KR19990080116A - Polyester film and its manufacturing method - Google Patents

Abstract

The present invention relates to a three-layer polyester white film having improved antistatic property, weather resistance, hiding property and printability. In the three-layer polyester film according to the present invention, at least 70% by weight of the repeating unit is made of ethylene terephthalate and a polyester resin having an intrinsic viscosity of 0.6 to 1.0 dl / g, titanium dioxide, talc, barium sulfide, silica, and carbonic acid. At least one selected from the group consisting of calcium and feldspar, which comprises 5 to 30% by weight of white fine particles having an average particle diameter of 0.1 to 5.0 μm and is biaxially oriented to the first film layer, and the polyester resin. , 0.01 to 0.05% by weight of a sulfonic acid metal salt derivative, 0.01 to 0.05% by weight of a benzophenone compound, and at least one selected from the group consisting of silica, alumina, and polymethyl methacrylate, each having a mean particle size of 0.01 to 0.1 μm. 2nd and 3rd film layers which are made by disperse | distributing 0.01 to 0.1 weight% and are uniaxially oriented and laminated on the upper and lower surfaces of the said 1st film layer, respectively. A polyester film comprising a film made of the second and third films in at least any one layer of the layer weight average molecular weight of 10,000 ~ 300,000 and an acrylic resin with a glass transition temperature of 30 ~ 100 ℃ 0.01 ~ 0.1g / m 2 It is characterized by being coated with a coating density of.

Description

Polyester film and its manufacturing method

The present invention relates to a polyester film and a method for manufacturing the same, and more particularly, to a three-layer polyester white film with improved antistatic property, weather resistance, concealability, and printability and a method for producing the same.

Currently, paper and white plastic films are generally used as substrates used for labels, flyers, cards, calendars, and the like. Polyvinyl chloride, polyolefin, polystyrene, etc. are used as said plastic.

However, the paper is excellent in processability, convenient disposal and recycling, but expensive, there is a problem such as discoloration or mold occurs when used for a long time. Polyvinyl chloride has excellent flexibility and good processability, but is limited in some countries due to environmental problems such as chlorine gas generated during combustion. Polyolefins are the most environmentally friendly, their usage is gradually increasing, but the mechanical properties are not good and there is a problem that scratches are generated due to low surface strength, there is a need to perform post-processing, such as coating. Polystyrene is excellent in workability and may break in winter.

On the other hand, polyester film represented by polyethylene terephthalate (PET) is physicochemically stable and excellent in mechanical strength, elastic modulus, dimensional stability, planarity, heat resistance, durability, chemical resistance, electrical insulation, etc. It is widely used in magnetic media, magnetic recording media and the like. In addition, the polyester film is made of a white film, the above mentioned flyers, cards, calendars, labels, magnetic recording cards, printer award papers, barcode printer award papers, posters, maps, dust-free paper, display boards, white boards, photo paper, Increasingly, the use of copy paper and printed publications for special purposes is increasing.

However, the polyester film has a high transparency and poor concealment, there is a problem in the application of the above. Therefore, while making excellent use of the excellent physical properties of the polyester film, the research for producing a white polyester film with improved transparency and whiteness by lowering the transparency is active, among which many techniques for using a white filler is known.

For example, Japanese Patent Application Laid-Open No. 62-243120 and Hei 2-206622 and the like added inorganic particles to polyester, Hei 2-185532 and the like used barium sulfate alone, and Hei 3-50241 and the like. The art which mix | blends a barium sulfate and calcium carbonate after mix | blending a polyolefin resin to this is disclosed.

However, according to the known technology, the concealability and / or whiteness of the film is improved, but there is a problem in post-processability and weather resistance, such as antistatic property and printability.

Accordingly, the technical problem to be achieved by the present invention is to provide a white polyester film having excellent concealability and excellent post-processability such as printability and antistatic property.

Another object of the present invention is to provide a method for producing the white polyester film.

In order to achieve the above technical problem, the present invention, in the polyester resin 70% by weight or more of the repeating unit is made of ethylene terephthalate and the ultimate viscosity is 0.6 ~ 1.0㎗ / g, titanium dioxide, talc, barium sulfide, silica, At least one selected from the group consisting of calcium carbonate, and feldspar, the first film layer being biaxially oriented and containing 5 to 30 wt% of white fine particles having an average particle diameter of 0.1 to 5.0 μm; And 0.01 to 0.05% by weight of a sulfonic acid metal salt derivative, 0.01 to 0.05% by weight of a benzophenone compound, and at least one selected from the group consisting of silica, alumina, and polymethyl methacrylate. A polyester film comprising a second and a third film layer, which is made by dispersing 0.01 to 0.1% by weight of fine particles having a thickness of 0.01 to 0.1 μm and is uniaxially oriented and laminated on upper and lower surfaces of the first film layer, respectively. At least one of the second and third film layer has a weight average molecular weight of 10,000 ~ 300,000 and a film made of acrylic resin having a glass transition temperature of 30 ~ 100 ℃ is coated with a coating density of 0.01 ~ 0.1g / m ² Provided is a polyester film.

In the present invention, the thickness of the first film layer is preferably 50 to 95% of the total thickness of the polyester film.

In the present invention, the sulfonic acid metal salt derivative is preferably represented by the following formula (1).

R-SO ₃ M

However, in Formula 1, R is an alkyl group of C ₅ ~ C ₂₀ , M is an alkaline earth metal or an alkali metal, such as Li, Na, K, Mg.

In the present invention, the benzophenone-based compound is at least one selected from the group consisting of 2-hydroxy-4-octoxybenzophenone and 2,2-dihydroxy-4,4-dioctoxybenzophenone desirable.

In order to achieve the above another technical problem, the present invention (a) 70% by weight or more of the repeating unit is made of ethylene terephthalate, the polyester resin having an intrinsic viscosity of 0.6 ~ 1.0 dl / g, titanium dioxide, talc, sulfide At least one selected from the group consisting of barium, silica, calcium carbonate, and feldspar is melted by extrusion of a polyester resin melt containing 5 to 30 wt% of white fine particles having an average particle diameter of 0.1 to 5.0 μm at 280 to 320 ° C. After the sheet is prepared, the melt sheet is cooled and solidified by bringing the molten sheet into close contact with a cooling roll at 0 to 20 ° C. to form an unstretched sheet; (b) stretching the unstretched sheet 2 to 5 times in one direction at 90 to 120 ° C. to form a first layer; (c) 0.01 to 0.05% by weight of a sulfonic acid metal salt derivative, 0.01 to 0.05% by weight of a benzophenone compound, and silica, alumina, and polymethyl methacrylate to the polyester resin of step (a) A polyester resin melt containing at least one selected from 0.01 to 0.1% by weight of fine particles having an average particle diameter of 0.01 to 0.1 µm is extruded at 280 to 320 ° C. so that the second and third layers are formed on the upper and lower surfaces of the first layer, respectively. Forming a stacked three layer sheet; (d) heat treating the three-layer sheet at 50 to 80 ° C; (e) stretching the three-layer sheet 2 to 5 times in a direction perpendicular to the one direction at 100 to 150 ° C. to form a three-layer film; (f) heat treating the three-layer film at 160 to 180 ° C; And (g) the acrylic resin in at least one of the second and third layers using a dispersion containing 10 to 50% by weight of an acrylic resin having a weight average molecular weight of 10,000 to 300,000 and a glass transition temperature of 30 to 100 ° C. It provides a method for producing a polyester film comprising the step of coating the film with a coating density of 0.01 ~ 0.1g / m ² .

The polyester film according to the present invention is excellent in concealability but also excellent in printability, antistatic property and weather resistance.

Hereinafter, the polyester film according to the present invention and a manufacturing method thereof will be described in detail, but in the present invention, unless otherwise specified, it means that the polyester resin is based on the polyester resin.

The polyester film according to the present invention is made by dispersing white fine particles in a polyester resin and having a biaxially oriented first film layer as a center layer, and a sulfonic acid metal salt derivative and a benzophenone compound in the polyester resin. And a three-layered polyester film made by dispersing fine particles and having second and third film layers uniaxially oriented as surface layers, wherein at least one of the second and third film layers has an acrylic resin film. It is a coated structure.

In the polyester resin, 70% by weight or more of the repeating unit is made of ethylene terephthalate, and the intrinsic viscosity is 0.6 to 1.0 dl / g. It is preferable that the intrinsic viscosity when the said polyester resin is used for a 2nd or 3rd film layer is 0.8-1.0 dl / g. If the intrinsic viscosity is less than 0.6 dl / g, the mechanical strength of the film cannot be maintained, and breakage occurs frequently during film production, resulting in unfavorable decrease in productivity. In addition, if the intrinsic viscosity exceeds 1.0 dl / g, the melt viscosity is too high, the extrusion pressure is too high, the extrusion process becomes unstable and gives a lot of pressure on the equipment. Moreover, it is preferable in thickness uniformity and appearance that viscosity of a 1st film layer is higher than the viscosity of a 2nd and 3rd film layer. On the other hand, if the viscosity of the second or third film layer is higher than the viscosity of the first film layer, the phenomenon that the polyester resins are entangled with each other during the extrusion process occurs, which is not preferable.

The polyester resin is composed of ethylene terephthalate produced by at least 70% by weight of the repeating unit by direct esterification of terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol. As the remaining 30% by weight or less of the copolymer component, both an acid component and an alcohol component can be used. Examples of the acid component include isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-sodium sulfopropoxyisophthalic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid and diphenoxy Ethanedicarboxylic acid, α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid, trimellitic acid, pyromellitic acid, adipic acid, azelaneic acid And bifunctional or polyfunctional aromatic or aliphatic basic acids such as sebacic acid and cyclohexanedicarboxylic acid. Examples of the alcohol component include trimethylene glycol, diethylene glycol, 2,2-dimethyl-1,3-propanediol, tetramethylene glycol, pentamethylene glycol, neopentyl glycol, hexamethylene glycol, cyclohexylene glycol, 1,4- Bifunctional aromatic or aliphatic alcohols such as cyclohexanedimethanol, 5-sodium sulforesosinol, p-xylene glycol, polyethylene glycol and the like.

The first film layer includes at least one selected from the group consisting of titanium dioxide, talc, barium sulfide, silica, calcium carbonate, and feldspar, and contains 5 to 30 wt% of white fine particles having an average particle diameter of 0.1 to 5.0 μm. If the average particle diameter is less than 0.1㎛ poor concealability, if it exceeds 5.0㎛ it is not preferable because the filter pressure during extrusion increases. In addition, when the content of the white fine particles is less than 5% by weight, the concealability is poor, and when the content of the white fine particles exceeds 30% by weight, breakage occurs during stretching.

The second and third film layers contain 0.01 to 0.05% by weight, preferably 0.02 to 0.04% by weight of the sulfonic acid metal salt derivative represented by Chemical Formula 1 as an antistatic agent. When the content of the sulfonic acid metal salt derivative is less than 0.01% by weight, the antistatic property is not sufficient. When the content of the sulfonic acid metal salt derivative is more than 0.05% by weight, the decomposition of the polyester resin is accelerated to greatly reduce the mechanical strength of the film. Specific examples of the sulfonic acid metal salt used in the present invention represented by Chemical Formula 1 include potassium octylbenzenesulfonate, potassium nonylbenzenesulfonate, potassium undecylbenzenesulfonate, and the like. The sulfonic acid metal salt derivative is excellent in heat resistance, and by containing the sulfonic acid metal salt derivative, the polyester film has increased surface tension and adhesion to ink and coating solution. The sulfonic acid metal salt derivative is effective as an antistatic agent for removing static electricity causing loss of recorded information in information recording materials such as magnetic cards.

The second and third film layers contain 0.01 to 0.05% by weight of a benzophenone compound as an ultraviolet absorber to improve weather resistance. When the content of the benzophenone-based compound is less than 0.01% by weight, the weather resistance improvement effect is insufficient, and when the content of the benzophenone-based compound exceeds 0.05% by weight, the compound flows out to the surface of the film, which lowers printability and discolors the film. The benzophenone-based compound serves to increase the weather resistance of the film by converting the absorbed energy into thermal energy harmless to the polymer structure, and the phenolic hydroxyl group preferably contains an element having a high electronegativity such as oxygen or nitrogen. Do. For example, 2-hydroxy-4-octoxybenzophenone, 2,2-dihydroxy-4,4-dioxoxybenzophenone, etc. are preferable.

The second and third film layer is also at least one selected from the group consisting of silica, alumina, and polymethyl methacrylate for the purpose of improving the activity of 0.01 to 0.1% by weight of fine particles having an average particle diameter of 0.01 ~ 0.1㎛ It contains. When the average particle diameter of the fine particles is less than 0.01 μm, the fine particles are aggregated to decrease processability. When the fine particles exceed 0.1 μm, the fine particles cause protrusions on the surface of the film and lower the glossiness of the film, which is not preferable. In addition, when the content of the fine particles is less than 0.01% by weight, the surface roughness of the film is too low to cause blocking phenomenon between the films, and when the content of the fine particles exceeds 0.1% by weight, the glossiness of the film is lowered, which lowers the aesthetics of the film appearance. not.

In addition, the polyester resin of the first to third film layer is a known additive, for example, a heat stabilizer, an electrostatic agent, a crystallization accelerator, an antiblocking agent, a nucleating agent, etc. within the range that does not impair the effects of the present invention. It may include.

In the present invention, as a method of adding additives such as white fine particles and fine particles, a method of dispersing in a slurry form during a polymerization reaction may be used, but after preparing a primary mixed resin by a compounding melt mixing method, the resin may be used. The remelt extrusion method is preferable because it improves the dispersibility between resins, increases the uniformity of physical properties of the produced film, and improves workability. In the latter case, it is preferable to melt-mix using a compounder having two rotational axes in the same or two directions, and the temperature of the portion where the resin and the additive are injected is 250 to 300 ° C., and the final portion where the melt mixing is finished. The temperature of is preferably adjusted to 260 ~ 320 ℃. When the temperature is lower than the temperature presented here, the polyester unmelted resin is present, and when the temperature is adjusted to high temperature, thermal decomposition of the polyester resin is promoted, and the resin turns yellow. It is preferable to adjust the rotational speed and the discharge amount of the rotating shaft so that the temperature of the mixed resin discharged is 270 ~ 320 ℃.

The polyester film according to the present invention comprises three layers as described above, and at least one of the second and third film layers forming the surface layer is coated to improve printability. The coating treatment is a weight average molecular weight of 10,000 ~ 300,000, preferably 20,000 ~ 200,000 and a film made of acrylic resin having a glass transition temperature of 30 ~ 100 ℃ 0.01 ~ 0.1g on the surface of the second and / or third film layer by coating at a coating density of / m ² . The acrylic resin is obtained by emulsion polymerization of at least one selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, n-acrylate, ethyl methacrylate, acrylamide, glycidyl methacrylate, and the like. will be. If the weight average molecular weight of the acrylic resin is less than 10,000, the surface hardness of the polyester film is too high, so the printability is not sufficient. If the weight average molecular weight of the acrylic resin exceeds 300,000, the frictional force is turned on, which decreases the activity. In addition, if the coating density of the coating film of the acrylic resin is less than 0.01g / m ² printability is not sufficient, if it exceeds 0.1g / m ² it takes a long time to dry, complicated equipment and productivity and workability of the post-process Lowers.

In the present invention, as a coating method that can be used, all known coating methods such as roll coating, knife coating, spray coating, curtain coating, etc. can be used, but in particular, the roll method is preferable in view of processability or workability.

The thickness ratio of the first film layer and the second and third film layers is preferably adjusted so that the thickness of the first film layer is 50 to 95% of the thickness of the entire film layer. If the thickness of the first film layer is less than 50% of the total film thickness, sufficient concealability cannot be guaranteed. If the thickness of the first film layer is greater than 95%, breakage occurs frequently during the stretching process, and the flexibility of the film is poor.

Next, the manufacturing method of the polyester film which concerns on this invention demonstrated so far is demonstrated.

First, a polyester resin melt containing the white fine particles dispersed in a polyester resin is extruded at 280 to 320 ° C. to produce a melt sheet, and then the melt sheet is cooled and solidified at 0 to 20 ° C. to form an unstretched sheet. do. The unstretched sheet is stretched 2 to 5 times in the longitudinal direction at 90 to 120 ° C. to form a first layer that is a central layer. Meanwhile, the polyester resin melt containing the sulfonic acid metal salt derivative, the benzophenone compound, and the fine particles dispersed in the polyester resin is extruded at 280 to 320 ° C., so that the second and third layers are respectively formed on the upper and lower surfaces of the first layer. A laminated three-layer sheet is formed. At this time, the three-layer sheet exhibits a warpage phenomenon, and in order to alleviate this, the three-layer sheet is heat-treated by staying for 0.1 to 1 second in an anneal roll having a warm air of 50 to 80 ° C. The three-layer sheet is stretched 2 to 5 times in the transverse direction at 100 to 150 ° C to form a three-layer film, and then heat-treated at 160 to 180 ° C. As a result, the first layer is biaxially oriented and the second and third film layers are uniaxially oriented, but all of the first to third layers may be biaxially oriented. Subsequently, at least one of the second and third layers was coated with the acrylic resin film at a coating density of 0.01 to 0.1 g / m ² using a dispersion containing 10 to 50% by weight of the acrylic resin. The preparation of the polyester film according to the invention is completed. On the other hand, when the concentration of the dispersion for applying the acrylic resin is less than 10% by weight there is a problem to thicken the coating layer, if it exceeds 50% by weight is not preferable because the blocking phenomenon occurs between the film. As the medium of the acrylic resin dispersion, it is preferable to mix water and an appropriate amount of C ₁ to C ₄ aliphatic alcohols in consideration of wetting.

On the other hand, the process of coating the acrylic resin film is preferably carried out after the first stretching step or after the second stretching step is preferably carried out just before the winding step.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples. In Examples and Comparative Examples of the present invention, various performance evaluation of the produced film was carried out by the following method.

(1) extreme viscosity

According to the three-point method, 0.05 g, 0.10 g, 0.20 g of the polymer was dissolved in 25 ml of ο-chlorophenol, and the relative viscosity was measured at 35 ° C., and then extrapolated to infinite lean concentration.

(2) light transmittance

The light transmittance was measured using a haze meter (model name: SEP-H) and a C-light source from Nippon Precision Optical Co., Ltd., and the case where the light transmittance was low was evaluated as being excellent in concealability. At this time, the measurement conditions were the diameter of the sample was 25mm, the scattering angle was 2.5 degrees.

(3) antistatic

Surface resistance was measured using an insulation resistance measuring instrument of the US Hewlett. The measurement conditions were 20 degreeC of temperature, 65% of a relative humidity, and 500V of applied voltages. The smaller the surface resistance, the better the antistatic property.

(4) weather resistance

The outdoor preservation period was calculated by evaluating the change of physical properties over time by using a Japanese Meteorological Radiograph's ultra-promoting weather tester (Model: UVP-2). The time when the film loses the polymer properties is calculated as the limit time, and 260 hours corresponds to one year when exposed to ultraviolet light.

(5) printability

Lacquer film for evaluation of the oil-based leaf composed of 27 parts by weight of water, 10 parts by weight of n-butanol, 25 parts by weight of methyl cellosolve, 10 parts by weight of methyl ethyl ketone, 25 parts by weight of cellulose acetate butyrate, and 3 parts by weight of rhodamine B dye It was apply | coated to the surface with wire bar # 18, and it fully dried at 90 degreeC for 1 minute in dryer. Subsequently, 100 scales were drawn on the surface using a cross cutter, and then peeled off with adhesive tape. At this time, the evaluation was performed based on the number of remaining scales which did not peel out of 100 scales. The more the number of the remaining scales, the better the printability.

100: No peeling at all (excellent) ~ 0: All peeled off (bad)

Example 1

After mixing dimethyl terephthalate and ethylene glycol in a 1: 2 equivalent ratio, 0.05 wt% of tributylene titanate was added to the mixture to condensate low molecular weights of bis-2-hydroxyethyl terephthalate (BHET) and BHET. Water was formed. Here, 0.1 wt% of trimethylene terephthalate as a heat stabilizer and 0.05 wt% of antimonitriacetate as a polymerization catalyst were added, and polycondensation was completed to prepare a polyester pellet having an ultimate viscosity of 0.75 dl / g.

15% by weight of the polyester pellet and titanium dioxide having an average particle diameter of 0.5 μm were mixed in a first extruder and extruded at 300 ° C. to prepare a melt sheet, followed by cooling the melt sheet by closely contacting a 5 ° C. cooling roll. It solidified to form an undrawn sheet. Subsequently, the unstretched sheet was stretched three times in the longitudinal direction at 105 ° C. to prepare a uniaxially stretched first layer film.

A second extruder was used for the polyester pellet having an intrinsic viscosity of 0.68 dl / g and 0.02 wt% of potassium octylbenzenesulfonate, 0.03 wt% of 2-hydroxy-4-octoxybenzophenone, and 0.05 wt% of silica having an average particle diameter of 0.08 μm. The mixture was added to and then extruded at 300 ° C. to form a three-layer sheet having a thickness of 270 μm on which upper and lower layers of the first layer film uniaxially stretched in the longitudinal direction were respectively laminated. Subsequently, the three-layer sheet was heat-treated for about 0.5 seconds in a hot air bath roll supplied with warm air in an atmosphere of about 60 ° C. to alleviate curvature in one direction depending on melting conditions and resin properties. The three-layer sheet was stretched three times in the transverse direction again at 140 ° C. and heat-treated at 150 ° C. to obtain a three-layer film having a thickness of 30 μm.

Subsequently, a coating liquid obtained by dispersing 15 parts by weight of polystyrene methacrylate (Zeneca, model name: XK-70) in a solvent consisting of 75 parts by weight of water and 15 parts by weight of isopropyl alcohol was reverse rolled on both surfaces of the three-layer film. Coated at a coating density of 0.05 g / m ² . Thus obtained three-layer polyester film was excellent in all concealability, antistatic properties, weather resistance, printability as shown in Table 1.

Examples 2-5

A three-layer polyester film was prepared in the same manner as in Example 1 except that the thickness and the additives of each film layer were adjusted as shown in Table 1 while the film overall thickness was fixed at 30 μm. As shown in Table 1, the film thus obtained was excellent in concealability, antistatic property, weather resistance, and printability.

Comparative Examples 1 to 5

3-layer poly fabricated in the same manner as in Example 1, except that the thickness of each film layer and additives were adjusted to deviate from the claims of the present invention as shown in Table 1 while fixing the overall film thickness to 30 μm. An ester film was prepared. As shown in Table 1, the concealability (light transmittance) was almost the same as in the examples, but the antistatic property, weather resistance, and printability were poor.

T: Titanium Dioxide De: Talc Sulfur: Barium Sulfide

Thread: Silica Tan: Calcium Carbonate Tablet: Dressing Stone

Egg: Alumina P: Polymethylmethacrylate SM: Styrene methacrylate

As described above, the polyester film according to the present invention is excellent in all concealability, antistatic properties, weather resistance, printability. Accordingly, the polyester film according to the present invention is used for magnetic cards, labels, printer papers, barcode printer papers, posters, maps, dust-free papers, display boards, white boards, photo papers, copy papers, and printed publications for special purposes. Suitable for

Claims (5)

At least 70% by weight of the repeating unit is made of ethylene terephthalate and has a ultimate viscosity of 0.6 to 1.0 dl / g, at least selected from the group consisting of titanium dioxide, talc, barium sulfide, silica, calcium carbonate, and feldspar Any one of the first film layer made by dispersing 5 to 30% by weight of the white fine particles having an average particle diameter of 0.1 ~ 5.0㎛; And 0.01-0.05% by weight of the sulfonic acid metal salt derivative, 0.01-0.05% by weight of a benzophenone compound, and at least one selected from the group consisting of silica, alumina, and polymethyl methacrylate, to the polyester resin, having an average particle size of 0.01 A polyester film comprising a second and a third film layer made by dispersing 0.01 to 0.1% by weight of fine particles having a thickness of 0.1 μm and being uniaxially oriented and laminated on upper and lower surfaces of the first film layer, respectively. At least one of the second and third film layer has a weight average molecular weight of 10,000 ~ 300,000 and a film made of acrylic resin having a glass transition temperature of 30 ~ 100 ℃ is coated with a coating density of 0.01 ~ 0.1g / m ² Polyester film. The thickness of the first film layer, Polyester film, characterized in that 50 to 95% of the total thickness of the polyester film. The method of claim 1, wherein the sulfonic acid metal salt derivative, A polyester film characterized by the following formula (1): <Formula 1> R-SO ₃ M However, in Formula 1, R is an alkyl group of C ₅ ~ C ₂₀ , M is an alkaline earth metal or an alkali metal, such as Li, Na, K, Mg. According to claim 1, The benzophenone-based compound, A polyester film, which is at least one selected from the group consisting of 2-hydroxy-4-octoxybenzophenone and 2,2-dihydroxy-4,4-dioctoxybenzophenone. (a) a group consisting of titanium dioxide, talc, barium sulfide, silica, calcium carbonate, and feldspar in a polyester resin having at least 70% by weight of the repeating unit consisting of ethylene terephthalate and having an ultimate viscosity of 0.6 to 1.0 dl / g The melted sheet is prepared by extruding a polyester resin melt containing 5 to 30% by weight of white fine particles having an average particle diameter of 0.1 to 5.0 μm as at least one selected from 280 to 320 ° C., and then melting the melted sheet to 0 to Cooling and solidifying by contacting the cold roll at 20 ° C. to form an undrawn sheet; (b) stretching the unstretched sheet 2 to 5 times in one direction at 90 to 120 ° C. to form a first layer; (c) 0.01 to 0.05% by weight of a sulfonic acid metal salt derivative, 0.01 to 0.05% by weight of a benzophenone compound, and silica, alumina, and polymethyl methacrylate to the polyester resin of step (a) A polyester resin melt containing at least one selected from 0.01 to 0.1% by weight of fine particles having an average particle diameter of 0.01 to 0.1 µm is extruded at 280 to 320 ° C. so that the second and third layers are formed on the upper and lower surfaces of the first layer, respectively. Forming a stacked three layer sheet; (d) heat treating the three-layer sheet at 50 to 80 ° C; (e) stretching the three-layer sheet 2 to 5 times in a direction perpendicular to the one direction at 100 to 150 ° C. to form a three layer film; (f) heat treating the three-layer film at 160 to 180 ° C; And (g) the acrylic resin film on at least one of the second and third layers using a dispersion containing 10 to 50% by weight of an acrylic resin having a weight average molecular weight of 10,000 to 300,000 and a glass transition temperature of 30 to 100 ° C. Method for producing a polyester film comprising the step of coating at a coating density of 0.01 ~ 0.1g / m ² .