TW201727284A - Polarizing plate and image display device containing the same - Google Patents

Abstract

The polarizing plate of this invention contains a polarizer and a polarizer protecting film adhered to at least one surface of the polarizer via an adhesive layer, wherein an elastic coefficient represented by the following function 1 is 13.0 to 29.0 MPa/ (N/2mm): [Function 1] Elastic coefficient = {(A+B) /C}/100 In function, A is a strength elastic coefficient (MPa) of the polarizer protection film at 25 DEG C, B is a storage elastic coefficient (MPa) of the adhesive layer at 30 DEG C, C is a shrinkage(N/2mm) on absorbent axis of the polarizer after being placed for 1 hour at 80 DEG C.

Description

Polarizing plate and image display device including polarizing plate

The present invention relates to a polarizing plate and an image display device including the polarizing plate, and more particularly to a polarizing plate excellent in durability against thermal shock and an image display device including the polarizing plate.

A polarizing plate used in various image display devices such as a liquid crystal display device (LCD), an electric field emission (EL) display device, a plasma display device (PDP), an electric field emission display device (FED), and an OLED generally includes an iodine system. The compound or the dichroic polarizing material has adsorbed a polarizer oriented on a polyvinyl alcohol (PVA) film, and has a polarizer protective film sequentially laminated on one side of the polarizer, and sequentially laminated on the other side of the polarizer. There are a polarizer protective film, an adhesive layer to be bonded to other members, and a multilayer structure of the release film.

The polarizer constituting the polarizing plate is applied to an image display device, and in order to provide an image excellent in color reproducibility, it is basically required to have both high transmittance and polarization. In order to achieve this, a polarizer is produced by modifying the polyvinyl alcohol-based film itself or by substituting a non-sublimating dichroic dye for a sublimation-containing iodine-based polarizing element.

Usually, the protective film is bonded immediately after the polarizer is washed and dried in the manufacturing step. This is because the physical strength of the polarizer after drying is weak, and if it is temporarily taken up, there is a problem that it is easily broken in the processing direction. Therefore, usually, a water-based adhesive which applies an aqueous solution of a polyvinyl alcohol-based resin to a polarizer immediately after drying, and a protective film are simultaneously bonded to both surfaces of the polarizer via the adhesive.

Such a polarizing plate can be exposed to various temperature environments such as in the manufacturing process, during transportation, and in use, and therefore sufficient durability must be exhibited in order to prevent defects such as cracks from occurring even in such an environment.

Therefore, the polarizing plate is subjected to the thermal shock durability test which is exposed to the low temperature environment and the high temperature environment after being manufactured, but the thermal shock durability test is usually exposed to each other for 30 minutes in an environment of low temperature and high temperature. This process was performed as one cycle, and 100 cycles or more were performed.

This thermal shock endurance test is an experiment in which a severe condition of cracking occurs in a polarizer in the case of a usual polarizing plate.

In order to develop a polarizing plate having excellent thermal shock durability which can suppress such cracking, a polarizing plate system which satisfies such requirements is not known.

Korean Patent Application Publication No. 2015-0087062 discloses a polarizing plate which can reduce the crack length at the time of thermal shock, but fails to suggest a solution that satisfies the above problems.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Korean Patent Application Publication No. 2015-0087062

An object of the present invention is to provide a polarizing plate which is excellent in thermal shock durability and which can significantly reduce cracking of a polarizer.

A polarizing plate comprising a polarizer and a polarizer protective film which is adhered to at least one surface of the polarizer via an adhesive layer, and an elastic modulus coefficient represented by the following formula 1 is 13.0 to 29.0 MPa/(N). /2mm): [Expression 1] modulus of elasticity = {(A+B)/C}/100

In the formula, the tensile modulus (MPa) of the A-type polarizer protective film at 25 ° C, the storage elastic modulus (MPa) of the B-based adhesive layer at 30 ° C, and the absorption axis of the polarizer of the C-system at 80 ° C for 1 hour. Contraction force (N/2mm).

2. The polarizing plate according to 1, wherein the A series is 1000 to 4000 MPa.

3. The polarizing plate according to the above 1 or 2, wherein the B system is 1000 to 4000 MPa.

4. The polarizing plate according to any one of the above 1 to 3, wherein the C system is 1.0 to 2.5 N/2 mm.

5. The polarizing plate according to any one of the above 1 to 4, wherein the adhesive layer is formed of a photoradical polymerizable adhesive composition or a photocationic polymerizable adhesive composition.

An image display device comprising the polarizing plate according to any one of the above 1 to 5.

The polarizing plate of the present invention is remarkably excellent in thermal shock durability, and the possibility of cracking is remarkably low when exposed to a high temperature and a low temperature environment.

The present invention relates to a polarizing plate including a polarizing plate and a polarizer protective film which is adhered to at least one surface of the polarizer via an adhesive layer, and has a flexibility as shown by a specific relationship. The rate coefficient is from 13.0 to 29.0 MPa/(N/2 mm), whereby the durability against thermal shock is excellent.

Hereinafter, the present invention will be described in detail.

The polarizing plate of the present invention comprises a polarizer and a polarizer protective film which is adhered to at least one surface of the polarizer via an adhesive layer, and an elastic modulus coefficient represented by the following formula 1 is 13.0 to 29.0 MPa/(N). /2mm): [Expression 1] modulus of elasticity = {(A+B)/C}/100

(In the formula, the tensile modulus at 25°C (MPa) of the A-type polarizer protective film, the storage elastic modulus (MPa) at 30°C of the B-based adhesive layer, and the absorption axis of the polarizer of the C-system at 80° C. for 1 hour. Directional contraction force (N/2mm))

The polarizing plate of the present invention is obtained by the absorption axis of the polarizer The contraction force, the tensile modulus of the polarizer protective film, and the storage elastic modulus of the adhesive layer satisfy the specific relationship as described above (the modulus of elasticity is 13.0 to 29.0 MPa/(N/2 mm)), even if a thermal shock is applied, the turtle The production of cracks is reduced. When exposed to high temperature and low temperature, it will cause shrinkage of the polarizing film when it becomes high temperature, and the polarizing film that shrinks when it returns to low temperature will swell, and it will be cracked when it is going back to its original state. Therefore, the hardness of the polarizer protective film and the adhesive layer in the vicinity of the normal temperature is an important characteristic for suppressing the occurrence of cracks with respect to the stress accumulated by the shrinkage at a high temperature.

If the modulus of elasticity of the present invention is less than 13.0 MPa/(N/2 mm) or exceeds 29.0 MPa/(N/2 mm), the occurrence of cracks in the polarizer during thermal shock is remarkably increased. When the modulus of elasticity is less than 13.0 MPa/(N/2 mm), the suppression of shrinkage of the polarizer by the polarizer protective film and the adhesive layer is insufficient, and cracking is liable to occur, and the modulus of elasticity exceeds 29.0 MPa/( When N/2 mm), the polarizer protective film and the adhesive layer are hardened, and the deformation due to shrinkage of the polarizer is not alleviated and cracking is liable to occur.

<Polarizer>

The polarizer of the present invention is not particularly limited as long as it has a contracting force that satisfies the absorption axis direction of the elastic modulus, and may be, for example, an absorption axis direction at 80 ° C for one hour of standing. The contraction force has a contraction force of 2.5 N/2 mm or less. The durability against thermal shock at a contraction force of 2.5 N/2 mm or less can be further improved. Further, the lower limit of the contraction force in the absorption axis direction may be 1.0 N/2 mm or more when left at 80 ° C for 1 hour.

The contraction force in the absorption axis direction of the polarizer of the present invention, The compound or the extension ratio used in the manufacture of the polarizer can be adjusted, preferably in the crosslinking step in which the maximum extension and crosslinking are carried out. For example, the contraction force in the absorption axis direction of the polarizer can be controlled by adjusting the content of the boron compound in the aqueous solution for crosslinking or the elongation ratio of the crosslinking step.

The polarizer of the present invention may have a thickness of 5 to 30 μm, preferably 10 to 28 μm, more preferably 15 to 26 μm. When the thickness of the polarizer is in the above range, the low shrinkage force and the operability of the polarizer in the absorption axis direction can coexist.

Hereinafter, a method of producing the polarizer of the present invention will be described.

The polarizer of the present invention is produced by a film for forming a polarizer. The film for forming a polarizer for producing a polarizer is not particularly limited as long as it can be used in the production of a polarizing plate, and a film which can be dyed by a dichroic substance such as iodine can be used in the art. For example, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film, a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film, A hydrophilic polymer film such as a saponified film; a polyvinyl alcohol-based film dehydrated, a polyalkylene oriented film such as a dechlorination-treated polyvinyl chloride film; and the like. Among these, not only the effect of enhancing the uniformity of the degree of polarization in the surface is excellent, but also the point of excellent dyeing affinity for iodine is preferably a polyvinyl alcohol film.

The method for producing a polarizer of the present invention may include a swelling step of a film for forming a polarizer, a dyeing step, a crosslinking step, a complementary color step, an extending step, a water washing step, and a drying step, which may be classified according to an extension method. For example, a dry stretching method, a wet stretching method, or a mixture of the above two kinds may be mentioned. Hybrid extension method of the extension method, and the like. Hereinafter, the method for producing the polarizer of the present invention will be described by taking the wet stretching method as an example, but the method is not limited thereto.

In the above-described steps, the remaining steps other than the drying step can be immersed in a bath for forming a polarizer in a constant temperature water bath filled with one or more kinds of solutions selected from various types of solutions. get on.

<Swelling step>

The swelling step is performed by immersing in a swelling tank filled with an aqueous solution for swelling before dyeing the film for forming an unpolarized polarizer, and removing impurities such as dust or an anti-caking agent deposited on the surface of the film for forming a polarizer to form a polarizer. The step of forming a film to swell, improving the elongation efficiency, preventing the dyeing unevenness, and improving the physical properties of the polarizer.

The aqueous solution for swelling is not particularly limited, and an aqueous solution for swelling which is known in the art can be used. For example, water (pure water, deionized water) can be used alone, and when a small amount of glycerin or potassium iodide is added thereto, the swelling of the polymer film can be enhanced and Processability. It is preferable that the content of glycerin is 5% by weight or less based on 100% by weight of the aqueous solution for swelling, and the content of potassium iodide is 10% by weight or less.

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

The execution time (swelling bath immersion time) of the swelling step is not particularly limited, and a known execution time in the art can be applied, and for example, it can be 180 seconds or less, preferably 90 seconds or less. When the immersion time is in the above range, swelling can be prevented from becoming excessively saturated, and the film for forming a polarizer can be prevented from being soft. The rupture caused by the crystallization, the adsorption of iodine becomes uniform during the dyeing step, and the degree of polarization can be improved.

The swelling step and the stretching step may be simultaneously performed, and in this case, the stretching ratio may be about 1.1 to 3.5 times, but is not limited, and preferably 1.5 to 3.0 times. If the aforementioned stretching ratio is less than 1.1 times, wrinkles may occur, and when it exceeds 3.5 times, initial optical characteristics may become weak.

<staining step>

In the dyeing step, the film for forming a polarizer is immersed in a dyeing tank filled with an aqueous solution for dyeing containing a dichroic substance such as iodine, and iodine is adsorbed to the film for forming a polarizer.

The aqueous solution for dyeing is not particularly limited, and an aqueous solution for dyeing known in the art can be used, and water, a water-soluble organic solvent or a mixed solvent thereof and iodine can be contained. The content of iodine may be from 0.4 to 400 mmol/L in the aqueous solution for dyeing, but is not limited thereto, and is preferably from 0.8 to 275 mmol/L, and most preferably from 1 to 200 mmol/L.

In order to improve the dyeing efficiency, the aqueous solution for dyeing may further contain iodide as a dissolution aid. The iodide is not limited, and an iodide known in the art may be used, for example, may be selected from the group consisting of potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, At least one of the group consisting of calcium iodide, tin iodide, and titanium iodide, and potassium iodide is preferred for the point where the solubility of water is large. The content of the iodide may be from 0.01 to 10% by weight, based on 100% by weight of water, but is not limited, and is preferably from 0.1 to 5% by weight.

Moreover, in order to increase the content of the iodine complex in the film for forming a polarizer, boric acid may be added in an amount of 0.3 to 5% by weight based on 100% by weight of water in the dyeing tank, but the invention is not limited thereto. When the boric acid of the dyeing tank is less than 0.3% by weight, there is a possibility that the effect of increasing the content of PVA-I ₃ ^- complex and PVA-I ₅ ^- complex is not obtained, and when the concentration of boric acid in the dyeing tank is higher than 5% by weight, the film The risk of rupture may become higher.

The temperature of the dyeing tank may be 5 to 42 ° C, but is not limited thereto, and is preferably 10 to 35 ° C. Further, the immersion time of the film for forming a polarizer 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 dyeing step and the stretching step may be simultaneously performed, and in this case, the stretching ratio may be 1.01 to 2.0 times, but is not limited thereto, and preferably 1.1 to 1.8 times.

Further, the cumulative stretching ratio including the swelling and the dyeing step up to the dyeing step may be 1.2 to 4.0 times. When the cumulative elongation ratio is less than 1.2 times, wrinkles of the film may occur to cause poor appearance, and when it exceeds 4.0 times, initial optical characteristics may become weak.

<Crosslinking step>

The crosslinking step is a step of immersing the dyed polarizer forming film in an aqueous solution for crosslinking to prevent the dyed property of the iodine molecule adsorbed by the physical property from being lowered by the external environment, thereby fixing the adsorbed iodine molecule.

When the crosslinking reaction is insufficient as the iodine of the dichroic dye, the iodine molecule may be detached due to the moist heat environment, and a sufficient crosslinking reaction is required. Further, in order to orient the iodine molecules between the molecules and the molecules at the position of the film for forming a polarizer, the optical characteristics can be improved, and the maximum elongation can be achieved in the crosslinking step. The extension is extended.

In the present invention, the method for producing a polarizer can be carried out, for example, by a crosslinking step comprising the first and second crosslinking steps, and one or more of the first and second crosslinking steps can be carried out using boron. An aqueous solution for crosslinking of the compound. Thereby, the optical characteristics of the polarizer and the durability of the color can be improved.

The aqueous solution for cross-linking is not particularly limited, and a cross-linking aqueous solution known in the art may be used, and may contain, for example, water belonging to a solvent, a boron compound such as boric acid or sodium borate, or an organic solvent which is mutually soluble with water and Iodide.

The boron compound can impart short-crosslinking bonds and rigidity to the polarizer, and suppress wrinkles in the film in the step, thereby raising the rationality of the film and exerting the task of forming the iodine orientation of the polarizer. Further, the contraction force in the absorption axis direction of the polarizer can be controlled by adjusting the content of the boron compound in the aqueous solution for crosslinking. Specifically, if the content of the boron compound is increased, the contraction force in the direction of the absorption axis can be increased, and if it is reduced, the contraction force in the direction of the absorption axis can be reduced.

The content of the aforementioned boron compound can be applied to a content known in the art, for example, from 1 to 10% by weight, preferably from 2 to 6% by weight, based on 100% by weight of water. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced, and it is difficult to impart rigidity to the polarizer. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated. It is difficult to carry out the crosslinking reaction of the organic crosslinking agent efficiently.

In this step, in order to maintain the uniformity of the degree of polarization of the polarizer in the plane, and in order to prevent the desorption of the dyed iodine, Use iodide. The iodide may be the same as the user in the dyeing step, and the content of the iodide may be 0.05 to 15% by weight with respect to 100% by weight of water, but is not limited, preferably 0.5 to 15% by weight. %. If the content is less than 0.05% by weight, the iodide ions in the film may be removed to increase the transmittance of the polarizer. When the content exceeds 15% by weight, the iodide ions in the aqueous solution may permeate into the film to 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 film for forming a polarizer in the cross-linking groove may be from 1 second to 15 minutes, but is not limited thereto, and is preferably from 5 seconds to 10 minutes.

In the method for producing a polarizer according to an embodiment of the present invention, the stretching step may be simultaneously performed in the crosslinking step, as in the foregoing, in the present crosslinking step, the stretching ratio can be maximized, and thereafter, the shrinking force is lowered. In terms of the aspect, stress relaxation is preferred. For example, the crosslinking step may include a first crosslinking step and a second crosslinking step, wherein the first crosslinking step is a high stretching step, and the second crosslinking step may be a stress relaxation step.

For example, the extension ratio of the first crosslinking step may be 2.0 to 3.0 times, preferably 2.2 to 2.8 times.

Further, the extension ratio of the second crosslinking step may be 0.85 to 1.0 times.

Further, the cumulative stretching ratio of the first and second crosslinking steps may be 1.5 to 3.0 times, but is not limited thereto, and preferably 1.98 to 2.8 times. When the cumulative elongation ratio is less than 1.5 times, the orientation effect of iodine may be insufficient. When the ratio exceeds 3.0 times, the stress due to elongation may increase and the contraction force may increase. Can increase.

<Complementary Steps>

The method for producing a polarizer of the present invention may further comprise a complementary color step as needed. Through the complementary coloring step, the iodine complex located between the molecule and the molecule in the film for polarizing film formation in which the iodine complex is physically adsorbed can be aligned in the vicinity of the cross-linking of the boric acid to stabilize the iodine complex. Moreover, the film for polarizer formation which is insufficient in the dyeing of the iodine complex in the said crosslinking process can be complement-filled by the color-filling process.

The aqueous solution for complementary color in the color-retaining step contains, for example, water belonging to a solvent and a boron compound such as boric acid, and may further contain an organic solvent and an iodide which are mutually soluble together with water.

In the present invention, the boron compound can impart short-crosslinking bonds and rigidity to the polarizer, and suppress wrinkles in the film in the step, thereby raising the rationality of the film and exerting the task of forming the iodine orientation of the polarizer.

The content of the above boron compound may be from 1 to 10% by weight based on 100% by weight of water, but is not limited thereto, and is preferably from 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 is difficult to impart rigidity to the polarizer. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated. Further, the crosslinking reaction of the organic crosslinking agent is difficult to carry out efficiently.

In this step, in order to maintain the uniformity of the degree of polarization of the polarizer in the plane, in order to prevent desorption of the dyed iodine, an iodide may be used. The iodide may be used in the same manner as the user in the dyeing step, and the content of the iodide may be 100% by weight relative to water. 0.05 to 15% by weight, but not limited thereto, preferably from 0.5 to 11% by weight. If the content is less than 0.05% by weight, the iodide ions in the film may be removed to increase the transmittance of the polarizer. When the content exceeds 15% by weight, the iodide ions in the aqueous solution may permeate into the film to reduce the transmittance of the polarizer.

In the present invention, the temperature of the complementary color tank may be 20 to 70 °C. The immersion time of the film for forming a polarizer in the complementary color groove may be from 1 second to 15 minutes, but is not limited thereto, and is preferably from 5 seconds to 10 minutes.

The stretching step may be carried out together with the aforementioned complementary coloring step. In this case, the stretching ratio of the complementary coloring step may be 1.01 to 1.25 times, but is not limited thereto, and preferably 1.05 to 1.20 times.

When the elongation ratio is less than 1.01 times, the effect of stabilization of the iodine complex and the orientation effect of the film for forming a polarizer may be insufficient, and when it exceeds 1.25 times, the film may be broken due to excessive elongation. And production efficiency may be reduced.

<Extension step>

In the present invention, the stretching step may be carried out simultaneously with other steps as described above, or may be carried out separately. The extension step can be performed at least once or multiple times. When the plurality of times are performed, it can be carried out separately at any step in the manufacturing steps of the polarizer.

In the present invention, the contraction force in the direction of the extension (absorption axis) of the polarizer can be adjusted by the elongation ratio, preferably as described above, and can be adjusted by the elongation ratio in the crosslinking step.

In the production method of the present invention, the total cumulative elongation ratio of the polarizer is preferably 5.0 to 7.0 times, more preferably 5.3 to 6 times.

In the present specification, the "cumulative stretch ratio" means the value of the product of the elongation ratio in each step.

<Washing step>

The method for producing a polarizer according to the present invention may further include a water washing step which immerses the film for forming a polarizer for crosslinking and stretching in a water washing tank filled with an aqueous solution for washing, as needed, until the water washing step In the step, an unnecessary residue such as boric acid adhered to the film for forming a polarizer is removed.

In the present invention, the aqueous solution for water washing is not particularly limited, and an aqueous solution for water washing known in the art may be used. For example, water may be used, and iodide may be further added thereto, but is not limited thereto.

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

The water washing step may be omitted, or may be performed at the end of the step before the water washing step such as the aforementioned dyeing step or the aforementioned crosslinking step. Further, it may be repeated more than once, and the number of repetitions thereof is not particularly limited.

<drying step>

In the manufacturing method of the present invention, the drying step is a step of drying the film for forming a water-washed polarizer, and the orientation of the dyed iodine molecule is improved by a neck-in by drying. A step of obtaining a polarizer excellent in optical characteristics. Further, the width of the inner shrinkage film is narrowed.

The drying method is not limited, and a drying method known in the art can be used. For example, natural drying, hot air drying, air drying, heat drying, far infrared drying, microwave drying, and the like can be used. Recently, only The microwave drying system in which the water in the film is activated and dried is reused, and it is usually mainly dried by hot air.

The execution temperature of the hot air drying is not particularly limited. However, in order to prevent deterioration of the polarizer, it is preferably carried out at a relatively low temperature, and may be, for example, 20 to 90 ° C, preferably 80 ° C or lower.

The execution time of the hot air drying described above is not particularly limited, and for example, it can be carried out for 1 to 10 minutes.

<Polarizing film protective film>

The polarizer protective film of the present invention is not particularly limited as long as it has a tensile modulus which satisfies the elastic modulus of the elastic modulus, and may be, for example, a tensile modulus of elasticity of from 1,000 to 4,000 MPa at 25 °C. When the tensile modulus of elasticity in the above range is obtained, the durability against thermal shock can be further improved. When the tensile modulus of the protective film is less than 1000 MPa, the cracking failure is more serious due to the difference in the modulus of elasticity of the adhesive layer between the protective film and the polarizer. If it exceeds 4000 MPa, it may be caused by external stress. Cracking of the protective film.

The tensile modulus of the polarizer protective film is determined by the raw material of the protective film. The material of the polarizer protective film is not particularly limited as long as it is a film having excellent transparency, mechanical strength, thermal stability, moisture shielding property, and the like, and is not particularly limited. Various transparent resin films containing at least one selected from the group consisting of an acrylic resin film, a cellulose resin film, a polyolefin resin film, and a polyester resin film are used.

Specific examples of the protective film include poly(methyl). Acrylic resin film such as methyl acrylate or poly(methyl) acrylate; polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate A polyester resin film such as a diester; a cellulose resin film such as diethyl hydrazine cellulose, triethylene sulfonyl cellulose or cellulose acetate propionate; polyethylene, polypropylene, ring system or A polyolefin-based resin film such as a polyolefin structure or an ethylene-propylene copolymer; or the like, but is not limited thereto.

The thickness of the protective film is not particularly limited and may be 10 to 200 μm, preferably 10 to 150 μm. In the case of the two-layer polarizer protective film of the polarizer, each of the protective films may have the same or different thickness.

<Next layer>

The adhesive layer of the present invention is formed by hardening an adhesive composition, and bonds the polarizer to the protective film.

The adhesive layer of the present invention is not particularly limited as long as it has a storage elastic modulus satisfying the above elastic modulus, and may be, for example, a storage elastic modulus of 1,000 to 4,000 MPa at 30 °C. When the storage modulus of elasticity in the above range is obtained, the durability against thermal shock can be further improved. When the storage modulus is less than 1000 MPa or exceeds 4,000 MPa, cracks may occur during thermal shock. The adjustment of the storage modulus of the layer can then be adjusted by the type and amount of each component of the adhesive composition.

The thickness of the layer is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.5 to 5 μm. If the thickness of the adhesive layer is in the above range, it is difficult to recognize foreign matter, and the adhesive composition is sufficiently hardened and Good adhesion. The thickness of the layer can then be adjusted by adjusting the coating thickness of the adhesive composition described later.

The adhesive composition of the present invention may be a photocurable adhesive composition or a thermosetting adhesive composition. When a productivity or the like is considered, a photocurable adhesive composition is preferred.

The photocurable adhesive composition may contain a photopolymerizable compound and a photopolymerization initiator.

The photopolymerizable compound may be a photoradical polymerizable compound or a photocationic polymerizable compound.

The photoradical polymerizable compound may, for example, be a 1 to 6 functional monomer, and specific examples thereof include methyl (meth)acrylate, allyl methacrylate, and 2-ethoxyethyl (meth)acrylate. , isodecyl (meth) acrylate, 2-dodecyl thioethyl methacrylate, octyl acrylate, 2-methoxyethyl acrylate, hydroxyethyl (meth) acrylate, (meth) acrylate Hydroxypropyl ester, hydroxybutyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl methacrylate, (methyl ) tetrahydrofuran methyl acrylate, phenoxyethyl (meth) acrylate, urethane acrylate, aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate Isofunctional monomer; 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(a) Acrylate, ethylene glycol di(meth)acrylate, bisphenol A-ethylene glycol diacrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate Polyethylene Di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) Acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone modified dicyclopentenyl bis(meth)acrylate, oxirane modification Di(meth)acrylate, bis(2-hydroxyethyl)trimeric isocyanate di(meth)acrylate, bis(propyleneoxyethyl)trimeric isocyanate, allyl (meth)acrylate Cyclohexyl ester, dimethylol dicyclopentane diacrylate, ethylene oxide modified hexahydrophthalic acid diacrylate, tricyclodecane dimethanol acrylate, neopentyl glycol modified trimer a bifunctional monomer such as methyl propane diacrylate or adamantane diacrylate; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified Pentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, ginseng (2-hydroxyethyl) a trifunctional monomer such as a trimeric isocyanate tri(meth)acrylate, ginseng(propyleneoxyethyl)trimeric isocyanate or tris(meth)acrylate; tetra(meth)propene a tetrafunctional monomer such as diglyceride, pentaerythritol tetra(meth)acrylate or ditrimethylolpropane tetra(meth)acrylate; propionic acid modified dipentaerythritol penta (methyl) a 5-functional monomer such as acrylate; and a hexa-caprolactone-modified hexa-pentaerythritol hexa(meth) acrylate or the like, and the like, and among these, a 1-3 monomer is preferred. . These may be used alone or in combination of two or more.

The photocationic polymerizable compound may, for example, be a bisphenol type epoxy resin such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin; a phenol novolak type epoxy resin or a cresol novolak type ring; Novolac type epoxy resin such as oxygen resin; aliphatic epoxy resin, alicyclic epoxy resin, naphthalene epoxy resin, polyfunctional epoxy resin, biphenyl ring Oxygen resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin; alcohol type epoxy resin such as hydrogenated bisphenol A type epoxy resin; bromination ring Halogenated epoxy resin such as oxygen resin; rubber modified urethane resin, urethane modified epoxy resin, epoxidized polybutadiene, epoxidized styrene-butadiene-styrene block copolymer a compound containing an epoxy group, a polyurethane resin containing an epoxy group, an epoxy group-containing acrylic resin, or the like, and an epoxy group-containing compound; phenoxymethyloxetane; 3,3-bis(methoxymethyl)oxetane, 3,3-bis(phenoxymethyl)oxetane, 3-ethyl-3-(phenoxymethyl) Oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-{[3-(triethoxyindenyl)propane Oxy]methyl}oxetane, phenol novolac oxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene The oxetane group-containing compound or the like may be used alone or in combination of two or more.

The photopolymerization initiator is used to increase the efficiency of the curing reaction, and examples thereof include optical liberation such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin alkyl ether. Base polymerization initiator; aromatic diazonium salt, aromatic sulfonium salt, aromatic iodine aluminum salt, benzoin sulfonate, and the like. Further, examples of the photocationic polymerization initiator include Optomer-SP-151, Optomer-SP-170, Optomer-SP-171 (Asahi Kasei Kogyo Co., Ltd.), Irgacure-261 (Ciba Co., Ltd.), Shade SI, which are commercially available products. -60L, UVI-6990 (Union Carbide), BBI-1C3, MPI-103, TPS-103, DTS-103, NAT-103, NDS-103 (Green Chemical Corporation), CPI-110A (San-Apro) Wait. These may be used alone or in combination of two or more.

The content of the photopolymerization initiator is not particularly limited, and may be, for example, 0.5 to 10 parts by weight based on 100 parts by weight of the photopolymerizable compound. When the content is within the above range, it has a suitable curing rate and has excellent durability.

<Method of Manufacturing Polarizing Plate>

The production of the polarizing plate can be carried out by bonding the polarizer to the polarizer protective film by using the above-described adhesive composition. Bonding of the polarizer using the adhesive composition to the protective film can be carried out by a suitable method, for example, by a casting method, a Meyer bar coating method, a gravure coating method, a spin coating method, or a die. A method of applying an adhesive composition to a bonding surface of a polarizer and/or a protective film by a coating method, a dip coating method, a spray method, or the like, and superimposing the two. The casting method is a method in which a polarizer or a protective film belonging to a coated object is moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction therebetween, and an adhesive composition is applied to the surface thereof.

The coating thickness of the subsequent composition is not particularly limited, and can be, for example, 0.01 to 10 μm, preferably 0.5 to 5 μm.

After the adhesive composition is applied, the polarizer and the protective film are sandwiched and joined by a nip roll.

Further, in order to improve the adhesion, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment may be appropriately performed on the surface of the polarizer and/or the protective film as needed. The saponification treatment may, for example, be a method of immersing in an aqueous solution of a base such as sodium hydroxide or potassium hydroxide.

After the polarizer and the polarizer protective film are laminated, the implementation is carried out Drying treatment. The drying treatment is carried out, for example, by spraying hot air, but the temperature at this time can be appropriately selected in the range of 50 to 100 degrees. The drying time is usually from 30 to 1,000 seconds.

The polarizing plate of the present invention can be applied not only to a general liquid crystal display device but also to various image display devices such as an organic electric field light-emitting display device (OLED), a plasma display device, and an electric field emission display device.

In the following, in order to facilitate the understanding of the present invention, the preferred embodiments are provided, but the embodiments are merely illustrative of the present invention and are not intended to limit the scope of the patent application, which should be apparent to those skilled in the art Various changes and modifications of the embodiments are possible within the scope and technical scope of the invention, and such changes and modifications are of course the scope of the patent application.

<Example 1> <Binder composition>

47 parts by weight of phenoxy glycidyl ether and 50 parts by weight of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid, photopolymerization initiator (CPI-110A, San-) Apro company) 3 parts by weight to produce a photocurable resin composition. The storage elastic modulus of the present adhesive composition after hardening is 1500 MPa.

<Polarizer>

A transparent unstretched polyvinyl alcohol film (PE60, KURARAY Co., Ltd.) 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), and then iodine. 1.25 mM/L and 100% by weight of water containing 1.25 wt% of potassium iodide and 0.3% by weight of boric acid in an aqueous solution for dyeing at 30 ° C for 2 minutes and 30 seconds for dyeing (dyeing step). this In the swelling and dyeing steps, the elongation ratio was extended by 1.7184 times and 1.5214 times, respectively, and the cumulative elongation ratio until the dyeing tank was 2.614 times.

Then, it was immersed in an aqueous solution for cross-linking containing 56% by weight of potassium iodide (15.0% by weight of potassium iodide and 25% by weight of boric acid) at 56° C. for crosslinking for 26 seconds (first crosslinking step), and at the same time 2.5 times. The extension ratio extends. Thereafter, the mixture was immersed in an aqueous solution for crosslinking of 56% by weight of potassium iodide (15.0% by weight of potassium iodide and 25% by weight of boric acid) for 20 seconds to crosslink (second crosslinking step), and simultaneously at 0.85. The extension ratio is extended.

Then, it was immersed in an aqueous solution for complementary color containing 40% by weight of potassium iodide and 2% by weight of boric acid at 40 ° C for 10 seconds (refilling step), and simultaneously extended to 1.08 times.

At this time, the total cumulative elongation ratio of the swelling, dyeing, cross-linking, and complementary color steps was made six times. After the completion of the crosslinking, the polyvinyl alcohol film was washed with deionized water (water washing step), and then dried in an oven at 80 ° C for 5 minutes (drying step) to produce a polarizing plate having a transmittance of 42.5%. The thickness of the polarizer was 23 μm.

<Polarizing plate>

The above-mentioned adhesive composition was applied onto a three-layered cellulose film (Fuji Film Co., Ltd.) having a thickness of 3,900 MPa and a corona-treated thickness of 60 μm, on one side of the polarizing plate to which the directional iodine was adsorbed, In order to make the thickness of the above-mentioned adhesive composition 2 to 3 μm, the polarizer and the triethylenesulfonated cellulose film were sandwiched by a nip roll and joined, and a high-pressure mercury lamp (UVA cumulative light amount of 500 mJ/cm ^{2 ) was used.} After curing the UV, the adhesive is bonded to produce a polarizing plate.

<Examples 2 to 7 and Comparative Examples 1 to 3>

The polarizing plate was produced in the same manner as in Example 1 except that the elastic modulus of the protective film and the adhesive layer and the contraction force in the absorption axis direction of the polarizer were adjusted as described in Table 1 below.

The modulus of elasticity of the protective film is the value determined for each article.

In Example 5, the photopolymerization initiator (CPI-110A, San-Apro Co., Ltd.) of Example 1 was changed to 4 parts by weight, and in Example 6, the photopolymerization initiator (CPI-110A) of Example 1 was used. , San-Apro Co., Ltd.) changed to 5 parts by weight to adjust the elastic modulus of the adhesive layer.

The contraction force in the absorption axis direction of the polarizer is adjusted by changing the boric acid content of the aqueous solution for crosslinking. The boric acid content in Table 1 means the boric acid content of the aqueous solution for crosslinking in the first crosslinking step and the second crosslinking step.

<Test example>

The physical properties of the polarizer and the polarizing plate produced in the above examples and comparative examples were measured by the following methods.

<1. Measurement of tensile modulus of protective film>

After cutting the protective film to a size of 25 mm × 100 mm, the punctuation distance was set to 50 mm, and the tensile tester (tensile tester, Shimadzu) The tensile test in the longitudinal direction was carried out, and the tensile strength was measured for the tangential direction of the initial curve of the S-S curve, and the tensile modulus was determined by dividing the strength value by the sectional area. At this time, the measurement was performed at a rate of 25 ° C and 4 mm / min.

<2. Measurement of storage elastic modulus of the subsequent layer>

On the surface of one of two sheets of a cycloolefin polymer (COP) film (Zeon Corporation) which was not corona treated, the adhesive composition was applied in a rod coater to a thickness of 10 μm. Thereafter, another one-piece COP film which was not corona-treated was bonded to the surface on which the adhesive composition was applied by a laminator, and UV-hardened by a high-pressure mercury lamp (UVA cumulative light amount: 500 mJ/cm ² ) to prepare a thickness of 4 μm. The adhesive film.

Thereafter, the adhesive film was peeled off from the COP film and cut into a size of 5.0 cm × 0.5 cm, and then the storage elastic modulus at 30 ° C was measured by DMA Q800 (Dynamic mechanical analyzer, TA) (temperature conditions were normal temperature to 200 ° C) . At this time, in order to maintain the polarizer in a flat state before measurement, a minimum load was applied to the thickness direction of the polarizer and measured.

<3. Determination of shrinkage force of polarizer>

Here, the contraction force in the absorption axis direction per 2 mm of the width of the polarizing plate in the transmission axis direction was measured. After the polarizer produced in the examples and the comparative examples was cut into a size of 2 mm (transmission axis direction) × 50 mm (absorption axis direction), the punctuation distance was set to 15 mm, and the isothermal state was allowed to stand at 80 ° C for 1 time. The contraction force in the longitudinal direction (absorption axis direction) was measured by DMA Q800 (Dynamic mechanical analyzer, TA Corporation). At this time, in order to maintain the polarizer in a flat state before the measurement, a minimum load was applied to the thickness direction of the polarizer and measured.

<4. Measurement of Thermal Shock Durability>

The polarizing plates produced in the examples and the comparative examples were cut into a size of 15.0 cm (absorption axis (MD) direction) × 11 cm (transmission axis (TD) direction), and then bonded to a glass plate using an adhesive to carry out autoclaving. (50 ° C, 20 minutes, 5 atmospheres) treatment. After standing for 24 hours, a thermal shock test was performed (40 ° C, 30 minutes, and 85 ° C, 30 minutes, 60 minutes as 1 cycle). After the produced sample was placed in an oven and completed for 100 cycles, it was confirmed whether or not cracking occurred in the polarizing plate (the number of samples was 5 for each of the examples or the comparative examples).

Referring to Table 2, it can be confirmed that the polarizing plate satisfying the range of the modulus of elasticity coefficient of the present invention is completely crack-free in the polarizer when it is subjected to thermal shock. Health.

Claims (6)

A polarizing plate comprising a polarizer and a polarizer protective film interposed on at least one surface of the polarizer via an adhesive layer, and an elastic modulus coefficient represented by the following formula 1 is 13.0 to 29.0 MPa/(N/2 mm) ): [Equation 1] Elasticity coefficient = {(A+B)/C}/100 where the tensile modulus (MPa) of the A-type polarizer protective film is 25°C, and the B-series layer is stored at 30°C. Elasticity (MPa), C is the contraction force (N/2 mm) in the absorption axis direction of the polarizer which is allowed to stand at 80 ° C for 1 hour. The polarizing plate of claim 1, wherein the aforementioned A is 1000 to 4000 MPa. The polarizing plate of claim 1 or 2, wherein the B is 1000 to 4000 MPa. The polarizing plate according to any one of claims 1 to 3, wherein the aforementioned C is 1.0 to 2.5 N/2 mm. The polarizing plate according to any one of claims 1 to 4, wherein the adhesive layer is formed of a photoradical polymerizable adhesive composition or a photocationic polymerizable adhesive composition. An image display device comprising the polarizing plate according to any one of claims 1 to 5.