surfaces of the release film and the surface protective film, and the like. When the dynamic friction coefficient is controlled by the surface resistivity, at least one of the release film and the surface protective film preferably has an antistatic function, and both preferably have an antistatic function.

Hereinafter, each member of the optical sheet will be described.
<Polarizing plate>
The polarizing plate 1 is a polarizing element including at least a polarizer, and usually further includes a thermoplastic resin film bonded to one side or both sides thereof. The thermoplastic resin film can be a protective film for protecting the polarizer, another optical film having an optical function different from that of the polarizer, or the like. A thermoplastic resin film is a resin layer (for example, a hard coat layer, an antistatic layer, an antiglare layer, a light diffusing layer, a retardation layer (a retardation layer having a quarter wavelength retardation value, etc.) ), At least one optical layer selected from an antireflection layer, a low refractive index layer, an antifouling layer, and the like. A thermoplastic resin film can be bonded to a polarizer via an adhesive layer or an adhesive layer. The surface protective film 2 may be laminated on the surface of this resin layer.

  The thickness of the polarizing plate 1 is not particularly limited, but the effect of the present invention is remarkable when the thickness is usually 200 μm or less, and multiple capture is likely to occur due to its own weight, which is 150 μm or less, and further 125 μm or less. The thickness of the polarizing plate 1 is preferably 30 μm or more, more preferably 50 μm or more.

(1) Polarizer The polarizer constituting the polarizing plate 1 absorbs linearly polarized light having a vibration surface parallel to the absorption axis, and linearly polarized light having a vibration surface orthogonal to the absorption axis (parallel to the transmission axis). An absorptive polarizer having a transmitting property, and a polarizing film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film can be suitably used. The polarizer is, for example, a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye; a polyvinyl on which the dichroic dye is adsorbed It can be produced by a method comprising a step of treating an alcohol-based resin film with a crosslinking solution such as an aqueous boric acid solution; and a step of washing with water after the treatment with the crosslinking solution.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamides having ammonium groups, and the like.

  In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl. The same applies to “(meth) acryloyl”, “(meth) acrylate”, and the like.

  The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined according to JIS K 6726.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer (polarizing film). The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol raw film is not particularly limited, but in order to make the thickness of the polarizer 15 μm or less, it is preferable to use a film having a thickness of 5 to 35 μm. More preferably, it is 20 μm or less.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during the crosslinking treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin film is swollen using a solvent or water. The draw ratio is usually 3 to 8 times.

  As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  As the crosslinking treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution is usually employed. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide.

  The thickness of the polarizer is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less. In particular, setting the thickness of the polarizer to 15 μm or less is advantageous for reducing the thickness of the optical sheet. The thickness of the polarizer is usually 2 μm or more.

(2) Protective film The protective film which can be laminated | stacked on the single side | surface or both surfaces of a polarizer has a translucent (preferably optically transparent) thermoplastic resin, for example, chain | strand-shaped polyolefin resin (polypropylene resin) Etc.), polyolefin resins such as cyclic polyolefin resins (norbornene resins, etc.); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; (Meth) acrylic resins such as methyl methacrylate resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile / butadiene / styrene resins; acrylonitrile / styrene resins; polyvinyl acetate resins; Resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polysulfone resin; Polyethersulfone resin; Polyarylate resin; Polyamideimide resin; Polyimide resin;

  As the chain polyolefin-based resin, polyethylene resin (polyethylene resin which is a homopolymer of ethylene or a copolymer mainly composed of ethylene), polypropylene resin (polypropylene resin which is a homopolymer of propylene, or propylene as a main component) And a copolymer composed of two or more chain olefins in addition to a chain olefin homopolymer such as

  The cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or their derivatives, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  The polyester-based resin is a resin having an ester bond excluding the following cellulose ester-based resin, and is generally composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A typical example of the polyester resin is polyethylene terephthalate which is a polycondensate of terephthalic acid and ethylene glycol.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50-100). % Methyl methacrylate resin is used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, these copolymers and those in which a part of the hydroxyl group is modified with other substituents are also included. Among these, cellulose triacetate (triacetyl cellulose) is particularly preferable.

  A polycarbonate resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group.

It is also useful to control the retardation value of the protective film to a value suitable for an image display device such as a liquid crystal display device. For example, in an in-plane switching (IPS) mode liquid crystal display device, it is preferable to use a film having a substantially zero retardation value as the protective film. The phase difference value of substantially zero means that the in-plane retardation value R ₀ at a wavelength of 590 nm is 10 nm or less, the absolute value of the thickness direction retardation value R _th at a wavelength of 590 nm is 10 nm or less, and a wavelength of 480 to 750 nm. It means that the absolute value of the thickness direction retardation value _Rth at 15 is 15 nm or less.

  For example, depending on the mode of the liquid crystal display device, the protective film may be stretched and / or shrunk to give a suitable retardation value. For example, a retardation layer (or film) having a single layer or a multilayer structure can be used as a protective film for the purpose of viewing angle compensation. In this case, the polarizing plate 1 can be an elliptically polarizing plate or a circularly polarizing plate including a laminated structure of a polarizer and a retardation layer, or a polarizing plate having a viewing angle compensation function including a retardation layer.

  Although the thickness of a protective film is 1-100 micrometers normally, it is preferable that it is 5-60 micrometers from viewpoints, such as intensity | strength and a handleability, and it is more preferable that it is 5-50 micrometers. When the thickness is within this range, the polarizer is mechanically protected, and the polarizer does not shrink even when exposed to a humid heat environment, and stable optical characteristics can be maintained.

  In the case where protective films are bonded to both surfaces of the polarizer, these protective films may be composed of the same kind of thermoplastic resin or may be composed of different kinds of thermoplastic resins. Moreover, the thickness may be the same or different. Furthermore, they may have the same phase difference characteristics or different phase difference characteristics.

  As described above, at least one of the protective films has a hard coat layer, an antiglare layer, a light diffusing layer, a retardation layer (1/4 wavelength position) on the outer surface (the surface opposite to the polarizer). A retardation layer having a phase difference value), an antireflection layer, a low refractive index layer, an antistatic layer, and a surface treatment layer (coating layer) such as an antifouling layer may be provided.

  From the viewpoint of suppressing the mixing of bubbles between the surface protective film and the polarizing plate, the surface of the polarizing plate 1 on the surface protective film 2 side (the surface to which the surface protective film 2 is bonded) is JIS B 0601: 2013. It is preferable that the arithmetic average roughness Ra based on the above is small. Specifically, Ra on the surface is preferably 0.3 μm or less, more preferably 0.2 μm or less, and further preferably 0.15 μm or less. The surface Ra is usually 0.001 μm or more, for example, 0.005 μm or more.

  The protective film can be bonded to the polarizer through an adhesive layer, for example. As the adhesive forming the adhesive layer, a water-based adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive can be used, and a water-based adhesive and an active energy ray-curable adhesive are preferable.

  Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. Among these, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used. Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer, or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can contain a crosslinking agent such as an aldehyde compound (glyoxal, etc.), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, and a polyvalent metal salt.

  When using a water-based adhesive, it is preferable to carry out a drying step for removing water contained in the water-based adhesive after pasting the polarizer and the protective film. After the drying process, for example, a curing process for curing at a temperature of 20 to 45 ° C. may be provided.

  The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and preferably ultraviolet curable adhesives. It is.

  The curable compound may be a cationic polymerizable curable compound or a radical polymerizable curable compound. Examples of the cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further includes a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  In laminating the polarizer and the protective film, a surface activation treatment may be applied to at least one of these laminating surfaces in order to enhance adhesiveness. As the surface activation treatment, dry treatment such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.) And wet treatment such as ultrasonic treatment using a solvent such as water and acetone, saponification treatment, and anchor coat treatment. These surface activation treatments may be performed alone or in combination of two or more.

  When protective films are bonded to both surfaces of the polarizer, the adhesive for bonding these protective films may be the same type of adhesive or different types of adhesives.

(3) Other optical film The polarizing plate 1 can contain other optical films other than a polarizer and a protective film, The representative example is a brightness enhancement film and retardation film. When the polarizing plate 1 contains another optical film, the surface protective film 2 may be laminated | stacked on the surface of this optical film, or the surface of the resin layer laminated | stacked on this optical film.

  The brightness enhancement film is also referred to as a reflective polarizing film, and a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmitted polarized light, reflected polarized light, or scattered polarized light is used. By arranging the brightness enhancement film on the polarizer, it is possible to improve the emission efficiency of linearly polarized light emitted from the polarizer by using retroreflected light that is reflected polarized light or scattered polarized light. The brightness enhancement film can be laminated on the polarizer via an adhesive layer. Another film such as a protective film may be interposed between the polarizer and the brightness enhancement film.

  The brightness enhancement film can be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is “DBEF” manufactured by 3M. (See JP-A-4-268505). Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ / 4 plate, and a specific example thereof is “PCF” manufactured by Nitto Denko Corporation (Japanese Patent Laid-Open No. 11-231130). Etc.). Yet another example of an anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer that emits reflected polarized light even in the visible light region by finely processing the metal (US Patent). No. 6288840, etc.), and a film obtained by adding metal fine particles to a polymer matrix and stretching (see JP-A-8-184701, etc.).

  As described above, on the outer surface of the brightness enhancement film, a hard coat layer, an antiglare layer, a light diffusion layer, a retardation layer (such as a retardation layer having a retardation value of ¼ wavelength), an antireflection layer, low refraction A surface treatment layer (coating layer) such as a rate layer, an antistatic layer or an antifouling layer may be provided. By forming such a layer, the adhesion to the backlight tape and the uniformity of the display image can be improved. Although the thickness of the brightness enhancement film 50 is usually 10 to 100 μm, it is preferably 10 to 50 μm, more preferably 10 to 30 μm from the viewpoint of thinning the polarizing plate 1.

(4) Adhesive layer It is preferable that the polarizing plate 1 has an adhesive layer in the outermost surface. This pressure-sensitive adhesive layer can be used for bonding the polarizing plate 1 to a display element (for example, a liquid crystal cell) or another optical member.
It is preferable that the release film 3 is laminated on the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer can also be used for laminating a polarizer and a protective film or a brightness enhancement film. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition mainly composed of a resin such as (meth) acrylic, rubber-based, urethane-based, ester-based, silicone-based, or polyvinyl ether-based. Especially, the adhesive composition which uses (meth) acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy ray curable type or a thermosetting type.

  Examples of the (meth) acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and (meth) acrylic acid 2- A polymer or copolymer having one or more (meth) acrylic acid esters such as ethylhexyl as a monomer is preferably used. The base polymer is preferably copolymerized with a polar monomer. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl ( Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as (meth) acrylate.

  The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a crosslinking agent. As a crosslinking agent, a metal ion having a valence of 2 or more, which forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound, which forms an amide bond with a carboxyl group; Examples thereof include epoxy compounds and polyols that form ester bonds with carboxyl groups; polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

  The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has an adhesive property even before irradiation with active energy rays. It is a pressure-sensitive adhesive composition having such a property that it can be adhered to an adherend such as the like and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably ultraviolet curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Furthermore, if necessary, a photopolymerization initiator, a photosensitizer, and the like can be contained.

  The pressure-sensitive adhesive composition comprises fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, antistatic agents, tackifiers, fillers (metal powders and Other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators, and other additives can be included.

  The pressure-sensitive adhesive layer can be formed by applying an organic solvent dilution of the above-mentioned pressure-sensitive adhesive composition onto a substrate and drying it. The substrate can be a polarizer, a protective film, another optical film such as a brightness enhancement film, a release film (for example, release film 3), or the like. When the active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the formed pressure-sensitive adhesive layer with active energy rays.

  The thickness of the pressure-sensitive adhesive layer is usually 1 to 40 μm, but from the viewpoint of reducing the thickness of the optical sheet and suppressing the dimensional change of the polarizing plate 1 while maintaining good processability, it is 3 to 25 μm (for example, 3 to 3 μm). 20 μm, more preferably 3 to 15 μm).

<Surface protection film>
The surface protective film 2 can include a base film and a pressure-sensitive adhesive layer laminated thereon. The surface protective film 2 is a film for protecting the surface of the polarizing plate 1 and is usually peeled and removed together with the pressure-sensitive adhesive layer it has after the optical sheet is bonded to, for example, a display element or another optical member. .

  The base film is preferably a thermoplastic resin film. The thermoplastic resin constituting the thermoplastic resin film is, for example, a polyolefin resin such as a polyethylene resin or a polypropylene resin; a cyclic polyolefin resin; a polyester resin such as polyethylene terephthalate or polyethylene naphthalate; a polycarbonate resin; (Meth) acrylic resins and the like can be mentioned. The base film may have a single layer structure or a multilayer structure.

  The thickness of the base film can be 20 to 150 μm (for example, 30 to 80 μm, preferably 30 to 60 μm), and the thickness of the surface protective film 2 can be 40 to 200 μm (for example, 50 to 160 μm). About the structure of an adhesive layer, the description about the adhesive layer which the polarizing plate mentioned above has is quoted fundamentally.

  In particular, the pressure-sensitive adhesive layer has a storage elastic modulus at 80 ° C. of preferably 0.15 MPa or less, more preferably 0.14 MPa or less, and further preferably 0.10 MPa or less. Usually, the storage elastic modulus at 80 ° C. of the pressure-sensitive adhesive layer is 0.01 MPa or more. In this specification, the storage elastic modulus of an adhesive layer can be measured using a commercially available viscoelasticity measuring apparatus, for example, the viscoelasticity measuring apparatus "DYNAMIC ANALYZER RDA II" by REOMETRIC.

The surface of the surface protective film 2 opposite to the polarizing plate 1 preferably has a surface resistivity of 1 × 10 ⁷ to 1 × 10 ¹² Ω / □. It can be said that the surface protective film having such a surface resistivity has an antistatic function. The surface protective film having such a surface resistivity is difficult to be charged and the dynamic friction coefficient is easily controlled to 0.40 or less. When the surface resistivity is more than 1 × 10 ¹² Ω / □, the surface protective film is easily charged. The surface resistivity is measured by the method described in Examples described later.

  The surface protective film 2 can contain an antistatic agent. The antistatic agent can be contained in the pressure-sensitive adhesive layer, for example. Instead of or containing an antistatic agent in the pressure-sensitive adhesive layer, an antistatic layer containing an antistatic agent may be provided on the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is laminated. Good.

Examples of the antistatic agent include ionic compounds. The ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion.
Two or more ionic compounds may be used.

<Peeling film>
The release film 3 is a film that is temporarily attached to protect the surface of the pressure-sensitive adhesive layer until it is bonded to a display element (for example, a liquid crystal cell) or another optical member. The release film 3 is usually composed of a thermoplastic resin film that has been subjected to a release treatment with a release agent such as silicone or fluorine on one side, and the release treatment surface is bonded to the adhesive layer. An antistatic layer is preferably formed on the surface of the release film 3 opposite to the polarizing plate 1.

When the optical sheet manufactured by roll-to-roll is cut to obtain the optical sheet 10, the release film is provided as a wound body in which the long release film is wound in manufacturing the long optical sheet. Sometimes. The wound body of the release film is in a state where the surface to be bonded to the pressure-sensitive adhesive layer (release treatment surface) and the surface that becomes the outermost surface of the optical sheet 10 are in contact with each other. There are cases where transfer is made to the surface of the sheet 10 which is the outermost surface. As a result of studies by the present inventor, it has been found that multiple transfer can be easily prevented by using transfer.
On the other hand, the surface of the release film 3 is beautifully dressed to remove protrusions such as an adhesive layer. Since the surface is cleaned by aesthetic decoration, the transferred silicon atoms are removed, and the existence ratio of silicon atoms is often low. Therefore, it is effective to prevent multiple shooting by applying appropriate beautification.

  From the viewpoint of preventing multiple capture, the surface of the release film 3 opposite to the polarizing plate 1 preferably has a silicon atom content of 2% or more, more preferably 4% or more, and 6%. It may be the above. On the other hand, since it is necessary to beautify appropriately, the abundance ratio of silicon atoms is usually 10% or less, preferably 8% or less. In the present invention, the abundance ratio of silicon atoms is a value determined by X-ray photoelectron spectroscopy, and details follow the description of Examples described later.

  Of course, silicone may be applied to the surface of the release film 3 to adjust the abundance ratio of silicon atoms.

  Further, the ratio of silicon atoms present on one surface and the other surface of the release film 3 may be the same or different.

The surface of the release film 3 opposite to the polarizing plate 1 preferably has a surface resistivity of 1 × 10 ⁷ to 1 × 10 ¹² Ω / □. It can be said that a release film having such a surface resistivity has an antistatic function. A release film having such a surface resistivity is difficult to be charged, and the dynamic friction coefficient is easily controlled to 0.40 or less. When the surface resistivity is more than 1 × 10 ¹² Ω / □, the release film is easily charged. The surface resistivity is measured by the method described in Examples described later.

  The surface resistivity of the release film can be controlled by forming an antistatic layer on the surface of the release film. The antistatic layer is formed, for example, by applying an antistatic spray to the release film, or applying and curing a resin composition containing an antistatic agent. As the static electricity removing spray, there can be mentioned a static eliminating liquid “SB-8” manufactured by Soka Chemical Co., Ltd. As the antistatic agent, those exemplified above can be used.

  The thermoplastic resin constituting the release film 3 can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, and the like. The thickness of the release film 3 is, for example, 10 to 50 μm.

<Marking>
The optical sheet 10 may have a marking 4 on at least one of the surface protective film 2 and the release film 3, and the release film preferably has the marking 4. The surface protective film 2 or the release film 3 preferably has a marking 4 on the surface opposite to the polarizing plate 1. When the optical sheet manufactured by roll-to-roll is cut to obtain the optical sheet 10, marking may be performed before cutting the long optical sheet, or marking may be performed after cutting.

By marking, for example, the absorption axis direction or the transmission axis direction of the polarizing plate 1 can be easily discriminated. For example, when the polarizing plate is bonded to a liquid crystal cell, alignment becomes easy.
On the other hand, it has been clarified by the inventors that the optical sheet has markings, so that multiple images are likely to occur. Although the present invention is not limited, it is considered that the reason is that the marking causes swell of the coating film on the surface of the optical sheet 10 and increases the coefficient of dynamic friction.

  From the viewpoint of preventing multiple capture, the ratio of the marking area to the release film area is preferably 10% or less, more preferably 5% or less, and even more preferably 2% or less.

  From the same viewpoint, the height of the marking (coating film) from the film surface is preferably 0.1 to 0.2 μm, and may be 0.3 to 0.5 μm.

  The marking 4 can be performed by an ink jet jet type or contact type pen using oil-based ink or water-based ink, and the marking can be a coating film thereof. The color of the marking can be red, yellow, green, cyan, blue, magenta, white, black, and a mixture of them, and can be marked with one color or with multiple colors Good.

  FIG. 3 is an example in the case of having the marking 4 on the release film 3, and the linear marking 4 is formed between two opposing sides of the optical sheet 10. The shape of the marking is not limited to this, and may be a straight line, a dotted line, a broken line, a curved line, and a combination thereof, as shown in FIGS. Further, it may be a figure such as a combination thereof, or may be a letter or a number.

<Laminated body of optical sheet>
By stacking a plurality of optical sheets, a laminated body of optical sheets can be obtained, and this can be provided to an optical sheet supply device. As shown in FIG. 2, the laminated body 100 of optical sheets is preferably overlapped so that the release film 3 of one optical sheet 10 and the surface protective film 2 of another optical sheet 10 are in contact with each other.

  The optical sheets 10 constituting the optical sheet laminate 100 may all be the same optical sheet, or may be optical sheets that are partially different. The number of optical sheets constituting the optical sheet laminate 100 is not particularly limited, but may be, for example, 100 to 500.

  The optical sheet 10 taken out from the laminated body 100 of optical sheets can peel the release film 3 and can be bonded to a display element (for example, a liquid crystal cell). Furthermore, the surface protective film 2 can be peeled off and incorporated into a display device (for example, a liquid crystal display device). In constructing the display device, the optical sheet 10 according to the present invention may be used for a polarizing plate disposed on the viewing side, may be used for a polarizing plate disposed on the backlight side, or may be used on the viewing side. And may be used for both polarizing plates on the backlight side.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

(1) Measuring method of dynamic friction coefficient Using the surface property measuring machine TYPE: 14FW of Shinto Kagaku Co., Ltd., the dynamic friction coefficient between the surface protective film and the release film was measured. Specifically, first, an optical sheet cut to a size of 11 cm × 6.3 cm was prepared and attached to a movable stage of the measuring machine and a fixing jig connected to the load cell. Two optical sheets were arranged so that the release film and the surface protective film face each other. Next, a load of 500 g is applied from above the overlapping films, and a moving distance of 15.0 mm is reciprocated 100 times at a speed of 5000 mm / min. From the magnitude of the force detected by the load cell, the dynamic friction coefficient is calculated. The average was calculated. Although the dynamic friction coefficient did not change depending on the marking direction and the moving direction of the movable stage provided in the embodiment, if there is anisotropy, the dynamic friction coefficient in the direction in which the dynamic friction coefficient is maximized is adopted.

(2) Method for measuring the abundance ratio of silicon atoms The abundance ratio of silicon atoms on the film surface was measured by X-ray photoelectron spectroscopy (XPS) using K-Alpha from Thermo Fisher Scientific Co., Ltd.
The measurement surface is the release film back surface (surface opposite to the surface in contact with the pressure-sensitive adhesive layer). The photoelectron take-off angle was 90 °, and after measuring carbon atoms, oxygen atoms, and silicon atoms, the detected amount of silicon atoms was calculated.

(3) Measuring method of film thickness It measured using digital micrometer "MH-15M" made from Nikon Corporation.

(4) Multiple-shot evaluation method Two optical sheets were placed so that the surface protective film surface and the release film surface overlapped, and rubbed 10 times while being pressed by hand. Thereafter, the stacked films were shifted by 1 cm and lifted by holding only one sheet. When the two sheets were stuck, it was shaken 3 times to check whether one of the sheets was dropped. If one of the sheets did not fall off after this operation, it was determined that multiple taking occurred.

(5) Surface resistivity measurement method Surface resistivity (Ω) of the release film surface (surface opposite to the polarizing plate in the release film) and surface protective film surface (surface opposite to the polarizing plate in the surface protective film) / □) was measured using MCP-HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd. “Over” in the table means that the surface resistivity is more than 1 × 10 ¹² Ω / □.

<Preparation of optical sheet 1>
A polarizing plate having the following layer structure was prepared.
Protective film 1 / Polarizer / Protective film 2
The protective film 1 was a cyclic olefin resin film and had a thickness of 23 μm.
The protective film 2 was a cyclic olefin resin film having a hard coat layer on the surface, and the thickness was 30 μm.
The polarizer was a film in which iodine was adsorbed and oriented on a PVA resin film, and the thickness was 8 μm.

A release film having an adhesive layer was laminated on the surface of the protective film 1 in the polarizing plate, and a surface protective film was laminated on the surface of the protective film 2 in the polarizing plate to produce an optical sheet 1.
As the surface protective film, a polyethylene terephthalate film (thickness: 38 μm) having an adhesive layer having a thickness of 20 μm was used. The thickness of the surface protective film was 58 μm. An antistatic layer was formed on the surface of the polyethylene terephthalate film opposite to the surface in contact with the pressure-sensitive adhesive layer, and the surface resistivity of the surface protective film surface was 1 × 10 ⁹ Ω / □. A polyethylene terephthalate film was used as the release film. The thickness of the release film was 38 μm. An adhesive layer having a thickness of 20 μm was formed on the release film. In addition, the adhesive layer on this peeling film is a member with which a polarizing plate is finally equipped.
Thereafter, the optical sheet 1 was cut into a rectangular shape having a long side of 110 mm and a short side of 63 mm.

<Optical sheet 2>
An optical sheet 2 was prepared in the same manner as the optical sheet preparation 1 except that a surface protective film having no antistatic layer was used. The optical sheet 2 was cut into a rectangular shape having a long side of 110 mm and a short side of 63 mm.

<Example 1>
Silicone was apply | coated to the peeling film surface (surface on the opposite side to the polarizing plate in a peeling film) in the obtained optical sheet 1, and the optical sheet for evaluation was produced. The proportion of silicon atoms present was 7%. No marking was made on the surface of the release film.

<Example 2>
Using a dry save 1 (blue, oil-based ink) manufactured by Teranishi Chemical Industry Co., Ltd., a straight line 1 as shown in FIG. 3 is formed along the absorption axis direction between two opposing sides of the optical sheet. An optical sheet for evaluation was produced in the same manner as in Example 1 except that the marking was formed by pulling.
The ratio of the marking area to the release film area was 1%. The height of the marking was 0.3 μm from the surface of the release film.

<Example 3>
An optical sheet for evaluation was produced in the same manner as in Example 2 except that three lines were drawn.
The ratio of the marking area to the release film area was 3%.

<Examples 4 to 6>
Optical sheets for evaluation were respectively produced in the same manner as in Examples 1 to 3, except that the silicone coating amount was adjusted so that the silicon atom content was 3%.

<Examples 7 to 9>
Instead of applying silicone to the release film surface (the surface opposite to the polarizing plate in the release film) of the obtained optical sheet 1, an electrostatic removal liquid “SB-8” manufactured by Showa Kako Co., Ltd. was applied. The surface resistivity was 1 × 10 ⁹ Ω / □. Other than that was carried out similarly to Examples 1-3, and produced the optical sheet for evaluation, respectively.

<Examples 10 to 12>
Optical sheets for evaluation were produced in the same manner as in Examples 7 to 9, except that the amount of static electricity removal liquid applied was adjusted to set the surface resistivity to 1 × 10 ¹² Ω / □.

<Example 13>
On the surface of the release film in the obtained optical sheet 2 (surface opposite to the polarizing plate in the release film), a static elimination liquid “SB-8” manufactured by Soka Chemical Co., Ltd. was applied, and the surface resistance of the release film The rate was 1 × 10 ¹² Ω / □. The surface protection film surface (the surface opposite to the polarizing plate in the surface protection film) is coated with a static removal liquid “SB-8” manufactured by Soka Chemical Co., Ltd. × 10 ¹² Ω / □. In this way, an optical sheet for evaluation was produced.

<Examples 14 to 16>
The optical sheet for evaluation was prepared in the same manner as in Example 13 except that the surface resistivity of the release film and the surface protective film was controlled to the values shown in Table 2 by adjusting the coating amount of the static eliminating liquid. Each was produced.

<Comparative Examples 1-3>
In Examples 1 to 3, the surface of the release film on the optical sheet was the same except that the surface was wiped several times with a cloth soaked with IP solvent (ethanol solvent obtained from Showa Processing Co., Ltd.). Each of the optical sheets for evaluation was prepared.

<Comparative example 4>
In Example 1, silicone was not applied to the release film surface, and the release film surface of the optical sheet was wiped several times with a cloth soaked with an IP solvent (ethanol solvent obtained from Showa Processing Co., Ltd.). An optical sheet for evaluation was produced in the same manner except that it was raised.

<Comparative Example 5>
The optical sheet for evaluation was prepared in the same manner as in Example 13 except that the surface resistivity of the release film and the surface protective film was controlled to the values shown in Table 2 by adjusting the coating amount of the static eliminating liquid. Produced. In addition, the static elimination liquid was not apply | coated to the surface protection film.

  Multiple evaluation was performed about the optical sheet for evaluation produced in the said Examples 1-16 and Comparative Examples 1-5. The results are shown in Tables 1 and 2.

  According to the present invention, it is useful because it is possible to provide an optical sheet that is unlikely to be subjected to multiple taking when the optical sheet is taken out one by one from a laminated body in which a plurality of optical sheets are stacked.

DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Surface protective film 3 Peeling film 4 Marking 10 Optical sheet 100 Laminated body of optical sheet

Claims (5)

It has a surface protective film, a polarizing plate, and a release film in this order,
An optical sheet having a coefficient of dynamic friction between the surface protective film and the release film of 0.4 or less. The optical sheet according to claim 1, wherein the surface of the release film opposite to the polarizing plate has a silicon atom content of 3% or more. 3. The optical sheet according to claim 1, wherein the surface of the release film opposite to the polarizing plate has a surface resistivity of 1 × 10 ⁷ to 1 × 10 ¹² Ω / □. 4. The optical sheet according to claim 1, wherein the surface of the surface protective film opposite to the polarizing plate has a surface resistivity of 1 × 10 ⁷ to 1 × 10 ¹² Ω / □. The release film has a marking on the surface opposite to the polarizing plate,
The optical sheet according to any one of claims 1 to 4, wherein a ratio of an area of the marking to an area of the release film is 2% or less.

Images