WO2009087942A1

WO2009087942A1 - Polarizer

Info

Publication number: WO2009087942A1
Application number: PCT/JP2008/073919
Authority: WO
Inventors: Kiyoshi Muto; Shinichi Kawamura
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2008-01-08
Filing date: 2008-12-24
Publication date: 2009-07-16
Also published as: CN101910890A; JP5429777B2; TW200941050A; JP2009186995A; KR20100117591A

Abstract

A polarizer is provided which, after bonded to a liquid-crystal cell, does not pose a problem such as the lifting of an edge part of the polarizer even when exposed to various environments. The polarizer comprises a polarizing film made of a polyvinyl alcohol resin, a pressure-sensitive adhesive layer superposed on each side thereof, and a protective film superposed on at least one side of the film through the pressure-sensitive adhesive layer. The polarizer is intended to be applied to a liquid-crystal cell. Of the pressure-sensitive adhesive layers, the pressure-sensitive adhesive layer located on the side near to the liquid-crystal cell has a storage elastic modulus of 0.15-1 MPa as determined in the temperature range of 23-80°C and has a peel strength in peeling from the polarizing film of 11 N/25 mm or higher.

Description

Specification

Polarizing plate technology

The present invention relates to a polarizing plate in which a pressure-sensitive adhesive layer is laminated on both sides of a polarizing film made of a polybulualcohol resin, and a protective film is laminated on at least one side thereof. Background art

A polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. Conventionally, a polarizing film made of polyvinyl alcohol resin and a transparent protective film made of triacetyl cellulose are used as such polarizing plates. In recent years, notebook personal computers for liquid crystal display devices, With the development of mobile phones and other mopile devices, as well as the development of large-screen TVs, there is a need to reduce the thickness and weight. In addition, because of the wide range of places used due to portability, there is a need for improved durability at the same time.

In general, a polarizing film is produced by impregnating a polybulal alcohol resin with a dichroic dye typified by iodine or the like and uniaxially stretching at a high magnification. For this reason, when a polarizing film is exposed to a dry heat environment, a large dimensional change with shrinkage occurs. For example, when a dimensional change rate before and after heating at 100 ° C. for 2 hours is measured for a polarizing film as described in Japanese Patent Laid-Open No. 6-10092 2 (Patent Document 1) A large shrinkage exceeding 10% is observed. For this reason, the dimensional change of the polarizing film is usually reduced by laminating a transparent protective film on both sides of the polarizing film via an adhesive layer or the like to produce a polarizing plate. Patent Document 1 describes the rate of dimensional change before and after heating at 100 ° C. for 2 hours for a polarizing plate in which triacetyl cellulose films are laminated on both sides of a polarizing film, but the shrinkage is 2% or less. It can be seen that the contraction is suppressed. JP-A-6-59 1 2 3 (Patent Document 2) describes a change in dimensions before and after heating a polarizing plate in which triacetyl cellulose cellulose film is laminated on both sides of a polarizing film at 80 ° C. for 4 hours. Although the rate is described, the shrinkage is 0.3% or less, which indicates that the shrinkage is suppressed.

However, in recent years, a polarizing plate in which a transparent protective film is laminated only on one surface of a polarizing film is also required because of its thin and light weight. Such a polarizing plate has been exposed to a dry high temperature environment. At the time, the shrinkage of the polarizing film could not be suppressed, and there was a tendency for defects to occur. For this reason, in the state which provided the adhesive layer in the polarizing film surface of the polarizing plate which laminated | stacked the transparent protective film only on one side of the polarizing film in this way, and bonded the adhesive layer to the liquid crystal cell, or When another optical film such as a retardation film is attached to the adhesive layer, and further exposed to a dry high temperature environment with the adhesive layer attached to the liquid crystal cell, the adhesive at the end of the polarizing plate is removed. The screen could be peeled off, or the edge of the polarizing plate could rise and distort the screen display. These defects were thought to be caused by the fact that only one side of the polarizing film was restrained by the protective film.

Therefore, the present inventors examined whether the problem could be solved by forming an adhesive layer on both sides of the polarizing film. An example in which an adhesive layer is formed on both sides of a polarizing film and a protective film is laminated is disclosed in, for example, Japanese Patent Laid-Open No. 5-212888 (Patent Document 3). Since crimping is necessary, there is a problem that the manufacturing becomes complicated. Further, in Japanese Laid-9 one 1 0 5 8 1 4 (Patent Document 4), the relaxation modulus in the relaxation time 1 0 ⁵ seconds 1 5 X 1 0 ⁵ dyn / c ² or less (0.1 5 (MPa or less) is shown as an example of applying an adhesive layer to an optical film. A liquid crystal cell using a polarizing plate formed by laminating such an adhesive on both sides of a polarizing film is heat resistant. When exposed to the environment, problems such as peeling off of the protective film and contraction of the polarizing film and floating of the edge of the polarizing plate occurred.

On the other hand, a pressure-sensitive adhesive having an increased life rate of stored ammunition I ¹ is also known. Is 0.3 MP a The pressure-sensitive adhesive for polarizing plates as described above is disclosed, and Japanese Patent Application Laid-Open No. 2 0 06-30 09 1 14 (Patent Document 6) discloses an acrylic copolymer and an active energy ray in a side chain. A pressure-sensitive adhesive for polarizing plates is prepared by irradiating an adhesive material containing an acrylic copolymer having a polymerizable group with active energy rays and having a storage elastic modulus at 23 ° C. of 0.3 to 10 MPa. It is disclosed. In these literatures, such a storage layer is used as an adhesive for adhering a three-layer polarizing plate in which triacetyl cellulose is bonded to both sides of a polyvinyl alcohol polarizing film (polarizer) to an optical component such as a liquid crystal cell. It has been proposed to use a material with a high elastic modulus. Disclosure of the invention

The present invention has been made in order to solve the above-described problems when the pressure-sensitive adhesive layer is formed on both surfaces of the polarizing film, and the object is to paste the liquid crystal cell to obtain a liquid crystal panel. In this case, it is an object of the present invention to provide a polarizing plate that does not cause problems such as floating of the end portion of the polarizing plate even when exposed to various environmental conditions.

In the polarizing plate of the present invention, a pressure-sensitive adhesive layer is laminated on both sides of a polarizing film made of polyvinyl alcohol resin, and a protective film is further laminated on at least one side of the polarizing film via the pressure-sensitive adhesive layer, and bonded to a liquid crystal cell. Among the pressure-sensitive adhesive layers, the pressure-sensitive adhesive layer close to the liquid crystal cell has a storage modulus of 23 ° C. or more and 80 ° C. or less in the temperature range. 15 MPa or more and IMPa or less, and the peel strength against the polarizing film is 1 1 NZ 25 mm or more. Here, the pressure-sensitive adhesive layer on the side close to the liquid crystal cell preferably has a thickness of 1 μm or more and 10 μm or less.

According to the present invention, there is also provided a liquid crystal display device in which the polarizing plate is disposed on at least one side of the liquid crystal cell. Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate according to the present invention. FIG. 2 is a schematic cross-sectional view showing an example in which the polarizing plate of the present invention is applied to a liquid crystal cell.

FIG. 3 is a schematic cross-sectional view showing another example in which the polarizing plate of the present invention is applied to a liquid crystal cell, and corresponds to the layer structure of an evaluation sample in Examples and Comparative Examples.

Explanation of symbols

1 first adhesive layer (liquid crystal cell side), 2 polarizing film, 3 second adhesive layer (opposite side of liquid crystal cell), 5 first protective film, 6 second protective film, 7 third Adhesive layer, 10 polarizing plate, 20 liquid crystal cell (glass). BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate according to the present invention. As shown in this figure, the polarizing plate 10 of the present invention has a first pressure-sensitive adhesive layer 1 and a second pressure-sensitive adhesive layer 3 laminated on both sides of a polarizing film 2 made of polyvinyl alcohol resin, respectively. The first protective film 5 and Z or the second protective film 6 are laminated on at least one surface thereof through the pressure-sensitive adhesive layer. As for the protective films 5 and 6, only one side may be arrange | positioned and both may be arrange | positioned. Such a polarizing plate constitutes a liquid crystal display device by being bonded to a liquid crystal cell, for example. In the present invention, the first adhesive layer 1 that is close to the liquid crystal cell when bonded to the liquid crystal cell is stored in a temperature range where the storage elastic modulus is 23 ° C. or more and 80 ° C. or less. . 15 MPa or more and IMPa or less, and the peel strength with respect to the polarizing film is 1 1 N 2 25 mm or more. <Polarizing film>

The polarizing film used in the present invention is made of a polybulualcohol resin, and specifically, a film made of such a polybulualcohol resin (simply polybivinylalcohol). Nyl alcohol rosin film) is dyed with uniaxially stretched dichroic dye, and the dichroic dye is adsorbed and oriented.

The polyvinyl alcohol resin that constitutes such a polarizing film is usually obtained by saponifying a poly (acetate butyl) resin. The saponification degree of the poly Bulle alcohol resin is usually 8 5 mole ⁰ /. Above, preferably 90 mol. / ₀ or more, more preferably 9 9-1 0 0 mole ^_0/0. Polyvinyl acetate resin includes poly (vinyl acetate), which is a single polymer of butyl acetate, and copolymers of butyl acetate and other monomers copolymerizable therewith, such as ethylene monoacetate butyl copolymer. Etc. Examples of other monomers copolymerizable with vinyl acetate include olefins including ethylene, unsaturated carboxylic acids, butyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polybulualcohol resin is usually in the range of 10:00 to 10:00, and preferably in the range of 1500 to 50000.

These polyvinyl alcohol resins may be modified, and for example, polyvinyl formal modified with aldehydes, polybulacetal, polyvinyl petital, and the like may be used. Usually, an unstretched film is used as a starting material for the production of a polarizing film. The film is a polybulal alcohol dew film having a thickness of 20 to 100 μm, preferably 30 to 80 μιη. Industrially, the width of the film is practically from 1500 to 400 mm. A polarizing film can be obtained by treating this unstretched film in the order of swelling treatment, dyeing treatment, boric acid treatment, and water washing treatment, uniaxially stretching in the steps up to boric acid treatment, and finally drying. The thickness of the polarizing film thus obtained is, for example, 5 to 50 m.

There are two main methods for producing a polarizing film. In the first method, a polyvinyl alcohol resin film is uniaxially stretched in air or in an inert 1 "raw 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. In the second method, the unstretched poly (vinyl alcohol) resin film is subjected to a solution treatment in the order of a swelling treatment with an aqueous solution, followed by a dyeing treatment step, a boric acid treatment step, and a water washing treatment step. The boric acid treatment process This is a method in which uniaxial stretching is performed wet in the step z or the previous step, followed by drying.

In any method, the uniaxial stretching may be performed in one step, or may be performed in two or more steps, but is preferably performed in a plurality of steps. As the 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, hot roll stretching method (for example, Patent No. 2 7 3 1 8 1 3) and tenter stretching. Basically, the process order is as described above, but there are no restrictions on the number of treatment baths or treatment conditions. Further, steps not described in the first and second methods may be added for another purpose. Examples of such processes include boric acid treatment followed by immersion treatment with an aqueous iodide solution not containing boric acid (iodide treatment) or immersion treatment with an aqueous solution containing zinc boric acid not containing boric acid (zinc treatment). ) And so on.

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 in such a range that these objectives can be achieved and in which defects 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 of 20 to 70 ° C., preferably 30 to 60 ° C. The film immersion time is from 30 to 300 seconds, preferably from 60 to 240 seconds. When swelling an unstretched original film from the beginning, for example, 10 to 50. C, preferably by immersing the film in an aqueous solution at 20 to 40 ° C. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds.

In the swelling process, problems such as film swelling in the width direction and wrinkles in the film are likely to occur, so widening rolls (expander rolls), spiral rolls, crown rolls, cross guiders, bend bars, tenter clips, etc. It is preferable to transport the film while removing the film with a known widening apparatus. In order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled with an underwater shower, or the edge position control device for EPC (film position control) prevents film meandering. It is also useful to use a combination of devices. 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 rolls before and after the treatment tank in order to eliminate sagging of the film in the transport direction. In addition to pure water, the swelling treatment bath used is boric acid (for example, described in JP-A-10-153709), salty salt (for example, described in JP-A-06-281816), inorganic acid, inorganic salts, water-soluble organic solvent, also an aqueous solution obtained by adding and alcohols in the range of 0.01 to 0.1 mass ^_0/0 can 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 in such a range that these objectives can be achieved and in which defects such as extreme dissolution and devitrification of the base film do not occur. When iodine is used as the dichroic dye, for example, iodine-iodine / water at a mass ratio of 10 to 45 ° C, preferably 20 to 35 ° C, and a mass ratio of 0.003 to 0.2 / 0.1. Use an aqueous solution with a concentration of ~ 10/100 for 30-600 seconds, preferably 60-300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used. In addition, other iodides may be used in combination with iodide power. In addition, compounds other than trioxides such as boric acid, salt / zinc, salt / cobalt, etc. may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. If 100 parts by mass of water contains 0.003 parts by mass or more of iodine, it can be regarded as a dyeing tank.

When a water-soluble dichroic dye is used as the dichroic dye, for example, the dichroic dye Z water = 0.001 to 20 to 80 ° C, preferably 30 to 70 ° C in a mass ratio. 0. A 1/100 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 auxiliary agent, for example, an inorganic salt such as sodium sulfate, a surfactant, etc. May be. 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 such as making the ep roll before and after the dyeing tank have a peripheral speed difference. In addition, as in the S treatment process, widening rolls (expander rolls), spiral rolls, crown rolls, cross guiders, bend bars, etc. can be installed in the dyeing bath and at the Z or bath entrance.

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 mass of boric acid with respect to 100 parts by mass of water. When the dichroic dye is iodine, it is preferable to contain 1 to 30 parts by mass of iodide.

Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, such as salt-zinc, salt-cobanole, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist. The boric acid treatment is carried out for water resistance and color adjustment (to prevent bluish tint) by crosslinking. When boric acid treatment is performed for water resistance by cross-linking, a cross-linking agent such as darioxal or glutaraldehyde can be used as required in addition to or together with boric acid. In addition, 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 is sometimes referred to as complementary color treatment, re-dyeing treatment, or the like.

This boric acid treatment is performed by appropriately changing the concentration of boric acid and iodide and the temperature of the treatment bath according to the purpose. Although boric acid treatment for water resistance and folic acid treatment for hue adjustment are not particularly distinguished, they can be carried out under the following conditions. When the raw film is subjected to swelling treatment, dyeing treatment, boric acid treatment, and the boric acid treatment is aimed at water resistance by crosslinking, boric acid is added to 3 to 1 per 100 parts by mass of water. A boric acid treatment bath containing 0 parts by mass and 1 to 20 parts by mass of iodide is used. Usually, it is carried out at a temperature of 50 to 70 ° C, preferably 55 to 65 ° C. The immersion time is 90 to 300 seconds. When the prestretched film is subjected to dyeing treatment and boric acid treatment, the temperature of the boric acid treatment bath is usually 50 to 85 ° C, preferably 55 to 80 ° C.

After boric acid treatment for water resistance, fluoric acid treatment for hue adjustment may be performed. For example, when the dichroic dye is iodine, for this purpose, boric acid treatment containing 1 to 5 parts by mass of boric acid and 3 to 30 parts by mass of iodide with respect to 100 parts by mass of water. A bath is used, usually at a temperature of 10 to 45 ° C. The immersion time is usually 3 to 300 seconds, preferably 10 to 240 seconds. Subsequent boric acid treatment for hue adjustment is usually performed at a lower boric acid concentration, higher iodide concentration, and lower temperature than boric acid treatment for water resistance.

When the dichroic dye is iodine, a treatment with an iodide solution may be performed to adjust the hue. For example, a treatment bath having 0.5 to 5 parts by mass of potassium iodide with respect to 100 parts by mass of water is used, and is usually performed at a temperature of 5 to 40 ° C. The immersion time is usually 3 to 300 seconds, preferably 5 to 120 seconds.

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 hydrofluoric acid treatment tank 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 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, for example, about 4 to 7 times, preferably 4.5 to 6.5 times. The cumulative draw ratio here means how much the length direction reference length of the original film has reached in all the films after the drawing process, for example, lm in the original film. If all the stretched parts are 5 m in the film after completion of the stretching process, the cumulative stretching ratio at that time will be 5 times. The total draw ratio is (length of the polarizing film after production) / (length of the original film) It can also be expressed as a ratio.

After boric acid treatment, washing with water is performed. The water washing treatment includes, for example, a method in which a polyvinyl alcohol resin film treated with boric acid for water resistance and / or hue adjustment is immersed in water, a method in which water is sprayed as a shower, a method in which immersion and spraying are used in combination, etc. Is done by. The temperature of water 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 hydrofluoric acid process. When the hydrofluoric acid treatment step is composed of a plurality of boric acid treatment steps, the film is stretched in the first or second boric acid treatment step, and the next of the hydrofluoric acid treatment step in which the stretch treatment is performed. Force to control tension in each process from hydrofluoric acid treatment process to water washing process The film is stretched in the boric acid treatment process from the first to the third stage, and the stretch treatment is followed by It is preferable to control the tension in each process from the boric acid treatment process to the water washing process, but industrially, the film is stretched in the first or second stage of the hydrofluoric acid treatment process. It is more preferable to control the tension in each step from the boric acid treatment step to the water washing step subsequent to the hydrofluoric acid treatment step in which the stretching step has been performed. In addition, when the above-described iodide treatment or zinc treatment is performed after the boric acid treatment, tension control can also be performed for these steps.

The tension in each step from the swelling treatment to the water washing treatment may be the same or different. The tension on the film in the tension control is not particularly limited, and is 15 per unit width. It is appropriately set within the range of 0 to 2 00 0 N / m, preferably 6 ° 0 to 1 5 0 ON / m. When the tension is less than 15 ON ^ m, the film tends to be easily crushed. On the other hand, the tension exceeds 2 00 0 N / m In other words, problems such as film breakage and shortened life 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 it is unavoidably 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 process is preferably carried out in a large number of stages by changing the tension little by little, but is usually performed in 2 to 3 stages due to equipment limitations. When performed in two stages, the tension in the first stage is preferably set from the range of 600 to 15 ON / m, and the tension in the second stage is preferably set from the range of 2500 to: 120,000 NZm. If the tension is too large, the film will be broken more, and if it is too small, the occurrence of wrinkles will increase. Further, it is preferable to set the drying temperature of the former stage from the range of 30 to 90 ° C and the drying temperature of the latter stage from the range of 50 to 100 ° C. If the temperature is too high, the film will break more, and the optical properties will deteriorate. If the temperature is too low, streaks will increase, which is undesirable. The drying treatment temperature can be set to, for example, 60 to 600 seconds, and the drying time in each stage may be the same or different. If the time is too long, it is not preferable in terms of productivity, and if the time is too short, drying is insufficient, which is not preferable.

The dimensional change rate of the polarizing film thus obtained is 2.7% or less, preferably 1.5% or less, and more preferably 1.0% or less. Note that the rate of dimensional change of the polarizing film is relative to the stretching axis direction of the test piece having a size of 10 O mm × 100 mm so that one side of the test piece is parallel to the stretching axis direction of the polarizing film. From the initial dimension A in the vertical direction (TD direction) and the dimension B in the TD direction after holding the specimen for 96 hours in a dry heat environment of 85 ° C, the following formula is used.

Dimensional change rate (%) = (A- B) / A X 1 0 0

A polarizing film having a dimensional change rate within the preferred range described above can be obtained, for example, by controlling the drying temperature Z or the drying time of the polarizing film. Further, the polarizing film obtained through the polarizing film preparation step is not particularly limited with respect to the moisture content, but is preferably in the range of 3 to 14% by mass, and more preferably It is preferably in the range of 3 to 10% by mass, particularly preferably in the range of 3 to 8% by mass. When the moisture content of the polarizing film is less than 3% by mass, it is difficult to handle because the polarizing film is brittle and easily tears along the stretching direction, and the moisture content of the polarizing film exceeds 14% by mass. In some cases, the polarizing film may easily shrink in a dry heat environment. The moisture content of the polarizing film can be calculated, for example, from the change in mass before and after being held at 105 ° C. for 1 hour under dry heat. A polarizing film having a moisture content within the above-mentioned preferred range can be obtained, for example, by controlling the drying temperature and the drying time of the polarizing film.

In this way, the polybulualcohol resin film is uniaxially stretched, dyed with a dichroic dye and treated with boric acid to obtain a polarizing film made of polybulcoalcohol resin. The thickness of this polarizing film is usually in the range of 5 / m to 50 m. Adhesive layer>

In the present invention, the pressure-sensitive adhesive layers 1 and 3 are laminated and formed on both surfaces of the polarizing film 2 made of the polyvinyl alcohol resin produced by the method described above. The first pressure-sensitive adhesive layer 1 on the side close to the liquid crystal cell when bonded to the liquid crystal cell has a temperature range of 23 ° C. or more and 80 ° C. or less of 0.15 MPa or more and 1 MP. It has a storage elastic modulus of a or less. If the storage elastic modulus is less than 0.15 MPa, the pressure-sensitive adhesive layer is too soft and it becomes difficult to suppress the shrinkage of the polarizing film that occurs when the polarizing film is exposed to a heat-resistant environment. On the other hand, when IMPa is exceeded, a polarizing plate (with a pressure-sensitive adhesive layer laminated on both sides of the polarizing film and a protective film laminated on at least one side of the polarizing film via the pressure-sensitive adhesive layer) is pasted on the liquid crystal cell. When exposed to a heat-resistant environment in a heated state, a deformation state that rises at the end of the polarizing plate tends to be easily observed. By making the pressure-sensitive adhesive layer having such properties into the first pressure-sensitive adhesive layer 1 that is close to the liquid crystal cell when being bonded to the liquid crystal cell, the shrinkage of the polarizing film is suppressed, and the end of the polarizing plate It is also possible to effectively suppress the swell phenomenon of the part. Such a pressure-sensitive adhesive layer is formed using various pressure-sensitive adhesives conventionally used for liquid crystal display devices such as acrylic, rubber-based, urethane-based, silicone-based, and polyvinyl ether-based pressure-sensitive adhesives. Can do. In addition, energy ray curable adhesives and thermosetting adhesives may be used. Among them, adhesives based on acrylic resins with excellent transparency, weather resistance, heat resistance, etc. (hereinafter referred to as “acrylic adhesives”). (Referred to as “agent”). Adhesives are also called pressure-sensitive adhesives. When they are adhered to the surface of other substances simply by pressing them, and they are peeled off from the adherend surface, there is almost no trace as long as the adherend has sufficient strength. Is a viscoelastic body that can be removed without any problem

The acrylic adhesive is not particularly limited, but (meth) acrylic acid propyl, (meth) acrylic acid ethyl, (meth) acrylic acid isooctyl, (meth) acrylic acid 2-ethylhexyl A (meth) acrylic acid ester base polymer or a copolymer base polymer using two or more of these (meth) acrylic acid esters is preferably used. In addition, polar monomers are copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, (meth) acrylic acid 2-hydroxypropyl, (meth) hydroxyl acrylate, (meth) acrylamide, Ν, Ν-dimethylaminoethyl (meth) acrylate And monomers having a functional group such as a carboxyl group, a hydroxyl group, an amide group, an amino group, and an epoxy group, such as glycidyl (meth) acrylate. These acrylic pressure-sensitive adhesives can of course be used alone, but usually a crosslinking agent is used in combination. The cross-linking agent is a divalent or polyvalent metal salt that forms a carboxylic acid metal salt with a carboxyl group, or a polyamine compound that forms an amide bond with a strong lpoxyl group. A polyepoxy compound, a polyol compound that forms an ester bond with a carboxyl group, a polyisocyanate compound that forms an amido bond with a carboxyl group, etc. Illustrated. 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 the irradiation with energy rays to adhere to an adherend such as a film. It is a pressure-sensitive adhesive that adheres and cures when irradiated 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 ray curable pressure-sensitive adhesive is generally composed mainly of an acrylic pressure-sensitive adhesive and an energy beam polymerizable compound. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator and a photosensitizer can be blended.

The adhesive layer used in ordinary image display devices or optical films therefor has a storage elastic modulus of at most about 0. IMP a, compared to the first adhesive layer used in the present invention. The storage elastic modulus of the agent layer is remarkably high between 0.15 MPa and IMP a. Here, the storage elastic modulus is “0.15 MPa or more and IMP a or less in the temperature range of 23 ° C. or more and 80 ° C. or less”. Means to take. The storage elastic modulus usually decreases gradually as the temperature rises. Therefore, if both the storage elastic modulus at 23 ° C and 80 ° C are within the above range, the storage elastic modulus in the above range is You can see that. If the storage elastic modulus at 80 ° C is less than 0.15 MPa, the polarizing film shrinks when it is made into a polarizing plate and then bonded to a liquid crystal cell and exposed to a heat-resistant environment. On the other hand, when the storage elastic modulus at 23 ° C exceeds IMpa, after forming a polarizing plate, it is bonded to a liquid crystal cell and exposed to a heat-resistant environment, or between the polarizing film and the protective film, or the polarizing plate. There is a risk of problems such as peeling or generation of bubbles between the cell and the liquid crystal cell.

In a temperature range of 23 ° C or higher and 80 ° C or lower, 0.115MPa or more and IMPa or less of stored ammunition 1. To make an adhesive layer with a life rate, for example, the normal adhesive as described above, In particular, an energy- and linear-curing adhesive that is cured by irradiating energy rays after blending an acrylic adhesive with an oligomer, specifically a urethane atollate oligomer, can be used. As the energy ray, ultraviolet rays are preferable. A sheet-like pressure-sensitive adhesive whose storage elastic modulus has been increased, that is, hardened by blending an ultraviolet curing component, is known per se and can be obtained from a pressure-sensitive adhesive manufacturer (for example, see also Patent Documents 5 and 6 above). .

Here, the storage elastic modulus) can be measured using a commercially available viscoelasticity measuring device. For example, a numerical value obtained by a torsional shear method using the following device is adopted.

Specimen: 8 πιπιΦ X 1 mm thick cylinder

Measuring instrument: DYNAMI C ANALYZER RDA I I (REOM ETR I C made)

Frequency: 1 Hz

Distortion amount: 1%

For the pressure-sensitive adhesive layer defined in the present invention, the adhesive strength, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. of the pressure-sensitive adhesive layer are adjusted as necessary according to the above-mentioned base polymer and crosslinking agent. For example, appropriate additives such as resins that are natural products and synthetic materials, tackifying resins, antioxidants, ultraviolet absorbers, dyes, pigments, antifoaming agents, corrosion inhibitors, photopolymerization initiators, etc. Can also be blended. Furthermore, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by containing fine particles.

In the present invention, the thickness of the first pressure-sensitive adhesive layer 1 on the side close to the liquid crystal cell is preferably 1 μm or more and 1 μμπι or less. When the thickness exceeds 10 μπι, a polarizing plate (with a pressure-sensitive adhesive layer laminated on both sides of the polarizing film and a protective film laminated on at least one side of the polarizing film via the adhesive layer) is attached to the liquid crystal cell. After exposure, when exposed to a heat-resistant environment, there is a tendency for appearance problems such as the surface of the polarizing plate to be deformed into a cocoon skin. On the other hand, if it is less than Ιμπι, problems such as a decrease in adhesiveness and the occurrence of bubbles when the polarizing plate is bonded to the liquid crystal cell are likely to occur.

The storage modulus of the second pressure-sensitive adhesive layer 3 on the side far from the liquid crystal cell is not particularly limited, but this is also 0.15 MPa or more in the temperature range of 23 ° C to 80 ° C. It is preferable that the storage inertia ratio is exhibited. Second adhesive layer 3 May exhibit a higher storage elastic modulus than that of the first pressure-sensitive adhesive layer 1, for example, a storage elastic modulus of about 5 MPa. The thickness of the second pressure-sensitive adhesive layer 3 is not particularly limited, but it is preferable that the thickness of the second pressure-sensitive adhesive layer 3 is as small as possible to express an appropriate pressure-sensitive adhesive property, because shrinkage of the polarizing film can be suppressed when exposed to a heat-resistant environment. The thickness is preferably not less than 1 μm and not more than 30 μπι, more preferably not less than 1 μm and not more than 20 m.

In the polarizing plate of the present invention, the first pressure-sensitive adhesive layer 1 needs to have a peel strength with respect to the polarizing film 2 of 11 N / 25 mm or more. This peel strength is an index indicating the adhesion between the polarizing film 2 and the first pressure-sensitive adhesive layer 1. 1 1 NZ 25 If less than 5 mm, a polarizing plate (with a pressure-sensitive adhesive layer laminated on both sides of the polarizing film, When a protective film is laminated on at least one side of the adhesive layer via a pressure-sensitive adhesive layer), it is peeled off between the polarizing film and the pressure-sensitive adhesive layer when exposed to a heat-resistant environment Problems such as bubbles may occur. If the peel strength is too high, rework (when attaching a polarizing plate to a liquid crystal cell, it tends to be difficult to reattach the polarizing plate due to a bonding error, etc.). 5 mm or less. The peel strength can be adjusted by the amount of the cross-linking agent combined in the pressure-sensitive adhesive. Specifically, the peel strength can be increased by increasing the blending amount of the crosslinking agent, and the peel strength can be decreased by decreasing the blending amount of the crosslinking agent.

In the present invention, the peel strength is measured by laminating a pressure-sensitive adhesive layer on both sides of a polarizing film, cutting out a 25 mm wide test piece without using a protective film, and using an autograph made by Shimadzu Corporation. 2 Perform under the conditions of 3 ° C, 50% relative humidity, peeling speed of 30 mm and peeling angle of 180 °. Here, since it is difficult to maintain the shape of the pressure-sensitive adhesive layer alone, the pressure-sensitive adhesive layer is measured in a state in which another film is laminated on the pressure-sensitive adhesive layer for which peel strength is to be obtained. As a specific example, with a pressure-sensitive adhesive layer laminated on a polarizing film, a plastic film is pasted on the pressure-sensitive adhesive layer whose peel strength is to be obtained, and the other pressure-sensitive adhesive layer is pasted on glass. Strength when peeling the plastic film together with the adhesive layer from the polarizing film Measure.

In the method for producing a polarizing plate of the present invention, the method for laminating (forming) the pressure-sensitive adhesive layer on the polarizing film is not particularly limited. For example, each component described above may be toluene or ethyl acetate. A pressure-sensitive adhesive composition dissolved or dispersed in an organic solvent such as the above is applied directly to the surface of the polarizing film and dried to form a pressure-sensitive adhesive layer, and then a silicone-based separator is applied. It may be obtained by laminating, or after forming an adhesive layer on a separator, it may be transferred to a polarizing film and laminated. In the case of using an energy ray curable pressure sensitive adhesive, a pressure sensitive adhesive composition containing an energy ray curable component such as urethane acrylate oligomer is applied and dried, and then the energy component is irradiated to radiate the cured component. Harden. In addition, when forming the pressure-sensitive adhesive layer on the polarizing film, at least one of the polarizing film and the adhesive layer may be subjected to an adhesion treatment, such as a corona treatment, if necessary. In addition, the surface of the formed adhesive layer is usually protected by a separator film that has been subjected to a release treatment, and the separator film is applied before the protective film described later is laminated or when the protective film is not laminated. Is peeled off before laminating the polarizing plate to a liquid crystal cell or optical film.

In the polarizing film having the pressure-sensitive adhesive layer provided on both sides as described above, a protective film is laminated on at least one side of the polarizing film via the pressure-sensitive adhesive layer. The protective film may be a non-oriented film of resin, or may be a film that is oriented to develop a retardation. For example, cycloolefin resin film, cellulose acetate resin film, polyester resin film such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene terephthalate, polycarbonate resin film, acrylic resin film, polypropylene film, etc. The film currently used can be mentioned.

Cycloolefin fin resin that can be used for the protective film in the polarizing plate of the present invention Is a thermoplastic resin (also referred to as a thermoplastic cycloolefin resin) having a monomer unit composed of cyclic polyolefin (cycloolefin) such as norbornene and polycyclic norbornene monomers. In the present invention, the cycloolefin resin may be a hydrogenated product of the above-mentioned ring-opening polymer of cycloolefin or a ring-opening copolymer using two or more kinds of cycloolefins. It may be an addition polymer with an aromatic compound having Those having a polar group introduced are also effective.

When a copolymer of cycloolefin and a chain olefin or / and an aromatic compound having a bur group is used, examples of the chain olefin include ethylene and propylene, and also an aromatic group having a vinyl group. Examples of the compound include styrene, hypermethylstyrene, and nuclear alkyl-substituted styrene. In such co-polymers, Yunitto 5 0 mol% of monomers comprising less from the Shikuroorefuin (preferably 1 5 to 5 0 mole ^_0/0) may be used. In particular, in the case of using a terpolymer of cycloolefin, a chain-shaped polyolefin and an aromatic compound having a bur group, the monomer unit comprising cycloolefin can be made in a relatively small amount as described above. In such terpolymers, units of monomers consisting of linear Orefin usually 5-8 0 mole ^_0/0, Yunitto aromatics or Ranaru monomers having Bulle group is usually 5 to 8 0 mol ^_0/0.

Cycloolefin resins are available on the market, such as Topas (manufactured by Ticona), Arton (manufactured by JSR), ZEONOR (manufactured by Nippon Zeon), ZEONEX (manufactured by Nippon Zeon) )), And Apel (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cycloolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. Also, commercial products of pre-formed cycloolefin resin films such as Essina (manufactured by Sekisui Chemical Co., Ltd.), SCA 40 (manufactured by Sekisui Chemical Co., Ltd.), Xenoah Film (manufactured by Optes Co., Ltd.) You can use it. The cycloolefin resin film may be uniaxially or biaxially stretched. By stretching, an arbitrary retardation value can be imparted to the cycloolefin resin film. Stretching is usually carried out continuously while rolling out the film roll, and in the heating furnace, the roll is stretched in the direction of travel of the roll, in the direction perpendicular to the direction of travel, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cycloolefin resin to the glass transition temperature + 100 ° C. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin resin film is in a roll state, the films tend to adhere to each other and easily cause blocking. Therefore, a protective film is usually attached to form a 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 applied to the surface to be bonded to the polarizing film. Is preferred. Of these, plasma treatment and corona treatment which can be carried out relatively easily are suitable.

The cellulose acetate resin that can be used for the protective film is a portion of cellulose acetate or a completely esterified 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, for example, Fujitac TD 40 UZ (Fuji Film Co., Ltd.), KC 4 UY (Koni Power Minolopt Co., Ltd.) or the like is preferably used. be able to.

In addition, in the polarizing plate of the present invention, a cellulose acetate resin film imparted with retardation characteristics as a protective film is also preferably used. WV BZ 4 3 8 (manufactured by Fuji Film Co., Ltd.), KC 4 FR-1 ( Koni-power Minoltaput Co., Ltd.). Cellulose acetate is also called acetyl cellulose and cellulose acetate.

The protective film provided with such retardation characteristics has both the characteristics as a protective film and the characteristics as a retardation film. But mainly the phase When using a film having only an action as a difference film, a film showing the characteristics as a protective film and a film showing the characteristics as a retardation film are laminated to form the protective film of the present invention. You can also. Thus, the protective film of the present invention can be composed of only one film, and can be a laminate of two or more films.

On the other hand, a cellulose acetate resin film may be stretched to impart a phase difference. Furthermore, this cellulose acetate resin film is usually subjected to saponification treatment in order to enhance the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an aqueous solution of alkaline power such as sodium hydroxide or lithium hydroxide can be employed. In addition, a reflective polarizing film that transmits certain kinds of polarized light and reflects polarized light that exhibits the opposite property can be used as a protective film. Specifically, for example, there can be mentioned a reflective polarizing film in which multiple layers of at least two kinds of polymer thin films are alternately laminated and utilizing the reflectance anisotropy due to the refractive index anisotropy. 'Examples of such a reflective linearly polarizing film include the DBEF series sold by 3M Corporation [Sumitomo 3EM Co., Ltd. in Japan].

The surface of the protective film may be subjected to a surface treatment such as a hard coat treatment, an antiglare treatment, an antireflection treatment, or an antistatic treatment depending on the application. Further, an optical layer such as a liquid crystal layer may be formed in order to improve the viewing angle characteristics. The method of performing these surface treatments and the method of forming the optical layer are not particularly limited, and a known method can be employed.

When such a protective film is in a roll state, the films tend to adhere to each other and block easily, so that the roll end can be processed with irregularities, a ribbon inserted into the end, Films are pasted and rolled.

In the present invention, the thickness of the protective film is preferably thin, but if it is too thin, the strength is lowered and the processability is poor. On the other hand, if it is too thick, problems such as decreased transparency and a longer curing time after lamination will occur. Therefore, 73919

twenty one

The appropriate thickness of the protective film used in the present invention is, for example, 5 or more and 20 or less, preferably 10 μm or more and 1500 m or less, more preferably 20 m or more and 10 0 / m or less. It is.

The method of bonding the protective film or retardation film to the pressure-sensitive adhesive layers formed on both surfaces of the polarizing film is not particularly limited, and the films may be stacked and bonded by a mouthful or the like. The roll used for bonding is preferably a combination of a rubber roll and a rubber roll or a combination of a rubber roll and a metal roll. The rubber types of rubber rubber include silicone rubber, butyl rubber, EPDM rubber, and nitrile rubber. Of these, silicone rubber is preferred from the viewpoint of durability. The rubber hardness of the rubber roll is a value measured in the A type of the spring type hardness test specified in JI S K 6 3 0 1 and is usually in the range of 20 to 90 degrees.

A polarizing plate laminated with a protective film or a polarizing plate laminated with a retardation film can be attached to a liquid crystal cell to form a liquid crystal panel or a liquid crystal display device. For sticking to the liquid crystal cell, it is preferable to use an adhesive from the viewpoint of simplicity and prevention of optical distortion. The pressure-sensitive adhesive is not particularly limited, and for example, an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyether, or the like as a base polymer can be used. In particular, like acrylic adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to substrates, and has weather resistance and heat resistance. However, it is preferable to select and use one that does not cause peeling problems such as floating or peeling under the condition of heating or humidification. The second adhesive layer 3 and the second protective film 6 are laminated in this order on one side of the polarizing film 2, and the other surface of the polarizing film 2 has a temperature range of 23 ° C to 80 ° 0. The polarizing plate of the present invention in which only the first pressure-sensitive adhesive layer 1 showing a storage elastic modulus of 0.15 MPa or more and IMP a or less is laminated on the first pressure-sensitive adhesive layer 1 side. When bonding to the liquid crystal cell, the first pressure-sensitive adhesive layer 1 can be bonded to the liquid crystal cell as it is.

The adhesive layer used for adhering to the liquid crystal cell is, for example, toluene or ethyl acetate The adhesive composition is dissolved or dispersed in an organic solvent such as to prepare a 10 to 40% by mass solution, and this is applied directly on the protective film or retardation film of the polarizing plate. It can be formed on a separator that has been subjected to a release treatment such as by transferring it onto a protective film of a polarizing plate or a retardation film. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength and the like, but is usually in the range of 1 μιηη to 50 im. When the formed adhesive layer is exposed on the surface, it is better to place a separator to prevent contamination. The same separator as described above is used as the separator. In addition, the pressure-sensitive adhesive layer used for sticking to the liquid crystal cell may contain fine particles for imparting light scattering, if necessary, glass fiber, glass beads, resin beads, metal powder, and others. It may contain fillers made of inorganic powders, pigments and colorants, antioxidants, ultraviolet absorbers and the like. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

In addition, you may laminate | stack an optical film on the surface of the polarizing plate of this invention. Examples of laminated optical films include: an optical compensation film coated with a liquid crystal compound on the surface of the base material, an oriented optical compensation film, a reflection that transmits polarized light of some sort, and reflects polarized light that exhibits the opposite properties. Type polarizing film, retardation film made of polycarbonate resin, phase difference film made of cyclic polyolefin resin, film with anti-glare function having an uneven shape on the surface, film with anti-reflection function on the surface, reflective film having a reflection function on the surface Examples thereof include a transflective film having both a reflection function and a transmission function. Commercially available products corresponding to the optical compensation film with the liquid crystal compound coated and oriented on the substrate surface include WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR film (manufactured by Nippon Oil Corporation). For example, the DBEF series (manufactured by 3M, Sumitomo 3EM Co., Ltd. in Japan) is available as a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties. Can be). Also annular Examples of commercially available products corresponding to retardation films made of polyolefin resin include Arton Film (manufactured by JSR Corporation), Essina (manufactured by Sekisui Chemical Co., Ltd.), Zeonor Film (manufactured by Optes Co., Ltd.), and the like. .

The polarizing plate produced according to the present invention usually has the form of a large roll material or sheet material, and has a sharp blade to obtain a polarizing plate having a desired shape and transmission axis. It is cut (chip cut) with a cutting tool. For this reason, in the polarizing plate chip obtained by cutting, a state in which the polarizing film is exposed to the outside at the outer peripheral end portion occurs, and therefore, the outer peripheral end surface can be continuously cut by the fly force method or the like. It is preferable.

LCD device>

The liquid crystal display device of the present invention is one in which the polarizing plate produced as described above is disposed on at least one side of the liquid crystal cell via the pressure-sensitive adhesive layer as described above. FIG. 2 is a schematic cross-sectional view showing an example in which the polarizing plate of the present invention is applied to a liquid crystal cell, and FIG. 3 is a schematic cross-sectional view showing another example in that case. As shown in FIG. 2, the second pressure-sensitive adhesive layer 3 and the second protective film 6 are laminated in this order on one side of the polarizing film 2, and the other side of the polarizing film 2 has a temperature of 23 ° C. or more. A polarizing plate on which only the first adhesive layer 1 showing a storage elastic modulus of 0.15 MPa or more and 1 MPa or less in the temperature range of ° C or less is laminated on the first adhesive layer 1 side. It can be bonded to the liquid crystal cell 20. In addition, as shown in FIG. 3, the first film having a storage elastic modulus of 0.15 MPa or more and 1 MPa or less in a temperature range of 23 ° C. or more and 80 ° C. or less on one surface of the polarizing film 2. The pressure-sensitive adhesive layer 1 and the first protective film 5 (for example, a retardation film) are laminated in this order, and the second pressure-sensitive adhesive layer 3 and the second protective film 6 are arranged in this order on the other surface of the polarizing film 2. The laminated polarizing plate can be laminated on the liquid crystal cell 20 on the first protective film 5 side. In the case of the example shown in FIG. 3, the third pressure-sensitive adhesive layer 7 can usually be used for bonding the first protective film 5 and the liquid crystal cell 20. In any of the examples, it is usual to arrange a polarizing plate on the other side of the liquid crystal cell 20, and the polarizing plate on the other side may be the same as or different from the above. There may be. Polarizing plate and liquid crystal cell The bonding method is not particularly limited, and may be generally known. For example, a method of bonding a polarizing plate to a liquid crystal cell using one rubber roll, a method of passing a liquid crystal cell and a polarizing plate between two rubber ports, and the like can be mentioned. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples,% and parts representing the content or amount used are based on mass unless otherwise specified.

(A) Polarizing film

A film made of polyvinyl alcohol with an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is uniaxially stretched by about 4.2 times in a dry process and kept in a tension state. The sample was immersed in pure water at 60 ° C. for 1 minute, and then immersed in an aqueous solution having a mass ratio of iodine / iridium iodide / water of 0.1 / 5/100 at 28 ° C. for 60 seconds. After that, it was immersed in an aqueous solution having a mass ratio of potassium iodide, Z boric acid and Z water of 10.5Z7.5 / 100 at 72 ° C for 300 seconds. Next, after washing with pure water at 10 ° C for 5 seconds and then drying at 90 ° C for 180 seconds, a polarizing film in which iodine is adsorbed and oriented on polybulal alcohol (a polarizing film made of polybulal alcohol resin in the present invention) Got. The thickness of this polarizing film was 25 μπι.

(Ii) High modulus adhesive

A release layer of a polyethylene terephthalate film (separator) that has been subjected to a release treatment by a pressure-sensitive adhesive layer in which a urethane acrylate oligomer and an isocyanate cross-linking agent are added to a copolymer of butyl acrylate and acrylic acid. In addition, a sheet-like adhesive formed with a thickness of 5 μπι was used. The storage elastic modulus of this pressure-sensitive adhesive layer was measured by the method described above, and found to be 0.6 MPa at 23 ° C and 0.19 MPa at 80 ° C. (C) Protective film

A film with a thickness of 43 μπι ([40CHC], manufactured by Toppan Printing Co., Ltd.), which has been hard-coated on one side of a film made of triacetyl cellulose, and surface-treated on one side (hard-coated) It was set as the protective film which was given.

(D) Retardation film

It consists of a stretched film of norbornene resin, has an in-plane retardation of 140 nm, which is λ / 4 with respect to the wavelength of light L, and a retardation film with a thickness of 25 / im (Essina Film, Sekisui Chemical Co., Ltd.) A sheet-like acrylic pressure-sensitive adhesive was pasted on one side of the product to obtain a retardation film with a pressure-sensitive adhesive layer. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.05 MPa at 23 and 0.04 MPa at 80 ° C. (E) Preparation of polarizing plate

The sheet-like adhesive shown in (B) was shelled on both surfaces of the polarizing film shown in (A) above to form an adhesive layer. Next, the separator was peeled off from one pressure-sensitive adhesive layer, and the protective film shown in the above (C) was stuck to the exposed surface of the pressure-sensitive adhesive layer on the surface not subjected to the hard coating treatment. Next, the separator was peeled off from the pressure-sensitive adhesive layer on the other side of the polarizing film, and the surface of the pressure-sensitive adhesive layer exposed surface on which the pressure-sensitive adhesive layer of the retardation film shown in (D) was not attached was attached. . Thus, a polarizing plate with an adhesive layer to which a retardation function was imparted was obtained. Separately, with the pressure-sensitive adhesive layer formed on both sides of the polarizing film as described above, the same retardation film as shown in (D) above (Essina Film without the pressure-sensitive adhesive layer) was formed on one side of the pressure-sensitive adhesive layer. ) Cut out a 25 mm wide test piece, attach the other adhesive layer to the glass, and peel off between the polarizing film and the adhesive layer. The strength was measured and found to be 16.2 N / 25 mm. Use the autograph made by Shimadzu Corporation, peel strength as above for retardation film at a temperature of 23 ° C, relative humidity of 50%, peel speed of 30 Omm / min, peel angle of 180 ° Was peeled off from the polarizing film together with the pressure-sensitive adhesive layer. Example 2>

A sheet-like pressure-sensitive adhesive different from that shown in (B) of Example 1 was used, and the others were the same as Example 1 to obtain a polarizing plate with a pressure-sensitive adhesive layer having a retardation function. With respect to the sheet-like pressure-sensitive adhesive used here, the storage elastic modulus of the pressure-sensitive adhesive layer was measured by the method described above, and it was 0.25 MPa at 23 ° C and 0.15 MPa at 80 ° C. The peel strength between the pressure-sensitive adhesive layer and the polarizing film was 20.0 N / 25 mm. Example 3>

Here, polarizing plates were produced by forming different types of pressure-sensitive adhesive layers on both sides of the polarizing film. The pressure-sensitive adhesives used are as follows.

First adhesive: Same as shown in Example 1 (B), storage modulus at 23 ° C 0.6 MPa, storage modulus at 80 ° C 0.19 MPa adhesive layer Is an adhesive sheet formed on a separator with a thickness of 5 μm. The peel strength for the polarizing film is 16.2 N / 25 mm.

Second adhesive: Storage elastic modulus at 23 ° C of 0.55 MPa, storage elastic modulus at 80 ° C of 0 · 27 MPa adhesive layer formed on the separator with a thickness of 5 μm Agent sheet. The peel strength for the polarizing film was 1.7 N / 25 mm. The first pressure-sensitive adhesive sheet was bonded to one side of the same polarizing film used in Example 1, and the second pressure-sensitive adhesive sheet was bonded to the other side to form a pressure-sensitive adhesive layer. The peel strength of the second pressure-sensitive adhesive layer with respect to the polarizing film is as follows. In this state, the same retardation film as used in Example 1 is attached to the second pressure-sensitive adhesive layer side, and the first pressure-sensitive adhesive layer side is Glass And measured by the same method as in Example 1. Then, instead of the protective film with a hard coat layer in Example 1, a reflective polarizing film (DBEF-P 2, manufactured by 3M) made of a polyester resin resin multilayer film was subjected to a hard coat treatment. Then, the surface not subjected to the hard coat treatment was bonded to the second pressure-sensitive adhesive layer, and the others were the same as in Example 1 to prepare a polarizing plate with a pressure-sensitive adhesive layer to which a retardation function was imparted. Example 4>

The second pressure-sensitive adhesive was changed to the following, and others were the same as in Example 3 to prepare a polarizing plate with a pressure-sensitive adhesive layer to which a retardation function was imparted.

Second adhesive: Light-diffusible compounded with fine particles, storage elastic modulus at 23 ° C 3. 97 MPa, storage elastic modulus at 80 ° C 1. 67 MPa adhesive layer Adhesive sheet formed with a thickness of 15 μηι on top. The peel strength against the polarizing film was 3.6 mm to 25 mm.

As shown in Table 1, a pressure-sensitive adhesive layer was formed using sheet-like pressure-sensitive adhesives having different “storage modulus”, “peeling strength” and “thickness” on the polarizing film surface as compared with Example 1. In other respects, a polarizing plate with a pressure-sensitive adhesive layer having the same retardation function as in Example 1 was obtained. Evaluation>

The polarizing plates of Examples 1 to 4 and Comparative Examples 1 to 4 prepared in this way were squeezed to a size of 40 mm x 4 Omm and evaluated by bonding them to glass with an adhesive layer on a retardation film. A sample was used. The evaluation sample produced here is the same as the layer configuration shown in FIG. 3 except that the liquid crystal cell 20 is changed to glass. For the evaluation sample immediately after fabrication, the following appearance defects, peeling, shrinkage, and edge bulge Then, each evaluation sample was held for 96 hours in an 85 ° C. dry heat environment, and the state after the dry heat test was evaluated. The results are shown in Table 1.

“Appearance” of the evaluation item is the result of visual observation of whether or not the surface state of the evaluation sample is a mirror surface. From the results in Table 1, it can be seen that when the thickness of the first pressure-sensitive adhesive layer is thin, the tendency is good. In addition, those with a poor appearance are marked as “coconut skin”. The evaluation item “peeling” is a visual observation using a 10 × magnifier, mainly to check whether there is any film peeling that tends to occur at the edge of the evaluation sample or bubbles that are likely to occur in the adhesive layer. It is the result. From the results in Table 1, it can be seen that if the peel strength of the first pressure-sensitive adhesive layer is 11 N / 25 mm or more, there is a tendency that peeling does not occur. The evaluation item “Shrinkage” indicates the amount of shrinkage of the polarizing film that occurs at the edge of the evaluation sample. The larger the amount of shrinkage, the more the polarizing film sandwiched between the protective film and the retardation film or the reflective polarizing film is located on the inner side. Thus, large gaps are formed between the end portions of the polarizing film and the respective end portions of the protective film and the retardation film or the reflective polarizing film. Such shrinkage is also called “open mouth” because the end of the polarizing film appears to be depressed and open. The larger the gap, the easier it is for the protective film to peel off due to external stress, or the influence of moisture (the phenomenon that the polarizing film loses iodine and the polarizing performance does not appear).

The amount of shrinkage, that is, the gap formed between the polarizing film and the protective film, retardation film or reflective polarizing film sandwiching it from both sides is MD direction (stretching axis direction of polarizing film) and TD direction (stretching axis described above). , Measured with a Nikon 2D measuring instrument (NEXIV VMR-1 2 0 7 2), and Table 1 shows the "shrinkage (MD direction)" And “shrinkage (TD direction)”. In the measurement, the edge of the evaluation sample attached to the glass is observed from above, and the outermost edge (which becomes the edge of the protective film, retardation film or reflective polarizing film) is detected. The part which is the end of the polarizing film on the inner side was detected and displayed as the maximum value of the difference (distance) between the two. In addition, The portion that is the end of the polarizing film can be identified by the color unique to the polarizing film. From the results in Table 1, it can be seen that the higher the storage modulus of the first pressure-sensitive adhesive layer is within the upper limit of 1 MPa, and the lower the thickness of the first pressure-sensitive adhesive layer, the more the same storage elastic modulus. The amount of shrinkage tends to be suppressed.

“Elevation at the end” of the evaluation item indicates a deformation state in which the polarizing plate generated at the end of the evaluation sample rises, and the height at the highest peak at the end of the evaluation sample and the center of the evaluation sample. This is the result of measuring the difference (μ πι) from the height of the horizontal plane. The measurement was performed using a confocal interference microscope Γ PL—μ 2 30 OJ manufactured by SENSOFAR. This measurement was carried out in two directions, MD direction and TD direction, and they were designated as “end swell (MD direction)” and “end swell (TD direction)”, respectively. From the results in Table 1, it can be seen that the lower the storage elastic modulus of the first pressure-sensitive adhesive layer, the lower the rise. Note that when the edge ridge height exceeds about lxm, it becomes easy to visually recognize, and when it is about 4 μm, distortion of reflected light is strongly recognized by visual observation, which is not preferable in appearance. . It means that the higher the end bulge exceeds 1 μπι, the more easily the end of the polarizing plate floats when the polarizing plate is bonded to a liquid crystal cell to form a liquid crystal panel.

Protective film T A C Triacetyl cellulose film with hard coat layer

D B E Reflective polarizing film

R F retardation film

As is clear from Table 1, the polarizing plate of the example of the present invention showed an excellent effect compared to the polarizing plate of the comparative example, and the configuration of the polarizing plate of the present invention (especially having a specific storage elastic modulus, An adhesive layer with excellent peel strength from the polarizing film is laminated on the liquid crystal cell side of the polarizing film. As described above, the embodiments of the present invention have been described, but it is also possible to combine the configurations of the embodiments described above as appropriate from the beginning. scheduled. Industrial applicability

Since the polarizing plate of the present invention has the above-described configuration, a transparent protective film is laminated on one side of a polarizing film made of polybulal alcohol resin via an adhesive layer, and an adhesive layer is provided on the other side. Compared to conventional polarizing plates such as this, even if they are attached to a liquid crystal cell to form a liquid crystal panel or liquid crystal display device and exposed to various environmental conditions, problems such as floating of the polarizing plate end may occur. It will be excellent in durability.

Claims

The scope of the claims

1. A pressure-sensitive adhesive layer is laminated on both sides of a polarizing film made of polybulal alcohol resin, and a protective film is further laminated on at least one side of the polarizing film via the pressure-sensitive adhesive layer. A polarizing plate,

Among the pressure-sensitive adhesive layers, the pressure-sensitive adhesive layer on the side close to the liquid crystal cell is

The storage elastic modulus is 0.15 MPa or more and IMP a or less in a temperature range of 23 ° C or more and 80 ° C or less, and

A polarizing plate with a peel strength of 1 IN / 25 mm or more for polarizing films.

2. The polarizing plate according to claim 1, wherein the pressure-sensitive adhesive layer on the side close to the liquid crystal cell has a thickness of 1 μm or more and 10 μm or less.

3. A liquid crystal display device characterized in that the polarizing plate according to claim 1 or 2 is disposed on at least one side of a liquid crystal cell.