KR102100354B1 - Optical film, preparation method thereof and optical component comprising same - Google Patents

Abstract

Provided are an optical film, a manufacturing method thereof, and an optical component including same. The optical film has an in-plane phase difference (Ro) of 600 nm or less and a thickness direction phase difference (Rth) of 4000 nm or more, has a heat shrinkage rate of 1.0% or less in a first direction (s1) at 85 °C and 24 hours when defining the first direction and a second direction perpendicular to each other in the plane, and has a rate (s2/s1) of a heat shrinkage rate in a second direction of 0.1 to 0.9 (s2) for the heat shrinkage rate (s1) in the first direction.

Description

Optical film, method for manufacturing the same, and optical component including the same {OPTICAL FILM, PREPARATION METHOD THEREOF AND OPTICAL COMPONENT COMPRISING SAME}

The following embodiments relate to an optical film having a controlled shrinkage ratio, a method for manufacturing the same, and an optical component including the optical film.

Recently, as demand for liquid crystal displays (LCDs) has rapidly increased, interest in polarizing plates, which can be regarded as essential parts thereof, has also increased. The polarizing plate serves to polarize the incident natural light while vibrating in various directions with light that vibrates only in one direction, and is an essential component for providing a constant transmitted light and changing the color tone of the transmitted light.

The polarizing plate has a structure in which a protective film is laminated on one or both surfaces of the polarizer, and a polyvinyl alcohol (PVA) film is mainly used as the polarizer. In addition, a triacetyl cellulose (TAC) film was mainly used as a protective film. Meanwhile, as the functions and uses of the liquid crystal display (LCD) are diversified, it is required to be able to operate normally even in a more severe environment. However, triacetylcellulose (TAC) is vulnerable to moisture and has poor durability, and thus has a problem of not meeting the above requirements.

Accordingly, recently, as in Japanese Unexamined Patent Publication Nos. 2011-532061 and 2010-118509, many attempts have been made to replace the TAC film with a polyester film. In particular, polyethylene terephthalate (PET) film can satisfy these needs because it has excellent mechanical properties, chemical resistance, moisture barrier properties, and the like.

Japanese Patent Application Publication No. 2011-532061 Japanese Patent Application Publication No. 2010-118509

When a low-phase difference optical film is implemented using a polyester resin such as polyethylene terephthalate (PET), shrinkage occurs at high temperature when applied to a polarizer protective film due to an increase in shrinkage, so that the edge portion joined to the substrate is lifted. As a result, reliability was lowered (see Fig. 1).

On the other hand, if the heat setting temperature is increased in the manufacturing process of the optical film in order to lower the shrinkage rate, the in-plane retardation rises to generate rainbow stains when applied as a polarizer protective film.

In addition, in the film manufacturing process, the shrinkage rate with respect to the width direction (TD) of the film can be relatively easily lowered by adjusting the stretching ratio in the width direction, while proceeding under a constant stress by the rotation of the roll to a certain level in the longitudinal direction (MD). It is difficult to lower the shrinkage rate in the longitudinal direction of the film by adjusting the stretching ratio in the longitudinal direction in general due to the process characteristics in which the stretching ratio of the film is forced.

Accordingly, as a result of the research conducted by the present inventors, it was found that the heat shrinkage in the length direction as well as the width direction can be reduced by adjusting the stretching conditions in the width direction without increasing the heat setting temperature in the process of manufacturing the film.

Accordingly, the following embodiments are intended to provide an optical film that does not generate rainbow stains due to a phase difference without lifting by shrinkage at high temperature, a method for manufacturing it by a simple process, and an optical component including the same.

According to an embodiment, when defining the first direction and the second direction perpendicular to each other in the plane having an in-plane retardation (Ro) of 600 nm or less and a thickness direction retardation (Rth) of 4000 nm or more, conditions of 85 ° C. and 24 hours In the first direction, the heat shrinkage rate (s1) of 1.0% or less, the ratio of the heat shrinkage rate (s2) of the second direction to the heat shrinkage rate (s1) of the first direction (s2 / s1) is 0.1 to 0.9 Phosphorus, an optical film is provided.

According to another embodiment, the method comprising the step of stretching the film including the polyester resin in the longitudinal direction and the width direction, wherein the widthwise stretching comprises at least two stages of the widthwise stretching, the manufacturing method of the optical film Is provided.

According to another embodiment, the polarizer; And an optical film according to the embodiment, which is disposed on at least one surface of the polarizer.

When the optical film according to the embodiment is applied to the polarizer protection film because the in-plane retardation is low while the excitation by shrinkage does not occur by adjusting the heat shrinkage ratios in the first and second directions perpendicular to each other in the plane. It may not cause rainbow stains.

Specifically, the optical film may be at least two stages of stretching in the width direction in the manufacturing process, so that the stress in the longitudinal direction can also be relieved through relaxation in the middle of stretching, as well as the shrinkage in the width direction without increasing the heat setting temperature. In addition, it is possible to prevent lifting by lowering the shrinkage in the longitudinal direction, and it is possible to implement a low in-plane retardation, thereby preventing rainbow staining.

In addition, the optical film according to the embodiment has excellent mechanical properties such as tensile strength and pencil hardness, and thus has good durability.

Accordingly, the optical film according to the above embodiment, the optical component including the same, has excellent shrinkage characteristics and optical characteristics, and can be normally operated in a harsh environment, and thus can be applied to various products such as liquid crystal displays and organic light emitting displays. .

1 shows that excitation occurs due to shrinkage when a conventional optical film is applied as a polarizer protective film.
2 and 3 show the stretching conditions in the case of performing one-stage or two-stage stretching in the width direction, respectively.
4 is a diagram for explaining the displacement in the width direction of the film and the center of the width.
5 is a sectional view of a polarizing plate according to an embodiment.
6 is a sectional view of a liquid crystal display according to an embodiment.
7 is a sectional view of an organic light emitting display device according to an embodiment.

In the case where each film, panel, or layer, etc. described in the following embodiments is described as being formed “on” or “under” of each film, panel, or layer, the “phase ( "on" "and" under "include both directly or indirectly formed through other components.

In addition, the size of each component in the drawings may be exaggerated for explanation, and does not mean the size actually applied.

In addition, it should be understood that all numerical ranges representing physical property values, dimensions, and the like of the components described in the present specification are modified to the term "about" in all cases unless otherwise specified.

[Optical film]

The optical film according to an embodiment has an in-plane retardation (Ro) of 600 nm or less and a thickness direction retardation (Rth) of 4000 nm or more, and when defining a first direction and a second direction perpendicular to each other in the plane, 85 ° C. and The heat shrinkage rate (s1) in the first direction is equal to or less than 1.0% under a 24-hour condition, and the ratio (s2 / s1) of the heat shrinkage rate (s2) in the second direction to the heat shrinkage rate (s1) in the first direction is 0.1 to 0.9.

Phase difference

The optical film may have an in-plane retardation (Ro) of 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. When within the above range, the occurrence of rainbow stains can be minimized.

In addition, the optical film may have a minimum in-plane retardation (Ro _min ) of 200 nm or less or 150 nm or less. Specifically, the minimum in-plane retardation of the optical film may be 120 nm or less, 100 nm or less, 85 nm or less, 75 nm or less, or 65 nm or less.

Meanwhile, the lower limit of the in-plane retardation of the optical film may be 0 nm, or the lower limit of the in-plane retardation (Ro) may be 10 nm or more, 30 nm or more, or 50 nm or more for balancing optical properties and mechanical properties. have.

In addition, the optical film may have a thickness direction retardation (Rth) of 4,000 nm or more, 5,000 nm or more, or 5,500 nm or more.

In addition, the optical film may have a maximum thickness direction retardation (Rth _max ) of 6,000 nm or more, for example, 6,500 nm or more, 7,500 nm or more, 8,000 nm or more, or 8,500 nm or more.

The retardation in the thickness direction may be a measurement value based on a thickness of 40 μm to 50 μm. When within the above range, the orientation of the molecules is large, and crystallization is promoted, which is preferable in terms of mechanical properties. In addition, since the ratio (Rth / Ro) of the thickness direction phase difference (Rth) to the in-plane phase difference (Ro) increases as the thickness direction retardation (Rth) increases, rainbow unevenness can be effectively suppressed.

On the other hand, considering the thickness limit and cost for eliminating rainbow stains in the optical film, the upper limit of the thickness direction retardation (Rth) may be 16,000 nm or less, 15,000 nm or less, or 14,000 nm or less.

The in-plane retardation (Ro) is anisotropy (Δnxy = ｜ nx-ny ｜) of refractive indices of two orthogonal axes (x-axis, y-axis) in the plane of the film, with reference to FIG. 4. As a parameter defined by the product (Δnxy × d) of the film thickness (d), it is a measure of optical isotropy or anisotropy. In addition, the minimum in-plane retardation (Ro _min ) means the lowest measured value when the in-plane retardation (Ro) is measured at multiple points in the plane of the film.

In addition, the thickness direction retardation (Rth) is a film of two birefringences Δnxz (= | nx-nz |) and △ nyz (= | ny-nz |), respectively, when viewed from a cross section in the film thickness direction. This parameter is defined as the average of the phase differences obtained by multiplying the thickness (d). In addition, the maximum thickness direction retardation (Rth _max ) means the highest measured value when each of the thickness direction retardation (Rth) is measured at multiple points in the plane of the film.

According to the film manufacturing process according to one embodiment, a minimum in-plane retardation and a maximum thickness direction retardation may appear in the center of the width of the film. Therefore, the minimum in-plane retardation of the film and the retardation in the maximum thickness direction may be values measured at the center of the width of the film. In the present specification, the 'width center' may be defined as an intermediate point (A, B) of the width of the film after stretching in the width direction (TD) and the length direction (MD) as shown in FIG. 4. The film does not have only one center of width, and can be set to infinity depending on the measurement point. On the other hand, the width center of the final film cut into various shapes after manufacture may not coincide with the width center of the first film (the film before cutting), and in this case, the minimum in-plane retardation and maximum thickness direction retardation from the width center of the film May not appear.

In addition, when the film is applied to an optical component for a large-screen application, it is preferable that the deviation of the in-plane phase difference within the effective width (that is, the difference between the maximum value and the minimum value) is small. Here, the effective width refers to the distance between the points (A ', A' ') that have moved a certain distance toward both ends along the width direction (x-axis) from the width center (A), as shown in FIG. For example, it can be defined as ± 1,500 mm from the center of the width, that is, about 3,000 mm. On the other hand, as described above, the width center of the final film cut into various shapes after manufacture may not coincide with the width center of the initial film (the film before the foundation). In this case, the effective width may refer to a distance between a point where a minimum in-plane retardation occurs in the film and a certain distance is moved toward both ends along the width direction.

The optical film has little variation in in-plane retardation within the effective width. Specifically, the amount of change (| ΔRo | / | Δx |) of the in-plane retardation with respect to the displacement in the width direction of the optical film may be 0 to 100 nm / mm. Specifically, | ΔRo | / | Δx | of the optical film. Values can be 0-50 nm / mm, 0-35 nm / mm, 0-25 nm / mm, or 0-20 nm / mm. Here, the displacement in the width direction (Δx) means a distance (x ₂ -x ₁ ) between predetermined points on the width direction (x-axis), and the amount of change in the in-plane phase difference (ΔRo) is the difference in the in-plane phase difference at each constant point ( Ro ₂ -Ro ₁ ). When within the above range, even if the width of the film is wide, since the in-plane retardation (Ro) does not increase significantly, it is possible to effectively prevent the occurrence of rainbow stains.

In addition, the optical film has little variation in retardation in the thickness direction within the effective width. Specifically, in the optical film, the amount of change in the retardation in the thickness direction (| ΔRth | / | Δx |) with respect to displacement in the width direction may be less than 1000 nm / 3 m, less than 700 nm / 3 m, or less than 500 nm / 3 m. have. Here, the displacement (Δx) in the width direction means a distance (x ₂ -x ₁ ) between predetermined points on the width direction (x-axis), and a change amount (ΔRth) of the thickness direction phase difference is the thickness direction phase difference at each constant point. It means the difference (Rth ₂ -Rth ₁ ).

In addition, the optical film may have a ratio (Rth / Ro) of a thickness direction phase difference (Rth) to an in-plane phase difference (Ro) of 10 or more, 15 or more, or 20 or more. The smaller the in-plane retardation (Ro) and the larger the thickness direction retardation (Rth), the better it is to prevent the occurrence of rainbow stains, so it is preferable to keep the ratio (Rth / Ro) of both numerical values large. In particular, the optical film may have a ratio (Rth _max / Ro _min ) of a maximum thickness direction phase difference (Rth _max ) to a minimum in-plane phase difference (Ro _min ) of 30 or more, 40 or more, 50 or more, or 60 or more.

Heat shrinkage rate

The optical film according to the embodiment may define a first direction and a second direction perpendicular to each other in a plane, for example, the first direction is a longitudinal direction (MD) and the second direction is a width direction (TD). You can.

In the optical film according to the embodiment, the thermal contraction rate (s1) in the first direction is 85% or less at 85 ° C. and 24 hours, and the thermal contraction rate in the second direction relative to the thermal contraction rate (s1) in the first direction. The ratio (s2 / s1) of (s2) is 0.1 to 0.9.

The first direction heat shrinkage (s1) is 3% or less, 2% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less , 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less. For example, the heat shrinkage ratio s1 in the first direction may be 0% to 1.0%, 0% to 0.8%, 0% to 0.6%, 0% to 0.4%, or 0% to 0.2%. Specifically, the heat shrinkage rate s1 in the first direction may be 0.1% to 0.8%.

In addition, the heat shrinkage ratio s2 in the second direction may be 1.5% or less, 1.0% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less have. For example, the heat shrinkage ratio s1 in the second direction may be 0% to 0.8%, 0% to 0.6%, 0% to 0.4%, or 0% to 0.2%. Specifically, the heat shrinkage rate s2 in the second direction may be 0.01% to 0.5%.

In addition, the ratio (s2 / s1) of the heat shrinkage rate is 0.1 to 0.9, 0.1 to 0.8, 0.1 to 0.7, 0.1 to 0.6, 0.1 to 0.5, 0.2 to 0.9, 0.3 to 0.9, 0.4 to 0.9, or 0.5 to 0.9 days You can. Specifically, the ratio (s2 / s1) of the heat shrinkage rate may be 0.1 to 0.6.

Since the optical film according to the embodiment has the above-described heat-shrinking properties, when applied as a polarizer protective film, lifting by shrinkage may not occur under high temperature conditions. Specifically, polyvinyl alcohol (PVA) used as a polarizer has a high shrinkage rate and is easily bent in a heat treatment process. If this is not suppressed, the optical film may be crushed and wavy, and accordingly, the visibility may be remarkably deteriorated by a glitter phenomenon. You can. Therefore, the optical film according to the embodiment is advantageous in preventing warping of the polarizer due to the above-described heat-shrinking properties, and accordingly, a wave pattern, a sparkling phenomenon, peeling between the optical film and the polarizer, and cracks can be prevented. .

Optical film properties

The thickness of the optical film may be 10 μm to 100 μm, 20 μm to 60 μm, or 40 μm to 60 μm. As an example, the optical film may have a thickness of 30 μm to 60 μm.

In addition, the optical film may have a tensile modulus at a high temperature (eg, 85 ° C.) of 3.0 Gpa or more or 3.5 Gpa or more. When within the above range, it is advantageous to prevent the curl of the optical component during heat treatment at a high temperature after introducing the optical film to the optical component.

In addition, the optical film has a moisture permeability of 10 g / m 2 · day to 100 g / m 2 · day, 10 g / m 2 · day to 50 g / m 2 · day or 10 g / m 2 · day to 30 g / m 2 · day. You can.

In addition, the optical film may have a light transmittance of 10% or less at a wavelength of 380 nm, and specifically, may have a light transmittance of 5% or less or 3% or less.

In addition, the optical film may have a surface hardness of 1H or more, 2H or more, or 3H or more, which may be a surface hardness upon hard coating treatment of 2 μm to 4 μm in thickness.

As an example, the optical film may have a moisture permeability of 10 g / m 2 · day to 50 g / m 2 · day, and a surface hardness of 2H or more.

Therefore, the optical film is used as a polarizer protective film, and can be used in the manufacture of a liquid crystal display device or an organic light emitting display device.

Composition of optical film

The optical film may include a polyester resin.

The polyester resin may be a homopolymer resin or a copolymer resin in which dicarboxylic acid and diol are polymerized. In addition, the polyester resin may be a blend resin in which the homopolymer resin or copolymer resin is mixed.

Examples of the dicarboxylic acid are terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5- Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclo Hexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2 , 2-dimethylglutaric acid, adipic acid, 2-methyladipic acid trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, dodecadicarboxylic acid and the like.

In addition, examples of the diol are ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, and the like.

Preferably, the polyester resin may be an aromatic polyester resin having excellent crystallinity, for example, polyethylene terephthalate (PET) resin as a main component.

As an example, the optical film may include at least about 85% by weight of PET resin, and more specifically, at least 90% by weight, at least 95% by weight, or at least 99% by weight. As another example, the optical film may further include other polyester resin in addition to the PET resin. Specifically, the optical film may further include a polyethylene naphthalate (PEN) resin of about 15% by weight or less. More specifically, the optical film may further include about 0.1% to 10% by weight, or about 0.1% to 5% by weight of PEN resin.

It is preferable that the optical film is a stretched film because of its high crystallinity and excellent mechanical properties. Specifically, the optical film may be a biaxially stretched polyester film, and may be, for example, a film stretched at a stretching ratio of 2.0 to 5.0 in the longitudinal direction (MD) and the transverse direction (TD), respectively.

In addition, the optical film by using a polyester as a main component, the crystallinity increases during the manufacturing process through heating, stretching, etc., and mechanical properties such as tensile strength can be improved.

For example, the optical film may have a crystallinity of 35% to 55%. When within the above range, mechanical properties such as tensile strength are excellent, but excessive crystallization can be prevented.

[Method of manufacturing optical film]

A method of manufacturing an optical film according to an embodiment includes stretching a film including a polyester resin in a length direction and a width direction, and the width direction stretching includes at least two steps of width direction stretching.

The film containing the polyester resin in the above production method can be obtained by extruding the polyester resin.

At this time, the composition of the polyester resin used as a raw material for the optical film is as exemplified above.

In addition, the extrusion may be carried out at a temperature condition of 230 ℃ to 300 ℃, or 250 ℃ to 280 ℃.

The film can be preheated at a constant temperature before stretching. The range of the preheating temperature may be Tg + 5 ° C to Tg + 50 ° C, specifically 70 ° C to 90 ° C, based on the glass transition temperature (Tg) of the polyester resin. When within the above range, the film can be easily stretched, and at the same time, it is possible to effectively prevent the phenomenon of breakage during stretching.

The stretching is performed by biaxial stretching, for example, biaxial stretching in the width direction (or tenter direction) (TD) and the longitudinal direction (or machine direction) (MD) through a simultaneous biaxial stretching method or a sequential biaxial stretching method. You can. Preferably, a sequential biaxial stretching method may be performed, first stretching in one direction, and then stretching in a direction perpendicular to the direction.

The speed of the stretching may be 6.5 m / min to 8.5 m / min, but is not particularly limited.

The lengthwise stretching ratio is in the range of 2.0 to 5.0, and more specifically, may be in the range of 2.8 to 3.5. In addition, the stretching ratio in the width direction is in the range of 2.0 to 5.0, and more specifically, may be in the range of 2.9 to 3.7. Preferably, the lengthwise stretching ratio d1 and the widthwise stretching ratio d2 are similar, and specifically, the ratio (d2 / d1) of the lengthwise stretching ratio d2 to the widthwise stretching ratio d1 is 0.5 to 1.0. , 0.7 to 1.0, or 0.9 to 1.0.

The stretching ratios d1 and d2 are ratios showing the length (or width) after stretching when the length (or width) before stretching is 1.0.

The widthwise stretching includes at least two stages of widthwise stretching, and may include, for example, primary widthwise stretching and secondary widthwise stretching.

2 and 3 show the stretching conditions in the case of performing one-stage or two-stage stretching with respect to the width direction (the film temperature in the drawing is represented by a line graph, and the film width is represented by an area graph). .

Compared to the case of performing high-magnification stretching at a time in the width direction as shown in FIG. 2, performing by dividing the stretching in at least two stages in the width direction as shown in FIG. 3 further aligns the arrangement of the polymers constituting the film in-plane The phase difference can be reduced.

In addition, by further performing relaxation between the primary stretching in the width direction and the stretching in the secondary width direction (see FIG. 3), stress due to stretching in the longitudinal direction and the width direction can be relaxed to further reduce the shrinkage. Particularly, through the relaxation, the stress in the longitudinal direction as well as in the width direction is partially relieved, and the shrinkage in the longitudinal direction, which is difficult to lower by a general method, can be easily lowered.

The relaxation may be performed at a relaxation rate of 0% to 10%, 0% to 5%, 0% to 3%, 0.1% to 10%, 0.5% to 5%, or 0.5% to 3% with respect to the width direction. have. As a specific example, the relaxation may be performed at a relaxation rate of 0% to 5% with respect to the width direction. The relaxation rate refers to the percentage of the width (or length) reduction in the relaxation process relative to the width (or length) before relaxation. Within the above-described preferred range, it is advantageous to suppress the increase in phase difference due to relaxation while reducing the shrinkage by relaxing the stress caused by stretching.

In addition, the relaxation may be performed for 1 second to 1 minute, 2 seconds to 30 seconds, or 3 seconds to 10 seconds.

The total stretching ratio of the at least two stages of widthwise stretching may be 2.0 to 5.0, 2.5 to 5.0, 3.0 to 5.0, 2.5 to 4.5, 3.0 to 4.5, or 3.5 to 4.5. In this case, the primary width direction stretching ratio may be 2.0 to 4.5, 2.0 to 4.0, 2.0 to 3.5, 2.5 to 4.5, or 3.0 to 4.5, or 3.0 to 4.0.

As a specific example, the widthwise stretching is performed at a total stretching ratio of 2.5 to 5.0, wherein the primary widthwise stretching may be performed at a stretching ratio of 2.0 to 4.0.

In addition, the primary widthwise stretching may be performed at a temperature of 100 ° C to 170 ° C, and the secondary widthwise stretching may be performed at a temperature of 170 ° C to 200 ° C.

The manufacturing method of the optical film may further include a step of heat-setting the stretched film after the stretching.

The heat setting may be performed at a temperature of 150 ° C to 250 ° C, specifically 150 ° C to 220 ° C.

The heat setting may be performed for 5 seconds to 1 minute, and more specifically, for 10 seconds to 45 minutes.

In addition, after starting the heat setting, the film may be relaxed in the longitudinal direction and / or the width direction, and the temperature range at this time may be 150 ° C to 250 ° C. The relaxation may be performed at a relaxation rate of 1% to 10%, 2% to 7%, or 3% to 5%. In addition, the relaxation may be performed for 1 second to 1 minute, 2 seconds to 30 seconds, or 3 seconds to 10 seconds.

[Optical parts]

The optical film according to the embodiment may be applied to an optical component.

The optical component can prevent lifting by shrinkage even at high temperatures by including the optical film according to the embodiment, and may have improved optical properties.

An optical component according to an embodiment includes a polarizer; And the optical film disposed on at least one surface of the polarizer.

The optical component may be specifically a polarizing plate.

5 is a sectional view of a polarizing plate according to an embodiment.

Referring to FIG. 5, the polarizing plate 10 according to an embodiment includes a polarizer 11 and an optical film 12 disposed on at least one surface of the polarizer.

The polarizer polarizes natural light incident on the polarizing plate with light vibrating only in one direction while vibrating in various directions. The polarizer may be a polyvinyl alcohol (PVA) layer dyed with iodine or the like. At this time, the PVA molecules included in the PVA layer may be aligned in one direction.

[Display device]

The optical component according to the embodiment may be applied to a display device.

The display device includes a display panel; And an optical component disposed on at least one of an upper surface and a lower surface of the display panel.

At this time, an optical component having the above-described configuration is used as the optical component.

The display device may be provided as a liquid crystal display device and an organic light emitting display device according to the type of display panel.

Liquid crystal display

6 is a cross-sectional view schematically showing a liquid crystal display according to an embodiment. Referring to FIG. 6, a liquid crystal display according to an embodiment includes a liquid crystal panel 70 and a backlight unit 80.

The backlight unit emits light to the liquid crystal panel. The liquid crystal panel displays an image using light from the backlight unit.

The liquid crystal panel 70 includes an upper polarizing plate 10, a color filter substrate 71, a liquid crystal layer 72, a TFT (thin film transistor) substrate 73, and a lower polarizing plate 10 '.

The TFT substrate and the color filter substrate are opposed to each other. The TFT substrate includes a plurality of pixel electrodes corresponding to each pixel, thin film transistors connected to the pixel electrodes, a plurality of gate wires respectively applying a driving signal to the thin film transistors, and the thin film transistors. A plurality of data lines applying a data signal to the pixel electrodes may be included.

The color filter substrate includes a plurality of color filters corresponding to respective pixels. The color filters may filter the transmitted light to implement red, green, and blue colors, respectively. Further, the color filter substrate may include a common electrode facing the pixel electrodes.

The liquid crystal layer is interposed between the TFT substrate and the color filter substrate. The liquid crystal layer may be driven by the TFT substrate. More specifically, the liquid crystal layer may be driven by an electric field formed between the pixel electrodes and the common electrode. The liquid crystal layer may control a polarization direction of light passing through the lower polarizing plate. That is, the TFT substrate may adjust a potential difference applied between the pixel electrodes and the common electrode in units of pixels. Accordingly, the liquid crystal layer may be driven to have different optical characteristics in units of pixels.

At least one of the upper polarizer and the lower polarizer may have substantially the same configuration as the polarizer according to the above-described embodiment.

The lower polarizing plate is disposed under the TFT substrate. The lower polarizing plate may be adhered to the lower surface of the TFT substrate.

The upper polarizing plate is disposed on the color filter substrate. The upper polarizing plate may be adhered to the upper surface of the color filter substrate.

The polarization directions of the upper polarizing plate and the lower polarizing plate may be the same or perpendicular to each other.

As described above, the upper polarizing plate and / or the lower polarizing plate include an optical film having improved performance. Accordingly, the liquid crystal display according to the exemplary embodiment may have improved brightness, image quality, and durability.

Organic electroluminescence display

7 is a cross-sectional view schematically showing an organic light emitting display device according to an embodiment. Referring to FIG. 7, an organic light emitting display device according to an exemplary embodiment includes a front polarizing plate 10 and an organic light emitting panel 90.

The front polarizing plate may be disposed on the front surface of the organic light emitting panel. More specifically, the front polarizing plate may be adhered to a surface on which an image is displayed in the organic electroluminescent panel. The front polarizing plate may have substantially the same configuration as the polarizing plate according to the above-described embodiment.

The organic light emitting panel 90 displays an image by self-emission in pixel units. The organic light emitting panel 90 includes an organic light emitting substrate 91 and a driving substrate 92.

The organic electroluminescent substrate includes a plurality of organic electroluminescent units, each corresponding to a pixel. The organic electroluminescent units each include a cathode, an electron transport layer, a light emitting layer, a hole transport layer and an anode.

The driving substrate is coupled to the organic electroluminescent substrate. That is, the driving substrate may be coupled to apply a driving signal such as a driving current to the organic light emitting substrate. More specifically, the driving substrate may drive the organic light emitting substrate by applying current to each of the organic light emitting units.

Since the front polarizer has improved optical properties, mechanical properties, and thermal properties, the organic light emitting display device according to an embodiment may have improved brightness, image quality, and durability.

[Example]

It will be described in more detail through the following examples, but is not limited to these ranges.

Examples and Comparative Examples: Preparation of polyester film

Polyethylene terephthalate (PET) resin (SKC) was extruded at about 280 ° C with an extruder and cast at about 30 ° C with a casting roll to prepare an unstretched sheet. The unstretched sheet was stretched in the length direction (MD) and the width direction (TD) under the conditions shown in Table 1 below. At this time, in Examples 1 to 3, while performing the widthwise stretching in two stages, about 2% of relaxation was performed in the middle of the two-stage widthwise stretching, and Comparative Examples 1 and 2 performed the widthwise stretching in one stage. Then, the stretched sheet was heat-set for about 13 seconds at the temperature shown in Table 1 below, and annealed and cooled to prepare a polyester film.

Test Example 1: Heat shrinkage rate

The film sample was cut to 100 mm x 100 mm and heat-treated at 85 ° C. for 24 hours, and dimensions for each of the longitudinal direction (MD) and the width direction (TD) before and after heat treatment were measured to calculate the heat shrinkage (%) therefrom. .

Test Example 2: Lifting evaluation

After attaching the film sample 12 by the adhesive layer 15 to one surface of the polarizer 11 as shown in FIG. 1, after attaching the TAC film 13 by the adhesive layer 16 to the other surface of the polarizer 11 , It was attached to the glass substrate 19 using the adhesive layer 17 to obtain a laminate.

After the laminate was treated at 85 ° C. for 500 hours, it was observed whether excitation occurred at the edge of the lamination region with the glass substrate 19, and then evaluated according to the following criteria.

-No lifting: There is no lifting on the edge or less than 1mm of lifting occurs.

-Excitation: Excitation of 1mm or more at the edge

Test Example 3: In-plane retardation

In-plane retardation (Ro), thickness direction retardation (Rth), and in-plane retardation (| ΔRo | / | Δx |) in the effective width were measured for the film samples.

First, the alignment axis direction of the film sample was obtained using two polarizing plates, and cut into a rectangle of 4 cm x 2 cm so that the alignment axis direction was orthogonal. In-plane retardation (Ro) and thickness direction retardation (Rth) were measured at the center of the width using a retardation measuring instrument (Axometrics, Axoscan, measuring wavelength 550 nm). In addition, the refractive index of the film sample, which is the basic data of the phase difference measuring instrument, was measured by an Abbe refractometer (manufactured by Atago, NAR-4T, measurement wavelength: 589.3 nm), and the thickness of the film was measured by an electric micrometer (manufactured by FineLuff, Millitron). 1245D).

Test Example 4: In-plane phase difference change amount

The in-plane retardation (Ro) in the entire effective width of the film sample was measured, and based on this, the amount of change (| ΔRo | / | Δx |) (nm / mm) of the in-plane retardation with respect to the displacement in the width direction was calculated.

Test Example 5: Rainbow stain evaluation

A film sample was attached to both sides of the polarizer to construct a polarizing plate. After applying the polarizing plate to the display device, it was visually observed whether rainbow stains and colors were generated in the front and inclined directions of the polarizing plate, and evaluated according to the following criteria.

-No rainbow spots: No rainbow spots were observed in any direction.

-Rainbow stains occur: Rainbow stains are observed in the oblique or frontal direction.

Test Example 6: Surface hardness

After forming a hard coating layer having a thickness of about 3 μm on the surface of the film sample, the surface hardness of the film sample was measured with a pencil hardness tester (Kipae E & T, KP-M5000M).

Test Example 7: UV transmittance

UV transmittance was measured by transmitting light having a wavelength of 380 nm to the film sample.

Test Example 8: moisture permeability

The moisture permeability tester (Permatran-W model 3/33, Mocon) was used for the film samples to measure the moisture permeability for 24 hours at 38 ° C and 100% RH.

The process conditions and test results of the above Examples and Comparative Examples are summarized in Tables 1 to 4 below.

division MD
Draw ratio TD
Stretch ratio * Heat setting
Temperature (℃) thickness
(㎛) Example 1 3.2 3.24 / 3.46 210 42 Example 2 3.3 3.31 / 3.52 190 50 Example 3 3.5 3.51 / 3.71 220 48 Comparative Example 1 3.3 3.71 190 45 Comparative Example 2 1.2 4.2 240 55 Comparative Example 3 3.4 4.1 220 45  * The TD stretching ratios of Examples 1 to 3 are described as the primary TD stretching ratio / total TD stretching ratio

division MD
Shrinkage (%) TD
Shrinkage (%) Shrinkage ratio
(TD / MD) Excitement
Occurrence Example 1 0.53 0.06 0.12 radish Example 2 0.49 0.14 0.29 radish Example 3 0.55 0.41 0.75 radish Comparative Example 1 0.65 0.59 0.91 Occurs Comparative Example 2 0.45 0.15 0.33 radish Comparative Example 3 0.5 0.75 1.5 Occurs

division Out of center
Ro (nm) Out of center
Rth (nm) In-plane retardation
Change amount (nm / mm) Rainbow stains
Occurrence Example 1 174 6854 254 radish Example 2 148 7586 197 radish Example 3 189 7123 318 radish Comparative Example 1 342 9745 1154 Occurs Comparative Example 2 5186 8924 650 Occurs Comparative Example 3 745 9874 2250 Occurs

division Moisture permeability
(g / ㎡day) Surface hardness UV transmittance
(%) Example 1 28 2H 1.1 Example 2 21 3H 2.5 Example 3 25 3H 4.3 Comparative Example 1 26 2H 25 Comparative Example 2 23 2H 82

As shown in Tables 1 to 4, the optical films of Examples 1 to 3 were subjected to two-stage TD stretching with relaxation, and as a result, had a low TD / MD shrinkage rate without increasing the heat setting temperature, so that excitation did not occur. At the same time, it was possible to realize a low in-plane retardation and did not generate rainbow stains.

On the other hand, as for the optical films of Comparative Examples 1 and 3, TD / MD shrinkage was not sufficiently low as a result of performing one-stage TD stretching, so that excitation occurred, and as a result of increasing the heat setting temperature in Comparative Example 2 to lower the shrinkage The in-plane retardation was increased and rainbow stains occurred.

10: (top) polarizing plate, 10 ': (bottom) polarizing plate,
11: polarizer, 12: optical film,
13: TAC film, 15, 16, 17: adhesive layer,
19: glass substrate, 70: liquid crystal panel,
71: color filter substrate, 72: liquid crystal layer,
73: TFT substrate, 80: backlight unit,
90: organic electroluminescent panel, 91: organic electroluminescent substrate,
92: driving substrate,
d: film thickness, A, B: center of width,
A ', A'',B', B '': A point shifted from the center of the width.

Claims (15)

In-plane retardation (Ro) of 600 nm or less and
Has a thickness direction retardation (Rth) of 4000 nm or more,
When defining the first and second directions perpendicular to each other in the plane,
The heat shrinkage rate (s1) in the first direction at 85 ° C. and 24 hours is 1.0% or less,
The ratio (s2 / s1) of the heat shrinkage ratio (s2) in the second direction to the heat shrinkage ratio (s1) in the first direction is 0.1 to 0.6,
The amount of change (| ΔRo | / | Δx |) of the in-plane phase difference with respect to the displacement in the width direction is 197 nm / mm to 254 nm / mm, where the displacement in the width direction (Δx) is the distance between certain points on the width direction (x axis) (x ₂ -x ₁ ), and the amount of change (ΔRo) of the in-plane phase difference means the difference (Ro ₂ -Ro ₁ ) of the in-plane phase difference at each of the predetermined points.
According to claim 1,
The first direction is the longitudinal direction (MD),
The second direction is the width direction (TD), the optical film.
According to claim 2,
The optical film having a thermal contraction rate (s1) of 0.1% to 0.8% in the first direction.
According to claim 2,
The optical film having a thermal contraction rate (s2) in the second direction of 0.01% to 0.5%.
delete According to claim 1,
The optical film
Moisture permeability of 10 g / m 2 · day to 50 g / m 2 · day, and
An optical film having a surface hardness of 2H or more.
According to claim 1,
The optical film has an optical transmittance of 5% or less at a wavelength of 380 nm.
According to claim 1,
The optical film, the optical film having a thickness of 30 ㎛ to 60 ㎛.
According to claim 1,
The optical film, wherein the optical film comprises a polyester resin.
According to claim 1,
The optical film is used as a polarizer protective film, an optical film.
A method of manufacturing an optical film according to claim 1, comprising stretching a film containing a polyester resin in a lengthwise direction and a widthwise direction, wherein the widthwise stretching includes at least two steps of widthwise stretching.
The method of claim 11,
The widthwise stretching includes primary widthwise stretching and secondary widthwise stretching,
A method of manufacturing an optical film, wherein relaxation is further performed between the stretching in the primary width direction and the stretching in the secondary width direction, and the relaxation is performed at a relaxation rate of 0% to 5% with respect to the width direction.
The method of claim 12,
The widthwise stretching is performed at a total stretching ratio of 2.5 to 5.0,
At this time, the primary width direction stretching is performed at a stretching ratio of 2.0 to 4.0, a method of manufacturing an optical film.
The method of claim 11,
The manufacturing method of the optical film,
After the stretching, further comprising the step of heat-setting the stretched film,
The heat setting is performed at a temperature of 150 ℃ to 220 ℃, the method of manufacturing an optical film.
Polarizer; And
An optical component comprising the optical film of claim 1 disposed on at least one surface of the polarizer.

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