KR20110113310A - A polarizing plate and method for preparing the same - Google Patents

Abstract

The present invention relates to a polarizing plate and a method of manufacturing the same, and more particularly, in manufacturing a polarizing plate using a polarizer protective film having a different moisture permeability, to prepare a intermediate by adhering a protective film of high moisture permeability on one side of the polarizer and drying. By sticking a low moisture-permeable protective film on the other side of the polarizer in a continuous process without winding the intermediate, the back curl is kept to 5 mm or less while the normal curl useful for bonding the polarizing plate to the liquid crystal cell is suitably 5 to 25 mm. It relates to a polarizing plate and a method of manufacturing the same that can be maintained as well as achieve process economics.

Description

Polarizing plate and manufacturing method thereof {A POLARIZING PLATE AND METHOD FOR PREPARING THE SAME}

The present invention relates to a polarizing plate and a method of manufacturing the same, which can not only ensure that the useful curl is properly maintained at 5 to 25 mm when the polarizing plate is bonded to the liquid crystal cell while the reverse curl is suppressed to 5 mm or less. .

Polarizers used in liquid crystal displays (LCDs) generally include a polarizer protective film laminated to protect both the polarizer and the polarizer. In addition, a retardation film, an optical compensation sheet, or the like has been used together with or instead of the protective film in order to extend the displayed image performance of the liquid crystal display and the viewing angle of the liquid crystal cell.

Triacetyl cellulose-based film has been used as a polarizer protective film, but in recent years, in order to express unusual optical properties, which have not been conventionally, polarizing plates having different physical properties and the like disposed on both sides of the polarizer are increasing. However, in the case of disposing different kinds of protective films on both sides of the polarizer according to the conventional method, since both sides of the polarizer are asymmetrical, there was a problem of curling in the polarizing plate. In particular, when a protective film having different moisture permeability is disposed on both sides of the polarizer, worse curls were generated.

Since the polarizing plate is required to be handled in accordance with the LCD's function improvement, brightness improvement and enlargement, it is desirable to suppress curl as much as possible. In addition, a polarizing plate in which curl occurs, particularly a polarizing plate in which reverse curl occurs, causes process problems such as generation of bonding bubbles when bonding to a liquid crystal cell.

In order to solve this problem of curling, Japanese Laid-Open Patent Publication No. 2003-256569 proposes a method of bonding a high polarizing transparent protective film at 80 ° C. for 24 hours and then bonding and drying the polarizer. However, this has a problem that a time constraint for heat-resistant treatment of the high moisture-permeability protective film occurs.

In addition, Japanese Patent Application Laid-Open No. 2002-196132 discloses bonding a first transparent protective film to a polarizer and drying the bonded body, and then bonding a second transparent protective film to a polarizer surface on which the first transparent protective film is not bonded. And a method of improving curl by drying. This can suppress the occurrence of curl, but there was a limit of time inefficiency due to the winding process after bonding the first transparent protective film and place restriction due to storage of the disc.

An object of the present invention is to provide a polarizing plate and a method of manufacturing the same that can be 5 to 25 mm, the normal curl is 5 mm or less.

Another object of the present invention is to provide a method of manufacturing a polarizing plate which can save production time and space.

1. A method of manufacturing an intermediate comprising adhering a protective film having high moisture permeability to one side of a polarizer and drying the adhesive film, and attaching a protective film having low moisture permeability to the other side of the polarizer while the intermediate body is flattened. The manufacturing method of the polarizing plate.

2. In the above 1, the low-moisture-permeability protective film is a method for producing a polarizing plate laminated with a pressure-sensitive adhesive layer and a release film on the side to be bonded to the polarizer.

3. In the above 1, the high moisture permeability protective film is a manufacturing method of a polarizing plate having a moisture permeability of 200 to 1000g / m ² · day at 40 ℃ and 90% RH.

4. In the above 1, the low-moisture-permeability protective film is a manufacturing method of a polarizing plate having a water vapor transmission rate of less than 200g / m ² · day at 40 ℃ and 90% RH.

5. In the above 3, the protective film of the moisture permeability of 200 to 1000g / m ² · day at 40 ℃ and 90% RH is made of triacetyl cellulose manufacturing method.

6. In the above 4, the protective film having a water vapor transmission rate of less than 200g / m ² · days at 40 ℃ and 90% RH is made of a polyolefin resin having a cyclo-based (cyclic) or norbornene structure.

7. A high moisture permeability protective film having a moisture permeability of 200 to 1000 g / m ² · day at 40 ° C. and 90% RH on one side of the polarizer is laminated with an adhesive, and at 40 ° C. and 90% RH on the other side of the polarizer. A polarizing plate in which a moisture permeability of a protective film of low moisture permeability of 200 g / m ² · day or less is laminated with an adhesive.

The present invention can produce a polarizing plate so that the curl of the polarizing plate generated due to the difference in moisture content of the protective film is 5 to 25 mm, the reverse curl is 5 mm or less, and can achieve process economics.

As a result, it becomes possible to manufacture a polarizing plate having excellent durability and polarization characteristics.

The winding step may be omitted in the polarizing plate manufacturing process, thereby saving time and space.

Since the protective film does not have to go through a drying step after adhering a low moisture permeability protective film, production efficiency is increased.

The manufacturing of the protective film asymmetric polarizing plate also has the advantage that can be used as conventional water-based adhesives, dryers, production lines.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the manufacturing method of the polarizing plate of this invention.

In the present invention, in manufacturing a polarizing plate using a polarizer protective film having a different moisture permeability, by adhering a protective film of high moisture permeability on one side of the polarizer and drying it to produce an intermediate and in a continuous process without winding the intermediate of the polarizer By adhering the low-moisture-permeability protective film in which the pressure-sensitive adhesive layer is laminated on the other side, the reverse curl is suppressed to 5 mm or less, and the useful curl when bonding the polarizer to the liquid crystal cell can be properly maintained at 5 to 25 mm. The present invention relates to a polarizing plate capable of achieving economical efficiency and a method of manufacturing the same.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The polarizing plate of the present invention is provided with a protective film having different moisture permeability on both sides of the polarizer. If the retardation film, optical compensation sheet or the like serves as a protective film these are also included in the protective film of the present invention.

The polarizer of this invention is not limited to a specific thing. For example, uniaxial stretching by adsorbing dichroic substances such as iodine or dichroic dye onto hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymerized partial saponified films And polyene-based oriented films such as dehydrated products of polyvinyl alcohol and dehydrochloric acid treated products of polyvinyl chloride. Among these, the polarizer which uniaxially stretched by adsorb | sucking dichroic substances, such as iodine, on a polyvinyl alcohol-type film is especially preferable because it has a high polarization dichroic ratio. The polarizer may contain boric acid, zinc sulfate, zinc chloride, etc. as needed. Although the thickness in particular of a polarizer is not restrict | limited, Usually, it is about 5-80 micrometers.

A high moisture permeability protective film (hereinafter also referred to as a first transparent protective film according to the context) is a film exhibiting a higher moisture permeability than a low moisture permeability protective film (hereinafter also referred to as a second transparent protective film according to the context) adhered to the other side of the polarizer. . An object of the present invention is to select two kinds of films having different moisture permeability among those listed as the second transparent protective film, the lower the moisture permeability of the second transparent protective film, the higher the moisture permeability of the first transparent protective film It can also be achieved when used as. In addition, a protective film other than those listed as the second transparent protective film may be used as the first transparent protective film.

As a high moisture permeability protective film, a cellulose resin film is mentioned, for example, A cellulose acetate type resin film, such as a triacetyl cellulose film and a diacetyl cellulose film, is included specifically ,. Among them, triacetyl cellulose is particularly preferable, and a saponified (saponified) triacetyl cellulose film is more preferable. The moisture permeability of the protective film of high moisture permeability is 200 to 1000 g / m ² · day at 40 ° C. and 90% RH, and more preferably 300 to 900 g / m ² · day.

The low moisture-permeable protective film is a film in which an adhesive (layer) is laminated by applying an adhesive on one side of the film. For example, the moisture-permeability is 200 g / m ² · day or less at 40 ° C. and 90% RH, preferably 0 to 100 g. / m ² · day. For example, specifically, polyester-based resin, such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate; Polycarbonate resins; Acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymers; Polyolefin-based resins such as polyethylene, polypropylene, cyclo-based (cyclic) or polyolefins having a norbornene structure, and ethylene-propylene copolymers; Vinyl chloride-based resins; Amide resins such as nylon and aromatic polyamides; Polyimide resin; Polyether sulfone resin; Sulfone resins; Polyether sulfone resin; Polyether ether ketone resins; Sulfided polyphenylene resins; Vinyl alcohol-based resins; Vinylidene chloride-based resins; Vinyl butyral resin; Allyl resins; Polyoxymethylene resin; And a film selected from the group consisting of thermoplastic resins such as epoxy resins, and the like, and films composed of blends of the thermoplastic resins may also be used. Moreover, you may use the film which consists of thermosetting resins, such as a (meth) acrylic-type, a urethane type, an acryl urethane type, an epoxy type, a silicone type, or an ultraviolet curable resin. More preferably, it is a film which consists of a polyolefin which has a cyclo system (cyclic) or norbornene structure in terms of an optical characteristic and durability.

When the adhesive is applied to the protective film of low moisture permeability, it may be accompanied by a treatment for improving adhesion between the adhesive and the film. Representative examples of such treatments include dry treatments, and specific examples of dry treatments include corona discharge treatment, plasma treatment, and low pressure UV treatment.

The pressure-sensitive adhesive applied to the low-moisture-permeability protective film is typically an acrylic copolymer, and is typically coated to have a thickness of 100 μm or less after drying, preferably 5 to 30 μm.

In the present invention, a protective film of high moisture permeability is adhered to one side of the polarizer, followed by drying to prepare an intermediate, and in the state where the intermediate is flattened, a low moisture permeability protective film is attached to the other side of the polarizer to prepare a polarizing plate. . According to this method, two kinds of protective films having different properties (for example, elastic modulus and moisture permeability) can be bonded without peeling.

For example, as shown in FIG. 1, after bonding the high-moisture-permeability protective film 10 to one surface of the polarizer 20 to form an intermediate and then winding the intermediate, the low-moisture-permeability in which the pressure-sensitive adhesive layer 31 is laminated. The protective film 30 is bonded while peeling off the release film 32, and a polarizing plate is obtained. After the protective film is bonded to both sides of the polarizer in a continuous process it may be laminated the pressure-sensitive adhesive layer 40 bonded to the liquid crystal cell. The pressure-sensitive adhesive layer 40 is laminated while the release film 42 is peeled off, and when the polarizing plate is later bonded to the liquid crystal cell, the other release film 41 is peeled off.

In this way, by bonding the low-moisture-permeability protective film without winding up the intermediate between the polarizer and the high-moisture-permeability protective film, blocking or cracking can be prevented, and abnormality in optical characteristics of the obtained polarizing plate can be prevented. In addition, the installation space of the manufacturing apparatus can be significantly reduced, and since there is no loss of time due to the winding process, the production efficiency can be greatly improved, and the manufacturing cost can be greatly reduced.

The bonding process of the low moisture-permeable protective film coated with the intermediate and the adhesive may be carried out continuously after the bonding process of the polarizer and the high-moisture-permeable protective film, and other operations (for example, a drying treatment and a treatment for improving the adhesive force) may be performed on the formed intermediate. You may implement after implementing. In the case of continuously adhering the low-moisture-permeability protective film to which the pressure-sensitive adhesive is applied, a polarizing plate is obtained with very excellent productivity. When performing another operation to an intermediate body, the polarizing plate which has the further outstanding characteristic according to the objective is obtained.

In embodiment, the adhesion process of an intermediate body and a low moisture permeability protective film can be performed after performing a drying process to an intermediate body. Since the excess moisture can be removed very well by the drying treatment, discoloration such as redness, light leakage, or a decrease in the degree of polarization due to an increase in transmittance can be significantly prevented.

The conditions (for example, drying temperature, drying time, drying method) of a drying process can be suitably set according to the objective. For example, the drying temperature is 40 to 90 ° C., and the drying time is 1 to 10 minutes. In addition, since the adhesive is coated with the second transparent protective film, since it is not affected by moisture, the phenomenon of color change light leakage such as redness and a decrease in polarization due to an increase in transmittance may be significantly prevented. In addition, there is no need for a separate drying furnace, which reduces space constraints.

Adhesion between the polarizer and the high moisture-permeable protective film and adhesion of the polarizer (intermediate) and the low-humidity protective film may be performed so that the state after adhesion is flat. In the present invention, whether the state after adhesion is flat is determined based on the curl amount.

The curl amount is a sample obtained by punching the intermediate or the polarizing plate obtained by adhesion into a size of 100 mm x 100 mm in a direction of 45 ° with respect to the absorption axis of the polarizer, and the space lifted from the flat surface when the sample is placed on the flat surface. It is represented by the distance P. The smaller the curl amount of the intermediate or the polarizing plate, the more flat the state after adhesion and tends to be preferable.

In the present invention, the normal curl means a curl when the polarizer is concave in the opposite direction of the liquid crystal cell to be bonded, and the reverse curl means a curl when the polarizer is concave toward the liquid crystal cell to be bonded. In addition, the secondary reverse curl indicates a reverse curl generated after peeling off the release film (separator) in order to bond the polarizing plate to the liquid crystal cell.

The polarizing plate produced according to the present invention has a normal curl of 5 to 25 mm, preferably 10 to 20 mm. In the case of the normal curl of 5 to 25 mm, bubbles are not mixed when the intermediate body or the polarizing plate is bonded to the liquid crystal cell, and the bonding can be performed more easily.

Further, the reverse curl is 5 mm or less, preferably no reverse curl is generated. Furthermore, the secondary reverse curl when peeling off a release film will be 10 mm or less. When the reverse curl exceeds 5 mm, process problems such as mixing of bubbles may occur when the polarizer is bonded to the liquid crystal cell.

Representative examples of the treatment in which the state after adhesion or adhesion are flattened include a method of adhering the polarizer and the high moisture-permeable protective film and the polarizer and the low-moisture-permeable protective film in a state where tension is applied.

This method is equally applicable to the adhesion of the intermediate (polarizer + high moisture permeability protective film) and the low moisture permeability protective film. As a method of providing a tension, the method of using the peripheral speed difference of the guide roll which conveys a polarizer and a transparent protective film is mentioned, for example. More specifically, for example, when adhering a polarizer and a high moisture permeability protective film, what is necessary is just to make the rotation speed of the roll of the winding side of FIG. 1 faster than the rotation speed of the roll of a sending side. The rotational speed of the roll may be appropriately set according to the purpose or the desired tension.

Adhesion of a polarizer and a high moisture permeability protective film is typically performed using an adhesive agent (layer). As the adhesive, any suitable adhesive having good adhesion to the polarizer and the transparent protective film may be employed. For example, when a polarizer is a polyvinyl alcohol (PVA) type film, the adhesive agent containing PVA type resin is preferable. It is because it is especially excellent in adhesiveness with a polarizer. Arbitrary suitable PVA resin can be employ | adopted as PVA system resin, As a typical example, PVA which has an unsubstituted PVA and a highly reactive functional group is mentioned. PVA having a highly reactive functional group is particularly preferred. This is because the durability of the obtained polarizing plate can be further remarkably improved. Specific examples of the PVA having a highly reactive functional group include acetoacetyl group-modified PVA resins.

The degree of polymerization of the binder resin (eg, PVA resin) of the adhesive is preferably 100 to 3,000. By having a polymerization degree in this range, the adhesion with the polarizer and the transparent protective film can be particularly good. Although the thickness of an adhesive bond layer can be suitably set according to the objective or use of the image display apparatus in which a polarizing plate is used, Preferably it is 30-300 nm, More preferably, it is 50-150 nm. The adhesive layer is also formed by applying and drying the adhesive composition.

Preferably, the adhesive may further contain a crosslinking agent. The crosslinking agent is preferably a water soluble crosslinking agent. Specific examples of the water-soluble crosslinking agent include boric acid, borax, glutaraldehyde, melamine, oxalic acid, and the like. If desired, the adhesive may further contain any suitable additives (eg, antioxidants, ultraviolet absorbers) and / or catalysts (eg, acids).

Bonding of an intermediate body (polarizer + high moisture permeability protective film) and a low moisture permeability protective film is performed using an adhesive (layer) typically. As the pressure-sensitive adhesive, any suitable pressure-sensitive adhesive having good adhesion to the polarizer and the low-moisture-permeability protective film may be employed, and the necessary treatment may be performed to improve the adhesion (adhesive force) between the pressure-sensitive adhesive and the low-moisture-permeability protective film. Representative examples of such treatments include dry treatments, and specific examples of dry treatments include corona discharge treatment, plasma treatment, and low pressure UV treatment.

The adhesive is applied to the polarizing plate using a sheet (release film / adhesive / release film) coated with a pressure-sensitive adhesive (layer) for bonding to the liquid crystal cell without directly winding the polarizing plate (high moisture-permeable protective film / polarizer / low moisture-permeable protective film). A lamination process may be added. At this time, the pressure-sensitive adhesive is applied by applying tension as an optical pressure-sensitive adhesive usually used in a polarizing plate.

At this time, the treatment for improving the adhesive force (adhesive force) of the low-moisture-permeability protective film of the polarizing plate and the pressure-sensitive adhesive for bonding the liquid crystal cell can be performed. Representative examples of such treatments include dry treatments, and specific examples of dry treatments include corona discharge treatment, plasma treatment, and low pressure UV treatment.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

[Example]

1. Production of transparent protective film

(1) Protective film a

A corona treatment of one side of a norbornene-based film (trade name: ZEONOR, manufactured by Xeon, Japan, 40 μm) with a discharge amount of 200 W · min / m 2 gave a transparent protective film a having a moisture permeability of 0.6 g / m 2 · day. An adhesive was applied to the corona treated surface.

(2) protective film b

65 parts by weight of a glutalimide copolymer (N-methyl glutalimide content of 75% by weight, acid content of 0.01 mEq / g or less, glass transition temperature of 147 ° C) consisting of N-methylglutalimide and methyl methacrylate And 35 parts by weight of acrylonitrile-styrene copolymers containing 28% by weight and 72% by weight of acrylonitrile and styrene, respectively. The resin composition obtained by melt-kneading these was extruded with the T die melt extruder, and the film of 135 micrometers in thickness was obtained. The film was stretched 1.7 times at 160 ° C. in the MD direction, and then stretched 1.8 times at 160 ° C. in the TD direction. The thickness of the obtained biaxially stretched transparent film was 50 micrometers. One side of the transparent protective film was corona treated with a discharge amount of 200 W · min / m 2 to obtain a transparent protective film b having a moisture permeability of 87 g / m 2 · day, and an adhesive was applied to the corona treated side.

(3) protective film c

A triacetyl cellulose film having a water vapor permeability of 900 g / m 2 · day subjected to a saponification treatment having a thickness of 40 μm was used.

2. Preparation of Polarizing Plate

(1) Example 1

Polyvinyl alcohol having a thickness of 75 µm and a polymerization degree of 2400 was stretched 2.5 times while immersing in pure water at 30 ° C for 1 minute. Subsequently, it extended | stretched 1.2 time, immersing for 1 minute at 30 degreeC in the dyeing bath of the iodide and potassium iodide combination. Next, it extended | stretched twice, immersing in 60 degreeC 4% boric acid bath for 2 minutes. Furthermore, after immersing for 5 seconds in 30 degreeC aqueous solution of 5% of potassium iodide concentration, it dried for 5 minutes at 35 degreeC, and obtained the polarizer.

The PVA-type adhesive was used to adhere the transparent protective film c to one side of this polarizer, and the intermediate body was formed. At the time of adhesion, the adhesion was controlled by controlling the tension so that the obtained intermediate was flat. After drying the obtained intermediate at 5 degreeC for 5 minutes (that is, without winding up and storing intermediate), the transparent protective film a which the adhesive was apply | coated to the other side of the polarizer was adhered, and the polarizing plate was obtained. At the time of adhesion, the tension was controlled and applied so that the polarizing plate obtained was flat.

(2) Example 2

A polarizing plate was produced in the same manner as in Example 1 except that the transparent protective film b was used instead of the transparent protective film a.

(3) Comparative Example 1

The polarizer was produced like Example 1, the transparent protective films c and a were adhere | attached simultaneously on both surfaces using PVA-type adhesive agent, and it dried for 5 minutes at 60 degreeC, and 5 minutes at 70 degreeC, and obtained the polarizing plate.

(4) Comparative Example 2

The polarizer was produced like Example 1, the transparent protective films c and b were bonded together using the PVA-type adhesive agent on both surfaces, and the polarizing plate was obtained.

(5) Comparative Example 3

A polarizer was produced in the same manner as in Example 1, and the transparent protective film a coated with an adhesive on both surfaces thereof was simultaneously bonded to obtain a polarizing plate.

(6) Comparative Example 4

In the same manner as in Example 1, a polarizer was obtained. The PVA-type adhesive was used to adhere the transparent protective film c to one side of this polarizer, and the intermediate body was formed. At the time of adhesion, the adhesion was controlled by controlling the tension so that the obtained intermediate was flat. After drying the obtained intermediate for 5 minutes at 50 ° C. (ie, without winding up and storing the laminate), the transparent protective film a was also adhered to the other side of the polarizer using a PVA-based adhesive, and then 60 ° C. It dried for 5 minutes at 70 degreeC for 5 minutes, and obtained the polarizing plate. In the case of adhesion | attachment, tension was controlled and bonded so that the polarizing plate obtained might become flat.

(7) Comparative Example 5

In the same manner as in Example 1, a polarizer was obtained. The transparent protective film a was adhere | attached on one side of this polarizer using the PVA-type adhesive agent, and the intermediate body was formed. At the time of adhesion, the adhesion was controlled by controlling the tension so that the obtained intermediate was flat. After drying the obtained intermediate for 5 minutes at 50 ° C. (ie, without winding up and storing the laminate), the transparent protective film c was also adhered to the other side of the polarizer using a PVA-based adhesive, and then 60 ° C. It dried for 5 minutes at 70 degreeC for 5 minutes, and obtained the polarizing plate. In the case of adhesion | attachment, tension was controlled and bonded so that the polarizing plate obtained might become flat.

3. Experimental example: curling amount, 80 ℃ durability test (light leakage) and the presence of additional equipment change

The amount of curl and the 80 degreeC durability test (light leakage) were measured about the polarizing plates of an Example and a comparative example.

The amount of curl is determined by punching the polarizing plate into a size of 100 mm x 100 mm in the direction of 45 ° with respect to the absorption axis of the polarizer, and measuring the spatial distance lifted from the flat surface when the sample is placed on the flat surface. Indented distance is indicated by the normal (+) and the reverse distance is represented by the reverse (-).

80 degreeC durability test (light leakage) was visually confirmed and it was determined whether light leakage was confirmed.

In addition, regarding the manufacturing process, the possibility of the use of existing facilities, the addition and modification of facilities were examined.

These results are summarized in Table 1 below.

division Curl amount (mm) 80 ℃ durability test
(Light leakage) Process equipment Example 1 18 (static) Good Can use existing equipment Example 2 20 (static) Good Can use existing equipment Comparative Example 1 -7 (reverse curl) Good Can use existing equipment Comparative Example 2 -8 (reverse curl) Good Can use existing equipment Comparative Example 3 2 (static) Good Can use existing equipment Comparative Example 4 -8 (reverse curl) Good Joining process and drying furnace
Need additional Comparative Example 5 18 (static) Good

As shown in the above table, according to the present invention, the polarizing plates of Examples 1 and 2, which were sequentially bonded and adhered to the protective film having different moisture permeability without winding, were not only generated in the desired range of normal curl, but also without the addition and modification of equipment. It was confirmed that manufacturing is possible.

On the other hand, Comparative Examples 1, 2, and 4 were found to have a reverse curl of 5 mm or more due to the problem of water movement. As a result of bonding this polarizing plate to the liquid crystal cell, bubbles were generated between the polarizing plate and the liquid crystal cell.

In addition, the polarizing plate of Comparative Example 3 is a polarizing plate produced by using a pressure-sensitive adhesive with a protective film of the same moisture permeability is not affected by the moisture permeability, hardly generated curl, so no problems such as mixing of bubbles during bonding with the liquid crystal cell. . However, due to the inherent optical properties of the protective film a, the polarizing plate having such a configuration is difficult to be applied to an actual liquid crystal display device.

In addition, the polarizing plate of Comparative Example 5 was confirmed to generate a normal range of the normal curl, but because the drying process is carried out twice, a continuous process requires two bonding processes and two drying furnaces, the equipment changes and space constraints.

The present invention can not only prevent curling of the polarizing plate due to the difference in moisture content of the protective film, but can also achieve process economics, and thus can be widely used in the field of manufacturing a polarizing plate and a liquid crystal display including the same.

10: high moisture permeability protective film 20: polarizer
30: low moisture permeability protective film 31: pressure-sensitive adhesive layer
32: release film 40: pressure-sensitive adhesive layer bonded to the liquid crystal cell
41: release film 42: release film

Claims (7)

Adhering a protective film of high moisture permeability to one side of the polarizer, followed by drying to prepare an intermediate, and adhering a low moisture permeability protective film to the other side of the polarizer while the intermediate is flattened. Manufacturing method.
The method of claim 1, wherein the protective film having a low moisture permeability is obtained by laminating an adhesive layer and a release film on a side to be bonded to the polarizer.
The method of manufacturing a polarizing plate according to claim 1, wherein the high moisture permeability protective film has a moisture permeability of 200 to 1000 g / m ² · day at 40 ° C. and 90% RH.
The method of manufacturing a polarizing plate according to claim 1, wherein the low moisture permeability protective film has a water vapor transmission rate of 40 g and 90% RH of 200 g / m ² · day or less.
The method of claim 3, wherein the protective film having a water vapor transmission rate of 200 to 1000 g / m ² · day at 40 ° C. and 90% RH is made of triacetyl cellulose.
The method of claim 4, wherein the protective film having a water vapor transmission rate of 200 g / m ² · day or less at 40 ° C. and 90% RH is made of a polyolefin resin having a cyclo-based (cyclic) or norbornene structure.
A high moisture permeability protective film having a moisture permeability of 200 to 1000 g / m ² · day at 40 ° C. and 90% RH on one side of the polarizer is laminated with an adhesive, and a moisture permeability at 40 ° C. and 90% RH on the other side of the polarizer. A polarizing plate in which a protective film having a low moisture permeability of 200 g / m ² · day or less is laminated with an adhesive.

Images