JP2006251224A - Method for manufacturing polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacture method for easily manufacturing a polarizing plate with less curls. <P>SOLUTION: The method for manufacturing a polarizing plate includes steps of subjecting only one surface of a protective film not to be in contact with a polarizing film to curling correction treatment, then laminating the polarizing film with the protective film, and drying. Alternatively, after a polarizing film and a protective film are laminated, the surface of the protective film is subjected to curling correction treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a polarizing plate that has an optical compensation function for various liquid crystal display devices and is easy to process with little curling.

In recent years, the demand for liquid crystal display devices is increasing as a display used for various applications such as a mobile phone, a television, and a computer.
The demand for polarizing plates is rapidly increasing with the spread of such liquid crystal display devices. In the polarizing plate, a protective film is generally bonded to both surfaces or one surface of a polarizing film having polarizing ability via an adhesive layer. The polarizing film used for the polarizing plate as described above is generally produced by stretching a polymer film made of polyvinyl alcohol or the like using a stretching machine or the like. As the protective film, cellulose triacetate is mainly used because it is optically transparent and has a small birefringence.

As the use of liquid crystal display devices spreads and the performance required for liquid crystal display devices is improved, the performance and functions required for polarizing plates have become highly functional and complex. The polarizing plate is required not only to have polarization characteristics but also to improve and diversify the optical compensation function for correcting the optical distortion inherent in the liquid crystal cell. As a result, it is required that the protective film to be bonded on both sides of the polarizing film be provided with various optical compensation characteristics, glare prevention function, antireflection function, antiglare function, and dirt adhesion prevention function.
In order to meet such demand, there is an increasing number of cases where protective films having different functions and completely different physical properties and chemical properties are bonded to both sides of the polarizing film. However, when a protective film having completely different physical properties and chemical properties is bonded, a new problem arises that significant curling occurs in the polarizing plate.

As a method for producing a polarizing plate having a small curl, Patent Document 1 proposes a method in which the water content of a cellulose triacetate film used as a protective film is from 0.9 to 2.0%. However, it is difficult to control the water content of the cellulose triacetate film from 0.9 to 2.0%, and there is a problem that the optical properties of the film are remarkably limited.
Patent Document 2 proposes a method of reducing the curl of the polarizing plate after bonding by correcting the curl value of the optical compensation sheet used for the polarizing plate protective film from 0 to 20 / m in advance. . However, this method also has a problem that the curling suppression effect is poor when the properties (thickness, moisture content, elastic modulus, etc.) of the two protective films bonded to the front and back of the polarizing film are greatly different.

  In Patent Document 3, before attaching two protective films having different rigidity, a small curl is applied in advance to a film having a small rigidity, and when it is attached to a polarizing plate, the overall curl balance is achieved. Has been proposed. This method is a very clever method and in many cases has an advantage that a preferable solution can be obtained. However, it is difficult to determine the optimal curl size in order to balance the entire curl, and it is necessary to find conditions by repeating many trials and errors.

Japanese Unexamined Patent Publication No. 2000-258631 JP 2002-71949 A JP 2003-262725 A

The known prior art including the techniques described in the above-mentioned prior literature is characterized by performing curl correction processing on a single layer film, and a multilayer film such as a polarizing plate is manufactured. In the same manner, after the curl correction treatment is similarly performed on the single layer film, these are laminated in a separate process.
These prior arts are particularly effective for single-layer films, but are not necessarily effective in all cases for multilayer films composed of two or more layers of different physical properties such as polarizing plates. It was difficult.

In particular, the following two problems may occur. The first is to curl the single-layer film and then wind it up once, and then unwind it again in a separate process to bond the protective film. Thus, new curl occurs between the curl correction process and the bonding process. This is a problem. The second problem is that the physical properties of the protective films on the front and back surfaces of the polarizing plate are different even after the lamination, resulting in a difference in the drying shrinkage force, which causes a new curl.
Such a curling problem complicates the subsequent bonding process, which not only causes an increase in manufacturing cost, but also causes a failure such as air bubbles entering the polarizing plate.

  In view of the above situation, an object of the present invention is to provide a manufacturing method capable of easily manufacturing a polarizing plate with less curling.

As a result of intensive studies, the inventors of the present invention, in the step of creating a polarizing plate by attaching a protective film to both sides of the polarizing film via an adhesive and drying, (I) the polarizing film of one protective film and After the curl correction treatment is applied only to the non-contact surface, for example, a method in which the polarizing film and the protective film are bonded together in the same process without winding up or transporting to another process, or (II) It has been found that the above problem can be solved by a method of applying a curl correction treatment to the surface of the protective film after laminating the polarizing film and the protective film.
Specifically, it has been found that the above problem can be solved by the following means.

1. A method of manufacturing a polarizing plate in which protective films are attached to both sides of a polarizing film, wherein the polarizing film and the protective film are bonded together after the curl correction treatment is performed on one protective film. Production method.
2. A method of manufacturing a polarizing plate having protective films attached to both sides of a polarizing film, wherein the polarizing film and the protective film are bonded together, and then the surface of one of the protective films is subjected to curl correction treatment. A manufacturing method of a board.
3. A method of manufacturing a polarizing plate in which protective films are attached to both sides of a polarizing film, wherein both protective films are subjected to curl correction processing with different processing strengths, and then the polarizing film and the protective film are bonded together A method for producing a polarizing plate.
4). A method of manufacturing a polarizing plate in which a protective film is attached to both sides of a polarizing film, and after the polarizing film and the protective film are bonded together, the surface of both protective films is subjected to curl correction processing having different processing strengths. The manufacturing method of the polarizing plate characterized by these.
5. 5. The method for producing a polarizing plate according to any one of 1 to 4 above, wherein the curl correction treatment is performed by applying water vapor or solvent vapor to a surface or surface of the protective film that does not contact the polarizing film.
6). 5. The method for producing a polarizing plate according to any one of 1 to 4, wherein the curl correction treatment is to apply a solvent to a surface or a surface of the protective film that does not contact the polarizing film.
7). 5. The method for producing a polarizing plate according to any one of 1 to 4 above, wherein the curl correction treatment is to apply a polymer solution to a surface or surface of the protective film that does not contact the polarizing film.

  According to the production method of the present invention, it is possible to easily obtain a polarizing plate with little curling, and a high-quality polarizing plate can be produced at low cost.

Hereinafter, the present invention will be described in more detail.
1. Configuration of Polarizing Plate First, the polarizing film and protective film of the present invention constituting the polarizing plate of the present invention will be described.
(1) Polarizing film The polarizing film used in the present invention is obtained by stretching polyvinyl alcohol (PVA). 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 saponification degree of PVA is not particularly limited, but is preferably 80 to 100 mol%, particularly preferably 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 in order to improve durability as described in Japanese Patent No. 2978219. Moreover, as described in Japanese Patent No. 3317494, PVA having a syndiotacticity of 45 to 52.5% can also be preferably used.

  PVA is preferably made into a film (raw film). As a method for producing a PVA film, a method of forming a film by casting a stock solution obtained by dissolving a PVA resin in water or an organic solvent is generally preferably used. The concentration of the polyvinyl alcohol resin in the stock solution is usually preferably 5 to 20% by mass. By forming this stock solution by casting, a PVA film having a thickness of preferably 10 to 200 μm (more preferably 85 μm to 200 μm) can be produced. The PVA raw film can be produced with reference to Japanese Patent No. 3342516, Japanese Patent Application Laid-Open No. 09-328593, Japanese Patent Application Laid-Open No. 2001-302817, and Japanese Patent Application Laid-Open No. 2002-144401.

  The film thickness of the PVA film before stretching (film thickness of the original film) is not particularly limited, but is preferably 1 μm to 1 mm, more preferably 20 to 200 μm from the viewpoint of film holding stability and stretching uniformity. Further, as described in JP-A-2002-236212, even if a thin PVA film is used in which the stress generated when stretched at a stretch ratio of 4 to 6 times in water is 10 N or less. Good.

  The crystallinity of the PVA film is not particularly limited, but as described in Japanese Patent No. 3251073, the average crystallinity (Xc) may be 50 to 75% by weight in order to improve durability and polarization performance. In addition, as described in JP-A-2002-236214, the crystallinity can be reduced to 38% or less in order to reduce in-plane hue variation.

The birefringence (Δn) of the PVA film is preferably small, and as described in Japanese Patent No. 3342516, the birefringence is preferably 1.0 × 10 ⁻³ or less. However, as described in JP-A-2002-228835, birefringence is preferably 0.002 or more and 0.01 or less in order to obtain a high degree of polarization while avoiding cutting during stretching of the PVA film. . Further, as described in JP-A-2002-60505, the value of (nx + ny) / 2-nz may be set to 0.0003 or more and 0.01 or less.
The in-plane retardation (Re) of the PVA film is preferably from 0 nm to 100 nm, and more preferably from 0 nm to 50 nm. Further, Rth (retardation in the film thickness direction) of the PVA film is preferably from 0 nm to 500 nm, and more preferably from 0 nm to 300 nm.

In addition, the polarizing plate of the present invention includes a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less described in Japanese Patent No. 3021494, 5 μm or more described in JP-A No. 2001-316492. PVA film having 500 or less optical foreign matter per 100 cm ² , PVA film having a hot water cutting temperature spot of 1.5 ° C. or less in the TD direction of the film described in JP-A-2002-030163, and glycerin PVA film formed from a solution prepared by adding 1 to 100 parts by weight of a 3-6 valent polyhydric alcohol such as the above, or a solution mixed with 15% by weight or more of a plasticizer described in JP-A-06-289225 is preferable. Can be used.

It is preferable to introduce a dichroic molecule into a PVA after forming a film. The dichroic molecules to be introduced into the PVA film, I ₃ ^- and I ₅ ^- can be preferably used higher iodine ion or a dichroic dye such as. In the present invention, higher-order iodine ions are particularly preferably used. Higher-order iodine ions are described in Nagata Ryo, “Application of Polarizing Plate”, CMC Publishing, “Industrial Materials”, Vol. 28, No. 7, p. As described in 39-45, a state where the PVA film is adsorbed and oriented by immersing the PVA film in a solution obtained by dissolving iodine in an aqueous potassium iodide solution (soaked in an aqueous boric acid solution if necessary). Can be generated.

  When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and a bisazo dye and a trisazo dye are particularly preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt. Specific examples of such dichroic dyes include CI Direct Red 37, Congo Red (CI Direct Red 28), CI Direct Violet 12, CI Direct Blue 90, CI Direct Blue 22, CI Direct Blue 1, CI Benzidines such as Direct Blue 151 and CI Direct Green 1, diphenylureas such as CI Direct Yellow 44, CI Direct Red 23 and CIDirect Red 79, stilbenes such as CI Direct Yellow 12, and dinaphthylamines such as CI Direct Red 31 And J acid series such as CI Direct Red 81, CI Direct Violet 9 and CI Direct Blue 78. Besides this, CI Direct Yellow 8, CI Direct Yellow 28, CI Direct Yellow 86, CI Direct Yellow 87, CI Direct Yellow 142, CI Direct Orange 26, CI Direct Orange 39, CI Direct Orange 72, CI Direct Orange 106, CI Direct Orange 107, CI Direct Red 2, CI Direct Red 39, CI Direct Red 83, CI Direct Red 89, CI Direct Red 240, CI Direct Red 242, CI Direct Red 247, CI Direct Violet 48, CI Direct Violet 51, CI Direct Violet 98, CI Direct Blue 15, CI Direct Blue 67, CI Direct Blue 71, CI Direct Blue 98, CI Direct Blue 168, CI Direct Blue 202, CI Direct Blue 236, CI Direct Blue 249, CI Direct Blue 270, CI Direct Green 59, CI Direct Green 85, CI Direct Brown 44, CI Direct Brown 106, CI Direct Brown 195, CI Direct Brown 210, CI Direct Brown 223, CI Direct Brown 224, CI Direct Black 1, CI Direct Black 17, CI Direct Black 19, CI Direct Bla ck 54 and the like. Further, JP-A-62-70802, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105, JP-A-1-265205. The dichroic dyes described in JP-A-7-261024 are also preferably used. In order to produce dichroic molecules having various hues, two or more of these dichroic dyes may be blended. When a dichroic dye is used, the adsorption thickness may be 4 μm or more as described in JP-A No. 2002-082222.

  If the content of the dichroic molecules in the PVA film is too small, the degree of polarization is low, and if it is too large, the single plate transmittance tends to decrease. On the other hand, it is preferable to adjust to the range of 0.01 mass% to 5 mass%.

  The thickness of the polarizing film is preferably 5 to 40 μm, more preferably 10 to 30 μm, and particularly preferably 5 to 22 μm. When the thickness of the polarizing film is reduced to 5 to 22 μm, the transmittance of 700 nm when the polarizing film is crossed Nicol is 0.001% or more and 0.3% or less and the transmittance of 410 nm is 0.001%. The aspect which is 0.3% or less is preferable. The upper limit of the 700 nm transmittance during crossed Nicols is preferably 0.3% or less, and preferably 0.2%. The upper limit of the transmittance at 410 nm is preferably 0.3% or less, more preferably 0.08% or less, and further preferably 0.05% or less. This improves the light leakage failure (picture frame failure) from the peripheral portion of the image display device caused by the contraction of the polarizing film due to change over time, and even if the display image size is a large screen of 17 inches or more, It shows a neutral gray color with little taste and can achieve good display image quality.

  As means for lowering the transmittance at 700 nm and the transmittance at 410 nm at the time of crossed Nicols, the above-mentioned dichroic dye having absorption in the corresponding wavelength region in addition to the dichroic material such as iodine is adjusted in the hue. It is effective to add it as an agent, or to add a hardening agent such as boric acid when adding a dichroic substance such as iodine. It is also effective to combine these.

  Two or more kinds of the hue adjusting agents may be blended. The dye to be added is preferably a dye having absorption at 410 nm or 700 nm, and more preferably has a main absorption at 380 nm to 500 nm or 600 nm to 720 nm. Further, the amount of the dye to be added can be arbitrarily determined depending on the absorbance, dichroic ratio, etc. of the dye to be used. In any case, there is no particular limitation as long as the transmittance at 700 nm during crossed Nicol is 0.3% or less and the transmittance at 410 nm is 0.3% or less.

  Moreover, as a method for adding the hue adjusting agent to the polarizing film, any method such as dipping, coating, spraying and the like can be used. Among them, dipping is preferable. The step of adding may be before stretching or after stretching, but is preferably before stretching from the viewpoint of improving the polarization performance. The addition step may be provided alone, or may be performed in either or both of the later-described dyeing step and hardener addition step.

The element content in the polarizing film is as follows: iodine 0.1-3.0 g / m ² , boron 0.1-5.0 g / m ² , potassium 0.1-2.0 g / m ² , zinc 0-2. It is preferably 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 polarizing film is described in JP-A No. 2000-35512. It is good also as 0.04 mass%-0.5 mass%.

  The ratio of the thickness of the polarizing film to the thickness of the protective film described later is 0.01 ≦ A (the thickness of the polarizing film) / B (the film of the protective film) as described in JP-A No. 14-174727. (Thickness) ≦ 0.16 is preferable.

(2) Protective film The polarizing film is preferably used by being bonded to both surfaces or one surface using an adhesive or a pressure sensitive adhesive with a transparent polymer film as a protective film. The protective film is required to have physical properties such as transparency, low birefringence, and moderate rigidity.
The material of 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. Examples of commercially available polymer films include ZEONEX manufactured by Nippon Zeon Co., Ltd. (reference materials: JP-A 63-218726, JP-A-5-25220, JP-A 9-183832), ZEONOR, Nippon Synthetic Rubber Co., Ltd. ) Manufactured by ARTON (reference materials: JP-A-1-24051, JP-A-5-97978), Fuji Photo Film Co., Ltd. (FUJITAC) (reference material: Japanese Society of Invention Disclosure Techniques 2001-1745), and the like. Most commonly, a cellulose acylate film is used, and among them, a cellulose acetate film is most often used.

  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 preferable in-plane retardation of the conventional protective film is 12 nm or less, more preferably 4 nm or less, and particularly preferably 0 to 2 nm. Similarly, the retardation in the thickness direction of the conventional protective film is preferably 85 nm or less, more preferably 60 nm or less, and particularly preferably 20 nm to 50 nm. However, at present, protective films having various optical characteristics corresponding to various liquid crystal cell modes are required, and preferable optical characteristics are diversified. There is a need for in-plane retardation in the range of 20 nm to 300 nm, and retardation in the thickness direction has various characteristics in the range of 150 nm to 400 nm. Some require a thickness direction retardation of −10 to +10 nm, and some require a thickness direction retardation of −100 nm to −300 nm.
The photoelastic coefficient of the polymer film used as the protective film is preferably 25.0 × 10 ⁻¹³ cm ² / dyne or less as described in JP-A-7-294732. In the present invention, 9 × 10 ⁻¹³ cm ² / dyne or less is particularly preferable.

The thickness of the protective film is preferably 20 μm or more and 200 μm or less, more preferably 30 μm or more and 110 μm or less, and most preferably 40 μm or more and 85 μm or less.
The moisture permeability coefficient (25 μm, 25 ° C., 90% RH) of the transparent polymer film used as the protective 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 as a protective film. The water content under conditions of 25 ° C. and 80% RH is preferably from 0.1 to 5%, more preferably from 1 to 3%.
The amount of change in mass of the film after 48 hours at 80 ° C. and 90% RH is preferably 5% or less, more preferably 3% or less. Similarly, the dimensional change after 24 hours at 60 ° C. and 90% RH or after 24 hours at 90 ° C. and 3% RH is preferably within ± 2%, more preferably within ± 1%.

The tensile strength value of the polymer film used as the protective film is preferably 50 to 1000 MPa, and the elongation at break is preferably 5% or more, more preferably 10 or more and 100% or less. Further, as described in JP-A-8-122525, a cellulose film having a tensile strength in the MD direction of 15 kg / mm ² or more and a tensile strength in the TD direction of 12.5 kg / mm ² or more is used as a protective film. Alternatively, as described in JP-A-9-251110, a cellulose film having a tensile strength of 13 kgf / mm ² or more may be used. The elastic modulus is preferably 2 to 8 GPa, more preferably 3 to 6 GPa.
1.0 or less is preferable and 0.7 or less is especially preferable for the dynamic friction coefficient with respect to the steel ball prescribed | regulated by preferable JIS of a protective film. The method for lowering the dynamic friction coefficient of the protective film to a preferred range is not limited, but for example, particles of alumina or silica having an average primary particle size of 0.001 to 1 μm, for example, on the entire film or only on the surface of the film can be improved in light transmittance and haze. This can be achieved by adding and dispersing a minute amount that does not cause an influence.

  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 in a viewing angle range within 30 degrees from the normal to the plane described in Japanese Patent No. 3327410, or a range described in JP 2000-204173 A A cellulose acylate film 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 in Ueda et al., “Wood Chemistry”, Kyoritsu Shuppan, 1968, pages 180-190.
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 acylate 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. preferable. Moreover, 2.50 or more and 2.86 or less described in Unexamined-Japanese-Patent No. 2001-356214 and the degree of acetyl substitution of 2.75 or more and 2.86 or less described in Unexamined-Japanese-Patent No. 2001-226495 are also preferable. If the degree of acetyl substitution is too low, the Re value tends to be larger than the desired value due to the conveyance tension during casting, and in-plane variations tend to occur. Further, the substitution degree of the acyl group at the 6-position is preferably 0.9 or more. When the degree of substitution is 0.9 or less, variations in Re and Rth tend to occur. In addition, the value computed according to ASTM D817 is employ | adopted for the substitution degree of the acyl group in this specification.

  In the present invention, the cellulose acylate film 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 used in the production is preferably 16% by mass to 30% by mass, and more preferably 18% by mass 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, it is also preferable to use an organic solvent that does not substantially contain a chlorinated solvent. Here, “substantially free” means that the ratio of the chlorinated solvent in the organic solvent is less than 10% by mass, preferably less than 5% by mass.

  In producing a cellulose acylate film, in order to prepare a cellulose acylate solution, swelling is first performed by adding cellulose acylate while stirring a solvent in a tank at room temperature. The swelling time is required to be at least 10 minutes, and insoluble materials remain after 10 minutes. The solvent temperature is preferably 0 to 40 ° C. If the temperature is 0 ° C. or lower, the swelling rate tends to decrease and insoluble matter tends to remain, and if the temperature is 40 ° C. or higher, the swelling rapidly occurs and the central portion may not swell sufficiently. 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 the cellulose acylate solution, it is preferable to filter off foreign matters such as undissolved matter, dust, and impurities using an appropriate filter medium such as sintered metal, wire mesh, paper, woven fabric or non-woven fabric. 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.

  Various additives according to the application can be added to the cellulose acylate solution 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.

  In the present invention, as a method and equipment for forming a cellulose acylate film, 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 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. If the amount of residual solvent is less than 2% by mass, creases may occur or the film may break in some cases. In the case of 30% by mass or more, the effect of stretching is small and there is a possibility that Re cannot be adjusted. 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 order to reduce the variation in film thickness and the variation in retardation, it is preferable to cast the cellulose acylate solution on a smooth band or drum as a metal support. The acylate liquid 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 is a band surface (drum surface) in the case of two layers. In the case of three or more layers, a layer located inside the outer layer is shown. Further, the cellulose acylate solution may be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer, etc.).

  Drying of the dope on the metal support involved in the production of 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 of the finished cellulose acylate film (after drying) is preferably in the range of 20 to 200 μm, more preferably in the range of 30 to 110 μm, and most preferably in the range of 40 to 85 μm. The film thickness 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 so as to obtain a desired thickness. When a cellulose triacetate film having a thickness of 50 μm or less is used, the breaking elongation in the MD direction (under 23 ° C./60% RH state) described in JP-A No. 2002-22961 is 0.75% or less. It is preferable that

The content of Fe, Ca, and Mg in the cellulose acylate film, as described in JP-A-2000-313766, the amount of Fe component is 1 ppm or less, the amount of Ca component is 60 ppm or less, the amount of Mg component Is also preferably in the range of 15 to 70 ppm. Further, as described in JP-A No. 2002-258049, when ATR analysis is performed on both sides of the film, the ratio Cx (Cx) of the maximum intensity peak Ax near 1488 cm ^{−1 on} the surface to the maximum intensity peak Bx near 1365 cm ^−1. = Ax / Bx) and the ratio Cy (Cy = Ay / By) of the maximum intensity peak Ay near 1488 cm ^{−1 and} the maximum intensity peak By near 1365 cm ⁻¹ on the back surface (Cy = Ay / By) is 1.0 ≦ Cx / Cy ≦ 1 A cellulose acylate film satisfying .2 is also preferable.

  The polarizing plate produced by the present invention may have a pressure-sensitive adhesive layer, a separate film, and a protective film as components other than the polarizing film and the protective film described above. In addition, on the surface of the protective film, an antiglare layer that prevents glare, an antireflection layer that prevents reflection of strong external light, a light scattering layer that blurs the shape of the reflected person's face and light, a hard coat layer that prevents scratches, Apply antifouling layer to reduce adhesion of dirt and grease, antistatic layer to reduce dusting due to electrification, antiscratch layer, optical compensation layer to correct phase delay or twist of light generated in liquid crystal cell, etc. Or may be laminated. Optical surfaces such as metal oxide layer, fine particle dispersion layer, layer with liquid crystal compound oriented and fixed, polyamide, polyimide, polyester, polyether ketone, polyamide imide, polyester imide, and polyaryl ether ketone on the surface of the protective film Anisotropic polymer coating layer, for example, a hydrophilic polymer layer such as polyvinyl alcohol, polyvinyl pyrrolidone or gelatin, for example, an adhesive layer or an adhesive layer made of a single or copolymerized hydrophobic polymer such as acrylate, styrene, acrylamide, butadiene, etc. However, it may be applied or laminated.

2. Next, the manufacturing process of the polarizing plate of the present invention will be described.
The production process of the polarizing plate in the present invention preferably includes a PVA swelling process, a dyeing process, a hardening process, a stretching process, a drying process, a curl correction treatment process, a protective film bonding process, and a drying process after bonding. The order of the dyeing process, the hardening process, and the stretching process may be arbitrarily changed, or several processes may be combined and performed simultaneously. In addition, as described in Japanese Patent No. 3331615, it is also preferable to provide a water washing step after the hardening step.
In the present invention, it is particularly preferable to sequentially perform the PVA swelling process, the dyeing process, the hardening process, the stretching process, the drying process, the protective film bonding process, and the post-bonding drying process in the order described. It is also preferable to provide an on-line surface inspection process during or after the aforementioned process.

The PVA swelling step is preferably performed only with water. However, as described in JP-A-10-153709, in order to stabilize optical performance and avoid wrinkling of the PVA film on the production line, PVA The degree of swelling of the polarizing plate substrate can be controlled by swelling the film with an aqueous boric acid solution.
Further, the temperature and time of the swelling step can be arbitrarily determined, but are preferably 10 ° C. to 50 ° C., 5 seconds or more, and when no dichroic dye is used, 30 ° C. to 50 ° C., preferably 35 It is preferable that the temperature is from 5 ° C. to 45 ° C. for 5 seconds to 600 seconds, preferably 15 seconds to 300 seconds.

For the dyeing step, the method described in JP-A No. 2002-86554 can be used. Moreover, as a dyeing method, not only immersion but any means such as application or spraying of iodine or a dye solution is possible. Further, as described in JP-A-2002-290025, a method of dyeing while stirring the iodine concentration, dye bath temperature, draw ratio in the bath, and bath solution in the bath may be used.
When higher-order iodine ions are used as the dichroic molecule, in order to obtain a high-contrast polarizing plate, it is preferable to use a solution obtained by dissolving iodine in an aqueous potassium iodide solution in the dyeing step. In this case, the iodine concentration of the iodine-potassium iodide aqueous solution is preferably 0.05 to 20 g / l, potassium iodide is preferably 3 to 200 g / l, and the weight ratio of iodine to potassium iodide is preferably 1 to 2000. 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, the weight ratio of iodine and potassium iodide is 30 to 120, the dyeing time is 30 to 600 seconds, and the 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 that the crosslinking agent is included by dipping or applying the solution to the crosslinking agent solution. Further, as described in JP-A-11-52130, the hardening process can be performed in several steps.
As the crosslinking agent, those described in US Reissue Patent No. 232897 can be used. In addition, as described in Japanese Patent No. 3357109, a polyvalent aldehyde can be used as a crosslinking agent in order to improve dimensional stability. As the crosslinking agent, boric acids are most preferably used.
When boric acid is used as a cross-linking agent used in the hardening step, metal ions may be added to a boric acid-potassium iodide aqueous solution that is a cross-linking agent solution. Zinc chloride is preferred as the metal ion. Further, as described in JP-A No. 2000-35512, zinc halides such as zinc iodide, zinc salts such as zinc sulfate and zinc acetate can be used instead of zinc chloride.

  In the present invention, a boric acid-potassium iodide aqueous solution to which zinc chloride is added may be prepared, and the PVA film may be immersed to perform hardening. In this case, 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 10 to 60. ° C is preferred. 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 50 ° C is preferable.

  For the stretching step, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515 or a tenter method as described in JP-A-2002-86554 can be preferably used. The preferred draw ratio is 2 to 12 times, more preferably 3 to 10 times, more preferably 4 to 8 times, and most preferably 5 to 8 times. Further, as described in JP-A No. 2002-40256, the relationship between the draw ratio, the thickness of the original fabric and the thickness of the polarizing film is as follows: (polarizing film + protective film) film thickness / original fabric film after bonding of the protective film (Thickness) × (total stretching ratio)> 0.17, or the relationship between the width of the polarizing film when leaving the final bath and the width of (polarizing film + protective film) when the protective film is bonded is disclosed in JP-A-2002-40247 It is also preferable that 0.80 ≦ ((polarizing film + protective film) width at the time of bonding the protective film / width of the polarizing film when leaving the final bath) ≦ 0.95 as described in .

  For the drying step, a method known in JP-A-2002-86554 can be used. A preferable temperature range in the drying step is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. Further, as described in Japanese Patent No. 3148513, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or as described in Japanese Patent Application Laid-Open Nos. 7-325215 and 7-325218. Aging in an atmosphere controlled in temperature and humidity can also be preferably performed.

  The protective film laminating step is a step of laminating a protective film on one or both sides of the polarizing film that has gone through the drying step. A method of bonding with a pair of rolls is preferably used so that the adhesive liquid is supplied immediately before bonding and the polarizing film and the protective film are overlapped. Further, as described in JP-A-2001-296426 and JP-A-2002-86554, the moisture content of the polarizing film at the time of bonding is suppressed in order to suppress the groove-like unevenness of the record due to stretching of the polarizing film. Is preferably adjusted. In the present invention, a moisture content of 0.1% to 30% is preferable.

The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA-based resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. However, 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.
In order to improve the adhesive force between the polarizing film and the protective film, it is preferable that the protective film is surface-treated to be hydrophilic and then bonded. The surface treatment method is not particularly limited, and a known method such as a saponification method using an alkaline 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 in the post-bonding drying step preferably follow the method described in JP-A-2002-86554. The preferable temperature range of the drying conditions is 30 ° C to 100 ° C, and the 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-7-325220.

In the present invention, the surface of the protective film is subjected to a curl correction process before or after the polarizing film and the protective film are bonded, or after the bonding and drying. At this time, either surface of the protective film may be subjected to a correction treatment, but preferably a surface that is not bonded to the polarizing film is subjected to a curl correction treatment. The curl correction treatment is preferably performed on the surface that curls and becomes convex.
The curl prevention treatment is usually performed only on one side of the polarizing plate (the side that is not bonded to the polarizing film of one protective film). However, especially when the curl is completely eliminated, or when slightly curling is left behind, or when the curl is precisely controlled, the curl correction process is applied to both sides of the polarizing plate (the side that is not bonded to the polarizing film of both protective films). Apply. In this case, it is preferable to perform curl correction processing on both protective films with different processing intensities. For example, when curl correction processing is performed on both protective films when it is desired to completely eliminate curling, the processing strength of the curl correction processing on the convex surface when not processing is greater than the processing strength on the opposite surface. Perform under conditions.

Specifically, the curl correction treatment includes a method of spraying water vapor or solvent vapor, a method of applying and drying a solvent, and a method of applying and drying a polymer solution.
(Steam treatment)
This method is a process in which water or an organic solvent vapor is wiped only on one surface of a protective film or a polarizing plate and exposed to the vapor. As the solvent type to be used, a solvent having solubility or swelling property with respect to the material of the protective film is effective and preferable. If the solubility is too strong, secondary inconvenience is likely to occur. Therefore, it is preferable to select a solvent with low solubility or a solvent that does not dissolve but easily swells. In the case of a cellulose acylate film, water is most preferable. Also preferred are alcohols having 1 to 8 carbon atoms, ketones, and esters having 4 or more carbon atoms. Halogen-containing solvents having 2 or less carbon atoms such as methylene chloride and chloroform and esters having 3 or less carbon atoms may be used alone, but they are mixed with water or other solvents to reduce the solubility in cellulose acylate. Therefore, it can be used as a more preferable solvent.
The solvent can be heated to a temperature equal to or higher than the boiling point of the solvent to be used and sprayed toward the surface of the protective film from the tip of a thin nozzle or a narrow slit. The solvent vapor concentration on the surface of the protective film is preferably from 2 to 100 mass%, more preferably from 10 mass% to 90 mass%, still more preferably from 30 mass% to 80 mass%. The time for which the protective film is exposed to the vapor is preferably 1 to 600 seconds, more preferably 2 to 120 seconds, and still more preferably 4 to 40 seconds. The temperature of the protective film when exposed to steam is preferably 10 ° C. or higher and 150 ° C. or lower, more preferably 40 ° C. or higher and 110 ° C. or lower, and further preferably 50 ° C. or higher and 80 ° C. or lower.

(Solvent application)
In this method, a solvent is applied to only one surface of a protective film or a polarizing plate and then dried. As the solvent type to be used, a solvent having solubility or swelling property with respect to the material of the protective film is effective and preferable. If the solubility is too strong, secondary inconvenience is likely to occur. Therefore, it is preferable to select a solvent with low solubility or a solvent that does not dissolve but easily swells. In the case of a cellulose acylate film, alcohols having 1 to 8 carbon atoms, ketones, esters having 4 to 8 carbon atoms and the like are preferable. Halogen-containing solvents having 2 or less carbon atoms such as methylene chloride and chloroform and esters having 3 or less carbon atoms may be used alone, but they are mixed with water or other solvents to reduce the solubility in cellulose acylate. Therefore, it can be used as a more preferable solvent. In addition, curling can be corrected more precisely by mixing and adjusting a plurality of solvents.
The coating amount of the solvent is preferably from 0.1 g to 100 g, more preferably from 0.5 g to 50 g, still more preferably from 2 g to 20 g per square meter. The application method is not particularly limited. It can be applied by a well-known general method such as a gravure coater, reverse coater or wire bar coater. The preferable temperature range of the drying conditions after application | coating is 30 to 100 degreeC, More preferably, it is 40 to 90 degreeC, More preferably, it is 50 to 80 degreeC. A preferable drying time is 15 seconds to 10 minutes, more preferably 20 seconds to 7 minutes, and further preferably 30 seconds to 3 minutes. The most preferable drying conditions are a temperature of 45 ° C. to 80 ° C. and 30 seconds to 3 minutes.

(Polymer solution coating)
In the case of using the method by polymer application, the restriction of the solvent to be used is less than that of the above method. In the case of using a solvent that dissolves the protective film well, as in the case of the solvent coating method, secondary inconveniences must be warned, but a solvent or water that does not dissolve or swell the protective film can also be used. There is almost no limit to the polymer to be applied. For example, water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone or gelatin, cellulose derivatives such as cellulose acetate, cellulose propionate, cellulose nitrate or ethyl cellulose, halogen-containing polymers such as polyvinyl chloride and polyvinylidene fluoride, 6 nylon, 6 Polyamides such as Nylon, 6 Nylon, 3, 4 Nylon, etc. can be used, and even polymers not described here cannot be used in the present invention. Even if it is not a polymer, for example, even if only a monomer or an oligomer is applied, it can be used in the present invention as long as the applied monomer or oligomer can react to form a polymer layer.
In addition, when performing a curl correction process on both protective films, the curl correction processing means for the protective film may be the same on both sides or different.

Although there is no restriction | limiting in particular in the polymer density | concentration in a coating solution, Generally it is 0.1-30 mass%, More preferably, it is 5-20 mass%, More preferably, it is 8-20 mass%. The viscosity of the coating solution is preferably 1 poise or less, and there is no lower limit. A small amount of a surfactant may be added to prevent liquid repelling. Especially in the case of an aqueous solution, the use of a surfactant is effective.
The amount of polymer applied per square meter is preferably 0.01 to 10 g, more preferably 0.05 to 5 g, and still more preferably 0.1 to 4 g. The application method is not particularly limited. It can be applied by a well-known general method such as a gravure coater, reverse coater or wire bar coater. The preferable temperature range of the drying conditions after application | coating is 30 to 100 degreeC, More preferably, it is 40 to 90 degreeC, More preferably, it is 50 to 80 degreeC. A preferable drying time is 15 seconds to 10 minutes, more preferably 20 seconds to 7 minutes, and further preferably 30 seconds to 3 minutes. The most preferable drying conditions are a temperature of 45 ° C. to 80 ° C. and 30 seconds to 3 minutes.

As described in Japanese Patent No. 3323255, in order to increase the dimensional stability of the polarizing plate, an organic titanium compound and / or an organic zirconium compound is used in any process selected from a dyeing process, a stretching process, and a hardening process. It can also be added to contain at least one compound selected from organic titanium compounds and organic zirconium compounds. A dichroic dye may be further added to adjust the hue of the polarizing plate.
The angle formed by the slow axis of the protective film and the absorption axis of the polarizing film may be any value, but is preferably parallel or an azimuth angle of 45 ± 20 °.

3. Characteristics of polarizing plate (1) Transmittance and polarization degree The single plate transmittance of the polarizing plate produced according to the present invention is preferably 41% or more and less than 50%. Further, the single plate transmittance is more preferably 42.5% or more and 49.5% or less, and particularly preferably 42.8% or more and 49.0% or less.
The degree of polarization is preferably 99.9% or more, and preferably less than 100%. Furthermore, 99.900% or more and 99.999% or less are more preferable, and 99.940% or more and 99.995% or less are particularly preferable. The degree of polarization is defined by the following formula (5).

In equation (5), the parallel transmittance is the transmittance of two polarizing plates (when parallel Nicols) are stacked so that the absorption axes are parallel to each other, and the orthogonal transmittance is the absorption axes being orthogonal to each other. It is the transmittance | permeability of the two polarizing plates piled up (at the time of cross Nicol).
It is preferably 36% or more and 42% or less of the parallel transmittance. The orthogonal transmittance is preferably 0.15% or less, and more preferably 0.001% or more and 0.05% or less.
Here, the transmittance is defined by the following formula (6) based on JIS Z8701.

In the formula (6), 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 color system τ (λ): spectral transmittance

  The dichroic ratio defined by the following formula (7) is preferably 48 or more and 1215 or less, and more preferably 53 or more and 525 or less.

In the polarizing plate of the present invention, the iodine concentration and the single plate transmittance may be within the ranges described in JP-A No. 2002-258051.
Regarding the parallel transmittance, it is also preferable that the wavelength dependency is small as in JP-A-2001-83328 and JP-A-2002-22950.
Furthermore, the optical characteristics when the polarizing plates are arranged in crossed Nicols may be in the range described in Japanese Patent Application Laid-Open No. 2001-91736, and the relationship between parallel transmittance and orthogonal transmittance is disclosed in Japanese Patent Application Laid-Open No. 2002-174728. It may be within the range described in the issue.

Furthermore, as described in JP-A-2002-221618, the standard deviation of parallel transmittance every 10 nm when the wavelength of light is between 420 and 700 nm is 3 or less, and 10 nm between 420 and 700 nm. It is also preferable that the minimum value of (parallel transmittance / orthogonal transmittance) is 300 or more.
JP-A-2002-258042 and JP-A-2002-258043 describe parallel transmittance and orthogonal transmittance at a wavelength of 440 nm, parallel transmittance and orthogonal transmittance at a wavelength of 550 nm, and parallel transmittance and orthogonal transmittance at a wavelength of 610 nm. A polarizing plate satisfying the described relationship is also preferable.

  In the present invention, the deflection width of the single plate transmittance in the longitudinal direction of the polarizing film obtained by stretching and the direction orthogonal thereto is preferably 0 to 1.5%, and more preferably 0 to 1.2. % Is preferred. Further, the deflection width of the polarization degree in the longitudinal direction of the film and the direction perpendicular thereto is preferably 0 to 0.03%, and more preferably 0 to 0.02%. By making the runout width within this range, film loss is reduced and productivity is improved, which is preferable.

(2) Hue The hue of the polarizing plate of the present invention is preferably evaluated using the lightness index L ^* and the chromaticness index a ^* and b ^* in the L ^* a ^* b ^* color system recommended as the CIE uniform perceptual space. Is done.
L ^* , a ^* , and b ^* are defined by the following formula (8) using X, Y, and Z of the XYZ color system.

In the formula (8), X ₀ , Y ₀ , Z ₀ represent tristimulus values of the illumination light source, and in the case of the standard light C, X ₀ = 98.072, Y ₀ = 100, Z ₀ = 118.225. In the case of the standard light D65, X ₀ = 95.045, Y ₀ = 100, Z ₀ = 108.892.

The preferable range of a ^* for a single polarizing plate is −2.5 or more and 0.2 or less, and more preferably −2.0 or more and 0 or less. A preferable range of b ^* of the single polarizing plate is 1.5 or more and 5 or less, and more preferably 2 or more and 4.5 or less. The preferable range of a ^* of the parallel transmitted light of the two polarizing plates is −4.0 to 0, and more preferably −3.5 to −0.5. The preferred range of b ^* of the parallel transmitted light of the two polarizing plates is 2.0 or more and 8 or less, more preferably 2.5 or more and 7 or less. The preferable range of a ^* of the orthogonally transmitted light of the two polarizing plates is −0.5 or more and 1.0 or less, and more preferably 0 or more and 2 or less. The preferable range of b ^* of the orthogonally transmitted light of the two polarizing plates is −2.0 or more and 2 or less, and more preferably −1.5 or more and 0.5 or less.

The hue may be evaluated by chromaticity coordinates (x, y) calculated from X, Y, and Z in the XYZ color system. For example, the chromaticity (x _p , y _p ) of parallel transmitted light and the chromaticity (x _c , y _c ) of orthogonal transmitted light are _calculated as disclosed in JP 2002-214436 ({(x _p −x _c ) ² + (y _p −y _c ) ² } ^1/2 <0.2), JP-A No. 2001-166136 (| x _p −x _c | <0.190, | y _p −y _c | <0.130). It is preferable to be in the range. Further, the hue (a _p , b _p ) of the parallel transmitted light and the hue (ac, bc) of the orthogonal transmitted light are disclosed in Japanese Patent Laid-Open No. 2002-214436 ({(a _p −ac _c ) ² + (b _p −b _c )). ² } ^1/2 <7.0) is also preferable. Furthermore, as described in the claims (claim 1) of JP-A No. 2002-169024, the hues of the parallel transmitted light and the orthogonal transmitted light may be determined. Furthermore, the orthogonal hue and the parallel hue measured according to JIS Z8729 are within the range described in the claims (Claim 1) of JP-A No. 2002-169024, and the relationship with the absorbance is also disclosed in JP-A No. 2001-311827. It is also preferable to make it the range as described in the claim (Claim 1).

(3) Viewing angle characteristics As shown in JP-A-2001-166135 and JP-A-2001-166137, vertical light is incident when a polarizing plate is arranged in crossed Nicol and light with a wavelength of 550 nm is incident. It is also preferable to make the transmittance ratio and the xy chromaticity difference between the case where the light is incident and the case where the light is incident at an angle of 40 degrees with respect to the normal from the direction of 45 degrees with respect to the polarization axis. Further, as described in JP-A-10-68817, the light transmittance (T0) in the vertical direction of the polarizing plate laminate having the crossed Nicols arrangement and the light transmittance in the direction inclined by 60 ° from the normal line of the laminate. The ratio (T60 / T0) to (T60) is 10000 or less, or natural light is incident on the polarizing plate at an arbitrary angle from the normal to an elevation angle of 80 degrees as described in JP-A-2002-139625. 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 6% or less, or as described in JP-A-8-248201, It is also preferable that the luminance difference of transmitted light at an arbitrary 1 cm distance is within 30%.

(4) Durability (4-1) Damp heat durability As described in JP-A No. 2001-116922, the polarizing plate of the present invention is the one when left in an atmosphere of 60 ° C. and 90% RH for 500 hours. It is preferable that the light transmittance and the change rate of the polarization degree before and after are 3% or less in absolute value. In particular, the change rate of the light transmittance is 2% or less, and the change rate of the degree of polarization is preferably 1.0% or less, more preferably 0.1% or less in absolute value. Further, as described in JP-A-7-77608, 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.

(4-2) Dry durability When the polarizing plate of the present invention is left in a dry atmosphere at 80 ° C. for 500 hours, the light transmittance before and after that and the rate of change in the degree of polarization are also 3% or less in absolute value. It is preferable. In particular, the change rate of the light transmittance is 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.

(4-3) Other Durability Further, as described in JP-A-6-167611, the polarizing plate of the present invention has a shrinkage ratio of 0.5% or less after being left at 80 ° C. for 2 hours. Is preferred. Further, as described in JP-A-10-68818, polarized light which takes x value and y value after leaving a polarizing plate laminate in which crossed Nicols are arranged on both sides of a glass plate in an atmosphere of 69 ° C. for 750 hours. A plate is also preferred.
Furthermore, 80 ° C., a change in the 105 cm ^-1 and 157cm ^-1 spectral intensity ratio by 200 hours standing after treatment of Raman spectroscopy in an atmosphere of RH 90%, JP-A-8-94834 and JP-A-9-197127 It is also preferable to make it the range described in the number.

(5) Orientation degree The higher the degree of orientation of PVA, the better the polarization performance, but the range of 0.2 to 1.0 is preferable as the order parameter value calculated by means such as polarization Raman scattering or polarization FT-IR. It is. 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 polarizing film and the orientation coefficient of the occupied molecule (0.75 or more) is at least 0. .15, or as described in Japanese Patent Laid-Open No. 04-204907, the orientation coefficient of the amorphous region of the polarizing film is 0.65 to 0.85, or higher-order iodine ions of I ₃ and I ₅ The degree of orientation can be preferably set to 0.8 to 1.0 as an order parameter value.

(6) Other properties In the polarizing plate of the present invention, as described in JP-A No. 2002-6133, the contraction force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is 4.0 N / When the temperature is less than cm or as described in JP-A No. 2002-236213, the dimensional change rate in the absorption axis direction and the dimensional change rate in the transmission axis direction are both set when heated at 70 ° C. for 120 hours. It is also preferable to make it within ± 0.6% or to make the moisture content of the polarizing plate 3% by weight or less as described in JP-A-2002-90546. Further, as described in JP-A No. 2000-249832, the surface roughness in the direction perpendicular to the stretching axis is set to 0.04 μm or less based on the center line average roughness, or described in JP-A No. 10-268294. As described above, the refractive index n0 in the transmission axis direction is made larger than 1.6, or the relationship between the thickness (a) of the polarizing plate and the thickness (b) of the protective film is described in JP-A-10-111411. It is also preferable that

4). Functionalization of Polarizing Plate The polarizing plate of the present invention includes a viewing angle widening film for LCD, a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, a brightness enhancement film, It is preferably used as a functionalized polarizing plate combined with an optical film having functional layers such as a coat layer, a forward scattering layer, and an antiglare (antiglare) layer.

  A configuration example in which the polarizing plate of the present invention and the above-described functional optical film are combined is shown in FIG. As shown in FIG. 1, a functional optical film may be used as a protective film on one side of the polarizing plate, and the polarizing film may be adhered via an adhesive (FIG. 1 (a)), or on both surfaces of the polarizing film. A functional optical film may be bonded to a polarizing plate provided with a protective film via an adhesive (FIG. 1B). In the former case, any transparent protective film can be used as the other protective film. As described in JP-A No. 2002-311238, the peel strength between each layer such as a functional layer or a protective film is preferably 4.0 N / 25 mm or more. The functional optical film can be arranged on the liquid crystal module side according to the intended function, or can be arranged 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.
(1) Viewing angle expansion film The polarizing plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Bend), VA (Vertically Aligned), and ECB (Electrically Bold). It can be used in combination with a viewing angle widening film proposed for the display mode.

  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 Wide view films (manufactured by Fuji Photo Film Co., Ltd.) described in JP-A-75115, JP-A-6-214116, JP-A-8-50206, and the like.

  A preferred configuration of the viewing angle widening film for the TN mode has an alignment layer and an optically anisotropic layer in this order on a transparent polymer film. The viewing angle widening film can be used by being bonded to a polarizing plate via an adhesive. SID'00 Dig. , P. As described in 551 (2000), it is particularly preferable to use a polymer film also as one of the protective films from the viewpoint of thinning.

  The alignment layer in the viewing angle widening film can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, or formation of a layer having a micro group. 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 polarizing film 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 in the viewing angle widening film preferably contains a liquid crystalline compound. As the liquid crystalline compound, a discotic compound (discotic liquid crystal) is particularly preferable. The discotic liquid crystal molecule has a disk-like core portion like the triphenylene derivative of the following D-1, and has a structure in which side chains extend radially therefrom (in the following D-1, R is a direct value). Represents a substituent such as an alkyl group, an alkoxy group, or a substituted benzoyloxy group in the chain). 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.

  In the vicinity of the alignment layer, the discotic liquid crystal molecules are aligned substantially parallel to the film plane with a pretilt angle in the rubbing direction, and on the opposite air surface side, the discotic liquid crystal molecules are aligned so as to be perpendicular to the plane. The entire discotic liquid crystal layer preferably has a hybrid alignment. As a result, the viewing angle of the TN mode TFT-LCD can be increased.

  The optically anisotropic layer in the viewing angle widening film is generally applied by applying a solution obtained by dissolving a discotic compound and other compounds (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent on the alignment layer, and drying. Subsequently, after heating to a desired liquid crystal phase formation temperature, polymerization is performed by irradiation with UV light or the like, and further cooling is performed. Examples of the liquid crystal phase include a discotic nematic liquid crystal phase, and the liquid crystal phase-solid phase transition temperature is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

Further, as a compound other than 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 does not inhibit the alignment. As long as any compound can be used. 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 polymer film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer. In addition, 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-7-198942, a compound having an optical axis in a direction intersecting the plate surface is used. It is also preferable to laminate with a retardation plate exhibiting anisotropy in refraction, or to make the dimensional change rate of the protective film and the optically anisotropic layer substantially the same as described in JP-A No. 14-258052. . As described in JP-A No. 2000-258632, the polarizing plate bonded to the viewing angle widening film has a moisture content of 2.4% or less, or as described in JP-A No. 2002-267839. It is also preferable that the contact angle of the surface of the enlarged angle film with water is 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 during black display when no electric field is applied, and is used for improving the viewing angle. In the IPS mode, black is displayed when no electric field is applied. At this time, the transmission axes of the pair of upper and lower polarizing plates of the liquid crystal cell 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 used in combination 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.

  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. For 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, or a disk-shaped compound is a substrate. In order to prevent the deterioration of the orthogonal transmittance in the oblique direction of the polarizing plate, the film in which the films arranged in parallel to each other, the stretched film having the same in-plane retardation value are laminated so that the slow axes are orthogonal, What laminated | stacked the film which consists of such rod-shaped compounds is preferable.

(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 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. Is preferred. "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, and it is particularly preferable that Re590-Re450 ≧ 10 nm.

  The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied. For example, JP-A-5-27118, JP-A-10-68816, JP-A-10-90521 A λ / 4 plate obtained by laminating a plurality of polymer films described in JP-A 2000-284126, a λ / 4 plate obtained by stretching one polymer film described in WO 00/65384 and WO 00/26705, and 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. In this case, 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, it is preferable that the slow axis of the λ / 4 plate and the transmission axis of the polarizing film intersect within a range of 45 ° ± 20 °. However, the slow axis of the λ / 4 plate and the transmission axis of the polarizing film may intersect within an arbitrary range other than the above.

  When the λ / 4 plate is formed by laminating the λ / 4 plate and the 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 / 4 plate are used. / 2 It is preferable to bond the plates so that the angles formed by the slow axis in the plane of the plate and the transmission axis of the polarizing plate are substantially 75 ° and 15 °, respectively.

(3) Antireflection film The polarizing plate of the present invention can be used in combination with an antireflection film. As an antireflection film, either a film having a reflectivity 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 reflectivity of 1% or less using multi-layer interference of a thin film. Can be used. 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 Further, an antireflection film described in Nitto Technical Report, vol. 38, No. 1, may, 2000, pages 26 to 28, JP-A No. 2002-301783, or the like can be preferably used.

In the case of a configuration in which a low refractive index layer, a high refractive index layer, or the like is laminated, it is preferable that the refractive index of each layer 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.
In this case, as the transparent support used for the antireflection film, the transparent polymer film used for the protective film of the polarizing plate can be preferably used.

The refractive index of the low refractive index layer of the antireflection film is preferably 1.20 to 1.55, and more 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 the scratch resistance, it is also preferable to impart slipperiness to the surface using a material containing a silicone group or fluorine.
Examples of the fluorine-containing compound include paragraph numbers [0018] to [0026] of JP-A-9-222503, paragraph numbers [0019] to [0030] of JP-A-11-38202, and paragraph numbers of JP-A-2001-40284. [0027] to [0028], compounds described in JP-A No. 2000-284102 and the like 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 (Japanese Patent Laid-Open No. 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 middle refractive index layer and the high refractive index layer of the antireflection film preferably have a structure in which ultrafine particles of high refractive index having an average particle diameter 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-11-295503, JP-A-11-153703, JP-A-2000-9908, anionic compound or organic Metal coupling agent: Japanese Patent Laid-Open No. 2001-310432, etc., a core-shell structure with high refractive index particles as a core (Japanese Patent Laid-Open No. 2001-166104, etc.), or a specific dispersant used together (eg, Japanese Patent Laid-Open No. 11-153703). And Japanese Patent Publication No. US6110858B1, Japanese Patent Application Laid-Open No. 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, 2001-296401. It is also possible to use a curable film obtained from a polyfunctional material described in JP-A-2001-293818 or a metal alkoxide composition described in JP-A-2001-293818.

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. The strength of the film is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400.

(4) Brightness improving film The polarizing plate of this invention can be used in combination with a brightness improving 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 in the LCD, and reflects or backscatters one circularly polarized light or linearly polarized light to the backlight side. . The re-reflected light from the backlight part partially changes the polarization state and partially transmits when it re-enters the brightness enhancement film and the polarizing plate. By repeating this process, the light utilization rate is improved. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection method and an anisotropic scattering method 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. About NIPOCS, Nitto Technical Report,
Vol. 38, No. 1, may, 2000, pages 19 to 21 can be referred to.

  Further, in the present invention, the positive values 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.

(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, a protective layer, and the like. It is also preferred to use it in combination with a functional optical film provided with 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.

(5-1) Hard Coat Layer The polarizing plate of the present invention is preferably combined with a functional optical film provided on the surface of the transparent support in order to impart mechanical strength such as scratch resistance. Done. 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 and / 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 K5400. Further, in the Taber test according to JIS K5400, 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. Triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin, etc. Celoxide 2021P, Celoxide 2081 GT-301, Epolide GT-401, EHPE3150CE (above, Oxetane, OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, manufactured by Toagosei Co., Ltd.), etc. Can be mentioned. 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.

  In the hard coat layer, fine particles of oxide such as silicon, titanium, zirconium, and aluminum are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and reduce curling of the hard coat treated article of the present invention. It is also preferable to add crosslinked fine particles such as crosslinked fine particles such as polyethylene, polystyrene, poly (meth) acrylic acid esters, polydimethylsiloxane, etc., and fine organic particles such as fine crosslinked rubber particles such as SBR and NBR. The average particle size of these crosslinked 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, since the affinity with the binder polymer is generally poor, it contains a metal such as silicon, aluminum, titanium, and the alkoxide group, carboxylic acid group, sulfonic acid group, phosphonic acid group, etc. It is also preferable to perform a surface treatment using a surface treatment agent having a functional group of

  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, in consideration of the heat resistance of the plastic itself, the heating temperature is preferably 140 ° C. or lower, more preferably 100 ° C. or lower.

(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. The construction of JP-A No. 199809, JP-A No. 2002-107512 or the like which 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.

(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-A No. 2000-271878), relatively large particles (particle size 0.05-2 μm). ) Is added in a small amount (0.1 to 50% by mass) (for example, Japanese Patent Application Laid-Open Nos. 2000-281410, 2000-95893, 2001-100004, and 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.) can be preferably used.

  These functional layers can be used by providing either one or both of the side bonded to the polarizing film to the support and the opposite side.

5. Next, the liquid crystal display device of the present invention in which the polarizing plate of the present invention is preferably used will be described. FIG. 2 shows an example of the liquid crystal display device of the present invention.

  The liquid crystal display device shown in FIG. 2 has a liquid crystal cell (5-9), and an upper polarizing plate 1 and a lower polarizing plate 12 that are arranged with the liquid crystal cell (5-9) interposed therebetween. The polarizing plate is sandwiched between a polarizing film and a pair of protective films, but is shown as an integrated polarizing plate in FIG. 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. 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 surface”), 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 size of the tilt angle can be controlled by the rubbing strength and the number of times of rubbing. The alignment film can be formed by applying and baking a polyimide film. The magnitude of the twist angle (twist angle) of the liquid crystal layer can be controlled 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 was added so that the twist angle was 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. It is preferable to set. In the IPS mode and ECB mode, the twist angle is preferably 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 perpendicularly to the upper and lower substrates.

  Here, the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn changes the brightness during white display. Therefore, in order to obtain the maximum brightness, it is preferable to set the range 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 in the TN and IPS modes, it is generally preferable to set the angle to be parallel or vertical. 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 polarizing film. 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]

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited thereto.

<Measurement method>
(Curl measurement method)
A polarizing plate cut into squares of 300 mm in length and breadth is placed on a horizontal and flat table so that the inner surface of the curl is on the top, and is allowed to stand in an atmosphere of 25 ° C. and 65% RH for 3 hours or more. The height raised from the four corners of the polarizing plate is measured and expressed as an average.

(Measurement of polarized Raman scattering spectrum)
The polarizing film A was cut out to 10 mm × 10 mm and irradiated with a YAG laser fundamental wave of 1064 nm as excitation light using a Raman spectrometer (manufactured by Bruker, RFS-100 type FT-Raman spectrometer). At that time, the scattered light intensities of Raman bands 108 cm ⁻¹ and 154 cm ⁻¹ were measured with the polarization direction of the polarizing film A as a measurement sample parallel and perpendicular to the polarization plane of the laser light, and the intensity ratio (Ib108 / The values of Ia108) and (Ib154 / Ia154) were calculated.

(Measurement of single plate transmittance and degree of polarization)
A sample of the polarizing plate A was cut to 30 × 50 mm, 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 plates have the same absorption axis, and H1 (%) is the transmission when the absorption axes are perpendicular to each other. )
P = [(H0−H1) / (H0 + H1)] ^1/2 × 100
Further, the single plate transmittance was obtained by using a single polarizing plate sample and correcting the transmittance of 400 to 700 nm with the visibility.

(Elastic modulus)
Sample 10mm × 200mm was conditioned at 25 ° C, 60% RH for 2 hours, and the tensile modulus was initially measured with a tensile tester (Strograph-R2 (manufactured by Toyo Seiki)) at an initial sample length of 100 mm and a tensile speed of 100 mm / min. It was calculated from the stress and elongation.

(Moisture content)
A sample 7 mm × 35 mm was conditioned at 25 ° C. and 60% RH for 2 hours, and measured with a Karl Fischer method trace moisture meter LE-20S (manufactured by Hiranuma Sangyo Co., Ltd.). The water content was calculated by dividing the moisture content (g) in the sample by the sample mass (g).

(Humidity dimensional change rate)
Sample 30 mm × 120 mm was aged for 2 hours at 25 ° C. and 10% RH, 6 mmφ holes were made at both ends at 100 mm intervals, and the automatic pin gauge (Shinto Kagaku Co., Ltd.) was used to measure the original punch interval (L ¹ ) Was measured to a minimum scale of 1/1000 mm. Further 25 ° C., then over time 80% RH2 hours and measuring the dimensions of the hole distance ^{(L 2).} Then, to determine the humidity dimensional change rate by ^{{(L 1 -L 2) /} L 1} / (80-10).

<Preparation of protective film>
A commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was prepared as the protective film P1. A commercially available cellulose acetate film (Fujitac T40UZ, manufactured by Fuji Photo Film Co., Ltd.) was prepared as the protective film P2. A commercially available retardation compensation film WV-SA (manufactured by Fuji Photo Film Co., Ltd.) was prepared as the protective film P4.

(Creation of cyclic polyolefin protective film P3)
The following composition was put into a mixing tank, stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm.

  Next, the following composition containing the cyclic polyolefin solution prepared by the above method was put into a disperser to prepare a mat agent dispersion.

  100 parts by mass of the cyclic polyolefin solution and 1.1 parts by mass of the matting agent dispersion were mixed to prepare a dope for film formation.

  The above dope was cast using a band casting machine. A film peeled off from the band with a residual solvent amount of about 22% by mass was stretched in the width direction at a stretch rate of 2% using a tenter, and hot air was applied while holding the film so as not to cause wrinkles. Dried. Then, the tenter transport was shifted to the roll transport, and further dried at 120 to 140 ° C. and wound up. The resulting cyclic polyolefin film had a thickness of 60 μm. This film was subjected to glow discharge treatment (frequency 3000 Hz, 4200 V applied between the upper and lower electrodes, treated for 20 seconds) between the upper and lower electrodes made of brass (argon gas atmosphere) to produce a cyclic polyolefin protective film P3. . The contact angle of pure water on the surface of the protective film treated with glow discharge was between 36 ° and 41 °. The contact angle was measured with a contact angle meter CA-X manufactured by Kyowa Interface Science Co., Ltd.

(Preparation of coating solution S-1 for light scattering layer)
50 g of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (PETA, Nippon Kayaku Co., Ltd.) was diluted with 38.5 g of toluene. Further, 2 g of a polymerization initiator (Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added and mixed and stirred. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.51.
Further, a 30% toluene dispersion of crosslinked polystyrene particles having an average particle size of 3.5 μm (refractive index: 1.60, SX-350, manufactured by Soken Chemical Co., Ltd.) dispersed in this solution for 20 minutes at 10,000 rpm with a Polytron disperser. Add 13.3 g of 30% toluene dispersion of 1.7 g and crosslinked acrylic-styrene particles having an average particle size of 3.5 μm (refractive index 1.55, manufactured by Soken Chemical Co., Ltd.), and finally, fluorine-based surface modification 0.75 g of agent (FP-1) and 10 g of silane coupling agent (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to obtain a finished solution.
The mixture solution was filtered through a polypropylene filter having a pore diameter of 30 μm to prepare a light scattering layer coating solution S-1.

(Preparation of coating solution S-2 for low refractive index layer)
First, sol solution a was prepared as follows. A stirrer, a reactor equipped with a reflux condenser, 120 parts of methyl ethyl ketone, 100 parts of acryloyloxypropyltrimethoxysilane (KBM5103, manufactured by Shin-Etsu Chemical Co., Ltd.), 3 parts of diisopropoxyaluminum ethyl acetoacetate were added and mixed. After adding 30 parts of ion-exchanged water and reacting at 60 ° C. for 4 hours, it was cooled to room temperature to obtain a sol solution a. The mass average molecular weight was 1600, and among the components higher than the oligomer component, the component having a molecular weight of 1000 to 20000 was 100%. Further, from the gas chromatography analysis, the raw material acryloyloxypropyltrimethoxysilane did not remain at all. Thermally crosslinkable fluorine-containing polymer having a refractive index of 1.42 (JN-7228, solid content concentration 6%, manufactured by JSR Corporation) 13 g, silica sol (silica, MEK-ST particle size difference, average particle size 45 nm, solid content 30% concentration, manufactured by Nissan Chemical Co., Ltd.) 1.3 g, 0.6 g of the above sol solution a, 5 g of methyl ethyl ketone, and 0.6 g of cyclohexano were added. After stirring, the mixture was filtered through a polypropylene filter having a pore size of 1 μm. Refractive index layer coating solution S-2 was prepared.

(Preparation of transparent protective film P5 with light scattering layer)
An 80 μm-thick cellulose acetate film (TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is unwound in a roll form, and the above functional layer (light scattering layer) coating solution S-1 has a line number of 180 lines / inch, Using a gravure pattern with a depth of 40 μm and a microgravure roll with a diameter of 50 mm and a doctor blade, it was applied under the conditions of a gravure roll rotation speed of 30 rpm and a conveyance speed of 30 m / min, dried at 60 ° C. for 150 seconds, and further purged with nitrogen Using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at 160 W / cm, the coating layer is cured by irradiating with ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 250 mJ / cm ^2. A layer was formed and wound up.
The cellulose acetate film coated with the functional layer (light scattering layer) is unwound again, and the prepared coating liquid S-2 for low refractive index layer is 180 lines / inch and the depth is 40 μm on the light scattering layer side. Using a microgravure roll with a diameter of 50 mm and a doctor blade having a gravure pattern, the coating was applied at a gravure roll rotation speed of 30 rpm and a conveyance speed of 15 m / min, dried at 120 ° C. for 150 seconds, and further at 140 ° C. for 8 minutes. After drying, using a 240 W / cm air-cooled metal halide lamp (made by Eye Graphics Co., Ltd.) under a nitrogen purge, irradiate ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 900 mJ / cm ² . A low refractive index layer was formed and wound up to obtain a protective film P5 with a light scattering layer.

(Preparation of coating liquid S-3 for hard coat layer)
750.0 parts by mass of trimethylolpropane triacrylate (TMPTA, Nippon Kayaku Co., Ltd.), 270.0 parts by mass of poly (glycidyl methacrylate) having a mass average molecular weight of 3000, 730.0 g of methyl ethyl ketone, 500.0 g of cyclohexanone and light A polymerization initiator (Irgacure 184, manufactured by Nippon Ciba-Geigy Co., Ltd.) 50.0 g was added and stirred. It filtered with the polypropylene filter with the hole diameter of 0.4 micrometer, and prepared the coating liquid S-3 for hard-coat layers.

(Preparation of titanium dioxide fine particle dispersion)
As the titanium dioxide fine particles, titanium dioxide fine particles (MPT-129, manufactured by Ishihara Sangyo Co., Ltd.) containing cobalt and surface-treated with aluminum hydroxide and zirconium hydroxide were used.
The following dispersant (38.6 g) and cyclohexanone (704.3 g) were added to 257.1 g of the particles and dispersed by dynomill to prepare a titanium dioxide dispersion having a mass average diameter of 70 nm.

(Preparation of medium refractive index layer coating solution S-4)
To 88.9 g of the above titanium dioxide dispersion, 58.4 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA), 3.1 g of a photopolymerization initiator (Irgacure 907), a photosensitizer (Kayacure DETX) 1.1 g of Nippon Kayaku Co., Ltd.), 482.4 g of methyl ethyl ketone and 1869.8 g of cyclohexanone were added and stirred. After sufficiently stirring, the solution was filtered through a polypropylene filter having a pore diameter of 0.4 μm to prepare a coating solution S-4 for a medium refractive index layer.

(Preparation of coating liquid S-5 for high refractive index layer)
To 56.8 g of the above titanium dioxide dispersion, 47.9 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.), photopolymerization initiator (Irgacure 907, Nippon Ciba Geigy ( Co., Ltd.) 4.0 g, photosensitizer (Kayacure-DETX, Nippon Kayaku Co., Ltd.) 1.3 g, methyl ethyl ketone 455.8 g, and cyclohexanone 1427.8 g were added and stirred. The solution was filtered through a polypropylene filter having a pore diameter of 0.4 μm to prepare a coating solution S-5 for a high refractive index layer.

(Preparation of coating solution S-6 for low refractive index layer)
A copolymer having the following structure was dissolved in methyl isobutyl ketone so as to have a concentration of 7% by mass, and a terminal methacrylate group-containing silicone resin X-22-164C (manufactured by Shin-Etsu Chemical Co., Ltd.) was 3% based on the solid content. The photo-radical generator Irgacure 907 (trade name) was added in an amount of 5% by mass based on the solid content to prepare a coating solution S-6 for a low refractive index layer.

(Preparation of transparent protective film P6 with antireflection layer)
On a cellulose acetate film having a thickness of 80 μm (TD80UF, manufactured by Fuji Photo Film Co., Ltd.), the hard coat layer coating solution S-3 was applied using a gravure coater. After drying at 100 ° C., an irradiance of 400 mW / cm using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) of 160 W / cm while purging with nitrogen so that the oxygen concentration becomes 1.0 vol% or less. ^{2. The} coating layer was cured by irradiating ultraviolet rays with an irradiation amount of 300 mJ / cm ² to form a hard coat layer having a thickness of 8 μm.
On the hard coat layer, a gravure coater having three coating stations for coating solution S-4 for medium refractive index layer, coating solution S-5 for high refractive index layer, and coating solution S-6 for low refractive index layer is used. Applied continuously.

The intermediate refractive index layer was dried at 100 ° C. for 2 minutes, and the ultraviolet curing condition was 180 W / cm air-cooled metal halide lamp (eye graphics) while purging with nitrogen so that the atmosphere had an oxygen concentration of 1.0% by volume or less. The irradiance was 400 mW / cm 2 and the irradiation amount was 400 mJ / cm ² . The medium refractive index layer after curing had a refractive index of 1.630 and a film thickness of 67 nm.
The drying conditions of the high refractive index layer and the low refractive index layer are both 90 ° C., 1 minute, 100 ° C., 1 minute, and the ultraviolet curing condition is nitrogen so that the atmosphere has an oxygen concentration of 1.0% by volume or less. While purging, a 240 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) was used to obtain an irradiation dose of 600 mW / cm ² and an irradiation dose of 600 mJ / cm ² .
The cured high refractive index layer had a refractive index of 1.905 and a film thickness of 107 nm, and the low refractive index layer had a refractive index of 1.440 and a film thickness of 85 nm. In this way, a transparent protective film P6 with an antireflection layer was produced.

(Protective film P7)
16.8 parts by mass of cellulose acetate LT-35 having an acetyl substitution degree of 2.87 (manufactured by Daicel Chemical Industries, Ltd.), 1.9 parts by mass of a retardation reducing agent having the following structure, and a wavelength dispersion adjusting agent having the following structure: 3 parts by mass was dissolved in 81 parts by mass of a mixed solvent (dichloromethane / methanol = 87/13 parts by mass), and further heated to 90 ° C. in a pressure-resistant sealed container to be completely dissolved. Silicon dioxide fine particles (primary particle size 20 nm, Mohs hardness of about 7) were added to this solution at a ratio of 0.05 parts by weight of fine particles to 100 parts by weight of cellulose acetate to prepare a dope.
This dope was cast using a band casting machine. The residual solvent amount is about 30% by mass and the film peeled off from the band is dried by applying hot air while preventing shrinkage in the width direction using a tenter, then transferred from the tenter conveyance to the roll conveyance, and further dried. Knurled and wound up. The film thickness was 92 μm. This film was designated as a protective film P7.

(Protective film P8)
To cellulose derived from cotton, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, acetic anhydride was added, and an acetylation reaction was performed at 40 ° C. Thereafter, the total substitution degree was adjusted to 2.81 and the 6-position substitution degree was adjusted to 0.91 by adjusting the amount of sulfuric acid catalyst, the amount of water and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acetate was removed by washing with acetone.
The prepared cellulose acetate was mixed with a plasticizer (a 2-to-1 mixture of triphenyl phosphate and biphenyl diphenyl phosphate), a retardation developer with the following structure, mixed solvent, dichloromethane / methanol (87/13 parts by mass) with solid content The mixture was stirred while being stirred so that the mass concentration became 19% by mass, and dissolved by heating and stirring. At the same time, 0.05 part by mass of fine particles [silicon dioxide (primary particle size 20 nm, Mohs hardness about 7)] was added to 100 parts by mass of cellulose acetate and stirred while heating. The addition ratio of the plasticizer and the retardation developing agent was 10 parts by mass when the cellulose acylate amount was 100 parts by mass. The plasticizer was 12 parts by mass and the retardation developing agent was 5 parts by mass.

  The above dope was cast using a band casting machine. A film peeled off from the band with a residual solvent amount of about 30% by mass was stretched in the width direction at a stretch rate of 23% using a tenter to produce an optical biaxial film of cellulose acetate. The tenter was stretched in the width direction while being dried by applying hot air, and then contracted by 5%, then transferred from the tenter conveyance to the roll conveyance, further dried, knurled and wound up. The stretch ratio at the tenter outlet was 18% of the film width at the tenter inlet, and the film thickness was 92 μm. This film was designated as a protective film P8.

(Saponification treatment)
A 1.5N aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.01 N dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The protective films P1, P2, P4, P5, P6, P7 and P8 were immersed in the above-mentioned aqueous sodium hydroxide solution for 2 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C. The protective films used in the examples and comparative examples described below were all saponified.
Table 3 shows the elastic modulus, water content, and humidity dimensional change rate of each protective film.

(Creating polarizing film)
A PVA film having an average degree of polymerization of 2400 and a film thickness of 75 μm is sent out and washed while passing through ion-exchanged water at 30 ° C. for 1 minute. The washed PVA film was then stretched three times in the direction of travel at 30 ° C. in an aqueous solution of iodine 3.0 g / l and potassium iodide 30.0 g / l, and further in a 50 ° C. aqueous solution of boric acid 40 g / l. Then, the film was stretched so that the total stretching ratio was 5.0 times, washed in a 30 ° C. water bath, and then dried at 50 ° C. for 4 minutes to obtain a polarizing film E. The thickness of the obtained polarizing film E was 27 μm.

  When the polarized Raman scattering spectrum was measured, the polarizing film E was (Ib108 / Ia108) = 92 and (Ib154 / Ia154) = 92.

  Thereafter, the protective film P1 is bonded to one surface of the polarizing film E, and the protective film P5 is bonded to the other surface of the polarizing film E through an adhesive of a 4% aqueous solution of PVA (Pura-124H manufactured by Kuraray Co., Ltd.). It heated at 70 degreeC for 30 minute (s), and the edge was cut with the cutter, and the polarizing plate F1 of the roll form of effective width 500mm and length 50m was produced. However, immediately before the polarizing film and the protective film were bonded, in the same process, high-humidity air containing water vapor was applied to the side of the protective film P1 opposite to the surface to be bonded to the polarizing film for 30 seconds. The high-humidity air used here contained 1.5 kg of water vapor per kg of air.

  When the single plate transmittance and the degree of polarization of the polarizing plate F1 were measured, the single plate transmittance was 42.8% and the degree of polarization was 99.97%. The light transmittance at a wavelength of 700 nm at the time of crossed Nicols was 0.07%. The curl was as small as 11.5 mm.

[Comparative Example 1]
A polarizing plate G1 was prepared in the same manner as in Example 1 except that the protective film P1 was not subjected to high-humidity air treatment. The curl of the polarizing plate G1 was as large as 31.5 mm.

(Creating polarizing film)
To a 5% aqueous solution of PVA (PVA-124H manufactured by Kuraray Co., Ltd.), 5% by weight of ethylene glycol diglycidyl ether was added to PVA to prepare a coating liquid L2.
A polarizing film E is prepared in the same manner as in Example 1, a protective film P5 is formed on one side of the polarizing film E, a protective film P2 is formed on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. The coating liquid L2 is applied to the surface of the protective film P2 with a bar coater at a rate of 5 g / m ² , then dried at 70 ° C. for 30 minutes, ear-cut with a cutter, and roll-shaped polarized light having an effective width of 500 mm and a length of 50 m. A plate F2 was produced.
When the single plate transmittance and the degree of polarization of the polarizing plate F2 were measured, the single plate transmittance was 42.8%, and the polarization degree was 99.97%. The light transmittance at a wavelength of 700 nm at the time of crossed Nicols was 0.07%. The curl was as small as 8.0 mm.

[Comparative Example 2]
A polarizing plate G2 was prepared in the same manner as in Example 2 except that the coating liquid L2 was not applied to the protective film P2. The curl of the polarizing plate G2 was as large as 61.5 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P5 is provided on one side of the polarizing film E, a protective film P4 is provided on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. The surface of the protective film P4 is wiped with high-humidity air containing 1.5 kg of water vapor per kg of air for 30 seconds, then dried at 70 ° C. for 30 minutes, ear-capped with a cutter, with an effective width of 500 mm and a length of 50 m. A roll-shaped polarizing plate F3 was produced.
The curl of the polarizing plate F3 was as small as 4.0 mm.

[Comparative Example 3]
A polarizing plate G3 was prepared in the same manner as in Example 3 except that high-humidity air was not wiped onto the protective film P4. The curl of the polarizing plate G3 was as large as 41.0 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P5 is formed on one side of the polarizing film E, a protective film P8 is formed on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. Apply 4 g / m ² of a mixed solution of ethyl acetate and ethanol 1 to 1 (mass ratio) on the surface of the protective film P5 with a bar coater, then dry at 70 ° C. for 30 minutes, and remove the ears with a cutter. A polarizing plate F4 in the form of a roll having a width of 500 mm and a length of 50 m was produced.
The curl of the polarizing plate F4 was as small as 14.0 mm.

[Comparative Example 4]
A polarizing plate G4 was prepared in the same manner as in Example 4 except that the mixed solvent was not applied to the protective film P5. The curl of the polarizing plate G4 was as large as 38.8 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P5 is provided on one side of the polarizing film E, a protective film P7 is provided on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 Bonding was carried out through an adhesive of a% aqueous solution and dried at 70 ° C. for 20 minutes. After that, high humidity air containing 1.5 kg of water vapor per kg of air is wiped on the surface of the protective film P7 for 30 seconds, and the edge is removed with a cutter to produce a roll-shaped polarizing plate F5 having an effective width of 500 mm and a length of 50 m. did.
The curl of the polarizing plate F5 was as small as 13.5 mm.

[Comparative Example 5]
A polarizing plate G5 was prepared in the same manner as in Example 5 except that high-humidity air was not wiped onto the protective film P7. The curl of the polarizing plate G5 was as large as 46.5 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P5 is provided on one side of the polarizing film E, a protective film P3 is provided on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. The coating liquid L2 is applied to the surface of the protective film P3 with a bar coater at 4 g / m ² , and then dried at 70 ° C. for 30 minutes, and then the edge is removed with a cutter. A plate F6 was produced. The curl of the polarizing plate F6 was as small as 8.5 mm.

[Comparative Example 6]
A polarizing plate G6 was prepared in the same manner as in Example 2 except that the coating liquid L2 was not applied to the protective film P3. The curl of the polarizing plate G6 was as large as 68.0 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P6 is provided on one side of the polarizing film E, a protective film P4 is provided on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. The surface of the protective film P4 is wiped with high-humidity air containing 1.5 kg of water vapor per kg of air for 30 seconds, then dried at 70 ° C. for 30 minutes, ear-capped with a cutter, having an effective width of 500 mm and a length of 50 m. A roll-shaped polarizing plate F7 was produced.
The curl of the polarizing plate F7 was as small as 10.0 mm.

[Comparative Example 7]
A polarizing plate G7 was prepared in the same manner as in Example 7 except that high-humidity air was not wiped onto the protective film P4. The curl of the polarizing plate G7 was as large as 42.0 mm.

(Creating polarizing film)
A polarizing film E is prepared in the same manner as in Example 1, a protective film P2 is formed on one side of the polarizing film E, a protective film P8 is formed on the opposite side of the polarizing film E, and PVA (PVA-124H manufactured by Kuraray Co., Ltd.) 4 It bonded together through the adhesive agent of% aqueous solution. The coating liquid L2 is applied to the surface of the protective film P8 with a bar coater at 4 g / m ² , and then dried at 70 ° C. for 30 minutes, and then the edge is removed with a cutter. A plate F8 was produced. The curl of the polarizing plate F8 was as small as 11.0 mm.

[Comparative Example 8]
A polarizing plate G8 was prepared in the same manner as in Example 2 except that the coating liquid L2 was not applied to the protective film P8. The curl of the polarizing plate G8 was as large as 66.5 mm.

  Immediately before bonding the protective film P1, the polarizing film E, and the protective film P5, high humidity air containing 1.5 kg of water vapor per kg of air was also applied to the protective film P5 for 5 seconds. Otherwise, a polarizing plate F9 was produced in the same manner as in Example 1. The curl of the polarizing plate F9 was as small as 3.0 mm.

  After bonding the protective film P4, the polarizing film E, and the protective film P5, high-humidity air containing 1.5 kg of water vapor per kg of air was applied to the protective film P5 for 5 seconds. Otherwise, a polarizing plate F10 was produced in the same manner as in Example 3. The curl of the polarizing plate F10 was as small as 5.5 mm.

It is a schematic sectional drawing of the structural example which combined the polarizing plate and functional optical film of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Upper polarizing plate Absorption axis 3 Upper optical anisotropic layer 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 optical anisotropic layer 11 Lower optical anisotropic layer orientation control direction 12 Lower polarizing plate 13 Lower polarizing plate absorption axis

Claims (7)

  A method of manufacturing a polarizing plate in which protective films are attached to both sides of a polarizing film, wherein the polarizing film and the protective film are bonded together after the curl correction treatment is performed on one protective film. Production method.   A method of manufacturing a polarizing plate having protective films attached to both sides of a polarizing film, wherein the polarizing film and the protective film are bonded together, and then the surface of one of the protective films is subjected to curl correction treatment. A manufacturing method of a board.   A method of manufacturing a polarizing plate in which protective films are attached to both sides of a polarizing film, wherein both protective films are subjected to curl correction processing with different processing strengths, and then the polarizing film and the protective film are bonded together A method for producing a polarizing plate.   A method of manufacturing a polarizing plate in which a protective film is attached to both sides of a polarizing film, and after the polarizing film and the protective film are bonded together, the surface of both protective films is subjected to curl correction processing having different processing strengths. The manufacturing method of the polarizing plate characterized by these.   The method for producing a polarizing plate according to any one of claims 1 to 4, wherein the curl correction treatment is performed by applying water vapor or solvent vapor to a surface or surface of the protective film that does not contact the polarizing film.   The method for producing a polarizing plate according to any one of claims 1 to 4, wherein the curl correction treatment is to apply a solvent to a surface or a surface of the protective film that is not in contact with the polarizing film.   The method for producing a polarizing plate according to any one of claims 1 to 4, wherein the curl correction treatment is to apply a polymer solution on a surface or surface of the protective film that does not contact the polarizing film. .

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