CN113287044A

CN113287044A - Polarizer and method for manufacturing the same

Info

Publication number: CN113287044A
Application number: CN201980088645.6A
Authority: CN
Inventors: 崔允硕; 朴旼奎; 朴重万; 赵天熙
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-01-23
Filing date: 2019-09-06
Publication date: 2021-08-20
Also published as: KR20200091741A; WO2020153566A1; JP2022517625A

Abstract

The present invention relates to a polarizer, a polarizing plate, and an image display device, and a method of manufacturing the polarizer. The polarizer is characterized in that the cross-tone b value is-1.0 or more and the absorbance (A) at a wavelength of 450nm₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) Is 2.5 or more, thereby reducing the transmittance of blue light (blue light source) in a wavelength band (about 430nm to 480nm), thereby reducing the influence of blue light on the user.

Description

Polarizer and method for manufacturing the same

Technical Field

The present application claims benefits based on the priority of korean patent application No. 10-2019-0008906, filed on 23.01.2019, and all the contents disclosed in the documents of this korean patent application are included as part of the present specification.

The present invention relates to a polarizer and a method of manufacturing the same.

Background

Blue light (Blue light) is 380nm to 500nm of Blue light in visible light, and is characterized by a short wavelength and high energy.

This blue light is originally from sunlight, and the sun rises to the highest level at noon, and radiates the most, and disappears completely after sunset, and plays a positive role in attention, time and emotion reflection in the daytime, but destroys circadian rhythm at night, and is considered as a healthy enemy.

Such blue light is also emitted through the liquid crystal screen of electronic equipment such as a smart phone, a tablet computer, a computer display, etc., which have been rapidly popularized recently, and particularly, in view of the increasing trend of users who also use electronic equipment at night, the users have to be exposed to blue light at night in practice.

Such direct exposure to blue light of the user not only causes dry eye, eye fatigue, and impaired vision, but also causes problems such as an adverse effect on the human body due to decreased function of the retina, and an adverse effect on the human body due to disturbance of the circadian rhythm of the human body and induction of sleep disturbance caused by disturbance of melatonin hormone.

Therefore, it is necessary to develop a technique for minimizing the influence of such blue light.

In connection with this, a technology for preventing harmfulness caused by blue light by including the following layers is disclosed in korean registration No. 10-1395498, namely: a glass layer attached to a liquid crystal screen of the electronic device to protect the liquid crystal screen of the electronic device, the glass layer having a bonding layer on a back surface thereof; a1 st release layer which is bonded to the surface of the glass layer by providing a1 st adhesive layer at a position corresponding to the surface of the glass layer in order to bond the release layer to the surface of the glass layer, and which is peeled from the surface of the bonded glass layer; a blue light cutting layer bonded to a bonding layer provided on the rear surface of the glass layer, for cutting blue light emitted from a liquid crystal screen of the electronic device; and a 2 nd release layer bonded to the back surface of the blue light-cutting layer and peeled from the back surface of the bonded blue light-cutting layer by providing a 2 nd adhesive layer at a position corresponding to the back surface of the blue light-cutting layer so as to be bonded to the back surface of the blue light-cutting layer. Since this structure has a structure in which an extra blue light-cut layer is laminated, it is necessary to add a step corresponding to this, and there is a problem that the process time becomes long and the productivity is lowered:

prior art documents

Patent document

Korean registration No. 10-1395498 (2014.05.14.)

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a polarizer and a method of manufacturing the same, which can reduce the influence of blue light by suppressing the transmittance of a blue light wavelength band only by the polarizer itself without requiring an additional process.

Means for solving the technical problem

The polarizer of the present invention for achieving the above object is characterized in that the cross-tone b value is-1.0 or more and the absorbance (A) at a wavelength of 450nm₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) Is 2.5 or more.

The polarizing plate of the present invention is characterized by comprising the above polarizer.

The image display device of the present invention is characterized by comprising the polarizing plate.

The method for manufacturing a polarizer of the present invention includes a swelling step, a dyeing step, a stretching step, a crosslinking step, a color correction step, a preheating step, a water washing step, and a drying step, and the color correction step is performed using a color correction liquid containing a boric acid compound and potassium iodide, and the potassium iodide is contained in an amount of 12 to 15 wt% with respect to 100 wt% of the entire color correction liquid.

Effects of the invention

The polarizer, the polarizing plate and the image display device of the present invention are advantageous in reducing the transmittance in the blue light band to reduce the influence of blue light.

The method of manufacturing a polarizer of the present invention is advantageous for manufacturing a polarizer that satisfies the conditions given in the present invention for reducing the influence of blue light.

Drawings

Fig. 1 and 2 show experimental results of transmittance at each wavelength of examples of the present invention and comparative examples.

Detailed Description

In the present invention, the term "on" a certain component includes not only a case where the certain component is in direct contact with another component but also a case where another component is present between the two components.

In the present invention, when a part "includes" a certain constituent element, unless otherwise stated to the contrary, it means that other constituent elements are not excluded, and other constituent elements may be included.

The present invention will be described in more detail below.

< polarizer >

A polarizer according to one embodiment of the present invention is characterized in that the cross-tone b value is-1.0 or more and the absorbance (A) at a wavelength of 450nm₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) The transmittance of the blue light (blue light source) in a wavelength band (about 430nm to 480nm) is reduced by 2.5 or more, which is advantageous for reducing the influence of the blue light on the user.

In the present invention, the cross color tone is a color tone obtained when natural light is irradiated onto two polarizers in which one polarizer is laminated with the other polarizer so that absorption axes are orthogonal to each other at right angles.

The orthogonal hue b value is a value representing a hue on the CIE coordinate system, and more specifically, the b value is calculated by the following equation 1, + b represents yellow or red, and-b represents blue. (wherein Xn, Yn and Zn correspond to X, Y, Z which is a standard white color tone.)

[ numerical formula 1]

b＝200[(Y/Yn)^1/3-(Z/Zn)^1/3]

That is, the cross-tone b value is a tone b value on the CIE coordinate system measured by a colorimeter for tones in which a pair of polarizers are arranged in a state where absorption axes are orthogonal to each other.

A polarizer according to an embodiment of the present invention facilitates: the orthogonal hue b is adjusted to-1 or more, a neutral black (neutral black) hue can be realized, and the more + the color becomes, the more red the color becomes, and the blue light can be cut off more effectively. When the cross-tone b shows a value lower than-1, the blue color tone is further improved, and the blue screen suppression effect may be reduced.

The cross-tone b may be preferably from-1 to 10, more preferably from 0 to 8, and still more preferably from 0 to 5. When the cross-tone b value is included in the above-described preferable range, the blue light cut effect can be further improved.

A is described₄₅₀And A₇₀₀The absorbance at the bottom (tail) of the absorption band on the short wavelength side (blue region) and the absorbance at the bottom of the absorption band on the long wavelength side (red region) are referred to, respectively. In the present invention, the intensity of the absorbance in the short wavelength side absorption band is increased and the absorbance in the long wavelength side absorption band is adjusted to a higher level than in the case of a polarizing plate manufactured by increasing the transmittance of a conventional polarizing plate₄₅₀/A₇₀₀The ratio is adjusted to 2.5 or more, thereby having an effect of reducing the transmittance of blue light. A above₄₅₀/A₇₀₀May be preferably 2.5 to 7.0, more preferably 2.5 to 5.5, the above-mentioned A₄₅₀/A₇₀₀When included in the above-described preferred range, the blue light cut-off effect is further improved.

A is described₄₅₀And A₇₀₀The incident light is natural light, which is a value that can be measured by an absorption photometer such as an ultraviolet-visible spectrophotometer. Will be incident onWhen the light intensity is To and the transmitted light intensity is T, the absorbance A is₄₅₀And A₇₀₀Calculated by the following equation 2.

[ numerical formula 2]

Absorbance (A)₄₅₀Or A₇₀₀)＝-log(T/To)

When the incident light to a polarizer sample is polarized, the resulting absorbance value may change depending on the orientation in which the sample is placed in the absorptiometry device. For example, in the absorption photometer, there are cases where a small amount of polarization of incident light is generated by the influence of a mirror, an optical element, or the like positioned between a light source and a sample, and cases where a polarization separation element such as a prism is incorporated, and therefore, attention is required for measurement. When such an absorptiometry is used, the polarization plate is measured at a certain angle (which means a certain direction around the optical axis), and then the polarization plate is measured again at a direction rotated by 90 degrees, and the absorbance is calculated from the average transmitted light intensity, whereby the influence of the polarization of incident light can be eliminated.

According to the polarizer of one embodiment of the present invention, the visibility correcting monomer transmittance (Ty) at a wavelength of 450nm may be 41% or more, and the visibility correcting polarization degree (Py) is 99.945% or more, preferably 99.960% or more, and more preferably 99.970% or more. When Ty and Py satisfy the above range, good sharpness of an image can be ensured when the display device is applied to an image display device.

The visibility correction individual transmittance (Ty) and the visibility correction polarization degree (Py) are values obtained by performing sensitivity correction called visibility correction on the individual transmittance and the polarization degree obtained at each wavelength. The monomer transmittance and the degree of polarization are calculated by the following numerical formula 3 or 4, respectively.

[ numerical formula 3]

Monomer transmittance of 0.5 × [ Tp (λ) + Tc (λ) ]

[ numerical formula 4]

Degree of polarization of 100 × [ (Tp (λ) -Tc (λ))/(Tp (λ) + Tc (λ)) ]

In the above equation 3 or 4, Tp (λ) is the transmittance (%) of the polarizing plate or polarizer measured by the relationship between incident linear polarized light having a wavelength of λ nm and parallel nicols, and Tc (λ) is the transmittance (%) of the polarizing plate or polarizer measured by the relationship between incident linear polarized light having a wavelength of λ nm and orthogonal nicols, and both refer to the measured values obtained by the measurement of the visible absorption spectrum of the polarizer by a spectrophotometer.

The visibility correcting monomer transmittance (Ty) and the visibility correcting polarization degree (Py) can be easily measured by, for example, an absorption spectrophotometer (model V7100) manufactured by Nippon spectral Co., Ltd.

The polarizer of the present invention may be a polarizer obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin layer.

As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin layer, a resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

Although not limited thereto, the polarizer may be a substrate film coated with a solution of the polyvinyl alcohol resin.

The polarizer may be oriented by stretching, preferably stretching at a stretch ratio of more than 5 times, more preferably more than 5 times and 17 times or less.

The saponification degree of the polyvinyl alcohol resin may be 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. When the saponification degree is less than 80.0 mol%, water resistance and moist heat resistance of the polarizing plate may be lowered in the production of the polarizing plate, and when a polyvinyl alcohol resin having a saponification degree of more than 99.5 mol% is used, the dyeing speed may be lowered to lower productivity, and it may be difficult to obtain a polarizer having sufficient polarizing performance.

In this case, the degree of saponification means the degree of acetoxy (acetoxy group: -OCOCH) contained in a polyvinyl acetate resin as a raw material of the polyvinyl alcohol resin₃) The ratio of hydroxyl groups to be converted by the saponification step is a value expressed as a unit ratio (mol%), and is calculated by the following numerical formula 5.

[ numerical formula 5]

Degree of saponification (% by mole) × 100 × [ (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) ]

The degree of saponification can be determined in accordance with JIS K6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and the lower the proportion of acetate groups inhibiting crystallization.

The polyvinyl alcohol resin may be partially modified polyvinyl alcohol. For example, a polyvinyl alcohol resin is prepared from an olefin such as ethylene or propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; and resins obtained by modifying unsaturated carboxylic acid alkyl esters, acrylamides, and the like. The modification ratio is preferably less than 30 mol%, more preferably less than 10%. When the modification is performed at more than 30 mol%, it is difficult to adsorb the dichroic dye, and it may be difficult to obtain a polarizer having sufficient polarization performance.

The polyvinyl alcohol resin preferably has an average polymerization degree of 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K6726 (1994).

Examples of commercially available products of the polyvinyl alcohol resin include "PVA 124" (degree of saponification: 98.0 to 99.0 mol%), "PVA 117" (degree of saponification: 98.0 to 99.0 mol%), "PVA 624" (degree of saponification: 95.0 to 96.0 mol%), "PVA 617" (degree of saponification: 94.5 to 95.5 mol%); "AH-26" (saponification degree: 97.0 to 98.8 mol%), "AH-22" (saponification degree: 97.5 to 98.5 mol%), "NH-18" (saponification degree: 98.0 to 99.0 mol%), "N-300" (saponification degree: 98.0 to 99.0 mol%); JAPAN VAM & POVAL CO., LTD., "JC-33" (saponification degree: 99.0 mol% or more), "JM-33" (saponification degree: 93.5 mol% to 95.5 mol%), "JM-26" (saponification degree: 95.5 mol% to 97.5 mol%), "JP-45" (saponification degree: 86.5 mol% to 89.5 mol%), "JF-17" (saponification degree: 98.0 mol% to 99.0 mol%), "JF-17L" (saponification degree: 98.0 mol% to 99.0 mol%), "JF-20" (saponification degree: 98.0 mol% to 99.0 mol%) and the like.

The dichroic pigment contained (adsorbed alignment) in the polarizer may be iodine or a dichroic organic dye. Examples of the dichroic organic dye include red BR, red LR, red R, pink LB, magenta (Rubin) BL, red date (Bordeaux) GS, Sky Blue (Sky Blue) LG, lemon yellow, Blue BR, Blue 2R, Navy Blue (Navy) RY, green LG, Violet LB, Violet B, black H, black B, black GSP, yellow 3G, yellow R, Orange LR, Orange 3R, Scarlet (Scarlet) GL, Scarlet KGL, congo red, bright purple (Brilliant Violet) BK, colorpeyer roban (Supra B ] ue) G, colorpex GL, colorpex Orange GL, Direct Sky Blue (Direct Sky Blue), Direct Fast Orange (Direct Orange) S, and Fast black. One of the above dichroic dyes may be used alone, or two or more thereof may be used in combination.

As the substrate film, for example, a film made of a thermoplastic resin can be used. As specific examples, the film is a film made of a light-transmitting thermoplastic resin, preferably an optically transparent thermoplastic resin, and examples thereof include polyolefin resins such as chain polyolefin resins (polypropylene resins and the like) and cyclic polyolefin resins (norbornene resins and the like); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins such as methyl methacrylate resins; a polystyrene-based resin; a polyvinyl chloride resin; acrylonitrile-butadiene-styrene resins; acrylonitrile-styrene resin; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; polyimide resin, etc., but is not limited thereto.

< polarizing plate >

The polarizing plate according to another embodiment of the present invention is advantageous in reducing the transmittance of blue light by including the aforementioned polarizer. The polarizing plate may be specifically a polarizing plate in which a protective film is bonded to at least one side of the polarizer of the present invention through an adhesive layer (adhesive layer) or a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer), and may further include other optical layers as necessary.

Protective film

The protective film may be a thermoplastic resin, for example, a polyolefin resin such as a chain polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins; or a mixture or copolymer thereof.

The cyclic polyolefin resin is a general term for resins obtained by polymerizing cyclic olefins as polymerization units, and examples thereof include those described in Japanese patent laid-open publication No. 1-240517, Japanese patent laid-open publication No. 3-14882, and Japanese patent laid-open publication No. 3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins and linear olefins such as ethylene and propylene, graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products thereof. Among these, norbornene-based resins using norbornene-based monomers such as norbornene-based monomers and polycyclic norbornene-based monomers are preferably used as the cyclic olefin.

The cyclic polyolefin-based resin may be commercially available, and examples of the commercially available resin include trade names "Topas" (manufactured by Topas Advanced Polymers GmbH, available from plastics co., ltd.), "ARTON" (manufactured by JSR Corporation), "ZEONOR" (manufactured by Zeon Corporation), "ZEONEX" and "APEL" (manufactured by Mitsui Chemicals inc.).

Further, commercially available products of FILM-formed cyclic polyolefin resin FILMs such as "Esc ena" (manufactured by Sekisui Chemical Co., ltd., "SCA 40" (manufactured by Sekisui Chemical Co., ltd.), "ZEONOR FILM" (manufactured by Zeon Co rpration) and the like can be used as the protective FILM.

The cellulose ester resin may be an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin may include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, copolymers thereof or those in which a part of the hydroxyl group is modified with another substituent may also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Cellulose triacetate is commercially available in a number of products and may be advantageous in terms of ease of availability or cost. Examples of commercially available cellulose triacetate include "Fujitac TD 80" (FUJIFILM co., ltd.), "Fujitac TD80 UF" (FUJIFILM co., ltd.), "Fujitac TD80 UZ" (FUJIFILM co., ltd.), "Fujitac TD40 UZ" (fufifilm co., ltd.), "KC 8U X2M" (Konica Minolta Opto, inc.), "KC 4 UY" (Konica Minolta Opto, inc.), and the like, which are commercially available under the trade names.

The protective film may also be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film to which an arbitrary retardation value is given by stretching (uniaxial stretching or biaxial stretching) a transparent resin film containing the above material, forming a liquid crystal layer on the film, or the like can be used.

The polarizing plate may further include a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, an antifouling layer, or the like. Such a surface treatment layer may be formed on the surface of the protective film, and a method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method may be used.

Adhesive layer

The adhesive forming the adhesive layer is not limited to this, but a water-based adhesive or a light-curable adhesive can be used.

Examples of the water-based binder include a binder containing a polyvinyl alcohol resin aqueous solution, a water-based two-pack type urethane emulsion binder, and the like. Among them, a water-based binder containing an aqueous solution of a polyvinyl alcohol-based resin can be suitably used.

As the polyvinyl alcohol resin, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, a modified polyvinyl alcohol polymer obtained by modifying a hydroxyl group portion thereof, and the like can be used.

The water-based binder may further include additives such as polyaldehydes, water-soluble epoxy compounds, melamine compounds, zirconium oxide compounds, zinc compounds, and the like. When a water-based adhesive is used, the thickness of the adhesive layer obtained therefrom may be generally 1 μm or less.

The bonding method using the water-based adhesive is not particularly limited, and examples thereof include a method in which the water-based adhesive is uniformly applied or poured onto one bonding surface, the other side is overlapped on the applied surface, and the bonding is performed using a roller or the like, followed by drying. Typically, the water-based adhesive may be applied at a temperature of 15 to 40 ℃ after preparation, and the bonding temperature may typically be 15 to 30 ℃.

In the case of using the water-based adhesive as described above, it is preferable to perform a drying step of removing water contained in the water-based adhesive after bonding. The drying may be performed, for example, by introducing the bonded film into a drying oven, and the drying temperature (temperature of the drying oven) is preferably 30 to 90 ℃, and if it is lower than 30 ℃, the bonded bodies are easily peeled from each other, and if it exceeds 90 ℃, the polarizing performance of the bonded bodies may be deteriorated by heat. The drying time may be, for example, 10 seconds to 1000 seconds.

After the drying step, it is preferable to have a maintenance step of maintaining the substrate at room temperature or a slightly higher temperature, for example, at a temperature of about 20 to 45 ℃ for about 12 to 600 hours. In this case, the maintenance temperature may be set to be lower than the drying temperature.

The photocurable adhesive is an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, and examples thereof include an adhesive that contains a polymerizable compound and a photopolymerization initiator, contains a photoreactive resin, and contains a binder resin and a photoreactive crosslinking agent.

Examples of the polymerizable compound include a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and an oligomer derived from a photopolymerizable monomer. Examples of the photopolymerization initiator include photopolymerization initiators containing a substance that generates an active species such as a neutral radical, an anionic radical, and a cationic radical by irradiation with an active energy ray such as ultraviolet ray. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, a photocurable adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

The joining method using a photocurable adhesive is not particularly limited, and examples thereof include a method in which a photocurable adhesive is applied to one joining surface by a casting method, a Mayer bar coating method, a gravure coating method, a comma coater method, a doctor blade method, a die coating method, a dip coating method, a spray method, and the like, the two are laminated, and the joining is performed by sandwiching the two between nip rolls (nip rolls) and the like. The casting method is a method of spreading an object to be coated by running down a binder onto the bonding surface while moving the object in a substantially vertical direction, a substantially horizontal direction, or an oblique direction therebetween. The thickness of the adhesive layer after joining with a nip roll or the like before drying or curing is preferably 0.01 to 5 μm.

When the photocurable adhesive is used, after the bonding, a drying step (in the case where the photocurable adhesive contains a solvent, etc.) may be performed as necessary, and then a curing step of curing the photocurable adhesive by irradiation with an active energy ray may be performed. The light source of the active energy ray is not particularly limited, but an active energy ray having an emission distribution at a wavelength of 400nm or less is preferable, and specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light, a microwave-excited mercury lamp, a metal halide lamp, or the like is preferably used.

The irradiation intensity of the light to the photocurable adhesive can be appropriately determined depending on the composition of the photocurable adhesive, and is preferably set so that the irradiation intensity in a wavelength region effective for the activation of the polymerization initiator is 0.1mW/cm²～6000mW/cm²The mode of (2) is set. When the irradiation intensity is within the above range, the reaction time is not excessively long, the efficiency can be improved, and yellowing of the photocurable adhesive or deterioration of the polarizer due to heat radiated from the light source and heat generation at the time of curing of the photocurable adhesive can be prevented.

The light irradiation time to the photocurable adhesive may be appropriately determined depending on the composition of the photocurable adhesive, and the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is preferably 10mJ/cm²To 10000mJ/cm²The mode of (2) is set. When the cumulative light amount is included in the range, a sufficient amount of active species derived from the polymerization initiator can be generated to more reliably perform the curing reaction, the irradiation time is not excessively long, and thus good productivity can be maintained.

Pressure sensitive adhesive layer

The polarizing plate may further include a pressure-sensitive adhesive layer, and for example, the pressure-sensitive adhesive layer may be used to laminate the polarizing plate to another structural layer such as a liquid crystal cell.

The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer may be, for example, a pressure-sensitive adhesive composition in which a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added to a base polymer such as a (meth) acrylic resin, a styrene resin, or a silicone resin, or may be a pressure-sensitive adhesive layer which further contains fine particles and exhibits light scattering properties.

The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing each component such as the above-mentioned base polymer may be applied to a protective film surface or a polarizer surface and dried to form a pressure-sensitive adhesive layer, or the pressure-sensitive adhesive layer may be formed on a separator (release film) and then transferred to the protective film surface or the polarizer surface. When the pressure-sensitive adhesive layer is formed on the protective film side or the polarizer side, or one side or both sides of the pressure-sensitive adhesive layer may be subjected to surface treatment, for example, corona treatment, as necessary.

Optical layer

The polarizing plate of the present invention may further include other optical layers.

Examples of the other optical layer include a reflective polarizer which transmits light of a certain polarization and reflects light of a polarization opposite to that of the light; a film having an antiglare function and having a concavo-convex shape on the surface; a film having an antireflection function on the surface thereof; a reflective film having a reflective function on a surface thereof; a semi-transparent and semi-reflective film having both a reflection function and a transmission function; a viewing angle compensation film, etc., but is not limited thereto.

Examples of commercially available reflective polarizers that transmit light of a certain polarization and reflect light of a polarization opposite thereto include "DBEF" (manufactured by 3M Company, available from Sumitomo 3M Limited in japan) and "APF" (manufactured by 3M Company, available from Sumitomo 3M Limited in japan).

Examples of the viewing angle compensating film include an optical compensating film in which a liquid crystalline compound is coated on the surface of a substrate and aligned and fixed, a retardation film made of a polycarbonate-based resin, and a retardation film made of a cyclic polyolefin-based resin.

Commercially available products corresponding to the optical compensation FILM in which a liquid crystalline compound is coated on the surface of the substrate and aligned and fixed include "WV FILM" (manufactured by FUJIFILM co., ltd), "NH FILM" (manufactured by JX Nikko Nisseki Energy), "NR FILM" (manufactured by JX Nikko Nisseki Energy).

Commercially available products corresponding to the above-mentioned retardation FILM made of a cyclic polyolefin resin include "ARTON FILM" (manufactured by JSR Corporation), "Escena" (manufactured by Sekisui Chemical co., ltd.) "ZEONOR FILM" (manufactured by Zeon Corporation), and the like.

< image display apparatus >

The image display device according to another embodiment of the present invention includes the polarizing plate, which has an excellent blue light cut-off effect and is advantageous in reducing the influence of blue light on a user.

The image Display device can be configured by attaching the aforementioned polarizing plate to one or both surfaces of a Display panel, such as a liquid crystal panel, a plasma panel, an organic light emitting panel, and a Quantum Dot panel, and accordingly, the image Display device can be a liquid crystal Display device (LCD), a plasma Display device (PDP), an organic light emitting Display device (OLED), and a Quantum Dot Display (Quantum Dot Display).

More specifically, the image display device may be a liquid crystal display device including a liquid crystal panel and polarizing plates provided on both sides of the liquid crystal panel, respectively, and in this case, at least one of the polarizing plates may be a polarizing plate including a polarizer according to the present invention.

In this case, the type of the liquid crystal panel included in the liquid crystal display device is not particularly limited. For example, without limitation to the type thereof, an active matrix type panel such as a TN (twisted nematic) type, STN (super twisted nematic) type, F (ferroelectric) type, or PD (polymer dispersed) type; passive matrix panels such as 2-terminal (two-terminal) and 3-terminal (three-terminal); all known panels such as In-Plane Switching (IPS) panels and Vertical Alignment (VA) panels. Further, the types of other structures constituting the liquid crystal display device, for example, the upper and lower substrates (for example, a color filter substrate or an array substrate) and the like are not particularly limited, and the structures known in the art can be adopted without limitation.

< method for producing polarizer >

The invention also provides a method for manufacturing the polarizer.

A method for producing a polarizer according to another embodiment of the present invention is characterized by comprising a swelling step, a dyeing step, a stretching step, a crosslinking step, a color-compensating step, a preliminary heat treatment step, a water-washing step, and a drying step, wherein the color-compensating step is performed using a color-compensating liquid containing a boric acid compound and potassium iodide, and the potassium iodide is contained in an amount of 12 to 15 wt% based on 100 wt% of the entire color-compensating liquid, thereby facilitating production of an absorbance (A) at a wavelength of 450nm, wherein the b value of an orthogonal color tone is-1, 0 or more₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) A polarizer of 2.5 or more.

Film for forming polarizer

The type of the film for forming a polarizer is not particularly limited as long as it is a film capable of being dyed with a dichroic substance, i.e., iodine, and the like, and examples thereof include a polyvinyl alcohol film and a partially saponified polyvinyl alcohol film; hydrophilic polymer films such as polyethylene terephthalate films, ethylene-vinyl acetate copolymer films, ethylene-vinyl alcohol copolymer films, cellulose films, and partially saponified films thereof; or a polyene-oriented film such as a dehydrated polyvinyl alcohol film or a polyvinyl alcohol film subjected to a desalting treatment. Among these, a polyvinyl alcohol film is preferable from the viewpoint of not only having an excellent effect of enhancing uniformity of polarization degree in a plane but also having excellent dyeing affinity for iodine.

The thickness of the polarizer-forming film is not particularly limited, and may be, for example, 5 to 100 μm, preferably 20 to 80 μm.

Swelling step

A method of manufacturing a polarizer according to one embodiment of the present invention includes a swelling step.

The swelling step is as follows: before dyeing an unstretched polarizer-forming film, the film is immersed in a swelling bath filled with an aqueous swelling solution to remove dust or impurities such as blocking preventive agents deposited on the surface of the polarizer-forming film and swell the polarizer-forming film, thereby improving the stretching efficiency and also preventing dyeing unevenness for improving the physical properties of the polarizer.

As the aqueous solution for swelling, water (pure water or deionized water) can be generally used alone, and when a small amount of glycerin or potassium iodide is added thereto, the polymer film swells and the processability can be improved.

The content of glycerin and potassium iodide is not particularly limited, and may be, for example, 5 wt% or less and 10 wt% or less, respectively, based on the total weight of the aqueous swelling solution.

The temperature of the swelling bath is not particularly limited, and may be, for example, 0 to 60 ℃, preferably 10 to 50 ℃. When the temperature of the swelling bath is within the above range, the subsequent stretching and dyeing efficiency is excellent, and the film expansion due to excessive swelling can be prevented.

Dyeing step

A method of manufacturing a polarizer according to one embodiment of the present invention includes a dyeing step.

The dyeing step comprises the following steps: the polarizer-forming film is immersed in a dyeing bath filled with a dyeing solution containing a dichroic substance such as iodine, and iodine is adsorbed to the polarizer-forming film.

The dyeing liquid may further contain water, a water-soluble organic solvent or a mixed solvent thereof, and iodine. In the staining solution, the concentration of iodine may be 0.4 to 400mmol/L, preferably 0.8 to 275mmol/L, more preferably 1 to 200 mmol/L.

The dyeing liquid may further contain an iodide as a dissolution aid for improving dyeing efficiency.

The kind of iodide is not particularly limited, and examples thereof include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, and potassium iodide is preferable from the viewpoint of high solubility in water. These may be used alone or in combination of two or more.

The content of the iodide is not particularly limited, and may be, for example, 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the dyeing liquid.

The staining solution may further contain a boric acid compound. The dyeing liquid contains the boric acid compound, so that the residence time of the boric acid compound before the crosslinking reaction is performed is increased, and the complex formation rate of the dichroic material of the film for forming the polarizer can be increased. Accordingly, the color tone durability of the polarizer can be improved, and the degree of polarization can be improved.

The concentration of the boric acid compound in the dyeing liquid is not particularly limited, and may be, for example, 0.1 to 5% by weight, preferably 0.3 to 3% by weight, based on the total weight of the dyeing liquid. If the concentration of the boric acid compound in the dyeing liquid is less than 0.1 wt%, the effect of increasing the formation of the iodine complex is reduced, and if it exceeds 5 wt%, the strain may increase and the breakage may occur.

The kind of the boric acid compound is not particularly limited, and examples of the boric acid compound include boric acid, sodium borate, potassium borate, lithium borate, and the like, and boric acid is preferable. These may be used alone or in combination of two or more.

The temperature of the dyeing bath is not particularly limited, and may be, for example, 5 to 42 ℃, preferably 10 to 35 ℃.

The time for immersing the polarizer-forming film in the dyeing bath is not particularly limited, and may be, for example, 1 to 20 minutes, preferably 2 to 10 minutes.

The stretching step may be performed simultaneously with the dyeing step, and in this case, the stretching ratio may be 1.01 to 2.0 times, preferably 1.1 to 1.8 times.

Also, the cumulative stretching ratio of the polarizer until the swelling and stretching step is preferably 1.2 to 4.0 times. The cumulative stretching ratio is less than 1.2 times, wrinkles may be generated in the film, and more than 4.0 times, the initial optical characteristics may be degraded.

Step of crosslinking

A method of manufacturing a polarizer according to one embodiment of the present invention includes a crosslinking step.

The crosslinking step comprises the following steps: the dyed polarizer-forming film is immersed in a crosslinking solution to fix the adsorbed iodine molecules so that the dyeability of the physically adsorbed iodine molecules is not lowered by the external environment.

The crosslinking liquid contains a boric acid compound. The crosslinking liquid contains a boric acid compound, thereby improving crosslinking efficiency, suppressing generation of wrinkles in the film in the process, and forming orientation of a dichroic material to improve optical properties.

Although the dichroic dye is not often eluted in a moisture-resistant environment, iodine is often dissolved or sublimated depending on the environment when the crosslinking reaction is unstable, and thus sufficient crosslinking reaction is required.

The crosslinking step may be performed in a1 st crosslinking step and a 2 nd crosslinking step, and the crosslinking solution used in one or more of the crosslinking steps may contain a boric acid compound.

The concentration of the boric acid compound in the crosslinking liquid is 1 to 4.5 wt%, preferably 1.5 to 3.8 wt%, with respect to 100 wt% of the entire crosslinking liquid. If the concentration of the boric acid compound in the crosslinking liquid is less than 1% by weight, the degree of polarization may be decreased, and if it exceeds 4.5% by weight, the shrinkage force may be increased.

At this time, the same boric acid compound as that used in the dyeing step may be used as the boric acid compound.

The crosslinking liquid may contain water as a solvent and an organic solvent which is mutually soluble together with water, and may further contain a small amount of potassium iodide for uniformity of the degree of polarization in the plane of the polarizer and prevention of desorption of iodine from the dye.

The concentration of potassium iodide in the crosslinking liquid is 1 to 15 wt%, preferably 5 to 11 wt%, based on 100 wt% of the entire crosslinking liquid. When the concentration of potassium iodide in the crosslinking liquid is less than 1% by weight, the degree of polarization may be lowered, and when it exceeds 15% by weight, the heat resistance may be lowered, and a red discoloration phenomenon may occur when exposed to high temperatures for a long time.

In addition, the crosslinking liquid may further contain the iodide as described above within a range not to impair the object of the present invention.

The temperature of the crosslinking bath is not particularly limited, and may be, for example, 20 to 70 ℃ and preferably 40 to 60 ℃.

The time for immersing the polarizer-forming film in the crosslinking bath is not particularly limited, and may be, for example, 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed simultaneously with the crosslinking step, and in this case, the stretching ratio of the 1 st crosslinking step may be 1.4 to 3.0 times, preferably 1.5 to 2.5 times. And, the stretching ratio of the 2 nd crosslinking step may be 1.01 to 2.0 times, preferably 1.2 to 1.8 times.

The cumulative stretching ratio of the 1 st and 2 nd crosslinking steps may be 1.5 to 5.0 times, preferably 1.7 to 4.5 times. If the cumulative stretching ratio is less than 1.5 times, the effect of improving the crosslinking efficiency may be insufficient, and if it exceeds 5.0 times, the film may be broken by excessive stretching, and the production efficiency may be lowered.

Color complementing step

A method of manufacturing a polarizer according to one embodiment of the present invention includes a complementary color step.

The color-complementing step is a step of additionally fixing iodine molecules which are insufficient in the crosslinking step.

The color correction liquid used in the color correction step of the present invention contains a boric acid compound. The color correction liquid contains a boric acid compound, thereby improving crosslinking efficiency, inhibiting the generation of wrinkles in the film in the process, and forming the orientation of a dichroic material to improve optical properties.

The concentration of the boric acid compound in the color correction liquid is 0.5 to 3 wt%, preferably 1 to 2.5 wt%, based on 100 wt% of the entire color correction liquid.

When the concentration of the boric acid compound in the color replenishment liquid is less than 0.5 wt%, the degree of polarization may be decreased, and when it exceeds 3 wt%, the shrinkage force may be increased.

The same applies to the specific contents of the boric acid compound as described above in the dyeing step.

The color replenishment solution may contain water as a solvent and an organic solvent which is miscible with water and is used together with water, and may further contain a small amount of potassium iodide for the purpose of uniformity of the degree of polarization in the plane of the polarizer and prevention of desorption of iodine from the dye.

According to an embodiment of the present invention, the concentration of potassium iodide in the color correction liquid is 12 to 15 wt%, preferably 13 to 15 wt%, with respect to 100 wt% of the entire color correction liquid containing potassium iodide. When the concentration of potassium iodide is within the above range, the desired orthogonal color tone b of the present invention can be produced to have a value of-1.0 or more and an absorbance (A) at a wavelength of 450nm₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) A polarizer of 2.5 or more. When the concentration of potassium iodide is less than 12 wt%, the absorbance on the short wavelength side is insufficient, and the degree of polarization required in the present invention is not achieved, whereas when the concentration exceeds 15 wt%, the absorbance on the long wavelength side is excessively decreased, and it is difficult to adjust the color tone of the polarizing plate.

In addition, the color correction liquid may further contain the iodide as described above within a range not to impair the object of the present invention.

The temperature of the color compensation tank is not particularly limited, and may be, for example, 20 to 70 ℃, preferably 40 to 60 ℃.

The time for immersing the polarizer-forming film in the color correction bath is not particularly limited, and may be, for example, 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed simultaneously with the complementary color step, in which case the stretching ratio of the complementary color step may be 1 to 1.15 times, preferably 1.01 to 1.1 times.

The cumulative draw ratio of the complementary color step may be 1.5 to 7 times, preferably 1.7 to 6 times. When the cumulative stretching ratio is less than 1.5 times, the effect of improving the crosslinking efficiency may be insufficient, and when it exceeds 7 times, the film may be broken by excessive stretching, and the production efficiency may be lowered.

Preheating partProcessing steps

The method for manufacturing a polarizer according to an embodiment of the present invention may further include a preliminary heat treatment step, and thus, when the preliminary heat treatment step is further included, it is advantageous to more easily manufacture the polarizer.

The preliminary heat treatment step may be performed between the complementary color step and the water washing step.

The preliminary heat treatment step can further promote additional crosslinking of boric acid (increase intramolecular crosslinking of the polymer), increase formation of iodine complex spaces within the polarizer-forming film, and increase the amount of the polymer (e.g., polyvinyl alcohol) -I3 complex of the polarizer-forming film. Accordingly, the cross b value is increased to improve the color tone, suppress uneven dyeing, and improve the degree of polarization. The washing Margin (Margin) in the washing step described later can be secured, and this will be described later in detail.

The heating method in the preliminary heat treatment step is not particularly limited, and a known method such as natural drying, heat drying, microwave drying, hot air drying, infrared ray, or the like may be used, and it is preferable to irradiate the film with infrared ray in order to improve the color tone, uneven dyeing, degree of polarization, or the like by promoting the crosslinking.

According to one embodiment of the present invention, the heat of infrared irradiation per unit volume of the film for forming a polarizer may be 1000 to 3000J/cm³Preferably 1200 to 2500J/cm³More preferably 1800 to 2200J/cm³. Thus, when the amount of infrared radiation heat is contained in the above range, it is advantageous to further increase the cross-tone b value, and further increase the visibility correction monomer transmittance (Ty) and visibility correction polarization (Py) values at a wavelength of 450 nm.

The amount of heat to which the polarizer-forming film is subjected can be adjusted by changing the heat treatment temperature, the distance from the heat source, the output, the wavelength of the heat source, the heat treatment time, and the like, but is not limited thereto.

The time for performing the preliminary heat treatment step is not particularly limited, and may be, for example, 0.1 minute to 10 minutes, preferably 0.1 minute to 5 minutes, and more preferably 0.1 minute to 1 minute.

As described above, when the preliminary heat treatment step is performed by irradiation with infrared rays, the wavelength of the infrared rays may be 1 to 5 μm. If the wavelength of the infrared ray is less than 1 μm, the effect of enhancing the boric acid crosslinking and improving the color tone may not be significant, and if it exceeds 5 μm, yellowing of the film for forming a polarizer may be induced. The boric acid crosslinking effect can be improved and yellowing can be suppressed, and more preferably 1.5 to 3 μm.

Step of Water washing

A method of manufacturing a polarizer according to one embodiment of the present invention includes a water washing step.

The water washing step comprises the following steps: the polarizer-forming film on which the crosslinking and stretching were completed was immersed in a washing tank filled with an aqueous washing solution to remove unnecessary residues such as boric acid attached to the polarizer-forming film in the previous step.

The aqueous washing solution may be water (deionized water), and iodide may be further added thereto. As the iodide, the same iodide as that used in the dyeing step may be used, and among these, sodium iodide or potassium iodide is preferably used. The content of the iodide is not particularly limited, and may be, for example, 0.1 to 10 parts by weight, preferably 3 to 8 parts by weight, based on the total weight of the aqueous solution for washing with water.

According to an embodiment of the present invention, the temperature of the water washing tank may be 4 ℃ or more and less than 18 ℃, more preferably 8 ℃ to 15 ℃, and still more preferably 10 ℃ to 13 ℃. If the washing temperature is not within the above range, the hue value may deviate from the range of the present invention and become yellowish or reddish, and if the washing temperature is beyond the above range, the cross-hue b value may decrease.

When the polarizer-forming film is exposed to water for a long time, the polymer (e.g., polyvinyl alcohol) -I3 complex may be excessively converted into a polymer-15 complex, and as a result, problems such as a decrease in the cross-b value and a change in color tone may occur. Therefore, in general, when a polarizer is manufactured, since water washing is performed in a short time in order to reduce loss of the I3-containing complex, foreign substances may remain on the polarizer-forming film after the water washing.

However, when the method for producing a polarizer further includes the aforementioned preliminary heat treatment step as in one embodiment of the present invention, the amount of the I3-containing complex increases, and the polarizer-forming film can be washed with water more sufficiently than in the prior art. Accordingly, it is advantageous to manufacture a polarizer having a smaller amount of foreign matter.

The water washing step may be performed each time the previous steps such as the dyeing step, the crosslinking step or the stretching step are completed. The number of repetitions is not particularly limited, and may be one or more.

Drying step

A method of manufacturing a polarizer according to one embodiment of the present invention includes a drying step.

The drying step comprises the following steps: the water-washed polarizer-forming film is dried, and the orientation of the iodine molecules dyed thereon is further improved, thereby providing excellent optical characteristics and durability.

The heating method in the drying step is not particularly limited, and known methods such as natural drying, heat drying, microwave drying, hot air drying, and infrared ray drying may be used.

The treatment temperature in the drying step is not particularly limited, and may be, for example, 60 to 120 ℃. The drying step may be performed for, for example, 30 seconds to 5 minutes, but is not limited thereto.

The surface temperature of the polarizer-forming film to be dried is preferably a temperature capable of eliminating the internal stress to the maximum, and may be, for example, 50 to 100 ℃. Within the range, the deterioration of the film polymer can be prevented while further improving the internal stress reduction effect. The internal stress relieving effect may not be significant when the temperature of the film is less than 50 c, and the film may be deteriorated when it exceeds 100 c.

In the drying step, the stretching ratio is not particularly limited, and for example, the stretching ratio may be 0.95 times to 1.0 times, preferably 0.96 times to 0.99 times.

According to an embodiment of the present invention, the stretching ratio of the drying step may be 0.96 times or more and less than 0.99 times, and more preferably 0.97 times to 0.98 times. If the stretching ratio in the drying step is less than the above range, there is a possibility that cracking or deterioration of optical properties due to sagging of the film may occur due to insufficient stretching, and if it exceeds the above range, cracking due to excessive stress increase may occur.

According to one embodiment of the present invention, when a polarizer is produced by the above-described method for producing a polarizer, it is advantageous to produce a polarizer having an orthorhombic b value of-1.0 or more and an absorbance (A) at a wavelength of 450nm₄₅₀) Absorbance at a wavelength of 700nm (A)₇₀₀) Ratio of (A)₄₅₀/A₇₀₀) A polarizer of 2.5 or more.

Hereinafter, preferred embodiments are given to aid understanding of the present invention, but the following embodiments are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical spirit of the present invention, and such changes and modifications are also within the scope of the appended claims. In the following examples and comparative examples, "%" and "part(s)" representing the content are based on weight unless otherwise mentioned.

Examples and comparative examples: fabrication of polarizers

Example 1

A transparent unstretched polyvinyl alcohol film (VF-PE #4500, average polymerization degree 2400, kurarayco, LTD.) having a length and width of 100cm, a thickness of 45 μm, and a saponification degree of 99.9% or more was immersed in water (deionized water) at 30 ℃ for 60 seconds to swell, and then immersed in an aqueous dyeing solution at 30 ℃ containing 1.0mmol/L of iodine, 1.25 wt% of potassium iodide, and 0.3 wt% of boric acid for 2 minutes to dye. At this time, in the swelling and dyeing steps, stretching was performed at a stretching ratio of 1.9 times and 1.4 times, respectively, so that the cumulative stretching ratio up to the dyeing tank became 2.66 times.

Subsequently, the resulting film was immersed in a crosslinking aqueous solution containing 9 wt% of potassium iodide and 4 wt% of boric acid at 53 ℃ for 60 seconds, and was stretched at a stretching ratio of 2.15 times while crosslinking the film. Then, in the color correction step, the resultant was immersed in an aqueous solution for color correction at 40 ℃ containing 13 wt% of potassium iodide and 4 wt% of boric acid for 10 seconds. At this time, the total cumulative draw ratio in the swelling, dyeing, crosslinking, and color-compensating steps was 5.72 times.

Then, the polarizer was washed with water in a pure water solution at 11 ℃ for 2 seconds to remove foreign matters adhering to the surface of the polarizer. After completion of the water washing, the polarizer was stretched by 0.97 times while being dried at 90 ℃ for 2 minutes, thereby producing a polarizer.

Examples 2 to 3 and comparative examples 1 to 3

A polarizer was produced in the same composition and method as in example 1, except that the conditions described in table 1 below were changed.

[ Table 1]

Examples 4 to 7

After the completion of the color compensation step, a preliminary heat treatment was performed under the conditions shown in table 2 below, and after the completion of the preliminary heat treatment, the polarizer was stretched at 0.98 times while drying the polarizer at 90 ℃ for 2 minutes after removing foreign matter adhering to the surface of the polarizer by washing with water in a pure water solution at 11 ℃ for 2 seconds, thereby producing a polarizer.

The preliminary heat treatment is performed by using infrared rays, and in this case, a Fast Response Medium wave (1.5um lamp) wavelength is used using an infrared ray heater made of Twin tube transparent quartz glass of Heraeus K.K. as a far Infrared Ray (IR) heater.

[ Table 2]

Experimental example 1: of orthogonal tones bMeasurement of

The polarizers manufactured in the examples and comparative examples were cut into a size of 4cm × 4cm, and then the cross-tone b value was measured by an ultraviolet-visible spectrometer (V-7100, JASC corporation), and the results thereof are described in table 3 below.

Experimental example 2: measurement of absorbance ratio (A700/A450) of polarizer

The polarizers obtained in the examples and comparative examples were measured for absorbance at a wavelength of 450nm (A) using an ultraviolet-visible spectrometer (V-7100, JASC Co.)₄₅₀) And absorbance at a wavelength of 700nm (A)₇₀₀) To determine the absorbance ratio (A)₄₅₀/A₇₀₀) The results are shown in table 3 below.

Experimental example 3: determination of polarization characteristics of polarizer

The visibility-corrected monomer transmittance (Ty) and the visibility-corrected polarization degree (Py) of the polarizers obtained in the above examples and comparative examples were measured by an ultraviolet-visible spectrometer (V-7100, JASC), and the results thereof are shown in table 3 below.

[ Table 3]

Distinguishing	Cross color tone b	A₄₅₀/A₇₀₀	Ty₄₅₀	Py₄₅₀
					Example 1	0.840	2.5	41.1	99.949
Example 2	1.200	2.6	41.2	99.945
					Example 3	0.820	2.7	41.2	99.968
Example 4	1.570	3.0	41.2	99.970
					Example 5	2.190	3.5	41.2	99.973
Example 6	3.250	4.3	41.2	99.977
					Example 7	4.360	5.1	41.1	99.979
Comparative example 1	-0.140	1.4	38.7	99.997
					Comparative example 2	-1.820	1.7	41.2	99.945
Comparative example 3	0.560	2.4	41.1	99.943

Referring to said table 3, it can be confirmed that all of examples 1 to 7 satisfy the polarization characteristics required in the present invention.

Experimental example 4: measurement of transmittance per wavelength of polarizer

The polarizers obtained in the examples and comparative examples were measured for the cross transmittance at each wavelength using an ultraviolet-visible spectrometer (V-7100, JASC corporation), and the results are graphically shown in fig. 1 and 2.

Referring to fig. 1 and 2, it can be confirmed that in the case of examples 1 to 7, each satisfying the polarization characteristics given in the present invention, the transmittance of blue light (blue light source) in the wavelength band of about 430 to 480nm is reduced, and at the same time, the transmittance in the long wavelength band of about 630nm or more is maintained high.

Claims

1. A polarizer, characterized in that,

the b value of the cross color tone is-1.0 or more,

absorbance A at wavelength of 450nm₄₅₀Absorbance A at a wavelength of 700nm₇₀₀Ratio of (A) to (B)₄₅₀/A₇₀₀Is 2.5 or more.

2. The polarizer according to claim 1,

the transmittance Ty of the visibility correction monomer of the polarizer under the wavelength of 450nm is more than 41%, and the transmittance Py of the visibility correction polarization degree is more than 99.945%.

3. The polarizer according to claim 1,

the crossed-tone b value of the polarizer is-1.0 to 10.

4. A polarizing plate characterized in that a polarizing plate,

comprising a polarizer according to claims 1 to 3.

5. An image display device is characterized in that,

comprising the polarizing plate according to claim 4.

6. A method for manufacturing a polarizer according to claim 1, comprising a swelling step, a dyeing step, a stretching step, a crosslinking step, a color-compensating step, a water-washing step, and a drying step,

the color correction step is performed using a color correction liquid containing a boric acid compound and potassium iodide, and the potassium iodide is contained in an amount of 12 to 15 wt% with respect to 100 wt% of the entire color correction liquid.

7. The method of manufacturing a polarizer according to claim 6,

the method for manufacturing the polarizer further comprises a preliminary heat treatment step.

8. The method of manufacturing a polarizer according to claim 6,

in the water washing step, the temperature of the cleaning bath is 4 ℃ or higher and lower than 18 ℃.

9. The method of manufacturing a polarizer according to claim 7,

in the pre-heat treatment step, the heat quantity of infrared irradiation per unit volume of the film for forming a polarizer is 1000 to 3000J/cm³。