阅读说明：本技术 表面保护薄膜及光学薄膜 (Surface protection film and optical film ) 是由 小川圭太 山形真人 片冈贤一 于 2019-06-27 设计创作，主要内容包括：提供对反射型偏光薄膜的防剥离带电、轻剥离性(再剥离性)、及防层间剥离性优异的、专门用于反射型偏光薄膜用途的表面保护薄膜、以及层叠有前述表面保护薄膜及反射型偏光薄膜的光学薄膜。本发明的反射型偏光薄膜用表面保护薄膜的特征在于,为具有粘合剂层的反射型偏光薄膜用表面保护薄膜,将前述粘合剂层的粘合面粘贴于反射型偏光薄膜之后进行剥离时的剥离带电电压为±0.7kV以下,前述粘合剂层的粘合面对前述反射型偏光薄膜的粘合力在拉伸速度30m/分钟、剥离角度180°下为0.8N/25mm以下。(Provided are a surface protective film which is excellent in anti-peeling electrification, light peeling (re-peeling) properties, and interlayer peeling resistance to a reflective polarizing film and is used exclusively for the purpose of a reflective polarizing film, and an optical film in which the surface protective film and the reflective polarizing film are laminated. The surface protection film for a reflection-type polarizing film of the present invention is a surface protection film for a reflection-type polarizing film having an adhesive layer, wherein a peel electrification voltage at the time of peeling the film after the adhesive layer is attached to the reflection-type polarizing film is ± 0.7kV or less, and an adhesive force of the adhesive layer to the reflection-type polarizing film is 0.8N/25mm or less at a stretching speed of 30 m/min and a peeling angle of 180 °.)

1. A surface protective film for a reflection type polarizing film, characterized by having an adhesive layer,

the peeling electrification voltage when peeling is performed after the adhesive surface of the adhesive layer is adhered to the reflection type polarization film is less than or equal to +/-0.7 kV,

the adhesive force of the adhesive surface of the adhesive layer to the reflection type polarization film is 0.8N/25mm or less at a stretching speed of 30 m/min and a peeling angle of 180 degrees.

2. The surface protective film for a reflection type polarizing film according to claim 1, wherein the adhesive layer is formed of an adhesive composition,

the adhesive composition comprises: a (meth) acrylic polymer containing at least a hydroxyl group-containing (meth) acrylic monomer as a monomer component, an isocyanate compound, and an ionic compound,

the equivalent ratio of the hydroxyl group-containing (meth) acrylic monomer to the isocyanate group of the isocyanate compound, that is, the hydroxyl group/isocyanate group, is less than 10.

3. The surface protective film for a reflection type polarizing film according to claim 2, wherein the adhesive composition contains a silicone component.

4. The surface protective film for a reflection type polarizing film according to any one of claims 1 to 3, wherein the adhesive layer is provided on at least one side of a base film.

5. An optical film comprising the surface protective film for a reflection type polarizing film according to any one of claims 1 to 4 and a reflection type polarizing film.

Technical Field

The present invention relates to a surface protective film and an optical film.

The surface protective film for a reflective polarizing film of the present invention is useful for protecting the surface of a reflective polarizing film used for a liquid crystal display or the like.

Background

In recent years, when transporting optical components and electronic components and mounting the components on a printed circuit board, the components are transported in a state of being packaged in a predetermined sheet or in a state of being attached with an adhesive tape. Among them, the surface protective film is particularly widely used in the field of optical/electronic parts.

The surface protecting film is generally stuck to a subject to be protected via an adhesive layer applied to the base film side, and is used for preventing scratches and dirt generated during processing and transportation of the subject to be protected (patent document 1). For example, a panel of a liquid crystal display is formed by attaching an optical film such as a polarizing film or a reflection-type polarizing film (e.g., a brightness enhancement film) to a liquid crystal cell via an adhesive layer. Among these optical films, a surface protective film is bonded via an adhesive layer, and scratches and stains generated during processing and transportation of a protected object are prevented.

In particular, in recent years, integration of optical films has been advanced, and a reflection type polarizing film is sometimes used by being stuck to a panel of a liquid crystal display in a state of being integrated with an optical film such as a polarizing plate or a polarizing film via an adhesive layer or an adhesive layer.

A reflection-type polarizing film (for example, a brightness enhancement film) is an optical film having a function of transmitting polarized light orthogonal to the reflection axis direction thereof and reflecting polarized light parallel to the reflection axis direction thereof, and a film having a multilayer structure is used in which films made of materials having different refractive index anisotropy are alternately laminated.

The following problems are reported: when a polarizing film with a reflection type polarizing film is used for a panel, except for the period until the reflection type polarizing film and the polarizing film are integrated, a surface protective film is attached to the surface of the reflection type polarizing film via an adhesive layer, but when the reflection type polarizing film is peeled from the reflection type polarizing film at a stage where the surface protective film is not needed later, if the adhesion of the surface protective film to the reflection type polarizing film is large, peeling occurs between layers of the reflection type polarizing film when the surface protective film is peeled.

In addition, when the surface protective film is peeled off from the reflective polarizing film, static electricity is charged, and when the reflective polarizing film is incorporated in a liquid crystal display, the following problems occur: the whitening phenomenon of the panel occurs, and the inspection efficiency is lowered. In particular, when the reflective polarizing film is formed in a multilayer structure, it is easily charged, which is problematic.

In recent years, an attempt has been made to improve the peeling electrification preventing property by using an alkali metal salt or the like as an antistatic agent for the pressure-sensitive adhesive layer constituting the surface protective film, and for example, when the surface protective film is peeled from the polarizing film, an attempt has been made to suppress the whitening phenomenon of the panel. However, the current situation is: there has not been obtained a surface protective film which has anti-peeling electrification property when peeling a surface protective film from a reflective polarizing film having a multilayer structure and is capable of preventing occurrence of interlayer peeling (interlayer peeling) of the reflective polarizing film having a multilayer structure.

Disclosure of Invention

Problems to be solved by the invention

Therefore, it is desired to develop a surface protective film which can protect the surface of a reflective polarizing film having a multilayer structure and which satisfies the requirements of a peeling electrification preventing property, a light peeling property (re-peeling property), and an interlayer peeling preventing property.

Accordingly, an object of the present invention is to solve the problems of the conventional reflective polarizing film, and to provide a surface protective film excellent in peeling electrification prevention, light peeling (re-peeling) resistance, and interlayer peeling resistance for the reflective polarizing film, and an optical film obtained by laminating the surface protective film and the reflective polarizing film.

Means for solving the problems

That is, the surface protection film for a reflection-type polarizing film of the present invention is characterized by comprising an adhesive layer, wherein the peel electrification voltage at the time of peeling after the adhesive surface of the adhesive layer is attached to the reflection-type polarizing film is ± 0.7kV or less, and the adhesive force of the adhesive surface of the adhesive layer to the reflection-type polarizing film is 0.8N/25mm or less at a stretching speed of 30 m/min and a peeling angle of 180 °.

In the surface protective film for a reflective polarizing film of the present invention, the pressure-sensitive adhesive layer is preferably formed from a pressure-sensitive adhesive composition containing: the resin composition comprises a (meth) acrylic polymer containing at least a hydroxyl group-containing (meth) acrylic monomer as a monomer component, an isocyanate compound, and an ionic compound, wherein the equivalent ratio of the hydroxyl group-containing (meth) acrylic monomer to the isocyanate group of the isocyanate compound (hydroxyl group/isocyanate group) is less than 10.

In the surface protective film for a reflection-type polarizing film of the present invention, the pressure-sensitive adhesive composition preferably contains a silicone component.

The surface protective film for a reflection type polarizing film of the present invention preferably has the pressure-sensitive adhesive layer on at least one side of a base film.

The surface protective film for a reflection-type polarizing film of the present invention preferably comprises the surface protective film for a reflection-type polarizing film and a reflection-type polarizing film.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention is useful for providing a surface protective film for a reflective polarizing film, which has excellent anti-peeling electrification property, light peeling property (re-peeling property), and interlayer peeling property with respect to a reflective polarizing film and is used exclusively for the purpose of the reflective polarizing film, and an optical film in which the surface protective film and the reflective polarizing film are laminated.

Drawings

Fig. 1 is a schematic cross-sectional view showing a polarizing film with a reflection-type polarizing film to which a surface protective film is attached according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a potential measuring section for measuring a peeling electrification voltage in an example and the like.

Attached pictureDescription of the invention

1 surface protective film

2 polarizing film with reflection type polarizing film

3 fixed station

4 electric potential measuring device

10 antistatic layer

20 base material film

30 adhesive layer

40 reflection type polarizing film

50 adhesive layer

60 polarizing plate

70 conductive adhesive layer (B)

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

< integral Structure of surface protective film >

The surface protective film disclosed herein is generally in the form of a pressure-sensitive adhesive sheet, pressure-sensitive adhesive tape, pressure-sensitive adhesive label, pressure-sensitive adhesive film, or the like, and is particularly suitable as a surface protective film for protecting the surface of a reflective polarizing film during processing or transportation of the reflective polarizing film. The pressure-sensitive adhesive layer in the surface protective film is typically formed continuously, but is not limited to this form, and may be formed in a regular or random pattern such as dots or stripes, for example. The surface protection film disclosed herein may be in the form of a roll or a sheet.

< substrate film >

The surface protective film for a reflective polarizing film of the present invention (hereinafter, may be simply referred to as "surface protective film") preferably has a base film. In the technique disclosed herein, the resin material constituting the base film may be used without particular limitation, and for example, a material excellent in properties such as transparency, mechanical strength, thermal stability, moisture-shielding property, isotropy, flexibility, and dimensional stability is preferably used. In particular, it is useful that the adhesive composition can be applied by a roll coater or the like by imparting flexibility to the base film, and can be wound up in a roll form.

As the base film, for example, a film formed of a polyester polymer such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate; cellulose polymers such as cellulose diacetate and cellulose triacetate; a polycarbonate-series polymer; acrylic polymers such as polymethyl methacrylate; a plastic film made of a resin material containing a cycloolefin polymer or the like as a main resin component (a main component in the resin component, typically, a component accounting for 50% by weight or more) is used as the base film. Other examples of the resin material include styrene polymers such as polystyrene and acrylonitrile-styrene copolymer; olefin polymers such as polyethylene, polypropylene, polyolefins having a cyclic and/or norbornene structure, and ethylene-propylene copolymers; a vinyl chloride polymer; amide polymers such as nylon 6,6 and aromatic polyamide; and the like as the resin material. Examples of the resin material include imide polymers, sulfone polymers, polyethersulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, and epoxy polymers. The base film may be a base film formed of a blend of 2 or more of the above polymers.

As the base film, a plastic film made of a transparent thermoplastic resin material can be preferably used. Among the above plastic films, a polyester film is more preferable. Here, the polyester film is a film containing, as a main resin component, a polymer material (polyester resin) having a main skeleton based on ester bonds, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate. The polyester film has properties preferable as a base film of a surface protective film, such as excellent optical properties and dimensional stability, and on the other hand, has a property of being easily charged in its original state.

The resin material constituting the base film may be blended with various additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a colorant (pigment, dye, etc.) and the like, as required. For example, a known or conventional surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and coating with a primer may be performed. Such a surface treatment may be, for example, a treatment for improving adhesion between the base film and the adhesive layer (anchoring property of the adhesive layer).

The surface protective film of the present invention may also use a plastic film subjected to antistatic treatment as the base film. The use of the base film is preferable because the electrification of the surface protective film itself at the time of peeling is suppressed. Further, by using a plastic film as the base film and subjecting the plastic film to antistatic treatment, a surface protection film which is reduced in electrification of the surface protection film itself and is excellent in antistatic ability to an adherend (reflection-type polarizing film) can be obtained. The method for imparting the antistatic function is not particularly limited, and conventionally known methods can be used, and examples thereof include: a method of applying an antistatic resin comprising an antistatic agent and a resin component, a conductive polymer, and a conductive resin containing a conductive substance; a method of evaporating or plating a conductive material; and, a method of incorporating an antistatic agent or the like; a method of forming an antistatic layer, and the like.

The thickness of the base film is usually about 5 to 200 μm, preferably about 10 to 100 μm. When the thickness of the base film is within the above range, the adhesion workability to an adherend (reflection-type polarizing film) and the peeling workability from the adherend are excellent, and therefore, the thickness is preferable.

The surface protective film disclosed herein may also be implemented in a manner of including an antistatic layer and further other layers in addition to the base material film and the adhesive layer. Examples of the other layer include an undercoat layer (anchor layer) for improving the anchoring properties of the antistatic layer and the adhesive layer.

< adhesive composition >

The pressure-sensitive adhesive composition of the present invention is not particularly limited as long as it contains a pressure-sensitive adhesive polymer having pressure-sensitive adhesiveness, and a pressure-sensitive adhesive layer can be formed from the pressure-sensitive adhesive composition. As the adhesive composition, for example, an acrylic adhesive, a urethane adhesive, a synthetic rubber adhesive, a natural rubber adhesive, a silicone adhesive, or the like can be used, among them, the adhesive polymer is more preferably at least 1 selected from the group consisting of a (meth) acrylic polymer, a urethane polymer and a silicone polymer, and more preferably (contains) at least 1 selected from the group consisting of an acrylic adhesive containing a (meth) acrylic polymer, a urethane adhesive containing a urethane polymer and a silicone adhesive containing a silicone polymer, and particularly preferably an acrylic adhesive, the acrylic pressure-sensitive adhesive uses a (meth) acrylic polymer as the pressure-sensitive adhesive polymer.

When an acrylic pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer, a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms can be used as a main monomer in a (meth) acrylic polymer that is a pressure-sensitive adhesive polymer constituting the acrylic pressure-sensitive adhesive. As the (meth) acrylic monomer, 1 or 2 or more species can be used. By using the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, the peel strength (adhesive strength) to an adherend (reflective polarizing film) can be easily controlled to be low, and a surface protective film having excellent light peelability (repeelability) can be obtained.

In the present invention, the term (meth) acrylic polymer means an acrylic polymer and/or a methacrylic polymer, and the term (meth) acrylate means an acrylate and/or a methacrylate. Further, as the (meth) acrylic monomer, 1 or 2 or more species may be used as the main component.

Specific examples of the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, and n-tetradecyl (meth) acrylate.

Among them, the surface protective film may include (meth) acrylic monomers having an alkyl group having 4 to 14 carbon atoms such as n-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, and n-tetradecyl (meth) acrylate, as suitable monomers. In particular, by using a (meth) acrylic monomer having an alkyl group having 4 to 14 carbon atoms, the peeling force (adhesive force) to an adherend (reflective polarizing film) can be easily controlled to be low, and the light peeling property (re-peeling property) is excellent.

In particular, the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms is preferably contained in an amount of 70% by weight or more, more preferably 80% by weight or more, further preferably 85 to 99% by weight, and particularly preferably 88 to 98% by weight, based on 100% by weight of the total amount of the monomer components constituting the (meth) acrylic polymer. If the content is less than 70% by weight, the adhesive composition will have an appropriate wettability and the cohesive strength of the adhesive layer will be poor, which is not preferable.

The (meth) acrylic polymer preferably contains at least a hydroxyl group-containing (meth) acrylic monomer as a monomer component. As the hydroxyl group-containing (meth) acrylic monomer, 1 or 2 or more species can be used. By using the hydroxyl group-containing (meth) acrylic monomer, crosslinking and the like of the pressure-sensitive adhesive composition can be easily controlled, and the balance between improvement of wettability by flow and reduction of peel force (adhesive force) at the time of peeling can be easily controlled.

Examples of the hydroxyl group-containing (meth) acrylic monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 4-hydroxymethylcyclohexyl (4-hydroxymethylcyclohexyl) methyl acrylate, and N-methylol (meth) acrylamide. In particular, the use of a hydroxyl group-containing (meth) acrylic monomer having an alkyl group of 4 or more carbon atoms is preferable because light peeling is facilitated at the time of high-speed peeling.

The hydroxyl group-containing (meth) acrylic monomer is preferably contained in an amount of 20 wt% or less, more preferably 18 wt% or less, still more preferably 0.1 to 16 wt%, and particularly preferably 1 to 14 wt% based on 100 wt% of the total amount of the monomer components constituting the (meth) acrylic polymer. When the content is within the above range, the balance between the wettability of the adhesive composition and the cohesive force of the resulting adhesive layer can be easily controlled, and therefore, this is preferable.

Further, as the other polymerizable monomer component, a polymerizable monomer or the like for adjusting the glass transition temperature and/or the peelability of the (meth) acrylic polymer so that the Tg is 0 ℃ or lower (usually-100 ℃ or higher) can be used within a range not impairing the effect of the present invention, from the viewpoint of easily obtaining the balance of the adhesive performance.

As the polymerizable monomer other than the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms and the hydroxyl group-containing (meth) acrylic monomer that can be used in the (meth) acrylic polymer, a carboxyl group-containing (meth) acrylic monomer can be used. The use of the carboxyl group-containing (meth) acrylic monomer is preferable because it suppresses an increase in adhesive strength of the surface protective film (pressure-sensitive adhesive layer) with time, and is excellent in light peelability (removability), prevention of an increase in adhesive strength, and workability, and also excellent in shear force together with cohesive force of the pressure-sensitive adhesive layer.

Examples of the carboxyl group-containing (meth) acrylic monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, and carboxypentyl (meth) acrylate.

The carboxyl group-containing (meth) acrylic monomer is preferably 0 to 3% by weight, more preferably 0.001 to 2% by weight, even more preferably 0.005 to 1% by weight, and particularly preferably 0.001 to 0.5% by weight, based on 100% by weight of the total amount of the monomer components constituting the (meth) acrylic polymer. When the content is within the above range, the balance between the wettability of the adhesive composition and the cohesive force of the resulting adhesive layer can be easily controlled, and therefore, this is preferable.

The other polymerizable monomer may be used without particular limitation as long as the properties of the present invention are not impaired. For example, a component for improving cohesive force/heat resistance such as a cyano group-containing monomer, a vinyl ester monomer, or an aromatic vinyl monomer, a component for improving peeling force (adhesive force) such as an amide group-containing monomer, an imide group-containing monomer, an amino group-containing monomer, an epoxy group-containing monomer, N-acryloylmorpholine, or a vinyl ether monomer, and a component having a functional group which functions as a crosslinking base point can be suitably used. Among them, nitrogen-containing monomers such as a cyano group-containing monomer, an amide group-containing monomer, an imide group-containing monomer, an amino group-containing monomer, and N-acryloylmorpholine are preferably used. These polymerizable monomers may be used in 1 kind or 2 or more kinds.

Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

Examples of the amide group-containing monomer include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N-dimethylacrylamide, N-dimethylmethacrylamide, N-diethylacrylamide, N-diethylmethacrylamide, N' -methylenebisacrylamide, N-dimethylaminopropylacrylamide, N-dimethylaminopropylmethacrylamide, diacetoneacrylamide and the like.

Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylate.

Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, and vinyl laurate.

Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethylstyrene, α -methylstyrene, and other substituted styrenes.

Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, and allyl glycidyl ether.

Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

The other polymerizable monomer is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, based on 100% by weight of the total amount of the monomer components constituting the (meth) acrylic polymer. The other polymerizable monomer may be suitably adjusted to obtain desired characteristics.

The (meth) acrylic polymer may further contain an alkylene oxide group-containing reactive monomer as a monomer component.

The weight average molecular weight (Mw) of the (meth) acrylic polymer is preferably 10 to 200 ten thousand, more preferably 20 to 100 ten thousand, still more preferably 30 to 80 ten thousand, and particularly preferably 30 to 70 ten thousand. When the weight average molecular weight is less than 10 ten thousand, the cohesive force of the adhesive layer becomes small, and adhesive residue tends to occur. On the other hand, when the weight average molecular weight exceeds 200 ten thousand, the fluidity of the polymer decreases, and the wetting of the adherend (reflective polarizing film) becomes insufficient, and the swelling tends to occur between the adherend and the pressure-sensitive adhesive layer of the surface protective film. The weight average molecular weight is a value measured by GPC (gel permeation chromatography).

The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably 0 ℃ or lower, more preferably-20 ℃ or lower, still more preferably-40 ℃ or lower, and particularly preferably-50 ℃ or lower (usually-100 ℃ or higher). When the glass transition temperature is higher than 0 ℃, the polymer is difficult to flow, and for example, the wetting of the adherend (reflective polarizing film) is insufficient, and the polymer tends to cause swelling between the adherend and the pressure-sensitive adhesive layer of the surface protective film. Among them, a pressure-sensitive adhesive layer having excellent wettability to an adherend and light peelability (removability) can be easily obtained by setting the glass transition temperature to-60 ℃ or lower. The glass transition temperature of the (meth) acrylic polymer can be adjusted to fall within the above range by appropriately changing the monomer components and the composition ratio used.

The polymerization method of the (meth) acrylic polymer is not particularly limited, and polymerization can be carried out by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, or suspension polymerization, and solution polymerization is a more preferable mode particularly from the viewpoint of handling properties and characteristics such as low staining property to an adherend (reflective polarizing film). The polymer obtained may be any of a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, and the like.

When a urethane adhesive is used for the adhesive layer, any appropriate urethane adhesive can be used. As such a urethane adhesive, an adhesive containing a urethane polymer that is an adhesive polymer obtained by reacting a polyol with a polyisocyanate compound is preferably used. Examples of the polyol include polyether polyol, polyester polyol, polycarbonate polyol, and polycaprolactone polyol. Examples of the polyisocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate.

When a silicone adhesive is used for the adhesive layer, any suitable silicone adhesive can be used. As such a silicone adhesive, an adhesive obtained by blending or aggregating a silicone polymer as an adhesive polymer is preferably used.

Examples of the silicone adhesive include an addition reaction curable silicone adhesive and a peroxide curable silicone adhesive. Among these silicone-based adhesives, addition reaction curing type silicone-based adhesives are preferred in that no peroxide (benzoyl peroxide or the like) is used and no decomposition products are generated.

In the case where a polyalkyl silicone-based adhesive is obtained, for example, as the curing reaction of the addition reaction curable silicone-based adhesive, a method of curing a polyalkyl hydrosiloxane composition using a platinum catalyst is generally exemplified.

< Ionic Compound >

The adhesive composition preferably contains an ionic compound as an antistatic agent. As the ionic compound, alkali metal salts and ionic liquids can be used, and among them, it is more preferable to contain an ionic compound which is in a liquid state at room temperature (25 ℃) and has a viscosity (25 ℃) of 550 mPas or less. The ionic compound is a so-called ionic liquid, which means a molten salt that is liquid at room temperature (25 ℃). By containing the ionic compound, excellent antistatic property and anti-peeling electrification property can be provided. The reason why the use of the ionic liquid provides excellent antistatic properties is not clear in detail, but it is considered that the addition to a pressure-sensitive adhesive (pressure-sensitive adhesive composition) and dispersion or dissolution are facilitated and excellent antistatic ability can be obtained, compared to an antistatic agent which is solid at room temperature, because the ionic liquid is liquid at room temperature (25 ℃). In particular, when antistatic property is required for an adherend (reflection-type polarizing film), it is considered that excellent peeling electrification preventing property of the adherend is achieved by transferring an ionic liquid to the adherend in a very small amount.

The ionic compound has a conductivity (25 ℃) of preferably 0 to 20mS/cm, more preferably 0.01 to 18mS/cm, and still more preferably 0.1 to 16 mS/cm. When the ionic compound has an electrical conductivity (conductivity) at 25 ℃ within the above range, the generated peeling electrification voltage can be rapidly released, and excellent peeling electrification preventing properties can be exhibited even in an adherend (reflection-type polarizing film) which has a multilayer structure and is easily electrified, which is a preferable embodiment.

The ionic compound preferably has a viscosity at 25 ℃ (room temperature) of 550 mPas or less, more preferably 500 mPas or less, even more preferably 450 mPas or less, particularly preferably 10 to 400 mPas, and most preferably 15 to 250 mPas. When the viscosity of the ionic compound at 25 ℃ is within the above range, the ionic compound tends to have high conductivity (electrical conductivity), and the resulting peeling electrification voltage can be rapidly released, and the ionic compound has high fluidity and good dispersion in the pressure-sensitive adhesive layer, and the ionic compound is likely to move on the surface of the pressure-sensitive adhesive layer in contact with the adherend (reflective polarizing film), and the high-dimensional peeling electrification can be prevented, which is a preferable mode. The viscosity in the present invention was measured at 25 ℃ using a viscometer (RE-85U, manufactured by Toyobo industries Co., Ltd.). The measurement may be performed using a conical rotor at a rotation speed of 12rpm and 1 ° 34' × R24.

< Ionic liquid >

The ionic liquid is preferably a liquid at room temperature (25 ℃) and has a viscosity (25 ℃) of 550mPa · s or less, and for example, a compound composed of a cationic component (organic cationic component) and an anionic component is preferably used.

Examples of the ionic compound (ionic liquid) include 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide salt, 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-methyl-3-propylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-hexyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-decyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-dodecylimidazolium bis (trifluoromethanesulfonyl) imide salt, and mixtures thereof, 1-Ethyl-2, 3-dimethylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1, 2-dimethyl-3-propylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-2-3-dimethylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-Ethyl-3-vinylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-vinylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-methyl-1-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-1-methylpyrrolidinium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-1-methylpiperidinium bis (trifluoromethanesulfonyl) imide salt, 4- (2-ethoxyethyl) -4-methylmorpholinium bis (trifluoromethanesulfonyl) imide salt ) Imide salts, 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-4-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide salt, 1-hexyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide salt, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide salt, tributyldodecylphosphonium bis (trifluoromethanesulfonyl) imide salt, trimethylpropylammonium bis (trifluoromethanesulfonyl) imide salt, butyltrimethylammonium bis (trifluoromethanesulfonyl) imide salt, triethylsulfonium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-methylpyridinium trifluoromethanesulfonic acid and the like, among which 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide salt, 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, triethylsulfonium bis (trifluoromethanesulfonyl) imide salt and 1-butyl-3-methylpyridinium trifluoromethanesulfonic acid are preferably used from the viewpoint of low viscosity and electrical conductivity (electrical conductivity), in particular.

These ionic compounds (ionic liquids and the like) may be used alone, or 2 or more kinds thereof may be used in combination.

The content of the ionic compound is, for example, preferably 0.01 to 5 parts by weight, more preferably 0.02 to 4 parts by weight, still more preferably 0.05 to 3 parts by weight, and particularly preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer constituting the adhesive composition. When the amount is within the above range, the surface protective film of the present invention is preferable because antistatic property and low staining property are easily compatible with an adherend (reflective polarizing film).

< organosilicon component >

The surface protective film for a reflection-type polarizing film of the present invention preferably contains a silicone component in the adhesive composition. By using the silicone component, the surface free energy of the pressure-sensitive adhesive layer surface formed of the pressure-sensitive adhesive composition is reduced, light peeling can be achieved at the time of peeling, and the ionic compound is promoted to move to the pressure-sensitive adhesive layer surface, so that the peeling electrification voltage can be suppressed, which is a preferable embodiment.

< organopolysiloxane having oxyalkylene chain >

As the silicone component, for example, an organopolysiloxane having an oxyalkylene chain can be used. The organopolysiloxane can be a known organopolysiloxane having a polyoxyalkylene main chain, and is preferably represented by the following formula.

(in the formula, R₁And/or R₂The polyoxyalkylene chain has an oxyalkylene chain having 1 to 6 carbon atoms, wherein an alkylene group in the oxyalkylene chain may be a straight chain or a branched chain, and a terminal of the oxyalkylene chain may be an alkoxy group or a hydroxyl group. In addition, R₁Or R₂Any of these may be a hydroxyl group, or may be an alkyl group or an alkoxy group, and a part of the alkyl group or the alkoxy group may be a functional group substituted with a hetero atom. n is an integer of 1 to 300. )

The organopolysiloxane is a substance having a siloxane-containing site (siloxane site) as a main chain and an oxyalkylene chain bonded to a terminal of the main chain. It is presumed that by using the organosiloxane having an oxyalkylene chain, for example, compatibility with the adhesive polymer and the ionic compound is balanced, and light peeling is achieved.

The organopolysiloxane used in the present invention can be, for example, the following one. Specifically, R in the formula₁And/or R₂An oxyalkylene chain having a hydrocarbon group containing 1 to 6 carbon atoms, and examples of the oxyalkylene chain include oxymethylene, oxyethylene, oxypropylene and oxybutylene,among them, oxyethylene and oxypropylene are preferable. In addition, R is₁And R₂When they have all oxyalkylene chains, they may be the same or different.

The hydrocarbon group of the oxyalkylene chain may be linear or branched.

Further, the terminal of the oxyalkylene chain may be an alkoxy group or a hydroxyl group, and among them, an alkoxy group is more preferable. When a separator is attached to the surface of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive surface, the hydroxyl-terminated organopolysiloxane may interact with the separator, and the adhesion (peeling) force may increase when the separator is peeled from the surface of the pressure-sensitive adhesive layer.

In addition, n is an integer of 1 to 300, preferably 10 to 200, and more preferably 20 to 150. When n is within the above range, compatibility with the base polymer is balanced, which is a preferable mode. Further, the molecule may have a reactive substituent such as a (meth) acryloyl group, allyl group, or hydroxyl group. The organopolysiloxane can be used alone, or 2 or more kinds can be used in combination.

Specific examples of the aforementioned organopolysiloxane having an oxyalkylene chain include commercially available products such as X-22-4952, X-22-4272, X-22-6266, KF-6004, KF-889 (manufactured BY shin-Etsu chemical Co., Ltd.), BY16-201, SF8427 (manufactured BY Toyo Corning Co., Ltd.), IM22 (manufactured BY Asahi Kasei Wacker Co., Ltd.), and the like. These compounds may be used alone, or 2 or more of them may be used in combination.

In addition, as the organosilicon component, in addition to an organosiloxane having (bonded) oxyalkylene chains in the main chain, an organosiloxane having (bonded) oxyalkylene chains in side chains may be used, and it is a more preferable mode to use an organosiloxane having oxyalkylene chains in side chains than in the main chain. The organopolysiloxane can be a known organopolysiloxane having a polyoxyalkylene side chain, and is preferably represented by the following formula.

(in the formula, R₁Is a 1-valent organic radical, R₂、R₃And R₄Is alkylene, R₅Is hydrogen or an organic group, and m and n are integers of 0 to 1000. Wherein m and n are not 0 at the same time. a and b are integers of 0 to 100. Wherein a and b are not 0 at the same time. )

The organopolysiloxane used in the present invention can be, for example, the following one. Specifically, R in the formula₁The 1-valent organic group exemplified by an alkyl group such as a methyl group, an ethyl group, or a propyl group, an aryl group such as a phenyl group or a tolyl group, or an aralkyl group such as a benzyl group or a phenethyl group may have a substituent such as a hydroxyl group. R₂、R₃And R₄Alkylene groups having 1 to 8 carbon atoms such as methylene, ethylene and propylene may be used. Here, R₃And R₄Being different alkylene radicals, R₂Can be reacted with R₃Or R₄The same or different. In order to increase the concentration of the ionic compound soluble in the polyoxyalkylene side chain, R is preferably₃And R₄Either of which is ethylene or propylene. R₅The organic group may be a 1-valent organic group exemplified by an alkyl group such as a methyl group, an ethyl group, or a propyl group, or an acyl group such as an acetyl group or a propionyl group, and each may have a substituent such as a hydroxyl group. These compounds may be used alone, or 2 or more of them may be used in combination. The molecule may have a reactive substituent such as a (meth) acryloyl group, allyl group, or hydroxyl group. Among the aforementioned organosiloxanes having a polyoxyalkylene side chain, an organosiloxane having a polyoxyalkylene side chain having a hydroxyl terminal is preferable because it is presumed that compatibility balance is easily obtained.

Specific examples of the aforementioned organosiloxanes include commercially available products of KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6022, X-22-6191, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017, X-22-2516 (manufactured by shin-Etsu chemical Co., Ltd.) SF8428, FZ-2162, SH3749, FZ-77, L-7001, FZ-2104, FZ-2110, L-7002, FZ-2122, FZ-2164, FZ-2203, FZ-7001, SH8400, SH8700, SF8410, SF8422 (manufactured by Tokyo Corning Co., Ltd.), TSZ-4440, TSF-4441, TSF-4445, TSF-4450, TSF-4446, TSF-4452, TSF-4460 (manufactured by MomentivePerformance Materials), BYK-333, BYK-307, BYK-377, BYK-UV3500, BYK-UV3570 (manufactured by BYK Japan KK), and the like. These compounds may be used alone, or 2 or more of them may be used in combination.

The organosiloxane used in the present invention preferably has an HLB (hydrophilic lipophilic balance) value of 1 to 16, more preferably 3 to 14. When the HLB value is outside the above range, staining property to an adherend (reflection-type polarizing film) is deteriorated, which is not preferable.

< organosilicon containing Ionic groups >

Further, as the silicone component, a silicone containing an ionic group can be used. By using the ionic group-containing silicone, the silicone component having a low surface energy is integrated with the ionic compound, and the ionic compound is easily moved to the surface of the pressure-sensitive adhesive layer, which is a preferable embodiment.

The ionic group-containing silicone is preferably an ionic group-containing silicone represented by the following formula (1). By including the ionic group-containing silicone in the pressure-sensitive adhesive composition, the ionic group-containing silicone remains on the surface of the pressure-sensitive adhesive layer without penetrating into the adherend (from the surface of the adherend to the inside of the adherend) even when stored in a high-temperature environment in a state where the pressure-sensitive adhesive layer is attached to the surface of the adherend (reflective polarizing film) due to the low surface free energy of the silicone chain, and therefore, the release electrification characteristics are stable even with the passage of time, and the antistatic performance can be maintained for a long period of time, which is a preferable embodiment. The "inside" of the pressure-sensitive adhesive layer refers to a case where the pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive composition containing the ionic group-containing silicone, for example, and the pressure-sensitive adhesive layer is included in the pressure-sensitive adhesive layer. In the case where the pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive composition mixed with or not mixed with the ionic group-containing silicone, for example, the "surface" of the pressure-sensitive adhesive layer refers to a case where the ionic group-containing silicone is transferred (transferred) from the surface of the separator to the surface of the pressure-sensitive adhesive layer when the surface of the separator to be attached to protect the surface of the pressure-sensitive adhesive layer is coated (laminated) with the ionic group-containing silicone in advance and the separator is attached to the pressure-sensitive adhesive layer.

R in the above formula (1)₁～R₄The alkyl group may be the same or different and may contain any of an alkyl group having 1 to 10 carbon atoms, an alkoxy group, an aryl group, an alicyclic group, a fluorine-substituted alkyl group, and an ionic group, R₁～R₄1 or more of (1) contains an ionic group. n is an integer of 0 to 100.

In addition, as R₁～R₄The ionic group contained in 1 or more of (1) above is preferably an ionic group having an ammonium cation group or a phosphonium cation group. Wherein R is₁～R₄Preferably, at least 1 of the above-mentioned groups is formed of a cationic structure represented by the following formula (a) or (b) and an anionic component, or a zwitterionic structure represented by the following formula (c) or (d).

R in the above formula (a)₅～R₇The alkyl groups may be the same or different and each represent any of an alkyl group, an aryl group and a fluorine-substituted alkyl group having 1 to 10 carbon atoms. m is an integer of 1 to 10.

R in the above formula (b)₈～R₁₀The alkyl groups may be the same or different and each represent any of an alkyl group, an aryl group and a fluorine-substituted alkyl group having 1 to 10 carbon atoms. m is an integer of 1 to 10.

On the other hand, the anionic component is not particularly limited, and for example, Cl can be used^-、Br^-、I^-、AlCl₄ ^-、Al₂Cl₇ ^-、BF₄ ^-、PF₆ ^-、ClO₄ ^-、NO₃ ^-、CH₃COO^-、CF₃COO^-、CH₃SO₃ ^-、CF₃SO₃ ^-、C₄F₉SO₃ ^-、(CF₃SO₂)₂N^-、(C₂F₅SO₂)₂N^-、(C₃F₇SO₂)₂N^-、(C₄F₉SO₂)₂N^-、(CF₃SO₂)₃C^-、AsF₆ ^-、SbF₆ ^-、NbF₆ ^-、TaF₆ ^-、F(HF)_n ^-、(CN)₂N^-、C₄F₉SO₃ ^-、(C₂F₅SO₂)₂N^-、C₃F₇COO^-、(CF₃SO₂)(CF₃CO)N^-、C₉H₁₉COO^-、(CH₃)₂PO₄ ^-、(C₂H₅)₂PO₄ ^-、C₂H₅OSO₃ ^-、C₆H₁₃OSO₃ ^-、C₈H₁₇OSO₃ ^-、CH₃(OC₂H₄)₂OSO₃ ^-、C₆H₄(CH₃)SO₃ ^-、(C₂F₅)₃PF₃ ^-、CH₃CH(OH)COO^-And (FSO)₂)₂N^-And the like.

R in the above formula (c)₁₁、R₁₂May be the same or different and represents any of an alkyl group, an aryl group and a fluorine-substituted alkyl group having 1 to 10 carbon atoms, R₁₁、R₁₂A ring may be formed, in which case it represents an alkylene group. m is an integer of 1 to 10, and p is an integer of 1 to 6.

R in the above formula (d)₁₃、R₁₄May be the same or different and represents any of an alkyl group, an aryl group and a fluorine-substituted alkyl group having 1 to 10 carbon atoms, R₁₃、R₁₄A ring may be formed, in which case it represents an alkylene group. m is an integer of 1 to 10, and p is an integer of 1 to 6.

Since such an ionic group-containing silicone contains a silicone chain, the ionic group-containing silicone remains on the surface of the pressure-sensitive adhesive layer without penetrating into the adherend (from the surface of the adherend to the inside of the adherend) even when stored in a high-temperature environment in a state where the pressure-sensitive adhesive layer is attached to the surface of the adherend (reflective polarizing film) due to the low surface free energy of the silicone chain, and therefore, the release charging characteristics are stable even with the passage of time, the antistatic performance can be maintained for a long period of time, and the silicone can be suitably used as an antistatic agent.

Examples of commercially available products of the ionic group-containing silicone include X-40-2450 and X-40-2750 (available from shin-Etsu chemical Co., Ltd.). These compounds may be used alone, or 2 or more of them may be used in combination.

The content of the silicone component is preferably 0.01 to 5 parts by weight, more preferably 0.03 to 3 parts by weight, and still more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the (meth) acrylic polymer as the adhesive polymer, for example. When the content is within the above range, both the antistatic property and the light releasability (repeelability) can be easily obtained, which is preferable.

< fluoro oligomers >

The adhesive composition may contain a fluorine-based oligomer. When the pressure-sensitive adhesive composition contains the fluorine-containing oligomer, the resulting pressure-sensitive adhesive layer (surface protective film) can exhibit a light peeling effect due to the low surface free energy of the fluorine portion in the fluorine-containing oligomer when the pressure-sensitive adhesive layer (surface protective film) is attached to an adherend (reflective polarizing film).

The fluorine-based oligomer has a hydroxyl value of 1 or more, preferably 5 or more, more preferably 10 or more, further preferably 20 or more, and particularly preferably 40 or more. When the hydroxyl value of the fluorine-based oligomer is 1 or more, the interaction between the fluorine-based oligomer and the adhesive polymer is enhanced, the amount of transfer to an adherend (reflection-type polarizing film) is reduced, and sliding (displacement), floating, peeling, and the like of the surface protective film can be suppressed. Further, a hydroxyl value of 20 or more is preferable because the stain resistance (low staining property) is more excellent. The hydroxyl value of the fluorine-based oligomer is preferably 500 or less, more preferably 400 or less. If the hydroxyl value of the fluorine-based oligomer exceeds 500, the reaction between the fluorine-based oligomer and the crosslinking agent is prioritized, the reaction between the original crosslinking agent and the adhesive polymer is inhibited, and the cohesive force may decrease, which is not preferable.

Specific examples of the fluorine-based oligomer include commercially available products such as MEGAFAC F-477, F-556, F-559, F-562, F-563, F-569 and F-571 (available from DIC). These compounds may be used alone, or 2 or more of them may be used in combination.

The content of the fluorine-based oligomer is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 4 parts by weight, further preferably 0.04 to 3 parts by weight, and most preferably 0.06 to 2 parts by weight, based on 100 parts by weight of the adhesive polymer (which is a base polymer, for example, a (meth) acrylic polymer, a urethane polymer, a silicone polymer, or the like) constituting the adhesive composition. When the amount is within the above range, the surface protective film used in the present invention is preferably capable of suppressing slipping (offset), floating, peeling, and the like after being stuck to an adherend (reflection-type polarizing film), and further has an excellent light peeling effect. In order to satisfy the appearance as a surface protective film, for example, the content of the fluorine-based oligomer is preferably 0.01 to 1.5 parts by weight based on 100 parts by weight of the adhesive polymer.

< crosslinking agent >

In the surface protection film of the present invention, the pressure-sensitive adhesive composition preferably contains a crosslinking agent. In the present invention, the adhesive layer can be formed using the adhesive composition. For example, when the pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive containing the (meth) acrylic polymer, a surface protection film (pressure-sensitive adhesive layer) having more excellent heat resistance can be obtained by crosslinking the composition by appropriately adjusting the constituent unit and the constituent ratio of the (meth) acrylic polymer, the selection and addition ratio of the crosslinking agent, and the like.

As the crosslinking agent used in the present invention, an isocyanate compound, an epoxy compound, a melamine resin, an aziridine derivative, a metal chelate compound, and the like can be used, and the use of an isocyanate compound is particularly preferable. These compounds may be used alone or in combination of 2 or more.

Examples of the isocyanate compound include aliphatic polyisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, Hexamethylene Diisocyanate (HDI) and dimer acid diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI) and 1, 3-bis (isocyanatomethyl) cyclohexane, 2, 4-tolylene diisocyanate and 4, 4' -diphenylmethane diisocyanate, aromatic isocyanates such as Xylylene Diisocyanate (XDI), and modified polyisocyanates obtained by modifying the isocyanate compounds with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds, and the like. For example, commercially available products include trade names of TAKENATE 300S, TAKENATE 500, TAKENATE 600, TAKENATE D165N, TAKENATE D178N (available from mitsui chemical co., ltd.), SUMIJULE 80, SUMIJULE L, Desmodur N3400 (available from Sumika Bayer urea co., ltd.), milonate MR, milonate MT, Coronate L, Coronate HL, and Coronate HX (available from tosohco corporation). These isocyanate compounds may be used alone, or 2 or more kinds may be used in combination, or a 2-functional isocyanate compound and a 3-functional isocyanate compound may be used in combination. By using a crosslinking agent in combination, it is possible to achieve both of the adhesion and the repulsion resistance (adhesion to a curved surface), and it is possible to obtain a surface-protecting film having more excellent adhesion characteristics.

Examples of the epoxy compound include N, N, N ', N' -tetraglycidyl-m-xylylenediamine (trade name TETRAD-X, manufactured by Mitsubishi gas chemical Co., Ltd.), 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane (trade name TETRAD-C, manufactured by Mitsubishi gas chemical Co., Ltd.), and the like.

Examples of the melamine resin include hexamethylolmelamine. Examples of aziridine derivatives include commercially available products such as HDU, TAZM, and TAZO (see Sogo Pharmaceutical Co., Ltd.).

The metal chelate compound includes, as the metal component, aluminum, iron, tin, titanium, nickel and the like, and as the chelate component, acetylene, methyl acetoacetate, ethyl lactate and the like.

The content of the crosslinking agent used in the present invention is, for example, preferably 0.01 to 20 parts by weight, more preferably 0.1 to 15 parts by weight, still more preferably 0.5 to 10 parts by weight, and particularly preferably 1 to 5 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer. When the content is less than 0.01 part by weight, crosslinking formation by the crosslinking agent is insufficient, the cohesive force of the obtained pressure-sensitive adhesive layer is reduced, and sufficient heat resistance may not be obtained, and the content tends to cause adhesive residue. On the other hand, when the content exceeds 20 parts by weight, the cohesive force of the polymer is large, the fluidity is lowered, the wetting with the adherend (reflective polarizing film) is insufficient, and the swelling tends to occur between the adherend and the pressure-sensitive adhesive layer (pressure-sensitive adhesive composition layer). These crosslinking agents may be used alone, or 2 or more kinds may be used in combination.

Further, the equivalent ratio (hydroxyl group/isocyanate group) of the hydroxyl group-containing (meth) acrylic monomer constituting the (meth) acrylic polymer and the isocyanate group of the isocyanate compound as a crosslinking agent is preferably less than 10, more preferably 9 or less, further preferably 8 or less, and particularly preferably 7 or less. When the equivalent ratio is 10 or more, the surface protective film is excessively adhered to an adherend (reflection-type polarizing film), and the light peelability (removability) is poor, and when the surface protective film is peeled from the adherend, the adherend is likely to be delaminated, which is not preferable.

The adhesive composition may further contain a crosslinking catalyst for more efficiently carrying out any of the above crosslinking reactions. Examples of the crosslinking catalyst include tin catalysts such as dibutyltin dilaurate and dioctyltin dilaurate, tris (acetylacetonato) iron, tris (hexane-2, 4-dionato) iron, tris (heptane-3, 5-dionato) iron, tris (5-methylhexano-2, 4-dionato) iron, tris (octane-2, 4-dionato) iron, tris (6-methylheptane-2, 4-dionato) iron, tris (2, 6-dimethylheptane-3, 5-dionato) iron, tris (nonane-2, 4-dionato) iron, tris (nonane-4, 6-dionato) iron, tris (2,2,6, 6-tetramethylheptane-3, 5-diketonato) iron, tris (tridecane-6, 8-diketonato) iron, tris (1-phenylbutane-1, 3-diketonato) iron, tris (hexafluoroacetylacetonato) iron, tris (ethyl acetoacetate) iron, tris (n-propyl acetoacetate) iron, tris (isopropyl acetoacetate) iron, tris (n-butyl acetoacetate) iron, tris (sec-butyl acetoacetate) iron, tris (tert-butyl acetoacetate) iron, tris (methyl propionylacetate) iron, tris (ethyl propionylacetate) iron, tris (n-propyl propionylacetate) iron, tris (isopropyl propionylacetate) iron, tris (n-butyl propionylacetate) iron, tris (sec-butyl propionylacetate) iron, tris (tert-butyl propionylacetate) iron, tris (benzyl acetoacetate) iron, tris (dimethyl malonate) iron, tris (diethyl malonate) iron, trimethoxyiron, tri (n-butyl acetoacetate) iron, tri (n-butyl acrylate) iron, tri (n-butyl propionylacetate) iron, tri (methyl malonate) iron, tri (diethyl malonate) iron, tri (trimethoxy iron, Iron-based catalysts such as triethoxy iron, triisopropoxy iron, and ferric chloride. These crosslinking catalysts may be used in 1 kind, or 2 or more kinds may be used in combination.

The content of the crosslinking catalyst is not particularly limited, and is, for example, preferably about 0.0001 to 1 part by weight, more preferably 0.001 to 0.5 part by weight, based on 100 parts by weight of the (meth) acrylic polymer. When the content is within the above range, the crosslinking reaction is accelerated in forming the pressure-sensitive adhesive layer, which is a preferable mode.

Further, the adhesive composition may contain a compound that causes keto-enol tautomerism. For example, the following may be preferably employed: the aforementioned manner of producing a keto-enol tautomerism compound is contained in an adhesive composition containing a crosslinking agent or an adhesive composition that can be used by compounding a crosslinking agent. This suppresses excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after blending the crosslinking agent, and can achieve the effect of extending the pot life of the pressure-sensitive adhesive composition. In the case of using at least an isocyanate compound as the aforementioned crosslinking agent, it is particularly interesting to contain a compound which causes keto-enol tautomerism. This technique can be preferably applied, for example, when the aforementioned adhesive composition is in the form of an organic solvent solution or a solvent-free form.

As the aforementioned compound which causes keto-enol tautomerism, various β -dicarbonyl compounds can be used. Specific examples thereof include β -diketones such as acetylacetone, 2, 4-hexanedione, 3, 5-heptanedione, 2-methylhexane-3, 5-dione, 6-methylheptane-2, 4-dione, and 2, 6-dimethylheptane-3, 5-dione; acetoacetic acid esters such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, and tert-butyl acetoacetate; propionyl acetic acid esters such as propionyl ethyl acetate, propionyl isopropyl acetate, propionyl tert-butyl acetate, and the like; isobutyrylacetic acid esters such as ethyl isobutyrylacetate, isopropyl isobutyrylacetate, and tert-butyl isobutyrylacetate; malonic esters such as methyl malonate and ethyl malonate; and the like. Among these, acetylacetone and acetoacetates are suitable examples. The above-mentioned compounds which cause keto-enol tautomerism may be used alone, or 2 or more kinds may be used in combination.

The content of the compound which causes keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, and usually 0.5 to 15 parts by weight (for example, 1 to 10 parts by weight) is suitable for 100 parts by weight of the (meth) acrylic polymer. When the amount of the compound is too small, it may be difficult to exhibit sufficient use effects. On the other hand, if the amount of the compound is more than necessary, the compound may remain in the pressure-sensitive adhesive layer, and the cohesive force may be lowered.

The pressure-sensitive adhesive composition may further contain other known additives, and for example, a lubricant, a colorant, powder such as a pigment, a plasticizer, a thickener, a low molecular weight polymer, a surface lubricant, a leveling agent, an antioxidant, an anticorrosive agent, a light stabilizer, an ultraviolet absorber, a polymerization inhibitor, a silane coupling agent, an inorganic or organic filler, a metal powder, a particulate material, a foil material, and the like may be appropriately added depending on the intended use.

< adhesive layer and surface protective film >

The surface-protecting film of the present invention preferably has a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition on at least one surface of the base film. The pressure-sensitive adhesive layer is obtained by crosslinking the pressure-sensitive adhesive composition, and is usually applied after the pressure-sensitive adhesive composition is applied, but a pressure-sensitive adhesive layer formed from the crosslinked pressure-sensitive adhesive composition may be transferred to a base film or the like.

The method for forming the pressure-sensitive adhesive layer on the base film is not particularly limited, and for example, the pressure-sensitive adhesive layer is formed on the base film by applying the pressure-sensitive adhesive composition (solution) to the base film and drying and removing the polymerization solvent or the like. Then, curing may be performed for the purpose of adjusting the movement of the components of the adhesive layer, adjusting the crosslinking reaction, and the like. In the case of preparing a surface-protecting film by applying the pressure-sensitive adhesive composition to a base film, one or more solvents other than the polymerization solvent may be newly added to the pressure-sensitive adhesive composition in order to uniformly coat the base film.

In addition, as a method for forming the pressure-sensitive adhesive layer in the production of the surface protection film of the present invention, a known method used for the production of pressure-sensitive adhesive tapes is used. Specific examples thereof include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and extrusion coating using a die coater.

The surface protection film of the present invention is generally produced so that the thickness of the adhesive layer is about 0.1 to 100 μm, preferably about 1 to 80 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, a proper balance between light peelability (removability) and pressure-sensitive adhesiveness is easily obtained, which is preferable.

The surface protective film of the present invention preferably has a total thickness of 8 to 300. mu.m, more preferably 10 to 200. mu.m, and most preferably 20 to 100. mu.m. When the content is within the above range, the adhesive properties (light peelability, removability, adhesiveness, etc.), workability, and appearance properties are excellent, and the preferred embodiment is. The total thickness is the sum of the thicknesses of all layers including the base film, the adhesive layer, and other layers.

The surface protection film for a reflection-type polarizing film of the present invention is characterized by comprising an adhesive layer, wherein the peel electrification voltage at the time of peeling after the adhesive surface of the adhesive layer is adhered to the reflection-type polarizing film is not more than ± 0.7kV, and the adhesive force of the adhesive surface of the adhesive layer to the reflection-type polarizing film is not more than 0.8N/25mm at a stretching speed of 30 m/min and a peeling angle of 180 °. When the peeling electrification voltage is ± 0.7kV or less when peeling is performed after the adhesive surface of the adhesive layer is adhered to the reflective polarizing film, the peeling electrification preventing property is excellent and useful even when peeling is performed after the adhesive layer is adhered to a reflective polarizing film or the like having a multilayer structure and being easily electrified. Further, by setting the adhesive force of the adhesive layer to the reflective polarizing film to 0.8N/25mm or less at a stretching speed of 30 m/min and a peeling angle of 180 °, even when the adhesive layer is peeled after being attached to a reflective polarizing film having a multilayer structure and in which interlayer peeling (interlayer peeling) is likely to occur, interlayer peeling (interlayer peeling) can be prevented, and the adhesive layer is excellent in non-destructiveness and useful.

< isolation body >

In the surface protection film of the present invention, it is preferable that a separator is attached to a surface of the pressure-sensitive adhesive layer opposite to a surface contacting the base film. The separator may be used by attaching a separator to the surface of the pressure-sensitive adhesive layer as needed for the purpose of protecting the pressure-sensitive adhesive surface, and peeling the separator when the separator is attached to the surface of the reflective polarizing film.

As the material constituting the separator, there are paper and a plastic film, but a plastic film is suitably used from the viewpoint of excellent surface smoothness. The film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples thereof include a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

The thickness of the separator is usually 5 to 200 μm, preferably about 10 to 100 μm. When the content is within the above range, the workability of attaching to the pressure-sensitive adhesive layer and the workability of detaching from the pressure-sensitive adhesive layer are excellent, and therefore, the preferred range is. The separator may be subjected to release and anti-fouling treatment with a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder or the like, or antistatic treatment of a coating type, a kneading type, a vapor deposition type or the like, as necessary.

< reflection type polarizing film >

In the case where a multilayer-structured polarizing film (for example, a single brightness enhancement film or a laminate of brightness enhancement films and polarizing films) is used as a reflective polarizing film to be protected by sticking the surface protective film (the surface of the pressure-sensitive adhesive layer), which is a target, the multilayer-structured polarizing film is formed by alternately laminating films made of materials having different refractive index anisotropies. On the other hand, the use of the optical film of the present invention is a preferable embodiment because it is excellent in antistatic property, light peelability (removability), and workability. In particular, when a reflection type polarizing film integrated with a polarizing film or the like, which has been increasingly used in recent years, is incorporated into a liquid crystal display or the like (after peeling off the surface protective film), the whitening phenomenon of the panel can be suppressed, and the workability and efficiency are also excellent, which is a preferable embodiment.

The reflection-type polarizing film in the present invention refers to a brightness enhancement film having a multilayer structure alone, a polarizing film in which the brightness enhancement film is laminated, and the like.

The brightness enhancement film included in the reflective polarizing film is a film exhibiting the following characteristics: when natural light is incident by a backlight of a liquid crystal display device or the like or reflection from the back side, linear polarized light having a predetermined polarization axis or circularly polarized light having a predetermined direction is reflected, and other light is transmitted. The brightness of the image display device is improved by reversing the light reflected by the brightness enhancement film through a reflection layer or the like provided on the rear side thereof, and then allowing the light to enter the brightness enhancement film, transmitting a part or all of the light in a predetermined polarization state, thereby increasing the amount of light transmitted through the brightness enhancement film, and supplying polarized light that is difficult to be absorbed to the polarizing plate, thereby increasing the amount of light that can be used for image display such as liquid crystal display. An integrated polarizing film in which a polarizing film and a brightness enhancement film are bonded is often used by being provided on the backlight side of a liquid crystal cell, but may be used by being provided on the viewing side of a liquid crystal cell as disclosed in international pamphlet on WO 2006/038404.

As the brightness enhancement film, for example, there can be suitably used: a film exhibiting properties of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer laminate of dielectric multilayer films and films having different refractive index anisotropy; suitable films include an oriented film of a cholesteric liquid crystal polymer, and a film which exhibits the property of reflecting either counterclockwise or clockwise circularly polarized light and transmitting other light, such as a film in which an oriented liquid crystal layer is supported on a film base.

< optical film >

The optical film of the present invention preferably comprises the surface protective film for a reflective polarizing film and the reflective polarizing film. Since the surface protective film has excellent peel electrification preventing properties and light peeling properties (re-peeling properties) when peeled off after the pressure-sensitive adhesive layer surface of the surface protective film is bonded to the surface of the reflective polarizing film, it is preferable that the surface protective film is peeled off from the reflective polarizing film at a stage where the surface protective film is not necessary, so that whitening of the panel due to static electricity is suppressed, and a decrease in inspection efficiency is suppressed, and further, the reflective polarizing film is not peeled off between layers. The optical film in the present invention is described as an optical film in which a surface protective film and a reflective polarizing film are laminated, but may be an optical film in which a polarizing film, another optical film, or the like is further laminated in addition to the reflective polarizing film.