WO2017061696A1 - Polarizing plate and manufacturing method thereof - Google Patents

Abstract

A polarizing plate and a manufacturing method thereof are provided. The polarizing plate includes: a polarizer; and a protective film laminated on at least one surface of the polarizer, wherein the protective film has an in-plane retardation (Re) of about 0 nm to about 300 nm and a thickness direction retardation (Rth) of about 0 nm to about 2,500 nm.

Description

Polarizing plate and manufacturing method thereof

The present invention relates to a polarizing plate and a method of manufacturing the same.

Recently, the display field has been rapidly developed, and various display devices having excellent performance of thinning, lightening, and low power consumption have been developed to replace the conventional cathode ray tube (CRT).

Specific examples of such display devices include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an organic light emitting device (Organic). Electroluminescence Device) etc. can be mentioned.

Among these, a liquid crystal display or an organic light emitting display obtains a gray level for each pixel by optically modulating the transmitted light according to an input video signal or by self-emitting luminance pixels according to the video signal. The layer which modulates such transmitted light and light emission luminance for each pixel is called a modulation function layer.

In the liquid crystal display device, the liquid crystal layer corresponds to the modulation function layer, and in the organic light emitting display device, the organic EL light emitting layer corresponds to the modulation function layer. Since the liquid crystal layer is not a light valve that completely blocks light by itself, in the case of a liquid crystal display device, polarizing plates may be disposed on both sides of the liquid crystal layer in the up and down direction of the liquid crystal layer, that is, the backlight side and the viewer's viewing side. have.

On the other hand, the polarizing plate used in the display device is composed of a polarizer and a protective film, the rainbow stain is recognized due to the birefringence of the protective film, which may cause a problem of poor visibility.

Accordingly, the technical problem to be solved by the present invention is to provide a polarizing plate to prevent the rainbow stain as described above.

In addition, to provide a polarizing plate manufacturing method that is easy to manufacture while preventing the rainbow stain as described above.

The objects of the present invention are not limited to the above-mentioned technical problem, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

Polarizing plate according to an embodiment of the present invention for achieving the above object includes a polarizer, and a protective film laminated on at least one surface of the polarizer, the in-plane retardation (Re) of the protective film is about 0nm to about 300nm, The thickness direction retardation R _th may be about 0 nm to about 2500 nm.

The protective film is a biaxially stretched film, the polarizer may be uniaxially stretched.

The polarizer may have a thickness of about 1 μm to about 15 μm.

At least one functional layer of a hard-coating layer, an anti-reflection layer, an anti-glare layer, and a diffusion layer may be disposed on at least one surface of the protective film.

The protective film may be a film formed of polyethylene terephthalate-based, polyethylene naphthalate-based, or a copolymer containing them.

The protective film may be a film obtained by triple coextrusion of the polyethylene terephthalate-based, polyethylene naphthalate-based, or a copolymer containing them.

Polarizing plate manufacturing method according to an embodiment of the present invention for achieving the above object is a step of preparing a non-stretched protective film, stretching the non-stretched protective film in one direction, polyvinyl alcohol on the stretched protective film Laminating a resin film to form a laminated film, and stretching the laminated film in a direction perpendicular to the one direction.

The stretching in one direction may be characterized by stretching the non-stretched protective film about 4 times to about 7 times.

The protective film stretched by the stretching in one direction may have an in-plane retardation (Re) of about 1000 nm or more, and a thickness direction retardation (R _th ) of about 1000 nm or more.

Stretching in the vertical direction may be characterized by stretching the laminated film about 4 times to about 7 times.

The protective film stretched by stretching in the vertical direction may have an in-plane retardation (Re) of about 0 nm to about 300 nm, and a thickness direction retardation (R _th ) of about 0 nm to about 2500 nm.

Polarizing plate manufacturing method according to another embodiment of the present invention for achieving the above object is a step of preparing a plurality of non-stretched protective film, stretching the plurality of non-stretched protective film in one direction, the plurality of stretched protection Forming a laminated film by laminating the polyvinyl alcohol-based resin film between the film, and stretching the laminated film in a direction perpendicular to the one direction.

The stretching in one direction may be performed by laminating the plurality of non-stretched protective films.

The stretching in one direction may be performed by stretching the plurality of non-stretched protective films, respectively.

The plurality of protective films drawn by the stretching in one direction may have an in-plane retardation Re of about 1000 nm or more, and a thickness direction retardation R _th of about 1000 nm or more.

The plurality of protective films drawn by the stretching in the vertical direction may have an in-plane retardation Re of about 0 nm to about 300 nm, and a thickness direction retardation R _th of about 0 nm to about 2500 nm.

Specific details of other embodiments are included in the detailed description and the drawings.

According to embodiments of the present invention has at least the following effects.

That is, the polarizing plate of the present invention can be applied to a display device to prevent rainbow spots, thereby improving visibility.

In addition, according to the polarizing plate manufacturing method of the present invention, it is possible to manufacture a polarizing plate capable of preventing the above-mentioned rainbow spots, it may be easy to manufacture the polarizing plate.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a perspective view schematically showing a polarizing plate according to an embodiment of the present invention.

2 is a perspective view schematically showing a polarizing plate according to another embodiment of the present invention.

3 to 5 are schematic views illustrating a method of manufacturing a polarizing plate according to an embodiment of the present invention.

6 to 10 is a view schematically showing a method of manufacturing a polarizing plate according to another embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims.

References to elements or layers "on" other elements or layers include all instances where another layer or other element is directly over or in the middle of another element. Like reference numerals refer to like elements throughout.

Although the first, second, etc. are used to describe various components, these components are of course not limited by these terms. These terms are only used to distinguish one component from another. Therefore, of course, the first component mentioned below may be a second component within the technical spirit of the present invention.

In addition, unless the steps constituting the manufacturing method described herein are sequential or sequential, or unless otherwise stated, one step and another step constituting one manufacturing method in the order described in the specification It is limited and not interpreted. Therefore, the order of construction steps of the manufacturing method can be changed within a range that can be easily understood by those skilled in the art, in which case the obvious changes to those skilled in the art will be included within the scope of the present invention.

Polarizer

Hereinafter, a polarizer according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a cross-sectional view schematically showing a polarizing plate according to an embodiment of the present invention.

Referring to FIG. 1, a polarizing plate 1 according to an embodiment of the present invention includes a polarizer 10 and a protective film 20 laminated on at least one surface of the polarizer 10, and the protective film 20. The in-plane retardation Re may be about 0 nm to about 300 nm, and the thickness direction retardation R _th may be about 0 nm to 2500 nm.

For example, the in-plane retardation Re of the protective film 20 is about 0 nm to about 250 nm, about 50 nm to about 250 nm, about 10 nm, about 20 nm, about 30 nm, about 40 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm, about 100 nm, about 110 nm, about 120 nm, about 130 nm, about 140 nm, about 150 nm, about 160 nm, about 170 nm, about 180 nm, about 190 nm, about 200 nm, about 210 nm, about 220 nm, about 230 nm, about 240 nm, About 250 nm. In addition, the thickness direction retardation R _th of the protective film 20 is, for example, about 1000 nm to about 2400 nm, about 1200 nm to about 2300 nm, about 1000 nm, about 1100 nm, about 1200 nm, about 1300 nm, about 1400 nm, about 1500 nm, About 1600 nm, about 1700 nm, about 1800 nm, about 1900 nm, about 2000 nm, about 2100 nm, about 2200 nm, about 2300 nm, about 2400 nm. By satisfying the above range, rainbow spots caused by birefringence can be prevented, whereby the visibility of the display device can be improved. The degree of biaxiality (NZ) of the protective film 20 may be about 5 or more, for example, about 5 to about 30, for example about 6 to about 25, for example about 6.5 to about 24. By satisfying the above range, rainbow spots caused by birefringence can be prevented, whereby the visibility of the display device can be improved.

In-plane retardation (Re), thickness direction retardation (R _th ) and the degree of biaxiality (NZ) are the thickness of the protective film 20 d, the refractive index of the in-plane slow axis direction n _x , the refractive index of the in-plane fastening axis direction When n _y and the refractive index in the thickness direction are defined as n _z , they may be defined by the following formulas, respectively.

Re = (n _x -n _y ) xd

R _th = (n _x -n _z ) xd

NZ = (n _x -n _z ) / (n _x -n _y )

In addition, the retardation value may be defined as a positive value as an absolute value.

The slow axis may be defined as a direction in which the in-plane refractive index of the protective film 20 is maximized, and the fast axis may be defined as a direction perpendicular to the slow axis in the plane.

In-plane retardation (Re) and thickness retardation (R _th ) were measured using a product name AxoScan (manufactured by Axometrics, a retardation measurement system) under a measurement wavelength of 550 nm under an environment of 23 ° C. Can be a value.

In general, when the fast axis of the protective film is Θr and the absorption axis is Θp, when the Θr-p value is not 90 ° or 0 °, that is, the slow axis (r) of the protective film and the absorption axis (p) of the polarizer If it is not perpendicular or parallel (0), rainbow spots are visually recognized by the influence of phase difference birefringence. When the protective film of the present invention is located at the end of the viewing direction, the rainbow stain may not be visualized without being affected by the Θr-p value.

On the other hand, the protective film 20 is a biaxially stretched film, the polarizer 10 may be uniaxially stretched. Since the protective film 20 is a biaxially stretched film, the protective film 20 may satisfy the phase difference range, thereby preventing rainbow spots and improving visibility.

The TD of the protective film 20 and the TD of the polarizer 10 may be substantially parallel, and the MD of the protective film 20 and the MD of the polarizer 10 may be substantially parallel. The "substantially parallel" means that the angle between the TD of the protective film 20 and the TD of the polarizer 10, the angle between the MD of the protective film 20 and the MD of the polarizer 10 is about -5 ° or more, respectively, about +5 It means below.

The polarizer 10 is a film that can be converted from natural light or polarized light into arbitrary polarized light, and can generally be converted to specific linearly polarized light. As the polarizer 10, dichroic substances such as iodine or dichroic dye are adsorbed and stretched onto hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films. Although polyene type oriented films, such as the thing of the dehydration process of filivinyl alcohol, and the dehydrochlorination process of polyvinyl chloride, etc. are mentioned, it is not limited only to these. In an exemplary embodiment, a polyvinyl alcohol-based film containing iodine, which may have a high degree of polarization and has excellent adhesion to the protective film 10, may be mentioned, but is not limited thereto.

The protective film 20 may include a polyester-based material. Examples of the polyester-based materials include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1, 5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfoncarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3 -Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2 Dicarboxylic acids such as 2-dimethylglutaric acid, adipic acid, 2-methyl adipic acid, trimethyl adipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, and dodecadicarboxylic acid Acids, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cycle Hexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis (4-hydroxyphenyl) propane, bis Although diols, such as (4-hydroxyphenyl) sulfone, can be mentioned, It is not limited only to these. A homopolymer obtained by polycondensing each of the above substances, or a copolymer obtained by polycondensing at least one dicarboxylic acid with at least two diols, or by condensing two or more dicarboxylic acids with at least one diol. The polyester resin in any one of the copolymer and the blend resin which blends 2 or more types of these homopolymers and copolymers is mentioned.

In an exemplary embodiment, in view of the polyester exhibiting crystallinity, aromatic polyesters can be used, for example, polyethylene terephthalate (PET) -based, polyethylene naphthalate (PEN) -based, or copolymers containing them. Although these are mentioned, It is not limited only to these.

In addition, the protective film 20 may be a structure in which a copolymer resin of polyethylene terephthalate-based, polyethylene naphthalate-based, and polyethylene terephthalate-based and polyethylene taphthalate-based coextruded in triplicate.

The polyester film can be obtained, for example, by a method of melt extruding the polyester resin in the form of a film, followed by cooling and solidifying with a casting drum to form a film.

Although not shown, an adhesive may be interposed between the polarizer 10 and the protective film 20 to adhere the polarizer 10 and the protective film 20. The adhesive may be an aqueous adhesive or an acrylic adhesive. Since the adhesive is commonly known in the art, a detailed description thereof will be omitted.

2 is a perspective view of a polarizing plate according to another embodiment of the present invention. Referring to FIG. 2, the polarizing plates 2 may have protective films 20 and 30 disposed on both surfaces of the polarizer 10. In this case, an adhesive may be interposed between the polarizer 10 and the protective films 20 and 30. In addition, both of the protective films 20 and 30 on both sides of the polarizer 10 may satisfy the in-plane retardation and thickness direction retardation ranges described above. However, the present invention is not limited thereto, and any protective film may not satisfy the retardation range.

When the protective film of the present invention is laminated on only one surface of the polarizer, and the protective film not having the retardation range is laminated on the other surface, the protective film that does not satisfy the retardation range is optically isotropic that is substantially birefringent or birefringent. Even if it has a low phase difference value or excellent in-plane uniformity in the optical axis direction can be used. Although it does not specifically limit as a material which has such a characteristic, A transparent polymer with a uniform optical characteristic can be used, and an amorphous polymer can be used from a transparency viewpoint. For example, cellulose resin, cyclic polyolefin resin (norbornene resin), polycarbonate resin, polyarylate resin, amorphous polyester resin, polyvinyl alcohol resin, polysulfone resin, polyimide type Although resin etc. are mentioned, It is not limited only to these.

Meanwhile, although not separately illustrated, when the protective film 20 is laminated only on one surface of the polarizer 10, only the adhesive may be formed on the other surface of the polarizer 10 with the protective film omitted. In this case, the pressure-sensitive adhesive may be interposed between the display panel and the polarizer to be described later, and may be used for adhering the polarizing plate and the display panel.

The protective film 20 may have a thickness of, for example, about 1 μm to about 40 μm, and may thin the polarizing plate in the above range.

In addition, the polarizer 10 may have a thickness of about 1 μm to about 15 μm, for example, about 10 μm or less, or preferably about 5 μm or less. While thinning the polarizing plate in the above range, it is possible to improve the rainbow stain with the protective film.

Display

Although not separately illustrated, the present invention provides a display device including the polarizing plate.

The display device may include a display panel and a polarizer disposed on at least one surface of the display panel, and the polarizer may be the polarizer of the present invention. The display device may be, for example, a liquid crystal display device or an organic light emitting display device, but is not limited thereto.

When the display device is a liquid crystal display device, the liquid crystal display device includes a liquid crystal cell for displaying an image, a backlight unit for providing a light source to the liquid crystal cell, a lower polarizer disposed between the liquid crystal cell and the backlight unit, and the recognition of the liquid crystal cell. It may include an upper polarizing plate disposed on the side.

Any one of the lower polarizing plate and the upper polarizing plate may include the polarizing plate of the present invention, and preferably, the polarizing plate of the present invention may be an upper polarizing plate disposed on the viewing side of the liquid crystal cell. Thereby, rainbow spots of a liquid crystal display can be prevented from occurring and visibility can be improved.

The liquid crystal cell may include a liquid crystal panel including a first substrate and a second substrate facing each other, and a liquid crystal layer encapsulated between the first substrate and the second substrate, and a lower polarizer is stacked on a lower surface of the second substrate. When two polarizing plates are positioned above and below the liquid crystal cell, the transmission axes of the polarizers of each polarizing plate may be orthogonal or parallel to each other.

The first substrate may be a color filter substrate, for example, a black matrix, a color filter of red, green, and blue, and ITO or IZO to prevent light leakage on a lower surface of a substrate made of a transparent insulating material such as glass or plastic. The common electrode which is an electric field generating electrode formed from transparent conductive oxides, such as these, can be included.

The second substrate may be a thin film transistor (TFT) substrate. For example, a thin film transistor including a gate electrode, a gate insulating film, a semiconductor layer, an ohmic contact layer, and a source / drain electrode is formed on a substrate made of a transparent insulating material such as glass or plastic, and a transparent conductive oxide such as ITO or IZO. It may include a pixel electrode that is an electric field generating electrode.

Meanwhile, other components of the liquid crystal display are well known in the art, and thus, detailed description thereof will be omitted.

In the case where the display device is an organic light emitting display device, the organic light emitting display device may include an organic light emitting diode (OLED) panel. The OLED panel may include respective pixels, and each of the pixels may include an OLED composed of an organic light emitting layer between an anode and a cathode and a pixel circuit driving the OLED independently. The pixel circuit may mainly include a switching thin film transistor (TFT), a capacitor, and a driving TFT. The switching thin film transistor charges the data voltage to the capacitor in response to the scan pulse, and the driving TFT controls the amount of current supplied to the OLED according to the data voltage charged to the capacitor, thereby adjusting the amount of light emitted from the OLED and displaying an image. I can display it.

In addition, the polarizing plate of the present invention may be disposed on the viewer side of the OLED panel of the organic light emitting display device. Other configurations of the organic light emitting display device are well known in the art, and thus a detailed description thereof will be omitted.

Polarizing Plate Manufacturing Method

Hereinafter, a method of manufacturing a polarizing plate according to various embodiments will be described with reference to FIGS. 3 to 5 and 6 to 10. In FIGS. 3 to 10, A and B denote stretching directions, solid lines indicating directions of A and B denote stretching processes, and dotted lines denote already stretched in a specific direction.

3 to 5 schematically show a method of manufacturing a polarizing plate according to an embodiment of the present invention.

3 to 5, the polarizing plate manufacturing method includes preparing a non-stretched protective film 21, stretching the non-stretched protective film 21 in one direction A, and the stretched protective film ( 22) forming a laminated film by laminating the polyvinyl alcohol-based resin film 11 on the sheet, and stretching the laminated film in a direction B perpendicular to the one direction A. .

More specifically, as shown in FIG. 3, the non-stretched protective film 21 may be prepared and stretched in one direction (A), thereby manufacturing the protective film 22 stretched in one direction (A). can do. As the component of the non-stretched protective film 21, since the components of the protective film have already been described in the description of the polarizing plate, a detailed description thereof will be omitted.

The step of preparing the non-stretched protective film 21 is not particularly limited, but for example, a melt extrusion method may be used. For example, after melting at or above the melting temperature of the polyester-based material, it may be discharged out of an extrusion facility to form a non-stretched film. Hereinafter, the melt extrusion method will be described in more detail.

If the content of moisture present in the raw material in the melt extrusion process is included in a certain level or more may cause product defects in the bubble state such as orange peel form, it should be managed to a water content below a certain level. The form of the dryer is not particularly limited, and examples thereof include a dehumidifying dryer and a hot air dryer, but are not limited thereto. The drying temperature may be carried out below the glass transition temperature of the film raw material. However, the drying temperature can be appropriately selected according to the type of resin and the glass transition temperature used. If the drying temperature is too low, there is no drying effect, on the contrary, if the drying temperature is higher than necessary, the properties of the raw material are changed, which is not appropriate. The drying time of the raw material may be about 0.5 hours to about 5 hours, but may be easily selected in consideration of the ambient humidity.

The dried raw material may be fed to a raw material reservoir (hopper) located at the inlet of the extrusion facility. In some cases, the filter may be passed with air circulated primarily in the reservoir to primarily remove impurities that may be included in the raw material.

The input raw material is filled in the first section of the screw inside the extrusion plant. The first section serves to transfer the raw material into the extrusion plant cylinder.

Thereafter, the second section is a section in which melting of the raw material starts, preferably set to a temperature higher than the glass transition temperature of the film raw material.

The third section is the section in which the raw material is completely converted into the melt, and the temperature setting can be maintained in the same range as the second section.

The fourth section increases the density of the melt by increasing the pressure of the molten raw material, thereby ensuring a stable discharge amount. In this process, the temperature condition may be maintained in the same range as the second and third sections so that the melt discharged is not cured.

In some cases, it passes through a gear pump section that transfers the melt to the T-die in a fixed amount. If the raw material is transferred directly to the T-die through the screw in the cylinder of the extrusion facility, the instantaneous amount of raw material is irregular and a good quality product cannot be obtained. Therefore, the gear pump can store the raw material irregularly injected from the extrusion equipment cylinder in a certain space and stably supply a certain amount of melt to the T-die to minimize the change in pressure distribution.

The section in which the melt is finally discharged out of the extrusion facility is the T-die section. The shape and manufacturing thickness of the film are determined by the form of the T-die. The die die may be classified into a “T” die, a coat hanger die, a fish tail die, and the like, but is not limited thereto. The type of Ti die can be selectively used depending on the flowability of the melt.

Meanwhile, the one direction A may be a transverse direction (TD) of the protective film 21. That is, the one direction A may be a width direction that is a direction perpendicular to a mechanical direction (MD) which is a direction in which the polarizer 10 to be described later is extended.

Next, as shown in FIG. 4, the polyvinyl alcohol-based resin film 11 may be laminated to the stretched protective film 22 to form a laminated film. The process of forming the laminated film by the lamination may be performed by using an aqueous adhesive or an acrylic adhesive between the polyvinyl alcohol-based resin film 11 and the stretched protective film 22.

Next, as shown in FIG. 5, the step of stretching the laminated film in a direction B perpendicular to the one direction A may be performed. The stretched protective film 22 is already stretched in one direction A, and may be biaxially stretched again in a direction B perpendicular to the one direction A in the process of stretching the laminated film. . Thereby, the protective film 20 which the in-plane phase difference Re mentioned above is about 0 nm-about 300 nm, and thickness direction phase difference R _th satisfy | fills about 0 nm-about 2500 nm can be manufactured.

As described above, the direction B perpendicular to the one direction A may be the machine direction of the polarizer 10, and the polyvinyl alcohol-based resin film 11 is uniaxially stretched in the process of stretching the laminated film. Dichroic substances such as iodine or dichroic dye in the polyvinyl alcohol-based resin film 11 can be oriented in a specific direction, that is, the vertical direction (B).

According to the present invention, after the protective film is uniaxially stretched in one direction, the polyvinyl alcohol-based resin film constituting the polarizer is laminated and stretched in a direction perpendicular to the one direction so that the protective film is biaxially stretched and the polarizer is uniaxially stretched. The manufacturing process may be easy. That is, when biaxially stretching the protective film separately and stretching the polarizer, a total of three stretches are required, whereas by stretching the laminated film on which the uniaxially stretched protective film is laminated, the biaxially stretched protective film and the biaxially stretched film are obtained by only two stretching processes. The polarizing plate containing the uniaxially-stretched polarizer can be manufactured.

In addition, the protective film itself uniaxially stretched during the stretching process of the polyvinyl alcohol-based resin film serves as a base film to prevent the polyvinyl alcohol-based resin film from breaking, and without separately removing the protective film after polarizer production. It can be used as a polarizing plate protective film, and can simplify the manufacturing process of a polarizing plate very much. That is, from the viewpoint of manufacturing the polarizer, the protective film itself may be used as the base film without using a separate base film, and after manufacturing the polarizer, a process of attaching a protective film separately may be omitted, thereby simplifying the manufacturing process. Can be. However, the present invention is not limited thereto.

Meanwhile, as the stretching of the non-stretched protective film 21, a general wet stretching method and / or dry stretching method in the art may be used.

Non-limiting examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, a compression stretching method, a tenter stretching method, and the like. Non-limiting examples include a tenter stretching method, an inter-roll stretching method, and the like.

In the case of the wet stretching method, stretching may be performed in alcohols, water or boric acid aqueous solution, and for example, a solvent such as methyl alcohol or propyl alcohol may be used, but is not limited thereto.

In addition, the extending step can employ | adopt the longitudinal uniaxial stretching method, the horizontal uniaxial stretching method, etc., As a extending | stretching means, it can be based on arbitrary suitable stretching machines, such as a roll stretching machine and a tenter stretching machine.

Stretching the non-stretched protective film 21 in one direction A may be performed by stretching the non-stretched protective film 21 about 4 times to about 7 times. In addition, the protective film 21 stretched by stretching in one direction may have an in-plane retardation (Re) of about 1000 nm or more, for example, about 3000 nm to about 10000 nm, or about 5000 nm to about 10000 nm. . In addition, the thickness direction retardation R _th may be about 1000 nm or more, for example, about 5000 nm to about 12000 nm, or about 6000 nm to about 12000 nm. By satisfying the said range, when extending | stretching a laminated | multilayer film in the direction B perpendicular | vertical to one direction mentioned later, a protective film can satisfy | fill a specific retardation range in a final polarizing plate.

The stretching in the direction B perpendicular to the one direction may be performed by stretching the laminated film by about 4 times to about 7 times, and the protective film 22 is stretched by stretching in the vertical direction. The in-plane retardation Re may be about 0 nm to about 300 nm, and the thickness direction retardation R _th may satisfy about 0 nm to about 2500 nm.

Meanwhile, the method may further include dyeing the polyvinyl alcohol-based resin film 11 with at least one of iodine and a dichroic dye. The dyeing step is a step of introducing iodine, a dye, a pigment or a mixture thereof into the polyvinyl alcohol-based resin film 11 to adsorb them into the film. The iodine, dye, or pigment molecule absorbs light oscillating in the stretching direction of the polarizer in the final polarizer and transmits light oscillating in the vertical direction, thereby obtaining polarized light having a specific vibration direction.

The dyeing step may be performed by impregnating the polyvinyl alcohol-based resin film 11 in a solution of iodine or dichroic material. For example, when the dyeing using the iodine described, the temperature of the iodine solution is in the range of about 20 ℃ to about 50 ℃, the impregnation time may be about 10 seconds to about 300 seconds. When the iodine solution is used as the iodine solution, an aqueous solution containing iodine (I ₂ ) and iodine ions, for example, potassium iodide (KI) used as a dissolution aid, may be used. In an exemplary embodiment, the concentration of iodine (I ₂ ) ranges from about 0.01% to about 0.5% by weight based on the total weight of the aqueous solution, and the concentration of potassium iodide (KI) is about 0.01% by weight based on the total weight of the aqueous solution. To about 10% by weight.

In an exemplary embodiment, the swelling step may further be included prior to carrying out the dyeing step. In the swelling step, the molecular chain of the polyvinyl alcohol-based resin film 11 is softened and the molecular chain is relaxed, so that a dichroic material is homogeneously dyed into the polyvinyl alcohol-based resin film 11 during staining to cause staining. It can play a role to prevent it.

The swelling ratio can be from about 150% to about 250%. In this swelling process, the polyvinyl alcohol-based resin film 11 may be partially stretched. When satisfying the swelling ratio and the elongation as described above, it is possible to achieve high permeability while preventing the occurrence of staining in the dyeing process without increasing the physical properties of the polarizer in the final manufactured polarizing plate and to improve the uniformity of optical properties. The swelling step can be performed by a dry method or a wet method. In an exemplary embodiment, it may be carried out by a wet method in a swelling bath containing swelling liquid. In addition, the swelling temperature may vary depending on the film thickness and the like, for example, may be about 15 ℃ to about 40 ℃.

In another exemplary embodiment, a crosslinking process may be further included after the dyeing step.

When molecules of iodine or dichroic material are dyed in the polyvinyl alcohol-based resin film 11 in the dyeing step, the dichroic molecules are formed by using boric acid, borate, or the like to polymer matrix of the polyvinyl alcohol-based resin film 11 To be adsorbed onto the bed. Examples of the crosslinking method include a deposition method in which the polyvinyl alcohol-based resin film 11 is immersed in an aqueous solution of boric acid or the like, but is not limited thereto. It may also be performed by.

On the other hand, the above-described steps such as dyeing, swelling, crosslinking may be performed after forming a laminated film obtained by laminating the protective film 22 stretched in one direction on the polyvinyl alcohol-based resin film 11.

6 to 10 are diagrams schematically showing a method of manufacturing a polarizing plate according to another embodiment of the present invention. 6 to 10, a method of manufacturing a polarizing plate may include preparing a plurality of non-stretched protective films 21 and 31, and stretching the plurality of non-stretched protective films 21 and 31 in one direction A. FIG. Step, laminating the polyvinyl alcohol-based resin film 11 between the plurality of stretched protective film (22, 32) to form a laminated film, and the laminated film perpendicular to the one direction Stretching in the direction B may be included.

That is, by extending | stretching the laminated | multilayer film which arrange | positioned the protective films 22 and 32 uniaxially stretched in one direction A on both surfaces of the polyvinyl alcohol-type resin film 11 in the direction B perpendicular to the said one direction The biaxially stretched protective films 20 and 30 may be disposed on both surfaces of the polarizer 10.

More specifically, the stretching of the plurality of non-stretched protective films 21 and 31 in one direction is performed by laminating the plurality of non-stretched protective films 21 and 31, as shown in FIG. As illustrated in FIG. 7, the separation of the protective films 22 and 32 stretched in one direction may be performed, but is not limited thereto. As illustrated in FIG. 8, the plurality of non-stretched protective films 21 and 31 may be used. It may also be carried out by stretching each.

Next, as shown in FIG. 9, the polyvinyl alcohol-based resin film 11 is disposed between the plurality of protective films 22 and 32 stretched in one direction to form a laminated film, and then, as shown in FIG. 10. By extending | stretching the said laminated | multilayer film in the direction (B) perpendicular | vertical to a direction, the polarizing plate of the state which the biaxially stretched protective film finally was arrange | positioned on both surfaces of the polarizer 10 can be manufactured. In addition, the biaxially stretched plurality of protective films 20 and 30 may each have an in-plane retardation Re of about 300 nm or less, and a thickness direction retardation R _th of about 2500 nm or less.

On the other hand, the other components have already been described in the embodiment of Figures 3 to 5, the overlapping description will be omitted.

Meanwhile, although not separately illustrated, when the polarizing plate is applied to the display device, the polarizing plate may further include a functional layer disposed on the outer surface of the protective film in the polarizing plate positioned at the viewing side of the display device.

The functional layer may include a hard-coating layer, an anti-reflection layer, an anti-glare layer, or a diffusion layer, but is not limited thereto and variously known in the art. It may include a functional layer. For example, the hard coating layer may improve the wet heat durability of the polarizing plate and prevent the dimensional change, the anti-reflection layer may reduce the reflection by extinguishing the light of the light incident from the outside, the anti-glare layer is the diffusion of light incident from the outside It can induce excessive reflection and prevent glare.

Hereinafter, the polarizing plate of the present invention will be described in more detail with reference to Examples.

Example  1 to Example  5

The protective film composed of polyethylene terephthalate resin was primarily stretched by TD of the protective film (the stretching drainage of Examples 1 to 5 is the same as in Table 1 below). A laminated film was prepared by laminating (PVA of Kuraray Co., Ltd.) so that the MD of PVA and the MD of the protective film were parallel to the protective film drawn in the TD, and the laminated film was used as the MD of PVA (stretched drainage of Examples 1 to 5). It is as shown in Table 1.) Secondary stretching to prepare a polarizing plate in the form of a biaxially stretched protective film attached to the PVA uniaxially stretched.

division	Primary stretching (stretched by TD of protective film)	Secondary stretching (stretched with MD of PVA)
Example 1	5.5	5.5
Example 2	5.6	5.7
Example 3	5.7	5.8
Example 4	5.8	5.9
Example 5	6.1	6.0

Experimental Example  One

In Examples 1 to 5, the in-plane retardation Re and the thickness direction retardation R _th of the protective film after primary stretching in TD were measured, and after laminating PVA, the laminate was MD of PVA. In-plane retardation (Re) and thickness direction retardation (R _th ) of the protective film after the secondary stretching in the furnace were measured and shown in Table 2 below.

division	Retardation (nm) of protective film after primary TD stretching		Retardation (nm) of protective film after secondary MD stretching
	Re	R th	Re	R th
Example 1	6000	7000	150	1300
Example 2	9050	10000	200	1350
Example 3	5500	6300	100	1500
Example 4	9500	11000	250	2300
Example 5	5300	6300	50	1200

Experimental Example  2

It was measured whether the rainbow stain of the polarizing plates prepared in Examples 1 to 5 was visually recognized, and the results are shown in Table 3 below.

division	Whether the rainbow stain poet
Example 1	Unacknowledged
Example 2	Unacknowledged
Example 3	Unacknowledged
Example 4	Unacknowledged
Example 5	Unacknowledged

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (16)

1. Polarizer; And

   A protective film laminated on at least one surface of the polarizer,

   The in-plane retardation (Re) of the protective film is about 0nm to 300nm, the thickness direction retardation (R _th ) is about 0nm to 2500nm.
2. The method of claim 1,

   The protective film is a biaxially stretched film,

   The polarizer is a uniaxially stretched polarizing plate.
3. The method of claim 1,

   The polarizer has a thickness of about 1 μm to about 15 μm.
4. The method of claim 1,

   And at least one functional layer of a hard-coating layer, an anti-reflection layer, an anti-glare layer, and a diffusion layer on at least one surface of the protective film.
5. The method of claim 1,

   The protective film is a polyethylene terephthalate-based, polyethylene naphthalate-based, or a polarizing plate which is a copolymer containing them.
6. The method of claim 5,

   The protective film is a polarizing plate having a structure in which the polyethylene terephthalate-based, polyethylene naphthalate-based, or a copolymer containing them triple coextruded.
7. Preparing a non-stretched protective film;

   Stretching the non-stretched protective film in one direction;

   Forming a laminated film by laminating a polyvinyl alcohol-based resin film on the stretched protective film; And

   And stretching the laminated film in a direction perpendicular to the one direction.
8. The method of claim 7, wherein

   The stretching in the one direction may be performed by stretching the non-stretched protective film about 4 times to about 7 times.
9. The method of claim 7, wherein

   The protective film stretched by stretching in one direction has an in-plane retardation (Re) of about 1000 nm or more, and a thickness direction retardation (R _th ) of about 1000 nm or more.
10. The method of claim 7, wherein

    Stretching in the vertical direction is a polarizing plate manufacturing method characterized in that for stretching the laminated film about 4 times to about 7 times.
11. The method of claim 7, wherein

    The protective film stretched by the stretching in the vertical direction has an in-plane retardation (Re) of about 0nm to about 300nm, the thickness direction retardation (R _th ) of about 0nm to about 2500nm.
12. Preparing a plurality of non-stretched protective films;

    Stretching the plurality of non-stretched protective films in one direction;

    Forming a laminated film by laminating a plurality of stretched protective films with a polyvinyl alcohol-based resin film interposed therebetween; And

    And stretching the laminated film in a direction perpendicular to the one direction.
13. The method of claim 12,

    Stretching in the one direction

    The method of manufacturing a polarizing plate, characterized in that to perform the laminating a plurality of non-stretched protective film.
14. The method of claim 12,

    Stretching in the one direction

    Method of manufacturing a polarizing plate, characterized in that carried out by stretching each of the plurality of non-stretched protective film.
15. The method of claim 12,

    The plurality of protective films stretched by stretching in one direction have an in-plane retardation (Re) of about 1000 nm or more, and a thickness direction retardation (R _th ) of about 1000 nm or more.
16. The method of claim 12,

    The plurality of protective films stretched by stretching in the vertical direction have an in-plane retardation (Re) of about 0 nm to about 300 nm, and a thickness direction retardation (R _th ) of about 0 nm to about 2500 nm.

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