KR102800725B1 - Polarizing Plate - Google Patents

Abstract

The present application relates to a polarizing plate. The present application can provide a polarizing plate including a polyester film that can utilize excellent low moisture permeability characteristics without causing optical defects and does not easily break or crack even when bent, and a display device using the polarizing plate.

Description

Polarizing Plate

This application relates to a polarizing plate and a display device.

A polarizing plate is an optical film used to control the state of light in various display devices. Usually, a polarizing plate is manufactured by attaching a protective film to one or both sides of a polarizing film with a polarizing function.

Polarizing plates are required to be durable because they are exposed to various temperature and humidity conditions depending on the usage environment of the display device. For example, polarizing plates must stably maintain designed optical characteristics even under external environments such as temperature and humidity, and mechanical defects such as cracks must not occur.

Polarizing films included in polarizing plates (especially, so-called PVA (poly(vinyl alcohol))-based polarizing films) have the property of being vulnerable to moisture, so there is a problem of deterioration when they come into contact with moisture during use. Therefore, efforts are being made to apply low moisture permeability materials as protective films laminated on one or both sides of the polarizing film, and the materials currently widely used are acrylic films or COP (cyclic olefin polymer) films.

Polyester materials, represented by PET (poly(ethylene terephthalate)), are known to have much better low moisture permeability characteristics than the acrylic film or COP film. However, since polyester materials have a phase difference, when applied to a polarizing plate, they cause optical defects, such as so-called rainbow spots, depending on the usage environment.

To solve the above problem, a technology exists for manufacturing polyester film using a high-stretch method to have a higher phase difference than usual (e.g., patent document 1).

The above conventional technology can solve optical defect problems such as rainbow spots and utilize the low moisture permeability characteristics of polyester films.

However, films like the above are expensive and not easily available because they are manufactured through special processes such as high-strength processes.

In addition, since the film above is manufactured using a high-stretch process, there is a problem that it is easily broken or cracked when bent, for example, around the stretching axis.

Japanese Patent No. 6521216

The present application provides a polarizing plate and a display device. The purpose of the present application is to provide a polarizing plate including a polyester film that can utilize excellent low moisture permeability characteristics without occurrence of optical defects and does not easily break or crack even when bent, etc., and a display device using the polarizing plate.

In this specification, terms such as vertical, parallel, orthogonal or horizontal, among those defining angles, mean substantial vertical, parallel, orthogonal or horizontal within a range that does not impair the intended effect, and the range of vertical, parallel, orthogonal or horizontal includes errors such as manufacturing errors or variations. For example, each of the above cases may include an error within about ±15 degrees, an error within about ±10 degrees, or an error within about ±5 degrees.

The optical properties mentioned in this specification, such as phase difference and refractive index, are properties based on a wavelength of 550 nm, unless specifically stated otherwise.

Among the properties mentioned in this specification, unless otherwise specifically specified, in cases where the measurement temperature affects the property, the property is a property measured at room temperature.

The term "room temperature" as used herein refers to a temperature in a state where it is not specifically heated or cooled, and may mean any temperature within a range of about 10°C to 30°C, for example, a temperature of about 15°C or higher, 18°C or higher, 20°C or higher, or about 23°C or higher, but about 27°C or lower. In addition, unless specifically specified otherwise, the unit of temperature mentioned in this specification is ℃.

Among the properties mentioned in this specification, unless otherwise specifically specified, in cases where the measurement pressure affects the property, the property is a property measured at atmospheric pressure.

The term atmospheric pressure in this specification means a natural pressure that is not specifically pressurized or depressurized, and is usually about 1 atm, the same as atmospheric pressure.

Unless otherwise specifically specified, among the properties mentioned in this specification, in cases where the measured humidity affects the property, the property is any one humidity within the range of about 0 RH% to 100 RH%, for example, about 90 RH% or less, about 80 RH% or less, about 70 RH% or less, about 60 RH% or less, about 50 RH% or less, about 40 RH% or less, about 30 RH% or less, about 20 RH% or less, about 18 RH% or less, about 15 RH% or less, or about 10 RH% or more, about 2 RH% or more, about 5 RH% or more, about 10 RH% or more, about 15 RH% or more, about 20 RH% or more, about 25 RH% or more, about 30 RH% or more, about 35 RH% or more, about 40 RH% or more, or about 45 RH%. It is a property measured at the relative humidity above. The unit RH% above means that the humidity is relative humidity (unit: %).

Unless otherwise specified, the angle formed by any two directions mentioned in this specification may be an acute angle among the acute or obtuse angles formed by the two directions, or a smaller angle among the angles measured in the clockwise and counterclockwise directions. Accordingly, unless otherwise specified, the angles mentioned in this specification are positive numbers. However, in some cases, in order to indicate the measurement direction between the angles measured in the clockwise or counterclockwise direction, one of the angles measured in the clockwise direction and the angles measured in the counterclockwise direction may be expressed as a positive number, and the other angle may be expressed as a negative number.

The present application relates to a polarizing plate. In this specification, the terms polarizing film and polarizing plate have different meanings. The term polarizing film means a functional element itself exhibiting a polarizing function, such as a PVA (poly(vinyl alcohol))-based film on which an anisotropic material such as iodine is adsorbed and oriented, and the polarizing plate means an element including other elements together with the polarizing film. Examples of other elements included together with the polarizing film include, but are not limited to, a protective film, an antistatic layer, a viewing angle compensation film, a hard coating layer, a phase difference film, an adhesive layer, an adhesive layer, or a low reflection layer of the polarizing film.

The polarizing plate of the present application can be applied to various purposes and exhibit excellent performance.

For example, the polarizing plate of the present application may have a square shape, such as a square or a rectangle, and the ratio (W/L) of its width (W) to length (L) may be within a range of 1.6 to 2. In this case, the ratio (W/L) may be about 1.65 or more, about 1.7 or more, or about 1.75 or more, or about 1.95 or less, about 1.9 or less, about 1.85 or less, or about 1.8 or less in other examples.

In another example, the polarizing plate of the present application may have a square shape, such as a square or a rectangle, and the ratio (W/L) of its width (W) to its length (L) may be in a range of 1 to 1.6. In such a case, the ratio (W/L) may be about 1.05 or more, about 1.1 or more, about 1.15 or more, about 1.2 or more, about 1.25 or more, or about 1.3 or more, or about 1.55 or less, about 1.5 or less, about 1.45 or less, about 1.4 or less, or about 1.35 or less.

The size of the above polarizing plate is a value determined by the specifications of the display device to which the polarizing plate is applied, for example, the screen ratio. The polarizing plate of the present application can exhibit the intended excellent performance regardless of the screen ratio to which the polarizing plate is applied.

Polarizing plates are formed with different light absorption axes depending on the application, for example, the mode of the display panel, etc. Usually, the polarizing film in the polarizing plate shrinks along the direction in which the light absorption axis is formed, so the direction in which the light absorption axis is formed is also a consideration in the optical and mechanical durability of the polarizing plate or in suppressing bending and twisting of the display device to which the polarizing plate is applied. The polarizing plate of the present application exhibits excellent performance regardless of the direction in which the light absorption axis is formed.

For example, in the polarizing plate, the smaller angle among the angles formed by one side of the polarizing film or the polarizing plate and the light absorption axis of the polarizing film may be within a range of 0 to 10 degrees or within a range of 80 to 100 degrees. In other examples, the angle may be 9 degrees or less, 8 degrees or less, 7 degrees or less, 6 degrees or less, 5 degrees or less, 4 degrees or less, 3 degrees or less, 2 degrees or less, or 1 degree or less. Additionally, the angle may be about 81 degrees or more, 82 degrees or more, 83 degrees or more, 84 degrees or more, 85 degrees or more, 86 degrees or more, 87 degrees or more, 88 degrees or more, 89 degrees or more, or 90 degrees or less, 99 degrees or less, 98 degrees or less, 97 degrees or less, 96 degrees or less, 95 degrees or less, 94 degrees or less, 93 degrees or less, 92 degrees or less, 91 degrees or less, or 90 degrees or less.

In another example, the smaller angle among the angles formed by one side of the polarizing film or the polarizing plate and the light absorption axis of the polarizing film may be within a range of 35 to 55 degrees or within a range of 125 to 145 degrees.

The above angle may be about 36 degrees or more, about 37 degrees or more, about 38 degrees or more, about 39 degrees or more, about 40 degrees or more, about 41 degrees or more, about 42 degrees or more, about 43 degrees or more, about 44 degrees or more, or about 45 degrees or more, or about 54 degrees or less, about 53 degrees or less, about 52 degrees or less, about 51 degrees or less, about 50 degrees or less, about 49 degrees or less, about 48 degrees or less, about 47 degrees or less, about 46 degrees or less, or about 45 degrees or less, and may also be about 126 degrees or more, about 127 degrees or more, about 128 degrees or more, about 129 degrees or more, about 130 degrees or more, about 131 degrees or more, about 132 degrees or more, about 133 degrees or more, about 134 degrees or more, or about 135 degrees or more, or about 144 degrees or less, It can be less than 143 degrees, less than 142 degrees, less than 141 degrees, less than 140 degrees, less than 139 degrees, less than 138 degrees, less than 137 degrees, less than 136 degrees, or less than 135 degrees.

Typically, polarizing films and polarizing plates are rectangular, such as squares or rectangles, and one side of the polarizing film or polarizing plate forming the angle with the light absorption axis can be any side of the rectangle. For example, if the rectangle is a rectangle, the one side can be the long side or the short side of the rectangle.

The polarizing plate of the present application may basically include a polarizing film and an optical film formed on one or both sides of the polarizing film. The optical film may be a protective film for the polarizing film. When the optical films are formed on both sides of the polarizing film, the two optical films may be the same film or different films, but at least one film is the optical film of the present application described below. In one example, at least the outer optical film is the optical film of the present application. The outer optical film in the above means an optical film that is positioned farther away from the polarizing film when the polarizing plate is applied to a device such as a display device. Therefore, for example, if the polarizing plate is a so-called viewer-side polarizing plate, the optical film of the present application is positioned at least on the viewer side relative to the polarizing film. For example, if the polarizing plate includes an adhesive layer or an adhesive layer, and the adhesive layer or the adhesive layer is used to attach the polarizing plate to a device such as a display device, the polarizing plate may include the optical film, polarizing film, and adhesive layer or adhesive layer of the present application in the above order.

In the present application, a polarizing film having a light absorption axis formed along one direction within the plane can be used as the polarizing film. Such polarizing films are known in various ways. In one example, a polyvinyl alcohol (PVA)-based polarizing film, which is a representative linear absorption-type polarizing film, can be used as the polarizing film. Such a polarizing film typically includes a PVA film and an anisotropic absorbent material adsorbed and oriented on the PVA film. As the anisotropic absorbent material, various dichroic dyes can be used, and an iodine-based material can be representatively used. Such a polarizing film is generally called an iodine-based absorbent linear PVA polarizing film.

For example, the PVA polarizing film can be manufactured by performing various treatments such as swelling, dyeing, crosslinking, and stretching on a PVA film, and then performing a washing and drying process. As described below, the shrinkage force of the polarizing film can be adjusted within a predetermined range, and the shrinkage force can be controlled by adjusting the process conditions in any one of the above processes. In general, the shrinkage force can be affected by the stretching ratio, etc. during the stretching process among the above processes. That is, when the stretching ratio is high, the shrinkage force increases, and when it is low, it can decrease. However, this method corresponds to one direction in which the shrinkage force can be controlled, and a person skilled in the art of manufacturing a polarizing film can easily manufacture a polarizing film having a desired shrinkage force depending on the purpose.

The polarizing film of the present application is the iodine-based absorption-type linear PVA polarizing film, which may include a PVA film and an anisotropic absorbent material that is adsorbed and oriented on the PVA film.

As the PVA film mentioned above, for example, a general PVA film used in a conventional polarizing film can be used. As a material of such a PVA film, PVA or a derivative thereof can be mentioned. As a derivative of PVA, polyvinyl formal or polyvinyl acetal can be mentioned, and in addition, those modified with an olefin such as ethylene or propylene, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid and an alkyl ester thereof, or acrylamide can be mentioned. The degree of polymerization of PVA is usually about 100 to 10,000, about 1,000 to 10,000, and the degree of saponification is about 80 mol% to 100 mol%, but is not limited thereto.

Examples of PVA films include hydrophilic polymer films such as partially saponified films of the ethylene vinyl acetate copolymer series, polyene-based oriented films such as dehydrated PVA products or dehydrochlorinated polyvinyl chloride products.

Among the PVA films, additives such as plasticizers or surfactants may be included. As the plasticizers mentioned above, polyols or condensates thereof may be exemplified, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, or polyethylene glycol. When such plasticizers are used, the proportion thereof is not particularly limited, and is typically about 20 wt% or less in the PVA film.

The type of anisotropic absorbent material that can be included in the polarizing film is also not particularly limited. In the present application, among known anisotropic absorbent materials, one that can satisfy the optical properties described above can be appropriately selected. Iodine can be cited as an example of the anisotropic absorbent material. The ratio of the anisotropic absorbent material in the polarizing film is also not particularly limited as long as it is within a range that can satisfy the desired physical properties.

A polarizing film can be manufactured, for example, by performing at least dyeing, cross-linking and stretching processes on a PVA film.

In the dyeing process, an anisotropic absorbent material such as iodine can be adsorbed and/or oriented on the PVA film. This dyeing process can be performed together with the stretching process. Dyeing can generally be performed by immersing the film in a solution containing an anisotropic absorbent material, for example, an iodine solution. As the iodine solution, for example, an aqueous solution containing iodine ions by iodine and an iodide compound which is a solubilizing agent can be used. As the iodide compound in the above, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide or titanium iodide can be used. The concentration of iodine and/or iodide ions in the iodine solution can be controlled within a normal range depending on the purpose. In the dyeing process, the temperature of the iodine solution is usually about 20°C to 50°C, or about 25°C to 40°C, and the immersion time is usually about 10 seconds to 300 seconds, or about 20 seconds to 240 seconds, but is not limited thereto.

The crosslinking process performed in the process of manufacturing a polarizing film can be performed using a crosslinking agent such as a boron compound, for example. The order of the crosslinking process is not particularly limited, and can be performed, for example, together with a dyeing and/or stretching process, or separately. The crosslinking process can be performed multiple times. As the boron compound, boric acid or borax, etc. can be used. The boron compound can generally be used in the form of an aqueous solution or a mixed solution of water and an organic solvent, and a boric acid aqueous solution is typically used. The boric acid concentration in the boric acid aqueous solution can be selected within an appropriate range in consideration of the degree of crosslinking and the resulting heat resistance, etc. The boric acid aqueous solution, etc. can also contain an iodide compound such as potassium iodide.

The treatment temperature of the crosslinking process is typically in the range of 25°C or higher, 30°C to 85°C, or 30°C to 60°C, and the treatment time is typically in the range of 5 seconds to 800 seconds, or 8 seconds to 500 seconds, but is not limited thereto.

The stretching process is generally performed by uniaxial stretching. This stretching may be performed together with the dyeing and/or crosslinking processes. The stretching method is not particularly limited, and for example, a wet stretching method may be applied. In this wet stretching method, for example, stretching is generally performed after dyeing, but stretching may be performed together with crosslinking, and may be performed multiple times or in multiple stages.

The treatment solution applied to the wet stretching method may contain an iodine compound such as potassium iodide. The treatment temperature in the stretching is usually in the range of 25°C or higher, 30°C to 85°C, or 50°C to 70°C, and the treatment time is usually in the range of 10 seconds to 800 seconds, or 30 seconds to 500 seconds, but is not limited thereto.

In the stretching process, the total stretching ratio can be controlled by considering the orientation characteristics, etc., and the total stretching ratio can be about 3 to 10 times, 4 to 8 times, or 5 to 7 times based on the original length of the PVA film, but is not limited thereto. The total stretching ratio as described above can mean a cumulative stretching ratio including the stretching in each process when stretching is also performed in a swelling process other than the stretching process. This total stretching ratio can be controlled within an appropriate range by considering the orientation, the processability of the polarizing film, the possibility of stretching and cutting, etc. As described above, the shrinkage force can be controlled by controlling the stretching ratio.

In the manufacturing process of polarizing films, a swelling process may be performed before performing the above processes in addition to the dyeing, crosslinking, and stretching. By swelling, contamination or anti-blocking agent on the surface of the PVA film can be cleaned, and there is also an effect of reducing unevenness such as dyeing deviation.

In the swelling process, water, distilled water or pure water can usually be used. The main component of the treatment solution is water, and if necessary, additives such as iodine compounds such as potassium iodide or surfactants, or alcohol, etc., can be included in small amounts.

The processing temperature in the swelling process is typically, but not limited to, about 20°C to 45°C or about 20°C to 40°C. Since swelling deviation can cause dyeing deviation, the process variables can be controlled so that the occurrence of such swelling deviation is suppressed as much as possible. If necessary, appropriate stretching can also be performed in the swelling process. The stretching ratio can be about 6.5 times or less, 1.2 to 6.5 times, 2 to 4 times, or 2 to 3 times based on the original length of the PVA film. The stretching in the swelling process can be controlled so that the stretching in the stretching process performed after the swelling process is small and the film is not broken during stretching.

In the process of manufacturing a polarizing film, metal ion treatment can be performed. This treatment is performed, for example, by immersing a PVA film in an aqueous solution containing a metal salt. Through this, metal ions can be contained in the polarizer. In this process, the color tone of the PVA polarizing film can be adjusted by controlling the type or ratio of the metal ions. Examples of the metal ions that can be applied include transition metal ions such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, or iron, and color tone can be adjusted by selecting an appropriate type among these.

In the manufacturing process of polarizing films, a cleaning process may be performed after dyeing, crosslinking, and stretching. This cleaning process may be performed using an iodine compound solution such as potassium iodide, or may be performed using water.

Washing with water and washing with an iodine compound solution may be combined, and solutions containing liquid alcohols such as methanol, ethanol, isopropyl alcohol, butanol or propanol may also be used.

After going through these processes, a drying process can be performed to manufacture a polarizing film. In the drying process, for example, it can be performed at an appropriate temperature for an appropriate time considering the moisture content required for the polarizing film, and these conditions are not particularly limited.

The thickness of the polarizing film applied in the present application may typically be within a range of about 5 μm to 25 μm. The thickness may be about 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, 19 μm or less, 18 μm or less, or 17 μm or less, in other examples, or may be about 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 15 μm or more, or 16 μm or more.

An optical film of the present application is disposed on at least one side or both sides of the polarizing film. The optical film may be a protective film for the polarizing film.

In the present application, as the optical film, a polyester film (for example, a PET (poly(ethylene terephthatlate) film) manufactured by a special stretching process described below is applied. Therefore, the optical film of the present application may be a stretched polyester film. The optical film of the present application has specific non-uniform optical characteristics. Due to these optical characteristics, the optical film of the present application does not cause optical stains such as so-called rainbow stains when applied to a polarizing plate even if a high phase difference due to high stretching is not provided. In addition, the non-uniform optical characteristics induce uniform mechanical characteristics, and thus the weak characteristics that appear in the conventional high-stretch polyester film are resolved. That is, the conventional high-stretch polyester film has a problem that it is easily broken or cracked when bent about the main axis of orientation, but the optical film of the present application does not have such a problem. Therefore, a polarizing plate to which the optical film is applied is suitable for manufacturing a curved device such as a so-called curved display. It's useful.

Hereinafter, the first direction in the plane of the optical film mentioned to describe the optical film may mean one of the MD (Machine Direction) and TD (transverse direction) directions when the optical film is a stretched polymer film, and the second direction may mean the other of the MD (Machine Direction) and TD (transverse direction) directions. Accordingly, the first and second directions may be approximately perpendicular to each other. The perpendicularity is when the angle formed by the first and second directions is within a range of about 80 to 100 degrees. The angle meaning the perpendicularity may be approximately 82 degrees or more, 84 degrees or more, 86 degrees or more, 88 degrees or more, or 98 degrees or less, 96 degrees or less, 94 degrees or less, 92 degrees or less, or 90 degrees or less in other examples.

In one example, the non-uniform optical properties of the optical film can be defined as optical axes that appear in different directions in each divided area when the optical film is virtually divided into three parts by a specific standard.

For example, when the optical film of the present application is divided into three regions of the same area by an imaginary line in a direction horizontal or perpendicular to the first or second direction in the plane of the optical film, the average optical axis direction of the central region may be different from the average optical axis direction of the left region or the right region. In the above, the optical axis means the ground axis or the true axis of the corresponding region.

For example, the angle formed by the average optical axis of the central region of the above-mentioned three-part region and the average optical axis of the left region or the right region is more than 10 degrees, 10 degrees or more, 11 degrees or more, 12 degrees or more, 13 degrees or more, 14 degrees or more, 15 degrees or more, 16 degrees or more, 17 degrees or more, 18 degrees or more, 19 degrees or more, 20 degrees or more, 21 degrees or more, 22 degrees or more, 23 degrees or more, 24 degrees or more, or 25 degrees or more, or 50 degrees or less, 49 degrees or less, 48 degrees or less, 47 degrees or less, 46 degrees or less, 45 degrees or less, 44 degrees or less, 43 degrees or less, 42 degrees or less, 41 degrees or less, 40 degrees or less, 39 degrees or less, 38 degrees or less, 37 degrees or less, 36 degrees or less, 35 degrees or less, 34 degrees or less, 33 degrees or less, 32 degrees. It can be below 31 degrees, below 30 degrees, below 29 degrees, below 28 degrees, below 27 degrees, or below 26 degrees.

In addition, in the optical film, the left and right regions of the three-divided region may exhibit similar or symmetrical average optical axes. For example, the angle formed by the average optical axis of the left region and the average optical axis of the right region of the three-divided region may be about 10 degrees or less, less than 10 degrees, 9 degrees or less, or 9.5 degrees or less, or about 0 degrees or more, 1 degree or more, 2 degrees or more, 3 degrees or more, 4 degrees or more, 5 degrees or more, 6 degrees or more, 7 degrees or more, or 8 degrees or more.

The above contents are explained with reference to the drawings.

For example, when a square indicated by the symbol 100 in Fig. 1 is referred to as any one surface of an optical film, and an imaginary line (a dotted line in the drawing, which may be parallel to the MD direction or the TD direction in the above-mentioned rigidly stretched polymer film) that is perpendicular or horizontal to the first or second direction in the plane of the optical film is divided into three parts, the surface of the optical film can be divided into a central region (M), a right region (R), and a left region (L). A typical stretched polymer film exhibits a roughly uniform optical axis determined according to the main stretching direction, but the present application exhibits different average optical axes in each of the three equally divided regions, which are defined by double-headed arrows in each region in Fig. 1. As roughly shown in the drawing, the tendency of the average optical axis exhibits a symmetrical characteristic in which the deviation is large in the central region and the right region, and in the central region and the left region, and small in the right and left regions. Surprisingly, these characteristics do not cause optical defects in the polarizing plate even when a high phase difference is not imparted by high elongation. The reason is not clear, but it is thought that the phenomenon causing optical defects is offset or alleviated by the non-uniform characteristics. Such non-uniformity of the optical axis can be expressed by the difference in the average optical axis. The average optical axis can be measured by the method described in the examples.

The above optical non-uniformity can also be expressed by the non-uniformity of the phase difference within the optical film.

For example, in the optical film, the difference (R _{in.max -R} in.min) between the minimum value (R _in.min ) and the maximum value (R _in.max ) of the in-plane retardation may be in the range of 200 nm to 1,000 nm. The difference (R _in.max -R _in.min ) may be, in other examples, 250 nm or more, 300 nm or more, 350 nm or more, or 400 nm or more, or 950 nm or less, 900 nm or less, 850 nm or less, 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less, 500 nm or less, or 450 nm or less. That is, while a typical stretched polymer film exhibits a substantially uniform retardation over the entire surface of the polymer film, the optical film of the present application exhibits non-uniform retardation characteristics as described above. It is thought that these non-uniform phase difference characteristics cancel out or alleviate phenomena that cause optical defects such as the rainbow phenomenon.

In this specification, the in-plane phase difference is a value typically expressed by the following mathematical formula 1.

[Formula 1]

Rin = dХ(nx-ny)

In Equation 1, d is the thickness of the film, nx is the refractive index along the superaxial direction, and ny is the refractive index along the superaxial direction.

In the above optical film, the minimum value of the in-plane phase difference (R _in.min ) can be within a range of approximately 10 to 300 nm. The above minimum value (R _in.min ) may be about 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 65 nm or more, or 70 nm or more, or 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, or 75 nm or less, in other examples.

In the above optical film, the maximum value of the in-plane phase difference (R _in.max ) can be within the range of 350 to 1,000 nm. The above maximum value (R _in.max ) is, in other examples, 360 nm or more, 370 nm or more, 380 nm or more, 390 nm or more, 400 nm or more, 410 nm or more, 420 nm or more, 430 nm or more, 440 nm or more, 450 nm or more, 460 nm or more, 470 nm or more, 480 nm or more, or 490 nm or more, or 990 nm or less, 980 nm or less, 970 nm or less, 960 nm or less, 950 nm or less, 940 nm or less, 930 nm or less, 920 nm or less, 910 nm or less, 900 nm or less, 890 nm or less, 880 nm or less, 870 nm or less, 860 nm or less, 850 nm or less, 840 nm or less, 830 nm or less, 820 nm or less, 810 It may be less than or equal to nm, less than or equal to 800 nm, less than or equal to 790 nm, less than or equal to 780 nm, less than or equal to 770 nm, less than or equal to 760 nm, less than or equal to 750 nm, less than or equal to 740 nm, less than or equal to 730 nm, less than or equal to 720 nm, less than or equal to 710 nm, less than or equal to 700 nm, less than or equal to 690 nm, less than or equal to 680 nm, less than or equal to 670 nm, less than or equal to 660 nm, less than or equal to 650 nm, less than or equal to 640 nm, less than or equal to 630 nm, less than or equal to 620 nm, less than or equal to 610 nm, less than or equal to 600 nm, less than or equal to 590 nm, less than or equal to 580 nm, less than or equal to 570 nm, less than or equal to 560 nm, less than or equal to 550 nm, less than or equal to 540 nm, less than or equal to 530 nm, less than or equal to 520 nm, less than or equal to 510 nm, less than or equal to 500 nm or less than or equal to 490 nm.

Additionally, the average in-plane retardation (R _in.AVG ) of the optical film can be in a range of approximately 100 to 1,000 nm. The above average in-plane phase difference (R _in.AVG ) is, in other examples, 150 nm or more, 200 nm or more, or 250 nm or more, or 990 nm or less, 980 nm or less, 970 nm or less, 960 nm or less, 950 nm or less, 940 nm or less, 930 nm or less, 920 nm or less, 910 nm or less, 900 nm or less, 890 nm or less, 880 nm or less, 870 nm or less, 860 nm or less, 850 nm or less, 840 nm or less, 830 nm or less, 820 nm or less, 810 nm or less, 800 nm or less, 790 nm or less, 780 nm or less, 770 nm or less, 760 nm or less, 750 nm or less, 740 nm or less, 730 nm or less, 720 nm or less, 710 nm or less, 700 nm or less, 690 nm or less, 680 nm or less, 670 nm or less, 660 nm or less, 650 nm or less, 640 nm or less, 630 nm or less, 620 nm or less, 610 nm or less, 600 nm or less, 590 nm or less, 580 nm or less, 570 nm or less, 560 nm or less, 550 nm or less, 540 nm or less, 530 nm or less, 520 nm or less, 510 nm or less, 500 nm or less, 490 nm or less, 480 nm or less, 470 nm or less, 460 nm or less, 450 nm or less, 440 nm or less, 430 nm or less, 420 nm or less, 410 nm or less, 400 nm or less, 390 nm or less, 380 nm or less, 370 nm or less, 360 nm or less, It may be less than 350 nm, less than 340 nm, less than 330 nm, less than 320 nm, less than 310 nm, less than 300 nm, or less than 290 nm.

In one example, when the protective film surface is divided into three equal parts in the same manner as described above, the minimum value (R _in.min ) of the in-plane phase difference can be confirmed in the central region (region M of Fig. 1), and the maximum value (R _in.max ) can be confirmed in the left region (region L of Fig. 1) or the right region (region R of Fig. 1).

In one example, the central region of the three-part region (region M in FIG. 1) shows a lower phase difference than the left and right regions (regions R and L in FIG. 1), and the left and right regions can show similar in-plane phase differences to each other.

For example, in the case of being divided into three equal parts as in the above drawing 1, the difference (RL-M) between the average in-plane phase difference (M) of the central region (M) and the average in-plane phase difference (RL) of the left region or the right region can be within the range of 50 nm to 1,000 nm. The above difference (R _in.max -R _in.min ) may be, in other examples, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more or 180 nm or more, or 950 nm or less, 900 nm or less, 850 nm or less, 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less, 500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less or 200 nm or less.

In addition, when divided into three equal parts as in the above drawing 1, the absolute value of the difference (R-L) between the average in-plane phase difference (L) of the left region and the average in-plane phase difference (R) of the right region may be about 45 nm or less. The absolute value of the difference may be about 0 nm or more, 1 nm or more, 2 nm or more, 3 nm or more, 4 nm or more, 5 nm or more, 6 nm or more, 7 nm or more, 8 nm or more, or 9 nm or more, or about 40 nm or less, 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less.

Additionally, the average value ( _M.AVG ) of the in-plane phase difference in the central region among the regions divided into three as shown in Fig. 1 can be within a range of approximately 10 to 290 nm. The above minimum value (R _in.min ) may be about 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 65 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, or 150 nm or more, or 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, or 160 nm or less, in other examples.

Additionally, as shown in Fig. 1, the average value ( _RL.AVG ) of the in-plane phase difference in the left or right region among the regions divided into three equal parts may be within the range of 300 to 1,000 nm. The above maximum value (R _in.max ) is, in other examples, 310 nm or more, 315 nm or more, 320 nm or more, 325 nm or more, 330 nm or more, 335 nm or more, or 400 nm or more, or 990 nm or less, 980 nm or less, 970 nm or less, 960 nm or less, 950 nm or less, 940 nm or less, 930 nm or less, 920 nm or less, 910 nm or less, 900 nm or less, 890 nm or less, 880 nm or less, 870 nm or less, 860 nm or less, 850 nm or less, 840 nm or less, 830 nm or less, 820 nm or less, 810 nm or less, 800 nm or less, 790 nm or less, 780 nm or less, 770 nm or less, 760 nm or less, 750 nm or less, 740 nm or less, 730 nm or less, 720 nm or less, 710 nm or less, 700 nm or less, 690 nm or less, 680 nm or less, 670 nm or less, 660 nm or less, 650 nm or less, 640 nm or less, 630 nm or less, 620 nm or less, 610 nm or less, 600 nm or less, 590 nm or less, 580 nm or less, 570 nm or less, 560 nm or less, 550 nm or less, 540 nm or less, 530 nm or less, 520 nm or less, 510 nm or less, 500 nm or less, 490 nm or less, 480 nm or less, 470 nm or less, 460 nm or less, 450 nm or less, 440 nm or less, 430 nm or less, 420 nm or less, 410 nm or less, 400 nm or less, 390 nm Below, it may be 380 nm or less, 370 nm or less, or 360 nm or less.

The desired properties can be effectively achieved by the unique optical properties described above.

The above-described unique optical properties are obtained by the manufacturing method of the present application described below.

The manufacturing method of the present application as described above also induces symmetrical properties from a mechanical aspect.

For example, the optical film of the present application may have a ratio (S1/S2) of the shrinkage force (S1) in the first direction and the shrinkage force (S2) in the second direction within a range of 0.7 to 1.2. The ratio (S1/S2) may be, in other examples, 0.75 or more, 0.8 or more, 0.85 or more, 0.9 or more, 0.95 or more, 1 or more, 1.05 or more, 1.1 or more, or 1.15 or less, 1.15 or less, 1.15 or less, 1.05 or less, 1 or less, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, or 0.75 or less.

In addition, in the present application, the contractile force (S1 or S2) in the first or second direction may be in the range of 0.5 N to 4 N. The contractile force (S1 or S2) may be, in other examples, about 1 N or more, about 1.5 N or more, about 2 N or more, about 2.5 N or more, about 3 N or more, or about 3.5 N or less, about 3 N or less, about 2.5 N or less, about 2 N or less, about 1.5 N or less, or about 1 N or less.

The term contractile force in this specification is measured by the method presented in the examples described below.

Due to the mechanical properties described above, the optical film of the present application exhibits excellent bending resistance. For example, the optical film exhibits a mandrel value of 10 pi or less in both the first and second directions. The mandrel value is a value obtained by a mandrel test.

The mandrel test is a test to check whether a specimen is destroyed when it is bent by inserting it into a cylindrical mandrel. The mandrel value is a value at which no defects such as cracks or breaks appear in the optical film (or polarizing plate, as described below) during the mandrel test.

The specific method of conducting the above mandrel test is as described in the examples.

In the case of a high-stretch polyester film, when it is bent about at least one direction among the MD and TD directions as an axis due to asymmetry caused by high stretching, it is easily broken or cracked, but the optical film of the present application does not exhibit such characteristics. The mandrel value may be 9 pi or less, 8 pi or less, 7 pi or less, or 6 pi or less in other examples, or 1 pi or more, 2 pi or more, 3 pi or more, 4 pi or more, 5 pi or more, 6 pi or more, or 7 pi or more.

In another example, the optical film may have a 10-pie mandrel resistance of 5 or more in both the first and second directions. The mandrel resistance refers to the number of times no defects such as breakage or cracking occur when a 10-pie mandrel test is repeated. The mandrel resistance may be 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or 15 or more in other examples, or 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, or 20 or less.

The polarizing plate of the present application arranges the optical film of the present application, for example, as a protective film, on at least one side or both sides of the polarizing film. Usually, in this arrangement, the MD or TD direction of the optical film is arranged so as to be perpendicular or horizontal to the light absorption axis of the polarizing film. Accordingly, the polarizing plate can reflect the characteristics of the optical film described above as follows.

That is, for example, when the optical film is divided into three regions of the same area by an imaginary line in a direction perpendicular or horizontal to the light absorption axis of the polarizing film in a polarizing plate, the angle formed by the average optical axis direction of the central region and the absorption axis and the angle formed by the average optical axis direction of the left region or the right region and the absorption axis may be different. In the above, the optical axis means the slow axis or the fast axis of the corresponding region.

For example, the angle formed by the average optical axis of the central region of the above-mentioned three-part region and the absorption axis may be within a range of about 0 to 29 degrees. The angle may be, in other examples, more than 1 degree, 2 degrees or more, 3 degrees or more, 4 degrees or more, 5 degrees or more, 6 degrees or more, 7 degrees or more, 8 degrees or more, 9 degrees or more, 10 degrees or more, 11 degrees or more, 12 degrees or more, 13 degrees or more, 14 degrees or more, 15 degrees or more, 16 degrees or more, or 17 degrees or more, or 28 degrees or less, 27 degrees or less, 26 degrees or less, 25 degrees or less, 24 degrees or less, 23 degrees or less, 22 degrees or less, 21 degrees or less, 20 degrees or less, 19 degrees or less, or 18 degrees or less.

Additionally, for example, the angle formed by the average optical axis of the left or right region of the divided region into three parts and the absorption axis may be 30 degrees or more. The above angle is, in other examples, 31 degrees or more, 32 degrees or more, 33 degrees or more, 34 degrees or more, 35 degrees or more, 36 degrees or more, 37 degrees or more, 38 degrees or more, 39 degrees or more, 40 degrees or more, 41 degrees or more, 42 degrees or more, or 43 degrees or more, or 90 degrees or less, 89 degrees or less, 88 degrees or less, 87 degrees or less, 86 degrees or less, 85 degrees or less, 84 degrees or less, 83 degrees or less, 82 degrees or less, 81 degrees or less, 80 degrees or less, 79 degrees or less, 78 degrees or less, 77 degrees or less, 76 degrees or less, 75 degrees or less, 74 degrees or less, 73 degrees or less, 72 degrees or less, 71 degrees or less, 70 degrees or less, 69 degrees or less, 68 degrees or less, 67 degrees or less, 66 degrees or less, 65 degrees or less, It may be 64 degrees or less, 63 degrees or less, 62 degrees or less, 61 degrees or less, 60 degrees or less, 59 degrees or less, 58 degrees or less, 57 degrees or less, 56 degrees or less, 55 degrees or less, 54 degrees or less, 53 degrees or less, 52 degrees or less, 51 degrees or less, 50 degrees or less, 49 degrees or less, 48 degrees or less, 47 degrees or less, 46 degrees or less, 45 degrees or less, 44 degrees or less, 43 degrees or less, 42 degrees or less, 41 degrees or less, 40 degrees or less, 39 degrees or less, 38 degrees or less, 37 degrees or less, 36 degrees or less, or 35 degrees or less.

In addition, the absolute value of the difference (B-A) between the angle (A) formed by the average optical axis of the optical film in the central region of the region divided into three equal parts in the same manner as in Fig. 1 in the polarizing plate and the average absorption axis of the polarizing film region overlapping the central region and the angle (B) formed by the average optical axis of the left or right region of the optical film and the average absorption axis of the polarizing film region overlapping the left or right region is more than 10 degrees, 10 degrees or more, 11 degrees or more, 12 degrees or more, 13 degrees or more, 14 degrees or more, 15 degrees or more, 16 degrees or more, 17 degrees or more, 18 degrees or more, 19 degrees or more, 20 degrees or more, 21 degrees or more, 22 degrees or more, 23 degrees or more, 24 degrees or more, or 25 degrees or more, or 50 degrees or less, 49 degrees or less, 48 degrees or less, 47 degrees or less, 46 degrees or less, 45 degrees or less, 44 degrees or less, or 43 degrees. Below, 42 degrees or less, 41 degrees or less, 40 degrees or less, 39 degrees or less, 38 degrees or less, 37 degrees or less, 36 degrees or less, 35 degrees or less, 34 degrees or less, 33 degrees or less, 32 degrees or less, 31 degrees or less, 30 degrees or less, 29 degrees or less, 28 degrees or less, 27 degrees or less, 26 degrees or less, 25 degrees or less, 24 degrees or less, 23 degrees or less, 22 degrees or less, 21 degrees or less, 20 degrees or less, 19 degrees or less, or 18 degrees or less.

Since the left and right regions of the three-part region in the optical film may exhibit similar or symmetrical average optical axes, for example, the absolute value of the difference (D-C) between the average value (C) of the angles formed by the average optical axis of the left region of the three-part region and the absorption axes of the polarizing film region overlapping the left region and the average value (D) of the angles formed by the average optical axis of the right region and the absorption axes of the polarizing film region overlapping the right region is 15 degrees or less, 14.5 degrees or less, 14 degrees or less, 13.5 degrees or less, 13 degrees or less, 12.5 degrees or less, 12 degrees or less, 11.5 degrees or less, 11 degrees or less, 10.5 degrees or less, 10 degrees or less, less than 10 degrees, 9 degrees or less, or 9.5 degrees or less, or 0 degrees or more, 1 degree or more, 2 degrees or more, 3 degrees or more, 4 degrees or more, 5 degrees or more, 6 degrees or more, 7 degrees or more, It could be 8 degrees or more, or even 9 degrees or more.

The regions of the polarizing film corresponding to the three-part central, left, and right regions of the optical film above mean regions that are observed to be in contact with the central, left, and right regions, respectively, or to overlap with the central, left, and right regions of the optical film in the normal direction. In addition, the difference between the average optical axis and the absorption axis, etc. can be obtained by a method according to the embodiment described below.

In addition, due to the excellent mechanical properties of the optical film described above, the polarizing plate also exhibits excellent bending resistance. For example, the polarizing plate exhibits a mandrel value of 10 pi or less in both the light absorption axis direction and the direction perpendicular thereto. The meaning of the mandrel value is as described in the optical film, and the specific method of conducting the mandrel test is as described in the examples. The mandrel value may be 9 pi or less, 8 pi or less, 7 pi or less, or 6 pi or less in other examples, or 1 pi or more, 2 pi or more, 3 pi or more, 4 pi or more, 5 pi or more, 6 pi or more, or 7 pi or more.

In another example, the polarizing plate may have a 10-pie mandrel resistance of 5 or more in both the light absorption axis direction and the direction perpendicular thereto. The mandrel resistance refers to the number of times no defect such as breakage or crack occurs when a 10-pie mandrel test is repeated. The mandrel resistance may be 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or 15 or more in other examples, or 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, or 20 or less.

The polarizing plate of the present application includes a specific optical film as described above, exhibits the above-described characteristics, and thus secures excellent low moisture permeability characteristics of a polyester film while at the same time having no optical defects and excellent bending resistance.

In one example, the optical film has a moisture permeability of 50 g/m ² ·day or less, 49 g/m ² ·day or less, 48 g/m ² ·day or less, 47 g/m ² ·day or less, 46 g/m ² ·day or less, 45 g/m ² ·day or less, 44 g/m ² ·day or less, 43 g/m ² ·day or less, 42 g/m ² ·day or less, 41 g/m ² ·day or less, 40 g/m ² ·day or less, 39 g/m ² ·day or less, 38 g/m ² ·day or less, 37 g/m ² ·day or less, 36 g/m ² ·day or less, 35 g/m ² ·day or less, 34 g/m ² ·day or less, 33 g/m ² ·day or less, 32 g/m ² ·day or less, 31 g/m ² ·day or less, or 30 g/m ² ·day or less, or 0 g/m ² ·day or more, 5 g/m ² ·day or more, 10 g/m ² ·day or more, 15 g/m ² ·day or more, 20 g/m ² ·day or more, or 25 g/m ² ·day or more. The water vapor transmission rate (WVTR) can be measured by a known method, and for example, it can be measured under the conditions of a test temperature of 37.6℃, a number of tests 10 times, a test time of 30 minutes (1 time), a volumetric flow rate of 9.92 SCCM (= cm ³ /min), and a penetration area of 50 cm ² according to the ASTM F1249 standard.

The thickness of the optical film is not particularly limited, and can be selected within an appropriate range considering the secured range of moisture permeability, etc. mentioned above, and the thickness of the optical film of a typical polarizing plate.

For example, the thickness of the optical film can typically be in a range of about 20 μm to 250 μm. The thickness can be about 200 μm or less, 150 μm or less, or 100 μm or less in other examples, or about 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, or 70 μm or more.

As the optical film, a polyester film, for example, a stretched polyester film, for example, a stretched PET film, can be used.

Typically, stretched PET film is a uniaxially or biaxially stretched film manufactured by melting/extruding PET resin into a film and stretching it.

PET resin usually means a resin in which 80 mol% or more of the repeating units are ethylene terephthalate, and may also include other dicarboxylic acid components and diol components. Examples of the other dicarboxylic acid components include isophthalic acid, p-beta-oxyethoxybenzoic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, and/or 1,4-dicarboxycyclohexane, and examples of the other diol components include, but are not limited to, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and/or polytetramethylene glycol.

The above dicarboxylic acid component or diol component can be used in combination of two or more as needed. In addition, an oxycarboxylic acid such as p-oxybenzoic acid can also be used in combination. As another copolymerization component, a dicarboxylic acid component or a diol component containing a small amount of amide bond, urethane bond, ether bond, and carbonate bond can also be used.

As a method for producing a PET resin, a method in which terephthalic acid, ethylene glycol and/or another dicarboxylic acid or another diol is directly polycondensed, a method in which a dialkyl ester of terephthalic acid and ethylene glycol and/or another dicarboxylic acid or another diol, if necessary, are transesterified and then polycondensed, and a method in which ethylene glycol ester of terephthalic acid and/or another dicarboxylic acid, if necessary, and/or another diol ester are polycondensed.

For each polymerization reaction, a polymerization catalyst including an antimony-based, titanium-based, germanium-based or aluminum-based compound, or a polymerization catalyst including a composite compound of the above can be used.

Polymerization reaction conditions can be appropriately selected depending on the monomer, catalyst, reaction device, and target resin properties used, and are not particularly limited, but for example, the reaction temperature is usually from about 150°C to about 300°C, from about 200°C to about 300°C, or from about 260°C to about 300°C. In addition, the reaction pressure is usually from atmospheric pressure to about 2.7 Pa, and may be on the pressure-reduced side in the latter half of the reaction.

The polymerization reaction proceeds by volatilizing leaving reactants such as diols, alkyl compounds, or water.

The polymerization device may be a complete reaction vessel or may be a plurality of reaction vessels connected together. Usually, depending on the degree of polymerization, the reactants are polymerized while being transported between reaction vessels. In addition, a horizontal reaction device may be provided in the latter half of the polymerization, and a method of volatilizing while heating/mixing may also be adopted.

After polymerization, the resin is discharged from the reaction tank or horizontal reactor in a molten state, and then cooled and crushed in a cooling drum or cooling belt, or introduced into an extruder and extruded in a string shape, and then obtained in the form of cut pellets. In addition, solid-state polymerization may be performed as needed to increase the molecular weight or reduce the low-molecular-weight component. Examples of low-molecular-weight components that can be included in the PET resin include a cyclic trimer component, but the content of such a cyclic trimer component in the resin is usually controlled to 5,000 ppm or less or 3,000 ppm or less.

The molecular weight of PET resin is usually in the range of 0.45 to 1.0 dL/g, 0.50 to 10 dL/g, or 0.52 to 0.80 dL/g when the resin is dissolved in a mixed solvent of phenol/tetrachloroethane = 50/50 (weight ratio) and expressed as the ultimate viscosity measured at 30°C.

PET resins may contain additives as needed. Examples of additives include lubricants, anti-blocking agents, heat stabilizers, antioxidants, antistatic agents, light-resistant agents, and impact-resistant improvers. It is preferable that the amount of additives be within a range that does not adversely affect optical properties.

PET resin is usually used in the form of pellets assembled by an extruder for mixing such additives or for film forming. The size and shape of the pellets are not particularly limited, but are usually cylindrical, spherical, or flat spherical with a height and diameter of 5 mm or less. The PET resin obtained in this way can be formed into a film and stretched to produce a transparent, homogeneous, high-mechanical-strength PET film. The method for producing it is not particularly limited, but for example, the following method is adopted.

The dried PET resin pellets are supplied to a melting extrusion device and melted by heating to a temperature higher than the melting point. Next, the molten resin is extruded from a die and rapidly cooled to a temperature lower than the glass transition temperature on a rotary cooling drum to solidify, thereby obtaining an unstretched film in a substantially amorphous state. This melting temperature is determined depending on the melting point of the PET resin used or the extruder and is not particularly limited, but is usually 250°C to 350°C. In addition, in order to improve the flatness of the film, it is preferable to increase the adhesion between the film and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. The electrostatic application adhesion method is a method in which a linear electrode is usually installed on the upper surface of the film in a direction perpendicular to the flow of the film, and a DC voltage of about 5 to 10 kV is applied to the electrode to provide an electrostatic charge to the film, thereby improving the adhesion between the rotary cooling drum and the film. In addition, the liquid coating adhesion method is a method of improving the adhesion between the rotary cooling drum and the film by uniformly applying a liquid to the entire or part of the surface of the rotary cooling drum (for example, only the part in contact with both ends of the film). The two can be used in combination, if necessary. The PET resin used can be a mixture of two or more resins, or resins with different structures or compositions, if necessary. For example, a method of mixing and using pellets mixed with a granular filler as an anti-blocking agent, an ultraviolet absorber, or an antistatic agent, and unblended pellets is exemplified.

The number of layers of the extruded film may be two or more, as needed. For example, pellets mixed with granular filler as an anti-blocking agent and pellets without mixing are prepared, and then fed from different extruders to the same die to extrude a film composed of two types and three layers of "filler mixing/no mixing/filler mixing."

The unstretched film formed in the above manner is usually stretched at a temperature above the glass transition temperature. The stretching temperature is usually 70°C to 150°C, 80°C to 130°C, or 90°C to 120°C.

In the present application, an optical film (polyester film) exhibiting the characteristic properties described above can be formed by applying stress in both directions perpendicular to the direction in which the film is stretched during the stretching process. This will be described with reference to Fig. 2. Typically, a stretching process for a polymer film is a continuous process, whereby the polymer film is stretched while progressing in one direction, and the stretching direction is perpendicular to the direction of progress, horizontal, or oblique.

Referring to FIG. 2, if the direction in which the unstretched film (1000) progresses while being stretched in FIG. 2 is the direction of the black dotted arrow, by applying stress in both directions (the direction of the red arrow in FIG. 2) perpendicular to the direction and making the stretching direction perpendicular or horizontal to the progressing direction, the aforementioned unique film having different optical properties in the central region and the left and right regions can be obtained due to the influence of the stress acting in both directions perpendicular to the progressing or stretching direction of the film. In addition, since this method can manufacture the film without performing a relatively high stretching in one direction unlike the existing highly stretched film, it is possible to obtain a film having excellent properties in terms of the bending characteristics described above.

In the above method, the method of applying stress in both directions perpendicular to the direction of travel of the film is not particularly limited. For example, by fixing both sides perpendicular to the direction of travel of the film with a fixing means and adjusting the fixing force by the fixing means, it is possible to apply stress in both directions while allowing travel of the film.

In the above process, the degree of elongation performed vertically or horizontally to the direction of progression is not particularly limited. For example, the elongation may be performed so that the elongation ratio in the elongation direction is approximately 1.1 to 6 times. The above extension ratio is, in other examples, 1.2 times or more, 1.3 times or more, 1.4 times or more, 1.5 times or more, 1.6 times or more, 1.7 times or more, 1.8 times or more, 1.9 times or more, 2.0 times or more, 2.1 times or more, 2.2 times or more, 2.3 times or more, 2.4 times or more, 2.5 times or more, 2.6 times or more, 2.7 times or more, 2.8 times or more, 2.9 times or more, 3.0 times or more, 3.1 times or more, 3.2 times or more, 3.3 times or more, 3.4 times or more, 3.5 times or more, 3.6 times or more, 3.7 times or more, 3.8 times or more, 3.9 times or more, 4.0 times or more, 4.1 times or more, 4.2 times or more, 4.3 times or more, 4.4 times or more, 4.5 times or more, 4.6 times or more, 4.7 times or more, 4.8 times or more, 4.9 times or more, 5.0 times or more, 5.1 times or more, 5.2 times or more, 5.3 times or more, 5.4 times or more, 5.5 times or more, 5.6 times or more, 5.7 times or more, 5.8 times or more, or 5.9 times or more, 5.8 times or less, 5.7 times or less, 5.6 times or less, 5.5 times or less, 5.4 times or less, 5.3 times or less, 5.2 times or less, 5.1 times or less, 5.0 times or less, 4.9 times or less, 4.8 times or less, 4.7 times or less, 4.6 times or less, 4.5 times or less, 4.4 times or less, 4.3 times or less, 4.2 times or less, 4.1 times or less, 4.0 times or less, It can be 3.9 times or less, 3.8 times or less, 3.7 times or less, 3.6 times or less, 3.5 times or less, 3.4 times or less, 3.3 times or less, 3.2 times or less, 3.1 times or less, 3.0 times or less, 2.9 times or less, 2.8 times or less, 2.7 times or less, 2.6 times or less, 2.5 times or less, 2.4 times or less, 2.3 times or less, 2.2 times or less, 2.1 times or less, 2.0 times or less, 1.9 times or less, 1.8 times or less, 1.7 times or less, 1.6 times or less, 1.5 times or less, 1.4 times or less, 1.3 times or less, or 1.2 times or less. When the above stretching ratio is made high, a relatively high phase difference is exhibited in the central region, and when it is made low, a relatively low phase difference is exhibited. Therefore, an appropriate stretching ratio can be set in consideration of this.

The above stretching ratio can be achieved through a single stretching process or by performing multiple stretching processes.

In the above process, the degree of stress applied in both directions perpendicular to the direction of progress is not particularly limited. The stress applied in both directions perpendicular to the direction of progress may be higher or lower than the stress applied to the film in the direction of progress.

For example, the stress applied to the film in the perpendicular directions may be within a range of 0.01 to 6 times the stress applied to the film in the forward direction. In another example, the stress applied to the film in the vertical directions is 0.02 times or more, 0.03 times or more, 0.04 times or more, 0.05 times or more, 0.06 times or more, 0.07 times or more, 0.08 times or more, 0.09 times or more, 0.1 times or more, 0.2 times or more, 0.3 times or more, 0.4 times or more, 0.5 times or more, 0.6 times or more, 0.7 times or more, 0.8 times or more, 0.9 times or more, 1.0 times or more, 1.1 times or more, 1.2 times or more, 1.3 times or more, 1.4 times or more, 1.5 times or more, 1.6 times or more, 1.7 times or more, 1.8 times or more, 1.9 times or more, 2.0 times or more, 2.1 times or more, 2.2 times or more, 2.3 times or more, 2.4 times or more, 2.5 times or more, 2.6 times or more, 2.7 times or more, 2.8 times or more, 2.9 times or more, 3.0 times or more, 3.0 times or more, 3.1 times or more, 3.2 times or more, 3.3 times or more, 3.4 times or more, 3.5 times or more, 3.6 times or more, 3.7 times or more, 3.8 times or more, 3.9 times or more, 4.0 times or more, 4.1 times or more, 4.2 times or more, 4.3 times or more, 4.4 times or more, 4.5 times or more, 4.6 times or more, 4.7 times or more, 4.8 times or more, 4.9 times or more, 5.0 times or more, 5.1 times or more, 5.2 times or more, 5.3 times or more, 5.4 times or more, 5.5 times or more, 5.6 times or more, 5.7 times or more, 5.8 times or more, or 5.9 times or more, or 5.9 times or less, 5.8 times or less, 5.7 times or less, 5.6 times or less, 5.5 times or less, 5.4 times or less, 5.3 times or less, 5.2 times or less, 5.1 times or less, 5.0 times or less, 4.9 times or less, 4.8 times or less, 4.7 times or less, 4.6 times or less, 4.5 times or less, 4.4 times or less, 4.3 times or less, 4.2 times or less, 4.1 times or less, 4.0 times or less, 3.9 times or less, 3.8 times or less, 3.7 times or less, 3.6 times or less, 3.5 times or less, 3.4 times or less, 3.3 times or less, 3.2 times or less, 3.1 times or less, 3.0 times or less, 2.9 times or less, 2.8 times or less, 2.7 times or less, 2.6 times or less, 2.5 times or less, 2.4 times or less, 2.3 times or less, 2.2 times or less, 2.1 times or less, 2.0 times or less, 1.9 times or less, 1.8 times or less, 1.7 times or less, 1.6 times or less, 1.5 times or less, 1.4 times or less, 1.3 times or less, 1.2 times or less, 1.1 times or less, 1.0 times or less, 0.9 times or less, 0.8 times or less, 0.7 times or less, 0.6 times or less, 0.5 times or less, 0.4 times or less, 0.3 times or less, 0.2 times or less, 0.1 times or less, 0.09 times or less, 0.08 times or less, 0.07 times or less, 0.06 times or less, 0.05 times or less, 0.04 times or less, 0.03 times or less or It may be less than 0.02 times. The above stress can be adjusted, for example, by using a fixing means as described above.

Heat treatment can be performed on the stretched film obtained as described above. In addition, relaxation treatment can be performed as needed. The heat treatment temperature is usually 150°C to 250°C, 180°C to 245°C, or 200°C to 230°C. In addition, the heat treatment time is usually 1 to 600 seconds, or 1 to 300 seconds, or 1 to 60 seconds.

The temperature of the relaxation treatment is usually 90 to 200°C or 120 to 180°C. In addition, the relaxation amount is usually 0.1 to 20% or 2 to 5%. The temperature and relaxation amount of the relaxation treatment can be set so that the heat shrinkage rate of the PET film after the relaxation treatment at 150°C becomes 2% or less.

If optionally required, after the above drawing treatment, additional drawing may be performed in a direction perpendicular to the main drawing direction. In this process, stress may be applied to both sides in the progress direction, or not. The drawing temperature is usually 70°C to 150°C, 80°C to 130°C, or 90°C to 120°C. In addition, the drawing ratio can be adjusted within the range mentioned in the first drawing. Thereafter, heat treatment and relaxation treatment may be performed. The heat treatment temperature is usually 150°C to 250°C, or 180°C to 245°C, or 200 to 230°C. The heat treatment time is usually 1 to 600 seconds, 1 to 300 seconds, or 1 to 60 seconds.

The temperature of the relaxation treatment is usually 100 to 230°C, 110 to 210°C, or 120 to 180°C. In addition, the relaxation amount is usually 0.1 to 20%, 1 to 10%, or 2 to 5%. The temperature and relaxation amount of the relaxation treatment can be set so that the heat shrinkage rate of the PET film after the relaxation treatment at 150°C becomes 2% or less, and the relaxation amount and the temperature during the relaxation treatment.

Following the above-described stretching process, additional heat treatments, etc. may be performed.

The optical film applied in the present application may include known functional layers such as an anti-glare layer, a conductive layer, a hard coating layer, a smoothing layer, an anti-blocking layer, a primer layer, and/or an anti-reflection layer.

The polarizing plate of the present application may include an adhesive layer, and the adhesive layer may be present to attach the polarizing plate to a display device such as an LCD or an OLED. In this case, as described above, the optical film, the polarizing film, and the adhesive layer of the present application may be included in the polarizing plate in the above order. The adhesive forming the adhesive layer is not particularly limited, and for example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, or a fluorine-based or rubber-based polymer may be appropriately selected and used as a base polymer. As described above, a release film may be temporarily attached and covered with the exposed surface of the adhesive layer for the purpose of preventing contamination, etc. until it is put into practical use.

The thickness of the adhesive layer can typically be in the range of 5 μm to 100 μm. In other examples, the thickness can be about 10 μm or more, 15 μm or more, or 20 μm or more, or about 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less.

The polarizing plate of the present application may include other necessary components in addition to the elements described above.

For example, the polarizing plate may additionally include an adhesive layer between the optical film and the polarizing film. This adhesive layer may be used to attach the optical film to the polarizing film.

As an adhesive, for example, an adhesive layer used to attach a polarizing film and an optical film in a conventional polarizing plate can be used.

The adhesive layer may include one or more kinds of, for example, a polyvinyl alcohol-based adhesive; an acrylic adhesive; a vinyl acetate-based adhesive; a urethane-based adhesive; a polyester-based adhesive; a polyolefin-based adhesive; a polyvinyl alkyl ether-based adhesive; a rubber-based adhesive; a vinyl chloride-vinylacetate-based adhesive; a styrene-butadiene-styrene (SBS) adhesive; a hydrogenated styrene-butadiene-styrene (SEBS)-based adhesive; an ethylene-based adhesive; and an acrylic acid ester-based adhesive. The adhesives described above may be formed using, for example, an aqueous, solvent-based or solvent-free adhesive composition. In addition, the adhesive composition may be a heat-curing type, a room temperature-curing type, a moisture-curing type, an active energy ray-curing type or a hybrid-curing type adhesive composition.

The method for forming an adhesive layer on a polarizing film is not particularly limited, and for example, a method of applying and curing an adhesive composition on a polarizing film or a droplet method may be used.

The thickness of such adhesive layer can be, for example, in the range of about 1 μm to 5 μm or about 2 μm to 4 μm.

As an additional configuration, the polarizing plate may further include a cured resin layer or an optical film between the polarizing film and the adhesive layer. The cured resin layer is also commonly referred to as a hard coating layer, and is generally applied instead of omitting any one of the optical films in the polarizing plate. There is no particular limitation on the type of the cured resin layer that can be applied in the present application, and various types of cured resin layers that are used to provide the thin polarizing plate can all be applied. Typically, such a cured resin layer may include an epoxy resin, an oxetane resin, a urethane resin, and/or an acrylic resin, and such resin layers are known in various ways. The thickness of such a cured resin layer may be, for example, in a range of about 4 μm to 10 μm or about 4.5 μm to 10 μm.

When an optical film exists between the polarizing film and the adhesive layer, a known optical film can be used as the optical film. Typically, a thermoplastic resin film having excellent transparency, mechanical strength, thermal stability, moisture barrier property, or isotropy, etc., is used. Examples of such resins include cellulose resins such as triacetyl cellulose (TAC), polyester resins such as poly(ethylene terephthalate) (PET), polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins such as norbornene resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, or mixtures thereof. The thickness of the optical film may be within the thickness range of the optical film described above.

Between the above polarizing film and the adhesive layer, there may be an appropriate composition among the above cured resin layer or optical film, but in terms of securing the desired shrinkage characteristics, etc., it is advantageous for the above cured resin layer to be present. That is, since the cured resin layer is a thin layer formed by curing a resin, its physical properties such as shrinkage and tensile characteristics are minimal compared to the optical film, and thus its influence on the overall characteristics of the polarizing plate is small, so it does not have a significant influence on the shrinkage characteristics formed by the relationship between the above-mentioned optical film and polarizing film.

The polarizing plate of the present application may additionally include one or more functional layers selected from the group consisting of other known configurations, for example, an anti-reflection layer, an anti-glare layer, a phase difference plate, a wide viewing angle compensation film, and/or a brightness enhancement film.

The present application also relates to a display device, for example, an LCD or an OLED. The display device, such as an LCD or an OLED, may include the polarizing plate of the present application. The display device may include a display panel, such as an LCD panel or an OLED panel, and the polarizing plate of the present application attached to the display panel.

The type of the display panel applicable to the display device of the present application, or the position of the polarizing plate attached to the panel, etc. are not particularly limited. That is, as long as the polarizing plate of the present application is applied, the display panel can be implemented in various known ways.

Typically, display devices such as OLED include one polarizing plate for purposes such as anti-reflection, and display devices such as LCD include two polarizing plates on both sides of the display panel (liquid crystal panel). In cases where two polarizing plates are included, the polarizing plate described above may be included in the display device as at least one of the two polarizing plates, and in some cases, the polarizing plate of the present application may be applied to both of the two polarizing plates.

For example, in one example of the present application, the display device includes the display panel (e.g., a liquid crystal panel) and first and second polarizing plates attached to both sides of the display panel, and either or both of the first and second polarizing plates can be the polarizing plates of the present application.

In one example, the first polarizing plate may be a polarizing plate on the viewer's side, and may be a polarizing plate closer to the viewer observing the display screen among the first and second polarizing plates. For example, if the display device is an LCD device, among the first and second polarizing plates, the first polarizing plate may be a polarizing plate that is positioned further away from the backlight than the second polarizing plate, and the second polarizing plate may be a polarizing plate that is positioned closer to the backlight.

In this case, at least the polarizing plate of the present application can be applied as the first polarizing plate, i.e., the polarizing plate on the viewer side. In this case, the second polarizing plate, i.e., the polarizing plate arranged closer to the backlight, can also be the polarizing plate of the present application, or another polarizing plate. In the case where another polarizing plate is applied, there is no particular limitation on the type of polarizing plate applied, and a known polarizing plate can be applied.

For example, a polarizing plate including a polarizing film, a protective film formed on one side of the polarizing film, and an adhesive layer formed on the other side of the polarizing film to attach the polarizing plate to the display panel may be used as the other polarizing plate. A protective film or protective layer (the above-described cured resin layer) may also be present between the polarizing film and the adhesive layer of the polarizing plate.

In the above structure, a known protective film can be applied as the protective film of the second polarizing plate. For example, the above-mentioned high-strength protective film (e.g., high-strength polyester film) can be applied as the protective film.

Such high-stretch polyester films typically exhibit very high in-plane retardation. Accordingly, when the high-stretch polyester film is applied, the second polarizing plate may include a protective film having an in-plane retardation (based on a wavelength of 550 nm) of 2,000 nm or more, 2,000 nm to 3,000 nm, or more than 2,000 nm to 3,000 nm or less.

The above display device may be an LCD device, in which case the display panel may be a liquid crystal panel.

The first and second polarizing plates can be arranged on both sides of the display panel so that their light absorption axes are perpendicular to each other.

In such cases, the first and second polarizing plates may be polarizing plates in which the smaller angle among the angles formed between one side of the polarizing film or polarizing plate and the light absorption axis of the polarizing film is within a range of 0 to 10 degrees or within a range of 80 to 100 degrees, or in which the smaller angle among the angles formed between one side of the polarizing film or polarizing plate and the light absorption axis of the polarizing film is within a range of 35 to 55 degrees or within a range of 125 to 145 degrees.

The present application can provide a polarizing plate including a polyester film that can utilize excellent low moisture permeability characteristics without occurrence of optical defects and does not easily break or crack even when bent, and a display device using the same.

Figure 1 is a drawing exemplarily showing a method of dividing an optical film or polarizing plate into three parts.
Figure 2 is a drawing exemplarily showing a process for manufacturing an optical film of the present application.
Figure 3 is a drawing showing points where the optical axis, absorption axis, and phase difference are evaluated in an embodiment.
Figure 4 is a photograph showing the process of evaluating mandrel characteristics.

The present application is specifically described through the following examples and comparative examples, but the scope of the present application is not limited by the following examples.

The term MD as used herein means Machine Direction of the stretched film unless specifically stated otherwise, and TD means Transverse direction of the stretched film unless specifically stated otherwise.

Manufacturing Example 1. Production of PVA polarizing film

A PVA (poly(vinyl alcohol)) film (Nippon Synthetic Co., Ltd., degree of polymerization: approximately 3,000) with a thickness of approximately 45 μm was swelled in a pure solution at a temperature ranging from approximately 20°C to 30°C, and then a dyeing process was performed in an iodine solution at a temperature of approximately 30°C to 40°C for approximately 10 to 30 seconds. Thereafter, a washing process was performed for approximately 20 seconds in a boric acid solution (concentration: approximately 2 wt%) at a temperature of approximately 40°C, and then stretched approximately 6 times in a boric acid solution at a temperature of 50°C to 60°C and a concentration of approximately 4.0 wt%, and after stretching, a complementary color process was performed in a KI solution at a concentration of approximately 2 to 4 wt%, and drying was performed to produce a polarizing film with a thickness of approximately 17 μm.

Manufacturing Example 2. Manufacturing of optical film

Polyester (A) manufacturing

The esterification reactor was heated to 200°C, and 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and with stirring, 0.017 parts by mass of antimony trioxide as a catalyst, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added. Through pressurization and temperature elevation, a pressure esterification reaction was performed under the conditions of a gauge pressure of 0.34 MPa and a temperature of 240°C, the reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. The temperature was increased to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, the product was dispersed with a high-pressure disperser, and the esterification reaction product was transferred to a polycondensation reactor and a polycondensation reaction was performed under reduced pressure at 280°C. After the reaction was completed, the mixture was filtered, extruded in a strand shape from a nozzle, and then cooled/solidified to produce pellets, thereby obtaining polyester (A) pellets.

Manufacturing of polyester (B)

10 parts by mass of an ultraviolet absorbent (2,2'-(1,4-phenylene) bis(4H-3,1-benzoxyzinon-4-one) and 90 parts by mass of the polyester (A) were mixed, and a polyester (B) including an ultraviolet absorbent was obtained by a mixing extruder.

Manufacturing of optical films

Polyester (A) pellets and polyester (B) pellets were mixed at a mass ratio (A:B) of 90:10, dried under reduced pressure (1 Torr) at 135°C for 6 hours, and then supplied to extruder 2 (for middle layer II). In addition, the polyester (A) pellets were dried, supplied to extruder 1 (for outer layer I and outer layer III), and dissolved at 285°C. Through the extrusion process using the extruders 1 and 2, an unstretched film having a three-layer structure having a thickness ratio of the I layer, II layer, and III layer of 10:80:10 was obtained.

While the above unstretched film was advanced in a stretching machine (in the direction of the black arrow in Fig. 2), it was stretched approximately 1.8 times parallel to the advancing direction. During the stretching process, both ends of the unstretched film, which are perpendicular to the advancing direction, were fixed by a fixing means so that stress (approximately 0.8 to 1.5 times the stress applied in the advancing direction) was applied. Subsequently, the stretched film was heat-treated and relaxed to obtain an optical film having a thickness of approximately 80 μm.

Example 1.

A polarizing plate was manufactured in the following manner. First, an epoxy-based ultraviolet-curable adhesive (thickness: 2 μm to 3 μm) was used to attach the optical film of Manufacturing Example 2 to one side of the PVA polarizing film manufactured in Manufacturing Example 1. When attaching, the optical film was attached so that the stretching direction of the optical film and the absorption axis direction of the PVA polarizing film were approximately perpendicular. Next, an epoxy-based hard coating layer was formed with a thickness of approximately 5 to 7 μm on the side of the PVA polarizing film to which the optical film was not attached. Thereafter, an acrylic adhesive layer with a thickness of approximately 25 μm was formed under the hard coating layer to manufacture a polarizing plate. The polarizing plate had a square shape, and was cut so that the angle formed by the long side of the square-shaped polarizing plate and the light absorption axis of the polarizing film was approximately 0 or 90 degrees.

The relationship and phase difference between the absorption axis of the polarizing film and the true axis of the optical film in the polarizing plate manufactured as described above were measured using AxoScan measuring equipment for the polarizing plate.

As shown in Fig. 3, the axial relationship and phase difference were measured at 100 mm intervals along the width direction of the polarizing plate (TD direction, dotted arrow direction in Fig. 3) with an arbitrary end portion of the polarizing plate as the reference (0 mm) in the polarizing plate surface. In the above, the absorption axis of the polarizing film and the true axis of the optical film were measured as angles formed by the axes with respect to the MD direction of the polarizing film (the direction perpendicular to the TD direction in Fig. 3).

The polarizer was placed at the measurement position, and the AxoScan measurement equipment and computer were turned on. The AxoScan engine was run, and when the green light came on, AxoView was run and waited for more than 20 minutes. The Number of Measurements to Average was changed from 1 to 80, and the Calibration was run to evaluate the above (Optical Wavelength 550 nm Air state Run Once then Calibrate → Place the standard sample, Run Once, then Ret Zero). During the measurement process, click Tip-Tilt Measurement, select Arbitary field-of-view, set the Number of Rotations to 4 to 6, keep the remaining conditions as they are, and click Accept to proceed with the measurement.

To obtain results using MLSP, run Axometrics Multi-Layer Analysis, input information such as nx, ny, nz and thickness of the film through Edit Layer, import AxoScan measurement information (Select all Import data), then Align and Optimize to output the data.

The above measurement results are summarized in Table 1.

Location (mm) Absorption axis angle (degrees) True axis angle (degrees) Phase difference (nm) 0 0.23 33.22 457 100 0.15 33.66 472 200 0.23 39.93 387 300 0.05 41.39 357 400 0.03 36.07 322 500 0.06 34.36 225 600 0.12 18.81 319 700 0.03 42.11 270 800 0.22 43.85 125 900 0.17 2.92 117 1000 0.15 15.21 71 1100 0.02 4.02 150 1200 0.02 9.56 180 1300 0.02 8.05 270 1400 0.04 39.73 200 1500 -0.11 40.83 110 1600 0.26 35.72 247 1700 0.12 42.92 299 1800 0.09 47.21 337 1900 0.15 49.51 388 2000 0.11 38.24 411 2100 0.15 44.28 454 2200 0.17 46.24 489 Position (mm): Distance from the reference position (0 mm in Figure 3) to the measurement position in the TD direction
Absorption axis angle (degrees): The angle formed by the absorption axis of the polarizing film and the MD direction of the polarizing plate (the direction perpendicular to the TD in Figure 3) (unit: degrees)
True axis angle (degrees): The angle formed by the true axis of the optical film and the MD direction of the polarizing plate (the direction perpendicular to the TD in Figure 3) (unit: degrees)
Phase difference: In-plane phase difference of an optical film (unit: nm)

The polarizing plate of Example 1 above was attached to an LCD panel as a viewing-side polarizing plate, and it was observed from the front and oblique directions to determine whether optical defects such as rainbow spots were recognized with the naked eye. No optical defects such as rainbow spots were recognized on the LCD panel with the polarizing plate mounted on the viewing side.

The above polarizing plate was evaluated for its mandrel characteristics. The evaluation was performed using a general cylindrical mandrel bending tester, and Fig. 4 is a photograph showing the process of the evaluation. The test rod conditions were 6 waves to 20 pie, and the evaluation was performed by replacing the rod at 2 pie intervals. The polarizing plate was cut to 300 mm and 30 mm in width and height to produce a sample, and the evaluation was performed. A sample having a length of 300 mm in the direction of the absorption axis of the polarizing film and a sample having a length of 300 m in the direction perpendicular to the absorption axis were prepared, respectively, and applied to the evaluation. After setting the application rod, it was fixed to the device, and one end of the sample was fixed to the Grap Jig of the tester. At this time, the surface of the optical film was made to be outside (i.e., the polarizing film was placed closer to the device than the optical film). As shown in Fig. 4, the sample was bent at a 90-degree angle for 2 seconds, then returned to its original position, and the sample was separated from the device. The presence or absence of cracks was evaluated by examining the transmission of light from a three-wavelength lamp. Cracks exceeding 15 mm in size were evaluated as having occurred.

The evaluation results showed that no cracks occurred up to a load of 8 pi when the polarizing plate was bent in a direction parallel to the light absorption axis, and no cracks occurred up to a load of 6 pi when it was bent in a direction perpendicular to the light absorption axis.

In addition, when a bending test was performed repeatedly by applying a 10-pie load, no cracks occurred up to 14 times when bending in a direction parallel to the light absorption axis, and no cracks occurred up to 15 times when bending in a direction perpendicular to the light absorption axis.

Claims (20)

A polarizing film having a light absorption axis formed in one direction within the plane; and an optical film formed on one surface of the polarizing film,
It exhibits a 10-pi mandrel resistance of 5 or more times in both the direction of the light absorption axis and the direction perpendicular to the light absorption axis direction,
A polarizing plate, wherein when the optical film is divided into three equal parts by an imaginary line in a direction horizontal or vertical to the light absorption axis of the polarizing film, an angle formed by the average optical axis of the central region of the optical film and the light absorption axis of the polarizing film is within a range of 0 degrees to 29 degrees, and an angle formed by the average optical axis of the left or right region of the optical film and the light absorption axis of the polarizing film is 30 degrees or more.
Polarizing plate. In the first paragraph, a polarizing plate in which the difference (Rin.max-Rin.min) between the minimum value (Rin.min) and the maximum value (Rin.max) of the in-plane phase difference in the optical film is within a range of 200 nm to 1,000 nm. In the second paragraph, a polarizing plate having a minimum value (Rin.min) of in-plane phase difference in the optical film within a range of 10 to 300 nm. In the first paragraph, a polarizing plate having a maximum value of in-plane retardation (Rin.max) in the optical film within a range of 350 to 1,000 nm. A polarizing plate in which, in the first paragraph, when the optical film is divided into three equal parts by an imaginary line in a direction horizontal or perpendicular to the light absorption axis of the polarizing film, the minimum value (Rin.min) of the in-plane phase difference is confirmed in the central region, and the maximum value (Rin.max) is confirmed in the left or right region. In the fifth paragraph, a polarizing plate wherein the difference (RL-M) between the average in-plane retardation (M) of the central region of the optical film and the average in-plane retardation (RL) of the left or right region is within a range of 50 nm to 1,000 nm. A polarizing plate in accordance with claim 5, wherein the absolute value of the difference (R-L) between the average in-plane retardation (L) of the left region of the optical film and the average in-plane retardation (R) of the right region is 45 nm or less. A polarizing plate in accordance with claim 5, wherein the average in-plane phase difference in the central region of the optical film is in the range of 10 to 290 nm. A polarizing plate in claim 5, wherein the average value of the in-plane phase difference in the left or right region among the three divided regions of the optical film is within a range of 300 to 1,000 nm. delete A polarizing plate in accordance with claim 1, wherein the absolute value of the difference (B-A) between the angle (A) formed by the average optical axis of the central region of the optical film and the average light absorption axis of the polarizing film region overlapping the central region and the angle (B) formed by the average optical axis of the left or right region of the optical film and the average light absorption axis of the polarizing film region overlapping the left or right region exceeds 10 degrees. In the first paragraph, a polarizing plate wherein the absolute value of the difference (D-C) between the average value (C) of the angles formed by the average optical axis of the left region of the divided regions of the optical film and the absorption axis of the polarizing film region overlapping the left region and the average value (D) of the angles formed by the average optical axis of the right region of the optical film and the absorption axis of the polarizing film region overlapping the right region is 15 degrees or less. A polarizing plate in accordance with claim 1, wherein the average in-plane retardation (based on a wavelength of 550 nm) of the optical film is in the range of 100 to 1,000 nm. In the first paragraph, the optical film is a polarizing plate having a moisture permeability of 50 g/ ^m2 ·day or less. A polarizing plate in claim 1, wherein the optical film is a polyester film. In the first paragraph, the polarizing film is a polarizing plate which is a polyvinyl alcohol polarizing film. A polarizing plate according to claim 1, further comprising an adhesive layer, wherein the optical film, the polarizing film, and the adhesive layer are arranged in the above order. A display device comprising a liquid crystal panel; first and second polarizing plates laminated on both sides of the liquid crystal panel, wherein at least one of the first and second polarizing plates is the polarizing plate of claim 1. A display device in claim 18, wherein the first polarizing plate is a polarizing plate on the viewing side, and the first polarizing plate is the polarizing plate of claim 1. In claim 19, the second polarizing plate comprises: a polarizing film; a protective film formed on one surface of the polarizing film; and an adhesive layer formed on the other surface of the polarizing film to attach the second polarizing plate to the liquid crystal panel, wherein the protective film has an in-plane phase difference of 2,000 nm or more for a wavelength of 550 nm.