JP4943757B2 - Antistatic polyester film - Google Patents

Description

  The present invention relates to an antistatic polyester film, and in particular, relates to an antistatic polyester film having good antistatic properties at room temperature and little deterioration in performance even when heated during post-processing.

  Polyester film represented by biaxially stretched polyethylene terephthalate film has various properties required for plastic film such as mechanical strength, electrical insulation, heat-resistant dimensional stability, solvent resistance, water resistance, and transparency, and cost. And is used in a wide variety of fields.

  However, although it is a polyester film having a good balance between cost and performance, as one of the problems to be overcome, there is a drawback that it is easily charged. In the past, many improvements have been proposed to overcome this drawback. Among them, the so-called in-line coating method, in which a coating solution containing a compound having antistatic properties is applied to the film surface in the film forming process and then further stretched and heat-set, is an excellent method in various respects. Therefore, it is one of the prescriptions frequently used.

  In this in-line coating method, compared to the method of applying to a biaxially stretched polyester film that has undergone orientation crystallization, film formation and application are simultaneously performed, so a wide product can be obtained at a relatively low cost. . Moreover, since a film and a coating film are simultaneously stretched and heat-set, there is an advantage that the adhesion with the film coating film becomes strong.

  In order to form a coating film having an antistatic property on a polyester film by using this in-line coating method, a method of adding an anionic or cationic ion conductive antistatic agent to a coating agent is often used. Among these antistatic agents, the polymer compound having a cationic property bleeds out on the surface of the coating film, and the antistatic agent is transferred to a material in contact therewith or laminated on the film by bleedout. Adhesiveness with the layer does not decrease, and practical antistatic performance can be obtained at a relatively low cost.

  An antistatic biaxially stretched polyester film is proposed in which a polymer having a pyrrolidinium ring in the main chain is selected as a cationic polymer compound used in in-line coating, and a coating film containing the polymer is provided (Patent Document 1). 2).

  By the way, in general, a cation polymer containing a quaternized nitrogen atom has a defect that is generally easily decomposed against heat, and among them, even a polymer containing a pyrrolidinium ring in the main chain, which is relatively stable. I cannot deny that there is a tendency.

  Specifically, when an antistatic coating film is applied to a polyester film by in-line coating, the coating film also inevitably undergoes a heat setting treatment of 200 ° C. or higher, but the degree of damage caused by heat at this time is Even in a polymer having a pyrrolidinium ring in the main chain having the same composition, different phenomena may occur depending on, for example, the production lot of the polymer. As a result, even when the antistatic polyester film is produced under the same conditions, a problem that the antistatic performance is not sufficient sometimes occurs. Another problem is that even if a certain level of antistatic performance is satisfied at room temperature, a defect that deteriorates the antistatic performance may occur due to some heat treatment during subsequent processing.

JP-A-1-146931 JP-A-1-174538

  The present invention has been made in view of the above circumstances, and its purpose is to have a practical antistatic performance at room temperature, and the antistatic performance is reduced even with heat applied during post-processing. An object of the present invention is to provide a biaxially stretched polyester film that does not often occur.

  As a result of intensive studies, the present inventors have found that the above problems can be overcome if the polyester film has a specific configuration, and the present invention has been completed.

That is, the gist of the present invention, have a pyrrolidinium ring in a main chain, was coated on at least one side a coating solution containing a polymer obtained by polymerization using a radical chain transfer agent during polymerization, obtained by stretching and heat setting the film The surface resistivity value of the coated surface is 1 × 10 ¹¹ Ω or less, and the rate of increase in the surface resistivity value of the coated surface after heat-treating the film at 250 ° C. for 1 minute in air is 50. It exists in the antistatic polyester film characterized by being below double.

Hereinafter, the present invention will be described in detail.
The antistatic polyester film of the present invention is not an unstretched film, but an oriented polyester film that is stretched in at least one direction, preferably biaxially stretched sequentially or simultaneously in the longitudinal direction and the width direction, and then heat-set.

  The polyester constituting the antistatic polyester film of the present invention contains 80 mol% or more of ethylene terephthalate, ethylene naphthalate, or a condensate of 1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol as its repeating unit. Preferably, it occupies 90 mol% or more. Among these, polyethylene terephthalate has a good balance between cost and characteristics, and is most preferably used.

  In addition, said polyester is dicarboxylic acid, such as isophthalic acid, 2, 6- naphthalene dicarboxylic acid, terephthalic acid, 4,4'- diphenyl dicarboxylic acid, 1, 4- cyclohexane dicarboxylic acid, adipic acid, sebacic acid, as a 3rd component. And ethylene oxide addition of ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, polyethylene glycol, bisphenol A Diols such as products can be exemplified. Such a polyester can be produced by a polycondensation reaction between a dicarboxylic acid or a derivative thereof and glycol according to a known method. At this time, when the intrinsic viscosity of the polyester (phenol: 1,1,2,2-tetrachloroethane = 50: 50% by weight, 30 ° C.) is 0.45 or more, the mechanical properties of the film after film formation This is preferable because the strength is improved. The upper limit of the intrinsic viscosity is not particularly limited, but is preferably 1.0 or less in view of industrial economy.

  A filler can be added to the polyester for the purpose of imparting slipperiness and improving workability, or for the purpose of making the film white or matte. Examples of these fillers include inorganic fine particles such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, titanium oxide, barium sulfate, kaolin, talc, and zeolite, or crosslinked silicone resin, crosslinked polystyrene resin, crosslinked acrylic resin, and urea resin. Organic fine particles made of a heat-resistant polymer such as urea resin or melamine resin can be used as necessary. In addition, stabilizers, antioxidants, ultraviolet absorbers, fluorescent brighteners, and the like can be added to the polyester.

  Although the thickness of the antistatic polyester film of this invention is not specifically limited, Usually, it is the range of 5-350 micrometers, It is preferable that it is the range of 10-250 micrometers, Furthermore, it is the range of 15-180 micrometers.

  The polymer having a pyrrolidinium ring in the main chain in the present invention is a polymer having a structural unit represented by the formula (1) or (2) as a main component in the molecule.

In the structure of the above formula (1) or (2), R ¹ and R ² are usually an alkyl group having 1 to 4 carbon atoms or hydrogen, and these may be the same group or different. Further, the alkyl group of R ¹ and R ² may be substituted with a hydroxyl group, an amide group, an amino group, or an ether group. Further, R ¹ and R ² may be chemically bonded and have a ring structure. X ⁻ in the formula (1) or (2) is a halogen ion, nitrate ion, methanesulfonate ion, ethanesulfonate ion, monomethylsulfate ion, monoethylsulfate ion, trifluoroacetate ion, or trichloroacetate ion. . In this, X ^- is the case of the chloride ion is preferable in that it is assumed that the antistatic performance was excellent.

  The polymer having the structural unit represented by the formula (1) or (2) as a main component is 50 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more of the polymer. Or it means that it is a structural unit of the formula (2). A polymer having a structural unit of the formula (1) can be obtained by polymerizing a diallylammonium salt represented by the following formula (3) as a monomer while ring-closing it by radical polymerization. The polymer having the structural unit of the formula (2) can be obtained by cyclopolymerizing the monomer of the formula (3) in a system using sulfur dioxide as a solvent.

  In addition to this, as a monomer component used as a copolymerization component, one or more compounds having a carbon-carbon unsaturated bond copolymerizable with the diallylammonium salt of the formula (3) can be selected.

  These are specifically acrylic acid and its salts, methacrylic acid and its salts, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) Acrylamide, N-methylol (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, maleic acid and its salt or maleic anhydride, fumaric acid and its salt or fumaric anhydride, monoallylamine And quaternized products thereof, acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylidene chloride, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acryloyloxyethyldialkylamine and its ammonium salt, (meth Acry Ilyloxypropyldialkylamine and its ammonium salt, (meth) acryloylaminoethyldialkylamine and its ammonium salt, (meth) acryloylaminopropyldialkylamine and its ammonium salt, etc. can be exemplified, but are not limited thereto is not.

  The polymer having the pyrrolidinium ring is composed of a monomer represented by the formula (3) as a main component and, if necessary, the above-described copolymerization component coexisting with water or methanol, ethanol, isopropanol, formamide, dimethylformamide. , Peroxides such as hydrogen peroxide, benzoyl peroxide and tertiary butyl peroxide, persulfates such as ammonium persulfate and potassium persulfate, 2,2′-azobis in polar solvents such as dioxane, acetonitrile and sulfur dioxide (2-Amidinopropane) addition salt, 2,2′-azobis (2-amidinobutane) addition salt, 2,2′-azobis (2-amidinopentane) addition salt, 2,2′-azobis (2-amidino-3) -Methylbutane) addition salt, 3,3'-azobis (3-amidinohexane) addition salt, 3,3 ' Azobis- (3-amidino-4-methylpentane) addition salt, 4,4′-azobis (4-amidinoheptane) addition salt, 2,2′-azobis-butyronitrile, 2,2′-azobis- (2,4 -It can superpose | polymerize using polymerization initiators, such as azo compounds, such as (dimethylvaleronitrile). Examples of the addition salt include addition salts such as hydrochloride, sulfate, phosphate, alkyl sulfate, alkyl sulfonate, and p-toluene sulfonate. In the polymerization of a polymer having a pyrrolidinium ring, the polymerization can be performed by heating in a range of room temperature to reflux temperature, preferably 50 to 90 ° C., preferably in an inert gas atmosphere.

  The antistatic polyester film of the present invention needs to be a film obtained by applying a coating liquid containing a polymer having a pyrrolidinium ring in the main chain to at least one side, and then stretching and heat setting.

  The coating solution used here is a solution in which the polymer having a pyrrolidinium ring in the main chain described above is preferably dissolved or dispersed in water. The medium of the coating solution is preferably water, but alcohols such as methyl alcohol, ethyl alcohol, isopropanol and ethylene glycol, and ethyl for improving the coating property of the substrate to the polyester film and the film forming property of the coating agent. It is also possible to mix an organic solvent compatible with water such as cellsolves such as cellsolve and t-butylcellsolve, ketones such as acetone and methyl ethyl ketone, water such as glycerin and N-methylpyrrolidone.

  In the coating solution of the present invention, in addition to the polymer having a pyrrolidinium ring in the main chain, the adhesion with the polyester film substrate, the adhesion of the coating film surface or the solvent resistance, or at the time of stretching For the purpose of improving the film forming property of the coating agent itself, a binder polymer can be contained. Specific examples of this binder polymer are selected from polyvinyl alcohol, polyacrylamide, polyalkylene glycol, methylcellulose, hydroxycellulose, polyalkyleneimine, polyurethane, polyester, polyacrylate, polyvinyl resin, polyethylene oxide, polypropylene oxide, waxes, and the like. At least one selected from the above can be contained.

  The coating solution in the present invention includes a melamine or urea that has been converted into methylol or other alkylol as a crosslinking agent in order to improve the blocking resistance, water resistance, solvent resistance, heat resistance, mechanical strength, etc. of the coating layer. And at least one selected from compounds such as acrylamide, epoxy compounds, isocyanate-containing compounds, carbodiimide compounds, oxazoline-containing compounds, and silane coupling agent compounds. In addition, inorganic fine particles such as silica, alumina, and zirconium can be added for the purpose of improving the slipperiness of the coating film. It is also possible to apply the zirconium compound described in JP-A-1-174538 to improve the transparency of the coating film.

  In the present invention, any known method can be applied as a method of applying the coating solution to the polyester film substrate. For example, a roll coating method, a gravure coating method, a micro gravure coating method, a reverse coating method, a bar coating method, a roll brush coating method, a spray coating method, an air knife coating method, a die coating method, etc. may be applied alone or in combination. Can do.

  By the above coating method, the coating liquid is applied to at least one side of the polyester film that becomes the substrate. At this time, the polyester film may be an unstretched film that is melt-extruded and formed into a film as it is. A uniaxially stretched film stretched in either the longitudinal direction or the transverse direction may be used. The film is further stretched after the above-described coating solution is applied to these films. In the case of an unstretched film, it is uniaxially stretched in the longitudinal direction or the transverse direction, or biaxially stretched in the longitudinal and transverse directions sequentially or simultaneously. In the case of a uniaxially stretched film stretched in either the longitudinal direction or the transverse direction, stretching is performed in a direction perpendicular thereto. Thereafter, the stretched film is subjected to a high temperature treatment of, for example, 200 ° C. or higher by heat setting. Among these coating / stretching methods, a coating solution is applied to a film that has been uniaxially stretched in the longitudinal direction in advance, then stretched in the transverse direction, and further heat-fixed. A method in which, after applying the coating solution, stretching in the longitudinal and lateral directions at the same time and further heat setting is preferably used.

  The thickness of the coating film in the present invention is a dry thickness after stretching and heat setting, and is usually 0.005 to 1 μm, preferably 0.01 to 0.5 μm, and more preferably 0.01 to 0.2 μm. . When the thickness is less than 0.005 μm, sufficient antistatic performance is often not obtained. Conversely, when the thickness exceeds 1 μm, the antistatic performance is no longer saturated and an economic merit is obtained. I can't.

As described above, the antistatic polyester film of the present invention is a film obtained by applying a coating solution containing a polymer having a pyrrolidinium ring in the main chain to at least one side, and then stretching and heat-setting the coating solution. The surface specific resistance value of the surface needs to be 1 × 10 ¹¹ Ω or less. This surface specific resistance value is a value measured in a state in which the film formed is not subsequently subjected to a treatment such as heating, and the value is preferably 5 × 10 ¹⁰ Ω or less, more preferably 1 × 10 ^10. Ω or less. If this surface resistivity exceeds 1 × 10 ¹¹ Ω, the antistatic performance of the original film is not so good, so there are almost no applications that can be applied at this time, and during the subsequent processing. When it is subjected to a heat treatment, the antistatic performance is often insufficient, which is not preferable.

  In the antistatic polyester film of the present invention, it is necessary that the increase rate of the surface specific resistance value of the coated surface after heat treatment at 250 ° C. for 1 minute in air is 50 times or less, and this increase rate is preferably 40 times or less, more preferably 30 times or less. The rate of increase here refers to the surface resistivity (Ω) of the antistatic coated surface of a film heat-treated at 250 ° C. for 1 minute in air by the method described later, and the antistatic of a film that has not been heat-treated after film formation. It is a value divided by the surface resistivity (Ω) of the coated surface. In the present invention, the evaluation is performed under severe heat treatment conditions of 250 ° C. for 1 minute in air, so that the antistatic performance of the film can be improved even during post-processing under a lower temperature condition (for example, 100 to 220 ° C.). It is possible to prevent defects that greatly decrease. A polymer having a pyrrolidinium ring in the main chain used as an antistatic agent when the rate of increase in surface resistivity of the coated surface exceeds 50 times after the film is heat-treated at 250 ° C. for 1 minute in air This is not preferable because the heat resistance is insufficient and the number of defects in which the antistatic performance is lowered due to heat applied in post-processing increases.

  In order for the antistatic polyester film of the present invention to have antistatic properties as described above, for example, among polymers having a pyrrolidinium ring in the main chain used as an antistatic polymer compound, those having a high thermal decomposition temperature It is effective to select This thermal decomposition temperature can be measured by TG-DTA as a heat loss start temperature. The heat loss starting temperature of a polymer having a pyrrolidinium ring in the main chain varies depending on the presence / absence, type, and amount of copolymerization of the polymer, but the heat loss starting temperature is 240 ° C or higher, more preferably 250 ° C or higher. It is preferred to select a polymer.

  Even if the polymer has a heat loss starting temperature of 240 ° C. or higher, the rate of increase in the surface resistivity of the coated surface after heat treatment at 250 ° C. for 1 minute in air may exceed 50 times. The reason for this is not clear, but it is presumed that such a phenomenon occurs when a polymer having a pyrrolidinium ring in the main chain contains a large amount of monomers and low polymerization degree components. Therefore, in order to improve this, it is considered effective to reduce monomers and low polymerization degree components from the polymer having a pyrrolidinium ring in the main chain.

  However, in order to carry out this, it is possible to remove monomers and low molecular weight substances by reprecipitation using a polymerized polymer such as acetone, but reprecipitation on an industrial scale requires a large amount of solvent. It is inevitable that it will be a factor in increasing costs, such as the need for environmental and safety considerations.

  On the other hand, in order to reduce the monomer and the low polymerization degree component, it is possible to simply take a longer polymerization time of the polymer, but in many cases, the polymerization degree of the whole polymer is also increased. As a result, the viscosity of the coating liquid using this also increases, which tends to cause the occurrence of coating streaks and the coating surface condition. It is preferable to set the polymerization conditions so as to make the molecular weight distribution of the polymer as sharp as possible in order to reduce the monomer and the low polymerization degree component without purifying the polymer while preventing such harmful effects. The polymerization conditions generally include, for example, the temperature setting in the polymerization tank and the stirring state, the speed at which the initiator and the raw material monomer are charged into the reaction system, the setting of the step to be charged, and the setting of the polymerization time. Refers to conditions that can be adjusted. Furthermore, in combination with these polymerization conditions, it is advantageous to use a molecular weight modifier together with an initiator during the polymerization to reduce the monomer and the low polymerization degree component while suppressing an increase in the polymerization degree of the whole polymer. As this molecular weight regulator, a radical chain transfer agent having sufficient water solubility, for example, mercaptans such as 3-mercaptopropionic acid and 2-mercaptoacetic acid, hypophosphorous acid or its sodium salt, potassium salt, ammonium salt, A typical example is an amine salt.

  The antistatic polyester film of the present invention is provided with a coating layer containing a polymer having a pyrrolidinium ring in the main chain on at least one side, but this coating layer may be provided on both sides or only on one side. It may be provided. In the latter case, it is possible to provide another coating layer on the opposite surface of the antistatic coating layer containing a pyrrolidinium ring. Examples of other coating layers include functional layers for the purpose of easy adhesion, slipperiness, releasability, etc., and these can be applied to the polyester film together with the antistatic coating layer when performing in-line coating. It is also possible to apply to the opposite surface and form simultaneously.

  The antistatic polyester film of the present invention has practical antistatic performance, and the antistatic performance is less likely to be lowered by heat applied during post-processing. As a result, for example, when applying an adhesive layer or a release layer as a protective film such as a polarizing plate or a separator, or when applying a hard coat as an antireflection film, the antistatic performance is sufficient. Can be maintained. In addition, when used as a transfer film for simultaneous molding transfer, etc., the heat applied when forming the top coat of the transfer foil on the film, and also the heat applied during annealing to reduce shrinkage However, in applications where heat is applied during post-processing, for example, the antistatic performance can be maintained, the range of use is extremely wide, and its industrial value is high.

  Hereinafter, the configuration and effects of the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Various physical properties and characteristics are measured or defined as follows.

(1) Surface resistivity (Ω), antistatic performance rank Using a high resistance measuring instrument HP4339B and measuring electrode HP16008B manufactured by Hewlett-Packard Japan, under a measurement atmosphere of 23 ° C. and 50% RH, an applied voltage of 100 V The surface specific resistance value (Ω) of the coating layer after 1 minute was measured. In addition, the rank of the antistatic performance was classified as follows according to the surface resistivity.
Less than 1 × 10 ¹⁰ Ω: Good antistatic performance (Rank A)
1 × 10 ¹⁰ to 1 × 10 ¹² Ω: antistatic performance is recognized (rank B)
Over 1 × 10 ¹² Ω: insufficient antistatic performance (rank C)

(2) Heat treatment in air at 250 ° C for 1 minute In a hot air oven manufactured by Tabai Espec, a hot air shielding plate with a small window made of stainless steel is installed, and the temperature inside the oven does not drop greatly even when the door is opened. A device capable of taking samples in and out of the window was used. The test sample was put into the oven through a small window of the hot air shielding plate in a state where the four sides of the film were fixed using a stainless steel frame so that no shrinkage was generated by heating. The atmosphere in the oven was air, and the temperature was set to 250 ° C. In this state, the test sample was put in an oven and returned to a temperature of 250 ± 2 ° C. after about 10 seconds. The test sample was taken out 1 minute after being put in the oven, immediately cooled with an electric fan, and removed from the stainless steel frame to obtain a heat-treated sample.

(3) Processing conditions for various post-processing and evaluation of anti-static polyester film after processing Anti-static polyester film is subjected to various post-processing and exposed (not processed) anti-static under the following processing conditions The surface resistivity (Ω) of the layer surface was measured.
-Acrylic adhesive layer formation After the acrylic adhesive layer was diluted with methyl ethyl ketone and coated on one side of the antistatic polyester film, it was dried in an air atmosphere at 130 ° C for 3 minutes to form an adhesive layer having a thickness of 25 µm.
Silicone release layer formation Addition reaction curable silicone was dissolved in a methyl ethyl ketone / toluene solution, a platinum catalyst was added thereto, and then applied to one side of an antistatic polyester film. Thereafter, drying and curing reactions were carried out by heating at 150 ° C. for 1 minute in an air atmosphere to form a silicone release layer having a thickness of 0.05 μm.
・ Formation of melamine resin-based topcoat layer for transfer foil Apply a methylethylketone / toluene solution of melamine resin on one side of an antistatic polyester film, dry it at 130 ° C for 1 minute in an air atmosphere, and then heat at 180 ° C for 1 minute. Then, a curing reaction was performed to form a melamine resin-based topcoat layer having a thickness of 1 μm.
・ Low shrinkage annealing treatment The antistatic polyester film is passed through a hot air oven set at 200 ° C. in an air atmosphere for 30 seconds, freely contracted in the width direction, and wound in the longitudinal direction with weak winding tension. Shrinkage treatment was performed.

The polymer aqueous solutions (a), (b), and (c) having a pyrrolidinium ring used in Examples and Comparative Examples were prepared as follows.
(A): After making the inside of the reactor equipped with a thermometer, a stirring rod and a reflux condenser into a nitrogen atmosphere, 162 g (0.6 mol) of 60 wt% diallyldimethylammonium chloride aqueous solution and 162 g of distilled water were charged, and hydrochloric acid was added. The pH was adjusted to 3-4. Next, 1.8 g of sodium hypophosphite was added and dissolved by stirring at 60 ° C. To this was added 0.5 g of 28.5 wt% ammonium persulfate aqueous solution. Thereafter, stirring was continued while maintaining the temperature of the reaction solution at 60 ° C., and 1.0 g of the same aqueous ammonium persulfate solution was added after 4 hours. Thereafter, 1.0 g of the same ammonium persulfate aqueous solution was added after another 8 hours. Thereafter, the reaction solution was reacted for 20 hours while maintaining the temperature at 60 ° C. to polymerize.

(B): In the same reactor as used in (a), the reactor was similarly filled with nitrogen, and then charged with 243 g (0.9 mol) of a 60 wt% diallyldimethylammonium chloride aqueous solution and 233 g of distilled water. The pH was adjusted to 3-4 with hydrochloric acid. To this, 9.9 g (0.1 mol) of N, N-dimethylacrylamide was added, and 2.1 g of sodium hypophosphite was further added and dissolved by stirring at 60 ° C. To this was added 1.2 g of 28.5% aqueous ammonium persulfate solution. Then, stirring was continued while maintaining the temperature of the reaction solution at 60 ° C., and 4.8 g of the same ammonium persulfate aqueous solution was added after 4 hours. Thereafter, the reaction solution was reacted for 20 hours while maintaining the temperature at 60 ° C. to polymerize.

(C): In the same reactor as used in (a), the reactor was similarly filled with a nitrogen atmosphere, and then charged with 162 g (0.6 mol) of a 60 wt% diallyldimethylammonium chloride aqueous solution and 162 g of distilled water. The pH was adjusted to 3-4 with hydrochloric acid. This was heated to 65 ° C., and 3.2 g of a 28.5 wt% aqueous ammonium persulfate solution was added. Then, stirring was continued while maintaining the temperature of the reaction solution at 65 ° C., and 2.4 g of the same aqueous ammonium persulfate solution was added after 4 hours. Thereafter, 2.4 g of the same aqueous ammonium persulfate solution was added after another 8 hours. Thereafter, the reaction solution was reacted for 20 hours while maintaining the temperature at 65 ° C. to polymerize.

<Manufacture of polyester>
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.03 part of silica particles having an average particle diameter of 2.2 μm dispersed in ethylene glycol and 0.03 part of antimony trioxide were added. A time polycondensation reaction was performed. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.1 kPa (absolute pressure). After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.66 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure, cooled, and then chipped. The intrinsic viscosity of the obtained polyester was 0.66.

<Manufacture of polyester film>
The above polyester chip was put into a vent type twin screw extruder, and melt extrusion was performed at a resin temperature of 295 ° C. while removing moisture from the vent port at a vacuum degree of 1 kPa (absolute pressure). A gear pump and a melt filter were connected to the extruder, and the molten polymer passed through these was extruded from a T-die and cast on a cooling drum at 20 ° C. by applying an electrostatic application adhesion method. The unstretched polyester sheet thus obtained was guided to the longitudinal stretching step. For the longitudinal stretching, a roll stretching method is used, a plurality of rolls are used, the polyester sheet is preheated to 90 ° C., and further stretched in the longitudinal direction at a stretching ratio of 3.5 times in combination with an IR heater. . After performing corona discharge treatment on both surfaces of this uniaxially stretched film, both coronas were applied so that the coating film thickness of each film after stretching and heat setting was 0.03 μm. It apply | coated to the discharge process surface by the micro gravure system. Next, this uniaxially stretched film was guided to a tenter, dried and preheated at 110 ° C., and then stretched in the width direction at a stretch ratio of 3.8 times. Then, after heat-fixing at 215 ° C. under tension in the same tenter, relaxation treatment was performed in the 3% width direction at 180 ° C. to obtain a biaxially oriented polyester film having a total thickness of 100 μm.

Example 1:
In order to form the antistatic coating layer, an aqueous coating solution having the following solid content composition was used using the aqueous polymer solution (a) having a pyrrolidinium ring.
Polymer having a pyrrolidinium ring (a) 50 parts by weight Polyvinyl alcohol (GOHSENOL GL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 40 parts by weight Methylolated melamine 10 parts by weight Using this film as an after-treatment, forming an acrylic adhesive layer, Silicone release layer formation, melamine resin-based topcoat layer formation for transfer foil, and low shrinkage annealing treatment were performed. The surface specific resistance value was measured for 25 points of each processed sample, and the frequency of exceeding 1 × 10 ¹² Ω (rank C: insufficient antistatic performance) was counted. The results are shown in Table 1 below, and the obtained antistatic polyester film has good antistatic performance, and the rate of increase in surface resistivity after heat treatment at 250 ° C. for 1 minute in air is small. For this reason, no case of insufficient antistatic ability was found even after various post-processing.

Example 2:
For the formation of the antistatic coating layer, an aqueous coating solution having the following solid content composition was used using the polymer aqueous solution (b) having a pyrrolidinium ring.
Polymer (b) v having pyrrolidinium ring 50 parts by weight Polyvinyl alcohol (GOHSENOL GL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 40 parts by weight 10 parts by weight of methylolated melamine Other than that, an antistatic polyester film was prepared in the same manner as in Example 1. did. Using this, various processes similar to Example 1 were performed and evaluated in the same manner. The results are shown in Table 1. As compared with Example 1, the rate of increase in the surface resistivity value before and after heat treatment at 250 ° C. in air for 1 minute was slightly increased. However, since the rate of increase was 50 times or less, the frequency of insufficient antistatic ability was extremely small even after various post-processing.

Comparative Example 1:
In order to form an antistatic coating layer, an aqueous coating solution having the following solid content composition was used using a polymer aqueous solution (c) having a pyrrolidinium ring.
Polymer (c) having pyrrolidinium ring 50 parts by weight Polyvinyl alcohol (GOHSENOL GL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 40 parts by weight Methylolated melamine 10 parts by weight Other than that, an antistatic polyester film was prepared in exactly the same manner as in Example 1. . Using this, various processes similar to Example 1 were performed and evaluated in the same manner. The results are shown in Table 1. Although the antistatic polymer having the same composition as in Example 1 was used, the surface specific resistance value at room temperature was slightly higher than that in Example 1. (However, 1 × 10 ¹¹ Ω or less) On the other hand, the increase rate of the surface resistivity before and after the film was heat-treated at 250 ° C. for 1 minute in the air exceeded 50 times. For this reason, the antistatic polyester film exhibited a phenomenon that the antistatic performance was insufficient after various processing.

  The film of the present invention can be suitably used, for example, in various applications that require antistatic performance.

Claims (3)

Have a pyrrolidinium ring in a main chain, was coated on at least one side a coating solution containing a polymer obtained by polymerization using a radical chain transfer agent during polymerization, a film obtained by stretching and heat setting, the coated surface The surface resistivity is 1 × 10 ¹¹ Ω or less, and the rate of increase in the surface resistivity of the coated surface after heat-treating the film at 250 ° C. for 1 minute in air is 50 times or less. Antistatic polyester film. The antistatic polyester film according to claim 1, wherein the radical chain transfer agent is water-soluble. The antistatic polyester film according to claim 1 or 2, wherein the radical chain transfer agent is hypophosphorous acid or a salt thereof.