KR20190071115A - Polyester multi-layer film and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a polyester multilayer film and a method for manufacturing the same. The present invention relates to a polyester multilayer film excellent in transparency and visibility, and a method for manufacturing the same. More specifically, the present invention relates to a polyester multilayer film comprising: a core layer comprising a polyester resin; and a skin layer laminated on at least one side of the core layer and comprising a polyester resin and particles. The internal haze of the entire film is 0.3% or less.

Description

[0001] POLYESTER MULTI-LAYER FILM AND MANUFACTURING METHOD THEREOF [0002]

The present invention relates to a polyester multilayer film and a method for producing the same, and relates to a polyester multilayer film excellent in transparency and visibility and a method for producing the same.

Polyester film is widely used as a protective film for protecting windows and windows of automobiles and buildings because of its excellent transparency, light resistance, moisture resistance and chemical resistance, and is used for protection of personal privacy and prevention of scattering of glass when a window is broken .

The polyester film used as the base film of the glass protective window film is hard coated on one side and vapor-deposited on the other side and bonded to the glass window through lamination process after adhesion coating. The polyester film used as the base film Is required. The better the transparency, the better the visibility of the finished window film, and it can be applied to advanced product groups.

However, a product having a high transparency has a disadvantage in that the processing yield is low due to a high incidence of defects such as a folding phenomenon during scratch and film processing in a post-processing step such as a winding and coating process at the time of processing.

In order to solve the above problems, the present invention aims to improve the yield in the post-processing process of the film by providing transparent and fine irregularities on the film surface.

In addition, in imparting fine irregularities, particles in the film are added. In order to solve the problem that the transparency is lowered due to the particles of the film, the size of the particles is adjusted to a specific range and the dispersibility of the particles is improved It is an object of the present invention to provide a polyester film which is excellent in transparency and can be applied to an advanced product group of a window film by reducing a defective rate in a post-processing process, which is aimed at reducing haze deterioration caused by internal defects due to agglomeration of particles.

More specifically, in the present invention, the dispersibility of the particles used for securing transparency is maximized, thereby preventing the visibility of particles from occurring due to the agglomeration of the particles, and a polyester film having low internal haze while simultaneously satisfying both running and transparency The purpose is to provide.

That is, it is an object of the present invention to provide a polyester film excellent in transparency and visibility, having a low occurrence rate of defects during scratch and film processing in a post-processing step such as a winding and coating process, and having excellent slipperiness.

In order to achieve the above object, one aspect of the present invention is to provide a core layer comprising a polyester resin, at least one layer laminated on both sides of the core layer, and a skin layer comprising a polyester resin and particles, And the internal haze of the film is 0.3% or less.

The polyester multi-layer film according to the present invention is excellent in transparency and visibility, and therefore can be suitably used as a window film used in automobiles or building glass windows.

The polyester multi-layer film according to the present invention can provide a polyester multi-layer film having excellent transparency and low winding-up property and defective rate in the post-processing step.

1 is a photograph of a film according to Example 1 of the present invention observed under an optical microscope (100 times).
2 is a photograph of a film according to Comparative Example 1 of the present invention observed under an optical microscope (100 times).
3 is a photograph of a film according to Comparative Example 2 of the present invention observed with an optical microscope (100 times).

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described more fully hereinafter with reference to the accompanying drawings, It should be understood, however, that the invention is not limited thereto and that various changes and modifications may be made without departing from the spirit and scope of the invention.

Unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention is merely intended to effectively describe a specific embodiment and is not intended to limit the invention.

Also, the singular forms as used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In the present invention, 'internal haze' refers to the haze measured when the particles imparted to the film are protruded when the film is extended to the surface during film stretching, and scattering of light generated by the roughness is blocked. That is, it means the haze measured by purely scattering only by the particles inside the film.

To prevent scattering of the surface of the film, a transparent coating liquid having the same refractive index as that of the polyester film is applied to both sides of the polyester multilayer film, and the haze is measured. When the refractive index is the same, it is preferable that the diffraction of light does not occur at the interface between the coating layer and the film. It is not limited as long as it can be applied to a thickness capable of controlling scattered light on the surface. More specifically, the transparent coating liquid can be used without limitation as long as it is a hard coating liquid usually used in the film field.

More specifically, the internal haze means the haze measured by the measuring method described later.

One aspect of the present invention is a laminated film comprising a core layer comprising a polyester resin, and a skin layer laminated on at least one surface of the core layer and comprising a polyester resin and particles, wherein the inner haze of the entire film is 0.3 % Or less.

In one embodiment of the present invention, the particle may have a particle size distribution ratio? Satisfying the following formula (1).

[Formula 1]

1??? 5

Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

In one embodiment of the present invention, the particles satisfying the formula (1) are obtained by centrifuging a particle slurry in which particles are dispersed in a glycol component, classifying the particles so that the D ₉₀ is 1.7 ± 0.1 μm or less, filtering with a filter of 6-8 μm And the like.

In one embodiment of the present invention, the particles included in the skin layer may have an average particle diameter of 0.5 to 1.0 탆 and a D ₉₀ of 1.7 ± 0.1 μm or less.

In one embodiment of the present invention, the content of the particles contained in the skin layer may be 0.01 to 0.3% by weight based on the total weight of the film.

In one aspect of the present invention, the particles may be selected from inorganic particles, organic particles, and mixtures thereof.

In one embodiment of the present invention, the inorganic particles are any one or a mixture of two or more selected from calcium carbonate, titanium oxide, silica, kaolin and barium sulfate,

The organic particles may be selected from the group consisting of silicone resin, crosslinked divinylbenzene polymethacrylate, crosslinked polymethacrylate, crosslinked polystyrene resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin and melamine-formaldehyde resin And may be any one or a mixture of two or more selected.

In one aspect of the present invention, the particles may be added in the polyester resin polymerization step.

In one embodiment of the present invention, the polyester multilayered film may have a haze of 0.7 to 1%.

In one embodiment of the present invention, the polyester multilayered film may have a static friction coefficient and a dynamic friction coefficient of 0.5% or less.

In one embodiment of the present invention, the polyester multilayered film may have a total light transmittance of 90% or more.

In one embodiment of the present invention, the polyester multilayered film may have a thickness of 10 to 300 mu m.

In one embodiment of the present invention, the core layer may be 70 to 90% by weight of the total film and the skin layer may be 10 to 30% by weight.

In one aspect of the present invention, the polyester multilayered film may further include the adhesive primer layer on one side or both sides.

Another embodiment of the present invention is a window film comprising the polyester multilayer film and further comprising a hard coating layer on one or both sides.

Another embodiment of the present invention is a method for producing a core layer, comprising the steps of: a) melt-extruding a composition for a skin layer containing particles and a polyester resin having particle size distribution ratios satisfying the following formula 1 and a core layer composition comprising a polyester resin, And a skin layer laminated on the surface of the skin layer;

[Formula 1]

1??? 5

Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

b) uniaxially stretching the sheet in the machine direction;

c) applying a water-dispersible coating solution to the uniaxially stretched film to form a good adhesion primer layer;

d) stretching in the width direction; And

e) heat treating and relaxing;

, Wherein the total haze of the film is 0.3% or less.

In one embodiment of the production method of the present invention, the composition for a skin layer is prepared by centrifuging a particle slurry in which particles are dispersed in a glycol component, classifying the particles so that D ₉₀ is 1.7 ± 0.1 μm or less, filtering with a filter of 6-8 μm And a polyester resin master batch chip produced by preparing the particle slurry satisfying the formula 1 and then adding the particle slurry in the polyester resin polymerization step.

Hereinafter, the present invention will be described in more detail.

One aspect of the polyester multilayer film of the present invention includes a core layer and a skin layer having at least one layer stacked on both sides of the core layer.

In one embodiment of the polyester multilayer film of the present invention, the core layer includes a polyester resin, and may not include particles. It does not exclude the inclusion of particles but it is preferable since it does not contain particles and can provide a film having better transparency. More specifically, the core layer may be made of a polyester resin, more specifically, a polyethylene terephthalate resin alone. The polyethylene terephthalate resin to be used herein may be one having an intrinsic viscosity of 0.6 to 0.7 dl / g. The polyethylene terephthalate resin may have excellent heat resistance in the above range and may not cause interface instability during co-extrusion.

In one embodiment of the polyester multilayer film of the present invention, the skin layer includes a polyester resin and particles, and when one or more layers are laminated, the types of the polyester resin and the particles of each layer may be the same or different from each other . More specifically, the skin layer may contain a polyester resin and an inorganic particle having an intrinsic viscosity of 0.6 to 0.7 dl / g. The multilayered film can be stably laminated with the core layer without interface instability in a range where the intrinsic viscosity satisfies the above range, and the processability is easy, but the present invention is not limited thereto.

One embodiment of the polyester multilayer film of the present invention may be one comprising a core layer comprising a polyester resin and a skin layer laminated on both sides of the core layer and comprising a polyester resin and particles.

In one embodiment of the present invention, the polyester resin may be one which uses a polyester resin which is usually used in a polyester film. For example, a composition for producing a conventional homopolymerized polyester or copolymer polyester which can be produced by esterification or transesterification reaction of a dicarboxylic acid or an ester derivative thereof and a diol or an ester derivative thereof, for example, a melt polycondensation method Lt; / RTI >

As the main component of the dicarboxylic acid, terephthalic acid or an alkyl ester thereof or a phenyl ester thereof is mainly used, but a part of the dicarboxylic acid is used as a main component such as isophthalic acid, oxyethoxybenzoic acid, adipic acid, sebacic acid and 5-sodium sulfoisophthalic acid It may be used by substituting with a bifunctional carboxylic acid or an ester-forming derivative thereof.

As the glycol component, ethylene glycol is a main object, but propylene glycol, neopentyl glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-bisoxyethoxy Benzene, bisphenol, and polyoxyethylene glycol. If the content is small, a monofunctional compound or a trifunctional compound may be used in combination.

The polyester resin can be produced by a conventional polymerization method, that is, a DMT polymerization method or the like, but is not limited thereto. In addition, it may further include any one or two or more components selected from additives commonly used in the field of film, such as a pinning agent, an antistatic agent, a UV stabilizer, a waterproofing agent, a slip agent and a heat stabilizer.

In one embodiment of the present invention, the particle is an important factor for determining not only the transparency of the film but also the running property and the workability. By controlling the particle size through classification and filtering, the particle can be used not only for transparency and visibility, And the like can be achieved.

More specifically, in one embodiment of the present invention, the particle may have a particle size distribution ratio? Satisfying the following formula (1).

[Formula 1]

1??? 5

Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

It is possible to prevent occurrence of defects due to the coarse protrusions because the particles are evenly and uniformly distributed in the range satisfying the above-described formula (1), and the total haze is 0.3% or less and the total light transmittance is 90% But is not limited to, it can provide a super-transparent film.

More specifically, in order to provide a film satisfying the above formula 1 and having an internal haze of 0.3% or less, the particle slurry in which the particles are dispersed in a glycol component is centrifuged to classify the D _{90 so as} to be 1.7 ± 0.1 μm or less And then removing the coarse particles by filtering using a filter of 6 to 8 mu m. By the classification and filtering, it is possible to increase the dispersibility of the particles in the resin, to prevent the particles from being re-agglomerated, to provide a film having better transparency and visibility of the film to be produced, An improved film can be provided.

The classification is a process of removing coarse particles by centrifuging the particle slurry in a centrifugal separator, and may be performed such that D ₉₀ is 1.7 ± 0.1 μm or less, more specifically 1.1 to 1.7 μm.

The filtering is a process of filtering the classified particle slurry again using a filter. The size of the filter used may be 6 to 8 탆, more specifically, 6.5 to 7.5 탆.

In one aspect of the invention, the particles obtained by the classification and filtering is the average particle diameter of 0.5 to 1.0 ㎛, may be in the D ₉₀ 1.7 ± 0.1 ㎛ or less, specifically 1.1 to 1.7㎛. It is possible to provide a super-transparent film having a total light transmittance of 90% or more without causing defects due to agglomerated particles in the evaluation of visibility in the range where the average particle diameter and the maximum particle diameter satisfy the above range, and to provide a film excellent in running property and post- And can provide a film having an internal haze of 0.3% or less of the whole film, but is not limited thereto.

In one aspect of the present invention, by controlling the maximum grain size of the particles through classifying and filtering the particles, the transparency and visibility are excellent, and at the same time, the number of effective peaks of the film is increased to improve the processability, And the appearance problems such as scratches can be improved. In addition, due to the removal of coarse particles and the improvement of dispersibility, protrusions and fish eye generation due to large particles can be suppressed. In addition to classifying and filter treatment methods, there are particle milling or dispersing agent addition methods by controlling the particle size. However, in the case of milling, in order to improve the dispersibility, It is necessary to selectively use a dispersing agent according to the characteristics of the inorganic particles and may cause a problem of inducing aggregation of the particles rather depending on the amount of the dispersing agent. However, one aspect of the present invention can provide a film having improved dispersibility of particles, solving agglomeration of particles, and thus having excellent visibility by removing coarse particles through classifying and filtering the particles.

In one embodiment of the present invention, the kind of particles is not limited, and may be inorganic particles, organic particles or a mixture of inorganic particles and organic particles, and one or a mixture of two or more kinds may be used. That is, it is also possible to use one kind or two or more types of inorganic particles, use one kind or two or more kinds of organic particles, or use one kind or two kinds or more kinds of inorganic particles and one kind or two kinds or more kinds of organic particles Do.

More specifically, for example, the inorganic particles may be any one or a mixture of two or more selected from calcium carbonate, titanium oxide, silica, kaolin, and barium sulfate. The organic particles may be selected from the group consisting of silicone resin, crosslinked divinylbenzene polymethacrylate, crosslinked polymethacrylate, crosslinked polystyrene resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin and melamine-formaldehyde resin And may be any one or a mixture of two or more selected.

In one embodiment of the present invention, the content of the particles may be 0.01 to 0.3% by weight based on the total weight of the film, and it is preferable to provide a film having excellent transparency and visibility within the above range, , But is not limited thereto.

In one embodiment of the present invention, the particles may be added in the polycondensation reaction step of the polyester resin or in the solid-phase polymerization step. When the particles are added in the form of a slurry dispersed in the glycol component, But is not limited to, it can prevent recondensation between particles.

In one embodiment of the present invention, the weight of the core layer may be 70-90 wt% of the entire film, and the weight of the skin layer may be 10-30 wt%. In the above range, it is possible to provide a film excellent in interfacial stability during coextrusion, easy to form, excellent in transparency, and excellent in slip property and post-processability, but is not limited thereto.

In one aspect of the present invention, the polyester multilayered film may have an internal haze of 0.3% or less. Specifically, the internal haze may be 0.01 to 0.3%, more specifically 0.1 to 0.3%. The film can be applied to a window film in a range where the internal haze satisfies the above range, and a film having excellent transparency and visibility can be provided.

Usually, a window film forms a hard coating layer made of a transparent resin on one side or both sides of a polyester base film. The haze of the film formed with the hard coating layer in this process may be different from the haze of the film before forming the hard coating layer. This is because the roughness of the surface of the film is removed by forming the hard coating layer so that the haze due to particles or the like in the film is substantially measured. Therefore, not only the haze but also the internal haze are important physical properties to be applied to the window film, and the lower the internal haze, the better the transparency. Further, in order to apply the hard coating solution to form the hard coating layer, the post-processability, that is, the physical properties such as coatability and running property, must be satisfied.

In one embodiment of the present invention, the polyester multilayered film may have a haze of 1% or less, specifically 0.1 to 1%, more specifically 0.7 to 1.0%. The film can be provided with excellent transparency within the above range, but is not limited thereto.

In one embodiment of the present invention, the polyester multilayer film may have a static friction coefficient and a dynamic friction coefficient of 0.5% or less, specifically 0.1 to 0.5%, more specifically 0.2 to 0.5%. In the above range, it is preferable to coat the hard coating solution, which is excellent in running property, to improve the productivity, but the present invention is not limited thereto.

In one embodiment of the present invention, the polyester multilayer film may have a transmittance of 90% or more, more specifically 90% to 95%, and is suitable for application to a window film because of its excellent transparency in the above range. It is not.

In one aspect of the present invention, the polyester multilayer film may have a thickness of 10 to 300 占 퐉, more specifically, a thickness of 50 to 250 占 퐉, and is suitable for application to a window film in this range, It is not.

In one aspect of the present invention, the polyester multilayered film may further include the adhesive primer layer on one side or both sides. The adhesive primer layer may be formed to further improve the adhesion with the hard coat layer to be coated in the post-process. The adhesive primer layer is not limited as long as it is usually coated in order to improve the adhesion with the hard coating layer in the field. Specifically, for example, a water dispersible composition containing a polyurethane resin, an acrylic resin and a polyester resin may be applied and is not limited thereto.

In one embodiment of the present invention, the thickness of the adhesive primer layer may be 10 to 500 nm, more specifically 50 to 400 nm. But is not limited thereto since it is sufficient to exhibit the desired adhesiveness within the above range.

In one aspect of the present invention, the adhesive primer layer may be formed by an in-line process at the time of producing the polyester multilayer film, or may be formed offline after the polyester multilayer film is produced.

In one aspect of the present invention, the production of a polyester multilayer film comprising a core layer and a skin layer is not limited, but can be obtained by casting after extrusion melt-extrusion in at least two melt extruders and by biaxial stretching. More specifically, a polyester is extruded from one extruder, a master batch chip containing polyester and particles and a base resin chip containing no particles are mixed and extruded in another extruder, and then the respective melts It can be co-extruded in a feed block, cast, cooled and then biaxially stretched sequentially to control the properties of the film by controlling the stretching, heat treatment and relaxation of the film in heat treatment and relaxation.

More specifically, the process for producing a polyester multilayer film of the present invention comprises

a) a composition for a skin layer containing a particle and a polyester resin having a particle size distribution ratio? satisfying the following formula 1, and a composition for a core layer comprising a polyester resin are melted and coextruded to obtain a sheet laminated with a core layer and a skin layer ;

[Formula 1]

1??? 5

Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

b) uniaxially stretching the sheet in the machine direction;

c) applying a water-dispersible coating solution to the uniaxially stretched film to form a good adhesion primer layer;

d) stretching in the width direction; And

e) heat treating and relaxing;

. ≪ / RTI >

In the step a), the composition for the skin layer may comprise a polyester resin master batch chip polymerized by adding particles in a polymerization step of the polyester resin. Specifically, the composition for the skin layer may be such that the polyester resin master batch chip and the polyester resin base chip containing no inorganic particles are mixed so that the content of the particles is 0.01 to 0.3% by weight in the total weight of the film.

The polyester resin master batch chip may be produced as follows. First, the particles are dispersed in a glycol component, specifically ethylene glycol, to prepare a particle slurry. In this case, the content of the particles in the particle slurry may be 10 to 50% by weight, and the dispersibility and viscosity can be easily controlled within the above range, but is not limited thereto.

Next, centrifuging the particle slurry to remove coarse particles may include centrifuging and classifying D ₉₀ to be 1.7 ± 0.1 μm or less, more specifically 1.1 to 1.7 μm.

Next, the classified particle slurry is filtered. In this case, the size of the filter used may be 6 to 8 占 퐉, more specifically, 6.5 to 7.5 占 퐉.

In one embodiment of the present invention, the particles obtained by the classifying and filtering may have an average particle diameter of 0.5 to 1.0 탆 and a D ₉₀ of 1.7 ± 0.1 탆 or less, and the particle size distribution ratio γ may satisfy the following formula 1 have.

[Formula 1]

1??? 5

Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

The particle slurry obtained by dispersing the particles in the glycol component as described above was centrifuged and classified so that the D ₉₀ was 1.7 ± 0.1 μm or less. The slurry was filtered with a filter of 6-8 μm to prepare a particle slurry satisfying the above formula 1 , The polymerization step of the polyester resin, more specifically, the polycondensation reaction step or the solid phase polymerization step, to prepare a polyester resin master batch chip.

In the step a), the co-extrusion may be performed by melt extrusion using a conventionally known tie die method and then laminating.

The step b) is a step of stretching the coextruded sheet to produce a film. The coextruded sheet is coextruded and extruded into a three-layer or more sheet having a core layer and a skin layer laminated on both sides thereof. The sheet is cooled in a casting roll, . The machine direction stretching may be from 1.2 to 10 times, more specifically from 2 to 7 times, and is not limited thereto. The stretching ratio in the machine direction does not lower the mechanical strength of the film in the above range and the stretching in the width direction can be performed stably, but is not limited thereto.

The stretching in the transverse direction in the step d) may be performed at a stretching ratio of 1.2 to 10 times, more specifically 2 to 7 times, but is not limited thereto. The stretching ratio in the width direction does not lower the mechanical strength of the film within the above range and prevents the film from being broken.

The step e) is a step of performing heat treatment and relaxation, and may be performed simultaneously with heat treatment and relaxation, or may be performed sequentially. The heat treatment may be performed at a temperature of 200 to 240 ° C, and the film may be shrunk within the above range, but is not limited thereto. The relaxation may be a relaxation of 1.1 to 7% with respect to the width direction. But the present invention is not limited thereto, for example, by performing a secondary relaxation of 0.1 to 2% in the width direction in the cooling section after the heat treatment and relaxation.

Another embodiment of the present invention is a window film comprising the polyester multilayer film. More specifically, it may include the polyester multilayer film and further include a hard coating layer on one side or both sides.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

The following physical properties were measured as follows.

1) Haze and total light transmittance

The haze was measured on the basis of ASTM D-1003. Seven portions were randomly extracted from two locations on the edge of the polyester film, one at the center, and then cut into pieces of 5 cm × 5 cm. The haze was measured with a haze meter (NDH 5000) And light having a wavelength of 400 to 700 nm was transmitted, and the average value except the maximum / minimum values was calculated by the following formula.

Haze (%) = (total scattered light / total transmitted light) × 100

The total light transmittance was also measured using the haze meter (NDH 5000, Nihon Denshoku).

2) Internal haze

A film sample of 5 cm x 5 cm in the machine direction and the width direction was prepared and a hard coating solution (Aekyung Chemical Co., RS-1000) was applied to both sides of the film specimen, followed by drying and curing to form a 3 탆 thick hard coating layer, , The haze was measured according to the above-mentioned method.

3) Average particle size and particle size distribution ratio

The average particle diameter and the particle size distribution ratio were measured using a particle size distribution analyzer (Beckman-Coulter, LS13 320).

The particle size distribution ratio? Was calculated according to the following formula (1).

γ = D ₉₀ - D ₁₀ / D ₅₀ [Formula 1]

In Formula 1, D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the particle diameter when the cumulative weight of the particles is 50% based on the total weight, D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.

4) Measurement of static friction coefficient and dynamic friction coefficient:

The measurement method was ASTM-D1894, and the polyester film was sampled 11 cm in the width direction and 20 cm in the length direction, and then a coefficient of friction meter (TOYOSEIKI A281300803) was used. The measurement was carried out in an atmosphere of a temperature of 23 ± 1 ° C. and a humidity of 50 ± 5% RH, and a load of 200 g was measured. The measurement speed was 300 mm / min.

5) Particle Visibility

A hard coating solution (Aekyung Chemical Co., RS-1000) was applied to both sides of the prepared film, dried and cured to form a hard coat layer having a thickness of 3 탆, and then the presence or absence of agglomerated particles was visually observed. When there was only one agglomerated particle in the full width of the film, it was determined to be defective, and in the case where no agglomerated particles were found, the case was evaluated as good.

6) Intrinsic viscosity

0.4 g of PET pellet (sample) was added to 100 ml of a reagent in which phenol and 1,1,2,2-tetrachloroethanol were mixed at a weight ratio of 6: 4, and the mixture was transferred to a Ubero's viscometer. For 10 minutes, and the falling seconds of the solution was determined using a viscometer and an aspirator. The number of drops of the solvent was also determined by the same method, and RV and IV values were calculated by the following equations (1) and (2).

In the following equation, C represents the concentration of the sample.

[Equation 1]

R.V. = Samples falling in water / solvent drops in seconds

&Quot; (2) "

[Example 1]

(Production of particle slurry)

The silica particles having an average particle diameter of 1.7 탆 were dispersed in ethylene glycol in an amount of 25% by weight, and classified by using a centrifugal separator so that the D ₉₀ was 1.7 賊 0.1 탆 or less, and filtered using a 7 탆 filter. 1 < / RTI > was prepared.

(Production of polyester resin master batch chip)

After mixing 100 parts by weight of dimethyl terephthalate with 50 parts by weight of ethylene glycol, 400 ppm of transesterification catalyst magnesium acetate was added and the temperature was elevated from 140 ° C to 230 ° C for 4 hours to carry out transesterification reaction to obtain a prepolymer BHET (bis- β-hydroxyethyl terephthalate). Methanol generated during the reaction was separated through a distillation column, and ethylene glycol, which was generated after completion of the esterification reaction, was also separated through a distillation column. The prepared silica particle slurry was added in an amount of 1.0 wt% based on the total weight of the polyester resin, 200 ppm of antimony trioxide catalyst was added thereto, and the temperature was gradually raised from 230 째 C to 283 째 C and the polycondensation reaction was continued for 4 hours To prepare a polyester resin having an intrinsic viscosity (IV) of 0.620 dl / g.

(Production of film)

25 wt% of the polyester resin prepared above and 75 wt% of a particle-free polyester resin (intrinsic viscosity: 0.630 dl / g) were blended and melt-extruded into a skin layer (B) Extruded into a B / A / B 3 layer using a non-particulate polyester resin (intrinsic viscosity of 0.630 dl / g) as a core layer (A) and then quenched and solidified by a casting drum having a surface temperature of 20 ° C to form a sheet Unstretched film). At this time, the weight of the skin layer was 20% by weight and the weight of the core layer was 80% by weight.

The prepared sheet was stretched 3.3 times in the longitudinal direction (MD) and 4.5 times in the transverse direction (TD), and then heat-settled and relaxed 5% at 238 DEG C to give a biaxially oriented film of 30 mu m in thickness having a particle content of 45 ppm in the final film .

The physical properties of the produced film were measured and are shown in Table 2 and Fig.

[Example 2 and Example 3]

Same as Example 1 except that a particle slurry was prepared by controlling the particle size distribution of the particle slurry as shown in the following Table 1, and a polyester resin master batch chip was prepared using the slurry and a film was prepared using the same as the skin layer Lt; / RTI >

The physical properties of the prepared film were measured and are shown in Table 2 below.

[Comparative Example 1]

(Production of particle slurry)

Silica particles having an average particle diameter of 1.7 탆 were dispersed in ethylene glycol in an amount of 25% by weight, and then D90 was classified to 1.8 탆 or less using a centrifugal separator. No filtering was performed. The particle size distribution of the prepared silica particles was measured and is shown in Table 1 below.

A film was prepared in the same manner as in Example 1, except that a polyester resin master batch chip was prepared using the prepared particle slurry and that the polyester resin master batch chip was used as a skin layer to produce a film.

The physical properties of the prepared film were measured and are shown in Table 2 and Fig. 2 below.

[Comparative Example 2]

(Production of particle slurry)

Silica particles having an average particle diameter of 1.7 탆 were dispersed in ethylene glycol in an amount of 25% by weight and then milled to prepare a silica particle slurry having particle sizes as shown in Table 1 below.

A film was prepared in the same manner as in Example 1, except that a polyester resin master batch chip was prepared using the prepared particle slurry and that the polyester resin master batch chip was used as a skin layer to produce a film.

The physical properties of the produced film were measured and are shown in Table 2 and FIG.

[Comparative Example 3]

Same as Example 1 except that a particle slurry was prepared by controlling the particle size distribution of the particle slurry as shown in the following Table 1, and a polyester resin master batch chip was prepared using the slurry and a film was prepared using the same as the skin layer Lt; / RTI >

The physical properties of the prepared film were measured and are shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 D ₉₀ (占 퐉) 1.7 1.5 1.7 1.8 - 1.7 Filter size
(탆) 7 7 6 - - 9 Average particle diameter
(탆) 0.64 0.51 0.61 0.66 0.72 0.63 D ₁₀ (占 퐉) 0.13 0.15 0.16 0.13 0.11 0.14 D ₅₀ (占 퐉) 0.36 0.32 0.33 0.38 0.32 0.32 D ₉₀ (占 퐉) 1.7 1.11 1.7 1.72 2.10 1.73 ? (占 퐉) 4.4 3 4.6 4.24 6.28 4.96 Slurry
Pretreatment Classification and filtering Classification and filtering Classification and filtering Classification milling Classification and filtering

In Table 1, D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the particle diameter when the cumulative weight of the particles is 50% based on the total weight , D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight, and? = D ₉₀ - D ₁₀ / D ₅₀ .

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Particle volume in skin layer 300ppm 300ppm 300ppm 300ppm 300ppm 300ppm Particle size in film 45ppm 45ppm 45ppm 45ppn 45ppm 45ppm Particle Visibility Good Good Good Bad Bad Good Haze (%) 0.98 0.97 0.98 1.13 1.25 0.97 Internal Haze (%) 0.28 0.28 0.26 0.39 0.41 0.35 Static friction coefficient / dynamic friction coefficient 0.37 /
0.43 0.35 /
0.41 0.37 /
0.42 0.4 /
0.5 0.41 / 0.55 0.36 /
0.41 Total light transmittance (%) 90.15 90.22 90.19 90.31 89.4 90.20

As shown in Table 2, it was confirmed that the film of the present invention had no aggregated particles observed at the time of evaluation of visibility, had a high transmittance, a low haze, and an internal haze of 0.3% or less. Also, as shown in Fig. 1, it was confirmed that there were no coarse projections.

In the case of Comparative Example 1, as shown in FIG. 2, the surface appearance was similar to that of Example 1 of FIG. 1, but the aggregate particles were found to be defective in the visibility evaluation, and the internal haze evaluation was 0.39% .

In the case of Comparative Example 2, the particles of the particle size distribution shown in Table 1 were produced by milling, and it was confirmed that the particle visibility was poor, the haze was high, and the internal haze exceeded 0.3%.

In the case of Comparative Example 3, when the filter having a size of 9 μm was used, it was confirmed that the internal haze was increased as D90 exceeded 1.7 ± 0.1 μm.

Claims (15)

A core layer comprising a polyester resin; and a skin layer laminated on at least one side of the core layer, the skin layer comprising a polyester resin and particles,
Wherein the total haze of the entire film is 0.3% or less. The method according to claim 1,
Wherein the particle has a particle size distribution ratio? Satisfying the following formula (1).
[Formula 1]
1??? 5
Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight. 3. The method of claim 2,
The particles satisfying the above-mentioned formula (1) are obtained by centrifuging the particle slurry in which the particles are dispersed in a glycol component, classifying the particles so that the D ₉₀ is 1.7 ± 0.1 μm or less, filtering with a filter of 6-8 μm, Multilayer film. 3. The method of claim 2,
Wherein the particles contained in the skin layer have an average particle diameter of 0.5 to 1.0 占 퐉 and a _D90 of 1.7 占 0 占 퐉 or less. The method according to claim 1,
Wherein the content of the particles contained in the skin layer is 0.01 to 0.3% by weight based on the total weight of the film. The method according to claim 1,
The particles may be any one or two or more inorganic particles selected from calcium carbonate, titanium oxide, silica, kaolin and barium sulfate; One selected from silicone resin, crosslinked divinylbenzene polymethacrylate, crosslinked polymethacrylate, crosslinked polystyrene resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin and melamine-formaldehyde resin Or two or more organic particles; And mixtures thereof. The method according to claim 1,
Wherein the particles are added in a polyester resin polymerization step. The method according to claim 1,
The polyester multilayer film has a haze of 0.7 to 1%. The method according to claim 1,
Wherein the polyester multilayer film has a static friction coefficient and a dynamic friction coefficient of 0.5% or less. The method according to claim 1,
The polyester multi-layer film has a total light transmittance of 90% or more. The method according to claim 1,
Wherein the core layer is 70 to 90% by weight of the total film and the skin layer is 10 to 30% by weight. The method according to claim 1,
Wherein the polyester multilayer film further comprises the adhesive primer layer on one or both sides. A window film comprising a polyester multilayer film of any one of claims 1 to 12, further comprising a hard coating layer on one or both sides. a) a composition for a skin layer containing a particle and a polyester resin having a particle size distribution ratio? satisfying the following formula 1, and a composition for a core layer comprising a polyester resin are melted and coextruded to obtain a sheet laminated with a core layer and a skin layer ;
[Formula 1]
1??? 5
Wherein D ₁₀ is the particle diameter when the cumulative weight of the particles is 10% based on the total weight, D ₅₀ is the cumulative weight of the particles (D ₉₀ - D ₁₀ ) / D ₅₀ , Is the particle diameter at 50% based on the total weight, and D ₉₀ is the particle diameter when the cumulative weight is 90% based on the total weight.
b) uniaxially stretching the sheet in the machine direction;
c) applying the water-dispersible coating liquid to the uniaxially stretched film to form the adhesive primer layer;
d) stretching in the width direction; And
e) heat treating and relaxing;
Wherein the total haze of the entire film is 0.3% or less. 15. The method of claim 14,
The composition for the skin layer is prepared by centrifuging the particle slurry in which the particles are dispersed in a glycol component, classifying the dispersion to have a D ₉₀ of 1.7 ± 0.1 μm or less, filtering with a filter of 6-8 μm, And a polyester resin master batch chip produced by adding the particle slurry in the polymerization step of the polyester resin.

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