JPH0720691B2 - Laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laminated polyester film. More specifically, it relates to a laminated polyester film having excellent properties as a base material for magnetic recording materials.

[Conventional technology]

The biaxially stretched polyester film is widely used as a magnetic recording medium base because it has excellent properties such as mechanical properties and dimensional stability. However, recently, there is a technical idea that the magnetic recording medium has a higher recording density and a longer recording time, and in addition to this, the base film is required to have various characteristics. In particular, magnetic tapes have the drawbacks that recording dust (drop-out) may occur due to the adhesion of dust due to static electricity generated during running, or tape misalignment or stray winding may occur. For this reason, it is essential that the magnetic recording medium has antistatic properties, and that the antistatic property of the magnetic recording medium is the antistatic property of the base film. It is considered to be indispensable for this purpose, and various studies have been made in the past. As such a polyester film, (1) a polyester film in which conductive carbon black is uniformly dispersed by a kneading method to impart antistatic properties. (Japanese Patent Publication No. 59-18804) (2) A polyester film having an antistatic property imparted by coating an organic polymer binder containing conductive carbon black on the film surface.

(3) A polyester film having antistatic properties imparted by coating or kneading a surfactant.

(4) A polyester film provided with an antistatic property by forming a metal thin film on the film surface by a vacuum vapor deposition method, sputtering, ion plating, electroplating or the like.

Are known.

[Problems to be solved by the invention]

However, the above-mentioned polyester film imparted with antistatic properties has the following problems.

In the above item (1), it is necessary to add 10% by weight or more of conductive carbon black in order to develop the antistatic property. However, when the addition amount is 3% by weight or more, the melt viscosity of the polymer is lowered and it becomes difficult to form an oriented film. Further, since the surface roughness of the film is promoted by the mixed particles, it becomes a base material on which recording is easily lost.

In the above item (2), the desired antistatic property can be obtained, but since the surface resistance in the longitudinal direction and the width direction of the film has no anisotropy, when used as a base material for a magnetic tape, winding deviation or stray winding occurs. Is more likely to occur.

In the above item (3), since neither durable nor antistatic effect can be obtained, the amount of charge increases during use, and it becomes easy to adsorb dust and the like. Furthermore, the antistatic property does not appear under the environmental conditions during use, especially in a dry atmosphere such as a relative humidity of 5% RH or less.

Further, in the above item (4), since the adhesive force between the film and the metal thin film formed on the surface is weak, when the magnetic tape substrate is used, running durability is poor and the magnetic layer is peeled or dropped.

The present invention solves these drawbacks of the prior art and provides a laminated polyester film having excellent running stability and antistatic property as a base material of a magnetic recording material.

[Means for solving problems]

The present invention is a laminated polyester film having a water-soluble polyester resin layer containing diethylene glycol and / or triethylene glycol containing conductive carbon black on at least one surface of the polyester film, wherein one surface of the water-soluble polyester resin layer is Direction (MD)
A laminated polyester film having a ratio (R _M / R _T ) of the resistance value R _{M of the above} to the resistance value R _T thereof in the direction (TD) is 1.03 to 3.0.

The polyester referred to in the present invention is a well-known one, specifically, terephthalic acid / isophthalic acid / naphthalenedicarboxylic acid / bis-α, β (2-chlorophenoxy) ethane-4,4′-dicarboxylic acid / adipine. Polyester obtained by polycondensing at least one bifunctional carboxylic acid such as acid / sebacic acid and at least one glycol such as ethylene glycol / triethylene glycol / tetramethylene glycol / hexamethylene glycol / decamethylene glycol Can be mentioned.
Further, the polyester may be blended with or copolymerized with another type of polymer within a range that does not impair the object of the present invention, and includes an antioxidant, a heat stabilizer, a lubricant, a pigment, an ultraviolet absorber and the like. May be. Intrinsic viscosity of polyester (25
C. (measured in ortho-chlorophenol at 0.degree. C.) is 0.4 to 2, preferably 0.5 to 1.0 is usually used.

In the present invention, when polyethylene terephthalate or polyethylene-2,6-naphthalate is used as the polyester, a particularly excellent effect is obtained.

The water-soluble polyester resin layer containing diethylene glycol and / or triethylene glycol referred to in the present invention (hereinafter,
Abbreviated as composite layer. ) Is a layer composed of a water-soluble polyester resin containing diethylene glycol and / or triethylene glycol and a conductive carbon black as a main component.

In the invention, such a diethylene glycol and / or triethylene glycol-containing water-soluble polyester resin layer is provided on at least one side of the polyester film. However, in the case where it is provided on both sides, the description of the layer described below is at least It applies to one side.

For conductive carbon black, the furnace black manufactured by the furnace method-ECF (Extra Condutive Furnac
e), -CF (Conductive Furnace), acetylene black, channel black manufactured by impact method -CC (Cond
uctive channel) and "Ketchen black" (manufactured by Lion Akzo Co., Ltd.), but "Ketchen black" is most preferably used in the film of the present invention in terms of conductivity. The average particle size of conductive carbon black is 10 ~
100 mμ, more preferably 15-80 mμ, even more preferably 25
It is desirable to be in the range of up to 60 mμ. Average particle size is 10mμ
In the following, coarse foreign matter is apt to be generated on the surface of the laminated film due to aggregation of carbon particles. If it exceeds 100 mμ, the surface of the laminated film is likely to be remarkably roughened or the abrasion resistance tends to be deteriorated. The average particle size as used herein is measured by using a conductive carbon black as an aqueous slurry and using a centrifugal sedimentation type particle size distribution measuring apparatus (SA-CP2 type manufactured by Shimadzu Corporation). The main component means that it occupies 60% or more in the composite layer.

The water-soluble polyester resin containing diethylene glycol and / or triethylene glycol is a polycondensation product of aromatic dicarboxylic acid and / or non-aromatic dicarboxylic acid and ester-forming sulfonic acid alkali metal salt compound with glycol and diethylene glycol and / or triethylene glycol. And is soluble in water at 20 ° C. of 0.5% by weight or more, preferably 1% by weight or more. (It may be dissolved in water at a high temperature of 50 to 100 ° C. and cooled to 20 ° C. to maintain its solubility at 0.5 wt% or more, preferably at 1 wt% or more.) Diethylene glycol and / or triethylene glycol Aromatic dicarboxylic acids of water-soluble polyester resin containing terephthalic acid, isophthalic acid, phthalic acid, 2,5
-Dimethylterephthalic acid, 1,4-naphthaldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenylcarboxylic acid, 1,2-bis (phenoxy) ethane-P, P'-dicarboxylic acid and their ester-forming derivatives And non-aromatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and their ester-forming derivatives. is there. Of these, the aromatic dicarboxylic acid and / or its ester-forming derivative preferably accounts for 60 mol% or more of the total dicarboxylic acid component, and within this range, several kinds of dicarboxylic acids may be used in combination.

Examples of the ester-forming sulfonic acid alkali metal salt compound include sulfoterephthalic acid, 5-sulfoisophthalic acid, and 4
-Sulfophthalic acid, 4-sulfonaphthalene, -2,7-dicarboxylic acid, sulfo-P-xylylene glycol, 2-
Examples thereof include alkali metal salts (alkali metal salts of sulfonic acid) such as sulfo-1,4-bis (hydroxyethoxy) benzene and ester-forming derivatives thereof, and 5-sulfoisophthalic acid, sodium sulfoterephthalic acid and their derivatives. Ester-forming derivatives are more preferably used. It is desirable that the addition amount of these ester-forming sulfonic acid alkali salt compounds is 7 to 40 mol%, preferably 10 to 20 mol% based on the total dicarboxylic acid.

Next, as the glycol component, aliphatic or alicyclic glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol are preferable. Further, the content of diethylene glycol and / or triethylene glycol is preferably 1 from the viewpoint of dispersibility of the conductive carbon black.
-60 mol%, more preferably 2-18 mol%. In some cases, diethylene glycol and triethylene glycol may be used together.

Further, the water-soluble polyester resin containing diethylene glycol and / or triethylene glycol may contain a polyether. The term "polyether" as used herein means a hydrophilic polymer having an ether bond as a main bonding chain, and particularly preferred is an aliphatic polyether, for example, polyethylene glycol, polypropylene glycol, glycerin ether, polyethylene glycol monoethyl ether. Is preferred. Polyethylene glycol is represented by HOCH ₂ CH _{2 n} OH (wherein n is an integer of 2 to 140), and its molecular weight range is 200 to 10,000, preferably 300 to 5,000, and more preferably 500 to 2,000. The preferred addition amount of the polyether is 1 to 30% by weight, more preferably 3 to 15% by weight. The polyether is copolymerized or blended with a water-soluble polyester resin containing diethylene glycol and / or triethylene glycol, but preferably, it is preferably copolymerized.

Further, the aqueous solution of the water-soluble polyester resin containing diethylene glycol and / or triethylene glycol preferably contains a surfactant in order to uniformly disperse the conductive carbon black. As the surfactant, any of cation type, anion type, amphoteric type and nonionic type can be used. The preferred content is 0.01 to 15% by weight.

The concentration of conductive carbon black in the composite layer is 2 to 65
Weight percent is preferred, with a range of 10-40 weight percent being more preferred. When the concentration of the conductive carbon black is less than 2% by weight, it is difficult to obtain a laminated film having a target surface specific resistance. If it exceeds 65% by weight, the adhesive strength to the polyester film is lowered and the surface roughness of the laminated film becomes remarkable, which is not preferable.

The polyoster film constituting the film of the present invention is biaxially oriented by a conventional method, and the thickness thereof is preferably 5 to 150 mμ, more preferably 6 to 100 mμ, and more preferable as a base of a magnetic recording medium in terms of practical handling. Is excellent.
Further, the surface roughness of the polyester film is preferably 0.03 μm or less. When the thickness is 0.03 μm or more, when the magnetic recording medium is used, the drop-out becomes defective, which is not preferable.

The laminate thickness of the composite layer constituting the film of the present invention is 0.01 ~
1.0 μm is preferable, and a range of 0.1 to 0.5 μm is more preferable. When the laminated thickness is less than 0.01 μm, it is difficult to obtain a laminated film having a desired surface resistance. If it exceeds 1.0 μm, the abrasion resistance may be deteriorated or the composite layer may be cracked due to bending during handling. The surface roughness of the composite layer is
It is preferably 0.05 μm or less.

The film of the present invention has a ratio of the resistance value R _M between two points in the longitudinal direction (MD) and the resistance value R _T between the two points having the same length in the width direction (TD) at right angles to it on the surface ( R _M / R _T ) is 1.03 to 3.0,
It should be in the range of preferably 1.07 to 2.0, more preferably 1.1 to 1.5. If the ratio of resistance values is less than 1.03, running stability is poor when used as a base material for magnetic tape, and winding deviation or stray winding occurs remarkably, which is not preferable. If the resistance ratio is 3.0 or more, the abrasion resistance of the composite layer deteriorates, or when used as a magnetic tape substrate,
It is not preferable because the running stability deteriorates. The surface resistivity of the film of the present invention is preferably in the range of 10 ⁵ to 10 ⁹ [Ω], more preferably 10 ⁶ to 10 ⁸ [Ω]. When the surface resistivity is less than 10 ⁵ [Ω], when used as a magnetic recording medium,
Since the surface resistivity is too low, the coercive force of the magnetic agent may be adversely affected or the surface may be roughened. 10 ⁹ (Ω)
When it exceeds the above range, the surface resistance becomes high when used as a magnetic recording medium, the antistatic property is deteriorated during use, and dust is adsorbed, which is not preferable.

The laminated polyester film of the present invention is preferably used as a magnetic recording medium by providing a magnetic layer on the surface of the composite layer.

The magnetic layer is a well-known magnetic layer, and γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ , oxide magnetic powder such as CrO ₂ and Fe, Co, Ni.
A magnetic layer formed by a coating method in which a metal-based ferromagnetic powder such as is dispersed in an organic polymer binder such as a known thermoplastic resin or thermosetting resin together with an auxiliary additive. The thickness of the magnetic layer is 0.3 to 10 μm, preferably 1 to 5 μm.

Next, a method for producing the film of the present invention will be described.

An example of using a polyethylene terephthalate (hereinafter abbreviated as PET) film as the polyester film will be described.

First, PET chips polymerized by a conventional method are used at 260 to 310 ° C.
Melt-extrudes from a slit-shaped die and cools it to 20-80 ℃ while applying an electrostatic charge to make an unstretched film. At this time, the intrinsic viscosity of the unstretched film was 0.
It is desirable that it is 5 or more.

Next, by a sequential biaxial stretching method, first, a PET unstretched film is stretched in the longitudinal direction, and conductive carbon black and diethylene glycol and / or triethylene glycol-containing water-soluble polyester resin are previously formed on at least one surface of the film. A laminated PET film is obtained by a method in which an aqueous solution prepared by adjusting the mixed composition of (1) to a predetermined amount is applied and then stretched in a direction perpendicular to the primary stretching direction.

The biaxial orientation conditions are usually a stretching temperature of 60 to 180 ° C. in the longitudinal direction, a stretching ratio of 2.0 to 7.5 times, and a width direction of 60 to 180.
℃, preferably 70 ~ 130 ℃, more preferably at a drawing temperature of 80 ~ 100 ℃, the draw ratio is 2.0 ~ 7.5 times, preferably 2.5 ~
It is 5.5 times, more preferably 3.0 to 4.5 times.

The coating is preferably dried at 50 to 90 ° C. for 10 seconds or less.

Further, the biaxially oriented film is optionally heat treated. The heat treatment conditions are 150 to 240 ° C. and the time is 0.5 to 120 seconds, preferably 1.0 to 60 seconds.

As a coating method, a known method such as a metering bar method, a reverse method or an air knife method can be used.
At this time, the composite layer can be more firmly formed on the surface of the film by subjecting the PET film to a known surface treatment such as corona discharge treatment before coating.

In order to uniformly disperse the conductive carbon black in the aqueous solution of diethylene glycol- and / or triethylene glycol-containing water-soluble polyester resin, the conductive carbon black was previously dispersed uniformly in water using a dispersant such as a surfactant. It is better to use one.

Further, by adding a cross-linking monomer such as a silane coupling agent or a known adhesion promoter to the aqueous solution of the composition, the advantage in post-processing can be increased.

[Evaluation method]

 The characteristic values of the present invention are based on the following measuring methods and evaluation criteria.

(1) Surface roughness According to JIS-B-0601, it was measured using a stylus type surface roughness meter SD-3 type manufactured by Kosaka Laboratory Ltd. The cutoff was 0.25 mm and the measurement length was 4 mm.

(2) Thickness of composite layer As for the thickness of the composite layer, cellophane tape is attached to the surface, and the resin layer at the end of the cell tape is dissolved and removed with a solvent such as dimethylformamide. After the dissolution-removed surface is dried, the cellophane tape is peeled off, and the boundary between the protected surface and the dissolution-removed surface is manufactured by Kosaka Laboratory Ltd.
The laminated thickness was obtained by measuring with an ET-10 high-precision level difference measuring device.

(3) Blocking resistance The blocking property of the laminated film surface was evaluated according to JIS-Z-0219 by applying a load of 500 g / 12 cm ² at 50 ° C. and 80 to 90 RH% for 24 hours. The criteria for judgment are as follows: ◯: good, Δ: slightly inferior, ×: poor.

(4) Adhesive strength The adhesive strength of the composite layer / base film is JIS-C for the composite layer.
-After applying an adhesive tape with a width of 18 mm specified in -2338, apply a load of about 5 kg using a hand roller and set it in the length direction (about 1
(0 cm) was pressed back and forth twice and the adhesive tape was peeled off by hand, and the degree of peeling of the composite layer was observed and evaluated. The criteria for judgment are as follows: ◯: good, Δ: slightly inferior, ×: poor.

(5) Abrasion resistance The composite layer surface of the tape-shaped film was repeatedly contacted and run 200 times with a metal (SUS) fixed guide (5 mmφ), and the abrasion resistance was evaluated by observing the amount of scratches adhering to the film. did. The criteria for evaluation are ◯: good, Δ: slightly inferior, and ×: poor.

(6) Surface resistivity The surface resistivity of 10 ⁶ [Ω] or more was measured using “Super Insulator VE-40 type” manufactured by Kawaguchi Electric Co., Ltd. If the surface resistivity is less than 10 ⁶ [Ω], the electrode of the ultra-insulator “P-601 type” and Takeda Riken Kogyo DIGITAL M
It measured using ULTIMETER "TR-6855".

(7) Ratio of surface resistance values R _M and R _T (R _M / R _T ) A needle electrode made of copper with a length of 30 mm and a diameter of 0.8 mmφ and a thin tip and a sharp tip is created for a certain distance (10 to 50 mm). Stand vertically on
DIGITAL MULTIMETER “TR-685” manufactured by Takeda Riken Kogyo Co., Ltd.
5 "longitudinal (MD) and perpendicular (TD) resistance
R _M and R _T were measured, and the resistance ratio (R _M / R _T ) was obtained from this.

(8) Charging property evaluation method SHSHID Co., Ltd. "Citatic Honest meter S-4104
It was measured by using a "mold". The judgment criteria were as follows: ◯: good (1 second or less), Δ: somewhat inferior (2 to 30 seconds), ×: poor (30 seconds or more).

(9) Holding power of magnetic recording medium A magnetic film having the following composition is applied to a sample film by a coating method,
A magnetic layer having a thickness of 2.5 μm was formed by drying to obtain a magnetic recording medium. The magnetic characteristics of this magnetic recording medium are measured with a sample vibrating magnetometer, and the coercive force is obtained from the Hysteris curve.
Judgment criteria are coercive force of 500 Oersted or more is good, 500
Less than Oerstedt was regarded as defective.

[Composition of magnetic agent]

・ Γ-Fe ₂ O ₃ powder 68 parts by weight ・ Carbon black 7 parts by weight ・ Vinyl chloride-vinyl acetate-vinyl alcohol copolymer
26 parts by weight ・ Acrylonitrile-butadiene copolymer 5 parts by weight ・ Polyisocyanate 2 parts by weight ・ Methyl isobutyl ketone 75 parts by weight ・ Toluene 75 parts by weight (10) Dropout of magnetic recording medium The magnetic tape prepared in (9) above. The original fabric was micro-slit to 1/2 inch to make a magnetic tape. This magnetic tape is run for 100 hours continuously on a home VTR (helical scan). After holding the tape at 40 ° C for 48 hours, the tape was returned to room temperature, recorded and played back, and the signal output of 50% or less was counted using a drop-out counter.

In addition, the measurement is performed for 10 rolls, with 1/2 inch width and 780 m as one roll, and the number of rolls per roll is less than 2; drop out; good; when 2 or more, drop out; It was judged to be defective.

(11) Running stability The magnetic tape stock prepared in (9) above was microslit to a width of 6.3 mm to form a magnetic tape having a length of 780 m. This magnetic tape was run using a tape recorder specified in JIS-C-5550, and the fluctuation amount in the tape width direction was measured by a photodetector (manufactured by "Siemens"). The measurement was made by running three times and the average was used as the fluctuation amount. If the fluctuation amount is less than ± 0.1 mm, it is good, ± 0.1 mm.
The above was considered defective. In addition, the occurrence of winding deviation and stray winding on the reel specified by JIS-C-5510 was visually observed.

〔The invention's effect〕

(1) Since the laminated polyester film has anisotropy in surface resistance, when it is used as a base material for a magnetic tape, the running stability is good, and the antistatic property is not affected by external temperature and humidity. It can be obtained stably for a long time without receiving it.

(2) When a laminated polyester film is used as a base material to form a magnetic recording medium, high-density recording is achieved, so that the magnetic recording medium can be made compact and the recording time can be lengthened.

(3) Since the laminated polyester film has a light-shielding property, the amount of the light-shielding property-imparting agent added to the magnetic layer can be reduced when manufacturing a magnetic recording medium.

(4) When the magnetic recording medium is manufactured, since the laminated polyester film has easy adhesiveness, the magnetic layer is firmly formed, so that the anchor coat becomes unnecessary and the process can be simplified.

The laminated polyester film of the present invention is a base film for magnetic recording media, a base film for capacitors, various photographic base films, graphic base films,
Also, it can be applied to a packaging base film and the like, but it is particularly preferable to use it as a magnetic tape as a base material of a magnetic recording medium.

〔Example〕

Next, embodiments of the present invention will be described based on examples. In the following, "parts" means "parts by weight".

Example 1 165 parts dimethyl terephthalate, 44.5 parts dimethyl 5-sodium sulfoisophthalate, ethylene glycol 124
Parts, 0.106 parts of manganese acetate tetrahydrate and 0.07 parts of calcium acetate dihydrate, methanol was distilled off at 140 to 220 ° C., an ester exchange reaction was performed, and then trimethyl phosphate was added.
0.09 parts, dimethylene glycol 7.2 parts, antimony trioxide 0.06 parts were added, the temperature was raised from 240 ° C to 280 ° C over 1 hour and 30 minutes, and the pressure was gradually decreased from atmospheric pressure to 0.5 mmHg.
Remove the generated ethylene glycol outside the system, and
This state was maintained for reaction for a minute to obtain a diethylene glycol-containing water-soluble polyester resin [η] = 0.57.

When the copolymerization component of the produced diethylene glycol-containing water-soluble polyester was analyzed, the diethylene glycol component in the total diol component was 17 mol% including the by-product during the reaction, and the 5-sodium sulfoisophthalic acid component in the total dicarboxylic acid component was It was contained at 14 mol%.

The obtained diethylene glycol-containing water-soluble polyester resin was dissolved in hot water at 85 ° C. to prepare a 6 wt% aqueous solution.
Then, "Ketjen Black EC" having an average particle diameter of 40 m was uniformly dispersed in water using sodium dodecylbenzenesulfonate as a dispersant to prepare an 8 wt% aqueous solution. This was added to the above aqueous solution to prepare a solid content composition ratio of diethylene glycol-containing water-soluble polyester resin of 85% by weight, "Ketjenblack EC" of 15% by weight, and total solid content concentration of the aqueous solution of 6% by weight. did.

On the other hand, polyethylene terephthalate with an intrinsic viscosity of 0.62
After melt extruding from a T-shaped die at 0 ° C., a cast unstretched sheet was formed on a cast drum at 20 ° C. to which electrostatic was applied, preheated to 80 ° C., and stretched 3,3 times in the longitudinal direction by roll stretching. .

The "Ketjen Black E
95 ° C after applying diethylene glycol-containing water-soluble polyester resin aqueous solution containing C "by the metering bar method.
Stretched 3.5 times in the width direction and 210 ° C while relaxing 2% in the width direction.
Was heat-treated for 5 seconds to obtain a 15 μm laminated film based on polyethylene terephthalate on which a resin layer of 0.25 μm was laminated.

The surface roughness of the laminated film thus obtained is 0.035μ.
m, surface resistance ratio (R _M / R _T ) is 1.26, surface resistivity is
It was 5.0 × 10 ⁵ [Ω]. Further, the composite layer was excellent in adhesiveness, abrasion resistance and blocking resistance. The characteristics when this film is used as a magnetic tape are
As shown in the table, the coercive force, drop out, antistatic property, and running stability were good.

Example 2, Comparative Examples 1 and 2 Using the same polyethylene terephthalate as in Example 1,
A coating material having the same composition as in Example 1 but having a different composition ratio was prepared and applied in the same manner as in Example 1, and then the transverse stretching conditions were slightly changed to obtain a composite layer surface resistance ratio (R _M / R _T ). A laminated film having a surface resistivity changed was obtained. The thickness of the composite layer is 0.22μ
m, and the total thickness of the laminated film was 15 μm. The characteristics when these films were used as magnetic tapes are shown in Table 1.

When the surface resistance ratio is outside the present invention (Comparative Examples 1 and 2),
A magnetic tape with good drop-out, antistatic properties and running stability could not be obtained.

Claims (3)

[Claims] 1. A laminated polyester film comprising a polyester film and a water-soluble polyester resin layer containing electrically conductive carbon black and containing diethylene glycol and / or triethylene glycol, the water-soluble polyester resin layer being provided. Resistance value R _M in one direction (MD) on the surface and resistance value in the direction perpendicular to it (TD)
A laminated polyester film having a ratio with R _T (R _M / R _T ) of 1.03 to 3.0. 2. The conductive carbon black has an average particle size of 10 to 10.
Claim (1) characterized in that it is 100 mμ
The laminated polyester film according to the item. 3. The surface resistance of the water-soluble polyester resin layer
The laminated polyester film according to claim (1) or (2), which is 10 ⁵ to 10 ⁹ [Ω].