KR102092879B1 - Polarizing plate protective film and manufacturing method thereof - Google Patents

Abstract

The embodiment relates to a protective film for a polarizing plate and a method for manufacturing the same, and more specifically, a polarization mura is not generated due to a difference in orientation angle between a central portion and an end portion, and a protective film for a polarizing plate having excellent mechanical properties and a manufacturing method thereof will be.

Description

Protective film for polarizing plate and manufacturing method therefor {POLARIZING PLATE PROTECTIVE FILM AND MANUFACTURING METHOD THEREOF}

The embodiment relates to a protective film for a polarizing plate and a method for manufacturing the same, and more specifically, a polarization mura is not generated due to a difference in orientation angle between a central portion and an end portion, and a protective film for a polarizing plate having excellent mechanical properties and a manufacturing method thereof will be.

Generally, a protective film for protecting a polarizer made of polyvinyl alcohol is attached to a polarizing plate as a protective film for one or both sides of the polarizer. A polyethylene terephthalate (PET) film was used as the protective film for the polarizing plate, but the polyethylene terephthalate film was difficult to apply as a protective film for the polarizing plate because anisotropy was largely generated depending on the stretching ratio.

As an alternative to this, triacetylcellulose (TAC) films having properties such as high light transmittance, optical isotropy, and defect-free surface were widely applied. Specifically, Korean Patent Registration No. 10-1222363 discloses a polarizing plate curling correction film whose main component is a cellulose ester, an in-plane retardation of 30 to 300 nm, and a thickness direction retardation of 80 to 400 nm.

However, the triacetylcellulose film has the disadvantages of high price, diverse supply, and susceptibility to moisture. Accordingly, protective films of various materials that can replace the triacetylcellulose film have been developed, for example, a method of using alone or mixed with cycloolefin polymer (COP), acrylic and polyester film, etc. It was proposed.

Republic of Korea Registered Patent No. 10-1222363

However, the acrylic film has a low processability due to the brittle property, and in order to overcome this, when using a copolymer copolymerized with other monomers, there is a problem in that the manufacturing cost increases.

Accordingly, an object of the embodiment is to provide a protective film for a polarizing plate having excellent mechanical properties and a method for manufacturing the polarizing mura, which does not generate polarization mura by minimizing the difference in the alignment angle between the center and the end while including PET.

One embodiment to achieve the above object,

(1) preparing a non-stretched sheet by melt-extruding a polyester resin composition;

(2) preheating the unstretched sheet and stretching less than 2 times in the longitudinal direction while applying heat at 750 ° C to 850 ° C using a far infrared heater (R / H);

(3) stretching the sheet stretched in the longitudinal direction at least three times in the width direction to produce a stretched film; And

(4) heat-setting the stretched film to prepare a protective film; includes,

The protective film provides a method of manufacturing a protective film for a polarizing plate, wherein the in-plane retardation (Re) is 6,000 nm or more.

Other embodiments,

The longitudinal and transverse modulus are 250kgf / mm ² or more and 500kgf / mm ² or more, and the tensile strength in the longitudinal and transverse direction is 9kgf / mm ² or more and 30kgf / mm ² or more, respectively, and elongation at break in the longitudinal and transverse directions Provides a protective film for a polarizing plate, wherein each is 30% or more and 60% or more, an in-plane retardation (Re) is 6,000 nm or more, and no polarization mura occurs.

The method of manufacturing a protective film for a polarizing plate according to an embodiment can prepare a protective film for a polarizing plate having excellent optical properties and mechanical properties by appropriately adjusting the stretching ratio in the longitudinal and transverse directions, and the process conditions during stretching.

In addition, the protective film for the polarizing plate according to the embodiment has a small difference in the orientation angle between the central portion and the end portion and a large in-plane retardation, so that polarization mura does not occur and has excellent optical properties, and the elongation at break and tensile strength in the width and length directions are appropriate. It is maintained and has excellent mechanical properties.

1 is a view showing a method of manufacturing a protective film for a polarizing plate according to an embodiment.
FIG. 2 is an enlarged view of part (A) of FIG. 1.
3 is a view showing a method of manufacturing a protective film for a polarizing plate according to an embodiment.
4 is a schematic view showing an alignment angle measurement system used in a test example.
Fig. 5 is a schematic diagram showing a film mounted on a display as a device used to confirm the polarization mura of the test example.

Hereinafter, the invention will be described in detail through embodiments. The embodiments are not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

In the present specification, when each film or layer is described as being formed on "on" or "under" of each film or layer, "on" and "under" “A” includes both formed “directly” or “indirectly”. In addition, the criteria for the top / bottom of each component will be described based on the drawings. The size of each component in the drawings may be exaggerated for explanation, and does not mean the size actually applied. In addition, the same reference numerals refer to the same components throughout the specification.

“Including” in the present specification means that other components may be further included unless otherwise specified.

In addition, it should be understood that all numbers and expressions indicative of the amount of ingredients, reaction conditions, and the like described in this specification are modified in all cases with the term "about" unless otherwise specified.

Manufacturing method of protective film for polarizing plate

Method of manufacturing a protective film for a polarizing plate according to an embodiment

(1) preparing a non-stretched sheet by melt-extruding a polyester resin composition;

(2) preheating the unstretched sheet and stretching less than 2 times in the longitudinal direction while applying heat at 750 ° C to 850 ° C using a far infrared heater (R / H);

(3) preparing a stretched film by stretching the sheet stretched in the longitudinal direction at least three times in the width direction; And

(4) heat-setting the stretched film to prepare a protective film; includes,

The protective film has an in-plane retardation (Re) of 6,000 nm or more.

Step (1)

In this step, the polyester resin composition is melt-extruded to prepare an unstretched sheet.

The polyester resin composition may be formed by polymerizing a diol component and a dicarboxylic acid component after transesterification. Specifically, the polyester resin composition may include polyethylene terephthalate. More specifically, the polyester resin composition may include 75 mol% or more, 80 mol% or more, 90 mol% or more, or 95 mol% or more of ethylene terephthalate as a monomer unit. When the polyester resin composition comprises 75 mol% or more of ethylene terephthalate as a monomer unit, the sheet prepared from the polyester resin composition has crystallinity, and the crystal surface of the sheet may have orientation in one direction.

The melt extrusion may be performed at a temperature of Tm + 10 ° C to Tm + 70 ° C. Specifically, the melt extrusion may be performed at a temperature of Tm + 20 ° C to Tm + 60 ° C, or Tm + 30 ° C to Tm + 60 ° C. At this time, the Tm is the melting temperature of the polyester resin composition. When melt extrusion is performed within the above-mentioned temperature range, melting of the resin is smooth and the viscosity of the extrudate is properly maintained.

Referring to FIG. 1, through the T-die 10, the polyester resin composition is melted and discharged, and the resin discharged on the casting roll 20 is coated to form the unstretched sheet 100. The unstretched sheet 100 may be formed by being cooled by the casting roll 20.

The surface temperature of the casting roll 20 is Tg-100 ° C to Tg + 20 ° C, Tg-80 ° C to Tg + 20 ° C, Tg-70 ° C to Tg + 20 ° C, Tg-70 ° C to Tg + 10 ° C, Or Tg-70 ° C to Tg-5 ° C. At this time, the Tg is the glass transition temperature of the polyester resin composition.

Step (2)

In this step, the unstretched sheet is preheated and stretched less than 2 times in the longitudinal direction while heating at 750 ° C to 850 ° C using a far infrared heater (R / H).

The preheating may be performed at 50 ° C to 110 ° C. Specifically, the preheating may be performed at 50 ° C to 100 ° C, 50 ° C to 90 ° C, 60 ° C to 90 ° C, or 70 ° C to 90 ° C.

The longitudinal stretching may be performed using two rollers spaced from 200 mm to 500 mm. Specifically, the longitudinal stretching may be performed by a circumferential speed difference between two rollers spaced apart (a) between 200 mm to 500 mm, 300 mm to 500 mm, 200 mm to 400 mm, or 400 mm to 500 mm (see FIG. 2). The speed difference can be adjusted according to the stretching ratio in the longitudinal direction.

The temperature difference between the two rollers may be 50 ° C to 60 ° C. Specifically, the temperature difference between the two rollers may be 52 ° C to 60 ° C, 52 ° C to 58 ° C, or 53 ° C to 57 ° C.

Referring to FIG. 1, the unstretched sheet 101 is in the longitudinal direction by the circumferential speed difference between the first stretch roll 31 and the second stretch roll 32 while applying heat using far-infrared heaters 41 and 42. Can be stretched. Specifically, the temperature of the first stretch roll is 70 ° C to 95 ° C, 80 ° C to 95 ° C, or 82 ° C to 93 ° C, and the temperature of the second stretch roll is 15 ° C to 45 ° C, 20 ° C to 45 ° C , 20 ℃ to 40 ℃, or 23 ℃ to 35 ℃.

The far-infrared heater is spaced from 40 mm to 150 mm from the unstretched sheet (c), and may be located on both sides of the top and bottom of the unstretched sheet (see FIGS. 1 and 2). Specifically, the far infrared heater is spaced from 70 mm to 150 mm, 70 mm to 100 mm, or 100 mm to 150 mm from the unstretched sheet, and may be located on both sides of the top and bottom of the unstretched sheet.

The heat treatment length (b) may be 70% or more based on the total distance (a) between the two rollers (see FIG. 2). Specifically, the heat treatment length may be 80% or more, or 80% to 95%, based on the total distance between the two rollers.

The temperature of the far infrared heater 42 located on the upper portion of the unstretched sheet is 20 ° C to 50 ° C, 30 ° C to 50 ° C, or 30 ° C to 40 ° C than the temperature of the far infrared heater 41 located on the lower part of the unstretched sheet. Can be high

The temperature of the far infrared heater located on the top of the unstretched sheet is 650 ° C to 850 ° C, 700 ° C to 840 ° C, 750 ° C to 850 ° C, or 800 ° C to 840 ° C, and the far infrared heater located below the unstretched sheet The temperature may be 650 ° C to 800 ° C, 700 ° C to 800 ° C, 700 ° C to 790 ° C, or 750 ° C to 790 ° C.

The far infrared heater may have a total output of 20kW to 50kW. Specifically, each of the far-infrared heaters located at the top and bottom of the unstretched sheet has an output of 5 kW to 20 kW, or 10 kW to 20 kW, so that the total output is 30 kW to 50 kW, 35 kW to 50 kW, or 20 kW to 45 kW. To 5 can be used.

In this step, it may be stretched from 1.4 to 1.8 times in the longitudinal direction. Specifically, in this step, the lengthwise stretching may be 1.45 times to 1.8 times, 1.5 times to 1.6 times, or 1.55 times to 1.6 times.

In this step, the unstretched sheet may be preheated while moving at a speed of 20 m / min to 100 m / min and stretched in the longitudinal direction while applying heat with a far infrared heater. Specifically, in this step, the unstretched sheet may be performed while moving at a speed of 20 m / min to 80 m / min, 20 m / min to 60 m / min, or 25 m / min to 50 m / min.

Step (3)

In this step, the stretched sheet is stretched three times or more in the width direction to produce a stretched film.

Referring to FIG. 3, the stretched film 102 may be manufactured by stretching the sheet 101 stretched in the longitudinal direction in the width W direction.

In this step, it is possible to stretch 4.0 times or more in the width direction. Specifically, in this step, 4.0 to 5.0 times, 4.0 to 4.8 times, or 4.0 to 4.5 times stretching in the width direction may be stretched.

The widthwise stretching may be performed at 80 ° C to 120 ° C. Specifically, the stretching in the width direction may be performed at 82 ° C to 110 ° C, or 85 ° C to 95 ° C.

The widthwise stretching may be performed while moving the sheet stretched in the longitudinal direction at a speed of 30 m / min to 100 m / min. Specifically, the widthwise stretching may be performed while moving the sheet stretched in the longitudinal direction at a speed of 30 m / min to 100 m / min, 40 m / min to 80 m / min, or 45 m / min to 75 m / min.

Step (4)

In this step, the stretched film is heat-set to prepare a protective film.

The heat setting may be performed at 150 ° C to 250 ° C for 0.2 seconds to 2 minutes. Specifically, the heat setting may be performed at 150 ° C to 220 ° C, 180 ° C to 250 ° C, or 180 ° C to 220 ° C for 0.2 seconds to 1.2 minutes, or 0.5 seconds to 1 minute.

Upon heat setting, the stretched film can be relaxed with a relaxation rate of 0% to 5%.

The protective film manufactured by the above-described manufacturing method has an in-plane retardation (Re) of 6,000 nm or more.

In-plane retardation is a parameter defined by the product of the anisotropy of the orthogonal biaxial refractive index on the film (△ Nxy = | Nx-Ny |) and the film thickness d (nm) (△ Nxy × d), which shows optical isotropy and anisotropy. It is a measure. The in-plane retardation (Re) is an in-plane retardation value at a wavelength of 550 nm, represented by Equation 3 below.

[Equation 3]

Re = (n _x -n _y ) × d

At this time, n _x is the refractive index in the uniaxial direction in the film plane, n _y is the refractive index in the uniaxial direction orthogonal to the x axis in the film plane, and d is the thickness (nm) of the film.

Protective film for polarizer

An exemplary protective film for polarizing plate according to the example, the longitudinal direction and the transverse direction modulus of each of 250kgf / mm ² or more and 500kgf / mm ² or more, and the longitudinal and transverse direction tensile strength of each of more than 9kgf / mm ² and 30kgf / mm ² The above, the elongation in the longitudinal direction and the width direction are 30% or more and 60% or more, respectively, and the in-plane retardation (Re) is 6,000 nm or more, and no polarization mura occurs.

The protective film for the polarizing plate has a longitudinal modulus of 250 kgf / mm ² To ^{350kgf / mm 2, 250kgf / mm} 2 to ^{300kgf / mm 2, 250kgf / mm} 2 to 270kgf / mm ^2, or 250kgf / mm ² to 268kgf / mm ^2, and the transverse direction modulus of 500kgf / mm ² to 600kgf / mm ² , 500kgf / mm ² to 580kgf / mm ² , 500kgf / mm ² to 550kgf / mm ² , or 520kgf / mm ² to 550kgf / mm ² .

The protective film for the polarizing plate has a longitudinal tensile strength of 9kgf / mm ² to 18kgf / mm ² , 9kgf / mm ² to 15kgf / mm ² , 9kgf / mm ² to 13kgf / mm ² , 9kgf / mm ² to 12kgf / mm ² , Or 9kgf / mm ² to 11kgf / mm ^2, and the tensile strength in the width direction is 30kgf / mm ² to 40kgf / mm ² , 30kgf / mm ² to 34kgf / mm ² , 30kgf / mm ² to 33kgf / mm ² , or 30kgf / mm ² to 32kgf / mm ² .

The protective film for the polarizing plate has a longitudinal elongation at break of 30% to 150%, 30% to 130%, 30% to 120%, 40% to 120%, or 45% to 110%, and a width elongation at break of 60%. To 85%, 65% to 85%, 67% to 85%, or 67% to 83%.

The protective film for the polarizing plate may satisfy the following equations 1 and 2 in tensile strength and elongation at break. Specifically, the protective film for the polarizing plate may satisfy the following equations 4 and 5 in tensile strength and elongation at break.

[Equation 1]

3.0 ≤ Tensile strength in the longitudinal direction (kgf / mm ² ) / Tensile strength in the width direction (kgf / mm ² ) ≤ 3.5

[Equation 2]

0.6 ≤ elongation at break (%) / elongation at break (%) ≤ 3.0

[Equation 4]

3.1 ≤ Tensile strength in the longitudinal direction (kgf / mm ² ) / Tensile strength in the width direction (kgf / mm ² ) ≤ 3.4

[Equation 5]

0.7 ≤ elongation at break (%) / elongation at break (%) ≤ 2.0

The elongation at break is a value measured for samples having a thickness of 80 mm to 125 mm.

The protective film for the polarizing plate may have an in-plane retardation (Re) of 6,000 nm to 20,000 nm, 6,000 nm to 15,000 nm, 7,000 nm to 15,000 nm, 7,000 nm to 12,000 nm, or 7,500 nm to 12,000 nm.

The protective film for the polarizing plate has an orientation angle deviation (optical axis) of ± 5.0 deg. (°) or less with respect to the full width, and ± 2.5 deg with respect to the center portion 2 m of the full width of the protective film. It may have the following orientation angle deviation. Specifically, the protective film for the polarizing plate is ± 0.1deg. To ± 5.0deg., ± 0.1deg. To ± 3.0deg., ± 0.1deg. To ± 2.5deg., ± 1.0deg. To ± 2.5 deg., Or ± 1.5 to ± 2.5 deg., And an angle of deviation of ± 1.5 deg., ± 0.1 deg for 2 m in the center of the full width of the protective film. To ± 2.5deg., ± 0.1deg. To ± 1.5 deg., ± 0.5 deg. To ± 1.3deg., Or ± 0.6deg. It may have an orientation angle deviation of ± 1.3deg.

As the orientation angle deviation approaches 0 deg., The luminance of the film improves, and within the above range, the occurrence of polarization mura is suppressed to prevent color distortion, and luminance of 5% or more can be improved.

The protective film for the polarizing plate is excellent in mechanical properties because no burr is generated on the cut surface even after cutting after laminating a plurality of layers, and polarization mura does not occur and the in-plane retardation is high, so that the optical properties are also excellent.

The protective film for the polarizing plate satisfies the physical properties as described above, and when observed from the side, polarization mura is not observed and has excellent mechanical properties. Therefore, the protective film for the polarizing plate has improved optical properties and mechanical properties and can be usefully used in the manufacture of the polarizing plate.

[Example]

Hereinafter, the present invention will be described in more detail by examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited to them.

Example  One.

Polyethylene terephthalate resin (100 mol% of ethylene glycol + 100 mol% of terephthalic acid, intrinsic viscosity (IV) 0.61 ㎗ / g, manufactured by SKC) was melt-extruded through an extruder at 280 ° C and cooled in a casting roll at 25 ° C, An unstretched sheet was prepared. Preheating the unstretched sheet to 82 ° C. while moving at a speed of 32 m / min, and moving a preheated unstretched sheet at a speed of 32 m / min, 80 mm spaced apart from the preheated unstretched sheet (radiation heater; R / The first stretching roll (85 ° C) and the second stretching roll spaced at a distance of 300 mm while heating at 810 ° C (total power: 25 kW) at the top and 780 ° C (total power: 20 kW) at the bottom. It stretched 155% in the longitudinal direction (MD direction) using (30 degreeC).

The sheet stretched in the longitudinal direction was stretched 419% in the width direction (TD direction) at 85 ° C while moving at a speed of 48 m / min. Thereafter, the stretched film was heat-set at a temperature of 200 ° C. for about 1 second to relax at a relaxation rate of about 5% to prepare a protective film for a polarizing plate having a thickness of 125 μm.

Example  2 and 3, and Comparative example  1 to 3.

A protective film for a polarizing plate was prepared in the same manner as in Example 1, except that the stretching ratio in the longitudinal direction and the width direction, the temperature of the upper and lower portions of the far infrared heater, and the output were changed as shown in Table 1.

Thickness (㎛) Stretch ratio (ship) R / H process conditions MD TD Output (kW) (upper / lower) Temperature (℃) (upper / lower) Example 1 125 1.55 4.19 25/20 810/780 Example 2 100 1.50 4.44 25.5 / 22 840/790 Example 3 80 1.58 4.42 23.5 / 21 800/755 Comparative Example 1 80 1.30 4.20 17/12 700/670 Comparative Example 2 100 3.10 4.25 21/16 750/720 Comparative Example 3 80 3.20 4.15 23.5 / 18.5 780/740

Test example . Property measurement

The protective films for polarizing plates prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated as follows, and the results are shown in Table 2.

(One) Modulus  evaluation

According to ASTM D 882, longitudinal and transverse elastic modulus were measured using a universal testing machine 4206-001 (Instron), respectively.

(2) Tensile strength evaluation

Tensile strength was measured by dividing the maximum load by the original cross-section of the film at an increased value by applying a load to the film according to KS B 5521.

(3) Rupture

After cutting the protective film for the polarizing plate into 15 mm × 100 mm (horizontal × vertical), the elongation at break was measured at a measurement condition of 200 mm / min using a fracture elongation measuring device (manufacturer: SKC UTM, model name: INSTRON 5566).

(4) Optical axis evaluation

The orientation angle of the film (sample film) was measured using the orientation angle measurement system as shown in FIG. 4, and the deviation (optical axis) of the angle between the measured orientation angle and the width direction was determined.

(5) Inside Phase difference (Re)

Regardless of the orientation direction of the film, the film was cut into a rectangle of 4 cm x 2 cm in the width direction of the film, and used as a sample for measurement. For this sample, the orthogonal biaxial refractive indexes (Nx, Ny) and the refractive index (Nz) in the thickness direction were obtained by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measuring wavelength 550 nm), and the difference in the refractive index of the biaxial The absolute value (| Nx-Ny |) was taken as the anisotropy (ΔNxy) of the refractive index. The thickness d (nm) of the film was measured using an electric micrometer (manufactured by FineLoop, Millitron 1245D), and the unit was converted to nm. The in-plane retardation (Re) was determined from the product of the anisotropy (ΔNxy) of the refractive index and the thickness d (nm) of the film (ΔNxy × d).

(6) Polarization mura  Occurrence

On one side of a polarizer (manufacturer: Samsung SDI) made of PVA and iodine, a film (sample film) obtained in the above Example or Comparative Example was affixed so that the absorption axis of the polarizer and the orientation axis of the film were perpendicular, and the A polarizing plate was produced by attaching a TAC film (manufacturer: Fujifilm Co., Ltd., product name: n-tac, thickness: 80 μm) to the other side. The polarizing plate is installed on the exit light side of a liquid crystal display device using a white LED composed of a light emitting device that combines a blue light emitting diode and a yttrium, aluminum, and garnet yellow phosphor as a light source (NSPW500CS, Nichia Chemical). Placed on the side. The liquid crystal display device had a polarizing plate having two TAC films as protective films for polarizers on the incident light side of the liquid crystal cell (see FIG. 5). The presence or absence of polarization mura was observed by visual observation from the front and inclined directions of the polarizing plate of the liquid crystal display device.

(7) Evaluating the cutting condition in the width and length directions

After stacking 10 protective films for polarizers of Examples and Comparative Examples of 800 mm × 1,000 mm (horizontal × vertical), they were cut in a width direction (TD direction) or a length direction (MD direction) using a cutting machine. Subsequently, the cut surface was observed under a microscope, and evaluated as poor if burrs were generated on the cut surface and good if not.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Modulus
(kgf / mm ² ) MD 252.9 264.3 266.8 271 382.7 378 TD 532.1 528.9 544.6 499.4 435.7 445 The tensile strength
(kgf / mm ² ) MD 9.3 9.8 10 8.7 19.6 20.1 TD 30.8 30.5 31.8 34.2 26 27.2 Elongation at break (%) MD 55 106 48 10 98 89 TD 69 81 68 88 42 51 Tensile strength ratio (MD / TD) 3.31 3.11 3.18 3.93 1.33 1.35 Elongation at break (TD / MD) 1.25 0.76 1.42 8.8 0.43 0.57 Overall width (5m) standard optical axis (deg.) 1.9 2.2 1.8 3.1 32 28 2m wide optical axis (deg.) 0.8 1.2 0.7 1.4 22 20 In-plane phase difference (Re) (nm) 11,052 10,523 7,929 8,100 4,691 3,426 Polarization mura Nothing Nothing Nothing Nothing Poet Poet Cutting state MD direction Good Good Good Good Good Good TD direction Good Good Good Bad Good Good

As shown in Table 2, Examples 1 to 3 are suitable for modulus, tensile strength and elongation at break, and the cut surfaces in the width direction and the length direction are clean, so that mechanical properties are excellent, and the protective film for polarizing plates deviates from the angular angle with respect to the full width. Is small, and the in-plane retardation is high, so it has excellent optical properties.

On the other hand, in Comparative Example 1 in which the elongation in the longitudinal direction was too small and the processing conditions for the far infrared heater were not appropriate, the tensile strength and elongation at break in the longitudinal direction were low, and the state of the cut surface in the width direction was poor. In addition, the biaxially stretched Comparative Examples 2 and 3 had a large orientation angle deviation with respect to the full width of the film, and there was polarization mura.

10: T-die 20: casting roll
31: first stretching roll 32: second stretching roll
41, 42: far infrared heater
100: unstretched sheet 101: sheet stretched in the longitudinal direction
102: stretched film
210: sample film 220: polarizer
230: protective film (TAC film) 240: LCD panel
250: polarizer 260: backlight unit
(a): Distance between first stretch roll and second stretch roll
(b): Heat treatment length using a far infrared heater
(c): Distance between the unstretched seat and the far infrared heater
W: width of the stretched film

Claims (12)

delete delete delete delete delete delete delete delete delete A longitudinal and transverse direction modulus of each of 250kgf / mm ² or more and 500kgf / mm ² or more,
A longitudinal and transverse direction tensile strength of each 9kgf / mm ² or more and 30kgf / mm ² or more,
The elongation at break in the longitudinal and transverse directions is 30% or more and 60% or more, respectively,
The tensile strength and the elongation at break satisfy the following equations 1 and 2,
In-plane retardation (Re) is 6,000 nm or more,
Protective film for polarizing plates without polarization mura:
[Equation 1]
3.0 ≤ Tensile strength in the longitudinal direction (kgf / mm ² ) / Tensile strength in the width direction (kgf / mm ² ) ≤ 3.5
[Equation 2]
0.6 ≤ elongation at break (%) / elongation at break (%) ≤ 3.0.
delete The method of claim 10,
The protective film has an orientation angle deviation of ± 5.0 deg. Or less with respect to the full width, and ± 2.5 deg with respect to the center 2 m of the full width of the protective film. A protective film for a polarizing plate having the following orientation angle deviation.

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