KR101955203B1

KR101955203B1 - Manufacturing method for thin polarizer, thin polarizer manufactured by thereof, polarizing plate and display device comprising thereof

Info

Publication number: KR101955203B1
Application number: KR1020150124347A
Authority: KR
Inventors: 정종현; 남성현; 나균일; 유혜민
Original assignee: 주식회사 엘지화학
Priority date: 2015-09-02
Filing date: 2015-09-02
Publication date: 2019-03-07
Also published as: KR20170027558A

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin polarizer, a thin polarizer manufactured by using the same, a polarizing plate including the thin polarizer, and a display device.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin polarizer, a thin polarizer manufactured thereby, a polarizing plate including the polarizer, and a display device using the thin polarizer,

A polarizer used in a polarizing plate is an optical element for converting natural light or arbitrary polarized light into polarized light in a specific direction, and is widely used in a display device such as a liquid crystal display element and an organic light emitting element (OLED). At present, as a polarizer used in the display device, a polyvinyl alcohol polarizing film in which molecular chains containing an iodine compound or a dichroic dye are oriented in a certain direction is generally used.

The polyvinyl alcohol (PVA) polarizing film is produced by dying iodine or a dichroic dye to a polyvinyl alcohol film, stretching it in a predetermined direction, and crosslinking, wherein the stretching process is an aqueous solution of boric acid or iodine Wet stretching performed in a solution such as an aqueous solution or dry stretching performed in the atmosphere, and the stretching magnification is generally 5 times or more. However, in such a conventional manufacturing process, it is required that the thickness of the polyvinyl alcohol-based film before stretching exceeds 60 占 퐉 in order to perform stretching without occurrence of breakage. When the thickness of the polyvinyl alcohol-based film before stretching is 60 m or less, the swelling degree of the polyvinyl alcohol-based film is increased, and the modulus of action per unit area in the stretching process becomes large due to the thin thickness.

On the other hand, according to recent tendency of thinning of display devices, polarizer is also required to have a thinner thickness. However, when a polyvinyl alcohol film having a thickness of more than 60 탆 is used as in the prior art, there is a limit in reducing the thickness of the polarizer. Therefore, studies for producing a polarizer with a thinner thickness have been attempted.

Korean Patent Laid-Open Publication No. 2010-0071998 discloses a method of producing a laminate by coating a hydrophilic polymer layer (PVA resin layer) on a base layer or co-extruding a base layer forming material and a hydrophilic polymer layer forming material (PVA resin) A method of producing a thin polarizing plate is disclosed. However, in the case of coating the PVA layer on the substrate layer or pneumatically releasing it, separation of the polyvinyl alcohol layer and the substrate layer after stretching is not easy and a high peeling force is required for separation. Therefore, The layer is liable to be damaged or deformed, and as a result, there is a problem that optical properties such as the degree of polarization of the prepared polyvinyl alcohol polarizer are deteriorated. When the coating method or the co-extrusion method is used, since the polyvinyl alcohol resin is melted and then extruded or prepared by coating with a coating solution, the polyvinyl alcohol resin is produced by extrusion, coating or film- The physical properties of the film tend to be changed, so that not only the physical properties of the finally produced polyvinyl alcohol are lowered but also uniform physical properties are difficult to be realized.

SUMMARY OF THE INVENTION The present invention provides a method of manufacturing a thin polarizer and a thin polarizer manufactured using the same to solve the above problems.

One embodiment of the present invention relates to a method for manufacturing a film laminate, comprising the steps of: forming an unstretched polyvinyl alcohol-based film having a thickness of 40 占 퐉 or less on at least one surface of a polymer film using a force or an adhesive;

Stretching the film laminate so that the thickness of the polyvinyl alcohol film after stretching becomes 10 占 퐉 or less; And separating the polymer film of the stretched film laminate from the polyvinyl alcohol film, wherein the polymer film has a shrinkage ratio (R) of 0.15 or less represented by the following formula (1).

[Formula 1]

R = (L ₀ - L _r ) / L ₀

L ₀ is the length of the polymer film in a state where the tension of the polymer film is maintained after the stretching of the polymer film and L _r is the length of the polymer film in the state in which the tensile force is removed after stretching the polymer film. Length.

One embodiment of the present invention provides a thin polarizer produced by the above manufacturing method.

One embodiment of the present disclosure provides a polarizing plate comprising the thin polarizer.

One embodiment of the present invention provides a display device including the polarizer.

The manufacturing method according to one embodiment of the present invention is advantageous in that a thin polarizer having a thickness of 10 탆 or less can be produced through a simple process and excellent in process stability.

The production method according to one embodiment of the present invention can remarkably lower the occurrence rate of breakage even when high-magnification stretching is performed, thereby increasing the degree of orientation of the PVA polarizer, and as a result, a thin polarizer having excellent optical properties can be produced.

1 is a schematic view showing a method of measuring an adhesive force or a peeling force using a texture analyzer.
2 is a graph showing the stretching behavior of the polymer films according to Examples and Comparative Examples.

When a member is referred to herein as being " on " another member, it includes not only a member in contact with another member but also another member between the two members.

Whenever a component is referred to as " comprising ", it is to be understood that the component may include other components as well, without departing from the scope of the present invention.

The inventors of the present invention have researched long time for producing a polyvinyl alcohol (PVA) -based polarizer having excellent performance and solving the problem of a method of forming a polyvinyl alcohol film by a solution process on a base film and then stretching it As a result, a method of manufacturing a polarizing plate according to an embodiment of the present invention has been found. Specifically, according to one embodiment of the present invention, a polymer film having a shrinkage ratio (R) of 0.15 or less represented by the following formula (1) is used as a base film, and after the polyvinyl alcohol film is attached, , It is possible to produce a polarizer having excellent performance by a simple process.

[Formula 1]

R = (L ₀ - L _r ) / L ₀

Furthermore, the manufacturing method according to one embodiment of the present invention minimizes the problems such as separation and separation of the polyvinyl alcohol-based film and the polymer film during the process, and remarkably reduces the breakage occurrence rate of the polyvinyl alcohol-based film have.

Hereinafter, the present invention will be described in more detail.

[Formula 1]

R = (L ₀ - L _r ) / L ₀

The present inventors have found that there is a problem of damaging the stretched polyvinyl alcohol film used as a polarizer due to the property of recovering the length before stretching when the stretching means is removed after the stretching of the polymer film used as the base film Respectively. Thus, the present inventors have found that when a thin film polarizer is manufactured using a polymer film having an export ratio (R) of 0.15 or less, the optical performance of the polarizer is excellent. Specifically, when a thin film polarizer is manufactured using a polymer film having an export ratio (R) of 0.15 or less represented by the formula 1, a high degree of polarization can be realized while maintaining the transmittance of the thin polarizer high.

Further, in the case of the film laminate, the wet stretching process for polarizer production effectively suppresses the peeling of the polyvinyl alcohol-based film and / or the separation phenomenon from the polymer substrate, which may occur as the degree of swelling of the polyvinyl alcohol-based film increases And the instability of the film laminate can be reduced.

According to an embodiment of the present invention, the polymer film may have an elastic modulus of 900 N / mm 2 or more and 1,000 N / mm 2 or less. Specifically, according to one embodiment of the present invention, the modulus of elasticity of the polymer film may be 900 N / mm2 or more and 950 N / mm2 or less. More specifically, according to one embodiment of the present invention, the modulus of elasticity of the polymer film may be 900 N / mm 2 or more and 940 N / mm 2 or less.

The elastic modulus can be measured using UTM (Universal Testing Machine) equipment.

When the modulus of elasticity of the polymer film is 900 N / mm < 2 > or more and 1,000 N / mm < 2 > or less, occurrence of breakage of the polymer film is remarkably suppressed during the stretching process, Further, when the elastic modulus of the polymer film is not less than 900 N / mm 2 and not more than 1,000 N / mm 2, it is possible to manufacture an excellent polarizer without disturbing the stretching of the polyvinyl alcohol film during the stretching of the film laminate.

According to one embodiment of the present invention, the maximum tensile force of the polymer film may be 25 N or less. Specifically, according to an embodiment of the present invention, the maximum tensile force of the polymer film may be 23 N or less. More specifically, according to one embodiment of the present invention, the maximum tensile force of the polymer film may be 21 N or less.

The maximum tensile force may mean the maximum force at which the film is broken when the polymer film is stretched at room temperature (25 DEG C). Specifically, the maximum tensile force may have the same meaning as the breaking force, which means that when both ends of the film are fixed and then a tensile force is applied in a direction perpendicular to the thickness direction of the film, the tensile force at the time of breaking the film For example, a tensile strength meter (Zwick / Roell Z010 UTM) or the like.

If the maximum tensile force of the polymer film is out of the above-described range, it may be difficult to draw at a high magnification, or breakage may occur during the stretching process.

According to one embodiment of the present invention, the maximum stretching magnification of the polymer film during dry drawing at 25 DEG C may be 4.5 times or more.

The polymer film used for the film laminate is for preventing the polyvinyl alcohol film from breaking in the stretching process and may be a polymer film having a maximum draw ratio of 4.5 times or more at 25 캜. At this time, the maximum draw ratio refers to the draw ratio immediately before the break occurs. Further, in the dry stretching for measuring the maximum stretching magnification of the polymer film, when the PVA is stretched at a constant speed (60 RPM) using a simple stretcher at 25 ° C., the distance and the initial distance ratio at the point where the film is broken are calculated And can be performed by measuring the maximum draw ratio.

According to one embodiment of the present invention, the polymer film may be formed of a low density polyethylene resin, a high density polyethylene resin, a copolymer resin containing ethylene vinyl acetate in high density polyethylene, a polypropylene resin, a polyurethane resin, a polyethylene terephthalate A resin, a water-soluble cellulose resin, and an acrylic resin.

Specifically, according to one embodiment of the present invention, the polymer film may be a high density polyethylene film, a polyurethane film, a polypropylene film, a polyolefin film, an ester film, a low density polyethylene film, a high density polyethylene and a low density polyethylene coextrusion film, A copolymer resin film containing ethylene vinyl acetate, an acrylic film, a polyethylene terephthalate film, a polyvinyl alcohol film, and a cellulose-based film.

Specifically, according to one embodiment of the present specification, the polymer film may be a polyurethane film, and more specifically, a thermoplastic polyurethane film.

According to one embodiment of the present invention, the polymer film may have a thickness of 20 占 퐉 to 100 占 퐉, preferably 30 占 퐉 to 80 占 퐉, and more preferably 40 占 퐉 to 60 占 퐉. If the thickness of the polymer film is less than 20 mu m, the polyvinyl alcohol film can not be sufficiently supported in the stretching process of the film laminate, resulting in breakage or the like. When the thickness of the polymer film is more than 100 占 퐉, the stretchability of the film laminate may be deteriorated, the width shrinkage free of the polyvinyl alcohol film during drying may be prevented, and the optical properties of the finally obtained polarizer Can be inhibited.

According to one embodiment of the present invention, it is preferable that the glass transition temperature of the polymer film is lower than the glass transition temperature of the unstretched polyvinyl alcohol-based film. For example, the glass transition temperature may be 20 ° C to 60 ° C, 60 < 0 > C. Considering that a general polyvinyl alcohol-based film has a glass transition temperature of about 70 to 80 캜, when the glass transition temperature of the polymer film satisfies the above-described numerical value range, the polymer film becomes more soft in the stretching temperature condition And as a result, the polyvinyl alcohol-based film can be further stretched. However, when the glass transition temperature of the polymer film is too low, breakage may occur at the time of high-magnification stretching. Therefore, the glass transition temperature of the polymer film is preferably 20 ° C or more. On the other hand, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, when a sample of about 10 mg is sealed in a dedicated pan of a differential scanning calorimeter (DSC) and heated at a constant temperature, the amount of heat absorbed and the amount of heat generated as the phase change occurs is plotted with temperature The transition temperature can be measured.

According to one embodiment of the present invention, the polymer film may have a modulus at room temperature (25 ° C) of 200 MPa to 1500 MPa, specifically 350 MPa to 1300 MPa. When the modulus of the polymer film is more than 1500 MPa, high-degree stretching may be difficult, and when the modulus is less than 200 MPa, breakage may occur during stretching. At this time, the modulus is measured by fixing the both ends of a sample prepared according to JIS-K6251-1 standard, and then applying a force in a direction perpendicular to the thickness direction of the film to measure a stress per unit area according to a tensile strain (Zwick / Roell Z010 UTM) or the like can be used as the measuring instrument.

According to one embodiment of the present invention, the polymer film may have a force at break point of 5 N to 40 N, specifically 10 N to 30 N at room temperature (25 ° C). In this case, the breaking force means a tensile force at the time when the film is broken when a tensile force is applied in a direction perpendicular to the thickness direction of the film after both ends of the film are fixed. For example, a tensile strength meter (Zwick / Roell Z010 UTM). When the breaking strength of the polymer film is out of the above range, it may be difficult to draw at a high magnification, or breakage may occur during the stretching process.

According to one embodiment of the present invention, the modulus of elasticity of the unstretched polyvinyl alcohol-based film may be 300 N / mm 2 to 400 N / mm 2. Specifically, according to one embodiment of the present invention, the unstretched polyvinyl alcohol-based film may have an elastic modulus of 300 N / mm 2 or more and 350 N / mm 2 or less.

When the modulus of elasticity of the non-stretched polyvinyl alcohol-based film is within the above range, the incidence of breakage is lowered and the optical properties of the polarizer produced are excellent. When the modulus of elasticity of the non-stretched polyvinyl alcohol-based film is less than 300 N / mm < 2 >, there is a problem that the rigidity of the film is insufficient to cause breakage of the film. If N / mm < 2 >, the elongation property of the film is lowered, and the optical properties of the produced polarizer are deteriorated.

According to one embodiment of the present disclosure, the step of forming the film laminate may be a step of attaching an unoriented polyvinyl alcohol-based film produced separately to the polymer film. Specifically, the film laminate does not form an unstretched polyalcohol-based film on a polymer film through a solution process or the like.

As described above, when an unstretched polyvinyl alcohol-based film is adhered to a polymer film, the adhesion force between the stretched polyvinyl alcohol-based film and the polymer film is not large, and the stretched polyvinyl alcohol It is possible to minimize damage to the film.

According to one embodiment of the present invention, the maximum draw ratio of the unstretched polyvinyl alcohol-based film may be three times or more at 25 占 폚. Specifically, according to one embodiment of the present invention, the maximum draw ratio of the unstretched polyvinyl alcohol-based film may be 3 times or more and 4 times or less or 3 times or more and 3.7 times or less at 25 占 폚.

According to one embodiment of the present invention, the maximum tensile force of the unstretched polyvinyl alcohol-based film may be 10 N or less.

The maximum tensile strength may mean the maximum force at which the film is broken when the unstretched polyvinyl alcohol film is stretched at room temperature (25 DEG C). Specifically, the maximum tensile force may have the same meaning as the breaking force, which means that when both ends of the film are fixed and then a tensile force is applied in a direction perpendicular to the thickness direction of the film, the tensile force at the time of breaking the film For example, a tensile strength meter (Zwick / Roell Z010 UTM) or the like.

If the maximum tensile force of the unstretched polyvinyl alcohol-based film is out of the above range, it may be difficult to draw at a high magnification, or breakage may occur during the stretching process.

According to one embodiment of the present invention, the thickness of the unstretched polyvinyl alcohol-based film may be 40 占 퐉 or less. Specifically, the thickness of the unstretched polyvinyl alcohol-based film may be 30 占 퐉 or less, or 20 占 퐉 or less. Further, according to one embodiment of the present invention, the thickness of the unstretched polyvinyl alcohol-based film may be 10 탆 or more.

When the thickness of the unstretched polyvinyl alcohol-based film is more than 40 탆, it is difficult to realize a thickness of 10 탆 or less even when stretched. When the thickness is less than 10 탆, breakage occurs during stretching to increase the defect rate May occur.

According to one embodiment of the present invention, the degree of polymerization of the unstretched polyvinyl alcohol-based film may be 2,600 or more and 3,200 or less.

As the non-stretched polyvinyl alcohol film, a commercially available polyvinyl alcohol film can be used. For example, M2005 grade, M2006 grade, PE20N of Kuraray Co., Ltd. and the like can be used. However, the present invention is not limited thereto, and a polyvinyl alcohol film satisfying the above physical properties can be applied.

According to one embodiment of the present invention, the step of stretching the film laminate can be performed so that the thickness of the polyvinyl alcohol-based film after stretching becomes 10 mu m or less. Specifically, the step of stretching the film laminate may be performed so that the thickness of the polyvinyl alcohol-based film after stretching is 1 占 퐉 to 10 占 퐉, 3 占 퐉 to 10 占 퐉, or 1 占 퐉 to 5 占 퐉.

According to one embodiment of the present disclosure, the step of stretching the film laminate may be performed at a stretching magnification of 5 times or more and 15 times or less at a temperature of 20 占 폚 to 85 占 폚. Specifically, the step of stretching the film laminate may be performed at a stretching magnification of 5 to 12 times at a temperature of 40 to 80 캜.

According to one embodiment of the present disclosure, the step of stretching the film laminate can be performed at a draw magnification of 5.5 times or more and 15 times or less, or 6 times or more and 15 times or less. According to an embodiment of the present invention, the step of stretching the film laminate can be performed at a draw magnification of 6.5 times or more and 15 times or less, or 7 times or more and 15 times or less.

According to one embodiment of the present disclosure, the step of stretching the film laminate may be performed in a dry or wet type. Specifically, according to one embodiment of the present disclosure, the step of stretching the film laminate may be carried out in a wet type. When the wet stretching is performed, the surface adhesion of the polymer film and the polyvinyl alcohol film becomes stronger than that of the dry stretching, so that the stretching can be performed stably without any separate adhesion means. In addition, the wet type has an advantage that drawing can be performed even at a low temperature as compared with dry drawing.

According to one embodiment of the present disclosure, the wet stretching may be performed in an aqueous boric acid solution. At this time, the boric acid concentration of the boric acid aqueous solution may be 1 wt% to 5 wt%.

According to one embodiment of the present invention, when stretching is carried out in an aqueous boric acid solution as described above, the fracture occurrence rate of the polyvinyl alcohol-based film is lowered due to the boric acid crosslinking, thereby increasing the process stability. It is possible to control the generation of wrinkles of the alcohol-based film.

On the other hand, the production process of the polarizer can be performed by washing, swelling, dying, washing, stretching, complementing, drying and the like.

According to one embodiment of the present disclosure, before the step of stretching the film laminate, the step of cleaning the film laminate may further be included. Specifically, according to one embodiment of the present disclosure, the step of cleaning the film laminate and / or the step of stretching the film laminate may be performed in an aqueous boric acid solution. More specifically, according to one embodiment of the present disclosure, the step of cleaning the film laminate can be performed in an aqueous boric acid solution having a boric acid concentration of 0.1 wt% to 2.5 wt%, specifically 0.5 wt% to 2 wt% have.

According to an embodiment of the present invention, the step of stretching the film laminate may be performed in an aqueous boric acid solution having a boric acid concentration of 1 wt% or more and 5 wt% or less, specifically 1.5 wt% or more and 4.5 wt% or less.

According to an embodiment of the present invention, the method may further include the step of dying at least one of iodine and dichroic dye to the unstretched polyvinyl alcohol-based film before stretching the film laminate.

On the other hand, the unstretched polyvinyl alcohol-based film is preferably a film in which iodine and / or a dichroic dye are dyed. More preferably, the unoriented polyvinyl alcohol-based film may be a film on which a swelling process and a dipping process have been carried out.

Specifically, according to one embodiment of the present specification, before the stretching of the film laminate, it may further comprise the step of salt-fixing the iodine and / or dichroic dye to the unstretched polyvinyl alcohol-based film. More specifically, according to one embodiment of the present invention, there is provided a method for producing a polyvinyl alcohol film, comprising swelling the unstretched polyvinyl alcohol-based film and adhering iodine and / or dichroic dye to the swelled unvulcanized polyvinyl alcohol- .

At this time, the step of swelling the unstretched polyvinyl alcohol-based film is intended to promote the adsorption and diffusion of iodine and / or dichroic dye onto the polyvinyl alcohol-based film and improve the stretchability of the polyvinyl alcohol-based film For example, by immersing the unstretched polyvinyl alcohol-based film in pure water at 25 ° C to 30 ° C for 5 seconds to 30 seconds, more preferably 10 seconds to 20 seconds. have. The swelling is preferably performed so that the degree of swelling of the unstretched polyvinyl alcohol-based film is about 36% to 44%, preferably about 38% to 42%. When the degree of swelling of the unstretched polyvinyl alcohol-based film satisfies the above-described numerical range, the optical characteristics such as the degree of polarization of the finally produced thin polarizer are excellent. On the other hand, the swelling degree was calculated as {(weight of polyvinyl alcohol film after swelling-weight of polyvinyl alcohol film before swelling) / weight of polyvinyl alcohol film before swelling} x 100.

In addition, in the step of adhering the iodine and / or dichroic dye to the unstretched polyvinyl alcohol film, the unstretched polyvinyl alcohol film is impregnated in a dyeing bath containing a dyeing solution containing iodine and / or dichroic dye Or a method of applying a dyeing solution containing iodine and / or a dichroic dye onto a polyvinyl alcohol-based film. At this time, water is generally used as a solvent for the dyeing solution, but an organic solvent having compatibility with water may be mixed. On the other hand, the content of iodine and / or dichroic dye in the dyeing solution may be 0.06 part by weight to 0.25 part by weight with respect to 100 parts by weight of the solvent. In addition to the iodine and / or dichroic dye, the dyeing solution may further contain an auxiliary agent for improving the efficiency of the dyeing. The auxiliary agent may include potassium iodide, lithium iodide, sodium iodide, aluminum iodide, lead iodide , Copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, or a mixture thereof. In this case, the content of the auxiliary agent may be 0.3 to 2.5 parts by weight based on 100 parts by weight of the solvent, and specifically, the weight ratio of the iodine to the iodide compound may be 1: 5 to 1:10. The dipping step may be performed at a temperature of 25 ° C to 40 ° C, and the dipping time may be 30 seconds to 120 seconds, but is not limited thereto.

According to one embodiment of the present invention, the step of separating the polymer film of the stretched film laminate from the polyvinyl alcohol film may be performed by applying a peeling force of 2 N / 2 cm or less.

According to one embodiment of the present invention, the film laminate can be produced by adhering a polymer film and an unstretched polyvinyl alcohol-based film via an adhesive layer using an adhesive, or by laminating without a separate adhesive layer.

On the other hand, when the polymer film and the unstretched polyvinyl alcohol-based film are adhered using a force, surface treatment may be performed on one side or both sides of the polymer film or the polyvinyl alcohol-based film, . At this time, the surface treatment can be carried out through various surface treatment methods well known in the art, for example, corona treatment, plasma treatment or surface modification treatment using a strong base aqueous solution such as NaOH or KOH.

On the other hand, the material of the adhesive is not particularly limited, and various adhesives known in the art can be used without limitation. For example, the adhesive layer may be formed of an aqueous adhesive or an ultraviolet curable adhesive.

More specifically, the adhesive layer may be formed of an aqueous adhesive containing at least one selected from the group consisting of a polyvinyl alcohol-based resin, an acrylic resin and a vinyl acetate-based resin.

According to one embodiment of the present invention, the adhesive layer may be formed by an aqueous adhesive including a polyvinyl alcohol-based resin having an acrylic group and a hydroxyl group. At this time, the polyvinyl alcohol resin having an acryl group and a hydroxyl group may have a degree of polymerization of 500 to 1,800.

According to one embodiment of the present invention, the adhesive layer may be formed using an aqueous adhesive containing an amine-based metal compound crosslinking agent in an acetacetyl group-containing polyvinyl alcohol-based resin. More specifically, the aqueous adhesive may be an aqueous solution containing 1 to 50 parts by weight of an amine-based metal compound crosslinking agent per 100 parts by weight of a polyvinyl alcohol-based resin containing an acetacetyl group.

The polymerization degree and degree of saponification of the polyvinyl alcohol-based resin are not particularly limited as long as they contain an acetacetyl group, but the degree of polymerization may be 200 to 4,000 and the saponification degree may be 70 to 99.9 mol%. Considering the flexible mixing with the contained material due to the freedom of molecular movement, the degree of polymerization of the polyvinyl alcohol-based resin may be 1,500 to 2,500, and the degree of saponification may be 90 to 99.9 mol%. At this time, the polyvinyl alcohol resin may contain the acetacetyl group in an amount of 0.1 mol% to 30 mol%. Within the above range, the reaction with the amine-based metal compound crosslinking agent can be smoothly performed, and the water resistance of the desired adhesive can be sufficiently enhanced.

The amine-based metal compound crosslinking agent may be in the form of a metal complex containing an amine-based ligand as a water-soluble crosslinking agent having a functional group having reactivity with the polyvinyl alcohol-based resin. As the central metal of the metal complex, zirconium (Zr), titanium (Ti), hafnium (Hf), tungsten (W), iron (Fe), cobalt (Co), nickel (Ni), ruthenium Transition metal such as rhodium (Rh), iridium (Ir), palladium (Pd), and platinum (Pt) can be used as the ligand. The ligand bonded to the center metal includes primary amines, Or at least one amine group such as ammonium hydroxide.

The solid content of the polyvinyl alcohol-based resin containing the acetacetyl group may be 1 wt% to 10 wt%. When the solid content of the polyvinyl alcohol-based resin is less than 1% by weight, water resistance is insufficient and the effect of lowering the fracture occurrence rate in the stretching step is small. When the solid content is more than 10% by weight, workability is deteriorated. Damage may occur to the surface of the vinyl alcohol film.

On the other hand, the pH of the adhesive may be 4.5 to 9. When the pH of the adhesive satisfies the above-described numerical value range, it is more advantageous in terms of durability in a storage and high humidity environment. The pH of the adhesive may be adjusted by adding an acid in an aqueous solution, and the acid used for adjusting the pH may be either strong acid or weak acid. For example, nitric acid, hydrochloric acid, sulfuric acid or acetic acid may be used.

The thickness of the adhesive layer formed by the adhesive is preferably 80 nm to 200 nm, particularly 80 nm to 150 nm before stretching the film laminate, and 10 nm to 100 nm, more preferably 10 nm to 100 nm, Lt; / RTI > When the thickness of the adhesive layer satisfies the above range, the adhesive strength between the base film and the polyvinyl alcohol film is maintained at an appropriate level, so that the fracture occurrence rate in the stretching process is reduced and the surface damage of the polarizer can be minimized at the time of peeling.

The adhesive causes a cross-linking reaction between the amine-based metal compound and the acetacetyl group of the polyvinyl alcohol-based resin at the time of curing, so that the water resistance of the adhesive layer after curing is excellent. Therefore, when the polymer film and the polyvinyl alcohol film are laminated using the adhesive, the phenomenon that the adhesive is dissolved in water at the time of the wet stretching can be minimized, so that the film can be particularly useful when wet stretching is performed .

The adhesive layer may be formed of an ultraviolet curable adhesive, for example, a first epoxy compound having a glass transition temperature of 120 DEG C or higher of a homopolymer, a second epoxy compound having a glass transition temperature of 60 DEG C or lower of a homopolymer, And may be formed of an ultraviolet curable adhesive containing a cationic photopolymerization initiator. Specifically, the ultraviolet curable adhesive is prepared by mixing 30 parts by weight to 100 parts by weight of a second epoxy compound having a homopolymer having a glass transition temperature of 60 ° C or less, 100 parts by weight of a first epoxy compound having a glass transition temperature of 120 ° C or higher, And 0.5 to 20 parts by weight of a photopolymerization initiator.

In this specification, the epoxy compound means a compound having at least one epoxy group in the molecule, preferably a compound having at least two epoxy groups in the molecule, and may be in the form of a monomer, a polymer or a resin &Lt; / RTI > Preferably, the epoxy compound of the present invention may be in the form of a resin.

The first epoxy compound may be an epoxy compound having a glass transition temperature of 120 ° C or higher and may be used without any particular limitation. For example, an alicyclic epoxy compound having a glass transition temperature of 120 ° C or higher and / Or an aromatic epoxy may be used as the first epoxy compound of the present invention. Specific examples of the epoxy compound having a glass transition temperature of 120 ° C or higher of the homopolymer include 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, vinylcyclohexene dioxide dicyclopentadiene dioxide, bis epoxycyclo Pentyl ether, bisphenol A-based epoxy compounds, and bisphenol F-based epoxy compounds. Meanwhile, the first epoxy compound may have a glass transition temperature of the homopolymer of 120 ° C to 200 ° C.

The second epoxy compound can be used without any particular limitation as long as it is an epoxy compound having a glass transition temperature of the homopolymer of 60 캜 or lower. For example, the second epoxy compound may be an alicyclic epoxy compound, an aliphatic epoxy compound, or the like.

As the alicyclic epoxy compound, a bifunctional epoxy compound, that is, a compound having two epoxies may be used. Specifically, a compound in which the two epoxy groups are all alicyclic epoxy groups may be used, but is not limited thereto.

The aliphatic epoxy compound may be an epoxy compound having an aliphatic epoxy group rather than an alicyclic epoxy group. For example, polyglycidyl ethers of aliphatic polyhydric alcohols; Polyglycidyl ethers of alkylene oxide adducts of aliphatic polyhydric alcohols; Polyglycidyl ethers of polyester polyols of aliphatic polyhydric alcohols and aliphatic polyvalent carboxylic acids; Polyglycidyl ethers of aliphatic polyvalent carboxylic acids; Polyglycidyl ethers of polyester polycarboxylic acids of aliphatic polyhydric alcohols and aliphatic polyvalent carboxylic acids; Dimers, oligomers or polymers obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate; Or an oligomer or polymer obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate and other vinyl monomers, and preferably an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof polyglycidyl Ether may be used, but is not limited thereto.

Examples of the aliphatic polyhydric alcohols include aliphatic polyhydric alcohols having 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or 2 to 4 carbon atoms, for example, ethylene 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl Pentanediol, 2-methyl-2,4-pentanediol, 2-methyl-2,4-pentanediol, Pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl- Aliphatic diols such as diol, 1,9-nonanediol, and 1,10-decanediol; Alicyclic diols such as cyclohexane dimethanol, cyclohexanediol, hydrogenated bisphenol A and hydrogenated bisphenol F; But are not limited to, trimethylolethane, trimethylolpropane, hexitol, pentitol, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, tetramethylol propane and the like.

The alkylene oxide may be an alkylene oxide having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, and specifically, ethylene oxide, propylene oxide or butyl But are not limited thereto.

Examples of the aliphatic polyvalent carboxylic acid include aliphatic polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, Methyl adipic acid, 3-methyl adipic acid, 3-methyl pentane diacid, 2-methyl octane diacid, 3,8-dimethyl decane diacid, 3,7-dimethyl decane diacid, An alicyclic dicarboxylic acid, a 1,2-cyclopentanedicarboxylic acid, a 1,3-cyclopentanedicarboxylic acid, a 1,2-cyclohexanedicarboxylic acid, a 1,3-cyclohexanedicarboxylic acid, 1,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 4-cyclobutane tetracarboxylic acid, and the like, but is not limited thereto.

The second epoxy compound may be one containing at least one glycidyl ether group, for example, 1,4-cyclohexanedimethanol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6 -Hexanediol diglycidyl ether, neopentyldiglycidyl ether, resorcinol diglycidyl ether, diethylene glycol di glycidyl ether, ethylene glycol diglycidyl ether, trimethylol propane triglycidyl ether , n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and o-cresyl glycidyl ether.

The second epoxy compound may have a glass transition temperature of the homopolymer of 0 ° C to 60 ° C.

Specifically, according to one embodiment of the present disclosure, the adhesive layer may be formed by a combination of a first epoxy compound containing at least one epoxidized aliphatic cyclic group as the epoxy compound and a second epoxy compound containing at least one glycidyl ether group And may be an ultraviolet curable adhesive to be used.

According to one embodiment of the present invention, the adhesion between the stretched polyvinyl alcohol-based film and the stretched polymer film after stretching of the film laminate is 2 N / 2 cm or less, specifically 0.1 N / 2 cm or more and 2 N / , More specifically 0.1 N / 2 cm or more and 1 N / 2 cm or less. When the adhesive force between the stretched polymer film and the stretched polyvinyl alcohol film satisfies the above range, surface damage can be minimized during the separation process.

According to one embodiment of the present invention, when an adhesive layer is formed between the polyvinyl alcohol-based film and the polymer film, not only the polyvinyl alcohol film and the polymer film but also the adhesive layer are stretched by stretching, The thickness of the polyvinyl alcohol-based film is reduced to about 10% to 50% of that before stretching. As a result, the adhesion between the polyvinyl alcohol-based film and the polymer film is reduced to 2 N / 2 cm or less.

On the other hand, the adhesive force is an adhesive force measured when sample films having a length of 2 cm are attached, and a specific measuring method is shown in FIG. According to one embodiment of the present invention, the adhesive force between the films is obtained by fixing the polyvinyl alcohol film (A) of the film laminate to the sample holder (H) as shown in Fig. 1, Refers to the magnitude of the peel strength measured while peeling the polyvinyl alcohol film (A) from the polymer film (B) by applying a force in a direction perpendicular to the surface direction. As the measuring instrument, a texture of Stable Micro Systems Analyzer (Model: TA-XT Plus) was used.

According to one embodiment of the present disclosure, the step of stretching the film laminate may further include a step of drying the stretched film laminate. At this time, the drying may be performed at 20 to 100 ° C, specifically 40 to 90 ° C, and the drying may be performed at the above temperature for 1 to 10 minutes. The step of drying may prevent degradation of the properties of the polarizer due to moisture during the production process of the polarizing plate by removing water on the surface and inside of the polyvinyl alcohol film and may cause smooth shrinkage of the stretched polyvinyl alcohol film during the drying process Thereby enhancing the polarizability of the polarizer by increasing the orientation of the complex composed of polyvinyl alcohol and iodine.

According to one embodiment of the present invention, the step of separating the polymer film and the polyvinyl alcohol-based film from the stretched film laminate is carried out by releasing the polyvinyl alcohol-based film from the polymer film by applying a weak peeling force . Specifically, the weak peeling force may be 2 N / 2 cm or less, specifically 0.1 N / 2 cm to 2 N / 2 cm or 0.1 N / 2 cm to 1 N / 2 cm.

According to the manufacturing method according to one embodiment of the present invention, since the peeling force required to separate the polyvinyl alcohol film and the polymer film from each other is very weak as compared with the case where the film is laminated using coating or coextrusion, Not only can the two films be easily separated, but also the polyvinyl alcohol-based film is less damaged in the separation step, so that excellent optical performance can be obtained.

According to a manufacturing method according to one embodiment of the present disclosure, a sheet-to-sheet process, a sheet-to-roll process, or a roll- A roll-to-roll process, or the like. At this time, the sheet-to-sheet process is a process using a sheet-like film cut to a predetermined size with a raw film (that is, a polyvinyl alcohol-based film and a polymer film) Refers to a method using a roll-shaped film wound with a long film and using a leaf-shaped film cut to a predetermined size as another raw film. In addition, the roll-to-roll process is a method of using a rolled film as a raw film. In consideration of continuity of the process and productivity, it is particularly preferable to use a roll-to-roll process.

Specifically, according to the manufacturing method according to one embodiment of the present invention, an unstretched polyvinyl alcohol film roll is disposed between the polymer film rolls, and a polyvinyl alcohol film and a polymer film are wound from the film rolls, Forming a film laminate including a polymer film and an unstretched polyvinyl alcohol-based film via an adhesive or adhesive layer having an adhesive force of not more than 2 cm / 2 cm; Stretching the film laminate so that the thickness of the polyvinyl alcohol film after stretching becomes 10 占 퐉 or less; And separating the polymer film and the polyvinyl alcohol-based film of the stretched film laminate.

According to one embodiment of the present invention, in the separating step, a separating means such as a peeling roll is inserted between the polymer film and the polyvinyl alcohol film to separate the interface between the polymer film and the polyvinyl alcohol film, The polymer film and the polyvinyl alcohol-based film may be wound on different rolls

The thickness of the polarizer produced by the above-described production method is very small, that is, 10 탆 or less, specifically 1 탆 or more and 10 탆 or less, more specifically, 3 탆 or more and 10 탆 or less. Even with such a thin thickness, the transmittance is 40% or more and 45% or less, and the degree of polarization is 99.95% or more, thus exhibiting excellent optical properties.

Specifically, the polarizer produced by the above-described production method exhibits excellent optical properties because the polarizability of the polarizer is 40% or more and 45% or less and the polarization degree is 99.995% or more.

One embodiment of the present invention provides a polarizer produced by the above production method.

Specifically, according to one embodiment of the present invention, a polarizing plate can be formed by laminating a transparent film on one surface or both surfaces of the polarizer. As the transparent film, various films used as a polarizer protective film or a retardation film in the related art can be used without limitation. For example, an acrylic film, a polyethylene terephthalate film, a polyethylene terephthalate film treated with an acrylic primer film , A cellulose-based film, a cycloolefin-based film, a polycarbonate-based film, a polynorbornene-based film, and the like.

The method of laminating the polarizer and the transparent film is not particularly limited and may be a film laminating method well known in the art, for example, after applying an adhesive or a pressure-sensitive adhesive on at least one side of the polarizer and / or the transparent film, And a method of laminating the above-mentioned materials. In this case, the pressure sensitive adhesive or the adhesive may be appropriately selected in consideration of the material of the transparent film to be used. For example, when using TAC (triacetyl cellulose) as the transparent film, an aqueous adhesive such as a polyvinyl alcohol- When an acrylic film, a COP (cyclo olefin polymer) film or the like is used as the transparent film, a photo-curing or thermosetting adhesive such as an acrylic adhesive or an epoxy adhesive can be used.

On the other hand, the lamination method of the polarizer and the transparent film is not particularly limited, but may be performed by a roll-to-roll method using a polarizer film roll and a transparent film roll in terms of productivity. A method of laminating a polarizer and a transparent film by a roll-to-roll method to produce a polarizing plate is well known in the art, and thus a detailed description thereof will be omitted. When such a polarizing plate is produced by the roll-to-roll method, a long roll-type polarizing plate can be obtained.

The polarizing plate may further include another functional optical layer such as a brightness enhancement film, a primer layer, a hard coat layer, an antiglare layer, an antireflection layer or an adhesive layer for adhesion with a liquid crystal panel, in addition to a transparent film. The method of forming these optical layers is not particularly limited, and known methods well known in the art can be used.

In addition, one embodiment of the present invention provides a display device including the polarizer.

The polarizing plate according to one embodiment of the present invention has excellent optical characteristics while being very thin compared to a conventional polarizing plate and can be usefully used in a display device such as a liquid crystal display panel, an organic electroluminescent device, and the like.

Hereinafter, the present invention will be described in detail by way of examples with reference to the drawings. However, the embodiments according to the present disclosure can be modified in various other forms, and the scope of the present specification is not construed as being limited to the embodiments described below. Embodiments of the present disclosure are provided to more fully describe the present disclosure to those of ordinary skill in the art.

[Example 1]

A polarizer was prepared by using a film laminate in which a polyvinyl alcohol film was adhered to both sides of a 40 탆 thick thermoplastic polyurethane (TPU) polymer film via an aqueous adhesive (4% Z3; LG Chem). At this time, the polyvinyl alcohol-based film used was a PVA film having a thickness of 20 μm of M2005 grade manufactured by Japan Synthetic Company.

On the other hand, the film laminate was subjected to a swelling process for 25 seconds in a pure solution of 25, followed by a dying process at a concentration of 0.3 wt% and 25 iodine solution for 60 seconds. Thereafter, the substrate was cleaned in an aqueous boric acid solution having a boric acid concentration of 1 wt% for 15 seconds, and then subjected to a 6-fold stretching process in an aqueous boric acid solution having a boric acid concentration of 56 wt% at 56 wt%. After the stretching, a 5 wt% KI solution was subjected to a complementary process, and then dried at 80 oven for 5 minutes to finally produce a thin polarizer having a thickness of 5.6 μm.

The physical properties of the polymer film in Example 1 are shown in Table 1 below.

The optical characteristics of the thin polarizer produced according to Example 1 are shown in Table 2 below.

[Comparative Example 1]

A thin polarizer having a thickness of 5.6 mu m was prepared in the same manner as in Example 1, except that the physical properties of the thermoplastic polyurethane (TPU) polymer film were made different.

The physical properties of the polymer film in Comparative Example 1 are shown in Table 1 below.

The optical characteristics of the thin polarizer produced according to Comparative Example 1 are shown in Table 2 below.

[Comparative Example 2]

The physical properties of the polymer film in Comparative Example 2 are shown in Table 1 below.

The optical characteristics of the thin polarizer produced according to Comparative Example 2 are shown in Table 2 below.

Shrinkage (R) Modulus of elasticity
(N / mm < 2 & Maximum tensile force
(N) Maximum draw ratio
(ship) Example 1 0.11 933.7 20.93 4.52 Comparative Example 1 0.18 1015.1 26.30 4.12 Comparative Example 2 0.17 1214.5 25.50 4.31

Unit transmittance
(%) Polarization degree
(%) Example 1 42.53 99.9973 Comparative Example 1 42.55 99.9911 Comparative Example 2 42.44 99.9874

It can be seen from Table 2 that the polarizers of the thin polarizers produced according to the examples are superior to the polarizers produced according to the comparative examples.

2 is a graph showing the stretching behavior of a polymer film used in Examples and Comparative Examples.

The drawing conditions in Fig. 2 are dry normal temperature (25 DEG C) conditions, and the X-axis shows the strain. Specifically, when the strain is 100%, the stretching is performed twice, and when the strain is 300%, the stretching is performed four times. The Y-axis represents the force required to deform the polymer film when it is deformed, and a smaller force at the same strain means that the stretching can be made easier. The elastic modulus can be obtained by converting the value of the Y axis (FORCE) into the STRESS value divided by the film cross section, and then by STESS / STRAIN of the specific section.

H: Holder
A: Polyvinyl alcohol film
B: polymer film
MD: longitudinal direction of stretching

Claims

Attaching an unstretched polyvinyl alcohol-based film having a thickness of 10 占 퐉 or more and 40 占 퐉 or less on at least one surface of the polymer film using a force or an adhesive to form a film laminate;
Stretching the film laminate so that the thickness of the polyvinyl alcohol film after stretching is not less than 1 占 퐉 and not more than 10 占 퐉; And
Separating the polymer film of the stretched film laminate and the polyvinyl alcohol film,
The elastic modulus of the polymer film is 900 N / mm < 2 > to 1,000 N / mm <
Wherein the polymer film has a shrinkage ratio (R) of 0.15 or less represented by the following formula (1): < EMI ID =
[Formula 1]
R = (L ₀ - L _r ) / L ₀
L ₀ is the length of the polymer film in a state where the tension of the polymer film is maintained after the stretching of the polymer film and L _r is the length of the polymer film in the state in which the tensile force is removed after stretching the polymer film. Length.

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The method according to claim 1,
Wherein the maximum tensile force of the polymer film is 25 N or less.

The method according to claim 1,
Wherein the polymer film has a maximum drawing magnification of 4.5 times or more when dry-drawn at 25 占 폚.

The method according to claim 1,
The polymer film may be formed of a low density polyethylene resin, a high density polyethylene resin, a copolymer resin containing ethylene vinyl acetate in high density polyethylene, a polypropylene resin, a polyurethane resin, a polyethylene terephthalate resin containing isophthalic acid, a water soluble cellulose resin and an acrylic resin And at least one selected from the group consisting of the above-mentioned materials.

The method according to claim 1,
Wherein the step of stretching the film laminate is performed at a stretching magnification of 5 times or more and 15 times or less at a temperature of 20 占 폚 to 85 占 폚.

The method according to claim 1,
Wherein the step of stretching the film laminate is carried out in an aqueous boric acid solution having a boric acid concentration of 1 wt% or more and 5 wt% or less.

The method according to claim 1,
Further comprising the step of dying at least one of iodine and a dichroic dye to the unstretched polyvinyl alcohol film before stretching the film laminate.

The method according to claim 1,
Wherein the step of separating the polymer film and the polyvinyl alcohol film of the stretched film laminate is performed by applying a peeling force of 0.1 N / 2 cm or more and 2 N / 2 cm or less.

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