KR20120026586A - White polyester reflection film with roughened surface for back-light unit - Google Patents

Abstract

PURPOSE: A white polyester reflective film for a roughened backlight unit is provided to reduce costs by removing post-processes. CONSTITUTION: The surface roughness of one layer is 0.8 micron or more. The 10-point average roughness of a roughened layer is 5 micron or more. The other layer contains bubble forming liquid functioning as optical reflection. The reflectivity of a reflective sheet is 93% or more.

Description

White polyester reflection film with roughened surface for back-light unit}

The present invention relates to a white polyester reflective sheet for a backlight unit, and more particularly, at least one layer comprises a layer having excellent reflectivity through in-line coextrusion during the sheet manufacturing process and at least one layer of the surface roughness It is a reflective sheet that prevents ring-like defects caused by sticking when contacted with a light guide plate by cotton, so that cost can be reduced by omitting the post-processing process. will be.

In recent years, liquid crystal displays have been used in various applications such as personal computers, monitors, and televisions as well as portable devices. Since the liquid crystal display itself is not a light emitter, there is a backlight unit device equipped with a light source, and such a backlight unit device includes a reflective sheet that reflects light at the bottom to prevent light from leaking behind the screen. It is becoming. Such a reflective sheet is required to have a high reflectance and not to be deformed by heat by a light source, to obtain uniform luminance, and to be more inexpensive to manufacture in a fiercely competitive market.

As a method of obtaining the reflecting sheet which meets the said subject, the film which uses incompatible resin as a bubble-forming nucleus agent is known conventionally (quotation patent (1), a nonpatent literature)

As another method, a method is known in which a large amount of barium sulfate is added to form bubbles to increase the reflectance (quotation patent (2)).

Furthermore, a method is known in which an antistatic agent or a silicone compound is applied to the surface of the light guide plate side of the reflective sheet containing a large amount of barium sulfate by using an in-line coating method in the film forming process to prevent scratches from occurring on the reflective sheet ( Cited Patent (3)

As another method, a method of mixing inorganic particles and incompatible resins is known (quotation patent (4)).

As another method, a method of laminating a polyester film obtained by depositing silver or aluminum with another biaxially oriented film is known (quotation patent (5)).

As another method, a method of improving the brightness of a liquid crystal display or improving the uniformity of brightness by applying beads to the reflective sheet in a post-processing manner is known. (Citation Patent (6))

Recently, screen sizes using liquid crystal displays have grown to 55 inches or more, starting with TVs, and 72 inches or more. As the display size increases, the size of the optical film mounted in the backlight unit also increases. Among them, the light guide plate used in the edge type has a thickness of 500 microns or more and usually 800 microns or more. do.

The reflective sheet is located directly below the light guide plate. Conventionally, when the screen size is small, there is no problem because the weight of the light guide plate is small and thus the load acting between the light guide plate and the reflector is small, but on a large screen, the ring shape is caused by sticking due to the large load between the light guide plate and the reflector due to the weight of the light guide plate. There is a problem that a defect occurs and the uniformity of the luminance decreases at the corresponding site. Furthermore, when the reflective sheet is exposed to heat generated by the LED used as the light source, there is a problem in that the liquid crystal display is uneven because a defect in the shape of the reflective sheet occurs due to a difference in local shrinkage and expansion.

To prevent this problem, the beads are applied on the finished biaxially oriented film to have a specific surface roughness in the post-processing line (offline) to prevent sticking and at the same time heat treatment using a dryer during the post-processing process to Techniques for improving thermal dimensional stability have been practiced (citation 7)

That is, the conventional biaxially stretched polyester film used for the reflective sheet has a surface roughened enough to prevent sticking on the film in the case of a film obtained only by the film manufacturing process, and thus the load of the light guide plate which is enlarged. In order to prevent sticking due to the inevitable post-processing to roughen the surface roughness of the film through the bead coating (roughing process) was the situation. In addition, the conventional biaxially stretched polyester film for the reflective sheet is caused by excessively lowering the heat treatment temperature during the film manufacturing process in order to obtain a high reflectance, or the problem caused by the difference in local expansion and contraction in the film when exposed to heat by the light source of the display. In order to improve this, a method of laminating (laminating and laminating) at least two layers of biaxially stretched polyester films by an adhesive was performed in a post-processing line.

Therefore, in the conventional method, since the bead for surface roughness is formed using a biaxially stretched polyester film, which has been manufactured, it is undergoing a complicated process of laminating it using another biaxially stretched polyester film and an adhesive. As the cost increases due to the increase and the adhesive contains the solvent, it is not environmentally friendly, and carbon dioxide emission is a large method due to energy consumption for processes such as application, drying, lamination, and aging.

Accordingly, the present inventors have diligently studied to solve the problems of the prior art. As a result, the manufacturing process, which does not require the post-processing described above, is conceived as a simpler method. It was confirmed that one problem can be solved at once, and the present invention has been reached.

JP 2002-50222, JP 2008-30459, JP 2008-69217 JP 2004-330727, WO2005 / 026241, JP 2005-125700 JP2008-188897A JP 2008-209851, JP 2008-309975, Korea Publication No. 10-2007-0052859, Korea Publication No. 10-2009-0066094, Korea Publication No. 10-2011-0023287 JP2007-157566A JP2009-20502A, JP2010-33053A JP2003-92018A, JP2004-85633, Korea Patent Publication 10-2011-0082327

Chapter 2 reflecting sheet for backlight in optical spraying film (2004, CMC publication)

In the process of manufacturing the biaxially stretched polyester reflective sheet, that is, by in-line co-extrusion, the surface roughness of at least one surface is roughened by laminating two or more layers, and at least one layer having excellent reflectance is laminated in the same sheet. The first object of the present invention is to prevent the ring-shaped defects due to sticking from appearing on the liquid crystal display when contacting the light guide plate without a separate post-processing bead coating process, and to reduce costs by omitting the post-processing process. Furthermore, it aims as a 2nd objective to prevent the generation | occurrence | production of the sheet | seat when exposed to the heat by a light source by ensuring said thermal dimensional stability by optimizing the composition of a reflective sheet raw material, and a film forming process.

In order to achieve the above object, the present invention,

(One)

In a laminated sheet made of polyethylene terephthalate as a main component and manufactured by a coextrusion method composed of at least two layers, the surface roughness of at least one layer (A) has an arithmetic mean roughness Ra of at least 0.8 micron and a ten point average. A roughened layer having a roughness Rz of 5 microns or more, at least one of the other layers B contains a bubble-forming nucleating agent that performs a light reflecting function, and the reflecting sheet has a reflectance of 93% or more. White Polyester Reflective Sheet for Unit

(2)

The white polyester reflective sheet for backlight units according to (1), wherein particles having an average particle diameter of 5 microns or more are contained in layer A with respect to the resin composition of layer B in an amount of 1% by weight or more.

(3)

10-65 weight% of bubble-forming nucleating agents are contained in B-layer with respect to B-layer resin composition weight in B layer, The white polyester reflective sheet for backlight units characterized by the above-mentioned.

(4)

The white polyester reflective sheet for a backlight unit according to (1), wherein the layer A contains 0.003% by weight or more of a compound having a surface tension of 36 dyne / cm 2 or less.

(5)

The composition of (1) is coated with a layer A containing 0.3% by weight or more of a compound having a surface tension of 36 dyne / cm 2 or less, wherein the white polyester reflective sheet for a backlight unit

According to the present invention, in the process of manufacturing a biaxially stretched polyester reflective sheet, that is, in the form of a laminated sheet of two or more layers through coextrusion in an in-line, the surface roughness of at least one surface is roughened and the reflectance is excellent in the same film. By laminating at least one layer, the ring-like defects due to sticking upon contact with the light guide plate without contacting the light guide plate without a separate post-processing bead coating process are prevented from appearing on the liquid crystal display, and the cost can be reduced by omitting the post-processing process.

In addition, by optimizing the composition of the reflective sheet raw material and the film forming process, it is possible to secure the thermal dimensional stability of the reflective sheet while preventing the lowering of the reflectance, thereby making it possible to manufacture the reflective sheet at the same time by eliminating the heat treatment incidentally applied in the post-processing process. do.

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

The invention consists of at least two layers and comprises at least one layer A and at least one layer B. The layer configuration of the reflective sheet uses a method in which layers A and B are laminated by coextrusion in the extrusion step before the casting process to form a laminate. Although it is most efficient to comprise two or three layers, you may comprise four or more layers, such as A / B / A / B. In the case of the second layer, it becomes A / B, and in the case of the third layer, forms of A / B / A, A / B / C, etc. are not limited thereto. At least one side of the layer A faces the light guide plate.

The reflective sheet of the present invention is preferably 50 to 500 microns, more preferably 75 to 400 microns and most preferably 100 to 350 microns. Below 50 microns, the reflectance is low and the rigidity of the reflecting sheet is not preferable. Exceeding 500 microns is uneconomical and undesirable.

The present invention is produced using polyethylene terephthalate as a main component, and the ethylene terephthalate repeating unit is 80 mol% or more, preferably 85 mol% or more, and most preferably 90 mol% or more.

If the ethylene terephthalate repeating unit is less than 80 mol%, deformation is caused in the dimensions of the reflecting sheet when exposed to heat generated from the light source of the backlight unit, resulting in uneven brightness or sticking with the light guide plate. not. The upper limit is 100 mol%, which means substantially homopolyester except for the components due to side reactions occurring during the polymerization.

It is necessary to comprise at least 2 layers or more of polyester which has said ethylene terephthalate as a main component as a resin composition, and one side is the layer (layer A) which faces the light guide plate side, and prevents sticking with a light guide plate. The arithmetic mean roughness Ra of the surface roughness parameters is preferably 0.8 micron or more and the ten point average roughness Rz of 5 microns or more. More preferably, Ra is at least 1.2 microns, Rz is at least 7 microns, most preferably Ra is at least 1.6 microns, and Rz is at least 9 microns. If Ra is less than 0.8 micron or Rz is less than 5 microns, the lack of sticking resistance is not preferable.

The reflectance of the layer A is preferably at least 93%, more preferably at least 95%, and most preferably at least 97%. If it is less than 93%, there is a problem that the screen brightness decreases due to lack of display brightness, and the upper limit of the reflectance is 120% in terms of film forming stability.

The particles added to layer A are preferably at least 5 microns, more preferably at least 7 microns and most preferably at least 10 microns. Particles may be used alone or in combination of two or more kinds having different average particle diameters. Less than 5 microns is not enough to prevent sticking,

The upper limit is preferably 40 microns or less in consideration of the permeability to the filter provided in the film forming process, the thickness of the layer A, and the chipping of the particles.

The particles added to layer A are preferably at least 1% by weight, more preferably at least 3% by weight, most preferably at least 5% by weight. If it is less than 1% by weight, the anti-sticking effect is insufficient, which is not preferable. The upper limit of the amount added depends on the thickness and melting point of the layer A, the film forming speed, the size of the particles, and the like, but is preferably 55% by weight or less in view of the shaving of the particles.

Particles added to layer A are acrylic crosslinked particles, styrene crosslinked particles, divinylbenzene-styrene crosslinked particles, silicone crosslinked particles, silicone resin particles, melamine formaldehyde condensed particles, melamine cyanurate particles, nylon particles, polyurethane particles, Teflon particles, PES particles, polyimide particles, core-shell type particles with internal bubbles (e.g., Rohm and Haas, PALALOID), organic-inorganic hybrid particles, silica, titanium oxide or oxide in spherical silica One or more selected from particles dispersed with zinc, calcium carbonate, calcium phosphate and feldspar may be used in combination, but the present invention is not limited thereto as long as the roughening effect of layer A can be obtained.

The shape of the particles may be any shape as long as the roughening effect can be obtained, such as plate-like, amorphous, spherical, and cubical, but in particular spherical particles (including the long diameter / short diameter ratio of 1.3 or less, or primary particles gathered into a star-shaped candy) It is preferable in terms of effectively forming surface roughness.

The resin composition for layer A may be added through a kneading method, a polymerization method, or by dry blending during film formation.

The melting point of layer A is 248 ° C. or less, more preferably 246 ° C. or less, and most preferably 244 ° C. or less. When melting | fusing point of layer A exceeds 248 degreeC, shaving of a particle will occur easily and it is unpreferable. There is no lower limit, but in view of heat resistance, the temperature is preferably 180 ° C or higher.

The reflective sheet of the present invention comprises at least one layer B. Layer B is a layer that performs a light reflection function and contains a bubble-forming nucleating agent therein. As the bubble-forming nucleating agent, an organic particle or a barium sulfate, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, or oxide in which a resin incompatible with polyester is kneaded with polyester using a vacuum vent type twin screw extruder and dispersed in fine size Magnesium, silica, kaolin, composite particles in which fine titanium oxide is dispersed in silica, and the like, and the like, but are not limited thereto. Specific examples of the incompatible resin are detailed in the cited patent document (2).

The addition amount of the bubble-forming nucleating agent added to layer B is 10 to 65% by weight. If it is less than 10% by weight, the reflectance is insufficient, and if it is more than 65% by weight, breakage occurs frequently during film formation, which is not preferable.

The polyester resin composition for layer B containing a bubble-forming nucleating agent for increasing the reflectance may be added by kneading, polymerization, or by dry blending during film formation. It is preferable to use a kneading method while using a compatibilizer (dispersant) together for dispersion. Any of the inorganic particles having a refractive index of 2.0 or less can be used in a polymerization method or a kneading method. In terms of kneading, a kneading method is preferable.

It is particularly preferable to add a compound having a surface tension of 36 dyne / cm or less to layer A in addition to adding the above-mentioned particles to prevent sticking with the light guide plate (hereinafter, the compound may be referred to as surface tension reducing agent). The inclusion of a compound having a surface tension of 36 dyne / cm or less in the layer A lowers the coefficient of friction and enables microscopic movement at the point of contact when the load of the light guide plate is applied, so that ring-shaped sticking does not occur. The method of adding such a compound to the layer A includes the method of addition into the inside of the layer A and the addition in the resin composition applied on the layer A before the longitudinal stretching is completed and before the transverse stretching, or before winding when the transverse stretching is completed and the roll is wound. There is a method of adding in the resin composition.

Compounds having a surface tension of 36 dyne / cm or less that can be added to the inside of layer A include silicone oils, silicone slip agents, fluorine oils or slip agents, waxes (including natural, synthetic and mineral), functional group-containing polyolefin high molecular weight waxes, and C10 or more. Higher fatty acid derivative compounds having a carbon number (e.g., sodium dodecylbenzenzen sulfonate, oleic acid ester, stearyl stearate, higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, etc.), surfactants, antistatic agents, etc. It is not limited to this as long as it is 36 dyne / cm or less. Such a compound may be added during polymerization, may be added through a kneading method, or may be added through a blending method during film formation. Moreover, you may manufacture and add the masterbatch which contains such a surface tension decreasing agent in high concentration. The addition amount is preferably 0.003% by weight or more, more preferably 0.03% by weight or more, and most preferably 0.08% by weight or more. If it is less than 0.003 weight%, it is not preferable because it lacks the function which prevents sticking with a light guide plate, and an upper limit is 25 weight% or less from a bleed-out side in the shaping | molding process and longitudinal stretch process in film forming.

Compounds having a surface tension of 36 dyne / cm or less that can be added to the composition applied on layer A include polyolefin emulsions (e.g., Dow Chemical HYPOD, Unitica ARROWBASE), silicone oils, fluorine-based oils or slip agents, waxes, mineral oils, Compounds, surfactants, antistatic agents or the like that are C10 or more long-chain aliphatic hydrocarbons or the like may be exemplified, but are not limited thereto. These surface tension reducing agents are solely selected from known binders used for application in the production process of the polyester film, that is, inline coating, for example polyurethane, acrylic, copolyester, epoxy, polyol, polyvinyl alcohol, and the like. Or two or more kinds of binders, and a known crosslinking agent such as melamine, epoxy, polyisocyanate, oxazoline, polycarbodiimide, urea, benzo guanamine, glycoril, silane or the like alone or in combination Application | coating can be performed by bridge | crosslinking. The amount of the surface tension reducing agent added is preferably 0.1% by weight or more, more preferably 1.0% by weight or more, and most preferably 3.0% by weight or more, based on the weight of the coating layer after drying. If it is less than 0.1% by weight is not preferable because the lack of a function to lower the friction coefficient, the upper limit is not secured to the reflective sheet as long as it is secured, from the economical point of view is preferably 85% by weight or less.

If necessary, by adding the crosslinking agent in an amount of 30% by weight or more relative to the total solid resin weight, it is possible to prevent scratches from occurring on the reflective sheet by increasing the curing density of the coating layer.

In addition, as the layer A, a compound having a surface tension of 36 dyne / cm or less is copolymerized with the binder itself. Among the above-mentioned compounds, copolymerized reactive compounds with polyurethane, acryl, copolyester, etc. may be exemplified, but are not limited thereto. Among these, C10 or more long-chain aliphatic compound, reactive silicone compound, or reactive fluorine compound is especially preferable. When the binder itself contains a compound having a surface tension of 36 dune / cm or less, the weight percentage of the compound added during the copolymerization is preferably 0.1% by weight or more based on the total monomer weight, more preferably 1.0% by weight or more, most preferably. Preferably 3.0% by weight or more. If it is less than 0.1% by weight, it is not preferable due to the lack of a function of lowering the coefficient of friction, and the upper limit is not limited to secure the adhesiveness to the reflective sheet, but is preferably 70% by weight or less from the economic point of view.

In addition, the layer A may be coated with a polyester binder such as a silicone binder, a film-forming fluorine compound, a polar group-containing polyolefin resin emulsion or a dispersion, and having a surface tension of 36 dyne / cm or less.

The surface tension of the surface tension lowering agent can be obtained from the force when the ring is pulled from the liquid through the Du Nouy ring method in the case of liquid, and water, ethylene glycol, formamide and Obtain the contact angle of the solid to be measured by using a contact angle meter using Methlene iodide, and solve the simultaneous equation from Fowkes's equation and Young's equation using the surface tension of each solution The sum of the component, the hydrogen bonding force component and the dispersing force component is the surface tension.

The resin composition to be applied on the layer A may be any solvent, aqueous, solvent-free, or UV-curable system, but an aqueous system is particularly preferable in terms of environmental friendliness and explosion-proof. An aqueous system may contain 30 weight% or less of the solvent which can be mixed with water from a viewpoint of applicability | paintability, storage stability, etc ..

By adding a surface tension reducing agent to the inside of the layer A or applying a composition containing the surface tension reducing agent on the layer A, the coefficient of friction of the layer A can be effectively lowered to effectively prevent sticking with the light guide plate. Since the friction coefficient is low when the printed, V-cut, or stamped pattern is in contact with the reflective sheet, a side effect of preventing a wound on the reflective sheet or vice versa is obtained.

In the present invention, it is necessary to lower the heat shrinkage rate as much as possible in order to prevent the occurrence of the phenomenon in the reflection sheet when exposed to heat emitted from the backlight unit light source without the heat treatment step in the post-processing. In order to achieve this, it is necessary to correlate and optimize melting | fusing point of the layer B resin composition of a reflective sheet and heat processing temperature in a film forming process. In the same resin composition, the higher the heat treatment temperature, the lower the reflectance, and the lower the heat treatment temperature, the contradiction in which the heat shrinkage rate increases. Therefore, it is necessary to optimize the heat treatment temperature according to the melting point of the resin, and preferably heat treatment for 3 seconds or more in the following temperature range.

55 ℃ ≤ Tm-Ta ≤10 ℃

Tm :: Melting Point Of Layer B

Ta: heat treatment temperature

Here, the heat treatment means only the heat treatment time in the temperature range, and does not include heat treatment until the temperature is reached to reach the heat treatment temperature. If the heat treatment temperature is lower than this, the heat shrinkage rate is high, so that a phenomenon occurs in the reflective sheet when exposed to heat generated from the light source, and when the heat treatment temperature is higher than the above, the reflectance decreases, which is not preferable.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited thereto.

{Measurement method and evaluation method of physical property}

Intrinsic viscosity

0.3 grams of polyester resin was dissolved in 25 ml of orthochlorophenol at 100 ° C. for 30 minutes, then cooled and held at 25 ° C. for 1 hour, and then the viscosity was measured with an Ostwald viscometer.

The viscosity of the melted resin polymer thus obtained is referred to as A. Viscosity A is given by

It was made into the intrinsic viscosity by compensating with the bubble-forming nucleating agent addition amount. The unit is dl / g.

Intrinsic viscosity = A / ｛(100-foamable particle content) / 100｝

Thickness of reflective sheet or film

One meter of film or sheet sample was cut in the TD direction and measured at 25 mm intervals with a calibrated digital micrometer (Millitron, Marh) to obtain an average value of the film thickness. The unit is micron.

The thickness of the layer A was averaged after measuring the thickness of the layer A ten points by the electron microscope after cutting a cross section sharply with a microtomer.

reflectivity

The reflectance was attached to a spectrophotometer (manufactured by Shimadzu Corporation, UV-2450), and then the reflectance when the barium sulfate white plate was 100% was measured at 550 nm to be a relative comparison value. A barium sulfate white plate was prepared by filling barium sulfate powder (Merck DIN5033) into a powder sample holder. Measure the reflectance on the layer A side of the reflective sheet five times, discard the highest and lowest values, and average the rest.

It was set as reflectance.

Surface roughness (Ra, Rz)

The layer B of the reflective sheet was measured using a two-dimensional surface roughness measuring instrument (KOSAKA, model name: SE-3H), and the cut-off value was set to 0.8 mm and the evaluation length was 20 mm.

Melting point Tm

About 20 mg of polyester reflective sheet, film or resin composition was enclosed in an aluminum pan for measurement and mounted on a differential scanning calorimeter (DSC-2, manufactured by Perkin Elmer) to 290 ° C at 25 ° C to 10 ° C / min. The temperature was raised, held at 290 ° C. for 3 minutes, then taken out and immediately quenched on ice. This pan was mounted on a differential scanning calorimeter again, and the temperature was maximized at 25 ° C to 10 ° C / min, and the temperature at which endotherm became maximum in the process of melting the crystal was set to the melting point Tm (° C). When the measurement object exists in the inner layer, the layer on either side was removed using a microscope and a blade, and the inner layer exposed was taken as a sample to measure the melting point.

Average particle size of the particles in the slurry

The particle size distribution of the particle slurry was determined by a particle size distribution analyzer (Malvern, Mastersizer), and the particle diameter at d50 was used as the average particle diameter.

Sticking degree evaluation

A light guide plate having a printing pattern at the bottom was placed on a reflective sheet having a size of A-4, and three samples of a form in which a load of 6 kg / m 2 was further applied on the light guide plate. This was left to stand in a constant temperature and humidity room maintained at 60 degreeC for 1 hour. Then, the light guide plate is considered and counted and averaged by the number of sticking occurrences of the light guide plate and the reflective sheet in the form of a ring, and when it is difficult to use the reflective sheet due to more than three pressing defects, the pressing defect is 1 If there are ~ 3 but can be applied as a reflective sheet, △, if the defect is less than 1 is indicated by ○.

Reflective sheet um occurs

The reflective sheet was cut to 1 meter each in size and width, and was placed in a constant temperature and humidity chamber maintained at 80 ° C. and exposed to heat for 1 hour. After that, the reflective sheet was taken out, placed on a flat glass plate, and left to stand for 1 hour to allow air between the glass and the reflective sheet to escape. After that, the reflection sheet was considered at a 45 degree angle to determine the hum of the reflection sheet as follows.

      ○: no help at all

      (Triangle | delta): One or two shallow humps, but there is no problem practically.

X: 5 or more severe graves occur and cannot be used

{Production of polyester resin composition 1 containing no particles}

86.5 parts by weight of terephthalic acid and 37.1 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol were kneaded in a reaction system obtained by melting and storing a low polymer (molar ratio of glycol component / acid component of 1.15) obtained at 86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol in an esterification reaction tube. A slurry was continuously supplied while maintaining the temperature in the reaction system at 242 ° C. to effect esterification, and the resulting water was discharged through a rectifying column to terminate the slurry supply, and then the esterification reaction was continued for 1 hour, followed by ester The reaction was terminated. Subsequently, the obtained reaction product was transferred to a polycondensation reaction tube, and then 270 ppm of trimethyl phosphate was added as a phosphorus compound, and after 5 minutes, 650 ppm of magnesium acetate and 230 ppm of antimony trioxide were added. Subsequently, the reaction system was depressurized and the polycondensation reaction was performed at reaction temperature of 288 degreeC, and the polyester resin composition which does not contain particle | grains was manufactured. The intrinsic viscosity was 0.670 dl / g and the melting point was 252.9 ° C.

{Copolymer resin composition 2 having high intrinsic viscosity without containing nucleating agent}

A polyester resin containing no foamable nucleating agent having an intrinsic viscosity of 0.72 dl / g copolymerized with 18 mol% of IPA and a melting point of 205.2 ° C.

{Copolymer resin composition 3 having high intrinsic viscosity without containing nucleating agent}

A polyester resin containing no foamable nucleating agent having an intrinsic viscosity of 0.72 dl / g copolymerized with 12 mol% of IPA and a melting point of 223.0 ° C.

{Preparation of foamable nucleating agent masterbatch resin composition 4}

49.75 parts by weight of ethylene glycol was added to the slurry preparation vessel, 0.25 parts by weight of sodium polyacrylate was added thereto as a dispersant, and stirred for 5 minutes. Then, 50 parts by weight of powder of barium sulfate (Sachtleben, Micro, refractive index 1.65, whiteness 99.8) was added to 30 Stirring for minutes gave a barium sulfate slurry. At this time, the average particle diameter was 2.42 microns. Subsequently, the slurry was supplied to a bead mill (manufactured by Netz, 1 mm phi bead, bead filling rate of 60%) and milled three times. The slurry thus obtained was passed through a 10 micron filter while liquefied into a reservoir, the concentration of barium sulfate was adjusted to 40% by weight in the reservoir, and the slurry was stored while continuously circulating through the 15 micron filter. At this time, the average particle diameter of the slurry was 0.78 micron. The temperature of the slurry was maintained at 120 ° C. by passing a heater in the circulation.

86.5 parts by weight of terephthalic acid and 37.1 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol were kneaded in a reaction system obtained by melting and storing a low polymer (molar ratio of glycol component / acid component of 1.15) obtained at 86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol in an esterification reaction tube. A slurry was continuously supplied while maintaining the temperature in the reaction system at 242 ° C. to effect esterification, and the resulting water was discharged through a rectifying column to terminate the slurry supply, and then the esterification reaction was continued for 1 hour, followed by ester The reaction was terminated. Subsequently, the obtained reactant was transferred to the first polycondensation reaction tube, and then the stirring speed of the reactor was set to the maximum value, the heating amount of the reactor heating device was adjusted to the maximum, and then 320 ppm of trimethyl phosphate was added as a phosphorus compound, and 5 minutes After the addition of 600ppm magnesium acetate, 350ppm antimony trioxide, 700ppm leucopur EGM and circulating the reactant through the melt pump, the barium sulfate slurry a was finally polymerized through the circulation pipe based on the barium sulfate particles. Slowly added via discharge pump over 20 minutes to 40% by weight of the composition. The reaction was then added for 20 minutes, and then the reaction proceeded to a secondary polycondensation reaction system. Subsequently, the reaction system was depressurized to carry out a polycondensation reaction at a reaction temperature of 288 占 폚 to prepare a masterbatch containing a high concentration of barium sulfate. The intrinsic viscosity was 0.680 dl / g and the melting point was 253 ° C.

{Preparation of foamable nucleating agent masterbatch resin composition 5}

50 parts by weight of a low-melting copolyester resin containing 12 mol% of an IPA copolymer component, a melting point of 223 DEG C, and an intrinsic viscosity of 0.720 dl / g, and 50 parts of barium sulfate as used in the masterbatch 2. After mixing the parts, the mixture was kneaded at a temperature of 270 ° C. for 3 minutes in a residence time through a kneading vacuum vent type twin screw extruder to prepare a master batch having a concentration of 50% by weight of barium sulfate. The inherent viscosity was 0.585 dl / g and the melting point was 222.8 ° C.

{Preparation of masterbatch 6 containing particle | grains for roughening}

70 parts by weight of the copolymer resin 3 having an IPA copolymer content of 12 mol% and an average particle diameter of 12 microns.

After mixing 30 parts by weight of the acrylic crosslinked particles, a kneading vacuum vent type twin screw extruder was kneaded at a residence time of 3 minutes at a temperature of 270 ° C. to prepare a masterbatch containing bead particles. The inherent viscosity was 0.640 dl / g and the melting point was 242.2 ° C.

{Preparation of masterbatch 7 containing particle | grains for roughening}

70 parts by weight of the copolymer resin 3 having an IPA copolymer content of 12 mol% and 30 parts by weight of acrylic crosslinked particles having an average particle diameter of 20 microns were mixed, and a residence time was 3 minutes at a kneading vacuum vent type twin screw extruder at a temperature of 270 ° C. A masterbatch containing bead particles was prepared. The inherent viscosity was 0.6402 l / g and the melting point was 242.4 ° C.

{Production of grain-containing masterbatch resin composition 8 for roughening}

86.5 parts by weight of terephthalic acid and 37.1 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol were kneaded in a reaction system obtained by melting and storing a low polymer (molar ratio of glycol component / acid component of 1.15) obtained at 86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol in an esterification reaction tube. A slurry was continuously supplied while maintaining the temperature in the reaction system at 242 ° C. to effect esterification, and the resulting water was discharged through a rectifying column to terminate the slurry supply, and then the esterification reaction was continued for 1 hour, followed by ester The reaction was terminated. Subsequently, the obtained reaction product was transferred to a polycondensation reaction tube, and then 320 ppm of trimethylphosphate was added as a phosphorus compound, after 5 minutes, 600 ppm of magnesium acetate, 350 ppm of antimony trioxide, and 100 ppm of fluorescent whitening agent (Leucopur EGM) were added, followed by an average particle diameter of 4.3 microns. Calcium Carbonate

The ethylene glycol slurry was slowly added over 20 minutes so that the polymerization was completed on the basis of the calcium carbonate particles and became 25% by weight based on the finally obtained resin composition. Subsequently, the reaction system was depressurized to carry out a polycondensation reaction at a reaction temperature of 288 占 폚 to prepare a masterbatch containing a high concentration of barium sulfate. The intrinsic viscosity was 0.680 dl / g and the melting point was 253 ° C.

{Preparation of surface tension reducing agent-containing masterbatch resin composition 9}

86.5 parts by weight of terephthalic acid and 37.1 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol were kneaded in a reaction system obtained by melting and storing an oligomer (mole ratio of glycol component / acid component of 1.15) obtained from 86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol in an esterification reaction tube. A slurry was continuously supplied while maintaining the temperature in the reaction system at 242 ° C. to effect esterification, and the resulting water was discharged through a rectifying column to terminate the slurry supply, and then the esterification reaction was continued for 1 hour, followed by ester The reaction was terminated. Subsequently, the obtained reaction product was transferred to a first polycondensation reaction tube, and then 320 ppm of trimethyl phosphate was added as a phosphorus compound, after 5 minutes, 600 ppm of magnesium acetate and 250 ppm of Vertec-C400 titanium catalyst of Johnson Massey were added and the reaction was allowed to proceed for 30 minutes. . Subsequently, canova wax (surface tension of 32 dyne / cm) dissolved at 100 degrees was added so as to be 4% by weight based on the completion of polymerization and finally obtained resin composition. The reaction was then transferred to a second polycondensation reaction system. Subsequently, the reaction system was depressurized to carry out a polycondensation reaction at a reaction temperature of 288 占 폚 to prepare a masterbatch containing a high concentration of barium sulfate. The intrinsic viscosity was 0.630 dl / g and the melting point was 251.5 ° C.

{Example 1}

Masterbatch 4 A mixture of 72.6 wt% of polyester resin and 27.4 wt% of polyester resin 1 was used as a resin composition for layer B, and 16.5 wt% of masterbatch-containing master batch 6, 4.0 wt% of masterbatch 7, and 14.0 wt% of copolymer resin 2 %, 45.5 weight% of polyester resin 1, and 20.0 weight% of surface tension-lowering agent-containing masterbatch resin composition 9 were used as layer A, and 34 weight% of copolymer resin composition 3 and 66 weight% of polyester resin 1 were mixed. This was made into layer C. The composition for layer B was dried for 6 hours in a hot air dryer at 165 ° C., and layer A and layer C were fed to an extruder heated to 285 ° C. through a vacuum vent twin screw extruder, and layer A and layer C were brought to 275 ° C. It was fed from a heated extruder and joined using a multi-manifold type T die so as to have an A / B / C = 1/36/1 layer configuration, and molded from the T die while maintaining a lamination state. Subsequently, the sheet was cooled and solidified in a cooling drum having a surface temperature of 25 ° C., then the unstretched film was heated to 82 ° C., stretched 3.4 times in the MD direction while irradiating infrared heaters from both the upper and lower sides, and cooled in a roll group at 28 ° C. did. Subsequently, both ends of the film were held by clips, guided by a tenter, preheated at 110 ° C, and stretched in a 3.5-fold TD direction while gradually raising the temperature from 115 ° C to 125 ° C. After that, heat-setting in four zones while raising the temperature from 210 ° C to 229 ° C in the tenter and maintaining it at 2229 ° C from the third zone of the heat setting, maintaining the heat treatment time at 2229 ° C for 12 seconds, and performing the relaxation treatment in the transverse direction. It carried out in stages, and provided the lateral relaxation rate of 5% in total, and then slowly cooled to room temperature to obtain the 320 micron biaxially stretched white reflective sheet. The structure and physical property of the obtained film are as Tables 1-2.

{Example 2}

A mixture of 90% by weight of the foamable nucleating agent masterbatch 5 and 10% by weight of the copolymer resin composition 3 was used as the resin composition for layer B, and 35.0% by weight of the masterbatch-containing masterbatch 6, 13.5% by weight of the masterbatch 7, poly 10 weight% of ester copolymer resin composition 2, 31.5 weight% of polyester copolymer resin composition 3, and 10 weight% of silicone masterbatch (Dow Corning, MB50-010, silicone surface tension 24 dyne / cm) which are surface tension reducing agents were mixed. As layer A, 10 weight% of copolymer resin composition 2 and 90 weight% of copolymer resin composition 3 were made into layer C. The composition for layer B was dried for 6 hours in a hot air dryer at 165 ° C., and layer A and layer C were fed to an extruder heated to 285 ° C. through a vacuum vent twin screw extruder, and layer A and layer C were brought to 275 ° C. It was fed from a heated extruder and joined using a multi-manifold tee die so as to have an A / B / C = 1/38/1 layered configuration and molded from the tee die while maintaining a lamination state. Subsequently, the sheet was cooled and solidified in a cooling drum having a surface temperature of 25 ° C., then the unstretched film was heated to 80 ° C., stretched 3.3 times in the MD direction while irradiating infrared heaters from both the upper and lower sides, and cooled in a roll group at 28 ° C. did. Subsequently, both ends of the film were held by clips, guided by a tenter, preheated at 105 ° C, and stretched in a 3.5-fold TD direction while gradually raising the temperature from 105 ° C to 110 ° C. After that, heat setting is carried out over four zones while raising the temperature from 170 ° C to 190 ° C in the tenter, and the heat treatment time at 190 ° C is maintained at 12.3 sec. Implement in stages to give a total lateral relaxation rate of 5% and tenter the winder while cutting with a knife on the film near the clip at the point where the film temperature reaches 140 ° C after the lateral relaxation starts. Compared with the lowering ratio by 0.5%, the longitudinal treatment was performed. Subsequently, it was cooled slowly to room temperature to obtain a 320 micron biaxially oriented white reflective sheet. The structure and physical property of the obtained film are as Tables 1-2.

{Example 3}

Master batch 4 A mixture of 65.0 wt% of polyester resin and 35.0 wt% of polyester resin 1 was used as a resin composition for layer B, and 22.0 wt% of masterbatch-containing master batch 6, 12.0 wt% of masterbatch 7 and 53.0 wt% of polyester resin for roughening %, Copolymer resin composition 2 10.0% by weight and the surface tension lowering agent-containing masterbatch resin composition 9 5% by weight was mixed as a layer A, 30.0% by weight of copolymer resin composition 3 and 70.0% by weight of polyester resin 1 are mixed One was made into layer C. The composition for layer B was dried for 6 hours in a hot air dryer at 165 ° C., and layer A and layer C were fed to an extruder heated to 285 ° C. through a vacuum vent twin screw extruder, and layer A and layer C were brought to 275 ° C. It was fed from a heated extruder and joined using a multi-manifold type T die so as to have an A / B / C = 1/36/1 layer configuration, and molded from the T die while maintaining a lamination state. Subsequently, the sheet was cooled and solidified in a cooling drum having a surface temperature of 25 ° C., then the unstretched film was heated to 82 ° C., stretched 3.4 times in the MD direction while irradiating infrared heaters from both the upper and lower sides, and cooled in a roll group at 28 ° C. did. The layer A was then subjected to corona treatment, and then the resin composition described below was applied onto layer A using a Mayer bar 4 so that the thickness after drying after tenter was 0.14 microns. Subsequently, both ends of the film were held with clips, guided by a tenter, dried and preheated at 110 ° C., and stretched in a 3.5-fold TD direction while gradually raising the temperature from 115 ° C. to 125 ° C. After that, heat-setting in four zones while raising the temperature from 210 ° C to 231 ° C in the tenter and maintaining it at 231 ° C from the fourth zone of the heat setting, maintaining the heat treatment time at 231 ° C for 6 seconds, and performing the relaxation treatment in the transverse direction. Implemented in stages to give a total of 5% transverse relaxation, 0.2% in the longitudinal direction while maintaining the temperature of the tenter exit zone at 130 ° C, exiting the tenter, and then cooled by hot air at 60 degrees. Next, it cooled slowly to room temperature and obtained the 320 micron biaxially stretched white reflecting sheet. The structure and physical property of the obtained film are as Tables 1-2.

        Content of coating resin composition: (parts by weight)

. Water: 77.3 parts by weight

. Isopropyl Alcohol: 5.0 parts by weight

. Acrylic Binder (Rohm & Haas, Primal 3208, 44% Solids): 7.3 parts by weight

. Melamine crosslinker (Cytec, Cymel 325, 80% solids): 4.0 parts by weight

. PE wax surface tension lowering agents (Michelman, Michem Emulsion 18325, 25% solids,

Surface tension 32 dyne / cm): 6.4 parts by weight

{Comparative Example 1}

After coating the coating liquid of the following composition on the surface of the reflective film (SKC, SY80, 188 microns) using a micro gravure roll to apply a coating thickness of 20 microns and dried and thermoset at 100 ℃ for 30 seconds.

    Anti-Sticking Layer Coating Resin Composition:

Methyl ethyl ketone: 32.6 wt%

Toluene: 32.6 wt%

Binder Resin (Aekyung A811): 29.5 wt%

-Polymerization initiator (thermal reaction curing agent, Aekyung DN980S): 3.0% by weight

General polymethylmethacrylate particles (Soken MR7HG) having an average diameter of 7 μm: 2.3 wt%

Subsequently, the following dry laminate adhesive was applied to a transparent biaxially stretched polyester film having a thickness of 125 microns so that the coating thickness was 3 microns, and dried at 80 ° C. for 30 seconds, and then laminated with a reflective film coated with the anti-sticking layer. And then aged in a 40 ℃ aging chamber for 3 days to prepare a reflective sheet.

     Adhesive composition for dry laminates:

-DIC dry laminate Dick Dry LX-903: 16 parts by weight,

-DIC KL-75 curing agent: 2 parts by weight

Ethyl acetate: 29.5 parts by weight

Mix and stir for 15 minutes to give a solid concentration of 20% by weight.

{Comparative Example 2}

A mixture of 72.6% by weight of masterbatch 4 and 27.4% by weight of polyester resin 1 was used as the resin composition for layer B, and 50.0% by weight of masterbatch 4 and 50.0% by weight of polyester resin 1 were used as layer A. A / B / A It was set as three layers of a structure. The composition for layers A and B was dried in a hot air dryer at 165 ° C. for 6 hours and then fed to an extruder heated to 285 ° C. using a multi-manifold type T die such that A / B / A = 1/36/1 layer configuration. By joining and molding from the tee die while maintaining the laminated state. Subsequently, the sheet was cooled and solidified in a cooling drum having a surface temperature of 25 ° C., then the unstretched film was heated to 82 ° C., stretched 3.4 times in the MD direction while irradiating infrared heaters from both the upper and lower sides, and cooled in a roll group at 28 ° C. did. Subsequently, both ends of the film were held by clips, guided by a tenter, preheated at 110 ° C, and stretched in a 3.5-fold TD direction while gradually raising the temperature from 115 ° C to 125 ° C. After that, heat-setting in four zones while raising the temperature from 210 ° C. to 229 ° C. in the tenter, and maintaining it at 229 ° C. from the third zone of heat setting, maintaining the heat treatment time at 229 ° C. for 12 seconds, and performing the relaxation treatment in the transverse direction. It carried out in stages, and provided the lateral relaxation rate of 5% in total, and then slowly cooled to room temperature to obtain the 320 micron biaxially stretched white reflective sheet. The structure and physical property of the obtained film are as Tables 1-2.

{Comparative Example 3}

It prepared like Example 1 except having set the composition of layer A to 40.0 weight% of resin composition 8, 30.0 weight% of polyester resin 1, and 30.0 weight% of copolymer resin composition 2. The structure and physical property of the obtained film are as Tables 1-2.

Laminated Reflective Sheet Input Material Characteristics Experiment number Floor composition Floor A Floor B Surface tension lowering agent thickness Added particles Melting point Bubble-forming nucleating agent Addition method weight% Kinds Average particle diameter Addition amount Kinds Average particle diameter Addition amount Example 1 A / B / C 8.4 acryl
acryl 12
20 4.95
1.2 252.8 Barium sulfate 0.78 29.0 Inside A floor 0.8 Example 2 A / B / C 8.4 acryl
acryl 12
20 10.5
4.0 222.9 Barium sulfate 0.78 45.0 Inside A floor 5.0 Example 3 A / B / C 8.4 acryl
acryl 12
20 6.0
3.6 253.0 Barium sulfate 0.78 26.0 Inside A floor
Inside coating layer 0.2
20.0 Comparative Example 1 Post Processing Paper
Bead / Reflective / Transparent 20 acryl 7 6.6 253.2 none - none none none Comparative Example 2 A / B / A 8.4 Barium sulfate 0.78 20.0 252.8 Barium sulfate 0.78 29.0 none none Comparative Example 3 A / B / C 8.4 Calcium carbonate 4.3 10.0 252.8 Barium sulfate 0.78 29.0 none none

1) Layer A thickness: When only a plurality of layer A, the thickness of the light guide plate side measured

2) The surface tension lowering agent is based on the weight of the layer A resin composition when added inside the layer A, and on the basis of the weight of the coating on the layer A after drying, if added to the material applied on the layer A.

Properties under the property of the reflective sheet Experiment number reflectivity Ra Rz Sticking degree Reflector withdrawal degree Economics Overall assessment Example 1 101 1.3 11.2 ○ ○ ○ ○ Example 2 100.5 1.2 9.5 ○ △ ○ ○ Example 3 101.2 1.7 13.4 ○ ○ ○ ◎ Comparative Example 1 99.2 1.3 4.5 ○ ○ × × Comparative Example 2 102 0.07 0.4 × ○ × × Comparative Example 3 99.8 0.6 4.8 × ○ ◎ ×

1) Economic and comprehensive evaluation: ◎ Very good, ○ Excellent, ×: Poor or uneconomic

As can be seen in Tables 1 and 2 above, at least one layer includes a layer having excellent reflectivity through in-line coextrusion during the film manufacturing process and at the same time separates the beads by post-processing by roughening the surface roughness of at least one layer. It was confirmed that a ring-shaped defect due to sticking when contacted with the light guide plate without the coating process did not appear on the liquid crystal display, and it was possible to reduce the cost by omitting post processing.

By simplifying the manufacturing process, it is possible to provide a reflective sheet for a liquid crystal backlight unit which is cheaper than the conventional manufacturing process and has good performance.

Claims (5)

In a laminated sheet made of polyethylene terephthalate as a main component and manufactured by a coextrusion method composed of at least two layers, the surface roughness of at least one layer (A) has an arithmetic mean roughness Ra of at least 0.8 micron and a ten point average. A roughened layer having a roughness Rz of 5 microns or more, at least one of the other layers B contains a bubble-forming nucleating agent that performs a light reflecting function, and the reflecting sheet has a reflectance of 93% or more. White Polyester Reflective Sheet for Unit 2. The white polyester reflective sheet for backlight unit according to claim 1, wherein particles having an average particle diameter of 5 microns or more are contained in the layer A in an amount of 1% by weight or more based on the resin composition of the layer B. 3. 10-65 weight% of bubble-forming nucleating agents are contained in B-layer with respect to the B-layer resin composition weight, The white polyester reflective sheet for backlight units characterized by the above-mentioned. The white polyester reflective sheet for a backlight unit according to claim 1, wherein the compound having a surface tension of 36 dyne / cm 2 or less is contained in 0.003% by weight or more. The white polyester reflective sheet for a backlight unit according to claim 1, wherein a composition containing 0.1 wt% or more of a compound having a surface tension of 36 dyne / cm 2 or less is applied to the layer A.