JPWO2017030144A1 - Polarizing plate and manufacturing method thereof - Google Patents

Abstract

A polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm; an adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; and A polarizing plate comprising: a protective film laminated on the adhesive layer.

Description

  The present invention relates to a polarizing plate excellent in both optical characteristics and appearance characteristics, a manufacturing method thereof, and an image display apparatus including the polarizing plate.

  An image display device is a universally used electronic product such as a watch, a cellular phone, a PDA, a notebook, a PC monitor, a DVD player, and a TV. A polarizing plate is used as a basic component of the image display device.

  When manufacturing a polarizing plate, increasing the draw ratio in order to improve the orientation of the iodine complex of the polarizer for the purpose of improving the performance of the polarizing plate reduces the width of the polarizer and causes uneven stripes on the polarizing plate. Appearance defects may occur.

  Here, Patent Document 1 (Korea Published Patent No. 2014-0114923) is an adhesive composition manufactured by adding a leveling agent of an acetylene skeleton, and discloses a technique for improving a contact angle and improving appearance defects. ing.

  However, even by such a method, it is not possible to improve the appearance defect of the polarizing plate and maintain the required excellent optical characteristics.

Korean Published Patent No. 2014-0114923

  An object of the present invention is to provide a polarizing plate and an image display device including the same that can prevent appearance defects without deteriorating optical characteristics such as transmittance and polarization degree.

  In addition, the present invention provides a polarizing plate excellent in physical properties such as adhesiveness, water resistance, moisture resistance, and heat resistance (hereinafter referred to as moisture resistance and heat resistance together) and an image display apparatus including the same. The purpose is to provide.

  1. A polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm; an adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; and A polarizing plate comprising: a protective film laminated on the adhesive layer.

  2. 2. The polarizing plate as described in 1 above, wherein the adhesive layer has a thickness of 300 to 800 nm.

  3. Said 1 WHEREIN: The said contact bonding layer is a polarizing plate formed with the adhesive composition containing the polyvinyl alcohol-type resin containing an acetoacetyl group, and a glyoxylate crosslinking agent.

  4). (I) a step of manufacturing a polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm; (ii) at least of the polarizer and the protective film A polarizing plate comprising: applying an adhesive composition on any one surface to form an adhesive layer having a thickness of 250 to 850 nm; and (iii) bonding the polarizer and a protective film through the adhesive layer. Production method.

  5. 4. The method for producing a polarizing plate according to 4, wherein the adhesive composition includes a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate crosslinking agent.

  6). In the above item 5, the polyvinyl alcohol-based resin containing an acetoacetyl group and the glyoxylate cross-linking agent are 2.5 to 6% by weight in total with respect to the total weight of the adhesive composition based on the solid content. Manufacturing method of polarizing plate contained.

  7). 4. The method for producing a polarizing plate according to 4 above, wherein a bonding speed for bonding the polarizer and the protective film is 10 to 35 m / min.

  8). The image display apparatus containing the polarizing plate as described in any one of said 1 thru | or 3.

  The polarizing plate according to the present invention has remarkably few appearance defects such as uneven stripes without lowering optical characteristics such as transmittance and degree of polarization.

  The polarizing plate according to the present invention can have excellent adhesion, water resistance, and moist heat resistance.

  According to the method for manufacturing a polarizing plate according to the present invention, it is possible to widen the range in which the polarizer can be used, and to reduce the defect rate, and an additional process for removing defects is unnecessary. Convenience, efficiency and economy can be secured.

FIG. 1 is a photograph of analyzing the surface of a polarizer manufactured in a manufacturing example of the present invention. FIG. 2 is a drawing schematically showing a water resistance evaluation test method for a polarizing plate according to the present invention.

<Polarizing plate>
In one embodiment of the present invention, a polarizer having an average unevenness interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm; a thickness 250 formed on at least one surface of the polarizer. It is related with the polarizing plate which was excellent in the optical characteristic and the external appearance characteristic by including the protective film laminated | stacked on the adhesive layer which is thru | or 850 nm; and the said adhesive layer.

<Polarizer>
The polarizing plate according to the present invention includes a polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm.

  The unevenness average interval (RSm) is a value defined by ISO 4287-1997, and the roughness curve is extracted from the reference length in the direction of the average line, and corresponds to one mountain and one valley adjacent to it. Means the value obtained by calculating the sum of the lengths of the average lines and averaging them within the reference length. In addition, said uneven | corrugated average space | interval (RSm) is corresponded to the average length (RSm) of a roughness curve element prescribed | regulated by JISB0601: 2013.

  The maximum height roughness (Rt) is a value defined by ISO 4287-1997, and means the sum of the maximum peak height and the maximum valley depth of the roughness curve at the reference length. The maximum height roughness (Rt) corresponds to the maximum cross-sectional height (Rt) of the roughness curve defined by JIS B 0601: 2013.

  The polarizer according to the present invention can produce a polarizing plate excellent in both optical characteristics and appearance characteristics by having the above-mentioned specific ranges of RSm and Rt. When RSm is less than 500 μm, there is a problem that optical characteristics are deteriorated, and when it exceeds 5000 μm, there is a problem that appearance defects cannot be improved. Further, when Rt is less than 100 nm, there is a problem that the optical characteristics are deteriorated, and when it exceeds 1000 nm, there is a problem that appearance defects cannot be improved. From the viewpoint of further improving the optical characteristics and further improving the appearance defect, preferably, RSm is 750 to 5000 μm, and Rt is 120 to 970 nm.

<Adhesive layer>
The polarizing plate according to the present invention includes an adhesive layer having a thickness of 250 to 850 nm on at least one surface of the polarizer.

  When the polarizer having the RSm and Rt ranges of the present invention is used in the production of a polarizing plate by a normal method, striped unevenness occurs. Therefore, in the present invention, by introducing an adhesive layer having a thickness in the above specific range, the unevenness of the striped pattern of the polarizing plate is remarkably reduced without deterioration of optical characteristics such as the degree of polarization or transparency. When the thickness of the adhesive layer is less than 250 nm, the appearance defect cannot be improved, and when it exceeds 850 nm, there is a problem that the optical characteristics are deteriorated. The thickness of the adhesive layer is more preferably 300 to 800 nm from the viewpoint of further reducing the unevenness of the striped pattern of the polarizing plate without lowering the optical characteristics.

  The method for increasing the thickness of the adhesive layer is not particularly limited. For example, a method for increasing the solid content concentration in the adhesive composition or increasing the bonding speed for bonding the polarizer and the protective film via the adhesive layer. Can be used.

<Protective film>
The protective film according to the present invention is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, etc. Specific examples include polyethylene terephthalate, polyethylene Polyester resins such as isophthalate and polybutylene terephthalate; Cellulosic resins such as diacetyl cellulose, triacetyl cellulose and cellulose acetate propionate; Polycarbonate resins; Polyacrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymers; polyolefin resins such as polyethylene, polypropylene, cyclo- or norbornene-structured polyolefins, and ethylene-propylene copolymers Polyamide resins such as nylon and aromatic polyamide; imide resins; polyethersulfone resins; sulfone resins; polyetherketone resins; sulfided polyphenylene resins; vinyl alcohol resins; vinylidene chloride resins; vinyl butyral resins An arylate resin; a polyoxymethylene resin; a film made of a thermoplastic resin such as an epoxy resin, and a film made of a blend of the thermoplastic resins can also be used. Also, a film made of a thermosetting resin such as (meth) acrylic, urethane, epoxy, or silicon, or an ultraviolet curable resin can be used.

  When a cycloolefin resin is used for the protective film, a cycloolefin resin known in the art can be used without particular limitation. For example, the cycloolefin resin may be a thermoplastic resin having a cycloolefin monomer unit such as norbornene or a polycyclic norbornene monomer, and the cycloolefin ring-opening polymer or 2 A hydrogenated product of a ring-opening copolymer using more than one kind of cycloolefin may be used, or an addition copolymer of a cycloolefin and an aromatic compound having a chain olefin or a vinyl group may be used. Moreover, the polar group may be introduce | transduced into cycloolefin type resin.

  Among the above-described resins, a film made of a cellulose resin, a polyolefin resin, or a polyacrylic resin is preferable in consideration of polarization characteristics or durability.

<Production method of polarizing plate>
In another embodiment of the present invention, a step of producing a polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm; the polarizer or the protective film And a step of forming an adhesive layer having a thickness of 250 to 850 nm by applying an adhesive composition to at least one surface of the substrate; and a step of bonding the polarizer and a protective film through the adhesive layer. .

  Hereinafter, the manufacturing method of the polarizing plate of this invention is demonstrated in detail.

  First, a polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm is manufactured (i).

  In order for the polarizer to have the specific RSm and Rt ranges described above, the manufacturing process conditions of the polarizer can be adjusted. For example, the stretching ratio, drying time, etc. can be adjusted. Hereinafter, an example of the manufacturing method of the polarizer by this invention is demonstrated concretely.

  As long as the polymer film for manufacturing a polarizer is a polymer film used for manufacturing a polarizing plate, a film that can be dyed with a dichroic substance (for example, iodine) that is known in the art is used without particular limitation. For example, polyvinyl alcohol film, partially saponified polyvinyl alcohol film; polyethylene terephthalate film, ethylene-vinyl acetate copolymer film, ethylene-vinyl alcohol copolymer film, cellulose film, these partially saponified Or a hydrophilic polymer film such as a dry film; or a polyene oriented film such as a dehydrated polyvinyl alcohol film, a dehydrochlorinated polyvinyl chloride film, or the like. Among these, a polyvinyl alcohol film is preferable because it not only has an excellent effect of enhancing the uniformity of the degree of polarization in the plane, but also has an excellent dyeing affinity for iodine.

  The manufacturing method of the polarizer may include a swelling step, a dyeing step, a crosslinking step, a complementary color step, a stretching step, a water washing step, and a drying step, and can be classified according to a stretching method. For example, a dry stretching method, a wet stretching method, or a hybrid stretching method in which the above-mentioned two kinds of stretching methods are mixed can be used. Below, although the manufacturing method of the polarizer of this invention is demonstrated taking the wet extending | stretching method as an example, it is not restrict | limited to this.

  In the above steps, the remaining steps except the drying step are performed by immersing the polyvinyl alcohol film in a constant temperature bath filled with at least one solution selected from various types of solutions. It can be carried out.

<Swelling step>
In the swelling step, before dyeing the unstretched polyvinyl alcohol film, it is immersed in a swelling tank filled with an aqueous solution for swelling to remove impurities such as dust or anti-blocking agent deposited on the surface of the polyvinyl alcohol film. This is a step for swelling the polyvinyl alcohol film, improving the stretching efficiency, preventing nonuniform dyeing, and improving the physical properties of the polarizer.

  As the aqueous solution for swelling, an aqueous solution for swelling known in the art can be used without particular limitation. For example, water (pure water, deionized water) may be used alone, and a small amount of glycerin or potassium iodide may be used. When is added, processability can be improved along with swelling of the polymer film. The glycerin content may be 5% by weight or less and the potassium iodide content may be 10% by weight or less with respect to 100% by weight of the swelling aqueous solution, but is not limited thereto.

  The temperature of the swelling tank is not particularly limited, but may be 20 to 45 ° C., for example, 25 to 40 ° C.

  As the performance time of the swelling step (swelling time in the swelling tank), a performance time known in the art can be applied without particular limitation, and may be, for example, 180 seconds or less, preferably 90 seconds or less. . When the immersion time is in the above range, it is possible to suppress the swelling from becoming excessively saturated, the breakage due to softening of the polyvinyl alcohol film is prevented, and the adsorption of iodine becomes uniform in the dyeing step, The degree of polarization can be improved.

  The stretching step can be performed together with the swelling step. At this time, the stretching ratio may be about 1.1 to 3.5 times, but is not limited, and preferably 1.5 to 3.0 times. Good. If the draw ratio is less than 1.1 times, wrinkles may occur. If it exceeds 3.5 times, the initial optical characteristics may be weakened.

<Dyeing step>
The dyeing step is a step of immersing the polyvinyl alcohol film in a dyeing tank filled with a dichroic substance, for example, an aqueous dyeing solution containing iodine, and adsorbing iodine to the polyvinyl alcohol film.

  As the aqueous dye solution, an aqueous dye solution known in the art can be used without particular limitation, and water, a water-soluble organic solvent, or a mixed solvent thereof and iodine can be contained. The iodine content may be 0.4 to 400 mmol / L with respect to the aqueous dyeing solution, but is not limited thereto, and is preferably 0.8 to 275 mmol / L, and most preferably 1 to 200 mmol / L. May be. In order to improve the dyeing efficiency, iodide may be further contained as a solubilizing agent. As the iodide, an iodide known in the art can be used without limitation. For example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, iodide At least one selected from the group consisting of barium iodide, calcium iodide, tin iodide, and titanium iodide can be included, and among these, potassium iodide is preferable because of its high solubility in water. The iodide content may be 0.01 to 10% by weight with respect to 100% by weight of the aqueous dyeing solution, but is not limited, and may preferably be 0.1 to 5% by weight.

In addition, in order to increase the content of iodine complex in the polyvinyl alcohol film, boric acid may be added to the dyeing tank at 0.3 to 5% by weight with respect to 100% by weight of the aqueous dyeing solution. It is not limited. When boric acid dyeing tank is less than 0.3 wt%, _{PVA-I 3} ^- complex and _{PVA-I 5} ^- it may not be effective in increasing the complex content, boric acid dyeing tank 5 If the concentration is higher than% by weight, the risk of film breakage may increase.

  The temperature of the dyeing tank may be 5 to 42 ° C, but is not limited thereto, and may preferably be 10 to 35 ° C. The immersion time of the polyvinyl alcohol film in the dyeing tank is not particularly limited, and may be 1 to 20 minutes, preferably 2 to 10 minutes.

  In the present invention, the stretching step can be performed together with the dyeing step. At this time, the stretching ratio may be 1.01 to 2.0 times, but is not limited thereto, and preferably 1. It may be 1 to 1.8 times.

  The cumulative stretch ratio up to the dyeing step including the swelling and the dyeing step may be 1.2 to 4.0 times. If the cumulative stretch ratio is less than 1.2 times, wrinkles of the film may occur and appearance defects may occur, and if it exceeds 4.0 times, the initial optical characteristics may be fragile.

<Crosslinking step>
The cross-linking step is a step of fixing the adsorbed iodine molecules by immersing the dyed polyvinyl alcohol film in an aqueous solution for cross-linking so that the dyeability by physically adsorbed iodine molecules is not deteriorated by the external environment. is there.

  When iodine, which is a dichroic dye, has insufficient crosslinking reaction, iodine molecules may be detached by a moist heat environment, and thus sufficient crosslinking reaction is required. In addition, in order to orient the iodine molecules located between the molecules of polyvinyl alcohol and to improve the optical properties, it is possible to perform stretching at the largest stretch ratio in the cross-linking step, but this is limited to this. Is not to be done.

  In the present invention, the method for producing a polarizer can perform a crosslinking step known in the art without particular limitation, for example, can perform a crosslinking step constituted by a first and a second crosslinking step, One or more of the first and second cross-linking steps can use an aqueous cross-linking solution containing a boron compound. This can improve the optical properties and color durability of the polarizer.

  As the crosslinking aqueous solution, a crosslinking aqueous solution known in the art can be used without particular limitation, and may contain, for example, water as a solvent and a boron compound such as boric acid or sodium borate, together with water. It may further contain a soluble organic solvent and iodide.

  Boron compounds impart short crosslinks and stiffness to the polarizer, and can suppress wrinkling of the film during the process, improving the handleability of the film and forming the iodine orientation of the polarizer Can play a role.

  A content of the boron compound may be a content known in the art, and may be, for example, 1 to 10% by weight, preferably 2 to 6% by weight with respect to 100% by weight of the aqueous crosslinking solution. Also good. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced, and it may be difficult to impart rigidity to the polarizer. When the content exceeds 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessive. When activated, the crosslinking reaction of the organic crosslinking agent may not proceed effectively.

  In the present invention, iodide can be used to maintain the uniformity of the degree of polarization in the plane of the polarizer and to prevent desorption of dyed iodine. The iodide may be the same as that used in the dyeing step, and its content may be 0.05 to 15% by weight with respect to 100% by weight of the aqueous crosslinking solution, but is not limited, Preferably, it may be 0.5 to 14% by weight. If the content is less than 0.05% by weight, iodine ions in the film may escape and increase the transmittance of the polarizer. If the content exceeds 15% by weight, iodine ions in the aqueous solution may be added to the film. It can penetrate and reduce the transmittance of the polarizer.

  In the present invention, the temperature of the crosslinking tank may be 20 to 70 ° C., but is not limited thereto. The immersion time of the polyvinyl alcohol film in the crosslinking tank may be 1 second to 15 minutes, but is not limited thereto, and may preferably be 5 seconds to 10 minutes.

  The stretching step can be performed together with the crosslinking step. At this time, the stretching ratio of the first crosslinking step may be 1.4 to 3.0 times, but is not limited thereto, preferably 1.5. Or it may be 2.5 times.

  The stretching ratio of the second crosslinking step may be 1.01 to 2.0 times, but is not limited thereto, and may preferably be 1.2 to 1.8 times.

  Further, the cumulative draw ratio of the first and second crosslinking steps may be 1.5 to 5.0 times, but is not limited thereto, and preferably 1.7 to 4.5 times. Good. If the cumulative stretching ratio is less than 1.5 times, the orientation effect of iodine may be insufficient, and if it exceeds 5.0 times, the film may break due to excessive stretching. Yes, production efficiency can be reduced.

<Complementary color step>
In the complementary color step, the iodine complex positioned between the molecules in the polyvinyl alcohol film on which the iodine complex is physically adsorbed is oriented near the boric acid bridge to stabilize the iodine complex. May be.

  Moreover, the step which correct | amends a color may be sufficient with respect to the polyvinyl-alcohol-type film with insufficient dyeing | staining of the iodine complex in the said bridge | crosslinking step.

  As the aqueous solution of the complementary color step, an aqueous solution known in the art can be used without particular limitation, and includes, for example, water as a solvent and a boron compound such as boric acid, and an organic solvent and iodide that are mutually soluble with water. May further be included.

  In the present invention, the boron compound imparts short crosslinks and rigidity to the polarizer, and suppresses wrinkling of the film during the process, thereby improving the handleability of the film and improving the iodine orientation of the polarizer. Can play a role to form.

  The content of the boron compound may be 1 to 10% by weight with respect to 100% by weight of the aqueous solution in the complementary color step, but is not limited thereto, and may preferably be 2 to 6% by weight. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced, and it may be difficult to impart rigidity to the polarizer. When the content exceeds 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessive. When activated, the crosslinking reaction of the organic crosslinking agent may not proceed effectively.

  In the present invention, iodide can be used to maintain the uniformity of the degree of polarization in the plane of the polarizer and to prevent desorption of dyed iodine. The iodide may be the same as that used in the dyeing step, and the content thereof may be 0.05 to 15% by weight with respect to 100% by weight of the aqueous solution in the complementary color step. However, it may be 0.5 to 11% by weight. If the content is less than 0.05% by weight, iodine ions in the film may escape and increase the transmittance of the polarizer. If the content exceeds 15% by weight, iodine ions in the aqueous solution may be added to the film. It can penetrate and reduce the transmittance of the polarizer.

  In the present invention, the temperature of the complementary color bath may be 20 to 70 ° C. The immersion time of the polyvinyl alcohol film in the complementary color bath may be 1 second to 15 minutes, but is not limited thereto, and may preferably be 5 seconds to 10 minutes.

  The stretching step can be performed together with the complementary color step. At this time, the stretching ratio of the complementary color step may be 1.01 to 1.1 times, but is not limited thereto, and preferably 1.01 to 1. It may be 08 times.

  If the draw ratio is less than 1.01, the stabilization effect of the iodine complex may be insufficient, and if it exceeds 1.1 times, the film may be broken by excessive stretching. Production efficiency can be reduced.

<Extension step>
In the present invention, the stretching step may be performed simultaneously with other steps as described above, or may be performed separately.

  Further, the stretching step may be performed at least once, or may be performed a plurality of times. When it is performed a plurality of times, it may be performed separately at any step in the manufacturing process of the polarizer.

  In the present invention, in order to increase Rt, the stretching ratio can be increased, and in order to decrease Rt, it can be adjusted by decreasing the stretching ratio. Moreover, in order to enlarge RSm, it can adjust by enlarging a draw ratio, and in order to make RSm small, it can adjust by making a draw ratio small.

In the production method of the present invention, the total cumulative draw ratio of the polarizer is preferably 4.0 to 7.0 times, and more preferably 5.3 to 6.5 times.
In the present specification, the “cumulative stretch ratio” may include a product of stretch ratios in each step.

<Washing step>
The polyvinyl alcohol-based film that has been crosslinked and stretched is immersed in a water-washing tank filled with an aqueous washing solution, and unnecessary residues such as boric acid adhered to the polyvinyl alcohol-based film in the steps up to the water washing step. A rinsing step can be performed.

  In the present invention, the aqueous washing solution may be an aqueous washing aqueous solution known in the art without particular limitation, and may be, for example, water, to which an iodide may be further added. Not.

  In the present invention, the temperature of the washing tank may be 10 to 60 ° C., but is not limited thereto, and preferably 15 to 40 ° C.

  The washing step can be omitted, and can be performed each time a step before the washing step such as the dyeing step or the crosslinking step is completed. Further, it may be repeated one or more times, and the number of repetitions is not particularly limited.

<Drying step>
In the present invention, the drying step of the method for producing a polarizer is to dry the washed polyvinyl alcohol film, improve the orientation of dyed iodine molecules by neck-in by drying, and have excellent optical properties. This is a step of obtaining a polarizer. Neck-in means that the width of the film is narrowed.

As a drying method, a drying method known in the art can be used without limitation, and methods such as natural drying, air drying, heat drying, far-infrared drying, microwave drying, and hot air drying can be used. Hot air drying can be performed at 20 to 100 ° C. for 1 to 10 minutes. Moreover, although drying temperature can be made low in order to prevent deterioration of a polarizer, it is not restrict | limited to this, Preferably it may be 100 degrees C or less.
In the present invention, in order to increase Rt, the drying time can be lengthened, and in order to reduce Rt, the drying time can be shortened. Moreover, in order to enlarge RSm, it can adjust by lengthening drying time and shortening drying time in order to make RSm small.

  After the polarizer is manufactured by the method as described above, an adhesive composition is applied to at least one of the polarizer and the protective film to form an adhesive layer having a thickness of 250 to 850 nm (ii).

  The adhesive layer can be formed using any adhesive composition known in the art without any particular limitation. For example, a water-based adhesive composition can be used, and the water-based adhesive composition has an aspect of improving water resistance. Therefore, an adhesive composition containing a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate cross-linking agent can be used.

<Acetoacetyl group-modified polyvinyl alcohol resin>
The acetoacetyl group-modified polyvinyl alcohol (PVA) resin can improve the adhesive force between a polyvinyl alcohol (PVA) polarizer and a protective film such as a cellulose film or an olefin film.

  In the present invention, the acetoacetyl group-modified polyvinyl alcohol (PVA) resin contains a functional group having a higher reactivity than modified polyvinyl alcohol resins such as carboxyl group modification, methylol group modification, amino group modification and the like. Excellent in terms of durability.

  The acetoacetyl group-modified polyvinyl alcohol resin can be used without particular limitation as long as it is a method known in the art, and can be produced by, for example, reacting a polyvinyl alcohol resin with diketene by a known method. An acetyl group-modified polyvinyl alcohol resin can be obtained. For example, after dispersing polyvinyl alcohol resin in a solvent such as acetic acid, diketene is added here. After dissolving polyvinyl alcohol resin in a solvent such as dimethylformamide or dioxane, diketene is added here. An acetoacetyl group-modified polyvinyl alcohol-based resin can be produced by a method in which the diketene gas or liquid diketene is brought into direct contact with the polyvinyl alcohol-based resin. The acetoacetyl group-modified polyvinyl alcohol resin is not particularly limited as long as the degree of acetoacetyl group modification is 0.1 mol% or more, and may be, for example, 0.1 to 40 mol%, preferably 1 to 20 mol. %, Most preferably 2 to 7 mol%. When the degree of modification of the acetoacetyl group is less than 0.1 mol%, the adhesive layer may have insufficient water resistance, resulting in incompatibility. When the degree of modification of the acetoacetyl group exceeds 40 mol% May have insufficient water resistance improvement effect.

  In the present invention, the saponification degree of the acetoacetyl group-modified polyvinyl alcohol resin is not particularly limited, but may be 80 mol% or more, and preferably 85 mol% or more. When the saponification degree of the polyvinyl alcohol-based resin contained in the adhesive composition is low, it becomes difficult for the adhesive composition to exhibit sufficient water solubility, and thus the adhesiveness may be insufficient.

  Polyvinyl alcohol used in producing the acetoacetyl group-modified polyvinyl alcohol resin is not particularly limited, but in order to develop high adhesion between the polarizer and the protective film in the polarizing plate, the average degree of polymerization is The average saponification degree may be in the range of 80 to 100 mol%.

  Examples of the product of the acetoacetyl group-modified polyvinyl alcohol resin include Z-100, Z-200, Z-200H, Z-210, Z-220, and Z-320 (Nippon Synthetic Chemical Co., Ltd. Gohsheimer). Can do.

<Glyoxylate cross-linking agent>
In the present invention, the glyoxylate crosslinking agent contained in the adhesive composition of the method for producing a polarizer includes an acetoacetyl group-modified polyvinyl alcohol (PVA) resin, a polyvinyl alcohol (PVA) polarizer, and cellulose. Adhesive force with a protective film such as a film or an olefin film can be improved.

  The glyoxylate may be an alkali metal salt or an alkaline earth metal salt of glyoxylic acid. In the present invention, the same effect can be obtained when either an alkali metal salt or alkaline earth metal salt of glyoxylic acid is used. The reason for this is not bound by any theory, but both alkali metals and alkaline earth metals are elements with low electronegativity, and their carboxylates have similar chemical properties and crosslinks of acetoacetyl-modified polyvinyl alcohol. It functions because it is the aldehyde part of glyoxylate.

  As the glyoxylate, a glyoxylate known in the art can be used without particular limitation. For example, as an alkali metal salt, lithium glyoxylate, sodium glyoxylate, potassium glyoxylate and the like may be used. The metal salt may be magnesium glyoxylate, calcium glyoxylate, strontium glyoxylate, barium glyoxylate and the like. Among them, alkali metal salts are preferable because they are easily dissolved in water, and sodium glyoxylate is particularly preferable.

  The glyoxylate may be in the range of 3 to 25 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin containing an acetoacetyl group. When the weight ratio of glyoxylate to 3 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin is less than 3 parts by weight, the water resistance of the adhesive layer when it is made into a polarizing plate is not sufficiently expressed. When the weight ratio of glyoxylate to 100 parts by weight of the resin exceeds 25 parts by weight, the optical characteristics of the polarizing plate can be deteriorated.

  The thickness of the adhesive layer according to the present invention can be adjusted, for example, by adjusting the concentration of the solid content in the adhesive composition. For example, the total of the polyvinyl alcohol-based resin containing an acetoacetyl group and the glyoxylate crosslinking agent may be included in an amount of 2.5 to 6% by weight based on the solid content with respect to the total weight of the adhesive composition. However, it may be contained preferably 3 to 5% by weight. If it is in said range, the thickness of an adhesive layer can be adjusted to the range of the thickness of the adhesive layer in the polarizing plate of this invention mentioned above.

  In the present invention, the adhesive composition can be used in a pH range of 4 to 10. When the pH of this aqueous solution is less than 4, when the polarizing plate is produced using this, the water resistance cannot be sufficiently expressed. When the pH of the aqueous solution exceeds 10, The agent composition can be gelled.

  The adhesive composition may have a viscosity at 20 ° C. of 3 to 25 mPa · sec. When the viscosity of the adhesive composition is less than 3 mPa · sec, when the polarizing plate is produced using the adhesive composition, the water resistance cannot be sufficiently exhibited, and the viscosity exceeds 25 mPa · sec. In some cases, the optical characteristics of the polarizing plate may be deteriorated.

  In the present invention, the adhesive composition is an appropriate addition known in the art, such as a plasticizer, a silane coupling agent, an antistatic agent, fine particles, an alcohol that improves diffusibility, and a metal salt, as long as the effect is not impaired. It may be formed by adding at least one selected from the group consisting of agents.

  As the form of the adhesive composition, a form known in the art can be applied without particular limitation. For example, a liquid for forming a uniform adhesive layer on the surface of a polarizer or a protective film as an adherend is used. It may be a mold. Such a liquid type adhesive may be a solution type or a dispersion type of various solvents, and is preferably a solution type in consideration of the coatability of the substrate, and water in consideration of the stability. Solution type or dispersion type as solvent may be compatible.

  For the purpose of shortening the drying process, a water / alcohol mixed solvent in which an alcohol solvent having a boiling point lower than that of water is blended in the adhesive solution can be used. The boiling point of the alcohol solvent is not particularly limited, and the boiling point may be 100 ° C. or lower and 80 ° C. or lower, but preferably 70 ° C. or lower.

  Next, a polarizer and a protective film are bonded via the adhesive layer (iii).

  As a method for bonding the protective film according to the present invention, a method known in the art can be used without particular limitation. For example, a casting method, a Mayer bar coating method, a gravure coating method, a die coating method, a dip coating method, a spray method, etc. Thus, the adhesive composition can be applied to the adhesive surface of the polarizer and / or the protective film, and both can be superimposed. Here, bonding means that the polarizer and the protective film are indirectly brought into contact with each other via an adhesive layer to be bonded.

  After apply | coating the said adhesive composition, it can also join by pinching | pinching a polarizer and a protective film with a nip roll.

  In the present invention, the joining speed can be applied without limitation as long as the joining speed can increase the thickness of the adhesive layer. For example, the joining speed for joining the protective film to the adhesive layer is 10 to 35 m / min. However, it may be 20 to 30 m / min. If it is in said range, the thickness of an adhesive layer can be adjusted to the range of the thickness of the adhesive layer in the polarizing plate of this invention mentioned above. Here, the bonding speed refers to the length of the polarizer and the protective film bonded via the adhesive layer per unit time.

  Moreover, in order to improve adhesiveness, the process well-known in the said field | area can be applied without a restriction | limiting in particular, For example, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame | frame treatment, the surface of a polarizer and / or a protective film, Surface treatment such as saponification treatment may be performed. The saponification treatment may include a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

  In this invention, after a polarizer, an adhesive layer, and a protective film are laminated | stacked, a drying process can be implemented. As the drying treatment, a drying treatment known in the art can be applied without particular limitation. For example, the drying treatment can be performed by spraying hot air, and the temperature at that time may be in the range of 50 to 100 ° C., The drying time may be 30 to 1,000 seconds, but is not limited thereto.

<Image display device>
Moreover, this invention provides the image display apparatus containing the said polarizing plate.

  The polarizing plate according to the present invention can be applied to an image display device further including a configuration known in the art in addition to the polarizing plate. The image display device to which the polarizing plate according to the present invention can be applied is not particularly limited as long as the polarizing plate can be applied. For example, a normal liquid crystal display device, an electroluminescence display device, a plasma display device can be used. Various image display devices such as a field emission display device may be used.

  The following preferred examples and examples are provided to aid the understanding of the present invention, but these examples and examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims. However, it will be apparent to those skilled in the art that various modifications and variations can be made to the manufacturing examples and the examples within the scope and spirit of the invention. These variations and modifications are within the scope of the appended claims. It is natural to belong.

<Production Example 1: Production of Polarizer>
After a transparent unstretched polyvinyl alcohol film (PE60, KURARAY) having a saponification degree of 99.9% or more was immersed in water (deionized water) at 25 ° C. for 1 minute and 20 seconds to swell (swelling step) Dyeing was carried out by immersing in an aqueous dyeing solution at 30 ° C. containing 1.25 mM / L iodine, 1.25% by weight potassium iodide and 0.3% by weight boric acid for 2 minutes and 30 seconds (dyeing step). At this time, in the swelling and dyeing steps, the film was stretched at stretch ratios of 1.56 times and 1.64 times, respectively, and stretched so that the cumulative stretch ratio up to the dyeing tank was 2.56 times. Next, the film was immersed in an aqueous solution for crosslinking at 56 ° C. containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 26 seconds (first crosslinking step) and crosslinked at a stretching ratio of 1.7 times. Stretched. Thereafter, the film was immersed in an aqueous solution for crosslinking at 56 ° C. containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 20 seconds (second crosslinking step), and crosslinked at a ratio of 1.34 times. And stretched. Next, the film was stretched 1.01 times while immersed for 10 seconds in a complementary color aqueous solution containing 5% by weight of potassium iodide and 2% by weight of boric acid (complementary color step). At this time, the total cumulative draw ratio of swelling, dyeing and crosslinking, and complementary color steps was set to 6 times. After the crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 90 ° C. for 4 minutes to produce a polarizer in which the unevenness of the striped pattern becomes Lv3 within the level described later (RSm = 3000 μm, Rt = 700 nm). .

The measuring method of RSm and Rt is as follows.
After preparing the polarizer manufactured in the manufacturing example so as to have a size of width 10 mm × length 10 mm, it is bent on the surface of the sample on the X / Y stage of a Bruker interferometer microscope (model Contour GT-I). Secure with tape to keep it from happening.

  The measurement method is as follows: Condition XR PSI Mode, Object 10X, Multiplier 1.0X, Measurement area 10 mm × 10 mm, Illumination Green, and then measuring the surface of the polarizer. RSm and Rt are calculated based on ISO 4287-1997. Calculated.

  As a reference, a photograph of the surface of the manufactured polarizer is shown in FIG.

  In the description of examples of the present invention, striped pattern irregularities are visually confirmed by the fluorescent lamp reflection method according to the following criteria. The fluorescent lamp reflection method is an evaluation method in which light from a fluorescent lamp is incident from an oblique direction of about 45 °, and unevenness of a polarizing plate is visually confirmed with reflected light.

Lv1. : Unevenness of striped pattern cannot be confirmed Lv2. : In the fluorescent lamp reflection method, striped pattern unevenness can be visually recognized, but cannot be visually confirmed. Lv3. : Stripe pattern irregularity is visible with fluorescent lamp reflection method and visual inspection

<Production Example 2: Production of Polarizer>
Same as Production Example 1 except that the temperature of the first and second cross-linking steps was changed from 56 ° C. to 59 ° C. and the total cumulative draw ratio of the swelling, dyeing, cross-linking and complementary color steps was changed to 6.1 times. A polarizer was manufactured. (Striped pattern unevenness: Lv3, RSm = 3700 μm, Rt = 790 nm).

<Production Example 3: Production of Polarizer>
The temperature of the first and second crosslinking steps was changed from 56 ° C. to 59 ° C., and the boric acid in the aqueous solution for crosslinking in the first and second crosslinking steps was changed from 3% by weight to 3.6% by weight. A polarizer was produced in the same manner as in Production Example 1 except that the total cumulative draw ratio of the crosslinking and complementary color steps was changed to 6.3 times. (Striped pattern unevenness: Lv3, RSm = 4900 μm, Rt = 950 nm).

<Production Example 4: Production of Polarizer>
The temperature of the first and second crosslinking steps was changed from 56 ° C. to 59 ° C., and the boric acid in the aqueous solution for crosslinking in the first and second crosslinking steps was changed from 3% by weight to 3.6% by weight. A polarizer was produced in the same manner as in Production Example 1 except that the total cumulative draw ratio of the crosslinking and complementary color steps was changed to 6.5 times. (Striped pattern unevenness: Lv3, RSm = 6000 μm, Rt = 1100 nm).

<Production Example 5: Production of polarizer>
The immersion time of the swelling step is changed from 1 minute 20 seconds to 50 seconds, the immersion time of the dyeing step is changed from 2 minutes 30 seconds to 2 minutes, and the cumulative stretch ratio until the dyeing step is increased from 2.56 times to 3 times. A polarizer was produced in the same manner as in Production Example 1 except that the total cumulative draw ratio in the dyeing, crosslinking and complementary color steps was changed from 6 times to 5.4 times. (Striped pattern unevenness: Lv1, RSm = 1000 μm, Rt = 140 nm).

<Example 1>
(A) Manufacture of adhesive composition Dissolve acetoacetyl group-modified polyvinyl alcohol resin (Gosenol Z-200, Nippon Synthetic Chemical Industry Co., Ltd.) having a saponification degree of 99.2 mol% in water (distilled water). An aqueous solution having a solid content of 3% by weight was prepared.

  This aqueous solution of acetoacetyl group-modified polyvinyl alcohol resin and sodium glyoxylate (10% aqueous solution) as a cross-linking agent are used as a solid content of sodium glyoxylate with respect to 100 parts by weight of solid content of acetoacetyl group-modified polyvinyl alcohol resin. Was mixed to make an adhesive composition having a total solid content of 3.3% by weight. At this time, the pH of the adhesive composition was 6.1 and the viscosity was 7.5 mPa · sec.

(B) Production of Polarizing Plate After applying the adhesive composition produced in (a) on both sides of the polarizer of Production Example 1, the triacetyl cellulose film KC8UX (Konica Saponified TAC) is a protective film on both sides. Were joined. The joining speed was 20 m / min.

  After bonding, the film was dried at a temperature of 80 ° C. for 5 minutes to produce a polarizing plate (adhesive layer thickness: 300 nm).

<Example 2-9 and Comparative Example 1-4>
As shown in Table 1, a polarizing plate was produced in the same manner as in Example 1 except that the concentration of the adhesive solid and the bonding speed were changed in order to adjust the thickness of the adhesive layer. However, as the cross-linking agent in the adhesive composition of Example 7, methylol melamine manufactured by Aldrich was used.

<Examples 10 and 11>
A polarizing plate was produced in the same manner as in Example 1 (Example 10) and Example 2 (Example 11), respectively, except that the polarizer of Production Example 2 was used.

<Examples 12 and 13>
A polarizing plate was produced in the same manner as in Example 1 (Example 12) and Example 2 (Example 13), respectively, except that the polarizer of Production Example 3 was used.

<Comparative Example 5>
A polarizing plate was produced in the same manner as in Example 1 except that the polarizer of Production Example 4 was used.

<Example 14>
A polarizing plate was produced in the same manner as in Example 1 except that the polarizer of Production Example 5 was used.

[Evaluation test]
The following evaluation tests were implemented with respect to each polarizing plate obtained in Examples 1-14 and Comparative Examples 1-5.

1. Adhesiveness (cutter evaluation)
After leaving each polarizing plate at room temperature for 1 hour, insert a cutter blade between each film of the polarizing plate (between the polarizer and one protective film and between the polarizer and the other protective film). The method of inserting the blade when pushing forward was evaluated according to the following criteria.
A: The cutter blade does not enter between the films.
○: Stops when the cutter edge enters 2 mm or less between the films.
Δ: When the blade is pushed forward, it stops when the blade enters between at least one film and greater than 2 mm and 5 mm or less.
X: When the blade is pushed forward, the blade enters between at least one of the films (if the blade can be inserted between the other films without difficulty, the blade does not enter the other, or 5 mm or less) Including the case where it stops when it enters.)

2. Water resistance Each polarizing plate which was allowed to stand for 24 hours in an environment of 23 ° C. and a relative humidity of 55% was subjected to the following water resistance test (warm water immersion test) to evaluate the water resistance. First, a sample was prepared by cutting the polarizing plate in a rectangular shape of 5 cm × 2 cm with the absorption axis (stretching direction) of the polarizing plate as the long side, and the dimension in the long side direction was accurately measured. Here, the sample shows a unique color uniformly over the entire surface due to iodine adsorbed on the polarizer. Here, FIG. 2 is a drawing schematically showing a water resistance evaluation test method. FIG. 2 (A) shows a sample (1) before immersion in warm water, and FIG. 2 (B) shows a sample (1 after immersion in warm water). ). As shown in FIG. 2 (A), one short side of the sample was gripped by the gripping part (5), and about 80% of the length direction was immersed in a 60 ° C. water bath and maintained for 4 hours. Then, the sample (1) was taken out from the water tank and the moisture was wiped off.

  The polarizer (4) of the polarizing plate contracts by immersion in warm water. The degree of contraction of the polarizer (4) was measured by measuring the distance from the end (1a) (end of the protective film) of the sample (1) at the center of the short side of the sample (1) to the end of the contracted polarizer (4). The shrinkage length was evaluated. Further, as shown in FIG. 2B, the polarizer (4) located in the middle of the polarizing plate is contracted by immersion in warm water, so that a region (2) where the polarizer (4) does not exist between the protective films. It is formed.

Moreover, iodine elutes from the peripheral part of the polarizer (4) in contact with the hot water by immersion in the hot water, and a part (3) where the color is lost is generated in the peripheral part of the sample (1). The degree of decolorization is evaluated by measuring the distance from the end of the contracted polarizer (4) at the center of the short side of the sample (1) to the region (6) where the specific color of the polarizing plate remains, and iodine. I made it a missing length. Further, the total of the shrinkage length and iodine removal length was defined as the total erosion length (X). That is, the total erosion length (X) is an area where the characteristic color of the polarizing plate remains from the end (1a) (end of the protective film) of the sample (1) at the center of the short side of the sample (1) (6 ). It can be judged that the adhesiveness (water resistance) in the presence of water is higher as the shrinkage length, iodine loss length and total erosion length (X) are smaller.
◎: Total erosion length X is less than 2 mm ○: Total erosion length X is 2 mm or more and less than 3 mm Δ: Total erosion length X is 3 mm or more and less than 5 mm ×: Total erosion length X is 5 mm or more

3. Stripe pattern unevenness level measurement After the polarizing plate was manufactured, the presence or absence of striped pattern unevenness was confirmed by the fluorescent lamp reflection method based on the above-mentioned criteria.

4). Optical properties (transmittance, degree of polarization)
After the manufactured polarizing plate was cut into a size of 4 cm × 4 cm, the transmittance was measured using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO). At this time, the degree of polarization is defined by Equation 1 below.

[Formula 1]
Polarization degree (P) = [(T1-T2) / (T1 + T2)] ^1/2
(In the formula, T1 is a parallel transmittance obtained when a pair of polarizers are arranged with the absorption axes parallel to each other, and T2 is obtained when a pair of polarizers are arranged with the absorption axes orthogonal to each other. Orthogonal transmission).

  Referring to Table 2, it can be confirmed that the polarizing plates of the examples are superior in optical characteristics (degree of polarization) and appearance characteristics (level of stripe pattern unevenness) as compared with the comparative examples.

  Moreover, it can confirm that Example 1 using sodium glyoxylate as a crosslinking agent is excellent in water resistance compared with Example 7 using methylol melamine as a crosslinking agent.

1: Sample 1a: Edge of the protective film 2: Area where the polarizer is not present 3: Area where the color is missing in the peripheral part of the sample 4: Polarizer 5: Holding part 6: Area where the characteristic color of the polarizing plate remains

Claims (8)

A polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm;
A polarizing plate comprising: an adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; and a protective film laminated on the adhesive layer.   The polarizing plate according to claim 1, wherein the adhesive layer has a thickness of 300 to 800 nm.   2. The polarizing plate according to claim 1, wherein the adhesive layer is formed of an adhesive composition containing a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate cross-linking agent. (I) a step of manufacturing a polarizer having an uneven average interval (RSm) of 500 to 5000 μm and a maximum height roughness (Rt) of 100 to 1000 nm;
(Ii) applying an adhesive composition to at least one of the polarizer and the protective film to form an adhesive layer having a thickness of 250 to 850 nm; and (iii) with the polarizer through the adhesive layer A method for producing a polarizing plate, comprising: bonding a protective film.   5. The method for producing a polarizing plate according to claim 4, wherein the adhesive composition includes a polyvinyl alcohol resin containing an acetoacetyl group and a glyoxylate crosslinking agent.   6. The polyvinyl alcohol-based resin containing an acetoacetyl group and the glyoxylate cross-linking agent according to claim 5, wherein the total weight of the adhesive composition is 2.5 to 6% by weight based on the solid content. The manufacturing method of the polarizing plate contained in.   The method for producing a polarizing plate according to claim 4, wherein a bonding speed for bonding the polarizer and the protective film is 10 to 35 m / min.   The image display apparatus containing the polarizing plate as described in any one of Claims 1 thru | or 3.