JP6776636B2 - Laminated polyester film - Google Patents

Description

The present invention relates to a laminated polyester film having excellent antistatic performance and at the same time having ultraviolet absorption performance.

The polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc. For example, a biaxially stretched polyester film is used as a base material, and a release layer containing a silicone resin or the like as a main component is provided. Release film is used in many fields.

Adhesive sheets are used for incorporating optical members such as polarizing plates (or retardation plates, etc.) and similar laminates. Further, as the adhesive sheet, a release film based on a polyester film may be used before being attached to a polarizing plate or the like. The release film may be attached for the purpose of surface protection, and it is removed by peeling after the assembly of the optical member is completed, but static electricity is generated during this peeling, and surrounding objects and dust are caught in it. There is a problem of being released.

Therefore, measures for antistatic measures are taken. Generally, a method of applying an antistatic resin to the surface of a film as a base material is performed (Patent Document 1).

As the antistatic agent coated on the polyester film, an anionic compound containing a high molecular weight cationic compound (Patent Document 2) and an anionic group represented by a sulfonate group or a phosphonate group is mainly used.

However, a quaternary ammonium base having a polymer side chain as described in Patent Document 2 generally has weak heat resistance, and when applied to an in-line coating method in which a stretched polyester film is applied during the film forming process. Since the temperature applied at that time becomes extremely high, decomposition is likely to occur, and the antistatic performance is deteriorated. In addition, ionic conductive antistatic agents are easily affected by ambient humidity and moisture. In particular, there is a drawback that the conductivity is lowered under low humidity and the desired antistatic performance cannot be obtained. This tendency is often more pronounced in anionic antistatic agents.

The electron conductive compound can exhibit more excellent antistatic property than the above ion conductive compound. Various electronically conductive compounds have been proposed. Among them, the polythiophene compound has excellent conductivity, and can exhibit high antistatic performance and transparency when applied to a film (Patent Document 3). 4). In a stretched polyester film, it is advantageous in terms of productivity and economy to provide a coating film by an in-line coating method, but a coating layer containing a polythiophene compound can exhibit sufficient antistatic performance by an in-line coating method. difficult. It is considered that this is because when the electron conductive layer is stretched as the film is stretched, it cannot follow the stretching of the film while holding the conductive mechanism, and as a result, the conductive mechanism is broken. Further, the coating layer in such a case was inferior in appearance. The release film has an opportunity to inspect the optical member in the attached state, and if the appearance of the coating layer is inferior, the inspectability deteriorates, which makes it difficult to apply.

Further, a UV curable pressure-sensitive adhesive may be used for incorporating a polarizing plate or an optical member of a laminated body similar thereto, and UV curing may be performed with the release film bonded. Therefore, the release film itself is required to have UV absorption performance.

With the spread of smartphones in recent years, the design and design of liquid crystal displays have become diverse, and it is advantageous from the viewpoint of workability when incorporating an optical member by using a UV curable adhesive. Further, it is advantageous from the viewpoint of processability and economy in proportion to the curing rate of the UV curable adhesive, but recently, the reaction of the UV curable adhesive proceeds even under a fluorescent lamp in a processing environment, and the handleability is easy. There is also a new problem of worsening. Therefore, there is a demand for a release film based on a polyester film having both ultraviolet absorption performance and antistatic performance.

Japanese Unexamined Patent Publication No. 7-262223 Japanese Unexamined Patent Publication No. 2004-123932 JP-A-2002-060736 Japanese Unexamined Patent Publication No. 2008-296380

The present invention has been made in view of the above circumstances, and a problem to be solved thereof is to provide a laminated polyester film having excellent antistatic performance and at the same time having ultraviolet absorption performance.

As a result of diligent studies on the above problems, the present inventors have found that the polyester film having a specific composition solves the above problems, and have completed the present invention.

That is, the gist of the present invention is a laminated polyester film having an antistatic layer on at least one surface of the polyester film, the polyester film contains an ultraviolet absorber, and the antistatic layer is the following compound (A). ), (B), and (C), a laminated polyester film.
(A): Polymer of thiophene or thiophene derivative doped with an anionic compound or self-doped with an anionic group (B): alkylene oxide adduct to glycerin (b1), polyglycerin (b2), glycerin or polyglycerin (B3), and one or more compounds selected from the group of polyalkylene oxides (b4) (C): Polyurethane resin

According to the present invention, it is possible to obtain a laminated polyester film having excellent antistatic performance and at the same time having ultraviolet absorption performance, and its industrial utility value is high.

[Polyester film]
The base film of the laminated polyester film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4'-diphenyldicarboxylic acid, and 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt-hypercondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol and 1,4-cyclohexanedimethanol. The polyester composed of these acid components and glycol components can be produced by using any of the usual methods.

For example, the lower alkyl ester of the aromatic dicarboxylic acid and the glycol are subjected to an ester exchange reaction, or the aromatic dicarboxylic acid and the glycol are directly esterified to substantially bisglycol the aromatic dicarboxylic acid. A method is adopted in which an ester or a low polymer thereof is formed, and then this is heated under reduced pressure to carry out polycondensation. Aliphatic dicarboxylic acids may be copolymerized according to the purpose.

Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, etc., but the above-mentioned acid component and glycol component are also used. It may be a polymerized polyester, or may contain other components or additives as required.

The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used. Examples thereof include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds and calcium compounds. Among these, antimony compounds have the advantages of being inexpensive and having high catalytic activity. Further, the titanium compound and the germanium compound have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film is high, which is preferable. Further, since the germanium compound is expensive, it is more preferable to use a titanium compound.

The polyester film in the present invention has a multi-layer structure of three or more layers, and it is necessary that one of the layers contains an ultraviolet absorber. In particular, it is preferable that the intermediate layer contains an ultraviolet absorber. Examples of the ultraviolet absorber contained in the polyester film include an organic ultraviolet absorber and an inorganic ultraviolet absorber. An organic ultraviolet absorber is preferable from the viewpoint of transparency and showing effective ultraviolet absorption performance with a small amount of addition.

Examples of the organic ultraviolet absorber include salicylic acid-based agents such as phenylsalicylate, pt-butylphenylsalicylate, p-octylphenylsalicylate and the like; benzophenone-based agents such as 2-hydroxy-4-benzyloxy. Benzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-octokibenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2 -2'-Dihydroxy-4,4'-dimethoxybenzophenone, etc .; benzotriazoles, such as 2- (2'-hydroxy-5'-t-octylphenyl) -benzotriazole, 2- (2'-hydroxy-5 ´-t-octylphenyl) -benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′5′-di-t-butylphenyl) benzotriazole , 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'5'-di-t-butylphenyl) 5 -Chlorobenzotriazole and the like; natural products such as oryzanol, shea butter, bicarin and the like; biological systems such as keratinocytes, melanin, urocanic acid and the like. These organic ultraviolet absorbers can be used alone or in combination of two or more. A hindered amine compound can be used in combination with these organic ultraviolet absorbers as an ultraviolet stabilizer.

Examples of inorganic ultraviolet absorbers include titanium oxide, zinc oxide, indium oxide, tin oxide, talc, kaolin, calcium carbonate, titanium oxide-based composite oxide, zinc oxide-based composite oxide, ITO (tin-doped indium oxide), and ATO. (Antimony-doped tin oxide) and the like. Examples of the titanium oxide-based composite oxide include silica and alumina-doped titanium oxide. These inorganic ultraviolet absorbers can be used alone or in combination of two or more. Further, the organic ultraviolet absorber and the inorganic ultraviolet absorber may be used in combination.

The content of the ultraviolet absorber is not particularly limited, but is preferably in the range of 1 to 20% by weight, more preferably 5 to 10% by weight. When the content rate is within the specified range, it is possible to have sufficient ultraviolet absorption performance and transparency.

Examples of the method of blending the ultraviolet absorber into the polyester film include a method of directly adding the ultraviolet absorber to the extruder, a method of adding a polyester resin in which the ultraviolet absorber is kneaded in advance to the extruder, and the like. Either one method may be adopted, or the two methods may be used in combination.

The polyester film of the present invention preferably has a light transmittance of 10% or less, more preferably 5% or less at a wavelength of 380 nm. If the light transmittance at a wavelength of 380 nm is larger than 10%, the ultraviolet absorption performance may be insufficient.

The polyester film in the present invention preferably contains particles in the surface layer for the purpose of ensuring the runnability of the film and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. , Crosslinked polymer particles, organic particles such as calcium oxalate, and precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester production process can also be used. Of the particles, titanium oxide and talc also have a role as the above-mentioned inorganic ultraviolet absorber.

On the other hand, the shape of the particles to be used is not particularly limited, and any of spherical, lumpy, rod-shaped, flat-shaped and the like may be used. Further, the hardness, specific gravity, color and the like are not particularly limited. Two or more kinds of these series of particles may be used in combination, if necessary.

The particle size and content of the particles are selected according to the use and purpose of the polyester film. The average particle size (d ₅₀ ) is preferably 3 μm or less, more preferably 0.02 μm to 2.8 μm, and further preferably 0.03 μm to 2.5 μm. If the average particle size is too large, the surface roughness of the film becomes too rough, and the particles tend to fall off from the film surface.

The content of the particles contained in the surface layer is preferably in the range of 3% by weight or less, more preferably 0.0003 to 1% by weight, and further preferably 0.0005 to 0.5% by weight. When there are no particles or there are few particles, the transparency of the film becomes high and the film becomes good, but the slipperiness may be insufficient. Therefore, by putting the particles in the antistatic layer, It may be necessary to take measures such as improving the slipperiness. Further, if the content of particles is too large, the transparency of the film may be insufficient.

The method of adding the particles to the surface layer of the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage in the production of the polyester constituting each layer, but it is preferably added after the esterification or transesterification reaction is completed.

In addition to the above-mentioned ultraviolet absorbers and particles, conventionally known antioxidants, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film of the present invention, if necessary.

The thickness of the polyester film in the present invention is not particularly limited as long as it can be formed as a film, but is preferably in the range of 10 to 300 μm, more preferably 20 to 200 μm, and further preferably 30 to 100 μm. is there.

The polyester film in the present invention has a laminated structure of three or more layers. The thickness of one side of the surface layer is usually 3.5 μm or more, preferably 6.0 μm or more, and more preferably 8.5 μm or more. By setting the thickness of one side of the surface layer to 3.5 μm or more, it is possible to reduce the bleed-out of the ultraviolet absorber from the polyester film.

As a film forming method for the polyester film film in the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, first, a sheet obtained by melt extrusion is stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then in a tenter, perpendicular to the previous stretching direction. A film is obtained by stretching 2 to 6 times in the direction at 80 to 160 ° C. and further performing heat treatment at 150 to 250 ° C. for 1 to 600 seconds. Further, at this time, a method of relaxing within 20% in the vertical direction and / or the horizontal direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

[Antistatic layer]
The antistatic layer in the present invention can be provided by either a so-called offline coating in which a coating layer is later provided on the film-formed film and a so-called in-line coating in which a coating layer is provided during film formation. It is preferably provided by in-line coating, particularly by a coating stretching method in which stretching is performed after coating.

The in-line coating is a method of coating in the process of manufacturing a polyester film, and specifically, a method of coating at an arbitrary stage from melt extrusion of polyester to heat fixing and winding after stretching. Usually, it can be used as a substantially amorphous unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat fixing, or a film after heat fixing and before winding. To coat. Although not limited to the following, for example, in sequential biaxial stretching, a method of coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) and then stretching in the lateral direction is particularly excellent. According to this method, film formation and antistatic layer coating can be performed at the same time, which has an advantage in terms of manufacturing cost. Since stretching is performed after coating, the antistatic layer can be uniformly coated with a thin film. The characteristics are stable. Further, the polyester film before biaxial stretching is first coated with a resin layer constituting the antistatic layer, and then the film and the antistatic layer are simultaneously stretched to strengthen the base film and the antistatic layer. It will be in close contact. Further, in the biaxial stretching of the polyester film, the film is restrained in the longitudinal / lateral direction by stretching in the lateral direction while gripping the end of the film with a tenter clip or the like, and wrinkles or the like do not occur in heat fixing. High temperature can be applied while maintaining flatness. Therefore, since the heat treatment applied after coating can be at a high temperature which cannot be achieved by other methods, the film-forming property of the antistatic layer is improved, and the antistatic layer and the polyester film are firmly adhered to each other. As a polyester film provided with an antistatic layer, the uniformity of the antistatic layer, the improvement of film forming property, and the adhesion between the antistatic layer and the film often produce favorable characteristics.

In the case of the coating and stretching method, the coating liquid to be used is preferably an aqueous solution or an aqueous dispersion for handling, working environment, and safety reasons, and it is preferable to use water as the main medium. An organic solvent may be contained as long as the gist of the present invention is not exceeded.

The laminated polyester film of the present invention is an essential requirement to have an antistatic layer containing the compounds (A), (B), and (C) on at least one surface of the polyester film. The antistatic layer may be provided on both sides of the polyester film, but as will be described later, it is preferably one side when used as a release film.
The compounds (A), (B) and (C) used in the present invention will be described. In addition, other components may be contained in the antistatic layer.

Compound (A) is a thiophene or thiophene derivative polymer doped with an anionic compound or self-doped with an anionic group. These substances show excellent conductivity and are suitable. As the compound (A), for example, a compound obtained by polymerizing a compound of the following formula (1) or (2) in the presence of a poly anion can be exemplified.

In the above formula (1), R ¹ and R ² independently represent hydrogen or an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or the like.

In the above equation (2), n represents an integer of 1 to 4.

Examples of the source of the poly anion used at the time of polymerization include poly (meth) acrylic acid, polymaleic acid, polystyrene sulfonic acid, and polyvinyl sulfonic acid. As a method for producing such a polymer, for example, a method as shown in JP-A-7-96060 can be adopted.

In the present invention, a preferred mode is a compound of the above formula (2) in which n is 2 and polystyrene sulfonic acid is used as a source of polyanions.

Also, some or all of these polyanions may be neutralized. Ammonia, organic amines, and alkali metal hydroxides are preferable as the base used for neutralization.

Examples of the polymer of thiophene or thiophene derivative in which the anionic group is self-doped include those in which the compound of the above formula (1) or (2) is doped with an anionic group.

Compound (B) is one or more compounds selected from the group consisting of glycerin (b1), polyglycerin (b2), glycerin or an alkylene oxide adduct to polyglycerin (b3), and polyalkylene oxide (b4). ..
Glycerin (b1) and polyglycerin (b2) are compounds represented by the following general formula (3).

The compound having n = 1 in the above formula (3) is glycerin (b1), and the compound having n or more is polyglycerin (b2). In the present invention, n in the formula is preferably in the range of 2 to 20, more preferably in the range of 2 to 10.

The alkylene oxide adduct (b3) to glycerin or polyglycerin has a structure in which an alkylene oxide is addition-polymerized to the hydroxyl group of glycerin or polyglycerin represented by the general formula (3).

Here, the structure of the alkylene oxide added may be different for each hydroxyl group of the glycerin or polyglycerin skeleton. Further, it is sufficient that at least one hydroxyl group in the molecule is added, and it is not necessary that an alkylene oxide or a derivative thereof is added to all the hydroxyl groups.

Preferred alkylene oxides added to glycerin or polyglycerin are ethylene oxide or propylene oxide. If the alkylene chain of the alkylene oxide becomes too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating liquid deteriorates, and the antistatic property and transparency of the antistatic layer tend to deteriorate. Particularly preferred is ethylene oxide. The number of additions thereof is preferably in the range of 200 to 2000 in terms of the weight average molecular weight of the final compound (b3), and more preferably in the range of 300 to 800.

Preferred as the polyalkylene oxide (b4) is polyethylene oxide or polypropylene oxide. If the alkyl chain in the alkylene oxide structure becomes too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating liquid deteriorates, and the antistatic property and transparency of the antistatic layer tend to deteriorate. Particularly preferred is polyethylene oxide. A weight average molecular weight of 200 to 2000 is more preferable.

In the present invention, particularly preferable modes of the compound (B) are polyglycerin (b2) and glycerin or an alkylene oxide adduct to polyglycerin (b3).

Compound (C) is a polyurethane resin.
The polyurethane resin (C) in the present invention is a polymer compound having a urethane bond in the molecule, and is preferably water-dispersible or water-soluble. In the present invention, it may be used alone or in combination of two or more.

In order to impart water dispersibility or water solubility, it is common and preferable to introduce a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a sulfonyl group, a phosphoric acid group or an ether group into the polyurethane resin. Among the above-mentioned hydrophilic groups, a carboxyl group or a sulfonic acid group is particularly preferable from the viewpoint of physical properties of the coating film and adhesion.

One of the methods for producing a polyurethane resin, which is a constituent component of the antistatic layer used in the present invention, is a reaction between a hydroxyl group and an isocyanate. As the hydroxyl group used as a raw material, a polyol is preferably used, and examples thereof include polyether polyols, polyester polyols, polycarbonate-based polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination of two or more.

Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol and the like.

Polypolypolyols include polyvalent carboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Products and polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-Methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol , 2-Methyl-2-propyl-1,3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2 , 5-Diol-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2 -Hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamine, lactonediol, etc.) can be mentioned.

Examples of the polycarbonate-based polyols include polycarbonate diols obtained by dealcoholization reaction from polyhydric alcohols and dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate and the like, for example, poly (1,6-hexylene) carbonate, poly ( 3-Methyl-1,5-pentylene) carbonate and the like can be mentioned.

Among these, a polyester polyol is preferable, and a polyester polyol having an aromatic ring is more preferable.

Examples of the polyisocyanate compound used to obtain a polyurethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylenedi isocyanate, naphthalenedi isocyanate, and trizine diisocyanate; -Adicyclic diisocyanate having an aromatic ring such as tetramethylxylylene diisocyanate; aliphatic diisocyanate such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate; cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Examples thereof include alicyclic diisocyanates such as methane diisocyanate and isopropyridene dicyclohexyl diisocyanate. These may be used alone or in combination of two or more.

A chain extender may be used when synthesizing the polyurethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with isocyanate groups, and is generally a hydroxyl group. Alternatively, a chain extender having two amino groups can be mainly used.

Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; esters such as neopentyl glycol hydroxypivalate. Examples of glycols such as glycols can be mentioned.

Examples of the chain extender having two amino groups include aromatic diamines such as tolylene diamine, xylylene diamine, and diphenylmethanediamine; ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3-propanediamine. , 2-Methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonandiamine, 1,10-decanediamine Ordiamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, 1,4-diaminocyclohexane, alicyclic diamines such as 1,3-bisaminomethylcyclohexane and the like. Can be mentioned.

Further, a method of introducing a carboxyl group into the urethane skeleton using dimethylolpropionic acid, dimethylolbutanoic acid, or the like and then neutralizing with a basic compound to make the urethane hydrophilic is also preferably used.

In the present invention, the compounds (A), (B) and (C) do not have any particular obstacle in selecting a compound containing no halogen atom. Therefore, in the present invention, it is easy and preferable that the antistatic layer is halogen-free.

The antistatic layer in the present invention may contain a surfactant (D) in order to improve the coatability on the film. When the surfactant (D) contains (poly) alkylene oxide, (poly) glycerin, or a derivative thereof in its structure, the antistatic property of the obtained antistatic layer is not impaired. More preferred.

The coating liquid for forming the antistatic layer in the present invention may contain a cross-linking reactive compound, if necessary. Crosslink-reactive compounds improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the antistatic layer mainly by cross-linking with functional groups contained in other resins and compounds and by self-crosslinking. can do. As the cross-linking reactive compound that can be used, amino resins such as melamine type, benzoguanamine type and urea type, isocyanate type, oxazoline type, epoxy type and glyoxal type are preferably used. Also included are polymer-type cross-linking reactive compounds in which other polymer backbones have reactive groups.

Further, if necessary, one kind or two or more kinds of binder resins other than (C) can be used in combination. Examples of such binder resins include polyether resins, polyester resins, acrylic resins, vinyl resins, epoxy resins, amide resins and the like. Each of these may have a substantially composite structure due to copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, vinyl resin graft polyurethane and the like. By containing these resins, the strength of the obtained antistatic layer and the adhesion to the base film can be improved.

The antistatic layer in the present invention is an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, a mold release agent, an organic particle, an inorganic particle, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, and a pigment. Etc. may be contained. These additives may be used alone, or two or more thereof may be used in combination if necessary. Further, as these additives, those containing (poly) alkylene oxide, (poly) glycerin, and derivatives thereof in the structure are used, because the antistatic property of the obtained antistatic layer is not impaired, which is more preferable. ..

Further, particles can be used in combination for forming the antistatic layer for the purpose of blocking and improving slipperiness. The average particle size is preferably 1.0 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less from the viewpoint of transparency of the laminated polyester film. Further, the lower limit is preferably 0.005 μm or more, more preferably 0.01 μm or more in order to improve the slipperiness more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, organic particles and the like. Among them, silica is preferable from the viewpoint of transparency.

The weight of compound (A) in the antistatic layer provided by the present invention is usually 0.5 to 15 mg / m ² , preferably 1 to 9 mg / m ² , and more preferably ² to 5 mg / m ² . If the amount of compound (A) is less than this, the antistatic property or the air exposure resistance may be insufficient. Also, if it is more than this, the cost will increase and coloring will be more difficult. Further, when it is stretched, it may cause a problem such as a decrease in transparency.

The ratio of the compound (A) to the non-volatile component in the coating liquid forming the antistatic layer is usually 1 to 80%, preferably 2 to 30%, more preferably 3 to 15%, still more preferably 4 to 4 by weight. It is 15%. If the ratio of compound (A) is higher than this, the strength, transparency or antistatic performance of the coating film may be insufficient. If the ratio of the compound (A) is lower than this, the antistatic performance may be insufficient, or the coating film for imparting sufficient antistatic performance may be thickened. The thicker the coating film, the worse the appearance and transparency, the blocking of the film, and the cost increase.

The ratio of the compound (B) to the non-volatile component in the coating liquid is usually 1 to 90%, preferably 5 to 85%, more preferably 20 to 85%, still more preferably 35 to 50% by weight. If it is out of this range, the antistatic performance and the appearance of the coating film tend to deteriorate.

The ratio of the compound (C) to the non-volatile component in the coating liquid is usually 2 to 90%, preferably 3 to 70%, more preferably 5 to 60%, still more preferably 45 to 60% by weight. If it exceeds this range, the antistatic performance and transparency tend to deteriorate. If it is less than this range, the strength and water resistance of the coating film tend to deteriorate.

The ratio of the surfactant (D) to the non-volatile component in the coating liquid is usually 0 to 20%, preferably 0.1 to 15%, more preferably 0.5 to 10%, still more preferably 1 to 5 by weight. %. By using it in this range, the film can be sufficiently coated within a range in which the antistatic property of the antistatic layer is not impaired.
The content ratios of (A) to (D) with respect to the non-volatile components in the coating liquid described above can be treated as synonymous with the content ratios in the antistatic layer of the laminated polyester film of the present invention.

The thickness of the antistatic layer is usually in the range of 0.003 μm to 1 μm, preferably 0.005 μm to 0.1 μm, and more preferably 0. It is in the range of 01 μm to 0.05 μm. If the thickness is thinner than 0.003 μm, the antistatic performance may be insufficient. If it is thicker than 1 μm, problems such as deterioration of the appearance of the antistatic layer and easy blocking may occur.

The polyester film in the present invention is required to have a high degree of transparency when inspected in a state of being attached to an optical member such as a polarizing plate. From this point of view, in order to cope with a high degree of transparency, the haze increase (ΔH) due to the antistatic layer is preferably 1.0% or less, more preferably 0.6% or less, still more preferably 0.3%. It is as follows. If ΔH exceeds 1.0%, the inspectability may deteriorate as the visibility decreases.

Specifically, the antistatic layer in the present invention is a coating layer having a low surface resistivity and a mechanism for leaking electric charges. It can be said that the lower the surface resistivity of the antistatic layer, the better the antistatic property. If the surface resistivity is usually 1 × 10 ¹² Ω or less, it can be said that it has antistatic properties, preferably 1 × 10 ⁸ Ω or less, and more preferably 1 × 10 ⁶ Ω or less, it has extremely good antistatic performance. I can say. If the surface resistivity is larger than the above range, it is likely to be charged at the time of friction, peeling of the adhesive layer, etc., and problems such as adhesion of foreign matter and dust, electrostatic discharge failure, etc. may occur.

[Release layer]
In the present invention, by providing a release layer on the opposite surface to the antistatic layer, it can be suitably used as a release film used for an adhesive sheet. The coating agent used for the release layer is not limited, but preferably contains a curable silicone resin. Specifically, a type containing a curable silicone resin as a main component may be used, or a modified silicone type or the like obtained by graft polymerization with an organic resin such as a urethane resin, an epoxy resin or an alkyd resin may be used.

Specific examples of the curable silicone resin include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-2461; DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, manufactured by Dow Corning Asia Co., Ltd .; YSR-3022, TPR-6700, TPR-6720, manufactured by Toshiba Silicone Co., Ltd. TPR-6721; SD7220, SD7226, SD7229, etc. manufactured by Toray Dow Corning Co., Ltd. can be mentioned. Further, a release control agent may be used in combination to adjust the release property of the release layer.

As the type of the curable silicone resin, any curing reaction type such as addition type, condensation type, ultraviolet curable type, electron beam curable type, and solvent-free type can be used. Among these, addition-type silicone that uses an addition reaction of a vinyl group and a group having a silicon-hydrogen bond in the curing process is preferable because it has excellent properties such as light peeling, migration, and low-temperature curing property.

In the addition type silicone used in the present invention, the content ratio (SiH / Vi ratio) of the SiH group and the vinyl group of the siloxane involved in the cross-linking reaction is usually 1.2 to 10, preferably 1.5 to 7. More preferably, it is 2 to 5.

As the polyhydrogensiloxane compound which is a cross-linking agent for the curable silicone resin used in the present invention, a commonly known compound can be adopted, and there is no particular limitation. For example, polymethylhydrogensiloxane, polymethylhydrogensiloxane-polymethylsiloxane copolymer and the like can be mentioned.

The form of the coating agent used for the release layer in the present invention is not particularly specified. Examples thereof include a so-called solvent type in which high-viscosity silicone is diluted with a solvent and applied, a solvent-free type in which low-viscosity silicone is applied as it is, and an aqueous dispersion type in which low-viscosity silicone is finely dispersed in an aqueous liquid.

Among these, in the polyester film in which the coating appearance is particularly important, the solvent type is preferably used as the form of the coating agent.

Examples of the diluting solvent used in the solvent type include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane and heptane, esters such as ethyl acetate and butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone. Examples thereof include ketones, alcohols such as ethanol and 2-propanol, and ethers such as diisopropyl ether and dibutyl ether, which are used alone or in combination in consideration of solubility, coatability, boiling point and the like.

The viscosity of the coating agent used for the release layer of the present invention is not particularly limited, but is selected according to the usage pattern and the coating equipment. In the solvent type, the viscosity of the 30% toluene solution is preferably 1000 to 100,000 mPa · s, more preferably 1000 to 20000 mPa · s, in terms of coatability and the like.

Further, an auxiliary agent such as a reaction adjusting agent, an adhesion strengthening agent, or a peeling adjusting agent may be added to the coating agent in order to adjust the characteristics of the release layer.

The release adjusting agent is not particularly limited, but a release adjusting agent of a type that reacts with the siloxane polymer when the coating agent is dried and is incorporated therein is preferable because the migration property can be suppressed.

In the present invention, as a method of providing the release layer on the polyester film, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, and doctor blade coating can be used.

The coating amount of the release layer in the present invention is usually in the range of 0.01 to 1 g / m ² as a dry film after the release layer is formed. The coating amount of the release layer can be calculated from the weight concentration and coating area of the coating agent and the amount of the coating agent used. If the coating amount is less than this, it becomes difficult to obtain uniform releasability, and if it is more than this, problems such as blocking occur.

It is also possible to determine the coating amount by checking the thickness of the release layer from the cross section with a transmission electron microscope as described above and dividing by the specific gravity. Generally, the specific gravity of curable silicone is about 0.9 to 1.2. The coating amount of the release layer having a thickness of 0.1 μm is 0.1 g / m ² when the specific gravity is 1.

In the present invention, the energy source in the curing treatment of the silicone release layer is not particularly limited, and heat treatment, ultraviolet irradiation, and electron beam irradiation can be exemplified. These are used alone or in combination, but heat treatment alone or combined treatment with heat and ultraviolet rays is preferably used.

The peeling force between the release film and the adhesive tape is usually 3 to 50 mN / cm, preferably 5 to 25 mN / cm. When the peeling force is within the above range, the problem that the adhesive is transferred to the release film and the release film floats before use does not occur.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

The evaluation methods in Examples and Comparative Examples are as follows.

(1) Measurement of light transmittance A spectrophotometer (UV-3100PC type manufactured by Shimadzu Corporation) is used to continuously measure the light transmittance in a low scanning speed, a sampling pitch of 2 nm, and a wavelength range of 300 to 700 nm. The light transmittance at the wavelength of 380 nm was detected.
⊚: Light transmittance at 380 nm wavelength 5% or less (level at which the liquid crystal panel does not deteriorate)
◯: Light transmittance at 380 nm wavelength of 10% or less (level that does not cause any problem in practical use)
X: Light transmittance at 380 nm wavelength of 11% or more (level at which the liquid crystal panel deteriorates)

(2) Bleed-out resistance After heating at 150 ° C. for 30 minutes, the presence or absence of precipitation of the ultraviolet absorber is confirmed by observing the surface of the sample under a microscope.
◯: No precipitation of UV absorber (level without practical problem)
×: Precipitation of UV absorber (level that causes practical problems)

(3) Transparency of coating layer (haze rise due to antistatic layer)
The haze of the film was measured by an integrating sphere type turbidity meter NDH-2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. according to JIS-K7136. The difference in haze between the film without the antistatic layer and the film with the coating layer was calculated, and the increase in haze (ΔH) due to the provision of the antistatic layer was calculated and evaluated as the transparency of the antistatic layer.

(4) Surface resistivity (Ω) of the antistatic layer
The surface resistivity of the film coating layer was measured based on the method (4-1) below. Since the surface resistivity higher than 1 × 10 ⁸ Ω cannot be measured by the method (4-1), the method (4-2) was used for the sample that could not be measured by (4-1).
(4-1) Using a low resistivity meter manufactured by Mitsubishi Chemical Corporation: Loresta GP MCP-T600, the surface resistivity was measured after adjusting the humidity of the sample for 30 minutes in a measurement atmosphere at 23 ° C. and 50% RH.
(4-2) Using a high resistance measuring instrument: HP4339B and a measuring electrode: HP16008B manufactured by Hewlett-Packard Japan, the surface resistivity was measured after adjusting the humidity of the sample for 30 minutes in a measuring atmosphere at 23 ° C. and 50% RH. ..

(5) After immersing the water-resistant film of the antistatic layer in warm water at 40 ° C. for 24 hours, the surface resistivity was measured and compared before and after the immersion.
◯: Increase in surface resistivity after treatment is less than 10 times ×: Increase in surface resistivity after treatment is 10 times or more

(6) the surface of the thickness measuring method antistatic layer of the antistatic layer was dyed with RuO _4, and embedded in epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, the cross section of the antistatic layer was measured using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V). The thickness was measured at a location not including the particle portion.

(7) Method for Measuring Extreme Viscosity of Polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and the measurement was carried out at 30 ° C.

(8) Measurement method of average particle size (d50: μm) 50% integration (weight basis) in equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) The value of was taken as the average particle size.

(9) Method for Measuring Release Force of Release Layer After attaching an adhesive tape (“No. 31B” manufactured by Nitto Denko KK, base material thickness 25 μm) to the release surface of the release film obtained in the present invention, It was cut into a size of 50 mm × 300 mm, and the peeling force after being left for 1 hour in a measurement atmosphere at 23 ° C. and 50% RH was measured. As the peeling force, "Intesco model 2001 type" manufactured by Intesco Co., Ltd. was used, and 180 ° peeling was performed under the condition of a tensile speed of 0.3 m / min.

The polyester used in Examples and Comparative Examples was prepared as follows.
<Manufacturing method of polyester (A)>
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.07 part of calcium acetate monohydrate were taken in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. It took about four and a half hours after the reaction started. Then, the temperature was raised to 230 ° C., and the transesterification reaction was substantially completed. Next, 0.04 part of phosphoric acid and 0.035 part of antimony trioxide were added, and the mixture was polymerized according to a conventional method. That is, the reaction temperature was gradually increased to 280 ° C., while the pressure was gradually reduced to 0.05 mmHg. After 4 hours, the reaction was terminated and chips were obtained according to a conventional method to obtain polyester (A). The solution viscosity IV of the obtained polyester chip was 0.65.

<Manufacturing method of polyester (B)>
When producing the polyester (A), 600 ppm of amorphous silica having an average particle size of 2.5 μm was added to prepare the polyester (B).

<Manufacturing method of polyester (C)>
When producing the polyester (A), the concentration of 2,2- (1,4-phenylene) bis [4H-3,1-benzoxazine-4-one] as an ultraviolet absorber is set to 10% by weight. Addition was made to make polyester (C).

<Antistatic layer>
In addition, the following was used as the composition contained in the coating liquid forming the antistatic layer.
(A1): A conductive agent composed of polyethylene dioxythiophene and polystyrene sulfonic acid (Orgacon ICP1010 manufactured by Agfa-Gevaert) neutralized with concentrated ammonia water to pH = 9.
(B1): A compound in which an average of 4 molecules of polyethylene oxide is added to a polyglycerin skeleton having n = 2 in the above formula (3).
(B2): Polyglycerin having n = 2 in the above formula (3).
(B3): Polyethylene oxide (weight average molecular weight 400).
(C1): When the polyester polyol containing 282 parts by weight of terephthalic acid, 282 parts by weight of isocyanate, 62 parts by weight of ethylene glycol, and 250 parts by weight of neopentyl glycol is (C1a), 876 parts by weight of (C1a), Polyester polyurethane containing 244 parts by weight of tolylene diisocyanate, 81 parts by weight of ethylene glycol, and 67 parts by weight of dimethylol propionic acid neutralized with ammonia and dispersed in water (concentration 20%, viscosity at 25 ° C.) 50 mPa · s)
(C2): When the polyester polyol containing 315 parts by weight of terephthalic acid, 299 parts by weight of isophthalic acid, 74 parts by weight of ethylene glycol, and 265 parts by weight of diethylene glycol is (B2a), 953 parts by weight of (B2a) and isophorone diisocyanate. Polyester polyurethane containing 267 parts by weight of ethylene glycol, 56 parts by weight of ethylene glycol, and 67 parts by weight of dimethylol propionic acid neutralized with ammonia and dispersed in water (concentration 23%, viscosity 30 mPa · s at 25 ° C.) )
(D1): A nonionic surfactant having a structure represented by the following formula (4) and having polyethylene oxide in the side chain. (M and n in the following formula (4) are integers indicating the number of moles of ethylene oxide added, and the average of m + n is 10.)

The coating agent for forming the release layer was prepared as follows.
<Adjustment of coating agent>
Curable silicone resin: KS-847H (manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts by weight Platinum-containing catalyst: catPL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by weight This is a mixed solvent of MEK / toluene / isooctane (mixed weight ratio is Diluted in 1: 4: 5) to prepare a coating agent having a solid content concentration of 2% by weight.

Example 1:
Two polyesters (A) and (B) blended at a weight ratio of 80/20 for the surface layer, and polyesters (A) and (C) blended at a weight ratio of 90/10 for the intermediate layer. After supplying each to the extruder of 285 ° C and heating and melting at 285 ° C, co-extruding with 3 layers of 2 types so that the thickness composition ratio becomes 9/57/9, and using the electrostatic adhesion method, a mirror surface with a surface temperature of 45 ° C. An unstretched polyethylene terephthalate film was prepared by cooling and solidifying while adhering to a cooling drum. While passing this film through a group of heated rolls at 85 ° C., the film was stretched 3.4 times in the vertical direction by utilizing the difference in peripheral speeds of the rolls, and then the aqueous coating liquid shown in Table 1 below was applied to one side of the vertically stretched film. 1 is applied, guided to a tenter stretching machine, stretched 4.0 times in the lateral direction at 100 ° C., further heat-treated at 230 ° C., and then relaxed by 2% in the lateral direction to increase the thickness after drying. A biaxially oriented polyethylene terephthalate film having a film thickness of 75 μm and having an antistatic layer of 0.03 μm was obtained. The characteristics of this film are shown in Table 3 below. The obtained polyester film showed excellent UV absorption performance and antistatic performance, and was good.

Next, a coating agent for the release layer was applied to the surface of the film opposite to the antistatic layer by a reverse gravure coating method so that the coating amount after drying was 0.1 g / m ² , and then 150 ° C. By drying and heat-treating for 30 seconds, a release film in which an antistatic layer was laminated on one surface of the polyester film and a release layer was laminated on the other surface was obtained. The film thus obtained showed excellent peeling power as shown in Table 3.

Examples 2-9:
In Example 1, the coating liquid of the antistatic layer was produced in the same manner as in Example 1 except that the composition of the coating liquid was changed to the compositions shown in Tables 1 and 2, and a polyester film and then a release film were obtained. The obtained film had the characteristics shown in Table 3, had both UV absorption performance and antistatic property, and had good peeling power even as a release film.

Examples 10, 11:
In Example 1, a polyester film and then a release film were obtained in the same manner as in Example 1 except that the compounding ratio of the intermediate layer was changed as shown in Table 2. The obtained characteristics are shown in Table 3.

Examples 12-14:
In Example 1, a polyester film and then a release film were obtained in the same manner as in Example 1 except that the thickness composition ratio was changed as shown in Table 2. The obtained characteristics are shown in Table 3.

Example 15:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that a release layer was not provided. The obtained characteristics are shown in Table 3.

Comparative Example 1:
In Example 1, it was produced in the same manner as in Example 1 except that the antistatic layer was not provided, and a polyester film and then a release film were obtained. The finished film has excellent UV absorption performance, but the antistatic performance is poor.

Comparative Examples 2-4:
In Example 1, the coating liquid of the antistatic layer was produced in the same manner as in Example 1 except that the composition of the coating liquid was changed to the compositions shown in Tables 1 and 2, and a polyester film and then a release film were obtained. The obtained film has the characteristics shown in Table 3 and is excellent in UV absorption performance, but the result is that any of antistatic performance, transparency, and water resistance is poor.

Comparative Example 5:
In Example 1, a polyester film and then a release film were obtained in the same manner as in Example 1 except that the compounding ratio of the intermediate layer was changed as shown in Table 2. The obtained film had poor UV absorption performance.

The laminated polyester film of the present invention has excellent antistatic performance and at the same time has ultraviolet absorption performance, and can be suitably used as a release film used when assembling optical members such as polarizing plates. ..

Claims (5)

A laminated polyester film having an antistatic layer on at least one surface of the polyester film, the polyester film has a laminated structure of three or more layers having a surface layer having a thickness of 8.5 μm or more on one side, and ultraviolet rays are applied to the intermediate layer thereof. It contains 2,2- (1,4-phenylene) bis [4H-3,1-benzoxazine-4-one] as an absorbent, and the antistatic layer contains the following compounds (A), (B), and A laminated polyester film containing (C).
(A): Polymer of thiophene or thiophene derivative doped with an anionic compound or self-doped with an anionic group (B): alkylene oxide adduct to glycerin (b1), polyglycerin (b2), glycerin or polyglycerin (B3), and one or more compounds selected from the group of polyalkylene oxides (b4) (C): Polyurethane resin The laminated polyester film according to claim 1, wherein the light transmittance at a wavelength of 380 nm is 10% or less. The laminated polyester film according to claim 1 or 2, wherein the content of the ultraviolet absorber is 1 to 20% by weight. The laminated polyester film according to any one of claims 1 to 3, wherein the thickness of the polyester film is 10 to 300 μm, and the thickness of the antistatic layer is 0.003 μm to 1 μm. A release film having a release layer on the surface opposite to the antistatic layer of the laminated polyester film according to any one of claims 1 to 4 .