KR20170021476A - Polarizing plate and method of preparing the same - Google Patents

Abstract

The present invention relates to a polarizing plate, a manufacturing method thereof, and an image display device. More specifically, the polarizing plate comprises: a polarizer of which the uneven average interval (Sm) is 0.5 nm to 5 mm and of which the maximum height roughness (Rt) is 100 nm to 1000 nm; an adhesive layer of which the thickness is 250 nm to 850 nm formed on at least one side of the polarizer; and a protective film which is stacked on the adhesive layer, thereby having improved optical properties and appearance characteristics of the polarizing plate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate,

The present invention relates to a polarizing plate having both excellent optical characteristics and external appearance characteristics, a method for producing the same, and an image display apparatus including the polarizing plate.

BACKGROUND OF THE INVENTION Image display devices such as watches, mobile phones, PDAs, notebook PCs, monitors for PCs, DVD players, TVs, and the like are electronic products commonly used. A polarizing plate is used as a basic component of the image display apparatus.

If the stretching magnification is increased in order to improve the orientation of the iodine complex of the polarizer for the purpose of improving the performance of the polarizer in the production of the polarizer, the width of the polarizer may be reduced, resulting in appearance defects such as streaks on the polarizer.

Korean Patent Laid-Open Publication No. 2014-0114923 discloses a technique for improving appearance defects by improving the contact angle with an adhesive composition prepared by adding a leveling agent of an acetylene skeleton.

However, even with this method, it is not possible to improve the defective appearance of the polarizing plate, and to maintain the optical characteristics as excellent as required.

Korea Patent Publication No. 2014-0114923

An object of the present invention is to provide a polarizing plate and an image display apparatus including the same that can prevent appearance defects without deteriorating optical properties such as transmittance and polarization degree.

It is another object of the present invention to provide a polarizing plate excellent in physical properties such as high adhesive property, moisture resistance and heat resistance, and an image display apparatus including the same.

1. A polarizer having an unevenness average spacing Sm of 0.5 to 5 mm and a maximum height illuminance Rt of 100 to 1000 nm; An adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; And a protective film laminated on the adhesive layer .

2. The polarizer according to 1 above, wherein the adhesive layer has a thickness of 300 to 800 nm.

3. The polarizing plate according to item 1 above, wherein the adhesive layer is formed from an adhesive composition comprising a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate crosslinking agent.

4. (S1) fabricating a polarizer having a concavo-convex mean spacing Sm of 0.5 to 5 mm and a maximum height illuminance Rt of 100 to 1000 nm; (S2) applying an adhesive composition to one surface of at least one of the polarizer and the protective film to form an adhesive layer of 250 to 850 nm; (S3) bonding the polarizer to the protective film via the adhesive layer.

5. The method of producing a polarizing plate according to 4 above, wherein the adhesive composition comprises a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate crosslinking agent.

6. The process for producing a polarizing plate according to 5 above, wherein the acetoacetyl group-containing polyvinyl alcohol resin and the glyoxylate crosslinking agent are contained in an amount of 2.5 to 6% by weight based on the total weight of the adhesive composition based on the solid content.

7. The production method of a polarizing plate according to item 4 above, wherein a bonding speed for bonding the protective film to the adhesive layer is 10 to 35 m / min.

8. An image display device comprising a polarizing plate according to any one of items 1 to 3 above.

The polarizing plate according to an embodiment of the present invention exhibits significantly poor appearance defects such as streaks of streaks without deteriorating optical properties such as transmittance and polarization degree.

The polarizing plate according to an embodiment of the present invention may have excellent adhesion, moisture resistance, and heat resistance.

According to the method of manufacturing a polarizing plate according to an embodiment of the present invention, it is possible to enlarge the usable range of the polarizer and to reduce the defect rate, and there is no need for an additional process for removing defects, so that convenience, .

1 is a photograph of a surface of a polarizer produced in the production example of the present invention.
2 is a view schematically showing a water resistance evaluation test method of a polarizing plate according to the present invention.

Polarizer

An embodiment of the present invention is a polarizer wherein the irregularity mean spacing Sm is 0.5 to 5 mm and the maximum height illuminance Rt is 100 to 1000 nm; An adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; And a protective film laminated on the adhesive layer to thereby provide a polarizing plate having both excellent optical characteristics and external appearance characteristics.

<Polarizer>

The polarizing plate according to the present invention includes a polarizer having a concavo-convex mean spacing Sm of 0.5 to 5 mm and a maximum height illuminance Rt of 100 to 1000 nm.

The mean spacing (Sm) of the irregularities means the average of the irregular intervals of the profile within the reference distance (evaluation distance).

The maximum height roughness (Rt) is the distance between the highest point and the lowest point of the profile within the reference distance (evaluation distance).

The polarizer according to the present invention has Sm and Rt in the above specific range, so that a polarizing plate having both excellent optical characteristics and external appearance characteristics can be produced. If Sm is less than 0.5 mm, there is a problem that optical characteristics are deteriorated. If Sm is more than 5 mm, appearance defects can not be improved. If Rt is less than 100 nm, there is a problem that optical characteristics are deteriorated. If Rt is more than 1000 nm, appearance defects can not be improved.

<Adhesive Layer>

The polarizer according to the present invention includes an adhesive layer having a thickness of 250 to 850 nm on at least one surface of the polarizer.

If the polarizer having the Sm and Ra ranges according to the present invention is manufactured as a polarizing plate by a conventional method, streaks will occur. Therefore, the present invention significantly reduces the streaks of the polarizing plate without lowering the optical characteristics such as the polarization degree and the transmittance by introducing the adhesive layer having the above-mentioned specific thickness. In this respect, the thickness of the adhesive layer may be more preferably 300 to 800 nm.

When the thickness of the adhesive layer is less than 250 nm, the defective appearance is not improved. When the thickness is more than 850 nm, the optical characteristics are deteriorated.

A method for increasing the thickness of the adhesive layer is not particularly limited, and for example, a method of increasing the concentration of the solid content in the adhesive composition or increasing the bonding speed for bonding the protective film to the adhesive layer may be used.

<Protection film>

The protective film according to an embodiment of the present invention is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. Specific examples thereof include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate A polyester-based resin; Cellulose-based resins such as diacetylcellulose, triacetylcellulose, and cellulose acetate propionate; Polycarbonate resin; Polyacrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymer; Polyolefin resins such as polyethylene, polypropylene, cycloolefins or norbornene structures, polyolefins and ethylene propylene copolymers; Polyamide resins such as nylon and aromatic polyamide; Imide resin; Polyether sulfone type resin; Sulfone based resin; Polyether ketone resin: a polyphenylene sulfide resin; Vinyl alcohol-based resin; Vinylidene chloride resins; Vinyl butyral resin; Allylate series resin; Polyoxymethylene type resin; Epoxy resin, and the like, and a film composed of the blend of the thermoplastic resin may also be used. Further, a film made of a thermosetting resin such as (meth) acrylic, urethane, epoxy, or silicone or a film made of an ultraviolet curable resin may be used.

When a cycloolefin-based resin is used for the protective film, a cycloolefin-based resin known in the art can be used without any particular limitation. For example, a monomer unit of a cycloolefin such as norbornene or a polycyclic norbornene- And may be a hydrogenated product of a ring-opening polymer of the cycloolefin or a ring-opening copolymer using two or more kinds of cycloolefins, as well as an addition product of a cycloolefin and an aromatic compound having a chain olefin or vinyl group It may be coalesced. In addition, a polar group may be introduced into the cycloolefin-based resin.

Of these, a cellulose-based film, a polyolefin-based film, and a polyacryl-based film are preferable in consideration of the polarization property or durability.

Method for producing polarizer

According to another embodiment of the present invention, there is provided a method of manufacturing a polarizer, comprising: preparing a polarizer having a concavo-convex mean spacing Sm of 0.5 to 5 mm and a maximum height roughness Rt of 100 to 1000 nm; Applying an adhesive composition to at least one side of the polarizer to form an adhesive layer of 250 to 850 nm; And laminating a protective film on the adhesive layer.

Hereinafter, one embodiment of the method for producing a polarizing plate of the present invention will be described in more detail.

First, a polarizer having an unevenness average spacing Sm of 0.5 to 5 mm and a maximum height roughness Rt of 100 to 1000 nm is manufactured (S1).

In order to make the polarizer have the above-mentioned specific Sm and Rt ranges, the production process conditions of the polarizer can be adjusted. For example, the stretching ratio, drying time, and the like can be controlled. Hereinafter, a method of manufacturing a polarizer according to the present invention will be described in detail.

The polymer film for producing a polarizer may be a polymer film used for producing a polarizing plate and may be a film that can be dyed by a dichroic substance (for example, iodine) known in the art without any particular limitation. For example, A polyvinyl alcohol film, a partially saponified polyvinyl alcohol film; A hydrophilic polymer film such as a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film, a partially saponified film thereof and the like; Or a dehydrated polyvinyl alcohol-based film, a dehydrochlorinated acid-treated polyvinyl alcohol-based film, or the like can be used. Of these, a polyvinyl alcohol-based film may be preferable in that it has an excellent effect of enhancing the uniformity of the degree of polarization in the plane and is excellent in dye affinity for iodine.

The method of producing the polarizer may include a swelling step, a dyeing step, a crosslinking step, a complementary coloring step, a stretching step, a washing step and a drying step, and may be classified by a stretching method. For example, a dry stretching method, a wet stretching method, or a hybrid stretching method in which the two kinds of stretching methods are mixed can be used. Hereinafter, a method of manufacturing a polarizer according to an embodiment of the present invention will be described with reference to a wet drawing method, but the present invention is not limited thereto.

The steps other than the drying step may be performed in a state in which the polyvinyl alcohol film is immersed in a constant temperature bath filled with at least one solution selected from various kinds of solutions.

<Swelling step>

The swelling step is carried out by immersing the unstretched polyvinyl alcohol film in a swelling tank filled with a swelling aqueous solution before dyeing to remove impurities such as dust and anti-blocking agent deposited on the surface of the polyvinyl alcohol film, And may be a step for improving physical properties of the polarizer by improving the drawing efficiency and preventing uneven dyeing by swelling the film.

As the swelling aqueous solution, a swelling aqueous solution known in the art may be used without limitation, if it is an aqueous swelling solution used in the swelling step. For example, water (pure water, deionized water) may be used alone, When a small amount of glycerin or potassium iodide is added to the polymer film, the swelling of the polymer film as well as the processability can be improved. The content of glycerin may be 5 wt% or less with respect to 100 wt% of the aqueous swelling solution, and the content of potassium iodide may be 10 wt% or less, but is not limited thereto.

The temperature of the swelling bath is not particularly limited, but may be 20 to 45 캜, and may be, for example, 25 to 40 캜.

The execution time of the swelling step (swelling bath immersion time) can be applied without any particular limitation, for example, 180 seconds or less, preferably 90 seconds or less. When the immersion time is within the above range, excessive swelling and saturation can be suppressed, so that breakage due to softening of the polyvinyl alcohol film can be prevented, the adsorption of iodine can be uniformed in the dyeing step, have.

The stretching step may be carried out together with the swelling step, wherein the stretching ratio may be about 1.1 to 3.5 times, but is not limited, and preferably 1.5 to 3.0 times. If the stretching ratio is less than 1.1 times, wrinkles may occur. If the stretching ratio is more than 3.5 times, initial optical characteristics may become weak.

<Stage of dyeing>

The dyeing step may be a step of immersing the polyvinyl alcohol-based film in a dyeing bath filled with a dyeing aqueous solution containing a dichroic substance, for example, iodine, to adsorb iodine on the polyvinyl alcohol-based film.

The aqueous solution for dyeing may be an aqueous solution for dyeing known in the art without any particular limitation, and may contain water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine may be 0.4 to 400 mmol / L, but not limited thereto, preferably 0.8 to 275 mmol / L, and most preferably 1 to 200 mmol / L with respect to 100% by weight of the aqueous solution for dyeing . Iodide may be further included as a dissolution aid so that the dyeing efficiency can be improved. As the iodide, iodide known in the art can be used without limitation, and examples thereof include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, calcium iodide, iodide Tin, and titanium iodide. Of these, potassium iodide may be preferable in view of high solubility in water. The content of iodide may be 0.01 to 10% by weight, but is not limited to, preferably 0.1 to 5% by weight based on 100% by weight of the dyeing aqueous solution.

In addition, to increase the iodine complex content in the polyvinyl alcohol-based film, boric acid in the dye bath may be added in an amount of 0.3 to 5 wt%, but is not limited thereto. If boric acid in the dyeing tank is 0.3 wt% or less, there is no effect on increasing the content of PVA-I3-complex and PVA-I5-complex. If boric acid in the dyeing tank is 5 wt% or more, the risk of cutting may be high.

The temperature of the dye bath may be 5 to 42 째 C, but is not limited thereto, preferably 10 to 35 째 C. The immersing time of the polyvinyl alcohol film in the dyeing bath is not particularly limited and may be 1 to 20 minutes, preferably 2 to 10 minutes.

The stretching step may be performed together with the dyeing step according to an embodiment of the present invention. The stretching ratio may be 1.01 to 2.0 times, but not limited thereto, preferably 1.1 to 1.8 times.

The cumulative stretching ratio up to the dyeing step including the swelling and the dyeing step may be 1.2 to 4.0 times. If the cumulative stretching ratio is less than 1.2 times, wrinkles of the film may occur to cause appearance defects. If the cumulative stretching ratio exceeds 4.0 times, the initial optical characteristics may be poor.

<Bridging stage>

The crosslinking step may be a step of immobilizing the adsorbed iodine molecules by immersing the dyed polyvinyl alcohol film in a crosslinking aqueous solution so that the dyeability due to physically adsorbed iodine molecules is not lowered by the external environment.

Although dichroic dyes are rarely eluted in a humidity environment, iodine molecules may be dissolved or sublimated depending on the environment when the crosslinking reaction is unstable, and sufficient crosslinking reaction may be required. In addition, in order to improve the optical characteristics by orienting the iodine molecules positioned between the polyvinyl alcohol molecule and the molecule, the stretching may be performed at the greatest stretching ratio in the crosslinking step, but the present invention is not limited thereto.

The method for producing a polarizer according to an embodiment of the present invention can be carried out without any particular limitation on the crosslinking step known in the art, for example, a crosslinking step composed of the first and second crosslinking steps can be carried out, One or more of the first and second crosslinking steps may be carried out using a crosslinked aqueous solution containing a boron compound. Whereby the optical characteristics and color durability of the polarizer can be improved.

The crosslinked aqueous solution may be a crosslinked aqueous solution known in the art without any particular limitation. For example, water as a solvent and a boron compound such as boric acid and sodium borate may be contained. An organic solvent and iodine More cargo may be included.

The boron compound imparts short crosslinking and rigidity to suppress wrinkling in the process, thereby improving handling properties and forming iodine orientation.

The content of the boron compound may be in a range known in the art, for example, 1 to 10% by weight, and preferably 2 to 6% by weight based on 100% by weight of the aqueous crosslinking solution. When the content is less than 1% by weight, the crosslinking effect of the boron compound may be decreased and it may be difficult to impart rigidity. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated, .

The iodide according to an embodiment of the present invention can be used to prevent the uniformity of the degree of polarization in the plane of the polarizer and the desorption of the dyed iodine. The iodide may be the same as that used in the dyeing step, and its content may be 0.05 to 15% by weight, but is not limited thereto, 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 if it exceeds 15% by weight, the iodide ion in the aqueous solution may penetrate into the film and the transmittance may be decreased.

The temperature of the crosslinking bath according to an embodiment of the present invention may be 20 to 70 캜, but is not limited thereto. The immersing time of the polyvinyl alcohol-based film in the crosslinking bath may be 1 second to 15 minutes, , Preferably 5 seconds to 10 minutes.

The stretching step may be performed together with the crosslinking step, wherein the stretching ratio of the first crosslinking step may be 1.4 to 3.0 times, but not limited thereto, preferably 1.5 to 2.5 times.

In addition, the stretching ratio of the second crosslinking step may be 1.01 to 2.0, but not limited thereto, preferably 1.2 to 1.8.

In addition, the cumulative stretching ratio of the first and second crosslinking steps may be 1.5 to 5.0 times, but not limited thereto, preferably 1.7 to 4.5 times. If the cumulative stretching ratio is less than 1.5 times, the iodine alignment effect may be insufficient. If the cumulative stretching ratio is more than 5.0 times, excessive stretching may cause breakage of the film and production efficiency may be lowered.

<Complementary phase>

The complementary step may be a step of stabilizing the iodine complex by orienting the iodine complex positioned between the molecule and the molecule near the cross-linking of the boric acid in a polyvinyl alcohol film on which the iodine complex is physically adsorbed.

In addition, the unsaturated iodine complex in the crosslinking step may be a step of correcting the color of the polyvinyl alcohol-based film to which the dye is stained.

The aqueous solution of the complementary coloring step may be an aqueous solution known in the art without any particular limitation, and may further include an organic solvent and an iodide mutually soluble with water, for example, water as a solvent and boric acid .

The boron compound according to an embodiment of the present invention may shorten cross-linking and rigidity to suppress wrinkling in the process, thereby improving handleability and forming iodine orientation.

The content of the boron compound may be 1 to 10% by weight based on 100% by weight of the aqueous crosslinked solution, but is not limited thereto, and preferably 2 to 6% by weight. If the content is less than 1% by weight, the crosslinking effect of the boron compound may be reduced and the polarizer may not be rigid. If the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated and the crosslinking reaction of the organic crosslinking agent is effectively It can be difficult to proceed.

The iodide according to one embodiment of the present invention can be 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 as that used in the dyeing step, and its content may be 0.05 to 15% by weight based on 100% by weight of the aqueous crosslinked solution, but is not limited thereto, preferably 0.5 to 11% . If the content is less than 0.05% by weight, the iodide ion in the film may escape to increase the transmittance of the polarizer, and if it exceeds 15% by weight, the iodide ion in the aqueous solution may penetrate into the film and transmittance of the polarizer may decrease.

The temperature of the complementary color bath according to an embodiment of the present invention may be 20 to 70 ° C, and the immersion time of the polyvinyl alcohol film in the sub-color bath may be 1 second to 15 minutes, but is not limited thereto, 5 seconds to 10 minutes.

The stretching step may be performed together with the complementary coloring step. In this case, the stretching ratio of the complementary coloring step may be 1.01 to 1.1 times, but not limited thereto, preferably 1.02 to 1.08 times.

If the stretching ratio is less than 1.01 times, the effect of stabilizing the iodine complex may be insufficient. If the stretching ratio is more than 1.1 times, excessive stretching may cause breakage of the film and production efficiency may be lowered.

<Stretching step>

In one embodiment of the present invention, the stretching step may be performed simultaneously with other steps as described above, or may be performed separately.

Further, the stretching step may be performed at least once, and in a case where a plurality of circuits are performed, the stretching step may be performed at any stage during the manufacturing process of the polarizer.

According to one embodiment of the production method of the present invention, the total cumulative stretching ratio of the polarizer may be preferably 4.0 to 7.0 times, more preferably 5.3 to 6 times.

As used herein, the term " cumulative stretching ratio "may include the value of the product of the stretching ratio at each step.

<Washing step>

The crosslinked and stretched polyvinyl alcohol film may be immersed in a water bath filled with an aqueous solution for washing to remove unnecessary residues such as boric acid attached to the polyvinyl alcohol film in the previous steps .

The aqueous solution for washing according to an embodiment of the present invention can be used without any particular limitation, and can be, for example, water, and iodide may be further added thereto, but the present invention is not limited thereto .

The temperature of the water bath according to an embodiment of the present invention may be 10 to 60 캜, but is not limited thereto, and may be preferably 15 to 40 캜.

The water washing step may be omitted and may be performed each time the previous steps such as the dyeing step or the crosslinking step are completed. It may also be repeated one or more times, and the number of repetition is not particularly limited.

<Drying step>

The drying step of the polarizer manufacturing method according to an embodiment of the present invention can dry the washed polyvinyl alcohol film and further improve the alignment of molecules of iodine dissolved in the neck by the drying, . &Lt; / RTI &gt;

As the drying method, a drying method known in the art can be used without limitation. For example, natural drying, air drying, heating drying, far infrared drying, microwave drying, hot air drying and the like can be used. Air-dried at 20 to 100 ° C for 1 to 10 minutes. In addition, the drying temperature may be low to prevent deterioration of the polarizer, but is not limited thereto, and may preferably be 100 ° C or less.

After the polarizer is prepared as described above, the adhesive composition is applied to one surface of at least one of the polarizer and the protective film to form an adhesive layer of 250 to 850 nm (S2).

The adhesive layer may be formed using an adhesive composition known in the art without particular limitation, for example, an aqueous adhesive composition may be used. As the aqueous adhesive composition, an acetoacetyl group , A crosslinking agent of a polyvinyl alcohol-based resin or a glyoxylate.

&Lt; Acetoacetyl group-modified polyvinyl alcohol-based resin &

The acetoacetyl modified polyvinyl alcohol (PVA) based resin can improve the adhesion to a protective film such as a polyvinyl alcohol (PVA) polarizer, a cellulose-based film, and an olefin-based film.

The acetoacetyl group-modified polyvinyl alcohol (PVA) resin according to one embodiment of the present invention contains a functional group having higher reactivity than the modified polyvinyl alcohol resin such as a carboxyl group modification, a methylol group modification, an amino group modification, etc., .

The acetoacetyl group-modified polyvinyl alcohol-based resin can be produced and used without particular limitation if it is a method known in the art. For example, a polyvinyl alcohol-based resin and diketene are reacted by a known method An acetoacetyl group-modified polyvinyl alcohol-based resin can be obtained. For example, a method of dispersing a polyvinyl alcohol-based resin in a solvent such as acetic acid and adding diketene thereto, a method of previously dissolving a polyvinyl alcohol-based resin in a solvent such as dimethylformamide or dioxane, The acetoacetyl group-modified polyvinyl alcohol-based resin can be produced by a method of adding tin or a method of directly contacting diketene gas or liquid diketene to a polyvinyl alcohol-based resin. The acetoacetyl group-modified polyvinyl alcohol-based resin is not particularly limited as long as the acetoacetyl group modification degree is 0.1 mol% or more, and may be, for example, 0.1 to 40 mol%, preferably 1 to 20 mol% Can be from 2 to 7 mol%. When the degree of modification of the acetoacetyl group is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient and may be inadequate. When the degree of modification of the acetoacetyl group exceeds 40 mol%, the effect of improving water resistance may be insignificant.

The degree of saponification of the acetoacetyl group-modified polyvinyl alcohol-based resin according to one embodiment of the present invention is not particularly limited, but may be 80 mol% or more, and preferably 85 mol% or more. If the degree of saponification of the polyvinyl alcohol-based resin contained in the adhesive composition is low, the sufficient water-solubility may be difficult to manifest, so that the adhesiveness may become insufficient.

The polyvinyl alcohol used in producing the acetoacetyl group-modified polyvinyl alcohol-based resin is not particularly limited, but in order to exhibit high adhesion between the polarizer and the protective film in the polarizing plate, the average degree of polymerization is in the range of 100 to 3,000 And preferably an average degree of saponification of from 80 to 100 mol%.

Examples of the products include Z-100, Z-200, Z-200H, Z-210, Z-220 and Z-320 (manufactured by Gohsefimer of Japan Synthetic Chemicals).

<Glyoxylate Crosslinking Agent>

The glyoxylate crosslinking agent included in the adhesive composition of the method for producing a polarizer according to an embodiment of the present invention can be prepared by reacting an acetoacetyl group-modified polyvinyl alcohol (PVA) resin with a polyvinyl alcohol (PVA) The adhesion to a protective film such as a film, an olefin-based film or the like can be improved.

The glyoxylate may be an alkali metal salt or an alkaline earth metal salt of glyoxylic acid. In one embodiment of the present invention, the same action and effect can be obtained even when any one of alkali metal salt and alkaline earth metal salt of glyoxylic acid is used. The reason for this is not limited to any theory, but the alkali metal and the alkaline earth metal are all elements having a low electronegativity, and the carboxylate salt thereof has a similar chemical property and functions as a crosslinking agent of the acetoacetyl group- May be due to the aldehyde portion of the oxalate.

The glyoxylate may be, for example, an alkali metal such as lithium glyoxylate, sodium glyoxylate, potassium glyoxylate, etc., and may be an alkaline earth metal Magnesium glyoxylate, calcium glyoxylate, strontium glyoxylate, barium glyoxylate, and the like. Among them, an alkali metal salt is preferable because it is easily dissolved in water, and sodium glyoxylate is particularly preferable.

The glyoxylate may be in the range of 3 to 25 parts by weight of the crosslinking agent of the glyoxylate relative to 100 parts by weight of the polyvinyl alcohol resin containing an acetoacetyl group. When the weight ratio of the glyoxylate to the polyvinyl alcohol-based resin is 3 or less, the water resistance of the adhesive layer in the case of using a polarizing plate becomes difficult to exhibit sufficiently, and when the weight ratio of the glyoxylate to the polyvinyl alcohol- , The optical characteristics of the polarizing plate may be deteriorated.

The thickness of the adhesive layer according to the present invention can be realized, for example, by adjusting the concentration of the solid content in the adhesive composition. For example, the polyvinyl alcohol resin and the glyoxylate crosslinking agent containing an acetoacetyl group based on the total weight of the adhesive composition may be contained in an amount of 2.5 to 6 wt% based on the solid content, preferably 3 to 5 wt% . &Lt; / RTI &gt; It is possible to effectively display the thickness of the adhesive layer according to the present invention within the above range.

The adhesive composition according to one embodiment of the present invention can be used with a pH in the range of 4 to 10. When the pH of the aqueous solution is less than 4, the water resistance of the polarizing plate can not be sufficiently exhibited when the polarizing plate is used, and when the pH of the aqueous solution exceeds 10, the adhesive composition can be gelled.

The viscosity of the adhesive composition at 20 ° C may range from 3 to 25 mPa · sec. When the viscosity of the adhesive composition is less than 3 mPa · sec, the water resistance of the polarizer can not be sufficiently exhibited when the polarizer is prepared. When the viscosity is 25 mPa · sec or more, the optical characteristics of the polarizer may be deteriorated.

In one embodiment of the present invention, the adhesive composition may include additives such as plasticizers, silane coupling agents, antistatic agents, fine particles, alcohols for improving spreadability, and metal salts, which are well known in the art, At least one selected from the group may be added.

The form of the adhesive composition may be a liquid form so as to form a uniform adhesive layer on the surface of the polarizer or the protective film, for example, the adhesive, which is known in the art without any particular limitation. Such a liquid type adhesive may be in the form of a solution or a dispersion of various kinds of solvents, and a solution type may be preferable in view of the coated surface of the substrate. Considering the stability, a solution type or dispersion type in which water is used as a solvent may be suitable have.

For the purpose of shortening the drying process, a water / alcohol mixed solvent in which an alcohol-based solvent is mixed with water and the boiling point of which is lower than that of water is blended may be used in the adhesive solution. The boiling point of the alcoholic solvent is not particularly limited and may have a boiling point of 100 占 폚 or lower and 80 占 폚 or lower, preferably 70 占 폚 or lower.

Next, the polarizer and the protective film are bonded to each other via the adhesive layer (S3).

The method of bonding the protective film according to an embodiment of the present invention may be performed by any method known in the art without any particular limitation. For example, a flexible method, a Meyer bar coating method, a gravure coating method, a die coating method, , And the adhesive composition is applied to the bonding surface of the polarizer and / or the protective film by a spraying method or the like, and both can be superimposed.

After applying the adhesive composition, the polarizer and the protective film may be bonded together with a nip roll interposed therebetween.

The bonding speed according to an embodiment of the present invention can be applied without limitation on the bonding speed at which the thickness of the adhesive layer can be increased. For example, when the bonding speed for bonding the protective film to the adhesive layer is 10 to 35 m / min But it may preferably be 20 to 30 m / min. It is possible to effectively display the thickness of the adhesive layer according to the present invention within the above range.

In order to improve the adhesiveness, processes known in the art can be applied without particular limitations. For example, the surface of the polarizer and / or the protective film may be subjected to plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame treatment, saponification treatment Or the like may be performed. As the saponification treatment, a method of immersing in an aqueous solution of an alkali such as sodium hydroxide, potassium hydroxide or the like may be included.

After the polarizer, the adhesive layer, and the protective film according to an embodiment of the present invention are laminated, a drying treatment may be performed. The drying treatment may be carried out by any method known in the art without limitation, and may be carried out, for example, by spraying hot air, and the temperature may be in a range of 50 to 100 ° C, but is not limited thereto, The drying time may be 30 to 1,000 seconds, but is not limited thereto.

Image display device

In addition, the present invention provides an image display device including the polarizing plate.

The polarizing plate according to the present invention can be applied to an image display device further including a configuration known in the art in addition to a polarizing plate. The image display device to which the polarizing plate according to the present invention can be applied is not particularly limited as long as the polarizing plate can be applied thereto. For example, various image display devices such as a liquid crystal display device, an electroluminescent display device, a plasma display device, And may be an image display device.

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

Manufacturing example  One: Polarizer  Produce

A transparent unoriented polyvinyl alcohol film (PE60, manufactured by KURARAY Co.) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 25 DEG C for 1 minute and 20 seconds to swell, followed by 1.25 mM / L of iodine and 1.25% And 0.3% by weight of boric acid was dipped in an aqueous solution for dyeing at 30 DEG C for 2 minutes and 30 seconds. At this time, stretching was performed at a stretching ratio of 1.56 times and 1.64 times at the swelling and dyeing steps, respectively, and the stretching ratio was increased to 2.56 times at the dyeing bath. Subsequently, the film was stretched at a drawing ratio of 1.7 times while immersing it in a crosslinking aqueous solution at 56 ° C containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 26 seconds (first crosslinking step) and crosslinking. Thereafter, the substrate was immersed in a crosslinking aqueous solution at 56 ° C containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 20 seconds (second crosslinking step) and stretched at a stretching ratio of 1.34 times while crosslinking. Then, it was stretched by 1.01 times while immersing for 10 seconds in a complementary color aqueous solution at 40 캜 containing 5% by weight of potassium iodide and 2% by weight of boric acid. At this time, the total cumulative stretching ratio of the swelling, dyeing, crosslinking and complementary phases was set to be six times. After the crosslinking is completed, the polyvinyl alcohol film is dried in an oven at 90 DEG C for 4 minutes to form a streaked stain Lv3 A polarizer was prepared (Sm = 3000 m, Rt = 700 nm).

The measurement methods of Sm and Rt are as follows.

Prepare the polarizer prepared in Preparation Example 10 mm in width and 10 mm in length, and then tape it on the X / Y stage of a Bruker interferometer microscope (Model Contour GT-I) to keep the surface of the sample from bending.

  Measure the surface of the polarizer after setting the conditions with AcuityXR PSI Mode, Object 10X, Multiplier 1.0X, Measurement area 10 mm * 10 mm, Illumination Green.

For reference, a photograph of the surface of the prepared polarizer is shown in Fig.

In describing the embodiment of the present invention, the streaks are visually confirmed by the fluorescent light reflection method on the basis of the following criteria.

Lv 1.: Unable to check for streaks

Lv 2.: Flourescent reflections can be streaked but not visible

Lv 3.: Fluorescent reflection method and visually streaked stain visible

Manufacturing example  2: Polarizer  Produce

A polarizer was prepared in the same manner as in Preparation Example 1, except that the temperatures of the first and second crosslinking steps were changed from 56 ° C to 59 ° C and the cumulative stretching magnification was changed to 6.1 times. (Stripe streak Lv 3, Sm = 3700 탆, Rt = 790 nm).

Manufacturing example  3: Polarizer  Produce

Except that the temperature of the first and second crosslinking steps was changed from 56 ° C to 59 ° C and the boric acid was changed from 3wt% to 3.6wt%, and the cumulative drawing magnification was changed to 6.3 times. Respectively. (Stripe streak Lv 3, Sm = 4900 탆, Rt = 950 nm).

Manufacturing example  4: Polarizer  Produce

A polarizer was prepared in the same manner as in Preparation Example 1, except that the temperature of the first and second crosslinking steps was changed from 59 ° C to 56 ° C, boric acid was changed from 3% to 3.6% by weight, and the cumulative stretching ratio was changed to 6.5 times. (Stripe streak Lv 3, Sm = 6000 탆, Rt = 1100 nm).

Example  One

(a) Preparation of adhesive composition

An acetoacetyl modified polyvinyl alcohol resin (Kosenol Z200, Nippon Synthetic Chemical Industry Co., Ltd.) having a saponification degree of 99.2 mol% was dissolved in water (distilled water) to prepare an aqueous solution having a solid content of 3 wt%.

This acetoacetyl group-modified polyvinyl alcohol-based resin aqueous solution and sodium glyoxylate (10% aqueous solution) to be a crosslinking agent were mixed so as to have a solid content of 10 parts by weight based on 100 parts by weight of the solid content of the acetoacetyl group-modified polyvinyl alcohol- An adhesive composition having a solids content of 3.3 wt% was prepared. At this time, the adhesive composition had a pH of 6.1 and a viscosity of 7.5 mPa · sec.

(b) Production of Polarizer

The adhesive composition prepared in (a) was coated on both surfaces of the polarizer of Production Example 1, and then a triacetyl cellulose film KC8UX (Konica Corp. saponification TAC), which was a protective film, was bonded to both sides, and the bonding speed was 20 m / min .

After the bonding, the laminate was dried at a temperature of 80 DEG C for 5 minutes to prepare a polarizing plate (thickness of the adhesive layer: 300 nm).

Example  2-9 and Comparative Example  1-4

As shown in Table 1, a polarizing plate was produced in the same manner as in Example 1 except that the concentration of the adhesive solid content and the bonding speed were changed to adjust the thickness of the adhesive. However, the adhesive crosslinking agent of Example 7 was methylol melamine of Aldrich.

Example  10 and 11

A polarizing plate was produced in the same manner as in Example 1 (Example 10) and Example 2 (Example 11) except that the polarizer of Production Example 2 was used.

Example  12 and 13

A polarizing plate was produced in the same manner as in Example 1 (Example 12) and Example 2 (Example 13), respectively, except that the polarizer of Production Example 3 was used.

Comparative Example  5

A polarizing plate was produced in the same manner as in Example 1, except that the polarizer of Production Example 4 was used.

division Adhesive Solids Concentration (%) Bonding speed
(m / min) Adhesive layer
Thickness (nm) Example 1 3.3 20 300 Example 2 3.8 20 400 Example 3 4.2 20 500 Example 4 3.3 25 600 Example 5 4.5 30 800 Example 6 3 20 280 Example 7 3.3 20 320 Example 8 3 15 250 Example 9 2.8 25 260 Example 10 3.3 20 300 Example 11 3.8 20 400 Example 12 3.3 20 300 Example 13 3.8 20 400 Comparative Example 1 2.2 20 150 Comparative Example 2 6.5 25 950 Comparative Example 3 3 5 170 Comparative Example 4 3 40 980 Comparative Example 5 3.3 20 300

[Evaluation test]

Each of the polarizers obtained in Examples 1 to 13 and Comparative Examples 1 to 5 was subjected to the following evaluation tests.

1. Adhesiveness (Cutter evaluation)

Each 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 protective film A and between the polarizing plate and the protective film B), and a blade And evaluated according to the following criteria.

A: The cutter blade does not enter any film.

O: The cutter stops when the edge of the cutter reaches 2 mm or less between the films.

DELTA: When the blade is pushed forward, it stops when the blade enters between 2 mm and 5 mm or less between at least one of the films.

X: When pushing the blade, the blade is easily inserted between at least one of the films (if the blade is inserted between any one of the films, the blade does not enter the other blade, Including stopping when entering.

2. Humidity Durability

Each of the polarizing plates left for 24 hours in an environment of 23 캜 and 55% relative humidity was subjected to the following humidity resistance thermostability test (hot water immersion test) to evaluate the water resistance. First, a sample was prepared by cutting a polarizing plate into a rectangular shape of 5 cm x 2 cm with the absorption axis (stretching direction) of the polarizing plate as a long side, 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. Here, FIG. 2 is a diagram schematically showing an evaluation test method for water resistance. FIG. 2 (A) shows sample 1 before immersion in hot water, and FIG. 2 (B) shows sample 1 after immersion in hot water. As shown in Fig. 2 (A), one short side of the sample was held in a gripping section (5), and about 80% in the longitudinal direction was immersed in a water bath at 60 deg. C and held for 4 hours. Thereafter, the sample (1) was taken out from the water tank to wipe out the water.

By the immersion in hot water, the polarizer 4 of the polarizing plate shrinks. The degree of shrinkage of the polarizer 4 was measured by measuring the distance from the end 1a of the sample 1 (the end of the protective film) at the center of the short side of the sample 1 to the end of the polarizer 4 contracted And evaluated as shrinkage length. As shown in Fig. 2 (B), the polarizer 4 located in the center of the polarizer plate is shrunk due to hot water immersion, so that the region 2 in which the polarizer 4 is not present between the protective films is formed.

Further, iodine elutes from the peripheral portion of the polarizer 4 which is in contact with the hot water due to the hot water immersion, and a portion 3 in which the color is missing in the peripheral portion of the sample 1 is generated. The degree of discoloration was evaluated by measuring the distance from the end of the shrunk polarizer 4 at the center of the shorter side of the sample 1 to the area where the color unique to the polarizer was left, and the value was regarded as the iodine dropout length. The total length of the shrinkage length and the iodine dropout length was defined as the total erosion length (X). That is, the total erosion length X is the distance from the end 1a of the sample 1 (the end of the protective film) at the center of the short side of the sample 1 to the region where the color unique to the polarizer remains. It can be judged that the smaller the shrinkage length, the iodine dropout length and the total erosion length X, the higher the adhesiveness (water resistance) in the presence of water.

◎: total erosion length X less than 2 mm

○: total erosion length X is 2 mm or more and less than 3 mm

DELTA: total erosion length X is 3 mm or more and less than 5 mm

X: total erosion length X of 5 mm or more

3. Streak stain level measurement

After the production of the polarizing plate, presence or absence of streaks of streaks was confirmed by the above-mentioned criteria by the fluorescent lamp reflection method.

4. Optical properties (transmittance, polarization degree)

The prepared polarizer was cut into a size of 4 cm x 4 cm and the transmittance was measured using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO). At this time, the polarization degree is defined by the following equation (1).

[Equation 1]

Polarization degree P = [(T1 - T2) / (T1 + T2)] * 1/2

(Where T1 is the parallel transmittance obtained when the pair of polarizers are arranged in parallel with the absorption axis, and T2 is the orthogonal transmittance obtained when the pair of polarizers are arranged with the absorption axis orthogonal).

division Adhesiveness Water temperature Transmittance (%) Polarization degree (%) Streaked stain level (Lv) Example 1 ◎ ◎ 43.1 99.994 1-2 Example 2 ◎ ◎ 43.0 99.994 One Example 3 ◎ ◎ 43.1 99.993 One Example 4 ◎ ◎ 42.9 99.993 One Example 5 ◎ ◎ 43.0 99.993 One Example 6 ◎ ◎ 43.1 99.995 2 Example 7 ◎ ○ 43.0 99.990 1-2 Example 8 ◎ ○ 43.1 99.994 2 Example 9 ◎ ○ 43.1 99.993 2 Example 10 ◎ ◎ 43.1 99.994 One Example 11 ◎ ◎ 43.0 99.994 One Example 12 ◎ ◎ 43.2 99.993 2 Example 13 ◎ ◎ 43.1 99.994 1-2 Comparative Example 1 ◎ ○ 43.0 99.994 3 Comparative Example 2 ○ △ 43.2 99.981 One Comparative Example 3 ◎ ○ 43.1 99.993 3 Comparative Example 4 △ △ 43.6 99.968 One Comparative Example 5 ◎ ◎ 43.2 99.980 3

Referring to Table 2, it can be seen that the polarizing plate of Examples has better optical characteristics (degree of polarization) and appearance characteristics (streaked smudge level) than Comparative Examples.

However, in the case of Example 7 in which methylol melamine was used as the crosslinking agent instead of sodium glyoxylate, it was confirmed that the resistance to humidity and humidity was somewhat lowered in comparison with the other examples.

1: sample
1a: end of protective film
2: area where no polarizer exists
3: a portion where the color is missing in the peripheral portion of the sample
4: Polarizer
5:

Claims (8)

A polarizer having a concavo-convex mean spacing Sm of 0.5 to 5 mm and a maximum height illuminance Rt of 100 to 1000 nm;
An adhesive layer having a thickness of 250 to 850 nm formed on at least one surface of the polarizer; And
And a protective film laminated on the adhesive layer.
The polarizing plate according to claim 1, wherein the adhesive layer has a thickness of 300 to 800 nm.
The polarizing plate according to claim 1, wherein the adhesive layer is formed of an adhesive composition comprising a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate crosslinking agent.
(S1) producing a polarizer having a concavo-convex mean spacing (Sm) of 0.5 to 5 mm and a maximum height illuminance (Rt) of 100 to 1000 nm;
(S2) applying an adhesive composition to one surface of at least one of the polarizer and the protective film to form an adhesive layer of 250 to 850 nm;
(S3) bonding the polarizer to the protective film via the adhesive layer.
5. The method of producing a polarizing plate according to claim 4, wherein the adhesive composition comprises a polyvinyl alcohol-based resin containing an acetoacetyl group and a glyoxylate crosslinking agent.
[6] The method according to claim 5, wherein the acetoacetyl group-containing polyvinyl alcohol resin and the glyoxylate crosslinking agent are contained in an amount of 2.5 to 6% by weight based on the total weight of the adhesive composition based on the solid content.
5. The method of manufacturing a polarizing plate according to claim 4, wherein a bonding speed for bonding the protective film to the adhesive layer is 10 to 35 m / min.
An image display device comprising the polarizing plate of any one of claims 1 to 3.

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