JP4404581B2 - Polarizer - Google Patents

Description

  The present invention relates to a thin film polarizer, a polarizing plate and an elliptically polarizing plate which are suitably used for a liquid crystal display device and have excellent hue.

  One or two polarizing plates are bonded to a module of a liquid crystal display device (hereinafter, LCD), and are a basic member that greatly affects the transmittance and hue of transmitted light and non-transmitted light. Generally, a polarizing plate is based on a structure in which a protective film is bonded to both sides of an absorptive polarizer that converts transmitted light into linearly polarized light, and a protective film is further bonded on the protective film. Or, it is shipped in a form in which an adhesive layer or a separate film is laminated for bonding with a liquid crystal module, and is used in the LCD industry.

The polarizer is mainly composed of iodine or a dichroic dye, boric acid, and polyvinyl alcohol (hereinafter, PVA). By highly orienting iodine or a dichroic dye, absorption dichroism is exhibited, and transmitted light can be linearly polarized. PVA functions as a highly oriented iodine or dichroic dye medium and is oriented in the same direction as the iodine or dichroic dye by stretching. Boric acid has a function of stabilizing the orientation state of PVA and further the orientation state of iodine or dichroic dye by crosslinking PVA.
In recent years, as the size of a liquid crystal display device increases, color unevenness and color leakage due to the shrinkage of a polarizer over time have become a problem. In order to improve color unevenness and color leakage in a large liquid crystal display device, a method of reducing the shrinkage force by reducing the thickness of a polarizer has been proposed (for example, see Patent Document 1).

However, as a result of studies by the present inventors, it has been found that the hue changes (bluish) particularly when the polarizer is thinned.
Conventionally, as a modification of the hue of the polarizing plate, for example, the method according to the phase difference control of the film with a light beam having a wavelength of bath temperature control and 900nm during dyeing and stretched in the dyeing bath (patent document 2), I ^- ions I in the polarizer by immersion in an aqueous solution containing ^- a method (Patent Document 3) for adjusting the ion content, and appropriately selecting the production conditions, the parallel transmittance in the wavelength range of 440 to 670nm of the polarizing film obtained A method (Patent Document 4) is proposed in which the difference ΔT between the maximum value T _Max and the minimum value T _Min is 6% or less. However, the inventors have found that the methods described in Patent Documents 2 to 4 have a poor hue improvement effect with a thin film polarizer.

JP 2002-6133 A JP 2002-022950 A JP 2002-258042 A JP 2001-083328 A

  An object of the present invention is to provide a polarizing plate using a polyvinyl alcohol-based polarizer, which is improved in color unevenness and color leakage and excellent in hue.

According to the present invention, a polarizing plate and a liquid crystal display device having the following constitution are provided, and the above object is achieved.
1. 0.001% by mass or more and 1.0% by mass or less of a dichroic dye whose absorption spectrum of an aqueous solution has a maximum in a wavelength region of 300 nm to 500 nm on at least one side of a polarizer made of a polyvinyl alcohol film hardened with boric acid. It is a polarizing plate in which a protective film is bonded using an adhesive containing ,
(I) The polarizer is formed by stretching a polyvinyl alcohol film having a film thickness of 20 μm or more and 60 μm or less in a longitudinal uniaxial direction 5 times or more, and has an absorption spectrum of iodine and an aqueous solution of 300 nm to 500 nm. Contains a dichroic dye exhibiting a maximum in the wavelength region , and the film thickness is 8 μm or more and 18 μm or less,
(Ii) A polarizing plate characterized by having a transmittance at 410 nm in a crossed Nicol range of 0.001% to 0.1%.
2 . 2. An elliptically polarizing plate, wherein a retardation film is laminated on the polarizing plate described in 1 above.
3 . 3. A liquid crystal display device comprising the polarizing plate according to 1 or 2 above.

  In the polarizing plate of the present invention, even when the polarizer is thinned, hue change such as bluishness is suppressed, and when applied to a large-sized liquid crystal display device, color unevenness and color leakage are small.

The polarizing plate of the present invention is a polarizing plate in which a protective film is bonded to at least one side of a polarizer made of polyvinyl alcohol hardened with boric acid.
The polarizer is obtained by stretching a polyvinyl alcohol film in the longitudinal uniaxial direction 5 times or more, and contains iodine. The film thickness of the polyvinyl alcohol film that is the original fabric is 20 μm or more and 60 μm or less, and the film thickness of the polarizer is 8 μm or more and 18 μm or less.
Further, the transmittance of 410 nm at the time of crossed Nicols is 0.001% or more and 0.1% or less.
According to the knowledge of the present inventor, in order to improve color unevenness and color leakage in a large liquid crystal display device, it is preferable to reduce the contraction force of the polarizer by setting the film thickness of the polarizer to 18 μm or less. On the other hand, when the thickness of the polarizer is less than 8 μm, it becomes difficult to maintain the polarization degree and the single plate transmittance. Therefore, the polarizer film thickness is preferably 8 μm or more and 18 μm or less. In order to set the film thickness of the polarizer to 8 μm or more and 18 μm or less, it is preferable that the film thickness of the polyvinyl alcohol film used as the raw fabric is 20 μm or more and 60 μm or less.
In order to adjust the hue change (bluing) when the polarizer is thinned, a mode in which a dichroic dye having a main absorption at 300 nm to 550 nm described later is used in combination with iodine is preferable.

Hereinafter, the polarizing plate of the present invention will be described in more detail.
(1) Configuration of Polarizing Plate First, the polarizer and protective film constituting the polarizing plate of the present invention will be described.
(1-1) Polarizer The polarizer of the present invention is preferably composed of polyvinyl alcohol (PVA) and a dichroic molecule.

  PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.

The degree of saponification of PVA is not particularly limited, but is preferably from 80 to 100 mol%, particularly preferably from 90 to 100 mol%, from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494. Can also be preferably used.

  After PVA is formed into a film, it is preferable to introduce a dichroic molecule to constitute a polarizer. As a method for producing a PVA film, a method of forming a film by casting a stock solution in which a PVA resin is dissolved in water or an organic solvent is generally preferably used. The concentration of the polyvinyl alcohol-based resin in the stock solution is usually 5 to 20% by mass, and a PVA film having a thickness of 10 to 200 μm can be produced by forming this stock solution by a casting method. The PVA film can be produced with reference to Japanese Patent No. 3342516, Japanese Patent Application Laid-Open Nos. 09-328593, 2001-302817, and 2002-144401.

  The crystallinity of the PVA film is not particularly limited, but in order to reduce the average crystallinity (Xc) of 50 to 75% by mass and the in-plane hue variation described in Japanese Patent No. 3251073, A PVA film having a crystallinity of 38% or less described in JP-A-2002-236214 can be used.

The birefringence (Δn) of the PVA film is preferably small, and a PVA film having a birefringence of 1.0 × 10 ⁻³ or less described in Japanese Patent No. 3342516 can be preferably used. However, as described in JP-A-2002-228835, in order to obtain a high degree of polarization while avoiding cutting during stretching of the PVA film, the birefringence of the PVA film is set to 0.02 or more and 0.01 or less. Alternatively, as described in JP-A-2002-060505, the value of (nx + ny) / 2-nz may be set to 0.0003 or more and 0.01 or less. The retardation (in-plane) of the PVA film is preferably from 0 nm to 100 nm, and more preferably from 0 nm to 50 nm. Moreover, 0 nm or more and 500 nm or less are preferable, and, as for Rth (film thickness direction) of a PVA film, 0 nm or more and 300 nm or less are more preferable.

In addition, the polarizing plate of the present invention has a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less described in Japanese Patent No. 3021494, described in JP-A No. 2001-316492. The PVA film in which the number of optical foreign matters of 5 μm or more is 500 or less per 100 cm ² , and the hot-water cutting temperature spot in the TD direction of the film described in JP-A-2002-030163 is 1.5 ° C. or less From a solution in which 1 to 100 parts by mass of a trivalent to hexavalent polyalcohol such as glycerin is added or a plasticizer described in JP-A-06-289225 is mixed in an amount of 15% by mass or more. A formed PVA film can be preferably used.

  The film thickness before stretching of the PVA film is preferably 20 μm or more and 60 μm or less, and particularly preferably 25 μm or more and 55 μm or less. As described in JP-A-2002-236212, a thin PVA film may be used in which the stress generated when stretching 4 to 6 times in water is 10 N or less.

Dichroic molecules of the present invention is I ₃ ^- is preferably used in combination dichroic dye showing a maximum absorption spectrum of the aqueous solution to iodide ion of higher within 300nm to the wavelength range of 500nm, such as ^- and I ₅ . In the wavelength range of 500 nm or less, I ₃ ⁻ color development is mainly involved, but the orientation of I ₃ ⁻ is lower than that of I ₅ ⁻ , and the dichroism exhibiting the maximum in the wavelength range of 300 nm to 500 nm, which has high dichroism. By using it in combination with a dye, the dichroism and the degree of polarization on the short wave side are increased, and preferable results are obtained. High-order iodine ions are dissolved in potassium iodide aqueous solution as described in “Application of Polarizing Plate” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p39-p45. By immersing PVA in the prepared liquid or boric acid aqueous solution, it is adsorbed to PVA and produced in an oriented state.

As the dichroic dye used in the present invention, any compound can be used as long as the absorption spectrum of the aqueous solution shows a maximum in the wavelength range of 300 nm to 500 nm, but a polymethine dye, a cyanine dye, a merocyanine dye, Rhodacyanine dyes, trinuclear merocyanine dyes, allopolar dyes, hemicyanine dyes, styryl dyes, and azo dyes can be preferably used.
For polymethine dyes, Organic Colorants (Elsevier) by M. Okawara, T. Kitao, T. Hirashima, and M. Matsuoka are used. For dyes, FMHarmer “Heterocyclic Compounds-Cyanine Dyes and Related Compounds”, John Wiley & Sons, New York, London, 1964, DMSturmer “Heterocyclic Compounds-Special Topics in Heterocyclic Chemistry”, Chapter 18, Section 14 482-515, US Pat. No. 5,340,694 and the like can be preferably used. As the azo-based dyes, "Latest application technology of functional dyes" supervised by Masahiro Irie, MC, Ryo Nagata "Applications of polarizing film", CM62, JP-A-62-17082, JP-A-1-161202 The dichroic dyes described in JP-A-1-172906 , JP-A-1-172907 , JP-A-1-183602 , and JP-A-7-261024 can also be preferably used. . In the present invention, it is particularly preferable to use an azo dye.

Specific examples of such dichroic dyes include, for example, diphenylurea such as CIDirect Yellow 44, stilbene such as CIDirect Yellow 12, and CIDirect Yellow 8, CIDirect Yellow 28, and CIDirect Yellow 86. CIDirect Yellow 87, CIDirect Yellow 142, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 72, CIDirect Orange 106, CIDirect Orange 107 and the like are preferably used. Two or more of these dichroic dyes may be blended for adjusting the hue.
Further, as described in JP-A-2002-082222, the adsorption thickness may be 4 μm or more.

  The dichroic dye is preferably water-soluble. For this reason, a hydrophilic group such as a sulfonic acid group, amino group, or hydroxyl group is introduced into the dichroic molecule, and the free acid, its alkali metal salt, ammonium salt, amines are introduced. It is preferably used in the form of a salt.

  The dichroic dye can be introduced in at least one of a swelling process, a dyeing process, a hardening process, and a bonding process of a protective film and a polarizer in the polarizing plate manufacturing process described later. When introducing in the swelling step, dyeing step, and hardening step, 0.01 mass of dichroic dye is added to the swelling water washing tank, dyeing solution, hardening solution, and when introducing in the protective film laminating step, into the adhesive solution. Preferably, it is introduced after being dissolved at a concentration of from 1.0% to 1.0% by mass. In this way, a dichroic dye having a maximum absorption spectrum in the wavelength range of 300 nm to 500 nm can be introduced into the polarizer. In addition, addition of a surfactant, sodium sulfate, etc. is also preferably performed to adjust the film concentration and improve the in-plane uniformity of the concentration.

  The content of the dichroic molecule in the film is 0.01% by mass with respect to the polyvinyl alcohol polymer constituting the film matrix from the viewpoint of maintaining the polarization degree and the single plate transmittance at appropriate values. To 5 mass%.

  A preferable film thickness of the polarizer is preferably 8 μm or more and 18 μm or less, and more preferably 12 μm or more and 18 μm or less. The ratio between the thickness of the polarizer and the thickness of the protective film described later is 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0. A range of 16 is also preferable.

(2) Protective film It is preferable that the polarizer is used on both surfaces or one surface by using a transparent polymer film as a protective film and bonding them with an adhesive or a pressure-sensitive adhesive. The protective film is required to have physical properties such as transparency, low birefringence, and moderate rigidity.
The transmittance of the transparent polymer film used for the protective film of the present invention is preferably 80% or more, and more preferably 87% or more. The haze of the transparent polymer film is preferably 2.0% or less, and more preferably 1.0% or less. The refractive index of the transparent polymer film is preferably 1.4 to 1.7.
The material for the transparent polymer film is not particularly limited, and examples thereof include norbornene resin, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyarylate, polysulfone, and cellulose acylate. Commercially available polymer films include ZEONEX and ZEONOR manufactured by Nippon Zeon Co., Ltd., ARTON manufactured by Nippon Synthetic Rubber Co., Ltd., and Fujitac manufactured by Fuji Photo Film Co., Ltd. Among them, Fujitac (Fuji Photo Film Co., Ltd.) And Zeonor (manufactured by Nippon Zeon Co., Ltd.) are particularly preferred. The transparent polymer films on both sides of the polarizer may be the same or different. These commercially available polymer films are disclosed in reference materials: JP-A 63-218726, JP-A-5-25220, JP-A-9-183832, JP-A-20004051, JP-A-5-97978, JP-A-5-97978. 7-11055 gazette, invention association disclosure technique 2001-1745, and the like.

The protective film disposed on the liquid crystal cell side is preferably a polymer film that does not substantially change the polarization state of light incident from the front, that is, has a small in-plane retardation (Re). Specifically, the Re value represented by the following formula (1) is preferably 0 nm or more and 20 nm or less, and particularly preferably 0 nm or more and 5 nm or less. The Rth value represented by the following formula (2) is preferably 0 nm or more and 200 nm or less, more preferably 40 nm to 150 nm, and most preferably 40 nm to 100 nm. The variation of the Re value and the Rth value is preferably within ± 3 nm of the average value, and most preferably ± 2 nm. The film thickness is preferably 20 μm to 100 μm, more preferably 20 μm to 80 μm, and most preferably 30 μm to 80 μm.
Formula (1): Re value = (nx−ny) × d
Formula (2): Rth value = ((nx + ny) / 2−nz) × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to nx in the film plane, nz is the refractive index in the thickness direction of the transparent support, and d is the transparent support. Represents the thickness of
The crossing angle between the slow axis of the protective film and the absorption axis of the polarizer may be any value, but is preferably parallel or an azimuth angle of 45 ± 20 °.

The thickness of the protective film is preferably 30 μm to 120 μm, more preferably 40 μm to 100 μm, and most preferably 40 μm to 80 μm.
The moisture permeability coefficient (25 μm, 25 ° C., 90% RH) of the transparent polymer film is preferably 0.0001 to 1000 g / m ² · day, and the temperature shrinkage is 2 × 10 ⁻⁵ / ° C. to 9 × 10 ⁻⁵ / ° C. is preferable, and the humidity shrinkage is preferably 7 × 10 ⁻⁵ /% RH or less. A transparent polymer film having a moisture permeability of 40 ° C. and 90% RH of 0.04 g / cm ² · 24 h or less as described in JP-A No. 2001-235625 can also be preferably used for the protective film.

The tensile strength value by the tensile test of the polymer film is preferably 50 to 1000 MPa, and the elongation at break is preferably 5% or more and 100% or less. As described in JP-A-08-122525, a cellulose film having a longitudinal tensile strength of 15 kg / mm ² or more and a TD tensile strength of 12.5 kg / mm ² or more may be used. As described in JP 09-251110 A, a cellulose-based film having a tensile strength of 13 kgf / mm ² or more may be used. The photoelastic coefficient of the polymer film may be 25.0 × 10 ⁻¹³ cm ² / dyne or less described in JP-A-07-294732, but in the present invention, it is 9 × 10 ⁻¹³ cm ² / dyne. The following are particularly preferred:

  When a cellulose acylate film is used for the protective film, it is preferable to use a cellulose acylate film described in JIII Journal of Technology 2001-1745. In addition, a cellulose acylate film having a phase difference of 8 nm or less within a viewing angle range of 30 degrees or less from a normal to the plane described in Japanese Patent No. 3327410, and foreign substances recognized in a crossed Nicol state are disclosed in Japanese Patent Application Laid-Open No. 3327410. A cellulose acylate film in the range described in 2000-204173 can also be preferably used as the polarizing plate of the present invention.

  As the raw material cotton of cellulose acetate used in the present invention, a known raw material can be used according to the Japan Society for Invention and Innovation technique 2001-1745. The cellulose acylate material can be synthesized by a known method such as wood chemistry 180-190 (Kyoritsu Shuppan, Mita et al., 1968). The viscosity average degree of polymerization of cellulose acylate is preferably 200 to 700, more preferably 250 to 500, and most preferably 250 to 350.

The acyl group of the cellulose acylate film is not particularly limited, but an acetyl group or a propionyl group is preferably used, and an acetyl group is particularly preferable. The degree of substitution of all acyl groups is preferably 2.7 to 3.0, more preferably 2.8 to 2.95. When cellulose acetate in which all acyl groups are acetyl groups is used, the degree of acetyl substitution is preferably 2.7 to 2.95, more preferably 2.8 to 2.95, and most preferably 2.84 to 2.89. . Further, the degree of acetyl substitution of 2.50 or more and 2.86 or less described in JP 2001-356214 A or 2.75 or more and 2.86 or less described in JP 2001-226495 A is also preferable. Can be used. If it is too low, Re tends to be larger than the desired value due to the conveyance tension during casting, and there is a problem that in-plane variations are likely to occur.
A 6-position acyl group having a substitution degree of 0.9 or more is preferably used from the viewpoint of suppressing the occurrence of variations in Re and Rth. In addition, the value computed according to ASTM D817 is employ | adopted for the substitution degree of the acyl group in this patent.

  The cellulose acylate film of the present invention is preferably produced by a solvent cast method. From the viewpoint of reducing variations in Re and Rth, the concentration of the cellulose acylate solution is preferably 16% by mass to 30% by mass, and more preferably 18 to 26% by mass. The organic solvent used is not particularly limited, but a mixture of a chlorinated solvent, alcohols, ketones and esters is preferably used. As alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, as esters, methyl acetate is used, and as ketones, acetone, cyclopentanone, and cyclohexanone are particularly preferably used. From the viewpoint of protecting the global environment and improving the working environment, an organic solvent substantially not containing a chlorinated solvent may be used. “Substantially free” means that the proportion of the chlorinated solvent in the organic solvent is less than 10% by mass, preferably less than 5% by mass.

In order to prepare a cellulose acylate solution, the cellulose acylate is first swelled by adding the cellulose acylate while stirring the solvent in the tank at room temperature. The swelling time is preferably at least 10 minutes for the purpose of avoiding the insoluble matter remaining. The solvent temperature is preferably 0 to 40 ° C. for the same purpose. When the temperature exceeds 40 ° C., the central portion may not swell sufficiently because swelling occurs rapidly.
As a method for dissolving cellulose acylate, either a cooling dissolution method, a high temperature dissolution method, or both may be used. As a specific method relating to the cooling dissolution method and the high temperature dissolution method, a known method described in JIII Journal of Technology 2001-1745 can be used. In some cases, the cellulose acylate solution obtained above can be preferably prepared by dissolving it at a low concentration and then concentrating it to an optimum concentration using a concentration means.

  Prior to casting, it is preferable to filter off foreign matters such as undissolved matter, dust, and impurities using a suitable filter medium such as a wire mesh, paper, or flannel. Although a method is not specifically limited, The well-known method described in the invention association open technique 2001-1745 grade etc. can be used.

  In the cellulose acylate solution of the present invention, various additives depending on the application can be added in each preparation step. These additives include plasticizers, UV inhibitors and degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines), and release agents. , Fine particles and the like. Further, a retardation adjusting agent may be used in order to control the retardation of the film and its wavelength dependency within a possible range. The retardation adjusting agent is not particularly limited, but preferably has a maximum absorption in the wavelength region of 250 to 400 nm and substantially no absorption in the visible region. The addition amount of each additive is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the polymer. Most preferably, it is used in the range of 5 to 2 parts by mass.

  As a method and equipment for forming the cellulose acylate film of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolution tank (pot) is temporarily stored in a stock tank, and the foam contained in the dope is defoamed for final preparation. The dope is fed from a dope discharge port to a pressurizing die through a pressurizing quantitative gear pump capable of quantitatively feeding the dope with high accuracy, and the dope is run endlessly from the die (slit) of the pressurizing die. The dry-dried dope film (also referred to as a web) is peeled from the metal support at the peeling point where the metal support has been uniformly cast on the substrate and has substantially gone around. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose.

  In the present invention, in order to obtain the desired Re, the film can be stretched by expanding the width of the tenter outlet from the tenter inlet. The draw ratio varies depending on the desired Re, but is preferably 1.0 to 1.3 times, more preferably 1.0 to 1.25 times. The amount of residual solvent in the stretched film is preferably 2% by mass to 35% by mass, and more preferably 2% by mass to 30% by mass. When the residual solvent amount is in the above range, occurrence of creases and wrinkles and film breakage are prevented, the effect of stretching is exhibited, and the adjustment of Re becomes easy. Further, in order to adjust Re, the tension during conveyance may be adjusted within a range that does not cause a problem in handling.

  In the present invention, in order to reduce variation in film thickness and decrease variation in retardation, it is preferable to cast the cellulose acylate solution on a smooth band or drum as a metal support. A plurality of cellulose acylate solutions may be co-cast. The co-casting method is not particularly limited, and a method known in JP-A-11-198285 can be applied. Moreover, the method of forming into a film by casting a cellulose acylate solution from two casting openings may be used. Alternatively, a cellulose acylate film casting method in which a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded may be used. In the case of co-casting, the thickness of each layer is not particularly limited, but preferably the outer layer is preferably thinner than the inner layer. In this case, the thickness of the outer layer is preferably 1 to 30 μm, particularly preferably 1 to 20 μm. Here, the outer layer refers to a surface that is not a band surface (drum surface) in the case of two layers, and layers on both surface sides of the completed film in the case of three or more layers. The inner layer refers to a band surface (drum surface) in the case of two layers, and a layer located inside the outer layer in the case of three or more layers.

  Further, the cellulose acylate solution may be cast simultaneously with a solution for forming other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer). .

  Drying of the dope on the metal support used for producing the cellulose acylate film is preferably performed at 30 to 250 ° C, more preferably 40 to 180 ° C, and most preferably 40 to 140 ° C.

  The thickness (after drying) of the cellulose acylate film of the present invention is in the range of 20 to 100 μm, more preferably in the range of 20 to 80 μm, and most preferably in the range of 30 to 80 μm. The thickness of the film may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like. When a triacetyl cellulose film having a thickness of 50 μm or less is used, the breaking elongation in the longitudinal direction (under the condition of 23 ° C./60% RH) described in JP-A-2002-022961 is 0. It is preferable to use a triacetyl cellulose film of .75% or less.

The maximum peak strength in the vicinity of 1488 cm ⁻¹ by the content of Ca, Fe, and Mg in the cellulose acylate film within the range described in JP 2000-313766 or ATR analysis on both sides of the film It is also preferable to use a triacetyl cellulose film whose ratio of the maximum peak strength in the vicinity of 1365 cm ⁻¹ is in the range described in JP-A No. 2002-258049.

  The polarizing plate of this invention may have an adhesive layer, a separate film, and a protective film as a component other than the above-mentioned polarizer and protective film.

(2) Manufacturing process of polarizing plate Next, the manufacturing process of the polarizing plate of this invention is demonstrated.
The manufacturing process of the polarizing plate in the present invention is preferably composed of a swelling process, a dyeing process, a hardening process, a stretching process, a drying process, a protective film bonding process, and a drying process after bonding. The order of the dyeing step, the hardening step, and the stretching step may be arbitrarily changed, or several steps may be combined and performed simultaneously. Further, as described in Japanese Patent No. 3331615, washing with water after the hardening step can be preferably performed.

  In the present invention, it is particularly preferable to sequentially perform the swelling process, the dyeing process, the hardening process, the stretching process, the drying process, the protective film bonding process, and the drying process after bonding in the order described. An on-line surface inspection step may be provided during or after the above-described steps.

  The swelling step is preferably performed by adding water or the above-described dichroic dye. However, as described in JP-A-10-153709, the optical performance is stabilized and the polarizing plate in the production line is used. In order to avoid wrinkling of the base material (raw fabric), the polarizing plate base material can be swollen with an aqueous boric acid solution to control the degree of swelling of the polarizing plate base material. A preferable concentration in the case of adding the dichroic dye is 0.001% by mass or more and 0.5% by mass or less. Moreover, although the temperature and time of a swelling process can be defined arbitrarily, 10 to 60 degreeC and 5 to 2000 second are preferable.

  For the dyeing step, the method described in JP-A-2002-86554 can be used. Further, as a dyeing method, not only immersion but any means such as application or spraying of iodine or a dichroic dye solution can be used. Further, as described in JP-A-2001-290025, a method of dyeing while stirring the concentration of iodine, dye bath temperature, draw ratio in the bath, and bath solution in the bath may be used.

  In order to obtain a high-contrast polarizing plate, high-order iodine ions are preferably used in the dyeing step by using a solution obtained by dissolving iodine in an aqueous potassium iodide solution. In this case, iodine in the iodine-potassium iodide aqueous solution is preferably in the range of 0.05 to 20 g / l, potassium iodide in the range of 3 to 200 g / l, and the mass ratio of iodine to potassium iodide in the range of 1 to 2000. Moreover, the preferable density | concentration in the case of adding the above-mentioned dichroic dye to a dyeing process is 0.001 mass% or more and 0.5 mass% or less. The dyeing time is preferably 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, iodine is 0.5 to 2 g / l, potassium iodide is 30 to 120 g / l, mass ratio of iodine and potassium iodide is 30 to 120, dyeing time is 30 to 600 seconds, and liquid temperature is 20-50 degreeC is good.

  Further, as described in Japanese Patent No. 3145747, boron compounds such as boric acid and borax may be added to the dyeing solution.

In the hardening step, it is preferable to immerse in the crosslinking agent solution or apply the solution to contain the crosslinking agent. Further, as described in JP-A-11-52130, the hardening process can be performed in several steps.
As the crosslinking agent (hardening agent), those described in US Pat. No. 2,328,977 can be used, and as described in Japanese Patent No. 3357109, the crosslinking agent is used to improve dimensional stability. Although polyvalent aldehydes can be used as the boric acid, boric acids are most preferably used. Moreover, the preferable density | concentration in the case of adding the above-mentioned dichroic dye to a hardening process is 0.001 to 0.5 mass%.
When boric acid is used as a crosslinking agent used in the hardening step, metal ions may be added to the boric acid-potassium iodide aqueous solution. Zinc chloride is preferable as the metal ion. However, as described in JP-A No. 2000-35512, zinc halide such as zinc iodide, zinc sulfate such as zinc acetate is used instead of zinc chloride. It can also be used.

  In the present invention, it is preferable to prepare a boric acid-potassium iodide aqueous solution to which zinc chloride has been added, and perform dura- tion by immersing the PVA film. Boric acid is preferably 1 to 100 g / l, potassium iodide is 1 to 120 g / l, zinc chloride is 0.01 to 10 g / l, hardening time is preferably 10 to 1200 seconds, and liquid temperature is preferably 10 to 60 ° C. . More preferably, boric acid is 10 to 80 g / l, potassium iodide is 5 to 100 g / l, zinc chloride is 0.02 to 8 g / l, hardening time is 30 to 600 seconds, and liquid temperature is 20 to 20 g / l. 50 ° C is preferable.

  The introduction of the dichroic dye into the polarizer may be performed by a method in which an aqueous solution tank of the dichroic dye is separately installed and immersed before and / or before the swelling process, the dyeing process, and the hardening process. Good. The preferable concentration of the dichroic dye in this case is also 0.001% by mass or more and 0.5% by mass or less.

  In the stretching process of the present invention, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515 is used. A preferable draw ratio is 5 times or more, more preferably 5 times or more and 12 times or less, and further preferably 6 times or more and 10 times or less. By setting the draw ratio to 5 times or more, the orientation of polyiodine ions proceeds and preferable optical performance is obtained. The relationship between the draw ratio, the thickness of the original fabric and the thickness of the polarizer is described in JP-A No. 2002-040256 (polarizer film thickness / raw film thickness after bonding of protective film) × (total draw ratio)> 0.17 or the relationship between the width of the polarizer when leaving the final bath and the width of the polarizer when bonding the protective film is 0.80 ≦ (protective film bonding) described in JP-A-2002-040247 It is also preferable that the polarizer width at the time / the width of the polarizer when leaving the final bath) ≦ 0.95. The stretching process described above is particularly preferably performed in a hardening liquid.

  A known method described in JP-A-2002-86554 can be used for the drying step, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. In addition, as described in Japanese Patent No. 3148513, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or described in JP-A-07-325215 and JP-A-07-325218. As described above, aging in a temperature and humidity controlled atmosphere can also be preferably performed.

  The protective film laminating step is a step of laminating both surfaces of the above-described polarizer that has gone through the drying step with two protective films. A method of bonding with a pair of rolls is preferably used so that the adhesive liquid is supplied immediately before bonding and the polarizer and the protective film are overlapped. Further, as described in JP-A-2001-296426 and JP-A-2002-86554, in order to suppress the groove-like unevenness of the record due to the stretching of the polarizer, It is preferable to adjust the moisture content. In the present invention, a moisture content of 0.1% to 30% is preferably used.

  The adhesive between the polarizer and the protective film is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 5 μm after drying, and particularly preferably 0.05 to 3 μm. A preferable concentration when the above-mentioned dichroic dye is added to the adhesive liquid is 0.001% by mass or more and 0.5% by mass or less.

  Moreover, in order to improve the adhesive force of a polarizer and a protective film, it is preferable to perform adhesion after surface-treating the protective film to make it hydrophilic. The surface treatment method is not particularly limited, and a known method such as a saponification method using an alkaline aqueous solution or a corona treatment method can be used. Further, an easy-adhesion layer such as a gelatin undercoat layer may be provided after the surface treatment. As described in JP-A-2002-267839, the contact angle of the protective film surface with water is preferably 50 ° or less.

  The drying conditions after the bonding are in accordance with the method described in JP-A-2002-86554, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. It is also preferable to perform aging in an atmosphere with temperature and humidity control as described in JP-A-07-325220.

Element content in the polarizer, iodine 0.1 to 3.0 g / m ^2, boron 0.1 to 10.0 g / m ^2, potassium 0.1 to 2.0 g / m ^2, the dichroic dye 0 It is preferably 0.001 to 1.0 g / m ² and zinc 0 to 1.0 g / m ² . Further, the potassium content may be 0.2% by mass or less as described in JP-A No. 2001-166143, and the zinc content in the polarizer is described in JP-A No. 2000-035512. It is good also as 0.04 mass% thru | or 0.5 mass%.

Next, the characteristics of the polarizing plate will be described.
(3) Characteristics of polarizing plate (3-1) Transmittance and degree of polarization Preferred single plate transmittance of the polarizing plate of the present invention is 42.5% or more and 49.5% or less, more preferably 42.8% or more. It is 49.0% or less. A preferable range of the degree of polarization defined by the following formula (4) is 99.900% or more and 99.999% or less, and more preferably 99.940% or more and 99.995% or less. A preferable range of transmittance during paranicol is 36% or more and 42% or less.

In the polarizing plate of the present invention, the transmittance at 410 nm at the time of crossed Nicols is preferably 0.001% or more and 0.1% or less, and more preferably 0.001% or more and 0.05% or less. When the transmittance at 410 nm at the time of crossed Nicol is in the above range, b * reduction at the time of crossed Nicol (orthogonal), that is, bluishness is suppressed, and a preferable result is obtained.
The preferable range of the dichroic ratio defined by the following mathematical formula (5) is 48 or more and 500 or less, and more preferably 53 or more and 150 or less.
The above-mentioned single plate transmittance is defined by the following mathematical formula (3) based on JIS Z 8701.

Formula (3)

Here, K, S (λ), y (λ), and τ (λ) are as follows.

S (λ): spectral distribution of standard light used for color display y (λ): color matching function in XYZ system τ (λ): spectral transmittance

Formula (4)

Formula (5)

The iodine concentration and the single plate transmittance may be within the ranges described in JP-A-2002-258051.
The parallel transmittance may be small in wavelength dependency as described in Japanese Patent Application Laid-Open No. 2001-083328 and Japanese Patent Application Laid-Open No. 2002-022950. The relationship between the parallel transmittance and the orthogonal transmittance may be within the range described in JP-A-2002-174728.

  As described in Japanese Patent Application Laid-Open No. 2002-221618, the standard deviation of the parallel transmittance every 10 nm when the light wavelength is 420 to 700 nm is 3 or less, and the light wavelength is 420 to 700 nm. The minimum value of (parallel transmittance / orthogonal transmittance) every 10 nm may be 300 or more.

  The parallel transmittance and orthogonal transmittance at a wavelength of 440 nm, the parallel transmittance and orthogonal transmittance at a wavelength of 550 nm, and the parallel transmittance and orthogonal transmittance at a wavelength of 610 nm of the polarizing plate are disclosed in JP-A No. 2002-258042 and JP-A No. 2002-258043. It is also preferable to make it the range described in the gazette.

(3-2) Hue The hue of the polarizing plate of the present invention is determined using the lightness index L ^* and the chromaticness index a ^* and b ^* in the L ^* a ^* b ^* color system recommended as the CIE uniform perception space. It is preferably evaluated.
L ^* , a ^* , and b ^* are defined by the following formula (6) using the above-described X, Y, and Z.

Formula (6)

Here, X ₀ , Y ₀ , and Z ₀ represent tristimulus values of the illumination light source. In the case of the standard light C, X ₀ = 98.072, Y ₀ = 100, Z ₀ = 118.225, and the standard light In the case of D ₆₅ , X ₀ = 95.045, Y ₀ = 100, Z ₀ = 108.892.
The preferable range of a ^* for a single polarizing plate is −2.0 or more and 0.2 or less, and more preferably −1.8 or more and 0 or less. A preferable range of b ^* of the single polarizing plate is 2 or more and 4.5 or less, and more preferably 2.5 or more and 4.3 or less. The preferable range of a ^* of the parallel transmitted light of the two polarizing plates is −3.6 to 0, and more preferably −3.4 to −0.5. The preferred range of b ^* of the parallel transmitted light of the two polarizing plates is 2.5 or more and 7.5 or less, and more preferably 3 or more and 6.5 or less. The preferable range of a ^* of the orthogonally transmitted light of the two polarizing plates is from −0.3 to 0.8, and more preferably from 0 to 0.7. The preferred range of b * of the orthogonally transmitted light of the two polarizing plates is from −1.5 to 1.5, and more preferably from −1 to 0.5.

The hue may be evaluated by the chromaticity coordinates (x, y) calculated from the aforementioned X, Y, and Z. For example, the chromaticity (x _p , y _p ) of the parallel transmitted light of the two polarizing plates. And the chromaticity (x _c , y _c ) of the orthogonal transmitted light are within the ranges described in JP 2002-214436 A, JP 2001-166136 A, JP 2002-169024 A, It is also preferable that the absorbance relationship be within the range described in JP-A-2001-311827.

(3-3) Viewing angle characteristics When a polarizing plate is placed in crossed Nicol and light with a wavelength of 550 nm is incident, when normal light is incident, and from the direction of 45 degrees with respect to the polarization axis with respect to the normal line It is also preferable that the transmittance ratio and the xy chromaticity difference when entering at an angle of 40 degrees are within the ranges described in Japanese Patent Laid-Open Nos. 2001-166135 and 2001-166137. Further, as described in JP-A-10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminated body arranged in a crossed Nicols state and the light in the direction inclined by 60 ° from the normal line of the laminated body The ratio (T ₆₀ / T ₀ ) with the transmittance (T ₆₀ ) is 10000 or less, or as described in JP-A No. 2002-139625, the polarizing plate has an arbitrary range from the normal to an elevation angle of 80 degrees. When natural light is incident at an angle, the transmittance difference of transmitted light within a wavelength range of 20 nm within the wavelength range of 520 to 640 nm of the transmission spectrum is set to 6% or less, or as described in JP-A-08-248201. It is also preferable that the difference in luminance of transmitted light at an arbitrary 1 cm distance on the film is within 30%.

(3-4) Durability (3-4-1) Wet Heat Durability As described in Japanese Patent Application Laid-Open No. 2001-116922, light before and after being left in an atmosphere of 60 ° C. and 90% RH for 500 hours It is preferable that the transmittance and the change rate of the polarization degree are 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value. Further, as described in JP-A-07-0777608, it is also preferable that the degree of polarization after standing at 80 ° C., 90% RH and 500 hours is 95% or more and the single transmittance is 38% or more.
(3-4-2) Dry durability It is preferable that the light transmittance and the rate of change of the degree of polarization before and after being left in a dry atmosphere at 80 ° C. for 500 hours are also 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value.
(3-4-3) Other durability Further, as described in JP-A-06-167611, the shrinkage after standing at 80 ° C. for 2 hours is 0.5% or less, or a glass plate The x and y values after leaving the polarizing plate laminate having the crossed Nicols arrangement on both sides in a 69 ° C. atmosphere for 750 hours are within the range described in JP-A-10-068818, the change in spectral intensity ratio of the 105 cm ^-1 and 157cm ^-1 due to 200 hours standing after treatment of Raman spectroscopy in an atmosphere of RH 90%, is described in JP-a-08-094834 and JP 09-197127 It is also preferable to set the range.

(3-5) Orientation degree The higher the degree of orientation of PVA, the better the polarization performance, but the order parameter value calculated by means such as polarization Raman scattering or polarization FT-IR is 0.2 to 1.0. This is a preferred range. Further, as described in JP-A-59-133509, the difference between the orientation coefficient of the polymer segment in the entire amorphous region of the polarizer and the orientation coefficient of the occupied molecule (0.75 or more) is at least 0. .15, or the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85 as described in JP-A No. 04-204907, or higher iodine ions of I ₃ and I ₅ It is also preferable to set the degree of orientation to 0.8 to 1.0 as an order parameter value.

(6) Other characteristics As described in JP-A-2002-006133, the contraction force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is 4.0 N / cm or less. As described in Japanese Unexamined Patent Publication No. 2002-236213, when the polarizing plate is placed under heating at 70 ° C. for 120 hours, the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarizing axis direction of the polarizing plate are In addition, it can be preferably carried out within a range of ± 0.6%, or the moisture content of the polarizing plate can be 3% by mass or less as described in JP-A-2002-090546. Further, as described in JP 2000-249832 A, the surface roughness in the direction perpendicular to the stretching axis is 0.04 μm or less based on the center line average roughness, or in JP 10-268294 A As described, the refractive index n ₀ in the transmission axis direction is made larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film is within the range described in JP-A-10-111411. Can also be preferably performed.

(4) Functionalization of polarizing plate The polarizing plate of the present invention includes an LCD viewing angle widening film, a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, and a brightness enhancement film. In addition, it is preferably used as a functionalized polarizing plate combined with an optical film having functional layers such as a hard coat layer, a forward scattering layer, and an antiglare (antiglare) layer.
A schematic cross-sectional view of a structural example in which the polarizing plate of the present invention and the above-described functional optical film are combined is shown in FIG. A functional optical film may be used as a protective film on one side of the polarizing plate, and the functional optical film and the polarizer may be bonded via an adhesive (FIG. 1A), or a protective film may be formed on both sides of the polarizer. A functional optical film may be bonded to a polarizing plate provided with a pressure-sensitive adhesive (FIG. 1B). In the former case, any transparent protective film can be used as the other protective film. The peel strength between layers such as a functional layer and a protective film is preferably 4.0 N / 25 mm or more described in JP-A No. 2002-311238. The functional optical film is preferably disposed on the liquid crystal module side according to the intended function, or on the side opposite to the liquid crystal module, that is, on the display side or the backlight side.

The functional optical film used in combination with the polarizing plate of the present invention will be described below.
(4-1) Viewing Angle Enlargement Film The polarizing plate of the present invention is composed of TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Bend), VA (Vertically Aligned), ECB (Electrically Bold). It can be used in combination with a viewing angle widening film proposed for such a display mode. A viewing angle widening film is synonymous with an optical compensation sheet.

  As a viewing angle widening film for TN mode, Journal of the Japan Printing Society Vol. 36, No. 3 (1999) p40-44, Monthly Display August (2002) p20-24, JP-A-4-229828, JP-A-6 -75115, JP-A-6-214116, JP-A-8-50206, JP-A-2001-100039, etc., preferably a combination of optical compensation films, particularly WV films manufactured by Fuji Photo Film Co., Ltd. Used.

  A preferable configuration of the viewing angle widening film for the TN mode has an alignment layer and an optically anisotropic layer in this order on the transparent polymer film used as the protective film. In this case, the said description regarding the transparent polymer film used as a protective film is applied including a preferable aspect. The most preferred transparent polymer film is a cellulose acetate film. The viewing angle widening film is used by being bonded to a polarizing plate through an adhesive, but also serves as one of the protective films of the polarizer as described in SID'00 Dig., P551 (2000). It is particularly preferable to use it from the viewpoint of thinning.

  The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, or formation of a layer having a microgroup. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field or light irradiation is also known, but an alignment layer formed by a rubbing treatment of a polymer is particularly preferable. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. It is preferable that the absorption axis direction and the rubbing direction of the polarizer are substantially parallel. As the polymer used for the alignment layer, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in JP-A-9-152509, and the like can be preferably used. The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer is preferably formed from a liquid crystalline compound. The liquid crystal compound used in the present invention particularly preferably has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like the triphenylene derivative of D-1 below, and has a structure in which side chains extend radially therefrom. In order to impart stability over time, it is also preferable to further introduce a group that reacts with heat, light or the like. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.

D-1

  In the above structure, R represents a monovalent organic group having a polymerizable group such as an acryloyl group at the terminal.

  The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented so that they are perpendicular to the plane on the opposite air side. is doing. The discotic liquid crystal layer as a whole has a hybrid alignment, and this layer structure can realize a wide viewing angle of a TN mode TFT-LCD.

  The optically anisotropic layer is generally a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) dissolved in a solvent, coated on the alignment layer, dried, and then discotic nematic. After heating to the phase formation temperature, it is obtained by polymerization by irradiation with UV light or the like and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

  In addition to the discotic compound added to the optically anisotropic layer, the compound has compatibility with the discotic compound and can give a preferable change in tilt angle to the liquid crystalline discotic compound or inhibit the alignment. Any compound can be used as long as it is not. Among these, additives for controlling the orientation on the air interface side such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), fluorine-containing triazine compounds, cellulose acetate, cellulose acetate Mention may be made of polymers such as pionate, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.

  The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.

  A preferred embodiment of the viewing angle widening film is composed of a cellulose acetate film as a transparent substrate film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer. The optically anisotropic layer is crosslinked by UV light irradiation.

  In addition to the above, when the viewing angle widening film and the polarizing plate of the present invention are combined, for example, as described in JP-A-07-198942, it has an optical axis in a direction intersecting the plate surface. It is laminated with a retardation plate exhibiting anisotropy in birefringence, or the dimensional change rate of the protective film and the optically anisotropic layer is substantially the same as described in JP-A-2002-258052. Can also be preferably performed. Further, as described in JP 2000-258632 A, the moisture content of the polarizing plate bonded to the viewing angle widening film is set to 2.4% or less, or described in JP 2002-267839 A. It is also preferable to make the contact angle with water on the surface of the viewing angle widening film 70 ° or less.

  The viewing angle widening film for an IPS mode liquid crystal cell is used for optical compensation of liquid crystal molecules aligned in parallel to the substrate surface and for improving the viewing angle characteristics of the orthogonal transmittance of the polarizing plate during black display without an electric field. In the IPS mode, black is displayed when no electric field is applied, and the transmission axes of the pair of upper and lower polarizing plates are orthogonal. However, when observed from an oblique direction, the crossing angle of the transmission axes is not 90 °, and leakage light is generated, resulting in a decrease in contrast. When the polarizing plate of the present invention is used in an IPS mode liquid crystal cell, the in-plane retardation as described in JP-A-10-54982 is close to 0 and the thickness direction is reduced in order to reduce leakage light. It is preferably used in combination with a viewing angle widening film having a phase difference.

  The OCB mode viewing angle widening film for liquid crystal cells is intended to improve the viewing angle characteristics of black display by optically compensating the liquid crystal layer that is vertically aligned at the center of the liquid crystal layer by applying an electric field and tilted near the substrate interface. used. When the polarizing plate of the present invention is used in an OCB mode liquid crystal cell, it is preferably combined with a viewing angle widening film in which a discotic liquid crystalline compound as described in US Pat. No. 5,805,253 is hybrid-aligned. Used.

  The viewing angle widening film for liquid crystal cells in the VA mode improves the viewing angle characteristics of black display in a state where liquid crystal molecules are vertically aligned with respect to the substrate surface in the absence of an electric field. As such a viewing angle widening film, a film having an in-plane retardation close to 0 and having a retardation in the thickness direction as described in Japanese Patent No. 2866372, A cholesteric liquid crystal layer having a range of Nz and Re (front phase difference) described in Japanese Patent Application Laid-Open No. 90531, Japanese Patent Application Laid-Open No. 2002-90542, Japanese Patent Application Laid-Open No. 2002-90542, and Japanese Patent Application Laid-Open No. 2002-107541 was applied. A stretched polycarbonate film, a two-layer retardation film described in JP-A No. 2002-131546, JP-A No. 2002-131547, JP-A No. 2002-148433, JP-A No. 2002-148434, JP-A-2002 -148437, JP-A 2002-148439, JP-A 2002-148438, JP 002-196135, JP longitudinal or transverse stretching a norbornene resin film described in 2002-196134 JP, or a film obtained by stretching in both directions is preferably used.

  The viewing angle widening film described above is intended for, for example, stretching a polymer film by an appropriate method such as uniaxial or biaxial, or imparting a refractive index anisotropy of nx≈ny> nz to one surface of the film. For example, a cholesteric liquid crystal polymer or a nematic liquid crystal polymer containing a chiral agent, a method of applying or transferring a compound that forms these liquid crystal polymers by polymerization treatment with light or heat, an alignment film, an electric field or a magnetic field by rubbing treatment, etc. It can be prepared by combining and laminating appropriate orientation treatment methods such as orientation treatment by application of the above. When a cholesteric liquid crystal layer is used for the viewing angle widening film, it is preferable not to exhibit selective reflection characteristics in the visible light region.

  For the formation of the adhesive layer used when laminating the polarizing plate and the viewing angle widening film, for example, an appropriate polymer such as acrylic polymer, silicone polymer, polyester, polyurethane, polyether or synthetic rubber is used. it can. Among these, acrylic pressure-sensitive adhesives are preferable from the viewpoints of optical transparency, adhesive properties, weather resistance, and the like.

  The viewing angle widening film described above is preferably used as an integral type bonded with a polarizer and an adhesive as one of the protective films.

(4-2) λ / 4 plate The polarizing plate of the present invention can be used as a circularly polarizing plate laminated with a λ / 4 plate. The circularly polarizing plate has a function of converting incident light into circularly polarized light, and is preferably used for a reflective liquid crystal display device, a transflective liquid crystal display device such as an ECB mode, or an organic EL element.
The λ / 4 plate used in the present invention is a retardation film having a retardation (Re) of approximately ¼ of the wavelength in the visible light wavelength range in order to obtain almost perfect circularly polarized light in the visible light wavelength range. It is preferable that "Retardation of approximately 1/4 in the wavelength range of visible light" means that the longer the wavelength is from 400 to 700 nm, the larger the retardation, and the retardation value (Re450) measured at a wavelength of 450 nm is 80 to 125 nm. And the range which satisfies the relationship whose retardation value (Re590) measured by wavelength 590nm is 120 to 160 nm is shown. It is more preferable that Re590-Re450 ≧ 5 nm is satisfied, and it is particularly preferable that Re590-Re450 ≧ 10 nm is satisfied.

  The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied, but for example, described in JP-A-5-27118, JP-A-10-68816, and JP-A-10-90521. A λ / 4 plate obtained by laminating a plurality of polymer films, a λ / 4 plate obtained by stretching a single polymer film described in WO00 / 65384, WO00 / 26705, JP 2000-284126 A, A known λ / 4 plate such as a λ / 4 plate in which at least one optically anisotropic layer is provided on a polymer film described in JP-A-2002-31717 can be used. Moreover, the direction of the slow axis of the polymer film and the orientation direction of the optically anisotropic layer can be arranged in any direction according to the liquid crystal cell.

  In the circularly polarizing plate, the slow axis of the λ / 4 plate and the transmission axis of the polarizer can intersect at an arbitrary angle, but preferably intersect within a range of 45 ° ± 20 °. Of course, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may intersect in a range other than the above.

  When laminating a λ / 4 plate and a λ / 2 plate, as described in Japanese Patent No. 3236304 and Japanese Patent Laid-Open No. 10-68816, the λ / 4 plate and the λ / 2 plate Bonding is preferably performed so that the angle formed by the in-plane slow axis and the transmission axis of the polarizing plate is substantially 75 ° and 15 °.

(4-3) Antireflection film The polarizing plate of the present invention can be used in combination with an antireflection film. For the anti-reflection film, either a film having a reflectance of about 1.5% only by applying a single layer of a low refractive index material such as a fluorine-based polymer, or a film having a reflectance of 1% or less using multilayer interference of a thin film is used. it can. In the present invention, a structure in which a low refractive index layer and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a middle refractive index layer) is laminated on a transparent support is preferably used. The In addition, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28, JP-A-2002-301783, and the like can also be preferably used.
The refractive index of each layer constituting the antireflection film preferably satisfies the following relationship.
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of transparent support> refractive index of low refractive index layer

As the transparent support used for the antireflection film, the transparent polymer film used for the protective film of the polarizing layer can be preferably used.
The refractive index of the low refractive index layer is 1.20 to 1.55, preferably 1.30 to 1.50. The low refractive index layer is preferably used as an outermost layer having scratch resistance and antifouling properties. In order to improve scratch resistance, it is also preferable to impart a slipperiness to the surface using a material such as a silicone-containing compound or a fluorine-containing compound.
Examples of the fluorine-containing compound include paragraphs [0018] to [0026] of JP-A-9-222503, paragraphs [0019] to [0030] of JP-A-11-38202, and JP-A-2001-40284. The compounds described in paragraph Nos. [0027] to [0028] and JP-A No. 2000-284102 can be preferably used.

  The silicone-containing compound is preferably a compound having a polysiloxane structure, but reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane at both ends (JP-A-11-258403), etc. An organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent may be cured by a condensation reaction in the presence of a catalyst (Japanese Patent Laid-Open No. 58-142958). Gazettes, 58-147483, 58-147484, JP-A-9-157582, 11-106704, JP-A-2000-117902, 2001-48590, 2002-2002. 53804).

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as fillers (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as additives other than the above. And a low refractive index inorganic compound, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, silane coupling agents, slip agents, surfactants, and the like are also preferably included. be able to.
The low refractive index layer may be formed by a vapor phase method (vacuum vapor deposition method, sputtering method, ion plating method, plasma CVD method, etc.), but is preferably formed by a coating method because it can be manufactured at low cost. . As the coating method, dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, and micro gravure can be preferably used.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

The medium refractive index layer and the high refractive index layer preferably have a constitution in which ultrafine particles of high refractive index having an average particle size of 100 nm or less are dispersed in a matrix material. Inorganic compound fine particles having a high refractive index include inorganic compounds having a refractive index of 1.65 or more, for example, oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and metal atoms thereof. A composite oxide or the like can be preferably used.
Such ultrafine particles may be obtained by treating the particle surface with a surface treatment agent (silane coupling agent, etc .: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds or (Organic metal coupling agent: JP-A-2001-310432, etc.), a core-shell structure with high refractive index particles as a core (JP-A-2001-166104, etc.), or a specific dispersant (for example, JP-A-11-11) -157033, U.S. Pat. No. 6,210,858, JP-A-2002-27776069, etc.).

As the matrix material, conventionally known thermoplastic resins, curable resin films, and the like can be used, but JP-A-2000-47004, 2001-315242, 2001-31871, and 2001-296401. It is also possible to use a curable film obtained from a polyfunctional material described in a gazette or the like or a metal alkoxide composition described in JP-A-2001-293818 or the like.
The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K 5400.

(4-4) Brightness Improvement Film The polarizing plate of the present invention can be used in combination with a brightness enhancement film. The brightness enhancement film has a function of separating circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and reflects or scatters one circularly polarized light or linearly polarized light back to the backlight side. Re-reflected light from the backlight part partially changes the polarization state and partially transmits when re-entering the brightness enhancement film and the polarizing plate, so the light utilization rate is improved by repeating this process. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection system and an anisotropic scattering system are known, and both can be combined with the polarizing plate of the present invention.

  In the anisotropic reflection system, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers and increasing the refractive index difference in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal systems (European Patent No. 606940A2, Japanese Patent Laid-Open No. Hei 8- No. 271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. )) Is preferably used in the present invention. Regarding NIPOCS, Nitto Giho, vol.38, No.1, may, 2000, pages 19 to 21 can be referred to.

  Further, in the present invention, positive numbers described in the specifications of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226 and JP-A-9-274108 and 11-174231 are described. It is also preferable to use it in combination with a brightness enhancement film of an anisotropic scattering method in which an intrinsic birefringent polymer and a negative intrinsic birefringent polymer are blended and uniaxially stretched. As the anisotropic scattering system brightness enhancement film, DRPF-H (manufactured by 3M) is preferable.

The polarizing plate and the brightness enhancement film of the present invention are preferably used as an integrated type in which one of the protective film of the polarizing plate and the protective film of the polarizing plate is bonded via an adhesive.

(4-5) Other functional optical films The polarizing plate of the present invention further includes a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, a gas barrier layer, a sliding layer, an antistatic layer, an undercoat layer and a protective layer. It is also preferable to use it in combination with a functional optical film provided with a layer or the like. These functional layers are preferably used in combination with each other or in the same layer as the above-described antireflection layer, optically anisotropic layer, or the like.

(4-5-1) Hard Coat Layer The polarizing plate of the present invention combines a hard coat layer with a functional optical film provided on the surface of a transparent support in order to impart mechanical strength such as scratch resistance. Is preferably performed. When the hard coat layer is applied to the above-described antireflection film, it is particularly preferable to provide it between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of the curable compound by light or heat. The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound. As specific constitutional compositions of the hard coat layer, for example, those described in JP-A Nos. 2002-144913, 2000-9908 and WO0 / 46617 can be preferably used.
The film thickness of the hard coat layer is preferably 0.2 to 100 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K 5400. Further, in the Taber test according to JIS K 5400, the smaller the wear amount of the test piece before and after the test, the better.

  As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group or a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferred examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol. Polyacrylates of polyols such as hexaacrylate; epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether; obtained by reaction of polyisocyanate and hydroxyl group-containing acrylate such as hydroxyethyl acrylate Examples of preferred compounds include urethane acrylates. Moreover, as a commercially available compound, EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (above, Daicel UCB Co., Ltd. product), UV -6300, UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.

  Preferred examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, glycerol triglycidyl ether as glycidyl ethers. Glycidyl ethers such as triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin; -301, Epolide GT-401, EHPE3150CE Manufactured by Daicel Chemical Industries, Ltd.), cycloaliphatic epoxies such as polycyclohexyl epoxy methyl ether of phenol novolak resin; OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, Toagosei Co., Ltd.) Oxetanes such as (manufactured). In addition, a polymer of glycidyl (meth) acrylate or a copolymer of a monomer that can be copolymerized with glycidyl (meth) acrylate may be used for the hard coat layer.

  For the hard coat layer, oxides of metals such as silicon, titanium, zirconium, and aluminum are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and curl of articles having the hard coat layer. Fine particles: It is also preferable to add crosslinked organic fine particles such as crosslinked particles such as polyethylene, polystyrene, poly (meth) acrylic esters, polydimethylsiloxane, and crosslinked rubber fine particles such as SBR and NBR. The average particle diameter of these fine particles is preferably 1 nm to 20000 nm. Further, the shape of the crosslinked fine particles can be used without particular limitation, such as a spherical shape, a rod shape, a needle shape, or a plate shape. The addition amount of the fine particles is preferably 60% by volume or less, more preferably 40% by volume or less of the hard coat layer after curing.

  In the case of adding the inorganic fine particles described above, in order to improve the affinity with the binder polymer, it contains a metal such as silicon, aluminum, titanium, and the alkoxide group, carboxylic acid group, sulfonic acid group, phosphonic acid group. It is also preferable to perform a surface treatment using a surface treatment agent having a functional group such as.

  The hard coat layer is preferably cured using heat or active energy rays. Among them, active energy rays such as radiation, gamma rays, alpha rays, electron rays, and ultraviolet rays are more preferred, and safety and productivity are improved. In view of the above, it is particularly preferable to use an electron beam or an ultraviolet ray. In the case of curing with heat, the heating temperature is preferably 140 ° C. or less, more preferably 100 ° C. or less, considering the heat resistance of the plastic produced by curing.

(4-5-2) Forward scattering layer The forward scattering layer is used to improve the viewing angle characteristics (hue and luminance distribution) in the vertical and horizontal directions when the polarizing plate of the present invention is applied to a liquid crystal display device. . In the present invention, a configuration in which fine particles having different refractive indexes are dispersed in a binder is preferable. For example, Japanese Patent Application Laid-Open No. 11-38208 in which a forward scattering coefficient is specified, and Japanese Patent Application Laid-Open No. 2000 in which a relative refractive index between a transparent resin and fine particles is in a specific range. The construction of JP-A No. 199809, JP-A No. 2002-107512 that defines the haze value as 40% or more can be used. In addition, in order to control the viewing angle characteristics of haze, the polarizing plate of the present invention is also preferably used in combination with “Lumisty” described in Sumitomo Chemical's technical report “Photofunctional Films” on pages 31-39. be able to.

(4-5-3) Antiglare layer The antiglare (antiglare) layer is used to scatter reflected light and prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
The method for forming irregularities on the film surface is, for example, a method of forming irregularities on the film surface by adding fine particles (for example, JP 2000-271878 A), relatively large particles (particle size 0.05 to 2 μm). ) In a small amount (0.1 to 50% by mass) to form a surface uneven film (for example, JP-A Nos. 2000-281410, 2000-95893, 2001-100004, 2001-2001). No. 281407, etc.), a method of physically transferring the uneven shape onto the film surface (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Etc.) and the like can be preferably used.

  These functional layers can be used as a protective film for the polarizer or provided on one or both surfaces of the polarizer via the protective film.

(5) Liquid crystal display device using polarizing plate Next, a liquid crystal display device using the polarizing plate of the present invention will be described.
FIG. 2 is a schematic view showing an example of a liquid crystal display device in which the polarizing plate of the present invention is used.
The liquid crystal display device shown in FIG. 2 includes a liquid crystal cell (5 to 9), and an upper polarizing plate 1 and a lower polarizing plate 12 that are disposed with the liquid crystal cell interposed therebetween. The polarizing plate is sandwiched between a polarizer and a pair of transparent protective films, but is shown as an integrated polarizing plate in FIG. 2, and the detailed structure is not shown. The liquid crystal cell includes a liquid crystal layer formed of an upper substrate 5 and a lower substrate 8 and liquid crystal molecules 7 sandwiched between them. The liquid crystal cell is different in the alignment state of liquid crystal molecules that perform ON / OFF display, and includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend), VA (Vertical Aligned Electron), ECB (Etc. However, the polarizing plate of the present invention can be used in any display mode regardless of the transmissive and reflective types.

  An alignment film (not shown) is formed on the surfaces of the substrates 5 and 8 that are in contact with the liquid crystal molecules 7 (hereinafter may be referred to as “inner surfaces”), and by a rubbing process or the like applied on the alignment film, The alignment of the liquid crystal molecules 7 in a state where no electric field is applied or a state where a low voltage is applied is controlled. Further, on the inner surfaces of the substrates 5 and 8, a transparent electrode (not shown) capable of applying an electric field to the liquid crystal layer made of the liquid crystal molecules 7 is formed.

The rubbing direction of the TN mode is applied in directions perpendicular to each other on the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle (twist angle) of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm is added so that the twist angle becomes 90 °.
The twist angle is in the vicinity of 90 ° (85 to 95 °) in the case of a notebook computer, a personal computer monitor, and a liquid crystal display device for a television, and is 0 to 70 ° in the case of use as a reflective display device such as a mobile phone. Set. In the IPS mode and the ECB mode, the twist angle is 0 °. In the IPS mode, electrodes are disposed only on the lower substrate 8 and an electric field parallel to the substrate surface is applied. In the OCB mode, there is no twist angle and the tilt angle is increased, and in the VA mode, the liquid crystal molecules 7 are aligned perpendicular to the upper and lower substrates.

Here, the brightness at the time of white display changes depending on the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn. Therefore, in order to obtain the maximum brightness, the range is set for each display mode.
In general, the crossing angle between the absorption axis 2 of the upper polarizing plate 1 and the absorption axis 13 of the lower polarizing plate 12 is generally approximately orthogonal to obtain a high contrast. The crossing angle between the absorption axis 2 of the upper polarizing plate 1 of the liquid crystal cell and the rubbing direction of the upper substrate 5 varies depending on the liquid crystal display mode, but is generally set to be parallel or vertical in the TN and IPS modes. In OCB and ECB modes, it is often set to 45 °. However, the optimum value differs in each display mode for adjusting the color tone and viewing angle of the display color, and the present invention is not limited to this range.

  The liquid crystal display device in which the polarizing plate of the present invention is used is not limited to the configuration of FIG. 2, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizer. In addition, the above-described viewing angle widening films 3 and 10 may be separately disposed between the liquid crystal cell and the polarizing plate. The polarizing plates 1 and 13 and the viewing angle widening films 3 and 10 may be arranged in a laminated form bonded with an adhesive, or a so-called integrated elliptical polarization using one of the liquid crystal cell side protective films for widening the viewing angle. It may be arranged as a plate.

  When used as a transmission type, a cold cathode or hot cathode fluorescent tube, or a backlight having a light emitting diode, field emission element, or electroluminescent element as a light source can be disposed on the back surface. Further, the liquid crystal display device in which the polarizing plate of the present invention is used may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back of the liquid crystal cell or under the liquid crystal cell. A reflective film is installed on the inner surface of the side substrate. Of course, a front light using the light source may be provided on the liquid crystal cell observation side.

[Example 1]
<Preparation of Polarizer A and Polarizing Plate A>
After applying an aqueous solution prepared by dissolving PVA powder having an average polymerization degree of 2400 and a saponification degree of 99.9% or more in pure water to 10% by mass on a polyester film and drying at 40 ° C. for 3 hours. Further, drying was performed at 110 ° C. for 60 minutes to obtain a PVA film having a thickness of 50 μm. The obtained film was swollen with warm water at 30 ° C. for 1 minute, and was dissolved in an aqueous solution of potassium iodide / iodine / CIDirect Yellow 44 (λmax = 420 nm) / sodium nitrate (mass ratio 10: 1: 0.2: 2) at 30 ° C. It was immersed and longitudinally uniaxially stretched 1.5 times. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to an iodine concentration of 0.38% by mass. Next, in a 4.25% boric acid aqueous solution at 50 ° C, the film was uniaxially stretched so that the total draw ratio was 7 times, immersed in a 30 ° C water bath, washed with water, dried at 50 ° C for 4 minutes, A polarizer A having a thickness of 12.5 μm was obtained.
Thereafter, a protective film (saponified Fuji Photo Film Co., Ltd. Fujitac (cellulose triacetate, retardation) was formed on both surfaces of the polarizer A using a 4% aqueous solution of PVA (PVA-124 manufactured by Kuraray Co., Ltd.) as an adhesive. And a polarizing plate A was prepared by further heating at 70 ° C. for 30 minutes.

<Preparation of Polarizer B and Polarizing Plate B>
An aqueous solution prepared by dissolving a PVA powder having an average degree of polymerization of 2400 and a degree of saponification of 99.9% or more in pure water to 12% by mass is applied onto a polyester film and dried at 40 ° C. for 3 hours. Further, drying was performed at 110 ° C. for 60 minutes to obtain a PVA film having a thickness of 50 μm. The obtained film was swollen with warm water at 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched uniaxially twice. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to an iodine concentration of 0.38% by mass. Next, it was longitudinally uniaxially stretched in a 4.25% by mass boric acid 50 ° C. aqueous solution so that the total draw ratio was 6.5 times, immersed in a 30 ° C. water bath, washed with water, and dried at 50 ° C. for 4 minutes. Thus, a polarizer B having a thickness of 16 μm was obtained.
Thereafter, on both sides of the polarizer B, PVA (PVA-124 manufactured by Kuraray Co., Ltd.) / CIDirect Yellow 28 (λmax = 400 nm) = 4% by mass / 0.15% by mass aqueous solution as an adhesive, a protective film (ken Fuji Photo Film Co., Ltd. Fujitac (cellulose triacetate, retardation value 3.0 nm, film thickness 80 μm)) was bonded together, and further heated at 70 ° C. for 30 minutes to prepare polarizing plate B.

<Preparation of Polarizer C and Polarizing Plate C>
An aqueous solution prepared by dissolving a PVA powder having an average degree of polymerization of 2400 and a degree of saponification of 99.9% or more in pure water to 12% by mass is applied onto a polyester film and dried at 40 ° C. for 3 hours. Further, drying was performed at 110 ° C. for 60 minutes to obtain a PVA film having a thickness of 50 μm. The obtained film was swollen with warm water at 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched uniaxially twice. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to an iodine concentration of 0.38% by mass. Subsequently, the total draw ratio becomes 6.5 times in a 52 ° C. aqueous solution of CI Direct Yellow 12 (λmax = 389 nm) / sodium nitrate / boric acid = 0.1 mass% / 1.2 mass% / 4.25 mass%. Thus, the film was stretched uniaxially, immersed in a 30 ° C. water bath, washed with water, and dried at 50 ° C. for 4 minutes to obtain a polarizer C having a thickness of 16 μm.
After that, on both sides of the PVA film, a protective film (saponified Fuji Photo Film Co., Ltd. Fujitac (cellulose triacetate, retardation value) was prepared by using a 4% aqueous solution of PVA (PVA-124 manufactured by Kuraray Co., Ltd.) as an adhesive. 3.0 nm, film thickness 80 μm)) were bonded together, and further heated at 70 ° C. for 30 minutes to prepare polarizing plate C.

<Production of Comparative Polarizer D and Polarizing Plate D>
A comparative polarizer D and a polarizing plate D were produced in the same manner as in Example 1 except that CIDirect Yellow 44 and sodium sulfate were removed from the staining solution.

<Production of Comparative Polarizer E and Polarizing Plate E>
A comparative polarizer E and a polarizing plate E were produced in the same manner as the comparative polarizing plate D, except that the original film thickness was 75 μm. The thickness of the polarizer E was 23 μm.

(Measurement of single-plate transmittance, degree of polarization, and 410 nm transmittance during crossed Nicols)
A sample of the polarizing plate A was cut into 2 × 5 cm, and the transmittance was measured with a Shimadzu autograph spectrophotometer UV3100. The degree of polarization P (%) is expressed by the following equation, where H0 (%) is the transmittance when the two polarizing plate absorption axes are overlapped and H1 (%) is the transmission when the absorption axes are orthogonally stacked. )
P = [(H0−H1) / (H0 + H1)] ^1/2 × 100
Further, the single plate transmittance was obtained by using one sample and correcting the transmittance of 400 to 700 nm with the visibility. The transmittance at 410 nm during crossed Nicols was also measured by this measurement.

(Evaluation of hue)
A * and b * in the CIELAB color system were determined using a spectrophotometer UV-3100PC manufactured by Shimadzu. The results are shown in Table 1.

Compared to comparative polarizing plate D and E of Table 1, the polarizing plate A to C is, b ^* decreases when the cross Nicol (orthogonal), i.e. it is clear that bluish reduction is suppressed. The polarizing plates A and C are reference examples.

[Example 2]
<Preparation of Optical Compensation Film (Viewing Angle Expansion Film) A>
130 g of water and 40 g of methanol are added to 30 g of linear alkyl-modified PVA (MP-203, manufactured by Kuraray Co., Ltd.), stirred and dissolved, and then filtered through a polypropylene filter having a pore size of 30 μm to prepare a coating solution for an alignment layer. did.
On the other hand, a triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.), which is a 100 μm-thick support having an undercoat layer of a gelatin thin film (0.1 μm), is prepared. The coating solution was applied using a bar coater. After coating, the film was dried at 60 ° C., and then rubbed in the longitudinal direction to form an alignment layer having a thickness of 0.5 μm.
Next, 1.6 g of a compound LC-1 having the following structure as a liquid crystalline discotic compound, 0.4 g of phenoxydiethylene glycol acrylate (M-101, manufactured by Toagosei Co., Ltd.), cellulose acetate butyrate (CAB531-1, Eastman) (Chemical Co., Ltd.) 0.05 g and photopolymerization initiator (Irgacure-907, Ciba Geigy Co., Ltd.) 0.01 g were dissolved in 3.65 g of methyl ethyl ketone, and then filtered through a polypropylene filter having a pore size of 1 μm to obtain optical anisotropy. A layer coating solution was prepared.

Compound LC-1

On the alignment layer, the coating liquid for optically anisotropic layer was applied using a bar coater and dried at 120 ° C. Thereafter, the mixture was further heated at 120 ° C. for 3 minutes, and the liquid crystal was aged to align the discotic compound. Further, using a 160 W air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at 120 ° C., the coating layer was irradiated with ultraviolet rays so that the irradiation intensity was 400 mW / cm ² and the irradiation energy amount was 300 mJ / cm ^2. Was cured to form an optically anisotropic layer having a thickness of 1.8 μm, thereby preparing an optical compensation film A.

<Preparation of elliptical polarizing plate A>
In Example 1 described above, after stretching and drying at 70 ° C. for 4 minutes, the process of bonding a protective film with PVA as an adhesive on both surfaces of the polarizer A was replaced with the following process. That is, after stretching and drying at 70 ° C. for 4 minutes, a protective film (manufactured by Fuji Photo Film Co., Ltd.) having both surfaces of the polarizer A saponified with PVA (the aforementioned PVA-124A) as an adhesive. Fujitac, cellulose triacetate, retardation value 3.0 nm, film thickness 80 μm) were bonded together using the optical compensation film A with the other surface saponified, and further heated at 70 ° C. for 30 minutes. At this time, the support surface on the side opposite to the side where the optically anisotropic layer is formed is bonded to the polarizer A so that the rubbing direction of the alignment layer of the optical compensation film A coincides with the stretching direction of the polarizer A. In this manner, the elliptically polarizing plate A of the present invention was produced.

[Example 3]
<Preparation of elliptically polarizing plates B, C, D, E>
Elliptical polarizing plates B, C, D, and E were produced in the same manner as in Example 2 except that the polarizer A was changed to the polarizers B, C, D, and E in Example 2 described above. At this time, the support surface on the side opposite to the side on which the optically anisotropic layer is formed is bonded to the polarizer so that the rubbing direction of the alignment layer of the optical compensation film coincides with the stretching direction of the polarizer. I did it.

<Production of transmissive liquid crystal display device>
In the transmissive liquid crystal display device of FIG. 2, the elliptically polarizing plate A is used as two polarizing plates sandwiching the liquid crystal cell (5-9), and the surface side of the optically anisotropic layer of the optical compensation sheet is used as an adhesive. Was pasted toward the liquid crystal cell (7) to produce a transmissive liquid crystal display device I. A liquid crystal cell for 20 inches was used.
Transmission type liquid crystal display devices II to V were produced in the same manner except that the elliptically polarizing plate was changed to B to E.

About the liquid crystal display device produced above, light leakage of the liquid crystal display device was evaluated by the following method. The results are shown in Table 2.
(Evaluation of light leakage of liquid crystal display devices)
After the produced liquid crystal display device was used at 40 ° C. and 30% RH for 1 month, the backlight of the liquid crystal display device was turned on, and after 1 hour, the entire surface was displayed in black, and light leakage was visually observed. The following four grades were evaluated.
◎: No light leakage ○: Slight light leakage at the edges of the four sides △: Clear light leakage at the edges of the four sides ×: Light leakage near the center of the film

From the results shown in Table 2, the liquid crystal display equipment using the elliptically polarizing plate of the present invention even after prolonged continuous use, it is clear that light leakage is small. The liquid crystal display device I using the polarizing plate A and the liquid crystal display device III using the polarizing plate C are reference examples.

It is a schematic sectional drawing which shows the structural example which combined the polarizing plate and functional optical film of this invention. It is a schematic sketch which shows an example (example of the liquid crystal display device produced in the Example) of the liquid crystal display device in which the polarizing plate of this invention is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Upper polarizing plate absorption axis 3 Upper viewing angle expansion film 4 Upper optical anisotropic layer orientation control direction 5 Liquid crystal cell upper electrode substrate 6 Upper substrate orientation control direction 7 Liquid crystal layer 8 Liquid crystal cell lower electrode substrate 9 Lower substrate Orientation control direction 10 Lower viewing angle expansion film 11 Lower optical anisotropic layer orientation control direction 12 Lower polarizing plate 13 Lower polarizing plate absorption axis

Claims (3)

0.001% by mass or more and 1.0% by mass or less of a dichroic dye whose absorption spectrum of an aqueous solution has a maximum in a wavelength region of 300 nm to 500 nm on at least one side of a polarizer made of a polyvinyl alcohol film hardened with boric acid. It is a polarizing plate in which a protective film is bonded using an adhesive containing ,
(I) The polarizer is formed by stretching a polyvinyl alcohol film having a film thickness of 20 μm or more and 60 μm or less in a longitudinal uniaxial direction 5 times or more, and has an absorption spectrum of iodine and an aqueous solution of 300 nm to 500 nm. Contains a dichroic dye exhibiting a maximum in the wavelength region , and the film thickness is 8 μm or more and 18 μm or less,
(Ii) A polarizing plate characterized by having a transmittance at 410 nm in a crossed Nicol range of 0.001% to 0.1%. An elliptically polarizing plate, wherein a retardation film is laminated on the polarizing plate according to claim 1. A liquid crystal display device comprising the polarizing plate according to claim 1.

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