KR20100108788A - White film and a method of manufacturing opaque white film - Google Patents

Abstract

PURPOSE: A white film and a manufacturing method thereof are provided to secure the excellent glossiness, mechanical strength, and opacity of the film, by using a controlled inorganic material. CONSTITUTION: A manufacturing method of a white film comprises the following steps: mixing 100 parts of polyester resin by weight, and 5~25 parts of non-crystalline polyester resin by weight, and forming a master batch including barium sulfate particles with the refractive index of 1.6~1.7; extruding the mixture of the polyester resin mixture and the master batch to make a sheet; extending the sheet; heat-processing the sheet in 180~230 deg C; and thermal fixing the heat-processed sheet.

Description

White film and A method of manufacturing Opaque White film

The present invention relates to a white film and a method for manufacturing the same, and more particularly, to a white film excellent in opacity for advertising billboards, placards, labels, food or beverage packaging materials and a method for producing the same.

Currently, paper, a white plastic film, and the like are generally used as substrates for labels, flyers, cards, calendars, and the like, and polyvinyl chloride, polyolefin, polystyrene, and the like are used as plastics.

In general, polyolefin films containing inorganic fine particles have been used as substrates for paper substitutes. However, polyolefin films have limited mechanical strength, heat resistance, weather resistance, and numerical stability. It is a tendency to use as a paper substitute of a use.

Polyester is widely used in the manufacture of medical and various industrial products due to its physical and chemical stability, high mechanical strength, excellent heat resistance, durability, chemical resistance, and electrical insulation. Among them, polyethylene terephthalate has excellent properties such as elastic modulus, dimensional stability, and flattening, so it is widely used for magnetic recording media, condenser, food or beverage packaging, photo film, label, and various graphic arts products. It is used. In addition, it is used for various magnetic cards (credit and communication cards), printer award papers, bar codes, posters, calendars, maps, dust-free papers, display boards, white boards, photo papers, copy papers and special printed publications.

Recently, as a method for controlling the high transparency of a polyester film having such high transparency and surface glossiness to use the film for various purposes, a method of adding white inorganic particles having a high refractive index has been studied. For example, in Korean Patent Laid-Open Publication No. 2000-0061237, inorganic particles such as calcium carbonate were added to polyester, but the amount of calcium carbonate added to control the amount of calcium carbonate caused by excessively high glossiness of the film surface causes eye fatigue. Increasing the film stiffened the workability was poor. Accordingly, Korean Patent Invention No. 773705 proposes a white film having low transparency by adding barium sulfate to polyester alone, but it is difficult to manufacture a white film having uniform physical properties because the particle size distribution of barium sulfate particles is not controlled. If the particle content is increased, crystallization may proceed excessively, and there may be a problem that breakage occurs during stretching. The amount of pores formed in the film by the added inorganic particles is excessive, the strength of the film falls, there is a problem that the breakage of the film often occurs during the film stretching process.

In order to solve the above problems, an object of the present invention is excellent in concealability and whiteness, minimization of crystallization during film production, there is no breakage of the film, good operability and excellent mechanical strength white film and its preparation To provide a way.

In order to achieve the above object, the present invention relates to a method for producing a white film, specifically, a) sulfuric acid having a refractive index of 1.6-1.7 by adding 5 to 25 parts by weight of an amorphous polyester resin to 100 parts by weight of a polyester resin. A masterbatch manufacturing step comprising barium particles; b) a sheet manufacturing step of extruding the mixture of the masterbatch and the polyester resin; c) drawing the sheet; d) heat-treating the stretched sheet with at least five stages of tenter; And e) a heat setting step of the heat treated sheet.

The white film manufactured as described above is characterized in that the crystallization rate measured at 210 ° C isothermal conditions using DSC is 60 seconds to 300 seconds, and minimizes the crystallization during film production, there is no breakage of the film, operability Provided is a good method for producing a white film.

Hereinafter, a preferred embodiment of the present invention will be described in detail. In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

As used herein, the terms "about", "substantially", and the like, are used at, or in close proximity to, numerical values when a manufacturing and material tolerance inherent in the stated meanings is given, and an understanding of the invention Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

First, the present invention a) 5 to 25 parts by weight of amorphous polyester resin is added to 100 parts of polyester resin, barium sulfate particles having a refractive index of 1.6-1.7 are added and kneaded in a twin screw extruder to prepare a master batch. Step; can proceed.

The polyester resin used for the white film according to the present invention preferably has an intrinsic viscosity of 0.60 to 0.70. When the intrinsic viscosity of the polyester resin depends on the processability and the physical properties of the film, if the intrinsic viscosity is less than 0.60, the strength of the film during processing can not be increased enough to satisfy the breakage at the time of stretching, productivity is lowered, exceeds 0.70, The melt viscosity is very high, and productivity in the post process is greatly reduced due to difficulties in the film forming process such as an increase in extrusion pressure.

The polyester resin used in the white film according to the present invention is not particularly limited, but it is preferable to use polyethylene terephthalate (PET) in consideration of the thermal stability and physical properties of the film. The PET is obtained by condensation polymerization of an acid component containing dicarboxylic acid as a main component and a glycol component containing alkyl glycol as a main component. Terephthalic acid or its alkyl ester or phenyl ester is mainly used as the main component of the dicarboxylic acid. In addition, as a glycol component, ethylene glycol is a main object.

In one embodiment of the present invention, the amorphous polyester resin is another acid component in place of terephthalic acid (TPA) in polyethylene terephthalate prepared by polymerizing terephthalic acid (TPA) and ethylene glycol (EG). , Copolymerized with 10 to 20 mol% of one component selected from other diol components and mixtures thereof instead of ethylene glycol (EG), such amorphous polyester resin is contained in 100 parts by weight of polyethylene terephthalate contained in the masterbatch. 5 to 25 parts by weight can be added.

In the present invention, the amorphous polyester resin is other acid component or ethylene glycol instead of terephthalic acid (TPA) in the structure of polyethylene terephthalate prepared by polymerizing terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG). 10-20 mol% copolymerization of other diol components instead of (EG). Examples of acid components include difunctional carbohydrates such as isophthalic acid, oxyethoxy benzoic acid, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid. The acid component selected from the group consisting of the main acid and its ester-forming derivatives can be used. Examples of the diol component include propylene glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-bisoxyethoxybenzene, bisphenol, polyoxyethylene glycol, Neopentyl glycol and mixtures thereof may be selected and used.

In the present invention, when the copolymerization content of each component is less than 10 mol%, the crystallization retardation effect due to amorphous is insufficient, and if it exceeds 20 mol%, the amorphousness is too large and the raw material drying process is difficult, thereby lowering the working efficiency.

Moreover, it is preferable that the intrinsic viscosity is 0.60-0.80 of the copolymer containing amorphous polyester used for the white film of this invention. The intrinsic viscosity of the copolymer influences the kneading process with the polyester resin and the physical properties of the film, but if the intrinsic viscosity is less than 0.60, it cannot be increased enough to satisfy the strength of the film during processing, so that the breakage occurs frequently during stretching, thereby decreasing productivity. If it exceeds 0.80, the melt viscosity is very high and productivity in the post process is greatly reduced due to difficulties in the film forming process such as an increase in extrusion pressure.

Particularly, in step a), the amorphous polyester resin may be included in an amount of 5 to 25 parts by weight based on 100 parts by weight of the polyester resin included together, and by using an amorphous polyester resin, satisfactory opacity of the white film may be obtained. At the same time to reduce the breakage of the film during the film manufacturing process to be described later. In addition, there is an advantage that the whiteness and opacity of the white film are uniform in the lot by suppressing the uneven stretching due to excessive crystallization. At this time, when the content of the amorphous polyester resin is less than 5 parts by weight, the crystallization inhibitory effect is small and the effect of fracture improvement is insufficient. When it exceeds 20 parts by weight, the crystallization inhibitory effect is so large that void formation is suppressed and the opacity characteristic of the white film is suppressed. The value is insufficient.

In one embodiment of the present invention, barium sulfate compounded by kneading in a twin screw extruder by adding barium sulfate particles having a refractive index of 1.6-1.7, if the refractive index is less than 1.6, the gloss will be out of the required level, 1.7 If it exceeds, the light absorbed may increase and the required whiteness may fall.

Specifically, the barium sulfate of the present invention has an average particle diameter of 1.0 to 1.5 µm by the original equivalent diameter, no particles having a particle diameter of 0.0001 to 0.3 µm, or 5 volume% or less, and no particles having a particle diameter of 3.0 to 10.0 µm or 5 It has a particle size distribution of less than Volume%, the ratio of the long diameter / short diameter is 0.7 ~ 1.0, 95-100% by volume of the particle size distribution can be used 0.3 ~ 3㎛. When the average particle diameter of the barium sulfate is less than 1.0 μm, the barium sulfate particles are aggregated to form aggregates, so that the dispersibility of the particles is reduced, and concealability cannot be improved. If it exceeds, the particle size becomes too large, the pore size increases when the film is stretched, resulting in poor operation, and there is a concern that whiteness and opacity may decrease.

Further, if the distribution of particles having a particle size of 0.0001 to 0.3 µm by the original equivalent diameter exceeds 5% by volume, and the distribution of particles having a particle diameter of 3.0 to 10.0µm exceeds 5% by volume, that is, the particle size distribution is in a certain range. When the number of particles deviates, the size of the particles becomes non-uniform, and the size and frequency of the pores during the stretching to the film also become uneven, which may cause an operation defect in which the breakage of the film occurs, making it difficult to obtain uniform physical properties of the final film. . The distribution of particles having a diameter of 0.0001-0.3 μm is better to include all of those having a particle diameter of 0.3 μm or less, and the distribution of particles having a size of 3.0-10.0 μm includes all of those having a particle size of 3.0 μm or more, but most of the particles in the above range. To achieve. In addition, it is preferable that the particle size of the original equivalent diameter is included in the distribution of particles having a particle size of 0.3 μm or less and 0.001-5% by volume of particles having a size of 3.0 μm or more, and more preferably, when there are no particles having the particle distribution in the above range. . In addition, it is preferable that the ratio of the long diameter / short diameter of the barium sulfate of the present invention is 0.7 to 1.0, and the ratio of the long diameter / short diameter of the above range is more preferable that the form of the barium sulfate of the present invention is close to the sphere, uniform and at least It can contribute to the formation of pores and the improvement of workability and the improvement of physical properties and whiteness of the final film.

The barium sulfate included in the white film of the present invention is used to enhance the whiteness, opacity (hiding force), and the pores are formed by the barium sulfate, which is an inorganic material of the present invention, and these pores absorb light of a specific wavelength. Without work, the light is constantly diffused to sufficiently bleach the film to improve whiteness. The shape, average particle size, or particle size distribution of barium sulfate affects whiteness, gloss, opacity, and operational stability.

In general, in the distribution of particle diameters in the particle group constituting the granules, the granules are composed of particles of irregular shape and uneven size, and Heywood's in representing the particle diameter of such irregularly shaped particles. diameter). Here, circle equivalent diameter means the diameter of a circle having the same width as the projection width of the particle.

Therefore, by adjusting the average particle size or particle size distribution, shape and refractive index of barium sulfate as described above, the size of the pores is uniform and minimized, there is no breakage during film stretching, white film having satisfactory whiteness, opacity and gloss Can be obtained.

The white film according to the present invention may be prepared by directly including barium sulfate with the polyester resin during extrusion, but is more preferably applied in the form of a masterbatch containing barium sulfate in the polyester resin.

The content of barium sulfate of the present invention may be included in 50 to 150 parts by weight of barium sulfate relative to 100 parts by weight of the polyester resin. That is, the master batch is prepared by adding 50 to 150 parts by weight of barium sulfate and more preferably 70 to 120 parts by weight to a twin screw extruder hopper to a polyester resin and 100 parts by weight of the polyester resin. It can manufacture. When the barium sulfate is less than 50 parts by weight, even if a large amount of masterbatch in the film production can not give the whiteness or concealability of the film, if it exceeds 150 parts by weight, the amount of polyester resin is reduced to reduce the strength of the film, It may cause breakage during stretching.

b) a sheet manufacturing step of extruding the mixture of the masterbatch and the polyester resin; can proceed. The masterbatch may be included in an amount of 10 to 100 parts by weight, preferably 30 to 70 parts by weight, and more preferably 50 to 60 parts by weight, based on 100 parts by weight of the polyester resin. If the masterbatch containing barium sulfate is less than 10 parts by weight, the whiteness or concealability of the film cannot be imparted, and if it is more than 100 parts by weight, it causes breakage during stretching.

The polyester resin is a polyester resin having an intrinsic viscosity of 0.6 to 0.7 to which particles are not added in the polymerization step. In addition, before extruding the mixture of the masterbatch and the polyester resin, it is preferable to use it by drying to a water content of 50 ~ 100ppm.

The dried mixture may be put in an extruder, melted, extruded from a T-die, quenched with a casting drum having a surface temperature of 10 to 50 ° C., and solidified to prepare a sheet having a thickness of 1,000 to 2,000 μm. Due to the quenching, it is possible to maintain the amorphousness of the film to the maximum, thereby reducing the occurrence of breakage of the film.

c) uniaxially or biaxially stretching the prepared sheet; can proceed. The c) stretching step is to stretch the sheet 2 to 4 times in the machine direction (MD) at 85 ~ 110 ℃ to cool to 20 ~ 35 ℃, after preheating at 110 ~ 140 ℃ 3.0 ~ 4.0 times in the width direction (TD) It is preferable to biaxially stretch.

By controlling the shape and size of the barium sulfate contained in the film of the present invention it is possible to produce a stable film even at a temperature lower than 140 ° C than the existing stretching temperature at a high temperature.

The stretching temperature in the machine direction is preferably stretched at a temperature of more than Tg of the polyester resin, that is, 85 to 110 ° C. When the stretching temperature in the machine direction is less than 85 ° C, the stretching stress is large, so that there is a possibility of breakage in tenter stretching. There is a high problem, it is difficult to control the thickness exceeds 110 ℃. In addition, when the draw ratio in the machine direction is less than 2 times, the thickness is poor and the physical properties are lowered, and when it exceeds 4 times, there is a high possibility of breaking during tenter stretching.

On the other hand, the white film of the present invention is preferably biaxially stretched to give strength and stability of the film. Therefore, it is preferable to preheat and stretch at 110-140 degreeC which is higher than the extending | stretching temperature to the said machine direction, and when the extending | stretching temperature of the said width direction is less than 110 degreeC, the possibility of film breakage is high and it exceeds 140 degreeC. There is a problem that the thickness is poor and the physical properties are lowered.

Thereafter, d) heat-treating the stretched sheet at 180 to 230 ° C. with a tenter of five or more stages. When the heat treatment of the sheet is 5 or more stages, it is advantageous in terms of reducing the heat shrinkage rate when using the film, and it is preferable to proceed to 5-10 stages in consideration of productivity or ease of operation.

In addition, after the d) the heat treatment step, it may further comprise the step of less than 10%, preferably 1.0 ~ 10.0% relative to the length of the machine direction or width direction. Through the relaxation process it is possible to significantly improve the stability of the film properties. It is good to loosen the said relaxation in the width direction. In addition, the relaxation has the advantage of reducing the heat shrink rate when using the film. When the relaxation rate exceeds 10.0%, there is a problem that the clip interval before the relaxation treatment is widened, resulting in large uneven physical properties of the clip gripping portion and the non gripping portion of the film.

e) heat-setting the relaxed or heat-treated sheet at 200 ~ 250 ℃; including the white film of the present invention can be completed.

The white film manufactured according to the method of the present invention may exhibit a crystallization rate of 60 seconds to 300 seconds measured at 210 ° C isothermal conditions using the DSC. The crystallization rate in the above range is a factor exhibited by the amorphous polyester added to the present invention, thereby reducing the occurrence of breakage during the film manufacturing process, so as to avoid excessive crystallization in the quench unstretched sheet manufacturing process and pre-stretch preheating process. It is possible to improve the uniformity of the physical properties (quality) of the white film in the lot (Lot) by suppressing and enabling uniform stretching as a result. In the present invention, the thickness is 10 ~ 500㎛, the opacity of the film is adjusted to 60 ~ 90% can be provided with a white film having a gloss of 50 ~ 70%. If the thickness of the film is less than 10㎛, there is a fear that the opacity is low and the physical properties are lowered, if it exceeds 500㎛ may be difficult to manufacture and the application of suitable uses.

The white film prepared as described above has excellent opacity and glossiness, less breakage during manufacture, and excellent operability.

In addition, the white film produced by the method of the present invention may be used for interior decoration, architectural exhibition stand, exhibition necessities, display, placard or label, in facilities outside a store or shop, as an advertisement necessity or laminate, or food. Or it is suitable for the application to beverage packaging material, Especially it can be used preferably for printing a label and a card.

As described above, the white film manufactured by the method of the present invention does not cause breakage during the manufacturing process by using an inorganic material in a controlled form, and has excellent gloss, whiteness, and opacity.

In addition, there is an effect of obtaining a film of uniform physical properties by controlling the stretching temperature, the stretching ratio, the heat treatment temperature during the film manufacturing process.

Through the following examples will be described in more detail.

Example 1

1) Preparation of Masterbatch

10 parts by weight of an amorphous polyethylene terephthalate copolymer (intrinsic viscosity = 0.70) containing 90 parts by weight of polyethylene terephthalate resin having an intrinsic viscosity (Intrinsic Viscosity) of 0.65 and 15 mol% of neopentyl glycol (NPG) 100 parts by weight of barium sulfate having an average particle diameter of 1.0 μm, equivalent volume of 0.0001-0.3 μm, 3 volume%, 3.0-10.0 μm, 2 volume%, long diameter / short diameter ratio of 0.9, and refractive index of 1.64. Part was quantitatively injected into the twin screw extruder hopper to prepare a compounding chip.

2) white film production

36 parts by weight of the prepared master batch chip and 64 parts by weight of polyethylene terephthalate chip having an intrinsic viscosity of 0.65 without particles added in the polymerization step were dried at 160 ° C. for 8 hours and mixed. At this time, the moisture content of the dried chip was less than 100ppm. The mixed chip was placed in an extruder, melted, and extruded in a T-die to prepare a quenched sheet.

The prepared sheet is stretched 3.0 times in the machine direction (MD) at 105 ° C., then cooled to room temperature, and then stretched 3.5 times in the width direction (TD) at 130 ° C., which is higher than the machine direction (MD) stretching temperature. Heat treatment was performed at 220 ° C. in the heat treatment zone of the tenter, and then the film was shrunk by 5% with respect to the length in the width direction at 210 ° C. and then cooled to prepare a biaxially stretched film having a thickness of 175 μm.

Example 2

Amorphous polyethylene terephthalate copolymerized with 15 mol% of isophthalic acid (IPA) in the polymerization reaction of 90 parts by weight of polyethylene terephthalate resin with Intrinsic Viscosity = 0.65 and terephthalic acid (TPA) and ethylene glycol It carried out similarly to Example 1 except adding 10 weight part of resin (intrinsic viscosity = 0.70).

Comparative Example 1

70 parts by weight of polyethylene terephthalate resin having Intrinsic Viscosity = 0.65 and 30 parts by weight of amorphous polyethylene terephthalate resin (high viscosity = 0.70) copolymerized with 15 mol% of NPG in the polymerization reaction of TPA and EG And it carried out similarly to Example 1.

Comparative Example 2

97 parts by weight of polyethylene terephthalate resin having Intrinsic Viscosity = 0.65 and 3 parts by weight of amorphous polypolyethylene terephthalate resin (high viscosity = 0.70) copolymerized with 15 mol% of NPG in the polymerization reaction of TPA and EG Except that was carried out in the same manner as in Example 1.

* Test Methods

1) intrinsic viscosity

It was measured at a concentration of 0.3 g per 25 ml of ortho-chloropetol at 35 ° C.

2) Measurement of average particle size and particle size distribution by circle equivalent diameter

The average particle size and particle size distribution of the particles dispersed in ethylene glycol were measured using a Beckman particle size analyzer Laser Diffraction Particle Size Analyzer (LS 13 320).

3) Measurement of long diameter / short diameter

The long and short diameters of the particles were measured in units of 0.1 μm through a scale by taking a picture of the particles using a scanning electron microscope (SEM).

4) Measurement of fracture

During the stretching of the prepared film or during the heat treatment, the film was broken in the process section, and it was visually confirmed to see a state in which normal operation was impossible.

5) Measurement of opacity

Measurement was performed using a Film Opacity Meter Series 6000 instrument.

6) Measurement of glossiness

Using a gloss measuring device (Model name 4011) of Labotron, Germany, it was measured according to the ASTM D523 method based on the black diameter at the measurement angle of 60 ㅀ.

7) Scanning electron microscope (SEM) measurement

Scanning electron microscope (SEM) Using a Jeol JSN 6700F instrument was observed at a magnification of 1000 ~ 5000 times.

8) Isothermal Crystallization Rate Differential Scanning Analyzer (DSC) Measurement

Using a differential scanning thermal analyzer (DSC 7 from Perkin Elmer), the crystallized peak is measured while being heated to 20 ° C./min at 280 ° C. for 5 minutes, cooled to 210 ° C., and maintained at a temperature. The time to reach the peak is measured by the crystallization rate.

TABLE 1

As a result of Table 1, in the case of Examples 1 and 2, the white film was produced in a fair processability and satisfactory in terms of physical properties without breaking, but in Comparative Example 1 an excessive amount of amorphous polyester resin in the production of the master batch The crystallization delay was excessively increased due to the addition, so that the fracture did not occur due to crystallization during stretching, but the void formation was so limited that the opacity was relatively insufficient. In the case of Comparative Example 2, too small amount of amorphous polyester resin was added, resulting in insufficient crystallinity retardation effect, resulting in high unevenness in formation and formation of large voids. Appeared.

The present invention described above is not limited to the above-described embodiments, and various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be obvious to him.

Claims (11)

a) adding 5-25 parts by weight of an amorphous polyester resin to 100 parts by weight of polyester resin, and producing a masterbatch comprising barium sulfate particles having a refractive index of 1.6-1.7; b) a sheet manufacturing step of extruding the mixture of the masterbatch and the polyester resin; c) drawing the sheet; d) heat-treating the stretched sheet at 180 to 230 ° C. with a tenter of five or more stages; And e) heat setting step of the heat treated sheet; Method for producing a white film comprising a. The method of claim 1, The amorphous polyester resin is isophthalic acid, oxyethoxy benzoic acid, adipic acid, sebacic acid, 5-sodium sulfophthalic acid, ester-forming derivatives thereof, and the like in a polyethylene terephthalate structure polymerized with terephthalic acid and ethylene glycol. Acid components selected from the group consisting of mixtures; Propylene glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-bisoxyethoxybenzene, bisphenol, polyoxyethylene glycol, neopentyl glycol and mixtures thereof A diol component selected from the group consisting of; And a component selected from the group consisting of a mixture thereof is prepared by copolymerizing 10 to 20 mol%. The method of claim 1, The barium sulfate has an average particle diameter of 1.0 to 1.5 µm by the circular diameter, no particles having a particle diameter of 0.0001 to 0.3 µm or no more than 5% by volume, and no particle having a particle diameter of 3.0 to 10.0µm or a particle size distribution of less than 5% by volume. The method for producing a white film having a long diameter / short diameter ratio of 0.7 to 1.0. The method of claim 3, The barium sulfate of step a) is a method for producing a white film containing 50 to 150 parts by weight of barium sulfate relative to 100 parts by weight of the polyester resin. The method of claim 1, The polyester resin is a method for producing a white film of polyethylene terephthalate. The method of claim 1, In the step b), the master batch is a method for producing a white film containing 10 to 100 parts by weight based on 100 parts by weight of polyethylene terephthalate resin. The method of claim 1, The c) stretching step is to stretch the sheet 2 to 4 times in the machine direction (MD) at 85 ~ 110 ℃ to cool to 20 ~ 35 ℃, 3.0 to 4.0 times in the width direction (TD) at 110 ~ 140 ℃ biaxial Method for producing a white film to stretch. The method of claim 1, After the heat treatment step, the manufacturing method of the white film further comprising a relaxation step of less than 10%. The white film produced by the method of any one of claims 1 to 8. 10. The method of claim 9, The white film is a white film having a crystallization rate of 60 seconds to 300 seconds measured at 210 ℃ isothermal conditions using DSC. The polyester resin includes 5 to 25 parts by weight of amorphous polyester resin and 50 to 150 parts by weight of barium sulfate particles having a refractive index of 1.6-1.7, and the crystallization rate measured at 210 ° C isothermal conditions using DSC is 60 seconds to 300 Super white film.