JP3527051B2 - Antistatic polyester film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic polyester film, and more specifically, coating appearance, transparency,
The present invention relates to an antistatic polyester film having excellent adhesiveness, blocking property under high humidity, and antistatic property under low humidity.

[0002]

2. Description of the Related Art Biaxially stretched polyester films are used in a wide range of applications because they are excellent in transparency, dimensional stability, mechanical properties, electrical properties and chemical resistance.

However, a general polyester film is
Since it has a high degree of electrical insulation, static electricity is likely to be generated and accumulated, which causes various failures due to static electricity. Among them, although it has been widely used as a film for OHP, the conventional polyester film for OHP has insufficient antistatic property and is a state where two or more films are overlapped by static electricity charged when used in a copying machine. This may cause troubles such as being transported (hereinafter referred to as “double feeding”).

Conventionally, as a method for improving the antistatic property, a method of kneading an anionic compound such as an organic sulfonate, a metal powder, a carbon powder or the like into a base film, a method of depositing a metal compound, etc. Is known,
There were problems such as a decrease in transparency and a high processing cost.

As a method for improving the antistatic property, there is known a method of forming a coating film on the film surface with a synthetic resin (binder) to which an antistatic agent is added in advance. In this case, an anionic compound or a cationic compound having a good coating property is used as the antistatic agent, but these have poor antistatic properties under low humidity. This drawback can be improved to some extent by using a large amount, but in this case, there is a new problem that the films are easily attached to each other (hereinafter referred to as blocking) due to their hydrophilicity under high humidity. As described above, it has been difficult for conventional antistatic agents to exhibit antiblocking properties and to satisfy antistatic properties under low humidity.

By the way, the phosphoric acid type antistatic agent is excellent in antistatic property even under low humidity, and is applied as a coating solution on an unstretched or uniaxially stretched polyester film, and then stretched and heat treated. It is disclosed in Japanese Patent Application Laid-Open No. 6-255055, Japanese Patent Publication No. 1-49114, etc. that excellent conductivity and antistatic property are exhibited even in the coating method). However, in this method, the wettability of the phosphoric acid-based antistatic agent to the polyester film is poor and thus the coatability is poor, and a good coating appearance cannot be obtained without pretreatment such as corona discharge treatment, and its application is It was limited. Further, there is a drawback that adhesion of toner, printing ink, etc. is impaired by bleeding out of the antistatic agent on the surface of the coating film.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that a specific surfactant and fine particles of a phosphate ester salt type antistatic agent having a branched alkyl chain. By combining with, it can be applied well as a coating liquid without pretreatment such as corona discharge treatment, so it can be manufactured at low processing cost, and has excellent coating appearance, antistatic property, blocking property and adhesiveness with time. It was found that an extremely useful antistatic polyester film having the following can be obtained, and the present invention has been completed.

[0008]

That is, the present invention provides (1) a phosphate ester salt-based antistatic agent having a branched alkyl chain on at least one side of a polyester film 5 to 40.
% By weight, (2) 1-20% by weight of a surfactant having an HLB of 12 or less, (3) 40-90% by weight of at least one binder selected from acrylic copolymers and polyester copolymers, and (4) average. Fine particles with a particle size of 10 to 500 nm 3 to 25% by weight
It is an antistatic polyester film obtained by applying a coating agent containing the composition, and then drying and stretching to apply a coating film.

In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene-2,6.
Examples thereof include naphthalene dicarboxylate, and copolymers of these or blends of these with small proportions of other resins are also included. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferable.

These polyesters are used, if necessary, for example, inorganic lubricants such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, titanium oxide, barium sulfate, crosslinked silicone resins and crosslinked polystyrene resins. Contains organic lubricants such as crosslinked acrylic resins, urea resins, melamine resins, etc., other resins such as polyethylene, polypropylene, ethylene-propylene copolymers, olefinic ionomers, antioxidants, UV absorbers, optical brighteners, etc. You can also do it.

In the present invention, the polyester film is a biaxially stretched film, preferably a transparent biaxially stretched film. Its thickness is 5-500 μm, preferably 20-500 μm,
Particularly preferably, it is 50 to 300 μm. If the thickness is less than 5 μm, the film may be stiff and unsuitable for some applications. On the other hand, if the film is too thick, for example, more than 500 μm, the film-forming property tends to be poor.

In the present invention, the antistatic coating provided on at least one surface of the polyester film is (1) a phosphate ester salt-based antistatic agent having a branched alkyl chain.
-40% by weight, (2) HLB 12 or less surfactant 1-20
% By weight, at least one binder selected from (3) acrylic copolymers and polyester copolymers 40 to 9
0% by weight and (4) Fine particles with an average particle size of 10 to 500 nm 3 to 2
After applying a coating containing a composition of 5% by weight, drying,
It is formed by stretching.

In the present invention, the phosphoric acid ester salt-based antistatic agent that constitutes the coating material must have a branched alkyl chain. When it has only a linear alkyl chain, it is not preferable because it is inferior in the adhesiveness with time. Examples of the phosphoric acid ester salt-based antistatic agent having a branched alkyl chain include conventionally known compounds. Among them, phosphoric acid ester salt-based low molecular weight compounds, for example, phosphoric acid isohexyl ester sodium salt, phosphorus Acid isohexyl ester potassium salt, phosphoric acid-sec-isohexyl ester sodium salt,
Phosphoric acid-sec-isohexyl ester potassium salt, phosphoric acid isoamyl ester sodium salt, phosphoric acid isoamyl ester potassium salt, phosphoric acid-sec-isoamyl ester sodium salt, phosphoric acid-sec-isoamyl ester potassium salt, phosphoric acid isobutyl ester sodium salt Salt, phosphoric acid isobutyl ester potassium salt, phosphoric acid-t-butyl ester sodium salt, phosphoric acid-t-butyl ester potassium salt, phosphoric acid diisohexyl ester sodium salt, phosphoric acid diisohexyl ester potassium salt, phosphoric acid diester -sec
-Isohexyl ester sodium salt, phosphoric acid di-sec-isohexyl ester potassium salt, phosphoric acid diisoamyl ester sodium salt, phosphoric acid diisoamyl ester potassium salt, phosphoric acid diisoamyl ester sodium salt, phosphoric acid diisoamyl ester potassium salt , Phosphate di-sec-
Preferred examples include isobutyl ester sodium salt, phosphoric acid di-sec-isobutyl ester potassium salt, phosphoric acid di-t-butyl ester sodium salt, phosphoric acid di-t-butyl ester potassium salt and the like. 1 selected from these
It is preferable to use one or a plurality of combinations. Among these, isoamyl phosphate sodium salt,
Phosphoric acid isoamyl ester potassium salt, phosphoric acid diisoamyl ester sodium salt, and phosphoric acid diisoamyl ester potassium salt are preferable.

In the present invention, the surfactant has an HLB of 1
2 or less surfactant. Here, HLB is Hydro
Abbreviation for hile-Lipophile Balance, it is a numerical representation of the balance of lipophilic and hydrophilic moieties in the molecule of the surfactant, and was proposed by Griffin of Atlas. The value can be calculated by the following formula (I).

[0015]

## EQU1 ## HLB = 20 (1-M _O / M) (where M _O is the molecular weight of the hydrophobic group and M is the molecular weight of the surfactant). The branched alkyl chain that constitutes the coating material in the present invention is The phosphate ester salt-based antistatic agent (1) has a drawback that coating repellency is likely to occur on the polyester film due to its high hydrophilicity, but when the above-mentioned low HLB surfactant is used in combination, The property is relaxed and uniform application becomes possible. When HLB exceeds 12, hydrophilicity becomes strong and cissing application spots occur.

As the surfactant having an HLB of 12 or less,
For example, polyethylene oxide / polypropylene oxide block copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene monoalkylate, polyoxyethylene fatty acid ester, sorbitan fatty acid ester,
Examples thereof include glycerin fatty acid ester. In some cases, these can be combined with other surfactants having an HLB of more than 12 in a range that does not cause coating unevenness.

Acrylic acid is used as a constituent of the acrylic copolymer used as a binder in the present invention.
Methyl acrylate, ethyl acrylate, butyl acrylate, sodium acrylate, ammonium acrylate, 2-
Hydroxyethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, sodium methacrylate, ammonium methacrylate,
2-hydroxyethyl methacrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-
Examples thereof include methylol acrylamide and N-methylol methacrylamide. These monomers include, for example, styrene, vinyl acetate, acrylonitrile,
It can also be used in combination with other unsaturated monomers such as methacrylonitrile, vinyl chloride, vinylidene chloride and divinylbenzene. The acrylic copolymer can also be used as a modified acrylic copolymer, for example, a block polymer or graft polymer obtained by modifying an acrylic copolymer with polyester, polyurethane, silicone, epoxy, phenol resin or the like.

In the present invention, the acid component forming the polyester copolymer includes terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, phthalic anhydride, 1,4-cyclohexanedicarboxylic acid, adipic acid, Examples include sebacic acid, phenylindanedicarboxylic acid, dimer acid and the like. Two or more kinds of these components can be used. Further, a small proportion of an unsaturated polybasic acid such as maleic acid, fumaric acid or itaconic acid or a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p- (β-hydroxyethoxy) benzoic acid may be used together with these components. it can. The proportion of unsaturated polybasic acid component and hydroxycarboxylic acid component is at most 10 mol%, preferably
It is 5 mol% or less.

The polyol component forming the polyester copolymer is ethylene glycol, 1,4-
Butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, poly (ethylene oxide) glycol, poly Examples thereof include (tetramethylene oxide) glycol, and ethylene oxide adducts and propylene oxide adducts of bisphenol A. These can use 2 or more types.

Among such polyol components, ethylene glycol, ethylene oxide adducts of bisphenol A and propylene oxide adducts, and 1,4-butanediol are preferable, and ethylene glycol is more preferable.
It is an ethylene oxide adduct or propylene oxide adduct of bisphenol A.

In order to facilitate the aqueous liquefaction of the polyester, it is possible and preferable to copolymerize a small amount of a compound having a sulfonate group or a compound having a carboxylic acid group.

Examples of such sulfonate group-containing compounds include 5-Nasulfoisophthalic acid, 5-ammoniumsulfoisophthalic acid, 4-Nasulfoisophthalic acid, 4-methylammoniumsulfoisophthalic acid, 2-
Na sulfoisophthalic acid, 5-K sulfoisophthalic acid,
Examples thereof include alkali metal sulfonate-based compounds such as 4-K sulfoisophthalic acid, 2-K sulfoisophthalic acid, and Na sulfosuccinic acid, or sulfonate amine salt-based compounds.

Examples of the carboxylic acid group-containing compound include trimellitic anhydride, trimellitic acid, pyromellitic dianhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid and the like, or their monoalkalis. Examples thereof include metal salts.

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

The binder polyester copolymer or acrylic copolymer in the present invention also exhibits easy adhesion (adhesion), and exhibits an excellent adhesion action to, for example, an OHP toner. From the viewpoint of this adhesive action, the polyester copolymer is more preferable.

In the present invention, the fine particles include inorganic fine particles such as calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide and zinc oxide, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles and fluororesin particles. Examples include organic fine particles such as crosslinked silicone resin particles and polyolefin particles. The particle size of the fine particles is 10 to 500 nm, preferably 20 to 300 nm. If the particle size of the fine particles is less than 10 nm, the blocking property tends to decrease, while if it exceeds 500 nm, the transparency tends to decrease.

In the present invention, the phosphate ester salt-based antistatic agent (1) having a branched alkyl chain and HLB is 12
The following surfactant (2), at least one binder selected from an acrylic copolymer and a polyester copolymer (3) and a composition comprising fine particles (4), the phosphate ester salt having a branched alkyl chain The proportion of the antistatic agent (1) is 5 to 40% by weight, preferably 10 to 30% by weight.
If this ratio exceeds 40% by weight, the blocking property and the adhesiveness will be insufficient, while if it is less than 5% by weight, the antistatic property will be insufficient, such being undesirable. The ratio of surfactant (2) is 1
-20% by weight, preferably 3-15% by weight. If this proportion exceeds 20% by weight, the blocking property becomes insufficient, while if it is less than 1% by weight, the wettability of the coating material to the polyester film is insufficient and the coating appearance deteriorates, which is not preferable. The proportion of fine particles (4) is 3 to 25% by weight, preferably 5 to
20% by weight. If this proportion exceeds 25% by weight, the transparency will decrease, while if it is less than 3% by weight, the blocking property will deteriorate, such being undesirable.

The antistatic coating material in the present invention is preferably an aqueous coating material, but it can also be used as a coating material (organic coating material) using an organic solvent as a solvent. Examples of the solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol, n.
-Propanol, isopropanol and the like can be exemplified. These may be used alone or in combination of two or more.

Such a coating agent may be, for example, an ultraviolet absorber, a pigment, a defoaming agent, or the like, as long as the object of the present invention is not impaired.
Addition of other additives such as coatability improver, lubricant, antiblocking agent, melamine-based, urea-based, guanamine-based, epoxy-based, aziridine-based, blocked isocyanate-based cross-linking agents, coupling agents, etc. You can

The solid content concentration of the coating material in the present invention is usually
It is 30% by weight or less, more preferably 20% by weight or less. This solid content concentration is preferably 0.4% by weight or more.

In the present invention, a coating agent containing the above-mentioned components is applied to at least one side of a polyester film, which is a polyester film before crystal orientation is completed.

As the polyester film before completion of the crystal orientation, an unstretched film obtained by melt-extruding polyester to form a film as it is, or an unstretched film was stretched and oriented in either the longitudinal direction or the transverse direction. Examples include a uniaxially stretched film, and a low-stretch stretched and oriented film in both the longitudinal and transverse directions (a biaxially stretched film before it is finally re-stretched in the longitudinal or transverse direction to complete the oriented crystallization). can do. Among these,
A film uniaxially stretched in the machine direction is preferred.

As a method of applying the coating agent to the polyester film, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a micro gravure coating method, a reverse coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method and a curtain coating method may be applied alone or in combination. The aqueous coating composition may contain a small amount of an organic solvent for the purpose of assisting the stability of the coating composition or the coating property of the coating composition.

The coating amount is preferably 0.5 to 50 g, more preferably 5 to 30 g per 1 m ² of the running film. The thickness of the final dry coating film (coating) is required to be 0.01 to 1 μm, preferably 0.02 to 0.6 μm. Coating thickness is 0.0
If it is less than 1 μm, sufficient antistatic property cannot be obtained.
On the other hand, when it exceeds 1 μm, the blocking property is deteriorated, which is not preferable.

The coating can be carried out on one side only or on both sides depending on the intended use of the film. After coating, it is dried to form a uniform coating film.

In the present invention, the polyester film is coated with the coating material and then dried and stretched. The drying is preferably carried out at 90 to 130 ° C. for 2 to 20 seconds. This drying can also serve as a preheat treatment for the stretching treatment or a heat treatment during the stretching.

The polyester film is stretched at a temperature
It is preferable to stretch at 70 to 140 ° C in the longitudinal direction of 2.5 to 7 times, in the transverse direction of 2.5 to 7 times, and in area magnification of 8 times or more, and further 9 to 28 times. In the case of re-stretching, it is preferable to stretch at a draw ratio of 1.05 to 3 times (however, the area magnification is the same as above). After stretching, the heat setting treatment is performed at a temperature higher than the final stretching temperature and below the melting point.
It is preferably carried out for 1 to 30 seconds. For example, polyethylene terephthalate film is preferably heat set at 170 to 240 ° C. for 2 to 30 seconds.

The antistatic polyester film thus obtained has, for example, a light transmittance of 90% or more, and a surface specific resistance (temperature 23 ° C., humidity 35%) of 1 × 10 ^12.
Ω / □ or less, and further, 1 × 10 ¹⁰ to 1 × 10 ¹¹ Ω / □, the film appearance, transparency, adhesiveness, humidity resistance under high humidity,
It has excellent antistatic properties under low humidity and does not deteriorate in adhesiveness over time, so it can be used for image receiving paper, magnetic tape, display, OHP, printing, plate making, packaging film, etc. And is particularly useful as an OHP film and a plate-making film.

[0039]

EXAMPLES The present invention will be further described below with reference to examples. The characteristics in the examples were obtained by the following methods.

1. Appearance of coating of coating film The appearance of coating of coating film is visually determined. The case where the coated surface is uniform and has no defects is marked with ◯, and the case where there are spots or cissing defects is marked with x.

2. Light transmittance (transparency) Measured by a Murakami Color Research Laboratory HR-100 type haze meter according to ASTM D1003.

3. Friction coefficient (sliding property) According to ASTM D1894-63, using a slippery measuring machine manufactured by Toyo Tester Co., Ltd., the front surface and the back surface of the film are aligned, and a static friction coefficient (μs) is measured by applying a load of 1 kg.

4. Blocking property (moisture resistance) The front surface and the back surface of a sample film cut into a width of 50 mm are combined, and under a load of 50 Kg / cm ² , 60 ° C. × 80% R
After treating with H for 17 hours, the peel strength (g / 50 mm) of the portion where the load is applied is measured by a tensile tester. The peel strength is evaluated as follows. Good blocking property: Peeling strength ≤ 10 Blocking property: Somewhat good: 10 <Peeling strength ≤ 30 Poor blocking property: 30 <Peeling strength

5. Toner Adhesion with Time (Adhesion Change with Time) After the coated film is treated at 60 ° C. × 80% RH for 17 hours, information is printed with a copying machine (vivace 500 type machine) manufactured by FUJI XEROX. Toner adhesion is observed and evaluated.

6. Surface resistivity (antistatic property) The surface resistivity of the sample film was measured by Takeda Riken.
Using a specific resistance measuring instrument, measuring temperature 23 ℃, measuring humidity 35%
Under the condition, the surface specific resistance value (Ω / □) after 1 minute at an applied voltage of 500 V is measured. It is preferably 1 × 10 ¹¹ Ω / square or less.

Example 1 Copolyester (Tg) having an intrinsic viscosity of 0.51 made from terephthalic acid, isophthalic acid, 5-Nasulfoisophthalic acid, ethylene glycol, and an ethylene oxide adduct of bisphenol A represented by the following structural formula. = 77 ° C.) was adjusted to an aqueous dispersion having a solid content concentration of 5% to obtain an aqueous liquid A.

On the other hand, a polyester made from terephthalic acid and ethylene glycol (intrinsic viscosity 0.65) was used at 20 ° C.
Melt-extruded on a rotary cooling drum maintained at 1, to obtain an unstretched film, and then stretched by 3.6 times in the machine axis direction, and then 60% by weight of the above-mentioned aqueous liquid A and diisoamyl ester phosphate potassium salt as an antistatic agent. Aqueous solution (concentration 5% by weight) 2
0% by weight and 10% by weight of an aqueous solution of polyoxyethylene nonyl ether (HLB = 11.3) as a surfactant (concentration 5% by weight) and crosslinked acrylic resin particles (particle size 60 n
An aqueous coating agent prepared by mixing 10% by weight of an aqueous dispersion (m) of concentration 5% by weight) was applied to both sides of the film by a kiss coating method in an amount of 5 g / m ² (wet). Subsequently, the film was stretched 3.9 times in the transverse direction to obtain a coating-coated biaxially stretched polyester film having a thickness of 100 μm.

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time and surface resistivity of the treated surface of this film are summarized in Table 1.

[Example 2] An acrylic copolymer (number average molecular weight: 263000) prepared from methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate and N-methylol methacrylamide was used at a solid concentration of 5%.
Aqueous dispersion B was prepared to obtain aqueous liquid B.

The aqueous liquid A used in Example 1 was replaced with the above aqueous liquid B.
A biaxially stretched polyester film coated with a coating film was obtained in exactly the same manner as in Example 1 except that

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time and surface specific resistance of the treated surface of this film are summarized in Table 1.

Example 3 The surfactant used in Example 1 was polyoxyethylene nonylphenyl ether (HLB).
A biaxially stretched polyester film coated with a coating film was obtained in exactly the same manner as in Example 1 except that the film thickness was changed to 10.7).

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion over time and surface resistivity of the treated surface of this film are summarized in Table 1.

[Example 4] The aqueous coating composition used in Example 1 was prepared by adding 35% by weight of an aqueous solution A, 30% by weight of an aqueous solution B, and an aqueous solution of potassium diisobutyl ester phosphate as an antistatic agent (concentration: 5% by weight). %) 20% by weight and polyoxyethylene nonylphenyl ether (HLB) which is a surfactant.
= 10.8) aqueous solution (concentration 5% by weight) and an aqueous dispersion (concentration 5% by weight) of crosslinked polystyrene resin particles (particle size 120 nm) 5% by weight. A coated film-coated biaxially stretched polyester film was obtained in exactly the same manner as in Example 1 except for changing the above.

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time and surface specific resistance of the treated surface of this film are summarized in Table 1.

Comparative Example 1 A biaxially stretched polyester film coated with a coating film was prepared in the same manner as in Example 1 except that the antistatic agent used in Example 1 was changed to potassium di-n-amyl ester phosphate. Obtained.

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time and surface resistivity of the treated surface of this film are summarized in Table 1.

Comparative Example 2 A biaxially stretched polyester film coated with a coating film was prepared in the same manner as in Example 1 except that the antistatic agent used in Example 1 was changed to potassium di-n-butyl ester phosphate. Obtained.

The coating appearance, light transmittance, friction coefficient, blocking property, aging toner adhesion and surface resistivity of the treated surface of this film are shown in Table. It shows collectively in 1.

[Comparative Example 3] The surfactant used in Example 1 was polyoxyethylene nonyl phenyl ether (HLB).
A biaxially stretched polyester film coated with a coating film was obtained in exactly the same manner as in Example 1 except that the change was made to 14.2).

Table 1 shows the coating appearance, light transmittance, friction coefficient, blocking property, aging toner adhesion property and surface specific resistance of the treated surface of this film.

Comparative Example 4 The coating composition used in Example 1 was 30% by weight of aqueous liquid A, and an aqueous solution of diisoamyl ester phosphate potassium salt as an antistatic agent (concentration 5% by weight) 5
0% by weight, 10% by weight of an aqueous solution of polyoxyethylene nonylphenyl ether (HLB = 10.7) as a surfactant (concentration 5% by weight), and an aqueous solution of crosslinked acrylic resin particles (particle size 60 nm) (concentration 5% by weight) %) A biaxially stretched polyester film coated with a coating film was obtained in exactly the same manner as in Example 1 except that the coating composition was changed to 10% by weight.

Table 1 shows the coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time, and surface resistivity of the treated surface of this film.

Comparative Example 5 The coating composition used in Example 1 was prepared by using 70% by weight of aqueous liquid A and an aqueous solution of potassium diisoamyl ester phosphate as an antistatic agent (concentration: 5% by weight).
Same as Example 1 except that the coating composition was changed to 0% by weight and 10% by weight of an aqueous solution (concentration 5% by weight) of polyoxyethylene nonylphenyl ether (HLB = 10.7) which is a surfactant. To obtain a coating film-covered biaxially stretched polyester film.

Table 1 shows the coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion property over time, and surface resistivity of the treated surface of this film.

[Comparative Example 6] Example 1 was repeated except that the antistatic agent used in Example 1 was changed to sodium dodecyl sulfonate.
A biaxially stretched polyester film coated with a coating film was obtained in the same manner as in.

The coating appearance, light transmittance, friction coefficient, blocking property, toner adhesion with time, and surface resistivity of the treated surface of this film are summarized in Table 1.

Comparative Example 7 The light transmittance, the friction coefficient, the blocking property, the toner adhesion property over time and the surface specific resistance of the surface of the biaxially stretched polyester film obtained in Example 1 without applying the coating liquid are shown. It shows collectively in 1.

[0069]

[Table 1]

[0070]

EFFECTS OF THE INVENTION In the present invention, since an antistatic coating film of a specific composition is provided on at least one side of a polyester film, it has an excellent coating appearance, and has blocking properties under high humidity and electrostatic charge under low humidity. It is possible to provide an antistatic polyester film having excellent preventive properties and having no change in adhesiveness over time, and it is particularly useful as a film for OHP and plate making.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-76443 (JP, A) JP-A-9-141802 (JP, A) JP-A-9-31225 (JP, A) JP-A-7- 156357 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08J ⁷ /04-7/06 B05D 5/12 B32B 7/02 B32B 27/00-27/42

Claims (10)

(57) [Claims] 1. A polyester film having at least one side thereof (1) 5-40% by weight of a phosphate ester salt-based antistatic agent having a branched alkyl chain, and (2) 1-20% by weight of a surfactant having an HLB of 12 or less. , (3) at least one binder selected from acrylic copolymers and polyester copolymers 40 to 90% by weight, and (4) a coating containing a composition consisting of 3 to 25% by weight of fine particles having an average particle size of 10 to 500 nm. An antistatic polyester film obtained by applying a coating agent, then drying and stretching to apply a coating film. 2. The amount of the phosphate ester salt-based antistatic agent having a branched alkyl chain is 10 to 30% by weight.
The antistatic polyester film described in 1. 3. The amount of surfactant having an HLB of 12 or less is 3
The antistatic polyester film according to claim 1, which is -15% by weight. 4. The antistatic polyester film according to claim 1, wherein the amount of fine particles is 5 to 20% by weight. 5. The antistatic polyester film according to claim 1, wherein the binder is a polyester copolymer. 6. The antistatic polyester film according to claim 1, wherein the branched alkyl chain is an isoamyl group. 7. The antistatic polyester film according to claim 1, wherein the coating has a thickness of 0.01 to 1 μm. 8. The antistatic polyester film according to claim 1, wherein the polyester film is a transparent film. 9. A plate-making film comprising the antistatic polyester film according to claim 8. 10. A film for OHP comprising the antistatic polyester film according to claim 8.