WO2003046620A2

WO2003046620A2 - Polarizing plate, production method thereof and liquid crystal display

Info

Publication number: WO2003046620A2
Application number: PCT/JP2002/012387
Authority: WO
Inventors: Keiichi Taguchi; Hiromoto Kitakouji; Kentaro Shiratsuchi
Original assignee: Fuji Photo Film Co., Ltd.
Priority date: 2001-11-29
Filing date: 2002-11-27
Publication date: 2003-06-05
Also published as: WO2003046620A3; AU2002347634A1; CN100424528C; TWI281991B; TW200300849A; KR20040066817A; CN1596375A

Abstract

The present invention provides: an inexpensive long and roll-form high-performance polarizing plate excellent in the smoothness and difficult to deteriorate due to exterior light, which comprises an obliquely stretched polarizing film capable of improving the yield in the step of punching out a polarizing plate; a production method of the polarizing plate; and a liquid crystal display using the polarizing plate. The long polarizing of the invention plate in a roll form comprises a polarizing film wherein the absorption axis of the polarizing film is neither parallel nor perpendicular to its longitudinal direction, the polarization degree is 80% or more at 550 nm, the single plate transmittance is 35% or more at 550 nm.

Description

DESCRIPTION Polarizing Plate, Production Method Thereof and Liquid Crystal Display

Technical Field

The present invention relates to a long polarizing plate from which a polarizing plate having excellent polarizing performance can be obtained in a high yield; production methods of these polarizing plates; and a liquid crystal display using the polarizing plate.

Background Art

With the popularization of a liquid crystal display (hereinafter referred to as "LCD"), demands for a polarizing plate are abruptly increasing. The polarizing plate generally comprises a polarizing layer having a polarizing ability and a protective film attached to both surfaces or one surface of the polarizing layer through an adhesive layer.

The material used for the polarizing film is mainly polyvinyl alcohol (hereinafter referred to as "PVA"). A PVA film is monoaxially stretched and then dyed with iodine or a dichromatic dye, or dyed and then stretched, and this film is further crosslinked with a boron compound to form a polarizing film for the polarizing layer. For the protective film, cellulose triacetate is mainly used because this film is optically transparent and small in the birefringence. The polarizing film is usually produced by monoaxially stretching a continuous film in the running direction (longitudinal direction) and therefore, the absorption axis of the polarizing film is almost in parallel to the longitudinal direction.

In conventional LCD, the polarizing plate is disposed by inclining its absorption axis at 45° with respect to the vertical or transverse direction of a picture plane and therefore, the polarizing plate produced in a roll form must be punched in the 45° direction with respect to the longitudinal direction of the roll in the punching step.

However, if the polarizing plate is punched in the 45° direction, a portion which cannot be used is generated in the vicinity of edges of the roll and particularly in the case of a large-size polarizing plate, the yield decreases, as a result, the waste disadvantageously increases .

The phase difference film is also used by adhering it to a polarizing plate or the like forming LCD for the purpose of preventing coloration or effecting optical compensation such as enlargement of view angle and is demanded to set its orientation axis at various angles with respect to the transmission axis of the polarizing plate. Conventionally, a method of cutting the phase difference film from a film monoaxially stretched in the longitudinal or transverse direction by punching out the periphery such that its orientation axis makes a predetermined tilt angle with respect to the side is used and the reduction in the yield is a problem similarly to the polarizing plate.

Furthermore, when another optical member, for example, a λ/4 plate is attached, this must be attached every each panel and the process is cumbersome. In addition, a production step of laminating a plurality of films while strictly controlling the angle is necessary and due to sliding of angles, light leakage is generated to cause a phenomenon that the color display in the black part changes into yellow or blue. Thus, roll-to-roll attaching is demanded.

In order to solve the above-described problem, several methods have been proposed where the orientation axis of the polymer is inclined at a desired angle with respect to the film conveyance direction (longitudinal direction) . JP-A-2000-9912 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") describes a technique where while monoaxially stretching a plastic film in the transverse or longitudinal direction, the film is tensile-stretched in the longitudinal or transverse direction different from the above-described stretching direction by changing the stretching speed between right and left sides of the stretching direction. However, according to this method, in the case of using, for example, a tenter system, the conveyance speed must be changed between right and left sides and this causes drawing, wrinkling or film slippage, as a result, a desired tilt angle (45° in the polarizing plate) can be hardly obtained. For reducing the difference in the speed between right and left sides, the stretching step must be prolonged and the equipment cost greatly increases .

JP-A-3-182701 discloses a method of producing a film having a stretching axis at an arbitrary angle θ with respect to the film running direction by using a mechanism where a plurality of laterally paired film-holding points each making an angle θ with the running direction are provided at both side edges of a continuous film and each pair of points can stretch the film to the θ direction as the film runs. Also in this method, since the film travelling speed differs between right and left sides of the film, drawing or wrinkling is generated on the film and for releasing this, the stretching step must be greatly prolonged, which gives rise to a problem that the equipment cost increases. JP-A-2-113920 discloses a production method of stretching the film in the direction obliquely crossing the machine direction of film by running the film while gripping both edges thereof between chucks aligned in two rows and running on tenter rails disposed such that the chucks run different distances in a predetermined running section. Also in this method, drawing or wrinkling is generated at the oblique stretching and this is disadvantageous for the optical film.

Korean Unexamined Patent Publication P2001-005184 discloses a polarizing plate where the transmission axis is inclined by a rubbing treatment. However, as generally known, the regulation of orientation by rubbing is effective only in the region from the film surface to at most a nano-order portion and a polarizer such as iodine or dichromatic dye cannot be satisfactorily oriented, as a result, the polarizing performance is disadvantageously poor.

In conventional methods of stretching the film in the longitudinal direction of roll, as the width of film stretched is larger, the film edge curls more intensely when the film is stretched at a high stretching magnification. This causes rupture or the like of film and handling in the stretching step is difficult. Furthermore, stretching using the multi-stage stretching method encounters difficulties in the handling, such as control of the rotation speed of roller or control of shrinkage and bending at the edge part of roll film.

Disclosure of the Invention

An object of the present invention is to provide a long and roll-form polarizing plate comprising an obliquely stretched polarizing film, which is capable of improving the yield in the step of punching out a polarizing plate.

Another object of the present invention is to provide a high-quality and inexpensive roll-form polarizing plate having excellent smoothness and difficult of deterioration due to exterior light.

A further object of the present invention is to provide a high-grade and inexpensive long polarizing plate having an working width (effective width) of 650 mm or more, which comprises an obliquely stretched polarizing film capable of improving the yield in the step of punching out a polarizing plate.

Still another object of the present invention is to provide a production method of the above-described polarizing plate, and a liquid crystal display using the polarizing plate. As a result of extensive investigations on the means for achieving the above-described object, the present inventors have found a method of obtaining oblique orientation without generating drawing, wrinkling, film slippage and the like, whereby a long polarizing plate can be prepared and a polarizing plate can be produced in a roll form. In the case where this long polarizing plate is rolled in 2 turns or more, exterior light is scarcely transmitted by virtue of the inclined absorption axis with respect to the longitudinal direction. Particularly, when the absorption axis is inclined at 45°, a cross nicol state is provided. Accordingly, outermost two turns (outmost two roll layers) of the polarizing plate absorb exterior light and three or more turns are hardly exposed to the exterior light, so that, the polarizing plate can be less deteriorated due to exterior light during storage.

The present inventors have found a method for obtaining oblique orientation having an working width of 650 mm without causing drawing, wrinkling, film slippage or the like, where the tension in the longitudinal direction of a polymer film for a polarizing film at the stretching and the environmental humidity at the stretching are optimized, the water content percentage of the polymer film for a polarizing film at the dyeing is also optimized and at the same time, the swelling percentage after stretching and drying is made lower than that before stretching.

More specifically, according to the present invention, a polarizing plate having the following constitution, a production method of the polarizing plate, and a liquid crystal display are provided and by these, the objects of the present invention can be attained.

1. A long polarizing plate comprising at least a polarizing film having: a polarizing ability; and an absorption axis neither in parallel nor perpendicular to the longitudinal direction, wherein the long polarizing plate has the polarization degree of 80% or more at 550 nm, the single plate transmittance of 35% or more at 550 nm and the length in the longitudinal direction of 1 m or more, and the long polarizing plate is in a roll-form, having three or more turns .

2. A long polarizing plate comprising at least a polarizing film having: a polarizing ability; and an absorption axis neither in parallel nor perpendicular to the longitudinal direction, wherein the long polarizing plate has the polarization degree of 80% or more at 550 nm and the single plate transmittance of 35% or more at 550 nm, and a working width perpendicular to the longitudinal direction in the long polarizing plate is 650 mm or more.

3. A method for producing a polarizing plate including a polarizing film having an absorption axis neither in parallel nor perpendicular to the longitudinal direction, the polarizing plate having .a polarization degree of 80% or more at 550 nm; and a single plate transmittance of 35% or more at 550 nm, wherein the method comprises: incorporating a volatile component into a polymer film for the polarizing film; reducing the content distribution of the volatile component in the polymer film to 5% or less, and then stretching the polymer film in an atmosphere at a temperature of 10 to 100°C and a humidity of 70% or more.

4. The polarizing plate as described in the items 1 or 2, wherein a protective film is attached to at least one surface of the polarizing plate, and the angle made by the phase lag axis of the protective film and the absorption axis of the polarizing film is not less than 10° and less than 90° .

5. The polarizing plate as described in the item 4, wherein the protective film is a transparent film, and the retardation of the polarizing plate at 632.8 nm is 10 nm or less.

6. A method for producing a polarizing plate, comprising : producing a polarizing film by a process which comprises : holding both edges of a continuously fed polymer film for the polarizing film by holding means; and stretching the polymer film while travelling said holding means to the longitudinal direction of the film and while applying tension to the film; wherein, when LI represents a trajectory of the holding means from a substantial holding start point until a substantial holding release point at one edge of the polymer film, L2 represents a trajectory of the holding means from a substantial holding start point until a substantial holding release point at the other edge of the polymer film, and W represent a distance between the two substantial holding release points, LI, L2 and W satisfy a relation represented by formula (2): |L2-L1| > 0.4W, the polymer film is stretched while keeping the supporting property of the polymer film and while allowing a volatile content ratio of 5% or more to be present, and then the polymer film is shrunk while reducing the volatile content ratio, and then the polymer film is rolled to be in roll-form; attaching a protective film to at least one surface of the polarizing film, in whi.ch the angle made by the phase lag axis of the protective film and the absorption axis of the polarizing film is not less than 10° and less than 90°.

7. The method for producing a polarizing plate as described in the item 6, wherein the polymer film for the polarizing film is once stretched to 2 to 10 times while allowing 10% or more of volatile content to be present, and then the polymer film is shrunk by 10% or more to incline the angle of the absorption axis direction with respect to the longitudinal direction of the film.

8. The method for producing a polarizing plate as described in the items 6 or 7, wherein the conveyance speed in the longitudinal direction of the polymer film for the polarizing film is 1 m/min or more.

9. The method for producing a polarizing plate as described in any one of the items 6 to 8, wherein the drying point of the polymer film for the polarizing film is present until the holding release point.

10. The method for producing a polarizing plate as described in any one of the items 6 to 9, wherein the polymer film for the polarizing film is stretched after reducing the foreign matters adhering to the surface thereof to 1% or less per the surface area.

11. The method for producing a polarizing plate as described in any one of the items 6 to 10, wherein the polymer film for the polarizing film is a polyvinyl alcohol-base polymer film.

12. The method for producing a polarizing plate as described in the item 11, wherein a polarizing element is adsorbed to the polyvinyl alcohol-base polymer film before or after stretching.

13. The method for producing a polarizing plate as described in any one of the items 6 to 12, wherein the shrinking after stretching is performed by drying.

14. The method for producing a polarizing plate as described in any one of the items 6 to 13, wherein the drying treatment temperature at the time of shrinking the film and reducing the volatile content percentage is from 40 to 90°C

15. The method for producing a polarizing plate as described in the item 13, wherein the expansion coefficient of the polymer film after drying is lower than that before stretching.

16. The method for producing a polarizing plate as described in the item 15, wherein the water content percentage of the polymer film before the stretching is 30% or more and the water content percentage of the polymer film after the drying is 10% or less.

17. The method for producing a polarizing plate as described in any one of the items 13 to 16, wherein a protective film is attached to at least one surface of the polymer film that is stretched after or during the drying, and then the laminate is after-heated. 18. The method for producing a polarizing plate as described in the item 17, wherein respective operations of stretching, drying, attaching of the protective film and after-heating are performed in a through continuous line.

19. The method for producing a polarizing plate as described in any one of the items 6 to 18, wherein the angle made by the longitudinal direction and the absorption axis direction of the polarizing film is from 20 to 70°.

20. The method for producing a polarizing plate as described in the item 19, wherein the angle made by the longitudinal direction and the absorption axis direction of the polarizing film is from 40 to 50°.

21. A liquid crystal display comprising a liquid crystal cell and polarizing plates disposed in both sides of the liquid crystal cell, wherein at least one of the polarizing plates is a polarizing plate punched out from at least one selecting from the group consisting of: the polarizing plate described in the items 1, 2, 4 or 5; and a polarizing plate produced by the method described in any one of the items 3, 6 to 20.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

Fig. 7 is a schematic plan view showing the state of punching a conventional polarizing plate.

Fig. 8 is a schematic plan view showing the state of punching the polarizing plate of the present invention. Fig. 9 is a schematic plan view showing the layer structure of the liquid crystal display of Example 5.

Fig. 10 is a schematic conceptual view of an air blow device .

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

Fig. 12 is a schematic conceptual view of a blade device .

The reference numbers in the figure are as follows,

(i) direction of introducing film

(ii) direction of conveying film to next step

(a) step of introducing film

(b) step of stretching film

(c) step of delivering stretched film to next step Al position of engaging film with holding means and position of starting stretching film (substantial holding start point: right)

Bl position of engaging film with holding means (left)

Cl position of starting stretching film (substantial holding start point: left)

Cx position of releasing film and final basis position of film stretching (substantial holding release point: left) Ay final basis position of film stretching (substantial holding release point: right)

|L1-L2| difference in pathway between right and left film holding means

W substantial width at the end of film stretching step θ angle made by stretching direction and film- travelling direction

11 center line of film in the introduction side

12 center line of film delivered to next step

13 trajectory of film holding means (left)

14 trajectory of film holding means (right)

15 film in the introduction side

16 film delivered to next step

17, 17' left and right points of starting holding (engaging) film

18, 18' left and right points of releasing film from holding means

21 center line of film in the introduction side

22 center line of film delivered to next step

23 trajectory of film holding means (left)

24 trajectory of film holding means (right)

25 film in the introduction side

26 film delivered to next step

27, 27' left and right points of starting holding (engaging) film

28, 28' left and right points of releasing film from holding means

33, 43, 53, 63 trajectory of film holding means (left)

34, 44, 54, 64 trajectory of film holding means (right)

35, 45, 55, 65 film in the introduction side

36, 46, 56, 66 film delivered to next step

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

The polarizing plate of the present invention comprises a polarizing film having a polarizing ability and on both surfaces or one surface of the polarizing film, a protective film is usually provided through an adhesive layer. In general, a long polarizing plate (usually in a roll form) is produced and punched according to use, whereby a practical polarizing plate is obtained. Unless otherwise indicated, the "polarizing plate" as used in the present invention includes both a long polarizing plate and a polarizing plate punched out.

The polarizing plate of the present invention is as described above characterized in that in a long polarizing plate, the absorption axis of the polarizing film is neither in parallel nor perpendicular to the longitudinal direction (hereinafter, this long polarizing plate is sometimes simply referred to as an "obliquely oriented" polarizing plate) . The tilt angle between the longitudinal direction and the absorption axis direction is preferably from 10° to less than 90°, more preferably from 20 to 70°, still more preferably from 40 to 50°, particularly preferably from 44 to 46°. With this angle, a single polarizing plate can be obtained in a high yield in the step of punching it out from the long polarizing plate.

In the present invention, the tilt angle can be freely set. Accordingly, an optimal angle can be freely selected when the polarizing plate is used by combining it with other optical member.

The polarizing plate of the present invention is also characterized in that the single plate transmittance is 35% or more at 550 nm and the polarization degree is 80% or more at 550 nm. The single plate transmittance is preferably 40% or more and the polarization degree is preferably 95.0% or more, more preferably 99% or more, particularly preferably 99.9% or more. The polarizing plate of the present invention has excellent single plate transmittance and polarization degree and therefore, when used as a liquid crystal display, the contrast can be advantageously elevated.

The obliquely oriented polarizing plate of the present invention can be easily obtained by the method described below. That is, oblique orientation is obtained by the stretching of a polymer film and at the same time, the volatile content percentage at the stretching of film, the shrinkage percentage at the shrinking of film, and the elastic modulus of film before stretching are designed. It is also preferred to control the amount of foreign matters adhering to the film before stretching.

The polarizing plate of the present invention can be used for various uses, however, by virtue of its characteristic feature that the orientation axis is inclined with respect to the longitudinal direction, particularly the polarizing film where the tilt angle of the orientation axis is from 40 to 50° with respect to the longitudinal direction, is preferably used as a polarizing plate for LCD (in all liquid crystal modes such as TN, STN, OCB, ROCB, ECB, CPA, IPS and VA) , a circularly polarizing plate for antireflection of organic EL displays, or the like .

Furthermore, the polarizing plate of the present invention is suitable also for uses combined with various optical members, for example, phase difference film such as λ/4 plate and λ/2 plate, view angle enlarged film, antiglare film and hard coat film.

In the present invention, the roll form is sufficient if the length is 1 m or more and the roll has three or more turns. The length is preferably larger, however, if the length is too large, the weight of roll is excessively increased. Therefore, the length is preferably 10,000 m or less. The number of turns is preferably larger and 10 or more. As the inner diameter of the roll is smaller, the number of turns is larger. However, rather the inner diameter is preferably not excessively small because curling habit is generated. The inner diameter is preferably 1 inch or more. The width is not particularly limited but if the width is too small, the roll form is broken. Therefore, the width is preferably 5 cm or more.

In forming a roll, a core may be used. The construction material of the core is not particularly limited and any material commonly used in industry may be used, such as paper, iron and aluminum.

In the present invention, it is important for forming a roll to increase the length in the longitudinal direction. For this purpose, important is to control the volatile content percentage of film at the stretching, the shrinkage percentage at the shrinking of film, the conveyance speed in the longitudinal direction, the drying point of film, the amount of foreign matters adhering to the film before stretching, the temperature and humidity at the stretching, and the drying temperature at the drying for reducing the volatile content. The stretching method is described below and thereafter, respective important items are described.

The "deterioration due to exterior light during storage" as used in the present invention means the fluctuation of polarization degree when exposed to light under the conditions at storage, for example, when exposed to a fluorescent lamp, an incandescent lamp or the like. In general, the polarization degree is liable to decrease when exposed to light.

In the polarizing plate of a second embodiment of the present invention, the working width perpendicular to the longitudinal direction is 650 mm or more, preferably 1,300 mm or more.

The obliquely oriented polarizing plate of a second embodiment of the present invention can be easily obtained by the method described below. That is, the oblique orientation is obtained by stretching a polymer film, the tension in the longitudinal direction of the polymer film for a polarizing film at the stretching and the environmental humidity at the stretching are optimized, the water content percentage of the polymer film for a polarizing film at the dyeing is also optimized, and the swelling percentage after stretching and drying is made lower than that before stretching. It is also preferred to control the amount of foreign matters adhering to the film before stretching. In the dyeing step, dyeing and hardening of film may be performed at the same time.

In order to obtain a wide polarizing plate having an working width of 650 mm or more of the present invention, particularly important is to optimize the water content percentage of film after dyeing, the environmental humidity and the tension in the longitudinal direction of roll at the stretching of film, and the swelling percentage after stretching. Respective important items are described below. <Working Width>

The working width as used in the present invention means a width in the direction perpendicular to the longitudinal direction of a polarizing plate in a roll form which is obtained by stretching and drying a polymer film for a polarizing film, usually attaching a protective film and then cutting the edges for engaging. The polymer film for a polarizing film is engaged with tenter clips and an unstretched engagement width continuously remains at the film edges. The engagement width part not only have no polarizing performance but also makes it unable to attach a protective film. Therefore, this engagement width part is cut off but in this case, as the width of edge cut off is larger, the working width usable as a. polarizing plate more decreases. In the present invention, the width of edge cut off is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less, of the film width after stretching.

The working width of the polarizing plate of the present invention is 650 mm or more, preferably 1,300 mm or more, whereby the percentage of the width of edge cut off can be reduced to fall within the above-described range, the percentage of the usable portion in the polymer film for a polarizing film can be increased and the cost of the polarizing plate can be decreased. <Humidity at Stretching>

If the humidity at the stretching of film is insufficient, not only the film cannot be stretched but also failure of the tenter is caused. On the other hand, when the humidity at the stretching is high, phenomena such as deterioration of polarizing performance do not occur and the stretching is facilitated, therefore, this is very effective. Also in the case of stretching a film having water as the volatile content, such as polyvinyl alcohol and cellulose acylate, the film can be of course stretched in a high humidity conditioning atmosphere. In the case of polyvinyl alcohol, the humidity is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more. <Tension in Longitudinal Direction>

In the step of engaging, stretching and drying the polymer film, a tension must be continuously applied in the longitudinal direction. If the tension is insufficient at the time of engaging the film, the engagement width decreases and the film comes off from the holding means during stretching, whereas if the tension is too strong, not only the film cannot ride on the holding means and cannot be engaged but also the engagement width part after the film is engaged disadvantageously curls. In the present invention, the film is preferably stretched, dried and taken up while applying a constant tension in the longitudinal direction of the film. In the present invention, the film is preferably kept in a tense state when both edges of the film are held by holding means, so as to facilitate the holding. Specific examples of the method therefor include a method of applying a tension in the longitudinal direction using a tension controller and thereby tensioning the film. The tension varies depending on the state of film before stretching but is preferably applied to such a degree of not loosening the film.

In the present invention, the optimum value of the tension in the longitudinal direction varies depending on the kind of polymer film and the film conveyance speed in the longitudinal direction. The optimal tension is a tension of providing a state such that the film edge on a conveyance roll immediately before engagement repeats contacting with the roll or lifting. The tension is preferably from 100 to 500 N/m, more preferably from 350 to 450 N/m. <Volatile Content Percentage>

As the right and left pathways come to differ in the stretching step, wrinkling or slippage of film is generated. For solving these problems, it is very preferred in the present invention to stretch the polymer film while keeping its supporting property by allowing 5% or more of volatile content to be present before ' stretching and then shrink the film to reduce the volatile content percentage. The volatile content percentage as used in the present invention means a volume of volatile components contained per the unit volume of film and is a value obtained by dividing the volatile component volume by the film volume.

In the present invention, at least one step for incorporating a volatile content is preferably provided before stretching the polymer film for a polarizing plate. The step of incorporating a volatile content is performed, for example, by casting the film and incorporating a solvent or water or by dipping, coating or spraying the film in or with a solvent or water. The dyeing step or the step of adding a hardening agent described later in <Dyeing Formulation/Method> and <Addition of Hardening Agent, Metal Salt> may be served also as the step of incorporating a volatile content. In the case where the dyeing step serves also as the step of incorporating a volatile content, the step of adding a hardening agent is preferably provided before stretching. In the case where the step of adding a hardening agent serves also as the step of incorporating a volatile content, the dyeing step may be provided either before or after the stretching. When provided before the stretching, the dyeing step and the stretching step may be performed simultaneously.

The preferred volatile content percentage varies depending on the kind of the polymer film. The maximum of the volatile content percentage may be any as long as the polymer film can keep the supporting property. The volatile content percentage is preferably from 10 to 100% for polyvinyl alcohol and preferably from 10 to 200% for cellulose acylate. distribution of Volatile Component Content>

In the case of manufacturing a lengthy, particularly roll-form polarizing plate by a through step, it is necessary that uneven dyeing or non-dyed spot is not present. If the volatile component in the film before the stretching has an uneven distribution (difference in. the volatile component amount depending on the site in the film plane), this causes uneven dyeing or non-dyed spot. Accordingly, the distribution of the volatile component content in the film before stretching is preferably smaller and this is preferably at least 5% or less. The distribution of the volatile component content means a ratio of a larger difference out of differences between the maximum value or minimum value and the average volatile content percentage, to the average volatile content percentage of the volatile content percentages defined above. For reducing the distribution of the volatile component content, a method of blowing the front and back surfaces of the film with a uniform air, a method of uniformly squeezing the film by nip rollers, or a method of wiping off the volatile component by a wiper (for example, a blade or a sponge) may be used, however, any method may be used insofar as the distribution can be made uniform. Figs. 10 to 12 show each example of the air blow device, the nip device and the blade device.

The distribution of the volatile component content means a fluctuation width (%) of the volatile content percentage per 1 m². The volatile content percentage means a volume (%) of volatile components contained per the unit volume of film, in other words, a value obtained by dividing the volatile component volume by the film volume.

For example, in the case of producing a polarizing plate using a polyvinyl alcohol-base film, the film is dipped in an aqueous iodine solution or the like as described later. At this time, the volatile component is water. The water content distribution can be determined as a ratio of the difference between the maximum and minimum water content amounts of 25 samples to the average value when 5 portions in a square of 1 cm x 1 cm are punched out uniformly from each of the vertical and transverse sides of a square film of 50 cm x 50 cm and the water content amount (volatile content percentage) is measured by a bone dry method. In the present invention, the distribution of the water content in the film plane as obtained by this measurement is set to 5% or less. <Water Content Percentage, Distribution of Water Content Percentage>

The polymer for a polarizing film of the present invention is preferably a polyvinyl alcohol-base polymer and in this case, the volatile content is preferably water

In the case of the polarizing plate of the present invention, for the purpose of increasing the stretching magnification in the cross direction, the film is preferably increased in the water content percentage before stretching, then stretched in a high-temperature and high-humidity atmosphere and thereafter rapidly reduced in the water content percentage. In the present invention, the water content percentage before the stretching of the polarizing plate is preferably 30% or more and a higher water content percentage is more preferred. Immediately after the stretching, the film is dried. The water content percentage immediately after the stretching is preferably 50% or less and a higher reduction rate of the water content percentage is more preferred. The polarizing film is then dried and attached with a protective film and at this time, the water content percentage is preferably 10% or less, more preferably 5% or less. The water content percentage as used in the present invention means a volume of water content contained per the unit volume of film and is a value obtained by dividing the water content volume by the film volume.

The distribution of water content percentage as used in the present invention means a ratio of a larger difference out of differences between the maximum value or minimum value of the water content percentage and the average water content percentage, to the average water content percentage in the cross direction of the roll-form film. For example, when the minimum value of the water content percentage is 44.0% and the maximum value is 44.5% at both edges of the film, the distribution of water content percentage is 0.5%. In the present invention, the distribution of water content percentage is preferably 20% or less, more preferably 10% or less, still more preferably 5% or less. The water content percentage distribution of the polymer film after the step of dyeing a polarizer and a hardening agent of the present invention is preferably smaller, because if this is large, unevenness and streaks are generated. <Through Step>

In the present invention, a drying step of shrinking the stretched polymer film to reduce the volatile content percentage and after attaching a protective film at least to one surface of the film after or during drying, a step of after-heating the film are preferably provided. Specific examples of the method for attaching the protective film include a method of attaching a protective film to the polarizing film using an adhesive while keeping the state of holding both edges of the polarizing film during the drying step and then cutting both edges, and a method of releasing the polarizing film from the both edges-holding part after drying, cutting both edges of the film and attaching a protective film thereto. For cutting edges, a general technique may be used, for example, a method of cutting edges using a cutter such as edged tool or a method of using a laser. The combined films are preferably after-heated so as to dry the adhesive and improve the polarizing performance. The after-heating condition varies depending on the adhesive but in the case of an aqueous adhesive, the heating temperature is preferably 30°C or more, more preferably from 40 to 100°C, still more preferably from 50 to 80°C These steps are preferably performed in a through production line in view of performance and production efficiency.

The obliquely oriented polarizing plate in the production method of the polarizing film of the present invention can be easily obtained by the method described below. That is, oblique orientation is obtained by the stretching of a polymer film and at the same time, the volatile component content distribution and volatile content percentage before the stretching of film and the stretching atmosphere at the stretching, such as stretching temperature and stretching humidity, are designed. It is also preferred to control the amount of foreign matters adhering to the film before stretching. By these, a high-grade inexpensive long polarizing plate can be obtained even if obliquely stretched, without causing drawing or wrinkling on the stretched film.

In the production method of the polarizing film of the present invention, both edges of a film for a polarizing film are held by holding means and therefore, the film is difficult to stretch in a solution as in ordinary polarizing plate producing means. Accordingly, the film is preferably stretched while applying humidity after dipping the film in a dyeing solution, a hardening solution or both thereof. The stretching atmosphere is preferably at a temperature of 10 to 100°C and a humidity of 70% or more, more preferably at a temperature of 40 to 50°C and a humidity of 80% or more.

Under these conditions, however, distribution of excess dyeing solution or hardening solution is present in the surface of film before stretching. This distribution gives rise to unevenness on a polarizing film after stretching. In order to prevent the generation of this unevenness, it is important in the present invention to provide a state such that the content distribution of a dyeing solution or a hardening solution in the film, namely, the volatile components in the film is 5% or less, before the stretching.

The stretching method is described below, and thereafter, respective important items are described. <Stretching Method>

Figs. 1 and 2 each is a schematic plan view showing an example of the method for obliquely stretching a polymer film according to the present invention. .

The stretching method of the present invention comprises (a) a step of introducing an original film in the direction of the arrow (i) , (b) a step of stretching the film in the cross direction, and (c) a step of conveying the stretched film to the next step in the direction of the arrow (ii) . The "stretching step" referred to hereinafter contains these steps (a) to (c) and indicates the entire step for performing the stretching method of the present invention.

The film is continuously introduced from the direction (i) and first held at the point Bl by the holding means in the left side seen from upstream. At this point, the other edge of the film is not held and tension is not generated in the cross direction. In other words, the point Bl is not a point where the holding is substantially started (hereinafter referred to as a "substantial holding start point") .

In the present invention, the substantial holding start point is defined as the point where both edges of the film are first held. The substantial holding start point includes two points, that is, a holding start point Al in the more downstream side and a point Cl where a straight line drawn almost perpendicularly to the center line 11 (Fig. 1) or 21 (Fig. 2) of the film in the introduction side from Al meets the trajectory 13 (Fig. 1) or 23 (Fig. 2) of the holding means in the opposite side.

Starting from these points, when the film is conveyed by the holding means at both edges at a substantially equal speed, Al moves to A2 , A3 ... An every each unit time and Cl similarly moves to C2, C3 ... Cn. That is, the straight line connecting points An and Cn where the holding means as the bases pass at the same time is the stretching direction at that time.

In the method of the present invention, as shown in Figs. 1 and 2, An is gradually delayed from Cn and therefore, the stretching direction is gradually inclined from the direction perpendicular to the conveyance direction. In the present invention, the point of substantially releasing the holding (hereinafter referred to as a "substantial holding release point") is defined by two points, that is, a point Cx where the film leaves from the holding means in the more upstream side, and a point Ay where a straight line drawn almost perpendicularly to the center line 12 (Fig. 1) or 22 (Fig. 2) of the film delivered to the next step from Cx meets the trajectory 14 (Fig. 1) or 24 (Fig. 2) of the holding means in the opposite side.

The angle of the final stretching direction of the film is determined by the ratio of the pathway difference between the right and left holding means at the substantial end point of the stretching step (substantial holding release point), Ay-Ax (that is, |L1-L2|), to the distance W between substantial holding release points (distance between Cx and Ay) . Accordingly, the tilt angle θ of the stretching direction with respect to the conveyance direction to the next step is an angle satisfying the relationship: tanθ = W/ (Ay-Ax), that is, tanθ = W/IL1-L2 |

The film edge in the upper side of Figs. 1 and 2 is held until 18 (Fig. 1) or 28 (Fig. 2) even after the point Ay, however, since the other edge is not held, the stretching in the cross direction is not newly generated. Therefore, 18 and 28 are not a substantial holding release point . In the present invention, as in the above, the substantial holding start points present at both edges of the film are not a point where the film is merely engaged with each of right and left holding means. To more strictly describe the two substantial holding start points of the present invention defined above, these are defined as points where a straight line connecting the left or right holing point and another holding point almost orthogonally meets the center line of the film introduced into the step of holding the film, and which are two holding points positioned most upstream.

Similarly, in the present invention, the two substantial holding release points are defined as points where a straight line connecting the left or right holding point and another holding point almost orthogonally meets the center line of the film delivered to the next step, and which are two holding points positioned most downstream.

The term "almost orthogonally meet" as used herein means that the center line of the film makes an angle of 90±0.5° with the straight line connecting the left and right substantial holding start points or substantial holding release points.

In the case of giving a difference between the left and right pathways by using a tenter-system stretching machine as in the present invention, due to the mechanical limitation such as rail length, there arises a large dislocation between the point of being engaged with the holding means and the substantial holding start point or between the point of being disengaged from the holding means and the substantial holding release point, however, as long as the pathway from the substantial holding start point to the substantial holding release point defined above satisfies the relationship in formula (1), the object of the present invention can be achieved.

The tilt angle of the orientation axis of the stretched film can be controlled and adjusted by the ratio of the outlet width W in the step (c) to the substantial difference in the pathway between the right and left holding means |L1-L2|.

For the polarizing plate and phase difference film, a film oriented at 45° with respect to the longitudinal direction is often required. In this case, for obtaining an orientation angle close to 45°, the following formula (2) is preferably satisfied: Formula (2): 0.9W< | L1-L2 | <1.1W,

More preferably, the following (3) is satisfied: Formula (3): 0.97W< | L1-L2 | <1.03W.

As long as the formula (1) is satisfied, the specific structure for the stretching step can be freely designed as shown in Figs. 1 to 6 by taking account of the equipment cost and productivity.

The angle made by the direction (i) of introducing the film into the stretching step and the direction (ii) of conveying the film to the next step may have an arbitrary numerical value, however, from the standpoint of minimizing the total installation area for the equipment including the steps before and after the stretching, this angle is preferably smaller and is preferably 3° or less, more preferably 0.5° or less. This value can be achieved, for example, by the structure shown in Figs. 1 and 4.

In such a method where the film travelling direction is substantially not changed, the orientation angle of 45° with respect to the longitudinal direction, which is preferred as a polarizing plate or phase difference film, is difficult to obtain only by the enlargement of the width of the holding means. As in Fig. 1, by providing a step of shrinking the film after the film is once stretched, |L1-L2| can be made large.

The stretching ratio is preferably from 1.1 to 10.0 times, more preferably from 2 to 10 times. The shrinkage percentage after that is preferably 10% or more. Furthermore, as shown in Fig. 4, the stretching-shrinking is also preferably repeated a plurality of times because |L1-L2| can be made large. From the standpoint of minimizing the equipment cost for the stretching step, the number of bends in the trajectory of the holding means and the angle of bend are preferably smaller. In this viewpoint, as shown in Figs. 2, 3 and 5, the film travelling direction is preferably bent while keeping the state of holding both edges of the film so that the angle made by the film travelling direction at the outlet of the step of holding both edges of the film and the substantial stretching direction of the film can be inclined at 20 to 70°.

In the present invention, the device for stretching the film by applying tension while holding both edges is preferably a tenter device as shown in Figs. 1 to 5. Other than the conventional two-dimensional tenter, a stretching step where, as shown in Fig. 6, a difference is spirally given between the pathways of the gripping means at both edges may also be used.

In many cases, the tenter-type stretching machine has a structure where a clip-fixed chain runs along the rail. However, when a vertically non-uniform stretching method as in the present invention is employed, the end terminal of one rail dislocates, as shown in Figs. 1 and 2, from the end terminal of another rail at the inlet and outlet of the step and engaging or disengaging does not occur simultaneously between left and right edges. In this case, the substantial pathway lengths Ll and L2 are not a simple engaging-to-disengaging distance but, as already described above, a length of pathway where the holding means hold both edges of the film.

If the film travelling speed is different between left and right edges at the outlet of the stretching step, wrinkling or slippage occurs. Therefore, right and left film gripping means are demanded to convey the film substantially at the same speed. The difference in the speed is preferably 1% or less, more preferably less than 0.5%, most preferably less than 0.05%. The speed as used herein means the length of trajectory which each of left and right holding means proceeds per minute. In a general tenter stretching machine or the like, according to the cycle of sprocket wheel driving the chain, the frequency of driving motor and the like, unevenness in the order of seconds or less is generated in the speed and unevenness of a few % is often generated, however, these do not come under the difference in the speed referred to in the present invention. <Conveyance Speed in Longitudinal Direction>

In the case of stretching a polyvinyl alcohol film imparted with a hardening agent, as the stretching time passes, the hardening of the film proceeds. Therefore, the conveyance speed in the longitudinal direction of the polymer film is preferably 1 m/min or more. A higher speed is preferred in view of productivity. In any case, the upper limit varies depending on the film stretched and the stretching machine. <Shrinking>

The shrinking of the stretched polymer film may be performed in either during or after stretching. Shrinking may suffice if it eliminates the wrinkling of polymer film generated at the orientation in the oblique direction. For shrinking the film, a method of heating the film and thereby removing the volatile content may be used, however, any means may be used if it can shrink the film. The film is preferably shrunk to 1/sinθ or more times, where θ is an orientation angle with respect to the longitudinal direction. The shrinkage percentage is preferably 10% or more . <Volatile Content Percentage>

As the right and left pathways come to differ, wrinkling or slippage of film is generated. In order to solve these problems, the present invention is characterized in that the polymer film is stretched while keeping the supporting property and allowing 5% or more of volatile content to be present, and then shrunk to reduce the volatile content percentage. The volatile content percentage as used in the present invention means a volume of volatile components contained per the unit volume of film and is a value obtained by dividing the volatile component volume by the film volume. Examples of the method of incorporating the volatile content include a method of casting the film and incorporating a solvent or water, a method of dipping, coating or spraying the film in or with a solvent or water before stretching, and a method of coating a solvent or water during stretching.- The hydrophilic polymer film such as polyvinyl alcohol contains water in a high-temperature high-humidity atmosphere and therefore, by stretching the film after humidity conditioning in a high-humidity atmosphere or stretching the film in a high-humidity condition, the volatile content can be incorporated. Other than these methods, any means may be used if the volatile content of the polymer film can be made 5% or more.

The preferred volatile content percentage varies depending on the kind of the polymer film. The maximum of the volatile content percentage may be any as long as the polymer film can keep the supporting property. The volatile content percentage is preferably from 10 to 100% for polyvinyl alcohol and preferably from 10 to 200% for cellulose acylate. <Elastic Modulus>

As for the physical properties of the polymer film before stretching, if the elastic modulus is too low, the shrinkage percentage during or after stretching decreases and the wrinkling difficultly disappears, whereas if it is excessively high, a great tension is applied at the stretching, as a result, the portion of holding both edges of the film must be increased in the strength and a load on the machine increases. In the present invention, the elastic modulus of the polymer film before stretching is preferably, in terms of Young's modulus, from 0.1 to 500 MPa, more preferably from 1 to 100 MPa . <Distance from Generation of Wrinkling to Disappearance>

The wrinkling of polymer film, generated at the orientation in the oblique direction, may be sufficient if it disappears until the substantial holding release point as referred to in the present invention. However, if a long time is spent from the generation of wrinkling to the disappearance, dispersion may be generated in the stretching direction. Therefore, the wrinkling preferably disappears in a travelling distance as short as possible from the point where the wrinkling is generated. For this purpose, for example, a method of increasing the volatilization speed of the volatile content may be used. <Foreign Matters>

In the present invention, if foreign matters are adhering to the polymer film before stretching, the surface becomes coarse. Therefore, the foreign matters are preferably removed. If foreign matters are present, particularly at the time of manufacturing a polarizing plate, these cause color/optical unevenness. It is also important that foreign matters do not adhere to the polymer film until a protective film is combined. Therefore, the polarizing plate is preferably manufactured in an environment where the floating dusts are reduced as much as possible. The amount of foreign matters as used in the present is a value obtained by dividing the weight of foreign matters adhering to the film surface by the surface area and is expressed by the gram number per square meter. The amount of foreign matters is preferably 1 g/m² or less, more preferably 0.5 g/m² or less. The smaller amount is more preferred.

The method for removing foreign matters is not particularly limited and any method may be used as long as it can remove the foreign matters without adversely affecting the polymer film before stretching. Examples thereof include a method of jetting a water flow to scrape off the foreign matters, a method of scraping off the foreign matters by a gas jet, and a method of scraping off the foreign matters using a blade of cloth, rubber or the like . <Drying: drying speed and drying point> In order to manufacture a lengthy, particularly roll- form polarizing plate, a protective film must be attached in the state where the volatile content is decreased. The polymer film preferably has a drying point before the holding of both edges is released. More preferably, the drying point is adjusted to come in a traveling distance as short as possible after a desired orientation angle is obtained. The drying point means a site where the surface temperature of film becomes equal to the atmosphere temperature in the environment. From this reason, the drying speed is also preferably as high as possible. <Drying Temperature>

The polymer film must be dried until it is combined with a protective film and therefore, in the case of preparing a polarizing plate using a polyvinyl alcohol film, the drying temperature is preferably from 20 to 100°C, more preferably from 40 to 90°C, still more preferably from 60 to 85°C. <Swelling Percentage>

In the present invention, when the polymer film is polyvinyl alcohol film and a hardening agent is used, the swelling percentage with water is preferably different between before and after the stretching so as not to relieve but to keep the state of being stretched in the oblique direction. More specifically, it is preferred that the swelling percentage before stretching is high and the swelling percentage after stretching and drying becomes low. More preferably, the swelling percentage with water before stretching is larger than 3% and the swelling percentage after drying is 3% or less. Prescription of Bending Part>

The rail of regulating the trajectory of the holding means in the present invention is often demanded to have a large bending ratio. For the purpose of avoiding interference of film gripping means with each other due to abrupt bending or avoiding local concentration of stress, the trajectory of the gripping means preferably draws a circular arc at the bending part. <Stretching Speed>

In the present invention, the speed at which the film is stretched is preferably higher and when expressed by the stretching magnification per unit time, this is 1.1 times/min or more, preferably 2 times/min or more. The travelling speed in the longitudinal direction is 0.1 m/min or more, preferably 1 m/min or more. A higher travelling speed is preferred in view of productivity. In either case, the upper limit varies depending on the film stretched and the stretching machine. <Tension in Longitudinal Direction>

In the present invention, at the time of holding both edges of the film by holding means, the film is preferably tensioned to facilitate the holding. Specific examples of the method therefor include a method of applying a tension in the longitudinal direction to make the film tense. The tension varies depending on the state of film before stretching but is preferably applied to such a degree of not loosening the film. <Temperature at Stretching>

In the present invention, the ambient temperature at the time of stretching the film may be sufficient if it is at least higher than the solidification point of volatile content contained in the film. In the case where the film is polyvinyl alcohol, the ambient temperature is preferably 25°C or more. In the case of stretching polyvinyl alcohol dipped in iodine/boric acid for the manufacture of a polarizing film, the ambient temperature is preferably from 30 to 90°C, more preferably from 40 to 90°C. <Humidity at Stretching>

In the case of stretching a film having water as the volatile content, the film is preferably stretched in a humidity conditioning atmosphere. Particularly, in the case where a hardening agent is imparted, if the amount of water contained decreases, the hardening of the film proceeds and the film becomes difficult to stretch. Accordingly, the humidity is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more. <Polymer Film for Polarizing Film>

In the present invention, the polymer film to be stretched is not particularly limited and a film comprising a polymer having appropriate thermoplasticity may be used. Examples of the polymer include PVA, polycarbonate, cellulose acylate and polysulfone.

The thickness of the film before stretching is not particularly limited, however, in view of stability of film holding and uniformity of stretching, the thickness is preferably from 1 μm to 1 mm, more preferably from 20 to 200 μm.

The polymer for a polarizing film is preferably PVA. PVA is usually obtained by saponifying polyvinyl acetate but may contain a component copolymerizable with vinyl acetate, such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins and vinyl ethers. Also, a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like may be used.

The saponification degree of PVA is not particularly limited but in view of solubility and the like, is preferably from 80 to 100 mol%, more preferably from 90 to 100 mol%. Also, the polymerization degree of PVA is not particularly limited but is preferably from 1,000 to 10,000, more preferably from 1,500 to 5,000. <Dyeing Formulation/Method>

The polarizing film is obtained by dyeing PVA and the dyeing step is performed by gas-phase or liquid-phase adsorption. As an example of the liquid-phase dyeing, when iodine is used, the dyeing is performed by dipping the PVA film in an aqueous iodine-potassium iodide solution. The iodine is preferably from 0.1 to 20 g/liter, the potassium iodide is preferably from 1 to 200 g/liter and the weight ratio of iodine and potassium iodide is preferably from 1 to 200. The dyeing time is preferably from 10 to 5,000 seconds and the liquid temperature is preferably from 5 to 60°C. The dyeing method is not limited only to dipping but any means can be used, such as coating or spraying of iodine or a dye solution. The dyeing step may be provided either before or after the stretching step of the present invention, however, the dyeing is preferably performed in liquid phase before the stretching step, because the film is appropriately swelled and the stretching thereof is facilitated.

In the process of producing a polarizing film by stretching PVA, an additive capable of crosslinking PVA is preferably used. Particularly, when the oblique stretching method of the present invention is used, if PVA is not sufficiently hardened at the outlet of the stretching step, the orientation direction of PVA may be shifted due to tension in the step. Therefore, a crosslinking agent is preferably incorporated into PVA by dipping PVA in a crosslinking agent solution or by coating the solution, in the step before stretching or in the stretching step. The means to impart the crosslinking agent to the PVA film is not particularly limited and any method such as dipping, coating or spraying the film in or with the solution may be used, however, a dipping method and a coating method are preferred. As the coating means, any commonly known means such as roll coater, die coater, bar coater, slide coater and curtain coater may be used. Also, a method of bringing a cloth, cotton, porous material or the like impregnated with the solution into contact with the film is preferred. As the crosslinking agent, those described U.S. Re232897 can be used, however, boric acid and borax are preferably used in practice. In addition, a metal salt such as zinc, cobalt, zirconium, iron, nickel and manganese may also be used in combination.

After the hardening agent is added, a rinsing/water washing step may be provided.

The hardening agent may be imparted before or after the film is engaged in the stretching machine. This may be performed in any step until the end of the step (b) in examples shown in Figs. 1 and 2, where the stretching in the cross direction is substantially finished. <Polarizer>

Other than iodine, it is also preferred to dye the film with a dichromatic dye. Specific examples of the dichromatic dye include dye-type compounds such as azo- base dye, stilbene-base dye, pyrazolone-base dye, triphenyl methane-base dye, quinoline-base dye, oxazine- base dye, thiadine-base dye and anthraquinone-base dye. A water-soluble compound is preferred but the present invention is not limited thereto. Also, a hydrophilic substituent such as sulfonic acid group, amino group and hydroxyl group is preferably introduced into these dichromatic molecules. Specific examples of the dichromatic molecule include C.I. Direct Yellow 12, C.I. Direct Orange 39, C.I. Direct Orange 72, C.I. Direct Red 39, C.I. Direct Red 79, C.I. Direct Red 81, C.I. Direct Red 83, C.I. Direct Red 89, C.I. Direct Violet 48, C.I. Direct Blue 67, C.I. Direct Blue 90, C.I. Direct Green 59, C.I. Acid Red 37 and dyes described in JP-A-62-70802, JP- A-l-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105, JP--A-1-265205 and JP-A-7-261024. These dichromatic molecules are used as a free acid, an alkali metal salt, an ammonium salt or a salt of amines. By blending two or more of these dichromatic molecules, a polarizer having various colors can be produced. A polarizing device or polarizing plate where a compound (dye) of providing black color when polarization axes are orthogonally crossed is blended or where various dichromatic molecules are blended to provide black color is preferred because both the single plate transmittance and the polarization degree are excellent. In the present invention, unless otherwise indicated, the transmittance means single plate transmittance.

The stretching method of the present invention is also preferably used in the production of a so-called polyvinylene-base polarizing film where PVA or polyvinyl chloride is dehydrated or dechlorinated to form a polyene structure and the polarization is obtained by the conjugate double bond. <Protective Film>

The polarizing film produced in the present invention is used as a polarizing plate after attaching a protective film to both surfaces or one surface of the polarizing film. The kind of the protective film is not particularly limited and, for example, cellulose acylates such as cellulose acetate and cellulose acetate butyrate, polycarbonate, polyolefin, polystyrene and polyester can be used. The protective film of a polarizing plate is required to have properties such as transparency, appropriate moisture permeability, low birefringence and appropriate rigidity and from the overall view, cellulose acylates are preferred and cellulose acetate is more preferred.

The protective film is usually fed in a roll form and preferably attached continuously to a long polarizing plate so that the longitudinal directions can agree. Here, the orientation axis (phase lag axis) of the protective film may run in any direction but in view of simplicity and easiness of operation, the orientation axis of the protective film is preferably in parallel to the longitudinal direction.

The angle between the phase lag axis (orientation axis) of the protective film and the absorption axis (stretching axis) of the polarizing film is also not particularly limited and may be appropriately set according to the purpose of the polarizing plate. The absorption axis of the long polarizing plate of the present invention is not in parallel to the longitudinal direction and therefore, when the protective film having an orientation axis in parallel to the longitudinal direction is continuously attached to the length polarizing plate of the present invention, a polarizing plate where the absorption axis of the polarizing film and the orientation axis of the protective film are not in parallel is obtained. The polarizing plate where the polarizing film and the protective film are combined such that the absorption axis of the polarizing film and the orientation axis of the protective film run not in parallel is excellent in the dimensional stability. This performance is advantageously exerted particularly when the polarizing plate is used for a liquid crystal display. The angle between. the phase lag axis of the protective film and the absorption axis of the polarizing film is preferably from 10° to less than 90°, more preferably from 40° to less than 50°. With this angle, a high dimensional stability effect is exerted.

The protective film may have any physical property values according to use end and representative preferred values in the case of using the protective film for normal transmission-type LCD are described below. In view of handleability and durability, the film thickness is preferably from 5 to 500 μm, more preferably from 20 to 200 μm, still more preferably from 20 to 100 μm. The retardation value at 632.8 nm is preferably from 0 to 150 nm, more preferably from 0 to 20 nm, still more preferably from 0 to 10 nm, particularly preferably from 0 to 5 nm. The phase lag axis of the protective film preferably runs substantially in parallel or orthogonally to the absorption axis of the polarizing film from the standpoint of avoiding the elliptic formation of the linear polarization. However, this does not apply when the protective film is imparted with a function of changing the polarization property, such as phase difference plate, and the absorption axis of the polarizing plate can make any angle with the phase lag axis of the protective film.

The visible light transmittance is preferably 60% or more, more preferably 90% or more. The dimensional decrease after the treatment at 90°C for 120 hours is preferably from 0.3 to 0.01%, more preferably from 0.15 to 0.01%. The tensile strength in the film tensile test is preferably from 50 to 1,000 MPa, more preferably from 100 to 300 MPa. The moisture permeability of the film is preferably from 100 to 800 g/m² -day, more preferably from 300 to 600 g/m²-day.

Of course, the present invention is not limited to these values.

The cellulose acylate which is preferred as the protective film is described in detail below. In a preferred cellulose acylate, the substitution degree to the hydroxyl group of cellulose satisfies all of the following formulae (I) to (IV): ( I ) 2 . 6<A+B<3 . 0

( I I ) 2 . 0<A<3 . 0

( I I I ) O≤B≤O . 8

( IV) 1 . 9<A-B wherein A and B each represents a substitution degree of an acyl group substituted to the hydroxyl group of cellulose, A is a substitution degree of an acetyl group and B is a substitution degree of an acyl group having from 3 to 5 carbon atoms. Cellulose has three hydroxyl groups in one glucose unit and the numerals above show the substitution degree for the hydroxyl group 3.0 and the maximum substitution degree is 3.0. In cellulose triacetate, the substitution degree A is generally from 2.6 to 3.0 (in this case, the hydroxyl group not substituted is maximally 0.4) and B is 0. The cellulose acylate used as a protective film of a polarizing plate is preferably cellulose triacetate where the acyl groups all are an acetyl group, or cellulose acylate where the acetyl group is 2.0 or more, the acyl group having from 3 to 5 carbon atoms is 0.8 or less and the hydroxyl group not substituted is 0.4 or less. The acyl group having from 3 to 5 carbon atoms is more preferably 0.3 or less in view of physical properties. The substitution degree can be obtained by calculating from the measured bonding degrees of acetic acid and fatty acid having from 3 to 5 carbon atoms substituted to the hydroxyl group of cellulose. The measurement may be performed by the method according to ASTM D-817-91.

The acyl group having from 3 to 5 carbon atoms other than acetyl group includes a propionyl group (C₂H₅CO-) , a butyryl group (C₃HCO-) (n-, iso-) and a valeryl group (C₄H₉CO-) (n-, iso-, sec-, tert-) . Among these, n- substituted groups are preferred in view of mechanical strength of film formed, easy dissolution and the like, and an n-propionyl. group is more preferred. If the substitution degree of acetyl group is low, the mechanical strength and resistance against humidity and heat are decreased. When the substitution degree of acyl group having from 3 to 5 carbon atoms is high, the dissolution property in an organic solvent is enhanced but when respective substitution degrees are within the above- described ranges, good physical properties are attained.

The polymerization degree (viscosity average) of cellulose acylate is preferably from 200 to 700, more preferably from 250 to 550. The viscosity average polymerization degree can be measured by the Ostwald viscometer. From the intrinsic viscosity [η] of cellulose acylate measured, the polymerization degree can be determined according to the following formula: DP=[η] /Km (wherein DP is a viscosity average polymerization degree and Km is a constant of 6xl0^-4) .

The cellulose as a raw material of the cellulose acylate includes cotton linter and wood pulp but cellulose acylates obtained from any raw material cellulose can be used or a mixture thereof may also be used.

The cellulose acylate is usually produced by a solvent casting method. In the solvent casting method, a cellulose acylate and various additives are dissolved in a solvent to prepare a thick solution (hereinafter referred to as a "dope") and cast on an endless support such as drum or band and the solvent is evaporated to form a film. The dope is preferably adjusted to a solid content concentration of 10 to 40 wt%. The drum or band is preferably finished to have a mirror surface. The casting and drying method in the solvent casting method are described in U.S. Patents 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069 and 2,739,070, British Patents 640,731 and 736,892, JP-B-45-4554, JP-B- 49-5614, JP-A-60-176834, JP-A-60-203430 and JP-A-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, the film may be produced by casting solutions containing the dope respectively from a plurality of casting ports provided at intervals in the support running direction to stack one on another and the methods described, for example, in JP-A-61-158414, JP-A-1-122419 and JP-A-11-198285 can be applied. The film may be also formed by casting cellulose acylate solutions from two casting ports and this can be practiced by the methods described, for example, in JP-B-60-27562 , JP-A-61-94724, JP-A-61-947245, JP-A-61-104813, JP-A-61-158413 and JP-A-6- 134933. Furthermore, the casting method described in JP-A- 56-162617 may also be preferably used, where the flow of a high-viscosity dope is wrapped with a low-viscosity dope and the high-viscosity and low-viscosity dopes are simultaneously extruded.

Examples of the organic solvent in which the cellulose acylate is dissolved include hydrocarbons (e.g., benzene, toluene), halogenohydrocarbons (e.g., methylene chloride, chlorobenzene) , alcohols (e.g., methanol, ethanol, diethylene glycol), ketones (e.g., acetone), esters (e.g., ethyl acetate, propyl acetate) and ethers (e.g., tetrahydrofuran, methyl cellosolve) . Among these, halogenohydrocarbons having from 1 to 7 carbon atoms are preferred and methylene chloride is most preferred. In view of solubility of cellulose acylate, strippability from support and physical properties of film such as mechanical strength and optical property, one or a plurality of alcohol (s) having from 1 to 5 carbon atoms is (are) preferably mixed in addition to methylene chloride. The content of alcohol is preferably from 2 to 25 wt%, more preferably from 5 to 20 wt%, based on the solvent as a whole. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol and n-butanol. Among these, methanol, ethanol, n-butanol and a mixture thereof are preferred.

In addition to the cellulose acylate, the dope may arbitrarily contain, as the component which becomes a solid content after drying, a plasticizer, an ultraviolet absorbent, an inorganic fine particle, a heat stabilizer such as alkaline earth metal salt (e.g., calcium, magnesium) , an antistatic agent, a flame retardant, a lubricant, an oil agent, a release accelerator from support, a hydrolysis inhibitor for cellulose acylate, and the like.

The plasticizer which is preferably added is a phosphoric acid ester or a carboxylic acid ester. Examples of the phosphoric acid ester include triphenyl phosphate (TPP) , tricresyl phosphate (TCP) , cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate and tributyl phosphate. Representative examples of the carboxylic acid ester include phthalic acid ester and citric acid ester. Examples of the phthalic acid ester include dimethyl phthalate (DMP) , diethyl phthalate (DEP) , dibutyl phthalate (DBP) , dioctyl phthalate (DOP) , diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP) . Examples of the citric acid ester include triethyl 0- acetylcitrate (OACTE) , tributyl O-acetylcitrate (OACTB) , acetyl triethyl citrate and acetyl tributyl citrate.

Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and trimellitic acid esters such as trimethyl trimellitate, Examples of the glycolic acid ester include triacetin, tributyrin, butylphthalyl butyl glycolate, ethylphthalyl ethyl glycolate and methylphthalyl ethyl glycolate.

Among these plasticizers, preferred are triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethylhexyl phthalate, triacetin, ethylphthalyl ethyl glycolate and trimethyl trimellitate, more preferred are triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethylphthalyl ethyl glycolate and trimethyl trimellitate. These plasticizers may be used individually or in combination of two or more thereof. The amount of the plasticizer added is preferably from 5 to 30 wt%, more preferably from 8 to 16 wt%, based on the cellulose acylate. These compounds may be added together with the cellulose acylate or solvent at the preparation of the cellulose acylate solution or may be added during or after the preparation of solution.

The ultraviolet absorbent may be freely selected according to the purpose and, for example, salicylic acid ester-base, benzophenone-base, benzotriazole-base, benzoate-base, cyanoacrylate-base and nickel complex salt- base absorbents can be used. Among these, benzophenone- base, benzotriazole-base and salicylic acid ester-base absorbents are preferred. Examples of the benzophenone- base ultraviolet absorbent include 2 , 4-dihydroxy- benzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy- 4-methoxybenzophenone, 2,2' -dihydroxy-4- methoxybenzophenone, 2,2' -dihydroxy-4 , 4 ' - methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2- hydroxy-4-dodecyloxybenzophenone and 2-hydroxy-4- (2- hydroxy-3-methacryloxy) propoxybenzophenone. Examples of the benzotriazole-base ultraviolet absorbent include 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 and 2- (2 ' -hydroxy-5 ' -tert-octyl- phenyl) benzotriazole . Examples of the salicylic acid ester-base ultraviolet absorbent include phenyl salicylate, p-octylphenyl salicylate and p-tert-butylphenyl salicylate , Among these ultraviolet absorbents, preferred are 2- hydroxy-4-methoxybenzophenone, 2,2' -dihydoxy-4, 4 ' - methoxybenzophenone, 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 and 2- (2 ' -hydroxy-3 ' , 5 ' -di- tert-butylphenyl) -5-chlorobenzotriazole .

A plurality of absorbents different in the absorption wavelength are preferably used in combination because a high shielding effect can be obtained over a wide wavelength range. The amount of the ultraviolet absorbent is preferably from 0.01 to 5 wt%, more preferably from 0.1 to 3 wt%, based on the cellulose acylate. The ultraviolet absorbent may be added simultaneously at the time of dissolving the cellulose acylate or may be added to the dope after the dissolution. In particular, a form of adding an ultraviolet absorbent solution to the dope using a static mixer or the like immediately before casting is preferred.

Examples of the inorganic fine particle added to the cellulose acylate include silica, kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide and alumina, and these may be freely used according to the purpose. The fine particles are preferably dispersed in a binder solution by arbitrary means such as high-speed mixer, ball mill, attritor or ultrasonic disperser before adding these to the dope. The binder is preferably a cellulose acylate. It is also preferred to disperse the fine particle together with other additives such as ultraviolet absorbent. Any dispersion solvent may be used but a dispersion solvent having a composition close to the dope solvent is preferred. The number average particle size of the particles dispersed is preferably from 0.01 to 100 μm, more preferably from 0.1 to 10 μm. The dispersion solution may be added simultaneously in the step of dissolving the cellulose acylate or may be added to the dope in any step, however, a form of adding the dispersion solution immediately before casting using a static mixer or the like is preferred, similarly to the ultraviolet absorbent.

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

In the case of using the cellulose acylate film for the protective film, hydrophilicity is preferably imparted to the film surface by means of saponification, corona treatment, flame treatment, glow discharge treatment or the like so as to enhance the adhesive property to PVA- type resin. It may be also possible to disperse a hydrophilic resin in a solvent having affinity for cellulose acylate and coat the solution to form a thin layer. Among these means, a saponification treatment is preferred because planeness and physical properties of the film are not impaired. The saponification treatment is performed by dipping the film in an aqueous solution of an alkali such as caustic soda. After the treatment, the film is preferably neutralized with an acid in a low concentration and thoroughly washed with water so as to remove the excess alkali.

The alkali saponification treatment which is preferably used as the surface treatment of the cellulose acylate film is specifically described below. This treatment is preferably performed by a cycle of dipping the cellulose acylate film surface in an alkali solution, neutralizing it with an acidic solution, and water washing and then drying the film. Examples of the alkali solution include a potassium hydroxide solution and a sodium hydroxide solution. The normal concentration of hydroxide ion is preferably from 0.1 to 3. ON, more preferably from 0.5 to 2. ON. The alkali solution temperature is preferably from room temperature to 90°C, more preferably from 40 to 70°C. The film is generally then washed with water and after passing an acidic aqueous solution, again washed with water to obtain a surface-treated cellulose acylate film. Examples of the acid used here include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid and oxalic acid. The concentration of the acid is preferably from 0.01 to 3. ON, more preferably from 0.05 to 2. ON. In the case of using the cellulose acylate film as a transparent protective film of a polarizing plate,, an acid treatment and an alkali treatment, namely, saponification treatment for the cellulose acylate, are preferably performed in view of the adhesion to the polarizing film.

The surface energy of a solid obtained by such a method can be determined, as described in Nure no Kiso to Oyo (Basis and Application of Wetting) , Realize Sha (December 10, 1989), by a contact angle method, a wetting heat method or an adsorption method. Among these, the contact angle method is preferred and the contact angle of water is preferably from 5 to 90°, more preferably from 5 to 70°.

On the protective film surface of the polarizing plate of the present invention, any functional layer can be provided such as an optical anisotropic layer for compensating the view angle of LCD, an antiglare or antireflection layer for improving visibility of the display, and a layer (e.g., polymer dispersion liquid crystal layer, cholesteric liquid crystal layer) having a function of separating PS wave due to anisotropic scattering or anisotropic optical interference for improving the brightness of LCD described in JP-A-4-229828, JP-A-6-75115 and JP-A-8-50206, a hard coat layer for elevating scratch resistance of the polarizing plate, a gas barrier layer for preventing diffusion of water content or oxygen, an easily adhesive layer for elevating the adhesive strength to polarizing film, adhesive or pressure-sensitive adhesive, and a layer for imparting slipperiness .

The functional layer may be provided in the polarizing film side or on the surface opposite the polarizing film. The side where the functional layer is provided is appropriately selected according to the purpose .

On one surface or both surfaces of the polarizing film of the present invention, various functional films can be directly attached as a protective film. Examples of the functional film include a phase difference film such as λ/4 plate and λ/2 plate, a light diffusion film, a plastic cell having an electroconductive layer provided on the surface opposite the polarizing plate, a brightness improving film having an anisotropic scattering or anisotropic optical interference function, a reflective plate, and a reflective plate having a transflective function.

As the protective film of the polarizing plate, one sheet of the preferred protective films described above or a plurality of sheets may be stacked. The same protective film may be attached to both surfaces of the polarizing film or protective films attached to both surfaces may have different functions and physical properties from each other. It is also possible to attach the above-described protective film only to one surface and not attach the protective film to the opposite surface but directly provide thereon a pressure-sensitive adhesive layer for directly attaching thereto a liquid crystal cell. In this case, a releasable separator film is preferably provided in the outer side of the pressure-sensitive adhesive.

The protective film is usually fed in a roll form and preferably attached continuously to a long polarizing plate so that the longitudinal directions can agree. Here, the orientation axis (phase lag axis) of the protective film may run in any direction but in view of simplicity and easiness of operation, the orientation axis of the protective film is preferably in parallel to the longitudinal direction. The angle between the phase lag axis (orientation axis) of the protective film and the absorption axis (stretching axis) of the polarizing film is also not particularly limited and may be appropriately set according to the purpose of the polarizing plate. The absorption axis of the long polarizing plate of the present invention is not in parallel to the longitudinal direction and therefore, when the protective film having an orientation axis in parallel to the longitudinal direction is continuously attached to the length polarizing plate of the present invention, a polarizing plate where the absorption axis of the polarizing film and the orientation axis of the protective film are not in parallel is obtained. The polarizing plate where the polarizing film and the protective film are combined such that the absorption axis of the polarizing film and the orientation axis of the protective film run not in parallel is excellent in the dimensional stability. This performance is advantageously exerted particularly when the polarizing plate is used for a liquid crystal display. The title angle between the phase lag axis of the protective film and the absorption axis of the polarizing film is from 10° to less than 90°, preferably from 20 to 80°. With this tilt angle, a high dimensional stability effect is exerted. <Adhesive>

The adhesive for combining the polarizing film and the protective film is not particularly limited but examples thereof include PVA-base resin (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxylic group and oxyalkylene group) and an aqueous solution of boron compound. Among these, PVA resin is preferred. To the PVA resin, a boron compound, an aqueous potassium iodide solution or the like may be added. The thickness of the adhesive layer after drying is preferably from 0.01 to 10 μm, more preferably from 0.05 to 5 μm. <Pressure-Sensitive Adhesive Layer>

In the polarizing plate of the present invention, a pressure-sensitive adhesive layer for the adhesion with other liquid crystal display member may be provided. On the surface of the pressure-sensitive adhesive layer, a release film is preferably provided. The pressure- sensitive adhesive layer is of course optically transparent and also exhibits appropriate viscoelasticity and adhesive property. The pressure-sensitive adhesive layer for use in the present invention may be provided, for example, by forming and curing a film using a polymer of an adhesive or pressure-sensitive adhesive, such as acryl-base copolymer, epoxy-base resin, polyurethane, silicone-base polymer, polyether, butyral-base resin, polyamide-base resin, polyvinyl alcohol-base resin or synthetic rubber, by a drying method, a chemical curing method, a heat curing method, a heat melting method or a photo-curing method. Among these, an acryl-base copolymer is preferred because the adhesive properties can be most easily controlled and the transparency, weather resistance and durability are excellent. <Through Step>

In the present invention, a drying step of shrinking the stretched film to reduce the volatile content percentage and after attaching the protective film at least to one surface of the film after or during drying, a step of after-heating the film are preferably provided. Specific examples of the method for attaching the protective film include a method of attaching the protective film to the polarizing film using an adhesive while keeping the state of holding both edges of the polarizing film during the drying step and then cutting both edges, and a method of releasing the polarizing film from the both edges-holding part after drying, cutting both edges of the film and attaching a protective film thereto. For cutting edges, a general technique may be used, for example, a method of cutting edges using a cutter such as edged tool or a method of using a laser. The combined films are preferably heated so as to dry the adhesive and improve the polarizing performance. The heating condition varies depending on the adhesive but in the case of an aqueous adhesive, the heating temperature is preferably 30°C or more, more preferably from 40 to 100°C, still more preferably from 50 to 80°C. These production steps are preferably performed in a through line in view of performance and production efficiency. <Punching>

Fig. 7 shows an example of punching a conventional polarizing plate 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 polarization, namely, the stretching axis agrees with the longitudinal direction 72, whereas in the polarizing plate of the present invention, as shown in Fig. 8, the absorption axis 81 of polarization, namely, the stretching axis is inclined at 45° with respect to the longitudinal direction 82 and this angle agrees with the angle made, when attached with a liquid crystal cell in LCD, between the absorption axis of the polarizing plate and the vertical or transverse direction of the liquid crystal cell itself, therefore, oblique punching is not necessary in the punching step. Moreover, as seen from Fig. 8, since the polarizing plate of the present invention is cut in a straight line along the longitudinal direction, a practical polarizing plate can also be produced without punching the long polarizing plate but by slitting it along the longitudinal direction, as a result, remarkably high productivity is attained, distribution of Volatile Component Content>

In the case of manufacturing a lengthy, particularly roll-form, polarizing plate by a through step, it is necessary that uneven dyeing or non-dyed spot is not present. If the volatile component in the film before the stretching has an uneven distribution (difference in the volatile component amount depending on the site in the film plane), this causes uneven dyeing or non-dyed spot. Accordingly, the distribution of the volatile component content in the film before stretching is preferably smaller and this is preferably at least 5% or less. The volatile content percentage as used in the present invention means the volume of volatile components contained per the unit volume of film and this is a value obtained by dividing the volume of volatile components by the volume of film. The distribution thereof means a fluctuation width of the volatile content percentage per 1 m² (a ratio of a larger difference out of differences between the maximum value or minimum value and the average volatile content percentage, to the average volatile content percentage) . For reducing the distribution of the volatile component content, a method of blowing the front and back surfaces of the film with a uniform air, a method of uniformly squeezing the film by nip rollers, or a method of wiping off the volatile component by a wiper may be used, however, any method may be used insofar as the distribution can be made uniform.

The present invention is described in greater detail below by referring to Examples, however, the present invention is not limited thereto.

[Example 1]

Both surfaces of a PVA film were washed with ion exchange water at a water flow rate of 2 liter/min and water on the surfaces was splashed out by air blowing to remove the foreign matters. This PVA film was then dipped in an aqueous solution containing 1.0 g/liter of iodine and 60.0 g/liter of potassium iodide at 25°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 25°C for 120 seconds. Subsequently, both surfaces of the film were air blown to remove excess water content and adjust the distribution of water content percentage in film to 2% or less and in this state, the film was introduced into a tenter stretching machine in the form of Fig. 1. The film was once stretched to 6.4 times in an atmosphere of 40°C and 95% while delivering 100 m at a conveyance speed of 5 m/min and then shrunk to 4.5 times.

Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter. The edges of 3 cm in the cross direction were cut using a cutter and this film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using as the adhesive an aqueous solution containing an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution and 4% of potassium iodide, heated at 60°C for 30 minutes and then taken up around a paper core having an outside diameter of 3 inch, whereby a roll-form polarizing plate having an working width of 650 mm and a length of 100 m could be produced without any trouble .

The drying point was in the middle of the zone c and the water content percentage of PVA film was 30% before the initiation of stretching and 1.5% after the drying.

The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 0°. Here, |L1- L2 I was 0.7 m, W was 0.7 m and a relationship of |L1-L2|=W was established. At the outlet of the tenter, wrinkling and deformation of film were not observed.

The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction and also inclined at 45° with respect to the phase lag axis of Fujitac. The transmittance of this polarizing plate at 550 nm was 40.6% and the polarization degree was 99.53%.

This polarizing plate roll was stored in an environment of 25°C, 50% and 2,000 lux for 30 days. The polarization degree was decreased in the outer two turns but not decreased from the third turn.

Furthermore, the polarizing plate was cut into a size of 310x233 mm as in Fig. 8, as a result, a polarizing plate having an area efficiency of 91.5% and having an absorption axis inclined at 45° with respect to the side could be obtained.

[Example 2]

Both surfaces of a PVA film were washed with ion exchange water at a water flow rate of 2 liter/min and water on the surfaces was splashed out by air blowing to remove the foreign matters. This PVA film was then dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 40°C for 60 seconds. Subsequently, both surfaces of the film were air blown to remove excess water content and adjust the distribution of water content percentage in film to 2% or less and in this state, the film was introduced into a tenter stretching machine in the form of Fig. 2. The film was stretched to 4.5 times while delivering 500 m at a conveyance speed of 15 m/min and then the tenter was bent as shown in Fig. 2 with respect to the. stretching direction. Thereafter, while keeping constant the width and shrinking the film, the film was dried in an atmosphere of 80°C and removed from the tenter. The edges of 3 cm in the cross direction were cut using a cutter and this film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using as the adhesive an aqueous solution containing an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution and 4% of potassium iodide and then heated at 60°C for 30 minutes, whereby a roll-form polarizing plate having an working width of 650 mm and a length of 500 m could be produced without any trouble.

The drying point was at the position of 1/3 of the zone c and the water content percentage of PVA film was 32% before the initiation of stretching and 1.5% after the drying .

The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 46°. Here, I Ll—L2 I was 0.7 m, W was 0.7 m and a relationship of | Ll— L2|=W was established. At the outlet of the tenter, the substantial stretching direction Ax-Cx was inclined at 45° with respect to the center line 22 of film delivered to next step. Wrinkling and deformation of film were not observed at the tenter outlet.

The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 nm was 42.1% and the polarization degree was 99.97%.

Furthermore, the polarizing plate was cut into a size of 310x233 mm as in Fig. 8, as a result, a polarizing plate having an area efficiency of 91.5% and having an absorption axis inclined at 45° with respect to the side could be obtained. [Comparative Example 1]

Both surfaces of a PVA film were washed with ion exchange water at a water flow rate of 2 liter/min and water on the surfaces was splashed out by air blowing to reduce the foreign matters adhering to the surface to 0.5% or less. This PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 40°C for 60 seconds. Subsequently, without air blowing both surfaces of the film and in the state where the distribution of water content percentage in film was 10%, the film was introduced into a tenter stretching machine in the form of Fig. 2 and stretched to 4.5 times. The tenter was bent as shown in Fig. 2 with respect to the stretching direction and thereafter, while keeping constant the width and shrinking the film, the film was dried in an atmosphere of

30°C and removed from the tenter. Dyeing unevenness was generated over the entire surface of the film, wrinkling remained and due to coarse surface, a protective film could not be attached, failing in manufacturing a roll- form polarizing plate. [Example 3 ]

Iodine-type polarizing plates 91 and 92 prepared in Example 2 were used as two sheets of polarizing plates between which a liquid crystal cell 93 for LCD was interposed. As shown in Fig. 9, the polarizing plate 91 was disposed as a polarizing plate in the display side and attached to the liquid crystal cell 93 through an adhesive to fabricate LCD.

The thus-fabricated LCD exhibited excellent brightness, view angle property and visibility and even after use for one month at 40°C and 30% RH, the display grade was not deteriorated.

(Measurement of Transmittance and Polarization Degree at 550 nm)

The transmittance was measured by Shimadzu Auto- recording Spectrometer UV2100. Furthermore, from the transmittance HO (%) when the absorption axes of superposed two polarizing plates were agreed and the transmittance HI (%) when the absorption axes were orthogonalized, the polarization degree P (%) was determined by the following formula: P=[ (H0-H1) / (H0+H1) ]^{1 2}xl00

(Measurement of Retardation)

The measurement was performed at 632.8 nm using KOBRA21DH manufactured by 0j i Test Instruments.

[Example 4]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30.0 g/liter of potassium iodide at 40°C for 120 seconds. Subsequently, the film was introduced into a tenter stretching machine in the form of Fig. 1 and after once stretched to 7.0 times in an atmosphere at a temperature of 62°C and a humidity of 96% while applying a constant tension of 370 N/m, shrunk to 5.3 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter.

Before the initiation of stretching, the water content percentage of PVA film was 42.3%, the distribution of water content percentage was 3.8% and the swelling percentage was 31.9%. After the drying, the water content percentage was 4.8% and the swelling percentage was 2.0%.

The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 0°. Here, | Ll— L2 I was 0.7 m, W was 0.7 m and a relationship of |L1-L2|=W was established. At the outlet of the tenter, wrinkling and deformation of film were not observed.

Then, the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution as the adhesive and dried at 80°C to obtain a polarizing plate having an working width of 670 mm. The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction and also inclined at 45° with respect to the phase lag axis of Fuj itac.

The transmittance of this polarizing plate at 550 nm was 43.0% and the polarization degree was 99.94%.

[Example 5]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30.0 g/liter of potassium iodide at 40°C for 120 seconds. Subsequently, the film was introduced into a tenter stretching machine in the form of Fig. 1 while keeping constant the tension in the longitudinal direction of film and after once stretched to 7.0 times in an atmosphere at a temperature of 62°C and a humidity of 96% while applying a constant tension of 390 N/m, shrunk to

5.3 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter.

Before the initiation of stretching, the water content percentage of PVA film was 43.1%, the distribution of water content percentage was 4.0% and the swelling percentage was 32.2%. After the drying, the water content percentage was 4.2% and the swelling percentage was 1.9%.

Then, the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution as the adhesive and dried at 80°C to obtain a polarizing plate having an working width of 680 mm. The absorption axis direction of the obtained polarizing plate was inclined at

45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 n was 43.4% and the polarization degree was 99.93%.

[Example 6]

A PVA film was washed with ion exchange water at a water flow rate of 2 liter/min and water on the surface was splashed out by air blowing to remove the foreign matters. This PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous . solution containing 40 g/liter of boric acid and 30.0 g/liter of potassium iodide at 40°C for 120 seconds. Subsequently, the film was air blown by an air blow device shown in Fig. 10 to splash out water on the surface. Then, the film was introduced into a tenter stretching machine in the form of Fig. 1 and after once stretched to 7.0 times in an atmosphere at a temperature of 64°C and a humidity of 91% while applying a constant tension of 375 N/m, shrunk to 5.3 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter.

Before the initiation of stretching, the water content percentage of PVA film was 44.2%, the distribution of water content percentage was 4.3% and the swelling percentage was 32.7%. After the drying, the water content percentage was 3.9% and the swelling percentage was 1.8%. The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 0°. Here, | Ll— L2 I was 0.7 m, W was 0.7 m and a relationship of |L1-L2|=W was established. At the outlet of the tenter, wrinkling and deformation of film were not observed.

Then, the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution as the adhesive and further dried at 80°C to obtain a polarizing plate having an working width of 675 mm. The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 nm was 43.1% and the polarization degree was 99.98%.

[Example 7]

A PVA film was washed with ion exchange water at a water flow rate of 2 liter/min and water on the surface was splashed out by air blowing to remove the foreign matters. This PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30.0 g/liter of potassium iodide at 40°C for 120 seconds. Subsequently, the film was air blown by a nip device shown in Fig. 11 to splash out water on the surface Then, the film was introduced into a tenter stretching machine in the form of Fig. 1 while keeping constant the tension in the longitudinal direction of the film and after once stretched to 7.0 times in an atmosphere at a temperature of 57°C and a humidity of 95% while applying a constant tension of 360 N/m, shrunk to 5.3 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter.

Before the initiation of stretching, the water content percentage of PVA film was 44.7%, the distribution of water content percentage was 4.4% and the swelling percentage was 33.1%. After the drying, the water content percentage was 3.7% and the swelling percentage was 1.6%.

Then, the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution as the adhesive and further dried at 80°C to obtain a polarizing plate having an working width of 685 mm. The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 nm was 43.9% and the polarization degree was 99.97%.

[Example 8: Fabrication of Liquid Crystal Display]

Iodine-type polarizing plates 91 and 92 prepared in Example 5 were used as two sheets of polarizing plates between which a liquid crystal cell 93 for LCD was interposed. As shown in Fig. 9, the polarizing plate 91 was disposed as a polarizing plate in the display side and attached to the liquid crystal cell 93 through an adhesive to fabricate LCD.

[Comparative Example 2]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 40°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30.0 g/liter of potassium iodide at 40°C for 120 seconds. Subsequently, the film was introduced into a tenter stretching machine in the form of Fig. 1 and after once stretched to 7.0 times in an atmosphere at a temperature of 60°C and a humidity of 45% while applying a constant tension of 330 N/m, shrunk to 5.3 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter.

Before the initiation of stretching, the water content percentage of PVA film was 28.9%, the distribution of water content percentage was 7.3% and the swelling percentage was 29.1%. After the drying, the water content percentage was 8.3% and the swelling percentage was 6.3%.

The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 0°. Here, | Ll— L2 I was 0.7 m, W was 0.7 m and a relationship of |L1-L2|=W was established. At the outlet of the tenter, although wrinkling and deformation of film were not observed, a large number of uneven parts were observed.

Then, the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution as the adhesive and dried at 80°C to obtain a polarizing plate having an working width of 450 mm. The absorption axis direction of the obtained polarizing plate was inclined at

45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 nm was 40.1% and the polarization degree was 96.38%.

(Measurement of Transmittance and Polarization Degree at 550 nm)

The transmittance was measured by Shimadzu Auto- recording Spectrometer UV2100. Furthermore, from the transmittance HO (%) when the absorption axes of superposed two polarizing plates were agreed and the transmittance Hi (%) when the absorption axes were orthogonalized, the polarization degree P (%) was determined by the following formula:

P=[ (H0-H1) / (H0+H1) ] ^{1 2}xl00 As apparent from the comparison between Comparative Example 2 and Examples 4 to 6, a polarizing plate having an working width of 650 mm or more can be obtained by controlling and optimizing the humidity at the stretching and the tension in the longitudinal direction of the film. Also, as clearly seen from Example 4, a polarizing plate more increased in the working width can be obtained by optimizing the humidity at the stretching, the tension in the longitudinal direction of the film, and the water content percentage before and after the stretching.

[Example 9]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 60.0 g/liter of potassium iodide at 25°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 25°C for 120 seconds. Both surfaces of this film were air blown by an air blow device shown in Fig. 10 to remove excess water content and reduce the water content percentage distribution in the film to 2% or less. In this state, the film was introduced into a tenter stretching machine in the form of Fig. 1 and after once stretched to 6.4 times in an atmosphere at a temperature of 40°C and a humidity of 95%, shrunk to 4.5 times. Thereafter, the film was dried at 60°C while keeping constant the width and removed from the tenter. The edges of 3 cm in the cross direction were cut using a cutter and then the PVA film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using as the adhesive an aqueous solution containing an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution and 4% of potassium iodide and heated at 60°C for 30 minutes, whereby a polarizing plate having an working width of 650 mm could be manufactured without any trouble.

The water content percentage of PVA film was 30% before the initiation of stretching and 1.5% after the drying.

The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction and also inclined at 45° with respect to the phase lag axis of Fujitac. The transmittance of this polarizing plate at 550 nm was 40.2% and the polarization degree was 99.50%. The surface state of the polarizing plate was good and unevenness was not observed with an eye.

[Example 10]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 30°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 30°C for 60 seconds. Both surfaces of this film were air blown by a nip device shown in Fig. 11 to remove excess water content and reduce the water content percentage distribution in the film to 2% or less. In this state, the film was introduced into a tenter stretching machine in the form of Fig. 1 and stretched to 4.5 times in an atmosphere at a temperature of 60°C and a humidity of 95% and then the tenter was bent as shown in Fig. 2 with respect to the stretching direction. Thereafter, while keeping constant the width and shrinking the film, the film was dried in an atmosphere of 80°C and removed from the tenter. The edges of 3 cm in the cross direction were cut using a cutter and this film was attached with saponified Fujitac (cellulose triacetate, retardation value: 3.0 nm) produced by Fuji Photo Film Co., Ltd., using as the adhesive an aqueous solution containing an aqueous 3% PVA (PVA-117H produced by Kuraray Co., Ltd.) solution and 4% of potassium iodide and then heated at 60°C for 30 minutes, whereby a polarizing plate having an working width of 650 mm could be produced without any trouble.

The water content percentage of PVA film was 32% before the initiation of stretching and 1.5% after the drying.

The difference in the conveyance speed between right and left tenter clips was less than 0.05% and the angle made by the center line of film introduced and the center line of film delivered to the next step was 46°. Here, |L1-L2| was 0.7 m, W was 0.7 m and a relationship of | Ll— L2 I =W was established. At the outlet of the tenter, the substantial stretching direction Ax-Cx was inclined at 45° with respect to the center line 22 of film delivered to next step. Wrinkling and deformation of film were not observed at the tenter outlet.

The absorption axis direction of the obtained polarizing plate was inclined at 45° with respect to the longitudinal direction. The transmittance of this polarizing plate at 550 nm was 41.9% and the polarization degree was 99.96%. The surface state of the polarizing plate was good and unevenness was not observed with an eye,

[Comparative Example 3]

A PVA film was dipped in an aqueous solution containing 1.0 g/liter of iodine and 120.0 g/liter of potassium iodide at 30°C for 90 seconds and further dipped in an aqueous solution containing 40 g/liter of boric acid and 30 g/liter of potassium iodide at 30°C for 60 seconds. Subsequently, without air blowing both surfaces of the film and in the state where the distribution of water content percentage in film was 10%, the film was introduced into a tenter stretching machine in the form of Fig. 2 and stretched to 4.5 times in an atmosphere at a temperature of 62°C and a humidity of 95%. The tenter was bent as shown in Fig. 2 with respect to the stretching direction and thereafter, while keeping constant the width and shrinking the film, the film was dried in an atmosphere of 30°C and removed from the tenter. Dyeing unevenness was generated over the entire surface of the film, wrinkling remained and due to coarse surface, a protective film could not be attached, failing in manufacturing a polarizing plate. [Example 11]

Iodine-type polarizing plates 91 and 92 prepared in Example 10 were used as two sheets of polarizing plates between which a liquid crystal cell 93 for LCD was interposed. As shown in Fig. 9, the polarizing plate 91 was disposed as a polarizing plate in the display side and attached to the liquid crystal cell 93 through an adhesive to fabricate LCD.

(Measurement of Transmittance and Polarization Degree at 550 nm)

The transmittance was measured by Shimadzu Auto- recording Spectrometer UV2100. Furthermore, from the transmittance HO (%) when the absorption axes of superposed two polarizing plates were agreed and the transmittance HI (%) when the absorption axes were orthogonalized, the polarization degree P (%) was determined by the following formula: P=[ (H0-H1) / (H0+H1) ]^1/2xl00 (Measurement of Retardation)

The measurement was performed at 632.8 nm using KOBRA21DH manufactured by 0j i Test Instruments. Industrial Applicability

According to the present invention, a lengthy and roll-form polarizing plate comprising an obliquely stretched polarizing film is obtained. This lengthy and roll-form polarizing plate can elevate the yield in the step of punching out a polarizing plate and therefore, the cost can be decreased. Moreover, the polarizing plate has excellent storability and high performance. By this polarizing plate, a liquid crystal display having excellent display grade is provided at a low cost.

Claims

1. A long polarizing plate comprising at least a polarizing film having: a polarizing ability; and an absorption axis neither in parallel nor perpendicular to the longitudinal direction, wherein the long polarizing plate has the polarization degree of 80% or more at 550 nm, the single plate transmittance of 35% or more at 550 nm and the length in the longitudinal direction of 1 m or more, and the long polarizing plate is in a roll-form, having three or more turns.

2. A long polarizing plate comprising at least a polarizing film having: a polarizing ability; and an absorption axis neither in parallel nor perpendicular to the longitudinal direction, wherein the long polarizing plate has the polarization degree of 80% or more at 550 nm and the single plate transmittance of 35% or more at 5-50 nm, and a working width perpendicular to the longitudinal direction in the long polarizing plate is 650 mm or more.

3. A method for producing a polarizing plate including a polarizing film having an absorption axis neither in parallel nor perpendicular to the longitudinal direction, the polarizing plate having a polarization degree of 80% or more at 550 nm; and a single plate transmittance of 35% or more at 550 nm, wherein the method comprises: incorporating a volatile component into a polymer film for the polarizing film; reducing the content distribution of the volatile component in the polymer film to 5% or less, and then stretching the polymer film in an atmosphere at a temperature of 10 to 100°C and a humidity of 70% or more.

4. The polarizing plate as claimed in claims 1 or 2, wherein a protective film is attached to at least one surface of the polarizing plate, and the angle made by the phase lag axis of the protective film and the absorption axis of the polarizing film is not less than 10° and less than 90°.

5. The polarizing plate as claimed in claim 4, wherein the protective film is a transparent film, and the retardation of the polarizing plate at 632.8 nm is 10 nm or less.

6. A method for producing a polarizing plate, comprising: producing a polarizing film by a process which comprises : holding both edges of a continuously fed polymer film for the polarizing film by holding means; and stretching the polymer film while travelling said holding means to the longitudinal direction of the film and while applying tension to the film; wherein, when Ll represents a trajectory of the holding means from a substantial holding start point until a substantial holding release point at one edge of the polymer film, L2 represents a trajectory of the holding means from a substantial holding start point until a substantial holding release point at the other edge of the polymer film, and W represent a distance between the two substantial holding release points, Ll, L2 and W satisfy a relation represented by formula (2): | L2-L1 | > 0.4W, the polymer film is stretched while keeping the supporting property of the polymer film and while allowing a volatile content ratio of 5% or more to be present, and then the polymer film is shrunk while reducing the volatile content ratio, and then the polymer film is rolled to be in roll-form; attaching a protective film to at least one surface of the polarizing film, in which the angle made by the phase lag axis of the protective film and the absorption axis of the polarizing film is not less than 10° and less than 90°.

7. The method for producing a polarizing plate as claimed in claim 6, wherein the polymer . film for the polarizing film is once stretched to 2 to 10 times while allowing 10% or more of volatile content to be present, and then the polymer film is shrunk by 10% or more to incline the angle of the absorption axis direction with respect to the longitudinal direction of the film.

8. The method for producing a polarizing plate as claimed in claim 6 or 7, wherein the conveyance speed in the longitudinal direction of the polymer film for the polarizing film is 1 m/min or more.

9. The method for producing a polarizing plate as claimed in any one of claims 6 to 8, wherein the drying point of the polymer film for the polarizing film is present until the holding release point.

10. The method for producing a polarizing plate as claimed in any one of claims 6 to 9, wherein the polymer film for the polarizing film is stretched after reducing the foreign matters adhering to the surface thereof to 1% or less per the surface area.

11. The method for producing a polarizing plate as claimed in any one of claims 6 to 10, wherein the polymer film for the polarizing film is a polyvinyl alcohol-base polymer film.

12. The method for producing a polarizing plate as claimed in claim 11, wherein a polarizing element is adsorbed to the polyvinyl alcohol-base polymer film before or after stretching.

13. The method for producing a polarizing plate as claimed in any one of claims 6 to 12, wherein the shrinking after stretching is performed by drying.

14. The method for producing a polarizing plate as claimed in any one of claims 6 to 13, wherein the drying treatment temperature at the time of shrinking the film and reducing the volatile content percentage is from 40 to 90°C ,

15. The method for producing a polarizing plate as claimed in claim 13, wherein the expansion coefficient of the polymer film after drying is lower than that before stretching.

16. The method for producing a polarizing plate as claimed in claim 15, wherein the water content percentage of the polymer film before the stretching is 30% or more and the water content percentage of the polymer film after the drying is 10% or less.

17. The method for producing a polarizing plate as claimed in any one of claims 13 to 16, wherein a protective film is attached to at least one surface of the polymer film that is stretched after or during the drying, and then the laminate is after-heated.

18. The method for producing a polarizing plate as claimed in claim 17, wherein respective operations of stretching, drying, attaching of the protective film and after-heating are performed in a through continuous line.

19. The method for producing a polarizing plate as claimed in any one of claims 6 to 18, wherein the angle made by the longitudinal direction and the absorption axis direction of the polarizing film is from 20 to 70°.

20. The method for producing a polarizing plate as claimed in claim 19, wherein the angle made by the longitudinal direction and the absorption axis direction of the polarizing film is from 40 to 50°.

21. A liquid crystal display comprising a liquid crystal cell and polarizing plates disposed in both sides of the liquid crystal cell, wherein at least one of the polarizing plates is a polarizing plate punched out from at least one selecting from the group consisting of: the polarizing plate described in claims 1, 2, 4 or 5 ; and a polarizing plate produced by the method described in any one of claims 3, 6 to 20.