KR101949003B1 - Polarizing film, polarizing plate and liquid crystal panel - Google Patents
Polarizing film, polarizing plate and liquid crystal panel Download PDFInfo
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- KR101949003B1 KR101949003B1 KR1020167033443A KR20167033443A KR101949003B1 KR 101949003 B1 KR101949003 B1 KR 101949003B1 KR 1020167033443 A KR1020167033443 A KR 1020167033443A KR 20167033443 A KR20167033443 A KR 20167033443A KR 101949003 B1 KR101949003 B1 KR 101949003B1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
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- Optics & Photonics (AREA)
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Abstract
A polarizing film having a shrinking force of 2 mm or less in width in the absorption axis direction for 4 hours at 80 DEG C of 1.5 N or less, a polarizing film having a shrinking force of 2 mm or less in width in the absorption axis direction at 80 DEG C for 4 hours, A polarizing plate comprising a film, a protective film disposed on at least one side thereof, and a liquid crystal panel using the polarizing plate.
Description
The present invention relates to a polarizing film, a polarizing plate and a liquid crystal panel suitably used in a liquid crystal display device.
The polarizing plate is widely used as a polarizing light supplying element in an image display apparatus such as a liquid crystal display apparatus. As a polarizing plate, a polarizing film is generally formed by bonding a protective film to an polarizing film using an adhesive (for example, JP-A-2013-148806 (Patent Document 1)).
Various mobile devices and thin liquid crystal televisions using a liquid crystal display device have been widely popularized. Accordingly, there is a demand for thinning of a polarizing plate and a liquid crystal cell constituting a liquid crystal panel of a liquid crystal display device.
In general, since a polarizing plate, particularly a thin polarizing plate, is usually produced by a stretching process, the polarizing plate has a polarizing plate in which an absorption axis direction (MD) of the polarizing film, and a transmission axis direction (a direction orthogonal to the absorption axis direction, TD), for example, under a high-temperature environment and under a high-humidity environment. When such a polarizing plate is bonded to a liquid crystal cell and a liquid crystal panel is manufactured, the liquid crystal cell is thin, and when the rigidity is low, the obtained liquid crystal panel is particularly bent. The warp of the liquid crystal panel may adversely affect the visibility of the liquid crystal display device.
Therefore, an object of the present invention is to provide a polarizing film capable of imparting a polarizing plate improved in warpage to sufficiently suppress warping of the liquid crystal panel, and a polarizing plate and a liquid crystal panel using the polarizing film.
The present invention provides the following polarizing film, polarizing plate and liquid crystal panel.
[1] A polarizing film having shrinkage force of 2 mm or less in width in the direction of the absorption axis when kept at 80 ° C for 4 hours.
[2] A polarizing film according to [1], which is a stretched film.
[3] A polarizing film according to [1] or [2], wherein the polarizing film has a thickness of 20 m or less.
[4] The polarizing film described in any one of [1] to [3], wherein the boron content is in the range of 0.5 to 2.0% by weight.
[5] The polarizing film described in any one of [1] to [4], wherein the visual sensitivity-corrected single-unit transmittance is 40% or more and the visual sensitivity correction polarity is 90% or more.
[6] A polarizing plate comprising a polarizing film having a shrinking force of 2 mm or less in width in the direction of the absorption axis when kept at 80 ° C for 4 hours,
A protective film disposed on at least one side of the polarizing film,
.
[7] The polarizer according to [6], wherein the protective film has a thickness of 50 μm or less.
[8] A polarizing plate comprising a protective film disposed on both surfaces of the polarizing film,
The polarizing plate described in [6] or [7], wherein the thickness ratio of the other protective film to one protective film is 1.5 or more.
[9] The polarizer according to any one of [6] to [8], wherein the polarizer has a rectangular shape of 8 cm or more on the long side and 5 cm or more on the short side.
[10] A liquid crystal panel comprising a liquid crystal cell and the polarizing plate described in any one of [6] to [9] arranged on at least one side thereof.
[11] The liquid crystal panel according to [10], wherein the thickness of the substrate constituting the liquid crystal cell is 0.5 mm or less.
According to the polarizing film of the present invention, it is possible to provide a polarizing plate improved in warping to such an extent that warping of the liquid crystal panel can be sufficiently suppressed. The liquid crystal panel using the polarizing plate of the present invention is suppressed from warping and can be suitably applied to a thin liquid crystal display device.
<Polarizing Film>
The polarizing film is an optical film having a property of absorbing linearly polarized light having a vibration plane parallel to the absorption axis thereof and transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis) The film is characterized in that the shrinking force per 2 mm in width in the absorption axis direction is 1.5 N or less. Hereinafter, the absorption axis direction is referred to as "MD", and the transmission axis direction (direction perpendicular to the absorption axis) is also referred to as "TD".
(1) Shrinking force of polarizing film
The present inventors have carried out various studies on the warpage of a polarizing plate formed by bonding a protective film to one surface or both surfaces of a polarizing film and have conducted various investigations using a cut sample of a polarizing plate according to a measuring method described in detail in [ (Hereinafter referred to as " MD / TD curvature ratio ") of the deflection amount (warping amount in the absorption axis direction) in the MD in the obtained polarizing plate and the warping amount ) Is adjusted to 1.0 or the vicinity thereof, it is possible to effectively suppress the warp of the liquid crystal panel manufactured using this polarizing plate.
As a concrete means for adjusting the ratio of the MD / TD warp of the polarizing plate to 1.0 or near thereto, the shrinkage force per 2 mm in width in the absorption axis direction of the polarizing film (hereinafter also referred to as " MD shrinkage force " ) Of 1.5 N or less is very effective.
As described above, the polarizing film is usually produced by a stretching process, and the stretching axis at this time is usually MD (the absorption axis is MD). Therefore, in the conventional polarizing plate, the ratio of MD / TD warpage is 1.0 or larger than the vicinity thereof. On the other hand, when the polarizing film of the present invention having an MD shrinking force of 1.5 N or less is used, the ratio of MD / TD warp of the polarizing plate can be set at or near 1.0.
The MD shrinkage force referred to herein means the MD shrinkage force of the polarizing film before the protective film is bonded to the polarizer, and is a shrinking force per 2 mm in width in the absorption axis direction when kept at 80 캜 for 4 hours. The MD shrinkage force is measured using a cut sample of the polarizing film, and the details of the measurement method are the same as those described in [Examples]. The MD shrinkage force is preferably from 0.1 to 1.3 N, more preferably from 0.3 to 1.1 N, since the MD / TD warping ratio of the polarizing plate is close to 1.0.
On the other hand, in the polarizing film of the present invention, the shrinkage force per 2 mm in the transmission axis direction (hereinafter also referred to as " TD shrinkage force ") when kept at 80 ° C for 4 hours is usually 0.1 to 1.0 N. Details of the measurement method of the TD shrinkage force are the same as those described in the [Examples] section. Here, the term "TD shrinkage force" also refers to the TD shrinkage force of the polarizing film before the polarizing plate is bonded to the protective film.
(2) Material, thickness, etc. of polarizing film
The polarizing film of the present invention may be a single (single layer) film made of a stretched thermoplastic resin film, and typically, a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol type resin film.
As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be mentioned in addition to polyvinyl acetate as a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include (meth) acrylamides having unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups. The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%.
In the present specification, "(meth) acryl" means at least one selected from acrylic and methacrylic. Quot ;, " (meth) acryloyl ", and the like.
The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain a desired polarizing performance. When the average degree of polymerization exceeds 10000, film formability may be poor.
The dichroic dye to be adsorbed and oriented on the polarizing film may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dyes include red BR, red LR, red R, pink LB, rubin BL, Borde GS, sky blue LG, regon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Kongogred, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, , Direct First Orange S, and First Black. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.
The thickness of the polarizing film is usually about 5 to 40 占 퐉. However, from the viewpoint of thinning of the polarizing plate and the liquid crystal panel, the thinner the thickness, the better the handling and durability can be secured. Therefore, the thickness of the polarizing film is preferably 20 占 퐉 or less, and more preferably 15 占 퐉 or less. However, since the ratio of MD / TD warpage tends to be larger than 1 as the thickness becomes thinner, it is preferable to lower the MD shrinkage force in order to bring the ratio of MD / TD warp close to 1.
(3) Polarization property of polarizing film
The polarization performance of the polarizing film can be represented by numerical values mainly referred to as a simple transmittance and a polarization degree,
(?) = 0.5 x (Tp (?) + Tc (?))
(?) = 100 × (Tp (?) - Tc (?)) / (Tp (?) + Tc
.
Here, Tp (?) Is the transmittance (%) of the polarizing film measured by the relationship between the linearly polarized light of incident wavelength? Nm and the parallel Nicol, Tc (?) Is the transmittance of the polarizing film measured by the linearly polarized light of incident? (%) Of the polarizing film measured in relation to the polarizing ultraviolet visible absorption spectrum by the spectrophotometer. The visual sensitivity-corrected single-beam transmittance Ty and the visibility-corrected polarized light intensity Py are referred to as sensitivity sensitivity corrections called visibility correction for the simplex transmittance lambda and the polarization degree lambda obtained for each wavelength. The values of Ty and Py can be measured using, for example, a spectrophotometer.
In order to ensure good clarity of an image when applied to a liquid crystal display device, it is preferable that the polarizing film has a visible transmittance, a transmittance (Ty) of at least 40%, and a visual sensitivity correction polarization degree Py of 90% Do. Ty is more preferably 42% or more, and Py is more preferably 99% or more. More preferably, Ty is 42.8% or more, and Py is 99.99% or more.
In order to increase Ty and Py, it is usually necessary to increase the stretching ratio, but in this case, the MD shrinking force tends to increase. Therefore, in the case of obtaining a polarizing film having a high Ty and Py, it is preferable that the MD shrinkage force is sufficiently lowered by a method described later.
(4) Boron content in polarizing film
In order to reduce the MD shrinkage force of the polarizing film, it is effective to lower the boron content in the polarizing film. For example, the boron content in the polarizing film is preferably 0.5 to 2.0 wt%. The boron content in the polarizing film can be calculated as follows. First, the weight of the polarizing film is measured, and then the polarizing film is completely melted by immersing it in hot water at 95 캜 for 60 minutes. Subsequently, the aqueous solution in which the polarizing film is dissolved is neutralized and titrated, and the boron content in the polarizing film is calculated from the weight and the amount of the polarizing film.
<Polarizer>
The polarizing plate of the present invention comprises a polarizing film and a protective film disposed on at least one side of the polarizing film.
(1) polarizing film
The MD shrinking force of the polarizing film is 1.5 N or less, preferably 0.1 to 1.3 N, more preferably 0.3 to 1.3 N, in order to adjust the MD / TD warping ratio of the polarizing plate to 1.0 or close thereto. 1.1 N. Further, the TD shrinkage force of the polarizing film included in the polarizing plate of the present invention is usually 0.1 to 1.0 N.
The MD and TD shrinking forces referred to herein are the same as the shrinking forces described in the section of < polarizing film > except that the shrinking force of the polarizing film obtained by removing the protective film from the polarizing plate. The details of the measurement method are the same as those described in [Example]. Since the thermal history before and after the protective film bonding may be different, the value of the contractive force in the < polarizing film > term and the value of the contractive force referred to herein may be slightly different.
With respect to the material, thickness, polarization characteristics, boron content, and the like of the polarizing film of the polarizing plate of the present invention, the technique in the above <polarizing film> is cited.
(2) Protective film
The protective film to be bonded and arranged on one side or both sides of the polarizing film may be a thermoplastic resin such as a polyolefin resin such as a chain polyolefin resin (polypropylene resin), a cyclic polyolefin resin (norbornene resin, etc.); Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins such as methyl polymethacrylate resins; Or a mixture or copolymer thereof, or the like. The protective film is usually laminated to the polarizing film through the adhesive layer.
The protective film may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxial stretching or biaxially stretching) a transparent resin film made of the above material, or forming a liquid crystal layer or the like on the film.
A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer may be formed on the surface opposite to the polarizing film in the protective film. The method of forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.
When a protective film is bonded to both surfaces of a polarizing film, these protective films may be films made of the same kind of resin or films made of different kinds of resins. From the viewpoint that the ratio of MD / TD deflection of the polarizing plate is more effectively close to 1.0, it is preferable that the both-side protective film is a film made of the same kind of resin, but even if it is made of different kinds of resins, The ratio of warpage can be made close to 1.0.
The thickness of the protective film is preferably thin in view of thinning of the polarizing plate, but if it is too thin, the strength is lowered and the workability is poor. Therefore, the thickness of the protective film is preferably 5 to 150 占 퐉, more preferably 5 to 100 占 퐉, and still more preferably 10 to 50 占 퐉. As another means for bringing the ratio of MD / TD warp close to 1.0, it is conceivable to increase the reinforcing effect by the protective film, for example, to increase the thickness of the protective film. However, this means is disadvantageous in the thinning of the polarizing plate. According to the present invention, even if the thickness of the protective film is reduced to 50 占 퐉 or less, the MD / TD warpage ratio can be made close to 1.0.
When a protective film is bonded to both surfaces of a polarizing film, these protective films may have the same thickness or different thicknesses. As another means for bringing the ratio of MD / TD warp close to 1.0, it is conceivable to use a reinforcing effect of these protective films by bonding a protective film to both sides of the polarizing film. However, in the case of this means, there arises a restriction that the thickness of the protective films on both sides must be equal or substantially equal. According to the present invention, even when the thickness ratio of the protective films on both sides is set to 1.5 or more, or more than 2.0, the MD / TD warpage ratio can be made close to 1.0.
As another means of bringing the ratio of MD / TD warp close to 1.0, it is also conceivable to use a reinforcing effect of the protective film by bonding a protective film to only one side of the polarizing film. In this case, There is a limitation in the usable protective film, such as thickness and rigidity of the material. According to the present invention, the ratio of MD / TD warpage can be made closer to 1.0 regardless of whether the protective film is laminated on one side or on both sides. As described above, the polarizing plate of the present invention is also advantageous in that it is possible to make the MD / TD warp ratio close to 1.0 while maintaining a wide degree of freedom such as the number of sheets, the material, and thickness of the protective film to be bonded.
(3) Configuration of Polarizer
The polarizing plate (polarizing film) may have an appropriate shape and size required for the liquid crystal display device to be applied, and may be a rectangular shape (for example, rectangular or square) having a long side of 8 cm or more and a short side of 5 cm or more. When the ratio of MD / TD curvature is large as in the conventional polarizing plate, the larger the size of the polarizer, the more the curvature of the liquid crystal panel tends to be remarkable. However, according to the present invention, The warpage of the liquid crystal panel can be suppressed well.
As described above, the ratio of MD / TD deflection in the polarizing plate of the present invention is 1.0 or near 1.0, more specifically 1.0 + 0.4, preferably 1.0 + 0.3, more preferably 1.0 + 0.2 . In this range, warping of the liquid crystal panel can be effectively suppressed.
The polarizing plate may have a pressure-sensitive adhesive layer for bonding to the liquid crystal cell. The pressure-sensitive adhesive layer can be laminated on the outer surface of the protective film (for example, when a protective film is laminated on both surfaces of the polarizing film) or on a polarizing film surface (for example, when a protective film is laminated on one surface of the polarizing film).
The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is usually composed of a pressure-sensitive adhesive composition in which a base polymer is a (meth) acrylic resin, a styrene resin, a silicone resin or the like and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto. The thickness of the pressure-sensitive adhesive layer may be about 1 to 40 mu m.
≪ Polarizing Film and Polarizing Plate Manufacturing Method >
A polarizing film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin film includes a step of uniaxially stretching a polyvinyl alcohol-based resin film; Dyeing a polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye; Treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing after treatment with an aqueous boric acid solution. The thickness of the polyvinyl alcohol-based resin film as a raw material is, for example, about 10 to 150 mu m. The thickness of the polyvinyl alcohol based resin film is preferably 40 占 퐉 or less since it is easy to produce a polarizing film having a thickness of 20 占 퐉 or less.
The uniaxial stretching of the polyvinyl alcohol based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed at a plurality of these steps.
In uniaxial stretching, the film may be uniaxially stretched between rolls having different circumferential velocities, or may be uniaxially stretched using a heat roll. The uniaxial stretching may be dry stretching which is stretched in the air or wet stretching in which the polyvinyl alcohol based resin film is stretched by using a solvent. The stretching magnification is usually about 3 to 8 times. In order to impart favorable polarization characteristics, the draw ratio is preferably at least 4 times, and more preferably at least 5 times.
Further, in order to reduce the MD shrinkage force of the polarizing film, it is preferable to carry out the uniaxial stretching separately before the boric acid treatment and during the boric acid treatment. In this case, the total draw ratio before the boric acid treatment is more than 1.0 times, preferably 1.01 to 2.5 times. The total draw ratio is more preferably 1.01 to 2.1 times, and still more preferably 1.01 to 1.7 times.
As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing a dichroic dye is employed. The polyvinyl alcohol-based resin film is preferably subjected to immersion treatment (swelling treatment) in water before the dyeing treatment.
When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally employed. The content of iodine in the dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing aqueous solution is usually about 20 to 40 ° C.
On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol-based resin film into a dyeing aqueous solution containing a dichroic organic dye is generally employed. The content of the dichroic organic dye in the dyeing aqueous solution is usually about 1 × 10 -4 to 10 parts by weight per 100 parts by weight of water and preferably about 1 × 10 -3 to 1 part by weight. The dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80 ° C.
The boric acid treatment after dyeing with the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The amount of boric acid in an aqueous solution containing boric acid is usually about 0.1 to 15 parts by weight per 100 parts by weight of water. As described above, in order to reduce the MD shrinkage force of the polarizing film, it is effective to lower the boron content in the polarizing film. For example, the boron content in the polarizing film is preferably 0.5 to 2.0 wt%. Therefore, in order to reduce the MD shrinkage force of the polarizing film, the amount of boric acid in the boric acid-containing aqueous solution is preferably 0.1 to 3 parts by weight, more preferably 0.1 to 1.3 parts by weight, per 100 parts by weight of water. In order to more effectively reduce the MD shrinkage force of the polarizing film, it is preferable to employ the above-described preferable stretching mode in addition to the boric acid concentration.
When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. The temperature of the boric acid-containing aqueous solution is usually about 50 to 85 占 폚.
The polyvinyl alcohol-based resin film after boric acid treatment is usually washed by immersion in water or an aqueous solution of potassium iodide. The temperature of the water or potassium iodide aqueous solution in the washing treatment is usually about 5 to 40 캜.
After the washing, a drying treatment is carried out to obtain a polarizing film. The drying treatment can be performed using a hot air dryer, a far infrared heater, a heat roll, or the like. The temperature of the drying treatment is usually about 30 to 100 캜, preferably 50 to 80 캜. The moisture content of the film before the drying treatment is preferably 25 to 55% by weight from the viewpoint of the drying efficiency. The moisture content of the film after the drying step is usually 5 to 35% by weight, but it is preferably 6 to 33% by weight from the viewpoint of transportability.
The polarizing plate can be obtained by bonding a protective film to one side or both sides of a polarizing film (single film) obtained as described above through an adhesive layer. As the adhesive forming the adhesive layer, an aqueous adhesive or a photo-curable adhesive can be used. When the protective film is bonded to both surfaces, the adhesive forming the two adhesive layers may be the same or different. For example, when a protective film is bonded to both surfaces, one surface may be bonded using an aqueous adhesive, and the other surface may be bonded using a photocurable adhesive.
Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component emulsion type urethane emulsion adhesive, and the like. Among them, an aqueous adhesive composed of a polyvinyl alcohol-based resin aqueous solution is suitably used.
Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate which is a homopolymer of vinyl acetate Or a modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl group thereof, and the like can be used. The water-based adhesive may include additives such as polyvalent aldehyde, water-soluble epoxy compound, melamine compound, zirconia compound, and zinc compound.
When an aqueous adhesive is used, it is preferable to carry out a drying step to remove the water contained in the aqueous adhesive after the bonding. The drying temperature is preferably 30 to 100 占 폚. If it is less than 30 DEG C, the protective film tends to peel off from the polarizing film. If the drying temperature exceeds 100 ° C, there is a fear that the polarization performance of the polarizing film may deteriorate due to heat. After the drying step, a curing process may be performed at a temperature of room temperature or slightly higher, for example, at a temperature of about 20 to 45 DEG C for about 12 to 600 hours.
The photo-curing adhesive refers to an adhesive that cures by irradiating active energy rays such as ultraviolet rays. Examples of the adhesive include a polymerizable compound and a photopolymerization initiator, a photoreactive resin, a binder resin and a photoreactive crosslinking agent And the like. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer and a photocurable urethane monomer, and oligomers derived from a photopolymerizable monomer. Examples of the photopolymerization initiator include materials which generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy-based monomer and a photocationic polymerization initiator can be preferably used.
In the case of using a photo-curable adhesive, after bonding, the photo-curable adhesive is cured by irradiating an active energy ray. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution with a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, A wave excitation mercury lamp, a metal halide lamp and the like are preferably used.
Prior to the bonding of the polarizing film and the protective film, the bonding surfaces of the polarizing film and / or the protective film may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, An adhesive treatment may be performed.
The polarizing plate of the present invention is not limited to the above-described method. For example, the polarizing plate may be formed by forming a polyvinyl alcohol-based resin layer on a base film such as described in Japanese Patent Application Laid-Open No. 2009-98653, ). ≪ / RTI > This method is advantageous for obtaining a polarizer layer of a thin film.
More specifically,
A resin layer forming step of forming a polyvinyl alcohol-based resin layer by coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of a base film and then drying,
A stretching step of stretching the laminated film to obtain a stretched film,
A dyeing step in which a polarizing layer (corresponding to a polarizing film) is formed by dying a polyvinyl alcohol-based resin layer of a drawn film with a dichroic dye to obtain a polarizing laminated film,
A first bonding step of bonding a protective film to the polarizer layer of the polarizing laminated film using an adhesive to obtain a bonded film,
A peeling step of peeling off the base film from the bonding film to obtain a polarizing plate having a one side protective film
In this order.
When a protective film is laminated on both sides of the polarizer layer,
And a second bonding step of bonding the protective film to the polarizing surface of the polarizing plate having the one-side protective film using an adhesive.
≪ Liquid crystal panel &
The liquid crystal panel of the present invention comprises a liquid crystal cell and the polarizing plate according to the present invention which is bonded to at least one surface of the liquid crystal cell. The polarizing plate is normally bonded to the liquid crystal cell through the pressure-sensitive adhesive layer. The liquid crystal panel may have the polarizing plate according to the present invention on one side only or on both sides. From the standpoint of suppressing the warp of the liquid crystal panel, the polarizer according to the present invention is preferably disposed on both sides of the liquid crystal cell.
The liquid crystal cell includes a pair of substrates (for example, a transparent substrate such as a glass substrate) opposed to each other with a predetermined distance therebetween by a spacer, and a liquid crystal layer in which liquid crystal is sealed between the pair of substrates. (Twisted Nematic) type, STN (Super-Twisted Nematic) type, VA (Vertical Alignment) type, IPS (In-Plane Switching) type or the like.
Though the thickness of the substrate constituting the liquid crystal cell is arbitrary, when the ratio of MD / TD curvature is large as in the conventional polarizing plate, the thinner the substrate, the more the warp of the liquid crystal panel tends to be remarkable. According to the present invention, even if the thickness of the substrate is reduced to, for example, 0.5 mm or less, and further to 0.3 mm or less, warpage of the liquid crystal panel can be satisfactorily suppressed.
The liquid crystal panel may have a suitable shape and size required for the liquid crystal display device to be applied, and may be a rectangular shape (for example, rectangular or square) having a long side of 8 cm or more and a short side of 5 cm or more. When the ratio of MD / TD curvature is large as in the conventional polarizing plate, the larger the size of the liquid crystal panel (and hence the polarizing plate), the more the warpage of the liquid crystal panel tends to become remarkable. According to the present invention, cm or more and shorter than 100 cm on the short side, the warpage of the liquid crystal panel can be suppressed well.
Example
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, the boron content in the polarizing film, the polarizing property of the polarizing film, the MD and TD shrinkage (before and after the protective film bonding) and the MD / TD curl were measured according to the following method .
[A] Boron content in polarizing film
The weight of the obtained polarizing film was measured, and then the polarizing film was immersed in hot water at 95 캜 for 60 minutes to completely dissolve the polarizing film. Subsequently, the aqueous solution in which the polarizing film was dissolved was neutralized and titrated, and the content of boron in the polarizing film was calculated from the weight and the amount of the polarizing film.
[B] Polarization property of polarizing film
With respect to the obtained polarizing film, the visibility-corrected single unit transmittance (Ty) and visual sensitivity correction polarity (Py) were measured using a spectrophotometer ("V-7100" manufactured by Nippon Bunko Co., Ltd.).
[C] MD and TD shrinkage of the polarizing film before the protective film lamination
From the obtained polarizing film, a sample for measuring the MD shrinkage force having a width of 2 mm and a length of 10 mm was cut out with the long axis in the absorption axis direction (MD, stretching direction). This sample was set on a thermomechanical analyzer (TMA) " EXSTAR-6000 ", manufactured by Esa Eye Nanotechnology Co., Ltd., and maintained at 80 DEG C for 4 hours while keeping the dimensions constant. (MD shrinkage force) of the absorbent core (absorption axis direction, MD) was measured. The TD shrinkage force was measured in the same manner as described above except that a sample having a width of 2 mm and a length of 10 mm was used as a long side in the transmission axis direction (TD perpendicular to the absorption axis direction).
[D] MD and TD shrinkage of the polarizing film after the protective film bonding
The obtained polarizing plate was cut into small pieces of 10 cm x 5 cm, immersed in 600 mL of methylene dichloride, and subjected to ultrasonic treatment at room temperature for 30 minutes to dissolve and remove the bonded protective film. From the polarizing film from which the protective film had been removed, a sample for MD shrinkage measurement having a width of 2 mm and a length of 10 mm was cut out in which the absorption axis direction (MD, stretching direction) was long. The MD shrinkage force was measured in the same manner as in [c] above except that this sample was used. Further, except that a polarizing plate piece having a width of 2 mm and a length of 10 mm is cut out from the polarizing film from which the protective film has been removed so that the longitudinal direction of the transmission axis (TD perpendicular to the absorption axis direction) is long, And the TD shrinkage force was measured.
[E] Ratio of MD / TD curl of polarizer
From the obtained polarizing plate, a sample for measuring the MD warping amount of 40 mm in width and 150 mm in length measuring long sides in the absorption axis direction (MD, elongation direction) was cut out. This sample was bonded to the center of the surface of a flat glass substrate (width 51 mm, length 156 mm, thickness 0.5 mm) using an acrylic pressure-sensitive adhesive. In this state, the amount of bending in the absorption axis direction was measured in the following procedure. One side of the short side of the sample was set at 0 mm, and the height at the 5 points (5 mm, 40 mm, 75 mm, 110 mm, and 145 mm at the center of the short side) The MD warping amount (mm) before heating was obtained as a difference between the maximum height and the minimum height, by measuring with a two-dimensional measuring machine. Thereafter, the sample was heated at 85 DEG C for 250 hours. After heating, one side of the short side of the sample was set to 0 mm, and five points (5 mm, 40 mm, 75 mm, 110 mm, and 145 mm) were placed along the long side direction ) Was measured by a two-dimensional measuring machine, and the MD warping amount (mm) after heating was obtained as a difference between the maximum height and the minimum height. The value obtained by subtracting the MD bending amount before heating from the MD bending amount after heating was defined as the MD bending amount. Further, except that a sample having a width of 40 mm and a length of 150 mm, which has long sides in the direction of the transmission axis (TD perpendicular to the absorption axis direction) was used, the amount of warping in the transmission axis direction (TD deflection (Mm) was measured, and the following formula:
Ratio of MD / TD warpage = MD warpage amount / TD warpage amount
, The ratio of MD / TD warpage was obtained.
≪ Example 1 >
(A) Production of polarizing film
After immersing in pure water at 30 DEG C for 97 seconds while continuously feeding a long original polyvinyl alcohol original film (width 450 cm, thickness 30 mu m, average degree of polymerization of polyvinyl alcohol about 2400, saponification degree 99.9 mol% or more) And potassium iodide / water at a weight ratio of 2/100 for 123 seconds to perform dyeing. Thereafter, the substrate was immersed in an aqueous solution at 56 DEG C having a weight ratio of potassium iodide / boric acid / water of 12 / 1.0 / 100 for 81 seconds to perform boric acid treatment. Thereafter, the film was dipped in a water bath filled with pure water at 5 DEG C for 2 seconds, and then the film was washed with water. Then, the film was passed through a hot-air drying furnace and dried at 60 DEG C for 160 seconds to adsorb iodine in polyvinyl alcohol To obtain a long polarizing film. During this period, the longitudinal uniaxial stretching treatment was performed mainly in the dyeing step and the boric acid treatment step, and the total draw ratio before the boric acid treatment step was 2.1 times and the total draw ratio from the original film was 5.5 times. The thickness of the polarizing film was 12.5 占 퐉, and the content of boron in the polarizing film was 1.5% by weight.
(B) Production of Polarizing Plate
A protective film (thickness: 40 mu m) made of triacetylcellulose was bonded to both surfaces of the polarizing film through an aqueous adhesive with a bonding roll while the long polarizing film obtained in the above (A) was continuously conveyed, And dried at 60 DEG C for 98 seconds to obtain a long polarizing plate having a protective film bonded to both surfaces of the polarizing film. To the aqueous adhesive, an aqueous solution of 10% concentration was prepared by dissolving an acetoacetyl group-modified polyvinyl alcohol-based resin (trade name: Gosepaima Z-200, manufactured by Nippon Gohsei Kagaku Kogyo Co., Ltd.) in pure water, Sodium glyoxylate was used as a crosslinking agent. Electron: the latter was mixed so that the weight ratio of solids was 1: 0.1 and further diluted with pure water so that 1 part by weight of the acetoacetyl group-modified polyvinyl alcohol resin was added to 100 parts by weight of water did.
≪ Examples 2 to 4 >
Except that the thickness of the original film made of polyvinyl alcohol, the drying temperature in the drying process of the polarizing plate (after the protective film was bonded), and the thickness of the obtained polarizing film were the same as those shown in Table 1, To prepare a polarizing film and a polarizing plate.
≪ Comparative Example 1 &
(A) Production of polarizing film
After being immersed in pure water at 20 캜 for 24 seconds while continuously conveying a long original polyvinyl alcohol original film (width 450 cm, thickness 30 탆, average degree of polymerization of polyvinyl alcohol about 2400, degree of saponification 99.9 mol% or more) And potassium iodide / water at a weight ratio of 2/100 for 74 seconds to perform dyeing. Subsequently, the substrate was immersed in an aqueous solution of 56 ° C having a weight ratio of potassium iodide / boric acid / water of 12 / 1.5 / 100 for 64 seconds to perform boric acid treatment. Thereafter, the film was dipped in a water bath filled with pure water at 5 캜 for 2 seconds to wash the film. Then, the film was passed through a hot-air drying furnace to perform a drying treatment at 60 DEG C for 160 seconds to obtain an elongated polarizing film in which iodine was adsorbed and aligned in polyvinyl alcohol. In the meantime, the longitudinal uniaxial stretching treatment was mainly performed in the dyeing step and the boric acid treatment step, and the total draw ratio before the boric acid treatment step was 3.7 times and the total draw ratio from the original film was 5.5 times. The thickness of the polarizing film was 13.2 占 퐉, and the content of boron in the polarizing film was 2.4% by weight.
(B) Production of Polarizing Plate
Using the elongated polarizing film obtained in the above (A), a polarizing plate was produced in the same manner as in Example 1.
≪ Comparative Example 2 &
A polarizing film and a polarizing plate were produced in the same manner as in Comparative Example 1 except that the drying temperature in the drying process of the polarizing plate (after the protective film was bonded) was changed to 90 캜.
The boron content in the polarizing films obtained in Examples and Comparative Examples, the polarizing properties of the polarizing film, the MD and TD shrinking forces of the polarizing films before and after the protective film bonding, the MD warping amount, the TD warping amount, and the MD / TD warping The ratios are shown in Table 1. The "amount of boric acid" in Table 1 indicates the content of boric acid per 100 parts by weight of water in the aqueous solution used for the treatment with boric acid.
[Table 1]
Claims (11)
A protective film disposed on both sides of the polarizing film through an adhesive layer
/ RTI >
An MD warping amount obtained for a polarizing plate sample having a width of 40 mm and a length of 150 mm which makes the absorption axis direction long and a polarizing plate sample having a width of 40 mm and a length of 150 mm, From the TD warping amount obtained for the following formula:
Ratio of MD / TD warpage = MD warpage amount / TD warpage amount
Wherein a ratio of MD / TD curvature calculated according to the following formula is 0.6 to 1.4.
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| JP2014107225A JP6219781B2 (en) | 2014-05-23 | 2014-05-23 | Polarizing film, polarizing plate and liquid crystal panel |
| PCT/JP2015/062191 WO2015178150A1 (en) | 2014-05-23 | 2015-04-22 | Polarizing film, polarizing plate and liquid crystal panel |
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| JP2017156399A (en) * | 2016-02-29 | 2017-09-07 | 住友化学株式会社 | Set of polarizing plates and liquid crystal panel |
| JP6858499B2 (en) * | 2016-06-27 | 2021-04-14 | 株式会社クラレ | Optical film manufacturing method |
| JP2018062377A (en) * | 2016-10-14 | 2018-04-19 | 昭和電工パッケージング株式会社 | Sealing material and container sealed by sealing material |
| JP2018091980A (en) * | 2016-12-02 | 2018-06-14 | 住友化学株式会社 | Polarizing film and manufacturing method of polarized laminate film |
| US20200026124A1 (en) * | 2017-03-31 | 2020-01-23 | Sharp Kabushiki Kaisha | Liquid crystal display panel and manufacturing method for liquid crystal display panel |
| CN110869840B (en) * | 2017-07-14 | 2023-01-06 | 杉金光电(苏州)有限公司 | Liquid crystal panel and method for manufacturing same |
| JP2020526797A (en) * | 2017-07-25 | 2020-08-31 | エルジー・ケム・リミテッド | Polarizing filter and liquid crystal display element including it |
| JP7025166B2 (en) * | 2017-09-28 | 2022-02-24 | 住友化学株式会社 | Polarizing plate, its manufacturing method, and display device |
| JP2019091023A (en) * | 2017-11-10 | 2019-06-13 | 住友化学株式会社 | Circularly polarizing plate |
| CN111527163B (en) * | 2018-05-21 | 2022-07-15 | 杉金光电(苏州)有限公司 | Polarizing plate, image display device including the same, and adhesive composition for polarizing plate |
| KR20200002427A (en) * | 2018-06-29 | 2020-01-08 | 주식회사 엘지화학 | Polarizing plate, liquid crystal panel, and display apparatus |
| US11650362B2 (en) | 2018-06-29 | 2023-05-16 | Lg Chem, Ltd. | Polarizing plate, liquid crystal panel and display device |
| KR102662107B1 (en) * | 2019-01-11 | 2024-05-02 | 산진 옵토일렉트로닉스 (난징) 컴퍼니 리미티드 | Preparation Method of Polarizing Plate |
| KR20200087435A (en) * | 2019-01-11 | 2020-07-21 | 주식회사 엘지화학 | Polarizing Plate |
| KR102621169B1 (en) * | 2019-01-11 | 2024-01-05 | 산진 옵토일렉트로닉스 (난징) 컴퍼니 리미티드 | Preparation Method of Polarizing Plate |
| CN109782478B (en) * | 2019-03-21 | 2021-12-24 | 南京汉旗新材料股份有限公司 | TN/STN polarizing film hue control method |
| JP2021173936A (en) * | 2020-04-28 | 2021-11-01 | 住友化学株式会社 | Polarizing plate and manufacturing method therefor |
| KR20230160238A (en) * | 2021-03-24 | 2023-11-23 | 미쯔비시 케미컬 주식회사 | Polyvinyl alcohol-based film, method for manufacturing same, and polarizing film and polarizing plate using the same |
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| JP2013148806A (en) | 2012-01-23 | 2013-08-01 | Sumitomo Chemical Co Ltd | Polarizing film and manufacturing method thereof and polarizer |
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