JP2011138032A - Method of manufacturing polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polarizing plate that is thin and has a small amount of concave defects. <P>SOLUTION: The method of manufacturing the polarizing plate includes a sticking step of putting a protective film, a polarizing film and a peel protective film between at least one pair of rolls so that the protective film comes in contact with one surface of the polarizing film while interposing an adhesive layer between them and the peel protective film comes in contact with the polarizing film on the surface being in no contact with the adhesive layer and rotating the pair of rolls to stick these films to one another. A rubber roll having the surface made of rubber is used as at least one roll of the pair of rolls. The method of manufacturing the polarizing plate satisfies inequality (A): (sticking speed)<SP>1/2</SP>/(rubber hardness)≥0.0375 [(m/minute)<SP>1/2</SP>/<SP>0</SP>]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a polarizing plate in which a protective film is laminated on one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer, and a peelable protective film is laminated on the other surface of the polarizing film. Is.

  A polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. Conventionally, a polarizing film made of polyvinyl alcohol having a protective film made of triacetyl cellulose bonded to both sides has been used as such a polarizing plate. Recently, mobile devices such as notebook personal computers and mobile phones for liquid crystal display devices have been used. Thinner and lighter weights are being demanded with the development of TVs and large TVs. Moreover, since the use place spreads over a wide range by carrying, the improvement of durability is also calculated | required simultaneously.

  For example, JP-A-10-186133 (Patent Document 1) proposes a polarizing plate in which a protective film is laminated only on one surface of a polarizing film in order to reduce the thickness and weight. Japanese Patent Laid-Open No. 2007-193333 (Patent Document 2) proposes a method of manufacturing a polarizing plate in which a protective film is laminated only on one surface of a polarizing film. However, as described in Patent Documents 1 and 2, when a polarizing plate having a protective film laminated on only one surface of a polarizing film is produced, a concave defect (referred to as a “dental defect”) is formed on the polarizing plate. There is a problem that is likely to occur. FIG. 1 shows a photograph of the unevenness on the surface of the polarizing plate in which a dent defect has been observed, observed with a confocal microscope (PLμ2300 (Sensofa Japan)). According to FIG. 1, it can be confirmed that some unevenness is generated on the surface of the polarizing plate. Such dent-like defects are presumed to be caused by film distortion (referred to as “bonding distortion”) that occurs during film bonding.

  The liquid crystal panel which bonded the polarizing plate with a dent-like defect produces the malfunction that the visibility of the defective part falls.

JP 10-186133 A (publication date: July 14, 1998) JP 2007-193333 A (publication date: August 2, 2007 (2007))

  Therefore, an object of the present invention is to have a protective film bonded to one side of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer and peelable to the other side of the polarizing film to which the protective film is not bonded. An object of the present invention is to provide a method of manufacturing a polarizing plate having a small number of dent-like defects, which is a polarizing plate obtained by laminating a simple peel protective film.

  As a result of intensive studies under such a purpose, the present inventors have found that a protective film is provided on one side of a polarizing film made of polyvinyl alcohol resin via an adhesive layer on the other side of the polarizing film. In manufacturing a polarizing plate having a peelable protective film laminated, when a polarizing film, a protective film, and a peelable protective film are laminated (laminated), bonding is performed under specific bonding (lamination) conditions ( It was found that a polarizing plate with few dent defects can be obtained by stacking. That is, the present invention is as follows.

  The manufacturing method of the polarizing plate concerning this invention is the other side of the polarizing film by which the protective film is bonded through the adhesive layer on the single side | surface of the polarizing film which consists of polyvinyl alcohol-type resin, and the said protective film is not bonded. A method for producing a polarizing plate in which a peelable protective film is bonded to a surface, wherein the protective film, the polarizing film, and the peeling protective film are in contact with one side of the polarizing film via an adhesive layer. And including a bonding step in which each film is bonded by rotating the roll between the pair of rolls so that the release protective film is in contact with the surface of the polarizing film that is not in contact with the adhesive layer. At least one of the pair of rolls uses a rubber roll whose roll surface is rubber and satisfies the following formula (A): It is characterized.

(Bonding speed) ^1/2 / Rubber hardness ≧ 0.0375 [(m / min) ^1/2 / °] (A)
Here, the bonding speed is the traveling speed [m / min] of each film sandwiched between rolls in the bonding process, and the rubber hardness is the hardness [°] of the roll surface of the rubber roll.

  In the method for producing a polarizing plate according to the present invention, the adhesive may be a water-based adhesive.

  The pair of rolls may both be rubber rolls.

  A protective film is bonded to one side of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer, and a peelable protective film is bonded to the other side of the polarizing film to which the protective film is not bonded. In the manufacturing method of the polarizing plate thus formed, the idea of paying attention to the hardness and bonding speed of the rubber roll used for bonding in order to reduce the dent-like defects has not been known at all, and the present inventors It is a new technical idea uniquely found by

  According to the present invention, since the protective film is laminated on one surface of the polarizing film made of polyvinyl alcohol-based resin, the polarizing plate thickness can be reduced compared to the polarizing plate in which the protective film is laminated on both sides. In addition, a polarizing plate with few dent defects can be produced.

It is the photograph which observed the unevenness | corrugation of the surface of the polarizing plate which the dent-like defect generate | occur | produced with the confocal microscope (PL (micro | micron | mu) 2300 (Sensofa Japan)). It is a schematic diagram which shows the structure of the polarizing plate produced by the manufacturing method of this invention. It is a figure for demonstrating one Embodiment of the manufacturing method of this invention. It is a plot figure which shows the relationship between the value (it describes with "A value") obtained from Formula (A), and the number of dent defects.

  An embodiment of the present invention will be described as follows. However, the present invention is not limited to this, and can be implemented in a mode in which various modifications are made within the described range. In the present specification, the description “X to Y” indicating a numerical range indicates that it is X or more and Y or less.

The manufacturing method of the polarizing plate concerning this invention (henceforth "the manufacturing method of this invention"), a protective film is bonded via the adhesive layer on the single side | surface of the polarizing film which consists of polyvinyl alcohol-type resin, The said protective film is The present invention relates to a method for producing a polarizing plate, in which a peelable protective film is bonded to the other surface of a polarizing film that is not bonded. In particular, the protective film, the polarizing film, and the peeling protective film are arranged so that the protective film is in contact with one side of the polarizing film via an adhesive layer, and the peeling protective film is in contact with the surface that is not in contact with the adhesive layer of the polarizing film. Including a laminating step of laminating each film by sandwiching at least a pair of rolls and rotating the rolls, and at least one of the pair of rolls uses a rubber roll whose roll surface is rubber, And it is a manufacturing method of the polarizing plate characterized by satisfy | filling following formula (A).
(Bonding speed) ^1/2 / Rubber hardness ≧ 0.0375 [(m / min) ^1/2 / °] (A)
Here, the bonding speed is the traveling speed [m / min] of each film sandwiched between rolls in the bonding process, and the rubber hardness is the hardness [°] of the roll surface of the rubber roll.

  FIG. 2 is a schematic diagram showing the configuration of the polarizing plate produced by the production method of the present invention. In the polarizing plate (10) shown in FIG. 2, a protective film (2) is bonded to one side of a polarizing film (1) made of polyvinyl alcohol resin via an adhesive layer (not shown), and the protective film. It is a polarizing plate (10) by which the peelable protective film (3) which can be peeled on the other surface of the polarizing film (1) which (2) is not bonded is bonded. When the polarizing plate (10) is used, the peeling protective film (3) is peeled off and used.

<Polarizing film>
Specifically, the polarizing film subjected to the bonding step in the production method of the present invention is uniaxially stretched and dyed with a dichroic dye on a polyvinyl alcohol-based resin film, and the dichroic dye is adsorbed and oriented. It has been made. The polyvinyl alcohol-based resin constituting the polarizing film is usually obtained by saponifying a polyvinyl acetate-based resin. The saponification degree of the polyvinyl alcohol-based resin is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% to 100 mol%. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Examples include coalescence. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000.

  These polyvinyl alcohol resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used. Usually, as a starting material for producing a polarizing film, an unstretched film of a polyvinyl alcohol-based resin film having a thickness of 20 to 100 μm, preferably 30 to 80 μm is used. Industrially, the practical width of the film is 1500 to 4000 mm. The unstretched film is processed in the order of swelling treatment, dyeing treatment, boric acid treatment, and water washing treatment, uniaxially stretched in the steps up to boric acid treatment, and finally dried to obtain a polarizing film having a thickness of, for example, 5 ~ 50 μm.

  There are roughly two methods for producing a polarizing film. In the first method, a polyvinyl alcohol-based resin film is uniaxially stretched in air or an inert gas, followed by solution treatment in the order of a swelling treatment step, a dyeing treatment step, a boric acid treatment step and a water washing treatment step, and finally drying. How to do it. In the second method, an unstretched polyvinyl alcohol-based resin film is solution-treated with an aqueous solution in the order of a swelling treatment step, a dyeing treatment step, a boric acid treatment step and a water washing treatment step, and the boric acid treatment step and / or the previous step. In this method, uniaxial stretching is performed in a wet process, followed by drying.

  In any method, the uniaxial stretching may be performed in one step or may be performed in two or more steps, but is preferably performed in a plurality of steps. As a stretching method, a known method can be adopted. For example, stretching between rolls in which stretching is performed with a peripheral speed difference between two nip rolls that transport a film, for example, heat described in Japanese Patent No. 2731813. Examples thereof include a roll stretching method and a tenter stretching method. The order of the steps is basically as described above, but there are no restrictions on the number of treatment baths, treatment conditions, and the like. Moreover, you may add the process which is not described in the said 1st and 2nd method for another objective. Examples of such processes include immersion treatment with an aqueous iodide solution not containing boric acid (iodide treatment) or immersion treatment with an aqueous solution containing zinc chloride not containing boric acid (zinc treatment) after boric acid treatment. Can be mentioned.

  The swelling treatment step is performed for the purpose of removing foreign matter on the film surface, removing the plasticizer in the film, imparting easy dyeability in the next step, and plasticizing the film. The processing conditions 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 base film do not occur. When the film previously stretched in the gas is swollen, for example, the film is immersed in an aqueous solution at 20 to 70 ° C, preferably 30 to 60 ° C. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds. In order to swell the unstretched raw film from the beginning, the film is immersed in an aqueous solution of 10 to 50 ° C., preferably 20 to 40 ° C., for example. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds.

  In the swelling process, since the film is likely to swell in the width direction and wrinkles into the film, a known wide roll (expander roll), spiral roll, crown roll, cross guider, bend bar, tenter clip, etc. It is preferable to convey the film while removing the wrinkles of the film with a widening device. In order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled by an underwater shower, EPC (Edge Position Control device: a device that detects the edge of the film and prevents the film from meandering), etc. It is also useful to use in combination. In this step, since the film swells and expands in the film transport direction, it is preferable to take measures such as controlling the speed of the transport roll before and after the treatment tank in order to eliminate the sag of the film in the transport direction. In addition to pure water, the swelling treatment bath used is boric acid (described in JP-A-10-153709), chloride (described in JP-A-06-281816), inorganic acid, inorganic salt, water-soluble An aqueous solution to which an organic solvent, alcohol or the like is added in an amount of 0.01 to 0.1% by weight can also be used.

  The dyeing process with the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye on the film. The processing conditions 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 base film do not occur. When iodine is used as the dichroic dye, for example, iodine / potassium iodide / water = 0.003 to 0.2 / 0.1 in a weight ratio of 10 to 45 ° C., preferably 20 to 35 ° C. An immersion treatment is performed for 30 to 600 seconds, preferably 60 to 300 seconds, using an aqueous solution having a concentration of 10/100. Instead of potassium iodide, other iodides such as zinc iodide may be used. Other iodides may be used in combination with potassium iodide. Furthermore, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. Any dye containing 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water can be regarded as a dyeing tank.

  When a water-soluble dichroic dye is used as the dichroic dye, for example, dichroic dye / water = 0.001 to 0.1 / by weight ratio under a temperature condition of 20 to 80 ° C., preferably 30 to 70 ° C. A 100-concentration aqueous solution is used for 30 to 600 seconds, preferably 60 to 300 seconds. The aqueous solution of the dichroic dye to be used may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate, a surfactant or the like. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

  As described above, the film may be stretched in a dyeing tank. Stretching is performed by a method of giving a peripheral speed difference between the nip rolls before and after the dyeing tank. Similarly to the swelling treatment step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar and the like can be installed in the dyeing bath and / or at the bath entrance / exit.

  The boric acid treatment is performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye in an aqueous solution containing 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye is iodine, it is preferable to contain 1 to 30 parts by weight of iodide. Examples of 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, etc. may coexist.

  The boric acid treatment is carried out for water resistance by crosslinking or hue adjustment (for example, to prevent bluish tint). When boric acid treatment is performed for water resistance by cross-linking, a cross-linking agent such as glyoxal or glutaraldehyde can be used in addition to boric acid or together with boric acid, if necessary. In addition, the boric acid treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment. In addition, boric acid treatment for hue adjustment may be referred to by a name such as complementary color treatment or re-dyeing treatment.

  This boric acid treatment is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose. The boric acid treatment for water resistance and the boric acid treatment for hue adjustment are not particularly distinguished, but can be carried out under the following conditions. When the raw film is subjected to swelling treatment, dyeing treatment, boric acid treatment, and boric acid treatment is aimed at water resistance by crosslinking, boric acid is added in an amount of 3 to 10 parts by weight with respect to 100 parts by weight of water. A boric acid treatment bath containing 1 to 20 parts by weight of iodide is used, and is usually performed at a temperature of 50 to 70 ° C, preferably 55 to 65 ° C. The immersion time is 90 to 300 seconds. In addition, when performing the dyeing | staining process and a boric-acid process to the film extended | stretched previously, the temperature of a boric-acid processing bath is 50-85 degreeC normally, Preferably it is 55-80 degreeC.

  You may make it perform the boric-acid process for hue adjustment after the boric-acid process for water resistance. For example, when the dichroic dye is iodine, a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide for 100 parts by weight of water is used for this purpose. Usually, it is carried out at a temperature of 10 to 45 ° C. The immersion time is usually 3 to 300 seconds, preferably 10 to 240 seconds. The subsequent boric acid treatment for adjusting the hue is usually performed at a lower boric acid concentration, a higher iodide concentration, and a lower temperature than the boric acid treatment for water resistance.

  These boric acid treatments may consist of a plurality of steps and are usually carried out in 2 to 5 steps. In this case, the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same or different within the above-described range. The boric acid treatment for water resistance and the boric acid treatment for hue adjustment may be performed in a plurality of steps, respectively.

  In the boric acid treatment step, the film may be stretched as in the dyeing treatment step. The final cumulative draw ratio is 4 to 7 times, preferably 4.5 to 6.5 times. The cumulative stretching ratio here means how long the reference length in the length direction of the original film is in all the films after the completion of the stretching process. For example, it is 1 m in the original film. If the portion is 5 m in all the films after the stretching treatment, the cumulative stretching ratio at that time is 5 times.

  After the boric acid treatment, a water washing treatment is performed. The water washing treatment is performed by immersing a polyvinyl alcohol resin film treated with boric acid for water resistance and / or hue adjustment in water, spraying water as a shower, or combining immersion and spraying. The water temperature in the water washing treatment is usually 2 to 40 ° C., and the immersion time is 2 to 120 seconds.

  Here, in each step after the stretching treatment, tension control may be performed so that the tension of the film becomes substantially constant. Specifically, when stretching is completed in the dyeing process, tension control is performed in the subsequent boric acid treatment process and the water washing process. When stretching is completed in the previous process of the dyeing process, tension control is performed in subsequent processes including the dyeing process and the boric acid process. When the boric acid treatment step is composed of a plurality of boric acid treatment steps, the film is stretched in the boric acid treatment step from the beginning or the first to the second step, and the next boric acid treatment step after the boric acid treatment step in which the stretching treatment is performed. Tension control is performed in each step from the acid treatment step to the water washing step, or the film is stretched in the boric acid treatment step from the first to the third stage, and the boric acid next to the boric acid treatment step in which the stretching treatment is performed. It is preferable to perform tension control in each process from the treatment process to the water washing process, but industrially, the film was stretched in the boric acid treatment process from the first or the first to the second stage, and the stretching process was performed. It is more preferable to perform tension control in each step from the boric acid treatment step next to the boric acid treatment step to the water washing step. In addition, when performing the above-described iodide treatment or zinc treatment after boric acid treatment, tension control can be performed also in these steps.

  The tension in each step from the swelling treatment to the water washing treatment may be the same or different. The tension to the film in the tension control is not particularly limited, and is appropriately set within a range of 150 to 2000 N / m, preferably 250 to 1500 N / m per unit width. When the tension is less than 150 N / m, the film is likely to be wrinkled. On the other hand, when the tension exceeds 2000 N / m, problems such as film breakage and life reduction due to bearing wear occur. The tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector. In addition, when tension control is performed, the film may be inevitably slightly stretched or shrunk, but this is not usually included in the stretching process.

  At the end of the polarizing film manufacturing process, a drying process is performed. The drying treatment is preferably carried out in a large number of stages by changing the tension little by little, but is usually carried out in 2 to 3 stages due to restrictions on equipment. When performed in two stages, the tension in the front stage is preferably set in the range of 250 to 1500 N / m, and the tension in the rear stage is preferably set in the range of 300 to 1200 N / m. When the tension becomes too large, the film breaks more, and when it becomes too small, the generation of wrinkles increases, which is not preferable. Moreover, it is preferable to set the drying temperature of a front | former stage from the range of 30-90 degreeC, and the drying temperature of a back | latter stage from the range of 50-100 degreeC. If the temperature is too high, the film will be ruptured and the optical properties will be deteriorated. If the temperature is too low, streaks will increase, which is not preferable. The drying time can be 60 to 600 seconds, for example, and the drying time in each stage may be the same or different. If the time is too long, it is not preferable in terms of productivity, and if the time is too short, drying is insufficient, which is not preferable.

  The polarizing film used in the method for producing a polarizing plate of the present invention is not particularly limited with respect to its moisture content, but is preferably in the range of 3 to 14% by weight, more preferably 3 to 10% by weight. Within the range, particularly preferably within the range of 3 to 8% by weight. When the moisture content of the polarizing film is less than 3% by weight, the polarizing film becomes brittle, easily tears along the stretching direction and becomes difficult to handle, and the moisture content of the polarizing film is 14% by weight. When exceeding, there exists a possibility that a polarizing film may become easy to shrink | contract in a dry-heat environment. In addition, the moisture content of a polarizing film can be computed from the weight change before and behind hold | maintaining, for example at 105 degreeC dry heat for 1 hour. A polarizing film having a moisture content within the above-described preferred range can be obtained, for example, by controlling the drying temperature and drying time of the polarizing film.

  In this way, the polyvinyl alcohol resin film is subjected to uniaxial stretching, dyeing treatment with a dichroic dye, and boric acid treatment to obtain a polarizing film. The thickness of this polarizing film is usually in the range of 5 to 40 μm.

<Protective film>
In the manufacturing method of the polarizing plate of this invention, a protective film is bonded (laminated | stacked) through the adhesive bond layer to one side in the above-mentioned polarizing film. The protective film is not particularly limited. For example, cycloolefin resin films, cellulose acetate resin films such as triacetyl cellulose and diacetyl cellulose, polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of the resin film, polycarbonate resin film, acrylic resin film, and polypropylene resin film include films that have been widely used in the field.

  The cycloolefin resin that can be used for the protective film in the present invention is an appropriate commercially available product such as Topas (manufactured by Ticona, registered trademark), ARTON (manufactured by JSR Corporation, registered trademark), ZEONOR. (Registered trademark) manufactured by Nippon Zeon Co., Ltd., ZEONEX (registered trademark manufactured by Nippon Zeon Co., Ltd.), Apel (registered trademark manufactured by Mitsui Chemicals, Inc.) and the like can be suitably used. 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, escina (manufactured by Sekisui Chemical Co., Ltd., registered trademark), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), zeonoa film (manufactured by Optes Co., Ltd., registered trademark), etc. A commercial product of a resin film 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 the film roll, and the film is stretched in a heating furnace in a roll traveling direction, a direction perpendicular to the traveling direction, or both. 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.

  Since the cycloolefin resin film generally has poor surface activity, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment is performed on the surface to be bonded to the polarizing film. preferable. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  Examples of the cellulose acetate-based resin film that can be used for the protective film in the present invention include commercially available products such as Fujitac TD80 (Fuji Film Co., Ltd.), Fujitac TD80UF (Fuji Film Co., Ltd.), and Fujitac TD80UZ (Fujitsu). Film Co., Ltd.), Fujitac TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.) and the like can be suitably used.

  The surface of the cellulose acetate-based resin film may be subjected to a surface treatment such as an antiglare treatment, a hard coat treatment, an antistatic treatment, or an antireflection treatment, depending on the application. Further, a liquid crystal layer or the like may be formed in order to improve the viewing angle characteristics. Moreover, in order to provide a phase difference, the cellulose resin film may be stretched. Further, this cellulose acetate-based resin film is usually subjected to a saponification treatment in order to enhance the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  When the protective film as described above is in a roll state, the films tend to adhere to each other and easily cause blocking, so that the roll end portion is subjected to uneven processing, a ribbon is inserted into the end portion, the protective film Or is rolled into a roll.

  The thickness of the protective film 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, the suitable thickness of a protective film is about 5-100 micrometers, for example, Preferably it is 10-80 micrometers, More preferably, it is 20-40 micrometers.

  The protective film preferably has fewer defects such as fish eyes. If there is a defect, the shape is transferred to the polarizing film, which may be a defect of the polarizing film.

<Adhesive layer>
In the method for producing a polarizing plate of the present invention, the polarizing film and the protective film are, for example, via an adhesive layer using a polyvinyl alcohol resin aqueous solution, an aqueous two-component urethane emulsion adhesive, a photocurable adhesive, or the like. Pasted together. As a photocurable adhesive agent, mixtures, such as a photocurable epoxy resin and a photocationic polymerization initiator, are mentioned, for example. From the viewpoint of thinning the adhesive layer, the adhesive is preferably an aqueous one, that is, an adhesive component dissolved in water or dispersed in water.

  In the case of using a cellulose acetate film whose surface to be bonded to the polarizing film is hydrophilized by a saponification process or the like as a protective film, an aqueous polyvinyl alcohol resin solution is suitably used as an 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 adhesive layer obtained therefrom is usually 1 μm or less, and even when the cross section is observed with a normal optical microscope, the adhesive layer is practically not observed.

<Peeling protection film>
When the peeling protective film (peelable film) used in the bonding step in the production method of the present invention bonds the polarizing film and the protective film, the surface of the polarizing film opposite to the protective film is scratched. It is used for protection. For example, when the polarizing plate is bonded to a liquid crystal panel or the like, the peeling protective film is peeled off when it is not necessary, for example, when an adhesive layer is formed on the polarizing film surface of the polarizing plate.

  As the material for the peel protection film, polyethylene resin, polypropylene resin, polystyrene resin, polyethylene terephthalate resin, etc., which are easy to handle and secure a certain degree of transparency, can be preferably used. A film obtained by molding a seed or two or more kinds into a single layer or a multilayer can be used as a release protective film.

  As such a peel protection film, specifically, the surface of the polyethylene terephthalate resin film is a Sanitect (SUNYECT) (sold by Sanei Kaken Co., Ltd.) having an adhesive layer formed on the surface of the polyethylene resin film. E-mask (E-MASK) (registered trademark, manufactured by Nitto Denko Co., Ltd.) having a pressure-sensitive adhesive layer formed thereon, and MASTACK (Fujimori Industry Co., Ltd.) having a pressure-sensitive adhesive layer formed on the surface of a polyethylene terephthalate resin film Commercial products such as manufactured and registered trademarks).

  Among these, the self-adhesive release protective film having adhesiveness to the polarizing film alone is simple because it does not need to protect the adhesive layer on the surface of the release protective film, and can be used more suitably. . As a commercial item of the self-adhesive resin film which shows suitable peeling force with respect to the said polarizing film, the Tretec (Toray Industries, Inc. make, registered trademark) etc. which consist of polyethylene resins can be mentioned, for example.

  The peeling force between the peeling protective film and the polarizing film is 0.01 to 5 N / 25 mm, preferably 0.01 to 2 N / 25 mm, more preferably 0.01 to 0.5 N / 25 mm. If the peel force is less than 0.01 N / 25 mm, the peel protective film may be partially peeled off because the adhesion between the polarizing film and the peel protective film is small. Moreover, when peeling force exceeds 5 N / 25mm, since it becomes difficult to peel a peeling protective film from a polarizing film, it is unpreferable.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer formed on the surface of the peel protection film, in addition to those having a high storage elastic modulus, those having a lower storage elastic modulus, for example, 0.1 MPa used for ordinary optical films An adhesive exhibiting a storage elastic modulus of a degree or less can also be used without particular limitation.

  Examples of the pressure-sensitive adhesive used in the present invention include acrylic, rubber-based, urethane-based, silicone-based, and polyvinyl ether-based resins. Moreover, energy ray curable adhesives and thermosetting adhesives are particularly useful as the above-mentioned adhesives having a high storage elastic modulus. Among these, an adhesive having an acrylic base polymer excellent in transparency, weather resistance, heat resistance and the like is preferable.

  Acrylic adhesive is not particularly limited, but (meth) acrylic such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate. An acid ester base polymer or a copolymer base polymer using two or more of these (meth) acrylic acid esters is preferably used. Furthermore, polar monomers are copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl (meth) And monomers having a functional group such as a carboxyl group, a hydroxyl group, an amide group, an amino group, and an epoxy group, such as acrylate.

  These acrylic pressure-sensitive adhesives can of course be used alone, but usually a crosslinking agent is used in combination. Crosslinking agents include divalent or polyvalent metal salts that form carboxylic acid metal salts with carboxyl groups, polyamine compounds that form amide bonds with carboxyl groups Examples thereof include polyepoxy compounds and polyol compounds that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable adhesive has the property of being cured by irradiation with energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with energy rays to adhere to an adherend such as a film. It is a pressure-sensitive adhesive that has the property of being adhered and cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable adhesive, it is particularly preferable to use an ultraviolet curable adhesive. The energy beam curable pressure-sensitive adhesive generally comprises an acrylic pressure-sensitive adhesive and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator and a photosensitizer can be blended.

  In addition to the base polymer and the crosslinking agent described above, the pressure-sensitive adhesive composition includes, for example, natural products and the like in order to adjust the pressure-sensitive adhesive strength, cohesive strength, tack, elastic modulus, glass transition temperature, etc. Appropriate additives such as synthetic resins, tackifier resins, antioxidants, ultraviolet absorbers, dyes, pigments, antifoaming agents, corrosion inhibitors, and photopolymerization initiators can also be blended. Further, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by containing fine particles.

  The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm. However, in order to obtain a thin polarizing plate that is the object of the present invention, it is desirable to apply a thin film within a range that does not impair the workability and durability characteristics. It is more preferably 3 to 25 μm from the viewpoint of maintaining excellent processability and suppressing dimensional change of the polarizer. If the pressure-sensitive adhesive layer is too thin, the tackiness is lowered, and if it is too thick, problems such as sticking out of the adhesive tend to occur.

  The peeling protective film may be bonded in the same manner as described above on the surface of the protective film that does not face the polarizing film. By doing in this way, the surface of a protective film can be protected from the friction crack etc. which are produced before using a polarizing plate. In addition, it is preferable that this peeling protective film has few defects, such as a fish eye, similarly to a protective film. If there is a defect, the shape is transferred to the polarizing film, which may be a defect of the polarizing film.

  In addition, in the manufacturing method of the polarizing plate of this invention, it does not restrict | limit especially as a method of forming an adhesive layer, The above-mentioned base polymer is included in the surface where the peeling protection film of a polarizing film is bonded. After applying a solution containing each component to be dried and forming a pressure-sensitive adhesive layer, it may be obtained by laminating (laminating) a separator film that has been subjected to a release treatment such as a silicone-based separator. After forming the pressure-sensitive adhesive layer on the film, it may be bonded to the polarizing film surface, and further, the surface to which the peeling protective film of the polarizing plate is bonded and the surface to which the polarizing film of the separator film is bonded and You may bond these, after forming an adhesive layer in both the surfaces where the polarizing film of a peeling protective film is bonded. Moreover, when forming an adhesive layer on a polarizing film, you may perform an adhesion | attachment process, for example, a corona treatment, etc. to at least one of the adhesive layer formation surface and adhesive layer of a polarizing film as needed. The surface of the formed pressure-sensitive adhesive layer is usually protected by a separator film that has been subjected to a release treatment, and the separator film is peeled off before the release protective film is bonded to the polarizing film.

<Bonding process and drying process>
In the production method of the present invention, the protective film, the polarizing film, and the peeling protective film described above are attached to the surface of the polarizing film that is in contact with the protective film through the adhesive layer and that is not in contact with the adhesive layer of the polarizing film. It includes a bonding step in which each film is bonded by rotating the rolls between at least a pair of rolls so that the peel protection film is in contact. At this time, at least one of the pair of rolls uses a rubber roll whose roll surface is rubber and satisfies the following formula (A).
(Bonding speed) ^1/2 / Rubber hardness ≧ 0.0375 [(m / min) ^1/2 / °] (A)
Here, the bonding speed is the traveling speed [m / min] of each film sandwiched between rolls in the bonding process, and the rubber hardness is the hardness [°] of the roll surface of the rubber roll.

  FIG. 3 shows a view for explaining an embodiment of the production method of the present invention. The production method of the present invention is not limited to this. The manufacturing method (one embodiment) of the present invention shown in FIG. 3 includes a pasting step and a drying step. However, the manufacturing method of this invention should just include the bonding process at least.

  In FIG. 3, the protective film (2), the polarizing film (1), and the peeling protective film (3) are provided on one side of the polarizing film (1) via an adhesive layer (not shown). It can be seen that the peel protection film (3) is in contact with the surface of the polarizing film (1) that is not in contact with the adhesive layer and is sandwiched between at least a pair of rubber rolls (4). In other words, three films laminated in the order of protective film (2) -adhesive layer-polarizing film (1) -peeling protective film (3) are sandwiched between a pair of rubber rolls (4). ing. The three films are bonded together by the pressure when sandwiched between the pair of rubber rolls. And the film bonded together advances by rotating a rubber roll (4), it dries in a drying furnace (5), and becomes a polarizing plate (10). The progress speed of the film at this time is the bonding speed V.

  The reason why a rubber roll is used for at least one of the rolls used in the bonding step as described above is that wrinkles are hardly generated in each film to be bonded, and uniform bonding is possible. . However, when both of the pair of rolls are rubber rolls, it is more preferable that curling (warping) of the polarizing plate obtained after bonding is easy to correct. The correction of curl can be adjusted by the tension and carry-in angle of the film conveyed to the roll and the tension and carry-out angle of the film carried out from the laminating roll. The pair of rolls is preferably the same roll or a roll made of a material having substantially the same hardness in order to prevent uniform bonding and curling of the polarizing plate. In addition, the roll used for bonding is not restricted to a pair, Two or more pairs may be sufficient.

  The rubber roll only needs to have a rubber roll surface, and is usually obtained by forming a rubber layer around a metal roll. The thickness of the rubber layer is usually 1 to 50 mm, preferably 5 to 40 mm, more preferably 10 to 30 mm. If the rubber thickness is too thin, the influence of the metal roll is strong, and wrinkles and the like are likely to occur on the film during bonding. On the other hand, if it is too thick, it takes a great deal of time to produce a rubber roll, which is not preferable from an economical viewpoint. The rubber layer may be formed by laminating a plurality of materials having different compositions from the viewpoint of adhesion to the metal roll.

  The rubber roll has a rubber hardness that is preferably soft because the film is less likely to be scratched, but if it is too soft, the roller surface is likely to be damaged, so that the roller surface is easily damaged, and is preferably 30 ° to 100 °, preferably 50 ° to 90 °, more preferably 60 ° to 90 °. °. Rubber hardness can be measured according to JIS K 7215 Durometer Type A (Shore A).

  Examples of the material for the rubber roll include silicone rubber, EPDM rubber, butyl rubber, nitrile rubber, and fluorine rubber. Among these, silicone rubber and EPDM rubber are preferably used from the viewpoint of dimensional stability and handling. These rubber rolls can be obtained from Metropolitan Roller Industries, Kasuki Roller, Meiwa Rubber, Toyo Chemical Industry, and the like.

  A faster laminating speed is preferable from the viewpoint of production efficiency. However, if the speed is too high, film fluttering and the like tend to increase and handling becomes difficult. Therefore, a pasting speed is 1-100 m / min normally, Preferably it is 2-50 m / min.

The production method of the present invention is characterized in that the above-described bonding speed and rubber roll hardness satisfy the following formula (A).
(Bonding speed) ^1/2 / Rubber hardness ≧ 0.0375 [(m / min) ^1/2 / °] (A)
When the value obtained by the formula (A) (referred to as “A value” as appropriate) is smaller than 0.0375, a dent-like defect is likely to occur in the polarizing plate. Therefore, the A value is preferably 0.0375 [(m / min) ^1/2 / °] or more, more preferably 0.0381 [(m / min) ^1/2 / °] or more, and 0.0400 [(( m / min) ^1/2 / °] or more is most preferable. In addition, although it does not specifically limit, it is preferable that the value obtained by Formula (A) is 0.333 or less. The above 0.333 is a value calculated from the lower limit (30 °) of the preferable range of rubber hardness and the upper limit (100 m / min) of the bonding speed. The production method of the present invention is not particularly limited, but as an example satisfying the condition of the above formula (A), when a rubber roll having a rubber hardness of 30 ° is used, bonding of 1.2 m / min or more is performed. Preferably it is speed. In addition, when a rubber roll having a rubber hardness of 100 ° is used, the bonding speed is preferably 14 m / min or more.

Since the visibility of the liquid crystal panel on which the polarizing plate having a dent defect is bonded is significantly reduced, it is difficult to use it as a polarizing plate. Therefore, the part in which a dent defect exists in a polarizing plate is not normally utilized as a product of a polarizing plate. In other words, it can be said that the more dent defects, the lower the economy and productivity in the production of polarizing plates. Therefore, it can be said that it is ideal that the number of dent defects in the produced polarizing plate is 0 / m ² . Although not particularly limited, from the viewpoint of economy and productivity in the production of polarizing plates, it is preferable that the number of dent defects in the produced polarizing plate is 50 / m ² or less. The concave defects of the polarizing plate can be determined visually, and those skilled in the art can easily count the number of defects.

  Although the preferable conditions of the pressure concerning a film when it is clamped with the roll in the bonding process of the manufacturing method of the present invention are not particularly limited, 0.01 to 10 MPa is preferable, and 0.1 to 5 MPa is more preferable. Most preferred is 0.1 to 1 MPa. When the said pressure is large, the bonding distortion will also become large and it exists in the tendency for a dent-like defect to occur easily. Moreover, when the said pressure is small, it will not be bonded uniformly and it exists in the tendency for defects, such as a bubble, to generate | occur | produce easily.

  The preferable conditions for the tension applied to each film during the bonding step may vary depending on the film material, the bonding temperature, etc., but the protective film, polarizing film, and release protective film before bonding have a thickness of 10 to 1000 N / m. Is preferable, and 50 to 500 N / m is more preferable. Moreover, 10-1000 N / m is preferable, as for the tension | tensile_strength applied to the film (polarizing plate) after bonding, 100-800 N / m is further more preferable, and 200-800 N / m is the most preferable. If it is smaller than the above preferred range, it tends to cause wrinkling and sagging of the film. If it is larger than the above preferred range, the film may be stretched or broken.

  When forming an adhesive bond layer in a polarizing film, an adhesive agent is normally apply | coated to a polarizing film under the temperature of 15-40 degreeC after preparation. The atmospheric temperature (bonding temperature) in the bonding process at this time is usually in the range of 15 to 30 ° C.

  When using a water-based adhesive as the adhesive, after bonding the polarizing film and the protective film, the bonded (laminated) film is dried in order to remove moisture contained in the water-based adhesive (drying step). ). A drying process is performed by passing a bonding film continuously in the drying furnace hold | maintained at appropriate temperature. For example, it can be performed by winding the laminated film (that is, the polarizing plate) after drying into a roll while continuously passing the laminated film through the drying furnace. is not.

  Preferred conditions for the drying temperature (temperature in the drying oven) may vary depending on the material of each film of the polarizing plate, the type of aqueous adhesive, the amount of water in the aqueous adhesive, etc., but usually 30 ° C. to 90 ° C., More preferably, it is 40 degreeC-80 degreeC, More preferably, it is 40 degreeC-60 degreeC. If the drying temperature is too high, curling tends to occur on the polarizing plate, which is not preferable. On the other hand, if the drying temperature is too low, it is difficult to remove moisture, which is not preferable.

  Preferred conditions for the drying time may vary depending on the drying temperature, the type of aqueous adhesive, the amount of water in the aqueous adhesive, etc., but are usually 10 to 1200 seconds, preferably 50 to 1000 seconds, more preferably 100 to 600. Seconds. If the drying time is too short, the polarizing film and the protective film are easily peeled off due to insufficient drying, and if it exceeds 1200 seconds, it is not preferable from the viewpoint of productivity.

<Other processes>
The manufacturing method of the polarizing plate of this invention may include the other process of the said process. For example, after the above-described drying step, curing may be performed at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C. for about 12 to 600 hours. The temperature at the time of curing is generally set lower than the temperature adopted at the time of drying.

  When the polarizing plate thus obtained is used for a liquid crystal panel or the like, the surface of the polarizing film and / or the polarizing film of the protective film is usually peeled off after the peeling protective film is peeled off. A pressure-sensitive adhesive layer is formed on the surface that does not face. When the pressure-sensitive adhesive layer is formed on the polarizing film surface of the polarizing plate, the pressure-sensitive adhesive used for this purpose preferably has a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. The pressure-sensitive adhesive used in ordinary optical film applications has a storage elastic modulus of about 0.1 MPa at most, and a pressure-sensitive adhesive having a higher value is suitably used for the polarizing film surface. By setting the storage elastic modulus of the pressure-sensitive adhesive within the above-described range, it is possible to suppress a dimensional change accompanying shrinkage of the polarizing film that occurs in a high-temperature environment, and good durability can be obtained. The storage elastic modulus of the pressure-sensitive adhesive can be obtained by using, for example, DYNAMIC ANALYZER RDA II (manufactured by REOMETRIC) and making the test piece a cylinder of 8 mmφ × 1 mm thickness and having a frequency of 1 Hz.

  The polarizing plate produced by the production method of the present invention usually has a form of a large roll material or sheet material, and a sharp blade is used to obtain a polarizing plate having a desired shape and transmission axis. It is cut (chip cut) by the holding cutting tool. For this reason, in the polarizing plate chip obtained by cutting, a state in which the polarizing film is exposed to the outside at the outer peripheral end portion occurs.

  When the polarizing plate chip in this state is subjected to a durability test such as a heat shock test, for example, compared with a polarizing plate that is generally used, that is, a polarizing plate in which both surfaces of the polarizing film are protected with a cellulose resin film or the like. There is a tendency that problems such as peeling and cracking are likely to occur. In order to avoid such problems, it is preferable to continuously cut the outer peripheral end face of the polarizing plate chip obtained by the present invention by a fly-cut method or the like.

  Hereinafter, examples will be shown, and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  Moreover, all the academic literatures and patent literatures described in this specification are incorporated herein by reference.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these examples. In the examples,% and parts representing the content or amount used are based on weight unless otherwise specified.

[Example 1]
A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is uniaxially stretched about 5 times in a dry method and further kept in a tension state, and 1% in pure water at 60 ° C. After dipping for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 ° C. for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 72 ° C. for 300 seconds. Subsequently, it was washed with pure water at 10 ° C. for 5 seconds and then dried at 90 ° C. for 180 seconds to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.

  Separately, in 100 parts of water, 3 parts of completely saponified polyvinyl alcohol (Kuraray Poval 117H, manufactured by Kuraray Co., Ltd.), acetoacetyl group-modified polyvinyl alcohol (Goseifamer (registered trademark) Z-200, Nippon Synthetic Chemical Industry ( 3 parts), 0.18 parts of zinc chloride (sold from Nacalai Tesque), and 1.4 parts of Glyoxal (sold from Nacalai Tesque) are dissolved to prepare a polyvinyl alcohol resin adhesive. did.

  On one side of the polarizing film obtained previously, a saponified triacetyl cellulose film having a thickness of 40 μm (KC4UY, manufactured by Konica Minolta Opto Co., Ltd.) was passed through the above adhesive and the other A polyethylene resin film (Trektec (registered trademark) 7332K (manufactured by Toray Industries, Inc.)) on the surface and 7.1 m / m by two pairs of bonding rolls coated with silicone rubber having a rubber thickness of 16.5 mm and a rubber hardness of 70 °. The polarizing plate was obtained by drying at 40 ° C. while maintaining the tension of the bonded product at 430 N / m.

[Examples 2 to 10 and Comparative Examples 1 to 3]
Hereinafter, as shown in Table 1, a polarizing plate was prepared by combining the rubber roll hardness and the bonding speed, and the appearance of the polarizing plate was evaluated. The conditions other than those shown in Table 1 are the same as in Example 1.

Table 1 and FIG. 4 show values obtained from the expression (A) (denoted as “A value”) and the number of dent defects (pieces / m ² ). From the results of Table 1 and FIG. 4, it was confirmed that when the A value is 0.0375 or more, the number of dent defects is significantly lower than 50 / m ² and the number of dent defects tends to decrease. .

  The present invention provides means capable of producing a polarizing plate that is thin and has few dent defects. Therefore, the present invention can be widely used in industries using polarizing plates.

DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Protective film 3 Peeling protective film 4 Rubber roll 5 Drying furnace 10 Polarizing plate

Claims (3)

A protective film is bonded to one side of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer, and a peelable protective film is bonded to the other side of the polarizing film to which the protective film is not bonded. A method for producing a polarizing plate, comprising:
The protective film, the polarizing film, and the peeling protective film are arranged so that the protective film is in contact with one side of the polarizing film through the adhesive layer, and the peeling protective film is in contact with the surface not in contact with the adhesive layer of the polarizing film, Including a laminating step of laminating each film by sandwiching at least a pair of rolls and rotating the rolls;
At least one of the pair of rolls uses a rubber roll whose roll surface is rubber and satisfies the following formula (A):
(Bonding speed) ^1/2 / Rubber hardness ≧ 0.0375 [(m / min) ^1/2 / °] (A)
Here, the bonding speed is the traveling speed [m / min] of each film sandwiched between rolls in the bonding process, and the rubber hardness is the hardness [°] of the roll surface of the rubber roll.   The method for producing a polarizing plate according to claim 1, wherein the adhesive is a water-based adhesive.   The method for producing a polarizing plate according to claim 1, wherein both of the pair of rolls are rubber rolls.