KR20170059139A - Polyester film having improved modulus - Google Patents

Polyester film having improved modulus Download PDF

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KR20170059139A
KR20170059139A KR1020150163055A KR20150163055A KR20170059139A KR 20170059139 A KR20170059139 A KR 20170059139A KR 1020150163055 A KR1020150163055 A KR 1020150163055A KR 20150163055 A KR20150163055 A KR 20150163055A KR 20170059139 A KR20170059139 A KR 20170059139A
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polyester film
modulus
film
inorganic particles
sheet
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KR1020150163055A
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Korean (ko)
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KR101750922B1 (en
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곽기열
이중규
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에스케이씨 주식회사
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B29C47/0021—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Organic Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Medicinal Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Nonlinear Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Materials Engineering (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Abstract

The present invention relates to a stretched film comprising a polyester resin in which inorganic particles having an average particle diameter of 5-150 nm are dispersed. The polyester film has a difference of 0-0.5 between a ratio (M1RT/M160) of a modulus (M1RT) at room temperature and a modulus (M160) at 60C in a first direction and a ratio (M2RT/M260) of a modulus (M2RT) at room temperature and a modulus (M260) at 60C in a second direction with respect to the first direction and the second direction, which are perpendicular in a plane. In the polyester film, change of the modulus at 60C compared to the room temperature can uniformly occur in a machine direction (MD) and a tender direction (TD). Therefore, the polyester film can prevent a wave phenomenon by preventing deformation by heat when the polyester film is applied as an optical sheet for a backlight unit.

Description

[0001] POLYESTER FILM HAVING IMPROVED MODULUS [0002]

The present invention relates to a polyester film having improved heat resistance, and more specifically, to a polyester film having improved heat resistance by introducing nano-inorganic particles into a polyester resin for use in a backlight unit (BLU).

As an optical sheet constituting a backlight unit (BLU) of a liquid crystal display (LCD), a diffusion sheet, a prism sheet and a reflective sheet are typical examples. A polyester film is mainly used as the base film.

Korean Laid-Open Patent Publication No. 2012-38650 discloses a biaxially oriented polyester film base material which does not contain inorganic particles, a polyurethane resin in which silica particles or alumina-silica composite oxide particles having an average particle size of 80 to 140 nm are dispersed on one surface or both surfaces To form a primer layer, thereby improving adhesion to a base material and improving optical properties.

On the other hand, the backlight unit mounted on the LCD has been slimmed up according to the slim trend of liquid crystal display devices in recent years. As the demand for high brightness characteristics increases, the heat received by the optical sheets tends to increase. It is required to improve the heat resistance characteristics of the polyester film.

In particular, the optical sheets attached to the high-temperature backlight unit are deformed with time to cause a wave phenomenon, thereby deteriorating optical quality.

In order to solve this problem, there has been an attempt to control the heat shrinkage rate of the film by adjusting the film forming process. However, such conventional attempts have not completely overcome the above problems.

Accordingly, the present inventors have found that the above problems can be solved by controlling the modulus of the polyester film, and the present invention has been completed.

Korean Patent Publication No. 2012-38650 (Apr. 24, 2012)

The present invention aims to provide a polyester film with improved modulus and a method for producing the same. The present invention also provides an optical sheet comprising the polyester film. The present invention also provides a backlight unit including the optical sheet.

The present invention relates to a stretched polyester film comprising a polyester resin in which inorganic particles having an average particle diameter of 5 to 150 nm are dispersed, wherein the stretched polyester film is a stretched polyester film having, in a first direction and a second direction perpendicular to each other in a plane, (M1 RT / M1 60 ) of the modulus (M1 RT ) at 60 ° C to the modulus (M1 60 ) at 60 ° C of the modulus (M2 RT ) of the difference between the percentage of the M2 60) (M2 RT / M2 60) 0 to 0.5, providing a polyester film.

In addition, the present invention relates to (1) Melt-extruding, molding and cooling a polyester resin in which inorganic particles of 5 to 150 nm are dispersed to produce a sheet; And (2) stretching the sheet in at least one of the machine direction (MD) and the tenter direction (TD).

The present invention also provides an optical sheet comprising the polyester film.

The present invention also provides a backlight unit including a light guide plate, a light source disposed adjacent to the light guide plate, and the optical sheet disposed on one side or both sides of the light guide plate.

The polyester film can improve the crystal properties by introducing nanosilica particles into the polyester resin. Accordingly, the polyester film can exhibit a modulus change at 60 ° C relative to the normal temperature uniformly in the machine direction (MD) and the tenter direction (TD), thereby preventing thermal deformation when applied to the backlight unit as an optical sheet It is possible to prevent a wave phenomenon.

1 is a schematic view of a polyester film according to an example of the present invention.
FIGS. 2A and 2B are photographs showing the lifting phenomenon by heat after attaching the polyester film produced in Example 1 and Comparative Example 1 to the light guide plate. FIG.
3A to 3D show cross-sectional views of optical sheets according to the present invention.
4 is a cross-sectional view of a backlight unit according to an example of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings. It is to be noted that the attached drawings can be illustrated with exaggerated size, thickness, etc. in order to facilitate understanding of the invention. In addition, an easily conceivable configuration can be omitted from the drawings for a clear understanding of the invention.

In the following detailed description, when each film, panel or layer is described as being formed "on" or "under" of each film, panel or layer, on "and" under "include all that is formed either" directly "or" indirectly "through" other elements ".

Hereinafter, the characteristics and constitution of the polyester film will be described in detail with reference to FIG.

The polyester film 100 is a stretched film including a polyester resin 110 in which inorganic particles 115 having an average particle diameter of 5 to 150 nm are dispersed.

The inorganic particles 115 may include silica particles. The average particle size of the inorganic particles may be specifically from 5 to 100 nm. More specifically, the inorganic particles may be silica particles having an average particle diameter of 10 to 80 nm, 10 to 50 nm, or 10 to 30 nm.

The inorganic particles may be included in an amount of 10 to 1000 ppm based on the total weight of the film. More specifically, the content of the inorganic particles may be from 15 to 800 ppm, from 20 to 700 ppm, or from 20 to 500 ppm.

The inorganic particles are dispersed in the polyester resin contained in the polyester film. More specifically, the inorganic particles may be dispersed in a polyester resin by dispersing in a monomer solution used for polymerization of the polyester resin and then polymerizing.

At this time, the inorganic particles such as the nano-sized silica act as a nucleating agent in the polyester resin, thereby inducing crystal properties in which crystals of the same size are relatively uniformly dispersed as compared with the case where such inorganic particles are not present, It is expected that the balance of the modulus of the film with respect to the MD and TD directions at 60 DEG C can be controlled.

The polyester film has a first direction and a second direction perpendicular to each other in a plane. The first direction and the second direction may be respectively a mechanical direction (MD) and a tentor direction (TD) at the time of film production. As another example, the first direction and the second direction may be a longitudinal direction (LD) and a transverse direction (TD), respectively.

The polyester film may be uniaxially or biaxially stretched.

For example, the polyester film may be a uniaxially stretched film only in the tenter direction (TD). At this time, the stretching ratio in the tenter direction (TD) may be 2.0 to 4.5 times, more specifically 2.5 to 4.3 times.

Preferably, the polyester film may be a biaxially stretched film with respect to the machine direction (MD) and the tenter direction (TD). In this case, the stretching ratio with respect to the machine direction (MD) may be 2.5 to 3.8 times, more specifically 2.8 to 3.5 times. In addition, the stretching ratio in the tenter direction (TD) may be 2.5 to 4.5 times, more specifically 2.5 to 4.3 times.

The polyester film at room temperature for modulus (M1 60) ratio (M1 RT / M1 60), and said second direction for at 60 ℃ of the modulus (M1 RT) at room temperature with respect to the first direction modulus ratio for modulus (M2 60) in 60 ℃ of (M2 RT) (RT M2 / M2 60) difference between the (i.e. │M1 RT / M1 60 - RT value of M2 / M2 │ 60) is 0 to 0.5 to be.

More specifically, the difference between the first ratio of the first direction (M1 RT / M1 60) and the ratio of the second direction (M2 RT / M2 60) may be from 0 to 0.3.

The polyester film may have a modulus (M1 RT ) of 280 kgf / mm < 2 > at room temperature in the first direction. Specifically, the modulus (M1 RT ) at room temperature in the first direction may be not less than 300 kgf / mm 2, not less than 330 kgf / mm 2, or not less than 350 kgf / mm 2.

The polyester film may be greater than or equal to the modulus (M1 60) is 120 ㎏f / ㎟ at 60 ℃ to the first direction. Specifically, the modulus (M1 60) in 60 ℃ to the first direction may be at least 150 ㎏f / ㎟ or more, 180 ㎏f / ㎟ or more, or 200 ㎏f / ㎟.

The polyester film may have a modulus (M2 RT ) of 280 kgf / mm < 2 > at room temperature in the second direction. Specifically, the modulus (M2 RT ) at room temperature in the second direction may be at least 300 kgf / mm 2, at least 330 kgf / mm 2, or at least 350 kgf / mm 2.

The polyester film may have a modulus (M2 60 ) at 60 캜 for the second direction of 120 kgf / mm 2 or more. Specifically, the modulus (M2 60 ) at 60 ° C for the second direction may be at least 150 kgf / mm 2, at least 180 kgf / mm 2, or at least 200 kgf / mm 2.

Preferably, the first direction and the second direction may be a machine direction (MD) and a tenter direction (TD) at the time of film production, respectively.

The polyester film may have a crystallinity of 45 to 60%. More specifically, the degree of crystallinity may be from 45 to 55%, or from 48 to 52%.

The polyester resin may have a crystal size of 40 to 60 angstroms. More specifically, the crystal size may be between 44 and 55 ANGSTROM.

The polyester film may have a transmittance of 86 to 95% for a wavelength of 550 nm. Specifically, the transmittance to the 550 nm wavelength may be 88 to 94%.

The polyester film may have a haze of 0.2 to 2.5%. More specifically, the haze may be 0.3 to 2.3%.

The polyester film as described above can improve the crystal properties by introducing nanosilica particles into the polyester resin.

For example, in a polyester film such as general polyethylene terephthalate (PET), the molecular shape (conformation) is changed by goush, trans, etc. due to heat. In the polyester film, inorganic particles such as nano- So that the effect on the back bone can be minimized even if the shape changes.

Accordingly, the polyester film can exhibit a modulus change at 60 ° C versus room temperature uniformly with respect to the machine direction (MD) and the tenter direction (TD), so that when applied as an optical sheet to a backlight unit, It is possible to prevent a wave phenomenon.

The method for producing the polyester film

(1) a step of producing a sheet by melt extrusion, molding and cooling a polyester resin in which inorganic particles having an average particle diameter of 5 to 150 nm are dispersed; And

(2) stretching the sheet in at least one of the machine direction (MD) and the tenter direction (TD).

The step (1) A step of melt-extruding, molding and cooling a polyester resin in which inorganic particles of 5 to 150 nm are dispersed to produce a sheet.

The polyester resin in which the inorganic particles are dispersed may be obtained by polymerizing a diol compound and a dicarboxylic acid compound in a solution in which the inorganic particles are dispersed. As a specific example, this step can be performed by preparing a diol solution in which the inorganic particles are dispersed, adding a dicarboxylic acid compound to the diol solution, and polymerizing.

The more preferable average particle diameter and specific kind of the inorganic particles are as exemplified in the polyester film.

Specific examples of the diol compound include ethylene glycol (EG), spiroglycol (SPG), 1,4-cyclohexanedimethanol (CHDM), 1,3-propanediol, Diol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2- 1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3- 1,5-pentanediol, and mixtures thereof.

Specific examples of the dicarboxylic acid compound include aromatic dicarboxylic acids such as terephthalic acid, dimethyl terephthalate, isophthalic acid, naphthalene dicarboxylic acid, and orthophthalic acid aromatic dicarboxylic acids; Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; Alicyclic dicarboxylic acids; Esters thereof; And mixtures thereof.

In the polyester resin, the diol compound and the dicarboxylic acid compound may be synthesized by transesterification and polymerization. An antimony catalyst may be used as the catalyst.

The polyester resin may be a homopolyester resin. Alternatively, the polyester resin may be a copolymerized polyester resin. As a specific example, the polyester resin may be a monopolymerized PET resin or a copolymerized PET resin.

Then, the polyester resin in which the inorganic particles are dispersed is melt-extruded, molded and cooled to produce a sheet. Such melt extrusion, molding and cooling can be carried out according to a conventional production process of a polyester film.

Step (2) is a step of stretching the sheet in the machine direction (MD) and the tenter direction (TD).

The non-oriented sheet can be stretched only in one of the first direction and the second direction. According to one example, the sheet can be stretched only in the second direction. Specifically, the sheet can be stretched only in the tenter direction. At this time, concrete examples of the stretching ratios in the second direction are as described above.

Or the sheet may be stretched both in the first direction and in the second direction perpendicular to each other in the plane. At this time, the sheet can be stretched by a biaxial sequential stretching method or a biaxial simultaneous stretching method. The first direction may be a mechanical direction (MD), and the second direction may be a tenter direction (TD). Here, concrete examples of the stretching ratios in the first and second directions are as described above.

According to one example, the sheet may be stretched at a higher stretch ratio with respect to the second direction than with the first direction. Specifically, the sheet is stretched at a higher stretch ratio with respect to the tenter direction than in the machine direction.

The optical sheet includes the polyester film described above.

That is, the optical sheet may be the same as the polyester film. Alternatively, the optical sheet may further have additional components in addition to the polyester film described above.

The optical sheet may be a diffusion sheet, a prism sheet, or a reflective sheet.

Referring to FIG. 3A, when the optical sheet is a diffusion sheet, the diffusion sheet 101 may have diffusion beads 140 dispersed on one side or both sides of the polyester film 100. At this time, a primer layer 120 may be further provided between the polyester film and the diffusion beads 140.

Referring to FIG. 3B, when the optical sheet is a prism sheet, the prism sheet 102 may include a prism lens pattern 150 formed on one side or both sides of the polyester film 100. At this time, a primer layer 130 may be further provided between the polyester film and the prism lens pattern 150.

Referring to FIG. 3C, the prism sheet 103 may be a prism sheet having a prism lens pattern on one side of the polyester film 100 and a diffusion bead layer on the other side to improve brightness .

Referring to FIG. 3D, when the optical sheet is a reflective sheet, the reflective sheet 104 may include a reflective layer 160 formed on one side or both sides of the polyester film 100. Alternatively, the reflective sheet 140 may be made of only the polyester film 100.

4, the backlight unit 10 includes a light guide plate 200, a light source 300 disposed adjacent to the light guide plate 200, and a light source 300 disposed on one side or both sides of the light guide plate 200, (103, 104).

The optical sheet may be a diffusion sheet, a prism sheet, or a reflective sheet.

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Comparative Example 1

Step 1) Production of polyester resin

Terephthalic acid (TPA) or dimethyl terephthalate (DMT) as a dicarboxylic acid was added to the ethylene glycol solution at the same molar ratio as ethylene glycol to prepare a mixed monomer solution. An additive such as an antimony catalyst was added to the mixed monomer solution and polymerized under the general polyester polymerization conditions. As a result, a polyester resin was prepared and processed into a chip form.

Step 2) Production of polyester film

The chip prepared in the step 1) of the above Comparative Example 1 was put into an extruder and melt-extruded at 280 ° C and formed into a sheet and cooled. The obtained sheet was stretched 3.2 times in the machine direction (MD), and then stretched 3.6 times in the tenter direction (TD). The stretched film was heat set at 238 占 폚. As a result, a polyester film having a thickness of 60 탆 was obtained.

Example 1

Step 1) Production of polyester resin in which nano silica is dispersed

To the ethylene glycol solution, nanosilica particles having an average particle diameter of about 12 nm were added and dispersed to prepare a dispersion solution. Terephthalic acid (TPA) or dimethyl terephthalate (DMT) as a dicarboxylic acid was added to the nanosilica-dispersed diol solution at the same molar ratio as ethylene glycol to prepare a mixed monomer solution. An additive such as an antimony catalyst was added to the mixed monomer solution and polymerized under the general polyester polymerization conditions. As a result, a polyester resin with nanosilica dispersed therein was prepared and processed into a chip form.

Step 2) Production of polyester film containing nanosilica

93.5 parts by weight of the polyester resin chip prepared in the step 1) of the Comparative Example 1 and 6.5 parts by weight of the polyester resin chip prepared in the step 1) of Example 1 were put into an extruder and blended. The blend resin in the extruder was melt-extruded at 280 占 폚 and molded and cooled into a sheet. The obtained sheet was stretched 3.2 times in the machine direction (MD), and then stretched 3.6 times in the tenter direction (TD). The stretched film was heat set at 238 占 폚. As a result, a polyester film having a thickness of 60 탆 and containing 20 ppm of nano-silica particles having an average particle diameter of about 12 nm was obtained.

Examples 2 and 3

The same procedure as in Example 1 was repeated except that a 60 占 퐉 -thick polyester film containing nanosilica particles having an average particle size of about 12 nm in an amount of 55 ppm and 300 ppm was prepared by changing the addition amount of the nanosilica particles in step 1) .

Test Example 1: Optical property measurement

The haze at room temperature and the transmittance to the wavelength of 550 nm were measured for each of the films prepared in the Examples and Comparative Examples using a hazemeter. The results are summarized in Table 1 below.

Test Example 2: Measurement of crystal properties

The crystallinity and the crystal size of each of the films prepared in Examples and Comparative Examples were measured by XRD. The results are summarized in Table 1 below.

Test Example 3: Modulus measurement

Modulus was measured for each of the films prepared in the Examples and Comparative Examples using a universal testing machine (UTM). Specifically, the modulus at room temperature and 60 占 폚 was measured for the machine direction (MD) and the tenter direction (TD) of the film, respectively.

The results are summarized in Table 2 below.

Test Example 4: Backlight unit mounting test

Each of the films prepared in Example 1 and Comparative Example 1 was placed on the top and bottom surfaces of a light guide plate having a size of 14 inches. The light guide plate was operated to maintain the surface temperature at about 60 DEG C and then maintained for 24 hours. Then, the wave state of the polyester film adhering to the surface of the light guide plate was observed. The results are shown in Figs. 2A and 2B.

division Nano silica
Amount added (ppm) Optical characteristic Crystal property Permeability (%) Haze (%) Crystallinity (%) Crystal size (A) Comparative Example 1 0 89.1 0.55 49.4 44 Example 1 20 89.2 0.25 58.5 45 Example 2 55 89.2 0.15 51 51 Example 3 300 89.1 0.35 51 45

division Room temperature modulus
(Kgf / mm < 2 & 60 ℃ modulus
(Kgf / mm < 2 & Room Temperature Modulus /
60 ℃ modulus MD TD MD TD MD TD Comparative Example 1 260 310 180 715 1.4 0.4 Example 1 305 355 205 225 1.5 1.6 Example 2 380 335 230 230 1.7 1.5 Example 3 288 350 125 185 2.3 1.9

As shown in Table 1, the polyester films of Examples 1 to 3 according to the present invention were not only higher in crystallinity than the film of Comparative Example 1, but also had optical properties equal to or greater than those of Comparative Example 1.

Further, as shown in Table 2, the polyester films of Examples 1 to 3 according to the present invention had a modulus at 60 DEG C that was substantially uniformly changed in the machine direction (MD) and the tenter direction (TD) On the other hand, in the polyester film of Comparative Example 1, the modulus at 60 ° C as compared with the room temperature showed a large rate of change with respect to the machine direction and the tenter direction.

As a result, as shown in FIGS. 2A and 2B, the polyester film according to the embodiment of the present invention maintained flat characteristics even when attached to a light guide plate having a surface temperature of 60 ° C., whereas the polyester film according to the comparative example had a It was observed that a wave occurred.

10: backlight unit, 100: polyester film,
101: diffusion sheet, 102, 103: prism sheet,
104: reflective sheet, 110: polyester resin,
115: inorganic particles, 120, 130: primer layer,
140: diffusion beads, 150: prism lens pattern,
160: reflective layer, 200: light guide plate,
300: light source, 500: direction of light emission.

Claims (13)

A stretched polyester film comprising a polyester resin in which inorganic particles having an average particle size of 5 to 150 nm are dispersed,
With respect to the first direction and the second direction perpendicular to each other in the plane,
Wherein the ratio of the modulus (M1 60) in 60 ℃ of the modulus (M1 RT) at room temperature for a first direction (M1 RT / M1 60), and
Wherein the difference between the modulus (M2 RT / M2 60 ) of the modulus (M2 RT ) at 60 C and the modulus (M2 60 ) at room temperature in the second direction is 0 to 0.5.
The method according to claim 1,
Wherein the inorganic particles comprise silica particles.
3. The method of claim 2,
Wherein the polyester film comprises the inorganic particles in an amount of 10 to 1000 ppm based on the total weight of the film.
The method according to claim 1,
Wherein the first direction and the second direction are a machine direction (MD) and a tenter direction (TD)
The polyester film
Stretched to 2.5 to 3.8 times with respect to the first direction,
Wherein the polyester film is stretched by 2.5 to 4.5 times with respect to the second direction.
The method according to claim 1,
Wherein the first direction is a machine direction (MD) at the time of film production, the modulus (M1 RT ) at room temperature in the first direction is 280 kgf / mm < 2 > (M1 60) is 120 ㎏f / ㎟ or more, a polyester film.
The method according to claim 1,
Wherein the second direction is the tenter direction (TD) at the time of producing the film, the modulus (M2 RT ) at room temperature in the second direction is 280 kgf / mm 2 or more, and the modulus (M2 60) is 120 ㎏f / ㎟ or more, a polyester film.
The method according to claim 1,
Wherein the polyester film has a crystallinity of 45 to 60%.
The method according to claim 1,
Wherein the polyester resin has a crystal size of 40 to 60 Angstroms.
(1) a step of producing a sheet by melt extrusion, molding and cooling a polyester resin in which inorganic particles having an average particle diameter of 5 to 150 nm are dispersed; And
(2) stretching the sheet in at least one of the machine direction (MD) and the tenter direction (TD).
10. The method of claim 9,
Wherein the inorganic particles comprise silica particles.
10. The method of claim 9,
In the step (1), the polyester resin is obtained by polymerizing a diol compound and a dicarboxylic acid compound in a solution in which the inorganic particles are dispersed.
An optical sheet comprising the polyester film of claim 1.
Light guide plate,
A light source disposed adjacent to the light guide plate, and
The backlight unit according to claim 12, which is disposed on one side or both sides of the light guide plate.
KR1020150163055A 2015-11-20 2015-11-20 Polyester film having improved modulus KR101750922B1 (en)

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KR20200053233A (en) * 2018-11-08 2020-05-18 에스케이씨 주식회사 Polyester protective film for flexible display device

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CN1249133C (en) 2001-11-02 2006-04-05 Skc株式会社 Heat-shrinkable polyester film
JP2004029648A (en) 2002-06-28 2004-01-29 Takiron Co Ltd Light diffusing sheet
JP2005272657A (en) * 2004-03-25 2005-10-06 Kanebo Ltd Manufacturing method of polyester resin and molded article made of the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20200053233A (en) * 2018-11-08 2020-05-18 에스케이씨 주식회사 Polyester protective film for flexible display device
KR20210058787A (en) * 2018-11-08 2021-05-24 에스케이씨 주식회사 Polyester protective film for flexible display device

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