KR20090045032A - A process for producing a polarizer - Google Patents

Abstract

It provides a manufacturing method of a polarizing plate which consists of polyvinyl alcohol-type resin, and laminates a transparent protective film only on one side of the polarizing film whose dimension change rate is 2.7% or less through an adhesive bond layer. In the manufacturing method of the said polarizing plate, it is preferable that a transparent protective film is a cellulose acetate type resin film, and it is preferable to form the adhesive layer which consists of acrylic resin on the other side of a polarizing film.

Description

Manufacturing method of polarizing plate {A PROCESS FOR PRODUCING A POLARIZER}

The present invention relates to a method of manufacturing a polarizing plate by laminating a transparent protective film on one side of a polarizing film made of polyvinyl alcohol-based resin through an adhesive layer.

A polarizing plate is a supply element of polarization in a liquid crystal display device, and is used widely as a detection element of polarization. As such a polarizing plate, what adhere | attached the transparent protective film which consists of triacetyl cellulose to the polarizing film which consists of polyvinyl alcohol-type resin conventionally is used, but in recent years, development in mobile devices, such as a notebook type personal computer and a mobile telephone of a liquid crystal display device, Furthermore, thinning and weight reduction is demanded in accordance with development to a large size television. In addition, as the place of use becomes wider due to portability, improvement in durability is also required.

A polarizing film is generally produced by impregnating a polyvinyl alcohol-based resin with a dichroic dye represented by iodine or the like and uniaxially stretching the film at high magnification. For this reason, when a polarizing film is exposed to a dry heat environment, big dimensional change accompanying shrinkage generate | occur | produces. 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, a large shrinkage of more than 10% is achieved. This is observed. For this reason, the dimensional change of a polarizing film is normally reduced by laminating a transparent protective film on both surfaces of a polarizing film through an adhesive bond layer, etc., and manufacturing a polarizing plate. In patent document 1, the triacetyl cellulose film is laminated | stacked on both surfaces of the polarizing film which shows high shrinkage as mentioned above, and it is set as the polarizing plate. Although the dimensional change rate before and after heating the polarizing plate at 100 degreeC for 2 hours is shown in the same table, the shrinkage rate of a polarizing plate is 2% or less, and it turns out that shrinkage is suppressed by laminating | stacking a triacetyl cellulose film on both surfaces. have.

Moreover, in Table 1 of Unexamined-Japanese-Patent No. 6-59123 (patent document 2), the dimension change rate before and after heating the polarizing plate which laminated | stacked the triacetyl cellulose film on both surfaces of the polarizing film at 80 degreeC for 4 hours is described. However, the shrinkage ratio is 0.3% or less, and it can be seen that the shrinkage is further suppressed by laminating the triacetylcellulose film on both sides.

However, in recent years, in order to reduce weight, the polarizing plate which laminated | stacked the transparent protective film only on one side of the polarizing film is also required, and such a polarizing plate cannot suppress the shrinkage of the polarizing film when exposed to a dry environment, and the problem is easy. There was a tendency to occur. For this reason, when the polarizing plate which laminated | stacked the transparent protective film only on one side of the polarizing film in this way is exposed to a liquid crystal cell bonded through an adhesive under a dry environment, the adhesive of the polarizing plate edge part will peel off or a polarizing plate edge part will generate | occur | produce the screen display distortion. There was a case.

This invention is made | formed in order to solve the said subject, The objective is the polarizing plate which laminated | stacked the transparent protective film through the adhesive bond layer only to one side of the polarizing film which consists of polyvinyl alcohol-type resin, and manufactures the polarizing plate which is excellent in durability. Is to provide a way to do it.

The manufacturing method of the polarizing plate of this invention consists of polyvinyl alcohol-type resin, It is characterized by laminating | stacking a transparent protective film only on one side of the polarizing film whose dimension change rate is 2.7% or less through an adhesive bond layer.

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 this invention, compared with the polarizing plate in which the transparent protective film is laminated | stacked on both surfaces of the polarizing film which consists of polyvinyl alcohol-type resin, the polarizing plate excellent in durability can be manufactured industrially advantageous while making thickness of a polarizing plate thin.

In the manufacturing method of the polarizing plate of this invention, a polarizing plate is manufactured by laminating | stacking a transparent protective film only on one side of the polarizing film which consists of polyvinyl alcohol-type resin through an adhesive bond layer. Specifically, the polarizing film used for this invention gives a polyvinyl alcohol-type resin film the uniaxial stretching and the dyeing process by a dichroic dye, and makes the dichroic dye adsorption-oriented. Basically, the manufacturing method of the polarizing plate of this invention is (1) polarizing film manufacturing process which produces a polarizing film using polyvinyl alcohol-type resin, (2) bonding a polarizing film and a transparent protective film using an adhesive agent, The bonding process of obtaining a laminated | multilayer film, and (3) The drying process of drying by passing a laminated | multilayer film through 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 it is a big feature that the dimension change rate of the polarizing film at the time of providing to a bonding process is 2.7% or less. Hereinafter, each process is explained in full detail.

(1) polarizing film production process

Polyvinyl alcohol-type resin which comprises a polarizing film is obtained by saponifying a polyvinyl acetate type resin normally. The saponification degree of polyvinyl alcohol-type resin is 85 mol% or more normally, Preferably it is 90 mol% or more, More preferably, it is 99-100 mol%. As polyvinyl acetate type resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate, for example, an ethylene-vinyl acetate copolymer, etc. are mentioned. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, etc. are mentioned, for example. The degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of 1000 to 10,000, and preferably in the range of 1500 to 5000.

These polyvinyl alcohol-based resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes can also be used. Usually, as a starting material of polarizing film manufacture, the unstretched film of the polyvinyl alcohol-type resin film whose thickness is 20-100 micrometers, Preferably 30-80 micrometers is used. Industrially, the width of the film is practically 1500 to 4000 mm. The unstretched film is treated in the order of swelling treatment, dyeing treatment, boric acid treatment, water washing treatment, uniaxial stretching in the steps up to boric acid treatment, and finally, the thickness of the polarizing film obtained by drying is, for example, 5 to 50 µm. to be.

As a manufacturing method of a polarizing film, there are two manufacturing methods largely divided. In the first method, the 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 a drying method. to be. The second method is a solution treatment of the unstretched polyvinyl alcohol-based resin film 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 wetted in the boric acid treatment step and / or the preceding step. It is a method of performing axial stretching and finally drying.

In either method, uniaxial stretching may be performed in one step or in two or more steps, but it is preferable to perform in a plurality of steps. A stretching method can employ | adopt a well-known method, for example, the inter-roll stretching which extends | stretches with a circumferential speed difference between two nip rolls conveying a film, for example, a heat roll like that described in Japanese Patent No. 2731813. Stretching method, tenter stretching method, etc. are mentioned. In addition, although the order of a process is basically the same as the above-mentioned, there is no restriction | limiting in the number of process baths, process conditions, etc. Moreover, you may add the process which is not described in the said 1st and 2nd method for another purpose. Examples of such a step include immersion treatment (iodide treatment) with an aqueous solution of iodide not containing boric acid or immersion treatment (zinc treatment) with an aqueous solution containing zinc chloride or the like that does not contain boric acid after boric acid treatment. Can be.

The swelling treatment step is performed for the purpose of removing foreign substances on the surface of the film, removing the plasticizer in the film, imparting easy dyeing in the next step, plasticizing the film, and the like. Treatment conditions are the range which can achieve these objectives, and is determined in the range which does not produce the problem, such as extreme dissolution of a base film, a loss of transparency, and the like. When swelling the film previously stretched in gas, it is performed by immersing a film in 20-70 degreeC, Preferably it is 30-60 degreeC aqueous solution. Immersion time of a film is for 30 to 300 second, Preferably it is for 60 to 240 second. When swelling an unstretched raw film from the beginning, it is performed by immersing a film in 10-50 degreeC, preferably 20-40 degreeC aqueous solution, for example. Immersion time of a film is for 30 to 300 second, Preferably it is for 60 to 240 second.

In the swelling treatment step, problems such as swelling of the film in the width direction and wrinkles in the film easily occur, and therefore, such as wide rolls (expander rolls), spiral rolls, crown rolls, cross guides, bend bars, tenter clips, etc. It is preferable to convey a film, taking out the wrinkles of a film with the widening apparatus of. In order to stabilize the conveyance of the film in the bath, the water flow in the swelling bath is controlled by an underwater shower, or by using an edge position control device (EPC) to detect the end of the film to prevent meandering of the film. useful. In this process, since a film swells and expands also in the conveyance direction of a film, in order to remove the looseness of the film of a conveyance direction, it is preferable to devise means, such as controlling the speed of the conveyance roll before and behind a processing tank. In addition to pure water, the swelling treatment bath used includes boric acid (described in JP-A-10-153709), chloride (described in JP-A-06-281816), an inorganic acid, The aqueous solution which added the inorganic salt, water-soluble organic solvent, alcohol, etc. in 0.01 to 0.1 weight% range can also be used.

The dyeing process with a dichroic dye is performed for the purpose of adsorb | sucking and orienting a dichroic dye to a film. The treatment conditions are determined in a range in which these objects can be achieved, and in a range in which problems such as extreme dissolution of the base film, loss of transparency, and the like do not occur. In the case of using iodine as a dichroic dye, an aqueous solution having a concentration of iodine / potassium iodide / water = 0.003 to 0.2 / 0.1 to 10/100 by weight ratio is, for example, under a temperature condition of 10 to 45 ° C, preferably 20 to 35 ° C. Immersion treatment is performed for 30 to 600 seconds, preferably 60 to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used. In addition, you may use another iodide together with potassium iodide. In addition, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, and the like, may coexist. When boric acid is added, it differs from the following boric acid treatment in the point which contains iodine. If it contains 0.003 weight part or more of iodine with respect to 100 weight part of water, it can be considered as a dyeing tank.

In the case of using a water-soluble dichroic dye as a dichroic dye, an aqueous solution having a dichroic dye / water concentration of 0.01 to 0.1 / 100 by weight ratio is used, for example, under a temperature condition of 20 to 80 ° C, preferably 30 to 70 ° C. Immersion treatment is performed 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 etc., for example, may contain inorganic salts, such as sodium sulfate, surfactant, etc. The dichroic dye may be used alone or in combination of two or more kinds of dichroic dyes.

As described above, the film may be stretched in the dye bath. Stretching is performed by, for example, giving a peripheral speed difference to the nip rolls before and after the dyeing tank. In addition, like the swelling treatment step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guide, a bend bar, or the like may be provided in the dye bath and / or in the bath entrance and exit.

Boric acid treatment is performed by immersing the polyvinyl alcohol-type resin film dyed by the dichroic dye in the aqueous solution containing 1-10 weight part of boric acid with respect to 100 weight part of water. When a dichroic dye is iodine, it is preferable to contain 1-30 weight part of iodides. Examples of iodide include potassium iodide, zinc iodide, and the like. In addition, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

Boric acid treatment is performed for water resistance by crosslinking, color adjustment (preventing bluish etc.), etc. When boric acid treatment is performed for water resistance by crosslinking, a crosslinking agent such as glyoxal, glutaraldehyde or the like can be used, if necessary, in addition to boric acid or together with boric acid. In addition, the boric acid treatment for water resistance may be called names, such as a water treatment process, a crosslinking process, and an immobilization process. In addition, the boric acid treatment for color adjustment may be referred to by names such as complementary color treatment, re-dyeing treatment and the like.

This boric acid treatment is performed by suitably changing the concentration of boric acid and iodide, and the temperature of a process bath for the purpose. The boric acid treatment for water resistance and the boric acid treatment for color adjustment are not particularly distinguished, but can be carried out under the following conditions. In the case of swelling treatment, dyeing treatment, and boric acid treatment of the raw film, when boric acid treatment is intended for water resistance by crosslinking, 3 to 10 parts by weight of boric acid and 1 to 1 part of iodide per 100 parts by weight of water are used. It is usually performed at 50-70 degreeC, Preferably it is 55-65 degreeC using the boric acid treatment bath containing 20 weight part. Immersion time is 90-300 second. Moreover, when dyeing and boric-acid process are performed to the film previously stretched, the temperature of a boric-acid treatment bath is 50-85 degreeC normally, Preferably it is 55-80 degreeC.

After the boric acid treatment for water resistance, the boric acid treatment for color adjustment may be performed. For example, when the dichroic dye is iodine, for this purpose, it is usually 10 to 45 DEG C using a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide with respect to 100 parts by weight of water. At a temperature of. Immersion time is 3 to 300 second normally, Preferably it is 10 to 240 second. The boric acid treatment for subsequent color adjustment is usually performed at a low boric acid concentration, a high iodide concentration, and a low temperature as compared to the boric acid treatment for water resistance.

These boric acid treatments may consist of several processes, and are usually performed by the process of 2-5. 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-mentioned range. The boric acid treatment for water resistance and the boric acid treatment for color adjustment may be performed in a plurality of steps, respectively.

Moreover, you may extend | stretch a film similarly to a dyeing process in a boric acid treatment process. 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 longitudinal direction reference length of the master film became in the film after the completion of all the stretching treatments, and for example, the film that was 1 m in the master film was the film after the completion of all the stretching treatments. If 5 m is, the cumulative draw ratio at that time is 5 times.

After the boric acid treatment, water washing treatment is performed. A water washing process is performed by immersing the polyvinyl alcohol-type film processed by boric acid in water for water resistance and / or color adjustment, spraying water as a shower apparatus, or using dipping and spraying together. The temperature of water in a water washing process is 2-40 degreeC normally, and immersion time is 2 to 120 second.

Here, in each process after an extending | stretching process, tension control may be performed so that the tension of a film may become substantially constant, respectively. Specifically, when stretching is finished in the dyeing treatment step, tension control is performed in the subsequent boric acid treatment step and water washing treatment step. When extending | stretching is complete | finished before the dyeing process, tension control is performed in the process after including a dyeing process and a 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 first or the first to the second stage, and from the next boric acid treatment step to the water washing step of the boric acid treatment step where the stretching treatment is performed. Tension control in each process, or stretching the film in the boric acid treatment process from the first to the third stage, and tension control in each process from the next boric acid treatment process to the washing process of the boric acid treatment process in which the stretching treatment was performed. Although it is preferable to carry out, industrially, each process from the next boric acid treatment process to the water washing process of the boric acid treatment process which extended | stretched the said film in the boric acid treatment process from the first or the beginning to the 2nd stage, and performed the extending process It is more preferable to perform tension control at. In addition, when performing the above-mentioned iodide treatment or zinc treatment after a boric acid treatment, tension control can also be performed about these processes.

As the nip roll for controlling the tension and the guide roll for controlling the conveying direction of the film, a rubber roll, a stainless steel polishing roll, a sponge rubber roll, or the like can be used. As a rubber roll, it consists of NBR etc., and the hardness is 60-90 degree, 70-80 degree on the JIS Shore C scale measured by the test method of JIS K 6301, and surface roughness of JIS B 0601 (surface roughness) The average spacing S at the top of the local peak 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, or the like, and for the purpose of achieving uniform film thickness, the surface roughness is the average spacing S at the top of the local peak of the roughness curve of JIS B O601 (surface roughness). It is preferable that it is 0.2-1S. As the sponge rubber roll, the hardness of the sponge is 20 to 60 degrees, more preferably 25 to 50 degrees, density is 0.4 to 0.6 g / m 3, and also 0.42 to 0.57 g on the JIS Shore C scale measured by the test method of JIS K 6301. It is preferable that / cm <3> and surface roughness are represented by the average space | interval S of the top of a local peak of the roughness curve of JISBO601 (surface roughness), and it is 10-30S, Furthermore, it is 15-25S.

The tension in each step from the swelling process to the water washing process may be the same or different. The tension to the film in tension control is not specifically limited, It is suitably set in the range of 150-2000 N / m, Preferably it is 600-1500 N / m per unit width. If tension is less than 150 N / m, wrinkles etc. will arise easily in a film. On the other hand, when the tension exceeds 2000 N / m, problems such as breakage of the film and low life due to wear of the bearing occur. In addition, the tension per unit width is calculated from the film width near the inlet of the step and the tension value of the tension detector. In addition, when tension control is performed, it may inevitably be slightly stretched and contracted, but in the present invention, this is not included in the stretching treatment.

At the end of the polarizing film preparation step, a drying treatment is performed. The drying treatment is preferably performed in a large number of steps by changing the tension little by little, but is usually performed in two to three steps due to equipment restrictions. In the case of performing in two steps, the tension in the previous step is preferably set in the range of 600 to 1500 N / m, and the tension in the subsequent step is set in the range of 250 to 1200 N / m. When the tension is too large, the breakage of the film increases, and when too small, the occurrence of wrinkles increases, which is not preferable. Moreover, it is preferable to set the drying temperature of a previous step from the range of 30-90 degreeC, and the drying temperature of a next step from the range of 50-100 degreeC. If the temperature is too high, the breakage of the film increases and the optical properties are lowered. If the temperature is too low, the line is too large, which is not preferable. The drying treatment temperature may be, for example, 60 to 600 seconds, and the drying time in each step may be the same or different. If the time is too long, it is not preferable in terms of productivity. 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 so that the dimensional change rate of the polarizing film obtained by the polarizing film preparation process in this way may be 2.7% or less. Moreover, the dimension change rate of the said polarizing film is the direction (TD direction) perpendicular | vertical to the extending | stretching axial direction of the test member which made the size of 100 mm x 100 mm so that one side of a test member may become parallel to the extending | stretching axial direction of a polarizing film. It is computed by the following formula from the initial dimension (A) in and the dimension B in the TD direction after hold | maintaining the test member for 96 hours in 85 degreeC dry heat environment.

Dimensional rate of change (%) = (A-B) / A × 100

In the manufacturing method of the polarizing plate of this invention, when the dimension change rate of the polarizing film at the time of providing to a bonding process exceeds 2.7%, the polarizing plate which laminated | stacked the protective film on one side of the polarizing film via the adhesive bond layer is the polarizing film When exposed in a dry heat environment in a state bonded to a liquid crystal cell or the like through a pressure-sensitive adhesive on the side, the distortion of the image display due to the rise of the end of the polarizing plate is remarkably observed by visually confirming. I may lose. In addition, the degree of distortion by visual confirmation is as follows: the rising height of the deformed end (difference between the height at the highest top at the end and the height of the horizontal plane at the main part) and the deformation distance (from the main part to the main part). Can be represented by a straight line distance to an area where unevenness is not observed with respect to the horizontal plane of?, And the higher the raising 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 dimension change rate of the polarizing film at the time of providing to a bonding process becomes like this. Preferably it is 1.5% or less, More preferably, it is 1% or less. When the rate of dimensional change is 1% or less, almost no distortion is observed by visual confirmation of the distortion of the image display due to the rise of the end of the polarizing plate. Moreover, the dimension change rate of the polarizing film at the time of providing to a bonding process is 0% or more normally.

As a method of making the dimension change rate of a polarizing film at the time of providing to a bonding process low as mentioned above, for example, the method of drying a polarizing film at high temperature (preferably 80-100 degreeC), and the state of storage force (preferably 250) Method of drying at the said high temperature with -400 N / m), The method of making glass transition temperature (Tg) of a polyvinyl alcohol-type resin film high (for example, the method of reducing the quantity of the plasticizer contained in a polyvinyl alcohol-type resin film). Or a method of copolymerizing a monomer having a glass transition temperature higher than the glass transition temperature of a polyvinyl alcohol-based resin when used as a homopolymer) or a method of reducing the boron content in the polarizing film in a range that does not impair the effect of boric acid crosslinking ( For example, the boric acid treatment is divided into at least two stages, and the boric acid concentration of the last treatment bath is lower than the boric acid concentration of the first treatment bath), boric acid treatment Methods for promoting the cross-linking of (for example, a method of how to set the temperature of the acid treatment and high, increasing the draw ratio of the boric acid in the treatment bath) may be at least one selected from the like.

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 specifically limited about the moisture content, Preferably it exists in the range of 3-14 weight%, More preferably, it is 3 It is in the range of -10 weight%, Especially preferably, it is in the range of 3-8 weight%. When the moisture content of the polarizing film is less than 3% by weight, the polarizing film is brittle and easily ruptures along the stretching direction, which makes the handing difficult, and when the moisture content of the polarizing film exceeds 14% by weight, the polarization is polarized. There exists a possibility that a film may shrink easily in a dry heat environment. Moreover, the moisture content of a polarizing film can be computed from the weight change before and after hold | maintaining, for example under 105 degreeC dry heat for 1 hour. The polarizing film which has a moisture content in the suitable range mentioned above can be obtained by controlling the drying temperature and drying time of a polarizing film, for example.

In this manner, the polyvinyl alcohol-based 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 in the range of 5-40 micrometers normally.

(2) bonding process

In the subsequent bonding process, a transparent protective film is laminated | stacked on one surface of the polarizing film obtained by the above-mentioned polarizing film preparation process through an adhesive bond layer, and it becomes a polarizing plate. Examples of the transparent protective film include a cycloolefin resin film, a cellulose acetate resin film, a polyester resin film such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, a polycarbonate resin film, an acrylic resin film, The film which has been widely used conventionally in the field, such as a polypropylene resin film, is mentioned.

Cycloolefin resin which can be used for the transparent protective film in the polarizing plate of this invention is thermoplastic resin (thermoplastic cyclo) which has a unit of the monomer which consists of cyclic olefin (cycloolefin), such as a norbornene and a polycyclic norbornene-type monomer, for example. Also called olefin resin). In the present invention, the cycloolefin resin may be a hydrogenated product of the ring-opening polymer of the cycloolefin or the ring-opening copolymer using two or more cycloolefins, or an addition polymer of a cycloolefin, a chain olefin, an aromatic compound having a vinyl group, or the like. good. It is also effective to introduce a polar group.

In the case of using a copolymer of a cycloolefin with a linear olefin or an aromatic compound having a vinyl group, as the chain olefin, ethylene, propylene, etc. may be mentioned, and examples of the aromatic compound having a vinyl group include styrene, α-methylstyrene, and nucleus. Alkyl substituted styrene, etc. are mentioned. In such a copolymer, the unit of the monomer which consists of cycloolefin may be 50 mol% or less (preferably 15-50 mol%). In particular, in the case of using a ternary copolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group, the unit of the monomer consisting of the cycloolefin can be made in a relatively small amount as described above. In such a terpolymer, the unit of the monomer which consists of linear olefins is 5 to 80 mol% normally, and the unit of the monomer which consists of an aromatic compound which has a vinyl group is 5 to 80 mol% normally.

Cycloolefin resins are suitable commercially available products such as Topas (manufactured by Ticona), Arton (manufactured by JSR Co., Ltd.), ZEONOR (manufactured by Japan Xeon Co., Ltd.), ZEONEX (Made in Japan) Corporation), Apel (made by Mitsui Chemicals Co., Ltd.), etc. can be used suitably. When forming a cycloolefin resin into a film and making into a film, well-known methods, such as the solvent casting method and the melt-extrusion method, are used suitably. Moreover, cycloolefin resin film previously formed into a film, such as Essina (made by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeano film (made by Optes), etc. You may use commercially available products.

The cycloolefin resin film may be uniaxially stretched or biaxially stretched. By extending | stretching, arbitrary phase difference values can be provided to a cycloolefin resin film. Stretching is normally performed continuously while unwinding a film roll, and it extends | stretches in the heating direction of a roll, the direction perpendicular | vertical to the advancing direction, or both. As for the temperature of a heating furnace, the range of glass transition temperature +100 degreeC is employ | adopted from the glass transition temperature vicinity of cycloolefin resin normally. The magnification of stretching is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When a cycloolefin resin film exists in a roll state, since films adhere | attach and there exists a tendency for blocking to occur easily, normally, a protective film is bonded together and wound up by a roll. Moreover, since cycloolefin resin film is generally inferior in surface activity, surface treatment, such as a plasma treatment, a corona treatment, an ultraviolet irradiation process, a flame | frame (flame) process, a saponification process, is performed to the surface to adhere | attach with a polarizing film. desirable. Especially, the plasma process and corona treatment which can be implemented comparatively easily are suitable.

Moreover, the cellulose acetate type resin which can be used for the transparent protective film in the polarizing plate of this invention is a triacetyl cellulose, a diacetyl cellulose, a cellulose acetate propionate etc. as a partial or complete acetate ester of cellulose, for example. . As a film of such a cellulose ester-type resin, a suitable commercial item, for example, FujiTak TD80 (made by Fujifilm), FujiTak TD80UF (made by Fujifilm), Fujitak TD80UZ (made by Fujifilm), KC8UX2M (Made by Konica Minolta Opt Co., Ltd.), KC8UY (made by Konica Minolta Opt Co., Ltd.), etc. can be used suitably.

Moreover, in the polarizing plate of this invention, the cellulose acetate type resin film which gave retardation characteristic is also used suitably, As a commercial item of the cellulose acetate type resin film provided with such retardation characteristic, WV BZ438 (manufactured by Fujifilm Co., Ltd.) And KC4FR-1 (manufactured by Konica Minolta Opt Co., Ltd.). The cellulose acetate is also called acetyl cellulose or cellulose acetate.

The surface of the cellulose acetate-based resin film may be subjected to surface treatment such as an antiglare treatment, a hard coat treatment, an antistatic treatment, an antireflection treatment, and the like depending on the use. Further, in order to improve the viewing angle characteristics, a liquid crystal layer or the like may be formed. Moreover, you may extend | stretch a cellulose resin film in order to provide retardation. In addition, in order to improve the adhesiveness with this polarizing film, this cellulose resin film is usually saponified. As a saponification process, the method of immersing in aqueous solution of alkalis, such as sodium hydroxide and potassium hydroxide, can be employ | adopted.

As for the transparent protective film used for the manufacturing method of the polarizing plate of this invention, a cellulose acetate-type resin film is preferable among the above. The use of an aqueous adhesive is conventionally used for the adhesion of the polarizing film and the protective film, and the cellulose acetate-based resin film has a high moisture permeability and is preferable for effectively removing moisture from the aqueous adhesive after the adhesive treatment. In addition, since the cellulose acetate-based resin film is a material most commonly used as a protective film for a polarizing plate, there are also many grades having additional functions (given by forming a coating layer such as a surface treatment layer or a liquid crystal compound), and various applications. Easily deploy the furnace.

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

Although it is preferable that the thickness of a transparent protective film is thin, when too thin, intensity | strength will fall and it will be inferior to workability. On the other hand, when too thick, problems, such as transparency fall or the curing time required after lamination | stacking will arise. 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 manufacturing method of the polarizing plate of this invention, a polarizing film and a transparent protective film are bonded together through the adhesive bond layer which used an aqueous solvent adhesive, an organic solvent adhesive, a hot melt adhesive, a solvent-free adhesive, etc. As the solvent-based adhesive, for example, an aqueous polyvinyl alcohol resin solution, an aqueous two-component urethane emulsion adhesive, or the like, and an organic solvent adhesive, for example, a two-component urethane adhesive or the like, and a solvent-free adhesive, for example, a one-component urethane adhesive or an epoxy-based adhesive Adhesives etc. are mentioned, respectively.

When the adhesive surface with a polarizing film uses the cellulose acetate type resin film hydrophilized by saponification etc. as a transparent protective film, the polyvinyl alcohol-type resin aqueous solution is used suitably as an adhesive agent. In addition to the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl alcohol-type resin used as an adhesive agent is obtained by saponifying a copolymer of vinyl acetate and the other monomer copolymerizable with this. And a modified polyvinyl alcohol polymer obtained by partially modifying these hydroxyl groups. Polyvalent aldehyde, a water-soluble epoxy compound, a melamine type compound, a zirconia compound, a zinc compound, etc. may be added to this adhesive agent as an additive. When such an aqueous adhesive is used, the adhesive layer obtained from it is usually 1 micrometer or less, and even if a cross section is observed with a normal optical microscope, the adhesive bond layer is hardly observed.

The method of bonding the polarizing film and the transparent protective film is not particularly limited, and 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 coating surface to be bonded by a roll or the like. And a method of drying. Usually, an adhesive agent is apply | coated under the temperature of 15-40 degreeC after the preparation, and joining temperature is the range of about 15-30 degreeC normally.

(3) drying process

When using an aqueous adhesive agent, after bonding a polarizing film and a transparent protective film, in order to remove the water contained in an aqueous adhesive agent, a laminated film is dried. Drying is performed by continuously passing the drying furnace maintained at appropriate temperature. Although this drying is not specifically limited, For example, it can carry out by winding the polarizing plate after drying in roll shape, passing continuously inside a drying furnace.

It is preferable to make temperature of a drying furnace into 30-60 degreeC. Since the polarizing plate manufactured by the manufacturing method of this invention laminated | stacks a transparent protective film only on one side of a polarizing film, when the temperature of a drying furnace exceeds 60 degreeC, remarkable curvature resulting from shrinkage of a polarizing film may arise. There is concern. Moreover, when the temperature of a drying furnace is less than 30 degreeC, it exists in the tendency to peel easily between a polarizing film and a transparent protective film. As for the temperature of a drying furnace, it is more preferable that it is 35 degreeC or more.

The residence time of the laminated film in a drying furnace can be 10-1000 second, for example, Especially from a viewpoint of productivity, Preferably it is 60-750 second, More preferably, it is 150-600 second.

After drying, it may also cure for about 12 to 600 hours at room temperature or a temperature slightly higher than it, for example, about 20-50 degreeC. The temperature at the time of curing is generally set lower than the temperature employed at the time of drying.

(4) Other processes in polarizing plate manufacture

As for the polarizing plate manufactured by the manufacturing method of this invention as mentioned above, the adhesive layer which consists of acrylic resin is formed in the other surface (namely, the surface opposite to the surface of the side which laminated | stacked the transparent protective film) of a polarizing film is formed. It is preferable. It is preferable that this adhesive has a storage elastic modulus of 0.15-1 MPa in the temperature range of 23-80 degreeC, These adhesive layers are the various adhesives conventionally used for liquid crystal display devices, such as acrylic type, rubber type, urethane type, It can form using adhesives, such as silicone type and polyvinyl ether. Moreover, you may use an energy-beam hardening type and a thermosetting adhesive, and the adhesive which made the base polymer the acrylic resin excellent in transparency, weather resistance, heat resistance, etc. among these is suitable.

The acrylic pressure-sensitive adhesive is not particularly limited, but (meth) acrylic acid ester base polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, and these ( The copolymer base polymer which used two or more types of meth) acrylic acid ester etc. is used suitably. In addition, polar monomers are copolymerized in these base polymers. Examples of the polar monomers include (meth) acrylic acid, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylate hydroxyethyl, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl The monomer which has functional groups, such as a carboxy group, a hydroxyl group, an amide group, an amine group, and an epoxy group, such as (meth) acrylate, is mentioned.

Although these acrylic adhesives can be used alone or of course, a crosslinking agent is usually used in combination. As a crosslinking agent, it is a divalent or polyvalent metal salt which forms a carboxylic acid metal salt between a carboxyl group, As a polyamine compound, forms an amide bond between a carboxyl group, As a polyepoxy compound or a polyol compound, a carboxyl group Forming an ester bond between and, As a polyisocyanate compound, forming an amide bond between a carboxyl group, etc. are illustrated. Especially, a polyisocyanate compound is used widely as an organic type crosslinking agent.

The energy ray-curable pressure-sensitive adhesive has a property of being cured by irradiation with energy rays such as ultraviolet rays or electron beams, has adhesiveness even before energy ray irradiation, adheres to adherends such as a film, and cures by irradiation of energy rays to adjust adhesion. It is a pressure-sensitive adhesive that can be. It is preferable to use an ultraviolet curable adhesive especially as an energy-ray hardening-type adhesive. The energy ray-curable pressure sensitive adhesive generally contains an acrylic pressure sensitive adhesive and an energy ray polymerizable compound as main components. Usually, a crosslinking agent is further mix | blended and you may mix | blend a photoinitiator and a photosensitizer as needed.

In addition to the base polymer and crosslinking agent mentioned above, an adhesive composition is, for example, in order to adjust the adhesive force, cohesion force, viscosity, elasticity modulus, glass transition temperature, etc. of an adhesive, for example, resin which is a natural product or a compound, tackifying resin, antioxidant, Appropriate additives, such as a ultraviolet absorber, dye, a pigment, an antifoamer, a corrosion inhibitor, a photoinitiator, can also be mix | blended. Moreover, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

It is preferable that the thickness of an adhesive layer is 1-40 micrometers, but in order to obtain the thin polarizing plate which is the objective of this invention, it is preferable to apply it thinly in the range which does not impair workability and durability characteristics, and maintains favorable workability and the dimension of a polarizer In the point which suppresses a change, it is 3-25 micrometers more preferably. If the pressure-sensitive adhesive layer is too thin, the adhesiveness is lowered. If the pressure-sensitive adhesive layer is too thick, problems such as excess of the adhesiveness easily occur.

As for the adhesive used for formation of the adhesive layer in this invention, as for the said adhesive, it is preferable that all the storage elastic modulus in the temperature range of 23-80 degreeC are 0.15-1 MPa. As for the pressure-sensitive adhesive used for a normal image display apparatus or an optical film for image display apparatuses, the storage elastic modulus is only about 0.1 MPa, On the other hand, the preferable storage elastic modulus 0.15-1 MPa of the adhesive used for this invention is a high value. Becomes 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 manufacturing method of the polarizing plate of this invention, by using the adhesive which has a storage elastic modulus higher than the normal adhesive in the above-mentioned range, the dimensional change by shrinkage of the polarizing film which generate | occur | produces in high temperature environment can be suppressed small, and good durability It becomes possible to manufacture the polarizing plate to have suitably.

Moreover, in the manufacturing method of the polarizing plate of this invention, it does not specifically limit as a method of forming an adhesive layer in a polarizing film, The solution containing each component including said base polymer is apply | coated to the other surface of a polarizing film, After drying and forming an adhesive layer, you may laminate | stack and obtain the separator on which the mold release process, such as a silicone type, is given, or after forming an adhesive layer on a separator, you may transfer and laminated | stack on a polarizing film. In addition, when forming an adhesive layer in a polarizing film, you may perform an adhesion | attachment process, for example corona treatment etc. to at least one of a polarizing film and an adhesive layer as needed. Moreover, the surface of the formed adhesive layer is normally protected by the separator film which performed the mold release process, and a separator film is peeled before bonding this polarizing plate with a liquid crystal cell, another optical film, etc.

The polarizing plate manufactured as mentioned above may laminate | stack the optical film which has optical functions other than a polarizing plate on the protective film surface or an adhesive layer surface. As an example of such an optical film, the optical compensation film by which the liquid crystalline compound is apply | coated on the surface of a base material, the reflection type polarizing film which transmits the polarized light of some kind, and reflects the polarized light which shows the opposite property, polycarbonate Retardation film made of resin-based resin, retardation film made of cyclic polyolefin resin, film with anti-glare function having irregular shape on the surface, film with surface anti-reflection function, reflective film with reflection function on the surface, reflection function and transmission function And a transflective film having the same. As a commercial item which corresponds to the optical compensation film by which the liquid crystalline compound is apply | coated and orientated on the base material surface, WV film (made by Fujifilm), NH film (made by Nippon Petroleum Co., Ltd.), NR film (New Nippon Oil) Co., Ltd.) etc. are mentioned. As a commercial item corresponding to the reflection type polarizing film which transmits some kind of polarized light and reflects the polarized light which shows the opposite property, it can obtain from DBEF (3M company make, Sumitomo 3M Co., Ltd. in Japan), for example. ), APF (manufactured by 3M Corporation, 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 type resin, Arton film (made by JSR Corporation), Essina (made by Sekisui Chemical Co., Ltd.), Zeano film (Optes) Production).

When providing such another optical film in the protective film side of the said polarizing plate, both are laminated | stacked normally through an adhesive. Although the same thing as what was demonstrated above can be used for the adhesive in this case, a storage elastic modulus may not be very large. In addition, when providing another optical film in the adhesive layer side of the said polarizing plate, an optical film is adhere | attached by the adhesive layer. In this case, it is common to provide an adhesive layer for bonding to a liquid crystal cell on the outside of the optical film.

The polarizing plate with an adhesive layer manufactured by the manufacturing method of this invention has a form of a large roll material or a sheet | seat material normally, and is cut by the cutting tool with a sharp edge in order to obtain the polarizing plate which has a desired shape and a transmission axis. (Chip cut). For this reason, in the polarizing plate chip obtained by cutting | disconnecting, the state by which the polarizing film was exposed to the outside in the outer peripheral edge part arises.

When the polarizing plate chip in this state is applied to durability tests, such as a heat shock test, for example, compared with the polarizing plate generally used, ie, the polarizing plate which protected both surfaces of the polarizing film with the cellulose resin film etc., it is a problem called peeling and a crack. This tends to occur easily. In order to avoid such a problem, it is preferable that the polarizing plate chip obtained by this invention cuts an outer peripheral cross section continuously by the fly cut method etc.

Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these examples. In the examples,% and parts indicating content to amount of use are based on weight unless otherwise noted.

<Example 1>

(A) Preparation of Polarizing Film

After uniaxially stretching a polyvinyl alcohol film having a thickness of about 75 µm with an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more by about 5 times in a dry manner, and immersing in pure water at 60 ° C. for 1 minute while maintaining a tension state. , The weight ratio of iodine / potassium iodide / water was immersed in an aqueous solution of 0.1 / 5/100 for 60 seconds at 28 ° C. Thereafter, the weight ratio of potassium iodide / boric acid / water was immersed in an aqueous solution of 10.5 / 7.5 / 100 for 300 seconds at 72 ° C. Subsequently, it washed with 10 degreeC pure water for 5 second, and it dried at 90 degreeC for 180 second, and obtained the polarizing film in which iodine adsorption-orientated to polyvinyl alcohol.

(B) Preparation of Adhesive

Separately, in 100 parts of water, 3 parts of fully saponified polyvinyl alcohol (Kurarefobal 117H, Kuraray Co., Ltd.), acetacetyl group-modified polyvinyl alcohol (Kose Chemical Z-200, Japan Synthetic Chemicals, Ltd.) 3 parts), 0.18 parts of zinc chloride (sold from Nakaray Tesque Co., Ltd.), and 1.4 parts of glyoxal (sold from Nakaray Tesque Co., Ltd.) were dissolved to prepare a polyvinyl alcohol-based resin adhesive.

(C) Preparation of the polarizing plate

On one side of the obtained polarizing film, a 40-micrometer-thick film (KC4UY manufactured by Konica Minolta Opt Co., Ltd.) consisting of triacetyl cellulose subjected to saponification treatment was bonded with a nip roll through the adhesive. It dried at 38 degreeC for 5 minutes, maintaining the tension of the joined body at 320 N / m, and obtained the polarizing plate.

(D) Formation of pressure-sensitive adhesive layer

The pressure-sensitive adhesive layer in which the urethane acrylate oligomer and the isocyanate-based crosslinking agent were added to the copolymer of butyl acrylate and acrylic acid was formed on the release treatment surface of the polyethylene terephthalate film (separator) to which the release treatment was carried out. The pressure-sensitive adhesive layer was formed. The storage elastic modulus of the adhesive layer was 0.41 MPa at 23 degreeC, and 0.22 MPa at 80 degreeC. The sheet-like adhesive was bonded to the other side of the polarizing film of the polarizing plate produced as mentioned above, and it was set as the polarizing plate with an adhesive.

(E) Lamination of Retardation Film

A retardation film composed of a stretched film of norbornene-based resin, having an in-plane retardation of 140 nm (λ / 4) with respect to the wavelength of light (λ), and having a thickness of 25 μm (Esshina Film, Sekisui Chemical Co., Ltd.) Sheet-shaped acrylic adhesive was bonded together to one side of manufacture), and it was set as the retardation film with an adhesive. The storage elastic modulus of this acrylic adhesive was 0.05 MPa at 23 degreeC, and 0.04 MPa at 80 degreeC. The retardation film surface (surface in which the adhesive layer is not formed) of the said retardation film with an adhesive was bonded to the adhesive surface of the polarizing plate with an adhesive produced in said (D), and the adhesive polarizing plate with a phase difference function was produced.

The polarizing plate with pressure sensitive adhesive provided with the phase difference function produced in (E) was cut into the size of 40 mm x 40 mm, it was bonded to glass by the adhesive layer provided in the outer side of retardation film, and it was set as the evaluation sample.

<Examples 2-5 and Comparative Examples>

As shown in Table 1, the polarizing film was produced by changing the drying temperature and time of a polarizing film, and produced the polarizing plate with an adhesive layer similarly to Example 1.

<Reference Example>

Polarization in which the polyvinyl alcohol film was adsorbed and oriented in polyvinyl alcohol in the same manner as in Example (A) except that the drying conditions after the dyeing treatment, the boric acid treatment and the water washing were changed from 90 ° C. to 140 seconds. A film was obtained. On both surfaces of this polarizing film, the film of 40 micrometers in thickness which consists of triacetyl cellulose to which the same saponification process used in Example 1 (C) was given through the polyvinyl alcohol-type adhesive agent prepared in Example 1 (B) was carried out. It bonded by the nip roll. It dried at 50 degreeC for 5 minutes, maintaining the tension of the joined body at 320 N / m, and obtained the polarizing plate.

On one side of the obtained polarizing plate, the acrylic adhesive film whose storage elastic modulus at 23 degreeC is 0.05 MPa, and the storage elastic modulus at 80 degreeC is 0.04 MPa similar to what was used for (E) of Example 1, is bonded, and a polarizing plate with an adhesive layer I did. Retardation film of retardation film in which the acryl-type adhesive layer of the storage elastic modulus in 23 degreeC and the storage elastic modulus in 80 degreeC is 0.04 MPa which is the same as used in (E) of Example 1 on the adhesive surface was provided in one side. The surface (surface in which an adhesive layer is not formed) was bonded together, and the polarizing plate with an adhesive with which the phase difference function was provided was produced.

<Evaluation test>

When manufacturing each polarizing plate in an Example, a comparative example, and a reference example, 100 mm x 100 mm so that one side of a test member may be parallel to the extending | stretching axial direction of a polarizing film from the polarizing film before bonding to the film which consists of triacetyl cellulose. After extracting a test member having a size of, and maintaining the initial dimension (A) in a direction perpendicular to the stretching axis direction of the test member (TD direction) and the test member in a dry heat environment at 85 ° C. for 96 hours. From the dimension (B) in a TD direction, the dimension change rate of a polarizing film was computed by the following formula.

Dimensional rate of change (%) = (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 for 96 hours in 85 degreeC dry heat environment, and the deformation distance of the edge part in a TD direction as a deformation state of a polarizing plate edge part (from an edge part). (Mm), the ascending height of the end in the TD direction (the height at the highest top at the end and the height of the horizontal at the main) (Micrometer) was measured, and it evaluated by visually observing the distortion of the said edge part. The results are shown in Table 1.

From the results shown in Table 1, when the dimensional change rate of the polarizing film immediately before transparent protective film bonding exceeded 2.7% like the comparative example, it turns out that distortion is large and the reflected light was observed and observed by the eye and distorted. Moreover, when the 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.

Claims (3)

The manufacturing method of the polarizing plate which consists of polyvinyl alcohol-type resin, and laminates a transparent protective film only on one side of the polarizing film whose dimension change rate is 2.7% or less through an adhesive bond 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 on the other surface of a polarizing film.