Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
  • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
  • G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
  • G02B5/305—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
  • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
  • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

• the present invention relates to a polarizing element and a polarizing plate having uniform transmittance at each wavelength.
• a polarizing element is generally produced by adsorbing and orienting iodine or dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film.
• a protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used for a liquid crystal display device or the like.
• a polarizing plate using iodine as a dichroic dye is called an iodine polarizing plate, while a polarizing plate using a dichroic dye as a dichroic dye is called a dye polarizing plate.
• dye-based polarizing plates have high heat resistance, high humidity heat durability, high stability, and are characterized by high color selectivity by blending, while having the same degree of polarization.
• the transmittance is low compared to the plate, that is, the contrast is low.
• the transmittance from 380 nm to 480 nm is lower than the transmittance from 500 nm to 600 nm, and the light emission uniformity at each wavelength cannot be maintained. It was. Therefore, for example, when the absorption axes of the polarizing elements are installed in parallel, an attempt has been made to improve each wavelength transmittance so as to have a certain transmittance.
• the wavelength of 380 nm to 480 nm, particularly the wavelength of 460 nm is higher than the transmittance near 550 nm where the visibility is high, and the contrast is lowered. there were. Therefore, there has been a demand for a polarizing element or a polarizing plate that has a high polarization performance, that is, a high contrast and can keep the wavelength transmittance in the visible region constant.
• Patent Document 1 discloses a technique of a polarizing element having a transmittance of 0.001% to 0.1% at 410 nm in crossed Nicols in a polarizing element having a film thickness of 8 to 18 ⁇ m. However, this technique only improves orthogonal color loss and hue, and does not improve the wavelength transmittance at the parallel position.
• Patent Document 2 discloses a technology of a polarizing element made of a film having a structure in which microregions are dispersed in a matrix formed of a water-soluble resin containing a divalent metal. However, even with this technique, a polarizing element or a polarizing plate in which the transmittance of each wavelength at the parallel position and the orthogonal position is constant has not been obtained.
• the inventor of the present invention has completed the present invention as a result of intensive studies to solve the above problems.
• the present invention “(1) A polarizing element comprising a base material having a polarizing function, which is composed of a hydrophilic polymer drawn by adsorbing boric acid and containing iodine,
• the visibility corrected single transmittance Ys is 40.0% to 42.5%, The difference between the visibility corrected single transmittance Ys and the single transmittance Ts 460 at 460 nm is within 1%;
• the difference between the visibility corrected single transmittance Ys and the single transmittance Ts 550 at 550 nm is within 1%;
• the difference between the visibility corrected single transmittance Ys and the single transmittance Ts 610 at 610 nm is within 1%
• Visibility corrected parallel transmittance Yp when the two base materials are measured parallel to the absorption axi
• the base material comprises a polyvinyl alcohol-based resin film, The polarizing element according to any one of (1) to (5) above, wherein the polymerization degree of the polyvinyl alcohol-based resin film is 3000 to 7000; (7) A polarizing plate provided with a support film on at least one surface of the polarizing element according to any one of (1) to (6) above; (8) A liquid crystal display device comprising the polarizing element according to any one of (1) to (6) or the polarizing plate according to (7); (9) A method for producing a polarizing element comprising a base material having a polarizing function comprising a hydrophilic polymer adsorbed with boric acid and stretched, and containing iodine, (I) adding a dichroic dye to the polyvinyl alcohol-based resin film and obtaining a film containing the dichroic dye; (Ii) stretching the film containing the dichroic dye to obtain a stretched film; (Iii) subject
• the present invention relates to a polarizing element and a polarizing plate having a constant transmittance at each wavelength, the polarizing element and the polarizing plate have a high transmittance, a high contrast ratio, and a very high color reproducibility. It can be used as a polarizing plate for a display, particularly a polarizing plate for a liquid crystal display.
• polarizing element for example, a step of swelling a hydrophilic polymer film, a dyeing step of containing a dichroic dye, a water-resistant treatment step if necessary, then a stretching step Next, a method of producing through a post-treatment step and finally a drying step can be mentioned.
• hydrophilic polymer film used for the polarizing element examples include films made of polyvinyl alcohol resin, amylose resin, starch resin, cellulose resin, polyacrylate resin, and the like.
• the film formed into a film is used.
• a polyvinyl alcohol resin (hereinafter sometimes abbreviated as “PVA”) film is preferable.
• PVA polyvinyl alcohol resin
• a polarizing element comprising a polyvinyl alcohol resin film and a dichroic substance such as iodine is most preferable.
• the thickness of these polarizing elements is not particularly limited, but is generally about 5 to 80 ⁇ m.
• the method for producing the polyvinyl alcohol resin is not particularly limited, and can be produced by a known method.
• a polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin.
• examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith.
• examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.
• This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. What formed the polyvinyl alcohol-type resin into a film is used as a polyvinyl alcohol-type resin film.
• the degree of polymerization of PVA needs to be 3000 to 10,000, and if the degree of polymerization of PVA is less than 3000, it is difficult to express high polarization performance. Become. When the degree of polymerization exceeds 7000, PVA becomes hard, the film forming property and stretchability are lowered, and the productivity is lowered. Therefore, it is preferably 10,000 or less from an industrial viewpoint.
• the degree of polymerization of PVA means the degree of polymerization (viscosity average degree of polymerization) measured as follows. 0.28 g of PVA is dissolved at 95 ° C. with 70 g of distilled water to prepare a 0.4% PVA aqueous solution and cooled to 30 ° C. It cools in a 30 degreeC constant temperature water tank, and is set as the sample for a polymerization degree measurement. Next, 10 mL of the polymerization degree measurement sample is dried in an evaporating dish for 20 hours with a dryer at 105 ° C., and the weight [ ⁇ (g)] after drying of the polymerization degree measurement sample is measured. The concentration C (g / L) of the sample for measuring the degree of polymerization is calculated by the following formula (i).
• a sample for measuring the degree of polymerization or distilled water is put into an Ostwald viscometer with a 10 mL whole pipette and stabilized in a constant temperature water bath at 30 ° C. for 15 minutes.
• the falling seconds t 1 (seconds) and the falling seconds t 0 (seconds) of the distilled water measurement sample were measured, and the viscosity average polymerization degree E was calculated from the following formulas (ii) to (iv). To do.
• the saponification degree of PVA is preferably 99 mol% or more, more preferably 99.5 mol% or more.
• the degree of saponification is less than 99 mol%, PVA is likely to elute, causing in-plane unevenness in optical properties, a decrease in dyeability in the dyeing process, and a cutting in the stretching process, thereby significantly reducing productivity. There is fear and it is not preferable.
• the PVA used in the present invention can be produced by saponifying a polyvinyl ester polymer obtained by polymerizing a vinyl ester.
• vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and the like. 1 type or 2 types or more are selected. Among these, vinyl acetate is preferably used.
• polymerization temperature When using methanol as a superposition
• PVA is not limited to a saponified vinyl ester homopolymer unless the effects of the present invention are impaired.
• a modified PVAl vinyl ester obtained by graft copolymerizing PVA with an unsaturated carboxylic acid or derivative thereof, an unsaturated sulfonic acid or derivative thereof, an ⁇ -olefin having 2 to 30 carbon atoms, etc.
• a film original can be obtained by forming a film of PVA obtained as described above.
• a PVA film forming method in addition to a method of melt-extruding hydrous PVA, a casting film forming method, a wet film forming method (discharging into a poor solvent), a gel film forming method (a PVA aqueous solution was once cooled and gelled). Thereafter, a solvent is extracted and removed), a cast film forming method (a PVA aqueous solution is poured onto a substrate and dried), a method using a combination of these, and the like, but are not limited thereto.
• Examples of the solvent used for film formation include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, Examples include, but are not limited to, ethylenediamine, diethylenetriamine, and water.
• One type of solvent may be used, or two or more types may be mixed and used.
• the amount of the solvent used for film formation is, for example, 50 to 95% by mass, preferably 70 to 95% by mass, but is not limited to these ranges.
• the amount of the solvent is less than 50% by mass, the viscosity of the film-forming stock solution becomes high, and filtration and defoaming at the time of preparation become difficult, and it is difficult to obtain a film original that does not contain foreign substances and has no defects. It becomes.
• the volatile content exceeds 95% by mass, the viscosity of the film-forming stock solution becomes too low, making it difficult to control the target thickness. Sex is reduced.
• a plasticizer may be used in the production of the original film.
• the plasticizer include glycerin, diglycerin, ethylene glycol and the like, but are not limited thereto.
• the amount of the plasticizer to be used is not particularly limited, but usually it is preferably within the range of 5 to 15 parts by mass with respect to 100 parts by mass of PVA.
• Examples of the method for drying the film after film formation include, but are not limited to, drying with hot air, contact drying using a hot roll, and drying using an infrared heater. One of these methods may be employed alone, or two or more may be combined and dried.
• the drying temperature is not particularly limited but is preferably in the range of 50 to 70 ° C.
• the heat treatment method of the film original after film formation include a method using hot air and a method of bringing the film original into contact with a hot roll, and are not particularly limited as long as the method can be processed by heat. One of these methods may be adopted alone, or two or more may be combined.
• the heat treatment temperature and time are not particularly limited, but are preferably within a range of 110 to 140 ° C., and a treatment of approximately 1 to 10 minutes is suitable, but is not particularly limited.
• the thickness of the original film thus obtained is preferably 20 to 100 ⁇ m, more preferably 20 to 80 ⁇ m, and further preferably 20 to 60 ⁇ m.
• the thickness is less than 20 ⁇ m, the film is easily broken.
• the thickness exceeds 100 ⁇ m, the stress applied to the film at the time of stretching increases, the mechanical load in the stretching process increases, and a large-scale apparatus is required to withstand the load.
• the swelling degree F of the original film is preferably 180 to 250%, more preferably 205 to 235%, and further preferably 210 to 230%.
• the degree of swelling F is less than 180%, the elongation at the time of stretching is small, the possibility of breaking at a low magnification becomes high, and it becomes difficult to perform sufficient stretching.
• the degree of swelling F exceeds 240%, the swelling becomes excessive, wrinkles and slack are generated, which causes cutting during stretching.
• a suitable degree of swelling F can be achieved depending on the temperature and time when the original film after film formation is heat-treated.
• the method for measuring the degree of swelling F of the original film is as follows.
• the original film is cut into 5 cm ⁇ 5 cm and immersed in 1 liter of distilled water at 30 ° C. for 4 hours.
• the soaked film is taken out from the distilled water, and after absorbing water droplets on the surface with two filter papers, the weight [ ⁇ (g)] of the film soaked in water is measured. Further, the film soaked and absorbed with water droplets was dried with a dryer at 105 ° C. for 20 hours, cooled with a desiccator for 30 minutes, and then the weight [ ⁇ (g)] of the dried film was measured.
• the swelling degree F of the original film is calculated by v).
• the polarizing element of the present invention is produced by a method including the steps described below.
• the film original fabric described above is subjected to a swelling process for swelling the film.
• the swelling is achieved by immersing the polyvinyl alcohol resin film in a solution at 20 to 50 ° C. for 15 seconds to 10 minutes.
• the solution at that time is preferably water, but may be a water-soluble organic solvent such as glycerin, ethanol, ethylene glycol, propylene glycol, or low molecular weight polyethylene glycol, or a mixed solution of water and a water-soluble organic solvent.
• the stretching ratio is preferably 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. It is.
• the swelling effect can be obtained also in the dyeing process at the time of iodine and iodide treatment, so this process may be omitted.
• the swollen polyvinyl alcohol resin film is subjected to a dyeing process in which the film is dyed with a solution containing a dichroic dye.
• the solvent of the solution is preferably water, but is not particularly limited.
• the dichroic dye include polyiodine ions obtained from a mixed solution of iodine and iodide, dichroic dyes of organic compounds, and the like.
• the iodide for example, potassium iodide, ammonium iodide, cobalt iodide, zinc iodide and the like can be used, but the iodide is not limited to the iodide shown here.
• the iodine concentration in the mixed solution of iodine and iodide is 0.0001 to 0.5 wt%, preferably 0.001 to 0.4 wt%.
• the concentration of iodide used is preferably 0.0001 to 8 wt%.
• a dichroic dye described in Non-Patent Document 1 may be used as the dichroic dye of the organic compound, and color correction may be performed within a range that does not impair the performance required by the present application.
• the dye is not limited, and a known dichroic dye can be used.
• the dye concentration is not particularly limited, but for example, it is preferably about 0.006 wt% to 0.3 wt%.
• a coloring aid such as sodium tripolyphosphate and / or sodium nitrate (sodium sodium sulfate) for dyeing.
• the dyeing temperature is 5 to 50 ° C., preferably 5 to 40 ° C., more preferably 10 to 30 ° C.
• the dyeing time can be appropriately adjusted according to the transmittance of the polarizing element to be obtained, but is about 30 seconds to 6 minutes, more preferably 1 minute to 5 minutes. Also in this step, it is preferable to stretch appropriately in order to prevent generation of wrinkles and folds.
• the draw ratio is preferably 0.90 to 2.00 times, more preferably 1.00 to 1.30 times.
• a crosslinking agent and / or a water-resistant agent may be added to the solution containing the dichroic dye.
• the crosslinking agent include boron compounds such as boric acid, borax and ammonium borate, polyhydric aldehydes such as glyoxal and glutaraldehyde, polyhydric isocyanate compounds such as biuret type, isocyanurate type and block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used.
• water-resistant agents examples include succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride.
• Acid is good.
• the concentration to be added is 0.1 to 5.0 wt%, preferably 2 to 4 wt% with respect to the solution containing the dichroic dye.
• a solvent for washing water is generally used, but an alcohol solvent, a glycol solvent, glycerin or a mixed solvent thereof can be used and is not particularly limited. Further, the temperature and time for washing may be appropriately adjusted according to the transmittance of the target polarizing element and the type of dichroic dye used.
• the dyed film is subjected to a water resistance treatment process in which water resistance treatment is performed as necessary.
• the film is treated with a solution containing a crosslinking agent or / and a water resistance agent.
• a crosslinking agent and / or water-resistant agent include boron compounds such as boric acid, borax and ammonium borate, polyvalent aldehydes such as glyoxal and glutaraldehyde, polyisocyanates such as biuret type, isocyanurate type and block type.
• titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether, polyamide epichlorohydrin, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin Examples thereof include diglycidyl ether, ammonium chloride, magnesium chloride, and boric acid is preferable.
• the solvent at that time for example, water, an alcohol solvent, a glycol solvent, glycerin or a mixed solvent thereof can be used.
• the concentration of the crosslinking agent or / and the waterproofing agent is preferably about 0.1 wt% to 6.0 wt%, more preferably 2 wt% to 4 wt%.
• the treatment temperature in this step is about 5 to 60 ° C., preferably about 5 to 45 ° C.
• the treatment time is preferably about 1 to 5 minutes. Also in this step, in order to prevent the occurrence of wrinkles and folds, it is preferable to stretch appropriately, and the stretching ratio is about 0.95 to 1.5 times.
• Stretching process Furthermore, it uses for the extending process which extends
• the stretching method either a wet stretching method or a dry stretching method may be used.
• the dry stretching method include, but are not particularly limited to, an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, and an infrared heating stretching method.
• the stretching temperature is preferably from room temperature to 180 ° C.
• the humidity is preferably from 20 to 95% RH. Stretching may be performed in a single stage or may be a multi-stage stretching of two or more stages.
• the wet stretching method is a method of stretching in water, a water-soluble organic solvent, or a mixed aqueous solution thereof.
• the water, the water-soluble organic solvent, or a mixed aqueous solution thereof contains the boric acid, borax.
• Boron compounds such as ammonium borate, polyhydric aldehydes such as glyoxal and glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type and block type, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether , Polyamide epichlorohydrin, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride, etc.
• the concentration of the cross-linking agent or / and the water-resistant agent is preferably 0.5 to 8 wt%, and more preferably 2.0 to 4.0 wt%.
• the draw ratio is preferably about 3 to 8 times, more preferably about 5 to 7 times.
• the stretching temperature is preferably 40 to 60 ° C, more preferably 45 to 55 ° C.
• the stretching time is preferably 30 seconds to 20 minutes, more preferably 2 minutes to 5 minutes.
• the stretching process may be one stage or multistage stretching of two or more stages.
• the surface of the polyvinyl alcohol resin film containing the stretched dichroic dye may be washed because foreign matter may be deposited or foreign matter may adhere to the surface.
• a solvent for washing water, an alcohol-based solvent, or the like can be used, but it is not limited to these.
• the cleaning solvent may contain a crosslinking agent such as boric acid and / or a waterproofing agent for the purpose of improving the durability of the film.
• concentration of the crosslinking agent and / or the waterproofing agent is not limited, but is, for example, 0.1 to 10 wt%.
• a post-treatment process is performed in which the film is post-treated.
• the uniaxially stretched polyvinyl alcohol-based resin film containing a dichroic dye is treated with a solution containing chloride or iodide.
• the chloride or iodide include iodides such as potassium iodide, sodium iodide, ammonium iodide, cobalt iodide and zinc iodide, and chlorides such as zinc chloride, potassium chloride and sodium chloride. One or two or more of them are mixed into the solution for treatment.
• the concentration of chloride or iodide in the solution is preferably 0.1 to 15 wt%, more preferably 0.15 to 10 wt%. Also in this step, in order to prevent the occurrence of wrinkles and folds, it is preferable to draw appropriately, and the draw ratio at that time is preferably 0.90 to 1.10.
• the treatment temperature is preferably, for example, 5 to 50 ° C. or less, more preferably 20 to 40 ° C.
• the treatment time is, for example, about 1 second to 5 minutes, preferably 5 seconds to 30 seconds.
• the cross-linking agent and / or water-resistant agent may be added.
• the concentration to be added is, for example, 0.5% to 10 wt%.
• the solvent used in the treatment steps so far for example, water, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or
• the solvent include alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine, but are not limited thereto. A mixture of one or more of these solvents can also be used.
• the most preferred solvent is water.
• the substrate of the polarizing element of the present invention is obtained through a drying step.
• the drying method include natural drying, compression with a roll, a method of removing moisture on the surface with an air knife or a water absorption roll, and drying by heating.
• the drying temperature in the case of heat drying is preferably 20 to 90 ° C, more preferably 40 to 70 ° C.
• the drying time is preferably about 30 seconds to 20 minutes, more preferably about 2 minutes to 10 minutes.
• the draw ratio at that time is preferably 0.95 to 1.10 times .
• the substrate of the polarizing element is obtained through the swelling process, the dyeing process, the optional water resistance treatment process, the stretching process, the post-treatment process, and the drying process.
• the base material thus obtained has a visibility corrected single transmittance Ys of 40.0% to 42.5% when measured by itself, and the visibility corrected single transmittance Ys is 460 nm.
• the difference between the transmittance Ts 460 is within 1%
• the difference between the visibility corrected single transmittance Ys and the transmittance Ts 550 at 550 nm is within 1%
• the visibility corrected single transmittance Ys with the transmittance at 610 nm is adjusted to 0.01% or less.
• the concentration of the chloride or iodide contained in the solution and the treatment time must be adjusted according to the stretching conditions. It is very important that the concentration and the treatment time are adjusted according to the state of impregnation of the polarizing element with iodine and an iodide such as potassium iodide and a chloride such as potassium chloride. It is. In particular, the concentration is affected by the stretching state in the stretching process, the temperature and humidity of the place where the polarizing element is produced, and therefore requires very delicate fine adjustment.
• the concentration of the chloride-containing solution or iodide-containing solution used in the post-treatment step is 1.0 to 150 parts by weight, preferably 1.5 to 150 parts by weight of chloride or iodide with respect to 1000 parts by weight of water. It was prepared by adding 100 parts by weight. Further, it is preferable to carry out the treatment while maintaining the stretch ratio and / or stretch tension so that the film shrinks or expands as little as possible. Furthermore, it is preferable to process in a state where there is no difference in relative speed between the film transport speed and the water flow speed in the post-processing step. It is more preferable to sufficiently treat the inside.
• the polarizing element of this application can be obtained by performing a post-processing process by the above method.
• the visibility corrected parallel transmittance Yp obtained by measuring two base materials parallel to the absorption axis direction is in the range of 33% to 37%.
• the difference between the transmittance Yp and the transmittance Tp 460 at 460 nm when the two substrates are measured parallel to the absorption axis direction is within 3%.
• it is necessary to adjust the transmittance of 295 nm and the transmittance of 360 nm obtained by measuring two substrates in parallel with the absorption axis direction. is there.
• the transmittance of 295 nm and the transmittance of 360 nm are said to vary due to the content of polyiodine such as I 3 ⁇ and I 5 ⁇ in the polarizing element.
• the transmittance at 295 nm and 360 nm can be adjusted, and the difference between Yp and Tp 460 can be adjusted within 3%. it can.
• the visibility correction transmittance Yp obtained by measuring the two base materials parallel to the absorption axis direction is in the range of 33% to 37%
• the transmittance Yp and the transmittance Tp 295 at 295 nm when the two substrates are measured parallel to the absorption axis direction satisfy the following formula (1)
• the Yp and the substrate 2 It is necessary to adjust the transmittance Tp 360 of 360 nm when the sheet is measured parallel to the absorption axis direction so as to satisfy the following formula (2).
• the orientation of polyiodine such as I 3 ⁇ and I 5 ⁇ of 295 nm and 360 nm is improved.
• the transmittance Tc 295 at 295 nm when satisfying the above formulas (1) and (2) and measuring the two substrates perpendicular to the absorption axis direction is as follows: More preferably, the transmittance Tc 360 of 360 nm when satisfying the formula (3) and measuring the two base materials parallel to the absorption axis direction satisfies the following formula (4).
• each of Yp 18.6 , Yp 19.4 , Yp 22.12 and Yp 22.67 represents a multiplier of the parallel transmittance Yp.
• the transmittance of the polarizing element is such that the transmittance at 460 nm is 0.035% or less when two substrates are measured perpendicular to the absorption axis direction, and the two substrates are in the absorption axis direction. It is preferable to prepare such that the transmittance at 610 nm is 0.01% or less when measured perpendicularly.
• the present application can be easily achieved by using a raw film made of a polyvinyl alcohol resin film having a polymerization degree of 3000 to 10,000 as the base material of the polarizing element. More preferably, the degree of polymerization of the polyvinyl alcohol film is 3500 to 6000, and more preferably 4500 to 6000.
• the polarizing plate of the present invention can be obtained by providing a transparent protective layer on at least one surface or both surfaces of the polarizing element of the present invention obtained through the above steps.
• the transparent protective layer can be provided by applying or laminating a polymer or film forming the protective layer to the polarizing element of the present invention.
• the transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. Furthermore, the thing which is excellent in moisture barrier property is more preferable.
• the material used as the transparent protective layer examples include cellulose acetate resin such as triacetyl cellulose and diacetyl cellulose or a film thereof, acrylic resin or a film thereof, polyester resin or a film thereof, polyarylate resin or a film thereof, and cyclic such as norbornene.
• Cyclic polyolefin resin or film thereof containing olefin as monomer, polyethylene, polypropylene, polyethylene terephthalate, polyolefin having a cyclo type or norbornene skeleton or copolymer thereof, main chain or side chain of imide or / and amide resin or polymer or its A film etc. are mentioned.
• polyvinyl alcohol resin generally functions as an alignment film
• rubbing treatment or alignment film coating and alignment treatment is applied to the surface of the obtained polarizing element to obtain liquid crystal properties.
• You may provide resin or its film which has.
• the thickness of the protective film is, for example, about 0.5 to 200 ⁇ m. When these films are provided on both surfaces of the polarizing element, the same film may be used or different films may be used.
• an adhesive When laminating the film as the transparent protective layer with the polarizing element of the present invention, it is preferable to use an adhesive.
• the adhesive include polyvinyl alcohol, urethane, acrylic, and epoxy adhesives.
• the polyvinyl alcohol-based adhesive include, but are not limited to, GOHSENOL NH-26 (manufactured by Nihon Gosei Co., Ltd.), EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and the like.
• a cross-linking agent and / or a waterproofing agent may be added to the adhesive.
• the adhesive may contain an inorganic acid or a salt thereof and / or an organic acid at a concentration of 0.0001 wt% to 20 wt%, and preferably 0.02 to 5 wt%.
• an adhesive obtained by mixing a maleic anhydride-isobutylene copolymer alone or in combination with a crosslinking agent can be used.
• maleic anhydride-isobutylene copolymers for example, isoban # 18 (manufactured by Kuraray), isoban # 04 (manufactured by Kuraray), ammonia-modified isoban # 104 (manufactured by Kuraray), ammonia-modified isoban # 110 (manufactured by Kuraray) ), Imidized isoban # 304 (manufactured by Kuraray), imidized isoban # 310 (manufactured by Kuraray), and the like.
• a water-soluble polyvalent epoxy compound can be used as the crosslinking agent at that time.
• the water-soluble polyvalent epoxy compound examples include Denacol EX-521 (manufactured by Nagase Chemtech) and Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.).
• the buffer, inorganic acid or salt thereof and / or organic acid, zinc compound, chloride or iodide, etc. more preferably, the buffer, inorganic acid or salt thereof and / or Alternatively, the durability can be similarly improved by containing an organic acid at a concentration of about 0.01 to 10 wt% with respect to the adhesive component.
• the viewing angle is improved on the surface of a protective layer or film that will be an unexposed surface later and / or Various functional layers for improving contrast, and a layer or film having brightness enhancement can also be provided.
• an adhesive In order to bond the polarizing plate to these films and display devices, it is preferable to use an adhesive.
• This polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface, that is, the exposed surface of the protective layer or film.
• various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface, that is, the exposed surface of the protective layer or film.
• a film having the function can be bonded via an adhesive or a pressure-sensitive adhesive.
• the various functional layers can be a layer or a film for controlling the phase difference.
• a polarizing element or polarizing plate having a constant transmittance at each wavelength can be obtained.
• the polarizing element or polarizing plate of the present invention thus obtained has high polarization performance, that is, high contrast, and can maintain a constant wavelength transmittance in the visible range, and is excellent in durability, and thus stable for a long time. The performance can be maintained.
• the image display device of the present invention can be obtained by using the polarizing plate of the present invention for a liquid crystal display, an electroluminescence display device, a CRT or the like.
• a liquid crystal display device can be obtained by bonding the polarizing plate of the present invention to both sides of a liquid crystal cell constituting a liquid crystal display with an adhesive together with a retardation film as necessary.
• the transmittance shown in each example was evaluated as follows. Each wavelength when the transmittance of each wavelength when measuring a polarizing element or polarizing plate with one sheet is a single transmittance Ts, and the two polarizing elements or polarizing plates are stacked so that their absorption axis directions are the same. The transmittance of each wavelength was defined as the parallel transmittance Tp, and the transmittance at each wavelength when the two polarizing plates were stacked so that their absorption axes were orthogonal to each other was defined as the orthogonal transmittance Tc.
• Each of the spectral transmittances Ts, Tp and Tc was measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.].
• the visibility corrected single transmittance Ys was calculated by the following formula (5) from the single transmittance Ts measured at predetermined wavelength intervals d ⁇ (here, 5 nm) in the wavelength region of 400 to 700 nm.
• P ⁇ represents a spectral distribution of standard light (C light source)
• y ⁇ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).
• the visibility corrected parallel transmittance Yp was calculated from the parallel transmittance Tp measured every predetermined wavelength interval d ⁇ (here, 5 nm) in the wavelength region of 400 to 700 nm by the following equation (6).
• P ⁇ represents a spectral distribution of standard light (C light source)
• y ⁇ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).
• the visibility-corrected orthogonal transmittance Yc was calculated from the orthogonal transmittance Tc measured at predetermined wavelength intervals d ⁇ (here, 5 nm) in the wavelength region of 400 to 700 nm by the following equation (7).
• P ⁇ represents a spectral distribution of standard light (C light source)
• y ⁇ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).
• the degree of polarization Py was obtained by the following formula (8) from the visibility corrected parallel transmittance Yp and the visibility corrected orthogonal transmittance Yc.
• Example 1 A polyvinyl alcohol film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 ⁇ m, a polymerization degree of 5500, and a saponification degree of 99% or more was swelled with hot water at 40 ° C., and then 1000 parts by weight of water and boric acid 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of iodine (made by Pa.), 0.25 parts by weight of iodine (made by Junsei Chemical), and 17.7 parts by weight of potassium iodide (made by Junsei Chemical). It was immersed for a minute and dyed. A dyed film is stretched 5 times at 58 ° C.
• Example 2 A polyvinyl alcohol film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 ⁇ m, a polymerization degree of 4000, and a saponification degree of 99% or more.
• a polarizing element was obtained in the same manner as in Example 1 except that (VF-PH) was used.
• Example 3 A polarizing element was obtained in the same manner as in Example 2 except that the time for the dyeing treatment was 1 minute 30 seconds.
• Example 4 A polarizing element was obtained in the same manner as in Example 1 except that the time for the dyeing treatment was 1 minute 30 seconds.
• Comparative Example 5 An iodine polarizing plate SKN-18242P manufactured by Polatechno Co., Ltd. was immersed in dichloromethane, and the polarizing element was extracted to obtain a comparative sample.
• Comparative Example 6 After stretching, the polarizing element was obtained in the same manner as in Example 1 except that the film was immersed in water and treated for 20 seconds to obtain a comparative sample.
• Table 1 shows parameters of the polarizing elements obtained in Examples 1 to 4 and Comparative Examples 1 to 6.
• the parameters shown in Table 1 are as follows. Visibility correction single transmittance Ys, Visibility correction parallel transmittance Yp, Visibility correction orthogonal transmittance Yc, 460 nm single transmittance Ts 460 , 460 nm parallel transmittance Tp 460 when two substrates are measured parallel to the absorption axis direction, 460 nm orthogonal transmittance Tc 460 when two substrates are measured perpendicular to the absorption axis direction, Single transmittance Ts 550 of 550 nm, 610 nm single transmittance Ts 610 , 610 nm orthogonal transmittance Tc 610 when two substrates are measured perpendicular to the absorption axis direction, 295 nm parallel transmittance Tp 295 when two substrates are measured parallel to the absorption axis direction, 295 nm orthogonal transmittance Tc
• the polarizing elements of Examples 1 to 4 are polarizing elements having substantially constant transmittance at each wavelength, and the visibility corrected single transmittance Ys when measured alone is 40.0%. 42.5%, the difference between the visibility corrected single transmittance Ys and the transmittance Ts 460 at 460 nm is within 1%, and the difference between the visibility corrected single transmittance Ys and the transmittance Ts 550 at 550 nm is It is within 1%, and the difference between the visibility corrected single transmittance Ys and the transmittance Ts 610 at 610 nm is within 1%, and is obtained by measuring the two base materials perpendicular to the absorption axis direction.
• the visibility corrected single transmittance Yc is 0.01% or less.
• a polarizing plate can be obtained by laminating a polarizing element with a protective layer.
• the transmittance of 380 nm to 480 nm is 500 nm to 650 nm.
• the optical characteristics were almost constant, and the light emission uniformity at each wavelength could be maintained.
• the visibility corrected orthogonal transmittance Yc is 0.01% or less, these polarizing elements have high contrast and are polarizing elements or polarizing plates that can make each wavelength transmittance constant in the visible range. I found out.
• the polarizing elements of Examples 1 to 4 obtained by the above method or polarizing plates produced using these polarizing elements have high transmittance, high contrast ratio, and very high color reproducibility. It can be used as a polarizing plate, particularly a polarizing plate for liquid crystal displays. In addition, a display using this is expected to be a display having high reliability, capable of maintaining high contrast over a long period of time, and having high color reproducibility.

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• 2014
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