KR101981358B1 - Polarization plate manufacturing method - Google Patents

Abstract

A method of producing a polarizing plate (4) having a thickness of 105 m or less, comprising the steps of bonding protective films (2a, 2b) to one surface or both surfaces of a polarizing film (1) And the polarizing plate 4 is obtained by joining the polarizing plates 4a and 4b to the polarizing plates 4a and 4b and the polarizing plates 4a and 4b, A pinch roll 6 is provided so that the polarizing plate 4 is widened by the pinch roll 6 when the polarizing plate 4 is dried.

Description

POLARIZATION PLATE MANUFACTURING METHOD [0002]

The present invention relates to a method of manufacturing a thin polarizing plate in which a protective film is bonded to one or both sides of a polarizing film.

The polarizing plate is widely used as a polarizing light supplying element and a polarizing light detecting element in a liquid crystal display. As such a polarizing plate, a polarizing plate has been generally used in which a protective film is bonded to both surfaces of a polarizing film. However, in recent years, the polarizing plate has been developed into a mobile device such as a notebook type personal computer and a mobile phone of a liquid crystal display device, , There is a demand for thinner and lighter weight. For this reason, various attempts have been made to reduce the thickness of a polarizing plate by bonding a protective film to only one side of the polarizing film or using a thin protective film (for example, Japanese Patent Application Laid-Open No. 2007-292872 (Patent Document 1) Open Publication No. 2009-181042 (Patent Document 2)).

Patent Document 1: Japanese Patent Application Laid-Open No. 2007-292872 Patent Document 2: JP-A-2009-181042

However, wrinkles and the like of waves appear on the thin film polarizer plate dried in a drying oven by bonding a protective film to only one side of the polarizing film, and there was a problem in appearance. Particularly, this problem was remarkable in a thin-film polarizer having a thickness of 105 mu m or less.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a method for producing a thin film polarizer having no wrinkles or the like and having good appearance.

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, found a solution with the following constitution, and have completed the present invention.

(1) A method for producing a polarizing plate having a thickness of 105 m or less,

A step of bonding the protective film to one side or both sides of the polarizing film through an adhesive,

And a step of drying the polarizing plate obtained by bonding the polarizing film and the protective film,

Wherein the polarizing plate is widened by a wider width roll in the drying step.

(2) In the drying step, the polarizing plate is dried in a drying furnace,

The method of manufacturing a polarizing plate according to the above (1), wherein the widened roll is provided near at least an inlet portion in the drying furnace.

(3) The method of producing a polarizing plate according to the above (1) or (2), wherein a plurality of the widened rolls are provided in the drying furnace along a conveying path of the polarizing plate.

(4) The widened roll described in any one of (1) to (3), wherein the widened roll is a pinch roll stuck to the side edge of the polarizing plate and the pinch roll is provided at both side ends in the width direction of the transport path of the polarizing plate Wherein the polarizing plate is a polarizing plate.

(5) The polarizing plate according to any one of (1) to (3), wherein the widened roll is a curved roll in which a central portion in the width direction orthogonal to the conveying direction of the polarizing plate is higher than both side ends in the width direction. Way.

According to the present invention, when a thin polarizing plate having a protective film bonded to one side or both sides of a polarizing film is dried, the polarizing plate is widened by a widening roll to obtain a thin polarizing plate having good appearance even when the thickness is 105 탆 or less.

1 is a schematic view showing a drying furnace in an embodiment of the present invention using a pinch roll as a wafers.
Fig. 2 (a) is a perspective view of adjacent guide rolls in the embodiment shown in Fig. 1, and Fig. 2 (b) is a plan view for explaining an installation angle of the pinch roll shown in Fig.
3 is a perspective view showing another example of a wafers roll suitably used in the manufacturing method of the present invention.

Hereinafter, one embodiment of the manufacturing method of the present invention will be described with reference to Figs. 1 and 2. Fig.

Fig. 1 is a schematic view showing a drying furnace according to an embodiment of the present invention, in which a pinch roll 6 is used as a wider roll. Fig. 2 (a) 2 (b) is a plan view for explaining the installation angle of the pinch roll 6. As shown in Fig.

In the embodiment shown in Fig. 1, the first protective film 2a and the second protective film 2b are bonded and integrated on both sides of the polarizing film 1 by the nip roll 3 to obtain the polarizing plate 4, The polarizing plate 4 thus obtained is conveyed into the drying furnace 5. In the drying furnace 5, the polarizing plate 4 is conveyed by the guide roll 7 while being widened by the pinch roll 6. In this way, the dried polarizer 4 passes through the drying furnace 5 to obtain the dried polarizer 4.

(Polarizing film 1)

The polarizing film (1) is a polarizing film made of a polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin is usually obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% to 100 mol%. Examples of the polyvinyl acetate resin include copolymers of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers and unsaturated sulfonic acids. Specific examples of the copolymer of vinyl acetate and other monomer copolymerizable therewith include ethylene-vinyl acetate copolymer and the like. The polymerization degree of the polyvinyl alcohol-based resin is usually about 1000 to 10000, and preferably about 1500 to 5000.

The polyvinyl alcohol resin may be modified, and examples thereof include polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like. Usually, an unoriented polyvinyl alcohol based resin film having a thickness of about 20 탆 to 100 탆, preferably about 30 탆 to 80 탆 is used as a starting material in polarizing film production. The width of the film is industrially practically about 1500 mm to 4000 mm, but the present invention is not limited to this. The thickness of the polyvinyl alcohol polarizing film obtained by treating the unstretched film in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment, performing uniaxial stretching in a boric acid treatment or a process before the treatment, For example, about 1 to 40 mu m.

The method for producing the polarizing film 1 is not particularly limited, and examples thereof include (i) uniaxially stretching the unstretched polyvinyl alcohol-based resin film in air or in an inert gas, then subjecting the film to swelling, dyeing with a dichroic dye (Ii) a method in which the unstretched polyvinyl alcohol based resin film is subjected to a swelling treatment, a dyeing treatment with a dichroic dye, a boric acid treatment, and a washing treatment , Followed by uniaxial stretching in a wet manner in the boric acid treatment step and / or the preceding step, and finally drying.

In any of the above methods (i) and (ii), the uniaxial stretching may be performed in one step or in a plurality of two or more steps, but is preferably performed in a plurality of steps. The stretching method may be a known method, for example, a roll-to-roll stretching method in which stretching is performed with a main speed difference between two nip rolls for transporting a film; A thermal roll drawing method as described in Japanese Patent No. 2731813; And a tenter stretching method. Basically, the procedure of the process is the same as described above, but there are no restrictions on the number of treatment baths and treatment conditions. In addition, the steps not described in the above methods (i) and (ii) may be added as necessary. Examples of such a process include an immersion treatment (iodide treatment) with an iodide aqueous solution containing no boric acid or an immersion treatment (zinc treatment) with an aqueous solution containing zinc chloride or the like not containing boric acid .

The swelling process is performed for the purpose of removing foreign substances on the film surface, removing the plasticizer in the film, imparting easiness of dyeing in the next process, plasticizing the film, and the like. The processing conditions are determined within a range that can achieve these objects and within a range in which problems such as extreme melting and devitrification of the polyvinyl alcohol resin film do not occur. When the film stretched in advance in the gas is swelled in advance as in the above method (i), swelling treatment is carried out by immersing the film in water or an aqueous solution of about 15 ° C to 70 ° C, preferably about 30 ° C to 60 ° C Is done. The immersion time of the film is about 30 seconds to 300 seconds, preferably about 60 seconds to 240 seconds. When the polyvinyl alcohol-based resin film is swollen in an unstretched state as in the method (ii), the film is immersed in water or an aqueous solution of about 10 ° C to 50 ° C, preferably about 20 ° C to 40 ° C, . The immersion time of the film is about 30 seconds to 300 seconds, preferably about 60 seconds to 240 seconds.

The swelling degree in the swelling treatment is preferably 1.05 to 2.5 times. Here, the degree of swelling is defined as mass after swelling / mass before swelling. If the degree of swelling is small, the removal of the plasticizer in the polyvinyl alcohol-based resin film often becomes insufficient, and if the degree of swelling is large, uneven dyeing tends to occur in the dyeing step performed after the swelling step.

In the method (ii), the uniaxial stretching process may be performed during the swelling process. In this case, it is preferable that the drawing magnification is three times or less. The stretching magnification is defined as the length after stretching / the length of the initial state. If the stretching magnification here is high, uneven dyeing tends to occur in the dyeing step.

The dyeing treatment step is carried out for the purpose of adsorbing and orienting a dichroic dye to a polyvinyl alcohol-based resin film. The processing conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme melting of the polyvinyl alcohol resin film and devitrification do not occur. When iodine is used as the dichroic dye, for example, iodine / potassium iodide / water = about 0.003 to 0.2 / about 0.1 to 10 at a temperature of about 10 to 45 캜, preferably about 20 to 35 캜 / 100 is used for immersion treatment for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used singly or other iodides and potassium iodide may be used in combination. Further, compounds other than iodide such as boric acid, zinc chloride, cobalt chloride, etc. may be coexistent. Further, the dyeing treatment in the case of adding an acid is distinguished from the boric acid treatment described below in that it contains iodine. If it contains about 0.003 part by mass or more of iodine with respect to 100 parts by mass of water, it can be regarded as a dyeing treatment bath.

When a water-soluble dichroic dye is used as the dichroic dye, the dichroic dye / water in an amount of about 0.001 to 0.1 / 100 in terms of mass ratio under a temperature of about 20 to 80 캜, preferably about 30 to 70 캜 , For about 30 seconds to 600 seconds, and preferably for about 60 seconds to 300 seconds. The aqueous solution of the dichroic dye to be used may contain a dyeing assistant or the like and may contain an inorganic salt such as sodium sulfate and a surfactant. The dichroic dye may be used singly or two or more dichroic dyes may be used in combination.

The boric acid treatment step is generally carried out by immersing a polyvinyl alcohol-based resin film dyed with a dichroic dye into an aqueous solution containing boric acid in an amount of about 1 to 10 parts by mass with respect to 100 parts by mass of water. When the dichroic dye is iodine, it is preferable that iodide is contained in an amount of about 1 to 30 parts by mass with respect to 100 parts by mass of water. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may be coexistent.

Here, the boric acid treatment step is carried out for water resistance and color adjustment (such as prevention of blueness) by crosslinking. When boric acid treatment is carried out for water resistance by crosslinking, a crosslinking agent such as glyoxal or glutaraldehyde may be used together with boric acid, if necessary. Further, the boric acid treatment for water resistance may be referred to as a water resistance treatment, a cross-link treatment or an immobilization treatment. The boric acid treatment for color adjustment may also be referred to as a complementary coloring treatment or a re-dyeing treatment.

In the boric acid treatment process, the boric acid treatment for water resistance and the boric acid treatment for color adjustment are not particularly distinguished, but it is preferable to appropriately change the concentration of boric acid and iodide and the temperature of the treatment bath in accordance with the purpose. For example, when the unvulcanized polyvinyl alcohol based resin film is subjected to a swelling treatment, a staining treatment and then a boric acid treatment as in the above (ii), when the boric acid treatment is aimed at water resistance by crosslinking Boric acid treatment bath containing boric acid in an amount of about 3 to 10 parts by mass and iodide in an amount of about 1 to 20 parts by mass based on 100 parts by mass of water is used and is usually about 50 ° C to 70 ° C, Lt; 0 > C. The immersion time is usually about 30 to 600 seconds, preferably about 60 to 420 seconds, and more preferably about 90 to 300 seconds. When the polyvinyl alcohol resin film subjected to the swelling treatment, the dyeing treatment and the stretching treatment is subjected to boric acid treatment for the purpose of water resistance by crosslinking as in the above method (i), the temperature of the boric acid treatment bath is usually It is preferably about 50 캜 to 85 캜, and preferably about 55 캜 to 80 캜. Otherwise, the above-mentioned unstretched polyvinyl alcohol based resin film may be subjected to the swelling treatment and the dyeing treatment, followed by the same treatment as the boric acid treatment.

 After the boric acid treatment for moisture resistance, the boric acid treatment for color adjustment may be performed. For example, when the dichroic dye is iodine, a boric acid treatment bath containing about 1 to 5 parts by mass of boric acid and about 3 to 30 parts by mass of iodine is used for boric acid treatment for water resistance, with respect to 100 parts by mass of water , Usually at a temperature of about 10 ° C to 45 ° C. The immersion time is usually about 3 to 300 seconds, preferably about 10 to 240 seconds. The subsequent boric acid treatment for color adjustment is usually performed at a lower boric acid concentration, higher iodide concentration, and lower temperature than boric acid treatment for water resistance.

The boric acid treatment step may be carried out in a single step or in a plurality of steps, but is usually carried out in two to five steps in many cases. In this case, the composition and temperature of the aqueous solution of each boric acid treatment bath used in each step may be appropriately adjusted and may be the same or different within the above-mentioned range. The boric acid treatment for the water resistance and the boric acid treatment for the color adjustment may be performed respectively in a plurality of steps.

 After the boric acid treatment step, a water washing treatment is carried out. The water washing treatment is carried out, for example, by immersing a polyvinyl alcohol-based resin film treated with boric acid for water resistance and / or color adjustment in water, spraying water as a shower, or using immersion and spray in combination. The temperature of the water in the water washing treatment is usually about 2 to 40 캜, and the immersion time is preferably about 2 to 120 seconds.

After the water washing process, the drying process is finally performed. It is preferable that the drying treatment is carried out in a large number of steps by slightly changing the tension, but it is usually carried out in two to five stages due to restrictions on facilities. It is preferable that the tension at the front end is set within the range of 600 to 1500 N / m and the tension at the rear end is set within the range of 300 to 1200 N / m. If the tensile strength is too large, the breakage of the polyvinyl alcohol-based resin film is increased, and if the tensile force is too small, the occurrence of wrinkles is increased, which is not preferable. It is also preferable to set the drying temperature of the front end within the range of 30 ° C to 90 ° C and the drying temperature of the rear end within the range of 50 ° C to 100 ° C. If the temperature is too high, breakage of the polyvinyl alcohol-based resin film increases, optical characteristics deteriorate, and if the temperature is too low, the number of stripes increases, which is not preferable. The drying treatment time may be, for example, 60 to 600 seconds, and the drying time at each stage may be the same or different. If the time is too long, it is not preferable from the viewpoint of productivity. If the time is too short, the drying becomes insufficient, which is not preferable.

Through the above-described steps, the polarizing film (1) is uniaxially stretched and made of a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented.

The thickness of the polarizing film 1 is not particularly limited as long as the total of the protective film and the protective film bonded to both surfaces of the polarizing film 1 is 105 占 퐉 or less and is usually about 1 to 40 占 퐉.

The moisture content of the polarizing film (1) after the drying treatment is preferably 3 to 14 mass%, more preferably 3 to 10 mass%, and still more preferably 3 to 8 mass%. If the moisture content exceeds 14 mass%, the polarizing film 1 is liable to shrink under the dry heat environment. The moisture content of the polarizing film (1) can be determined from the change in weight before and after holding at 105 캜 under dry heat for 1 hour.

(Protective film)

The protective film is laminated and bonded to one side or both sides of the above-mentioned polarizing film 1 through an adhesive layer. The first protective film 2a and the second protective film 2b may be the same or different protective films.

Examples of the protective film include a cycloolefin-based resin film such as a norbornene resin; Acetic acid cellulose based resin film; Polyester based resin films such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; A polycarbonate-based resin film; Acrylic resin film; Polypropylene resin films, and the like, which have been widely used in the related art.

The cycloolefin resin is preferably a commercially available product such as Topas (manufactured by Ticona), Aton (manufactured by JSR Corporation), ZEONOR (manufactured by Nippon Zeon Corporation), Zeonex (manufactured by Nippon Zeon) ) And Arpel (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When the cycloolefin resin is formed into a film, known methods such as a solvent casting method and a melt extrusion method are suitably used. Further, a preformed cycloolefin resin film such as Essen (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.) and ZeonoAfilm (manufactured by Nippon Zeon Co., Ltd.) May be used.

The cycloolefin-based resin film may be uniaxially or biaxially-stretched. By stretching, an arbitrary retardation value can be imparted to the cycloolefin-based resin film. The stretching is usually carried out continuously while unwinding the film roll, and in the heating furnace, it is stretched in the direction of the roll, in the direction perpendicular to the direction of the roll, or both. The temperature of the heating furnace is usually in the range of the glass transition temperature of the cycloolefin-based resin [glass transition temperature + 100 DEG C]. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin-based resin film is stretched, its stretching direction is arbitrary, but it is generally 0 °, 45 °, and 90 ° with respect to the flow direction of the film. The retardation characteristics of the film having the stretching direction of 0 ° often have perfect uniaxiality, and the retardation characteristics of the films at 45 ° and 90 ° often have weak biaxiality. The characteristic affects the viewing angle of the display device, but may be selected in a timely manner depending on the type of the liquid crystal display device or the type of the composite polarizing plate to be applied. The retardation value is preferably used preferably in a range of? / 4 and? / 2, and is often in the range of 90 to 170 nm in the case of? / 4 and in the retardation range of 200 to 300 nm in the case of? / 2.

Since the cycloolefin-based resin film generally has a low surface activity, the surface to be adhered to the polarizing film 1 is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, flame treatment, . Of these, plasma treatment and corona treatment, which can be performed relatively easily, are suitable.

Examples of the cellulose acetate-based resin that can be used for the protective film include cellulose acetate partially or fully acetic acid esters such as triacetylcellulose, diacetylcellulose, and cellulose acetate propionate.

As a film of such a cellulose ester resin, a suitable commercially available product such as "KC4UY" (manufactured by Konica Minolta Opt.) Can be suitably used.

WC BZ 438 (manufactured by Fuji Photo Film Co., Ltd.), KC4FR-2 (trade name, manufactured by Fuji Photo Film Co., Ltd.), and the like are commercially available as commercially available cellulose acetate resin films to which such retardation properties are imparted. 1 " (manufactured by Konica Minolta Opt.), And the like. Acetate cellulose is also referred to as acetylcellulose or cellulose acetate.

When the cellulose based resin film is laminated with the polarizing film 1 by using an aqueous adhesive, the saponification treatment is carried out in order to improve the adhesiveness with the polarizing film 1. As the saponification treatment, a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide can be employed.

The protective film as described above tends to cause blocking when the films adhere to each other when the film is in a roll state. Therefore, the protective film is usually formed by performing concave-convex processing on a roll end, inserting a ribbon into an end portion, And wrapped in a roll.

The thickness of the protective film is not particularly limited as long as the total of the polarizing film 1 and the protective film bonded to both surfaces of the polarizing film 1 is 105 탆 or less and is preferably thin, The strength is lowered and the workability is lowered. On the other hand, if it is too thick, the transparency is lowered, the curing time required after bonding is prolonged, and problems such as against the demands of customers for thinning occur. Therefore, the suitable thickness of the protective film is, for example, 1 to 50 mu m, preferably 5 to 40 mu m.

<Step of Bonding Polarizing Film (1) and Protective Film>

The polarizing film 1 and the protective film are joined and integrated by the nip roll 3 before being conveyed into the drying furnace 5 to become the polarizing plate 4. [

The total thickness (after drying) of the polarizing film 1 and the protective film bonded to both surfaces of the polarizing film 1 is 105 占 퐉 or less, preferably 10 占 퐉 or more and 105 占 퐉 or less, more preferably 50 占 퐉 or more It is preferable to set it to 105 탆 or less.

The polarizing film 1 and the protective film may be integrally bonded to each other by bonding the polarizing film 1 and the protective film simultaneously with the nip roll 3. The protective film may be provided on one side of the polarizing film 1 by a nip roll After bonding, the protective film may be successively joined to the other side of the polarizing film 1 by the nip roll, and the polarizing film 1 and the protective film may be sequentially bonded.

Before bonding the polarizing film (1) and the protective film, an adhesive is applied to at least one of the polarizing film (1) and the protective film so that the polarizing film (1) and the protective film can be bonded.

The adhesive applying apparatus is not particularly limited, and examples thereof include a roll coating apparatus, a gravure coating apparatus, and a spray coating apparatus.

The adhesive may be, for example, an aqueous adhesive, that is, an adhesive agent dissolved in water or an adhesive agent dispersed in water; A thermosetting adhesive or the like can be used.

As the water-based adhesive, for example, a composition comprising an isocyanate compound, an epoxy compound and the like may be used in order to improve adhesiveness by using a polyvinyl alcohol resin or a urethane resin as a main component. When such a water-based adhesive is used, the thickness of the adhesive layer is usually 1 占 퐉 or less, and even if a cross section is observed with an ordinary optical microscope, the adhesive layer is practically not observed.

When a polyvinyl alcohol resin is used as the main component of the adhesive, in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, a methylol group-modified polyvinyl alcohol, A modified polyvinyl alcohol resin such as alcohol may be used. When such a polyvinyl alcohol-based resin is used, an aqueous solution of a polyvinyl alcohol-based resin is used as an adhesive. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

The thickness of the adhesive layer after drying is usually about 0.001 to 5 mu m, preferably 0.01 mu m or more, more preferably 2 mu m or less, and further preferably 1 mu m or less. If the thickness of the adhesive layer becomes too thick, the appearance of the polarizing plate tends to be poor.

<Step of drying polarizing plate 4>

The polarizing plate 4 obtained as described above is conveyed into the drying furnace 5. In the drying furnace 5, the polarizing plate 4 is conveyed along the guide roll 7 while being widened by the wider roll 6, and passes through the drying furnace 5.

The drying furnace (5) is not particularly limited, and examples thereof include a hot-air drying furnace, an infrared drying furnace, a hot-air drying furnace and an infrared drying furnace.

The total length of the conveying path of the polarizing plate in the drying furnace 5 is normally 10 to 60 m, preferably 20 to 50 m. The drying temperature in the drying furnace 5 is usually 30 ° C to 100 ° C, and more preferably 60 ° C to 100 ° C. If the drying temperature is too high, the polarizing plate 4 tends to be curled, which is not preferable. On the other hand, if the drying temperature is too low, it becomes difficult to remove moisture when using an aqueous adhesive, which is not preferable.

The time from the time when the polarizing plate 4 is brought into the drying furnace 5 until the polarizing plate 4 passes through the drying furnace 5 is usually from 50 to 1200 seconds, 1000 seconds, and more preferably 100 to 600 seconds. If the drying time is too short, the polarizing film (1) and the protective film tend to peel off due to insufficient drying, and if it exceeds 1200 seconds, it is not preferable from the viewpoint of productivity.

The drying furnace 5 may be constituted by a plurality of drying furnaces having different drying temperatures. In this case, the drying temperature may be suitably adjusted according to the kind of the adhesive or the like.

A guide roll 7 is provided in the drying furnace 5 in order to control the conveying path of the polarizing plate 4 and a pinch roll 6 is provided along the conveying path of the polarizing plate 4. These pinch rolls 6 and guide rolls 7 are driven rollers and are driven by the driving of a winding roller (not shown) for winding the polarizing plate 4 to move the polarizing plate 4 .

The pinch roll 6 and the guide roll 7 are preferably in contact with the polarizing plate 4 so that a metal roll such as a stainless steel polishing roll having a low thermal conductivity, a plastic roll, a rubber roll, or the like is preferably used.

The polishing roll made of stainless steel is made of SUS304, SUS316 or the like and has a surface roughness of about 0.2 to 1.0 S expressed as an average spacing (S) of roughness curves of JIS B 0601 (surface roughness) desirable.

The size of the pinch roll 6 is not particularly limited and preferably the roll diameter is about 10 to 50 mm phi and the length of the pinch roll 6 is preferably at least 2 (The length in which one pinch roll 6 narrows the side end portion of the polarizing plate 4) shown in Fig. 4A is preferably about 2% to 10% with respect to the entire width of the polarizing plate 4 . Since both sides of the polarizing plate 4 are affected by heat and the protective film is likely to contract in the width direction of the conveying path, by setting the length of the pinch roll 6 within the above range, generation of wrinkles and the like can be effectively suppressed can do. Particularly, when an aqueous adhesive is used as the adhesive, water is easily released from both side ends of the polarizing plate 4, which is effective.

The pinch roll 6 is provided at both ends of the conveying path, as shown in Fig. 2 (a), from the viewpoint of obtaining a polarizing plate 4 having no unevenness. 2 (b), the pinch roll 6 may be inclined at an angle a in the conveying direction of the polarizing plate 4, or may be inclined at an angle a in the direction opposite to the conveying direction ). Incidentally, FIG. 2 (b) shows a state in which the pinch roll 6 is inclined in the transport direction (indicated by an arrow). Specifically, the angle alpha is defined by an angle alpha formed by the central axis of the pinch roll 6 with respect to the transverse direction perpendicular to the longitudinal direction of the transport path is 0 to 45 deg., Preferably 0 to 30 More preferably 0 to 15 deg., And particularly preferably 0 deg. (Provided that when the polarizing plate 4 is in the carrying direction is set to + and the polarizing plate 4 is placed in the opposite direction to the carrying direction of the polarizing plate 4 Time -).

2 (b) shows only one of the pinch rolls 6, 6 on both sides, but the other is the same.

The pinch rolls 6 and 6 may also be inclined in the vertical direction (vertical direction) of the conveying path. The inclination angle in this case is set such that the tip end (the tip located at the center side of the polarizing plate 4) with respect to the rear end of the pinch roll 6 is 0 to 45 deg., Preferably 0 to 30 deg. 0 to +/- 15 deg., Particularly preferably 0 deg. (Note that when the tip of the pinch roll 6 is at the upper side, the tip is at the upper side, and when it is at the lower side, the tip is at the minus side).

It is preferable that the pinch roll 6 is provided at least in the vicinity of the inlet of the drying furnace 5. The polarizing plate 4 immediately after being conveyed into the drying furnace 5 is susceptible to the influence of heat and is liable to contract in the width direction and thus the pinch roll 6 is provided at least near the inlet of the drying furnace 5, It is possible to effectively suppress occurrence of wrinkles and the like.

The vicinity of the inlet in the drying furnace 5 refers to a region having a length of 1/4 to 1/3 from the inlet with respect to the entire length of the conveying path of the polarizing plate 4 in the drying furnace 5. One or a plurality of pinch rolls 6 may be provided in the vicinity of this inlet.

1, four pinch rolls 6 are provided in the drying furnace 5 and four guide rolls 7 are provided in the drying furnace 5 as shown in Fig. May be installed in 1 to 10 places, preferably 2 to 8 places in the drying furnace 5. As described above, when the pinch roll 6 is provided in a plurality of locations, it is possible to restrain the polarizing plate 4 from being contracted in the width direction of the conveying path under the influence of heat, so that occurrence of wrinkles or the like can be suppressed more effectively have.

3 is a perspective view showing another example of a wafers roll suitably used in the manufacturing method of the present invention. In this embodiment, the curved roll 8 shown in Fig. 3 is used in place of the pinch roll 6 described above.

As the curved roll 8 for widening the polarizing plate 4, metal such as stainless steel, plastic, rubber roll, or the like can be used.

In the present invention, as the wafers, the curved rolls and the pinch rolls may be suitably used in combination.

(Polarizing plate 4)

By carrying out the widening treatment of the polarizing plate 4 at the time of drying as described above, it is possible to obtain the polarizing plate 4 having good appearance without wrinkles.

Example

Hereinafter, the present invention is described in detail by way of examples, but the present invention is not limited to these examples.

&Lt; Example 1 >

A polyvinyl alcohol film having a thickness of 75 탆 was uniaxially stretched by a dry method, immersed in pure water while being further maintained in a stretched state, and immersed in an aqueous solution of iodine / potassium iodide / water. Thereafter, the film was immersed in an aqueous solution of potassium iodide / boric acid / water, followed by washing with pure water, followed by drying to obtain a polarizing film (1) in which iodine was adsorbed and oriented in polyvinyl alcohol. The thickness of the polarizing film 1 was 28 占 퐉.

Separately, 3 parts by weight of a carboxyl group-modified polyvinyl alcohol ("Kurarupofal KL318", Kuraray Co., Ltd.) and 100 parts by weight of a water-soluble polyamide epoxy resin ("Sumirez Resin 650" Ltd.) (aqueous solution having a solid content concentration of 30%) was dissolved to prepare a water-based adhesive containing a polyvinyl alcohol-based resin as a main component.

On one side of the resulting polarizing film 1, a norbornene-based resin film ("ZeonoAFIL (registered trademark)" manufactured by Nippon Zeon Co., Ltd., thickness: 33 μm, hereinafter referred to as "COP" (Thickness: 40 占 퐉, hereinafter sometimes referred to as "TAC") made of triacetylcellulose ("KC4UYW" manufactured by Konica Minolta Opt Co., Ltd.) And bonded to each other by a nip roll (3) through an aqueous adhesive to obtain a polarizing plate (4). Subsequently, it was passed through the drying furnace 5 and dried at 70 캜 for 220 seconds to obtain a polarizing plate 4. The total thickness of the obtained polarizing plate 4 was 101 탆, and there was no problem in appearance as confirmed by visual inspection.

The drying furnace 5 is a hot-air drying furnace and has the structure shown in Fig. Each pinch roll 6 has a roll diameter of 20 mmφ and is disposed at the side end of the conveying path at an angle α of +10 ° as shown in FIG. 2 (b).

The pinch rolls 6 and 6 were disposed on both sides of the conveying path so that both side ends of the polarizing plate 4 were widened at the same time, and the polarizing plate 4 was conveyed while being stuck. At this time, the narrowed length W of the pinch roll 6 was 4% with respect to the entire width of the polarizing plate 4.

&Lt; Examples 2 to 5 &

A polarizing plate was obtained in the same manner as in Example 1 except that the first protective film, the polarizing film and the second protective film shown in Table 1 were used.

&Lt; Comparative Examples 1 to 5 &

A polarizing plate was obtained in the same manner as in Example 1 except that the first protective film, the polarizing film and the second protective film shown in Table 1 were used and the pinch roll was not used in the drying furnace.

&Lt; Reference Example 1 &

A polarizing plate was obtained in the same manner as in Example 1 except that TAC (thickness: 40 mu m) was used as the first protective film.

<Reference Example 2>

A polarizing plate was obtained in the same manner as in Reference Example 1 except that the pinch roll was not used in the drying furnace.

Table 1 shows the total thickness of the polarizing plates obtained in Examples 1 to 5, Comparative Examples 1 to 5, and Reference Examples 1 and 2, and the visual evaluation results obtained by visual inspection. Further, in Table 1, the case where no abnormality such as wrinkles was seen on the appearance of the polarizing plate was defined as &quot; 1 &quot;, and the case where an abnormality such as corrugation appeared on the appearance was defined as &quot; 2 &quot;.

As shown in Table 1, the polarizing plate obtained in Reference Examples 1 and 2 had a total thickness of 108 占 퐉, so that no problem was observed in the appearance regardless of wrinkling treatment in the drying furnace. As shown in Table 1, the polarizing plates of Examples 1 to 5 had a total thickness of 101 mu m or less, and widening processing was performed in the drying furnace, so that no problem was seen in appearance. On the contrary, as shown in Table 1, the polarizing plates of Comparative Examples 1 to 5 had a total thickness of 101 mu m or less, and the widening treatment was not performed in the drying furnace.

1: polarizing film
2a: first protective film
2b: second protective film
3: Nip roll
4: polarizer
5: Drying furnace
6: Pinch roll
7: guide roll
8: curl roll

Claims (5)

As a method for producing a polarizing plate having a thickness of 105 m or less,
A step of bonding a protective film to one side or both sides of the polarizing film through an adhesive,
And a step of drying the polarizing plate obtained by bonding the polarizing film and the protective film,
Wherein the polarizing plate is widened by a wider width roll in the drying step. The method according to claim 1, wherein in the drying step, the polarizing plate is passed through a drying oven to dry it,
Wherein the widened roll is provided near at least an inlet portion in the drying furnace. The method of manufacturing a polarizing plate according to claim 2, wherein a plurality of the widening rolls are provided in the drying furnace along a conveying path of the polarizing plate. 4. The polarizing plate according to any one of claims 1 to 3, wherein the widened roll is a pinch roll for narrowing the side edge of the polarizing plate, and the pinch roll is provided at both side ends in the width direction of the conveying path of the polarizing plate , And a method for producing a polarizing plate. The polarizing plate manufacturing method according to any one of claims 1 to 3, wherein the widened roll is a curved roll in which a central portion in a width direction orthogonal to a carrying direction of the polarizing plate is higher than both side ends in the width direction .

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