KR101561288B1 - Low gloss white polyester film, method of manufacturing the same and reflective sheet thereof - Google Patents

Abstract

The present invention relates to a low-gloss white polyester film, a method for producing the same, and a reflective sheet using the same. More specifically, the present invention relates to a low-gloss white polyester film, In addition, it is possible to easily obtain the desired gloss through the use thereof, to realize optical characteristics excellent in hiding power and reflectivity, to reduce the visibility of defects, to suppress the lamp blur, and to uniformly adjust the brightness of the surface light source. Film, a method of producing the same, and a reflective sheet using the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a low gloss white polyester film, a method of manufacturing the same, and a reflective sheet using the low gloss white polyester film,

The present invention relates to a low-gloss white polyester film, a method for producing the same, and a reflective sheet using the same. More specifically, the present invention relates to a low-gloss white polyester film, In addition, it is possible to easily obtain the desired gloss through the use thereof, to realize optical characteristics excellent in hiding power and reflectivity, to reduce the visibility of defects, to suppress the lamp blur, and to uniformly adjust the brightness of the surface light source. Film, a method of producing the same, and a reflective sheet using the same.

BACKGROUND ART A liquid crystal display used in an information display device or the like employs a method in which a surface light source called a backlight is provided on the rear surface of a display to ensure high brightness and to irradiate light.

Such a backlight not only needs to illuminate the light but also needs to illuminate the entire screen uniformly. As a method for satisfying this, there is a planar light source structure called edge type and direct type. In the edge type, the light source is located at the corner of the display and directs the light to the front side using the light guide plate, whereas in the direct type, it is located at the rear side of the display and directly irradiates light to the front side.

The white polyester film used for the conventional reflection plate for such a purpose is prepared by mixing a polyolefin resin with a polyester resin and mixing the white pigment-added poly It is common to form a cavity inside the film by extrusion together with an ester resin.

However, in the case of a white polyester film in which pores are formed in a film known in the prior art and a white pigment is added, since the surface roughness of the film is low, particles having a large particle size may be added, . Therefore, in the case of the prior art, there is a problem that the efficiency of the production is reduced due to the reduction of the cycle of the lip cleaning due to the addition of large particles, and the risk of breakage due to the addition of the process is increased.

The present inventors have made efforts to overcome the problems of the white polyester film used in the conventional reflection plate. As a result, the present inventors have found that the surface layer portion of the polyester resin laminated by two or three layer co- To reduce the gloss and to produce a low-gloss white polyester film having stable film-forming properties, productivity, and good physical properties of the film.

Korean Patent Publication No. 2004-0021274 Korean Patent Publication No. 2009-0071425

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method and apparatus for improving film surface roughness by inducing diffuse reflection, A low gloss white polyester film which can easily obtain the optical characteristics of the surface light source and can realize optical characteristics excellent in hiding power and reflectance as well as lowering the visibility of defects and suppressing lamp blurring and uniformly adjusting the brightness of the surface light source, And a reflective sheet using the same.

These and other objects and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof.

The object is achieved by a low-gloss white polyester film characterized by being produced by coextrusion, a base layer containing a cavity, and a support layer formed on at least one side of the base layer, Lt; / RTI >

Here, the raw material composition of the base layer includes 1 to 50 parts by weight of white inorganic particles relative to 100 parts by weight of a resin composition comprising a mixture of a polyester resin and an amorphous cyclic olefin copolymer which is an incompatible resin for the polyester .

Preferably, the resin composition comprises 65 to 95% by weight of the polyester resin and 5 to 35% by weight of the amorphous cyclic olefin copolymer.

Preferably, the amorphous cyclic olefin copolymer has a glass transition temperature of 120 to 200 ° C.

Preferably, the amorphous cyclic olefin copolymer has an average particle diameter of 0.5 to 5.0 mu m.

Preferably, the white inorganic particles are selected from barium sulfate particles or titanium dioxide particles, or a combination thereof, and have an average particle diameter of 0.1 to 3.0 占 퐉.

Preferably, the gloss of the base layer is 30% or less.

Preferably, the total thickness of the base layer and the support layer is 50 to 500 占 퐉, and the thickness of the support layer is 4% to 50% of the total thickness.

Preferably, the thickness of the support layer is 4% to 20% of the total thickness.

Preferably, the substrate layer is peeled off from the substrate layer to degrade the gloss of the substrate layer.

More preferably, the release rate of the support layer is 2 cm / s to 45 cm / s.

The above-mentioned object is achieved by a method for producing a laminated sheet, which comprises melt-co-extruding a raw material composition containing a polyester resin as a main component of a resin to form a sheet having at least two layers of a base material layer containing a cavity and a support layer formed on at least one surface of the base material layer A second step of cooling the unstretched sheet in a casting drum, a third step of uniaxially stretching the cooled sheet, a step of biaxially stretching the uniaxially stretched film A fourth step of producing a white polyester film by post-heat treatment, and a fifth step of peeling off the support layer of the biaxially stretched white polyester film by a process for producing a low-gloss white polyester film .

Here, the fifth step is a step of peeling the support layer from the base layer by a roll-to-roll method.

Preferably, the releasing rate of the supporting layer is 2 cm / s to 45 cm / s.

Preferably, the fifth step is a step of removing the supporting layer from the base layer by a roll-to-roll method.

Preferably, the low-gloss white polyester film composed of the base layer has an average center-line roughness (Ra) of 1 to 50 占 퐉.

The object is achieved by a process for producing a low-gloss white polyester comprising a substrate layer containing a hollow through a co-extrusion process and a substrate layer formed on at least one side of the substrate layer, And a film is used.

Here, the gloss of the low-gloss white polyester film is deteriorated by peeling the support layer from the base layer.

According to the present invention, a white polyester reflecting film having a structure having pores inside a film is produced through a biaxial stretching process of a melt-extruded white polyester sheet, and the white polyester reflecting film supporting layer is peeled off, To induce diffuse reflection, thereby lowering the gloss of the film.

Further, the surface gloss can be controlled by controlling the peeling speed of the support layer, and the desired glossiness can be obtained easily.

Thus, the low-gloss white polyester film according to the present invention can lower the gloss of the surface to 30% or less due to high surface roughness, thereby realizing optical characteristics excellent in hiding power and reflectivity, And the brightness of the surface light source can be uniformly adjusted.

In addition, the reflective sheet using the low-gloss white polyester film of the present invention can reduce the visibility of defects, suppress the lamp blur, prevent wettability with the light guide plate, or prevent the reflection of the light guide plate or the reflective sheet due to friction And so on.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the surface of a substrate layer after mechanically peeling a support layer of a low-gloss white polyester film according to the present invention. Fig.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

Unless otherwise stated, all percentages, parts, and percentages are by weight. It will also be understood that when an amount, concentration, or other value or parameter is given in any one of a range, a preferred range, or a list of preferred upper limits and preferred lower limits, it is understood that any upper limit range, It should be understood that specifically all ranges formed from any pair of range limits or desirable values are to be understood. Where a range of numerical values is referred to in this specification, unless otherwise stated, the range is intended to include all the integers and fractions within the endpoint and its range. The scope of the present invention is not intended to be limited to the specific values that are mentioned when defining the scope.

When the term "about" is used to describe the endpoint of a value or range, it is to be understood that the present disclosure encompasses the particular value or endpoint mentioned.

As used herein, the terms "comprise," "include," "including," "including," "containing," " Having ", " having ", " having ", or any other variation thereof, are intended to cover an inclusion not exclusive. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to such elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus It is possible. Also, unless explicitly stated to the contrary, "or" does not mean " comprehensive " or " exclusive "

Where an applicant defines an invention or portion thereof in an open term such as "comprising ", it should be readily understood that the description should be interpreted as describing the invention using the term" consisting essentially & do.

A method of producing a low-gloss white polyester film according to the present invention will be described with reference to Fig. 1, which is a schematic cross-sectional view showing the surface of a substrate layer after mechanically peeling off the support layer of the low-gloss white polyester film according to the present invention.

(1) A raw material composition containing a polyester resin as a main resin component is melt-co-extruded to form at least two layers of a base material layer containing a cavity and a base material layer formed on at least one surface of the base material layer, A first step of manufacturing a new sheet,

(2) a second step of cooling the unstretched sheet in a casting drum,

(3) a third step of uniaxially stretching the cooled sheet,

(4) a fourth step of biaxially stretching the monoaxially stretched film and then heat-treating the monoaxially stretched film to produce a white polyester film;

(5) a fifth step of peeling off the support layer of the biaxially stretched white polyester film.

The low-gloss white polyester film produced therefrom is characterized by having a substrate layer containing a hollow in the center and a supporting layer formed on at least one side of the substrate layer. The film has a high reflectivity and a low gloss of 30% or less.

Hereinafter, the method of producing the white polyester film of the present invention will be described in detail.

In the first step of the production method of the present invention, a raw material composition containing a polyester resin as a main resin component is melt-co-extruded to form at least two layers, and a base layer containing a cavity and a support layer Is formed by melt-co-extruding a raw material composition containing a polyester resin as a main resin component to form a sheet having at least two layers (base layer / support layer) And a step of producing an unstretched sheet.

A raw material composition for a substrate layer contains 1 to 50 parts by weight of white inorganic particles relative to 100 parts by weight of a resin composition comprising a mixture of a polyester resin and an amorphous cyclic olefin copolymer which is an incompatible resin for the polyester.

At this time, it is preferable that the polyester resin used as the base resin of the polyester film is composed of a dicarboxylic acid component and a diol component and has a basic constitution of polyethylene terephthalate with high film-forming stability and low cost.

As the dicarboxylic acid component, it is preferable to use terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid and sebacic acid. Can be selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like.

In the material composition constituting the substrate layer, the polyester resin is preferably contained in an amount of 65 to 95% by weight, more preferably 70 to 90% by weight. At this time, if the content of the polyester resin is out of the above range, it can not be formed into a film containing a large number of cavities.

When polyethylene terephthalate is used as the base resin, it is preferably 1 to 15 mol%, more preferably 3 to 14 mol%, and most preferably 5 to 13 mol%, based on the total dicarboxylic acid component, By mole of a copolymerizable polyester component containing a copolymerization component of 1 to 15% by mole, more preferably 3 to 14% by mole, and most preferably 5 to 13% by mole, based on the total diol component May be used. At this time, if it is less than 1 mol%, it is difficult to form a film containing a large number of cavities, whereas when it exceeds 15 mol%, film formation is also difficult.

The dicarboxylic acid component may be selected from the group consisting of isophthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid and sebacic acid. have. The diol component may be selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like. Among these copolymerization components, it is preferable to use isophthalic acid or 2,6-naphthalenedicarboxylic acid in order to obtain good film formability, and 1,4-cyclohexanedicarboxylic acid having an effect of stabilizing the dispersion state of the non- Methanol is preferably used.

In the resin composition of the raw material composition constituting the base layer of the first step, an amorphous cyclic olefin copolymer is used as the incompatible resin for the polyester resin. At this time, as the amorphous cyclic olefin copolymer used in the present invention, bicyclo [2,2,1] hept-2-ene, 6-methylbicyclo [2,2,1] hept- - dimethylbicyclo [2,2,1] hept-2-ene, 1-methylbicyclo [2,2,1] hepto-2-ene, 6-ethylbicyclo [2,2,1] - ene, 6-n-butylbicyclo [2,2,1] hepto-2-ene, 6-i-butylbicyclo [2,2,1] hept- , 2,1] hept-2-ene, tricyclo [4,3,0,12.5] -3-decene, 2-methyl-tricyclo [ - tricyclo [4,3,0,12.5] -3-decene, tricyclo [4,4,0,12.5] -3-decene, 10-methyl-tricyclo [4,4,0,12.5] Or a crystalline polyolefin resin such as ethylene, propylene, butene or methylpentene copolymerized with the amorphous cyclic olefin resin may be used.

The incompatible resin in the polyester resins listed above may be a polymer composed of a single component, a copolymer composed of more than this component, or a mixture of two or more kinds of these components. Particularly, a resin having a large difference in critical surface tension from the polyester resin and hardly being deformed by heat treatment after stretching is preferable, and a copolymer of ethylene and bicycloalkene is most preferable.

The content of the amorphous cyclic olefin copolymer in the resin composition is preferably 5 to 35% by weight, more preferably 10 to 30% by weight based on the total weight of the resin composition. At this time, if the content is less than 5% by weight, the effect of whitening is weak and high reflectivity can not be realized. On the other hand, if it exceeds 35% by weight, the mechanical properties such as the strength of the film itself are lowered and the amorphous cyclic olefin copolymer tends to aggregate.

At this time, the amorphous cyclic olefin copolymer to be used is obtained by separating from the polyester composition and using a differential scanning calorimeter and measuring the transition temperature according to JIS K7121-1987 measurement method, .

In an embodiment of the present invention, a copolymer resin between ethylene and norbornene is used as an amorphous cyclic olefin copolymer which is an incompatible resin for a polyester resin as a most preferable example. The copolymer resin between ethylene and norbornene can be prepared by the liquid phase polymerization method exemplified in the well-known Japanese Patent Application Laid-Open No. 61-271308.

The amorphous cyclic olefin copolymer of the present invention obtained by the above method preferably satisfies a glass transition temperature of 120 to 200 ° C or less. If the glass transition temperature is less than 120 占 폚, when the film is stretched, the cyclic olefin copolymer is plastically deformed to inhibit the formation of voids. On the other hand, when the glass transition temperature exceeds 200 캜, when the polyester resin and the amorphous cyclic olefin copolymer are melt-kneaded using an extruder or the like and discharged into a sheet, the dispersion of the amorphous cyclic olefin copolymer becomes insufficient The shape and number of the cavities can not be attained to a desired level.

Therefore, the glass transition temperature of the amorphous cyclic olefin copolymer used in the base material composition of the first step of the present invention is more preferably 135 to 185 캜, and most preferably 140 to 150 캜. At this time, the glass transition temperature can be adjusted by changing the copolymerization ratio of the cyclic olefin and the non-cyclic olefin in the amorphous cyclic olefin copolymer. The glass transition temperature is measured by using a differential scanning calorimeter at a rate of temperature increase of 20 ° C / It is determined as the midpoint of JIS K7121-1987 when the temperature is raised.

The amorphous cyclic olefin copolymer preferably has an average particle diameter of 0.5 to 5.0 μm or less. When the particle diameter is less than 0.5 탆, it is difficult to form a void at the time of stretching. When the particle diameter exceeds 5.0 탆, the film tends to be torn at the time of stretching, which deteriorates film formability.

The white inorganic particles used in the raw material composition of the base layer of the first step of the present invention preferably contain 1 to 40 parts by weight per 100 parts by weight of the resin composition.

At this time, particles having an average particle diameter (particle diameter) of 0.1 to 3.0 占 퐉, more preferably 0.2 to 2.0 占 퐉, and most preferably 0.3 to 1.0 占 퐉 are used in order to obtain good dispersibility and film-forming stability.

The preferred inorganic particles to be used are selected from barium sulfate particles or titanium dioxide particles, alone or in combination thereof, and are contained within the above content range.

In the present invention, the average particle diameter (particle diameter) means the number average particle diameter, and the particle diameters are arbitrarily determined for each particle before being added to the resin (film) at a magnification of 10,000 times by a scanning electron microscope, Determine the size. In this case, when the particle is not spherical, it is approximated to the closest ellipse, and the ellipse (long diameter + short diameter) / 2 is determined. Here, particles smaller than 0.01 탆 in diameter and particles of 10 탆 or larger in diameter are excluded do.

The content of the white inorganic particles used in the present invention is 1 to 50 parts by weight, more preferably 2 to 30 parts by weight, and most preferably 3 to 20 parts by weight based on 100 parts by weight of the resin composition. If the amount is less than 1 part by weight, scattering light due to the inorganic particles is insufficient and sufficient light reflectivity can not be obtained. When the amount is more than 50 parts by weight, the film forming stability remarkably decreases.

Further, the total thickness of the substrate layer and the support layer is preferably 50 to 500 占 퐉, and the thickness of the support layer is preferably 4% to 50% of the total thickness, preferably 4% to 20% in terms of reduction of the raw material.

The method of blending barium sulfate particles or titanium dioxide particles, which are inorganic particles, into the polyester composition can be carried out by using the following known methods (a) to (d).

Concretely, the method (A) is a method in which particles are added before the transesterification reaction or the end of the esterification reaction in the synthesis of the polyester, or the addition of the particles before the initiation of the polycondensation reaction. When added at the time of synthesis, the titanium dioxide particles are preferably prepared as a slurry dispersed in glycol, and then added to the reaction system.

The method (B) is a method in which particles are added to a polyester and melt-kneaded, and the method (C) is a method of producing a master pellet in which a large amount of particles are added in the method And then kneading these and a polyester not containing an additive to make a predetermined amount of the additive. In addition, the method (D) can be carried out by directly using the master pellet (C).

At this time, in the embodiment of the present invention, it is preferable that the mixing method of the barium sulfate particles or the titanium dioxide particles is performed by the method (c) or (d) in consideration of the dispersibility of the particles.

The base material composition of the present invention may contain various additives such as fluorescent whitening agents, crosslinking agents, heat stabilizers, oxidation stabilizers, ultraviolet absorbers, organic lubricants, inorganic fine particles, A filler, an anti-light agent, an antistatic agent, a nucleating agent, a dye, a dispersing agent, a coupling agent and the like may be added.

Next, the support material composition of the first step of the present invention may be a polyester resin such as a base layer, and may or may not contain inorganic particles and organic particles.

The first step is completed by extruding the raw material composition from the die and producing an unstretched sheet molded into a sheet form.

In the manufacturing method of the present invention, the second step is to cool the unstretched sheet produced in the first step in the casting drum.

In the production method of the present invention, the third step is to uniaxially stretch the cooled sheet to prepare a uniaxially stretched film. The unstretched sheet is heated by a heating means such as a roll heating or an infrared heating (heater), and is first stretched in the longitudinal direction to obtain a monoaxially stretched film. This stretching is preferably carried out using the main speed difference of two or more rolls, and the stretching temperature is preferably set to a temperature equal to or higher than the glass transition temperature (Tg) of the polyester resin, and the stretching magnification is preferably 2.5 to 4.0 times.

In the manufacturing method of the present invention, the fourth step is a step of biaxially stretching the monoaxially stretched film and then heat-treating the monoaxially stretched film to produce a white polyester film. In the third step, the uniaxially stretched film is continuously stretched in the longitudinal direction (Hereinafter, also referred to as "width direction"). At this time, the stretching in the transverse direction is carried out while raising the temperature to 5 to 70 ° C higher than the glass transition temperature (Tg), starting from a temperature higher than the glass transition temperature (Tg) of the polyester resin. The temperature rise in the widthwise stretching process may be continuous or may be stepwise (sequential), but the temperature is usually increased sequentially. For example, the width direction stretching zone of the tenter is divided into a plurality of portions along the film running direction, and the temperature is raised by flowing a heating medium at a predetermined temperature for each zone. At this time, the magnification of stretching in the width direction is set to 2.5 to 4.5 times. Thereafter, the film is subjected to heat treatment such as heat fixation or heat relaxation in a sequential manner to produce a biaxially oriented white polyester film.

Further, in order to complete the crystal orientation of the obtained biaxially stretched film and to impart planarity and dimensional stability, the film is then subjected to heat treatment at 120 to 240 캜 for 1 to 30 seconds in a tenter, uniformly cooled to room temperature Followed by winding to obtain the porous polyester film of the present invention. At this time, during the heat treatment step, a relaxation treatment of 3 to 12% in the width direction or the longitudinal direction may be carried out if necessary.

In the manufacturing method of the present invention, it is preferable that the fifth step is a step of separating the support layer of the white polyester film produced, and the sheath is peeled off by the roll-to-roll method with the thickness of the support layer. In order to peel off the base layer easily, it is preferable to attach an adhesive tape to the roll or to apply the adhesive to the surface of the white polyester film to facilitate the initial peeling. 1, it can be seen that the surface roughness of the substrate layer is greatly increased by mechanical peeling, and that the degree of gloss of the film can be greatly reduced by raising the surface roughness to induce diffuse reflection.

Therefore, the glossiness can be controlled in the fifth step of the present invention, which can be achieved by controlling the peeling speed. Although the degree of gloss varies depending on the combination of the base material and the support layer, it is possible to adjust the glossiness only by the peeling speed when the composition is fixed. The peeling speed of the support layer is preferably 2 cm / s to 45 cm / s. If the peeling speed is less than 2 cm / s, there is no problem in the film forming property but the process speed is too slow. If the peeling speed is more than 45 cm / s, the peeling speed becomes too fast and breakage occurs.

Further, the present invention provides a reflective sheet using a low-gloss white polyester film produced from the above-mentioned production method.

The center-plane average roughness (Ra) of the low-gloss white polyester film according to the present invention satisfies 1 탆 or more, and more preferably 1 to 50 탆. Further, by lowering the gloss (%) of the film surface to 30% or less, optical characteristics excellent in hiding power and reflectance can be realized.

Thus, the reflective sheet using the low-gloss white polyester film of the present invention can reduce the visibility of defects, suppress the lamp blur, prevent wettability with the light guide plate, or prevent the reflection of the light guide plate or the reflective sheet due to friction have. Therefore, it can be effectively used for a backlight device for image display, a reflective sheet for a lamp reflector, a reflective sheet for an illumination device, a reflective sheet for an illuminated signboard, and a backside reflector sheet for a solar cell.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Example 1]

10 parts by weight of a copolymer resin of ethylene and norbornene as an amorphous cyclic olefin copolymer, and 20 parts by weight of inorganic particles having an average particle diameter of 1 mu m as an emulsion resin for a polyester resin with respect to 100 parts by weight of a polyester resin And 5 parts by weight of silica particles having a diameter of 4.5 탆 were added to 100 parts by weight of the polyester resin as the supporting layer constitution.

Then, co-extruded at 280 占 폚 to obtain a three-layer structure of A / B / A of the support layer / substrate layer / support layer, the rod was set so that the substrate layer thickness after biaxial orientation was 250 占 퐉, Mu m. At this time, the resin composition is composed of 90% by weight of a polyester resin and 10% by weight of a copolymer resin of ethylene and norbornene, and the additive such as an emergency polyolefin resin or inorganic particles is preliminarily mixed with a polyester resin It was used in the form of pellets. The particle size of the emergency polyolefin resin in the master pellet was 1 to 3 占 퐉.

The thus-introduced raw material was discharged from a T-die of an extruder to form a sheet. The sheet thus formed was cooled and solidified in a casting drum having a surface temperature of 20 DEG C to obtain an unstretched film. Subsequently, both ends of the uniaxially stretched film were led to a tenter while being held by a clip, and stretched in a direction perpendicular to the length (width direction) at a magnification of 3.7 in a heated atmosphere.

Thereafter, heat fixation was performed in the tenter, and the solution was cooled to room temperature to obtain a biaxially oriented film, and the support layer was peeled at a rate of 5 cm / s.

[Example 2]

The same procedure as in Example 1 was carried out except that the rod was set so that the thickness of the support layer after biaxial stretching in Example 1 was 30 占 퐉.

[Example 3]

The same procedure as in Example 2 was carried out except that the release rate of the support layer in Example 2 was 10 cm / s.

[Example 4]

The procedure of Example 3 was repeated, except that the release rate of the support layer in Example 2 was 20 cm / s.

[Example 5]

Example 3 was carried out in the same manner as in Example 3 except that the rod was set such that the thickness of the support layer after biaxial stretching was 100 占 퐉.

[Comparative Example 1]

Example 3 was carried out in the same manner as in Example 3, except that the rod was set such that the thickness of the support layer after biaxial stretching was 5 占 퐉.

[Comparative Example 2]

The same procedure as in Example 3 was carried out except that the release rate of the support layer in Example 3 was set to 1 cm / s.

[Comparative Example 3]

The procedure of Example 3 was repeated, except that the release rate of the support layer in Example 3 was 50 cm / s.

Using the polyester films according to Examples 1 to 5 and Comparative Examples 1 to 3, physical properties were measured through the following experimental examples, and the results are shown in Table 1 below.

[Experimental Example]

1. Gloss (60 ° measurement)

The biaxially stretched polyester films prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured on a basis of S K7105 (1981 edition) by JI using a Sugar Shikenki Digital Polarized Gloss System (UGV-4D) The degree of gloss was measured by adjusting the incident angle and the light receiving angle to 60 °. At this time, three samples of each reflection sheet were measured, and the average value thereof was calculated by the glossiness (60 DEG) of the reflection film.

2. Evaluation of Film Stability

If it is possible to stably form a film for one hour or more with respect to the films prepared in Examples 1 to 5 and Comparative Examples 1 to 3, it is judged as "o ", and if breakage occurs within one hour, X ".

Support layer thickness (탆) Support layer separation speed (cm / s) 60 ° gloss (%) Film forming property Example 1 20 5 20 ○ Example 2 30 5 19 ○ Example 3 30 10 8 ○ Example 4 30 20 5 ○ Example 5 100 10 8 ○ Comparative Example 1 5 10 - X Comparative Example 2 30 One 28 ○ Comparative Example 3 30 50 - X

As can be seen from the above Table 1, the polyester films prepared in Examples 1 to 5 of the present invention showed good results in terms of gloss, reliability, and film-forming stability.

First, when the stability of the film formation was analyzed, in Comparative Example 1, the peeling thickness (support layer thickness) was thin compared to Example 3, so that the peeling occurred during peeling, resulting in a problem of film forming stability. In Comparative Example 2, 1 cm / s, there is no problem in the film forming property but the process speed is too slow. In Comparative Example 3, the peeling speed was too fast as compared with Example 4 to cause breakage, which was disadvantageous to the film forming stability.

Next, the effect of the thickness of the support layer on the glossiness of the film was similar to that of Example 1 and Example 2, but the thickness of Example 2 was thicker and the gloss was 1% lower. However, when comparing Example 3 with Example 5, the peel rate was equal to 10 cm / s, but the gloss was the same despite the thicker thickness of Example 5. Thus, it was found that the thickness of the support layer had little or no effect on the glossiness.

Finally, the influence of the removal rate of the support layer on the glossiness is as follows. In Examples 2 to 4, the thickness of the support layer is the same, but the peeling speed is increased. As a result, 60 ㅀ gloss decreased from 19% to 5% as the peeling speed increased, and it can be seen that the gloss can be controlled by adjusting the peeling speed.

It is to be understood that the present invention is not limited to the above embodiments and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

10: Support layer
20: substrate layer

Claims (18)

delete delete delete delete delete delete delete delete delete delete delete A method for producing an unstretched sheet by melt co-extruding a raw material composition containing a polyester resin to form a sheet having at least two layers of a base material layer containing a cavity and a support layer formed on at least one surface of the base material layer, Step 1,
A second step of cooling the unstretched sheet in a casting drum,
A third step of uniaxially stretching the cooled sheet;
A fourth step of biaxially stretching the uniaxially stretched film and then heat-treating the uniaxially stretched film to produce a white polyester film;
And a fifth step of peeling off the support layer of the biaxially stretched white polyester film. 13. The method of claim 12,
Wherein the fifth step is a step of peeling the support layer from the base layer in a roll-to-roll manner. 13. The method of claim 12,
And the peeling speed of the support layer is 2 cm / s to 45 cm / s. delete 15. The method according to any one of claims 12 to 14,
(Ra) of the low-gloss white polyester film composed of the base layer is 1 to 50 占 퐉. delete delete

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