JP2007254640A - Antistatic biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antistatic biaxially oriented polyester film having little aggregate of an antistatic agent. <P>SOLUTION: The antistatic biaxially oriented polyester film containing 0.1-15 wt.% organic antistatic agent in a polyester substantially free from particles comprises a polyester which is regulated so that the number of bulky particles having ≥1 μm diameters is ≤100 (/0.01 g). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antistatic biaxially oriented polyester film in which an antistatic agent is kneaded, and particularly relates to an antistatic biaxially oriented polyester film with less aggregates of the antistatic agent.

Biaxially oriented polyester films are widely used as various optical films because of their excellent transparency, dimensional stability, and chemical resistance.
In particular, the base film for prism lens sheets used in LCD, hard coat processing, the base film for AR (anti-reflection) film and the anti-crushing film for CRT are required to have excellent strength and dimensional stability. Therefore, a relatively thick film is preferably used. The film used for such an optical film is required to have excellent transparency and excellent adhesion to prism lens processing, hard coat processing, and AR processing, and minute foreign substances contained in the film are also optical defects. Therefore, it is desired that the number be as small as possible, and this tendency has been increasing in recent years as the image display device has been improved in definition.

  Furthermore, in order to maintain high transparency, it is important to smooth the surface of the film, but if there are minute irregularities on the surface, the optical properties such as transparency and haze will be reduced, leading to deterioration in quality. It was.

  On the other hand, the polyester film has excellent characteristics, but as a common problem with plastic films, static electricity is likely to be generated, and there are drawbacks in that various troubles occur during the film forming process, the processing process, and the use of the product.

  As a method for preventing such electrostatic damage, (1) a method of applying an anionic compound or cationic compound or so-called conductive particles, (2) a method of depositing a metal compound, (3) an organic sulfonate or organic phosphorus A method of kneading an anionic compound such as an acid salt is known.

  In the method of applying an antistatic agent such as an anionic compound or a cationic compound, the coating layer is often sticky, and the winding property of the film is remarkably lowered. In order to improve the winding property, when a large amount of inorganic particles is added to the coating layer, the transparency is lowered, which is not preferable when used as an optical base film. Although there is a method of adding a slipperiness improving agent such as polyethylene wax to improve slipperiness, the adhesion to the hard coat layer, the light diffusion layer, and the Pruss layer may be remarkably lowered. Further, the method of applying conductive carbon or conductive metal particles has an advantage that the antistatic effect is relatively good and can be manufactured at a relatively low cost, but the transparency of the film is deteriorated.

  In addition, the method of vapor-depositing the metal compound of (2) is excellent in antistatic properties, and in recent years the use is expanding as a transparent conductive film, but the production cost is high and suitable for specific uses. It is difficult to use as a general antistatic film.

  Moreover, although the method of kneading the antistatic agent of (3) can be manufactured at a low cost, the organic antistatic agent is uniformly and not finely dispersed in the polyester resin. In addition, because of the aggregation of the organic antistatic agent, irregularities may be seen on the surface of the film, resulting in inferior optical properties such as transparency.

According to Patent Document 1, at the stage of polymerizing a polyester resin, an antistatic agent is added in an amount of 0.1 to 15% by weight, and the obtained polyester resin is again extruded using a biaxial extruder, and charged. It is intended to reduce the preventive spots and the generation of aggregates of the antistatic agent. However, although antistatic spots can be reduced, the effect of reducing the generation of aggregates of the antistatic agent is not sufficient, and the yellowness of the resin is increased by reextrusion, which is inappropriate for optical applications.
Japanese Patent No. 3629878

  An object of the present invention is to provide an antistatic biaxially oriented polyester film in which the aggregates of the antistatic agent are few in view of the above-mentioned problems of the prior art.

  As a result of diligent research, the present inventors have come to obtain an antistatic film with extremely little aggregate formation of the antistatic agent by adding a highly purified antistatic agent in the polymerization stage of the polyester resin.

That is, the said subject can be achieved by the following solution means.
1st invention is the antistatic biaxially-oriented polyester film which contains 0.1-15 weight% of organic antistatic agents in the polyester which does not contain particle | grains substantially, The number of coarse things with a diameter of 1 micrometer or more is included. It is an antistatic biaxially oriented polyester film characterized by comprising a polyester of 100 (pieces / 0.01 g) or less.

  The second invention is the antistatic biaxially oriented polyester film (B) according to the first invention on at least one side of the biaxially oriented polyester film (A layer) substantially free of particles and an organic antistatic agent. Layer) is an antistatic laminated biaxially oriented polyester film.

  According to a third aspect of the present invention, there is provided the antistatic laminated biaxially oriented polyester film according to the first or second aspect, further comprising a coating layer (C layer) comprising a composition containing an adhesion modifying resin and particles. It is.

  The antistatic biaxially oriented polyester film of the present invention has an antistatic property and has the advantage that there are very few coarse aggregates derived from the antistatic agent.

Embodiments of the present invention will be described below.
In the present invention, the polyester composition used as a raw material for the film contains 0.1 to 15% by weight of an organic antistatic agent in the polyester which does not substantially contain particles.

  The polyester is not particularly limited, but polyethylene terephthalate (PET) and poly (ethylene-2,6-naphthalenedicarboxylate) (PEN) are preferable. In addition, 2 or more types of polymers may be mixed within the range which does not inhibit the objective of this invention, and a copolymer may be used. Moreover, it may be added to such an extent that additives such as antioxidants, heat stabilizers, ultraviolet absorbers and the like are usually added within a range not impairing the object of the present invention.

  In the present invention, the polyester composition used as a raw material for the film does not contain particles for the purpose of imparting slipperiness after film processing. If the easy-adhesion layer laminated in-line in the film production process contains fine particles having a uniform particle size and imparts slipperiness, it is possible to impart good winding properties and a function to prevent scratches. Therefore, particles in the polyester base film are unnecessary, and it is more suitable not to add particles in the polyester base film to obtain a highly transparent film.

  The polyester composition used as a raw material for the film of the present invention contains 0.1 to 15% by weight of an organic antistatic agent. Although it does not specifically limit as an organic type antistatic agent, The higher ester normally called a wax which consists of a C14-28 fatty acid and a C5-C34 alcohol, or an alkylsulfonic acid metal salt derivative etc. Preferably exemplified. Among these, higher esters composed of a divalent fatty acid having 18 to 22 carbon atoms and an alcohol having 6 to 18 carbon atoms or alkali metal dodecylbenzenesulfonate are particularly preferable.

  The content of the organic antistatic agent is 0.1 to 15% by weight, preferably 0.5 to 10% by weight, and more preferably 1 to 10% by weight from the viewpoint of fine dispersion of the additive. If the content is less than this range, other expected effects such as antistatic properties are small, and if it is more than this range, other physical properties of the polyester such as the melting point, even if the additive is finely dispersed. Therefore, physical properties such as mechanical strength may be reduced when the film is processed.

In the present invention, the organic antistatic agent is added in the polymerization stage of the polyester composition. In the present invention, it is important that the organic antistatic agent is added after highly purified.
A specific purification method will be described later.

  Next, although the preferable manufacturing method of the polyester composition used as a film raw material by this invention is demonstrated to a polyethylene terephthalate as an example, it is not limited to this.

  The polyester used in the polyester film of the present invention can be produced by using a polycondensation catalyst and adding a magnesium compound and a phosphorus compound as a resistance adjuster and a heat resistance improver as necessary. Details thereof will be described later.

  The polyester used for the polyester film of the present invention is preferably such that the main ester unit (repeating unit) is composed of ethylene terephthalate from the viewpoint of having a desired high degree of clarity, specifically, all ester units (repeating units). ) Preferably 80 mol% or more (more preferably 90 to 100 mol%) of ethylene terephthalate is suitable.

  As the copolymerization component, as the dicarboxylic acid component, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and dimer acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid; And aromatic dicarboxylic acids such as acid, isophthalic acid, naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. In addition, as glycol components, aliphatic glycols such as trimethylene glycol, tetramethylene glycol, neopentyl glycol, pentamethylene glycol and hexamethylene glycol; fats such as 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol Cyclic glycols; aromatic glycols such as p-xylylene glycol and m-xylylene glycol. Any one of these dicarboxylic acid components and glycol components may be used alone, or two or more thereof may be used in combination at any ratio.

  When an antimony compound is used as the polyester polycondensation catalyst used in the antistatic polyester film of the present invention, for example, antimony trioxide, antimony pentoxide, antimony acetate, antimony glycoxide, etc. may be mentioned. A seed may be used independently or 2 or more types may be used together. Antimony trioxide is particularly preferable.

  The antimony compound is preferably added in such an amount that the content of antimony atoms with respect to the finally obtained polyester is 100 to 200 ppm. If it is less than 100 ppm, the polymerization productivity is lowered, and conversely if it exceeds 200 ppm. Insoluble foreign matter is likely to occur. A more preferable content of antimony atoms is 140 to 170 ppm.

  In the present invention, a polymerization catalyst other than the antimony compound may be used in combination. Examples of the polymerization catalyst other than the antimony compound include a germanium compound and a titanium compound. The amount of these used is such that the content of germanium atoms or titanium atoms in the finally obtained polyester is at most 50 ppm.

  The polyester resin used for the polyester film of the present invention can be produced by using a polycondensation catalyst and adding an organic antistatic agent or the like. At that time, it is preferable to bring the esterification reaction can to a pressure higher than normal pressure, and at this stage, add an organic antistatic agent, and if necessary, a resistance adjusting agent such as a magnesium compound and a phosphorus compound, and a heat resistance improving agent. In addition, the esterification reaction is carried out using three or more cans, and the organic antistatic agent is homogeneously added in two or more of the three or more cans. It is further preferable when mixing with.

  In addition, in the manufacturing method of the polyester resin of this invention, the addition time in particular of a polymerization catalyst is not restrict | limited. That is, it may be added at an initial stage in the esterification reaction or may be added thereafter. Moreover, it is preferable to add an organic antistatic agent and, if necessary, a resistance adjusting agent such as a magnesium compound and a phosphorus compound, and a heat resistance improving agent as an ethylene glycol solution from the viewpoint of supply accuracy.

  Also. The temperature in the can (reaction system) in the esterification reaction can of 3 or more can be 240-280 degreeC normally, Preferably it is 255-265 degreeC. If it is less than 240 ° C., the reaction rate is lowered, which is not preferable. On the other hand, if it exceeds 280 ° C., the organic antistatic agent may be altered, and the amount of by-product of DEG increases, This is not preferable because the hue of the polymer tends to change. The esterification reaction can is preferably 5 cans or less from the viewpoint of polyester production efficiency.

  The final product (polymer) is preferably filtered before being chipped. For such filtration, a filter having an opening of about 3 to 20 μm is usually used, but it is 7 μm or less, preferably 5 μm or less.

  Particles are not substantially contained in the polyester film of the base material of the present invention. For example, in the case of inorganic particles, when the inorganic elements are quantified by fluorescent X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, and most preferably the detection limit or less. means. This is because contaminants derived from foreign substances may be mixed without positively adding particles to the base film.

(Purification of organic antistatic agent)
In general, an organic antistatic agent such as an alkyl sulfonic acid metal salt derivative is added to the esterification reaction can step and the like, and even in an agitated state, an aggregate of the organic antistatic agent exists. When a polyester film having an antistatic function is produced using a polyester resin that has been polymerized, this aggregate serves as a nucleus, causing irregularities and lowering optical properties such as transparency. In addition, a necessary antistatic function may not be obtained. In order to prevent this, it is important in the present invention to perform advanced purification before adding an organic antistatic agent.

  Although there is no restriction | limiting in particular in the method of reducing the aggregate content in an organic type antistatic agent, For example, the method as described below is mentioned. An organic antistatic agent is dissolved in a solvent to form a solution, and the solution is filtered through a filter having a filtration particle size of 0.5 μm or more and 1 μm or less under a liquid temperature of 15 ° C. or more and less than 35 ° C., and then 50 ° C. or more. , After heating to less than 70 ° C., further cooling to 15 ° C. or more and less than 35 ° C., and filtering under a filter particle size of 0.5 μm or more and 1 μm or less under these conditions is preferred. .

  The solvent for dissolving the organic antistatic agent in a solvent is not particularly limited as long as the organic antistatic agent dissolves. For example, for a water-soluble or water-dispersible polyester resin, water, Alcohols such as ethanol, isopropyl alcohol, and benzyl alcohol can be suitably used, and water and isopropyl alcohol are most preferable.

  More specifically, for example, a solvent is added to the organic antistatic agent and stirred to obtain a solution having a solid content concentration of 2% by mass to a solubility limit concentration, preferably 5% by mass to a solubility limit concentration. This solution is allowed to stand as it is, and coarse aggregates are allowed to settle. The standing time is preferably 5 to 20 days, and the temperature during standing is preferably less than 35 ° C. If it is 35 ° C. or higher, the aggregates may not be sufficiently settled. About 9/10 of the supernatant is preferably taken out of the left standing liquid and subjected to a microfiltration treatment. By the microfiltration treatment, aggregates generated during the standing period are removed.

  The filter medium used for the microfiltration has a filtration particle size (initial filtration efficiency: 95%) of 1 μm or less and 0.5 μm or more as filtration performance. It is more preferable to use a combination of two or more filters having different filtration performance within the range. When the filtration particle size exceeds 1 μm, removal of aggregates tends to be insufficient. When the filtration performance is less than 0.5 μm, the filtration pressure increases and the filtration efficiency deteriorates. In the case of using a combination of filters having different filtration performances, it is effective to make a filter in order from a filter with a larger filtration particle size.

  The type of filter medium for microfiltration of the solution is not particularly limited as long as it has the above performance, and examples thereof include a filament type, a felt type, and a mesh type. The material of the filter medium for microfiltration of the solution is not particularly limited as long as it has the above-described performance and does not adversely affect the solution. Examples thereof include stainless steel, polyethylene, polypropylene, and nylon. The number of times of filtration through the filter is 2 times or more, preferably 5 times or more, and more preferably 20 times or more. There is no upper limit on the number of times of filtration, but considering efficiency, it may be about 50 times at the maximum.

  The filtrate of this solution is then heated to 50 ° C. or higher and lower than 70 ° C., preferably 55 ° C. or higher and lower than 65 ° C. At this time, in order to keep the temperature of the solution uniform, it is preferable to stir as necessary. The heating time is preferably 1 hour or more and less than 3 hours. If it is less than 1 hour, a sufficient effect cannot be obtained. The effect does not change even after 3 hours.

  Thereafter, the temperature is lowered and the mixture is allowed to stand to allow fine aggregates to settle, and the microfiltration treatment is performed again. By this refiltration treatment, the aggregates produced again are removed. The standing time is preferably 2 to 10 hours, and the temperature during standing is preferably less than 30 ° C. The filter particle size (initial filtration efficiency: 95%) of the filter used for the refiltration treatment is 0.5 to 1 μm. Filtration temperature is 15 degreeC or more and less than 35 degreeC, and 20 degreeC or more and less than 35 degreeC are preferable. Further, the number of times of filtration passing through the filter is 2 times or more, preferably 5 times or more, and more preferably 20 times or more. There is no upper limit on the number of times of filtration, but considering efficiency, it may be about 50 times at the maximum.

Next, the obtained solution is mixed with ethylene glycol at an arbitrary ratio, heated, and the solvent other than ethylene glycol is evaporated to 10% or less.
An ethylene glycol solution of the obtained organic antistatic agent is added so as to have a predetermined blending amount.

By using an antistatic agent obtained by a purification treatment as exemplified above, a polyester resin with a low content of aggregates derived from the antistatic agent is obtained, and the diameter defined by the present invention is effectively provided. A polyester resin film having an excellent antistatic property and an optical characteristic of 100 (pieces / 0.01 g) or less of coarse particles having a size of 1 μm or more can be obtained.
In addition, the layer structure of the polyester film used as a substrate in the present invention may be a single layer or a structure in which a layer containing an organic antistatic agent is laminated on at least one side. In the case of a laminated structure, a coextrusion method is preferable.

  If the intermediate layer is made of a polyester resin that does not contain an organic antistatic agent and the layers on both surfaces are made of an organic antistatic agent, the amount of organic antistatic agent used can be reduced. In addition, the total number of aggregates derived from the organic antistatic agent per unit area can be reduced, which is more preferable.

  As a manufacturing method of the polyester film of a base material, the following method is mentioned, for example. After containing the organic antistatic agent obtained by the above method and substantially drying the thermoplastic resin pellets not containing particles for the purpose of imparting slipperiness sufficiently, supply to the extruder, An unoriented thermoplastic resin sheet is formed by melting and extruding into a sheet at a temperature equal to or higher than the melting temperature and cooling and solidifying.

  In order to transfer the pellet, it is usually carried out by air using a predetermined pipe. In this case, it is preferable to use purified air by using a HEPA filter in order to prevent dust contamination. The HEPA filter used at this time is preferably a filter having a performance of cutting 95% or more of dust having a nominal filtration accuracy of 0.5 μm or more.

  At this time, high-precision filtration is performed in order to remove foreign matters contained in the resin at an arbitrary place where the molten resin is maintained at about 280 ° C. The filter medium used for high-precision filtration of molten resin is not particularly limited, but the filter medium of the sintered stainless steel is excellent in removal performance of aggregates and high-melting-point organic substances mainly composed of Si, Ti, Sb, Ge, Cu. It is.

  Furthermore, the filter particle size (initial filtration efficiency 95%) of the filter medium is preferably 15 μm or less. When the thickness is 15 μm or more, the foreign matters of 20 μm or more cannot be sufficiently removed. (Initial filtration efficiency of 95%) is indispensable for obtaining an optical film with few optical defects, although productivity may be reduced by performing high-precision filtration of molten resin using a filter medium of 15 μm or less. .

  The obtained unstretched sheet is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film. Furthermore, the edge part of a film is hold | gripped with a clip, is guide | induced to the hot air zone heated at 80-180 degreeC, and is extended | stretched 2.5 to 5.0 times in the width direction after drying. Subsequently, the film is guided to a heat treatment zone of 160 to 240 ° C., and heat treatment is performed for 1 to 60 seconds to complete crystal orientation. In this heat treatment step, 1 to 12% relaxation treatment may be performed in the width direction or the longitudinal direction as necessary.

  A coating liquid for modifying adhesiveness is applied to at least one surface of the polyester film at an arbitrary stage in this process. The coating layer made of a composition containing an adhesion-modifying resin and particles, which is laminated on the optically laminated polyester film of the present invention, acts to increase adhesion when a hard coat layer is laminated on the laminated polyester film. Is.

  Examples of the adhesion-modifying resin for the coating layer include copolymer polyester resins, polyurethane resins, acrylic resins, styrene-maleic acid graft polyester resins, acrylic graft polyester resins, ethylene-vinyl acetate copolymers, maleic acid grafts. Examples thereof include modified polyethylene, polyolefin such as polypropylene, and the like. At least these resins are used alone, or these resins are used by polymer blending. In the case of a single layer consisting only of a copolyester resin, if the adhesion is insufficient, a polymer blend is recommended. Among these, copolymer polyester resins, blends of polyester resins, blends of copolymer polyester resins and polyurethane resins, styrene-maleic acid graft polyester resins, and acrylic resins are particularly preferable because of their excellent adhesion. The blending ratio of the two resins is preferably blended at a mass ratio of 10 to 90:90 to 10 in consideration of the occurrence of interference fringes and adhesion.

  In the case of using the copolyester resin used in the coating layer, the copolyester resin preferably includes a branched glycol component as a constituent component. Examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2-methyl-2-butyl-1,3-propane. Diol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2 2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2- Examples include di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol. It is.

  The branched glycol component is contained in a proportion of preferably 10 mol% or more, more preferably 20 mol% or more with respect to the total glycol component. As the glycol component other than the above compounds, ethylene glycol is most preferable. If it is a small amount, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4 cyclohexanedimethanol or the like may be used.

  The dicarboxylic acid component contained in the copolymer polyester resin is most preferably an aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid. If the amount is small, other dicarboxylic acids; diphenylcarboxylic acid and 2,6-naltalenedicarboxylic acid aromatic dicarboxylic acid may be added and copolymerized.

  In addition to the dicarboxylic acid component, 5-sulfoisophthalic acid or an alkali metal salt thereof is preferably used in the range of 1 to 10 mol% in order to impart water dispersibility. For example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid, 5- (4-sulfophenoxy) isophthalic acid and salts thereof can be used.

  Next, the case where a polyurethane resin is used as the resin constituting the coating layer constituting the antistatic polyester film of the present invention will be described.

  The polyurethane resin is, for example, a resin containing a block type isocyanate group, and includes a heat-reactive water-soluble urethane in which a terminal isocyanate group is blocked with a hydrophilic group (hereinafter referred to as a block). Examples of the isocyanate group blocking agent include bisulfites and sulfonic acid group-containing phenols, alcohols, lactam oximes and active methylene compounds.

  The blocked isocyanate group makes the urethane prepolymer hydrophilic or water-soluble. When heat energy is applied to the resin during drying or heat setting during film production, the blocking agent is released from the isocyanate group, so the resin fixes a water-dispersible copolyester resin mixed in a self-crosslinked stitch. And reacts with the terminal groups of the resin. The resin under preparation of the coating solution is hydrophilic and has poor water resistance, but when the thermal reaction is completed by coating, drying and heat setting, the hydrophilic group of the urethane resin, that is, the blocking agent is released, so the water resistance is good. A coating film is obtained.

  Among the above blocking agents, bisulfites are most preferred as those that are suitable for heat treatment and heat treatment and are widely used industrially.

  The chemical composition of the urethane prepolymer used in the above resin is (1) an organic polyisocyanate having two or more active hydrogen atoms in the molecule, or a molecular weight having at least two active hydrogen atoms in the molecule. 200 to 20,000 compounds, (2) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (3) a chain extender having at least two active hydrogen atoms in the molecule. The resulting compound has a terminal isocyanate group.

  The compound (1) generally known is a compound containing two or more hydroxyl groups, carboxyl groups, amino groups or mercapto groups in the terminal or molecule, and particularly preferred compounds include polyether polyols. And polyether ester polyols.

  Examples of polyether polyols are compounds obtained by polymerizing alkylene oxides such as ethylene oxide and propylene oxide, styrene oxide and epichlorohydrin, or the like, or random polymerization, block polymerization, or addition polymerization to a polyhydric alcohol. There are compounds.

  Examples of the polyester polyol and the polyether ester polyol mainly include linear or branched compounds. Polyvalent saturated or unsaturated carboxylic acids such as succinic acid, adipic acid, phthalic acid and maleic anhydride, or the carboxylic acid anhydride, ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1 Condensation with polyvalent saturated and unsaturated alcohols such as 1,6-hexanediol and trimethylolpropane, polyalkylene ether glycols such as relatively low molecular weight polyethylene glycols and polypropylene glycols, or mixtures of these alcohols Can be obtained.

  Furthermore, polyesters obtained from lactones and hydroxy acids can be used as polyester polyols, and polyether esters obtained by adding ethylene oxide or propylene oxide to polyesters prepared in advance can be used. it can.

  Examples of the organic polyisocyanate (2) include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4. -Alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or a single or a plurality of these compounds with trimethylolpropane and the like in advance. Examples include added polyisocyanates.

  Examples of the chain extender having at least two active hydrogens in (3) above include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol, glycerin, trimethylolpropane, and Examples thereof include polyhydric alcohols such as pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine, and piperazine, amino alcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water.

  In order to synthesize the urethane polymer of the above (3), it is usually 5 minutes or less at a temperature of 150 ° C. or less, preferably 70 to 120 ° C., by a single-stage or multi-stage isocyanate polyaddition method using the chain extender. Let react for several hours. The ratio of isocyanate groups to active hydrogen atoms can be freely selected as long as it is 1 or more, but it is necessary that free isocyanate groups remain in the obtained urethane prepolymer. Furthermore, the content of free isocyanate groups may be 10% by mass or less, but considering the stability of the urethane polymer aqueous solution after being blocked, it is preferably 7% by mass or less.

  The urethane prepolymer obtained is preferably blocked using bisulfite. Mix with aqueous bisulfite solution and allow reaction to proceed with good agitation for about 5 minutes to 1 hour. The reaction temperature is preferably 60 ° C. or lower. Thereafter, it is diluted with water to an appropriate concentration to obtain a heat-reactive water-soluble urethane composition. When the composition is used, it is prepared to have an appropriate concentration and viscosity. However, when heated to about 80 to 200 ° C., the bisulfite of the blocking agent is dissociated and the active isocyanate group is regenerated, so that the prepolymer In some cases, a polyurethane polymer is produced by a polyaddition reaction that occurs within or between the molecules, and an addition reaction to other functional groups may occur.

  As an example of the resin (B) containing a block-type isocyanate group described above, a trade name Elastron manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. is typically exemplified. Elastolone is a compound in which an isocyanate group is blocked with sodium bisulfite, and is water-soluble due to the presence of a carbamoylsulfonate group having strong hydrophilicity at the molecular end.

  When the coating liquid is prepared by mixing the copolymerized polyester resin (A) containing a branched glycol component and the resin (B) containing a block type isocyanate group used in the present invention, the resin (A) and the resin The mass ratio of (B) is preferably (A) :( B) = 90: 10 to 10:90, more preferably (A) :( B) = 80: 20 to 20:80. If the ratio of the said resin (A) with respect to solid content mass is less than 10 mass%, the applicability | paintability to a base film is unsuitable, and the adhesiveness between a surface layer and this film will become inadequate. In the case of less than 10% by mass, practical adhesion cannot be obtained in the UV curing type hard coat.

  In order to promote the thermal crosslinking reaction, a catalyst may be added to the aqueous coating solution used in the present invention, such as various inorganic substances, salts, organic substances, alkaline substances, acidic substances and metal-containing organic compounds. These chemicals are used. Moreover, in order to adjust pH of aqueous solution, you may add an alkaline substance or an acidic substance.

  When the aqueous coating solution is applied to the surface of the substrate film, a necessary amount of a known surfactant can be added and used in order to increase wettability to the film and coat the coating solution uniformly. . As the solvent used in the coating solution, alcohols such as ethanol, isopropyl alcohol and benzyl alcohol may be mixed in addition to water until the ratio of the total coating solution is less than 50% by mass. Furthermore, if it is less than 10 mass%, you may mix in the range which can melt | dissolve organic solvents other than alcohol. However, the total of alcohols and other organic solvents in the coating solution is less than 50% by mass.

  If the addition amount of the organic solvent is less than 50% by mass, the drying property is improved at the time of coating and drying, and the appearance of the coating film is improved as compared with the case of using only water. If it exceeds 50% by mass, the evaporation rate of the solvent is high, the coating solution concentration changes during coating, the viscosity rises and the coating property is lowered, and there is a risk of causing poor appearance of the coating film, Furthermore, there is a risk of fire.

  The solution viscosity of the coating solution is preferably 1.0 PaS (Pascal Sec) or less. When the pressure is 1.0 PaS (Pascal Sec) or higher, streaky coating thickness spots are likely to occur.

This coating layer is made of a composition containing an adhesion modifying resin and particles.
Examples of the particles include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and mica, and crosslinked polymer particles. And organic particles such as calcium oxalate.

  Among these particles, silica is most suitable because it has a relatively close refractive index to that of the polyester resin and high transparency is easily obtained. The average particle diameter of the particles can be 0.01 to 3 μm in terms of equivalent circle diameter by electron microscopy. However, when the polyester film of the present invention is used as a base material for an optical functional film, an average of preferable particles is used. The particle diameter is 0.02 to 1.0 μm. The content of the particles in the coating layer after drying can be arbitrarily determined in consideration of the fact that it does not affect the refractive index and transparency of the adhesion-modified resin, polyester resin, etc., but usually 0.05 to 30 It is preferable to set it as the mass%, specifically 2-20 mass%.

  The average particle size of the particles of a specific embodiment is usually 1.0 μm or less, preferably 0.5 μm or less, more preferably 0.1 μm or less. When the average particle diameter exceeds 1.0 μm, the film surface becomes rough and the transparency of the film tends to be lowered. Further, the particle content contained in the coating solution is such that the particle content of the coating film is usually 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less after coating and drying. Added. When the particle content of the coating film exceeds 30% by mass, not only the transparency of the film is deteriorated, but also the adhesion may be impaired.

  Two or more kinds of the above particles may be blended in the coating layer, or the same kind of particles having different particle diameters may be blended. In any case, it is preferable that the average particle diameter of the whole particle and the total content satisfy the above-mentioned range. When applying the coating solution, it is important to dispose the filter medium so that the coating solution is precisely filtered immediately before coating in order to remove coarse aggregates of particles in the coating solution.

  The aqueous coating solution can be applied by any known method. Examples include reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method and curtain coating method. These methods can be performed alone or in combination.

  The degree of cleanliness when applying the coating solution is preferably class 1000 or less in order to reduce adhesion of dust.

Although the process of apply | coating the said aqueous coating liquid may be a normal application process, ie, the process of apply | coating to the base film which carried out biaxial stretching and heat setting, apply | coating during the manufacturing process of this film is more preferable. More preferably, it is applied to the substrate film before the crystal orientation is completed. The solid content concentration in the aqueous solution is usually 30% by weight or less, preferably 10% by weight or less. The aqueous coating solution is applied such that 0.04 to 5 g, preferably 0.2 to 4 g, is adhered per 1 m ² of the running film. The film coated with the aqueous coating solution is guided to a tenter for stretching and heat setting, and heated there to form a stable film by a thermal crosslinking reaction, and becomes a polyester-based film.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all by these Examples. In the following examples and comparative examples, TPA is terephthalic acid, and EG is ethylene glycol. Each characteristic and physical property value were measured by the following test methods.

(1) Number of coarse products The coating layers of the biaxially stretched polyester films obtained in Examples and Comparative Examples were wiped off using Kimwipe impregnated with methyl ethyl ketone (WIPRS S200: manufactured by Crecia). A solvent other than methyl ethyl ketone may be used as long as it can remove the coating layer.

  0.2 mg of the film from which the coating layer has been removed is weighed and melted at 270 ° C. on a cover glass. Press from above with the same cover glass and quench. Using a NIRECO image analyzer (Luzex-Fs), the number of foreign matters having a size of 1 μm or more was measured with a microscope by a transmission dark field method. At this time, CF Plan DM 40X was used as an objective lens.

Example 1
As the esterification reaction apparatus, a continuous esterification reaction apparatus comprising a three-stage complete mixing tank having a stirrer, a partial condenser, a raw material charging port and a product take-out port is used, TPA is set to 2 ton / hr, EG The amount of antimony trioxide is 2 mol to 1 mol of TPA, and the amount of Sb atoms is 160 ppm with respect to the produced PET. These slurries are continuously supplied to the first esterification reactor of the esterification reactor, and the atmospheric pressure is reached. The reaction was conducted at an average residence time of 4 hours at a reaction temperature of 255 ° C.

  Next, the reactive organism in the first esterification reaction can is continuously taken out of the system and supplied to the second esterification reaction can. Further, 5 wt.% Of lithium dodecylbenzenesulfonate is added to the generated PET. % Of the EG solution of lithium dodecylbenzenesulfonate purified by the method described later was added and reacted at 260 ° C. at an average residence time of 1.5 hours at normal pressure.

Further, the reaction product in the second esterification reactor can be continuously taken out of the system and supplied to the third esterification reactor, and reacted at 260 ° C. with an average residence time of 0.5 hours at normal pressure. It was.
The esterification reaction product produced in the third esterification reaction can is continuously supplied to a three-stage continuous polycondensation reaction apparatus to carry out polycondensation, and further, a filter medium of a stainless sintered body (nominal filtration accuracy of 5 μm). The polyester resin pellets (A) having an intrinsic viscosity of 0.62 dl / g were obtained.

(1) Preparation of EG solution of organic antistatic agent A 20% by mass aqueous dispersion of lithium dodecylbenzenesulfonate was allowed to stand for 10 days, and about 9/10 of the supernatant was taken out. This aqueous solution is filtered with a felt type filter having a filtration particle size of 5 μm under the condition of a liquid temperature of 25 ° C. until the number of circulation reaches 5 times, and further, with a felt type filter having a filtration particle size of 1 μm until the number of circulation is 30 times Filtered. Next, the mixture was heated to 60 ° C. and held for 2 hours, and further filtered under a condition of 25 ° C. with a felt type filter having a filtration particle size of 1 μm until the number of circulation was 5 times.
Subsequently, the obtained aqueous solution was mixed with ethylene glycol at a ratio of 1: 1, and then heated, and water was distilled off until it became 1% by weight or less.

(2) Preparation of coating solution The coating solution used in the present invention was prepared according to the following method.
A reaction vessel was charged with 95 parts by weight of dimethyl terephthalate, 95 parts by weight of dimethyl isophthalate, 35 parts by weight of ethylene glycol, 45 parts by weight of neopentyl glycol, 0.1 part by weight of zinc acetate and 0.1 part by weight of antimony trioxide, and 180 ° C. The transesterification was carried out over 3 hours. Next, 6.0 parts by mass of 5-sodium isophthalic acid was added and an esterification reaction was performed at 240 ° C. over 1 hour, followed by heavy polymerization over 2 hours at 250 ° C. under reduced pressure (10 to 0.2 mmHg). A condensation reaction was performed to obtain a polyester resin having a molecular weight of 19,500 and a softening point of 60 ° C.

  6.7 parts by mass of an aqueous dispersion of 30% by mass of the obtained copolyester resin and a 20% by mass aqueous solution of a self-crosslinking polyurethane resin containing an isocyanate group blocked with sodium bisulfite (manufactured by Daiichi Kogyo Seiyaku) : 40 parts by trade name Elastron H-3), 0.5 parts by weight of elastron catalyst (Cat 64), 47.8 parts by weight of water and 5 parts by weight of isopropyl alcohol, respectively, and 1 surfactant. 5% by mass of colloidal silica (manufactured by Nissan Chemical Industries, Snowtex OL) was added to prepare a coating solution.

  The polyester resin pellet (A) obtained by the above method was dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, then supplied to an extruder, melted and extruded into a sheet at about 280 ° C., and maintained at a surface temperature of 20 ° C. The film was rapidly cooled and solidified on a roll to obtain a cast film.

  At this time, a stainless sintered filter medium having a filtration particle size of 15 μm (initial filtration efficiency of 95%) was used as a filter medium for removing foreign substances from the molten resin. Next, this cast film was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with a roll group having a difference in peripheral speed to obtain a uniaxially oriented PET film.

  Thereafter, the coating solution was precisely filtered with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency of 95%) of 25 μm, and the coating solution was applied to one side by a reverse roll method and dried. Subsequently, after coating, the edge of the film is gripped with a clip, guided to a hot air zone heated to 130 ° C., stretched 4.0 times in the width direction after drying, and further heat fixed at 230 ° C. for 10 seconds. The biaxially stretched polyester film having a thickness of 125 μm was obtained by performing a 3% relaxation treatment in the transverse direction at 130 ° C. At this time, the thickness of the coating layer was 0.07 μm.

  As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse products, the number of coarse products was 39 / 0.01 g.

Example 2
A base polyester film having a three-layer structure of A / B / A was formed by a coextrusion method by the following method. In addition, the polyester resin containing the organic type antistatic agent obtained in Example 1 was used for the A layer, and the polyethylene terephthalate pellet (RE-553 by Toyobo Co., Ltd.) which does not contain particles was used for the B layer.

  Polyethylene terephthalate resin pellets containing 5% by mass of lithium dodecylbenzenesulfonate similar to Example 1 as a polyester resin material for layer A were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Next, polyethylene terephthalate resin pellets (RE-553, manufactured by Toyobo Co., Ltd.) containing no particles as the raw material for the B layer are dried in an extruder 1 under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and then supplied to the extruder 2. Dissolved at 285 ° C. After filtering these two polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy: 95% cut of particles of 10 μm or more), laminating them in a three-layer confluence block, and extruding them into a sheet form from the die The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the lamination ratio of the thicknesses of the B layer, the A layer, and the B layer was 10:80:10.

  During the film formation, a stainless sintered filter medium having a filtration particle size (initial filtration efficiency of 95%) of 15 m was used as a filter medium for removing foreign substances from the molten resin. Next, this unstretched film was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with a roll group having a peripheral speed difference to obtain a uniaxially oriented PET film.

Thereafter, a biaxially stretched ester film having a thickness of 125 μm and having a coating layer was obtained in the same manner as in Example 1.
As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse materials, it was 7 / 0.01 g.

Example 3
A polyester resin pellet (B) was obtained in the same manner as in Example 1 except that the blending amount was changed so that the content of lithium dodecylbenzenesulfonate with respect to the generated PET was 13% by mass. Next, a 125 μm-thick biaxially stretched ester film having a coating layer was obtained in the same manner as in Example 1.
As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse products, the number of coarse products was 95 / 0.01 g.

Example 4
Polyester resin pellets (C) were obtained in the same manner as in Example 1 except that the blending amount was changed so that the content of lithium dodecylbenzenesulfonate with respect to the generated PET was 0.3% by weight. Next, a biaxially stretched polyester film having a thickness of 125 μm and having a coating layer was obtained in the same manner as in Example 1.
As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse products, the number of coarse products was 5 / 0.01 g.

Comparative Example 1
As the esterification reaction apparatus, a continuous esterification reaction apparatus comprising a three-stage complete mixing tank having the same stirrer, partial condenser, raw material charging port and product take-out port as in Example 1 was used, and TPA was 2 tons. / Hr, 2 mol of EG with respect to 1 mol of TPA, antimony trioxide with an amount of 160 ppm of Sb atoms with respect to the produced PET, and these slurries are continuously connected to the first esterification reactor of the esterification reactor The reaction was carried out at normal pressure and an average residence time of 4 hours at a reaction temperature of 255 ° C.

  Next, the reactive organism in the first esterification reaction can is continuously taken out of the system and supplied to the second esterification reaction can. Further, 5 wt.% Of lithium dodecylbenzenesulfonate is added to the generated PET. % Of an unpurified EG solution of lithium dodecylbenzenesulfonate was added and allowed to react at 260 ° C. with an average residence time of 1.5 hours at normal pressure.

  Next, the reaction product in the second esterification reactor can be continuously taken out of the system and supplied to the third esterification reactor, and the average residence time is 0.5 hours at 260 ° C. at normal pressure. Reacted.

  The esterification reaction product produced in the third esterification reaction can is continuously supplied to a three-stage continuous polycondensation reaction apparatus to carry out polycondensation, and further, a filter medium of a stainless sintered body (nominal filtration accuracy of 5 μm). The polyester resin pellets having an intrinsic viscosity of 0.620 dl / g were obtained. The pellets were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, then supplied to an extruder, and melt-extruded into pellets at about 280 ° C. to obtain polyester resin pellets (D).

Next, a 125 μm-thick biaxially stretched ester film having a coating layer was obtained in the same manner as in Example 1.
As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse products, the number of coarse products was 145 / 0.01 mg.

Comparative Example 2
A polyester resin pellet (E) was obtained in the same manner as in Example 1 except that the blending amount was changed so that the content of lithium dodecylbenzenesulfonate was 20% by mass with respect to the generated PET. Next, a 125 μm-thick biaxially stretched ester film having a coating layer was obtained in the same manner as in Example 1.
As a result of evaluating the obtained biaxially stretched polyester film by the aforementioned method for measuring the number of coarse products, the number of coarse products was 197 / 0.01 g.

  The antistatic biaxially oriented polyester film of the present invention has antistatic properties and is extremely useful as a base film for optical functional films because it has very few coarse aggregates derived from the antistatic agent.

Claims (3)

  In an antistatic biaxially oriented polyester film containing 0.1 to 15% by weight of an organic antistatic agent in a polyester containing substantially no particles, the number of coarse materials having a diameter of 1 μm or more is 100 (pieces / 0.00. 01g) An antistatic biaxially oriented polyester film, characterized in that it is made of the following polyester.   The antistatic biaxially oriented polyester film (B layer) according to claim 1 is laminated on at least one side of a biaxially oriented polyester film (A layer) substantially free of particles and an organic antistatic agent. Antistatic laminated biaxially oriented polyester film.   Furthermore, the antistatic laminated biaxially-oriented polyester film of Claim 1 or 2 which provides the coating layer (C layer) which consists of a composition containing adhesiveness modification resin and particle | grains.