KR20180105604A - Method of manufacturing polarizer - Google Patents

Abstract

The purpose of the present invention is to provide a method of manufacturing a polarizer which has less scratches, wrinkles or stripes, is free from cutting, and has excellent appearance. The present invention is the method of manufacturing a polarizer, which comprises performing at least a swelling treatment process, a dyeing treatment process, and a crosslinking treatment process on a polyvinyl alcohol-based film, wherein, when performing at least one of the treatment processes, a stretching process is performed by using at least one of width expansion rolls as a guide roll in a treatment bath, and the width expansion rolls are arranged to make a position of the polyvinyl alcohol-based film spaced apart from the width expansion rolls satisfy expression (1), -40° <= θ <= 40° when performing the stretching process. In expression (1), θ is, at a position in which an arc in an axial direction of the width expansion rolls has a maximum height, an intersecting angle of a straight line A and a straight line B, wherein the straight line A connects an exit side contact point of the polyvinyl alcohol-based film brought into contact with the width expansion rolls and a central point of the width expansion rolls, and the straight line B connects a point, at which the arc of the width expansion rolls has the maximum height, and the central point of the width expansion rolls. Provided that the intersecting angle is a plus intersecting angle in case of a forward direction with respect to a proceeding direction of the film based on the straight line B, and is a minus intersecting angle in case of a backward direction with respect to the proceeding direction of the film based on the straight line B.

Description

[0001] METHOD OF MANUFACTURING POLARIZER [0002]

The present invention relates to a method for producing a polarizer. The present invention also relates to a polarizing plate using the polarizer. The polarizer and the polarizing plate can be used alone or as an optical film laminated thereon to form an image display apparatus of a flat panel display such as a liquid crystal display or an organic EL display.

Conventionally, as a polarizer used for a liquid crystal display device or the like, an absorption dichromatic polarizer formed by uniaxially stretching a polyvinyl alcohol film with iodine or a dichroic dye is widely used. In addition, the polarizer is used as a polarizer in which a transparent protective film such as triacetyl cellulose treated by saponification on both sides or one side of a polarizer is bonded to the polarizer and its strength is supplemented.

The production of the polarizer is largely divided into a swelling process, a dyeing process, a crosslinking process and a stretching process of a polyvinyl alcohol film. In practice, in many cases, the stretching process, the dyeing process, and the crosslinking process are simultaneously stretched at the same time, so that the stretching process and the other processes can not be distinguished from each other in many cases. Further, before and after the swelling step, the dyeing step, or the crosslinking step, there is a case where a cleansing bath is provided and a washing step is carried out, respectively.

During the production of the polarizer, in the wet stretching step, when the polyvinyl alcohol film is transported or stretched into the stretching bath, film breakage occurs in which the polyvinyl alcohol film is folded in the flow direction. Particularly, at the time of passing through a guide roll in a drawing bath or through a pinch roll at both sides of a drawing bath, a film bending portion is pressed against a roll, and a film bending die is attached to the overlapping portion, There is a problem that the marks are left, the portions appear as staining streaks, and further, the polyvinyl alcohol film becomes a polarizer in a folded state, and the portions become defective (defects).

In recent years, with the advancement of the liquid crystal display device in which a polarizer is used, development of a polarizer which is less scratched and wrinkled than a conventional polarizer and has no incision is desired. As a method of manufacturing such a polarizer, for example, the following techniques have been proposed.

Patent Document 1 discloses a technique in which a width expansion roll is used as at least one guide roll in a treatment liquid and a maximum width extension amount? Of a width expansion roll obtained by the following equation (1) (A) a width expansion roll is arranged at a position where?>?, And / or (b) a width expansion roll is arranged at a position where?> Is satisfied, and / or? gamma &lt; / RTI &gt; is used as the polarizing film.

β = B ₁ × α × r / R ... ... ... ... (One)

(Where B ₁ is the film width in contact with the widthwise extension roll,? Is the contact angle of the width extension roll, r is the radius of the width extension roll, and R is the radius of curvature of the extension roll).

? = 0.2055 x B ₁ x exp (-0.0273 x? ₁ ) -exp (-0.0273 x?)} ... ... (2)

(Where B ₁ is the same as above, θ is the running time in the liquid until the film is separated from the width extension roll, and θ ₁ is the running time in the liquid until the film contacts the extension roll) .)

In the cleaning process (1), the film conveyed from the first pinch roll passes through at least the first and second guide rolls, and the three Followed by being led into a second pinch roll while being immersed in a lustering process and subjected to a cleaning while stretching in a range of 1.2 to 2.9 times in stretching magnification using the difference in peripheral speed between the first pinch roll and the second pinch roll, , The first guide roll and the second guide roll are both provided in the cleaning bath and the pass line length (a) of the film between the first guide roll and the second guide roll is adjusted to 50 cm or more, And the second guide roll uses an expander roll having a surface length of 2300 mm or more.

Further, in Patent Document 3, in the swelling step, at least a first guide roll is disposed in a swelling bath, and when the polyvinyl alcohol film is immersed in an aqueous solvent and further the inside of the aqueous solvent is moved, The alcoholic film is brought into contact with the first guide roll before the polyvinyl alcohol film is swollen abruptly and the time required until the polyvinyl alcohol film comes into contact with the first guide roll after coming into contact with the aqueous solvent And the time (a) is 0.6 to 12 seconds.

If the above production method is employed, a polarizer having a small degree of scratches and wrinkles can be obtained, but a new improvement is required.

Japanese Patent Application Laid-Open No. 2005-227650 Japanese Patent Application Laid-Open No. 2007-226035 Japanese Patent No. 4198559 Specification

An object of the present invention is to provide a method of manufacturing a polarizer which has few scratches, wrinkles and streaks and is excellent in appearance without infiltration.

As a result of intensive investigations to solve the above problems, the present inventors have found that the above-described object can be attained by the polarizer producing method described below, and the present invention has been accomplished.

That is, the present invention relates to a method of producing a polarizer that at least performs a swelling treatment, a dyeing treatment and a crosslinking treatment on a polyvinyl alcohol film,

The stretching is performed using at least one width expansion roll as a guide roll in the treatment bath at the time of at least one of the treatments, and the position where the polyvinyl alcohol film is spaced apart from the width expansion roll satisfies the following formula (1) And a width expanding roll is disposed so that the width expanding roll is disposed.

-40 °??? 40 ° (One)

(In the formula, &amp;thetas; represents the distance between the exit-side contact point of the polyvinyl alcohol-based film and the center point of the width-extending roll at the position where the arc height in the axial direction of the width- A straight line A and an intersection angle of a straight line B connecting a point at which the arc height of the widthwise extension roll becomes maximum and a center point of the widthwise extension roll are connected to each other, + &Gt; in the forward direction and - &lt; - &gt; in the reverse direction).

The width expansion roll (expander roll) is constituted by a curved center and a covering material (for example, a sponge or the like) covering the center, and the center is fixed without rotating, and the covering material is rotatably installed. The width expansion roll has a characteristic in which the width of the polyvinyl alcohol-based film (hereinafter also simply referred to as &quot; film &quot;) is effectively expanded in the course of moving toward the arc height along the roll. The wrinkle spreading effect can be obtained to some extent by simply using the width expansion roll, but an effect that can be satisfied can not be obtained.

The inventors of the present invention found that a polarizer having few scratches, wrinkles and streaks and having no infiltration was obtained by disposing the width expansion roll so that the position where the film being transported is spaced from the width expansion roll satisfies the above formula (1) Respectively. Hereinafter, this will be described in detail with reference to Figs. 1 and 2. Fig.

Fig. 1 is a schematic plan view in the axial direction of the width expanding roll 1. Fig. 2 is a schematic cross-sectional view of the width expanding roll 1 when viewed from the direction Y of Fig. In Fig. 2, the cross section at the position X in Fig. 1 is indicated by a dotted line. The position X is a position at which the arc height in the axial direction of the width expanding roll 1 becomes maximum.

As shown in Fig. 2, on the surface of the width expanding roll 1, there are provided a D zone for giving a width expansion effect to the film 2, an E zone for giving a holding effect to the film 2, It is considered that there are four zones, an F zone for providing a relaxation effect and a G zone for imparting a shrinking effect to the film (2).

The present inventors have found that by adjusting the arrangement angle of the width expansion rolls so that the position where the film contacts the width expansion roll is at least the D zone and the position where the film is spaced apart from the width expansion roll is the E or F zone, It was found that a polarizer having less stripe and no infiltration was obtained.

Here, in the E and F zones, at the position X at which the arc height in the axial direction of the width expansion roll becomes maximum, the exit side contact M of the film in contact with the width expansion roll, The straight line A connecting the center point C and the intersection angle of the straight line B connecting the point H where the arc height of the width extension roll is the maximum and the center point C of the width extension roll. However, the crossing angle is defined as + in the forward direction with respect to the traveling direction of the film with reference to the straight line B, and as - in the reverse direction.

When the crossing angle [theta] in the E zone is -40 DEG to 0 DEG (preferably -30 DEG to 0 DEG), or the crossing angle in the F zone is 0 DEG to 40 DEG When the film is spaced apart from the widthwise extension roll at a position at which the film is stretched at 30 DEG, the film is given a holding effect or a relaxation effect, and the shrinking force in the width direction of the film is reduced. Therefore, scratches, wrinkles, .

When the crossing angle &amp;thetas; in the E zone exceeds -40 DEG, scratches, wrinkles, or infiltration can be suppressed to some extent, but since the film is greatly expanded, The film shrinks in the transverse direction at an instant, and scratches, wrinkles, or incisions occur in the film. When the crossing angle [theta] in the F zone exceeds 40 DEG, the film is in the process of shrinking, so that scratches, wrinkles, or infiltration occur in the film.

The wrap angle of the film in the widthwise extension roll is preferably 45 ° to 135 °, more preferably 45 ° to 90 °. The wrap angle is the contact angle of the surface where the film is in contact with the width extension roll. When the wrap angle is less than 45 deg., The sufficient widening effect can not be obtained and the wrinkle stretching effect becomes small. When the wrap angle exceeds 135 deg., The width expanding effect becomes too large and the film is stretched in the transverse direction, have.

The present invention also relates to a polarizing plate in which a transparent protective film is laminated on at least one of the polarizer obtained by the above-mentioned production method and the polarizer.

Further, the present invention relates to an optical film in which at least one polarizer or the above polarizing plate is laminated.

The present invention also relates to an image display apparatus including the optical film.

The polarizer obtained by the production method of the present invention has few scratches, wrinkles and streaks, and is excellent in appearance without infiltration. By using the polarizer, a high-quality image display device can be manufactured.

1 is a schematic plan view in the axial direction of a width expansion roll;
Fig. 2 is a schematic sectional view of the width expansion roll when viewed from the direction of the line of sight in Fig. 1; Fig.
3 is a schematic view showing an example in which a width expansion roll is disposed in a treatment bath;
4 is a schematic view showing an arrangement state of a width expansion roll in the first embodiment;
5 is a schematic view showing an arrangement state of a width expansion roll in the second embodiment;
6 is a schematic view showing an arrangement state of a width expansion roll in Comparative Example 1. Fig.

As the material of the polyvinyl alcohol-based film applied to the polarizer of the present invention, polyvinyl alcohol or a derivative thereof is used. Examples of derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, as well as olefin such as ethylene and propylene, unsaturated carboxylic acid glycol alkyl esters such as acrylic acid, methacrylic acid and crotonic acid, and acrylamide . The degree of polymerization of polyvinyl alcohol is generally about 1000 to 10000, and the degree of saponification is about 80 to 100 mol%.

The film may contain an additive such as a plasticizer and a surfactant. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, trichlserine, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer or the like to be used is not particularly limited, but is preferably 20% by weight or less in the film. Normally, a film having a thickness of about 30 to 150 mu m is used.

The width of the raw material of the film is not particularly limited, but generally 2000 to 4000 mm is used. Usually, the polyvinyl alcohol film is swollen by about 10% to 40% when it is immersed in water. That is, when the polyvinyl alcohol film is immersed in water, it is expanded by 10% to 40% in the MD direction (film transport direction) and the TD direction (width direction), respectively.

The polarizer of the present invention is produced by subjecting the above film to at least a swelling treatment, a dyeing treatment and a crosslinking treatment.

The swelling treatment is carried out before the dyeing treatment. The swelling treatment can be used to clean the surface of the polyvinyl alcohol film and prevent the unevenness of dyeing by swelling the polyvinyl alcohol film.

The swelling treatment is usually carried out by immersing the film in the treatment liquid. As the treatment liquid, water, distilled water and pure water are usually used. If the main component is water, the treatment liquid may contain a small amount of an additive such as an iodide compound, a surfactant, or an alcohol. When the iodinated compound is contained in the treatment liquid, the concentration of the iodinated compound is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.

The treatment temperature in the swelling treatment is preferably adjusted to about 20 to 45 캜, and more preferably 25 to 40 캜. In addition, if swelling unevenness occurs, the portion is unevenly stained in the staining process, so that the swelling unevenness is not caused. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

The swelling treatment may be performed together with the stretching treatment. In this case, it is preferable to stretch the film 1.2 to 4 times, more preferably 1.6 to 3 times, the original length.

The dyeing treatment is carried out by adsorbing and orienting iodine or dichromatic dye on the film. The dyeing treatment may be carried out together with the stretching treatment.

The dyeing treatment is usually carried out by immersing the film in a dyeing solution. Iodine solutions are common for dyeing solutions. As the iodine aqueous solution used as the iodine solution, iodine and an aqueous solution in which iodide ions are contained, for example, by potassium iodide or the like as a dissolution aid are used. In addition, auxiliary agents such as lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, iodide such as iodine iodide and titanium iodide may be used. The iodine concentration is about 0.01 to 0.5% by weight, preferably 0.02 to 0.4% by weight, and the concentration of potassium iodide is about 0.01 to 10% by weight, preferably 0.02 to 8% by weight. In iodine staining, the temperature of the iodine solution is usually about 20 to 50 캜, preferably 25 to 40 캜. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

In the crosslinking treatment, a boron compound is usually used as a crosslinking agent. The crosslinking treatment may be performed together with the stretching treatment. The crosslinking treatment can be carried out plural times. Examples of the boron compound include boric acid, borax and the like. The boron compound is generally used in the form of an aqueous solution or a water-organic solvent mixed solution. Normally, an aqueous solution of boric acid is used. The boric acid concentration of the aqueous solution of boric acid is about 0.1 to 13% by weight, preferably 2 to 13% by weight. A boric acid aqueous solution or the like may contain an iodide compound such as potassium iodide. When the iodide compound is contained in the aqueous boric acid solution, the concentration of the iodide compound is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.

The crosslinking treatment can be carried out by immersing the film in an aqueous boric acid solution or the like. Alternatively, the film may be coated or sprayed with a boron compound or the like. The treatment temperature in the crosslinking treatment is usually 25 占 폚 or higher, preferably 30 to 85 占 폚, and more preferably 30 to 60 占 폚. The treatment time is usually 10 to 800 seconds, preferably 30 to 500 seconds.

The stretching treatment is usually performed by performing uniaxial stretching. As the drawing method, both the wet drawing method and the dry drawing method can be employed, but it is preferable to use a wet drawing method. As the wet stretching method, for example, it is common to perform stretching in a solution in a swelling treatment or after a dyeing treatment. Further, the stretching can be performed together with the crosslinking treatment. On the other hand, in the case of dry stretching, examples of stretching means include a roll-to-roll stretching method, a heated roll stretching method, and a compression stretching method. The stretching process may be performed in multiple stages.

The draw ratio can be appropriately set according to the purpose, but the total draw ratio is about 2 to 7 times, preferably 4.5 to 6.8 times, more preferably 5 to 6.5 times.

Thereafter, the film may be subjected to a cleaning treatment. By the washing treatment, the precipitate generated on the surface of the stretched film can be removed.

The cleaning treatment can be performed, for example, by water cleaning such as water, distilled water, or pure water. The water washing treatment is usually carried out by immersing the film in a water washing bath. The cleaning treatment can also be performed by immersing in an aqueous solution containing iodide such as potassium iodide. For example, as the aqueous solution, the concentration of potassium iodide is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. The temperature of the cleansing bath in the cleansing treatment is usually 5 to 50 占 폚, preferably 10 to 45 占 폚, and more preferably 15 to 40 占 폚. The immersion time is usually 1 to 300 seconds, preferably 10 to 240 seconds. The cleaning with the aqueous solution can be performed in combination with the water cleaning, and can be performed before or after the water cleaning.

In the method for producing a polarizer according to the present invention, at least one of the above-described treatments is stretched by using at least one width expansion roll as a guide roll in the treatment bath. At this time, it is necessary to arrange the width expansion roll so that the position where the film is spaced from the width expansion roll satisfies the following formula (1).

-40 占??? 40 占 (1)

(In the formula, &amp;thetas; represents the distance between the exit-side contact point of the polyvinyl alcohol-based film and the center point of the width-extending roll at the position where the arc height in the axial direction of the width- A straight line A and an intersection angle of a straight line B connecting a point at which the arc height of the widthwise extension roll becomes maximum and a center point of the widthwise extension roll are connected to each other, + &Gt; in the forward direction and - &lt; - &gt; in the reverse direction).

The crossing angle? Is preferably -30 °??? 30 °.

Particularly, in the swelling treatment, since the film swells in the width direction, scratches or wrinkles are likely to enter the film and the incisions tend to occur. Therefore, at the time of the swelling treatment, at least one width expansion roll is used as a guide roll in the treatment bath , It is preferable to conduct the drawing under the above conditions. This will be described in detail with reference to Fig.

Fig. 3 is a schematic view showing an example in which a width-widening roll is disposed in a treatment bath. The film 2 is conveyed through the guide rolls 3 and 4 in the atmosphere, the guide roll 5 disposed in the treatment bath and the width expanding roll 1, and treated with the treatment liquid. The film 2 enters the treatment liquid at the point I and contacts the guide roll 5 at point J and is spaced from the guide roll 5 at point K and contacts the width expanding roll 1 at point L, Is spaced apart from the width expanding roll 1 and exits from the treatment liquid at point N. The number of the width expanding rolls 1 is not particularly limited and may be two or more.

At this time, it is necessary to dispose (adjust the angle) the width expanding roll 1 so as to satisfy the above formula (1) at the position where the film 2 is separated from the width expanding roll 1, that is, at the M point. Further, the center of the width expanding roll 1 is fixed without rotating, and only the covering member is rotated. Therefore, the point H at which the arc height of the widthwise extension roll 1 becomes maximum is always constant.

Regarding the change in the width of the film in the swelling treatment, there are three zones in the treatment liquid, that is, the initial stage of swelling, the middle stage of swelling and the latter stage of swelling. The initial stage of the swelling is a stage in which the path length ratio is not less than 0 and not more than 0.2 when the entire path length of the film in the treatment bath is set to 1 and almost no swelling occurs. The swelling middle stage is a stage when the path length ratio is 0.2 or more and less than 0.6 when the entire path length of the film in the treatment bath is set to 1 and the abrupt width change is caused by the rapid swelling. The swelling late period is a step in which the width variation is in a constant state when the total path length of the film in the treatment bath is 1 and the path length ratio is 0.6 to 1.

It is preferable that the width expansion roll is disposed at the position of the latter half of swelling. Accordingly, occurrence of scratches, wrinkles, or infiltration of the film can be suppressed more effectively, and the effect of expanding the width by the width expanding roll is maximized. On the other hand, if the width expanding roll is disposed at the initial swelling position, the film is not scratched, wrinkled, or inflated, but most of the film is not swelled. Further, if the width expansion roll is disposed at the position of the swelling middle stage, the film tends to be easily scratched, wrinkled, or infiltrated. In the middle of swelling, the swelling speed of the film, that is, the expansion speed of the film is excessively large, so that even if a width expansion roll is used, scratches, wrinkles, or incisions easily occur in the film.

After the above-mentioned treatment, the film may be subjected to a drying treatment.

The obtained polarizer may be a polarizing plate provided with a transparent protective film on at least one side thereof according to a conventional method. The transparent protective film may be provided as a coating layer of a polymer or as a laminate layer of a film or the like. As the transparent polymer or film material for forming the transparent protective film, a suitable transparent material can be used, but those having excellent transparency, mechanical strength, heat stability and moisture barrier property are preferably used. Examples of the material for forming the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, Styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin), polycarbonate polymers, and the like. Further, polyolefin polymers such as polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, Based polymer, a polyether ether ketone-based polymer, a polyphenylene sulfide-based polymer, a vinyl alcohol-based polymer, a vinylidene chloride-based polymer, a vinyl butyral-based polymer, an arylate-based polymer, a polyoxymethylene-based polymer Polymers, epoxy-based polymers, or blends of the above-mentioned polymers may be mentioned as examples of the polymer forming the transparent protective film. The transparent protective film may be formed as a cured layer of a thermosetting or ultraviolet curing resin such as acrylic, urethane, acrylic urethane, epoxy or silicone.

Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in its side chain and (B) And / or a resin composition containing a thermoplastic resin having an unsubstituted phenyl and nitrile group. Specific examples thereof include a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile styrene copolymer. The film may be a film composed of a mixture of resin compositions and the like. Since such a film has a small retardation and a small photoelastic coefficient, problems such as nonuniformity due to distortion of the polarizing plate can be solved, and moisture permeability is small, so that durability against humidification is excellent.

The thickness of the transparent protective film can be appropriately determined, but generally it is about 1 to 500 μm from the viewpoints of workability such as strength and handling properties and thin layer properties. Particularly preferably 1 to 300 mu m, more preferably 5 to 200 mu m.

It is preferable that the transparent protective film has as little coloration as possible. Therefore, the retardation value in the film thickness direction represented by Rth = (nx-nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness) A transparent protective film having a thickness of 90 nm to + 75 nm is preferably used. By using the retardation value (Rth) in the thickness direction of -90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate due to the protective film can be substantially eliminated. The thickness direction retardation value (Rth) is more preferably -80 nm to +60 nm, particularly preferably -70 nm to +45 nm.

As the protective film, a triacetyl cellulose film, a norbornene film, a cycloolefin film and an acrylic resin film are preferable from the viewpoints of polarization characteristics and durability. A triacetylcellulose film is particularly suitable. When a protective film is provided on both sides of the polarizer, a protective film made of the same polymer material may be used for the front and back sides, or a protective film made of other polymer materials or the like may be used.

The surface of the transparent protective film on which the polarizer is not adhered may be a hard coat layer or a surface treated for anti-reflection treatment, anti-sticking, diffusion or anti-glare treatment.

In addition, the antireflection layer, the anti-sticking layer, the diffusion layer, the antiglare layer, and the like can be provided on the transparent protective film itself or may be provided as a separate optical layer as a separate material from the transparent protective film.

An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex-based, and a water-based polyester. As the adhesive, an adhesive comprising an aqueous solution is usually used.

The polarizing plate of the present invention is produced by bonding the transparent protective film and the polarizer using the adhesive. The application of the adhesive may be carried out either in the transparent protective film or the polarizer, or in both cases. After the bonding, a drying step is carried out to form an adhesive layer comprising a coating and drying layer. The polarizer and the transparent protective film can be bonded by a laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 mu m.

The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, it is used for forming a liquid crystal display device such as a reflection plate, a semitransmissive plate, a retardation plate (including a wave plate of 1/2 or 1/4) One or more optical layers can be used. In particular, a reflective polarizing plate or a transflective polarizing plate in which a reflecting plate or a transflective reflecting plate is laminated on the polarizing plate of the present invention, an elliptically polarizing plate or a circular polarizing plate in which a retardation plate is laminated in addition to the polarizing plate, Or a polarizing plate in which a brightness enhancement film is further laminated on a polarizing plate.

The polarizing plate or optical film of the present invention can be suitably used for forming various devices such as a liquid crystal display device. Formation of a liquid crystal display device can be performed in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as needed, and incorporating a driving circuit. In the present invention, Or an optical film is used, and there is no particular limitation, and it is possible to comply with the conventional method. For the liquid crystal cell, any type of TN type, STN type, or π type, for example, can be used.

[Example]

Hereinafter, embodiments and the like that specifically describe the structure and effects of the present invention will be described. In the examples, parts and% are based on weight unless otherwise specified.

Example 1

As shown in Fig. 3, a guide roll and a width expansion roll were disposed in a swelling bath, and pure water as a swelling solvent was placed in the bath and kept at 30 캜. Further, the width expansion roll was disposed at a position where the path length ratio was 0.8. Further, as shown in Fig. 4, the width expansion rolls were arranged so that the wrap angle was 50 deg. And the crossing angle [theta] was -30 deg.

Then, the PVA film (product name: VF-PS # 7500, manufactured by Kuraray Co., Ltd.) having a thickness of 75 탆 was fed into a swelling bath by a guide roll to swell the film in the swelling bath, And stretching was carried out so as to be 1.8 times.

Thereafter, the film was dipped in a mixed solution (dyeing bath) of 0.04% iodine and 0.4% potassium iodide and stretched so as to be three times the length of the raw material in the dyeing bath, and the film was dyed. This film was again dipped in a 3.5% boric acid aqueous solution (drawing bath) and stretched so as to be six times as much as the raw material, thereby producing a polarizer. Then, a TAC film (product name: TD-80U, manufactured by Fuji Film Co., Ltd.) having a thickness of 80 占 퐉 was saponified and bonded to both surfaces of the polarizer using a 1% PVA aqueous solution and dried to prepare a polarizing plate.

Further, when the running property and the surface condition of the PVA film were observed, there was no occurrence of scratches, wrinkles or incisions, and the surface state of the polarizer after drying was good.

Example 2

As shown in Fig. 5, a polarizer and a polarizing plate were produced in the same manner as in Example 1, except that the width expansion rolls were arranged so that the angle of overlap was 50 deg. And the angle of intersection 30 was 30 deg..

Further, when the running property and the surface condition of the PVA film were observed, there was no occurrence of scratches, wrinkles or incisions, and the surface state of the polarizer after drying was good.

Comparative Example 1

As shown in Fig. 6, a polarizer and a polarizing plate were produced in the same manner as in Example 1, except that a width expansion roll was arranged so that the angle of repose was 50 degrees and the angle of intersection was 90 degrees.

Further, when the running property and the surface condition of the PVA film were observed, wrinkles and infiltration occurred, and wrinkles, streaks and color dropout also occurred in the polarizer after drying.

1: width expansion roll 2: polyvinyl alcohol film
3, 4, 5: guide roll C: center point
h: arc height H: point at which arc height becomes maximum

Claims (1)

A method for producing a polarizer which comprises subjecting a polyvinyl alcohol film to at least a swelling treatment, a dyeing treatment and a crosslinking treatment,
Wherein at least one of the widthwise extension rolls is used as a guide roll in the treatment bath at least during the swelling treatment, and at that time, the position where the polyvinyl alcohol-based film is spaced apart from the widthwise extension roll is represented by the following formula (1) And a wrap angle of the polyvinyl alcohol film in the widthwise extension roll is set to 45 to 90 degrees,
Wherein the width expansion roll at the time of swelling treatment is arranged at a position having a path length ratio of 0.6 to 1 when the entire path length of the film in the swelling treatment bath is 1.
0 占??? 40 占 (1)
(In the formula, &amp;thetas; represents the distance between the exit-side contact point of the polyvinyl alcohol-based film and the center point of the width-extending roll at the position where the arc height in the axial direction of the width- A straight line A and an intersection angle of a straight line B connecting a point at which the arc height of the widthwise extension roll becomes maximum and a center point of the widthwise extension roll are connected to each other, + &Gt; in the forward direction and - &lt; - &gt; in the reverse direction).

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