JP2014109740A - Method for manufacturing polarizing film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing film having excellent production efficiency and a good appearance without causing breakage or dewatering failure, from a thin polarizing film obtained by subjecting an original film to treatments of dyeing, stretching, crosslinking and cleaning, when a polarizing film is manufactured by using a rolled film having a thickness of 1 to 60 μm and made of a polyvinyl alcohol resin, and to provide a method for manufacturing a polarizing plate having a good appearance by using the above polarizing film.SOLUTION: A polarizing film after a cleaning treatment is subjected to a draining treatment in such a way that while the polarizing film is wound on a first roll that is disposed on one surface side of the film and subjected to a tension of 200 to 1500 N/m tension, air is blown to the film surface on the opposite side to the first roll, and then while the film is wound on a second roll, where the air-blown surface is in contact with the second roll, air is blown to the film surface on the opposite side to the second roll for draining, and that the water removed by air is recovered through a first chamber and a second chamber respectively disposed near the air-blowing positions.

Description

  The present invention relates to a method for producing a polarizing film and a method for producing a polarizing plate by bonding a protective film to the polarizing film obtained thereby.

  Conventionally, a polarizing film obtained by adsorbing and orienting a dichroic dye such as iodine on a polyvinyl alcohol-based resin film has been used. This polarizing film is usually used as a polarizing plate by attaching a protective film such as triacetyl cellulose via an adhesive on at least one side, usually both sides, and used for liquid crystal displays such as liquid crystal televisions, monitors for personal computers, and mobile phones. Used in equipment.

  The polarizing film is produced by subjecting a polyvinyl alcohol-based resin film to swelling treatment, dyeing treatment, stretching treatment, crosslinking treatment (boric acid treatment) and washing treatment, and finally drying. In such a production process, when the polyvinyl alcohol-based resin film is usually lifted from each treatment bath and conveyed to the next process, the film surface is drained using a nip roll or the like.

  As a method for this draining treatment, for example, in paragraph [0034] of Japanese Patent Application Laid-Open No. 2011-180576 (Patent Document 1), the film is pulled up from each treatment bath in order to prevent dripping that occurs during the production of the polarizing film. In this case, a method is described in which excess water is removed from the film surface by using a liquid break roll such as a pinch roll or by scraping off the liquid with an air knife. Japanese Patent Laid-Open No. 2011-232016 (Patent Document 2) describes a guide for stretching a long sheet to perform draining of the long sheet that has been cleaned and conveyed to a drying furnace. Disclosed is a drainage treatment apparatus comprising a roll, an air knife that blows air obliquely onto a long sheet stretched around the guide roll, and an exhaust chamber that collects the water blown off by the blown air. An example of applying it to the manufacture of a polarizing film is also shown.

  As in Patent Document 1, when an air knife is used for draining, moisture attached to the film surface can be removed efficiently, and foreign matters such as dust can be removed, so that a film with few defects can be manufactured. it can. However, when water droplets on the film surface are removed by blowing off with an air knife, the scattered water may contaminate the production equipment. On the other hand, as in Patent Document 2, by providing an exhaust chamber for collecting moisture, contamination due to scattering of water is prevented.

  On the other hand, the polarizing film and the polarizing plate are required to be further thinned as compared with the conventional film. For example, a 75 μm-thick polyvinyl alcohol-based resin film has been conventionally used as the original film of the polarizing film. In recent years, a polarizing film is also produced from a raw film having a thickness of 60 μm or less. If a thin polarizing film in a wet state obtained by dyeing, stretching, cross-linking and washing is used with a thin film, the film will break when air is blown from an air knife. Or the appearance of the polarizing film may be defective due to a partial water drainage defect on the film surface or foreign matter remaining after adhering to the film surface.

JP 2011-180576 A JP 2011-233201 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a polarizing film having excellent production efficiency and good appearance. Another subject of this invention is providing the manufacturing method of the polarizing plate using said polarizing film.

  When manufacturing a polarizing film from a thin-walled polyvinyl alcohol-based resin film (raw film), the present inventors, while disclosing the film on a guide roll as disclosed in Patent Document 2, Found that the method of blowing air to the opposite film surface and collecting the drained water in a chamber and draining it, especially the method of sequentially performing such draining on both sides of the film, was found to be effective. Thus, the present invention has been completed.

  That is, the present invention is a method for producing a polarizing film by subjecting a polyvinyl alcohol resin film having a thickness of 1 to 60 μm to a dyeing treatment, a crosslinking treatment, and a washing treatment in this order, after the washing treatment. While applying a tension of 200 to 1500 N / m to the film, air is blown on the film surface opposite to the first roll while the film is held on the first roll provided on one side thereof, and then air is blown. Drain the water by blowing air on the film surface opposite to the second roll while holding the surface on the second roll, and the water removed by the air is provided in the vicinity of the air blowing position, respectively. The manufacturing method of the polarizing film which performs the draining process collect | recovered with a chamber and a 2nd chamber is provided.

In this manufacturing method, the air blown onto the film can have an air volume of 2 to 20 m ³ / min. Air is blown onto the film from the nozzle at the tip of the air knife, and this nozzle has an angle of 30 to 80 ° with respect to the film surface at the center line passing through the tip of the outlet, and from the tip of the outlet to the film surface. The distance can be 1.5 mm or less.

  The chamber for collecting the removed water can be arranged so that the distance from the suction port tip to the film surface is 2 mm or less.

  In the manufacturing method of this invention, after performing a draining process as mentioned above, a drying process can be given further. In this case, it is effective to install a nip roll inside the drying furnace or after the drying furnace in addition to the nip roll installed before the draining process. In this form, the draining process and the drying process are performed by these processes. Can be performed in a state where a tension of 200 to 800 N / m is applied to the film by a pair of nip rolls provided before and after the film.

  The present invention also provides a method for producing a polarizing plate by bonding a protective film to a polarizing film produced by the above-described method including a drying treatment using an ultraviolet curable adhesive.

  According to the present invention, in the draining treatment of the polyvinyl alcohol-based resin film, since the water removed by the air knife is collected by the chamber, the contamination of the manufacturing equipment is suppressed, and thus manufacturing problems caused by this, etc. The film productivity can be increased.

  In addition, according to the present invention, even when the raw film is thin, a polarizing film having a good appearance can be produced without causing film breakage or poor water drainage. Fewer defects and good quality.

It is a cross-sectional schematic diagram which shows the suitable example of an arrangement | positioning of the apparatus in the manufacturing method of a polarizing film. It is a cross-sectional schematic diagram which shows the example of arrangement | positioning in the drainer 23. FIG. It is a cross-sectional schematic diagram which shows the suitable arrangement | positioning conditions in the draining device.

  In the present invention, a polarizing film is produced by subjecting a polyvinyl alcohol resin film to swelling treatment, dyeing treatment, crosslinking treatment and washing treatment in this order. A draining process is performed after the cleaning process. The method for producing a polarizing film by performing a draining treatment according to the present invention comprises: bonding a protective film to a polarizing film obtained by performing a drying treatment after the draining treatment via an ultraviolet curable adhesive; Is preferably used in the method of producing Hereinafter, the present invention will be described in detail with reference to the drawings as appropriate.

[Production method of polarizing film]
Specifically, the polarizing film is one in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. The polyvinyl alcohol resin used as a raw material is usually obtained by saponifying a polyvinyl acetate resin. The degree of saponification is usually 85 mol% or more, preferably 90 mol% or more, more preferably 99 mol% or more. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, unsaturated sulfonic acids, vinyl ethers and the like. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000.

  The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used.

  In the present invention, a polyvinyl alcohol-based resin film having a thickness of 1 to 60 μm is used as the original film of the polarizing film. The thickness of the film is preferably about 20 to 60 μm, more preferably about 30 to 60 μm. Industrially, a film having a width of about 1500 to 6000 mm is practical.

  The polarizing film is obtained by subjecting the original film made of the above polyvinyl alcohol resin to solution treatment in the order of swelling treatment, dyeing treatment, crosslinking treatment, and washing treatment, and during the crosslinking treatment and if necessary, before the crosslinking treatment. Is obtained by performing uniaxial stretching and finally drying. Uniaxial stretching performed during the crosslinking treatment is wet stretching, and even when uniaxial stretching is performed in the previous swelling treatment or dyeing treatment, wet stretching is also performed. However, it is also possible to carry out dry uniaxial stretching before the swelling treatment.

  Thus, uniaxial stretching may be performed only in one process, may be performed in two or more processes, and a well-known stretching method can be adopted. Specific examples of the stretching method include inter-roll stretching that stretches with a difference in peripheral speed between two nip rolls that transport the film, hot roll stretching as described in Japanese Patent No. 2731813, tenter stretching, and the like. . The order of the steps is basically as described above, but there is no restriction on the number of treatment baths or treatment conditions.

  Moreover, processes other than those described above can be added for other purposes. Examples of treatments that can be added include immersion treatment (iodide treatment) in an aqueous iodide solution that does not contain boric acid, or immersion in an aqueous solution that does not contain boric acid and contains zinc chloride, etc. Treatment (zinc treatment).

  FIG. 1 is a schematic cross-sectional view showing a preferred arrangement example of a production apparatus used in the method for producing a polarizing film according to the present invention. In this manufacturing apparatus, an original film 10 made of a polyvinyl alcohol resin is unwound from a feeding roll 11 and sequentially passes through a swelling tank 13, a dyeing tank 15, a crosslinking tank 17 and a washing tank 19, and then into a draining device 23. It is conveyed so that it finally passes through the drying furnace 25. Although not clearly shown in FIG. 1, uniaxial stretching is performed in the crosslinking tank 17 or in front thereof. Moreover, although the example which provided the swelling tank 13, the dyeing tank 15, the bridge | crosslinking tank 17, and the washing tank 19 one each was shown in FIG. 1, several processing tanks with respect to a certain process are shown as needed. May be provided. The manufactured polarizing film 30 is conveyed to the process of sticking the next protective film as it is. Hereinafter, processing performed in the present invention will be described.

(Swelling treatment)
The swelling treatment is performed by contacting with water for the purpose of removing foreign substances on the surface of the polyvinyl alcohol-based resin film, removing the plasticizer in the film, imparting easy dyeability in the subsequent dyeing treatment, and plasticizing the film. . The conditions for the swelling treatment are determined within a range in which these objects can be achieved and in a range in which defects such as devitrification and extreme dissolution of the film do not occur.

  When first performing a swelling process with respect to the raw film which consists of polyvinyl alcohol-type resin, it is performed by immersing a film in the processing bath of the temperature of about 10-50 degreeC, Preferably about 20-40 degreeC, for example. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds. When the swelling treatment is performed on the polyvinyl alcohol resin film previously stretched in the air, for example, the film is immersed in a treatment bath at a temperature of about 20 to 70 ° C., preferably about 30 to 60 ° C. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

  In the swelling treatment, the polyvinyl alcohol-based resin film swells in the width direction, and problems such as wrinkling of the film are likely to occur. Therefore, widening roll (expander roll), spiral roll, crown roll, cross guider, bend bar, tenter clip, etc. It is preferable to transport the film while removing the wrinkles of the film using a known widening device. Also, for the purpose of stabilizing the film transport in the bath, the water flow in the swelling tank 13 is controlled by an underwater shower, or the EPC device (Edge Position Control device: detects the edge of the film to prevent film meandering) It is also useful to use a combination of such devices.

  In the swelling treatment, since the film swells and expands in the film transport direction, if the film is not actively stretched, for example, a transport roll before and after the swelling tank 13 in order to eliminate sagging of the film in the transport direction. It is preferable to take measures such as controlling the peripheral speed. Moreover, when performing in order of a swelling process, a dyeing process, and a crosslinking process with respect to an original fabric film, you may perform uniaxial stretching in a swelling process, The stretch ratio in that case is 1.2 to 3 times normally, Preferably 1.3 to 2.5 times.

  The treatment bath used in the swelling tank 13 includes pure water, boric acid (JP-A-10-153709), chloride (JP-A-06-281816), inorganic acid, inorganic salt, water-soluble organic solvent. An aqueous solution to which alcohols and the like are added in the range of about 0.01 to 10% by weight can also be used.

(Dyeing process)
The dyeing process is performed by immersing the film in a treatment bath containing a dichroic dye such as iodine and a water-soluble dichroic dye, for the purpose of adsorbing the dichroic dye on the polyvinyl alcohol-based resin film. . The conditions for the dyeing treatment are determined within a range in which these objects can be achieved and in a range in which problems such as extreme dissolution and devitrification of the polyvinyl alcohol-based resin film do not occur.

  When iodine is used as the dichroic dye, the treatment bath (dye bath) has, for example, a concentration of iodine / potassium iodide / water by weight ratio of about 0.003 to 0.2 / about 0.1 to 10 /. An aqueous solution of 100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment described later in that it contains iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, Can be considered. The temperature of the dyeing bath when dipping the film is about 10 to 45 ° C., preferably 20 to 35 ° C., and the dipping time of the film is about 30 to 600 seconds, preferably 60 to 300 seconds.

  When a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a concentration of dichroic dye / water = about 0.001 to 0.1 / 100 by weight can be used for the treatment bath. . In this treatment bath, a dyeing assistant or the like may coexist, and for example, an inorganic salt such as sodium sulfate or a surfactant may be contained. Moreover, a dichroic dye may be used independently and may use 2 or more types of dichroic dye together. The temperature of the dyeing bath when dipping the film is about 20 to 80 ° C., preferably 30 to 70 ° C., and the dipping time of the film is about 30 to 600 seconds, preferably 60 to 300 seconds.

  When the polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment, and crosslinking treatment in this order, the film is usually stretched in a dyeing tank. The film is stretched by a method such as giving a difference in peripheral speed between nip rolls installed before and after the dyeing tank. The cumulative draw ratio up to the dyeing process (if there is no drawing process before the dyeing process, the draw ratio in the dyeing process) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times. If the draw ratio is less than 1.6, the frequency of film breakage increases, and the yield tends to deteriorate.

  Also, in the dyeing process, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, and the like are provided in the dyeing tank 15 in order to convey the polyvinyl alcohol resin film while removing wrinkles of the film as in the swelling process. Can be installed inside and / or at the doorway.

(Crosslinking treatment)
The crosslinking treatment is carried out in a treatment bath containing 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water for the purpose of water resistance and hue adjustment (such as preventing the film from being bluish) by crosslinking. It is carried out by immersing a polyvinyl alcohol-based resin film dyed with a chromatic dye. When the dichroic dye used in the dyeing treatment is iodine, the treatment bath preferably contains iodide in addition to boric acid, and the amount thereof is 1 to 30 parts by weight with respect to 100 parts by weight of water. be able to. Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist. In addition, the crosslinking treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment. In addition, the crosslinking process for hue adjustment may be referred to as a complementary color process, a re-dyeing process, or the like.

  In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the treatment bath can be appropriately changed according to the purpose. The crosslinking treatment for water resistance and the crosslinking treatment for adjusting the hue are not particularly distinguished, and are performed under the following conditions. The purpose of the cross-linking treatment is water resistance by cross-linking, and when the raw film made of polyvinyl alcohol resin is subjected to swelling treatment, dyeing treatment and cross-linking treatment in this order, the treatment bath has a concentration of boric acid / It can be an aqueous solution of iodide / water = 3 to 10/1 to 20/100. As needed, it may replace with boric acid and may use crosslinking agents, such as a glyoxal and glutaraldehyde, and may use boric acid and a crosslinking agent together. The temperature of the treatment bath is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the immersion time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably 20 to 200. Seconds. Moreover, when performing the dyeing | staining process and the crosslinking process in this order with respect to the polyvinyl alcohol-type resin film previously extended | stretched, the temperature of a crosslinking process bath is about 50-85 degreeC normally, Preferably it is 55-80 degreeC.

  You may perform the crosslinking process for the purpose of hue adjustment after the crosslinking process for water resistance. For example, when the dichroic dye used in the dyeing process is iodine, the conditions for the crosslinking treatment for adjusting the hue are: boric acid / iodide / water = 1-5 / 5-30 / One hundred treatment baths can be used. The temperature of the treatment bath is usually about 10 to 45 ° C., and the immersion time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

  These crosslinking treatments may be performed a plurality of times, and are usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking treatment bath to be used may be the same or different as long as they are within the above range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment may be performed in a plurality of steps, respectively.

(Cleaning process)
The washing treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine attached to the polyvinyl alcohol-based resin film after the crosslinking treatment. The washing treatment is performed, for example, by immersing a polyvinyl alcohol-based resin film subjected to crosslinking treatment for water resistance and / or color tone adjustment in water, or spraying water as a shower on the film, or using these in combination.

  In FIG. 1, the example in the case of performing a washing | cleaning process by immersing a polyvinyl alcohol-type resin film in water was shown. The temperature of water in the washing treatment is usually about 2 to 40 ° C., and the immersion time is about 2 to 120 seconds. In the crosslinking treatment and the washing treatment, a widening roll can be used for the purpose of conveying the polyvinyl alcohol resin film while removing wrinkles.

(Draining process)
The draining treatment of the polyvinyl alcohol-based resin film performed in the present invention is performed by blowing air on the film surface using an air knife for the purpose of removing deposits such as water and foreign matters on the film surface. Specifically, the polyvinyl alcohol-based resin film that has undergone the cleaning treatment is transported to the draining device 23 in a state where a predetermined tension is applied, and air is blown onto the film surface by an air knife installed in the device. A draining process is performed. Hereinafter, the draining process performed in the present invention will be sequentially described with reference to FIGS. 2 and 3 as appropriate.

  FIG. 2 is a schematic cross-sectional view showing an arrangement example of the devices in the draining device 23. Referring to FIG. 2, two sets of rolls, air knives, and chambers are arranged in the draining device 23, and the film is drained side by side. The polyvinyl alcohol-based resin film conveyed into the draining device 23 has a first air knife 42 on the film surface opposite to the first roll while the film is held by the first roll 40 provided on one side thereof. Then, air is blown from the second air knife 48 onto the film surface opposite to the second roll while the air blown surface is held by the second roll 46 provided downstream in the conveying direction. Drain the water. The water removed by the air is respectively collected by the first chamber 44 and the second chamber 50 provided in the vicinity of the air blowing position.

  FIG. 3 is a schematic cross-sectional view showing an arrangement condition in a water draining apparatus suitable for performing the water draining process. Referring to FIG. 3, the first air knife 42 is disposed on the downstream side in the film conveyance direction before the film contacts the first roll 40, and air is directed from the downstream side in the film conveyance direction toward the upstream side. Spray. The first air knife 42 blows out air from the nozzle at the tip, and the nozzle is 30 to 30 centimeters from the center line (dotted line in FIG. 3) passing through the tip of the blowout port and the tangent line of the first roll 40. It arrange | positions so that it may become an angle (80 of FIG. 3). Further, the distance from the tip of the blowout port to the film surface is arranged to be 1.5 mm or less. When the angle at which the air knife is installed and the distance to the film surface are in the above range, the film breakage caused by the air can be suppressed, and efficient draining can be performed.

  The first chamber 44 described above is arranged in the film passing over the first roll 40 in the form where the opening of the chamber faces the air knife side in the vicinity of the position where air is blown. At this time, it can arrange | position so that the distance from the opening part front-end | tip of a chamber to the film surface on a roll may be 0.3-2 mm. When the distance between the chamber and the film is 2 mm or less, the air blown from the air knife hits the film and then smoothly enters the chamber together with the water adhering to the film, so that the removed water can be efficiently recovered. it can. Further, when the distance between the chamber and the film is 0.3 mm or more, the film can be prevented from being broken by the contact between the chamber and the film. The water collected in the chamber is collected from the inner wall by suction in the chamber and discharged to the waste liquid line through the waste liquid duct.

  The 2nd roll 46, the 2nd air knife 48, and the 2nd chamber 50 can be arrange | positioned similarly to the above-mentioned 1st roll 40, the 1st air knife 42, and the 1st chamber 44, respectively.

  The draining treatment performed in the present invention is performed while applying a tension of 200 to 1500 N / m to the polyvinyl alcohol resin film after the cleaning treatment. When the tension is within this range, fluttering of the film due to air can be suppressed when performing a draining process with an air knife, so that the film does not contact the chamber and breaks, and the film productivity is improved. be able to. Further, the nip roll can be provided after the draining device 23 or the drying furnace 25 in addition to the one installed after the cleaning tank 19, whereby the film can be tensioned. Considering the presence or absence of contamination of the nip roll due to water droplets that could not be removed by the water draining device 23, it is preferable to provide a nip roll inside the drying furnace 25 or after the drying furnace 25, as shown in FIG. The tension between the nip rolls (the tension during the draining process and the drying process) is in the range of 200 to 800 N / m.

  The tension can be measured by installing a guide roll incorporating a commercially available load cell or a tension roll sensor using a strain gauge. The tension is measured by bringing these guide rolls into contact with the polyvinyl alcohol resin film. The load cell or tension sensor roll for measuring the tension is used only for the measurement, and is usually disposed so as not to contact the film.

The air volume blown from the air knife can be 2 to 20 m ³ / min. If the air volume is less than 2 m ³ / min, the wind pressure is too weak to drain the water sufficiently, and a polarizing film is produced without removing water and foreign matter adhering to the film surface. There is a possibility of defects when applied. On the other hand, if the air volume is higher than 20 m ³ / min, the wind pressure is too strong and the film may be broken.

  The draining process described above can be appropriately adjusted within the range of the arrangement condition and the processing condition. Within the above range, even when the thickness of the raw film of the polyvinyl alcohol resin is as thin as 60 μm, the draining process can be performed without causing partial draining failure. For this reason, it is possible to suppress the generation of crystal foreign matter on the film surface, and when manufacturing a polarizing plate to which a polarizing film is applied, particularly using an active energy ray curable adhesive such as an ultraviolet curable adhesive, When manufacturing, the defect resulting from said foreign material can be suppressed effectively.

(Drying process)
A polarizing film can be produced by drying the polyvinyl alcohol-based resin film after the draining treatment. The film can be dried in the drying furnace 25 at a temperature of about 30 to 100 ° C. for about 30 to 600 seconds, for example.

  The final integrated draw ratio of the polarizing film produced in this manner is usually 4.5 to 7 times, preferably 5 to 6.5 times.

[Production method of polarizing plate]
In the method for producing a polarizing plate of the present invention, a protective film is bonded to at least one surface of the polarizing film produced as described above via an adhesive.

(Protective film)
Examples of the material constituting the protective film include cycloolefin resins and cellulose acetate resins, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resins, acrylic resins, and polypropylene resins. For example, film materials that have been widely used in the art can be given. When a protective film is bonded on both surfaces of a polarizing film, each protective film may be the same and may be a different kind of film.

  The cycloolefin-based resin is a thermoplastic resin having a monomer unit made of a cyclic olefin (cycloolefin) such as norbornene or a polycyclic norbornene-based monomer, and is also called a thermoplastic cycloolefin-based resin. The cycloolefin-based resin may be a hydrogenated product of the above-described cycloolefin ring-opening polymer or a ring-opening copolymer using two or more kinds of cycloolefins. It may be an addition polymer with an aromatic compound having a polymerizable double bond. Moreover, what introduce | transduced the polar group into a cycloolefin type resin is also effective.

  When the first protective film is formed using a copolymer of a cycloolefin and an aromatic compound having a chain olefin and / or vinyl group, examples of the chain olefin include ethylene and propylene. Examples of the aromatic compound having a vinyl group include styrene, α-methylstyrene, and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less, but is preferably about 15 to 50 mol%. In particular, when the first protective film is formed using a terpolymer of cycloolefin, chain olefin, and aromatic compound having a vinyl group, the monomer unit composed of cycloolefin is compared as described above. Less amount. In such a terpolymer, the monomer unit composed of a chain olefin is usually 5 to 80 mol%, and the monomer unit composed of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

  When using a copolymer of a cycloolefin and a chain olefin or / and an aromatic compound having a vinyl group, examples of the chain olefin include ethylene and propylene, and examples of the aromatic compound having a vinyl group include styrene, Examples include α-methylstyrene and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). In particular, when a terpolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group is used, the amount of the monomer unit comprising the cycloolefin can be made relatively small as described above. In such a terpolymer, the monomer unit composed of a chain olefin is usually 5 to 80 mol%, and the monomer unit composed of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

  Cycloolefin-based resins are commercially available as appropriate, such as “TOPAS” (manufactured by Topas Advanced Polymers GmbH), “Arton” (manufactured by JSR Corporation), “ZEONOR” and “ZEONEX” “ZEONEX” ”(manufactured by Nippon Zeon Co., Ltd.),“ Apel ”(manufactured by Mitsui Chemicals, Inc.),“ Oxis (OXIS) ”(manufactured by Okura Kogyo Co., Ltd.), etc. When such a cycloolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, for example, “Essina” and “SCA40” (manufactured by Sekisui Chemical Co., Ltd.), “Zeonor Film” (manufactured by Nippon Zeon Co., Ltd.), etc. Commercial products may be used.

  The cycloolefin resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be given to the cycloolefin-based resin film. Stretching is usually performed continuously while unwinding a film roll, and in a heating furnace, the roll traveling direction (film longitudinal direction), the direction perpendicular to the traveling direction (film width direction), or both Stretched. As the temperature of the heating furnace, a range from the vicinity of the glass transition temperature of the cycloolefin resin to the glass transition temperature + 100 ° C. is usually employed. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

  When the cycloolefin-based resin film is in a roll-wound state, the films tend to adhere to each other and easily cause blocking. Therefore, the cycloolefin-based resin film is usually rolled after the protective film is bonded. Moreover, since the surface activity of a cycloolefin-based resin film is generally inferior, surface treatment such as plasma treatment, corona treatment, saponification treatment, ultraviolet irradiation treatment and flame (flame) treatment is performed on the surface to be bonded to the polarizing film. Is preferred. Among these, plasma treatment that can be carried out relatively easily, particularly atmospheric pressure plasma treatment and corona treatment are preferable.

  The cellulose acetate-based resin is a cellulose partial or completely esterified product, and examples thereof include a film composed of cellulose acetate ester, propionate ester, butyrate ester, mixed ester thereof, and the like. More specifically, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like can be given. As such a cellulose ester-based resin film, an appropriate commercially available product can be suitably used. As mentioned above, “Fuji Film Co., Ltd.”, “KC8UX2M”, “KC8UY”, “KC4UYW” and “KC6UAW” [above, manufactured by Konica Minolta Advanced Layer Co., Ltd.] can be used.

  Moreover, the cellulose acetate type-resin film which provided the phase difference characteristic as a protective film is also used suitably. As commercial products of the cellulose acetate-based resin film provided with such retardation characteristics, “WV BZ 438” (manufactured by Fuji Film Co., Ltd.), “KC4FR-1”, “KC4CR-1” and “ KC4AR-1 ″ [manufactured by Konica Minolta Advanced Layer Co., Ltd.] and the like. Cellulose acetate is also called acetyl cellulose or cellulose acetate.

  The thickness of the protective film used in the method for producing a polarizing plate of the present invention is preferably thin, but if it is too thin, the strength is lowered and the processability is poor. On the other hand, when it is too thick, problems such as a decrease in transparency and a longer curing time after lamination occur. Therefore, an appropriate thickness of the protective film is, for example, 5 to 200 μm, preferably 10 to 150 μm, and more preferably 10 to 100 μm.

  In order to improve the adhesiveness between the adhesive and the polarizing film and / or protective film, the polarizing film and / or protective film may be subjected to corona treatment, flame treatment, plasma treatment, ultraviolet treatment, primer coating treatment, saponification treatment, etc. A surface treatment may be applied.

  In addition, the protective film may be subjected to surface treatments such as anti-glare treatment, anti-reflection treatment, hard coat treatment, antistatic treatment and antifouling treatment, either singly or in combination of two or more. The protective film may contain an ultraviolet absorber such as a benzophenone compound and a benzotriazole compound, and a plasticizer such as a phenyl phosphate compound and a phthalate compound.

  Further, the protective film has a function as a retardation film, a function as a brightness enhancement film, a function as a reflection film, a function as a transflective film, a function as a diffusion film, and a function as an optical compensation film. Functional functions can be provided. In this case, for example, such a function can be achieved by laminating an optical functional film such as a retardation film, a brightness enhancement film, a reflection film, a transflective film, a diffusion film, and an optical compensation film on the surface of the protective film. In addition, the protective film itself can be given such a function. In addition, a protective film may have a plurality of functions such as a diffusion film having a function of a brightness enhancement film.

  The function as a retardation film is, for example, subjected to the stretching process described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, etc., or the process described in Japanese Patent No. 3168850, to the protective film described above. It can be given by doing.

  The retardation characteristics of the retardation film can be appropriately selected, for example, such that the front retardation value is in the range of 5 to 100 nm and the thickness direction retardation value is in the range of 40 to 300 nm. In addition, the function as a brightness enhancement film can be achieved by forming fine holes in the above protective film by a method as described in JP 2002-169025 A or JP 2003-29030 A, or by selective reflection. It can be provided by superimposing two or more cholesteric liquid crystal layers having different center wavelengths.

  The function as a reflective film or a transflective film is formed by forming a metal thin film on the protective film by vapor deposition or sputtering, and the function as a diffusion film is obtained by coating the protective film with a resin solution containing fine particles, respectively. Can be granted. The function as an optical compensation film can be imparted by coating and aligning a protective film with a liquid crystal compound such as a discotic liquid crystal compound. The protective film may contain a compound that develops a retardation, and various optical functional films may be directly bonded to the polarizing film using an appropriate adhesive. Examples of commercially available optical functional films include brightness enhancement films such as “DBEF” (manufactured by Sumitomo 3M Co., Ltd. in Japan) and “WV film” [Fuji Film ( ”, Etc.”, “Arton Film” (manufactured by JSR Corporation), “ZEONOR FILM” (manufactured by ZEON CORPORATION), “Essina” (manufactured by Sekisui Chemical Co., Ltd.), “ Examples thereof include retardation films such as “VA-TAC film” (manufactured by Konica Minolta Advanced Layer Co., Ltd.) and “Sumikalite” (manufactured by Sumitomo Chemical Co., Ltd.).

(Adhesive layer)
Examples of the adhesive constituting the adhesive layer include a water-based adhesive and an active energy ray-curable adhesive.

  Examples of the water-based adhesive include a polyvinyl alcohol-based resin aqueous solution and a water-based two-component urethane emulsion adhesive. Polyvinyl alcohol resins used as adhesives include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as other single quantities copolymerizable with vinyl acetate. And vinyl alcohol copolymers obtained by saponifying the copolymer with the polymer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive. When such an aqueous adhesive is used, the resulting adhesive layer is usually much thinner than 1 μm. The aqueous adhesive is applied at a temperature of 15 to 40 ° C. after the preparation, and the bonding temperature is usually in the range of 15 to 30 ° C.

  As the active energy ray-curable adhesive, an epoxy compound that does not contain an aromatic ring in the molecule is preferably used as the adhesive from the viewpoint of weather resistance, refractive index, cationic polymerization, and the like. Examples of such an epoxy compound include a glycidyl ether of a polyol having an alicyclic ring, an aliphatic epoxy compound, and an alicyclic epoxy compound. An epoxy compound suitably used for such an active energy ray-curable adhesive is described in detail in, for example, Japanese Patent No. 4306270 (= Japanese Patent Laid-Open No. 2004-245925), but the outline is also described here. I will do it.

  The glycidyl ether of a polyol having an alicyclic ring is obtained by glycidyl etherifying a nuclear hydrogenated polyhydroxy compound obtained by selectively hydrogenating an aromatic polyol under pressure in the presence of a catalyst. Can be. Examples of the aromatic polyol include bisphenol type compounds such as bisphenol A, bispheel F, and bisphenol S; novolac type resins such as phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolac resin; tetrahydroxydiphenylmethane, Examples thereof include tetrahydroxybenzophenone and polyfunctional compounds such as polyvinylphenol. Glycidyl ether can be obtained by reacting an alicyclic polyol obtained by hydrogenating the aromatic ring of these aromatic polyols with epichlorohydrin. Among the glycidyl ethers of polyols having such alicyclic rings, it is preferable to use hydrogenated bisphenol A diglycidyl ether.

  The aliphatic epoxy compound can be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, 1,4-butanediol diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerin triglycidyl ether; trimethylolpropane triglycidyl ether; polyethylene glycol diglycidyl ether; propylene Diglycidyl ether of glycol; Polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol or glycerin Examples thereof include glycidyl ether.

  The alicyclic epoxy compound means an epoxy compound having one or more epoxy groups bonded to the alicyclic ring in the molecule. The “epoxy group bonded to the alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula (I). In the following formula (I), m is an integer of 2 to 5.

A compound in which a group in the form of removing one or more hydrogen atoms in (CH ₂ ) _m in the above formula (I) is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring [m = 3 in the above formula (I)] or an oxabicycloheptane ring [m = 4 in the above formula (I)] It is preferably used because it exhibits excellent adhesion between the polarizing film and the protective film. Although the alicyclic epoxy compound used preferably below is specifically illustrated, it is not limited to these compounds.

(A) Epoxycyclohexylmethyl epoxycyclohexanecarboxylates: represented by the following formula (II), wherein R ¹ and R ² are each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. Represents.

(B) Epoxycyclohexanecarboxylates of alkanediol: represented by the following formula (III), wherein R ³ and R ⁴ are each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. N represents an integer of 2-20.

(C) Epoxycyclohexylmethyl esters of dicarboxylic acid: represented by the following formula (IV), wherein R ⁵ and R ⁶ are each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. P represents an integer of 2-20.

(D) Epoxycyclohexyl methyl ethers of polyethylene glycol: represented by the following formula (V), wherein R ⁷ and R ⁸ are each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. Q represents an integer of 2 to 10.

(E) Epoxycyclohexyl methyl ethers of alkanediol: represented by the following formula (VI), wherein R ⁹ and R ¹⁰ are each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. And r represents an integer of 2 to 20.

(F) diepoxy trispiro compound: represented by the following formula (VII), wherein R ¹¹ and R ¹² each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(G) Diepoxy monospiro compound: represented by the following formula (VIII), wherein R ¹³ and R ¹⁴ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(H) Vinylcyclohexene diepoxide: represented by the following formula (IX), wherein R ¹⁵ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(I) Epoxycyclopentyl ethers: represented by the following formula (X), wherein R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(J) Diepoxytricyclodecane: represented by the following formula (XI), wherein R ¹⁸ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

Among the alicyclic epoxy compounds exemplified above, for example, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate [compound of R ¹ = R ² = H in formula (II)], 3,4- Epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate [compound of formula (II) where R ¹ = 4-CH ₃ , R ² = 4-CH ₃ ], ethylene bis (3,4 -Epoxycyclohexanecarboxylate) [compound of formula (III), R ³ = R ⁴ = H, n = 2], bis (3,4-epoxycyclohexylmethyl) adipate [in formula (IV), R ⁵ = R ⁶ = H, p = 4 compound], bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate [in formula (IV), R ⁵ = 4 -CH ₃ , R ⁶ = 4-CH ₃ , p = 4 compound], ethylene glycol bis (3,4-epoxycyclohexyl methyl ether) [in the formula (VI), R ⁹ = R ¹⁰ = H, r = 2 Is a compound that is commercially available or an analogue thereof, and is more preferably used because it is relatively easy to obtain.

  In the active energy ray-curable adhesive, the epoxy compound may be used alone or in combination of two or more. The epoxy equivalent of the epoxy compound used in this composition is generally 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, there is a possibility that the flexibility of the protective film after curing is lowered or the adhesive strength is lowered. On the other hand, when it exceeds 3000 g / equivalent, compatibility with other components may be lowered.

  The active energy ray-curable adhesive may contain an oxetane compound in addition to the above epoxy compound. By adding an oxetane compound, the viscosity of the adhesive described above can be lowered and the curing rate can be increased.

  The oxetane compound is a compound having at least one oxetane ring (four-membered ether) in the molecule, such as 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3 -Oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane And phenol novolac oxetane. The amount of the oxetane compound is usually 50% by weight or less, preferably 10 to 40% by weight, based on the whole active energy ray-curable compound. Oxetane compounds can be easily obtained as commercial products. For example, all of them are trade names sold by Toagosei Co., Ltd., “Aron Oxetane OXT-101”, “Aron Oxetane OXT-121”. , “Aron oxetane OXT-211”, “Aron oxetane OXT-221”, “Aron oxetane OXT-212”, and the like.

  In this adhesive, from the viewpoint of reactivity, cationic polymerization is preferably used as a curing reaction of the epoxy compound, and a cationic polymerization initiator is preferably added to the composition. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and starts an epoxy group polymerization reaction. Hereinafter, a cationic polymerization initiator that generates a cationic species or a Lewis acid upon irradiation with active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”.

  The method of curing the adhesive by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at room temperature, reducing the need to consider the heat resistance of the polarizing film or distortion due to expansion, and the polarizing film. It is advantageous in that the protective film can be adhered well. In addition, since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an adhesive.

  The photocationic polymerization initiator may be of any type, but specific examples include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene There are complexes.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate. Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and di (4-nonylphenyl) iodonium hexafluorophosphate.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis (diphenylsulfonio) diphenylsulfide bishexa. Fluorophosphate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bis Hexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone Hexafluoroantimonate, 7- [di (p-tolui) ) Sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenyl Sulfonio-diphenyl sulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide, tetrakis (pentafluorophenyl) borate, and the like.

  Examples of the iron-arene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II). And tris (trifluoromethylsulfonyl) methanide.

  Commercially available products of these photocationic polymerization initiators can be easily obtained. For example, “Kayarad PCI-220” and “Kayarad PCI-620” [Nippon Kayaku Co., Ltd. "UVI-6990" (manufactured by Dow Chemical Co.), "Adekaoptomer SP-150" and "Adekaoptomer SP-170" (manufactured by ADEKA Corporation), "CI-5102", " "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" and "CIP-2064S" (manufactured by Nippon Soda Co., Ltd.), "DPI-101", "DPI-102" , “DPI-103”, “DPI-105”, “MPI-103”, “MPI-105”, “BBI-101”, “BBI-102”, “BBI-10” 3 ”,“ BBI-105 ”,“ TPS-101 ”,“ TPS-102 ”,“ TPS-103 ”,“ TPS-105 ”,“ MDS-103 ”,“ MDS-105 ”,“ DTS-102 ” And “DTS-103” (manufactured by Midori Chemical Co., Ltd.), “PI-2074” (manufactured by Rhodia), and the like.

  These photocationic polymerization initiators may be used alone or in combination of two or more. Among these, in particular, the aromatic sulfonium salt has an ultraviolet absorption property even in a wavelength region of 300 nm or more, so it has excellent curability, gives good mechanical strength, and is good between the polarizing film and the protective film. Since it can give the hardened | cured material which has adhesiveness, it is used preferably.

  The compounding amount of the cationic photopolymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the total of the cationic polymerizable compounds including the epoxy compound and the oxetane compound. is there. If the amount of the cationic photopolymerization initiator is small, the curing becomes insufficient, and the mechanical strength and the adhesion between the polarizing film and the protective film tend to be lowered. On the other hand, if the amount of the cationic photopolymerization initiator is too large, the amount of ionic substances in the cured product will increase, resulting in an increase in the hygroscopicity of the cured product, which may reduce the durability of the resulting adhesive layer. is there.

  Active energy ray-curable adhesives include ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, leveling agents, plasticizers, antifoaming agents, etc. Additives can be blended. Examples of the ion trapping agent include antimony-based, powdered bismuth-based, magnesium-based, aluminum-based, calcium-based, titanium-based and mixed inorganic compounds, and antioxidants include hindered phenol-based antioxidants. Agents and the like.

  Active energy ray-curable adhesives can be used as solventless adhesives that are substantially free of solvent components, but each coating method has an optimum viscosity range, A solvent may be included. As the solvent, it is preferable to use a solvent that dissolves the epoxy compound constituting the adhesive well without degrading the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, etc. And organic solvents such as esters. The viscosity of the active energy ray-curable adhesive used in the present invention is, for example, in the range of about 5 to 1000 mPa · s, preferably 10 to 200 mPa · s, and more preferably 20 to 100 mPa · s. . There is no particular limitation on the coating method of the active energy ray-curable adhesive, and for example, a protective film or a polarizing film can be applied by various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater. What is necessary is just to apply to a bonding surface.

Thus, the above-mentioned protective film is bonded onto the adhesive layer formed on the polarizing film. When bonding a protective film on both surfaces of a polarizing film, two protective films may be bonded one step at a time, and both surfaces may be bonded in one step. The laminated body of the polarizing film and the protective film is irradiated with active energy rays to cure the adhesive. The light source used for irradiation with active energy rays is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, microwave excitation A mercury lamp, a metal halide lamp, etc. can be used. The light irradiation intensity is determined for each target composition and is not particularly limited. However, the irradiation intensity in the wavelength region effective for activation of the initiator is preferably 10 to 5000 mW / cm ^2. . When the light irradiation intensity is less than 10 mW / cm ² , the reaction time becomes too long, and when it exceeds 5000 mW / cm ² , yellowing of the adhesive layer is caused by heat radiated from the lamp and heat generated during polymerization of the composition. And the polarizer may be deteriorated.

The irradiation time of the active energy ray is controlled for each composition to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ / cm ^2. It is preferable to set to. When the above integrated light quantity is less than 10 mJ / cm ² , the active species derived from the initiator is not sufficiently generated, and the resulting protective film may be insufficiently cured, while the integrated light quantity is 5000 mJ. If it exceeds / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity. The thickness of the adhesive layer after curing is usually 0.1 to 10 μm, more preferably 0.2 to 4 μm.

  The polarizing plate produced as described above includes a polarizing film and a protective film bonded to at least one surface of the polarizing film, and can be used as a polarizing plate that is a constituent member of a liquid crystal display device.

  Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Moreover, the transmission inspection of the polarizing film was performed by the following method.

For the transmission inspection of the polarizing film, a film piece having a width of 1 m and a length (film transport direction) of 20 m was cut out from the produced polarizing film, and this piece was visually observed through a light source such as a backlight and detected to be 100 μm or more. The number of foreign matters was counted, and the number of foreign matters per 1 m ^{2 of} the polarizing film was calculated.

[Example 1]
A 60-μm-thick polyvinyl alcohol film (trade name “Kuraray Vinylon VF-PE # 6000” manufactured by Kuraray Co., Ltd., polymerization degree 2400, saponification degree 99.9 mol% or more) with swelling at 30 ° C. in pure water The film was immersed in the bath for 100 seconds while maintaining a tension state so that the film did not loosen, and the film was sufficiently swollen. Next, after uniaxial stretching was performed for 90 seconds by immersing iodine / potassium iodide / water in a 30 ° C. dyeing tank having a weight ratio of 0.02 / 1.5 / 100, potassium iodide / boric acid / water The film was immersed for 60 seconds in a 55 ° C. crosslinking tank having a weight ratio of 12 / 4.4 / 100, and uniaxially stretched until the cumulative draw ratio from the original fabric became 5.5 times while being water-resistant. Then, after immersing in a 40 ° C. boric acid aqueous solution in which boric acid / potassium iodide / water is 9.0 / 2.9 / 100 in weight ratio for 10 seconds, it is placed in a washing tank containing 12 ° C. pure water. Soaked for 2 seconds. With respect to the polyvinyl alcohol film having been subjected to each of the above treatments, using a draining device as shown in FIG. 2, air of 10 m ³ / min was blown onto the surface of the film one by one to drain the film on both sides. At this time, the conditions of each draining treatment were as follows: the film tension was 600 N / m (the tension between the nip rolls 21 and 27 in FIG. 1), the angle between the air nozzle and the film was 40 °, and the distance between the air nozzle and the film. Was 0.6 mm, and the distance between the chamber and the film was 1 mm. After draining, it was dried at 70 ° C. for 3 minutes to produce a polarizing film. As a result of the transmission inspection of this polarizing film, the number of defects of 100 μm or more was 0.05 / m ² .

[Example 2]
Using a 50 μm thick polyvinyl alcohol film (trade name “Kuraray Vinylon VF-PE # 5000” manufactured by Kuraray Co., Ltd., polymerization degree 2400, saponification degree 99.9 mol% or more), the tension applied to the film during draining treatment A polarizing film was produced in the same manner as in Example 1 except that was changed to 500 N / m. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 0.05 pieces / m ² .

Example 3
Using a 30 μm-thick polyvinyl alcohol film (trade name “Kuraray Vinylon VF-PE # 3000” manufactured by Kuraray Co., Ltd., polymerization degree 2400, saponification degree 99.9 mol% or more), the tension applied to the film during draining treatment A polarizing film was produced in the same manner as in Example 1 except that was changed to 450 N / m. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 0.10 / m ² .

Example 4
A polarizing film was produced in the same manner as in Example 1 except that the angle between the nozzle at the tip of the air knife and the film was changed to 20 ° in the draining process. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 0.8 / m ² .

Example 5
A polarizing film was produced in the same manner as in Example 1 except that the angle between the nozzle at the tip of the air knife and the film was changed to 90 ° in the draining process. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 1.2 pieces / m ² .

Example 6
A polarizing film was produced in the same manner as in Example 1 except that the distance between the nozzle at the tip of the air knife and the film was changed to 2 mm in the draining process. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 2.1 pieces / m ² .

Example 7
A polarizing film was produced in the same manner as in Example 1 except that the distance between the chamber and the film was changed to 3 mm in the draining treatment. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 2.3 / m ² .

[Comparative Example 1]
A polarizing film was produced in the same manner as in Example 1 except that the polyvinyl alcohol film was drained only with a nip roll after the washing tank without draining with a draining device. As a result of the transmission inspection of the obtained polarizing film, the number of defects of 100 μm or more was 5.2 / m ² .

[Comparative Example 2]
Except that the tension applied to the film in the draining process was changed to 150 N / m, an attempt was made to produce a polarizing film in the same manner as in Example 1. However, the film fluttered and contacted the chamber, causing the film to break, and the polarizing film Could not be produced.

  Table 1 below shows the manufacturing conditions and the results of the transmission inspection of Examples 1 to 7 and Comparative Examples 1 and 2 described above.

  Example 1 in which a polarizing film was produced by the production method of the present invention, and Comparative Example 1 in which a polarizing film was produced by a method not corresponding to the production method of the present invention using the same polyvinyl alcohol film (raw film) as in Example 1 From the comparison of (2) and (2), it can be seen that defects produced in the polarizing film are effectively suppressed when produced in a state satisfying the conditions for draining treatment. In addition, from the results of Examples 4 to 7, the defect that occurs in the polarizing film is any one of the conditions for the draining treatment specified in the present invention as long as the tension applied to the film and the air volume of the air are satisfied. It turns out that it is suppressed also when it is outside the range. Moreover, from the results of Examples 2 and 3 in which a raw film having a film thickness thinner than that of Example 1 was used, the conditions for the draining treatment specified in the present invention were also effective when manufacturing a polarizing film having a small thickness. It can be seen that it is.

10: Raw film made of polyvinyl alcohol resin,
11 ... Feed roll,
13 ... swelling tank,
15 …… Dyeing tank,
17 …… Crosslinking tank,
19 …… Cleaning tank,
21, 27 ... A pair of nip rolls,
23 …… Draining device,
25 …… Drying furnace,
30: Polarized film,
40 …… The first roll,
42 …… First air knife,
44 …… First chamber,
46 …… The second roll,
48 …… Second air knife,
50 ... Second chamber.

Claims (7)

A method for producing a polarizing film by subjecting a polyvinyl alcohol resin film having a thickness of 1 to 60 μm to a dyeing treatment, a crosslinking treatment, and a washing treatment in this order,
After the cleaning treatment, while applying a tension of 200 to 1500 N / m to the film, air is applied to the film surface opposite to the first roll while holding the film on the first roll provided on one side thereof. Blow, then blow the air on the film surface opposite to the second roll while holding the air blown surface on the second roll, drain the water, and each of the water removed by the air is near the air blowing position A method for producing a polarizing film, comprising: performing draining treatment to be recovered by a first chamber and a second chamber provided in the substrate. The method for producing a polarizing film according to claim 1, wherein air is blown at an air volume of 2 to 20 m ³ / min.   Air is blown from the nozzle onto the film, and the nozzle has an angle of 30 to 80 ° with respect to the film surface at the center line passing through the tip of the outlet, and the distance from the tip of the outlet to the film surface is 1 The manufacturing method of the polarizing film of Claim 1 or 2 arrange | positioned so that it may become 0.5 mm or less.   The method for producing a polarizing film according to any one of claims 1 to 3, wherein the chamber is arranged such that a distance from the suction port tip to the film surface is 2 mm or less.   The manufacturing method of the polarizing film in any one of Claims 1-4 which performs a drying process after the draining process.   The draining process and the drying process are performed while applying a tension of 200 to 800 N / m to the film by a nip roll provided before the draining process and a nip roll provided inside the drying process or after the drying process. The manufacturing method of the polarizing film of description.   A method for producing a polarizing plate, comprising: bonding a protective film to a polarizing film produced by the method according to claim 5 or 6 using an ultraviolet curable adhesive.

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