JP2002275296A - Laminated polyester film for surface-protected film and surface-protected film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film useful for producing a transparent surface-protected film causing slight electrification during rubbing or peeling and scarcely sticking foulings to the surface. SOLUTION: This laminated polyester film for the surface-protected film having at least one surface thereof coated with an antistatic coat comprising a composition composed of (1) 40-85 wt.% of at least one kind of binder resin selected from a copolyester resin and an acrylic copolymer, (2) 5-50 wt.% of an antistatic agent consisting essentially of a repeating unit represented by the following formula (I) (wherein, Y<-> is a halide ion, nitrate ion, sulfate ion, an alkyl sulfate ion, sulfonate ion or an alkylsulfonate ion) and (3) 1-10 wt.% of a surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film and a surface protective film for a surface protective film, and more particularly to a laminated film which is transparent, has little friction and a small amount of charge when peeled off, hardly adheres dirt on the surface, and is laminated. The present invention relates to a laminated polyester film useful for a surface protective film which is provided with an improved pressure-sensitive adhesive layer which is easily peeled off from the protected surface regardless of aging and does not impair the inspectability of the bonded protected surface, and the surface protective film .

[0002]

2. Description of the Related Art Transparent protective films such as polyethylene and polypropylene are usually used for surface protection on the surface of various displays such as word processors, computers and televisions, or optical components such as polarizing plates and laminates corresponding thereto. It is laminated.

[0003] These protective films are often peeled and removed after the incorporation of a liquid crystal display or the like, for example, but there is a problem that static electricity is generated at the time of peeling and the surrounding dust is involved. Furthermore, in recent years, in a liquid crystal display using a TFT method corresponding to high definition, a TFT film is formed by peeling charging when a protective film is peeled.
A trouble that the element is destroyed may occur.

[0004] The protective film also has poor transparency and many gels such as fish eyes.
For example, if a product is inspected with these protective films attached during the production of a polarizing plate or a liquid crystal display, etc., the defect of the film may cause the product defect to be overlooked or erroneously detected. Making it difficult to do well. This problem is an important problem today when the inspection process needs to be simplified.

In addition, once a surface protective film is applied to a polarizing plate, a liquid crystal display, or the like, the surface protective film may remain attached for a long time until the next manufacturing process, such as when the surface protective film is used in an inspection process. Many. If the peeling is heavy when the surface protective film is peeled off after the inspection or the like, workability deteriorates, and a part of the adhesive remains on a protected surface such as a display.
The latter problem is an important problem because it causes defects such as foreign matter and distortion in surface inspection and the like.

Furthermore, some liquid crystal display components such as a polarizing plate have a surface having fine irregularities in order to suppress the glare of the display portion, thereby suppressing the reflection of light. A surface protective film is also used for these, but the pressure-sensitive adhesive layer of the surface protective film generally has reduced adhesive strength in order to have removability. As a means for weakening the adhesive strength, generally, measures such as increasing the cohesive strength of the adhesive, or including a component having a high glass transition temperature (Tg) or a large amount of hard segments are taken. When a surface protective film having a layer is adhered to a surface to be protected such as a polarizing plate provided with irregularities on the surface, the adhesive of the surface protective film does not sufficiently wet and spread due to the irregularities, and there are many parts that do not contact, At that portion, there is a problem that air cannot escape. This problem is an important problem because the air becomes bubbles and hinders the appearance of foreign substances and the like during an inspection.

On the other hand, films made of polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate are excellent in transparency, fisheye, water resistance, chemical resistance, mechanical strength, dimensional stability, electrical properties, etc. It is widely used for general industrial materials such as plate making films, electronic materials, OHP films, packaging films, labels, magnetic cards, and magnetic recording materials such as magnetic tapes. Such a polyester film has an advantage of being superior in transparency as compared with a film of polyethylene, polypropylene or the like, but has a disadvantage that it is easily charged like the film.
This drawback causes the same trouble as the conventional protective film.

Means for imparting antistatic properties to the film include a method of kneading an anionic compound such as an organic sulfonate group, a metal powder, a carbon powder, and the like into polyester, and a method of evaporating a metal compound on the surface of the film. It has been proposed and put into practical use. However, these methods have a problem that the transparency of the film is reduced and a problem that the processing cost is high.

As another method, various methods for forming an antistatic coating film on the film surface have been proposed and put into practical use. As an antistatic agent to be contained in this antistatic coating film, a low-molecular type or a high-molecular type is known,
Each has a length. For example, as a low molecular weight antistatic agent, a surfactant type anionic antistatic agent such as a long chain alkyl compound having a sulfonate group (JP-A-4-28728) is known. As the polymer type antistatic agent, a polymer having an ionized nitrogen element in the main chain (JP-A-3-255139, JP-A-Hei.
-288127, JP-A-6-320390) and sulfonic acid group-modified polystyrene (JP-A-5-320394).
No.) etc. are known.

However, in an antistatic coating film using a low-molecular type antistatic agent, there is a problem that a part of the antistatic agent moves in the coating film, accumulates at the interface, and migrates to the opposite surface of the film. In addition, there is a problem that the antistatic property decreases with time. On the other hand, in the case of an antistatic coating using a polymer type antistatic agent, a large amount of antistatic agent needs to be blended in order to obtain good antistatic properties, or a thick antistatic coating has a large thickness. Is not economical because it is necessary to form In addition, when a scrap film that has not become a product (for example, a film end portion cut and removed in a manufacturing process) is collected and used as a reclaimed material for film production, it is included in the reclaimed material during melt film formation. There are problems such as the coating film components being thermally degraded and the resulting film being markedly colored and lacking practicality (recoverability is poor). In addition, disadvantages such as difficulty in peeling (blocking) between the films and easiness of shaving of the coating film occur, and a solution to the problem is desired. Therefore, it is necessary to properly use the characteristics of the antistatic agent according to the application.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the prior art, to maintain the inspectability of the bonded protected surface, and to perform a pretreatment such as a corona discharge treatment. The antistatic film can be applied at low processing cost, and has excellent antistatic properties, slipperiness, blocking resistance, adhesiveness, backside transferability, abrasion resistance, and recoverability. It is an object of the present invention to provide a laminated polyester film useful for producing a surface protective film having a releasability which does not vary due to the above, and a surface protective film based on the film.

[0012]

According to the present invention, it is an object of the present invention to provide (1) at least one surface selected from (1) a copolymerized polyester resin and an acrylic copolymer on at least one surface of a polyester film. Binder resin 4
0 to 85% by weight, (2) 5 to 50% by weight of an antistatic agent mainly composed of a repeating unit having a structure represented by the following formula (I)
And (3) a laminated film provided with an antistatic coating containing a composition comprising 1 to 10% by weight of a surfactant, wherein the length of one side of the film is 210 mm and the length of a side perpendicular thereto is 148 mm. Size (area 310.8cm ² )
No foreign matter having a size of 25 μm or more
a surface protection film characterized in that there are no more than 10 foreign substances having a size of not less than 25 μm and less than 25 μm, and the surface specific resistance of the film at 23 ° C. and 50% humidity is not more than 2 × 10 ¹¹ (Ω / □). Laminated polyester film for

[0013]

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(Wherein R ¹ and R ² are each H or CH ₃ , R ³ is an alkylene group having 2 to 10 carbon atoms, R ⁴ ,
R ⁵ is a saturated hydrocarbon group having 1 to 5 carbon atoms, R ⁶ is an alkylene group having 2 to 10 carbon atoms, m is a number of 1 to 20, n
Is a number of 1 to 40, and Y ^- is a halogen ion, a mono- or polyhalogenated alkyl ion, a nitrate ion, a sulfate ion, an alkyl sulfate ion, a sulfonate ion or an alkyl sulfonate ion. )
And (2) a composite film in which an adhesive layer is provided on one surface and a protective layer is provided on the other surface of the laminated polyester film according to (1), wherein the adhesive layer has the following (a)
Characteristics (a) to (f) the glass transition temperature is −60 ° C. or more and −20 ° C. or less, and (b) the tensile elastic modulus is 0.1 MPa or more and 0.2 M.
(C) The surface tension is 15 μN / cm or more and 25 μN / cm or less. (D) Adhesive strength (A) after adhering to a stainless steel plate and allowed to stand at 60 ° C. for 1 day is 3
(E) The value obtained by dividing the adhesive force (B) after being left at 60 ° C. for 1 week after being bonded to a stainless steel plate, is 0.5 to 2 mN / 25 mm or more and 500 mN / 25 mm or less. And (f) the thickness is 3 μm or more and 50 μm or less at the same time.

Hereinafter, the present invention will be described in detail.

In the present invention, the polyester is a linear saturated polyester comprising a dicarboxylic acid component and a glycol component. Preferred examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid. be able to. In particular, terephthalic acid, 2,6-
Naphthalenedicarboxylic acid is preferred.

The glycol components include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, polyethylene Glycol and the like can be preferably exemplified. Particularly, ethylene glycol is preferred from the viewpoint of the rigidity of the film.

Among such polyesters, polyethylene terephthalate or polyethylene-2,6-naphthalate is used for forming a film having excellent mechanical properties (for example, high Young's modulus) and excellent thermal properties (for example, heat-resistant dimensional stability). preferable.

The above-mentioned polyethylene terephthalate or polyethylene-2,6-naphthalate is a copolyester obtained by copolymerizing a dicarboxylic acid component other than terephthalic acid or 2,6-naphthalenedicarboxylic acid or a glycol component other than ethylene glycol as a third component. Or a copolyester copolymerized in a small amount within a range (for example, 5 mol% or less) in which a polyester from which a trifunctional or higher polycarboxylic acid component or a polyol component can be obtained is substantially linear. .

The above polyester can be produced by a conventional method. The intrinsic viscosity (orthochlorophenol, 35 ° C.) of the polyester is preferably 0.45 or more, more preferably 0.5 or more and 1.0 or less. This intrinsic viscosity is 0.
When it is 45 or more, the mechanical properties such as high rigidity of the film are improved.

In order to improve the slipperiness of the film, the above polyester has an average particle size of 0.0 as a lubricant.
Organic or inorganic fine particles of about 1 to 2.0 μm can be contained, for example, in a blending ratio of 0.01 to 5% by weight. Specific examples of such fine particles include silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, titanium oxide, inorganic fine particles such as barium sulfate, a crosslinked silicone resin, a crosslinked polystyrene resin,
Organic fine particles made of a heat-resistant polymer such as a crosslinked acrylic resin, a urea resin, a melamine resin and the like can be preferably exemplified.

In addition to the fine particles, coloring agents, known antistatic agents, organic lubricants (sliding agents), catalysts, stabilizers, antioxidants, ultraviolet absorbers, optical brighteners, polyethylene, polypropylene, ethylene-propylene copolymer If necessary, other resins such as olefin-based ionomers may be contained.

The thickness of the polyester film in the present invention is from 20 to 500 μm, more preferably from 50 to 450 μm,
In particular, it is preferably from 75 to 300 μm. If the thickness is less than 20 μm, the stiffness of the film becomes weak, while if the film is too thick, for example, if it exceeds 500 μm, the film-forming properties tend to be inferior.

The polyester film in the present invention comprises:
The length of one side is 210 mm and the length of the side orthogonal to it is 148
It is necessary that no foreign matter having a size of 25 μm or more is present in a film per mm width (area of 310.8 cm ² ) and that no more than 10 foreign matters have a size of 5 μm to less than 25 μm. When a foreign substance having a size of 25 μm or more is present, a void is generated at the time of applying or transferring the adhesive, and the adhesive is removed or swells only in that portion beyond the size, so that it can be visually confirmed. May have local appearance defects. The size is 5μ
If there are more than 10 foreign particles having a size of m or more and less than 25 μm, the size of the particles is hard to be confirmed by visual inspection, but the defects may be noticeable due to the large number. Below, the length of one side 2
The number of foreign substances having a size of 25 μm or more existing in the film per 10 mm and the length of the side orthogonal to the 148 mm (area of 310.8 cm ² ) is visually recognized. Sometimes referred to as the number of foreign substances.

The antistatic film according to the present invention is provided on at least one side of a polyester film, (1)
50 to 80% by weight of at least one binder resin selected from a copolymerized polyester resin and an acrylic copolymer, (2) an antistatic agent 10 containing a repeating unit having a structure represented by the following formula (I) as a main component: 40% by weight and (3)
It is a coating containing a composition comprising 3 to 10% by weight of a surfactant. The coating is provided by applying an aqueous coating solution containing these compositions to a film, drying and stretching.

[0026]

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(Where R ¹ and R ² are each a hydrogen or methyl group; R ³ is an alkylene group having 2 to 10 carbon atoms;
R ⁴ and R ⁵ each represent a saturated hydrocarbon group having 1 to 5 carbon atoms;
R ⁶ is an alkylene group having 2 to 10 carbon atoms, m is a number of 1 to 20, n is a number of 1 to 40, Y ⁻ is a halogen ion, a mono- or polyhalogenated alkyl ion, a nitrate ion, a sulfate ion, Alkyl sulfate ion,
It is a sulfonate ion or an alkyl sulfonate ion. Further, two R ³ in the above formula may be the same or different. )

In the present invention, the acid component constituting the copolymerized polyester resin used as the binder resin (1) includes terephthalic acid, isophthalic acid, phthalic acid,
Preferred examples include 6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, phenylindanedicarboxylic acid, and dimer acid. Two or more of these components can be used. Furthermore, maleic acid, fumaric acid,
Unsaturated polybasic acids such as itaconic acid and hydroxycarboxylic acids such as p-hydroxybenzoic acid and p- (β-hydroxyethoxy) benzoic acid can be used in a small proportion. The proportion of the unsaturated polybasic acid component or hydroxycarboxylic acid component is at most 10 mol%, preferably 5 mol% or less. Further, as the polyol component, ethylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol,
1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, poly (ethyleneoxy) glycol, poly (tetramethyleneoxy) glycol, and further represented by the following formula Oxide and propylene oxide adducts of bisphenol A

[0029]

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[0030]

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Preferred examples can be given. Two or more of these can be used.

Among these polyol components, ethylene glycol, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct, and 1,4-butanediol are preferable, and ethylene glycol is more preferable.

Further, the copolymerized polyester resin includes:
In order to facilitate aqueous liquefaction, it is possible to copolymerize a small amount of a compound having a sulfonic acid group or a compound having a carboxylic acid group, which is more preferable. Examples of the compound having a sulfonic acid group include 5-sodium sulfo-isophthalic acid, 5-ammonium sulfo-isophthalic acid, 4-sodium sulfo-isophthalic acid, 4-methylammonium sulfo-isophthalic acid,
-Alkali metal salts of sulfonic acid such as sodium sulfo-isophthalic acid, 5-potassium sulfo-isophthalic acid, 4-potassium sulfo-isophthalic acid, 2-potassium sulfo-isophthalic acid, sodium sulfo-succinic acid or amine salt of sulfonic acid A compound having a compound or the like is preferably exemplified. Examples of the compound having a carboxylic acid group include, for example, trimellitic anhydride, trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid, etc. Metal salts and the like. The free carboxyl group is converted to a carboxylate group by the action of an alkali metal compound or an amine compound after copolymerization.

The copolymerized polyester resin is a modified polyester copolymer, for example, a block polymer or a graft polymer obtained by modifying the polyester copolymer with components such as acrylic resin, polyurethane, silicone resin, epoxy resin and phenol resin. Can also be used.

Such a copolymerized polyester resin can be produced by a conventionally known or used polyester production technique. For example, 2,6-naphthalenedicarboxylic acid or its ester-forming derivative (especially dimethyl ester), isophthalic acid or its ester-forming derivative (especially dimethyl ester) and trimellitic anhydride are propylene oxide adducts of ethylene glycol and bisphenol A To form a monomer or oligomer, followed by a polycondensation reaction under vacuum to give a specific intrinsic viscosity (orthochlorophenol, 35 ° C.), preferably an intrinsic viscosity of 0.2
To 0.8, and a method in which a free carboxy group is reacted with an alkali compound or an amine compound to form a salt. At that time, it is preferable to use a catalyst for accelerating the reaction, for example, an esterification or transesterification catalyst, a polycondensation catalyst, and the like, and various additives such as a stabilizer can be added.

In the present invention, the main components of the acrylic copolymer used as the binder resin (1) are acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, sodium acrylate, ammonium acrylate, -Hydroxyethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, sodium methacrylate, ammonium methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, acrylic methacrylate, sodium vinyl sulfonate, sodium methallylsulfonate , Sodium styrenesulfonate, acrylamide, methacrylamide, N-methylol methacrylamide, and the like. These monomers include, for example, styrene, vinyl acetate, acrylonitrile,
It can be used in combination with other unsaturated monomers such as methacrylonitrile, vinyl chloride, vinylidene chloride and divinylbenzene.

As the acrylic copolymer, a modified acrylic copolymer, for example, a block polymer obtained by modifying the acrylic copolymer with a component such as polyester, polyurethane, silicone resin, epoxy resin, phenol resin, or graft polymer It can also be used as a union.

In the present invention, the antistatic agent (2) used for forming a film is a compound containing a repeating unit having a structure represented by the following formula (I) as a main component.

[0039]

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(Where R ¹ and R ² are each a hydrogen or methyl group; R ³ is an alkylene group having 2 to 10 carbon atoms;
R ⁴ and R ⁶ each represent a saturated hydrocarbon group having 1 to 5 carbon atoms;
R ⁶ is an alkylene group having 2 to 10 carbon atoms, m is a number of 1 to 20, n is a number of 1 to 40, Y ⁻ is a halogen ion, a mono- or polyhalogenated alkyl ion, a nitrate ion, a sulfate ion, Alkyl sulfate ion,
It is a sulfonate ion or an alkyl sulfonate ion. )

[0041] Among the anti-static agent, Y in Formulas (I) ^- is R ⁷ SO ₃ ^- alkyl sulfonate ion represented by (wherein, R ⁷ is a saturated hydrocarbon group having 1 to 5 carbon atoms) be ,
R ^{3 of} — (OR ³ ) m— is an ethylene group, and m is 1 to 20;
Number ^{of, - (R 6 O) R} 6 in n- is an ethylene radical, n is 1
Compounds having a number of from 40 to 40 are preferable because they have good adhesion between the coating film and the polyester film and heat resistance of the coating film, and particularly have excellent antistatic properties.

The antistatic agent can be preferably produced, for example, by the following method.

That is, the acrylate monomer is
Weight average molecular weight of 2,000 to 10,000 by emulsion polymerization
A polyacrylic ester, and then reacted with N, N-dialkylaminoalkylamine (eg, N, N-dimethylaminopropylamine, N, N-diethylaminopropylamine) to amidate, and finally quaternary hydroxy It can be produced by performing an alkylation reaction to introduce a quaternary cation pair.

The average molecular weight (number average molecular weight) of the antistatic agent is arbitrary, but is preferably 3,000 to 300,000, and more preferably 50 to 50.
It is preferably from 100 to 100,000. If the average molecular weight is less than 3,000, the back transferability of the antistatic agent tends to deteriorate, while the average molecular weight is less than 300,000.
Exceeding the viscosity is not preferred because the viscosity of the aqueous coating solution becomes too high, making it difficult to apply the film uniformly to the film.

The antistatic agent is represented by Y in the above formula (I).
^{- _{is, CH 3 SO 3 -, C}} 2 H 5 SO 3 - are or C ₃ H ₇ SO ₃ over, - (OR ³⁾ m- is - (OC ₂ H ₄₎ is m-, and m
Is preferably 1 to 5. Also, - (R ⁶ O) n-
There - (C ₂ H ₄ O) a n-, and n is preferably 1 to 10.

The antistatic coating film of the present invention has a strong adhesiveness between the coating film and the polyester film,
In order to improve the blocking resistance of the laminated film, a surfactant (3) is blended. Examples of the surfactant (3) include an alkylene oxide homopolymer, an alkylene oxide copolymer, and an aliphatic alcohol.
Alkylene oxide adducts, non-chain surfactants such as long-chain aliphatic-substituted phenol / alkylene oxide addition polymers, polyhydric alcohol aliphatic esters, and long-chain aliphatic amide alcohols, compounds having a quaternary ammonium salt,
Examples thereof include cationic or anionic surfactants such as compounds having an alkylpyridinium salt and compounds having a sulfonate salt. Particularly, a nonionic surfactant is used as an adhesive between a coating film and a base film or an antistatic polyester film. Is preferred because of its excellent effect on blocking resistance.

In the present invention, the ratio of the binder resin (1) to the total amount of the binder resin (1), the antistatic agent (2) and the surfactant (3) is 40 to 85.
% By weight, preferably 50 to 80% by weight. If the proportion is less than 40% by weight, the adhesion of the coating to the polyester film is insufficient, which is not preferable. On the other hand, when the content exceeds 85% by weight, the blocking property of the coated film is undesirably deteriorated. The proportion of the antistatic agent (2) is 5 to 50% by weight, preferably 10 to 40% by weight.
If the proportion is less than 5% by weight, the antistatic property is insufficient, while if it exceeds 50% by weight, the adhesion of the coating to the polyester film is insufficient, which is not preferable. Furthermore, the ratio of the surfactant (3) is 1 to 15% by weight, preferably 3 to 1% by weight.
0% by weight. If this proportion is less than 1% by weight, the wettability of the aqueous coating solution to the polyester film may be insufficient, while if it exceeds 15% by weight, the adhesion of the coating to the polyester film may be insufficient or the blocking resistance may be poor. There is a shortage, which is not preferable.

In the present invention, the composition of the components forming the antistatic film is preferably applied to the film as an aqueous coating liquid (using water as a medium), but may be applied using an organic solvent as a solvent. It is. As the organic solvent, methyl ethyl ketone, acetone, ethyl acetate,
Tetrahydrofuran, dioxane, cyclohexanone,
Examples thereof include n-hexane, toluene, xylene, methanol, ethanol, n-propanol, and isopropanol. These can be used alone or in combination of two or more.

In the present invention, a film is preferably formed by using an aqueous coating liquid containing the above-mentioned composition. However, the aqueous coating liquid may contain other surfactants and ultraviolet rays as long as the object of the present invention is not impaired. Other additives such as an absorbent, a pigment, a lubricant, an anti-blocking agent, a cross-linking agent such as melamine, epoxy and aziridine, and other antistatic agents can be blended.

In the present invention, the solid content of the coating solution is usually 30% by weight or less, and preferably 0.5 to 30% by weight. If this ratio is less than 0.5% by weight, the coatability on the polyester film is insufficient, while
If the content exceeds% by weight, the appearance of the coating film deteriorates, which is not preferable.

In the present invention, a coating solution containing the above-mentioned components is applied to at least one surface of a polyester film.
As the film, a polyester film before completion of the crystal orientation is preferable. As the polyester film before the completion of the oriented crystal, an unstretched film obtained by heat-melting the polyester to form a film as it is, a uniaxially stretched film obtained by orienting the unstretched film in either the longitudinal direction or the transverse direction. For example, a film stretched and oriented at a low magnification in two directions of a longitudinal direction and a lateral direction (a biaxially stretched film before being finally stretched in a longitudinal direction and a lateral direction to complete oriented crystallization) and the like can be exemplified. it can.

As a method for applying the coating liquid to the polyester film, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a microgravure coating method, a reverse coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination. When an aqueous coating liquid is used, a small amount of an organic solvent may be contained for the purpose of assisting the stability of the coating liquid.

The coating amount is preferably from 0.5 to 50 g, more preferably from 5 to 30 g, per m ² of the running film. The thickness of the final dried coating film (coating) is 0.02 to 1 μm
Is required, and the thickness is preferably 0.05 to 0.8 μm. When the thickness of the coating film is less than 0.02 μm, the antistatic property becomes insufficient. On the other hand, when the thickness exceeds 1 μm, the blocking resistance decreases, which is not preferable. Coating can be performed on only one side or on both sides depending on the use of the film. After coating, the coating is dried to form a uniform coating.

In the present invention, after the polyester film is coated with the antistatic coating solution, drying is performed, preferably a stretching treatment. The drying is preferably performed at 90 to 130 ° C. for 2 to 20 seconds. This drying can serve as a pre-heat treatment for the stretching treatment or a heat treatment for the stretching. The stretching process of the polyester film is performed at a temperature of 70 to 140 ° C., and is stretched 2.5 to 7 times in the vertical direction, 2.5 to 7 times in the horizontal direction, 8 times or more in area magnification, and further 9 to 28 times. Is preferred. When re-stretching, it is preferable to stretch at a magnification of 1.05 to 3 times (however, the area magnification is the same as described above). The heat setting after the stretching is preferably performed at a temperature higher than the final stretching temperature and lower than the melting point for 1 to 30 seconds. For example, in the case of polyethylene terephthalate film, 2-3
It is preferable to heat set for 0 seconds.

The laminated polyester film thus obtained has a surface resistivity of 2 × 10 ¹¹ (Ω / □) or less, preferably 7 × 10 ¹⁰ (Ω / □) or less, and is excellent in antistatic properties. It is. Furthermore, it is excellent in transparency, slipperiness, adhesiveness, blocking resistance, back transferability, abrasion resistance, recoverability, etc., and various displays such as word processors, computers and televisions, or polarizing plates and It is extremely useful as a base film for a surface protective film of an optical component such as a laminate according to the standard.

[Adhesive Layer] The surface protective film of the present invention is obtained by providing an adhesive layer on one surface and a protective layer on the other surface of the above-mentioned laminated polyester film. It is necessary to have characteristics that can be easily adhered to a protected surface (such as a polarizing plate or a stainless steel plate) and can be easily peeled off, and have the following characteristics (a) to (f).

(A) The glass transition temperature (Tg) is -60 ° C.
(B) Tensile modulus is 0.1 MPa or more and 0.2 MPa or less.
(C) The surface tension is 15 μN / cm or more and 25 μN / cm or less; (d) The adhesive strength (A) after being stuck to a stainless steel plate and allowed to stand at 23 ° C. for 1 day is 30 mN / 25 mm or more and 500 or more.
(e) The value obtained by dividing the adhesive strength (B) by the adhesive strength (A) after adhering to a stainless steel plate and allowing to stand at 60 ° C. for 1 week is 0.
And (f) the thickness is 3 μm or more and 50 μm or less.

The glass transition temperature (Tg) of the pressure-sensitive adhesive layer is-
If it is lower than 60 ° C. or the tensile elasticity of the pressure-sensitive adhesive layer is less than 0.1 MPa, it is extremely soft even in a normal use environment such as room temperature, and spreads unnecessarily on the bonded protected surface and adheres excessively. Poor peelability with enhanced power. On the other hand, the glass transition temperature (Tg) of the pressure-sensitive adhesive layer is -20.
° C or the tensile modulus of the adhesive layer is 0.2M
When it exceeds Pa, it lacks softness in an environment such as room temperature and does not sufficiently spread on the bonded protective surface. On the other hand, if the surface tension of the adhesive layer is less than 15 μN / cm, a desired adhesive force with the protected surface to be bonded cannot be obtained, and on the other hand, 25 μN / cm.
If it exceeds, an unnecessary adhesive force is generated between the surface and the surface to be protected, resulting in lack of releasability.

Further, it is bonded at 23 ° C.
Adhesive strength (A) after leaving for 1 day at 30 mN / 25 mm
If it is less than the above, end-turning occurs or the film is easily peeled off by any contact. Here, the end turn refers to the temperature and temperature of the polarizing plate when the polarizing plate is cut into a specific rectangle, for example.
Because of the large shrinkage / expansion under humidity, the displacement cannot be sufficiently absorbed, meaning that the protection film (protection film) tends to peel off particularly at the corners. On the other hand, if the adhesive strength (A) exceeds 500 mN / 25 mm, the adhesive may not be easily peeled off in the step of peeling from the protected surface and may damage the protected surface. In addition, the said adhesive force A may only be hereafter called adhesive force A.

Furthermore, it is necessary that the adhesion to the stainless steel plate does not change with time, and the adhesion (B) after being attached to the stainless steel plate and left at 60 ° C. for one week is determined by the above-mentioned adhesion (A). If the divided value is less than 0.5 times or greater than 2 times, the adhesive force will change excessively, making setting and management when automatically peeling off the surface protective film by a machine complicated and even worse. May damage the protected surface at the time of peeling, or may peel off before peeling and may no longer protect the protected surface. Note that the adhesive strength may be simply referred to as adhesive strength B below.

Lastly, when the thickness of the pressure-sensitive adhesive layer is less than 3 μm, when the pressure-sensitive adhesive layer is adhered to a polarizing plate or the like having irregularities, it is governed by the hardness of the biaxially oriented polyester film which is the base material of the surface protective film, The pressure-sensitive adhesive does not sufficiently spread on the surface of the polarizing plate, or a partial lifting occurs when the pressure-sensitive adhesive is laminated without obtaining the required adhesive strength. On the other hand, if the thickness is more than 50 μm, the adhesive strength becomes excessively high, or uneven thickness occurs when applying the adhesive, or the applied adhesive layer cannot be uniformly cured, Furthermore, the production cost rises.

The preferred embodiment of the pressure-sensitive adhesive layer in the present invention will be described below.

The center line average roughness (Ra) of the pressure-sensitive adhesive layer in the present invention is preferably 2 nm or more and 500 nm or less. If the center line average roughness is small, there is no particular problem, but if it is larger than 500 nm, the thickness, adhesive strength, and peeling strength of the pressure-sensitive adhesive layer satisfy the above ranges when bonded to a polarizing plate or the like. Even if it does, it does not adhere completely, distortion occurs,
In addition, bubbles and the like may be generated in the recessed portion.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer according to the present invention does not deteriorate not only indoors but also outdoors, can withstand various light rays at the time of inspection, particularly ultraviolet rays, and further has a bonded protected surface. It is preferable to have characteristics such as no migration of the component of the pressure-sensitive adhesive layer to the adhesive layer, and from these points, an acrylic pressure-sensitive adhesive is particularly preferable. As an acrylic adhesive,
There are a solvent-based adhesive and an emulsion-based adhesive, and a solvent-based adhesive which easily provides the above-mentioned physical properties of the adhesive is particularly preferable. The acrylic solvent-based pressure-sensitive adhesive can be produced by solution polymerization so as to satisfy various properties, and as a raw material, a known material for solution polymerization of an acrylic pressure-sensitive adhesive can be used.

Preferred acrylic solvent-based pressure-sensitive adhesives include
The main monomer that is the skeleton is an acrylate ester such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate or octyl acrylate, and vinyl acetate, acrylonitrile, styrene or methyl methacrylate is used as a comonomer for improving cohesion, Further, as a functional group-containing monomer which promotes high crosslinking and imparts stable and low adhesive strength, there may be mentioned those using methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate or glycidyl methacrylate. Among them, those having a low tackiness and tackiness and a high cohesive force can be highly crosslinked with an isocyanate-based curing agent, an aziridine-based curing agent, and the like, and those containing a large amount of hydroxyl groups are preferable. Further, in order to prevent the generation of air bubbles when bonded to a protected surface having irregularities, it is necessary to make the pressure-sensitive adhesive layer softer than usual, which has a low glass transition temperature (Tg) among the above components. It is preferable to use a large number of main monomer components that form the skeleton and to reduce the number of copolymer components that increase Tg and improve cohesion.

The method for synthesizing the pressure-sensitive adhesive in the present invention can be carried out by a method known per se. For example, in the presence of an organic solvent such as ethyl acetate or toluene, the necessary raw materials are charged into a reaction tank, and a peroxide system such as a peroxide such as benzoyl peroxide or an azobis system such as azobisisobutyronitrile is added. The polymerization may be performed under heating as a catalyst. In order to increase the molecular weight, for example, it is preferable to use ethyl acetate because, at the beginning, the monomer is charged all at once, and in the organic solvent used, toluene has a large chain transfer coefficient and suppresses the growth of the polymer. At this time, the weight average molecular weight (Mw) is preferably 300,000 or more,
More than 400,000 is more preferable. If the average molecular weight is less than 300,000, even if cross-linked with an isocyanate cross-linking agent, sufficient cohesive strength cannot be obtained. When aged after being attached to a layer or the like, the adhesive may remain on a protected surface such as a stainless steel plate or a polarizing plate when peeled off. In order to increase the molecular weight, control at the polymerization stage is important.However, in general, even if a solvent system has sufficient adhesive strength, the molecular weight does not increase. It is necessary to improve the crosslinking rate.

The curing agent for the pressure-sensitive adhesive is not specified, but in particular, in the case of an acrylic solvent, a general isocyanate-based, epoxy-based, or aziridine-based curing agent can be used. The adhesive may contain additives such as a stabilizer, an ultraviolet absorber, a flame retardant, and an antistatic agent. Further, the additive is necessary to suppress the increase in the adhesive force by using an adhesive having a low glass transition temperature, and also to suppress the increase in the adhesive force over time. As an additive, an organic resin such as wax, a silicone oil, a fluorine-based resin, or the like can be used. However, it is preferable that these components do not migrate to the bonded surface to be protected and do not impair testability. Therefore, it is good to partially react with the adhesive component.For example, in an organic resin such as a wax, a higher fatty acid ester having a reactive functional group such as a hydroxyl group, a carboxyl group, an epoxy group, an amino group, and an isocyanate group is used. Preferably, it is used.

The application of the pressure-sensitive adhesive solution to the biaxially oriented polyester film can be performed at any stage. Also,
When applying the solution to the biaxially oriented polyester film, if necessary, a flame treatment, a corona discharge treatment, a plasma discharge, etc. may be applied to the biaxially oriented polyester film as a preliminary treatment for improving adhesion and coating properties. The adhesive and the biaxially oriented polyester are subjected to a physical surface treatment such as treatment, or to a chemical surface treatment of applying an organic resin-based or inorganic resin-based paint during or after film formation. The adhesion of the film can be strengthened.

As the method of applying the pressure-sensitive adhesive, any known method can be used, and for example, a die coater method, a gravure roll coater method, a blade coater method, a spray coater method, an air knife coat method, a dip coat method and the like are preferable. And can be used alone or in combination. The drying temperature when applying the pressure-sensitive adhesive is preferably such that the residual solvent is as small as possible. Specifically, it is preferable to dry at a drying temperature of 50 to 150 ° C. for a drying time of 10 seconds to 5 minutes. Since the pressure-sensitive adhesive has fluidity, when an isocyanate-based cross-linking agent or the like is used as a cross-linking agent, the reaction is not completed immediately after heating and drying, and the reaction is completed to obtain a stable adhesive force. Preferably, curing is performed. In general, curing is preferably performed at room temperature for about one week or more, and when heating, for example, about 50 ° C. for three days or more. In the case of heating, if the temperature is too high, the planarity of the biaxially oriented polyester film as the base material may be deteriorated.

[Protective Layer] The protective layer in the present invention destroys the protected engineering component, for example, a transistor of a TFT type display plate, by the peeling charge generated when the pressure-sensitive adhesive layer is peeled from the counterpart structure. It is preferable to prevent the surface protection film from adhering dirt to the surface of the surface protective film or to easily remove dirt adhering to the surface of the surface protective film, and preferably contains a release agent and an antistatic property. It can be obtained by providing a release layer on the film coated with the antistatic agent described above. When the surface of the protective layer is a release layer, the release force of the release layer from the pressure-sensitive adhesive layer is 10 mN / 25 mm or more and 5000 mN / 25 mm from the viewpoint of preventing contamination of the surface protective film surface and improving dirt wiping properties. The following is preferred. This peeling force is 5000 mN / 25
If it exceeds mm, it is not preferable because deposits such as dirt cannot be easily removed. Examples of such a release agent include a silicone-based, fluorine-based or alkyl polymer-based release agent, and an alkyl polymer having a low migration property is preferable in order to prevent contamination in the process. A preferred acrylic polymer system is a polymer having a long alkyl chain, and a copolymer of acrylic acid and an alkyl acrylate having an alkyl group having 12 or more carbon atoms, particularly 16 to 20 carbon atoms is preferred. The alkyl acrylate has one alkyl chain
If it is less than 2, sufficient releasability may not be obtained. Among them, copolymers obtained by long-chain alkylation of polyvinyl alcohol or polyethylene imine with chlorinated alkylol or alkyl isocyanate are particularly preferable.

In the method for forming a protective layer in the present invention, a coating liquid for forming a protective layer may be applied after the biaxially oriented polyester film is formed after the crystal orientation is completed. As a method for coating the biaxially oriented polyester film, any known method can be applied. For example, a roll coating method, a gravure coating method, a reverse coating method, a spray coating method, or the like can be used alone or in combination. The coating of the protective layer is performed by applying a coating liquid containing the components for forming each of the protective layers to a substrate, and drying by heating to form a coating film. The heating conditions are 80 to 160 ° C. for 10 to 120 seconds, especially 120 to 160 ° C.
Preferably at 150 ° C. for 20 to 60 seconds.

[Transparency] The surface protective film of the present invention preferably has excellent transparency, and more specifically, preferably has a visible light transmittance of 70% or more and a haze of 10% or less. Because of these properties, product inspection with the protective film attached can be performed efficiently.

[Optical parts] The surface protective film of the present invention can be coated with an antistatic film at a low processing cost without impairing the inspectability of the bonded surface to be protected and without performing a pretreatment such as a corona discharge treatment. It has excellent antistatic properties, sliding properties, blocking resistance, adhesiveness, backside transferability, abrasion resistance, and recoverability, and has both excellent sticking properties and releasability that does not change over time. It is useful as an optical component, particularly a protective film for a polarizing plate, a retardation plate, a viewing angle widening film or a laminate thereof.

[0074]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. The evaluation in the present invention was performed by the following method.

1. Surface resistivity (antistatic property) The surface resistivity of the sample film was measured by Takeda Riken
Using a specific resistance measuring instrument, measured temperature 23 ° C, measured humidity 60
%, The surface specific resistance (Ω / □) after one minute at an applied voltage of 500 V is measured.

2. Coefficient of friction (slipperiness) According to ASTM D 1894-63, a slipper measuring device manufactured by Toyo Tester Co., Ltd. is used, the front and back surfaces of the sample film are combined, and a load of 1 kg is applied to measure the static friction coefficient. If the coefficient of friction exceeds 0.6, film transportability is impaired.

3. Number of foreign particles in the film A sample film is cut into a length of 210 mm and a width of 148 mm (area: 310.8 cm ² ), and the entire area of the film is visually inspected by a crossed Nicols method. Next, the detected foreign matter in the sample film is observed with transmitted light using an optical microscope, and the maximum diameter of a portion observed as an optically abnormal range is defined as the size of the foreign matter. When a void (void) existing around the foreign particle is observed as an optically abnormal range, it is included in the size of the foreign particle. Then, the size of the foreign particles is divided into those having a size of 5 μm or more and less than 25 μm and those having a size of 25 μm or more, which are counted to obtain the number of foreign materials.

4. Blocking resistance The coated surface of the sample film cut to a width of 50 mm and the non-coated surface are superposed on each other, and subjected to a load of 6 kg under a load of 50 kg / cm ^2.
After treatment at 0 ° C. × 80% RH for 17 hours, the peeling force between the coated surface and the non-coated surface is measured, and the blocking resistance is evaluated as follows. Rank A: Peeling force ≦ 10 g (good blocking resistance) Rank B: 10 g <peeling force ≦ 30 g (slightly poor blocking resistance) Rank C: 30 g <peeling force (poor blocking resistance)

5. Back transferability 6 kg by applying the coated side of the sample film and the non-coated side
/ Cm ² under a condition of 50 ° C. × 70% RH.
After the time treatment, the water contact angle (θ: substitute property of backside transferability) of the non-coated surface is measured and evaluated according to the following criteria. Rank A: θ ≧ 55 ° (backside transferability is good) Rank B: 55 °> θ ≧ 48 ° (backside transferability is somewhat good) Rank C: 48 °> θ (backside transferability is poor) The water contact angle is the above sample film Was set on a contact angle measuring device (manufactured by Elma) with the non-coated side facing up, and the temperature was set to 23.
It measures by reading the contact angle 1 minute after dropping a water drop under the condition of ° C. The water contact angle of the film having no backside transferability is 60 to 72 °, the water contact angle of the film having good backside transferability is 55 ° or more, and the backside transferability is remarkable (poor backside transferability). Has a water contact angle of less than 48 °.

6. Using a film sample cut to a width of 20 mm, the coated surface of the film was applied to a cylindrical stainless steel fixed bar having a diameter of 10 mm, and was run for 80 m under a load of 200 g. Observe the white powder of the film and evaluate the abrasion resistance as follows. Rank A: No white powder adhered to the bar (good abrasion resistance) Rank B: White powder slightly adhered to the bar (slightly poor abrasion resistance) Rank C: Large amount of white powder adhered to the bar (poor abrasion resistance)

7. Degree of coloring (recovery) of regenerated film A film without a coating film is pulverized, and extruded to about 300
The mixture is melted at 0 ° C. to form chips, and then the obtained chips are melt-formed to form a blank film. The coloring degree of this film is defined as a blank. On the other hand, a sample film provided with a coating film is pulverized, melted at about 300 ° C. with an extruder to form chips, and then melt-formed using the obtained chips to produce a regenerated film. The degree of coloring of this film is evaluated according to the following criteria. Rank A: The degree of coloring is similar to that of a blank film. Rank B: The film is slightly colored. Rank C: The degree of coloring of the film is large and lacks practicality.

8. Peeling force Nitto 31B tape (manufactured by Nitto Denko Corporation) is adhered to the protective layer surface of the surface protective film with a rubber roller, and reciprocated once from above with a 2 kg rubber roller to make close contact.
3 at the temperature of 23 ° C and the humidity of 55 ± 5% RH
Leave for 0 minutes and cut into 25 mm wide strips. This was measured with a tensile tester (Strograph manufactured by Toyo Seiki Co., Ltd.)
Pull the B tape at 180 ° at 300mm / min,
The strength is defined as the peeling force.

9. Adhesive force with stainless steel plate (A) The adhesive layer surface of the surface protection film is directly adhered to the washed stainless steel plate with a rubber roller,
Reciprocate one time with a kg rubber roller to make close contact. It is left as it is under the condition of a temperature of 23 ° C. and a humidity of 55 ± 5% RH for one day, and then cut into strips having a width of 25 mm. This was mounted on a tensile tester (Strograph, Toyo Seiki Co., Ltd.), and a stainless steel plate was fixed.
Per minute, and the strength is defined as the adhesive strength (A) to the stainless steel plate.

10. Adhesive force with stainless steel plate (B) A sample prepared in the same manner as the adhesive force (A) was subjected to 60 ° C.
For 1 week, return to room temperature, measure the adhesive strength after standing for 30 minutes with a tensile tester, and determine the strength as the adhesive strength (B) with the stainless steel plate.

11. Glass transition temperature (Tg) Only the pressure-sensitive adhesive layer was made into a sheet having a uniform thickness, and a dynamic viscoelasticity measuring device (A & D Corp., Vibron) was used.
The measurement is performed under the conditions of a frequency of 110 Hz and a heating rate of 3 ° C./min. The storage modulus (E ') is greatly reduced and tan δ
Is the glass transition temperature (Tg).

12. Tensile Modulus of Adhesive Only the adhesive layer is made into a uniform sheet to make a 10 mm wide strip. At this time, the thickness of the sheet is measured. Next, this was attached to a tensile tester (Strograph, Toyo Seiki Co., Ltd.) and pulled at a speed of 5 mm / min to create a stress / strain curve. The slope of the tangent at the time of rising is determined, divided by the cross-sectional area, and defined as the tensile modulus.

13. Surface tension of pressure-sensitive adhesive Water (surface tension: 72.8 μN / cm, non-polar component 21.8 μN / cm, polar component 51.0 μN /
cm), ethylene glycol (surface tension 48.0 μN /
cm, non-polar component 29.0 μN / cm, polar component 1
9.0 μN / cm), diiodomethane (surface tension 50.
Three liquids of 8 μN / cm, a nonpolar component of 50.8 μN / cm, and a polar component of 0 μN / cm) are dropped, and the contact angles of the respective liquids are measured. Expand Fork from each of these components
The surface tension of the pressure-sensitive adhesive is calculated using the equation of es.

14. Light transmittance At a wavelength of 550 nm, the transmittance is measured (Poic haze meter SEP-HS-D, manufactured by Nippon Seimitsu Kogaku Co., Ltd.).
Type 1).

15. Number of surface defects The obtained surface protective film was stuck on a polarizing plate,
A 10 mm × width 148 mm (area: 310.8 cm ² ) is cut out, and a fluorescent lamp is used to count a surface of which the level can be visually confirmed by reflected light.

[Example 1] Polyethylene terephthalate (PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.65 was melted and cast on a cooling drum. Stretched 6 times. Terephthalic acid (64
mol%)-isophthalic acid (36 mol%)-ethylene glycol (42 mol%)-diethylene glycol (15 mol%)-neopentyl glycol (39 mol)
1%)-polyethylene glycol having a molecular weight of 1000 (5
mol%), (A-1) 65 wt%, a repeating unit represented by the following formula (I-2), and a molecular weight of 1
A 10 wt% aqueous liquid having a solid content composition of 30 wt% of a polymer antistatic agent of 0000 and 5 wt% of polyoxyethylene lauryl ether is applied on one side of the film by a microgravure coating method at an application amount of 4 g / m ² (wet). did. After drying, the film was stretched 3.6 times in the transverse direction and heat-treated at 230 ° C. to obtain a laminated biaxially stretched polyester film for a surface protection film having a thickness of 100 μm. Table 1 summarizes the properties of this film.

[0091]

Embedded image

Example 2 Copolymerized polyester resin (A
-1) with methyl methacrylate (40 mol%), ethyl acrylate (45 mol%), acrylonitrile (10
mol%) and N-methylol methacrylamide (5 m
ol%), a laminated biaxially oriented polyester film for a surface protective film was obtained in exactly the same manner as in Example 1, except that the acrylic copolymer (number average molecular weight: 258,000) (B-1) was prepared. . Table 1 summarizes the properties of this film.

Example 3 The solid content of the copolymer was 30 wt% of the copolymerized polyester resin (A-1) and the acrylic copolymer (B
-1) Completely the same as Example 1 except that the composition was changed to 35 wt%, 30 wt% of the polymer antistatic agent composed of the repeating unit represented by the above formula (I-2), and 5 wt% of polyoxyethylene lauryl ether. Similarly, a laminated biaxially oriented polyester film for a surface protective film was obtained. Table 1 summarizes the properties of this film.

Example 4 As a polymer antistatic agent, [Y
^-] is C ₂ H ₅ SO ₃ ^- except for changing the antistatic agent (I-3), to obtain a surface protective film laminated biaxially oriented polyester film in the same manner as in Example 2. Table 1 summarizes the properties of this film.

Example 5 The solids content of the acrylic copolymer (B-1) was 49% by weight, the polymer antistatic agent comprising the repeating unit represented by the above formula (I-2) was 46% by weight, and polyoxyethylene lauryl was used. A laminated biaxially stretched polyester film for a surface protective film was obtained in exactly the same manner as in Example 1, except that the composition was changed to 5 wt% of ether.
Table 1 summarizes the properties of this film.

Example 6 The solid content was 88 wt% of the acrylic copolymer (B-1), 7 wt% of a polymer antistatic agent comprising a repeating unit represented by the formula (I-2), and polyoxyethylene lauryl. A laminated biaxially stretched polyester film for a surface protective film was obtained in exactly the same manner as in Example 1, except that the composition was changed to 5 wt% of ether. Table 1 summarizes the properties of this film.

[Example 7] Polyethylene terephthalate
A laminated biaxially oriented polyester film for a surface protective film was obtained in the same manner as in Example 2, except that (PET) was changed to polyethylene-2,6-naphthalate (PEN). Table 1 summarizes the properties of this film.

Comparative Example 1 The solid content of the copolymer was 82% by weight of the copolymerized polyester resin (A-1), 3% by weight of the polymer antistatic agent comprising the repeating unit represented by the formula (I-2), and polyoxyethylene. A laminated biaxially oriented polyester film for a surface protective film was obtained in exactly the same manner as in Example 1, except that the composition was changed to 5 wt% of lauryl ether. Table 1 summarizes the properties of this film.

[Comparative Example 2] The solid content was changed to methyl methacrylate (30 mol%) and ethyl acrylate (55 mol%).
1%), acrylonitrile (10 mol%) and N-methylol methacrylamide (5 mol%) acrylic copolymer (number average molecular weight: 262000)
(B-1) Example 1 was repeated except that the composition was changed to 35 wt%, a composition comprising 60 wt% of a polymer antistatic agent comprising the repeating unit represented by the formula (I-2) and 5 wt% of polyoxyethylene lauryl ether. A laminated biaxially oriented polyester film for a surface protection film was obtained in exactly the same manner. Table 1 summarizes the properties of this film.

Comparative Example 3 Except that the solid content composition was changed to a composition comprising 71 wt% of the copolymerized polyester resin (A-1) and the antistatic agent consisting of 24 wt% of sodium polystyrene sulfonate and 5 wt% of polyoxyethylene lauryl ether. In the same manner as in Example 1, a laminated biaxially oriented polyester film for a surface protective film was obtained. Table 1 summarizes the properties of this film.

Comparative Example 4 A solid content composition was changed to a composition comprising 71% by weight of a copolymerized polyester resin (A-1), 24% by weight of sodium dodecylbenzenesulfonate and 5% by weight of polyoxyethylene nonylphenyl ether. A laminated biaxially oriented polyester film for a surface protection film was obtained in exactly the same manner as in Example 1. Table 1 summarizes the properties of this film.

Comparative Example 5 The properties of the biaxially stretched polyester film obtained in Example 1 without coating the composition are shown in Table 1.

[0103]

[Table 1]

[Example 8] Polyethylene terephthalate (PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.65 was melted and cast on a cooling drum. Stretched 6 times. Methyl methacrylate (40 mol%) and ethyl acrylate (45 mol
%), Acrylonitrile (10 mol%) and N-methylol methacrylamide (5 mol%), an acrylic copolymer (number average molecular weight: 258,000) (B
-1) 4 g / m ^{2 of} a 10 wt% aqueous liquid having a solid content composition of 65 wt%, a polymer antistatic agent comprising 30 wt% of a repeating unit represented by the following formula (I-2) and 5 wt% of polyoxyethylene lauryl ether; (Wet) was applied on one side of the film by a microgravure coating method. After drying, stretched 3.6 times in the transverse direction,
To obtain a laminated biaxially oriented polyester film for a surface protective film having a thickness of 100 μm.

[0105]

Embedded image

A release layer was provided on this treatment layer. The release layer is composed of 40 parts by weight of polyethyleneimine octadecyl carbamate (manufactured by Nippon Shokubai Co., Ltd., RP-20), and a polyester resin (Hitachi Chemical Industry Co., Ltd.) as a binder component.
100 parts by weight, manufactured by Espel 1510) and melamine resin (Nikarac NS-11, manufactured by Sanwa Chemical Co., Ltd.) 3
A coating liquid obtained by mixing 0 parts by weight was applied so that the thickness after drying became 0.2 μm, and dried and cured at 140 ° C. for 1 minute to prepare a coating liquid.

On the other hand, as the acrylic pressure-sensitive adhesive, 2-ethylhexyl acrylate (main monomer), n-butyl acrylate (main monomer), vinyl acetate (comonomer), and hydroxyethyl methacrylate (functional group-containing monomer) were 5: 2: 2. : 1 part by weight of the composition and an additive composed of epoxy-modified stearyl acrylate were added in an amount of 0.5 part by weight of the latter additive to 10 parts by weight of the former composition. Was subjected to solution polymerization using azobisisobutyronitrile as a reaction catalyst to prepare a pressure-sensitive adhesive polymer having a weight average molecular weight of about 350,000. After adding a TDI-based isocyanate cross-linking agent to this pressure-sensitive adhesive polymer, it was applied to one surface of a release paper so that the thickness after drying was 15 μm, to obtain a laminate of the release paper and the pressure-sensitive adhesive.

Then, a corona treatment is applied to the surface of the laminated polyester film opposite to the surface on which the release layer is laminated, the surface of the laminated body on the side of the pressure-sensitive adhesive is laminated, dried at 100 ° C. for 2 minutes, and wound up. Aging treatment was performed at 45 ° C. for one week to obtain a laminate of the surface protective film and the release paper. Table 2 shows the properties of the obtained surface protective film.

[Example 9] In Example 8, the composition used for solution polymerization of the acrylic pressure-sensitive adhesive was changed to 2-ethylhexyl acrylate, n-butyl acrylate, vinyl acetate and hydroxyethyl methacrylate in the form of 2:
Changed to a mixture in a weight ratio of 4: 2.5: 1.5,
The same operation was repeated except that the amount of the epoxy-modified stearyl acrylate was changed to 0.7 parts by weight with respect to 10 parts by weight of the composition. The weight average molecular weight of the obtained pressure-sensitive adhesive polymer was about 400,000. The thickness of the pressure-sensitive adhesive layer applied to the release paper was 5 μm. Table 2 shows the properties of the obtained surface protective film.

[Example 10] In Example 8, the composition used for solution polymerization of the acrylic pressure-sensitive adhesive was changed to 2-ethylhexyl acrylate, vinyl acetate and hydroxyethyl methacrylate in a ratio of 7.5: 1.5: 1. The same operation was repeated except that the mixture was changed to a mixture by weight, and the addition amount of the epoxy-modified stearyl acrylate was changed to 0.8 parts by weight with respect to 10 parts by weight of the composition. The weight average molecular weight of the obtained pressure-sensitive adhesive polymer was about 440,000. The thickness of the pressure-sensitive adhesive layer applied to the release paper was 23 μm.
And Table 2 shows the properties of the obtained surface protective film.

[Comparative Example 6] In Example 8, the composition used for solution polymerization of the acrylic pressure-sensitive adhesive was prepared by mixing 2-ethylhexyl acrylate, n-butyl acrylate and hydroxyethyl methacrylate in a weight ratio of 7: 2: 1. And the addition amount of the epoxy-modified stearyl acrylate was changed to 0.1 with respect to 10 parts by weight of the composition.
The same operation was repeated except that the weight part was changed. Table 2 shows the properties of the obtained surface protective film.

[Comparative Example 7] In Example 8, the base material of the surface protective film was a polyethylene film having a density of 0.925 and a melt index of 2.5 formed by inflation. The same operation was repeated, except that the procedure was changed to. Table 2 shows the properties of the obtained surface protective film.

[Comparative Example 8] In Example 8, the composition used for solution polymerization of the acrylic pressure-sensitive adhesive was changed to 2-ethylhexyl acrylate, n-butyl acrylate, vinyl acetate and hydroxyethyl methacrylate in the form of 2:
The same operation was repeated except that the mixture was changed to a mixture having a weight ratio of 3: 3: 2, and the addition amount of the epoxy-modified stearyl acrylate was changed to 2 parts by weight with respect to 10 parts by weight of the composition. The weight average molecular weight of the obtained polymer for a pressure-sensitive adhesive was about 250,000. The thickness of the pressure-sensitive adhesive layer applied to the release paper was 10 μm. Table 2 shows the properties of the obtained surface protective film.

[0114]

[Table 2]

[0115]

The laminated polyester film for a surface protective film according to the present invention is transparent, has less friction and less electrification when peeled off, is less likely to adhere to the surface, and is less likely to adhere to the surface. An improved pressure-sensitive adhesive layer is provided that peels off from the protective surface lightly regardless of time, and does not impair the testability of the bonded protected surface,
It is useful for surface protection of optical components such as a display.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 33/26 C08L 33/26 67/00 67/00 G02B 1/10 G02B 5/30 5/30 1 / 10 Z F term (reference) 2H049 BB13 BB20 BB23 BB28 BB51 BB54 BC03 BC14 BC22 2K009 BB24 CC24 CC34 DD02 DD06 EE03 4F006 AA35 AB24 AB35 AB69 BA07 CA05 4F100 AH03B AK25B AK41B AK42 BA10 BA00 BA10 BA00 BA02 BA00 GB41 GB90 JA05C JG01 JG04 JK02C JL06 JL13C JL14D JN01D YY00C YY00D 4J002 BC12W BG01W BG04W BG05W BG06W BG07W BG13W BG13X BQ00W CD19W CF03W CF04W CF05W CF10W EU14FDCH02

Claims (9)

[Claims] At least one surface of at least one binder resin selected from (1) a copolymerized polyester resin and an acrylic copolymer is provided on at least one surface of a polyester film.
85% by weight, (2) 5 to 50% by weight of an antistatic agent mainly composed of a repeating unit having a structure represented by the following formula (I), and (3) 1 to 10% by weight of a surfactant. A laminated film on which a protective coating is applied,
Length width of 148mm sides orthogonal thereto and length 210mm of one side of the film (area 310.8cm ²⁾ per absent size 25μm or more foreign objects, size 5μ
m and less than 25 μm, and the film has a surface resistivity of 2 at 23 ° C. and 50% humidity.
× 10 ¹¹ (Ω / □) or less, a laminated polyester film for a surface protection film. Embedded image (However, R ¹ and R ² in the formula are each hydrogen or a methyl group,
R ³ is an alkylene group having 2 to 10 carbon atoms, R ^4, R ⁵ are each a saturated hydrocarbon group having 1 to 5 carbon atoms, R ⁶ is a carbon number 2
10 to 10 alkylene groups, m is a number of 1 to 20, n is 1 to 40
The number of, Y ^- is a halogen ion, a mono- or polyhalogenated alkyl ion, nitrate ion, sulfate ion, alkyl sulfate ion, sulfonate ion or an alkyl sulfonate ion. ) 2. An antistatic coating comprising a composition comprising (1) 50 to 80% by weight of a binder resin, (2) 10 to 40% by weight of an antistatic agent, and (3) 3 to 10% by weight of a surfactant. The laminated polyester film for a surface protective film according to claim 1, which is a coating containing the same. 3. An antistatic coating comprising: (1) 40 to 85% by weight of at least one kind of binder resin selected from a copolymerized polyester resin and an acrylic copolymer; and (2) the formula (I). 5 to 50% by weight of an antistatic agent mainly composed of a repeating unit having a structure and (3) surfactant 1
The laminated polyester film for a surface protective film according to claim 1, wherein an aqueous coating liquid containing a composition of from 10 to 10% by weight is applied to at least one surface of the film, dried and stretched. 4. The laminated polyester film for a surface protective film according to claim 1, wherein the polyester film is a film made of polyethylene terephthalate or polyethylene-2,6-naphthalate. 5. A composite film comprising the laminated polyester film according to claim 1, wherein an adhesive layer is provided on one surface and a protective layer is provided on the other surface, wherein the adhesive layer has the following (a) to (c).
Characteristics of (f) (a) Glass transition temperature is −60 ° C. or more and −20 ° C. or less, (b) Tensile modulus is 0.1 MPa or more and 0.2 MPa.
(C) The surface tension is 15 μN / cm or more and 25 μN / cm or less. (D) The adhesive force (A) after being stuck to a stainless steel plate and left at 60 ° C. for 1 day is 30 mN / 25 mm or more and 500 or more.
mN / 25 mm or less. (e) The value obtained by dividing the adhesive force (B) after being stuck to a stainless steel plate and allowed to stand at 60 ° C. for 1 week by the adhesive force (A) is 0.5.
(2) and (f) a thickness of 3 μm or more and 50 μm or less. 6. The protective layer contains a release agent, and the peel strength of the protective layer from the pressure-sensitive adhesive layer is 10 mN / 25 mm or more.
The surface protective film according to claim 5, which has a thickness of 000 mN / 25 mm or less. 7. The visible light transmittance of the surface protective film is 7
The surface protective film according to claim 5, wherein the haze is 0% or more and the haze is 10% or less. 8. The surface protective film according to claim 5, which is used for protecting the surface of an optical component. 9. The surface protection film according to claim 8, wherein the optical component is a polarizing plate, a retardation plate, a viewing angle widening film, or a laminate thereof.