JP5473035B2 - Polarizing film and polarizing film - Google Patents

Description

  The present invention relates to a polarizing film and a polarizing film.

  In a liquid crystal display device which is a typical image display device, it is indispensable to dispose polarizing films on both sides of the liquid crystal cell due to the image forming method. The polarizing film is usually formed by laminating protective films on both sides of the polarizing film. The polarizing film is typically produced by uniaxially stretching and dyeing a polyvinyl alcohol-based resin film (see, for example, Patent Document 1 and Patent Document 2). However, the polarizing film is easily affected by changes in temperature and humidity, and there is a problem in durability such that cracks are generated due to a rapid temperature change.

JP-A-10-288709 Japanese Patent Laid-Open No. 11-49878

  The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a polarizing film having both excellent optical characteristics and excellent durability.

  The present inventors have found that the problem of durability is more likely to occur as the optical property (for example, the degree of polarization) is higher, and that the crack tends to occur along the stretching direction, and the present invention is completed. It came to.

The polarizing film of the present invention is composed of a polyvinyl alcohol resin film containing a dichroic material, the Nz coefficient of the polyvinyl alcohol-based resin film is Ri der 1.10 to 1.50, thickness der less than 10μm that.
According to another aspect of the present invention, a polarizing film is provided. This polarizing film has the polarizing film and a protective film laminated on at least one side of the polarizing film.

The polarizing film of the present invention is composed of a polyvinyl alcohol-based resin film having an Nz coefficient within a specific range, and its orientation (alignment state of the polyvinyl alcohol-based resin molecule) is controlled, so that excellent optical characteristics are obtained. In addition, a polarizing film having both excellent durability can be provided. Specifically, by using the polarizing film of the present invention, it is possible to provide a polarizing film in which generation of cracks due to a rapid temperature change is suppressed while maintaining excellent optical characteristics. Furthermore, according to this invention, durability can be improved markedly by making the thickness of a polarizing film less than 10 micrometers.

It is a graph explaining the calculation method of the Nz coefficient of a PVA-type resin film. It is the schematic explaining the specific example of the manufacturing method of a polarizing film. It is the schematic explaining the specific example of the manufacturing method of a polarizing film.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

(Definition of terms and symbols)
The definitions of terms and symbols in this specification are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), “ny” is the refractive index in the direction perpendicular to the slow axis in the plane, and “nz” "Is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
The in-plane retardation (Re) is obtained by Re = (nx−ny) × d, where d (nm) is the thickness of the film (layer).
(3) Thickness direction retardation (Rth)
The thickness direction retardation (Rth) is obtained by Rth = {(nx + ny) / 2−nz} × d, where d (nm) is the thickness of the film (layer).
(4) Nz coefficient An Nz coefficient is calculated | required by Nz = (nx-nz) / (nx-ny).

A. Polarizing Film The polarizing film of the present invention is composed of a polyvinyl alcohol resin (hereinafter referred to as “PVA resin”) film containing a dichroic substance.

  Examples of the dichroic substance include iodine and organic dyes. These may be used alone or in combination of two or more. Preferably, iodine is used.

  Any appropriate resin can be used as the PVA resin for forming the PVA resin film. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

  The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

  The Nz coefficient of the PVA resin film is preferably 1.10 or more. On the other hand, the Nz coefficient of the PVA resin film is preferably 1.50 or less, more preferably 1.40 or less. By setting the Nz coefficient within such a range, it is possible to obtain a polarizing film having excellent durability while maintaining the optical characteristics of the polarizing film. If the Nz coefficient is less than 1.10, the orientation (uniaxiality) of the PVA-based resin film becomes too high, and sufficient durability may not be obtained. If the Nz coefficient exceeds 1.50, for example, the display quality required for a liquid crystal television may not be obtained.

The Nz coefficient of the PVA resin film is an index of molecular chain orientation of the PVA resin film, and is calculated from the phase difference of the PVA resin film. The phase difference (a value) of the PVA-based resin film is measured by changing the measurement wavelength (λ) to measure the phase difference of the polarizing film, and as shown in FIG. 1, the phase difference of the polarizing film is plotted with the horizontal axis as the measurement wavelength. Then, an approximate curve is created based on the following equation, and an asymptote (a value) is calculated from the approximate curve. Here, the retardation of the polarizing film is measured from the front and oblique directions.
R = a + b / (λ ² −600 ² )
Here, R: retardation of the polarizing film, a: retardation of the PVA resin film, b: constant.

  The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The degree of polarization at a single transmittance of 40% of the polarizing film is preferably 99.9% or more, more preferably 99.93% or more, and still more preferably 99.95% or more.

The thickness of the polarizing film is less than 10 μm. Usually, the polarizing film has a larger shrinkage force than the protective film, and a stress may be generated at the interface between the polarizing film and the protective film to cause cracks. The contraction force of the polarizing film depends on the thickness. The thinner the thickness, the smaller the contraction force. Commercially available polarizing films usually have a thickness of about 20 μm to 25 μm, which is relatively thick and insufficient in durability. However, according to the present invention, a polarizing film having excellent durability can be obtained. That is, the durability can be remarkably improved by setting the thickness to less than 10 μm. On the other hand, the thickness is preferably 1 μm or more. If the thickness is less than 1 μm, sufficient optical properties may not be obtained.

  The polarizing film of the present invention can be used in any appropriate form. Typically, a polarizing film is used by laminating a protective film on at least one side thereof (as a polarizing film). Examples of the material for forming the protective film include (meth) acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. , Polyamide resins, polycarbonate resins, copolymer resins thereof, and the like. In addition, you may use the below-mentioned thermoplastic resin base material as a protective film as it is.

  The thickness of the protective film is preferably 20 μm to 100 μm. The protective film may be laminated on the polarizing film via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be laminated in close contact with the polarizing film (without an adhesive layer). Also good. The adhesive layer is formed of any appropriate adhesive. Examples of the adhesive include a vinyl alcohol adhesive.

B. Method for Producing Polarizing Film The polarizing film of the present invention is produced by any appropriate method as long as the Nz coefficient can be satisfied. The polarizing film is typically produced by subjecting a PVA resin film to treatments such as stretching and dyeing as appropriate.

B-1. PVA-based resin film The PVA-based resin film is typically formed in a long shape. The thickness of the PVA resin film is preferably less than 100 μm. The PVA resin film may be, for example, a PVA resin film or a PVA resin layer formed on a thermoplastic resin substrate. The PVA resin film is preferably used when a polarizing film having a thickness of 10 μm or more is produced. The thickness of the PVA resin film is preferably 50 μm to 80 μm. The laminate of the thermoplastic resin substrate and the PVA resin layer is preferably used when a polarizing film having a thickness of less than 10 μm is produced. The thickness of the PVA resin layer is preferably 5 μm to 20 μm. Even such a thin thickness can be satisfactorily stretched by using a thermoplastic resin substrate.

  The thickness (before stretching) of the thermoplastic resin base material constituting the laminate is preferably 50 μm to 250 μm. If it is less than 50 μm, there is a risk of breaking during stretching. In addition, the thickness may become too thin after stretching, which may make conveyance difficult. If it exceeds 250 μm, an excessive load may be applied to the stretching machine. Moreover, there exists a possibility that conveyance may become difficult.

  Examples of the material for forming the thermoplastic resin substrate include ester resins such as polyethylene terephthalate resin, cycloolefin resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, cycloolefin resins (for example, norbornene resins) and amorphous polyethylene terephthalate resins are preferable. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol as a glycol.

  The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 170 ° C. or lower. By using such a thermoplastic resin base material, it is possible to stretch the laminate at a temperature at which crystallization of the PVA resin does not proceed rapidly, and defects due to the crystallization (for example, the PVA resin layer due to stretching). Which prevents orientation). In addition, a glass transition temperature (Tg) is a value calculated | required according to JISK7121.

  Arbitrary appropriate methods can be employ | adopted for the formation method of the said PVA-type resin layer. Preferably, a PVA-based resin layer is formed by applying a coating solution containing a PVA-based resin on a thermoplastic resin substrate and drying it. The PVA-based resin layer thus obtained is not only used as a laminate (as it is formed on the thermoplastic resin substrate), but is peeled off from the thermoplastic resin substrate and used as a PVA-based resin film. Also good.

  The coating solution is typically a solution obtained by dissolving the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferable. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the thermoplastic resin substrate can be formed.

  You may mix | blend an additive with a coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting PVA resin layer.

  Any appropriate method can be adopted as a coating method of the coating solution. Examples thereof include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method, etc.).

  It is preferable that the said drying temperature is below the glass transition temperature (Tg) of a thermoplastic resin base material, More preferably, it is below Tg-20 degreeC. By drying at such a temperature, the thermoplastic resin base material is prevented from being deformed before the PVA resin layer is formed, and the orientation of the resulting PVA resin layer is prevented from deteriorating. Can do.

B-2. Stretching The Nz coefficient can be controlled by appropriately selecting stretching conditions such as a stretching method, a stretching ratio, and a stretching temperature. Examples of the stretching method include fixed end stretching using a tenter stretching machine, free end stretching using rolls having different peripheral speeds, biaxial stretching using a simultaneous biaxial stretching machine, and sequential biaxial stretching. These may be employed alone or in combination of two or more. Specifically, as shown in FIG. 3, when the PVA-based resin film 10 is stretched (free end stretching) in the transport direction (MD) through rolls 31, 31, 32, 32 having different peripheral speeds, for example, The form combined with the extending | stretching to the direction (TD) orthogonal to a conveyance direction is mentioned. Hereinafter, preferred embodiments will be specifically described.

  In a preferred embodiment, the polarizing film of the present invention is produced by shrinking a PVA resin film in the first direction and stretching it in the second direction. According to such a manufacturing method, the Nz coefficient can be satisfactorily satisfied.

  In one embodiment, the first direction is the transport direction (MD) of the PVA resin film. The transport direction is preferably the long direction of the long PVA-based resin film, and may include a direction of −5 ° to + 5 ° counterclockwise with respect to the long direction of the PVA-based resin film. In another embodiment, the first direction is a direction (TD) orthogonal to the transport direction. The direction orthogonal to the transport direction is preferably the width direction of the long PVA resin film, and includes the direction of 85 ° to 95 ° counterclockwise with respect to the long direction of the PVA resin film. Can do. In the present specification, the term “orthogonal” includes the case of being substantially orthogonal. Here, “substantially orthogonal” includes the case of 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, more preferably 90 ° ± 1.0 °.

  Shrinkage may be performed simultaneously with stretching or may be performed at another timing. Also, the order is not limited, and it may be contracted in one step or may be contracted in multiple steps. In one embodiment, preferably, the PVA resin film is contracted in the first direction while being stretched in the second direction. In another embodiment, preferably, the PVA-based resin film is contracted in the first direction and then stretched in the second direction.

  In the present embodiment, for example, the Nz coefficient can be satisfactorily satisfied by adjusting the shrinkage rate of the PVA resin film. The shrinkage ratio in the first direction of the PVA-based resin film is preferably 40% or less, more preferably 35% or less, and particularly preferably 20% or less. Excellent durability can be achieved. On the other hand, the shrinkage rate is preferably 5% or more. If it is less than 5%, sufficient optical properties may not be obtained.

  The second direction can be set to any appropriate direction depending on the desired polarizing film. Preferably, the second direction and the first direction are orthogonal to each other. Specifically, when the first direction is the transport direction (MD) of the PVA-based resin film, the second direction is preferably a direction (TD) orthogonal to the transport direction. When the first direction is a direction (TD) orthogonal to the transport direction, the second direction is preferably the transport direction (MD). Note that the second direction is substantially the absorption axis direction of the obtained polarizing film.

  The stretching of the PVA resin film may be performed in one stage or in multiple stages. When performed in multiple stages, the stretch ratio of the PVA-based resin film described later is the product of the stretch ratios of the respective stages. In addition, the stretching method in this step is not particularly limited, and may be an air stretching (dry stretching) method or an underwater stretching (wet stretching) method.

  The stretching temperature can be set to any appropriate value depending on the stretching method, the stretching target, and the like. For example, the stretching temperature in the case of stretching a laminate of a thermoplastic resin substrate and a PVA resin layer by an air stretching method is set to any appropriate value depending on the material for forming the thermoplastic resin substrate. be able to. The stretching temperature is typically at least the glass transition temperature (Tg) of the thermoplastic resin substrate, preferably the glass transition temperature (Tg) of the thermoplastic resin substrate + 10 ° C. or more, more preferably Tg + 15 ° C. or more. . On the other hand, the stretching temperature is preferably 170 ° C. or lower. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin, and to suppress problems due to the crystallization (for example, breakage during stretching of the PVA-based resin film).

  The stretching temperature when the PVA-based resin film is stretched by the air stretching method is typically 70 ° C to 130 ° C, preferably 80 ° C to 120 ° C.

  When employing an underwater stretching method, the stretching temperature is preferably 85 ° C. or lower, more preferably 30 ° C. to 65 ° C. If the temperature exceeds 85 ° C., there is a risk that iodine adsorbed on the PVA-based resin may be eluted, or that the PVA-based resin may be eluted, and the optical characteristics of the obtained polarizing film may be deteriorated.

  When employing an underwater stretching method, it is preferable to stretch the PVA resin film in an aqueous boric acid solution. By using a boric acid aqueous solution, the PVA resin film can be provided with rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can generate a tetrahydroxyborate anion in an aqueous solution and can be cross-linked with a PVA resin by hydrogen bonding, and can impart rigidity and water resistance. As a result, for example, a higher polarizing film contrast ratio can be realized. The aqueous boric acid solution is obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is usually 1 part by weight to 10 parts by weight with respect to 100 parts by weight of water. The immersion time of the PVA resin film in the stretching bath is preferably about 15 seconds to 5 minutes.

  The second direction stretching ratio is preferably 4.0 times or more with respect to the original length of the PVA-based resin film. By contracting in the first direction, stretching at such a high magnification becomes possible, and a polarizing film having excellent optical properties can be obtained. On the other hand, the draw ratio is preferably 6.0 times or less, and more preferably 5.5 times or less.

  A specific example of the shrinking / stretching process is shown in FIG. In the illustrated example, the PVA-based resin film 10 is contracted in the transport direction (MD) using a simultaneous biaxial stretching machine while the PVA-based resin film 10 is transported in the longitudinal direction, and the direction orthogonal to the transport direction. Stretch to (TD). Specifically, the PVA resin film 10 held by the left and right clips 21 and 21 at the tenter inlet is TD-stretched while being conveyed at a predetermined speed. In the illustrated example, the shrinkage of the PVA-based resin film is controlled, for example, by gradually decelerating the moving speed of the clip in the transport direction and shortening the distance between the clips. The shrinkage rate can be controlled by adjusting the distance L1 between the clips in the transport direction of the tenter inlet and the distance L2 between the clips in the transport direction of the tenter outlet (the moving speed of the clips in the transport direction). Specifically, the desired shrinkage rate can be achieved by setting the speed of the tenter outlet of the clip to the speed of the tenter inlet × the shrinkage rate. In FIG. 2, the broken line indicates the rail of the clip 21.

  As shown in FIG. 2, when performing shrinkage | contraction and extending | stretching of a PVA-type resin film using a simultaneous biaxial stretching machine, Preferably, after making a PVA-type resin film shrink, it extends | stretches. Specifically, TD stretching is performed after the distance between clips in the transport direction is shortened. According to such an embodiment, a force is applied uniformly by the PVA-based resin film during stretching, and the clip gripping portion can be prevented from being selectively stretched. Specifically, it is possible to prevent the portion that is not gripped by the clip from being bent inward at the edge of the PVA-based resin film. As a result, uniformity can be improved.

B-3. Other treatments Examples of the treatment for producing the polarizing film include a dyeing treatment, an insolubilization treatment, a crosslinking treatment, a washing treatment, and a drying treatment in addition to the stretching treatment. These processes can be performed at any appropriate timing.

  The dyeing process is typically a process of dyeing a PVA resin film with the dichroic material. Preferably, the dichroic substance is adsorbed on the PVA resin film. Examples of the adsorption method include a method of immersing a PVA resin film in a dye solution containing a dichroic substance, a method of applying a dye solution to the PVA resin film, a method of spraying the dye solution on the PVA resin film, and the like. Is mentioned. Preferably, the PVA-based resin film is immersed in a staining solution containing a dichroic substance. It is because a dichroic substance can adsorb | suck favorably.

  When iodine is used as the dichroic substance, the staining solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.04 to 5.0 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide salt to the aqueous iodine solution. Examples of the iodide salt 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. Among these, potassium iodide and sodium iodide are preferable. The compounding amount of the iodide salt is preferably 0.3 to 15 parts by weight with respect to 100 parts by weight of water.

  The liquid temperature during staining of the staining liquid is preferably 20 ° C to 40 ° C. When the PVA resin film is immersed in the staining liquid, the immersion time is preferably 5 seconds to 300 seconds. Under such conditions, the dichroic substance can be sufficiently adsorbed on the PVA resin film.

  The insolubilization treatment and the crosslinking treatment are typically performed by immersing a PVA resin film in an aqueous boric acid solution. The cleaning treatment is typically performed by immersing a PVA resin film in an aqueous potassium iodide solution. The drying temperature in the drying treatment is preferably 30 ° C to 100 ° C.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of the thickness of the obtained polarizing film is as follows.
(Thickness of polarizing film)
Using a dial cage (manufactured by PEACOCK, product name “DG-205 type pds-2”), the thickness of the PVA resin layer or the PVA resin film was measured after the dyeing treatment described later.

[Example 1]
<Production of laminate>
(Thermoplastic resin base material)
As a thermoplastic resin base material, a long cycloolefin resin film (trade name “ARTON” manufactured by JSR Corporation) having a thickness of 200 μm and a Tg of 123 ° C. was used.
(Preparation of coating solution)
Polyvinyl alcohol (PVA) resin having a polymerization degree of 1800 and a saponification degree of 98 to 99% (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSENOL (registered trademark) NH-18”) is dissolved in water to a concentration of 7% by weight. An aqueous polyvinyl alcohol solution was prepared.
(Formation of PVA resin layer)
The coating solution was applied to one side of a stretched thermoplastic resin substrate by a die coater (die coating method) and then dried at 100 ° C. for 180 seconds to form a 9 μm thick PVA resin layer. In this way, a laminate was produced.

<Shrinking and stretching treatment>
As shown in FIG. 2, the obtained laminate is contracted by 40% in the first direction (MD) at 140 ° C. using a simultaneous biaxial stretching machine, and at the same time in the second direction (TD). The film was dry-drawn 5.0 times.

<Dyeing process>
Next, the laminate was immersed in an aqueous iodine solution at 25 ° C. (iodine concentration: 0.5 wt%, potassium iodide concentration: 10 wt%) for 30 seconds.

<Crosslinking treatment>
The layered product after dyeing was immersed in an aqueous boric acid solution at 60 ° C. (boric acid concentration: 5% by weight, potassium iodide concentration: 5% by weight) for 60 seconds.

<Cleaning process>
After the crosslinking treatment, the laminate was immersed in a 25 ° C. aqueous potassium iodide solution (potassium iodide concentration: 5% by weight) for 5 seconds.
Thus, a polarizing film having a thickness of 3 μm was produced on the thermoplastic resin substrate.

  A protective film (thickness: 80 μm, manufactured by Fuji Film, trade name “TD80UL”) was bonded to the polarizing film side of the laminate through a vinyl alcohol adhesive. Next, the thermoplastic resin substrate is peeled off from the polarizing film, and a protective film (thickness: 40 μm, manufactured by Toyo Kohan Co., Ltd., trade name “Fine Cast”) is bonded to the peeled surface via a vinyl alcohol adhesive. Thus, a polarizing film was produced.

[Example 2]
In the production of the laminate, a PVA resin layer having a thickness of 10 μm was formed, the shrinkage in the first direction was set to 35% in the shrinkage / stretching process, and the iodine concentration was 0.45% by weight in the dyeing process. A polarizing film was produced in the same manner as in Example 1 except that. In addition, the thickness of the obtained polarizing film was 3 micrometers.

[Example 3]
During the production of the laminate, a 13 μm thick PVA-based resin layer was formed, the shrinkage in the first direction was 15% in the shrinkage / stretching process, and the iodine concentration was 0.35% by weight during the dyeing process. A polarizing film was produced in the same manner as in Example 1 except that. In addition, the thickness of the obtained polarizing film was 3 micrometers.

(Comparative Example 1)
A PVA-based resin film (trade name “PE-6000”, manufactured by Kuraray Co., Ltd.) having a thickness of 60 μm was used in place of the laminate, and the shrinkage rate in the first direction was 48% at a shrinkage / stretching temperature of 110 ° C. A polarizing film was produced in the same manner as in Example 1 except that the draw ratio in the second direction was 6.0 times and that the iodine concentration was 0.25% by weight in the dyeing treatment. In addition, the thickness of the obtained polarizing film was 19 micrometers.

(Comparative Example 2)
A polarizing film in the same manner as in Example 1, except that a 7 μm thick PVA resin layer was formed and the shrinkage in the first direction was set to 55% in the shrinkage / stretching process when the laminate was produced. Was made. In addition, the thickness of the obtained polarizing film was 3 micrometers.

(Comparative Example 3)
During the production of the laminate, a PVA resin layer having a thickness of 15 μm was formed, it was not shrunk in the first direction in the shrinking / stretching process (shrinkage was set to 0%), and the iodine concentration during the dyeing process A polarizing film was produced in the same manner as in Example 1 except that the content was 0.3 wt%. In addition, the thickness of the obtained polarizing film was 3 micrometers.

The polarizing films obtained in each example and comparative example were evaluated. Evaluation methods and evaluation criteria are as follows. The measurement results are shown in Table 1.
1. Nz coefficient of PVA resin film Wavelength (λ) 848.2 nm, 903.4 nm, 954.7 nm at 23 ° C. using a phase difference measuring device (trade name “KOBRA 31X100 / IR” manufactured by Oji Scientific Instruments) The retardation of the polarizing film was measured with light of 1000.9 nm, 1045.9 nm, and 1089.0 nm. Specifically, the phase difference (R30) measured by tilting the front phase difference (Re) of each wavelength and the absorption axis as an inclination axis by 30 ° is measured, and the three-dimensional refractive index is calculated from the obtained phase difference value. Nz coefficient was calculated | required using software (N-Calc.Ver.1.23). In addition, the measurement performed the frequency | count that the determination coefficient regarding the said approximated curve becomes 0.9 or more.
2. Durability A test piece (1150 mm × 650 mm) having a short side in the second direction (TD) was cut out from the obtained polarizing film. Ten test pieces were prepared for each example and comparative example. The test piece was bonded to a glass plate with an adhesive, and this was left in an oven where the environmental temperature changed suddenly, and the crack generation rate of the polarizing film after being left was examined. The details of the environmental temperature change, the calculation formula of the crack occurrence rate, and the evaluation criteria are as follows.
(Details of environmental temperature change)
The normal temperature → 85 ° C. → −45 ° C. → normal temperature was taken as one cycle, and the occurrence of cracks after 200 cycles was observed. The time required for one cycle was 1 hour.
(Calculation formula of crack occurrence rate)
Crack occurrence rate (%) = (cracks generated number of samples) / 10 × 100
(Evaluation criteria)
A: 0% to 10%
○: 20% to 30%
Δ: 40% to 50%
X: 60% or more Polarization degree Using a spectrophotometer (Murakami Color Co., Ltd., product name “Dot-41”), a single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) of a polarizing film (polarizing film) Was measured, and the degree of polarization (P) at a single transmittance of 40% was determined by the following equation. In addition, these transmittance | permeability is a Y value which measured by the 2nd visual field (C light source) of JISZ8701, and performed the visibility correction | amendment.
Polarization degree (P) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
(Evaluation criteria)
A: 99.95% or more B: 99.93% or more X: less than 99.9%

  The polarizing film of each example had excellent durability and excellent optical properties. On the other hand, Comparative Examples 1 and 2 had a high degree of polarization but low durability, and Comparative Example 1 having a thick polarizing film was particularly low. Although the comparative example 3 was excellent in durability, the polarization degree was low.

  The polarizing film and polarizing film of the present invention are suitable for liquid crystal panels such as liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copy machines, printers, fax machines, watches, and microwave ovens. Used.

  10 PVA resin film

Claims (2)

Consists of a polyvinyl alcohol resin film containing a dichroic substance,
Nz coefficient of the polyvinyl alcohol-based resin film is 1.10 or more and 1.50 or less,
Thickness Ri der less than 10μm,
The stretching and dyed polyvinyl alcohol-based resin film Ru obtained by a production method comprising washing with an aqueous potassium iodide solution, a polarizing film. The polarizing film according to claim 1;
A polarizing film comprising: a protective film laminated on at least one side of the polarizing film.

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