WO2009060923A1

WO2009060923A1 - Polarizing plate

Info

Publication number: WO2009060923A1
Application number: PCT/JP2008/070256
Authority: WO
Inventors: Kiyoshi Muto; Shinichi Kawamura
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2007-11-07
Filing date: 2008-10-30
Publication date: 2009-05-14
Also published as: KR101614961B1; JP5252477B2; KR20100093061A; CN101849202A; TW200946987A; JP2009116103A

Abstract

Disclosed is a polarizing plate wherein a removable protective film is arranged on both sides of a polarizing film which is composed of a polyvinyl alcohol resin. In this polarizing plate, the release strength between the polarizing film and the protective films is within the range of 0.01-0.5 N/25 mm. The protective films may be self-adhesive and directly bonded to the surfaces of the polarizing film, or alternatively the protective films may respectively have an adhesive layer and bonded to the surfaces of the polarizing film through the adhesive layers.

Description

Specification

Polarizing plate technology

The present invention relates to a polarizing plate in which a peelable protective film is laminated on both surfaces of a polarizing film made of a polybulualcohol resin. Background art

A polarizing plate is widely used as a polarized light supplying element in a liquid crystal display device and as a polarized light detecting element. Conventionally, as this polarizing plate, a polarizing film made of polybutanolol has been used with a protective film made of triacetyl cellulose bonded to the surface of the polarizing film. Recently, notebook personal computers have been used in mobile devices such as mobile phones. With the development of liquid crystal display devices to be applied, and further to the development of large-screen television liquid crystal display devices, polarizing plates are required to be thinner and lighter.

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, the polarizing film is easy to tear in a direction parallel to the stretching direction, and the polarizing film alone is difficult to handle. Therefore, usually, immediately after manufacturing the polarizing film, a protective film is laminated on at least one surface of the polarizing film using an adhesive to form a polarizing plate. However, in the case where a protective film is bonded via an adhesive layer, there is a limit to making the protective film thin from the viewpoint of the alignment and properties during work, and the adhesive on the polarizing film. Since it is necessary to form two layers of a protective film layer and a protective film layer, it was difficult to reduce the thickness and weight of the polarizing plate.

In Japanese Patent Laid-Open No. 2 0 5-4 3 8 5 8, a release film is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol resin film through a protective layer made of a water-soluble film-forming composition. A polarizing plate is disclosed. However However, the polarizing plate has a protective layer even after the release film is peeled off, and there are limits to further thinning and light weight. Further, in the polarizing plate described in JP-A No. 2 0 5-4 3 8 5 8, it is necessary to perform a drying treatment in order to cure the film-forming composition, and the manufacturing process is increased accordingly. It will be. Disclosure of the invention

The present invention has been made to solve the above-mentioned problems, and its purpose is easy to handle, can prevent the polarizing film from being broken until it is used, and can be made thinner and lighter. It is providing the made polarizing plate.

As a result of intensive studies, the present inventors have found that the above object is achieved by a polarizing film in which protective films having appropriate adhesion and capable of being peeled off as needed are laminated on both sides of the polarizing film. Found that is achieved.

That is, according to the present invention, a protective film that can be peeled is laminated on both surfaces of a polarizing film made of a polybulualcohol resin, and the peeling force between the polarizing film and the protective film is 0.1 to 1. A polarizing plate is provided which is in the range of 0.5 N 25 mm.

Here, the said protective film may be laminated | stacked in contact with the polarizing film surface. Moreover, it is one of the preferable forms that a protective film consists of self-adhesive resin, and it is preferable that the protective film in this case consists of a polyethylene resin. On the other hand, the protective film may have an adhesive layer, and may be laminated on the surface of the polarizing film via the adhesive layer. In this case, the protective film is preferably made of polyethylene resin or polyethylene terephthalate resin. Les. In addition, according to the present invention, a mouth-shaped polarizing plate formed by winding the polarizing plate is provided. BEST MODE FOR CARRYING OUT THE INVENTION

The polarizing film in the present invention is a polarizing film made of polyvinyl alcohol resin. Polybulualcohol resin is usually saponified Can be obtained. The saponification degree of the polyvinyl alcohol resin is generally about 8 5 mole ^_0/0, preferably greater than about 9 0 mole ^_0/0 or more, and more preferably about 9 9 mole% 1 0 0 mole%. Examples of the polyacetate resin include the power of polyacetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with butyl acetate include unsaturated carboxylic acids, olefins, butyl ethers, and unsaturated sulfonic acids. Specific examples of the copolymer of the above-mentioned butyl acetate and other monomers copolymerizable therewith include, for example, ethylene monoacetate butyl copolymer. The degree of polymerization of the polybulualcohol resin is usually about 100000 to 100000, preferably about 15500 to 500.

The polyvinyl alcohol resin may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polybutyl butyral, and the like may be used. Usually, the starting material in the production of polarizing film is about 20 μm to 100 μm thick, preferably about 30 π! An unstretched film of a polyvinyl alcohol resin film of ~ 80 / xm is used. The film width is about 1 5 0 O mn industrially! ~ 400 mm is practical, but not limited to this. This unstretched film is processed in the order of swelling treatment, dyeing treatment, boric acid treatment, and water washing treatment, then uniaxially stretched in the boric acid treatment or in the previous step, and finally dried to obtain a polybulu alcohol polarizing film. For example, the thickness is about 5 μπ! ~ 50 / m.

In the present invention, the method for producing the polarizing film is not particularly limited. For example, (1) The unstretched polyvinyl alcohol resin film is uniaxially stretched in air or an inert gas, then subjected to swelling treatment, dyeing treatment with a dichroic dye. Boric acid treatment and water washing treatment, followed by drying, and (2) swelling treatment of the unstretched polyvinyl alcohol resin film, dyeing treatment with dichroic dye, boric acid treatment and water washing treatment. In this order, it is possible to adopt a method in which the boric acid treatment step and / or the previous step are wet-uniaxially stretched and finally dried. In any of the above methods, uniaxial stretching may be performed in one step or in two or more steps, but is preferably performed in a plurality of steps. As a stretching method, a known method can be adopted. For example, stretching between rolls in which stretching is performed with a difference in peripheral speed between two nip rolls conveying a film, described in Japanese Patent No. 2 7 3 1 8 1 3 There are a hot roll stretching method and a tenter stretching method. The order of the processes is basically as described above, but there are no restrictions on the number of treatment baths or treatment conditions. In addition, steps that are not described in the methods (1) and (2) may be added as necessary. Examples of this process 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 chloride not containing boric acid (zinc treatment), etc. Are listed.

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 problems such as extreme dissolution and devitrification of the polyvinyl alcohol resin film do not occur. In the case of swelling a film stretched in advance in a gas, for example, by immersing the film in water or an aqueous solution of about 15 ° C to 70 ° C, preferably about 30 ° C to 60 ° C. Swelling treatment is performed. The immersion time of the film is about 30 seconds to 30 seconds, preferably about 60 seconds to 240 seconds. In the case of swelling the polybulal alcohol resin film in an unstretched state, for example, the film is immersed in water or an aqueous solution of about 10 ° C. to 50 ° C., preferably about 20 ° C. to 40 ° C. It is done. The immersion time of the film is about 30 seconds to 30 seconds, preferably about 60 seconds to 240 seconds.

A preferable swelling degree in the swelling treatment is 1.0 to 2.5 times. Here, the degree of swelling is defined as the mass after swelling Z and the mass before swelling. If the degree of swelling is small, plasticizer removal in the polyvinyl alcohol resin film is often insufficient, and if the degree of swelling is large, there is a tendency to cause uneven dyeing in the dyeing process performed after the swelling process. is there. In the method (2) above, a uniaxial stretching treatment may be performed during the swelling treatment step. In this case, the draw ratio is preferably 3 times or less. The draw ratio is defined as the length after drawing and the initial length (the same applies hereinafter). If the draw ratio here is high, uneven dyeing tends to occur in the dyeing process.

In the swelling treatment process, the polyvinyl alcohol resin film swells in the width direction and easily causes problems such as wrinkles in the film. Therefore, widening mouth (expander ronor), spirano ronorole, crown ronole It is preferable to transport the film while removing the film with a known widening device such as a cross guider, a bend bar or a tenter clip.

In order to stabilize the film transport in the swelling treatment bath, the water flow in the swelling treatment bath is controlled by an underwater shower, or an EPC device (Ed g e Po s i t i o n

It is also useful to use a control device that detects the end of the film and prevents the film from meandering. In this process, since the film swells and expands in the film running direction, measures such as controlling the speed of the transport roll before and after the swelling treatment bath should be taken in order to eliminate sagging of the film in the transport direction. Is preferred. In addition to pure water, the swelling treatment bath used is boric acid (described in JP-A-10-153709), salted salt (described in JP-A-06-281816), inorganic acid, inorganic salt Also, an aqueous solution to which a water-soluble organic solvent, alcohols and the like are added in the range of about 0.01 mass% to 10 mass% can be used.

The dyeing process is performed for the purpose of adsorbing and orienting the dichroic dye on the polybulualcohol resin film. The treatment conditions are determined in such a range that these objectives can be achieved and in which a defect such as extreme dissolution or devitrification of the polyvinyl alcohol resin film does not occur. When iodine is used as the dichroic dye, for example, iodine at a temperature ratio of about 10 ° C. to 45 ° C., preferably about 20 ° C. to 35 ° C. 0.2 About 0.1-: An aqueous solution having a concentration of 10Z100 is used for immersion for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide May be used. Also, other iodides can be used in combination with potassium iodide. In addition, compounds other than iodide, such as boric acid, zinc chloride, and cobalt chloride, may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. Any dye containing about 0.03 parts by mass or more of iodine with respect to 100 parts by mass of water can be regarded as a dyeing treatment bath.

When a water-soluble dichroic dye is used as the dichroic dye, for example, about 20 ° C. to 80 ° C., preferably about 30 ° C. to 70 ° C. Color dye / water immerse for about 30 seconds to 60 seconds, preferably about 60 seconds to 300 seconds, using an aqueous solution having a concentration of about 0.00 1 to 0.11 100 The dyeing process is performed. The aqueous solution of the dichroic dye to be used may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

As described above, in the method (2), a uniaxial stretching process may be performed during the dyeing process. Uniaxial stretching is performed by a method such as providing a difference in peripheral speed between the nip rolls before and after the dyeing treatment bath. In addition, as with the stretching process in the swelling process, widening ronore (extract / kunda bite / nore), Su / Iranole ronole, crown ronole, cross guider, bend bar, etc. are used in the dyeing treatment bath and at the entrance / exit of the bath. It can also be installed.

The boric acid treatment is generally performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye in an aqueous solution containing about 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 about 1 to 30 parts by mass of iodide with respect to 100 parts by mass of water. Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate may coexist.

Here, the boric acid treatment is carried out for water resistance and hue adjustment (to prevent bluishness, etc.) by crosslinking. Boric acid treatment is carried out for water resistance by crosslinking. If necessary, a crosslinking agent such as darioxal or dartaldehyde can be used 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 or re-dyeing treatment.

In boric acid treatment, boric acid treatment for water resistance and boric acid treatment for hue adjustment are not particularly distinguished, but depending on the purpose, the concentration of boric acid and iodide, the treatment bath It is preferable to change the temperature appropriately. For example, in the case where boric acid treatment is performed after swelling and dyeing an unstretched polyvinyl alcohol resin film, and the boric acid treatment is aimed at water resistance by cross-linking, the water is added to 100 parts by weight. On the other hand, a hydrofluoric acid treatment bath containing about 3 to 10 parts by mass of boric acid and about 1 to 20 parts by mass of iodide is used, and usually about 50 to 70 ° C, preferably about 5 Performed at temperatures between 5 ° C and 65 ° C. The immersion time is usually about 30 to 60 seconds, preferably about 60 to 42 seconds, and more preferably about 90 to 300 seconds. When boric acid treatment is performed for the purpose of water resistance by cross-linking, the temperature of the boric acid treatment bath is usually about 50 ° C to 8 ° C. 5 ° C, preferably about 55 ° C to 80 ° C.

After boric acid treatment for water resistance, boric acid treatment for hue adjustment may be performed. For example, when the dichroic dye is iodine, as the first boric acid treatment for water resistance, about 1 to 5 parts by weight of boric acid and about 3 to 3 parts of iodide for 100 parts by weight of water

Using a boric acid treatment bath containing 30 parts by mass, boric acid treatment is usually performed at a temperature of about 10 ° C to 45 ° C. The immersion time is usually about 3 to 300 seconds, preferably about 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.

The boric acid treatment may consist of a single step or a plurality of steps, but is usually performed in steps 2 to 5. In this case, use each The aqueous solution composition and temperature of the boric acid treatment bath may be the same or different within the above ranges. The boric acid treatment for water resistance and the boric acid treatment for hue adjustment may be performed in a plurality of steps, respectively.

Note that the polybulu alcohol resin film may be stretched during the boric acid treatment step. In this case, a partial stretching treatment may or may not be performed in advance before the boric acid treatment step (for example, the dyeing treatment step). The final cumulative draw ratio is about 4 to 7 times, preferably about 4.5 to 6.5 times. The cumulative draw ratio here means how much the reference length in the length direction of the polybulu alcohol resin film is in all the stretched films. If the portion of the alcohol resin film that is lm is 5 m in all the stretched films, the cumulative draw ratio at that time is 5 times.

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

Here, in each step after the stretching treatment, tension control may be performed so that the tension of the polyvinyl alcohol resin 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 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 boric acid treatment process consists of a plurality of boric acid treatment processes, the film is stretched in the first or second boric acid treatment process, and the boric acid next to the boric acid treatment process in which the stretch treatment is performed. The ability to control tension in each process from the treatment process to the water washing process, boric acid treatment following the boric acid treatment process after stretching the film in the boric acid treatment process from the first to the third stage From the process to the washing process It is preferable to control the tension in each process, but industrially, the boric acid treatment is performed by stretching the film in the boric acid treatment process from the first or the first to the second stage, and then performing the stretching process. It is more preferable to perform tension control in each process from the boric acid treatment process to the water washing process following the process. In addition, when performing the above-described oxide treatment or zinc treatment after the boric acid treatment, the 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 applied to the polyvinyl alcohol resin film in tension control is not particularly limited, and the unit width may be reduced to about 150Ν / π! ~ 2 000 N / m, preferably about 600 ΝΖπ! It is set appropriately within the range of up to 1500 N, m. When the tension is less than about 15 ONZm, it becomes easier to see the film. On the other hand, if the tension exceeds about 200 ONZm, problems such as film breakage and reduced life due to bearing wear will 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 the tension control is performed, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not included in the stretching process.

As a nip roll for controlling the tension and a guide roll for controlling the film transport direction, a rubber roll, a stainless steel polishing roll and a sponge rubber roll can be used. The rubber roll is made of NBR or the like, and its hardness is about 60 to 90 degrees, preferably about 70 to 80 degrees with a JIS Shore C scale measured by the test method of JISK 6301, and the surface roughness is JISB 06 01 (surface Roughness) is expressed in terms of the average interval S of the local peaks of the roughness curve, and is preferably about 0.1 to 5 S, preferably about 0.5 to 1 S.

The stainless steel polishing roll is made of SUS 304, SUS 316, etc., and the surface roughness is the average of the local peaks of the roughness curve of JISB 0601 (surface roughness) in order to make the film thickness uniform. The distance S is preferably about 0.2 to 1. OS. As a sponge rubber roll, the hardness of the sponge is JIS Shore C scale measured by the test method of JISK 6300, about 20 to 60 degrees, and further about 25 to 50 degrees, and the density is about 0.4. ~ 0.6 g / cm ³ , or even about 0.4 2 to 0.57 g / cm ³ , and the average of the local peaks of the roughness curve with a surface roughness of JISB 0 60 1 (surface roughness) The distance S is preferably about 10 to 30 S, more preferably about 15 to 25 S.

Finally, 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 it is usually carried out in 2 to 5 stages due to equipment limitations. When performed in two stages, it is preferable that the tension in the first stage is set from the range of 600 to NZm and the tension in the second stage is set from the range of 3 to 0 120 NZm. If the tension is too high, the film will break more, and if it is too low, wrinkles will increase, which is not preferable. 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 be broken more, the optical properties will be lowered, and if the temperature is too low, streaks will increase, which is not preferable. The drying time can be, 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. Through the above steps, a polarizing film made of a polyvinyl alcohol resin film uniaxially stretched and adsorbed and oriented with a dichroic dye is obtained. The thickness of the polarizing film is usually about 5 to 40 μπι.

The moisture content of the polarizing film after the drying treatment is preferably 3 to 14% by mass, more preferably 3 to 10% by mass, and still more preferably 3 to 8% by mass. / ₀ . When the moisture content exceeds 14% by mass, the polarizing film tends to shrink in a dry heat environment. The moisture content of the polarizing film can be obtained from the weight change before and after being held for 1 hour under dry heat at 105 ° C.

The polarizing plate of the present invention has a peelable protective film laminated on both sides of the polarizing film. The peel force between the polarizing film and the protective film is from 0.0 1 to 0.5 NZ25 mm, preferably 0.01 to 0.2 N, 25 mm, more preferably 0.01 to 0.15 NZ25 mm. Even when a protective film is laminated on one side of the polarizing film so as to exhibit the peeling force in the above range, the polarizing film is effective in preventing cracking, but a protective film is provided on both sides to improve handling. It is preferable to laminate them, and the effect of preventing cracking of the polarizing film is further enhanced. If the peel strength is less than 0.01 N 25 mm, the adhesive strength between the polarizing film and the protective film is small, so that the protective film may be partially peeled off, or the polarizing plate may be stored in a roll shape. There is a tendency for the polarizing film to tear along the stretching direction (in a direction parallel to the stretching direction). Also, if the peel strength exceeds 0.5N Z25mm, it becomes difficult to peel the protective film from the polarizing film, and therefore the polarizing film tends to tear along the stretching direction when the protective film is peeled off. In the present invention, the protective film being “peelable” means that the polarizing film and the protective film can be separated without damaging or damaging the polarizing film and the protective film.

Here, the peeling force is obtained by cutting a polarizing plate on which a protective film is laminated to a width of 25 mm and measuring the force when peeling the protective film from the polarizing film in the 180 ° direction. The peel force is measured in an environment with a temperature of 23 ± 2 ° C and a relative humidity of 50 ± 5%.

The protective film is made of polyethylene resin, polypropylene resin, polystyrene resin, polyethylene terephthalate because it is easy to handle, secures a certain level of transparency, and is produced in large quantities in the industry and inexpensive. A tartar resin or the like can be preferably used, and a film in which one or more of these are formed into a single layer or a multilayer can be used as a protective film. 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 reduced transparency arise. Accordingly, a suitable thickness of the protective film is, for example, about 5 to 100 im, and preferably about 10 to 80 m. The protective film is laminated in contact with the surface of the polarizing film so that the peeling force between the polarizing film and the protective film is from 0.01 to 0.525 mm. The protective film may be composed of self-adhesive 1 "raw resin, which may be laminated as it is on the surface of the polarizing film, or may be composed of a film having an adhesive layer, and the adhesive layer through It may be laminated on the surface of the polarizing film, but if an adhesive layer is interposed, the adhesive layer residue remains on the surface of the polarizing film when the protective film is peeled off from the polarizing film. Therefore, it is preferable to laminate a protective film directly on the polarizing film using a self-adhesive protective film.

In the case of using a self-adhesive protective film, the protective film is a film made of a resin having self-adhesiveness to the polarizing film (self-adhesive '14). A polyethylene resin film having a relatively soft property can be preferably used. In addition, a film in which a polyethylene resin layer is laminated on a polypropylene resin film can also be laminated on a polarizing film as it is because the polyethylene resin layer exhibits self-adhesiveness. Examples of commercially available self-adhesive resin films that exhibit suitable peel strength for polarizing films made of the above-mentioned polyvinyl alcohol resin film include “Tretec” (trade name) made of polyethylene resin manufactured by Toray Industries, Inc. Can be mentioned.

On the other hand, as a pressure-sensitive adhesive in the case where a film having a pressure-sensitive adhesive layer is used as a protective film, as long as the peel force between the polarizing film and the protective film is from 0. Q 1 to 0.5 N / 25 mm. However, there is no particular limitation. Specific examples of the pressure-sensitive adhesive include, for example, those having an acrylic resin, an epoxy resin, a urethane resin, a silicone resin, or the like as a base polymer. In addition to the base polymer, the adhesive usually contains a crosslinking agent. Adhesives with adjusted adhesive strength are commercially available by appropriately designing the type and degree of polymerization of the base polymer and the combination with the cross-linking agent. Please select and use one within the above range. The thickness of the adhesive layer is not particularly limited. For example, it can be about 5 to 40 m. Moreover, when using the protective film which has an adhesive layer, a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyethylene terephthalate resin etc. can be used as a base film in which an adhesive layer is formed. Among these, polyethylene resins and polyethylene terephthalate resins are preferably used because they are available at low cost.

Moreover, the film which gave the adhesive to the resin film surface illustrated above is marketed, Such a film can also be used suitably as a protective film of this invention.

Specific examples of commercially available products include “Sanitec” (trade name, sold by Sanei Kaken Co., Ltd.), which has an adhesive layer on the surface of polyethylene resin film, and an adhesive layer on the surface of polyethylene terephthalate resin film. “E-Mask” (trade name, sold by Nitto Denko Corporation), “Mastak” (trade name, Fujimori Kogyo Co., Ltd.) with an adhesive layer formed on the surface of polyethylene terephthalate resin film More sold). Since these commercially available films with pressure-sensitive adhesives are also designed with various adhesive forces, the peel strength between them and the polarizing film is 0.1 to 0.

You can select and use 5 N / 2 5 mm.

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

The polarizing film surface may be subjected to surface treatment such as plasma treatment, corona treatment, or ultraviolet irradiation treatment. By such surface treatment, the adhesion to the protective film can be improved or decreased, and thereby the peeling force can be adjusted within the above range.

The method of laminating the polarizing film and the protective film is not particularly limited. The roll used for pasting is preferably a combination of rubber mouthpiece and rubber mouthpiece or a combination of rubber mouthpiece and metal mouthpiece. Rubber type of rubber roll is silicone rubber, butyl rubber, EP DM rubber, nitrile rubber, etc. Of these, silicone rubber is preferred from the viewpoint of durability. The rubber hardness of the rubber roll is a value measured by a spring type hardness test stipulated in JISK 6300 and is usually in the range of 20 to 90 degrees.

In the polarizing plate of the present invention, since the protective film can be peeled off, the single-sided or double-sided protective film can be peeled off as necessary. As a result, for example, when a polarizing plate is bonded to a liquid crystal cell or the like, it is possible to bond the polarizing film itself by peeling off the protective film, thereby reducing the thickness and weight of the liquid crystal display device. be able to. Moreover, in the present invention, it is not necessary to perform a treatment that can reduce the optical properties of the polarizing film such as heat drying when the protective film is laminated, and therefore a polarizing plate that maintains good optical properties can be obtained.

The polarizing plate of the present invention may be stored and used, for example, in the form of a sheet, but it is preferable that a sheet-shaped polarizing plate is wound to form a roll-shaped polarizing plate. The mouth-shaped polarizing plate wound in a state where such protective films are laminated can be applied, for example, to the production of a liquid crystal panel as follows. First, the polarizing film drawn from the roll-shaped polarizing plate is peeled off from the protective film on one or both sides, and the polarizing film surface is exposed. On the surface of the polarizing film, another protective film drawn out from the roll-like body is coated with an optical compensation film such as a retardation film, or an adhesive film to be applied to a liquid crystal cell. The body is bonded to the liquid crystal cell. Finally, the laminate (polarizing plate) is separated from the drawn sheet to obtain a liquid crystal panel. By continuous production using such a roll-shaped polarizing plate, it becomes possible to produce a liquid crystal panel efficiently. 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.

<Example 1> A polyvinyl alcohol film with an average degree of polymerization of about 2,400, saponification degree of 99.9 mol% or more and a thickness of 75 μm was uniaxially stretched about 5 times in a dry process to maintain 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 / potassium iodide / water of 0.1 Z 5/100 at 28 ° C. for 60 seconds. Thereafter, it was immersed in an aqueous solution having a mass ratio of potassium iodide / boric acid Z water of 8 10.5 / 7.5-1100 at 72 ° C. for 30 seconds. Subsequently, it was washed with pure water at 10 ° C. for 5 seconds, and then dried at 80 ° C. for 3 minutes to obtain a polarizing film in which iodine was adsorbed and oriented on a polybulal alcohol resin film. A self-adhesive polyethylene film “Tretec 7 3 3 2 K” (manufactured by Toray Industries, Inc.) was bonded to both surfaces of the obtained polarizing film to obtain a polarizing plate. The polarizing plate had one side perpendicular to the stretching direction with both hands, and it was difficult to tear even if a force was applied in the opposite direction with each hand, and the tear resistance was imparted by the presence of the protective film. Moreover, when the protective film was peeled off with fingers, it was easily peeled off (peelability test).

Furthermore, about the said polarizing plate, the peeling force between a polarizing film and a protective film was measured. For the measurement, the polarizing plate was cut out to a width of 25 mm and used as a measurement sample, and the protective film was removed from the polarizing film using the Autograph AG-IS precision universal testing machine manufactured by Shimadzu Corporation. The force when peeling in the 0 ° direction was measured in an environment with a temperature of 2 3 ± 2 ° C and a relative humidity of 50 0 ± 5%. The results are shown in Table 1. <Example 2>

Same as Example 1 except that the protective film was changed to polyethylene film with adhesive “Sanitect PAC 2 — 70” (manufactured by Sanei Kaken Co., Ltd.) and the adhesive side was bonded to the polarizing film. Thus, a polarizing plate was produced. As in Example 1, a peelability test was performed. As a result, a slight force was required as compared with Example 1, but peeling was possible. Table 1 shows the peel force measurement results. Comparative Example 1> Polarizing plate in the same manner as in Example 1 except that the protective film was changed to polyethylene terephthalate film “PETE 5 1 00 1 5 0” (manufactured by Toyobo Co., Ltd.) (abbreviated as PET in Table 1). Was made. When the peelability test was performed, there was no adhesion between the polarizing film and the protective film, and the protective film was simply placed on the polarizing film, and both peeled off very easily. Therefore, the polarizing film was torn in the stretching direction in the subsequent handling. Table 1 shows the peel force measurement results.

The protective film was changed to a polyethylene terephthalate film with adhesive, “Masterk NBO— 0 4 2 4” (Fujimori Kogyo Co., Ltd.) (abbreviated as PET with adhesive in Table 1), and the adhesive side was polarized A polarizing plate was produced in the same manner as in Example 1 except that it was bonded to a film. When the peelability test was performed, peeling was possible, but the adhesive film between the polarizing film and the protective film was too strong, and the polarizing film was torn when the protective film was peeled off. Table 1 shows the peel force measurement results. table 1

Industrial applicability

In the polarizing plate of the present invention, the protective film is configured to be peelable while having an appropriate adhesion to the polarizing film. Therefore, the polarizing plate of the present invention prevents the polarizing film from being damaged by the laminated protective film, and also peels off the protective film on one side or both sides as necessary. A single layer film consisting only of an optical film can be easily obtained. According to the polarizing plate of the present invention, since the protective film can be peeled off immediately before bonding to a liquid crystal cell or the like, and only the polarizing film can be bonded to the liquid crystal cell or the like, it is mounted on the liquid crystal display device. The thickness and weight of the polarizing plate can be reduced, thereby contributing to the reduction in thickness and weight of the liquid crystal display device.

Claims

The scope of the claims

1. A polarizing plate in which a peelable protective film is laminated on both sides of a polarizing film made of polyvinyl alcohol resin,

The peeling force between the polarizing film and the protective film is a polarizing plate in a range of 0.01 to 0.5N 25 mm.

2. The polarizing plate according to claim 1, wherein the protective film is laminated in contact with the surface of the polarizing film.

3. The polarizing plate according to claim 1, wherein the protective film is made of self-adhesive resin.

4. The polarizing plate according to claim 3, wherein the protective film is made of polyethylene resin.

5. The polarizing plate according to claim 1, wherein the protective film has an adhesive layer, and is laminated on the surface of the polarizing film via the adhesive layer.

6. The polarizing plate according to claim 5, wherein the protective film is made of polyethylene resin or polyethylene terephthalate resin.

7. A mouth-shaped polarizing plate obtained by rolling the polarizing plate according to claim 1.