JP2003248120A - Polarizing plate, manufacturing method thereof, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate made of a polarizing film that is obliquely elongated for improving yield ratio in a punching process, a manufacturing method of the polarizing plate, and a liquid crystal display using the manufacturing method. <P>SOLUTION: In the polarizing plate, the method for manufacturing the polarizing plate, and the liquid crystal display; absorption axis of a polarizing film is neither parallel with nor vertical to a longitudinal direction, a single panel transmittance is equal to or more than 40% at 550 nm, and the degree of polarization calculated by an expression (1) as P=[(H0-H1)/(H0+H1)]<SP>1/2</SP>×100 is equal to or more than 95% at 550 nm (a); and the variation width of the transmittance at 550 nm after being left for 500 hours under an atmosphere of a temperature of 60° and a moisture of 90% is within ±10% as compared with an initial value (b-1), and the variation width of the degree of polarization at 550 nm is within ±10% or less as compared with the initial value (b-2), (b). In the expression (1), H0 indicates transmittance (%) when two polarizing plates are overlapped while absorption axes are matched, and H1 indicates transmittance (%) when two polarizing plates are overlapped while the absorption axes orthogonally cross each other. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long polarizing plate capable of obtaining a polarizing plate with a high yield, a method for producing the long polarizing plate, and a liquid crystal display device using the polarizing plate.

[0002]

2. Description of the Related Art A polarizing plate is a liquid crystal display device (hereinafter, LCD).
With the spread of, the demand is rapidly increasing. In the polarizing plate, a protective film is generally attached to both sides or one side of a polarizing layer having a polarizing ability via an adhesive layer. The material of the polarizing layer is polyvinyl alcohol (hereinafter PVA)
Is mainly used, and a PVA film is uniaxially stretched, and then dyed with iodine or a dichroic dye, or dyeed and then stretched, and further crosslinked with a boron compound to form a polarizing film for a polarizing layer. It is formed.

Recent liquid crystal display devices are not limited to indoors,
The outdoor use is also increasing. For example, a large-sized display intended for street advertising, a liquid crystal display device for a car navigation system, and a mobile medium liquid crystal display device typified by a mobile phone can be cited. However, due to such a change in the use environment, there is a rapid demand for a liquid crystal display device in which the tint does not change even in a high temperature and high humidity environment and the fluctuations in the transmittance and the polarization degree are small. Along with such changes, polarizing plates are required to have small variations in transmittance and hue over the entire display screen even in a hot and humid environment.

In order to solve this problem, some methods have been proposed in which the orientation axis of the polymer is tilted at a desired angle with respect to the film transport method. In Japanese Patent Laid-Open No. 2000-9912, while stretching a plastic film uniaxially in the transverse or longitudinal direction, the left and right of the stretching direction are stretched at different speeds in a longitudinal or transverse direction different from the preceding stretching direction to obtain an orientation axis. It has been proposed to incline with respect to the uniaxial stretching direction. However, in this method, for example, when a tenter system is used, a conveyance speed difference needs to be provided on the left and right sides, and as a result, deviations, wrinkles, and film deviations occur, and a desired tilt angle (45 ° for a polarizing plate) is obtained. Hard to get. If it is attempted to reduce the left-right speed difference, the stretching process must be lengthened, and the equipment cost becomes very large.

Further, in JP-A-3-182701, a plurality of pairs of left and right film holding points forming an angle θ with the running direction are provided at both left and right ends of the continuous film, and each pair of film holding points is formed as the film runs. There has been proposed a method for producing a film having a stretching axis at an arbitrary angle θ with respect to the running direction of the film by a mechanism in which the points can be stretched in the direction of θ. However, even in this method, the film advancing speed changes depending on the left and right of the film, so that the film has cracks and wrinkles, and in order to mitigate the wrinkles, it is necessary to lengthen the stretching process extremely, and there is a drawback that the equipment cost increases. It was

Further, in Japanese Patent Laid-Open No. 2-113920, both ends of the film are gripped between two rows of chucks traveling on a tenter rail arranged so that the traveling distances of the chucks in a predetermined traveling section are different. A manufacturing method has been proposed in which the film is stretched in a direction oblique to the length direction of the film by running the film. However, even in this method, cracks and wrinkles are generated when obliquely crossed, which is inconvenient for an optical film. The conventional stretching method has a problem in that the orientation is not uniform and the degree of polarization as an average value is lowered due to variations in the tension distribution during tenter stretching.

In addition, Korean Laid-Open Publication P2001-0051.
No. 84 proposes a polarizing plate whose transmission axis is inclined by rubbing treatment. It is generally known that the alignment regulation by rubbing is effective only from the film surface up to the nano-order part, and iodine, dichroic dye and other polarizers cannot be sufficiently aligned, resulting in There was a defect that the polarization performance was low. The polarization degree of the polarizing plates produced by the above-mentioned methods other than this was also insufficient.

A conventional method is disclosed in Japanese Patent Laid-Open No. 6-1.
Japanese Patent Publication No. 67611 proposes a liquid crystal display device using a polarizing plate having a small shrinkage rate under high temperature and high humidity conditions. Further, in JP-A-12-035512, zinc addition,
By controlling the degree of PVA polymerization and the degree of PVA saponification, a polarizing plate with little change in transmittance at high temperatures is provided. Further, in JP-A-13-083329, there is described an iodine polarizing film with less deterioration of polarization performance under high temperature and high humidity by defining the pH value of a boric acid-containing aqueous solution, but as an object of improving durability. Was not enough.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to comprise a polarizing film which is obliquely stretched, which makes it possible to improve the yield in a polarizing plate punching process, and to prevent deterioration of the polarizing performance under high temperature and high humidity. It is an object of the present invention to provide a high-performance and inexpensive polarizing plate that is suppressed, that is, has excellent durability, and a method for manufacturing the same. A further object of the present invention is to provide a liquid crystal display device using the above polarizing plate.

[0010]

According to the present invention, a polarizing plate having the following constitution, a method for producing the same, and a liquid crystal display device are provided, and the above object of the present invention is achieved. 1. A long polarizing plate having a polarizing film having a polarizing ability and a protective film on at least one surface, wherein (a) the absorption axis of the polarizing film is neither parallel nor perpendicular to the longitudinal direction, and has a single plate transmittance of 55.
It is 40% or more at 0 nm, and the polarization degree calculated from the following formula (1) is 95% or more at 550 nm or more. (B) After being left in an atmosphere at a temperature of 60 ° C. and a humidity of 90% for 500 hours, (b-1 ) The fluctuation range of the transmittance at 550 nm is within ± 10% of the initial value, and (b-2) 550
A polarizing plate characterized in that the fluctuation range of the degree of polarization in nm is within ± 10% of the initial value. Formula (1): P = [(H0-H1) / (H0 + H1)] ^1/2 × 100 where H0 is the transmittance (%) when two polarizing plates are stacked with their absorption axes aligned, H1 is the transmittance (%) when two polarizing plates are stacked with their absorption axes orthogonal to each other. 2. At least one surface of the polarizing film is protected by a transparent protective film, the inclination angle between the slow axis of the protective film and the absorption axis of the polarizing film is 10 ° or more and less than 90 °, and the fluctuation range of the transmittance is
The polarizing plate according to the above 1, which is within ± 5% of the initial value. 3. The above-mentioned 1 including a step of forming a polarizing film by holding both ends of a polymer film for a polarizing film, which are continuously supplied, by holding means, and applying tension while stretching the holding means while advancing in the longitudinal direction of the film to stretch the film. Or the method for producing a polarizing plate according to 2, further comprising the step of adding a metal salt to the polymer film, wherein the polymer film for a polarizing film has a number average degree of polymerization of 1,000 or more and 1,000 or more.
In the step of forming a polarizing film by using a film of 0 or less and stretching, (i) the locus of the holding means from the substantial holding start point to the substantial holding release point at one end of the polarizing film polymer film. The locus L2 of the holding means from L1 and the other end of the polymer film from the substantial holding start point to the substantial holding release point, and the distance W between the two substantial holding release points satisfy the following formula (2). And (ii) maintaining the supportability of the polymer film, stretching in a state in which the volatile content is 5% or more, and (iii) subsequently shrinking to reduce the volatile content. Production method. Formula (2): | L2-L1 |> 0.4W 4. The method for producing a polarizing plate as described in 3 above, wherein a film of polyvinyl alcohol having a number average degree of polymerization of 2000 or more and 5000 or less is used as the polymer film for the polarizing film. 5. The method for producing a polarizing plate as described in 3 or 4 above, wherein the step of adding the metal salt is performed by immersing the polymer film in a solution containing the metal salt. 6. The metal salt concentration of the solution containing the metal salt is 0.01 to 1
It is 0.0 mass%, The manufacturing method of the polarizing plate of said 5 characterized by the above-mentioned. 7. The method for producing a polarizing plate according to claim 6, wherein the solution containing the metal salt contains 0.04 to 0.5% by mass of zinc. 8. A liquid crystal display device, wherein a polarizing plate punched out from the polarizing plate described in 1 or 2 is used for at least one of the polarizing plates arranged on both sides of a liquid crystal cell.

The polarizing plate of the present invention has excellent durability.
That is, there is little variation in polarization performance under high temperature and high humidity conditions. Moreover, in the present invention, for the first time, a long polarizing plate having a length of 10 m or more and excellent in durability can be prepared in a roll form. As a result, it becomes possible to bond other optical members, for example, a λ / 4 plate with a roll-to-roll, and productivity can be improved. Further, because of the roll form, there is an advantage that it is excellent in packing property and storability. Furthermore, it becomes possible to punch a polarizing plate for a liquid crystal display device from a roll-shaped polarizing plate with a high yield.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention has a polarizing film having a polarizing ability, and usually a protective film (protective film) is provided on both sides or one side of the polarizing film via an adhesive layer. Also, usually, a long polarizing plate (usually roll form) is manufactured,
A practical polarizing plate can be obtained by punching it out according to the application. "Polarizing plate" in the present invention
Is used to mean both a long polarizing plate and the punched polarizing plate unless otherwise specified.

As described above, the polarizing plate of the present invention is a long polarizing plate in which the absorption axis is neither parallel nor perpendicular to the longitudinal direction (hereinafter, such a long polarizing plate is simply referred to as a “diagonally oriented” polarizing plate). Sometimes referred to). The angle formed by the longitudinal direction and the absorption axis direction is preferably 10 ° to less than 90 °, more preferably 20 ° to 70 °, further preferably 40 ° to 50 °,
Particularly preferably, it is 44 to 46 °. Thereby, a single-plate polarizing plate can be obtained with high efficiency in the punching process from a long polarizing plate. In the present invention, the angle formed by the longitudinal direction and the absorption axis direction can be freely set.
Therefore, the optimum angle can be selected even when used in combination with other optical members.

The polarizing plate of the present invention has a single plate transmittance of 5%.
It is characterized in that 40% or more at 50 nm and the polarization degree calculated from the above formula (1) are 95% or more at 550 nm. The single plate transmittance is preferably 40% or more, particularly preferably 43% or more. The polarization degree is preferably 99% or more, more preferably 99.9% or more. In this specification, unless otherwise specified, the transmittance is a single plate transmittance. Since the polarizing plate of the present invention has excellent single-plate transmittance and polarization degree, it is advantageous because it can increase the contrast when used as a liquid crystal display device.

Further, the polarizing plate of the present invention was measured at 550 after being left for 500 hours in an atmosphere of a temperature of 60 ° C. and a humidity of 90%.
The fluctuation range of the transmittance at nm is within ± 10% of the initial value, and the fluctuation range of the polarization degree at 550 nm is within ± 10% of the initial value. As described above, the polarizing plate of the present invention is suppressed in deterioration of polarization performance under high temperature and high humidity, and has excellent durability. Here, the initial value means a value before exposure to a high temperature and high humidity environment.

The obliquely oriented polarizing plate of the present invention can be easily obtained by the method described below. That is, while obtaining the oblique orientation by stretching the polymer film,
It can be obtained by devising the volatile content during stretching of the film, addition of a metal salt to the film, and the degree of polymerization of the polymer constituting the film. Furthermore, it is also preferable to adjust the amount of foreign matter attached to the film before stretching. The stretching method and each important item will be described below.

<Durability> When a liquid crystal display device is used outdoors for a long time, problems such as a decrease or increase in transmittance of a display screen, a change in tint such as discoloration or discoloration, and a deterioration in polarization degree occur. When the polarizing plate is allowed to stand in an atmosphere of a temperature of 60 ° C. and a humidity of 90%, the phenomenon that the support is thermally contracted and the polarizing film and the protective film are deteriorated can be seen, and it can be used as a test for accelerating the deterioration of the polarizing plate. From the viewpoints of heat resistance and wet heat resistance, the polarizing plate of the present invention preferably has a small fluctuation range of the transmittance and the degree of polarization in the deterioration acceleration test. Specifically, place the polarizing plate in an atmosphere of temperature 60 ° C and humidity 90%.
After standing for 00 hours, the fluctuation range of the transmittance is
Within ± 10%, preferably within ± 5%, and more preferably within ± 2%. The fluctuation range of the polarization degree is
Within ± 10% of the initial value, preferably ± 5
%, And more preferably within ± 2%. In order for the polarizing plate of the present invention to have the above durability, the number average degree of polymerization of the polymer film for polarizing film is 100.
0 or more and 10000 or less, preferably 2000 or more and 500
It is possible to use a film made of a polymer of 0 or less and to add a metal salt to the polarizing film. But,
You are not limited to this method.

<Dyeing recipe / method> A polarizing film is obtained by dyeing a polymer film for a polarizing film, such as PVA, and the dyeing step is carried out by gas phase or liquid phase adsorption. As an example of the case of using the liquid phase, when iodine is used as the polarizer, it is carried out by immersing the polymer film for polarizing film in an iodine-potassium iodide aqueous solution. Iodine is 0.1-20
g / l, potassium iodide is preferably 1 to 200 g / l, and the mass ratio of iodine to potassium iodide is preferably 1 to 200. Dyeing time is preferably 10 to 5000 seconds, and liquid temperature is 5 to 60
C is preferred. As a dyeing method, not only dipping but also any means such as application or spraying of iodine or dye solution can be used. The dyeing step may be performed before or after the stretching step of the present invention, but it is particularly preferable to perform dyeing in a liquid phase before the stretching step because the film is appropriately swollen and the stretching is facilitated.

<Polarizer> In addition to iodine, it is also preferable to use a dichroic dye as a polarizer and dye with the dichroic dye. Specific examples of the dichroic dye include, for example, azo dyes,
Examples thereof include stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. Water-soluble compounds are preferable, but not limited thereto. Further, it is preferable that hydrophilic substituents such as sulfonic acid group, amino group and hydroxyl group are introduced into these dichroic molecules. Specific examples of the dichroic molecule include, for example, C.I. Eye. direct. Yellow 12, Sea. Eye. direct. Orange 39, C.I. Eye. direct. Orange 72, C.I. Eye. direct. Red
39, C.I. Eye. direct. Red 79, sea. Eye. direct. Red 81, sea. Eye. direct. Red 83, sea. Eye. direct. Red
89, C. Eye. direct. Violet 4
8, sea. Eye. direct. Blue 67, Sea. Eye. direct. Blue 90, Sea. Eye. direct. Green 59, C.I. Eye. Acid. Red 3
7 and the like, and further, JP-A-62-070802,
JP-A-1-161202, JP-A-1-172906
JP-A-1-172907, JP-A-1-18360
No. 2, JP-A-1-248105, and JP-A 1-22652.
No. 05, JP-A No. 7-261024, and the like. These dichroic molecules are used as free acids, or alkali metal salts, ammonium salts, and salts of amines. By mixing two or more kinds of these dichroic molecules, a polarizer having various hues can be manufactured. As a polarizing element or a polarizing plate, a compound (dye) that exhibits a black color when the polarization axes thereof are orthogonal to each other or a mixture of various dichroic molecules that exhibits a black color is preferable because both the single plate transmittance and the polarization rate are excellent.

Further, a polyene structure is formed by dehydrating PVA or dehydrochlorinating polyvinyl chloride,
The stretching method of the present invention can also be preferably used for producing a so-called polyvinylene-based polarizing film that obtains polarized light by a conjugated double bond.

<Addition of Hardener (Crosslinking Agent) and Metal Salt> The hardener (crosslinking agent) will be described by taking a case where a PVA film is used as a polymer film for a polarizing film as an example. PV
In the process of producing the polarizing film by stretching the A film, PV is used.
It is preferable to use a hardening agent that crosslinks the A film. In particular, when the oblique stretching method of the present invention is used, if the PVA film is not sufficiently hardened at the exit of the stretching step, the orientation of the PVA film may shift due to the tension of the step. It is preferable that the hardening agent (crosslinking agent) is contained in the hardening agent (crosslinking agent) solution by dipping or coating the solution in the step. Hardener (crosslinking agent)
There is no particular limitation on the means for imparting PVA to the PVA film, and any method such as dipping, coating or spraying the film in a liquid can be used, but the dipping method and coating method are particularly preferable. As the coating means, a roll coater, a die coater, a bar coater, a slide coater, a curtain coater, etc.
Any commonly known means can be used. A method in which a cloth, cotton, or a porous material impregnated with the solution is brought into contact with the film is also preferable. As the hardener (crosslinking agent), those described in US Reissue Patent No. 232897 can be used, but boric acid and borax are practically preferably used.

The hardening agent (crosslinking agent) may be applied before or after being bitten in the stretching machine, and the stretching in the width direction is substantially completed, as shown in FIGS. 1 and 2. It may be performed in any step up to the end of the step (b) in the above example.
A washing / water washing step may be provided after adding the hardener (crosslinking agent). Above, PV as a polymer film for polarizing film
Although the case where the A film is used has been described, the above description can be almost applied to the case where another polymer film is used, with a slight change depending on the kind of the polymer.

The present invention is characterized in that the presence of a metal salt in the polarizing film maintains the degree of orientation of the polarizer and obtains a high single plate transmittance. It is considered that this is because the presence of the metal salt stabilizes the higher-order ionic species because the metal ion forms a salt with the polyiodine ion. As the metal used in the present invention, a metal element capable of forming polyvalent ions is preferable, and among them, a metal element belonging to a transition element is particularly preferable. Specific examples include zinc, cobalt, zirconium, iron, nickel, manganese and the like, with zinc being preferred.

To contain zinc, before dyeing, at the time of dyeing,
It can be performed in any step of attaching the polarizing film and the protective film before stretching, after stretching, and after drying. Zinc ions may be added to the dyeing solution or the hardening solution, or another zinc-containing aqueous solution may be prepared and added. Any addition method may be used as long as zinc can be added, such as a dipping method, a coating method, and a spraying method. In order to contain zinc ions, a zinc salt may be dissolved in each aqueous solution. In the present invention, from the viewpoint of ease of production, it is preferable to dissolve zinc salt in the hardening liquid and to add zinc at the same time as the immersion treatment in the hardening liquid. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate. The amount of the zinc salt used may be such that the zinc content in the obtained polarizing film or polarizing plate is the amount specified in the present invention. For example, in the case of dipping and adding, the zinc concentration in the dipping solution, It can be arbitrarily selected depending on the immersion time and the immersion temperature. For example, the immersion time is 60 to 2
When the immersion temperature is 00 seconds and the immersion temperature is 30 to 40 ° C., the amount of zinc chloride used is 0.5 to 15 parts by weight, preferably 0.7 to 5 parts by weight, based on 100 parts of water.

The zinc content of the polarizing film or polarizing plate thus obtained is in the range of 0.04% by mass to 0.5% by mass. If it is less than 0.04% by mass or exceeds 0.5% by mass, the durability under high temperature and high humidity tends to decrease, and the degree of polarization and the single plate transmittance tend to decrease. The zinc content contained in the polarizing film or the polarizing plate is a numerical value showing the weight of zinc contained in 100 parts by weight of the polarizing film in%.

The method of adding the metal salt to the film is not particularly limited, but any of the step of dyeing the polarizer with the film, the step of adding a hardening agent to the film, and the step of laminating the polarizing film and the protective film. It can be performed in one of the steps. Above all, it is preferable to add the metal salt in the step of dyeing the polarizer and / or the step of adding the hardening agent to the film. In a more preferred embodiment, 0.01 to 10.0% by mass of a metal salt is added to both iodine / potassium iodide aqueous solution which is a polarizer aqueous solution and boric acid / potassium iodide aqueous solution which is a hardener aqueous solution. , A method of dyeing a film and adding a hardening agent to the film, and then adding a metal salt thereto. A particularly preferred embodiment is boric acid / water which is an aqueous hardener solution.
The metal salt was added in an amount of 0.01 to 10.
This is a method in which 0 mass% is added, and the metal salt is added together with the operation of adding the hardener.

<Polarizing Film> The polymer film to be stretched in the present invention is not particularly limited, and a film made of an appropriate thermoplastic polymer can be used. Examples of polymers include PVA, polycarbonate, cellulose acylate, polysulfone, and the like.

When used for producing a polarizing film, PVA is preferably used as the polymer. PVA is generally a saponified product of polyvinyl acetate. For example, unsaturated carboxylic acid, unsaturated sulfonic acid, olefins,
A component copolymerizable with vinyl acetate such as vinyl ethers may be contained. Further, a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like can also be used.

The degree of saponification of PVA is not particularly limited,
From the viewpoint of solubility and the like, 80 to 100 mol% is preferable,
90 to 100 mol% is particularly preferable. The degree of polymerization of PVA is not particularly limited, but it is preferably 1000 to 10000, and particularly preferably 1500 to 5000.

If the elastic modulus of the polymer film before stretching is too low, the shrinkage rate after stretching during stretching becomes low, and wrinkles are difficult to disappear. On the other hand, if it is too high, the tension applied during stretching becomes large, and it becomes necessary to increase the strength of the portions holding both ends of the film, which increases the load on the machine. The elastic modulus of the preferable film is 0.1 MP when expressed by Young's modulus.
It is not less than a and not more than 500 MPa, more preferably not less than 1 MPa and not more than 100 MPa.

The thickness of the film before stretching is not particularly limited, but is preferably 1 μm to 1 mm, particularly preferably 20 to 200 μm, from the viewpoint of stability of holding the film and homogeneity of stretching. Further, the film thickness of the polymer film after stretching is preferably 2 to 100 μm, and is 10 for improving light leakage.
-25 μm is preferable.

<Stretching Method> An example of the method of the present invention for obliquely stretching a polymer film is shown in FIGS. 1 and 2 as a schematic plan view. The stretching method of the present invention comprises a step of introducing a raw film shown in (a) in the direction of arrow (a), a width direction stretching step shown in (b), and a stretched film shown in (c) in the next step. That is, the step of sending in the (b) direction is included. Hereinafter, the term "stretching step" refers to the entire steps for carrying out the stretching method of the present invention, including these steps (a) to (c). The film is continuously introduced from the direction of (a), and B1 is attached to the holding means on the left side when viewed from the upstream side.
First held in terms. At this point, one film edge is not held yet, and no tension is generated in the width direction.
That is, the B1 point is the substantial holding start point of the present invention (hereinafter,
It does not correspond to the “substantial holding start point”). In the present invention, the substantial retention start point is defined as the point where both ends of the film are retained for the first time. The substantial holding start point is the holding start point A1 on the more downstream side and the center line 11 of the introduction side film from A1.
(Fig. 1) or 21 (Fig. 2)
It is indicated by two points C1 intersecting the trajectory 13 (FIG. 1) or 23 (FIG. 2) of the holding means on the opposite side. Starting from this point, when the holding means at both ends is conveyed at a substantially constant speed, A1 moves to A2, A3 ... An and C1 similarly moves to C2, C3 ... Cn every unit time. That is, the straight line connecting the points An and Cn through which the holding means serving as the reference passes at the same point is the stretching direction at that time.

In the method of the present invention, as shown in FIGS.
Since n gradually lags behind Cn, the stretching direction is gradually inclined from the direction perpendicular to the transport direction. The substantial holding release point of the present invention (hereinafter referred to as “substantial holding release point”) is a Cx point that is released from the holding means at a more upstream side, and a center line 12 of the film sent from Cx to the next step (FIG. 1). Or 22
A straight line drawn substantially perpendicular to (FIG. 2) is defined by two points Ay intersecting the trajectory 14 (FIG. 1) or 24 (FIG. 2) of the holding means on the opposite side. The final angle in the stretching direction of the film is determined by the stroke difference Ay-Ax (that is, | L1-L2) of the left and right holding means at the end point (substantially holding release point) of the substantial stretching step.
|) And the distance W between the substantial holding release points (distance between Cx and Ay)
And the ratio. Therefore, the inclination angle θ formed by the stretching direction with respect to the conveying direction to the next step is tan θ = W / (Ay−Ax), that is, an angle satisfying tan θ = W / | L1-L2 |. The upper film edge in FIGS. 1 and 2 is held up to 18 (FIG. 1) or 28 (FIG. 2) even after the Ay point, but no new widthwise stretching occurs because the other end is not held. No. 18 and 28 are not the substantial release points of the present invention.

As described above, in the present invention, the substantial holding start points at both ends of the film are not the simple biting points into the left and right holding means. The two substantial holding start points of the present invention are, if the above definition is described more strictly, a film in which a straight line connecting either the left or right holding point and the other holding point is introduced in the step of holding the film. Is substantially orthogonal to the centerline of the, and these two holding points are defined as the most upstream positions. Similarly,
In the present invention, the two substantial holding release points, a straight line connecting either the left or right holding point and the other holding point is a point substantially orthogonal to the center line of the film sent to the next step,
Moreover, these two holding points are defined as being located at the most downstream. Here, “substantially orthogonal” means that the straight line connecting the center line of the film and the left and right substantial holding start points or substantial holding release points is 90 ± 0.5 °.

When an attempt is made to make a difference in left and right strokes using a tenter type stretching machine as in the present invention, due to mechanical restrictions such as rail length, the biting point into the holding means and the actual holding start point are often set. Although a large deviation may occur or a large deviation may occur between the detachment point from the holding means and the substantial holding release point, the process between the substantial holding start point and the substantial holding release point defined above is the relationship of the above equation (2). The object of the present invention is achieved if the following are satisfied.

In the above, the inclination angle of the orientation axis in the obtained stretched film is controlled and adjusted by the ratio of the exit width W in the step (c) and the stroke difference | L1-L2 | of the two left and right holding means. can do. For polarizing plates and retardation films, films oriented at 45 ° with respect to the longitudinal direction are often required. In this case, in order to obtain an orientation angle close to 45 °, it is preferable that the following formula (3) is satisfied, and the formula (3): 0.9W <| L1-L2 | <1.1W is more preferable. It is preferable to satisfy 4). Formula (4): 0.97W <| L1-L2 | <1.03W

The concrete structure of the stretching step is represented by the above formula (2).
As long as the above conditions are satisfied, as shown in FIGS. 1 to 6, it can be arbitrarily designed in consideration of equipment cost and productivity.

The film introduction direction (a) into the stretching step,
The angle formed by the film transport direction (b) to the next step can be any value, but from the viewpoint of minimizing the total installation area of equipment including the steps before and after stretching, this angle should be smaller. It is preferably within 3 °, more preferably within 0.5 °. For example, with the structure illustrated in FIGS. 1 and 4,
This value can be achieved. In such a method in which the film advancing direction does not substantially change, it is difficult to obtain an orientation angle of 45 ° with respect to the longitudinal direction, which is preferable as a polarizing plate or a retardation film, only by increasing the width of the holding means. .
Therefore, as shown in FIG. 1, | L1-L2 | can be increased by providing a step of once stretching and then contracting. The stretch ratio is preferably 1.1 to 10.0 times, more preferably 2 to 10 times, and the shrinkage ratio thereafter is preferably 10% or more. Further, as shown in FIG. 4, it is also preferable to repeat stretching and shrinking a plurality of times because | L1-L2 | can be increased.

From the viewpoint of minimizing the equipment cost of the stretching process, the smaller the number of bendings and the bending angle of the locus of the holding means, the better. From this point of view, as shown in FIGS. 2, 3 and 5, the angle between the film advancing direction at the exit of the step of holding both ends of the film and the substantial stretching direction of the film is inclined by 20 to 70 °. It is preferable to bend the film in a state where both ends of the film are held in the traveling direction.

In the present invention, as an apparatus for stretching the film by applying tension while holding both ends, so-called FIG.
A tenter device such as that of FIG. 5 is preferred. In addition to the conventional two-dimensional tenter, it is also possible to use a stretching step in which the gripping means at both ends is spirally provided with a path difference as shown in FIG.

In the case of a tenter type stretching machine, there are many structures in which a chain to which a clip is fixed advances along a rail.
When the stretching method is uneven as shown in FIGS. 1 and 2, as a result of the present invention, as shown in FIGS. 1 and 2, the rail ends are displaced at the process entrance and exit, and the left and right sides are not simultaneously bitten and disengaged. is there. In this case, the actual process lengths L1 and L2 are not the simple distance between the bite and the disengagement as described above, but as described above, the stroke of the portion where the holding means holds both ends of the film. Be long.

If there is a difference in the advancing speed on the left and right of the film at the exit of the stretching process, wrinkles and deviations occur at the exit of the stretching process. Therefore, the difference in transport speed between the left and right film gripping means is substantially the same. Desired. The speed difference is preferably 1% or less, more preferably less than 0.5%, most preferably less than 0.05%. The speed described here is the length of the trajectory of the left and right holding means per minute. In a typical tenter stretching machine, etc., there are speed irregularities that occur on the order of seconds or less depending on the cycle of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. It does not correspond to the speed difference described in the invention.

<Shrinking: Shrinkage During Stretching and After Stretching> The stretched polymer film may be shrunk at any step during and after stretching. Shrinkage should be such that wrinkles in the polymer film that occur when oriented in an oblique direction are eliminated,
Examples of means for shrinking the film include a method of removing volatile matter by applying temperature, but any means may be used as long as the film shrinks. A preferable shrinkage ratio of the film is that it shrinks by 1 / sin θ or more using the orientation angle θ with respect to the longitudinal direction.

<Volatile Content> In the stretching step, as the difference between the left and right strokes occurs, the film becomes wrinkled and deviated. In order to solve this problem, in the present invention, the polymer film is stretched while maintaining the supportability and allowing the polymer film to have a volatile content of 5% or more. At this time, the volatile content may always be maintained at 5% or more during the stretching operation, or the volatile content may be 5% only in a part of the stretching operation.
% Or more may be maintained. In the latter case, it is preferable that the stretching start point is a starting point, and the stretch ratio is 1% or more and less than 40%, and the volatile content is 5% or more. In any case, it is more preferable to allow the volatile content to be 5% or more before the stretching. The volatile content in the present invention represents the volume of the volatile component contained per unit volume of the film, and is the value (%) obtained by dividing the volatile component volume by the film volume. In the present invention, it is preferable to provide at least one step of incorporating a volatile component before stretching the polymer film for polarizing plate. The step of containing a volatile component is performed by casting a film to contain a solvent, water, etc., dipping in a solvent, water, etc., coating, spraying, and the like. The dyeing step or the hardener adding step described in the section of <Dyeing prescription, dyeing method>, <Hardening agent (crosslinking agent), addition of metal salt> may also serve as a step of incorporating volatile matter. When the dyeing step also serves, it is preferable to provide the hardening agent adding step before stretching. When the hardener addition step also serves, the dyeing step may be provided either before or after stretching. In addition, the dyeing step and the stretching step may be performed at the same time before the stretching.

The preferred volatile content depends on the type of polymer film. The maximum volatile content is possible as long as the support of the polymer film is maintained. For polyvinyl alcohol, the volatile content is preferably 10% to 100%.
Cellulose acylate is preferably 10% to 200%.

<Distribution Distribution of Volatile Components> When a long-sized, particularly roll-shaped polarizing plate is produced in an integrated process, it is necessary that there be no unevenness in dyeing or omission. If there is uneven distribution of the volatile components in the film before stretching (difference in the amount of volatile components depending on the location in the film surface), uneven dyeing and loss may occur. Therefore, the content distribution of the volatile component in the film before stretching is preferably small, and is preferably at least 5% or less. The content distribution of the volatile component means the fluctuation range per 1 m ^{2 of the} volatile content defined above (the ratio of the larger difference between the maximum value or the minimum value and the average volatile content to the average volatile content). ) Represents. As a method for reducing the content distribution of volatile components, there are methods such as blowing the front and back surfaces of the film with uniform air, squeezing uniformly with a nip roller, and wiping with a wiper (blade, sponge wiping, etc.). Any method may be used as long as the distribution becomes uniform. 10 to 12 show an example of an air blow device, a nip device, and a blade device.

<Distance from Wrinkle Generation to Disappearance> The wrinkle of the polymer film generated when the film is oriented in an oblique direction has only to disappear until the substantial holding release point in the present invention. However, if it takes time from the generation of wrinkles to the disappearance of the wrinkles, variations in the stretching direction may occur, and it is preferable that the wrinkles disappear at a transition distance as short as possible from the point where the wrinkles occur. For this purpose, there is a method of increasing the volatilization rate of the volatile content.

<Drying: Drying Speed, Drying Point> Any drying condition may be used as long as the generated wrinkles disappear. Preferably, after the desired orientation angle is obtained, it is preferable to adjust so that the drying point comes at the shortest moving distance. From this, it is preferable that the drying rate is as high as possible.

<Drying temperature> The drying conditions may be any as long as the generated wrinkles disappear, but it depends on the film to be stretched. When a polarizing plate is prepared using a polyvinyl alcohol film, the temperature is preferably 20 ° C or higher and 100 ° C or lower, more preferably 40 ° C or higher and 9 ° C or higher.
It is 0 ° C or lower.

<Swelling ratio> In the present invention, when the polymer film is polyvinyl alcohol and a hardening agent is used, in order to keep the stretched state in an oblique direction without relaxation,
It is preferable that the swelling ratio in water is different before and after stretching.
Specifically, it is preferable that the swelling rate before stretching is high and the swelling rate after stretching / drying is low. More preferably, the swelling ratio in water before stretching is 3% or more, and the swelling ratio after drying is preferably 3% or less.

<Refraction Part> In the present invention, a rail that regulates the locus of the holding means is often required to have a large bending rate.
For the purpose of avoiding interference between film gripping means due to abrupt bending or local stress concentration, it is desirable that the trajectory of the gripping means draws an arc at the bent portion.

<Stretching speed> The speed for stretching the film is
Expressed as a draw ratio per unit time, 1.1 times / min or more,
It is preferably 2 times / minute or more, and the earlier is preferable. In addition, the traveling speed in the longitudinal direction is 0.1 m / min or more, preferably 1 m / min or more, and the higher speed is preferable from the viewpoint of productivity. In either case, the upper limit depends on the film to be stretched and the stretching machine.

<Foreign matter> In the present invention, if foreign matter adheres to the polymer film before stretching, the surface becomes rough, so it is preferable to remove the foreign matter. The presence of foreign matter causes color unevenness and optical unevenness, especially when a polarizing plate is manufactured. It is also important that no foreign matter adheres before the protective film is attached, and it is preferable to manufacture in an environment where floating dust is minimized. The amount of foreign matter in the present invention is a value obtained by dividing the mass of foreign matter attached to the film surface by the surface area, and represents the number of grams per square meter. The amount of foreign matter is preferably 1 g / m ² or less, more preferably 0.5 g / m ² or less, and the smaller the amount, the more preferable.

The method of removing foreign matter is not particularly limited,
Without adversely affecting the polymer film before stretching,
Any method may be used as long as the foreign matter can be removed. For example, a method of scraping off a foreign object by blowing a water stream, a method of scraping off a foreign object by jetting a gas, a cloth,
A method of scraping off a foreign substance by using a blade such as rubber may be used.

<Tension in the longitudinal direction> In the present invention, when both ends of the film are held by the holding means, it is preferable that the film is stretched so as to be easily held. Specifically, a method of applying tension in the longitudinal direction to stretch the film may be used. The tension varies depending on the state of the film before stretching, but it is preferable that the tension does not sag.

<Temperature at Stretching> The environmental temperature at the time of stretching the film may be at least the freezing point of the volatile components contained in the film. When the film is a PVA alcohol film, the temperature is preferably 25 ° C or higher. When stretching PVA soaked with iodine and boric acid for producing a polarizing film, the temperature is preferably 25 ° C or higher and 90 ° C or lower.

<Humidity during Stretching> When a film having a volatile content of water, such as polyvinyl alcohol or cellulose acylate, is stretched, it may be stretched in a humidity controlled atmosphere. In the case of polyvinyl alcohol, 50% or more is preferable, 80% or more is more preferable, and 90 is more preferable.
% Or more.

<Protective Film> On the polarizing film of the present invention, protective films are attached on both sides or one side. The type of the protective film is not particularly limited, and cellulose acylates such as cellulose acetate and cellulose acetate butyrate, polycarbonate, polyolefin, polystyrene, polyester and the like can be used. Physical properties such as transparency, appropriate moisture permeability, low birefringence, and appropriate rigidity are required for the protective film of the polarizing plate, and synthetically, cellulose acylates are preferable, and cellulose acetate is particularly preferable.

The physical properties of the protective film can be set to any values depending on the application, but typical preferred values for use in ordinary reflective LCDs are shown below. The film thickness is preferably 5 to 500 μm from the viewpoint of handleability and durability, and 20 to 200 μm.
m is more preferable, and 20 to 100 μm is particularly preferable.
For the purpose of improving light leakage, it is preferably 30 to 75 μm. Generally, the retardation of the protective film is preferably low, but when the absorption axis of the polarizing film and the slow axis of the protective film are not parallel as in the present invention, the retardation value of the protective film is particularly a certain value or more. Then, since the polarization axis and the alignment axis (slow axis) of the protective film are obliquely displaced, linearly polarized light is changed to elliptically polarized light, which is not preferable. Therefore, the retardation of the protective film is preferably 10 nm or less at 632.8 nm, more preferably 5 nm or less. From the viewpoint of such low retardation, the polymer used as the protective film is particularly preferably cellulose triacetate. Further, polyolefins such as ZEONEX, ZEONOR (both manufactured by Zeon Corporation) and ARTON (manufactured by JSR Corporation) are also preferably used. In addition, for example, JP-A-8-110402 or JP-A-11-29311
Non-birefringent optical resin materials such as those described in No. 6 are mentioned.

The visible light transmittance is preferably 60% or more,
90% or more is particularly preferable. The dimensional reduction after treatment at 90 ° C. for 120 hours is preferably 0.3 to 0.01%, particularly preferably 0.15 to 0.01%.
The tensile strength value by the tensile test of the film is 50 to 10
00 MPa is preferable, and 100 to 300 MPa is particularly preferable. The water vapor transmission rate of the film is 100 to 800 g / m ^2.
・ Day is preferable, 300 to 600 g / m ² · day
Is particularly preferable. Of course, the application of the present invention is not limited to the above values.

Details of cellulose acylate preferable as a protective film are shown below. A preferred cellulose acylate is one in which the degree of substitution of cellulose with hydroxyl groups satisfies all of the following formulas (I) to (IV).

(I) 2.6 ≦ A + B ≦ 3.0 (II) 2.0 ≦ A ≦ 3.0 (III) 0 ≦ B ≦ 0.8 (IV) 1.9 <A-B

Here, A and B in the formula represent the substituents of the acyl group substituted by the hydroxyl group of cellulose, A is the degree of substitution of the acetyl group, and B is the substitution of the acyl group having 3 to 5 carbon atoms. It is degree. Cellulose has 3 in 1 glucose unit
There is one hydroxyl group, and the above number represents the degree of substitution for the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a degree of substitution of A of 2.6 or more and 3.0 or less (in this case, the maximum number of unsubstituted hydroxyl groups is 0.4), and B = 0 is cellulose triacetate. Cellulose acylate used as a protective film for a polarizing plate includes cellulose triacetate in which all acyl groups are acetyl groups, and 2.0 in acetyl groups.
As described above, the acyl group having 3 to 5 carbon atoms is 0.8 or less,
It is preferable that the non-substituted hydroxyl group is 0.4 or less. In the case of an acyl group having 3 to 5 carbon atoms, 0.3 or less is particularly preferable from the viewpoint of physical properties. The degree of substitution is obtained by measuring the degree of bonding of acetic acid and fatty acids having 3 to 5 carbon atoms, which substitute for the hydroxyl groups of cellulose. The measuring method can be carried out according to ASTM D-817-91.

Other acyl groups having 3 to 5 carbon atoms other than acetyl group are propionyl group (C ₂ H ₅ CO-), butyryl group (C ₃ H ₇ CO-) (n-, iso-), valeryl group ( C
₄ H ₉ CO-) (n-, iso-, sec-, tert
-), Among these, n-substituted ones are preferable in terms of mechanical strength when formed into a film, ease of dissolution, etc., and particularly n-
A propionyl group is preferred. Further, if the substitution degree of the acetyl group is low, mechanical strength and resistance to moist heat are deteriorated. When the substitution degree of the acyl group having 3 to 5 carbon atoms is high, the solubility in the organic solvent is improved, but when the substitution degree is within the above range, good physical properties are exhibited.

The degree of polymerization (viscosity average) of the cellulose acylate is preferably 200 to 700, and particularly 250 to 550.
Are preferred. The viscosity average degree of polymerization can be measured with an Ostwald viscometer, and is calculated from the measured intrinsic viscosity [η] of cellulose acylate by the following formula. DP = [η] / Km (where DP is the viscosity average degree of polymerization,
Km is a constant 6 × 10 ^-4 )

Cellulose acylate raw materials include, for example, cotton linter and wood pulp. Cellulose acylate obtained from any raw material cellulose can be used, or a mixture thereof can be used.

The above-mentioned cellulose acylate is usually produced by a solvent casting method. The solvent cast method is to prepare a concentrated solution (hereinafter referred to as a dope) by dissolving cellulose acylate and various additives in a solvent,
This is cast on an endless support such as a drum or band, and the solvent is evaporated to form a film.
The concentration of the dope is preferably adjusted so that the solid content is 10 to 40% by weight. The surface of the drum or band is preferably mirror-finished. Regarding the casting and drying methods in the solvent cast method, US Pat. Nos. 2,336,310 and 2,367,603,
No. 2492078, No. 2492977, No. 2492
No. 978, No. 2607704, No. 2739069,
No. 2739070, British Patent No. 640731, and No. 73.
6892, Japanese Patent Publications 45-4554 and 4
9-5614, JP-A-60-176834, 60
-203430 and 62-115035.

A method of casting two or more layers of dope is also preferably used. In the case of casting a plurality of dopes, a film may be produced by casting and laminating a solution containing a dope from a plurality of casting ports provided at intervals in the traveling direction of a support, for example, Kaisho 61-158414
No. 1,122,419 and No. 11-1982.
The method described in No. 85, etc. can be applied. Further, the cellulose acylate solution may be cast from two casting ports to form a film.
0-27562, JP-A-61-94724, JP-A-61-942245, JP-A-61-104813,
JP-A-61-158413, JP-A-6-134933
No., can be carried out. In addition, JP-A-56-1
A casting method described in No. 62617, in which a high-viscosity dope flow is wrapped with a low-viscosity dope and the high- and low-viscosity dopes are simultaneously extruded, is also preferably used.

Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg, benzene, toluene), halogenated hydrocarbons (eg, methylene chloride, chlorobenzene), alcohols (eg, methanol, ethanol, diethylene glycol), Examples thereof include ketones (eg, acetone), esters (eg, ethyl acetate, propyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve) and the like. Halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peelability from a support, mechanical strength of a film, optical properties, etc., in addition to methylene chloride, it has 1 carbon atom.
It is preferable to mix one to several kinds of alcohols (5) to (5). The content of alcohol is 2 to the whole solvent.
25 wt% is preferable, and 5 to 20 wt% is more preferable. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n
-Butanol or mixtures thereof are preferably used.

In addition to cellulose acylate, the components that become solid after drying include a plasticizer, a UV absorber, inorganic fine particles, a heat stabilizer such as a salt of an alkaline earth metal such as calcium and magnesium, and a charge. It may optionally contain an inhibitor, a flame retardant, a lubricant, an oil agent, a release accelerator from the support, a hydrolysis inhibitor of cellulose acylate, and the like.

As the plasticizer preferably added, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TC).
P), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like. Typical carboxylic acid esters are phthalic acid esters and citric acid esters. Examples of phthalates include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DO).
P), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate. Examples of other carboxylic acid esters include trimellitic acid esters such as butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate, and the like.

Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, It is preferable to use diethylhexyl phthalate, triacetin, ethylphthalylethyl glycolate, trimethyl trimellitate and the like. In particular, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethylphthalyl ethyl glycolate and trimethyl trimellitate are preferable. These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 5 to 30% by weight, and particularly preferably 8 to 16% by weight or less with respect to the cellulose acylate. These compounds may be added together with the cellulose acylate or the solvent when preparing the cellulose acylate solution, or may be added during or after the solution preparation.

As the ultraviolet absorber, any kind can be selected according to the purpose, and a salicylate-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex salt-based absorbent or the like is used. However, benzophenone type, benzotriazole type, and salicylic acid ester type are preferable. Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2'-di-hydroxy-4,4 '
-Methoxybenzophenone, 2-hydroxy-4-n-
Octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2
-Hydroxy-3-methacryloxy) propoxybenzophenone and the like can be mentioned. As a benzotriazole-based ultraviolet absorber, 2 (2′-hydroxy-3 ′)
-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5 '
-Tert-butylphenyl) benzotriazole, 2
(2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2 (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5
-Chlorobenzotriazole, 2 (2'-hydroxy-
5'-tert-octylphenyl) benzotriazole and the like can be mentioned. Examples of salicylic acid ester include phenyl salicylate, p-octylphenyl salicylate, p-tert-butylphenyl salicylate and the like. Among these exemplified ultraviolet absorbers, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-) are particularly preferable.
tert-Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-
tert-butylphenyl) benzotriazole, 2
(2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2 (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5
-Chlorobenzotriazole is particularly preferred.

It is particularly preferable to use a plurality of absorbents having different absorption wavelengths in combination, because a high blocking effect can be obtained in a wide wavelength range. The amount of the ultraviolet absorber is preferably 0.01 to 5% by weight with respect to the cellulose acylate,
1-3% by weight is particularly preferred. The ultraviolet absorber may be added at the same time when the cellulose acylate is dissolved, or may be added to the dope after the dissolution. Particularly, it is preferable to use a static mixer or the like and add the ultraviolet absorbent solution to the dope immediately before casting.

The inorganic fine particles added to the cellulose acylate include silica, kaolin, talc, diatomaceous earth,
Quartz, calcium carbonate, barium sulfate, titanium oxide, alumina, etc. can be arbitrarily used according to the purpose.
Before adding these fine particles to the dope, use a high speed mixer,
It is preferable to perform dispersion in the binder solution by any means such as a ball mill, an attritor, an ultrasonic disperser or the like. Cellulose acylate is preferable as the binder. It is also preferable to carry out dispersion with other additives such as an ultraviolet absorber. Although the dispersion solvent is arbitrary, it is preferable that the composition be similar to that of the dope solvent. The number average particle diameter of dispersed particles is 0.0
1 to 100 μm is preferable, and 0.1 to 10 μm is particularly preferable. The above dispersion may be added to the cellulose acylate dissolution step at the same time or may be added to the dope at any step, but it is preferable to add it just before casting using a static mixer or the like like an ultraviolet absorber.

As the release accelerator from the support, a surfactant is effective, and phosphoric acid type, sulfonic acid type, carboxylic acid type, nonionic type and cationic type are not particularly limited.
These are described, for example, in JP-A-61-243837.

When the above-mentioned cellulose acylate film is used as a protective film, in order to enhance the adhesion with the PVA type resin, the film surface is made hydrophilic by means such as saponification, corona treatment, flame treatment, glow discharge treatment and the like. It is preferable to add. Further, the hydrophilic resin may be dispersed in a solvent having an affinity for cellulose acylate and applied in a thin layer. Among the above means, saponification treatment is particularly preferable because the flatness and physical properties of the film are not impaired. The saponification treatment is performed by immersing the film in an aqueous alkaline solution such as caustic soda. After the treatment, in order to remove excess alkali, it is preferable to neutralize with a low-concentration acid and sufficiently wash with water.

On the surface of the protective film of the polarizing plate of the present invention, in addition to the reflective polarizer, LCDs described in, for example, JP-A-4-229828, JP-A-6-75115 and JP-A-8-50206. Optical anisotropic layer for viewing angle compensation of
Anti-glare layer or anti-reflection layer for improving visibility of display, hard coat layer for enhancing scratch resistance of polarizing plate, gas barrier layer for suppressing diffusion of moisture and oxygen, adhesion to polarizing film or adhesive, adhesive It is possible to provide any functional layer such as an easy-adhesion layer for enhancing strength and a layer for imparting slipperiness.
The functional layer may be provided on the polarizing film side or the surface opposite to the polarizing film, and can be appropriately selected depending on the purpose.

As the polarizing plate protective film, one or a plurality of the preferable protective films described above can be laminated and used. The same protective film may be attached to both sides of the polarizing film,
Protective films having different functions and physical properties may be attached to both surfaces. Further, since the protective film is attached only on one surface and the liquid crystal cell is directly attached on the opposite surface, it is possible to directly provide an adhesive layer and not attach the protective film. In this case, it is preferable to provide a peelable separator film on the outside of the adhesive.

It is preferable that the protective film, which is usually supplied in the form of a roll, is continuously bonded to a long polarizing plate so that the longitudinal directions thereof coincide with each other. Here, the orientation axis (slow axis) of the protective film may be in any direction, but it is preferable that the orientation axis of the protective film is parallel to the longitudinal direction from the viewpoint of easy operation.

<Adhesive> The adhesive between the polarizing film and the protective layer is not particularly limited, but a PVA resin (acetoacetyl group,
(Including modified PVA having a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc.), an aqueous solution of a boron compound, or the like, among which PVA resin is preferable. You may add and use a boron compound, a potassium iodide aqueous solution, etc. to PVA resin. The thickness of the adhesive layer after drying is preferably 0.01 to 10 μm, particularly preferably 0.05 to 5 μm.

<Consistent Step> In the present invention, there is a drying step in which the polymer film for a polarizing film is stretched and then contracted to reduce the volatile content, and after the drying or during the drying, a protective film is attached to at least one side. It is preferable to have a post-heating step. As a concrete sticking method, during the drying step, the protective film is stuck to the film with an adhesive while holding both ends, and then both ends are eared, or after drying, the film is released from both end holding parts. Alternatively, there is a method of cutting off both ends of the film and then attaching a protective film. As a method of cutting the edges, a general technique such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After the bonding, it is preferable to heat the adhesive for drying and improving the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° C or higher, more preferably 40 ° C or higher and 100 ° C or lower, and further preferably 50 ° C or higher and 80 ° C or lower. It is more preferable in terms of performance and production efficiency that these steps are performed on a consistent production line.

<Adhesive Layer> The adhesive layer of the present invention is not only optically transparent, but also exhibits appropriate viscoelasticity and adhesive properties. Examples of the adhesive layer in the present invention include acrylic copolymers, epoxy resins, polyurethanes,
Silicone polymer, polyether, butyral resin, polyamide resin, polyvinyl alcohol resin,
A polymer such as an adhesive or a pressure-sensitive adhesive such as a synthetic rubber can be used to form a film and cure by a drying method, a chemical curing method, a heat curing method, a heat melting method, a light curing method or the like.
Among them, the acrylic copolymer is most preferably used because it is most easy to control the adhesive property and is excellent in transparency, weather resistance and durability.

<Punching> FIG. 7 shows an example of conventional polarizing plate punching, and FIG. 8 shows an example of punching the polarizing plate of the present invention.
In the conventional polarizing plate, as shown in FIG. 7, the absorption axis 71 of the polarized light, that is, the stretching axis coincides with the longitudinal direction 72, whereas the polarizing plate of the present invention, as shown in FIG. The absorption axis 81 of the polarized light, that is, the stretching axis is 4 with respect to the longitudinal direction 82.
It is inclined by 5 °, and this angle corresponds to the angle formed by the absorption axis of the polarizing plate when it is attached to the liquid crystal cell in the LCD and the vertical or horizontal direction of the liquid crystal cell itself. No punching is required. Moreover, as can be seen from FIG. 8, the polarizing plate of the present invention can be manufactured by slitting along the longitudinal direction without punching because the cutting is straight along the longitudinal direction.
Productivity is also outstanding.

<Uses> The polarizing plate of the present invention can be used for various purposes. However, due to the characteristic that the alignment axis is inclined with respect to the longitudinal direction, in particular, the inclination angle of the alignment axis is 40 to 40 with respect to the longitudinal direction.
The polarizing film at 50 ° is a polarizing plate for LCD (for example, TN,
STN, OCB, ROCB, ECB, CPA, IPS,
(In all liquid crystal modes such as VA), it is preferably used for an antireflection circular polarizing plate of an organic EL display. It is also suitable when used in combination with various optical members such as retardation films such as λ / 4 plate and λ / 2 plate, viewing angle widening film, antiglare film, hard coat film and the like.

[0086]

EXAMPLES In order to explain the present invention in detail, examples will be given below, but the present invention is not limited thereto.

Example 1 <Preparation of Polarizing Plate> A PVA film having a number average degree of polymerization of 1700 was used in an amount of 1.0 g / l iodine and 60.0 g / potassium iodide.
After immersing in an aqueous solution of 1 for 90 seconds at 40 ° C. and further dipping in an aqueous solution of boric acid 40 g / l and potassium iodide 30.0 g / l containing 1.0% by mass of iron chloride at 40 ° C. for 120 seconds. Then, it was introduced into the tenter stretching machine of the form shown in FIG. 1, once stretched to 7.0 times and then shrunk to 5.3 times, thereafter the width was kept constant, dried at 60 ° C., and then removed from the tenter. The water content (volatile content) of the PVA film before the start of stretching is 31.
%, The water content after drying was 1.5%. The difference in transport speed between the left and right tenter clips is less than 0.05%,
The angle formed by the center line of the film introduced and the center line of the film sent to the next step was 0 °. Where | L1-
L2 | is 0.7 m, W is 0.7 m, and | L1-L2
| = W. The substantial stretching direction Ax-Cx at the exit of the tenter was inclined by 45 ° with respect to the center line 22 of the film sent to the next step. Wrinkles and film deformation at the tenter exit were not observed. Furthermore, PV
Fuji Fuji Film (cellulose triacetate, retardation value 3.0 nm) manufactured by Fuji Photo Film Co., Ltd., which was saponified with an aqueous solution containing 3% of A (PVA-117H manufactured by Kuraray Co., Ltd.) and 4% of potassium iodide. The pieces were stuck together and further dried at 80 ° C. to obtain a polarizing plate having an effective width of 650 mm. The absorption axis of the obtained polarizing plate was inclined at 45 ° with respect to the longitudinal direction, and the slow axis of Fujitac was also at 45 °.
It was inclined. The transmittance of this polarizing plate at 550 nm was 42.9%, and the polarization degree was 99.89%. Further, when it was cut into a size of 310 × 233 mm as shown in FIG. 8, a polarizing plate having an absorption axis inclined by 45 ° with respect to the side could be obtained with an area efficiency of 91.5%.

The fluctuation range of the single plate transmittance in the heat resistance and humidity heat resistance test of the obtained polarizing plate was 9.2%, and the fluctuation range of the polarization degree was 8.3%.

<Evaluation of Moisture and Heat Resistance> (Exposure to high humidity and high temperature) Yamato Scientific Co., Ltd. constant temperature and humidity machine (I
G-42M), the polarizing plate was allowed to stand for 500 hours in an atmosphere of a temperature of 60 ° C. and a humidity of 90% to obtain a measurement sample. (Transmissivity fluctuation range) Shimadzu self-recording spectrophotometer UV2100
Then, the transmittance at 550 nm was measured, and the fluctuation range was calculated according to the following formula. Variation range of transmittance (%) = (| T ₁ −T ₀ | / T ₀ ) × 10
0 Here, T ₁ is the transmittance of the sample exposed to high humidity and high temperature, and T ₀ is the transmittance before the exposure. (Fluctuation range of the degree of polarization) The transmittance at 550 nm was measured with a Shimadzu spectrophotometer UV2100, and the formula (1) was used.
The degree of polarization P (%) was obtained in accordance with the above, and the fluctuation range was calculated by the following formula. Polarization degree fluctuation range (%) = (| P ₁ −P ₀ | / P ₀ ) × 10
0 Here, P ₁ is the polarization degree of the sample exposed to high humidity and high temperature, and P ₀ is the polarization degree before the exposure.

<Evaluation of heat resistance> (Exposure to high temperature) A polarizing plate was left in a Shimadzu Dry thermostat (DN63) at a temperature of 80 ° C. and a humidity of 30% RH for 500 hours to prepare a measurement sample. (Evaluation of fluctuation range of transmittance and fluctuation range of polarization degree) The fluctuation range of transmittance and the fluctuation range of polarization degree were evaluated in the same manner as in <Evaluation of moist heat resistance>.

Example 2 <Preparation of Polarizing Plate> A PVA film having a number average degree of polymerization of 1700 was used in an amount of 1.0 g / l iodine and 60.0 g / potassium iodide.
After dipping in an aqueous solution of 1 l for 90 seconds at 40 ° C., and further dipping in an aqueous solution of boric acid 40 g / l and potassium iodide 30.0 g / l to which zinc chloride was added at a concentration of 1.0% by mass for 120 seconds at 40 ° C. 1 was introduced into the tenter stretching machine of the form shown in FIG.
The film was once stretched twice and then shrunk to 5.3 times, then kept constant in width, dried at 60 ° C., and then separated from the tenter.
The water content (volatile content) of the PVA film before the start of stretching was 31%, and the water content after drying was 1.5%. Also,
As a result of elemental analysis, the zinc content was 0.2% by mass.
The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the film introduced and the center line of the film sent to the next step was 0 °. Here, | L1-L2 | is 0.7 m, W is 0.7 m, and |
There was a relationship of L1-L2 | = W. Wrinkles and film deformation at the tenter exit were not observed. Furthermore, P
Fujitac (cellulose triacetate, retardation value 3.0 nm) manufactured by Fuji Photo Film Co., Ltd., which was saponified with an aqueous solution containing 3% VA (PVA-117H manufactured by Kuraray Co., Ltd.) and 4% potassium iodide. Laminated and dried at 80 ℃, effective width 650mm
To obtain a polarizing plate. . The absorption axis direction of the obtained polarizing plate was inclined at 45 ° with respect to the longitudinal direction, and the slow axis of Fujitak was 4
It was tilted 5 °. The transmittance of this polarizing plate at 550 nm was 43.0%, and the polarization degree was 99.95%.

The fluctuation range of the single plate transmittance in the heat resistance and humidity heat resistance test of the obtained polarizing plate was 2.4%, and the fluctuation range of the polarization degree was 1.2%.

Example 3 <Preparation of Polarizing Plate> A PVA film having a number average degree of polymerization of 2400 was used in an amount of 1.0 g of iodine and 60.0 g of potassium iodide.
After dipping in an aqueous solution of 1 l for 90 seconds at 40 ° C., and further dipping in an aqueous solution of boric acid 40 g / l and potassium iodide 30.0 g / l to which zinc chloride was added at a concentration of 1.0% by mass for 120 seconds at 40 ° C. 1 was introduced into the tenter stretching machine of the form shown in FIG.
The film was once stretched twice and then shrunk to 5.3 times, then kept constant in width, dried at 60 ° C., and then separated from the tenter.
The water content (volatile content) of the PVA film before the start of stretching was 31%, and the water content after drying was 1.5%. Also,
As a result of elemental analysis, the zinc content was 0.2% by mass.
The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the film introduced and the center line of the film sent to the next step was 0 °. Here, | L1-L2 | is 0.7 m, W is 0.7 m, and |
There was a relationship of L1-L2 | = W. Wrinkles and film deformation at the tenter exit were not observed. Furthermore, P
Fujitac (cellulose triacetate, retardation value 3.0 nm) manufactured by Fuji Photo Film Co., Ltd., which was saponified with an aqueous solution containing 3% VA (PVA-117H manufactured by Kuraray Co., Ltd.) and 4% potassium iodide. Laminated and dried at 80 ℃, effective width 650mm
To obtain a polarizing plate. The absorption axis direction of the obtained polarizing plate was inclined at 45 ° with respect to the longitudinal direction, and the slow axis of Fujitak was 45 degrees.
It was inclined. The transmittance of this polarizing plate at 550 nm was 43.2%, and the polarization degree was 99.74%.

The fluctuation range of the single-plate transmittance of the obtained polarizing plate before and after the heat resistance and humidity heat resistance tests was 0.8%, and the fluctuation range of the polarization degree was 0.3%.

Example 4 <Preparation of Liquid Crystal Display Device> Next, as shown in FIG. 9, two polarizing plates sandwiching the liquid crystal cell 93 of the LCD with the iodine type polarizing films 91 and 92 prepared in Example 2 therebetween. As the polarizing plate 91
Was bonded to the liquid crystal cell 93 via an adhesive as a display side polarizing plate to prepare an LCD. The LCD thus produced exhibits excellent brightness, viewing angle characteristics, and visibility, and is at 40 ° C and 30 ° C.
No deterioration in display quality was observed even after 1 month of use at% RH.

Comparative Example 1 <Preparation of Polarizing Plate> A PVA film having a number average degree of polymerization of 1700 was used in an amount of iodine of 1.0 g / l and potassium iodide of 60.0 g / l.
dip in an aqueous solution of 1 at 40 ° C. for 90 seconds, and further add boric acid 4
4 g in an aqueous solution of 0 g / l and potassium iodide 30.0 g / l
After dipping for 120 seconds at 0 ° C., it was introduced into the tenter stretching machine of the form shown in FIG. 1, stretched once to 7.0 times and then contracted to 5.3 times, and thereafter kept constant in width and dried at 60 ° C. I left the tenter. The water content of the PVA film before the stretching was 31% (volatile content), and the water content after drying was 1.5%. The difference in transport speed between the left and right tenter clips is 0.
It was less than 05%, and the angle formed by the center line of the film introduced and the center line of the film sent to the next step was 0 °. Here, | L1-L2 | was 0.7 m, W was 0.7 m, and there was a relationship of | L1-L2 | = W. Wrinkles and film deformation at the tenter exit were not observed. Furthermore, PVA (PVA-117H manufactured by Kuraray Co., Ltd.) 3%
Fujitac (cellulose triacetate, manufactured by Fuji Photo Film Co., Ltd., which has been saponified with an aqueous solution containing 4% of potassium iodide as an adhesive, and a retardation value of 3.
In the saponification treatment of 0 nm, the cellulose acetate film was prepared by immersing the cellulose acetate film in an aqueous solution of 1.5 N sodium hydroxide at 55 ° C. for 2 minutes.
It was washed in a water-washing bath at room temperature and neutralized at 30 ° C. with 0.1 N sulfuric acid. Again, wash in a water bath at room temperature,
Further, it was dried with warm air of 100 ° C. In this way, the surface of the cellulose acetate film was saponified. ), And dried at 80 ℃ to obtain an effective width of 650 mm
To obtain a polarizing plate. The absorption axis direction of the obtained polarizing plate was inclined at 45 ° with respect to the longitudinal direction, and the slow axis of Fujitak was 45 degrees.
It was inclined. The transmittance of this polarizing plate at 550 nm was 43.3%, and the polarization degree was 99.98%.

The fluctuation range of the single plate transmittance before and after the heat resistance and humidity heat resistance test of the obtained polarizing plate was 13.5%, and the fluctuation range of the polarization degree was 12.7%.

As is clear from the comparison between Comparative Example 1 and Examples 1 and 3, the use of a high degree of polymerization PVA or a metal salt resulted in heat resistance and a transmittance after a heat and humidity resistance test without causing discoloration or discoloration. It is possible to suppress the fluctuation rate of the polarization degree. Further, from the comparison of Examples 1 and 2, it is possible to further suppress the fluctuation rate of the transmittance and the polarization degree after the heat resistance and moisture heat resistance test by using zinc among the metal salts, and further, the comparison of Examples 2 and 3 From the above, it is clear that the variation range of the transmittance and the degree of polarization can be minimized by using the high degree of polymerization PVA and the metal salt together.

[0099]

According to the present invention, there is provided a high-performance and inexpensive polarizing plate which is composed of a diagonally stretched polarizing film capable of improving the yield in the polarizing plate punching step and which is excellent in heat resistance and wet heat resistance. It Furthermore, a liquid crystal display device having excellent display quality using this polarizing plate can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 2 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 3 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 4 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 5 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 6 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 7 is a schematic plan view showing how a conventional polarizing plate is punched out.

FIG. 8 is a schematic plan view showing how a polarizing plate of the present invention is punched out.

9 is a schematic plan view showing the layer structure of the liquid crystal display device of Example 5. FIG.

FIG. 10 is a schematic conceptual view of an air blowing device.

FIG. 11 is a schematic conceptual view of a nip device.

FIG. 12 is a schematic conceptual diagram of a blade device.

[Explanation of symbols]

(A) Film introducing direction (b) Film conveying direction to the next step (a) Step of introducing the film (b) Step of stretching the film (c) Step of sending the stretched film to the next step A1 Bite position and starting point of film stretching (substantially holding start point: right) B1 Biting position into holding means of film (left) C1 Starting point of film stretching (substantially holding start point: left) Cx Film release position and film Stretching end point reference position (substantially holding release point: left) Ay Film stretching end point reference position (substantially holding release point:
Right) | L1-L2 | Stroke difference between left and right film holding means W Substantial width θ at the end of the stretching process of the film θ Angle between the stretching direction and the film advancing direction 11 Center line of the introducing side film 12 Center of the film sent to the next process Line 13 Trajectory of film holding means (left) 14 Trajectory of film holding means (right) 15 Introducing film 16 Film 17 and 17 'sent to the next process Left and right film holding start (biting) points 18 and 18' Left and right Departure point from film holding means 21 Center line of introduction side film 22 Center line of film sent to next step 23 Trail of film holding means (left) 24 Trail of film holding means (right) 25 Introduction side film 26 Next step Films 27, 27 'to be fed Left and right film holding start (biting) points 28, 28' Left and right film holding means detachment points 3 , 43, 53, 63 Film holding means locus (left) 34, 44, 54, 64 Film holding means locus (right) 35, 45, 55, 65 Introducing side film 36, 46, 56, 66 Film 71 Absorption axis (stretching axis) 72 Longitudinal direction 81 Absorption axis (stretching axis) 82 Longitudinal direction 91, 92 Iodine type polarizing film (polarizing layer) 93 Liquid crystal cell 94 Backlight 101 Air blow device 111 Nip device 121 Blade device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiromune Kitakoji             Fuji Photo, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture             Within Film Co., Ltd. F-term (reference) 2H049 BA02 BA27 BB03 BB33 BB43                       BB51 BB62 BC01 BC03 BC09                       BC13 BC22                 2H091 FA08X FA08Z FB02 FB13                       FC08 FC16 FC21 FD06 FD15                       KA02 KA10 LA04 LA06 LA12                       LA30                 4F210 AA19 AE10 AG01 AH73 AR07                       AR12 QA02 QC03 QD06 QD13                       QD19 QG01 QG18 QL02 QL04                       QW17

Claims (6)

[Claims] 1. A long polarizing plate having a polarizing film having a polarizing ability and a protective film on at least one surface, wherein (a) the absorption axis of the polarizing film is neither parallel nor perpendicular to the longitudinal direction, and is a single plate. The transmittance is 40% or more at 550 nm, and the polarization degree calculated from the following formula (1) is 95% at 550 nm or more.
The above is (b) 5 at a temperature of 60 ° C. and a humidity of 90%.
After being left for 00 hours, (b-1) the fluctuation range of the transmittance at 550 nm is within ± 10% of the initial value, and (b
-2) A polarizing plate characterized in that the fluctuation range of the degree of polarization at 550 nm is within ± 10% of the initial value. Formula (1): P = [(H0-H1) / (H0 + H1)] ^1/2 × 100 where H0 is the transmittance (%) when two polarizing plates are stacked with their absorption axes aligned, H1 is the transmittance (%) when two polarizing plates are stacked with their absorption axes orthogonal to each other. 2. A polarizing film is formed by holding both ends of a continuously supplied polymer film for a polarizing film by holding means and applying tension while stretching the holding means while advancing in the longitudinal direction of the film. The method for producing a polarizing plate according to claim 1, further comprising the step of adding a metal salt to the polymer film, wherein the number average polymerization degree of the polymer is 1,000 or more as a polymer film for a polarizing film.
In the step of forming a polarizing film by using a film of 000 or less and stretching, (i) the locus of the holding means from the substantial holding start point of one end of the polymer film for a polarizing film to the substantial holding release point. The locus L2 of the holding means from L1 and the other end of the polymer film from the substantial holding start point to the substantial holding release point, and the distance W between the two substantial holding release points satisfy the following formula (2). And (ii) maintaining the supportability of the polymer film, stretching in a state in which the volatile content is 5% or more, and (iii) subsequently shrinking to reduce the volatile content. Production method. Formula (2): | L2-L1 |> 0.4W 3. The method for producing a polarizing plate according to claim 2, wherein the step of adding the metal salt is performed by immersing the polymer film in a solution containing the metal salt. 4. The method of manufacturing a polarizing plate according to claim 3, wherein the concentration of the metal salt in the solution containing the metal salt is 0.01 to 10.0 mass%. 5. The solution containing the metal salt is zinc
The manufacturing method of the polarizing plate according to claim 4, wherein the content is 04% by mass to 0.5% by mass. 6. A liquid crystal display device, wherein the polarizing plate punched out from the polarizing plate according to claim 1 is used for at least one of the polarizing plates arranged on both sides of a liquid crystal cell.