TWI405775B - Iodine polarized film and its manufacturing method - Google Patents

Abstract

PURPOSE: An iodine-based polarizing film and a process for producing the same are provided to prevent light leakage by increasing adsorption of iodine and optical absorption in a long wave region of visible light. CONSTITUTION: An iodine-based polarizing film comprises a polyvinyl alcohol film and iodine absorbed and originated to the polyvinyl alcohol film and includes Group 2 elements. The Group 2 element is present in the amount of 5.6×10 ~ 9.7×10 mol/g. A method for preparing the iodine-based polarizing film comprises the steps of: absorbing and orientating iodine to a polyvinyl alcohol film; and contacting an aqueous solution containing salts of Group 2 elements with the polyvinyl alcohol film.

Description

Iodine-based polarizing film and method of producing the same Technical field

The present invention relates to an iodine-based polarizing film used in a screen display device such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED). Production method. Further, the present invention relates to a polarizing plate using the iodine-based polarizing film.

Background technique

The polarizing film used in the image display device (particularly, a liquid crystal display device) needs to have high transmittance and polarization in order to provide a bright image with good color reproducibility. Such a polarizing film has conventionally been produced by adsorbing and aligning a dichroic substance such as iodine having a dichroic property and a dichroic dye on a polyvinyl alcohol (PVA) film.

Among these polarizing films, the iodine-based polarizing film which adsorbs iodine is superior to the dye-based polarizing film in that it has a high transmittance and a high degree of polarization, that is, a high contrast characteristic. Therefore, an iodine-based polarizing film is widely used as a component of a liquid crystal display device.

However, in the liquid crystal display device in which the two polarizing plates to which the iodine-based polarizing film is applied are disposed such that the light transmission axes thereof are perpendicular to each other, there is a problem that visible light is leaked and the display screen is discolored. In particular, an iodine-based polarizing film in which iodine is adsorbed to a polyvinyl alcohol film has a light absorption ratio in a short wavelength range (360 to 410 nm) and a long wavelength range (700 to 830 nm) in the visible light range (360 to 830 nm). Less, I hope to have this improvement.

[Patent Document 1] Japanese Patent Application No. Sho 56-207374

The present invention has been made in view of the above problems, and an object of the invention is to provide a long-wavelength range in the visible light range when two polarizing plates are disposed in a liquid crystal display device such that their light transmission axes are perpendicular to each other. An iodine-based polarizing film which can suppress the occurrence of light leakage and which can suppress discoloration of a display screen, and a method for producing the same.

The present inventors have found that an iodine-based polarizing film containing a Group 2 element can improve light absorption in a long wavelength range and a short wavelength range of visible light, thereby completing the present invention.

In other words, the iodine-based polarizing film of the present invention is an iodine-based polarizing film in which iodine is adsorbed to a polyvinyl alcohol film, and is characterized in that it contains a Group 2 element.

The present inventors believe that an iodine-based polarizing film composed of polyvinyl alcohol is made to be light in a long wavelength range (700 to 830 nm) of visible light (360 to 830 nm) by a complex formed of polyvinyl alcohol and iodine. absorb. On the other hand, the present inventors also considered that the cation of the Group 2 element initiates the formation of an iodine adsorption site on the surface of the film. Therefore, as described above, the iodine-based polarizing film containing the Group 2 element forms iodine on the surface of the film. The adsorption site promotes the adsorption of iodine. As a result, light absorption greater than a long wavelength range or a short wavelength range of visible light can be achieved, and light leakage can be prevented. Further, since the standard electrode potential of the Group 2 element is lower than that of the other polyvalent transition metal standard electrode, the Group 2 element does not promote the oxidation-reduction reaction of iodine even if the iodine-based polarizing film of the present invention is used under severe conditions. . As a result, since the light absorption performance in the long wavelength range of visible light is not lowered, the optical reliability is also excellent.

In the above configuration, the amount of the Group 2 element present is in the range of 5.6 × 10 ^-5 to 9.7 × 10 ^-5 mol/g. If the amount of the Group 2 element is within the above numerical range, the balance of the vertical transmittance in the short wavelength range and the long wavelength range of visible light can be made good. If the amount is less than 5.6 × 10 ^-5 mol/g, the vertical transmittance of the short wavelength range (360 to 410 nm) of visible light may become too high, and there may be a case where light leakage occurs in the aforementioned short wavelength range. On the other hand, if the amount is more than 9.7 × 10 ^-5 mol/g, the vertical transmittance in the long wavelength range of visible light becomes too high, and there is a light leakage occurring in the aforementioned long wavelength range. situation.

In the method for producing an iodine-based polarizing film of the present invention, the iodine-based polarizing film is a method in which iodine is adsorbed to a polyvinyl alcohol film, and the production method includes an aqueous solution containing a salt of a group 2 element and the above-mentioned The step of iodine adsorption contacting the aligned polyvinyl alcohol film.

According to the above method, by bringing the aqueous solution containing the salt of the Group 2 element into contact with the surface of the polyvinyl alcohol film, the cation of the Group 2 element can cause the formation of the iodine adsorption site on the surface of the film. Accordingly, the formation of an iodine adsorption site on the surface of the film can further promote the adsorption of iodine. As a result, it is possible to manufacture an iodine-based polarizing film which can absorb light in a long wavelength range larger than visible light and prevent light leakage from occurring. Further, since the polarizing film obtained by the above method does not promote the redox reaction of iodine by the contained Group 2 element, it can suppress the decrease in the amount of iodine adsorption even when used under severe conditions. Thereby, an iodine-based polarizing film which can suppress a decrease in light absorption in a long wavelength range of visible light and which is excellent in optical reliability can be obtained.

In the above method, the foregoing steps are preferably carried out after the step of stretching the polyvinyl alcohol film, the step of dyeing the polyvinyl alcohol film in an aqueous solution containing iodine and potassium iodide, and dipping in an aqueous solution containing boric acid. The step of treating the dyed polyvinyl alcohol film.

Further, in the above method, the aqueous solution containing the salt of the Group 2 element is preferably an aqueous solution of an iodide of the Group 2 element.

Further, the polarizing plate of the present invention is characterized in that a transparent protective film is provided on at least one surface of the iodine-based polarizing film described above.

The present invention achieves the effects described below by the method described above.

In other words, according to the iodine-based polarizing film of the present invention, by contacting a polyvinyl alcohol film with an aqueous solution containing a salt of a Group 2 element to contain a Group 2 element, formation of an iodine adsorption site on the surface thereof can be initiated. And the strong adsorption of iodine. According to this, light absorption in a long wavelength range larger than visible light can be prevented, and light leakage can be prevented from occurring. Moreover, since the Group 2 element does not promote the redox reaction of iodine in comparison with other polyvalent transition metals, the light absorption performance in the long wavelength range of visible light does not decrease even under severe conditions. . As a result, it is also excellent in optical reliability.

Further, according to the method for producing an iodine-based polarizing film of the present invention, the formation of an iodine adsorption site can be initiated on the surface of the film by contacting only the aqueous solution containing the salt of the Group 2 element with the surface of the polyvinyl alcohol film. Therefore, an iodine-based polarizing film which can adsorb iodine more can be produced. As a result, an iodine-based polarizing film which can prevent generation of light leakage and is excellent in optical reliability can be obtained.

Best form for implementing the invention

The iodine-based polarizing film (hereinafter referred to as "polarizing film") of the present embodiment is immersed in a solution containing a salt of a Group 2 element by a polyvinyl alcohol film (hereinafter referred to as "PVA film"). Contains the composition of the aforementioned Group 2 elements.

The PVA film is composed of a polyvinyl alcohol-based resin, and is obtained, for example, by alkalizing a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include a homopolymer of vinyl acetate, polyvinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers.

The degree of polymerization of the polyvinyl alcohol-based resin is generally from 500 to 10,000, preferably in the range of 1,000 to 8,000, more preferably in the range of 1,400 to 7,000. Further, in the case of alkalization, the degree of alkalization is preferably, for example, 75 mol% or more from the viewpoint of water solubility, and preferably 98 mol% or more, and 98.3 mol%. The above range is better.

The method for producing a PVA film composed of a polyvinyl alcohol-based resin can be suitably used: a film formed by a method such as a flow-through method, a cast coating method, or an extrusion method in which a raw liquid dissolved in water or an organic solvent is formed into a film. By. The phase difference at this time can be 5 nm to 100 nm. Further, in order to obtain a uniform polarizing film in the plane, the phase difference variation in the plane of the PVA film is preferably as small as possible, and the in-plane phase difference of the PVA film as a green film is preferably 10 nm or less at a measurement wavelength of 1000 nm. It is preferably 5 nm or less.

The Group 2 element, specifically, at least one selected from the group consisting of strontium, magnesium, calcium, strontium, barium, and radium. Among these Group 2 elements, magnesium and calcium are preferred from the viewpoints of safety and ease of handling. These Group 2 elements may be used singly or in combination of two or more. It has been considered that the cation of the Group 2 element (i.e., the divalent cation) can initiate the formation of an iodine adsorption site on the surface of the PVA film. Therefore, as described above, by contacting the film with an aqueous solution containing a salt of the Group 2 element, an iodine adsorption site is formed on the surface of the film. As a result, the adsorption of iodine on the surface of the PVA film can be more promoted. Further, the ionic strength of the multivalent ions is proportional to the square of the valence of the ions. Therefore, the cation strength of the divalent cation is higher than that of the monovalent cation, and as a result, the initiating force of the divalent cation to form the iodine adsorption site is also high. Moreover, other multivalent transition metals have higher standard electrode potentials than Group 2 elements. If a polarizing film containing such a polyvalent transition metal is used under stringent conditions, the polyvalent transition metal promotes the iodine redox reaction, resulting in reduced iodine. The amount of adsorption. Thereby, the light absorption performance in the long wavelength range (700 to 830 nm) of visible light (360 to 830 nm) is lowered, which causes the occurrence of light leakage and reduces optical reliability.

The amount of the above-mentioned Group 2 element in the polarizing film is preferably in the range of 5.6 × 10 ^-5 to 9.7 × 10 ^-5 mol / g, and is in the range of 6.4 × 10 ^-5 to 7.3 × 10 ^-5 mol / g It is better inside. In the range of 5.6 × 10 ^-5 to 9.7 × 10 ^-5 mol/g, the balance of the short-wavelength range (360 to 410 nm) and the vertical transmittance in the long wavelength range can be made good. If the amount is less than 5.6 × 10 ^-5 mol/g, the vertical transmittance in the short wavelength range may be too high, and there may be a case where light leakage occurs in a short wavelength range. On the other hand, if it is larger than 9.7 × 10 ^-5 mol/g, the vertical transmittance in the long wavelength range may be too high, and there may be a case where light leakage occurs in the long wavelength range.

The thickness of the polarizing film is not particularly limited, but is generally about 5 to 80 μm. The polarizing plate can be formed by laminating a transparent protective film on one or both sides of the polarizing film (details will be described later).

The polarizing film according to the embodiment of the present invention is produced by bringing an aqueous solution containing a salt of a Group 2 element into contact with a polyvinyl alcohol film which is subjected to iodine adsorption alignment. This step is preferably carried out after a series of steps of swelling, dyeing, crosslinking, stretching, etc., of the initial green film, that is, the polyvinyl alcohol film. Further, the polarizing film of the present embodiment can be produced by performing the drying step after this step. In each of the steps other than the drying step, it is preferred to carry out the respective treatments while immersing in a bath composed of various solutions. At this time, the order, the number of times, and the presence or absence of each step are not particularly limited, and a plurality of processes may be simultaneously performed in one process step, or a plurality of processes may not be performed. For example, the stretching treatment may be performed after the dyeing treatment, or may be performed simultaneously with the swelling or dyeing treatment, or may be performed after the stretching treatment. Alternatively, the washing step may be performed after all the steps, or may be performed only after the specific treatment.

The swelling step may be, for example, immersed in a swelling bath filled with water. By washing the PVA film by this, the dirt or the anti-caking agent on the surface of the PVA film can be washed, and the PVA film can be swollen to have an effect of preventing unevenness such as uneven dyeing. In the swell bath, glycerin or potassium iodide may be added as appropriate, and in the case of glycerin, the concentration is preferably 5% by weight or less, and in the case of potassium iodide, the concentration is preferably 10% by weight or less. The temperature of the swelling bath is preferably in the range of 20 to 45 ° C, and preferably 25 to 40 ° C. The immersion time for immersing in the swelling bath is preferably 2 to 180 seconds, preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. Further, in the swelling bath, the PVA film can be stretched, and the stretching ratio at this time also includes stretching due to swelling, and is about 1.1 to 3.5 times with respect to the film in the unstretched state.

The dyeing step can be carried out, for example, by immersing the PVA film in a dye bath containing a dichroic substance such as iodine so that the dichroic substance is adsorbed on the PVA film.

As the dichroic substance, those conventionally known can be used, and examples thereof include iodine or an organic dye. For organic dyes, for example: RED-BR, RED-LR, RED-R, PINK-LB, RUBIAN-BL, BORDO GS, SKY BLUE-LG, LEMON YELLOW, BLUE-BR, BLUE-2R, NAVY-RY, GREEN -LG, VIOLET-LB, VIOLET-B, BLACK-H, BLACK-B, BLACK-GSP, YELLOW-3G, YELLOW-R, ORANGE-LR, ORANGE-3R, SCARLET-GL, SCARLET-KGL, CONGO RED, BRILLIANT VIOLET-BK, SUPRA BLUE-G, SUPRA BLUE-GL, SUPRA ORANGE-GL, direct dye SKY BLUE, high fastness direct dye ORANGE-S, high fastness BLACK, etc.

These dichroic substances may be used in one type or in combination of two or more types. When the organic dye is used, for example, from the viewpoint of achieving neutralization in the visible light range, it is preferred to combine two or more types. Specific examples include, for example, a combination of CONGO RED and SUPRA BLUE-G, a combination of SUPRA ORANGE-GL and direct dye SKY BLUE, or a combination of direct dye SKY BLUE and high fastness BLACK.

A solution obtained by dissolving the above-mentioned dichroic substance in a solvent can be used as the solution of the dye bath. Generally, water is used as the solvent, but an organic solvent compatible with water is further added. The concentration of the dichroic substance is preferably in the range of 0.010 to 10% by weight, more preferably in the range of 0.020 to 7% by weight, and particularly preferably in the range of 0.025 to 5% by weight.

Further, when iodine is used as the dichroic substance, it is preferable to add an iodide from the viewpoint of further improving the dyeing efficiency. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The proportion of such iodide added to the dye bath is preferably from 1010 to 10% by weight, more preferably from 0.10 to 5% by weight. Among them, potassium iodide is more preferably added, and the ratio (weight ratio) of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, and preferably in the range of 1:6 to 1:80. : The range of 7~1:70 is particularly good.

The immersion time for immersing the PVA film in the dye bath is not particularly limited, but is preferably in the range of 1 to 20 minutes, and preferably in the range of 2 to 10. Further, the temperature of the dyeing bath is preferably in the range of 5 to 42 ° C, and preferably in the range of 10 to 35 ° C. Furthermore, the PVA film can also be stretched in the dye bath, and the cumulative total stretch ratio at this time is about 1.1 to 4.0 times.

Further, the dyeing treatment may be, for example, a method of applying or spraying an aqueous solution containing a dichroic substance onto the PVA film, in addition to the method of immersing in the dye bath, as described above, or in addition to the PVA. A dichroic substance is mixed in advance when the film is formed.

The crosslinking step can be carried out, for example, by immersing the PVA film in a bath containing a crosslinking agent. As the aforementioned crosslinking agent, those which have hitherto been known can be used. For example, a boron compound such as boric acid or borax, or glyoxal or glutaraldehyde can be mentioned. One type may be used, and two or more types may be used in combination. When two or more types are used in combination, for example, a combination of boric acid and borax is preferred, and the addition ratio (mol ratio) is preferably in the range of 4:6 to 9:1, and 5.5:4.5. The range of ~7:3 is better, and the best is 6:4.

As the solution of the crosslinking bath, a solution obtained by dissolving the above crosslinking agent in a solvent can be used. For example, water may be used as the solvent, but in addition to this, an organic solvent solution compatible with water may be contained. The concentration of the crosslinking agent in the solution is not limited thereto, but is preferably in the range of 1 to 10% by weight, and preferably 2 to 6% by weight.

From the viewpoint of obtaining in-plane uniformity characteristics of the polarizing film, iodide may be added to the crosslinking bath. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The combination of boric acid and potassium iodide is preferred, and the ratio (weight ratio) of boric acid to potassium iodide is preferably in the range of 1:0.1 to 1:3.5, and is in the range of 1:0.5 to 1:2.5. good.

The temperature of the crosslinking bath is generally in the range of 20 to 70 ° C, and the immersion time of the PVA film is usually in the range of 1 second to 15 minutes, and preferably 5 seconds to 10 minutes. Further, the crosslinking treatment is the same as the dyeing treatment, and a method of coating or spraying a solution containing a crosslinking agent may be used, and a PVA film may be extended in the crosslinking bath, and the cumulative total stretching ratio at this time is 1.1 to 4.0 times. about.

The above-mentioned stretching step may, for example, be a wet stretching method in which it is extended in a state of being immersed in a bath so that the cumulative total stretching ratio is about 2 to 7 times.

The solution of the stretching bath is not particularly limited, and for example, a solution in which a compound of various metal salts, iodine, boron or zinc is added is used. As the solvent of the solution, water, ethanol or various organic solvents can be suitably used. Among them, a solution obtained by adding boric acid and/or potassium iodide in an amount of about 2 to 18% by weight is preferably used. When the boric acid and potassium iodide are used at the same time, the ratio (weight ratio) thereof is used in a ratio of about 1:0.1 to 1:4, and is preferably used in a ratio of about 1:0.5 to 1:3.

The temperature of the stretching bath is preferably in the range of 40 to 67 ° C, and preferably 50 to 62 ° C.

The step of bringing the PVA film into contact with the aqueous solution containing the salt of the Group 2 element can be carried out, for example, by immersing the PVA film in the aqueous solution. Thereby, an iodine adsorption site can be formed on the surface of the PVA film. The aqueous solution containing a salt of the Group 2 element may, for example, be an aqueous solution of an iodide selected from at least one of a group consisting of strontium, magnesium, calcium, strontium, barium, and radium. Further, the concentration of the Group 2 element salt is preferably 2.2 to 3.8 wt%, and more preferably 2.7 to 3.3 wt%. If the concentration is less than 2.2% by weight, light absorption in a short wavelength range of visible light may be insufficient. On the other hand, when the concentration is more than 3.8% by weight, light in the long wavelength range of visible light may be insufficient. Moreover, the immersion time is preferably 3 to 25 seconds, preferably 5 to 15 seconds. Furthermore, the bath temperature is preferably from 10 to 60 ° C, and preferably from 15 to 40 ° C. Moreover, the number of times of the immersion treatment in this step is not particularly limited and is performed plural times. Further, the type or concentration of the additive in the bath may be appropriately changed depending on the number of times.

In the washing step, for example, an unnecessary residue such as boric acid adhered to the previous treatment can be washed away by immersing the PVA film in the aqueous washing bath solution. A salt of the above-described Group 2 element may be added to the aqueous solution, and the base may be used, for example, as an iodide of the Group 2 element. When a salt of a Group 2 element is added to the washing bath, the concentration is usually 2.2 to 3.8% by weight, and preferably 2.7 to 3.3% by weight. Further, the temperature of the washing bath is preferably from 10 to 60 ° C, and preferably from 15 to 40 ° C. In addition, the number of times of the washing step is not particularly limited, and may be carried out after a plurality of times after the above steps. Further, the type or concentration of the additive in each washing bath can be changed.

Further, in order to prevent the occurrence of dripping when the PVA film is pulled up from the respective treatment baths, a liquid removal roller such as a pinch roller which is well known can be used, or it can be cut by an air knife. A method such as a liquid removes excess water.

Although the drying step can be carried out by a suitable method such as natural drying, air drying, or heat drying, it is usually preferred to use heat drying. In the heating and drying, for example, the heating temperature is about 20 to 80 ° C, and the drying time is preferably about 1 to 10 minutes.

The final total stretch ratio of the polarizing film produced through each of the above steps is preferably 3.0 to 7.0 times and preferably 5.5 to 6.2 times the PVA film before the treatment. When the final total stretch ratio is less than 3.0 times, it is difficult to obtain a polarizing film having a high degree of polarization, and if it is more than 7.0 times, the film is easily broken.

The polarizing film of the present embodiment is obtained by the above-described production method, and the monomer transmittance when measured by the polarizing film monomer is preferably 40% or more, and preferably 42.0 to 45.0%.

A transparent protective film may be provided on at least one side of the polarizing film. As a constituent material of the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and isotropic property can be used. Specific examples of such a thermoplastic resin include a cellulose resin such as triethyl fluorenyl cellulose, a polyester resin, a polyether oxime resin, a polyfluorene resin, a polycarbonate resin, a polyamide resin, and a polyimine. Resin, polyolefin resin, (meth)acrylic resin, cyclic polyolefin resin A mixture of an olefinic resin, a polyarylate resin, a polystyrene resin, a polyvinyl alcohol resin, and the like. Further, the transparent protective film may be bonded to the one side of the polarizing film by the adhesive layer, but the (meth)acrylic, urethane or urethane acrylate may be used on the other side. A thermosetting resin such as an epoxy resin or a polyoxygen oxide or an ultraviolet curable resin is used as the transparent protective film. One or more optional additives may be contained in the transparent protective film. The additive may, for example, be an ultraviolet absorber, an antioxidant, a slip agent, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a colorant or the like. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and most preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the original high transparency of the thermoplastic resin or the like may not be sufficiently exhibited.

Further, the transparent protective film may be a polymer film described in JP-A-2001-343529 (WO01/37007), for example, containing the following resin composition: (A) having a substitution on the side chain and/or A non-substituted quinone imine-based thermoplastic resin, and (B) a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitrile group in a side chain. Specific examples include a film comprising a resin composition of an alternating copolymer of isobutylene and N-methylbutyleneimine and an acrylonitrile/styrene copolymer. As the film, a film composed of a mixed extrusion of a resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, the unevenness due to the deformation of the polarizing plate can be eliminated, and the moisture permeability is small, so that the humidifying durability is excellent.

Although the thickness of the transparent protective film can be appropriately determined, it is generally about 1 to 500 μm from the viewpoints of workability such as strength and workability, and thin layer properties. In particular, it is preferably 1 to 300 μm, and more preferably 5 to 200 μm. The transparent protective film is particularly suitable when it is 5 to 150 μm.

Further, when a transparent protective film is provided on both sides of the polarizing film, a protective film formed of the same polymer material may be used in the front surface thereof, and a protective film formed of a different polymer material may also be used.

As the transparent protective film of the present embodiment, at least one selected from the group consisting of a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, and a (meth)acrylic resin is preferably used.

The cellulose resin is an ester of cellulose and a fatty acid. Specific examples of such a cellulose ester-based resin include triethyl fluorenyl cellulose, diethyl hydrazine cellulose, tripropyl cellulose, and dipropyl cellulose. Among them, triethyl fluorenyl cellulose is particularly preferred. Triethylenesulfonyl cellulose has many commercially available products, and is therefore advantageous from the viewpoint of availability and cost. For example, the product name "UV-50", "UV-80", "SH-80", "TD-80U" manufactured by Fuji Photo Film Co., Ltd., and the like are commercially available. "TD-TAC", "UZ-TAC", "KC Series" made by KONICA, etc. In general, the in-plane retardation (Re) of the triacetyl cellulose is substantially zero, but the thickness direction retardation (Rth) is about 60 nm.

A specific example of the cyclic polyolefin resin is preferably a drop An olefinic resin. The cyclic olefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit, and the like, for example, Japanese Laid-Open Patent Publication No. Hei No. Hei. The resin described. Specific examples thereof include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (a representative random copolymer). And a graft polymer obtained by denaturation of an unsaturated carboxylic acid or a derivative thereof, and a hydride or the like thereof. Specific examples of cyclic olefins can be mentioned An olefinic monomer.

The cyclic polyolefin resin is commercially available as various products. Specific examples include the product names "ZEONEX" and "ZEONOR" manufactured by Zeon Co., Ltd., the product name "ARTON" manufactured by JSR Co., Ltd., and the product name "TOPAS" manufactured by TICONA Co., Ltd., manufactured by Mitsui Chemicals, Inc. The product name is "APEL".

The (meth)acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C or more, more preferably 120 ° C or more, more preferably 125 ° C or more, and most preferably 130 ° C or more. By setting the Tg to 115 ° C or more, the durability of the polarizing plate can be improved. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, but is preferably 170 ° C or less from the viewpoint of moldability. A film having an in-plane retardation (Re) and a thickness direction retardation (Rth) of substantially zero can be obtained from the (meth)acrylic resin.

The (meth)acrylic resin can be any suitable (meth)acrylic resin insofar as it does not impair the effects of the present invention. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymerization, methyl methacrylate-(meth)acrylate copolymer, and methyl group may be mentioned. Methyl acrylate-acrylate-(meth) propylene copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-A) Cyclohexyl acrylate copolymer, methyl methacrylate-(meth) acrylate Ester copolymers, etc.). Preferably, poly-C1-6 alkyl methacrylate such as methyl (meth) acrylate is used. More preferably, a methacrylic resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) may be mentioned.

Specific examples of the (meth)acrylic resin include Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and (meth)acrylic acid having a ring structure in the molecule described in JP-A-2004-70296. A resin, a high Tg (meth) methacrylate resin obtained by intramolecular crosslinking or intramolecular cyclization.

As the (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure can be used. Due to its high heat resistance, high transparency, and high mechanical strength due to biaxial stretching.

The (meth)acrylic resin having a lactone ring structure, for example, is disclosed in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544 A (meth)acrylic resin having a lactone ring structure described in JP-A-2005-146084.

The transparent protective film is generally used in which the front phase difference is less than 40 nm and the thickness direction retardation is less than 80 nm. The front phase difference Re is represented by Re = (nx - ny) × d. The thickness direction phase difference Rth is represented by Rth = (nx - nz) × d. Further, the Nz coefficient is expressed by Nz = (nx - nz) / (nx - ny). [However, the refractive indices of the film in the slow axis direction, the phase axis direction, and the thickness direction are respectively nx, ny, nz, and the thickness of the d (nm) film. The retardation axis direction is the direction in which the refractive index in the plane of the film becomes the largest. ]. Also, the transparent protective film should be as colored as possible. It is preferable to use a protective film having a thickness direction retardation of -90 nm to +75 nm. By using such a thickness direction retardation value (Rth) of -90 nm to +75 nm, the polarizing plate coloring (optical coloring) caused by the transparent protective film can be eliminated. The thickness direction retardation value (Rth) is preferably from -80 nm to +60 nm, and particularly preferably from -70 nm to +45 nm.

On the other hand, as the transparent protective film, a phase difference plate having a front phase difference of 40 nm or more and/or a thickness direction of a retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When the phase difference plate is used as a transparent protective film, the phase difference plate also functions as a transparent protective film, so that the thickness can be reduced.

The transparent protective film may also be subjected to surface modification treatment before the application of the adhesive. Specific treatments include, for example, corona treatment, plasma treatment, primer treatment, alkalization treatment, and the like.

On the surface of the transparent protective film which is not attached to the polarizing film, a hard coating layer or an anti-reflection treatment may be applied, and the treatment for adhesion inhibition, diffusion, or even anti-glare may be applied.

Further, the antireflection layer, the adhesion suppressing layer, the diffusion layer, the antiglare layer, and the like may be provided on the transparent protective film, or may be provided as an optical layer for other uses as a separate from the transparent protective film.

The polarizing plate of the present invention is produced by laminating a transparent protective film and a polarizing film by using the above-mentioned adhesive. The production method includes a step of applying the adhesive on the surface of the adhesive layer forming surface of the polarizing film and/or the adhesive layer forming surface of the transparent protective film, and bonding the polarizing film with the adhesive for the polarizing plate. The step of transparently protecting the film.

The polarizing plate of the present embodiment can be used as an optical film laminated with an optical layer in actual use. Although the optical layer is not particularly limited, for example, one or two or more reflective or semi-transmissive plates, a retardation plate (including a wavelength plate of 1/2, 1/4, etc.), a viewing angle compensation film, or the like can be used. An optical layer of a liquid crystal display device or the like is formed.

An optical film obtained by laminating the optical layer on a polarizing plate can be formed by laminating in a sequential manner in a manufacturing process of a liquid crystal display device or the like. However, an optical film formed by laminating in advance has quality stability and is superior to each other. The assembly work improves the advantages of the manufacturing steps of the liquid crystal display device or the like. The laminate system may use an appropriate bonding method such as an adhesive layer. When the polarizing plate or another optical film is attached, the optical axis of the polarizing plate or the like may be set to an appropriate arrangement angle in accordance with the phase difference characteristic or the like.

An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate or the optical film in which at least one polarizing plate is laminated. The adhesive for forming the adhesive layer is not particularly limited, and, for example, the following may be appropriately selected: an acrylic polymer, a polyoxymethylene polymer, a polyester, a polyurethane, a polyamide, a poly A polymer such as an ether, a fluorine-based or a rubber-based polymer is used as a base polymer. In particular, an acrylic pressure-sensitive adhesive is preferably used, which is excellent in optical transparency, exhibits appropriate wettability, cohesiveness and adhesion properties, and is excellent in weather resistance and heat resistance.

For the exposed surface of the adhesive layer, it may be temporarily covered with a separator to prevent it from being contaminated until it is actually used. Thereby, contact with the adhesive layer in the conventional operation state can be prevented. In addition to the aforementioned thickness conditions, for example, a suitable sheet such as a plastic film, a rubber sheet, a paper, a cloth, a non-woven fabric, a net, a foamed sheet, a metal foil, or the like may be used, and the like may be used as needed. Those who apply a suitable release agent such as a polyoxymethylene system, a long-chain alkyl group, a fluorine-based or a molybdenum sulfide are suitable according to the existing standards.

The polarizing plate of the present embodiment can be suitably used for various image display devices such as liquid crystal display devices and organic electroluminescence devices. When applied to a liquid crystal display device, the polarizing plate of the present embodiment can be disposed such that the light transmission axis is perpendicular to the surface and the inside of the liquid crystal cell. Thereby, a liquid crystal display device capable of reducing light leakage in the visible light wavelength range and preventing discoloration of the display screen can be obtained. The liquid crystal cell is not particularly limited, and for example, any of TN type, STN type, π type, VA type, IPS type, or the like can be suitably used.

Example

Hereinafter, preferred embodiments of the present invention will be exemplarily described in detail. However, the materials, the blending amounts, and the like described in the examples are not limited to the description, and the scope of the present invention is by no means limited to the scope of the invention.

(Example 1)

A polyvinyl alcohol (PVA) film having a thickness of 75 μm, a film width of 50 mm, a polymerization degree of 2,400, and a degree of alkalinity of 99.9% or more was subjected to each step in the following order to prepare an iodine-based polarizing film of the present Example.

<Swelling step>

The PVA film was transferred to a swelling bath filled with pure water, and immersed in pure water at 30 ° C for 30 seconds to swell. Furthermore, one-axis stretching was performed until the stretching ratio was 2.2 times.

<staining step>

The PVA film was transferred to a dye bath filled with an iodine dyeing solution containing iodine in an amount of 0.035 wt%, and immersed in an iodine dyeing solution at 30 ° C for 27 seconds while stretching one axis until the stretching ratio became 3.3 with respect to the initial PVA film. Dye and dye.

<Crosslinking step>

The PVA film was transferred to a cross-linking bath filled with an aqueous solution of boric acid containing 3.0% by weight of potassium iodide and 3.0% by weight of boric acid, and immersed in an aqueous solution of boric acid at 30° C. for 28 seconds while stretching one axis until the stretching ratio became relative to the initial The PVA film was crosslinked by 3.6 times.

<Extension step>

The PVA film subjected to the above treatment was transferred to an extension bath filled with a boric acid aqueous solution containing 5.0% by weight of potassium iodide and 4.0% by weight of boric acid, and immersed in a boric acid aqueous solution at 60 ° C for 58 seconds while performing one-axis extension until the stretching ratio thereof. It was 5.9 times as large as that of the initial PVA film.

<Group 2 element import step>

The PVA film was transferred to a bath filled with an aqueous solution containing 0.093 mol/l of MgI ₂ , and immersed in the aforementioned aqueous solution at 30 ° C for 10 seconds.

Thereafter, the drying of the PVA film was carried out using an oven. The drying conditions were a drying temperature of 60 ° C, and the time passed through the oven was set to 4 minutes.

(Examples 2 and 3)

2 and in Example 3, lines such as shown in the following Table 2, except that the second elements are introduced into the step _2, BaI2 ₂ instead of outside MgI _2, with the same manner as in Example 1 an iodine-based polarizer with each CaI film.

(Comparative examples 1 to 3)

In Comparative Examples 1 to 3, as in the following Table 3, the same procedure as in Example 1 was carried out except that 0.16 mol/l of LiI, NaI, and KI were used instead of MgI ₂ in the group 2 element introduction step. Each iodine-based polarizing film was produced.

(Examples 4 to 10)

In each of Examples 4 to 10, each iodine-based polarizing film was produced in the same manner as in the above Example 1, except that the concentration of MgI ₂ was changed as shown in the following Table 4 in the group 2 element introduction step. Further, the amount of Mg present in each polarizing film is a value measured by chelation titration using an EDTA (ethylenediaminetetraacetic acid) standard solution and an EBT (dyeing black T) indicator.

(Comparative Example 4)

In Comparative Example 4, in addition to elements introduced in the second step to 0.093mol / l in place of ZnI2 ₂ MgI _2, with the same manner as in Example 1 an iodine-based polarizing film.

<Vertical band>

The monomer transmittance and the vertical transmittance of the polarizing film were measured by a spectrophotometer (V7100, manufactured by JASCO Corporation) equipped with an integrating sphere. The transmittance with respect to each linearly polarized light was measured by setting the total polarized light obtained by the Glanterra-稜鏡 polarizing film to 100%. The measurement wavelength of the vertical transmittance is performed at wavelengths of 410 nm and 700 nm. Further, the monomer transmittance is expressed by a Y-value of the visual sensitivity adjustment by a 2 degree field of view (C light source) of JIS Z8701 together with a measurement result of a measurement wavelength of 380 nm to 780 nm. The results are shown in Tables 2 to 5.

(production of polarizing plate)

As the transparent protective film, a triethylenesulfonated cellulose film having a thickness of 80 μm was used. Further, the adhesive for bonding the iodine-based polarizing film obtained in each of the examples and the comparative examples and the transparent protective film was prepared as follows. That is, at a temperature of 30 ° C, it is relative to a polyvinyl alcohol resin containing an ethyl sulfonium group (average degree of polymerization 1200, degree of alkalinity 98.5 mol%, degree of acetylation 5 mol% 100 parts by weight of 32 parts by weight of methylol melamine was dissolved in pure water to prepare an aqueous solution of an adhesive having a solid portion concentration adjusted to 3.2%.

Using the above-mentioned adhesive, the transparent protective film was bonded to both surfaces of the iodine-based polarizing film produced in Example 1 and Comparative Example 4 at a temperature of 24 ° C, and then dried at 60 ° C. A polarizing plate was obtained in 12 minutes. The obtained polarizing plate was evaluated for the degree of polarization.

(polarization)

The obtained polarizing plate was allowed to stand under heating at a temperature of 80 ° C for 120 hours, and the degree of polarization before and after the measurement was measured. The results are shown in Table 5. Further, the degree of polarization was measured using a spectrophotometer (V7100, manufactured by JASCO Corporation) equipped with an integrating sphere and measuring wavelengths of 380 nm to 780 nm. Further, the degree of polarization is obtained by using the following formula: the transmittance (parallel transmittance: H ₀ ) when the same two polarizing plates are overlapped in such a manner that the light transmission axes of the two are perpendicular to each other, and both The transmittance of the transmission axis perpendicularly coincides with the transmittance (vertical transmittance: H ₉₀ ).

Polarization degree (%)={(H ₀ -H ₉₀ )/(H ₀ +H ₉₀ )} ^1/2 ×100

Each of the transmittances was set to 100% with complete polarization obtained by the Glanterra-稜鏡 polarizing film. The Y value of the visual sensitivity adjustment is expressed by a 2 degree field of view (C light source) of JIS Z8701.

(result)

As is apparent from the above-mentioned Tables 2 to 4, it was confirmed that the iodine-based polarizing films of the present inventions of Examples 1 to 10 can be suppressed to have a low vertical transmittance at a wavelength of 700 nm, and can be achieved in a long wavelength range of visible light. Prevention of leakage. On the other hand, it was confirmed that the vertical transmittance of any of the polarizing films of Comparative Examples 1 to 3 was large, and light leakage occurred.

Further, as apparent from the above Table 4, it was confirmed that the iodine-based polarized light of Examples 5 to 9 in which the amount of Mg per 1 g of the polarizing film was in the range of 5.6 × 10 ^-5 to 9.7 × 10 ^-5 mol/g. The film has a good balance of vertical transmittance at 410 nm and 700 nm and can prevent light leakage in both wavelength ranges.

Further, the polarizing plate using the polarizing film of Example 1 and the polarizing plate using the polarizing film of Comparative Example 4 were subjected to an endurance test at 80 ° C for 120 hours, and after investigating the degree of polarization, it was found that the polarizing film of Example 1 was used. The plate has less reduction in its degree of polarization. Thereby, it was confirmed that the polarizing plate of the present invention is excellent in optical reliability even under severe conditions.

Claims (4)

An iodine-based polarizing film comprising iodine adsorbed to a polyvinyl alcohol film and containing an iodide of a Group 2 element, wherein the Group 2 element is present in a amount of 5.6×10 ^-5 to 9.7×10 ^-5 Within the range of mol/g. A method for producing an iodine-based polarizing film, wherein the iodine-based polarizing film is configured to adsorb iodine to a polyvinyl alcohol film, and the method comprises the step of: concentrating an aqueous solution of an iodide of a Group 2 element with the iodine adsorbed The step of contacting the vinyl alcohol film, wherein the amount of the Group 2 element in the iodine-based polarizing film is in the range of 5.6 × 10 ^-5 to 9.7 × 10 ^-5 mol/g. The method for producing an iodine-based polarizing film according to the second aspect of the invention, wherein the step is performed after the step of stretching a polyvinyl alcohol film, and dyeing the polyvinyl alcohol film in an aqueous solution containing iodine and potassium iodide. The step of immersing the dyed polyvinyl alcohol film in an aqueous solution containing boric acid. A polarizing plate is provided with a transparent protective film on a surface of at least one side of the iodine-based polarizing film of claim 1 of the patent application.