KR20150031351A - Method of removing water from polarizer - Google Patents

Abstract

The present invention relates to a crosslinking solution for manufacturing a polarizer using the same, and a method for manufacturing a polarizer using the same and, more specifically, to a crosslinking solution including a surfactant to reduce the contact angle for the surface of a polarizer to improve dehydration properties on the surface of the polarizer to not needing wet wash after crosslinking, and to a method for manufacturing polarizer by using the same.

Description

[0001] METHOD OF REMOVING WATER FROM POLARIZER [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of declining a polarizer, and more particularly, to a declining method of a polarizer that improves the water resistance of the surface of the polarizer.

Liquid crystal display devices used in watches, mobile phones, PDAs, notebook PCs, monitors for PCs, DVD players, TVs, and the like are rapidly increasing in usage. A polarizer is used as a basic component of a liquid crystal display device.

Polarizers are generally prepared by swelling, dyeing, crosslinking, stretching, washing, washing and drying a polymer film such as a polyvinyl alcohol (PVA) film. However, in many cases, the stretching process may be performed separately in any of the swelling process, the dyeing process, and the crosslinking process, so that the stretching process and other processes can not be distinguished from each other in many cases. Further, before and after the swelling process, the dyeing process, and the crosslinking process, a cleaning bath may be formed to perform a cleaning process.

Typically, after the crosslinking process of the polarizer is completed, the cleaning process is a wet cleaning process for removing residual impurities attached to the surface of the polarizer through previous processes using a cleaning liquid.

However, the cleaning liquid used in the wet cleaning process is completely removed from the polarizer after the cleaning process. If the cleaning liquid is not removed, the impurities dissolved / dispersed in the cleaning liquid may remain on the surface of the polarizer, have.

An object of the present invention is to provide a method for improving the tenderness of the surface of a polarizer.

It is another object of the present invention to provide a method for removing polarizers that improves tenderness on the surface of a polarizer of a treatment solution used in producing polarizers.

1. A method for wet-making a polarizer produced by dying a dichroic substance onto a stretched polymer film, wherein a surfactant is added to a treatment solution used in a wet process after the dyeing step.

2. The method of claim 1, wherein the surfactant is at least one selected from the group consisting of an ionic surfactant, a nonionic surfactant, a silicone surfactant, and a fluorinated surfactant.

3. The method of claim 2, wherein the silicone surfactant comprises a silicon-based compound.

4. The silicone surfactant of claim 2, wherein the silicone surfactant is selected from the group consisting of BYK-301, BYK-306, BYK-307, BYK-320, BYK-325, BYK-331, BYK-333, BYK- At least one compound selected from the group consisting of BYK-341, BYK-344, BYK-346, BYK-347, BYK-348, BYK-379, BYK-370, BYK- , A method of declining a polarizer.

5. The method of claim 1, wherein the treatment solution is a crosslinking solution, a cleaning solution, or both.

6. The method of claim 5, wherein when the treatment solution is a crosslinking solution, the surfactant to be added is a silicone surfactant.

7. The method of claim 1, wherein the surfactant is contained in an amount of 0.05 to 10% by weight based on the total weight of the solution in the solution tank.

8. The method of claim 1, wherein the treatment solution has a contact angle to the polarizer surface of 30 DEG or less.

9. A poling method for polarizing a polarizer having undergone a swelling process and a dyeing process by crosslinking with a crosslinking solution of a top 5 and then performing a shrinking process.

10. A poling method of a polarizer, wherein the polarizer is subjected to a swelling process, a dyeing process,

The method of tilting the polarizer according to the present invention can improve the water-splitting property of the surface of the polarizer of the treatment solution by adding a surfactant to the treatment solution used in the production of the polarizer by the wet process.

In the method for removing a polarizer according to the present invention, when a surfactant is added to a crosslinking solution as a treatment solution, a separate wet cleaning step after the crosslinking step is not required. Thus, it is possible to manufacture an economical polarizer.

In addition, since the crosslinking solution for polarizer production of the present invention is completely removed from the surface of the polarizer, other impurities remaining on the surface of the polarizer can be completely removed together.

On the other hand, when a surfactant is added to the cleaning liquid as a treatment solution, the cleaning liquid has improved tenderness while keeping the cleaning power at least the same, and therefore does not remain on the surface of the polarizer in the water-splitting step, thereby effectively removing impurities on the surface of the polarizer .

The present invention relates to a process for producing a polarizer produced by dying a dichroic substance onto a stretched polymer film, wherein a surfactant is added to the treatment solution used in the wet process after the dyeing step, To reduce the contact angle of the polarizer, thereby improving the tenderness on the surface of the polarizer.

Hereinafter, the present invention will be described in more detail.

The wet-making process of the polarizer usually includes a swelling process, a dyeing process, a crosslinking process, a stretching process, and a cleaning process, and each process is performed by immersing the polymer film for a polarizer in a solution tank containing a treatment solution. However, the stretching process can be performed outside the solution tank.

In such a wet manufacturing process, the treatment solution needs to be completely removed after the wet process is completed. The treatment solution remaining on the surface of the polarizer may cause defective polarizers if impurities are dissolved or dispersed and can not be removed.

Therefore, the present invention solves the above problems by adding a surfactant to the treatment solution used in the wet process after the dyeing step, thereby improving the tenderness on the surface of the polarizer of the treatment solution. The surfactant is added to the treatment solution to improve the tenderness by lowering the contact angle of the treatment solution on the surface of the polarizer.

The surfactant according to the present invention can be used singly or in combination of two or more of ionic surfactant, nonionic surfactant, silicone surfactant and fluorinated surfactant, and preferably used in the process for producing polarizers A silicone surfactant having excellent compatibility with a solution can be used.

As the ionic surfactant, at least one of an anionic surfactant, a cationic surfactant and an amphoteric surfactant can be used.

Examples of the anionic surfactant include a carboxylic acid salt surfactant, a sulfonate salt surfactant, a sulfuric acid ester salt surfactant, and a phosphoric acid ester salt surfactant, which are used in the art, either singly or in combination. Examples of the carboxylate surfactant include higher fatty acid alkali salts, N-acrylamino acid salts, alkyl ether carbonates, acylated peptides and the like. Examples of the sulfonate salt surfactants include dodecylbenzenesulfonate, alkylbenzenesulfonate, Sulfonic acid salts, lignosulfonic acid salts and sulfo-carboxyl compounds. Examples of the sulfuric acid ester salt surfactants include sulfuric acid, alkyl sulfates, alkyl ether sulfates, alkylaryl ether sulfates and alkylamide sulfates. Examples of the phosphoric acid ester salt surfactant include alkyl phosphates, alkyl ether phosphates, alkyl aryl ether phosphates and the like.

As the cationic surfactant, an aliphatic amine salt, a quaternary ammonium salt surfactant, an aromatic quaternary ammonium salt surfactant, and a heterocyclic quaternary ammonium salt surfactant, which are used in the art, may be used alone or in combination of two or more thereof . Commercially available products include SAT-6C of Japan Sun Pharm, and ROFAMIN ST of Ecogreen.

As the amphoteric surfactant, a betaine surfactant, an amidazoline surfactant, a beta-alanine surfactant, and an amino surfactant, which are used in the art, may be used alone or in combination of two or more.

As the nonionic surfactant, ether surfactants, ester ether surfactants, ester surfactants, nitrogen-containing surfactants, and the like, which are used in the art, may be used singly or in combination of two or more. Examples of the ether surfactants include alkyl and alkylaryl polyoxyethylene ethers, alkylaryl formaldehyde condensed polyoxyethylene ethers, block copolymers having polyoxypropylene as a hydrophilic group, and ester ether surfactants include glycerin esters Polyoxyethylene ethers of sorbitol esters, polyoxyethylene ethers of sorbitol esters and the like. Examples of the ester type surfactants include polyethylene glycol fatty acid esters, glycerin esters, sorbitan esters, propylene glycol esters, And sugar ester. Examples of the nitrogen-containing surfactant include fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, amine oxide and the like. Commercially available products include HOMOTEX PT from KAO.

In the above-mentioned surfactants, alkyl and alkane may be independently of each other alkyl and alkane having 1 to 20 carbon atoms, and aryl may be aryl having 6 to 18 carbon atoms.

As the silicone surfactant, the silicone surfactant used in the art can be used without any particular limitation. Commercial products include BYK-301, BYK-306, BYK-307, BYK-320, BYK-325, BYK-331, BYK-333, BYK-335, BYK-337, BYK- , BYK-346, BYK-347, BYK-348, BYK-379, BYK-375, BYK-377 and BYK-378.

Preferably, the silicone surfactant comprises a silicone compound, more preferably a silicone compound which undergoes hydrogen bonding with the polarizer. The silicone-based surfactant that makes a hydrogen bond with the polarizer can be preferably used because it does not form a precipitate in the treatment solution, and therefore can be added to the crosslinking solution.

When the silicone surfactant is added to the crosslinking solution according to an embodiment of the present invention, the contact angle of the crosslinking solution to the surface of the polarizer can be lowered. The crosslinking liquid having a low contact angle with respect to the surface of the polarizer can be substantially completely removed from the surface of the polarizer even if the shrinkage effect is improved and the shrinking process is performed immediately without a subsequent wet cleaning process.

As the fluorine-based surfactant, a fluorine-based surfactant used in the art can be used without any particular limitation. More specifically, any surfactant containing a fluorine-based compound can be used without limitation, and more specific examples include ionic fluorine surfactants. Examples of commercially available products include BYK-388 manufactured by BYK.

According to another embodiment of the present invention, preferably, the surfactant other than the silicon surfactant in the above-mentioned surfactant can cause precipitation in the treatment solution, so that the surfactant added to the cleaning liquid used in the cleaning process during the production process good. The cleaning liquid according to this embodiment may contain a surfactant to lower the contact angle of the cleaning liquid with respect to the surface of the polarizer. The cleaning liquid having a low contact angle with respect to the surface of the polarizer has improved tenderness and does not remain on the surface of the polarizer in the spinning process.

The surfactant according to the present invention may be contained in an amount of 0.05 to 10% by weight, preferably 0.3 to 10% by weight, more preferably 0.5 to 10% by weight based on the total weight of the treatment solution. When the content is less than 0.05% by weight, the surface contact angle is insignificantly improved and the effect of the water-reducing effect is difficult to improve. If the content is more than 10% by weight, the adhesion between the polarizer and the protective film may be deteriorated.

As described above, the treatment solution of the present invention containing a surfactant is preferable in that the contact angle at the surface of the polarizer is 30 DEG or less, in order to ensure excellent water resistance.

The above-described method of subjecting a polarizer of the present invention can be usefully applied to the production process of a polarizer. Hereinafter, a method for removing a polarizer according to the present invention will be described in more detail.

< Polarizer >

A polarizer is one in which a dichroic dye is adsorbed and oriented on a stretched polymer film.

The polymer film constituting the polarizer is not particularly limited as long as it is a film which can be dyed with a dichroic substance such as iodine. Specifically, the polymer film may be a polyvinyl alcohol film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film , Cellulose films, partially saponified films thereof, and the like; Or a dehydrated polyvinyl alcohol film, a dehydrochloric acid-treated polyvinyl alcohol film, and the like. Of these, a polyvinyl alcohol-based film is preferable because it has an excellent effect of enhancing the uniformity of the degree of polarization in the plane and is excellent in dye affinity for a dichroic substance.

More preferably, it may be a polyvinyl alcohol-based film obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include acrylamide monomers having an unsaturated carboxylic acid type, an unsaturated sulfonic acid type, an olefin type, a vinyl ether type, and an ammonium group.

The polyvinyl alcohol resin may also be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polymerization degree of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

Such a polyvinyl alcohol-based resin film is used as the original film of the polarizer. The method of forming the film of the polyvinyl alcohol-based resin is not particularly limited, and a known method can be used. The thickness of the original film is not particularly limited, and may be, for example, 10 to 150 mu m.

< Swelling process >

The swelling process is performed by immersing an unstretched polyvinyl alcohol film in a swelling tank filled with a swelling liquid to remove impurities such as dust and anti-blocking agent deposited on the surface of the polyvinyl alcohol film, Is a process for improving physical properties of a polarizer by swelling a film to improve elongation efficiency and prevent uneven dyeing.

As the swelling liquid, water (pure water, deionized water) can be used alone, and when a small amount of glycerin or potassium iodide is added thereto, the swelling of the polymer film and the processability can be improved. The content of glycerin is preferably 5% by weight or less based on 100% by weight of the swollen liquid, and the content of potassium iodide is preferably 10% by weight or less. In addition, boric acid, chloride, inorganic acid, inorganic salt, water-soluble organic solvent, alcohols and the like may be further added in an amount of about 0.01-10% by weight.

The swelling bath temperature is preferably 20 to 45 캜, more preferably 25 to 40 캜. The execution time (swelling tank immersion time) of the swelling step is preferably 180 seconds or less, more preferably 90 seconds or less. When the immersion time is within the above range, it is possible to prevent the swelling from becoming excessive and saturation, to prevent breakage due to softening of the polyvinyl alcohol film and to improve the polarization degree by uniformly adsorbing iodine in the dyeing step have.

The stretching process may be performed together with the swelling process, and the stretching ratio is preferably about 1.1 to 3.5 times. The swelling process may be omitted and swelling may be performed simultaneously in the staining process.

In the swelling process, the film is likely to be swollen in the width direction to cause wrinkles in the film. Therefore, an expander roll, a spiral roll, a crown roll, a cross guider ), A bend bar, a tenter crip, or the like, while conveying the film while removing the wrinkles of the film.

<Dyeing Process>

The dyeing process is a process in which a polyvinyl alcohol-based film is dipped in a dyeing tank filled with a dyeing liquid containing a dichroic substance, for example, iodine, to adsorb iodine on the polyvinyl alcohol-based film.

The iodine molecules are arranged in parallel with the stretching direction of the polyvinyl alcohol film when the dyed polyvinyl alcohol film is stretched or the stretched polyvinyl alcohol film is dyed. Since the iodine molecules thus arranged have high dichroism, light oscillating in the stretching direction is absorbed, and light oscillating perpendicularly to the stretching direction is transmitted. As a result, it becomes possible to obtain polarized light that vibrates in a specific direction from the natural light transmitted through the polarizing plate.

The dyeing solution may contain water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine is preferably 0.4 to 400 mmol / L, more preferably 0.8 to 275 mmol / L, and most preferably 1 to 200 mmol / L with respect to 100 wt% of the aqueous solution for dyeing. To further improve the dyeing efficiency, iodide may be further included as a dissolution aid.

As the iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide may be used alone or in combination of two or more. Of these, potassium iodide is preferable in view of high solubility in water. The content of iodide is preferably 0.010 to 10% by weight, more preferably 0.100 to 5% by weight, based on 100% by weight of the dyeing solution.

Further, compounds other than iodide such as boric acid, zinc chloride, cobalt chloride, etc. may be used together. Even if boric acid is added in the present step, it is distinguished from the following crosslinking (boric acid treatment) process in that it is used together with iodine.

 The temperature of the dye bath is preferably 5 to 42 ° C, more preferably 10 to 35 ° C. The immersion time of the polyvinyl alcohol film in the dyeing bath is not particularly limited, and is preferably 1 to 20 minutes, and more preferably 2 to 10 minutes.

The stretching process may be performed together with the dyeing process, and in this case, the cumulative stretching ratio is preferably 1.1 to 4.0 times. In the present specification, "cumulative stretching ratio" represents the value of the product of the stretching ratio at each step.

< Crosslinking process >

The crosslinking process is a process for immobilizing a dyed polyvinyl alcohol film in an aqueous crosslinking solution to immobilize adsorbed iodine molecules so that the dyeability due to physically adsorbed iodine molecules is not deteriorated by the external environment.

Although dichroic dyes are not often eluted in a humidity environment, iodine molecules often dissolve or sublimate depending on the environment when the crosslinking reaction is unstable, and sufficient crosslinking reaction is required. Further, in order to improve the optical characteristics by orienting the iodine molecules positioned between all the polyvinyl alcohol molecules and the molecules, the crosslinking process is important because the crosslinking process generally needs to be stretched to the greatest stretching ratio.

The crosslinking solution may further comprise water as a solvent, boron compounds such as boric acid and sodium borate, iodide and the like, and an organic solvent mutually soluble with water. Further, according to embodiments of the present invention, the above-mentioned surfactant, preferably a silicone surfactant, may be further included.

The boron compound imparts short crosslinking and rigidity to suppress wrinkling during processing, thereby improving handling properties and forming iodine alignment. The content of the boron compound is preferably 1 to 10% by weight, more preferably 2 to 6% by weight based on 100% by weight of the aqueous crosslinking solution.

Iodide is used to prevent the uniformity of the degree of polarization in the plane of polarizers and the desorption of dyed iodine. The iodide may be the same one as used in the dyeing process, and the content thereof may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on 100% by weight of the aqueous crosslinking solution. If the content is less than 0.05% by weight, the iodide ion in the film may escape to increase the transmittance and the color value of the polarizer may change, There is a problem that the transmittance is reduced.

The temperature of the crosslinking bath is 20 to 70 캜, and the immersion time of the polyvinyl alcohol film in the crosslinking bath may be 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching process may be performed together with the crosslinking process, and in this case, it is preferable that the stretching is performed such that the total cumulative stretching ratio is 3.0 to 7.0 times.

< Stretching process >

The stretching process may be carried out with at least one of the swelling process, the dyeing process and the crosslinking process, as described above, or may be carried out in air or an inert gas while transferring the film after the processes, and a separate stretching May be performed by an independent stretching process using a coater. Alternatively, the unstretched polyvinyl alcohol film may be stretched in air or an inert gas before the swelling process, and then the film may be subjected to swelling, dyeing, crosslinking, washing and drying processes.

The stretching may be carried out in one step or in two or more steps, but preferably in two or more steps. The stretching may be carried out by a method such as setting the difference in peripheral speed of the nip roll or the like. Further, as in the swelling process, the expander roll, the spiral roll, the crown roll, the cross guider, the bend bar, and the like can be installed in the bath and / or the bath door.

The final draw ratio is about 4.5 to 7.0 times, preferably about 5.0 to 6.5 times.

<Wet Cleaning Process>

In the production process of the present invention, a wet cleaning process can be optionally performed as required. The addition of the surfactant to the crosslinking solution can be carried out, for example, after the swelling and / or dyeing step, and even after the crosslinking step if no surfactant is added to the crosslinking solution.

The wet cleaning process is a process of immersing a polyvinyl alcohol film in a manufacturing process in a water bath filled with a cleaning liquid to remove unnecessary residues such as boric acid adhering to the polyvinyl alcohol film in the previous process.

The cleaning liquid may be water (pure water, deionized water), and if necessary, iodide may be further added. In addition, the surfactant may further include the above-described surfactant according to one embodiment of the present invention.

The temperature of the water bath is preferably 5 to 60 ° C, more preferably 10 to 40 ° C. The cleaning process may be carried out whenever necessary as the previous steps such as the dyeing process, the crosslinking process or the stretching process are completed. It may also be repeated one or more times, and the number of repetition is not particularly limited.

&Lt;

The water-drop process is a process for removing a liquid component including a treatment solution remaining on the surface of a polyvinyl alcohol film that has been subjected to dyeing, crosslinking and stretching.

The water-reducing process may be performed using a glass bar, an air knife, a nip roll, etc. The above process may be used singly or in combination, and may be repeated one or more times , The number of repetitions thereof is not particularly limited.

According to the present invention, when a treatment solution to which a surfactant is added is used, since the contact angle of the treatment solution with respect to the surface of the polyvinyl alcohol-based film (polarizer) is relatively low, the treatment solution can be easily removed in the pouring step. Thus, a polyvinyl alcohol-based film can be obtained in which impurities are effectively removed together with the treatment solution on its surface.

<Drying step>

The drying process is a process for drying a polyvinyl alcohol-based film and drying the dried polyvinyl alcohol-based film to further improve the orientation of the iodine molecules dissolved by the drying agent to obtain a polarizer excellent in optical characteristics.

As the drying method, natural drying, air drying, heating and drying, far infrared ray drying, microwave drying, hot air drying and the like can be used. Recently, microwave drying in which only water in the film is activated and dried is newly used, Drying is mainly used. For example, it may be hot air dried at 20 to 90 DEG C for 1 to 10 minutes. The drying temperature is preferably low in order to prevent deterioration of the polarizer, more preferably 80 ° C or lower, and most preferably 60 ° C or lower.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example  One

(VF-PS, KURARAY Co.) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 30 DEG C for 2 minutes and swelled. Then, 3.5 mmol / L of iodine and 2 wt% of potassium iodide Was dipped in an aqueous solution for dyeing at 30 DEG C for 4 minutes. At this time, the stretching process was also performed so that the stretching ratio was 1.3 times and 1.4 times that in the swelling and dyeing processes, respectively. Subsequently, an aqueous solution (crosslinking solution) containing 50 wt% of potassium iodide, 10 wt% of boric acid, 3.7 wt% of boric acid and 0.3 wt% of a quaternary ammonium salt surface active agent SAT-6C Followed by immersion and crosslinking. At this time, stretching was also performed so that the total cumulative stretching ratio was 6.0 times in the crosslinking step. Subsequently, a water-repellent process was performed using a glass bar, and a polyvinyl alcohol film, which had been subjected to the water-repellent process, was dried in an oven at 60 ° C for 4 minutes to prepare a polarizer. A triacetylcellulose (TAC) film was laminated on both sides of the prepared polarizer to prepare a polarizing plate.

Example  2 to 21 and Comparative Example  One

A polarizing plate was produced in the same manner as in Example 1, except that the surfactant was used in the components and contents shown in Table 1. [

However, in Examples 11 to 16 using the cleaning liquid, a wet cleaning process in which the polyvinyl alcohol film was immersed in an aqueous solution (cleaning liquid) at 10 ° C for 10 seconds was performed after the crosslinking process. In Comparative Example 1, A wet cleaning process in which the vinyl alcohol film was immersed for 10 seconds was performed after the crosslinking process.

Test Example

One. Number of foreign bodies  Measurement (automatic checker)

Defact Per Meter The number of defects detected by the automatic tester per 1 m of polarizer was measured by an automatic tester.

The lower the number of defects, the less foreign objects are considered.

2. Water characteristic

The contact angle of the prepared polarizer was measured through a contact angle meter.

The lower the contact angle, the higher the tenderness.

3. Adhesion (Cutter Evaluation)

The prepared polarizing plate was allowed to stand at room temperature for 1 hour, and then a cutter blade was inserted between each polarizing plate (between the polarizing plate and the polarizing plate protective film), and the way in which the blade was pushed was evaluated according to the following criteria .

A: The cutter blade does not enter any film.

○: When pushing the blade, it stops when the blade reaches 1 to 2 mm between at least one of the films.

?: When the blade is pushed, it stops when the blade enters 3 to 5 mm between at least one of the films.

X: When pushing the blade, the blade is easily inserted between at least one of the films.

4. Water resistance

The prepared polarizing plate was allowed to stand for 24 hours under an environment of 23 ° C and a relative humidity of 55%, and tested for water resistance at room temperature. First, the polarizing plate was cut into a rectangular shape of 5 cm x 2 cm with the absorption axis (stretching direction) of the polarizing plate as the long side to prepare a sample, and the dimension in the long side direction was measured accurately. Here, the sample exhibits uniform color uniformly over the entire surface due to iodine adsorbed on the polarizer. About 8% of the sample in the longitudinal direction is immersed in a hot water tank at 60 DEG C and held for 4 hours. When the immersion is completed, the sample is taken out of the water tank to wipe out the water, and the degree of shrinkage of the polarizer is measured. Specifically, the distance from the end of the protective film at the center of the short side of the sample to the end of the shrunk polarizer was measured and defined as the shrinkage length. In addition, iodine elutes from the peripheral portion of the polarizer which is in contact with the hot water due to the hot water immersion, resulting in a portion in which the color is missing in the peripheral portion of the sample. The degree of discoloration was measured as the distance from the end of the shrunk polarizer at the center of the short side of the sample to the area where the color unique to the polarizing plate remained, and this was taken as the iodine drop length. The sum of the shrinkage length and the iodine dropout length is taken as the total erosion length, that is, the total erosion length is the distance from the end of the sample at the center of the short side of the sample to the region where the color unique to the polarizer remains. It can be concluded that the smaller the shrinkage length, the iodine dropout length and the total erosion length are, the higher the adhesiveness (water temperature resistance) is in the presence of water.

◎: total erosion length <2 mm

?: 2 mm? Total erosion length <3 mm

?: 3 mm? Total erosion length <5 mm

×: 5 mm ≦ total erosion length

5. Precipitation

It was confirmed whether or not the surfactant was precipitated in the crosslinking solution and / or the cleaning solution to which the polarizing plate surfactant was added.

<Criteria>

○: No precipitation and no change in color

DELTA: no precipitation occurred and the liquid color change oil

X: occurrence of precipitation and change in color

Crosslinking solution Cleaning liquid Interface
Activator Number of foreign bodies Water characteristic Adhesion Water resistance Sedimentation
Whether DPM Contact angle (°) Example 1 0.3 - A-1 0.4 41 ◎ ◎ ○ Example 2 0.5 - A-1 0.2 35 ◎ ◎ ○ Example 3 One - A-1 0.1 28 ◎ ◎ ○ Example 4 5 - A-1 0.1 22 ◎ ○ ○ Example 5 10 - A-1 0.1 18 ◎ ○ ○ Example 6 0.3 - A-2 0.1 29 ◎ ◎ ○ Example 7 0.5 - A-2 0.1 24 ◎ ◎ ○ Example 8 0.7 - A-2 0.1 18 ◎ ◎ ○ Example 9 0.7 - A-3 0.1 22 ◎ ◎ ○ Example 10 0.7 - A-4 0.1 24 ◎ ◎ ○ Example 11 - One A-1 0.1 30 ◎ ◎ ○ Example 12 - 0.7 A-2 0.1 19 ◎ ◎ ○ Example 13 - 0.7 A-3 0.1 23 ◎ ◎ ○ Example 14 0.5 0.5 A-2 0.1 22 ◎ ◎ ○ Example 15 0.7 0.1 A-2 0.1 17 ◎ ◎ ○ Example 16 0.1 0.7 A-2 0.1 20 ◎ ○ ○ Example 17 12 - A-2 0.1 15 ○ ◎ △ Example 18 0.5 - A-5 0.8 28 ◎ ◎ × Example 19 0.5 - A-6 0.4 24 ◎ ◎ △ Example 20 0.5 - A-7 1.0 26 ◎ ◎ × Example 21 0.5 - A-8 1.1 19 ◎ ◎ × Comparative Example 1 - - - 1.2 56 ○ ○ ○ A-1: SAT-6C (Cationic Surfactant, Japan Sun Pharm)
A-2: BYK-331 (silicone surfactant, BYK)
A-3: BYK-333 (silicone surfactant, BYK)
A-4: BYK-348 (silicone surfactant, BYK)
A-5: Dodecylbenzenesulfonate (anionic surfactant, Aldrich)
A-6: HOMOTEX PT (nonionic surfactant, KAO)
A-7: ROFAMIN ST (a cationic surfactant, Ecogreen)
A-8: BYK-388 (fluorine surfactant, BYK)

As shown in Table 1, it can be seen that the examples using the treating solution (crosslinking solution, washing solution) containing the surfactant showed a decrease of at least about 50% in the number of foreign matters compared with Comparative Example 1 in which the surfactant was not used, And the basic physical properties of the polarizer are not deteriorated.

Particularly, in the case of Examples 1-10 and 17-21, it can be confirmed that the number of foreign matters remaining on the surface is remarkably small even if the wet cleaning is not performed after the crosslinking step.

In addition, in the examples, it can be seen that the number of foreign matters is further reduced when the contact angle is 30 DEG or less, and it can be seen that among the examples, the silicon based surfactant does not precipitate and is more preferable.

However, in the case of Example 17 in which the surfactant is contained in an excess amount, it can be confirmed that the adhesive strength of the polarizer to the protective film is somewhat lowered.

Claims (10)

In a wet process for producing a polarizer produced by dyeing a dichroic substance onto a stretched polymer film,
A surfactant is added to the treatment solution used in the wet process after the dyeing step.
The method according to claim 1, wherein the surfactant is at least one selected from the group consisting of an ionic surfactant, a nonionic surfactant, a silicone surfactant, and a fluorinated surfactant.
The method according to claim 2, wherein the silicone surfactant comprises a silicone compound.
The silicone surfactant according to claim 2, wherein the silicone surfactant is selected from the group consisting of BYK-301, BYK-306, BYK-307, BYK-320, BYK-325, BYK-331, BYK-333, BYK- At least one selected from the group consisting of BYK-341, BYK-344, BYK-346, BYK-347, BYK-348, BYK-349, BYK-370, BYK- .
The method according to claim 1, wherein the treatment solution is a crosslinking solution, a cleaning solution or both.
[7] The method according to claim 5, wherein when the treatment solution is a crosslinking solution, the surfactant to be added is a silicone surfactant.
The method according to claim 1, wherein the surfactant is contained in an amount of 0.05 to 10% by weight based on the total weight of the solution in the solution tank.
The method according to claim 1, wherein the treatment solution has a contact angle with respect to the surface of the polarizer of 30 ° or less.
Wherein the polarizer having undergone the swelling process and the dyeing process is crosslinked with the crosslinking solution of claim 5 and then subjected to a shrinking process.
A swelling process, a dyeing process, and a crosslinking process, is washed with the cleaning liquid of claim 5, and then the shrinking process is performed.