JP6988840B2 - Oligomer precipitation prevention polyester film - Google Patents

Description

The present invention relates to a polyester film used for industrial use and packaging. More specifically, the present invention relates to a polyester film having excellent post-heating oligomer precipitation prevention properties.

Polyester films typified by polyethylene terephthalate film have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and are excellent in cost performance, so they are used in various applications. Has been done.

Polyester is usually a linear polymer produced by a polycondensation reaction from a dicarboxylic acid component and a glycol component. However, conventionally known polyesters contain a few percent of oligomers such as cyclic trimers. Such oligomers such as cyclic trimers have a problem that when the polyester film is heat-treated, the oligomer is deposited on the film surface and the film is whitened. In particular, as the use of polyethylene terephthalate film is diversified, the processing conditions and usage conditions of the film are also diversified. For example, when oligomer precipitation on the film surface requires high transparency for optical applications, etc. Has become a big problem. From the viewpoint of productivity, as the heat treatment temperature applied to the post-processing becomes higher, the precipitation of oligomers due to the heat treatment is becoming more serious.

Therefore, as a method of suppressing the precipitation of oligomers due to heating, it has been proposed to reduce the amount of cyclic oligomers of the polyester raw material by a solid phase polymerization method in order to reduce the oligomers in the polyester film (see Patent Documents 1 and 2). Although the cyclic oligomer can be reduced by this method, the polycondensation reaction of the polyester also proceeds at the same time, the degree of polymerization of the obtained polyester is increased, and there is a problem that the load is increased when the extrusion molding is performed.

Further, it has been proposed to suppress the precipitation of oligomers after heating by applying a specific coating layer to a general polyester film and modifying the surface. (See Patent Document 3)

Japanese Unexamined Patent Publication No. 9-99530 Japanese Unexamined Patent Publication No. 2000-141570 Japanese Unexamined Patent Publication No. 2005-336394.

However, when the heating conditions of the polyester film are higher and the demand for transparency is high, the effect of preventing the precipitation of oligomers may be insufficient only by surface modification with a known coating layer. Specifically, when the polyester film is wound into a roll, stored and transported, the oligomer precipitation prevention function may be deteriorated as compared with the polyester film before winding.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a polyester film having excellent transparency after heat processing and extremely little precipitation of oligomers.

As a result of diligent studies to solve the above problems, the present inventors have found that the following polyester film remarkably exhibits an oligomer precipitation preventing effect. That is, the present invention has the following configuration.

1. 1. On at least one surface of a polyester film substrate, a laminated polyester film comprising a coating fabric layer is provided, the polyester resin constituting the polyester film substrate, a polyester of more than 60 mol% and repeating units of ethylene terephthalate The Tg of the resin used for the coating layer is 90 ° C. or higher and 200 ° C. or lower, and the Δ haze, which is the amount of increase in haze before and after heat treatment at 150 ° C. for 60 minutes, is 0.3% or less. An oligomer precipitation-preventing polyester film characterized by a haze of 1.5% or less before heat treatment.
2. 2. The oligomer precipitation-preventing polyester film according to the first aspect, wherein the static friction coefficient μs of the contact surfaces when one side of the film and the other side thereof are overlapped with each other is 0.1 or more and 0.6 or less. ..
3. 3. The oligomer precipitation prevention polyester film according to the first or second above, wherein the coating layer contains particles, the average particle size of the particles is 50 nm or more and 200 nm or less, and is larger than the thickness of the coating layer.

The oligomer precipitation prevention polyester film of the present invention has excellent transparency after heat processing, and there is almost no oligomer precipitation. Therefore, since post-processing can be performed at a high temperature, this film is suitably used in industrial applications such as optical applications where high quality is required.

The reason why the polyester film of the present invention exhibits the effect of preventing oligomer precipitation is considered as follows. That is, the precipitation of oligomers, which cannot be completely prevented by surface modification by the conventional film coating layer, is deposited on the surface through the defects of the extremely minute coating layer, and the cause of such defects is the surface of the film. It is considered that it is due to the local frictional force applied to the film.

In the present invention, the coefficient of static friction between one side of the film and the opposite side is set to a certain value or less to reduce the frictional force to the coating layer, and by keeping the value to a certain value or more, the film is wound into a roll. It is considered that the local pressure load due to the unwinding at the time was alleviated, the transparency after heat processing was preferably excellent, and the precipitation of the cyclic oligomer was prevented.

Hereinafter, the present invention will be described in detail.
The oligomer precipitation-preventing polyester film of the present invention is a laminated polyester film having a coating layer on at least one side of a polyester film base material. The polyester film base material is a film obtained by melt-extruding and stretching a polyester resin using a known method, and a film having a thickness of 10 to 250 μm is preferably used. Further, the polyester film base material may contain various stabilizers, ultraviolet rays, antistatic agents, lubricants, pigments, antioxidants, plasticizers and the like.

The polyester resin may be a homopolyester or a copolymerized polyester. When it is made of homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic diol. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, 1,3-propanezyl, 1,4-butanediol and 1, Examples thereof include 4-cyclohexanedimethanol. Typical homopolyesters include polyethylene terephthalate (PET), polyethylene terephthalate (PEN), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT) and the like, and polyethylene terephthalate is particularly preferable. On the other hand, the dicarboxylic acid component of the copolymerized polyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, P-oxybenzoic acid) and the like. One or more selected ones or more, and one selected from ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentylglycol and the like as the diol component. Or two or more types can be mentioned. In any case, the polyester referred to in the present invention is usually 60 mol% or more, preferably 80 mol% or more, preferably a polyester having ethylene terephthalate as a repeating unit.

The lower limit of the amount of oligomer contained in the polyester film substrate is preferably 0.25% by mass, more preferably 0.3% by mass, and even more preferably 0.35% by mass. When the amount of the oligomer contained in the polyester film substrate is 0.25% by mass or more, the treatment for reducing the amount of the oligomer does not require a particularly long time, which is preferable in terms of productivity.

The upper limit of the amount of the oligomer contained in the polyester film base material is preferably 1% by mass, more preferably 0.95% by mass, and further preferably 0.9% by mass. When the amount of the oligomer contained in the polyester film base material is 1% by mass or less, the effect of suppressing the precipitation of the oligomer by the coating layer is particularly likely to be exhibited, which is preferable.

The oligomer precipitation-preventing polyester film of the present invention has a remarkable effect of preventing oligomer precipitation when it is rolled up in a roll shape. In the film roll made of the oligomer-preventing polyester film of the present invention, the width of the film roll is not particularly limited, but from the viewpoint of ease of handling, the lower limit of the width of the film roll is 0.7 m or more. It is preferably 1.0 m or more, and more preferably 1.0 m or more. On the other hand, the upper limit of the width of the film roll is determined by the size of the device of the customer to be post-processed, but at present, 2.2 m is considered to be the maximum width, and 2.0 m or less is more preferable. It is more preferably 5 m or less. In addition, the winding length of the film roll is not particularly limited, but from the viewpoint of ease of winding and handling, when the film has a thickness of about 10 μm, it is preferably 10,000 m or less, and more preferably 8,000 m or less. preferable. When the film has a thickness of about 250 μm, it is preferably 2000 m or less, and more preferably 1800 m or less. Therefore, when the thickness of the film is in the middle of 10 to 250 μm, it is preferable to set the winding length to be 500 m or more and 10000 m or less. The lower limit of the winding length is preferably 100 m. When the winding length is 100 m or more, the effect of optimizing the slipperiness of the front and back surfaces in the present invention is more clearly exhibited.

As the take-up core, paper, plastic cores, metal cores such as 3 inches, 6 inches, and 8 inches can be usually used.

The type of resin used for the coating layer of the polyester film of the present invention is not particularly limited, and preferred examples thereof include PMMA resin, aminoacrylic resin, and cycloolefin polymer.

The Tg of the resin used for the coating layer is preferably 90 ° C. or higher and 200 ° C. or lower, more preferably 95 ° C. or higher and 170 ° C. or lower, and further preferably 100 ° C. or higher and 150 ° C. or lower. When Tg is 90 ° C. or higher, the oligoblocking property is not deteriorated, which is preferable. A resin having a Tg of more than 200 ° C. is unlikely to be suitably used as a transparent resin.

As a means for developing the slipperiness of the front and back of the film while maintaining the transparency of the film itself, a method of adding particles to the coating layer for preventing the precipitation of oligomers or a surface opposite to the coating layer for preventing the precipitation of oligomers. Examples thereof include a method of coating an easy-slip layer and a method of providing a layer in which particles are dispersed only on the surface layer of a film as a base material.

When particles are added to the coating layer, the lower limit of the average particle size of the particles contained in the coating layer is preferably 50 nm, more preferably 60 nm, and even more preferably 70 nm. When the average particle size is 50 nm or more, the slipperiness is not insufficient and scratches are less likely to occur, so that oligomers are less likely to precipitate, which is preferable.

The upper limit of the average particle size of the particles contained in the coating layer is preferably 200 nm, more preferably 180 nm, and even more preferably 160 nm. When the average particle size of the particles is 200 nm or less, haze is low and transparency is maintained, which is preferable. The average particle size of the particles is preferably larger than the thickness of the coating layer. When the average particle size of the particles is larger than the thickness of the coating layer, an appropriate slipperiness can be effectively obtained, and as a result, an oligomer precipitation suppressing effect can be obtained. More preferably, the average particle size of the particles is more preferably 15 nm or more larger than the thickness of the coating layer, and particularly preferably 20 nm or more. However, if the average particle size of the particles is too large with respect to the thickness of the coating layer, the particles are likely to fall off due to rubbing. Therefore, the average particle size of the particles may be larger in the range of 100 nm or less than the thickness of the coating layer. preferable.

The average particle size of the particles was measured by observing the particles in the cross section of the laminated film after processing with a scanning electron microscope, observing 100 particles, and using the average value as the average particle size.

The shape of the particles is not particularly limited as long as it satisfies the object of the present invention, and spherical particles and amorphous non-spherical particles can be used. The particle size of the amorphous particles can be calculated as the equivalent circle diameter. The equivalent circle diameter is a value obtained by dividing the observed particle area by π, calculating the square root, and doubling it.

The type of particles contained in the coating layer is not particularly limited, but for example, siloxane copolymer acrylic resin, crosslinked polystyrene, polystyrene-divinylbenzene, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product, and poly. Organic particles such as tetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silicone resin, acrylic resin, silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, granite, molybdenum disulfide, carbon black , Any of inorganic particles such as barium sulfate can be used. Further, core-shell type particles having a multi-layer structure composed of substances having different internal and external properties may be used. Silica is preferable.

The lower limit of the particle content contained in the coating layer is preferably 4% by mass (%, vs. resin), and more preferably 5% by mass (%, vs. resin). When it is 4% by mass or more, slipperiness is maintained and scratches are less likely to occur, so that oligomers are less likely to precipitate, which is preferable.

The upper limit of the particle content contained in the coating layer is preferably 20% by mass (%, vs. resin), more preferably 17% by mass (%, vs. resin), and even more preferably 15% by mass (%, vs. resin). Is. When it is 20% by mass or less, the haze is not too high and the transparency is maintained, which is preferable. The particle content is expressed as a mass% of the particle content with respect to the resin solid content of the coating layer.

The lower limit of the thickness of the coating layer is preferably 20 nm, more preferably 30 nm, and even more preferably 40 nm. When the thickness of the coating layer is 20 nm or more, the effect of suppressing oligomer precipitation becomes clear, which is preferable.

The upper limit of the thickness of the coating layer is preferably 150 nm, more preferably 130 nm, and even more preferably 120 nm. When the thickness of the coating layer is 150 nm or less, blocking problems are less likely to occur, which is preferable.

The lower limit of the ratio of the thickness of the coating layer / the average particle size of the particles in the coating layer is preferably 0.1, more preferably 0.2, and even more preferably 0.3. When the ratio of the thickness of the coating layer / the average particle size of the particles in the coating layer is 0.1 or more, the particles do not fall off, the film surface is not likely to be scratched, and the oligomer is difficult to precipitate, which is preferable.

The upper limit of the ratio of the thickness of the coating layer / the average particle size of the particles in the coating layer is preferably 0.9, more preferably 0.85, and even more preferably 0.83. When the ratio of the thickness of the coating layer / the average particle size of the particles in the coating layer is 0.9 or less, the slipperiness is not insufficient and the film surface is not easily scratched, so that the oligomer is less likely to precipitate and is preferable.

An undercoat layer may be provided on the surface of the polyester film base material, but the resin of the undercoat layer is preferably a polyester resin. It is preferable to contain a naphthalenedicarboxylic acid as an acid component of the polyester resin, and it is preferable to contain a naphthalodisicarboxylic acid because the refractive index is increased and the iris-like color under a fluorescent lamp is easily suppressed. These can be expected to improve the adhesiveness with the oligoblock layer and adjust the refractive index to improve the light transmittance. Further, a cross-linking agent may be contained in the undercoat layer. By containing a cross-linking agent, the solvent resistance when applying the coating layer for suppressing oligomer precipitation can be enhanced. Examples of the cross-linking agent include urea-based, epoxy-based, melamine-based, isocyanate-based, and oxazoline-based. Of these, melamine-based, isocyanate-based, and oxazoline-based are more preferable because of the stability of the coating liquid over time and the effect of improving adhesion under high-temperature and high-humidity treatment. Further, in order to promote the cross-linking reaction, it is also preferable to appropriately use a catalyst or the like as needed.

The lower limit of the thickness of the undercoat layer is preferably 5 nm, more preferably 10 nm. When the thickness of the undercoat layer is 5 nm or more, the adhesion to the oligoblock layer is high, which is preferable.

The upper limit of the thickness of the undercoat layer is preferably 100 nm, more preferably 80 nm. When the thickness of the undercoat layer is 100 nm or less, the haze does not become too large and the high transparency is not impaired, which is preferable.

The lower limit of the refractive index of the undercoat layer is preferably 1.5, more preferably 1.53, and even more preferably 1.55. When the refractive index of the undercoat layer is 1.5 or more, the effect of improving the light transmittance becomes clear, which is preferable.

The upper limit of the refractive index of the undercoat layer is preferably 1.7, more preferably 1.67, and even more preferably 1.65. When the refractive index of the undercoat layer is 1.7 or less, the haze does not become too high, and high transparency is maintained, which is preferable.

In order to adjust the refractive index of the undercoat layer to a high level, it is preferable to include high refractive index particles in the undercoat layer. The high-refractive index particles in the undercoat layer are not particularly limited, and specific examples thereof include metal oxide particles having a refractive index of 1.7 or more and 3.0 or less. Examples of such metal oxides include TiO2 (refractive index 2.7), ZnO (refractive index 2.0), Sb2O3 (refractive index 1.9), SnO2 (refractive index 2.1), and ZrO2 (refractive index 2). .4), Nb2O5 (refractive index 2.3), CeO2 (refractive index 2.2), Ta2O5 (refractive index 2.1), Y2O3 (refractive index 1.8), La2O3 (refractive index 1.9), In2O3 (Refractive index 2.0), Cr2O3 (refractive index 2.5) and the like, and composite oxides containing these metal atoms and the like can be mentioned.
Can be mentioned.

In the present invention, as a method of providing a coating layer having an oligomer precipitation suppressing effect on a polyester film substrate, a polyester film is produced by using a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating device other than these. A method of applying outside the process is preferable. Although it may be applied during the film manufacturing process, the former method of applying outside the polyester film manufacturing process is more preferable in that care must be taken not to cause minute defects in the coating layer during stretching after coating. be.

The lower limit of the solid content concentration of the coating liquid forming the coating layer is preferably 0.1% by mass, more preferably 0.2% by mass. When the solid content of the coating liquid is 0.1% by mass or more, the solvent resistance of the coating film is satisfied, and when it is rolled, a part of the coating layer does not transfer to the back surface side, which is preferable.

The upper limit of the solid content concentration of the coating layer is preferably 10% by mass, more preferably 5% by mass. When the solid content concentration of the coating layer is 10% by mass or less, the viscosity does not become too high, the coatability is good, and the coating layer tends to be uniform, which is preferable.

The lower limit of the drying temperature after coating is preferably 70 ° C, more preferably 80 ° C, and even more preferably 90 ° C. When the drying temperature is 70 ° C. or higher, the resin is less likely to be sufficiently cured, and the effect of suppressing oligomer precipitation is effectively exhibited.

The upper limit of the drying temperature after coating is 180 ° C., preferably 170 ° C., and more preferably 160 ° C. When the drying temperature is 180 ° C. or lower, there is no risk of deformation of the base material due to heat, and flatness is maintained, which is preferable.

The lower limit of the drying time after coating is 10 seconds, preferably 15 seconds or more, and more preferably 20 seconds or more. When the drying time is 10 seconds or more, curing failure does not occur and the effect of suppressing oligomer precipitation can be reliably obtained.

The upper limit of the drying time after coating is 120 seconds, preferably 90 seconds or less, and more preferably 60 seconds or less. When the drying time after coating is 120 seconds or less, there is no problem of deformation of the base material due to heat, and flatness is maintained, which is preferable.

The lower limit of the coefficient of static friction of the contact surface when one side of the film and the other side of the film are overlapped so as to be in contact with each other is preferably 0.1. The coefficient of static friction is about 0.1 as a range that can be mass-produced industrially.

The upper limit of the coefficient of static friction of the contact surface when one side of the film and the other side of the film are overlapped so as to be in contact with each other is preferably 0.6, more preferably 0.5. When the coefficient of static friction is 0.6 or less, there is no risk of scratches, and the effect of suppressing oligomer precipitation is remarkably obtained, which is preferable.

It is more preferable that the coefficient of static friction between the contact surfaces when one side of the polyester film base material finally provided with the coating layer and the opposite surface are in contact with each other is 0.2 or more and 0.5 or less. Particularly preferably, it is 0.3 or more and 0.4 or less. When the coefficient of static friction is 0.6 or less, the frictional force applied to the coating layer does not become too large, and the coating layer is not scratched or cracked, so that the oligomer precipitation prevention property is not impaired. On the other hand, when the coefficient of static friction is 0.1 or more, there is no problem of slipping too much after winding, and winding misalignment is difficult to feed, so there is no problem of applying local pressure, and there is a risk of scratches or cracks in the coating layer. No.

After production, the upper limit of the initial haze that has not been particularly heat-treated is preferably 1.5%, more preferably 1.3%, still more preferably 1.2%, and particularly preferably 1.0%. An initial haze of 1.5% or less is preferable in terms of transparency.

The upper limit of Δ haze, which is the amount of increase in haze before and after heat treatment at 150 ° C. for 60 minutes, is preferably 0.3%, more preferably 0.2%, and even more preferably 0.1%. When the Δhaze is 0.3% or less, the transparency of the film after heating is maintained and the optical properties are maintained. Further, when the Δ haze is 0.3% or less, oligomer precipitation is suppressed when the roll-shaped film is unwound after long-term storage, and transparency is maintained, which is preferable.

The Δhaze in the present invention is an index of the ease of whitening due to heating, and is represented by Δhaze = (haze after heating) − (haze before heating). The range of Δhaze 0.3 or less corresponds to the amount of increase in haze before and after heating when it is judged that there is no whitening due to heating by irradiating the film with a strong light in a dark room and visually confirming whitening.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples. In addition, "part" in an Example and a comparative example means a "part by weight".

[Evaluation method]
(1) Haze Measurement was performed in accordance with JIS K 7105 “Optical property test method for plastics” haze (fog value). An NDH-300A type turbidity meter manufactured by Nippon Denshoku Kogyo Co., Ltd. was used as the measuring instrument.

(2) Evaluation of increase in haze before and after heat treatment (△ haze) Before heat treatment is performed in accordance with JIS K 7105 “Optical property test method for plastics” haze (cloud value) by cutting a film into 50 mm × 75 mm squares. The initial haze was measured. An NDH-300A type turbidity meter manufactured by Nippon Denshoku Kogyo Co., Ltd. was used as the measuring instrument. In order to measure the haze after heating, a protective film (PC-T073 manufactured by Fujimori Kogyo Co., Ltd.) is adhered to the surface of the sample film piece that was not evaluated for haze before the heat treatment by using a roller so as to prevent air bubbles from entering. With the protective film attached, the film is set in an oven heated to 150 ° C., and after 60 minutes, the film is taken out. After that, the protective film is peeled off, the haze of the film is measured by the same method as described above, and the haze is obtained after heating. This difference in haze before and after heating is defined as Δhaze.
Δ Haze (%) = (Haze after heating)-(Haze before heating)

(3) Measurement of the coefficient of static friction The coefficient of static friction of the contact surface when one side of the film and the other side of the film are overlapped so as to be in contact with each other using a universal testing machine (AGS-1kNG manufactured by Shimadzu Corporation). (Μs) was measured under the following conditions according to JIS K-7125.
Specimen: width 50 mm x length 60 mm
Load: 4.4 kg
Test speed: 200 mm / min

(Example 1)
Amino acrylic resin (Hitachi Kasei Polymer Co., Ltd .: Tessfine 322: solid content 40%) 2.5 parts, P-toluenesulfonic acid (Hitachi Kasei Polymer Co., Ltd .: dryer 900) 0.025 parts, silica sol as lubricant 0.3 parts of methyl ethyl ketone dispersion (manufactured by Nissan Chemical Industries, Ltd .: MEK-ST-L: solid content 30%) was dissolved in a mixed solution of 50 parts of toluene and 47.2 parts of methyl ethyl ketone to prepare 1% by weight of solid content. The coating liquid was applied to a non-slip surface of a biaxially stretched polyethylene terephthalate film (manufactured by Toyo Spinning Co., Ltd .: A4100) having a thickness of 125 μm and dried at 150 ° C. for 1 minute to make the thickness of the coating layer 75 nm.

(Example 2)
A film was prepared in the same manner as in Example 1 except that the coating liquid of Example 1 was coated so that the coating film thickness would be 25 nm after drying.

( Reference example 3 )
3.0 parts of polyester resin (Toyobo Co., Ltd .: Byron 20SS: solid content 30%), 0.13 parts of isocyanate (Nippon Polyurethane Co., Ltd .: Coronate L: solid content 75%) as a curing agent, silica solmethyl ethyl ketone dispersion liquid (silicasol methyl ethyl ketone dispersion liquid) as a lubricant Nissan Chemical Industry Co., Ltd .: MEK-ST-L: solid content 30%) 0.3 parts, 50 parts toluene and 46.8 parts methyl ethyl ketone were dissolved in a mixed solution to prepare a coating solution with a solid content of 1% by weight. It was applied to a non-slip surface of a biaxially stretched polyethylene terephthalate film (manufactured by Toyobo Co., Ltd .: A4100) having a thickness of 125 μm and dried at 150 ° C. for 1 minute to make the thickness of the applied layer 75 nm.

(Example 4)
Methyl polymethacrylate (manufactured by Mitsubishi Rayon Co., Ltd .: BR-80: solid content 100%) 1.0 part, silica solmethyl ethyl ketone dispersion as a lubricant (manufactured by Nissan Chemical Industry Co., Ltd .: MEK-ST-L: solid content 30%) 0. A coating solution having a solid content of 1% by weight prepared by dissolving 3 parts in a mixed solution of 50 parts of toluene and 48.7 parts of methyl ethyl ketone was prepared without a biaxially stretched polyethylene terephthalate film (manufactured by Toyobo Co., Ltd .: A4100) having a thickness of 125 μm. The coating layer was applied to a smooth surface and dried at 150 ° C. for 1 minute to make the thickness of the coating layer 75 nm.

(Example 5)
Amino acrylic resin (Hitachi Kasei Polymer Co., Ltd .: Tessfine 322: solid content 40%) 2.5 parts, P-toluenesulfonic acid (Hitachi Kasei Polymer Co., Ltd .: dryer 900) 0.025 parts, silica sol as lubricant 0.18 parts of methyl ethyl ketone dispersion (manufactured by Nissan Chemical Industries, Ltd .: MEK-ST-L: solid content 30%) was dissolved in a mixed solution of 50 parts of toluene and 47.3 parts of methyl ethyl ketone to prepare 1% by weight of solid content. The coating liquid was applied to a non-slip surface of a biaxially stretched polyethylene terephthalate film (manufactured by Toyo Spinning Co., Ltd .: A4100) having a thickness of 125 μm and dried at 150 ° C. for 1 minute to make the thickness of the coating layer 25 nm.

(Comparative Example 1)
A mixed solution of 50 parts of ethyl silicate (Colcoat N-103X), 25 parts of water, and 25 parts of isopropyl alcohol was applied to the non-slip surface of (Toyobo: A4100) with wire bar # 5 and at 150 ° C. It was dried for 1 minute. The thickness of the coating layer was 75 nm.

(Comparative Example 2)
Amino acrylic resin (Hitachi Kasei Polymer Co., Ltd .: Tessfine 322: solid content 40%) 2.5 parts, P-toluenesulfonic acid (Hitachi Kasei Polymer Co., Ltd .: dryer 900) 0.025 parts, silica sol as lubricant 0.1 part of methyl ethyl ketone dispersion (manufactured by Nissan Chemical Industries, Ltd .: MEK-ST-L: solid content 30%) was dissolved in a mixed solution of 50 parts of toluene and 47.4 parts of methyl ethyl ketone to prepare 1% by weight of solid content. The coating liquid was applied to a non-slip surface of a biaxially stretched polyethylene terephthalate film (manufactured by Toyo Spinning Co., Ltd .: A4100) having a thickness of 125 μm and dried at 150 ° C. for 1 minute to make the thickness of the coating layer 7.5 nm.

(Comparative Example 3)
Amino acrylic resin (Hitachi Kasei Polymer Co., Ltd .: Tessfine 322: solid content 40%) 2.5 parts, P-toluenesulfonic acid as an acid catalyst (Hitachi Kasei Polymer Co., Ltd .: dryer 900) 0.025 parts Toluene 50 parts , A coating solution having a solid content of 1% by weight prepared by dissolving in a mixed solution of 47.5 parts of methyl ethyl ketone was applied to a non-slip surface of a biaxially stretched polyethylene terephthalate film (manufactured by Toyo Spinning Co., Ltd .: A4100) having a thickness of 125 μm. It was dried at ° C. for 1 minute, and the thickness of the coating layer was adjusted to 75 nm.

The oligomer precipitation prevention polyester film of the present invention has excellent transparency after heat processing and has almost no oligomer precipitation, so that post-processing treatment at high temperature is possible, including optical applications requiring high quality. It is a film that is suitably used in industrial applications and general packaging applications.

Claims (5)

A laminated polyester film in which a coating layer is provided on at least one side of a polyester film base material, and the polyester resin constituting the polyester film base material is:
More than 60 mol% is polyester whose repeating unit is ethylene terephthalate.
The resin contained in the coating layer is an aminoacrylic resin (however, it does not have a polyethylene glycol group).
The Tg of the resin contained in the coating layer is 90 ° C. or higher and 200 ° C. or lower, and the Δ haze, which is the amount of increase in haze before and after heat treatment at 150 ° C. for 60 minutes, is 0.3% or less, and the heat treatment is performed. The previous haze is less than 1.5%,
The coating layer contains particles, and the average particle size of the particles is 50 nm or more and 200 nm or less, which is larger than the thickness of the coating layer.
An oligomer precipitation-preventing polyester film. The oligomer precipitation-preventing polyester film according to claim 1, wherein the static friction coefficient μs of the contact surfaces when one side of the film and the other side thereof are overlapped with each other is 0.1 or more and 0.6 or less. .. The oligomer precipitation-preventing polyester film according to claim 1 or 2, wherein the coating layer has a thickness of 20 nm or more and 150 nm or less. The oligomer precipitation-preventing polyester film according to any one of claims 1 to 3, wherein the ratio of the thickness of the coating layer to the average particle size of the particles in the coating layer is 0.1 or more and 0.9 or less. The oligomer precipitation-preventing polyester film according to any one of claims 1 to 4, wherein the particle content contained in the coating layer is 4% by mass (against resin) or more and 20% by mass (against resin) or less.