KR20100124044A - Polarizer having improved durability, preparing method thereof and polarizing plate comprising the same - Google Patents

Abstract

PURPOSE: A polarizer having improved durability, a preparing method thereof and a polarizing plate comprising the same are provided to solve a crack by forming a polarizer of a chelate structure. CONSTITUTION: A surface protection film(1) protects a polarizer. The polarizer(3) is formed as a chelate structure through a coordination bond of a copper metal atom and the hydroxy of a polyvinyl alcohol group. A release film(5) is a protective film. The polarizer has a polarizer protection film(2) one side and has surface protection film as need while having a polarizer protection film, adhesive layer, and the release film which are successively laminated on the other side.

Description

Durable polarizer with improved durability, manufacturing method thereof and polarizing plate equipped with it {POLARIZER HAVING IMPROVED DURABILITY, PREPARING METHOD THEREOF AND POLARIZING PLATE COMPRISING THE SAME}

The present invention relates to a polarizer having improved durability, a method of manufacturing the same, and a polarizing plate having the same, which has excellent toughness and improved crack generation problem of the polarizer due to stress.

Polarizers used in various image display devices such as liquid crystal display (LCD), electroluminescence (EL) display, plasma display (PDP), field emission display (FED), etc. are generally polyvinyl alcohol, PVA) film includes a polarizer having an iodine-based compound or a dichroic polarizing material adsorbed and aligned, one side of the polarizer is laminated with a polarizer protective film in order, and the other side of the polarizer is bonded with a polarizer protective film, a liquid crystal cell It has a multilayered structure in which the pressure-sensitive adhesive layer and the release film are laminated in order.

The polarizer constituting the polarizing plate having such a structure is manufactured through a complicated process of swelling, dyeing, stretching, crosslinking, washing and drying the PVA film, and stress is generated during such a complicated process or handling process, Cracks are easily caused in a direction parallel to the stretching direction (MD direction). In addition, the polarizing plate is repeatedly contracted and expanded under repeated high and low temperature conditions, causing stress, which causes cracks easily.

In particular, in recent years, various image display apparatuses have gradually increased in size, and thus polarizers and polarizing plates used have also increased in size. Therefore, handling becomes more disadvantageous in the handling process during the process, and the amount of deformation generated under repeated high temperature and low temperature environments during use is further increased, thereby requiring a polarizing plate having excellent durability.

As a method for imparting durability to a polarizing plate, Japanese Patent Laid-Open No. 11-29683 discloses a method of improving the toughness of the PVA-based film itself by adding starch and sugars during the production of the PVA-based film. However, in the case of the PVA-based film to which starch and sugars are added, it is not suitable for the optical material, and there is a problem in that a part of the component is leaked during swelling and the physical properties are lowered.

Japanese Patent Application Laid-Open No. 2006-126313 discloses a polarizer which is formed in a direction parallel to the MD direction under process handling and repeated high and low temperature environments by forming PVA polarizing fibers and birefringent fibers in parallel to form an isotropic material in a film. A method of improving cracks is disclosed. However, in order to form a film using polarizing fibers and birefringent fibers, a polyethylene terephthalate (PET) film must be used as a substrate, which can complicate the process and increase the manufacturing cost since the PET film must be removed after film formation. .

In addition, Japanese Laid-Open Patent Publication No. 2005-309219 discloses a method of preventing cracks by laminating a protective film made of a cyclic olefin resin on at least one surface of a polarizer to suppress residual stress of the polarizer generated under a high temperature and high humidity environment. . However, since the protective film must be laminated on the polarizer rather than improving the properties of the polarizer itself, the process can be complicated and cost can be increased.

As described above, the conventional method does not solve the problem of crack generation of the polarizer itself with respect to the generated stress, and the durability of the polarizing plate is also reduced.

The present invention provides a resistance to stress due to the excellent toughness of the polarizer itself, and thus cracks in a direction parallel to the MD direction of the polarizer due to stress occurring under the manufacturing process and handling process of the polarizing plate, and repeated high and low temperature conditions. An object of the present invention is to provide a polarizer with improved durability that can solve a problem that occurs.

Moreover, another object of this invention is to provide the manufacturing method of the said polarizer.

In addition, another object of the present invention is to provide a polarizing plate provided with the polarizer.

In addition, another object of the present invention is to provide a liquid crystal display device having the polarizing plate.

The present invention provides a polarizer having a toughness of 2.0 to 16.0 MPa by forming a chelate structure by a copper atom on a polyvinyl alcohol-based film.

In addition, the present invention is added to the copper compound in the washing step immediately after the stretching and crosslinking of the polyvinyl alcohol-based film, the capacity of the copper compound is 0.05 to 0.75% by weight relative to 100% by weight of the aqueous solution used in the washing step It provides a method for producing a polarizer characterized in that.

In addition, the present invention provides a polarizing plate in which a polarizer protective film is laminated on at least one surface of the polarizer.

In addition, the present invention provides a liquid crystal display device having the polarizing plate on at least one side of the liquid crystal cell.

The polarizer according to the present invention has excellent optical performance, but has a chelate structure formed by copper atoms on the PVA-based film, thereby improving toughness and tensile distance with respect to the stress of the polarizer itself, thereby producing and handling a polarizing plate, and repetitive processes. It is possible to prevent a crack problem occurring in a direction parallel to the MD direction of the polarizer due to the stress generated under high and low temperature environmental conditions. In addition, it is economical because it can impart improved durability directly to the polarizer in a simple manner without additional processing.

The present invention relates to a polarizer having improved durability, a method of manufacturing the same, and a polarizing plate having the same, which has excellent toughness and improved crack generation problem of the polarizer due to stress.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The polarizer of the present invention is characterized in that toughness is 2.0 to 16.0 MPa.

Moreover, the polarizer of this invention is characterized in that the chelate structure by a copper atom is formed in the polyvinyl alcohol-type film. In more detail, the hydroxy group [OH ⁻ ] of the PVA film and the copper metal atom are coordinated to bond to form a chelate structure such as the following Structural Formula 1 on the inside and the surface of the film. At this time, when the coordination bond of copper metal atoms to the hydroxy group of the PVA-based film increases the coordination bond position is increased, resulting in increased toughness and tensile distance of the PVA-based film, thereby providing improved durability against stress changes .

 [Formula 1]

(Wherein a is a polyvinyl alcohol chain, n is an integer of n> 0 and is a value determined by the degree of polymerization of the PVA film, and b is a chelate structure.)

In the present invention, the polymer film for preparing a polarizer is not only excellent in the effect of enhancing the uniformity of the degree of polarization in the plane, but also in consideration of the excellent dyeing affinity for a dichroic material, for example, iodine as a polarizer PVA-based films such as PVA films, partially saponified PVA films and the like are preferably used.

However, the type is not particularly limited as long as it is a film capable of forming a chelate structure by coordinating with a copper compound in addition to the PVA film. For example, hydrophilic polymer films such as polyethylene terephthalate film, ethylene-vinyl acetate copolymer film, cellulose film, partially gumified film thereof, and the like, poly such as dehydrated PVA film, dehydrochlorinated polyvinyl chloride, etc. Y-oriented film can be used.

The method for producing the PVA film is not particularly limited, and examples thereof include a flow cast method, a cast method, an extrusion method, and the like, which form a film by flow casting a polymer stock solution decomposed into water or an organic solvent. In this case, in order to obtain the polarizer which is excellent in the uniformity of the polarization degree in the surface of a film, it is preferable that the in-plane retardation deviation of a PVA system film is small. Therefore, the retardation deviation in the PVA-based film as the raw material film before processing is preferably 1 to 100 nm, more preferably 10 nm or less, most preferably 5 nm or less when measured at a measurement wavelength of 1000 nm.

The degree of polymerization of the PVA film is usually 500 to 10,000, preferably 1,000 to 6,000, and more preferably 1,400 to 4,000. In the case of the PVA-based saponification film, the saponification degree is preferably 95.0 mol% or more, more preferably 99.0 mol% or more, and most preferably 99.9 mol% or more from the viewpoint of solubility.

Copper atoms are used to impart excellent toughness and tensile distance, ie, improved durability, by forming a chelate structure on the PVA-based film. In addition, any metal atom capable of providing durability by forming a chelate structure can be used. A copper atom is preferable at the point which does not reduce transparency and an optical characteristic.

The content of the copper atom forming the chelate structure is preferably 200 to 2600 ppm, more preferably 500 to 2500 ppm with respect to the polyvinyl alcohol-based film. If the content of the copper atom is less than 200ppm it is difficult to prevent cracks due to the durability improvement effect is small, and if it exceeds 2600ppm may surface staining. At this time, ppm represents the mg of copper contained per kilogram of polyvinyl alcohol-based film.

Toughness of a polarizer is a resistance which arises when plastically deforms a polarizer, and means the characteristic which a polarizer extends and spreads well. Such toughness is preferably 2.0 to 16.0 MPa, more preferably 3.0 to 15.0 MPa. Therefore, the conventional polarizer is not given toughness, so it is easy to solve the problem that cracks are generated when stress is applied from the outside, and the toughness is improved to the polarizer itself, so that the durability against stress from the outside is excellent as the tensile distance increases. It is possible to prevent the occurrence of cracks.

The thickness of the polarizer is not particularly limited and may be usually 5 to 80 μm.

The transmittance of the polarizer is preferably 40.0% or more, and more preferably 41.0 to 45.0%.

It is preferable that the orthogonal transmittance measured on the conditions which superimposed two sheets mutually so that the absorption axis of a polarizer may cross | intersect 90 degree with each other is more preferable, More preferably, it is 0.030% or less, Most preferably, it is 0.020% or less.

The polarization degree is preferably 98 to 100%, more preferably 99 to 100%.

Next, the manufacturing method of the polarizer of this invention is demonstrated.

The manufacturing method of the polarizer of this invention is characterized by adding a copper compound to the washing | cleaning step immediately after extending | stretching and crosslinking of a polyvinyl alcohol-type film is completed.

Usually, the method of manufacturing a polarizer includes a swelling step, a dyeing step, a crosslinking step, an stretching step, and a washing and drying step, and are mainly classified according to the stretching method. For example, a dry stretching method of stretching and dyeing a polymer film as a raw material by stretching in a hot roll, a wet stretching method of simultaneously stretching and crosslinking while impregnated with hot water, or a combination of the two stretching methods Hybrid drawing method is mentioned. Among these, this invention is demonstrated based on the wet drawing method.

The swelling, dyeing, crosslinking, stretching and washing steps are performed in a state in which the PVA-based film is immersed in a bath filled with at least one solution selected from several kinds of solutions. In addition, the order of the steps and the number of repetitions are not particularly limited, and the steps may be performed simultaneously or sequentially, and some steps may be omitted.

The copper compound is preferably added to the washing step immediately after stretching and crosslinking are completed. If the copper compound is added before the cleaning step, in particular during the dyeing or crosslinking step, copper iodide (CuI) may form and precipitate, which may lower the concentration of iodine and affect the optical properties. It is preferably added to the washing step immediately after completion.

Copper compound is to give excellent toughness and tensile distance, that is, improved durability by forming chelate structure by coordinating with hydroxy group of PVA film, and if it is a compound that can give durability by forming chelate structure in addition to copper compound, its kind Although there is no restriction | limiting in particular, A copper compound is preferable at the point which does not reduce transparency and an optical characteristic of a polarizer.

In particular, it is preferable that a copper compound is not a form of particle | grains but a compound of the aqueous solution state containing a copper atom. In the case where a particulate copper compound is used, light is scattered when light is transmitted, thereby decreasing the degree of polarization and transmittance.

The copper compound is not particularly limited as long as it can form a chelate structure, and specifically, copper sulfate anhydrides such as cuprous sulfate and cuprous sulfate and copper sulfate hydrates such as copper sulfate pentahydrate can be used. Or it can use in combination of 2 or more type. Among these, copper sulfate pentahydrate is preferable.

The copper compound is preferably used so that the content of copper atoms to the PVA-based film is preferably 200 to 2600 ppm, more preferably 500 to 2500 ppm. If the content of the copper atom is less than 200ppm it is difficult to prevent cracks due to the small effect of improving the durability, if the content of more than 2600ppm may cause surface stains on the polarizer due to the color of the copper itself.

The swelling step is a step of immersing the unstretched PVA film in a swelling tank filled with an aqueous solution for swelling. Through this step, impurities such as dust or blocking agents deposited on the surface of the PVA-based film may be cleaned, and the PVA-based film may be swollen to improve the stretching efficiency and to prevent dyeing unevenness.

Deionized water may be used alone as the aqueous solution for swelling, and when a small amount of glycerin or potassium iodide is added thereto, the processability may be improved along with the swelling of the PVA-based film. The content of glycerin in 100% by weight of the aqueous solution for swelling is preferably 5% by weight or less, and the content of potassium iodide is 10% by weight or less.

It is preferable that the temperature of a swelling tank is 20-45 degreeC, More preferably, it is 25-40 degreeC.

The execution time (immersion time) of the swelling step is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, most preferably 60 to 120 seconds.

The stretching step may be performed together with the swelling step, wherein the stretching ratio is preferably 1.10 to 3.50 times.

The dyeing step is a step of adsorbing iodine on the PVA-based film by immersing the swollen PVA-based film in a dye bath filled with a dichroic material, for example, an aqueous solution for dyeing including iodine.

The aqueous solution for dyeing may include deionized water or a water-soluble organic solvent and iodine. The content of iodine is preferably 0.010 to 10% by weight, more preferably 0.020 to 7% by weight, most preferably 0.025 to 5% by weight based on the total amount of the aqueous solution for dyeing (100% by weight).

In addition, iodide may be further included together with iodine to further improve dyeing efficiency. As iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. may be used alone or in combination of two or more thereof. Of these, potassium iodide is preferred. The content of iodide is preferably 0.01 to 10% by weight, more preferably 0.10 to 5% by weight relative to 100% by weight of the aqueous solution for dyeing. The weight ratio of iodine to iodide (potassium iodide) is preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80, and most preferably 1: 7 to 1:70.

Moreover, it is preferable that the aqueous solution for dyeing further contains a small amount of crosslinking agents. As the crosslinking agent, one or more selected from boron compounds such as boric acid and sodium borate, glyoxal and glutaraldehyde can be used, and preferably, a combination of boric acid and sodium borate is used. When such a component is further included, there is an effect of further strengthening the crosslinking of the iodine molecule. The content of the crosslinking agent is preferably 0.01 to 6% by weight, more preferably 0.10 to 3% by weight based on the total amount of the aqueous solution for dyeing (100% by weight).

It is preferable that the temperature of a dye bath is 5-42 degreeC, More preferably, it is 10-35 degreeC. Moreover, the immersion time of a PVA system film in a dyeing tank is not specifically limited, Preferably it is 1 to 20 minutes, More preferably, it is 2 to 10 minutes.

The stretching step may be performed together with the dyeing step, and the cumulative stretching ratio may be 1.10 to 4.00 times.

In addition to the above-described dyeing method, a method of applying or spraying a dye solution containing iodine on the PVA-based film may be used, or iodine may be dyed by mixing with PVA resin before casting the PVA-based film.

The crosslinking step is a step of fixing the adsorbed iodine molecules by immersing the dyed PVA film in an aqueous solution for crosslinking.

The aqueous solution for crosslinking may include at least one crosslinking agent selected from deionized water as a solvent, a boron compound such as boric acid, sodium borate, glyoxal and glutaldehyde. In addition, the organic solvent may be further dissolved together with the deionized water. The content of the crosslinking agent is not particularly limited and is preferably 1 to 10% by weight, more preferably 2 to 6% by weight based on 100% by weight of the aqueous solution for crosslinking.

In addition, the aqueous solution for crosslinking may further include a small amount of iodide in order to obtain uniformity of the degree of polarization in the polarizer plane. Iodide may be the same as used in the dyeing step, the content may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight relative to the total content of the aqueous solution for crosslinking (100% by weight). Most preferably, a combination of boric acid and potassium iodide is used. In this case, the weight ratio of boric acid and potassium iodide is preferably 1: 0.1 to 1: 3.5, more preferably 1: 0.5 to 1: 2.5.

The temperature of the crosslinking bath is 20 to 70 ° C., and the immersion time of the PVA film in the crosslinking bath may be 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed together with the crosslinking step, and may be stretched so that the final cumulative stretching ratio is 3.00 to 7.00 times.

In addition to the crosslinking method as described above, a method of applying or spraying a crosslinking solution containing a crosslinking agent on a PVA-based film may be used.

The stretching step may be performed as an independent stretching step using a separate drawing tank filled with an aqueous solution for drawing.

The type of the aqueous solution for stretching is not particularly limited, and may be a solution containing at least one selected from a solvent such as water, ethanol or an organic solvent and a metal salt, iodine, boron, and a zinc compound. In particular, a solution containing 2 to 18% by weight boric acid, 2 to 10% by weight potassium iodide or mixtures thereof is preferred. In addition, when boric acid and potassium iodide are used together, their weight ratio is preferably 1: 0.1 to 1: 4, more preferably 1: 0.5 to 1: 3.

It is preferable that the temperature of a drawing tank is 40-67 degreeC, More preferably, it is 50-62 degreeC.

The stretching method is not particularly limited, and for example, in the case of roll stretching, a stretching method may be used based on a difference in circulation speed between rolls.

Typically the final cumulative draw ratio can be 3.00 to 7.00 times. In the present invention, the "cumulative draw ratio" represents the value of the product of the draw ratios of the steps.

The washing step is a step of removing unnecessary residues such as boric acid deposited on the PVA film in the previous steps by dipping the PVA-based film completed stretching and crosslinking in a cleaning tank filled with an aqueous solution for cleaning.

The aqueous cleaning solution may be deionized water, and an iodine compound may be further added thereto. As the iodide, the same ones as used in the dyeing step can be used, and among them, it is preferable to use sodium iodide or potassium iodide. The content of potassium iodide may be 0.1 to 10% by weight with respect to 100% by weight of the aqueous solution for washing, preferably 3 to 8% by weight.

In the washing step, a copper compound is added, and the content thereof is preferably 0.05 to 0.75% by weight, more preferably 0.10 to 0.70% by weight based on 100% by weight of the aqueous solution for cleaning. If the content is less than 0.05% by weight, the effect of improving the toughness is insignificant, and when the content is more than 0.75% by weight may cause surface staining due to the color of the copper compound itself.

The washing step may be repeated one or more times, and the number of repetitions is not particularly limited but is preferably repeated two or more times. In addition, the type and content of the components of the aqueous solution for cleaning may be changed according to the number of times repeated. As such, when the washing step is repeated two or more times, the copper compound is preferably added only to the first washing step (first cleaning bath) immediately after the stretching and crosslinking are completed. When the copper compound is added to the second (second cleaning bath) or subsequent washing step, CuI, which is a copper compound bonded to the iodine component on the surface of the PVA-based film, remains, which is not preferable because it acts as a foreign material.

It is preferable that the temperature of a washing tank is 10-60 degreeC, More preferably, the temperature of a 1st washing degree is 20-40 degreeC, and the temperature of a 2nd washing tank is 10-30 degreeC.

The washing step may be performed whenever previous steps such as swelling step, dyeing step, crosslinking step or stretching step are completed. However, the addition of the copper compound is carried out in the first washing step immediately after stretching and crosslinking are completed.

In the steps as described above, when the PVA-based film is raised in the air from the reaction tank, in order to prevent the liquid, such as a solution attached to the PVA-based film from falling, conventionally known liquid cutting rolls such as pinch rolls ( A liquid-cutting roll may be used, or excess solution may be removed by a liquid cutting method using an air knife.

The drying step is a step of drying the washed PVA-based film to obtain a final polarizer with iodine adsorption orientation.

As a drying method, a method such as natural drying, air drying, heating drying, etc. may be used, and heat drying is preferably used. For example, it may be heat dried at 20 to 80 ° C. for 1 to 10 minutes. The drying temperature is preferably low in order to prevent deterioration of the polarizer, more preferably 60 ° C. or less, most preferably 45 ° C. or less.

According to the manufacturing method of the polarizer of the present invention as described above, among the steps carried out in the aqueous solution, especially in the hydroxy group and the copper compound of the inside and the surface of the PVA film by adding a copper compound in the washing step immediately after the stretching and crosslinking is completed. The chelate structure is formed in the PVA film by coordinating copper metal atoms. Due to these structural characteristics, the toughness and tensile distance of the polarizer itself are improved, thereby showing excellent durability.

Polarizing plate of the present invention is characterized in that the polarizer protective film is laminated on at least one surface of the polarizer.

In the polarizing plate according to the exemplary embodiment of the present invention, as shown in FIG. 1, a polarizer protective film 2 and a surface protective film 1 are laminated in order on one surface of the durable polarizer 3, and the other On one side, the polarizer protective film 2, the pressure-sensitive adhesive layer 4, and the release film 5 may be stacked in this order.

The structure of the polarizing plate is not particularly limited, and various kinds of optical layers capable of satisfying required optical properties may be laminated on the polarizer. For example, a structure in which a polarizer protective film for protecting the polarizer is laminated on at least one surface of the polarizer; A structure in which a surface treatment layer such as a hard coating layer, an antireflection layer, an anti-sticking layer, a diffusion barrier layer, an antiglare layer, or the like is laminated on at least one surface of the polarizer or the polarizer protective film; It may have a structure in which an alignment liquid crystal layer or another functional film is laminated on at least one surface of the polarizer or the polarizer protective film. In addition, a phase difference including a wavelength plate (including a λ plate) such as an optical film, a reflector, a semi-transmissive plate, a 1/2 wave plate, or a quarter wave plate, such as a polarization conversion device used to form various image display devices At least one of the plate, the viewing angle compensation film, and the brightness enhancement film may be laminated with an optical layer. More specifically, a polarizer having a structure in which a polarizer protective film is laminated on one surface of a polarizer, the polarizing plate comprising a reflective polarizer or a semi-transparent polarizer in which a reflector or a transflective reflector is laminated on the laminated polarizer protective film; An oval or circular polarizing plate in which retardation plates are stacked; A wide viewing angle polarizer on which a viewing angle compensation layer or a viewing angle compensation layer is stacked; Or the polarizing plate in which the brightness improving film was laminated | stacked is preferable.

The surface protection film 1 is for protecting a polarizing plate, and can use a conventional surface protection film in which an adhesive layer is formed on a base film.

As the polarizer protective film 2, films each having excellent transparency, mechanical strength, thermal stability, moisture shielding, and isotropy may be used. Specific examples thereof include polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate. Polyester film; Cellulose films such as diacetyl cellulose and triacetyl cellulose; Polycarbonate film; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene films such as polystyrene and acrylonitrile-styrene copolymers; Polycarbonate film; Polyolefin-based films such as polyethylene, polypropylene, cyclo-based or norbornene-structured polyolefins, ethylene propylene copolymers; Vinyl chloride film; Amide films such as nylon and aromatic polyamides; Imide film; Polyether sulfone-based film; Sulfone film; Polyether ether ketone film; Sulfided polyphenylene-based films; Vinyl alcohol film; Vinylidene chloride-based film; Polyoxymethylene film; Epoxy type film etc. are mentioned. In addition, the polarizer protective film may be a cured layer formed from a thermosetting or ultraviolet curable resin such as aryl resin, urethane resin, acrylic-urethane resin, epoxy resin, silicone resin and the like. Among these, especially the cellulose type film which has the surface saponified by alkali etc. is preferable in consideration of polarization characteristic or durability. In addition, in consideration of polarization characteristics, durability and bonding characteristics, it is preferable that the surface of the polarizer protective film is saponified by alkali or the like.

The thickness of the polarizer protective film is not particularly limited, and may be usually 500 μm or less, preferably 1 to 300 μm, more preferably 5 to 200 μm.

In addition, the polarizer protective film may also have a function as a retardation film according to the mode of the liquid crystal display device.

The polarizer 3 has a chelate structure formed by coordinating a copper metal atom and a hydroxyl group of a PVA-based film, thereby providing excellent toughness and tensile distance to itself, and thus having excellent durability.

It is preferable that the toughness of the polarizer 3 is 2.0-16.0 MPa, More preferably, it is 3.0-15.0 MPa.

It is preferable that copper atom is contained in the PVA system film of the polarizer 3 as 200-2600 ppm, More preferably, it is 500-2500 ppm.

The pressure-sensitive adhesive layer 4 may be formed of a common pressure-sensitive adhesive such as acrylic, silicone, polyester, polyurethane, polyether or rubber. The pressure-sensitive adhesive layer absorbs moisture in consideration of peeling phenomenon due to moisture absorption, bubble generation and distortion of the liquid crystal cell due to differences between coefficients of thermal expansion, and prevention of deterioration of optical characteristics, such as moldability of an image display device excellent in quality and durability. It is preferable that the rate is low and excellent in heat resistance. It is also desirable to not require any high temperature treatment, such as curing or drying, or to require long term curing or drying in view of the optical properties. From this point of view, acrylic pressure-sensitive adhesives are preferably used.

The release film 5 is a film for protecting the pressure-sensitive adhesive layer, the type is not particularly limited as long as it is a film commonly used in the art. Specific examples include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethylacrylic Polyolefin type films, such as a rate copolymer and an ethylene-vinyl alcohol copolymer; Polyester-based films such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polyamide films such as polyacrylate, polystyrene, nylon 6 and partially aromatic polyamide; Polyvinyl chloride film; Polyvinylidene chloride film; Or polycarbonate films. These may be those which have been appropriately released by a release agent such as silicon-based, fluorine-based or silica powder.

The liquid crystal display of the present invention is characterized in that the polarizing plate is provided on at least one side of the liquid crystal cell.

In the present invention, since the liquid crystal display device is well known to those skilled in the art of the present invention, a detailed description of each configuration is omitted.

In addition to the liquid crystal display device, the present invention can be applied to various image display devices such as electroluminescent display devices, plasma display devices, and field emission display devices.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

Example 1

PVA film (VF-PS, KURARAY Co., Ltd.) was swelled by dipping for 2 minutes in a swelling tank filled with deionized water at 30 ° C., and then swelled in an aqueous solution for dyeing at 30 ° C. containing 0.04% by weight of iodine and 1.2% by weight of potassium iodide. Dyeing was carried out for minutes, and the resultant was crosslinked by dipping for 3 minutes in an aqueous 58 ° C crosslinking solution containing 11.0% by weight of potassium iodide and 3.5% by weight of boric acid. At this time, the draw ratio in each step is 1.49, 1.51. The drawing was made to be 2.51 times and the drawing was made so that the total cumulative drawing ratio was 5.65 times. After stretching and crosslinking are completed, the solution is immersed in an aqueous cleaning solution (first cleaning bath) containing 0.05% by weight of copper sulfate pentahydrate for 2 minutes, and then immersed in a general cleaning solution (second cleaning tank) containing no copper sulfate pentahydrate. After immersion, it was dried for 3 minutes in an oven at 60 ℃ to prepare a polarizer.

Example 2

In the same manner as in Example 1, 0.10% by weight of copper sulfate pentahydrate was used in the first washing tank.

Example 3

In the same manner as in Example 1, 0.20% by weight of copper sulfate pentahydrate was used in the first washing tank.

Example 4

The same process as in Example 1, except that 0.40% by weight of copper sulfate pentahydrate was used in the first washing tank.

Example 5

In the same manner as in Example 1, 0.60% by weight of copper sulfate pentahydrate was used in the first washing tank.

Comparative Example 1

In the same manner as in Example 1, 0.80% by weight of copper sulfate pentahydrate was used in the first washing tank.

Comparative Example 2

In the same manner as in Example 1, 0.20% by weight of copper sulfate pentahydrate was used in the second washing tank.

Comparative Example 3

The same process as in Example 1, except that copper sulfate pentahydrate was not used.

Test Example

Physical properties of the polarizers prepared in Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

(1) Copper content (ppm) contained in polarizer (PVA system film)

The copper content contained in the prepared polarizer was measured twice using an inductively coupled plasma atomic emission spectrometer (JY2000s, Jobin Yvon) and then expressed as the average value.

(2) toughness (MPa)

The TD direction of the manufactured polarizer was tested three times by using a universal testing machine (UNIVERSAL TESTING MACHINE) (INSTRON 5567, manufactured by INSTRON) according to the ASTM measuring method, and then expressed as an average value.

(3) polarization degree (%)

The polarization degree of the produced polarizer was measured twice using an ultraviolet visible light spectrometer (V-7100, manufactured by JASCO Co., Ltd.) twice for an area of 2.5 cm in width and 2.5 cm in height, and then expressed as an average value.

(4) durability

The polarizers were repeatedly subjected to thermal shock for 100 cycles from -30 ° C to 70 ° C, and then visually observed for cracks, and evaluated based on the following criteria.

○: no cracks (good)

×: crack generation (defect)

(5) surface staining observation

Whether the surface of the produced polarizer was unevenly observed was visually observed and evaluated based on the following criteria.

○: no surface unevenness (good)

△: some surface unevenness (usually)

×: Surface unevenness is clearly present (bad)

(6) foreign material occurrence observation

Whether the foreign material of the produced polarizer was observed visually and evaluated based on the following criteria.

○: no surface foreign matter (good)

△: some surface foreign matter (usually)

×: The surface foreign matter is clearly present (defect)

division Immersion
Cleaning tank In PVA
Copper
content Polarization degree tenacity
(MPa) durability surface
stain bow
Occur (ppm) (%) Breaking
starting point Breaking
Complete Example 1 First cleaning 258.54 99.05 2.15 2.28 ○ ○ ○ Example 2 First cleaning 562.38 98.85 6.54 7.34 ○ ○ ○ Example 3 First cleaning 1417.81 98.75 8.90 10.43 ○ ○ ○ Example 4 First cleaning 1984.25 99.79 9.12 11.82 ○ ○ ○ Example 5 First cleaning 2567.43 99.48 11.10 15.05 ○ ○ ○ Comparative Example 1 First cleaning 2753.15 99.89 16.22 18.68 ○ × ○ Comparative Example 2 Second cleaning article 1386.58 98.56 6.78 9.27 ○ ○ × Comparative Example 3 - - 99.50 1.58 1.69 × ○ ○

As shown in Table 1, the polarizers of Examples 1 to 5 prepared by adding a copper compound in the washing step immediately after stretching and crosslinking were completed according to the present invention were improved compared with Comparative Example 3 without adding the copper compound. It was confirmed that the crack and the occurrence of cracks can be prevented under repeated high and low temperature conditions by having the toughness and tensile distance values. Moreover, the surface stain generate | occur | produced the comparative example 1 which added the excess copper compound, and the foreign material defect generate | occur | produced the comparative example 2 which added the copper compound to the 2nd washing tank.

As described above, the polarizer of the present invention can be applied to various image display devices such as a liquid crystal display device, an electroluminescence display device, a plasma display device, or an field emission display device which require improvement in durability.

1 is a view showing a polarizing plate equipped with a polarizer of the present invention.

Explanation of symbols on the main parts of the drawings

1: surface protective film 2: polarizer protective film

3: polarizer 4: adhesive layer

5: release film

Claims (8)

The polarizer whose chelate structure by a copper atom is formed in a polyvinyl alcohol-type film, and toughness is 2.0-16.0 Mpa. The polarizer of claim 1, wherein the polarizer has a content of 200 to 2600 ppm of copper atoms in the polyvinyl alcohol-based film. The copper compound is added to the cleaning step immediately after the stretching and crosslinking of the polyvinyl alcohol-based film is completed, wherein the capacity of the copper compound is 0.05 to 0.75% by weight based on 100% by weight of the aqueous solution used in the cleaning step. Method of manufacturing a polarizer. The method of manufacturing a polarizer according to claim 3, wherein the copper compound is in an aqueous solution containing a copper atom. The method of claim 3, wherein the copper compound is at least one member selected from the group consisting of cuprous sulfate, cuprous sulfate, and cuprous sulfate pentahydrate. The method of claim 5, wherein the copper compound is copper sulfate pentahydrate. Claim 1 or claim 2 or the polarizer of the polarizer protective film laminated on at least one side of the polarizer produced by the manufacturing method of any one of claims 3 to 6. Liquid crystal display device provided with a polarizing plate of claim 7.

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