TWI498608B - A process for producing a polarizer - Google Patents

Description

Polarizing plate manufacturing method

The present invention relates to a method for producing a polarizing plate in which a protective film is laminated on at least one side of a polarizing film composed of a polyvinyl alcohol resin.

The polarizing plate is usually provided on one side or both sides of a polarizing film composed of a polyvinyl alcohol resin which adsorbs a dichroic dye, and passes through an adhesive layer to represent a protective film (for example, triethylene cellulose) A protective film of cellulose acetate) laminated structure. A polarizing plate having such a laminated structure is bonded to a liquid crystal element through an adhesive film as needed through another optical film to form a constituent member of the liquid crystal display device.

Usually, the polarizing plate can be manufactured by laminating a protective film with an adhesive on a polarizing film and drying it. In the case of a polarizing film composed of a polyvinyl alcohol resin, when a polyvinyl alcohol resin is used as the resin for the adhesive, the polarizing film and the adhesive are the same system resin, and it is expected to have good adhesion to the polarizing film. On the other hand, since the polyvinyl alcohol resin is often used as an aqueous solution in terms of solubility, a water-based adhesive containing a polyvinyl alcohol resin is often used as an adhesive for the polarizing film and the protective film.

For example, in JP-A-2002-365432 (Patent Document 1), when the polarizing film is bonded to the protective film, if the adhesive viscosity is 3 to 20 mPa ‧ (25 ° C), a polarized film having good appearance can be obtained. The plate and the adhesive are examples in which an aqueous adhesive using a polyvinyl alcohol resin is exemplified.

On the other hand, the protective film and the adhesive must also have good adhesion. Generally, the surface of the film is protected, and under the purpose of adhering to the adhesive, the functional groups of the hydroxyl group, the carbonyl group, the carboxyl group, the amine group and the like are imparted on the surface of the protective film by alkalizing treatment, corona treatment, plasma treatment, and the like. Surface activation treatment. For example, Japanese Laid-Open Patent Publication No. 2004-318054 (Patent Document 2) discloses a standard of the degree of surface activation treatment such that the contact angle with respect to water is in the range of 20 to 50 degrees.

However, even if the adhesive of the viscosity range described in the above-mentioned Patent Document 1 is used, or even if the protective film of the contact angle range described in Patent Document 2 is used, depending on the type of the adhesive and the protective film, the polarizing film and the polarizing film are used. After the protective film is bonded, a portion (bubble) where the adhesive does not exist between the polarizing film and the protective film occurs, and the appearance of the polarizing plate is poor, and the polarizing plate is disposed on the liquid crystal display device or the like due to the bubble. , the occurrence of swing and contrast reduction, image skew, etc.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing a polarizing plate in which a protective film is laminated using at least one side of a polarizing film composed of a polyvinyl alcohol resin. A method in which bubbles are not generated between the polarizing film and the protective film, and a polarizing plate having a good appearance can be produced.

As a result of intensive research based on such a purpose, the present inventors have found that when a protective film is laminated on at least one side of a polarizing film composed of a polyvinyl alcohol resin, a protective film is laminated using a water-based adhesive to produce a polarizing plate. A water-based adhesive having a viscosity that satisfies a specific relationship at a contact angle of the surface of the protective film, so that the polarizing film and the protective film are adhered to each other, no bubbles are generated between the polarizing film and the protective film, and a polarizing plate having a good appearance can be manufactured. . That is, the present invention is as follows.

In the method for producing a polarizing plate of the present invention, at least one side of the polarizing film comprising the polyvinyl alcohol resin is laminated with a water-based adhesive protective film having a viscosity satisfying the following formula (1).

Y<5X (1)

(In the above formula (1), X is the viscosity (mPa ‧) of the water-based adhesive at 25 ° C, and Y is the contact angle (°) of water on the surface of the protective film at 25 ° C).

Moreover, the present invention also provides a method of producing a polarizing plate comprising the steps of: washing a protective film with water and at least one side of a polarizing film comprising a polyvinyl alcohol resin, using a viscosity having a relationship satisfying the following formula (1) The water-based adhesive is a step of laminating the washed protective film.

Y<5X (1)

(In the above formula (1), X is the viscosity (mPa ‧) of the water-based adhesive at 25 ° C, and Y is the contact angle (°) of water on the surface of the protective film at 25 ° C).

In the method for producing a polarizing plate of the present invention, the contact angle of water on the surface of the protective film at 25 ° C is preferably 45 or less.

Further, in the method for producing a polarizing plate of the present invention, the viscosity of the water-based adhesive at 25 ° C is preferably 3 to 10 mPa·s.

Further, in the method for producing a polarizing plate of the present invention, the water-based adhesive is preferably an adhesive containing a modified polyvinyl alcohol resin.

According to the present invention, a polarizing plate in which a protective film is laminated using a water-based adhesive can be produced in at least one side of a polarizing film composed of a polyvinyl alcohol resin in a state in which the appearance is good. The polarizing plate manufactured according to the manufacturing method of the present invention can be suitably used, for example, in a large-screen liquid crystal display device.

A method of producing a polarizing plate according to the present invention is characterized in that a protective film is laminated on at least one side of a polarizing film composed of a polyvinyl alcohol resin using a specific water-based adhesive. The method for producing a polarizing plate of the present invention basically includes (1) a step of producing a polarizing film using a polyvinyl alcohol resin film to produce a polarizing film, and (2) bonding the polarizing film and the protective film with a water-based adhesive. The step of bonding the laminated film and (3) the drying step of drying the laminated film through a drying oven. Hereinafter, each step will be described in detail.

(1) Polarizing film production steps

The polyvinyl alcohol resin constituting the polarizing film is usually obtained by alkalizing a polyvinyl acetate resin. The degree of alkalization of the polyvinyl alcohol resin is usually 85 mol% or more, preferably 90 mol% or more, and more preferably 99 to 100 mol%. Polyvinyl acetate resin In addition to the polyvinyl acetate monoester polyvinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith may be mentioned, for example, an ethylene-vinyl acetate copolymer. Other monomers which may be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and the like. The degree of polymerization of the polyvinyl alcohol resin is usually in the range of from 1,000 to 10,000, preferably from 1,500 to 5,000.

These polyvinyl alcohol resins may also be modified, for example, aldehyde-modified polyvinyl acetal, polyvinyl acetal, polyvinyl butyral, and the like. In general, a starting material for producing a polarizing film may be a non-stretched film of a polyvinyl alcohol resin film having a thickness of 20 to 100 μm, preferably 30 to 80 μm. Industrially, the width of the film is practically 1500 to 4000 mm. The unstretched film is sequentially treated by a swelling treatment, a dyeing treatment, a boric acid treatment, a water washing treatment, and a uniaxial stretching is performed until the step of boric acid treatment, and the thickness of the polarizing film obtained by the final drying is, for example, 5 to 50 μm.

The manufacturing method of the polarizing film can be roughly divided into two manufacturing methods. In the first method, the polyvinyl alcohol resin film is subjected to one-axis stretching in air or an inert gas, and then subjected to solution treatment in the order of the swelling treatment step, the dyeing treatment step, the boric acid treatment step, and the water washing treatment step, and finally drying. method. The second method is to carry out solution treatment of the unstretched polyvinyl alcohol resin film in the order of the swelling treatment step, the dyeing treatment step, the boric acid treatment step and the water washing treatment step, and in the boric acid treatment step and/or before The step is to carry out the uniaxial stretching in a wet manner and finally to dry.

In either method, the uniaxial stretching can be carried out in one step, and it can also be carried out in two or more steps, but it is preferably carried out in a plurality of steps. The stretching method may be carried out by a known method, for example, a circumferential speed difference between two nip rolls for conveying a film, and a stretching between the rolls, for example, a hot roll stretching method described in Japanese Patent No. 2731813, The machine is extended and so on. Further, the basic sequence of steps is as described above, but the number of processing baths, processing conditions, and the like are not limited. Further, the steps not described in the first and second methods may be added for other purposes. Examples of such a step include a immersion treatment (iodide treatment) or an aqueous solution containing boric acid containing no boric acid, followed by immersion treatment (zinc treatment) or the like after boric acid treatment.

The swelling treatment step is performed by removing the foreign matter on the surface of the film and removing the plasticizer in the film, and the following step is carried out for the purpose of imparting dyeability, plasticization of the film, and the like. The treatment conditions are determined within a range in which the above objects can be attained, and the disadvantages such as extreme dissolution and devitrification of the base film are not caused. In the case where the film which has been stretched in advance in the gas is swollen, for example, the film may be immersed in an aqueous solution of 20 to 70 ° C, preferably 30 to 60 ° C. The immersion time of the film is from 30 to 300 seconds, preferably from 60 to 240 seconds. In the case where the master film which has not been stretched in advance is swollen, for example, a film may be immersed in an aqueous solution of 10 to 50 ° C, preferably 20 to 40 ° C. The immersion time of the film is from 30 to 300 seconds, preferably from 60 to 240 seconds.

In the swelling treatment step, since the film is swollen in the width direction and is easy to cause wrinkles in the film, the stretching roller (spreading roller), the spiral roller, the crown roller, the cross roller, the bending bar, and the stretching A known widening device such as a web clip is preferable in that the film is conveyed while removing wrinkles of the film. In order to stabilize the film in the bath, the water in the swelling bath is controlled by spraying in the water, and the EPC (Edge Position Control device: detecting the end of the film to prevent the film from snaking) is also used. it works. In this step, since the film is swollen and expanded in the direction in which the film is conveyed, in order to prevent the film from being slack in the conveyance direction, for example, a means for controlling the conveyance roller speed before and after the treatment tank is preferably employed. In addition, the swelling treatment bath to be used may be a boric acid (described in JP-A-10-153709) or a chloride (described in JP-A No. 06-281816). An aqueous solution of an inorganic acid, an inorganic salt, a water-soluble organic solvent, or ethanol.

The dyeing treatment step of the dichroic dye is carried out for the purpose of absorbing and aligning the dichroic dye to a film or the like. The treatment conditions are determined within a range in which the above objects can be attained, and the disadvantages such as extreme dissolution and devitrification of the base film do not occur. When iodine is used as the dichroic dye, for example, at a temperature of 10 to 45 ° C, preferably 20 to 35 ° C, the weight ratio is used, and iodine/potassium iodide/water = (0.003-0.2) / (0.1 to 10) / The aqueous solution having a concentration of 100 is subjected to an immersion treatment for 30 to 600 seconds, preferably 60 to 300 seconds. Other iodides such as zinc iodide may be used instead of potassium iodide. Further, other iodides may be used in combination with potassium iodide. Further, a compound other than the iodide such as boric acid, zinc chloride, cobalt chloride or the like may be allowed to coexist. When boric acid is added, it contains iodine, which is different from the following boric acid treatment. When it contains 0.003 part by weight or more of iodine with respect to 100 parts by weight of water, it can be regarded as a dyeing tank.

When a water-soluble dichroic dye is used as the dichroic dye, for example, at a temperature of 20 to 80 ° C, preferably 30 to 70 ° C, a weight ratio, dichroic dye/water = (0.001 to 0.1) / The aqueous solution having a concentration of 100 is subjected to an immersion treatment for 30 to 600 seconds, preferably 60 to 300 seconds. The aqueous solution of the dichroic dye to be used may further 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 singly or in combination of two or more kinds of dichroic dyes.

As described above, the film can also be stretched in the dyeing tank. The stretching is carried out by a method in which the rolls before and after the dyeing tank have a circumferential speed difference or the like. Further, similarly to the swelling treatment step, a widening roller (expansion rod), a spiral roller, a crown roller, a cross guide roller, a bending bar, or the like may be provided in the dye bath and/or the bath inlet and outlet.

The boric acid treatment can be carried out 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 per 100 parts by weight of water. When the dichroic dye is iodine, it is preferably 1 to 30 parts by weight of iodide. Examples of the iodide include potassium iodide, zinc iodide, and the like. Further, a compound other than the iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate or the like may be allowed to coexist.

The boric acid treatment is carried out in order to make it resistant to hydration and to adjust the hue (preventing blue color, etc.) by crosslinking. In the case where the boric acid treatment is carried out in order to make it resistant to hydration by crosslinking, a crosslinking agent such as glyoxal or glutaraldehyde may be used in addition to or in addition to boric acid. Further, the boric acid treatment for hydration resistance may be referred to as a water resistance treatment, a crosslinking treatment, or an immobilization treatment. Further, the boric acid treatment for adjusting the hue is sometimes referred to by the names of the complementary color treatment and the re-dye treatment.

This boric acid treatment is carried out by appropriately changing the concentration of boric acid and iodide according to the purpose and treating the temperature of the bath. The boric acid treatment for hydration resistance and the boric acid treatment for adjusting the hue are not particularly different and can be carried out under the following conditions. When the master film is subjected to a swelling treatment, a dyeing treatment, or a boric acid treatment, the boric acid treatment is carried out for the purpose of hydrating the mixture by crosslinking, and 3 to 10 parts by weight of boric acid and 1 to 30 parts by weight of water are used. The boric acid treatment bath of 20 parts by weight of iodide is usually carried out at a temperature of 50 to 70 ° C, preferably 55 to 65 ° C. The immersion time is usually 30 to 600 seconds, preferably 60 to 420 seconds, more preferably 90 to 300 seconds. Further, the pre-stretched film is subjected to dyeing treatment, and in the boric acid treatment, the temperature of the boric acid treatment bath is usually 50 to 85 ° C, preferably 55 to 80 ° C.

After the boric acid treatment with water resistance, the boric acid treatment for adjusting the hue may be performed. For example, when the dichroic dye is iodine, for this purpose, a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide per 100 parts by weight of water is used, usually 10 to 45. The temperature is °C. The immersion time is usually from 3 to 300 seconds, preferably from 10 to 240 seconds. Next, the boric acid treatment for adjusting the hue is usually carried out at a low boric acid concentration, a high iodide concentration, and a low temperature as compared with the boric acid treatment for hydration resistance.

In the case where the dichroic dye is iodine, further, in order to adjust the hue, it may be treated with an iodide solution. For example, a treatment bath having 0.5 to 5 parts by weight of potassium iodide per 100 parts by weight of water is used, and usually, it is carried out at a temperature of 5 to 40 °C. The immersion time is usually from 3 to 300 seconds, preferably from 5 to 120 seconds.

These boric acid treatments may also consist of a plurality of steps, usually in two to five steps. In this case, the aqueous solution composition and the temperature of each of the boric acid treatment tanks used may be the same or different in the above range. The boric acid treatment for hydration resistance described above may be carried out by a plurality of steps for the boric acid treatment for adjusting the hue.

Further, in the boric acid treatment step, the stretching of the film may be carried out in the same manner as the dyeing treatment step. The final integrated stretching ratio is 4.5 to 7 times, preferably 5 to 6.5 times. The term "expansion stretching ratio" as used herein means the length of the base film in the length direction of the master film, and the length of the film after the end of the stretching process. For example, the 1 m portion of the master film is finished at the end of the process. When the film becomes 5 m in the subsequent film, the integrated stretch magnification at this time is 5 times.

After boric acid treatment, it is washed with water. A polyvinyl alcohol resin film which is subjected to boric acid treatment with water resistance and/or a hue adjustment is immersed in water, and is washed with water, or dipped and sprayed, and then subjected to a water washing treatment. 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 process, the tension of the film may be controlled substantially uniformly by the tension of the film. Specifically, the tension is controlled by the dyeing treatment step, and the tension control is performed by the subsequent boric acid treatment step and the water washing treatment step. In the case where the stretching is completed in the step before the dyeing step, the tension control is performed by the steps including the dyeing step and the boric acid treatment step. When the boric acid treatment step is constituted by a plurality of boric acid treatment steps, the film is stretched by a boric acid treatment step from the first or the first to the second stage, and the next boric acid treatment step in the boric acid treatment step of the extension treatment is carried out. The tension control is performed in each step up to the water washing step, or the film is stretched by the boric acid treatment step from the first to the third stage, and the boric acid treatment step to the water washing step is performed by the boric acid treatment step in which the stretching treatment is performed. It is preferred to carry out the tension control in each step. Industrially, the film is stretched by the boric acid treatment step from the first or the first to the second stage, and the next boric acid treatment step of the boric acid treatment step of the stretching step is carried out until the water is washed. Tension control is preferably performed in each step up to the step. Further, in the case where the above iodide treatment or zinc treatment is carried out after the boric acid treatment, the tension control may be performed for these steps.

The tension in each step from the swelling treatment to the water washing treatment may be the same or different, and the tension of the film in the tension control is not particularly limited, and the unit width is 150 to 2000 N/m, preferably 600 to ～. Set appropriately within the range of 1500 N/m. If the tension is less than 150 N/m, wrinkles are likely to occur in the film. On the other hand, if the tension exceeds 2000 N/m, problems such as film breakage and wear life due to wear of the bearing ring may occur. Further, the tension per unit width can be calculated from the film width in the vicinity of the step entrance and the tension value of the tension detector. In addition, in the case of performing tension control, although there are unavoidable stretches and contractions, it is usually not included in the stretching step.

At the end of the polarizing film production step, a drying treatment is performed. The drying treatment is preferably carried out with a slight change in tension and in a plurality of stages, but it is usually carried out in a range of 2 to 3 in terms of restrictions on the apparatus and the like. When the two stages are used, the front tension is set in the range of 600 to 1500 N/m, and the rear tension is preferably set in the range of 300 to 1200 N/m. If the tension is too large, the fracture of the film is increased, and if it is too small, the occurrence of wrinkles is increased and it is not preferable. Further, the drying temperature in the preceding stage is set in the range of 30 to 90 ° C, and the drying temperature in the subsequent stage is preferably set in the range of 70 to 100 ° C. When the temperature is too high, the film is broken and the optical characteristics are lowered. If the temperature is too low, the conditions are increased and the temperature is not good. The drying treatment time is, for example, 60 to 600 seconds, and the drying time in each stage may be the same and may be different. If the time is too long, the productivity is not good. If the time is too short, the drying is insufficient, which is not good.

(2) Lamination step

Next, the bonding step is to bond the protective film with a specific water-based adhesive on at least one side of the polarizing film produced as described above and obtain a laminated film. In the method for producing a polarizing plate of the present invention, the water-based adhesive is a viscosity X (mPa ‧ s) using a water-based adhesive at 25 ° C, and a protective film surface at 25 ° C (adhesive to polarized light) The contact angle Y (°) of water on the surface of the film side is a relationship satisfying the following formula (1).

Y<5X (1)

Here, FIG. 1 is a graph showing the relationship between the viscosity X (mPa ‧ s) of the water-based adhesive at 25 ° C and the contact angle Y (°) of water on the surface of the protective film at 25 ° C, and the presence or absence of bubbles in the polarizing plate. The vertical axis is the contact angle Y (°) of water on the surface of the protective film at 25 ° C, and the horizontal axis is the viscosity X (mPa ‧ s) of the water-based adhesive at 25 ° C, and ○ in the figure indicates no bubble Occurs, × is the result of the occurrence of bubbles. In addition, FIG. 1 is a result of drawing the results of the examples and comparative examples described later. As shown in FIG. 1 , when a water-based adhesive having a viscosity that does not satisfy the relationship of the above formula (1) is used, after the polarizing film and the protective film are bonded, no adhesion occurs between the polarizing film and the protective film. Part of the agent (bubbles). When such a bubble is provided in a liquid crystal display device, such a bubble becomes a factor of a drop point, a contrast reduction, an image skew, and the like.

The water-based adhesive used in the method for producing a polarizing plate of the present invention is not particularly limited as long as it has a viscosity satisfying the following formula (1). For example, a polyvinyl alcohol resin aqueous solution or a water system may be used alone or in combination. Two-liquid urethane emulsion adhesive and the like. Among them, the polyvinyl alcohol resin aqueous solution is generally used because it has excellent adhesion to a polarizing film. As the polyvinyl alcohol resin as the water-based adhesive, in addition to the vinyl alcohol homopolymer obtained by alkalizing the vinyl acetate monomer vinyl acetate, vinyl acetate and other monomers copolymerizable therewith may be mentioned. The copolymer is subjected to alkalization treatment of a vinyl alcohol copolymer, and copolymerization via a monomer having a functional group and modification after polyvinylation, in which an ethyl hydrazide group, a carboxyl group, a decylamino group, a sulfonium group are introduced. A modified polyvinyl alcohol resin such as an amine group or a thiol group. Among them, from the viewpoint of adhesion to the protective film, a modified polyvinyl alcohol resin is preferable, and in particular, a polyvinyl alcohol resin modified with an ethyl acetate group and a polyvinyl alcohol resin modified with a carboxyl group are used. Very good.

In the method for producing a polarizing plate of the present invention, the viscosity of the water-based adhesive is preferably in the range of 2 to 20 mPa·s at 25 ° C, and more preferably in the range of 3 to 12 mPa·s. In the case where the viscosity of the water-based adhesive used in the present invention is less than 2 mPa ‧ at 25 ° C, the viscosity of water is about 1 mPa ‧ s, so that the amount of added resin and additive is remarkably small, and the adhesiveness is changed. Poor tendency. Further, in the case where the viscosity of the water-based adhesive at 25 ° C exceeds 20 mPa ‧ s, the polarizing plate after bonding tends to be plaque-prone. Furthermore, from the viewpoint of the polarization characteristics of the polarizing plate (measured by using a spectrophotometer V-7100 (manufactured by JASCO Corporation)), the water-based adhesive is 25 The viscosity in °C is particularly good in the range of 3 to 10 mPa ‧ s. In the case where the viscosity of the water-based adhesive exceeds 10 mPa ‧ at 25 ° C, there is concern that the polarizing performance of the polarizing plate is lowered. Further, the viscosity of the adhesive is measured using a B-type viscometer, an E-type viscometer, a vibrating viscometer, etc., but is susceptible to the measurement temperature. Therefore, the viscosity of the water-based adhesive of the present invention is determined by maintaining the measurement temperature at 25 ° C in a heat preservation apparatus, and using a tuning fork type vibrating viscometer SV-10 (manufactured by A&D Co., Ltd.). value.

Further, in the water-based adhesive used in the present invention, a polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound or the like may be added as an additive. These additives are mainly used for the purpose of improving the water resistance of the adhesive.

Further, in the method for producing a polarizing plate of the present invention, in the case where a water-based adhesive is used to laminate the protective film on both surfaces of the polarizing film, if the relationship shown in the above formula (1) is satisfied, the same can be used. Water-based adhesives, and water-based adhesives different from each other may be used.

The protective film laminated on the polarizing film may, for example, be a cyclic olefin resin film, a cellulose acetate resin film such as triacetyl cellulose or diethyl cellulose, polyethylene terephthalate or polyethylene naphthalate. A polyester resin film such as a diester or a polybutylene terephthalate, a polycarbonate resin film, or an acrylic resin film, which has been widely used in the field.

In the case of using a cycloolefin resin film as a protective film, for example, Topas (manufactured by Ticona Co., Ltd.), Aton (manufactured by JSR Co., Ltd.), ZEONOR (manufactured by Zeone, Japan), and ZEONEX (manufactured by Zeone, Japan) can be suitably used. ), Apel (Mitsui Chemical Co., Ltd.) and other appropriate commercial products. When a film of such a cycloolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method can be suitably used. Further, for example, a film made of a pre-formed cycloolefin resin such as Esusina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), or ZEONOR FILM (manufactured by Optes) may be used. Product.

In the case of using a cellulose acetate resin film as the protective film, for example, Fujitac TD40UL (made by Fujifilm Co., Ltd.), Fujitac TD80UZ (made by Fujifilm Co., Ltd.), and Fujitac TD80 (Fujit TD80) can be used as appropriate. ), Fujitac TD80UF (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opt Co., Ltd.), KC4UY (Konica Minolta Co., Ltd.) and other suitable commercial products. Further, the cellulose acetate resin film is adhered to the opposite side of the surface of the polarizing film, and a surface treatment agent such as an antiglare treatment, a hard coating treatment, an antistatic treatment, an antireflection treatment, and the like, and a liquid crystal compound are formed. A coating layer composed of a molecular weight compound or the like may be used. A commercially available product of such a film may be a surface treatment film provided with an antiglare treatment layer on the surface of a triacetyl cellulose film (DTAC AG6 UV40, Dainippon Printing Co., Ltd.) A surface-treated film (made by 40CHC, letterpress printing) provided with a hard coating layer on the surface of a triacetonitrile cellulose film, and a liquid crystal compound formed on the surface of the triacetyl cellulose film. The coating layer is a Wild View (WV film) (made by Fujifilm Co., Ltd.), a Japanese stone NH film (manufactured by Nippon Oil Co., Ltd.), and the like.

In the method for producing a polarizing plate of the present invention, it is preferred that the protective film and the polarizing film are washed immediately before lamination. That is, the present invention also provides a method for producing a polarizing plate comprising the steps of: washing a protective film with water and at least one side of a polarizing film comprising a polyvinyl alcohol resin, using a water system having a viscosity satisfying the relationship of the above formula (1) Adhesive, a step of laminating a water-washed protective film. After the water washing step, foreign matter or the like on the surface of the protective film can be removed.

The water temperature in the water washing step is not particularly limited, but is preferably 5 to 80 ° C, more preferably 10 to 50 ° C. In the case where the washing temperature is less than 5 ° C, there is condensation on the surface of the protective film after the water washing step, and in the case where the washing temperature exceeds 80 ° C, the film is liable to wrinkle due to heat, and the operation tends to be difficult. The washing time is usually from 3 to 180 seconds, more preferably from 5 to 120 seconds. If the water washing step is too short, it is difficult to remove foreign matter on the surface of the protective film, and if it is too long, it is economically disadvantageous. After washing with water, a spiral roller and a glass rod are used, and an air knife or the like is removed to remove water remaining on the surface of the protective film.

When the water washing step is included, the protective film may be dried after the water washing step. The drying temperature is set at about 20 to 120 °C. When the drying temperature exceeds 120 ° C, the film is wrinkled depending on the material of the protective film.

The thickness of the protective film is preferably as thin, and if it is too thin, the strength is lowered and the workability is deteriorated. On the other hand, when it is too thick, transparency will fall, and the time of aging which becomes necessary after lamination will become long. Therefore, the thickness of the protective film is usually 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm.

In addition, when a water-based adhesive is used in combination with a polarizing film, on the surface of the protective film, in order to improve the adhesion, corona treatment, fire trap treatment, plasma treatment, ultraviolet irradiation, and primer coating treatment are applied. Surface activation such as alkalizing treatment. In the method for producing a polarizing plate of the present invention, it is preferable to apply the surface activation, and in the case where the protective film is a cellulose acetate resin film, alkalization treatment is appropriate, and in the case of other resin films. Corona treatment is appropriate.

The surface of the protective film after the surface activation treatment (the surface adhered to the side of the polarizing film) preferably has a contact angle of 45 or less with water at 25 ° C. In the case where the contact angle of the water on the surface of the protective film exceeds 45° at 25° C., in the water washing step, the water is easily bounced, and in addition to the effect of the water washing to reduce the foreign matter, the water bounces and sometimes occurs. It turned into a bad appearance. Further, the contact angle of the water protecting the surface at 25 ° C was 0 ° or more. The contact angle of the surface of the protective film on water at 25 ° C means a value measured by a contact angle meter CA-X (manufactured by Kyowa Interface Science Co., Ltd.).

Further, in the method for producing a polarizing plate of the present invention, in order to improve the adhesion between the water-based adhesive and the polarizing film, the polarizing film may be subjected to electric power treatment, flame treatment, plasma treatment, ultraviolet irradiation, and coating. Surface treatment such as coating treatment, alkalizing treatment, and the like.

The method of bonding the polarizing film and the protective film is not particularly limited, and for example, a water-based adhesive is uniformly applied to the surface of the polarizing film and/or the protective film, and another film is superposed on the coated surface and attached via a roller or the like. Method of combining, drying, etc. Usually, the water-based adhesive is applied at a temperature of 15 to 40 ° C after the preparation thereof, and the bonding temperature is usually in the range of about 15 to 30 ° C.

(3) Drying step

After the polarizing film is bonded to the protective film, the laminated film is dried in order to remove water contained in the water-based adhesive. Drying is carried out by passing the laminated film continuously through a total of N (N≧2) in a drying furnace maintained at a suitable temperature. The drying is not particularly limited. For example, the laminated film can be continuously wound through a plurality of drying ovens, and the dried laminated film can be wound into a roll shape.

The temperature of the drying oven is preferably from 30 ° C to 100 ° C, and the residence time is preferably from 10 to 1200 seconds. If the temperature of the drying oven is less than 30 ° C, there is a tendency to easily peel off between the polarizing film and the protective film. More preferably, the temperature of the drying oven is 40 ° C or higher. When the temperature of the drying furnace is more than 100 ° C, the parallel hue of the produced polarizing plate tends to yellow due to deterioration.

In the above drying step, it is preferred that the laminated film is dried in an additional tension state. The tension is preferably from 100 to 1,500 N/m, more preferably from 100 to 1,000 N/m. The tension applied to the laminated film can be adjusted by continuously adjusting the pulling force between the feeding side nip roll and the outlet side nip roll when the laminated film is continuously passed through the drying furnace which is continuously disposed.

After the drying step, in order to harden the water-based adhesive, laminating is carried out at a temperature of 15 to 85 ° C, preferably 20 to 50 ° C, more preferably 35 to 45 ° C, usually about 1 to 90 days. The film may be additionally dried (cured). The humidity in the ripening is usually 70% or less in relative humidity (RH). If the relative humidity exceeds 70%, problems such as condensation may occur. Further, the aging period is usually about 1 to 30 days, and when productivity is considered, it is preferably 1 to 7 days. Usually, the aging is carried out in a state of being wound into a roll.

In this manner, a polarizing plate in which a protective film of a water-based adhesive is laminated on at least one side of a polarizing film made of a polyvinyl alcohol resin is used. Thus, the polarizing plate manufactured by the method of the present invention does not generate bubbles between the polarizing film and the protective film, and has a good appearance. When the polarizing plate is disposed on a liquid crystal display device or the like, no wave break occurs due to bubbles. Since the contrast is lowered, the image is skewed, and the like, it can be suitably used, for example, in a large-screen liquid crystal display device.

The polarizing plate manufactured by the present invention can also impart a function as a retardation film to the protective film, as a function of improving the brightness film, a function as a reflective film, a function as a transflective film, and a function as a diffusion film. The optical function of the optical compensation film is optical. In this case, for example, on the surface of the protective film, an optical functional film such as a laminated retardation film, a brightness improving film, a reflective film, a semi-transmissive reflective film, a diffusion film, an optical compensation film, or the like may have such a function. In addition, the protective film itself can also impart such functions. Further, as with a diffusion film having a function of improving the brightness of the film, the protective film itself has a plurality of functions.

More specifically, the protective film described above can be subjected to a stretching treatment as described in Patent No. 2841377, Patent No. 3094117, etc., and a treatment as described in Patent No. 3168850 or the like can be applied to the protective film. The function as a retardation film is imparted. In the above-mentioned protective film, fine pores are formed by the method described in JP-A-2002-169025, and JP-A-2003-29030, or two or more cholesteric liquid crystal layers having different reflection center wavelengths are overlapped and selected. It can be imparted as a function to improve the brightness of the film. Further, by forming a metal thin film by vapor deposition, sputtering, or the like on the above protective film, it is possible to impart a function as a reflective film or a semi-transmissive reflective film. When the resin film containing fine particles is applied to the above protective film, the function as a diffusion film can be imparted. In addition, by applying a liquid crystal compound such as a disk-type liquid crystal compound and aligning the protective film, the function as an optical compensation film can be imparted. In addition, a modified light-reducing film, a WV film (Fuji Film Co., Ltd.), etc., which is a modified viewing angle film or a product name, such as a DBF (available from Sumitomo 3M) in Japan, can be used. A commercially available optical functional film such as a phase difference film such as Sumicalite (registered trademark) (manufactured by Sumitomo Chemical Co., Ltd.) may be directly bonded to a protective film.

[Examples]

Hereinafter, the present invention will be described in further detail based on examples, but the present invention is not limited by such examples. In the examples, the % and the parts indicating the content or the amount used are based on the mass unless otherwise specified.

<Example 1>

A polyvinyl alcohol film having an average degree of polymerization of about 2400, a degree of alkalinity of 99.9 mol% or more and a thickness of 75 μm is about 4 times in a dry uniaxial stretch, and is still kept in a state of tension, and is immersed in pure water at 60 ° C. After a minute, it was immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.05/5/100 at 28 ° C for 60 seconds. Thereafter, it was immersed at 72 ° C for 300 seconds in an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 8.5 / 8.5 / 100. Then, it was washed with pure water of 10 ° C for 5 seconds, and then dried at 95 ° C for 152 seconds to obtain a polarizing film in which iodine was adsorbed and aligned to polyvinyl alcohol.

In addition, in 100 parts of water, 3 parts of polyethylene (CURALE POVAL 117H, manufactured by CURALE), polyvinyl alcohol modified by acetonitrile (GOSE Farmer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 3 parts, zinc chloride (sold by Nakara Itesuc), 0.18 parts, and glyoxal (sold by Nakara Itesuc) were dissolved in 1.4 parts to prepare an aqueous binder of a modified polyvinyl alcohol resin. The viscosity of the water-based adhesive at 25 ° C was 9.3 mPa ‧ when measured using a tuning fork vibrating viscometer SV-10 (manufactured by A&D Co., Ltd.).

Furthermore, a surface-treated film (DTAC AG6 UV40, manufactured by Dainippon Printing Co., Ltd.) having a thickness of 43 μm of an anti-glare treatment layer was prepared on the surface of the triethylene fluorene fiber film, and a concentration of 5 mol/liter of hydrogen at 50 ° C was prepared. After immersing in an aqueous potassium oxide solution, washing with water, drying, and alkalizing treatment. The contact angle of the film with the polarizing film (the opposite side of the anti-glare treatment) at 25 ° C was 31 ° when measured by a contact angle meter CA-X (Kyowa Interface Science Co., Ltd.).

The alkalized surface-treated film was applied, immersed in water at 40 ° C for 20 seconds, and then dried at 40 ° C for 20 seconds. Thereafter, on the side of the previously obtained polarizing film, the surface-treated film which has been washed and dried as described above is passed through the side of the reverse side of the surface treatment layer (the alkalized triethylenecellulose surface) The water-based adhesive is bonded by a nip roll. The polarizing plate was obtained by drying at 37 ° C for 370 seconds while maintaining the tension of the composition at 430 N/m. With respect to this polarizing plate, there was no bubble generation between the polarizing film and the protective film by visual observation, and it had a good appearance.

<Example 2>

A polarizing plate was produced in the same manner as in Example 1 except that the immersion time in the potassium hydroxide aqueous solution was changed during the alkalization treatment, and the surface treatment film having a contact angle of 41° with water at 25 ° C was used. With respect to the obtained polarizing plate, when observed in the same manner as in Example 1, no bubbles occurred and the appearance was good.

<Comparative Example 1>

A polarizing plate was produced in the same manner as in Example 1 except that the immersion time of the potassium hydroxide water-soluble water at the time of the alkalization treatment was changed, and the surface-treated film having a contact angle of 53° with water at 25 ° C was used. With respect to the obtained polarizing plate, bubbles were observed when observed in the same manner as in Example 1.

<Comparative Example 2>

The polyvinyl alcohol film having an average polymerization degree of about 2400, an alkalinity of 99.9 mol% or more and a thickness of 75 μm was kept in a state of tension, and was immersed in pure water at 30 ° C, and was elongated in the long axis direction. Pull until the extension ratio is 1.3 times. The polyvinyl alcohol film was dyed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.05/2/100 at a temperature of 30 ° C to maintain the above-mentioned stretching ratio, and thereafter, potassium iodide/boric acid at 54 ° C / The aqueous solution having a water mass ratio of 12/5/100 was subjected to cross-linking treatment, and was stretched at a total magnification of 5.6 times, and then washed with pure water at 12 °C. The washed polyvinyl alcohol film was dried at 65 ° C to obtain a polarizing plate in which iodine in the polyvinyl alcohol was adsorbed and aligned.

Further, in 100 parts of water, one part of a carboxyl group-modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), and a water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex Co., Ltd.) The aqueous solution having a solid concentration of 30% was dissolved in 0.5 part to prepare a water-based adhesive of the modified polyvinyl alcohol resin. The viscosity of the water-based adhesive at 25 ° C was 2.7 mPa ‧ when measured in the same manner as in Example 1.

Further, a triacetyl cellulose film (KC8UX2M, manufactured by Konica Minolta Opt Co., Ltd.) having a thickness of 80 μm was prepared, and immersed in a potassium hydroxide solution having a concentration of 5 mol/liter at 50 ° C, washed with water, dried, and applied. Treated by alkalization. The contact angle of the film with the water of the polarizing film at 25 ° C was 15 ° as measured in Example 1.

Further, a triacetyl cellulose film (KC4FR-1, manufactured by Konica Minolta Opt Co., Ltd.) having a thickness of 43 μm was prepared, and immersed in a potassium hydroxide solution having a concentration of 5 mol/liter at 50 ° C, washed with water, and dried. The alkalization treatment is applied. The contact angle of the film with the water of the polarizing film at 25 ° C was 20 ° C as measured in Example 1.

On the side of the previously obtained polarizing film, a trithicellulose film (KC4FR-1, Konica Minolta Opt (manufactured by Konica Minolta Opt)) having a thickness of 43 μm which has been subjected to alkalization as the first protective film, another On the other side, a 38 μm thick triacetyl cellulose film (KC8UX2M, manufactured by Konica Minolta Opt Co., Ltd.) which has been alkalized as the second protective film is passed through the above-mentioned water-based adhesive to be pressed. The rolls are attached. The laminated film was maintained at a tension of 450 N/m, and passed through a drying oven having an inlet temperature of 50 ° C and an outlet temperature of 90 ° C to obtain a polarizing plate. In the polarizing plate, when bubbles were observed between the polarizing film and the first protective film and between the polarizing film and the second protective film, air bubbles were generated. In addition, when the luminosity-corrected polarizing plate of this polarizing plate was evaluated by a spectrophotometer V-7100 (manufactured by JASCO Corporation), it was 99.993%, and a good luminosity correction polarization degree was exhibited.

The state of occurrence of bubbles between the above polarizing film and the protective film is determined as follows. That is, on one side of the protective film side of one of the obtained polarizing plates (sample polarizing plates), another commercially available polarizing plate (which is regarded as a photodetector without defects) is disposed in a crossed Nicols type. In this state, if the photodetector side on the opposite side of the photodetector is observed, it is generally blackened completely. If there is a defect (bubble) between the polarizing film of the sample polarizing plate and the photodetector side protective film, this part is observed. To leak light. Further, even if there is a defect (bubble) between the protective film on the opposite side of the photodetector on the opposite side of the sample polarizing plate, the polarized state of the light emitted from the photodetector side is not affected, and no light leakage is observed. Therefore, when such light leakage is observed, it is determined that there is a bubble between the photodetector side protective film and the polarizing film of the sample polarizing plate, and when no light leakage is observed, the photodetector side protective film and the polarizing film of the sample polarizing plate can be determined. There are no bubbles between them.

<Comparative Example 3>

In 100 parts of water, 1.5 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) The aqueous solution having a concentration of 30% was dissolved in 0.75 parts to prepare a water-based adhesive of the modified polyvinyl alcohol resin. The viscosity of the water-based adhesive at 25 ° C was 3.6 mPa ‧ when measured in the same manner as in Example 1. In the same manner as in Comparative Example 2 except that this water-based adhesive was used, a polarizing plate was obtained. In the polarizing plate, when bubbles are observed between the polarizing film and the first protective film and between the polarizing film and the second protective film, bubbles are generated between the polarizing film and the first protective film. No air bubbles occurred between the polarizing film and the second protective film. In addition, when the luminosity-corrected polarizing plate of this polarizing plate was evaluated by a spectrophotometer V-7100 (manufactured by JASCO Corporation), it was 99.993%, and a good luminosity correction polarization degree was exhibited.

Example 3

In 100 parts of water, 1.8 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) The aqueous solution of the modified polyvinyl alcohol resin was prepared by dissolving 0.9 parts of an aqueous solution having a concentration of 30%. The viscosity of the water-based adhesive at 25 ° C was 5.6 mPa ‧ when measured in the same manner as in Example 1. In the same manner as in Comparative Example 2 except that this water-based adhesive was used, a polarizing plate was obtained. With respect to this polarizing plate, when the state of occurrence of bubbles between the polarizing film and the first protective film and between the polarizing film and the second protective film was observed by visual observation, both of them did not generate bubbles, and had a good appearance. In addition, when the luminosity-corrected polarizing plate of this polarizing plate was evaluated by a spectrophotometer V-7100 (manufactured by JASCO Corporation), it was 99.993%, and a good luminosity correction polarization degree was exhibited.

<Example 4>

In 100 parts of water, 2 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) One part of the aqueous solution having a concentration of 30% was dissolved to prepare an aqueous adhesive of the modified polyvinyl alcohol resin. The viscosity of the water-based adhesive at 25 ° C was 6.8 mPa ‧ when measured in the same manner as in Example 1. In the same manner as in Comparative Example 2 except that this water-based adhesive was used, a polarizing plate was obtained. With respect to this polarizing plate, when the state of occurrence of bubbles between the polarizing film and the first protective film and between the polarizing film and the second protective film was observed by visual observation, both of them did not generate bubbles, and had a good appearance. In addition, when the luminosity-corrected polarizing plate of this polarizing plate was evaluated by a spectrophotometer V-7100 (manufactured by JASCO Corporation), it was 99.993%, and a good luminosity correction polarization degree was exhibited.

<Example 5>

In 100 parts of water, 2.5 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) The aqueous solution of the modified polyvinyl alcohol resin was prepared by dissolving 1.25 parts of an aqueous solution having a concentration of 30%. The viscosity of the water-based adhesive at 25 ° C was 11.0 mPa ‧ when measured in the same manner as in Example 1. In the same manner as in Comparative Example 2 except that this water-based adhesive was used, a polarizing plate was obtained. With respect to this polarizing plate, when the state of occurrence of bubbles between the polarizing film and the first protective film and between the polarizing film and the second protective film was observed by visual observation, both of them did not generate bubbles, and had a good appearance. In addition, the illuminance correction polarization of the polarizing plate was 99.991% when evaluated by a spectrophotometer V-7100 (manufactured by JASCO Corporation).

<Example 6>

In 100 parts of water, 3 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) The aqueous solution of the modified polyvinyl alcohol resin was prepared by dissolving 1.5 parts of an aqueous solution having a concentration of 30%. The viscosity of the water-based adhesive at 25 ° C was 16.8 mPa ‧ when measured in the same manner as in Example 1.

In addition, a surface-treated film (CV02, manufactured by Fujifilm Co., Ltd.) having an anti-glare treatment layer having a thickness of 85 μm was prepared on the surface of the triacetonitrile cellulose film, and a concentration of 5 mol/liter of potassium hydroxide at 50 ° C was prepared. After immersion in water solution, it is washed with water, dried, and subjected to alkalization treatment. The contact angle of the film with the water of the polarizing film at 25 ° C was 15 ° as measured in Example 1.

The above-mentioned water-based adhesive (viscosity: 16.8 MPa ‧ s) was used, and a surface-treated film (CV02, manufactured by Fujifilm Co., Ltd.) having a thickness of 85 μm which was subjected to the above alkalization treatment was used as the first protective film, and the same comparison was made. In Example 2, a polarizing plate was obtained. With respect to this polarizing plate, when the state of occurrence of bubbles between the polarizing film and the first protective film and between the polarizing film and the second protective film was observed by visual observation, both of them did not generate bubbles, and had a good appearance. In addition, the illuminance correction polarization of this polarizing plate was 99.990% when it was evaluated using the spectrophotometer V-7100 (manufactured by JASCO Corporation).

<Example 7>

In 100 parts of water, 2.2 parts of carboxyl modified polyvinyl alcohol (CURALE POVAL KL318, manufactured by CURALE), water-soluble polyamide resin (Sumilase Resin 650, manufactured by Chem Chemex) The aqueous solution of the modified polyvinyl alcohol resin was prepared by dissolving 1.1 parts of an aqueous solution having a concentration of 30%. The viscosity of the water-based adhesive at 25 ° C was 8.1 mPa ‧ when measured in the same manner as in Example 1.

Further, a stretched film of triacetyl cellulose (WV Film WV BZ 438, manufactured by Fujifilm Co., Ltd.) having a thickness of 82 μm was prepared and immersed in a concentration of 5 mol/liter potassium hydroxide aqueous solution at 50 ° C, Washed, dried, and alkalized. The contact angle of the film with the water of the polarizing film at 25 ° C was 30 ° as measured by the treatment of Example 1.

The above-mentioned water-based adhesive (viscosity: 8.1 mPa s) was used, and a stretched film of triethyl fluorene cellulose (WV Film WV BZ 438, Fujifilm) manufactured by the alkalization treatment and having a thickness of 82 μm was used. In the same manner as in Comparative Example 2 except that the first protective film was produced, a polarizing plate was obtained. With respect to this polarizing plate, when the state of occurrence of bubbles between the polarizing film and the first protective film and between the polarizing film and the second protective film was observed by visual observation, both of them did not generate bubbles, and had a good appearance. In addition, the illuminance correction polarization degree of this polarizing plate was 99.995% when it was evaluated by the spectrophotometer V-7100 (manufactured by JASCO Corporation), and the good luminosity correction polarization degree was exhibited.

Here, FIG. 1 shows the viscosity X (mPa ‧ s) of the water-based adhesive at 25 ° C of each of the polarizing plates produced in Examples 1 to 7 and Comparative Examples 1 to 3, and the surface of the protective film at 25 ° C The contact angle Y (°) of the water is related to the presence or absence of bubbles in the polarizing plate. In the graph of Fig. 1, the vertical axis is the contact angle Y (°) of water on the surface of the protective film in 25 ° C, and the horizontal axis is the viscosity X (mPa ‧ s) of the water-based adhesive in 25 ° C, ○ indicates that no bubbles have occurred, and × indicates that bubbles have occurred. As can be seen from Fig. 1, in order to prevent the occurrence of bubbles, as shown by the boundary line A, the relationship of Y < 5X (1) must be satisfied. Further, as can be seen from Fig. 1, as shown by the boundary line B, the contact angle of water on the surface of the protective film at 25 ° C is preferably 45 or less, and further, the viscosity of the water-based adhesive at 25 ° C. It is especially good for 3~10mPa‧s.

[Fig. 1] shows the relationship between the viscosity X (mPa ‧ s) of the water-based adhesive at 25 ° C and the contact angle Y (°) of water on the surface of the protective film at 25 ° C, and the presence or absence of bubbles in the polarizing plate. In the figure, the vertical axis is the contact angle Y (°) of water on the surface of the protective film at 25 ° C, and the horizontal axis is the viscosity X (mPa ‧ s) of the water-based adhesive at 25 ° C, and ○ in the figure indicates no bubble Occurs, × indicates that a bubble has occurred.

Claims (4)

A method for producing a polarizing plate, characterized in that at least one side of a polarizing film composed of a polyvinyl alcohol resin is laminated with a water-based adhesive having a viscosity satisfying the following formula (1), Y< 5X (1) (in the above formula (1), X is the viscosity (mPa ‧ s) of the water-based adhesive at 25 ° C, and Y is the contact angle (°) of water on the surface of the protective film at 25 ° C), and The contact angle of water on the surface of the protective film at 25 ° C was 45 or less. A method for producing a polarizing plate, characterized by comprising a step of washing a protective film and a water-based adhesive having a viscosity satisfying the following formula (1) on at least one side of a polarizing film composed of a polyvinyl alcohol resin. , the step of laminating the washed protective film, Y<5X (1) (in the above formula (1), X is the viscosity of the water-based adhesive at 25 ° C (mPa ‧ s), and Y is 25 ° C The contact angle (°) of water on the surface of the protective film was adjusted, and the contact angle of water on the surface of the protective film at 25 ° C was 45 or less. The method for producing a polarizing plate according to claim 1 or 2, wherein the viscosity of the water-based adhesive at 25 ° C is 3 to 10 mPa ‧ s. The method for producing a polarizing plate according to claim 1 or 2, wherein the water-based adhesive is an adhesive containing a modified polyvinyl alcohol-based resin.