TWI765070B - Optical sheet - Google Patents

Abstract

An object of the present invention is to provide an optical sheet with which a problem of undesirably picking up a plurality of optical sheets in one time pick-up (so called multiple picking-up) when the optical sheet is to be picked up one-by-one from a stack formed of a plurality of the optical sheets is difficult to occur.

The optical sheet of the present invention has a surface protective film, a polarizing plate, and a release film in this order, and a dynamic friction coefficient between the surface protective film and the release film is 0.40 or less. A surface of the release film opposite to side of the polarizing plate preferably has a silicon atom content of 3% or more.

Description

Optical sheet

The present invention relates to an optical sheet.

Polarizing plates are widely used in video display devices such as liquid crystal display devices, and in particular, in recent years, they have been widely used in various portable devices such as smartphones. Conventionally, a protective film is used as a polarizing plate by bonding a protective film to one or both surfaces of a polarizer in which a dichroic dye has been adsorbed and aligned on a polyvinyl alcohol-based resin film.

Polarizing plates are generally circulated in the market in the form of optical sheets, which are peelable surface protective films (also known as protect films) and peeling films (also known as peeling films) used to prevent contamination and scratches on the surface of the polarizing plates. separate film) attached to the surface.

When attaching a polarizing plate to a display element such as a liquid crystal cell, one optical sheet is taken out at a time from a laminate in which a plurality of the above-mentioned optical sheets are stacked. Then, the release film is peeled off from the optical sheet, and is bonded to the display element via the exposed pressure-sensitive adhesive layer.

In order to efficiently perform the extraction step of the optical sheet, Patent Document 1 proposes to automate the extraction of the optical sheet by a machine (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 in one take out (hereinafter, there is a case of "multiple take").

In addition, when the polarizer is thick, the optical sheets are separated due to the weight of the optical sheet including the polarizer, so multiple acquisitions are not easy to occur. And the effect of separation becomes smaller, so it is easy to produce multiple acquisitions.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2006-308912

An object of the present invention is to provide an optical sheet that does not easily produce multiple take-out each time one optical sheet is taken out from a laminate in which a plurality of optical sheets are overlapped.

[1] An optical sheet including a surface protection film, a polarizing plate, and a release film in this order, wherein the coefficient of kinetic friction between the surface protection film and the release film is 0.40 or less.

[2] The optical sheet according to the first invention, wherein on the surface of the release film on the opposite side to the polarizer, the presence ratio of silicon atoms is 3% or more.

[3] The optical sheet according to the first invention or the second invention, wherein the peeling film has a mark on the surface opposite to the polarizing plate, and the area ratio of the mark to the area of the peeling film is 2 %the following.

The present invention can provide an optical sheet in which multiple take-out is unlikely to occur every time one optical sheet is taken out from a laminate in which a plurality of optical sheets are stacked.

1‧‧‧Polarizer

2‧‧‧Surface protection film

3‧‧‧Peeling film

4‧‧‧Mark

10‧‧‧Optical Sheet

100‧‧‧Laminated bodies of optical sheets

Fig. 1 is a schematic cross-sectional view showing an example of the layer structure of the optical sheet of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of a laminate formed by stacking a plurality of optical sheets of the present invention.

Fig. 3 is a schematic plan view showing the optical sheet of the present invention viewed from the release film side.

FIG. 4 is a schematic diagram showing an example of the mark.

<Optical sheet>

Fig. 1 is a schematic cross-sectional view showing an example of the optical sheet of the present invention. The optical sheet 10 shown in FIG. 1 is a laminated film which has the surface protection film 2, the polarizing plate 1, and the peeling film 3 in this order. In the optical sheet 10, it is preferable that the surface protective film 2, the polarizing plate 1, and the peeling film 3 are laminated|stacked in this order. In the optical sheet 10, it is preferable that the surface protection film 2 and the peeling film 3 constitute the outermost members of the optical sheet, respectively.

The optical sheet 10 can be obtained by manufacturing an elongated optical sheet by a roll-to-roll method while conveying the respective members constituting the optical sheet 10, and cutting it, or by separately preparing a predetermined Each member of the shape is laminated in sequence.

The shape of the optical sheet is not particularly limited, and can be a polygon such as a rectangle and a triangle, a circle, an ellipse, and a combination of these shapes.

The area of the optical sheet is not particularly limited, for example, it is preferably 18600 to 2500 mm ² , and preferably 12600 to 6870 mm ² . When the area of the optical sheet is less than 18600 mm ² , as described above, it is not easy to separate into individual optical sheets due to its own weight, so 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 with long sides and short sides, the length of the long side is preferably 17.3 to 6.6 cm, preferably 15.5 to 11.0 cm, and the length of the short side is 10.8 cm It is preferably to 3.7cm, preferably 8.7 to 6.2cm.

In the present invention, the coefficient of kinetic friction between the surface protective film and the release film is 0.40 or less, preferably 0.30 or less. On the other hand, when peeling off a surface protective film etc. using a peeling tape, from the viewpoint of improving the adhesion between the peeling tape and the surface protective film etc., the kinetic friction coefficient is preferably 0.10 or more, and may be 0.20 or more. The measurement method of the coefficient of kinetic friction was in accordance with the method described in the examples described later.

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

Hereinafter, each member included in the optical sheet will be described.

<Polarizer>

The polarizing plate 1 is a polarizing element including at least a polarizer, and usually further includes a thermoplastic resin film bonded to one or both surfaces thereof. The thermoplastic resin film can be a protective film for protecting polarizers, other optical films having different optical functions from polarizers, or the like. The thermoplastic resin film may also have a resin layer (for example, selected from the group consisting of a hard coat layer, an antistatic layer, an anti-glare layer, a light diffusion layer, a retardation layer (with a retardation value of 1/4 wavelength) laminated on its surface. layer, etc.), antireflection layer, low refractive index layer, antifouling layer, etc. at least one optical layer). The thermoplastic resin film system can be bonded to the polarizer via an adhesive layer or an adhesive layer. The surface protective film 2 may be laminated on the surface of the resin layer.

The thickness of the polarizing plate 1 is not particularly limited, but is usually 200 μm or less, and the effect of the present invention is remarkable in the case of 150 μm or less, or even 125 μm or less, which is likely to be multiplied due to its own weight. 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 has the property of absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis) As an absorption type polarizer, a polarizing film obtained by adsorbing and aligning a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin film can be suitably used. The polarizer can be produced by, for example, a method including the following steps: a step of uniaxially extending a polyvinyl alcohol-based resin film; and a dichroic adsorption by dyeing the polyvinyl alcohol-based resin film with a dichroic dye The step of using the cross-linking liquid such as boric acid aqueous solution to treat the polyvinyl alcohol-based resin film with the dichroic pigment adsorbed thereon; and the step of washing with water after the treatment with the cross-linking liquid.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers thereof and other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth)acrylamides having an ammonium group, and the like.

In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryloyl", "(meth)acrylate", and the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 to 100 mol %, preferably 98 mol % or more. The polyvinyl alcohol-based resin may be modified, for example, aldehyde-modified polyvinyl formaldehyde, polyvinyl acetal, or the like can also be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined based on JIS K 6726.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film of a polarizer (polarizing film). The method of forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be employed. The thickness of the polyvinyl alcohol-based green film is not particularly limited, but in order to make the thickness of the polarizer 15 μm or less, 5 to 35 μm is preferably used. Preferably it is 20 micrometers or less.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before the dyeing of the dichroic dye, simultaneously with the dyeing, or after the dyeing. When the uniaxial stretching is carried out after dyeing, the uniaxial stretching may be carried out before or during the cross-linking treatment. In addition, uniaxial stretching may be performed in these plural stages.

When uniaxially extending, the uniaxial extension can be performed between rollers with different peripheral speeds, or a hot roller can be used to uniaxially extend. In addition, the uniaxial stretching may be dry stretching in which the stretching is performed in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is swelled with a solvent or water. The elongation ratio is usually 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film using a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye can be employed. As the dichroic dye, iodine or a dichroic organic dye can be used. In addition, it is preferable that the polyvinyl alcohol-based resin film is immersed in water before the dyeing treatment.

As a crosslinking treatment after dyeing with a dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution is generally employed. When iodine is used as a 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, preferably 15 μm or less, and more preferably 10 μm or less. In particular, setting the thickness of the polarizer to 15 m or less is advantageous for thinning the optical sheet. The thickness of the polarizer is usually 2 μm or more.

(2) Protective film

The protective film that can be laminated on one or both sides of the polarizer can be a film composed of a light-transmitting (preferably optically transparent) thermoplastic resin, such as a chain polymer. Polyolefin-based resins of olefin-based resins (polypropylene-based resins, etc.), cyclic polyolefin-based resins (norbornene-based resins, etc.); cellulose-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins of ethylene phthalate and polybutylene terephthalate; polycarbonate resins; (meth)acrylic resins such as methyl methacrylate resins; polystyrene resins; polyvinyl chloride resin; acrylonitrile/butadiene/styrene resin; acrylonitrile/styrene resin; polyvinyl acetate resin; polyvinylidene chloride resin; polyamide resin ; Polyacetal resin; Modified polyphenylene ether resin; resin, etc.

Examples of the chain polyolefin-based resin include polyethylene resins (polyethylene resins which are homopolymers of ethylene and copolymers mainly composed of ethylene) and polypropylene resins (polypropylene resins which are homopolymers of propylene). , propylene-based copolymers) of chain olefin homopolymers, and copolymers composed of two or more chain olefins.

Cyclic polyolefin-based resins are a general term for resins polymerized by using cyclic olefins as polymerized units, for example, Japanese Patent Application Laid-Open No. 1-240517, Japanese Patent Application Laid-Open No. 3-14882, and Japanese Patent Application Laid-Open No. 3-122137 are listed. resins described in Gazette No. Specific examples of cyclic polyolefin-based resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymerization of cyclic olefins with linear olefins such as ethylene and propylene. Compounds (representatively random copolymers), graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. In particular, norbornene-based resins containing, as cyclic olefins, norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers can be suitably used.

The polyester-based resin is a resin that does not include the following cellulose ester-based resin and has an ester bond, and is usually composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As a 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 naphthalene dicarboxylate. ester. As a polyhydric alcohol, a dihydric diol can be used, for example, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol are mentioned. A typical example of the polyester-based resin includes 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)acrylates such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate -(meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; (meth)acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate Copolymers with compounds having alicyclic hydrocarbon groups (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylate copolymer, etc.). It is preferable to use a polymer with poly(meth)acrylate C _1-6 alkyl as the main component such as poly(meth)acrylate, and it is preferable to use methyl methacrylate as the main component (50 to 100% by weight, preferably 70 to 100% by weight) of methyl methacrylate resin.

Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, these copolymers and a part of the hydroxyl group modified with other substituents can also be mentioned. Among these cellulose esters, cellulose triacetate (cellulose triacetate) is particularly preferred.

Polycarbonate resins are engineering plastics composed of polymers that bond monomer units through carbonate groups.

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 a liquid crystal display device in a lateral electric field effect (IPS; In-Plane Switching) mode, it is preferable to use a film with a substantially zero retardation value as a protective film. The so-called substantially zero retardation value means that the in-plane retardation value R ₀ is 10 nm or less at the wavelength of 590 nm, the absolute value of the retardation value R _th in the thickness direction at the wavelength of 590 nm is 10 nm or less, and the absolute value of the retardation value R th at the wavelength of 590 nm is 10 nm or less. The absolute value of the retardation value R _th in the thickness direction 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, for the purpose of viewing angle compensation, a retardation layer (or thin film) of a single-layer or multi-layer structure can be used as a protective film. At this time, the polarizing plate 1 can be an elliptical polarizing plate or a circular polarizing plate including a laminated structure of a polarizer and a retardation layer, or a polarizing plate including a retardation layer and a viewing angle compensation function.

The thickness of the protective film is usually 1 to 100 μm, preferably 5 to 60 μm, and more preferably 5 to 50 μm from the viewpoints of strength, handleability, and the like. If the thickness is within this range, the polarizer can be mechanically protected, and the polarizer can maintain stable optical properties without shrinking even when exposed to a humid and heat environment.

When the protective films are attached to both sides of the polarizer, the protective films may be composed of the same kind of thermoplastic resin, or may be composed of different kinds of thermoplastic resins. In addition, the thickness may be the same or different. Moreover, it may have the same phase difference characteristics or may have different phase difference characteristics.

As described above, at least any one of the protective films may be provided with, for example, a hard coat layer, an anti-glare layer, a light diffusion layer, a retardation layer (with a 1/4 The retardation layer of the retardation value of the wavelength, etc.), the antireflection layer, the low refractive index layer, the antistatic layer, the surface treatment layer (coating layer) of the antifouling layer.

From the viewpoint of suppressing the intrusion of air bubbles between the surface protective film and the polarizing plate, the surface on the surface protective film 2 side of the polarizing plate 1 (the surface on which the surface protective film 2 is attached) is based on the arithmetic in accordance with JIS B 0601:2013. The smaller average roughness Ra is better. Specifically, the Ra system on the surface is preferably 0.3 µm or less, preferably 0.2 µm or less, and more preferably 0.15 µm or less. The Ra system on the surface is usually 0.001 μm or more, for example, 0.005 μm or more.

The protective film system can be bonded to a polarizer with an adhesive layer interposed therebetween, for example. As the adhesive for forming the adhesive layer, an aqueous adhesive, an active energy ray curable adhesive, or a thermosetting adhesive can be used, and an aqueous adhesive and an active energy ray curable adhesive are preferred.

As the water-based adhesive, an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like can be mentioned. In particular, a water-based adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin can be suitably used. The polyvinyl alcohol-based resin includes a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymerization of vinyl acetate and other monomers that can be copolymerized therewith. A polyvinyl alcohol-based copolymer obtained by saponification of the substance, or a modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl groups thereof. The water-based adhesive can contain a crosslinking agent such as an aldehyde compound (glyoxal, etc.), an epoxy compound, a melamine-based compound, a methylol compound, an isocyanate compound, an amine compound, and a polyvalent metal salt.

When a water-based adhesive is used, it is preferable to perform a drying step for removing water contained in the water-based adhesive after bonding the polarizer and the protective film. After the drying step, for example, an aging step of aging at a temperature of 20 to 45° C. may be provided.

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

The above-mentioned curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include epoxy-based compounds (compounds having one or more epoxy groups in the molecule), oxetane-based compounds (having one epoxy group in the molecule) or two or more oxetane rings), or a combination of these. Examples of the radically polymerizable curable compound include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), radically polymerizable Other vinyl compounds with double bonds, or a combination of these. A cationically polymerizable curable compound and a radically polymerizable curable compound may be used in combination. The active energy ray-curable adhesive may further contain a cationic polymerization initiator and/or a radical polymerization initiator for starting the curing reaction of the above-mentioned curable compound.

When bonding a polarizer and a protective film, surface activation treatment may be performed on the bonding surface of at least any one of these to improve adhesiveness. Examples of surface activation treatment include 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.) ) dry treatment; such as ultrasonic treatment, saponification treatment, and wet treatment of anchor coating treatment using solvents such as water and acetone. These surface activation treatments may be performed alone or in combination of two or more.

When the protective films are attached to both sides of the polarizer, the adhesive used to attach the protective films can be the same type of adhesive or different types of adhesive.

(3) Other optical films

The polarizing plate 1 can include other optical films other than the polarizer and the protective film, and representative examples thereof are a brightness enhancement film and a retardation film. When the polarizing plate 1 includes other optical films, the surface protection film 2 may be laminated on the surface of the optical film, or may be laminated on the surface of the resin layer already laminated on the optical film.

The brightness enhancement film is also called a reflective polarizing film, which uses a polarization conversion element having a function of separating the light emitted from a light source (backlight) into transmission polarized light and reflected polarized light or scattered polarized light. By arranging the brightness enhancement film on the polarizer, the output efficiency of the linearly polarized light emitted from the polarizer can be improved by utilizing the returned light belonging to the reflected polarized light or the scattered polarized light. The brightness enhancement film system can be laminated on the polarizer with an adhesive layer interposed therebetween. Other thin films such as protective films may also be interposed between the polarizer and the brightness enhancement film.

The brightness enhancement film system can be, for example, an anisotropic reflective polarizer. An example of an anisotropic reflective polarizer is an anisotropic multi-layer film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction. Japanese Patent Application Laid-Open No. 4-268505, etc.). Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ/4 plate, a specific example of which is "PCF" manufactured by Nitto Denko Co., Ltd. (refer to Japanese Patent Laid-Open No. 11-231130, etc.) . Yet another example of the anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer that performs microprocessing on metal and emits reflective polarized light even in the visible light region (refer to U.S. Patent No. 6,288,840). Specifications, etc.), a thin film formed by adding metal fine particles to a polymer matrix and extending (refer to Japanese Patent Laid-Open No. 8-184701, etc.).

As mentioned above, the outer surface of the brightness enhancement film can also be provided with a hard coat layer, an anti-glare layer, a light diffusion layer, a retardation layer (a retardation layer with a retardation value of 1/4 wavelength, etc.), an anti-reflection layer , Surface treatment layer (coating layer) of low refractive index layer, antistatic layer and antifouling layer. By forming such a layer, the adhesiveness with the backlight tape and the uniformity of the displayed image can be improved. The thickness of the brightness enhancement film 50 is usually 10 to 100 μm, and from the viewpoint of thinning the polarizing plate 1 , it is preferably 10 to 50 μm, more preferably 10 to 30 μm.

(4) Adhesive layer

The polarizing plate 1 preferably has an adhesive layer on its outermost surface. This adhesive layer system can be used for bonding the polarizing plate 1 to a display element (eg, a liquid crystal cell) or other optical members. Preferably, the release film 3 is laminated on the adhesive layer. In addition, the adhesive can also be used in the case of laminating a polarizer and a protective film or a brightness enhancement film. The adhesive layer can be composed of an adhesive composition mainly composed of (meth)acrylic, rubber, urethane, ester, polysiloxane, and polyvinyl ether resins. In particular, it is preferable to use a (meth)acrylic resin having excellent transparency, weather resistance, heat resistance, etc. as a matrix polymer as an adhesive composition. The adhesive composition may also be of an active energy ray hardening type or a thermosetting type.

As the (meth)acrylic resin (matrix polymer) used in the adhesive composition, for example, butyl (meth)acrylate, ethyl (meth)acrylate, and isopropyl (meth)acrylate can be suitably used, for example. A polymer or copolymer of one or more of octyl ester and (meth)acrylate of 2-ethylhexyl (meth)acrylate as a monomer. The matrix polymer is preferably a copolymer of polar monomers. As polar monomers, for example, (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylacrylate can be mentioned. Monomers with carboxyl group, hydroxyl group, amide group, amine group, epoxy group, etc. of aminoethyl (meth)acrylate and glycidyl (meth)acrylate.

The adhesive composition may contain only the above-mentioned matrix polymer, and usually further contains a crosslinking agent. Examples of the crosslinking agent include: those belonging to metal ions having a valence of at least two and forming a metal carboxylate salt with a carboxyl group; those belonging to a polyamine compound and forming an amide bond with a carboxyl group; those belonging to a polycyclic Oxygen compounds or polyols that form ester bonds with carboxyl groups; belong to polyisocyanate compounds that form amide bonds with carboxyl groups. In particular, polyisocyanate compounds are preferred.

The so-called active energy ray hardening type adhesive composition has the property of being hardened by the irradiation of active energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before the irradiation of the active energy rays, so that it can adhere to the film, etc. An adhesive composition having a property of being hardened by irradiation with active energy rays and being able to adjust the adhesive force of the adherend. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable type. The active energy ray-curable adhesive composition may further contain an active energy ray polymerizable compound in addition to the matrix polymer and the crosslinking agent. In addition, a photopolymerization initiator, a photosensitizer and the like can also be contained as needed.

The adhesive composition may contain fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than matrix polymers, antistatic agents, adhesion imparting agents, fillers ( Metal powder, other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators, etc. additives.

The adhesive layer can be formed by applying the organic solvent diluent of the above-mentioned adhesive composition on a substrate and drying it. The substrate can be a polarizer, a protective film, other optical films such as a brightness enhancement film, a release film (eg, release film 3 ), and the like. When an active energy ray hardening-type adhesive composition is used, it can become the hardened|cured material which has the required hardening degree by irradiating active energy ray to the formed adhesive layer.

The thickness of the adhesive layer is usually 1 to 40 μm, and is set to 3 to 25 μm ( For example, 3 to 20 μm, more preferably 3 to 15 μm) is preferable.

<Surface protection film>

The surface protective film 2 can contain a base film and an adhesive layer laminated thereon. The surface protection film 2 is a film used to protect the surface of the polarizing plate 1 , and usually, after the optical sheet is attached to, for example, a display element or other optical components, it is peeled off together with the adhesive layer it has.

The base film is preferably a thermoplastic resin film. The thermoplastic resin constituting the thermoplastic resin film includes, for example, polyolefin-based resins such as polyethylene-based resins and polypropylene-based resins; cyclic polyolefin-based resins; such as polyethylene terephthalate, polyethylene naphthalate Polyester-based resins of ethylene glycol; polycarbonate-based resins; (meth)acrylic resins and the like. The base film may have a single-layer structure or a multi-layer structure.

The thickness of the base film can be 20 to 150 μm (eg 30 to 80 μm, preferably 30 to 60 μm), and the thickness of the surface protection film 2 can be 40 to 200 μm (eg 50 to 160 μm). About the structure of an adhesive bond layer, the description about the adhesive bond layer which the said polarizing plate has basically can be cited.

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

The surface resistivity of the surface protective film 2 on the opposite side to the polarizing plate 1 is preferably 1×10 ⁷ to 1×10 ¹² Ω/□. The surface protective film with such surface resistivity can be said to have antistatic function. The surface protection film system which has such a surface resistivity is not easy to be electrified, and it is easy to control a kinetic friction coefficient to 0.40 or less. When the surface resistivity exceeds 1×10 ¹² Ω/□, the surface protective film is easily charged. The surface resistivity was measured using the method described in the examples described later.

The surface protection film 2 can contain an antistatic agent. The antistatic agent can be contained in the adhesive layer, for example. In addition to containing an antistatic agent in the adhesive layer, an antistatic layer containing an antistatic agent may be simultaneously provided on the surface of the base film opposite to the surface on which the adhesive layer is laminated, or instead of containing an antistatic agent in the adhesive layer The case of antistatic agents.

As an antistatic agent, an ionic compound can be mentioned. An ionic compound is a compound which has an inorganic cation or an organic cation, and an inorganic anion or an organic anion. Two or more ionic compounds may also be used.

<Release film>

The peeling film 3 is a film temporarily adhered to protect the surface of a display element (eg, a liquid crystal cell) or other optical members before the adhesive layer is attached. The release film 3 is usually composed of a thermoplastic resin film that has been subjected to a mold release treatment using a polysiloxane-based, fluorine-based mold release agent, etc., on one side, and the mold release treated surface is attached to the adhesive layer. By. It is preferable that an antistatic layer is formed on the surface of the peeling film 3 on the opposite side to the polarizing plate 1 .

In the case where the optical sheet 10 is obtained by cutting the optical sheet produced by the roll-to-roll method, when producing an elongated optical sheet, the release film may be a roll formed by winding the elongated release film. way to supply. Since the roll body of the release film is in a state of being in contact with the surface of the adhesive layer (release treatment surface) and the outermost surface of the optical sheet 10, the components of the release treatment surface may be transferred to the optical sheet. the outermost surface of the sheet 10. Furthermore, as a result of investigations by the present inventors, it has been found that multiple acquisition can be easily prevented by using transfer. On the other hand, the surface of the release film 3 is subjected to a cosmetic treatment in order to remove excess portions such as the adhesive layer and the like. Since the surface is cleaned by the aesthetic treatment, the transferred silicon atoms are removed, so that the presence ratio of silicon atoms is likely to be low. Therefore, implementing appropriate aesthetic treatments is effective in preventing multiple acquisitions.

From the viewpoint of preventing multiple acquisition, on the surface of the release film 3 opposite to the polarizing plate 1, the presence ratio of silicon atoms is preferably 2% or more, more preferably 4% or more, and may be 6% above. On the other hand, since it is necessary to appropriately perform aesthetic treatment, the presence ratio of silicon atoms is usually 10% or less, preferably 8% or less. In the present invention, the presence ratio of silicon atoms is a value determined by X-ray photoelectron spectroscopy, and the details are in accordance with the description of the following examples.

Of course, polysiloxane can also be coated on the surface of the release film 3 to adjust the presence ratio of silicon atoms.

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

The surface resistivity of the peeling film 3 on the opposite side to the polarizing plate 1 is preferably 1×10 ⁷ to 1×10 ¹² Ω/□. A release film having such a surface resistivity can be said to have an antistatic function. The release film system with such surface resistivity is not easy to be electrified, and it is easy to control the kinetic friction coefficient below 0.40. When the surface resistivity exceeds 1×10 ¹² Ω/□, the release film is likely to be charged. The surface resistivity can be measured using the method described in the 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 can be formed by, for example, applying an antistatic spray to a release film, or applying and curing a resin composition containing an antistatic agent. As the static electricity removing spray, the static electricity removing liquid "SB-8" manufactured by Shanghe Chemical Co., Ltd. can be mentioned. As the antistatic agent, those exemplified above can be used.

The thermoplastic resin constituting the release film 3 can be, for example, polyethylene-based resins such as polyethylene, polypropylene-based resins such as polypropylene, polyesters such as polyethylene terephthalate, and polyethylene naphthalate. resin, etc. The thickness of the release film 3 is, for example, 10 to 50 μm.

<tag>

The optical sheet 10 may have the mark 4 on at least one of the surface protection film 2 and the release film 3 , and the release film preferably has the mark 4 . It is preferable that the surface protective film 2 or the peeling film 3 has a mark 4 on the surface opposite to the polarizing plate 1 . When cutting the optical sheet manufactured by the roll-to-roll method to obtain the optical sheet 10, marking may be carried out before cutting the elongated optical sheet, or marking may be carried out after cutting.

By marking, for example, the absorption axis direction or the transmission axis direction of the polarizing plate 1 can be easily distinguished, and when, for example, the polarizing plate is attached to a liquid crystal cell, alignment can be facilitated. On the other hand, according to the study of the present inventors, it has been found that multiple acquisition is easy to occur by providing the optical sheet with a mark. Although the present invention is not limited, the reason for this is considered to be that the coating film is raised on the surface of the optical sheet 10 due to the marking, thereby increasing the coefficient of kinetic friction.

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

From the same viewpoint, the height of the mark (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 type or a contact type pen using oil-based ink, water-based ink, and the marking can be a coating film of these inks. The color of the marking can be red, yellow, green, cyan, blue, magenta, white, black, and a mixture of these, and one color can be used for the marking, or a plurality of colors can be used for the marking. mark.

FIG. 3 is an example in which the marking 4 is provided on the release film 3 , and the marking 4 in the form of a straight line is formed between the opposing two sides of the optical sheet 10 . The shape of the mark is not limited by this. As shown in Figure 4 (a) to (d), it can be a straight line, a dotted line, a dashed line, a curved line, and a combination of these lines, or a circle, a polygon, and the The figures such as the combination of etc. may also be characters or numbers.

<Laminated body of optical sheet>

By stacking a plurality of optical sheets, a laminated body of the optical sheets can be obtained, and the laminated body can be supplied to the supply device of the optical sheets. As shown in FIG. 2, it is preferable that the laminated body 100 of the optical sheet is superimposed so that the release film 3 of one optical sheet 10 and the surface protection film 2 of the other optical sheet 10 are in contact with each other.

Optical Sheets The optical sheets 10 constituting the laminate 100 may be all the same optical sheets, or may be some different optical sheets. Optical Sheet The number of optical sheets constituting the laminate 100 is not particularly limited, but can be set to 100 to 500 sheets, for example.

The optical sheet 10 taken out from the laminated body 100 of the optical sheet can be attached to a display element (eg, a liquid crystal cell) by laminating the release film 3 . Furthermore, the surface protection film 2 can be incorporated in a display device (for example, a liquid crystal display device). When constructing a display device, the optical sheet 10 of the present invention can be used for the polarizing plate arranged on the viewing side, the polarizing plate arranged on the backlight side, or both the viewing side and the backlight side. polarizer.

[Example]

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

(1) Determination method of dynamic friction coefficient

The kinetic friction coefficient between the surface protection film and the release film was measured using a surface property measuring machine TYPE: 14FW of Shinto Science Co., Ltd. Specifically, an optical sheet that has been cut into a size of 11 cm×6.3 cm is prepared and attached to a fixing aid connected to the movable stage of the measuring machine and the dynamometer, respectively. Two optical sheets were arrange|positioned so that a peeling film and a surface protection film might mutually face. Next, apply a load of 500g from the top of the overlapping films, and make it move back and forth 15.0mm for 100 times at a speed of 5000mm/min. Calculate the coefficient of kinetic friction from the force detected by the dynamometer at this time. average. In addition, although the kinetic friction coefficient does not change depending on the marking direction provided in the embodiment and the moving direction of the movable stage, when there is anisotropy, the kinetic friction coefficient in the direction with the largest kinetic friction coefficient is used.

(2) Method for measuring the presence ratio of silicon atoms

The presence ratio of silicon atoms on the surface of the thin film was measured by X-ray Photoelectron Spectroscopy (XPS; X-ray Photoelectron Spectroscopy) using K-Alpha of Thermo Fisher Scientific Co., Ltd.

The measurement surface is the back surface of the release film (the surface on the opposite side to the surface in contact with the adhesive layer). After setting the photoelectron extraction angle to 90° and measuring carbon atoms, oxygen atoms, and silicon atoms, the detection amount of silicon atoms was calculated.

(3) Measurement method of film thickness

Measured using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

(4) Evaluation method of multiple acquisition

Two optical sheets were arrange|positioned so that the surface protection film surface and the peeling film surface might overlap, and were mutually rubbed 10 times, holding it by hand. Then, the overlapping films were offset by 1 cm, and only one of them was held and lifted up. When 2 sheets are attached, shake 3 times to check whether one sheet comes off. When one of the pieces did not fall off even after this operation, it was judged that multiple acquisitions would occur.

(5) Measurement method of surface resistivity

The surface of the release film (the surface on the opposite side of the release film to the polarizing plate) and the surface of the surface protection film (the surface on the opposite side of the surface protective film to the polarizing plate) were measured using MCP-HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd. Resistivity (Ω/□). "Over" in the table means that the surface resistivity exceeds 1×10 ¹² Ω/□.

<Manufacture 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 is a cyclic olefin-based resin film, and has a thickness of 23 μm.

The protective film 2 is a cyclic olefin-based resin film having a hard coat layer on the surface, and has a thickness of 30 μm.

The polarizer is a thin film formed by adsorbing and aligning iodine on a PVA-based resin film, with a thickness of 8 μm.

The optical sheet 1 is produced by laminating the release film provided with the adhesive layer on the surface of the protective film 1 of the polarizing plate, and laminating the surface protective film on the surface of the protective film 2 of the polarizing plate.

As a surface protective film, the polyethylene terephthalate film (thickness 38 micrometers) provided with the adhesive bond layer of thickness 20 micrometers was used. The thickness of the surface protection film was 58 μm. An antistatic layer was formed on the surface of the polyethylene terephthalate film on the opposite side to the surface in contact with the adhesive layer, and the surface resistivity of the surface protective film was 1×10 ⁹ Ω/□. The release film system used a polyethylene terephthalate film. The thickness of the release film was 38 μm. An adhesive layer with a thickness of 20 μm was formed on the release film. In addition, the adhesive layer on the peeling film is a member provided at the end of the polarizing plate.

Subsequently, the optical sheet 1 was cut out into a rectangular shape having a long side of 110 mm and a short side of 63 mm.

<Optical Sheet 2>

The optical sheet 2 was manufactured in the same manner as the manufacture of the optical sheet 1 except that the surface protection film on which the antistatic layer was not formed was used. The optical sheet 2 was cut out into a rectangular shape with a long side of 110 mm and a short side of 63 mm.

<Example 1>

The surface of the release film of the obtained optical sheet 1 (the surface on the opposite side to the polarizing plate of the release film) was coated with polysiloxane to manufacture an optical sheet for evaluation. The presence ratio of silicon atoms is 7%. No marking was applied to the surface of the release film.

<Example 2>

Except using DRYSAVE 1 (blue, oil-based ink) manufactured by Terai Chemical Industry Co., Ltd., and drawing a straight line as shown in Fig. 3 along the absorption axis between the opposite sides of the optical sheet Except for forming a mark, it carried out similarly to Example 1, and produced the optical sheet for evaluation.

The area ratio of the mark with respect to the area of the release film was 1%. The height of the mark was 0.3 μm from the surface of the release film.

<Example 3>

Except having drawn out three lines, it carried out similarly to Example 2, and produced the optical sheet for evaluation.

The area ratio of the mark with respect to the area of the release film was 3%.

<Examples 4 to 6>

Except having adjusted the coating amount of polysiloxane and making the existence ratio of a silicon atom into 3%, it carried out similarly to Examples 1-3, and produced the optical sheet for evaluation, respectively.

<Examples 7 to 9>

In addition to coating the surface of the release film of the optical sheet 1 obtained (the surface of the release film on the opposite side to the polarizer), instead of coating polysilicon The optical sheets for evaluation were produced in the same manner as in Examples 1 to 3, except that the surface resistivity was 1×10 ⁹ Ω/□.

<Examples 10 to 12>

The optical sheets for evaluation were produced in the same manner as in Examples 7 to 9, except that the coating amount of the static electricity removing liquid was adjusted so that the surface resistivity was 1×10 ¹² Ω/□.

<Example 13>

The electrostatic removal liquid "SB-8" manufactured by Shanghe Chemical Co., Ltd. was applied to the surface of the release film of the obtained optical sheet 2 (the surface of the release film on the opposite side to the polarizing plate) so that the surface resistivity was 1. ×10 ¹² Ω/□. Similarly, the static electricity removal liquid "SB-8" manufactured by Sunhe Chemical Co., Ltd. was applied on the surface of the surface protection film (the surface on the opposite side of the surface protection film to the polarizing plate) so that the surface resistivity was 1× 10 ¹² Ω/□. The optical sheet for evaluation was produced in this way.

<Examples 14 to 16>

Optical sheets for evaluation were produced in the same manner as in Example 13, except that the surface resistivity of the release film and the surface protective film surface was controlled to the values shown in Table 2 by adjusting the coating amount of the static electricity removing liquid.

<Comparative Examples 1 to 3>

In Examples 1 to 3, except that the surface of the release film of the optical sheet was wiped several times with a cloth impregnated with IP SOLVENT (an ethanol-based solvent obtained from Shanghe Processing Co., Ltd.) optics used.

<Comparative Example 4>

In Example 1, except that the surface of the release film was not coated with polysiloxane, the surface of the release film of the optical sheet was wiped several times with a cloth impregnated with IP SOLVENT (an ethanol-based solvent obtained from Shanghe Processing Co., Ltd.). , and the rest were carried out in the same manner to manufacture an optical sheet for evaluation.

<Comparative Example 5>

Optical sheets for evaluation were produced in the same manner as in Example 13 except that the surface resistivity of the release film and the surface protective film surface was controlled to the values shown in Table 2 by adjusting the coating amount of the static electricity removing liquid. In addition, the static electricity removing liquid was not apply|coated to the surface protective film.

For the optical sheets for evaluation produced in Examples 1 to 16 and Comparative Examples 1 to 5 described above, multiple acquisition evaluations were performed. The results are shown in Table 1 and Table 2.

(Industrial Availability)

According to the present invention, it is possible to provide an optical sheet in which multiple take-out is not likely to occur every time one optical sheet is taken out from a laminate in which a plurality of optical sheets are stacked, which is useful.

1‧‧‧Polarizer

2‧‧‧Surface protection film

3‧‧‧Peeling film

10‧‧‧Optical Sheet

Claims (6)

An optical sheet comprising a surface protection film, a polarizing plate, and a release film in sequence, and the coefficient of kinetic friction between the surface protection film and the release film is 0.4 or less, wherein the coefficient of kinetic friction is measured in the following manner : Prepare the above-mentioned optical sheet that has been cut into a size of 11 cm × 6.3 cm, and install the two optical sheets on the fixing aids connected to the movable stage of the measuring machine and the dynamometer respectively, and make the above-mentioned peeling film. The two optical sheets were arranged in such a way that the aforementioned surface protection films faced each other, and then, a load of 500 g was applied from above the overlapping films, and the moving distance of 15.0 mm back and forth was 100 times at a speed of 5000 mm/min. The average coefficient of kinetic friction is calculated from the magnitude of the force detected by the dynamometer at this time. The optical sheet according to claim 1, wherein on the surface of the peeling film on the opposite side to the polarizing plate, the presence ratio of silicon atoms is 3% or more. The optical sheet according to claim 1 or 2, wherein the surface resistivity of the peeling film on the opposite side to the polarizing plate is 1×10 ⁷ to 1×10 ¹² Ω/□. The optical sheet according to claim 1 or 2, wherein the surface resistivity of the surface protective film on the opposite side to the polarizing plate is 1×10 ⁷ to 1×10 ¹² Ω/□ . The optical sheet according to claim 1 or 2, wherein the release film has a mark on the surface opposite to the polarizing plate, and The ratio of the area of the mark to the area of the release film is 5% or less. The optical sheet according to claim 5, wherein the height of the mark from the surface of the release film is 0.5 μm or less.

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