KR101610822B1 - 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 manufacturing method thereof, and a reflective sheet using the same and, more specifically, to a low-gloss white polyester film reducing gloss of the film by inducing diffused reflection through increasing the surface roughness of the film, forming two films by separating a single film, and controlling the surface gloss, thereby easily obtaining wanted gloss, not only realizing optical properties with excellent hiding power and reflectivity, but also reducing defect visibility and equalizing brightness of surficial light source by controlling lamp stains. The present invention also relates to a method for manufacturing the low-gloss white polyester film, and to 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, It can be made of two films, and the surface gloss can be controlled. Therefore, it is possible to easily obtain the desired glossiness, and it is possible not only to realize optical characteristics excellent in hiding power and reflectivity, The present invention relates to a low-gloss white polyester film capable of uniformly adjusting the brightness of a surface light source, a method of manufacturing the same, and a reflective sheet using the same.

2. Description of the Related Art In general, a liquid crystal display used in an information display device or the like employs a method of irradiating light by providing a surface light source called a backlight on the rear surface of a display in order to secure a high luminance.

Such a backlight not only needs to illuminate the light but also needs to illuminate the entire screen uniformly. An edge-type or direct-bottom type surface light source structure is used as a method for satisfying this. 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 in the conventional reflection plate is a polyester resin which is obtained by mixing a polyolefin resin with a polyester resin and by mixing the polyester resin with a white pigment added thereto and a polyester resin with a white pigment added thereto as disclosed in Korean Patent Application Laid-open Nos. 2004-0021274 and 2009-0071425 And extruded together to form a cavity inside the film.

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, . Accordingly, when a large amount of large particles are loaded, the lip material (the polymer is discharged from the T die through the extruder, the foreign materials are accumulated on the T die outlet over time, and the stripes are formed on the film. There is a problem in that productivity efficiency is reduced due to a reduction in cycle time, and there is a problem that the risk of breakage increases due to the addition of the process.

Therefore, in order to solve the problems of the conventional white polyester film used for the conventional reflection plate, the present inventors have found that the surface layer portion of the polyester resin laminated by the three-layer coextrusion is peeled off instead of the conventional white polyester film production method, And invented a method for producing a low-gloss white polyester film which imparts stable film-forming properties, productivity, and good physical properties to the film.

In addition, if the surface layer of the film produced by the co-extrusion of two or three layers is peeled off to control the glossiness, there is a disadvantage that an additional process is required to discard or recycle the peeled surface layer. The surface layer to be peeled off by changing the film structure can be used as a white film, and the gloss can be controlled.

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 improve the surface roughness of a film to induce diffuse reflection to lower the gloss of the film, It is possible to adjust the surface gloss so that desired glossiness can be easily obtained and optical characteristics with excellent hiding power and reflectivity can be realized, the visibility of defects can be lowered, the brightness of the surface light source can be uniformized And a reflective sheet using the low-gloss white polyester film.

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

The above object is achieved by a three-layer structure film formed by a coextrusion method comprising a support layer and a base layer containing cavities on both sides of the support layer, wherein one of the base layers is peeled off from the support layer. White polyester film.

Here, the raw material composition of the base layer contains 1 to 50 parts by weight of white inorganic particles per 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, And the raw material composition of the support layer comprises a polyester resin.

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 total thickness of the base layer and the support layer of the three-layer structure film is 60 to 500 탆, and the thickness of the support layer is 5% to 20% of the total thickness.

Preferably, the thickness of the base layer is 30 占 퐉 or more.

Preferably, the supporting layer is peeled off at a peeling speed of 2 cm / s to 45 cm / s.

Preferably, the gloss of the surface of the peeled base layer or the surface of the base layer from which the base layer is peeled off is 30% or less.

The object is also achieved by a co-extruded low-gloss white polyester film characterized by comprising a support layer and a base layer peeled from the support layer in a three-layer structure film formed of a base layer containing cavities on both sides of the support layer Lt; / RTI >

Here, the gloss of the surface of the peeled base layer is 30% or less.

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.

Further, the above-described object is achieved by a method for producing a three-layer structure comprising melt-co-extruding a raw material composition containing a polyester resin as a main resin component and molding the same into a sheet having a base layer and a base layer containing cavities formed on both sides of the base 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 polyester film, and a fifth step of peeling off one of the base layers of the base layer of the biaxially stretched white polyester film from the support layer, characterized in that a low gloss white polyester film . ≪ / RTI >

Here, in the fifth step, the one substrate layer is peeled off at a peeling rate of 2 cm / s to 45 cm / s.

Preferably, in the fifth step, the one base layer is peeled off in a roll-to-roll manner.

The above object is also achieved by a reflective sheet characterized by using the aforementioned low-gloss white polyester film.

According to the present invention, a white polyester reflection film having a structure having pores inside a film is produced through a biaxial stretching process of a melt-extruded white polyester sheet, and one layer of a white polyester reflection film produced in a three- There is an advantage that two films can be produced by peeling, and the surface roughness of the film produced by interfacial peeling is increased to induce diffuse reflection, thereby reducing the gloss of the film.

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

Accordingly, the low-gloss white polyester film according to one aspect of the present invention lowers the gloss of the surface to 30% or less owing to its high surface roughness, thereby achieving optical characteristics excellent in hiding power and reflectivity, It is possible to uniformly adjust the brightness of the surface light source by suppressing the lamp unevenness.

Further, the reflective sheet using the low-gloss white polyester film according to one aspect of the present invention lowers the visibility of defects, suppresses lamp blurring, causes a wet-out phenomenon with the light guide plate, or a shattering phenomenon of the light- And the like.

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

1 is a schematic cross-sectional view of a low-gloss white polyester film according to an aspect of the present invention.

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. Also, 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.

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 "

1, which is a schematic cross-sectional view of a low-gloss white polyester film according to an aspect of the present invention, base layers A and C (10 and 30) are formed on both sides of a support layer B 20, It can be confirmed that the surface roughness greatly increases on the surfaces of the base layer A 10 and the support layer B 20 after peeling off.

In the low gloss white polyester film, one layer of the base layer is peeled off from the support layer in a three-layer structure film formed of a base layer and a base layer containing cavities on both sides of the base layer through a coextrusion method.

If the surface layer of the film produced by the co-extrusion of two or three layers is peeled off and the degree of gloss is controlled, an additional step is required to discard or recycle the peeled surface layer. According to the present invention, ), Not only a white film composed of the base layer C (30) and the support layer B (20) but also a base layer A (10) which is a surface layer to be peeled can be used as a white film.

The construction of the low-gloss white polyester film according to one aspect of the present invention will be described in detail through a method for producing a low-gloss white polyester film according to another aspect of the present invention.

A process for producing a low-gloss white polyester film according to another aspect of the present invention includes the following steps.

(1) A three-layer structure in which a raw material composition containing a polyester resin as a main resin component is melt-co-extruded and formed into a sheet having a base layer and a base layer containing cavities formed on both sides of the base layer to produce an unoriented sheet A first step of,

(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 one of the base layers of the biaxially stretched white polyester film from the support layer.

The low-gloss white polyester film produced therefrom is made of two films, a film made of a base layer containing a hollow and a support layer formed on one side of the base layer, and has a high reflectance and a brightness of 30% or less Low.

Hereinafter, a method for producing a film will be described in detail in a stepwise manner.

In the first step, a raw material composition containing a polyester resin as a main resin component is melt-co-extruded to form a three-layer structure, which is formed into a sheet having a middle support layer and a base layer containing cavities formed on both sides of the support layer, Is a step of melt-co-extruding a raw material composition containing a polyester resin as a main resin component to form an unstretched sheet by molding into a sheet having a three-layer structure (base layer / support layer / base layer) .

The raw material composition constituting the substrate layer contains 1 to 50 parts by weight of white inorganic particles per 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 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 Laid-Open No. 61-271308.

The amorphous cyclic olefin copolymer obtained by this method preferably has a glass transition temperature of 120 to 200 캜 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 of the cavity and its number can not be achieved to the 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 50 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 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.

In the three-layer structure film, the total thickness of the base layer and the support layer is 60 to 500 占 퐉, and the thickness of the support layer preferably has a thickness of 5% to 20% of the entire thickness.

Further, if the thickness of the base layer is small, the base layer tends to break at the time of peeling, so that the thickness of the base layer is preferably 30 占 퐉 or more.

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 may contain various additives such as a fluorescent brightening agent, a crosslinking agent, a heat stabilizer, an oxidation stabilizer, an ultraviolet absorber, an organic lubricant, an inorganic fine particle, a filler, 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 for the first step 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, the fifth step is preferably a step of peeling one of the base layers of the produced white polyester film from the support layer, peeling the base layer one roll thicker by roll-to-roll method . 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.

Therefore, if the surface layer of the film produced by the two- or three-layer co-extrusion is peeled off to control the glossiness, there is a disadvantage that an additional step is required to discard or recycle the peeled surface layer. According to the present invention, The layer can also be used as a white film, and the gloss can also be adjusted.

Referring to FIG. 1, it can be seen that the surface roughness of the substrate layer and the support layer is greatly increased by mechanical peeling, and that the degree of gloss of the film can be greatly reduced by increasing the surface roughness and inducing diffuse reflection.

In the fifth step of the present invention, the glossiness can be controlled by adjusting 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 substrate 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, in order to improve the film forming stability in the fifth step of the present invention, the thickness of the base layer needs to be thick enough to withstand the peeling force. The thickness of the support layer at that time is preferably 5 to 20%, more preferably 10 to 15%, of the entire thickness of the support layer. good.

Further, according to another aspect of the present invention, a reflective sheet using the above low gloss white polyester film can be provided.

The center-plane average roughness (Ra) of the low-gloss white polyester film according to one aspect of 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.

Therefore, the reflective sheet using the low-gloss white polyester film according to another aspect of the present invention lowers the visibility of defects and suppresses lamp blurring, and causes a wet-out phenomenon with the light guide plate or a shattering of the light- The phenomenon can be prevented. 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.

Thereafter, co-extrusion was carried out at 280 占 폚 to prepare an A / B / C three-layer structure of base layer / support layer / base layer. The rod was set so that base layer thickness after biaxial orientation was 30 占 퐉 In the comparative example, the thicknesses of the base layer A and the base layer C were the same), and the rod was set so that the thickness of the support layer was 10 mu m so that the total thickness was 70 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 film was cooled to room temperature to obtain a biaxially oriented film. The base layer A was peeled from the support layer B at a rate of 10 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 base layer after biaxially stretching in Example 1 was 50 占 퐉.

[Example 3]

The same procedure as in Example 1 was carried out except that the rod was set so that the substrate layer thickness after biaxial stretching in Example 1 was 80 占 퐉.

[Example 4]

Example 2 was carried out in the same manner as in Example 2 except that the rod was set such that the thickness of the support layer after biaxial stretching was 15 占 퐉.

[Example 5]

Example 2 was carried out in the same manner as in Example 2 except that the rod was set so that the support layer thickness after biaxial stretching was 20 占 퐉.

[Example 6]

The same procedure as in Example 2 was carried out except that the rod was set such that the rate of peeling the base layer from the support layer after biaxial stretching in Example 2 was 5 cm / s.

[Example 7]

The procedure was carried out in the same manner as in Example 2, except that the load was set so that the rate of peeling the substrate layer from the support layer after biaxial stretching in Example 2 was 20 cm / s.

[Comparative Example 1]

The same procedure was followed as in Example 1 except that the rod was set so that the thickness of the substrate layer after biaxial stretching in Example 1 was 10 占 퐉.

[Comparative Example 2]

The procedure of Example 1 was repeated except that the rod was set so that the thickness of the substrate layer after biaxial stretching in Example 1 was 15 占 퐉.

[Comparative Example 3]

The same procedure as in Example 1 was carried out except that the rod was set so that the thickness of the base layer after biaxial stretching in Example 1 was 20 占 퐉.

[Comparative Example 4]

The same procedure as in Example 1 was carried out except that the rod was set so that the substrate layer thickness after biaxial stretching in Example 1 was 200 占 퐉.

[Comparative Example 5]

Example 2 was carried out in the same manner as in Example 2 except that the rod was set so that the thickness of the support layer after biaxial stretching was 5 占 퐉.

[Comparative Example 6]

The same procedure as in Example 2 was carried out except that the release rate of the support layer in Example 2 was set to 1 cm / s.

[Comparative Example 7]

The same procedure as in Example 2 was carried out except that the release rate of the support layer in Example 2 was 50 cm / s.

The properties of the polyester films according to Examples 1 to 8 and Comparative Examples 1 to 7 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 7 and Comparative Examples 1 to 7 were evaluated on the basis of S K7105 (1981 edition) by JI using a Sugar Shikenki Digital Polarized Gloss System (UGV-4D) The glossiness of the base layer surface peeled off from the support layer and the glossiness of the support layer surface from which the base layer was peeled off were measured with an incident angle and a light receiving angle of 60 degrees. 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

The biaxially stretched polyester films prepared in Examples 1 to 7 and Comparative Examples 1 to 7 were judged as "Good" when film formation was possible stably for 30 minutes or more, and fracture occurred within 30 minutes, Quot; was judged to be "x ".

A Thickness (탆) B Thickness (탆) C Thickness (탆) Peeling speed
(cm / s) Film forming property Glossiness
(Base layer side) Glossiness
(Supporting layer side) Example 1 30 10 30 10 ○ 8.1 13.1 Example 2 50 10 50 10 ○ 7.8 12.8 Example 3 80 10 80 10 ○ 7.8 12.8 Example 4 50 15 50 10 ○ 8.1 13.1 Example 5 50 20 50 10 ○ 8 13 Example 6 50 10 50 5 ○ 19 24 Example 7 50 10 50 20 ○ 5 10 Comparative Example 1 10 10 10 10 × 8.2 13.2 Comparative Example 2 15 10 15 10 × 7.8 12.8 Comparative Example 3 20 10 20 10 × 7.9 12.9 Comparative Example 4 200 10 200 10 × 8.1 13.1 Comparative Example 5 50 5 50 10 × 8 13 Comparative Example 6 50 10 50 One ○ 27 32 Comparative Example 7 50 10 50 50 × - -

As can be seen from the above Table 1, it can be confirmed that the polyester films prepared in Examples 1 to 7 according to the present invention can obtain good results in terms of gloss, reliability and film-forming stability.

First, Comparative Example 1, Comparative Example 2, and Comparative Example 3 had thinner substrate layers than Comparative Example 1 in terms of film-forming stability, resulting in breakage during peeling, resulting in poor film forming stability. In Comparative Example 4, , The difference in thickness between the base layer and the support layer was large, so that the support layer B and the base layer C were peeled off at the time of peeling. In Comparative Example 5, the base layer was thinner than the base layer in Example 2, but the support layer was thin as 5 탆, so that the support layer peeled or torn from the base layer C during peeling. Compared with Example 2, Comparative Example 6 had a low peeling rate of 1 cm / s and had a disadvantage in that the film formation stability was not affected, but the process speed was too slow. In Comparative Example 7, the peeling speed was too fast at 50 cm / s as compared with Example 2, so that breakage occurred, which was disadvantageous to the film forming stability.

Next, the influence of the thickness of the support layer on the glossiness of the film was examined. In Examples 4 and 5, the thickness and the peeling rate of the base layer were the same as in Example 2, but the thicknesses of the support layers were thicker, 15 and 20 占 퐉, respectively. However, the gloss of the substrate layer after peeling did not change, and the thickness of the support layer did not affect the glossiness. Comparing Examples 1, 2 and 3 in order to see the effect of the thickness of the base layer on the glossiness of the film, the thickness of the base layer and the peeling speed are constant, but the thickness of the base layer is different. However, it can be seen that there is little or no change in the gloss according to the thickness change of the base layer, and the thickness of the base layer has little or no effect on the gloss of the base layer.

Finally, in terms of the influence of the peeling speed on the base layer on the glossiness, the peeling speeds of Comparative Examples 6, 6, and 7 are slower or faster than those of Example 2, respectively, at 1, 5, and 20 cm / s . The glossiness after peeling showed higher glossiness as the peeling speed was higher and glossiness was lower as the peeling speed was faster. Using these results, it was found that the glossiness after peeling can be adjusted by the peeling speed of the base layer .

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: substrate layer A
20: support layer B
30: base layer C

Claims (17)

delete delete delete delete delete delete delete delete delete delete delete delete delete A first step of forming an unstretched sheet by molding into a three-layer structure obtained by melt-co-extruding a raw material composition containing a polyester resin, the sheet being formed into a sheet having a base layer and a substrate layer containing a cavity on both sides of the base layer;
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 one of the base layers of the base layer of the biaxially stretched white polyester film from the support layer. 15. The method of claim 14,
Wherein the one base layer is peeled off at a peeling rate of 2 cm / s to 45 cm / s in the fifth step. 15. The method of claim 14,
And the fifth step comprises peeling the one base layer in a roll-to-roll manner. delete

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