KR101819414B1 - A polarizing film - Google Patents

Abstract

The present invention provides a polarizing film having enhanced strength under an environment repeating high and low temperatures. The polarizing film of the present invention comprises a polyvinyl alcohol based resin as a forming material, and has a dichroic substance. A degree of orientation in an azimuthal distribution measured by a wide angle X-ray diffraction method is 81.0 % or more.

Description

A POLARIZING FILM [0002]

The present invention relates to a polarizing film.

A liquid crystal display device is known as a conventional image display device. The liquid crystal display device has a liquid crystal panel and a polarizer provided on both surfaces of the liquid crystal panel. As a polarizer, a polarizing film in which a dichroic dye is adsorbed and oriented on a stretched film obtained by stretching a polyvinyl alcohol (PVA) based resin film is known (for example, Patent Document 1).

Patent Document 1: JP-A-2009-098653

BACKGROUND ART [0002] In recent years, a liquid crystal display device has been required to be reduced in size and thickness in order to reduce the weight thereof. Accordingly, thinning of a polarizing film constituting a liquid crystal display device has been studied. For this reason, a polarizing film having sufficient strength (for example, suppressing cracking of a polarizing film under an environment in which a high temperature and a low temperature are repeated) is required even if it is thinned.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polarizing film which has enhanced strength under an environment of repeating high temperature and low temperature.

In order to solve the above-mentioned problems, the polarizing film of one embodiment of the present invention is a polarizing film having a dichroic substance, which comprises a polyvinyl alcohol resin as a forming material and is measured by a wide-angle X- , And the degree of orientation in the azimuthal distribution is 81.0% or more.

The above polarizing film is configured such that the ratio of the confinement noncontact portion to the total of the crystal portion, the confinement noncontact portion and the noncontact portion obtained from the spin-spin relaxation time obtained by the pulse NMR ( ¹ H) is 40% or more and 95% or less It is also good.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polarizing film having increased strength under an environment of repeating high temperature and low temperature.

1 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate of the first embodiment.
2 is a schematic diagram showing the microstructure of the polyvinyl alcohol-based resin of the polarizing film of the first embodiment.
Fig. 3 is a flow chart showing an example of a production method of the polarizing film of the first embodiment.
4 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate of the second embodiment.
5 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate of the third embodiment.

Hereinafter, the polarizing film according to the present embodiment will be described with reference to the drawings. In all of the following drawings, dimensions, ratios, and the like of the respective components are appropriately made different from each other in order to make the drawings easy to see.

[First Embodiment]

<Polarizer>

1 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate 1 according to the first embodiment.

The polarizing plate 1 is a polarizing plate having a one-side protective film. The polarizing plate 1 includes a polarizing film 5, a protective film (protective film) 10 positioned on one surface side of the polarizing film 5, a bonding agent (protective film) 10 bonding the polarizing film 5 and the protective film 10 15).

The polarizing plate 1 of the present embodiment may be a polarizing plate disposed on the visual (front) side of an image display element such as a liquid crystal cell when embedded in an image display device such as a liquid crystal display device, For example, a backlight side of a liquid crystal display). Compared with the polarizing plate disposed on the back side, the polarizing plate disposed on the viewer side tends to cause condensation and the like, and cracks tend to enter the polarizing film. According to the polarizing plate 1 of the present embodiment, Can be significantly suppressed.

<Polarizing Film>

The polarizing film 5 is made of a polyvinyl alcohol-based resin (PVA-based resin) as a forming material and is dyed with a dichroic substance (dichroic dye). As the PVA resin, a polyvinyl alcohol resin or a polyvinyl alcohol resin derivative is used. Hereinafter, polyvinyl alcohol will be abbreviated as PVA in the present specification.

Examples of the PVA resin derivative include polyvinylformal, polyvinyl acetal, polyvinyl butyral, and modified products thereof. Examples of the modified substance include those obtained by modifying the PVA resin derivative described above with an olefin such as ethylene or propylene, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, or an alkyl ester or acrylamide of an unsaturated carboxylic acid .

The degree of polymerization of the PVA-based resin is preferably from 1,000 to 10,000, more preferably from 1,500 to 5,000. The degree of saponification of the PVA resin is preferably 85 mol% or more, more preferably 90 mol% or more, and still more preferably 99 mol% or more.

The polarizing film 5 may contain an additive such as a plasticizer. Examples of the plasticizer include condensates of polyols or polyols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The content of the plasticizer in the polarizing film (5) is not particularly limited, but is preferably 20% by mass or less.

Examples of the dichroic substance used for dyeing the PVA resin of the polarizing film 5 include dichroic substances known as iodine and coloring matters for a polarizing film, and iodine is preferable.

Hereinafter, the description will be limited to the case where iodine is used as the dichroic substance. For dyeing the PVA resin layer according to the present embodiment, an iodine solution is used, and an iodine aqueous solution is preferably used. As the iodine aqueous solution, an iodine and an aqueous solution containing iodide ions dissolved in iodide as a dissolution aid are used. As the iodide, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide or titanium iodide is preferable and potassium iodide is more preferable.

The thickness of the polarizing film 5 is, for example, 30 占 퐉 or less, more preferably 20 占 퐉 or less, but is preferably 10 占 퐉 or less and more preferably 8 占 퐉 or less from the viewpoint of thinning of the polarizing plate. The thickness of the polarizing film is usually 2 占 퐉 or more. According to the present embodiment, since the intensity per unit film thickness can be increased, a polarizing film having a thin shape and excellent strength can be obtained.

The average degree of polymerization of the PVA resin constituting the polarizing film 5 is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the PVA resin can also be determined in accordance with JIS K 6726 (1994).

It is known that crystals of PVA form crystals of a folded structure, which is generally called lamellar crystal, in which polymer chains are repeatedly folded and formed.

Fig. 2 is a schematic diagram showing the microstructure of the PVA-based resin of the polarizing film 5. Fig.

And is a schematic diagram showing a part of the polymer chain constituting the lamellar type crystal. The lamellar crystal (crystal of PVA) 50 is formed by folding the polymer chains 51 repeatedly in the width direction to form a folded structure, and this folded structure is repeatedly formed continuously in the depth direction.

It is said that the molecules of PVA are aligned in the absorption axis direction. The degree of orientation is shown in the form of degree of orientation, and the degree of orientation of the polarizing film of the present invention is 81.0% or more, and preferably 81.5% or more. If the degree of orientation is 81.0% or more, the cause is unknown, but the occurrence rate of cracking of the polarizing film can be remarkably suppressed even for a load repeated at high and low temperatures such as in a thermal shock test. The degree of orientation can be measured by a wide angle X-ray diffraction (WAXD) method, and specifically, it can be measured by the method described in Examples of later-described examples.

The polarizing film 5 preferably has a stuck strength per unit thickness of 6.0 g / m or more. If the stuck strength is 6.0 g / 탆 or more, the rate of occurrence of cracking of the polarizing film can be remarkably suppressed even for a load caused by a temperature difference such as a thermal shock test.

The crystal size of the lamellar type crystal 50 can be adjusted by the thermal history of the PVA type resin as described later. The adjustment of the thermal history is performed by, for example, adjusting the amount of heat applied during film-drying of the PVA resin, that is, adjusting the temperature or time, or adjusting the stretching temperature.

PVA is a crystalline polymer, and crystal and noncrystalline are present. Recent advances in analytical techniques have found that there is a so-called constraint decoy, such as the middle between decision-making and non-governmental organizations. It is considered that the constraint is not constrained to the crystal part and the molecule is slightly elongated to the degree of non-crystallization, and the crystal is slightly loosened.

It is considered that the optical characteristics are stabilized in the heat resistance test and the moisture heat resistance test, and the strength of the polarizing film is also increased. The reason why the optical characteristics are stable is that when iodine enters the confinement and confinement portion and PVA and iodine form a complex, the molecules are harder to move than the non-crystal portion originally. Therefore, resistance to environmental changes such as heat and humidity is strong . The reason for the increase in the strength of the polarizing film is that iodine is introduced into the constraint non-crystal portion, which is a portion in which the PVA molecular chains are slightly loosened from the crystal portion, to form a PVA-iodine complex, It is considered that the strength of the polarizing film is increased. Preferably, the ratio of the constraint to the total of the decision unit, the constraint noncontiguous state, and the noncontiguous state is preferably more than 20%, more preferably not less than 30%. In addition, the more preferable ratio of the constraint nonconformity is 40% or more. The upper limit is not particularly limited, but may be 95% or less. In the present invention, the ratio of the constraint non-blocking portion is calculated from the spin-spin relaxation time obtained by the measurement of the pulse NMR ( ¹ H) according to the description of the embodiment to be described later.

In the polarizing film 5 of the present embodiment, the distance Wa between the lamellar crystals in the stretching direction (absorption axis direction) of the polarizing film can be set to 7.0 nm or more and 30.0 nm or less, and in the direction perpendicular to the stretching direction (The direction of the transmission axis), the distance Wb between the lamellar crystals can be 1.0 nm or more and 10.0 nm or less. In the present invention, the distance between the lamellar crystals adopts the value measured from the incineration X-ray scattering method (SAXS) according to the description of the embodiment to be described later.

The polarization performance of the polarizing film 5 of the present embodiment will be described. The polarization performance of the polarizing film is usually evaluated by two parameters called &quot; Visibility-corrected single-unit transmittance Ty &quot; and &quot; Visibility-corrected polarized light Py. These parameters are the transmittance and the degree of polarization in the visible region (wavelength 380 to 780 nm) in which the weight around 550 nm, which is the highest sensitivity of human eyes, is corrected to be the largest. Light having a wavelength of less than 380 nm is not considered in Ty and Py because it can not be seen by human eyes.

The visible light transmittance Ty of the polarizing film 5 may be a value usually found in an image display apparatus such as a liquid crystal display apparatus to which the polarizing film 5 and the polarizing plate 1 including the polarizing film 5 are applied. It is preferable that the visual sensitivity correcting unit transmittance Ty of the polarizing film 5 is in the range of 40 to 47%. The visibility-corrected corrected single-beam transmittance Ty is more preferably in the range of 41 to 45%, and in this case, the balance between the visual sensitivity-corrected single-unit transmittance Ty and visually- If the visual sensitivity-corrected single-beam transmittance Ty is excessively high, the visual sensitivity correction polarization degree Py is lowered and the display quality of the image display device is lowered. When the visibility-corrected corrected single-beam transmittance Ty is excessively low, the luminance of the image display device is lowered and the display quality is lowered or the input power is increased in order to sufficiently increase the luminance. The visual sensitivity correction polarization degree Py of the polarizing film 5 is preferably 99.9% or more, more preferably 99.95% or more, and 99.99% or more.

<Protection film>

As shown in Fig. 1, the protective film 10 is bonded to one surface of the polarizing film 5 through a bonding agent 15. [ The protective film 10 is preferably made of a thermoplastic resin having translucency (preferably optically transparent) such as a polyolefin resin such as a chain polyolefin resin (polypropylene resin), a cyclic polyolefin resin (norbornene resin, etc.) , A cellulose ester resin such as cellulose triacetate and cellulose diacetate, a polyester resin, a polycarbonate resin, a (meth) acrylic resin, a polystyrene resin or a mixture or copolymer thereof.

The protective film 10 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxial stretching or biaxially stretching) a film made of a thermoplastic resin, or forming a liquid crystal layer or the like on the film.

In the protective film 10, a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer may be formed on the surface opposite to the polarizing film 5. The protective film 10 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent and an antioxidant.

The thickness of the protective film 10 is preferably 90 占 퐉 or less, more preferably 50 占 퐉 or less, and still more preferably 30 占 퐉 or less, from the viewpoint of thinning of the polarizing plate. The thickness of the protective film 10 is usually 5 占 퐉 or more from the viewpoints of strength and handleability.

<Bonding agent (adhesive or pressure-sensitive adhesive)>

The bonding agent 15 is positioned between the polarizing film 5 and the protective film 10 as shown in Fig. The bonding agent (15) forms a layer for adhering and fixing the protective film (10) to one surface of the polarizing film (5). As the bonding agent 15, an adhesive or a pressure-sensitive adhesive may be employed.

When an adhesive is used as the bonding agent 15, the bonding agent 15 is preferably an active energy ray-curable adhesive containing a curable compound which is cured by irradiation of active energy rays such as ultraviolet rays, visible light, electron beams and X- May be an aqueous adhesive in which the adhesive component is dissolved or dispersed in water.

When an adhesive is used as the bonding agent 15, the thickness of the bonding agent 15 is usually about 0.001 to 5 mu m, preferably 0.01 to 3 mu m. More preferably 0.1 to 1.5 占 퐉. The adhesive as the bonding agent (15) exhibits good adhesiveness as an active energy ray curable adhesive, and therefore an active energy ray curable adhesive composition comprising a cationically polymerizable curable compound and / or a radically polymerizable curable compound can be preferably used .

The active energy ray curable adhesive may further comprise a cation polymerization initiator and / or a radical polymerization initiator for initiating the curing reaction of the curable compound. From the viewpoint of adhesiveness, an adhesive containing a cationically polymerizable curable compound is preferably used.

When an adhesive is used as the bonding agent 15, the thickness of the bonding agent 15 is 1 to 40 mu m, preferably 3 to 25 mu m. The pressure sensitive adhesive as the bonding agent 15 is usually composed of a pressure sensitive adhesive composition in which a base polymer is a (meth) acrylic resin, a styrene resin, a silicone resin or the like and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto. It is also possible to use a pressure-sensitive adhesive exhibiting light scattering properties by containing fine particles.

The polarizing plate 1 of the present embodiment is composed of a polarizing film 5, a bonding agent 15 and a protective film 10. The polarizing plate 1 may further include another optical layer. Examples of the other optical layer include a reflective polarizing film that transmits polarized light of a certain kind through the polarized light and exhibits properties opposite to that of the polarized light, a film having an antiglare function having a concavo-convex shape on the surface, A reflection film having a reflection function on the surface, a transflective film having a reflection function and a transmission function, and a viewing angle compensation film.

&Lt; Polarizing Film Production Method >

Next, a method of manufacturing the polarizing film 5 of the present embodiment will be described.

3 is a flow chart showing an example of a method of manufacturing the polarizing film 5. The manufacturing method of the polarizing film 5 of the present embodiment includes a resin layer forming step including step S1, a lamination step including step S2, and a crosslinking step including steps S3 and S4.

(A step of forming a PVA resin layer (step S1))

In step S1, a resin layer (PVA resin layer) made of PVA resin is formed on at least one surface of the base film. Thus, a laminated film comprising a base film and a PVA-based resin layer is formed.

As shown in Fig. 3, step S1 includes a coating step (step S11) of applying a PVA-based resin solution to the base film and a drying step (step S12) of drying the PVA-based resin solution.

(Coating step (step S11))

The coating step of step S11 is a step of forming a coating layer by coating an aqueous solution containing a PVA resin on at least one surface of a substrate film while conveying the strip-shaped base film in the longitudinal direction. A method of forming a coating layer by coating on a base film and forming a PVA resin film (PVA resin layer) as the coating layer is advantageous in that it is easy to obtain a PVA resin film as a thin film and further a polarizing film of a thin film It is advantageous in point.

The base film coated with the aqueous solution containing the PVA resin serves as a base for suppressing breakage of the layer of the PVA resin when the PVA resin is stretched to form a thin film. The base film may be peeled off from the polarizing film 5 after the polarizing film 5 is formed on the surface, or may be used as a protective film without peeling.

The base film may be composed of a thermoplastic resin and is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, heat stability, stretchability, and the like. Specific examples of such thermoplastic resins include polyolefin resins such as chain polyolefin resins, cyclic polyolefin resins (norbornene resins and the like), polyester resins, (meth) acrylic resins, cellulose triacetate, cellulose diacetate Based resin, polyvinyl acetate-based resin, polyarylate-based resin, polystyrene-based resin, polyether sulfone-based resin, polysulfone-based resin, polyamide-based resin, polyimide-based resin Resins, and mixtures and copolymers thereof.

The base film may be a single layer structure composed of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a multilayer structure in which a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated. The base film is preferably composed of a resin that can be stretched at a stretching temperature suitable for stretching the layer of the PVA-based resin in the stretching step in the polarizing film production method described later.

The base film may contain an additive. Specific examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant.

The thickness of the base film is usually 1 to 500 占 퐉, preferably 1 to 300 占 퐉, more preferably 5 to 200 占 퐉, and still more preferably 5 to 150 占 퐉, in view of strength and handleability.

The aqueous solution coated on the base film is an aqueous solution of PVA resin containing PVA resin and water. The aqueous solution may contain an additive such as a solvent other than water, a plasticizer, and a surfactant if necessary. Examples of solvents other than water include organic solvents compatible with water, such as alcohols represented by methanol, ethanol, propanol, and polyhydric alcohols (preferably, glycerin).

The initial water content of the coating layer composed of the aqueous solution containing the PVA resin can be set to a value exceeding 30% by weight. When the initial moisture content exceeds 30% by weight, the aqueous solution containing the PVA resin becomes a homogeneous solution, and it is possible to prevent unintentional crystallization from occurring before the drying step. From the viewpoint of handleability in coating an aqueous solution containing a PVA resin, the initial water content is preferably 40% by weight or more, more preferably 50% by weight or more.

The method of applying the aqueous solution coated on the base film to the base film may be a roll coating method such as a wire bar coating method, a reverse coating method and a gravure coating method, a die coating method, a comma coating method, a lip coating method, , Fountain coating method, dipping method, spray method and the like. The coating layer may be formed on only one side of the base film or on both sides of the base film.

In order to improve the adhesion between the base film and the PVA resin layer prior to coating of the aqueous solution coated on the base film, at least the surface of the base film on which the coat layer is formed is subjected to corona treatment, plasma treatment, flame treatment Or the like may be performed. For the same reason, a coating layer may be formed on a base film through a primer layer or the like.

(Drying step (step S12))

The drying step of step S12 is a step of removing water from a coating layer having a moisture content exceeding 30% by weight to form a PVA-based resin layer. Drying of the coating layer (removal of water) can be performed by heating, but drying by reduced pressure or the like may be used in combination. Examples of the heating method include a method in which a substrate film is brought into contact with a warmed roll (hot roll), a method in which hot air is blown, and combinations thereof. The drying temperature in the drying step is, for example, in the range of 50 to 200 占 폚, preferably in the range of 60 to 150 占 폚.

In the drying step, water is removed from the coating layer having a moisture content exceeding 30% by weight (hereinafter, the water content of the coating layer immediately before the drying step is referred to as "initial moisture content W1" Final water content W2 &quot;), and a PVA-based resin layer is formed on the base film. In this case, when the water content is 30% by weight (i.e., the moisture content (% by weight) is lower than 30% Of 30 to 10% by weight), it is important to appropriately adjust the average water removal rate. In the present embodiment, either or both of them are set in the range of 0.01 to 1.8% by weight / second. Hereinafter, the removal rate of water at the time when the moisture content of the coating layer becomes 30% by weight is referred to as &quot; removal rate V (30) &quot;, and the removal of the water when the water content of the coating layer is in the range of 30 to 10% The speed is also referred to as &quot; average removal speed Vave (30-10) &quot;. By adjusting the drying conditions so that the removal rate V (30) and / or the average removal rate Vave (30-10) are within the above range, the crystal size of PVA can be reduced and the distance between crystals can be shortened, can do. As described above, by decreasing the crystal size of the PVA and shortening the distance between crystals, it is possible to increase the ratio of the confinement noncontact portion to the total of the crystal portion, the confinement noncorrection portion and the noncorrection portion.

The reason why the crystal size of PVA and the distance between crystals can be shortened by adjusting the removal rate V (30) and / or the average removal rate Vave (30-10) within the predetermined range is presumed as follows. That is, the reason why high polarization performance is exhibited is that crystal nuclei of the PVA resin start to be generated when the water content is 30 wt% or near (between 30 and 10 wt%), and when the coating layer is 30 wt% and / Or the water removal rate V (30) and / or the average removal rate Vave (30-10) when the water content near the water removal rate Vave is within the above range, . By forming a lot of crystal nuclei in this manner, the density of the crystallites is increased, and a denser crystal structure can be formed.

On the other hand, in the region where the water content exceeds 30% by weight, the PVA-based resin is uniformly dissolved in water, and it is considered that the state (solution) in which the molecular chains of the PVA-based resin are uniformly present is stable. Actually, in a region where the water content exceeds 30% by weight, generation of stable crystal nuclei exceeding the critical size hardly occurs. If the water content is lowered to about 30% by weight, crystal nuclei of a stable critical size or larger are formed, which is considered to be more stable in forming crystal nuclei and crystallizing.

As described above, crystal nuclei of the PVA-based resin start to form when the water content decreases to about 30% by weight, and crystal nuclei are generated even in the vicinity thereof, that is, in the water content range of 30 to 10% by weight. In the region below the% by weight, generation of crystal nuclei stable at a critical size or more is hard to occur. This is presumably because the amount of water used is very small and the mobility of the molecular chain of the PVA resin is excessively lowered.

In the drying step, the removal rate V (30) at the time when the water content at which the crystal nucleus of the PVA resin starts to be 30 wt% may be adjusted to be within the range of 0.01 to 1.8 wt% / sec, The average removal rate Vave (30-10) at a water content ratio of 30 to 10% by weight at which crystal nuclei are generated may be adjusted within a range of 0.01 to 1.8% by weight / second. However, it is preferable to adjust at least the average removal rate Vave (30-10) within the above range, because the crystal nuclei can be sufficiently generated over the entire water content range in which the crystal nuclei are generated, and the removal rates V (30) and It is more preferable to adjust both of the average removal speed Vave (30-10) within the above range.

As a method for lowering the removal rate V (30) and / or the average removal rate Vave (30-10) up to the upper limit of the above range, there are a method of lowering the surface temperature of the hot roll, For example, a method of lowering the temperature and / or the wind speed of the hot air can be mentioned. In addition, the humidity of the environment in which drying is performed may be increased. From the viewpoint of productivity, it is preferable to increase the removal rate of water by increasing the drying degree in the region where the water content greatly exceeds 30% by weight. However, in the operation of the drying equipment, It is more difficult to lower the removal rate at a point in time before reaching the water content of 30% by weight because the removal rate V (30) and / or the average removal rate Vave (30- 10) within the above range.

Further, when drying is performed from the initial moisture content W1 to the final moisture content W2 at a constant drying condition, the temperature of the coating layer gradually increases, and the removal rate of water during drying tends to remarkably increase. Therefore, in order to set the removal rate V (30) and / or the average removal rate Vave (30-10) within the above-described range, it is preferable that the drying conditions are not made constant during the drying process but the drying conditions are relaxed on the way.

The upper limit of the removal rate V (30) and the average removal rate Vave (30-10) is preferably 1.65% by weight / second or less, more preferably 1.5% by weight / second or more from the viewpoint of increasing the density of crystal nuclei of the PVA- Or less. If the removal rate is too low, the density of crystal nuclei becomes too high, and the production of a polarizing film (to be described later) The dyeing efficiency in the dyeing step in the dyeing step is lowered. From this point of view, in view of productivity of the polarizing film 5, the lower limit is preferably 0.15 wt% / second or more, and more preferably 0.5 wt% / second or more.

Next, a method of measuring the removal rate V (30) and the average removal rate Vave (30-10) will be described. The reduction rate curve of the water content obtained by plotting the water content of the coating layer with respect to the elapsed time from the start of the drying process Curve). If the measurement data of water content (measurement point) is sufficiently dense, the inclination (removal rate V (30)) can be accurately obtained from the differential value at the time when the water content is 30% by weight. However, in actual measurement, it is difficult to obtain continuous measurement data, and in many cases, measurement data that is sufficiently dense can not be obtained. Therefore, in this case, the removal rate V (30) is obtained as an average value of a predetermined range of measurement data including a time point when the water content is 30% by weight. More specifically, in this case, the removal rate V (30)

Removal rate V (30) = 4 [wt%] / (time required for water content to become 28 wt% to 32 wt%) [a]

(I.e., 4% by weight) at a water content of 32 to 28% by weight calculated on the basis of the fitting curve is calculated as the time required for the water content to be from 32% by weight to 28% by weight Sec].

In obtaining the fitting curve, in order to accurately calculate the removal rate, measurement data of water content is obtained at an interval of about 2 wt%.

The average removal rate Vave (30-10) is also obtained in the same manner as in the above equation [a]. That is, the average removal rate Vave (30-10) is expressed by the following equation [b]:

Average removal rate Vave (30-10) = 20% by weight / (Time required for water content to become 10% by weight from 30% by weight) [b]

(I.e., 20% by weight) at a moisture content of 30 to 10% by weight, calculated on the basis of the fitting curve, to the time required for the water content to be from 30% by weight to 10% by weight Sec].

The final moisture content of the PVA resin layer in the laminate thus obtained is preferably 0.15% or more, more preferably 0.30% or more, and 0.40% or more. The upper limit value is not particularly limited, but may be 10% or less.

The reason why the final moisture content is important is that, when the initial moisture content of the coating liquid is the same and the final moisture content is high in the case of drying at the same drying time, compared with the case where the final moisture content is low , And it is considered that the PVA coating liquid can be dried relatively gently. By gently drying in this manner, the distance between crystals is small and many fine crystals are formed. On the contrary, when the final moisture content is low, the final moisture content is high, compared to the case where the final moisture content is high, so that the distance between crystals is large and relatively large crystals are formed in a small number.

The reason for this difference is as follows. When the PVA coating is rapidly dried, the difference in the temperature distribution in the PVA coating solution becomes large, so that the formation amount of nuclei of very small initial crystals is not large. Thereafter, Since the growth of the nuclei of the formed small crystals proceeds preferentially, it is considered that a large number of crystals are formed in a small amount. On the other hand, in the case of gentle drying, since the difference in temperature distribution is small in the PVA coating liquid, the nuclei of very small initial crystals can be formed in a large amount, and thereafter, as the PVA concentration becomes high, Since there are many small crystals, it is thought that it is hard to increase finally.

In the present invention, the moisture content of the final PVA resin layer is determined from the calibration curve obtained from the dry weight method and the IR moisture content meter according to the examples of the later-described examples.

By adjusting the moisture content in the drying step of the PVA resin layer, the degree of orientation of the PVA and the content ratio of the constraining non-crystal portion can be adjusted.

(Drawing step (step S2))

In the stretching step of step S2, the laminate obtained in step S1 is stretched while being transported in the longitudinal direction. By stretching the laminate, the base film and the PVA resin layer are laminated to obtain a stretched base film.

The stretching step is a step of stretching a laminated film comprising a base film and a PVA-based resin layer. The stretching treatment in the stretching step is usually uniaxial stretching.

The stretching magnification of the laminated film can be appropriately selected in accordance with the desired polarization characteristics and the thickness of the lamellar crystal. It is preferably 1.1 to 17 times, more preferably 1.5 to 8 times the original length of the laminated film. When the draw ratio is more than 17 times, the film tends to be broken at the time of stretching, and the thickness of the laminated film becomes thinner than necessary, which may lower the workability and handleability in subsequent steps.

The stretching treatment is not limited to stretching in one stage but may be performed in multiple stages. In this case, all of the multi-stage drawing process may be performed continuously before the dyeing process, and the drawing process after the second step may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process. In such a multi-stage stretching treatment, it is preferable to stretch all the stages of the stretching treatment so as to have a stretching ratio of more than four times.

The stretching treatment may be longitudinal stretching in which stretching is performed in the longitudinal direction of the film (film transport direction), transverse stretching or oblique stretching in stretching in the film width direction, or the like. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck. The transverse stretching method includes a tenter method and the like. Any of the wet drawing method and the dry drawing method can be used for the drawing treatment, but a dry drawing method is preferable because the drawing temperature can be selected within a wide range.

The stretching temperature is set to be equal to or higher than the temperature at which the whole of the PVA resin layer and the base film can be stretched so as to exhibit fluidity and is preferably set in the range of -30 占 폚 to + 30 占 폚 of the phase transition temperature (melting point or glass transition temperature) More preferably in the range of -30 ° C to + 5 ° C, and more preferably in the range of -25 ° C to + 0 ° C. When the base film is composed of a plurality of resin layers, the phase transition temperature means the phase transition temperature which is the highest among the phase transition temperatures seen in the plurality of resin layers.

If the stretching temperature is lower than -30 캜 of the phase transition temperature, high-magnification stretching exceeding 4 times is not easily attained, or the fluidity of the base film is too low to make the stretching process difficult. If the stretching temperature exceeds + 30 ° C of the phase transition temperature, the fluidity of the base film becomes too high, and the stretching tends to be difficult. The stretching temperature is within the above range, more preferably 120 deg. C or more, since it is easier to achieve a high draw ratio of more than 4 times.

Further, as the PVA resin, it is more preferable to set the drawing temperature to not less than 120 ° C and not more than 170 ° C. It is possible to suppress the growth of the lamellar crystal 50 (see FIG. 2) due to heat at the time of stretching, to reduce the crystal size of the lamellar crystal 50 and to shorten the distance between crystals, As shown in FIG.

Examples of the heating method of the laminated film in the stretching treatment include a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace blowing hot air and adjusted to a predetermined temperature) A method of heating the roll itself, a heater heating method (a method of heating an infrared heater, a halogen heater, a panel heater or the like on the upper and lower sides of a laminated film and heating it by radiant heat), and the like. In the roll-to-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

Here, the stretching temperature means the atmospheric temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and the heating temperature in the furnace means the atmospheric temperature in the furnace. In the case of the method of heating the roll itself, it means the surface temperature of the roll.

Prior to the stretching process, a preheating process for preheating the laminated film may be performed. As the preheating method, the same method as the heating method in the stretching treatment can be used. The preheating temperature is preferably in the range of -50 占 폚 to 占 0 占 폚 of the stretching temperature, and more preferably in the range of -40 占 폚 to -10 占 폚 of the stretching temperature.

After the stretching treatment in the stretching step, a heat fixing treatment step may be performed. The heat setting process is a process of performing heat treatment at a crystallization temperature or higher while keeping the end portion of the oriented laminated film in a state of being held in a state of being held by a clip. By this heat setting treatment, the crystallization of the stretched film is promoted. The temperature of the heat setting treatment is preferably in the range of -0 to -80 占 폚 of the stretching temperature and more preferably -0 to -50 占 폚 of the stretching temperature.

(Dyeing step (step S3))

In the dyeing step of step S3, the PVA-based resin layer is dyed with a dichroic substance and adsorbed and oriented.

The dyeing step can be carried out by immersing the entire laminated film composed of the base film and the PVA-based resin layer in a solution (aqueous dyeing solution) containing iodine. As the dyeing aqueous solution, a solution in which iodine is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of iodine in the dyeing aqueous solution is preferably 0.01 to 10% by weight, and more preferably 0.02 to 7% by weight.

It is preferable to add iodide to the dyeing aqueous solution because the dyeing efficiency can be 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 titanium iodide. The concentration of iodide in the dyeing aqueous solution is preferably 0.01 to 20% by weight. It is preferable to add potassium iodide even in iodide. When potassium iodide is added, the weight ratio of iodine to potassium iodide is preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80.

The temperature of the dyeing aqueous solution is preferably from 10 to 60 캜, more preferably from 20 to 40 캜.

(Crosslinking step (step S4))

In the step of crosslinking in step S4, a resin film (hereinafter referred to as a dyed film) dyed with a dichroic substance is immersed in a crosslinking bath containing the first crosslinking agent. At this time, the resin film is stretched in the longitudinal direction in the crosslinking bath. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more. As the solvent of the crosslinking solution, water may be used, but an organic solvent which is compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably 0.2 to 20% by weight, and more preferably 0.5 to 10% by weight.

The crosslinking solution may further comprise iodide. By adding iodide, the polarization performance in the plane of the polarizing film 5 can be made more uniform. Specific examples of the iodide are the same as described above. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, and more preferably 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably 1 to 90 占 폚.

The crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing aqueous solution. The treatment of immersing in a crosslinking solution may be carried out two or more times using two or more crosslinking solutions having different compositions.

After the crosslinking step of step S4, it is preferable to carry out a washing step and a drying step. The cleaning process usually includes a water cleaning process. The water washing treatment can be performed by immersing the film after the dyeing treatment or the crosslinking treatment on pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 to 50 占 폚, preferably 4 to 20 占 폚. The cleaning process may be a combination of a water cleaning process and a cleaning process using an iodide solution. As the drying step performed after the cleaning step, any suitable method such as natural drying, air blow drying, and heat drying can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

Further, after the cleaning step and the cleaning step, the polarizing film 5 can be formed by peeling the PVA resin layer from the base film. The method of peeling off the base film is not particularly limited, and conventionally known methods can be used.

The polarizing film 5 can be formed by carrying out the above steps. The polarizing plate 1 shown in Fig. 1 can be formed by bonding the protective film 10 to one surface of the polarizing film 5 through the bonding agent 15. [

According to the polarizing film 5 of the present embodiment, the film strength can be increased by appropriately adjusting the orientation degree of the PVA and the content ratio of the constraining non-crystal portion. In addition, the degree of orientation of the PVA and the content ratio of the constraining non-crystal phase can be adjusted by the thermal history in the manufacturing process. More specifically, the degree of orientation and the content ratio of the constraining non-crystal portion can be adjusted by the moisture content in the drying step of the PVA-based resin layer during the production process.

[Second Embodiment]

4 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate 2 of the second embodiment.

The polarizing plate 2 of the present embodiment differs from the first embodiment in that a protective film 10 is formed on both sides of the polarizing film 5 in comparison with the first embodiment. The constituent elements in the same mode as those of the above-described embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

The polarizing plate 2 includes a polarizing film 5 and a protective film 10 positioned on both side surfaces of the polarizing film 5 and a polarizing film 5 and a protective film 10 (Adhesive or pressure sensitive adhesive) 15. In the present embodiment, the pair of protective films 10 provided on both sides of the polarizing film 5 are of the same structure, but may be protective films made of different kinds of resins or protective films having different thicknesses. Similarly, the bonding agent 15 for bonding the pair of protective films 10 to the polarizing film 5 may be mutually different kinds of bonding agents.

[Third embodiment]

5 is a schematic cross-sectional view showing an example of the layer configuration of the polarizing plate 3 of the third embodiment. The constituent elements in the same mode as those of the above-described embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

The polarizing plate 3 of this embodiment includes a polarizing film 5 and an adhesive layer 16 laminated on one surface of the polarizing film 5. [ The adhesive layer 16 is used for bonding the polarizing plate 3 to another member (for example, a liquid crystal cell in the case of applying to a liquid crystal display device). In the polarizing plate 3 of the present embodiment, the adhesive layer 16 is formed on only one side of the polarizing film 5, but it may be formed on both sides.

While the preferred embodiments of the present invention have been described with reference to the accompanying drawings, it is needless to say that the present invention is not limited to these examples. The shape, combination, and the like of each constituent member shown in the above-described example are merely examples, and can be variously changed based on a design requirement or the like without departing from the gist of the present invention.

[Example]

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

IR water content meter (IR multi-component) "IRMA-5162S" manufactured by Kabushiki Kaisha Shino was used for water content measurement of the coating layer.

The calibration curves were obtained by preparing 10 film samples with different water contents and measuring the water content according to the following formula [c] (dry weight method) with respect to these samples and measuring the water content by using the IR moisture meter "IRMA- 5162S" And plotting the corresponding relationship between the obtained water content and the intensity of infrared absorption, and approximating it by a linear equation. As the film sample, a coated film having a coated layer formed by coating an aqueous solution containing polyvinyl alcohol (PVA) on the same base film as used in each of the Examples and Comparative Examples was used. This aqueous solution contains only water as a volatile component.

(1), (2) and (3) are sequentially performed on each of the film samples to measure the water content according to the above formula (c) (dry weight method)

Moisture content =

(Measured value of (1) - measured value of (2)] / [measured value of (1) - measured value of (3)

The moisture content by the dry weight method was determined.

(1) Measuring the weight (before drying treatment) of the coated film as a film sample,

(2) The weight of the coated film after drying at 105 ° C for 2 hours was measured,

(3) Peeling off the coating layer to measure the weight of the remaining base film.

At this time, the water content in each of the examples and the comparative examples was calculated by substituting the measured value by the IR moisture content meter "IRMA-5162S" into the first equation of the calibration curve.

&Lt; Example 1 >

(1) Primer layer formation process

PVA powder (&quot; Z-200 &quot;, average degree of polymerization 1100, saponification degree: 99.5 mol%) manufactured by Nippon Gosei Chemical Industry Co., Ltd. was dissolved in hot water at 95 캜 to prepare a PVA aqueous solution having a concentration of 3% by weight. The obtained aqueous solution was mixed with 5 parts by weight of a crosslinking agent ("Sumirez Resin (registered trademark) 650" manufactured by Daoka Chemical Co., Ltd.) per 6 parts by weight of the PVA powder to obtain a coating solution for forming a primer layer.

Subsequently, a non-stretched polypropylene (PP) film (melting point: 163 DEG C) having a thickness of 90 mu m was prepared as a base film, one side of which was subjected to corona treatment, and then a corona- A coating solution for forming a primer layer was applied and dried at 80 DEG C for 10 minutes to form a primer layer having a thickness of 0.2 mu m.

(2) Production of laminated film (coating process, drying process)

PVA powder ("PVA 124" manufactured by Kabushiki Kaisha Kurara Co., Ltd., average degree of polymerization: 2400, degree of saponification: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a PVA aqueous solution having a concentration of 7.5% by weight. A PVA aqueous solution having a concentration of 7.5% by weight was applied to the surface of the primer layer of the base film having the primer layer prepared in the above (1) using a die coater to form a coating layer having a thickness of 130 탆 (coating step).

Thereafter, the coated layer was dried by spraying hot air at 85 캜 (drying step).

At this time, when the moisture content during drying was monitored by the IR moisture meter "IRMA-5162S", the drying process was terminated when the moisture content of the PVA resin layer reached 0.58 wt%, and the base film / primer layer / PVA film Based resin layer) was obtained. The thickness of the PVA film was 9.3 탆.

(3) Production of stretched film (stretching process)

The laminated film prepared in (2) above was subjected to free uniaxial stretching at 150 캜 at a stretching ratio of 5.3 times using a longitudinal uniaxial stretching apparatus for floatation to obtain a stretched film. The thickness of the PVA film after stretching was 5.1 占 퐉.

(4) Production of a polarizing laminated film (dyeing process)

The stretched film prepared in the above (3) was measured in a later evaluation with a dyeing aqueous solution containing iodine and potassium iodide (containing 0.6 parts by weight of iodine and 5.0 parts by weight of potassium iodide per 100 parts by weight of water) The modified film was subjected to dyeing treatment by appropriately adjusting the immersion time such that the visually-perceptible corrected single-beam transmittance Ty was about 41.5%, and then the excess dyeing solution was washed with pure water at 10 占 폚.

Subsequently, the resultant was immersed in a first crosslinked aqueous solution (containing 9.0 parts by weight of boric acid per 100 parts by weight of water) containing boric acid at 180 DEG C for 180 seconds, and then a second crosslinked aqueous solution of boric acid and potassium iodide (Containing 5.0 parts by weight of boric acid and 4.4 parts by weight of potassium iodide per 100 parts by weight of water) for 90 seconds to carry out crosslinking treatment. Thereafter, the substrate was immersed in pure water at 10 캜 for about 10 seconds, and immediately thereafter, water adhering to the surface was removed by using an air blower. The film was then put into an oven at 65 캜 for 240 seconds, A polarizing laminated film was obtained.

(5) Production of a polarizing plate having a protective film (joining step, peeling step)

On the polarizing film of the polarizing laminated film produced in the above (4), a protective film (cyclo-cyclohexane-based polymer) was laminated on the polarizing film of the polarizing laminated film prepared in the above (4) through an adhesive layer composed of an ultraviolet ray curable adhesive ("KR-75T", which is a cationically polymerizable curable compound manufactured by ADEKA, And a transparent protective film made of an olefin resin (&quot; Zeonoa (registered trademark) &quot;, manufactured by Nippon Zeon Co., Ltd., thickness of 23 mu m) was bonded.

Subsequently, the adhesive layer was cured by irradiating ultraviolet rays using a high-pressure mercury lamp to obtain a polarizing laminated film having a protective film (first bonding step). Thereafter, the base film was peeled off from the polarizing laminated film having the obtained protective film to obtain a polarizing plate having a one-side protective film (peeling step). Thereafter, a protective film ("Zeonoa (registered trademark)" with a thickness of 23 μm) was bonded to the surface on which the base film was peeled and removed through "KR-75T". Subsequently, the adhesive layer was cured by irradiating ultraviolet rays using a high-pressure mercury lamp to obtain a polarizing plate having a double-side protective film (second bonding step).

The visual sensitivity correction of the obtained polarizing plate was 41.7%, and the visual sensitivity correction polarization degree was 99.995%. The distance between crystals was 16.4 nm in the stretching direction (absorption axis direction) of the polarizing film and 2.8 nm in the direction orthogonal thereto (transmission axis direction).

(6) Measurement of polarization degree

With respect to the polarizing plate having the obtained double-sided protective film, the visual sensitivity-corrected single-unit transmittance Ty and visibility-corrected polarized light Py were measured using a spectrophotometer ("V7100" manufactured by Nippon Bunko Co., Ltd.). In the measurement, a polarizing plate sample having a double-side protective film was set so that incident light was irradiated on the polarizing film side. The measurement results of Ty and Py are shown in Table 1.

(7) Measurement of sting intensity

The sticking test was carried out by fixing a polarizing film to a small desk tester (trade name "EZ Test (registered trademark)" manufactured by Shimadzu Seisakusho Co., Ltd.) equipped with a sticking jig having a diameter of 1 mm and a radius of curvature of 0.5 R . The measurement was carried out under the conditions of a temperature of 23 占 占 폚 and at a threshing speed of 0.33 cm / sec. The stab intensity measured in the stab test was determined by four averages excluding the top three and the bottom three of the numerical values with respect to the strength when the test piece was thrown in the transmission axis direction by performing the stab test on the ten test pieces. The average value was divided by the film thickness of the polarizing film, and the stuck intensity per unit film thickness was obtained.

(8) WAXD

Orientation degree &quot; indicating the orientation in the absorption axis direction (MD, stretching direction) of the PVA resin constituting the polarizing film was determined by the through-angle method of wide angle X-ray diffraction (WAXD). First, a plurality of rectangular films having long sides in the MD direction were cut out from the obtained polarizing film. The cut films were stacked so that their MDs were parallel to each other and used as measurement samples. The thickness of the measurement sample was about 0.05 mm. The following X-ray diffraction apparatus was used to irradiate one surface of the sample for measurement with X-rays under the following X-ray output conditions from the direction perpendicular to the surface of the sample for measurement, and the diffraction image by the transmission method was picked up .

X-ray diffraction apparatus: "NANO-Viewer" manufactured by Rigaku Corporation,

X-ray output conditions: Cu target, 40 kV, 20 mA.

From the obtained diffraction image, an undefined azimuth distribution curve (azimuth angle (beta angle) - intensity distribution curve) was calculated by annular integration in the range of 2? = 19.5 to 20.5 with respect to the peak near the diffraction angle 2? . The uncorrected azimuth distribution curve refers to an azimuth distribution curve before background correction is performed. Subsequently, measurements were made under the same conditions except that the sample for measurement was removed on the X-ray optical axis, and the background of the azimuth distribution curve was calculated. After the transmittance correction was performed, the background was removed from the above-mentioned unmodified azimuth distribution curve, and an azimuth distribution curve after the background correction (hereinafter simply referred to as "azimuth distribution curve") was obtained. The peak in this azimuth distribution curve is an orientation peak. In this measurement, the MD of the sample for measurement is provided in the vertical direction, and the angle beta at the maximum intensity of the orientation peak appearing in the horizontal direction is set to 0 DEG. The? -Angle (0 ° and 180 °) in the maximum intensity of the orientation peak is derived from the component oriented in the MD of the polarizing film. From the obtained azimuth distribution curve,

(%) = (360-W) / 360

. And W is the sum of the total peak width at which the integral value becomes 50% when the integrated value of the entire peak of the azimuth distribution curve is 100% and the total peak width is obtained with respect to all the orientation peaks. The center position (°) in the entire peak width agrees with the beta angle (°) at which the peak shows the maximum intensity.

(9) SAXS

The lamellar size of the PVA-based resin constituting the polarizing film was determined by the through-passing method of SAXS (Small Angle X-ray Scattering).

A polarizing film cut in the same manner as WAXD in (8) above was stacked and fixed several times so that their MDs were parallel to each other, and this was used as a measurement sample. The thickness of the measurement sample was about 0.05 mm. The following X-ray output conditions were used to irradiate one surface of the sample for measurement from the direction perpendicular to the surface of the sample for measurement by the following incineration X-ray scattering apparatus, Ray image.

Incinerating X-ray scattering device: "NANO-Viewer" manufactured by Rigaku Co.,

X-ray output conditions: Cu target, 40 kV, 20 mA.

(Sector (q) -strength distribution) in the MD direction and the TD direction by sector averaging the range of ± 10 degrees from the respective azimuth angles with respect to the MD direction and the TD direction from the obtained small angle X-ray scattering image Respectively. The uncompensated sector profile refers to a sector profile before background correction is performed. Subsequently, measurement was performed under the same conditions except that the measurement sample was removed on the optical axis of the X-ray to calculate the background of the sector profile. After performing the transmittance correction, the background is removed from the above-mentioned uncompensated sector profile to obtain a sector profile after background correction (hereinafter simply referred to as "sector profile"). The distances Wa and Wb between the lamella type crystals were obtained from the peak top qa and qb of the peak top in the curved line obtained by multiplying the sector profile in the MD direction and the TD direction by q ² according to the following equation.

Wa = 2 pi / qa

Wb = 2? / Qb

(10) Amorphous component amount in polarizing film

The amount of the amorphous component of the PVA resin constituting the polarizing film was determined by a pulse NMR ( ¹ H). First, about 50 mg of a polarizing film cut to a size of about 5 mm x 5 mm was immersed in an NMR tube together with 1 mL of heavy water. The NMR tube was heated in a hot water bath at 60 占 폚 for 1 hour. After that, the film was allowed to stand at room temperature for 24 hours, and the spin-spin relaxation time T2 was measured by using pulsed NMR. The measurement conditions are as follows.

Pulse NMR apparatus: minispec mq20 manufactured by Bruker BioSpin Co., Ltd.

Pulse series: Solid echo method

Pulse width: 2.8 ㎲

Pulse repetition time: 1 s

Accumulation count: 256 times

Measuring temperature: 30 ° C

(FID) signal obtained by the measurement is fitted to the following equation by the linear least squares method to calculate the crystalline component amount A1, the constrained amorphous component amount A2 and the amorphous component amount A3 from the difference in relaxation time of each component, And the percentage (%) of each component with respect to the sum (A1 + A2 + A3) of these three components was calculated.

(11) Confirmation of PVA crack at the time of cold shock test

The second protective film side of the polarizing plate sample having the double-sided protective film was subjected to corona treatment, and a separator on one surface was peeled off from the surface of the pressure sensitive adhesive sandwiched between the separator films on both surfaces thereof and the peeled surface was adhered to the pressure sensitive adhesive layer. Thereafter, this laminate was peeled from the side of the separator film of the pressure-sensitive adhesive by a super cutter (PNI-600, manufactured by Ogino Seiki Co., Ltd.) at 120 mm in the stretching direction of the polarizing plate, 70 mm. The separator on the pressure-sensitive adhesive side of the cut film was removed and bonded to a glass (Eagle XG [manufactured by Corning Incorporated]) with a roller to obtain an evaluation sample. The polarizing plate and the glass laminate were subjected to a thermal shock test for 30 minutes at -35 DEG C for 30 minutes and at 85 DEG C for 30 minutes to confirm that cracking of PVA occurred every 100 cycles.

At this time, the confirmation was confirmed by using a digital microscope "VHX-500"

The case where a crack of 1 mm or more occurred even when one strand was formed was judged as NG, and the case where no such crack occurred also was judged as OK.

&Lt; Example 2 >

The same procedure as in Example 1 was carried out except that the moisture content in the drying step was adjusted as shown in Table 1 by adjusting the time to leave the hot air. The water content of the PVA resin layer after the drying step was 0.35% by weight. Further, the visual sensitivity corrected single-unit transmittance of the obtained polarizing plate was 41.7% and the visual sensitivity correction polarization degree was 99.995%. The distance between crystals was 16.1 nm with respect to the stretching direction (absorption axis direction) of the polarizing film, and 2.7 nm with respect to the direction orthogonal thereto (transmission axis direction).

&Lt; Comparative Example 1 &

The same procedure as in Example 1 was carried out except that the moisture content in the drying step was adjusted as shown in Table 1 by adjusting the time to leave the hot air. The water content of the PVA resin layer after the drying step was 0.14% by weight. The visual sensitivity corrected single-use transmittance of the obtained polarizing plate was 41.5%, and the visual sensitivity correction polarization degree was 99.997%. The distance between crystals was 16.3 nm for the stretching direction (absorption axis direction) of the polarizing film, and 2.7 nm for the direction orthogonal thereto (transmission axis direction).

WAXD Pulse NMR Sting intensity
[g / 탆]
HS test Orientation
[%] A1:
[%] A2: Constrained non-governmental
[%] A3: Non-governmental
[%] Example 1 81.8 7 38 55 8.8 OK Example 2 83.6 9 45 46 6.1 OK Comparative Example 1 80.7 8 25 69 5.8 NG

Table 1 shows the results of confirmation of the PVA crack at the stuck strength and the cold / heat impact test. A high degree of orientation and a large number of unrestricted nonconjugated parts gave good results in the sting strength and PVA crack test. From these results, it was confirmed that the polarizer was excellent in strength when the degree of orientation was high and the amount of unrestricted non-crystallization was large.

1, 2, 3: polarizer
5: polarizing film
10: protective film (protective film)
50: lamellar crystal (crystal of polyvinyl alcohol)
Wa: distance between crystals (absorption axis direction)
Wb: distance between crystals (transmission axis direction)

Claims (2)

As a polarizing film having a polyvinyl alcohol-based resin as a forming material and having a dichroic substance,
The thickness of the polarizing film is not less than 2 탆 and not more than 8 탆,
The degree of orientation in the azimuthal distribution measured by a wide angle X-ray diffraction method is 81.0% or more,
Wherein the ratio of the constraint non-confinement portion to the total of the crystal portion, the constraint non-crystal portion and the non-crystal portion obtained from the spin-spin relaxation time obtained by the pulse NMR ( ¹ H) is 40% or more and 95% or less. delete

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