KR102004088B1 - White polyester reflective film and reflective sheet using the same and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a white polyester reflective film used for a backlight unit of a light emitting diode (LED) light source including a light guide plate in a liquid crystal display, which is capable of preventing an inorganic particle from going out and protruding to a surface, a reflective sheet using the same, and a manufacturing method thereof. According to the present invention, the white polyester reflective film comprises a reflective layer and a surface layer which is formed on at least one surface of the reflective layer and is made of a resin composition containing an inorganic particle. The surface layer includes a protrusion formed by the inorganic particle and a resin coating layer not containing the particle is formed on at least one side of the surface layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester reflective film and a reflective sheet using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester reflective film and a reflective sheet using the same, and more particularly, to a white polyester reflective film used in a backlight unit for an LED light source having a light guide plate in a liquid crystal display, Sheet and a method for producing the same.

BACKGROUND ART Conventionally, a white polyester film for use as a reflector in a back light unit for an LED light source having a light guide plate has been disclosed in Korean Patent Laid-Open Publication No. 2015-0058336, in which organic particles whose shape is non- As disclosed in Japanese Patent Publication No. 2012-0014916, organic particles or inorganic particles contained in a reflector are co-extruded to form a surface roughness, thereby suppressing scratches that may be caused by friction between the light guide plate and the reflector.

However, when the particles are coated on the film as in the above-described known techniques, particles tend to fall off from the surface of the reflective film as the particle size increases. Also, when the particle adhesion is increased by increasing the thickness of the resin coating layer, A problem that curling easily occurs occurs.

In addition, when the organic particles are co-extruded, the particles tend to fall off because the organic particles form pores on the surface of the film. When the inorganic particles are co-extruded, the particles fall off from the surface of the reflective film or protrude from the surface of the film, There is a problem that scratches are generated on the surface of the light guide plate. Also, if the surface roughness is not sufficiently formed, the light guide plate and the reflective film are in contact with each other. There is a problem that a phenomenon of being visually recognized as a white spot occurs due to a phenomenon of out-of-focus (WET-OUT).

Korean Patent Laid-Open Publication No. 2015-0058336 Korean Patent Publication No. 2012-0014916

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflective film which prevents inorganic particles from falling off and protruding from a surface thereof, And a reflective sheet using the same, and a process for producing 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 white laminated polyester film having a reflective layer and a surface layer composed of a resin composition containing at least one surface of the reflective layer and containing inorganic particles, wherein the surface layer has projections formed by inorganic particles, Wherein the surface layer has a 10-point average roughness (z) formed by the inorganic particles of 1 to 3 占 퐉, the resin coating layer has a thickness of 100 to 500 nm, and the surface layer The 10-point average roughness (z) and the thickness (t) of the resin coating layer satisfy the following formula (1)

(1)

z / 30? t? z / 6

And a white polyester reflective film.

Here, the thickness of the resin coating layer may be 100 to 190 nm.

Preferably, the inorganic particles may be at least one of silica, barium sulfate, calcium carbonate, and titanium dioxide.

Preferably, the resin coating layer may be a thermosetting resin binder coated with a coating liquid containing an acrylate type, a polyester type, an epoxy type, a melamine type, a urethane type or a urethane acrylate type resin.

Preferably, the resin coating layer may contain 1 to 50 parts by weight of amphiphilic fibers per 100 parts by weight of the thermosetting resin binder.

Preferably, the white polyester reflective film may be one used for a backlight unit having a light guide plate.

The above object is also achieved by a reflective sheet characterized by using the white polyester reflective film described above.

The above object is also achieved by a method for producing a non-stretched sheet, comprising the steps of: 1) melt-co-extruding a raw material composition containing a polyester resin as a main component in the form of a surface layer / A step of cooling the casting drum in a casting drum, 3) longitudinally stretching the cooled unoriented sheet to produce a uniaxially stretched film, and 4) forming a resin coating layer not containing particles on the longitudinally stretched film And 5) a step of transversely stretching the film to which the longitudinal stretching and coating layer is applied to prepare a biaxially stretched film and then heat treating the surface layer, wherein the surface layer is formed by a 10-point average (Z) is 1 to 3 占 퐉, the thickness of the resin coating layer is 100 to 500 nm, the 10 point average roughness (z) of the A layer and the thickness (t) Satisfactory white polyester It is achieved by the method for producing the film.

Here, the raw material composition of the surface layer contains 90 to 99.5% by weight of a polyester resin and 0.5 to 10% by weight of the inorganic particles in the total weight of the composition, and the raw material composition of the reflection layer contains 65 to 95 wt% And 5 to 35% by weight of the amorphous cyclic olefin copolymer.

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

Preferably, the inorganic particles may be at least one of silica, barium sulfate, calcium carbonate, and titanium dioxide.

Preferably, the resin coating layer is applied as a thermosetting resin binder to a coating liquid containing an acrylate type, a polyester type, an epoxy type, a melamine type, a urethane type or a urethane acrylate type resin, And 1 to 50 parts by weight of an amphipathic fiber.

According to the present invention, there is such an effect that the reflection film can prevent the inorganic particles from falling off and protruding to the surface.

Further, the present invention can prevent the reflection of light from the light guide plate due to friction between the reflection film and the light guide plate, and can prevent defects due to adhesion between the reflection film and the light guide plate, that is, It is possible to improve the visibility of the white spot on the front side of the BLU due to the wet-out phenomenon.

Further, the present invention has an effect such as excellent coating appearance upon application.

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.

1 is a schematic cross-sectional view of a white polyester reflection film according to a preferred embodiment of the present invention.
2 is a view schematically showing an apparatus for confirming the degree of grinding of the light guide plate.
3 is a view schematically explaining an apparatus for evaluating visibility of a white spot caused by a wet-out phenomenon occurring when a light guide plate and a reflective film come into contact with each other.

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 .

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

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.

In describing and / or claiming the present invention, the term "copolymer" is used to refer to a polymer formed by copolymerization of two or more monomers. Such copolymers include binary copolymers, terpolymers, or higher order copolymers.

First, a white polyester reflective film according to one aspect of the present invention will be described in detail with reference to FIG. 1, which is a schematic cross-sectional view of a white polyester reflective film according to a preferred embodiment of the present invention.

1, a white polyester reflective film according to an aspect of the present invention includes a reflective layer 10, a surface layer 20 made of a resin composition containing at least one surface of the reflective layer 10 and inorganic particles 30, Wherein the surface layer 20 has a projection formed by the inorganic particles 30 and a resin coating layer 40 that does not contain particles on at least one side of the surface layer 20. The white laminated polyester film according to claim 1,

The surface layer 20 has a 10-point average roughness z formed by the inorganic particles of 1 to 3 탆, a thickness of the resin coating layer 40 of 100 to 500 nm, and a 10-point average roughness z of the surface layer 20 And the thickness t of the resin coating layer 40 satisfy the following expression (1).

(1)

z / 30? t? z / 6

The white polyester reflection film according to the present invention can be produced by coating a resin layer on one side of a reflection plate containing inorganic particles by a coextrusion method instead of applying the organic particles to the surface of the reflection plate, It is possible to prevent the particles from falling off and protruding to the surface, and to suppress the occurrence of defects due to abrasion and adhesion due to friction between the reflective film and the light guide plate. Accordingly, it is possible to omit the step of applying the organic particles to the surface of the conventional reflective film and to solve problems such as particle dropout that may occur upon co-extrusion of the particles in the film and scattering of the light guide plate due to protruded particles on the surface .

According to a preferred embodiment of the present invention, the surface layer 20 preferably has a 10-point average roughness (z) formed by the inorganic particles of 1 to 3 占 퐉.

According to a preferred embodiment of the present invention, the thickness of the resin coating layer 40 is preferably 100 to 500 nm. More preferably, the thickness of the resin coating layer is 100 to 190 nm. When the thickness of the applied layer is in the above range, the inorganic particles forming the protrusions of the surface layer are prevented from dropping out or protruding, and the effect as described in the effect of the invention is obtained. When the thickness of the coating layer is as thin as less than 100 nm, it is difficult to prevent the inorganic particles from coming off or protruding, which may cause chipping due to friction with the light guide plate. If the thickness of the coating layer is thick enough to exceed 500 nm, This is because the reflector and the light guide plate are in contact with each other, and the white point due to the wet-out phenomenon is visible, or the light guide plate pattern directly contacts the reflection plate, thereby causing damage due to surface jamming.

According to a preferred embodiment of the present invention, it is preferable that the 10-point average roughness z of the surface layer 20 and the thickness t of the resin coating layer 40 satisfy the following expression (1).

(1)

z / 30? t? z / 6

The above formula (1) according to the present invention can optimally control the thickness of the resin coating layer to the surface roughness of the surface layer to minimize the decrease in surface roughness caused by the resin coating layer while suppressing the protrusion or dropout of the inorganic particles on the surface of the reflective film I have a technical sense of what I can do.

That is, if the thickness of the resin coating layer is too thin as compared with the 10-point average roughness (z) of the surface layer, the inorganic particles fall off or protrude from the surface layer, and the inorganic particles and the light guide plate are in direct contact with each other, If the thickness of the layer is too thick, the reflector can not form sufficient projections by lowering the surface roughness, and there is a high possibility that the reflective film and the light guide plate come into contact with each other to cause white spot due to wet-out phenomenon.

In one embodiment, the inorganic particles 30 contained in the surface layer 20 are made of silica, barium sulfate, calcium carbonate, titanium dioxide, or a mixture thereof, and they may be used alone or in combination of two or more.

In one embodiment, a thermosetting resin binder is applied to the resin composition constituting the resin coating layer 40, and the material is selected from the group consisting of an acrylate type, a polyester type, an epoxy type, a melamine type, a urethane type, a urethane acrylate type, Can be used alone or in combination of two or more.

In one embodiment, amphiphilic fibers may be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the thermosetting resin binder in order to improve the surface wettability of the resin application layer 40. If the amount of the amphiphilic fibers is less than 1 part by weight, a sufficient effect of applying a uniform thickness to the base layer forming the surface roughness can not be expected. If the amount is more than 50 parts by weight, the flowability of the resin coating liquid deteriorates, And the like.

Such amphiphilic fibers may be selected from the group consisting of hydroxymethylcellulose, hydroxyethylcellulose and 2-hydroxypropylcellulose, sodium carboxymethylcellulose, 2-hydroxyethylcellulose, 2-hydroxypropyl, methylcellulose, 2-hydroxyethylmethyl Cellulose, 2-hydroxybutyl methylcellulose, 2-hydroxyethylethylcellulose; Starch, modified starch and the like, and the like.

In one embodiment, the white polyester reflective film described above is preferably used for a backlight unit having a light guide plate.

Further, in the present invention, it is possible to provide a reflective sheet characterized by using the white polyester reflective film described above.

Hereinafter, a method of manufacturing a white polyester reflection film according to another aspect of the present invention will be described, and a white polyester reflection film will be described in more detail.

A method of producing a white polyester reflective film according to another aspect of the present invention comprises the steps of 1) melt-co-extruding a raw material composition containing a polyester resin as a main component in the form of a surface layer / a reflection layer / a surface layer (A layer / B layer / A layer) 2) a step of cooling the unstretched sheet in a casting drum; 3) longitudinally stretching the cooled unoriented sheet to produce a uniaxially stretched film; and , 4) applying a resin coating layer not containing particles on the longitudinally stretched film, and 5) longitudinally stretching and transversely stretching the film coated with the application layer to prepare a biaxially stretched film, .

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

In the production method of the present invention, the raw material composition of the surface layer (A layer) in step 1) contains 90 to 99.5% by weight of the polyester resin and 0.5 to 10% by weight of the inorganic particles in the total weight of the composition, The raw material composition contains 65 to 95% by weight of the polyester resin and 5 to 35% by weight of the amorphous cyclic olefin copolymer in the total weight of the composition.

The polyester resin used as the base resin of the polyester film is preferably composed of polyethylene terephthalate having a dicarboxylic acid component and a diol component and having 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.

Of the raw materials of the step 1), the polyester resin of the raw material composition of the B layer preferably contains 65 to 95% by weight, more preferably 70 to 90% by weight. 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 component containing a copolymerization component in an amount 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.

At this time, the dicarboxylic acid component as the copolymerization 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 . The diol component may be selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like. Among the copolymerization components, it is preferable to use isophthalic acid or 2,6-naphthalenedicarboxylic acid in order to obtain good film formability, and 1,4-cyclohexanedimethanol having an effect of stabilizing the dispersion state of the incompatible resin Is preferably used.

The resin composition in the raw material composition of step 1) contains an amorphous cyclic olefin copolymer as an incompatible resin for a 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] , And amorphous cyclic olefin resin and a crystalline polyolefin resin such as ethylene, propylene, butene, and methylpentene copolymerized with each other may be used.

The incompatible resin for the polyester resin listed above may be a polymer composed of a single component, a copolymer composed of two or more components, or a mixture of two or more components in combination. 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 raw material composition of the layer B is preferably 5 to 35% by weight, more preferably 10 to 30% by weight based on the total weight of the composition. If it is contained in an amount of less than 5% by weight, the effect of whitening is weak and high reflectivity can not be realized. If the content is more than 35% by weight, mechanical properties such as strength of the film itself are deteriorated, Is likely to occur.

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

Thus, the glass transition temperature of the amorphous cyclic olefin copolymer used in the raw material composition of step 1) 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. If the average particle diameter is less than 0.5 占 퐉, it is difficult to form voids during stretching, and if the average particle diameter exceeds 5.0 占 퐉, film tearing may occur during stretching, which deteriorates film formability.

The raw material composition of the first step of the present invention may contain various additives such as a fluorescent whitening agent, a crosslinking agent, a heat stabilizer, an oxidation stabilizer, an ultraviolet absorber, an organic lubricant, 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.

The first step is completed when the raw material composition as described above is extruded from a die and an unstretched sheet molded into a sheet form is produced.

In the production process of the present invention, step 2) is a step of cooling the unstretched sheet produced in step 1) in the casting drum. Since the second step is well known in the art, a detailed description will be omitted.

Next, step 3) of the method of the present invention is a step of uniaxially stretching a cooled unoriented sheet in step 2) to prepare a uniaxially stretched film, which is then subjected to roll heating, infrared heating ), And is first stretched in the longitudinal direction to obtain a uniaxially 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.

Next, step 4) of the manufacturing method of the present invention is a step of applying a resin composition containing no particles on one side of the uniaxially stretched sheet. The coating liquid can be obtained by arbitrarily diluting the components constituting the coating layer with a solvent so as to facilitate mixing and coating. At this time, water is preferable as a solvent. The application method of the coating liquid is not particularly limited, but preferred methods include a sub-roll coating method, a gravure coating method, a die coating method and a wire bar coating method.

Next, step 5) of the manufacturing method of the present invention is a step of longitudinal stretching and stretching the applied film in the transverse direction, followed by heat treatment to produce a film.

The step of biaxially stretching a uniaxially stretched film to produce a biaxially stretched film comprises the step of continuously stretching the uniaxially stretched film in the longitudinal direction of the step 3) in a direction perpendicular to the longitudinal direction (hereinafter also referred to as a "width direction" And then biaxially stretching it. At this time, the transverse stretching is performed while raising the temperature to 5 to 70 캜 higher than the glass transition point (Tg) starting from a temperature higher than the glass transition point (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 the widthwise stretching is set to 2.5 to 4.5 times.

In the step of heat-treating the biaxially stretched film, a biaxially oriented film is successively subjected to heat treatment such as heat fixing or thermal relaxation while running the biaxially stretched film to produce a biaxially oriented film. Thus, in order to complete the crystal orientation of the obtained biaxially stretched film to impart planarity and dimensional stability, the film was subsequently subjected to heat treatment at 120 to 240 캜 for 1 to 30 seconds in a tenter, uniformly and slowly cooled, To obtain a white polyester film according to 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 performed, if necessary.

In step 5), the coating liquid applied in step 4) is dried and cured by heat.

Further, the present invention can provide a white polyester reflective film produced from the process for producing a white polyester reflective film and a reflective sheet using the same.

As described above, according to the present invention, by improving the surface roughness of the white polyester reflection film, the white point visibility of the front side of the BLU due to the WET-OUT phenomenon caused by the reflection plate and the light guide plate contacting each other in the backlight unit of the edge type light source is improved , And also has a property that the light guide plate blurring caused by the friction between the reflection film and the light guide plate is also improved.

Thus, the reflective sheet using the white polyester reflection film of the present invention has the resin coating layer which does not contain particles on at least one side of the surface layer in which the projections are formed by the inorganic particles contained in the surface layer and the surface roughness is formed, It is possible to control the roughness and the coating thickness so as to sufficiently secure the surface roughness while suppressing the protrusion or detachment of the inorganic particles in the surface layer and the additional effect of omitting the step of further applying the organic particles to the surface of the substrate, Can be obtained.

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]

As a non-permanent resin for a polyester resin, 100 parts by weight of a polyester resin (A9093, manufactured by Toray Industries, Ltd.), 10 parts by weight of a copolymer resin of ethylene and norbornene as amorphous cyclic olefin copolymer, A layer obtained by adding 1 part by weight of inorganic particles of silicon dioxide having an average particle diameter of 7 mu m to 100 parts by weight of an inorganic filler (A9093, manufactured by Toray Industries, Ltd.) was fed to an extruder heated to 280 DEG C by a co- To form the structure of A / B / A layer.

At this time, an additive such as an emergency polyolefin resin was used in the form of a master pellet previously compounded with a polyester resin. The average particle diameter of the emergency polyolefin resin in the master pellet was 1 to 3 占 퐉.

Next, the formed sheet was cooled and solidified in a casting drum having a surface temperature of 20 캜 to obtain an unstretched film, which was heated to 3.7 times in the longitudinal direction and then cooled.

Subsequently, on one side of the uniaxially stretched reflective sheet, a coating liquid having the following composition was directly coated with a gravure coater. At this time, the coated layer was dried to a thickness of 100 nm.

Composition of coating liquid

- binder resin / (Dow, E3082): 3 weight%

- Cellulose emulsion (Dow, DR-73): 1 wt%

- Leveling agent (Kyoeisha Chemical, GW-1500): 0.1 wt%

- distilled water: 95.9 wt%

Next, both ends of the uniaxially stretched film in the longitudinal direction were led to a tenter while being held by a clip, and stretched at a magnification of 3.7 in a direction perpendicular to the length (width direction) in a heated atmosphere.

Thereafter, heat fixation was carried out in the tenter and cooled to room temperature to prepare a biaxial oriented film. The physical properties of the obtained film are shown in Table 1 below.

[Example 2]

A film was produced in the same manner as in Example 1, except that the coating thickness after drying of the coating layer in Example 1 was 110 nm.

[Example 3]

Except that 2 parts by weight of inorganic particles of silicon dioxide having an average particle diameter of 4 mu m were contained in the layer A in Example 1 and the coating thickness after drying of the coating layer was 190 nm, Respectively.

[Example 4]

A film was prepared in the same manner as in Example 3, except that the coating thickness after drying of the coating layer in Example 3 was 150 nm.

[Comparative Example 1]

A film was produced in the same manner as in Example 1 except that the coating thickness after drying of the coating layer in Example 1 was 70 nm.

[Comparative Example 2]

A film was produced in the same manner as in Example 1, except that the coating thickness after drying of the coating layer in Example 1 was 600 nm.

[Comparative Example 3]

A film was produced in the same manner as in Example 1, except that the coating thickness after drying of the coating layer in Example 1 was 50 nm.

[Comparative Example 4]

A film was produced in the same manner as in Example 3 except that the coating thickness after drying of the coating layer in Example 3 was 450 nm.

The properties of the white polyester reflecting film according to Examples 1 to 4 and Comparative Examples 1 to 4 were measured through the following experimental examples, and the results are shown in Table 1 below.

[Experimental Example]

1. Coating layer thickness

The reflection film was micro-torch in the thickness direction, and the cross-section was enlarged 10,000 times with SEM (Hitachi, S-4800) as shown in Fig. 1 to measure the coating layer thickness.

2. Surface roughness measurement

The biaxially stretched polyester film prepared in Example 1 and Comparative Examples 1 and 2 was measured with a contact type surface roughness meter (SE-3FA) manufactured by Kosaka Kenshuko Co., Ltd., and the radius of the stylus tip was 0.5 탆, , A measurement length of 0.8 mm and a cutoff value of 0.08 mm, and the surface average roughness (Ra) was measured. The results are shown in Table 1 below.

3. Appearance evaluation of coating layer

When the appearance of the reflective film after coating was observed under a fluorescent lamp, it was judged to be "x" when longitudinal stripes (living) were observed, and "o"

4. Evaluation of LGP

As shown in FIG. 2, the light guide plate was placed on the reflection sheet so that the light guide plate was in contact with the reflection sheet. Then, 1 kg weight was attached and fixed with a double-sided adhesive agent. &Quot; "if the number of scratches of 10 mu m or more is 5 or less, and" x "

5. WET-OUT EVALUATION

As shown in Fig. 3, when the edge LED type BLU is assembled and a rod-shaped 3 kg weight is placed facing 5 cm apart at intervals, when the white point (WET-OUT) or white line due to close contact between the light guide plate and the reflector is not visible, ", And when it was confirmed, it was judged as" x ".

division Properties Exterior Reliability evaluation 10 point average illumination
(탆) Coating layer thickness
(nm) Appearance layer appearance WET-OUT Light guide panel Example 1 2.8 100 ○ ○ ○ Example 2 2.3 110 ○ ○ ○ Example 3 1.3 190 ○ ○ ○ Example 4 1.1 150 ○ ○ ○ Comparative Example 1 2.8 70 ○ ○ X Comparative Example 2 2.3 600 X ○ ○ Comparative Example 3 3.3 50 ○ ○ X Comparative Example 4 0.8 450 ○ X ○

As can be seen from Table 1 above, the white polyester reflective film produced according to the embodiment of the present invention has a sufficient surface roughness and coating thickness to suppress the light guide plate shrinkage and wet-out phenomenon, Respectively.

However, if the thickness of the coating layer is too low as compared with the surface roughness of the surface layer, the white polyester reflection film produced according to Comparative Examples 1 to 4 may cause the inorganic particles of the surface layer to fall off or protrude, The surface roughness is lowered to cause problems such as visibility of the white spot due to wet-out or appearance defects such as longitudinal coating when the resin is applied.

Thus, the reflective sheet using the white polyester reflective film according to the present invention can form a sufficient surface roughness while suppressing the falling or protrusion of the inorganic particles on the surface of the reflective film by controlling the coating thickness of the resin coated layer, It can be seen that the shaking phenomenon of the light guide plate due to vibration or vibration of the white spot or the white line in the image due to the WET-OUT caused by the close contact between the light guide plate and the reflection plate in the unit can be suppressed.

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: Reflective layer containing internal pores
20: Surface layer containing inorganic particles
30: inorganic particles
40: resin coating layer
50: light guide plate
51: Light guide plate pattern
52: 1 kg weight
60: Reflective film coated with resin
70: Reflective film - Light guide plate - Diffusion film - Prism film - DBEF
80: Cover Bottom including edge type LED light source
90: Bar weighing weight

Claims (12)

A white laminated polyester film having a reflective layer (10) and a surface layer (20) comprising a resin composition containing at least one surface of the reflective layer (10) and inorganic particles (30)
The surface layer 20 has protrusions formed by the inorganic particles 30,
And a resin coating layer (40) that does not contain particles on at least one side of the surface layer (20)
The surface layer 20 has a 10-point average roughness z formed by the inorganic particles of 1 to 3 탆, a thickness of the resin coating layer 40 of 100 to 500 nm, (z) and the thickness (t) of the resin coating layer (40) satisfy the following formula (1)
(1)
z / 30? t? z / 6
Lt;
Wherein the resin coating layer comprises 1 to 50 parts by weight of amphiphilic fibers per 100 parts by weight of the thermosetting resin binder. The method according to claim 1,
Wherein the resin coating layer has a thickness of 100 to 190 nm. The method according to claim 1,
Wherein the inorganic particles are at least one of silica, barium sulfate, calcium carbonate and titanium dioxide. The method according to claim 1,
Characterized in that the resin coating layer (40) is coated with a coating liquid containing an acrylate-based, polyester-based, epoxy-based, melamine-based, urethane-based or urethane acrylate-based resin as a thermosetting resin binder. film. delete 5. The method according to any one of claims 1 to 4,
Wherein the white polyester reflective film is used for a backlight unit having a light guide plate. A reflective sheet comprising a white polyester reflection film according to any one of claims 1 to 4. A method for producing a white polyester reflective film,
1) A step of melt-co-extruding a raw material composition containing a polyester resin in the form of a surface layer / a reflection layer / a surface layer to form an unoriented sheet by molding into a sheet,
2) cooling the unstretched sheet in a casting drum,
3) longitudinally stretching the cooled unoriented sheet to produce a monoaxially stretched film;
4) applying a resin coating layer not containing particles on the longitudinally stretched film;
5) transversely stretching the film to which the longitudinally stretched and coated layers are applied to produce a biaxially stretched film and then subjecting it to heat treatment;
Wherein the surface layer has a 10-point average roughness (z) formed by the inorganic particles of 1 to 3 탆, a thickness of the resin coating layer is 100 to 500 nm, and a 10-point average roughness (z) Wherein the thickness t satisfies the following formula (1)
(1)
z / 30? t? z / 6
Wherein the polyester resin is a polyester resin. 9. The method of claim 8,
The raw material composition of the surface layer contains 90 to 99.5% by weight of a polyester resin and 0.5 to 10% by weight of the inorganic particles in the total weight of the composition,
Wherein the raw material composition of the reflective layer comprises 65 to 95% by weight of a polyester resin and 5 to 35% by weight of an amorphous cyclic olefin copolymer in the total weight of the composition. 10. The method of claim 9,
Wherein the average particle diameter of the amorphous cyclic olefin copolymer is 0.5 to 5.0 mu m. 10. The method of claim 9,
Wherein the inorganic particles are at least one of silica, barium sulfate, calcium carbonate, and titanium dioxide. 9. The method of claim 8,
The resin coating layer 40 is applied as a thermosetting resin binder with a coating liquid containing an acrylate type, a polyester type, an epoxy type, a melamine type, a urethane type, and a urethane acrylate type resin,
And 1 to 50 parts by weight of an amphipathic fiber to 100 parts by weight of the thermosetting resin binder.

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