JP2008129293A - Manufacturing method of polarizer, polarizer, polarizing plate, optical film and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polarizer by which its optical characteristics can be improved without necessitating excess stretching. <P>SOLUTION: The manufacturing method of the polarizer has a dyeing process of executing dyeing processing of a hydrophilic polymer film with a dichroic substance in a dyeing bath and a stretching process of executing stretching processing of the hydrophilic polymer film in a stretching bath and further has a stretching relaxation process of executing relaxation processing to the hydrophilic polymer film by holding the hydrophilic polymer film in a state of being applied with extension of intensity giving no stretching to the hydrophilic polymer film in the stretching direction for a definite time in the middle of the stretching processing or after the stretching processing of the hydrophilic polymer film in the bath. The stretching relaxation process is executed in at least one process among the dyeing process, the stretching process and another process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polarizer, a polarizer, a polarizing plate, an optical film, and an image display device.

Polarizers are used in various liquid crystal display devices such as televisions, personal computers, and mobile phones. Usually, the polarizer is produced by dyeing and uniaxially stretching a polyvinyl alcohol (PVA) film. When the PVA film is uniaxially stretched, the dichroic material adsorbed (stained) on the PVA molecules is oriented, so that a polarizer is obtained. Here, as a method for enhancing the optical properties of the polarizer by highly orienting the dichroic material, a method of increasing the draw ratio of the PVA film has been proposed (for example, see Patent Document 1). However, in this method, there is a certain limit to increasing the draw ratio, and there is a problem that excessive stretching causes breakage of the PVA film.
JP 2002-28971 A

  Then, an object of this invention is to provide the manufacturing method of the polarizer which can improve an optical characteristic.

In order to achieve the above object, the method for producing a polarizer of the present invention comprises:
A dyeing process for dyeing a hydrophilic polymer film with a dichroic substance in a dyeing bath;
And a stretching process for stretching the hydrophilic polymer film in a stretching bath, further comprising:
In the bath, the hydrophilic polymer film is stretched, and during the stretching process or after the stretching process, the hydrophilic polymer film is stretched in the stretching direction in the stretching direction with respect to the hydrophilic polymer film. Has a stretching relaxation step of relaxing and maintaining the state added for a certain time,
The stretching relaxation step is performed in at least one of the steps different from the dyeing step, the stretching step, and the both steps.

  The polarizer of the present invention is a polarizer manufactured by the method for manufacturing a polarizer of the present invention.

  The polarizing plate of the present invention is a polarizing plate in which a protective layer is disposed on at least one surface of a polarizer, and the polarizer is the polarizer of the present invention.

  The optical film of the present invention is an optical film in which a retardation plate is disposed on at least one surface of a polarizer or a polarizing plate, wherein the polarizer is the polarizer of the present invention, and the polarizing plate is It is the polarizing plate of the present invention.

  The image display device of the present invention is an image display device including at least one of a polarizer, a polarizing plate and an optical film, wherein the polarizer is the polarizer of the present invention, and the polarizing plate is the book. The polarizing plate of the invention is characterized in that the optical film is the optical film of the invention.

  The present inventors have made a series of studies in order to achieve the above object. In the course of the research, in the production of a polarizer, it was found that the optical properties of the polarizer were improved when the hydrophilic polymer film was in the relaxed state as described above during or after the stretching of the hydrophilic polymer film. It was. According to the method for producing a polarizer of the present invention, a polarizer having excellent optical characteristics can be obtained without excessive stretching.

  In the present invention, the “optical characteristics” include, for example, a retardation value, a dichroic substance content of a polarizer (for example, iodine efficiency described later), a single transmittance (T), a polarization degree (P), and the like. It is. In the present invention, one or more of these characteristics can be improved. The dichroic substance content, single transmittance (T) and degree of polarization (P) of the polarizer can be measured, for example, by the method described in Examples described later.

  In the production method of the present invention, the other steps include, for example, a swelling step for swelling the hydrophilic polymer film in a swelling bath, and a crosslinking step for crosslinking the hydrophilic polymer film in a crosslinking bath. In the production method of the present invention, the stretching relaxation step may be performed independently from other steps.

  In the production method of the present invention, it is preferable that the hydrophilic polymer film is continuously processed while being conveyed in at least one step selected from the group consisting of the swelling step, the dyeing step, the crosslinking step, and the stretching step. . However, the production method of the present invention is not limited to continuous processing, and may be batch processing.

  It is preferable to carry out the stretching relaxation step in at least the dyeing step of the production method of the present invention.

  In the production method of the present invention, the hydrophilic polymer film is preferably a polyvinyl alcohol film, and the dichroic substance is preferably iodine.

  In the production method of the present invention, the time for maintaining the tension in the stretching relaxation step is preferably 15 seconds or more.

  Next, an example is given and the manufacturing method of the polarizer of this invention is demonstrated below. The production method of the present invention uses a hydrophilic polymer film as a material, and has, for example, a series of processes such as a swelling process, a dyeing process, a crosslinking process, a stretching process, an adjusting process, and a drying process, and at least one of these processes. The stretching relaxation step is performed in or separately.

(1) Hydrophilic polymer film The hydrophilic polymer film is not particularly limited, and a conventionally known film can be used. Specifically, for example, hydrophilic polymers such as polyvinyl alcohol (PVA) film, partially formalized PVA film, polyethylene terephthalate (PET) film, ethylene / vinyl acetate copolymer film, and partially saponified films thereof. A film etc. are mentioned. In addition to these, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products, stretched and oriented polyvinylene films, and the like can also be used. Among these, since it is excellent in the dyeability by the iodine which is a dichroic substance mentioned later, a PVA-type polymer film is preferable.

  As a raw material polymer of the PVA polymer film, for example, saponified after polymerizing vinyl acetate, or a small amount of a copolymerizable monomer such as unsaturated carboxylic acid or unsaturated sulfonic acid with respect to vinyl acetate. Examples thereof include a copolymerized polymer. The polymerization degree of the PVA polymer is not particularly limited, but is preferably in the range of 500 to 10,000, more preferably 1000 to 6000, from the viewpoint of solubility in water. The saponification degree is preferably 75 mol% or more, and more preferably 98 to 100 mol%.

  The size of the hydrophilic polymer film (for example, PVA film) is not particularly limited, but the thickness is, for example, in the range of 15 to 110 μm, preferably in the range of 38 to 110 μm, more preferably, It is 50-100 micrometers, More preferably, it is 60-80 micrometers. When the production method of the present invention is carried out by continuous processing, the hydrophilic polymer film (for example, PVA-based film) is preferably in the form of a raw film wound on a roll. In this case, while conveying the film, Processing is performed in each process. Moreover, when the manufacturing method of this invention is implemented by batch processing, the hydrophilic polymer film (for example, PVA-type film) cut into the predetermined magnitude | size is used.

(2) Stretching relaxation step As described above, the stretching relaxation step stretches the hydrophilic polymer film in a bath, and is applied to the hydrophilic polymer film during or after the stretching treatment. In the stretching direction, a relaxation treatment is performed by maintaining a state in which a tension of a strength at which the hydrophilic polymer film is not stretched is applied for a certain time. The tensile strength that does not stretch is not particularly limited. For example, in the dyeing process described later, when the temperature of the dyeing bath is 30 ° C., for example, it is in the range of 10 to 30 N / 25 cm ² , preferably about 20 N / 25 cm ² . Moreover, as above-mentioned, time to hold | maintain the said state is 15 seconds or more, More preferably, it is 1 minute or more. Specifically, the time for maintaining the state is, for example, in the range of 15 to 300 seconds, preferably in the range of 20 to 240 seconds, and more preferably in the range of 20 to 180 seconds. For example, when the non-stretching tension is continuously processed while transporting the hydrophilic polymer film between two rolls, the rotational speed of the carry-in roll is made larger than the rotational speed of the carry-out roll. However, it can be realized by making the hydrophilic polymer film not so large that it does not stretch. In the middle of the stretching, the stretching may be temporarily stopped and the relaxation treatment may be performed, and then the stretching treatment may be resumed. Alternatively, the stretching treatment may be performed after the stretching processing is finished. In the case of continuous processing, it is preferable to carry out the above-mentioned holding in a state in which a tensile strength that is not stretched is applied while conveying the film between rolls. As described above, the stretching relaxation process may be performed in each process such as a swelling process, a dyeing process, a crosslinking process, a stretching process, and an adjusting process, or may be performed separately.

(3) Swelling step The hydrophilic polymer film is immersed and swollen in a swelling bath, and uniaxially stretched in the longitudinal direction (MD direction) in the swelling bath.

  Examples of the swelling bath solution that can be used include water, an aqueous glycerin solution, and an aqueous potassium iodide solution. The temperature of the swelling bath is, for example, in the range of 20 to 45 ° C, preferably in the range of 25 to 40 ° C, and more preferably in the range of 27 to 37 ° C. The immersion time in the swelling bath is not particularly limited, but is, for example, in the range of 30 to 300 seconds, preferably in the range of 60 to 180 seconds, and more preferably in the range of 60 to 120 seconds.

  By immersing in the swelling bath, the hydrophilic polymer film normally swells 1.1 to 1.5 times the length of the film (original fabric) before swelling. In this step, the hydrophilic polymer film is further uniaxially stretched in the MD direction in the swelling bath. The stretching ratio of the hydrophilic polymer film in this step is preferably in the range of 1 to 2 times the swelling amount, and more preferably in the range of 1.05 to 1.5 times the swelling amount. As a means for uniaxially stretching the hydrophilic polymer film, any appropriate stretching machine such as a roll stretching machine, a tenter stretching machine, or a hand stretching machine is used.

  In this step, in order to carry out the stretching relaxation step, for example, in the uniaxial stretching, stretching is stopped in the middle of stretching, or after uniaxial stretching, the film is not stretched and tension is applied. Hold for a certain period of time. The method, conditions, etc. in the stretching relaxation step in this case are as described above.

(4) Dyeing step The hydrophilic polymer film is pulled up from the swelling bath, immersed in a dyeing bath containing a dichroic substance, and uniaxially stretched in the longitudinal direction (MD direction) in the dyeing bath. That is, the dichroic substance is adsorbed on the hydrophilic polymer film by the immersion, and the dichroic substance is oriented in one direction by the uniaxial stretching.

  A conventionally known substance can be used as the dichroic substance, and examples thereof include iodine and organic dyes. When using the said organic dye, it is preferable to combine 2 or more types from the point which aims at neutralization of the visible region, for example.

  As the dye bath solution, a solution in which the dichroic substance is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further added. Although the density | concentration of the dichroic substance in the said solution is not restrict | limited in particular, For example, it is the range of 0.005-0.10 weight%, Preferably, it is 0.01-0.08 weight%.

  In addition, when iodine is used as the dichroic substance, it is preferable to further add an iodide as an auxiliary agent in addition to iodine because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.05 to 10% by weight, more preferably 0.10 to 5% by weight in the dyeing bath.

  For example, when iodine and potassium iodide are used in combination, the ratio (A: B (weight ratio)) of iodine (A) and potassium iodide (B) in the solution is, for example, 1: 5 to 1: The range is 100, preferably 1: 7 to 1:50, more preferably 1:10 to 1:30.

  The immersion time of the hydrophilic polymer film in the dyeing bath is not particularly limited, but is, for example, in the range of 18 to 120 seconds, preferably in the range of 18 to 90 seconds, and more preferably in the range of 25 to 60. A range of seconds. Moreover, the temperature of the said dyeing bath is the range of 5-42 degreeC, for example, Preferably, it is the range of 10-35 degreeC, More preferably, it is the range of 12-30 degreeC. Moreover, it is preferable to set this temperature 3-15 degreeC lower than the temperature of the said swelling process, for example, More preferably, it sets 5-12 degreeC low, More preferably, it sets 8-10 degreeC low.

  The draw ratio in this step is, for example, preferably in the range of 1.05 to 4 times, more preferably in the range of 1.1 to 3 times the length of the polymer film after the swelling step. Yes, more preferably in the range of 1.1 to 2 times. The means for uniaxially stretching the polymer film is the same as the swelling step described above. In this step, in order to carry out the stretching relaxation step, for example, in the uniaxial stretching, stretching is stopped in the middle of stretching, or after uniaxial stretching, the film is not stretched and tension is applied. Hold for a certain period of time. The method, conditions, etc. in the stretching relaxation step in this case are as described above.

(5) Crosslinking step The polymer film is pulled up from the dyeing bath, immersed in a crosslinking bath containing a crosslinking agent, and uniaxially stretched in the longitudinal direction (MD direction) in the crosslinking bath.

  As the crosslinking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid, borax, glyoxal, and glutaraldehyde. These may be used alone or in combination of two or more. As the solution of the crosslinking bath, a solution in which the crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included.

  The concentration of the crosslinking agent in the solution is not particularly limited, but is preferably in the range of 0.1 to 10 parts by weight, more preferably 1.5 to 100 parts by weight with respect to 100 parts by weight of the solvent (for example, water). It is the range of 8 weight part, More preferably, it is the range of 2-6 weight part.

  In addition to the boric acid compound, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, and iodide can be used for the cross-linking agent-containing solution in addition to the boric acid compound because uniform characteristics in the plane of the polarizer can be obtained. Auxiliaries such as iodides such as aluminum, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide may be included. Among these, a combination of boric acid and potassium iodide is preferable. The content of the auxiliary agent in the solution is, for example, in the range of 0.05 to 15% by weight, and preferably in the range of 0.5 to 8% by weight.

  Although the temperature of the said crosslinking bath is not specifically limited, For example, it is the range of 20-70 degreeC, Preferably it is the range of 40-60 degreeC. Although the immersion time of the said polymer film is not specifically limited, For example, it is 12 to 120 second, Preferably, it is 18 to 60 second.

  The draw ratio in this step is, for example, in the range of 1 to 3 times, preferably in the range of 1 to 2 times, more preferably, with respect to the length of the polymer film after the dyeing step, The range is 1 to 1.5 times. The means for uniaxially stretching the polymer film is the same as the swelling step described above. In this step, in order to carry out the stretching relaxation step, for example, in the uniaxial stretching, stretching is stopped in the middle of stretching, or after uniaxial stretching, the film is not stretched and tension is applied. Hold for a certain period of time. The method, conditions, etc. in the stretching relaxation step in this case are as described above.

(6) Stretching step The hydrophilic polymer film is pulled up from the crosslinking bath, immersed in a stretching bath, and uniaxially stretched in the longitudinal direction (MD direction) in the stretching bath.

  The stretching bath solution is not particularly limited, and for example, a solution containing boric acid, potassium iodide, various metal salts, other iodide compounds, zinc compounds, and the like can be used. As a solvent of this solution, for example, water, ethanol or the like can be used. Specifically, for example, it is preferable to contain boric acid and potassium iodide, and the content of both is, for example, in the range of 2 to 18% by weight in total, preferably 4 to 17% by weight in total. More preferably, the total content is in the range of 6 to 15% by weight. The content ratio (A: B (weight ratio)) of the boric acid (A) and potassium iodide (B) is, for example, in the range of 1: 0.1 to 1: 4, preferably 1 : 0.2 to 1: 3.5, and more preferably 1: 0.5 to 1: 3.

  The temperature of the stretching bath is, for example, in the range of 40 to 75 ° C, preferably 50 to 70 ° C.

  The draw ratio in this drawing step is, for example, in the range of 1.05 to 3 times, preferably in the range of 1.1 to 2 times, with respect to the length of the polymer film after the crosslinking step. More preferably, it is in the range of 1.2 to 2 times. The stretching treatment time is, for example, in the range of 30 to 180 seconds, and preferably in the range of 30 to 60 seconds. The means for uniaxially stretching the polymer film is the same as the swelling step described above. In this step, in order to carry out the stretching relaxation step, for example, in the uniaxial stretching, stretching is stopped in the middle of stretching, or after uniaxial stretching, the film is not stretched and tension is applied. Hold for a certain period of time. The method, conditions, etc. in the stretching relaxation step in this case are as described above.

(7) Adjustment / drying step The hydrophilic polymer film is pulled out of the stretching bath, immersed in an iodide-containing aqueous solution (conditioning bath), and then dried to obtain the polarizer of the present invention.

  As the iodide in the iodide-containing aqueous solution, those described above can be used, and among them, for example, potassium iodide and sodium iodide are preferable. With this iodide-containing aqueous solution, the remaining boric acid used in the stretching step can be washed away from the hydrophilic polymer film.

  When the aqueous solution is an aqueous potassium iodide solution, the concentration thereof is, for example, in the range of 0.5 to 20% by weight, preferably in the range of 1 to 15% by weight, more preferably 1.5 to It is in the range of 7% by weight. The temperature of the aqueous solution is, for example, in the range of 15 to 40 ° C, and preferably in the range of 20 to 35 ° C. The immersion time in the aqueous solution is, for example, in the range of 2 to 15 seconds, and preferably in the range of 3 to 12 seconds.

  Drying is not particularly limited, for example, natural drying, air drying, heat drying, etc., but in the case of heat drying, the temperature is preferably in the range of 25-80 ° C, more preferably in the range of 30-75 ° C, and even more preferably. Is in the range of 35-70 ° C.

  In this step, it is possible to carry out the stretching relaxation step. The method, conditions, etc. in the stretching relaxation step in this case are as described above.

  The swelling process, the dyeing process, the crosslinking process, the stretching process, and the adjustment / drying process have been described above. These steps may be performed separately, but the steps that can be combined into one step may be performed collectively. Moreover, you may implement an adjustment and a drying process after completion | finish of each process.

  Through such a series of steps, a polarizer having excellent optical characteristics can be produced. The polarizer is usually used after being cut into a predetermined size.

(8) Polarizer The polarizer of the present invention is excellent in optical properties such as retardation value, dichroic substance content of the polarizer, single transmittance (T) and degree of polarization (P). In the polarizer of the present invention, the retardation value is, for example, in the range of 800 to 1500 nm, preferably in the range of 900 to 1400 nm, more preferably in the range of 1000 to 1300 nm, and the dichroic substance The content is, for example, in the range of 0.3 to 5% by weight, preferably in the range of 0.5 to 4% by weight, and more preferably in the range of 0.6 to 3% by weight. The transmittance (T) is, for example, in the range of 36 to 50%, preferably in the range of 42 to 44%, more preferably in the range of 42.5 to 43.5%, and the degree of polarization ( P) is, for example, in the range of 94 to 100%, preferably in the range of 99 to 100%, and more preferably in the range of 99.9 to 100%. The thickness of the polarizer of the present invention is not particularly limited, but is, for example, in the range of 5 to 40 μm, preferably in the range of 10 to 37 μm, and more preferably in the range of 15 to 35 μm.

(9) Polarizing plate Next, the polarizing plate of the present invention has a configuration in which a protective layer is disposed on at least one surface of the polarizer of the present invention. The protective layer may be disposed only on one side of the polarizer, or may be disposed on both sides. When arrange | positioning on both surfaces, the same kind of protective layer may be used and a different kind of protective layer may be used, for example.

  In FIG. 1, sectional drawing of an example of the polarizing plate of this invention is shown. As shown in the figure, the polarizing plate 10 has protective layers 2 disposed on both sides of the polarizer 1.

  The protective layer 2 is not particularly limited, and a conventionally known protective film can be used. For example, a protective layer that is excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. Specific examples of the material of such a protective layer include cellulose resins such as triacetylcellulose (TAC), polyester-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, Examples thereof include acrylic resins, acetate resins, polyolefin resins, and the like. Further, examples thereof include thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins.

  In addition to this, as described in JP-A No. 2001-343529 and WO 01/37007, for example, an alternating copolymer composed of isobutene and N-methylmaleimide, an acrylonitrile / styrene copolymer, A film made of a mixed extrudate of a resin composition containing bismuth can be used.

  Furthermore, the surface of these protective films may be saponified with an alkali or the like, for example. Among these, a TAC film is preferable from the viewpoints of polarization characteristics and durability, and more preferably a TAC film whose surface is saponified.

  The thickness of the protective layer can be determined as appropriate, but is, for example, in the range of 1 to 500 μm from the viewpoints of workability such as strength and handleability, and thinning. When the thickness of the protective layer is within the above range, the polarizer is mechanically protected, and even when exposed to high temperature and high humidity, the polarizer is prevented from contracting and stable optical characteristics can be maintained. The thickness of the protective layer is preferably in the range of 5 to 200 μm, and more preferably in the range of 10 to 150 μm.

  As the protective layer, it is preferable to use a layer having an optimized retardation value. If such a protective layer is used, the viewing angle characteristics of the image display device are not affected.

  As the retardation value of the protective layer, the in-plane retardation value (Re) is preferably in the range of 0 to 5 nm, more preferably in the range of 0 to 3 nm, and still more preferably 0. The thickness direction retardation value (Rth) is preferably in the range of 0 to 15 nm, more preferably in the range of 0 to 12 nm, and still more preferably in the range of 0 to 5 nm. And most preferably in the range of 0 to 3 nm.

  The protective layer can be appropriately formed by a conventionally known method such as a method of applying the various transparent resins to a polarizer, a method of laminating the resin film or the like on the polarizer, and a commercially available product is used. You can also.

  The protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, an antisticking treatment, a treatment for diffusion, antiglare, or the like.

  The adhesion method between the polarizer and the protective layer is not particularly limited, and can be performed by a conventionally known method. In general, a pressure-sensitive adhesive, other adhesives, and the like are used, and the type can be appropriately determined depending on the type of the polarizer and the protective layer. Specific examples include adhesives and pressure-sensitive adhesives composed of PVA-based, modified PVA-based, and urethane-based polymers. These adhesives and pressure-sensitive adhesives are used for improving durability, for example, vinyl alcohol type such as boric acid, borax, glutaraldehyde, melamine, oxalic acid, chitin, chitosan, metal salt, alcoholic solvent, etc. A water-soluble crosslinking agent that crosslinks the polymer may be added. In the case where the polarizer is, for example, a PVA film, a PVA adhesive or pressure-sensitive adhesive is preferable from the viewpoint of the stability of the adhesion treatment. These adhesives and pressure-sensitive adhesives may be applied to the surface of the polarizer or the protective layer as they are, for example, as an aqueous solution of the adhesive or pressure-sensitive adhesive to form an adhesive layer or pressure-sensitive adhesive layer. An adhesive layer such as a tape or sheet made of an adhesive or an adhesive layer may be disposed on the surface. In addition, when apply | coating the said adhesive agent or an adhesive, you may mix | blend another additive and catalysts, such as an acid, with the said aqueous solution, for example. The thickness of such an adhesive layer or pressure-sensitive adhesive layer is not particularly limited, but is, for example, in the range of 1 to 500 nm, preferably in the range of 10 to 300 nm, and more preferably in the range of 20 to 100 nm. .

  When the polarizer and the protective layer are bonded by the adhesive, for example, a drying process is performed to prevent peeling due to the influence of humidity and heat, and to obtain a polarizing plate excellent in light transmittance and degree of polarization. It is preferable to apply. It does not restrict | limit especially as drying temperature, For example, it is the range of 20-90 degreeC, Preferably, it is the range of 30-60 degreeC. The drying time is not particularly limited, but is, for example, in the range of 1 to 20 minutes, and preferably in the range of 3 to 20 minutes.

  Moreover, since the polarizing plate of this invention becomes easy to laminate | stack to a liquid crystal cell etc., for example, it is preferable to have an adhesive layer in the outermost layer further. In FIG. 2, sectional drawing of the polarizing plate which has such an adhesive layer is shown. In FIG. 2, the same parts as those in FIG. As illustrated, the polarizing plate 20 has a configuration in which an adhesive layer 3 is further disposed on the surface of one protective layer 2 of the polarizing plate 10.

  The pressure-sensitive adhesive layer is formed on the surface of the protective layer by, for example, adding a solution or a melt of the pressure-sensitive adhesive directly to a predetermined surface of the protective layer by a developing method such as casting or coating. It can be performed by a method of forming, a method of forming a pressure-sensitive adhesive layer on a separator, which will be described later, and transferring it to a predetermined surface of the protective layer. In addition, although such an adhesive layer may be formed in any one surface of a polarizing plate like the said FIG. 2, it is not limited to this, You may arrange | position on both surfaces as needed. .

  The pressure-sensitive adhesive layer can be formed by appropriately using, for example, a conventionally known pressure-sensitive adhesive such as acrylic, silicone, polyester, polyurethane, polyether, or rubber. In particular, the moisture absorption rate is low in terms of preventing foaming and peeling due to moisture absorption, reducing optical characteristics due to thermal expansion differences, preventing warping of liquid crystal cells, and forming liquid crystal display devices with high quality and durability. It is preferable to use an adhesive having excellent heat resistance. Examples of such an adhesive include acrylic, silicone, acrylic silicone, polyester, and heat resistant rubber adhesives. Moreover, the adhesive layer etc. which show the light diffusibility containing microparticles | fine-particles etc. may be sufficient.

  The surface of the pressure-sensitive adhesive layer is preferably covered with a separator for the purpose of preventing contamination. This separator can be formed by, for example, a method of providing a release coat with a release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide on a thin film such as the protective film.

  Although the thickness of the said adhesive layer is not restrict | limited in particular, For example, it is the range of 5-35 micrometers, Preferably, it is the range of 10-25 micrometers, More preferably, it is the range of 15-25 micrometers.

(10) Optical film Next, the optical film of the present invention has a configuration in which a retardation plate is disposed on at least one surface of the polarizer of the present invention or the polarizing plate of the present invention.

  The type of the retardation plate is, for example, various wavelength plates such as a 1 / 2λ plate or a 1 / 4λ plate, a liquid crystal layer for the purpose of compensating for coloring due to birefringence or viewing angle compensation such as viewing angle expansion, etc. It may have a phase difference according to the purpose of use, or may be a tilted alignment film in which the refractive index in the thickness direction is controlled. Further, a laminate or the like in which two or more kinds of retardation plates are laminated and optical characteristics such as retardation are controlled may be used.

  Examples of the material of the retardation plate include polycarbonate, PVA, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, polyamide, polynorbornene, and other birefringent films, liquid crystal polymer Examples include an alignment film, a laminate in which an alignment layer of a liquid crystal polymer is supported by a film, and the like.

  The tilted orientation film is, for example, a method in which a heat-shrinkable film is bonded to a polymer film, and the polymer film is subjected to stretching treatment or shrinkage treatment under the action of the shrinkage force by heating, or a liquid crystal polymer is obliquely oriented. It can obtain by the method of making it.

  The retardation plate may be made by itself or a commercially available product may be used.

(11) Applications The polarizer, polarizing plate and optical film of the present invention can be preferably used for various image display devices such as a liquid crystal display (LCD) and an EL display (ELD). The liquid crystal display device of the present invention has the same configuration as the conventional liquid crystal display device except that at least one of the polarizer, the polarizing plate and the optical film of the present invention is used. In the liquid crystal display device of the present invention, for example, a liquid crystal cell, an optical member such as the polarizer of the present invention, and various components such as an illumination system (backlight or the like) are appropriately assembled to incorporate a drive circuit. Etc. can be manufactured.

  In the present invention, the configuration of the liquid crystal display device is not particularly limited, and a liquid crystal display device in which an optical member such as the polarizer of the present invention is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector is used for an illumination system. Liquid crystal display devices. When optical members such as the polarizer of the present invention are arranged on both sides of the liquid crystal cell, they may be the same or different. Furthermore, in the liquid crystal display device of the present invention, for example, optical members and optical components such as a diffusion plate, an antiglare layer, an antireflection layer, a protective plate, a prism array, and a lens array sheet may be disposed.

  The image display device of the present invention is used for any appropriate application. Applications include, for example, OA equipment such as desktop personal computers, notebook personal computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Household electrical equipment, back monitor, car navigation system monitor, car audio and other in-vehicle equipment, display equipment for commercial store information monitors, security equipment such as monitoring monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

  Next, examples of the present invention will be described together with comparative examples. The present invention is not limited or restricted by the following examples and comparative examples. In addition, various properties and physical properties in each example and each comparative example were measured and evaluated by the following methods.

(1) Phase difference value The phase difference value was measured using the product name "KOBRA31 * 100 / IR" by Oji Scientific Instruments.

(2) Single transmittance (T) and degree of polarization (P)
The single transmittance (T) was measured using a UV-Vis spectrophotometer [manufactured by JASCO Corporation, trade name “V-7100 / VAP-7070”] with a two-degree field of view (C The Y value subjected to visibility correction was measured by a light source and obtained. The degree of polarization (P) is measured by measuring the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizer using the UV-visible spectrophotometer, and the formula: degree of polarization (%) = { (H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. These transmittances are Y values obtained by correcting the visibility with the two-degree visual field (C light source) defined in JlS Z 8701-1982.

(3) Iodine Content The iodine content was measured using a fluorescent X-ray analyzer [manufactured by Rigaku Denki Kogyo Co., Ltd., trade name “ZSX100e”].

(4) Orthogonal Absorbance at 480 nm Orthogonal absorbance at 480 nm was determined by measuring the orthogonal transmittance Tc at 480 nm of the polarizer using the UV-visible spectrophotometer, and obtaining the orthogonal absorbance at 480 nm = Log ₁₀ Tc.

(5) Iodine efficiency Iodine efficiency was calculated by dividing the 480 nm orthogonal absorbance determined in (4) above by the iodine content determined in (3) above (iodine efficiency = 480 nm orthogonal absorbance / iodine content ( weight%)).

[Example 1]
(Preparation of PVA film)
Cut the original PVA film [trade name “VF-PS” manufactured by Kuraray Co., Ltd.] so that the length in the longitudinal direction (MD direction) is 6 cm and the length in the width direction (TD direction) is 5 cm. As a result, a sample PVA film was obtained. The thickness of this PVA film was 75 μm.

(Production of polarizer)
(1) Swelling step The PVA film is immersed in a 30 ° C. water bath (swelling bath) and is 1.50 times longer than the length of the PVA film before swelling using a hand stretcher. Thus, uniaxial stretching was performed in the MD direction. After the uniaxial stretching, the PVA film is left in the swelling bath for 1 minute without removing it from the manual stretching machine, so that the PVA film is stretched in the stretching direction and the PVA film does not stretch. It was kept in a state (relaxed state).

(2) Dyeing step The PVA film is pulled up from the swelling bath, immersed in a 30 ° C. aqueous solution (dye bath) containing water, iodine and potassium iodide in a ratio of 92: 7: 1, and a hand drawing machine. Was uniaxially stretched in the MD direction so as to be 1.50 times the length of the PVA film after the swelling step. After the uniaxial stretching, the PVA film is left in the dyeing bath for 1 minute without removing it from the manual stretching machine, so that the tension is applied in the stretching direction and the PVA film does not stretch. It was kept in a state (relaxed state).

(3) Crosslinking step The PVA film is lifted from the dyeing bath, immersed in a 30 ° C. aqueous solution (crosslinking bath) containing 3% by weight of boric acid and 3% by weight of potassium iodide for 20 seconds, and then a hand drawing machine. Was uniaxially stretched in the MD direction so as to be 1.50 times the length of the PVA film after the dyeing step. After the uniaxial stretching, the PVA film is left in the crosslinking bath for 1 minute without removing it from the manual stretching machine, so that the PVA film is stretched in the stretching direction and the PVA film does not stretch. It was kept in a state (relaxed state).

(4) Stretching step The PVA film is lifted from the crosslinking bath, immersed in a 60 ° C. aqueous solution (stretching bath) containing 4% by weight boric acid and 5% by weight potassium iodide, using a hand stretching machine. The uniaxial stretching was performed in the MD direction so as to be 1.70 times the length of the PVA film after the crosslinking step.

(5) Adjustment / drying step The PVA film was pulled up from the stretching bath and immersed in an aqueous solution (conditioning bath) at 30 ° C. containing 4% by weight of potassium iodide for 10 seconds. Subsequently, this PVA film was dried at 60 ° C. for 4 minutes to obtain a polarizer of this example.

[Example 2]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute, in the swelling bath, in the dyeing bath, and in the crosslinking bath, respectively. The polarizer of this example was obtained in the same manner as in Example 1 except that the sample was allowed to stand (relaxed) for 3 minutes.

[Example 3]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute each, except leaving it alone (relaxing) in the swelling bath. The polarizer of this example was obtained in the same manner as in Example 1.

[Example 4]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute each, except leaving it in the swelling bath only for 3 minutes (relaxing). The polarizer of this example was obtained in the same manner as in Example 1.

[Example 5]
The PVA film was left (relaxed) for 1 minute only in the dyeing bath instead of left (relaxed) for 1 minute in each of the swelling bath, the dyeing bath, and the crosslinking bath, The polarizer of this example was obtained in the same manner as Example 1.

[Example 6]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute each, except leaving it in the dyeing bath only for 3 minutes (relaxing). The polarizer of this example was obtained in the same manner as in Example 1.

[Example 7]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute each, except leaving it alone (relaxing) in the crosslinking bath. The polarizer of this example was obtained in the same manner as in Example 1.

[Example 8]
Instead of leaving (relaxing) the PVA film in the swelling bath, in the dyeing bath, and in the crosslinking bath for 1 minute each, except leaving it alone (relaxing) in the crosslinking bath for 3 minutes. The polarizer of this example was obtained in the same manner as in Example 1.

[Comparative Example 1]
Instead of leaving (relaxing) the PVA film in the swelling bath, the dyeing bath, and the crosslinking bath for 1 minute, after the uniaxial stretching of the swelling step, after the uniaxial stretching of the dyeing step, A polarizer of this comparative example was obtained in the same manner as in Example 1 except that the film was allowed to stand (relaxed) for 1 minute in the air after uniaxial stretching in the crosslinking step.

[Comparative Example 2]
Instead of leaving (relaxing) the PVA film in the swelling bath, the dyeing bath, and the crosslinking bath for 1 minute, after the uniaxial stretching of the swelling step, after the uniaxial stretching of the dyeing step, A polarizer of this comparative example was obtained in the same manner as in Example 1, except that the film was allowed to stand (relax) for 3 minutes in the air after uniaxial stretching in the crosslinking step.

[Comparative Example 3]
The polarizer of this comparative example was obtained in the same manner as in Example 1 except that the PVA film was not left (relaxed) for 1 minute in each of the swelling bath, the dyeing bath, and the crosslinking bath. Obtained.

  Table 1 below shows the relaxation conditions and the characteristics and physical properties of the polarizer in each Example and each Comparative Example. The graph of FIG. 3 shows the relationship between the single transmittance (T) and the degree of polarization (P) of the polarizer in each example and each comparative example. And the graph of FIG. 4 shows the change of the phase difference value of a polarizer by the relaxation time in relaxation in Examples (Examples 1 and 2) and relaxation in air (Comparative Examples 1 to 3). Furthermore, the iodine efficiency of the polarizer in Examples 1, 2 and Comparative Examples 1-3 is shown in the graph of FIG. Furthermore, the graph of FIG. 6 shows the change in the retardation value of the polarizer depending on the relaxation time in the swelling bath, dyeing bath, and crosslinking bath. Furthermore, the iodine efficiency of the polarizer in Examples 3-8 and Comparative Example 4 is shown in the graph of FIG.

  As can be seen from Table 1 and FIG. 3, in each Example, the single transmittance (T) tended to be lower and the degree of polarization (P) tended to be higher than in each Comparative Example. Further, as can be seen from Table 1 and FIGS. 4 and 5, in the relaxation in the bath (Examples 1 and 2), the retardation value increases and the iodine efficiency increases as the relaxation time becomes longer. In relaxation (Comparative Examples 1 to 3), there was almost no change in the retardation value and iodine efficiency even when the relaxation time was increased. As can be seen from Table 1 and FIGS. 6 and 7, when relaxed in the dyeing bath, the increase in retardation value and iodine efficiency was most noticeable, and when relaxed in the crosslinking bath and relaxed in the swelling bath. Even when the phase difference value and iodine efficiency were increased.

  As described above, according to the method for producing a polarizer of the present invention, it is possible to obtain a polarizer having excellent optical characteristics without requiring excessive stretching. Applications of the polarizer of the present invention and polarizing plates, optical films and image display devices using the polarizer are, for example, OA devices such as desktop personal computers, notebook personal computers, copy machines, mobile phones, watches, digital cameras, and portable information terminals ( PDAs), portable devices such as portable game machines, household electric devices such as video cameras, televisions, and microwave ovens, back monitors, car navigation system monitors, car audio and other in-vehicle devices, commercial store information monitors, etc. Examples include exhibition equipment, security equipment such as monitoring monitors, nursing care / medical equipment such as nursing care monitors, medical monitors, etc. The use thereof is not limited and can be applied to a wide range of fields.

FIG. 1 is a cross-sectional view showing a configuration of an example of the polarizing plate of the present invention. FIG. 2 is a cross-sectional view showing the configuration of another example of the polarizing plate of the present invention. FIG. 3 is a graph showing the relationship between the single transmittance of the polarizer and the degree of polarization in the example of the present invention. FIG. 4 is a graph showing the change in the retardation value of the polarizer according to the relaxation time in the example of the present invention. FIG. 5 is a graph showing the iodine efficiency of the polarizer in the example of the present invention. FIG. 6 is a graph showing the change in the retardation value of the polarizer according to the relaxation time in the swelling bath, dyeing bath and crosslinking bath in the example of the present invention. FIG. 7 is a graph showing the iodine efficiency of a polarizer in another example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Protective layer 3 Adhesive layer 10, 20 Polarizing plate

Claims (10)

A dyeing process for dyeing a hydrophilic polymer film with a dichroic substance in a dyeing bath;
And a stretching process for stretching the hydrophilic polymer film in a stretching bath, further comprising:
In the bath, the hydrophilic polymer film is stretched, and during the stretching process or after the stretching process, the hydrophilic polymer film is stretched in the stretching direction in the stretching direction with respect to the hydrophilic polymer film. Has a stretching relaxation step of relaxing and maintaining the state added for a certain time,
The method for producing a polarizer, wherein the stretching relaxation step is performed in at least one of the dyeing step, the stretching step, and the steps different from the both steps. 2. The polarizer according to claim 1, wherein the another step includes at least one of a swelling step of swelling the hydrophilic polymer film in a swelling bath and a crosslinking step of crosslinking the hydrophilic polymer film in a crosslinking bath. Production method. The method for producing a polarizer according to claim 2, wherein in the at least one step selected from the group consisting of the swelling step, the dyeing step, the crosslinking step, and the stretching step, the hydrophilic polymer film is continuously processed while being conveyed. . The manufacturing method of the polarizer as described in any one of Claim 1 to 3 which implements the said extending | stretching relaxation process at least in the said dyeing | staining process. The method for producing a polarizer according to any one of claims 1 to 4, wherein the hydrophilic polymer film is a polyvinyl alcohol film, and the dichroic substance is iodine. The method for producing a polarizer according to any one of claims 1 to 5, wherein a time for which the tension is applied in the stretching relaxation step is 15 seconds or more. The polarizer manufactured by the manufacturing method as described in any one of Claim 1 to 6. The polarizing plate, wherein a protective layer is disposed on at least one surface of the polarizer, wherein the polarizer is the polarizer according to claim 7. An optical film in which a retardation plate is disposed on at least one surface of a polarizer or a polarizing plate, wherein the polarizer is the polarizer according to claim 7, and the polarizing plate is the polarization according to claim 8. An optical film that is a plate. It is an image display apparatus containing at least one of a polarizer, a polarizing plate, and an optical film, Comprising: The said polarizer is a polarizer of Claim 7, The said polarizing plate is a polarizing plate of Claim 8. The image display device, wherein the optical film is the optical film according to claim 9.

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