JP2009109860A - Method of manufacturing polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polarizing plate of excellent durability laminated with a transparent protection film on only one face of a polarizing film comprising a polyvinyl alcohol resin via an adhesive. <P>SOLUTION: The present invention discloses the method of manufacturing the polarizing plate laminated with the transparent protection film on the only one face of the polarizing film comprising the polyvinyl alcohol resin and having 2.7% or less of dimension change rate, via the adhesive. In the method of manufacturing the polarizing plate, the transparent protection film is preferably a cellulose acetate resin film, and an adhesive layer comprising an acrylic resin is preferably formed on the other face of the polarizing plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polarizing plate by laminating a transparent protective film on one surface of a polarizing film made of a polyvinyl alcohol resin through an adhesive layer.

  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 a polyvinyl alcohol resin and a transparent protective film made of triacetyl cellulose are used as such polarizing plates. In recent years, 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 equipment and even with large televisions. Moreover, since the place of use is wide due to portability, improvement in durability is also demanded at the same time.

  The polarizing film is generally produced by impregnating a polyvinyl alcohol resin with a dichroic dye typified by iodine and the like and uniaxially stretching at a high magnification. For this reason, when the polarizing film is exposed to a dry heat environment, a large dimensional change accompanied by shrinkage occurs. For example, as described in Table 1 of JP-A-6-109922 (Patent Document 1), when the rate of dimensional change before and after heating the polarizing film at 100 ° C. for 2 hours is measured, it exceeds 10%. Shrinkage is observed. For this reason, the dimensional change of a polarizing film is usually reduced by laminating | stacking a transparent protective film on both surfaces of a polarizing film via an adhesive layer etc., and manufacturing a polarizing plate. In Patent Document 1, a triacetyl cellulose film is laminated on both surfaces of a polarizing film exhibiting a high shrinkage rate as described above to form a polarizing plate. Although the dimensional change rate before and after heating the polarizing plate at 100 ° C. for 2 hours is also described in the same table, the contraction rate of the polarizing plate is 2% or less, and a triacetyl cellulose film is laminated on both sides. This shows that the shrinkage is suppressed.

  In Table 1 of JP-A-6-59123 (Patent Document 2), dimensional change rates before and after heating a polarizing plate in which a triacetyl cellulose film is laminated on both sides of a polarizing film at 80 ° C. for 4 hours are described. However, the shrinkage rate is 0.3% or less, and it can be seen that the shrinkage is also suppressed by laminating the triacetyl cellulose film on both sides.

However, in recent years, a polarizing plate in which a transparent protective film is laminated only on one surface of a polarizing film has been demanded in order to reduce the thickness and weight. Such a polarizing plate is polarized when exposed to a dry environment. The shrinkage of the film could not be suppressed, and there was a tendency for defects to occur. For this reason, when the polarizing plate in which the transparent protective film is laminated only on one surface of the polarizing film in this way and the liquid crystal cell bonded through the adhesive is exposed to a dry environment, the adhesive at the end of the polarizing plate May peel off, or the edge of the polarizing plate may rise to distort the screen display.
JP-A-6-109922 JP-A-6-59123

  The present invention has been made in order to solve the above-described problems, and the object is to laminate a transparent protective film on only one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer. Another object of the present invention is to provide a method for producing a polarizing plate having excellent durability.

  The manufacturing method of the polarizing plate of this invention consists of laminating | stacking a transparent protective film through an adhesive layer only on one side of the polarizing film which consists of polyvinyl alcohol-type resin, and a dimensional change rate is 2.7% or less. Features.

  It is preferable that the transparent protective film in the manufacturing method of the polarizing plate of this invention is a cellulose acetate type-resin film.

  Moreover, in the manufacturing method of the polarizing plate of this invention, it is preferable to form the adhesive layer which consists of acrylic resin in the other surface of a polarizing film.

  According to the present invention, compared with a polarizing plate in which a transparent protective film is laminated on both sides of a polarizing film made of a polyvinyl alcohol resin, a polarizing plate having excellent durability while being thin in thickness is industrially produced. Can be advantageously produced.

  In the manufacturing method of the polarizing plate of this invention, a polarizing plate is manufactured by laminating | stacking a transparent protective film through an adhesive bond layer only on one side of the polarizing film which consists of polyvinyl alcohol-type resin. Specifically, the polarizing film used in the present invention is obtained by subjecting a polyvinyl alcohol resin film to uniaxial stretching and a dyeing treatment with a dichroic dye, and adsorbing and orienting the dichroic dye. The polarizing plate production method of the present invention basically includes (1) a polarizing film production step of producing a polarizing film using a polyvinyl alcohol-based resin, and (2) an adhesive between the polarizing film and the transparent protective film. The pasting process which uses and bonds and obtains a lamination film, (3) The drying process which dries by letting a lamination film pass a drying furnace is included. In the manufacturing method of the polarizing plate of this invention, it is produced through the said polarizing film preparation process, and the dimensional change rate of the polarizing film at the time of using for a bonding process is 2.7% or less, It is a big characteristic. . Hereinafter, each step will be described in detail.

(1) Polarizing film preparation process The polyvinyl alcohol-type resin which comprises a polarizing film is normally obtained by saponifying a polyvinyl acetate type resin. The saponification degree of the polyvinyl alcohol-based resin is usually 85 mol% or more, preferably 90 mol% or more, and more preferably 99 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 copolymers. Etc. 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 in the range of 1000 to 10000, preferably in the range of 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 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 difference in peripheral speed between two nip rolls for transporting a film, for example, a hot roll as described in Japanese Patent No. 2731813 There are a 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 treatment 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 together. 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 film treated with boric acid for water resistance and / or hue adjustment in water, spraying water as a shower, or using both immersion and spraying together. 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 the boric acid treatment, tension control can also be performed for these steps.

As the nip roll for controlling the tension and the guide roll for controlling the film conveyance direction, a rubber roll, a stainless steel polishing roll, a sponge rubber roll, and the like can be used. The rubber roll is made of NBR or the like, and has a hardness of 60 to 90 degrees, further 70 to 80 degrees, and a surface roughness of JIS B 0601 (surface roughness) as measured by the test method of JIS K 6301. ), The average interval S of the local peaks of the roughness curve is preferably 0.1 to 5S, more preferably 0.5 to 1S. The stainless steel polishing roll is made of SUS304, SUS316, etc., and in order to make the film thickness uniform, the surface roughness is the average interval S of the local peaks of the roughness curve of JIS B 0601 (surface roughness). What is represented and is 0.2-1S is preferable. As the sponge rubber roll, the hardness of the sponge is 20-60 degrees on the JIS Shore C scale measured by the test method of JIS K 6301, further 25-50 degrees, the density is 0.4-0.6 g / m ³ , 0.42 to 0.57 g / cm ³ , and the surface roughness is 10 to 30 S, further 15 to 25 S, expressed by the average interval S of the local peaks of the roughness curve of JIS B 0601 (surface roughness). It is preferable.

  The tension in each step from the swelling treatment to the water washing treatment may be the same or different. The tension on the film in the tension control is not particularly limited, and is 150 to 2000 N per unit width. / M, preferably within the range of 600 to 1500 N / m. 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, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not 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 600 to 1500 N / m, and the tension in the rear stage is preferably set in the range of 250 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 treatment temperature 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.

  In the manufacturing method of the polarizing plate of this invention, it is made for the dimensional change rate of the polarizing film obtained at the polarizing film preparation process to become 2.7% or less. In addition, the dimensional change rate of the polarizing film is a direction (TD direction) perpendicular to the stretching axis direction of the test piece having a size of 100 mm × 100 mm so that one side of the test piece is parallel to the stretching axis direction of the polarizing film. ) And the dimension B in the TD direction after the test piece is held for 96 hours in a dry heat environment at 85 ° C.

Dimensional change rate (%) = (A−B) / A × 100
In the manufacturing method of the polarizing plate of this invention, when the dimensional change rate of the polarizing film at the time of using for a bonding process exceeds 2.7%, the protective film was laminated | stacked through the adhesive bond layer on the single side | surface of the polarizing film. When the polarizing plate is exposed to a dry heat environment in a state where the polarizing film is bonded to a liquid crystal cell or the like via an adhesive on the polarizing film side, the distortion of the image display due to the rising of the end of the polarizing plate is significantly observed visually, In addition, the pressure-sensitive adhesive at the end of the polarizing plate may peel off along with the rise. In addition, the degree of distortion by visual observation is the height of the bulge of the deformed end (the difference between the highest height at the end and the height of the horizontal plane at the main part) and the deformation distance (from the end to the horizontal plane at the main part). On the other hand, it can be expressed by a linear distance to a region where no unevenness is observed, and the higher the bulge height and the longer the deformation distance, the larger the distortion is observed.

  In the manufacturing method of the polarizing plate of this invention, the dimensional change rate of the polarizing film at the time of using for a bonding process becomes like this. Preferably it is 1.5% or less, More preferably, it is 1% or less. If the dimensional change rate is 1% or less, the distortion of the image display due to the rising of the end portion of the polarizing plate is hardly observed visually. In addition, the dimensional change rate of the polarizing film at the time of using for a bonding process is 0% or more normally.

  As a method of reducing the dimensional change rate of the polarizing film when it is used in the bonding step as described above, for example, a method of drying the polarizing film at a high temperature (preferably 80 to 100 ° C.), a low tension state ( A method of drying at the above high temperature preferably at 250 to 400 N / m), a method of increasing the glass transition temperature (Tg) of the polyvinyl alcohol resin film (for example, the amount of plasticizer contained in the polyvinyl alcohol resin film) And a method in which a monomer having a glass transition temperature higher than that of a polyvinyl alcohol resin is copolymerized), and the boron content in the polarizing film is damaged by the boric acid crosslinking effect. A method that reduces the amount of the boric acid in a range that does not exist (for example, boric acid treatment is performed in at least two stages, and the boric acid concentration in the final treatment bath is first A method of lowering the boric acid concentration of the treatment bath), a method of promoting crosslinking by the boric acid treatment (for example, a method of setting a higher temperature of the boric acid treatment, a method of increasing the draw ratio in the boric acid treatment bath) And at least one selected from the above.

  Moreover, in the manufacturing method of the polarizing plate of this invention, although the polarizing film obtained through a polarizing film preparation process is not restrict | limited especially about the moisture content, Preferably it exists in the range of 3 to 14 weight%, More preferably It is in the range of 3 to 10% by weight, particularly preferably in 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.

(2) Bonding process In the subsequent bonding process, a transparent protective film is laminated | stacked on one surface of the polarizing film obtained at the polarizing film preparation process mentioned above through an adhesive bond layer, and it is set as a polarizing plate. Examples of transparent protective films include cycloolefin resin films, cellulose acetate resin films, polyester resin films such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resin films, acrylic resin films, and polypropylene films. Examples thereof include films that have been widely used in the art, such as resin films.

  The cycloolefin resin that can be used for the transparent protective film in the polarizing plate of the present invention is, for example, a thermoplastic resin having a monomer unit composed of a cyclic olefin (cycloolefin) such as norbornene and a polycyclic norbornene monomer ( It is also called a thermoplastic cycloolefin resin. In the present invention, the cycloolefin resin may be a hydrogenated product of the above ring-opening polymer of cycloolefin or a ring-opening copolymer using two or more kinds of cycloolefin, and cycloolefin and chain olefin, It may be an addition polymer with an aromatic compound having a vinyl group. Those having a polar group introduced are also effective.

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

  Cycloolefin-based resins may be commercial products such as Topas (manufactured by Ticona), Arton (manufactured by JSR Corporation), ZEONOR (manufactured by Nippon Zeon Co., Ltd.), ZEONEX (manufactured by Nippon Zeon Corporation). ) And Apel (Mitsui Chemicals) can be preferably 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, commercially available cycloolefin resin films such as Essina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa Film (manufactured by Optes Co., Ltd.), etc. You may use goods.

  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.

  When the cycloolefin-based resin film is in a roll state, the films tend to adhere to each other and easily cause blocking. Therefore, the protective film is usually bonded to roll. In addition, since cycloolefin resin films generally have poor surface activity, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment is performed on the surface to be bonded to the polarizing film. Is preferred. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  The cellulose acetate-based resin that can be used for the transparent protective film in the polarizing plate of the present invention is a cellulose part or a complete acetate ester, and examples thereof include triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate. As such a cellulose ester resin film, an appropriate commercially available product such as Fujitac TD80 (Fuji Film Co., Ltd.), Fujitac TD80UF (Fuji Film Co., Ltd.), Fujitac TD80UZ (Fuji Film Co., Ltd.) KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC8UY (manufactured by Konica Minolta Opto Co., Ltd.) and the like can be suitably used.

  Moreover, in the polarizing plate of this invention, the cellulose acetate type-resin film provided with the phase difference characteristic is also used suitably, As a commercial item of the cellulose acetate type-resin film provided with this phase difference characteristic, WV BZ 438 ( Fuji Film Co., Ltd.), KC4FR-1 (Konica Minolta Opto Co., Ltd.) and the like. Cellulose acetate is also called acetyl cellulose or cellulose acetate.

  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. In addition, this cellulose 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.

  Among the above-described transparent protective films used in the method for producing a polarizing plate of the present invention, a cellulose acetate-based resin film is preferable. In the past, water-based adhesives have been used to bond the polarizing film and the protective film, and the cellulose acetate-based resin film has a high water vapor transmission rate, which effectively removes moisture from the water-based adhesive after bonding. Preferred for removal. In addition, since the cellulose acetate-based resin film is the most commonly used material as a protective film for a polarizing plate, an additional function (provided by forming a coating layer such as a surface treatment layer or a liquid crystal compound) There are many grades that have, and it is easy to develop for various uses.

  When the transparent protective film is in a roll state, the films tend to adhere to each other and easily cause blocking. Therefore, the roll end part is subjected to uneven processing, a ribbon is inserted into the end part, or a protective film is bonded. Or rolled.

  The transparent 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 transparent protective film is 5-200 micrometers, for example, Preferably it is 10-150 micrometers, More preferably, it is 20-100 micrometers.

  In the method for producing a polarizing plate of the present invention, the polarizing film and the transparent protective film are an adhesive layer using an aqueous solvent adhesive, an organic solvent adhesive, a hot melt adhesive, a solventless adhesive, or the like. It is pasted through. Examples of the aqueous solvent-based adhesive include a polyvinyl alcohol-based resin aqueous solution and an aqueous two-component urethane emulsion adhesive, and the organic solvent-based adhesive includes, for example, a two-component urethane adhesive. Examples of the adhesive include a one-pack type urethane adhesive and an epoxy adhesive.

  When a cellulose acetate-based resin film whose surface to be bonded to the polarizing film is hydrophilized by saponification or the like is used as a transparent protective film, a polyvinyl alcohol-based resin aqueous 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 to the adhesive as an additive. 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.

  The method for bonding the polarizing film and the transparent protective film is not particularly limited. For example, an adhesive is uniformly applied to the surface of the polarizing film and / or the transparent protective film, and the other film is laminated on the coated surface. For example, a method of laminating with a roll or the like and drying. Usually, an adhesive agent is apply | coated at the temperature of 15-40 degreeC after the preparation, and the bonding temperature is the range of about 15-30 degreeC normally.

(3) Drying step When using an aqueous adhesive, after laminating the polarizing film and the transparent protective film, the laminated film is dried in order to remove water contained in the aqueous adhesive. Drying is performed by continuously passing through a drying furnace maintained at an appropriate temperature. Although such drying is not specifically limited, For example, it can carry out by winding the polarizing plate after drying in roll shape, making the inside of a drying furnace pass continuously.

  The temperature of the drying furnace is preferably 30 to 60 ° C. Since the polarizing plate produced by the production method of the present invention has a configuration in which a transparent protective film is laminated only on one surface of the polarizing film, when the temperature of the drying oven exceeds 60 ° C., the polarizing film shrinks. There is a risk that a remarkable folding will occur. Moreover, when the temperature of a drying furnace is less than 30 degreeC, it exists in the tendency which becomes easy to peel between a polarizing film and a transparent protective film. The temperature of the drying furnace is more preferably 35 ° C. or higher.

  The residence time of the laminated film in the drying furnace can be, for example, 10 to 1000 seconds, and is preferably 60 to 750 seconds, more preferably 150 to 600 seconds, particularly from the viewpoint of productivity.

  After drying, the film can be further cured at room temperature or slightly higher, for example, at a temperature of about 20 to 50 ° C. for about 12 to 600 hours. The temperature during curing is generally set lower than the temperature employed during drying.

(4) Other steps in polarizing plate production The polarizing plate produced by the production method of the present invention as described above is the other side of the polarizing film (that is, the side opposite to the side on which the transparent protective film is laminated). It is preferable that an adhesive layer made of an acrylic resin is formed on the surface. This pressure-sensitive adhesive preferably has a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C., and such a pressure-sensitive adhesive layer has various pressure-sensitive adhesives conventionally used for liquid crystal display devices. It can be formed using an adhesive such as an acrylic, rubber, urethane, silicone, polyvinyl ether or the like. In addition, an energy ray curable adhesive or a thermosetting adhesive may be used, and among them, an adhesive having an acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer 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) ) A monomer having a functional group such as a carboxy group, a hydroxyl group, an amide group, an amine 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 cross-linking agent described above, the pressure-sensitive adhesive composition includes, for example, natural products and the like in order to adjust the pressure-sensitive adhesive force, cohesive force, viscosity, 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.

  As described above, the pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer in the present invention preferably has a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. A pressure-sensitive adhesive used in a normal image display device or an optical film therefor has a storage elastic modulus of about 0.1 MPa at most, and in comparison with this, a preferable storage elastic modulus of the pressure-sensitive adhesive used in the present invention. 0.15 to 1 MPa is a high value. In addition, a storage elastic modulus can be measured using a commercially available viscoelasticity measuring apparatus, for example, DYNAMIC ANALYZER RDA II (made by REOMETRIC).

  In the method for producing a polarizing plate of the present invention, by using a pressure-sensitive adhesive having a higher storage elastic modulus than a normal pressure-sensitive adhesive within the above-described range, the dimensional change accompanying the shrinkage of the polarizing film that occurs in a high-temperature environment is reduced. Accordingly, it is possible to suitably manufacture a polarizing plate having good durability.

  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 in a polarizing film, Each component including the above-mentioned base polymer is provided in the other surface of a polarizing film. After forming a pressure-sensitive adhesive layer by applying a solution containing, a separator that has been subjected to a release treatment such as silicone may be laminated, or a pressure-sensitive adhesive layer is formed on the separator Then, it may be transferred to a polarizing film and laminated. Moreover, when forming an adhesive layer in a polarizing film, you may perform an adhesion | attachment process, for example, a corona treatment, etc. to at least one of a polarizing film and an adhesive layer as needed. In addition, the surface of the formed pressure-sensitive adhesive layer is usually protected with a separator film that has been subjected to a release treatment, and the separator film is bonded to a liquid crystal cell or other optical film before the polarizing plate is bonded. It is peeled off.

  In the polarizing plate produced as described above, an optical film having an optical function other than the polarizing plate may be laminated on the protective film surface or the pressure-sensitive adhesive layer surface. Examples of such an optical film include an optical compensation film coated with a liquid crystal compound on the surface of a substrate, an optical compensation film that is oriented, and a reflection type polarized light that transmits a certain kind of polarized light and reflects polarized light having the opposite property. Film, phase difference film made of polycarbonate resin, phase difference film made of cyclic polyolefin resin, film with antiglare function having an uneven shape on the surface, film with surface antireflection function, reflection film having reflection function on the surface, reflection Examples thereof include a transflective film having both a function and a transmission function. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). For example, DBEF (manufactured by 3M, available in Japan from Sumitomo 3M Co., Ltd.) is a commercially available product that corresponds to a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties. , APF (manufactured by 3M, available from Sumitomo 3M Co., Ltd. in Japan) and the like. Moreover, as a commercial item corresponding to the retardation film which consists of cyclic polyolefin resin, for example, Arton Film (made by JSR Corporation), Essina (made by Sekisui Chemical Co., Ltd.), Zeonoor Film (made by Optes Co., Ltd.) Etc.

  When such other optical films are provided on the protective film side of the polarizing plate described above, both are usually laminated via an adhesive. In this case, the same adhesive as described above can be used as the pressure-sensitive adhesive, but the storage elastic modulus may not be so large. Moreover, when providing another optical film in the adhesive layer side of an above-described polarizing plate, an optical film is adhere | attached by the adhesive layer. In this case, it is usual to provide an adhesive layer for bonding to the liquid crystal cell on the outside of the optical film.

  In order to obtain a polarizing plate having a desired shape and transmission axis, the polarizing plate with the pressure-sensitive adhesive layer produced by the production method of the present invention usually has a form of a large roll material or sheet material. Then, it is cut (chip cut) by a cutting tool having a sharp blade. 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.

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

<Example 1>
(A) Production of Polarizing Film A polyvinyl alcohol film having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was uniaxially stretched about 5 times in a dry process and further kept in a tension state. After being immersed in pure water at 60 ° C. 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.

(B) Preparation of adhesive Separately, in 100 parts of water, 3 parts of fully saponified polyvinyl alcohol (Kuraray Poval 117H, manufactured by Kuraray Co., Ltd.), acetoacetyl group-modified polyvinyl alcohol (Gosefimer Z-200, Nippon Gosei Co., Ltd.) 3 parts by Chemical Industry Co., Ltd., 0.18 parts of zinc chloride (sold from Nacalai Tesque), 1.4 parts of Glyoxal (sold from Nacalai Tesque), dissolved in polyvinyl alcohol resin An agent was prepared.

(C) Production of Polarizing Plate Adhering the above-mentioned polarizing film having a thickness of 40 μm (KC4UY, manufactured by Konica Minolta Opto Co., Ltd.) made of saponified triacetyl cellulose to one surface of the polarizing film obtained above. It bonded by the nip roll through the agent. While maintaining the tension of the bonded product at 320 N / m, it was dried at 38 ° C. for 5 minutes to obtain a polarizing plate.

(D) Formation of pressure-sensitive adhesive layer Polyethylene terephthalate film (separator) in which a pressure-sensitive adhesive layer obtained by adding a urethane acrylate oligomer and an isocyanate-based crosslinking agent to a copolymer of butyl acrylate and acrylic acid is subjected to a release treatment A pressure-sensitive adhesive layer was formed using a sheet-like pressure-sensitive adhesive formed with a thickness of 15 μm on the mold release surface. The storage elastic modulus of the pressure-sensitive adhesive layer was 0.41 MPa at 23 ° C. and 0.22 MPa at 80 ° C. The sheet-like pressure-sensitive adhesive was bonded to the other surface of the polarizing film of the polarizing plate produced as described above to obtain a polarizing plate with a pressure-sensitive adhesive.

(E) Lamination of retardation film A retardation film (Essina film) made of a stretched film of norbornene-based resin, having an in-plane retardation of 140 nm that is λ / 4 with respect to light wavelength λ, and a thickness of 25 μm A sheet-like acrylic pressure-sensitive adhesive was bonded to one side of Sekisui Chemical Co., Ltd. to obtain a pressure-sensitive retardation film. The storage elastic modulus of this acrylic pressure-sensitive adhesive was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C. The retardation film surface of the above-mentioned retardation film with an adhesive (the surface on which the adhesive layer is not formed) is bonded to the adhesive surface of the polarizing plate with an adhesive prepared in (D) above, and a retardation function is obtained. A polarizing plate with a pressure-sensitive adhesive to which no.

  The polarizing plate with the pressure-sensitive adhesive provided with the retardation function prepared in the above (E) is cut into a size of 40 mm × 40 mm, and bonded to glass with the pressure-sensitive adhesive layer provided on the outside of the retardation film. It was.

<Examples 2 to 5 and Comparative Example>
As shown in Table 1, a polarizing film was produced by changing the drying temperature and time of the polarizing film, and a polarizing plate with an adhesive layer was produced in the same manner as in Example 1.

<Reference example>
The polyvinyl alcohol was treated with iodine in the same manner as in (A) of Example 1 except that the drying conditions after the dyeing treatment, boric acid treatment and washing with water were changed to 140 seconds at 90 ° C. An adsorption-oriented polarizing film was obtained. From triacetyl cellulose subjected to the same saponification treatment as used in (C) of Example 1 via the polyvinyl alcohol-based adhesive prepared in (B) of Example 1 on both surfaces of this polarizing film A film having a thickness of 40 μm was bonded by a nip roll. While maintaining the tension of the bonded product at 320 N / m, the laminate was dried at 50 ° C. for 5 minutes to obtain a polarizing plate.

  On one side of the obtained polarizing plate, the same acrylic adhesive film having a storage elastic modulus at 23 ° C. of 0.05 MPa and a storage elastic modulus at 80 ° C. of 0.04 MPa as used in (E) of Example 1 Were laminated to obtain a polarizing plate with an adhesive layer. The acrylic adhesive layer having a storage elastic modulus at 23 ° C. of 0.05 MPa and a storage elastic modulus at 80 ° C. of 0.04 MPa, which is the same as that used in Example 1 (E), is provided on one side. The retardation film surface of the provided retardation film (surface in which the adhesive layer is not formed) was bonded, and the polarizing plate with the adhesive to which the retardation function was provided was produced.

<Evaluation test>
When producing each polarizing plate in Examples, Comparative Examples and Reference Examples, one side of the test piece is parallel to the stretching axis direction of the polarizing film from the polarizing film before being bonded to the film made of triacetylcellulose. Then, a test piece having a size of 100 mm × 100 mm was cut out, the initial dimension A in the direction perpendicular to the stretching axis direction of the test piece (TD direction), and the test piece was 96 hours under a dry heat environment of 85 ° C. From the dimension B in the TD direction after being held, the dimensional change rate of the polarizing film was calculated by the following formula.

Dimensional change rate (%) = (A−B) / A × 100
Moreover, about each polarizing plate with an adhesive layer produced by the Example, the comparative example, and the reference example, it hold | maintains in a 85 degreeC dry-heat environment for 96 hours, and is the edge part in a TD direction as a deformation | transformation state of a polarizing plate edge part. Deformation distance (linear distance from the edge to the area where no irregularities are observed with respect to the horizontal surface in the main part) (mm), raised height of the end in the TD direction (height at the highest apex at the end and at the main part While measuring (difference with the height of a horizontal surface) (micrometer), the distortion of the said edge part was evaluated by visual observation. The results are shown in Table 1.

  From the results shown in Table 1, when the dimensional change rate of the polarizing film just before the transparent protective film bonding was over 2.7% as in the comparative example, the deformation was large, and the reflected light looked distorted by visual observation. I understand that. In addition, when a transparent protective film was bonded on both surfaces of a polarizing film like a reference example, even if the dimensional change rate of the polarizing film just before bonding was large, there was little deformation | transformation.

Claims (3)

  A method for producing a polarizing plate, comprising a polyvinyl alcohol resin and laminating a transparent protective film on only one surface of a polarizing film having a dimensional change rate of 2.7% or less via an adhesive layer.   The manufacturing method of the polarizing plate of Claim 1 whose transparent protective film is a cellulose acetate type-resin film.   The manufacturing method of the polarizing plate of Claim 1 or 2 which forms the adhesive layer which consists of acrylic resin in the other surface of a polarizing film.