JP2003195034A - Method for manufacturing polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate with which a yield in a punching process is improved, which can use a hydrophobic protective film and is of high performance and at a low cost, and a liquid crystal display device using the polarizing plate. <P>SOLUTION: In this method for manufacturing the polarizing plate that is stretched inclinedly with ≥80% degree of polarization and ≥35% transmittance, a stretching process for advancing a holding means for a film in a longitudinal direction and stretching the film while giving tension and a process for sticking a protective film to a polarizing film are included. In the stretching process, a locus L1 of a holding means of one end of the film, a locus L2 of a holding means of the other end, and a distance W between two substantially holding release points satisfy the following expression (1): |L2-L1|>0.4W. With the bearing properties off the film maintained, the film is stretched while providing ≥12% volatile matter rate, and the film is later contracted to lower the volatile matter rate and to form a polarizing film. In a protective film sticking process, the volatile matter rate of the polarizing film is less than 10% just before sticking the protective film during and after the contraction. <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 method for producing a long polarizing plate which can obtain a polarizing plate having a high yield and excellent dimensional stability, and a liquid crystal display device using the polarizing plate produced by the manufacturing method. .

[0002]

2. Description of the Related Art Polarizing plates are liquid crystal display devices (hereinafter referred to as LC
With the spread of D), the demand is rapidly increasing. In the polarizing plate, generally, a protective film is attached to both surfaces or one surface of a polarizing film having a polarizing ability via an adhesive layer. Polyvinyl alcohol (hereinafter referred to as PVA) is mainly used as a material for the polarizing film. The PVA film is uniaxially stretched and then dyed with iodine or a dichroic dye, or dyeed and then stretched, and further boron is added. By crosslinking with a compound, a polarizing film for a polarizing plate is formed. As the protective film, cellulose triacetate is mainly used because it is optically transparent and has a small birefringence.

In the twisted nematic type TFT-LCD, which is the main type of the TFT-LCD, the absorption axis of the polarizing plate is inclined by 45 ° with respect to the vertical or horizontal direction of the screen, and thus it is manufactured in a roll form. The resulting polarizing plate was punched in the direction of 45 ° with respect to the longitudinal direction of the roll. However, when punching in the direction of 45 °, there was a problem that an unusable portion was generated in the vicinity of the end of the roll, and particularly in a large-sized polarizing plate, the yield was low. In addition, there is a problem that it is difficult to reuse the material of the polarizing plate after the bonding, and as a result, the amount of waste increases.

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 difference in the conveyance speed must 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. Is difficult. 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 JP-A-2-113920, both ends of the film are gripped between two rows of chucks traveling on tenter rails 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 that the orientation is not uniform and the degree of polarization as an average value is lowered due to the variation in the tension distribution during the 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 It had the drawback of low polarization performance. The polarizing plates produced by using the above-mentioned methods other than this also had an insufficient degree of polarization. The polarization degree of the polarizing plates produced by the above-mentioned methods other than this was also insufficient.

Further, in the conventional manufacturing method, since the water content at the time of laminating the protective film is large, if an attempt is made to increase the line speed and improve the productivity, a large capital investment is required for improving the capacity of the drying zone after laminating. There was a necessary problem. Further, even if an attempt is made to use a cycloolefin polymer having excellent dimensional stability for the protective film, the water permeability of the cycloolefin polymer is low, so that the water present in the polarizing film volatilizes slowly and it is difficult to impart high productivity. It was

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-performance and inexpensive polarizing plate manufacturing method with improved yield. Another object of the present invention is to provide a method for producing a polarizing plate which enables the use of a hydrophobic protective film having high dimensional stability. Still another object of the present invention is to provide a liquid crystal display device using the polarizing plate manufactured by the above manufacturing method.

[0010]

Means for Solving the Problems The inventors of the present invention have made earnest studies on the means for solving the above problems, and as a result, the above-mentioned object of the present invention can be achieved by a polarizing plate manufacturing method and a liquid crystal display device having the following constitution. Found. That is, the present invention is as follows. 1. Stretching step of forming a polarizing film 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 in the longitudinal direction of the film to form a polarizing film. A method of manufacturing a polarizing plate, which comprises a step of laminating a protective film on the polarizing plate, wherein the absorption axis of the polarizing film constituting the manufactured polarizing plate is neither parallel nor perpendicular to the longitudinal direction, and the polarization degree of the polarizing plate is 80% at 550 nm
The above is the above, and the single plate transmittance is 35% or more at 550 nm, and [II] in the above stretching step, (i) a substantial holding release from one holding start point of one end of the polymer film for a polarizing film. The locus L1 of the holding means to the point, the locus L2 of the holding means from the substantial holding start point at the other end of the polymer film to the substantial holding release point, and the distance W between the two substantial holding release points are Satisfies the following formula (1),
(Ii) Maintaining the support of the polymer film and having a volatile content of 1
The stretching operation is performed in the presence of 2% or more, and (ii
i) After that, the operation of forming a polarizing film by shrinking to reduce the volatile content is performed, and [III] in the above step of attaching a protective film to the formed polarizing film, after or after the operation of (iii) above. A method for manufacturing a polarizing plate, characterized in that the protective film is attached to at least one surface of the formed polarizing film having a water content of less than 10% immediately before being attached or the polarizing film being formed. . Formula (1): | L2-L1 |> 0.4W 2. 2. The method for producing a polarizing plate as described in 1 above, wherein the polymer film for polarizing film is a polyvinyl alcohol polymer film. 3. 3. The method for producing a polarizing plate as described in 1 or 2, wherein the polarizing film has a thickness of 5 μm or more and 100 μm or less. 4. 4. The method for producing a polarizing plate according to any one of 1 to 3, wherein the protective film has a thickness of 30 μm or more and 120 μm or less. 5. The retardation of the protective film at 632.8 nm is 10 nm or less, and the method for producing a polarizing plate as described in any one of 1 to 4 above. 6. The absorption axis of the polarizing film and the slow axis of the protective film are 20 ° or more 7
The above 1 to 1 characterized in that the angle is less than 0 °
5. The method for producing a polarizing plate according to any one of 5 above. 7. The absorption axis of the polarizing film and the slow axis of the protective film are 40 ° or more 5
7. The method for producing a polarizing plate as described in 6 above, wherein the polarizing plate has an angle of less than 0 °. 8. The absorption axis of the polarizing film and the slow axis of the protective film are 20 ° or more 7
The method for producing a polarizing plate as described in 6 above, wherein the polarizing film has an angle of less than 0 °, the film thickness of the polarizing film is 5 μm or more and 100 μm or less, and the film thickness of the protective film is 30 μm or more and 120 μm or less. . 9. The absorption axis of the polarizing film and the slow axis of the protective film are 40 ° or more 5
The method for producing a polarizing plate as described in 7 above, wherein the polarizing film has an angle of less than 0 °, the film thickness of the polarizing film is 5 μm or more and 100 μm or less, and the film thickness of the protective film is 30 μm or more and 120 μm or less. . 10. The method for producing a polarizing plate according to any one of 1 to 9 above, wherein the stretching ratio of the polarizing film is 3 to 10 times. 11. 11. The method for producing a polarizing plate as described in any one of 1 to 10 above, wherein the protective film is made of cellulose triacetate. 12. 11. The method for producing a polarizing plate according to any one of 1 to 10 above, wherein the protective film is made of an olefin polymer. 13. 13. The method for producing a polarizing plate as described in any one of 1 to 12 above, wherein an operation of stretching is performed in a state where the volatile content is 15% or more. 14. The method for producing a polarizing plate as described in 13 above, wherein an operation of stretching is performed in a state where the volatile content is 20% or more. 15. A liquid crystal display device, wherein a polarizing plate punched out from the polarizing plate manufactured by the method according to any one of 1 to 14 above is used for at least one of the polarizing plates arranged on both sides of the liquid crystal cell.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention has a polarizing film having a polarizing ability, and a protective film (protective film) is provided on both sides or one side of the polarizing film via an adhesive layer. In addition, usually, a long polarizing plate (usually roll form) is produced and punched out according to the intended use to obtain a practically used polarizing plate. Unless otherwise specified, the “polarizing plate” in the present invention is meant to include both a long polarizing plate and the punched polarizing plate.

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 90 °, more preferably 20 ° to 70 °, further preferably 40 ° to 50 °, and particularly preferably 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.

Further, the polarizing plate of the present invention has a single plate transmittance of 5%.
35% or more at 50 nm and 80% at 550 nm polarization degree
The above is characterized. The single plate transmittance is preferably 40% or more, and the polarization degree is preferably 95.0% or more, more preferably 99% or more, and particularly preferably 99.
It is 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.

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 a reduction in the volatile content when stretching the film and the volatile content when shrinking the film. Furthermore, it is also preferable to adjust the amount of foreign matter attached to the film before stretching. This makes it possible to obtain a polarizing film having excellent surface smoothness without causing wrinkles or cracks in the stretched film even when obliquely stretched.

Further, in the method of the present invention, it is preferable to dye a polymer film for a polarizing film, for example, a polyvinyl alcohol film, with an aqueous solution containing a polarizer such as iodine-potassium iodide before the stretching step. Then, it is subjected to a stretching step, and includes a step of bonding with the protective film after the stretching step or near the final stage of the stretching step. Hereinafter, the manufacturing method of the present invention will be described in more detail.

<Polymer film for polarizing film> In the present invention,
The polymer film to be stretched to form the polarizing film 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.
Preferred are polyvinyl alcohol-based polymers including PVA. PVA is generally saponified polyvinyl acetate, but may contain a small amount of a component copolymerizable with vinyl acetate, such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins and vinyl ethers. Absent. Further, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc. is also included in the polyvinyl alcohol-based polymer and can be preferably used. Among them, PVA is the most preferable.

Although 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. Although the degree of polymerization of PVA is not particularly limited, it is preferably 1000 to 10000, and particularly preferably 1500 to 5000.

The preferred elastic modulus of the polymer film before stretching is 0.01 Mpa or more and 5000, expressed as Young's modulus.
Mpa or less, more preferably 0.1 Mpa or more and 500 M
It is less than or equal to pa. If the elastic modulus is too low, the shrinkage rate during and after stretching will be low, and wrinkles will be hard to disappear, and if it is too high, the tension applied during stretching will be large, and it will be necessary to increase the strength of the part holding both ends of the film. , The load on the machine increases.

Although the thickness of the film before stretching is not particularly limited, it is preferably 1 μm to 1 mm, particularly preferably 20 to 200 μm, from the viewpoint of stability of film holding and homogeneity of stretching.

<Polarizer> Polarizer preferably used in the present invention.
Photons are I-generated with iodine-potassium iodide. ₃ ^-, I_Five ^-
Polyiodine and / or organic dichroic dyes such as
It Specific examples of the dichroic dye include, for example, azo dyes,
Stilbene dyes, pyrazolone dyes, triphenylmeth
Tan dye, quinoline dye, oxazine dye, thia
Dye-based dyes, anthraquinone-based dyes and other dye-based compounds
Can be mentioned. It is preferably water-soluble, but
Not as long. In addition, sulfonic acid is added to these dichroic molecules.
Groups, amino groups, hydrophilic groups such as hydroxyl groups have been introduced
Is preferred. Specific examples of dichroic molecules include
For example, Sea. Eye. direct. Yellow 12, Sea. A
I. direct. Orange 39, C.I. Eye. Dilek
G. Orange 72, C.I. Eye. direct. Red
39, C.I. Eye. direct. Red 79, sea. A
I. direct. Red 81, sea. Eye. Dilek
G. Red 83, sea. Eye. direct. Red 8
9, C. Eye. direct. Violet 48, shi
-. Eye. direct. Blue 67, Sea. Eye. Da
Erect. Blue 90, Sea. Eye. direct. Gu
Lean 59, C. Eye. Acid. Red 37 etc.
And JP-A-62-70802, JP-A-62-70802.
1-161202, JP-A-1-172906, JP-A
JP-A-1-172907, JP-A-1-183602,
Kaihei 1-248105, JP-A 1-265205,
Examples thereof include dyes described in JP-A-7-261024.
To be These dichroic molecules are free acids or
Used as a remetal salt, ammonium salt, or salt of amines
Be done. These dichroic molecules should be blended in two or more
Can produce polarizers with various hues.
It It exhibits a black color when the absorption axis is orthogonal to it as a polarizing plate.
Various dichroic molecules such as compounds (pigments) and black
The combination of is excellent in both single plate transmittance and polarization degree,
Good In the present invention, especially iodine-potassium iodide is used.
I₃ ^-, I_Five ^-Polyiodine ions such as
It

<Dyeing> The polarizing film is obtained by orienting a polymer film for polarizing film, for example, a PVA film, and dyeing it with a polarizer. The PVA film can be dyed by gas phase or liquid phase adsorption, but is preferably liquid phase. I ₃ ⁻ produced by iodine-potassium iodide, I
₅ ^- When using a multi-iodide ion, such as a polarizer, iodine - carried out by immersing the PVA film in an aqueous potassium iodide solution. Iodine is preferably 0.1 to 20 g / l, potassium iodide is 1 to 200 g / l, and the mass ratio of iodine to potassium iodide is preferably 1 to 200. Staining time is 10-50
00 seconds is preferable, and the liquid temperature is preferably 5 to 60 ° C. 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 either before or after the stretching step of the present invention, but since the water content during bonding is less than 10%,
It is particularly preferred to dye in the liquid phase before the stretching step.

<Addition of Hardener (Crosslinking Agent), Metal Salt> In the step of producing a polarizing film by stretching a polymer film for a polarizing film, for example, a PVA film, it is preferable to use an additive that crosslinks PVA. Especially when the oblique stretching method of the present invention is used, if the film is not sufficiently hardened at the exit of the stretching step, the orientation direction of the film may be displaced due to the tension of the step, and therefore, in the pre-stretching step or the stretching step. It is preferable that the hardener (crosslinking agent) is contained by dipping or coating the solution in the crosslinking agent solution. Hardener (crosslinking agent)
Means for imparting to the polymer film for polarizing film is not particularly limited, dipping in a liquid of the film, coating,
Although any method such as spraying can be used, a dipping method and a coating method are particularly preferable. As a coating means, any known means such as a roll coater, a die coater, a bar coater, a slide coater, and a curtain coater 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. Further, metal salts such as zinc, cobalt, zirconium, iron, nickel and manganese can also be used together.

The hardener (crosslinking agent) may be applied before being bitten in the stretching machine or after being bitten in the stretching machine, so that the widthwise stretching is substantially completed. 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).

<Stretching Method> FIGS. 1 and 2 are schematic plan views showing an example of a method for obliquely stretching a polymer film preferably used in the present invention. The stretching method used in the present invention includes 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). To the next step, that is, the step of sending in the (b) direction. 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 (a), and is first held by the holding means on the left side as viewed from the upstream side at point B1.
At this point, one film edge is not held yet, and no tension is generated in the width direction. That is, the point B1 does not correspond to the substantial holding start point (hereinafter referred to as “substantial holding start point”) of the present invention. 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
1 to the center line 11 (FIG. 1) or 21 of the introduction side film
A straight line drawn substantially perpendicular to (FIG. 2) 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 substantially the same speed, A1 becomes A per unit time.
2, A3 ... An, C1 is C2, C3 ... C
Move to n. 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 process is tan θ = W / (Ay−A
x), that is, an angle that satisfies 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, a mechanical constraint such as a rail length often causes a catching point and a substantial holding start point to the holding means. 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 has the relationship of the above formula (1). 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 outlet width W in the step (c) and the stroke difference | L1-L2 | between the two substantial holding means on the left and right. 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 (2) is satisfied, and the formula (2): 0.9W <| L1-L2 | <1.1W is more preferable. It is preferable to satisfy 3). Formula (3): 0.97W <| L1-L2 | <1.03W

The specific structure of the stretching step can be arbitrarily designed in consideration of equipment cost and productivity as shown in FIGS. 1 to 6 as long as the formula (1) is satisfied.

The film introduction direction (a) to 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 stretching ratio is preferably 3.0 to 10.0 times. 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 bends 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 the direction of film advance while holding both ends of the film.

In the present invention, the apparatus for stretching the film by applying tension while holding both ends is 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, a chain to which a clip is fixed often moves 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 substantial process lengths L1 and L2 are not the simple bite-release distances as described above, but the strokes of the portions where the holding means holds both ends of the film, as already described. Be long.

If there is a difference in the advancing speed on the left and right of the film at the exit of the drawing process, wrinkles and deviations occur at the exit of the drawing 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.

<Volatile content> In the stretching process, wrinkles and deviations occur in the film as the difference in the left and right strokes occurs. 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 case of the latter, 50% or more of the total stretching section from the stretching start point as a starting point,
The volatile content is preferably 12% or more. In any case, it is more preferable that the state where the volatile content is 12% or more is present 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. <Dyeing recipe, dyeing method>, <
The dyeing step or the hardening agent addition step described in the section <Adding hardening agent (crosslinking agent) or metal salt> may also serve as a step of incorporating a volatile component. 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 or omission of dyeing. 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 distribution of the volatile component means the ratio of the larger difference between the maximum value or the minimum value and the average volatile content to the average volatile content of the volatile content defined above. 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. Figure 1
An example of an air blow device, a nip device, and a blade device is shown in 0-12.

<Shrinkage: Shrinkage During Stretching and After Stretching> Shrinkage of the stretched polymer film may be performed at any step during stretching and after stretching. Shrinkage may be achieved by eliminating wrinkles in the polymer film that occur when the film is oriented in an oblique direction.Means for shrinking the film include a method of removing volatile components by heating, but the film shrinks. Any means may be used as long as it is possible. 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.

<Distance from Wrinkle Occurrence 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. However, it is preferable to adjust the drying point so that the drying point comes as short as possible after the desired orientation angle is obtained. The dry point means a place where the surface film temperature of the film becomes the same as the ambient atmospheric temperature. 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 according to the present invention, the temperature is preferably 20 ° C or higher and 100 ° C or lower, more preferably 40 ° C or higher and 90 ° C or lower.

<Water Content in Bonding Protective Film> As the polymer for the polarizing film of the present invention, a polyvinyl alcohol polymer is preferable, and in this case, water is preferable as the volatile component. Then, it is preferable to dry so that the water content (volatile content) at the time of attaching the protective film is less than 10%. The more preferable water content is less than 8%.

<Swelling ratio> In the present invention, when the polymer film is a polyvinyl alcohol-based polymer film and a hardening agent is used, swelling in water before and after stretching in order to keep the stretched state in the oblique direction without relaxation. Different rates are preferred. Specifically, the swelling rate before stretching is high,
It is preferable that the swelling rate after stretching and drying becomes 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.

<Bent section> In the present invention, a rail that regulates the locus of the holding means is often required to have a large bend 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> In the present invention, the speed at which the film is stretched is 1.1 in terms of the stretching ratio per unit time.
Double / minute or more, preferably double / minute or more, and the earlier one 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 weight of foreign matter adhering 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 for 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 the 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> In the present invention, 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 polyvinyl alcohol-based polymer film, the temperature is preferably 25 ° C or higher. Further, in the case of stretching a polyvinyl alcohol-based polymer film in which iodine / boric acid is immersed for producing a polarizing film, 25 ° C. or higher and 90 ° C. or lower is preferable, and a more preferable temperature range is 40 ° C. or higher and 90 ° C. or lower. .

<Humidity at 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. If it is polyvinyl alcohol, 50% or more 1
00% or less is preferable, and the more preferable humidity range is 80.
% Or more and 100% or less.

<Protective film>

The polarizing film produced by the present invention is used as a polarizing plate by attaching protective films 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 transmissive 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.
Retardation value is 0 to 15 at 632.8 nm
0 nm is preferable, 0 to 20 nm is more preferable, and 0 to
5 nm is particularly preferred. It is preferable that the slow axis of the protective film is made substantially parallel or orthogonal to the absorption axis of the polarizing film from the viewpoint of avoiding elliptical polarization of linearly polarized light. However, when the protective film has a function of changing the polarization property such as a phase difference plate, the invention is not limited to this, and the absorption axis of the polarizing plate and the slow axis of the protective film can take an arbitrary angle. The visible light transmittance is preferably 60% or more, particularly preferably 90% or more. 9
Dimension reduction after treatment at 0 ° C for 120 hours is 0.3-0.01.
% Is preferable, and 0.15 to 0.01% is particularly preferable. The tensile strength value by the tensile test of the film is preferably 50 to 1000 MPa, and 100 to 100 MPa.
300 MPa is particularly preferred. The moisture permeability of the film is 1
0 to 800 g / m ² · day is preferable, 300 to 6
00 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 In the formula, A and B represent a substituent of an acyl group substituted by a hydroxyl group of cellulose, A is a substitution degree of an acetyl group, and B is a substitution degree of an acyl group having 3 to 5 carbon atoms. Cellulose has three hydroxyl groups in one glucose unit, and the above number represents the degree of substitution with respect to 3.0 of the hydroxyl groups, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a degree of substitution of A of 2.6 to 3.0.
Below (in this case, there is a maximum of 0.4 hydroxyl groups not substituted), and the case of B = 0 is cellulose triacetate. Cellulose acylate used as a polarizing plate protective film is a cellulose triacetate having all acetyl groups, and an acetyl group of 2.0 or more and an acyl group of 3 to 5 carbon atoms, 0.8 or less, which is not substituted. Those having a hydroxyl group of 0.4 or less are preferable. 3 to 3 carbon atoms
In the case of the acyl group of 5, 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. As a measuring method, AST
It can be carried out according to D-817-91 of M.

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 degree of substitution of the acyl group having 3 to 5 carbon atoms is high, the solubility in an organic solvent is improved, but when the degree of substitution 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. D
P = [η] / Km (where DP is the viscosity average degree of polymerization, K
m is a constant 6 × 10 ^-4 )

Examples of the cellulose as a raw material for cellulose acylate include cotton linter and wood pulp. Cellulose acylates obtained from any raw material cellulose may be used, or they may be mixed and 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.
It is preferable to adjust the concentration of the dope so that the solid content is 10 to 40% by mass. 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 mass% is preferable and 5 to 20 mass% 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 or 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 mass, and particularly preferably 8 to 16% by mass or less based on 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 type 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 mass, particularly preferably 0.1 to 3% by mass, based on the cellulose acylate. 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, cationic type and the like 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 to the PVA 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, JP-A-4-229828, JP-A-6-75115 and JP-A-8-
50206, etc., an optically anisotropic layer for compensating the viewing angle of the LCD, an antiglare layer or an antireflection layer for improving the visibility of the display, or anisotropic scattering or anisotropy for improving the LCD brightness. A layer having a function of separating PS waves by optical interference (polymer dispersed liquid crystal layer, cholesteric liquid crystal layer, etc.), a hard coat layer for enhancing the scratch resistance of a polarizing plate, a gas barrier layer for suppressing the diffusion of moisture and oxygen, a polarizing film or an adhesive. Agent,
It is possible to provide any functional layer such as an easy-adhesion layer that enhances the adhesion with the pressure-sensitive adhesive and a layer that imparts 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.

On the polarizing film of the present invention, various functional films can be directly bonded on one side or both sides as a protective film. Examples of the functional film include a retardation film such as a λ / 4 plate and a λ / 2 plate, a light diffusion film, a plastic cell provided with a conductive layer on the surface opposite to the polarizing plate, and anisotropic scattering or anisotropic optical interference. Examples thereof include a brightness enhancement film having functions and the like, a reflector, a reflector having a semi-transmissive function, and the like.

As the polarizing plate protective film, one or a plurality of the above-mentioned preferred protective films may 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.

<Attachment Angle of Protective Film and Polarizing Film> In the present invention, when the orientation axis (slow axis) of the protective film and the stretching axis (absorption axis) of the polarizing film are not parallel to each other, It has the effect of being excellent in dimensional stability. The angle is preferably 10 ° or more and less than 90 °. A more preferable range is 20 ° or more and less than 70 °, and a particularly preferable range is 40 ° or more and less than 50 °.

<Adhesive> The adhesive between the polarizing film and the protective layer is not particularly limited, but a PVA resin (acetoacetyl group,
Examples thereof include modified PVA having a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc.), an acrylic pressure-sensitive adhesive, a boron compound aqueous solution, and the like, and among them, 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 is 0.0 after drying.
1 to 10 μm is preferable, and 0.05 to 5 μm is particularly preferable.

<Consistent Step> In the present invention, in order to avoid troubles such as film tearing during handling due to the thin film thickness of the polarizing film, in the drying step in which the film is stretched and then contracted to reduce the volatile content, It is preferable to have a step of laminating a protective film on at least one surface during or immediately after drying and post-heating. As a specific sticking method, during the drying process, sticking a protective film to the film with an adhesive while holding both ends, and then picking both ends, as a method of ear cutting, use a cutter such as a knife A general technique such as a cutting method or a method using a laser can be used. Immediately after bonding, it is preferable to heat the adhesive in order to dry it and improve 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 preferable that these steps be performed on a consistent production line in terms of performance and productivity.

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

[0077]

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 protective film A> (Preparation of fine particle dispersion liquid a) Silica (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) 0.67% by mass Cellulose acetate (Substitution degree 2.8) 2. 93% by mass triphenyl phosphate 0.23% by mass biphenyldiphenyl phosphate 0.12% by mass methylene chloride 88.37% by mass methanol 7.68% by mass was prepared, and the volume average particle size was adjusted to 0.
Dispersion was performed so as to have a thickness of 7 μm.

(Preparation of Raw Material Dope) Cellulose triacetate (degree of substitution 2.8) 89.3% by mass Triphenyl phosphate 7.1% by mass Biphenyldiphenylphosphate 3.6% by mass With respect to 100 parts by mass of solid content, the above content is obtained. Particulate dispersion a 1
7.9 parts by mass was added, and a mixed solvent of 92% by mass of dichloromethane and 8% by mass of methanol was appropriately added and dissolved by stirring to prepare a dope. The solid content concentration of the dope was (18.5)%. After filtering this dope with filter paper (Toyo Roshi Kaisha, Ltd., # 63), a sintered metal filter (Nippon Seisen Co., Ltd. 06N,
It was filtered with a nominal pore diameter of 10 μm) and further with a mesh filter (RM manufactured by Nippon Pall Co., Ltd., nominal pore diameter of 45 μm).

(Preparation of Ultraviolet Absorber Solution b) 2 (2′-Hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole 5.83% by Mass 2 (2′-hydroxy- 3 ', 5'-di-tert-amylphenyl) benzotriazole 11.66% by mass Cellulose acetate (degree of substitution 2.8) 1.48% by mass Triphenyl phosphate 0.12% by mass Biphenyldiphenyl phosphate 0.06 Mass% Methylene chloride 74.38 mass% Methanol 6.47 mass% An ultraviolet absorbent solution was prepared according to the above formulation, and filtered with an Astropore 10 filter manufactured by Fuji Photo Film Co., Ltd.

For the above dope, a static mixer was used to adjust the amount of the ultraviolet absorber solution b so that the amount of the ultraviolet absorber was 1.04% by mass with respect to the solid content in the dope. And mixed in. This dope was cast on an endless support, dried with hot air until it had a self-supporting property, and peeled as a film. The residual solvent at the time of peeling was 38% by mass. This film was introduced into a tenter type dryer, dried while holding both ends and applying tension until the residual solvent became 14% by mass.
After that, it is dried in a roller drying zone and the residual solvent is 0.1
Dry to mass%. The thickness of the finished film is 80
μm, the retardation was 3.1 nm, and the tensile strength in the longitudinal direction of the film was 140 MPa. This film was saponified with a 1.5N NaOH aqueous solution for 180 seconds, washed with water and neutralized, and used as the protective film A. (Measurement of Retardation) KOBRA21DH manufactured by Oji Scientific Co., Ltd. was used for measurement at a wavelength of 632.8 nm.

<Production of Polarizing Plate> The average degree of polymerization is 1700,
Both sides of the PVA film having a thickness of 75 μm were washed with ion-exchanged water at a water flow of 2 L / min.
After air-blowing with an air-blowing device shown in Fig. 1 to remove surface moisture to remove foreign matter, the PVA film is immersed in an aqueous solution of 1.0 g / l iodine and 60.0 g / l potassium iodide at 25 ° C for 90 seconds. And further boric acid 40 g /
1, potassium iodide in an aqueous solution of 30 g / l at 25 ° C.
After soaking for 20 seconds, both sides of the film were air-blown to remove excess water, and the water content in the film was set to 32%, and its distribution was set to 2% or less. Introduced. 100 at a transport speed of 5 m / min
m, the temperature was 40 ° C. and the humidity was 90%, and the film was once stretched to 4.4 times and then shrunk to 3.4 times. Then, the width was kept constant and the moisture content of the stretched film was 6 during drying at 65 ° C. %, PVA (PVA-1 manufactured by Kuraray Co., Ltd.)
17H) An aqueous solution containing 3% and 4% potassium iodide was used as an adhesive to bond the protective film A with the above-mentioned protective film A.
Heated for 30 minutes. After this, remove from the tenter, 3 cm from the width direction, and use a cutter to cut the edges to obtain an effective width of 65
A roll-shaped polarizing plate having a length of 0 mm and a length of 100 m was produced. No trouble such as tearing occurred during film handling. The film thickness of the polarizing film was 30 μm. The drying point was in the middle of the zone (c), the water content of the PVA film before the start of stretching was 30%, and the water content of the polarizing plate in roll form was 1.5%. The difference in transport speed between the left and right tenter clips is 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 is:
It 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. The absorption axis direction 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.

(Measurement of 550 nm Transmittance and Polarization Degree) The transmittance was measured by Shimadzu's own spectrophotometer UV2100. Two
The transmittance when the two polarizing plates are stacked with their absorption axes aligned is H
0 (%), the transmittance when the absorption axis is orthogonal to each other and the transmittance is H
The degree of polarization P (%) was determined by the following equation, assuming 1 (%). P = [(H0-H1) / (H0 + H1)] ^1/2 × 100 The transmittance of this polarizing plate at 550 nm is 41.2%,
The polarization degree was 99.63%.

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 91.9%.

Example 2 <Protective Film B> A 100 μm-thick film made of ZEONOR 1420R manufactured by Nippon Zeon Co., Ltd. was used as the protective film B.

<Production of Polarizing Plate> The average degree of polymerization is 1700,
Both sides of a PVA film having a film thickness of 75 μm were washed with ion-exchanged water at a water flow of 2 L / min, and air was blown by a nip device shown in FIG. 11 to remove surface moisture to remove foreign matters, and then the PVA film was removed. 85 at 40 ° C. in an aqueous solution of 1.2 g / l of iodine and 110.0 g / l of potassium iodide.
Second soak, boric acid 40g / l, potassium iodide 3
After dipping in a 0 g / l aqueous solution at 40 ° C. for 60 seconds, both sides of the film were air blown to remove excess water, and the water content in the film was 40% and its distribution was 2% or less. It was introduced into the tenter stretching machine of the form shown in FIG. At a conveying speed of 10 m / min, 500 m was delivered, and stretched 4.2 times in a temperature of 50 ° C. and a humidity of 90%, the tenter was bent as shown in FIG. 2 with respect to the stretching direction, and the width was kept constant thereafter.
When the water content of the stretched film reached 3.5% during drying at 65 ° C., a 2% ethyl acetate solution of an acrylic pressure-sensitive adhesive was used as an adhesive to bond the protective film B with the above-mentioned protective film B.
After heating for a minute, a roll-shaped polarizing plate having an effective width of 650 mm and a length of 500 m could be produced without any problem. The film thickness of the polarizing film is 2
It was 0 μm. The dry point is 1/3 of the zone (c), the water content of the PVA film before the start of stretching is 33%,
The water content after drying was 0.9%. 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 46 °. Where | L1-L2
| Is 0.7 m, W is 0.7 m, and | L1-L2 | =
There was a W relationship. The substantial stretching direction Ax-Cx at the tenter exit is the center line 22 of the film sent to the next step.
It was inclined at 45 ° with respect to. Wrinkles and film deformation at the tenter exit were not observed. The absorption axis direction of the obtained polarizing plate was inclined by 45 ° with respect to the longitudinal direction.
The transmittance of this polarizing plate at 550 nm is 42.8%,
The polarization degree was 99.85%. Further, as shown in FIG.
When it was cut into a size of 0 × 233 mm, a polarizing plate having an absorption axis inclined by 45 ° with respect to the side could be obtained with an area efficiency of 90.9%.

Comparative Example 1 <Production of Polarizing Plate> Average degree of polymerization is 1700, film thickness is 75 μm.
Both sides of the PVA film of No. 2 are washed with ion exchange water at a water flow of 2 L / min, and both sides of the film are blown with an air blower shown in FIG. 1.2 g of iodine /
l, 40 ° C in an aqueous solution of 110.0 g / l potassium iodide
At 80 ° C. for 60 seconds at 40 ° C. in an aqueous solution of 40 g / l boric acid and 30 g / l potassium iodide.
Both sides of the film are blown with air to remove excess water, and the water content in the film is 38% and its distribution is 2%.
It was introduced into the tenter stretching machine of the form shown in FIG. 2 in the following state. At a conveying speed of 10 m / min, 500 m was fed out, stretched 4.2 times in a temperature of 50 ° C. and a humidity of 90%, the tenter was bent in the stretching direction as shown in FIG. When the water content of the stretched film reached 15% during drying at ℃, a 2% ethyl acetate solution of an acrylic pressure-sensitive adhesive was used as an adhesive to bond with the above-mentioned protective film B.
It was attempted to produce a roll-shaped polarizing plate by heating it at 30 ° C. for 30 minutes, but the polarizing plate could not be reduced in the water content of the polarizing plate in the end, resulting in many color irregularities, and the in-plane uniformity of the degree of polarization was extremely low. It was

[Embodiment 3] Next, as shown in FIG.
The iodine-based polarizing films 91 and 92 prepared in Step 2 are used as two polarizing plates sandwiching the liquid crystal cell 93 of the LCD.
1 as a display-side polarizing plate and a liquid crystal cell 93 through an adhesive.
LCD was prepared by bonding to. LCD created in this way
Showed excellent brightness, viewing angle characteristics, and visibility.

[0089]

EFFECT OF THE INVENTION The present invention provides a high-performance and inexpensive polarizing plate manufacturing method which improves the yield in the polarizing plate punching process and can also use a hydrophobic protective film, and further by the method of the present invention. A liquid crystal display device using the manufactured polarizing plate is provided.

[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 3. 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 Trajectory of film holding means (left) 34, 44, 54, 64 Trajectory of film holding means (right) 35, 45, 55, 65 Introducing side film 36, 46, 56, 66 Send to next process 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

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Hiromune Kitakoji Minamiashigara City, Kanagawa Prefecture Nakanuma 210 address Fuji photo film Co., Ltd. in the F-term (reference) 2H049 BA02 BA27 BB33 BB43 BC01 BC03 BC14 BC22 2H091 FA08X FA08Z FA41Z FB02 FC07 FD08 KA02 KA10 LA12 LA30 4F210 AA19 AE10 AG01 AG03 AH73 AM32 AR08 AR12 AR20 QA02 QC03 QD01 QD13 QD17 QD19 QG01 QG18 QL04 QW17 QW50

Claims (15)

[Claims] 1. 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. A method for manufacturing a polarizing plate, which comprises a stretching step and a step of bonding a protective film to a polarizing film,
[I] The absorption axis of the polarizing film constituting the manufactured polarizing plate is neither parallel nor perpendicular to the longitudinal direction, and the polarization degree of the polarizing plate is 55.
80% or more at 0 nm and single plate transmittance of 550 n
m is 35% or more, [II] in the stretching step,
(I) Trajectory L1 of the holding means from the substantial holding start point of one end of the polymer film for polarizing film to the substantial holding release point and the substantial holding from the substantial holding start point of the other end of the polymer film Locus L2 of the holding means up to the release point
And the distance W between the two substantial holding release points satisfies the following formula (1), and (ii) the polymer film is supported, and the stretching is performed in the state where the volatile content is 12% or more. And (iii) after that, an operation of shrinking to reduce the volatile content to form a polarizing film is performed, and [III] the above step (iii) in the step of attaching the protective film to the formed polarizing film. After or during the operation, an operation of adhering to at least one surface of the formed polarizing film having a water content of less than 10% immediately before attaching the protective film or the polarizing film being formed is performed. Method of manufacturing a plate. Formula (1): | L2-L1 |> 0.4W 2. The method for producing a polarizing plate according to claim 1, wherein the polymer film for polarizing film is a polyvinyl alcohol polymer film. 3. The method for producing a polarizing plate according to claim 1, wherein the polarizing film has a thickness of 5 μm or more and 100 μm or less. 4. A protective film having a thickness of 30 μm or more and 120 μm
It is the following, The manufacturing method of the polarizing plate in any one of Claims 1-3 characterized by the following. 5. The method for producing a polarizing plate according to claim 1, wherein the protective film has a retardation at 632.8 nm of 10 nm or less. 6. The absorption axis of the polarizing film and the slow axis of the protective film are 2
The method for producing a polarizing plate according to claim 1, wherein the angle is 0 ° or more and less than 70 °. 7. The absorption axis of the polarizing film and the slow axis of the protective film are 4
The method for producing a polarizing plate according to claim 6, wherein the polarizing plate forms an angle of 0 ° or more and less than 50 °. 8. The absorption axis of the polarizing film and the slow axis of the protective film are 2
It forms an angle of 0 ° or more and less than 70 °, the thickness of the polarizing film is 5 μm or more and 100 μm or less, and the thickness of the protective film is 3
7. The method for producing a polarizing plate according to claim 6, wherein the thickness is 0 μm or more and 120 μm or less. 9. The absorption axis of the polarizing film and the slow axis of the protective film are 4
The angle is 0 ° or more and less than 50 °, the film thickness of the polarizing film is 5 μm or more and 100 μm or less, and the film thickness of the protective film is 3
The method for producing a polarizing plate according to claim 7, wherein the thickness is 0 μm or more and 120 μm or less. 10. The method for producing a polarizing plate according to claim 1, wherein the polarizing film has a stretching ratio of 3 to 10 times. 11. The method for producing a polarizing plate according to claim 1, wherein the protective film is made of cellulose triacetate. 12. The method for producing a polarizing plate according to claim 1, wherein the protective film is made of an olefin polymer. 13. A stretching operation is carried out in the presence of a volatile content of 15% or more.
A method for producing a polarizing plate according to any one of 1. 14. The method for producing a polarizing plate according to claim 13, wherein the stretching is carried out in the presence of a volatile content of 20% or more. 15. A polarizing plate punched out from the polarizing plate manufactured by the method according to any one of claims 1 to 14 is used as at least one of the polarizing plates arranged on both sides of the liquid crystal cell. Liquid crystal display device.